HYDROSTATIC TRANSMISSION SYSTEM AND POWER LIMITER CONTROL THEREFOR

摘要

An improved closed-loop hydrostatic transmission system is provided of the type including a pump (11), a motor (13), and a pair of conduits (15 and 17). The system includes a main control valve (43) and a charge pump (23) which is the sole source of make-up fluid to the closed-loop system and the sole source of control fluid for varying the pump. The system includes a power limiting means comprising first and second pressure relief valve means (75 and 77) operable to provide fluid communication from whichever side of the closed-loop is at high pressure to the system reservoir whenever system pressure exceeds the predetermined maximum pressure. The motor is adapted to transmit drive torque to a reversible load (37) of the type having a known inertia and a predeterminable time of deceleration from maximum speed operation in one direction to a standstill condition. A flow restriction means (44) in series relationship between the charge pump and a fluid pressure responsive means (31,33) of the pump is selected such that reversal of the main control valve (43) from maximum displacement in one direction to maximum displacement in the opposite direction results in destroking of the pump in a time period approximately equal to the time of deceleration of the reversible load, thereby substantially preventing cavitation and high-pressure spikes.