Hydraulic control apparatus for a servomotor

摘要

The invention relates to a steering control unit for a bidirectional servomotor which is connectable to steerable wheels. A steering wheel controlled quantity setting unit of a known type has ports connectable to a pump and a return tank and two control ports through which metered quantities of fluid flow to opposite sides of the servomotor and to other parts of the apparatus for actuating the servomotor. A directional control valve for selectivity directing pressurized fluid from a power circuit to opposite sides of the servomotor is controlled by a control circuit containing the setting unit. A utility valve having pressure regulating and control and power valve capabilities is provided. In cases wherein the quantity setting apparatus is remotely located from the regulating valve the length of the signal channels add to the reaction time. Such reaction time is reduced herein by connecting the metering throttle as a fixed throttle between the regulating valve and quantity setting apparatus so that the regulating valve feeds a substantially constant quantity to the control cicuit, and that the quantity setting apparatus comprises a short circuit path to the tank which closes with an increase in the quantity.