Rolling die set

Abstract

To provide a rolling die set that can suppress a raw material to be rolled from deforming as quickly as possible, without requiring a die to be enraged in size and requiring a core bar, in rolling-processing a hollow material.SOLUTION: In a rolling die set, a plurality of line grooves 6 extending in a straight line in a rolling direction in a planar view are formed, in parallel with a predetermined interval in a width direction of each rolling die 1, on processing teeth 5 in a predetermined range in the rolling direction extending from a starting end side of a biting part 2 of the rolling die 1. A plurality of dividing processing teeth 5a are formed, in an aligned state in the rolling direction and in a tooth trace direction, by the line grooves 6. The dividing / processing teeth 5a of each rolling die 1 are formed to positionally deviate in the tooth trace direction with respect to dividing / processing teeth 5a of the other rolling die 1 which is paired with the rolling die. When the raw material W to be rolled is rolled by one half or by two third, the whole of a rolling width of the raw material W to be rolled is processed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a rolling die set consisting of two or three rolling dies. [Background technology]

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

[0003] Compared to cutting, this rolling process has the following advantages: it is highly suitable for mass production and is therefore ideal for mass production; the surface of the rolled product becomes harder and stronger due to work hardening; and the burnishing effect between the rolling die's processing teeth and the rolled material results in a good 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 splines (rolled products) not only as solid products but also as hollow products with a circular cross-section along the central axis of an approximately cylindrical shape.

[0005] However, when the material to be rolled is made hollow and rolling processing is performed on the outer surface of this hollow material, the material to be rolled 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 material to be rolled may crack.

[0006] In order to prevent the material to be rolled (hollow material) from being stretched and deformed in the circumferential and axial directions as much as possible, one method has been to perform the rolling process by inserting a rod-shaped core (sometimes called a mandrel) into a hole along the central axis of the approximately cylindrical shape.However, simply using a core has the problem that it is difficult to obtain a product with the desired tooth shape.

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

[0008] Attempts have been made to prevent the rolled material (hollow material) from elongating and deforming in the circumferential and axial directions by reducing the inclination of the tooth tip line of the processing teeth at the chamfering portion and gradually applying the rolling load to the rolled material, but this did not solve the problem of difficulty in obtaining a product with the desired tooth shape, and there was also the problem that the length of the chamfering portion needed to be increased, which in turn required the rolling die to be made larger.

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

[0010] Therefore, methods of 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] Japanese Patent Application Laid-Open No. 2014-054644 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-143970 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 consisting of multiple hard balls is placed in the through hole of a hollow material having a through hole communicating with two end openings, jigs are inserted through the two end openings, the hollow material is positioned while pressurizing the group of hard balls with the two jigs, the tooth-shaped processing surface of a rolling die is pressed against the outer peripheral surface of the hollow material to roll the outer peripheral 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 instead of a rod-shaped core with a circular cross section (a so-called round bar), and requires the steps of placing the group of hard balls in the through-hole of the hollow material, positioning the hollow material while applying pressure to the group of hard balls, and removing the group of hard balls from the through-hole after rolling. This results in a problem of excessive processing time, and does not take advantage of the advantages of rolling, which is excellent for mass production and is ideal for mass production.

[0014] Furthermore, Patent Document 2 discloses a method for manufacturing a hollow gear, in which an inner diameter mandrel having concave and convex portions on its outer peripheral surface that extend axially parallel to each other and are continuously provided in the circumferential direction is inserted into the central axial hole of a cylindrical workpiece, and the workpiece is rotated together with the inner diameter mandrel while the tooth-forming surface of a rolling die is pressed against the outer peripheral surface of the workpiece to form a tooth profile on the outer peripheral surface.Since the rolling is performed while the convex portions on the outer peripheral surface of the inner diameter mandrel are pressed against the inner peripheral surface of the workpiece, the convex portions can restrict the circumferential flow of material on the inner peripheral surface of the workpiece, and the circumferential length of the workpiece can be prevented from increasing in the circumferential direction.

[0015] However, in this method, the convex portions on the outer surface of the inner diameter mandrel (core metal) are pressed against the inner peripheral surface of the workpiece while the rolling is performed, which not only deforms the inner peripheral surface of the workpiece and makes it impossible to meet the dimensional specifications for the inner diameter of the workpiece, but also takes a long time to remove the workpiece from the inner diameter mandrel (core metal), and in some cases it may not even be possible to remove it.

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

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

[0018] A rolling die set is configured as a set of two or three rolling dies 1 each having a chamfering portion 2, a finishing portion 3, and a relief portion 4, each of which is provided with processing teeth 5, from the starting end side in the rolling direction to the terminal end side in the rolling direction, and each processing tooth 5 is used to plastically deform the outer circumferential surface of the material W to be rolled to roll a desired tooth profile, and each rolling die 1 has a predetermined region 7 from the starting end side of the chamfering portion 2 to a predetermined position in the rolling direction of the chamfering portion 2, and each processing tooth 5 is provided with a plurality of parallel grooves 6 extending linearly in the rolling direction in a plan view at predetermined intervals in the width direction of the rolling die 1, so that a plurality of dividing processing teeth 5a are formed in the predetermined region 7 aligned in the rolling direction and the tooth trace direction, and the rolling die 1 is provided with The grooves 6 formed on one rolling die 1 are each offset in the width direction of the rolling die 1 relative to the grooves 6 formed on the other rolling dies 1 of the pair, so that the dividing teeth 5a are each formed offset in the tooth trace direction relative to the dividing teeth 5a formed on the other rolling dies 1 of the pair, and further, the dividing teeth 5a of each rolling die 1 are configured so that when two rolling dies 1 are configured as a set, the entire rolling width of the rolled material W is machined in 1 / 2 rotation of the rolled material W, and when three rolling dies 1 are configured as a set, the entire rolling width of the rolled material W is machined in 2 / 3 rotation of the rolled material W.

[0019] Furthermore, in the rolling die set described in claim 1, the grooves 6 of each rolling die 1 are arranged at equal intervals in the width direction of the rolling die 1 with a constant groove width W2.

[0020] Furthermore, in the rolling die set described in claim 2, the rolling die set is characterized in that the rolling dies 1 are configured in pairs, and when the tooth width of the dividing processing tooth 5a is W1 and the groove width of the groove 6 is W2, the groove 6 formed in each rolling die 1 is configured so that the amount of positional deviation δ in the width direction of the rolling die 1 relative to the groove 6 formed in the other rolling die 1 in the pair is (W1 + W2) / 2.

[0021] Furthermore, in the rolling die set described in claim 2, the rolling dies 1 are configured in a set of three, and when the tooth width of the dividing processing tooth 5a is W1 and the groove width of the groove 6 is W2, the groove 6 formed in each rolling die 1 is configured so that the amount of positional deviation δ in the width direction of the rolling die 1 relative to the groove 6 formed in the other rolling die 1 in the same set is (W1 + W2) / 3.

[0022] The present invention also relates to a rolling die set as set forth in claim 3, characterized in that the dividing teeth 5a have a tooth width W1 of 3.3 mm or less.

[0023] The present invention also relates to a rolling die set as set forth in claim 4, characterized in that the dividing teeth 5a have a tooth width W1 of 3.3 mm or less.

[0024] Furthermore, in the rolling die set described in any one of claims 1 to 6, the specified region 7 is characterized in that it extends from the starting position of the chamfer 2 to a position that is 60% to 95% of the length L2 of the chamfer 2.

