Injection rate control cam

摘要

A cam for controlling the injection rate of fuel in a fuel injection system having a four part cam profile is disclosed. The first 120 DEG is the plunger advancement segment. The next 80 DEG is the advanced dwell segment. The next 100 DEG is the plunger retraction segment and the last 60 DEG is the retracted dwell segment. The plunger advancement segment is divided into three subsegments: pre-injection stroke, injection stroke, and overtravel stroke. The pre-injection subsegment achieves minimum velocity and acceleration at the start of injection. In the injection subsegment, the cam follower acceleration is achieved as rapidly as can Hertz stress permits to increase the injection pressure and to achieve the maximum injection rate. The overtravel subsegment achieves a sharp and clean end of injection. Preferably, this cam causes injection of less than 20 mm3 of fuel per stroke during the first ten cam angle degrees of cam rotation. The injection pressure and the amount of injection are reduced at the beginning of injection, timing is advanced, and optimal control over the rate of fuel injection is provided.