JPH08170933A - Method and device for measuring axial force of bolt and measuring jig therefore - Google Patents

Abstract

PURPOSE: To provide a method and a device by which the axial force of bolt can be measured accurately and easily and a jig for its measurement. CONSTITUTION: The title measuring device consists of a pair of ultrasonic oscillators that can be arranged on the side faces 10a and 10b of a nut 10 engaged with and tightened on a bolt 9, an ultrasonic oscillating means constituted by one ultrasonic oscillator 1a and an ultrasonic receiving means constituted by the other ultrasonic oscillator lb. Since the contact pressure between the threads of the bolt 9 and nut 10 is changed depending on the axial force of bolt and the intensitity of the ultrasonic wave is changed, the axial force of the bolt 9 can be measured based on the ultrasonic wave received by the ultrasonic receiving means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for measuring the axial force of a bolt used as a member tightening means, and a jig for the measurement.

[0002]

2. Description of the Related Art Conventionally, as a method of measuring the axial force of a bolt, a method of estimating the axial force from the torque of a torque wrench,
A method is known in which the ultrasonic wave transmission speed is measured in the axial direction of the bolt, a minute extension of the bolt in the axial direction is calculated, and converted into an axial force.

[0003]

In the above measuring method, the method using a torque wrench has an accurate correspondence between the torque and the axial force so that the rotation angle of the nut may be different even with the same torque. There is a problem that it is difficult to obtain and accurate axial force cannot be measured.

The method of measuring the ultrasonic wave transmission velocity can theoretically make accurate measurement, but since it measures a minute extension of the bolt, the length of the bolt before applying the tightening force is measured. There was a problem that had to be obtained precisely. In addition, ultrasonic waves are introduced in the axial direction of the bolt from the flat surface of the bolt head, but the bolt head is often provided with markings or other markings. With such bolts, the axial force cannot be measured. There was also the problem that it could not be done.

The present invention has been made in view of the above problems, and an object thereof is to provide a method and apparatus for easily and accurately measuring the axial force of a bolt, and a jig used for the measurement. There is.

[0006]

SUMMARY OF THE INVENTION The present invention, which has been made based on the above object, changes the contact pressure and the contact area between the thread of the bolt and the thread of the nut according to the axial force of the bolt, and this change causes the change. Nut-bolt-in the direction that crosses the nut
Since the intensity of the ultrasonic wave transmitted through the nut changes, the axial force of the bolt is determined from the intensity of the transmitted ultrasonic wave.

That is, the invention of claim 1 oscillates ultrasonic waves on one side of the nut that is screwed into the bolt and tightened, and the bolt is based on the intensity of the ultrasonic wave transmitted to the other side opposite to the one side of the nut. It is a method for measuring the axial force of a bolt, characterized in that the axial force of

According to a second aspect of the invention, the oscillation of ultrasonic waves and the reception of transmitted ultrasonic waves are performed on a plurality of opposing side surfaces of the nut,
The bolt axial force measuring method according to claim 1, wherein the intensity of the transmitted ultrasonic wave is obtained as an average value.

A third aspect of the present invention is the bolt axial force measuring method according to the first or second aspect, wherein the frequency of the ultrasonic wave is determined in consideration of the diameter of the bolt.

According to a fourth aspect of the present invention, one side surface of the nut screwed into the bolt and tightened and one side surface facing the one side surface are provided.
At least a pair of ultrasonic transducers that can be arranged respectively,
An ultrasonic wave oscillating means configured via one oscillator of each pair of ultrasonic oscillators and an ultrasonic wave receiving means configured via the other oscillator It is an axial force measuring device.

According to a fifth aspect of the present invention, there is provided the axial force measuring device for a bolt according to the fourth aspect, wherein the ultrasonic transducer is a plurality of pairs, and the ultrasonic oscillating means and the receiving means can be sequentially configured for each pair. is there.

A sixth aspect of the invention is the bolt axial force measuring device according to the fourth or fifth aspect, wherein the ultrasonic wave oscillating means and the receiving means are variable in frequency.

According to a seventh aspect of the present invention, there is provided a tubular portion that can be axially fitted from the end portion of the bolt to the nut that is screwed and tightened on the bolt, and the inner wall of the tubular portion has at least the tubular portion. A jig for axial force measurement of a bolt, wherein a pair of ultrasonic vibrators are provided so as to be able to contact the side wall of the nut.

