TWI901959B - Rolling dies - Google Patents

Abstract

This invention provides a rolling die that, in the rolling of hollow materials, avoids the need for an enlarged rolling die and eliminates the need for a specially constructed core during rolling. It maximally suppresses the elongation and deformation of the rolled material in both the circumferential and axial directions, thereby obtaining a product with the desired tooth profile. The roller die of this invention, extending from the starting end of the guide portion (2) to a specific position in the roller direction of the guide portion (2), has a plurality of grooves (6) on each machining tooth (5) that, in a top view, are inclined at a specific inclination angle α in the roller direction. These grooves (6) form a plurality of segmented machining teeth (5a), each of which is configured to have a phase difference in the width direction of the die body (1) in the roller direction.

Description

Roller mold

This invention relates to a roller die.

Traditionally, rolling is widely used in the manufacture of metal splines, serrations, gears, screws, lead screws, worm gears, and other similar products. This process utilizes a rolling die with pre-formed rolling teeth (machined teeth) to clamp a slightly cylindrical workpiece. While applying pressure, the outer circumference of the workpiece undergoes plastic deformation to form the desired tooth shape. Compared to machining, this rolling process offers several advantages: good manufacturability, making it suitable for mass production; increased surface hardness and strength of the rolled part through work hardening; and improved surface roughness of the rolled part through the burnishing effect between the die teeth and the rolled material. Furthermore, grooves and teeth are widely used in automotive parts such as drive shafts and steering shafts. In recent years, with the increasing demand for lightweight vehicles, the demand for these groove-like products (rolled parts) is no longer limited to solid products; there is also a surge in demand for hollow products with holes having a circular cross-section along a slightly cylindrical central axis. However, when hollow material is used as the rolling stock and its outer circumferential surface is rolled, the rolled stock elongates and deforms in both the circumferential and axial directions, making it impossible to obtain a product with the desired tooth profile. Furthermore, in cases of excessive rolling load, the rolled stock may sometimes split. In order to minimize the risk of elongation and deformation of the hollow material being rolled (in both the circumferential and axial directions), a rolling process is performed with a rod-shaped core (also called a mandrel or mandrel shaft) inserted into a hole along a slightly cylindrical central axis. However, the following problem remains: using only the core makes it difficult to obtain a product with the desired tooth profile. Furthermore, the guide portion of a typical flat roller die, or a slightly rounded roller die (a roller die with a partially cut-off outer periphery, exhibiting a slightly cylindrical shape), is formed, comprising an inlet portion, a finishing portion, and an outlet portion. As the rolling process at this guide portion progresses (towards the end in the rolling direction), the machining teeth pair... As the amount of material pressed into the roll increases (processing amount), for example, in a roll forming die, the machining teeth of the guide section are designed such that the leading edge line of the machining teeth (the virtual line connecting the leading edges of the machining teeth) is inclined from the starting end side in the roll direction towards the ending end side in the roll direction, getting closer to the material being rolled. Although attempts are made to prevent the hollow material from elongating and deforming in both the circumferential and axial directions by "gradually applying rolling load to the workpiece by mitigating the inclination of the leading edge of the teeth of the guide section," the problem of "difficulty in obtaining products with the desired tooth profile" remains unresolved. Furthermore, it necessitates extending the length of the guide section, thus requiring a larger rolling die. Therefore, in the manufacture of the aforementioned hollow products, the following manufacturing method is typically employed: after performing a rolling process on a slightly cylindrical solid material to "form the desired tooth shape such as a groove," a hole with a circular cross-section is machined along the central axis of the slightly cylindrical shape. This method, due to the added hole machining step, results in increased manufacturing costs. In view of this, rolling methods for hollow materials, as described in Patents 1 and 2, have been proposed to date. [Prior Art] [Patents] [Patent 1] Japanese Patent Application Publication No. 2014-054644 [Patent 2] Japanese Patent Application Publication No. 2002-143970

[Problem to be Solved by the Invention] Patent 1 disclosed a method for rolling a hollow material. A group of hard balls, consisting of a plurality of hard balls, is housed in a through hole in a hollow material having two end openings. Fixtures are inserted through the two end openings. While the two fixtures apply pressure to the group of hard balls, the hollow material is positioned. The toothed surface of the rolling die is pressed against the outer circumferential surface of the hollow material to roll it. After rolling, the group of hard balls is removed from the through hole, thus producing a hollow rolled product. However, this method, lacking a rod-shaped object with a circular cross-section (the so-called round rod) serving as the core, uses a group of hard balls formed by multiple hard spheres. Because it requires steps such as "accommodating the group of hard balls within a through hole in the hollow material," "positioning the hollow material while pressurizing the group of hard balls," and "removing the group of hard balls from the through hole after rolling," it suffers from the problem of "excessive processing time," failing to utilize the advantages of "rolling processing, which offers good mass production capabilities and is most suitable for mass production." Furthermore, in the aforementioned patent document 2, a method for manufacturing a hollow gear is disclosed. An inner diameter mandrel with recesses and protrusions extending parallel to each other in the axial direction and continuously arranged in the circumferential direction is inserted into the central shaft hole of a cylindrical workpiece. Simultaneously, as the workpiece rotates with the inner diameter mandrel, the tooth profile of the roller die is machined. The tooth profile is pressed against the outer peripheral surface of the workpiece and rolled onto that surface. Because the rolling process occurs simultaneously with pressing the protrusions on the outer peripheral surface of the inner diameter spindle against the inner peripheral surface of the workpiece, the protrusions can restrict the circumferential flow of material in the workpiece, thus suppressing the expansion of the circumference of the workpiece extending towards the inner peripheral surface. However, this method involves pressing the protrusions on the outer circumferential surface of an inner diameter mandrel (core) against the inner circumferential surface of the workpiece during rolling. This not only causes deformation of the