JP3375041B2 - Gear forming method and forming apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear forming method and a gear forming apparatus used for forming a gear by a press.

[0002]

2. Description of the Related Art FIGS. 8 and 9 are views for explaining a conventional gear forming process. The illustrated gear 101 is
As shown in FIG. 9 (g), it has external teeth 101a and is hollow, and has a flange portion 101b on one side thereof.
Is integrally provided with a hollow shaft portion 101c through
A serration 101d is provided on the tip side of the shaft 101c.

To form the gear 101, the material is cut in a block B101 shown in FIG. 8 to prepare a gear material 100 shown in FIG. 9A, and the gear material 100 is heat-treated (annealed) in a block B102. , Block B
In step 103, the gear material 100 is shot blasted, and further in block B104, a lubrication process is performed, and then in block B105, the first cold forging (op1) is performed to form the gear material 100 in the shape shown in FIG. 9B. To mold.

After that, the heat treatment, shot blasting, lubrication treatment and cold forging shown in blocks B102 to B105 are repeated, and in the second cold forging (op2),
The hollow portion 100e is formed as shown in FIG. 9C, and in the third cold forging (op3), the shaft portion 100c is formed together with the entire forming as shown in FIG. 9D, and the fourth cold forging is performed. In (op4), the flange portion 100b is formed together with the entire forming as shown in FIG. 9 (e), and the fifth cold forging (o
In p5), as shown in FIG. 9 (f), the outer teeth 100a are formed together with the whole forming, and the final sixth cold forging (op
6), the gear material 100 is provided with the external tooth 101a, the flange portion 101b, the shaft portion 101c and the serration 101.
The gear 101 having d is molded. The appearance of the gear 101 molded in this way is visually checked in block B106, and the presence or absence of molding defects is confirmed.

[0005]

However, in the conventional gear forming as described above, since it is formed by cold forging, the number of forming steps is very large and a large-sized cold forging press device is used. There is a problem that is necessary, and the problem was to solve such a problem.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and it is possible to reduce the number of molding steps in molding gears by a press, and to reduce equipment and labor. It is an object of the present invention to provide a method for forming a gear that can achieve the above.

[0007]

According to a first aspect of the present invention, there is provided a method for forming a gear according to claim 1, wherein when forming the gear, the gear material is formed into a predetermined shape including a tooth portion by hot forging and then cooled. A method of forming a gear material into a gear by hot forging, wherein the tooth portion of the gear material formed in hot forging is ironed in cold forging, and the tooth tip surface is formed in ironing of the tooth portion of gear material. And a tooth bottom having an ironing amount smaller than an ironing amount of the tooth surface, wherein the gear has external teeth and is hollow, and in cold forging, a gear material formed into a hollow shape Is formed by enlarging the inner diameter of the gear, a white mold release agent to which a solid lubricant is added is used in hot forging as claimed in claim 3, and hot forging is carried out when molding a gear as claimed in claim 4. By gear A method of forming a gear material into a gear by cold forging after forming a material into a predetermined shape including a tooth portion, wherein the gear has a hollow shaft portion on one side through an inward flange portion. At the same time, the shaft portion has serrations and a small diameter portion at its tip, and the serration tip has a chamfered portion.In hot forging, a tapered portion having a small diameter on the tip side is formed on the outer periphery of the tip portion of the shaft portion. In the cold forging, a serration having a chamfered portion and a small diameter portion are formed in the cold forging, and in the cold forging, a serration having a chamfered portion and a chamfered portion having a chamfered portion are caused to flow inward in the cold forging. A structure for forming a portion,
Assuming that the angle of the chamfered part with respect to the line orthogonal to the axis of the gear is θ1 and the outer diameter of the small diameter part of the gear is φ1, the taper of the tapered part with respect to the line orthogonal to the axis of the shaft is hot forged. The angle θ2 is formed in the range of θ1 + 5 ° to θ1 + 15 °, and the diameter φ2 of the small diameter end of the taper portion is formed to φ1-1 mm. The above configuration serves as means for solving the conventional problems.

