WO2016145133A1

WO2016145133A1 - Guided tappet assembly method and apparatus

Info

Publication number: WO2016145133A1
Application number: PCT/US2016/021644
Authority: WO
Inventors: Chin-Pei Wang; Eric A. BENHAM; Richard E. DUNCAN; Alexander LESIN; Kyle BREWER
Original assignee: Cummins Inc.
Priority date: 2015-03-10
Filing date: 2016-03-10
Publication date: 2016-09-15

Abstract

A fuel pump is provided, comprising, a first tappet assembly positioned within a first cylinder bore, the first tappet assembly having a first guide slot, a second tappet assembly positioned within a second cylinder bore and separated from the first cylinder bore by a wall, the second tappet assembly having a second guide slot, and a guide assembly disposed between the first and second tappet assemblies at least partially within an opening in the wall, the guide assembly including a guide pin having a first end that extends into the first guide slot and a second end that extends into the second guide slot.

Description

GUIDED TAPPET ASSEMBLY METHOD AND APPARATUS

PRIORITY CLAIM

[0001] This application claims priority to U.S. Provisional Application No. 62/130,676, which is entitled "GUIDED TAPPET ASSEMBLY METHOD AND APPARATUS," and was filed on March 10, 2015, the entire disclosure of which is expressly incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The present invention relates generally to fuel pumps and more particularly to mechanisms for guiding tappet assemblies during reciprocating motion.

BACKGROUND

[0003] Various fuel pumps for internal combustion engines are driven by a lobed camshaft that reciprocally displaces a tappet assembly with a roller that rolls along a cam on the lobed camshaft. The reciprocating motion of the tappet assembly generates fuel flow that is used by the internal combustion engine to generate power. Such fuel pumps are frequently used in common rail fuel system applications where high fuel pressures are required. In such fuel pumps, the reciprocating tappet assembly is guided so that the centerline of the roller and the centerline of the camshaft are maintained in an aligned, parallel orientation with respect to each other.

[0004] Some conventional fuel pumps utilize a solid dowel pin that is pressed into the housing of the fuel pump from the exterior and cooperates with a feature of the tappet assembly to maintain the orientation of the tappet assembly relative to the camshaft lobe. In this regard, the housing of the fuel pump is generally provided with a hole that extends through the housing so that the dowel pin can be inserted. The tappet assembly feature typically includes a key slot into which the dowel pin extends, thereby guiding reciprocal displacement of the tappet assembly while preventing rotation of the tappet assembly (and its roller) relative to the camshaft.

[0005] One concern with this configuration is the potential that lubricant used with the tappet assembly may leak past the dowel pin through the pump housing. Additionally, in fuel pumps having multiple tappet assemblies, multiple dowel pins must be used, resulting in additionally machining of the pump housing and increase risk of lubricant leakage. Therefore, there exists a need for an improved fuel pump and methods that minimize these limitations.

SUMMARY

[0006] According to one embodiment, the present disclosure provides a fuel pump, comprising, a first tappet assembly positioned within a first cylinder bore, the first tappet assembly having a first guide slot, a second tappet assembly positioned within a second cylinder bore and separated from the first cylinder bore by a wall, the second tappet assembly having a second guide slot, and a guide assembly disposed between the first and second tappet assemblies at least partially within an opening in the wall, the guide assembly including a guide pin having a first end that extends into the first guide slot and a second end that extends into the second guide slot. In one aspect of this embodiment, the guide assembly further comprises a collar that engages the opening, the collar including at least one groove that extends between a first end of the collar and a second end of the collar, the at least one groove permitting lubricant to flow between the first cylinder bore and the second cylinder bore. In a variant of this aspect, the guide pin is press fit within a central opening of the collar and extends from the collar beyond the first end and the second end.

