Rolling die

Abstract

The present invention provides a rolling die that optimizes the flow of a rolled material during rolling, prevents the formation of an incomplete shape of a tooth tip of a product, and does not require a removal process of a protrusion after rolling. The rolling die is used when a helical tooth shape (21) is formed by rolling an outer peripheral surface of a rolled material (20), wherein the rolling die has a bite portion (1), a finishing portion (2), and a retreat portion (3) from a rolling direction start end side toward a rolling direction end end side, a machining tooth that comes into contact with the rolled material (20) is provided in each of the bite portion (1), the finishing portion (2), and the retreat portion (3), the machining tooth (4) of the bite portion (1) has a mountain-shaped tip portion (7) that protrudes toward a tip end at a tooth tip, the mountain-shaped tip portion (7) is configured to be offset from a tooth thickness center line (C r ) of the machining tooth (4) in a direction of a tooth thickness, and the wall amount of the rolling direction start end side becomes a wall amount that is larger than the wall amount of the rolling direction end end side.

Description

Technical Field

[0001] This invention relates to rolling dies. Background Technology

[0002] In the past, rolling was widely used in the manufacturing of threads, lead screws, and worm gears. This process involves using a rolling die with rolling teeth to clamp a roughly cylindrical material and apply pressure while performing plastic deformation. Compared to machining, rolling offers advantages such as excellent mass production capability, suitability for large-scale production, increased hardness of the workpiece by approximately 20%–30% through work hardening, and improved surface roughness due to the polishing effect of the rolling die and the workpiece.

[0003] Furthermore, in this rolling process, when continuously processing a long strip of material to be rolled, a through-rolling processing apparatus (through-rolling processing apparatus) using circular dies, as shown in Patent Documents 1 to 5, is used. This through-rolling processing apparatus consists of a pair of circular dies with spiral rolling teeth on their outer circumferential surfaces arranged side-by-side, rotating in the same direction relative to the rotation axis, and having the rotation axes of the pair of circular dies respectively arranged at predetermined angles in opposite directions relative to the axial direction of the material to be rolled. This allows for continuous processing of the long strip of material to be rolled by utilizing the "movement phenomenon" of the material moving axially.

[0004] Furthermore, the circular die used in this feed-through rolling processing apparatus typically has a structure with a biting part, a finishing part, and a retraction part having different inclination angles relative to the rolling direction, starting from the beginning end of the cylindrical bottom surface at one end. Specifically, the biting part is formed as an expanding conical shape in which the rotation trajectory of the tooth tip of the processing tooth expands from the beginning end of the rolling direction to the end end of the rolling direction. The finishing part is formed as a cylindrical shape in which the diameter of the rotation trajectory of the tooth tip of the processing tooth is the same as the diameter of the end position of the biting part. The retraction part is formed as a contracting conical shape in which the rotation trajectory of the tooth tip of the processing tooth contracts towards the end end of the rolling direction.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2004-66272

[0006] Patent Document 2: Japanese Patent Application Publication No. 2001-300675

[0007] Patent Document 3: Japanese Published Patent No. 46-22426

[0008] Patent Document 4: Japanese Patent Application Publication No. 2009-95883

[0009] Patent Document 5: Japanese Utility Model Application Publication No. 5-88733

[0010] However, in the circular die, in the past, there has been a circular die in which the shape of the processed tooth is formed into a tooth right-angle cross-sectional trapezoidal shape in which the tip of the tooth is flat in the finish part and the retreat part, and a tooth right-angle cross-sectional home base shape in which the tip of the tooth has a mountain shape (isosceles triangle) part having left-right symmetry in the bite part.

[0011] However, in the case where the processed tooth of the bite part is formed into the above shape, as shown in Figure 22 is shown, since the feed-through roll processing is a processing method in which the teeth surface of the roll die 30 is pressed against the rolled material 40 while being rotated and the rolled material 40 is made to flow from the tip of the teeth of the roll die 30 toward the root of the teeth, thereby transferring / plastically deforming (rolling) the shape of the processed tooth 31, a frictional force in the direction in which the rolled material 40 flows toward the root of the die is applied to the roll direction terminal side tooth flank 32 (the tooth flank in the teeth surface toward the roll direction terminal side) of the processed tooth 31 of the bite part of the rolled die 30, and the portion of the rolled material 40 processed by the processed tooth 31 of the bite part of the rolled die 30 that contacts the roll direction terminal side tooth flank 32 is greatly raised compared to the portion that contacts the roll direction initial end side tooth flank 33 (the tooth flank in the teeth surface toward the roll direction initial end side) of the processed tooth 31. Figure 22 In the roll direction shown by the arrow in

[0012] In the case where such a raised portion is generated, as shown in Figure 23 is shown, a raised portion 42 is formed at the tip of the tooth shape 41 of the rolled material 40, and the tooth shape 41 becomes an incomplete shape, and in the case of using a product having such a tooth shape 41, there are problems such as the operation sound (vibration sound) becoming large due to interference with an object member or the life being affected due to abrasion of the object member.

[0013] Therefore, in the past, the raised portion 42 was removed by grinding processing after the roll processing, thereby solving the above problems, but new problems such as a decrease in throughput and an increase in cost were generated due to the addition of the raised portion 42 removal processing. SUMMARY

[0014] The present application was completed in view of such a situation, and has an object to provide a roll die that can optimize the flow of the rolled material at the time of roll processing, prevent the tip of the product from being formed into an incomplete shape, and does not require the raised portion 42 removal processing after the roll processing.

