Exhaust gas recirculation control valve

Claim 1

An exhaust gas recirculation control valve assembly for use on an internal combustion engine having an induction passage for air flow to the engine, a throttle disposed in said induction passage for controlling air flow therethrough, an exhaust passage for exhaust gas flow from the engine, and an exhaust gas recirculation passage having a first portion extending from said exhaust passage and a second portion extending to said induction passage downstream of said throttle, said control valve assembly comprising a valve body having an inlet for receiving exhaust gases from said first portion of said recirculation passage, an outlet for discharging exhaust gases to said second portion of said recirculation passage, an orifice formed in said inlet, and a pair of upwardly facing valve seats aligned coaxially above said inlet, a pair of valve members associated with said valve seats for controlling the flow of exhaust gases therethrough, a hollow stem interconnecting said valve members for concurrent movement, said hollow stem having an open lower end for receiving exhaust gases from the zone between said orifice and the lower of said valve seats and further having a lateral port for discharging exhaust gases above the upper of said valve seats, a pressure responsive bellows connected to the upper end of said stem and responsive to the pressure transmitted from said zone through said stem to lift said valve members from said valve seats upon an increase in pressure in said zone, thereby permitting increased flow of exhaust gases upwardly through said lower valve seat and downwardly through said upper valve seat, and to lower said valve members toward said valve seats upon a decrease in pressure in said zone, thereby reducing flow of exhaust gases through said valve seats, whereby the pressure in said zone is maintained at a substantially constant value and exhaust gases may be recirculated through an orifice into a zone of substantially constant pressure to thereby provide recirculation of exhaust gases at a rate which varies in accordance with exhaust gas pressure in said exhaust passage and is thereby proportional to the rate of air flow through said induction passage.