Rolling die set

Abstract

The invention provides a rolling die set capable of suppressing deformation of a rolled material as much as possible without requiring large size of a die and a core bar in rolling processing of a hollow member. The rolling die set is configured in such a manner that a plurality of grooves (6) extending in a straight line in the rolling direction in plan view are provided in parallel at predetermined intervals in the width direction of the rolling dies (1) on the machining teeth (5) within a predetermined range in the rolling direction from the start end side of the nip section (2) of each rolling die (1). A plurality of divided machined teeth (5a) are formed through the grooves (6) in a state that the divided machined teeth (5a) are arranged in the rolling direction and the tooth trace direction, and the divided machined teeth (5a) of each rolling die (1) are formed in a state that the positions of the divided machined teeth (5a) of the other rolling dies (1) in the group are offset in the tooth trace direction. The whole rolling width area of the rolled raw material (W) is processed when the rolled raw material (W) rotates by 1 / 2 or 2 / 3.

Description

Technical Field

[0001] The present invention relates to a rolling die set including two or three rolling dies as a set. Background Art

[0002] Conventionally, in the manufacture of metal splines, serrations, gears, threads, lead screws, worms, etc., rolling processing as described below has been widely used: a rolling die having a rolling tooth profile (processing tooth) is used to hold a substantially cylindrical rolled raw material, and while applying pressure, the outer peripheral surface of the rolled raw material is plastically deformed to form a desired tooth profile.

[0003] This rolling processing has the advantages of excellent mass productivity and being most suitable for mass production compared to cutting processing, the hardness and strength of the surface of the rolled product becoming higher due to processing hardening, and the surface roughness of the processed surface of the rolled product becoming good due to the burnishing effect of the processing teeth of the rolling die on the rolled raw material.

[0004] In addition, splines and serrations are also widely used in automotive components such as drive shafts and steering shafts. Along with the recent requirements for vehicle lightweighting, there is an increasing demand for the above-mentioned spline products (rolled products) not only to be solid products but also to be hollow products having a hole with a circular cross-section along the central axis of a substantially cylindrical shape.

[0005] However, when the rolled raw material is a hollow member and the outer peripheral surface of the hollow member is subjected to rolling processing, the rolled raw material elongates and deforms in the circumferential and axial directions, and a product having a desired tooth profile cannot be obtained. In addition, when the rolling load is too large, the rolled raw material sometimes breaks.

[0006] In order to prevent such elongation and deformation of the rolled raw material (hollow member) in the circumferential and axial directions as much as possible, a means of performing rolling processing with a rod-shaped core (sometimes also referred to as a mandrel, a core shaft, etc.) inserted into a hole along the central axis of a substantially cylindrical shape has also been adopted. However, if only the core is used, there is a problem that it is difficult to obtain a product having a desired tooth profile.

[0007] In addition, in a normal rolling flat die or a rolling split die (a rolling die having a shape in which a part of the outer periphery of a substantially cylindrical shape is cut off) formed with a biting portion, a finishing portion, and a retracting portion, the biting portion is formed such that as the rolling processing at the biting portion progresses (towards the end side in the rolling direction), the amount of press-in (processing amount) of the processing teeth into the rolled raw material increases. For example, in a rolling flat die, the processing teeth of the biting portion are arranged such that the tooth top line (an imaginary line connecting the tooth tops of the processing teeth) of the processing teeth forms an inclination that approaches the rolled raw material more from the start side in the rolling direction towards the end side in the rolling direction.

[0008] Although attempts have been made to prevent the circumferential and axial elongation deformation of the raw material to be rolled (hollow part) by gradually applying a rolling load to the raw material to be rolled by making the inclination of the tooth top line of the machining teeth of the biting part gentle, the problem of difficulty in obtaining a product with a desired tooth shape cannot be solved, and there is also a problem that the length of the biting part needs to be increased, so the rolling die has to be enlarged.

[0009] Therefore, in the case of manufacturing a hollow product as described above, a manufacturing method is generally adopted in which a solid piece having a substantially cylindrical shape is subjected to rolling processing to form a desired tooth shape such as a spline, and then a hole with a circular cross-section is machined along the central axis of the substantially cylindrical shape to manufacture a hollow product. However, in this method, since the hole machining process is added, there is a problem of increased manufacturing cost.

[0010] Therefore, heretofore, rolling processing methods for hollow parts as shown in Patent Documents 1 and 2 have been proposed.

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-054644

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 2002-143970

[0013] The above-mentioned Patent Document 1 discloses a rolling processing method for a hollow part as follows: a hard ball group composed of a plurality of hard balls is accommodated in the through hole of a hollow part having a through hole communicating with two end openings, jigs are inserted from the two end openings, the hollow part is positioned while pressing the hard ball group with the two jigs, the tooth profile machining surface of the rolling die is pressed against the outer peripheral surface of the hollow part to roll the outer peripheral surface of the hollow part, and the hard ball group is taken out from the through hole after rolling to manufacture a hollow rolled product.

[0014] However, this method uses a hard ball group composed of a plurality of hard balls instead of a rod-shaped part with a circular cross-section (so-called round bar) as the core. Since it requires processes such as accommodating a hard ball group composed of a plurality of hard balls in the through hole of the hollow part, positioning the hollow part while pressing the hard ball group, and taking out the hard ball group from the through hole after rolling, there is a problem of excessive processing time, and the advantages of excellent mass productivity and rolling processing most suitable for mass production cannot be exerted.

[0015] In addition, the above-mentioned Patent Document 2 discloses the following manufacturing method of a hollow gear: An inner diameter mandrel having concavo-convex portions on its outer peripheral surface, where the concave portions and the convex portions extend parallel to each other in the axial direction and are continuously arranged in the circumferential direction, is inserted into the central axis hole of a cylindrical workpiece. While rotating the workpiece and the inner diameter mandrel together, the tooth profile machining surface of a rolling die is pressed against the outer peripheral surface of the workpiece, and the tooth profile is roll-formed on this outer peripheral surface. Since the roll-forming is performed while pressing each convex portion provided on the outer peripheral surface of the inner diameter mandrel against the inner peripheral surface of the workpiece, it is possible to restrict the circumferential material flow of the inner peripheral surface of the workpiece by each convex portion, and it is possible to suppress the expansion of the circumference extending in the circumferential direction of the workpiece.

[0016] However, in this method, since the roll-forming is performed while pressing each convex portion provided on the outer peripheral surface of the inner diameter mandrel (core) against the inner peripheral surface of the workpiece, not only does the inner peripheral surface of the workpiece deform and fail to meet the dimensional standard of the inner diameter of the workpiece, but also it takes time to remove the workpiece from the inner diameter mandrel (core), and in some cases, it is even impossible to remove it. Summary of the Invention

[0017] The present invention has been completed in view of such a situation, and its object is to provide the following rolling die set: In the rolling process of a hollow part, neither the rolling die is enlarged nor a core with a special structure is used during the rolling process, and it is possible to suppress as much as possible the elongation deformation of the raw material to be rolled in the circumferential and axial directions, so as to obtain a product with a desired tooth profile.

[0018] The key points of the present invention will be described with reference to the accompanying drawings.

[0019] A rolling die set, in which the rolling die 1 is configured in a group of two or a group of three. The rolling die 1 is configured to have a biting portion 2, a finishing portion 3, and a retracting portion 4, each provided with a processing tooth 5, from the start end side in the rolling direction toward the end side in the rolling direction. The outer peripheral surface of the raw material W to be rolled is plastically deformed by each of the processing teeth 5 to roll out a desired tooth profile. It is characterized in that, in each of the rolling dies 1, a plurality of strip grooves 6 extending linearly in the rolling direction in a plan view are provided in parallel at a prescribed interval in the width direction of the rolling die 1 on each of the processing teeth 5 in a prescribed region 7 provided from the start end side of the biting portion 2 to a prescribed position in the rolling direction of the biting portion 2. Thus, a plurality of divided processing teeth 5a are formed in a state arranged along the rolling direction and the tooth line direction in the prescribed region 7. Moreover, the strip grooves 6 provided in each of the rolling dies 1 are provided in a state of being positionally offset in the width direction of the rolling die 1 with respect to the strip grooves 6 provided in the other rolling dies 1 in the group. Thus, the divided processing teeth 5a are formed in a state of being positionally offset in the tooth line direction with respect to the divided processing teeth 5a provided in the other rolling dies 1 in the group. Further, when the rolling die 1 is configured in a group of two, the divided processing teeth 5a of each of the rolling dies 1 are configured to process the entire rolling width region of the raw material W to be rolled when the raw material W to be rolled rotates half a turn. When the rolling die 1 is configured in a group of three, the divided processing teeth 5a of each of the rolling dies 1 are configured to process the entire rolling width region of the raw material W to be rolled when the raw material W to be rolled rotates two-thirds of a turn.

[0020] In addition, in the rolling die set according to Technical Solution 1, it is characterized in that the strip grooves 6 of each of the rolling dies 1 are provided at equal intervals in the width direction of the rolling die 1 with a constant groove width W2.

