Servo pressure control valve

Abstract

A valve for controlling pressure in a system is provided. The valve includes a housing, a servo spool and a piston positioned within the housing with the piston and the servo spool being movable relative to each other. The piston defines a first orifice configured to communicate with a supply of pressurized fluid and a second orifice configured to communicate with a portion of the system exterior to the valve. A first chamber is arranged such that force due to fluid pressure in the first chamber is configured to move the piston in a first direction. The first chamber includes a third orifice configured to communicate with a controlled pressure in the system. A second chamber is at least partially defined by the housing and the piston and includes a fourth orifice configured to communicate with a low pressure fluid source. A biasing element is arranged in the second chamber. First and second fluid passages are provided in the servo spool and are configured such that in at least one relative position of the piston and the servo spool the first passage provides communication between the first orifice and the second orifice and in at least one other relative position the second passage provides communication between the second orifice and the fourth orifice.