JP2020001083A - Bolt manufacturing method - Google Patents

Abstract

To provide a bolt manufacturing method suitable for an axial force measurement using ultrasonic waves by smoothly finishing an end face of a bolt.SOLUTION: A bolt manufacturing method for manufacturing a bolt having smooth both end faces comprises: a cutting process for cutting a wire rod to a prescribed length; an end face correction process for smoothening both the end faces by diameter-contracting both end parts 23a, 23b of a cut rod-shaped raw material 23 as progressing toward tips; a compression process for finishing both the end face smooth by compressing the rod-shaped raw material from both the end faces; a throttle process for molding a shaft part by throttle-processing a tip part of the rod-shaped raw material; a preparatory molding process for preparatorily molding a head part by pressing the other end part of the rod-shaped raw material; and a finishing process for press-molding the head part by pressing the other end part of the preparatorily-molded rod-shaped raw material.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for manufacturing a bolt which is fastened while detecting an axial force in fastening an automobile suspension or the like.

  It is well known that proper management of the axial force is important in bolt fastening. Therefore, there is an ultrasonic bolt axial force measuring device that measures the axial force of a bolt using ultrasonic waves (for example, see Patent Document 1). This device is configured to transmit an ultrasonic wave from an ultrasonic probe into a bolt, propagate the ultrasonic wave in the bolt, and receive a reflected wave by the ultrasonic probe. Then, based on the timing at which the reflected wave is obtained, the time during which the ultrasonic wave propagates inside the bolt is measured.

  After the tightening compared to before the tightening, the bolt is extended by the tightening axial force, so that the ultrasonic wave propagation path becomes longer. Further, when the bolt is tightened and an axial force is applied to the bolt to generate a tensile stress, the ultrasonic wave propagation speed also decreases. That is, the propagation time of the ultrasonic wave propagating in the bolt before and after the tightening is different. For this reason, it is possible to measure the axial force of the bolt by using the ultrasonic bolt axial force measuring device to know the difference in the propagation time before and after tightening.

JP 2001-174343 A

  To accurately measure the axial force of the bolt from the propagation time of the ultrasonic wave, it is necessary to accurately detect the incident wave and reflected wave of the ultrasonic wave, and the head end face and the shaft end face of the bolt must be smooth. Must. However, a bolt produced by such a rod-shaped material is distorted in a cutting process of cutting a wire into a predetermined length to prepare a rod-shaped material in a cutting process. Are not smooth on both end surfaces (head surface and shaft end surface). For this reason, there has been a problem that additional processing such as polishing is required to smooth both end faces.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a bolt manufacturing method suitable for measuring axial force by ultrasonic waves by smoothing the end surface of the bolt.

  The above problems are a cutting step of cutting a wire rod into a predetermined length, an end face correction step of smoothing both end faces by reducing the diameters of both ends of the cut rod-shaped material according to the tip, and a step of removing the rod-shaped material from both end faces. A compression process for smoothing both end surfaces by compressing, a drawing process for drawing the tip of the rod-shaped material to form a shaft, and a preliminary process for pressing the other end of the rod-shaped material to preform the head The problem can be solved by a bolt manufacturing method for manufacturing a bolt having both flat end faces by a forming step and a finishing step of pressing the other end of the preformed rod-shaped material and forging the head.

  In the end face correcting step, a receiving piece having an insertion hole into which a rod-shaped material can be inserted is used, and the inner peripheral surface of the insertion hole has a tapered portion whose diameter is reduced according to the depth, and the full angle θ of the tapered portion is , 0 <θ ≦ 32 °, and the cross-sectional reduction ratio φ of both end faces of the rod-shaped material reduced in diameter by being inserted into the tapered portion is set to 60% ≦ φ ≦ 80%. Is preferred.

  According to the method for manufacturing a bolt of the present invention, both end faces of the rod-shaped material are smoothed to some extent by the end face correcting step, and then both end faces of the rod-shaped material are finished smoothly by the compression process. As described above, since both ends of the rod-shaped material are finished smoothly, then the head and the shaft of the bolt are formed by forging, a bolt having excellent smoothness on both ends (the surface of the head of the bolt and the end of the shaft). Can be manufactured.

FIG. 4 is a process diagram showing a cutting step in the method for manufacturing a bolt of the present invention. It is a flowchart showing the end face straightening process in the bolt manufacturing method of the present invention. FIG. 4 is a process diagram showing a compression step in the method for manufacturing a bolt of the present invention. FIG. 4 is a process chart showing a drawing step in the method for manufacturing a bolt of the present invention. FIG. 4 is a process diagram showing a preforming step in the method for manufacturing a bolt of the present invention. It is a flowchart showing a finishing process in a bolt manufacturing method of the present invention.

