High pressure engine fuel injection system - has injector pump piston hydraulically returned by differential piston

摘要

The high pressure pump for an engine fuel injection system receives fuel in the usual manner from a low pressure lift pump. It then delivers the metered fuel volume to the injectors (14) via a delivery valve, a pressure pipe (7) and a differential piston cylinder arrangement (8). This arrangement has a large diameter piston (10) and a smaller piston (11). The large piston is subject to injection pump pressure and the small piston is subject to lift pump pressure via a non return valve (12). The two pistons are separate pieces able to move axially inside corresponding cylinder sleeves (21, 22) secured to the pump housing by collars (23, 24). The small piston has a spherical surface (9) in contact with the large piston. An annular gap (25, 26) is left between the respective cylinder sleeves (21, 22) and filled with fuel. The free ends of the sleeves could form annular restrictors (27, 28) with the pump housing.