Title:
Cooling Pump for Internal Combustion Engine and Cooling System Using the Cooling Pump
Kind Code:
A1


Abstract:
A cooling pump for an internal combustion engine and a cooling system including the pump. The pump is driven by an electrically-operated motor so as to rotate in a positive direction for supplying cooling water in a reservoir tank to the engine and in a reverse direction for returning the cooling water in the engine to the reservoir tank. The cooling system includes a controller that is coupled with the motor of the pump and generates a first control signal for operating the motor to rotate the pump in the reverse direction so as to return the cooling water in the engine to the reservoir tank and generates a second control signal for operating the motor to rotate the pump in the positive direction so as to supply the cooling water in the reservoir tank to the engine, on the basis of an operating condition of the engine.



Inventors:
Takarai, Kenya (Atsugi-shi, JP)
Application Number:
12/188653
Publication Date:
02/12/2009
Filing Date:
08/08/2008
Assignee:
Hitachi, Ltd. (Tokyo, JP)
Primary Class:
International Classes:
F01P7/00
View Patent Images:
Related US Applications:



Primary Examiner:
NGUYEN, HUNG Q
Attorney, Agent or Firm:
CROWELL & MORING LLP (WASHINGTON, DC, US)
Claims:
What is claimed is:

1. A cooling pump for an internal combustion engine, comprising: an electrically-operated motor; a pump impeller that is driven by the motor so as to rotate in a positive direction and a reverse direction; and a control device coupled with the motor, the control device operating the motor to rotate the pump impeller in the positive direction for supplying cooling water to the engine and rotate the pump impeller in the reverse direction for discharging the cooling water from the engine, in response to a control signal based on an operating condition of the engine.

2. The cooling pump as claimed in claim 1, wherein the control device operates the motor to rotate the pump impeller in the reverse direction for discharging the cooling water from the engine when a temperature of the cooling water in the engine in a start-up state is not more than a first preset value, and rotate the pump impeller in the positive direction for supplying the cooling water to the engine when the temperature of the engine is more than the first preset value.

3. The cooling pump as claimed in claim 1, wherein the control device operates the motor to rotate the pump impeller in the reverse direction for discharging the cooling water from the engine until a time elapsed from start-up of the engine reaches a predetermined value, and rotate the pump impeller in the positive direction for supplying the cooling water to the engine when the time elapsed from start-up of the engine exceeds the predetermined value.

4. The cooling pump as claimed in claim 1, wherein the control device operates the motor to rotate the pump impeller in the reverse direction for discharging the cooling water from the engine when a temperature of the cooling water in the engine in a start-up state is not more than a first preset value, and rotate the pump impeller in the positive direction for supplying the cooling water to the engine when the temperature of the cooling water in the engine in a start-up state is more than the first preset value and a time elapsed from start-up of the engine exceeds a predetermined value.

5. The cooling pump as claimed in claim 1, wherein the control device operates the motor to rotate the pump impeller in the reverse direction for discharging the cooling water from the engine when a temperature of the cooling water in the engine in a stop state is not more than a first preset value.

6. A cooling system for an internal combustion engine, comprising: a reservoir tank that stores cooling water for cooling the engine; a pump that is driven by an electrically-operated motor so as to rotate in a positive direction for supplying the cooling water in the reservoir tank to the engine and in a reverse direction for returning the cooling water in the engine to the reservoir tank; and a controller coupled with the motor, the controller generating a first control signal for operating the motor to rotate the pump in the reverse direction so as to return the cooling water in the engine to the reservoir tank and generating a second control signal for operating the motor to rotate the pump in the positive direction so as to supply the cooling water in the reservoir tank to the engine, on the basis of an operating condition of the engine.

7. The cooling system as claimed in claim 6, wherein the controller generates the first control signal when a temperature of the cooling water in the engine in a start-up state is not more than a first preset value, and generates the second control signal when a temperature of the engine is more than the first preset value.

8. The cooling system as claimed in claim 6, wherein the controller generates the first control signal until a time elapsed from at start-up of the engine reaches a predetermined value, and generates the second control signal when the time elapsed from start-up of the engine exceeds a predetermined value.

9. A cooling system for an internal combustion engine, comprising: a reservoir tank that stores cooling water for cooling the engine; a pump that is driven by an electrically-operated motor so as to rotate in a positive direction for supplying the cooling water in the reservoir tank to the engine and in a reverse direction for returning the cooling water in the engine to the reservoir tank; a radiator that cools the cooling water heated while flowing in the engine; a cooling water passage that allows communication between the reservoir tank and the pump via the radiator; a bypass passage that allows communication between the reservoir tank and- the pump to bypass the radiator, the bypass passage having one end connected with the reservoir tank and the other end connected with the cooling water passage between the radiator and the pump, a thermostatically-operated valve that is disposed at a connection between the cooling water passage and the other end of the bypass passage, the thermostatically-operated valve being operative on the basis of a temperature of the cooling water; and a controller coupled with the motor, the controller generating a first control signal for operating the motor to rotate the pump in the reverse direction for returning the cooling water in the engine to the reservoir tank via the bypass passage when a temperature of the cooling water in the engine in a start-up state is not more than a first preset value, the controller generating a second control signal for operating the motor to rotate the pump in the positive direction so as to supply the cooling water in the reservoir tank to the engine when a temperature of the engine is more than the first preset value.

10. The cooling system as claimed in claim 9, wherein the thermostatically-operated valve is operative to open the cooling water passage and close the bypass passage for supplying the cooling water to the engine through the radiator in the cooling water passage when the temperature of the cooling water in the engine is more than the second preset value during rotation of the pump in the positive direction.

11. The cooling system as claimed in claim 9, wherein the thermostatically-operated valve is operative to close the cooling water passage and open the bypass passage for supplying the cooling water to the engine through the bypass passage when the temperature of the cooling water in the engine is more than the first preset value and not more than the second preset value during rotation of the pump in the positive direction.

12. The cooling system as claimed in claim 9, further comprising a return passage that allows communication between the reservoir tank and the engine and returns the cooling water that circulates the engine during the positive rotation of the pump, to the reservoir tank, wherein a first communication port through which the return passage is communicated with the reservoir tank is placed in a height position higher than a second communication port through which the cooling water passage is communicated with the reservoir tank, and a third communication port through which the bypass passage is communicated with the reservoir tank is placed in a height position substantially same as the second communication port or in a height position lower than the second communication port.

13. The cooling system as claimed in claim 9, further comprising a return passage that allows communication between the reservoir tank and the engine and returns the cooling water that circulates the engine during the positive rotation of the pump, to the reservoir tank, and a check valve that allows the cooling water to flow from the return passage into the reservoir tank, the check valve being disposed at a first communication port through which the return passage is communicated with the reservoir tank.

14. The cooling system as claimed in claim 9, further comprising a flow control valve that-is disposed in the cooling water passage between the pump and the thermostatically-operated valve, the flow control valve being operative to control an amount of the cooling water.

15. The cooling system as claimed in claim 9, further comprising a communication passage that communicates the pump and the engine with each other, the communication passage being branched into a high-temperature side passage and a low-temperature side passage which are connected to a high-temperature portion of the engine and a low-temperature portion of the engine, respectively, and a directional control valve that is operative to distribute a flow of the cooling water between the high-temperature side passage and the low-temperature side passage on the basis of an operating condition of the engine.

16. The cooling system as claimed in claim 15, wherein when a temperature of the cooling water in one of the high-temperature portion and the low-temperature portion of the engine in a start-up state is not more than the first preset value, the controller generates the first control signal and a third control signal for controlling the directional control valve so as to return the cooling water in the one of the high-temperature portion and the low-temperature portion of the engine to the reservoir tank, and when the temperature of one of the high-temperature portion and the low-temperature portion of the engine is more than the first preset value, the controller generates the second control signal and a fourth control signal for controlling the directional control valve so as to supply the cooling water in the reservoir tank to the one of the high-temperature portion and the low-temperature portion of the engine.

