EP3292299A1

EP3292299A1 - High pressure diesel fuel pumps and shoe guides

Info

Publication number: EP3292299A1
Application number: EP16713945.0A
Authority: EP
Inventors: Stephen MACLANE
Original assignee: Delphi International Operations Luxembourg SARL
Current assignee: Delphi International Operations Luxembourg SARL
Priority date: 2015-05-06
Filing date: 2016-04-05
Publication date: 2018-03-14
Also published as: WO2016177524A1; GB201507709D0

Abstract

The invention discloses a high pressure diesel fuel pump comprising a pumping assembly and a drivetrain assembly (100). The pumping assembly comprises a pump housing and a plunger mounted along a pumping axis (A- A'). The drivetrain assembly (100) comprises 5 a drive shaft (110) and a cam mounted within a cambox (115) of a drivetrain housing (105). The plunger is arranged for reciprocating linear movement along the pumping axis (A- A') within a pumping chamber of the drivetrain housing (105) upon rotation of the cam. The drivetrain assembly (100) further comprises a shoe guide (130) mounted between the cam and the plunger within a guide chamber (120) and being adapted to receive a cam follower for contact with a driven end of the plunger. The shoe guide (130) is adapted to provide at least one flow passage (125) between the shoe guide (130) and an internal wall of the guide chamber (120).

Description

HIGH PRESSURE DIESEL FUEL PUMPS AND SHOE GUIDES

BACKGROUND

Technical Field

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

Description of the Related Art

Known high pressure diesel fuel pumps comprise one or more plungers movable within plunger bores, to pressurise fuel within respective pumping chambers. Those chambers deliver the fuel onwards to a fuel injection system of an engine. Each plunger is reciprocally movable along a pumping axis by a cam arrangement (driven by a drive shaft to perform a fuel-pressurising pumping stroke and a plunger return spring to effect a plunger return stroke. In a shoe-guide arrangement, each of the plungers is driven within its bore via an intermediate roller-shoe assembly, the movement of which is directed by a shoe guide. A return spring acts on the top of the roller-shoe assembly to allow it to follow the cam profile to a dropped position. In current single plunger pumps, a low pressure inlet typically feeds directly into the cambox to provide lubrication and cooling flow of fluid to the driveshaft components. In such arrangements, as the cam rotates and the roller-shoe assembly and plunger oscillates, a pressure wave is created in the cambox. The pressure wave becomes trapped within the confines of the internal drillings Such pressure waves would usually attenuate as they travel further away from the source of the wave, but due to current engine packaging restrictions, distances that are long enough are not typically available in a pump and within a system as a whole. Accordingly, the pressure wave can have detrimental effects on pump and upstream engine components. It has been observed that the pressure waves are often much worse where fluid motion encounters moving parts of a drivetrain assembly.

Figure 1 shows the pressure wave velocities that are often observed in a pump employing a shoe-guide arrangement where the cam is at 150° rotation. Within the cambox 12 at points A and B, large pressure spikes are shown. In the case of point A, pressure increases as the fluid is forced against a close fitting shoe guide 18 mounted within a pumping chamber 14 in a drivetrain housing 10 by clockwise rotation of a cam 16, which decreases the volume of the cambox 12 at that point. Almost opposite point A, at point B pressure increases again as the clearance distance between the cam 16 and the cambox 12 is squeezed and the fluid is forced against an internal wall of the cambox 12 by clockwise rotation of the cam 16. Finally, at point C, as the fluid is forced through the narrow space within the pumping chamber 14 past the shoe guide 18, pressure increases again.

Therefore, it is now desired to provide an improved arrangement for a high pressure diesel fuel pump to minimise the effects of such pressure waves. More particularly, it is desired to provide an improved drivetrain assembly and shoe guide for high pressure diesel fuel pumps.

