Title:
Refrigerant cycle device and heat-exchanger integrated unit with temperature sensor for the same
Kind Code:
A1


Abstract:
A refrigerant cycle device includes an ejector having a nozzle portion for decompressing refrigerant and a refrigerant suction port from which refrigerant is drawn by a high-speed refrigerant stream jetted from the nozzle portion, and a refrigerant branch passage branched from an upstream side of the nozzle portion in a refrigerant flow such that refrigerant flows into the refrigerant suction port through the refrigerant branch passage. Furthermore, a first heat exchanger is disposed to evaporate refrigerant flowing out of the ejector, a second heat exchanger is disposed in the refrigerant branch passage to evaporate refrigerant, and a temperature sensor is located to detect a temperature so as to detect a frost in the second heat exchanger. In addition, a controller performs a frost prevention control for reducing the frost in the second heat exchanger, in accordance with the temperature detected by the temperature sensor.



Inventors:
Nakamura, Tomohiko (Obu-city, JP)
Application Number:
11/810523
Publication Date:
12/20/2007
Filing Date:
06/06/2007
Assignee:
DENSO Corporation (Kariya-city, JP)
Primary Class:
Other Classes:
62/278, 62/500
International Classes:
F25D21/00; F25B1/06; F25B47/00
View Patent Images:
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Primary Examiner:
GONZALEZ, PAOLO
Attorney, Agent or Firm:
HARNESS DICKEY (TROY) (Troy, MI, US)
Claims:
What is claimed is:

1. A refrigerant cycle device comprising: a compressor for sucking and compressing refrigerant; a radiator located to cool high-pressure refrigerant discharged from the compressor; a refrigerant adjusting unit located to adjust a refrigerant amount flowing from the radiator to a downstream side such that a super-heating degree of refrigerant to be sucked to the compressor approaches to a predetermined degree; an ejector that includes a nozzle portion for decompressing refrigerant flowing from the refrigerant adjusting unit, and a refrigerant suction port from which refrigerant is drawn by a high-speed refrigerant stream jetted from the nozzle portion; a refrigerant branch passage that is branched from an upstream side of the nozzle portion in a refrigerant flow such that refrigerant flows into the refrigerant suction port through the refrigerant branch passage; a first heat exchanger disposed to evaporate refrigerant flowing out of the ejector; a second heat exchanger disposed in the refrigerant branch passage to evaporate refrigerant to be drawn into the refrigerant suction port; a′ temperature sensor located to detect a temperature so as to detect a frost in the second heat exchanger; and a controller which performs a frost prevention control to reduce the frost in the second heat exchanger, in accordance with the temperature detected by the temperature sensor.

2. The refrigerant cycle device according to claim 1, wherein: the second heat exchanger includes a plurality of tubes in which refrigerant flows, and upper and lower tanks located at upper and lower sides of the plurality of tubes to distribute refrigerant into or collect the refrigerant from the plurality of tubes; and the temperature sensor is located at a predetermined position of the second heat exchanger, at which refrigerant flows upwardly from the lower tank.

3. The refrigerant cycle device according to claim 1, wherein the first heat exchanger and the second heat exchanger are located to perform heat exchange with a common heat-exchanging medium.

4. The refrigerant cycle device according to claim 3, wherein the second heat exchanger is located downstream of the first heat exchanger in a flow direction of the heat-exchanging medium such that the heat-exchanging medium after passing through the first heat exchanger passes through the second heat exchanger.

5. The refrigerant cycle device according to claim 1, wherein the controller reduces a discharge capacity of refrigerant discharged from the compressor during the frost prevention control.

6. The refrigerant cycle device according to claim 1, wherein the controller stops operation of the compressor during the frost prevention control.

7. The refrigerant cycle device according to claim 1, wherein the temperature sensor is located to detect a temperature of air immediately after passing through the second heat exchanger.

8. The refrigerant cycle device according to claim 2, wherein: the second heat exchanger further includes a plurality of fins located between the tubes; and the temperature sensor is located to detect a temperature of one of the fins and the tubes.

9. The refrigerant cycle device according to claim 1, wherein the predetermined position is close to the lower tank.

10. A heat-exchanger integrated unit for a refrigerant cycle device, the integrated unit comprising: a heat exchanger for evaporating refrigerant; an ejector that includes a nozzle portion for decompressing refrigerant, and a refrigerant suction port from which refrigerant from the heat exchanger is drawn by a high-speed refrigerant flow jetted from the nozzle portion; and a temperature sensor for detecting a temperature so as to detect a frost in the heat exchanger, wherein the temperature sensor is located in the heat exchanger at a predetermined position at which refrigerant flows upwardly from below.

11. A heat-exchanger integrated unit for a refrigerant cycle device that includes an ejector having a nozzle portion for decompressing refrigerant, the integrated unit comprising: a first heat exchanger located to perform heat exchange between refrigerant and a heat-exchanging medium; a second heat exchanger located downstream from the first heat exchanger in a flow direction of the heat-exchanging medium to perform heat exchange between refrigerant and the heat-exchanging medium flowing from the first heat exchanger; and a temperature sensor located to detect a temperature of the second heat exchanger so as to detect a frost in the second heat exchanger, wherein: the first heat exchanger is located to evaporate refrigerant flowing out of the ejector; and the second heat exchanger has at least a suction-side heat exchanging portion that is located to evaporate refrigerant to be drawn into a refrigerant suction port of the ejector, from which refrigerant is drawn into the ejector by a high-speed refrigerant stream jetted from the nozzle portion.

12. The heat-exchanger integrated unit according to claim 11, wherein: the second heat exchanger includes a plurality of tubes in which refrigerant flows, and upper and lower tanks located at upper and lower sides of the plurality of tubes to distribute refrigerant into or collect the refrigerant from the plurality of tubes; and the temperature sensor is located at a predetermined position of the second heat exchanger, at which refrigerant flows upwardly from the lower tank.

13. The heat-exchanger integrated unit according to claim 12, wherein the ejector is located in the upper tank of the second heat exchanger.

14. The heat-exchanger integrated unit according to claim 11, further comprising: a throttle unit which is located at an upstream side of a heat exchanging portion of the second heat exchanger in a refrigerant flow, to decompress refrigerant while adjusting a refrigerant flow amount supplied to the second heat exchanger, wherein the throttle unit is integrated with the second heat exchanger.

Description:

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2006-165106 filed on Jun. 14, 2006, the contents of which are incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a refrigerant cycle device that includes an ejector serving as refrigerant decompression means and refrigerant circulation means, and a plurality of evaporators. For example, the evaporator is suitable to an air conditioner for a vehicle, or a refrigeration unit for a vehicle for freezing and refrigerating goods mounted on the vehicle. More particularly, the present invention relates to a heat-exchanger integrated unit with a temperature sensor for a refrigerant cycle device having an ejector.

BACKGROUND OF THE INVENTION

JP-A-2001-74388 (corresponding to U.S. Pat. No. 6,449,979) discloses a refrigerant cycle device that includes a first evaporator connected to a downstream side of an ejector, and a second evaporator connected to a refrigerant suction port of the ejector. In the refrigerant cycle device, an evaporation temperature of refrigerant in the second evaporator is lower than that in the first evaporator.

The first and second evaporators are adapted to cool a common space to be cooled, and the first evaporator is disposed on the upstream side in the flow direction of air, while the second evaporator is disposed on the downstream side in the flow direction of air. Thus, the refrigerant cycle device is constructed by combining the first evaporator on the refrigerant downstream side of the ejector and the second evaporator on the refrigerant suction side of the ejector, thereby cooling the common space to be cooled.

JP-A-2005-308384 (corresponding to US 2005/0268644 A1) discloses an evaporator for allowing refrigerant to flow snaking through tubes and tank portions which are arranged in the evaporator in even rows in the flow direction of external fluid.

Furthermore, in a conventional vapor-compression refrigerant cycle device, when a load to be cooled is small and the temperature of an evaporator is decreased, frost (frosting) occurs on the evaporator. As a result, a cooling function is not performed effectively. For this reason, a contact type fin temperature sensor is inserted into an appropriate portion of a fin of the evaporator to detect the surface temperature of the fin. Alternatively, a non-contact type air temperature sensor is used to detect the temperature of air on the post-evaporator side. In this case, a compressor is intermittently operated so as to prevent the formation of the frost on the evaporator.

However, the distribution of refrigerant and air velocity always becomes nonuniform in the evaporator. In the conventional method, the temperature sensor cannot be attached to any position of the evaporator. At this time, the higher the temperature of a detection point of the temperature sensor, the more the timing of stopping the compressor is delayed, resulting in an excess amount of supply of the refrigerant, which leads to frosting of the evaporator. Accordingly, air cannot flow downwind smoothly due to the frost, and thus the cooling cannot be performed sufficiently. In this case, the air temperature sensor senses high air temperature with the formation of the frost, and continues rotating the compressor, which may lead to breakage of the cycle or failure of the compressor. Although the fin temperature sensor can control such a condition, the cycle cannot be activated until the frosted part is melted, resulting in decrease in cooling operating efficiency.

For this reason, an appropriate attachment position is required to be determined by various tests for every type evaporator such that the temperature sensor is attached to a position where the fin temperature or blown-air temperature of the evaporator becomes lowest.

SUMMARY OF THE INVENTION

In view of the foregoing problems, it is an object of the present invention to provide a refrigerant cycle device in which a frost prevention control can be effectively performed.

It is another object of the present invention to provide a heat-exchanger integrated unit for a refrigerant cycle device, in which a temperature sensor used for a frost prevention control can be easily attached at a suitable position of a heat exchanger.

According to a first example of the present invention, a refrigerant cycle device includes a compressor for sucking and compressing refrigerant, a radiator located to cool high-pressure refrigerant discharged from the compressor, a refrigerant adjusting unit located to adjust a refrigerant amount flowing from the radiator to a downstream side such that a super-heating degree of refrigerant to be sucked to the compressor approaches to a predetermined degree, an ejector that includes a nozzle portion for decompressing refrigerant flowing from the refrigerant adjusting unit and a refrigerant suction port from which refrigerant is drawn by a high-speed refrigerant stream jetted from the nozzle portion, a refrigerant branch passage that is branched from an upstream side of the nozzle portion in a refrigerant flow such that refrigerant flows into the refrigerant suction port through the refrigerant branch passage, a first heat exchanger disposed to evaporate refrigerant flowing out of the ejector, a second heat exchanger disposed in the refrigerant branch passage to evaporate refrigerant to be drawn into the refrigerant suction port, a temperature sensor located to detect a temperature so as to detect a frost in the second heat exchanger, and a controller which performs a frost prevention control to reduce the frost in the second heat exchanger in accordance with the temperature detected by the temperature sensor. Accordingly, it is possible to reduce and prevent frost generated on the second heat exchanger when being used as an evaporator. Furthermore, because the refrigerant adjusting unit is located to adjust a refrigerant amount flowing from the radiator to a downstream side such that a super-heating degree of refrigerant to be sucked to the compressor approaches to a predetermined degree, operation efficiency of the refrigerant cycle device can be effectively improved.