[0021] In addition, in the rolling die set according to Technical Solution 2, it is characterized in that when the rolling die 1 is configured in a group of two, the tooth width of the divided processing tooth 5a is set as W1, and the groove width of the strip groove 6 is set as W2, the positional offset amount δ in the width direction of the rolling die 1 of the strip grooves 6 provided in each of the rolling dies 1 with respect to the strip grooves 6 provided in the other rolling dies 1 in the group is (W1 + W2) / 2.

[0022] In addition, for the rolling die set according to Technical Solution 2, it is characterized in that when the rolling die 1 is configured in a group of three, the tooth width of the cutting tooth 5a is set as W1, and the groove width of the strip groove 6 is set as W2, the strip grooves 6 provided in each of the rolling dies 1 are respectively configured such that the offset amount δ in the width direction of the rolling die 1 with respect to the strip grooves 6 provided in the other rolling dies 1 in the group is (W1 + W2) / 3.

[0023] In addition, for the rolling die set according to Technical Solution 3, it is characterized in that the rolling die set is configured such that the tooth width W1 of the cutting tooth 5a is 3.3 mm or less.

[0024] In addition, for the rolling die set according to Technical Solution 4, it is characterized in that the rolling die set is configured such that the tooth width W1 of the cutting tooth 5a is 3.3 mm or less.

[0025] In addition, for the rolling die set according to any one of Technical Solutions 1 to 6, it is characterized in that the specified region 7 is at a position of 60% to 95% of the length L2 of the biting portion 2 from the starting end position of the biting portion 2.

[0026] In addition, for the rolling die set according to any one of Technical Solutions 1 to 6, it is characterized in that the specified region 7 is at a position of 60% to 95% of the length L2 of the biting portion 2 from a position separated from the starting end of the biting portion 2 by a specified distance in the rolling direction.

[0027] In addition, for the rolling die set according to any one of Technical Solutions 1 to 6, it is characterized in that a tapered portion 7a is provided within a specified range on the rolling direction terminal side of the specified region 7 where the cutting tooth 5a is provided. The tapered portion 7a is configured such that the groove depth D of the strip groove 6 gradually becomes shallower toward the rolling direction terminal, and the groove width W2 of the strip groove 6 gradually becomes narrower.

[0028] In addition, for the rolling die set according to Technical Solution 7, it is characterized in that a tapered portion 7a is provided within a specified range on the rolling direction terminal side of the specified region 7 where the cutting tooth 5a is provided. The tapered portion 7a is configured such that the groove depth D of the strip groove 6 gradually becomes shallower toward the rolling direction terminal, and the groove width W2 of the strip groove 6 gradually becomes narrower.

[0029] In addition, for the rolling die set according to Technical Solution 8, it is characterized in that a tapered portion 7a is provided within a specified range on the rolling direction terminal side of the specified region 7 where the cutting tooth 5a is provided. The tapered portion 7a is configured such that the groove depth D of the strip groove 6 gradually becomes shallower toward the rolling direction terminal, and the groove width W2 of the strip groove 6 gradually becomes narrower.

[0030] The present invention is configured as described above, and thus realizes the following rolling die set: in the rolling process of a hollow part, neither the rolling die is enlarged, nor a mandrel with a special structure is used during the rolling process, and the elongation deformation of the raw material to be rolled along the circumferential and axial directions can be suppressed as much as possible, so as to obtain a product with a desired tooth shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 FIG. is a schematic explanatory view of the rolling process using the present embodiment (rolling flat die).

[0032] Figure 2 FIG. is an explanatory top view showing the present embodiment.

[0033] Figure 3 FIG. is an explanatory top view showing a specified area (segmented machining tooth area part) of the biting part of the present embodiment.

[0034] Figure 4 FIG. is an explanatory view showing the positional deviation state in the width direction of the grooves of the lower rolling die (the other rolling die) with respect to the grooves of the upper rolling die (one rolling die) of the present embodiment.

[0035] Figure 5 FIG. is an explanatory side view showing the grooves and segmented machining teeth of the present embodiment.

[0036] Figure 6 FIG. is an explanatory top view showing the tapered part of the biting part of the present embodiment.

[0037] Figure 7 FIG. are an explanatory front view and an explanatory side view showing the biting part of the present embodiment.

[0038] Figure 8 FIG. are an explanatory side view (a) and an explanatory top view (b) showing the grooves and segmented machining teeth of another example (a type with a shallower groove depth) of the present embodiment.

[0039] Figure 9 FIG. is an explanatory top view showing another example (a type in which the specified area (segmented machining tooth area part) is provided at a specified distance from the start end of the biting part) of the present embodiment.

[0040] Figure 10 FIG. is a schematic explanatory view of the rolling process using another example (the case of applying to a pair of rolling roundless dies) of the present embodiment.

[0041] Figure 11 FIG. is a schematic explanatory view of the rolling process using another example (the case of applying to a set of three rolling roundless dies) of the present embodiment.

[0042] Figure 12 It shows Figure 11 An explanatory diagram showing the positional deviation state in the width direction of the groove of each other rolling non-circular die with respect to the first to third rolling non-circular dies of other examples of the present embodiment shown.

[0043] Figure 13 An explanatory diagram showing the processing state of the first groove of the raw material to be rolled in the case of using the present embodiment (a structure in pairs).

[0044] Figure 14 An explanatory diagram showing the processing state of the first groove of the raw material to be rolled in the case of using the present embodiment (a structure in threes).

[0045] Figure 15 An explanatory diagram showing the processing state of the first groove of the raw material to be rolled in the case of using the existing example.

[0046] Figure 16 An explanatory diagram showing the processing teeth (segmented processing teeth) for processing the first groove of the raw material to be rolled in the present embodiment.

[0047] Figure 17 A chart showing the measurement results of the over pin diameter in Experiment 1.

[0048] Figure 18 A chart showing the measurement results of the root circle diameter in Experiment 1.

[0049] Figure 19 A chart showing the measurement results of the cumulative pitch error in Experiment 1.

[0050] Figure 20 A chart showing the measurement results of the vibration of the tooth groove in Experiment 1.

[0051] Figure 21 A chart showing the measurement results of the over pin diameter in Experiment 3.

[0052] Figure 22 A chart showing the measurement results of the root circle diameter in Experiment 3.

[0053] Figure 23 A chart showing the measurement results of the tooth profile error in Experiment 3.

[0054] Figure 24 A chart showing the measurement results of the tooth trace error in Experiment 3.

[0055] Figure 25 A chart showing the measurement results of the cumulative pitch error in Experiment 3.

[0056] Figure 26 It is a graph showing the measurement results of the vibration of the tooth grooves in Experiment 3.

[0057] Reference numeral description

[0058] 1: Rolling die; 2: Biting-in part; 3: Finishing part; 4: Retreating part; 5: Machining tooth; 5a: Divided machining tooth; 6: Groove; 7: Specified area; 7a: Gradually decreasing part; δ: Position offset; D: Depth of the groove of the groove; L2: Length of the biting-in part; W: Rolled raw material. Detailed implementation manner

[0059] The operation of the present invention is shown according to the accompanying drawings, and the preferred embodiments of the present invention are briefly described.

[0060] In the present invention, in each machining tooth 5 of the specified area 7 provided in each rolling die 1 from the start end side of the biting-in part 2 to the specified position in the rolling direction of the biting-in part 2, a plurality of grooves 6 extending linearly in the rolling direction in a plan view are provided in parallel at a specified interval in the width direction of the rolling die 1, and the machining tooth 5 is divided by the groove 6. Thus, a plurality of divided machining teeth 5a are formed in a state arranged along the rolling direction and the tooth line direction in the specified area 7. Furthermore, the grooves 6 provided in each rolling die 1 are respectively provided in a state where the position in the width direction of the rolling die 1 is offset by a specified amount with respect to the grooves 6 provided in other rolling dies 1 of the set. Thus, the divided machining teeth 5a formed in each rolling die 1 are offset in the tooth line direction with respect to the divided machining teeth 5a provided in other rolling dies 1 of the set, and are configured to process the entire rolling width area of the rolled raw material W when the rolled raw material W rotates half a turn (when the rolling die 1 is configured in a set of two) or rotates two-thirds of a turn (when the rolling die 1 is configured in a set of three). Therefore, in the specified area 7 where the divided machining teeth 5a are formed in the biting-in part 2, the rolled raw material W is intermittently processed. In addition, the processing load is concentrated on the tooth tips of the divided machining teeth 5a whose pressing area is smaller than that of the machining tooth 5. Even when rolling the rolled raw material W of a hollow part with a relatively thin wall thickness, it is possible to suppress as much as possible the elongation deformation of the rolled raw material W in the circumferential direction and the axial direction.

