Engine start control device and engine start control method for hybrid electric vehicle

An engine start control device for a hybrid electric vehicle, the vehicle comprising a drive wheel, an electric motor, an internal combustion engine, a first frictional engagement element connecting the electric motor and the internal combustion engine, a second frictional engagement element connecting the electric motor and the drive wheel, and an accelerator pedal that inputs a requested acceleration amount to the vehicle, the device comprising:

• an accelerator opening sensor that detects the requested acceleration amount;
• and
• a programmable controller programmed to:
• determine to start the internal combustion engine using an output torque of the electric motor, when the vehicle is running in an electric vehicle mode in which the vehicle travels by a power of the electric motor while the internal combustion engine is inoperative;
• decrease a torque transmission amount of the second frictional engagement element to a torque transmission amount in a slip state in which the second frictional engagement element transmits a torque while slipping,
• increase the output torque of the electric motor by a predetermined increment in response to the requested acceleration amount, and
• engage the first frictional engagement element to input the output torque of the electric motor into the internal combustion engine,
• wherein the controller is further programmed to:
• determine whether or not the requested acceleration amount exceeds a predetermined amount, and
• when the requested acceleration amount exceeds the predetermined amount during a period from a start of decrease in the torque transmission amount of the second frictional engagement element until an engagement of the first frictional engagement element, advance a start timing of increasing the output torque of the electric motor by the predetermined increment, increase the predetermined increment, or increase a variation rate of the output torque of the electric motor until when the predetermined increment is materialized compared to a case where the requested acceleration amount does not exceed the predetermined mount.