BOLT

Abstract

The objective is to provide a bolt which can more effectively suppress occurrence of seizure due to both oblique insertion and biting of foreign substances. The bolt includes a tapered surface, a guide portion, and a threaded portion in order from a distal end side and further includes a plurality of recesses provided on the tapered surface and a plurality of cutout portions provided at a distal end portion of the threaded portion.

Claims

1.-7. (canceled)

8. A bolt comprising a tapered surface, a guide portion, and a threaded portion in order from a distal end side, the bolt further comprising a plurality of recesses provided on the tapered surface, and a plurality of cutout portions provided at a distal end portion of the threaded portion.

9. The bolt according to claim 8, wherein the guide portion exists on extension of a same helix as a thread root of the threaded portion and is formed between a groove portion formed at a distal end portion of the threaded portion so that a depth in a radial direction is deeper than the thread root and a surface end position on a base end side of the tapered surface, the guide portion has a shape extending in a direction around an axis of the bolt from a starting end portion to a terminal end portion and expanding in an axial direction of the bolt in transition from the starting end portion to the terminal end portion, the starting end portion being an intersection between the surface end position on the base end side of the tapered surface and a helix according to the groove portion, a diameter of the guide portion is smaller than a minor diameter of the internal thread corresponding to the bolt and larger than a diameter of the thread root of the bolt, the guide portion and the threaded portion are continuously formed such that the distal end portion of the threaded portion overlaps with the terminal end portion of the guide portion, and in a region of the guide portion, an angle in the direction around the axis of the bolt from the starting end portion is in the range of 90 to 360.

10. The bolt according to claim 8, wherein in the tapered surface, an angle with respect to an axis of the bolt is in the range of 15 to 45, and a diameter at a distal end of the bolt is 0.7 to 0.9 times a nominal diameter of the bolt.

11. The bolt according to claim 8, wherein in a distal end portion of the threaded portion, a ridge has a complete height when the angle in the direction around the axis of the bolt is in the range of 30 to 180.

12. The bolt according to claim 8, wherein a radial dimension of the bolt in the guide portion with reference to a bottom of the groove portion is 0.4 to 0.6 times the height of the ridge in the threaded portion with reference to a bottom of the thread root of the bolt.

13. The bolt according to claim 8, wherein the recesses are provided at two to eight positions in the direction around the axis of the bolt, each of the recesses has a depth of 0.2 to 1 mm, and a width in a tangential direction in the range of 20% to 30% with respect to the nominal diameter of the bolt.

14. The bolt according to claim 8, wherein the cutout portions are provided at two to eight positions in the direction around the axis of the bolt in the range of 1 to 5 pitches in the axial direction of the bolt, a range of an angle of each of the cutout portions with respect to the axis of the bolt is 15 to 80, and a width of each of the cutout portions in a circumferential direction of a thread major diameter circle is 2% to 10% with respect to the nominal diameter of the bolt.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0023] FIG. 1 is a schematic view of a bolt of the present embodiment.

[0024] FIG. 2(a) is an enlarged view of a portion II in FIG. 1, and FIG. 2(b) is a view showing a tapered surface in the bolt of the present embodiment.

[0025] FIG. 3 is a view showing the vicinity of a rising edge of a threaded portion in the bolt of the present embodiment.

[0026] FIG. 4 is a view showing a positional relationship between a guide portion, a threaded portion, and a cutout portion in the bolt of the present embodiment.

[0027] FIG. 5 is a view showing a state in which a tilt angle of the bolt of the present embodiment with respect to an axis of an internal thread is larger than an attitude correction limit.

[0028] FIG. 6(a) is a view showing a state in which the bolt tilts in a state in which the tilt angle of the bolt of the present embodiment with respect to the axis of the internal thread is smaller than the attitude correction limit, and FIG. 6(b) is a view showing a state in which the tilt is corrected in the state in which the tilt angle of the bolt of the present embodiment with respect to the axis of the internal thread is smaller than the attitude correction limit.

[0029] FIG. 7 is a view showing a state in which foreign substances are removed when the bolt of the present embodiment is fastened.

DESCRIPTION OF EMBODIMENT

[0030] An embodiment of the present invention will be described below.

[0031] As shown in FIG. 1, a bolt 1 of the present embodiment includes a head 2 and a shank 3 arranged on a same axis Ax. As shown in FIG. 2(a), the bolt 1 includes, at a distal end portion of the shank 3, a tapered surface 11, a guide portion 12, and a threaded portion 13 having a ridge 13A and a thread root 13B in order from the distal end side.

[0032] In the following description, a base end side refers to the head 2 side of the bolt 1 in the direction of the axis Ax, and a distal end side refers to the shank 3 side of the bolt 1 in the direction of the axis Ax. In addition, a circumferential direction refers to a direction around the axis of the bolt 1, and a radial direction refers to a radial direction of the bolt 1.

