JP2002113546A - Bolt and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bolt and its producing method with which the axial tension of a male thread member, such as the bolt, can be measured with ultrasonic wave and the suitable fastening is obtained. SOLUTION: One side or both sides in respective end surfaces of both end parts of the bolt, are preformed with a cold-forging so as to bulge to the outside of the bolt axial direction in an intermediate process, and thereafter, the preformed bulging part 21 is cold-forged to the flat with a punch, etc., to form a reference plane 23 having almost right angle to the bolt axis. At this time, the preformed bulging part 21 is formed as a recessed shape with the punch, etc., and the cold-forging is applied so that the bottom surface in the recessed part becomes the flat then, this bottom surface can be formed as the reference plane 23 having almost right angle to the bolt axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bolt and a method for manufacturing the bolt.

[0002]

2. Description of the Related Art An impact wrench or the like that completes tightening when a tightening torque reaches a predetermined value so that a tightening force of a bolt, a nut, or the like does not become excessive or excessive is widely used. However, if the bolts and nuts are not properly engaged or foreign matter is caught, the tightening torque may increase to the set value even if the tightening is not completed, and the tightening may stop. Can occur.

[0003] Instead of or in addition to such a tightening torque, there is also an attempt to complete the tightening by referring to the tensile force (bolt axial force) generated in the bolt shaft when the bolt or nut is tightened. . Therefore, the bolt slightly expands in the axial direction as the bolt axial force increases (the length in the bolt axial direction slightly increases). The extension of the bolt is measured using ultrasonic waves, and the elongation reaches a predetermined value. It is conceivable that the tightening is completed when it becomes. In that case,
Ultrasonic waves are emitted in the axial direction of the bolt, and the axial propagation force of the bolt and thus the axial force of the bolt can be measured by observing the increase in the propagation time of the ultrasonic wave that is repeatedly reflected and reciprocated at both axial end faces of the bolt.

[0004]

However, generally, the end faces at both ends in the axial direction of the bolt are defined by surfaces formed by forging, casting, or the like. It usually has a dimensional form. Therefore, even if the ultrasonic wave is reciprocated in the bolt axis direction, the transmitted ultrasonic wave is reflected obliquely or irregularly with respect to the axial direction at the end face, making it difficult to determine the propagation time, or The error was so large that it could not be put to practical use.

[0005] A direct object of the present invention is to provide a bolt capable of measuring the axial force of the bolt by ultrasonic waves and realizing proper tightening, and a method of manufacturing the bolt.

[0006]

According to the present invention, one or both of the end faces at both ends of the bolt are provided.
Preforming by forging so as to bulge outward in the axial direction of the bolt in an intermediate step, and thereafter, the preformed bulging portion is flattened by a punch or the like to provide a reference plane substantially perpendicular to the bolt axis. I do.

Here, the preformed bulging portion is forged by a punch or the like so that the bottom surface of the concave portion becomes flat, and the bottom surface is set as a reference plane substantially perpendicular to the bolt axis. Can also. Alternatively, the concave portion may remain in the final product, or the raised portion around the concave portion may be removed by grinding or cutting or other methods.

[0008] A predetermined range centering on the bolt axis in the head end face of the bolt, and a range in which the whole or a part of the cross section of the bolt shaft is projected or a region including the range is formed into a concave shape by forging. It can be processed so that the concave bottom surface becomes one reference plane. In addition, although cold forging is suitable as a processing method, in addition to that, hot forging,
Warm forging is also possible.

As described above, one or both of the end surfaces of both ends of the bolt are preformed by forging so as to bulge outward in the axial direction of the bolt in an intermediate step, and then the preformed bulge is formed. By processing the part flat with a punch,
Good plastic deformation (movement of the flesh) occurs at the bulging part, and the perpendicularity of the flat processed reference plane to the bolt axis,
Flatness, surface roughness, and the like can be increased. for that reason,
Even when measuring bolt axial force using ultrasonic waves or the like, since a highly accurate reference plane is formed on the bolt end face, the reflected wave is greatly inclined with respect to the bolt axis line or irregularly reflected in the reflection of ultrasonic waves or the like. This makes it easy to detect a change in propagation time due to reflection of ultrasonic waves or the like, thereby enabling highly accurate bolt axial force measurement. Conventionally, when a bolt or the like is tightened, the tightening torque is controlled by the tightening torque. However, the tightening torque does not always correspond to the axial force of the bolt due to engagement of the threaded portion, resistance, and the like. Therefore, the actual tightening torque is often set to be larger than the calculation in consideration of safety. Therefore, in order to withstand the tightening torque, a bolt or the like having a large diameter tends to be used. By using this as a bolt that can be tightened by measuring the bolt axial force, the safety aspect is ensured and the size of the bolt can be reduced, so that equipment using a large number of bolts (such as automobiles)
It also leads to weight reduction of.

[0010] A predetermined range centered on the bolt axis in the head end face of the bolt, and a range in which the whole or a part of the cross section of the bolt shaft is projected or a region including the range is formed into a concave shape by forging. By processing, the concave bottom surface (the surrounding raised portion may be left, or may be removed by grinding, cutting or other methods) is used as a reference plane on the bolt head side, for example, with the bolt shaft portion Only the corresponding bolt head end face is partially set as the reference plane, and the remaining head end face area can be a general rough machined surface. As a result, a reflection surface is formed only on the portion of the bolt head portion corresponding to the bolt shaft portion, and it is possible to accurately reflect ultrasonic waves and the like reciprocating in the bolt shaft portion in the axial direction, and the entire end surface of the bolt head portion Processing is easier and lower cost than when processing is performed with high accuracy.

Further, in the bolt obtained through the above-described manufacturing method, the perpendicularity of each end face (reference plane) at both ends of the bolt to the bolt axis is 0.0005 to 0.1 mm. Further, tan θ is set to 0.02 or less with respect to an actual angle θ of each end face of both ends of the bolt with respect to an imaginary axis perpendicular plane perpendicular to the axis of the bolt. Furthermore, the flatness of each end face of both ends of the male screw member is set to 0.0005 to 0.1 m.
m, the ten-point average roughness Rz of each end face of the both end portions is 1 to 15
It can be.

Here, the perpendicularity (perpendicularity tolerance) is defined as 0.0005 to 0.1 mm in which each end face of both ends of the bolt is perpendicular (perpendicular) to the bolt axis (axial straight line: datum straight line).
It means that it is defined between two parallel virtual planes that are separated only by a distance (see JISB0021). When the squareness is in this range, the ultrasonic wave etc. is reflected well at each end face of both ends in measuring the bolt tightening axial force by the ultrasonic wave etc., and the ultrasonic wave etc. repeats at both ends in the axial direction An increase in the reciprocating propagation time due to the elongation of the bolt can be detected, and the tightening can be completed when the proper axial force is reached while referring to the axial force of the bolt.

If the perpendicularity exceeds 0.1 mm, the reflection angle of the ultrasonic wave is considerably inclined with respect to the axis of the male screw member.
The propagation time of the ultrasonic wave and the elongation of the bolt become difficult to correspond,
If the squareness is smaller than 0.0005 mm, the manufacturing process becomes complicated and the cost of manufacturing equipment increases, so the squareness is defined in the above range.

