JP2020051524A - Male screw body with cap, male screw body, and cap - Google Patents

Abstract

To provide means which can be fastened by predetermined torque without limiting a fastened object and producing wastes and enables a head portion to be set to a given phase after fastening with a simple structure.SOLUTION: A male screw body 1 with a cap has: a male screw body 10 having a shaft part in which a male screw spiral groove is formed on an outer peripheral surface and a head part provided at one end of the shaft part; and a cap 20 attached to the head part and enclosing the outer peripheral surface of the head part. The male screw body 1 with the cap includes a relative rotation restriction mechanism between the head part and the cap. The rotation restriction mechanism restricts relative rotation of the cap relative to the head part. When torque higher than or equal to a predetermined value acts on the cap, the cap may rotate relative to the head part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a male screw body with a cap, a male screw body, and a cap.

  2. Description of the Related Art Conventionally, a screw fastening structure including a male screw body (bolt or the like) formed with a male screw and a female screw body (nut or the like) formed with a female screw has been used for fixing or positioning various members in various fields. As the male screw body, a polygonal shape such as a hexagonal shape for engaging with a fastening tool, a round shape having a cross shape on the top surface, and the like have been proposed (for example, Patent Documents). 1). Further, as another male screw body, there is a male screw body having a head formed with a slot or a hexagonal hole on the top surface, and a fastening tool is engaged with the outer shape of the head of such a male screw body or a hole on the top surface. ing.

  Further, as a male screw-shaped screw fastener (male screw body) capable of controlling torque when fastening a male screw body, a torcia-type bolt is disclosed (for example, see Patent Document 2). This torcia-type bolt manages the tightening torque by applying a torque to the extent that the pin tail is twisted off during the tightening operation.

JP 2018-052279 A JP 2011-47479 A

  However, when the male screw body described in Patent Literature 1 described above is fastened to the fastening body, the head cannot be set to an arbitrary direction (phase). For example, when a fastened object is fastened with a plurality of male screw bodies for the purpose of decoration, it is difficult to align the heads of the male screw bodies in the same phase. For example, even if the same plate is used, the optimum tightening torque of each male screw body may differ depending on the fastening location, so taking into account the tightening torque, the head of each male screw body after fastening should be aligned. There is a problem that it is very difficult to set a predetermined phase.

  Further, when the torcia-type bolt described in Patent Document 2 described above is used, the pin tail that has been twisted at the time of fastening becomes waste. The torcia bolt can be fastened to a nut or a member having a penetrated female screw hole, but cannot be used for a member having a non-through female screw hole because the pin tail cannot be held down. There is a problem that the fastening target is limited.

  The present invention has been made in earnest by the inventors of the present invention in view of the above problems, and has a simple structure, which eliminates waste such as pin tails and enables fastening with a predetermined torque without limiting the fastening object. It is another object of the present invention to provide a means for setting the head to an arbitrary phase even after fastening.

  A male screw body with a cap according to the present invention includes a male screw body having a shaft portion having a male screw spiral groove formed on an outer peripheral surface thereof and a head portion provided at one end of the shaft portion, and an outer peripheral surface of the head mounted on the head portion. A surrounding cap, and a male screw body with a cap, comprising a relative rotation regulating mechanism between the head and the cap, wherein the rotation regulating mechanism regulates the relative rotation of the cap with respect to the head, and the cap has a predetermined or more When a torque is applied, the cap can rotate relative to the head.

  Further, the male screw body with a cap has a first protruding portion in which the relative rotation restricting mechanism protrudes radially outward from the outer peripheral surface of the head, and a second protruding portion protruding radially inward from the inner peripheral surface of the cap. The first protruding portion and the second protruding portion intersect with each other, and at least one of the first protruding portion and the second protruding portion is press-contacted so as to be elastically deformable.

