JPH0780590A - Manufacture of bevel gear - Google Patents

Abstract

PURPOSE:To prevent generation of die breakage at a part corresponding to the bottom part on the top face side of a tooth profile die even in the segment structure of a forming die where burrs formed at the segmented position of the tooth profile dies can be removed forming the center hole of a bevel gear. CONSTITUTION:In manufacturing a bevel gear where the pitch diameter is different at each end by forging, the forging of a gear stock is executed by a forming die where the segmenting position of a punch 11 and a tooth profile die 12 is shifted toward the gear center side from the corresponding part 12a of the bottom part on the top surface side where the pitch diameter of the tooth profile 12 is small. Before this forging, the preforming of the gear stock where the prescribed space S is formed between the bottom part corresponding part 12a on the top surface side of the tooth profile die 12 and a gear 15 is executed when the forging by the forming die is started.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bevel gear manufacturing method used for manufacturing a bevel gear having different pitch circle diameters at both ends.

[0002]

2. Description of the Related Art There are various types of gears for transmitting rotation between two axes. Particularly, a bevel gear having a conical surface as a pitch surface and different pitch circle diameters at both ends is a straight bevel gear. , Bevel gears, spiral bevel gears, spiral bevel gears, and various other types are also used as bevel gears, differential gears, pinion mates, side gears, and the like.

Since such a bevel gear is different in tooth profile between the side having a small pitch circle diameter and the side having a large pitch circle diameter, it is considerably difficult to manufacture a tooth, but it is produced by a conventional manufacturing process by cutting. The manufacturing process has changed to a forging with good properties, and in particular, it is often manufactured by closed forging or closed forging, which belong to precision forging technology.

In this closed forging, a double-acting die having an upper punch and a lower punch is used, and the cavity of a die which has been closed in advance is filled with upper and lower punches. A hydraulic closing forging machine or a dedicated machine combining a mechanical press and a hydraulic mechanism was developed. After that, by incorporating the hydraulic closing mechanism in the die set, it became possible to perform closing forging even with an existing single-action press.

FIG. 8 shows a conventional process for manufacturing a bevel gear having different pitch circle diameters at both ends by closed forging, in which a top surface side of a bevel gear 31 having a small pitch circle diameter is added by an upper punch 32. While pressing, the tooth profile portion 31a is molded by the tooth profile die 33, and the tooth profile die 33 is configured such that the mold is divided at the tooth bottom portion corresponding portion 31b on the top surface side of the bevel gear 31.

However, in such a closed forging method, as shown in FIG. 9, since the burrs 34 are formed in the divided parts of the die, the top surface side of the bevel gear 31 cannot be made to have a black skin specification. There was a problem.

Therefore, as shown in FIG.
1 and the tooth profile die (upper die) 42, the lower die 43, and the lower punch 44, when the gear material 45 is processed by the closed forging, the tooth profile die (upper die) 42 is divided into the tooth profile die ( (Upper die) 42 having a smaller pitch circle diameter than the tooth bottom portion corresponding portion 42a on the top surface side and shifted to the gear center side, and as shown in FIG. 11, after the forging process for forming the tooth profile portion 46a, the bevel gear rough The position where the center hole 46b is formed in the molded body 46 is selected so that the burr 47 formed in the bevel gear rough molded body 46 may be removed when the center hole 46b is formed.

On the other hand, when a pinion mate, which is a kind of bevel gear, is formed by forging, in particular, as shown in FIG. 12, the tooth profile portion 51a having different pitch circle diameters at both ends and the end face on the larger pitch circle diameter side are formed. Back surface 51 formed on
In addition to c, when the pinion mate 51 having the web 51b formed on the tooth bottom portion is formed by forging in order to improve the gear strength, in the sense of preventing interference with a differential case (not shown), Back surface 51c
Is provided inside the maximum diameter of the web 51b, and the tooth profile back surface 51d has a black skin specification.

Further, in such a pinion mate 51 with a web, when it is formed by warm forging or cold forging, the back spherical surface 51c side is made to be entirely ground.

