Patent ID: 7025044

Claim:
A system for regulating the flow of working fluid to a high-pressure pump that supplies pressurized working fluid for a fuel injection system of an internal combustion engine, the system comprising: a body, an inlet throttle valve in the body, an inlet passage in fluid communication with the inlet throttle valve to flow low-pressure working fluid to the valve, an outlet passage in fluid communication with the inlet throttle valve to flow working fluid from the inlet throttle valve to the pump, a control passage to communicate pilot fluid to the inlet throttle valve for controlling fluid flow through the valve, a spring biasing the inlet throttle valve to an operating position, and control means for automatically controlling the flow of pilot fluid through the control passage in response to a signal representing the desired position of the valve; the inlet throttle valve comprising a bore in the body extending along an axis, the bore having axially opposed first and second ends, a wall extending between the ends, a spool in the bore, the spool axially movable along the bore to regulate the flow of fluid through the valve, and a chamber in the bore between the spool and the first end of the bore; the spool comprising axially opposed closed ends and a cylindrical wall extending between the ends, and inlet and outlet openings extending through the spool wall for flowing working fluid into and out of the spool; the inlet passage comprising a first opening in the bore wall in registration with the spool inlet opening to flow working fluid from the inlet passage into the spool; the outlet passage comprising a second opening in the bore wall in registration with the spool outlet opening to flow working fluid from the spool into the outlet passage; the control passage opening into the chamber, the control passage configured to flow pilot fluid into and out of the chamber; and the spring biasing the spool towards the first end of the bore; wherein the position of the spool in the bore and thereby the flow of working fluid through the inlet throttle valve are determined by a pressure balance between the spring and the pilot fluid in the chamber independently of the pressure of the working fluid.