[0025] Furthermore, in the rolling die set described in any one of claims 1 to 6, the specified region 7 is characterized in that it extends from a position that is a specified distance from the start of the chamfer 2 in the rolling direction to a position that is 60% to 95% of the length L2 of the chamfer 2.

[0026] Furthermore, in the rolling die set described in any one of claims 1 to 6, a gradually decreasing portion 7a is provided in a predetermined range on the rolling direction terminal side of the predetermined region 7 in which the dividing processing tooth 5a is provided, and this gradually decreasing portion 7a is configured so that the groove depth D of the groove 6 gradually becomes shallower toward the rolling direction terminal and the groove width W2 of the groove 6 gradually becomes narrower.

[0027] Furthermore, in the rolling die set described in claim 7, a gradually decreasing portion 7a is provided in a predetermined range on the rolling direction end side of the predetermined region 7 in which the dividing processing tooth 5a is provided, and this gradually decreasing portion 7a is configured so 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.

[0028] In addition, the rolling die set described in claim 8 is characterized in that a gradually decreasing portion 7a is provided in a predetermined range on the rolling direction end side of the predetermined region 7 in which the dividing processing tooth 5a is provided, and this gradually decreasing portion 7a is configured so 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. [Effects of the Invention]

[0029] Since the present invention is configured as described above, it provides a rolling die set that can minimize the circumferential and axial elongation and deformation of the material to be rolled in the rolling process of hollow materials, without having to increase the size of the rolling die or use a core bar with a special configuration during the rolling process, and can produce products with the desired tooth profile. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a schematic explanatory diagram of rolling processing using the present embodiment (flat rolling die). [Figure 2] FIG. 1 is an explanatory plan view showing the present embodiment. [Figure 3]10 is an explanatory plan view showing a predetermined region (cutting processing tooth region) of the chamfering portion of the present embodiment. FIG. [Figure 4] FIG. 2 is an explanatory diagram showing the state of positional deviation in the width direction of the rolling die of the grooves of the lower rolling die (another rolling die) relative to the grooves of the upper rolling die (one rolling die) in this embodiment. [Figure 5] FIG. 4 is an explanatory side view showing the grooves and dividing teeth of the present embodiment. [Figure 6] FIG. 10 is an explanatory plan view showing a tapered portion of the chamfer portion of the present embodiment. [Figure 7] 3A and 3B are explanatory front and side views showing the chamfer portion of the present embodiment. [Figure 8] 10A and 10B are an explanatory side view and an explanatory plan view showing grooves and dividing teeth of another example (a type in which the groove depth is shallow) of this embodiment. [Figure 9] FIG. 10 is an explanatory plan view showing another example of the present embodiment (a type in which a predetermined region (cutting tooth region) is provided at a predetermined distance from the start of the chamfer). [Figure 10] FIG. 10 is a schematic explanatory diagram of a rolling process using another example of this embodiment (when applied to a pair of rolling notched circular dies). [Figure 11] FIG. 10 is a schematic explanatory diagram of a rolling process using another example of this embodiment (when applied to a set of three circular rolling dies). [Figure 12] This is an explanatory diagram showing the state of positional deviation in the width direction of the grooves of other segmented circular rolling dies relative to the grooves of the first to third segmented circular rolling dies of another example of this embodiment shown in Figure 11. [Figure 13] FIG. 10 is an explanatory diagram showing the state of machining the first groove of the material to be rolled when this embodiment (two-set configuration) is used. [Figure 14] FIG. 10 is an explanatory diagram showing the state of machining the first groove of the material to be rolled when this embodiment (a set of three) is used. [Figure 15] FIG. 10 is an explanatory diagram showing the state of machining the first groove of the material to be rolled when a conventional example is used. [Figure 16] 10 is an explanatory view showing a processing tooth (dividing processing tooth) for processing the first groove of the rolled material in this embodiment. FIG. [Figure 17]10 is a graph showing the measurement results of the over-pin diameter in Experiment 1. [Figure 18] 10 is a graph showing the measurement results of the root diameter in Experiment 1. [Figure 19] 10 is a graph showing the measurement results of cumulative pitch error in Experiment 1. [Figure 20] 10 is a graph showing measurement results of tooth space runout in Experiment 1. [Figure 21] 10 is a graph showing the measurement results of the over-pin diameter in Experiment 3. [Figure 22] 10 is a graph showing the measurement results of the root diameter in Experiment 3. [Figure 23] 10 is a graph showing the measurement results of tooth profile error in Experiment 3. [Figure 24] 10 is a graph showing the measurement results of tooth trace error in Experiment 3. [Figure 25] 10 is a graph showing the measurement results of the cumulative pitch error in Experiment 3. [Figure 26] 10 is a graph showing measurement results of tooth space runout in Experiment 3. DETAILED DESCRIPTION OF THE INVENTION

[0031] A preferred embodiment of the present invention will be briefly described below, illustrating the operation of the present invention with reference to the drawings.

[0032] In the present invention, grooves 6 extending linearly in the rolling direction in a plan view are provided in parallel with each other at predetermined intervals in the width direction of the rolling die 1 in each processing tooth 5 provided in a predetermined region 7 from the start side of the chamfer 2 of each rolling die 1 to a predetermined position in the rolling direction of the chamfer 2, and the processing tooth 5 is divided by these grooves 6, so that a plurality of divided processing teeth 5a are formed in the predetermined region 7 in an aligned state in the rolling direction and the tooth trace direction, and further, the divided processing teeth 5a formed in each rolling die 1 are provided in a state in which the grooves 6 provided in each rolling die 1 are displaced by a predetermined amount in the width direction of the rolling die 1 with respect to the grooves 6 provided in other rolling dies 1 that form a pair. The cutting teeth 5a are misaligned in the tooth trace direction relative to the die 1, and the rolled material W is configured to be processed over the entire rolling width in 1 / 2 rotation (when the rolling dies 1 are configured in a set of two) or 2 / 3 rotation (when the rolling dies 1 are configured in a set of three).Therefore, in the specified area 7 where the cutting teeth 5a of the cutting portion 2 are formed, the rolled material W is processed intermittently, and further, the processing load is concentrated on the tooth tips of the cutting teeth 5a, which have a smaller pressing area than the processing teeth 5, so that even when rolling a rolled material W that is a hollow material with a thin wall thickness, the elongation and deformation of the rolled material W in the circumferential and axial directions can be suppressed as much as possible.

[0033] That is, in the rolling process using the conventional rolling die, as shown in FIG. 15, the entire tooth tips of the processing teeth 25 extending in the tooth trace direction of the rolling die 21 are pressed into the tooth grooves of the material W to be rolled. Therefore, when the material W to be rolled is a hollow material with a thin wall thickness, the action of the material swelling up in the tooth grooves of the rolling die 21 as when processing a solid material does not work well. Therefore, if a core bar is not used, the material W to be rolled 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, resulting in the predetermined tooth shape. However, in the present invention, as shown in Figure 13 (in the case of a pair of teeth) and Figure 14 (in the case of a pair of teeth), the pressing position of the dividing teeth 5a into the rolling material W moves in the tooth trace direction as the rolling process progresses, and intermittent processing is performed, and furthermore, the area where the rolling material W is pressed is smaller than in the above-mentioned conventional example, the processing load is concentrated on the tooth tips of the dividing teeth 5a, improving the bulging of the rolling material W and making it possible to form it into the desired shape. As a result, even if the rolling material W is a hollow material with a thin wall thickness, it is possible to suppress elongation deformation in the circumferential and axial directions. [Example]

[0034] Specific embodiments of the present invention will be described with reference to the drawings.