[0061] That is, as Figure 15As shown, in the rolling process using a conventional rolling die, the entire crest surface of the machining tooth 25 extending along the tooth line direction of the rolling die 21 is pressed into the tooth groove of the workpiece W to be rolled. Therefore, when the workpiece W to be rolled is a hollow part with a thin wall thickness, the function of wall bulging cannot be well exerted in the tooth groove of the rolling die 21 for machining solid parts. Thus, without using a core, it will be crushed radially. Additionally, even when a core is used, the workpiece W to be rolled will deform in the axial and circumferential directions and cannot be plastically processed into a specified tooth shape. However, in the present invention, for example, as Figure 13 (in the case of a pair), Figure 14 (in the case of a group of three) shown, the segmented machining tooth 5a moves intermittently along the tooth line direction while the pressing position of the workpiece W to be rolled changes as the rolling process progresses. Furthermore, the area pressed into the workpiece W to be rolled is smaller than that in the above-mentioned prior art example, and the machining load is concentrated on the crest of each segmented machining tooth 5a, which can improve the bulging of the wall of the workpiece W to be rolled and form a desired shape. Thus, even when the workpiece W to be rolled is a hollow part with a thin wall thickness, elongation deformation in the circumferential and axial directions can be suppressed.

[0062]

Embodiment

[0063] Specific embodiments of the present invention will be described with reference to the drawings.

[0064] This embodiment relates to a rolling die set in which the rolling die 1 is configured in a group of two or a group of three. The rolling die 1 is configured to have a biting portion 2, a finishing portion 3, and a retracting portion 4 provided with machining teeth 5 from the start side in the rolling direction toward the end side in the rolling direction. The outer peripheral surface of the workpiece W to be rolled is plastically deformed by each machining tooth 5 to roll a desired tooth shape. Specifically, this embodiment applies the rolling die set of the present invention to Figure 1 the case of a rolling die set composed of a pair (a group of two) of rolling flat dies such as splines, saw teeth, and gears arranged vertically and horizontally in rolling as shown. Additionally, in this embodiment, when the upper and lower rolling dies 1 in Figure 1 are taken as objects respectively (in the case of being shared in the upper and lower rolling dies 1), it is called "rolling die 1". Additionally, when only the upper rolling die 1 located on the upper side in Figure 1 is taken as an object, it is called "upper rolling die 1a", and when only the other rolling die 1 located on the lower side in Figure 1 is taken as an object, it is called "lower rolling die 1b" (the upper and lower sides represent the upper and lower in Figure 1 , and do not specify the positional relationship when using a pair of rolling dies 1).

[0065] Hereinafter, each part of the structure of this embodiment will be described in detail.

[0066] As Figure 2 shown, each rolling die 1 is formed in a rectangular shape when viewed from above. As Figure 1 shown, the bottom surface 8 is formed into a flat surface that serves as a reference surface. In addition, a plurality of machining teeth 5 for forming tooth shapes on the rolled raw material W are provided on the upper surface on the opposite side of the bottom surface 8. The tooth top line (imaginary line connecting the tooth tops of the machining teeth 5) of the machining teeth 5 is shown by a solid line in the explanatory front view of Figure 1 .

[0067] In addition, for the purpose of preventing slip of the rolled raw material W (preventing the position of the rolled raw material W from shifting relative to the machining teeth 5), each rolling die 1 performs shot peening on the surface (upper surface) of the machining teeth 5 provided in a specified range (in this embodiment, a range of approximately 2 / 3 of the length (total length) of the biting portion 2 indicated by reference numeral L2 in the figure (range indicated by reference numeral SB in the figure)) from the start end side in the rolling direction toward the end side in the rolling direction. In addition, reference numeral L1 in the figure represents the sum of the rolling direction ranges (lengths) of the biting portion 2, the finishing portion 3, and the retracting portion 4.

[0068] In addition, each rolling die 1 in this embodiment is a rolling flat die for machining ordinary splines (splines formed with tooth shapes parallel to the axial direction of the rolled raw material W). In each rolling die 1, the machining teeth 5 of the biting portion 2, the finishing portion 3, and the retracting portion 4 are each formed in a mountain shape (substantially trapezoidal shape) when viewed in the front view, and are configured as straight machining teeth that extend linearly in the width direction of the rolling die 1 (specifically, the direction perpendicular to the rolling direction), and are arranged side by side at a specified interval in the rolling direction. In addition, by setting the extending direction of the machining teeth 5 to a direction inclined with respect to the direction perpendicular to the rolling direction, it can be applied to rolling dies for machining spiral splines, helical gears (spiral gears), etc.

[0069] Specifically, the machining teeth 5 of the biting portion 2 are configured such that the tooth height gradually increases from the start end side in the rolling direction toward the end side in the rolling direction, and gradually press into the outer peripheral portion of the rolled raw material W to form a raised tooth shape. In addition, the machining teeth 5 of the finishing portion 3 are set to a constant tooth height (substantially the same tooth height as the machining teeth 5 at the end of the biting portion 2), and are configured to finish the tooth shape formed by the biting portion 2 to the product size. In addition, the machining teeth 5 of the retracting portion 4 are provided on an inclined surface that slopes downward toward the end side in the rolling direction, and are configured such that the position of the front end surface gradually becomes lower as it goes toward the end side in the rolling direction.

[0070] In addition, as Figure 2 shown, regarding the biting portion 2 of each rolling die 1, in a specified region 7 from the start end position to a specified position in the rolling direction, strip grooves 6 are provided on each machining tooth 5. As Figure 3As shown, each processing tooth 5 is segmented by the strip groove 6 in the width direction of the rolling die 1, constituting a segmented processing tooth region portion in which a plurality of segmented processing teeth 5a are formed. In addition, Figure 2 In the figure, the reference numeral X indicates the rolling direction range (length) of the specified region 7 (segmented processing tooth region portion).

[0071] Specifically, as Figure 4 shown, the strip grooves 6 of each rolling die 1 are respectively arranged in a state where they are displaced in the width direction of the rolling die 1 with respect to the strip grooves 6 of other rolling dies 1 in a group. By arranging the strip grooves 6 in a displaced state, the segmented processing teeth 5a formed by the strip grooves 6 are also respectively formed in a state where they are displaced in the tooth line direction with respect to the segmented processing teeth 5a provided on other rolling dies 1 in a group.

[0072] That is, in the present embodiment, the strip grooves 6 provided on the lower rolling die 1b are arranged in a state where they are displaced by a specified amount in the width direction of the rolling die 1 with respect to the strip grooves 6 provided on the upper rolling die 1a. By arranging the strip grooves 6 of the upper rolling die 1a and the strip grooves 6 of the lower rolling die 1b in a displaced state with respect to each other, the segmented processing teeth 5a of the lower rolling die 1b are formed in a state where they are displaced by a specified amount in the tooth line direction (tooth line direction of the processing tooth 5) of the segmented processing teeth 5a of the upper rolling die 1a.

[0073] More specifically, the strip grooves 6 of each rolling die 1 are set to a constant groove width W2, and in a plan view, they extend in a straight line (straight and continuously) at equal intervals in the width direction of the rolling die 1 along the rolling direction (parallel to the rolling direction). Thus, as Figure 3 shown, the segmented processing teeth 5a of each rolling die 1 are formed in a state where they are arranged in the rolling direction and the tooth line direction (width direction of the rolling die 1) in the specified region 7 (segmented processing tooth region portion). In addition, in the tooth line direction (width direction of the rolling die 1) of the processing tooth 5, each segmented processing tooth 5a of the lower rolling die 1b is formed to have a position offset amount δ (phase difference) with respect to each segmented processing tooth 5a of the upper rolling die 1a such that the entire rolling width region of the rolled raw material W is processed when the rolled raw material W rotates half a turn using both the segmented processing teeth 5a of the upper rolling die 1a and the segmented processing teeth 5a of the lower rolling die 1b.

[0074] In addition, the strip groove 6 is not limited to extending in a straight line as described above, and may be arranged as shown in (b) of Figure 8 to be a straight line shape that is straight and intermittent in the rolling direction in a plan view. In addition, the rolling width refers to the axial range in which a tooth shape is formed on the rolled raw material W by rolling.

[0075] In addition, a specified region 7 (segmented machining tooth region portion) of each rolling die 1 is set at a position of 60% to 95% of the length L2 from the start end position of the biting portion 2 to the biting portion 2.

[0076] By providing the specified region 7 (segmented machining tooth region portion) where the segmented machining teeth 5a are formed starting from the start end of the biting portion 2, it is possible to set a relatively large range for the specified region 7 (segmented machining tooth region portion) in the biting portion 2 of a specified length. As a result, rolling using the segmented machining teeth 5a is performed more frequently, and the effect of the present invention, that is, the effect of suppressing elongation deformation of the rolled raw material W in the circumferential and axial directions, is exhibited more favorably.

[0077] In addition, regarding the specified region 7 (segmented machining tooth region portion), it is not necessarily structured to start from the start end of the biting portion 2. As Figure 9 shown, it may also be structured to start from a position appropriately spaced from the start end of the biting portion 2. In this case, the position where the specified region 7 (segmented machining tooth region portion) is provided (the position where the specified region 7 (segmented machining tooth region portion) starts, in other words, the start end position of the groove 6) is preferably a position spaced by an amount corresponding to 0.5 to 2 revolutions of the rotation of the rolled raw material W.

