A New Approach To Smooth Shifting: Electro-Hydraulic Feedback Control For Automatic Transmissions

A. closed loop control system has been developed to minimize vehicle acceleration fluctuation during power-on upshift of an automatic transmission. This system senses the revolution speed of torque converter turbine runner, and controls the hydraulic pressure of clutch actuating cylinder during the shift sequence using a linear solenoid type electro-hydraulic pressure modulation valve so as to regulate the turbine runner speed on schedule.

By the torsional rigidity of drive train, shorter torque phase brings smoother shifting. Opposing requirement exist to complete the torque phase quickly and to carefully limit clutch torque capacity. Discernment of clutch facing contact using pressure sensors is able to satisfy the requirement.