Chrysler Corporation

Robert J Schichtel

Howard L Benford

Allen D Adam

The present invention provides a method and apparatus for controlling the hydraulic line pressure in an automatic transmission for a vehicle in response to the torque transmitted through the transmission such that a minimum hydraulic line pressure is provided to the frictional elements to achieve a no-slip condition through the transmission increasing transmission efficiency, thereby increasing the fuel economy of the vehicle. Hydraulic line pressure is controlled by activating a solenoid activated valve which allows fluid recirculation from the high-pressure side of the hydraulic pump to the low-pressure side of the pump. Control signals are generated based on engine speed, turbine speed, output speed (vehicle speed), hydraulic line pressures, driver selected gear, the operating gear and the torque converter operating condition for energizing the solenoid-actuated valve. The present invention further provides closed-loop adaptive control technology to learn the minimum line pressure requirements to compensate for production variability of clutch return springs, friction characteristics, surface finishes and flatness, as well as hydraulic response resulting from valve body part variation, wear, and changes over the life of the transmission.

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Holly, MI, United States of America

Robert J Schichtel