JP2007283391A - Apparatus for forging gears - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an apparatus for forging gears, wherein loss in thickness of teeth is prevented and the quality of the formed product is stabilized. <P>SOLUTION: The apparatus for forging the gears is constituted so that an annular die (23) for forging tooth-profile shaped teeth (24) in the inner periphery of a center hole (23a), is pressed into a fastening metal (16), and a punch for pushing a blank (40) having smooth circular shaped outer peripheral surface into the die (23) is provided, wherein the tooth-profile shaped teeth (24) in the die (23), are extension-formed over almost the whole length of the center hole (23a) with the teeth shape almost corresponding to the product, and when the above die (23) is pressed into the fastening metal (16), the blank back-pressure depending on the wear caused by the friction of the tooth-profile shaped teeth at the pushing-into time, is adjusted by making smaller of the pushing-into rate at the blank exhausting side to the pushing-into rate at the blank introducing side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a gear forging device for forming gears, spline shafts and the like by cold forging.

As for forging gears in the cold, forging in which an annular die with teeth forming teeth on the inner periphery is fitted into a clamp, and a cylindrical material is pushed into the die by a punch to form teeth on the outer periphery The device is generally known.

By the way, the die used in the conventional forging apparatus is as shown in FIG. That is, the tooth forming tooth 2 formed in the center hole of the die 1 forms a molding land 2b having a tooth height and a cross-sectional shape corresponding to the product in a short area of the upper and lower intermediate parts, and in a long area on the upper side and the lower side. The material introduction slope 2a and the material discharge slope 2c whose tooth height gradually decreases from the molding land 2b were formed.

In the prior art, since the molding land 2b of the tooth forming tooth 2 is shortened, the frictional force of the tooth formed on the material side with respect to the tooth forming tooth 2 is reduced, and the back of the material due to the friction of the tooth forming tooth during pushing is reduced. The pressure could not be increased. For this reason, it is easy to generate a lack of thickness in a tooth to be molded, and particularly, the lack of thickness is remarkably generated at a tooth end portion on the pushing-in progress side of the material. For this reason, it is necessary to use a long material in consideration of the removal of the missing teeth, and it is necessary to cut and remove the end portion where the missing teeth occur after the tooth formation, leading to waste of the material, The post-processing is troublesome. In addition, since the molding land 2b is shortened, the material tends to tilt when pushed in, and the quality of the molded product becomes unstable.
JP 11-240883 A

It is an object of the present invention to obtain a novel gear forging device that prevents the occurrence of missing teeth and stabilizes the quality of a molded product.

The present invention is configured as follows to achieve the above object. That is, in a gear forging device provided with a punch for press-fitting a material having a smooth circular outer peripheral surface into the die by press-fitting an annular die having teeth forming teeth on the inner periphery of the center hole into the clamp The tooth profile of the die is formed so as to extend over the entire length of the center hole with a tooth profile substantially corresponding to the product, and when the die is press-fitted into the clamp, the press-fitting rate on the material discharge side is determined as the material. By making it smaller than the press-fitting rate on the introduction side, the material back pressure due to the friction of the tooth forming teeth at the time of pushing is adjusted.

When the material is pushed into the die by the punch, teeth are formed on the outer peripheral portion of the material by the teeth forming teeth of the die. In this case, the tooth forming tooth has a tooth shape substantially corresponding to the product over substantially the entire length of the center hole, so that the tooth formed on the material contacts the tooth forming tooth on the die side with a large frictional force and pushes in. The material back pressure due to the friction of the tooth forming teeth at the time increases. As a result, the tooth shape of the tooth forming tooth is transferred with high accuracy over the entire length of the tooth formed on the material. In addition, since the tooth forming teeth extend over substantially the entire length of the center hole, the holding force for holding the material coaxially increases, and the quality of the molded product is stabilized.

Embodiments of the present invention will be described below with reference to the drawings. 1 is a cross-sectional view of a forging device according to the present invention, FIG. 2 is an enlarged cross-sectional view of the main part of FIG. 1, FIG. 3 is an enlarged cross-sectional end view of the main part of the die according to the present invention, and FIG. It is the partial expanded view by IV line.