[0015] The gist of the present application will be described with reference to the accompanying drawings.

[0016] A rolling die used when a helical tooth profile 21 is formed by rolling a peripheral surface of a rolled material 20, characterized by having, from a rolling direction start side toward a rolling direction end side, an engagement portion 1, a finishing portion 2, and a retreat portion 3, each provided with a processing tooth that comes into contact with the rolled material 20, the processing tooth 4 of the engagement portion 1 having a mountain-shaped tip portion 7 that protrudes toward a tip at a tip end, the mountain-shaped tip portion 7 being configured so as to be biased toward the rolling direction start side with respect to a tooth thickness center line C r of the processing tooth 4.

[0017] Further, the rolling die according to the first aspect is characterized in that a tip portion 7a of the mountain-shaped tip portion 7 at a tip end is biased toward the rolling direction start side with respect to the tooth thickness center line C r .

[0018] Further, the rolling die according to the second aspect is characterized in that the mountain-shaped tip portion 7 is configured so as to have a tooth square cross-sectional shape that is triangular.

[0019] Further, the rolling die according to the second aspect is characterized in that a degree of bias of the tip portion 7a with respect to the tooth thickness center line C r , calculated by the following formula (1), is 12% or more,

[0020] Degree of bias (%) = D / (W-(W dL -W rL )) x 100... Formula (1)

[0021] Here, D is a bias amount of the tip portion 7a of the processing tooth 4 with respect to the tooth thickness center line C r in a tooth square cross-section of the processing tooth 4 of the engagement portion 1, W is a tooth tip thickness at a tip end of a processing tooth 5 of the finishing portion 2, W dL is a tooth thickness at a position separated by a distance L in a tooth tip direction from a root adjacent to a rolling direction end side of the processing tooth 5 of the finishing portion 2, and W rL is a tooth thickness at a position separated by a distance L in a tooth tip direction from a root adjacent to a rolling direction end side of the processing tooth 4 of the engagement portion 1.

[0022] Further, the rolling die according to the third aspect is characterized in that a degree of bias of the tip portion 7a with respect to the tooth thickness center line C r , calculated by the following formula (1), is 12% or more,

[0023] Degree of bias (%) = D / (W-(W dL -W rL )) x 100... Formula (1)

[0024] Here, D is an amount of bias of the top 7a of the working tooth 4 in the tooth straight cross section of the working tooth 4 of the bite-in portion 1 with respect to the tooth thickness center line C r , W is a tooth tip thickness at a tip of the working tooth 5 of the finish portion 2, W dL is a tooth thickness at a position separated by a distance L from a root adjacent to a rolling direction terminal side of the working tooth 5 of the finish portion 2 toward a tooth tip direction, and W rL is a tooth thickness at a position separated by a distance L from a root adjacent to a rolling direction terminal side of the working tooth 4 of the bite-in portion 1 toward a tooth tip direction.

[0025] Further, the rolling die according to the fourth aspect is characterized in that the bias degree is 24% or more and 44% or less.

[0026] Further, the rolling die according to the fifth aspect is characterized in that the bias degree is 24% or more and 44% or less.

[0027] Further, the rolling die according to any one of the first to seventh aspects is characterized in that a tip of each of the working tooth 5 provided to the finish portion 2 and the working tooth 6 provided to the retreat portion 3 is formed as a flat surface, and further, the working tooth 5 provided to the finish portion 2 is narrower in width of the flat surface as closer to the bite-in portion 1 side within a prescribed range on the bite-in portion 1 side.

[0028] Further, the rolling die according to any one of the first to seventh aspects is characterized in that the rolling die is a circular die that rotates around a die rotation axis O, the bite-in portion 1 is formed in an expanding taper shape in which a rotating locus of a tooth tip line T1 of the working tooth 4 of the bite-in portion 1 expands in diameter from the rolling direction start side toward the rolling direction terminal side, the finish portion 2 is formed in a cylindrical shape in which a rotating locus of a tooth tip line T2 of the working tooth 5 of the finish portion 2 has the same diameter as a diameter at a terminal position of the bite-in portion 1, and the retreat portion 3 is formed in a contracting taper shape in which a rotating locus of a tooth tip line T3 of the working tooth 6 of the retreat portion 3 contracts in diameter toward the rolling direction terminal side.

[0029] Further, the rolling die according to the eighth aspect is characterized in that the rolling die is a circular die configured to rotate around a die rotation axis O, the bite portion 1 is formed in an expanding taper shape in which a rotational locus of a tooth tip line T1 of a machining tooth 4 of the bite portion 1 expands in diameter from the rolling direction start end side toward the rolling direction end end side, the finish portion 2 is formed in a cylindrical shape in which a diameter of a rotational locus of a tooth tip line T2 of a machining tooth 5 of the finish portion 2 is the same diameter as a diameter at an end position of the bite portion 1, and the retreat portion 3 is formed in a contracting taper shape in which a rotational locus of a tooth tip line T3 of a machining tooth 6 of the retreat portion 3 contracts in diameter toward the rolling direction end end side.

[0030] According to the present application, the flow of the rolled material during rolling is optimized, and the tooth tip of the product is prevented from being formed in an incomplete shape as much as possible.

[0031] Therefore, by using the present application, the removal process of the protrusion (bump) after rolling is not required, and the effects of improvement of productivity and reduction of cost due to reduction of working hours are obtained. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is an explanatory front view showing the present embodiment.