[0035] This embodiment relates to a rolling die set consisting of two or three rolling dies 1, each having a cutting portion 2, a finishing portion 3, and a relief portion 4, each with a processing tooth 5, from the starting end of the rolling direction to the terminal end of the rolling direction, and configured to plastically deform the outer surface of the material W to be rolled by each processing tooth 5 to roll the desired tooth profile. Specifically, this embodiment is a case in which the rolling die set of the present invention is applied to a rolling die set consisting of a pair (a set of two) of rolling flat dies for rolling splines, serrations, gears, etc., arranged above and below, as shown in Figure 1. In this embodiment, when referring to each of the upper and lower rolling dies 1 in Figure 1 (when it is common to both the upper and lower rolling dies 1), it will be referred to as ``rolling die 1'', and when referring to only one rolling die 1 located on the upper side in Figure 1, it will be referred to as ``upper rolling die 1a'', and when referring to only the other rolling die 1 located on the lower side in Figure 1, it will be referred to as ``lower rolling die 1b'' (upper and lower refer to the top and bottom in Figure 1 and do not specify the positional relationship when the pair of rolling dies 1 are in use).

[0036] Each component of this embodiment will be described in detail below.

[0037] As shown in Figure 2, each rolling die 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, as shown in Figure 1.Furthermore, on the top surface opposite this bottom surface 8, a large number of processing teeth 5 are provided that form tooth profiles in the material W to be rolled, 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.

[0038] Furthermore, in each rolling die 1, in order to prevent slippage of the rolled material W (preventing misalignment of the rolled material W relative to the processing teeth 5), shot blasting is performed on the surfaces (top surfaces) of the processing teeth 5 provided in a predetermined range (in this embodiment, a range of approximately 2 / 3 of the length (total length) of the chamfering portion 2 indicated by reference symbol L2 in the figure (range indicated by reference symbol SB in the figure)) from the starting end of the rolling direction toward the terminal end of the rolling direction. Note that reference symbol L1 in the figure indicates the sum of the ranges (lengths) in the rolling direction of the chamfering portion 2, finishing portion 3, and relief portion 4.

[0039] Furthermore, each rolling die 1 of this embodiment is a flat rolling die for processing ordinary splines (splines in which the tooth profile is formed parallel to the axial direction of the material W to be rolled), and in each rolling die 1, the processing teeth 5 of the lead portion 2, finishing portion 3, and relief portion 4 are formed in a mountain shape (approximately trapezoidal) when viewed from the front, and are configured as linear processing teeth that extend linearly in the width direction of the rolling die 1, specifically, in a direction perpendicular to the rolling direction, and are arranged side by side at predetermined intervals in the rolling direction. Note that by making the extension direction of the processing teeth 5 inclined with respect to the direction perpendicular to the rolling direction, the rolling die can be applied to rolling dies for processing helical splines, helical gears, etc.

[0040] 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 in the outer periphery of the material W to be rolled 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 relief portion 4 are provided on an inclined surface that slopes downward toward the end side of the rolling direction, and are configured so that the position of the tip surface gradually becomes lower as it approaches the end side of the rolling direction.

[0041] As shown in Fig. 2, the chamfering portion 2 of each rolling die 1 has grooves 6 formed in each processing tooth 5 in a predetermined region 7 from the starting position to a predetermined position in the rolling direction, and as shown in Fig. 3, each processing tooth 5 is divided in the width direction of the rolling die 1 by these grooves 6, forming a dividing processing tooth region in which a plurality of dividing processing teeth 5a are formed. Note that the symbol X in Fig. 2 indicates the range (length) in the rolling direction of the predetermined region 7 (dividing processing tooth region).

[0042] Specifically, as shown in Figure 4, the grooves 6 of each rolling die 1 are arranged in a state where they are shifted in the width direction of the rolling die 1 relative to the grooves 6 of the other rolling die 1 with which it is paired, and because these grooves 6 are arranged in a shifted state, the dividing teeth 5a formed by the grooves 6 are also formed in a state where they are shifted in the tooth trace direction relative to the dividing teeth 5a provided on the other rolling die 1 with which it is paired.

[0043] In other words, in this embodiment, each groove 6 formed in the lower rolling die 1b is arranged with a predetermined amount of positional shift in the width direction of the rolling die 1 relative to each groove 6 formed in the upper rolling die 1a, and the grooves 6 of the upper rolling die 1a and the grooves 6 of the lower rolling die 1b are arranged with a relative shift in position, so that the dividing processing teeth 5a of the lower rolling die 1b are formed with a predetermined amount of positional shift in the tooth trace direction of the dividing processing teeth 5a (tooth trace direction of the processing teeth 5) relative to the dividing processing teeth 5a of the upper rolling die 1a.

[0044] More specifically, the grooves 6 of each rolling die 1 are set to a constant groove width W2, and extend in a straight line (linearly and continuously) along the rolling direction (parallel to the rolling direction) at equal intervals in the width direction of the rolling die 1 in a plan view. As a result, the dividing teeth 5a of each rolling die 1 are aligned in the rolling direction and the tooth trace direction of the processing teeth 5 (width direction of the rolling die 1) in a predetermined region 7 (dividing tooth region), as shown in FIG. Furthermore, in the tooth trace direction of the processing teeth 5 (width direction of the rolling die 1), each dividing processing tooth 5a of the lower rolling die 1b is formed with a positional deviation amount δ (phase difference) relative to each dividing processing tooth 5a of the upper rolling die 1a so that the entire rolling width of the rolled material W is processed in 1 / 2 rotation by both the dividing processing teeth 5a of the upper rolling die 1a and the dividing processing teeth 5a of the lower rolling die 1b.

[0045] The groove 6 is not limited to extending in a straight line as described above, but may be provided in a straight line that is linear and discontinuous along the rolling direction in a plan view, as shown in Fig. 8(b). The rolling width refers to the axial range in which a tooth profile is formed by rolling the material W to be rolled.

[0046] Furthermore, the predetermined region 7 (dividing processing tooth region) of each rolling die 1 is provided from the start position of the chamfer 2 to a position that is 60% to 95% of the length L2 of the chamfer 2.

[0047] By providing the predetermined region 7 (cutting tooth region) where the cutting teeth 5a are formed from the start of the cutting portion 2, the range of the predetermined region 7 (cutting tooth region) can be set widely in the cutting portion 2 of a predetermined length, which results in more rolling processing being performed using the cutting teeth 5a, and the effect of the present invention, i.e., the effect of suppressing elongation deformation of the rolled material W in the circumferential and axial directions, is more effectively exerted.

[0048] The predetermined region 7 (dividing tooth region) does not have to start at the start of the chamfer 2, but may start at a position an appropriate distance from the start of the chamfer 2, as shown in Fig. 9. In this case, the position where the predetermined region 7 (dividing tooth region) is provided (the position where the predetermined region 7 (dividing tooth region) starts, in other words, the start position of the groove 6) is preferably a position away from the rolling material W by a distance of 0.5 to 2 revolutions.

