JP2002139015A - Bolt fastening method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bolt fastening method for preventing the looseness of a nut. SOLUTION: The bolt fastening method comprises an insertion step of inserting a tapered bolt 10 having screw portions 14 at both ends and a small- diameter portion 18a and a large-diameter portion 18b at the center 18 and a sleeve 12, in which the bolt is inserted, having a tapered inner periphery face to be matched with the outer periphery face at the center of the bolt, an expansion step of operating tensile force of first predetermined stress on the small-diameter portion side of the bolt to expand the sleeve in the radial direction in the state that the bolt and the sleeve are inserted into a through- hole, a first fastening step of operating tensile force of second predetermined stress on the small-diameter portion side of the bolt in the state that the sleeve is expanded and fastening nuts 16a, 16b to screw portions at both ends of the bolt in the state that the tensile force is operated, and a second fastening step of operating tensile force of the second predetermined stress on the large- diameter portion side of the bolt in the state that the sleeve is expanded and further fastening the nut 16b of the screw portion on the large-diameter portion side of the bolt in the state that the tensile force is operated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bolt tightening method, and more particularly to a bolt tightening method for tightening a bolt using a nut on a coupling member on which a large torque acts.

[0002]

2. Description of the Related Art Conventionally, when a bolt is tightened using a nut, a tension is applied to the bolt in advance by a hydraulic tensioner, and the bolt is tightened by the nut in a state where the tension is applied. Force) to prevent loosening of the nut. Further, recently, in addition to applying a tensile force to the bolt, a central portion of the bolt is formed into a tapered shape, and further, a sleeve having a tapered inner peripheral surface shape that matches the outer peripheral surface of the central portion of the bolt. In addition, a bolt tightening method has been proposed in which, in addition to the pulling force, the binding force of the bolt and the sleeve is used to prevent the bolt from being loosened. Hereinafter, a conventional bolt tightening method using this sleeve will be described with reference to FIGS.

FIG. 1 is a partial cross-sectional view showing a coupling portion for connecting an end of a generator rotor and an end of a governor rotor, and FIG. 2 is a rightward (governor) in FIG. FIG. 3 (a) to FIG. 3 (e) are views showing steps of a conventional bolt tightening method. First, as shown in FIGS. 1 and 2, reference numeral 1 denotes a coupling member. The coupling member 1 has an end 2 of a generator rotor (generator rotor) and an end of a governor rotor (governor rotor). And a spacer 6 (see FIG. 3) inserted between the end 2 of the generator rotor and the end 4 of the governor rotor. A large number of through holes 8 are formed on the outer peripheral sides of the ends 2 and 4 of the coupling member 1 and the spacer 6, and a bolt 10 and a sleeve 12 are inserted into these through holes 8. Nuts 16 are fastened to screw portions 14 at both ends.

[0004] Such a coupling member 1 is connected to a bolt 1
When fastening with 0, the following steps are performed. First, as shown in FIG.
A bolt 10 and a sleeve 12 are inserted into through holes 8 formed in the end 4 of the governor rotor and the spacer 6. Here, the bolt 10 is configured such that the outer peripheral surface of the central portion 18 has a tapered shape. Further, the sleeve 12 has the bolt 10 inserted therein, and the inner peripheral surface thereof has the bolt 10.
Has a tapered shape that matches the tapered shape of the central portion 18 of FIG. In the example of FIG. 3, the tapered shape of the bolt 10 and the sleeve 12 is such that the end portion 2 (right side) of the generator rotor has a small diameter portion and the end portion 4 side (left side) of the governor rotor has a large diameter. It has a diameter.

[0005] Next, as shown in FIG. 3 (b), a first hydraulic tensioner 20 is attached to the small diameter end of the bolt 10, and a first predetermined tension is applied to the bolt 10 by the first hydraulic tensioner 20. A force (sleeve expansion hydraulic pressure) is applied. At this time, since the tapered outer peripheral surface of the central portion 18 of the bolt 10 and the tapered inner peripheral surface of the sleeve 12 are aligned, the central portion 18 of the bolt 10 extends to the left in the figure,
The extension of the bolt 10 causes the sleeve 12 to expand radially outward. Next, the first hydraulic tensioner 20 is removed from the bolt 10 as shown in FIG. At this time, the sleeve 12 is in a state of being expanded in the radial direction. In addition, since the small diameter side portion 18a of the central portion 18 of the bolt 10 is engaged with the inner peripheral surface of the sleeve 12,
It slightly returns to its original shape, while the central part 1 of the bolt 10
The large-diameter portion 18b (between the fixing point A and the large-diameter end portion) relatively strongly engages with the inner peripheral surface of the sleeve 12 by frictional force. It is in a state where no tensile force acts. This is a phenomenon (state) found by the present inventors as described later.