[0078] In addition, the reason for setting the range where the segmented machining teeth 5a are provided to a position of 60% to 95% of the length L2 of the biting portion 2 is as follows: When the segmented machining teeth 5a only reach a position less than half of the length of the biting portion 2, the desired effect cannot be exhibited. In addition, if it is provided over the entire length of the biting portion 2, in other words, if it is provided up to the boundary position with the finishing portion 3, the tooth line of the tooth profile formed on the rolled raw material W may be irregular even after rolling using the machining teeth 5 of the finishing portion 3, and flaws (groove marks caused by the groove 6) may remain on the tooth surface after rolling. Therefore, the upper limit position of the range where the segmented machining teeth 5a are provided only needs to be set slightly ahead (on the start end side in the rolling direction) of the boundary position with the finishing portion 3, and more preferably, it is set to a position of 95% of the length L2 of the biting portion 2.

[0079] In addition, the groove 6 (the groove 6 that segments the machining teeth 5) that forms the segmented machining teeth 5a is formed into a tapered groove whose groove width widens upward from the bottom side by grinding with a grinding tool. In addition, the formation of the groove 6 is not limited to the above-mentioned grinding process, and for example, it may also be formed by laser processing or the like. Figure 5 shown.

[0080] In addition, when the groove width W2 of the strip groove 6 of each rolling die 1 is too narrow relative to the tooth width W1 of the subsequent cutting tooth 5a, it will be close to the shape of the existing product (without the strip groove 6 and without forming the cutting tooth 5a). Therefore, the deformation suppression effect cannot be fully obtained in the rolled raw material W with a thin wall thickness. In addition, when the groove width W2 of the strip groove 6 of each rolling die 1 is too wide relative to the tooth width W1 of the cutting tooth 5a, an unprocessed portion will be formed. As a result, the processing load on the finishing portion 3 will become too large and the rolled raw material W will be deformed. Therefore, the groove width W2 of the strip groove 6 needs to be set according to the tooth width W1 of the cutting tooth 5a.

[0081] On this basis, the groove width W2 of the strip groove 6 of each rolling die 1 can be appropriately set within the range that does not impair the effect of this embodiment. However, in the rolling die set composed of two as a group in this embodiment, it is preferably a groove width equal to or narrower than the tooth width W1 of the cutting tooth 5a. Specifically, it is preferably set such that the ratio W1 / W2 of the tooth width W1 of the cutting tooth 5a to the groove width W2 of the strip groove 6 is 0.9 or more. Specifically, it is preferably set to 0.9 to 1.8.

[0082] In addition, the specification with the ratio W1 / W2 of the tooth width W1 of the cutting tooth 5a to the groove width W2 of the strip groove 6 being 0.9 (the specification of Experimental Example 2 described later) is a specification in which the groove width W2 of the strip groove 6 is slightly wider than the tooth width W1 of the cutting tooth 5a. In this case, a small amount of unprocessed portion will remain in the specified area 7 (cutting tooth area portion) of the biting portion 2, but almost the entire area of the rolling width is processed. Therefore, the processing load on the finishing portion 3 will not become too large. Therefore, it is included within the above-mentioned preferred range and is included in "equal to the tooth width W1 (of the groove width)" of the cutting tooth 5a.

[0083] In addition, in this embodiment, as Figure 5 shown, the groove width W2 of the strip groove 6 refers to the groove width in the width direction of the rolling die 1 at the upper edge portion (the portion with the widest groove width) of the strip groove 6. In addition, in this embodiment, as Figure 5 shown, the tooth width W1 of the cutting tooth 5a refers to the tooth width in the width direction of the rolling die 1 at the front end face of the cutting tooth 5a.

[0084] In addition, the strip groove 6 of each rolling die 1 is provided along the inclination of the processing tooth 5 of the biting portion 2 (the inclination of the tooth crest line of the processing tooth 5 shown Figure 1 as) from the start end side in the rolling direction toward the end side in the rolling direction. The groove depth D of the strip groove 6 is set to a constant depth based on the tooth crest of the processing tooth 5. In addition, the groove depth D of the strip groove 6 can be appropriately set within the range that does not impair the effect of this embodiment, and it can also be set to a constant depth not based on the tooth crest of the processing tooth 5.

[0085] In addition, the groove depth D of the strip groove 6 of each rolling die 1 is set to a depth equal to or greater than the tooth height of the machined tooth 5, and is configured to completely divide the machined tooth 5.

[0086] In addition, regarding the groove depth D of the strip groove 6, as long as it is a specified depth that exhibits the effects of this embodiment, as shown in (a) of Figure 8 , it can be set to a depth shallower than the tooth height of the machined tooth 5. For example, the groove depth D of the strip groove 6 can be set according to the workability of the rolled raw material W. When the rolled raw material W is a material that easily bulges through rolling (a material with high ductility), the groove depth D of the strip groove 6 can be set deeper (for example, set to be equal to or greater than the tooth height of the machined tooth 5). When the rolled raw material W is a material that is difficult to bulge (a material with high work hardening), in order to prevent defects during rolling due to a decrease in the strength of the divided machined tooth 5a, the groove depth D of the strip groove 6 can be set shallower (set to be shallower than the tooth height of the machined tooth 5, for example, a depth of 50% of the tooth height of the machined tooth 5).

[0087] In addition, the strip grooves 6 of each rolling die 1 are arranged at equal intervals along the tooth line direction of the machined tooth 5 such that the tooth width W1 of the divided machined tooth 5a is 3.3 mm or less (in order to sufficiently obtain the deformation suppression effect of the rolled raw material W with a thin wall thickness, it is preferable to set the tooth width W1 of the divided machined tooth 5a to 3.3 mm or less).

[0088] In addition, as described above, this embodiment is a rolling flat die for machining a normal spline (a spline formed with tooth profiles parallel to the axial direction of the rolled raw material W), so the tooth line direction of the machined tooth 5 is the same as the width direction of the rolling die 1.

[0089] The narrower the tooth width W1 of the divided machined tooth 5a, the more the deformation suppression effect of the rolled raw material W can be obtained. However, conversely, defects are more likely to occur, and there will be a problem of shorter tool life. Therefore, the setting of the tooth width W1 of the divided machined tooth 5a needs to consider the balance between the deformation suppression effect of the rolled raw material W and the tool life.

[0090] Specifically, the tooth tip width in the rolling direction of the first tooth of the rolling die 1 is set as a threshold value. When the tooth width W1 of the divided machined tooth 5a is narrower than this threshold value, defects are very likely to occur. Therefore, the tooth width W1 of the divided machined tooth 5a is preferably set to be equal to or greater than the tooth tip width in the rolling direction of the first tooth of the rolling die 1.

[0091] On this basis, the strip grooves 6 of each rolling die 1 are arranged in parallel at equal intervals along the tooth line direction of the machined tooth 5 such that the tooth width W1 of the divided machined tooth 5a in the complete shape (the state divided by two adjacent strip grooves 6) is 0.5 mm or more and 3.3 mm or less.

[0092] In addition, as described above, this embodiment is configured such that the splitting teeth 5a of the upper rolling die 1a and the splitting teeth 5a of the lower rolling die 1b are used to process the entire rolling width region of the raw material W to be rolled when the raw material W to be rolled rotates half a turn. The slot 6 of the lower rolling die 1b is displaced in the width direction of the rolling die 1 relative to the slot 6 of the upper rolling die 1a. The splitting teeth 5a formed through the slots 6 are formed with a phase difference in the width direction of the rolling die 1 between the upper rolling die 1a and the lower rolling die 1b. However, in the case of the tooth width W1 of the splitting teeth 5a configured as described above, by setting the displacement amount δ in the width direction of the rolling die 1 of the slot 6 of the lower rolling die 1b relative to the slot 6 of the upper rolling die 1a to (W1 + W2) / 2, that is, 1 / 2 of the juxtaposed arrangement interval (P: pitch) of the slots 6 of each rolling die 1 (i.e., P / 2), a structure can be obtained that can process the entire rolling width region of the raw material W to be rolled when the raw material W to be rolled rotates half a turn (no unprocessed part is formed). In addition, when the tooth width W1 of the splitting teeth 5a is larger than the slot width W2 of the slot 6, correspondingly, the displacement amount δ can also deviate from P / 2. For example, the displacement amount δ can be set within the range of W2 ≤ δ ≤ W1. However, when the tooth width W1 of the splitting teeth 5a is smaller than the slot width W2 of the slot 6, it is preferably that the displacement amount δ does not deviate from P / 2 as much as possible. For example, in a rolling die set with a specification where the ratio W1 / W2 of the tooth width W1 of the splitting teeth 5a to the slot width W2 of the slot 6 is 0.9 (Experimental Examples 2, 8, 10 described later), it is preferred to set the displacement amount δ within the range of δ = ((W1 + W2) / 2) ± ((W2 - W1) / 4). In this embodiment, the above displacement amount δ is set to (W1 + W2) / 2, that is, 1 / 2 of the juxtaposed arrangement interval (P: pitch) of the slots 6 of each rolling die 1 (i.e., P / 2) (refer to Figure 4 ).

[0093] In addition, in this embodiment, the amount (maximum machining amount) by which the splitting teeth 5a are pressed deepest into the raw material W to be rolled in the tooth height direction is set to be within 0.14 mm.

