| 摘要 |
A compact (e.g., hand held) vacuum generator having particular application for creating a vacuum within the evaporative emissions system (e.g., a gas tank) of a motor vehicle so that a vacuum-decay test can be performed to test the system for leaks while mitigating the hazardous effects of potentially explosive hydrocarbon vapors. The vacuum generator includes a spool valve that has an internal passage and is capable of sliding through a spool valve bore in response to a pushing force. During an at-rest stage of the spool valve within the spool valve bore, the system to be tested is disconnected from the vacuum generator. During a transition stage of the spool valve within the spool valve bore, inlet gas under pressure is blown through the internal passage of the spool valve to the atmosphere by way of a vacuum generating venturi, whereby a vacuum begins to form in a vacuum passage. During a vacuum stage of the spool valve within the spool valve bore, the vacuum passage is connected between the vacuum generating venturi and the system under test at a dual vacuum inlet port so that the system will be evacuated to the atmosphere as inlet gas under pressure is blown to the atmosphere through the internal passage of the spool valve and the vacuum generating venturi. A vacuum gauge coupled to the dual vacuum inlet port is responsive to the decay of the vacuum created within the system under test to provide an indication of a leak.
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