| 摘要 |
PURPOSE:To accumulate a power source of a defined negative pressure at all times without need for using a vacuum switch by operating a pump means when the consumption exceeded a certain value, and supplying a power source to a means for accumulating a power source from said pump means. CONSTITUTION:The negative pressure of a surge tank ST is introduced into a negative pressure chamber A of a negative pressure actuator AC via a valve V1 which controls the negative pressure, a vent valve V2, and a release valve V3. The valves V1 and V2 are duty-ratio controlled by an electronic control unit CPU. The consumption of negative pressure which is accumulated in the surge tank ST is calculated by integrating the opening time of the valve V1, enabling the surge tank St to be always supplied with compensating negative pressure for consumption from a vacuum pump BP. Accordingly, the negative pressure accumulated in the surge tank ST can be always maintained at a defined value without being lowered below a certain value.
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