workpiece's inner circumferential surface, preventing it from conforming to the workpiece's inner diameter specifications, but also makes removing the workpiece from the inner diameter mandrel (core) extremely time-consuming, and sometimes impossible. This invention addresses the aforementioned problems. Its purpose is to provide a rolling die that, in the rolling of hollow materials, avoids the need for a large rolling die and a specially constructed core during rolling, maximally suppresses elongation deformation of the workpiece in both the circumferential and axial directions, and produces a product with the desired tooth profile. [Solution to the Problem] The essence of the invention is explained with reference to the drawings. A rolling die has an inlet portion 2, a finishing portion 3, and an outlet portion 4, each having machining teeth 5 "provided from the starting end side of the die body 1 in the rolling direction toward the ending end side." The die uses the machining teeth 5 to cause plastic deformation of the outer peripheral surface of the workpiece W, thereby rolling out the desired tooth shape. Its characteristic is that from the starting end side of the aforementioned inlet portion 2 toward the ending end side in the rolling direction, the machining teeth 5... Up to a specific position in the rolling direction of the guide section 2, each of the aforementioned machining teeth 5 is provided with a plurality of grooves 6 that, in a top view, are inclined at a specific angle α in the rolling direction. These grooves 6 form a plurality of segmented machining teeth 5a, each of which is configured to have a phase difference in the width direction of the aforementioned die body 1 in the rolling direction. Furthermore, in the rolling die described in claim 1, the aforementioned segmented machining teeth 5a are configured to have a phase difference that allows processing of the entire rolling width of the aforementioned workpiece material W within the segmented machining tooth area 7 where the segmented machining teeth 5a are provided. Furthermore, in the roller die described in claim 1, the aforementioned groove 6 is provided at a position from the starting end of the aforementioned guide portion 2 to a position at 60% to 95% of the length L2 of the guide portion 2. Furthermore, in the roller die described in claim 2, the aforementioned groove 6 is provided at a position from the starting end of the aforementioned guide portion 2 to a position at 60% to 95% of the length L2 of the guide portion 2. Furthermore, in the roller die described in claim 1, the aforementioned groove 6 is provided at a position at a specific distance from the starting end of the aforementioned guide portion 2 to a position at 60% to 95% of the length L2 of the guide portion 2. Furthermore, in the roller die described in claim 2, the aforementioned groove 6 is provided at a position a certain distance from the starting end of the aforementioned guide portion 2, extending to a position at 60% to 95% of the length L2 of the guide portion 2. Furthermore, in the roller die described in claim 1, the tooth width W1 of the aforementioned machining teeth 5a is 3.3 mm or less, and the aforementioned groove 6 is provided at equal intervals in the direction of the tooth intersection of the aforementioned machining teeth 5a. Furthermore, in the roller die described in claim 2, the tooth width W1 of the aforementioned machining teeth 5a is 3.3 mm or less, and the aforementioned groove 6 is provided at equal intervals in the direction of the tooth intersection of the aforementioned machining teeth 5a. Furthermore, in the rolling die described in claim 3, the tooth width W1 of the aforementioned segmented teeth 5a is 3.3 mm or less, and the aforementioned grooves 6 are provided at equal intervals in the direction of the tooth intersection of the aforementioned segmented teeth 5a. Furthermore, in the rolling die described in claim 4, the tooth width W1 of the aforementioned segmented teeth 5a is 3.3 mm or less, and the aforementioned grooves 6 are provided at equal intervals in the direction of the tooth intersection of the aforementioned segmented teeth 5a. Furthermore, in the rolling die described in claim 5, the tooth width W1 of the aforementioned segmented teeth 5a is 3.3 mm or less, and the aforementioned grooves 6 are provided at equal intervals in the direction of the tooth intersection of the aforementioned segmented teeth 5a. Furthermore, in the rolling die described in claim 6, the tooth width W1 of the aforementioned segmented machining teeth 5a is 3.3 mm or less, and the aforementioned grooves 6 are provided at equal intervals in the direction of the tooth intersection of the aforementioned segmented machining teeth 5a. Furthermore, in the rolling die described in any one of claims 1 to 12, the aforementioned tilt angle α is 0.35° to 7.10°. Furthermore, in the rolling die described in any one of claims 1 to 12, the aforementioned grooves 6 are straight lines in a top view. Furthermore, in the rolling die described in claim 13, the aforementioned grooves 6 are straight lines in a top view. Furthermore, in any of claims 1 to 12, in the rolling die, a reducing portion 7b is provided in a specific range on the end side of the rolling direction of the aforementioned dividing machining tooth region 7, where the aforementioned dividing machining tooth 5a is provided. This reducing portion 7b is configured such that, towards the end in the rolling direction, the groove depth D of the aforementioned groove 6 gradually decreases, and the groove width W2 of the aforementioned groove 6 gradually decreases. Furthermore, in the roller die described in claim 13, a reducing portion 7b is provided in a specific range on the roller-direction end side of the aforementioned dividing machining tooth area 7 where the aforementioned dividing machining teeth 5a are provided. This reducing portion 7b is configured such that, towards the roller-direction end, the groove depth D of the aforementioned groove 6 gradually decreases, and the groove width W2 of the aforementioned groove 6 gradually decreases. Furthermore, in the roller die described in claim 14, a reducing portion 7b is provided in a specific range on the roller-direction end side of the aforementioned dividing machining tooth area 7 where the aforementioned dividing machining teeth 5a are provided. This reducing portion 7b is configured such that, towards the roller-direction end, the groove depth D of the aforementioned groove 6 gradually decreases, and the groove width W2 of the aforementioned groove 6 gradually decreases. Furthermore, in the roller die described in claim 15, a reducing portion 7b is provided in a specific range on the roller-direction end side of the aforementioned dividing machining tooth area 7 where the aforementioned dividing machining teeth 5a are provided. This reducing portion 7b is configured such that, towards the roller-direction end, the groove depth D of the aforementioned groove 6 gradually decreases, and the groove width W2 of the aforementioned groove 6 gradually decreases. [Effects of the Invention] Based on the structure described above, this invention provides a rolling die that, in the rolling of hollow materials, avoids the need for a large rolling die and a specially constructed core during rolling, maximally suppresses the elongation and deformation of the rolled material in both the circumferential and axial directions, and produces a product with the desired tooth profile.

