Title:
Hybrid compressor system
Kind Code:
A1


Abstract:
A hybrid compressor system in a vehicle air conditioner includes a variable displacement hybrid compressor, a detector for detecting information for air conditioning, a thermal load calculator and a controller. The compressor is selectively driven by an engine and an electric motor. The calculator calculates a thermal load based on the detected information. The controller compares the thermal load with a predetermined value. The controller changes displacement of the compressor to a first predetermined displacement value and selects the engine as a drive source of the compressor when the thermal load is larger than the predetermined value. The controller changes the displacement of the compressor to a second predetermined displacement value that is smaller than the first predetermined displacement value and selects the electric motor as the drive source of the compressor when the thermal load is equal to, or smaller than the predetermined value.



Inventors:
Iwata, Kitaru (Kariya-shi, JP)
Kawaguchi, Masahiro (Kariya-shi, JP)
Odachi, Yasuharu (Kariya-shi, JP)
Hayashi, Hirohito (Kariya-shi, JP)
Sonobe, Masanori (Kariya-shi, JP)
Iwasa, Jiro (Kariya-shi, JP)
Iguchi, Masao (Kariya-shi, JP)
Yamanouchi, Akihito (Kariya-shi, JP)
Application Number:
10/459862
Publication Date:
03/11/2004
Filing Date:
06/12/2003
Assignee:
IWATA KITARU
KAWAGUCHI MASAHIRO
ODACHI YASUHARU
HAYASHI HIROHITO
SONOBE MASANORI
IWASA JIRO
IGUCHI MASAO
YAMANOUCHI AKIHITO
Primary Class:
Other Classes:
62/236, 62/230
International Classes:
F04C23/00; B60H1/22; B60H1/32; F04B35/00; F04B35/01; F04B49/06; F04C18/02; F04C23/02; F04C29/00; (IPC1-7): F25B1/00; F25B27/00; F25B49/00
View Patent Images:
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Primary Examiner:
TAPOLCAI, WILLIAM E
Attorney, Agent or Firm:
BakerHostetler (Philadelphia, PA, US)
Claims:

What is claimed is:



1. A hybrid compressor system in use for a vehicle air conditioner comprising: a variable displacement hybrid compressor for compressing refrigerant; a drive source for driving a vehicle operatively connected to the compressor; an electric motor operatively connected to the compressor, the compressor being selectively driven by one of the drive source for driving the vehicle and the electric motor; an air conditioning information detector for detecting information for air conditioning; a thermal load calculator electrically connected to the air conditioning information detector, the thermal load calculator calculating a thermal load based on the detected information from the air conditioning information detector; and a controller electrically connected to the thermal load calculator, the controller comparing the thermal load with a predetermined value, the controller changing displacement of the compressor to a first predetermined displacement value and selecting the drive source for driving the vehicle as a drive source of the compressor when the thermal load is larger than the predetermined value, the controller changing the displacement of the compressor to a second predetermined displacement value and selecting the electric motor as the drive source of the compressor when the thermal load is equal to, or smaller than the predetermined value, the second predetermined displacement value being smaller than the first predetermined displacement value.

2. The hybrid compressor system according to claim 1, wherein the drive source for driving the vehicle is an engine.

3. The hybrid compressor system according to claim 2, wherein the controller changes the displacement of the compressor to the second predetermined displacement value and selects the electric motor as the drive source of the compressor when the thermal load is equal to, or smaller than the predetermined value and when the engine is in a stopped state, the controller selecting the engine as the drive source of the compressor when the thermal load is equal to, or smaller than the predetermined value and when the engine is in a running state.

4. The hybrid compressor system according to claim 3, further comprising a residual quantity detector for detecting a residual quantity of a battery for the electric motor, the residual quantity detector providing the detected residual quantity of the battery to the controller, the controller comparing the detected residual quantity of the battery with a predetermined quantity, wherein the controller changes the displacement of the compressor to the second predetermined displacement value and selects the electric motor as the drive source of the compressor when the thermal load is equal to, or smaller than the predetermined value, when the engine is in the running state, and when the detected residual quantity of the battery is equal to, or larger than the predetermined quantity, the controller selecting the engine as the drive source of the compressor when the thermal load is equal to, or smaller than the predetermined value, when the engine is in the running state, and when the detected residual quantity of the battery is smaller than the predetermined quantity.

5. The hybrid compressor system according to claim 3, wherein the controller changes the displacement of the compressor to the second predetermined displacement value and selects the engine as the drive source of the compressor when the thermal load is equal to, or smaller than the predetermined value and when the engine is in the running state.

6. The hybrid compressor system according to claim 2, wherein the compressor comprises: a housing; and one of a speed increasing mechanism provided in the housing for increasing a rotational speed obtained from the engine and a speed reducing mechanism provided in the housing for decreasing a rotational speed obtained from the electric motor.

7. The hybrid compressor system according to claim 6, wherein the electric motor is provided in the housing and includes a stator, one of the speed increasing mechanism and the speed reducing mechanism being arranged inside the stator.

8. The hybrid compressor system according to claim 2, wherein the first predetermined displacement value is a maximum value, the second predetermined displacement value being a minimum value, the displacement of the compressor being switched between the maximum value and the minimum value.

9. The hybrid compressor system according to claim 2, wherein the compressor is a scroll type.

10. The hybrid compressor system according to claim 2, wherein the electric motor is formed without a permanent magnet.

11. The hybrid compressor system according to claim 2, wherein the controller controls a rotational speed of the electric motor in accordance with the thermal load when the electric motor drives the hybrid compressor.

12. The hybrid compressor system according to claim 2, wherein the information includes a temperature in a vehicle compartment.

