Advance arrangement

Abstract

An advance arrangement for use in controlling timing of fuel delivery by a fuel pump comprises an advance piston which is moveable within a first bore and which cooperates, in use, with a cam arrangement of a fuel pump to adjust the timing of fuel delivery by the pump. A surface associated with the advance piston is exposed to fuel pressure within an advance piston control chamber. A light load piston is moveable relative to the advance piston against a spring load due to a light load control spring to adjust the timing under light load conditions. A temperature control valve is operable to control fuel pressure applied to the light load piston depending on engine temperature so as to permit adjustment of the timing depending on engine temperature. An adjustment piston co-operates with the light load control spring to vary the spring load acting on the light load piston in response to speed-dependent variations in fuel pressure applied to the adjustment piston, thereby to permit adjustment of the timing depending on engine temperature at relatively low engine speeds.

Dependencies are inferred from the claim text.