Anti-tipping Roller Follower

Abstract

An anti-tipping feature for a roller follower is provided that is positioned at the socket end of a Type II roller follower. The anti-tipping feature is designed to fit around the plunger of a lash adjuster. The feature has legs that extend down around the plunger to provide stability for the roller follower. Tipping of the roller follower is controlled by the formed legs that extend down the plunger. The length of the legs and clearance determine the amount of roller follower tipping. The valve guide wall height can be shortened enough to still provide valve containment and reduce moving mass which comprises a key component to engine performance.

Description

[0001] This invention relates to a roller follower for a Type II internal combustion engine and more particularly to a roller follower devised with an anti-tipping feature placed at the socket end of the rocker arm.

BACKGROUND OF THE INVENTION

[0002] A key factor for roller follower design is mass at the valve end. Reducing the amount of moving mass can improve engine performance by using more aggressive valve lift profiles, which in turn can improve engine power, raise limiting speed, and reduce hydrocarbon emissions. It is common knowledge a Type II valve train roller follower is configured to include a socket end to engage a lash adjuster, a valve pad end to engage a valve, and a bearing between the ends that contacts an over head cam. When the roller follower is placed in the head on the lash adjuster and valve, before the cam shaft is installed, there is a degree of freedom for the roller follower to tip side to side. The roller follower needs that side to side freedom for any misalignment that may have occurred when the bearing was installed into the roller follower. This misalignment allows the roller follower to still be functional and perform as designed. During engine operation if the bearing is not exactly parallel to the valve pad the roller follower, without any valve containment feature, can slide off the valve stem causing the cylinder to misfire and reducing engine performance. To keep the roller follower from sliding off the valve integral formed guide walls or an additional part is added to the roller follower at the valve pad end.

[0003] Another important function of the rocker arm valve guide walls is to prevent the roller follower from tipping over and falling into the engine head during the automated engine assembly process. Once the cam shaft is put into place during the assembly process the roller follower will be securely held on the lash adjuster and valve tip. To keep the roller follower from tipping the rocker arm valve guide walls need to be greater than about 3 mm in height. This provides enough valve stem to guide wall contact to limit how much the roller follower can tip and not fall off. By adding wall height to control tipping you also add additional moving mass which is undesirable for engine performance.

[0004] Consequently, there exists a need for a roller follower that combines using guide walls less then 3 mm to reduce valve pad end mass and still provide enough stability to not tip during engine assembly.

SUMMARY OF THE INVENTION

[0005] The anti-tipping arrangement of the invention comprises providing legs of a suitable height at the socket end of a Type II roller follower. This anti-tipping feature of the invention is advantageously devised with legs that extend down around the lash adjuster plunger to provide stability for the roller follower.

[0006] The stability providing feature of the invention has no significant impact on, i.e., is not a detriment to, the mass at the valve end. Additional advantages of the invention will be apparent from the detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 is a diagrammatic representation of a valve train including an overhead camshaft with cam lobes, lash adjuster, valve and roller follower.

[0008] FIG. 2 is a perspective disassembled bottom view of the clip and roller follower with roller.

[0009] FIG. 3 is a perspective more detailed bottom view of the roller follower per se, i.e., with roller omitted.

[0010] FIG. 4 is a perspective view of the assembled roller follower with clip in place.

[0011] FIG. 5 is another perspective view of the assembled roller follower with clip in place.

[0012] FIG. 6 is a fragmentary cross-sectional view through the top of the lash adjuster with the roller follower of the invention in place.

[0013] FIG. 7 is a perspective view of the pivot clip of the invention provided with an outer socket clearance hole, a plunger body clearance hole and flat clip legs.

[0014] FIG. 8 is a fragmentary perspective view of the roller follower with the clip device of FIG. 7 in place.

[0015] FIG. 9 is a fragmentary perspective view of the roller follower with an alternative anti-tipping device comprising a wire clip in position on the roller follower.