SUMMARY OF THE INVENTION

In a first aspect of the present invention there is provided a high pressure diesel fuel pump comprising a pumping assembly and a drivetrain assembly, the pumping assembly comprising a pump housing and a plunger mounted along a pumping axis, the drivetrain assembly comprising a drive shaft and a cam mounted within a cambox of a drivetrain housing, the plunger being arranged for reciprocating linear movement along the pumping axis within a pumping chamber of the drivetrain housing upon rotation of the cam, the drivetrain assembly further comprising a shoe guide mounted between the cam and the plunger within a guide chamber and being adapted to receive a cam follower for contact with a driven end of the plunger, characterised in that the shoe guide is adapted to provide at least one flow passage between the shoe guide and an internal wall of the guide chamber.

In other words, the shoe guide comprises an adapted external shape that provides at least one flow passage between the shoe guide and an internal wall of the guide chamber, such that a larger flow volume is possible from the cambox to the guide chamber and beyond of the drivetrain housing.

By 'guide chamber' what is meant is at least the chamber or chambers housing the shoe guide.

With this arrangement, pressure waves caused by fluid being forced against the lower end of the guide chamber by the cam rotation has an escape route from the cambox into the pumping chamber past the shoe guide. This reduces the intensity of the pressure waves and provides time for the waves to attenuate to a level that has minimal effect on the pump components and the rest of the system. The reduction of the pressure wave has similar knock-on effects throughout the rest of the assembly. In addition, the flow of fluid is encouraged to take a defined path through the cambox and guide chamber, thereby minimising reverse flow. The improved guide therefore, helps to maintain the integrity of bearings and seals.

Preferably, the shoe guide is adapted to provide two flow passages between the shoe guide and the internal wall of the guide chamber. The shoe guide may be adapted to provide at least two flow passages between the shoe guide and the internal wall of the guide chamber.

Preferably, the shoe guide is adapted to provide the two flow passages approximately opposite one another within the guide chamber. Where the shoe guide is adapted to provide more than two flow passages, the shoe guide may be adapted to provide the flow passages approximately equally spaced from one another between the shoe guide and the internal wall of the guide chamber. Preferably, the shoe guide is adapted to provide substantially linear flow passages between the shoe guide and the internal wall of the guide chamber. Alternatively, the shoe guide may be adapted to provide non-linear flow passages between the shoe guide and the internal wall of the guide chamber.

Preferably, the shoe guide comprises a body with substantially elongate upper and lower faces.

Preferably, the faces comprise a long axis and a short axis. Preferably, the faces comprise a long axis of symmetry and a short axis of symmetry. Preferably, the long axis is arranged substantially perpendicularly to the short axis.

Preferably, the upper face and the lower face are substantially equal in size. Preferably, the upper face and the lower face comprise an oval. Accordingly, the body of the shoe guide is preferably an oval cylinder.

Alternatively, the upper face and the lower face both comprise an elongate polygon, or an oblong or an ellipse. Preferably, the upper face and the lower face are substantially equal and disposed in substantial registration with one another.

Preferably, the guide chamber is adapted to retain the shoe guide.

Preferably, the guide chamber is adapted to directly receive the shoe guide, although the guide chamber may comprise an adapter that is itself mounted directly within the chamber to provide a mounting means.

Preferably, the guide chamber and the shoe guide comprise cooperative mounting means.

Preferably, the mounting means comprises male and female cooperative parts. Most preferably, the mounting means comprises a female receiving portion within the guide chamber and a male resenting portion on the shoe guide. Preferably, the male presenting portions on the shoe guide are disposed diametrically opposite one another on the long axis of symmetry. Preferably, the male presenting portions comprise lobes of said elongate body.

Preferably, the female receiving portions within the guide chamber are disposed diametrically opposite one another. Preferably, the female receiving portions comprise grooves within said guide chamber. Preferably, the grooves are substantially vertically disposed within a wall of the guide chamber.

Preferably, the male portions of the shoe guide are press-fit into the female portions of the guide chamber. Preferably, the lobes of the shoe guide are press-fit into the grooves of the guide chamber. Preferably, the shoe guide is mounted substantially coaxially with a longitudinal axis of the guide chamber. Preferably, the longitudinal axis of the guide chamber is mounted substantially coaxially with the pumping axis.

