JP2010014226A - Rolling bolt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bolt of a double thread configuration with improved durability, mechanical strength, and productivity. <P>SOLUTION: In the rolling bolt of the double thread configuration, a coarse thread of a standard first pitch, and a fine thread of a second pitch being smaller than the first pitch are manufactured on an outer circumference part by rolling. In a thread crest 53 of the coarse thread, a thread face 53c is formed in a trough bottom side from a substantially center part of the thread crest. Thread ridges 52 of the fine thread are protrusions periodically formed in a top side from the substantially center part of the thread crest of the coarse thread. A small crest side of crest parts on both sides of a trough part of the fine thread formed on the thread crest of the coarse thread is formed as a flat part conforming to a height of a trough bottom part of the thread crest 52 of the fine thread within a predetermined angle range. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rolled bolt having a loosening prevention function. More specifically, the present invention relates to a rolling bolt having a double screw structure having a function of preventing loosening by rolling coarse threads and fine threads.

  In recent years, various bolts having a loosening prevention function and manufacturing methods thereof have been researched and developed, and various results have been proposed. For example, a coarse thread portion having a pitch P formed from the front end portion of the bolt shaft portion to a predetermined position, and at least the entire length of the coarse screw portion of the bolt shaft portion or the coarse screw portion from the front end portion to a predetermined position of the coarse screw portion. A bolt configuration including a fine screw portion having a pitch p (p = P / n, where n is an integer of 2 or more) formed so as to overlap the portion is disclosed (for example, see Patent Document 1).

  In this bolt, after the coarse nut is screwed onto the coarse screw portion of the bolt, the fine nut is overlapped with the coarse nut and screwed onto the coarse nut, and the bolt and both nuts are fastened. it can. At this time, since the pitch between the fine nut and the coarse nut is different, if both rotate together in the same direction, a repulsive force acts on the contact surface between the two nuts, and the coarse nut rotates in the loose direction. Can be prevented.

Patent Document 1 describes that such a bolt can be processed by a lathe cutting process, a coarse flat die, a roll process using a fine flat die, a roll roll die, or a roll process using a fine roll die. .
Further, the inventors of the present invention also provide a thread portion of a coarse thread in which at least one of the thread rolling dies has developed a coarse thread, and a spiral winding in the same direction as the coarse thread in a valley portion of the coarse thread. A fine screw having a pitch smaller than that of the coarse screw (however, the pitch ratio between the coarse screw and the fine screw is a to b, and a and b are the minimum integer ratio). Protrusions corresponding to fine thread threads that appear periodically for each b winding of the coarse thread threads according to a phase shift from the coarse thread threads when deployed so as to be higher than the valley bottom of the fine thread threads. The technique regarding the manufacturing method and manufacturing apparatus of the bolt which has is disclosed (for example, refer patent document 2).

Furthermore, a technique related to a method for manufacturing a screw rolling die related to this is also disclosed (for example, see Patent Document 3).
Japanese Patent No. 3770320 Japanese Patent No. 3546211 Japanese Patent No. 3534117

  A screw rolling die for manufacturing a rolling screw having a double screw structure is manufactured by subjecting a thread rolling die material to predetermined cutting to form a screw rolling portion. With this screw rolling die, a rolled bolt is manufactured while being pressed and rolled onto a round bar-shaped bolt material. When this screw rolling die is used, a large number of rolling bolts can be manufactured in a short time.

  The rolling bolt having a loosening prevention function is, for example, a rolling bolt having a double screw structure in which coarse screws and fine screws are provided as described above. When rolling with a screw rolling die to manufacture this rolled bolt, the round bar-shaped bolt material is gradually pressed to gradually deform the outer shape of the round bar-shaped bolt material into a screw shape.

  The depth of the periodically changing groove of the thread rolling die is such that the position of the bottom of the coarse thread and the position of the bottom of the fine thread of the fine thread developed to form the protrusions best overlap each other. It is the deepest and the shallowest in the part where the positions of the two are shifted most. For this reason, when rolling a threaded bolt with a double screw configuration with a conventional screw rolling die, the cross-sectional area of the groove, which is a cross section at each angular position, is different, so there is a difference in the material filling rate in the groove at each cross section. Occurs. That is, the grooves are filled in order from the part having the smallest cross-sectional area, and the part having the larger cross-sectional area of the groove is filled last. In particular, at the end of processing, since the filling rate of the material into the groove is high, there is no place for surplus material to escape.

  As a result, when rolling, there is a risk of chatter vibration, noise, and the like. In addition, depending on the degree of chatter vibration, there is a possibility that a precision failure may be caused, the tool life may be significantly shortened, and the manufacturing apparatus may be adversely affected.

  Furthermore, in the conventional screw rolling die 101, the shape of the fine screw thread (small protrusion) 106 formed on a part of the coarse thread thread is small, and the small valley protrusions 106A and Otani are formed on both sides of the convex portion of the partial small protrusion. There is a portion where the portion 106B is formed (see FIG. 18). In such a portion, as the rolling progresses, the Otani portion 106A side is filled first, so a difference occurs between the pressing force F1 from the Otani portion 106A side and the pressing force F2 from the Otani portion 106B side. Therefore, on the rolling bolt 103 side, the screw thread shape of the rolling bolt 103 is deformed to cause a decrease in accuracy, and the rolling bolt 103 may become a defective product. Further, on the screw rolling die 101 side, the shape of the fine screw thread may be deformed or damaged.

