WO2022006517A1

WO2022006517A1 - Anti-rotation feature on a drawn cup tappet

Info

Publication number: WO2022006517A1
Application number: PCT/US2021/040287
Authority: WO
Inventors: Josh Ferguson; Dennis Miller; Joe BOEHM
Original assignee: Koyo Bearings North America Llc
Priority date: 2020-07-02
Filing date: 2021-07-02
Publication date: 2022-01-06

Abstract

A tappet mechanism movable within a bore, having an outer cup with a cylindrical side wall, an annular lip portion disposed at a first end of the side wall, and a radially-outwardly extending anti-rotation feature in the form of a protrusion formed in the side wall, an inner cup including a pair of shaft apertures, a shaft having a first end and a second end, each being disposed in a shaft aperture, and a roller rotatably received on the shaft wherein the anti-rotation feature includes a pair of apertures, each being disposed on a corresponding side of the anti-rotation feature at an intersection of the anti-rotation feature and the outer surface of the outer cup.

Description

ANTI-ROTATION FEATURE ON A DRAWN CUP TAPPET

CUAIM OF PRIORITY

[0001] This application claims priority to U.S. Provisional Application No. 63/047,647, filed July 2, 2020, the entire disclosure of which is incorporated by reference herein.

FIEUD OF THE INVENTION

[0002] The present invention relates generally to drawn cup tappets, and more particularly, to anti-rotation features for use therewith.

BACKGROUND OF THE INVENTION

[0003] Tappet mechanisms are often used in a valve train of an internal combustion engine to transmit motion from a camshaft of the engine to one or more intake or exhaust valves. As the camshaft rotates, the tappet mechanisms receive both a sideways force and a downward force from corresponding lobes on the camshaft, but only transmit the downward force to the valves to open and/or close the valves. Tappet mechanisms thereby reduce the possibility of bending or otherwise damaging the valve stems of the valves. As well, tappet mechanisms are often used in camshaft driven, high-pressure fuel pumps which are used in gasoline direct injection systems.

[0004] Existing bucket-type tappet mechanisms typically include either a stamped or cold formed bucket. A roller is typically supported on a shaft that is directly fixed to the bucket such as by staking, swaging, etc. As such, the bucket is a load bearing member and, therefore, requires heat treatment and operations such as grinding. As well, tappet mechanisms often have some form of alignment device, or anti-rotation feature, carried in an aperture defined by the bucket such that rotation of the tappet mechanism within its corresponding bore is prevented.

One example of known alignment devices includes a mushroom- shaped pin that is fixed in an aperture of the tappet mechanism's bucket. Such pins can be difficult to manufacture because of their complicated shapes. As well, required heat treatments of the bucket can cause distortion of the aperture which receives the alignment device, thereby complicating assembly. Such alignment devices are often fixed in their corresponding apertures by an interference fit.

[0005] One of the components of a tappet may be an outer cup with an anti-rotation feature extending outwardly from the outside of the cup. Forming this feature on an as formed drawn up is often difficult to do without cracking. The ability to form the anti-rotation feature often requires an annealing step to relieve stresses in the cup to make the anti-rotation feature easier to form without uncontrolled cracking/tearing. This extra step adds additional resources and time and, thus, extra cost to the process. Current processes may also create a part that has a blend radius between the anti-rotation feature and the cup along the sides of the anti-rotation feature, which can cause interference issues in application.

[0006] The present invention recognizes and addresses considerations of prior art constructions and methods.

SUMMARY OF THE INVENTION

[0007] One embodiment of the present disclosure provides a tappet mechanism movable within a bore along a longitudinal center axis of the bore, having an outer cup having an inner surface and an outer surface defining a substantially cylindrical side wall, an annular lip portion disposed at a first end of the side wall, and a radially-outwardly extending anti-rotation feature in the form of a protrusion formed in the side wall, an inner cup including a pair of shaft apertures, the inner cup being disposed in the outer cup, a shaft having a first end and a second end, each of the first end and the second end being disposed in a corresponding one of the shaft apertures, a roller rotatably received on the shaft such that a portion of the roller tappet extends axially outwardly beyond the annular lip portion of the outer cup, and wherein the anti-rotation feature formed in the outer cup includes a pair of apertures extending axially along its length, one of the apertures being disposed on each side of the anti-rotation feature at an intersection of the anti rotation feature and the outer surface of the outer cup.