Based on the figures illustrating the function of the invention, a simplified description of an embodiment of the invention deemed suitable will be provided. In this invention, from the starting end of the guide portion 2 to a specific position in the roller direction of the guide portion 2, each machining tooth 5 is provided with a plurality of grooves 6 that "in plan view, tilt at a specific tilt angle α relative to the roller direction." These grooves 6 divide the machining tooth 5, thereby forming a plurality of segmented machining teeth 5a. Each segmented machining tooth 5a has a phase difference in the width direction of the mold body 1 in the roller direction (the segmented machining teeth 5a adjacent to the roller direction are not arranged along...). The configuration is such that the material is staggered in the direction of tooth intersection rather than in the direction of rolling. Therefore, in the dividing processing tooth area 7 of the guide section 2, the rolled material W is processed intermittently, and the processing load is concentrated on the leading edge of the dividing processing tooth 5a, which has a smaller pressing area than the processing tooth 5. Even when rolling is performed on the rolled material W, which is a hollow material with a thin material thickness, the elongation deformation of the rolled material W in the circumferential and axial directions can be suppressed to the greatest extent. That is, in this type of conventional roll die, as shown in Figure 16, because the machining teeth 25, which are arranged to extend towards the tooth intersection line of the die body 21, are pressed into the grooves of the workpiece material W, the material W is not properly lifted (bulged) towards the grooves of the die used to process solid material when it is a thin hollow material. Consequently, radial failure occurs when a core is not used. Furthermore, even when a core is used, radial failure will occur. The material W being rolled cannot be plastically processed into a specific tooth shape due to deformation in the axial and circumferential directions. For example, as shown in Figures 14 and 15, the pressing position of the segmented processing teeth 5a on the material W being rolled moves sequentially towards the tooth intersection line and performs intermittent processing as the rolling process progresses. Furthermore, by reducing the area of the material W being pressed in, the processing load is concentrated on the leading edge of each segmented processing tooth 5a, improving the "material bulge of the material W being rolled," and thus forming the desired shape. This results in a rolling die that can suppress elongation deformation in the circumferential and axial directions, even when the material W being rolled is a thin, hollow material. [Example] A specific embodiment of the present invention will be described with reference to the drawings. This embodiment relates to a rolling die having an inlet section 2, a finishing section 3, and an outlet section 4, each having machining teeth 5 from the starting end side of the die body 1 in the rolling direction toward the end side in the rolling direction. The machining teeth 5 cause plastic deformation of the outer peripheral surface of the rolled material W to roll out the desired tooth profile. Specifically, this embodiment is an example of applying the rolling die of the present invention to a rolling die for rolling grooves, teeth, and gears. The structure of each part of this embodiment will be described in detail below. In this embodiment, the mold body 1, as shown in FIG1, is rectangular in top view. The bottom surface 8 forms a "flat surface that serves as a reference surface". In addition, on the top surface opposite to the bottom surface 8, a large number of machining teeth 5 are provided to "form a tooth shape for the rolled material W". The leading edge lines of the machining teeth 5 (the dotted lines that connect the leading edges of the machining teeth 5) are shown as solid lines in the front view of FIG1 (the lower part of FIG1). Furthermore, in this embodiment, the mold body 1, for the purpose of preventing the workpiece W from slipping (preventing the workpiece W from shifting its position relative to the machining teeth 5), performs shot blasting treatment on a specific range from the starting end of the rolling direction on the top surface of the mold where the machining teeth 5 are located to the ending end of the rolling direction (in this embodiment, shot blasting treatment is performed on approximately 2/3 of the length (total length) of the guide portion 2 indicated by reference numeral L2 in the drawing (the range indicated by reference numeral SB in the drawing)). Reference numeral L1 in the drawing indicates the sum of the rolling direction ranges (lengths) of the guide portion 2, the finishing portion 3, and the guide portion 4. Furthermore, this embodiment is a general-purpose rolling die for machining helical splines (grooves with tooth profiles parallel to the axial direction of the rolled material W). In the die body 1, the machining teeth 5 of the guide section 2, the finishing section 3, and the guide section 4 are formed into a mountain shape (slightly trapezoidal) in the front view angle, and constitute straight machining teeth that "extend linearly in the width direction of the die body 1, more specifically, in the direction orthogonal to the rolling direction," and are arranged side by side at specific intervals in the rolling direction. By defining the extension direction of the machining teeth 5 as a direction inclined to the "direction orthogonal to the rolling direction," it can be applied to rolling dies for machining helical splines, helical gears, etc. Specifically, the machining teeth 5 of the guide section 2 are configured such that the tooth depth gradually increases from the starting end side in the rolling direction toward the ending end side in the rolling direction, and gradually presses into the outer periphery of the material W being rolled, thus raising to form a tooth shape. In addition, the machining teeth 5 of the finishing section 3 are configured such that a certain (constant) tooth depth (approximately the same tooth depth as the machining teeth 5 at the end of the guide section 2) is set, and the tooth shape formed in the guide section 2 is finished to the product size. In addition, the machining teeth 5 of the guide section 4 are configured such that they are "an inclined surface that slopes downward toward the ending end side in the rolling direction", and the position of the front end face gradually decreases as it moves toward the ending end side in the rolling direction. Furthermore, in this embodiment, the guide section 2, as shown in FIG1, forms a segmented machining tooth domain section 7 from the starting end position to a specific position in the rolling direction. This segmented machining tooth domain section 7 is provided with a plurality of segmented machining teeth 5a, formed by a plurality of grooves 6 dividing each machining tooth 5 in the width direction of the mold body 1. The reference numeral X in the figure indicates the rolling direction range (length) of the aforementioned segmented machining tooth domain section 7. In this segmented machining tooth domain section 7, as shown in FIG2, the segmented machining teeth 5a are arranged in a straight line in the width direction of the mold body 1, and furthermore, in the rolling direction, they are arranged to have a phase difference in the width direction of the mold body 1. Specifically, the segmentation machining teeth 5a within the segmentation machining tooth region 7 are configured to have a phase difference that allows machining of "the entire roll width of the workpiece W, or approximately the entire roll width" within the segmentation machining tooth region 7. The roll width referred to here is the range along the axis in which the tooth shape is formed on the workpiece W through rolling machining. Furthermore, in this embodiment, the segmentation machining tooth region 7 is located at a position from the starting end of the guide portion 2 to 60% to 95% of the length L2 of the guide portion 2. By providing the segmented machining tooth domain 7, i.e., the segmented machining tooth 5a, starting from the beginning of the guide section 2, the range of the segmented machining tooth domain 7 can be widened within the guide section 2 of a predetermined length. This allows for a greater volume of rolling operations performed by the segmented machining tooth 5a, thus better realizing the effect of the invention: suppressing the "elongation and deformation of the rolled material W in the circumferential and axial directions." Furthermore, the segmented machining tooth domain 7 may not start from the beginning of the guide section 2, but rather, as shown in Figure 23, start from a position "appropriately separated from the beginning of the guide section 2." In this case, the position of the segmented machining tooth area 7 (the starting position of the segmented machining tooth area 7, that is, the starting position of the groove 6) is preferably set at a distance of "0.5 to 2 rotations of the rolled material W". Furthermore, the reason for defining the range of the segmented machining teeth 5a as "the position of 60% to 95% of the length L2 of the guide portion 2" is that: when the segmented machining teeth 5a are only located at a position less than half the length of the guide portion 2, the desired effect cannot