JP2012077837A - Bolt, screw roll-forming die, and roll-forming method of bolt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make constant a fastening axial force by which a nut actually fastens a female screw by specifying an abutting position between a male screw and the female screw, and to reduce the manufacturing cost of a roll-forming tool by simplifying the shape of the male screw.SOLUTION: For example, when an angle A1 of a valley 5 formed of opposing slopes 4a inside an effective diameter D1 is set at 57°, and when an angle of a valley 6 formed of slopes 4b at the outside of the effective diameter D1 is set at a wide angle of 63°, the female screw 7 line-contacts with the male screw 2 on the effective diameter D1 when screwed with a nut 3 in which an angle of a mountain of the female screw 7 is set at 60°, the fastening axial force by which the bolt actually fastens the female screw by specifying an abutting position of the male screw 2 of the bolt 1 and the female screw 7 of the nut 3 is made constant, and thereby the manufacturing cost of a round die 21 which is the roll-forming tool can be reduced by simplifying the shape of the male screw 2.

Description

  The present invention relates to a bolt, and more particularly, to a bolt technology that can make the tightening axial force with which a bolt actually tightens a female screw constant.

  If the force that feeds the tap forming the female thread of the nut is too large or too small and the tap feed does not match the pitch, the shape of the thread formed on the nut will collapse, and the thread of the tap will be accurately It cannot be projected and may have a ridged screw. Moreover, the direction of the bolt screwed into the nut does not necessarily coincide with the direction of the tap that cuts the nut. If the screw is loose or the direction of the bolt that is screwed into the nut is different, even if tightened with the same torque, the tightening axial force with which the bolt actually tightens the female screw will vary. There was a problem that management was impossible.

  Patent Document 1 describes a bolt that solves such a problem. In the bolt described in Patent Document 1, adjacent engaging protrusions face each other in a V shape, and the opening angle is set in a range of 60 ° ± 20 ′. The lower thread slope from the adjacent engagement protrusion surface to the valley diameter is opposed in a V shape, the opening angle is set in the range of 45 ° to 58 °, and the outer diameter from the adjacent engagement protrusion surface The upper thread slope reaching the side faces in a V shape, and the opening angle is set in the range of 62 ° to 75 °.

  The engaging protrusion is provided so as to swell outside the thread slope of the bolt, and the engagement protrusion comes into contact with the thread slope of the female thread when the nut is tightened into the bolt. The abutting position between the female screw of the nut and the male screw of the bolt is specified as the engaging protrusion, and the tightening axial force for actually tightening the female screw by the bolt is made constant.

JP 2009-299884 A

  In the bolt described in Patent Document 1, the engagement protrusion contacting the thread slope of the female thread is provided so as to swell outside the thread slope, and further, the lower thread extending from the engagement protrusion to the valley diameter. Since the slope and the upper thread slope extending from the engagement protrusion surface to the outer diameter side are formed, there is a problem that the shape of the rolling tool for forming the male thread of the bolt becomes complicated and the manufacturing cost increases.

  The object of the present invention is to solve such a problem. The abutting position between the male screw of the bolt and the female screw of the nut is specified, and the tightening axial force at which the bolt actually tightens the female screw is made constant. To reduce the production cost of the rolling dies.

  In order to solve this problem, the invention according to claim 1 is directed to a male screw formed on a bolt, wherein the angle of the valley formed by the inclined surfaces facing each other is greater than the effective diameter of the valley bottom formed inside the effective diameter. The outer portion of the is formed larger. According to a second aspect of the present invention, in the thread rolling die provided with a male threaded portion that forms a male thread on the bolt, the male threaded portion has a trough angle greater than the angle of the peak. In the invention of claim 3, the screw is rolled into the blank by pressing and rotating toward the center of the blank using a screw rolling die having a trough angle larger than the crest angle of the male screw. This is a method of rolling a bolt.

  According to the first aspect of the present invention, in the male screw formed on the bolt, the angle of the valley formed by the inclined surfaces facing the male screw is greater in the outer portion of the effective diameter than in the valley bottom portion formed inside the effective diameter. Therefore, for example, the angle of the valley formed by the slopes facing each other inside the effective diameter is set to 57 °, and the angle of the valley formed by the slopes outside the effective diameter is as wide as 63 °. When the angle is set, the slope of the female thread does not come into contact with the slope of the inner trough of the effective diameter when the nut whose thread angle is set to 60 ° is screwed. The internal thread is not in contact with the slope of the outer trough of the effective diameter, and the internal thread is in line contact with the external thread on the effective diameter, so the position of contact between the external thread of the bolt and the internal thread of the nut must be specified. The bolt is actually female Flip with the axial force constant tightening tightening the, it is possible to manufacture cost reduction of rolling die the shape of the male thread to simplify.

