Controller for hybrid electric vehicle and method for controlling hybrid electric vehicle

A controller for a hybrid electric vehicle including an engine, a motor generator, a belt connecting the engine and the motor generator, a battery configured to supply the motor generator with power, and a starter configured to start the engine, the controller comprising:

• processing circuitry configured to execute an engine starting process when an execution condition for starting the engine is satisfied, wherein:
• the engine starting process includes
• a first starting process that drives the motor generator by supplying the motor generator with power from the battery to crank the engine, and
• a second starting process executed under a condition in which an engine rotation speed, which is a rotation speed of the engine, becomes less than zero in the first starting process;
• the second starting process includes suspending the supply of power from the battery to the motor generator during a suspension period and then driving the motor generator by supplying the motor generator with power from the battery to crank the engine;
• in response to an elapsed time from when the first starting process is initiated becoming greater than a first threshold value and the engine rotation speed remaining less than an engine rotation speed threshold value during the first starting process, the processing circuitry is configured to determine that the motor generator failed to start the engine;
• in response to the elapsed time becoming greater than a second threshold value and the engine rotation speed remaining less than the engine rotation speed threshold value during the second starting process, the processing circuitry is configured to determine that the motor generator failed to start the engine, the second threshold value being greater than the first threshold value;
• in response to determining that the motor generator failed to start the engine, the processing circuitry is configured to start the engine with the starter;
• and
• the suspension period, during which the supply of power from the battery to the motor generator is suspended in the second starting process, ends simultaneously with a timing at which the engine rotation speed switches from being less than zero to being greater than or equal to zero.

A method for controlling a hybrid electric vehicle including an engine, a motor generator, a belt connecting the engine and the motor generator, a battery configured to supply the motor generator with power, and a starter configured to start the engine, the method comprising:

• executing an engine starting process when an execution condition for starting the engine is satisfied, wherein the engine starting process includes:
• a first starting process that drives the motor generator by supplying the motor generator with power from the battery to crank the engine;
• and
• a second starting process executed in response to an engine rotation speed, which is a rotation speed of the engine, becoming less than zero in the first starting process or in response to the engine rotation speed being maintained at zero for a predetermined period or longer in the first starting process,
• the second starting process including suspending the supply of power from the battery to the motor generator during a suspension period and then driving the motor generator by supplying the motor generator with power from the battery to crank the engine;
• in response to an elapsed time from when the first starting process is initiated becoming greater than a first threshold value and the engine rotation speed remaining less than an engine rotation speed threshold value, determining that the motor generator failed to start the engine during the first starting process;
• in response to the elapsed time becoming greater than a second threshold value and the engine rotation speed remaining less than the engine rotation speed threshold value, determining that the motor generator failed to start the engine during the second starting process, the second threshold value being greater than the first threshold value;
• in response to determining that the motor generator failed to start the engine, starting the engine with the starter;
• and
• the suspension period, during which the supply of power from the battery to the motor generator is suspended in the second starting process, ends simultaneously with a timing at which the engine rotation speed switches from being less than zero to being greater than or equal to zero.