be achieved. If it is set to extend throughout the entire length of the guide portion 2, that is, set to the boundary position with the finishing portion 3, even if the machining teeth 5 of the finishing portion 3 performs rolling, the tooth intersection line formed on the tooth shape of the rolled material W cannot be aligned, which may lead to the possibility that scratches (caused by the grooves 6) remain on the tooth surface after rolling. Therefore, the upper limit position of the range of the segmented machining teeth 5a is set to be "slightly forward (slightly towards the starting end in the rolling direction) compared to the boundary position with the finishing section 3", with "the position up to 95% of the length L2 of the guide section 2" being optimal. Furthermore, the groove 6 forming the segmented machining teeth 5a (the groove 6 that divides the machining teeth 5) is formed by grinding with a grinding stone: as shown in Figure 3, it is a tapered groove that widens from the bottom side towards the top. The formation of the groove 6 is not limited to the aforementioned processing; for example, it can also be formed using laser processing. Furthermore, in cases where the groove width W2 of the groove 6 is "too narrow compared to the tooth width W1 of the segmented processing tooth 5a described later," it becomes similar to the shape of a conventional product (a product without the groove 6 and without the segmented processing tooth 5a), and therefore cannot achieve sufficient deformation suppression for the thin-thickness roll material W. In addition, in cases where the groove width W2 is "too wide compared to the tooth width W1," the production of the unprocessed portion increases the processing load of the finishing portion 3, leading to deformation of the roll material W. Therefore, it is necessary to set the groove width W2 of the groove 6 according to the tooth width W1 of the segmented processing tooth 5a. Based on this, the groove width W2 of the groove 6 can be appropriately set within a range that does not impair the function of this embodiment. The groove width is preferably equal to or narrower than the tooth width W1 of the split-machined tooth 5a. Specifically, it is preferably set such that the ratio of the tooth width W1 of the split-machined tooth 5a to the groove width W2 of the groove 6 is 0.9 to 1.8. The specification where the ratio of the tooth width W1 of the split-machined tooth 5a to the groove width W2 of the groove 6 is 0.9 (the specification of Experimental Example 2 described later) is a specification where "the groove width W2 is slightly wider than the tooth width W1". In this case, although there are some unprocessed parts remaining in the split-machined tooth area 7 of the guide section 2, since the roll width is processed in almost the entire area, there is no situation where "the machining load of the finishing section 3 is too large". Therefore, as described above, it is within the optimal range and is a specification that includes "the groove width equal to the tooth width W1 of the split-machined tooth 5a". Furthermore, in this embodiment, the groove width W2 of the groove 6, as shown in Figure 3, means "the groove width in the width direction of the mold body 1 at the upper edge of the groove 6 (the widest part of the groove)". In addition, in this embodiment, the tooth width W1 of the cutting tooth 5a, as shown in Figure 3, means "the tooth width in the width direction of the mold body 1 at the front end face of the cutting tooth 5a". Furthermore, in this embodiment, the groove 6 is provided from the starting end side in the rolling direction towards the rear end side in the rolling direction, along the inclination of the machining tooth 5 of the guide part 2 (the inclination of the leading edge line of the machining tooth 5). The groove depth D of the groove 6, with the leading edge of the machining tooth 5 as the reference, is set to a constant depth. The groove depth D of the groove 6 can be appropriately set within the range that does not impair the effect of this embodiment, and it is acceptable even if it is not set to a constant depth with the leading edge of the machining tooth 5 as the reference. Furthermore, although in this embodiment, the groove depth D of the groove 6 is set to a depth greater than the tooth depth of the machined tooth 5, thus completely dividing the machined tooth 5, it can also be set to a depth shallower than the tooth depth of the machined tooth 5, as shown in Figure 11, as long as a specific depth is sufficient to achieve the desired effect of this embodiment. For example, the groove depth D of the groove 6 can correspond to the machinability setting of the rolled material W. When the material W to be rolled is a material that is "easily bulging due to rolling (a material with high ductility)," simply set the groove depth D of the groove 6 to be deeper (for example, set it to be greater than the tooth depth of the machined tooth 5). When the material is a material that is "not easily bulging (a material with high work hardening)," in order to prevent losses during rolling due to the reduced strength of the split machined tooth 5a, simply set the groove depth D of the groove 6 to be shallower (shallower than the tooth depth of the machined tooth 5, for example, set it to 50% of the tooth depth of the machined tooth 5). Furthermore, in this embodiment, the groove 6 is arranged at equal intervals along the tooth intersection line direction of the dividing teeth 5a in order to make the tooth width W1 of the dividing teeth 5a less than 3.3 mm (if the tooth width W1 of the dividing teeth 5a is set to a value larger than the aforementioned value (a wide value), the thin-thick rolled material W will not be able to obtain a sufficient deformation suppression effect). In this embodiment, as previously described, since it is a roller flat die for processing general pin grooves (pin grooves with teeth formed parallel in the axial direction of the rolled material W), the tooth intersection line direction is consistent with the width direction of the die body 1. While a narrower tooth width W1 of the cutting tooth 5a can reduce deformation of the rolled material W, it also makes it easier to create gaps, leading to a shorter tool life. Therefore, the setting of the tooth width W1 of the cutting tooth 5a must consider the balance between the deformation reduction effect on the rolled material W and the tool life. Specifically, the leading edge width of the first tooth of the die in the rolling direction is defined as a threshold. If the tooth width W1 is narrower than this threshold, gaps are very likely to occur. Therefore, the tooth width W1 is best set to be greater than the leading edge width of the first tooth of the die in the rolling direction. Based on this, in order to make the tooth width W1 of the segmented machining teeth 5a, which are divided into complete shapes (distinguished by two grooves 6), 0.5 mm or more and 3.3 mm or less, the grooves 6 of this embodiment are provided at equal intervals in the direction of the tooth intersection line of the segmented machining teeth 5a. In addition, the grooves 6 of this embodiment are set relative to the rolling direction to be inclined towards the "width direction of the mold body 1", that is, the "direction of the tooth intersection line of the machining teeth 5". Specifically, in the top view (tooth depth direction view), the grooves are inclined at a specific angle α relative to the rolling direction. Furthermore, as shown in FIG. 2, each groove 6 is arranged in the rolling direction as a straight line (linear and continuous) in the top view. By arranging the grooves 6 in the above manner, it is easy to configure the segmented machining teeth 5a in the rolling direction with a phase difference in the width direction of the mold body 1. The grooves 6 are not limited to being "arranged as a straight line in the top view as in this embodiment," but can also be arranged as a straight line (linear and discontinuous) in the top view as in other examples of this embodiment shown in FIG. 11(b). Specifically, in this embodiment, the groove 6 is inclined at an angle of 0.35° to 7.10° (inclination angle α) relative to the rolling direction in a top view. In this embodiment, the "maximum pressing amount (maximum machining amount) by which the cutting tooth 5a presses the workpiece into the tooth depth direction" is defined as within 0.14mm. By setting the groove 6 at the aforementioned angle, in the cutting tooth area 7, During the 0.5 to 2 rotations of the rolled material W, the entire or approximately the entire roll width of the rolled material W is processed, thus forming an "unprocessed portion" (if the tilt angle α becomes larger, an axial load will be applied to the rolled material W during rolling, increasing the risk of bending in the rolled material W; therefore, the tilt angle α should preferably be set not to exceed the aforementioned range). The reason why the maximum machining amount of the split machining tooth 5a must be set to within 0.14mm is based on the results of various experiments, including Experimental Examples 1 to 3 (in this embodiment: the maximum machining amount of the split machining tooth 5a is 0.14mm). When the maximum machining amount exceeds 0.14mm, the machining load on the workpiece will become too large, causing the workpiece W to elongate and deform in both the circumferential and axial directions. For example, in the case of a mold for machining a groove with a