POWDER METAL ROCKER ARM
A powder metal rocker arm is provided. The rocker arm may be connected to a cylinder head of an engine to assist in transferring motion between engine components. The rocker arm includes a pivot aperture formed therein to facilitate pivoting of the rocker arm with respect to the cylinder head. The rocker arm is formed of a metal alloy powder. The metal alloy powder is compacted to form an intermediate member. Secondary features, such as apertures and other weight reducing features may be formed in the intermediate member. The intermediate member is then sintered to form the rocker arm.
This application claims benefit from U.S. Provisional Patent Application No. 61/198,726, entitled “Powder Metal Rocker Arm,” filed on Nov. 7, 2008, which is hereby incorporated by reference in its entirety.
FIELD OF INVENTIONThe present invention relates generally to rocker arms and methods of manufacturing rocker arms, more specifically, the present invention relates to powder metal rocker arms and manufacturing rocker arms from power metals.
BACKGROUNDDiesel and gasoline internal combustion engines typically include one or more pistons situated in cylinders. Engines generate motion by igniting a mixture of fuel and air in a cylinder, causing a piston to move within the cylinder. The fuel and air enters the cylinder through an intake valve located in the body of the cylinder. Exhaust generated by the ignition of the fuel and air mixture exits the cylinder through an exhaust valve located in the housing of the cylinder. An engine timely opens and closes such valves to facilitate the ignition of the fuel and air mixture and expulsion of the exhaust generated by the ignition.
A rocker arm may be situated in the engine to facilitate the opening and closing of the intake and exhaust valves. One end of a rocker arm is generally directly or indirectly coupled to a camshaft of the engine and the other end of the rocker arm is generally directly or indirectly in contact with a valve. The rocker arm may be arranged to pivot on a roller shaft or ball pivot such that as the camshaft moves one end of the rocker arm, the other end of the rocker arm opens or closes a valve.
Rocker arms for automobile and truck engines are typically manufactured from high-alloy steel castings or forgings. Rocker arms often include apertures passing through the body of the arm and features and contours on the surface of the arm. Such apertures and surface features may be formed by secondary, post-casting operations. For example, apertures are formed in the rocker arm by drilling through the high-alloy steel arm and surface features are formed by milling away material on the surface of the arm. The surfaces of cast or forged rocker arms typically need to be treated with secondary operations to improve rocker arm surface properties, such as wear resistance.
Secondary and post-casting operations are often complex, difficult and time consuming, which results in increases in cost, scrap rate, and manufacturing time. There exists a need in the art for rocker arms and methods for manufacturing rocker arms that lower time and cost of manufacturing arms and produce more precise and consistent rocker arms.
SUMMARYA powder metal rocker arm is provided. The rocker arm includes a pivot aperture formed therein to allow the rocker arm to pivot with respect to a structure. The rocker arm may be connected to a cylinder head of an engine to assist in transferring motion between engine components.
In an embodiment, the rocker arm is formed of a metal alloy powder. The metal alloy powder is compacted to form an intermediate member. Secondary features, such as apertures and other weight reducing features may be formed in the intermediate member. The intermediate member is then sintered to form the rocker arm.
Objects and advantages together with the operation of the invention may be better understood by reference to the following detailed description taken in connection with the following illustrations, wherein:
The present invention provides for novel rocker arms and novel methods for manufacturing rocker arms from powder metals. The rocker arm may be manufactured from power metal such that the time and cost needed for secondary operations to manufacture the rocker arm are substantially reduced or eliminated.
A rocker arm 10 is provided. The rocker arm 10 may be assembled in an engine as illustrated in
The rocker arms 10 may be arranged to pivot with respect to a portion of the cylinder head 12. For example, the rocker arms 10 may be connected to a rocker arm support 14. The rocker arm support 14 may be mounted to the cylinder head 12. The rocker arm support 14 may include a pivot pin 16 to allow the rocker arms 10 to pivot with respect to the cylinder head 12. The pivot pin 16 may be integrally connected to the rocker arm support 14 or alternatively connected thereto. As shown in
The rocker arms 10 may be connected to components of the cylinder block 12 to transfer motion from one component to another component. For example, a first end 18 of each rocker arm 10 may be attached to a rod 20. The rod 20 may be coupled to a camshaft (not shown). The rod 20 may be attached to the rocker arm such that the rocker arm 10 pivots in response to vertical movement of the rod 20. One or more apertures may be formed in the first end 18 of the rocker arm 10 to receive a portion of the rod 20. The apertures may be threaded to receive a threaded portion of the rod 20. Alternatively, the rod 20 may be connected to the rocker arm 10 by any means known in the art.
A second end 22 of each rocker arm 10 may contact a second component of the cylinder head 12, such as a valve stem 24. The second end 22 of the rocker arm 10 may include a touch pad 25. The touch pad 25 may contact the valve stem 24 to transfer the pivoting motion to the valve stem 24. For example, downward pivoting motion of the second end 22 may move the stem 24 downward to open the valve. The cylinder head may further include a spring 26 to bias the valve to a given position. For example, as the second end 22 of the rocker arm 10 moves upward, the spring 26 may bias the valve into the closed position.
In the arrangement illustrated in
The arrangement of the rocker arm 10, as described above, makes it necessary for the rocker arm 10 to include a number of apertures. For example, as seen in
In an embodiment best seen in
Typically, known rocker arm manufacturing methods form apertures and weight-reducing features through secondary operations after the casting or forging of a rough rocker arm. For example, apertures may be drilled into the body of the rocker arm 50, weight-reducing features may be milled into the surface of the rocker arm 50, and the body of the rocker arm 50 may be grinded to form or finalize the touch pad. Such secondary operations add time and cost to the manufacturing of a rocker arm. The present invention reduces or eliminates the cost and time needed for such secondary operations.