Regarding the formation of bevel gears and the like by such a forging process, for example, "Automotive Technology Handbook <4th Volume> Production / Quality / Maintenance Edition", September 1, 1991, Issue 1 Technical Association Page 71-
The explanation is also given on page 80, “2.2 Forging”.

[0011]

However, as shown in FIG.
And as shown in FIG. 11, the tooth profile die (upper mold) 42
As the dividing position 45b of the bevel gear rough formed body 46, a position where the center hole 46b is formed in the bevel gear rough formed body 46 is selected.
If the burr 47 formed on the upper part of the tooth die (upper die) 42 is removed when the center hole 46b is formed, it is easy to cause a die crack at the tooth bottom portion corresponding portion 42a on the top surface side. There was a problem, and it was an issue to prevent such mold cracking from occurring at an early stage.

Further, as shown in FIG. 12, in order to improve the strength of the gear, a pinion mate 51 having a web 51b formed on the tooth bottom portion on the side of the back spherical surface 51c is formed by cold forging, and processed. To reduce the number of steps and stock removal, the tooth back surface 51d has a black skin specification and the back surface 51c
In the case where only the only one is subjected to the total shaving, the web 51b becomes dead metal, and as shown in FIGS. 13 and 14, there is a problem that a crack 52 may occur at the tooth bottom portion of the tooth profile 51a. The problem was to prevent cracks from occurring at the tooth bottom of various workpieces.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and in the case of forming a bevel gear, a differential gear, a pinion mate, a side gear and the like bevel gears by forging, the division of the tooth profile die is performed. Even if the position is such that the center hole of the bevel gear is formed and the burr formed at the dividing position of the tooth profile die is removed when forming the center hole of the bevel gear, the tooth profile die It is possible to prevent early mold cracking at the tooth bottom corresponding portion on the top surface side of the tooth profile back surface by forming a web on the tooth root portion on the back spherical surface side to improve the gear strength. It is possible to prevent the occurrence of cracks in the root part of the tooth profile of the work even when the black skin specification is used and only the back spherical surface is completely machined. It is an object to provide a method.

[0014]

According to the method for manufacturing a bevel gear according to claim 1 of the present invention, when a bevel gear having different pitch circle diameters at both ends is manufactured by forging, the positions where the punch and the tooth profile die are divided are determined. Before the forging is performed on the gear material with the molding die set to be shifted toward the gear center side from the tooth bottom corresponding part on the top surface side where the pitch circle diameter of the tooth profile die is small, It is characterized in that preforming is performed such that a required amount of space is formed between the tooth blank die corresponding to the top surface side of the tooth bottom and the gear material at the start of forging.

Further, in the method for manufacturing a bevel gear according to claim 2 of the present invention, the bevel gears have different pitch circle diameters at both ends and have a back spherical surface on the end surface on the side where the pitch circle diameter is large, and at the bottom of the back spherical surface side. When manufacturing a bevel gear with a web formed by forging, using a forming die having a web forming portion,
It is characterized in that the gear material is forged by a forming die for forming the outer diameter of the back surface and the outer diameter of the web equally.

[0016]

In the method for manufacturing a bevel gear according to the first aspect of the present invention, the split position between the punch and the tooth profile die is set to be shifted toward the gear center side from the tooth bottom die corresponding portion on the top surface side of the tooth profile die. When performing forging forming on a gear material with a forming die, before performing this forging forming, for the gear material, at the start of forging forming by the forming die, the tooth bottom part corresponding to the top face side of the tooth profile die and the gear Since preforming is performed to form a required amount of space with the material, the burr formed at the dividing position of the forming die shifts to the gear center side rather than the tooth bottom on the top side of the bevel gear. When the center hole of the gear is formed, the burr can be removed at the same time when the center hole of the gear is formed, and the top surface of the tooth profile die is formed when the bevel gear is formed. Early in the part corresponding to the bottom of the tooth So that the resulting mold cracking of is prevented.