module of 0.3, 66 teeth in the groove, and a machining amount of 0.055mm/rev in the guide section, if a groove 6 is set to machine the entire or approximately the entire width of the roller during the two rotations of the workpiece W, the maximum machining amount of the dividing machining teeth 5a (machining amount in the second rotation) is reduced from 0.1375mm to within 0.14mm, thus achieving the effect of the present invention. In contrast, in the case of a dies for machining a bolt groove with a module of 1.0, 27 teeth in the groove, and a machining allowance of 0.14 mm/rev in the guide section, if the groove 6 is set to machine the entire or approximately the entire width of the roller during the two rotations of the workpiece W, the maximum machining allowance of the dividing machining teeth 5 (machining allowance in the second rotation) will become 0.35 mm, exceeding 0.14 mm. As a result, the workpiece W will elongate and deform in both the circumferential and axial directions, and good results cannot be obtained. In this case, in order to prevent the maximum machining amount from exceeding 0.14mm, the groove 6 must be set in the manner of "machining the entire or approximately the entire width of the roller every 0.5 rotations". Specifically, in the case of a "tooth leading edge circle diameter φ21, module 0.3, and number of teeth 66" groove, when the total length L of the mold body 1 is 410mm, the length L2 of the guide part 2 is 289mm, and the pitch P of the groove 6 is defined as 0.782mm, when the entire or approximately the entire width of the roller is processed during the two rotations of the rolled material W, the tilt angle α is 0.35° (MIN). When the pitch P of the groove 6 is defined as 6.967mm, when the entire or approximately the entire width of the roller is processed during the one rotation of the rolled material W, the tilt angle α becomes 5.88° (MAX). Furthermore, in the case of a "tooth leading edge circle diameter φ17.4, module 0.47, and number of teeth 36" pin groove, when the total length L of the mold body 1 is 410mm, the L2 of the guide part 2 is 304mm, and the pitch P of the groove 6 is defined as 1.347mm, when the entire or approximately the entire width of the roller is processed during the two rotations of the rolled material W, the tilt angle α is 0.73° (MIN). When the pitch P of the groove 6 is defined as 6.967mm, when the entire or approximately the entire width of the roller is processed during the one rotation of the rolled material W, the tilt angle α becomes 7.10° (MAX). Furthermore, in cases where the tooth leading edge circle diameter is φ27.5, the module is 1.0, and the number of teeth is 27, the tilt angle α is 1.79° to 4.13° (see Experimental Examples 1 to 4 described later). In addition, a reduction section 7b is provided on the end side of the roller direction of the dividing machining tooth domain 7 in this embodiment. Specifically, the reducing section 7b is located in the area of the machining teeth 5 containing 6 to 12 teeth at the end of the dividing machining tooth region 7. The grooves 6 of each machining tooth 5 in the reducing section 7b are set to have a shallower groove depth and a narrower groove width compared to the grooves 6 of the dividing machining tooth region 7 located in the dividing machining tooth region 7 that are closer to the starting end of the roller direction than the reducing section 7b. Furthermore, the grooves 6 located in the area of the machining teeth 5 that are closer to the end of the reducing section 7b are set to have a shallower groove depth and a narrower groove width. Furthermore, the groove depth of the groove 6 at the reducing section 7b can also be linearly shallowed from the boundary between the starting end side segmented machining tooth area 7a and the reducing section 7b toward the end of the reducing section 7b. For example, it can also be gradually and linearly shallowed along the slope of the reducing angle g (see Figure 4) set as follows. The reduction angle g = arctan(groove depth D of the groove 6 at the boundary between the starting end segmented machining tooth area 7a and the reduction section 7b / length of the reduction section 7b in the rolling direction). By providing the reduction section 7b, the shape change of the machining tooth 5 caused by the presence of the groove 6 in the "starting end segmented machining tooth area 7a" and the "guide section 2, which is closer to the end of the rolling direction than the segmented machining tooth area 7" tends to be stable. This can suppress the rapid change of machining load and suppress the elongation deformation of the rolled material. As shown in FIG1, the guide section 2 of this embodiment has a fixed (constant) slope of the tooth leading edge line. That is, the processing amount of the guide section 2 (the processing amount of the rolled material W per rotation) is fixed (constant). The guide section 2 can also be configured such that a specific range measured at the starting end of the guide section 2 is defined as the first guide layer, and the remaining guide section 2 is defined as the second guide layer. The slope of the tooth leading edge line of the first guide layer is increased, and the slope of the tooth leading edge line of the second guide layer is decreased. The processing amount in the first guide layer is increased, and the processing amount in the second guide layer is decreased. Furthermore, although this embodiment, as previously described, applies the roller rolling die of the present invention to the flat roller rolling die shown in FIG12, the roller rolling die of the present invention can also be applied to the under-rounded roller rolling die shown in FIG13. The under-rounded roller rolling die rotates in the roller rolling direction, and the roller rolling teeth formed on its outer peripheral surface are sequentially provided from the starting end side in the roller rolling direction as follows: an inlet 2, the distance from the rotation axis of the under-rounded roller rolling die to the leading edge of the machining tooth 5 is different for each part; a finishing part 3; and an outlet part 4. In the case of a roller rolling die for under-rounding, the groove 6 is spirally arranged around the rotation axis of the under-rounding die with a lead angle (also called the lead angle) α, which is equivalent to the tilt angle α of the roller rolling die (see Figure 13(b)). In this way, by making the groove 6 spirally arranged around the rotation axis of the under-rounding die, the groove 6 is tilted at a specific tilt angle α relative to the rolling direction in the top view of the guide portion 2 of the under-rounding die where the groove 6 is formed, and is arranged to be a straight line (a slightly curved, almost straight line) in the rolling direction in the top view. In other words, as shown in Figure 13(b), in the unfolded state where the outer peripheral surface of the under-rounded roller die has been unfolded into a plane, the groove 6, like the flat roller die, is inclined at a specific angle α relative to the rolling direction, and is set to be a straight line in the rolling direction from a top view angle. Therefore, in the under-rounded roller die, by setting the groove 6 in a spiral shape around the rotation axis of the under-rounded roller die, the same effect as the effect of the flat roller die described below can be achieved. Since the roller rolling die is slightly cylindrical, the groove 6 located at the left and right ends (rolling direction) of the visible range appears slightly curved when viewed from above. In this embodiment, this slightly curved appearance is also included in "appearing as a straight line when viewed from above". Because this embodiment is configured as described above, in the dividing machining tooth domain 7 of the guide section 2, the "position where the dividing machining tooth 5a presses into the rolled material W" moves in the width direction of the mold body 1 while intermittently performing machining. Moreover, the area pressed into the rolled material W is smaller than in the case where the "rolled material W is pressed in by the machining tooth 5". By concentrating the machining load on the leading edge of each dividing machining tooth 5a, the dividing machining tooth 5a can more easily guide (bite into) the rolled material W. Even in the case where the "rolled material W is a thin hollow material", elongation deformation in the circumferential and axial directions can be suppressed. In the rolling process of grooves in hollow materials, the greater the ratio of the groove depth to the thickness of the rolled material W, the greater the elongation deformation in the circumferential and axial directions, making it difficult to form the desired tooth profile. In addition, the greater the ratio of the inner diameter (the diameter of the hollow part of the rolled material W) to the outer diameter (the diameter of the rolled material W), that is, the thinner the material W, the greater the elongation deformation in the circumferential and axial directions, making it difficult to form the desired tooth profile. Specifically, based on the applicant's current track record, when assuming a slot with a module of 0.3 to 1.1, examples of successfully machining hollow roll stock W without the use of a core (without elongation deformation) are limited to cases where "the ratio of the slot tooth depth to the thickness of the roll stock W is less than 17%, and the inner diameter of the roll stock W ( The ratio of the