METHOD OF MAKING A ROCKER ARM

Abstract

A method of making a rocker arm is provided that includes the integration, into a single piece, of three separate parts namely, a central longitudinal member, a push-rod plate; and a valve end plate in which the push-rod plate and the valve end plate are secured to opposing ends of the central member to create the integrated rocker arm.

Description

TECHNICAL FIELD

This application is a continuation-in-part of application Ser. No. 10/953,952, filed Sep. 29, 2004.

The present invention relates to rocker arm assemblies for internal combustion engines and, in particular, to rocker arms constructed by combining three discrete parts to form an integrated rocker arm composite and to the method for making the rocker arm. The rocker arm assemblies of the present invention have efficient unique lubrication systems and also permit both a bearingless and a roller bearing type rocker arm shaft assembly to be interchangeably mounted in a same engine.

BACKGROUND OF THE INVENTION

Rocker arm assemblies are utilized in internal combustion engines for actuating intake and exhaust valves. As an engine cam shaft rotates, a push rod is selectively actuated by cam lobes located on the cam shaft and the push rod, in turn, directs 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. In the prior art, rocker arms are conventionally cast as an integral piece. The cast piece is then machined as necessary to form the rocker arm to its final dimensions. This prior art process requires separate tooling to produce each intake and exhaust component and is often time consuming and/or expensive.

Accordingly, a need exists for a more expeditious and less costly method for the production of rocker arms.

SUMMARY OF THE INVENTION

According to the invention, a novel means for the production of a rocker arm that includes a push-rod plate at one end, a valve plate at the opposite end, and a longitudinal central member between the two ends is provided. The length of the central member, preferably a cylindrical member, and the angle of rotation between the push-rod plate end and the valve plate end of the rocker arm may each be varied such that the rocker arm may be adapted for use with many different cylinder valve assemblies.

More specifically, the method of the invention provides for the rapid formation of a rocker arm by making discrete parts such as by stamping and then integrating the parts such as by welding or brazing techniques, as distinguished from casting the unit with its parts as a whole. The method of the invention provides for adapting the rocker arm for use with many different cylinder valve assemblies utilizing the same basic tooling configurations.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and inventive aspects of the present invention will become more apparent upon reading the following detailed description, claims, and drawings, of which the following is a brief description:

FIG. 1 is a partial perspective view of an exemplary cylinder valve assembly.

FIG. 2 is an isolated view of an inlet valve assembly of the cylinder valve assembly of FIG. 1

FIG. 3 is a perspective view of three component parts that comprise a typical rocker arm according to the invention.

FIG. 4A is a top view of an exemplary rocker arm.

FIG. 4B is a front side view of the rocker arm shown in FIG. 3A.

FIG. 5 is a flowchart illustrating an exemplary method of forming a rocker arm.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A rocker arm is described herein for use as part of an engine cylinder assembly. The rocker arm is coupled to push rods and valves for opening and closing the intake and exhaust valves of an engine cylinder. The rocker arm includes a push-rod plate and a valve plate each secured to opposite ends of a tubular member. The push rod socket end and the valve pad end are separated by the linear distance of the tubular member. The push-rod plate and valve pad plate may be formed using a rapid formation process, such as stamping. Thereafter, these respective plates are secured to the appropriate end of the tubular member using well known techniques, such as brazing or welding to form an integrated unit. As used herein, the term integrated unit is intended to connote the assembly of the separate or distinct members, i.e., the two end plates to the central member, to form a unitary structure by suitable means such that the assembly is essentially equivalent to a member that is created initially as an integral unit.

A configuration fabricated in this manner reduces the time and complexity involved in forming the rocker arm by known conventional methods such as by casting and machining to the discrete final form, the rocker arm with integrally cast push socket end plate and valve pad end plate. Accordingly, the invention provides for the joining of the three separate parts substantially reduces the cost of forming the rocker arm. Further, the length of the tubular member used in making the rocker arm can be readily selected to vary the linear distance between the push-rod plates and the valve plates and as a consequence, the resulting rocker arm may be adapted for a variety of valve configurations and angles. In addition, the push-rod end plates and valve end plates may be used for both air inlet and exhaust valve applications, thereby reducing the total number of unique parts used in a cylinder valve assembly and lowering the cost of such an assembly.

