Rolling Dies

Abstract

To provide a thread rolling die capable of providing a product of a desired tooth profile by suppressing a material to be thread-rolled from being elongated and deformed in a peripheral direction and an axis direction in a thread rolling process of a hollow material without enlarging the thread rolling die and using a specially configured core metal during the thread rolling process.SOLUTION: The thread rolling die is configured such that from the start end side of a chamfer 2 to the prescribed position of the chamfer 2 in a thread rolling direction, a plurality of strip grooves 6 are provided in each processing tooth 5 so as to incline at a prescribed angle α in the thread rolling direction in a plan view, a plurality of divided processing teeth 5a are formed by the strip grooves 6, and each divided processing tooth 5a is installed with a phase difference in the width direction of a die body 1 in the thread rolling direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a rolling die. [Background technology]

[0002] Conventionally, in the manufacture of metal splines, serrations, gears, screws, lead screws, worms, and the like, a rolling process has been widely used in which a roughly cylindrical rolled material is clamped between rolling dies on which a rolling tooth form (machined teeth) is formed, and the outer circumferential surface of the rolled material is plastically deformed while applying pressure to form the desired tooth form.

[0003] Compared to cutting, this rolling process has the following advantages: it is highly manufacturable and ideal for mass production; the surface of the rolled product becomes harder and stronger due to work hardening; and the burnishing effect between the processing teeth of the rolling die and the rolled material results in improved surface roughness of the rolled product.

[0004] 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-mentioned splines (rolled products) not only as solid products, but also as hollow products with a circular cross-section along the central axis of a roughly cylindrical shape.

[0005] However, when the rolling material is made into a hollow material and rolling processing is performed on the outer surface of this hollow material, the rolled material elongates and deforms in the circumferential and axial directions, making it impossible to obtain a product with the desired tooth shape, and if the rolling load is too large, the rolled material may crack.

[0006] In order to prevent the material to be rolled (hollow material) from stretching and deforming in the circumferential and axial directions as much as possible, a method has been used in which the rolling process is performed with a rod-shaped core bar (sometimes called a mandrel) inserted into a hole along the central axis of the approximately cylindrical shape. However, there is a problem in that simply using a core bar makes it difficult to obtain a product with the desired tooth shape.

[0007] In addition, the cutting portion of a typical rolling flat dies or rolling partial circular dies (rolling dies shaped like a cylinder with part of its outer periphery cut out) which have a cutting portion, finishing portion and escape portion is formed, is formed so that the amount by which the processing teeth are pressed into the rolled material (processing amount) increases as the rolling process progresses in this cutting portion (towards the end of the rolling direction); for example, in a rolling flat dies, the processing teeth of the cutting portion are arranged so that the tooth tip line of this processing tooth (an imaginary line connecting the tooth tips of the processing teeth) is inclined so that it approaches the rolled material as it moves from the start side of the rolling direction to the end side of the rolling direction.

[0008] Attempts have been made to prevent the material to be rolled (hollow material) from elongating and deforming 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 to be 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 it was necessary to increase the length of the biting portion, which in turn required the use of larger rolling dies.

[0009] For this reason, when manufacturing hollow products such as those described above, a typical manufacturing method involves performing a rolling process on a roughly cylindrical solid material to form the desired tooth profile, such as a spline, and then drilling a hole with a circular cross section along the central axis of the roughly cylindrical shape to produce a hollow product.However, this method has the problem of increasing manufacturing costs due to the additional hole drilling process.

[0010] In view of this, methods for rolling hollow materials have been proposed so far, as shown in Patent Documents 1 and 2. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2014-054644 A [Patent Document 2] JP 2002-143970 A Summary of the Invention [Problem to be solved by the invention]

[0012] The above-mentioned Patent Document 1 discloses a method for rolling a hollow material, in which a group of hard balls is placed in a through hole of a hollow material having a through hole communicating with two end openings, jigs are inserted from the two end openings, the hollow material is positioned while pressurizing the group of hard balls with the two jigs, the tooth-shaped surface of a rolling die is pressed against the outer circumferential surface of the hollow material to roll the outer circumferential surface of the hollow material, and after rolling, the group of hard balls is removed from the through hole to produce a hollow rolled product.

[0013] However, this method uses a group of hard balls rather than a rod-shaped core with a circular cross section (a so-called round bar), and requires a step of placing a group of hard balls in the through hole of the hollow material, a step of positioning the hollow material while applying pressure to the group of hard balls, and a step of removing the group of hard balls from the through hole after rolling. This results in a problem that the processing time is excessive, and the advantage of rolling, which is excellent for mass production and is optimal for mass production, cannot be utilized.