For example, the second heat exchanger includes a plurality of tubes in which refrigerant flows, and upper and lower tanks located at upper and lower sides of the plurality of tubes to distribute refrigerant into or collect the refrigerant from the plurality of tubes. In this case, the temperature sensor is located at a predetermined position of the second heat exchanger, at which refrigerant flows upwardly from the lower tank.

The controller can reduces a discharge capacity of refrigerant discharged from the compressor during the frost prevention control, or can stop operation of the compressor during the frost prevention control. Furthermore, the temperature sensor can be located to detect a temperature of air immediately after passing through the second heat exchanger, or can be located to detect a temperature of one of fins and tubes of the second heat exchanger. Furthermore, the predetermined position may be set close to the lower tank.

According to another example of the present invention, a heat-exchanger integrated unit for a refrigerant cycle device includes a heat exchanger for evaporating refrigerant, an ejector that includes a nozzle portion for decompressing refrigerant and a refrigerant suction port from which refrigerant from the heat exchanger is drawn by a high-speed refrigerant flow jetted from the nozzle portion, and a temperature sensor for detecting a temperature so as to detect a frost in the heat exchanger. Furthermore, the temperature sensor is located in the heat exchanger at a predetermined position at which refrigerant flows upwardly from below. Therefore, when the heat exchanger is used as an evaporator, frost generated on the heat exchanger can be suitably reduced by using the temperature detected by the temperature sensor.

According to another example of the present invention, a heat-exchanger integrated unit for a refrigerant cycle device includes a first heat exchanger located to perform heat exchange between refrigerant and a heat-exchanging medium, a second heat exchanger located downstream from the first heat exchanger in a flow direction of the heat-exchanging medium to perform heat exchange between refrigerant and the heat-exchanging medium flowing from the first heat exchanger, and a temperature sensor located to detect a temperature of the second heat exchanger so as to detect a frost in the second heat exchanger. Furthermore, the first heat exchanger is located to evaporate refrigerant flowing out of an ejector of the refrigerant cycle device, and the second heat exchanger has at least a suction-side heat exchanging portion that is located to evaporate refrigerant to be drawn into a refrigerant suction port of the ejector, from which refrigerant is drawn into the ejector by a high-speed refrigerant stream jetted from the nozzle portion. Because the temperature sensor is located to detect the temperature of the second heat exchanger having a refrigerant temperature lower than that of the first heat exchanger, front can be easily detected using the temperature sensor, thereby effectively reducing and preventing front generated on the second heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of preferred embodiments when taken together with the accompanying drawings. In which:

FIG. 1 is a schematic diagram of an ejector-type refrigerant cycle device of one embodiment to which the present invention is applied;

FIG. 2 is a perspective view showing a schematic construction of a heat-exchanger integrated unit for the ejector-type refrigerant cycle device of FIG. 1;

FIG. 3 is a longitudinal sectional view of an upper tank portion of the integrated unit of FIG. 2;

FIG. 4 is a lateral sectional view of a part of the upper tank portion of the integrated unit of FIG. 2;

FIG. 5A is a perspective view of a fin temperature sensor, and FIG. 5B is a partial sectional view showing the structure of a sensor portion of the fin temperature sensor of FIG. 5A;

FIG. 6 is a perspective view of an air temperature sensor;

FIG. 7 is a diagram of temperature distribution at a second evaporator when being viewed from the downstream side of an air flow;

FIG. 8 is a graph representing a relationship of a refrigeration operating efficiency with respect to a flow ratio of refrigerant passing through the second evaporator;

FIG. 9 is a schematic diagram of an ejector-type refrigerant cycle device of a modified example of FIG. 1 of the present invention;

FIG. 10 is a perspective view showing a heat-exchanger integrated unit according to a first modified example of the embodiment of the present invention;

FIG. 11 is a perspective view showing a heat-exchanger integrated unit according to a second modified example of the embodiment of the present invention;

FIG. 12 is a perspective view showing a heat-exchanger integrated unit according to a third modified example of the embodiment of the present invention; and

FIG. 13 is a perspective view showing a heat-exchanger integrated unit according to a fourth modified example of the embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to preferred embodiments of an ejector-type refrigerant cycle device and a heat-exchanger integrated unit for the ejector-type refrigerant cycle device according to the present invention.

In order to constitute the refrigerant cycle device including an ejector, the heat-exchanger integrated unit is connected to other components of the refrigerant cycle device, e.g., a radiator and a compressor, via piping. The heat-exchanger integrated unit of this example is used in applications for cooling air to serve as indoor equipment. The heat-exchanger integrated unit of another example can also be used as outdoor equipment.

In an ejector-type refrigerant cycle device 10 of the embodiment, a compressor 11 for sucking and compressing refrigerant is rotatably driven by an engine for vehicle running (not shown) via an electromagnetic clutch 11a, a belt, and the like.

As the compressor 11, may be used either of a variable displacement compressor for being capable of adjusting a refrigerant discharge capacity depending on a change in compression capacity, or a fixed displacement compressor for adjusting a refrigerant discharge capacity by changing an operating efficiency of the compressor by intermittent connection of an electromagnetic clutch 11a. The electromagnetic clutch 11a shown in FIG. 1 is controlled by an output from a controller (ECU, control means) 50 to be intermittently connected. When the compressor 11 is an electric compressor, the compressor 11 can adjust its refrigerant discharge capacity by adjustment of the number of revolutions of an electric motor.

A radiator 12 (refrigerant cooler) is disposed on a refrigerant discharge side of the compressor 11. The radiator 12 exchanges heat between high-pressure refrigerant discharged from the compressor 11 and the outside air (i.e., air outside a vehicle compartment) blown by a cooling fan not shown to cool the high-pressure refrigerant. In this embodiment, refrigerant whose high pressure does not exceed the critical pressure, such as a Freon-based or HC-based refrigerant, is used to form a vapor-compression subcritical cycle. In this case, the radiator 12 serves as a condenser for cooling and condensing the refrigerant.

A liquid receiver 12a is provided at an outlet side of the radiator 12. The liquid receiver 12a has a vertically oriented tank-like shape to be well known, and serves as a liquid/vapor separator for separating the refrigerant into liquid and vapor phases to store the excess liquid refrigerant in the refrigerant cycle. The liquid refrigerant is guided to flow out of the lower part of the tank-shaped inside at the outlet of the liquid receiver 12a. The liquid receiver 12a is integrally formed with the radiator 12 in this example.

The radiator 12 may have the known structure including a heat exchanging portion for condensation disposed on the upstream side of refrigerant flow, the liquid receiver 12a for receiving refrigerant introduced from the heat exchanging portion for condensation to separate the refrigerant into liquid and vapor phases, and a heat exchanging portion for supercooling of the saturated liquid refrigerant from the liquid receiver 12a. A thermal expansion valve 13 is disposed at an outlet side of the liquid receiver 12a. The thermal expansion valve 13 serves as adjustment means for adjusting an amount of the liquid refrigerant from the liquid receiver 12a, and has a temperature sensing portion 13a disposed in a passage on the suction side of the compressor 11.

The thermal expansion valve 13 detects a degree of superheat SH of the refrigerant on the suction side of the compressor 11 based on the temperature and pressure of the suction side refrigerant of the compressor 11 (i.e., refrigerant on the outlet side of the evaporator 15), and adjusts a degree of opening of its valve (refrigerant flow amount) such that the degree of superheat SH of the compressor suction-side refrigerant is a predetermined value, as is known in general.

An ejector 14 is disposed at an outlet side of the thermal expansion valve 13. The ejector 14 serves as decompression means for decompressing the refrigerant, and also as refrigerant circulation means (kinetic vacuum pump) for circulating the refrigerant by a suction action (entrainment action) of a refrigerant flow ejecting at high velocity.

The ejector 14 includes a nozzle portion 14a that decreases the sectional area of passage of refrigerant having passed through the expansion valve 13 (intermediate-pressure refrigerant) so as to reduce the pressure of the refrigerant and to expand the refrigerant. The ejector 14 also includes a refrigerant suction port 14b that is arranged in the same space as a refrigerant ejection port of the nozzle portion 14a so as to suck the vapor-phase refrigerant from a second evaporator (a second heat exchanger, a second heat exchanging portion) 18 to be described later.

A mixing portion 14c is provided on a downstream side of the nozzle portion 14a and the refrigerant suction port 14b to mix the high-velocity refrigerant flow from the nozzle portion 14a with the suction refrigerant drawn into the refrigerant suction port 14b from the second evaporator 18. A diffuser portion 14d serving as a booster (pressure-increasing portion) is arranged on the downstream side of the refrigerant flow of the mixing portion 14c. The diffuser portion 14d is formed in such a shape to gradually increase the passage area of the refrigerant, and has an effect of reducing the velocity of the refrigerant flow to increase the refrigerant pressure, that is, an effect of converting the velocity energy of the refrigerant to the pressure energy thereof.

A first evaporator 15 is connected to a refrigerant outlet side of the diffuser portion 14d of the ejector 14, and a refrigerant outlet of the first evaporator 15 is connected to the refrigerant suction side of the compressor 11. In contrast, a refrigerant branch passage 16 is branched from the inlet side of the ejector 14 (i.e., an intermediate part between the outlet side of the thermal expansion valve 13 and the inlet side of the nozzle 14a of the ejector 14). The refrigerant branch passage 16 has the downstream side thereof connected to the refrigerant suction port 14b of the ejector 14. A point “zz” in FIG. 1 indicates a branch point of the refrigerant branch passage 16.

A throttle unit 17 is disposed in the refrigerant branch passage 16, and the second evaporator 18 is disposed on a downstream side of the refrigerant flow away from the throttle unit 17. The throttle unit 17 is decompression means serving to exhibit an adjustment effect of the refrigerant flow ratio into the second evaporator 18. Specifically, the throttle unit 17 is constructed of, for example, a capillary tube, or an orifice.

In this embodiment, the first and second evaporators 15 and 18 are assembled to a heat-exchanger integrated unit 20 with the following structure. For example, the two evaporators 15 and 18 are accommodated in an air conditioning case not shown, and a common electric blower 19 blows air (i.e., air to be cooled) through an air passage formed in the air conditioning case in the direction of arrow. The blown air of the electric blower 19 is cooled by the two evaporators 15 and 18. In this embodiment, air is a medium for heat exchange. The electric blower 19 is an electric fan driven by a motor 19a. The motor 19a is rotatably driven by a control voltage output from the controller 50.

The cold air cooled by the two evaporators 15, 18 may be blown into the common space to be cooled (not shown). Accordingly, the common space can be cooled by the two evaporators 15, 18. When the ejector-type refrigerant cycle device 10 of this embodiment is used for a refrigerant cycle device for vehicle air conditioning, a space in the compartment of the vehicle is the space to be cooled. When the ejector-type refrigerant cycle device 10 of this embodiment is used for a refrigerant cycle device for a freezer car, a freezer and refrigerator space of the freezer car is a space to be cooled.