  Further, when rolling bolt 103 is rolled, chatter vibration, severe load fluctuations, etc. cause damage to weak parts of screw rolling die 101. When the screw rolling die 101 is damaged, it is necessary to replace it with a new screw rolling die. This causes a decrease in productivity due to the screw rolling die exchange and also causes an increase in the cost of the rolling bolt.

  The present invention was devised to solve such problems of the prior art, and achieves the following object.

  An object of the present invention is to provide a rolling screw having a double screw structure that can be manufactured with high quality and high productivity.

  Another object of the present invention is to provide a rolling bolt having a double screw structure that is rolled with a screw rolling die that does not generate chatter vibration, load fluctuation, etc. during thread rolling.

The present invention takes the following means in order to achieve the object.
The rolled bolt of the present invention 1
Rolling of a double screw structure in which a standard first pitch coarse thread and a second pitch fine thread smaller than the first pitch are formed on the outer periphery by rolling. The screw thread of the coarse screw has a thread surface formed on the bottom side from a substantially central part of the screw thread, and the screw thread of the fine screw is a screw of the coarse screw. From the substantially central part of the mountain to the mountain peak side, the protrusions are periodically formed, and the small mountain part side of the mountain parts on both sides of the valley part of the fine screw formed on the screw thread of the coarse screw, Within a predetermined angle range, a flat portion is formed in accordance with the height of the bottom of the thread of the fine screw.

The rolled bolt of the present invention 2 is the present invention 1,
A boundary portion between the flat portion and the flank of the coarse screw has an R shape.

The rolled bolt of the present invention 3 is the present invention 1 or 2,
The rolling bolt is formed by rolling with a screw rolling die.

The rolled bolt of the present invention 4 is the present invention 3,
In the thread rolling die, the first rolling tool having a shape with a flat top corresponding to the coarse thread is formed on the thread rolling die material, and the maximum height of the protrusion corresponding to the fine thread By feeding to the following position and removing a part of the thread rolling die material, a coarse thread ridge is formed on the thread rolling die, and the thread rolling die material after the thickness removal is formed. And moving the second metal removal tool having the shape of the fine screw thread from the valley of the thread portion of the coarse screw thread on the screw rolling die according to the shape of the protrusion corresponding to the fine screw thread, By removing the thread rolling die material, the fine screw thread valleys of the thread rolling die, and the small thread side of the valleys formed on both sides of the fine screw thread peak parts are arranged on the fine thread side. Protrusions that become flat according to the height of the top of the mountain And characterized in that.

The rolled bolt of the present invention 5 is the present invention 4,
The protrusions of the fine screw threads are formed in a tip shape having a radius larger than the tip shape of the second metal removal tool on the screw rolling die material partially thinned by the first metal removal tool. After forming the fine screw thread valley portion within a predetermined angle range by the third metal removal tool, the fine screw thread valley portion within the remaining angle range by the second metal removal tool, and The protrusion is formed.

In the present invention 4 or 5, the rolled bolt of the present invention 6 is
The processing by the second removal tool and the third removal tool is performed in a direction around the axis of the thread rolling die, a direction parallel to the axis, and a position in a direction orthogonal to the axis. It is a cutting process in which the speed is synchronously controlled and the thread rolling die material is thinned.

  As described above, the rolling bolt of the double screw configuration, which is the rolling bolt of the present invention, equalizes the load accompanying rolling and rolls it with a screw rolling die in a balanced state. It is possible to form coarse threads and fine threads that have been manufactured and have improved mechanical strength and durability. Therefore, this double-screwed rolled bolt can be mass-produced, and can have a quality with improved mechanical strength and durability. Moreover, since it can manufacture in large quantities by the rolling process by a screw rolling die, it can supply cheaply and the economic effect is also large.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a rolling bolt having a double screw structure (hereinafter referred to as a double screw bolt) that is a rolling bolt of the present invention will be described in detail with reference to the drawings. This double screw bolt is manufactured by rolling with a screw rolling die.

  FIG. 1 is an external view showing a double screw bolt of the present invention, and FIG. 2 is a developed view of a screw shape of a shaft portion of the double screw bolt. FIG. 3 is a cross-sectional view showing a state in which fine nuts and coarse nuts are screwed into a double screw bolt rolled by the first screw rolling die, and FIG. 4 is rolled by the second screw rolling die. It is sectional drawing which shows the state which screwed the fine nut and the coarse nut into the processed double screw bolt.

The double screw bolts 50 and 55 are composed of a head portion 50B and a shaft portion 50A. In addition, in FIG. 1, although the bolt type is illustrated as a hexagon bolt, other types of bolts such as a square bolt, a hexagon socket head cap screw, a slotted bolt, a slotted machine screw, a cross-head machine screw, It may be a screw or the like.
The shaft portion 50A of the double screw bolt 50 includes a screw thread (coarse screw thread) 53 having a standard pitch defined by the screw standard, and a pitch smaller than the pitch of the coarse screw (in this embodiment). In the form, a fine screw thread (fine screw thread) 52, a flat part 51, and the like are formed. The coarse screw is a screw formed at a standard pitch having a valley portion in which a screw surface 53c is formed on the valley bottom 53b side from a substantially central portion of the coarse screw thread 53. The fine screw is a screw composed of protrusions periodically formed at a pitch smaller than the pitch of the coarse screw from the substantially central portion of the coarse screw thread 53 to the peak 52b side.

