Exhaust gas recirculation control

Claim 2

An exhaust gas recirculation control assembly (22, 44, 74) for an engine having an induction passage (12) for induction air flow and a recirculation passage (18) for exhaust gas recirculation to said induction passage, said assembly comprising an orifice (24) dividing said recirculation passage into a control pressure zone (60) and a backpressure zone (78) upstream of said control pressure zone, and a control valve (28) in said recirculation passage operated to provide exhaust gas recirculation at rates which maintain the pressure in said control pressure zone proportional to a reference pressure, characterised in that the reference pressure is maintained directly proportional to the backpressure in said backpressure zone (78), so that exhaust gas recirculation is provided as a proportion of induction air flow with said proportion being independent of induction air flow.

Claim 3

An exhaust gas recirculation control assembly according to claim 1, characterised in that the assembly includes a reference pressure chamber (66) having ports (76, 80) opening to said backpressure zone and to another zone (82), and a flow control member associated with at least one of said ports (76, 80) to create said reference pressure in said chamber (66), whereby the proportion'of exhaust gas recirculation to induction air flow is established by said ports (76, 80).

Claim 4

An exhaust gas recirculation control assembly according to claim 2, characterised in that said flow control member is a valve (86) modulating at least one of said ports (76, 80), a valve (52) regulates an operating pressure in response to a deviation of the pressure in said control pressure zone (60) from a selected proportion of said reference pressure, and a pressure responsive member (32) positions said control valve (28) in accordance with said operating pressure, whereby the proportion of exhaust gas recirculation to induction air flow is established by said modulating valve (86).

Claim 5

An exhaust gas recirculation control assembly according to claim 3, characterised in that said pressure responsive member is an operating diaphragm (32) defining a portion of an operating pressure chamber (34) having an aperture (40) for sensing a subatmospheric pressure signal and also having an air bleed (46) and combining the pressures sensed through said aperture (40) and said bleed (46) to form said operating pressure, a diaphragm assembly (44) includes a control diaphragm face (50) defining a portion of a control pressure chamber (54) connected to sense the pressure in said control pressure zone (60) and further includes a reference diaphragm face (64) defining.a portion of said reference pressure chamber (66), and the valve which regulates said operating pressure is a bleed valve (52) positioned by said diaphragm assembly (44) to obstruct flow through said bleed (46) when the pressure in said control pressure chamber (54) exceeds a selected proportion of said reference pressure.

Claim 6

An exhaust gas recirculation control assembly according to any one of claims 2 to 4, characterised in that said flow control member is a duty cycle-operated valve (86) connecting said reference pressure chamber (66) to said backpressure zone (78) during a portion of the duty cycle and to an atmospheric pressure zone (82) during the remainder of the duty cycle, whereby the proportion of exhaust gas recirculation to induction air flow is established by the duty cycle.