| 摘要 |
A multiple stage pump for delivering fuel to an engine is disclosed which includes a pump housing, a boost stage operable at engine start to draw fuel into the pump housing at a boost stage pressure, a first pumping stage operable upon engine start for receiving fuel from the boost stage and delivering the fuel from the pump housing to a fuel metering unit, a second pumping stage operable upon engine start and during engine cruise operation for receiving fuel from the boost stage and delivering the fuel from the pump housing to said fuel metering unit, and a switching valve in fluid communication with the first and second pumping stages, and configured to control fuel flow through the first pumping stage in dependence on changes in boost stage conditions such as pressure or shaft speed. |
