Ring gear and manufacturing method for such a ring gear
A method of manufacturing a forged article including a surface. The method includes defining a negative tooling pattern based on the surface and providing a tooling set having an anvil and a top and bottom die. An upper surface of the bottom die conforms to the negative tooling pattern. When the tooling is assembled the anvil extends through the bottom die and defines an axis. Additionally, the bottom and top dies cooperate to define a die cavity. A hollow blank is placed on an anvil and into the die. In a single stroke, the hollow blank is pressed between the top and bottom dies in a pressing direction that is parallel to the axis. During the pressing, the blank initially flows in the pressing direction to form the surface of the article. Thereafter, the blank flows in a direction perpendicular to the pressing direction to fill the die cavity.
The present invention relates to a method of manufacturing a ring gear and more particularly to a method of manufacturing a ring gear from a billet.
BACKGROUND OF THE INVENTIONTraditionally, automotive ring gears have been manufactured by press forging solid blanks at temperatures approaching 2200° F. Immediately after the pressing operation the “as forged” ring gear blanks enjoy significantly improved mechanical properties over that of the solid blanks. However, because of the exacting tolerances generally required of such ring gears, the as forged ring gear blanks must be machined to their final, or net, shape. The forging process, though, hardens the material to such an extent that machining the ring gear is economically impractical. Accordingly, the ring gears are typically annealed after forging and then machined. Thus, the traditional method of manufacturing ring gears cannot take full advantage of the superior “as forged” properties. Moreover, because annealing requires the application of heat to the ring gear for a period of time, annealing consumes energy. Additionally, the annealing and machining processes consume time and other manufacturing resources.
Additionally, because ring gears often rotate about a shaft (as opposed to being rigidly attached to a differential casing for example) the finished ring gear requires a central aperture through which the shaft fits. Thus, provisions must be made during the manufacture of the ring gear for the central aperture. For instance, a separate mandrel, or punch, may be employed to create the aperture through the solid blank or the ring gear. However, the separate actions required to form the aperture give rise to an offset between the center of the aperture and the center of the pitch diameter of the ring gear. If placed in service in this condition, the ring gear would tend to vibrate as it rotates, causing deleterious wear e.g., on the teeth of the ring gear, the shaft, the shaft bearings, and the overall machine. Consequently, it is frequently necessary to machine the aperture to eliminate or minimize the offset between the center of the aperture and the center of the pitch diameter of the ring gear.
SUMMARY OF THE INVENTIONThe present invention provides a method of manufacturing a forged article including a surface. The method includes defining a negative tooling pattern based on the surface and providing a tooling set having an anvil and a top and bottom die. An upper surface of the bottom die conforms to the negative tooling pattern. When the tooling is assembled the anvil extends through the bottom die and defines an axis. Additionally, the bottom and top dies cooperate to define a die cavity. A hollow blank is placed on an anvil and into the die. In a single stroke, the hollow blank is pressed between the top and bottom dies in a pressing direction that is parallel to the axis. During the pressing, the blank initially flows in the pressing direction to form the surface of the article. Thereafter, the blank flows in a direction perpendicular to the pressing direction to fill the die cavity.
In another embodiment, the present invention provides a method of manufacturing a ring gear including a surface having teeth. The method includes defining a negative tooling pattern based on the surface and providing a tooling set having an anvil and a top and bottom die. An upper surface of the bottom die conforms to the negative tooling pattern. When the tooling is assembled the anvil extends through the bottom die and defines an axis. Additionally, the bottom and top dies cooperate to define a die cavity. A hollow blank is placed on an anvil and into the die. In a single stroke, the hollow blank is pressed between the top and bottom dies in a pressing direction that is parallel to the axis. During the pressing, the blank initially flows in the pressing direction to form the surface of the ring gear. Thereafter, the blank flows in a direction perpendicular to the pressing direction to fill the die cavity.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGSThe present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. While the invention is herein described with reference to an exemplary ring gear, the invention should not be construed to be so limited.
With reference to
In
Briefly, to form the ring gear 10, the sleeve 32 is placed over the anvil 30 with the bottom die 34 being centered over the sleeve 32 and the anvil 30. The ring shaped blank 38 is then centered over the anvil 30 so that it rests on an upper surface 40 of the bottom die 34. The top die 36 is then centered over the anvil 30 so that it rests on a top 42 of the ring shaped blank 38 as illustrated. Next, force is applied to the top die 36 to force it down against the ring shaped blank 38. As the force applied increases, the material of the ring shaped blank 38 yields initially flowing down to fill the voids between the blank 38 and the upper surface 40 of the bottom die 34. Thereafter, the material flows radially outward, or laterally, to fill the void between the blank 38 and the top die 36. When the material of the blank 38 has filled the voids between the blank 38 and the top die 36, the force is removed and the ring shaped gear 10 has been formed.
