Diesel fuel injection pump with electromagnetic fuel spilling valve

Abstract

A fuel injection pump for a diesel engine includes a housing and a plunger which slides in a bore in the housing, with a high pressure chamber defined at an end of the plunger. The plunger rotates with the crankshaft and reciprocates so as to pump fuel from the high pressure chamber to the engine cylinders, under the control of an electromagnetic valve. This valve includes a pilot valve which selectively vents the high pressure chamber, which is operated to open and close by selective supply of electrical energy thereto, and a balance member which is driven by a fluid force arising when the pilot valve is thus opened and a relatively small flow of fuel is released from the high pressure chamber, and which when so driven releases a relatively large flow of fuel from the high pressure chamber. Thereby the response of the electromagnetic valve as a whole is made quick, so that it is possible to inject a pilot fuel injection spirt before the main spirt of fuel injection, thus slowing down the combustion speed when the engine is functioning under low load conditions, and thereby providing smooth and gradual combustion, thus preventing diesel knocking. Optionally, the pump may include a means for, after said electromagnetic valve has been actuated by supply of electric current in a particular direction, supplying electric current in the direction opposite to said particular direction thereto, so as to avoid problems caused by magnetization effects of the solenoid core.