  Hereinafter, an embodiment of a bolt manufacturing method according to the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 6, the method of manufacturing the bolt includes a cutting step of cutting the wire 20 to a predetermined length, and a cutting step of cutting the tip end 23 a and the other end 23 b of the rod-shaped material 23 cut in the cutting step. An end face correction step of reducing the diameter of both ends, a compression step of compressing the reduced diameter bar-shaped material 23 from both ends, and a drawing step of drawing the tip 23a of the rod-shaped material 23 to form a shaft of a bolt; A preforming step of pressing the other end 23b of the rod-shaped material 23 to preform the head, a finishing step of pressing the other end 23b of the preformed rod-shaped material 23 and forging the head of the bolt. by.

  As shown in FIG. 1, in the cutting step, the metal wire 20 is inserted into the through hole 21 a of the cutting piece 21, and the wire 20 is fed out until the tip of the wire 20 contacts the stopper 22. In this step, the wire 20 protruding from the opening is cut into a predetermined length to produce a rod-shaped material 23 which is an example of a metal piece. The cutting of the wire 20 is performed by a cutter 24 that moves in a direction (direction indicated by an arrow A) orthogonal to the axis of the wire 20.

  As shown in FIG. 2 (a), the end face correcting step is a step of narrowing down the other end 23 b of the bar-shaped material 23 cut by the cutting step to a small diameter using the receiving piece 31. The receiving piece 31 has an insertion hole 31a into which the rod-shaped material 23 can be inserted, and an inner peripheral surface of the insertion hole 31a has a tapered portion 31b whose diameter is reduced according to the depth.

  Therefore, in the end face correcting step, first, the rod-shaped material 23 is inserted into the insertion hole 31 a of the receiving piece 31. Subsequently, the tip portion 23a of the bar-shaped material 23 is pressed by the pin 32 and is pushed in the direction shown by the arrow B. Then, the other end 23b of the rod-shaped material 23 flows into the tapered portion 31b due to plastic deformation, and is reduced in diameter. Finally, the other end 23b of the bar-shaped material 23 is pressed by the knockout pin 33 inserted from the receiving piece 31 side and moved in the direction shown by the arrow C, whereby the bar-shaped material 23 is discharged from the receiving piece 31.

  Further, in the end face correcting step, as shown in FIG. 2B, the front and rear of the bar-shaped material 23 are exchanged, and as shown in FIG. 2A, the diameter of the other end 23b of the bar-shaped material 23 is reduced. The tip 23a of the bar-shaped material 23 is reduced in diameter in the same manner as described above. On the other hand, since the other end 23b of the rod-shaped material 23 is compressed by the pin 32, the diameter is expanded to the inner diameter of the insertion hole 31a. Finally, the bar-shaped material 23 is discharged from the receiving piece 31, and shifts to the compression stroke.

  As shown in FIG. 3, the compression step is a step of compressing the rod-shaped material 23 from both ends. First, the rod-shaped material 23 is inserted into a through-hole 41 a formed on the center line of the receiving piece 41. The inner diameter of the through hole 41a is set to be the same as the maximum diameter of the inner diameter of the insertion hole 31a of the receiving piece 31 over the entire length, that is, the same as the maximum diameter of the rod-shaped material 23. A knockout pin 42 is inserted into the through-hole 41a from an opening opposite to the opening into which the rod-shaped material 23 is inserted, and the rod-shaped material 23 inserted into the through-hole 41a is Supported. Subsequently, the other end 23b of the rod-shaped material 23 inserted into the through hole 41a is pressed by the pin 41 in the direction shown by the arrow B, so that the rod-shaped material 23 is compressed from both ends by the pin 41 and the knockout pin 42. Finally, the rod-shaped material 23 is discharged from the receiving piece 41 by moving the knockout pin 42 in the direction shown by the arrow C.

  As shown in FIG. 4, in the drawing step, first, the rod-shaped material 23 is inserted into the insertion hole 51b of the drawing piece 51 from the tip end 23a. Subsequently, the rod-shaped material 23 is pressed by the squeezing pin 52 in the direction in which the squeezing hole 51a is located (the direction indicated by the arrow B). Then, the tip portion 23a of the rod-shaped material 23 flows into the drawing hole 51a having an inner diameter smaller than the insertion hole 51b by plastic deformation, and the shaft of the bolt is formed. Finally, the rod-shaped material 23 is discharged from the drawing piece 51 by moving the knockout pin 53 inserted from the drawing hole 51a side of the drawing piece 51 in the direction in which the insertion hole 51b is located (the direction shown by the arrow C). .