Further, in the method for manufacturing a bevel gear according to claim 2 of the present invention, when a bevel gear having a web formed on the root portion on the back spherical surface side is manufactured by forging to improve the strength of the gear, the web forming is performed. Since the gear material is forged using a molding die that has parts, and the outer diameter of the back surface is the same as the outer diameter of the web, the tooth back surface is reduced to reduce the machining process and machining allowance. Even when it is decided to shave only the back surface with black skin specification,
It is possible to prevent cracks from occurring in the tooth bottom portion of the tooth profile of the bevel gear which is the work.

[0018]

1 and 2 show an embodiment of a method for manufacturing a bevel gear according to the present invention. As shown in FIG. 1, an upper punch 11 and a tooth profile die (upper die) 12 are provided. , A lower die 13 and a lower punch 14 are used for forging the gear material 15 into a bevel gear shape by forging, and before the forging, as shown in FIG.
The gear material is preformed by a preforming die composed of an upper die 16, a lower die 17, and a lower punch 18 to form a preformed gear material 15.

Next, this preformed gear material 15 is shown in FIG.
It is charged into the forging die shown in Fig. 2, but the upper punch 11, the tooth die (upper die) 12, the lower die 13 and the lower punch 14 are used to forge the preformed gear material 15 in this way. At the start, a sufficient space S is formed between the preform gear material 15 and the tooth bottom portion corresponding portion 12a on the top surface side where the pitch circle diameter of the tooth profile die (upper die) 12 is small.

Then, with such a sufficient space S formed, the upper punch 11 and the tooth profile die (upper die) 12 are formed.
The bevel gear is formed by forging the preformed gear material 15 with the lower die 13 and the lower punch 14.

As described above, by forming a predetermined amount of sufficient space S between the tooth bottom portion corresponding portion 12a on the top surface side of the tooth profile die (upper die) 12 and the preformed gear material 15, A portion 12a corresponding to the tooth bottom where mold cracking was likely to occur
Since the timing at which the flesh of the molding material is stretched is delayed, and the flesh of the molding material is stretched from the lower side rather than from the inner diameter side at the tooth root corresponding portion 12a, the early portion at the tooth bottom corresponding portion 12a It is possible to prevent the mold from cracking.

3 to 7 show another embodiment of the method for manufacturing a bevel gear according to the present invention.

In the method for manufacturing a bevel gear according to this embodiment, when a pinion mate having a web for improving gear strength at the tooth bottom portion on the back spherical surface 21c side is manufactured by forging, as shown in FIG. The outer diameter of the back spherical surface 21c of the pinion mate forging gear material 21 having the portion 21a is made equal to the outer diameter of the web 21b.

When finishing the back surface 21 side, as shown in FIG. 4, it is possible to extend the surface processing of the conventional back surface 21c, and there is no interference with the differential case. In some cases, as shown in FIG. 5, the processing of the spherical surface of the back spherical surface 21c can be performed in the conventional manner and the outside thereof can be processed to escape.

FIG. 6 shows a forging die used in the present invention, which is composed of an upper die 23, a lower die 24, and a lower punch 25, and has a back spherical surface outer diameter and a web outer diameter of a forging material 27. Are molded equally.

Further, although FIG. 6 shows a forming die for single push closed forging, as shown in FIG. 7, it is also possible to use a double push closed forging forming die having an upper punch 26. In this case, Also, the outer diameter of the back surface of the forged material 27 and the outer diameter of the web are formed to be equal.

Therefore, the web 21b of the forging material 21
It is possible to obtain a pinion mate material with a web that does not cause cracks 52 at the tooth bottom portion of the work as shown in FIG. 14 by cold forging, and the tooth profile back surface has a black skin specification. It is possible to leave.

[0028]

In the method for manufacturing a bevel gear according to the first aspect of the present invention, the split position between the punch and the tooth profile die is set to be shifted to the gear center side from the tooth bottom die corresponding portion on the top surface side of the tooth profile die. When performing forging forming on a gear material with a forming die, before performing this forging forming, for the gear material, at the start of forging forming by the forming die, the tooth bottom part corresponding to the top face side of the tooth profile die and the gear Since preforming is performed to form a required amount of space with the material, the burr formed at the dividing position of the forming die shifts to the gear center side rather than the tooth bottom on the top side of the bevel gear. When the center hole of the gear is formed, it is possible to remove the burrs at the same time when the center hole of the gear is formed. On the top tooth side It is possible to prevent the early type cracking occurs Te.