  Further, the male screw body with the cap is configured such that the relative rotation restricting mechanism has a protruding portion protruding radially outward from the outer peripheral surface of the head, and is pressed so that the protruding portion can elastically deform the inner peripheral surface of the cap. It is characterized by doing.

  Further, the male screw body with a cap has an inner cylinder in which the cap abuts the outer peripheral surface of the head, and an outer cylinder having a larger diameter than the inner cylinder. Characterized in that it can be elastically deformed in the gap between the outer cylinder and the outer cylinder.

  In addition, the male screw body with the cap is configured such that the relative rotation restricting mechanism has a protruding portion protruding radially inward from the inner peripheral surface of the cap, and the protruding portion abuts on the outer peripheral surface of the head and can be elastically deformed. It is characterized by the following.

  Further, the male screw body of the present invention has a shaft part having a male screw spiral groove formed on the outer peripheral surface, and a head part provided at one end of the shaft part, the outer circumference of which is covered by a separate cap. Wherein the head has a pressing portion that can slidably contact the inner peripheral surface of the cap with a pressing force of a predetermined value or more and regulates relative rotation of the cap relative to the head.

  Further, the male screw body of the present invention is characterized in that the pressing portion is a rib provided on the outer peripheral surface of the head in the axial direction and / or the circumferential direction.

  Further, the male screw body of the present invention is characterized in that the rib is provided in a direction crossing the rib formed on the inner peripheral surface of the cap.

  Further, the male screw body of the present invention is characterized in that the head has an outer peripheral shape in which the distance from the axial center varies along the circumferential direction.

  Further, the cap of the present invention is a cap that is attached to the head of the male screw body and surrounds the outer peripheral surface of the head, and protrudes radially inward on the inner peripheral surface, and has a pressing portion that presses the head. The pressing portion can slide on the head while urging the head with a predetermined pressing force.

  Further, the cap of the present invention is characterized in that the pressing portion is a rib provided on the inner peripheral surface in the axial direction and / or the circumferential direction.

  Further, the cap of the present invention is characterized in that the rib is provided in a direction crossing the rib formed on the outer peripheral surface of the head.

  Further, the cap according to the present invention is characterized in that the inner peripheral surface has an outer peripheral shape whose distance from the axial center varies along the circumferential direction.

  ADVANTAGE OF THE INVENTION According to this invention, although it is a simple structure, it does not generate waste, can be fastened with a predetermined torque without limiting the fastening object, and can set the head part to an arbitrary phase even after fastening. Can be provided.

It is a figure showing the male screw object with a cap concerning this embodiment. It is a front sectional view showing the male screw object with a cap concerning this embodiment. It is a figure showing the male screw object concerning this embodiment. It is a figure showing the cap concerning this embodiment. It is sectional drawing which shows the male screw body with a cap fastened to the to-be-fastened member. It is a figure which shows a mode that the caps of which phases are not aligned were aligned. It is a figure showing other shapes of the head of a male screw object. It is a figure showing other head side ribs and cap side ribs. It is a figure showing other separation regulation mechanisms. It is a figure showing other separation regulation mechanisms. 5A and 5B show another male screw body, in which FIG. 5A is a plan view and FIG. It is sectional drawing which shows another cap.

  Hereinafter, an embodiment of a male screw body with a cap of the present invention will be described with reference to the drawings. FIG. 1 shows a male screw body 1 with a cap according to the present embodiment, in which (a) is a plan view and (b) is a front view. FIG. 2 is a front sectional view showing the male screw body 1 with a cap according to the present embodiment. The male screw body 1 with a cap is formed by mounting a cylindrical cap 20 having a bottom on the head 14 of the male screw body 10.

  3A and 3B show the male screw body 10 according to the present embodiment, wherein FIG. 3A is a plan view and FIG. 3B is a front view. The male screw body 10 includes a shaft 12 and a head 14. The shaft portion 12 has a male screw portion 16 in which a male screw spiral groove is formed from the base end side to the distal end side. The head 14 is located on the base end side of the shaft portion 12 and has a substantially circular outer peripheral surface.