The first evaporator 15, which is connected to a main flow path on the downstream side of the ejector 14, is disposed on the upstream side of the air flow, and the second evaporator 18, which is connected to the refrigerant suction port 14b of the ejector 14, is disposed on the downstream side of the air flow. A temperature sensor 40, which will be described later, is disposed in the second evaporator 18 on a downwind side to serve as a detection member for detecting frost (frosting) occurring on the two evaporators 15, 18. A temperature signal detected by the temperature sensor 40 is input to the controller 50, whereby the control of frost prevention (i.e., frost prevention control) is performed by the controller 50 according to the temperature signal as described later.

In this embodiment, the ejector 14, the first and second evaporators 15, 18, the throttle unit 17, and the temperature sensor 40 are assembled as one integrated unit 20 (heat-exchanger integrated unit). Now, concrete examples of this integrated unit 20 will be described with reference to FIGS. 2 to 6. FIG. 2 is a perspective view showing an outline of the entire structure of this integrated unit 20 (20A). FIG. 3 is a longitudinal (lengthwise) sectional view of the upper tank portions 15b, 18b of the first and second evaporators 15, 18. FIG. 4 is a lateral sectional view of the upper tank portion 18b of the second evaporator 18.

Now, an example of the integrated structure including the two evaporators 15,18 will be explained with reference to FIG. 2. In the example shown in FIG. 2, the two evaporators 15, 18 are completely integrated as one heat exchanger structure. Thus, the first evaporator 15 constitutes an upstream side area of the air flow in the one heat exchanger structure, and the second evaporator 18 constitutes a downstream side area of the air flow in the one heat exchanger structure.

The up, down, left, and right arrows in FIG. 2 respectively indicate the following. That is, the side of the second evaporator 18 on which the ejector 14 is disposed corresponds to the up direction, the side of the second evaporator 18 on which the ejector 14 is not disposed corresponds to the down direction, the upstream side of the nozzle portion 14a of the ejector 14 corresponds to the left direction, and the downstream side of the diffuser portion 14d of the ejector 14 corresponds to the right direction, when being viewed from the downstream side of the flow direction of the blown air. The up, down, left, and right directions in the following description are the same as those in FIG. 2.

The first evaporator 15 and the second evaporator 18 have the same basic structure, each including heat-exchange core portion 15a, 18a, and tank portions 15b, 15c, 18b, 18c positioned on both up and down sides of the heat-exchange core portion 15a, 18a, respectively. The heat-exchange core portion 15a, 18a include a plurality of tubes 21 extending vertically. Between the plurality of tubes 21, a passage is formed through which a heat-exchanged medium, for example, air, passes in this embodiment. Fins 22 are disposed between these tubes 21, and brazed to the tubes 21.

Each of the heat-exchange core portions 15a, 18a is constructed of a laminated structure including the tubes 21 and the fins 22. These tubes 21 and fins 22 are alternately laminated in the lateral direction of the heat-exchange core portions 15a, 18a. In another embodiment, a structure without fins 22 may be employed. Although FIG. 2 shows only a part of the laminated structure including the tubes 21 and the fins 22, the laminated structure including the tubes 21 and the fins 22 may be formed over the entire areas of the heat-exchange core portions 15a, 18a. The blown air of the electric blower 19 passes through voids of the laminated structure.

The tube 21 forms therein a refrigerant passage, and is constructed of a flat tube having a flat section extending along the air flow direction. The fin 22 is a corrugated fin formed by bending a thin plate in a wave-like shape, and is connected to the flat outer surface of the tube 21 to expand an air side heat-transmission area. The tubes 21 of the heat-exchange core portion 15a and the tubes 21 of the heat-exchange core portion 18a respectively construct the refrigerant passages that are independent from each other. The tank portions 15b, 15c on both up and down sides of the first evaporator 15, and the tank portions 18b, 18c on both up and down sides of the second evaporator 18 construct the refrigerant passage spaces that are independent from each other.

Both the up and down ends of the tube 21 of the heat-exchange core portion 15a are inserted into the tank portions 15b and 15c on both up and down sides of the first evaporator 15. The tank portions 15b and 15c have tube engagement holes not shown. Both the up and down ends of the tube 21 are made in communication with the inner spaces of the tank portions 15b, 15c. Similarly, both up and down ends of the tube 21 of the heat-exchange core portion 18a are inserted into the tank portions 18b and 18c on both up and down sides of the second evaporator 18. The tank portions 18b and 18c have tube engagement holes not shown. Both the up and down ends of the tube 21 are made in communication with the inner spaces of the tank portions 18b, 18c.

Thus, the tank portions 15b, 15c, 18b, 18c on both the up and down sides serve to distribute the refrigerant to the respective tubes 21 of the heat-exchange core portions 15a, 18a, and to collect the refrigerant stream from the tubes 21. The two upper tank portions 15b and 18b as well as the two lower tank portions 15c and 18c are adjacent to each other, and thus can be formed integrally.

Alternatively, the two upper tank portions 15b and 18b, and the two lower tank portions 15c and 18c may be constructed independently in the integrated unit 20A(20). Aluminum which is a metal having excellent thermal conductivity and brazing property is suitable as specific materials of components of the evaporator, including the tube 21, the fin 22, and the tank portions 15b, 15c, 18b, 18c. Each component is formed using the aluminum material, and all components of the first and second evaporators 15 and 18 are assembled and then connected integrally by brazing.

In this embodiment, the throttle unit 17 is constructed of first and second connection blocks 23 and 24 of the refrigerant passages shown in FIG. 3 and the capillary tube, and is integrally assembled to the first and second evaporators 15 and 18 by brazing. In contrast, because the ejector 14 has fine passages formed in the nozzle portion 14a with high accuracy, if the ejector 14 is brazed, the nozzle portion 14a may be thermally deformed due to the high temperature in brazing (brazing temperature of aluminum: about 600 degrees). This cannot keep the shape and dimension of the passage in the nozzle portion 14a according to a predetermined design.

Thus, in this embodiment, after integrally brazing the first and second evaporators 15,18, the first and second connection blocks 23, 24 and the throttle unit 17, the ejector 14 is assembled to the integrally brazed member. The throttle unit 17 and the first and second connection blocks 23, 24 are formed of aluminum material, like the evaporator components.

The first connection block 23, as shown in FIG. 3, is brazed and fixed to one end side in the longitudinal direction of each of the upper tank portions 15b, 18b of the first and second evaporators 15, 18. The first connection block 23 forms a refrigerant inlet 25 and a refrigerant outlet 26 of the integrated unit 20 shown in FIG. 1. The refrigerant inlet 25 is branched into a main passage 25a serving as a first passage directed to the inlet side of the nozzle 14a of the ejector 14, and the branch passage 16 serving as a second passage directed to the inlet side of the throttle unit 17 at a point (e.g., midpoint) of the first connection block 23 in the thickness direction of the first connection block 23.

The branch passage 16 of the first connection block 23 corresponds to an inlet part of the branch passage16 shown in FIG. 1. Therefore, the branch point z of FIG. 1 is located inside the first connection block 23. In contrast, the refrigerant outlet 26 is constructed by one simple passage hole (a circular hole and the like) penetrating through the first connection block 23 in the thickness direction. The branch passage 16 of the first connection block 23 is tightly connected to one end of the throttle unit 17 (left end shown in FIGS. 2 and 3) by brazing.

The second connection block 24 is disposed substantially at a center area in the longitudinal direction of the inner space of the upper tank portion 18b of the second evaporator 18, and brazed to the inner wall surface of the upper tank portion 18b. This second connection block 24 is located to partition the inner space of the upper tank portion 18b into two spaces in the tank longitudinal direction, that is, a left space 27 and a right space 28. The other end (right end) of the throttle unit 17 penetrates a support hole 24a of the second connection block 24 to be opened in the right space 28 of the upper tank portion 18b, as shown in FIG. 3.

An interface between the outer peripheral surface of the throttle unit 17 and the support hole 24a is sealed by brazing with an interface between both left and right spaces 27 and 28 being shut down. Among the ejector 14, the nozzle portion 14a is made of stainless, brass, or the like, and parts other than the nozzle portion 14a (including a housing portion forming the refrigerant suction port 14b, the mixing portion 14c, the diffuser portion 14d, and the like) is made of metal material, such as copper or aluminum, but may be made of resin (non-metallic material).

After the completion of integrated assembly of the first and second evaporators 15 and 18 by brazing (brazing step), the ejector 14 is inserted into the upper tank portion 18b through the refrigerant inlet 25 and a hole of the main passage 25a of the first connection block 23. The inserted tip end in the longitudinal direction of the ejector 14 corresponds to an outlet portion of the diffuser portion 14d shown in FIG. 1. The tip end of the ejector is inserted into a circular recess 24b of the second connection block 24, and gas-tightly fixed in the circular recess 24b using an O-ring 29a.

The tip end of the ejector is in communication with a communication hole 24c of the second connection block 24. A partition plate 30 is disposed substantially at a center area in the longitudinal direction of the inner space of the upper tank portion 15b of the first evaporator 15. The inner space of the upper tank portion 15b is partitioned by the partition plate 30 into two spaces in the longitudinal direction, that is, a left space 31 and a right space 32. The communication hole 24c of the second connection block 24 is in communication with the right space 32 of the upper tank portion 15b of the first evaporator 15 via a through hole 33a of an intermediate wall surface 33 of both the upper tank portions 15b, 18b.

The left end of the ejector 14 in the longitudinal direction (left end of FIG. 3) corresponds to an inlet portion of the nozzle portion 14a shown in FIG. 1, and is fitted into and fixed to the inner wall surface of the main passage 25a of the first connection block 23 using the O-ring 29b to be sealed therebetween. Fixing of the ejector 14 in the longitudinal direction may be performed using, for example, screw fixing means not shown. The O-ring 29a is held in a groove (not shown) of the second connection block 24, and the O-ring 29b is held in a groove (not shown) of the first connection block 23.

In the first connection block 23, the refrigerant outlet 26 is formed to be in communication with the left space 31 of the upper tank portion 15b, and the main passage 25a is formed to be in communication with the left space 27 of the upper tank portion 18b. The first connection black 23 is brazed to the side walls of the upper tank portions 15b, 18b such that the branch passage 16 is made in communication with one end of the throttle unit 17. The refrigerant suction port 14b of the ejector 14 is set in communication with the left space 27 of the upper tank portion 18b of the second evaporator 18.

In this embodiment, the second connection block 24 partitions the inside of the upper tank portion 18b of the second evaporator 18 into left and right spaces 27 and 28. The left space 27 serves as a collecting tank for collecting the refrigerant from the plurality of tubes 21, and the right space 28 serves as a distribution tank for distributing the refrigerant into the tubes 21. The ejector 14 has an elongated cylindrical shape extending in an axial direction of the nozzle portion 14a, and the longitudinal direction of the elongated cylindrical shape is made to correspond to the longitudinal direction of the upper tank portion 18b, so that the ejector 14 is elongated in parallel with the upper tank portion 18b.