Description:

BACKGROUND OF THE INVENTION

The present invention relates to a water pump that is applicable to a water-cooled internal combustion engine, in particular relates to a water cooling pump for the internal combustion engine which is driven by an electrically-operated motor, and a cooling system using the cooling pump.

As generally known in the art, a water-cooled internal combustion engine is equipped with a so-called water pump that supplies the engine with a pressurized cooling water that is stored in a reservoir tank in order to cool the engine. A water pump that is driven by a driving force of the engine has been widely adopted.

Recently, there have been various kinds of cooling systems with the water pump which aims at minimizing a cooling operating time for cooling the engine in consideration of such a problem that fuel economy is deteriorated due to increase in friction between sliding parts in the engine which is caused at start-up of an engine cooling operation.

Japanese Patent Application First Publication No. 6-101476 discloses a cooling system for an internal combustion engine which includes a reservoir tank for cooling water, cooling water passages which are respectively connected with a high temperature portion and a low temperature portion of the engine, a plurality of valves which are disposed in the cooling water passages and control a flow of coolant water passing through the cooling water passages, and a water pump for supplying the cooling water in the reservoir tank to the engine. When the engine is in a cooled state, the cooling water is supplied to the high temperature portion of the engine while the cooling water is prevented from being supplied to the low temperature portion of the engine and the cooling water in the low temperature portion is discharged therefrom to be returned to the reservoir tank, by controlling the valves. The cooling system thus aims at facilitating warm-up of the engine.

SUMMARY OF THE INVENTION

However, in the cooling system of the above-described conventional art, the cooling water in the low temperature portion of the engine is discharged by gravity due to its own weight. Therefore, the cooling water in the low temperature portion of the engine cannot be efficiently discharged and the cooling water might remain in the low temperature portion of the engine. This results in failure to sufficiently enhance a warm-up performance of the engine.

It is an object of the present invention to solve the above-described problem in the technologies of the conventional art and to provide a cooling pump for an internal combustion engine and a cooling system using the cooling pump which can forcibly discharge a cooling water in the engine to thereby sufficiently enhance a warm-up performance of the engine.

In one aspect of the present invention, there is provided a cooling pump for an internal combustion engine, comprising:

  • an electrically-operated motor;
  • a pump impeller that is driven by the motor so as to rotate in a positive direction and a reverse direction; and
  • a control device coupled with the motor, the control device operating the motor to rotate the pump impeller in the positive direction for supplying cooling water to the engine and rotate the pump impeller in the reverse direction for discharging the cooling water from the engine, in response to a control signal based on an operating condition of the engine.

In a further aspect of the present invention, there is provided a cooling system for an internal combustion engine, comprising:

  • a reservoir tank that stores cooling water for cooling the engine;
  • a pump that is driven by an electrically-operated motor so as to rotate in a positive direction for supplying the cooling water in the reservoir tank to the engine and in a reverse direction for returning the cooling water in the engine to the reservoir tank; and
  • a controller coupled with the motor, the controller generating a first control signal for operating the motor to rotate the pump in the reverse direction so as to return the cooling water in the engine to the reservoir tank and generating a second control signal for operating the motor to rotate the pump in the positive direction so as to supply the cooling water in the reservoir tank to the engine, on the basis of an operating condition of the engine.

In a still further aspect of the present invention, there is provided a cooling system for an internal combustion engine, comprising:

  • a reservoir tank that stores cooling water for cooling the engine;
  • a pump that is driven by an electrically-operated motor so as to rotate in a positive direction for supplying the cooling water in the reservoir tank to the engine and in a reverse direction for returning the cooling water in the engine to the reservoir tank;
  • a radiator that cools the cooling water heated while flowing in the engine;
  • a cooling water passage that allows communication between the reservoir tank and the pump via the radiator;
  • a bypass passage that allows communication between the reservoir tank and the pump to bypass the radiator, the bypass passage having one end connected with the reservoir tank and the other end connected with the cooling water passage between the radiator and the pump,
  • a thermostatically-operated valve that is disposed at a connection between the cooling water passage and the other end of the bypass passage, the thermostatically-operated valve being operative on the basis of a temperature of the cooling water; and
  • a controller coupled with the motor, the controller generating a first control signal for operating the motor to rotate the pump in the reverse direction for returning the cooling water in the engine to the reservoir tank via the bypass passage when a temperature of the cooling water in the engine in a start-up state is not more than a first preset value, the controller generating a second control signal for operating the motor to rotate the pump in the positive direction so as to supply the cooling water in the reservoir tank to the engine when a temperature of the engine is more than the first preset value.

The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram that shows a cooling system with a cooling pump according to a first embodiment of the present invention.

FIG. 2 is a cross-section of the cooling pump of the first embodiment, taken along a rotation axis of the cooling pump.

FIG. 3 is a schematically explanatory diagram that illustrates a state of the cooling system of the first embodiment when the cooling pump is rotated in a reverse direction.

FIG. 4 is a schematically explanatory diagram that illustrates a state of a reservoir tank in the cooling system of the first embodiment when the cooling pump is rotated in the reverse direction.

FIG. 5 is a schematically explanatory diagram that illustrates a state of the cooling system of the first embodiment when the cooling pump is rotated in a positive direction.

FIG. 6 is a schematically explanatory diagram that illustrates a state of the reservoir tank in the cooling system of the first embodiment when the cooling pump is rotated in the positive direction.

FIG. 7 is a schematically explanatory diagram that illustrates a state of the cooling system of the first embodiment when a cooling water is circulated via a radiator during the rotation of the cooling pump in the positive direction.

FIG. 8 is a flow chart of a control routine of the cooling system of the first embodiment.

FIG. 9 is a schematically explanatory diagram that illustrates a state of the reservoir tank in the cooling system according to a second embodiment when the cooling pump is rotated in the reverse direction.

FIG. 10 is a schematically explanatory diagram that illustrates a state of the reservoir tank in the cooling system of the second embodiment when the cooling pump is rotated in the positive direction.

FIG. 11 is a schematically explanatory diagram that illustrates a state of the reservoir tank of a modification of the second embodiment when the cooling pump is rotated in the reverse direction.

FIG. 12 is a schematically explanatory diagram that illustrates a state of the reservoir tank of the modification of the second embodiment when the cooling pump is rotated in the positive direction.

FIG. 13 is a flow chart of a control routine of the cooling system according to a third embodiment of the present invention.

FIG. 14 is a schematic diagram that shows the cooling system with the cooling pump, according to a fourth embodiment of the present invention.

FIG. 15 is a flow chart of a control routine of the cooling system of the fourth embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1 through FIG. 8, a cooling pump and a cooling system using the cooling pump according to a first embodiment of the present invention, is explained. In this embodiment, the cooling pump and the cooling system are applied to a water-cooled internal combustion engine for vehicles.

As shown in FIG. 1, internal combustion engine 1 includes cylinder block 1a with a plurality of cylinders, and cylinder head 1b that is fixedly disposed on an upper portion of cylinder block 1a. Cylinder block 1a is a low temperature portion of engine 1 which undergoes a relatively low temperature during engine operation, and cylinder head 1b is a high temperature portion of engine 1 which undergoes a temperature higher than that of cylinder block 1a during engine operation. Cooling system 10 is provided in order to prevent engine 1 from overheating and carries out cooling of engine 1 by cooling water (cooling fluid) which is circulated in cooling system 10.

Cooling system 10 includes electrically-operated pump 11, reservoir tank 3, first water jacket 2a, second water jacket 2b, and radiator 4. Electrically-operated pump 11 pressurizes the cooling water and circulates the pressurized cooling water in cooling system 10. Reservoir tank 3 temporarily stores the cooling water in order to absorb volumetric variation of the cooling water which occurs along with temperature change of the circulated cooling water. First water jacket 2a and second water jacket 2b are formed inside cylinder block 1a and cylinder head 1b, respectively, and define respective cooling water passages in which the cooling water flows. Radiator 4 cools the cooling water that is heated while passing through respective water jackets 2a and 2b.

