| 摘要 |
A fuel injector has an injector body (11) defining a low pressure space (15), a trapped volume (21) and a fuel pressurization chamber (20). A needle valve member (30) is positioned in the injector body and movable between an injection position in which the fuel pressurization chamber (20) is open to a nozzle outlet (14) and a closed position in which the nozzle outlet (14) is blocked to the fuel pressurization chamber (20). At least one of the needle valve member (30) and the injector body define a pressure release passage (53) between the trapped volume (21) and a low pressure space (15). A pressure regulating valve (50) is positioned in the pressure release passage (53) and has a regulating valve member, i.e. ball (51), movable to an open position when fluid pressure in the trapped volume (21) is above a pop-off pressure. An alternative embodiment may have a plate type regulating valve member. At idle operating conditions there is time for pressure that has built up in the trapped volume (21) to decay before the next injection event. Therefore the next event opening pressure is low. At higher speeds, for example rated, there is insufficient time for the pressure to decay so a greater opening pressure is required.
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