JP6892046B2 - Fastening member - Google Patents

Description

The present invention relates to a fastening member, and more particularly to a fastening member that fixes the first member to the second member.

Conventionally, in various industrial products, screws (tap screws) or screws and nuts, which are examples of fastening members, are used for assembling a plurality of parts. Assembling between parts with screws is different from other assembling methods such as bonding, welding, welding, and caulking, and parts can be assembled, disassembled, and replaced extremely easily by rotating the screws in the tightening or loosening direction. have. On the other hand, the ease of loosening, which is one of the characteristics of screws, is also a drawback of loosening the fastening state between parts depending on the usage conditions. That is, when an external force due to vibration or impact is applied to the screw fastening portion, the screw rotates little by little, so that the screw loosens (called rotation loosening).

Therefore, for example, in Patent Document 1, in a screw composed of a head and a leg, a thread is formed in the leg, and a screw is screwed into a female screw hole in which a female screw is formed, an angle formed by a flank surface on the valley side of the male screw is formed. The angle formed by the flank surface forming the female thread is smaller than the angle formed by the flank surface forming the female thread, the apex angle formed by the top flank surface of the male thread is an obtuse angle larger than 90 °, and the valley side flank surface and the top flank surface are connected by an arc surface. , A loosening set screw having a structure in which the width of the top of the male screw is wider than the width of the valley of the female screw that matches this has been proposed.
According to the loosening set screw of Patent Document 1, the loosening prevention action is generated on the screw thread top side of the male screw, and the female screw can be efficiently contacted and interfered with, and the loosening of the male screw due to rotational loosening is surely prevented. can do.

Japanese Unexamined Patent Publication No. 2012-117606

However, the cause of loosening the fastening state between the parts by the fastening member is also loosening (called non-rotational loosening) due to a decrease in axial force due to stress relaxation and creep in the fastening member.
Such non-rotational loosening cannot be prevented by the loosening set screw of Patent Document 1.

An object of the present invention is to provide a fastening member capable of preventing rotational loosening and non-rotational loosening.

(1) A fastening member for fixing the first member to the second member.
The head locked to the first member and
A shaft portion that extends from the head and has a spirally formed male thread on the outer surface, and the male thread is screwed with a female thread formed on the second member.
The male thread is
At the top side, the inclination angle of the ridge with respect to a direction orthogonal to the direction in which the shaft portion extends is, the inclination angle with respect to the perpendicular direction of the valley ridges of the internal thread is the same,
On the valley side, the inclination angle of the ridgeline with respect to the orthogonal direction is acuteer than the inclination angle of the top side ridgeline of the female thread with respect to the orthogonal direction.
When the second member is tightened to the shaft portion, the male thread is elastically deformed and stores elastic strain energy.
The elastic strain energy is Ri Do and the axial force acting in a direction to close the first member and the second member to each other,
A fastening member in which when the male thread reaches the upper limit of elastic deformation, the amount of movement of the side surface of the female thread becomes 1/20 of the pitch of the male thread.

According to the invention of (1), the fastening member includes a head portion and a shaft portion, with the first member fixed to the second member.
The head is locked to the first member.
The shaft portion extends from the head and has a spirally formed male thread on the outer surface, and the male thread is screwed with the female thread formed on the second member.
On the top side of the male thread, the inclination angle of the ridgeline with respect to the direction orthogonal to the direction in which the shaft extends is substantially the same as the inclination angle of the valley side ridgeline of the female thread with respect to the orthogonal direction. The inclination angle of the ridgeline with respect to the direction is sharper than the inclination angle of the top side ridgeline of the female thread with respect to the orthogonal direction.
Then, when the second member is tightened to the shaft portion, the male thread is elastically deformed and stores elastic strain energy, and the elastic strain energy acts in a direction in which the first member and the second member are brought close to each other. It will be a force.