[0049] The reason why the range in which the dividing teeth 5a are provided is set to a position that is 60% to 95% of the length L2 of the chamfering portion 2 is that if the dividing teeth 5a are provided only up to a position that is less than half the length of the chamfering portion 2, the desired effect will not be achieved, and if the dividing teeth 5a are provided over the entire length of the chamfering 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 in the rolled material W will not be aligned even after rolling by the processing teeth 5 of the finishing portion 3, and scratches (groove marks caused by the grooves 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 just a little short of the boundary position with the finishing portion 3 (towards the starting end in the rolling direction), and it is more preferable to set it up to a position that is 95% of the length L2 of the chamfering portion 2.

[0050] The grooves 6 that form the dividing processing teeth 5a (grooves 6 that divide the processing teeth 5) are formed by grinding with a grindstone into tapered grooves whose groove width increases from the bottom side toward the top, as shown in Fig. 5. Note that the formation of the grooves 6 is not limited to the grinding process, and they may also be formed by, for example, laser processing or the like.

[0051] Furthermore, if the groove width W2 of the groove 6 of each rolling die 1 is too narrow compared to the tooth width W1 of the dividing teeth 5a described below, the shape will be similar to that of a conventional product (one that does not have grooves 6 and does not have dividing teeth 5a), and therefore the deformation suppression effect will not be sufficient for thin-walled rolled material W; and if it is too wide compared to the tooth width W1 of the dividing teeth 5a, unmachined portions will be created, causing the processing load in the finishing section 3 to become too large and deforming the rolled material W, so the groove width W2 of this groove 6 needs to be set from the tooth width W1 of the dividing teeth 5a.

[0052] Taking this into consideration, the groove width W2 of the groove 6 of each rolling die 1 can be set appropriately within a range that does not impair the effect of this embodiment, but in the rolling die set configured as a pair in this embodiment, a groove width that is equal to or narrower than the tooth width W1 of the dividing processing tooth 5a is preferable, and specifically, it is preferable to set the ratio W1 / W2 of the tooth width W1 of the dividing processing tooth 5a to the groove width W2 of the groove 6 to be 0.9 or more, specifically 0.9 to 1.8.

[0053] In addition, in the specification where the ratio W1 / W2 of the tooth width W1 of the cutting 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 of the groove 6 is slightly wider than the tooth width W1 of the cutting tooth 5a.In this case, a small amount of unmachined portion remains in the specified region 7 (cutting tooth region) 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, and therefore, as described above, this is within the preferable range and is included in the category of "equivalent (groove width) to the tooth width W1 of the cutting 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 rolling die 1 at the upper edge portion of the groove 6 (the widest portion of the groove) as shown in Figure 5, and in this embodiment, the tooth width W1 of the dividing tooth 5a means the tooth width in the width direction of the rolling die 1 at the tip end surface of the dividing tooth 5a as shown in Figure 5.

[0055] Furthermore, the grooves 6 of each rolling die 1 are provided from the starting end in the rolling direction to the rear end in the rolling direction along the inclination of the working teeth 5 of the lead portion 2 (the inclination of the tip line of the working teeth 5 shown in FIG. 1), and the groove depth D of the grooves 6 based on the tip of the working teeth 5 is set to a constant depth. Note that the groove depth D of the grooves 6 can be set appropriately within a range that does not impair the effects of this embodiment, and does not have to be set to a constant depth based on the tip of the working teeth 5.

[0056] Further, the groove depth D of the grooves 6 of each rolling die 1 is set to a depth equal to or greater than the tooth height of the processing teeth 5, and is configured to completely separate the processing teeth 5.

[0057] 8(a), the groove depth D of the groove 6 may be set to a depth shallower than the tooth height of the processing teeth 5, as long as it is a predetermined depth that achieves the effects of this embodiment. For example, the groove depth D of the groove 6 may be set in accordance with the workability of the material W to be rolled. If the material W to be rolled is a material that easily bulges during rolling (a material with high ductility), the groove depth D of the groove 6 may be set deep (for example, set to be greater than the tooth height of the processing teeth 5), and if the material is not easily bulged (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 teeth 5, for example, set to a depth that is 50% of the tooth height of the processing teeth 5) to prevent breakage during rolling due to a decrease in the strength of the dividing processing teeth 5a.

[0058] In addition, the grooves 6 of each rolling die 1 are arranged at equal intervals in the tooth trace direction of the processing teeth 5 so that the tooth width W1 of the dividing processing teeth 5a is 3.3 mm or less (in order to fully obtain the deformation suppression effect in the thin-walled rolling material W, it is preferable to set the tooth width W1 of the dividing processing teeth 5a to 3.3 mm or less).

[0059] As mentioned above, this embodiment is a rolling flat die for processing ordinary splines (splines in which the tooth profile is formed parallel to the axial direction of the material W to be rolled), so the tooth trace direction of the processing teeth 5 and the width direction of the rolling die 1 are the same.

[0060] The narrower the tooth width W1 of the dividing teeth 5a, the more effective it is in suppressing deformation of the material W to be rolled, but on the other hand, chipping becomes more likely to occur, resulting in problems of shortened tool life. 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.

[0061] Specifically, the tooth tip width in the rolling direction of the first tooth of the rolling die 1 is set as a threshold value, and if the tooth width W1 of the dividing processing tooth 5a is made narrower than this, chipping becomes very likely to occur, so it is preferable to set the tooth width W1 of the dividing processing tooth 5a to be equal to or greater than the tooth tip width in the rolling direction of the first tooth of the rolling die 1.

[0062] Taking this into consideration, the grooves 6 of each rolling die 1 are arranged at equal intervals in the tooth trace direction of the processing tooth 5 so that the tooth width W1 of the dividing processing tooth 5a in its complete shape (divided by two adjacent grooves 6) is 0.5 mm or more and 3.3 mm or less.

[0063] As described above, in this embodiment, the grooves 6 of the lower rolling die 1b are shifted in position in the width direction of the rolling die 1 relative to the grooves 6 of the upper rolling die 1a so that the entire rolling width of the rolled material W can be processed in 1 / 2 rotation by both the dividing teeth 5a of the upper rolling die 1a and the dividing teeth 5a of the lower rolling die 1b, and the dividing teeth 5a formed by the grooves 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. When the tooth width W1 of the dividing teeth 5a is configured as described above, the amount of positional deviation δ in the width direction of the rolling die 1 of the grooves 6 of the lower rolling die 1b relative to the grooves 6 of the upper rolling die 1a is set to (W1+W2) / 2, that is, 1 / 2 (i.e., P / 2) of the parallel spacing (P: pitch) of the grooves 6 of each rolling die 1, so that the entire rolling width of the rolled material W can be machined in 1 / 2 rotation of the rolled material W (no unmachined portions are formed). If the tooth width W1 of the dividing tooth 5a is larger than the groove width W2 of the groove 6, the positional deviation δ may deviate from P / 2 accordingly. For example, the positional deviation δ may be set in the range of W2≦δ≦W1. However, if the tooth width W1 of the dividing tooth 5a is smaller than the groove width W2 of the groove 6, it is better to keep the positional deviation δ as close to P / 2 as possible. For example, in a rolling die set having specifications in which the ratio W1 / W2 of the tooth width W1 of the dividing tooth 5a to the groove width W2 of the groove 6 is 0.9 (Experimental Examples 2, 8, and 10 described below), it is preferable to set the positional deviation δ in the range of δ=((W1+W2) / 2)±((W2-W1) / 4). In this embodiment, the positional deviation amount δ is set to (W1+W2) / 2, i.e., 1 / 2 (i.e., P / 2) of the parallel spacing (P: pitch) of the grooves 6 of each rolling die 1 (see Figure 4).