Thus, the ejector 14 and the evaporator 18 can be disposed in a compact manner, and further the entire unit can be made compact. The ejector 14 is disposed in the left space 27 serving as the collecting tank of the evaporator 18, and has the refrigerant suction port 14b set to be directly opened in the left space 27 serving as the collecting tank. This structure further can decrease the number of refrigerant pipes.

This example has an advantage in that the collection of the refrigerant from the plurality of tubes 21 and the supply of the refrigerant to the ejector 14 (suction of the refrigerant) can be performed only using one tank. The first evaporator 15 is disposed adjacent to the second evaporator 18, and the ejector 14 is set such that the downstream side end of the ejector 14 is adjacent to the distribution tank of the first evaporator 15 (i.e., the right space 32 of the upper tank portion 15b).

Thus, even when the ejector 14 is disposed to be incorporated into the tank portion on the second evaporator 18 side, the outflow refrigerant from the ejector 14 can be supplied to the first evaporator 15 side through a short simple refrigerant passage (including holes 24c and 33a). The refrigerant flow path of the entire integrated unit 20 with the above-mentioned structure will be described below with reference to FIGS. 2 and 3.

The refrigerant inlet 25 of the first connection block 23 is branched into the main passage 25a and the branch passage 16 within the first connection block 23. First, the refrigerant from the main passage 25a is decompressed through the ejector 14 (the nozzle portion 14a, the mixing portion 14c, and the diffuser portion 14d, in this order), and the low-pressure refrigerant decompressed flows into the right space 32 of the upper tank portion 15b of the first evaporator 15 as indicated by the arrow “aa” through the connection hole 24c of the second connection block 24 and the through hole 33a of the intermediate wall surface 33.

The refrigerant from the right space 32 flows through the plurality of tubes 21 on the right side of the heat-exchange core portion 15a as indicated by the arrow “bb” to flow into the right side part of the lower tank portion 15c. Since no partition plate is provided in the lower tank portion 15c, the refrigerant from the right side part of the lower tank portion 15c moves to the left side thereof as indicated by the arrow “cc”.

The refrigerant from the left side part of the lower tank portion 15c rises through the plurality of tubes 21 on the left side of the heat-exchange core portion 15a as indicated by the arrow “dd” to flow into the left space 31 of the upper tank portion 15b, and then to the refrigerant outlet 26 of the first connection block 23 as indicated by the arrow “ee”. In contrast, the refrigerant from the branch passage 16 of the first connection block 23 is first decompressed through the throttle unit 17, and the decompressed low-pressure refrigerant flows into the right space 28 of the upper tank portion 18b of the second evaporator 18 as indicated by the arrow “ff”.

The refrigerant from the right space 28 flows through the plurality of tubes 21 on the right side of the heat-exchange core portion 18a as indicated by the arrow “gg” to flow into the right portion of the lower tank portion 18c. Since no partition plate is provided in the lower tank portion 18c, the refrigerant from the right side part of the lower tank portion 18c moves to the left side thereof as indicated by the arrow “hh”.

The refrigerant from the left side part of the lower tank portion 18c rises through the plurality of tubes 21 on the left side of the heat-exchange core portion 18a as indicated by the arrow “ii” to flow into the left space 27 of the upper tank portion 18b. The refrigerant suction port 14b of the ejector 14 is opened in the left space 27, and thus the refrigerant in the left space 27 is drawn from the refrigerant suction port 14b into the ejector 14. Since the integrated unit 20 has the refrigerant flow path structure as described above, only one refrigerant inlet 25 may be provided at the first connection block 23 in the entire integrated unit 20, and only one refrigerant outlet 26 may be provided at the first connection block 23.

The integrated unit 20 of the embodiment includes the temperature sensor 40 integrally provided in the heat-exchange core portion 18a of the second evaporator 18 on the downwind side, for detecting the frost on the first and second evaporators 15, 18. The temperature sensor 40 may be a contact type fin temperature sensor 40A for detecting the temperature of fins (evaporator), or a non-contact type air temperature sensor 40B for detecting the blown-air temperature on the post-evaporator flow side. The sensor 40 (40A, 40B) can be located at a suitable position in the integrated unit 20.

FIG. 5A is a perspective view of the fin temperature sensor 40A, and FIG. 5B is a diagram showing the structure of a sensor portion 42. FIG. 6 is a perspective view of the air temperature sensor 40B. The structure of the fin temperature sensor 40A will be described below. The fin temperature sensor 40A includes a sensor portion 42 disposed on one end of a lead wire 43 and inserted into a fin portion of the evaporator, and a resin clamp 41 having an anchor portion 41a inserted into and fixed to the fin portion together with the sensor portion 42, while holding the root side of the sensor portion 42.

As shown in FIG. 5B, the sensor portion 42 includes a temperature sensing semiconductor 42a whose resistance value changes depending on the temperature of the tip end of the lead wire 43 and which is connected to the tip end of the lead wire 43. The sensor portion 42 also includes an epoxy resin 42b or the like fixed to the periphery of the temperature sensing semiconductor 42a, and a conductive filler filling a gap in the sensor portion 42. These elements constituting the sensor portion 42 are inserted into an aluminum case 42c (made of A1000 aluminum). The lead wire 43 is derived so as to output the resistance value of the sensor portion 42 to a controller as an electric signal. A connector 44 is connected to the other end of the lead wire 43 for connection with the electric circuit.

As shown in FIG. 6, the air temperature sensor 40B is constructed of a sensor portion 42, lead wire 43, and a connector 44. The sensor portion 42 includes a temperature sensing semiconductor 42a connected to the tip end of the lead wire 43 and the epoxy resin 42b or the like fixed to the periphery of the semiconductor 42a. The air temperature sensor 40B has a support part near the sensor portion 42 supported by the resin clamp 41. Either sensor 40 (40A, 40B) is integrally fixed to the heat exchange core portion of the integrated unit 20 by inserting the anchor portion 41a of the clamp 41 into the fin portion at the appropriate part of the integrated unit 20. In the fin temperature sensor 40A of FIG. 5A, the sensor portion 42 protrudes in the same direction as the anchor portion 41a for the attachment. That is, the sensor portion 42 is held by the resin clamp 41 approximately in parallel with the protruding direction of the anchor portion 41a. In contrast, in the air temperature sensor 40B of FIG. 6, the sensor portion 42 protrudes in an extending line of the lead wire 43 to be approximately perpendicular to the protruding direction of the anchor portion 41a for the attachment.

FIG. 7 is a diagram showing temperature distribution of the second evaporator 18 when being viewed from the downstream side of the air flow (inlet air temperature: 10 degrees, relative humidity: 80% RH). FIG. 7 shows that unevenness of the temperature distribution occurs at a part in which the refrigerant stream flows from the lower tank portion 18c. In particular, the refrigerant is suspended (stopped) in the lower tank portion 18c (on the left side of the embodiment), which has the lowest temperature (e.g., temperature T equal to or lower than 2.5° C.) in the second evaporator 18 on the lower temperature side, as shown in FIG. 7.

This tendency is common to a modified example to be described later in which a refrigerant flow path pattern is changed in the integrated unit 20. In this embodiment, a part MC in which the refrigerant stream rises up and flows from the lower tank portion 18c of the second evaporator 18 (see FIGS. 2 and 7) is used as an appropriate attachment position in which the above-mentioned temperature sensor 40 (40A or 40B) is set.

The part MC is a part in which the refrigerant flows from the lower side of the heat exchange core portion of the evaporator 18 to the upper side thereof. When a plurality of parts MC, in which the refrigerant flows from the lower side to the upper side thereof, are provided in the evaporator serving as a heat exchanging portion disposed on the suction side of the ejector 14, the temperature sensor 40 can be provided in a position where the frost is observed at the most early stage. For example, the temperature sensor 40 can be positioned nearest to the ejector 14 in the plurality of MC parts.

Reference will now be made to an operation of the refrigerant cycle device of the embodiment. When the compressor 11 is driven by the engine for vehicle running, the high-temperature and high-pressure refrigerant compressed and discharged by the compressor 11 flows into the radiator 12. The high-temperature refrigerant is cooled and condensed by the outside air in the radiator 12. The high-pressure refrigerant flowing from the radiator 12 flows into the liquid receiver 12a, in which the refrigerant is separated into liquid and vapor phases. The liquid refrigerant is fed from the liquid receiver 12a to pass through the expansion valve 13.

The expansion valve 13 has a valve opening degree (refrigerant flow amount) adjusted such that a degree of superheat SH of the refrigerant at the outlet of the first evaporator 15 (refrigerant drawn into the compressor) is a predetermined value to decompress the high-pressure refrigerant. The refrigerant having passed through the expansion valve 13 (intermediate pressure refrigerant) flows into the refrigerant inlet 25 provided in the first connection block 23 of the integrated unit 20.

The refrigerant stream from the refrigerant inlet 25 is divided into a refrigerant flow directed from the main passage 25a of the first connection block 23 to the ejector 14, and a refrigerant flow directed from the refrigerant branch passage 16 of the first connection block 23 to the throttle unit 17. The refrigerant entering the nozzle portion 14a of the ejector 14 is decompressed and expanded by the nozzle portion 14a. Thus, the pressure energy of the refrigerant is converted to the velocity energy thereof at the nozzle portion 14a. The refrigerant from an ejection port of the nozzle portion 14a is ejected at high velocity.

The decrease in refrigerant pressure around the ejection port sucks the refrigerant (vapor-phase refrigerant) having passed through the second evaporator 18 of the branch refrigerant passage 16 from the refrigerant suction port 14b. The refrigerant ejected from the nozzle portion 14a and the refrigerant drawn into the refrigerant suction port 14b are mixed by the mixing portion 14c positioned on the downstream side of the nozzle portion 14a to flow into the diffuser portion 14d. The velocity (expansion) energy of the refrigerant is converted to the pressure energy thereof by enlarging the passage area in the diffuser portion 14d, resulting in an increased pressure of the refrigerant.

The refrigerant flowing out of the diffuser portion 14d of the ejector 14 flows through refrigerant flow paths of the first evaporator 15 as indicated by the arrows “aa” to “ee” of FIG. 2. During this time, the low-temperature and low-pressure refrigerant absorbs heat from the blown air to be evaporated in the heat-exchange core portion 15a of the first evaporator 15. The evaporated vapor-phase refrigerant from the refrigerant outlet 26 is drawn into the compressor 11, and compressed again.

In contrast, the refrigerant flow entering the refrigerant branch passage 16 is decompressed by the throttle unit 17 to be low-pressure refrigerant, which flows through the refrigerant flow paths of the second evaporator 18 as indicated by the arrows “ff” to “ii” of FIG. 2. During this time, in the heat-exchange core portion 18a of the second evaporator 18, the low-temperature and low-pressure refrigerant absorbs heat from the blown air having passed through the first evaporator 15 so as to be evaporated. The vapor-phase refrigerant after evaporation is drawn from the refrigerant suction port 14b into the ejector 14.