It is sectional drawing of the thread part of the volt | bolt which concerns on one Embodiment of this invention. It is sectional drawing of the state which the volt | bolt and the nut meshed | engaged. 2 is a schematic view of a biaxial screw rolling round die 21. FIG. 3 is a cross-sectional view of a threaded portion of a round die 21. FIG.

  Hereinafter, a bolt according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a thread portion of a bolt 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the bolt 1 and the nut 3 engaged with each other. The effective diameter D1 is a virtual cylindrical diameter such that the width of the thread groove is equal to the width of the thread.

  A trough is formed by the slopes 4a and 4b facing the male screw 2, but the slope 4b is more than the angle A1 of the trough 5 formed inside the male screw effective diameter D1 (hereinafter referred to as the effective diameter D1) by the slope 4a. As a result, the angle B1 of the valley 6 formed outside the effective diameter D1 is formed larger. In the present embodiment, the angle A1 of the valley 5 formed by the slope 4a facing the inside of the effective diameter D1 is set to 57 °, and the angle B1 of the valley 6 formed by the slope 4b facing the outside of the effective diameter D1 is set. Is set to 63 °. The slope 4b at the outer portion of the effective diameter D1 is inclined in a state of being opened outward from the valley portion 5 formed by the slope 4a at the inner portion of the effective diameter D1.

  The angle A1 of the valley portion 5 formed by the slopes 4a facing each other inside the effective diameter D1 is set to 57 °, and the angle B1 of the valley portion 6 formed by the slope 4b outside the effective diameter D1 is as wide as 63 °. Therefore, when the nut 3 whose angle of the crest portion of the female screw 7 is set to 60 ° is screwed, the inclined surface 8 of the female screw 7 is the inner valley portion of the effective diameter D1, as shown in FIG. 6 and the female screw 7 does not contact the inclined surface 4b of the outer trough portion 6 having the effective diameter D1. The female screw 7 is in line contact with the male screw 2 on the effective diameter D1. 2 indicates the effective diameter of the nut 3. In addition, the bolt 1 in which the slope 4b of the outer portion exceeds the position of the effective diameter D1 and reaches the inner portion of the effective diameter D1 passes through the stop gauge of the screw limit gauge and is rejected.

  In this way, the contact position between the female screw 7 of the nut 3 and the male screw 2 of the bolt 1 can be specified on the effective diameter D1, so that the tightening axial force that actually tightens the female screw by further limiting the contact position. Can be stabilized. Furthermore, the inclined surfaces 4a and 4b facing the male screw 2 have a simplified shape that is simply bent at the position of the effective diameter D1, and the manufacturing cost of the thread rolling die can be reduced.

  In the present embodiment, the angle A1 of the valley portion 5 formed by the facing slope 4a inside the effective diameter D1 is set to 57 °, and the valley portion 6 formed by the facing slope 4b outside the effective diameter D1. The angle B1 is set to 63 °, but is not limited to this.

  Next, the biaxial screw rolling round die 21 will be described as an embodiment of the screw rolling die. FIG. 3 is a schematic view of the biaxial thread rolling round die 21, and FIG. 4 is a cross-sectional view of the threaded portion of the round die 21. For example, high-speed steel is used for the biaxial screw rolling round die 21 (hereinafter referred to as the round die 21), and the Rockwell hardness is 64 to 65.5. By pressing and rotating the round die 21 toward the center of the blank 22, the blank 22 is plastically deformed to form the male screw 2.

  The thread portion is formed such that the angle of the valley portion 24 is larger than the angle of the peak portion 23. For example, the angle F1 of the valley portion 24 formed by the slopes 25a facing each other inside the effective diameter D1 is 63 °, and the angle E1 of the valley portion formed by the slopes 25b facing each other outside the effective diameter D1 is 57 °. The As a result, the thread slope 8 on the female screw 7 side shown in FIG. 2 makes line contact on the effective diameter D1 of the male screw 2 and does not contact the inner part and the outer part of the effective diameter D1, so that the male screw 2 of the bolt 1 and the nut 3 The abutting position with the female screw 7 is specified, the tightening axial force at which the bolt actually tightens the female screw is made constant, the shape of the male screw 2 is simplified, and the manufacturing cost of the round die 21 can be reduced. In this embodiment, the thread rolling round die has been described. However, the present invention is not limited to this, and the present invention is applicable to a thread rolling flat die, a thread rolling segment die, and the like.