diameter of the hollow portion of the rolled material W to the outer diameter (diameter of the rolled material W) is less than 47%. Furthermore, even when a core is used, it is only applicable when "the ratio of the tooth depth of the stud groove to the material thickness of the rolled material W is less than 20%, and the ratio of the inner diameter (diameter of the hollow portion of the rolled material W) to the outer diameter (diameter of the rolled material W) is less than 47%." In cases where the ratio of the inner diameter (diameter) to the outer diameter (diameter of the rolled material W) is 55% or less, good machining is possible. However, by adopting this embodiment, as long as the conditions are met that "the ratio of the tooth depth of the groove to the material 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) is 55% or less", It can also be machined well without using a core. Furthermore, by using a core, it is possible to machine objects that meet the conditions that "the ratio of the tooth depth of the groove 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) is 70% or less". The following is an experiment (evaluation experiment) supporting the above-mentioned effect of this embodiment. <Experiment 1> As shown in Tables 1 and 2, a total of 6 conventional roll forming dies (hereinafter referred to as "Conventional Example 1" and "Conventional Example 2") were used to perform conventional core-shaped grooved roll forming on the hollow material W. The presence of circumferential and axial elongation deformation of the material W was evaluated. For each symbol recorded in Table 1, L is the length of the mold body 1, L2 is the length of the guide part 2, X is the rolling direction range (length) of the segmented machining tooth domain 7, and X/L2 is the ratio of the range X (length of the rolling direction range of the segmented machining tooth domain 7) to the length L2 (length L2 of the guide part) of the guide part 2 (please refer to Figure 1). Furthermore, for the symbols recorded in Table 2, where W1 is the tooth width of the segmented machining tooth 5a, W2 is the groove width of the groove 6, P is the pitch of the groove 6, α is the inclination angle of the groove 6, β is the groove angle of the groove 6, D is the groove depth of the groove 6, W3 is the leading edge width of the first tooth in the roller direction of the segmented machining tooth domain 7 in the guide section 2, W1/W3 is the tooth width ratio of the segmented machining tooth 5a, DP is the pin groove pitch of the mold (the pitch of the machined teeth in the pin groove in the roller direction), and W1/W2 is the ratio of the tooth width of the segmented machining tooth 5a to the groove width of the groove 6 (please refer to Figures 2 and 3). Specifically, when faced with hollow stock material W (material thickness 4mm~8mm) of varying thickness, the pin groove rolling process is performed using a core and under the following conditions. The pin diameter, root circle diameter, tooth profile error, tooth intersection error, cumulative pitch error, and groove deflection are measured. Based on these measurements, the circumferential and axial elongation deformation of the stock material W is evaluated. <Processing Conditions> • Pin Groove Specifications: Tooth leading edge diameter φ27.5×Z27×m1.0×PA37.5° Tooth depth: 1.2mm Where Z is the number of teeth in the pin groove, m is the module, and PA is the symbol representing the pressure angle. • Material of the workpiece: Carbon steel (S45C) • Material diameter: 26.46mm • Machining allowance: 0.14mm/rev in conventional example 1 and experimental examples 1-3; 0.09mm/rev in conventional example 2 and experimental example 4 • Tooth depth h of the first tooth of guide part 2: 0.6964mm in conventional example 1 and experimental examples 1-3; 0.6464mm in conventional example 2 and experimental example 4 • Material of the rolling die: Die steel (SKD11) • Distance traveled by the workpiece in the rolling direction per revolution: 83.1mm (= pitch DP3.0777mm × Z27 of the machined teeth of the slot in the rolling direction) • Machining conditions: The core is positioned at the center of the roll width, with the center value of the through-pin diameter specification as the target. • Material: Carbon steel (quenched) • Core dimensions and inner diameter: Please refer to Table 3 below. Furthermore, to further illustrate Experiments 1-4, the number of grooves on the rolled material W is based on the first tooth of the die (the first groove). In Experiments 1-3, when the length L2 of the die's guide portion is set to 449 mm and the number of teeth in the guide portion 2 is designed to be 146, as shown in Figure 6, the first, 28th, 55th, 82nd, and 109th teeth of the lower die... The 136th tooth, machining tooth 5, becomes the tooth used to machine the first groove of the rolled material W. In addition, the upper mold, by rotating the rolled material W half a circle, machines the same groove as the "groove machined by the first tooth of the lower mold". Therefore, the 14th tooth, the 41st tooth, the 68th tooth, the 95th tooth, and the 122nd tooth, machining tooth 5, become the teeth used to machine the first groove of the rolled material W. In Experiment 4, when the guide length L2 of the mold is set to 754mm and the number of teeth of the guide 2 is designed to be 245, as shown in Figure 6, the machining teeth 5 of the lower mold, namely the 1st, 28th, 55th, 82nd, 109th, 136th, 163rd, 190th, 217th, and 244th teeth, become the teeth used to process the workpiece material. In addition, the upper mold, through the half-turn rotation of the rolled material W, processes the same groove as the "groove processed by the first tooth of the lower mold". Therefore, its 14th tooth, 41st tooth, 68th tooth, 95th tooth, 122nd tooth, 149th tooth, 176th tooth, 203rd tooth and 230th tooth 5 become the teeth used to process the first groove of the rolled material W. In addition to the above explanation, in Experiments 1-4, the phase of the groove 6 (the offset of the die body 1 in the width direction) was set to process the entire or approximately the entire width of the roller width in each half-turn (0.5 rotations) of the workpiece W. The specifications for each measurement item are shown in Table 4. Furthermore, the evaluation results are shown in Table 5. In the evaluation results, for all items included in the evaluation—pipe diameter, tooth root circle diameter, tooth profile error, tooth intersection error, pitch cumulative error, and tooth groove deflection—those meeting the specifications shown in Table 4 are marked "○", while those not meeting the specifications are marked "×". Those that did not undergo an evaluation are marked with "-". As shown in Table 5, in the conventional example 1, although a good processing shape with suppressed elongation deformation in the circumferential and axial directions can be obtained when facing roll blanks W with material thicknesses of 8mm, 7mm and 6mm, it is confirmed that elongation deformation occurs in the circumferential and axial directions when the roll blanks W with material thicknesses of 5mm or less are subjected to such deformation. In contrast, in all the molds of Experimental Examples 1-4 (this embodiment), it can be confirmed that even when facing a roll material W with a material thickness of 5mm, a good processing shape with suppressed elongation deformation in the circumferential and axial directions can be obtained. In addition, although in Conventional Example 2, where the guide length L2 is set to be longer than that of Conventional Example 1 and Experimental Examples 1-3, it was confirmed that elongation deformation in the circumferential and axial directions occurred when facing a roll material W with a material thickness of 4mm, in Experimental Example 4 (this embodiment), where the guide length L2 is set to be the same as that of Conventional Example 2, it can be confirmed that a good processing shape with suppressed elongation deformation in the circumferential and axial directions can be obtained even when facing a roll material W with a material thickness of 4mm. In addition, Table 6 and Figures 7-10 show the detailed results of slotted rolling of the roll material W with a thickness of 5 mm in Conventional Example 1 and Experimental Examples 1-4. As shown in Table 6, in Conventional Example 1, due to elongation deformation in the circumferential and axial directions, non-compliance occurred in three items: pin diameter, cumulative pitch error, and tooth groove deflection. In contrast, in this embodiment (Experiments 1-4), all items met the specifications, and a good machining shape with suppressed elongation deformation in the circumferential and axial directions was obtained. Based on the mold specifications of Experiment 1, the groove depth D of groove 6 was changed to a shallower depth of 0.10 mm, and the pin groove rolling process and evaluation were carried out under the same conditions as the above experiments. Similar to the case where the groove depth D of groove 6 is 0.95mm (Example 1), all evaluation items meet the specifications, and a good machining shape with suppressed elongation deformation in both the circumferential and axial directions is obtained. In the grooved roller rolling process of Example 1, in the area 7 of the dividing machining teeth of the guide section 2, for every 0.5 rotations of the rolled material W, the dividing machining teeth 5a contact the same tooth groove on the rolled material W at different positions in the