JPH07280677A - Method and device for measuring bolt axial tension - Google Patents

Abstract

PURPOSE:To accurately measure the bolt axial tension by a relatively simple mechanism by carrying out such steps as measurement of reflecting wave, phase integration, detection of maximum reflecting wave and calculation of bolt axial tension. CONSTITUTION:A nut runner 11 is provided with a shaft 17 and is rotated 17 by an instruction 12. The shaft 17 is coupled 13 and the rotation 17 is transmitted 14. The tip of a joint 14 is engaged with the outer circumference of the bolt head, rotating the bolt as a socket 15, and the bolt is tightened by its rotation 14. On the other hand, an ultrasonic probe 15 is arranged inside the joint 14, and when the bolt is tightened, the probe 16 is pressed down to the upper end face of the bolt head. Then, the probe 16 is connected with a controller 12 through a cable 18 and it supplies 12 reflecting wave signals that an ultrasonic pulse is sent/received to/by the bolt based on the signals sent from the controller 12. At this time, the controller 12 measures the duration from the transmission of the ultrasonic pulse to the reception of the reflecting wave, and it measures the bolt axial tension. Further, since the relative positions of the upper end face of the bolt and the probe 16 are displaced and measured plural times in the initial measurement, the initial measurement can be accurately performed, thereby reducing the measurement errors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention finds the bolt length from the time it takes for an ultrasonic pulse to enter the bolt to be tightened from one end face in the axial direction until the reflected wave returns.
The present invention relates to bolt axial force measurement for calculating bolt axial force from the bolt length.

[0002]

2. Description of the Related Art Conventionally, in order to securely tighten a bolt, there is a device that measures the tightening force (bolt axial force) to obtain a predetermined bolt axial force. There are some that use pulses. In this device, ultrasonic transmission / reception means (ultrasonic probe) is attached to the upper end surface of the head side of the bolt, from which ultrasonic pulses are emitted in the axial direction of the bolt, and ultrasonic waves reflected at the tip of the bolt are transmitted. Measure the time until the pulse returns and find the bolt length.
The bolt length has a predetermined relationship with the bolt axial force, that is, as the bolt axial force increases, the bolt length increases. Therefore, the bolt axial force is obtained from the bolt length.

This device can always detect the bolt axial force. Therefore, this device can be used to tighten the bolt with a desired bolt axial force.

[0004]

However, in this apparatus, if the ultrasonic probe is fixed to the upper end surface of the bolt, the ultrasonic probe will rotate as the bolt rotates. It is not realistic to rotate the entire device, and either the ultrasonic probe and the transmitter / receiver can be rotated relative to each other, or the ultrasonic probe is pressed against the upper end surface of the bolt so as to be in close contact. It will make them slidable.

First, in order to enable relative rotation between the ultrasonic probe and the transceiver, a slip ring or the like or radio is used, but in any case, the mechanism is complicated. In addition, it becomes expensive and the noise becomes loud.

On the other hand, when the ultrasonic probe is pressed and fixed to the upper end surface of the bolt, the mechanism is simplified, but (i) the relative position between the probe and the upper end surface of the bolt is deviated, so that the initial value is measured. And the measured value at the time of actual axial force measurement is displaced,
(Ii) If there is a problem with the material of the bolt or if the probe is not properly applied, diffuse reflection or attenuation at the contact portion becomes large, and accurate measurement cannot be performed.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a bolt axial force measuring method and apparatus capable of performing accurate measurement with a relatively simple mechanism.

[0008]

According to the present invention, an ultrasonic pulse is applied to a bolt from one end face in the bolt axial direction to detect a reflected wave from the other end face in the bolt axial direction, and based on the detection result. In the bolt axial force measuring method for calculating the bolt axial force, the step of performing the ultrasonic pulse incidence and the measurement of the reflected wave a plurality of times, the step of integrating the phases of the plurality of measured reflected waves, and integrating, The step of detecting the largest reflected wave from the waveform of the reflected wave as a reflected wave on the other end face in the bolt axis direction, and measuring the time from the incidence of the ultrasonic pulse to the arrival of the reflected wave for the detected reflected wave, And a step of calculating a bolt axial force.