[0014] Furthermore, Patent Document 2 discloses a method for manufacturing a hollow gear, in which an inner diameter mandrel having an uneven surface on which each concave and convex portion extends axially parallel to each other and is arranged continuously in the circumferential direction is inserted into the central axial hole of a cylindrical workpiece, and the tooth profile processing surface of a rolling die is pressed against the outer peripheral surface of the workpiece while rotating the workpiece together with the inner diameter mandrel, thereby rolling-forming a tooth profile on the outer peripheral surface. Since the roll-forming is performed while each convex portion on the outer peripheral surface of the inner diameter mandrel is pressed against the inner peripheral surface of the workpiece, the circumferential flow of material on the inner peripheral surface of the workpiece can be restricted by each convex portion, and the circumferential length of the workpiece can be suppressed from increasing in the circumferential direction.

[0015] However, with this method, the convex portions on the outer peripheral surface of the inner diameter mandrel (core metal) are pressed against the inner peripheral surface of the workpiece while being roll-formed, which not only deforms the inner peripheral surface of the workpiece and makes it impossible to meet the dimensional standards for the inner diameter of the workpiece, but also makes it time-consuming to remove the workpiece from the inner diameter mandrel (core metal), and sometimes makes it impossible to remove it at all.

[0016] The present invention has been made in consideration of the current situation, and has an object to provide a rolling die that can minimize the circumferential and axial elongation deformation of the rolled material in the rolling process of hollow material, and can produce a product with the desired tooth profile, without having to make the rolling die larger or use a core bar with a special configuration during rolling. [Means for solving the problem]

[0017] The gist of the present invention will now be described with reference to the accompanying drawings.

[0018] A rolling die has a chamfering portion 2, a finishing portion 3, and a relief portion 4, each of which is provided with a processing tooth 5, from the starting end of the rolling direction of the die body 1 toward the terminal end of the rolling direction, and these processing teeth 5 plastically deform the outer circumferential surface of the material W to be rolled 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 these grooves 6 form a plurality of dividing processing teeth 5a, and each dividing processing tooth 5a is arranged so as to have a phase difference in the width direction of the die body 1 in the rolling direction. In addition, a gradually tapered portion 7b is provided in a predetermined range on the rolling direction terminal side of the dividing tooth region 7 where the dividing teeth 5a are provided, and this gradually tapered 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. The present invention relates to a rolling die characterized in that

[0019] In the rolling die according to claim 1, the dividing teeth 5a are arranged The above The present invention relates to a rolling die characterized in that in the dividing processing tooth region 7, the cutting teeth are arranged with a phase difference such that the entire rolling width of the material W to be rolled is processed.

[0020] Moreover, in the rolling die described in claim 1, the groove 6 is provided from the starting end position of the chamfer 2 to a position that is 60% to 95% of the length L2 of the chamfer 2.

[0021] In addition, the rolling die described in claim 2 is characterized in that the groove 6 is provided from the starting end position of the chamfer 2 to a position that is 60% to 95% of the length L2 of the chamfer 2.

[0022] Furthermore, in the rolling die described in claim 1, the groove 6 is characterized in that it is provided from a position a predetermined distance from the start end of the chamfer 2 to a position that is 60% to 95% of the length L2 of the chamfer 2.

[0023] Furthermore, in the rolling die described in claim 2, the groove 6 is characterized in that it is provided from a position a predetermined distance from the start end of the chamfer 2 to a position that is 60% to 95% of the length L2 of the chamfer 2.

[0024] Also, claim 1 ~6 Any one of the items The rolling die described herein is characterized in that the tooth width W1 of the cutting teeth 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 teeth 5a.

[0025] In addition, claims 1 to 6 In the rolling die described in any one of the above, the inclination angle α is 0.35° to 7.10°.

[0026] The present invention relates to a rolling die as recited in claim 7, wherein the inclination angle α is 0.35° to 7.10°.

[0027] In addition, claims 1 to 6 The rolling die according to any one of the above aspects is characterized in that the groove 6 is provided in a straight line in a plan view.

[0028] In addition, claims 7 The rolling die described herein is characterized in that the grooves 6 are provided in a straight line when viewed from above.

[0029] The rolling die according to claim 8 is characterized in that the groove 6 is provided in a straight line in a plan view.

[0030] The rolling die according to claim 9 is characterized in that the groove 6 is provided in a straight line in a plan view. Effect of the Invention

[0031] Since the present invention is configured as described above, it provides a rolling die that can minimize the circumferential and axial elongation deformation of the rolled material in the rolling process of hollow material and can produce a product with the desired tooth profile, without having to increase the size of the rolling die or use a core bar with a special configuration during rolling. [Brief description of the drawings]

