Controller for hybrid vehicle

#This application is based on Japanese Patent Application No. 2012-221945 filed on Oct. 4, 2012, the disclosure of which is incorporated herein by reference.

#The present disclosure relates to a controller for a hybrid vehicle provided with an engine, a motor and an inverter.

#A hybrid vehicle and an electric vehicle have been developed to reduce emission and improve fuel economy. In such a hybrid vehicle and an electric vehicle, the direct current voltage of a battery is changed into the alternating voltage by an inverter to drive a motor. JP-2008-5615A shows a system which avoids overheat of the inverter. In this system, the coolant is circulated between the inverter and the radiator. When the temperature of the inverter exceeds a predetermined threshold, the motor is controlled to reduce the output torque.

#The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

#FIG. 1 is a schematic view showing a cooling system of a plug-in hybrid vehicle according to an embodiment;

#FIG. 2 is a chart for explaining a relationship between an inverter temperature and an allowable current;

#An embodiment will be described hereinafter. First, a cooling system of a plug-in hybrid vehicle is explained based on FIG. 1. The vehicle is provided with an engine 11 and a motor 12. An inverter 13 driving the motor 12 is connected to a battery 14. The motor 12 receives electric power from the battery 14 through the inverter 13. In the present embodiment, the vehicle has a plug-in charge configuration in which an external power source (not shown) can be connected to the battery 14 so that the battery 14 is charged. Moreover, a switching element (for example, SiC-MOSFET) made from SiC (silicon carbide) is used to form a switching circuit of the inverter 13.

#The engine 11 and the inverter 13 have a coolant passage (not shown). An exit of the coolant passage of the engine 11 is connected to an inlet of the radiator 16 through a first coolant pipe 16. An exit of the radiator 15 is connected to an inlet of the coolant passage of the inverter 13 through a second coolant pipe 17. An exit of the coolant passage of the inverter 13 is connected to an inlet of the coolant passage of the engine 11 through a third coolant pipe 18. Thereby, a coolant circulation circuit 19 is configured, in which the coolant flows through the first coolant pipe 16, the radiator 15, the second coolant pipe 17, the inverter 13, the third coolant pipe 18 and the engine 11. In the coolant circulation circuit 19, an electric water pump 20 is provided to circulate the coolant.

#The coolant circulation circuit 19 is provided with a bypass passage 21 which bypasses the coolant passage of the engine 11. Each end of the bypass passage 21 is connected to the first coolant pipe 16 and the second coolant pipe 18. At an inlet portion of the bypass passage 18, a passage-switching valve 22 is provided. The passage-switching valve 22 switches between the coolant passage of the engine 11 and the bypass passage 21. The bypass passage 21 and the passage-switching valve 22 are arranged downstream of the water pump 20.