As mentioned above, according to this embodiment, the refrigerant on the downstream side of the diffuser portion 14d of the ejector 14 can be supplied to the first evaporator 15, while the refrigerant on the refrigerant branch passage 16 side can be supplied to the second evaporator 18 through the throttle unit 17a, so that both the first and second evaporators 15 and 18 can exhibit the cooling effect at the same time. Thus, the cold air cooled by both the first and second evaporators 15 and 18 is blown off into a space to be cooled, thereby refrigerating (cooling) the space.

At this time, the refrigerant evaporation pressure of the first evaporator 15 is a pressure of the refrigerant whose pressure is increased by the diffuser portion 14d. In contrast, because the refrigerant outlet side of the second evaporator 18 is connected to the refrigerant suction port 14b of the ejector 14, the lowest pressure directly after the decompression by the nozzle portion 14a can be applied to the second evaporator 18.

Thus, the refrigerant evaporation pressure (refrigeration evaporation temperature) of the second evaporator 18 can be made lower than that of the first evaporator 15. The first evaporator 15 whose refrigerant evaporation temperature is higher is disposed on the upstream side with respect to the flow direction of the blown air, while the second evaporator 18 whose refrigerant evaporation temperature is lower is disposed on the downstream side in air flow. In this case, both a difference between the refrigerant evaporation temperature of the first evaporator 15 and the temperature of air flowing into the first evaporator 15, and also a difference between the refrigerant evaporation temperature of the second evaporator 18 and the temperature of air flowing into the second evaporator 18 can be ensured.

Thus, both the first and second evaporators 15 and 18 can effectively exhibit cooling capacities. Therefore, the cooling capacity for the common space to be cooled can be improved effectively by the combination of the first and second evaporators 15 and 18. The suction pressure of the compressor 11 can be increased by a pressure increasing effect of the diffuser portion 14d thereby decreasing a driving power of the compressor 11.

The refrigerant flow amount of the second evaporator 18 can be adjusted independently by the throttle unit 17 without depending on the function of the ejector 14, so that the refrigerant flow amount flowing into the first evaporator 15 can be adjusted by a throttle function of the ejector 14. This can facilitate adjustment of the refrigerant flow amounts flowing into the first and second evaporators 15 and 18 according to respective thermal loads.

Under the condition of a small cycle thermal load, a difference in pressure of the refrigerant cycle is decreased, so that the refrigerant flow amount of the ejector 14 becomes small. In this embodiment, the refrigerant having passed through the expansion valve 13 is branched at the upstream part of the nozzle portion 14a of the ejector 14, and the branched refrigerant is drawn into the refrigerant suction port 14b through the refrigerant branch passage 16. The refrigerant branch passage 16 is in parallel connection with the nozzle portion 14a of the ejector 14.

Thus, the refrigerant can be supplied to the refrigerant branch passage 16 using not only the refrigerant suction capacity of the ejector 14, but also the refrigerant suction and discharge capacities of the compressor 11. This can reduce the degree of decrease in refrigerant flow amount on the second evaporator 18 side even when the refrigerant flow amount flowing into the nozzle portion 14a of the ejector 14 decreases. Thus, even under the condition of the low thermal load, the cooling capacity of the second evaporator 18 can be ensured easily.

Reference will now be made to the control of prevention of frost (frosting) by the above-mentioned structure. When the refrigeration capacity of the refrigerant cycle device exceeds the cooling load, the refrigeration evaporation pressure in the evaporator decreases, so that the evaporator air-side surface temperature is below the freezing point (0° C.). The freezing of condensed water on the evaporator proceeds to interfere with the flow of passing air in the evaporator, further leading to a decrease in evaporation pressure of the refrigerant. To prevent such problems, the refrigeration capacity of the refrigerant cycle device is controlled to prevent the frost on the evaporator.

In this embodiment, ON-OFF control of a compressor 11 may be performed as this control method. The ON-OFF control involves turning off the compressor 11 when a refrigerant evaporation temperature becomes below the freezing point. This control is the most common method for frost prevention. Specifically, a fin temperature or a blown-air temperature of the integrated unit 20 is detected by the above-mentioned temperature sensor 40 (40A, 40B). Then, electric current supplied to the electromagnetic clutch 11a is turned off by the clutch 11a when the detected fin temperature or blown-air temperature is lowered to 3° C., for example. In contrast, the clutch 11a is turned on again when the detected fin temperature or blown-air temperature is increased to 4° C., for example. In the use of a variable displacement compressor or an electric compressor as the compressor, the compressor capacity control for controlling a discharge capacity of the compressor can be performed so as to reduce the frost.

In the embodiment of the present invention, the expansion valve 13 is provided for adjusting the flow amount of refrigerant on the downstream side of the radiator 12 such that a degree of superheat SH is a predetermined value (predetermined range). The superheat degree SH is represented by a difference between the superheat temperature and the saturation temperature of the refrigerant at the outlet of the first evaporator 15. This adjusts the refrigerant flow amount into the second evaporator 18 on the low-temperature side to an appropriate value. As a result, frost on the second evaporator 18 can be detected and determined by the temperature sensor 40 so as to perform the frost prevention control. This can reduce the frost in the second evaporator 18 and/or prevent the frost from being formed on the first and second evaporators 15 and 18 due to the excessive supply of the refrigerant, thereby improving the operating ratio of the refrigerant cycle.

FIG. 8 is a graph showing a relationship of a refrigeration operating efficiency with respect to a flow amount of refrigerant passing through the second evaporator 18. Here, the refrigeration operating efficiency is represented by a relationship of a stopped time period of the refrigerant cycle due to the detection of the temperature sensor 40, with respect to a cycle operating time on the same air condition. In FIG. 8, the refrigerant flow ratio is a ratio of the refrigerant amount flowing into the second evaporator 18 to the total refrigerant amount in the refrigerant cycle. Note that the operating efficiency of the conventional cycle is set to 100 in FIG. 8.

Generally, the decrease in total refrigerant flow amount in the evaporator 18 improves resistance to frost, but inevitably leads to a decrease in cooling performance. In the embodiment, the cooling operation property can be improved effectively over the entire range of flow amounts of the refrigerant passing through the second evaporator 18. The smaller the cooling load (that is, the lower the air temperature and humidity), or/and the smaller the thermal capacity of air to be heat exchanged, the smaller the necessary refrigerant amount. This causes excessive refrigerant on the side of the second evaporator18, so that the great cooling effect can be obtained in a cooling load range of 5 to 50° C. of air temperature and in a range of 20 to about 100% of relative humidity.

In this embodiment, the temperature sensor 40 is disposed at the part MC where the refrigerant flows upwardly from the lower tank portion 18c of the second evaporator 18. This is based on findings that the lowest temperature area is the part MC in which the refrigerant flows upwardly from the lower tank portion 18c in the second evaporator 18. Accordingly, determination of an attachment position of the temperature sensor 40 can be easily performed during the control of frost prevention. As shown in FIG. 7, the part MC is a lower area of the core portion of the second evaporator 18, close to the lower tank portion 18c.

The first evaporator 15 and the second evaporator 18 are adapted to cool the air, which serves as a common heat-exchange medium. The first evaporator 15 and the second evaporator 18 are disposed so as to exchange heat between the refrigerant of the second evaporator 18 and the air after being heat-exchanged with the refrigerant of the first evaporator 15. Because the temperature of the second evaporator 18 generally becomes lower, the air flowing from the first evaporator 15 can be effectively cooled.

The ejector-type refrigerant cycle device includes the ejector 14 for sucking the refrigerant from the refrigerant suction port 14b by the high-velocity refrigerant stream ejecting from the nozzle portion 14a, which is adapted to decompress and expand the refrigerant. The refrigerant cycle device also includes the second evaporator 18 (heat exchanging portion) for evaporating the refrigerant to be drawn into the refrigerant suction port 14b. The refrigerant cycle device further includes the temperature sensor 40 disposed at the part MC of the second evaporator 18, in which the refrigerant flows from the lower side to the upper side to detect the frost of the second evaporator 18.

Thus, the integrated construction of the ejector 14, the second evaporator 18 and the temperature sensor 40 can be handled as an integrated unit, thereby improving the handling properties in delivery and assembly. The reason why the temperature sensor 40 is provided at the part of the second evaporator 18, at which the refrigerant rises up and flows from the lower side to the upper side is the following. The lowest temperature area of the second evaporator 18 is found to be the part MC where the refrigerant flow rises up and flows from the lower tank portion 18c, as described above. Thus, in the ejector-type refrigerant cycle device, the temperature sensor 40 can be attached to an optimal position of the second evaporator 18, for control of the frost prevention.

The ejector-type refrigerant cycle device includes the first evaporator 15 disposed on the upstream side of the air flow, the second evaporator 18 disposed on the downstream side of the air flow with respect to the first evaporator 15, and the temperature sensor 40 for determining the frost. The first evaporator 15 allows the outflow refrigerant from the ejector 14 to evaporate, and the second evaporator 18 allows the refrigerant on the suction port side to be drawn into the refrigerant suction port 14b of the ejector 14 to evaporate. The temperature sensor 40 is disposed in the second evaporator 18.

Thus, the first and second evaporators 15 and 18, and the temperature sensor 40 can be integrally formed to be handled as an integrated unit, thereby improving the handling properties in delivery and assembly. The reason why the temperature sensor 40 is disposed in the second evaporator 18 is that the temperature of the second evaporator 18 is lower than the temperature of the first evaporator 15.

Furthermore, the temperature sensor 40 is disposed at the part MC in which the refrigerant flow rises up and the refrigerant flows from the lower tank portion 18c of the second evaporator 18. This is because the lowest temperature area is positioned at the part MC of the second evaporator 18 on the lower side in which the refrigerant flows upwardly from the lower tank portion 18c. Accordingly, the temperature sensor 40 can be attached to an optimal position, such that the control of frost prevent for the second evaporator 18 can be suitably performed.

In the above-described embodiment, the ejector 14 disposed on the upstream side of the refrigerant flow of the first evaporator 15, and the throttle unit 17 disposed on the upstream side of the refrigerant flow of the second evaporator 18 are integrally mounted on the first evaporator 15 and the second evaporator 18. However, any one of the ejector 14 and the throttle unit 17 may be integrally mounted on the first and second heat exchangers 15 and 18, which are relatively large, so as to construct the integrated unit 20.

Thus, a mounting operation for mounting the ejector-type refrigerant cycle device on an attachment object such as a vehicle, can be performed very efficiently. In this way, because the integrated unit 20 is used, the length of each connection passage can be reduced in the integrated unit 20 of the refrigerant cycle device, thereby reducing the cost and space for mounting.