13. A control system for a variable displacement hybrid compressor in a vehicle air conditioner having two drive sources including an engine for driving a vehicle and an electric motor, the hybrid compressor being selectively driven by one of the engine and the electric motor, the control system comprising: an air conditioning information detector for detecting information for air conditioning; a thermal load calculator electrically connected to the air conditioning information detector, the thermal load calculator calculating a thermal load based on the detected information from the air conditioning information detector; and a controller electrically connected to the thermal load calculator, the controller comparing the thermal load with a predetermined value, the controller changing displacement of the compressor to a first predetermined displacement value and selecting the engine as a drive source of the compressor when the thermal load is larger than the predetermined value, the controller changing the displacement of the compressor to a second predetermined displacement value and selecting the electric motor as the drive source of the compressor when the thermal load is equal to, or smaller than the predetermined value, the second predetermined displacement value being smaller than the first predetermined displacement value.

14. A method for controlling a hybrid compressor system in use for a vehicle air conditioner, the hybrid compressor system having a variable displacement hybrid compressor and two drive sources including an engine for driving a vehicle and an electric motor, the hybrid compressor being selectively driven by one of the engine and the electric motor, the method comprising the steps of: (a) switching on the air conditioner; (b) detecting information for air conditioning; (c) calculating a thermal load based on the detected information; (d) comparing the thermal load with a predetermined value; (e) selecting the drive source of the compressor based on the comparison; and (f) changing displacement of the compressor based on the selection.

15. The method according to claim 14, wherein step (e) includes the steps of: (g) selecting the engine as a drive source of the compressor when the thermal load is larger than the predetermined value; and (h) selecting the electric motor as the drive source of the compressor when the thermal load is equal to, or smaller than the predetermined value.

16. The method according to claim 15, wherein step (f) includes the steps of: (i) changing the displacement of the compressor to a maximum value when the thermal load is larger than the predetermined value; and (j) changing the displacement of the compressor to a minimum value when the thermal load is equal to, or smaller than the predetermined value.

17. The method according to claim 15, further comprising the step of (k) judging whether the engine is in a running state after step (d) when the thermal load is equal to, or smaller than the predetermined value.

18. The method according to claim 17, wherein step (h) includes the steps of: (l) selecting the engine as the drive source of the compressor when the engine is in the running state; and (m) selecting the electric motor as the drive source of the compressor when the engine is in a stopped state.

19. The method according to claim 18, further comprising the steps of: (n) detecting residual quantity of a battery for the electric motor after step (k) when the engine is in the running state; and (o) comparing the detected residual quantity with a predetermined quantity.

20. The method according to claim 19, wherein step (I) includes the steps of: (p) selecting the electric motor as the drive source of the compressor when the residual quantity is equal to, or larger than the predetermined quantity; and (q) selecting the engine as the drive source of the compressor when the residual quantity is smaller than the predetermined quantity.

21. The method according to claim 15, further comprising the steps of: (r) judging whether the engine is in a running state after step (g); and (s) starting the engine when the engine is in a stopped state.

Description:

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a hybrid compressor system in use for a vehicle air conditioner.

[0002] In an idle stop control, an engine is automatically stopped when it is an idle state, that is, for example, when a vehicle stops running to wait for a traffic signal to change. For fuel saving, the idle stop control has been generalized recently. A hybrid compressor in a vehicle air conditioner utilizes not only an engine but also an electric motor as a drive source. Therefore, the air conditioner is capable of performing air conditioning even when the engine is in a stopped state. However, if the power of the electric motor for driving the compressor is requested to be substantially as large as that of the engine for driving the compressor, the electric motor becomes large-sized. Therefore, for example, when the electric motor is accommodated in a housing of the compressor, the compressor also becomes large-sized. Meanwhile, the displacement of the compressor per one rotation of a rotary shaft is set at a small value such that the compressor can be driven even by a small-sized electric motor. In this case, when the engine drives the compressor at a relatively low rotational speed, a large amount of discharged refrigerant by the compressor per a predetermined period cannot be ensured. Therefore, cooling performance is decreased.

[0003] In order to solve such a problem, a technique disclosed in Japanese Unexamined Patent Publication No. 11-93876 has been proposed. In the technique, a first drive part transmits power from an electric motor to a rotary shaft of a compressor for driving the rotary shaft of the compressor. A second drive part transmits power from the engine to the rotary shaft of the compressor for driving the rotary shaft of the compressor. A speed change mechanism that changes a rotational speed and transmits power to the rotary shaft is arranged at one of the first and second drive parts. Namely, for example, a speed reducing mechanism is arranged at the first drive part. Therefore, the compressor can be driven in a state that the displacement of the compressor per one rotation of the rotary shaft is set at a relatively large value and the rotational speed of the compressor is relatively low without a large-sized electric motor. Even when the engine drives the compressor at the relatively low rotational speed, the relatively large amount of the discharged refrigerant by the compressor per the predetermined period can be ensured. As a result, the cooling performance is ensured preferably.

[0004] Also, for example, a speed increasing mechanism is arranged at the second drive part. Therefore, the compressor can be driven in a state that the displacement of the compressor per one rotation of the rotary shaft is set at a relatively small value and a rotational speed of the compressor is relatively high. Driving torque for the compressor can become small. As a result, the electric motor can be miniaturized.

[0005] However, when the speed reducing mechanism is arranged at the first drive part, the speed reducing ratio of the speed reducing mechanism needs to be set at a relatively large value in order to drive the compressor with the relatively large displacement by the small-sized electric motor. When the speed increasing mechanism is arranged at the second drive part, the speed increasing ratio of the speed increasing mechanism needs to be set at a relatively large value, in order to ensure the relatively large amount of the discharged refrigerant per the predetermined period by driving the compressor with the relatively small displacement by the engine at the relatively low rotational speed.

