Exhaust gas re-circulation system for an internal combustion engine

Claim 1

An exhaust gas re-circulation system for an internal combustion engine, comprising an exhaust gas re-circulation pipeline extending between intake and exhaust systems of the internal combustion engine for re-introducing a part of the exhaust gas from the exhaust system into the intake system, a single flow-control valve for regulating the flow of the re-introduced exhaust gas, which valve comprises: an orifice element arranged in a portion of the exhaust gas re-circulation pipeline to provide said portion with an orifice through which the exhaust gas flows from said exhaust system toward said intake system; a valve element movably placed over the orifice and having an axially extended valve stem; a first displaceable diaphragm member connected to the valve stem for actuating movement of the valve element away from said orifice; a second displaceable diaphragm member axially spaced apart from the first diaphragm member and having means for limiting the movement of said valve element; a first closed pressure-control chamber defined between the first and second diaphragm members; a second closed pressure-control chamber arranged adjacent to, but separated from said first closed pressure-control chamber by said second diaphragm member, and; an atmospheric pressure chamber arranged adjacent to, but separated from said first closed pressure-control chamber by said first diaphragm member, and means for generating in first said first and then in said second pressure-control chambers, individual vacuum pressures changing in response to change in the opening position of a throttle valve of the intake system from the closed position thereof, said vacuum pressure generating means comprising a first vacuum pressure line extending from said first pressure-control chamber of the flow-control valve to a first vacuum port provided in said intake system, and a second vacuum pressure line extending from said second-pressure control chamber of the flow-control valve to a second vacuum port provided in said intake system, said first and second vacuum ports being located such that when said throttle valve is opened gradually from the closed position thereof, an edge of said throttle valve moves past said first and second vacuum ports in sequence, said separate vacuum pressures of said first and second pressure-control chambers causing sequential displacements of said first and second diaphragm members thereby moving said valve element away from said orifice in a two step-like manner.