Further, in the method for manufacturing a bevel gear according to a second aspect of the present invention, when a bevel gear having a web formed on the root portion on the back spherical surface side is manufactured by forging to improve the gear strength, the web forming is performed. Since the forging of the gear material is carried out with a forming die that has parts, and the outer diameter of the back surface and the outer diameter of the web are formed equally, the tooth profile back surface is reduced to reduce the machining process and machining allowance. Even when it is decided to shave only the back surface with black skin specification,
It is possible to prevent cracks from being generated in the tooth bottom portion of the tooth profile of the bevel gear, which is the workpiece, which is extremely advantageous.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of a forging mold for forging a preformed gear material according to an embodiment of the present invention.

FIG. 2 is a cross-sectional explanatory view of a preforming die that preforms a gear material in an example of the present invention.

FIG. 3 is an explanatory view showing a case where the outer diameter of the back spherical surface of the gear material and the outer diameter of the web are formed to be equal in another embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an example of finishing processing on the back spherical surface side.

FIG. 5 is an explanatory view showing another example of finishing processing on the back spherical surface side.

FIG. 6 is an explanatory view of a forging die used in another embodiment of the present invention.

FIG. 7 is an explanatory view of a forging die that can be used in another embodiment of the present invention.

FIG. 8 is a cross-sectional explanatory view showing a conventional forging die for manufacturing a bevel gear by closed forging.

9 is a cross-sectional explanatory view showing a state in which burrs are formed in the bevel gear rough-molded body molded by the forging mold of FIG.

FIG. 10 is a cross-sectional explanatory view showing a case where forging is performed with a forging die in which a division position of the tooth profile die is shifted toward a gear center side from a tooth bottom portion corresponding portion on the top surface side of the tooth profile die.

11 is a cross-sectional explanatory view showing a state in which burrs are formed in the bevel gear rough-molded body molded by the forging mold of FIG.

FIG. 12 is an explanatory cross-sectional view of a pinion mate having a web formed on a tooth bottom portion.

13 is a cross-sectional explanatory view showing a portion where a crack is likely to occur during processing of the pinion mate shown in FIG.

14 is an explanatory bottom view in the direction of arrow A in FIG.

[Explanation of symbols]

11 Upper Punch (Forging Mold) 12 Tooth Profile Die (Forging Mold) 12a Top Bottom Side Corresponding Part of Tooth Profile Die 13 Lower Die (Forging Die) 14 Lower Punch (Forging Die) 15 Preformed Gear Material 16 Upper mold (preforming mold) 17 Lower mold (preforming mold) 18 Lower punch (preforming mold) S Space between the tooth bottom part corresponding to the top side of the tooth profile die and the gear material 21 Gear material 21a Tooth profile 21b Web 21c Back spherical surface 23 Upper die (forging die) 24 Lower die (forging die) 25 Lower punch (forging die) 26 Upper punch (forging die)

Claims (2)

[Claims] 1. When manufacturing a bevel gear having different pitch circle diameters at both ends by forging, the split position of the punch and the tooth profile die is set to be smaller than that of the tooth bottom portion corresponding to the tooth bottom portion on the top surface side where the pitch circle diameter of the tooth profile die is small. Before forging the gear material with the forming die set to be shifted to the center side, for the gear material, at the start of forging by the forming die, the tooth bottom part corresponding to the top surface side of the tooth profile die and the gear material A method for manufacturing a bevel gear, which comprises performing preforming so that a required amount of space is formed between the bevel gear and the bevel gear. 2. When manufacturing a bevel gear having a back spherical surface on the end surface on the side having different pitch circle diameters and a large pitch circle diameter at both ends and forming a web on the tooth bottom portion on the back spherical surface side by forging, a web is used. Using a mold with a molding part,
A method for manufacturing a bevel gear, which comprises forging a gear material with a molding die for molding the outer diameter of the back surface and the outer diameter of the web equally.