JP3116298B2 - Bolt axial force measuring method and apparatus and measuring jig - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as a method of measuring an axial force of a bolt, a method of estimating an axial force from a torque of a torque wrench,
There is known a method of measuring the transmission speed of an ultrasonic wave in the axial direction of a bolt, calculating a minute extension of the bolt in the axial direction, and converting it into an axial force.

[0003]

In the above-mentioned measuring method, a method using a torque wrench has an exact correspondence between the torque and the axial force so that the rotation angle of the nut is different even with the same torque. There was a problem that it was difficult to obtain, and it was not possible to measure the axial force accurately.

[0004] The method based on the measurement of the transmission speed of the ultrasonic wave enables theoretically accurate measurement. However, since the method measures the minute elongation of the bolt, the length of the bolt before applying a tightening force is measured. Had to be determined precisely. In addition, ultrasonic waves are introduced from the flat surface of the bolt head in the axial direction of the bolt, but marks or other markings are often provided on the bolt head. There was also a problem that it was not possible.

The present invention has been made in view of the above problems, and has as its object to provide a method and apparatus capable of easily and accurately measuring the axial force of a bolt and a jig used for the measurement. I have.

[0006]

SUMMARY OF THE INVENTION According to the present invention, which has been made with the above object, the contact pressure and the contact area between the thread of the bolt and the thread of the nut change according to the axial force of the bolt. Nut-bolt-across 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, according to the first aspect of the present invention, an ultrasonic wave is oscillated on one side of a nut which is screwed and tightened to a bolt, and the bolt is formed based on the intensity of the ultrasonic wave transmitted to the other side opposite to the one side of the nut. And measuring the axial force of the bolt.

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

According to a third aspect of the present invention, there is provided a 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 of a nut screwed and tightened to a bolt and the other side facing the one side include:
At least one pair of ultrasonic transducers each capable of being arranged,
Ultrasonic oscillation means configured through one transducer of each pair of ultrasonic transducers, and ultrasonic receiving means configured through the other transducer, It is an axial force measuring device.

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

According to a sixth aspect of the present invention, there is provided the bolt axial force measuring apparatus according to the fourth or fifth aspect, wherein the ultrasonic oscillation means and the receiving means are variable in frequency.

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

The invention according to claim 8 is provided with a cylindrical portion which can be axially fitted from an end of the bolt to a nut which is screwed and tightened to the bolt, and at least an inner wall of the cylindrical portion has A pair of ultrasonic vibrators are provided so as to be able to face the side surfaces of the nut, and a medium supply path for filling a gap between the ultrasonic vibrator and the side surfaces of the nut with a couplant is provided by the ultrasonic vibrator. A jig for measuring the axial force of a bolt, characterized in that the jig is opened in the vicinity of the bolt.

According to a ninth aspect of the present invention, there is provided a bolt shaft according to the eighth aspect, wherein a ball held by an elastic member is provided on the inner wall of the cylindrical portion, and the ball is in contact with a side surface of the nut. It is a jig for force measurement.

According to a tenth aspect of the present invention, there is provided the jig for measuring an axial force of a bolt according to any one of the seventh to ninth aspects, wherein the cylindrical portion has an inner wall having a hexagonal cross section.

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

[0018]

According to the method and apparatus for measuring the axial force of a bolt according to the present invention, the intensity of transmitted ultrasonic waves and the axial force of the bolt have a certain correspondence, so that the axial force of the bolt can be accurately measured. .

Further, according to the jig for measuring the axial force of the bolt of the present invention, the ultrasonic vibrator can be easily arranged on the opposite side surface of the nut, and the operation of measuring the axial force can be simplified. it can.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an apparatus for measuring the axial force of a bolt according to an embodiment.
It comprises a pair of ultrasonic transducers 1 a and 1 b and an ultrasonic flaw detector 2. The ultrasonic vibrators 1a and 1b each have a body 3
The ultrasonic transducer 1a is provided so as to be exposed in the flat surfaces of the ultrasonic flaw detector 2 and the control output of the ultrasonic flaw detector 2 through the connection cable 5a from the external connector 4 provided on the body 3a. Connected to the end 6, an ultrasonic oscillation unit is configured in cooperation with a circuit in 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 An ultrasonic receiving unit is configured in cooperation with the ultrasonic detecting device 2. The intensity of the ultrasonic wave received by the receiving unit can be analyzed in the ultrasonic flaw detector 2.

In FIG. 1, 8a and 8b are plate-like steel materials,
9 is a bolt inserted through the steel material 8a, 8b, 10 is a bolt 9
Is a hexagon nut that is screwed into the nut to tighten the steel materials 8a and 8b. A vessel 3a provided with the ultrasonic transducers 1a and 1b,
3b are connected to the side surfaces 1 of the hexagon nut 10 facing each other.
0a and 10b, the ultrasonic transducers 1a and 1b
Can be arranged in contact with the side surfaces 10a and 10b.