Further, according to the present invention, an ultrasonic pulse is applied to a bolt from one end face in the bolt axial direction to detect a reflected wave from the other end face in the bolt axial direction, and the bolt axial force is detected based on the detection result. In the bolt axial force measuring method for calculating, a step of temporarily stopping the tightening of the bolt and performing the ultrasonic pulse incidence and the reflected wave measurement a plurality of times, and a step of integrating the phases of the plurality of measured reflected waves The step of detecting the largest reflected wave from the accumulated reflected wave waveforms as the reflected wave on the other end face in the bolt axis direction, and the time from the incidence of the ultrasonic pulse for the detected reflected wave to the arrival of the reflected wave. A step of measuring and calculating a bolt axial force.

As the bolt tightening progresses, when the increase rates of the plurality of reflected waves detected are out of the predetermined range,
It is characterized in that the detected reflected wave is canceled.

Further, according to the present invention, an ultrasonic pulse is applied to a bolt from one end face in the bolt axial direction to detect a reflected wave from the other end face in the bolt axial direction, and the bolt axial force is detected based on the detection result. In the bolt axial force measuring device for calculating, tightening of the bolt is intermittently stopped, and a tightening mechanism for tightening the bolt, an ultrasonic pulse is incident from one end surface of the bolt, and a transmitting / receiving means for receiving reflection, Relative rotation means for rotating the transmission / reception means relative to the end face of the bolt with the bolt tightened, and reflections obtained by a plurality of measurements performed by rotating the transmission / reception means by the relative rotation means. Integrating means for integrating the phases of the waves and integrating means, and detecting means for detecting the largest reflected wave from the integrated reflected wave waveforms as a reflected wave on the other end face in the bolt axis direction, By measuring the time until the arrival of the reflected wave from the incident ultrasonic pulse for the reflected wave, characterized in that it has a calculation means for calculating a bolt axial force, the.

[0012]

In the present invention, the ultrasonic wave is incident from the head of the bolt and the reflected wave reflected by the tip surface of the bolt is received. Then, the time from transmission to reception of the reflected wave is measured. The bolt length is calculated by multiplying the measured time by the speed of the sound wave. The bolt is expanded according to the axial force when tightening, and the bolt length (extension from the state before tightening) is determined from the characteristic values of the bolt length and the material of the bolt.
Can be converted into bolt axial force, and bolt axial force can be obtained. Usually, within the range of elastic deformation, elongation and axial force are proportional.

In the present invention, when measuring the axial force of the bolt, the same axial force is measured a plurality of times. Then, by accumulating the received data obtained by matching the phases,
Remove noise to get accurate bolt length data. Therefore, an accurate axial force can be measured from this bolt length. In particular, before the seating of the bolt, the accurate bolt length can be measured, and the accuracy of the measurement at the time of tightening can be improved.

Further, when the bolt is tightened, the tightening is stopped, a plurality of measurements are performed in that state, and the obtained plurality of received data are integrated in phase. This eliminates noise and provides accurate bolt length data to allow accurate axial force measurements.

Further, when the data at the time of tightening is held in time series and the increase rate of the obtained measured value is not within the predetermined range with respect to the previous value, this data is excluded.
As a result, abnormal values can be effectively eliminated and accurate measurement can be performed.

Further, by rotating the ultrasonic wave transmitting / receiving means, a plurality of reception data can be obtained at different positions with respect to the upper end surface of the bolt, and by integrating the phases, these data can be extremely integrated at the time of tightening. Accurate axial force measurement is possible.

