Manufacturing a rocker lever using cold forming and welding

Abstract

A method and system for forming a rocker assembly includes cold forming a metal blank to produce a portion of the rocker assembly. This portion has a tubular portion that rotatably engages a shaft and an arm that couples with a pushrod. This portion is welded to a valve lever to form the rocker assembly.

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present divisional application claims the benefit of U.S. Nonprovisional Application Ser. No. 11/063,915, filed on Feb. 23, 2005, which is incorporated herein by reference thereto.

FIELD OF THE INVENTION

The present invention relates to rocker arms for valve-type engines. More specifically, the invention relates to cold forming a shaft portion of a rocker assembly.

BACKGROUND OF THE INVENTION

In automotive and other applications, an engine typically utilizes a plurality of rocker arms for alternately actuating intake and exhaust valves. As an engine cam shaft rotates, a push rod is selectively actuated by cams connected to the cam shaft. The push rods, in turn, direct an upward force on one end of a rocker arm to cause the rocker arm to pivot about a mounting shaft. As the rocker arm pivots, its opposite end generates a downward force to selectively open an intake or exhaust engine valve.

Typically, rocker arms are integral, one-piece parts having a generally U-shaped cross-section including a pair of opposing side walls separated by a bottom wall and a pair of end walls disposed between the side walls. Rocker arms are conventionally cast an integral piece. This piece is then machined to its final dimensions. This process may involve multiple forming steps or processing stages and, therefore, require additional expense to produce a finished rocker assembly.

Rocker arms can be manufactured in a variety of ways, such as by casting metals, blanking and forming, ceramic molding, and other methods. Stamping a metal blank to form a cam-engaged rocker arm is one known method of manufacturing. The rocker arms are typically formed using a stamping, folding or coining process. During the coining process, an upper die and a lower die punch an area of the metal blank to plastically deform the metal blank. While previous methods of producing a rocker arm have been employed with some success, the manufacture of rocker arms has been an area of constant innovation. Specifically, methods to reduce the time and complexity involved in forming a rocker arm, thereby reducing the associated costs are desirable.

SUMMARY OF THE INVENTION

The present invention overcomes the deficiencies of the prior art by preparing a blank of generally uniform thickness for forming a tubular member of a rocker assembly. In one embodiment, a rocker assembly for an engine is provided. The rocker assembly includes a tubular member having a first axial end, a second axial end, and an integrally formed arm adjacent said first axial end with a valve lever coupled to the tubular member adjacent the second axial end.

In another embodiment, a method of manufacturing a cam-engaged rocker is provided. The method includes obtaining a metal blank that is defined, at least in part, by a first surface, an opposing second surface, a peripheral surface intersecting both the first surface and the second surface, and a projection. The metal blank contains a predetermined amount of a metal. The method further includes forming at least a portion of the metal blank by exerting a force on the metal blank adjacent the first surface, where a tubular portion is formed by the flow of a portion of said metal.

In yet another embodiment, a method of manufacturing a cam-engaged rocker that includes obtaining an annular metal blank that is defined, at least in part, by an outer cylindrical surface, an inner cylindrical surface, a valve end and a cup end. The annular metal blank contains a predetermined amount of a metal. The method further includes forming at least a portion of the annular metal blank by exerting a force on the annular metal blank adjacent the cup end, where a projection is formed by the flow of a portion of said metal.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a valve train assembly illustrating an embodiment of the rocker arm of the present invention.

FIG. 2 is a perspective view of the rocker arm of FIG. 1.

FIG. 3 is an exploded side view of the rocker arm of FIG. 1.

FIG. 4 is a perspective of an embodiment of a metal blank before forming a shaft portion of the rocker arm of FIG. 1.

FIG. 5 is a perspective view of an embodiment of an intermediate article of manufacture in accordance with the present invention.

FIG. 6 is a perspective view of the tubular portion of the rocker arm of FIG. 3.

