JPH0712514B2 - Plastic forming method for differential pinion - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plastic working method for a differential pinion, which plastically works a differential pinion used in a differential gear in a cold state.

[Conventional technology]

Generally, a differential pinion is often used for a differential device of a self-propelled vehicle such as an automobile or a tractor.

Conventionally, such a differential pinion is generally manufactured by forging or the like into a predetermined shape and subjecting a material having a through hole in the center to gear cutting and finishing the end face and the through hole by cutting or the like. Has been done.

On the other hand, recently, from the viewpoint of improving productivity, a differential pinion is manufactured by plastic working, and as a method of forming by plastic working, for example,
As shown in Fig. 11, the tooth space 11 corresponding to the tooth profile of the differential pinion to be plastically machined is put into the die 17 in which the large diameter end 13 is engraved so that the large diameter end 13 is on the punch 15 side. Then punch this material 19 from the top 15
The raw material 19 is compressed by and is pressed in the axial direction or the radial direction to be plastically deformed to form a predetermined differential pinion.

[Problems to be Solved by the Invention]

However, such a conventional plastic working method for a differential pinion mainly has the following first to fifth problems.

That is, the first problem is that in the above-described method, the material 19 flows from the tooth bottom portion 21 of the die 17 in the direction of the arrow 23 in the figure, and
In the middle of the process, the small-diameter end 27 of the tooth profile 25 is closed, so spaces 29 and 31 are created at the corners of the tooth profile 25, where lubricant and scale remain, and a highly accurate molded product can be obtained. Is difficult.

The second problem is that in the method described above, the space at the corner of the tooth profile 25 is
In the vicinity of 29,31, at the final stage of forging, finally the material 19
Die 17 near this corner space 29,31 to reach
The stress at the joint between the material 19 and the material 19 is extremely low compared to the stress at other parts, and the springback when the molded product is taken out causes partial variation, which improves the accuracy of the mold and the This is a problem that it becomes difficult to transfer with accuracy.

A third problem is that, in the above-described method, when an annular surplus portion 33 is generated between the punch 15 and the die 17, and the surplus portion 33 is not allowed to be left due to the function of the differential pinion, it will be later. However, it is necessary to remove the surplus portion 33 by cutting or the like, which not only deteriorates the material yield but also shortens the life of the cutting tool due to intermittent cutting and causes burrs. The problem is that this burr needs to be removed in order to avoid interference with the gear.

A fourth problem is that in the above-mentioned method, the tooth profile portion of the die 17 forming the tooth profile 25 of the differential pinion is
Since it is formed toward the open end side of the 17, it is difficult to sufficiently reinforce the tooth profile portion, and the tooth profile 25 portion of the die 17 is easily damaged.

The fifth problem is that, in the above-described method, a through hole for inserting the shaft needs to be formed in the center later by machining or the like. Therefore, when forming the through hole at the same time,
For example, as shown in FIG. 12, molding is performed with the mandrel 39 inserted in the through hole 37 at the center of the ring-shaped material 35. At this time, the material flows as shown by the arrow 41 in the figure. Therefore, the through hole 37 corresponding to the tip of the tooth where the stress is particularly low is
, A space 43 is generated, and at the final stage of pressurization, this space is
43 is a problem that there is a possibility that defects such as crushed materials overlap with each other.

As a method for solving the above-mentioned third problem, that is, the problem that the annular excess thickness portion 33 is formed between the punch 15 and the die 17, for example, as shown in FIG. Although a method of closed forging by using is known, in this method, since the flow state of the material 47 is almost the same as the method of FIG. 13 described above, the first and second problems described above still remain. The fourth problem is inevitable due to the rest and the mold structure. Further, according to this method, when the through holes 37 are simultaneously formed, the above-mentioned fifth problem occurs, and in order to solve this problem, for example, the projections 53, 55 are formed on the punch 49 and the counter punch 51. Is limited to the extent that the pits are formed and the depressions are formed.

On the other hand, as shown in FIG.
57 In the container part 65 of the mold having a cylindrical container part 65 that is equal to or slightly larger than the outer diameter of the large diameter end of the tooth space,
Material 67 with an outer diameter slightly smaller than the inner diameter of the container 65
Then, insert the material 67 into the die section with the punch 69.
A method of performing forward extrusion on the 57 side is known, but in this method, an annular unpushed portion 71 is generated between the punch 69 and the die portion 57, and the above-mentioned third problem occurs.

The present invention has been made in order to solve such a conventional problem, and it is possible to significantly improve the molding accuracy as compared with the conventional one, eliminate the occurrence of a surplus portion, and improve the strength of the tooth profile portion of the die. An object of the present invention is to provide a plastic working method for a differential pinion that can be used.