[0006] When a transmission ratio (speed reducing ratio or speed increasing ratio) is set at a relatively large value, the speed change mechanism needs to be large-sized. Therefore, for example, when the speed change mechanism is accommodated in the housing, the compressor becomes large-sized. Namely, in the conventional technique, the miniaturization of the electric motor is difficult to be compatible with the miniaturization of the speed change mechanism.

[0007] In the hybrid compressor, when the relatively large amount of the discharged refrigerant by compressor per the predetermined period is required for cooling by driving the electric motor, the rotational speed of the electric motor requires to be high. Therefore, combined with the smallness of the electric motor, step out occurs in the electric motor, and the electric motor runs in an unstable manner.

[0008] The present invention provides a hybrid compressor system in which an electric motor is miniaturized and runs in a stable manner and in which a transmission mechanism that transmits power from an engine or the electric motor is miniaturized.

[0009] In accordance with the present invention, a hybrid compressor system in a vehicle air conditioner has a variable displacement hybrid compressor for compressing refrigerant, a drive source for driving a vehicle and an electric motor. The drive source for driving the vehicle is operatively connected to the compressor. The electric motor is operatively connected to the compressor, and the compressor is selectively driven by one of the drive source for driving the vehicle and the electric motor. The hybrid compressor system also has an air conditioning information detector for detecting information for air conditioning, a thermal load calculator and a controller. The air conditioning information detector is electrically connected to the air conditioning information detector and calculates a thermal load based on the detected information from the air conditioning information detector. The controller is electrically connected to the thermal load calculator. The controller compares the thermal load with a predetermined value. The controller changes displacement of the compressor to a first predetermined displacement value and selects the drive source for driving the vehicle as a drive source of the compressor when the thermal load is larger than the predetermined value. The controller changes the displacement of the compressor to a second predetermined displacement value and selects the electric motor as the drive source of the compressor when the thermal load is equal to, or smaller than the predetermined value. The second predetermined displacement value is smaller than the first predetermined displacement value.

[0010] The present invention also provides a method for controlling a hybrid compressor system in use for a vehicle air conditioner. The hybrid compressor system has a variable displacement hybrid compressor and two drive sources including an engine for driving a vehicle and an electric motor. The hybrid compressor is selectively driven by one of the engine and the electric motor. The method includes the steps of switching on the air conditioner, detecting information for air conditioning, calculating a thermal load based on the detected information, comparing the thermal load with a predetermined value, selecting the drive source of the compressor based on the comparison, and changing displacement of the compressor based on the selection.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

[0012] FIG. 1 is a longitudinal cross-sectional view of a hybrid compressor of a first preferred embodiment according to the present invention;

[0013] FIG. 2 is a flow chart illustrating air conditioning control by an air conditioner ECU for the first preferred embodiment; and

[0014] FIG. 3 is a longitudinal cross-sectional view of a hybrid compressor of a second preferred embodiment according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A first and second preferred embodiments according to the present invention will be described.

[0016] Now, the first preferred embodiment will be described. As shown in FIG. 1, a hybrid compressor C that constitutes a refrigerant cycle in a vehicle air conditioner has a housing 11 for compressing refrigerant. The left side and the right side of the drawing respectively correspond to the front side and the rear side in FIG. 1. An electric motor 21 and a compression unit 12 are accommodated in the housing 11. A power transmission mechanism 22 is arranged at the front end of the housing 11 outside the housing 11. The compression unit 12 is a scroll type and a variable displacement type. The power transmission mechanism 22 transmits power from an engine E (an internal combustion engine) as a drive source.

[0017] The compressor C is selectively driven by the engine E through the power transmission mechanism 22 and by the electric motor 21. The air conditioner includes the electric motor 21. When the engine E is in a stopped state, the compressor C is driven by the electric motor 21. Therefore, the air conditioner is capable of continuously performing air conditioning even when the engine E is in the stopped state. The air conditioner in the present first preferred embodiment is suitable for an idle stop vehicle that performs an idle stop control and a hybrid vehicle.

[0018] A pulley shaft 13 and a compressor shaft 19 are rotatably supported in the housing 11 at the front side of the housing 11 and at the middle of the housing 11 respectively. The pulley shaft 13 and the compressor shaft 19 are arranged such that the axis of the pulley shaft 13 corresponds to the axis of the compressor shaft 19. The compressor shaft 19 are inserted into the pulley shaft 13 through a bearing 56 at the position where the rear end of the pulley shaft 13 faces the front end of the compressor shaft 19, so as to rotate relative to the pulley shaft 13.

[0019] A speed increasing mechanism 23 that is constituted of a planetary gear mechanism is arranged between the pulley shaft 13 and the compressor shaft 19 in the housing 11. The speed increasing mechanism 23 increases the rotational speed of the pulley shaft 13 and transmits power to the compressor shaft 19. The speed increasing mechanism 23 has a known structure that includes a sun gear 45, an internal gear 46, a holder 47 and a plurality of planetary gears 48. The sun gear 45 is secured to the compressor shaft 19 so as to rotate integrally with the compressor shaft 19. The internal gear 46 is integrally formed with the housing 11. The holder 47 is secured to the pulley shaft 13 so as to rotate integrally with the pulley shaft 13. The planetary gear 48 is rotatably held by the holder 47 and is interposed between the sun gear 45 and the internal gear 46.

