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What is claimed is:

1. An engine cooling system which cools an engine by circulating cooling water in a circulation passage and controls a cooling degree of the engine according to an operating condition of the engine, the system including:

a flow rate regulating valve for regulating a circulation flow rate of the cooling water;

stop determining means for determining whether the engine is stopped; and

after-engine-stop control means for controlling the flow rate regulating valve to open at a predetermined opening whenever the engine is determined as being stopped by the stop determining means.

2. The engine cooling system according to claim 1, wherein the flow rate regulating valve includes a valve element, a valve seat corresponding to the valve element, an actuator for moving the valve element with respect to the valve seat,

the valve element is moved by operation of the actuator between a full-closed position in which the valve element is in full contact with the valve seat and a full-opened position in which the valve element is fully separated from the valve seat, and

the after-engine-stop control means, when the engine is determined as being stopped by the stop determining means, controls the actuator to move the valve element with respect to the valve seat to determine the predetermined opening degree.

3. The engine cooling system according to claim 2 further including an ignition switch which is operated to selectively start and stop the engine, wherein the stop determining means determines that the engine is stopped at the time when the ignition switch is turned off.

4. The engine cooling system according to claim 3, wherein the full-opened position corresponds to a 100% opening of the flow rate regulating valve, the full-closed position corresponds to a 0% opening, and the predetermined opening degree is a 50% opening with respect to the 100% opening.

5. The engine cooling system according to claim 3 further including cooling control means for controlling the cooling degree of the engine,

wherein the cooling control means controls the actuator of the flow rate regulating valve according to the operating condition of the engine to move the valve element for regulation of the circulation flow rate of the cooling water.

6. The engine cooling system according to claim 3, wherein the engine includes a cylinder block and an engine head both of which include a cooling-water passage including a water jacket, and the cooling-water passage is provided with an outlet and an inlet each of which is connected with a main piping line,

the main piping line includes a radiator, the flow rate regulating valve, and a water pump, which are disposed at predetermined positions respectively in the line,

the circulation passage includes the cooling-water passage and the main piping line, and

the water pump when actuated produces a flow of the cooling water in the main piping line to cause circulation of the cooling water through the cooling-water passage and the main piping line.

7. The engine cooling system according to claim 6 further including:

water temperature detection means which is disposed at an adjacent position to the outlet of the cooling-water passage and detects a temperature of the cooling water flowing out of the cooling-water passage;

operating condition detection means which detects the operating condition of the engine; and

cooling control means which controls the cooling degree of the engine by calculating a target water temperature according to the detected engine operating condition and feedback controlling the opening of the flow rate regulating valve based on the calculated target water temperature to bring the outlet side water temperature close to the target water temperature.

8. The engine cooling system according to claim 7, wherein the stop determining means, the after-engine-stop control means, and the cooling control means are constituted of an electronic control unit including a central processing unit, a memory, an external input circuit, and an external output circuit.

9. The engine cooling system according to claim 6 further including a by pass piping line disposed providing communication between a part of the main piping line positioned adjacent to the outlet of the cooling-water passage and the flow rate regulating valve,

wherein the valve element includes a first valve element for regulating a flow rate of the cooling water flowing through the main piping line and a second valve element for regulating a flow rate of the cooling water flowing through the bypass piping line, and

the valve seat includes a first valve seat corresponding to the first valve element and a second valve seat corresponding to the second valve element,

the first and second valve elements being moved simultaneously by operation of the actuator with respect to the corresponding first and second valve seats so that the first valve element is moved between a full-closed position in which the first valve element is in full contact with_the first valve seat and a full-opened position in which the valve element is fully separated from the first valve seat and the second valve element is moved between two closed positions in which the second valve element is in substantial contact with the second valve seat, the second valve element being fully opened at a predetermined position between the two closed positions.

10. The engine cooling system according to claim 9, wherein the full-opened position of the first valve element with respect to the first valve seat corresponds to a 100% opening and the full-closed position of the same corresponds to a 0% opening, and

the predetermined opening degree is a 50% opening with respect to the 100% opening.