[0032] [Figure 1] 1A and 1B are an explanatory plan view and an explanatory front view showing the present embodiment. [Diagram 2] FIG. 4 is an explanatory plan view showing a cutting tooth region of the chamfering portion of the present embodiment. [Diagram 3] FIG. 4 is an explanatory side view showing the grooves and the cutting teeth of the present embodiment. [Figure 4] 3A and 3B are explanatory front and side views showing the chamfering portion of the present embodiment. [Diagram 5] FIG. 4 is an explanatory plan view showing a tapered portion of the chamfering portion of the present embodiment. [Figure 6] FIG. 2 is an explanatory diagram showing a processing tooth (a dividing processing tooth) for processing a first groove of the rolled material in this embodiment. [Figure 7] 13 is a graph showing the measurement results of the over-pin diameter in Experiment 1. [Figure 8] 1 is a graph showing measurement results of root diameter in Experiment 1. [Figure 9] 13 is a graph showing measurement results of a cumulative pitch error in Experiment 1. [Figure 10] 1 is a graph showing measurement results of tooth space runout in Experiment 1. [Figure 11] 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). [Figure 12] FIG. 2 is a schematic explanatory diagram of the rolling process using the present embodiment (flat rolling die). [Figure 13] 1A is a schematic explanatory diagram of a rolling process using another example of this embodiment (when applied to a rolling segmented circular die), and FIG. 1B is an exploded plan view of a main portion. [Figure 14] FIG. 11 is an explanatory diagram showing the machining state of the first groove of the rolling material when this embodiment is used. [Figure 15] FIG. 11 is an explanatory diagram showing the machining state of the first groove of the rolling material when this embodiment is used. [Figure 16] FIG. 11 is an explanatory diagram showing the machining state of the first groove of the rolling material when a conventional example is used. [Figure 17] 13 is a graph showing the measurement results of the over-pin diameter in Experiment 3. [Figure 18] 13 is a graph showing the measurement results of the root diameter in Experiment 3. [Figure 19] 13 is a graph showing measurement results of tooth profile error in Experiment 3. [Figure 20] 13 is a graph showing the measurement results of tooth trace error in Experiment 3. [Figure 21] 13 is a graph showing measurement results of a cumulative pitch error in Experiment 3. [Figure 22] 13 is a graph showing the measurement results of tooth space runout in Experiment 3. [Diagram 23] FIG. 13 is an explanatory plan view showing another example of the present embodiment (a type in which a cutting tooth region is provided at a predetermined distance from the start end of the biting portion). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] A preferred embodiment of the present invention will be briefly described below with reference to the drawings to illustrate the operation of the present invention.

[0034] In the present invention, from the starting end of the cutting portion 2 to a predetermined position in the rolling direction of the cutting 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 planar view, and the processing tooth 5 is divided by these 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 not aligned with the rolling direction but are shifted in the tooth trace direction).Therefore, in the dividing processing tooth region 7 of the cutting processing tooth portion 2, the rolled material W is processed intermittently, 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 of the rolled material W in the circumferential and axial directions can be suppressed as much as possible.

[0035] That is, in the conventional rolling die 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 that when the rolled material W is a hollow material with a thin wall thickness, the action of the material swelling up into the tooth grooves of the die, as occurs when a solid material is processed, does not work well, and therefore, if a core bar is not used, the material will be crushed in the radial direction, and even if a core bar is used, the material W will be deformed 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 dividing 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 dividing 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 when the workpiece W to be rolled is a hollow material with a thin wall thickness, elongation deformation in the circumferential and axial directions can be suppressed. EXAMPLES

[0036] A specific embodiment of the present invention will now be described with reference to the drawings.

[0037] This embodiment relates to a rolling die having a cutting portion 2, a finishing portion 3 and a clearance portion 4, each of which is provided with processing teeth 5, from the starting end of the rolling direction of the die body 1 to the terminal end of the rolling direction, and which uses these processing teeth 5 to plastically deform the outer surface of the material W to roll a desired tooth shape. Specifically, this embodiment is an application of the rolling die of the present invention to a flat rolling die for rolling splines, serrations, gears, etc.

[0038] Each component of this embodiment will be described in detail below.

[0039] In this embodiment, as shown in Figure 1, the die body 1 is formed in a rectangular shape when viewed from above, and the bottom surface 8 is formed as a flat surface that serves as a reference surface. Also, on the upper surface opposite this bottom surface 8, a large number of processing teeth 5 are provided which form a tooth profile in the rolled material W, and the tooth tip lines of these processing teeth 5 (virtual 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).

[0040] Furthermore, in order to prevent slippage of the rolled material W (to prevent 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 starting end in the rolling direction to the terminal end in 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 about 2 / 3 of the length (total length) of the biting portion 2 indicated by the symbol L2 in the figure (the range indicated by the symbol SB in the figure).) The symbol L1 in the figure indicates the sum of the ranges (lengths) in the rolling direction of the biting portion 2, the finishing portion 3 and the relief portion 4.

[0041] Moreover, this embodiment is a rolling flat die for machining a normal spline (a spline in which a tooth profile is 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. Note that by making the extension direction of the machining teeth 5 a direction inclined with respect to the direction perpendicular to the rolling direction, this embodiment can be applied to a rolling die for machining a helical spline, a helical gear, etc.