[0008] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS [0009] A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended drawings, in which;

[0010] Figures 1A and IB are perspective views of an embodiment of a tappet assembly, including an alignment device in accordance with the present disclosure;

[0011] Figure 2 is an exploded perspective view of the tappet assembly shown in Figures

1A and IB;

[0012] Figures 3A, 3B, and 3C are cross-sectional views of the tappet assembly shown in

Figures 1A and IB;

[0013] Figures 4A and 4B are perspective views of an inner cup of the tappet assembly shown in Figures 1A and IB; [0014] Figure 5 is a perspective view of an outer cup of the tappet assembly shown in

Figures 1A and IB;

[0015] Figures 6A through 6C are perspective views of steps in forming the embodiment of the anti-rotation feature shown in Figures 1A through 5, in accordance with the present disclosure;

[0016] Figures 7A through 7C are perspective views of steps in forming an alternate embodiment of an anti-rotation feature in accordance with the present disclosure; and [0017] Figure 8 is a partial cross-sectional view of a high-pressure fuel pump including the tappet mechanism shown in Figure 1.

[0018] Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention according to the disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0019] Reference will now be made in detail to presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation, not limitation, of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope and spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. [0020] As used herein, terms referring to a direction or a position relative to the orientation of the tappet assembly, such as but not limited to "vertical," "horizontal," "upper," "lower," "above," or "below," refer to directions and relative positions with respect to the assembly's orientation in its normal intended operation, as indicated in the Figures herein. Thus, for instance, the terms "vertical" and "upper" refer to the vertical direction and relative upper position in the perspectives of the Figures and should be understood in that context, even with respect to a tappet assembly that may be disposed in a different orientation.

[0021] Further, the term "or" as used in this disclosure and the appended claims is intended to mean an inclusive "or" rather than an exclusive "or." That is, unless specified otherwise, or clear from the context, the phrase "X employs A or B" is intended to mean any of the natural inclusive permutations. That is, the phrase "X employs A or B" is satisfied by any of the following instances: X employs A; X employs B; or X employs both A and B. In addition, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more" unless specified otherwise or clear from the context to be directed to a singular form. Throughout the specification and claims, the following terms take at least the meanings explicitly associated herein, unless the context dictates otherwise. The meanings identified below do not necessarily limit the terms, but merely provided illustrative examples for the terms. The meaning of "a," "an," and "the" may include plural references, and the meaning of "in" may include "in" and "on." The phrase "in one embodiment," as used herein does not necessarily refer to the same embodiment, although it may.

[0022] As shown in Figures 1A through 3C, an example embodiment of a tappet assembly 100 in accordance with the present disclosure includes a substantially cylindrical outer cup 120, an inner cup 140 received therein, a roller follower 160 supported by inner cup 140, and an alignment device 102 formed in outer cup 120. As shown in Figure 8, tappet assembly 100 is used in a high-pressure fuel pump 180 of an internal combustion engine, although other uses for tappet assembly 100 are possible. As a camshaft 182 of the engine rotates, a lobe 184 of camshaft 182, or a rocker arm (not shown) connected to camshaft 186, engages roller follower 160 of tappet assembly 100 to convert the rotational motion of camshaft 182 into linear motion of tappet assembly 100 within a bore 186 of a corresponding cylinder head 188. A pump stem 190 of pump 180 is positioned within and connected to tappet assembly 100 such that, as tappet assembly 100 moves in a linear direction within bore 186, pump stem 190 is altematingly moved left (as shown) by spring 192 and right by tappet assembly 100. Forces from camshaft 182 are thereby transmitted through tappet assembly 100 to pump 180 such that only forces in substantially the same direction as the motion of pump stem 190 act on pump 180. In addition, tappet assembly 100 serves as a torsional vibration isolation device between camshaft 182 and pump 180 to inhibit rotational forces from being transmitted. An alignment device 102, or anti rotation feature, is formed by an outwardly-extending projection formed in the side wall of outer cup 120, a portion of which is slidably received in a correspondingly shaped alignment groove (not shown) defined by the inner wall of bore 186. As shown, the projection forming alignment device 102 is elongated in a direction parallel to a longitudinal center axis of tappet assembly 100 and includes a semi-cylindrical outer surface and end walls 103. Alternate embodiments may include protrusions of varying shapes for the alignment device 102.

