EP3368766B1

EP3368766B1 - High pressure fuel pump

Info

Publication number: EP3368766B1
Application number: EP16782287.3A
Authority: EP
Inventors: Stephen Hutchins; Stephen Joseph MACLANE
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2015-10-27
Filing date: 2016-10-19
Publication date: 2021-04-07
Anticipated expiration: 2036-10-19
Also published as: EP3368766A1; GB201518964D0; WO2017072006A1

Description

BACKGROUND

Technical Field

The present invention relates generally to the field of high pressure fuel pumps. More particularly, but not exclusively, the present invention concerns an adapted shoe for high pressure diesel fuel pumps.

Description of the Related Art

As shown in Figure 1, a typical high pressure diesel fuel pump adopting a roller-shoe arrangement as part of the drivetrain, comprises a plunger 2 extending from a hydraulic head 1 along a pumping axis A-A'. A plunger return spring 3 is seated around the head 1 and extends to the top of a spring seat 4 fixed near a lower end 2a of the plunger 2. The lower end 2a of the plunger 2 contacts an upper face of a shoe 5. The shoe 5 slides within an axial bore 6a (disposed along the pumping axis A-A') of a shoe guide 6. A roller 7 is mounted and retained within an aperture provided at a lower end of the shoe 5 and slides within the bore 6a with the shoe 5. The roller 7 contacts a surface of a cam 8, which is driven to rotate by a rotating driveshaft (not shown) to provide upward sliding motion along the pumping axis A-A'.
Fuel residing in the clearance between the roller 7 and the shoe 5 forms a hydrodynamic film therebetween. To maintain the film and prevent collapse, a constant supply of fuel into the clearance between the roller 7 and the shoe 5 is required.
If the interface between the roller 7 and the shoe 5 is not adequately lubricated, the arrangement has a tendency to seize during use. This, in turn, causes unnecessary wear on the cam 8 and disrupts smooth and efficient running of the drivetrain. Accordingly, the interface between the roller 7 and the shoe 5 requires a continuous supply of fuel during use.
It is an object of the present invention to address one or more of the problems of known designs, particularly, but not exclusively in high pressure diesel fuel pumps.
Therefore, it is now desired to provide an improved drivetrain arrangement for a high pressure fuel pump that is capable of delivering increased lubrication to the roller-shoe interface. More particularly, it is desired to provide an improved shoe for a drivetrain arrangement of a high pressure diesel fuel pump JP H05 180116 A discloses a high pressure fuel pump with a tappet and a roller guided in the tappet, the roller having an oil supply bore from the side of the tappet towards the roller shaft having a reduced diameter compared to the roller and a dripping oil bore from the top of the tappet to the roller itself.