In
In
In
The bottom die 34 may also include a body 58 that defines a central aperture 60. In the example provided, the central aperture 60 facilitates the centering of the bottom die 34 relative to the sleeve 32. During the pressing operation, the body 58 serves to support the negative tooling pattern 52 rigidly against the blank 38.
In
As shown in
After being sectioned from the tubular billet 78, the ring shaped blank 38 has a first end surface 84, a second end surface 86, and a circumferential surface 87. Additionally, the ring shaped billet defines a central axis 88 in the direction between the end surfaces 84, 86. In the example provided, the central axis 88 is generally perpendicular to the end surfaces 84, 86 and coincident to the axis of the central aperture 82. Those skilled in the art will appreciate from this disclosure, however, that the central axis 88 is a reference axis and may be oriented differently with respect to one or more of the end surfaces 82, 84 and the central aperture 82 as desired. Additionally, an inner wall 83 of the blank 38 defines the central aperture 82.
If desired, the blank 38 may be treated in a secondary operation to alter the characteristics of the blank 38 prior to forging and/or to improve the characteristics of the forged article. For example, the blank 38 may be annealed or processed through a shot blasting operation to reduce or eliminate residual stress and/or provide the surfaces of the blank 38 with a desired surface finish. A coating 89 may also be applied to one or more of the surfaces 82, 84, and/or 87 of the ring shaped blank 38. The coating 89 may be a lubricant suitable for use at forging temperatures, such as a graphite-based lubricant, to provide lubricity between the surfaces of the blank 38 and corresponding surfaces of the tool set 28 during the pressing operation.
Returning to
Moreover, the ring shaped blank 38 is shown, in
In some circumstances, for example where the end surfaces 84, 86 are not generally parallel one another, there may be a need to orient the blank 38 into the die cavity 76 in a predetermined manner. Similarly, the other end surface of the ring shaped blank 38 (i.e., end surface 84 in the example provided) will form the back 26 of the ring gear 10. Also, a plurality of teeth voids 92 may be seen defined between the negative tooling pattern 52 and the bottom 86 of the ring shaped blank 38. Similarly, an annular void 94 may be seen defined between the circumferential surface 87 of the ring shaped blank 38 and the inner surface 74 (with the arc 68, the pressing surface 70, and the bottom die 34 completing the definition of the annular void 94).
In operation, the tubular billet 78 is sectioned to form the ring shaped blank 38. In the particular example provided, a 1.5-inch section of a 5.0 inch inner diameter by 8.0 inch outer diameter steel tube forms the ring shaped blank 38. It should be noted that the die cavity 76 of the top die 36 is designed so that when the ring shape blank 38 has been pressed to the desired thickness the resulting ring gear just fills the die cavity 76 around the anvil 30 (except, of course, for the portion of the die cavity 76 accounted for by the stroke of the top die). In the particular example provided the die cavity 76 is designed to accommodate a 11 pound ring gear 10 made from an 18 pound solid billet.
After sectioning, the blank 38 in this example was shot blasted and a coating 89 was applied to the ring shaped blank 38 to reduce friction between the blank and the tool set 28 during the pressing operation.
With reference now to
The induction heater 128 may be employed to heat the blank 38 to a predetermined temperature prior to the forming of the blank 38. In the example provided, the predetermined temperature may be about 1700 degrees Fahrenheit to about 1800 degrees Fahrenheit. In addition, the anvil 30, sleeve 32, and the dies 34 and 36 may be heated in press 120 by a gas fire to about 300° F.
The pressing stroke is initiated wherein the ram 124 moves toward the platen 122 so that the top die 36 is translated toward the bottom die 34 via hydraulic pressure that is supplied by the hydraulic system 126. The pressure on the blank 38 builds rapidly beyond the yield point of the blank 38 causing the material that forms the blank to flow in an axial direction generally parallel to the pressing stroke into the teeth voids 92.
When the bottom of the blank 38 conforms to the top of the negative tooling pattern 52 that was originally directly under the blank 38, the axial flow of the material that forms the blank 38 stops and flows instead in a radial direction that is generally perpendicular to the pressing stroke. Any voids that may have existed between the anvil 30 and the blank 38 (e.g., due to run out or differences in concentricity), the material that forms the blank 38 flows laterally inward to fill the void. The material that forms the blank 38 will also flow radially outward, thereby filling the annular void 94.
The pressing stroke is halted when the radial flow (that follows the axial flow) has been halted. If the blank 38 included excess material, it will appear on the back 26 of the ring gear 10. Thus to minimize excess material on the ring gear 10, the blank 38 may be volumetrically controlled (i.e., one or more of the height, outer diameter and inner diameter may be machined as necessary to put the blanks 38 in a condition wherein they are of a predetermined volume) or the blank 38 may be controlled by weight (i.e., one or more of the height, outer diameter and inner diameter may be machined as necessary to put the blanks 38 in a condition wherein they are of a predetermined weight).