[0023] Referring additionally to Figures 6 A through 6C, a preferred embodiment of the anti-rotation feature 102 for a drawn outer cup 120 in accordance with the present disclosure is formed by purposefully separating material on the sides of the anti-rotation feature 102, via a cutting or piercing operation. This can be achieved by lancing or cutting the material on the sides of the feature (Figures 7 A through 7C), or piercing out material on the sides of the anti rotation feature (Figures 6 A through 6C) so that apertures 101 exist on both sides of the anti rotation feature 102. These steps eliminate the need for an anneal operation between forming outer cup 120 and forming anti-rotation feature 102. Note, the lancing, cutting, piercing operation may be done in one step where the lancing/cutting/piercing happens during the same operation as the anti-rotation bulge 102 forming. In the alternative, the lancing/cutting/piercing operations can be done in two or more steps where the lancing/cutting/piercing happens in an operation prior to the anti -rotation feature 102 forming. Lancing/cutting/piercing on either side of the anti-rotation feature 102 eliminates the blend radius between the outer cup 120 and the anti-rotation feature 102 which was present in previous designs. These steps eliminate the secondary anneal operation required to form the anti-rotation feature without uncontrolled cracking/tearing, and the blend radius that can cause interference in application.

[0024] Referring additionally to Figure 5, outer cup 120 of the present embodiment includes a cylindrical outer surface 124 and a cylindrical inner surface 126 substantially concentric therewith. Outer cup 120 is preferably formed from a sheet metal blank of low, medium, or high carbon plain or alloy steel by a precision drawing process that results in very good control of the surface finish, the outer diameter size, and roundness of the outer cup. Additionally, outer cup 120 includes an annular lip 128 and 134 formed at each of its opposing ends. Annular lip 128 is thinner in the radial direction than the remaining side wall of outer cup 120, forming an annular ledge 130 therewith. In its initial state, prior to fully assembling tappet assembly 100, annular lip 128 extends axially outwardly parallel to a longitudinal center axis 132 of outer cup 120, whereas annular ledge 130 lies in a plane that is transverse to longitudinal center axis 132. When forming outer cup 120, annular lip 134 may be initially formed depending radially inwardly as the other components of the roller follower are preferably placed into outer cup 120 from the end at which annular lip 128 is disposed.

[0025] Referring additionally to Figures 4 A and 4B, inner cup 140 preferably includes a cylindrical side wall 144, a semi-spherical bottom portion 146, an upper lip 148 extending radially outwardly from an upper perimeter of the side wall, and a pair of shaft apertures 150 defined by side walls 144. As best seen in Figures 1A, 3 A, and 3B, when fully inserted in outer cup 120, upper lip 148 of inner cup 140 rests on annular ledge 130 of outer cup 120. Once fully inserted in outer cup 120, inner cup 140 is retained therein by folding annular lip 128 over inwardly, such as by crimping, spin curling, punch forming, etc., so that upper lip 148 is non- rotatably squeezed between annular lip 128 and annular ledge 130. Note, since outer cup 120 does not directly support shaft 162 of roller follower 160, it does not require the heat treatment and grinding processes that are typically performed on the outer cups of known tappet assemblies. As such, the folding/crimping operation performed on annular lip 128 is facilitated. However, in those applications where heat treatment of outer cup 120 is desired for wear purposes, the heat treatment process occurs after the formation of alignment device 102. Next, prior to folding, crimping, etc., annular lip 128 over inwardly, annular lip 128 is tempered to facilitate the operation and help prevent cracking.

[0026] Preferably, inner cup 140 is formed from a sheet metal blank by a stamping process, or drawing process, and is subjected to heat treatment processes as it directly supports shaft 162 of tappet assembly 100 and supports the cyclical force exerted by pump stem 190 (Figure 7) on the bottom of inner cup 140. Prior to the heat treatment processes, shaft apertures 150 are pierced in side wall 144 of inner cup 140 and extruded so that a boss 152 is formed about each shaft aperture 150. Similarly, lubrication apertures 154 are also pierced in semi-spherical bottom portion 146 of inner cup 140 prior to any heat treatment processes. As shown, preferably, a portion of semi- spherical bottom portion 146 may be flattened, thereby forming a bottom wall 156 that is perpendicular to longitudinal center axis 132 of tappet assembly 100. Bottom wall 156 facilitates the transfer of forces from tappet assembly 100 to the corresponding pump stem 190, or in the alternative, valve stem. Note, however, in alternate embodiments, the cross-sectional shape of bottom portion 146 may have a constant radius of curvature. Alternatively, bottom portion 146 may be simply dome-shaped.

