SHEET METAL ROCKER ARM WITH INTEGRALLY FORMED CROSS MEMBER

Abstract

A sheet metal rocker arm of the end pivot rocker arm type formed by bending into a U shape a precursor sheet metal piece and characterized by having a reinforcing cross member which is integrally formed by bending a tab that is cut in the central portion of the connecting part of a U-channel element to yield a reinforcing cross member to provide a unitary structure that introduces substantially enhanced stiffness to the rocker arm. The method of creating integrally formed reinforcing cross-members by appropriately cutting slits that provide reinforcing members can be applied to any stamped rocker arm that has a U-channel architecture, e.g., including, for example, rocker arms for pushrod type valvetrains as well as roller finger follower type rocker arms. Provision of the integrally formed cross member abutting the inner wall of the sides of the U-shaped rocker arm renders stiffness to the rocker arm that enables an engine to operate at a higher rpm and thereby improves horsepower output.

Description

This invention relates to an improved rocker arm formed from sheet metal and characterized by an integrally formed cross member which provides advantageous added stiffness to the rocker arm.

BACKGROUND OF THE INVENTION

Generally, prior art rocker arms formed from sheet metal are bent to a U-shape and then provided with an opening in the center, flat section. The U-channel can be oriented up or down and is provided with an opening or “window” at the center, either for a pivot attachment or for mounting a roller assembly. The window is made by punching out the material and discarding the punched out portion.

These prior art rocker arms from sheet metal typically have a U-shaped lateral cross-section and have no reinforcing cross members between opposing sides. Under load these rocker arms deflect such that opposing sides move outward and their ends move upwards, resulting in a loss of longitudinal stiffness. Lack of stiffness in rocker arms detracts from efficiency especially when operating at high engine speeds. The buckling from the desired shape and insufficiency of rocker arm stiffness detract from the capability to achieve maximum engine power.

As disclosed in U.S. Pat. No. 7,185,618 a sheet metal rocker arm with reinforcing cross members is provided by bending tabs formed on a tube insert so that the tabs of the tube insert abut the sides a U shape rocker arm formed by bending a sheet metal precursor to form a U shape.

In the present invention as distinguished from that of U.S. Pat. No. 7,185,618 wherein the reinforcing cross members are provided by bending tabs on a tubular insert, introduced into the axle assembly holes, the reinforcing bent tubular cross members are integral to the sheet metal piece, i.e.,.are provided by bending a tab in the sheet metal piece itself from which the U shape rocker arm is shaped.

The present invention accordingly provides an economical and expeditious means for providing a sheet metal rocker arm possessing greater relative stiffness by an improved construction configuration.

SUMMARY OF THE INVENTION

The invention provides an improved rocker arm of the roller finger follower type formed from sheet metal and characterized by having at least one cross member which is integrally formed within the rocker arm itself and which yields a unitary structure that provides substantial stiffness without adding additional weight to the rocker arm. The method of the invention can be applied to any stamped rocker arm that has a U-channel architecture, e.g., including, for example, rocker arms for pushrod type valvetrains as well as roller finger follower type rocker arms. Provision of the integrally formed cross member renders stiffness to the rocker arm, tends to prevent distortion and enables an engine to operate at a higher rpm and thereby to produce more horsepower.

In the rocker arm forming method of the invention, a flat patterned sheet metal piece is bent into a U-shape precursor. In creating the desired reinforcing cross-member, the U-shape precursor a tab or a multiplicity of tabs are formed by slitting the sheet meal precursor and subsequently to provide an opening or “window” while at the same time creating a reinforcing cross-member. This piercing of the sheet metal as in the present invention without punching out and removing the material is referred to as lancing. However, this is not intended to indicate that part of the sheet metal resulting by bending the slit portion may not be discarded to lessen the overall weight. The tab or tabs according to the method of the invention are properly sized and bent such that the side edges of the bent tabs contact the interior opposite sidewalls of the U-shaped precursor without interfering with the placement of the roller assembly. It should be noted that most rocker arms are shaped as to be narrower at each end than at the center where the window is contained. In the invention, the tab or tabs created by the slots that provide a cross-member is bent sufficiently so that side edges of the bent tab can be brazed, welded or otherwise secured to the interior side walls of the rocker arm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a conventional prior art roller finger follower rocker arm.

FIGS. 2-8 depict the manufacturing progression of a roller finger follower rocker arm which is manufactured by bending a sheet metal precursor in which a reinforcing tab is cut and bent to form the reinforcing cross member in accordance with the invention.

FIG. 2 depicts the flat metal piece from which the rocker arm is formed.

FIG. 3 depicts the subsequent step of forming the U-shaped precursor.

FIG. 4 depicts the next step wherein a pair of lanced tabs in an H-configuration is manufactured in accordance with the invention resulting in the provision of two tabs that are bent in opposite directions.

FIG. 5 depicts the step wherein the tabs have been bent into position to provide formed-in-place cross members between the interior sides of the rocker arm.

FIG. 6 depicts an alternative embodiment shown in FIG. 4 wherein a single lanced tab is provided by bending a single lancing in a U-shape is bent to provide the reinforcing cross member in accordance with the invention.

FIG. 7 depicts the step wherein the single tab of FIG. 6 has been bent into position to provide a formed-in-place cross member between the interior sides of the rocker arm.

FIG. 8 depicts the finished roller finger follower rocker arm of FIG. 5 provided pivot socket, valve rod and roller assembly axle holes.

