INTRODUCTION

Vehicles employing hybrid powertrain systems for propulsion may include an internal combustion engine and an electric machine that transfer torque to a driveline via a transmission. Transmissions employ pressurized hydraulic fluid to activate clutches to effect torque transfer at different speed ranges, wherein the pressurized hydraulic fluid is supplied via a hydraulic pump. Known systems may employ an electrically-driven hydraulic pump to supply pressurized hydraulic fluid for transmission operation when the engine is in an off state, i.e., not rotating, such as during an autostop event that may be commanded at an intersection. An electrically-driven hydraulic pump is able to supply pressurized hydraulic fluid during a subsequent vehicle launch event. In the absence of pressurized hydraulic fluid to the transmission being delivered by an electrically-driven hydraulic pump, a launch may be delayed while awaiting an increase in the hydraulic pressure, which may be generated by engine start and associated spinning of a torque converter pump element. However, an electrically-driven hydraulic pump adds electrical and control complexity to the system, increases costs, consumes energy, and requires packaging space in an underhood environment.

SUMMARY

The concepts described herein provide a creative arrangement of a hybrid powertrain for a vehicle and associated methods for control thereof. The hybrid powertrain system includes an electric machine, a torque converter, a transmission, a hydraulic pump, and a controller, and it is arranged to transfer mechanical power to a driveline. The torque converter includes a clutch, a pump, and a turbine, and the electric machine is rotatably coupled to the hydraulic pump and to the torque converter pump. The hydraulic pump is fluidly connected to the transmission, and the controller is operably connected to the electric machine and the torque converter clutch. The controller includes an instruction set that is executable to determine an operator command, and control the electric machine to spin the hydraulic pump in a speed control mode and control the torque converter clutch in an open state. Upon achieving a desired minimum pump speed, the torque converter clutch is applied in a slip state and the electric machine is controlled in response to the operator command.

An aspect of the disclosure includes an internal combustion engine, wherein the internal combustion engine is selectively couplable to the torque converter pump via an intervening disconnect clutch, and wherein the internal combustion engine is decoupled from the torque converter pump.

Another aspect of the disclosure includes the instruction set being executable to detect an operator command to launch the vehicle.

Another aspect of the disclosure includes the instruction set being executable to determine an operator command for braking the vehicle.

Another aspect of the disclosure includes the instruction set being executable to determine an operator command for idling the vehicle.

Another aspect of the disclosure includes the desired minimum pump speed being a minimum pump speed that is associated with a desired transmission pressure.

Another aspect of the disclosure includes the instruction set being executable to control the electric machine to generate torque in response to the operator command.

Another aspect of the disclosure includes the instruction set being executable to control the torque converter clutch to decrease magnitude of clutch slip, and lock the torque converter clutch.

Another aspect of the disclosure includes the hydraulic pump being a mechanically-driven hydraulic pump, wherein the electric machine is rotatably coupled to the mechanically-driven hydraulic pump.

The above features and advantages, and other features and advantages, of the present teachings are readily apparent from the following detailed description of some of the best modes and other embodiments for carrying out the present teachings, as defined in the appended claims, when taken in connection with the accompanying drawings.

