Fuel pump having dual profile cam ring for driving low and high pressure reciprocating plungers

In a fuel pump connected to a fuel supply and having rotary drive means;

• a high pressure pump with a pump body with a pumping chamber with an annular arrangement of a plurality of pairs of pumping plunger bores extending radially outwardly from a cam axis, a pumping plunger mounted in each pumping plunger bore for reciprocation and first cam means surrounding the pump body and rotatable about said cam axis by the rotary drive means for reciprocating each pumping plunger to provide alternating intake and pumping phases of operation of the high pressure pump at a frequency determined by the speed of the rotary drive means, for respectively receiving an intake charge of fuel and delivering fuel from the pumping chamber at high pressure;
• and a transfer pump for raising the pressure of fuel from the fuel supply for transfer to the pumping chamber;
• wherein the improvement comprises:
• the transfer pump includes means defining a transfer plunger bore, and a transfer plunger mounted in said transfer plunger bore for reciprocation therein to provide alternating intake and transfer phases of operation of the transfer pump;
• and
• second cam means, the first cam means and the second cam means being provided by respective inner and outer profiles on an annular cam ring surrounding the pump body such that the second cam means is rotatable by the rotary drive means for reciprocating the transfer plunger in predetermined synchronism with the high pressure pump to raise the pressure of fuel from the fuel supply for transfer to the high pressure pump.

In a fuel pump of the type having a rotary drive means, a high pressure pump with a pump body which defines a pumping chamber comprising an annular arrangement of a plurality of pumping plunger bores extending radially outwardly from a cam axis, a pumping plunger mounted in each pumping plunger bore for reciprocation, and a transfer pump for transferring fuel under pressure to the pumping chamber, wherein the improvement comprises:

• means for defining a single transfer plunger bore within the transfer pump;
• a transfer plunger reciprocally mounted in said transfer plunger bore to provide alternating intake and transfer phases of operation of the transfer pump;
• and
• an annular cam ring surrounding the pump body, said cam ring being rotatably mounted for rotation about the cam axis, being driven by the rotary drive means, and comprising first and second camming surfaces, said first camming surface cooperating with the pumping plungers to cause reciprocation thereof at a frequency determined by the speed of the rotary drive means whereby the high pressure pump receives and delivers fuel at high pressure during respective and alternating intake and pumping phases of operation, said second camming surface cooperating with said transfer plunger to cause reciprocation thereof in predetermined synchronism with the high pressure pump.