[0033] Figure 2 is an enlarged explanatory sectional view showing a boundary portion between the bite portion and the finish portion of the present embodiment.

[0034] Figure 3 is an explanatory view showing the machining tooth of the bite portion of the present embodiment.

[0035] Figure 4 is a symbol explanatory view related to the machining tooth of the bite portion and the finish portion of the present embodiment.

[0036] Figure 5 is an explanatory view showing the flow state of the rolled material in the bite portion in a case where the present embodiment is used.

[0037] Figure 6 is an explanatory view showing the rolled material after rolling using the present embodiment.

[0038] Figure 7 is an explanatory view showing the machining tooth of the bite portion of Experimental Example 1 of the present embodiment.

[0039] Figure 8 is an explanatory view showing the machining tooth of the bite portion of Experimental Example 2 of the present embodiment.

[0040] Figure 9 is an explanatory view showing the machining tooth of the bite portion of Experimental Example 3 of the present embodiment.

[0041] Figure 10 Fig. 14 is an explanatory view showing the processed tooth of the bite portion of Experimental Example 4 of the present embodiment.

[0042] Figure 11 Fig. 15 is an explanatory view showing the processed tooth of the bite portion of Experimental Example 5 of the present embodiment.

[0043] Figure 12 Fig. 16 is an explanatory view showing the processed tooth of the bite portion of Experimental Example 6 of the present embodiment.

[0044] Figure 13 Fig. 17 is an explanatory view showing the processed tooth of the bite portion of Experimental Example 7 of the present embodiment.

[0045] Figure 14 Fig. 18 is an explanatory view showing the processed tooth of the bite portion of Experimental Example 8 of the present embodiment.

[0046] Figure 15 Fig. 19 is an explanatory view showing the processed tooth of the bite portion of Experimental Example 9 of the present embodiment.

[0047] Figure 16 Fig. 20 is an explanatory view showing the processed tooth of the bite portion of Experimental Example 10 of the present embodiment.

[0048] Figure 17 Fig. 21 is an explanatory view showing the processed tooth of the bite portion of Experimental Example 11 of the present embodiment.

[0049] Figure 18 Fig. 22 is an explanatory view showing the processed tooth of the bite portion of the comparative example.

[0050] Figure 19 Fig. 23 is a table summarizing the evaluation results of the present experiment.

[0051] Figure 20 Fig. 24 is a table summarizing the details related to the S2 / S1 area ratio of the present experiment.

[0052] Figure 21 Fig. 25 is a view showing the determination criteria for the bulge evaluation of the present experiment.

[0053] Figure 22 Fig. 26 is an explanatory view showing the flow state of the rolled material at the bite portion in the case of using the prior example (comparative example).

[0054] Figure 23 Fig. 27 is an explanatory view showing the rolled material after the roll processing using the prior example (comparative example).

[0055] Explanation of Reference Signs

[0056] 1: bite portion; 2: finish portion; 3: retreat portion; 4: (bite portion) processing tooth; 5: (finish portion) processing tooth; 6: (retreat portion) processing tooth; 7: mountain tip portion; 7a: top; 20: rolled material; 21: tooth profile; C r : tooth thickness center line of (bite portion processing tooth); O: die rotation axis; T1: tooth tip line of (bite portion processing tooth); T2: tooth tip line of (finish portion processing tooth); T3: tooth tip line of (retreat portion processing tooth). DETAILED DESCRIPTION

[0057] The operation of the present application is illustrated with reference to the accompanying drawings and a preferred embodiment of the present application is described simply.

[0058] The processing tooth 4 of the bite portion 1 of the present application has a mountain tip portion 7 protruding toward the tip at the tooth tip, and the mountain tip portion 7 is configured to protrude toward the tip (tooth tip side) with respect to the tooth thickness center line C r of the processing tooth 4 of the bite portion 1. r The wall amount on the rolling direction initial end side becomes more than the wall amount on the rolling direction terminal end side, and thus, at the time of rolling processing, the pressing amount (bite amount) of the rolling direction initial end side of the processing tooth 4 of the bite portion 1 into the rolled material becomes more than the pressing amount of the rolling direction terminal end side with respect to the tooth thickness center line C r of the processing tooth 4 of the bite portion 1.

[0059] Thus, in the present application, compared with the case where rolling processing is performed using the processing tooth 31 having a tooth right-angle cross-sectional base shape formed with a mountain (isosceles triangle) portion having the conventional left-right symmetry, the flow amount of the rolled material 20 to the rolling direction initial end side tooth flank 9 of the processing tooth 4 of the bite portion 1 becomes more (the bias of the flow to the rolling direction terminal end side tooth flank 8 of the processing tooth 4 of the bite portion 1 is reduced), the flow of the rolled material 20 to the rolling direction initial end side and the rolling direction terminal end side of the processing tooth 4 of the bite portion 1 is substantially equal, and thus, the tooth tip of the product is prevented from being formed in an incomplete shape (a protrusion 42 is formed due to a bulge).

[0060] Therefore, by using the present application, the removal processing of the protrusion 42 (bulge) after rolling processing is not required, and the effects of productivity improvement and cost reduction due to work hour reduction can be obtained.