FIG. 7 is a perspective view of an embodiment of an annular blank in accordance with the present invention.

FIG. 8 is a flow chart illustrating an embodiment of a method of producing a rocker assembly in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a valve train assembly 20 is illustrated. Valve train assembly 20 includes a plurality of valves 22, cam lobes 24, lifters, or tappets, 26, pushrods 28, rocker assemblies 30, and rocker shafts 32. As illustrated, valve train assembly 20 operates as a camshaft (not shown) is rotated, causing cam lobes 24 to rotate and push lifters 26. Lifters 26 push pushrods 28 causing pushrods 28 to rotate the rocker assemblies 30 about the rocker shafts 32.

With reference to FIGS. 2 and 3, the rocker assembly 30 made in accordance with the present invention is illustrated in greater detail. Rocker assembly 30 includes a tubular member 34 and a valve lever 36. Tubular member 34 includes a tubular portion 38 defining a first axial end 40, a second axial end 42, and an arm 44 protruding from the first axial end 40. In one embodiment, arm 44 is integrally formed with first axial end 40. Tubular member 34 further includes an inner surface 46 and an outer surface 48. Arm 44 includes a contoured outer surface 50, with a cup 52 formed therein.

Valve lever 36 includes a central body portion 60 having a valve contacting portion 62 formed thereon and a circular inner surface 66 defining an aperture 68. Valve lever 36 is further defined by a first side 70, a second side 72, and an outer surface 74 intersecting therebetween. Valve contacting portion 62 includes an outer protuberate surface 80 with a valve contacting surface 82 formed thereon. As illustrated, valve contacting portion 62 has a greater thickness, measured parallel to the axis of aperture 68, than central body portion 60. Circular inner surface 66 intersects both the first side 70 and the second side 72.

As shown in FIGS. 2 and 3, the first side 70 of valve lever 36 abuts the second axial end 42 of the tubular member 34. Circular inner surface 66 of aperture 68 and inner surface 46 are aligned such that rocker shaft 32 (FIG. 1) may be positioned through both circular inner surface 66 and inner surface 46 during operation. While valve lever 36 and tubular member 34 are illustrated as coupled wherein valve lever 36 abuts tubular member 34, valve lever 36 may alternatively be positioned about the outer surface 48 of tubular member 34, such that circular inner surface 66 encircles a portion of outer surface 48.

Referring now to FIG. 4, a metal blank 90 is shown according to an embodiment of the present invention. As illustrated, metal blank 90 has a first surface 92, a second surface 94, and a peripheral surface 96 intersecting both the first surface 92 and the second surface 94. Metal blank 90 includes a central body portion 100 and an arm portion 102 extending therefrom.

FIG. 5 illustrates an embodiment of an intermediate article of manufacture in the method of forming rocker assembly 30 as a formed article 134. Formed article 134 is illustrated to include a tubular portion 138 defining a first axial end 140, a second axial end 142, and a projection 144 protruding from the first axial end 140. Formed article 134 further includes an inner surface 146 and an outer surface 148. Projection 144 is illustrated to include a contoured outer surface 150. Formed article 134 is preferably cold formed, as discussed herein.

FIG. 6 illustrates the tubular member 34 of rocker assembly 30 in greater detail. FIG. 7 illustrates an embodiment of a tubular blank 170 in accordance with the present invention. Tubular blank 170 includes a first end 172, a second end 174, an inner surface 176, and an outer surface 178. First end 172 is defined by an extended annular surface 180 that intersects the inner surface 176 and the outer surface 178.

FIG. 8 illustrates a method of manufacturing the rocker assembly 30. The method includes step 300, wherein a blank material is obtained for producing the tubular member 34. In step 310, the blank material is formed into a blank of a desired shape. In one embodiment of step 310, the desired shape is the metal blank 90, as illustrated in FIG. 4. In an alternative embodiment of step 310, the desired shape is the tubular blank 170, as illustrated in FIG. 7. In step 320, the blank is formed into a formed article. In one embodiment of step 320 the article formed is the formed article 134, as illustrated in FIG. 5. Preferably, step 320 involves cold forming the blank, although other suitable forming means, such as heated extrusion, may be used. In step 330, a cup 52 is formed. In one embodiment of step 330, the article that is formed is the tubular member 34, as illustrated in FIG. 6. Steps 320 and 330 may be performed concurrently with a suitable forming process.

