| 摘要 |
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.
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