DETAILED DESCRIPTION OF THE INVENTION

[0016] Referring to the figures of the drawings, FIG. 1 refers to a Type II Valve Train design which includes overhead camshaft 16 provided with cam 10 having a cam lobe 11, lash adjuster 12, valve 13 and roller follower 14. The roller follower 14 is in contact with the camshaft cam lobe 11. As the lobe camshaft 16 and cam 11 rotate the cam lobe 11 displaces the roller follower 14. The roller follower 14 pivots, i.e., reciprocates on the lash adjuster 12. The lash adjuster is devised to maintain zero clearance between the cam, rocker arm and valve throughout the lift event so that there is no separation between the valve contact portion 22 of the rocker arm and valve 13 causing what is known as valve loss motion resulting in poor engine performance. The roller follower 14 translates the rotating camshaft motion into linear motion which opens and closes the valve 13.

[0017] As shown in FIG. 2 and FIG. 3, elements of the roller follower are illustrated. The roller follower 14 comprises a main body 18 with side walls 20 generally comprising U-shape cross-section, pivot socket 19 which engages the lash adjuster 12 and valve contacting portion 22. An opening 21 is provided in the side walls 20 to mount a shaft 26 which passes through the roller follower body and is preferably surrounded by t multiple needle bearings 27 (shown in FIG. 1) and roller 17. Roller 17 is positioned between side walls 20 and pivot socket 19 and valve contacting portion, valve pad 22. The valve contact portion is provided with guide extensions 23 that are parallel to side walls 20. As shown in FIG. 2, roller follower 14 is illustrated in accompaniment but not engaged with the anti-tipping clip 15.

[0018] In FIGS. 4 and 5 the anti-tipping clip 15 shown separate in FIG. 2 and FIG. 7 is engaged on the assembled roller follower 14.

[0019] FIG. 6 illustrates a cross-section at the top of the lash adjuster 12 which engages the pivot socket 19 of the roller follower.

[0020] In FIG. 7 the pivot clip 15 which contains socket clearance hole 24, plunger body clearance hole 26 and clip leg 25 is shown.

[0021] In the enlarged fragmentary view of FIG. 8, the clip 15 in position is illustrated in greater detail.

[0022] FIG. 9 illustrates an alternated clip 30 with wire form legs 31 and 32, secured to the roller follower body 18a. Reference numbers followed by the lower case "a" in FIG. 9 identify elements that function similar to the earlier mentioned elements bearing similar numbers.

[0023] To keep the roller follower 14 from sliding off the valve 13 integral formed guide walls 23 or an additional part is added to the roller follower contiguous to the valve pad 22 end. Another important function of the rocker arm valve guide walls is to prevent the roller follower from tipping over and falling into the engine head during automated engine assembly process, e.g., in order to keep the roller follower from tipping the rocker arm valve guide walls need to be greater than about 3 mm in height. This provides reasonable assurance that enough valve stem to guide wall contact is provided so that any occurring tipping of the roller follower will not result in a displacement of the roller follower. It is to be noted that adding wall height to control tipping also results in additional moving mass which is undesirable for engine performance. It is thus seen that a roller follower is provided that uses minimum necessary guide walls of the order of less than 3 mm to reduce valve pad end mass and still provide enough stability to prevent tipping during engine assembly. The anti-tipping feature of the invention is advantageously devised with legs that extend down around the lash adjuster plunger to provide stability for the roller follower. The stability providing anti-tipping adjunct of the invention does not introduce a significant impact on, i.e., is not a detriment to, the mass at the valve end of the roller follower.

[0024] Although the invention has been described in terms of a specific embodiment, one skilled in the art can vary or substitute other obvious elements or embodiments and these are meant to be included herein. The invention is only to be limited by the scope of the appended claims.

Claims

1. In a roller follower that pivots about a lash adjuster of internal combustion engines comprising a one-piece, cold-formed, elongate metal body having a generally U-shaped cross-section and having an intermediate portion, a first valve contact end portion, and a second lash adjuster contact end portion, said intermediate portion having two substantially parallel side walls and a large elongate upper opening, said first end portion having a top wall and two side walls extending downwardly therefrom generally inverted U-shaped recess to receive an end of a valve stem, said second end lash adjuster contact portion having a second top wall and side walls extending downwardly there from, the improvement comprises an anti-tipping clip secured to the lash adjuster end and having a pair of legs extended around the lash adjuster contact so as to afford stability for the assembly.

2. The roller follower of claim 1 wherein legs of the lash adjuster clip comprises a flat configuration.

3. The roller follower of claim 1 wherein the lash adjuster clip comprises a wire leg configuration.