Control device for a hybrid electric vehicle

Abstract

A hybrid electric vehicle is arranged such that a driving force of an electric motor can be transmitted to driving wheels and that a rotary shaft of the electric motor can be coupled with an output shaft of an engine. The vehicle comprises a starter motor provided separately from the electric motor, an electric power source provided separately from a battery that supplies power to the electric motor, to supply power to the starter motor, and a braking force maintaining device configured to be activated by power from the power source to maintain a braking force on the vehicle. When a request for starting the engine is made, if a specified abnormal condition which makes the starting of the engine by the electric motor impracticable is detected, an ECU causes the engine to be started by the starter motor when the braking force maintaining device is not active.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein:

FIG. 1 is a diagram showing the schematic structure of a hybrid electric vehicle to which an embodiment of the present invention is applied;

FIG. 2 is a connection diagram for the hybrid electric vehicle of FIG. 1, with a vehicle ECU at the center; and

FIG. 3 is a flow chart of an engine start control performed in the hybrid electric vehicle of FIG. 1.

Claims

1. A control device for a hybrid electric vehicle arranged such that a driving force of an electric motor can be transmitted to driving wheels and that a rotary shaft of the electric motor can be coupled with an output shaft of an engine, comprising: a starter motor provided separately from the electric motor and capable of starting the engine by transmitting a driving force to the output shaft of the engine;a battery that supplies electric power to the electric motor;an electric power source provided separately from the battery to supply electric power to the starter motor;a braking force maintaining means configured to be activated by electric power from the electric power source to maintain a braking force on the vehicle;an abnormality detection means for detecting a specified abnormal condition which makes the starting of the engine by the electric motor impracticable; anda control means which, in a case where a request for starting the engine is made, if the abnormality detection means does not detect the abnormal condition, causes the engine to be started by the electric motor, and if the abnormality detection means detects the abnormal condition, causes the engine to be started by the starter motor when the braking force maintaining means is not active.

2. The control device for a hybrid electric vehicle according to claim 1, wherein: when a request for starting the engine is made, if the abnormality detection means detects the abnormal condition and if the braking force maintaining means is active, the control means suspends the starting of the engine by the starter motor until the braking force maintaining means is deactivated.

3. The control device for a hybrid electric vehicle according to claim 1, further comprising: a parking brake configured to be operated by a driver of the vehicle to produce a braking force on the vehicle, whereinwhen a request for starting the engine is made, if the abnormality detection means detects the abnormal condition and if the braking force maintaining means is active, the control means suspends the starting of the engine by the starter motor until the parking brake is operated to produce a braking force on the vehicle.

4. The control device for a hybrid electric vehicle according to claim 1, further comprising: a brake pedal configured to be depressed by a driver of the vehicle to produce a braking force on the vehicle, wherein when a request for starting the engine is made, if the abnormality detection means detects the abnormal condition and if the braking force maintaining means is active, the control means suspends the starting of the engine by the starter motor until the brake pedal is depressed.

5. The control device for a hybrid electric vehicle according to claim 1, further comprising: a warning means for giving a warning, if the abnormality detection means detects the abnormal condition and if the braking force maintaining means is active when a request for starting the engine is made.