JP2847014B2 - Gear material forging method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forging a gear material.

[Prior art]

A transmission gear of an automobile transmission has a first toothed portion and a second coaxially and axially adjacent second toothed portion having a smaller diameter.
An integral gear member having a tooth profile is used. Conventionally, when manufacturing this type of integral gear, the large-diameter first tooth portion is close to the large-diameter first tooth portion, even though the large-diameter first tooth portion can be machined. Since machining is not possible, for example, as shown in FIG.
After forging the first gear material forming the first gear material 1, the first gear material is machined to form the first gear portion 111 to produce the first gear member 110, and the second gear portion 121 is formed. After forging the second gear material for forming, the second gear material is machined to form the second tooth portion 121 to produce the second gear member 120, and the first gear member 110 is provided with the second gear member 110. Electron beam welding was performed on the welded portion 130 after fitting the outer surface 120 by press-fitting, thereby producing the integrated gear member 100 in which the two gear members 110 and 120 were integrated. However, in this case, there are problems in that the number of manufacturing steps is large, the manufacturing cost is high, and thermal distortion accompanying electron beam welding occurs in the second gear member 120.

On the other hand, Japanese Patent Publication No. 56-33173 (first publication) discloses a cylinder having a first tooth profile forming portion, a second tooth profile forming portion having a smaller diameter than this, a boss forming portion, and a shaft hole. By forming a cylindrical material, this cylindrical material is plastically deformed in the axial direction by forging, and plastically deformed in the radial direction,
A method of manufacturing a transmission gear forming a second tooth profile and a boss is described. Japanese Patent Application Laid-Open No. 3-221233 (No. 2) discloses a gear material having a first tooth profile forming portion and a second tooth profile portion having a smaller diameter than the first tooth profile forming portion by forging a disc-shaped material having holes. A forging method is described, in which a forging method for forming a cylindrical portion having a second tooth profile portion and an upsetting process for forming an outer shape of the first tooth profile forming portion are performed using the same die. . Japanese Patent Publication No. 3-5251 (Third Publication) discloses a method of forging a gear material similar to that of the second publication, wherein a second tooth profile longer in a tooth trace direction than a finished shape by preliminary forging. The second tooth profile is then rounded to the root of the second tooth profile by pre-upset molding, then formed into a roof shape at the top of the second tooth profile by final upset molding and the second tooth profile is axially And a method of forging a gear material for forming an undercut in the second tooth profile portion.

[0004]

In the technique disclosed in the first publication, there is not much problem in the case where the space between the first tooth profile and the second tooth profile is machined to form an annular groove. 1
In the case where the tooth profile and the second tooth profile are integrated in the axial direction, there is a problem that a defect is apt to occur in the joining of the metal at the boundary. In the technique of the second publication, there is a problem that the flow of metal when forming the second tooth profile tends to be insufficient, and the underfill defect is likely to occur in some tooth profiles of the second tooth profile. Further, even if the second tooth profile does not have any underfill defect, there is a problem that it is difficult to sufficiently secure the metallographic strength of the second tooth profile.

[0005] The technique disclosed in the third publication discloses that a roof is formed at the top of the second tooth profile, a root portion of the second tooth profile is rounded, and an undercut is formed at the second tooth profile.
It is a very good technology. However, in the pre-forged state, only the second tooth section is formed in a state of extending in the tooth trace direction, and only the second tooth section is independent of the inner base material portion by final upset molding. Due to the compression in the axial direction, the metallographic strength of the second tooth profile and the base material on the inner peripheral side thereof tends to decrease, and the fatigue strength of the inner peripheral portion at the top of the second tooth profile tends to decrease. There's a problem. An object of the present invention is to provide a method of forging a gear material that can easily and surely form a tooth portion having excellent fatigue strength and wear resistance.

[0006]

According to a first aspect of the present invention, there is provided a method of forging a gear material, comprising: a first tooth profile forming portion for forming a first tooth profile portion; and a shaft having a smaller diameter and a coaxial shape than the first tooth profile forming portion. In a forging method for forging a gear material in which a second tooth profile part adjacent in the direction is integrated, in a first step, a first tooth profile forming part and a second tooth profile part are forged and the second tooth profile part is formed. And a substantially annular excess portion in which a portion near the inner peripheral side protrudes in the tooth trace direction to the opposite side of the first tooth profile forming portion, and an annular slim groove located on the inner peripheral side of the excess portion. In the second step, the second tooth profile portion and a portion near the inner peripheral side thereof are forged with a shape such that the excess portion does not protrude from the bottom surface of the groove.