In step 340, a blank is obtained for forming a valve lever. In step 350, the blank is formed into a valve lever. Step 350 may involve multiple process operations wherein a first predetermined shape is formed, such as by coining a metal sheet, and then the predetermined shape is further processed to form the valve contacting portion 62. In step 370, the valve lever is positioned adjacent the tubular member in a desired radial alignment. This desired radial alignment is determined by a predetermined radial offset, or relative angle, between cup 52 and valve contacting surface 82. As will be appreciated, differing rocker assemblies 30 can be produced by varying the predetermined radial offset. In step 380, the valve lever is fixedly secured to the tubular member to produce a rocker assembly. In one embodiment, the valve lever is welded to the tubular member. Acceptable welding processes include laser welding, pulsed plasma arc welding, and electron beam welding.

The forming processes discussed herein may include, but are not limited to, cold forming a tubular portion, such as by using a drawing die or mandrel, or forming a portion of a blank by punching, or pressing, a portion of the blank into a cavity formed within into a die (not shown). In this type of forming process, the blank is positioned adjacent a die and at least a portion of the blank is formed into a desired, or predetermined, shape as the blank material is plastically deformed.

Additionally, the axial length of the tubular member 34, or the positioning of cup 52 along the axial length of tubular member 34, may be varied, as desired, to vary the linear distance between the cup 52 and the valve lever 36. As a result, the rocker assembly 30 may be adapted for a variety of valve configurations and desired relative angles. In addition, the tubular member 34 and valve lever 36 may be used for both inlet and exhaust valve applications, thereby reducing the total number of parts used in a cylinder valve assembly. A reduced part count further reduces the cost of such an assembly.

While the invention has been described with respect to specific examples including preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques that fall within the spirit and scope of the invention as set forth in the appended claims.

Claims

1. A method of manufacturing a cam-engaged rocker comprising:

obtaining a metal blank, said metal blank defined, at least in part, by a first surface, an opposing second surface, a peripheral surface intersecting both said first surface and said second surface, and a projection, wherein said metal blank contains a predetermined amount of a metal; and

forming at least a portion of said metal blank by exerting a force on said metal blank adjacent said first surface, wherein a tubular portion is formed by the flow of a portion of said metal.

2. The method of claim 1, wherein forming said metal blank includes cold forming a central portion of said metal blank.

3. The method of claim 1, further comprising forming a cup in said projection.

4. The method of claim 1, further comprising radially aligning a valve lever to said tubular portion.

5. The method of claim 1, further comprising welding a valve lever to said tubular portion.

6. The method of claim 5, wherein said welding comprises laser welding.

7. A method of manufacturing a cam-engaged rocker comprising:

obtaining an annular metal blank, said annular metal blank defined, at least in part, by an outer cylindrical surface, an inner cylindrical surface a valve end, and a cup end, wherein said annular metal blank contains a predetermined amount of a metal; and

forming a projection on said annular metal blank by exerting a force on at least a portion of said annular metal blank adjacent said cup end, wherein a projection is formed by the flow of a portion of said metal, the projection extending from a tubular portion.

8. The method of claim 7, further comprising:

positioning said annular metal blank adjacent a die, wherein said die includes a cavity, wherein forming the annular metal blank includes exerting a force on said annular metal blank in a predetermined direction thereby causing a flow of the metal into said cavity.

9. The method of claim 7, further comprising forming a cup in said projection.

10. The method of claim 7, further comprising welding a valve lever to said tubular portion.

11. The method of claim 10, wherein said welding comprises laser welding