The cold forging in claim 1 includes ironing, sizing and drawing.

Further, in claim 6, in the hot forging, the angle θ2 of the taper portion with respect to the line orthogonal to the axis line of the shaft portion.
Is set to θ1 + 5 ° to θ1 + 15 ° because the angle θ2 is θ
If the angle is smaller than 1 + 5 °, the fluidity of the meat at the tip of the shaft (the portion where the serration and the small diameter part is formed) will be sufficient when forming the serration having a chamfered part on the shaft and the small diameter part in cold forging. This is because it may not be obtained, and buckling may occur in the continuous portion of the flange portion and the shaft portion, or shrinkage may occur in the valley portion of the serration tip. Further, if the angle θ2 is made larger than θ1 + 15 ° This is because the angle θ1 of the chamfered part to be finally formed becomes too large, the thickness of the chamfered part is insufficient, and the chamfered part may be lacking in thickness. Further, the reason why the diameter φ2 of the small diameter end of the taper portion is set to φ1-1 mm is to reduce the resistance of the tip end portion during cold forging to improve the formability, and when it is smaller than φ1-1 mm. This is because the resistance becomes too small and flesh is likely to occur.

Further, a molding apparatus according to claim 7 of the present invention can be used for carrying out the above-mentioned gear molding method, and is an apparatus for molding a hollow gear having external teeth, which is made of a gear material. Equipped with a punch to be inserted inside and a die into which the gear material is press-fitted together with the punch.As the setting of the ironing amount based on the distance between the punch and the die, the ironing amount of the tooth bottom surface rather than the ironing amount of the tooth tip surface and tooth surface Is made smaller.

[0011]

In the method for forming a gear according to the first aspect of the present invention, since the gear material including the tooth portion is formed into a state close to the completed dimension by the hot forging, the formation of the tooth portion is minimized. Can be formed by cold forging, whereby the number of forming steps can be significantly reduced, and the gear can be formed without using a large-sized cold forging press device. Further, in cold forging, the tooth profile accuracy of the tooth portion is obtained in the cold forging by ironing the tooth portion of the gear material formed by hot forging. Further, in the ironing process of the tooth portion of the gear material, the ironing amount of the tooth bottom surface was made smaller than the ironing amount of the tooth top surface and tooth surface. When the tooth bottom surface has a slightly rougher tooth profile accuracy than the tooth crest and tooth surface, the contact with the mold (for example, the die) that molds this is weakened, and galling against the mold Will be prevented.

[0012]

[0013]

In the gear forming method according to the second aspect of the present invention, the gear has external teeth and is hollow, and in cold forging, the hollow material is formed by expanding the inner diameter of the gear material. Since this is performed, a predetermined tooth profile accuracy can be obtained with a small ironing amount.

In the gear forming method according to the third aspect of the present invention, since the white mold release agent to which the solid lubricant is added is used in the hot forging, the lubricity is good, and the cold forging later is performed. As a gear material to be sent to, a gear material having a small draft can be obtained.

In the gear forming method according to the fourth aspect of the present invention, since the gear material including the tooth portion is formed into a state close to the completed dimension by the hot forging, the minimum shaping such as the tooth portion is formed. Can be performed by cold forging, which allows
The number of forming steps is significantly reduced, and the gear can be formed without using a large-sized cold forging press device. Further, the gear has a hollow shaft portion on one side through an inward flange portion, has a serration and a small diameter portion at its tip on the shaft portion, and has a chamfered portion at the tip of the serration. , When molding this gear,
By forming a taper portion having a small diameter on the tip side on the outer circumference of the tip portion of the shaft portion in hot forging, the fluidity of the meat at the tip portion of the shaft portion in cold forging is ensured. In other words, the length and diameter of the shank formed by hot forging may vary, and if the error becomes large, the tip of the shank will be cut when forming the serration on the shank during cold forging. The fluidity of the meat of the part is reduced, it is difficult to generate excess meat on the tip side, buckling occurs at the connecting part between the flange part and the shaft part, and shrinkage occurs at the valley part of the serration tip. Sometimes. On the other hand, in the gear forming method, since the tapered portion is formed on the outer periphery of the tip portion of the shaft portion in the hot forging, the fluidity of the meat at the tip portion of the shaft portion is increased in the cold forging, It is easy to form serrations, and excess thickness is likely to occur on the tip side.
Without causing molding defects such as buckling or shrinkage,
It is possible to form the serration having the chamfered portion on the shaft portion and the small diameter portion.