Here, when an external force or an external vibration is applied to the first member and the second member fixed by the fastening member, the fastening member is loosened in rotation. The resistance torque of the fastening member against this rotational loosening is the frictional binding force on the contact surface between the first member and the head locked to the first member, and the second male thread and the male thread of the shaft are screwed together. It depends on the magnitude of the frictional binding force with the female thread formed on the member.
The frictional binding force of the head and the frictional binding force of the shaft portion are proportional to the axial force of the fastening member in the fastened state.

According to the present invention, the inclination angle of the male thread of the shaft portion on the top side is substantially the same as the inclination angle of the valley side ridge line of the female thread, and the inclination angle on the valley side is the inclination angle of the top side ridge line of the female thread. It is sharper than the tilt angle. As a result, as the second member is tightened to the shaft portion, the peak side of the female screw thread is elastically deformed in the axial direction of the shaft portion while maintaining a close contact state with the valley side of the female thread, and elastic strain energy is stored.
Then, this elastic strain energy becomes an axial force acting in a direction in which the first member and the second member are brought close to each other, so that the axial force is improved.
Therefore, the friction binding force of the head portion and the friction binding force of the shaft portion are improved, and the resistance torque of the fastening member against the loosening of rotation is improved.

Further, by improving the axial force, it is possible to suppress a decrease in the axial force due to an external force or vibration and a decrease in the axial force with the passage of time, so that non-rotational loosening can be prevented.
Therefore, it is possible to provide a fastening member capable of preventing rotational loosening and non-rotational loosening.

(2) the external thread is either one or both ridges of the top side and the valley side is a curve shape,
The fastening member according to (1), wherein the elastic strain energy serves as an axial force acting in a direction in which the first member and the second member are brought close to each other.

According to the invention of (2), the fastening member is screwed to the second member by forming the ridgeline of either one or both of the top side and the valley side of the male thread into a curved shape close to the ridgeline of the female thread. When mating, the fastening member rotates smoothly, which improves work efficiency.

(3) The fastening member according to (1) or (2), wherein the shaft portion has a contact portion that abuts on the top of the female thread in the valley of the male thread.

According to the invention of (3), when the abutting portion abuts on the top of the female thread, a minute deviation or gap between the male thread and the female thread is compensated for, and the fastening member and the second member are more integrated. It becomes stronger and it becomes possible to further prevent loosening of the fastening member due to external force or vibration.

According to the present invention, it is possible to provide a fastening member capable of preventing rotational loosening and non-rotational loosening.

FIG. 1 is a diagram illustrating an outline of a fastening member 1 according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a portion surrounded by a broken line in FIG. FIG. 3 is a diagram illustrating the operation of the fastening member 1 according to the embodiment of the present invention. FIG. 4 is a diagram illustrating the operation of the fastening member 1 according to the embodiment of the present invention. FIG. 5 is a diagram illustrating a shaft portion 20A of the fastening member 1A according to a modified example of the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same components will be designated by the same reference numerals, and the description thereof will be omitted or simplified.
FIG. 1 is a diagram illustrating an outline of a fastening member 1 according to an embodiment of the present invention.

[Structure of fastening member 1]
The fastening member 1 fixes the first member 100 to the second member 200, and includes a head portion 10 and a shaft portion 20. In the example shown in FIG. 1, the fastening member 1 is configured, the first member 100 is composed of two members connecting to each other, and the second member 200 is configured by a nut.

The fastening member 1 is not limited to a bolt, and is composed of an arbitrary fastening member (for example, a screw, a tapping screw, etc.) having a spirally formed male thread and screwing with a member having a female thread. Can be done. For example, when the fastening member is composed of a screw formed on one of two members to be connected to each other and a screw to be screwed, the member on which the female thread is formed is the second member, and the fastening member is fastened to the second member. The other member arranged between the member and the head of the member becomes the first member.

The head 10 is locked to the first member 100. In the example shown in FIG. 1, the head 10 is directly in contact with and locked to the first member 100, but the head 10 is not limited to this, and the head 10 is indirectly connected with an inclusion such as a washer or packing. May be locked.