[0061] In addition, in the present application, the mountain tip portion 7 of the tooth tip of the processing tooth 4 of the bite portion 1 refers to a portion (for example, the diagonal portion shown in the drawing) formed as a mountain protruding toward the tip side (tooth tip side) at a position separated by a predetermined distance in the tooth tip direction from the tooth root adjacent to the rolling direction terminal end side of the processing tooth 4 of the bite portion 1. Figure 3

[0062]

EXAMPLE

[0063] A specific embodiment of the present application will be described with reference to the accompanying drawings.

[0064] This embodiment relates to a rolling die used when a tooth shape 21 is formed by rolling the outer peripheral surface of a rolled material 20, and particularly relates to a circular die used when a helical tooth shape 21 is formed by feed-through rolling (through-rolling) on the outer peripheral surface of a long bar-shaped rolled material 20, as shown in Figure 1 The circular die is composed of a bite portion 1, a finish portion 2, and a retreat portion 3, wherein the bite portion 1 is formed in an expanding taper shape in which the rotational locus of the tooth tip line T1 of the tooth 4 expands in diameter from the start end side of the rolling direction toward the end side of the rolling direction, the finish portion 2 is continuously provided with the bite portion 1 and is formed in a cylindrical shape in which the rotational locus of the tooth tip line T2 of the tooth 5 has the same diameter as the diameter of the end position of the bite portion 1, and the retreat portion is continuously provided with the finish portion 2 and is formed in a reducing taper shape in which the rotational locus of the tooth tip line T3 of the tooth 6 reduces in diameter toward the end side of the rolling direction, and helical machining teeth (rolling tooth type) are provided on the outer peripheral surface of each of the bite portion 1, the finish portion 2, and the retreat portion 3.

[0065] Here, the tooth tip line T1 is an imaginary line connecting the tooth tips of the tooth 4 of the bite portion 1, the tooth tip line T2 is an imaginary line connecting the tooth tips of the tooth 5 of the finish portion 2, and the tooth tip line T3 is an imaginary line connecting the tooth tips of the tooth 6 of the retreat portion 3. In Figure 1 the tooth tip lines T1, T2, and T3 are shown in solid lines to show the outline of the circular die.

[0066] Specifically, the helical machining teeth are formed around the die rotational axis O.

[0067] In addition, in the tooth, as shown in the enlarged view in Figure 1 , the tooth 5 provided in the finish portion 2 and the tooth 6 provided in the retreat portion 3 are formed in a substantially right-angled trapezoidal shape in which the tip (tooth tip) is formed in a flat surface and the tooth thickness becomes thinner toward the tip side, and the shape is substantially symmetrical to the left and right.

[0068] In addition, in the finish portion 2, as shown in Figure 2 , the tip flat surface of the tooth 5 in a prescribed range on the bite portion 1 side is narrower in width as it approaches the bite portion 1 side, and the tip flat surface approaches the bite portion 1. By being formed in this shape, the sharp shape change of the tooth 4 of the bite portion 1 and the tooth 5 of the finish portion 2 is gradually moderated, and the occurrence of processing defects (scratches and cracks in the root portion of the rolled product, etc.) caused by the gap in the shape is prevented, and thus this is suitable when a rolled product having a tooth shape with higher quality is obtained.

[0069] In addition, the prescribed range on the side of the bite-in portion 1 refers to 70% or less of the width of the finish-processed portion 2 (the distance in the direction of the die rotation axis O from the boundary of the bite-in portion 1 and the finish-processed portion 2 to the boundary of the finish-processed portion 2 and the retreat portion 3). In the case where the processed tooth 5 having a width of the tip flat surface that is narrower than 70% of the width of the finish-processed portion 2 is formed, the processing in the finish-processed portion 2 at the processed tooth 5 where the width of the tip flat surface formed on the side of the retreat portion 3 is not narrowed becomes insufficient, and it can be impossible to finish-process the rolled material 40 into a desired shape.

[0070] In addition, the processed tooth 4 of the bite-in portion 1 is configured to be inclined with respect to the tooth thickness center line C r The wall amount on the side of the start end of the rolling direction becomes a wall amount that is more than the wall amount on the side of the end of the rolling direction.

[0071] Here, the above wall amount can be compared by being converted into a cross-sectional area as shown below.

[0072] Specifically, as shown in Figure 3 the processed tooth 4 of the bite-in portion 1 is a structure in which the tooth tip is formed into a mountain-shaped tip portion 7 that protrudes toward the tip, that is, the processed tooth 4 of the bite-in portion 1 of the present embodiment is a structure in which the tooth tip is formed into a mountain shape (mountain-shaped tip portion 7) that protrudes toward the tip, the mountain-shaped tip portion 7 being configured to be inclined with respect to the tooth thickness center line C r The wall amount on the side of the start end of the rolling direction becomes a wall amount that is more than the wall amount on the side of the end of the rolling direction.

[0073] More specifically, the mountain-shaped tip portion 7 is formed into a generally triangular convex shape in which, when viewed in the tooth right-angle cross section, the top 7a is inclined toward the side of the start end of the rolling direction with respect to the tooth thickness center line C r , the cross-sectional area S2 (the left descending slant portion in r , the cross-sectional area S1 (the right descending slant portion in Figure 3 ) on the side of the end of the rolling direction is larger than the cross-sectional area S1 (the right descending slant portion in Figure 3 ), in other words, the mountain-shaped tip portion 7 is formed into a generally triangular convex shape in which the length of the slant edge on the side of the end of the rolling direction is longer than the length of the slant edge on the side of the start end of the rolling direction and the inclination angle is gentle.