Next, as shown in FIG. 3D, a second hydraulic tensioner 22 is attached to the end of the bolt 10 on the small diameter side, and the second hydraulic tensioner 22 applies a second predetermined tension to the bolt 10. Apply force (bolt tightening oil pressure).
With this tensile force acting, nuts 16 are fastened to the threaded portions 14 at both ends of the bolt 10. Next, FIG.
As shown in (e), the second hydraulic tensioner 22 is removed, and the bolt tightening operation is completed.

[0007]

In the steps shown in FIGS. 3 (b) and 3 (c) of the conventional bolt tightening method described above, the inventors of the present invention set the large diameter portion 18b of the central portion 18 of the bolt 10. (Between the fixed point A and the large-diameter end) is relatively strongly engaged with the inner peripheral surface of the sleeve 12 by frictional force, so that no tensile force acts on the large-diameter portion 18b. I discovered that it was in a state. As a result of the study by the present inventors, the second hydraulic tensioner 22
Even if a predetermined tensile force (bolt tightening oil pressure) is applied, the large diameter portion 18b (between the fixed point A and the large diameter side end) is kept in the second position because the fixed point A exists. The tensile force of the hydraulic tensioner 22 does not act, and the presence of the fixing point A causes the nut 16b on the large-diameter portion (speed governor side) to be slacker than the nut 16a on the small-diameter portion (generator side). The problem of easy access became clear.

The present invention has been made to solve the problems of the prior art found by the present inventors.
An object of the present invention is to provide a bolt tightening method capable of preventing a nut from being loosened.

[0009]

In order to achieve the above object, a method for tightening a bolt according to the present invention is characterized in that a through hole formed in a coupling member is provided with a thread portion at both ends and a small diameter portion at the center. A tapered bolt having a large diameter portion and a sleeve having a tapered inner peripheral surface into which the bolt is inserted and which is aligned with the outer peripheral surface of the central portion of the bolt; and In the inserted state, a tensile force of a first predetermined stress is applied to the small-diameter portion side of the bolt to expand the sleeve in the radial direction, and in the expanded state, the small-diameter portion side of the bolt is expanded. And a first tightening step of tightening the nuts to the threaded portions at both ends of the bolt while the tensile force of the second predetermined stress is applied to the bolt while the tensile force is applied. Large diameter side of Is characterized by having a further tightening with the second clamping step bolts large diameter portion side of the screw portion of the nut in a state where the tensile force with the action of tensile force of the second predetermined stress is applied, the.

In the expanding step, the present inventors apply a first predetermined stress tensile force to the small-diameter portion of the bolt in a state in which the bolt and the sleeve are inserted into the through holes, thereby causing the sleeve to move in the radial direction. At this time, the large-diameter portion side of the central portion of the bolt engages with the inner peripheral surface of the sleeve by frictional force, and no tensile force is applied, which is a cause of the loosening of the nut on the large-diameter portion side. I found that it was the cause. Therefore, according to the present invention, in a state where the sleeve is expanded, a tensile force of the second predetermined stress is applied to the small-diameter portion side of the bolt, and each nut is connected to both ends of the bolt while the tensile force is applied. After performing the first tightening step of tightening the threaded portion of the portion, in a state where the sleeve is expanded, a tensile force of the second predetermined stress is applied to the large diameter portion side of the bolt and the tensile force is applied. In this state, a second tightening step of further tightening the nut of the screw portion on the large diameter portion side of the bolt is performed. As a result, according to the present invention, it is possible to apply the same amount of tensile force (axial force) to the threaded portions at both ends of the bolt, thereby preventing the loosening of the nut on the large-diameter portion side, which has become a problem. can do.