[Embodiment 1]
Embodiment 1 of the double screw bolt will be described with reference to FIGS.
In the double screw bolt 50 of the first embodiment, the peak portion of the coarse nut 48 in which the female screw as the coarse screw is formed is screwed into the valley portion of the coarse screw thread 53 (see FIG. 3). A fine nut 47 formed with a female screw as a fine screw is screwed into the fine screw thread 52 of the fine screw (see FIG. 3). Since the fine nuts 47 and the coarse nuts 48 have different pitches, when they rotate together in the same direction, a repulsive force acts on the contact surface between the fine nuts 47 and the coarse nuts 48, and It is possible to prevent the eye nut 48 from rotating in the loosening direction.

  For example, if the center position of the double screw bolt 50 is 180 °, the upper end position is 270 °, and the lower end position is 90 °, the shape of the double screw bolt 50 is as shown in FIG. In FIG. 1, the positions of the part 135 ° and the part 225 ° are boundary positions where the fine screw thread 52 becomes the flat part 51. Further, the valley portion of the coarse thread 53 has a spiral shape that is continuous at a predetermined pitch (a standard pitch determined by a screw standard). When the double screw formed on the shaft portion 50A of the double screw bolt 50 is developed, it is as shown in FIG.

  3A is a cross-sectional view showing the angular position of the part 0 ° in FIG. 1, FIG. 3B is a cross-sectional view showing the angular position of the part 90 ° in FIG. 1, and FIG. 2 is a cross section showing an angular position of a part 180 ° in 1. FIG. In addition, sectional drawing which shows the angle position of the site | part 270 degrees is a thing of the shape of the selfishness of the site | part 90 degrees, and illustration is abbreviate | omitted. As shown in the angular position of the part 90 ° (FIG. 3B), the small mountain portion 52s of the large mountain portion and small mountain portion formed in the fine screw thread 52 is set to the height of the valley bottom of the valley portion of the fine screw thread. A flat portion 51 that is flattened together is formed. The corner portion between the flat portion 51 of the double screw bolt 50 and the flank of the coarse screw thread 53 may be formed in a small R shape.

  As shown in FIGS. 1 and 2, the flat portion 51 has a flat shape without forming a mountain portion on the side of the small mountain portion 52 s as described above in a range excluding the position of the region from 135 ° to 225 °. As shown in FIG. 2, the flat portion 51 is formed over one round of the double screw bolt.

  In FIG. 3, in the position 180 ° position and in the vicinity of the portion 180 °, both peak portions have the same size, and a valley portion is formed in the middle. The range of the angular position from 135 ° to 225 ° across the position of the portion 180 ° is such that the small mountain side is gently inclined and the positions of the portion 135 ° and the portion 225 ° (or the vicinity of the portion 135 ° and the portion 225 ° It is inclined so as to be flat at the position of the vicinity. The reason for flattening in this way is to improve the mechanical strength and durability of the double screw bolt 50.

[Embodiment 2]
A second embodiment of the double screw bolt will be described with reference to FIGS.
In the figure, the double screw bolt 55 according to the second embodiment is a normal screw in which a female screw that is a coarse screw is formed in a valley portion of a coarse screw thread 53a (corresponding to the coarse screw thread 53 of the first embodiment). The crest of the eye nut 48 is screwed (see FIG. 4). A fine nut 47 formed with a female screw, which is a fine screw, is screwed into the fine screw thread 52a (corresponding to the coarse screw thread 52 of the first embodiment) (see FIG. 4).

The double screw bolt 55 according to the second embodiment is configured such that the corner 51b between the flat portion 51a (corresponding to the flat portion 51 of the first embodiment) and the flank of the coarse thread 53a has a large R shape. It is. Parts other than the corner 51b are not different from the double screw bolt 50 of the first embodiment described above. Therefore, an external view of the double screw bolt 55 corresponds to FIG. 1, and a developed view of the double screw formed on the shaft portion corresponds to FIG.
4A is a cross-sectional view showing the angular position of the part 0 ° in FIG. 1, FIG. 4B is a cross-sectional view showing the angular position of the part 90 ° in FIG. 1, and FIG. 2 is a cross section showing an angular position of a part 180 ° in 1. FIG.
As described above, the double screw bolt 55 has a configuration in which the corner portion 51b of the flat portion 51a between the fine screw thread 52a and the valley portion of the coarse screw thread 53a has an R shape (FIG. 4). reference). Other configurations are the same as those of the first embodiment, and a description thereof will be omitted.

[Double screw bolt manufacturing equipment]
Next, an apparatus for manufacturing the double screw bolt of the present embodiment by rolling will be described.
FIG. 5 is a schematic view showing a basic configuration of a double screw bolt manufacturing apparatus, and FIG. 6 is an external view of a screw rolling die for rolling and manufacturing the double screw bolt shown in FIGS. As shown in FIGS. 5 and 6, the double screw bolt manufacturing apparatus has a pair of screw rolling dies 1 and a round bar-shaped bolt material (hereinafter referred to as “workpiece”) 3 arranged in a predetermined position. And a bolt support part (work rest) 2 supported by

  Further, in the screw rolling die 1 shown in FIG. 6, a transfer pattern 4 which is a spiral unevenness for forming a double screw bolt is formed on the outer periphery of a cylindrical die (round die). The transfer pattern 4 has a spiral shape in accordance with a nut shape screwed into the double screw bolts 50 and 55. Basic techniques and configurations relating to the thread rolling die 1 are described in detail in Patent Documents 2 and 3, but in order to facilitate understanding of the present embodiment, the thread rolling die 1 that is the premise thereof is described. An outline of the configuration will be described.