[0074] More specifically, the mountain-shaped tip portion 7 is formed into a generally triangular convex shape in which, when viewed in the tooth right-angle cross section, the top 7a is inclined toward the side of the start end of the rolling direction with respect to the tooth thickness center line C rThe tooth height h is set to the same height as the finish part 2 and the retreat part 3. Here, the tooth height h of the machining tooth 4 of the bite-in part 1 and the machining tooth 5 of the finish part 2 is the radial direction distance of the die from the dedendum adjacent to the terminal end side of the rolling direction of each machining tooth to the cusp, and the tooth height h of the machining tooth 6 of the retreat part 3 is the radial direction distance of the die from the dedendum adjacent to the terminal end side of the rolling direction of the machining tooth 6 to the cusp.

[0075] In addition, in the machining tooth 4 of this bite-in part 1, if the rolling direction terminal end side tooth flank 8 is formed to the same shape as the rolling direction terminal end side tooth flank 10 (refer to Figure 4 ) of the machining tooth 5 of the finish part 2 in a range exceeding 50% of the tooth height h, the inclination angle of the inclined surface from the top 7a to the rolling direction terminal end side tooth flank 8 becomes small, and in the bite-in part 1, the effect of increasing the flow amount of the rolled material 20 to the rolling direction terminal end side tooth flank 9 is suppressed, and therefore, the range in which the rolling direction terminal end side tooth flank 8 is formed to the same shape as the rolling direction terminal end side tooth flank 10 (refer to Figure 4 ) of the machining tooth 5 of the finish part 2 is preferably 50% or less of the tooth height h from the dedendum, and in the present embodiment, the shape of the portion from the dedendum to 42% or less of the tooth height h is formed to the substantially same shape as the machining tooth 5 of the finish part 2.

[0076] In addition, the machining tooth 4 of this bite-in part 1 is configured such that the degree of bias of the top 7a of the substantially triangular tooth right angle cross section of the above-described mountain-shaped cusp part 7 with respect to the tooth thickness center line C r calculated by the following formula (1) is 12% or more, and preferably 24% or more and 44% or less.

[0077] Degree of bias (%) = D / (W-(W dL -W rL )) x 100... Formula (1)

[0078] Here, referring to Figure 4 , D is the degree of bias of the top 7a of the tooth right angle cross section of the machining tooth 4 (indicated by a solid line in Figure 4 ) of the bite-in part 1 with respect to the tooth thickness center line C r , W is the cusp tooth thickness at the cusp of the machining tooth 5 (indicated by a dashed line in Figure 4 ) of the finish part 2, W dL is the tooth thickness at a position separated by a distance L in the cusp direction from the dedendum adjacent to the terminal end side of the rolling direction of the machining tooth 5 of the finish part 2, and W rL is the tooth thickness at a position separated by a distance L in the cusp direction from the dedendum adjacent to the terminal end side of the rolling direction of the machining tooth 4 of the bite-in part 1.

[0079] Further, the distance L is a range (arbitrary portion of the tooth flank angle al of the rolling direction terminal side tooth flank 8 and the tooth flank angle a2 of the rolling direction initial end side tooth flank 9) from the root of the machined tooth 4 of the bite-in portion 1 on the rolling direction terminal side at which the hill-shaped tip portion 7 is not formed and in which the tooth shape is maintained as a substantially trapezoidal shape. Here, the tooth flank angles al and a2 are the angles of the tooth thickness center line C r (parallel straight line thereto) with each tooth flank.

[0080] Further, C d is the tooth thickness center line in the tooth straight angle cross section of the machined tooth 5 of the finish machining portion 2.

[0081] Further, in the present embodiment, the tooth flank angle al of the rolling direction terminal side tooth flank 8 and the tooth flank angle a2 of the rolling direction initial end side tooth flank 9 are the same angle, but can also be different angles.

[0082] Further, regarding the tip tooth thickness W of the machined tooth 5 of the finish machining portion 2, in the case where the flat surface of the tip (tip) and the rolling direction initial end side tooth flank 11 or the rolling direction terminal side tooth flank 10 are connected by a curved surface or a chamfered machining surface, the distance between the intersection points of the extensions of the flat surface and the two tooth flanks is taken as the tip tooth thickness W.

[0083] Further, regarding the shape of the tip 7a of the machined tooth 4 of the bite-in portion 1, if it is a sharp shape, it is easy to cause edge collapse, and the die life becomes short, so it is preferable to have an R shape as shown in the drawing or a chamfered shape of a surface that slopes downward from the tip 7a toward the rolling direction initial end side. Figure 3

[0084] Next, the effects of the present embodiment configured as above will be described.

[0085] In the present embodiment, the machined tooth 4 of the bite-in portion 1 has a hill-shaped tip portion 7 in which the tip is protruding toward the tip, and the hill-shaped tip portion 7 is configured so that the tip 7a is offset by 12% or more, preferably 24% or more and 44% or less, with respect to the tooth thickness center line C r of the machined tooth 4, and the wall amount on the rolling direction initial end side is made larger than the wall amount on the rolling direction terminal side. r The hill-shaped tip portion 7 is configured so that the tip 7a is offset by 12% or more, preferably 24% or more and 44% or less, with respect to the tooth thickness center line C r of the machined tooth 4, and the wall amount on the rolling direction initial end side is made larger than the wall amount on the rolling direction terminal side. r Therefore, during the rolling process, the amount of pressing (bite-in amount) of the rolling direction initial end side with respect to the tooth thickness center line C r ​The amount of flow of the rolled material 20 to the rolling direction terminal side tooth flank 9 of the cutting tooth 4 of the bite portion 1 is increased (the bias of the flow to the rolling direction terminal side tooth flank 8 of the cutting tooth 4 of the bite portion 1 is reduced) compared to the case where the rolling is performed using a machining tooth whose tooth straight cross section is a trapezoidal shape formed in a mountain shape (isosceles triangle) having the conventional left-right symmetry, and as shown in Figure 5 , the flow of the rolled material 20 to the rolling direction initial side and the rolling direction terminal side of the cutting tooth 4 of the bite portion 1 is substantially equal, thereby preventing the tooth tip of the product (screw) from being formed in an incomplete shape (a protrusion 42 is formed due to a bulge), and the rolling forms a tooth shape 21 in an appropriate shape as shown in Figure 6 .