[0020] A rotor 14 and a stator constitute the electric motor 21. The rotor 14 is mounted on the compressor shaft 19 in the housing 11 so as to rotate integrally with the compressor shaft 19. The rotor 14 is constituted of an iron core and a conductor fixed to the iron core, which is not shown. A plurality of stator cores 16 is fixed to the inner circumference of the housing 11 so as to surround the rotor 14. A coil 15 is formed around each of the stator cores 16. The stator core 16 and the coil 15 constitute the stator Namely, the electric motor 21 is a reluctance motor without a permanent magnet. The coil 15 is arranged so as to surround the speed increasing mechanism 23 at its front side. Namely, the speed increasing mechanism 23 is arranged inside the stator.

[0021] The power transmission mechanism 22 includes a pulley 17 and an electromagnetic clutch (EC) 18. The pulley 17 is rotatably supported by the housing 11 and transmits power from the engine E to compressor shaft 19 through the pulley shaft 13. When the electromagnetic clutch 18 is switched on (energized), the electromagnetic clutch 18 permits power transmission from the pulley 17 to the pulley shaft 13. When the electromagnetic clutch 18 is switched off (de-energized), the electromagnetic clutch 18 blocks the power transmission.

[0022] The compression unit 12 includes a fixed scroll member 20, a crankshaft 19a and a movable scroll member 24. The crankshaft 19a is secured to the rear end of the compressor shaft 19. The movable scroll member 24 is supported by the crankshaft 19a. A plurality of compression chambers 26 is defined by the fixed scroll member 20 and the movable scroll member 24. A suction chamber 30 is defined in the housing 11 at the outer circumference of the movable scroll member 24, and a discharge chamber 28 is defined in the housing 11 at the rear side of the housing 11. The movable scroll member 24 orbits around an axis of the fixed scroll member 20 based on the rotation of the compressor shaft 19. As the compression chamber 26, which is defined between the fixed scroll member 20 and the movable scroll member 24, is radially and inwardly moved in accordance with the orbital movement of the movable scroll member 24, the volumes of the compression chamber 26 decreases. Therefore, the refrigerant gas in the compression chamber 26 is compressed to a predetermined pressure value. Then, the refrigerant gas in the compression chamber 26 near the center of the fixed scroll member 20 is discharged into the discharge chamber 28.

[0023] A movable valve body chamber 31 is formed in the fixed scroll member 20. Communication ports 32 and 36 are formed between the movable body chamber 31 and the compression chamber 26 in the fixed scroll member 20 so as to interconnect the compression chambers 26 with the movable valve body chamber 31. The communication ports 32 are arranged in the fixed scroll member 20 at a position where the volume of the compression chamber 26 is, for example, 50% with respect to its maximum volume. The communication ports 36 are arranged in the fixed scroll member 20 at a position where the volume of the compression chamber 26 is, for example, 20% with respect to its maximum volume. A communication hole 33 is formed in the fixed scroll member 20 so as to interconnect the suction chamber 30 with the movable valve body chamber 31 through an intermediate chamber 33a and a communication passage, which is not shown.

[0024] A movable valve body 34 is movably accommodated in the movable valve body chamber 31. The movable valve body 34 includes large diameter portions 34a, 34b and 34c and a small diameter portion 34d. The large diameter portions 34a through 34c are arranged in a longitudinal direction of the movable valve body 34 (a vertical direction in FIG. 1). The outer diameters of the large diameter portions 34a through 34c are substantially as equal as the diameter of the inner circumference of the movable valve body chamber 31. The small diameter portion 34d is arranged between the large diameter portions 34a and 34b and between the large diameter portions 34b and 34c so as to connect the large diameter portions 34a through 34c. A coil spring 35 is arranged between the upper surface of the movable valve body chamber 31 and the large diameter portion 34a arranged at the upper end of the movable valve body 34 to press the movable valve body 34 downward.

[0025] A pressure control chamber 31a is defined between the lower surface of the movable valve body chamber 31 and the lower end of the movable valve body 34 in the movable valve body chamber 31. The pressure control chamber 31a is interconnected with the discharge chamber 28 through a supply passage 37. High-pressure refrigerant having a pressure substantially equal to a discharge pressure is supplied from the discharge chamber 28 into the pressure control chamber 31a through the supply passage 37.

[0026] The pressure control chamber 31a is capable of being interconnected with the suction chamber 30 through a bleed passage 38. A control valve (CV) 39 constituted of an electromagnetic valve is arranged on the bleed passage 38. The control valve 39 is capable of interconnecting the pressure control chamber 31a with the suction chamber 30 through the bleed passage 38 and of blocking the interconnection. When the control valve 39 is switched on (energized), the control valve 39 blocks the interconnection between the pressure control chamber 31a and the suction chamber 30. When the control valve 39 is switched off (de-energized), the control valve 39 interconnects the pressure control chamber 31a with the suction chamber 30 through the bleed passage 38.

[0027] When the control valve 39 is energized, the high-pressure refrigerant in the pressure control chamber 31a does not flow out into the suction chamber 30 through the bleed passage 38. Therefore, the pressure in the pressure control chamber 31a keeps high. The movable valve body 34 is pushed upward against the urging force of the coil spring 35 by the high pressure in the pressure control chamber 31a (a state as shown in FIG. 1). In this state, the large diameter portions 34athrough 34care located at positions corresponding to the openings of the communication ports 32 and 36 at the rear side. Therefore, the interconnection is blocked between the compression chambers 26 and the suction chamber 30 through a path including one of the communication ports 32 and 36, the movable valve body chamber 31, the communication hole 33 and the intermediate chamber 33a. At the time, the compressed refrigerant gas in the compression chamber 26 does not flow out into the suction chamber 30 through the path. As a result, the amount of the discharged refrigerant by the compression unit 12 per one rotation of the compressor shaft 19, or, the displacement of the compressor C, becomes the maximum, or a first predetermined displacement value.