The head 14 has a head-side rib 18 (first protruding portion) that is a band-shaped row-shaped projection that protrudes radially outward from the outer peripheral surface and is arranged in two rows along the axial direction. The head-side rib 18 has an annular shape, and the longitudinal direction of the band of the protrusion coincides with the circumferential direction.
When the cap 20 is mounted on the head 14, the head-side ribs 18 are elastically deformable and fit so that they come into contact with the cap-side ribs 26 (see FIG. 4) and engage with each other. The width (length in the short direction of the band), the height (length protruding in the radial direction), the shape, the number, the interval between the ribs, and the like are set. The number of the head side ribs 18 is not limited to two, but may be set to one or three or more.

  4A and 4B show the cap 20 according to the present embodiment, wherein FIG. 4A is a plan view, FIG. 4B is a front view, FIG. 4C is a bottom view, and FIG. The cap 20 is a bottomed cylindrical member having a hexagonal outer peripheral surface 20a and a circular inner peripheral surface 20b. An opening 22 is formed at one axial end of the cap 20. In addition, on the inner peripheral surface 20b of the cap 20, a plurality of cap-side ribs 26 (second protruding portions), which are band-shaped row-like projections arranged in parallel in the circumferential direction, are formed.

  The inner peripheral surface 20b and the opening 22 may be set to have a radial length so as not to come into contact with the head 14 when the cap 20 is mounted on the head 14. That is, the radial length of the inner peripheral surface 20b and the opening 22 can be set slightly larger than the outer diameter of the head side rib 18.

  The cap-side rib 26 protrudes radially inward from the inner peripheral surface 20b, and the longitudinal length of the band coincides with the axial direction. Here, six cap-side ribs 26 are formed at regular intervals with a phase difference of 60 ° in the circumferential direction. The cap-side ribs 26 are set to have a width, height, shape, quantity, rib spacing, and the like that can be elastically fitted by contacting the head-side ribs 18 when the cap 20 is mounted on the head 14. Further, it is preferable to set the number and spacing of the cap-side ribs 26 so that the head-side ribs 18 can be urged with substantially uniform pressing force along the circumferential direction.

  The head-side rib 18 and the cap-side rib 26 have different longitudinal directions of the band, and when the cap 20 is attached to the male screw body 10, they intersect and contact each other while pressing the other while elastically deforming each other at the intersection. Pressure contact). That is, the head-side rib 18 is pressed by the cap-side rib 26 at the intersection, and is elastically deformed radially inward. The cap-side rib 26 is pressed by the head-side rib 18 at the intersection, and elastically deforms radially outward. Therefore, the head-side rib 18 and the cap-side rib 26 are pressed into each other at the intersection and engaged with each other in the axial direction and the circumferential direction.

  Therefore, the intersection between the head-side rib 18 and the cap-side rib 26 is a relative rotation restricting mechanism that suppresses the relative rotation of the cap 20 with respect to the male screw body 10 and a separation restriction that prevents the cap 20 from separating from the male screw body 10. Functions as a mechanism. The male screw body 10 and the head 20 are held in a fitted state in which relative rotation between them is suppressed.

  Next, the fastening of the male screw body 1 with a cap to the member to be fastened 30 will be described with reference to FIG. Here, the member to be fastened 30 has a female screw hole 32, and a female screw spiral strip with which the male screw part 16 can be screwed is formed on the inner peripheral surface of the female screw hole 32. Therefore, the male screw body 1 with a cap is fastened to the member 30 to be fastened by screwing the male screw portion 16 into the female screw hole 32 of the member 30 to be fastened.