In the gear forming method according to the fifth aspect of the present invention, in cold forging, the meat at the tip of the shaft portion is caused to flow inward to form the serration having the chamfered portion and the small diameter portion. Also, the reduction rate of the cross-sectional area of the small-diameter portion is small, so that defective molding due to buckling stress at the time of pressing can be prevented.

In the method for forming a gear according to claim 6 of the present invention, when the angle of the chamfered portion with respect to the line orthogonal to the axis of the gear shaft is θ1 and the outer diameter of the small diameter portion of the gear is φ1, the heat In the cold forging, the angle θ2 of the taper portion with respect to the line orthogonal to the axis of the shaft portion is formed to be θ1 + 5 ° to θ1 + 15 °, and the diameter φ2 of the small diameter end portion of the taper portion is formed to φ1-1 mm. In the above, the fluidity of the meat at the tip of the shaft portion is not insufficient, and the chamfered portion does not become insufficiently thicker than the angle θ1 of the chamfered portion finally formed. Buckling of the continuous part of the flange part and shaft part, thinning of the valley part of the serration tip,
Alternatively, it is possible to prevent defective molding such as lack of thickness of the chamfered portion.

In the gear forming apparatus according to the seventh aspect of the present invention, cold forging is performed by the cooperation of the punch and the die, and when the external teeth are ironed as the cold forging, the hollow gear is punched by the punch. The inner shape of the material is retained or the inner diameter of the gear material is enlarged to achieve the desired tooth profile accuracy with a small amount of ironing.In addition, the amount of ironing based on the distance between the punch and the die is set. As the ironing amount of the tooth bottom surface is smaller than the ironing amount of the tooth top surface and the tooth surface, the tooth top surface and tooth surface that require particularly accurate tooth profile are formed with a sufficient ironing amount. If the tooth bottom surface has a slightly rougher tooth profile accuracy than the leading and tooth surfaces, the contact with the die is weakened to prevent galling.

[0020]

According to the gear forming method of the first aspect of the present invention, since the step of performing cold forging after hot forging is completed, the gear material including the tooth portion is completed by hot forging. It is possible to mold in a state close to the dimensions, and to perform minimum molding such as molding of teeth by cold forging, and the number of molding processes is significantly larger than the conventional method in which molding was performed only by cold forging. The gears can be sufficiently formed without using a large-sized cold forging press device, which shortens the manufacturing time, improves workability and productivity,
This will lead to equipment reduction, labor saving, and cost reduction. Further, particularly in cold forging, by ironing the tooth portion of the gear material formed by hot forging, a good tooth profile accuracy of the tooth portion can be obtained in the cold forging. Furthermore, it is possible to form the tooth top surface and tooth surface, which require particularly tooth profile accuracy, with a sufficient ironing amount. On the other hand, the tooth bottom surface, which has a slightly rougher tooth profile accuracy than the tooth top surface and tooth surface, can be formed. In this case, it is possible to prevent the die from being galled by weakening the contact with the die for molding the die, improve the releasability, and extend the life of the die.

[0021]

[0022]

According to the gear forming method of the second aspect of the present invention, the same effect as that of the first aspect can be obtained, and in the cold forging, the outer tooth and the hollow gear are formed. Since the forming is performed such that the inner diameter of the material is enlarged, a predetermined tooth profile accuracy can be obtained with a small ironing amount, which can contribute to further labor saving of the cold forging press device.

According to the gear forming method of the third aspect of the present invention, the same effects as those of the first and second aspects can be obtained, and in the hot forging, the white mold release containing the solid lubricant is added. By adopting the agent, the lubricity is enhanced, a gear material with a small draft can be obtained as a gear material to be sent to the subsequent cold forging, or a gear material having a shape closer to the finished size can be obtained. The load in the subsequent cold forging can be further reduced.

