Abstract: An engine exhaust gas recirculation (EGR) valve assembly consists of twin force actuating mechanisms within a single housing provided by two spaced flexible diaphragms one of which engages the another at times to control movement of the EGR valve, the diaphragms defining a lower manifold vacuum chamber connected to the EGR valve, an intermediate atmospheric pressure chamber, and an upper ported or spark port vacuum chamber, to provide an EGR flow schedule that varies as a function of engine load.

Abstract: An exhaust gas recirculating (EGR) valve is provided in a line connecting engine exhaust gases to the intake manifold to control the flow; a positioning servo is attached to the EGR valve and is operated by the pressure from an engine driven air pump; a position regulator servo is actuated by a modified air pump pressure to move an air bleed device normally bleeding the air pump pressure so that the EGR valve does not open; the air bleed device minimizes the hunting of the positioning servo and fixes the EGR valve in the position called for by the positioning regulator.

Abstract: An engine exhaust gas recirculating (EGR) valve assembly that maintains the EGR valve in the position to which it is actuated by means of a rolling diaphragm air bleed device that alternately covers and uncovers an atmospheric vent opening until an equilibrium position is maintained.