Further, by setting tan θ to 0.02 or less with respect to the actual angle θ of each end face of both ends of the bolt with respect to a virtual (geometric) axis perpendicular plane perpendicular to the bolt axis, the axial force of the bolt is The repetition of reflection of ultrasonic waves or the like for measurement can be performed with high accuracy, and the measurement of the axial force of the bolt and the completion time of the tightening can be set more accurately.
When the tan θ of the actual angle θ of each of the end faces exceeds 0.02, the deviation between the reflection direction of the ultrasonic wave reflected at each of the end faces and the axial direction of the bolt increases, and the propagation time of the ultrasonic wave or the like increases. It is difficult to determine whether the increase is due to elongation due to a tensile force (axial force) acting in the axial direction of the bolt or to oblique reflection of ultrasonic waves or the like.
Set in the range of anθ.

Further, the flatness is represented by the distance between the two parallel planes when the distance between the two parallel planes is minimized when each end face of both ends of the bolt is sandwiched by two geometric parallel planes ( JISB0621). Since the flatness of each end face of the both ends of the bolt is 0.0005 to 0.1 mm, ultrasonic waves or the like are repeatedly propagated in the axial direction for measuring the axial force of the bolt, and the propagation time is increased. In this case, the reflected waves at both end surfaces are hardly diffused, the directivity of the propagated signal is improved, and the reliability of the axial force measurement is improved. When the flatness exceeds 0.1 mm, ultrasonic waves and the like are dispersed due to the undulation of the bolt, and it becomes difficult or ambiguous to determine which signal wave to measure the propagation time.
If it is less than mm, the manufacturing process becomes complicated and the cost of the bolt increases, so it is desirable to set the flatness within the above range.

Further, when the ten-point average roughness Rz of each end face of the both ends of the bolt is set to 1 to 15, when the ultrasonic force or the like is used in the measurement of the axial force, the ultrasonic wave or the like is hardly irregularly reflected at each end face. Therefore, the directivity and strength of the signal wave for detecting an increase in the propagation time of ultrasonic waves or the like are increased, and highly reliable axial force measurement can be performed. When the surface roughness Rz is 15 or more,
Signal waves such as ultrasonic waves are irregularly reflected at each end face,
If the strength is reduced and the above-mentioned Rz becomes 1 or less, the processing steps become complicated and costly. Therefore, it is desirable to define the surface roughness Rz in the above range.

When the tightening is performed while measuring the axial force of the bolt, the means for measuring the axial force is not limited to the ultrasonic wave.
It is also possible to use a predetermined radio wave, vibration wave, shock wave, or the like, and the above-described feature of the bolt is also effective for an axial force measuring medium other than the ultrasonic wave.

[0018] Further, at the distal end of the bolt intermediate member, there is a round corner portion whose diameter gradually decreases in an arc shape in cross section from an outer diameter substantially equal to the effective screw diameter or the outer diameter of the screw, and a distal end surface following the round corner portion. Can be formed in advance with a flat surface substantially perpendicular to the screw axis, and the screw thread can be formed so that the screw end is located at the center of the round corner portion of the extended portion. When such a round corner portion remains at the tip of the bolt, when the screw is engaged with a female screw member such as a nut, the round corner portion comes into contact with the female screw opening end of the other nut or the like, and the nut and the bolt are connected to each other. Even if each axis is inclined, it is possible to produce an effect of correcting the axes coaxially. In general, the thread end of a bolt tip is an imperfect thread part having a thin and long cross section, and when it hits something, a thin thread falls down (crushing of the thread end) or a dent While the screw end is located in the middle of the radius corner, the height of the imperfect thread at the screw end is reduced, and the height and thickness are well balanced. Problems such as falling down hardly occur. Overall, it is possible to measure bolt axial force with high accuracy at the time of tightening, to correct the inclination of the axis when screwing, and to provide a bolt that does not easily have a dent on the screw end of the bolt end. Becomes

[0019]

Embodiments of the present invention will be described below with reference to embodiments shown in the drawings. A bolt 1 as a male screw member shown in FIG. 1 has a head 2 and a shaft 3. Each of the end faces of both ends of the bolt, in other words, the end face 4 of the head 2 and the end face 5 of the shaft 3 have a perpendicularity to the bolt axis A of 0.0.
005 to 0.1 mm, especially 0.0
It is formed in the range of 0.01 to 0.08 mm, particularly 0.01 to 0.07 mm. That is, as shown in FIG. 2, each of the end faces 4 and 5 of the bolt 1 is perpendicular (perpendicular to) the bolt axis A and two parallel virtual planes P separated by the range (distance t).
1, defined between P2.

As shown in FIG. 3, an angle (intersecting angle) θ between the end faces 4 and 5 at both ends of the bolt 1 with respect to a geometric plane P perpendicular (perpendicular) to the bolt axis A is tan
(B / a in the figure) is 0.02 or less (0.00003 as the lower limit), and especially 0.00006 to 0.01.
6, especially in the range of about 0.0006 to 0.014. If this is converted into a theta (can also be called ^{tan -1} theta although) theta or ^{tan -1} theta 1.2 degrees or less (0.001 degrees as the lower limit value), among others from 0.003 to 0.9 degrees, In particular, it can be set to about 0.03 to 0.8 degrees.

The flatness of each of the end faces 4 and 5 at both ends of the bolt 1 is 0.0005 to 0.1 mm, especially 0.001 to 0.08, especially 0.002 (or 0.02 mm).
1) It is set to about 0.07.

Further, the end faces 4, 5 at both ends of the bolt 1
Has a surface roughness of 15 or less (for example, 1 as a lower limit) in terms of a ten-point average roughness Rz.
5 to 11. In particular, Rz is 2 to 8 (further 5 to 5
7) is desirable.

By determining the perpendicularity, flatness and surface roughness of both end surfaces 4 and 5 of the bolt as described above, for example, as shown in FIG. When the nut 7 is tightened, the tightening process or operation can be performed with a tightening device or tool such as an impact wrench while measuring the axial force Tf (FIG. 5) of the bolt using ultrasonic waves. The bolt axial force Tf is a tensile force generated in the axial direction of the bolt by tightening. If the tensile force (bolt axial force) increases, the bolt slightly expands in the axial direction. The bolt axial force is measured indirectly by detecting the increase in
The tightening is completed when a predetermined bolt axial force is reached.

For example, as shown in FIG.
A detecting unit (transducer: for example, a piezoelectric element) of the ultrasonic bolt axial force meter 10 is mounted on either the head end surface 4 or the shaft end surface 5 (the head end surface 4 of the bolt 1 if the nut 7 is tightened). Then, ultrasonic waves are emitted for a fixed short period of time by applying a voltage, and thereafter, the ultrasonic waves propagated by repetition of reflection and converted into electric signals are applied, and the ultrasonic waves are emitted in the axial direction of the bolt. The ultrasonic wave is reflected on the end face 5 of the bolt 1, returns to the head side of the bolt, and is reflected again on the end face 4 of the bolt. ~ Thousands of times). By measuring the propagation time of this ultrasonic wave, the elongation of the bolt 1 due to the tightening, and thus the axial force of the bolt 1 can be measured. In the case of FIG. 4 (a), one transducer 11 performs both transmission and reception of ultrasonic waves. However, as shown in FIG. 4 (b), both ends 4 and 5 of the bolt 1 are used for transmission and reception, respectively. The transducers 11 and 12 may be applied, and even in this case, a change in the propagation time of the ultrasonic wave that has reciprocated many times will be observed.