SUMMARY OF THE INVENTION

In a first aspect of the present invention as defined by independent claim 1 there is provided a high pressure diesel fuel pump comprising a pumping assembly and a drivetrain assembly, the pumping assembly comprising a plunger extending from a pump head along a pumping axis, the drivetrain assembly comprising a drive shaft and a cam mounted thereon within a cambox of a housing, a shoe for contact with a lower end of the plunger, a roller mounted within a cavity of the shoe for contact with the cam, and a shoe guide mounted within a guide chamber of the housing substantially between the cam and the plunger and adapted to receive the shoe and roller within a bore thereof, wherein the plunger is arranged for reciprocating linear movement along the pumping axis within a pumping chamber of the housing upon rotation of the cam, characterised in that the shoe comprises at least one fuel delivery means extending between an upper surface of the shoe and an unloaded region of the cavity.
With this arrangement, the fuel delivery means constantly supplies fuel to the interface between the roller and the shoe within the cavity, to promote the creation and maintenance of a hydrodynamic film. The drivetrain assembly has a reduced tendency to seize and therefore, runs smoothly and efficiently during use, whilst minimising wear on the cam.
By 'unloaded region of the cavity', what is meant is one or more segments of the cavity that is/are (a) not located directly under the plunger contact area, and (b) above the diametric line that lies laterally across the cavity. By 'plunger contact area' what is meant is a central 30% of the upper surface of the shoe.
Preferably, the fuel delivery means comprises a bore through a body of the shoe connecting the upper surface of the shoe with the cavity.
Preferably, the bore comprises an internal opening in a wall of the cavity in said unloaded region of the cavity.
According to the invention, the internal opening is located in a segment of the cavity wall extending between approximately 15° and approximately 75° from the pumping axis (in any direction). The internal opening may be located in a segment of the cavity wall extending between approximately 30° and approximately 60° from the pumping axis (in any direction). The internal opening may be located in a segment of the cavity wall extending between approximately 15° and approximately 30° from the pumping axis (in any direction). Alternatively, the internal opening may located in a segment of the cavity wall extending between approximately 60° and approximately 89° from the pumping axis (in any direction). The internal opening may be located at approximately 45° from the pumping axis (in any direction).
Preferably, the internal opening comprises a single aperture. Preferably, the internal opening is disposed approximately centrally along a length of the cavity.
According to the invention, the internal opening terminates in a reservoir provided in the cavity wall. Preferably, the reservoir comprises a recess cut into said cavity wall. Preferably, the recess extends longitudinally along substantially the length of the cavity wall. Preferably, the recess is a closed-ended channel, e.g. does not extend the full length of the cavity so as to be closed to end walls of the shoe. Preferably, the recess extends along approximately between 60% and 90% of the length of the cavity wall.
The bore may comprise an external opening in the upper surface of the shoe. According to the invention however, the bore comprises an external opening into a link. By 'link' what is meant is a connecting passage between the external opening and the upper surface of the shoe.
The link may be provided internally of the body of the shoe. According to the invention however, the link is provided in the side wall of the shoe, e.g. open to the side wall of the shoe. Preferably, the link comprises a hollow cut into said side face and open to the upper surface of the shoe. Preferably, the link is closed to a bottom end of the shoe. Most preferably, the link extends from the upper surface to just below the external opening of the bore.
Preferably, the bore is disposed on a downwardly sloping angle between external opening and the internal opening. Preferably, the angle comprises between approximately 15° and approximately 75° relative to the pumping axis. More preferably, the angle comprises between approximately 30° and approximately 60° relative to the pumping axis. Most preferably, the angle comprises approximately 45° relative to the pumping axis.
The fuel delivery means may comprise a plurality of bores disposed in said body relative to one side wall of the shoe each connecting the upper surface of the shoe and the cavity. Each bore may therefore, comprise a separate link at the external opening and/or a separate reservoir at the internal opening. However, the plurality of bores may share a universal link and/ or a universal reservoir. The universal link may extend substantially along significant proportion of a side wall/ upper surface of the shoe to encompass all of the bores. According to the invention, the universal link is a reservoir comprising a recess and the recess extends between approximately 60% and 90% of the length of the side wall/ upper surface.
Alternatively, the fuel delivery means may comprise a primary bore connected to the upper surface of the shoe and a plurality of secondary bores branching off to the cavity therefrom. In this case, the plurality of bores may share a universal link at the external opening of the primary bore and a universal reservoir at the internal opening. Accordingly, the universal link may comprise a narrow hollow that is disposed substantially centrally on the side wall/ upper surface of the shoe.
Where there are a plurality of bores, preferably, the bores are substantially equally spaced along a length of the body of the shoe.
Preferably, both the internal opening and the external opening of a specific bore are located at substantially the same distance from an end wall of the shoe, e.g. the plane of a bore relative to end walls of the shoe remains constant from the external opening to the internal opening.
Preferably, the shoe comprises fuel delivery means arranged to supply fuel to both sides of the cavity. Therefore, preferably, the shoe comprises one fuel delivery means commencing in one side face of the shoe terminating in one side of the cavity wall and a second fuel delivery means commencing in an opposing side face of the shoe terminating in an opposing side of the cavity wall. Preferably, the two fuel delivery means are disposed on opposite sides of the pumping axis.
Preferably, the fuel delivery means are configured to be the same in both side faces. This not only brings balance to the shoe, but also enables the shoe to be used in two different orientations within the bore of the shoe guide.
According to the invention, the pump is a diesel pump.
According to the present invention the high pressure fuel pump comprises a drivetrain assembly comprising a drive shaft and a cam mounted thereon within a cambox of a housing, a shoe for contact with a lower end of the plunger, a roller mounted within a cavity of the shoe for contact with the cam, and a shoe guide mounted within a guide chamber of the housing substantially between the cam and the plunger and adapted to receive the shoe and roller within a bore thereof, characterised in that the shoe comprises at least one fuel delivery means extending between an upper surface of the shoe and an unloaded region of the cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show how exemplary embodiments may be carried into effect, reference will now be made to the accompanying drawings in which:

