Patent ID: 6374722
Filing Date: 2002-04-23
Classification: F04B

Abstract:
An apparatus for controlling a discharge pressure of a variable displacement hydraulic pump, the discharge pressure being located at a pump output port, comprising:a swashplate pivotally attached to the pump; a valve plate located on the pump to allow hydraulic fluid to enter the pump through an intake port on the valve plate, and to exit the pump through a discharge port on the valve plate, the hydraulic fluid entering and exiting the pump responsively creating a pressure carry over angle &ggr;; a control servo operable to control an angle of the swashplate relative to the pump; a servo valve having an output port hydraulically connected to the control servo and an input port hydraulically connected to the pump output port; and means for controlling the servo valve as a function of the discharge pressure of the pump and responsively balancing a torque induced by the pressure carry over angle &ggr; with a torque generated by a control pressure Pc at the control servo.