In the following description, for purposes of illustrative explanation, numerous specific details are set forth in order to provide a thorough understanding of the present method and apparatus. It will be apparent, however, to one skilled in the art that the present method and apparatus may be practiced without various of these specific details. Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearance of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.

Referring to the drawing, FIG. 1 illustrates a partial view of a cylinder valve assembly 100. The cylinder valve assembly 100 is configured to control the flow of fuel into an engine cylinder and to control the flow of exhaust out of the engine cylinder. The cylinder valve assembly 100 generally includes a rocker arm 105, an inlet valve assembly 110 and an exhaust valve assembly 115, each coupled to lobed cams 120-1, 120-2.

Each rocker arm 105 includes a push-rod plate 130 and a valve plate 135 each coupled to either of opposite ends of a cylindrical or tubular member 140. Each rocker arm 105 is supported by central support shafts 140. The configuration of the rocker arm will be described in more specific detail with reference to FIGS. 3A-3B. The operation of the cylinder valve assembly 100 will first be discussed more particularly to provide context for the function of the rocker arm 105, beginning with the operation of the inlet valve assembly 110 and followed by the exhaust valve assembly 115.

As previously mentioned, the inlet valve assembly 110 includes a rocker arm 105 supported by a central support shaft 145. The push-rod plate 130 is coupled to a push rod 150 and tappet 155, which in turn are in contact with the lobed cam 120-1. A conventional biasing mechanism, which is not shown, maintains the tappet 155 in contact with the lobed cam 120-1.

Preferably, the push rod 150 is hollow and provides lubrication to a push-rod socket (not shown) for reducing wear caused by friction. Alternatively, if a solid push rod is utilized, then a mechanism for lubricating the interface may also be included. FIG. 2 illustrates a side view of an inlet valve assembly 110. The lobed cam 120-1 is coupled to a cam shaft such that when the cam shaft rotates, the lobed cam 120-1 rotates. The profile of the lobed cam 120-1 includes lobed profile portion and a constant radius profile portion. As the lobed cam 120-1 rotates, the tappet profiles the profile of the lobed portion. As a result, when the lobed cam 120-1 rotates the tappet 155 follows the profile of the lobed portion profile.

As the tappet 155 comes into contact with the lobed portion of the cam 120-1, the push rod 150 is moved upwardly. This motion of the push rod 150 causes the entire rocker arm 105 to rotate. In this instance, the rocker arm 105, including the valve plate 135 rotates, i.e., moves in the counter-clockwise direction. The valve plate 135 is coupled to an inlet valve 160. As the valve plate 135 rotates counter-clockwise, the valve 160 is moved to an open position. Accordingly, the push rod (130) moves upwardly in response to the rotation of the lobed cam 120-1.

The continued rotation of the lobed cam 120-1 causes the tappet 155 to move from contact with the lobed profile portion of the lobed cam 120-1 to contact with the constant radius profile portion. As a result, the push rod 150 falls, thereby causing the rocker arm 105 to rotate in the opposite direction, or clockwise. As the rocker arm 105 rotates in a clockwise direction, the valve 160 is moved to a closed position.

The exhaust valve assembly 115 is also in contact with a lobed cam 120-2 such that the exhaust valve assembly 115 operates in a similar fashion to the inlet valve assembly 110 to move an exhaust valve 165 (FIG. 1) between an open and closed position. The lobed cam 120-2 of the exhaust valve assembly 115 lags behind the lobed cam 120-1 of the inlet valve assembly 110 with respect to rotation.

The rocker arm 105, the make up of which is discussed above, reduces the cost of a cylinder valve assembly 100 because the rocker arm 105 may be more expeditiously formed. Further, multiple rocker arms 105 may be used with each cylinder valve assembly 100. In addition, the configuration of the rocker arm 105 may be readily adapted for use with a variety of cylinder valve assemblies. One exemplary configuration will now be discussed in more detail.

