| 摘要 |
The RPM bias valve combines a first fluid signal which varies inversely with the throttle position or with other engine conditions and a second fluid signal which varies with engine speed to produce a modulated output signal which varies as a function of both. A pressure responsive diaphragm (68) separates a first signal chamber (62) and a modulated output signal chamber (66). The diaphragm is also biased by an extension spring (90) which is connected with a cam follower (104). The position of the cam follower, hence, the biasing force or pressure applied by the extension spring, is controlled by a cam (102) and a rolling diaphragm (106) which is operated upon by the second fluid signal. A first valve (70) selectively connects the first and modulated signal chambers to reduce the vacuum in the modulated output signal chamber when the pressure responsive diaphragm (68) is out of its equilibrium position in one direction. A second valve (72) selectively provides fluid communication between the modulated output signal chamber and a vacuum supply port (56) when the pressure reponsive diaphragm (68) is out of its equilibrium position in the other direction. In this manner, a change in the pressure on the diaphragm (68) from the second fluid signal or from the first fluid signal by way of the extension spring (90) causes the diaphragm to move in such a manner that the appropriate one of the first and second valves is opened to adjust the vacuum in the modulated output signal chamber (66) to restore the diaphragm to the equilibrium position. The modulated output signal from the modulated output signal chamber thus varies as a function of both the first and second fluid signals.
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