[0086] Further, in the present embodiment, the shape of the top 7a of the cutting tooth 4 of the bite portion 1 is formed in an R shape, and therefore, chipping is not easily generated, and the die life is extended.

[0087] Therefore, by using the present embodiment, the removal process of the protrusion 42 (bulge) after the rolling is not required, and the effects of the improvement of the productivity and the reduction of the cost due to the reduction of the working hours can be obtained.

[0088] Next, the experimental results (performance evaluation results) that demonstrate the effects of the present embodiment will be described.

[0089] In the present experiment, a through-rolling round die for manufacturing a screw in which the twist direction is right (right twist) was used. Specifically, a round die in which the top 7a of the mountain-shaped tip portion 7 of the cutting tooth 4 of the bite portion 1 was formed in a shape different in the bias amount D of the top 7a with respect to the tooth thickness center line C r as shown in Figure 7 (Experimental Example 1) to Figure 17 (Experimental Example 11) and a round die in which the cutting tooth 4 of the bite portion 1 was formed in the existing shape (bias amount D = 0) as shown in Figure 18 (comparison example) were used, and a screw in which the tooth shape 21 was formed on the rolled material 20 was manufactured by through-rolling, the bulge state of the tooth shape 21 of the rolled material 20 was confirmed, and the die life of each round die was confirmed.

[0090] The specifications of these screws were 8 mm in outer diameter, 1.96 mm in pitch, and 5 in the number of threads in Experimental Examples 1, 2, and 9, 8 mm in outer diameter, 2.5 mm in pitch, and 6 in the number of threads in Experimental Examples 3, 4, and 10, and 9 mm in outer diameter, 2.55 mm in pitch, and 4 in the number of threads in Experimental Examples 5 to 8, 11, and the comparison example.

[0091] In addition, the tooth profile of each of these ball screws is a tooth profile in which the shoulder of the tooth tip of the tooth profile 21 is formed in a shape with a rounded corner, that is, the first tooth flank 23 (see Figure 21 ) that contacts the rolling direction terminal side tooth flank of the machined tooth 5 of the finish rolling portion 2 of the rolling round die at the time of rolling and the second tooth flank 24 (see Figure 21 ) that contacts the rolling direction initial side tooth flank of the machined tooth 5 of the finish rolling portion 2 of the rolling round die at the time of rolling have a rounded corner portion 22 that protrudes outward from the connecting portion of the tooth tip upper surface.

[0092] In addition, in the finish rolling portion 2 of the round die, the width of the region formed in a manner that the width of the tip flat surface of the machined tooth 5 narrows is 61.0% with respect to the width of the finish rolling portion 2 in Experimental Examples 1, 2, and 9, is 68.7% in Experimental Examples 3, 4, and 10, and is 51.2% in Experimental Examples 5 to 8 and 11.

[0093] <Protrusion Evaluation>

[0094] The protrusion evaluation of the tooth profile 21 of the rolled material 20 is performed in association with the degree of protrusion of the tip 7a in the tooth square cross-sectional shape of the mountain-shaped tip portion 7 of the machined tooth 4 of the bite-in portion 1 and the area ratio of the rolling direction initial side cross-sectional area S2 / rolling direction terminal side cross-sectional area S1 in the tooth square cross-sectional shape of the mountain-shaped tip portion 7.

[0095] The degree of protrusion of each of the experimental examples is calculated using the following formula (1).

[0096] Degree of protrusion (%) = D / (W-(W dL -W rL )) x 100... Formula (1)

[0097] Here, D is the amount of protrusion of the tip 7a of the machined tooth 4 with respect to the tooth thickness center line C r in the tooth square cross-sectional shape of the machined tooth 4 of the tooth profile 1, W is the tooth thickness at the tip of the machined tooth 5 of the finish rolling portion 2, W dL is the tooth thickness at a position separated by a distance L in the tip direction from the root adjacent to the rolling direction terminal side of the machined tooth 5 of the finish rolling portion 2, and W rL is the tooth thickness at a position separated by a distance L in the tip direction from the root adjacent to the rolling direction terminal side of the machined tooth 4 of the bite-in portion 1 (see Figure 4 ).

[0098] In addition, the maximum value of the degree of protrusion calculated from the above formula (1) is 50%.