As shown in FIG. 1, first water jacket 2a extends to surround the respective cylinders. First water jacket 2a includes a plurality of branches that extend from a side of one end portion of first water jacket 2a, namely, a lower side of first water jacket 2a when viewed in FIG. 1, toward cylinder head 1b along partition walls that are disposed between the adjacent two cylinders and define the respective cylinders. First water jacket 2a has a port at one end thereof which is communicated with reservoir tank 3 through cooling water passage 5. First water jacket 2a further has a port at the other end thereof which is opened to an upper end surface of cylinder block 1a which abuts on a lower end surface of cylinder head 1b. The other end of first water jacket 2a is communicated with second water jacket 2b of cylinder head 1b.

Second water jacket 2b is formed to be merged with the other end of first water jacket 2a. Second water jacket 2b has a port at one end thereof which is opened to the lower end surface of cylinder head 1b and connected with the other end of first water jacket 2a. Second water jacket 2b further has a port at the other end thereof which is communicated with reservoir tank 3 through return passage 6.

Thus, cooling system 10 has a closed loop cooling water circuit for the cooling water which is constituted of the cooling water paths of respective water jackets 2a and 2b, cooling water passage 5 and return passage 6. The cooling water is circulated through the cooling water circuit kept in the hermetically sealed state, while being pressurized.

Reservoir tank 3 has a generally rectangular cross-section and a volumetric capacity capable of storing all amounts of the cooling water that is circulated through cooling system 10. Reservoir tank 3 includes opposed two side walls, an upper wall and a bottom wall opposed to the upper wall in a vertical direction of reservoir tank 3. A communication port is formed at a lower end portion of one of the side walls of reservoir tank 3, to which one end of cooling water passage 5 is connected. Further, a communication port is formed in the upper wall of reservoir tank 3, to which one end of return passage 6 is connected. The communication port through which return passage 6 is communicated with reservoir tank 3 is placed in a height position higher than the communication port through which cooling water passage 5 is communicated with reservoir tank 3, in a direction of a height of reservoir tank 3. Reservoir tank 3 is thus arranged to allow the cooling water to be circulated always passing through reservoir tank 3. Further, reservoir tank 3 acts to temporarily store the cooling water as a surplus which remains in the cooling water circuit, and separate and remove air entrapped in the circulated cooling water from the cooling water.

Radiator 4 is disposed in cooling water passage 5 and configured to cool fluid, i.e., cooling water, which passes through an inside of radiator 4 by heat exchange between the fluid and air that is fed to radiator 4 by natural ventilation or a motor-fan. Specifically, after flowing in respective water jackets 2a and 2b, the cooling water is returned to reservoir tank 3 through return passage 6 and then fed to radiator 4 upon required. While flowing in respective water jackets 2a and 2b, the cooling water absorbs the heat generated in engine 1 to thereby raise a temperature of the cooling water. Thus heated cooling water is cooled by radiator 4 and then supplied to engine 1 again.

Electrically-operated pump 11 is driven by a claw pole motor that is rotatable in both a positive direction and a reverse direction. Electrically-operated pump 11 is a so-called axial flow pump that has functions of feeding pressurized fluid from one side to the other side upon rotating in one direction, and feeding the pressurized fluid from the other side to the one side upon rotating in an opposite direction. Electrically-operated pump 11 is disposed at the connection between the other end of cooling water passage 5 and the one end of first water jacket 2a.

In this embodiment, electrically-operated pump 11 is constructed to feed the pressurized cooling water from a side of reservoir tank 3 toward engine 1 during rotation in a positive direction, and feed the pressurized cooling water from a side of engine 1 toward reservoir tank 3 during rotation in a reverse direction. The construction of electrically-operated pump 11 will be explained in detail later.

Inside engine 1, there are provided a water temperature sensor (not shown) that detects a temperature of the cooling water flowing in each of water jackets 2a and 2b, and temperature sensors (not shown) that detect temperatures of walls of cylinder block 1a and cylinder head 1b, respectively. These sensors always monitor the temperature of the cooling water and the temperatures of the walls of cylinder block 1a and cylinder head 1b, respectively. The sensors are coupled to electronic controller 50. Electronic controller 50 receives the temperature information from the sensors and generates a control signal for controlling electrically-operated pump 11 so as to rotate in a predetermined direction on the basis of the temperature information. Electronic controller 50 includes a microcomputer which has an input/output interface (I/O), a random access memory (RAM), a read-only memory (ROM), and a microprocessor or a central processing unit (CPU).

Bypass passage 7 is connected to reservoir tank 3 in parallel to cooling water passage 5 and allows fluid communication between reservoir tank 3 and first water jacket 2a by bypassing radiator 4. Bypass passage 7 has one end directly connected to a communication port that is formed in the bottom wall of reservoir tank 3. The communication port through which bypass passage 7 is communicated with reservoir tank 3 is placed in a height position substantially same as the communication port between cooling water passage 5 and reservoir tank 3 or in a height position lower than the communication port between cooling water passage 5 and reservoir tank 3 in the direction of a height of reservoir tank 3. The other end of bypass passage 7 is connected to thermostatically-operated valve 8 that is disposed in cooling water passage 5 between radiator 4 and electrically-operated pump 11. Bypass passage 7 is thus communicated with cooling water passage 5 through thermostatically-operated valve 8.

Thermostatically-operated valve 8 is operative to carry out changeover of a passage of the cooling water to be circulated in the cooling water circuit on the basis of a temperature of the cooling water passing through thermostatically-operated valve 8. That is, thermostatically-operated valve 8 is operative to close one of cooling water passage 5 and bypass passage 7 and open the other thereof on the basis of the temperature of the cooling water passing through thermostatically-operated valve 8. Flow control valve 9 is disposed in the other end portion of cooling water passage 5 between thermostatically-operated valve 8 and electrically-operated pump 11. Flow control valve 9 is operative to control an amount of a flow of the cooling water that flows in the other end portion of cooling water passage 5.

Referring now to FIG. 2, the construction of electrically-operated pump 11 is explained. As shown in FIG. 2, electrically-operated pump 11 includes generally cylindrical pump housing 12 that is mounted to a front end portion of cylinder block 1a, and generally cylindrical partition 13 that divides an interior of pump housing 12 into pump chamber 12a for pump elements on an outer side of the interior, and motor chamber 12b for motor elements on an inner side of the interior. Drive shaft 14 extends through the interior of pump housing 12 along a central axis of pump housing 12, namely, a rotation axis of electrically-operated pump 11. Generally cylindrical pump rotor 15 is supported within pump chamber 12a via drive shaft 14 so as to be rotatable about the rotation axis. Cylindrical permanent magnet 16 is fixed to an inner circumferential periphery of pump rotor 15. Stator 17 is fixedly disposed within motor chamber 12b so as to be opposed to permanent magnet 16 in a radial direction of pump housing 12 via partition 13 that is interposed between permanent magnet 16 and stator 17. Cooling water passage 18 is formed between an inner circumferential surface of pump housing 12, inner and outer circumferential surfaces of pump rotor 15, and an outer circumferential surface of partition 13.

Pump housing 12 is made of a non-magnetic synthetic resin material. Pump housing 12 includes housing body 21 having a one end-closed cylindrical shape, and tubular connector 22 that is connected to a front end portion of housing body 21 by means of a suitable fastening member such as a bolt. Connector 22 includes first connecting portion 22a that is formed into a nipple shape and projects from the front end portion of housing body 21 in the axial direction of pump housing 12. First connecting portion 22a is connected to the other end of cooling water passage 5. Connector 22 further includes second connecting portion 22b that is formed into a nipple shape and connected to the one end of first water jacket 2a. Working chamber 22c is disposed within connector 22 between first connecting portion 22a and second connecting portion 22b.