In FIG. 1, reference numeral 10 denotes a forging device, which includes a die unit 11 and a punch unit 30. In the die unit 11, an annular center block 13 and a lower peripheral ring 14 are coaxially fitted and placed on a metal receiver 12, and a counter punch 15 is erected and fixed to an axial center portion of the metal receiver 12. An annular inner clamp 16, an outer clamp 18, and an upper peripheral ring 19 are coaxially press-fitted and placed on the center block 13 and the lower peripheral ring 14, and these are held by a large-diameter holding ring 20. Tighten and integrate.

The inner clamp 16 is formed with a holding hole 17 at its axial center, and a cylindrical guide 22 is fitted into the upper part 17a of the holding hole 17 and a die 23 is fitted into the lower part 17b. The upper portion 17a of the holding hole 17 is a tapered hole that shrinks upward at a large angle (3 to 5 degrees), and the guide 22 is taper-fitted to this portion. The lower portion 17b of the holding hole is a compound taper hole. That is, as shown in FIG. 2, the entire lower portion 17b is formed into a tapered hole that shrinks upward at a small angle (1 to 2 degrees), and an upper stage 17b corresponding to a material introduction slope 24a of a tooth forming tooth 24 described later. -1 with a small diameter stepwise with respect to the lower step 17b-3, in this example, with a step of about 0.1 mm, the upper step 17b-1 and the lower step 17b-3 are smoothly connected by a small middle step 17b-2. .

Tooth-forming teeth 24 for forming a helical gear are formed on the inner periphery of the center hole 23a of the die 23. As shown in FIGS. 3 and 4, the tooth-forming tooth 24 has an upper end portion into which the material is pushed into a material introduction inclined surface 24 a whose tooth height gradually decreases toward the upper end, and the center hole 23 a extends from the material introduction inclined surface 24 a. The front teeth forming teeth 24b and the rear teeth forming teeth 24c reaching the lower end of the tooth have substantially the same tooth profile as that of the product whose tooth height and tooth thickness do not change. As shown in FIG. 4, the material introduction inclined surface 24 a is formed on a surface (surface perpendicular to the tooth) that is substantially orthogonal to the tooth thickness direction with respect to the line L that the tooth forming tooth 24 extends.

The outer periphery of the die 23 is a simple taper surface that decreases at a small angle (1 to 2 degrees) upward, and its outer diameter is slightly larger than the inner diameter of the lower portion 17b of the holding hole 17. In the example, it is 0.4 mm in diameter and press-fitted into the lower part 17b. Accordingly, the upper portion of the die 23 has a press-in rate of 0.5% to 0.6% and the lower portion of the die 23 has a lower press-in rate than the holding hole 17, and the phantom line-solid line in FIG. As shown in FIG. 6, when the inner clamp 16 is press-fitted, the upper portion of the die 23 is elastically deformed in the axial direction slightly larger than the lower portion.

The change in the press-fitting rate is achieved by adjusting the material back pressure due to the friction of the tooth forming teeth when the material 40 is pushed (dried) into the die 23, and smoothly filling the tooth forming teeth 24 with the meat on the outer periphery of the material. This is for transferring the tooth profile of the molded tooth 24 onto the material with high accuracy. If the press-in rate is not changed as described above, the frictional force between the material 40 and the tooth forming teeth 24 becomes too large, the material back pressure rises abnormally, the die 23 is damaged, or the material is pushed into the die 23. It will disappear. In the present invention, the material back pressure is adjusted by making the press-fit rate of the lower portion of the die 23 smaller than the press-fit rate of the upper portion. This eliminates a material back pressure adjusting member that is operated by hydraulic pressure or the like on the lower side of the die, thereby simplifying the structure.

In FIG. 1, reference numeral 27 denotes an annular water chamber for heat exchange formed between the outer clamp 18 and the upper peripheral ring 19. A supply port 27 a and a discharge port 27 b formed on the side of the upper peripheral ring 19 are provided. Then, warm water or cooling water is circulated through the water chamber 27. In this example, at the start of molding, warm water was circulated through the water chamber 27, the guide 22 and the die 23 were preheated to 45 ° C. to 65 ° C. via the inner clamp 16 and the outer clamp 18, and molding was started. After that, cooling water is circulated in the water chamber 27 to keep the guide 22 and the die 23 at 100 ° C. or less, and the friction coefficient between the material and the mold is managed. As a result, the material 40 can be smoothly molded. Reference numeral 28 denotes an air ejection path for separating a molded product formed in the center block 13.