[0017]

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

[First Embodiment] FIG. 1 is a view showing the schematic arrangement of an apparatus according to the first embodiment. The apparatus is a nut runner 1.
1, a control device 12, an offset gear box 13, a hollow joint 14, a socket 15, an ultrasonic probe 16, a shaft 17, and a cable 18.

The nut runner 11 has a shaft 17 and rotates the shaft 17 according to an instruction from the control device 12. The shaft 17 is connected to the offset gear box 13, and the rotation of the shaft is transmitted to the hollow joint 14. The end of the hollow joint 14 engages with the outer circumference of the head of the bolt, and the socket 15 rotates the bolt.
The rotation of the hollow joint 14 tightens the bolt. On the other hand, an ultrasonic probe 16 is arranged inside the hollow joint 14, and when the bolt is tightened, the ultrasonic probe 16 is pressed against the upper end surface of the head of the bolt. . The ultrasonic probe 16 is connected to the control device 12 via a cable 18, and the ultrasonic probe 16 transmits and receives an ultrasonic pulse to a bolt according to a transmission signal from the control device 12. A signal about the reflected wave is supplied to the controller 12. Therefore, the control device 12 measures the time from the transmission of the ultrasonic pulse to the reception of the reflection and measures the axial force of the bolt.
In addition, both the upper and lower surfaces of the bolt (the upper end surface of the head on which ultrasonic waves are incident and the distal end surface on which ultrasonic waves are reflected) are polished,
Oil is applied to the upper end surface of the head to reduce the attenuation of ultrasonic waves.

Here, in the apparatus of this embodiment, in the initial measurement before the start of tightening the bolt, the measurement is performed while rotating the bolt as shown in FIG. That is, a bolt is attached to the socket 15, the hollow joint 14 is rotated by the nut runner 11, and the rotation of the bolt is started (S11). At this time, the ultrasonic probe 16 is only pressed against the upper end surface of the bolt and does not rotate. For example, the ultrasonic probe 16 may be fixed to the body side of the offset gear box 13.

The axial force of the bolt is 0 until the bolt is seated (the bottom surface of the bolt head contacts the tightening side).
Is. Therefore, first, it is determined whether or not the user is seated (S12), and if it is before this sitting, ultrasonic waves are transmitted (S13), and the received data after that is A / D converted and recorded (S14). Then, it is determined whether the reception is completed (S15), and the process is repeated until the reception of the reflected wave is completed. When the reception is completed, the received waveform is superimposed on the synthesized waveform up to the previous time (S16), S
Return to the seating determination of 12. The measurement from S13 to S16 is called routine A. This superimposition is performed by integrating the received waveforms in the same phase at the same transmission time. Then, this measurement is repeated until sitting. Thereby, the transmission of the ultrasonic pulse and the reception of the reflected wave are repeated a plurality of times, and the control device 12 stores the data about the reflected wave received after the time of transmitting the ultrasonic pulse. With this, while the bolt is rotated with respect to the probe 16 with the axial force being 0, measurement is performed every time the rotation angle becomes a constant angle, and the result is integrated.

That is, in the control device 12, for example, at times t, t + 1, t + 2, and t + 3, waveforms as shown in FIG. 3 are obtained, respectively. These waveforms are such that the relative positions of the bolt and the ultrasonic probe 16 are different. Then, the integrated waveform is obtained by integrating the waveforms obtained by A / D converting this. By such processing, even when relatively large noise is generated in a time of about 1/2 of the regular reflected wave like t + 1, or when regular reflection cannot be obtained like t + 2, it is possible to obtain the final value. Therefore, the correct reflected wave position can be detected, and accurate initial bolt length measurement can be performed. Then, the seating of the bolt ends the initial measurement. Note that the above S1
By setting the recording period T of the received data in S4 and S15 sufficiently smaller than the ultrasonic wave transmission interval, the reflected wave can be reliably detected.