[0007] In another variant of this aspect, the first end and the second end of the collar define a first length therebetween, the collar comprising a central opening that extends between the first end and the second end. In a variant of this variant, the guide pin extends through the central opening and the first end of the guide pin and the second end of the guide pin define a second length therebetween which is greater than the first length. In another aspect of this embodiment, the guide assembly further comprises a collar comprising a plurality of lobes that are spaced apart and that extend radially outward from a central opening of the collar. In a variant of this aspect, the collar further comprises a plurality of grooves, each groove being disposed between a pair of adjacent lobes, and wherein the plurality of grooves and the plurality of lobes extend between a first end of the collar and a second end of the collar. In another variant of this aspect, the guide pin comprises a central opening in fluid communication with the first and second cylinder bores, the central opening permitting fuel to flow between the first and second cylinder bores. [0008] According to another embodiment, the present disclosure provides a guide assembly, comprising, a collar having a first end and a second end defining a first length there between, and a central opening extending between the first end and the second end, and a guide pin having a body that extends through the central opening, the body having a first end for guiding movement of a first tappet assembly and a second end for guiding movement of a second tappet assembly, the first end and the second end defining a second length therebetween which is greater than the first length. In one aspect of this embodiment, the collar comprises at least one groove that extends between the first end and the second end of the collar to permit lubricant to flow between the tappet assemblies. In a variant of this aspect, the collar further comprises a plurality of lobes that extend radially outward from the central opening, the lobes being spaced apart from one another circumferentially about the central opening and defining an outer diameter of the collar. In another aspect of this embodiment, the guide pin is press fit within the central opening of the collar and extends from the collar beyond the first end of the collar and the second end of the collar. In a variant of this aspect, the guide pin comprises an outer diameter that is larger than an inner diameter of the central opening of the collar to permit the guide pin to be press fit into the central opening. In yet another aspect of this embodiment, the guide pin comprises a substantially cylindrical outer surface that corresponds to an inner surface of the central opening of the collar.

[0009] According to yet another embodiment, the present disclosure provides a method for guiding tappet assemblies in a fuel pump, comprising, positioning a first tappet assembly within a first cylinder bore of the fuel pump, the first tappet assembly having a first guide slot, positioning a guide assembly within an opening of a wall of the fuel pump such that a first end of a first portion of the guide assembly extends into the first guide slot, positioning a second tappet assembly within a second cylinder bore of the fuel pump, the second tappet assembly having a second guide slot, and the first and second cylinder bores being separated by the wall, pressing the first portion of the guide assembly toward the second tappet assembly such that a second end of the first portion extends into the second guide slot.

[0010] In one aspect of this embodiment, the method further comprises pressing the first portion of the guide assembly into a central opening of a collar of the guide assembly such that the second end of the first portion is substantially planar with a first end of the collar. In a variant of this aspect, the method further comprises permitting fuel to flow between the first and second cylinder bores through a central opening of the first portion in fluid communication with the first and second cylinder bores. In another variant of this aspect, the method further comprises lubricating one or more contact areas with lubricant that flows between the tappet assemblies through at least one groove extending between the first end of the collar and a second end of the collar, the contact areas being located at least between the guide pin and the first and second guide slots. In another aspect of this embodiment, the method further comprises simultaneously guiding the first and second tappet assemblies during reciprocating movement of the tappet assemblies. In a variant of this aspect, simultaneously guiding the first and second tappet assemblies comprises the first end of the first portion guiding movement of the first tappet assembly and the second end of the first portion guiding movement of the second tappet assembly.

[0011] While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The above-mentioned and other features of this disclosure and the manner of obtaining them will become more apparent and the disclosure itself will be better understood by reference to the following description of embodiments of the present disclosure taken in conjunction with the accompanying drawings, wherein:

[0013] FIG. 1 is a partial cross-sectional view of a fuel supply high pressure pump according to one embodiment of the present disclosure;

[0014] FIGs. 2A-B are side sectional views of a tappet assembly of FIG. 1, movement of which being guided by a guide assembly according to the present disclosure;

[0015] FIG. 3 is a perspective view of a guide assembly according to the present disclosure;

[0016] FIG. 4 is a side sectional view of portion A of FIG. 1 depicting a guide assembly according to the present disclosure installed in a fuel pump to guide movement of two adjacent tappet assemblies; [0017] FIG. 5 is a top of a portion of the pump of FIG. 1 with the guide assembly of

FIG. 3 installed;

[0018] FIGs. 6A-B are side section views depicting assembly of components of a guide assembly according to the present disclosure; and

[0019] FIGs. 7A-8B are partial cross-sectional views of a pump depicting an installation procedure for tappet assemblies and a guide assembly according to the present disclosure.