[0064] In this embodiment, the amount by which the dividing teeth 5a push the rolling material W deepest in the tooth height direction (maximum machining amount) is set to be within 0.14 mm.

[0065] The reason for setting the maximum machining amount of the cutting teeth 5a within 0.14 mm is based on the results of various experiments, including Experimental Examples 1 to 3 described below (this embodiment: maximum machining amount of the cutting teeth 5a 0.14 mm), and is that if the maximum machining amount exceeds 0.14 mm, the machining load on the rolled material W becomes too large, and there is a risk that the rolled material W will be stretched and deformed in the circumferential and axial directions.

[0066] Further, a gradually tapering portion 7a is provided at the rolling direction terminal end side of the predetermined region 7 (dividing tooth region) where the dividing teeth 5a of each rolling die 1 are provided.

[0067] This gradually tapering portion 7a is set in a range including 6 to 12 processing teeth 5 at the end of the specified region 7 (dividing processing tooth region), and the grooves 6 provided in each processing tooth 5 of this gradually tapering portion 7a are set to a shallower groove depth D and a narrower groove width W2 than the grooves 6 provided in the specified region 7 (dividing processing tooth region) closer to the starting end of the rolling direction than the gradually tapering portion 7a.

[0068] Specifically, as shown in FIG. 6, the gradually tapering portion 7a is configured so that the groove depth D of the groove 6 gradually becomes shallower toward the end in the rolling direction, and the groove width W2 of the groove 6 gradually becomes narrower.

[0069] The groove depth D of the groove 6 in this gradually decreasing portion 7a may become shallower in a curved manner from the start of the gradually decreasing portion 7a to the end thereof, or may gradually become shallower in a linear manner along the gradient of the gradually decreasing angle g (gradual decrease angle g = arctan (groove depth D of the groove 6 at the start of the gradually decreasing portion 7a / length of the gradually decreasing portion 7a in the rolling direction)), as shown in Figure 7, for example.

[0070] By providing this gradually tapering portion 7a, the change in the shape of the processing tooth 5 due to the presence or absence of the groove 6 is made gentler in the area of ​​the specified region 7 (cutting processing tooth area) closer to the starting end in the rolling direction than the gradually tapering portion 7a, and in the biting portion 2 closer to the end in the rolling direction than the specified region 7 (cutting processing tooth area), thereby suppressing sudden changes in the processing load and preventing elongation deformation of the rolled material W.

[0071] As shown in FIG. 1, the chamfer 2 in this embodiment has a constant gradient of the tooth tip line, i.e., the machining amount at the chamfer 2 (the machining amount per rotation of the rolled material W) is set constant. However, the chamfer 2 may be configured such that a predetermined range at the start of the chamfer 2 is the first chamfer stage and the remaining chamfer 2 is the second chamfer stage, with the gradient of the tooth tip line at the first chamfer stage being large and the gradient of the tooth tip line at the second chamfer stage being small, so that the machining amount is large at the first chamfer stage and small at the second chamfer stage.

[0072] Furthermore, as described above, this embodiment is a case in which the rolling die set of the present invention is applied to a rolling flat die as shown in Figure 1, but the rolling die set of the present invention can also be applied to a rolling partial circular die 1.

[0073] The rolling die 1 rotates in the rolling direction, and the rolling tooth form formed on its outer circumferential surface is provided with a lead 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 die 1 to the tip of the processing tooth 5. In the case of the rolling die 1, the groove 6 is provided in an arc shape around the rotation axis of the rolling die 1 along the rotation direction (rolling direction).

[0074] By providing the grooves 6 in an arc shape around the rotation axis of the rolling die 1 in the direction of rotation (rolling direction), the grooves 6 are provided so as to be linear (slightly curved, approximately linear) in plan view in the rolling direction of the chamfer 2 in which the grooves 6 of the rolling die 1 are formed. In other words, when the outer peripheral surface of the rolling die 1 is developed on a plane, the grooves 6 are provided along the rolling direction (parallel to the rolling direction) and linear in plan view in the rolling direction, similar to the case of the flat rolling die shown in Figure 2. Therefore, by providing the grooves 6 in an arc shape around the rotation axis of the rolling die 1 in the rolling die 1, the same effects as those when applied to the flat rolling die described below can be achieved. It should be noted that, due to the rolling recessed circular die 1 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, but in this embodiment, this slightly curved state is also included in the term "straight line when viewed in a plane."

[0075] Specifically, when the rolling die set of the present invention is applied to a rolling segmented circular die 1, it can be applied to a configuration in which a pair (two) of rolling segmented circular dies 1, consisting of a first rolling segmented circular die 1a and a second rolling segmented circular die 1b, as shown in Figure 10, is set up, and to a configuration in which a set of three, consisting of a first rolling segmented circular die 1a, a second rolling segmented circular die 1b, and a third rolling segmented circular die 1c, is set up, as shown in Figure 11.

[0076] When a pair (two) of rolling recessed circular dies 1 are configured as a set, the same configuration as when applied to the above-mentioned rolling flat die is used, and the grooves 6 of the second rolling recessed circular die 1b are arranged in a position shifted in the width direction of the rolling recessed circular die 1 relative to the grooves 6 of the first rolling recessed circular die 1a so that the entire rolling width of the rolling material W can be processed in 1 / 2 rotation, and the dividing processing teeth 5a formed by the grooves 6 are formed in a position shifted in the tooth trace direction (with a phase difference) relative to the dividing processing teeth 5a provided on the first rolling recessed circular die 1a and the second rolling recessed circular die 1b.

[0077] Specifically, by setting the widthwise positional deviation δ of the grooves 6 of the second rolling notched circular die 1b relative to the grooves 6 of the first rolling notched circular die 1a to (W1+W2) / 2, i.e., 1 / 2 (i.e., P / 2) of the parallel spacing (P: pitch) of the grooves 6 of each rolling notched circular die 1 (see Figure 4), a rolling die set is obtained in which the entire rolling width of the rolled material W can be processed in 1 / 2 rotation of the rolled material W (no unprocessed portions are formed).

[0078] In addition, the preferred setting range of the positional deviation amount δ when the tooth width W1 of the dividing processing tooth 5a is larger than the groove width W2 of the groove 6 (W2≦δ≦W1), and the preferred setting range of the positional deviation amount δ when the tooth width W1 of the dividing processing tooth 5a is smaller than the groove width W2 of the groove 6 (δ=((W1+W2) / 2)±((W2-W1) / 4)) are the same as in the case of the above-mentioned rolling flat die set (upper rolling die 1a and lower rolling die 1b).