The term “integrated” as used herein may include an integrated structure in which a part of a casing of the ejector 14 or the throttle unit 17 is shared with members, including the tank portions 15b, 15c, 18b, 18c of the first and second evaporators 15 and 18. Alternatively, it may include integration of a relationship of connection, for example, strong connection using welding or the like, or weak connection using a clamp or a screw. The refrigerant flow path constructed by such integration can be embodied in various embodiments to be described in the following modified examples, and cannot be limited to this embodiment and the modified examples as described later.

(Modifications)

In the following first to fourth modified examples, as shown in FIG. 9, the ejector 14, the first and second evaporators 15 and 18, and the temperature sensor 40 are integrally constructed as one integrated unit 20.

In the example of FIG. 9, the throttle unit 17 is not integrally constructed in the integrated unit 20. However, the throttle unit 17 may be integrally constructed in the integrated unit 20, like the above-described embodiment.

(First Modification)

FIG. 10 shows an integrated unit 20B (20) of the first modification.

As shown in FIG. 10, a separator 15e is disposed in the upper tank portion 15b of the first evaporator 15 to partition the inner space of the upper tank portion 15b into a left inner space C′ and a right inner space D′ such that the left space C′ occupies about one third of the inside of the upper tank portion 15b and the right space D′ occupies about two thirds thereof. A separator 15f is disposed in the lower tank portion 15c of the first evaporator 15 to partition the inner space of the lower tank portion 15c into a left inner space E′ and a right inner space F′ such that the left space E′ occupies about two thirds of the inside of the lower tank portion 15c and the right space F′ occupies about one third thereof.

Separators 18e and 18f are disposed in the upper tank portion 18b of the second evaporator 18 to partition the inside of the upper tank portion 18b into about three inner spaces G′, H′, and I′. A separator 18g is disposed in the lower tank portion 18c of the second evaporator 18 to partition the inner space of the lower tank portion 18c into a left inner space J′ and a right inner space K′ such that the left space J′ occupies about two thirds of the inside of the lower tank portion 18c and the right space K′ occupies about one third thereof. In this example of FIG. 10, the second evaporator 10 is separated into a suction-side refrigerant evaporation portion 18a and an outflow refrigerant evaporation portion 18a′ by the separators 18e and 18f.

In this example of FIG. 10, the inner space G′ of the upper tank portion 18b of the second evaporator 18 is connected to the downstream side of the refrigerant branch passage 16. The inner space F′ of the lower tank portion 15c of the first evaporator 15 and the inner space K′ of the lower tank portion 18c of the second evaporator 18 allow the refrigerant to pass therethrough via a connection hole (not shown) therebetween.

The ejector 14 is disposed inside the upper tank portion 18b of the second evaporator 18 such that the longitudinal direction of the ejector 14 is parallel to that of the upper tank portion 18b. The nozzle portion 14a of the ejector 14 is connected to the downstream side of the main passage 25a as mentioned above. The refrigerant suction port 14b is disposed in the inner space H′ of the upper tank portion 18b disposed in the second evaporator 18. The outlet of the diffuser portion 14d is attached to be positioned in the inner space I′ of the upper tank portion 18b.

Therefore, the refrigerant suction port 14b is directly opened in the inner space H′ of the upper tank portion 18b, and the outflow refrigerant flowing from the diffuser portion 14d flows directly into the inner space I′ of the upper tank portion 18b. As shown in FIG. 10, the ejector 14, the first evaporator 15, the second evaporator 18, and the respective tank portions 15b to 18c are completely integrated as one integrate unit 20B, such that the first evaporator 15 is disposed on the upstream side of the air flow and the second evaporator 18 is disposed on the downstream side of the air flow.

The ejector 14 is inserted to penetrate through holes (not shown) provided in the separators 18e, 18f from the end in the longitudinal direction of the upper tank portion 18b of the second evaporator 18 and is attached and fixed by fixing means, such as screwing, after a brazing step of integrally brazing the first evaporator 15 and the second evaporator 18.

The ejector 14 and the separators 18e, 18f are air-tightly fixed via O-rings (not shown) so as to prevent the refrigerant from leaking from attachment portions between the ejector 14 and the separators 18e, 18f (through holes). Therefore, the inner spaces G′ and H′ of the upper tank portion 18b, and the inner spaces H′ and I′ of the upper tank portion 18b are not in communication with each other via the above-mentioned attachment portions (through holes).

The refrigerant flow path of the entire integrated unit 20B with the above-mentioned structure will be described below. First, the refrigerant on the downstream side of the main passage 25a flows directly into the nozzle portion 14a of the ejector 14 in the direction of arrow “aa”. Then, the refrigerant passes through the ejector 14 (the nozzle portion 14a, the mixing portion 14c, and the diffuser portion 14d, in this order) to be decompressed. The low-pressure refrigerant decompressed by the ejector 14 is collected in the inner space I′ of the upper tank portion 18b of the second evaporator 18.

The refrigerant in the inner space I′ of the upper tank portion 18b is distributed into the plurality of tubes 21 on the right side of the second evaporator 18 in FIG. 10 to flow downwardly as indicated by the arrow “bb”, and then to be collected in the inner space K′ of the lower tank portion 18c of the second evaporator 18. The inner space K′ is in communication with the inner space F′ of the lower tank portion 15c of the first evaporator 15, thus allowing the refrigerant to flow into the inner space F′.

The refrigerant in the inner space F′ is distributed into the plurality of tubes 21 on the right side of the first evaporator 15 to flow upwardly as indicated by the arrow “cc”, and then to flow into the inner space D′ of the upper tank portion 15b of the first evaporator 15. The refrigerant flowing into the inner space D′ moves leftward in the inner space D′. The refrigerant moving leftward in the inner space D′ is distributed into the plurality of tubes 21 at the center area of the first evaporator 15 to flow downwardly as indicated by the arrow “dd”, and then to flow into the inner space E′ of the lower tank portion 15c.

The refrigerant flowing into the inner space E′ moves leftward in the inner space E′. The refrigerant moving leftward in the inner space E′ is distributed into the plurality of tubes 21 on the left side of the first evaporator 15 to flow upwardly as indicated by the arrow “ee”, and then to be collected in the inner space C′ of the upper tank portion 15b. The refrigerant collected in the inner space C′ of the upper tank portion 15b flows from the upper tank portion 15b as indicated by the arrow “ff” to the suction side of the compressor 11. Thus, the outflow refrigerant having passed though the outflow refrigerant evaporation portion 18a′ of the second evaporator 18 changes a flow direction twice (more than one time) in the first evaporator 15 while passing through the first evaporator 15 to be brought into a vapor phase having an appropriate degree of superheat at a superheat area that is positioned on the left upper part of the first evaporator 15 in FIG. 10.

The low-pressure refrigerant on the downstream side of the refrigerant branch passage 16 and decompressed by the throttle unit 17 flows into the inner space G′ of the upper tank portion 18b of the second evaporator 18. The refrigerant in the inner space G′ of the upper tank portion 18b is distributed into the plurality of tubes 21 on the left side of the second evaporator 18 to flow downwardly in the direction of arrow “gg”, and then to flow into the inner space J′ of the lower tank portion 18c of the second evaporator 18.

The refrigerant flowing into the inner space J′ moves rightward in the inner space J′ of the lower tank portion 18c. The refrigerant moving rightward in the inner space J′ is distributed into the plurality of tubes 21 at the center area of the second evaporator 18 to flow upwardly as indicated by the arrow “hh”, and then to be collected in the inner space H′ of the upper tank portion 18b. The refrigerant collected in the inner space H′ of the upper tank portion 18b is drawn into the ejector 14 from the refrigerant suction port 14b of the ejector 14.

Thus, the refrigerant passing through the suction-side refrigerant evaporation portion 18a of the second evaporator 18 changes a flow direction once in the second evaporator 18 to be brought into a vapor phase having an appropriate degree of superheat at a superheat area positioned on the left upper part of the first evaporator 15. The refrigerant flowing into the suction-side refrigerant evaporation portion 18a exchanges heat only at the area indicated by the arrows gg to hh of FIG. 10, among the second evaporator 18.

The ratio of use of the second evaporator 18 on the downstream air side, which occupies the suction-side refrigerant evaporation portion 18a, is about two thirds (about 70%) of the second evaporator 18 by arrangement and positioning of the separators 18f and 18g. In this way, the arrangement ratio between the suction-side refrigerant evaporation portion 18a and the outflow refrigerant evaporation portion 18a′ in the second evaporator 18 on downwind side can be adjusted easily by arrangement and positioning of the separators 18f and 18g. The temperature sensor 40 is disposed at the part MC (on the lower side of the flow part indicated by the arrow “hh” in this modified example) in which the refrigerant flows upwardly from the lower tank portion 18c of the second evaporator 18, at a position close to the lower tank portion 18c, like the above-mentioned embodiment. Furthermore, similarly to the above-described embodiment, the frost prevention control of the second evaporator 18 is performed by the controller 50 based on the signal detected by the temperature sensor 40 (40A, 40B).

(Second Modification)

In the above-mentioned first modified example, the ejector-type refrigerant cycle device 10 using the integrated unit 20B has been explained. However, in the second modified example, an integrated unit 20C (20) shown in FIG. 11 is used for the ejector-type refrigerant cycle device 10. FIG. 11 is a perspective view showing an outline of the entire structure of the integrated unit 20C, in which the basic structures of the first evaporator 15 and the second evaporator 18 are similar to those of the first modified example.

The integrated unit 20C of FIG. 11 differs from the integrated unit 20B of the first modified example in arrangement and positioning of the separators disposed in the tank portions 15b to 18c, as well as in arrangement and positioning of the ejector 14, and thus in the refrigerant flow path. Ah shown in FIG. 11, a separator 15e′ is disposed in the upper tank portion 15b of the first evaporator 15 to partition the inner space of the upper tank portion 15b into a left inner space L′ and a right inner space M′ such that the left space L′ occupies about one half of the inside of the upper tank portion 15b and the right space M′ occupies about one half thereof. No separator is disposed in the lower tank portion 15c of the first evaporator 15, in which one inner space N′ is formed.

A separator 18e′ is disposed in the upper tank portion 18b of the second evaporator 18 to partition the inner space of the upper tank portion 18b into a left inner space O′ and a right inner space P′ such that the left space O′ occupies about one half of the inside of the upper tank portion 18b and the right space P′ occupies about one half thereof. No separator is disposed in the lower tank portion 18c of the second evaporator 18 to construct one inner space Q′. In this modified example, the inner space O′ of the upper tank portion 18b of the second evaporator 18 is connected to the downstream side of the refrigerant branch passage 16.

In addition, the ejector 14 is disposed inside the upper tank portion 18b of the second evaporator 18, the nozzle portion 14a of the ejector 14 is connected to the downstream side of the main passage 25a, and the refrigerant suction port 14b is attached to be positioned in the inner space P′ of the upper tank portion 18b. Therefore, the refrigerant suction port 14b is directly opened in the inner space P′ of the upper tank portion 18b.