According to the gear forming method of the fourth aspect of the present invention, the same effect as that of the first aspect can be obtained in the molding of the flange portion, the shaft portion, the serration having the chamfered portion at the tip and the gear having the small diameter portion. Besides being able to obtain
By forming the tapered portion in the hot forging, the fluidity of the meat at the tip of the shaft can be improved in the cold forging even if the dimensions of the shaft after the hot forging vary. It is possible to accurately form serrations and small-diameter parts that have ridges, and prevent molding defects such as buckling of the continuous part of the flange part and shaft part, thinning of the valley part of the serration tip, or lack of chamfered parts. It is possible to mold high quality gears.

According to the gear forming method of the fifth aspect of the present invention, the same effect as that of the fourth aspect can be obtained, and in the cold forging, the serration with respect to the shaft portion and the disconnection of the small diameter portion are cut off. By reducing the area reduction rate, it is possible to prevent defective molding due to buckling stress at the time of push cutting,
It can contribute to further improvement of the quality of gears.

According to the gear forming method of the sixth aspect of the present invention, the same effects as those of the fourth and fifth aspects can be obtained, and in cold forging, the flow of the meat at the tip portion of the shaft portion can be achieved. As a result, it is possible to more reliably prevent defective molding, and it is possible to obtain a highly accurate gear having a flange portion, a shaft portion, a serration having a chamfered portion at the tip, and a small diameter portion.

According to the gear forming apparatus of the seventh aspect of the present invention, when the outer teeth are ironed by cold forging,
The inner shape of the hollow gear material can be securely held by the punch, or the inner diameter of the gear material can be expanded to obtain a predetermined tooth profile accuracy with a small ironing amount. As the ironing amount is set based on the interval between and, the ironing amount at the tooth bottom is made smaller than the ironing amount at the tooth tip surface and tooth surface. On the other hand, it is possible to form with a squeezing amount.On the other hand, on the tooth bottom surface where the tooth profile accuracy is slightly rough compared to the tooth tip surface and tooth surface, it is possible to weaken the contact with the die and prevent galling. It is possible to improve the moldability and the life of the die.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a gear forming method and a gear forming apparatus according to the present invention will be described below with reference to the drawings. Figure 2
The gear 1 of this embodiment shown in (c) is used, for example, as a hub assembly high clutch in an automatic transmission of an automobile, and has outer teeth 2 as teeth and is hollow. , The flange part 3 on one side
The hollow shaft portion 4 is integrally provided via the
Serration 5 is provided on the tip side of the. Further, the serration 5 has a small diameter portion 6 further on the tip side.

To form the gear 1, the material is cut in a block B1 to obtain an initial gear material (see FIG. 9A), as shown in FIG. After this, block B
After the hot forging is performed in No. 2 and the shot blasting of the block B3 and the lubrication process of the block B4 are finished, the cold forging of the block B5 is performed. In this embodiment, for the purpose of molding the gear 1 having the shaft portion 4 described above, as a step of cold forging, cold axial drawing of the block B6 and cold sizing of the block B7 are performed, and particularly cold rolling is performed. In the sizing, the outer teeth 2 and the serrations 5 that are tooth portions are ironed. Gear 1 molded in this way
The presence or absence of a molding defect is confirmed by visually observing the appearance of the block B8.

In the above-mentioned forming process, the gear material 11 hot-forged as shown in FIG. 2 (a) has an external tooth 12 as a tooth portion having a predetermined front shape, a flange portion 13 and a shaft portion 14. Has been molded, and the shape is close to the final size. As described above, in the hot forging, the gear material cut from the material is formed into the shape of the gear material 11 shown in FIG. 2A. The heat treatment, the shot blasting, and the lubrication treatment are repeated as in the cold forging. Compared with the case, the number of steps can be reduced.

Further, in the hot forging, a white mold release agent having a high lubricating performance, to which a solid lubricant such as boron nitride is added, is used, which allows the gear material to be sent to the subsequent cold forging to have a declination gradient. Less gear material 11 is obtained.