[0020] While the present disclosure is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The present disclosure, however, is not to limit the particular embodiments described. On the contrary, the present disclosure is intended to cover all modifications, equivalents, and alternatives falling within the scope of the appended claims.

DETAILED DESCRIPTION

[0021] Referring now to FIG. 1, a fuel supply high pressure pump 10 is shown in partial cross-section. Pump 10 generally includes a pump housing 12 that encloses one or more cylinder bores 14 and a lobed camshaft 16 disposed below cylinder bores 14. A tappet assembly 18 is disposed in each bore 14 for reciprocal motion along an axis 20 to pump fuel for use by the internal combustion engine being serviced by pump 10. As is further described below, rollers 22 of tappet assemblies 18 ride on eccentric lobes 24 of camshaft 16 as camshaft 16 rotates about axis 26. As rollers 22 follow the surfaces of lobes 24, tappet assemblies 18 are caused to move (with the return movement caused by biasing springs (not shown)) in a reciprocating fashion within bores 14. As is also further described below, tappet assemblies 18 are guided in this reciprocal motion to prevent rotation about axis 20 by a guide assembly 28 according to the present disclosure.

[0022] FIGs. 2A-B depict tappet assembly 18 in greater detail. As shown, tappet assembly 18 generally includes a body 30 that defines an upper chamber 32 having a side wall 34 and retains roller 22 on an axle 36. Side wall 34 includes at least one elongated slot 38 that extends longitudinally and in parallel relationship with axis 20 (FIG. 1) when tappet assembly 18 is installed in pump bore 14.

[0023] Referring now to FIG. 3, guide assembly 28 generally includes a collar 40 and a guide pin 42. In one embodiment of the present disclosure, collar 40 includes a body 44 having a central opening 46 that extends between a first end 48 and a second end 50 and a plurality of lobes 52 that extend radially outward from central opening 46, are spaced apart from one another circumferentially about central opening 46 and define an outer diameter of collar 40. A plurality of grooves 54 extend between ends 48, 50, each groove 54 being located between a pair of adjacent lobes 52. It should be understood that while in FIG. 3 four lobes 52 are shown with three corresponding grooves 54, more or fewer of each element may be employed in other embodiments of the present disclosure. Also, while grooves 54 are shown as being formed along an outer surface of collar 40, grooves 54 may be implemented as any type of passage between ends 48, 50 of collar 40, including passages such as bores that extend into and through body 44.

[0024] Guide pin 42 includes a body 56 having a first end 58 and a second end 60, and a central opening 62 that extends between ends 58, 60. In the embodiment shown, guide pin 42 has a substantially cylindrical outer surface 64 that corresponds to the inner surface of central opening 46 of collar 40. Guide pin 42 is slightly larger in outer diameter than the inner diameter of central opening 46 to permit guide pin 42 to be press fit into central opening 46 of collar 40. In alternative embodiments, guide pin 42 is provided without central opening 62. As shown in the figures, guide pin 42 has a length between ends 58, 60 that is greater than the length between ends 48, 50 of collar 40 to permit guide pin 42 to extend beyond end of the ends 48, 50 of collar 40 as is further described below.