In order to measure the axial force of the bolt using ultrasonic waves, if the perpendicularity of both end surfaces 4 and 5 of the bolt deviates from the aforementioned range as shown in FIG. Since the sound wave is reflected so as to be inclined in the bolt axis direction and also reflected on the side surface of the bolt shaft portion, the propagation path becomes longer, so that it is impossible to distinguish the increase in propagation time due to the elongation of the bolt.
If the flatness of both end surfaces 4 and 5 of the bolt 1 deviates from the above-mentioned range as shown in FIG. 3B, the reflected wave of the ultrasonic wave is dispersed on the undulating end surface, and the propagation time of the ultrasonic wave is grasped. It becomes difficult. Further, as shown in FIG.
If the surface roughness Rz of the sample 5 is out of the above range, the ultrasonic waves are irregularly reflected at the end faces 4 and 5 and the intensity thereof is reduced (attenuated), so that it is difficult to generate a directional reciprocal wave of the ultrasonic wave.

In the above embodiment, the squareness, flatness, and surface roughness of both end faces of the bolt are synergistically defined.
With the detection of the reflection of the ultrasonic wave and, consequently, the propagation time, the ultrasonic wave is easy to follow along the bolt axis direction and is hard to disperse, and the irregular reflection is suppressed, so that the bolt axial force can be measured and its accuracy is high. Become.

Next, an embodiment of a method for manufacturing a bolt will be described with reference to an embodiment shown in the drawings. In FIG. 7, when the above-described reference plane of the perpendicularity, flatness, and surface roughness is formed on the end face of the bolt head, the end face of the head of the bolt (material) 20 of the intermediate product as shown in FIG. Cold forging (hereinafter, also referred to as cold forging) is performed so that the raised portion 21 is generated. The built-up portion 21 functions as a bulging portion, and the bulging portion has a shape that bulges outside the bolt axis (for example, a spherical shape, a smooth mountain shape, a trapezoidal mountain shape, a two-stage three-stage shape, or the like). The end surface of the bulging portion 21 may be a flat surface close to a right angle to the bolt axis.

Thereafter, as shown in FIG. 3B, a concave portion 22 is formed by cold forging with a predetermined punch so that the overlaid portion 21 (bulged portion) is dented. The bottom surface 23 of the recess 22
Is the reference plane on the bolt head side or the base plane (preformed surface) of the reference plane. The concave portion 22 is formed in a predetermined range centered on the bolt axis, and its planar shape can be appropriately selected from a circular shape and a polygonal shape (for example, a regular hexagon in the case of a hexagonal bolt). The size of the recess 22 is determined by the bolt (material) 2
0 is approximately equal to or larger than the diameter of the shaft portion 24 (in this case, the surface that projects the entire cross section of the bolt shaft portion 24 is included in the bottom surface 23 of the concave portion 22, in other words, the bottom surface 2
3 is larger than the cross section of the bolt shaft portion 25). Conversely, the bottom surface 23 of the concave portion can be made smaller than the section perpendicular to the axis of the bolt shaft portion 25. In this case, the end surface of the bolt shaft portion described later is also formed by recessing around the bolt axis.
When the base of the recess is used as a reference plane on the side of the bolt shaft, the recess plane on the shaft and the bottom of the recess on the head side can be set to a size (area) substantially corresponding to each other. .

The raised portion 24 around the concave portion 22
If the bottom surface 23 of the recess 22 is formed by cold forging, the bottom surface 23 can be used as a final reference plane if it remains in the final bolt product. Alternatively, as shown in FIGS. 7C and 7D,
The raised portion 24 around the concave bottom surface 23 can be removed so as to be flush with the bottom surface 23 by grinding or cutting in a later step. In addition, the concave bottom surface 23 may be ground or the like to increase the surface roughness or the like.

FIG. 8 shows an example of a process for forming a reference plane on the end face of the bolt shaft. There are a forging die 30 and a punch 31, and an end face (a face for forming an end face of a bolt shaft) 32 of the punch 31 has a concave spherical shape or other appropriate concave shape. The punch 31 is positioned as shown in (a) and (b), and the bolt material 33 is cold forged as shown in (c) to form an intermediate form of the bolt shaft. This allows
As shown in (d), the intermediate form 33 of the bolt shaft portion has an end face 34 bulging outward with respect to the bolt axis.
The swelling shape can be an appropriate shape such as a convex spherical shape (an arc shape in terms of cross section), a smooth mountain shape, a trapezoidal mountain shape, a multi-level mountain shape, or a navel shape protruding only at the center. is there. Then, as shown in (e), this end surface (bulging portion)
34 is further subjected to cold forging by a punch 35 having a flat forming surface to obtain a reference plane 36 as shown in FIG. As a result, a high-precision reference plane 36 that is substantially perpendicular to the bolt axis is formed on the shaft end face.

As shown in FIG. 9A, the forging die 30
When the punch 31 is positioned to intentionally retreat (lower in the figure) with respect to the predetermined position, and the cold forging of the bolt shaft is performed, the bolt shaft 33 of the intermediate product as shown in FIG. However, the central portion thereof partially protrudes to form a bulging portion 37. The bulging portion 37 is subjected to cold forging with the punch 35 described above, so that a flat reference plane 38 can be formed on the bolt shaft portion.

In the example shown in FIG. 10, a concave spherical surface or a smooth concave curved surface 40 is formed at a portion corresponding to the end of the bolt shaft portion of the forging die 39, and the concave curved surface 40 and the end surface 32 of the punch 31 are formed. The end face of the punch 31 is also formed in a concave curved surface shape so that is smoothly continuous. By performing cold forging with such a forging die 39 and a punch 31, the end surface 42 of the bolt shaft portion 41 in the intermediate stage protrudes outside the bolt axis into a spherical shape or a smooth convex spherical shape as shown in FIG. End face 42
The reference plane 36 can be formed on the end face of the bolt shaft by cold forging the end face 42 (bulging portion) with the above-mentioned punch having a flat end face.

Further, as shown in FIG.
9 (or the forging die 30 in FIG. 8) and the punch 43 having a flat forming surface, the position where the punch 43 is intentionally retracted from the normal forming position during cold forging of the bolt shaft portion 41. And cold forging in this state,
As shown in (b), the wall portion of the end face of the bolt shaft portion partially bulges outward in the direction of the bolt axis to form a bulge portion 44 having a navel shape (the center portion protrudes more than the others). Outgoing part 44
Can be cold forged with the above-mentioned forming punch to form a reference plane 36 of the bolt shaft 33 as shown in FIG.

At the time of forming the end face of the bolt shaft portion, the bulging portion is formed in advance as described above, and the flat surface is formed by further cold forging to form a flat surface. Can be processed well. For example, the surface is made clean by the formation of the bulging portion, and the bulging portion is cold forged to cause the movement of the meat, thereby improving the flatness and the surface roughness. Further, by forming a smooth concave curved surface 40 or the like in the forging die as shown in FIG. 10, the movement of the meat becomes smoother at the time of cold forging, and in addition to the improvement of the life of the die, the protrusion on the end surface of the bolt shaft portion is obtained. It becomes easy to form a part. Conversely, if the movement of the meat is not performed well, intermittent portions and concave portions will occur, and it will be difficult to obtain a clean flat surface even if it is formed flat later. By promoting the movement of the meat at the time and forming the bulge portion, the flat surface is further subjected to cold forging, whereby the accuracy of forming the flat surface is improved.

The forging shapes shown in FIGS. 8 to 11 are schematic. In actual forging, so-called sink marks such as the front end face in cold forging, and roundness (roundness) at corners are used.
And the like, but such details are omitted.