Figure 1 is a cross-sectional side view of a high pressure diesel fuel pump according to an embodiment of the invention;
Figure 2 is cross-sectional exploded side view of the pump of Figure 1;
Figure 3 is a schematic cross-sectional end view of the shoe for a drivetrain assembly of a high pressure fuel pump according to Figure 1;
Figure 4 is a schematic perspective side view of the shoe for a drivetrain assembly of a high pressure fuel pump according to the invention;
Figure 5 is a schematic cross-sectional end view of the shoe for a drivetrain assembly of a high pressure fuel pump according to Figure 4;
Figure 6 is a schematic perspective side-end view of a shoe for a drivetrain assembly of a high pressure fuel pump according to Figure 4; and
Figure 7 is a schematic perspective bottom view of the shoe for a drivetrain assembly of a high pressure fuel pump according to Figure 4.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

One embodiment of the invention is shown in Figures 1 to 3. A high pressure diesel fuel pump 1 comprises a pumping assembly 10 and a drivetrain assembly 20, the pumping assembly comprising a plunger 12 extending from a pump head 11 along a pumping axis A-A', the drivetrain assembly 20 comprising a drive shaft and a cam 80 mounted thereon within a cambox 21 of a housing 22, a shoe 50 for contact with a lower end 12a of the plunger 12, a roller 70 mounted within a cavity 52 of the shoe 50 for contact with the cam 80, and a shoe guide 60 mounted within a guide chamber 23 of the housing 22 substantially between the cam 80 and the plunger 12 and adapted to receive the shoe 50 and roller 70 within a bore 62 thereof, wherein the plunger 12 is arranged for reciprocating linear movement along the pumping axis A-A' within a pumping chamber 24 of the housing 22 upon rotation of the cam 80, characterised in that the shoe 50 comprises at least one fuel delivery means 90 extending between an upper surface 53 of the shoe 50 and an unloaded region 52a of the cavity 52.
The shoe 50 comprises a generally cuboidal body 51 with the upper face 53 and a lower face 54. The cavity 52 for the roller 70 is provided in the bottom face 54, whilst the upper face 53 contacts the lower end 12a of the plunger 12. Between the upper face 53 and the lower face 54, the body 51 comprises a pair of opposing side faces 55a, 55b and a pair of opposing end faces 56a, 56b. The cavity 52 for the roller 70 extends between the pair of end faces 56a, 56b and is open to both. The side faces 55a, 55b are substantially closed to the cavity 52.
The side faces 55a, 55b are elongate compared with the end faces 56a, 56b. At the junction between the side faces 55a, 55b and the end faces 56a, 56b, the body 51 comprises blunted corners 51a. The body 51 of the shoe 50 is sized appropriately to fit snugly between two pairs of internal retaining walls 62a/b, 62c/d (62d not shown) of the bore 62 of the shoe guide 60.
The cavity 52 provided within the body 51 at the lower end 54 comprises slightly more than a half-cylindrical open-ended aperture sized to accommodate and retain the rotating roller 70.
The fuel delivery means 90 comprises a link 91, a bore 92 and a reservoir 93.
The side face 55a of the shoe 50 comprises the link 91 in the form of a recess cut into an upper portion of the side face 55a and open to the upper surface 53. The link 91 comprises a short vertically disposed recess with a rounded bottom. The link 91 substantially centrally located on the side face 55a between the two end faces 56a, 56b of the shoe 50.
Close to the rounded bottom of the link 91, an external opening 92a to the bore 92 is provided. Accordingly, the external opening 92a is set back relative to the side face 55a and is substantially centrally located on the side face 55a (between the two end faces 56a, 56b) of the shoe 50.
The bore 92 comprises a generally cylindrical, substantially uniform shaft that slopes downwardly between the external opening 92a and an internal opening 92b that is open to the cavity 52. The bore 92 is substantially centrally located within the body 51 of the shoe 50 and adopts a planar path relative to the two end faces 56a, 56b.
The bore 92 terminates at the internal opening 92b. Due to the planar path taken by the bore 92, the internal opening 92b is also substantially centrally located within the cavity 52 relative to the two end faces 56a, 56b of the shoe 50.