Furthermore, the outflow refrigerant flowing from the diffuser portion 14d of the ejector 14 is allowed to flow into the inner space M′ of the upper tank portion 15b of the first evaporator 15 via piping (not shown) disposed outside the upper tank portion 18b. It is apparent that a passage for guiding the outflow refrigerant into the inner space M′ may be constructed in the upper tank portion 18b. Also in the integrated unit 20C, the ejector 14 is assembled to the inside of the upper tank portion 18b of the second evaporator 18, like the first modified example, after integrally connecting the first and second evaporators 15, 18 and the tank portions 15b, 18c by brazing.

The refrigerant flow path of the entire integrated unit 20C with the above-mentioned structure will be described below. First, the refrigerant on the downstream side of the main passage 25a flows directly into the nozzle portion 14a of the ejector 14 as indicated by the arrow “aa” in FIG. 11. Then, the refrigerant passes through the ejector 14 to be decompressed. The low-pressure refrigerant decompressed by the ejector 14 flows into the inner space M′ of the upper tank portion 15b of the first evaporator 15 via external piping of the upper tank portion 18b.

The refrigerant flowing into the inner space M′ is distributed into the plurality of tubes 21 on the right side of the first evaporator 15 to flow downwardly as indicated by the arrow “ii”, and then to flow into the inner space N′ of the lower tank portion 15c of the first evaporator 15. The refrigerant flowing into the inner space N′ moves leftward in the inner space N′ of the lower tank portion 15c. The refrigerant moving leftward in the inner space N′ is distributed into the plurality of tubes 21 on the left side of the first evaporator 15 to flow upwardly as indicated by the arrow “jj”, and then to be collected in the inner space L′ of the upper tank portion 15b.

The refrigerant collected in the inner space L′ of the upper tank portion 15b flows from the upper tank portion 15b to the suction side of the compressor 11 as indicated by the arrow “ff”. Thus, the outflow refrigerant flowing out of the diffuser portion 14d to pass through the first evaporator 15 changes a flow direction once in the first evaporator 15 to be brought into a vapor phase having an appropriate degree of superheat at a superheat area positioned on the left upper part of the first evaporator 15.

The low-pressure refrigerant on the downstream side of the refrigerant branch passage 16 and decompressed by the throttle unit 17 flows into the inner space O′ of the upper tank portion 18b of the second evaporator 18. The refrigerant flowing into the inner space O′ is distributed into the plurality of tubes 21 on the left side of the second evaporator 18 to flow downwardly as indicated by the arrow “kk”, and then to flow into the inner space Q′ of the lower tank portion 18c of the second evaporator 18. The refrigerant flowing into the inner space Q′ moves rightward in the inner space Q′ in FIG. 11.

The refrigerant moving rightward in the inner space Q′ of the lower tank portion 18c of the second evaporator 18 is distributed into the plurality of tubes 21 on the right side of the second evaporator 18 to flow upwardly as indicated by the arrow “ll”, and then to be collected in the inner space P′ of the upper tank portion 18b. The refrigerant collected in the inner space P′ is drawn from the refrigerant suction port 14c of the ejector 14 into the ejector 14. Thus, the suction-port side refrigerant passing through the second evaporator 18 changes a flow direction once in the second evaporator 18 to be brought into a vapor phase having an appropriate degree of superheat at a superheat area positioned on the right upper part of the second evaporator 18.

Because the refrigerant passes through the integrated unit 20C as mentioned above, the second evaporator 18 constructs only the suction-side refrigerant evaporating portion 18a, and not the outflow refrigerant evaporating portion 18a′ of first modified example of FIG. 10. Other components have the same structures as those in the first modified example. The temperature sensor 40 (not shown) is disposed at the part MC in which the refrigerant flow flows upwardly from the lower tank portion 18c of the second evaporator 18 (on the lower side of the flow part as indicated by the arrow ll in this modified example), like the above-mentioned embodiments and modified examples. Furthermore, the part MC is located at a position close to the lower tank portion 18c. In addition, similarly to the above-described embodiment, the frost prevention control of the second evaporator 18 is performed by the controller 50 based on the signal detected by the temperature sensor 40 (40A, 40B).

(Third Modification)

In the above-mentioned examples, the ejector-type refrigerant cycle device 10 employing the integrated unit 20A, 20B, 20C has been explained. However, in the third modified example, an integrated unit 20D (20) shown in FIG. 12 is used for the ejector-type refrigerant cycle device 10. FIG. 12 is a perspective view showing an outline of the entire structure of the integrated unit 20D. Also in the integrated unit 20D, the ejector 14, the first and second evaporators 15 and 18, and the temperature sensor 40 are integrally constructed, like the integrated unit 20B, 20C.

The basic structures of the first and second evaporators 15 and 18 of the integrated unit 20D are the same as those of the first or second modified example. The integrated unit 20D differs from the integrated unit 20B, 20C in arrangement and positioning of the separators disposed in the tank portions 15b to 18c and in arrangement and positioning of the ejector 14. Thus, the third modified example differs from the first or second modified example in refrigerant flow path.

As shown in FIG. 12, no separator is disposed in the upper tank portion 15b of the first evaporator 15, so that one inner space R′ is formed in the upper tank portion 15b. A separator 15f is disposed in the lower tank portion 15c of the first evaporator 15 to partition the inner space of the lower tank portion 15c into a left inner space S′ and a right inner space T′ such that the left space S′ occupies about one half of the inside of the lower tank portion 15c and the right space T′ occupies about one half thereof.

A separator 18e′ is disposed in the upper tank portion 18b of the second evaporator 18 to partition the inner space of the upper tank portion 18b into a left inner space O′ and a right inner space P′ such that the left space O′ occupies about one half of the inside of the upper tank portion 18b and the right space P′ occupies about one half thereof. A separator 18f′ is disposed in the lower tank portion 18c of the second evaporator 18 to partition the inner space of the lower tank portion 18c into a left inner space U′ and a right inner space V′ such that the left space U′ occupies about one half of the inside of the lower tank portion 18c and the right space V′ occupies about one half thereof.

In this modified example, the inner space U′ of the lower tank portion 18c of the second evaporator 18 is connected to the downstream side of the refrigerant branch passage 16. The refrigerant can be circulated through the inner space T′ of the lower tank portion 15c of the first evaporator 15 and the inner space V′ of the lower tank portion 18c on the lower side of the second evaporator 18 via a communication hole (not shown) therebetween.

The ejector 14 is disposed in the upper tank portion 18b of the second evaporator 18. The nozzle portion 14a of the ejector 14 is connected to the downstream side of the main passage 25a. The refrigerant suction port 14b is positioned in the inner space O′ of the upper tank portion 18b. The outlet of the diffuser portion 14d is attached to be disposed in the inner space P′ of the upper tank portion 18b.

Thus, the refrigerant suction port 14b is directly opened in the inner space O′ of the upper tank portion 18b, and the outlet of the diffuser portion 14d is directly opened in the inner space P′ of the upper tank portion 18b. Also in the integrated unit 20D, the ejector 14 is assembled to the inside of the upper tank portion 18b of the second evaporator 18 after integrally connecting the first and second evaporators 15 and 18 and the tank portions 15b and 18c by brazing, like the above-mentioned embodiment.

Now, the refrigerant flow path of the entire integrated unit 20D with the above-mentioned structure will be described below. First, the refrigerant on the downstream side of the main passage 25a flows directly into the nozzle portion 14a of the ejector 14 as indicated by the arrow “aa” in FIG. 12. Then, the refrigerant passes through the ejector 14 to be decompressed. The low-pressure refrigerant decompressed by the ejector 14 flows into the inner space P′ of the upper tank portion 15b of the first evaporator 15.

The refrigerant flowing into the inner space P′ of the upper tank portion 18b is distributed into the plurality of tubes 21 on the right side of the second evaporator 18 to flow downwardly as indicated by the arrow “mm”, and then to be collected in the inner space V′ of the lower tank portion 18c of the second evaporator 18. Since the inner space V′ of the lower tank portion 18c communicates with the inner space T′ of the lower tank portion 15c of the first evaporator 15, the refrigerant flows into the inner space T′ of the lower tank portion 15c from the inner space V′ of the lower tank portion 18c.

The refrigerant flowing into the inner space T′ is distributed into the plurality of tubes 21 on the right side of the first evaporator 15 to flow upwardly as indicated by the arrow “nn”, and then to flow into the inner space R′ of the upper tank portion 15b. The refrigerant flowing into the inner space R′ moves leftward in the inner space R′ of the upper tank portion 15b. The refrigerant moving leftward in the inner space R′ is distributed into the plurality of tubes 21 on the left side of the first evaporator 15 to flow downwardly as indicated by the arrow “oo”, and then to flow into the inner space S′ of the lower tank portion 15c of the first evaporator 15.

The refrigerant flowing into the inner space S′ flows from the lower tank portion 15c to the suction side of the compressor 11 as indicated by the arrow “pp”. Thus, the outflow refrigerant flowing from the diffuser portion 14d to pass through the first evaporator 15 changes a flow direction once in the first evaporator 15 and in the second evaporator 18 to be brought into a vapor phase having an appropriate degree of superheat at a superheat area positioned on the left lower part of the first evaporator 15.

The low-pressure refrigerant on the downstream side of the refrigerant branch passage 16 and decompressed by the throttle unit 17 flows into the inner space U′ of the lower tank portion 18c of the second evaporator 18. The refrigerant flowing into the inner space U′ is distributed into the plurality of tubes 21 on the left side of the second evaporator 18 to flow upwardly as indicated by the arrow “qq”, and then to be collected into the inner space O′ of the upper tank portion 18b. The refrigerant collected in the inner space O′ of the upper tank portion 18b is drawn from the refrigerant suction port 14c of the ejector 14 to the inside of the ejector 14.

Thus, the refrigerant is brought into the vapor phase having the appropriate superheat degree at the superheat area on the upper left portion of the second evaporator 18. The suction-port side refrigerant to be drawn into the refrigerant suction port 14c of the ejector 14 exchanges heat in the second evaporator 18 only at the area indicated by the arrow “qq” of FIG. 12. Thus, in this modified example, the ratio of the suction-side refrigerant evaporation portion 18a is about one half (about 50%) of the second evaporator 18, and the ratio of the outflow refrigerant evaporation portion 18a′ is about one half (about 50%) of the second evaporator 18, by arrangement and positioning of the separators 18e′ and 18f.

The throttle unit 17 of this modified example is controlled such that a flow ratio Ge/G of a flow amount Ge of the suction-port side refrigerant to a flow amount G of the refrigerant discharged from the compressor 11 is about 0.5. Other components are the same as those of the first modified example. The temperature sensor 40 (not shown) is positioned at the part MC in which the refrigerant flows upwardly from the lower tank portion 18c of the second evaporator 18 (on the lower side of the flow part indicated by the arrow “qq” in this modified example), at a position close to the lower tank portion 18c, like the above-mentioned embodiment and modified examples.