  FIG. 7 is a development view of the outer periphery of the screw rolling die 1, and the transfer pattern 4 is schematically developed in a plane. The parts at different angular positions of the outer peripheral double screw configuration are shown in six divisions A to F along the transfer pattern 4 around the double screw bolt 50, and cross-sectional views corresponding to the respective parts A to F are shown in FIG. (A) to (F). Accordingly, (A), (B), (C), (D), (E), and (F) of FIG. 8 are respectively taken along AA, BB, and C- in FIG. This corresponds to a C sectional view, a DD sectional view, an EE sectional view, and an FF sectional view.

  As shown in FIG. 7, a screw shape of the transfer pattern 4 of the screw rolling die 1 corresponding to the double screw bolts 50 and 55 to be manufactured is formed on the outer periphery of the screw rolling die 1. Is equivalent to 16 rounds of the double screw bolts 50 and 55. Therefore, on the outer periphery of the screw rolling die 1, the angular position of 22.5 degrees is equivalent to one turn of the double screw bolts 50 and 55, and the transfer pattern 4 corresponding to that is formed.

  As shown in FIG. 8, the transfer pattern 4 of the thread rolling die 1 is a part of a coarse screw thread (hereinafter referred to as “coarse screw thread”) that becomes a reference screw thread in which the coarse screw is developed on the surface of the round die. Part 5) and additional protrusions 6 formed periodically (constant pitch) in the valley 5a of the coarse screw thread. The protrusion 6 has a spiral winding in the same direction as the coarse screw thread of the developed coarse screw thread portion 5, and is a fine screw thread (see an imaginary line 6a in FIG. 8) in which a fine screw having a smaller pitch than the coarse screw is developed. And a periodic shape according to the phase shift 7 between the coarse thread ridges 5.

  Here, when the ratio of the pitch between the coarse screw and the fine screw is 2 to 1, the protrusion 6 has the coarse screw thread portion 5 of the coarse screw thread portion 5 according to the phase shift from the coarse screw thread when the fine screw is developed. Each turn becomes a part of a fine thread that appears periodically. As shown in FIG. 8, the fine screw thread indicated by an imaginary line 6 a has a portion protruding from the coarse screw thread as an additional protrusion 6 due to a phase shift 7 from the coarse screw thread. 5 appears in the valley 5a.

  That is, the protrusion 6 is not the fine thread itself, but is a protrusion additionally protruded from the coarse thread so as to correspond to the imaginary line 6a of the fine thread corresponding to the phase shift 7. It is. The cross section of the coarse thread thread is a part excluding a part of the fine thread thread (surface of the protrusion 6) appearing on the surface of the thread rolling die 1.

  In the examples shown in the cross-sectional views of FIGS. 8A to 8F, the valley bottom 5b of the reference thread valley 5a and the valley bottom of the fine screw thread imaginary line 6a corresponding to the protrusion 6 are used. Although the position with 6b is made to correspond, it is not restricted to this.

  Next, a method for manufacturing a screw rolling die for rolling the double screw bolts 50 and 55 will be described. FIG. 9 is a flowchart showing an outline of the manufacturing process of the first screw rolling die 31 and the second screw rolling die 31A. FIG. 10A is a plan view showing a first cutting tool (thickening tool) 20 used for manufacturing the first screw rolling die and the second screw rolling die, and FIG. It is a top view which shows the 2nd cutting tool (thickening tool) 25 used for manufacture of 1 screw rolling die and 2nd screw rolling die. FIG.10 (c) is a top view which shows the 3rd cutting tool (thickening tool) 125 used for manufacture of the 2nd screw rolling die.

[First thread rolling die]
FIG. 11 is an explanatory diagram for explaining a process of processing a coarse thread formed on the first thread rolling die 31. FIG. 12 is an explanatory diagram for explaining a process of processing the protrusion (fine screw thread). First, a cutting tool for cutting the thread of the first thread rolling die 31 will be described. As shown in FIG. 10 (a), the first cutting tool (thickening tool) 20 has a flat tip 22 (the peak of the coarse thread 21), and both corners of the tip are rounded. A substantially trapezoidal bit formed in R1. In FIG. 10A, an imaginary line 23 is a line indicating the shape of a cutting tool used when forming a coarse screw thread on a normal screw rolling die. As indicated by the imaginary line 23, the first cutting tool 20 in the present embodiment corresponds to a tool in which the tip of a bit having a normal coarse thread shape is cut into a required shape (flat). Is.

  A second cutting tool (thickening tool) 25 shown in FIG. 10B is a cutting tool having a shape corresponding to a fine screw thread, and a rounded edge R2 of the cutting edge is formed at the tip 27. That is, the tip portion (the peak portion of the fine screw thread shape 26) 27 of the second cutting tool 25 is preferably formed in an arc or a curve (plan view) in plan view. A rounded edge R2 is formed at the tip. In the third cutting tool (thickening tool) 125 shown in FIG. 10C, the roundness R3 of the cutting edge larger than the rounding R2 of the cutting edge of the second cutting tool 25 is the tip (the peak portion of the fine screw thread shape 126) 127. Bytes formed in

  As shown in FIG. 9, when the first screw rolling die 31 is manufactured, first, a turning process of the screw rolling die material 30 (see FIG. 11) as a raw material is performed (step S11), followed by a coarse screw. A mountain processing step (step S12) and a protrusion (corresponding to a fine screw thread) processing step (step S13) are performed.