[0094] The reason for setting the maximum machining amount of the splitting teeth 5a to be within 0.14 mm is based on the results of various experiments including Experimental Examples 1 to 3 described later (this embodiment: the maximum machining amount of the splitting teeth 5a is 0.14 mm). Because when the maximum machining amount exceeds 0.14 mm, the machining load on the raw material W to be rolled becomes too large, and the raw material W to be rolled may elongate and deform in the circumferential direction and the axial direction.

[0095] In addition, a tapered portion 7a is provided on the rolling direction end side of a specified region 7 (segmented machining tooth region portion) where the segmented machining teeth 5a are provided in each rolling die 1.

[0096] The tapered portion 7a is set in the range of 6 to 12 machining teeth 5 including the end of the specified region 7 (segmented machining tooth region portion). The groove 6 of each machining tooth 5 provided in the tapered portion 7a is set to have a groove depth D shallower and a groove width W2 narrower than the groove 6 on the rolling direction start side of the tapered portion 7a in the specified region 7 (segmented machining tooth region portion).

[0097] Specifically, as Figure 6 shown, the tapered portion 7a is configured such that the groove depth D of the groove 6 gradually becomes shallower toward the rolling direction end, and the groove width W2 of the groove 6 gradually becomes narrower.

[0098] In addition, the groove depth D of the groove 6 in the tapered portion 7a may also become shallower curvilinearly from the start end to the end of the tapered portion 7a. For example, as Figure 7 shown, it may also gradually become shallower linearly along the gradient of the tapered angle g (tapered angle g = arctan (groove depth D of the groove 6 at the start end position of the tapered portion 7a / length in the rolling direction of the tapered portion 7a)).

[0099] By providing the tapered portion 7a, it is possible to smooth the change in the shape of the machining tooth 5 caused by the presence or absence of the groove 6 in the region on the rolling direction start side of the tapered portion 7a in the specified region 7 (segmented machining tooth region portion) and in the biting portion 2 on the rolling direction end side of the specified region 7 (segmented machining tooth region portion). Thereby, it is possible to suppress a sharp change in the machining load and suppress the elongation deformation of the rolled raw material W.

[0100] In addition, as Figure 1 shown, in the biting portion 2 of the present embodiment, the gradient of the tooth crest line is set to be constant, that is, the machining amount (machining amount per one rotation of the rolled raw material W) of the biting portion 2 is set to be constant. However, regarding the biting portion 2, it may also be configured such that a specified range on the start end side of the biting portion 2 is the first-stage bite, the remaining biting portion 2 is the second-stage bite, the gradient of the tooth crest line of the first-stage bite is increased, the gradient of the tooth crest line of the second-stage bite is reduced, the machining amount is larger in the first-stage bite, and the machining amount is smaller in the second-stage bite.

[0101] In addition, as described above, the present embodiment is a case where the rolling die set of the present invention is applied to Figure 1 a rolling flat die as shown, but the rolling die set of the present invention can also be applied to a rolling ovality die 1.

[0102] The rotation direction of the rolling ovality die 1 is the rolling direction. The rolling tooth profiles formed on its outer peripheral surface are successively and continuously provided with a biting portion 2, a finishing portion 3, and a retracting portion 4 having different distances from the rotation axis of the rolling ovality die 1 to the tooth tip of the processed tooth 5 starting from the starting end side in the rolling direction. In addition, in the case of the rolling ovality die 1, the strip groove 6 is arranged in an arc shape around the rotation axis of the rolling ovality die 1 along the rotation direction (rolling direction).

[0103] By arranging the strip groove 6 in an arc shape around the rotation axis of the rolling ovality die 1 along the rotation direction (rolling direction) in this way, the strip groove 6 is arranged to be in a straight line shape (a substantially straight state with a slight bend) when viewed from above in the rolling direction of the biting portion 2 of the rolling ovality die 1 where the strip groove 6 is formed. In other words, in the unfolded state where the outer peripheral surface of the rolling ovality die 1 is unfolded into a plane, the strip groove 6 is the same as in the case of the rolling flat die shown in Figure 2 and is arranged along the rolling direction (parallel to the rolling direction) and is in a straight line when viewed from above in the rolling direction. Therefore, in the rolling ovality die 1, by arranging the strip groove 6 in an arc shape around the rotation axis of the rolling ovality die 1, the same effect as that in the case of the rolling flat die described below can be achieved. In addition, since the rolling ovality die 1 has a substantially cylindrical shape, when viewed from above, the strip groove 6 located on the end side in the left-right direction (rolling direction) of the visual confirmation range seems to be slightly bent, but in this embodiment, this seemingly slightly bent state is also included in the "being in a straight line shape when viewed from above".

[0104] Specifically, when the rolling die set of the present invention is applied to the rolling ovality die 1, it can be applied to a structure in which a pair (two) of rolling ovality dies 1, namely the first rolling ovality die 1a and the second rolling ovality die 1b, are used as a set, as shown in Figure 10 and a structure in which three rolling ovality dies 1, namely the first rolling ovality die 1a, the second rolling ovality die 1b, and the third rolling ovality die 1c, are used as a set, as shown in Figure 11 In the case where a pair (two) of rolling ovality dies 1 are configured as a set, they are configured in the same structure as in the case of the above-mentioned rolling flat die, and in such a way that when the rolled raw material W rotates half a turn, the entire rolling width area of the rolled raw material W is processed. The strip groove 6 of the second rolling ovality die 1b is arranged in a state where it is offset in the width direction of the rolling ovality die 1 with respect to the strip groove 6 of the first rolling ovality die 1a, and the divided processing teeth 5a formed by the strip groove 6 are formed in a state where they are offset in the tooth line direction (having a phase difference) with respect to the divided processing teeth 5a provided on the first rolling ovality die 1a and the second rolling ovality die 1b.

[0105]

[0106] ​Specifically, by setting the offset δ in the width direction of the rolling die 1 between the slot 6 of the second rolling non-circular die 1b and the slot 6 of the first rolling non-circular die 1a to (W1 + W2) / 2, that is, 1 / 2 of the juxtaposed interval (P: pitch) of the slots 6 of each rolling non-circular die 1 (i.e., P / 2) (see Figure 4 ), a rolling die set can be obtained that can process the entire rolling width region of the raw material W to be rolled (no unprocessed part is formed) when the raw material W to be rolled rotates half a turn.

[0107] In addition, when the tooth width W1 of the cutting tooth 5a is larger than the slot width W2 of the slot 6, the preferred setting range of the offset δ (W2 ≤ δ ≤ W1), and when the tooth width W1 of the cutting tooth 5a is smaller than the slot width W2 of the slot 6, the preferred setting range of the offset δ (δ = ((W1 + W2) / 2) ± ((W2 - W1) / 4)) are the same as those of the above-mentioned rolling flat die set (the upper rolling die 1a and the lower rolling die 1b).

[0108] In addition, when three rolling non-circular dies 1 are configured as a group, they are configured such that the slot 6 of the second rolling non-circular die 1b is set in a state of being displaced in the width direction of the rolling non-circular die 1 relative to the slot 6 of the first rolling non-circular die 1a in such a way that the entire rolling width region of the raw material W to be rolled is processed when the raw material W to be rolled rotates 2 / 3 of a turn, and the slot 6 of the third rolling non-circular die 1c is set in a state of being displaced in the width direction of the rolling non-circular die 1 relative to the slot 6 of the second rolling non-circular die 1b, as Figure 12 shown, a phase difference is set for the slot 6 between the first rolling non-circular die 1a, the second rolling non-circular die 1b, and the third rolling non-circular die 1c, and the cutting teeth 5a of the first rolling non-circular die 1a, the second rolling non-circular die 1b, and the third rolling non-circular die 1c are formed in a state where they are displaced in the tooth line direction (with a phase difference) relative to the cutting teeth 5a of the other rolling non-circular dies 1 in the group.

[0109] Specifically, a phase difference is set for the slot 6 between each rolling non-circular die 1, that is, the offset δ in the width direction of the rolling non-circular die 1 between the slot 6 of the second rolling non-circular die 1b and the slot 6 of the first rolling non-circular die 1a, the offset δ in the width direction of the rolling non-circular die 1 between the slot 6 of the third rolling non-circular die 1c and the slot 6 of the second rolling non-circular die 1b, and the offset δ in the width direction of the rolling non-circular die 1 between the slot 6 of the first rolling non-circular die 1a and the slot 6 of the third rolling non-circular die 1c are set to (W1 + W2) / 3, that is, 1 / 3 of the juxtaposed interval (P: pitch) of the slots 6 of each rolling non-circular die 1 (i.e., P / 3) (seeFigure 12 ), thereby becoming a rolling die set capable of processing the entire rolling width area of the raw material W to be rolled (no unprocessed part is formed) when the raw material W to be rolled rotates 2 / 3 of a turn.

