| 摘要 |
A hydraulic control unit for automatically controlling the speed of a hydraulic motor subjected to a variable load in a hydraulic circuit wherein a power unit is connected to the hydraulic motor through a supply line and a return line. The hydraulic control unit comprises a metering orifice (12) which is spring biased in the closed direction and to which a control piston (14) is mechanically linked, with pressure from the hydraulic motor pressure port (A) acting on the control piston, and a balanced piston flow divider (11) through which excess flow is returned to tank (T) and which is connected at one end to the supply line at a point between the pump (P) and the metering orifice and at the other end to the return line. In operation, and with the pressure at the pressure port (A) decreasing, the metering orifice is progressively closed resulting in an increasing pressure drop occurring across the metering orifice. This pressure drop acts on the balanced piston flow divider to increaslingly direct flow back to tank. Conversely, with the pressure at the pressure port (A) increasing, a progressively reduced flow is directed back to tank. Two applications for the control unit are disclosed, one being the control of a pole raising device, the other being the control of separate hydraulic motors driving the wheels of an all-terrain vehicle. |