  In the coarse thread thread machining step of step S12, the first cutting tool (thickening tool) 20 is used. As shown in FIG. 11, in the coarse screw thread machining step, the screw rolling die material 30 held by the chuck at the front end of the main shaft (not shown) and fixed to the main shaft side is moved at a predetermined rotation speed (number of rotations). While rotating, the first cutting tool 20 is placed on the thread rolling die material 30 in the X-axis direction (direction perpendicular to the main axis) in FIG. It is fed to a position below the maximum height and moved in the Z-axis direction (direction parallel to the main axis) in FIG. 11 at a pitch of coarse threads. At this time, synchronous control is performed in which the first cutting tool 20 moves in the Z-axis direction by one pitch of the coarse screw thread for one rotation of the main shaft. In other words, the direction around the axis of the main axis and the Z-axis direction are controlled in synchronization. A part of the thread rolling die material 30 is cut by cutting (thickening) by the first cutting tool 20. In other words, the thread rolling die material 30 is turned by the first cutting tool 20. Thereby, the coarse screw thread part 5 is formed in the screw rolling die material 30.

  In the projection processing step of step S13, a second cutting tool (thickening tool) 25 is used. The protrusion machining process by the second cutting tool 25 is illustrated in FIGS. 12 (a) to 12 (h). As shown in FIGS. 12A to 12H, in the protrusion processing step, the screw rolling die material 30 is rotated at a predetermined rotational speed (number of rotations), and after being cut in the coarse screw thread processing step. The second rolling tool 25 is moved to the screw rolling die material 30 in the X-axis direction (direction orthogonal to the main shaft axis) and the Z-axis direction (direction parallel to the main shaft axis), and the coarse screw thread portion 5 (a thinning process) is performed on the valleys 5a of the fine screw threads and the protrusions 6 and the like. That is, a screw thread of a screw rolling die having a desired shape can be manufactured by simultaneously controlling the three axes of the direction around the main axis, the X-axis direction, and the Z-axis direction in synchronization. In other words, the thread rolling die material 30 is subjected to compound turning with the second cutting tool 25.

By performing such control, the threaded thread valleys and the protrusions 6 are formed in the thread rolling die material 30.
12 (a) to 12 (h) show the processing state of the second cutting tool 25 and the screw rolling die material 30 every 45 ° in the direction around the main axis (the processing state of the valleys and protrusions of the fine screw thread). It is the figure which showed the relationship with) as a cross-sectional view. In addition, in FIG. 12, the fine screw thread is illustrated with an imaginary line. Further, the state of FIG. 12A is set to 0 ° around the main axis, and (b) is shown as 45 °, (c) is shown as 90 °, and (h) is shown as 315 °. .

  Such machining by the first cutting tool 20 and the second cutting tool 25 may be performed by a machine tool called an NC (numerical control) lathe, an NC compound lathe, a turning center, or the like. That is, using the control function of an NC device, CNC (computer numerical control) device, etc., the direction around the spindle axis, the X-axis direction (direction perpendicular to the spindle axis), and the Z-axis direction (direction parallel to the spindle axis) 3 Machining can be performed by controlling the axes simultaneously. Further, the NC program used for the machining may be easily programmed by using a function called automatic programming or the like.

  Thereafter, a heat treatment step (step S14) of (1) quenching and (2) tempering is performed (see FIG. 9). Thereby, the 1st screw rolling die 31 which has the cross-sectional shape shown in a figure is obtained.

  Next, in the configuration of the first screw rolling die 31, characteristic portions will be described. FIG. 13 is a cross-sectional view of the first thread rolling die 31 and is a cross-sectional view of the thread rolling die corresponding to FIG. A section corresponding to a double screw bolt is divided into eight sections, and a transfer pattern 32 up to a 180 ° range at different angles is shown at angular positions of 0 °, 45 °, 90 °, 135 °, and 180 °. FIG. FIG. 13 is a cross-sectional view when the R shape 33 at the corner between the flank of the coarse thread B and the flat portion (in the cross-sectional shape) is small.

  Further, at the respective angular positions of 225 °, 270 °, and 315 ° of the first screw rolling die 31, the portion 225 ° is a shape pattern that is different from the case of the portion 135 °, and the portion 270 ° is the portion 90. In the case of °, the shape pattern is different from that in the case of “°”, and the portion 315 ° is a shape pattern in the case of 45 °. In FIG. 13, a portion 34 indicates a valley portion formed in the first screw rolling die 31, and a reference numeral 39 indicates a portion corresponding to a flat portion formed in the first screw rolling die 31. Yes.

  Of the valleys formed on both sides of the fine thread A, the small valley 38 side (FIG. 13) is made flat according to the height of the peak of the fine thread A peak. For example, in the case of an angle position of a part of 135 °, if the part of the boundary with the coarse thread B in the pattern shown in the figure is conventional, the figure shows where the shape of the small valley part 38 indicated by a two-dot chain line should be formed. So that it is flat.

  The flat portion 39 does not form a valley portion on the small valley portion 38 side as described above at an angular position excluding an angular position of 135 ° to 225 ° of the portion, and the upper portion on the projection side, that is, the summit of the fine screw thread A The part has a flat shape. This flat shape is provided so as to correspond to a flat portion (in a sectional view) of the double screw bolt.

