JP2001248623A - Bolt tightening structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bolt tightening structure preventing the generation of a torsional stress due to a rotary force in a bolt shaft part under a high shaft force and optimum for tightening a plastic region. SOLUTION: This bolt tightening structure is provided with a tightened member 7B in which a female screw part 8 to be screw-fitted in a first screw part 3 formed in the vicinity of one end part of a bolt shaft 1 is formed, a nut 6 to be screw-fitted in a second screw part 4 formed in the vicinity of the other end part of the bolt shaft 1, a spanner 9 fixing a hexagonal tool fixing part 5 formed in the other end part of the bolt shaft 1, and tightened members 7A, 7B in which the bolt shaft 1 is inserted and which are tightened by the female screw part 8 and the nut 6. After the female screw part 8 is screw-fitted and tightened in the first screw part 3, the tool fixing part 5 is fixed by the spanner 9, and the nut 6 screw-fitted in the second screw part 4 in advance is rotated to tighten the tightened members 7A, 7B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bolt fastening structure, and more particularly, to a bolt fastening structure in which a rotational force when tightening or loosening a bolt shaft is not applied.

[0002]

2. Description of the Related Art As a method of connecting two or more structures (flanges and the like), as shown in FIGS.
A bolt fastening method using a member to be fastened 102 having a female thread structure 00 and a female thread structure 101 (in the case of FIG. 5) and a bolt fastening method using a bolt 100 and a nut 103 (in the case of FIG. 6) are well known. This is the screw 1 formed on the bolt 100
By rotating the bolt 100 or the nut 103 by the screwing of 00a, an elongation is generated in the bolt 100 by the screw pitch (lead) to generate an axial force, and the member to be fastened 102 is connected by the axial force. is there. still,
In FIG. 6, reference numeral 104 denotes a spanner for fixing the nut 103.

[0003]

By the way, in the bolt fastening method described above, a wrench suitable for the shape of the head 100b of the bolt 100 (a polygon such as a hexagon or a hexagonal hole) is used.
Rotational force (torque) on bolt 100 using a tool such as a wrench
, The screw portions 100a mesh with each other, and the bolt 100 enters the member to be fastened 102 according to the screw pitch (lead). At this time, the head 10 of the bolt 100
0b becomes the resistance, and the lower part 100c of the bolt 100 is stretched to generate an axial force.

In recent years, plastic region tightening in which the elongation of bolts is tightened in a plastic region has been used for fastening a flange structure for gas sealing or a cylinder head portion of an automobile engine. As shown in Fig. 7, the feature of this plastic region tightening is to use the yielding phenomenon of the bolt material to reduce variations due to tightening conditions such as torque and rotation angle in a high load region and obtain a stable axial force. And is used for bolt fastening in places where high reliability is required.

However, in the conventional bolt fastening method, since the entire bolt is rotated and screwed in to increase the axial force, the frictional resistance of the screw portion 100a increases under a high axial force and the tightening rotational resistance is reduced. In addition, torsional shear stress occurs in the lower neck portion 100c in addition to the tensile stress due to the axial force (see arrows in FIGS. 5 and 6).

That is, in the conventional bolt fastening method, both tensile stress and torsional shear stress are applied at the time of fastening the bolt, and the lower portion 100c of the bolt 100 needs to have strength against tensile and torsional loads. Lower neck 100
There is naturally a limit in reducing the diameter of c, and it is not possible to reduce the diameter. In addition, there is a concern about secondary damage such as galling and torsion of the screw portion 100a when fastening the bolt under a high axial force.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bolt fastening structure which is suitable for tightening in a plastic region without generating torsional stress due to rotational force on a bolt shaft under a high axial force.

[0008]

In order to achieve the above object, a bolt fastening structure according to the present invention comprises a first fastening member screwed to a first screw portion formed near one end of a bolt shaft. A second fastening member screwed to a second screw portion formed near the other end of the bolt shaft, a fixing tool for fixing a tool fixing portion formed at the other end of the bolt shaft, A bolt member is inserted, and a member to be fastened by the first fastening member and the second fastening member is provided. After the first fastening member is screwed into the first screw portion, the tool fixing portion is fixed. By fixing with a tool, the second screw portion and the second fastening member are screwed together to fasten the member to be fastened, so that only a tensile stress due to an axial force is generated on the bolt shaft under a high axial force. I made it.