[0007]

According to the forging method of a gear material according to the first aspect, in the first step, the first tooth profile forming portion and the second
A substantially annular excess portion formed by forging a tooth profile portion and projecting the second tooth profile portion and an inner peripheral portion thereof in the tooth trace direction to the opposite side of the first tooth profile forming portion; And forging an annular knurled groove located on the inner peripheral side of the forging. Next, in the second step, the second tooth profile portion and a portion near the inner peripheral side thereof are forged so that the excess portion does not protrude from the bottom surface of the groove. The excess portion includes a circumferentially discontinuous portion in which the second tooth profile extends in the tooth trace direction and an annular portion in which a portion near the inner peripheral side of the second tooth profile extends in the tooth trace direction. There is
In the second step, in order to forge the surplus portion into a state in which the excess portion disappears, the metal filling into the second tooth profile and the metal into the annular edge near the inner peripheral side of the second tooth profile are performed. The filling property is improved.

As described above, while improving the metal filling property, the pressure receiving area in the second step is reduced in order to form the slim grooves, the forging molding pressure is increased, and the metal fluidity is ensured. Since the forging is performed, the second tooth profile and the portion near the inner peripheral side thereof can be formed into a desired shape without underfill, and a metal structure having excellent strength and wear resistance can be obtained. Moreover, when forging in the second step,
Since the second tooth profile and the inner peripheral side portion are integrally compression-molded in the axial direction, the metal structure at the boundary between the second tooth profile and the inner peripheral base material is defective or fragile. Does not occur, and the fatigue strength of the inner peripheral portion of the tip portion of the second tooth profile does not decrease.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. The present embodiment is an example in which the present invention is applied to a forging method for forging a gear material for manufacturing a gear member of an automobile transmission. First, the gear material will be described.

As shown in FIG. 1, the first gear blank 10 is
The large-diameter portion 11, the middle-diameter portion 12 that is smaller in diameter and coaxial than the large-diameter portion 11 and continues to the upper end surface of the large-diameter portion 11, and the boss portion 13 that continues to the upper end surface of the middle-diameter portion 12 are integrated. It has a simplified configuration. A first tooth profile forming portion 14 for forming a first tooth profile portion 14a is formed on a peripheral surface portion of the large diameter portion 11. A second tooth profile portion 15 including a plurality of spline teeth is formed on the peripheral surface portion of the middle diameter portion 12, and the tip of each tooth of the second tooth profile portion 15 is a chamfer 1 as shown in FIG.
5 b, an annular sulcus groove 16 is formed on the upper end surface of the middle diameter part 12 and located on the inner peripheral side of the second tooth part 15.

As shown in FIG. 2, the tip 15a of the second toothed portion 15 and the portion 17 near the inner periphery thereof projecting upward from the bottom surface of the slim groove 16 and have an annular shape having a triangular cross section. The inner peripheral side portion 17 is formed in a surplus portion 18 protruding upward in the tooth trace direction. For each dimension, for example, a = 1.4 mm, b = 8.0 mm, c = 4.0
mm, d = 4.6 mm.

As shown in FIGS. 2 and 3, a second gear blank 20 obtained by cold-forging the first gear blank 10 has substantially the same shape as the first gear blank 10, but has a surplus thickness. The portion 18 is forged and formed so as not to protrude from the bottom surface of the slim groove 16, and is formed until the position of the bottom surface 16 a of the slim groove 16 is slightly lowered. For each dimension, for example, e
= 6.0 mm, f ≦ 1.0 mm.

Next, a gear member material having a predetermined shape (not shown)
A description will now be given of a forging method for manufacturing the second gear blank 20 via the first gear blank 10. First, in the preforming step, the gear member material is forged into a predetermined shape,
This preforming step may be omitted. Next, in a first step, the gear member material is hot forged using a predetermined forging die and a forging device substantially similar to those shown in FIGS. I do.

Next, in a second step, the first gear material 10 is cold forged using the upper die 30 and the lower die 40 and a forging device shown in FIGS. To produce This second step will be described with reference to FIGS. As shown in FIG.
Is fixed to the lower surface of the upper base plate 32 via an upper die set 33 and a punch mounting flange 34. Further, with respect to the lower die 40, the mandrel 41 and the die 42 externally fitted thereto are fixed to the upper surface of the lower base plate 44 via a lower die set 45 and a die mounting flange 46. Note that an ejector pin 43 is also provided.