  For fastening the male screw body 1 with a cap, a fastening tool such as a wrench or a socket is used. More specifically, a fastening tool is engaged with the outer surface of the cap 20, and a torque in a fastening direction is applied to the cap 20 via the fastening tool, thereby rotating the male screw body 1 with a cap. At this time, since the cap 20 is restrained from rotating relative to the male screw body 10 in the circumferential direction by the relative rotation restricting mechanism, the torque applied to the cap 20 is transmitted to the male screw body 10, and as a result, the male screw body with cap 1 rotates in the fastening direction.

  When the male screw body 1 with a cap is rotated in the loosening direction with respect to the member 30 to be fastened, the torque in the loosening direction is transmitted to the male screw body 10 via a fastening tool to loosen the male screw body 1 with a cap. Rotate in the direction.

  Next, a phase adjusting method for adjusting the cap 20 of the male screw body 1 with a cap fastened to the fastened member 30 to an arbitrary phase will be described. When the male screw body 1 with a cap is fastened to the member 30 to be fastened, the seating surface of the head 14 and / or the seating surface of the cap 20 abuts on the end surface (seat surface) of the member 30 to be fastened, and further fastening directions. Rotation is regulated.

  Here, when a predetermined torque or more is further applied to the male screw body 1 with a cap in the fastening direction, the cap 20 can rotate relative to the male screw body 10 against the relative rotation restricting mechanism. When the cap 20 rotates relative to the male screw body 10, the cap-side rib 26 moves relative to the head-side rib 18 in the circumferential direction. That is, when a torque capable of rotating the cap 20 relative to the male screw body 10 is applied to the cap 20, the cap-side rib 26 slides on the head-side rib 18, and the cap-side rib 18 The intersection with 26 is displaced in the circumferential direction.

  In this manner, by applying a predetermined torque or more to the male screw body 1 with a cap fastened to the member 30 to be fastened, the cap 20 can be rotated relative to the male screw body 10 and adjusted to an arbitrary phase. Becomes For example, when the male screw body 1 with a cap engraved with the letters “ABC” on the top surface of the cap 20 is fastened to the member 30 to be fastened, as shown in FIG. Even if the directions of the characters "ABC" are not uniform, the directions of the characters "ABC" can be made uniform as shown in FIG. 6B by performing the above-described phase adjustment.

  As described above, according to the male threaded body with a cap of the present embodiment, by applying a predetermined torque or more to the cap after fastening the member to be fastened, the cap, which is the head portion of the male threaded body with the cap, becomes a male threaded body. , The cap can be set to any phase.

  Also, between the male screw body 10 and the cap 20, the head-side rib 18 and the cap-side rib 26 are elastically deformed at their intersections to form a relative rotation restricting mechanism and a separation restricting mechanism. Even if it rotates relative to the male screw body 10, the state where both ribs are elastically deformed at the intersection does not change. Therefore, even after the rotation of the cap 20, the relative rotation regulating mechanism and the separation regulating mechanism can be maintained.

  Further, the male screw body 1 with a cap is used as a male screw-shaped screw fastener that can be fastened with a constant torque because only the cap 20 relatively rotates with respect to the male screw body 10 when a predetermined torque or more is applied. Is possible. In a general male screw body, the tightening torque is managed by setting the tightening torque on a manual or electric rotary tool side. On the other hand, the male screw body 1 with a cap according to the present invention can be fastened with a predetermined torque even if an excessive tightening torque is applied. That is, when the tightening torque is equal to or more than a predetermined value, the cap 20 rotates relative to the male screw body 10, so that the male screw body 1 with the cap can be fastened to the member to be fastened with a constant torque.

  As described above, since the male screw body 1 with a cap is fastened with a constant torque even when an excessive torque is applied, it is possible to suppress a load caused by applying an excessive tensile force to the male screw body by the fastening. Further, breakage of the male screw body due to excessive tightening torque can be prevented. Furthermore, since the fastening can be performed with a constant torque, the occurrence of loosening of the male screw body due to an excessively small tightening torque can be prevented, and an appropriate fastening state can be obtained.