As described above, in this embodiment, in the initial measurement, the relative position values of the upper end surface of the bolt and the ultrasonic probe 16 are shifted, and the measurement is performed a plurality of times. Therefore, the initial measurement becomes very accurate and the measurement error can be reduced.

Next, the operation after sitting will be described with reference to FIG. When the seating is detected in S12 of FIG. 2, this processing is started. First, an ultrasonic pulse is transmitted (S41). Then, the received data is A / D changed and recorded (S42), and it is determined whether the reception of the reflected wave is completed (S42).
43). If not, the process returns to S42 and repeats this process until the reflection of the transmitted ultrasonic pulse is received. Note that the cycle of this processing is T
Is.

Then, in S43, when the reception of the reflected wave is completed, the axial force is calculated based on the time from the transmission of the ultrasonic pulse to the reception of the reflected wave and the specific value such as the elastic coefficient of the bolt ( S44), it is determined whether the axial force has reached a prescribed magnitude (S45). Then, when the value does not reach the specified value, the process returns to S41 and the process is repeated. In this way, the change in axial force due to the rotation of the bolt is detected,
This is repeated until a predetermined axial force is reached. In S45, when the predetermined axial force is obtained, the nut runner 11 is stopped and the bolt tightening is completed.

Further, in the present embodiment, the result of the measurement at the time of tightening is predicted from the data at the time of the initial measurement and the result of the previous measurement, and if the predicted range is exceeded, the data is not adopted. Therefore, false detection can be prevented.

That is, as shown in FIG. 5, when seated, the initial value is first registered (S21). Then, the bolt starts to extend due to the rotation of the bolt by the nut runner 11, but the data is not acquired until the rotation angle of the bolt reaches the constant angle θL (S22). This is because until then, the relationship between the tightening angle and the bolt axial force is not stable due to the influence of buckling or the like. In S22, when the rotation angle of the bolt exceeds θ L, the measurement (routine A) is repeated (S23), but (i) the measurement reflection time does not become shorter than the previous data (ii) predetermined value The data is selected under such a condition that it does not become longer than the value (this predetermined value can be adjusted in the tightened state. For example, the range can be set from the inclination at that time).

Note that this selection is performed by storing data on the measurement reflection time x (corresponding to the volt length) as a data string and excluding values out of continuity, as shown in FIG. And good. In this case, the data at that time may be interpolated by the previous value interpolation or the estimation from the average value of the previous value and the previous two values.

When the reflection time x becomes equal to or greater than the predetermined value θH and the axial force approaches the target axial force (S24),
With respect to the validated data, the angle θ at which the target axial force (measurement reflection time) is obtained is calculated by the linear expression x = k1θ + k2 (S25), and when this angle is reached (S2
6), stop tightening the bolts. The normal bolt tightening ends when elastic deformation of the bolt ends and plastic composition deformation begins. Therefore, in this embodiment, at the end, by using the above-described linear expression,
Finally, the tightening angle is determined and the completion of tightening is determined.

In the above description, the measurement was performed without stopping the rotation of the bolt by the nut runner 11. However, if the rotation of the bolt is stopped and the bolt is stopped, the measurement can be performed a plurality of times. The accuracy can be increased. In particular, this method is particularly effective for the measurement after seating, because the same bolt length can be measured only after the rotation of the bolt is stopped.

[Second Embodiment] FIG. 7 shows an apparatus according to the second embodiment. This device is basically the same as the embodiment shown in FIG. 1, and only a mechanism for rotating the ultrasonic probe 16 is added. Therefore, the apparatus of FIG. 6 can be applied to the first embodiment unless the ultrasonic probe 16 is rotated.

The shaft 17, which is the output shaft of the nut runner 11 in FIG. 1, is inserted in the offset gear box 13. A pair of gears 22 a and 22 b are arranged in the offset gear box 13, and the shaft 1
The rotation of 7 is transmitted to the hollow joint 14. A socket 15 is formed at the lower end of the hollow joint 14, and the socket 15 is engaged with the outer circumference of the head of the bolt 28.
Therefore, the nut runner 11 can rotate the socket 15 and tighten the bolt 28.

