Fuel pump for a direct injection system with a better hydraulic sealing of the intake valve

1. A fuel pump ( 4 ) for a direct injection system ( 1 ) provided with a common rail ( 3 ); the fuel pump ( 4 ) comprises:

a pumping chamber ( 14 ) defined in a main body ( 12 );

a piston ( 15 ), which is mounted in a sliding manner on the inside of the pumping chamber ( 14 ) so as to cyclically vary the volume of the pumping chamber ( 14 );

an intake channel ( 17 ), which originates from a wall of the pumping chamber ( 14 ) and has a housing portion ( 28 ), which is arranged in the area of the pumping chamber ( 14 );

an intake valve ( 18 ), which is inserted into the housing portion ( 28 ) of the intake channel ( 17 );

a delivery channel ( 19 ), which originates from a wall of the pumping chamber ( 14 );

a delivery valve ( 20 ), which is arranged along the delivery channel ( 19 ) in the area of the pumping chamber ( 14 );

a locking ring nut ( 30 ) with an annular shape, which is threaded and is screwed into the housing portion ( 28 ) of the intake channel ( 17 ) so as to strike against the intake valve ( 18 );

wherein the housing portion ( 28 ) of the intake channel ( 17 ) has an annular abutment ( 29 ), which reduces the diameter of the housing portion ( 28 ) and against which the intake valve ( 18 ) strikes;

the fuel pump ( 4 ) is characterized in that:

the intake valve ( 18 ) is made of a metal material having a greater hardness than the metal material of which the annular abutment ( 29 ) is made; and

the locking ring nut ( 30 ) is screwed into the housing portion ( 28 ) of the intake channel ( 17 ) with a tightening force that is sufficient to determine a plastic deformation of the annular abutment ( 29 ) against the intake valve ( 18 ).

2. A fuel pump ( 4 ) according to claim 1 , wherein:

the intake valve ( 18 ) comprises a disc ( 25 ) having a series of feeding through holes ( 26 ), through which fuel can flow, and a flexible lamina ( 27 ), which rests against a base of the disc ( 25 ), thus closing the passage through the feeding holes ( 26 ); and

the flexible lamina ( 27 ) comprising an outer edge ( 32 ) with a circular shape, which rests against the annular abutment ( 29 ), thus determining the plastic deformation of the annular abutment ( 29 ).

3. A fuel pump ( 4 ) according to claim 2 , wherein the flexible lamina ( 27 ) is made of a metal material having a greater hardness than the metal material of which the annular abutment ( 29 ) is made.

4. A fuel pump ( 4 ) according to claim 2 , wherein the disc ( 25 ) of the intake valve ( 18 ) is made of a metal material having a greater hardness than the metal material of which the annular abutment ( 29 ) is made.

5. A fuel pump according to claim 2 , wherein the flexible lamina ( 27 ) comprises a series of thin stems ( 33 ), which originate from the outer edge ( 32 ); and a shutter body ( 34 ), which is supported by the stems ( 33 ).

6. A fuel pump ( 4 ) according to claim 1 , wherein an intermediate element, which acts as a bearing, is interposed between the locking ring nut ( 30 ) and the intake valve ( 18 ).

7. A fuel pump ( 4 ) according to claim 1 , wherein the intake valve ( 18 ) is driven into the housing portion ( 28 ) of the intake channel ( 17 ).

8. A fuel pump ( 4 ) according to claim 1 , wherein the locking ring nut ( 30 ) strikes against the intake valve ( 18 ) on the opposite side relative to the annular abutment ( 29 ).

9. A fuel pump ( 4 ) according to claim 1 , wherein the intake valve ( 18 ) strikes, on one side, against the annular abutment ( 29 ) of the housing portion ( 28 ) and, on the opposite side, against the locking ring nut ( 30 ).