In the present invention, the second predetermined stress is preferably 75% to 85% of the bolt yield stress. Further, in the present invention, in the second tightening step, before applying a tensile force of the second predetermined stress to the large diameter portion side of the bolt, a stress larger than the second predetermined stress and smaller than the yield stress is applied. Is preferably acted upon. In the present invention, it is preferable that the first predetermined stress is a value that causes a predetermined restraining force to be generated when the outer peripheral surface on the large diameter portion side of the bolt and the inner peripheral surface of the sleeve come into contact with each other.

[0012] In the present invention, the sleeve is a second sleeve.
In the tightening step, it is preferable that the length is set such that the large-diameter portion comes into contact with the nut. In the present invention, it is preferable that the radius of the through hole formed in the coupling member is smaller at a portion on the large diameter portion that is not engaged with the sleeve than at a portion engaged with the sleeve.
Furthermore, it is preferable that the present invention includes a driving step of driving a wedge having a rotation preventing function into the screw portion at the end on the large diameter portion side of the bolt and the nut tightened to the screw portion after the second tightening step. .

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 4A to 4F, a first embodiment of the bolt tightening method of the present invention will be described. 4A to 4F are views showing each step of the bolt tightening method according to the first embodiment of the present invention. First, FIG. 4A
The coupling member 1 formed on the end 2 of the generator rotor, the end 4 of the governor rotor and the spacer 6 as shown in FIG.
The bolt 10 and the sleeve 12 are inserted into the through-hole 8 of FIG.
This step is the same as the above-described conventional step of FIG. That is, the bolt 10 has a threaded portion 14 at each end and a tapered outer peripheral surface of the central portion 18. The bolt 10 is inserted into the sleeve 12, and the inner peripheral surface of the sleeve 12 has a central portion 18 of the bolt 10.
The taper shape matches with the taper shape of FIG. In the present embodiment, the central portion 1 of the bolt 10
The tapered shape of the sleeve 8 and the sleeve 12 is such that the right side is a large diameter part and the left side is a small diameter part.

Next, as shown in FIG. 4B, a first hydraulic tensioner 20 is attached to the end of the bolt 10 on the small diameter side, and the first hydraulic tensioner 20 applies a first predetermined tensile force (sleeve) to the bolt 10. Expansion hydraulic pressure). The magnitude of the first predetermined tensile force is determined by the length of the sleeve 12 and the like. At this time, the central portion 18 of the bolt 10
Since the outer peripheral surface of the tapered shape and the inner peripheral surface of the tapered shape of the sleeve 12 are aligned with each other, the central portion 18 of the bolt 10 extends to the left in the drawing, and the extension of the bolt 10 causes the sleeve 12 to move radially outward. Be extended.

Next, as shown in FIG. 4C, the first hydraulic tensioner 20 is removed from the bolt 10. At this time, the sleeve 12 is in a state of being expanded in the radial direction.
The small-diameter portion 18a of the central portion 18 of the bolt 10 is
Since it is engaged with the inner peripheral surface of the sleeve 12, it slightly returns to the original shape, while the large-diameter portion 18b of the central portion 18 of the bolt 10 (between the fixing point A and the large-diameter end). Engages relatively strongly with the inner peripheral surface of the sleeve 12 by frictional force,
Therefore, no tensile force acts on the large-diameter side portion 18b.

Next, as shown in FIG. 4D, a second hydraulic tensioner 2 is attached to an end (left side in FIG. 4) of the bolt 10 on the small diameter side.
2, and using this second hydraulic tensioner 22,
A second predetermined tensile force (bolt tightening oil pressure) is applied to the bolt 10 along the axis, and in a state where the tensile force is applied, a nut 16 is attached to the threaded portions 14 at both ends of the bolt 10.
Tighten (16a, 16b). Thereafter, the second hydraulic tensioner 22 is removed from the small-diameter end of the bolt 10.
Here, in the first embodiment, the second predetermined tensile force (bolt tightening oil pressure) is 75% of the yield stress of the bolt 10.

Next, as shown in FIG. 4E, the second hydraulic tensioner 22 is connected to the large-diameter end of the bolt 10 (right side in FIG. 4).
And the second hydraulic tensioner 22 is used to move the bolt 10 along the axis thereof to a yield stress of the bolt 10 of 75%.
% Second tension (stress hydraulic pressure)
The nut 16b is fastened to the screw portion 14 at the large-diameter end of the bolt 10 while the tensile force is acting. Thereafter, the second hydraulic tensioner 22 is removed from the large-diameter end of the bolt 10. Next, as shown in FIG. 4F, the second hydraulic tensioner 22 is removed from the large-diameter portion end of the bolt 10, and the tightening operation of the bolt 10 is completed.