[0042] Specifically, the processing teeth 5 of the cutting portion 2 are configured so that their 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 processing teeth 5 of the finishing portion 3 are set to a constant tooth height (approximately the same tooth height as the processing teeth 5 at the end side 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; and the processing teeth 5 of the escape 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 face gradually becomes lower as it approaches the end side of the rolling direction.

[0043] 1, the biting portion 2 in this embodiment is configured as a dividing tooth region 7 in which a plurality of dividing teeth 5a are provided, each of the teeth 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 range (length) of the dividing tooth region 7 in the rolling direction.

[0044] 2, in this dividing tooth region 7, the dividing teeth 5a are linearly arranged in the width direction of the die body 1, and are arranged in the rolling direction with a phase difference in the width direction of the die body 1. 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.

[0045] Here, the rolling width refers to the axial range in which a tooth profile is formed in the rolled material W by rolling processing.

[0046] Further, the dividing 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.

[0047] By providing this cutting tooth area 7, in other words the cutting teeth 5a, from the starting end of the biting portion 2, the range of the cutting tooth area 7 can be set widely in the biting portion 2 of a predetermined length. As a result, more rolling is 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 exerted.

[0048] Incidentally, the dividing tooth region 7 does not have to start from the start of the biting portion 2, but may start at a position an appropriate distance away from the start of the biting portion 2 as shown in Fig. 23. In this case, the position where the dividing tooth region 7 is provided (the position where the dividing tooth region 7 starts, in other words, the start position of the groove 6) is preferably a position separated by a distance of 0.5 to 2 revolutions of the rolled material W.

[0049] The reason why the range in which the dividing teeth 5a are provided is set to 60% to 95% of the length L2 of the biting portion 2 is that if the dividing teeth 5a are provided only to a position that is less than half the length of the biting portion 2, the desired effect will not be achieved, and if the dividing teeth 5a are provided over the entire length of the biting portion 2, in other words, if they are provided 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 due to the streaks 6) may remain on the tooth surface after rolling. Therefore, the upper limit position of the range in which the dividing teeth 5a are provided may be set slightly before the boundary position with the finishing portion 3 (the starting end side in the rolling direction), and it is more preferable to set it to a position that is 95% of the length L2 of the biting portion 2.

[0050] Moreover, the groove 6 forming the dividing processing tooth 5a (the groove 6 dividing the processing tooth 5) is formed into a tapered groove whose groove width becomes wider 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 processing, and it may be formed by, for example, laser processing or the like.

[0051] Furthermore, if the groove width W2 of the groove 6 is too narrow relative to the tooth width W1 of the cutting teeth 5a described below, the shape will be similar to that of a conventional product (one that does not have a groove 6 and does not have a cutting tooth 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 relative to the tooth width W1, an unmachined portion will be created, causing the processing load in the finishing portion 3 to become too large and deforming the rolled material W. Therefore, the groove width W2 of the groove 6 needs to be set from the tooth width W1 of the cutting teeth 5a.

[0052] Taking this into consideration, the groove width W2 of the groove 6 can be set appropriately 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 processing tooth 5a is preferable, and specifically, it is preferable to set the ratio of the tooth width W1 of the cutting processing tooth 5a to the groove width W2 of the groove 6 to be 0.9 to 1.8.

[0053] In addition, in the specification where the ratio of the tooth width W1 of the cutting processing tooth 5a to the groove width W2 of the groove 6 is 0.9 (the 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 processing tooth area 7 of the biting portion 2, but since almost the entire rolling width is machined, the processing load in the finishing portion 3 does not become too large. Therefore, as described above, this falls within the preferable range and is included in the "groove width equivalent to the tooth width W1 of the cutting processing tooth 5a."

[0054] In addition, 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 portion of the groove 6 (the widest portion) as shown in Figure 3, and in this embodiment, the tooth width W1 of the cutting processing tooth 5a means the tooth width in the width direction of the die body 1 at the tip surface of the cutting processing tooth 5a as shown in Figure 3.

[0055] Moreover, the groove 6 in this embodiment is provided along the inclination of the processing tooth 5 of the biting portion 2 (the inclination of the tip line of the processing tooth 5) from the starting end side in the rolling direction toward the rear end side in the rolling direction, and the groove depth D of the groove 6 based on the tip of the processing tooth 5 is set to be a constant depth. Note that the groove depth D of the groove 6 can be appropriately set 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 processing tooth 5.

[0056] 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 divide the processing tooth 5, but as long as the predetermined depth is sufficient to exert 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) in order to prevent chipping during rolling due to a decrease in the strength of the dividing processing tooth 5a.

[0057] Furthermore, in this embodiment, the grooves 6 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 larger than the above value (a wider value), the deformation suppression effect on the thin-walled rolling material W cannot be sufficiently obtained).

