| 摘要 |
<p>A fluid injector 10, eg for fuel, which functions as a positive displacement pump comprises a piston 11 which draws fluid into a piston chamber via a one-way inlet valve 32 and then expels the fluid via a one-way outlet valve 25-29. The inlet comprises a passage 24 through a housing 12 which opens on to the pumping chamber as an inlet orifice, eg annular, provided in a piston chamber end face (40, fig.6c) facing an opposed piston face of the piston. The outlet comprises a passage 30 through the housing 12 which opens on to the pumping chamber via an outlet orifice in the piston chamber end face spaced apart from the inlet orifice. The one-way inlet valve 32 comprises a sealing element, eg annular, which is aligned with the inlet orifice and which can engage the piston end face spanning the inlet orifice to seal the inlet orifice. The piston 11 may force the sealing element into engagement with the piston chamber end face. The piston face may have a recess (40, figs. 8, 9, 10A) aligned with the sealing element allowing fluid to flow around the sealing element.</p> |