Shown in FIG. 3 is a typical perspective representation of the components which are readily available either as stock items such as the central element 140, or are readily fabricated by known means such as by stamping the parts 130 and 135 and securing them conventionally such as by welding to provide the desired rocker arm.

In addition, the cylindrical member 140 is of a length adapted to accurately position the rocker arm 105 with an adjacent push rod and engine valve. By varying the angle of the push-rod plate 130 relative to the length of cylindrical member 140, the rocker arm 105 may be designed to precisely engage valves in almost any engine geometry layout, including offset valves. This angle may be controlled easily during the formation of the rocker arm 105, as may also be the length of the cylindrical member 140.

Referring to FIGS. 4A-4B the rocker arm 105 includes a push-rod plate 130, a valve plate 135, and a cylindrical section 140. The push-rod plate 130 will be described first, followed by a discussion of the valve plate 135 and the cylindrical section 140.

As shown in FIG. 4A, the push-rod plate 130 includes a push rod contact end 300 that includes a lower edge 305 having a generally hollow semi-spherical recess formed therein such that a generally hemispherical outer projection is formed on the push-rod plate 130. The hemispherical recess is adapted to receive an end of a push rod as discussed above with reference to FIGS. 1-2. The valve plate 135 has a valve contact end 310 that includes a lower edge 315 that preferably has a convex valve contact surface, but may be formed with other suitable surface for contacting an end of a valve as discussed with reference to FIGS. 1-2.

The relative orientation of the push rod contact end 300 and the valve contact end 310 depends, at least in part, on the angle of rotation between the push rod contact end 300 and the valve contact end 310 and on the length of the cylindrical member 140. The angle of rotation between the valve contact end 300 and the valve contact end 310 may be varied by rotating the position of the push-rod plate 130 relative to the valve plate 135 during the formation of the rocker arm 105.

One exemplary method of forming a rocker arm will now be described in reference to the flow diagram of FIG. 5. The method is initiated by the forming the elemental components of the rocker arm including (1) forming a push-rod plate (Step 400); (2) forming a valve plate (Step 410); and (3) forming or selecting a central, preferably, cylindrical member (Step 420). Each of these components may be and is preferably made of a metallic material, including, without limitation, steel alloys and aluminum alloys, although the use of environmentally suitable plastic compositions may also be suitable.

The push-rod plates and valve plates may be rapidly formed as separate members by a stamping operation or other suitable methods. The use of a stamping operation in forming the push-rod plates and valve plates decrease the time of forming the plates, as compared to the use of a casting operation.

The rocker arm also includes a suitable central member which, for convenience because of ready availability, is preferably cylindrical member. The cylindrical member (Step 420) may be formed using known techniques, such as by extrusion or other suitable techniques or by using suitable available stock tubular members.

Once the components (Steps 400-420) of the rocker arm have been formed, the relative orientation of each of the components is then determined. In particular, the length of the cylindrical member is determined and formed or cut to the desired predetermined length. The length of cylindrical member affects, at least in part, the linear or axial distance that the push-rod plate and valve plate are separated from one another. This distance is relative to the interaction between the given cylinder valves and push-rods. For example, one linear or axial distance may be required for the rocker arm to operate properly with a cylinder valve assembly while a longer or shorter axial or linear distance may be required for proper operation of the rocker arm in another cylinder valve assembly. The separate three-part configuration of the rocker arm of the invention, because of the variety of the central member, allows the linear or axial offset to the rocker arm to be readily adapted for operation with any number of cylinder valve assemblies. Moreover, as discussed hereafter, the angle of rotation between the push-rod plate and the valve plate may also be readily varied for operation in any number of cylinder valve assemblies.

When the desired angle of rotation (Step 450) between the push-rod plate and the valve plate is determined, this angle of rotation between the push-rod plate and the valve plate, and in particular between the push rod socket and the valve pad, may then be varied accordingly to allow the rocker arm to be used in any number of cylinder valve assemblies. In other words, once the desired angle of rotation (Step 450) has been selected, the push-rod plate and valve end plate are oriented with respect to each other according to the selected angle of rotation (Step 460). Thereafter, the push-rod plate and valve plate are each secured to the cylindrical member (Step 470).