[0058] As mentioned above, this embodiment is a rolling flat die for processing 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 coincide.

[0059] The narrower the tooth width W1 of the dividing 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 dividing 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.

[0060] Specifically, the tooth tip width in the rolling direction of the first tooth of the die is set as a threshold value, and if the tooth width W1 is made narrower than this, chipping becomes very likely to occur, so it is preferable to set the tooth width W1 to be greater than or equal to the tooth tip width in the rolling direction of the first tooth of the die.

[0061] Taking this into consideration, the grooves 6 in this embodiment are arranged at equal intervals in the tooth trace direction of the cutting processing tooth 5a so that the tooth width W1 of the cutting processing tooth 5a in its complete shape (state divided by two grooves 6) is 0.5 mm or more and 3.3 mm or less.

[0062] Moreover, 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 in a straight line (straight and continuous) in a plan view in the rolling direction, as shown in Fig. 2. By providing the grooves 6 in this manner, it becomes possible to easily arrange the dividing processing teeth 5a in a state having a phase difference in the width direction of the die body 1 in the rolling direction.

[0063] In addition, the groove 6 is not limited to being arranged in a straight line when viewed from above as in this embodiment, but may be arranged in a straight line (straight and intermittent) along a straight line when viewed from above as in another example of this embodiment shown in Figure 11 (b).

[0064] Specifically, in this embodiment, the groove 6 is obliquely provided at an angle (inclination angle α) of 0.35° to 7.10° with respect to the rolling direction when viewed in a plane. In this embodiment, the amount by which the dividing processing tooth 5a pushes the rolled material deepest in the tooth height direction (maximum processing amount) is within 0.14 mm, and by providing the groove 6 at this angle, 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 processing tooth area 7, and no unprocessed portion is formed (if the inclination angle α becomes large, a load is applied in the axial direction to the rolled material W 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-mentioned range).

[0065] 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 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 will be elongated and deformed in the circumferential and axial directions.

[0066] For example, in the case of a spline processing die having 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 in 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 having 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 in the second rotation) is 0.35 mm, which exceeds 0.14 mm, and the rolled material W is elongated 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 substantially the entire rolling width is processed every 0.5 revolutions.

[0067] Specifically, in the case of a spline having a tooth tip circle diameter φ21, a module 0.3, and 66 teeth, the total length L of the die body 1 is 410 mm, the length L2 of the cutting portion 2 is 289 mm, the pitch P of the groove 6 is 0.782 mm, and when the entire rolling width or approximately the entire rolling width of the rolled material W is processed in two rotations, 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 approximately the entire rolling width of the rolled material W is processed in one rotation, the inclination angle α is 5.88° (MAX).

[0068] In addition, in the case of a spline having a tooth tip circle diameter of φ17.4, a module of 0.47, and 36 teeth, the total length L of the die body 1 is 410 mm, L2 of the cutting portion 2 is 304 mm, the pitch P of the groove 6 is 1.347 mm, and when the entire rolling width or approximately the entire rolling width of the rolled material W is processed in two rotations, 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 approximately the entire rolling width of the rolled material W is processed in one rotation, the inclination angle α is 7.10° (MAX).

[0069] Furthermore, when the 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 later).

[0070] Further, a gradually tapering portion 7b is provided at the terminal end side in the rolling direction of the divided tooth region 7 of this embodiment.

[0071] Specifically, the gradually tapering portion 7b is set in a range including 6 to 12 processing teeth 5 at the end of the dividing processing tooth region 7, and the grooves 6 provided in each processing tooth 5 of this gradually tapering portion 7b are set to a shallower groove depth and narrower groove width than the grooves 6 provided in the starting end side dividing processing tooth region 7a of the dividing processing tooth region 7, which is closer to the starting end side in the rolling direction than the gradually tapering portion 7b.Furthermore, the grooves 6 provided in the processing teeth 5 closer to the end of the gradually tapering portion 7b are set to have a shallower groove depth and narrower groove width.

[0072] In addition, the groove depth of the groove 6 in this gradually tapering portion 7b may become shallower in a curved manner from the boundary between the starting end side cutting processing tooth area portion 7a and the gradually tapering portion 7b toward the end of the gradually tapering portion 7b, or may gradually become shallower in a linear manner along the gradient of the gradually tapering angle g (see Figure 4) that is set, for example, as follows.

[0073] The tapered angle g = arctan (the groove 6 at the boundary between the starting end cutting tooth region 7a and the tapered portion 7b) (D) / (Length of tapered portion 7b in the rolling direction)

[0074] By providing this gradually tapering portion 7b, the change in the shape of the processing tooth 5 due to the presence or absence of the groove 6 at the starting end cutting processing tooth area 7a and at the end side of the cutting processing tooth area 7 in the rolling direction of the biting portion 2 is made gentler, thereby suppressing sudden changes in the processing load and preventing elongation deformation of the rolled material.