[0025] Referring now to FIG. 4, a magnified view of portion A of FIG. 1 is shown depicting guide assembly 28 installed in pump 10. As shown, collar 40 of guide assembly 28 is disposed within an opening 66 formed in a housing wall 68 separating one cylinder bore 14A from an adjacent cylinder bore 14B. End 58 of guide pin 42 extends into slot 38A of tappet assembly 18A disposed within cylinder bore 14A and end 60 of guide pin 42 extends into slot 38B of tappet assembly 18B disposed within cylinder bore 14B. As end 48 of collar 40 is larger than the opening formed by slot 38 A, and end 50 of collar 40 is larger than the opening formed by slot 38B, collar 40 cannot slide into either tappet assembly 18 A, B and remains situated within opening 66. Central opening 62 of guide pin 42 permits fuel to flow between bores 14A and 14B and thereby prevent pressure build up in one bore during a pumping stroke from forcing guide pin 42 toward the other bore.

[0026] In one embodiment of the present disclosure, grooves 54 of collar 40 permit lubricant to flow between adjacent cylinder bores 14. More specifically, as shown in FIG. 5, when guide assembly 28 is installed between cylinder bore 14A and cylinder bore 14B in the manner described above, lubricant (such as oil) can flow (as indicated by arrows 70) through grooves 54 between bores 14A,B during pumping events carried out by tappet assemblies 18A,B. This lubricant flows into the interfaces between tappet assemblies 18A,B and bores 14A,B and the contact areas between guide pin 42 and slots 38A,B of tappet assemblies 18A,B. In this manner, grooves 54 facilitate reduced wear of the various components of pump 10.

[0027] Also, as should be apparent from the foregoing, only one opening 66 is needed in pump housing 12 to permit guided movement of two tappet assemblies 18A,B using guide assembly 28 of the present disclosure, and that opening 66 is formed between bores 14A,B rather than from a bore to an outer surface of housing 12. Accordingly, use of guide assembly 28 of the present disclosure prevents leakage of lubricant to the environment outside housing 12 and reduces the amount of machining required during fabrication of housing 12.

[0028] Referring now to FIGs. 6A-B, the initial steps of a process for assembling and installing guide assembly 28 are depicted. As shown in FIG. 6A, guide pin 42 is pressed into central opening 46 of collar 40 in the direction of arrow 72. As shown in FIG. 6B, guide pin 42 is initially pressed into collar 40 until end 60 of guide pin 42 is substantially planar with end 50 of collar 40. When in this configuration, guide assembly 28 is ready to be installed as described with references to FIGs. 7A-B.

[0029] As shown in FIG. 7A, tappet assembly 18A is first installed in cylinder bore 14A as indicated by arrow 74. After tappet assembly 18A is installed in cylinder bore 14A, guide assembly 28 is installed through opening 66 of wall 68 in the direction of arrow 76. As shown in FIG. 7B, guide assembly 28 is pressed into opening 66 such that guide pin 42 extends through slot 38A of tappet assembly 18A and collar 40 engages tappet assembly 14 A. As should be understood from the foregoing, neither guide pin 42 nor collar 40 protrude into bore 14B when positioned as shown in FIG. 7B.

[0030] Next, as shown in FIG. 8 A, tappet assembly 18B is installed into cylinder bore

14B as indicated by arrow 78. Finally, as shown in FIG. 8B guide pin 42 of guide assembly 28 is pressed from within tappet assembly 14A in the direction of arrow 80 toward tappet assembly 18B until guide pin 42 passes into slot 38B of tappet assembly 18. When in the position of FIG. 8B, guide pin 42 of guide assembly extends into slots 38A,B of tappet assemblies 18A,B to simultaneously guide both tappet assemblies 18A,B during reciprocating movement as described above.

[0031] Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present invention is intended to embrace all such alternatives, modifications, and variations as fall within the scope of the claims, together with all equivalents thereof.

Claims

CLAIMS We claim:

1. A fuel pump, comprising:

a first tappet assembly positioned within a first cylinder bore, the first tappet assembly having a first guide slot;

a second tappet assembly positioned within a second cylinder bore and separated from the first cylinder bore by a wall, the second tappet assembly having a second guide slot; and a guide assembly disposed between the first and second tappet assemblies, the guide assembly being at least partially within an opening in the wall, the guide assembly comprising a guide pin having a first end that extends into the first guide slot and a second end that extends into the second guide slot.