[0110] In addition, when the tooth width W1 of the cutting tooth 5a is larger than 1 / 2 of the groove width W2 of the strip groove 6 (that is, larger than 1 / 3 of the pitch P of the strip groove 6), correspondingly, the position offset δ can also deviate from P / 3. For example, the position offset δ can be set within the range of W2 / 2 ≤ δ ≤ W1. However, when the tooth width W1 of the cutting tooth 5a is smaller than 1 / 2 of the groove width W2 of the strip groove 6, that is, when the groove width W2 of the strip groove 6 is larger than twice the tooth width W1 of the cutting tooth 5a, the position offset δ is preferably not deviated from P / 3 as much as possible. For example, in a rolling die set with a specification where the ratio 2W1 / W2 of the tooth width W1 of the cutting tooth 5a to the groove width W2 of the strip groove 6 is 0.9 (W1 / W2 = 0.45), it is preferable to set the position offset δ within the range of δ = ((W1 + W2) / 3) ± ((W2 - 2W1) / 6).

[0111] Since the present embodiment is configured as described above, in the specified area 7 (cutting tooth area part) of the biting part 2, the cutting teeth 5a of each rolling die 1 (rolling missing circle die 1) intermittently process while moving the pressing position along the width direction of the rolling die 1 (tooth line direction of the cutting tooth 5a) relative to the raw material W to be rolled every time the raw material W to be rolled rotates 1 / 2 of a turn (1 / 3 of a turn in the case of three in a group). Moreover, compared with the case of pressing the raw material W to be rolled using the processing tooth 5, the area of pressing the raw material W to be rolled becomes smaller, and the processing load is concentrated on the tooth tips of each cutting tooth 5a. Thus, the cutting teeth 5a can easily bite into the raw material W to be rolled. Even when the raw material W to be rolled is a hollow part with a thin wall thickness, elongation deformation along the circumferential and axial directions can be suppressed.

[0112] In the rolling process of the spline for a hollow part, the larger the ratio of the tooth height of the spline to the wall thickness of the raw material W to be rolled, the greater the elongation deformation along the circumferential and axial directions, and the more difficult it is to form the desired tooth shape. In addition, the larger the ratio of the inner diameter of the raw material W to be rolled (the diameter of the hollow part of the raw material W to be rolled) to the outer diameter (the diameter of the raw material W to be rolled), that is, the thinner the wall thickness of the raw material W to be rolled, the greater the elongation deformation along the circumferential and axial directions, and the more difficult it is to form the desired tooth shape.

[0113] Specifically, based on the applicant's past performance to date, when envisioning a spline with a module of 0.3 to 1.1, the case where the hollow workpiece's raw material W to be roll-formed can be processed well (without elongation deformation) without a mandrel is limited to the case where the ratio of the tooth height of the spline to the wall thickness of the raw material W to be roll-formed is 17% or less, and the ratio of the inner diameter (the diameter of the hollow portion of the raw material W to be roll-formed) to the outer diameter (the diameter of the raw material W to be roll-formed) of the raw material W to be roll-formed is 47% or less. Additionally, even when using a mandrel, good processing can only be achieved when the ratio of the tooth height of the spline to the wall thickness of the raw material W to be roll-formed is 20% or less and the ratio of the inner diameter (the diameter of the hollow portion of the raw material W to be roll-formed) to the outer diameter (the diameter of the raw material W to be roll-formed) of the raw material W to be roll-formed is 55% or less. However, by using this embodiment, even when the conditions that the ratio of the tooth height of the spline to the wall thickness of the raw material W to be roll-formed is 20% or less and the ratio of the inner diameter (the diameter of the hollow portion of the raw material W to be roll-formed) to the outer diameter (the diameter of the raw material W to be roll-formed) of the raw material W to be roll-formed is 55% or less are met, processing can be carried out well without a mandrel. Additionally, by using a mandrel, even when the conditions that the ratio of the tooth height of the spline to the wall thickness of the raw material W to be roll-formed is 30% or less and the ratio of the inner diameter (the diameter of the hollow portion of the raw material W to be roll-formed) to the outer diameter (the diameter of the raw material W to be roll-formed) of the raw material W to be roll-formed is 70% or less are met, good processing can be achieved.

[0114] The following is an experiment (evaluation experiment) to prove the effects of the above-described embodiment.

[0115] <Experiment 1>

[0116] As shown in Tables 1 and 2, a total of 6 sets of roll-flat dies, including the existing conventional roll-flat dies (hereinafter referred to as "Existing Example 1" and "Existing Example 2") and the roll-flat dies of Experimental Examples 1 to 4 with different structures such as the tooth width of the segmented processing teeth 5a in this embodiment, were used for spline roll-forming of the raw material W to be roll-formed of the hollow workpiece using a normal mandrel, and the presence or absence of elongation deformation in the circumferential and axial directions of the raw material W to be roll-formed was evaluated.

[0117] In addition, regarding each reference numeral recorded in Table 1, L: the length of the roll die 1, L2: the length of the biting portion 2, X: the roll direction range (length) of the specified area 7 (segmented processing tooth area portion), X / L2: the ratio of the range X of the specified area 7 (segmented processing tooth area portion) (the length in the roll direction range of the specified area 7 (segmented processing tooth area portion)) to the length L2 of the biting portion 2 (biting portion length L2) (refer to Figure 2 ).

[0118] In addition, regarding the reference numerals described in Table 2, W1: the tooth width of the cut tooth 5a, W2: the groove width of the strip groove 6, P: the pitch of the strip groove 6, α: the groove angle of the strip groove 6, D: the groove depth of the strip groove 6, W3: the width of the tooth tip in the rolling direction of the first tooth in the specified region 7 (cut tooth region part) in the biting part 2, W1 / W3: the tooth width ratio of the cut tooth 5a, DP: the spline pitch of the rolling die 1 (the pitch of the processed teeth of the spline in the rolling direction), W1 / W2: the ratio of the tooth width of the cut tooth 5a to the groove width of the strip groove 6 (see Figure 3 , Figure 5 ).

[0119] In addition, in the rolling die 1 (rolling flat die set) of the present embodiment, the phase difference of the strip groove 6 (position offset δ, phase difference of the cut tooth 5a) is P / 2.

[0120]

Table 1

[0121]

[0122]

Table 2

[0123]

[0124] Specifically, for the rolled raw material W of the hollow member with different wall thicknesses (wall thickness 4 mm to 8 mm), spline rolling is performed using a core bar under the following conditions, and the roller diameter, root circle diameter, tooth profile error, tooth line error, cumulative pitch error, and vibration of the tooth groove are measured for each. Based on the measurement results, the presence or absence of elongation deformation in the circumferential and axial directions of the rolled raw material W is evaluated.

[0125] <Processing conditions, etc.>

[0126] · Spline specifications: tip circle diameter

[0127] Tooth height: 1.2 mm

[0128] Here, Z is a symbol representing the number of teeth of the spline, m is a symbol representing the module, and PA is a symbol representing the pressure angle.

[0129] · Material of the rolled raw material: carbon steel (S45C)

[0130] · Raw material diameter: 26.46 mm

[0131] · Processing amount: Existing Example 1 and Experimental Examples 1 to 3: 0.14 mm / rev,

[0132] Existing Example 2 and Experimental Example 4: 0.09 mm / rev

[0133] · Tooth height h of the first tooth of the biting part 2: Existing Example 1 and Experimental Examples 1 to 3: 0.6964 mm,

[0134] Existing Example 2 and Experimental Example 4: 0.6464 mm

[0135] · Material of the rolling die: Die steel (SKD11)

[0136] · Distance in the rolling direction that the raw material to be rolled advances per one revolution: 83.1 mm

[0137] (= Pitch DP3.0777 mm × Z27 of the machined teeth of the spline in the rolling direction)

[0138] · Processing conditions: Aiming at the standard central value of the roller diameter at the center position of the rolling width

[0139] <The mandrel used>

[0140] · Material: Carbon steel (quenched)

[0141] · Mandrel size and inner diameter size: Refer to Table 3 below

[0142]

Table 3

[0143]

[0144] In addition, for Experimental Examples 1 to 4, further explanation is made. Regarding the number of grooves of the raw material W to be rolled, with the first tooth of the lower rolling die 1b as the reference (the first groove), when the biting part length L2 of the rolling die 1 is designed to be 449 mm and the number of teeth of the biting part 2 is designed to be 146 teeth in Experimental Examples 1 to 3, as Figure 16 shown, in the lower rolling die 1b, the machining teeth 5 of the first tooth, the 28th tooth, the 55th tooth, the 82nd tooth, the 109th tooth, and the 136th tooth become the teeth for machining the first groove of the raw material W to be rolled. In addition, in the upper rolling die 1a, when the raw material W to be rolled rotates half a revolution, the same groove as the groove machined by the first tooth of the lower rolling die 1b is machined. Therefore, the machining teeth 5 of the 14th tooth, the 41st tooth, the 68th tooth, the 95th tooth, and the 122nd tooth become the teeth for machining the first groove of the raw material W to be rolled. When the biting part length L2 of the rolling die 1 is designed to be 754 mm and the number of teeth of the biting part 2 is designed to be 245 teeth in Experimental Example 4, as Figure 16As shown, in the lower rolling die 1b, the machining teeth 5 of the 1st tooth, 28th tooth, 55th tooth, 82nd tooth, 109th tooth, 136th tooth, 163rd tooth, 190th tooth, 217th tooth, and 244th tooth become the teeth for machining the 1st groove of the raw material W to be rolled. Additionally, in the upper rolling die 1a, when the raw material W to be rolled rotates half a turn, the same groove as the one machined by the 1st tooth of the lower rolling die 1b is machined. Therefore, the machining teeth 5 of the 14th tooth, 41st tooth, 68th tooth, 95th tooth, 122nd tooth, 149th tooth, 176th tooth, 203rd tooth, and 230th tooth become the teeth for machining the 1st groove of the raw material W to be rolled.