Further, when the first screw portion and the second screw portion are threaded in opposite directions, the first fastening member screwed to the first screw portion when the second fastening member is screwed and the fastening member. Even if the member is a rotating body, it does not rotate integrally with the second fastening member, and there is no need to fix the first fastening member and the member to be fastened, thereby improving workability.

When the pitch of the second screw portion is formed smaller than the pitch of the first screw portion, the assembling speed is improved by the first screw portion having the large screw pitch, and the second screw having the small screw pitch is formed. The fastening force is adjusted with high precision at the portion.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a bolt fastening structure according to the present invention will be described in detail with reference to the drawings using embodiments.

[First Embodiment] FIG. 1 is a fastening process diagram of a bolt fastening structure showing a first embodiment of the present invention, FIG. 2 is an explanatory view of a bolt structure, and FIG. 3 is a sectional view showing a modification of a tool fixing portion. FIG.

As shown in FIG. 2, a first screw portion (male screw portion) 3 is formed near one end of the bolt shaft 1 with the neck lower portion 2 interposed therebetween, and the first screw portion 3 is formed near the other end. A second thread portion (male thread portion) 4 having a small thread pitch and a reverse thread cutting direction is formed. At the other end of the bolt shaft 1, a polygonal or other polygonal tool fixing portion (grip portion) 5 is formed.
A nut 6 as a second fastening member is screwed into the second screw portion 4 to form a bolt head.

As shown in FIG. 1, the members 7A, 7B
Is fastened with the above-mentioned bolt, first, the whole bolt (in the illustrated example, a state in which the nut 6 is screwed into the second screw portion 4 is shown, but the nut 6 may be screwed in the next step. Is good), and a bolt is screwed into the fastened member 7B in which the female screw portion 8 as the first fastening member to be screwed with the first screw portion 3 is screwed by the first screw portion 3 to perform initial tightening (primary fastening). (See FIG. 1A).

At this time, since the nut 6 is in a state of light contact with the member 7A to be fastened, no high axial force is generated on the bolt shaft 1, and the torsional stress due to the rotational force is very small.

Next, the tool fixing portion 5 is fixed with a wrench 9 as a fixing tool, the rotation of the bolt shaft 1 is stopped, and then the nut 6 screwed to the second screw portion 4 is fixed to the nut 6 by a predetermined means (spanner or the like). Final tightening (secondary tightening) is performed by applying a rotational force (see FIG. 1B). As shown in FIG. 3, if the tool fixing portion 5 is formed with a hexagonal hole or the like, it is fixed with a hexagon wrench 9A or the like.

At this time, the upward pulling force (bolt elongation) by the second screw portion 4 acts on the bolt shaft 1 and the first screw portion 1
The screw portion 3 becomes a resistance, and an axial force is generated due to the extension of the neck lower portion 2, whereby the members 7A and 7B to be fastened are firmly fastened.

As described above, in this embodiment, only the tensile stress due to the axial force is generated in the neck lower portion 2 of the bolt shaft 1 at the time of tightening. Therefore, the diameter of the neck lower portion 2 is reduced by setting the strength only by the tensile load (therefore, the diameter is reduced). And weight of the bolt).

Further, even under a high axial force, no torsional stress is generated on the bolt shaft 1 due to a rotational force (tightening torque), so that torsional breakage such as threading can be avoided beforehand, which is optimal for plastic region tightening. Further, a stable axial force can be obtained by controlling the rotation angle and the like of the nut 6 without being influenced by the contact state (friction coefficient or the like) between the nut 6 and the member 7A to be fastened, so that the reliability of the bolted structure is improved. .

Further, since the thread pitch of the second thread portion 4 is formed smaller than the thread pitch of the first thread portion 3, the assembling speed is improved by the first thread portion 3 having a large thread pitch, and The fastening force is accurately adjusted by the second thread portion 4 having a small pitch.