When the ram 124 returns the top die 36 to a condition that is elevated above the lower die 34, the anvil 30 ejects the net formed ring gear 10 from the bottom die 34. Importantly, the ring gear 10 is concentric and the teeth 18 have been net formed (as shown in
While the invention has been described in the specification and illustrated in the drawings with reference to various embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as defined in the claims. Furthermore, the mixing and matching of features, elements and/or functions between various embodiments is expressly contemplated herein so that one of ordinary skill in the art would appreciate from this disclosure that features, elements and/or functions of one embodiment may be incorporated into another embodiment as appropriate, unless described otherwise, above. Moreover, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this invention, but that the invention will include any embodiments falling within the foregoing description and the appended claims.
Claims
1. A method of manufacturing a forged article including a surface, the method comprising:
- defining a negative tooling pattern based on the surface;
- providing a tooling set having a bottom die, a top die and an anvil, the bottom die being formed with an upper die surface that conforms to the negative tooling pattern, the anvil extending through the bottom die and defining an axis, the bottom die and the top die cooperating to define a die cavity;
- placing a hollow blank on an anvil and into the die cavity between a top die and the bottom die; and
- pressing the hollow blank between the top and bottom dies in a pressing direction that is generally parallel to the axis to form the forged article in single stroke, the hollow blank initially flowing in the pressing direction to substantially completely form the surface of the forged article and thereafter flowing in a direction generally perpendicular to the pressing direction to thereby fill the die cavity.
2. The method according to claim 1, wherein before the hollow blank is pressed between the top and bottom dies, the method further comprises heating the hollow blank.
3. The method according to claim 2, wherein the hollow blank is heated to a temperature of about 1700 degrees Fahrenheit to about 1800 degrees Fahrenheit.
4. The method according to claim 1, further comprising dynamically re-crystallizing a material of the hollow blank to an ASTM grain size of about 7 to about 8 as the hollow blank is being pressed.
5. The method according to claim 1, further comprising coating the hollow blank with a lubricant.
6. The method according to claim 1, wherein the forged article is net shaped or near-net shaped.
7. The method according to claim 1, further comprising forming the hollow blank such that it conforms to a predetermined volumetric size to thereby control a weight of the forged article.
8. The method according to claim 1, further comprising sectioning a tube shaped billet to create the hollow blank.
9. The method according to claim 1, further comprising removing an amount of excess material from a second surface of the forged article opposite the surface.
10. The method according to claim 1, wherein the hollow blank is ring-shaped.
11. The method according to claim 1, further comprising moving the anvil in a direction opposite the pressing direction to push the forged article away from the bottom die.
12. A method of manufacturing a ring gear including a surface having teeth, the method comprising:
- defining a negative tooling pattern based on the surface;
- providing a tooling set having a bottom die, a top die and an anvil, the bottom die being formed with an upper die surface that conforms to the negative tooling pattern, the anvil extending through the bottom die and defining an axis, the bottom die and the top die cooperating to define a die cavity;
- placing a hollow blank on an anvil and into the die cavity between a top die and the bottom die; and
- pressing the hollow blank between the top and bottom dies in a pressing direction that is generally parallel to the axis to form the ring gear in single stroke, the hollow blank initially flowing in the pressing direction to substantially completely form the surface of the ring gear and thereafter flowing in a direction generally perpendicular to the pressing direction to thereby fill the die cavity.
13. The method according to claim 12, wherein before the hollow blank is pressed between the top and bottom dies, the method further comprises heating the hollow blank.
14. The method according to claim 13, wherein the hollow blank is heated to a temperature of about 1700 degrees Fahrenheit to about 1800 degrees Fahrenheit.
15. The method according to claim 12, further comprising dynamically re-crystallizing a material of the hollow blank to an ASTM grain size of about 7 to about 8 as the hollow blank is being pressed.
16. The method according to claim 12, further comprising coating the hollow blank with a lubricant.
17. The method according to claim 12, wherein the ring gear is net shaped or near-net shaped.
18. The method according to claim 12, further comprising forming the hollow blank such that it conforms to a predetermined volumetric size to thereby control a weight of the ring gear.
19. The method according to claim 12, further comprising sectioning a tube shaped billet to create the hollow blank.
20. The method according to claim 12, further comprising removing an amount of excess material from a second surface of the ring gear opposite the surface.
21. The method according to claim 12, wherein the hollow blank is ring-shaped.
22. The method according to claim 12, further comprising moving the anvil in a direction opposite the pressing direction to push the ring gear away from the bottom die.
Type: Application
Filed: Jan 30, 2004
Publication Date: Aug 4, 2005
Inventor: Bamidele Oyekanmi (Southfield, MI)
Application Number: 10/769,740