FIG. 12 shows a more specific example of the bolt manufacturing method. In FIG. 12, equipment such as a forging die is omitted, and a change in the form of the bolt is focused on. In this cold forging process, first, as shown in (a), the wire is cut into a fixed length to form an axial bolt material 46,
Next, in (b), the tip of the bolt on the shaft portion side is rounded.
That is, as described above, the bulging portion 42 or 44 is formed by a forging die or a punch. Next, in (c), the bulging portion 42 of the bolt shaft portion is cold forged with a predetermined punch to form a concave dent (forming a concave portion 48), and a bottom surface 49 thereof.
To a reference plane 49 on the shaft side substantially perpendicular to the bolt axis.
And As mentioned above, the cold forging method on the bolt head side,
It can be used also on the end face of the bolt shaft. In addition, as shown in FIGS. 9 to 11, without forming the concave portion 48 on the end surface of the bolt shaft portion, it can be formed flat by a punch. On the head side, a preformed portion 51 of the head is formed by cold forging.
This portion is formed, for example, as a (tapered) end portion that is formed to have a large diameter by a certain amount from the boundary of the shaft portion and that the diameter gradually decreases toward the head-side end surface.

Then, as shown in (d), the preformed portion 51 corresponding to the head is further forged to form a bulged portion 52 which bulges outward from the bolt axis (preliminary molding at this time). Part is 55). Further, a shaft portion 53 which is reduced by a certain amount is formed on the bolt shaft portion so as to form a screw lower diameter. It should be noted that the reference end face 49 in the step (c) is maintained on the bolt shaft side end face or the punch is applied with high precision to further improve the accuracy of the reference face 49. Then, as shown in FIG.
The concave portion 56 is cold forged into 2 and its bottom surface 57 is used as a reference plane. The preformed portion of the head is set to 58, and a step of forming the preformed portion 58 in a hexagonal shape is performed in the step (f). For example, a cold forging process may be performed by cutting off the periphery of the preformed portion 58 into a hexagon using a forging die.
Reference numeral 60 indicates the removed portion. In this step (f), a bolt-side reference plane is formed as the bottom surface 57 of the concave portion 56 on the head 62 of the intermediate product 61 of the bolt, and the shaft portion 63
A shaft-side reference plane is also formed on the side end surface as the bottom surface 49 of the concave portion 48.

Further, as a subsequent step, the bolt shaft 6
For example, a male screw is formed in the small-diameter portion 53 by rolling,
After that, it undergoes a heat treatment, a plating step, and the like, and becomes a bolt as a final product. Here, the raised portion 59 around the concave portion 57 in the step (f), the raised portion 50 of the concave portion 48 on the shaft portion side, and the like are formed by, for example, a double-side grinding machine or the like.
And 48 so as to be substantially flush with the bottom surfaces 57, 49. Further, the processing allowance such as grinding is increased, and the bottom surfaces 57 and 49 are subjected to finishing treatment such as grinding or polishing after heat treatment, so as to improve the positional accuracy and surface accuracy of the reference plane, and then to perform plating treatment and the like. It may be.

FIG. 13 shows the steps shown in FIG. 12 together with the cold forging apparatus.
The step (f) corresponds to the steps (a) to (f) in FIG. In FIG. 13, in (a) to (f), a first die 71 to 75 (for example, an upper die) is used as a cold forging device.
And second molds 81 to 85 (for example, lower molds) are used.
The first molds 71 to 75 include mold main bodies 71a to 75a,
The first molds 71 and 72 include punches 71b and 72b,
In the step (f), a die 75 for forming a hexagonal portion is formed.
b. Also, the second mold (lower mold) 81 to 85
Is provided with mold main bodies 81a to 85b and punches 81b to 85b.

In the step (a), the wire is cut into the bolt material 46, and in (b), the bolt material 46 is cold forged by the punches 71b and 81b. At this time, the above-mentioned bulging portion is formed on the end surface of the bolt material 46 on the bolt shaft portion side. Contrary to this, the tip of the punch 81 is bulged toward the tip in the axial direction (for example, a spherical shape or the like), and a concave curved surface (81
A concave portion such as c) may be formed. That is, one or both of the end faces of the both end faces of the bolt are preformed by forging so as to be recessed inward in the axial direction of the bolt in the intermediate step, and then the cold forging is performed so that the preformed part becomes a plane. The plane is defined as the reference plane on the side of the bolt shaft substantially perpendicular to the bolt axis. In the step (c), the aforementioned preformed portion 51 is formed on the head of the bolt material 46 by the punches 72b and 82b, and the punch 82b is formed on the opposite end surface of the shaft portion with respect to the aforementioned bulging portion. A concave portion is formed, or the bulged portion is flattened by a flat punch to serve as a reference plane. When the shaft-side end surface of the bolt material 46 is formed in a concave curved surface (recess) in the step (b), the punch 82b of (c) abuts against the concave curved surface to flatten the flat surface. I do. In the step (c), it is of course possible to form the recess 48 as shown in FIG. 12 and use the bottom surface 49 as a reference plane.

In the step of FIG. 13D, the first mold 73 is used.
And the second die 83 and the punch 83b (also a part of the second die) to form the preformed portion 55 of the head bulging outward and the small diameter portion for thread rolling. 53 is formed. In the step (e), the above-mentioned concave portion is formed by the first mold 74 with respect to the preformed portion 55 which further bulges outward, and the bottom surface is used as a reference plane. further,
In the step (f), the hexagon 62 is formed by the die 75b of the first die 73.

As shown in FIG. 14A, a recess 56 is formed on the head side end surface of the bolt 76, and a recess 48 is also formed on the shaft side end surface. The reference plane and the bottom surface 49 of the recess 48 can be used as the reference plane on the shaft side. In this case, the width of the bottom surface 57 on the head side is set to be substantially equal to, for example, a plane on which the cross section d of the bolt shaft is projected, or to be smaller or narrower around the bolt axis. can do. Further, the bottom surface 49 of the concave portion 48 on the shaft portion side is smaller than the shaft portion cross section d. The relationship between the diameter d1 of the reference plane 57 on the head side (a diagonal line indicating the size of the polygon in the case of a polygon) and the diameter d2 of the bottom surface 49 on the shaft side is d1> d2, d1
<D2 or d1 = d2 is possible.

As shown in FIG. 14B, the width (d1) of the reference plane 57 on the head side of the bolt 77 and the width (d2) of the reference plane 49 on the shaft side are coaxial with the bolt axis. Is present in a region (d1 = d2) equal to the position of (1), ultrasonic waves can be repeatedly reflected and reciprocally propagated in a region inside a cylindrical (for example, cylindrical) connecting these reference planes 57 and 49. Therefore, the reference plane necessary for the reflection of the ultrasonic wave can be minimized, and the formation area of the high-precision reference plane can be small, so that the processing is easy and the manufacturing cost can be suppressed.

As shown in FIG. 14C, the shaft end surface 36 of the bolt 78 is not formed as the bottom surface of the concave portion, but the shaft end surface is entirely formed as a flat surface to serve as the reference plane 36. The concave portion 56 as described above is formed on the head side, and the bottom surface 57 can be used as a reference plane. In this case, the width d1 of the bottom surface 57 can be formed equal to or slightly larger than the cross section d of the bolt shaft portion. In this case, the ratio of the width of d1 to d is, for example, d1 = 0.7d
1.3d, especially 0.9d to 1.1d. As shown in FIG. 14A, concave portions 56 and 4 are provided at both ends.
8, the ratio of the size of each reference plane is d1 =
0.5d2 to 2d2, especially 0.7d2 to 1.3d2, especially about 0.8d2 to 1.2d2, and d1 = d2
Is substantially equivalent to the example shown in FIG.