The counter punch 15 has an upper portion 15a fitted to the guide 22 having a small diameter and an intermediate portion 15b fitted to the die 23 having a large diameter. The taper portion 15c is formed in a tapered portion 15c that is located on the slope 24a portion and expands downward.

A punch unit 30 is provided above the die unit 11 described above. The punch unit 30 has a cylindrical punch 33 projecting and fixed downward on the axial center of a punch holder 32 moved up and down by a ram 31, and a cylindrical positioning member 34 is fitted to the outer periphery of the punch 33. The punch holder 32 is engaged. When the punch 33 is moved downward, the punch 33 can be fitted into a gap between the guide 22 of the die unit 11 and the upper portion of the counter punch 15. The positioning member 34 is for contacting the upper surface of the guide 22 and confirming the bottom dead center position of the punch 33 when the punch 33 moves downward by a predetermined amount.

The punch 33 intermittently pushes the short and cylindrical material 40 (40-1, 40-2, 40-3) sequentially into the gap between the guide 22 and the counter punch 15. In this case, the bottom dead center position of the punch 33 is set as follows. That is, the lower material 40-1 passes through the lower part of the material introduction slope 24a of the die 23, that is, the top (corresponding to the molding land) 24a-1 shown in FIG. When the lower end (advance end) of the middle stage material 40-2 arrives at the lower point M (FIG. 2) of the material introduction slope 24a, the bottom dead center position of the punch 33 is set, and the middle stage material 40-2 is here. Pause. Thereby, the joint pattern due to the interruption of the movement of the material does not occur on the teeth of the product (helical gear) 41 formed by the die 23.

According to the embodiment, when the material 40 is pushed into the die 23 by the punch 33, teeth are formed on the outer peripheral portion of the material 40 by the tooth forming teeth 24 of the die 23. In this case, the tooth profile forming tooth 24 has a tooth profile substantially corresponding to the product over substantially the entire length of the center hole 23a, so that the tooth formed on the material 40 contacts the tooth forming tooth 24 with a large frictional force. In addition, the material back pressure due to the friction of the tooth forming teeth at the time of pushing increases. As a result, the tooth shape of the tooth forming tooth 24 is transferred with high accuracy over the entire length of the teeth formed on the material 40. Furthermore, since the tooth forming teeth 24 extend over substantially the entire length of the center hole 23a, the holding force for holding the material 40 coaxially increases, and the quality of the molded product is stabilized.

Note that the material 40 described above may be a solid cylinder. In this case, the counter punch 15 is omitted. Further, when forming a spur gear, the tooth-forming teeth 24 are formed in a straight shape extending linearly in the axial direction.

It is sectional drawing of the forging apparatus by this invention. It is a principal part expanded sectional view of FIG. It is a principal part expanded sectional end view of the die | dye by this invention. FIG. 4 is a partial development view taken along line IV-IV in FIG. 3. It is a cross-sectional end view of a conventional tooth forming tooth.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Forging device 11 Die unit 12 Receptacle 13 Center block 14 Lower peripheral ring 15 Counter punch 16 Inner clamp 17 Holding hole 17a Upper part 17b Lower part 17b-1 Upper stage 17b-2 Middle stage 17b-3 Lower stage 18 Outer clamp 19 Upper peripheral ring 20 retaining ring 22 guide 23 die 23a central hole 24 tooth forming tooth 24a material introduction slope 24b front tooth forming tooth 24c rear tooth forming tooth 26 ring nut 27 water chamber 27a supply port 27b discharge port 28 air ejection path 30 punch unit 31 ram 32 Punch holder 33 Punch 34 Positioning member 40 (40-1, 40-2, 40-3) Material 41 Product (helical gear)

Claims (1)

An annular die (23) having tooth-forming teeth (24) formed on the inner periphery of the center hole (23a) is press-fitted into the clamp (16), and a material (40) having a smooth circular outer peripheral surface is inserted into the die. In the gear forging device provided with a punch to be pushed into (23), the tooth-forming tooth (24) of the die (23) is extended substantially over the entire length of the center hole (23a) with a tooth profile substantially corresponding to the product. When forming the extension and press-fitting the die (23) into the clamp (16), by reducing the press-in rate on the raw material discharge side relative to the press-in rate on the raw material introduction side, Gear forging device characterized by adjusting the material back pressure due to friction.

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