In order to measure the axial force of the bolt 9 with the axial force measuring device of the above embodiment, the ultrasonic vibrator 1a constituting the ultrasonic oscillating means is vibrated so that the ultrasonic wave (longitudinal wave) is applied to the hexagonal nut 1
The shaft of the nut and the bolt 9 is transmitted through the one side surface 10a of the nut 0. Then, the ultrasonic wave transmitted through the nut and bolt shafts is transmitted to the ultrasonic vibrator 1 constituting the ultrasonic wave receiving means.
b, the intensity of the ultrasonic wave transmitted by the ultrasonic wave receiving means is analyzed. The contact pressure between the thread of the bolt 9 and the thread of the hexagonal nut 10 changes according to the axial force of the bolt 9, and the magnitude of this contact pressure depends on the strength of transmitted ultrasonic waves received on the ultrasonic vibrator 1b side. Since the reflection is reflected, the axial force at the time of tightening the bolt 9 can be known from the intensity of the transmitted ultrasonic wave.

For the M36 (SCR440) bolt, the axial force of the bolt was measured with a load cell, and the intensity of the transmitted ultrasonic wave of the hexagonal nut was measured with the axial force measuring device and method. As shown in FIG.

The frequency of the ultrasonic wave was 5 MHz. A glycerin-based couplant (eg, “Sonicoat” manufactured by Nichiai Acetylene Co., Ltd.) is applied to the side surface of the nut, and an ultrasonic vibrator is brought into contact with the glycerin-based couplant so that an air layer does not intervene in the contact portion. I made it. The horizontal axis in FIG. 2 is the axial force measured by the load cell, and the vertical axis is the intensity of transmitted ultrasonic waves. The measurement of the transmitted ultrasonic wave was performed between three sets of opposing side surfaces of the hexagon nut. The intensity of the ultrasonic wave 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 comparison between the intensity of the ultrasonic wave transmitted through the nut and the axial force of the bolt. The “variation” of the measured values is based on the bolt axis,
It is recognized that one reason is the coincidence between the ultrasonic transducers 1a and 1b and the lines facing each other. Therefore, in the measurement shown in FIG. 2, the measurement was performed between the three sets of opposing side surfaces of the hexagon nut, an average value was obtained, and a comparison relationship between the axial force and the transmitted ultrasonic intensity was found. If the positions of the opposing lines 1a and 1b can be correctly set, the average value of the transmitted ultrasonic intensities between the two sets of opposing sides and 1
A value of the transmitted ultrasonic intensity between the opposing sides of the set;
It is possible to establish a proportional relationship with the axial force.

The frequency of the transmitted ultrasonic wave is 5 MHz, but may be lower if the diameter is larger than M36, or 5 MHz if the diameter is smaller than M36 because the beam path becomes shorter. It is preferable to ensure the measurement accuracy as a higher frequency. Therefore, it is advantageous that the ultrasonic oscillation means and the ultrasonic reception means configured via the ultrasonic flaw detector 2 have variable frequencies.

FIG. 3 shows a measuring jig 11 in which the ultrasonic vibrators 1a and 1b are accurately opposed on a line perpendicular to the axis of the bolt. The measuring jig 11 is configured such that a cylindrical portion 12a of a support 12 having a cylindrical shape with a bottom is screwed into a bolt,
It can be fitted to the tightened hex nut 10. The cylindrical portion 12a has an inner wall having a regular hexagonal cross section. An ultrasonic vibrator 1a is provided flush with one of the inner walls facing each other, and an ultrasonic vibrator 1b is placed on the other of the opposing inner walls. One is provided.

Each of the ultrasonic vibrators 1a and 1b is connected to an external connector 4 radially provided on the outer wall of the cylindrical portion 12a via a lead wire 13, and is connected to the ultrasonic flaw detector 2. The connection can be made.

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 required.
a is fitted to the hexagonal nut 10 to perform this. When the measurement is performed on the three sets of side surfaces facing each other, the fitted cylindrical portion 12a is removed, rotated by 60 degrees, and 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 on a line perpendicular to the axis of the bolt, the measurement can be performed by one set of opposed side surfaces. The rotation of the tubular portion 12a and the repeated fitting may be avoided.

The ultrasonic vibrators 1a and 1b provided on the inner wall of the cylindrical portion 12a may be provided on three opposing inner walls in pairs. 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 unit. , Measuring jig 11
And a connection dial (not shown) provided between the external connection connector 4 provided on the outer wall of the support 12 and the pair of ultrasonic vibrators 1a and 1b provided on the inner wall of the cylindrical 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 denoted by the same reference numerals. The cylindrical portion 12a of the support 12 can be fitted to the hexagon nut 10 with a small gap 14 therebetween.
For this reason, a plurality of balls 15 are held on each inner wall of the cylindrical portion 12a having a regular hexagonal cross section by a resilient member such as a coil spring 16 or a rubber material. The gaps 14 with the respective side surfaces are formed as opposed gaps having the same distance. The support 12 is provided with the couplant in a gap 14 formed between the ultrasonic vibrators 1 a and 1 b and the side faces 10 a and 10 b of the hexagon nut 10.
A medium supply path 17 is formed in order to supply the ultrasonic vibrators 1a and 1b to one end of the medium supply path 17.
The opening 17a is provided in the vicinity of
1 is open at the outer end face.

