Hydrostatic transmission having an overspeed control

摘要

PCT No. PCT/US80/01096 Sec. 371 Date Aug. 20, 1980 Sec. 102(e) Date Aug. 20, 1980 PCT Filed Aug. 20, 1980 PCT Pub. No. WO82/00617 PCT Pub. Date Mar. 4, 1982.An underspeed actuator (18) is connected to the displacement control (17) for controlling the displacement of a variable displacement pump (11) of a hydrostatic transmission (10) in response to the pressure differential between low and high pressure control signals (A,B) wherein the pressure differential is directly proportional to the engine speed. An overspeed control valve means (41) is connected to the low and high pressure signals and decreases the pressure level of the high pressure signal received by the underspeed actuator (18) in response to the pressure differential exceeding a predetermined magnitude. This reduces the displacement of the variable displacement pump (11) thereby controlling the amount of engine overspeed caused by the hydrostatic transmission (10) driving the engine when the vehicle is descending a steep hill.