Cooling device for internal combustion engine and control method for cooling device

1. A cooling device for an internal combustion engine, comprising:

a plurality of cooling liquid lines including a first cooling liquid line routed by way of a radiator and a cylinder head of the internal combustion engine while bypassing a cylinder block thereof, and a second cooling liquid line routed by way of the cylinder block while bypassing the radiator;

an electric flow rate control valve which has a plurality of inlet ports connected to outlets respectively of the plurality of cooling liquid lines, and which controls supply rates of cooling liquid respectively to the plurality of cooling liquid lines;

a bypass line that branches off from the first cooling liquid line at a point between the cylinder head and the radiator and that connects with an outlet port of the flow rate control valve while bypassing the radiator;

a mechanical water pump which is driven by the internal combustion engine to circulate the cooling liquid; and

an electric water pump which is driven by a motor to circulate the cooling liquid.

2. The cooling device for the internal combustion engine according to claim 1 , further comprising, as one of the plurality of cooling liquid lines, a third cooling liquid line routed by way of the cylinder head and a heater core while bypassing the radiator.

3. The cooling device for the internal combustion engine according to claim 2 , further comprising, as one of the plurality of cooling liquid lines, a fourth cooling liquid line routed by way of the cylinder head and a power transmission device of the internal combustion engine while bypassing the radiator.

4. The cooling device for the internal combustion engine according to claim 1 , wherein

the outlet port of the flow rate control valve is connected to an intake port of the mechanical water pump,

an outlet of the bypass line is connected to a point between the outlet port of the flow rate control valve and the intake port of the mechanical water pump, and

the electric water pump is disposed on the bypass line.

5. The cooling device for the internal combustion engine according to claim 1 , further comprising:

a first temperature sensor for measuring a temperature of the cooling liquid at an outlet of the cylinder head; and

a second temperature sensor for measuring a temperature of the cooling liquid at an outlet of the cylinder block.

6. The cooling device for the internal combustion engine according to claim 2 , wherein the flow rate control valve has a position at which all the plurality of inlet ports are closed, a position at which the inlet port connected to the third cooling liquid line is opened while the other inlet ports are closed, a position at which the inlet port connected to the second cooling liquid line and the inlet port connected to the third cooling liquid line are opened while the other inlet ports are closed, and a position at which all the plurality of inlet ports are opened.

7. The cooling device for the internal combustion engine according to claim 3 , wherein the flow rate control valve has a position at which all the plurality of inlet ports are closed, a position at which the inlet port connected to the third cooling liquid line is opened while the other inlet ports are closed, a position at which the inlet port connected to the second cooling liquid line and the inlet port connected to the third cooling liquid line are opened while the other inlet ports are closed, a position at which all the plurality of inlet ports are opened, and a position at which the inlet port connected to the first cooling liquid line is closed while the other inlet ports are opened.

8. The cooling device for the internal combustion engine according to claim 6 , further comprising a control unit for controlling the electric water pump and the flow rate control valve, wherein

the control unit causes the electric water pump to operate during temporary stop of the internal combustion engine, and

during the temporary stop of the internal combustion engine, the control unit controls the flow rate control valve at the position at which all the plurality of inlet ports are closed or at the position at which the inlet port connected to the third cooling liquid line is opened while the other inlet ports are closed.

9. The cooling device for the internal combustion engine according to claim 8 , wherein

when heat exchange in the heater core is requested, the control unit controls the flow rate control valve at the position at which the inlet port connected to the third cooling liquid line is opened while the other inlet ports are closed, and

when the heat exchange in the heater core is not requested, the control unit controls the flow rate control valve at the position at which all the plurality of inlet ports are closed.

10. The cooling device for the internal combustion engine according to claim 1 , further comprising a control unit for controlling the electric water pump and the flow rate control valve, wherein

the control unit causes the electric water pump to operate during temporary stop of the internal combustion engine, and

during the temporary stop of the internal combustion engine, the control unit controls the flow rate control valve so that the supply rates of the cooling liquid to the plurality of cooling liquid lines are reduced as compared to before the temporary stop of the internal combustion engine.

11. The cooling device for the internal combustion engine according to claim 2 , further comprising a control unit for controlling the electric water pump and the flow rate control valve, wherein

the control unit causes the electric water pump to operate during temporary stop of the internal combustion engine, and

during the temporary stop of the internal combustion engine, the control unit controls the flow rate control valve so that the supply rates of the cooling liquid to, among the plurality of cooling liquid lines, the cooling liquid lines other than the third cooling liquid line are reduced as compared to before the temporary stop of the internal combustion engine.

12. The cooling device for the internal combustion engine according to claim 2 , further comprising a control unit for controlling the electric water pump and the flow rate control valve, wherein

the control unit causes the electric water pump to operate during temporary stop of the internal combustion engine, and

when the heat exchange in the heater core is not requested during the temporary stop of the internal combustion engine, the control unit controls the flow rate control valve so that the supply rates of the cooling liquid to, among the plurality of cooling liquid lines, the cooling liquid lines other than the third cooling liquid line are reduced as compared to before the temporary stop of the internal combustion engine, and

when heat exchange in the heater core is requested during the temporary stop of the internal combustion engine, the control unit controls the flow rate control valve so that the supply rates of the cooling water to the plurality of cooling liquid lines are reduced as compared to before the temporary stop of the internal combustion engine.

13. The cooling device for the internal combustion engine according to claim 8 , wherein, during the temporary stop of the internal combustion engine, the control unit increases a discharge rate of the electric water pump along with an increase in a temperature of the cylinder head.

14. The cooling device for the internal combustion engine according to claim 8 , wherein, when heat exchange in the heater core is requested during the temporary stop of the internal combustion engine, the control unit increases a discharge rate of the electric water pump as compared to when the heat exchange is not requested.

15. The cooling device for the internal combustion engine according to claim 8 , wherein the control unit activates the electric water pump after a predetermined delay period elapses from issue of a command to temporarily stop the internal combustion engine.

16. A control method for a cooling device for an internal combustion engine, the cooling device including

a plurality of cooling liquid lines including a first cooling liquid line routed by way of a radiator and a cylinder head of the internal combustion engine while bypassing a cylinder block thereof, and a second cooling liquid line routed by way of the cylinder block while bypassing the radiator,

an electric flow rate control valve which has a plurality of inlet ports connected to outlets respectively of the plurality of cooling liquid lines, and which controls supply rates of cooling liquid respectively to the plurality of cooling liquid lines,

a bypass line that branches off from the first cooling liquid line at a point between the cylinder head and the radiator and that connects with an outlet port of the flow rate control valve while bypassing the radiator,

a mechanical water pump which is driven by the internal combustion engine to circulate the cooling liquid, and

an electric water pump which is driven by a motor to circulate the cooling liquid,

the control method comprising the steps of:

detecting temporary stop of the internal combustion engine;

causing the electric water pump to operate in response to the temporary stop of the internal combustion engine; and

switching a position of the flow rate control valve in response to the temporary stop of the internal combustion engine.