초록 ▼

A hydrostatic transmission has a pair of overcenter variable displacement pumps, each having a flow control element controlled by a double acting actuator to control direction and flow rate of the pump. Fluid pressure in first and second chambers of each actuator are equal at a neutral position of t

A hydrostatic transmission has a pair of overcenter variable displacement pumps, each having a flow control element controlled by a double acting actuator to control direction and flow rate of the pump. Fluid pressure in first and second chambers of each actuator are equal at a neutral position of the transmission. A forward control valve controllably communicates the first chambers of both actuators to a tank through a first orifice to reduce the pressure in the first chambers to simultaneously move the flow control elements in a first direction for forward travel. A reverse control valve controllably communicates the second chambers of both actuators to the tank through a second orifice to reduce the pressure in the second chambers to simultaneously move the flow control elements in a second direction for reverse travel. A right turn is made by selectively reducing the pressure in the second chamber of the right actuator during forward travel and in the first chamber during reverse travel by establishing fluid flow to the tank from the first or second chamber through a right turn position diverter valve and a right turn control valve. A left turn is made by selectively reducing the pressure in the second chamber of the left actuator during forward travel and in the first chamber during reverse travel by establishing fluid flow to the tank from the first or second chamber through one of another pair of orifices and a left two position diverter valve with a left turn control valve.

대표청구항 ▼

[ What is claimed is:] [1.] A control system for a hydrostatic transmission having a pair of reversible variable displacement hydraulic pumps each of which has a flow control element disposed to control the direction and flow rate of fluid output from the associated variable displacement pump, and a

[ What is claimed is:] [1.] A control system for a hydrostatic transmission having a pair of reversible variable displacement hydraulic pumps each of which has a flow control element disposed to control the direction and flow rate of fluid output from the associated variable displacement pump, and are of a first and second double acting actuator connected to the flow control element and having first and second actuating chambers and a spring disposed in each chamber to bias the flow control element to a centered zero output position, the control system comprising:a source of pilot fluid including a supply conduit and a tank;a first conduit communicating the supply conduit with the first chambers;a first orifice disposed in the first conduit;a second conduit communicating the supply conduit with the second chambers;a second orifice disposed in the second conduit;a forward control valve disposed between the tank and the first conduit downstream of the first orifice, the forward control valve having a closed position blocking the first conduit from the tank and being movable to establish a variable orifice communicating the first conduit with the tank;a reverse control valve disposed between the tank and the second conduit downstream of the second orifice, the reverse control valve having a closed position blocking the second conduit from the tank and being movable to establish a variable orifice communicating the second conduit with the tank; andlever means for actuating each of the forward and reverse control valves individually of the other to establish the variable orifices.