Further, as shown in FIG. 14D, the bottom surface 57 of the recess 56 on the bolt head side is made as large as possible, and the bottom surface 49 of the recess 48 on the bolt shaft side is made as large as possible. be able to. In other words, it means that the raised portion 59 of the concave portion 56 and the raised portion 50 of the concave portion 48 are minimized. In this case, the reference planes 57 and 49 that contribute to the reflection of ultrasonic waves and the like can be widened.

The raised portion 59 of the concave portion 56 and the raised portion 50 of the concave portion 48 are removed by, for example, a double-ended grinding machine as described above, and as shown in FIG. It is possible to form a reference plane 57 that is substantially flat throughout the entire surface by eliminating the concave portion on the end face, and eliminates the concave portion on the shaft portion side as well. Such raised portions 59 and 50 in the post-process.
14 is scheduled to be removed by grinding or the like.
By minimizing the raised portions 59 and 50 as in (d), the amount of cutting by grinding can be reduced, and grinding and the like in a later step can be easily performed. In addition to cutting off the raised portions 59 and 50, the reference planes 57 and 49 formed by cold forging can also be ground with a slight grinding allowance to finally adjust the surface roughness and flatness. Even in this case, since a plane with high accuracy such as a squareness is formed in advance by cold forging, a reference plane with higher surface accuracy can be obtained by grinding or the like.

Further, as shown in FIG. 15 (b), the reference planes 57, 49 by cold forging at the beginning (or the surfaces whose surfaces have been finished by grinding or the like) with the raised portions removed as described above. As for the widths d1 and d2 centered on the bolt axis, the ratio between d1 and d2 can be determined as described in the concave portions 56 and 48 described above.

Further, instead of the idea of forming the reference plane by cold forging as described above, the d1 reference is applied to the bolt head from the rough end face of the bolt head and the end face of the shaft part by the finish processing such as grinding. It is also possible to form a d2 reference plane on the bolt shaft portion, respectively.

In the above description, a general bolt is taken as an example. However, the present invention can be applied to all bolts without a head, stud bolts, and other shaft bolts having male threads. In this sense, the bolt here is synonymous with the male screw member.

Also, forging in the method of manufacturing a bolt is as follows:
Although the description has been given on the assumption of cold forging, hot forging, warm forging, or the like may be used depending on conditions such as the type, size, and purpose of use of the bolt.

As yet another embodiment, a rounded corner is added to the tip of the bolt, and the flat surface following the rounded corner is a reference on the bolt leg side (shaft side) substantially perpendicular to the bolt axis. It can be flat. The embodiment will be described with reference to FIG. Bolt 1 in FIG.
01 has a head end surface 104 on the bolt head 102 and a shaft end surface 105 on the leg (bolt shaft) 103, and these become a reference plane substantially perpendicular to the bolt axis.
In the vicinity of 5, a guide extension (guide protruding portion) 107 having a rounded corner portion 106 is formed. The screw end 108a of the male screw portion 108 is located in the middle of the round corner portion 106. In other words, the male screw portion 108 starts (or can be said to end) from the middle of the round corner portion 106. A shaft end face 105 which is a flat surface substantially perpendicular to the axis is formed.

As shown in FIG. 17, the radius corner portion 106 is formed of a part of a substantially spherical surface or a part of a curved surface approximating a spherical surface, and has a radius of curvature of rc. One end of the round corner portion 106 is formed such that an arc cross section or an arc cross section curve defining the corner portion 106 substantially contacts the effective screw diameter db of the male screw portion 104, and the other end of the round corner portion 106 is formed. The end is formed such that its arc-shaped cross section or arc-shaped cross-sectional curve substantially contacts the shaft end face 105 which is a flat surface. The length (projection amount) of the extension (guide extension) 107 including the round corner 106 in the bolt axis direction is L.
The diameter of the shaft end surface (flat surface) 105 about the bolt center line O is φ.

As will be described later, in the bolt intermediate product before the male screw is formed, the bolt shaft portion and the round corner portion 106 before the male screw are formed are smoothly continuous with each other. Are connected in a tangential manner to the bolt shaft portion. Then, as shown conceptually in FIG. 18, when a male screw is rolled (rolled screw),
The end of the radius corner portion 106 is formed because the flesh of the portion that becomes the thread root moves to form a thread and an external thread is formed (the thread rolling lower diameter becomes the shaft diameter of the bolt intermediate product before thread formation). Is formed with the screw effective diameter db as a starting point or an end point, and comes between the screw inner diameter dc and the screw outer diameter da.

On the other hand, as shown in FIG. 19, when a male screw of a bolt is formed by cutting (cutting screw), a portion corresponding to a thread root is removed by cutting to form a screw thread (thread cutting lower diameter). Is the diameter of the shaft portion of the bolt intermediate product before thread formation), so that the end of the rounded corner portion 106 is formed with the screw outer diameter da as a starting point or an end point. However, in the following, it will be represented by an example of a rolled screw.

As described above, since the tip of the extension 107 is the shaft end face 105 and the outer periphery of the extension 107 is the round corner 106, the bolt shaft is formed by the shaft end face 105 as described above. In addition to forming a good reflection surface such as ultrasonic waves at the time of force measurement, when the rounded corner portion 106 is screwed with a mating female screw member such as a nut, both the bolt and the nut etc. A function of guiding the axes of the screw members to be aligned is provided. FIG. 20 conceptually illustrates this.
It is assumed that the axis O2 of the nut 110 is inclined at an angle θ with respect to the axis O1 of the bolt 101 when screwing the nut 110 with the nut 110. In general, the two axes of the bolt and nut are not ideally coaxial at the time of screwing, and the axes are more or less inclined relative to each other.

When the bolt / nut is pressed (or one of them is rotated while pressing) in the inclined state, the nut 110 is moved along the spherical round corner 106 formed at the tip of the bolt 101. Of the nut 110 slides (slids), and the axis O2 of the nut 110 is relatively rotated in a direction coaxial with the axis O1 of the bolt 101, thereby correcting the inclination of both axes of the bolt and nut. Act like so. Thereby, even if the axis is tilted to some extent, the bolt / nut can start screwing well, and it is possible to prevent or reduce biting (biting) or seizing due to the axis tilt. Thereafter, the bolt is tightened while checking the axial force of the bolt with an ultrasonic wave or the like, whereby an appropriate fastening state can be obtained.

Further, as shown in FIG. 26, in the conventional general bolt 201 having no rounded corner, the screw end 208a, which is an incompletely threaded portion of the externally threaded portion 208, tends to have an elongated thin section. As a result, a “fall” may occur in which the screw end is deformed so as to deviate from the normal spiral. On the other hand, the above-described radius corner portion R (10
In the bolt 101 formed with 6), the outer diameter gradually decreases spherically due to the round corner portion 106 to reach the shaft end face 105, and from the middle of the round corner portion 106 to the screw end 1.
Since 08a starts (or ends), a thin screw end having a low strength, and thus "falling" of the screw end is less likely to occur, which is advantageous in terms of the strength of the screw end, and the strength against dents which are likely to occur during transportation or machining drop. Higher and more reliable.