[0033] As shown in FIGS. 2(a) and (b), the tapered surface 11 is formed so as to have a smaller diameter toward the distal end side.

[0034] In the tapered surface 11, an angle 1 of the bolt 1 with respect to the axis Ax is desirably set in the range of 15 to 45. Further, in the tapered surface 11, a diameter d1 at the distal end of the bolt 1 is desirably set to 0.7 to 0.9 times a nominal diameter d3 of the bolt 1.

[0035] In the tapered surface 11 thus set, it is possible to prevent interference between the distal end of the bolt 1 and an entrance of the internal thread.

[0036] On the tapered surface 11, a plurality of recesses 111 are provided.

[0037] It is desirable to provide the recesses 111 at two to eight positions in the circumferential direction. In the present embodiment, the recesses 111 are provided at six positions. An interval between the recesses 111 in the circumferential direction is not particularly limited, and is usually set to be equal intervals.

[0038] It is desirable that the depth of the recess 111 with respect to the tapered surface 11 be in the range of 0.2 to 1 mm.

[0039] A width w1 of the recess 111 in a tangential direction is desirably in the range of 20% to 30% with respect to the nominal diameter d3 of the bolt 1.

[0040] The recess 111 thus set makes it possible to remove relatively large foreign substances such as spatters deposited on the inside of the internal thread corresponding to the bolt 1 when fastening the bolt 1.

[0041] As shown in FIGS. 2(a) and 4, a plurality of cutout portions 131 are provided at a distal end portion of the threaded portion 13. In FIG. 4, in order to reduce the complexity of appearance, the recess 111 is omitted.

[0042] It is desirable that the cutout portions 131 be provided at two to eight positions in the circumferential direction in the range of 1 to 5 pitches in the direction of the axis Ax of the bolt 1. In the present embodiment, the cutout portions 131 are provided at four positions in the circumferential direction in the range of 1 pitch in the direction of the axis Ax of the bolt 1. An interval between the cutout portions 131 in the circumferential direction is not particularly limited, and is usually set to be equal intervals.

[0043] It is desirable that an angle 2 of the cutout portion 131 with respect to the axis Ax of the bolt 1 be in the range of 15 to 80.

[0044] A width w2 of the cutout portion 131 in the circumferential direction of a thread major diameter circle is desirably 2% to 10% with respect to the nominal diameter d3 of the bolt 1.

[0045] The cutout portion 131 thus set makes it possible to remove a thick film (hereinafter also referred to as coated thick film for short) formed by painting applied to the internal thread when fastening the bolt 1 and makes it possible to minimize a reduction in tensile strength of the bolt 1.

[0046] As shown in FIGS. 2(a) and 3, a groove portion 14 is formed at the distal end portion of the threaded portion 13 such that the depth in the radial direction is slightly deeper than that of the thread root 13B of the threaded portion 13.

[0047] The guide portion 12 is formed between the groove portion 14 and a surface end position on the base end side of the tapered surface 11.

[0048] FIG. 3 shows the guide portion 12 developed in a plane. The guide portion 12 is formed between a line 12c showing a helix according to the groove portion 14 and a line 12d showing the surface end position on the base end side of the tapered surface 11. A starting end portion 12a of the guide portion 12 is provided at an intersection between the line 12c (helix according to the groove portion 14) and the line 12d (surface end position on the base end side of the tapered surface 11). A terminal end portion 12b of the guide portion 12 is provided at a position extending clockwise from the starting end portion 12a in the circumferential direction. The guide portion 12 has a shape in which the guide portion 12 expands toward the base end side in transition from the starting end portion 12a to the terminal end portion 12b.

[0049] By setting in this manner, the starting end portion 12a of the guide portion 12 is located toward the base end to be deviated from the extension of a helix 13C passing through the crest of the ridge 13A of the threaded portion 13. Consequently, as shown in FIG. 5, in a case where the bolt 1 is inserted in a state in which the axis Ax of the bolt 1 tilts with respect to the axis Ax2 of the internal thread and the bolt 1 is to be tightened, when a tilt angle b1 of the bolt 1 is larger than an attitude correction limit, the guide portion 12 does not forcibly catch the internal thread, and the bolt 1 easily idles, so that it is possible to suppress occurrence of seizure due to oblique insertion.

[0050] As shown in FIG. 2(a), the groove portion 14 exists on the extension of the same helix as the thread root 13B of the threaded portion 13. The height (radial dimension) of the guide portion 12 with reference to a bottom of the groove portion 14 is desirably 0.4 to 0.6 times the height of the ridge 13A with reference to a bottom of the thread root 13B.

