ROLLER FINGER FOLLOWER WITH SWIVELABLE VALVE PALLET

Abstract

A finger follower having an inner and outer body and a torsional lost motion spring acting between the bodies is provided. A roller cam follower is connected to the inner body. The inner body is switchable from a fixed state, in which it moves with the outer body to transfer a cam lift to a valve stem, to a released state, in which the inner body can move relative to the outer body so that the cam lift is not transferred to the valve stem. A separate valve pallet that acts on the valve stem is press fit or otherwise rotationally fixed on a pivot pin connecting the inner and outer bodies.

Description

INCORPORATION BY REFERENCE

The following documents are incorporated herein by reference as if fully set forth: U.S. Provisional Application No. 61/589,505, filed Jan. 23, 2012.

FIELD OF INVENTION

The invention relates to roller finger followers that are used in overhead cam type internal combustion engines and, more particularly, to switchable roller finger followers that have a lift and a no lift mode.

BACKGROUND

Switchable roller finger followers that have at least one lift mode and a no lift mode are known. Typically, such finger followers have an outer elongated body, one end of which contacts a valve stem and operates on the valve stem, and a second end which is in contact with a hydraulic lash adjuster. The end which contacts the valve stem is formed on the outer elongated body and includes side walls to ensure that its position on the valve stem is maintained. This requires complex machining or formation of the outer elongated body. An inner elongated body is located in the outer elongated body and houses a cam follower that is contacted by the cam so as to provide motion to the finger follower to open or close the valve. The inner elongated body has two modes, a locked mode and an unlocked mode. A latching mechanism on the outer elongated body is used to lock the inner elongated body in a fixed position relative to the outer body. When the inner elongated body is locked in a stationary position, the cam which is fixed to the cam shaft of the engine translates movement to the finger follower which in turn translates into movement of the valve via the valve stem. In order to deactivate the finger follower, the latching mechanism is released and the inner elongated body is unlocked and can travel freely up and down in conjunction with the cam without transferring the cam motion to the outer body and valve stem.

U.S. Pat. No. 7,909,007 discloses a roller finger follower of this type. This provides a lost motion spring to maintain contact between the cam follower and the cam.

It would be desirable to provide a finger follower of the type noted above with simpler manufacturing and reduced costs.

SUMMARY

A switchable roller finger follower is provided having an outer elongated body with a valve stem end, a lash adjuster end and two outer elongated body side walls. A first inner cavity is located in said outer elongated body. An inner elongated body is positioned in the first inner cavity and has a first end pivotally attached to the outer elongated body at the valve stem end via a pin. A second end of the inner elongated body is located adjacent to the lash adjuster end of the outer elongated body. A lost motion spring is located between the inner and outer elongated bodies. A latching mechanism is provided to lock the inner elongated body in a fixed position relative to the outer elongated body, and can be released in order to allow movement between the inner and outer elongated bodies. A valve stem pallet is located between the two outer elongated body side walls and is connected in a rotationally fixed manner to the pivot pin. The valve stem pallet can be separately manufactured via cold forming, machining, punching and/or bending up sheet metal, or by various other methods. By separately forming the valve stem pallet from the outer elongated body, manufacturing is simplified and costs are reduced.

In another aspect of the invention, the motion of the valve stem pallet is limited by stops on or connected to the outer elongated body.

Other aspects of the invention are described below and in the claims, and have not been repeated here.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing Summary and the following detailed description will be better understood when read in conjunction with the appended drawings, which illustrate a preferred embodiment of the invention. In the drawings:

FIG. 1 is a perspective view of a finger follower in accordance with the prior art.

FIG. 2 is a perspective view of a finger follower in accordance with the present invention.

FIG. 3 is an enlarged perspective view of a portion of the finger follower of FIG. 2.

FIG. 4 is a perspective view of a valve stem pallet used in connection with the finger follower of FIGS. 2 and 3.

FIG. 5 is a perspective view of an alternate embodiment of the valve stem pallet similar to the valve stem pallet shown in FIG. 4.

FIG. 6 is a cross-sectional view through the valve stem pallet shown in FIG. 5 taken along line 6-6 in FIG. 5.

FIG. 7 is a cross-sectional view through a second embodiment of a valve stem pallet according to the invention.