According to the first embodiment, in the step shown in FIG. 4E, the second end is attached to the large-diameter end (right side in FIG. 4) of the bolt 10.
A predetermined tensile force (bolt tightening oil pressure) is applied, and in a state where the tensile force is applied, the nut 16b is tightened to the thread portion of the large-diameter end of the bolt 10. It is possible to eliminate the problem in which the tensile force does not act on the large-diameter side portion 18b (between the fixing point A and the large-diameter side end) of the central portion 18 of the bolt 10, which has been a problem. As a result, in the first embodiment, a tensile force (axial force) of the same magnitude can be applied to the threaded portions 14 at both ends of the bolt 10, which is a problem with the nut 16 b on the large diameter portion side. Looseness can be reliably prevented.

In the first embodiment, the bolt 1
The value of the second predetermined tensile force (bolt tightening oil pressure) acting on each of the small-diameter portion side and the large-diameter portion side of 0 is set to 75% of the yield stress of the bolt 10 in the first embodiment. As a modified example, the value of the second predetermined tensile force may be a value of 85% of the yield stress of the bolt 10. As a result, when a larger tensile force acts on the bolt 10, the nut 16
a, 16b, so that the nut 16
a, 16b can be prevented from being loosened.

Further, as another modified example of the first embodiment,
When each end of the bolt 10 is pulled by the second hydraulic tensioner 22, first, the bolt 10 is pulled at a stress of 85% of the yield stress, and then the tensile force is reduced to a value of 75% of the yield stress. The nuts 16a and 16b are tightened in a state where 75% of the stress is applied.
In this case, when the bolt 10 is pulled with a larger stress (85% of the yield stress), the amount of elongation of the bolt 10 increases, but the nuts 16a and 16b are tightened with a smaller stress (75% of the yield stress). As a result, the load acting on the bolt 10 is reduced. That is,
Since the amount of extension of the bolt 10 is increased and the load acting on the bolt 10 is reduced, the nut 1
6a, 16b can be prevented from being loosened.

Next, a second embodiment of the present invention will be described.
In the above-described first embodiment, in the step shown in FIG. 4B, the first predetermined tensile force (sleeve expanding hydraulic pressure) is applied to the small-diameter portion side of the bolt 10 so that the sleeve 12
Is expanded radially outward, but in the second embodiment,
The value of the first predetermined tensile force is the 80% stress of the first embodiment. 4A, 4C, 4
D, the steps shown in FIGS. 4E and 4F are the same as in the first embodiment. According to the second embodiment, by reducing the tensile force acting on the small-diameter portion side of the bolt 10 for expanding the sleeve 10 as described above, the central portion of the bolt 10 shown in FIG. The binding force due to the frictional force between the portion 18b (from the fixing point A to the large-diameter end portion) and the sleeve 12 is reduced. As a result, the bolt 1
When the process shown in FIG. 4E is performed, the amount of elongation of the large-diameter side portion 18b of the bolt 10 increases, and the loosening of the nut 16b can be more effectively prevented. As described above, the first predetermined stress is a value that causes the outer peripheral surface on the large diameter portion side of the bolt to contact the inner peripheral surface of the sleeve to generate a predetermined restraining force.

Next, a third embodiment of the present invention will be described with reference to FIG. In the third embodiment, the sleeve 12 is
It is formed longer than that of the first embodiment so that the large diameter portion contacts the nut 16b. As a result, in the step of FIG. 5 corresponding to the step of FIG. 4E, a tensile force acts on the large-diameter portion side of the bolt 10 by the second hydraulic tensioner 22, whereby the large-diameter portion side end portion 12 b of the sleeve 12 is formed.
Contact the surface of the nut 16b. As a result, nut 1
6b is larger than that of the first embodiment by the contact area with the sleeve 12, and the nut 16
Is increased, and loosening of the nut 16b can be prevented. The other steps of the third embodiment are the same as those of the first embodiment.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In the fourth embodiment, the coupling member 1, that is, the through hole 8 formed at the end of the governor rotor 4
Of the region 24 between the large-diameter end of the sleeve 10 and the portion in contact with the nut 16b is R2, and R2 is smaller than R1. . As a result, the contact area of the nut 16b is larger than that of the first embodiment by the width of (R2-R1), and the nut 16b can be prevented from being loosened accordingly. The other steps of the fourth embodiment are the same as those of the first embodiment.