According to an eighth aspect of the present invention, there is provided a tubular portion that can be axially fitted from the end portion of the bolt to the nut that is screwed and tightened on the bolt, and at least the inner wall of the tubular portion is provided. A pair of ultrasonic transducers are provided so as to face the side surfaces of the nut, and a medium supply path for filling a contact medium in a gap between the ultrasonic transducers and the side surfaces of the nut is provided with the ultrasonic transducers. It is a jig for measuring axial force of a bolt, which is opened in the vicinity of.

According to a ninth aspect of the present invention, a ball supported by an elastic member is provided on the inner wall of the tubular portion, and the ball is in contact with the side surface of the nut. It is a force measuring jig.

A tenth aspect of the present invention is the axial force measuring jig for a bolt according to any one of the seventh to ninth aspects, wherein the inner wall of the tubular portion has a hexagonal cross section.

According to a ninth aspect of the present invention, the ultrasonic transducer is made up of a plurality of pairs, and each pair is connected to a connector for each portion via a switching dial. This is a jig for measuring the axial force of a bolt.

[0018]

According to the bolt axial force measuring method and apparatus of the present invention, since the intensity of the transmitted ultrasonic wave and the bolt axial force have a certain correspondence, the bolt axial force can be accurately measured. .

According to the axial force measuring jig for a bolt of the present invention, the ultrasonic transducer can be easily arranged on the opposite side surfaces of the nut, and the axial force measuring operation can be simplified. it can.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a bolt axial force measuring device according to an embodiment.
It is composed of a pair of ultrasonic transducers 1a and 1b and an ultrasonic flaw detector 2. The ultrasonic transducers 1a and 1b are each a body 3
The ultrasonic transducer 1a is provided so as to be exposed in the flat surfaces of a and 3b, and one of the ultrasonic transducers 1a outputs the control output of the ultrasonic flaw detector 2 from the external connector 4 provided on the body 3a through the connection cable 5a. The ultrasonic wave oscillating means is configured to be connected to the end 6 and cooperate with the circuit inside the ultrasonic flaw detector 2. Similarly, the other ultrasonic transducer 1b is connected to the control input terminal 7 of the ultrasonic flaw detector 2 from the external connection connector 4 of the body 3b through the connection cable 5b, and is connected to the circuit inside the ultrasonic flaw detector 2. The ultrasonic wave receiving means is jointly configured, and the intensity of the ultrasonic wave received by this receiving means can be analyzed in the ultrasonic flaw detector 2.

In FIG. 1, 8a and 8b are plate-shaped steel materials,
9 is a bolt inserted through the steel materials 8a and 8b, and 10 is a bolt 9
It is a hexagonal nut that is screwed to and tightens the steel materials 8a and 8b. A body 3a provided with the ultrasonic transducers 1a and 1b,
3b to the side faces 1 of the hexagon nut 10 that face each other.
0a, 10b, ultrasonic transducers 1a, 1b
However, it can be placed in contact with the side surfaces 10a, 10b.

In order to measure the axial force of the bolt 9 with the axial force measuring device of the above-mentioned embodiment, the ultrasonic vibrator 1a constituting the ultrasonic wave oscillating means is vibrated to generate ultrasonic waves (longitudinal waves) in the hexagon nut 1.
The shaft of the nut and the bolt 9 is made transparent from the one side surface 10a of 0. Then, the ultrasonic wave transducer 1 which constitutes ultrasonic wave receiving means for the ultrasonic wave transmitted through the shafts of the nut and the bolt.
The intensity of the ultrasonic wave received at b and transmitted by the ultrasonic wave receiving means is analyzed. The contact pressure between the screw thread of the bolt 9 and the screw thread of the hexagonal nut 10 changes according to the axial force of the bolt 9, and the magnitude of this contact pressure changes depending on the strength of the transmitted ultrasonic wave received on the ultrasonic transducer 1b side. Since it is reflected, the axial force when tightening the bolt 9 can be known from the intensity of the transmitted ultrasonic wave.

While measuring the axial force of the M36 (SCR440) bolt with a load cell, the strength of the transmitted ultrasonic wave of the hexagonal nut is measured by this and the axial force measuring device and method described above. As shown in FIG.

The ultrasonic frequency used was 5 MHz. Apply a glycerin-based contact medium (for example, "Sonicoat" manufactured by Nigo Acetylene Co., Ltd.) to the side surface of the nut, and then contact the ultrasonic vibrator from above to prevent the air layer from intervening in the contact part. I chose The horizontal axis of FIG. 2 is the axial force measured by the load cell, and the vertical axis is the intensity of the transmitted ultrasonic waves. The transmitted ultrasonic wave was measured between the three facing side surfaces of the hexagon nut. The intensity of ultrasonic waves is shown as a percentage with the maximum value at an axial force of 45 tons being 100%.