Next, the gear material 11 formed by hot forging
As shown in FIG. 2 (b), the cold shaft drawing is performed.
In this case, the shaft portion 14 is formed by reducing its thickness and extending it in the axial direction. The molding of only the shaft portion 14 can be performed without using a large-sized cold forging press device that performs cold forging as a whole.

After that, the gear material 11 is finally cold-sized by the cold forging press device shown in FIG. FIG. 5 shows an embodiment of a molding apparatus that can be used for carrying out the gear molding method and a gear molding apparatus according to the present invention.

The cold forging press device comprises a lower fixed die 2
1, the die 22 is provided, and the upper movable die 23 is provided with a punch 24. The die 22 has a plurality of blocks 22.
a to 22e are combined and these blocks 22
The die case 25 holds the entire circumference of the side portions a to 22e. A push-out mechanism 26 is provided below the die 22. The push-out mechanism 26 has a plurality of knockout pins 27a to 27 for pushing out the work.
c is provided.

As shown in FIG. 3, the die 22 has a molding concave portion 28 corresponding to the outer shape of the gear material (11). The molding concave portion 28 is a shaft portion (1) of the gear material (11).
4) has a molding portion 28a of the inner toothed serration 5 at a position corresponding to the tip side, and a molding portion 28b of the small diameter portion 6 continuous to the molding portion 28a is provided. Internal teeth 28c are provided for ironing the external teeth (12) which are the parts.

The punch 24 has a molding portion 24a corresponding to the inner shape of the gear material (11) and is equipped with a mandrel 29 in a state of protruding downward on the axis, and the protruding portion of the mandrel 29 is the shaft portion. It corresponds to the molding part of (14). Further, the punch 24 is provided with a step portion 30 having a diameter smaller than that of the main body portion at the tip of the mandrel 29. As a result, when the punch 24 is completely pressed, the shaft portion (1
The meat at the tip of 4) is allowed to flow into the step portion 30 and the shaft portion (1
The serration 5 and the small-diameter portion 6 with respect to 4) are formed into a shape in which the reduction rate of the cross-sectional area is small to prevent defective molding due to buckling stress at the time of push cutting.

Further, in the die 22 and the punch 24, as the setting of the ironing amount based on the distance between them, as shown in FIG. 4, the ironing amount of the tooth bottom surface 2c is larger than the ironing amount of the tooth top surface 2a and the tooth surface 2b. It is designed to be small. That is, with respect to the shape after hot forging shown by an imaginary line in FIG.
The interval between the die 22 and the punch 24 is set so that the shape after cold forging shown by the solid line in FIG. 4 is obtained,
In other words, the gear material after hot forging (1
(1) is ironed using a die having internal teeth shown by solid lines. In FIG. 4, the distance between the virtual line and the solid line on the tooth bottom surface 2c is smaller than that of the other portion, and the tooth bottom surface 2c
This indicates that the ironing amount is small.

When the gear material 11 is formed by the cold forging press forming apparatus having the above structure, the gear material 11 is set in the forming recess 28 of the die 22 and then the punch 24 is lowered to remove the gear material 11 from the gear material 11. By press-fitting the gear material 11 into the molding recessed portion 28 by press-fitting the gear material 11 into the forming recess 28, the inside of the gear material 11 is squeezed by the punch 24 and at the same time, the outer teeth 12 are ironed. And then punch 2
When the punch 4 is lowered, the molding of the serration 5 is started, and when the punch 24 is finally pushed down, the serration 5 and the small diameter portion 6 are molded on the tip side of the shaft portion 14, and the outer tooth 2, the flange portion 3 and the shaft portion are formed. The gear 1 having 4 is completed.

As described in the above embodiment, in the gear forming method, the gear material 11 including the tooth portion is formed into a state close to the completed dimension by hot forging, so that the outer tooth 2 which is the tooth portion is formed. Minimal molding such as molding of is performed by cold forging,
In the same cold forging, the tooth profile accuracy of the outer teeth 2 can be obtained by ironing, which significantly reduces the number of forming steps and allows the gear 1 to be formed without using a large cold forging press device. obtain.

