Hybrid vehicle powertrain and control therefor

A hybrid vehicle powertrain comprising a throttle controlled internal combustion engine, a multiple-ratio power transmission and an electric motor;

• the transmission having multiple-ratio gearing and clutch and brake means for establishing and disestablishing multiple torque flow paths through the gearing;
• a friction clutch;
• a torque input member of the transmission being connected directly to the engine through the clutch;
• and
• an electric motor drivably connected to the torque input member in parallel disposition with respect to the engine whereby each is capable of delivering driving torque to the torque input member;
• the friction clutch, when it is disengaged, interrupting torque delivery from the engine to the torque input member;
• the motor forming a source of driving torque that complements driving torque of the engine when the friction clutch is engaged and forming a source of torque independent of the engine when the friction clutch is disengaged;
• means for combining electric motor torque with engine torque during launch of the vehicle including means for computing vehicle speed during launch as a function of clutch gain;
• means for detecting actual vehicle speed and engine throttle position during launch;
• an electronic controller including a stored functional relationship between throttle position and actual vehicle speed to determine desired power from the electric motor;
• means for determining a target engine speed as a function of throttle position and computed vehicle speed;
• and
• means for controlling friction clutch gain as a function of the error between target engine speed and actual engine speed whereby a smooth vehicle launch is accomplished.

A hybrid vehicle powertrain comprising an internal combustion engine, a power transmission and an electric motor;

• a friction clutch;
• a torque input member of the transmission being connected to the engine through the clutch;
• the electric motor being drivably connected to the torque input member in parallel disposition with respect to the engine whereby each is capable of delivering driving torque to the torque input member;
• the clutch, when it is disengaged, interrupting torque delivery from the engine to the torque input member;
• the motor forming a source of driving torque that complements driving torque of the engine when the clutch is engaged and forming a source of torque independent of the engine when the friction clutch is disengaged;
• the clutch comprising driving and driven clutch discs in a disc assembly and a clutch piston actuator for applying a clutch disc engaging force to the disc assembly;
• a fluid pressure clutch chamber defined in part by the clutch piston actuator;
• the clutch chamber, when pressurized, creating a clutch disc engaging force on the clutch piston actuator;
• and
• a clutch spring acting on the clutch piston actuator thereby creating a threshold clutch disc engaging force that creates a reduced delay in establishing clutch torque capacity as clutch piston actuator pressure is distributed to the clutch chamber.

A hybrid vehicle powertrain comprising an internal combustion engine, a multiple-ratio power transmission mechanism, and an electric motor;

• the transmission mechanism having multiple-ratio gearing and clutch and brake means for establishing and disestablishing multiple torque flow paths through the gearing;
• the clutch and brake means including a controllable, pressure-actuated friction clutch in a torque flow path between the engine and torque input elements of the gearing;
• a torque input shaft of the transmission mechanism being connected to the engine through the friction clutch;
• the electric motor being drivably connected to the torque input shaft in parallel disposition with respect to the engine whereby each is capable of delivering driving torque to the torque input shaft;
• the motor thereby forming a source of driving torque that complements driving torque of the engine when the engine is activated and forming a sole source of driving torque when the engine is deactivated;
• means for controlling electronic engagement of the friction clutch during engine idle comprising means for detecting engine torque and determining a torque signal indicative of engine idle torque;
• means for combining engine torque during idle with electric motor torque and for maintaining a regulated clutch actuating pressure responsive to the torque signal whereby engine idle torque variations are modified during engine idle by electric motor torque to effect electronic damping of engine torque during engine idle;
• means for combining electric motor torque with engine torque during launch of the vehicle including means for computing vehicle speed during launch as a function of friction clutch gain;
• means for detecting actual vehicle speed and engine throttle position during launch;
• an electronic controller including a stored functional relationship between throttle position and actual vehicle speed to determine desired power from the electric motor;
• means for determining a target engine speed as a function of throttle position and computed vehicle speed;
• and
• means for controlling clutch gain as a function of the error between target engine speed and actual engine speed whereby a smooth vehicle launch is accomplished.