As shown in FIG. 2, it can be seen that there is a comparative relationship between the intensity of ultrasonic waves transmitted through the nut and the axial force of the bolt. The "variation" of the measured value is the axis of the bolt,
It is recognized that the matching relationship between the ultrasonic transducers 1a and 1b and the opposing line is one of the reasons. Therefore, the measurement shown in FIG. 2 was performed between three sets of opposite side surfaces of the hexagon nut, the average value was obtained, and a comparative relationship between the axial force and the transmitted ultrasonic wave intensity was found. If the positions of the opposing lines 1a and 1b can be correctly set, the average value of the transmitted ultrasonic wave intensity between the two pairs of opposing side surfaces or 1
The value of the transmitted ultrasonic intensity between opposite sides of the set,
It is also possible to establish a proportional relationship with the axial force.

The frequency of the ultrasonic wave to be transmitted is set to 5 MHz, but if the diameter is larger than M36, the frequency may be lower than this, and if the diameter is smaller than M36, the beam path is shortened, and the frequency is 5 MHz. It is advisable to ensure measurement accuracy with a higher frequency. Therefore, it is advantageous that the ultrasonic oscillating means and the ultrasonic receiving means configured via the ultrasonic flaw detector 2 have variable frequencies.

FIG. 3 shows a measuring jig 11 in which the ultrasonic transducers 1a and 1b are accurately opposed to each other on a line orthogonal to the axis of the bolt. In the measuring jig 11, the tubular portion 12a of the support body 12 having a tubular shape with a bottom is screwed into a bolt,
It can be fitted into the tightened hexagon nut 10. The cylindrical portion 12a has an inner wall having a regular hexagonal cross section, and the ultrasonic transducer 1a is provided flush with one of the inner walls facing each other, and the ultrasonic transducer 1b has a surface facing the other inner wall. It is provided in one.

Each of the ultrasonic transducers 1a and 1b is connected via a lead wire 13 to an external connection connector 4 provided radially on the outer wall of the cylindrical portion 12a, and is connected to the ultrasonic flaw detector 2. It is possible to connect.

In order to perform the above-mentioned measurement using the measuring jig 11 of this embodiment, the cylindrical portion 12 of the support 12 is used.
It is performed by fitting a into the hexagon nut 10. When the measurement is performed on three sets of side surfaces facing each other, the fitted tubular portion 12a is removed, rotated by 60 degrees, and then fitted again for each measurement of one set of side surfaces.

According to such a measuring jig 11, since the ultrasonic transducers 1a and 1b can be accurately opposed to each other on the line orthogonal to the axis of the bolt, the measurement is performed with a pair of opposed side surfaces. It is possible that the rotation and fitting of the tubular portion 12a are repeated.

The ultrasonic transducers 1a and 1b provided on the inner wall of the tubular portion 12a may be provided on each of the three inner walls facing each other one by one. There are a method of preparing three ultrasonic flaw detectors 2 for three pairs of ultrasonic transducers 1a and 1b, and a method of changing the connection between the connection cables 5a and 5b and the external connection connector 4 with one. , Measuring jig 11
A switching dial (not shown) is provided on the connection between the external connection connector 4 provided on the outer wall of the support body 12 and the pair of ultrasonic transducers 1a, 1b provided on the inner wall of the tubular portion 12a. It makes sense to be able to change the relationship.

FIG. 4 shows another embodiment of the measuring jig 11. The same members as those in the embodiment of FIG. 3 are designated by the same reference numerals. The tubular portion 12a of the support 12 can be fitted into the hexagonal nut 10 with a minute gap 14 maintained.
For this reason, a plurality of balls 15 are elastically supported on each inner wall of the cylindrical portion 12a having a regular hexagonal cross-section by a coil spring 16 and an elastic member such as a rubber material. The gaps 14 with the respective side faces of the above are so as to be facing gaps of the same distance. Further, in the support body 12, the contact medium is provided with a gap 14 formed between the ultrasonic transducers 1 a and 1 b and the side surfaces 10 a and 10 b of the hexagon nut 10.
A medium supply path 17 is formed to supply the ultrasonic transducers 1a, 1b.
The opening 17a is formed in the vicinity of the
The outer end surface of No. 1 is opened.

In the case of this embodiment, since the inner wall of the cylindrical portion 12a has a margin with respect to the hexagon nut 10, the hexagon nut 1
It becomes easy to fit into 0. When the contact medium is press-fitted through the medium supply passage 17 after the tubular portion 12a is fitted, the contact medium is filled in the gap 14 between the ultrasonic transducers 1a and 1b and the side surfaces 10a and 10b of the hexagon nut 10, and It becomes possible to measure the axial force of the bolt as described above.