In an embodiment of the present invention, the rocker arm 10 or 50 is manufactured from a power metal, preferably a low-alloy powder iron. The powder metal is transformed to a rocker arm through a powder metallurgy process. As illustrated in
The powder metallurgy process provides for several advantages over known cast or forged rocker arms. For example, the green rocker arm—i.e., after compacting and prior to sintering—has sufficient structural integrity to undergo modification through secondary operations. Thus, the process for forming a rocker arm 50 may include the step of forming features in the intermediate component 66. For example, features such as the pivot pin aperture 30, rod aperture 32, threaded aperture 36, and valve stem aperture 52 may all be drilled through the green rocker arm. Although the green rocker arm has sufficient structural integrity to undergo a drilling operation, it is substantially easier to drill through a green rocker arm than one that is produced by casting or forging of high-alloy metals. In additional examples, the touch pad 25 may be finalized by grinding the green rocker arm and the weight reduction features 56 may be finalized by milling the green rocker arm. Grinding and milling a green rocker arm is substantially easier than grinding or drilling a cast or forged rocker arm. Performing secondary operations on the rocker arm 10 and 50 prior to sintering reduces the cost and time needed to produce a rocker arm 10 and 50, when compared to known cast or forged rocker arms.
The nature of powder metallurgy processes, along with performing secondary operations prior to sintering, produces sintered rocker arms that are either the shape desired or have a net shape that is substantially closer to the final shape desired than the net shape of cast or forged rocker arms. When a sintered rocker arm is the desired shape, no additional secondary operations are needed, providing time and cost savings over known rocker arms. When the net shape of a sintered rocker arm needs additional secondary operations to reach a final desired shape, such operations are minor as compared to the operations needed to finalize cast or forged rocker arms, which provides time and cost savings. In addition, net shapes closer to the desired shape can reduce errors in secondary processing and reduce scrap rates.
Additional advantages include reduction in raw material costs and elimination or reduction of post-casting or post-forging surface treatment. Low-alloy powder is commonly less expensive than high-alloy casting or forging steel. In addition, cast or forged rocker arms normally require additional surface treatment to improve surface properties, such as wear resistance. Surfaces produced by compacting and sintering typically provide sufficient surface properties for a rocker arm.
Although the preferred embodiments of the present invention has been illustrated in the accompanying drawing and described in the foregoing detailed description, it is to be understood that the present invention is not to be limited to just the preferred embodiment disclosed, but that the invention described herein is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the claims hereafter.
Claims
1. A rocker arm comprising:
- a first end;
- a second end opposite said first end;
- a pivot aperture capable of receiving a pivot pin;
- wherein said rocker arm is comprised of a metal alloy powder that is compacted and sintered to form said rocker arm; and
- wherein at least one aperture is formed in said rocker arm prior to said rocker arm being sintered.
2. The rocker arm of claim 1 further comprising a recessed portion formed in said rocker arm.
3. The rocker arm of claim 2 wherein said recessed portion is formed in said rocker arm prior to said rocker arm being sintered.
4. The rocker arm of claim 1 wherein said pivot aperture is formed in said rocker arm prior to said rocker arm being sintered.
5. The rocker arm of claim 1 wherein said first end is connected to a rod coupled to a camshaft.
6. The rocker arm of claim 1 further comprising a touch pad formed in said second end of said rocker arm.
7. The rocker arm of claim 6 wherein said touch pad is formed in said rocker arm prior to said rocker arm being sintered.
8. A rocker arm assembly comprising:
- a rocker arm support member;
- a pivot pin connected to said rocker arm support member
- a first rocker arm pivotally connected to said pivot pin;
- wherein said first rocker arm is comprised of a metal alloy powder that is compacted and sintered to form said first rocker arm; and
- wherein at least one secondary feature is formed in said first rocker arm prior to said first rocker arm being sintered.
9. The rocker arm assembly of claim 8 wherein said secondary feature includes an aperture formed in said first rocker arm.
10. The rocker arm assembly of claim 8 further comprising a second rocker arm connected to said rocker arm support member.
11. The rocker arm assembly of claim 8 wherein said rocker arm support member is connected to a cylinder block of an engine.
12. The rocker arm assembly of claim 11 wherein a first end of said first rocker arm is connected to a rod.
13. The rocker arm assembly of claim 12 wherein a second end of said first rocker arm is connect to a valve stem.
14. The rocker arm assembly of claim 12 wherein said first end of said first rocker arm includes an aperture configured to receive said rod.
15. A method of forming a rocker arm comprising:
- compacting a metal alloy powder into a die to form an intermediate rocker arm member;
- forming a secondary feature in said intermediate rocker arm member; and
- sintering said intermediate rocker arm member to form a rocker arm.
16. The method of claim 15 wherein said secondary feature includes a weight reducing feature formed in said intermediate rocker arm member.
17. The method of claim 15 wherein said secondary feature includes an aperture formed in said intermediate rocker arm member.
18. The method of claim 17 wherein said aperture is a pivot aperture formed in said intermediate rocker arm member.
19. The method of claim 15 further comprising the step of mixing said alloy powder prior to compacting said alloy powder.
20. The method of claim 15 further comprising the step of forming a touch pad in an end of said intermediate rocker member.
Type: Application
Filed: Nov 9, 2009
Publication Date: Jul 8, 2010
Inventor: Jose Correa Neto (Campinas)
Application Number: 12/614,927
International Classification: F01L 1/18 (20060101); B22F 3/12 (20060101); B22F 1/00 (20060101);