Partition 13 is made of the same non-magnetic synthetic resin material as that of pump housing 12, and formed into the generally cylindrical shape having a closed end. Partition 13 is integrally formed with housing body 21. Partition 13 includes cylindrical support shaft 13a that extends from an end wall of partition 13 along a central axis of partition 13, and flange 13b that is formed on a side of a rear end of partition 13. Support shaft 13a is integrally formed with partition 13 and receives and supports drive shaft 14. Flange 13b is integrally formed with partition 13 and connected with inner circumferential surface 21a of housing body 21 at an outer circumferential edge thereof.

Drive shaft 14 is made of a metal material and fixed into support shaft 13a by molding. Cylindrical bushing 23 is fixed onto an outer circumferential surface of a distal end portion of drive shaft 14 by means of screw 24 that is tightened in an axial direction of bushing 23.

Pump rotor 15 includes tubular rotor body 25 that is disposed between housing body 21 and partition 13, disk-shaped support 26 that is disposed at a side of a front end of rotor body 25, and pump impeller 27 that is fixed to a front end surface of support 26. Rotor body 25 extends in an axial direction thereof between housing body 21 and partition 13 and has a cylindrical groove on an inner circumferential surface thereof into which permanent magnet 16 is fixedly fitted. Support 26 includes inner circumferential portion 26a having generally truncated cone-shape, and bearing bore 26b that extends through a central part of inner circumferential portion 26a. Drive shaft 14 with bushing 23 extends into support shaft 13a through bearing bore 26b. Support 26 is rotatably supported on an outer circumferential surface of bushing 23.

Impeller wheel 27 is disposed within pump chamber 12a on a front side of pump chamber 12a. Impeller wheel 27 is rotatable together with pump rotor 15 to thereby suck the cooling water from first connecting portion 22a into pump chamber 12a and discharge the cooling water in pump chamber 12a into second connecting portion 22b. Specifically, when pump impeller 27 rotates in a positive direction, the cooling water is allowed to flow from a side of reservoir tank 3 into pump chamber 12a through first connecting portion 22a and flow from pump chamber 12a into first water jacket 2a through second connecting portion 22b. On the other hand, when pump impeller 27 rotates in a reverse direction, the cooling water is allowed to flow from first water jacket 2a into pump chamber 12a through second connecting portion 22b and flow from pump chamber 12a to the side of reservoir tank 3 through first connecting portion 22a.

Stator 17 is fixed to partition 13 such that an outer circumferential surface of stator 17 is in contact with an inner circumferential surface of partition 13 Stator 17 carries electromagnetic coil 28 that is wound around the outer periphery of stator 17. Electromagnetic coil 28 is electrically connected to drive circuit 29a of control device 29 that is fixedly disposed in a rear end portion of motor chamber 12b. Control device 29 is coupled to electronic controller 50 and always electronically communicated with electronic controller 50.

Cooling water passage 18 is constructed to guide a part of the cooling water that flows in pump chamber 12a as pump impeller 27 rotates, along the outer circumferential periphery of partition 13 and cool stator 17 and electromagnetic coil 28 by the part of the cooling water. A flow of the part of the cooling water which is guided through cooling water passage 18 is indicated by arrows in FIG. 2.

Thus constructed electrically-operated pump 11 is operated as follows. When drive circuit 29a of control device 29 actuates to energize electromagnetic coil 28 in response to the signal output from electronic controller 50, stator 17 is excited to rotatively drive pump rotor 15 in a predetermined rotational direction. Depending on the predetermined rotational direction, the cooling water on a side of first connecting portion 22a is pressurized and fed to a side of second connecting portion 22b or the cooling water on the side of second connecting portion 22b is pressurized and fed to the side of first connecting portion 22a.

Referring to FIG. 3 to FIG. 8, an operation of cooling system 10 of this embodiment is explained hereinafter. FIG. 8 is a flow chart of a control routine that is executed by electronic controller 50.

When an ignition switch is turned on, the control routine of electronic controller 50 starts and goes to step S1 shown in FIG. 8. In step S1, a temperature of the cooling water in engine 1, namely, a temperature of the cooling water in each of water jackets 2a and 2b, is detected by the water temperature sensor provided in engine 1. Then, the routine proceeds to step S2.

In step S2, electronic controller 50 judges whether or not the detected temperature of the cooling water in engine 1, namely, the detected temperature of the cooling water in each of water jackets 2a and 2b, is a first preset value or less. That is, in step S2, electronic controller 50 compares the detected cooling water temperature with the first preset value on the basis of the information of the detected cooling water temperature which is transmitted from the water temperature sensor. In this embodiment, the first preset value of the cooling water temperature is set to 50° C. When the answer to step S2 is in the affirmative indicative that the detected temperature of the cooling water in engine 1 is not more than the first preset value, the routine proceeds to step S3.

In step S3, electronic controller 50 transmits a control signal for reverse rotation of electrically-operated pump 11 to control device 29 of electrically-operated pump 11. In response to the control signal, control device 29 is actuated to rotate electrically-operated pump 11 in the reverse direction. Then, electrically-operated pump 11 is rotated in the reverse direction to thereby discharge the cooling water that remains in return passage 6 and water jackets 2a and 2b therefrom toward reservoir tank 3 via flow control valve 9 and thermostatically-operated valve 8 as shown in FIG. 3.

In this embodiment, a valve opening temperature at which thermostatically-operated valve 8 is opened is set at a second preset value larger than the first preset value, i.e., 50° C., of the cooling water temperature. In this embodiment, the second preset value is set to 82° C. Thermostatically-operated valve 8, therefore, is kept in the closed state under the condition that the cooling water temperature is not more than the first preset value. That is, when the cooling water temperature is not more than the first preset value, cooling water passage 5 is closed by thermostatically-operated valve 8, and therefore, the cooling water discharged from engine 1 by electrically-operated pump 11 is returned to reservoir tank 3 through bypass passage 7.

Further, under the condition that electrically-operated pump 11 is rotated in the reverse direction, the cooling water returned into reservoir tank 3 can be prevented from flowing into engine 1 through return passage 6. This is because, as shown in FIG. 4, reservoir tank 3 has the volumetric capacity capable of storing a whole amount of the cooling water in the respective passages of cooling system 10, and reservoir tank 3 is connected on the upper wall thereof with return passage 6. Particularly, the communication port through which reservoir tank 3 is communicated with return passage 6 is provided on the upper wall of reservoir tank 3. With this simple construction, the cooling water within reservoir tank 3 can be prevented from flowing into engine 1 through return passage 6.

As described above, when engine 1 is in the cooled state, the cooling water remaining within engine 1 is forcibly discharged from engine 1 by rotating electrically-operated pump 11 in the reverse direction. Therefore, there is no possibility of disturbing a warm-up performance of engine 1 due to the cooling water as cooling medium. This results in facilitating warm-up of engine 1.

Next, electronic controller 50 monitors temperatures of the respective walls of cylinder block 1a and cylinder head 1b by the temperature sensors. Electronic controller 50 further compares the temperature of the respective walls of cylinder block 1a and cylinder head 1b with the first preset value on the basis of the temperature information input from the temperature sensors. In step S4 shown in FIG. 8, the temperature of the wall of cylinder head 1b is detected by the corresponding temperature sensor. In step S5, it is judged whether or not the temperature of the wall of cylinder head 1b is more than the first preset value.

When the answer to step S5 is in the affirmative indicative that the temperature of the wall of cylinder head 1b is more than the first preset value, that is, engine 1 is in the warmed state, the routine proceeds to step S6 shown in FIG. 8, where positive rotation of electrically-operated pump 11 is provided. When the answer to step S5 is in the negative indicative that the temperature of the wall of cylinder head 1b is the first preset value or less, the routine goes back to step S4. Electrically-operated pump 11 is kept rotating in the reverse direction until the temperature of the wall of cylinder head 1b becomes more than the first preset value.