Further, in the gear forming method and the gear forming apparatus, the punch 24 holds the inner shape of the hollow gear material 11 when ironing the outer teeth 2 (12) which are the tooth portions by cold forging. Alternatively, the inner diameter of the gear material 11 is enlarged so as to obtain a predetermined tooth profile accuracy with a small ironing amount, and further, the tooth bottom surface 2c of the tooth bottom surface 2a and the tooth surface 2b has a smaller toothing amount than the tooth surface 2c. Since the ironing amount is set to be small, the tooth top surface 2a and the tooth surface 2b, which are particularly required for the tooth profile accuracy, are formed with a sufficient ironing amount, and the tooth profile accuracy is higher than that of the tooth top surface 2a and the tooth surface 2b. If the tooth bottom surface 2c is slightly rough, the contact with the die 22 is weakened, and in particular, galling is prevented in the continuous portion A of the tooth surface 2b and the tooth bottom surface 2c shown in FIG.

FIGS. 6 and 7 are views for explaining another embodiment of the gear forming method according to the present invention.

The gear 1 shown in FIG. 6 (c) has the same structure as the gear described in the previous embodiment (see FIG. 2 (c)), and has external teeth 2 as tooth portions. In addition, it is hollow and has a hollow shaft portion 4 coaxially on one side thereof with an inwardly facing flange portion 3 interposed therebetween, and a serration 5 is provided on the outer periphery of the tip end side of the shaft portion 4. Further, a chamfered portion 5a is provided at the tip portion of the serration 5, and a small diameter portion 6 whose outer circumference corresponds to the valley portion of the serration 5 is provided further on the tip side of the serration 5.

In order to form the gear 1 described above, the material is cut to obtain an initial gear material, as in the previous embodiment.
The gear material 11 shown in FIG. 6A is formed by hot forging. The gear material 11 includes external teeth 12 and a flange portion 13.
And the shaft portion 14 is formed. Further, the gear material 11 has a taper portion 1 having a small diameter on the outer periphery of the tip end portion of the shaft portion.
7 is formed.

The tapered portion 17 of the gear material 11 has a chamfered portion 5 with respect to a line orthogonal to the axis C of the shaft portion 4 of the gear 1.
When the angle of a is θ1, the angle θ2 of the shaft portion 14 with respect to the line orthogonal to the axis C is in the range of θ1 + 5 ° to θ1 + 15 °. Further, when the outer diameter of the small diameter portion 6 of the gear 1 is φ1, the diameter φ2 of the small diameter end of the tapered portion 17 is φ1-1 mm.

The hot forging described above is carried out by the hot forging press device shown in FIG. The hot forging press machine is
A punch 41 corresponding to the inner shape of the gear material 11 and a die 43 having a molding recess 42 corresponding to the outer shape of the gear material 11 are provided. The punch 41 includes a mandrel 44 that is in a penetrating state inside the shaft portion 14. Die 43
Includes an inner tooth 45 forming the outer tooth 12 and a shaft hole 46 forming the shaft portion 14 between the mandrel 44 and the like, and a taper portion 17 is formed at a predetermined position in the shaft hole 46. It has an upward facing step portion 47 for. A knockout member 48 for pressing the tip end of the shaft portion 14 to push the gear material 11 out of the die 43 is housed in the shaft hole 46.

Then, the gear material 11 obtained by the hot forging press device is subjected to shot blasting and lubrication treatment, and then, as a first step of cold forging, as shown in FIG.
As shown in (b), cold shaft drawing is performed to extend the shaft portion 14 and reduce the wall thickness of the coaxial portion 14, and then, as the second step of cold forging, the outer teeth 12 and the serrations are formed. Ironing of 5 and small diameter part 6 (cold sizing)
As a result, the gear 1 having the outer teeth 2, the flange portion 3, the shaft portion 4, the serration 5 having the chamfered portion 4a at the tip and the small diameter portion 6 is obtained as shown in FIG. 6 (c).