  As shown in FIG. 5, the preforming step is to use the receiving piece 61 and the preforming punch 62 to bring the other end 23b of the rod-shaped material 23 formed in the drawing step closer to the completed shape of the head of the bolt. It is a process of. The receiving piece 61 has an insertion hole 61a which is the tip portion 23a of the rod-shaped material 23, that is, the insertion hole 61a is set to have an inside diameter capable of inserting a shaft portion of a bolt and not allowing the other end portion 23b to be inserted. The other end 23 b of the rod-shaped material 23 projects from the receiving piece 61.

  Further, the preforming punch 62 has a preforming recess 62a on an end surface. The preforming recess 62a of the preforming punch 62 is pressed toward the other end 23b of the rod-shaped material 23 (in the direction indicated by arrow B). Thereby, the other end 23b of the rod-shaped material 23 is deformed so as to expand along the inner peripheral surface of the preformed concave portion 62a so that the head of the bolt is preformed. Finally, the rod-shaped material 23 is discharged from the receiving piece 61 by moving the knockout pin 63 in the direction indicated by the arrow C.

  As shown in FIG. 6, the finishing step is a step for completing the other end 23b of the rod-shaped material 23 preformed using the receiving piece 71 on the head of the bolt. It has an insertion hole 71a drilled on the central axis, and a stepped portion 72b is formed at the opening of the insertion hole 71a. The rod-shaped material 23 is inserted into the insertion hole 71a from the tip 23a, and the other end 23b is hooked on the stepped portion 72b. In this state, the other end 23b of the bar-shaped material is pressed by the punch 72, and the other end 23b of the bar-shaped material 23 is plastically deformed so as to fill the stepped portion 72b, whereby the head 11 is completed. . Finally, by moving the knockout pin 73 in the direction indicated by the arrow C, the bolt formed with the head (the other end 23b of the rod-shaped material 23) and the shaft (the tip 23a of the rod-shaped material 23) is received. Is discharged from

  Here, in the end face correcting step, the full angle θ of the tapered portion 31b of the insertion hole 31a is set to 20 °. As shown in FIG. 2A, the other end 23b of the rod-shaped material 23 is pushed into the tapered portion 31b until the cross-sectional reduction ratio φ of the other end surface of the rod-shaped material 23 becomes 57%. As shown in (b), the distal end portion 23a of the rod-shaped material 23 is pushed into the tapered portion 31b until the cross-sectional reduction rate φ of the distal end surface becomes 66%.

  Further, the full angle θ and the cross-sectional reduction rate φ are not limited to the numerical values described above, and the full angle θ of the tapered portion 31b is set to 0 <θ ≦ 32 ° and is inserted into the tapered portion 31b. The cross-sectional reduction ratio φ of both end surfaces of the rod-shaped material 23 reduced in diameter by this is set to 60% ≦ φ ≦ 80%. Within this numerical range, the end surfaces of both end portions 23a and 23b of the rod-shaped material 23 become smooth, but if the diameter is reduced within this numerical range, the central portion of the end surface is dented in the process of plastic deformation and does not become smooth. A phenomenon occurs. As described above, according to the bolt manufacturing method of the present invention, both end faces of the rod-shaped material 23 are smoothed to some extent by the end face correcting step, and then both end faces of the rod-shaped material are finished smoothly by the compression process. As described above, before forming the head and the shaft of the bolt, both end surfaces of the rod-shaped material 23 are finished smoothly, and then the head and the shaft of the bolt are formed by forging. A bolt having excellent smoothness on the surface and the end face of the shaft can be manufactured.

23 rod-shaped material 31 receiving piece 31a insertion hole 31b taper portion

Claims (2)

A cutting step of cutting the wire into a predetermined length,
An end face correction process for smoothing both end faces by reducing the diameter of both end parts of the cut rod-shaped material according to the tip,
A compression process that finishes both end surfaces smoothly by compressing the rod-shaped material from both end surfaces,
A drawing process of forming the shaft by drawing the tip of the rod-shaped material;
A preforming step of pressing the other end of the rod-shaped material to preform the head,
A finishing step of forging the head by pressing the other end of the preformed rod-shaped material,
A method of manufacturing a bolt, characterized in that a bolt having smooth both end faces is manufactured by the method. In the end face correcting step, a receiving piece having an insertion hole into which a rod-shaped material can be inserted is used, and the inner peripheral surface of the insertion hole has a tapered portion whose diameter is reduced in accordance with the depth, and the full angle θ of the tapered portion is 0. <Θ ≦ 32 °, and the cross-sectional reduction rate φ of both end faces of the rod-shaped material reduced in diameter by being inserted into the tapered portion is set to be 60% ≦ φ ≦ 80%. The method for manufacturing a bolt according to claim 1.

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