[0027] As best seen in Figure 2, roller follower 160 includes shaft 162, an outer race 166, and a plurality of rollers 164 disposed therebetween such that race 166 is freely rotatable about shaft 162. Opposite ends of shaft 162 are received in shaft apertures 150 of inner cup 140 such that roller follower 160 is mounted to outer cup 120 of tappet assembly 100 by way of the inner cup. When assembled, roller follower 160 extends axially outwardly beyond the top edge of outer cup 120 such that outer surface of race 166 engages a corresponding lobe 184 of camshaft 182, as shown in Figure 7. Preferably, the diameters of shaft apertures 150 are slightly larger than the diameter of shaft 162 such that shaft 162 is free to rotate within shaft apertures 150 during operation. Alternately, the opposing ends of shaft 162 can be staked, swaged, etc., to inner cup 140 such that rotation relative thereto is prevented. Note, when shaft 162 is free to rotate within shaft apertures 150, the axial motion of shaft 162 is limited by abutment at either end with inner surface 126 of outer cup 120. Preferably, a washer 158 is disposed at each end of race 160 to limit the motion of both race 160 and rollers 164 along shaft 162. Preferably, annular beveled edges 168 are provided on the opposite ends of outer race 166 to allow the overall size of outer race 166 to be maximized, yet not make contact with the inner surface of semi- spherical bottom portion 146 of inner cup 140. [0028] While one or more preferred embodiments of the invention are described above, it should be appreciated by those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit thereof. It is intended that the present invention cover such modifications and variations as come within the scope and spirit of the appended claims and their equivalents.

Claims

1. A tappet mechanism movable within a bore along a longitudinal center axis of the bore, comprising: an outer cup having an inner surface and an outer surface defining a substantially cylindrical side wall, an annular lip portion disposed at a first end of the side wall, and a radially-outwardly extending anti-rotation feature in the form of a protrusion formed in the side wall; an inner cup including a pair of shaft apertures, the inner cup being disposed in the outer cup; a shaft having a first end and a second end, each of the first end and the second end being disposed in a corresponding one of the shaft apertures; a roller rotatably received on the shaft such that a portion of the roller tappet extends axially outwardly beyond the annular lip portion of the outer cup, and wherein the anti-rotation feature formed in the outer cup includes a pair of apertures extending axially along its length, one of the apertures being disposed on each side of the anti rotation feature at an intersection of the anti-rotation feature and the outer surface of the outer cup.

2. The tappet mechanism of claim 1, wherein the side wall of the inner cup is cylindrical and the inner cup further includes a semi-spherical bottom portion disposed at a bottom end of the side wall.

3. The tappet mechanism of claim 2, wherein the inner cup further comprises at least one lubrication aperture defined by the semi-spherical bottom portion.

4. The tappet mechanism of claim 1, wherein the roller further comprises an outer race and a plurality of rollers, wherein the plurality of rollers is disposed between the outer race and the shaft.

5. An internal combustion engine comprising: a cylinder head defining an elongated bore therein; a camshaft including a cam lobe disposed thereon; a fuel pump including a pump stem; and a tappet mechanism movable within the bore along a longitudinal center axis of the bore, comprising: an outer cup having an inner surface and an outer surface defining a substantially cylindrical side wall, an annular lip portion disposed at a first end of the side wall, and a radially-outwardly extending anti-rotation feature in the form of a protrusion formed in the side wall; an inner cup including a pair of shaft apertures, the inner cup being disposed in the outer cup; a shaft having a first end and a second end, each of the first end and the second end being disposed in a corresponding one of the shaft apertures; a roller rotatably received on the shaft such that a portion of the roller tappet extends axially outwardly beyond the annular lip portion of the outer cup, and wherein the anti-rotation feature formed in the outer cup includes a pair of apertures extending axially along its length, one of the apertures being disposed on each side of the anti rotation feature at an intersection of the anti-rotation feature and the outer surface of the outer cup.

6. The internal combustion engine of claim 5, wherein the side wall of the inner cup is cylindrical and the inner cup further includes a semi- spherical bottom portion disposed at a bottom end of the side wall.

7. The internal combustion engine of claim 6, wherein the inner cup further comprises at least one lubrication aperture defined by the semi- spherical bottom portion.

8. The internal combustion engine of claim 5, wherein the roller further comprises an outer race and a plurality of rollers, wherein the plurality of rollers is disposed between the outer race and the shaft.