  In the above-described embodiment, the head 14 of the male screw body 10 has a larger diameter than the diameter of the shaft portion 12, but is not limited to this. For example, as shown in FIG. 7A, the diameter may be smaller than that of the shaft 12, or as shown in FIG. 7B, the diameter may be the same as that of the shaft 12. Further, the diameter of the head 14 may be set to be the same as the diameter of the male thread 16, or may be set to be the same as the diameter of the root of the male screw 16.

  Further, in the above-described embodiment, the head-side rib 18 has the longitudinal direction of the belt coincident with the circumferential direction, and the cap-side rib 26 has the longitudinal direction of the belt coincident with the axial direction. The longitudinal direction of the band can be set appropriately as long as the and the cap-side rib 26 intersect each other. Here, FIG. 8 is a diagram showing another head side rib 70 and a cap side rib 80, and the cap 20 in FIG. 8 shows a cross-sectional shape. As shown in FIG. 8A, the head side rib 70 may be set so that the longitudinal direction of the band coincides with the axial direction, and the cap side rib 80 may be set so that the longitudinal direction of the band coincides with the circumferential direction. . Further, as shown in FIG. 8B, the longitudinal direction of the band of the head-side rib 70 and the cap-side rib 80 is set so as to be inclined with respect to the axial direction so that the longitudinal directions of the bands are different from each other. Is also good.

  Alternatively, the cap-side ribs may be omitted, and the head-side ribs 18 may simply urge the inner peripheral surface of the cap 20 with a predetermined pressing force to form a relative rotation regulating mechanism and a separation regulating mechanism. Alternatively, the head-side rib may be omitted, and the cap-side rib 26 may simply urge the outer peripheral surface of the head 14 with a predetermined pressing force to form a relative rotation regulating mechanism and a separation regulating mechanism.

  Further, the separation restricting mechanism is configured by intersecting the head side rib 18 and the cap side rib 26, but it goes without saying that another separation restricting mechanism may be added. For example, as shown in FIG. 9, a first engaging claw portion 40 protruding inward in the radial direction formed on a peripheral end on the opening 22 side of the cap 20 and a shaft portion 12 on the outer periphery of the head portion 14 are formed. The second engagement claw 42 projecting radially outward may be engaged in the axial direction to constitute a separation restricting mechanism. In this case, the second engaging claw 42 is entirely engaged with the second engaging claw 42 in the axial direction regardless of the position of the first engaging claw 40 in any position. It is preferable to form the ring so as to extend around the circumference. Of course, it goes without saying that the first engagement claw portion 40 may be formed in an annular shape.

  Further, the separation restricting mechanism may be constituted by a pair of fixing pieces 50 extending in the axial direction from the peripheral edge of the cap 20 on the opening 22 side of the cap 20 shown in FIG. That is, after the cap 20 is attached to the head 14, the fixing piece 50 is bent inward in the radial direction and is brought into close contact with the end face of the head 14 on the shaft portion 12 side, thereby preventing the cap 20 from being separated from the male screw body 10. Is also good.

  The male screw body 10 and the cap 20 may be made of metal or nonmetal such as resin. For example, the male screw body 10 is made of metal (or nonmetal), and the cap 20 is made of nonmetal (or The external thread body 10 and the cap 20 may be made of metal (or non-metal).

  Further, in the above-described embodiment, the relative rotation regulating mechanism is configured by intersecting the head-side rib 18 and the cap-side rib 26 so as to engage in the circumferential direction. However, the present invention is not limited to this. For example, when the head 14 is fitted into the cap 20, the outer shape of the head 14 and / or the inner shape of the cap 20 may be such that the head 14 and the cap 20 are fitted and engaged in the circumferential direction. May be formed such that the distance from the axis varies along the circumferential direction.