The shaft portion 20 extends from the head portion 10 and has a spirally formed male thread 22 (see FIG. 2 described later) on the outer surface 21, and the male thread 22 is formed into a second member 200. It is screwed with 201 (see FIG. 2 described later).

FIG. 2 is an enlarged cross-sectional view of a portion surrounded by a broken line in FIG.
In the shaft portion 20, a plurality of male threads 22 are arranged with a male thread valley 23 interposed therebetween, for example, at a pitch p based on the Japanese Industrial Standards.
The male screw thread 22 has a top portion 221 which is the outer diameter of the male screw thread 22, a top side inclined portion 222 which inclines downward from the top portion 221 to the male screw valley 23 side, and a valley which inclines downward from the top side inclined portion 222 to the male screw valley 23 side. It has a portion-side inclined portion 223 and.

In the top-side inclined portion 222, the inclination angle of the ridge line with respect to the orthogonal direction (OI direction in FIG. 2) orthogonal to the direction in which the shaft portion 20 extends (HE direction in FIG. 2) is the direction orthogonal to the valley 202 side ridge line of the female thread 201. It is substantially the same as the inclination angle α (for example, 30 °) with respect to.

In the valley side inclined portion 223, the inclination angle of the ridge line with respect to the orthogonal direction (OI direction in FIG. 2) orthogonal to the direction in which the shaft portion 20 extends (HE direction in FIG. 2) is orthogonal to the top 203 side ridge line of the female thread 201. It is sharper than the inclination angle α with respect to the direction (OI direction in FIG. 2).

As a result, when the male thread 22 of the fastening member 1 is screwed into the female thread 201 of the second member 200, the top-side inclined portion 222 comes into contact with the female thread 201, but the valley-side inclined portion 223 has a female thread. Does not come into contact with 201.

The male thread 22 has an inclination angle of the shaft portion 20 with respect to an orthogonal direction (OI direction in FIG. 2) orthogonal to the direction in which the shaft portion 20 of the ridge line on the top 221 side and the male screw valley 23 side extends (HE direction in FIG. 2). The base end side (H side in FIG. 2) and the tip end side (E side in FIG. 2) are substantially the same. In this way, by setting the male threads adjacent to each other to have substantially the same inclination angle in the direction in which the shaft portion extends, the fastening member is screwed to the second member as compared with the case where the inclination angles of the male threads adjacent to each other are changed. When mating, the fastening member rotates smoothly, which improves work efficiency.

Further, the male thread 22 may have a curved shape in which the ridgeline of either one or both of the top-side inclined portion 222 and the valley-side inclined portion 223 is close to the ridgeline of the female thread 201.

Further, in the example shown in FIG. 2, the boundary between the top-side inclined portion 222 and the valley-side inclined portion 223 is set to the vicinity of the position A which is the effective diameter of the fastening member 1, but this boundary is required for the fastening member 1. When the axial force to be applied is applied, the male thread 22 can be elastically deformed and can be set at an arbitrary position as long as it is not plastically deformed.

Further, from the position where the width b on the male thread valley 23 side of the male thread 22 (the end of the valley side inclined portion 223 on the head 10 side (H) is connected to the male thread 22), the tip side (E) of the shaft portion 20 The dimension up to the position where the end of the valley side inclined portion 223 is connected to the male thread 22) is preferably smaller than 1 time and larger than 1/2 times the pitch p of the male thread 22.