Here, the above ironing process is performed by the cold forging press device (see FIGS. 3 and 5) described in the previous embodiment, and is provided with the mandrel (29) having the step portion (30). With the punch (24), the serration 5 and the small diameter portion 6 having the chamfered portion 5a are formed in a state where the meat at the tip of the shaft portion 14 is caused to flow inward. In this way, by letting the meat at the tip of the shaft portion 14 flow out inward, the cross-sectional area reduction rate of the portion of the serration 5 and the small diameter portion 6 with respect to the shaft portion 4 becomes small, and molding failure due to buckling stress at the time of push-cutting occurs. Is prevented.

Further, in the method for forming a gear, in the hot forging, the tapered portion 17 having a small diameter on the tip side is formed on the outer periphery of the tip portion of the shaft portion 14 of the gear material 11, so that the shaft in the subsequent cold forging is formed. The fluidity of the meat at the tip of the portion 14 is secured. That is, in the hot forging, the length and diameter of the shaft portion 14 may vary in dimension. In this case, when the shaft portion 14 is pushed into the serration forming portion (reference numeral 28a in FIG. 3) in cold forging, the shaft portion 1
No. 4 tip part (formation part of serration and small diameter part)
The fluidity of the meat is reduced, excess thickness is less likely to occur on the tip side, buckling occurs at the connecting portion between the flange portion and the shaft portion, and shrinkage occurs at the valley portion at the tip of the serration 5. I have something to do.

Therefore, in the gear forming method, the taper portion 17 is formed on the outer periphery of the tip end portion of the shaft portion 14 in the hot forging, and at this time, the angle θ2 of the taper portion 17 is set to the angle θ1 of the chamfered portion 5a. By forming it from θ1 + 5 ° to θ1 + 15 ° and forming the diameter φ2 of the small diameter end portion of the taper portion 17 to φ1-1 mm with respect to the outer diameter φ1 of the small diameter portion 6, the tip portion of the shaft portion 14 in cold forging is formed. The fluidity of the meat is increased and made appropriate to facilitate the formation of the serrations 5 and also to allow excess thickness to easily occur on the tip side, which causes molding defects such as buckling and shrinkage. Without this, the serration 5 and the small diameter portion 6 having the chamfered portion 5a can be formed on the shaft portion 4.

Here, several gear materials are formed by making the angle θ2 of the taper portion 17 different by hot forging, and a gear having an R shape which approximates the angle θ1 of the chamfered portion 5a instead of the taper portion 17. A raw material was formed, and cold forging (cold axial drawing and cold sizing) was performed on these to form a serration 5 having a chamfered portion 5a and a small diameter portion 6. The diameter φ2 of the small diameter end of the tapered portion 17 was φ1-1 mm. In the process of cold forging,
In the cold axial stop, θ2 was about −10 ° with respect to θ1. Further, the R-shaped one was in a state close to a sharp corner in the cold shaft drawing. Then, for each gear material, the presence or absence of defective molding after cold sizing was confirmed.
The results are shown in the table below

[Table 1]

As is apparent from the table, the taper portion 17 having the angle θ2 equal to the chamfer angle θ1 and the one having the R shape have buckling at the continuous portion of the flange portion 13 and the shaft portion 14. , There was shrinkage at the valley of the serration tip. This is because the fluidity of the meat at the tip portion of the shaft portion 14 (the portion where the serration 5 and the small diameter portion 6 are formed) is insufficient. Further, the angle θ2 of the taper portion 17 is set to θ1 + 2
When the angle was 0 °, the chamfered portion 5a was lacking in thickness. This is because the angle θ2 of the tapered portion 17 becomes larger than the angle θ1 of the chamfered portion 5a to be finally formed, and the thickness of the chamfered portion 5a is insufficient. It was confirmed that the taper portion 17 having the angle θ2 of θ1 + 5 ° to θ1 + 15 ° had no defective molding.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a method of molding a gear according to the present invention.

FIG. 2 is a cross-sectional view illustrating a gear material (a) formed by hot forging, a gear material (b) subjected to axial drawing, and a gear (c) obtained by cold sizing.