  Specifically, as shown in FIG. 11A, the outer shape of the head 14 may be set to a Reuleaux triangular shape. At this time, each corner of the triangle may be rounded. Further, the cap 20 may be set so that its inner peripheral shape is similar to the outer peripheral shape of the head 14 in a Reuleaux triangle shape, but is preferably set in a cylindrical shape. The inner circumference of the cap 20 is preferably approximately equal to the circumference of the head 14. Thereby, the cap 20 is engaged with the male screw body 10 in the circumferential direction and functions as a relative rotation restricting mechanism. When a predetermined torque or more is applied to the cap 20, the outer periphery of the head 14 and / or the inner periphery of the cap 20 can be elastically deformed with each other, and the cap 20 can be relatively rotated with respect to the male screw body 10.

  When the outer peripheral shape of the head 14 and the inner peripheral shape of the cap 20 are triangular, engaging caps protruding radially inward are provided on the outer periphery of the cap 20, and the outer peripheral surface of the head 14 is provided on the outer peripheral surface of FIG. As shown in (b), a separation restricting mechanism is formed by providing a circumferential groove 52 which is formed in a circular shape and into which the engaging claw of the cap 20 is fitted, and which is fitted into the groove 50. You may do so. Of course, the engaging claw portion may be provided on the head portion 14 and the orbiting groove portion may be provided on the inner peripheral surface side of the cap 20. Further, the first engagement claw portion 40 may be provided on the inner peripheral surface of the cap 20, and the second engagement claw portion 42 may be provided on the outer peripheral surface of the head portion 14.

  In the case where the cap 20 omitting the cap-side rib 26 is used, the outer shape of the cap 20 may be deformed when the inner circumferential surface is urged by the male screw body 10 and elastically deformed. Therefore, the cap 20 can have a double cylinder structure of the inner cylinder part 60a and the outer cylinder part 60b shown in FIG. Thereby, the head 14 may be fitted to the inner cylinder portion 60a, and only the inner cylinder portion 60a may be elastically deformed to prevent the outer peripheral shape of the cap 20 from being deformed.

  Further, the outer peripheral surface 20a of the cap 20 has been described as having a hexagonal shape, but is not limited to this, as long as the cap 20 can be engaged with a fastening tool. For example, the outer peripheral surface 20a of the cap 20 may have a polygonal shape other than an elliptical shape and a hexagonal shape. Further, the outer peripheral surface 20a may be formed in a circular shape, and a groove (slit, etc.) and a hole (cross hole, hexagonal hole, etc.) for engaging a fastening tool such as a driver may be provided on the top surface.

  Although the above-described head-side rib 18 and cap-side rib 26 have been described as being elastically deformed at the intersection, they are not limited to this. For example, one of the head-side rib 18 and the cap-side rib 26 may be formed of a material having higher rigidity with respect to the other, and the other may be elastically deformed while the other is not elastically deformed. In this case, one of the regulation effect of the relative rotation and the regulation effect of the separation can be made stronger.

Specifically, when the head-side rib 18 is elastically deformed and the cap-side rib 26 is not elastically deformed, the relative rotation restricting mechanism acts more strongly than the separation restricting mechanism. That is, since the cap-side rib 26 bites into the head-side rib 18, when the cap 20 is relatively rotated with respect to the male screw body 10, it is necessary to apply a torque for displacing the biting portion in the head-side rib 18. When the cap 20 is relatively moved in the axial direction so as to be separated from the head 14, the biting portion of the head-side rib 18 does not change. Therefore, the relative rotation regulating mechanism acts more strongly than the separation regulating mechanism.
When the head side rib 18 is not elastically deformed and the cap side rib 26 is elastically deformed, the separation restricting mechanism acts more strongly than the relative rotation restricting mechanism. That is, since the head-side rib 18 is engaged with the cap-side rib 26, when the cap 20 is relatively moved in the axial direction so as to be separated from the head 14, the force for displacing the engagement portion of the cap-side rib 26. However, when the cap 20 is relatively rotated with respect to the male screw body 10, the biting portion in the cap-side rib 26 does not change. Therefore, the separation regulating mechanism acts more strongly than the relative rotation regulating mechanism.