Preferably, the shoe guide comprises an aperture extending between the first and second faces and open at both ends to provide guided sliding contact with the cam follower. Preferably, the aperture is substantially centrally located in the shoe guide body. The central location of the aperture helps to provide balance to the shoe guide body in addition to providing accurate location of the cam follower within the aperture.

Preferably, the drivetrain housing comprises a first part comprising the cambox and a second part comprising the guide chamber and a spring chamber. Both parts comprise generally cylindrical chambers therein. The chambers within the second part are arranged perpendicularly to the chamber of the first part.

In a second aspect of the present invention there is provided a drivetrain assembly for a high pressure diesel fuel pump, comprising a drive shaft and a cam mounted within a cambox of a drivetrain housing, a pumping chamber of the drivetrain housing adapted to receive a reciprocating plunger, and a shoe guide mounted between the cam and the plunger within a guide chamber and being adapted to receive a cam follower for contact with a driven end of the plunger, characterised in that the shoe guide is adapted to provide at least one flow passage between the shoe guide and an internal wall of the guide chamber.

It will be appreciated that the preferred features described in relation to the first aspect of the invention apply to the second aspect of the invention. In a third aspect of the present invention there is provided a shoe guide of a drivetrain assembly for a high pressure diesel fuel pump, the shoe guide being mounted between the cam and the plunger within a guide chamber and being adapted to receive a cam follower for contact with a driven end of the plunger, characterised in that the shoe guide is adapted to provide at least one flow passage between the shoe guide and an internal wall of the guide chamber.

It will be appreciated that the preferred features described in relation to the first and second aspects of the invention apply to the third aspect of the invention. In a fourth aspect of the present invention there is provided a drivetrain assembly for a high pressure diesel fuel pump, comprising a drive shaft and a cam mounted within a cambox of a drivetrain housing, a pumping chamber of the drivetrain housing adapted to receive a reciprocating plunger, and a shoe guide mounted between the cam and the plunger within a guide chamber and being adapted to receive a cam follower for contact with a driven end of the plunger, characterised in that the guide chamber is adapted to provide at least one flow passage between the shoe guide and an internal wall of the guide chamber.

Preferably, the guide chamber is adapted to provide two flow passages between the shoe guide and the internal wall of the guide chamber. The guide chamber may be adapted to provide at least two flow passages between the shoe guide and the internal wall of the guide chamber. Preferably, the guide chamber is adapted to provide the two flow passages approximately opposite one another therein. Where the guide chamber is adapted to provide more than two flow passages, the guide chamber may be adapted to provide the flow passages approximately equally spaced from one another therein.

Preferably, the guide chamber is adapted to provide substantially linear flow passages.

Alternatively, the guide chamber may be adapted to provide non-linear flow passages.

Preferably, the guide chamber of the fourth aspect of the invention is adapted to provide mounting means for the shoe guide. Preferably, the shoe guide is adapted to be press-fit into the mounting means.

Preferably, the mounting means within the guide chamber comprises male or female parts at designated circumferential points for cooperation with receptive parts on the shoe guide. Most preferably, the mounting means comprises one or more female receiving portions within the guide chamber. The female portions may comprise grooves within the chamber.

Alternatively, the mounting means in the guide chamber may comprise a tight interference fit between the periphery of the shoe guide and the circumference of the guide chamber. In this case, the flow passages may comprise cut-outs within the wall of the guide chamber.

It will be appreciated that the preferred features described in relation to the first, second and third aspects of the invention apply to the fourth aspect of the invention. 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 prior art drive train housing for a high pressure diesel fuel pump showing fluid flow and pressure fluctuations at a 150° cam rotation;

Figure 2 is a cross sectional side view of a drive train housing for a high pressure diesel fuel pump according to a first exemplary embodiment of the invention;

Figure 3 is a cross sectional plan view (through a guide chamber) showing a shoe guide within the drive train housing according to Figure 2;

Figure 4 is a first cross-sectional perspective side view of the shoe guide within a guide chamber of the drive train housing according to Figure 2; Figure 5 is a second cross-sectional perspective side view of the shoe guide within a guide chamber of the drive train housing from Figure 4 rotated through 90°;

