(57) A sinusoidal hydraulic pump that is particularly suitable for use as a high pressure
pump for a fuel injection system of a compression ignition engine. The pump includes
first and second plungers, a filling plunger (110) and a delivery plunger (112), each
of which is reciprocable within a respective bore (120, 122) provided in a pump housing
(124) under the influence of a respective cam (114, 116) mounted upon a common cam
shaft (118). The bores (120, 122) communicate with each other at their uppermost ends
(in the orientation shown) and define, together with end surfaces of the filling and
delivery plungers (110, 112), a pump chamber (126) for receiving fuel through a pump
inlet port (130) provided in a wall of the pump housing (124). The filling plunger
(110) cooperates with the inlet port (130) to provide a means for controlling fuel
flow into the pump chamber (126) from a low pressure fuel supply. A delivery port
(132) is also provided in the pump housing (124) in the region of the bore (122),
and the outer surface of the delivery plunger (112) cooperates with the delivery port
(132) to provide a means for controlling the delivery of pressurised fuel from the
pump chamber (126) to a high pressure fuel volume.
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