[0145] Table 4 shows the standards for each measurement item. Additionally, Table 5 shows the evaluation results. In the evaluation results, when all items of the roller diameter, root circle diameter, tooth profile error, tooth trace error, cumulative pitch error, and vibration of the tooth groove as evaluation items are within the standards shown in Table 4, it is set as "○", and when even one of the evaluation items is out of the standard, it is set as "×". Items that are not evaluated are set as "-".

[0146]

Table 4

[0147] Item Standard Roller diameter [mm] 29.793～29.853 Bottom circle diameter of tooth [mm] 24.90～25.10 Tooth profile error [μm] Below 15 Helix error [μm] Below 20 Cumulative pitch error [μm] Below 41 Vibration of tooth space [μm] Below 32

[0148]

Table 5

[0149]

[0150] As shown in Table 5, in the existing example 1, for the raw material W to be rolled with wall thicknesses of 8 mm, 7 mm, and 6 mm, a good machining shape with suppressed circumferential and axial elongation deformation was obtained. However, in the raw material W to be rolled with a wall thickness of 5 mm or less, circumferential and axial elongation deformation was confirmed to occur. In contrast, in Experimental Examples 1 to 4 (this embodiment), in all rolling die sets, it was confirmed that even for the raw material W to be rolled with a wall thickness of 5 mm, a good machining shape with suppressed circumferential and axial elongation deformation could be obtained. Moreover, even in Existing Example 2 where the bite-in portion length L2 was set longer compared to Existing Example 1 and Experimental Examples 1 to 3, it was confirmed that circumferential and axial elongation deformation occurred for the raw material W to be rolled with a wall thickness of 4 mm. However, in Experimental Example 4 (this embodiment) where the bite-in portion length L2 was set to the same length as Existing Example 2, it was confirmed that even for the raw material W to be rolled with a wall thickness of 4 mm, a good machining shape with suppressed circumferential and axial elongation deformation could be obtained.

[0151] Additionally, Table 6 and Figures 17 - 20It is the detailed results when the raw material W with a wall thickness of 5 mm is subjected to spline rolling in Existing Example 1 and Experimental Examples 1 to 4.

[0152]

Table 6

[0153]

[0154] As shown in Table 6, in Existing Example 1, due to the occurrence of circumferential and axial elongation deformations, non - standard conditions occurred in three items: roller diameter, cumulative pitch error, and vibration of tooth grooves. In contrast, in this embodiment (Experimental Examples 1 to 4), no non - standard conditions occurred in all items, and a good processed shape with suppressed circumferential and axial elongation deformations could be obtained.

[0155] In addition, based on the specifications of the rolling die 1 in Experimental Example 1, the groove depth D of the spline groove 6 was changed to a shallower depth of 0.10 mm, and spline rolling and evaluation were also carried out under the same conditions as the above experiment. Similar to the case where the groove depth D of the spline groove 6 was 0.95 mm (Experimental Example 1), no non - standard conditions occurred in all items, and a good processed shape with suppressed circumferential and axial elongation deformations could be obtained.

[0156] In the spline rolling of Experimental Example 1, in the specified area 7 (segmented machining tooth area part) of the biting part 2, for every 0.5 - turn (half - turn) rotation of the raw material W to be rolled, the segmented machining tooth 5a contacts the same tooth groove on the raw material W to be rolled at different positions in the rolling width direction (axial direction of the raw material W to be rolled). This is because: since the machining amount is 0.14 mm / turn, as long as the groove depth D is set at a depth of 0.07 mm (0.14 mm×0.5) or more, the spline groove 6 will not contact the raw material W to be rolled during the rolling process.

[0157] <Experiment 2>

[0158] In Experiment 2, using Existing Example 1 and Experimental Examples 1 to 4 used in Experiment 1, for the raw material W to be rolled of a hollow part with different wall thicknesses (wall thickness 6 mm to 8 mm), spline rolling was carried out under the same conditions as in Experiment 1 without using a core bar, and the roller diameter, root circle diameter, tooth profile error, tooth trace error, cumulative pitch error, and vibration of tooth grooves were measured respectively. Based on the measurement results, the presence or absence of circumferential and axial elongation deformations of the raw material W to be rolled was evaluated.

[0159] Table 7 shows the evaluation results. In addition, in the evaluation results, similar to Experiment 1, when all items of the roller diameter, root circle diameter, tooth profile error, helix error, cumulative pitch error, and vibration of the tooth groove as evaluation items are within the standards shown in Table 4, it is set as "○", and when a non-standard situation occurs in even one of the evaluation items, it is set as "×".

[0160]

Table 7

[0161]

[0162] As shown in Table 7, in Existing Example 1, if the wall thickness is not 7 mm or more, a good processed shape with circumferential and axial elongation deformation suppressed cannot be obtained. However, in Experimental Examples 1 to 4 (this embodiment), excellent results were confirmed that for the rolled raw material W with a wall thickness of 6 mm, a good processed shape with circumferential and axial elongation deformation suppressed can be obtained even without using a core.

[0163] <Experiment 3>

[0164] In Experiment 3, rolling was performed under conditions different from those of Experiment 1, such as the spline specifications and the material of the rolled raw material, and the presence or absence of circumferential and axial elongation deformation of the rolled raw material W was evaluated.

[0165] Specifically, using the rolling flat die sets of Experimental Examples 5 to 8, which have different specifications from those of the rolling flat die sets of Experimental Examples 1 to 4 in this embodiment as shown in Tables 8 and 9, spline rolling was performed on the hollow rolled raw material W without using a core, and the roller diameter, root circle diameter, tooth profile error, helix error, cumulative pitch error, and vibration of the tooth groove were measured. Based on the measurement results, the presence or absence of circumferential and axial elongation deformation of the rolled raw material W was evaluated (Experimental Examples 7 and 8 evaluated the presence or absence of circumferential and axial elongation deformation of the rolled raw material W when the tooth width W1 of the segmented machining tooth 5a was set to the minimum width (Experimental Example 7) and the maximum width (Experimental Example 8)). In addition, the descriptions of the respective reference numerals recorded in Tables 8 and 9 are the same as those in Experiment 1, so they are omitted.

[0166] In addition, in the rolling die 1 (rolling flat die set) of this embodiment, the phase difference (position offset δ, phase difference of the segmented machining tooth 5a) of the strip groove 6 is P / 2.

[0167]

Table 8

[0168]

[0169]

Table 9

[0170]

[0171] <Processing conditions, etc.>

[0172] · Spline specifications: Pitch diameter φ17.4 × Z36 × m0.47 × PA45°

[0173] Tooth height: 0.512 mm

[0174] Here, Z is a symbol representing the number of teeth of the spline, m is a symbol representing the module, and PA is a symbol representing the pressure angle.

[0175] · Material of the raw material to be rolled: Carbon steel (S43C)

[0176] · Raw material diameter: 16.91 mm

[0177] · Amount of processing: In Experimental Examples 5, 7, and 8: 0.05 mm / rev, in Experimental Example 6: 0.031 mm / rev

[0178] · Tooth height h of the first tooth of the biting portion 2: 0.289 mm

[0179] · Material of the rolling die: Die steel (SKD11)

[0180] · Distance in the rolling direction that the raw material to be rolled advances per one rotation: 53.0 mm

[0181] · Processing conditions: Aiming at the standard central value of the roller diameter at the central position of the rolling width

[0182] · Without using a mandrel (holding both ends of the raw material W to be rolled at the center)

[0183] In addition, in Experiment 3, the presence or absence of elongation deformation in the circumferential and axial directions was evaluated in the raw materials W to be rolled (wall thickness 4.2 mm and 3.5 mm) of two types of hollow parts with different wall thicknesses.

[0184] Table 10 shows the standards for each measurement item. In addition, Table 11 shows the evaluation results. In addition, Figures 21 - 26 shows the measurement results for each measurement item of Experimental Examples 5 and 6. In the evaluation results, all items of the roller diameter, root circle diameter, tooth form error, tooth line error, cumulative pitch error, and vibration of the tooth groove as evaluation items within the standards shown in Table 10 are set as "○", and when even one of the evaluation items is non-standard, it is set as "×".

[0185]

Table 10

[0186] Item Standard Roller diameter [mm] 18.52～18.60 Bottom circle diameter of tooth [mm] 16.35～16.40 Tooth profile error [μm] Below 15 Helix error [μm] Below 20 Cumulative pitch error [μm] Below 60 Vibration of tooth space [μm] Below 35

[0187]

Table 11

[0188]

[0189] As shown in Table 11, in all of the experimental examples 5 to 8, it was confirmed that a good processed shape with suppressed circumferential and axial elongation deformation could be obtained for any wall thickness.