  In the cross-sectional view of FIG. 13, all the small valley portions at the angular positions of 0 °, 45 °, 90 °, and 135 ° other than the angular position of the portion 180 ° have a flat shape. In other words, the small valley portion side within a predetermined range is a cylindrical surface that matches the peak of the fine screw thread. In the case of an angular position of 180 °, the size of both valleys is the same, and valleys are arranged on both sides. In addition, the range of the angular position from 135 ° to 225 ° across the angular position of 180 ° of the region is such that the small valley side is gently inclined, and the region 135 ° or the vicinity of 135 ° and the region 225 ° or the region It is inclined so as to be flat in the vicinity of 225 °. The flattening of the fine screw thread A that appears in the region near the site 90 ° to the region near 270 ° (for example, the region near the site 90 °, the region near the site 270 °, etc.) is made flat. This is because, when the shallower groove (the small valley portion 38) is removed and the rolling process is performed with the screw rolling die, the stress concentration generated in the portion is alleviated.

The material flow state of the rolling process of the double screw bolt 50 by the first screw rolling die 31 will be described.
FIG. 14 is a cross-sectional view at the angular positions of 0 °, 90 °, and 180 ° in FIG. 1, and shows the progress of material flow in seven stages, i, b, c, d, e, h, and g. It is a figure. In other words, the flow change state of the material when the pair of first screw rolling dies 31 is rotated in the same direction and the distance between them is reduced is schematically shown.

As shown in FIGS. 14A to 14C, as the first screw rolling die 31 is gradually pushed into the work 3, the work 3 first follows the surface of the coarse thread B of the first screw rolling die 31. The trough of the coarse screw thread (groove of the cross section) is filled while plastically deforming. That is, the coarse screw thread 53 of the double screw bolt 50 is formed.
As shown in FIG. 14N, the first thread rolling die 31 is gradually pushed into the work 3 to fill the valleys of the fine thread A and the coarse thread B. At this time, the valleys are filled in along the surface of the flat part 39 while being deformed. And the workpiece | work 3 is filled to a groove part in order of the site | part 180 degrees, the site | part 90 degrees, and the site | part 0 degree. That is, the coarse screw thread 53 and the fine screw thread 52 of the double screw bolt 50 are formed.
Conventionally, when the region is 90 °, the pressing forces F1 and F2 indicated by the arrows are unbalanced as shown in FIG. 18, so that the screw thread of the double screw bolt 50 is deformed and the thread thread of the screw rolling die is fine. There was a risk of deformation or deficiency.

  However, the first screw rolling die 31 has the shallower groove (the small valley portion 38) of the fine screw thread appearing in the region near the portion 90 °, the region near the portion 270 °, etc. removed during rolling. It is possible to alleviate the stress concentration generated in the portion. Further, the difference in groove area at each angular position of the first screw rolling die 31 can be reduced more than the screw rolling die manufactured by the conventional manufacturing method. By reducing the difference in groove area in this way, chatter vibration, noise and the like can be reduced when performing rolling. Accordingly, it is possible to suppress the occurrence of poor accuracy of the double screw bolt 50 due to the chatter vibration, the reduction of the tool life of the screw rolling die 31 and the adverse effect on the manufacturing apparatus.

[Second thread rolling die]
A method for manufacturing the second screw rolling die 31A will be described. The manufacturing process of the second screw rolling die 31A is substantially the same as the first screw rolling die 31, and the manufacturing method of the first screw rolling die 31 is different from the projection processing step S13. The process will be described mainly. That is, between the cutting of the coarse thread B by the first cutting tool 20 and the cutting by the second cutting tool 25, the cutting by the third cutting tool 125 is performed, and fine details in a predetermined angle range are obtained. Part of the processing of the thread valley.

FIG. 15 is an explanatory view showing a processing step for processing the protrusion (fine thread thread) of the second screw rolling die, and FIG. 16 is a sectional view of the screw rolling die of the second screw rolling die. FIGS. 17A and 17B are explanatory diagrams for explaining a flow state when the rolling process is performed with the second screw rolling die.
FIGS. 15A to 15H show the processing states of the second cutting tool 25, the third cutting tool 125, and the screw rolling die material 30 every 45 ° in the direction around the spindle axis (fine thread mountain valleys). It is the figure which showed the relationship between a part and the process state of a processus | protrusion etc. as sectional drawing. In addition, in FIG. 15, the fine screw thread is illustrated with an imaginary line. Further, the state of FIG. 15A is set to 0 ° in the direction around the main axis, and (b) is shown as 45 °, (c) is shown as 90 °, and (h) is shown as 315 °. .

  As shown in FIGS. 15A to 15H, in the projection processing step according to this manufacturing method, the thread rolling die material 30 is rotated at a predetermined rotational speed (number of rotations), and in the coarse thread processing step. The third rolling tool 125 and the second cutting tool 25 are applied to the thread rolling die material 30 after being cut, in the X-axis direction (direction perpendicular to the main axis line) and the Z-axis direction (direction parallel to the main axis line). Then, the trough portion 5a of the fine screw thread portion and the projection 6 are processed from the trough portion 5a which is a part of the coarse screw thread portion 5. That is, a screw thread of a screw rolling die having a desired shape can be manufactured by simultaneously controlling the three axes of the direction around the main axis, the X-axis direction, and the Z-axis direction in synchronization. In other words, the thread rolling die material 30 is subjected to a complex turning process using the second cutting tool 25 and the third cutting tool 125. As a result, fine thread valleys and protrusions 6 are formed on the thread rolling die material 30.