[Means for Solving the Problems]

The differential pinion plastic working method of the present invention is a differential pinion plastic working method for forming a differential pinion in which a through hole is formed in the center by plastic working, and a tooth profile corresponding to the tooth profile of the differential pinion to be plastically worked. A die part in which the space is engraved so that the large diameter end is on the punch side, and a container part in which a substantially spur gear-shaped tooth profile space is formed which is continuous with the large diameter end of the tooth profile space of this die part. In the tooth profile space of the container part of the mold having a through hole is formed in the center, smaller than the tip diameter of the tooth profile space of the container part,
After inserting a spur gear-shaped material having a tooth tip diameter larger than the tooth root diameter and having a substantially spur gear-shaped outer diameter shape that can be inserted into the tooth profile space of the container part, With a mandrel inserted through the through hole formed at the center, a die that fits into the tooth space of the container is used to perform forward extrusion on the die side.

[Work]

In the plastic working method of the differential pinion of the present invention, after the spur gear-shaped material is put into the tooth profile space of the container portion, the mandrel is inserted into the through hole formed in the center of the spur gear-shaped material, and the tooth profile of the container portion is formed. When the punch that fits in the space is pressed to the die part side, the spur gear-shaped material is filled from the large-diameter end side of the tooth profile space of the die part in order, and the spur gear-shaped material is formed to have a large tooth profile. The part is deformed into a small tooth profile in the die part while sequentially expanding in the axial direction.

In the method of the present invention, the mandrel is inserted into the through hole formed in the center of the spur gear-shaped material, and the forward extrusion is performed. Since the area ratio of the mandrel gradually increases toward the portion, the area reduction rate of the material becomes larger toward the small diameter end side, and the flow of the material becomes good.

〔Example〕

 Hereinafter, the details of the present invention will be described with reference to the drawings.

1 and 2 show a plastic working apparatus for a differential pinion used in an embodiment of the plastic working method for a differential pinion according to the present invention. In the drawings, reference numeral 73 designates a die portion 75 and a container portion 77. 3 shows a mold having and.

The die part 75 has a tooth profile space in which a tooth profile 79 corresponding to the tooth profile of the differential pinion to be plastically machined is engraved.
81 is engraved so that the large-diameter end portion 83 faces upward.

Further, in the container part 77, a spur gear-shaped tooth profile space 85 continuous with the large-diameter end portion 83 of the tooth profile space 81 of the die part 75 is formed.

In the figure, reference numeral 87 indicates a punch.
A tooth profile 89 having a shape that fits into the tooth profile space 81 of the container portion 77 is formed on the 87.

In this embodiment, a substantially straight mandrel 91 is inserted in the center of the punch 87, and a knockout pin 93 is arranged in the center of the die.

An embodiment of the method of the present invention is carried out as described below by using the differential pinion plastic working apparatus constructed as described above.

That is, in the method of the present invention, first, the container part of the mold 73 is
The spur gear-shaped material 95 is put into the tooth space 85 of 77.

As shown in FIGS. 3 and 4, the spur gear-shaped material 95 is smaller than the tip diameter A of the tooth space 85 of the container 77,
The tip diameter C is larger than the root diameter B and the container part
It has a spur gear-shaped outer diameter shape that can be inserted into the tooth space 85 of 77.

In this embodiment, the tooth tip diameter C of the spur gear-shaped material 95 is 0.9 times or more the tooth tip diameter A of the tooth profile space 85 of the container 77, and the center of the spur gear-shaped material 95 is almost straight. -Shaped through holes 97 are formed.

Thereafter, in the method of the present invention, the mandrel 91 is inserted into the through hole 97 of the spur gear-shaped material 95, and in this state, the punch 87 fitted in the tooth profile space 85 of the container part 77 is moved to the die part 75 side. A predetermined differential pinion is molded by the forward extrusion process, and thereafter, the molded product is taken out by raising the knockout pin 93.

Therefore, as described above, in the plastic working method for the differential pinion of the present invention, the tooth profile space corresponding to the tooth profile of the differential pinion to be plastically worked.
81 is a die part 75 that is engraved so that its large-diameter end part 83 is on the punch 87 side, and the large-diameter end part 83 of the tooth space 81 of this die part 75.
In the tooth profile space 85 of the container part 77 of the mold 73 having a container part 77 in which a spur gear-shaped tooth profile space 85 continuous to
A through hole 97 is formed at the center, has a tip diameter C smaller than the tip diameter A of the tooth space of the container portion 77 and larger than the root diameter B, and can be inserted into the tooth shape space 85 of the container portion 77. After introducing the spur gear-shaped material 95 having a spur gear-shaped outer diameter shape,
With the mandrel 91 inserted into the through hole 97 of the spur gear-shaped material 95, the spur gear-shaped material 95 is inserted into the tooth space of the container 77.
Since the punch 87 that fits into the 85 is used to extrude forward to the die part 75 side, it is possible to significantly improve the molding accuracy compared to the conventional one, and to prevent the occurrence of excess thickness and the tooth profile of the die. The strength of the part can be improved.