[0099] In addition, with respect to the area ratio of the rolling direction initial side cross-sectional area S2 / rolling direction terminal side cross-sectional area S1, as Figure 3As shown, from the tooth shape region that is the same as the machining tooth 5 of the finishing part 2 formed on the tip of the mountain-shaped portion 7 and the root side, that is, from the point a and point b on the respective boundaries of the two inclined surfaces constituting the tip of the mountain-shaped portion 7 and the terminal tooth surface 8 or the starting tooth surface 9 in the rolling direction, a point located on the tooth root side is drawn out along the tooth thickness centerline C. r For a perpendicular straight line, calculate the cross-sectional area S1 of the end side of the rolling direction and the cross-sectional area S2 of the beginning side of the rolling direction, which are closer to the tip side (tooth tip side) than this line (refer to...). Figure 20 ).

[0100] Additionally, when points a and b are arc-shaped, draw a line C from the starting point of the arc, at the position closest to the tooth root, parallel to the tooth thickness centerline. r For a perpendicular straight line, calculate the cross-sectional area S1 of the end side of the rolling direction and the cross-sectional area S2 of the beginning side of the rolling direction that are closer to the tip side (tooth tip side) than the straight line.

[0101] Figure 19 The results of the elevation evaluation for Experimental Examples 1 to 11 and the comparative examples are shown. Furthermore, regarding the determination of the elevation evaluation, such as... Figure 21 As shown, the case where the first tooth side surface 23 and the second tooth side surface 24 of the screw tooth profile 21 of the rolled material 20 form an outwardly protruding arc portion 22 at the connection between the two tooth side surfaces and the upper surface of the tooth tip, and the upper surface of the tooth tip of the tooth profile 21 is flat, is designated as "A". The case where, although some unfilled portions are observed, the material reaches the tip of the tooth profile 21 of the screw tooth of the rolled material 20, and an arc portion 22 is formed at the connection between the first tooth side surface 23 and the second tooth side surface 24 and the upper surface of the tooth tip, is designated as "B". The case where the second tooth side surface 24 has insufficient bulge and no arc portion 22 is formed, and there is a significant protrusion 42 at the tip of the tooth tip of the screw tooth profile 21 of the rolled material 20, is designated as "C". In the shape of "C", it will lead to operating noise due to interference with the object component and a deterioration in service life due to wear of the object component. In contrast, forming an arcuate portion 22 within the shape of "B" allows for smooth contact with the object component, thus avoiding the problems that occur in the shape of "C," and is therefore a preferred method. "A" is an even more preferred method.

[0102] like Figure 19 As shown, regarding the evaluation of bulges, only in the comparative example (0% bias), a noticeable protrusion 42 was observed at the tip of the tooth cusp 21 of the lead screw of the rolled material 20.

[0103] In addition, in Experimental Examples 1 to 11 in which the protrusion 42 was not observed, Experimental Example 5 having a bias degree of 12.6% and Experimental Example 1 having a bias degree of 23.2% were determined as B. Further, Experimental Examples 1 and 5 were determined as A. According to this result, it was confirmed that Experimental Examples 1 to 11 were in a good raised state.

[0104] In addition, the area ratio S2 / S1 of the cross-sectional area S2 on the start end side of the rolling direction to the cross-sectional area S1 on the end side of the rolling direction was 1.30 to 1.79, and this area ratio substantially corresponded to the above bias degree, and the area ratio of Experimental Example 5 having the smallest bias degree was the smallest.

[0105] <Die Life Evaluation>

[0106] The die life evaluation was to confirm whether or not the cutting tooth 4 of the bite-in portion 1 was chipped after 300 times of rolling processing of the rolled material 20 having a length of 2.5 m, and to determine the die life by the presence or absence of the chipping. In this experiment, the absence of chipping was set as "A", and the presence of chipping was set as "B".

[0107] As shown in Figure 19 , in the three circular dies of Experimental Examples 9, 10, and 11, the occurrence of chipping was confirmed. In Experimental Examples 9 to 11, as shown in Figure 15 to Figure 17 , the top 7a of the cutting tooth 4 of the bite-in portion 1 was formed in a sharp shape. That is, in the case where the top 7a was formed in an R shape, the occurrence of chipping was not observed.

[0108] <Comprehensive Determination>

[0109] Figure 19 The comprehensive determination result based on the results of the above raised evaluation and the die life evaluation is shown. The comprehensive determination is determined in three stages of "A", "B", and "C" in order from the best result, and the example in which both the raised evaluation and the die life evaluation are A is set as the comprehensive determination A, the example in which either one of the raised evaluation and the die life evaluation is A and the other is B and the example in which both the raised evaluation and the die life evaluation are B are set as the comprehensive determination B, and the example in which the raised evaluation result is C is set as the comprehensive determination C. In the comprehensive determination A, the raised state is the best state, and the die life is also good, so it is the best mode. In the comprehensive determination B, at least before the chipping of the cutting tooth of the bite-in portion occurs and the die life is determined, the thread form 21 of the screw is in a good raised state. On the contrary, in the case of the comprehensive determination C, the protrusion 42 occurs regardless of the die life.

[0110] As a result of the evaluation, Experimental Examples 2 to 4 and Experimental Examples 6 to 8 were the comprehensive determination A, Experimental Examples 1, 5, 9 to 11 were the comprehensive determination B, and the comparative example was the comprehensive determination C.

[0111] In view of the results of the above protrusion evaluation, the mold life evaluation, and the comprehensive determination, the degree of bias of the top 7a in the tooth right-angle cross-sectional shape of the gable tip portion 7 is 12% or more, preferably 24% or more and 44% or less (the area ratio of S2 / S1 is 1.56 or more), and the shape of the top 7a is preferably an R shape (R = 0.1 mm to 0.3 mm or so) or a chamfered shape, with respect to the machined tooth 4 of the undercut portion 1.