The groove contour corresponding to the valley portion of the fine screw thread is first processed according to the fine groove contour by the third cutting tool 125 having a rounded edge R3 (≧ R2). In this case, the fine groove depth is constant in the region from 0 ° to 90 ° and from 270 ° to 360 °, and the region from 90 ° to 270 ° is gradually shallower in accordance with the fine groove contour. To be processed.
Next, the fine groove in the region from the part 90 ° to the part 270 ° is machined according to the fine groove contour by the second tool 25 having a rounded edge R2 (≦ R3). Further, processing is performed so as to remove the shallower grooves (small valleys 38) appearing in the region near 90 ° of the region, the region near 270 °, and the like. By cutting with the second cutting tool 25 and the third cutting tool 125, the fine thread thread valleys and the protrusions 6 can be formed on the thread rolling die material 30.

FIG. 16 shows the second thread rolling die 31A, which corresponds to the cross-sectional view of the thread rolling die in FIG. A section corresponding to a double screw bolt is divided into eight sections, and a transfer pattern 32 up to a 180 ° range at different angles is shown at angular positions of 0 °, 45 °, 90 °, 135 °, and 180 °. FIG.
FIG. 16 is a cross-sectional view in the case where the R shape 33 at the corner between the flank and the flat portion (in cross-sectional shape) of the coarse thread B is large. Further, in FIG. 16, a portion 34 indicates a trough formed in the second screw rolling die 31A, and a reference numeral 39 indicates a portion corresponding to a flat portion formed in the first screw rolling die 31A. Show.

  Also in the second thread rolling die 31A, among the valleys formed on both sides of the peak part of the fine screw thread A, the small valley part 38 side (FIG. 16) is set to the height of the peak part of the peak part of the fine screw thread A. It is flattened together. For example, in the conventional case, the shape of the valley portion 38 indicated by a two-dot chain line is flattened as shown in the figure.

  The flat portion 39 does not form a valley portion on the small valley portion 38 side as described above at an angular position excluding an angular position of 135 ° to 225 ° of the portion, and the upper portion on the projection side, that is, the summit of the fine screw thread A The part has a flat shape. This flat shape is provided so as to correspond to a flat portion (in a sectional view) of the double screw bolt. That is, the small valley side in the predetermined range is a cylindrical surface that matches the peak of the fine screw thread.

  In the cross-sectional view in FIG. 16, all the small valley side of the angular positions of 0 °, 45 °, 90 °, and 135 ° other than the angular position of the portion 180 ° are flat. In the case of an angular position of 180 °, the size of both valleys is the same, and valleys are arranged on both sides. In addition, the range of the angular position from 135 ° to 225 ° across the angular position of 180 ° of the region is such that the small valley side is gently inclined, and the region 135 ° or the vicinity of 135 ° and the region 225 ° or the region It is inclined so as to be flat in the vicinity of 225 °. The reason for flattening in this way is to increase the rigidity of the protruding portion of the second screw rolling die 31A. This flattening configuration is the same for other screw threads.

The material flow state of the rolling process of the double screw bolt 55 by the second screw rolling die 31A will be described.
FIG. 17 is a cross-sectional view at the angular positions of 0 °, 90 °, and 180 ° in FIG. 1, and shows the progress of material flow in seven stages, i, b, c, d, h, f, and g. It is a figure. The flow change state of the material when the pair of second thread rolling dies 31A is rotated in the same direction and the distance between them is narrowed is schematically shown.

  In addition, as shown in FIGS. 17A to 17D, the work 3 is gradually pushed into the second screw rolling die 31A to fill the valleys of the fine screw threads B and the coarse screw threads A. At this time, the valleys are filled in along the surface of the flat part 39 while being deformed. That is, the coarse screw thread 53 and the fine screw thread 52 of the double screw bolt 55 are formed. As shown in FIGS. 17 to 17, the second screw rolling die 31 </ b> A can further reduce the difference in groove area at each angular position than the first screw rolling die 31. Further, the second thread rolling die 31A has a shallower thread A that appears in a region near 90 ° to 270 ° (for example, a region near 90 °, a region near 270 °, etc.). The groove (the small valley portion 38) is removed, and the stress concentration generated in that portion during rolling can be alleviated.

  As described above, the first and second screw rolling dies 31 and 31A can minimize the occurrence of chatter vibration, noise, and the like when performing rolling processing by reducing the difference in groove area. . Moreover, the stress concentration which generate | occur | produces in one part at the time of rolling can be eased. Therefore, it is possible to suppress the occurrence of poor accuracy of the double screw bolts 50 and 55 due to the chatter vibration, the reduction of the tool life of the screw rolling die, and the adverse effect on the manufacturing apparatus.

Therefore, it is possible to minimize the occurrence of additional fluctuations during thread rolling, damage the thread rolling die, and eliminate the need to frequently replace the damaged thread rolling die. It does not deteriorate the sex.
Further, the double screw bolts 50 and 55 of the present embodiment are made to be machined by the screw rolling dies 31 and 31A in a balanced state so as to equalize the load associated with the rolling. It is possible to form the coarse thread 53 and the fine thread 52 with improved strength and durability. Further, the double screw bolts 50 and 55 can be mass-produced and have a quality with improved mechanical strength and durability.