On the other hand, a tube 25 is arranged inside the hollow joint 14 so as to be rotatable relative to it, and an ultrasonic probe 16 is inserted into the lower end of the tube 25 so as to be slidable in the axial direction. . In this example, the inner circumference of the lower end of the tube 25 and the outer circumference of the ultrasonic probe 16 are polygonal so that they do not rotate relative to each other. A compression spring 27 is inserted above the ultrasonic probe 16 at the lower end of the tube 25, and the ultrasonic probe 16 is urged downward by the compression spring 27.
Therefore, when the socket 15 is engaged with the head of the bolt 28, the bottom surface of the ultrasonic probe 16 is pressed against the top end surface of the head of the bolt 28.

In the present embodiment, the upper portion of the tube 25 penetrates the offset gear box 13 and projects upward, and the gear 26a is attached to the upper end portion thereof. This gear 26a is engaged with the gear 26b, and the gear 2
6b is reciprocally rotatable by a motor 29.
That is, by rotating the motor 29 in the normal range and in the reverse direction, the tube 25 rotates in the normal range in the normal range.
Reverse. This causes the ultrasonic probe 16 to rotate on the upper end surface of the bolt. Here, since the rotation range of the ultrasonic probe 16 is not so large, there is no problem of twisting the cable 18 extending from the ultrasonic probe 16.

When tightening the bolt 28 in such an apparatus, first, as shown in FIG.
Perform initial measurements before sitting. When the seating is detected in S12, the initial value is first registered as shown in FIG. 8 (S31). Then, the nut runner 11 rotates the bolt 28 by the angle θ1 (S32). After rotating the bolt by θ1, the nut runner 11 is stopped (S33), and the ultrasonic probe 1 is rotated by the rotation of the motor 29.
The rotation of 6 is started (S34).

In this way, the measurement is performed while rotating the ultrasonic probe 16 while the rotation of the bolt 28 is stopped, so that the bolt 28 and the ultrasonic probe 16 are rotated relative to each other as in the initial measurement. It is possible to perform the measurement while performing the measurement. Therefore, the above-described measurement of S13 to S16 (routine A) is performed (S35), and the rotation of the ultrasonic probe 16 is θ2.
This is repeated up to (S36). The data on the reflected wave obtained in this way is calculated from the multiple measurement data obtained for one bolt length, and is very accurate. However, the ultrasonic probe 16
The direction of rotation shall be alternating between forward and reverse.

Since the axial force measurement for the rotation of the bolt by θ1 is completed, it is judged whether the axial force obtained by the measurement is the target axial force (S37), and this is repeated.

As described above, according to this embodiment, the ultrasonic probe 16 is moved with respect to the upper end surface of the bolt 28 for each predetermined rotation of the bolt to perform the measurement. Therefore, it is possible to effectively reduce the measurement error due to the sliding movement of the ultrasonic probe 16 and the upper end surface of the bolt 28, and perform accurate axial force measurement. The determination of the end of tightening may be performed by calculating the final rotation angle from the linear expression as described above.

Further, with respect to the data obtained by this embodiment, the measured value is predicted in the same manner as described above, and the data outside the predetermined range may be deleted.

[0040]

As described above, in the present invention, when measuring the axial force of the bolt, the same axial force is measured a plurality of times. Then, the obtained received data is phase-matched and integrated to remove noise, thereby obtaining accurate data on the bolt length. Therefore, an accurate axial force can be measured from this bolt length. In particular, before the seating of the bolt, the accurate bolt length can be measured, and the accuracy of the measurement at the time of tightening can be improved.

When the bolt is tightened, the tightening is stopped, a plurality of measurements are performed in that state, and the obtained plurality of received data are integrated in phase. This eliminates noise and provides accurate bolt length data to allow accurate axial force measurements.