[0051] A diameter d2 of the guide portion 12 is slightly smaller than the minor diameter of the internal thread corresponding to the bolt 1 and slightly larger than a diameter d4 of the thread root 13B of the bolt 1. Since the bolt 1 having the guide portion 12 thus set can be prevented from entering an internal thread hole too much when inserted in a state where the bolt 1 tilts with respect to the axis of the internal thread, it is possible to reduce the probability of occurrence of biting by the bolt 1 due to pitch deviation between an external thread and the internal thread.

[0052] As shown in FIG. 4, a region of the guide portion 12 is in a range of an angle 3 in the circumferential direction between the starting end portion 12a and the terminal end portion 12b. At the distal end portion of the threaded portion 13, a starting end portion of the ridge 13A overlaps with the terminal end portion 12b of the guide portion 12, and the guide portion 12 and the threaded portion 13 are continuously formed.

[0053] In view of the structure of the bolt 1, the circumferential angle 3 indicating the region of the guide portion 12 is necessarily 90 to 360.

[0054] At the distal end portion of the threaded portion 13, the height of the ridge 13A gradually increases in the circumferential direction from the starting end, and the ridge 13A reaches the complete height (the same height as the other ridges 13A) at an angle 4 (hereinafter referred to as rising angle 4) in the circumferential direction. The value of the rising angle 4 is desirably 30 to 180.

[0055] The value of the rising angle 4 of a general external thread is 360 or more. That is, the threaded portion 13 is set so that the ridge 13A has the complete height at an earlier stage than a general external thread. By setting in this manner, it is possible to make a force for correcting deviation of the axis between the bolt and the internal thread in the bolt 1 larger than the general external thread.

[0056] FIG. 5 shows a case where the tilt angle b1 of the axis Ax of the bolt 1 with respect to the axis Ax2 of the internal thread is larger than the attitude correction limit. In this case, the guide portion 12 does not come into contact with the internal thread, and since the starting end portion 12a of the guide portion 12 is positionally deviated from the extension of the helix 13C passing though the crest of the ridge 13A toward the base end, the guide portion 12 does not forcibly catch the internal thread. The distal end portion of the threaded portion 13 is formed so as to overlap with the terminal end portion 12b of the guide portion 12. Thus, unless the guide portion 12 forcibly catches the internal thread, the probability that the threaded portion 13 of the bolt 1 meshes with the internal thread with their pitches shifted from each other is small, and the bolt 1 is liable to idle, so that the probability of occurrence of seizure is small.

[0057] FIG. 6(a) shows a case where a tilt angle b2 of the axis Ax of the bolt 1 with respect to the axis Ax2 of the internal thread is smaller than the attitude correction limit. In this case, the guide portion 12 comes into contact with the internal thread to enter a state where the internal thread can be caught. When an attempt is made to tighten the bolt 1 in this state, the internal thread is guided from the terminal end portion 12b of the guide portion 12 to the starting end portion of the threaded portion 13, and as shown in FIG. 6(h), the attitude of the bolt 1 is corrected so that the pitch of the threaded portion 13 is matched with the pitch of the internal thread, so that normal fastening can be performed.

[0058] The attitude correction limit value is set to be preferably less than 10, more preferably 8 or less, still more preferably 6 or less. When the attitude correction limit value is 10 or more, the incidence of seizure increases.

[0059] When the bolt 1 can be normally fastened without idling, as shown in FIG. 7, the recess 111 on the tapered surface 11 is caught in the bolt 1 in a rotating state during fastening to peel a spatter Sp which is a relatively large foreign substance deposited on the inside of the internal thread, or the spatter Sp is impacted by repeated contacts with the recesses 111 to be removed.

[0060] A coated thick film Cf formed inside the internal thread is removed by being scraped with the cutout portion 131 of the threaded portions 13 in the bolt 1 in the rotating state during fastening.

[0061] As described above, foreign substances such as the spatter Sp and the coated thick film Cf are removed from the inside of the internal thread by the recess 111 and the cutout portions 131. As a result, biting of foreign substances between the bolt 1 and the internal thread during fastening is prevented, so that occurrence of seizure is suppressed.

[0062] Since the main point of the present invention lies in a shape near the distal end of the bolt, although the shape of a head of the bolt is not particularly limited and is a hexagonal prism shape in FIG. 1, the shape of the head may be, for example, a round head with a hexagon socket, a cylindrical shape, an inverted truncated cone shape, a ring shape, a butterfly shape, or the like. Alternatively, the head 2 may be omitted, and the bolt 1 may be a stud bolt.

[0063] The material of the bolt 1 is not particularly limited, and examples thereof include steel, stainless steel, alloy such as aluminum alloy and titanium alloy, synthetic resins, and the like, depending on the application.

REFERENCE SIGNS LIST

[0064] 1 bolt [0065] 11 tapered portion [0066] 111 recess [0067] 12 guide portion [0068] 13 threaded portion [0069] 131 cutout portion [0070] 14 groove portion