[0079] In addition, when three rolling recessed circular dies 1 are configured as a set, the grooves 6 of the second rolling recessed circular die 1b are provided in a state where they are shifted in position in the width direction of the rolling recessed circular die 1 relative to the grooves 6 of the first rolling recessed circular die 1a so that the entire rolling width of the rolling material W is processed in 2 / 3 rotation of the rolling material W, and the grooves 6 of the third rolling recessed circular die 1c are positioned in the width direction of the rolling recessed circular die 1 relative to the grooves 6 of the second rolling recessed circular die 1b. As shown in Figure 12, a phase difference is provided in the grooves 6 between the first rolling recessed circular die 1a, the second rolling recessed circular die 1b and the third rolling recessed circular die 1c, and the dividing teeth 5a of the first rolling recessed circular die 1a, the second rolling recessed circular die 1b and the third rolling recessed circular die 1c are formed in a state where they are shifted in position in the tooth trace direction (with a phase difference) relative to the dividing teeth 5a of the other rolling recessed circular die 1 that is paired with them.

[0080] Specifically, by setting the phase difference of the grooves 6 between each rolling recess circular die 1, i.e., the widthwise positional deviation δ of the grooves 6 of the second rolling recess circular die 1b relative to the grooves 6 of the first rolling recess circular die 1a, the widthwise positional deviation δ of the grooves 6 of the third rolling recess circular die 1c relative to the grooves 6 of the second rolling recess circular die 1b, and the widthwise positional deviation δ of the grooves 6 of the first rolling recess circular die 1a relative to the grooves 6 of the third rolling recess circular die 1c, to (W1+W2) / 3, i.e., 1 / 3 (i.e., P / 3) of the spacing (P: pitch) of the grooves 6 of each rolling recess circular die 1 (see Figure 12), the rolling die set can process the entire rolling width of the rolled material W in 2 / 3 rotation of the rolled material W (no unprocessed portions are formed).

[0081] If the tooth width W1 of the dividing tooth 5a is larger than 1 / 2 of the groove width W2 of the groove 6 (i.e., larger than 1 / 3 of the pitch P of the groove 6), the positional deviation amount δ may deviate from P / 3 accordingly, and for example, the positional deviation amount δ may be set in the range of W2 / 2≦δ≦W1. However, if the tooth width W1 of the dividing tooth 5a is smaller than 1 / 2 of the groove width W2 of the groove 6, that is, if the tooth width W If the groove width W2 of the groove 6 is greater than twice 1, it is better to keep the positional deviation δ as close to P / 3 as possible. For example, in a rolling die set having specifications in which the ratio 2W1 / W2 of the tooth width W1 of the dividing processing tooth 5a to the groove width W2 of the groove 6 is 0.9 (W1 / W2 = 0.45), it is preferable to set the positional deviation δ within the range of δ = ((W1 + W2) / 3) ± ((W2 - 2W1) / 6).

[0082] Since this embodiment is configured as described above, in the predetermined region 7 (dividing tooth region) of the cutting portion 2, the dividing teeth 5a of each rolling die 1 (rolling notched circular die 1) move their pushing position in the width direction of the rolling die 1 (tooth trace direction of the dividing teeth 5a) relative to the rolled material W every 1 / 2 rotation (1 / 3 rotation in the case of a set of three) of the rolled material W, and they perform intermittent machining. Furthermore, the area in which the rolled material W is pushed is smaller than when the rolled material W is pushed by the processing teeth 5, and the processing load is concentrated on the tooth tips of each dividing tooth 5a, so that the dividing teeth 5a push the rolled material W.5a This makes it easier for the rolling material W to bite into the workpiece, and even when the workpiece W is a hollow material with a thin wall thickness, it is possible to suppress elongation deformation in the circumferential and axial directions.

[0083] In the rolling process of splines onto hollow material, the greater the ratio of the spline tooth height to the thickness of the material W to be rolled, the greater the circumferential and axial extension deformation, making it more difficult to form the desired tooth profile.Furthermore, the greater the ratio of the inner diameter (diameter of the hollow part of the material W to be rolled) to the outer diameter (diameter of the material W to be rolled), i.e., the thinner the material W to be rolled, the greater the circumferential and axial extension deformation, making it more difficult to form the desired tooth profile.

[0084] 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 machined well (without elongation deformation) without a core bar only when the ratio of the tooth depth 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 of the material W to be rolled) is 47% or less, and even if a core bar is used, the ratio of the tooth depth 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 of the material W to be rolled) is 55% or less. In the past, good machining was only possible in the following cases. However, by using this embodiment, it is possible to machine well without a core bar up to the condition that the ratio of the spline tooth height to the thickness of the rolled material W is 20% or less and the ratio of the inner diameter (diameter of the hollow part of the rolled material W) to the outer diameter (diameter of the rolled material W) of the rolled material W is 55% or less.Furthermore, by using a core bar, it is possible to machine well up to the condition that the ratio of the spline tooth height to the thickness of the rolled material W is 30% or less and the ratio of the inner diameter (diameter of the hollow part of the rolled material W) to the outer diameter (diameter of the rolled material W) of the rolled material W is 70% or less.

[0085] The following is an experiment (evaluation experiment) that supports the effects of this embodiment described above.

[0086] <Experiment 1> A total of six rolling flat die sets, 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 this embodiment, which have different configurations such as the tooth width of the dividing processing teeth 5a, 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 rolling flat die sets W was evaluated.

[0087] For each symbol in Table 1, L: length of rolling die 1, L2: length of chamfer 2, X: range (length) of predetermined region 7 (separation processing tooth region) in the rolling direction, and X / L2: ratio of range X of predetermined region 7 (separation processing tooth region) (length in the rolling direction range of predetermined region 7 (separation processing tooth region)) to length L2 of chamfer 2 (chamfer length L2) (see FIG. 2).

[0088] Furthermore, 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: 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 in the specified region 7 (dividing tooth region) in the chamfer 2, W1 / W3: tooth width ratio of the dividing tooth 5a, DP: spline pitch of the rolling die 1 (pitch of the spline processing 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 3 and 5).

[0089] In the rolling die 1 (flat rolling die set) of this embodiment, the phase difference of the grooves 6 (positional deviation amount δ, phase difference of the dividing teeth 5a) was set to P / 2.

[0090] [Table 1]

[0091] [Table 2]

[0092] Specifically, spline rolling was performed using a core wire under the following conditions on hollow rolling material W (thickness 4mm to 8mm) of different thicknesses, and the overpin diameter, root circle diameter, tooth profile error, tooth trace error, cumulative pitch error, and tooth groove runout of each were measured, and the presence or absence of circumferential and axial elongation deformation of the rolling material W was evaluated based on these measurement results.

[0093] <Processing conditions etc.> Spline specifications: Tooth tip diameter φ27.5×Z27×m1.0×PA37.5° Tooth height: 1.2 mm Here, Z is the number of teeth of the spline, m is the module, and PA is the pressure angle. Material of rolling material: Carbon steel (S45C) Material diameter: 26.46mm Processing volume: Conventional example 1 and experimental examples 1-3: 0.14 mm / rotation Conventional Example 2 and Experimental Example 4: 0.09 mm / rotation 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 Rolling die material: Die steel (SKD11) Distance in the rolling direction per revolution of the rolled material: 83.1 mm (= Spline tooth pitch in the rolling direction DP 3.0777 mm x Z 27) Processing conditions: Aim for the center of the pin diameter standard at the center of the rolling width <Core used> Material: Carbon steel (hardened) Core dimensions and inner diameter: See Table 3 below

[0094] [Table 3]

[0095] Further explaining experimental examples 1 to 4, when the number of grooves in the rolled material W is based on the first tooth of the lower rolling die 1b (first groove), and in experimental examples 1 to 3, the chamfer length L2 of the rolling die 1 is designed to be 449 mm and the number of teeth in the chamfer 2 is 146, as shown in Figure 16, on the lower rolling die 1b, the processing teeth 5 of the 1st, 28th, 55th, 82nd, 109th and 136th teeth become the teeth that process the first groove in the rolled material W, and on the upper rolling die 1a, since the rolled material W processes the same groove as the groove processed by the first tooth of the lower rolling die 1b in 1 / 2 rotation, the processing teeth 5 of the 14th, 41st, 68th, 95th and 122nd teeth become the teeth that process the first groove in the rolled material W. In experimental example 4, when the chamfer length L2 of the rolling die 1 is designed to be 754 mm and the number of teeth of the chamfer 2 is designed to be 245, as shown in Figure 16, in the lower rolling die 1b, 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 in the rolled material W, and in the upper rolling die 1a, since the rolled material W processes the same groove as the groove processed by the 1st tooth of the lower rolling die 1b in 1 / 2 rotation, 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 in the rolled material W.