In the related art, as shown in FIG. 27, there is a bolt 211 having a nut hole insertion projection 212 protruding in a spherical shape with a two-step shaft at the tip of the bolt. The outer diameter de of the protrusion 212 is much smaller than the diameter (thread effective diameter db) and smaller than the screw inner diameter dc. After the thread is rolled, there is a gap between the screw inner diameter dc and the protrusion diameter de. G occurs. That is,
Since the screw end 218a of the male screw portion 218 is not formed in the middle of the projection 212, there is no effect of preventing the above-mentioned fall. Also, the protrusion 212 makes the axes of the bolts and nuts approach each other within a certain distance range (constraining the coaxiality of the bolts and nuts under a certain range of conditions) so that the screwing can be performed smoothly. It is not intended to correct even a certain range of coaxial misalignment. Therefore, the larger the allowable range of the misalignment, in other words, the larger the gap G, and the smaller the protrusion amount, the more the screwing starts. Poor engagement at the time was likely to occur. On the other hand, the above-mentioned round corner portion 106 is intended to relatively rotate the nut by sliding with the opening edge portion of the nut, and so to speak, the relative inclination of the bolt and nut like a spherical joint. It has a function to correct (displacement of the axes of each other) as much as possible until it becomes coaxial, make both axes more concentric, and start the screwing of both smoothly.

Next, the round corner portion 10 as described above is used.
6 and a method of manufacturing the bolt 101 having a flat surface at its end will be described. The whole flow is almost the same as that of FIGS. 12 and 13 when forging is performed. The difference is mainly in the step of providing the round corner portion 106.

As shown in FIG. 21, the wire is cut into a simple axial bolt material 146 (a), and then the end of the bolt material 146 on the side where the radius corner portion 106 is provided is tapered. (B). Further, the head preformed portion 151 is forged so as to have a larger diameter than the other shaft portions at the end portion on the side which becomes the bolt head in the step (c). Also, on the opposite end,
The round corner preform 143 in which the taper angle of the tapered portion 142 is further increased and the axial dimension is also compressed is forged. In other words, in the step (c), the tapered portion 142 is further forged to form a forged product immediately before forming the final shaft end face 149 (105) and the rounded corner portion 106, and the predetermined tapered portion 142 is formed. Forging the tapered portion 143 immediately before having the angle θ.
The taper angle θ of the tapered portion 143 is about 60 to 150.
°, in particular, for example, a range of 90 to 120 ° is desirable. By setting the taper angle θ in such an angle range in the forging process, the squareness, flatness, and surface roughness of the final shaft end surface 149 (105) in FIG. An end surface 149 can be formed. In addition, by setting the taper angle θ as described above, the finish surface of the rounded corner portion 106 which will be planned later also
The state is higher in accuracy and surface roughness is better. In addition,
The taper angle θ as described above can be formed by two-stage or multiple-stage forging shown in FIGS. 21B and 21C in addition to the one-stage forging. In that case, if the first taper angle θ ₁ and the next taper angle θ ₂ ,
It is possible to increase the taper angle so that θ ₁ <θ ₂ . However, in the step of FIG. 21B, instead of the tapered portion 142, the tapered portion 14 having a taper angle θ in advance is used.
3 may be forged, and in the step (c), the taper angle θ may be maintained. In short, the final shaft end surface 1
It is recommended to give a taper angle θ as a forging shape immediately before forging such as 49. In addition, the step (b) can be omitted. In that case, the process shifts from the step (a) to the step (c) in the same figure. The taper angle θ in the range may be set as a pre-process for forming the shaft end face 149 and the rounded corner portion 106 to be formed later, or as the rounded corner portion 10.
If 6 is not formed, it is provided as a pre-process for forming the shaft end face 149 with high accuracy. In addition, the step (b) may be left, and the step (c) may be omitted. In such a case, the taper angle θ at the shaft end in the step (b) is 60 to 150 °, preferably 90. ~ 120 °
Is formed, and then the process proceeds to the step (d). In any case, the axial dimension of the round corner preformed portion 143 (step (c) or step (b)) is the same as the round corner portion 10 shown in FIGS.
6 can be set to be larger than the axial protrusion amount L of the extension portion 107 having the same, and the outer peripheral surface of the preformed portion 143 has a conical surface shape or the final rounded corner portion 106.
Can be formed in a spherical shape having a radius of curvature larger than the radius of curvature rc of

Thereafter, as shown in (d), a portion of the bolt shaft portion where an external thread is to be formed is formed into a rolled lower diameter portion 120 prior to thread rolling so as to be thinner than other bolt shaft portions. Forging. The diameter of the rolled lower diameter portion 120 is substantially the same as the final effective diameter of the male screw portion, and the bolt shaft portion on which the male screw is not formed is substantially the same as the screw outer diameter of the male screw portion. Further, the rounded corner preformed portion 143 is further forged to form a spherical final rounded corner portion 106 having a radius rc, and a shaft end face 149 substantially perpendicular to the bolt axis is also forged. The round corner portion 106 is made to smoothly contact the effective screw diameter. Also, by this stage (prior to thread rolling), the bolt head 102 has been forged to a final configuration having a shaft end face 104.
The stepwise process of forging the bolt head (a detailed process from the preforming portion 151 to the bolt head 102) is omitted. Further, as described later, the taper angle θ
When the end face of the tapered portion 143 is forged by, for example, hitting with a punch, a relief portion (free space) that allows free expansion of the tapered portion 143 is set on the inner surface of the mold (FIG. 24). ), The tapered portion 143 having the taper angle θ is freely deformed by the impact of the punch 183b, and a good radius corner portion 106 can be easily formed. According to the method of the relief portion, there is an advantage of extending the life of the mold. Of course, as shown in FIG. 23, the round corner portion 106 may be formed on the inner surface of the mold.

Then, as shown in (e), the screw is roll-formed so that the screw end is located with the middle of the round corner 106 as a start point or an end point, and the effective screw diameter of the rolled screw and the round corner are obtained. The starting point or the ending point of the unit 106 substantially coincides. By this thread rolling, the final bolt 101 is formed, and as shown in an enlarged view in FIG. 22, the screw end is located in the middle of the round corner portion 106, and the spherical round corner is determined from the effective screw diameter of the rolled thread portion. Part 10
6 has begun (or can be said to be over).

As a forging die used in the forging process from (c) to (d) of FIG. 21, for example, as shown in FIG. 23, the round corner portion 106 is transferred to the bolt intermediate product 146 on the inner surface of the die 183a. For this purpose, a forging die having a concave spherical forging surface 142 having a curvature radius rc can be used. This mold 186a is filled with a bolt intermediate product 146,
By hitting or pressing in the bolt axis direction with the punch 183b,
The body of the bolt intermediate product 146 escapes and comes into close contact with the concave spherical forged surface 142, the surface of which is transferred to the shaft end of the bolt intermediate product 146, and the flat tip surface of the punch 183b is the rounded corner. Following the portion 106, the shaft end face 105 is provided at the tip thereof as a reference plane on the bolt shaft side. This round corner portion 106 is formed at the tip end of the thread rolling lower diameter portion 120 set to the screw effective diameter da as described above, and the other bolt shaft portions correspond to the screw outer diameter da. It is assumed.

Incidentally, instead of the forging die 183a of FIG. 23,
Rather than having a concave spherical surface 142 for transfer of the rounded corner portion 106, as shown in FIG. 24, it has a relief portion 143 at the time of forging, and allows the meat of the bolt intermediate product 146 to escape at the time of forging. Forging die 183a 'that forms a convex curved rounded corner (R') 106 '(which may not be an accurate spherical shape) by projecting outward to bulge into portion 143. Can also be used.

