FINGER FOLLOWER ASSEMBLY

FIELD OF THE INVENTION

[0001] The present invention relates generally to finger follower assemblies used with internal combustion engines. More particularly, the present invention relates to designs and assembly methods of finger follower assemblies.

BACKGROUND OF THE INVENTION

[0002] Referring to Figures 3 and 4, finger follower assemblies 10 are often used in valve trains of internal combustion engines to transmit motion from a camshaft 20 (Figure 3) of the engine to one or more intake or exhaust valves 22. As shown, finger follower assembly 10 includes a housing 12 that rotatably supports a cam roller 15 on a plurality of needle rollers 17 that are in turn rotatably supported in a bearing shaft 19. As camshaft 20 rotates, finger follower assembly 10 receives a downward force from a corresponding lobe 24 on the camshaft, and transmits the downward force to valve 22 to open and/or close the valve. A first end 14 of finger follower assembly 10 is pivotably received on top of a lash adjuster 26 so that the second end 16 of finger follower assembly 10 moves up and down in a vertical plane. The second end of the finger follower assembly engages an upper end of a valve stem 23 of a corresponding valve 22, thereby transmitting downward forces to the valve. A spring 30 constantly urges second end 16 of finger follower assembly 10 upward. [0003] As best seen in Figure 4, cam roller 15 extends through an aperture 32 formed in a bottom wall of housing 12. Typically, side walls 34 of the aperture 32 are spaced at a width that is slightly greater than the width of cam roller 15. As such, side walls 34 of the aperture limit the axial travel of cam roller 15 along bearing shaft 19. As shown, when cam roller 15 comes into contact with one of side walls 34, it does so along the entire length of that side wall. Although this feature may contribute to increased stability of the cam roller, this large area of contact can contribute to increased friction, between the cam roller and housing 12 and, therefore, increased wear of the components. In yet other known follower housings, axial travel of the cam roller along the bearing shaft is limited through contact of the cam roller's end faces with the inside surfaces of the side walls of the housing. This configuration leads to large contact areas and, therefore, frictional forces between the end faces of the cam rollers and side walls of the housing.

[0004] The present invention recognizes and addresses considerations of prior art constructions and methods.

SUMMARY OF THE INVENTION

[0005] One embodiment of the present disclosure provides a finger follower assembly comprising a follower housing having a pair of opposed side walls extending from a first end to a second end of the follower housing, each side wall defining a bore aperture, and a base wall extending between the side walls of the follower housing, the base wall defining a bearing aperture defined by a pair of opposed side walls extending between a pair of opposed end walls. A bearing shaft has a first end received in a corresponding shaft aperture and a second end received in a corresponding shaft aperture, and a roller bearing including an outer race that is rotatably received about the bearing shaft with a plurality of roller elements that are rotatably received between the outer race and the bearing shaft. Each bearing aperture side wall includes a roller guide surface that is disposed closer to a first plane that passes through a longitudinal center axis of the follower housing than a remainder of the corresponding bearing aperture side wall.

[0006] 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

[0007] 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;

[0008] Figures 1A, IB and 1C are perspective, bottom and top views, respectively, of a finger follower assembly in accordance with the present disclosure;

[0009] Figures 2A and 2B are bottom and top views, respectively, of an alternate embodiment of a finger follower assembly in accordance with the present disclosure;

[0010] Figure 3 is a side view of a prior art finger follower assembly as used in a valve train assembly of an internal combustion engine; and

[0011] Figure 4 is a bottom view of the prior art finger follower assembly shown in

Figure 3.

[0012] 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

[0013] 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.

[0014] Referring now to Figures 1A, IB and 1C, an embodiment of a finger follower assembly 100 in accordance with the present disclosure is shown. As shown, finger follower assembly 100 includes a follower housing 110 that rotatably supports a roller bearing 150 on a bearing shaft 140. Roller bearing 150 includes an outer race 152, or cam roller, that is configured to engage a camshaft 20 including a cam lobe 24 (Figure 3). As previously noted, as cam lobe 24 engages roller bearing 150, finger follower assembly 100 pivots about a first end 112 which is supported on a lash adjuster 26 so that its second end 114 moves downwardly. Downward motion of second end 114 of finger follower assembly 100 causes downward motion of valve 22. Valve 22 is returned to the up position by spring 30.