[0096] Table 4 shows the standards for each measurement item. Table 5 shows the evaluation results. In the evaluation results, if all of the evaluation items, over-pin diameter, root 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 a circle, and if any of the evaluation items were outside the standards, they were marked with an ×. Items for which no evaluation was performed were marked with a -.

[0097] [Table 4]

[0098] [Table 5]

[0099] As shown in Table 5, in Conventional Example 1, good processed shapes in which elongation deformation in the circumferential and axial directions was suppressed were obtained for rolling material W with wall thicknesses of 8 mm, 7 mm, and 6 mm, but it was confirmed that elongation deformation in the circumferential and axial directions occurred for rolling material W with wall thicknesses of 5 mm or less. In contrast, in Experimental Examples 1 to 4 (this example), it was confirmed that good processed shapes in which elongation deformation in the circumferential and axial directions was suppressed were obtained for rolling material W with a wall thickness of 5 mm in all rolling die sets. Furthermore, it was confirmed that even in Conventional Example 2, in which the chamfer length L2 was set longer than in Conventional Example 1 and Experimental Examples 1 to 3, elongation deformation in the circumferential and axial directions occurred for rolling material W with a wall thickness of 4 mm, but in Experimental Example 4 (this example), in which the chamfer length L2 was set to the same length as Conventional Example 2, it was confirmed that good processed shapes in which elongation deformation in the circumferential and axial directions was suppressed were obtained for rolling material W with a wall thickness of 4 mm.

[0100] Table 6 and FIGS. 17 to 20 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.

[0101] [Table 6]

[0102] As shown in Table 6, in Conventional Example 1, due to the occurrence of elongation deformation in the circumferential and axial directions, non-standard results occurred in three items: over-pin diameter, cumulative pitch error, and tooth groove runout. In contrast, in the present examples (Experimental Examples 1 to 4), no non-standard results occurred in any items, and a good processed shape was obtained in which elongation deformation in the circumferential and axial directions was suppressed.

[0103] Spline rolling and evaluation were also carried out under the same conditions as in the above experiment, with the groove depth D of the groove 6 being set to a shallower depth of 0.10 mm, based on the specifications of the rolling die 1 in 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-specification 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.

[0104] In the spline rolling process in Experimental Example 1, in the predetermined region 7 (dividing tooth region) of the chamfer 2, the dividing teeth 5a come into contact with the same tooth groove on the rolling material W at a different position in the rolling width direction (axial direction of the rolling material W) every 0.5 rotation (1 / 2 rotation) of the rolling 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 groove 6 will not come into contact with the rolling material W during the rolling process.

[0105] <Experiment 2> In Experiment 2, using Conventional Example 1 and Experimental Examples 1 to 4 used in Experiment 1, spline rolling was performed on hollow rolling material W (thickness 6mm to 8mm) of different thicknesses without using a core wire under the same conditions as Experiment 1, and the overpin diameter, root circle diameter, tooth profile error, tooth trace error, cumulative pitch error and tooth groove runout of each were measured, and the presence or absence of circumferential and axial elongation deformation of the rolling material W was evaluated based on these measurement results.

[0106] 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 diameter, tooth profile error, tooth lead error, cumulative pitch error, and tooth space runout, were within the specifications shown in Table 4, and an × when any of the evaluation items was outside the specifications.

[0107] [Table 7]

[0108] As shown in Table 7, in Conventional Example 1, unless the wall thickness was 7 mm or more, it was not possible to obtain a good processed shape in which circumferential and axial elongation deformation was suppressed. However, in Experimental Examples 1 to 4 (this embodiment), excellent results were confirmed, in that a good processed shape in which circumferential and axial elongation deformation was suppressed could be obtained even for a rolling material W with a wall thickness of 6 mm, without using a core wire.

[0109] <Experiment 3> In Experiment 3, rolling was performed under processing conditions such as spline specifications and the material of the rolled material that were different from those in Experiment 1, and the presence or absence of circumferential and axial elongation deformation of the rolled material W was evaluated.

[0110] Specifically, as shown in Tables 8 and 9, in this example, the rolling flat die sets of Experimental Examples 5 to 8, which have different specifications from the rolling flat die sets of Experimental Examples 1 to 4, were used to perform spline rolling on a hollow material W to be rolled without using a core, and the overpin diameter, root diameter, tooth profile error, tooth lead error, cumulative pitch error, and tooth groove runout were measured, and the presence or absence of circumferential and axial elongation deformation of the rolling material W was evaluated from these measurement results (Experimental Examples 7 and 8 evaluate the presence or absence of circumferential and axial elongation deformation of the rolling material W when the face width W1 of the dividing teeth 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.

[0111] In the rolling die 1 (flat rolling die set) of this embodiment, the phase difference of the grooves 6 (the amount of positional deviation δ, the phase difference of the dividing teeth 5a) was set to P / 2.

[0112] [Table 8]

[0113] [Table 9]

[0114] <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 rolling material: Carbon steel (S43C) Material diameter: 16.91mm Machining volume: Experimental examples 5, 7, and 8: 0.05 mm / rotation, Experimental example 6: 0.031 mm / rotation Chamfer 2, 1st tooth height h: 0.289 mm Rolling die material: 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 metal is used (both ends of the rolled material W are held at the center) 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).

[0115] Table 10 shows the standards for each measurement item. Table 11 shows the evaluation results. Figures 21 to 26 show the measurement results for each measurement item for Experimental Examples 5 and 6. In the evaluation results, if all of the evaluation items, i.e., over-pin diameter, root diameter, tooth profile error, tooth lead error, cumulative pitch error, and tooth space runout, were within the standards shown in Table 10, they were marked with an O, and if any of the evaluation items were outside the standards, they were marked with an X.

[0116] [Table 10]

[0117] [Table 11]

[0118] As shown in Table 11, it was confirmed that in all of Experimental Examples 5 to 8, a good processed shape was obtained in which elongation deformation in the circumferential and axial directions was suppressed for any thickness.

[0119] 21 to 26, better results were obtained overall in Experimental Example 6 than in Experimental Example 5. This is thought 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 narrowed by half, thereby improving the deformation suppression effect.

[0120] <Experiment 4> In Experiment 4, for a spline with specifications different from those in Experiment 3 (tooth tip diameter φ21 × Z66 × m0.3 × PA30°), the rolling flat die sets of Experimental Examples 9 and 10 in this embodiment, as shown in Tables 12 and 13, were used to set the diameter of the rolled material W to 20.42 mm (material: carbon steel (S45C)), and rolling was performed on the hollow rolled material W without using a core bar, and the presence or absence of elongation deformation in the circumferential and axial directions of the rolled material W was evaluated.