[0112] As described above, as an experiment to demonstrate the effects of the present embodiment, a feed-through rolling round die for manufacturing a lead screw with a right twist (right twist) was used, but the present application is not limited to a right twist lead screw and can also be applied to a feed-through rolling round die for manufacturing a lead screw with a left twist (left twist).

[0113] In addition, in the case of rolling processing for a lead screw with a left twist (left twist), as long as the same rolling direction is taken as a precondition, that is, in the present embodiment, as shown in FIG. 6, the rolled material 20 is moved from the right side to the left side as a precondition, with respect to the setting in the rolling processing of a right twist lead screw, a round die with the helical direction of the machining tooth in the opposite direction is used, a pair of round dies are arranged with the direction in which the die rotation axis is inclined set to the opposite direction, and the rotation direction of the round dies is set to the opposite direction. Figure 5

[0114] In addition, the rolling die of the present embodiment is not limited to a lead screw and can also be applied to rolling processing of a rolled material having a helical tooth shape such as a trapezoidal thread, a worm, and the like.

[0115] In addition, the present application is not limited to the present embodiment and the specific configurations of the respective components can be appropriately designed.​

Claims

1. A rolling die used to roll a material to form a spiral tooth shape on its outer circumferential surface, characterized in that, The rolling die has an engagement section, a finishing section, and a retraction section from the beginning side of the rolling direction to the end side of the rolling direction. The biting part, the finishing part, and the retraction part are each provided with processing teeth that abut against the material being rolled. The processing teeth of the biting part have a mountain-shaped tip that protrudes towards the tip at the tooth tip. The pointed tip of the mountain shape is configured such that, relative to the center line of the tooth thickness of the machined tooth, the wall thickness at the beginning of the rolling direction is greater than the wall thickness at the end of the rolling direction. In addition, in the finishing section, the machining teeth within a defined range on the biting side have a tip with a tip flat surface formed close to the biting part, and the tip flat surface becomes narrower the closer it is to the biting part.

2. The rolling die according to claim 1, characterized in that, The tip of the mountain-shaped tip is offset towards the starting end side of the rolling direction relative to the center line of the tooth thickness.

3. The rolling die according to claim 2, characterized in that, The pointed tip of the mountain is formed with a right-angled tooth-like cross-section that is triangular in shape.

4. The rolling die according to claim 2, characterized in that, The deviation of the top relative to the center line of the tooth thickness, as determined by the following formula (1), is more than 12%. Bias (%) = D / (W - (W) dL -W rL Equation (1) × 100 Here, D is the offset of the top of the machined tooth relative to the center line of the tooth thickness in the right-angle section view of the machined tooth of the biting part. W represents the tooth tip thickness at the tip of the machining teeth in the finishing section. W dL It is the tooth thickness located at a distance L from the tooth root adjacent to the end side of the machining tooth in the rolling direction of the finishing section towards the tooth tip. W rL It is the tooth thickness at a position L away from the tooth root adjacent to the end side of the machining tooth in the rolling direction of the biting part, and at a distance L from the tooth tip.

5. The rolling die according to claim 3, characterized in that, The deviation of the top relative to the center line of the tooth thickness, as determined by the following formula (1), is more than 12%. Bias (%) = D / (W - (W) dL -W rL Equation (1) × 100 Here, D is the offset of the top of the machined tooth relative to the center line of the tooth thickness in the right-angle section view of the machined tooth of the biting part. W represents the tooth tip thickness at the tip of the machining teeth in the finishing section. W dL It is the tooth thickness located at a distance L from the tooth root adjacent to the end side of the machining tooth in the rolling direction of the finishing section towards the tooth tip. W rL It is the tooth thickness at a position L away from the tooth root adjacent to the end side of the machining tooth in the rolling direction of the biting part, and at a distance L from the tooth tip.

6. The rolling die according to claim 4, characterized in that, The degree of bias is above 24% and below 44%.

7. The rolling die according to claim 5, characterized in that, The degree of bias is above 24% and below 44%.

8. The rolling die according to any one of claims 1 to 7, characterized in that, The tips of the machining teeth provided in the finishing section and the machining teeth provided in the retraction section each form a flat tip surface.

9. The rolling die according to any one of claims 1 to 7, characterized in that, The rolling die is configured as a circular die that rotates about the die's axis of rotation. The biting portion is formed as an expanding conical shape in which the rotation trajectory of the tooth tip line of the biting portion expands from the beginning side of the rolling direction to the end side of the rolling direction. The finishing section is formed in a cylindrical shape such that the diameter of the rotation trajectory of the tooth tip line of the finishing section is the same as the diameter at the end position of the biting section. The retraction portion is formed as a tapered shape in which the rotation trajectory of the tooth tip line of the retraction portion is reduced towards the end side of the rolling direction.

10. The rolling die according to claim 8, characterized in that, The rolling die is configured as a circular die that rotates about the die's axis of rotation. The biting portion is formed as an expanding conical shape in which the rotation trajectory of the tooth tip line of the biting portion expands from the beginning side of the rolling direction to the end side of the rolling direction. The finishing section is formed in a cylindrical shape such that the diameter of the rotation trajectory of the tooth tip line of the finishing section is the same as the diameter at the end position of the biting section. The retraction portion is formed as a tapered shape in which the rotation trajectory of the tooth tip line of the retraction portion is reduced towards the end side of the rolling direction.

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