[0015] As shown, follower housing 110 includes a pair of substantially parallel side walls 116 that extend from first end 112 to second end 114 of the housing. First end 112 of follower housing 110 includes a semi-spherically shaped ball socket 132 that is configured to receive the correspondingly shaped top end of lash adjuster 26 (Figure 3), and second end 114 of follower housing 110 defines a valve pallet 134 that engages the top end of valve stem 23 (Figure 3). Each side wall 116 defines a bore aperture 120 that is configured to receive a corresponding end of bearing shaft 140. Bearing shaft 140 may be non-rotatably fixed to follower housing 110 by staking, tack welding, etc. , but is preferably free to rotate within the bore apertures 120 to help equalize surface loading of bearing shaft 140 over time. Follower housing 110 further includes a base wall 118 that extends between the lower most edges of side walls 116. As shown, base wall 118 defines a bearing aperture 122 whose perimeter is defined by a pair of opposed side walls 124 and a pair of opposed end walls 126 that extend therebetween. Bearing aperture 122 is configured to allow a portion of roller bearing 150 to extend through base wall 118.

[0016] Outer race 152 of roller bearing 150 is rotatably received about bearing shaft

140. A plurality of roller elements 156 is disposed about an outer surface of bearing shaft 140 within a shaft bore 154 defined by outer race 152. Axial travel of each roller element 156 in a direction parallel to a longitudinal center axis 142 of bearing shaft 140 is limited by contact of the roller elements' end faces with the inside surfaces 117 of the housing's side walls 116. In contrast, as best seen in Figure IB, the axial travel of outer race 152 of roller bearing 150 in a direction parallel to longitudinal center axis 142 of bearing shaft 140 is limited by contact of the outer race's end faces 158 with a roller guide surface 128 defined on each side wall 124 of bearing aperture 122.

[0017] As shown in Figures IB and 1C, each bearing aperture side wall 124 defines a roller guide surface 128 and is symmetrical with respect to longitudinal center axis 142 of bearing shaft 140. As well, each roller guide surface 128 is defined by a portion of the corresponding bearing aperture side wall 124 that is closer to a longitudinal center axis 121 of follower housing 110 than is the remainder of the corresponding bearing aperture side wall 116. As such, roller guide surfaces 128 are the only portions of the bearing aperture side walls 124 that come into contact with the end faces of outer race 152, thereby limiting its travel along bearing shaft 140. In the embodiment shown, each bearing aperture side wall 124 is defined by a convex surface such that the corresponding end face of outer race 152 makes contact with the corresponding bearing aperture side wall 124 tangentially at only roller guide surfaces 128. As such, the contact area between follower housing 110 and outer race 152 of roller bearing 150 is reduced as compared to the previously discussed prior art embodiments, as shown in Figure 4. Note, in alternate embodiments, roller guide surface 128 may be formed by a planar portion of the corresponding side wall as opposed to the apex of a curved side wall.

[0018] Referring now to Figures 2A and 2B, an alternate embodiment of a follower housing 210 in accordance with the present disclosure is shown. Similarly to the previously described embodiment, follower housing 210 includes a pair of substantially parallel side walls 216 that extend from a first end 212 defining a ball socket 232 to a second end 214 defining a valve pallet 234. Each side wall 216 defines a bore aperture 220 for receiving a corresponding end of a bearing shaft. As well, follower housing 210 includes a base wall 218 that extends between the lower edges of the following housings side walls 216, wherein base wall 218 defines a bearing aperture 222. Bearing aperture 222 is defined by a pair of opposed side walls 224 that are connected at their ends by a pair of opposed end walls 226.

[0019] Similarly to the previously discussed embodiment, each side wall 224 of bearing aperture 222 defines a roller guide surface 228 that is defined by a portion of each side wall 224 that is closer to a longitudinal center axis 221 of follower housing 210 than is the remainder of the corresponding bearing aperture side wall 224. Note, however, each bearing aperture side wall 224 is not symmetric about a longitudinal center axis 242 of the corresponding bearing shaft (not shown). Rather, each roller guide surface 228 is disposed axially along longitudinal center axis 221 of the follower housing so as to be spaced a desired distance from the bearing shaft's longitudinal center axis 242. For example, Figures 2A and 2B show roller guide surfaces 128 disposed to the left side of longitudinal center axis 242. As such, when viewing Figure 1A, roller guide surfaces 228 will contact the end faces 158 of outer race 152 to the left of a vertical axis that intersects and is perpendicular to both longitudinal center axis 242 of bearing shaft 140 and longitudinal center axis 221 of follower housing 210. In this position, roller guide surfaces 228 help to maintain lubrication of a finger follower assembly that is top lubricated and configured to have outer race 152 of roller bearing 150 rotate in the counter-clockwise direction when viewing Figure 1A. Alternately, if the desired rotation of outer race 152 of roller bearing 150 is in the clockwise direction, roller guide surfaces 228 would preferably be moved axially along longitudinal center axis 221 of follower housing 210 to the right of longitudinal center axis 242 of the bearing shaft.

[0020] 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.