On the lower surface of the punch 31, a molding portion of a predetermined shape is formed for molding the end surface side and the outer peripheral side of the large diameter portion 11 of the second gear blank 20, and the mandrel 41 and the die 42 have: A molding part having a predetermined shape for molding the second tooth profile 15 and the boss 13 of the second gear blank 20 is formed.
As shown in FIG. 6, on the mandrel 41 and the die 42,
In a state where the first gear blank 10 is set in a posture inverted from the posture of FIG. 2, as shown in FIG. 7, the upper mold 30 is lowered and forged with a predetermined forging load to form the second gear. The material 20 is manufactured.

FIG. 2 is an enlarged view of a main part of the first gear blank 10, and the shape after forging in the second step is shown by a chain line. Tip 15a of second tooth profile 15
And a marginal portion 18 formed of an inner peripheral side neighboring portion 17 and an annular inner peripheral side neighboring portion 17 are compression-molded to a state shown by a dashed line by forging in the second step, and a slim groove 16 is formed. Is formed to be slightly lower than the bottom surface 16a.

After the second step, the second tooth profile 15 of the second gear blank 20 is rolled, for example, so that the second tooth profile 15 has an undercut whose tooth width decreases toward the large-diameter portion 11. Formed into a desired shape, and then the first tooth profile forming portion 1
The first tooth profile portion 14a is formed on the substrate 4 by machining.

The operation of the forging method for a gear material described above will be described. In order to form a surplus portion 18 in the first gear blank 10 and to forge the excess gear portion 18 in a state where the surplus portion 18 disappears, the metal filling property of the second tooth portion 15 and the second tooth portion 15 And the filling of the metal into the annular edge portion 19 on the inner peripheral side is improved. In order to improve the metal filling property and to form the squeeze groove 16, the pressure receiving area in the second step is reduced, the forging pressure is increased, and forging is performed in a state where the fluidity of the metal is secured. Accordingly, the second tooth profile portion 15 and the annular edge portion 19 on the inner peripheral side thereof can be formed into a desired shape with no underfill, and a metal structure excellent in strength and wear resistance can be obtained.

In addition, when forging in the second step, the second tooth profile 15 and the inner peripheral side portion 17 are integrally compression-molded in the axial direction. There is no defect or fragile portion in the metal structure at the boundary 15b with the peripheral portion, and the fatigue strength of the inner peripheral portion of the tip portion of the second tooth profile 15 does not decrease. The second
The gear material 20 corresponds to the gear material of the present invention.

The above embodiment is merely an example, and the specifications and shapes of the first gear blank 10 and the second gear blank 20 are not limited to those of the above embodiment.
The outer diameter of the second tooth profile 15 must be smaller than the root diameter of the first tooth profile 14a.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a first gear material according to an embodiment.

FIG. 2 is a sectional view of a first gear material obtained by forging the first gear material.

FIG. 3 is a perspective view of one tooth of a second tooth profile portion of a second gear material.

FIG. 4 is an enlarged sectional view of a main part of a first gear material.

FIG. 5 is a sectional view of an upper die and a lower die for forging a second gear material.

6 is a cross-sectional view of a state in which a first gear material is set in an upper mold and a lower mold of FIG. 5;

FIG. 7 is a cross-sectional view of a state where the second gear material is forged by the upper die and the lower die of FIG. 5;

FIG. 8 is a sectional view of an integrated gear member according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 1st gear material 14a 1st tooth profile part 14 1st tooth profile formation part 15 2nd tooth profile part 16 Nutsumi groove 18 Excess wall part 20 2nd gear material

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-203240 (JP, A) JP-A-1-138034 (JP, A) JP-A-3-221233 (JP, A) JP-A-3-3-233 287320 (JP, A) JP 58-28014 (JP, B2) JP 56-33173 (JP, B2) JP 3-5251 (JP, B2) Jiko 1-20042 (JP, Y2) (58) Field surveyed (Int.Cl. ⁶ , DB name) B21K 1/00-31/00 B21J 1/00-13/14 B21J 17/00-19/04

Claims (1)

(57) [Claims] 1. A gear material comprising a first tooth profile forming part for forming a first tooth profile and a second tooth profile axially adjacent to and coaxial with a smaller diameter than the first tooth profile forming part. In the first step, the first tooth profile forming part and the second tooth profile part are forged in a first step, and the second tooth profile part and the inner peripheral side vicinity thereof are first tooth profile in the tooth trace direction. A substantially annular excess portion protruding to the opposite side of the forming portion and an annular slim groove located on the inner peripheral side of the excess portion are forged and formed. A forging method for a gear material, comprising: forging a second tooth profile portion and a portion near the inner peripheral side thereof so as not to protrude from a bottom surface of the gear material.