That is, in the plastic working method for the differential pinion of the present invention, after the spur gear-shaped material 95 is put into the tooth profile space 85 of the container part 77, the punch 87 that fits into the tooth profile space 85 of the container part 77 is placed on the die part 75 side. When pressed, spur gear material 95
However, since the tooth space 81 of the die portion 75 is sequentially filled from the large-diameter end portion 83 side, a space is generated at a corner portion of the tooth profile, which is the first conventional problem, and a lubricant and a scale are provided at this portion. It will not remain, and it will be possible to obtain a highly accurate molded product.

Further, in the method of the present invention, the portion of the spur gear-shaped material 95 formed into a large tooth profile is deformed into a small tooth profile while sequentially expanding in the axial direction in the die part 75, The contact stress between the material and the material gradually increases, the stress imbalance disappears, and the second problem of the related art, springback when the molded product is taken out, is extremely less likely to cause partial variations. The accuracy of the mold 73 can be reliably transferred to the accuracy of the molded product.

Further, in the method of the present invention, the unpressed shape becomes a spur gear shape due to the mold structure, which is a third problem of the related art. It is possible to improve the yield of the material because the annular surplus portion is not generated.

Furthermore, in the method of the present invention, since the die part 75 is formed in the center of the die 73, it is possible to sufficiently reinforce the tooth profile part of the die part 75 and reduce damage to the tooth profile part of the die. be able to.

Further, in the method of the present invention, since the spur gear-shaped material 95 is plastically worked by the forward extrusion processing method, a compressive stress always acts on the through hole 97 of the spur gear-shaped material 95. It is possible to surely eliminate a problem that a space is generated between the through hole 97 and the mandrel 91 and a defect that the space is crushed and the materials are overlapped is generated.

Further, in the method of the present invention, since the front extrusion is performed with the mandrel 91 inserted in the through hole 97 formed in the center of the spur gear-shaped material 95, the large diameter of the tooth space 81 of the die part 75 is obtained. Since the ratio of the cross-sectional area occupied by the straight mandrel 91 gradually increases from the end portion 83 toward the small diameter end portion 84, the area reduction rate of the material increases toward the small diameter end portion 84 side, and the flow of the material flows. Is improved, and as a result, the space where the material is not filled is not generated on the side of the small diameter end portion 84 of the die portion 75.

Furthermore, since the front extrusion process is performed with the mandrel 91 inserted in the through hole 97 formed in the center of the spur gear-shaped material 95, the through hole is not required to be processed later and the differential pinion is used. It is possible to improve the concentricity of the through holes formed in the.

As described above, according to the plastic working method for bevel gears of the present invention, it is possible to solve the first to fifth problems of the related art all at once.

Further, in the method of the present invention, the spur gear-shaped material 95 is only further extruded into a small gear, and since the surface of the tooth profile of the spur gear-shaped material 95 becomes large, the spur gear-shaped material 95 There is an advantage that the lubricant is sufficiently replenished and seizure hardly occurs.

Further, by using the spur gear-shaped material 95, the molding load can be reduced, and as a result, the deformation of the mold is reduced and the molding accuracy is improved.

FIG. 5 shows an example of the manufacturing process of the spur gear-shaped material 95 used in the plastic working method for the differential pinion of the present invention described above. In this example, first, as shown in (a), the press The long columnar material 101 is cut into a predetermined length by a machine or the like, and thereafter, as shown in (b), preforming is performed so that it can be easily put into (c) in the next step.

After that, as shown in FIG. 6, compression spout molding is performed by a spur gear-shaped die 103 and a punch 105, and a material 107 is formed.
Is molded into a spur gear-shaped material 109, but the spur gear-shaped shape at this time is a material shape, so high accuracy is not required. At this time, deficiencies such as 111 and 113 in the figure are also tolerated, and since molding is relatively easy, it is much cheaper than when using a mold or the like in which a differential pinion is engraved. It can be molded.

Thereafter, as shown in (d), the spur gear-shaped material 109 is perforated to form the spur gear-shaped material 95 used in the method of the present invention. By molding, the differential pinion 115 as shown in (e) is molded.

The method for producing the spur gear-shaped material 95 is not limited to the method described above. For example, as shown in FIG. 7, closed forging by a closed plate 117 may be used, and stacking may be performed. Needless to say, it can be produced by continuous extrusion molding, sawing of a drawn material, punching from a plate material, or the like.

Furthermore, although the mandrel 91 is mounted on the upper mold in the above-described embodiments, it goes without saying that this may be mounted on the lower mold.