[0075] In this embodiment, the cutting portion 2 has a constant gradient of the tooth tip line as shown in FIG. 1, i.e., the machining amount at the cutting portion 2 (the machining amount per rotation of the rolled material W) is set to be constant. However, the cutting portion 2 may be configured such that a predetermined range at the start of the cutting portion 2 is the first cutting stage and the remaining cutting portion 2 is the second cutting stage, with the gradient of the tooth tip line at the first cutting stage being large and the gradient of the tooth tip line at the second cutting stage being small, so that the machining amount is large at the first cutting stage and small at the second cutting stage.

[0076] As described above, this embodiment is an example in which 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.

[0077] The rolling recess circular die rotates in the rolling direction, and the rolling tooth form formed on its outer circumferential surface is provided with a cutting portion 2, a finishing portion 3, and a relief portion 4, which are successively provided from the starting end in the rolling direction, and 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. In the case of the rolling recess circular die, the groove 6 is provided in a spiral shape with a lead angle α around the rotation axis of the rolling recess circular die, and this lead angle α corresponds to the inclination angle α in the rolling flat die (see FIG. 13(b)).

[0078] By providing the groove 6 in a spiral shape around the rotation axis of the rolling die in this way, the groove 6 is inclined at a predetermined inclination angle α with respect to the rolling direction in a 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 a plan view in the rolling direction (slightly curved, approximately linear state). In other words, as shown in FIG. 13(b), in a 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 a 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 that when applied to the rolling flat die described below is achieved. Incidentally, due to the rolling recessed circular die having an approximately cylindrical shape, when viewed in a plane, the grooves 6 located at the left and right ends of the visible range (rolling direction) appear to be slightly curved; however, in this embodiment, this slightly curved state is also included in the term "straight when viewed in a plane."

[0079] Since this embodiment is configured as described above, in the cutting tooth area 7 of the biting portion 2, the cutting teeth 5a intermittently process the rolled material W by moving the pushing position in the width direction of the die body 1 relative to the rolled material W, and further, 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, and 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.

[0080] In the rolling of splines into hollow material, the greater the ratio of the spline tooth height to the thickness of the rolled material W, the greater the circumferential and axial extension deformation, making it more difficult to form the desired tooth profile. Also, 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) of the rolled material W, i.e., the thinner the thickness of the rolled material W, the greater the circumferential and axial extension deformation, making it more difficult to form the desired tooth profile.

[0081] Specifically, in the past experience of the present applicant, assuming a spline with a module of 0.3 to 1.1, the hollow material W to be rolled can be processed well (without elongation deformation) without a core bar only when the ratio of the tooth height of the spline to the thickness of the material W to be rolled is 17% or less and the ratio of the inner diameter (diameter of the hollow part of the material W to the outer diameter (diameter of the material W to be rolled) of the material W to be rolled is 47% or less. Also, even if a core bar is used, the ratio of the tooth height of the spline to the thickness of the material W to be rolled is 20% or less and the ratio of the inner diameter (diameter of the hollow part of the material W to the outer diameter (diameter of the material W to be rolled) of the material W to be rolled is 55% or less. In the past, good machining was only possible in the cases below, but 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 portion 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 portion of the rolled material W) to the outer diameter (diameter of the rolled material W) of the rolled material W is 70% or less.

[0082] The following is an experiment (evaluation experiment) that supports the effects of this embodiment described above.

[0083] <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.

[0084] For each symbol in Table 1, L: length of die body 1, L2: length of chamfer 2, X: range (length) of cutting tooth region 7 in the rolling direction, and X / L2: ratio of range X of cutting tooth region 7 (length of cutting tooth region 7 in the rolling direction) to length L2 of chamfer 2 (chamfer length L2) (see FIG. 1).

[0085] In addition, the symbols listed 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: tooth tip width in the rolling direction of the first tooth of the dividing tooth area 7 in the cutting 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).

[0086] [Table 1]

[0087] [Table 2]

[0088] Specifically, spline rolling was performed using a core wire under the following conditions on hollow rolled materials W (thickness 4 mm to 8 mm) of different thicknesses, and the overpin diameter, bottom circle diameter, tooth profile error, tooth lead error, cumulative pitch error and tooth groove runout of each were measured. Based on these measurement results, the presence or absence of elongation deformation in the circumferential and axial directions of the rolled materials W was evaluated.