Next, a fifth embodiment of the present invention will be described with reference to FIG. In the fifth embodiment, in the step of FIG. 4F, after the nut 16b is attached to the end of the bolt 10 with the second predetermined tensile force acting on the bolt 10, both the nut 10b and the bolt 10 Is formed, a tapered wedge 28 is driven into the hole 26, and then a predetermined portion of the tapered wedge 28 is welded to prevent rotation. According to the fifth embodiment, loosening of the nut 16b can be completely prevented.

[0025]

As described above, according to the bolt tightening method of the present invention, loosening of the nut can be prevented.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a coupling portion for coupling an end of a generator rotor and an end of a governor rotor.

FIG. 2 is a side view as viewed from the right (the governor side) in FIG.

FIG. 3 is a diagram showing steps of a conventional bolt tightening method.

FIG. 4A is a diagram showing a step of the bolt tightening method according to the first embodiment of the present invention.

FIG. 4B is a diagram showing a step of the bolt tightening method according to the first embodiment of the present invention.

FIG. 4C is a diagram showing a step of the bolt tightening method according to the first embodiment of the present invention.

FIG. 4D is a diagram showing a step of the bolt tightening method according to the first embodiment of the present invention.

FIG. 4E is a diagram showing a step of the bolt tightening method according to the first embodiment of the present invention.

FIG. 4F is a view showing a step of the bolt tightening method according to the first embodiment of the present invention.

FIG. 5 is a view showing a part of steps of a bolt tightening method according to a third embodiment of the present invention.

FIG. 6 is a view showing a part of steps of a bolt tightening method according to a fourth embodiment of the present invention.

FIG. 7 is a view showing a part of steps of a bolt tightening method according to a fifth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coupling member 2 End of generator rotor 4 End of governor rotor 6 Spacer 8 Through hole 10 Bolt 12 Sleeve 14 Bolt thread 16 Nut 18 Bolt center 20 First hydraulic tensioner 22 Second hydraulic tensioner 24 area 26 hole 28 tapered wedge

Claims (7)

[Claims] 1. A tapered bolt having a threaded portion at both ends and a central portion having a small diameter portion and a large diameter portion in a through hole formed in the coupling member, and a bolt having the small diameter portion and the large diameter portion inserted therein. An insertion step of inserting a sleeve having a tapered inner peripheral surface aligned with the outer peripheral surface, and in a state where the bolt and the sleeve are inserted into the through holes,
An expanding step of radially expanding the sleeve by applying a tensile force of a first predetermined stress to the small-diameter portion side of the bolt; and a second step of applying a second force to the small-diameter portion side of the bolt with the sleeve expanded.
A first tightening step of tightening the nuts to the threaded portions at both ends of the bolt while applying the tensile force of the predetermined stress, and the large diameter of the bolt with the sleeve expanded. Second on the part side
A second tightening step of applying a tensile force of a predetermined stress and further tightening a nut of a screw portion on the large diameter side of the bolt in a state where the tensile force is applied. Method. 2. The bolt tightening method according to claim 1, wherein the second predetermined stress has a value of 75% to 85% of a yield stress of the bolt. 3. In the second tightening step, before applying a tensile force of a second predetermined stress to the large-diameter portion side of the bolt,
2. The method according to claim 1, wherein a stress greater than the second predetermined stress and smaller than the yield stress is applied. 4. The bolt according to claim 1, wherein the first predetermined stress is a value that generates a predetermined restraining force when the outer peripheral surface of the large diameter portion of the bolt comes into contact with the inner peripheral surface of the sleeve. Tightening method. 5. The bolt tightening method according to claim 1, wherein the sleeve is set to a length such that a large-diameter portion of the sleeve contacts a nut in the second tightening step. 6. The coupling member according to claim 1, wherein a radius of a through hole formed in the coupling member is smaller at a portion on a large diameter portion that is not engaged with the sleeve than at a portion engaged with the sleeve.
The bolt tightening method described. 7. A driving step of, after the second tightening step, driving a wedge having a rotation preventing function into a screw portion at an end of the bolt on the large-diameter portion side and a nut tightened to the screw portion. The bolt tightening method according to claim 1, further comprising: