Automatic transmissions require that the transition or shift quality between the various gears be smooth and uniform. Driveability is improved by optimizing the shift time of certain gear changes. An added benefit of improved shift quality is reduced clutch wear.
During the investigation of an electronic transmission control system for agricultural, off highway and, heavy duty on highway vehicles, it became apparent that a key element in the hydraulic system was the need to accurately regulate oil pressure to the various clutches in the gear train.
The valve described herein accurately regulates oil pressure at low levels and progressively increases pressure, with respect to time, by means of an electronically programmable pressure vs time control to any level up to supply pressure.