[0089] <Processing conditions etc.> Spline specifications: Tooth tip diameter φ27.5×Z27×m1.0×PA37.5° Tooth length: 1.2mm 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: 26.46mm - Machining volume: 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 chamfer 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 traveled in the rolling direction per revolution of the rolled material: 83.1 mm (= spline tooth pitch in the rolling direction DP3.0777mm x Z27) Processing conditions: Aim for the center of the pin diameter standard at the center of the rolling width

[0090] <Core used> Material: Carbon steel (hardened) Core dimensions and inner diameter: See Table 3 below

[0091] [Table 3]

[0092] Further explaining experimental examples 1 to 4, when the number of grooves in the rolled material W is based on the 1st tooth of the lower die (1st 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 1st groove in 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 in half a rotation of the rolled material W, so the processing teeth 5 of the 14th, 41st, 68th, 95th and 122nd teeth become the teeth that process the 1st groove in the rolled material W. In experimental example 4, when the die cutting portion length L2 is designed to be 754 mm and the cutting portion 2 has 245 teeth, 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 almost the entire rolling width was machined every half rotation (0.5 rotation) of the rolling material W.

[0093] Table 4 shows the standards for each measurement item. Table 5 shows the evaluation results. In the evaluation results, if all the evaluation items, over pin diameter, root circle diameter, tooth profile error, tooth lead error, cumulative pitch error, and tooth space 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 -.

[0094] [Table 4]

[0095] [Table 5]

[0096] As shown in Table 5, in Conventional Example 1, a good processed shape was obtained in which the circumferential and axial elongation deformation was suppressed for the rolling material W having a thickness of 8 mm, 7 mm, and 6 mm, but it was confirmed that the rolling material W having a thickness of 5 mm or less had circumferential and axial elongation deformation. In contrast, in Experimental Examples 1 to 4 (this embodiment), it was confirmed that a good processed shape was obtained in which the circumferential and axial elongation deformation was suppressed for the rolling material W having a 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 the rolling material W having a thickness of 4 mm had circumferential and axial elongation deformation, 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 the circumferential and axial elongation deformation was suppressed for the rolling material W having a thickness of 4 mm.

[0097] Table 6 and Figs. 7 to 10 show detailed results when the rolling material W having a wall thickness of 5 mm in Conventional Example 1 and Experimental Examples 1 to 4 was subjected to spline rolling.

[0098] [Table 6]

[0099] As shown in Table 6, in Conventional Example 1, due to the occurrence of elongation deformation in the circumferential and axial directions, three items, namely over-pin diameter, cumulative pitch error, and tooth groove runout, were out of specification. In contrast, in the present embodiment (Experimental Examples 1 to 4), no out-of-specification occurred in any item, and a good processed shape was obtained in which elongation deformation in the circumferential and axial directions was suppressed.

[0100] In addition, spline rolling and evaluation were also performed under the same conditions as the above experiment, with the groove depth D of the groove 6 being changed to a shallow depth of 0.10 mm based on the die specifications of Experimental Example 1. 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 elongation deformation suppressed in the circumferential and axial directions.

[0101] In the spline rolling process in Experimental Example 1, in the dividing tooth region 7 of the cutting portion 2, the dividing 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 rotation of the rolled material W. Since the processing amount is 0.14 mm / rotation, if the groove depth D is set to a depth of 0.07 mm (0.14 mm x 0.5) or more, the streak groove 6 will not come into contact with the rolled material W during rolling.

[0102] <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 rolled 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, root 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 rolled material W was evaluated based on the measurement results.

[0103] The evaluation results are shown in Table 7. As in Experiment 1, the evaluation results were marked with an ◯ when all the evaluation items, i.e., 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 × when any of the evaluation items was out of standard.

[0104] [Table 7]

[0105] As shown in Table 7, in conventional example 1, unless the wall thickness was 7 mm or more, a good processed shape in which elongation deformation in the circumferential and axial directions was suppressed could not be obtained. 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 wall thickness of 6 mm, without using a core wire.

[0106] <Experiment 3> In experiment 3, the rolling process was performed under processing conditions, such as the spline specifications and the material of the rolled material, which were different from those in experiment 1, and the presence or absence of elongation deformation in the circumferential and axial directions of the rolled material W was evaluated.

[0107] 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, bottom circle diameter, tooth profile error, tooth trace error, cumulative pitch error, and tooth groove runout were measured, and the presence or absence of elongation deformation in the circumferential and axial directions of the rolling material W was evaluated from the measurement results (Experimental Examples 7 and 8 are evaluations of the presence or absence of elongation deformation in the circumferential and axial directions of the rolling 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.

[0108] [Table 8]

[0109] [Table 9]

[0110] <Processing conditions etc.> Spline specifications: Tooth tip diameter φ17.4×Z36×m0.47×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: 16.91mm - Machining volume: Experimental examples 5, 7, 8: 0.05mm / revolution, Experimental example 6: 0.031mm / revolution -Tooth height of the first tooth of the chamfer 2: h: 0.289 mm · Material of rolling dies: Die steel (SKD11) Distance in the rolling direction per revolution of the rolled material: 53.0 mm Processing conditions: Aim for the center of the pin diameter standard at the center of the rolling width No core bar 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 rolling material W with different wall thicknesses (wall thicknesses of 4.2 mm and 3.5 mm).

