High pressure fuel pump

Abstract

A high pressure fuel pump includes a pump head from which extends a turret, a bore extends along a main axis from a pumping chamber through the turret to an open end. A piston is arranged in the bore and protrudes out of the turret, an outer extremity being provided with a cam follower. A spring is arranged around the piston and slipped over the turret, the spring is compressed between the cam follower and the main part of the pump head. A cup shaped sleeve is arranged around the turret and defines a volume between the turret and the peripheral wall which fills with fuel that has leaked between the piston and the blind bore from the pumping chamber. A bottom face of the sleeve is provided with a hole through which the piston extends. An opening in the peripheral wall allows fuel to exit the volume.

Claims

1. A high pressure fuel pump comprising: a pump head having a main part and a cylindrical turret protruding along a main axis from the main part to a distant disc face, a blind bore extending along the main axis from a pumping chamber, inside the pump head then through the cylindrical turret to an open end in the distant disc face and a low pressure inlet and a high pressure outlet opening in the pumping chamber which flow fuel in and out of the blind bore respectively, a piston arranged to be slidably guided in the blind bore, the piston extending from a compression extremity in the pumping chamber of the blind bore to an outer extremity outside the pump head, the outer extremity being provided with a cam follower, a spring arranged around the piston and slipped over the cylindrical turret such that the spring circumferentially surrounds the cylindrical turret, the spring being compressed between the cam follower and the main part of the pump head, and a sleeve having a cup shape with a bottom face and a peripheral wall, the sleeve being arranged around the cylindrical turret defining a volume between the cylindrical turret and the peripheral wall which fills with fuel that has leaked between the piston and the blind bore from the pumping chamber, the bottom face of the sleeve being provided with a hole through which the piston extends and the sleeve also being provided with an opening in the peripheral wall which allows fuel to exit the volume, wherein the sleeve is further provided with a radial disc face radially extending from an edge of the peripheral wall that is distant from the bottom face, the radial disc face being in abutment against the pump head, the opening in the peripheral wall being located between the bottom face and the radial disc face, and the spring surrounding the sleeve and being compressed against the radial disc face of the sleeve.

2. A high pressure fuel pump as set forth in claim 1 wherein the cylindrical turret is provided with a radial hole which extends radially through the cylindrical turret and which allows fuel that has leaked between the piston and the blind bore from the pumping chamber to pass to the thin volume.

3. A high pressure fuel pump as set forth in claim 1 wherein, relative to the main axis, the peripheral wall is radially between the turret and the spring.

4. A high pressure fuel pump as set forth in claim 1 wherein, relative to the main axis, the opening in the peripheral wall is radially aligned with the spring.

5. A high pressure fuel pump as set forth in claim 1 wherein the turret is of unitary construction with the main part.

6. A high pressure fuel pump as set forth in claim 1 wherein the radial disc face is in abutment against the main part of the pump head in a direction parallel to the main axis.

7. A high pressure fuel pump as set forth in claim 1 wherein one side of the radial disc face engages the main part of the pump head in a direction parallel to the main axis and another side of the radial disc face, which is opposite said one side of the radial disc face, engages the spring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is now described by way of example with reference to the accompanying drawings in which:

(2) FIG. 1 is an axial section of a high pressure pump as per the invention.

(3) FIG. 2 is a detail of the pump of FIG. 1.

(4) FIG. 3 is a similar detail as FIG. 2 but of another embodiment of the invention.

(5) FIG. 4 is an isometric representation of a sleeve that is arranged on the pump of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) In the following description, similar elements will be designated with the same reference numbers. Also, to ease and clarify the description a top-down orientation will be followed in reference to the orientation of the figures. Therefore, words and expressions such as top, upper, lower, over, under, etc. may be utilized without any intention to limit the scope of the invention.

