The Design and Development of a Four Speed Powershift Transmission with Electronic Clutch Pressure Modulation

A four speed powershift transmission has been designed and developed which utilizes an electronic system to control clutch pressure during clutch engagements. The advantage of this type of control is the ability to easily tailor clutch operational characteristics. This electro-hydraulic system makes use of a pulse-width modulated proportional solenoid in conjunction with a pilot pressure controlled regulating valve and microprocessor based control circuit. Also a methodology is shown that allows the prediction of transmission bearing life based upon system reliability.