Transmission oil pressure control during engine autostart

摘要

A vehicle includes an engine having autostart functionality, a source of fluid pressure when the engine is off, a flow control solenoid that outputs a variable clutch pressure, a transmission, an electric motor, and a controller. The transmission includes a clutch in fluid communication with the solenoid. The clutch applies via the clutch pressure to establish a first gear launch state. The motor is powered via a rechargeable energy storage system. The controller executes a method to transmit pulse width modulation (PWM) control signals to the solenoid upon detection of a set of conditions triggering the autostart event to lower clutch pressure to a first calibrated level. Restart of the engine is commanded, and the clutch pressure increases toward a second calibrated level while engine speed is increasing. The controller discontinues the PWM control signals and increases clutch pressure to line pressure when the input speed exceeds a calibrated threshold.

主权项

1. A vehicle comprising:
an internal combustion engine having autostart functionality; a source operable to provide fluid pressure when the engine is off; a flow control solenoid in fluid communication with the source, wherein the flow control solenoid is configured to output a variable clutch pressure; a transmission having a stationary member, a gear set, an output member, and a designated clutch in fluid communication with the flow control solenoid, wherein the designated clutch is applied via the variable clutch pressure after restart of the engine to connect the gear set to the stationary member and to thereby launch the vehicle; an electric motor; drive wheels connected to the output member of the transmission; and a controller having a processor and tangible, non-transitory memory on which is recorded instructions for controlling the variable clutch pressure to the designated clutch during a predetermined autostart event of the engine, wherein execution of the instructions by the processor causes the controller to:
transmit a set of pulse width modulation (PWM) control signals to the flow control solenoid in response to a predetermined set of conditions triggering the predetermined autostart event to thereby lower the variable clutch pressure to a calibrated level;command an automatic restart of the engine via the electric motor;determine an input speed to the transmission while the engine is actively increasing in speed; anddiscontinue transmitting the set of PWM control signals to the flow control solenoid while increasing the variable clutch pressure at a calibrated rate to full line pressure, thereby applying the designated clutch to connect a node of the gear set to the stationary member to thereby transmit output torque from the transmission, via another node of the gear set, to the drive wheels of the vehicle via the output member and launch the vehicle, when the input speed to the transmission exceeds a calibrated threshold.