[0028] On the other hand, when the control valve 39 is de-energized, the pressure control chamber 31a is interconnected with the suction chamber 30 through the bleed passage 38. Therefore, the pressure in the pressure control chamber 31a becomes low. The urging force of the coil spring 35 presses the movable valve body 34 downward from the position of the movable valve body 34 shown in FIG. 1. In this state, the openings of the communication ports 32 and 36 except the communication port 32 at the lowest position are opened to the movable valve body chamber 31. The compression chambers 26 corresponding to the communication ports 32 and 36, whose openings are open to the movable valve body chamber 31, are interconnected with the suction chamber 30 through the path. The refrigerant gas in the corresponding compression chambers 26 leaks into the suction chamber 30 through the path. As a result, the displacement of the compressor C becomes the minimum, or a second predetermined displacement value. Namely, the displacement of the compressor C is switched between the maximum and the minimum.

[0029] As a control system of the vehicle air conditioner, the vehicle air conditioner includes an air conditioner ECU (Electric Control Unit) 40 that is similar to a computer, and an air conditioning information detector 50. The air conditioner ECU 40 includes a thermal load calculator 41 and a controller 42. The thermal load calculator 41 is electrically connected to the controller 42. The controller 42 is communicably connected to an engine ECU 60 that is similar to a computer and that controls the engine E.

[0030] The air conditioning information detector 50 includes an air conditioner switch (ACS) 51, or an on-off switch for the vehicle air conditioner, a temperature-setting device 52 for setting a temperature in a vehicle compartment and a temperature sensor 53 for detecting the temperature in the vehicle compartment. The thermal load calculator 41 is electrically connected to the air conditioning information detector 50. The air conditioning information detector 50 provides to the air conditioner ECU 40 information on an on-off state of the air conditioner switch 51, a temperature Tr in the vehicle compartment and a set temperature Ts. The thermal load calculator 41 calculates a thermal load of the air conditioner based on the information from the air conditioning information detector 50.

[0031] A residual quantity sensor 58 as a residual quantity detector is arranged at a battery B for the electric motor 21 and the other electric equipment. The residual quantity sensor 58 detects a residual quantity Br (quantity of accumulation of electricity) of the battery B and provides the residual quantity information Br of the battery B to the engine ECU 60. The residual quantity Br of the battery B is provided from the engine ECU60 to the controller 42. The controller 42 compares the residual quantity of the battery B with a predetermined quantity. The engine ECU 60 performs an idle stop control in which the engine E is stopped while the vehicle stops running to wait for a traffic signal to change for fuel saving. The residual quantity Br of the battery B is one of parameters when the engine ECU 60 determines whether to perform the idle stop control. When the residual battery Br is lower than the predetermined quantity Bs, the idle stop control is stopped, even if other information meets requirements to continue the idle stop control. The engine ECU 60 restarts the engine E so as to recharge the battery B to the predetermined quantity Bs or more. The controller 42 controls the electromagnetic clutch 18, the electric motor 21 and the control valve 39 based on the thermal load from the thermal load calculator 41, the information from the air conditioning information detector 50 and the information from the engine ECU 60.

[0032] The air conditioner ECU 40 (the thermal load calculator 41 and the controller 42) performs air conditioning control shown by a flow chart in FIG. 2 according to a pre-stored program. In a step S101, the on-off state of the air conditioner switch 51 is monitored until the air conditioner switch 51 is switched on. When the air conditioner switch 51 is switched on, the process proceeds to a step S102. In the step S102, the thermal load of the air conditioner is calculated, and it is judged whether the calculated thermal load is large or small. Specifically, the thermal load of the air conditioner is calculated by subtracting a set temperature Ts provided by the temperature sensor 53 from a detected temperature Tr provided by the temperature-setting device 52. In the above judgment, it is judged whether the remainder from the subtraction, or the thermal load is larger than a predetermined value α. Namely, the controller 42 compares the thermal load with the predetermined value α (>0). Hereafter, the controller 42 performs the air conditioning control.

[0033] In the present embodiment, if the judgment is YES in the step S102, that is, if the thermal load is larger than the predetermined value α, the controller 42 always selects the engine E as a drive source of the compressor C, and air conditioning is conducted. Meanwhile, if the judgment is NO in the step S102, that is, if the thermal load is equal to, or smaller than the predetermined value α, under the condition that the engine E is in the stopped state, the controller 42 selects the electric motor 21 as the drive source of the compressor C, and the air conditioning is conducted. Also, if the judgment is NO in the step S102, under the condition that the engine E is in a running state and the residual quantity Br of the battery B is equal to, or larger than the predetermined quantity Bs, the controller 42 selects the electric motor 21 as the drive source of the compressor C, and the air conditioning is conducted. In short, in the present first preferred embodiment, the compressor C is driven by the electric motor 21 only when the thermal load is equal to, or smaller than the predetermined value α.

[0034] Namely, if the judgment is YES in the step S102, the process proceeds to a step S103 where it is judged whether the engine E is in the running state based on information on a condition of the engine E (e.g. a rotational speed of the engine E and a running speed of the vehicle) that is provided by the engine ECU 60. For example, when the vehicle is in an idle stop state, the judgment is NO in the step S103. In this state, the engine E cannot drive the compressor C. Therefore, the process proceeds to a step S104 where the controller 42 instructs the engine ECU 60 to start the engine E. The engine ECU 60 starts the engine E according to the instruction from the controller 42, and the vehicle is released from the idle stop state.