[Action of fastening member 1]
Next, the operation of the fastening member 1 will be described.
3 and 4 are views for explaining the operation of the fastening member 1 according to the embodiment of the present invention.
As shown in FIG. 3, the shaft portion 20 of the fastening member 1 is inserted through the two first members 100 which are the objects to be fastened, and the male screw thread 22 of the shaft portion 20 is the female screw thread of the second member 200 which is a nut. It is screwed with 201, and the second member 200 is rotated by a wrench 300 and tightened. As a result, the head 10 of the fastening member 1 is locked to one first member 100, and the second member 200 is locked to the other first member 100. At this time, the first member 100 sandwiched between the seat surface of the head portion 10 and the end surface of the second member 200 is a shaft portion 20 of the fastening member 1 facing from both sides when the second member 200 is rotated and tightened. In response to the axial pressing force (axial force indicated by the solid line arrow in FIG. 3), as shown in FIG. 4, the top-side inclined portion 222 of the male thread 22 is in close contact with the female thread 201 of the second member 200. Elastic strain energy is stored by elastically deforming the valley side inclined portion 223. That is, when the second member 200 is tightened to the shaft portion 20, the male thread 22 formed in a spiral shape on the outer surface 21 is elastically deformed and stores elastic strain energy, and this elastic strain energy is used as the first member. It is an axial force that acts in the direction in which the 100 and the second member 200 are brought close to each other.

Specifically, the male thread 22 of the fastening member 1 located in the region where the female thread 201 of the second member 200 meshes with and in the vicinity thereof is rotated in the head 10 direction (H direction in FIG. 4) before the tightening is completed. By further slightly rotating the second member 200 (the spiral of the female thread 201 of the second member 200) in the state where the movement is stopped, the axial portion 20 is added in the axial direction from the side surface of the female thread 201 of the second member 200. It is elastically deformed by receiving pressure (axial force indicated by the solid line arrow in FIG. 3) and stores elastic strain energy.

Further, the object to be fastened (first member 100), which has been tightened by completing the above tightening operation, has an axial repulsive force of the shaft portion 20 (dotted line arrow in FIG. 3) due to the elastic strain energy stored at the time of tightening. Axial force indicated by) is generated.

In addition to this, the male thread 22 of the fastening member 1 located in and near the region meshed with the female thread 201 of the second member 200 is the end face of the second member 200 due to the repulsive force due to the elastic strain energy stored at the time of tightening. Is pressed against the body to be fastened (first member 100), and the seating surface of the head 10 is pressed against the body to be fastened (first member 100) by the reaction thereof. Axial force indicated by arrow) is generated.

Here, the frictional binding force of the seat surface of the head 10 and the frictional binding force of the male screw thread 22, which are resistances to rotational loosening, become larger as the axial force of the fastening member 1 is larger, and thus are in the fastened state. The greater the axial force of the fastening member 1 (for example, bolt) and the second member 200 (for example, nut), the more difficult it is to loosen.
In screw fastening using the fastening member 1 according to the present embodiment, the axial force in the fastened state is larger than that in the case of using a general screw, and the resistance torque against rotational loosening is also large. That is, loosening of rotation is unlikely to occur. Further, the shape of the male thread 22 of the elastically deformed fastening member 1 impairs the consistency with the shape of the female thread 201 of the second member 200, thereby further making the rotation loosening of the second member 200 less likely to occur. Further, the top-side inclined portion 222 of the male thread 22 of the fastening member 1 is kept in close contact with the valley side of the female thread 201 of the second member 200, and at the same time, the pongee force acts on the same top-side inclined portion 222. The central point of action of the friction binding force against the loose rotation is closer to the outer diameter of the fastening member 1 (the moment arm becomes longer), and the resistance torque against the loose rotation increases.

Next, the rotation angle of the retightening when the fastening member 1 according to the present embodiment is applied will be described.
In the examples shown in FIGS. 3 and 4, the top of the male thread 22 of the fastening member 1 elastically deforms as the side surface of the female thread 201 of the second member 200 moves due to the rotation of the second member 200 (nut: spiral female thread). The upper limit of the elastic deformation of the male screw thread 22 is when the side surface portion of the side inclined portion 222 (the side surface portion from the top portion 221 to the intermediate position between the effective diameter and the valley diameter) is in close contact with the side surface of the female screw thread 201 of the second member 200. Therefore, the movement amount (upper limit value) e of the side surface of the female thread 201 of the second member 200 is about 1/20 of the pitch p, and can be expressed by the following equation.
e = (1/20) x p