In this embodiment, since the inner wall of the cylindrical portion 12a has room for the hexagon nut 10, the hexagon nut 1
It becomes easy to fit into zero. When the couplant is press-fitted through the medium supply path 17 after the fitting of the cylindrical portion 12a, the couplant is filled in the gap 14 between the ultrasonic vibrators 1a and 1b and the side surfaces 10a and 10b of the hexagon nut 10, and the couplant is filled. It is possible to measure the axial force of the bolt as shown in FIG.

A plurality of types of the measuring jigs 11 are prepared in advance with supports 12 of various sizes corresponding to the size of the hexagon nut. Since the nut may be a hexagon or a quad, the nut may have a rectangular cross-section on the inner wall of the cylindrical portion.

[0036]

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

According to the jig for measuring the axial force of a bolt according to the present invention, the ultrasonic vibrator can be correctly arranged on a line orthogonal to the axis of the bolt, eliminating measurement variations and improving accuracy. There is an effect that can be done.

[Brief description of the drawings]

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

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

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

FIG. 4 is a view of another embodiment of the measuring jig of the present invention;
(A) is a longitudinal front view, (b) is a longitudinal side view.

[Explanation of symbols]

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

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Enya Enya 5-4-16 Neukansen Izumi, Komae-shi, Tokyo Nishi Aircraft Co., Ltd. (56) References JP-A-1-142426 (JP, A) JP-A Heisei JP-A-2-205736 (JP, A) JP-A-2-264837 (JP, A) JP-A-5-26749 (JP, A) JP-A-57-161526 (JP, A) JP-A-1-131422 (JP, A A) Japanese Utility Model 1983-151848 (JP, U) Japanese Utility Model Application Hei 4-109365 (JP, U) European Patent 589271 (EP, A1) US Patent 5,208,839 (US, A) (58) Fields investigated (Int. . ^7, DB name) G01L 5/00 G01L 5/24 G01N 29/24

Claims (11)

(57) [Claims] An ultrasonic wave is oscillated on one side of a nut screwed and tightened to a bolt, and the axial force of the bolt is obtained based on the intensity of the ultrasonic wave transmitted to the other side opposite to the one side of the nut. A method for measuring the axial force of a bolt, characterized in that: 2. The method for measuring the axial force of a bolt according to claim 1, wherein the oscillation of the ultrasonic waves and the reception of the 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 method for measuring the axial force of a bolt according to claim 1, wherein the frequency of the ultrasonic wave is determined in consideration of the diameter of the bolt. 4. One side of a nut screwed and tightened to a bolt, at least one pair of ultrasonic vibrators that can be disposed on the other side opposite to the one side, and a pair of ultrasonic vibrators. An axial force measuring device for a bolt, comprising: an ultrasonic oscillator configured via one vibrator; and an ultrasonic receiver configured via another vibrator. 5. The bolt axial force measuring apparatus according to claim 4, wherein the ultrasonic vibrator is a plurality of pairs, 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 oscillating means and the receiving means are variable in frequency. 7. A cylindrical portion which can be axially fitted from the end of the bolt to a nut which is screwed and tightened to the bolt, and at least one pair of ultrasonic vibrations is provided on the inner wall of the cylindrical portion. A jig for measuring an axial force of a bolt, wherein a child is provided so as to be able to abut on a side surface of the nut. 8. A cylindrical part which can be axially fitted from an end of the bolt to a nut screwed and tightened to the bolt, and at least one pair of ultrasonic vibrations is provided on an inner wall of the cylindrical part. The armature is provided so as to be able to face the side surface of the nut, and a medium supply path for filling the couplant in the gap between the ultrasonic oscillator and the side surface of the nut is opened in the vicinity of the ultrasonic oscillator. A jig for measuring an axial force of a bolt, the jig being provided. 9. A jig for measuring an axial force of a bolt according to claim 8, wherein a ball held by an elastic member is provided on an inner wall of the cylindrical portion, and the ball comes into contact with a side surface of the nut. . 10. The jig for measuring an axial force of a bolt according to claim 7, wherein an inner wall of the cylindrical portion has a hexagonal cross section. 11. The axial force measurement of a bolt according to claim 7, wherein a plurality of pairs of ultrasonic transducers are provided, and each pair is connected to an external connector via a switching dial. Jig.