Further, when the data at the time of tightening is held in time series, and the increase rate of the obtained measured value is not within the predetermined range with respect to the previous value, this data is excluded.
As a result, abnormal values can be effectively eliminated and accurate measurement can be performed.

Further, by rotating the ultrasonic wave transmitting / receiving means, a plurality of reception data can be obtained at different positions with respect to the upper end surface of the bolt, and by integrating these data by matching the phases, it is possible to greatly reduce the tightening time. Accurate axial force measurement is possible.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a first embodiment.

FIG. 2 is a flowchart illustrating the operation of the first embodiment.

FIG. 3 is an explanatory diagram showing a state of waveform integration.

FIG. 4 is a flowchart illustrating an operation after sitting.

FIG. 5 is a flowchart illustrating an abnormal value elimination operation.

FIG. 6 is a characteristic diagram showing a change state of measured values.

FIG. 7 is a diagram showing a configuration of a second exemplary embodiment.

FIG. 8 is a diagram showing a flowchart of a second embodiment.

[Explanation of symbols]

 11 Nutrunner 12 Control Device 13 Offset Gear Box 14 Hollow Joint 15 Socket 16 Ultrasonic Transducer

Claims (4)

[Claims] 1. A bolt shaft that receives an ultrasonic pulse from one end face in the bolt axial direction to a bolt, detects a reflected wave from the other end face in the bolt axial direction, and calculates the bolt axial force based on the detection result. In the force measurement method, the step of performing the ultrasonic pulse incidence and the measurement of the reflected wave a plurality of times, the step of integrating the phases of the plurality of measured reflected waves together, and the largest of the waveforms of the integrated reflected waves A step of detecting the reflected wave as a reflected wave on the other end surface in the bolt axis direction, and a step of calculating the bolt axial force by measuring the time from the incidence of the ultrasonic pulse for the detected reflected wave to the arrival of the reflected wave. A method for measuring bolt axial force, comprising: 2. A bolt shaft which receives an ultrasonic pulse from one end face in the bolt shaft direction to a bolt, detects a reflected wave from the other end face in the bolt shaft direction, and calculates the bolt axial force based on the detection result. In the force measurement method, the steps of temporarily stopping the tightening of bolts and measuring the incidence of ultrasonic pulses and the measurement of reflected waves, and the step of integrating the phases of the measured multiple reflected waves and integrating them are integrated. The process of detecting the largest reflected wave from the waveform of the reflected wave as the reflected wave on the other end face in the bolt axis direction, and measuring the time from the incidence of the ultrasonic pulse to the arrival of the reflected wave for the detected reflected wave, A bolt axial force measuring method comprising: a step of calculating a bolt axial force. 3. The method according to claim 2, wherein the detected reflected waves are canceled when an increase rate of the plurality of detected reflected waves is out of a predetermined range as the bolt tightening progresses. Measuring method of bolt axial force. 4. A bolt shaft that receives an ultrasonic pulse from one end face in the bolt shaft direction to a bolt, detects a reflected wave from the other end face in the bolt shaft direction, and calculates the bolt axial force based on the detection result. In the force measuring device, the bolt tightening is stopped intermittently to tighten the bolt, the ultrasonic pulse is incident from one end surface of the bolt, the transmitting / receiving means for receiving the reflection, and the bolt tightening. In the stopped state, the relative rotation means for rotating the transmission / reception means relative to the end face of the bolt and the phase of the reflected wave obtained by the plurality of measurements performed by rotating the transmission / reception means by the relative rotation means The integrating means for integrating and integrating, the detecting means for detecting the largest reflected wave from the integrated reflected wave waveforms as the reflected wave on the other end face in the bolt axis direction, and the detected reflected wave A bolt axial force measuring device comprising: a calculating unit that calculates a bolt axial force by measuring the time from the incidence of the ultrasonic pulse to the arrival of the reflected wave.