Distributor-type injector pump, for multi-cylinder compression-ignition internal combustion engines

Claim 1

A fuel injection pump for a multi-cylinder compression-ignition internal combustion engine of the direct-injection type, said pump comprising: a pump body having an internal cylindrical cavity and a compression chamber, means for the introduction of fuel in the said compression chamber, piston means slidable within the body for compressing fuel in the said compression chamber, means defining a number of delivery apertures in the wall of the cylindrical cavity of the body for communication with each of the cylinders of the engine, a rotary distributor member located in the said cylindrical cavity, said distributor member being rotatable by drive transmitted from the engine in use of the pump to effect one complete revolution in said cavity in each cycle of the engine, two distinct fuel passage means, formed in said rotary distributor member and each having an inlet end permanently communicating with the compression chamber and an outlet end in the external surface of the distributor member, the outlet ends of the said passage means being situated in two areas angularly separated from each other such that they come intermittently into communication, upon rotation of the distributor member, with successive said apertures to effect, in correspondence with each fuel delivery stroke of the said piston means, two injections of fuel into two different cylinders of the engine, so that the pump delivers to each cylinder of the engine in each cycle thereof a principal injection of fuel substantially at the end of the compression stroke in said cylinder, preceded by a pre-injection of fuel, means sensitive to the engine rotational speed for advancing the start of the delivery stroke of the piston means upon increase in the engine rotational speed, wherein the angle between the outlet ends of the said two fuel passage means is such that when the engine rotational speed is lower than a threshold value substantially equal to half the maximum speed of rotation of the engine, only one of said two fuel passage means communicates with one of said delivery apertures during each fuel delivery stroke of said piston means, whereby only the principal injection is delivered to each cylinder of the engine in each cycle thereof when the rotational speed of the engine is lower than said threshold value.