FIG. 3 is a cross-sectional view illustrating a gear, a punch and a die in cold forging.

FIG. 4 is a partial horizontal sectional view of a gear explaining a shape after cold forging with respect to a shape after hot forging.

FIG. 5 is a cross-sectional view illustrating the entire cold forging press device.

FIG. 6 shows a gear material (a) formed by hot forging, a gear material (b) subjected to cold axial drawing, and a gear (c) obtained by cold sizing in the gear forming method according to the present invention. It is each sectional drawing explaining.

FIG. 7 is a cross-sectional view of a main part for explaining a hot forging press device.

FIG. 8 is a block diagram illustrating a conventional method of forming a gear.

9A and 9B are side views (a) and (b) and sectional views (c) to (g) illustrating a process of forming a gear material obtained by cutting a material into a gear in a conventional gear forming method.

[Explanation of symbols]

1 gear 2 External teeth (tooth) 2a Tooth surface 2b tooth surface 2c Bottom of tooth 3 Flange part 4 shafts 5 serrations 5a Chamfer 6 Small diameter part 11 gear material 12 External teeth (tooth part) of gear material 13 Flange part of gear material 14 Shaft part of gear material 17 Tapered part 22 die 24 punch

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Akio Ota No. 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Atsushi Ikeuchi No. 2, Takara-cho, Kanagawa-ku, Yokohama Nissan Automobile Co., Ltd. (56) Reference JP-A-7-132342 (JP, A) JP-A-6-79392 (JP, A) JP-A-63-112038 (JP, A) JP-A-3-124340 (JP , A) JP 59-89395 (JP, A) JP 55-75839 (JP, A) JP 52-93649 (JP, A) JP 9-108771 (JP, A) (58) Fields studied (Int.Cl. ⁷ , DB name) B21J 1/00-13/14 B21J 17/00-19/04 B21K 1/00-31/00

Claims (7)

(57) [Claims] 1. A method for forming a gear into a gear by hot forging after forming the gear material into a predetermined shape including a tooth portion by hot forging. Characterized by ironing the teeth of the formed gear material in cold forging, and by ironing the teeth of the gear material, the ironing amount of the tooth bottom surface was made smaller than the ironing amount of the tooth top and tooth surfaces. And method of forming gears. 2. The gear has external teeth and is hollow,
The method for forming a gear according to claim 1, wherein, in the cold forging, forming is performed by enlarging the inner diameter of the gear material formed into a hollow shape. 3. The method for forming a gear according to claim 1, wherein a white mold release agent containing a solid lubricant is used in hot forging. 4. A method of forming a gear into a gear by hot forging after forming the gear material into a predetermined shape including a tooth portion, and then forming the gear material into a gear by cold forging. In addition to having a hollow shaft part through an inward flange part, the shaft part has a serration and a small diameter part at its tip and a chamfered part at the tip of the serration. A method for forming a gear, characterized in that a taper portion having a small diameter on the tip side is formed on the outer periphery of the tip portion, and serrations having a chamfered portion on the shaft portion and a small diameter portion are formed in cold forging. 5. The method for forming a gear according to claim 4, wherein in the cold forging, the meat at the tip of the shaft portion is caused to flow inward to form the serration and the small diameter portion having the chamfered portion. 6. The angle of the chamfer with respect to a line orthogonal to the axis of the gear shaft is θ1, and the outer diameter of the small diameter part of the gear is φ1.
In the case of, the angle θ2 of the taper part with respect to the line orthogonal to the axis of the shaft part in the hot forging is θ1 + 5 ° to θ1 + 15.
The diameter of the small diameter end of the taper part to φ1-1.
The method for molding a gear according to claim 4 or 5, wherein the gear is formed to have a thickness of mm. 7. A device for forming a hollow gear having external teeth, comprising a punch to be inserted inside a gear material and a die into which the gear material is press-fitted together with the punch, and a gap between the punch and the die. As a setting of the ironing amount based on, the gear forming device is characterized in that the ironing amount of the tooth bottom surface is smaller than the ironing amount of the tooth top surface and the tooth surface.