[0190] In addition, as Figures 21 - 26 shown, compared with experimental example 5, experimental example 6 could obtain overall good results. It is considered that this is because the pitch P of the strip grooves 6 was halved and the tooth width W1 of the segmented machining teeth 5a was narrowed to half, thereby improving the deformation suppression effect.

[0191] <Experiment 4>

[0192] In Experiment 4, regarding a spline (pitch circle diameter φ21×Z66×m0.3×PA30°) with specifications different from those in Experiment 3, as shown in Tables 12 and 13, in this embodiment, the rolling flat die set of experimental examples 9 and 10 was used, the raw material diameter of the raw material W to be rolled was set to 20.42 mm (material: carbon steel (S45C)), and the raw material W to be rolled of the hollow part was roll-formed without using a core bar, and the presence or absence of circumferential and axial elongation deformation of the raw material W to be rolled was evaluated.

[0193] Specifically, the roller diameter, root circle diameter, and gauge evaluation were measured in the case where the tooth width W1 of the segmented machining teeth 5a was set to the minimum width (experimental example 9) and the maximum width (experimental example 10) as shown in Table 12, and based on the measurement results, the presence or absence of circumferential and axial elongation deformation of the raw material W to be rolled was evaluated. In addition, the setting conditions of each rolling die 1 in experimental examples 9 and 10 are shown in Table 13. In addition, the explanations of the respective reference numerals described in Tables 12 and 13 are the same as those in Experiment 1, and thus are omitted.

[0194] In addition, in the rolling die 1 (rolling flat die set) of this embodiment, the phase difference of the strip grooves 6 (position offset amount δ, phase difference of the segmented machining teeth 5a) is P / 2.

[0195]

Table 12

[0196]

[0197]

Table 13

[0198]

[0199] Table 14 shows the standards for each measurement item. In addition, Table 15 shows the evaluation results. In addition, in the evaluation results, the case where all evaluation items are within the standards is set as "○", and the case where even one of the evaluation items is out of the standards is set as "×".

[0200]

Table 14

[0201] Item Standard Roller diameter [mm] 21.307～21.507 Bottom circle diameter of tooth [mm] 19.754～20.080 Gauge evaluation OK, NG

[0202]

Table 15

[0203]

[0204] As shown in Table 15, in Experimental Example 9 where the tooth width W1 of the segmented machining tooth 5a is set to the minimum width of 0.503 mm and Experimental Example 10 where the tooth width W1 is set to the maximum width of 3.3 mm, results within the standards for all evaluation items can be obtained for any wall thickness.

[0205] <Experiment 5>

[0206] In Experiment 5, the rolling process was performed on the rolled raw material W of the hollow part without using a core bone using a rolling die 1 (rolling flat die set) with different positions of the specified area 7 (segmented machining tooth area part), and the presence or absence of elongation deformation in the circumferential and axial directions of the rolled raw material W was evaluated.

[0207] Specifically, for the case where the specified area 7 (segmented machining tooth area part) is provided starting from the start end of the biting part 2 as shown in Table 16 (refer to Experimental Example 11, Figure 2 ) and the case where the specified area 7 (segmented machining tooth area part) is provided starting from a position separated by a distance equal to two rotations of the rolled raw material W from the start end of the biting part 2 (refer to Experimental Example 12, Figure 9 ), the roller diameter, root circle diameter, tooth profile error, tooth line error, cumulative pitch error, and vibration of the tooth groove were measured, and based on the measurement results, the presence or absence of elongation deformation in the circumferential and axial directions of the rolled raw material W was evaluated.

[0208] In addition, in Experiment 5, for a spline with a spline specification of outside diameter of teeth φ18×Z22×m0.8×PA40°, the raw material diameter of the rolled raw material W was set to 16.89 mm (material: carbon steel (S45C)). In addition, the setting conditions of each rolling die 1 in Experimental Examples 11 and 12 are shown in Table 17. In addition, the descriptions of the respective reference numerals recorded in Tables 16 and 17 are the same as those in Experiment 1, and thus are omitted.

[0209] In addition, in the rolling die 1 (rolling flat die set) of the present embodiment, the phase difference of the strip grooves 6 (position offset δ, phase difference of the segmented machining teeth 5a) is P / 2.

[0210]

Table 16

[0211]

[0212]

Table 17

[0213]

[0214] Table 18 shows the evaluation results. In addition, in the evaluation results, the case where all evaluation items are within the standard is set as "○", and the case where a non-standard situation occurs in even one of the evaluation items is set as "×".

[0215]

Table 18

[0216]

[0217] As shown in Table 18, even when the specified area 7 (the divided machining tooth area part) is provided at a position separated from the start end of the biting part 2 by a distance corresponding to two revolutions of the rolled raw material W, it is possible to obtain results where all evaluation items are within the standard for each wall thickness.

[0218] In addition, in the above Experiments 1 to 5 of this embodiment, the rolled raw material W was set as a hollow member and excellent effects of the present invention were confirmed. However, even when the rolled raw material W is set as a solid member for rolling processing, it is possible to suppress as much as possible the circumferential and axial elongation deformation of the rolled raw material W, and excellent products with a desired tooth shape can be obtained.

[0219] In addition, the present invention is not limited to this embodiment, and the specific structures of the respective constituent elements can be appropriately designed.

Claims

1. A rolling die set, wherein the rolling dies are formed into a group of two or three, and the rolling dies are formed to have a biting portion, a finishing portion and a retreat portion respectively provided with processing teeth from the starting end side of the rolling direction toward the terminal side of the rolling direction, and the outer peripheral surface of the rolled raw material is plastically deformed by each of the processing teeth to roll out a desired tooth shape, characterized in that: In each of the rolling dies, a plurality of strip grooves extending in a straight line in the rolling direction when viewed from above are arranged in parallel at predetermined intervals on each of the processing teeth arranged in a predetermined area from the starting end side of the biting portion to a predetermined position in the rolling direction of the biting portion, thereby forming a plurality of divided processing teeth in the predetermined area in a state of being arranged in the rolling direction and the tooth line direction, and the strip grooves arranged in each of the rolling dies are respectively arranged in a state of being positionally offset in the width direction of the rolling dies relative to the strip grooves arranged in the other rolling dies in the group, thereby The breaking processing teeth are respectively formed in a state where they are positionally offset along the tooth line direction relative to the breaking processing teeth of other rolling dies arranged in the group, and when the rolling dies are configured as a group of two, the breaking processing teeth of each rolling dies are configured to process the entire rolling width area of ​​the rolled material when the rolled material rotates 1 / 2 circle, and when the rolling dies are configured as a group of three, the breaking processing teeth of each rolling dies are configured to process the entire rolling width area of ​​the rolled material when the rolled material rotates 2 / 3 circle.

2. The rolling die set according to claim 1, characterized in that: The strip grooves of each of the rolling dies are arranged at equal intervals along the width direction of the rolling dies with a constant groove width.

3. The rolling die set according to claim 2, characterized in that: When the rolling dies are constituted into a group of two, the tooth width of the dividing processing teeth is set to W1, and the groove width of the strip groove is set to W2, the strip grooves arranged in each of the rolling dies are respectively constituted to have a position offset of (W1+W2) / 2 along the width direction of the rolling dies relative to the strip grooves arranged in other rolling dies in the group.

4. The rolling die set according to claim 2, characterized in that: When the rolling dies are constituted into a group of three, the tooth width of the dividing processing teeth is set to W1, and the groove width of the strip groove is set to W2, the strip grooves arranged in each of the rolling dies are respectively constituted to have a position offset of (W1+W2) / 3 along the width direction of the rolling dies relative to the strip grooves arranged in other rolling dies in the group.

5. The rolling die set according to claim 3, characterized in that: The rolling die set is configured so that the tooth width of the segmented processing teeth is 3.3 mm or less.

6. The rolling die set according to claim 4, characterized in that: The rolling die set is configured so that the tooth width of the segmented processing teeth is 3.3 mm or less.

7. The rolling die set according to any one of claims 1 to 6, characterized in that: The predetermined area is a position from the starting end position of the biting portion to 60% to 95% of the length of the biting portion.

8. The rolling die set according to any one of claims 1 to 6, characterized in that: The predetermined region is a region extending from a position separated by a predetermined distance from the start end of the biting portion in the rolling direction to a position which is 60% to 95% of the length of the biting portion.

9. The rolling die set according to any one of claims 1 to 6, characterized in that: A tapering portion is provided within a predetermined range on the rolling direction terminal side of the predetermined region where the breaking processing teeth are provided, wherein the groove depth of the strip groove gradually becomes shallower toward the rolling direction terminal and the groove width of the strip groove gradually becomes narrower.

10. The rolling die set according to claim 7, characterized in that: A tapering portion is provided within a predetermined range on the rolling direction terminal side of the predetermined region where the breaking processing teeth are provided, wherein the groove depth of the strip groove gradually becomes shallower toward the rolling direction terminal and the groove width of the strip groove gradually becomes narrower.

11. The rolling die set according to claim 8, characterized in that: A tapering portion is provided within a predetermined range on the rolling direction terminal side of the predetermined region where the breaking processing teeth are provided, wherein the groove depth of the strip groove gradually becomes shallower toward the rolling direction terminal and the groove width of the strip groove gradually becomes narrower.

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