Some methods which may be used to attach the push-rod plate and valve plate to the cylindrical member to form an integrated unit, include, without limitation, the conventional means such as welding, brazing, staking, laser welding, and other suitable known means. Welding, staking, or brazing are relative rapid, efficient and are preferable operations that are applicable in reducing the cost of forming the rocker arm assembly of the invention. The use of pulse welding is particularly preferable as a rapid and efficient mode for attaching the push-rod and valve plates to the respective opposite ends of the elongated central member.

The method of the present invention allows a variety of rocker arms to be formed using the same basic tooling configurations. In particular, as previously discussed, the push-rod plate and the valve plate may be each be used with many different cylinder valve assemblies by varying the relative angle of rotation between them and by selecting the desired length of the longitudinal central piece, e.g., the cylindrical member used in creating the rocker arm.

Accordingly, it is seen that the method of the present invention provides for the formation of a rocker arm by integrating three separate pieces that include a central member, push-rod plate at one end, and a valve end plate at the opposite end of the central member. The method of the invention also provides for the formation of a rocker arm that is readily adapted for use with a variety of cylinder valve assemblies. Further, the method of the present invention provides for the rapid formation of rocker arms, which substantially reduces the cost of cylinder valve assemblies and engines.

It is thus seen that a method for creating a rocker arm has been described herein that includes a push-rod plate, a valve plate, and a central longitudinal, preferably cylindrical, member. The length of the central member and the angle of rotation between the push-rod plate and the central member may be each varied such that the rocker arm may be adapted for use with many different cylinder valve assemblies. Additionally, the method herein described for forming a rocker arm facilitates the expeditious construction of rocker arms with precision dimensions using relatively inexpensive and efficient techniques such as stamping the push rod end and valve end plates and welding and/or brazing the parts to form the desired integrated rocker arm. The method of the present invention it is seen provides for adapting the thus formed rocker arms for use with many different cylinder valve assemblies using the same basic tooling configurations.

The invention has been described in such detail as to illustrate the essence of the applicable method. The description provided is not intended to be exhaustive or to limit the disclosure to any precise form disclosed. It is apparent that many modifications and variations are possible in light of the above teaching. Accordingly, it is intended that the invention is to be limited only by the scope of the following claims.

Claims

1. A method of making an integrated rocker arm comprising joining separate parts including:

a central longitudinal member;

a push-rod plate; and

a valve plate

to form a unitary member wherein said push-rod plate and said valve plate are integrally secured to opposing ends of said central member.

2. The method of claim 1 wherein said central member, said push-rod plate, and said valve plate comprise a metallic material.

3. The method of claim 1 wherein said central member is cylindrical.

4. The method of claim 2 wherein said metallic material comprises aluminum alloy.

5. The method of claim 2 wherein said metallic material comprises a steel alloy.

6. The method of claim 1 wherein said push-rod plate and said valve plate are welded to said central member.

7. The method of claim 1 where said push-rod plate and said valve plate are pulse welded to said central member.

8. The method of claim 1 wherein said push-rod plate and said valve plate are laser welded to said central member

9. The method of claim 1 wherein said push-rod plate and said valve plate are staked to said central member.

10. The method of claim 1 wherein said push-rod plate and said valve plate are brazed to said central member.

11. An cylinder valve assembly, comprising:

I. an inlet valve assembly including a rocker arm formed by the method of claim 1; a tappet configured to contact a rotating cam; a push rod coupled to said tappet and the push rod plate of the rocker arm; and a valve coupled to the valve plate of said rocker arm, and

II. an exhaust valve assembly including

a rocker arm formed by the method of claim 1;

a tappet configured to contact a rotating cam;

a push rod coupled to said tappet and the push rod plate of said rocker arm; and

a valve coupled to the valve plate of said rocker arm.

12. The assembly of claim 10 wherein said push-rod plate and said valve plate of said inlet valve assembly and said push-rod plate and said valve plate of said exhaust valve assembly are substantially similar.