Further, in the embodiment described above, the example in which the spur gear-shaped material 95 is filled in the tooth space 81 of the die portion 75 at the end of the forward extrusion processing is described, but the present invention is not limited to this embodiment. For example, as shown in FIG. 8, a surplus portion 121 may be formed on the side of the small diameter end 119 of the differential pinion, and as shown in FIG. 9, the small diameter end 119 of the differential pinion. Side through hole 123
The volume may be adjusted by the space 125 formed in advance, and as shown in FIG.
Boss 1 on the large diameter end 127 side of the differential pinion
Of course, the shape provided with 29 may be used.

Furthermore, depending on the required shape of the final product, for example,
As described in Japanese Patent Application No. 1-242517 previously filed by the applicant, the connecting surface of the tooth profile space of the die part and the tooth profile space of the container part is almost the same as the large end face of the cone distance of the differential pinion to be plastically machined. Using molds formed in parallel, to which the spur gear-shaped material of the method of the present invention is put,
By performing the plastic working, a highly accurate molded product can be obtained.

Further, in the embodiment described above, the spur gear-shaped material 95 is
Although an example in which the spur gear has a shape very close to that of the spur gear has been described as shown in FIG. 4 and FIG. 4, the present invention is not limited to such an embodiment, and for example, the outer circumference is very rough. It is needless to say that the lower half part may have a bevel gear shape or a curved shape.

〔The invention's effect〕

As described above, in the plastic working method for the differential pinion of the present invention, the tooth space corresponding to the tooth profile of the differential pinion to be plastically worked has a die portion in which its large-diameter end is punched. A through-hole is formed in the center of the tooth profile space of the container part of the die having a container part in which a substantially spur gear-shaped tooth profile space continuous with the large-diameter end part of the tooth profile space of the die part is formed. , A spur gear-shaped material having a tip diameter smaller than the tooth tip diameter of the tooth profile space of the container portion and larger than the tooth root diameter, and having a substantially spur gear outer diameter shape that can be inserted into the tooth profile space of the container portion After that, the spur gear-shaped material is forward extruded to the die part side by a punch fitted in the tooth space of the container part, with the mandrel inserted through the through hole formed at the center of the material. Since the way, it is possible to significantly improve the molding accuracy than conventional, eliminating the generation of excess thickness portion, also, it is possible to improve the strength of the tooth portions of the die.

Furthermore, by using a spur gear-shaped material, the molding load can be reduced, which results in less deformation of the mold, which improves molding accuracy, which is also beneficial for lubricants, and wear of the mold. Less.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a differential pinion plastic working apparatus used in an embodiment of the differential pinion plastic working method of the present invention. FIG. 2 is a transverse sectional view taken along the line II-II in FIG. FIG. 3 is a top view of the spur gear-shaped material of FIG. FIG. 4 is a sectional view of the spur gear-shaped material of FIG. FIG. 5 is an explanatory view showing an example of a process for forming the spur gear-shaped material of FIG. FIG. 6 is an explanatory view showing an apparatus for forming the spur gear-shaped material of FIG. 5 (c). FIG. 7 is an explanatory view showing another apparatus for forming the spur gear-shaped material of FIG. 5 (c). 8 to 10 are longitudinal sectional views showing another differential pinion manufactured by the method of the present invention. 11 to 14 are explanatory views showing a conventional plastic working method for a differential pinion. [Explanation of symbols for main parts] 73 …… Mold 75 …… Die section 77 …… Container section 81,85 …… Tooth profile space 83 …… Large-diameter end section 87 …… Punch 91 …… Mandrel 95 …… Flat Gear-shaped material 97 ... through hole.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-54-66372 (JP, A) JP-A-56-91950 (JP, A) JP-A-56-91951 (JP, A) JP-A 61- 150733 (JP, A)

Claims (1)

[Claims] 1. In a plastic working method of a differential pinion for forming a differential pinion having a through hole at its center by plastic working, a tooth space corresponding to the tooth profile of the differential pinion to be plastic worked has a large diameter end. Of the die having a die part that is engraved so that the part is on the punch side, and a container part in which a substantially spur gear-shaped tooth profile space is formed that is continuous with the large diameter end of the tooth profile space of the die part. A through hole is formed in the center of the tooth profile space of the container part, and it has a tip diameter smaller than the tooth tip diameter of the container part tooth space and larger than the root diameter, and can be inserted into the container tooth profile space. After inserting a spur gear-shaped material having a substantially spur gear-shaped outer diameter, the spur gear-shaped material is inserted into the through hole formed in the center of the mandrel, By a punch to be fitted to the tooth space of the container section, plastic working method of differential pinions, characterized in that the forward extrusion on the die side.