High flow gas force balanced egr valve

Abstract

A relatively simple pressure balanced high flow exhaust gas recirculation (EGR) valve includes an actuator and a separately formed valve assembly retained to the actuator by a deformed lip. The valve body has dual seats controlled by axially spaced heads which are pressure balanced when closed and allow high gas flow when open. The valve body and the associated valve shaft, or portions thereof, are formed of materials having similar coefficients of thermal expansion so that the shaft and body experience similar thermal growth and good seating of the spaced valves is maintained regardless of gas temperature variations. Thickened portions at the valve seats comprise annular ends of a control portion which resist distortion of the seats. The valve body is configured for installation in a cylindrical bore or recess of an associated manifold or other gas passage defining member. Seal rings, preferably of elastomeric material, seal the controlled flow passages and maintain a small gap between the valve body walls and the passage defining member to minimize heat transfer and assist equalization of the body and valve shaft expansion rates. One or both of the valve heads may be attached to the shaft by a press and spin or crimping process to promote ease of assembly. The valve shaft may be supported by a single bushing carried in the mounting portion. A shaft seal in the bushing may include a lip responsive to gas pressures to vary the sealing force, for example, under turbocharged conditions.