Thermal management system for vehicle

1. A thermal management system for a vehicle, the thermal management system comprising:

a first flow path through which a heating medium flows;

a first pump that is located on the first flow path and that circulates the heating medium in the first flow path;

a first temperature sensor that is located on the first flow path and that is configured to measure a first temperature of the heating medium;

a second flow path through which the heating medium flows;

a second pump that is located on the second flow path and that circulates the heating medium in the second flow path;

a second temperature sensor that is located on the second flow path and that is configured to measure a second temperature of the heating medium;

a switching valve configured to switch between a first mode in which the first flow path and the second flow path are separated and a second mode in which a part of the first flow path and a part of the second flow path are connected to constitute a third flow path; and

a control unit that determines whether the switching valve is in a slightly open state, wherein:

a temperature of the heating medium in the second flow path is higher than a temperature of the heating medium in the first flow path; and

in the first mode, the control unit

acquires a measured value of the first temperature from the first temperature sensor and a measured value of the second temperature from the second temperature sensor at first predetermined time that is when a predetermined amount of time has passed since at least one of the first temperature and the second temperature started to rise,

acquires an estimated value of the first temperature and an estimated value of the second temperature at the first predetermined time that are estimated values when the switching valve is not in the slightly open state, and

determines that the switching valve is in the slightly open state when the measured value of the first temperature is higher than the estimated value of the first temperature by a value greater than a first predetermined threshold and the measured value of the second temperature is lower than the estimated value of the second temperature by a value greater than a second predetermined threshold.

2. The thermal management system according to claim 1 , further comprising a third temperature sensor that is located on the third flow path and that is configured to measure a third temperature of the heating medium, wherein:

the first temperature sensor is located on the first flow path at a part that does not constitute the third flow path;

the second temperature sensor is located on the second flow path at a part that does not constitute the third flow path;

a temperature of the heating medium in the third flow path is higher than the temperature of the heating medium in the first flow path and the temperature of the heating medium in the second flow path; and

in the second mode, the control unit

acquires the measured value of the first temperature from the first temperature sensor, the measured value of the second temperature from the second temperature sensor, and a measured value of the third temperature from the third temperature sensor at second predetermined time that is when a predetermined amount of time has passed since the third temperature started to rise,

acquires the estimated value of the first temperature, the estimated value of the second temperature, and an estimated value of the third temperature at the second predetermined time that are estimated values when the switching valve is not in the slightly open state, and

determines that the switching valve is in the slightly open state when the measured value of the first temperature is higher than the estimated value of the first temperature by a value greater than the first predetermined threshold, the measured value of the second temperature is higher than the estimated value of the second temperature by a value greater than the second predetermined threshold, and the measured value of the third temperature is lower than the estimated value of the third temperature by a value greater than a third predetermined threshold.

3. The thermal management system according to claim 2 , further comprising a heat generation map showing amounts of heat to be generated by heat generation sources in the first to third flow paths in various operating states, wherein

the estimated value of the first temperature, the estimated value of the second temperature, and the estimated value of the third temperature are obtained based on the heat generation map.

4. The thermal management system according to claim 1 , wherein when the control unit determines that the switching valve is in the slightly open state in the first mode, the control unit

performs a flow rate regulating process of regulating a flow rate of at least one of the first pump and the second pump so as to reduce a pressure difference between a first pressure and a second pressure, the first pressure being a pressure on a side of the switching valve at the first flow path, and the second pressure being a pressure on a side of the switching valve at the second flow path,

while performing the flow rate regulating process, performs a process of changing the switching valve to a state corresponding to a mode other than the first mode and then returning the switching valve to a state corresponding to the first mode, and

performs a process of ending the flow rate regulating process.

5. The thermal management system according to claim 4 , wherein in the flow rate regulating process,

at least one of a process of reducing the flow rate of the first pump and a process of increasing the flow rate of the second pump is performed when the first pressure is higher than the second pressure, and

at least one of a process of reducing the flow rate of the second pump and a process of increasing the flow rate of the first pump is performed when the second pressure is higher than the first pressure.

6. The thermal management system according to claim 4 , wherein in the flow rate regulating process, the first pump and the second pump are stopped so as to substantially balance the first pressure and the second pressure.

7. The thermal management system according to claim 4 , wherein:

the switching valve includes a valve element that contacts a valve seat in the first mode;

the first pressure is applied to one side of the valve element, and the second pressure is applied to another side of the valve element; and

in the flow rate regulating process, the flow rate of at least one of the first pump and the second pump is regulated so as to cause a pressure difference in such a direction that the valve element moves toward the valve seat.

8. The thermal management system according to claim 1 , wherein in the first mode,

the control unit acquires the measured value of the first temperature from the first temperature sensor and the measured value of the second temperature from the second temperature sensor at third predetermined time that is when a predetermined amount of time has passed since at least one of the first temperature and the second temperature started to rise, and

when the first temperature and the second temperature are equal to each other, the control unit determines that the switching valve is broken.