The invention is based on a speed governor of the generic type described hereinafter. A speed or rpm governor of this kind is the subject of German Patent Application P No. 33 01 416.7, in which the governor spring is a pre-stressed compression spring disposed between the two supporting parts with those parts being embodied such that they are pressed against one another under the influence of a compression spring. To maintain spacing and accommodate the compression spring, one of the supporting parts is embodied as an actuating rod guided on the other supporting part and coupled to the governor lever.
In this embodiment of the speed governor, the fuel injection pump must be shut off and opened up in order to vary the spring characteristic, that is, the effective length or pre-stressing of the spring. Because of manufacturing tolerances of the various parts of an rpm governor such as the flyweights, and because of the governor spring characteristic, component part tolerances and installation tolerances, deviations in the speed droop, or P degree, occur--that is, deviations in the breakaway curve upon attaining the maximum rpm. Especially in internal combustion engines provided for driving engine-generator sets, the associated fuel injection pump must be regulated very accurately, and the P degree in particular must be adhered to very exactly.