Modulating control for hydrostatic drive

摘要

A normally closed solenoid valve operates conjunctively with a two position pilot valve to limit the amount of engine braking through the drive train of a vehicle by reducing the drive relief valve setting in the disengaged side of a hydrostatic transmission. A second normally closed solenoid valve operates a second two position pilot valve to modulate the rate that the forward drive relief valve in the engaged side of the transmission hydrostatic drive loop permits drive pressure to build up as the vehicle is started in motion. An electrical switch on the transmission control rod initiates activation of the normally closed solenoid valves when the vehicle operator selects a direction of travel.