[0035] When the judgment is YES in the step S103, or when the process finishes in the step S104, the process proceeds to a step S105. In the step S105, the control valve 39 is energized, and the displacement of the compressor C becomes the maximum. In a step S106, the electromagnetic clutch 18 is energized, and power is transmitted from the engine E to the compressor C. Also, the speed increasing mechanism 23 is arranged in the compressor C. Accordingly, if the displacement of the compressor C is the maximum, enough displacement of the compressor C per a predetermined period is ensured even by the engine E in an idling state. The detected temperature Tr is decreased toward the set temperature Ts. When the detected temperature Tr approaches the set temperature Ts to some extents, the judgment is NO in the step S102 next time. Namely, when the thermal load becomes equal to, or smaller than the predetermined value α, the judgment is No in the step S102.

[0036] If the judgment is NO in the step S102, it is judged whether the engine E is in the running state in a step S107. If the judgment is YES in the step S107, that is, if the engine E is in the running state, it is judged whether the residual quantity Br of the battery B that is provided by the engine ECU 60 is equal to, or larger than the predetermined quantity Bs in a step S108.

[0037] If the judgment is NO in the step S108, that is, if the residual quantity Br of the battery B is smaller than the predetermined quantity Bs, the running state of the engine E is probably the state that is released from the idle stop state only for recharging the battery B. At the time, the engine E is selected as the drive source of the compressor C.

[0038] Namely, the control valve 39 is de-energized in a step S109, and the displacement of the compressor C becomes the minimum. In a step S110, it is judged whether the detected temperature Tr from the temperature sensor 53 is larger than the set temperature Ts from the temperature-setting device 52. In a step S111, it is judged whether the detected temperature Tr is smaller than the set temperature Ts. If the judgments are NO both in the steps S110 and S111, the detected temperature Tr is equal to the set temperature Ts. Therefore, the state of the compressor C (run or stop), which affects the temperature in the vehicle compartment, or the state of the electromagnetic clutch 18 (on or off) is not changed.

[0039] On the other hand, if the judgment is YES in the step S110, the controller 42 instructs the electromagnetic clutch 18 to be energized so as to start the compressor C in a step S112. Since the compressor C is started, the temperature Tr in the vehicle compartment is decreased.

[0040] If the judgment is YES in the step S111, the controller 42 instructs the electromagnetic clutch 18 to be de-energized so as to stop the compressor C in a step S113. Since the compressor C is stopped, the temperature Tr in the vehicle compartment is increased.

[0041] As mentioned above, in the step S112 and/or the step S113, the on-off control of the electromagnetic clutch 18 is performed. Even when the detected temperature Tr is different from the set temperature Ts, the temperature Tr in the vehicle compartment converges around the set temperature Ts by the on-off control soon.

[0042] If the judgment is NO in the step S107, that is, if the engine E is in the stopped state, the electric motor 21 is selected as the drive source of the compressor C. Or if the judgment is YES in the step S108, that is, if the engine E is in the running state and the residual quantity Br of the battery B is equal to, or larger than the predetermined quantity Bs, the electric motor 21 is selected as the drive source of the compressor C. Namely, the control valve 39 is de-energized in a step S114. Therefore, the displacement of the compressor C becomes the minimum. The electromagnetic clutch 18 is de-energized in a step S115, and the controller 42 instructs the electric motor 21 to start in a step S116. When the displacement of the compressor C becomes the minimum, driving torque for driving the compressor C becomes the minimum.

[0043] In a step S117, it is judged whether the detected temperature Tr from the temperature sensor 53 is larger than the set temperature Ts from the temperature-setting device 52. In a step S118, it is judged whether the detected temperature Tr is smaller than the set temperature Ts. If the judgments are NO both in the steps S117 and S118, the detected temperature Tr is equal to the set temperature Ts. Namely, the displacement of the compressor C is at a suitable value per the predetermined period. Therefore, the rotational speed of the electric motor 21 (RSEM) is not changed for changing the displacement of the compressor C. Then, the process according to the flow chart in FIG. 2 returns.

[0044] On the other hand, if the judgment is YES in the step S117, air-conditioning by the air conditioner is not enough, that is, the displacement of the compressor C is not large enough. Therefore, in a step S119, the controller 42 instructs the electric motor 21 to increase the rotational speed of the electric motor 21 by a predetermined value. The rotational speed of the compressor C increases, and the displacement of the compressor C per the predetermined period increases. As the displacement of the compressor C per the predetermined period increases, the temperature in the vehicle compartment decreases.

[0045] If the judgment is YES in the step S118, the air-conditioning by the air conditioner is excessively cooled, that is, the displacement of the compressor C is too large. Therefore, in a step S120, the controller 42 instructs the electric motor 21 to decrease the rotational speed of the electric motor 21 by a predetermined value. The rotational speed of the compressor C decreases, and the displacement of the compressor C per the predetermined period decreases. As the displacement of the compressor C per the predetermined period decreases, the temperature in the vehicle compartment increases.

[0046] As mentioned above, in the step S119 and/or in the step S120, the rotational speed of the electric motor 21 is changed. Namely, when the electric motor 21 drives the compressor C, the rotational speed of the electric motor 21 is controlled in accordance with the thermal load. Even when the detected temperature Tr is different from the set temperature Ts, the rotational speed of the electric motor 21, or the displacement of the compressor C per the predetermined period gradually has been controlled to be close to the desired value according to the above control for the electric motor 21. As a result, the detected temperature Tr converges into the set temperature Ts.