DESCRIPTION OF SYMBOLS 1 ... Male screw body with a cap, 10 ... Male screw body, 12 ... Shaft part, 14 ... Head part, 16 ... Male screw part, 18, 70 ... Head side rib, 20 ... Cap, 20a ... Outer peripheral surface, 20b ... Inner peripheral surface , 22 ... opening, 26, 80 ... cap side rib, 30 ... fastening member, 32 ... female screw hole, 40 ... first engagement claw, 42 ... second engagement claw, 50 ... fixing piece, 52 ... groove , 60a ... inner cylinder part, 60b ... outer cylinder part

Claims (13)

A male screw body having a shaft portion having an external thread spiral groove formed on the outer peripheral surface and a head portion provided at one end of the shaft portion,
A cap attached to the head and surrounding the outer peripheral surface of the head,
A relative rotation regulating mechanism is provided between the head and the cap,
The rotation restricting mechanism restricts the relative rotation of the cap with respect to the head, and when a torque greater than a predetermined value acts on the cap, the cap can rotate relative to the head. Male screw body. The relative rotation restricting mechanism includes a first protruding portion that protrudes radially outward from an outer peripheral surface of the head, and a second protruding portion that protrudes radially inward from an inner peripheral surface of the cap. ,
The male screw body with a cap according to claim 1, wherein the first projecting portion and the second projecting portion intersect with each other and at least one of the first projecting portion and the second projecting portion is pressed so as to be elastically deformable. The relative rotation restricting mechanism is configured to have a protruding portion that protrudes radially outward from an outer peripheral surface of the head,
The male screw body with a cap according to claim 1, wherein the projecting portion presses the inner peripheral surface of the cap so as to elastically deform the inner peripheral surface. The cap has an inner cylinder that comes into contact with the outer peripheral surface of the head, and an outer cylinder that has a larger diameter than the inner cylinder,
The male screw body with a cap according to claim 3, wherein the inner cylinder can be elastically deformed in a gap between the inner cylinder and the outer cylinder by being pressed from the head. The relative rotation regulating mechanism is configured to have a protruding portion that protrudes radially inward from an inner peripheral surface of the cap,
The male screw body with a cap according to claim 1, wherein the protruding portion is in contact with an outer peripheral surface of the head and can be elastically deformed. A shaft portion having an external thread spiral groove formed on the outer peripheral surface,
A head provided at one end of the shaft portion, the outer periphery of which is covered by a separate cap,
A male screw body having a pressing portion capable of slidingly contacting the head while urging an inner peripheral surface of the cap with a predetermined pressing force or more, and restricting relative rotation of the cap with respect to the head.   The male screw body according to claim 6, wherein the pressing portion is a rib provided on an outer peripheral surface of the head in an axial direction and / or a circumferential direction.   The male screw body according to claim 7, wherein the rib is provided so as to intersect a rib formed on an inner peripheral surface of the cap.   The male screw body according to claim 6, wherein the head has an outer peripheral shape whose distance from an axial center varies along a circumferential direction. A cap attached to the head of the male screw body and surrounding the outer peripheral surface of the head,
Protruding radially inward on the inner peripheral surface, comprising a pressing portion for pressing the head,
A cap, wherein the pressing portion can slide on the head while urging the head with a predetermined pressing force.   The cap according to claim 10, wherein the pressing portion is a rib provided on the inner peripheral surface in an axial direction and / or a peripheral direction.   The cap according to claim 11, wherein the rib is provided in a direction crossing a rib formed on an outer peripheral surface of the head. The cap according to claim 10, wherein the inner peripheral surface has an outer peripheral shape whose distance from an axial center varies along a circumferential direction.