Battery temperature raising device for hybrid vehicle

1. A battery temperature raising device for a hybrid vehicle, which raises a temperature of a battery in a low temperature state in the hybrid vehicle, the hybrid vehicle having an engine travelling mode using an internal combustion engine as a power source and a motor travelling mode using a motor generator that mutually converts an electric power of the battery and a mechanical power as the power source, the battery temperature raising device comprising:

an engine cooling circuit through which cooling water for cooling the internal combustion engine circulates;

a motor generator cooling circuit through which a refrigerant for cooling the motor generator circulates and which is independent of the engine cooling circuit;

a first battery circuit which is connected in parallel to the engine cooling circuit and in which cooling water circulates through the battery;

a first bypass flow path which bypasses the internal combustion engine, is connected in parallel to the engine cooling circuit, and forms, together with a part of the engine cooling circuit and the first battery circuit, a closed circuit through which cooling water circulates;

a heat exchanger which is arranged in the first bypass flow path and performs heat exchange between the cooling water of the engine cooling circuit and the refrigerant of the motor generator cooling circuit;

a first switching unit which switches connection/disconnection of the first battery circuit to the engine cooling circuit;

a second switching unit which switches connection/disconnection of the first bypass flow path to the engine cooling circuit;

a battery temperature sensor which detects the temperature of the battery;

an engine cooling water temperature sensor which detects a temperature of the cooling water of the internal combustion engine;

a motor generator temperature sensor which detects a temperature of the motor generator; and

a temperature raising control unit, wherein in the engine travelling mode, the temperature raising control unit performs a first temperature raising control for raising the temperature of the battery by connecting the first battery circuit to the engine cooling circuit with the first switching unit and introducing the cooling water in the engine cooling circuit into the first battery circuit when the detected engine cooling water temperature is higher than a predetermined cooling water temperature; and in the motor travelling mode, the temperature raising control unit performs a second temperature raising control for raising the temperature of the battery by respectively connecting the first battery circuit and the first bypass flow path to the engine cooling circuit with the first and the second switching units and introducing the cooling water raised in temperature by heat exchange with the refrigerant in the heat exchanger into the first battery circuit when the detected motor generator temperature is higher than the detected battery temperature.

2. The battery temperature raising device for hybrid vehicle according to claim 1 , further comprising:

a heat accumulator circuit which is connected in parallel to the engine cooling circuit and through which the cooling water flowing out from the internal combustion engine circulates;

a heat accumulator which is arranged in the heat accumulator circuit, stores the cooling water, and accumulates heat of the cooling water;

a second battery circuit which is connected in parallel at a downstream side of the heat accumulator in the heat accumulator circuit and in which the cooling water circulates through the battery;

a third switching unit which switches connection/disconnection of the second battery circuit to the heat accumulator circuit; and

a heat accumulator cooling water temperature sensor which detects a temperature of the cooling water in the heat accumulator;

wherein in the motor travelling mode, the temperature raising control unit performs, before performing the second temperature raising control, a third temperature raising control for raising the temperature of the battery by connecting the second battery circuit to the heat accumulator circuit with the third switching unit and introducing the cooling water in the heat accumulator into the second battery circuit when the heat accumulator cooling water temperature is higher than the battery temperature.

3. The battery temperature raising device for hybrid vehicle according to claim 2 , further comprising:

an electric heater which is arranged at an upstream side of a connection portion with the first battery circuit in the engine cooling circuit and heats the cooling water in the engine cooling circuit;

a second bypass flow path which bypasses the internal combustion engine, is connected in parallel at an upstream side of the electric heater in the engine cooling circuit, and forms, together with a part comprising the electric heater of the engine cooling circuit and the first battery circuit, a closed circuit through which cooling water circulates; and

a fourth switching unit which switches connection/disconnection of the second bypass flow path to the engine cooling circuit;

wherein in the motor travelling mode, the temperature raising control unit performs a fourth temperature raising control for raising the temperature of the battery by making the electric heater operate, and respectively connecting the first battery circuit and the second bypass flow path to the engine cooling circuit with the first and the fourth switching units and introducing the cooling water heated by the electric heater into the first battery circuit when the heat accumulator cooling water temperature is below the battery temperature.