In step S6, electronic controller 50 transmits a control signal for positive rotation of electrically-operated pump 11 to control device 29 of electrically-operated pump 11. In response to the control signal, control device 29 is actuated to rotate electrically-operated pump 11 in the positive direction Then, electrically-operated pump 11 is rotated in the positive direction to thereby supply the cooling water stored in reservoir tank 3 toward engine 1 as shown in FIG. 5 and FIG. 6. Thus, cooling of engine 1 is started.

In this condition, when the temperature of the cooling water is below the second preset value, thermostatically-operated valve 8 is kept in the closed state in which the cooling water is introduced into engine 1 through bypass passage 7.

Further, an amount of the cooling water to be supplied toward engine 1 is controlled by flow control valve 9 such that the flow of the cooling water is gradually increased depending on the temperature condition of engine 1. Owing to the control by flow control valve 9, engine 1 immediately after the warm-up is completed can be prevented from being rapidly cooled by supplying a large amount of the cooling water thereto. This serves for suppressing malfunction of engine 1 which is caused due to the rapid temperature change.

Since the temperature of engine 1 in the warmed state gradually rises even though the cooling water is circulated through engine 1, the temperature of the cooling water in engine 1 is monitored even after completion of the warm-up of engine 1. Therefore, in step S7 shown in FIG. 8, the temperature of the cooling water in engine 1 is detected. The routine then proceeds to step S8 shown in FIG. 8, where electronic controller 50 compares the temperature of the cooling water in engine 1 with the second preset value on the basis of the temperature information input from the temperature sensors. That is, in step S8, electronic controller 50 judges whether or not the temperature of the cooling water in engine 1 is the second preset value or less.

When the answer to step S8 is in the negative indicative that the detected cooling water temperature is more than the second preset value, the routine proceeds to step S9 shown in FIG. 8. Incidentally, when the temperature of the cooling water in engine 1 already exceeds the second preset value at the engine start-up, the routine jumps to step S9.

In step S9, thermostatically-operated valve 8 is operated to move to an open position in which cooling water passage 5 is opened and bypass passage 7 is closed. In this state, the communication between cooling water passage 5 and electrically-operated pump 11 is allowed, while the communication between bypass passage 7 and electrically-operated pump 11 is blocked. The cooling water cooled by radiator 4 is allowed to be supplied into engine 1 through cooling water passage 5 as shown in FIG. 7.

When the answer to step S2 is in the negative indicative that electronic controller 50 judges that the temperature of the cooling water at the engine start-up already exceeds the first preset value, the routine proceeds to step S6. That is, when engine 1 is already in the warmed state at start-up of engine 1, the routine proceeds to step S6.

When the answer to step S8 is in the affirmative indicative that the detected cooling water temperature is not more than the second preset value, the routine goes back to step S7.

Electrically-operated pump 11 and cooling system 10 according to the first embodiment of the present invention have the following functions and effects.

Since electrically-operated pump 11 is driven to rotate in both the positive direction and the reverse direction, sucking and discharging of cooling water can be readily performed by changing the rotational direction of electrically-operated pump 11 between the positive direction and the reverse direction on the basis of an operating condition of engine 1. Further, cooling system 10 can perform suitable cooling of engine 1 depending on the temperature condition of engine 1. Further, cooling system 10 can forcibly discharge the cooling water in engine 1 from engine 1 when engine 1 is in the cooled state. The cooling water remaining in engine 1, therefore, can be efficiently discharged. As a result, a warm-up performance of engine 1 can be surely and sufficiently enhanced.

Further, in this embodiment, the warm-up of engine 1 can be facilitated by simply controlling the rotational direction of electrically-operated pump 11. Owing to the simple control, it is unnecessary to conduct complicated control for warm-up of engine 1 by using multiple control valves. It is also unnecessary to increase the number of parts of electrically-operated pump 11 and complicate the construction of cooling system 10. This serves for minimizing the production costs.

Further, in cooling system 10, the cooling circuit for circulating the cooling water is not opened to atmosphere. Cooling system 10 can be applied to a so-called pressure-type cooling circuit that currently comes dominate.

Furthermore, the condition for returning the cooling water in engine 1 to reservoir tank 3 by rotating electrically-operated pump 11 in the reverse direction is not limited to the first embodiment in which the cooling water in engine 1 is returned to reservoir tank 3 under the condition that the temperature of the cooling water in engine 1 is not more than the first preset value when the ignition switch of engine 1 is turned on. Return of the cooling water in engine 1 to reservoir tank 3 may be carried out under the condition that the temperature of the cooling water in engine 1 is not more than the first preset value after engine 1 is stopped. In such a case, when the ignition switch of engine 1 is turned on the next time, the cooling water has been already discharged from engine 1. Therefore, it is possible to further facilitate warm-up of engine 1.

Referring to FIG. 9 and FIG. 10, there is shown the cooling system of a second embodiment, which differs from the first embodiment in arrangement of the communication port between reservoir tank 3 and return passage 6 and provision of an outflow block device of suppressing an outflow of the cooling water in reservoir tank 3 toward engine 1 through return passage 6.

As shown in FIG. 9 and FIG. 10, the communication port through which reservoir tank 3 is communicated with return passage 6 on the other side wall opposed to the one side wall to which cooling water passage 5 is connected. The communication port between reservoir tank 3 and return passage 6 is disposed on a lower portion of the other side wall of reservoir tank 3 so as to be opposed to the communication port through which reservoir tank 3 is communicated with cooling water passage 5. Check valve 31 is disposed near the communication port between reservoir tank 3 and return passage 6 on the other side wall of reservoir tank 3. Check valve 31 is operative to block an outflow of the cooling water which flows from reservoir tank 3 into return passage 6 and thus serves as the outflow block device.

Specifically, check valve 31 is arranged on an inner surface of the other side wall of reservoir tank 3 and includes flap 32 that is pivotally moveably disposed on the inner surface of the other side wall of reservoir tank 3. Flap 32 is formed into a generally rectangular shape and has such an area as to cover the communication port between reservoir tank 3 and return passage 6 which is exposed to return passage 6 through the other side wall of reservoir tank 3. Flap 32 is pivotally moveable about one of four side edges thereof which is supported by a periphery of the opening of reservoir tank 3. Each of the four side edges of flap 32 has a length larger than a diameter of the communication port between reservoir tank 3 and return passage 6. With this construction, flap 32 can be prevented from pivotally moving toward an outside of reservoir tank 3 but can be permitted to pivotally move toward an inside of reservoir tank 3.

When electrically-operated pump 11 is rotated in the reverse direction to thereby return the cooling water in engine 1 to reservoir tank 3, flap 32 of check valve 31 is brought into press-contact with the periphery of the communication port between reservoir tank 3 and return passage 6 as shown in FIG. 9 in accordance with a pressure of the pressurized cooling water that is fed by electrically-operated pump 11. The communication port between reservoir tank 3 and return passage 6 is fully covered with flap 32, so that the cooling water in reservoir tank 3 can be prevented from flowing into return passage 6 from the communication port between reservoir tank 3 and return passage 6.

On the other hand, when the cooling water in respective water jackets 2a and 2b of engine 1 is circulated into reservoir tank 3 through return passage 6 under the condition that electrically-operated pump 11 is rotated in the positive direction to thereby circulate the cooling water through cooling system 10, flap 32 of check valve 31 is urged to move toward the inside of reservoir tank 3 against the pressure of the cooling water in reservoir tank 3 as shown in FIG. 10 in accordance with a pressure of the pressurized cooling water that is fed by electrically-operated pump 11. The communication port between reservoir tank 3 and return passage 6 becomes uncovered, so that the cooling water can be permitted to flow into reservoir tank 3 through return passage 6.

In the second embodiment provided with thus simply constructed check valve 31 in reservoir tank 3, an outflow of the cooling water from reservoir tank 3 into return passage 6 can be surely suppressed as well as the first embodiment. Particularly, since check valve 31 has a remarkably simplified construction, the production costs which is caused by using check valve 31 can be minimized.

Referring to FIG. 11 and FIG. 12, there is shown check valve 131 of a modification of the second embodiment, which differs in construction and arrangement from check valve 31 of the second embodiment.

