1483771 Centrifugal governors ROBERT BOSCH GmbH 2 Oct 1974 [3 Oct 1973] 42676/74 Heading G3B A speed governor for a fuel injection pump comprises a centrifugal governor 20 locatable in a fuel suction chamber 7 of the pump and adapted to adjust the pump metering member 3 against the action of a working chamber 41 whose volume is varied over a predetermined speed range, and which is communicable with chamber 7 by way of throttle opening 42. In operation, as the engine speed increases, centrifugal governor 20 pivots a lever 18 against the force of idling spring 31, so that a sliding valve 16 is displaced downwards on the rotary and reciprocatable pump piston 3 and the flow of fuel to the injection valves via chamber 7 and passages 6, 5, 4, 8, 9, 10, 11, is reduced, due to fuel flowing back to chamber 7 via a transverse passage 17. The fuel is supplied to chamber 7 by a pump 13, and the pressure is controlled by a valve 15. As the speed continues to increase, lever 18 is further deflected, until its abuts a stop 32 and the main control spring 33 is compressed, and as piston 40 moves to reduce the volume of chamber 41 fuel is forced into chamber 7 through throttle opening 42 to provide a damping of any vibrations which may occur. The pre-tensioning of spring assembly 21 can be varied by moving a piston 34 in a bore 35 by a lever and rack and pinion assembly 36, 37, and a full load stop 28 is provided. The part of the speed range which is attenuated may be the idling range, the range controlled by the main spring 33, or a mixture of both, and this is determined by the different forms of spring assemblies, working chamber 41, and throttle openings 42, Figs. 3, 5, 7 (not shown).