Figure 6 is a first side view of the shoe guide for a drivetrain housing according to a second exemplary embodiment of the invention;

Figure 7 is a second side view of the shoe guide for a drivetrain housing according to Figure 6 rotated through 90°;

Figure 8 is a bottom view of the shoe guide for a drivetrain housing according to Figure 6;

Figure 9 is a perspective side-end view of a shoe guide showing the bottom end according to Figure 6; Figure 10 is a top plan view of the shoe guide for a drivetrain housing according to Figure 6; and

Figure 11 is a cross sectional plan view through a guide chamber of the drive train housing according to Figure 2.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS Figure 2 is a side view of a drive train assembly of a high pressure diesel fuel pump according to a first exemplary embodiment of the invention.

As shown in Figures 2 and 3, a high pressure diesel fuel pump comprises a pumping assembly (not shown) and a drivetrain assembly 100, the pumping assembly comprising a pump housing (not shown) and a plunger (not shown) mounted along a pumping axis A-5 A', the drivetrain assembly 100 comprising a drive shaft 110 and a cam (not shown) mounted within a cambox 115 of a drivetrain housing 105, the plunger being arranged for reciprocating linear movement along the pumping axis A- A' within a pumping chamber (not shown) of the drivetrain housing 105 upon rotation of the cam, the drivetrain assembly 100 further comprising a shoe guide 130 mounted between the cam and the plunger within a guide chamber 120 and being adapted to receive a cam follower (not shown) for contact with a driven end of the plunger, characterised in that the shoe guide 130 is adapted to provide at least one flow passage 125 between the shoe guide 130 and an internal wall of the guide chamber 120.

Figures 4 to 10 show an exemplary version of the shoe guide 130.

As shown in most clearly in Figures 6 and 7, the shoe guide 130 comprises a body 131, which is substantially an oval cylinder in shape. Therefore, the body 131 comprises a longitudinal axis B-B' between a first end 132 and a second end 133. From Figures 8 to 10, it can be seen that each end 132, 133 comprises a generally oval shape and is open to a substantially centrally located open-ended aperture 134 extending between the two ends 132, 133 (on longitudinal axis B-B'). Each end 132, 133 comprises a long axis L-L' of symmetry extending across the aperture 134 and a pair of opposing lobes 136a, 136b. A short axis S-S' of symmetry extends perpendicularly to the long axis L-L' across the aperture 134 and a pair of opposing flanks 137a, 137b. The aperture 134 is adapted to provide guided sliding contact with a cam follower shoe (not shown). Therefore, the aperture 134 defines a shape that generally corresponds with the external shape of the cam follower shoe. In an exemplary embodiment, the aperture 134 comprises a substantially rectangular cross-section defined by four substantially straight walls 134a-d and generally convexly rounded bulging corners 135a-d therebetween. However, it is to be appreciated that a plurality of walls may be shaped and contoured to define a substantially circular, or other shaped aperture 134 to fit with an alternatively shaped cam follower shoe. The first end 132 of the body 131, shown in detail in Figure 10, is configured as an upper end of the shoe guide 130 and as such, is disposed adjacent a spring chamber 118 of the housing 105.

The first end 132 comprises a substantially flat face.

Each of the pair of lobes 136a, 136b comprises a shallow ledge 138 cut into the walls 134a, 134c of the aperture 134 and as such are open to both the aperture 134 and the first end 132. Each ledge 138 takes the form of a segment of substantially rectangular cavity.

Each of the pair of flanks 137a, 137b comprises a shallow opening 139 cut into the first end 132 extending between the aperture 134 and an external wall of the body 131 (and 5 as such are open to both the aperture 134, the first end 132 and the external wall of the body 131). Each opening 139 takes the form of a circumferential segment of a shallow cylinder. Together, the ledges 138 and the openings 139 are arranged to provide a seat for a plunger return spring housed within the spring chamber 118.

The second end 133 of the body 131, shown in detail in Figures 8 and 9, is configured as a lower end of the shoe guide 130. This second end 133 is therefore configured to receive a portion of a roller (not shown).

