| 摘要 |
A valve assembly (10) is provided for controlling the recirculation of exhaust gases in an internal combustion engine. The assembly includes a lower housing portion (20) having an exhaust gas inlet (24) and an exhaust outlet port (28). An upper housing member (30) has mounted therein an upper flexible diaphragm (48) biased by a spring (72) a predetermined amount in an upward direction, and a lower diaphragm (76) which is also biased by a spring (102) a predetermined amount in a downward direction. The upper and lower diaphragms define a control chamber (108) which is communicated with an engine intake manifold vacuum source. An axially movable valve member (90) is connected to the lower end of a valve stem (88) which is in turn connected to the lower diaphragm. An adjustment feature (62, 66, 98, 104) permits the preload on both of the biasing springs to be precisely adjusted in order that a desired precise exhaust gas recirculation flow as a function of intake manifold vacuum can be achieved after final assembly of the valve. An alternate embodiment of the invention incorporates a bleed valve assembly (202) responsive to exhaust gas back pressure which enables the valve to discriminate between various engine loadings.
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