ANTI-TIPPING ROLLER FOLLOWER
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.
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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 INVENTIONA 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.
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.
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 INVENTIONThe 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.
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
Referring to the figures of the drawings,
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In the enlarged fragmentary view of
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.
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.
Type: Application
Filed: Mar 24, 2006
Publication Date: Sep 27, 2007
Applicant: GenTek Technologies Marketing, Inc. (Parsippany, NJ)
Inventors: Scott Smith (Temperance, MI), Blaine Lingenfelter (Hartland, MI), John Brune (Stockbridge, MI)
Application Number: 11/277,468
International Classification: F01L 1/02 (20060101); F01L 1/18 (20060101);