Control system and control method for a hybrid electric vehicle powertrain

A method and strategy for a hybrid electric vehicle powertrain having a throttle-controlled internal combustion engine, an electric motor/generator with an electrical power source and a power transmission, the transmission having pressure-activated friction elements that define torque slow paths, a clutch for establishing and disestablishing a connection between the engine and the torque input side of the transmission, a torque output side of the transmission being connected to vehicle traction wheels, the motor being drivably connected to a hydraulic pump for pressurizing the friction elements;

• the method and strategy comprising:
• controlling motor speed to maintain transmission control pressure for the transmission friction elements, including a minimal transmission control pressure at zero vehicle speed;
• establishing an engine drive zone characterized by speed-torque relationships that are functions of engine throttle position throughout a first range of torque values and throughout a first range of speed values;
• establishing a motor drive zone characterized by a speed-torque relationship throughout a second range of torque values that is smaller than the first range of torque values and throughout a second range of speed values that is smaller than the first range of speed values;
• and
• emulating the speed-torque relationship of the engine by the motor/generator when the speed and torque values are within the second torque and speed ranges, respectively.

A method and strategy for a hybrid electric vehicle powertrain having an internal combustion engine, an electric motor/generator with an electrical power source, a power transmission with friction elements for establishing and disestablishing torque flow paths, a clutch for establishing and disestablishing a connection between the engine and the torque input side of the transmission, a torque output side of the transmission being connected to vehicle traction wheels, the method and strategy comprising:

• establishing an engine drive zone characterized by speed-torque relationships that are functions of engine control input throughout a first range of torque values and throughout a first range of speed values;
• establishing a motor drive zone characterized by a speed-torque relationship throughout a second range of torque values that is smaller than the first range of torque values and throughout a second range of speed values that is smaller than the first range of speed values;
• and
• emulating the speed-torque relationship of the engine by the motor/generator when the torque and speed values are within the second torque and speed ranges, respectively.

A method and strategy for a hybrid electric vehicle powertrain having an internal combustion engine, an electric motor/generator with an electrical power source, a power transmission with friction elements for establishing and disestablishing torque flow paths, a clutch for establishing and disestablishing a connection between the engine and the torque input side of the transmission, a torque output side of the transmission being connected to vehicle traction wheels, the method and strategy comprising:

• establishing an engine drive zone characterized by speed-torque relationships that are functions of engine control input throughout a first range of torque values and throughout a first range of speed values;
• establishing a motor drive zone characterized by a speed-torque relationship throughout a second range of torque values that is smaller than the first range of torque values and throughout a second range of speed values that is smaller than the first range of speed values;
• establishing an intermediate operating zone intermediate the engine drive zone and the motor drive zone;
• and
• emulating the engine speed-torque relationship of the engine when the powertrain operates in the engine drive zone by using the motor/generator during operation in the intermediate operating zone when the clutch disconnects the engine.