2. The fuel pump of claim 1, wherein the guide assembly further comprises a collar that engages the opening, the collar comprising at least one groove that extends between a first end of the collar and a second end of the collar, the at least one groove permitting lubricant to flow between the first cylinder bore and the second cylinder bore.

3. The fuel pump of claim 2, wherein the guide pin is press fit within a central opening of the collar and extends from the collar beyond the first end of the collar and the second end of the collar.

4. The fuel pump of claim 2, wherein the first end and the second end of the collar define a first length therebetween, the collar comprising a central opening that extends between the first end and the second end.

5. The fuel pump of claim 4, wherein the guide pin extends through the central opening and the first end of the guide pin and the second end of the guide pin define a second length therebetween which is greater than the first length.

6. The fuel pump of claim 1, wherein the guide assembly further comprises a collar comprising a plurality of lobes that are spaced apart and that extend radially outward from a central opening of the collar.

7. The fuel pump of claim 6, wherein the collar further comprises a plurality of grooves, each groove being disposed between a pair of adjacent lobes, and wherein the plurality of grooves and the plurality of lobes extend between a first end of the collar and a second end of the collar.

8. The fuel pump of claim 6, wherein the guide pin comprises a central opening fluidly coupling the first and second cylinder bores.

9. A guide assembly, comprising:

a collar having a first end and a second end defining a first length therebetween, and a central opening extending between the first end and the second end; and

a guide pin having a body that extends through the central opening, the body having a first end for guiding movement of a first tappet assembly and a second end for guiding movement of a second tappet assembly, the first end and the second end defining a second length therebetween which is greater than the first length.

10. The guide assembly of claim 9, wherein the collar comprises at least one groove that extends between the first end and the second end of the collar to permit lubricant to flow between the tappet assemblies.

11. The guide assembly of claim 10, wherein the collar further comprises a plurality of lobes that extend radially outward from the central opening, the lobes being spaced apart from one another circumferentially about the central opening and defining an outer diameter of the collar.

12. The guide assembly of claim 9, wherein the guide pin is press fit within the central opening of the collar and extends from the collar beyond the first end of the collar and the second end of the collar.

13. The guide assembly of claim 12, wherein the guide pin comprises an outer diameter that is larger than an inner diameter of the central opening of the collar to permit the guide pin to be press fit into the central opening.

14. The guide assembly of claim 9, wherein the guide pin comprises a substantially cylindrical outer surface that corresponds to an inner surface of the central opening of the collar.

15. A method for guiding tappet assemblies in a fuel pump, comprising:

positioning a first tappet assembly within a first cylinder bore of the fuel pump, the first tappet assembly having a first guide slot;

positioning a guide assembly within an opening of a wall of the fuel pump such that a first end of a first portion of the guide assembly extends into the first guide slot;

positioning a second tappet assembly within a second cylinder bore of the fuel pump, the second tappet assembly having a second guide slot, and the first and second cylinder bores being separated by the wall;

pressing the first portion of the guide assembly toward the second tappet assembly such that a second end of the first portion extends into the second guide slot.

16. The method of claim 15, further comprising pressing the first portion of the guide assembly into a central opening of a collar of the guide assembly such that the second end of the first portion is substantially planar with a first end of the collar.

17. The method of claim 15, further comprising simultaneously guiding the first and second tappet assemblies during reciprocating movement of the tappet assemblies.

18. The method of claim 17, wherein simultaneously guiding the first and second tappet assemblies comprises the first end of the first portion guiding movement of the first tappet assembly and the second end of the first portion guiding movement of the second tappet assembly.

19. The method of claim 16, further comprising permitting fuel to flow between the first and second cylinder bores through a central opening of the first portion in fluid communication with the first and second cylinder bores.

20. The method of claim 16, further comprising lubricating one or more contact areas with lubricant that flows between the tappet assemblies through at least one groove extending between the first end of the collar and a second end of the collar, the contact areas being located at least between the guide pin and the first and second guide slots.