A plurality of kinds of the measuring jigs 11 are prepared in advance by using the supports 12 having various sizes according to the size of the hexagon nut. Since there are nuts having a hexagonal shape and a quadrangular shape, a nut having an inner wall with a quadrangular cross section may be prepared.

[0036]

As described above, according to the present invention, the axial force of the bolt can be accurately measured by a simple method. Therefore, inspection of structures such as steel towers and bridges is easy.

Further, according to the bolt axial force measuring jig of the present invention, the ultrasonic transducer can be correctly arranged on the line orthogonal to the axis of the bolt, eliminating the variation in measurement and improving the accuracy. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a diagram of an embodiment of the present invention, in which (a) is a configuration diagram,
(B) is a front view of the measured hexagon nut.

FIG. 2 is a graph of the axial force and the intensity (echo height) of transmitted ultrasonic waves measured in an example of the present invention.

FIG. 3 is a diagram of an embodiment of a measuring jig of the present invention,
Is a vertical sectional front view, and (b) is a vertical sectional side view.

FIG. 4 is a diagram of another embodiment of the measuring jig of the present invention,
(A) is a vertical sectional front view, and (b) is a vertical sectional side view.

[Explanation of symbols]

 1a, 1b Ultrasonic transducer 2 Ultrasonic flaw detector 3a, 3b Body 4 External connection connector 5a, 5b Connection cable 6 Control output end 7 Control input end 8a, 8b Steel material 9 Bolt 10 Hexagon nut 10a, 10b Side surface 11 For measurement Jig 12 Support 12a Cylindrical part 13 Lead wire 14 Gap 15 Ball 16 Coil spring 17 Medium supply path 17a Opening

Front Page Continuation (72) Inventor Kazuo Aizawa 1-17-10 Kyobashi, Chuo-ku, Tokyo Himeno Tokyo Headquarters (72) Inventor Kenya Tanaka 5-4-16 Kanakaizumi, Komae-shi, Tokyo West cabin

Claims (11)

[Claims] 1. An ultrasonic wave is oscillated on one side surface of a nut which is screwed into a bolt and tightened, and the axial force of the bolt is obtained based on the intensity of the ultrasonic wave transmitted to the other side surface facing the one side surface of the nut. A method for measuring the axial force of a bolt. 2. The axial force measuring method for a bolt according to claim 1, wherein the oscillation of ultrasonic waves and the reception of transmitted ultrasonic waves are performed on a plurality of opposing side surfaces of the nut, and the intensity of the transmitted ultrasonic waves is obtained as an average value. 3. The bolt axial force measuring method according to claim 1, wherein the frequency of the ultrasonic waves is determined in consideration of the diameter of the bolt. 4. A nut that is screwed into a bolt and tightened, and one side surface of the nut, and at least one pair of ultrasonic transducers that can be respectively disposed on the other side surface that faces the one side surface. An axial force measuring device for a bolt, comprising: an ultrasonic wave oscillating means configured via one oscillator and an ultrasonic wave receiving means configured via the other oscillator. 5. The bolt axial force measuring device according to claim 4, wherein a plurality of pairs of ultrasonic vibrators are provided, and the ultrasonic oscillating means and the receiving means can be sequentially configured for each pair. 6. The bolt axial force measuring device according to claim 4, wherein the ultrasonic wave oscillating means and the receiving means are variable in frequency. 7. A nut that is screwed into a bolt and tightened is provided with a tubular portion that can be fitted axially from the end of the bolt, and at least a pair of ultrasonic vibrations are provided on the inner wall of the tubular portion. A jig for axial force measurement of a bolt, wherein a child is provided so as to be able to come into contact with a side surface of the nut. 8. A nut, which is screwed into a bolt and tightened, is provided with a tubular portion that can be axially fitted from the end of the bolt, and at least a pair of ultrasonic vibrations are provided on the inner wall of the tubular portion. A child is provided so as to be able to face the side surface of the nut, and a medium supply path for filling the gap between the ultrasonic vibrator and the side surface of the nut with the contact medium is opened near the ultrasonic vibrator. A jig for measuring the axial force of a bolt. 9. The jig for measuring the axial force of a bolt according to claim 8, wherein a ball elastically supported by an elastic member is provided on the inner wall of the tubular portion, and the ball abuts the side surface of the nut. . 10. The jig for measuring axial force of a bolt according to claim 7, wherein an inner wall of the tubular portion has a hexagonal cross section. 11. The axial force measurement of a bolt according to claim 7, wherein the ultrasonic transducer is made up of a plurality of pairs, and each pair is connected to an external connector through a switching dial. Jig.