  As mentioned above, although embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to the content demonstrated by this embodiment. For example, the screw rolling die for rolling a double screw bolt may be a flat die. That is, a rolling process using a so-called flat die may be performed in which a flat die having a shape in which a transfer pattern of a round die is developed on a plane is arranged above and below, and rolling is performed by moving the upper and lower flat dies in parallel. .

FIG. 1 is an external view showing a rolled bolt of the present invention. FIG. 2 is a development view of the thread shape of the rolled bolt. FIG. 3 is a cross-sectional view showing a state in which a fine nut and a coarse nut are screwed into a rolled bolt rolled by a first screw rolling die. FIG. 4 is a cross-sectional view showing a state in which a fine nut and a coarse nut are screwed into a rolled bolt rolled by a second screw rolling die. FIG. 5 is a schematic view showing a rolling bolt manufacturing apparatus. 6 is an external view showing the screw rolling die of FIG. FIG. 7 is a plan development view of a part of the transfer pattern on the outer periphery of the thread rolling die of FIG. 8 is a cross-sectional view of each part shown in FIG. 7, and (A), (B), (C), (D), (E), and (F) are respectively taken along line AA in FIG. It is sectional drawing cut | disconnected by the BB line, CC line, DD line, EE line, and FF line. FIG. 9 is a flowchart showing the manufacturing process of the thread rolling die. FIG. 10 is a partial plan view showing a cutting tool for manufacturing a thread rolling die, where (a) shows a first cutting tool, (b) shows a second cutting tool, (c ) Is a diagram showing a third cutting tool. FIG. 11 is an explanatory view showing a processing step of processing a coarse thread of a thread rolling die. FIG. 12 is an explanatory view showing a processing step of processing the protrusion (fine thread thread) of the first screw rolling die. FIG. 13 is a cross-sectional view of the thread rolling die of the first thread rolling die, and is a view shown for each angle portion. FIG. 14 is an explanatory diagram for explaining a flow state when the rolling process is performed with the first screw rolling die. FIG. 15 is an explanatory diagram showing a processing step of processing the protrusion (fine thread thread) of the second screw rolling die. FIG. 16 is a cross-sectional view of the screw rolling die of the second screw rolling die, and is a view shown for each angle portion. FIG. 17 is an explanatory diagram for explaining a flow state when the rolling process is performed by the second screw rolling die. FIG. 18 is a cross-sectional view for explaining problems of the conventional rolling process.

Explanation of symbols

1, 31, 31A ... Screw rolling die 2 ... Bolt support part 3 ... Bolt material (workpiece)
4, 32 ... Transfer pattern 5 ... Coarse screw thread 5a ... Valley 5b ... Valley bottom 6 ... Projection 6a ... Imaginary line of fine thread 6b ... Valley bottom 20 ... First cutting tool 25 ... Second cutting tool 125 ... 3rd cutting tool 30 ... Screw rolling die material 39 ... Flat part 50, 55 ... Rolling bolt 51, 51a ... Flat part 52, 52a ... Protrusion (fine screw thread)
53, 53a ... Coarse screw thread 50A ... Shaft 50B ... Head A ... Fine screw thread B ... Coarse screw thread

Claims (6)

Rolling of a double screw structure in which a standard first pitch coarse thread and a second pitch fine thread smaller than the first pitch are formed on the outer periphery by rolling. Bolts,
The screw thread of the coarse screw has a thread surface formed on the bottom side from the substantially central part of the screw thread,
The screw thread of the fine screw is a protrusion formed periodically from the substantially central part of the screw thread of the coarse screw to the peak side, and the screw thread of the fine screw formed on the screw thread of the coarse screw. Rolling is characterized in that the ridge portion side of the ridge portions on both sides of the valley portion is a flat portion that matches the height of the valley portion of the thread ridge of the fine screw within a predetermined angle range. bolt. The rolled bolt according to claim 1,
A rolling bolt, wherein a boundary portion between the flat portion and a thread flank of the coarse screw has an R shape. In the rolling bolt according to claim 1 or 2,
The rolling bolt is formed by rolling with a screw rolling die. In the rolled bolt according to claim 3,
The screw rolling die is
The screw rolling die material is fed with a first removal tool having a shape with a flat top corresponding to the coarse thread to a position below the maximum height of the protrusion corresponding to the fine thread, By removing a portion of the thread rolling die material, a thread portion of a coarse thread is formed on the thread rolling die,
A second thread removal tool having a fine screw thread shape is applied to the thread rolling die material after the metal removal from the valley of the thread portion of the coarse thread thread on the screw rolling die to the fine thread thread. By moving according to the shape of the corresponding protrusion and removing the thread rolling die material, it is formed on the both sides of the fine screw thread valley portion and the fine thread thread mountain portion of the screw rolling die. A rolling bolt characterized in that a protrusion that is flattened in accordance with the height of the top of the fine screw thread is formed on the small valley side of the valley. In the rolling bolt according to claim 4,
The protrusion of the fine screw thread is
Predetermined by a third removal tool formed in a tip shape having a radius larger than the tip shape of the second removal tool on the screw rolling die material partially removed by the first removal tool After forming the fine screw thread valleys within the angle range, the fine screw thread valleys and the protrusions within the remaining angle range are formed by the second metal removal tool. Rolled bolt characterized by that. In the rolling bolt according to claim 4 or 5,
Processing by the second removal tool and the third removal tool is as follows:
It is a cutting process in which the position and speed of a direction around the axis of the thread rolling die, a direction parallel to the axis, and a direction perpendicular to the axis are controlled to remove the thread rolling die material. Rolled bolt characterized by

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