  Thus, in the male screw 2 formed on the bolt 1, the angles A1 and B1 of the valley formed by the inclined surfaces 4a and 4b facing the male screw 2 are valleys that are valley bottoms formed inside the effective diameter D1. Since the valley portion 6 of the outer portion of the effective diameter D1 is formed larger than 5, the angle A1 of the valley portion 5 formed by the inclined surface 4a facing the inside of the effective diameter D1 is set to 57 °, for example. If the angle of the valley 6 formed by the slope 4b outside the effective diameter D1 is set to a wide angle of 63 °, the nut 3 having the angle of the peak of the female screw 7 set to 60 ° is screwed together. The slope 8 of the female screw 7 does not contact the slope 4a of the inner valley portion 5 having the effective diameter D1, and the slope 8 of the female screw 7 contacts the slope 4b of the outer valley portion 6 having the effective diameter D1. Of course, the internal thread 7 has an effective diameter D. Since it is in line contact with the male screw 2 at the top, the abutment position between the male screw 2 of the bolt 1 and the female screw 7 of the nut 3 is specified, and the tightening axial force for actually tightening the female screw is made constant. The manufacturing cost of the round die 21 which is a rolling die can be reduced.

  Furthermore, in the round die 21 provided with the threaded portion that forms the male screw 2 on the bolt 1, the threaded portion has an angle of the trough portion 24 larger than that of the peak portion 23. The male screw 2 is formed in which the angle A1 of the valley 5 formed by the slope 4a is set to 57 °, and the angle of the valley 6 formed by the slope 4b outside the effective diameter D1 is set to a wide angle of 63 °. When the nut 3 in which the angle of the crest of the female screw 7 is set to 60 ° is screwed into the male screw 2, the inclined surface 8 of the female screw 7 is brought into the inclined surface 4a of the inner valley portion 5 having the effective diameter D1. There is no contact, and the inclined surface 8 of the female screw 7 does not contact the inclined surface 4b of the outer trough portion 6 of the effective diameter D1, and the male screw 2 that makes line contact with the female screw 7 on the effective diameter D1 can be formed. , Simplify the shape of the thread It can be a round die 21.

  Furthermore, since the screw is rolled into the blank 22 by pressing and rotating toward the center of the blank 22 using the round die 21 in which the angle of the valley portion 24 is larger than the angle of the peak portion 23 of the male screw 2, for example, The angle A1 of the valley portion 5 formed by the slopes 4a facing each other inside the effective diameter D1 is set to 57 °, and the angle of the valley portion 6 formed by the slope 4b outside the effective diameter D1 is as wide as 63 °. Can be formed, and when the nut 3 with the angle of the crest of the female screw 7 set to 60 ° is screwed into the male screw 2, the slope 8 of the female screw 7 is effective for the male screw 2. There is no contact with the inclined surface 4a of the inner valley portion 5 having the diameter D1, and the inclined surface 8 of the female screw 7 does not contact with the inclined surface 4b of the outer valley portion 6 having the effective diameter D1, so that the female screw 7 and the male screw 2 are effective. Line tangent on diameter D1 It can be.

1 bolt 2 male screw 3 nut
4a, 4b, 8, 24a, 24b Slope 5,6 Valley 7 Female thread 21 Round die 22 Blank 23 Mountain 24 Valley

Claims (3)

In the male thread formed on the bolt,
The bolt is characterized in that the angle of the valley formed by the inclined surfaces facing each other of the male screw is formed larger in the outer portion of the effective diameter than in the valley bottom portion formed inside of the effective diameter. In a thread rolling die with a male thread part that forms a male thread on the bolt,
A thread rolling die characterized in that the male thread part has a valley part angle larger than a peak part angle. A method for rolling a bolt, in which a screw is rolled into a blank by pressing and rotating toward the center of the blank 22 using a screw rolling die having a trough angle larger than a crest angle of a male screw.

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