As a result, for example, when the fastening member 1 is composed of M6 screws, p = 1 mm, so that the movement amount (upper limit value) e is 0.05 mm.
Further, when the fastening member 1 is composed of M4 screws, p = 0.7 mm, so the movement amount (upper limit value) e is 0.035 mm.
Further, when the fastening member 1 is composed of M3 screws, p = 0.5 mm, so the movement amount (upper limit value) e is 0.025 mm.
Further, when the fastening member 1 is composed of M2 screws, p = 0.4 mm, so the movement amount (upper limit value) e is 0.02 mm.

The rotation angle θ for moving the second member 200 in the movement amount (upper limit value) e of the side surface of the female thread 201 of the second member 200 in the above case can be expressed by the following equation.
θ = 360 × (1/20) = 18 °
(M6 screw, M4 screw, M3 screw, M2 screw all have the same value)
That is, it is desirable that the retightening rotation angle θ is in the range of 0 to 18 °.
The retightening corresponding to the above θ can be displayed by the tightening torque (Nm) by the implementation test.

[Modification example]
Next, the shaft portion 20A of the fastening member 1A according to the modified example of the embodiment of the present invention will be described.
FIG. 5 is a diagram illustrating a shaft portion 20A of the fastening member 1A according to a modified example of the embodiment of the present invention.
The shaft portion 20A is formed with a contact portion 231 in contact with the top portion 203 of the female thread 201 at the male thread valley 23.

The contact portion 231 may have a convex shape in a part of the male screw valley 23 (for example, the central portion of the male screw valley 23), or may provide a small protrusion in the central portion of the male screw valley 23.
According to the fastening member 1A according to such a modification, the fastening member 1A and the second member 200 (nut) have the same convex surface or the same small protrusion of the contact portion 231 formed in each of the plurality of male screw valleys 23. In the meshed state, it becomes a support that compensates for minute deviations and gaps in the meshed part, and has the effect of strengthening the integration of the fastening member 1A and the second member 200, resulting in a screw that is resistant to external vibration and does not loosen easily. Be done.

The present invention is not limited to the above-described embodiments and modifications, and modifications, improvements, and the like within the range in which the object of the present invention can be achieved are included in the present invention.

1,1A Fastening member 10 Head 20, 20A Shaft 21 Outer surface 22 Male thread 23 Male thread valley 100 First member 200 Second member 201 Female thread 202 Female thread valley 203 Female thread top 221 Male thread top 222 Top Side inclined part 223 Valley side inclined part 231 Contact part 300 Wrench

Claims (3)

A fastening member that fixes the first member to the second member.
The head locked to the first member and
A shaft portion that extends from the head and has a spirally formed male thread on the outer surface, and the male thread is screwed with a female thread formed on the second member.
The male thread is
At the top side, the inclination angle of the ridge with respect to a direction orthogonal to the direction in which the shaft portion extends is, the inclination angle with respect to the perpendicular direction of the valley ridges of the internal thread is the same,
On the valley side, the inclination angle of the ridgeline with respect to the orthogonal direction is acuteer than the inclination angle of the top side ridgeline of the female thread with respect to the orthogonal direction.
When the second member is tightened to the shaft portion, the male thread is elastically deformed and stores elastic strain energy.
The elastic strain energy is Ri Do and the axial force acting in a direction to close the first member and the second member to each other,
A fastening member in which when the male thread reaches the upper limit of elastic deformation, the amount of movement of the side surface of the female thread becomes 1/20 of the pitch of the male thread. The external thread is either one or both ridges of the top side and the valley side is a curve shape,
The fastening member according to claim 1, wherein the elastic strain energy serves as an axial force acting in a direction in which the first member and the second member are brought close to each other. The fastening member according to claim 1 or 2, wherein the shaft portion has an abutting portion that abuts on the top of the female thread in the valley of the male thread.

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