FIG. 11 shows check valve 131 in a closing position, and FIG. 12 shows check valve 131 in an open position. As shown in FIG. 11 and FIG. 12, check valve 131 includes valve body 33 that is moveable in a direction perpendicular to the other side wall of reservoir tank 3, and valve support 34 that supports valve body 33.

Specifically, valve body 33 includes small-diameter shaft portion 33a that has a predetermined axial length, and large-diameter portion 33b that is connected with small-diameter shaft portion 33a and formed to be stepwisely increased in diameter with respect to small-diameter shaft portion 33a. Small-diameter shaft portion 33a is formed in the middle of valve body 33 and supported by valve support 34 so as to be slidable relative to valve support 34 in an axial direction of valve body 33. Large-diameter portion 33b is configured to cover the communication port between reservoir tank 3 and return passage 6.

Large-diameter portion 33b has generally conical tapered portion 33c at a connection with small-diameter shaft portion 33a, and a tip end portion formed into a generally spherical shape. Tapered portion 33c has a diameter that gradually increases from the side of small-diameter shaft portion 33a toward the distal end of valve body 33. As shown in FIG. 11, when check valve 131 is in the closing- position, valve body 33 is urged toward return passage 6 by the pressure of the cooling water in reservoir tank 3 to thereby press tapered portion 33c of large-diameter portion 33b against the periphery of the communication port between reservoir tank 3 and return passage 6. Large-diameter portion 33b thus acts to fully cover the communication port between reservoir tank 3 and return passage 6.

Valve support 34 includes annular support portion 34a that has an inner diameter slightly larger than an outer diameter of small-diameter shaft portion 33a, and fixing portion 34b that fixes annular support portion 34a to an inner wall surface of a pipe which defines return passage 6. Annular support portion 34a is disposed within return passage 6 and surrounds small-diameter shaft portion 33a of valve body 33. In this modification, four fixing portions 34b are arranged on an outer circumferential periphery of annular support portion 34a at intervals of about 90 degrees in the circumferential direction of annular support portion 34a. Fixing portion 34b is formed into a projection shape that projects from the outer circumferential periphery of annular support portion 34a in a radial direction of annular support portion 34a.

Valve body 33 further includes intermediate-diameter portion 33d that is connected to small-diameter shaft portion 33a at a rear end portion of valve body 33 so as to for a stepped portion with respect to small-diameter shaft portion 33a. Intermediate-diameter portion 33d has an outer diameter larger than an inner diameter of annular support portion 34a of valve support 34. With the provision of intermediate-diameter portion 33d, when valve body 33 is moved toward the inside of reservoir tank 3 to thereby open the communication port between reservoir tank 3 and return passage 6, valve body 33 can be prevented from being removed from valve support 34.

When electrically-operated pump 11 is rotated in the reverse direction to thereby return the cooling water in engine 1 to reservoir tank 3, valve body 33 of check valve 131 is urged to move toward return passage 6 and tapered portion 33c of large-diameter portion 33b is brought into press-contact with the periphery of the communication port between reservoir tank 3 and return passage 6 as shown in FIG. 11 owing to a pressure of the pressurized cooling water that is fed by electrically-operated pump 11. The communication port between reservoir tank 3 and return passage 6 is fully covered with tapered portion 33c, so that the cooling water in reservoir tank 3 can be prevented from flowing into return passage 6 through the communication port between reservoir tank 3 and return passage 6.

On the other hand, when the cooling water in respective water jackets 2a and 2b of engine 1 is circulated into reservoir tank 3 through return passage 6 under the condition that electrically-operated pump 11 is rotated in the positive direction to thereby circulate the cooling water through cooling system 10, the cooling water is allowed to flow through a space between the inner wall surface of return passage 6 and an outer circumferential surface of annular support portion 34a of valve support 34 and reach the one end of return passage 6. Valve body 33 of check valve 31 is urged to move toward the inside of reservoir tank 3 against the pressure of the cooling water in reservoir tank 3 as shown in FIG. 12 owing to a pressure of the pressurized cooling water that is fed by electrically-operated pump 11. The communication port between reservoir tank 3 and return passage 6 becomes open, so that the cooling water can be permitted to flow into reservoir tank 3 through return passage 6.

As described above, check valve 131 is constructed such that tapered portion 33c of valve body 33 is brought into press-contact with the periphery of the communication port between reservoir tank 3 and return passage 6 to thereby close the communication port between reservoir tank 3 and return passage 6. With the provision of check valve 131, hermeticity of reservoir tank 3 can be enhanced, serving for more effectively suppress an outflow of the cooling water from reservoir tank 3 into return passage 6.

Further, valve body 33 has tapered portion 33c on large-diameter portion 33b which is opposed to the communication port between reservoir tank 3 and return passage 6 and tapered from the side of reservoir tank 3 toward the side of return passage 6. With the provision of tapered portion 33c, when the cooling water flows from the communication port into reservoir tank 3 through return passage 6, the cooling water is guided along an outer circumferential surface of tapered portion 33c. This results in reduction of flow resistance of the cooling water flowing-from return passage 6 into reservoir tank 3, serving for smooth introduction of the cooling water into reservoir tank 3.

Referring to FIG. 13, the cooling system of a third embodiment of the present invention is explained, which differs from the first embodiment in control of electrically-operated pump 11. That is, in the third embodiment, electrically-operated pump 11 is controlled by a so-called timer control that is conducted on the basis of an elapsed time from a moment at which the ignition switch is turned on. The construction and the function of electrically-operated pump 11 and other components, such as reservoir tank 3 and flow control valve 9, of the cooling system of this embodiment are the same as those of the first embodiment, and therefore, detailed explanations therefor are omitted.

FIG. 13 is a flow chart of a control routine that is executed by electronic controller 50 in the third embodiment. When the ignition switch is turned on, the control routine of electronic controller 50 starts and goes to step S11 shown in FIG. 13. In step S11, a temperature of the cooling water in engine 1, namely, a temperature of the cooling water in each of water jackets 2a and 2b, is detected by the water temperature sensor provided in engine 1. Then, the routine proceeds to step S12.

In step S12, electronic controller 50 judges whether or not the detected temperature of the cooling water in engine 1, namely, the detected temperature of the cooling water in each of water jackets 2a and 2b, is a first preset value (50° C. in this embodiment) or less. That is, electronic controller 50 compares the detected cooling water temperature with the first preset value on the basis of the information of the detected cooling water temperature which is transmitted from the water temperature sensor. When the answer to step S12 is in the affirmative indicative that the detected cooling water temperature is not more than the first preset value, the routine proceeds to step S13.

In step S13, electronic controller 50 transmits a control signal for reverse rotation of electrically-operated pump 11 to control device 29 of electrically-operated pump 11. In response to the control signal, control device 29 is actuated to rotate electrically-operated pump 11 in the reverse direction. Then, electrically-operated pump 11 is rotated in the reverse direction to thereby discharge the cooling water that remains in return passage 6 and water jackets 2a and 2b therefrom toward reservoir tank 3 via flow control valve 9 and thermostatically-operated valve 8 as shown in FIG. 3. The routine proceeds to step S14.

In step S14, a time elapsed from the moment at which the ignition switch is turned on is counted. The routine proceeds to step S15 where electronic controller 50 judges whether or not counting of a predetermined time that corresponds to a warm-up time for engine 1 is completed by comparing the elapsed time with the predetermined time. When the answer to step S15 is in the affirmative indicative that the elapsed time reaches the predetermined time and the predetermined time counting is completed, the routine proceeds to step S16. When the answer to step S15 is in the negative, the routine goes back to step S16. That is, until the predetermined time has elapsed, electrically-operated pump 11 is kept rotating in the reverse direction to thereby return the cooling water to reservoir tank 3.