roller width direction (axial direction of the rolled material W). This is because: since the processing amount is 0.14mm/rev, as long as the groove depth D is set to a depth of 0.07mm (0.14mm×0.5) or more, the groove 6 will not come into contact with the rolled material W during the rolling process. <Experiment 2> In Experiment 2, using the same traditional Example 1 and Examples 1-4 as in Experiment 1, hollow stock materials W with varying thicknesses (6mm-8mm) were rolled under the same conditions as in Experiment 1 without the use of a core. The pin diameter, root circle diameter, tooth profile error, tooth intersection error, cumulative pitch error, and groove deflection were measured. Based on these measurements, the circumferential and axial elongation deformation of the stock material W was evaluated. The evaluation results are shown in Table 7. In the evaluation results, as in Experiment 1, all items that meet the specifications shown in Table 4, including overpin diameter, tooth root circle diameter, tooth profile error, tooth intersection line error, cumulative pitch error, and tooth groove deflection, are marked with "○" if they are in compliance with the specifications, and marked with "×" if one of them does not meet the specifications. As shown in Table 7, in Conventional Example 1, once the material thickness is not greater than 7 mm, it is impossible to obtain a "good processing shape in which elongation deformation in the circumferential and axial directions is suppressed". However, in Experimental Examples 1 to 4 (this embodiment), the following excellent results can be confirmed: even when facing a roll stock W with a material thickness of 6 mm, and without using a core, a good processing shape in which elongation deformation in the circumferential and axial directions is suppressed can be obtained. <Experiment 3> In Experiment 3, roll forming was performed under processing conditions such as "groove specifications and roll stock material" that are different from those in Experiment 1, and whether the roll stock W produces elongation deformation in the circumferential and axial directions was evaluated. Specifically, as shown in Tables 8 and 9, in this embodiment, the rolling dies of Examples 5-8, which have different specifications from those of "rolling dies of Examples 1-4", are used to perform pin-groove rolling on the hollow material W without using a mandrel. The pin diameter, root circle diameter, tooth profile error, tooth intersection line error, and cumulative pitch error are measured. The tooth groove deflection was then assessed, and based on the measurement results, an evaluation was made as to whether the rolled material W experienced elongation deformation in the circumferential and axial directions (Examples 7 and 8 are evaluations of whether the rolled material W experienced elongation deformation in the circumferential and axial directions when the tooth width W1 of the segmented machining tooth 5a was set to the minimum width (Example 7) and the maximum width (Example 8)). The symbols recorded in Tables 8 and 9 are identical to those in Experiment 1, so their explanations are omitted. <Machining conditions, etc.> • Plunger groove specifications: Tooth leading edge diameter φ17.4×Z36×m0.47×PA45° Tooth depth: 0.512mm In the above, Z is the number of teeth in the pin groove, m is the module, and PA is the symbol indicating the pressure angle. • Material of the workpiece: Carbon steel (S43C) • Workpiece diameter: 16.91mm • Machining allowance: 0.05mm/rev in Examples 5, 7, and 8; 0.031mm/rev in Example 6 • Tooth depth h of the first tooth of guide part 2: 0.289mm • Material of the rolling die: Die steel (SKD11) • Distance traveled by the workpiece in the rolling direction per rotation: 53.0mm • Machining conditions: At the center of the roll width, aiming at the center value of the overpin diameter specification. • No mandrel is used (to hold both ends of the workpiece W at the correct center). In Experiment 3, two types of hollow stock with different thicknesses (4.2 mm and 3.5 mm) were used as roll materials to evaluate whether circumferential and axial elongation deformation occurred. The specifications for each measurement item are shown in Table 10. Furthermore, the evaluation results are shown in Table 11. Additionally, Figures 17-22 show the measurement results for each measurement item in Experiments 5 and 6. In the evaluation results, for all evaluation items—pipe diameter, root circle diameter, tooth profile error, tooth intersection error, cumulative pitch error, and groove deflection—those meeting the specifications shown in Table 10 are marked "○", while those not meeting the specifications are marked "×". As shown in Table 11, in all experimental examples 5-8, it can be confirmed that a good processing shape with suppressed elongation deformation in both the circumferential and axial directions can be obtained regardless of the material thickness. Furthermore, as shown in Figures 17-22, Experimental example 6 achieves better overall performance compared to Experimental example 5. This is believed to be due to the improved deformation suppression effect achieved by halving the pitch P of the groove 6 and reducing the tooth width W1 of the split machining tooth 5a by half. <Experiment 4> In Experiment 4, for a groove with different specifications than that in Experiment 3 (tooth leading edge circle diameter φ21×Z66×m0.3×PA30°), the diameter of the rolled material W was defined as 20.42mm (material: carbon steel (S45C)). The hollow rolled material W was rolled without using a mandrel, and the circumferential and axial elongation deformation of the rolled material W was evaluated. Specifically, as shown in Table 12, measurements were performed on the "through diameter, root circle diameter, and gauge evaluation" for the cases where the tooth width W1 of the split machining tooth 5a was set to the minimum width (Example 9) and the cases where it was set to the maximum width (Example 10). Based on these measurements, the roll material W was evaluated to determine whether it experienced elongation deformation in the circumferential and axial directions. The setting conditions for each mold body 1 in Examples 9 and 10 are shown in Table 13. Furthermore, since the symbols recorded in Tables 12 and 13 are the same as those in Example 1, their explanations are omitted. The specifications for each measurement item are shown in Table 14. Furthermore, the evaluation results are shown in Table 15. In the evaluation results, all evaluation items that meet the specifications are marked with "○", while any item that does not meet the specifications is marked with "×". As shown in Table 15, in Experiment 9, where the tooth width W1 of the segmented machining tooth 5a was set to the minimum width of 0.503 mm, and in Experiment 10, where the tooth width W1 was set to the maximum width of 3.3 mm, the results of each evaluation item met the specifications regardless of the material thickness. <Experiment 5> In Experiment 5, the workpiece material W was rolled without using a mandrel, using dies with different positions of the segmented machining tooth area 7. The results of whether the workpiece material W underwent elongation deformation in the circumferential and axial directions were evaluated. Specifically, as shown in Table 16, measurements are taken for the following cases: when the segmented machining tooth area 7 is set from the starting end of the guide section 2 (Example 11), and when the segmented machining tooth area 7 is set from the position "a distance of two rotations of the rolled material W from the starting end of the guide section 2" (Example 12). The measurements are then taken for the following cases: "pipe diameter, tooth root circle diameter, tooth profile error, tooth intersection line error, pitch accumulation error, and tooth groove deflection". Based on the measurement results, it is evaluated whether the rolled material W has circumferential and axial elongation deformation. In Experiment 5, the pin groove specification was a pin groove with a leading edge circle diameter of φ18×Z22×m0.8×PA40°, and the diameter of the rolled material W was defined as 16.89mm (material: carbon steel (S45C)). Furthermore, the setting conditions of the mold body 1 in Experiments 11 and 12 are shown in Table 17. Additionally, the symbols recorded in Tables 16 and 17 are the same as those in Experiment 1, so their explanations are omitted. The evaluation results are shown in Table 18. In the evaluation results, all evaluation items that meet the specifications are marked with "○", and even if one item does not meet the specifications, it is marked with "×". As shown in Table 18, even when the segmented machining tooth area 7 is set from the position "a distance of two rotations of the rolled material W from the starting end of the guide section 2", the evaluation items all meet the specifications for each material thickness. In this embodiment, hollow material was used as the rolled material W in Experiments 1 to 5 above, and the good effect of the invention was confirmed. Even when rolling was performed using solid material as the rolled material W, the elongation deformation of the rolled material W in the circumferential and axial directions was suppressed to the maximum extent, and a high-quality product with the desired tooth shape can be obtained. Furthermore, the invention is not limited to this embodiment, and the specific structure of each component can be appropriately designed.