The internal opening 92b is located in the cavity 52 at a radial position of approximately 45° relative to the pumping axis A-A'. This radial position advantageously avoids the internal opening 92b from being located under the part of the body 51 of the shoe 50 that is subject to significant load from the plunger 12.
During rotation of the roller 70 in the cavity 52 in a direction D, one side face 55a of the shoe 50 is biased towards a corresponding internal wall 62a of the bore 62 of the shoe guide 60. In the Figures 1 to 3, the direction of rotation of the roller 70 is clockwise and as such, the appropriate faces are side face 55a and internal wall 62a. The area of the respective side face 55a and wall 62a that are affected is generally around the horizontal diameter of the cavity 52/ roller 70, e.g. perpendicular to the pumping axis A-A'. However, the 45° radial position of the internal opening 92b also avoids being located in an area of the cavity 52 which is subjected to such significant side loads from the roller 70. Alternative radial positions for the internal opening 92b are possible, whilst avoiding plunger and side loads and radial positions between approximately 15° and 75° are generally thought to be acceptable.
It is to be appreciated, however, that the opposite side face 55b of the shoe 50 and opposite internal wall 62b of the guide 60 would be subjected to the abovementioned side loads should the direction of rotation D be reversed (anti-clockwise), in which case, the fuel delivery means 90 would be provided on the opposite side face 55b of the shoe 50.
The cavity 52 provides the reservoir 93 in the form of an elongate, shallow recess or channel cut into the wall of the cavity 52. The reservoir 93 comprises a substantially uniform profile therealong. The reservoir 93 extends between the two end faces 56a, 56b of the shoe 50 within the cavity 52, but is closed to the end faces 56a, 56b, so as to form a pocket in the cavity 52. The reservoir 53 is substantially centrally located relative to the two end faces 56a, 56b of the shoe 50 and extends across approximately 80% of the length of the cavity 52. The reservoir 93 encompasses the internal opening 92b at an approximately central position, both longitudinally and laterally thereof.
In an alternative embodiment as shown in Figures 4 to 6, the shoe comprises two fuel delivery means 90 each located substantially opposite one another on the shoe 50 in mirror image of one another.
During assembly, the shoe 50 is disposed in the bore 62 such that the end faces 56 of the shoe 50 contact the internal walls 62c, 62d and the side faces 55a, 55b of the shoe 50 contact the internal walls 62a, 62b. Accordingly, the link 91 of the fuel delivery means 90 is/ are located against internal walls 62a and/or 62b of the shoe guide 60.
In use, since the link 91 of the fuel delivery means 90 is open to the upper surface 53 of the shoe 50 at all times, the link 91 is able to be constantly flooded with fuel. The fuel is able to travel through the link 91 to the external opening 92a of the bore 92, through the bore 92 and to the internal opening 92b. Upon exiting the internal opening 92b, the fuel is distributed along the reservoir 93 and from there, the fuel is dragged into the clearance between the roller 70 and the cavity 52 of the shoe 50 by the rotation of the roller 70, to form/ replenish and maintain the hydrodynamic film therebetween.
Since the internal opening 92b and also the reservoir 93 are located within the cavity 52 in a radial position that minimises any load subjected by the roller 70 or the plunger 12, the flow of fuel into the clearance between the roller 70 and the shoe 50 is relatively unhindered.
Advantageously, with the invention as described, the fuel delivery means 90 constantly supplies fuel to the interface between the roller 70 and the shoe 50 within the cavity 52, to promote the creation and maintenance of the lubricating hydrodynamic film. The drivetrain assembly has a reduced tendency to seize and therefore, runs smoothly and efficiently during use, whilst minimising wear on the cam 80.
Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