In step S16, electronic controller 50 transmits a control signal for positive rotation of electrically-operated pump 11 to control device 29 of electrically-operated pump 11. In response to the control signal, control device 29 is actuated to rotate electrically-operated pump 11 in the positive direction. Then, electrically-operated pump 11 is rotated in the positive direction to thereby supply the cooling water stored in reservoir tank 3 toward engine 1 as shown in FIG. 5 and FIG. 6. Thus, cooling of engine 1 is started.

Since the temperature of engine 1 in the warmed state gradually rises even though the cooling water is circulated in engine 1, the temperature of the cooling water in engine 1 is monitored even after completion of the warm-up of engine 1. Therefore, in step S17 shown in FIG. 13, where the temperature of the cooling water in engine 1 is detected. The routine then proceeds to step S18 shown in FIG. 13, where electronic controller 50 judges whether or not the temperature of the cooling water in engine 1 is not more than a second preset value (82° C. in this embodiment) more than the first preset value on the basis of the temperature information input from the temperature sensors.

When the answer to step S18 is in the negative indicative that the detected cooling water temperature is more than the second preset value, the routine proceeds to step S19. Incidentally, when the temperature of the cooling water in engine 1 already exceeds the second preset value at the engine start-up, the routine jumps to step S19.

In step S19, thermostatically-operated valve 8 is operated to move an open position in which cooling water passage 5 is opened and bypass passage 7 is closed. The cooling water cooled by radiator 4 is allowed to be supplied into engine 1 through cooling water passage 5 as shown in FIG. 7.

When the answer to step S12 is in the negative indicative that electronic controller 50 judges that the temperature of the cooling water at the engine start-up already exceeds the first preset value, the routine proceeds to step S16. That is, when engine 1 is already in the warmed state at start-up of engine 1, the routine proceeds to step S16.

When the answer to step S18 is in the affirmative indicative that the detected cooling water temperature is not more than the second preset value, the routine goes back to step S17.

In the third embodiment, completion of the warm-up of engine 1 is judged by the timer control as described above. It is possible to enhance the warm-up performance of engine 1 using the thus simplified control. This serves for effectively suppressing increase in the production costs.

Further, the control of the rotational direction of electrically-operated pump 11 is not limited to this embodiment in which the rotational direction of electrically-operated pump 11 is selected on the basis of the temperature of the cooling water in engine 1 as shown in steps S11 and S12. The control of the rotational direction of electrically-operated pump 11 may be conducted only on the basis of the timer control as shown in step S13 to step S19. For instance, the rotational direction of electrically-operated pump 11 may be controlled as follows. When the ignition switch is turned on, electrically-operated pump 11 is allowed to rotate in the reverse direction and when the predetermined time has elapsed from the moment at which the ignition switch is turned on, the rotational direction of electrically-operated pump 11 is switched from the reverse direction to the positive direction. In such a case, it is possible to enhance the warm-up performance of engine 1 by the remarkably simple control, thereby serving for more effectively suppressing the production costs.

Referring to FIG. 14 and FIG. 15, there is shown cooling system 300 according to a fourth embodiment of the present invention, which differs from the first embodiment in that first water jacket 2a in cylinder block 1a and second water jacket 2b in cylinder head 1b are formed independently from each other, and changeover of the cooling water passage between first and second water jackets 2a and 2b is carried out depending on the respective temperatures of cylinder block 1a and cylinder head 1b.

As shown in FIG. 14, electrically-operated pump 11 is connected to the front end portion of cylinder block 1a through communication passage 42 that extends between electrically-operated pump 11 and the front end portion of cylinder block 1a. Communication passage 42 is branched into first communication passage 35 that is connected to one end of first water jacket 2a, and second communication passage 36 that is connected to one end of second water jacket 2b. First communication passage 35 serves as low-temperature side passage that is connected to a low-temperature portion, i.e., cylinder block 1a, of engine 1, and second communication passage 36 serves as high-temperature side passage that is connected to a high-temperature portion, i.e., cylinder head 1b, of engine 1. Directional control valve 37 is disposed at a branch point between first and second communication passages 35 and 36. Directional control valve 37 is electrically connected to electronic controller 50 and operative to distribute the flow of the cooling water between first and second communication passages 35 and 36 in an optional ratio. A part of the flow of the cooling water which is distributed to first communication passage 35 is supplied to first water jacket 2a, and the remainder of the flow of the cooling water which is distributed to second communication passage 36 is-supplied to second water jacket 2b.

First circulating passage 38 extends from the other end of first water jacket 2a toward return passage 6. Second circulating passage 39 extends from the other end of second water jacket 2b toward return passage 6. First circulating passage 38 and second circulating passage 39 are joined with each other and merged into return passage 6. Thus, first and second circulating passages 38 and 39 constitute a part of return passage 6. Further, flow control valve 40 is disposed in second water jacket 2b on the side of one end of second circulating passage 39. Flow control valve 40 is operative to control an amount of the flow of the cooling water which is circulated to reservoir tank 3 through second water jacket 2b.

Referring to FIG. 15, a control routine of cooling system 300 of the fourth embodiment is explained hereinafter. When an ignition switch of engine 1 is turned on, the control routine starts and goes to step S21 shown in FIG. 15. In step S21, a temperature of the cooling water in engine 1, namely, a temperature of the cooling water in each of water jackets 2a and 2b, is detected by the water temperature sensor provided in engine 1. Then, the routine proceeds to step S22.

In step S22, electronic controller 50 judges whether or not the detected temperature of the cooling water in engine 1, namely, the detected temperature of the cooling water in each of water jackets 2a and 2b, is a first preset value (50° C. in this embodiment) or less. That is, in step S22, electronic controller 50 compares the detected cooling water temperature with the first preset value on the basis of the information of the detected cooling water temperature which is transmitted from the water temperature sensor. When the answer to step S22 is in the affirmative indicative that the detected cooling water temperature is not more than the first preset value, the routine proceeds to step S23.

In step S23, electronic controller 50 transmits a control signal for reverse rotation of electrically-operated pump 11 to control device 29 of electrically-operated pump 11. In response to the control signal, control device 29 is actuated to rotate electrically-operated pump 11 in the reverse direction. Then, electrically-operated pump 11 is rotated in the reverse direction to thereby discharge the cooling water in first water jacket 2a and a part of the cooling water in return passage 6 therefrom toward reservoir tank 3 via first communication passage 35 shown in FIG. 14. At the same time, the cooling water in second water jacket 2b and the remainder of the cooling water in return passage 6 are discharged therefrom toward reservoir tank 3 via second communication passage 36 shown in FIG. 14. In this condition, similar to the first embodiment, thermostatically-operated valve 8 is in the closed position where cooling water passage 5 is closed and bypass passage 7 is opened. The discharged cooling water, therefore, is returned to reservoir tank 3 through bypass passage 7.

Subsequently, electronic controller 50 monitors temperatures of the respective walls of cylinder block 1a and cylinder head 1b by the temperature sensors. Electronic controller 50 further compares the temperatures of the respective walls of cylinder block 1a and cylinder head 1b with the first preset value on the basis of the temperature information input from the temperature sensors. Here, since the temperature of cylinder head 1b rises earlier than the temperature of cylinder block 1a, in step S24 shown in FIG. 15, the temperature of the wall of cylinder head 1b is detected by the corresponding temperature sensor, and in step S25 shown in FIG. 15, it is judged whether or not the temperature of the wall of cylinder head 1b is more than the first preset value on the basis of the temperature information input from the corresponding temperature sensor.

When the answer to step S25 is in the affirmative indicative that the temperature of the wall of cylinder head 1b is more than the first preset value even when the temperature of the wall of cylinder block 1a is below the first preset value, the routine proceeds to step S26. In step S26, electronic controller 50 transmits a control signal for operating directional control valve 37 so as to close first communication passage 35. Then, the routine proceeds to step S27 where electronic controller 50 transmits a control signal for positive rotation of electrically-operated pump 11 to control device 29 of electrically-operated pump 11.