DETAILED DESCRIPTION OF THE INVENTION

The rocker arm of the invention is produced by the sheet metal stamping process. During a conventional sheet metal stamping process, openings are created in one or more surfaces by material removal, i.e., by punching out a “window.” In accordance to the method of the invention for making a roller finger follower rocker arm from sheet metal, essentially no material need be removed in forming the opening for the roller, except for material that may be required to provide die clearance or determine to be suitable to reduce the mass of the rocker arm. Instead, the opening is formed by making slits from which one or two bent tabs are created. Material at the slit portion instead is bent to create reinforcing cross-members connected to the interior sides of the rocker arm. An opening in a rocker arm that comprises a U-shaped slit where a single tab is formed, i.e., tab or an H-shaped slit comprising two tabs 52 and 54 in FIG. 4 that provide a pair of cross members. The system of the invention, accordingly, is distinguished by cutting, i.e., slitting, an outline to form the intended opening, or window, after which the tab or tabs are bent in a subsequent forming operation, wherein the tab, conforming to the slit position is bent inward and has to be in contact with the interior side walls of the rocker arm, forming either, respectively, one or two cross-members which are secured at their edges to the sides of the adjacent rocker arm interior surfaces by staking, welding, brazing, etc. The addition of this formed-in-place cross-member improves the structural integrity of the rocker arm and, most importantly, increases stiffness without increasing weight which would result from supplemental reinforcements; high rocker arm stiffness is essential for operation at high engine speeds necessary to achieve maximum engine power.

The method of the invention is applicable to rocker arms used in overhead cam valvetrains described as end-pivot, center-pivot and in cam-in-block pushrod valvetrains as well as roller finger follower rocker arms. All other rocker arm types will benefit from the stiffness derived by the addition of formed-in-place cross members. Although only one type of roller finger follower rocker arm is illustrated and defined, the essence of the method of the invention for creating an integrally formed cross-member is applicable to all types in addition to the described welded and brazed roller finger follower rocker arm.

Referring in particular to the drawings, FIG. 1 depicts a conventional prior art roller finger follower rocker arm 10 which lacks any cross-member to provide reinforcement between the inner walls of opposing sides 12 and 14 of the rocker arm. A window 16 is formed in the central portion of and through the top 18 of the rocker arm 10. Also shown are the location 20 of the pivot socket, the valve pad 22, and roller axle holes 24.

FIG. 2 depicts the preshaped flat cut-out sheet metal precursor 30 from which the U-shape precursor for the rocker arm of the invention is formed.

FIG. 3 shows the rocker arm U-shape precursor 40 with sides 42 and 44 formed from the flat shape shown in FIG. 2.

As shown in FIG. 4, the distinguishing feature of the rocker arm 50 invention involves the creation of an H-shaped slit or a pair of opposing U-shaped slits comprising tabs 52 and 54 that are used in forming cross-members 62 and 64, respectively, as shown in FIG. 5. Also shown in FIG. 4 is an optional hole 55 which can be suitably resized and/or reshaped to reduce the overall increase in mass of the rocker arm due to the addition of the cross-members. The tabs are shown in relationship to the valve pad 56 end and the location 58 of the pivot socket to be formed in a later processing step. A conventional bending tool (not shown) is used to bend the tabs 52 and 54 as shown in FIG. 4 into position, forming the top window 67 and cross members 62 and 64 between the inside walls 66 and 68 of the rocker arm 60 as shown in FIG. 5. An optional cut out or hole 65 in cross-member 62 is also shown.

FIGS. 6 and 7 show an alternative embodiment of the rocker arm of the invention. As shown in FIG. 6, the distinguishing feature of the rocker arm 70 invention involves the creation of a U-shaped slit 74 comprising tab 72 used in forming cross-member 82 as shown in FIG. 7. The tab 72 is shown in relationship to the valve pad 76 end and the location 78 of the pivot socket to be formed in a later processing step. A conventional bending tool (not shown) is used to bend the tab 72 as shown in FIG. 6 into position, forming the top window 84 and cross member 82 between the inside walls 86 and 88 of the rocker arm 80 as shown in FIG. 7.

FIG. 8 shows the finished rocker arm 100 including the pivot socket at 110, configured pad end 108, cross-members 112 and 114 abutting the inner walls 102 and 104 of the rocker arm, and roller assembly axle holes 116.

Although the invention has been described in terms of particular embodiments, one skilled in the art will recognize that various changes in the sequence of steps for lancing the sheet metal and securing the tab-formed cross-member piece and equipment applied in the operative method can be made based on the concept herein provided and such are meant to be included herein. Accordingly, the invention is only to be limited by the scope of the appended claims.

Claims

1. A method for manufacturing a sheet metal rocker arm having integrally reinforcing cross members and substantially enhanced relative structural integrity and stiffness comprising

(a) bending a patterned sheet metal precursor blank to form a longitudinal U-channel with straight sides generally conforming to a rocker arm and a central portion connecting the sides and having dimensions; and

(b) lancing a shaped opening comprising a tab in the central portion; and

(c) bending the end of said tab inwardly into the U-channel to form a cross-member transverse to sides of the U-channel and such that side edges of said tab abut against the inner sidewalls of the U-channel sides; and

(d) securing said tab side to the inner sidewalls of the U-channel to integrate said tab and said side members to produce a rigid structure.

2. The method of claim 1 wherein the shaped opening in the central portion comprises a U-shape to produce a single tab yielding a single cross-member between the U-channel sides.

3. The method of claim 1 wherein the slit generally comprises an H-shape to produce two tabs to yield a pair of cross-members between the U channel sides.

4. The method of claim 2 wherein the tab has one or more holes to reduce the total mass of the rocker arm.

5. The method of claim 3 wherein a portion of one or both tabs is discarded to reduce the total mass of the rocker arm.

6. A rocker arm formed by the method of claim 1.

7. A rocker arm formed by the method of claim 2.

8. A rocker arm formed by the method of claim 3.

9. A rocker arm formed by the method of claim 4.

10. A rocker arm formed by the method of claim 5.