HYDROSTATIC TRANSMISSION CONTROL SYSTEMS

摘要

1493975 Hydrostatic transmission control EATON CORP 17 March 1975 [17 June 1974 10980/75 Heading F2W In a control system for a motor vehicle hydrostatic transmission wherein a control valve 20 meters pressure liquid from an engine-driven pump 106 to a spring centred pump displacement adjusting servo 34 through a reversing valve 32 and the valve 20 is responsive to engine speed, the liquid pressure supplied to the servo 34 and, above a predetermined throttle setting, to accelerator pedal position, means are provided to retard rapid movement of the valve 20 when the accelerator pedal is depressed rapidly. An engine driven centrifugal governor 92, 94 acts through a rod 146 against the bias of a spring 102 to move the spool 22 of the valve 20 right. The spool 22 meters pressure liquid from the pump 106 to a line 70 and the resulting pressure build-up therein is fed additionally through a duct 130 in the valve spool 22 to a chamber 134. The pressure in the chamber 134 moves the valve spool 22 left against the bias of the engine governor to a position in which it prevents further pressure build-up in the line 70. The pressure in the line 70 which is supplied to the displacement adjusting servo 34 is thus proportional to engine speed. When the pump attains its maximum displacement a lever 198 connected to an engine throttle pedal 84 engages a collar 144 against which the engine governor spring 102 reacts. Thereafter further depression of the accelerator pedal 84 increases the load on the governor spring 102 to balance the accompanying increase in engine governor force on the rod 146. The accelerator pedal 84 is connected to the lever 198 through a spring lostmotion coupling 194 and a rod 196. The movement of the rod 196 is damped by a one-way dash pot 206 when the accelerator pedal 84 is depressed rapidly to compensate for the lag in the accompanying increase in engine speed. Throttles 220, 224 in the pump delivery line 104 and a return line 56 limits the rate of increase and decrease of pump displacement. A servce braxe pedal 236 acts on a linkage 110, 120 between the servo 34 and the pump displacement adjusting lever 124 to override the normal control and reduce pump displacement to zero prior to application of the vehicle brakes.