In response to the control signal, control device 29 is actuated to rotate electrically-operated pump 11 in the positive direction. Then, electrically-operated pump 11 is rotated in the positive direction to thereby supply the cooling water stored in reservoir tank 3 toward engine 1. Since first communication passage 35 is closed by directional control valve 37 as described above, the cooling water in reservoir tank 3 is supplied to only second water jacket 2b through second communication passage 36. At this time, if the temperature of the cooling water in engine 1 is below a second preset value (82° C. in this embodiment) more than the first preset value, the cooling water is introduced into second communication passage 36 through bypass passage 7.

Specifically, owing to the positive rotation of electrically-operated pump 11, the cooling water stored in reservoir tank 3 is introduced into second communication passage 36 through cooling water passage 5 between thermostatically-operated valve 8 and electrically-operated pump 11. The cooling water passes through second water jacket 2b, then flowing into return passage 6 via second circulating passage 39. The cooling water is returned to reservoir tank 3 through return passage 6. That is, when only the temperature of the wall of cylinder head 1b exceeds the first preset value, the cooling water is circulated through only cylinder head 1b without flowing through cylinder block 1a.

Electronic controller 50 further transmits a control signal for controlling electrically-operated pump 11 such that an amount of the cooling water suitable for the temperature condition of cylinder head 1b is supplied to cylinder head 1b. As the temperature of cylinder head 1b rises, the amount of the cooling water to be supplied is gradually increased. As a result, cylinder head 1b can be prevented from being rapidly cooled to thereby suppress malfunction of engine 1 which is caused due to the rapid cooling of cylinder head 1b.

Next, the routine proceeds to step S28 shown in FIG. 15, where the temperature of the wall of cylinder block 1a is detected by the corresponding temperature sensor. The routine then proceeds to step S29 shown in FIG. 15, where electronic controller 50 judges whether or not the temperature of the wall of cylinder block 1a is more than the first preset value on the basis of the temperature information input from the corresponding temperature sensor.

When the answer to step S29 is in the affirmative indicative that the temperature of the wall of cylinder block 1a is more than the first preset value, the routine proceeds to step S30. In step S30, electronic controller 50 transmits a control signal for operating directional control valve 37 so as to open first communication passage 35 in addition to second communication passage 36. The cooling water is thus supplied into first water jacket 2a through first communication passage 35 and second water jacket 2b through second communication passage 36. At this time, directional control valve 37 is controlled so as to gradually introduce the cooling water into first water jacket 2a in order to avoid rapid cooling of cylinder block 1a.

Since the temperature of engine 1 in the warmed state gradually rises even though the cooling water is circulated through engine 1, electronic controller 50 monitors the temperature of the cooling water in engine 1 even after completion of the warm-up of engine 1. Therefore, in step S31 shown in FIG. 15, where the temperature of the cooling water in engine 1 is detected. The routine then proceeds to step S32 shown in FIG. 15, where electronic controller 50 judges whether or not the temperature of the cooling water in engine 1 is the second preset value or less on the basis of the temperature information input from the temperature sensors.

When the answer to step S32 is in the negative indicative that the detected cooling water temperature is more than the second preset value, the routine proceeds to step S33 shown in FIG. 15. In step S33, thermostatically-operated valve 8 is operated to move to the open position in which cooling water passage 5 is opened. The cooling water cooled by radiator 4 is allowed to be supplied into engine 1 through cooling water passage 5.

When the answer to step S22 is in the negative indicative that electronic controller 50 judges that the temperature of the cooling water at the engine start-up already exceeds the first preset value, the routine jumps to step S31. That is, when engine 1 is already in the warmed state at start-up of engine 1, the routine jumps to step S31.

When the answer to step S25 is in the negative indicative that the temperature of the wall of cylinder head 1b is the first preset value or less, the routine goes back to step S24.

When the answer to step S29 is in the negative indicative that the temperature of the wall of cylinder block 1a is the first preset value or less, the routine goes back to step S28.

Incidentally, when the temperature of the cooling water in engine 1 already exceeds the second preset value at the engine start-up, the routine jumps to step S33.

The fourth embodiment can attain the same functions and effects of the first embodiment. In addition, in the fourth embodiment, there are provided the separate cooling water passages, namely, first and second communication passages 35 and 36, for feeding the cooling water to cylinder block 1a and cylinder head 1b which are different in temperature rising speed from each other. With this construction, introduction of the cooling water into different parts of engine 1 which are in a warmed state and in a cooled state, respectively, can be carried out separately. That is, it is possible to introduce the cooling water into a part of engine 1 when the part of engine 1 has been completed in warming-up, and prevent the cooling water from being introduced into another part of engine 1 which is in a cooled state. As a result, the part of engine 1 which has been completed in warming-up can be prevented from being overheated, and the part of engine 1 which is in a cooled state can be prevented from being deteriorated in warm-up performance thereof. This serves for more effectively enhancing the warm-up performance of engine 1.

Further, the construction of first water jacket 2a in cylinder block 1a and second water jacket 2b in cylinder head 1b is not limited to the fourth embodiment in which first water jacket 2a and second water jacket 2b are formed in engine 1 independently from each other without being communicated with each other. For instance, even in a case where first water jacket 2a and second water jacket 2b are communicated with each other as explained in the first embodiment, the same function and effect as those of the fourth embodiment can be obtained by separately providing the introducing passages for introducing the cooling water into respective water jackets 2a and 2b and the circulating passages for returning from respective water jackets 2a and 2b to reservoir tank 3 and by providing a partition between water jackets 2a and 2b which blocks the communication therebetween.

Further, layout of respective water jackets 2a and 2b and layout of piping of the cooling water circuit which acts as passages for the cooling water are not limited to the above embodiments and may be optionally modified on the basis of specifications of vehicles.

Further, the so-called timer control as described in the third embodiment can be applied to the fourth embodiment. For instance, the timing in supplying the cooling water into cylinder block 1a and the timing in supplying the cooling water into cylinder head 1b can be controlled by using an elapsed time from a moment at which the ignition switch is turned on. In this case, it is possible to effectively enhance a warm-up performance of engine 1 by using the simple control.

Further, regulation of an amount of the cooling water which is supplied into engine 1 immediately after completion of the warm-up of engine 1 is not limited to the regulation using flow control valve 9 as explained in the above embodiments. The amount of the cooling water can be regulated by controlling an amount of the cooling water which is discharged by electrically-operated pump 11, without using flow control valve 9.

Further, in the above embodiments, the rotational direction of electrically-operated pump 11 is selectively controlled on the basis of the temperature of the cooling water in engine 1. However, the control of the rotational direction of electrically-operated pump 11 can be carried out on the basis of only a temperature of the wall of engine 1 or a temperature of thermostatically-operated valve 8. Especially, in a case where the control of the rotational direction of electrically-operated pump 11 is carried out on the basis of only the temperature of the wall of engine 1, it is not necessary to use temperature information that is input from the water temperature sensors. Therefore, in this case, the control of the rotational direction of electrically-operated pump 11 can be conducted by further simplified control, serving for suppressing the production cost of the cooling system.

Furthermore, in the first and fourth embodiments, the temperature of the wall of engine 1 is used as a reference for judgment as to whether or not warm-up of engine 1 is completed. However, the completion of warm-up of engine 1 can be judged using the temperature of the cooling water remaining in engine 1. In this case, the respective temperature sensors for sensing the temperature of the wall of engine 1 can be omitted, and therefore, the cooling system can be more simplified in construction and the rotational direction of electrically-operated pump 11 can be controlled by further simplified control. This serves for further suppressing the production cost of the cooling system.

This application is based on a prior Japanese Patent Application No. 2007-207349 filed on Aug. 9, 2007. The entire contents of the Japanese Patent Application No. 2007-207349 are hereby incorporated by reference.

Although the invention has been described above by reference to certain embodiments of the invention and modifications of the embodiments, the invention is not limited to the embodiments and modifications described above. Further modifications and variations of the embodiments and modifications described above will occur to those skilled in the art in light of the above teachings. The scope of the invention is defined with reference to the following claims.