Claims

A high pressure diesel fuel pump (1) comprising a pumping assembly (10) and a drivetrain assembly (20), the pumping assembly (10) comprising a plunger (12) extending from a pump head (11) along a pumping axis (A-A'), the drivetrain assembly (20) comprising a drive shaft and a cam (80) mounted thereon within a cambox (21) of a housing (22), a shoe (50) for contact with a lower end (12a) of the plunger (12), a roller (70) mounted within a cavity (52) of the shoe (50) for contact with the cam (80), and a shoe guide (60) mounted within a guide chamber (23) of the housing (22) substantially between the cam (80) and the plunger (12) and adapted to receive the shoe (50) and roller (70) within a bore (62) thereof, wherein the plunger (12) is arranged for reciprocating linear movement along the pumping axis (A-A') within a pumping chamber (24) of the housing (22) upon rotation of the cam (80), characterised in that the shoe (50) comprises at least one fuel delivery means (90) extending between an upper surface (53) of the shoe (50) and an unloaded region (52a) of the cavity (52), the unloaded region (52a) of the cavity (52) being one or more segments of the cavity (52) that is/are not located directly under the plunger contact area, and above the diametric line that lies laterally across the cavity (52), the plunger contact area being a central 30% of the upper surface of the shoe (50), wherein the fuel delivery means (90) comprises a bore (92) through a body (51) of the shoe (50) connecting the upper surface (53) of the shoe (50) with the cavity (52),
wherein the bore (92) comprises an external opening (92a) into a link (91). wherein the link (91) is provided in the side wall (55a, 55b) of the shoe (50) and open to the side wall (55a, 55b) of the shoe (50) and,
wherein the bore (92) comprises an internal opening (92b) in a wall of the cavity (52) in said unloaded region (52a) of the cavity (52) and,
wherein the internal opening (92b) is located in a segment of the cavity wall extending between approximately 15° and approximately 75° from the pumping axis (A-A') (in any direction) and,
wherein the internal opening (92b) terminates in a reservoir (93) provided in the cavity wall and,
wherein the reservoir (53) comprises a recess cut into said cavity wall extending longitudinally along substantially the length of the cavity wall and,
wherein the recess extends along approximately between 60% and 90% of the length of the cavity wall.
The pump (1) according to claim 1, wherein the internal opening (92b) comprises a single aperture disposed approximately centrally along a length of the cavity (52).
The pump (1) according to claim 1, wherein the link (91) comprises a hollow cut into said side face (55a, 55b) and open to the upper surface (53) of the shoe (50).
The pump (1) according to claim 3, wherein the link (91) extends from the upper surface (53) to just below the external opening (92a) of the bore (92).
The pump (1) according to any one of claims 3 to 4, wherein the bore (92) is disposed on a downwardly sloping angle between external opening (92a) and the internal opening (92b) at an angle comprising between approximately 15° and approximately 75° relative to the pumping axis (A-A').
The pump (1) according to any one of claims 1 to 5, wherein the shoe (50) comprises fuel delivery means (90) arranged to supply fuel to both sides of the cavity (52) comprising one fuel delivery means (90) commencing in one side face (55a) of the shoe (50) terminating in one side of the cavity wall and a second fuel delivery means (90) commencing in an opposing side face (55b) of the shoe (50) terminating in an opposing side of the cavity wall.
The pump (1) according to claim 6, wherein the two fuel delivery means (90) are disposed on opposite sides of the pumping axis (A-A').