Variable injection timing and injection pressure control arrangement

Abstract

In accordance with preferred embodiments of the invention a timing adjustment device includes a cam follower that is engaged between an overhead cam and an injector rocker arm, and is mounted on a rotatable eccentric shaft. The geometry of the eccentric shaft and cam follower is designed so that, as timing is varied by rotation of the eccentric shaft, no change is produced in the vertical height of the rocker arm when the cam shaft is on the outer base circle and the injector is bottomed, in order to assure that the 'mechanical crush' of the PT type injector is constant despite changes in timing. In a first application of the timing arrangement, it is used together with a simple injector, which does not utilize a multi-plunger arrangement to form a hydraulic link, to achieve lower parasitic losses. To obtain independent control over injection pressure and timing, a fuel injector in which a hydraulic link is formed between plungers of a multi-plunger arrangement is used with the timing arrangement in order to allow the injection pressure to be maintained constant over a wide range of engine speeds without interfering with engine timing.