1: Mold body 2: Guide section 3: Finishing section 4: Guide section 5: Machining teeth 5a: Segmented machining teeth 6: Groove 7: Segmented machining tooth area 7b: Reduction section D: Groove depth L2: Guide section length W: Roller blank W1: Segmented machining tooth width W2: Groove width α: Groove inclination angle

[Figure 1] is a top view and a front view illustrating this embodiment. [Figure 2] is a top view illustrating the section machining tooth area of the guide section of this embodiment. [Figure 3] is a side view illustrating the groove and section machining teeth of this embodiment. [Figure 4] is a front view and a side view illustrating the guide section of this embodiment. [Figure 5] is a top view illustrating the reducing section of the guide section of this embodiment. [Figure 6] is an explanatory diagram showing the machining teeth (section machining teeth) used to machine the first groove of the workpiece in this embodiment. [Figure 7] is a chart showing the measurement results of the overpin diameter (OPD) in Experiment 1. [Figure 8] is a chart showing the measurement results of the tooth root circle diameter in Experiment 1. [Figure 9] is a chart showing the measurement results of the cumulative pitch error in Experiment 1. [Figure 10] is a chart showing the measurement results of the tooth groove deflection in Experiment 1. [Figure 11] is a diagram showing the grooves and segmented teeth of other examples of this embodiment (shallow groove types), where (a) is an illustrative side view and (b) is an illustrative top view. [Figure 12] is a schematic illustrative diagram of the rolling process using the flat dies of this embodiment. [Figure 13] is a diagram showing the rolling process in another example of this embodiment (applied to rolling incremental dies), where (a) is a schematic diagram and (b) is a top view showing the important parts. [Figure 14] is an explanatory diagram showing the processing status of the first groove of the workpiece in the case of this embodiment. [Figure 15] is an explanatory diagram showing the processing status of the first groove of the workpiece in the case of this embodiment. [Figure 16] is an explanatory diagram showing the processing status of the first groove of the workpiece in the case of the conventional example. [Figure 17] is a chart showing the measurement results of the pin diameter in Experiment 3. [Figure 18] is a chart showing the measurement results of the "tooth root circle diameter" in Experiment 3. [Figure 19] is a chart showing the measurement results of the "tooth profile error" in Experiment 3. [Figure 20] is a chart showing the measurement results of the "tooth intersection line error" in Experiment 3. [Figure 21] is a chart showing the measurement results of the "pitch accumulation error" in Experiment 3. [Figure 22] is a chart showing the measurement results of the "tooth groove deflection" in Experiment 3. [Figure 23] is a top view showing another example of this embodiment (a type where the machining tooth area is divided and set at a predetermined distance from the starting end of the guide section).

1: Mold body 2: Guide section 3: Finishing section 4: Guide section 5: Machining teeth 5a: Segmenting teeth 6: Groove 7: Segmenting teeth area 7a: Starting end segmenting area 7b: Reduction section 8: Bottom surface L: Total length of the mold body L1: Rolling direction range (length) of each roller in the guide section, finishing section, and guide section L2: Length of the guide section SB: Range of bead impact treatment X: Rolling direction range (length) of the segmenting teeth area

Claims (13)

A rolling die has an inlet portion, a finishing portion, and an outlet portion with machining teeth respectively provided from the starting end side of the die body in the rolling direction towards the ending end side. The machining teeth cause plastic deformation of the outer peripheral surface of the workpiece to roll the desired tooth profile. Its features are: From the starting end of the aforementioned guide portion to a specific position in the rolling direction of the guide portion, each of the aforementioned machining teeth is provided with a plurality of inclined grooves that, in a top view, are formed at a specific inclination angle relative to the rolling direction, thereby forming a plurality of segmented machining teeth. Each segmented machining tooth is configured to have a phase difference in the width direction of the aforementioned mold body in the rolling direction. Furthermore, in a specific range on the end side of the rolling direction of the segmented machining teeth, in the domain of the aforementioned segmented machining teeth, a reducing portion is provided. This reducing portion is configured such that, towards the end of the rolling direction, the groove depth of the aforementioned groove gradually becomes shallower, and the groove width of the aforementioned groove gradually becomes narrower. As described in claim 1, the aforementioned dividing machining teeth are configured to have a phase difference that allows the entire rolling width of the aforementioned roll material to be processed in the aforementioned dividing machining tooth domain where the dividing machining teeth are provided. As described in claim 1, the aforementioned groove is provided at a position from the starting end of the aforementioned guide portion to 60% to 95% of the length of the guide portion. As described in claim 2, the aforementioned groove is provided at a position from the starting end of the aforementioned guide portion to 60% to 95% of the length of the guide portion. As described in claim 1, the aforementioned groove is provided at a position from the starting end of the aforementioned guide portion at a specific distance to a position at 60% to 95% of the length of the guide portion. As described in claim 2, the aforementioned groove is provided at a position from the starting end of the aforementioned guide portion at a specific distance to a position at 60% to 95% of the length of the guide portion. The rolling die described in any one of claims 1 to 6, wherein the width of the aforementioned cutting teeth is 3.3 mm or less, and the aforementioned grooves are provided at equal intervals in the direction of the intersection of the aforementioned cutting teeth. The roller die described in any one of claims 1 to 6, wherein the aforementioned tilt angle is 0.35° to 7.10°. The roller die as described in claim 7, wherein the aforementioned tilt angle is 0.35° to 7.10°. The rolling die described in any of claims 1 to 6, wherein the aforementioned groove is configured to be straight in a top view. As described in claim 7, the aforementioned groove is configured to be straight in a top view. As described in claim 8, the aforementioned groove is configured to be straight in a top view. As described in claim 9, the aforementioned groove is configured to be straight in a top view.