Hybrid drive system for motor vehicle

A hybrid drive system for a motor vehicle, comprising:

• an engine operated as a first drive power source by combustion of a fuel;
• an electric energy storage device which is charged with an electric energy by operation of said engine;
• an electric motor operated as a second drive power source by the electric energy stored in said electric energy storage device;
• a transmission for transferring an output of one of said first and second drive power sources to a drive wheel of the vehicle, when one of said first and second drive power sources is selected depending upon a running condition of the vehicle;
• and
• a controller for controlling said transmission to change a speed ratio thereof depending upon said running condition,
• and wherein said controller comprises:
• emergency drive control means operated in the event of a failure of one of said engine and said electric motor as said first and second drive power sources, for operating the other of said first and second drive power sources;
• and
• emergency shift control means for changing a predetermined relationship between said running condition of the vehicle and said speed ratio of said transmission, when said other of said first and second drive power sources is operated by said emergency drive control means.

A hybrid drive system for a motor vehicle, comprising:

• an engine operated by combustion of a fuel;
• an electric energy storage device which is charged with an electric energy by operation of said engine;
• an electric motor operated by the electric energy stored in said electric energy storage device;
• an electric motor operated by the electric energy stored in said electric energy storage device;
• an automatic transmission whose speed ratio is variable;
• and
• a controller for operating at least said electric motor to drive the vehicle, said controller comprising energy-saving shift control means operated in response to a failure of said engine, for shifting said automatic transmission to change said speed ratio so as to reduce an amount of consumption of the electric energy by said electric motor by operating said automatic transmission and electric motor in an energy saving mode as a function of a running condition of the vehicle represented by an amount of power currently required by an operator of the vehicle to drive the vehicle, depending upon at least an energy conversion efficiency of said electric motor.

A hybrid drive system for a motor vehicle, comprising:

• an engine operated by combustion of a fuel;
• an electric energy storage device which is charged with an electric energy by operation of said engine;
• an electric motor operated by the electric energy stored in said electric energy storage device;
• and
• a controller for operating at least said electric motor to drive the vehicle when an amount of said electric energy stored in said electric energy storage device is greater than a predetermined lower limit and when said engine is functioning in a normal manner for hybrid operation of the motor vehicle,
• said controller comprising lower limit reducing means for reducing said predetermined lower limit of the electric energy stored in said electric energy storage device, energy which is stored in said electric energy storage device and to be available for consumption by the electric rotor in the event of said failure of said engine.