| 摘要 |
A hydrostatic transmission control system is provided of the type utilizing a main control valve to vary the control pressure being ported to the strokers which control the swashplate position of a variable displacement pump. The control valve includes a control port connected to a source of control pressure fluid and a pair of stroker ports, each of which is connected to one of the strokers. The control valve includes a valve member having a valve land associated with each of the stroker ports, the lands preferably being either zero-lapped or under-lapped and disposed to provide a substantially zero neutral band to provide an improved control response when it is necessary for the valve member to cross the neutral band and port control pressure to the opposite stroker. The control system further includes a positive neutral arrangement wherein movement of the control lever to the neutral setting energizes a valve, preferably a solenoid valve, which interconnects the lines leading from the stroker ports to the stroking cylinders, to insure zero swashplate displacement, despite the use of the zero neutral band control valve.
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