The second end 133 comprises a substantially contoured face. The end 133 comprises a curved channel 140 cut into the face. The curve of the channel 140 dips downwardly from each of the flanks 137a, 137b, whereas, the channel 140 extends across the pair of lobes 136a, 136b and the aperture 134. Accordingly, the flanks 137a, 137b meet the walls 134b, 134d of the aperture 134 to provide abounding walls to the curved channel 140.

From the walls 134b, 134d of the aperture 134, the flanks 137a, 137b taper downwardly 141 towards the outer wall of the body 131 , such that an upper end of the outer wall of the body of 20 the shoe guide 130 presents a substantially continuous planar peripheral edge. The bottom of the tapers 141 generally correspond with the bottom of the channel 140. The shoe guide 130 is configured to be press-fitted within the guide chamber 120 of the drivetrain housing 105, which is adapted to receive the oval shape of the shoe guide 130.

Figure 11 shows an exemplary version of the adapted guide chamber 120.

As can be seen in Figure 11, the guide chamber 120 is substantially cylindrical, with a generally circular cross-section. A minor axis of symmetry M-M' extends across the circular cross-section of the chamber 120. However, perpendicular to the minor axis M-M', the chamber 120 comprises an elongated axis of symmetry E-E', accommodated by the chamber wall 121 bulging outwardly to provide vertically running concave grooves 123 a, 123b of generally circular cross-section. 30 The grooves 123a, 123b run substantially the full depth of the guide chamber 120 and into the spring chamber 118 (Figure 5).

The generally circular grooves 123a, 123b are shaped to receive the pair of lobes 136a, 136b of the shoe guide body 131. The fit between the lobes 136a, 136b and the grooves 123a, 123b is a tight press-fit which retains the vertical position of the shoe guide 130 within the guide chamber 120. In addition, the location of the lobes 136a, 136b within the grooves 123 a, 123b prevents any rotational movement of the shoe guide 130 within the chamber 120.

As illustrated in Figure 3, when the shoe guide 130 is press-fit into the chamber 120, the long axis L-L' of the shoe guide 130 extends across the guide chamber 120 on the 5 elongated axis EE'.

Accordingly, the short axis S-S' of the shoe guide 130 sits on the minor axis M- M' of the chamber 120. The shorter dimension of the shoe guide 130 across the short axis S-S' incorporating the pair of flanks 137a, 137b is smaller than the diameter of the chamber 120 across the minor axis M-M'. Accordingly, the fit of the shoe guide 130 within the chamber 120 provides two flow passages 125a, 125b between the pair of flanks 137a, 137b and the chamber wall 121 of generally crescent shape (best seen in Figure 3).

The passages 125a, 125b allow greater fluid communication between the cambox 115 (below the guide chamber 120) and the guide chamber 120 up into the spring chamber 118 (located above the guide chamber 120). Accordingly, the chambers 115, 118, 120 are generally open to 15 one another, e.g. flow of fluid is permissible therebetween and around the drive assembly 100 components.

In the exemplary embodiment described, the shoe guide 130 is configured to be oval in shape and the guide chamber 120 comprises grooves adapted to receive the appropriately shaped rounded lobes 136a, 136b of the shoe guide 130. However, it is to be appreciated that the shoe guide 130 may comprise an alternative shape comprising a long axis and a short axis, such as an elongated polygon, or oblong. In use, the shoe guide 130 is press-fit into the guide chamber 120 (with guide 130 longitudinal axis B-B' overlying the pumping axis A- A') and establishing two generous flow passages 125a, 125b on two opposing sides. A roller (not shown) is located at the second lower end 133 of the shoe guide 130 within the channel 140. The configuration of the channel 140 restrains lateral movement of the roller transversely across the short axis S-S' of the shoe guide 130

.

The roller is disposed directly above the cam on the drive shaft 110 within the cambox 115.