[0047] As mentioned above, in the present embodiment, when the judgment is NO in the step S103, the controller 42 instructs the engine ECU 60 to start the engine E in the step S104. The engine ECU 60 starts the engine E, and the vehicle is released from the idle stop state. In this case, when the judgment is NO in the step S102 later, the controller 42 dose not instruct the engine ECU 60 to run the engine E. Therefore, the engine ECU 60 stops the engine E if the other requirements for the idle stop are met.

[0048] Following effects are obtained in the present embodiment.

[0049] (1-1) When the calculated thermal load is larger than the predetermined value α, the controller 42 changes the displacement of the compressor C per one rotation to the maximum and selects the engine E as the drive source of the compressor C. Even when the rotational speed of the compressor C is low, a relatively large amount of discharge refrigerant by the compressor C per the predetermined period can be ensured. Enough cooling performance can be ensured, and the air conditioning is steadily performed. Therefore, as mentioned in the present first preferred embodiment, even when the speed increasing mechanism 23 that increases the rotational speed obtained from the engine E is arranged, the speed increasing ratio of the speed increasing mechanism 23 can be set at a relatively small value. The speed increasing mechanism 23 can be miniaturized. Also, a transmission mechanism that transmits the power from the engine E can be miniaturized.

[0050] (1-2) When the thermal load calculated by the thermal load calculator 41 is equal to, or smaller than the predetermined value α, the controller 42 changes the displacement of the compressor C per one rotation to the minimum and selects the electric motor 21 as the drive source of the compressor C. The driving torque for driving compressor C with the minimum displacement is small. Therefore, the electric motor 21 can be miniaturized without a speed reducing mechanism that decreases the rotational speed obtained from the electric motor 23. When the thermal load is equal to, or smaller than the predetermined value α, the rotational speed of the electric motor 21 does not increase relatively. As a result, the electric motor 21 can run in a stable manner.

[0051] (1-3) When the thermal load calculated by the thermal load calculator 41 is equal to, or smaller than the predetermined value α and when the engine E is in the running state, the controller 42 selects the engine E as the drive source of the compressor C. Therefore, for example, the residual quantity Br of the battery B for the other electric equipment (e.g. a headlamp) as well as the electric motor 21 is not decreased at a relatively large degree. The operation of the electric equipment other than the electric motor 21 can be ensured.

[0052] (1-4) When the thermal load calculated by the thermal load calculator 41 is equal to, or smaller than the predetermined value α and when the engine E is in the running state, the controller 42 selects the engine E as the drive source of the compressor C and changes the displacement of the compressor C to the minimum. The electromagnetic clutch 18 is not frequently switched on and off due to the minimum displacement of the compressor C. Therefore, deterioration of drivability of the vehicle due to the shock caused by the on-off control action of the electromagnetic clutch 18 can be suppressed.

[0053] (1-5) When the thermal load calculated by the thermal load calculator 41 is equal to, or smaller than the predetermined value α, when the engine E is in the running state, and when the residual quantity Br of the Battery B is smaller than the predetermined quantity Bs, the controller 42 selects the engine E as the drive source of the compressor C. Therefore, since the electric motor 21 is in the stopped state, the engine E is not prevented from recharging the battery B due to the consumption of the power of the battery B by the electric motor 21. The residual quantity Br of the battery B can be steadily increased. Therefore, the operation of the electric equipment other than the electric motor 21 can be ensured further.

[0054] (1-6) The compressor C includes the speed increasing mechanism 23 that increases the rotational speed from the power transmission mechanism 22 and transmits the power to the compression unit 12. Therefore, the electric motor 21 can be miniaturized further. The speed increasing mechanism 23 is arranged in the housing 11 of the compressor C. As mentioned above, the speed increasing mechanism 23 may be small-sized. Therefore, even though the speed increasing mechanism 23 is accommodated in the housing 11, the compressor C is not large-sized. Since the speed increasing mechanism 23 is accommodated in the housing 11, the compressor C and the speed increasing mechanism 23 can be handled together. Therefore, when the vehicle air conditioner is installed in the vehicle, the compressor C is easy. to handle with the speed increasing mechanism 23.

[0055] (1-7) The electric motor 21 is arranged in the housing 11 of the compressor C. As mentioned above, the electric motor 21 may be small-sized. Therefore, even though the electric motor 21 is accommodated in the housing 11, the compressor C is not large-sized. Since the electric motor 21 is accommodated in the housing 11, the compressor C and the electric motor 21 can be handled together. Therefore, when the vehicle air conditioner is installed in the vehicle, the compressor C is easy to handle with the electric motor 21.

[0056] The speed increasing mechanism 23 is arranged inside the stator of the electric motor 21. Therefore, space in the housing 11 is saved by a part where the speed increasing mechanism 23 overlaps with the stator in an axial direction, and the compressor C does not need to be lengthened by the length of the part in the axial direction. Such an arrangement prevents the compressor C from increasing its size in the axial direction. Namely, since the speed increasing mechanism 23 may be small-sized as mentioned above, the speed increasing mechanism 23 is easily arranged inside the stator in the present preferred embodiment.

[0057] (1-8) The compressor C is a scroll type, and the displacement of the compressor C is switched between the maximum and the minimum. For example, the energy efficiency of a scroll type compressor is better than that of a piston type compressor. Also, the displacement of the compressor C is switched between the maximum and the minimum by simple control, or on-off control of the control valve 39.

[0058] Furthermore, the electric motor 21 does not include a permanent magnet. When the engine E drives the compressor C, the rotor 14 of the electric motor 21 is rotated. Electromotive force is not generated in the electric motor 21 even when the rotor 14 of the electric motor 21 is rotated. Therefore, power loss of the engine E, which is caused by the generation of the electromotive force, is avoided.

