| 摘要 |
A fuel pump for use in a common rail fuel engine, the fuel pump comprising a pumping plunger (18a) reciprocal within a plunger bore (20a) under the influence of a drive member (28a) so as to pressurise fuel within a pump chamber (22a), the drive member (28a) being co-operable with a cam rider (14) so as to impart axial drive to the plunger (18a) to reduce the volume of the pump chamber (22a), in use, whilst permitting lateral sliding movement of the cam rider (14) relative to the drive member (28a). The pumping plunger (18a) performs a pumping cycle include a forward stroke during which the pumping plunger (18a) moves between bottom-dead-centre and top-dead-centre and fuel within the pump chamber (22a) is pressurised to a relatively high level, and a return stroke during which the pumping plunger (18a) moves between top-dead-centre and bottom-dead-centre to allow the pump chamber (22a) to fill with fuel at relatively low pressure. The pump comprises means (32a, 34a) for reducing the load on the drive member (28a) due to fuel pressure within the pump chamber (22a) at least during that period of the forward stroke for which the relative velocity of sliding movement between the drive member (28a) and the cam rider (14) is at a minimum, thereby to reduce wear of the drive member (28a).
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