FIG. 8 is a perspective view of the valve stem pallet shown in FIG. 7.

FIG. 9 is a flat pattern for a valve stem pallet in accordance with a third embodiment of the invention.

FIG. 10 is a valve stem pallet made from the flat pattern shown in FIG. 9.

FIG. 11 is a view of a valve stem pallet located in a finger follower having rotation limit stops for limiting a pivoting movement of the valve stem pallet.

FIG. 12 is a cross-sectional view taken along lines 12-12 in FIG. 11.

FIG. 13 is another embodiment of a finger follower having an arrangement for limiting rotation of the valve stem pallet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Certain terminology is used in the following description for convenience only and is not limiting. The words “front,” “rear,” “upper” and “lower” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward and away from the parts referenced in the drawings. A reference to a list of items that are cited as “at least one of a, b, or c” (where a, b, and c represent the items being listed) means any single one of the items a, b, or c, or combinations thereof. The terminology includes the words specifically noted above, derivatives thereof and words of similar import.

FIG. 1 shows a prior art finger follower 10 being acted on by cam 12. The finger follower 10 pivots on and is in contact with a lash adjuster 14, and through its pivot action operates on a valve stem 16 to open and close a valve in a cylinder of an internal combustion engine (not shown). The finger follower 10 pivots about a pivot point 18 formed on top of the lash adjuster 14. The finger follower 10 has an outer elongated body 20 having a valve stem end 22, a lash adjuster end 24, and two elongated body side walls 26 and 28. A first inner cavity 30 in the outer elongated body 20 is defined between the valve stem end 22, the lash adjuster end 24 and the side walls 26 and 28. Affixed to the outer elongated body 20, at its lash adjuster end 24, are lost motion spring pins 32 and 34. Each of the side walls 26 and 28 provide lost motion spring stops 36 and 38.

An inner elongated body 40 is positioned in the first inner cavity 30. The inner elongated body 40 has a first end which is pivotally attached to the valve stem end 22 of the outer elongated body 20, by a pin 41, a second end which is adjacent to the lash adjuster end 24, and two inner elongated side walls. A center cam follower in the form of a roller 56 is mounted in the inner elongated body 40. A latch assembly 58 forms part of the outer elongated body 20. The latch assembly 58 is a conventional latch assembly which is operated in a conventional manner in order to lock the inner elongated body 40 to the outer elongated body 20 for transferring movement from the cam to the valve stem 16. When the latch assembly 58 is unlocked, the cam movement simply results in the inner elongated body 40 pivoting up and down inside the outer elongated body.

A lost motion torsional spring 60 is located between the inner and outer elongated bodies, and includes helical spring parts 62 and 63 positioned on pins 32 and 34 respectively. The action of the spring 60 is described in detail in U.S. Pat. No. 7.909,007, which is incorporated herein by reference as if fully set forth.

Referring now to FIGS. 2 and 3, a finger follower 110 in accordance with the present invention is shown. The finger follower 110 according to the invention is similar to the prior art finger follower 10 in that it includes an outer elongated body 120 as well as an inner elongated body 140 which are connected together in a pivotable manner at the valve stem end 122 via a pin 141. A lost motion spring 160 is provided connected to the spring holding pins 132 and 134 and has spring parts 162 and 163 as shown which act on spring pallets 152 and 154 on the inner elongated body 140 in order to maintain contact of the cam follower roller 156 with the cam (not shown). A latch assembly 158 is provided which, in a latched position, fixes the inner elongated body 140 in position relative to the outer elongated body 120, and which can be released in order to allow movement between the inner and outer elongated bodies 140, 120.