[0111] Table 10 shows the standards for each measurement item. Table 11 shows the evaluation results. Figures 17 to 22 show the measurement results for each measurement item for Experimental Examples 5 and 6. In the evaluation results, a circle is indicated when all the evaluation items, i.e., over-pin diameter, bottom circle diameter, tooth profile error, tooth lead error, cumulative pitch error, and tooth groove runout, are within the standards shown in Table 10, and an X is indicated when any one of the evaluation items is outside the standards.

[0112] [Table 10]

[0113] [Table 11]

[0114] As shown in Table 11, it was confirmed that in all of Experimental Examples 5 to 8, a good processed shape in which elongation deformation in the circumferential and axial directions was suppressed was obtained for any wall thickness.

[0115] 17 to 22, better results were obtained overall in Experimental Example 6 than in 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 dividing teeth 5a was halved, thereby improving the deformation suppression effect.

[0116] <Test 4> In experiment 4, for a spline with different specifications from experiment 3 (tooth tip circle diameter φ21 × Z66 × m0.3 × 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 wire, and the presence or absence of elongation deformation in the circumferential and axial directions of the rolled material W was evaluated.

[0117] Specifically, the overpin diameter, bottom circle 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. Explanations of the symbols in Tables 12 and 13 will be omitted as they are the same as those in Experiment 1.

[0118] [Table 12]

[0119] [Table 13]

[0120] The standards for each measurement item are shown in Table 14. The evaluation results are shown in Table 15. In addition, the evaluation results were marked with an O when all evaluation items were within the standards, and an X when even one of the evaluation items was out of the standards.

[0121] [Table 14]

[0122] [Table 15]

[0123] As shown in Table 15, in experimental example 9 in which the tooth width W1 of the cutting tooth 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.

[0124] <Test 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.

[0125] Specifically, the overpin diameter, bottom circle diameter, tooth profile error, tooth lead error, cumulative pitch error and tooth groove runout were measured in the case where the cutting tooth region 7 as shown in Table 16 was provided from the starting end of the cutting portion 2 (Experimental Example 11) and in the case where the cutting tooth region 7 was provided at a position two rotations of the rolled material W away from the starting end of the cutting portion 2 (Experimental Example 12), 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.

[0126] In Experiment 5, the spline had a tooth tip diameter of φ18×Z22×m0.8×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 of the symbols in Tables 16 and 17 are omitted because they are the same as those in Experiment 1.

[0127] [Table 16]

[0128] [Table 17]

[0129] The evaluation results are shown in Table 18. In addition, in the evaluation results, when all evaluation items were within the specifications, it was marked with an O, and when even one of the evaluation items was out of the specifications, it was marked with an X.

[0130] [Table 18]

[0131] As shown in Table 18, even when the cutting tooth region 7 was located at a position 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.

[0132] In this embodiment, the excellent effects of the present invention were confirmed in the above experiments 1 to 5, where the rolled material W was a hollow material. However, even when the rolled material W is rolled as a solid material, it is possible to suppress as much as possible the elongation and deformation of the rolled material W in the circumferential and axial directions, and obtain an excellent product having the desired tooth profile.

[0133] Furthermore, the present invention is not limited to the present embodiment, and the specific configuration of each component can be designed as appropriate. [Explanation of symbols]

[0134] 1 Dice body 2. Meal section 3 Finishing Section 4 Relief 5 Machining teeth 5a Cutting teeth 6 grooves 7 Cutting tooth area 7b Tapered section D Groove depth L2 Length of chamfer W Rolled material W1 Width of cutting teeth W2 groove width α Groove inclination angle

Claims

1. 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. 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.

3. 2. The rolling die according to claim 1, wherein the groove is provided from a start position of the chamfer to a position that is 60% to 95% of the length of the chamfer.

4. 3. The rolling die according to claim 2, wherein the groove is provided from a start position of the chamfer to a position that is 60% to 95% of the length of the chamfer.

5. 2. The rolling die according to claim 1, wherein the groove is provided from a position a predetermined distance away from the start of the chamfer to a position that is 60% to 95% of the length of the chamfer.

6. 3. The rolling die according to claim 2, wherein the groove is provided from a position a predetermined distance away from the start of the chamfer to a position that is 60% to 95% of the length of the chamfer.

7. The 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.

8. The rolling die according to any one of claims 1 to 6, wherein the inclination angle is 0.35° to 7.10°.

9. A rolling die as described in claim 7, characterized in that the inclination angle is 0.35° to 7.10°.

10. 7. The rolling die according to claim 1, wherein the groove is provided in a straight line in a plan view.

11. 8. The rolling die according to claim 7, wherein the groove is provided in a straight line in a plan view.

12. A rolling die as described in claim 8, characterized in that the grooves are arranged in a straight line when viewed in a plane.

13. A rolling die as described in claim 9, characterized in that the grooves are arranged in a straight line when viewed in a plane.

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