(7) The invention is now described in reference to FIGS. 1-4. FIG. 1 is a cross section of a high pressure fuel pump 10 comprising a pump head 12 having a main part 14, and from a lower face of said main part 14 the pump head 12 is provided with a protruding turret 16 downwardly extending along a main axis A from the main part 14 until a disc face 18. The pump head 12 is further provided with a bore 20 downwardly extending along a main axis A from a pumping chamber 22, inside the pump head 12 to a downward opening 24 centrally arranged in the disc face 18 of the turret 16.

(8) The pump head 12 is further provided with a fuel inlet 26 arranged at the very top of the bore 20. A poppet valve 28 controls the opening and closing of fuel inlet 26. A fuel outlet 30, which opening and closing are controlled by a ball pressed against a seat, is arranged laterally in the pump head 12 and opens in the pumping chamber 22. Multiple variants of inlet valves and outlets exist in the art, and the description made does not limit the invention to this specific embodiment.

(9) In the bore 20 is slidably arranged a piston 32 that extends from an inner end 34, or top end, inside the bore 20, to an outer end 36, or bottom end, outside the pump head 12. At the outer end 36 is arranged a spring seat 38 that holds a spring 40 compressed between spring seat 38 and the main part 14 of the pump head 12. The spring 40 is arranged around the piston 32 and is slipped around the turret 16. At the very bottom end of the piston is arranged a non-represented cam follower, that in operation cooperates with a rotating cam.

(10) As seen on the figures, a sleeve 42 is arranged around the turret 16. The sleeve 42 is blanked and deep drawn from a thin metal sheet and has a cup shape with a transversal bottom face 44 from which extends a substantially cylindrical peripheral wall 46 and an upper disc face 48 that radially extends from the upper edge of the peripheral wall 46. The sleeve 42 is further provided with a hole 50 centrally arranged in the bottom face 44 in order to enable the piston 32 to extend through, and with at least one opening 52 in the peripheral wall 46. On the figures, the openings 52 are represented at about mid distance between the bottom face 44 and the upper disc face 48 but they could be closer to either one of the transversal faces.

(11) When in place, the sleeve 42 is maintained in place as the spring 40 is slipped around the sleeve 42 and it abuts against the under face of the upper disc face 48. A thin volume 54 surrounding the turret 16 remains between the turret 16 and the sleeve 42.

(12) In operation the non-represented cam actuates the cam follower and the piston 32 in a reciprocal up-and-down movement. The fuel that has flowed in the pumping chamber 22 is pressurized before being expelled though the outlet 30. During this operation fuel in the pumping chamber 22 heats up and all parts thermally expand. A small quantity of the pressurized fuel leaks, as indicated by the reference L, through the clearance between the bore 20 and the piston 32 lubricating the surfaces. Further substantial heating of the leaking fuel occurs due to fluid shear in the clearance. The leaking fuel finally exits said clearance at the bottom of the turret 16 and instead of continuing to flow downwardly, the leaked fuel is captured inside the sleeve 42 where it fills the thin volume 54, wetting with hot fuel the outer surface of the turret 16. The fuel flows up in the sleeve until it exits via the openings 52. Thanks to this, the temperature gradient across the turret 16 is minimized and so is the risk of gripping of the piston 32 within the bore 20 due to differential thermal expansions.

(13) In another embodiment detailed in FIG. 3, the turret 16 is provided with radial holes 56 arranged close to the disc face 18 of the turret. In this embodiment the fuel leaks via these radial holes 56 then fill the thin volume 54.

(14) In the above description the following references have been utilized: 10 pump 12 pump head 14 main part of the pump head 16 turret 18 disc face 20 bore 22 pumping chamber 24 opening of the bore 26 fuel inlet 28 poppet valve 30 fuel outlet 32 piston 34 inner end of the piston 36 outer end of the piston 38 spring seat 40 spring 42 sleeve 44 bottom face 46 peripheral wall 48 upper disc face 50 hole in the sleeve 52 opening in the sleeve 54 thin volume 56 radial holes A main axis L fuel leak path