Fuel pump with an improved maximum-pressure valve for a direct-injection system

A fuel pump (1) for a direct-injection system;

• the fuel pump (1) comprises:
• at least one pumping chamber (14);
• a piston (15), which is mounted so as to slide inside the pumping chamber (14) to cyclically change the volume of the pumping chamber (14);
• an intake channel (17), which is connected to the pumping chamber (14) and is regulated by an intake valve (18);
• a delivery channel (22), which is connected to the pumping chamber (14) and is regulated by a one-way delivery valve (23), which only permits a fuel flow flowing out of the pumping chamber (14);
• and
• a drain channel (32), which originates in the delivery channel (22) and is regulated by a one-way, maximum-pressure valve (33), which opens when the fuel pressure in the delivery channel (22) exceeds a threshold value;
• wherein the maximum-pressure valve (33) comprises:
• a shutter (34), which is movable along the drain channel (32), a valve body (36), which is provided with a valve seat (35) designed to be engaged in fluid-tight manner by the shutter (34), a spring (38), which is calibrated to push the shutter (34) towards an engaging position where it engages the valve seat (35) in a fluid-tight manner;
• and a plate (39), which is arranged in contact with the shutter (34) on the opposite side of the valve seat (35);
• wherein the plate (39) of the maximum-pressure valve (33) has a first annular groove (42), which is arranged around the shutter (34);
• and
• wherein the valve body (36) of the maximum-pressure valve (33) has a second annular groove (43), which is arranged around the shutter (34) and at least partially faces the first annular groove (42) of the plate (39).