As shown in detail in FIGS. 2 and 3, a valve stem pallet 170 is located between the two outer elongated body sidewalls 126, 128 and is connected in a rotational fixed manner to the pivot pin 141. This connection can be via a press fit, splined fit, welding or any other suitable manner. The pivot pin 141 is slidably and rotatably located in the holes defined through the sidewalls 126, 128 of the outer elongated body 120 as well as the sidewalls 146, 148 of the inner elongated body 140. The construction of the valve stem pallet 170 can be varied. In the embodiment shown in FIGS. 2 and 3, which is shown in detail in FIG. 4, the valve stem pallet 170 is a cold forged or machined part having a center lug 171 with downwardly extending sidewalls 172, 174 at each end in order to provide guides for capturing the end of the valve stem (16 in FIG. 1). An opening 176 is defined through the lug 171 which is adapted for a press fit with the pin 141. The bottom surface 182 of the lug 171 is a convex surface, preferably having a three dimensional curvature. The convex surface 182 can be formed as a partial spherical surface or any other suitable convex surface form. As shown in FIG. 4, rotation limiters in the form of projections 174, 175 extend from the sidewalls that are received in corresponding grooves 147, 149 defined on the inner surfaces of the sidewalls 146, 148 of the inner elongated body 140. These rotation limiters prevent over-rotation of the valve stem pallet 170 while in use. By separately manufacturing the valve stem pallet 170, this eliminates the need for forming a valve stem pallet as part of the outer elongated body as previously known in the art which involve higher manufacturing costs as well as more complex packaging. A preferred material for the pallet 170 is steel which is preferably surface hardened or heat treated at least in the area of the convex surface 182.

Referring to FIGS. 5 and 6, an alternate embodiment of a forged or machined valve stem pallet 170′ is shown. This embodiment is similar to the valve stem pallet 170; however, instead of the lug 171 with a single opening 176, the sidewalls 172′, 174′ extend upwardly past a cross member 180′ on which the convex surface 182′ is defined. The sidewalls 172′, 174′ include aligned openings 176′, 178′ for receiving the pin 141. This embodiment can offer reduced weight in comparison to the valve stem pallet 170. Rotation limiters could also optionally be provided.

Referring to FIGS. 7 and 8, a second embodiment of the valve stem pallet 190 is shown. The second embodiment of the valve pallet 190 is similar to the first embodiment except that it is formed as a turned part and includes a circular casing 192 with a cross member 196 extending across the medial portion. The upper end of the circular casing is deformed inwardly to form a top section 194 that engages with a connecter portion 198 that is affixed to the pin 141 via a press fit through an opening defined through the connecter portion 198. The valve stem pallet 190 is preferably formed of steel and is hardened at least in the area of the cross member 196. The cross member 196 can also have a convex form in the contact area for the valve stem 16, in a similar manner as described in connection with the first embodiment of the valve stem pallet 170. A further alternative is to locate the cross member 196 at the bottom of the circular casing 192, eliminating any extension of the casing 192 past the convex contact area with the valve stem.

Referring to FIGS. 9 and 10, the third embodiment of a valve stem pallet 200 is shown. The third embodiment of the valve stem pallet 200 is formed from sheet metal and can be made via a punched blank 202 shown in FIG. 9. The blank 202 is bent-up in order to form the flanges 204, 206 having holes 208, 210, respectively defined therethrough for receiving the pin 141. The base 212 extends between the flanges 204, 206, and side members 214, 216 are bent around along the underside of the base in an area beneath the flanges 204, 206 in order to provide guides for maintaining the valve stem in position on the base 212 in use. The side members 214, 216 can be welded in place. The base 212 can be formed convexly in the area of contact with the valve stem by a stamping operation, and is preferably formed of steel and hardened, at least in the area of the base 212.

Referring now to FIGS. 11 and 12, an alternate embodiment of the finger follower 110 is shown in which the side walls 126, 128 of the outer elongated body 120 at the valve stem end 122 include rotation limiters 123 formed thereon. The rotation limiters 123 are preferably in the form of inwardly directed curved flanges having a curve or other shape adapted to limit a pivoting movement of the valve stem pallet 170′ via contact with adjacent edges of the sidewalls 172′, 174′ in a maximum pivoted position. In this embodiment, the inner elongated body 140 is formed with a single flange that extends between the side walls 172′, 174′ of the valve stem pallet 170′. The pin 141 has a press fit with the openings 176′, 178′ in the side walls 172′, 174′ of the valve stem pallet 170′ and a slip fit in the holes defined in both the outer elongated body 120 and the inner elongated body 140.