[Second Embodiment] FIG. 4 is a sectional view of a bolt fastening structure showing a second embodiment of the present invention.

This is an example in which a rotary shaft of an auxiliary machine such as an alternator of an automobile engine is connected to a pulley by using the bolt shown in FIG. 2, and the rotary shaft serves as a first fastening member shown in FIG. To be fastened member 7B having female screw portion 8 formed
And the pulley corresponds to the member 7A to be fastened.

According to this, the same operation as that of the first embodiment is obtained.
The effect is obtained, and the first screw portion 3 and the second screw portion 4 are threaded in opposite directions. Therefore, when the nut 6 is screwed, the rotation shaft 7B and the pulley 7A do not rotate, so that the rotation is prevented. There is no need to perform a rotation stopping process for the shaft 7B and the pulley 7A, and an advantage is obtained in that assembly work can be performed safely and smoothly in front of the engine.

The present invention is not limited to the above embodiments,
Various changes are possible, such as threading the first screw portion 3 and the second screw portion 4 in the same direction and using a nut instead of the female screw portion 8 for the second fastening member without departing from the gist of the present invention. Needless to say.

[0025]

As described above, according to the first aspect of the present invention, the first fastening member screwed to the first screw portion formed near one end of the bolt shaft, and the other end of the bolt shaft. A second fastening member screwed into a second screw portion formed near the portion, a fixing tool for fixing a tool fixing portion formed on the other end of the bolt shaft, and the bolt shaft is inserted. The first fastening member and a member to be fastened by a second fastening member. After the first fastening member is screwed into the first screw portion, the tool fixing portion is fixed with a fixing tool, The second threaded portion and the second fastening member are screwed together to fasten the member to be fastened, so that only a tensile stress due to axial force is generated on the bolt shaft under a high axial force. The diameter and weight can be reduced, and the reliability of the fastening structure can be improved.

According to the second aspect of the present invention, the first and second screw portions are threaded in opposite directions.
At the time of screw rotation of the second fastening member, even if the first fastening member and the member to be fastened to the first screw portion are rotating bodies, they do not rotate integrally with the second fastening member. Since it is not necessary to fix the first fastening member and the member to be fastened, workability is improved.

According to the third aspect of the present invention, since the pitch of the second thread portion is formed smaller than the pitch of the first thread portion, the assembling speed is improved with the first thread portion having a large thread pitch. The fastening force is accurately adjusted by the second screw portion having a small screw pitch.

[Brief description of the drawings]

FIG. 1 is a fastening process diagram of a bolt fastening structure showing a first embodiment of the present invention.

FIG. 2 is a structural explanatory view of a bolt similarly.

FIG. 3 is a cross-sectional view showing a modification of the tool fixing unit.

FIG. 4 is a sectional view of a bolt fastening structure showing a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of a conventional bolt fastening structure.

FIG. 6 is a sectional view of a different bolt fastening structure of a conventional example.

FIG. 7 is a graph showing characteristics of plastic region tightening in relation to bolt elongation and bolt axial force.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bolt shaft 2 Neck lower part 3 1st screw part 4 2nd screw part 5 Tool fixing part 6 Nut 7A Fastened member (pulley) 7B Fastened member (rotary shaft) 8 Female screw part 9 Spanner 9A Hex wrench 10 Bearing

Claims (3)

[Claims] A first bolt formed near one end of a bolt shaft.
A screw portion, a second screw portion formed near the other end of the bolt shaft, a tool fixing portion formed at the other end of the bolt shaft and fixable by a fixing tool, the first screw portion , A second fastening member screwed into the second screw portion, and a member to which the bolt shaft is inserted and fastened by the first fastening member and the second fastening member. A bolt fastening structure including a fastening member, wherein after the first fastening member is screwed into the first screw portion, the tool fixing portion is fixed by a fixing tool, and the second screw portion and the second fastening member are fixed. Wherein the member to be fastened is screwed together to fasten the member to be fastened. 2. The bolt fastening structure according to claim 1, wherein the first screw portion and the second screw portion are threaded in opposite directions. 3. The device according to claim 1, wherein the pitch of the second thread is smaller than the pitch of the first thread.
Or the bolt fastening structure according to 2.