[0059] Next, the second preferred embodiment will be described. In the second preferred embodiment, the only difference between the first and second preferred embodiments will be described. The same reference numerals denote substantially identical elements as those in the first preferred embodiment.

[0060] As shown in FIG. 3, in the second preferred embodiment, the speed increasing mechanism 23 is deleted form the above-mentioned first preferred embodiment. The pulley shaft 13 and the compressor shaft 19 (hereafter a shaft 13) are integrally formed so as to rotate integrally and so as to have the same axis. The rotor 14 is supported by the shaft 13 through a bearing 57 so as to rotate relative to the shaft 13. A speed reducing mechanism 65 is arranged between the rotor 14 of the electric motor 21 and the shaft 13. The speed reducing mechanism 65 decreases the rotational speed obtained from the electric motor 21 and transmits the power to the shaft 13.

[0061] The speed reducing mechanism 65 has a known structure that includes a sun gear 66, an internal gear 67, a holder 68 and a plurality of planetary gears 69. The sun gear 66 can rotate integrally with the rotor 14 and can rotate relative to the shaft 13. The internal gear 67 is integrally formed with the housing 11. The holder 68 is mounted on the shaft 13 so as to rotate integrally with the shaft 13. The planetary gear 69 is rotatably held by the holder 68 and is interposed between the sun gear 66 and the internal gear 67.

[0062] The compressor C includes the speed reducing mechanism 65. Therefore, even if the minimum displacement of the compressor C is set at a value that is larger than the above-mentioned first preferred embodiment, the electric motor 21 does not need to be large-sized. The ratio between the minimum and maximum displacements of the compressor C is limited. Since the minimum displacement of the compressor C can be set at the value that is larger than the above-mentioned first preferred embodiment, the maximum displacement of the compressor can be also set at a relatively larger value. Therefore, even when the rotational speed of the engine E is low, a relatively large amount of the discharged refrigerant by the compressor C per the predetermined period, which is substantially as large as the above-mentioned first preferred embodiment, can be ensured without the speed increasing mechanism 23.

[0063] Following effects are obtained in the present embodiment.

[0064] (2-1) When the thermal load is larger than the predetermined value α, the controller 42 changes the displacement of the compressor C per one rotation to the maximum and selects the engine E as the drive source of the compressor C. Therefore, even when the rotational speed of the engine E is low, the relatively large amount of the discharged refrigerant by the compressor C per the predetermined period can be ensured. A speed increasing mechanism that increases the rotational speed obtained from the engine E is unnecessary.

[0065] (2-2) When the thermal load is equal to, or smaller than the predetermined value α, the controller 42 changes the displacement of the compressor C to the minimum and selects the electric motor 21 as the drive source of the compressor C. The driving torque for driving compressor C with the minimum displacement is small. Therefore, even though the speed reducing mechanism 65, which decreases the rotational speed obtained from the electric motor 21, is arranged, the speed reducing ratio may be relatively small. The speed reducing mechanism 65 can be miniaturized, and also a transmission mechanism that transmits the power from the electric motor 21 can be miniaturized. The miniaturization of the speed reducing mechanism 65 and the transmission mechanism can be compatible with the miniaturization of the electric motor 21. Furthermore, when the thermal load is equal to, or smaller than the predetermined value α, the rotational speed of the electric motor 21 is not increased relatively. Therefore, the electric motor 21 runs in the stable manner. The same advantageous effects are obtained as mentioned in paragraphs (1-3) through (1-8) according to the first preferred embodiment.

[0066] Following alternative embodiments may be practiced.

[0067] The speed increasing mechanism 23 may be deleted in the above-mentioned first preferred embodiment. The speed reducing mechanism 65 may be deleted in the above-mentioned second preferred embodiment.

[0068] In each preferred embodiment, the compression unit 12 has a structure for switching between the two displacement values including the maximum and the minimum. The compression unit 12 may have a structure for switching among three, four, five, six, or seven displacement values. In this case, the maximum displacement value may be considered the first predetermined displacement value, and the others may be considered the second predetermined displacement value. Also, the minimum displacement value may be considered the second predetermined displacement value, and the others may be considered the first predetermined displacement value. Further, the displacements values that are equal to, or larger than a certain value may be considered the first predetermined displacement value, and the other displacement values that are smaller than the certain value may be considered the second predetermined displacement value.

[0069] In the above embodiment, it is judged whether the thermal load of the air conditioner is large by comparing the detected temperature Tr with the set temperature Ts. It may be judged by referring to a refrigerant pressure (a suction pressure) at an outlet side (a suction chamber side) of an evaporator that constitutes the refrigerant cycle. It may also be judged by referring to the temperature at the outlet of the evaporator.

[0070] In the above embodiment, when the electric motor 21 drives the compressor C, the electric motor 21 is started after the electromagnetic clutch 18 is de-energized. The electromagnetic clutch 18 may be de-energized after the electric motor 21 is started.

[0071] The electric motor 21 may be a SR motor (a switched reluctance motor), or a VR motor (a variable reluctance motor). The electric motor 21 may be also an induction motor without a permanent magnet. Since starting torque of a reluctance motor is larger than that of an inductance motor, the reluctance motor is more advantageous than the inductance motor for ensuring starting torque.

[0072] The electric motor 21 may include a permanent magnet. The scroll type compression unit 12 is utilized in the above preferred embodiment. A piston type variable displacement compression unit may be utilized. A vehicle that does not perform an idle stop control may be utilized as the vehicle.

[0073] Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.