Above the shoe guide 130, a spring (not shown) is located within the spring chamber 118 and is seated on the first upper end 132 of the shoe guide 130 within the ledges 138 and the openings 139. A plunger shoe is disposed within the aperture 134 of the shoe guide and above the roller for reciprocating sliding movement along the pumping axis A- A' within the aperture of the shoe guide 130 facilitated by the rotation of the cam. In turn, the reciprocating movement of the shoe in the shoe guide 130 translates into reciprocating movement of the plunger along the pumping axis A-A.'

During the rotation of the cam, at point A where the cambox 115 meets the guide chamber 120, the flow passages 125 provide an escape route for the volume of fluid that is being forced around with the cam, thereby reducing the intensity of any pressure waves at that point (A) and into the guide chamber 120 (point C). In turn, the reduced pressure at point A has a knock-on effect at point B, where the fluid volume is able to flow more easily past the cam. Therefore, 5 the problem of pressure waves being trapped within the confines of the drivetrain housing 105 is minimised, thereby helping to maintain the integrity of the various drivetrain components. 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 comprising a pumping assembly and a drivetrain assembly (100);

the pumping assembly comprising a pump housing and a plunger mounted along a pumping axis (A- A'), the drivetrain assembly (100) comprising a drive shaft (110) and a cam mounted within a cambox (115) of a drivetrain housing (105)

the plunger being arranged for reciprocating linear movement along the pumping axis (A- A') within a pumping chamber of the drivetrain housing (105) upon rotation of the cam;

the drivetrain assembly (100) further comprising a shoe guide (130) mounted between the cam and the plunger within a guide chamber (120) and being adapted to receive a cam follower for contact with a driven end of the plunger, characterised in that the shoe guide (130) is adapted to provide at least one flow passage (125) between the shoe guide (130) and an internal wall of the guide chamber (120).

The pump according to claim 1, wherein the shoe guide (130) is adapted to provide two flow passages (125) between the shoe guide (130) and the internal wall of the guide chamber (120).

The pump according to claim 2, wherein the shoe guide (130) is adapted to provide the two flow passages (125) approximately opposite one another within the guide chamber (120).

The pump according to any one of claims 1 to 3, wherein the shoe guide (130) is adapted to provide substantially linear flow passages (125) between the shoe guide (130) and the internal wall of the guide chamber (120). The pump according to any one of claims 1 to 4, wherein the shoe guide (130) comprises a body (131) with substantially elongate upper and lower faces.

The pump according to claim 5 when dependent upon any one of claims 1 to 3, wherein the faces comprise a long axis of symmetry (L-L') arranged substantially perpendicularly to a short axis of symmetry (S-S').

The pump according to any one of claims 5 to 6, wherein the upper face and the lower face comprise an oval and as such the body (131) of the shoe guide (130) is an oval cylinder.

The pump according to any one of claims 1 to 7, wherein the guide chamber (120) is adapted to retain the shoe guide (130).

The pump according to claim 8, wherein the guide chamber (120) and the shoe guide (130) comprise cooperative mounting means (136, 123).

The pump according to claim 9, wherein the mounting means (136, 123) comprises female receiving portions (123) within the guide chamber (120) and male presenting portions (136) on the shoe guide (130).

The pump according to claim 10, wherein the male presenting portions (136) on the shoe guide (130) comprise lobes disposed diametrically opposite one another on the long axis (LL').

The pump according to any one of claims 10 to 11, wherein the female receiving portions (123) within the guide chamber (120) are disposed diametrically opposite one another.

The pump according to any one of claims 10 to 12, wherein the female receiving portions (123) comprise substantially vertical grooves within a wall of said guide chamber (120). The pump according to claim 13, wherein the lobes (136) of the shoe guide (130) are pressfit into the grooves (123) of the guide chamber (120).

A shoe guide (130) of a drivetrain assembly (100) for a high pressure diesel fuel pump, the shoe guide (130) being mounted between a cam of the drivetrain assembly (100) and a plunger of the drivetrain assembly (100) within a guide chamber (120) of the drivetrain assembly (100) and being adapted to receive a cam follower for contact with a driven end of the plunger, characterised in that the shoe guide (130) is adapted to provide at least one flow passage (125) between the shoe guide (130) and an internal wall of the guide chamber (120).