By the way, the following can be said as a more preferable embodiment of the bolt 101 in which the above-described round corner portion 106 (106 ') is formed. For example, when the protrusion amount of the guide extension portion (guide protrusion portion) 107 in the screw axis direction is L (see FIGS. 17 to 19 and the like), and the radius of curvature of the round corner portion 106 of the guide extension portion 107 is rc, L / Rc is desirably 0.65 to 1.5. When the diameter of the flat surface (reference plane) 105 formed at the tip of the guide extension 107 is φ, rc
/ Φ is preferably 0.15 to 0.35, and L / φ is also preferably 0.15 to 0.35.
Further, with respect to the above L, rc and φ, L: rc: φ is
14-18: 35: 3-5: 14-18 is preferable. The surface roughness of the rounded corner portion of the guide extension portion 106 (ten-point average roughness as Rz) is 0.3 to
It is recommended to be 12.5 Rz. By setting the radius in the above range, a good guide function (such as an axis matching function) for the round corner portion 106 with respect to the nut and the like and durability against the above-mentioned dents and the like, and an axial force for reflecting ultrasonic waves and the like on the reference plane The effect of improving the measurement accuracy is synergistically obtained.

In order to evaluate from another aspect, FIG.
5, the pitch of the male threaded portion 108 of the bolt 101 is P, the radius of curvature of the rounded corner portion 106 is rc, the angle of the first end of the rounded corner portion 106 to a reference line (reference surface) C1 perpendicular to the bolt axis is α, Are corner 1
Reference line (reference plane) C parallel to the bolt axis at the second end of the reference line 06
Let β be the angle to 2. Here, a generally possible range of each value, a desirable range usually adopted, and an optimum value are as follows.

For α, the generally possible range is 0 to ±
It can be said that the preferable range is 0 to ± 20 °, and the optimum value is about α = 0 °. Regarding β, a generally possible range is ± 20 ° to ± 30 °, a desirable range usually adopted is 0 to ± 20 °, and an optimum value is about β = 0 °. Further, as for rc, a generally possible range is P to 3P, and a desirable range usually adopted is 1.5P to 2.P.
5P, the optimal value can be said to be about rc = 2P. In other words, the radius of curvature rc of the rounded corner portion 106 is equivalent to about 1 to 3 pitches of the pitch P of the external thread, preferably 1.5 to 2.5 pitches, particularly preferably about 2 pitches. It is recommended that

The radius of curvature r of the round corner portion 106
If c is too small, the portion of the rounded corner portion 106 remaining after the formation of the screw becomes very small, and it becomes difficult to obtain the guide function for the nut and the like described above. Conversely, if rc is too large (the curvature is small), Since it is difficult to obtain a function of rotating a nut or the like so as to correct the screwing from the state where the axis is relatively inclined, it is desirable to determine the range or value as described above. Also, for α and β, when the values in the minus direction become large and the formation angle range of the rounded corner portion 106 becomes much smaller than 90 °, the guide function for the nut and the like described above becomes insufficient, and conversely , Α, and β in the positive direction become large and the formation angle range of the rounded corner portion 106 greatly exceeds 90 °, the flat surface between the thread rolling lower diameter portion and the tip of the bolt shaft portion. Is not preferred because a discontinuous step is generated between them.

[Brief description of the drawings]

FIG. 1 is a front view showing a bolt according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a perpendicularity of an end face of a bolt.

FIG. 3 is a diagram illustrating an angle of an end face of a bolt with respect to a geometric reference plane.

FIG. 4 is a diagram illustrating an example of measuring an axial force of a bolt.

FIG. 5 is a diagram conceptually showing propagation (reflection) of an ultrasonic wave.

FIG. 6 is a diagram conceptually showing propagation (reflection) of an ultrasonic wave in relation to a squareness of an end face, flatness, and surface roughness.

FIG. 7 is a process diagram showing an example of the manufacturing process of the present invention by focusing on the bolt head side.

FIG. 8 is a process diagram showing an example of the manufacturing process of the present invention focusing on the end portion on the bolt shaft portion side.

FIG. 9 is a process chart showing a modification of FIG. 8;

FIG. 10 is a process chart showing still another modification.

FIG. 11 is a process chart showing a further modification of FIG. 10;

FIG. 12 is a process diagram showing an example of a more specific manufacturing process of the present invention, focusing on the form of each step of the bolt.

FIG. 13 is a process diagram showing a process for adding a forging die to the process of FIG. 12;

FIG. 14 is a diagram schematically showing some specific examples of the bolt of the present invention.

FIG. 15 is a view schematically showing still another example of FIG. 14;

FIG. 16 is a view showing a bolt according to another embodiment of the present invention.

FIG. 17 is an enlarged view showing a main part of FIG. 16;

FIG. 18 is a diagram conceptually showing the position and form of a rounded corner in FIG. 17;

FIG. 19 is a view showing a modification of FIG. 17;

FIG. 20 is a diagram conceptually illustrating a guide function of a round corner portion.

FIG. 21 is a diagram showing an example of a bolt manufacturing process of FIG. 16 focusing on a work form for each process.

FIG. 22 is an enlarged view of a main part of a bolt obtained through the step of FIG. 21;

FIG. 23 is a view showing an example of a forging die that can be adopted in the step of FIG. 21;

FIG. 24 is a view showing a modification of FIG. 23;

FIG. 25 is a diagram illustrating a preferred form of forming a round corner portion.

FIG. 26 is a view for explaining a conventional bolt in comparison with a bolt of the present invention having a round corner.

FIG. 27 is a diagram showing an example of a conventional two-stage shaft protruding from a bolt shaft end.

[Explanation of symbols]

 Reference Signs List 1 bolt (male screw member) 4 end face (of bolt head) 5 end face (of bolt shaft) 21, 37, 42, 44, 52 bulging portion 22, 48, 56 concave portion 23, 49, 57 bottom surface (reference plane) 24, 50, 59 Protruding portion 103 Bolt shaft portion 105 Shaft end surface (reference plane) 106 106 'Round corner portion 107 Extended portion (guide protrusion) 108 Male screw portion

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16B 35/00 F16B 35/00 M (72) Inventor Makoto Torisu 22 Miyagoshi, Teratsu-cho, Nishio-shi, Aichi Co., Ltd. Within Sugiura Works (72) Inventor Kaoru Sugiura 22nd Miyakoshi, Teratsu-cho, Nishio-shi, Aichi F-term in Sugiura Works Co., Ltd. (Reference) 4E087 AA08 CA13 CA14 CA19 CA33 CB03 CC01 DA04 DA05 DB04 DB08 DB24 EC02 EC13 EC22 EE02 HA53

Claims (23)