[0121] Specifically, the overpin diameter, root diameter, and gauge evaluation were measured when the face 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 rolling material W was evaluated from the measurement results. The setting conditions for each rolling die 1 in Experimental Examples 9 and 10 are as shown in Table 13. The explanation of each symbol in Tables 12 and 13 is omitted because it is the same as in Experiment 1.

[0122] In the rolling die 1 (flat rolling die set) of this embodiment, the phase difference of the grooves 6 (the amount of positional deviation δ, the phase difference of the dividing teeth 5a) was set to P / 2.

[0123] [Table 12]

[0124] [Table 13]

[0125] The standards for each measurement item are shown in Table 14. The evaluation results are shown in Table 15. In the evaluation results, a ○ was given when all evaluation items were within the standards, and an × was given when even one of the evaluation items was out of the standards.

[0126] [Table 14]

[0127] [Table 15]

[0128] As shown in Table 15, in Experimental Example 9, in which the tooth width W1 of the dividing 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.

[0129] <Experiment 5> In Experiment 5, rolling was performed on a hollow material W to be rolled without using a core wire using a rolling die 1 (flat rolling die set) with a different position of the specified region 7 (cutting processing tooth region), and the presence or absence of circumferential and axial elongation deformation of the material W to be rolled was evaluated.

[0130] Specifically, the overpin diameter, root circle diameter, tooth profile error, tooth trace error, cumulative pitch error, and tooth groove runout were measured when the specified region 7 (dividing processing tooth region) as shown in Table 16 was set from the start of the cutting portion 2 (see Experimental Example 11, Figure 2), and when the specified region 7 (dividing processing tooth region) was set from a position two rotations of the rolled material W away from the start of the cutting portion 2 (see Experimental Example 12, Figure 9).The measurement results were used to evaluate whether or not the rolled material W had undergone elongation deformation in the circumferential and axial directions.

[0131] In Experiment 5, the spline specifications were tooth tip diameter φ18 × Z22 × m0.8 × PA40°, and the diameter of the material W to be rolled was 16.89 mm (material: carbon steel (S45C)). The setting conditions for each rolling die 1 in Experimental Examples 11 and 12 are as shown in Table 17. The explanations for each symbol in Tables 16 and 17 are omitted because they are the same as those in Experiment 1.

[0132] In the rolling die 1 (flat rolling die set) of this embodiment, the phase difference of the grooves 6 (positional deviation amount δ, phase difference of the dividing teeth 5a) was set to P / 2.

[0133] [Table 16]

[0134] [Table 17]

[0135] The evaluation results are shown in Table 18. In the evaluation results, a mark of ○ was given when all evaluation items were within the specifications, and a mark of × was given when even one evaluation item was out of the specifications.

[0136] [Table 18]

[0137] As shown in Table 18, even when the specified region 7 (cutting tooth region) was positioned at a distance of two revolutions of the rolled material W from the start of the cutting portion 2, all evaluation items for each thickness were within the standard.

[0138] In this embodiment, the excellent effects of the present invention were confirmed in the above experiments 1 to 5, using the rolled material W as 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 with the desired tooth profile.

[0139] 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]

[0140] 1. Rolling dies 2. Meal section 3 Finishing section 4 Relief 5 processed teeth 5a Cutting teeth 6 grooves 7 Predetermined area 7a tapering part δ Position deviation amount D Groove depth L2 Length of chamfer W Rolled material

Claims

1. A rolling die set is configured as a set of two or three rolling dies each having a chamfering portion, a finishing portion, and a relief portion, each of which is provided with processing teeth, from the starting end side in the rolling direction to the terminal end side in the rolling direction, and configured so that each processing tooth plastically deforms the outer circumferential surface of the material to be rolled to roll a desired tooth profile, wherein each rolling die has a plurality of parallel grooves extending linearly in the rolling direction in a plan view at predetermined intervals in the width direction of the rolling die, on each processing tooth provided in a predetermined region from the starting end side of the chamfering portion to a predetermined position in the rolling direction of the chamfering portion, so that a plurality of dividing processing teeth are formed in the predetermined region in an aligned state in the rolling direction and the tooth trace direction, and each rolling die has a rolling die set characterized in that the grooves formed in one rolling die are each offset in the width direction of the rolling die relative to the grooves formed in the other rolling dies of the same pair, so that the dividing teeth are each formed offset in the tooth trace direction relative to the dividing teeth formed in the other rolling dies of the same pair, and further, the dividing teeth of each rolling die are configured so that when the rolling dies are configured in a pair, the entire rolling width of the rolled material is processed in 1 / 2 of a rotation of the rolled material, and when the rolling dies are configured in a pair, the entire rolling width of the rolled material is processed in 2 / 3 of a rotation of the rolled material.

2. 2. The rolling die set according to claim 1, wherein the grooves of each of the rolling dies have a constant groove width and are provided at equal intervals in the width direction of the rolling die.

3. 3. The rolling die set according to claim 2, wherein the rolling dies are configured in pairs, and when the face width of the dividing teeth is W1 and the groove width of the groove is W2, the grooves formed in each rolling die are configured so that the amount of positional deviation in the width direction of the rolling die relative to the grooves formed in the other rolling die in the pair is (W1 + W2) / 2.

4. 3. The rolling die set according to claim 2, wherein the rolling dies are configured in a set of three, and when the face width of the dividing teeth is W1 and the groove width of the groove is W2, the grooves formed in each rolling die are configured so that the amount of positional deviation in the width direction of the rolling die relative to the grooves formed in the other rolling die in the same set is (W1 + W2) / 3.

5. 4. The rolling die set according to claim 3, wherein the dividing teeth have a tooth width of 3.3 mm or less.

6. 5. The rolling die set according to claim 4, wherein the dividing teeth have a tooth width of 3.3 mm or less.

7. 7. The rolling die set according to claim 1, wherein the predetermined region is from the start position of the chamfer to a position that is 60% to 95% of the length of the chamfer.

8. 7. The rolling die set according to claim 1, wherein the predetermined region extends from a position that is a predetermined distance from the start of the chamfer in the rolling direction to a position that is 60% to 95% of the length of the chamfer.

9. A rolling die set according to any one of claims 1 to 6, characterized in that a gradually tapering portion is provided in a predetermined range on the rolling direction end side of the predetermined area in which the dividing processing teeth are provided, and this gradually tapering portion is configured so that the groove depth of the groove groove gradually becomes shallower toward the rolling direction end and the groove width of the groove groove gradually becomes narrower.

10. 8. The rolling die set according to claim 7, wherein a gradually tapering portion is provided in a predetermined range on the rolling direction end side of the predetermined area in which the dividing processing teeth are provided, and this gradually tapering portion is configured so that the groove depth of the groove groove gradually becomes shallower toward the rolling direction end and the groove width of the groove groove gradually becomes narrower.

11. 9. The rolling die set according to claim 8, wherein a gradually tapering portion is provided in a predetermined range on the rolling direction end side of the predetermined area in which the dividing processing teeth are provided, and this gradually tapering portion is configured so that the groove depth of the groove groove gradually becomes shallower toward the rolling direction end and the groove width of the groove groove gradually becomes narrower.

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