Referring now to FIG. 13, an alternate embodiment of the rotation limiter for the valve stem pallet 170′ is shown. In this embodiment, the pin 141′ includes a head 143′. The pin 141′ is press fit through the openings 176′, 178′ in the valve stem pallet 170′ and includes a slip fit with the corresponding holes in the outer elongated body 120 and the inner elongated body 140. An anchor pin 145′ is connected through the head 143′ and into the side wall 128 of the outer elongated body 120 so that the valve stem pallet 170 is locked in rotation via the pin 141′ to the outer elongated body 120. Alternatively, the anchor pin 145′ extends into a slot in the sidewall 128 so that a limited pivoting movement for the pin 141′ and the valve stem pallet 170′ is possible. This prevents excess or unwanted pivoting movement of the valve stem pallet 170′. Alternatively, instead of the pin 141′ with a head 143′, other means for fixation to the outer elongated body 120, such as a keyed opening, welding, or any other suitable connection means.

As a further alternative, the guides provided on the valve stem pallets discussed above that are adapted to capture the ends of the valve stem 16 can be eliminated from the valve stem pallets according to the invention, and instead be provided as downwardly directed extensions of the sidewalls 126, 128 or 146, 148 of the outer or inner elongated bodies 120, 140 on either side of the valve stem pallet that are adapted to capture an end of the valve stem.

Having thus described the present invention in detail, it will be appreciated and apparent to those skilled in the art that many physical changes, only a few of which are exemplified in the detailed description of the invention, could be made without altering the inventive concepts and principles embodied therein. It is also to be appreciated that numerous embodiments incorporating only part of the preferred embodiment are possible which do not alter, with respect to those parts, the inventive concepts and principles embodied therein. The preferred embodiments and optional configurations are therefore to be considered in all respects as exemplary and/or illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all alternate embodiments and changes to this embodiment which come within the meaning and range of equivalency of said claims are therefore to be embraced therein.

Claims

1. A switchable roller finger follower comprising:

an outer elongated body having a valve stem end, a lash adjuster end and two outer elongated body side walls;

a first inner cavity in said outer elongated body;

an inner elongated body positioned in said first inner cavity and having a first end pivotally attached to said outer elongated body at said valve stem end via a pin, a second end adjacent said lash adjuster end of said outer elongated body, and two inner elongated body sidewalls;

a lost motion spring located between the inner and outer elongated bodies;

a latching mechanism used to lock the inner elongated body in a fixed position relative to the outer elongated body; and

a valve stem pallet located between the two outer elongated body side walls and connected in a rotationally fixed manner to the pivot pin.

2. The switchable roller finger follower of claim 1, further comprising at least one rotation limiter that limits a pivoting movement between the valve stem pallet and the outer elongated body.

3. The switchable roller finger follower of claim 1, wherein the valve stem pallet includes a sidewalls with a cross member defined therebetween, the cross member includes a convex surface adapted to contact a valve stem.

4. The switchable roller finger follower of claim 3, wherein the sidewalls extend past the convex surface to define guides adapted to maintain a valve stem in position.

5. The switchable roller finger follower of claim 1, wherein the valve stem pallet includes a cylindrical casing and an intermediate cross member adapted to contact a valve stem.

6. The switchable roller finger follower of claim 1, wherein the valve stem pallet is a formed sheet metal part having bent-up flanges with holes that are connected to the pivot pin, with a base extending between the flanges, and side members bent around along an underside of the base in an area beneath the flanges that are adapted to maintain a valve stem in position.

7. The switchable roller finger follower of claim 1, wherein the pivot pin includes a head that is fixed to the outer elongated body to at least limit a pivoting movement of the pivot pin relative to the outer elongated body.

8. The switchable roller finger follower of claim 1, wherein guides extend from the outer or inner elongated bodies on either side of the valve stem pallet that are adapted to capture an end of the valve stem.

9. The switchable roller finger follower of claim 1, further comprising at least one rotation limiter that limits a pivoting movement between the valve stem pallet and the outer elongated body, the at least one rotation limiter is formed on the outer elongated body at the valve stem end as an inwardly directed flange having a shape adapted to limit a pivoting movement of the valve stem pallet via contact with an adjacent edge of the valve stem pallet.

10. A valve stem pallet for a finger follower having a valve stem end, a lash adjuster end and two outer elongated side walls, the valve stem pallet comprising:

a body having sidewalls with a cross member defined therebetween, the cross member includes a convex surface adapted to contact a valve stem; and

at least one opening defined through the sidewalls for a pivotal connection to the outer elongated side walls of the finger follower at the valve stem end.