[Claims] 1. A method for manufacturing a bolt, wherein one or both of end faces of both ends of the bolt are preformed by forging so as to bulge outward in the axial direction of the bolt in an intermediate step, and then the preliminary A method for manufacturing a bolt, characterized in that a formed bulging portion is forged flat to form a reference plane substantially perpendicular to an axis of the bolt. 2. A method of manufacturing a bolt, wherein one or both of end faces of both ends of the bolt are preformed by forging so as to bulge outward in the axial direction of the bolt in an intermediate step. A method for manufacturing a bolt, comprising: forging a molded bulging portion into a concave shape, and flattening the bottom surface of the concave portion, and making the bottom surface a reference plane substantially perpendicular to a bolt axis. 3. A method for manufacturing a bolt, wherein one or both of end faces of both ends of the bolt are preformed by forging so as to bulge outward in the axial direction of the bolt in an intermediate step, and then the preliminary The formed bulging portion is formed into a concave shape, and forging is performed so that the bottom surface of the concave portion is flat, and the bottom surface is set as a reference plane substantially perpendicular to the bolt axis, and further, a raised portion around the concave portion is ground or ground. A method for producing a bolt, characterized by being removed by cutting or other methods. 4. A predetermined range centered on the bolt axis in the head end surface of the bolt, and a range in which all or a part of the cross section of the bolt shaft is projected or a region including the range is bolted by forging. The bolt manufacturing method according to any one of claims 1 to 3, wherein the bolt is machined into a plane substantially perpendicular to the axis, and the plane is the reference plane on the bolt head side. 5. A predetermined range centering on the bolt axis of the head end surface of the bolt, and a range in which all or a part of the cross section of the bolt shaft is projected or a region including the range is concavely formed by forging. The bolt manufacturing method according to any one of claims 1 to 3, wherein the concave bottom surface is formed as the reference plane on the bolt head side substantially perpendicular to the bolt axis. 6. A predetermined range centered on the bolt axis in the head end face of the bolt, a range in which the whole or a part of the cross section of the bolt shaft is projected or a region including the range is concavely formed by forging. So that the concave bottom surface is the reference plane on the bolt head side that is substantially perpendicular to the bolt axis,
The method according to any one of claims 1 to 3, further comprising removing a raised portion around the concave portion by grinding, cutting, or another method. 7. The bolt manufacturing method according to claim 1, wherein the forging or forging is cold forging or cold forging. 8. A bolt formed by the manufacturing method according to claim 1, wherein a perpendicularity of each end face, which is the reference plane, of both ends of the bolt to an axis of the bolt is 0.0005 to 0.0005. A bolt having a diameter of 0.1 mm. 9. A bolt formed by the manufacturing method according to claim 1, wherein a perpendicularity of each end face, which is the reference plane, of both ends of the bolt to a bolt axis is 0.0005 to 0.0005. A bolt having a thickness of 0.1 mm and a flatness of each end face of the both ends of 0.0005 to 0.1 mm. 10. A bolt formed by the method according to claim 1, wherein a right angle of each end face of both ends of the bolt with respect to the bolt axis is 0.0005 to 0.5 mm.
A bolt characterized by being 1 mm and having a ten-point average roughness Rz of 1 to 15 on each end face of the both end portions. 11. A bolt formed by the manufacturing method according to any one of claims 1 to 7, wherein a perpendicularity of each end face, which is the reference plane, at both ends of the bolt with respect to a bolt axis is 0.0005 to 0.0005. 0.1 mm, and the flatness of each end face of the both ends is 0.0005 to 0.1 mm, and the ten-point average roughness Rz of each end face of the both ends is 1 to 15 Features bolts. 12. A bolt formed by the manufacturing method according to claim 1, wherein each of the reference planes at both ends of the bolt with respect to an imaginary plane perpendicular to the axis of the bolt. A bolt characterized in that tan θ is set to 0.02 or less with respect to the actual angle θ of the end face. 13. A bolt formed by the manufacturing method according to claim 1, wherein each of the reference planes at both ends of the bolt with respect to an imaginary plane perpendicular to an axis of the bolt. A bolt characterized in that, with respect to the actual angle θ of the end face, tan θ is set to 0.02 or less, and the flatness of each end face of the both ends is set to 0.1 mm or less. 14. A bolt formed by the manufacturing method according to claim 1, wherein each of the reference planes at both ends of the bolt with respect to an imaginary plane perpendicular to an axis of the bolt. A bolt characterized in that, with respect to the actual angle θ of the end face, tan θ is set to 0.02 or less, and the ten-point average roughness Rz of each end face of the both ends is set to 15 or less. 15. A bolt formed by the manufacturing method according to claim 1, wherein each of the reference planes at both ends of the bolt with respect to an imaginary plane perpendicular to an axis of the bolt. For the actual angle θ of the end face, tan θ is 0.02 or less, the flatness of each end face of the both ends is 0.1 mm or less, and the ten-point average roughness Rz of each end face of the both ends is 15 A bolt characterized by the following. 16. The method for manufacturing a bolt according to claim 7, wherein one or both of the end faces of both ends of the bolt are bulged outward in the axial direction of the bolt in an intermediate step. So that, at the tip of the bolt intermediate member, a round corner portion that gradually reduces in diameter in a circular cross section from an outer diameter substantially equal to the effective diameter of the screw or the outer diameter of the screw is preformed by forging, and further the round corner portion is formed. So that the preformed bulging portion is flatly forged to form a reference plane substantially perpendicular to the axis of the bolt, and a thread is formed so that a screw end comes in the middle of the remaining radius corner portion. A method of manufacturing a bolt. 17. A method of manufacturing a bolt, comprising a rounded corner portion at an end of the bolt intermediate member, the radius of which is gradually reduced in an arc shape in cross section from an outer diameter substantially equal to an effective screw diameter or an outer diameter of the screw. An extension is formed in advance so that the end face that substantially coincides with the end of the corner is a flat surface that is substantially perpendicular to the screw axis, and the screw thread is placed so that the screw end comes to the middle of the radius corner of the extension. A method for manufacturing a bolt, comprising forming the bolt. 18. An extension having the rounded corner portion and a flattened tip at a tip end of the bolt intermediate member is formed in advance by forging together with a bolt body portion, and the radius of the extension portion is formed. 18. The method of manufacturing a bolt according to claim 17, wherein the thread is formed by rolling or cutting such that the screw end comes in the middle of the corner and the rounded corner and the flat surface remain. Method. 19. A method for manufacturing a bolt, comprising a rounded corner portion at an end portion of the bolt intermediate member that gradually reduces in diameter in an arc shape in cross section from an outer diameter substantially equal to the effective diameter of the screw, and continues to the rounded corner portion. It is characterized in that an extension portion whose front end surface is a flat surface substantially perpendicular to the screw axis is formed in advance, and the thread is rolled so that the screw end comes in the middle of the radius corner portion of the extension portion. Bolt manufacturing method. 20. A method of manufacturing a bolt, comprising a rounded corner portion at an end portion of the bolt intermediate member that gradually reduces in diameter in an arc-shaped cross section from an outer diameter substantially equal to the outer diameter of the screw, and follows the rounded corner portion. A bolt characterized in that an extension portion whose front end surface is a flat surface substantially perpendicular to the screw axis is formed in advance, and a screw thread is cut so that a screw end comes to the middle of a radius corner portion of the extension portion. Manufacturing method. 21. The method for manufacturing a bolt according to claim 1, wherein prior to forming the reference plane,
The tapered portion having a taper angle in the range of 60 to 150 ° is forged at the shaft end of the bolt material, and then the reference plane is formed by forging through further forging of the tapered portion. A method for manufacturing a bolt, comprising: 22. The method for manufacturing a bolt according to claim 16, wherein a taper angle in a range of 60 to 150 ° is applied to a shaft end of the bolt material prior to forming the rounded corner. A method for manufacturing a bolt, comprising: forging a tapered portion that has been forged; and then forging a rounded corner portion from the tapered portion. 23. The bolt manufacturing method according to claim 21, wherein the taper angle is set in a range of 90 to 120 °.