11. The engine cooling system according to claim 10 further including cooling control means for controlling the cooling degree of the engine,

wherein the cooling control means controls the actuator of the flow rate regulating valve according to the operating condition of the engine to move the first and second valve elements for regulation of the circulation flow rate of the cooling water.

12. The engine cooling system according to claim 1, wherein the flow rate regulating valve includes a valve element, a valve seat corresponding to the valve element, an actuator for moving the valve element with respect to the valve seat,

the valve element is moved by operation of the actuator between a full-closed position in which the valve element is in full contact with the valve seat and a full-opened position in which the valve element is fully separated from the valve seat, and

the after-engine-stop control means controls the actuator to move the valve element to the full-closed position so that the valve element is brought into contact with the valve seat once and then move the valve element toward the full-opened position with reference to the full-closed position to determine the predetermined opening degree.

13. The engine cooling system according to claim 12 further including an ignition switch which is operated to selectively start and stop the engine, wherein the stop determining means determines that the engine is stopped at the time when the ignition switch is turned off.

14. The engine cooling system according to claim 13, wherein the full-opened position corresponds to a 100% opening of the flow rate regulating valve, the full-closed position corresponds to a 0% opening, and the predetermined opening degree is a 50% opening with respect to the 100% opening.

15. The engine cooling system according to claim 13 further including cooling control means for controlling the cooling degree of the engine,

wherein the cooling control means controls the actuator of the flow rate regulating valve according to the operating condition of the engine to move the valve element for regulation of the circulation flow rate of the cooling water.

16. The engine cooling system according to claim 13, wherein the engine includes a cylinder block and an engine head both of which include a cooling-water passage including a water jacket, and the cooling-water passage is provided with an outlet and an inlet each of which is connected with a main piping line,

the main piping line includes a radiator, the flow rate regulating valve, and a water pump, which are disposed at predetermined positions respectively in the line,

the circulation passage includes the cooling-water passage and the main piping line, and

the water pump when actuated produces a flow of the cooling water in the main piping line to cause circulation of the cooling water through the cooling-water passage and the main piping line.

17. The engine cooling system according to claim 16 further including:

water temperature detection means which is disposed at an adjacent position to the outlet of the cooling-water passage and detects a temperature of the cooling water flowing out of the cooling-water passage;

operating condition detection means which detects the operating condition of the engine; and

cooling control means which controls the cooling degree of the engine by calculating a target water temperature according to the detected engine operating condition and feedback controlling the opening of the flow rate regulating valve based on the calculated target water temperature to bring the outlet side water temperature close to the target water temperature.

18. The engine cooling system according to claim 17, wherein the stop determining means, the after-engine-stop control means, and the cooling control means are constituted of an electronic control unit including a central processing unit, a memory, an external input circuit, and an external output circuit.

19. The engine cooling system according to claim 16, further including a bypass piping line disposed providing communication between a part of the main piping line positioned adjacent to the outlet of the cooling-water passage and the flow rate regulating valve,

wherein the valve element includes a first valve element for regulating a flow rate of the cooling water flowing through the main piping line and a second valve element for regulating a flow rate of the cooling water flowing through the bypass piping line,

the valve seat includes a first valve seat corresponding to the first valve element and a second valve seat corresponding to the second valve element,

the first and second valve elements being moved simultaneously by operation of the actuator with respect to the corresponding first and second valve seats so that the first valve element is moved between a full-closed position in which the first valve element is in full contact with the first valve seat and a full-opened position in which the valve element is fully separated from the first valve seat and the second valve element is moved between two closed positions in which the second valve element is in substantial contact with the second valve seat, the second valve element being fully opened at a predetermined position between the two closed positions.

20. The engine cooling system according to claim 19, wherein the full-opened position of the first valve element with respect to the first valve seat corresponds to a 100% opening and the full-closed position of the same corresponds to a 0% opening, and

the predetermined opening degree is a 50% opening with respect to the 100% opening.



Related entries:

Water pump, cooling system