(Fourth Modification)

In the above-mentioned first modified example, the ejector-type refrigerant cycle device 10 employing the integrated unit 20B has been explained. However, in the fourth modified example, an integrated unit 20E (20) shown in FIG. 13 is used for the ejector-type refrigerant cycle device 10. FIG. 13 is a perspective view showing an outline of the entire structure of the integrated unit 20E. Also in the integrated unit 20E, the ejector 14, the first and second evaporators 15 and 18, and the temperature sensor 40 are integrally constructed, like the integrated unit 20B.

The basic structures of the first and second evaporators 15 and 18 of the integrated unit 20E are the same as those of the integrated unit 20B of the first modified example. The integrated unit 20E differs from the integrated unit 20B in arrangement and positioning of the separators disposed in the tank portions 15b to 18c and in arrangement and positioning of the ejector 14. Thus, this modified example differs from the first modified example in refrigerant flow path.

A separator 15e″ is disposed in the upper tank portion 15b of the first evaporator 15 to partition the inner space of the upper tank portion 15b into a left inner space W′ and a right inner space X′ such that the left space W′ occupies about two thirds of the inside of the upper tank portion 15b and the right space X′ occupies about one third thereof. A separator 15f″ is disposed in the lower tank portion 15c of the first evaporator 15 to partition the inner space of the lower tank portion 15c into a left inner space Y′ and a right inner space Z′ such that the left space Y′ occupies about one third of the inside of the lower tank portion 15c and the right space Z′ occupies about two thirds thereof.

A separator 18e′ is disposed in the upper tank portion 18b of the second evaporator 18 to partition the inner space of the upper tank portion 18b into a left inner space O′ and a right inner space P′ such that the left space O′ occupies about one half of the inside of the upper tank portion 18b and the right space P′ occupies about one half thereof. No separator is disposed in the lower tank portion 18c of the second evaporator 18, in which one inner space Q′ is formed. Note that in this modified example, the inner space P′ of the upper tank portion 18b of the second evaporator 18 is connected to the downstream side of the refrigerant branch passage 16.

The ejector 14 is disposed inside the upper tank portion 18b of the second evaporator 18, like the first modified example. The nozzle portion 14a of the ejector 14 is connected to the downstream side of the main passage 25a, and the refrigerant suction port 14b is disposed in the inner space O′ of the upper tank portion 18b. The outlet of the diffuser portion 14d is attached to be positioned in an upper space part of the inner space P′ of the upper tank portion 18b. Thus, the refrigerant suction port 14b is directly opened in the inner space O′ of the upper tank portion 18b, and further the outlet of the diffuser portion 14d is directly opened in the inner space P′ of the upper tank portion 18b.

As mentioned above, the refrigerant on the downstream side of the refrigerant branch passage 16 and the refrigerant flowing from the diffuser portion 14d flow into the inner space P′. Thus, in this embodiment, the inner space P′ is divided into two independent spaces, that is, a space into which the refrigerant on the downstream side of the refrigerant branch passage 16 flows and a space into which the refrigerant flowing from the diffuser portion 14d flows.

Specifically, a partition plate not shown is provided for vertically dividing the inner space P′ into the two spaces. In this case, the refrigerant flowing from the diffuser portion 14d flows into the upper space, and the refrigerant on the downstream side of the refrigerant branch passage 16 flows into the lower space. Furthermore, the refrigerant can flow through this upper space and the inner space X′ of the upper tank portion 15b of the first evaporator 15 via a communication hole not shown.

A passage or the like may be provided inside the upper tank portion 18b to allow the refrigerant flowing from the diffuser portion 14d to flow directly into the inner space X′ and not into the inner space P′ without dividing the inner space P′ into the two independent spaces. Also in the integrated unit 20E, the ejector 14 is assembled to the inside of the upper tank portion 18b of the second evaporator 18 after integrally connecting the first and second evaporators 15, 18 and the tank portions 15b to 18c by brazing, like the first modified example.

Now, the refrigerant flow path of the entire integrated unit 20E with the above-mentioned structure will be described below. First, the refrigerant on the downstream side of the main passage 25a flows directly into the nozzle portion 14a of the ejector 14 as indicated by the arrow “aa”. Then, the refrigerant passes through the ejector 14 to be decompressed. The low-pressure refrigerant decompressed flows into the inner space X′ of the upper tank portion 15b of the first evaporator 15 via the upper space of the inner space P′ of the upper tank portion 18b of the second evaporator 18.

The refrigerant flowing into the inner space X′ is distributed into the plurality of tubes 21 on the right side of the first evaporator 15 to flow downwardly as indicated by the arrow “rr”, and then to flow into the inner space Z′ of the lower tank portion 15c of the first evaporator 15. The refrigerant flowing into the inner space Z′ moves leftward in the inner space Z′. The refrigerant moving leftward in the inner space Z′ is distributed into the plurality of tubes 21 at the center area of the first evaporator 15 to flow upwardly as indicated by the arrow “ss”, and then to flow into the inner space W′ of the upper tank portion 15b of the first evaporator 15.

The refrigerant flowing into the inner space W′ of the upper tank portion 15b moves leftward inside the inner space W′. The refrigerant moving leftward inside the inner space W′ is distributed into the plurality of tubes 21 on the left side of the first evaporator 15 to flow downwardly as indicated by the arrow tt, and then to be collected in the inner space Y′ of the lower tank portion 15c of the first evaporator 15. The refrigerant collected in the inner space Y′ flows from the lower tank portion 15c to the suction side of the compressor 11 as indicated by the arrow “pp”.

Thus, the outflow refrigerant flowing out of the diffuser portion 14d to pass thorough the first evaporator 15 changes a flow direction twice (more than one time) in the first evaporator 15 to be brought into a vapor phase having an appropriate degree of superheat at a superheat area positioned on the left lower part of the first evaporator 15. In contrast, the low-pressure refrigerant on the downstream side of the refrigerant branch passage 16 depressed by the throttle unit 17 flows into a lower space part of the inner space P′ of the upper tank portion 18b of the second evaporator 18.

The refrigerant flowing into the lower space part of the inner space P′ is distributed into the plurality of tubes 21 on the right side of the second evaporator 18 to flow downwardly as indicated by the arrow “uu”, and then to flow into the inner space Q′ of the lower tank portion 18c. The refrigerant flowing into the inner space Q′ moves leftward inside the inner space Q′. The refrigerant moving leftward in the inner space Q′ is distributed into the plurality of tubes 21 on the left side of the second evaporator 18 to flow upwardly as indicated by the arrow “vv” and then to be collected into the inner space O′. The refrigerant collected in the inner space O′ is drawn into the ejector 14 from the refrigerant suction port 14c of the ejector 14.

Thus, the refrigerant is brought into a vapor phase having an appropriate degree of superheat at a superheat area positioned on the left upper part of the second evaporator 18. The refrigerant passes through the integrated unit 20E as mentioned above, and thus the second evaporator 18 constructs only the suction-side refrigerant evaporation portion 18a and not the outflow refrigerant evaporating portion 18a′. Other components have the same structures as those in the first modified example. The temperature sensor 40 not shown is disposed at the part MC where the refrigerant flows upwardly from the lower tank portion 18c of the second evaporator 18 (on the lower side of the flow part as indicated by the arrow “vv” in this modified example), at a position close to the lower tank portion 18c, like the above-mentioned embodiment and modified examples.

(Other Modifications)

Although the present invention has been fully described in connection with the embodiment and the modified examples thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.

(1) In the above-mentioned embodiment, other components except for the ejector 14, that is, the first and second evaporators 15 and 18, the first and second connection blocks 23 and 24, and the throttle unit 17 are integrally brazed when these components of the integrated unit 20A are integrally assembled. However, these components can be integrally assembled by various fixing means other than brazing, including screwing, caulking, welding, adhesion and the like.

In the above-described embodiment, exemplary fixing means of the ejector 14 is the screwing, but any other fixing means that may not be thermally deformed can be used instead of the screwing. Specifically, fixing means, such as caulking or adhesion, may be used to fix the ejector 14.

(2) Although the above-mentioned embodiment has described a vapor-compression subcritical cycle using refrigerant whose high pressure does not exceed the critical pressure, such as a Freon-based or HC-based refrigerant, the present invention may be applied to a vapor-compression supercritical cycle using refrigerant whose high pressure exceeds the critical pressure, such as carbon dioxide (CO2). In this case, the compressor discharge refrigerant only radiates heat in the supercritical state using the radiator 12 in the supercritical cycle, the refrigerant is not condensed, and thus the liquid receiver 12a disposed on the high-pressure side cannot exhibit a vapor-liquid separation effect of the refrigerant and a storage effect of the excessive liquid refrigerant. The supercritical cycle may employ an accumulator (not shown) constructing a low-pressure side vapor-liquid separator disposed on the refrigerant outlet side of the first evaporator 15.

(3) In the above-mentioned embodiment, the throttle unit 17 may be constructed of a fixed throttle, such as a capillary tube or an orifice. However, the throttle unit 17 may be constructed of an electric control valve whose valve opening degree (opening degree of throttle passage) is adjustable by an electric actuator. Alternatively, the throttle unit 17 may be constructed of a combination of a fixed throttle, such as a capillary tube or a fixed throttle hole, and an electromagnetic valve.

(4) In the above-mentioned embodiment, the ejector 14 is a fixed ejector with a fixed nozzle portion 14a whose passage area is constant. However, the ejector 14 may be a variable ejector having a variable nozzle portion whose passage area is adjustable. Specifically, the variable nozzle portion may be constructed of a mechanism which is adapted to adjust a nozzle passage area by controlling the position of a needle inserted into a passage of the variable nozzle portion by an electric actuator.

(5) In the above-mentioned embodiment, a vehicle compartment space or a freezer and refrigerator space of a freezer car serves as a space to be cooled by the first and second evaporator 15 and 18. However, the present invention is not limited to such a vehicle space, and can be used for various refrigerant cycle devices, including stationary one.

(6) In the above-mentioned embodiment, the thermal expansion valve 13 and the temperature sensing portion 13a are independently provided from the integrated unit 20 of the ejector-type refrigerant cycle device, as shown in FIG. 1. However, the thermal expansion valve 13 and the temperature sensing portion 13a may be integrally assembled to the integrated unit 20 of the ejector-type refrigerant cycle device. For example, the thermal expansion valve 13 and the temperature sensing portion 13a can be accommodated in the first connection block 23 of the integrated unit 20. In this case, the refrigerant inlet 25 is located between the liquid receiver 12a and the thermal expansion valve 13, and the refrigerant outlet 26 is located between a passage part with the temperature sensing portion 13a set therein and the compressor 11.

(7) Furthermore, the temperature sensor 40 can be located to detect any one of its fin temperature and its tube temperature so as to detect the frost of the second evaporator 18, and can be located to detect an air temperature immediately after passing through the second evaporator 18 so as to detect the frost of the second evaporator 18. Even in this case, the controller 50 can perform the frost prevention control in accordance with the temperature detected by the temperature sensor 40.

Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims.