JP7600304B2 - Rolling Dies - Google Patents

Description

The present invention relates to a rolling die.

Conventionally, in the manufacture of metal splines, serrations, gears, screws, lead screws, worms, etc., rolling has been widely used in which a roughly cylindrical rolled material is clamped between rolling dies on which rolling teeth (machined teeth) are formed, and the outer periphery of the rolled material is plastically deformed while applying pressure to form the desired tooth shape.

Compared to cutting, this rolling process has the advantages of being highly productive and ideal for mass production, the hardness and strength of the surface of the rolled product increases due to work hardening, and the burnishing effect between the rolling die's teeth and the rolled material results in good surface roughness of the rolled product.

Splines and serrations are also widely used in automotive parts such as drive shafts and steering shafts, and with the recent demand for lighter automobiles, there is an increasing demand for products such as the above splines (rolled products) not only as solid products, but also as hollow products with a circular cross-section hole aligned with the central axis of an approximately cylindrical shape.

However, if the material to be rolled is made hollow and rolling is performed on the outer surface of this hollow material, the material to be rolled will elongate and deform in the circumferential and axial directions, making it impossible to obtain a product with the desired tooth shape. Also, if the rolling load is too large, the material to be rolled may crack.

In order to prevent the material to be rolled (hollow material) from being stretched and deformed in the circumferential and axial directions as much as possible, a method has been used in which a rod-shaped core (sometimes called a mandrel) is inserted into a hole along the central axis of the roughly cylindrical shape before rolling. However, there is a problem in that it is difficult to obtain a product with the desired tooth shape simply by using a core.

In addition, the chamfer of a typical rolling flat die, which has a chamfer, a finishing portion, and a clearance portion, or a rolling notched circular die (a rolling die shaped like a cylinder with a portion of its outer periphery cut out) is formed so that the amount of pressing of the processed teeth into the rolled material (amount of processing) increases as the rolling process progresses in the chamfer (towards the end of the rolling direction); for example, in a rolling flat die, the processed teeth of the chamfer are arranged so that the tooth tip line of the processed tooth (the imaginary line connecting the tooth tips of the processed teeth) is inclined so that it approaches the rolled material as it moves from the start of the rolling direction to the end of the rolling direction.

Attempts have been made to prevent the material being rolled (hollow material) from elongating in the circumferential and axial directions by making the inclination of the tooth tip line of the cutting teeth at this biting portion gentler and gradually applying the rolling load to the material being rolled. However, this did not solve the problem of the difficulty in obtaining a product with the desired tooth shape, and there was also the problem that the length of the biting portion needed to be increased, which meant that the rolling dies had to be made larger.

For this reason, when manufacturing hollow products such as those described above, a typical manufacturing method involves rolling a roughly cylindrical solid material to form the desired tooth shape, such as a spline, and then drilling a circular cross-section hole along the central axis of the roughly cylindrical shape to create a hollow product. However, this method has the problem of increasing manufacturing costs due to the additional hole drilling process.

As a result, methods for rolling hollow materials have been proposed, such as those shown in Patent Documents 1 and 2.

JP 2014-054644 A JP 2002-143970 A

The above-mentioned Patent Document 1 discloses a method of rolling a hollow material in which a group of hard balls is placed in a through hole of a hollow material that has a through hole that communicates with two end openings, jigs are inserted from the two end openings, the hollow material is positioned while the group of hard balls is pressurized with the two jigs, the tooth-shaped surface of a rolling die is pressed against the outer periphery of the hollow material to roll the outer periphery of the hollow material, and after rolling, the group of hard balls is removed from the through hole to produce a hollow rolled product.

However, this method uses a group of hard balls instead of a rod-shaped one with a circular cross section (a so-called round bar) as the core metal, and requires a process of placing the group of hard balls in the through hole of the hollow material, a process of positioning the hollow material while applying pressure to the group of hard balls, and a process of removing the group of hard balls from the through hole after rolling. This results in a problem of excessive processing time, and does not take advantage of the advantages of rolling, which is excellent for mass production and is optimal for mass production.

The above-mentioned Patent Document 2 also discloses a method for manufacturing a hollow gear, in which an inner mandrel having concave and convex portions on its outer circumferential surface that extend axially parallel to each other and are continuously arranged in the circumferential direction is inserted into the central axial hole of a cylindrical workpiece, and the tooth-shaped processing surface of a rolling die is pressed against the outer circumferential surface of the workpiece while rotating the workpiece together with the inner mandrel, thereby rolling-forming the teeth on the outer circumferential surface. Since the convex portions on the outer circumferential surface of the inner mandrel are pressed against the inner circumferential surface of the workpiece while rolling-forming, the circumferential flow of material on the inner circumferential surface of the workpiece can be restricted by the convex portions, and the circumferential length of the workpiece can be suppressed from increasing in the circumferential direction.

However, with this method, because the protrusions on the outer periphery of the inner mandrel (core metal) are pressed against the inner periphery of the workpiece during roll forming, not only does the inner periphery of the workpiece deform, but the dimensional specifications for the inner diameter of the workpiece may not be met. In addition, removing the workpiece from the inner mandrel (core metal) takes time, and sometimes it is even impossible to remove it.

The present invention was developed in consideration of the current situation, and aims to provide a rolling die that can minimize the circumferential and axial elongation deformation of the material being rolled in the rolling process of hollow materials, without enlarging the size of the rolling die or using a core bar with a special configuration during rolling, and can produce a product with the desired tooth profile.

The gist of the present invention will be explained with reference to the attached drawings.

A rolling die has a chamfering portion 2, a finishing portion 3, and a relief portion 4, each of which is provided with processing teeth 5, from the starting end of the rolling direction of a die body 1 toward the terminal end of the rolling direction, and these processing teeth 5 plastically deform the outer circumferential surface of a rolled material W to roll a desired tooth profile. From the starting end of the chamfering portion 2 to a predetermined position in the rolling direction of the chamfering portion 2, each processing tooth 5 is provided with a plurality of grooves 6 inclined at a predetermined inclination angle α with respect to the rolling direction in a plan view, and the grooves 6 form a plurality of divisions. The rolling die is characterized in that cutting teeth 5a are formed, each of which is arranged so as to have a phase difference in the width direction of the die body 1 in the rolling direction , and a gradual decrease portion 7b is provided in a predetermined range on the rolling direction terminal side of the cutting tooth area 7 where the cutting teeth 5a are provided, and this gradual decrease portion 7b is configured so that the groove depth D of the groove 6 gradually becomes shallower and the groove width W2 of the groove 6 gradually becomes narrower toward the rolling direction terminal .

In addition, in the rolling die described in claim 1, the cutting processing teeth 5a are arranged with a phase difference in the cutting processing tooth area 7 in which the cutting processing teeth 5a are arranged so that the entire rolling width of the rolled material W is processed.

The rolling die described in claim 1 is characterized in that the groove 6 is provided from the start position of the chamfer 2 to a position that is 60% to 95% of the length L2 of the chamfer 2.

The rolling die described in claim 2 is characterized in that the groove 6 is provided from the start position of the chamfer 2 to a position that is 60% to 95% of the length L2 of the chamfer 2.

The rolling die described in claim 1 is characterized in that the groove 6 is provided from a position a predetermined distance away from the start of the chamfer 2 to a position that is 60% to 95% of the length L2 of the chamfer 2.

The rolling die described in claim 2 is characterized in that the groove 6 is provided from a position a predetermined distance away from the start of the chamfer 2 to a position that is 60% to 95% of the length L2 of the chamfer 2.

The present invention also relates to a rolling die as described in any one of claims 1 to 6 , characterized in that the tooth width W1 of the cutting tooth 5a is configured to be 3.3 mm or less, and the grooves 6 are arranged at equal intervals in the tooth trace direction of the cutting tooth 5a.

The present invention also relates to a rolling die according to any one of claims 1 to 6 , characterized in that the inclination angle α is 0.35° to 7.10°.

The present invention relates to a rolling die as set forth in claim 7, wherein the inclination angle α is 0.35° to 7.10°.

The present invention relates to a rolling die according to any one of claims 1 to 6 , characterized in that the groove 6 is provided in a straight line in a plan view.

In addition, the present invention relates to a rolling die as recited in claim 7 , characterized in that the groove 6 is provided in a straight line when viewed from above.

The present invention relates to a rolling die as recited in claim 8, wherein the groove 6 is provided in a straight line in a plan view.

The present invention relates to a rolling die as recited in claim 9, wherein the grooves 6 are provided in a straight line in a plan view.

As the present invention is configured as described above, it is possible to provide a rolling die that can minimize the elongation and deformation of the rolled material in the circumferential and axial directions and produce a product with the desired tooth profile without enlarging the size of the rolling die or using a core bar with a special configuration during rolling of hollow materials.

1A and 1B are an explanatory plan view and an explanatory front view showing the present embodiment. FIG. 4 is an explanatory plan view showing a cutting tooth region of the chamfering portion of the present embodiment. FIG. 4 is an explanatory side view showing the grooves and the cutting teeth of the present embodiment. 3A and 3B are explanatory front and side views showing the chamfering portion of the present embodiment. FIG. 4 is an explanatory plan view showing a tapered portion of the chamfering portion of the present embodiment. FIG. 10 is an explanatory diagram showing the machining teeth (cutting machining teeth) for machining the first groove of the rolled material in this embodiment. 13 is a graph showing the measurement results of the over-pin diameter in Experiment 1. 1 is a graph showing measurement results of root diameter in Experiment 1. 13 is a graph showing measurement results of a cumulative pitch error in Experiment 1. 1 is a graph showing measurement results of tooth space runout in Experiment 1. 1A and 1B are an explanatory side view and an explanatory plan view showing grooves and cutting teeth of another example of this embodiment (a type in which the groove depth is shallow). FIG. 2 is a schematic explanatory diagram of the rolling process using the present embodiment (flat rolling die). 1A is a schematic explanatory diagram of a rolling process using another example of this embodiment (when applied to a rolling missing circular die), and FIG. 1B is an exploded plan view of a main part. FIG. 11 is an explanatory diagram showing the machining state of the first groove of the rolling material when this embodiment is used. FIG. 11 is an explanatory diagram showing the machining state of the first groove of the rolling material when this embodiment is used. FIG. 11 is an explanatory diagram showing the machining state of the first groove of the rolling material when a conventional example is used. 13 is a graph showing the measurement results of the over-pin diameter in Experiment 3. 13 is a graph showing the measurement results of the root diameter in Experiment 3. 13 is a graph showing measurement results of tooth profile error in Experiment 3. 13 is a graph showing measurement results of tooth trace error in Experiment 3. 13 is a graph showing measurement results of a cumulative pitch error in Experiment 3. 13 is a graph showing measurement results of tooth space runout in Experiment 3. FIG. 11 is an explanatory plan view showing another example of the present embodiment (a type in which the dividing tooth region is provided at a predetermined distance from the start end of the biting portion).

The preferred embodiment of the present invention will be briefly explained below, showing the operation of the invention based on the drawings.

In the present invention, from the start of the biting portion 2 to a predetermined position in the rolling direction of the biting portion 2, each processing tooth 5 is provided with a plurality of grooves 6 that are inclined at a predetermined inclination angle α with respect to the rolling direction in a plan view, and the processing tooth 5 is divided by the grooves 6 to form a plurality of dividing processing teeth 5a, and each dividing processing tooth 5a is arranged so that it has a phase difference in the width direction of the die body 1 in the rolling direction (the dividing processing teeth 5a adjacent to each other in the rolling direction are shifted in the tooth trace direction rather than along the rolling direction), so that in the dividing processing tooth region 7 of the biting portion 2, the rolled material W is intermittently processed, and further, the processing load is concentrated on the tooth tips of the dividing processing teeth 5a, which have a smaller pressing area than the processing teeth 5, and even when rolling a rolled material W that is a hollow material with a thin wall thickness, the elongation deformation in the circumferential and axial directions of the rolled material W can be suppressed as much as possible.

In other words, in conventional rolling dies of this type, as shown in FIG. 16, the entire tooth tips of the processing teeth 25 extending in the tooth trace direction of the die body 21 are pressed into the tooth grooves of the rolled material W, so when the rolled material W is a hollow material with a thin wall thickness, the action of the material swelling up in the tooth grooves of the die, as when processing a solid material, does not work well, and therefore, if a core bar is not used, it will be crushed in the radial direction, and even if a core bar is used, the rolled material W will deform in the axial and circumferential directions, making it impossible to plastically process it to the specified tooth shape. However, in the present invention, for example, as shown in FIG. 14 and FIG. 15, the pressing position of the cutting processing teeth 5a into the rolled material W moves sequentially in the tooth trace direction as the rolling process progresses, and intermittent processing is performed, and further, the area into which the rolled material W is pressed becomes smaller, and the processing load is concentrated on the tooth tips of each cutting processing tooth 5a, improving the swelling of the material W and making it possible to form it into the desired shape. As a result, even if the material W to be rolled is a hollow material with a thin wall thickness, it is possible to suppress elongation deformation in the circumferential and axial directions.

Specific examples of the present invention will be described with reference to the drawings.

This embodiment relates to a rolling die having a cutting section 2, a finishing section 3, and a clearance section 4, each of which is provided with processing teeth 5, from the starting end of the rolling direction of the die body 1 toward the terminal end of the rolling direction, and which uses these processing teeth 5 to plastically deform the outer circumferential surface of the material W to be rolled, thereby rolling the desired tooth shape. Specifically, this embodiment applies the rolling die of the present invention to a rolling flat die for rolling splines, serrations, gears, etc.

The components of this embodiment are described in detail below.

In this embodiment, as shown in Figure 1, the die body 1 is formed in a rectangular shape in a plan view, the bottom surface 8 is formed as a flat surface that serves as a reference surface, and the upper surface located opposite this bottom surface 8 is provided with a large number of processing teeth 5 that form a tooth profile in the rolled material W, and the tooth tip lines of these processing teeth 5 (imaginary lines connecting the tooth tips of the processing teeth 5) are shown by solid lines in the explanatory front view of Figure 1 (the lower diagram of Figure 1).

In addition, in order to prevent slippage of the rolled material W (prevention of misalignment of the rolled material W relative to the processing teeth 5), the die body 1 of this embodiment is shot blasted over a predetermined range from the start of the rolling direction to the end of the rolling direction on the upper surface of the die where the processing teeth 5 are provided (in this embodiment, the shot blasting is applied over a range of approximately 2/3 of the length (total length) of the biting portion 2 indicated by reference symbol L2 in the figure (range indicated by reference symbol SB in the figure). Note that reference symbol L1 in the figure indicates the sum of the rolling direction ranges (lengths) of the biting portion 2, the finishing portion 3, and the relief portion 4.

This embodiment is a rolling die for machining normal splines (splines in which the teeth are formed parallel to the axial direction of the material W to be rolled), and in the die body 1, the machining teeth 5 of the lead portion 2, the finishing portion 3, and the relief portion 4 are formed in a mountain shape (approximately trapezoidal) when viewed from the front, and are configured as linear machining teeth that extend linearly in the width direction of the die body 1, specifically, in a direction perpendicular to the rolling direction, and are arranged side by side at a predetermined interval in the rolling direction. By making the extension direction of the machining teeth 5 inclined with respect to the direction perpendicular to the rolling direction, the present embodiment can be applied to rolling dies for machining helical splines, helical gears, etc.

Specifically, the machining teeth 5 of the cutting portion 2 are configured so that the tooth height gradually increases from the start side of the rolling direction toward the end side of the rolling direction, gradually pushing into the outer periphery of the rolled material W and forming a raised tooth profile. The machining teeth 5 of the finishing portion 3 are set to a constant tooth height (approximately the same tooth height as the machining teeth 5 at the end of the cutting portion 2) and are configured so that the tooth profile formed by the cutting portion 2 is finished to the product dimensions. The machining teeth 5 of the relief portion 4 are provided on an inclined surface that slopes downward toward the end side of the rolling direction, and are configured so that the position of the tip surface gradually decreases as it approaches the end side of the rolling direction.

As shown in FIG. 1, the biting portion 2 in this embodiment is configured in a dividing tooth region 7 in which a plurality of dividing teeth 5a are provided, with each tooth 5 being divided in the width direction of the die body 1 by a plurality of grooves 6 from the starting position to a predetermined position in the rolling direction. Note that the symbol X in the figure indicates the rolling direction range (length) of the dividing tooth region 7.

In the dividing tooth region 7, as shown in FIG. 2, the dividing teeth 5a are linearly arranged in the width direction of the die body 1, and are arranged with a phase difference in the width direction of the die body 1 in the rolling direction. Specifically, the dividing teeth 5a in the dividing tooth region 7 are arranged with a phase difference such that the entire rolling width or substantially the entire rolling width of the rolled material W is processed in the dividing tooth region 7.

Here, the rolling width refers to the axial range in which the tooth profile is formed by rolling the rolled material W.

In addition, the cutting tooth region 7 in this embodiment is provided from the start position of the biting portion 2 to a position that is 60% to 95% of the length L2 of the biting portion 2.

By providing this cutting tooth region 7, in other words the cutting teeth 5a, from the beginning of the biting portion 2, the range of the cutting tooth region 7 can be set widely in the biting portion 2 of a predetermined length, which allows more rolling to be performed using the cutting teeth 5a, and the effect of the present invention, i.e., the effect of suppressing the elongation deformation of the rolled material W in the circumferential and axial directions, is more effectively achieved.

The cutting tooth region 7 does not have to start at the start of the biting portion 2, but may start at a position an appropriate distance from the start of the biting portion 2, as shown in FIG. 23. In this case, it is preferable that the position where the cutting tooth region 7 is provided (the position where the cutting tooth region 7 starts, in other words, the start position of the groove 6) is a position 0.5 to 2 rotations away from the rolled material W.

The reason why the range in which the cutting teeth 5a are provided is set to 60% to 95% of the length L2 of the biting portion 2 is that if the cutting teeth 5a are provided only up to a position less than half the length of the biting portion 2, the desired effect will not be achieved, and if they are provided over the entire length of the biting portion 2, in other words, up to the boundary position with the finishing portion 3, the tooth traces of the tooth profile formed on the rolled material W will not be aligned even after rolling by the processing teeth 5 of the finishing portion 3, and scratches (groove marks caused by the streaks 6) may remain on the tooth surface after rolling. Therefore, the upper limit position of the range in which the cutting teeth 5a are provided may be set slightly before the boundary position with the finishing portion 3 (towards the start end of the rolling direction), and it is more preferable to set it up to 95% of the length L2 of the biting portion 2.

The groove 6 that forms the dividing tooth 5a (the groove 6 that divides the cutting tooth 5) is formed into a tapered groove whose width increases from the bottom side toward the top as shown in FIG. 3 by grinding with a grindstone. Note that the formation of the groove 6 is not limited to the above-mentioned processing, and may be formed by, for example, laser processing, etc.

In addition, if the groove width W2 of the groove 6 is too narrow compared to the tooth width W1 of the cutting teeth 5a described below, the shape will be similar to that of a conventional product (one without the groove 6 and without the cutting teeth 5a), and the deformation suppression effect will not be sufficient for the thin-walled rolled material W. Also, if the groove width W2 is too wide compared to the tooth width W1, an unmachined portion will be created, which will cause the processing load in the finishing portion 3 to become too large and deform the rolled material W. Therefore, the groove width W2 of the groove 6 needs to be set based on the tooth width W1 of the cutting teeth 5a.

In light of this, the groove width W2 of the groove 6 can be set as appropriate within a range that does not impair the effect of this embodiment, but a groove width equal to or narrower than the tooth width W1 of the cutting tooth 5a is preferable, and specifically, it is preferable to set the ratio of the tooth width W1 of the cutting tooth 5a to the groove width W2 of the groove 6 to be 0.9 to 1.8.

In addition, in the specification where the ratio of the tooth width W1 of the cutting tooth 5a to the groove width W2 of the groove 6 is 0.9 (specification of Experimental Example 2 described later), the groove width W2 is slightly wider than the tooth width W1. In this case, a small amount of unmachined portion remains in the cutting tooth region 7 of the engagement portion 2, but since almost the entire rolling width is machined, the processing load in the finishing portion 3 is not too large. Therefore, as described above, this is within the preferred range and is included in the "groove width equivalent to the tooth width W1 of the cutting tooth 5a."

In this embodiment, the groove width W2 of the groove 6 means the groove width in the width direction of the die body 1 at the upper edge of the groove 6 (the widest part) as shown in Figure 3, and in this embodiment, the tooth width W1 of the cutting tooth 5a means the tooth width in the width direction of the die body 1 at the tip surface of the cutting tooth 5a as shown in Figure 3.

The groove 6 in this embodiment is provided along the inclination of the machining teeth 5 of the biting portion 2 (the inclination of the tip line of the machining teeth 5) from the starting end in the rolling direction to the rear end in the rolling direction, and the groove depth D of the groove 6 based on the tip of the machining teeth 5 is set to a constant depth. The groove depth D of the groove 6 can be set appropriately within a range that does not impair the effect of this embodiment, and does not have to be set to a constant depth based on the tip of the machining teeth 5.

In this embodiment, the groove depth D of the groove 6 is set to a depth equal to or greater than the tooth height of the processing tooth 5, and is configured to completely separate the processing tooth 5. However, as long as the predetermined depth is sufficient to achieve the effect of this embodiment, it may be set to a depth shallower than the tooth height of the processing tooth 5, as shown in FIG. 11. For example, the groove depth D of the groove 6 may be set according to the workability of the rolled material W. If the rolled material W is a material that is easily swollen by rolling (a material with high ductility), the groove depth D of the groove 6 may be set deep (for example, set to a depth equal to or greater than the tooth height of the processing tooth 5), and if the material is not easily swollen (a material with high work hardening), the groove depth D of the groove 6 may be set shallow (shallower than the tooth height of the processing tooth 5, for example, set to a depth of 50% of the tooth height of the processing tooth 5) to prevent chipping during rolling due to a decrease in the strength of the dividing processing tooth 5a.

The grooves 6 in this embodiment are arranged at equal intervals in the tooth trace direction of the cutting teeth 5a so that the tooth width W1 of the cutting teeth 5a is 3.3 mm or less (if the tooth width W1 of the cutting teeth 5a is set to a value greater than the above value (a wider value), the deformation suppression effect on the thin-walled rolled material W cannot be sufficiently obtained).

As mentioned above, this embodiment is a rolling flat die for machining normal splines (splines in which the teeth are formed parallel to the axial direction of the material W to be rolled), so the tooth trace direction and the width direction of the die body 1 are the same.

The narrower the tooth width W1 of the cutting teeth 5a, the more effective it is at suppressing deformation of the material W to be rolled, but on the other hand, chipping becomes more likely, and problems arise in that the tool life is shortened. Therefore, when setting the tooth width W1 of the cutting teeth 5a, it is necessary to consider the balance between the effect of suppressing deformation of the material W to be rolled and the tool life.

Specifically, the width of the tip of the first tooth of the die in the rolling direction is set as the threshold value, and if the tooth width W1 is narrower than this, chipping becomes very likely to occur, so it is preferable to set the tooth width W1 to be equal to or greater than the width of the tip of the first tooth of the die in the rolling direction.

In consideration of this, the grooves 6 in this embodiment are arranged at equal intervals in the tooth trace direction of the cutting teeth 5a so that the tooth width W1 of the cutting teeth 5a in its complete shape (a state in which the cutting teeth 5a are divided by two grooves 6) is 0.5 mm or more and 3.3 mm or less.

The grooves 6 in this embodiment are inclined toward the width direction of the die body 1 with respect to the rolling direction, in other words, toward the tooth trace direction of the processing teeth 5. Specifically, they are inclined at a predetermined inclination angle α with respect to the rolling direction in a plan view (viewed in the tooth height direction), and each groove 6 is arranged in a straight line (straight and continuous) in a plan view in the rolling direction, as shown in FIG. 2. By arranging the grooves 6 in this way, it is possible to easily arrange the dividing processing teeth 5a with a phase difference in the width direction of the die body 1 in the rolling direction.

The grooves 6 are not limited to being arranged in a straight line in plan view as in this embodiment, but may be arranged in a straight line (straight and intermittent) along a straight line in plan view as in another example of this embodiment shown in Figure 11 (b).

Specifically, the grooves 6 in this embodiment are obliquely provided at an angle (inclination angle α) of 0.35° to 7.10° with respect to the rolling direction in a plan view. In this embodiment, the amount by which the dividing teeth 5a push the rolled material deepest in the tooth height direction (maximum processing amount) is within 0.14 mm, and the grooves 6 are provided at this angle, so that the entire rolling width or almost the entire rolling width of the rolled material W is processed while the rolled material W rotates 0.5 to 2 times in the dividing teeth area 7, and no unprocessed portion is formed (if the inclination angle α is large, a load is applied to the rolled material W in the axial direction during rolling, increasing the risk of bending the rolled material W, so it is preferable to set the inclination angle α so as not to exceed the above range).

The reason why the maximum machining amount of the cutting teeth 5a must be set within 0.14 mm is based on the results of various experiments, including Experimental Examples 1 to 3 (this embodiment: maximum machining amount of the cutting teeth 5a is 0.14 mm). If the maximum machining amount exceeds 0.14 mm, the machining load on the rolled material becomes too large, and the rolled material W is stretched and deformed in the circumferential and axial directions.

For example, in the case of a spline processing die with a module of 0.3, a number of spline teeth of 66, and a cutting amount of 0.055 mm/revolution, if the groove 6 is set so that the entire rolling width or substantially the entire rolling width is processed during two rotations of the rolled material W, the maximum cutting amount of the cutting teeth 5a (cutting amount at the second rotation) is 0.1375 mm, which is within 0.14 mm, and the effect of the present invention is obtained. In contrast, in the case of a spline processing die with a module of 1.0, a number of spline teeth of 27, and a cutting amount of 0.14 mm/revolution, if the groove 6 is set so that the entire rolling width or substantially the entire rolling width is processed during two rotations of the rolled material W, the maximum cutting amount of the cutting teeth 5a (cutting amount at the second rotation) is 0.35 mm, which exceeds 0.14 mm, and the rolled material W is stretched and deformed in the circumferential and axial directions, and good results are not obtained. In this case, in order to prevent the maximum processing amount from exceeding 0.14 mm, the groove 6 must be set so that the entire rolling width or nearly the entire rolling width is processed every 0.5 rotations.

Specifically, in the case of a spline with a tooth tip diameter of φ21, a module of 0.3, and 66 teeth, the total length L of the die body 1 is 410 mm, the length L2 of the chamfering portion 2 is 289 mm, the pitch P of the groove 6 is 0.782 mm, and when the entire rolling width or substantially the entire rolling width of the rolled material W is machined in two revolutions, the inclination angle α is 0.35° (MIN), and when the pitch P of the groove 6 is 6.967 mm, and the entire rolling width or substantially the entire rolling width of the rolled material W is machined in one revolution, the inclination angle α is 5.88° (MAX).

In the case of a spline with a tooth tip diameter of φ17.4, module 0.47, and number of teeth of 36, the total length L of the die body 1 is 410 mm, L2 of the chamfer 2 is 304 mm, the pitch P of the groove 6 is 1.347 mm, and when the entire rolling width or substantially the entire rolling width of the rolled material W is machined in two revolutions, the inclination angle α is 0.73° (MIN), and when the pitch P of the groove 6 is 6.967 mm, and the entire rolling width or substantially the entire rolling width of the rolled material W is machined in one revolution, the inclination angle α is 7.10° (MAX).

Furthermore, when the tooth tip diameter is φ27.5, the module is 1.0, and the number of teeth is 27, the inclination angle α is 1.79° to 4.13° (see Experimental Examples 1 to 4 described below).

In addition, in this embodiment, a tapered portion 7b is provided at the end of the rolling direction of the divided tooth region 7.

Specifically, the tapered portion 7b is set in a range including 6 to 12 teeth of the machining teeth 5 at the end of the dividing tooth region 7, and the grooves 6 provided in each machining tooth 5 of this tapered portion 7b are set to a shallower groove depth and narrower groove width than the grooves 6 provided in the starting end side dividing tooth region 7a of the dividing tooth region 7, which is closer to the starting end side of the rolling direction than the tapered portion 7b. Furthermore, the grooves 6 provided in the machining teeth 5 closer to the end of the tapered portion 7b are set to a shallower groove depth and narrower groove width.

The groove depth of the groove 6 in the tapered portion 7b may be curved and shallower from the boundary between the starting-end cutting tooth region 7a and the tapered portion 7b toward the end of the tapered portion 7b, or may be linearly and gradually shallower along the gradient of the tapered angle g (see FIG. 4), which is set as follows:

Tapered angle g = arctan (the groove 6 at the boundary between the starting end side divided tooth region 7a and the tapered portion 7b)
(D)/(Length of tapered portion 7b in the rolling direction)

By providing this tapered portion 7b, the change in the shape of the processing teeth 5 due to the presence or absence of the groove 6 at the starting end side of the dividing processing tooth region 7a and at the end side of the cutting processing tooth region 7 of the biting portion 2 in the rolling direction is made gentler, thereby suppressing sudden changes in the processing load and preventing elongation deformation of the rolled material.

In the present embodiment, the cutting edge 2 has a constant gradient of the tooth tip line as shown in FIG. 1, i.e., the machining amount at the cutting edge 2 (the amount of machining per rotation of the workpiece W to be rolled) is set constant. However, the cutting edge 2 may be configured such that a predetermined range at the start of the cutting edge 2 is the first cutting step and the remaining cutting edge 2 is the second cutting step, with the gradient of the tooth tip line at the first cutting step being large and the gradient of the tooth tip line at the second cutting step being small, so that the amount of machining is large at the first cutting step and small at the second cutting step.

As described above, this embodiment shows the case where the rolling die of the present invention is applied to a rolling flat die as shown in FIG. 12, but the rolling die of the present invention can also be applied to a rolling partial circular die as shown in FIG. 13.

The rolling recess circular die rotates in the rolling direction, and the rolling tooth form formed on its outer periphery is provided with a continuous lead portion 2, a finishing portion 3, and a relief portion 4, each of which has a different distance from the rotation axis of the rolling recess circular die to the tip of the processing tooth 5, starting from the starting end in the rolling direction. In the case of the rolling recess circular die, the groove 6 is formed in a spiral shape around the rotation axis of the rolling recess circular die with a lead angle α, which corresponds to the inclination angle α in the rolling flat die (see Figure 13 (b)).

In this way, by providing the groove 6 in a spiral shape around the rotation axis of the rolling die, the groove 6 is inclined at a predetermined inclination angle α with respect to the rolling direction in the plan view of the chamfering portion 2 in which the groove 6 of the rolling die is formed, and is provided so as to be linear in the plan view in the rolling direction (slightly curved, approximately linear state). In other words, as shown in FIG. 13 (b), in the developed state in which the outer peripheral surface of the rolling die is developed on a plane, the groove 6 is inclined at a predetermined inclination angle α with respect to the rolling direction, as with the rolling flat die, and is provided so as to be linear in the plan view in the rolling direction. Therefore, by providing the groove 6 in a spiral shape around the rotation axis of the rolling die in the rolling die, the same effect as the effect when applied to the rolling flat die described below is achieved. In addition, because the rolling die is roughly cylindrical in shape, the grooves 6 located at the left and right ends of the visible range (rolling direction) appear slightly curved when viewed from above, but in this embodiment, this slightly curved state is also included in the "straight line when viewed from above."

Since this embodiment is configured as described above, in the cutting tooth region 7 of the biting portion 2, the cutting teeth 5a intermittently process the rolled material W while moving the pushing position in the width direction of the die body 1. Furthermore, the area in which the rolled material W is pushed is smaller than when the rolling teeth 5 push the rolled material W, and the processing load is concentrated on the tips of the cutting teeth 5a, making it easier for the cutting teeth 5 to bite into the rolled material W. Even if the rolled material W is a hollow material with a thin wall thickness, it is possible to suppress elongation deformation in the circumferential and axial directions.

In the rolling of splines into hollow materials, the greater the ratio of the spline tooth height to the thickness of the material W being rolled, the greater the circumferential and axial elongation deformation, making it more difficult to form the desired tooth shape. Also, the greater the ratio of the inner diameter (diameter of the hollow part of the material W being rolled) to the outer diameter (diameter of the material W being rolled), i.e., the thinner the material W being rolled, the greater the circumferential and axial elongation deformation, making it more difficult to form the desired tooth shape.

Specifically, based on the applicant's experience to date, assuming a spline with a module of 0.3 to 1.1, the hollow material W to be rolled can be machined well (without elongation deformation) without a core bar only when the ratio of the spline tooth height to the thickness of the rolled material W is 17% or less, and the ratio of the inner diameter (diameter of the hollow part of the rolled material W) to the outer diameter (diameter of the rolled material W) of the rolled material W is 47% or less. Even if a core bar is used, the ratio of the spline tooth height to the thickness of the rolled material W is 20% or less, and the ratio of the inner diameter (diameter of the hollow part of the rolled material W) to the outer diameter (diameter of the rolled material W) of the rolled material W is 55% or less. In the past, good machining was only possible in the following cases. However, by using this embodiment, it is possible to machine well without a core bar up to the condition that the ratio of the spline tooth height to the thickness of the rolled material W is 20% or less, and the ratio of the inner diameter (diameter of the hollow part of the rolled material W) to the outer diameter (diameter of the rolled material W) of the rolled material W is 55% or less. Furthermore, by using a core bar, it is possible to machine well up to the condition that the ratio of the spline tooth height to the thickness of the rolled material W is 30% or less, and the ratio of the inner diameter (diameter of the hollow part of the rolled material W) to the outer diameter (diameter of the rolled material W) of the rolled material W is 70% or less.

The following is an experiment (evaluation experiment) that supports the effects of this embodiment described above.

<Experiment 1>
A total of six rolling flat dies, including conventional general rolling flat dies (hereinafter referred to as "Conventional Example 1" and "Conventional Example 2") as shown in Tables 1 and 2, and rolling flat dies of Experimental Examples 1 to 4 in which the configurations of the tooth width, etc. of the dividing processing teeth 5a in this embodiment are different, were used to perform spline rolling processing using a general core bar on a hollow material to be rolled W, and the presence or absence of elongation deformation in the circumferential and axial directions of the rolled material W was evaluated.

For each symbol in Table 1, L is the length of the die body 1, L2 is the length of the chamfer 2, X is the range (length) of the cutting tooth region 7 in the rolling direction, and X/L2 is the ratio of the range X of the cutting tooth region 7 (the length of the cutting tooth region 7 in the rolling direction range) to the length L2 of the chamfer 2 (chamfer length L2) (see Figure 1).

The symbols in Table 2 are: W1: tooth width of the dividing tooth 5a, W2: groove width of the groove 6, P: pitch of the groove 6, α: inclination angle of the groove 6, β: groove angle of the groove 6, D: groove depth of the groove 6, W3: tip width in the rolling direction of the first tooth of the dividing tooth region 7 in the engagement portion 2, W1/W3: tooth width ratio of the dividing tooth 5a, DP: spline pitch of the die (pitch of the spline teeth in the rolling direction), and W1/W2: ratio of the tooth width of the dividing tooth 5a to the groove width of the groove 6 (see Figures 2 and 3).

Specifically, spline rolling was performed using a core bar under the following conditions on hollow rolled material W (thickness 4mm to 8mm) with different wall thicknesses, and the overpin diameter, tooth root circle diameter, tooth profile error, tooth trace error, cumulative pitch error, and tooth groove runout of each were measured, and the presence or absence of elongation deformation in the circumferential and axial directions of the rolled material W was evaluated based on the measurement results.

<Processing conditions, etc.>
・Spline specifications: Tooth tip diameter φ27.5 x Z27 x m1.0 x PA37.5°
Tooth length: 1.2 mm
Here, Z is the number of teeth of the spline, m is the module, and PA is the pressure angle.
- Material of the rolled material: Carbon steel (S45C)
Material diameter: 26.46 mm
Processing amount: Conventional Example 1 and Experimental Examples 1 to 3: 0.14 mm/revolution,
Conventional Example 2 and Experimental Example 4: 0.09 mm/revolution; Tooth height h of the first tooth of the cutting portion 2: Conventional Example 1 and Experimental Examples 1 to 3: 0.6964 mm,
Conventional Example 2 and Experimental Example 4: 0.6464 mm
・Material of rolling dies: Die steel (SKD11)
Distance in the rolling direction per rotation of the rolled material: 83.1 mm
(= spline tooth pitch in the rolling direction DP 3.0777 mm x Z 27)
・Processing conditions: Aiming for the median value of the pin diameter standard at the center position of the rolling width

<Core metal used>
-Material: Carbon steel (hardened)
・Core dimensions and inner diameter: See Table 3 below

To further explain experimental examples 1 to 4, when the number of grooves in the rolled workpiece W is based on the first tooth of the lower die (first groove), and in experimental examples 1 to 3, the die biting portion length L2 is designed to be 449 mm and the number of teeth in the biting portion 2 is designed to be 146, as shown in Figure 6, in the lower die, the processing teeth 5 of the 1st, 28th, 55th, 82nd, 109th and 136th teeth become the teeth that process the first groove in the rolled workpiece W, and in the upper die, because the same groove is processed by the 1st tooth of the lower die in half a rotation of the rolled workpiece W, the processing teeth 5 of the 14th, 41st, 68th, 95th and 122nd teeth become the teeth that process the first groove in the rolled workpiece W. In experimental example 4, when the cutting portion length L2 of the die is designed to be 754 mm and the number of teeth of the cutting portion 2 is designed to be 245, as shown in FIG. 6, in the lower die, the processing teeth 5 of the 1st, 28th, 55th, 82nd, 109th, 136th, 163rd, 190th, 217th, and 244th teeth become the teeth that process the first groove of the rolled material W, and in the upper die, the same groove as the groove processed by the 1st tooth of the lower die is processed by half a rotation of the rolled material W, so that the processing teeth 5 of the 14th, 41st, 68th, 95th, 122nd, 149th, 176th, 203rd, and 230th teeth become the teeth that process the first groove of the rolled material W. In addition, in experimental examples 1 to 4, the phase of the grooves 6 (the amount of deviation in the width direction of the die body 1) was set so that the entire rolling width or nearly the entire rolling width was machined every half rotation (0.5 rotation) of the rolled material W.

Table 4 shows the standards for each measurement item. Table 5 shows the evaluation results. In the evaluation results, if all of the evaluation items, over pin diameter, root circle diameter, tooth profile error, tooth lead error, cumulative pitch error, and tooth groove runout, were within the standards shown in Table 4, they were marked with an O, and if any of the evaluation items were outside the standards, they were marked with an X. Items for which no evaluation was performed were marked with a -.

As shown in Table 5, in Conventional Example 1, a good processed shape was obtained in which circumferential and axial elongation deformation was suppressed for the rolled material W with a wall thickness of 8 mm, 7 mm, and 6 mm, but it was confirmed that circumferential and axial elongation deformation occurred for the rolled material W with a wall thickness of 5 mm or less. In contrast, in Experimental Examples 1 to 4 (this embodiment), it was confirmed that a good processed shape was obtained in which circumferential and axial elongation deformation was suppressed even for the rolled material W with a wall thickness of 5 mm in all dies. Furthermore, in Conventional Example 2, in which the chamfer length L2 was set longer than in Conventional Example 1 and Experimental Examples 1 to 3, it was confirmed that circumferential and axial elongation deformation occurred for the rolled material W with a wall thickness of 4 mm, but in Experimental Example 4 (this embodiment), in which the chamfer length L2 was set to the same length as Conventional Example 2, it was confirmed that a good processed shape was obtained in which circumferential and axial elongation deformation was suppressed even for the rolled material W with a wall thickness of 4 mm.

Table 6 and Figures 7 to 10 show the detailed results of spline rolling on the 5 mm-thick rolled material W in Conventional Example 1 and Experimental Examples 1 to 4.

As shown in Table 6, in Conventional Example 1, due to the occurrence of elongation deformation in the circumferential and axial directions, three items, over-pin diameter, cumulative pitch error, and tooth groove runout, were out of specification. In contrast, in this embodiment (Experimental Examples 1 to 4), none of the items were out of specification, and a good processed shape was obtained in which elongation deformation in the circumferential and axial directions was suppressed.

Using the die specifications of Experimental Example 1 as a base, the groove depth D of the groove 6 was changed to a shallow depth of 0.10 mm, and spline rolling and evaluation were also performed under the same conditions as the above experiment. As in the case where the groove depth D of the groove 6 was 0.95 mm (Experimental Example 1), no out-of-standard results were observed in any of the evaluation items, and a good processed shape was obtained with suppressed elongation deformation in the circumferential and axial directions.

In the spline rolling process in Experimental Example 1, in the cutting tooth region 7 of the engagement portion 2, the cutting teeth 5a come into contact with the same tooth groove on the rolled material W at a different position in the rolling width direction (axial direction of the rolled material W) every 0.5 rotations of the rolled material W. Since the processing amount is 0.14 mm/revolution, if the groove depth D is set to a depth of 0.07 mm (0.14 mm x 0.5) or more, the groove 6 will not come into contact with the rolled material W during rolling.

<Experiment 2>
In Experiment 2, using Conventional Example 1 and Experimental Examples 1 to 4 used in Experiment 1, spline rolling was performed on hollow rolling material W of different thicknesses (thickness 6 mm to 8 mm) without using a core wire under the same conditions as in Experiment 1, and the overpin diameter, bottom circle diameter, tooth profile error, tooth lead error, cumulative pitch error and tooth groove runout of each were measured, and the presence or absence of elongation deformation in the circumferential and axial directions of the rolling material W was evaluated based on the measurement results.

The evaluation results are shown in Table 7. As in Experiment 1, the evaluation results were marked with an O if all of the evaluation items, over-pin diameter, root circle diameter, tooth profile error, tooth lead error, cumulative pitch error, and tooth groove runout, were within the standards shown in Table 4, and marked with an X if any of the evaluation items were outside the standards.

As shown in Table 7, in Conventional Example 1, unless the thickness was 7 mm or more, it was not possible to obtain a good processed shape in which elongation deformation in the circumferential and axial directions was suppressed. However, in Experimental Examples 1 to 4 (this embodiment), excellent results were confirmed, in that a good processed shape in which elongation deformation in the circumferential and axial directions was suppressed could be obtained even for a rolling material W with a thickness of 6 mm, without using a core bar.

<Experiment 3>
In experiment 3, the rolling process was performed under processing conditions, such as the spline specifications and the material of the rolling workpiece, which were different from those in experiment 1, and the presence or absence of elongation deformation in the circumferential and axial directions of the rolling workpiece W was evaluated.

Specifically, as shown in Tables 8 and 9, the rolling flat dies of Experimental Examples 5 to 8, which have different specifications from the rolling flat dies of Experimental Examples 1 to 4 in this embodiment, were used to perform spline rolling on the hollow material W to be rolled without using a core metal, and the overpin diameter, tooth root diameter, tooth profile error, tooth trace error, cumulative pitch error, and tooth groove runout were measured, and the presence or absence of circumferential and axial elongation deformation of the rolled material W was evaluated from the measurement results (Experimental Examples 7 and 8 evaluate the presence or absence of circumferential and axial elongation deformation of the rolled material W when the tooth width W1 of the dividing processing tooth 5a is set to the minimum width (Experimental Example 7) and the maximum width (Experimental Example 8). Note that the explanation of each symbol in Tables 8 and 9 is omitted because it is the same as in Experiment 1.

<Processing conditions, etc.>
・Spline specifications: Tooth tip diameter φ17.4 x Z36 x m0.47 x PA45°
Tooth length: 0.512mm
Here, Z is the number of teeth of the spline, m is the module, and PA is the pressure angle.
・Material of the rolled material: Carbon steel (S43C)
Material diameter: 16.91 mm
Machining amount: Experimental Examples 5, 7, and 8: 0.05 mm/revolution, Experimental Example 6: 0.031 mm/revolution Tooth height h of the first tooth of the cutting edge 2: 0.289 mm
・Material of rolling dies: Die steel (SKD11)
Distance in the rolling direction per rotation of the rolled material: 53.0 mm
・Processing conditions: Aim for the center of the over-pin diameter standard at the center of the rolling width. ・No core metal is used (both ends of the rolled material W are held at the center).
In addition, in experiment 3, the presence or absence of elongation deformation in the circumferential and axial directions was evaluated for two types of hollow material W to be rolled that had different wall thicknesses (wall thicknesses of 4.2 mm and 3.5 mm).

Table 10 shows the standards for each measurement item. Table 11 shows the evaluation results. Figures 17 to 22 show the results of each measurement item for Experimental Examples 5 and 6. In the evaluation results, if all of the evaluation items, over pin diameter, root circle diameter, tooth profile error, tooth lead error, cumulative pitch error, and tooth groove runout, were within the standards shown in Table 10, they were marked with an O, and if any of the evaluation items were outside the standards, they were marked with an X.

As shown in Table 11, in all experimental examples 5 to 8, it was confirmed that a good processed shape was obtained in which elongation deformation in the circumferential and axial directions was suppressed for all wall thicknesses.

In addition, as shown in Figures 17 to 22, experimental example 6 gave better results overall than experimental example 5. This is believed to be due to the fact that the pitch P of the grooves 6 was halved and the tooth width W1 of the cutting teeth 5a was halved, improving the deformation suppression effect.

<Experiment 4>
In experiment 4, for a spline with different specifications from experiment 3 (tooth tip circle diameter φ21 x Z66 x m0.3 x PA30°), the material diameter of the rolled material W was 20.42 mm (material: carbon steel (S45C)), and rolling was performed on the hollow rolled material W without using a core bar, and the presence or absence of elongation deformation in the circumferential and axial directions of the rolled material W was evaluated.

Specifically, the overpin diameter, tooth root diameter, and gauge evaluation were measured when the tooth width W1 of the dividing teeth 5a was set to the minimum width (Experimental Example 9) and when it was set to the maximum width (Experimental Example 10) as shown in Table 12, and the presence or absence of elongation deformation in the circumferential and axial directions of the rolled material W was evaluated from the measurement results. The setting conditions of each die body 1 in Experimental Examples 9 and 10 are as shown in Table 13. The explanation of each symbol in Tables 12 and 13 is omitted because it is the same as in Experiment 1.

Table 14 shows the standards for each measurement item. Table 15 shows the evaluation results. In the evaluation results, a circle was given if all evaluation items were within the standards, and an X was given if even one of the evaluation items was outside the standards.

As shown in Table 15, in Experimental Example 9, in which the tooth width W1 of the cutting teeth 5a was set to the minimum width of 0.503 mm, and in Experimental Example 10, in which the tooth width W1 was set to the maximum width of 3.3 mm, all evaluation items were within the standard for both thicknesses.

<Experiment 5>
In experiment 5, rolling was performed on a hollow material W to be rolled using dies with different positions of the cutting tooth area 7 without using a core wire, and the presence or absence of elongation deformation in the circumferential and axial directions of the material W to be rolled was evaluated.

Specifically, the overpin diameter, bottom circle diameter, tooth profile error, tooth trace error, cumulative pitch error, and tooth groove runout were measured for the case where the divided tooth region 7 was provided from the start of the biting portion 2 as shown in Table 16 (Experimental Example 11) and the case where the divided tooth region 7 was provided from a position separated from the start of the biting portion 2 by a distance equivalent to two rotations of the rolled material W (Experimental Example 12).The presence or absence of elongation deformation in the circumferential and axial directions of the rolled material W was evaluated from the measurement results.

In Experiment 5, the spline specifications were tooth tip diameter φ18 x Z22 x m0.8 x PA40°, and the diameter of the rolled material W was 16.89 mm (material: carbon steel (S45C)). The setting conditions for each die body 1 in Experimental Examples 11 and 12 are as shown in Table 17. The explanations for each symbol in Tables 16 and 17 are omitted because they are the same as those in Experiment 1.

The evaluation results are shown in Table 18. In addition, in the evaluation results, if all evaluation items were within the specifications, it was marked with an O, and if even one of the evaluation items was out of specifications, it was marked with an X.

As shown in Table 18, even when the cutting tooth region 7 is located at a position that is two revolutions of the rolled material W away from the start of the biting portion 2, all evaluation items for each thickness were within the standard.

In the present embodiment, the excellent effects of the present invention were confirmed in the above experiments 1 to 5, in which the rolled material W was a hollow material. However, even when the rolled material W is a solid material and rolled, it is possible to minimize the elongation and deformation of the rolled material W in the circumferential and axial directions, and obtain an excellent product with the desired tooth profile.

Furthermore, the present invention is not limited to this embodiment, and the specific configuration of each component can be designed as appropriate.

1 Die body 2 Chamfering portion 3 Finishing portion 4 Relief portion 5 Processing tooth 5a Dividing processing tooth 6 Groove 7 Dividing processing tooth region 7b Tapered portion D Groove depth of groove L2 Length of chamfering portion W Rolled material W1 Tooth width of dividing processing tooth W2 Groove width of groove α Inclination angle of groove

Claims (13)

a rolling die having a chamfering portion, a finishing portion, and a relief portion, each of which is provided with processing teeth, from a starting end of the rolling direction of the die body toward a terminal end of the rolling direction, and which uses these processing teeth to plastically deform the outer circumferential surface of the material to be rolled to roll a desired tooth profile, wherein from the starting end of the chamfering portion to a predetermined position in the rolling direction of the chamfering portion, each processing tooth is provided with a plurality of grooves that are inclined at a predetermined angle with respect to the rolling direction in a plan view, and wherein these grooves form a plurality of cutting processing teeth, and each of these cutting processing teeth is arranged so as to have a phase difference in the width direction of the die body in the rolling direction, and a gradual taper portion is provided in a predetermined range on the rolling direction terminal side of the cutting processing tooth region where the cutting processing teeth are provided, and this gradual taper portion is configured so that the groove depth of the groove gradually becomes shallower and the groove width of the groove gradually becomes narrower toward the terminal end in the rolling direction. 2. The rolling die according to claim 1, wherein the dividing processing teeth are arranged with a phase difference such that the entire rolling width of the rolled material is processed in the dividing processing tooth region in which the dividing processing teeth are arranged. The rolling die according to claim 1, characterized in that the groove is provided from the start position of the chamfer to a position that is 60% to 95% of the length of the chamfer. The rolling die according to claim 2, characterized in that the groove is provided from the start position of the chamfer to a position that is 60% to 95% of the length of the chamfer. The rolling die according to claim 1, characterized in that the groove is provided from a position a predetermined distance from the beginning of the chamfer to a position 60% to 95% of the length of the chamfer. The rolling die according to claim 2, characterized in that the groove is provided from a position a predetermined distance away from the start of the chamfer to a position 60% to 95% of the length of the chamfer. A rolling die according to any one of claims 1 to 6, characterized in that the dividing teeth are configured to have a tooth width of 3.3 mm or less, and the grooves are provided at equal intervals in the tooth trace direction of the dividing teeth. The rolling die according to any one of claims 1 to 6 , wherein the inclination angle is 0.35° to 7.10°. 8. The rolling die according to claim 7, wherein the inclination angle is 0.35° to 7.10°. The rolling die according to any one of claims 1 to 6 , wherein the groove is provided in a straight line in a plan view. 8. The rolling die according to claim 7 , wherein the groove is provided in a straight line in a plan view. 9. The rolling die according to claim 8, wherein the groove is provided in a straight line in a plan view. 10. The rolling die according to claim 9, wherein the groove is provided in a straight line in a plan view.

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