JP7372624B2 - Looseness detection system - Google Patents

Description

The present invention relates to a loosening detection system and a sensor base material, and particularly to a loosening detection system and the like for detecting loosening of nuts that fasten members.

Patent Document 1 describes that a piezoelectric element is attached to a washer base material, and a natural frequency is determined based on the vibration state of the washer base material detected by the piezoelectric element, thereby detecting loosening of a bolt fastened body. .

Japanese Patent Application Publication No. 2005-069312

However, in Patent Document 1, in order to obtain the natural frequency, it was necessary to vibrate the washer base material.

Therefore, an object of the present invention is to provide a loosening detection system and the like that can detect the loosening of a nut without using the natural frequency.

A first aspect of the present invention is a loosening detection system for detecting loosening of a nut that fastens a member, the system comprising a sensor base material fastened together with the member by the nut, and a sensor base material that is fastened together with the member by the nut. The sensor device includes a sensor device that receives a reflected wave of the ultrasonic wave reflected at the end face of the nut.

A second aspect of the present invention is the loosening detection system of the first aspect, wherein the sensor device includes a piezoelectric film part, the sensor base material has at least one surface in contact with the nut, and the sensor The device transmits ultrasonic waves toward the nut in the sensor base material, and receives reflected waves reflected from the end face of the nut.

A third aspect of the present invention is the loosening detection system according to the second aspect, wherein the piezoelectric film portion is present on a surface of the sensor base material that is different from a surface in contact with the nut, and the piezoelectric film portion In the sensor base material, an ultrasonic wave is emitted toward a surface in contact with the nut, and a reflected wave reflected from an end surface of the nut is received.

A fourth aspect of the present invention is a loosening detection system according to any one of the first to third aspects, wherein the magnitude of the reflected wave received when the nut is in the first state and the second state. When the first evaluation value indicates that the reflected wave is larger than the second evaluation value, the nut in the first state is set as a first evaluation value and a second evaluation value, respectively. , an ultrasonic processing device including a processing device that evaluates that the fastening torque is greater than that of the nut in the second state.

A fifth aspect of the present invention is a sensor base material fastened together with a member by a nut, and includes a sensor device that receives a reflected wave in which an ultrasonic wave transmitted to the sensor base material is reflected at an end surface of the nut. .

A sixth aspect of the present invention is the sensor base material according to the fifth aspect, wherein the sensor device includes a piezoelectric film part, and at least one surface of the sensor base material is in contact with the nut, and the sensor base material has a piezoelectric film part. The membrane portion is present in the sensor base material on a surface different from the surface in contact with the nut, and the piezoelectric film portion transmits ultrasonic waves toward the surface in contact with the nut in the sensor base material, A reflected wave reflected from the end face of the nut is received.

According to each aspect of the present invention, loosening of the nut can be detected without using vibration by using reflected waves of ultrasonic waves on the end face of the nut.

FIG. 1A is a diagram showing an example of the configuration of a loosening detection system according to an embodiment of the present invention, and FIGS. 2B and 2C are diagrams showing examples of reflected waves. FIG. 2 is a flow diagram showing an example of the operation of the looseness detection system 1 of FIG. 1. FIG. The sensor base material used in the experiment conducted by the inventors to confirm the correlation between fastening torque and reflected waves is shown. A piezoelectric film and electrodes are formed on the sensor base material of FIG. 3, and wiring is performed. (a) shows an apparatus for generating and receiving ultrasonic waves; and (b) shows reflected waves observed in the sensor substrate of FIG. 4; It is shown assembled and with Loctite applied as a sensor protection material. FIG. 3 is a diagram for explaining the situation in which the experiment was conducted. The nuts used in the experiment are shown. (a) and (b) are the waveforms of the reflected waves when there is no nut and when the nut is tightened by hand, respectively. (a) and (b) are the waveforms of reflected waves in the case of 100 N·m and 200 N·m, respectively. (a) and (b) are the waveforms of reflected waves in the case of 300 N·m and the limit, respectively. In each of the graphs in FIGS. 9 to 11, (a) a comparison of waveforms, and (b) a comparison of the second reflected wave cut out for 10 to 15 μsec. This is a comparison of the peak values of the second reflected waves. FIG. 2 is a diagram for explaining an experiment conducted by the inventors to confirm the correlation between fastening torque and tapping sound. One representative data point for each of the measured fastening torques is compared.

Embodiments of the present invention will be described below with reference to the drawings. Note that the embodiments of the present invention are not limited to the following examples.

FIG. 1 is a diagram showing (a) an example of the configuration of a looseness detection system according to an embodiment of the present invention, and (b) and (c) diagrams showing examples of reflected waves.

Referring to FIG. 1(a), a loosening detection system 1 includes a nut 3, a sensor base material 5 (an example of a "sensor base material" in the claims of the present application), a piezoelectric film part 7, an electrode part 9 ( A combination of the piezoelectric film part 7 and the electrode part 9 is an example of a "sensor device" in the claims of the present application), a sensor protection material 11, and an ultrasonic processing device 13.

Nut 3 is a hexagonal nut in this example. The nut 3 is one of the fastening parts used for assembling machines and the like. An opening called a female thread is cut in the center of the cylinder, and is used in combination with a male thread such as a bolt (not shown) to fasten and fix a member (not shown). The end surface 4 is a terminal surface of the nut 3 that faces the surface that is in contact with the sensor base material 5 . The end surface 4 is the surface of the nut 3 that is opposite to the surface that contacts the sensor base material 5.

The sensor base material 5 is fastened together with the member by a nut 3. In this example, there is no other member between the nut 3 and the sensor base material 5, and they are in contact with each other. In the following, the surface of the sensor base material 5 that is in contact with the nut 3 will be referred to as a boundary surface.

A piezoelectric film portion 7 is formed on the sensor base material 5 on the surface facing the boundary surface (the surface on the opposite side to the boundary surface). An electrode portion 9 is formed on the piezoelectric film portion 7 . When an alternating current voltage is applied to the electrode section 9, the piezoelectric film section 7 can vibrate in accordance with the frequency and emit ultrasonic waves. Further, when vibration is applied, a voltage is generated and can be detected at the electrode section 9. In this way, the piezoelectric film section 7 and the electrode section 9 function as a reflective sensor.

The sensor protection material 11 is a protection material for protecting the piezoelectric film part 7 and the electrode part 9.

The ultrasonic processing device 13 is connected to the electrode section 9 by wiring. The transmitting device provided in the ultrasonic processing device 13 applies an electric signal to the electrode section 9 and transmits an ultrasonic wave toward the nut 3 using the piezoelectric film section 7 in the sensor base material 5 . The ultrasonic waves reflected at the boundary between the nut 3 and the sensor base material 5 are buried in the dead zone of the sensor formed by the piezoelectric film portion 7 and cannot be observed. The receiving device included in the ultrasonic processing device 13 receives from the electrode section 9 the reflected wave that passes through at least the boundary surface of the sensor base material 5 and is generated at the end surface 4 of the nut 3 . The sensor using the piezoelectric film portion 7 can detect a reflected wave that passes through the boundary surface of the sensor base material 5 and is generated at the end surface 4 of the nut 3.

With reference to FIGS. 1(b) and 1(c), the transmitted ultrasonic waves that are transmitted to the nut 3 side and those that are reflected at the boundary between the sensor base material 5 and the nut 3 will be described.

FIG. 1(b) shows the case where no nut tightening tool is used. In this case, the fastening torque is small and the waves transmitted from the sensor base material 5 to the nut 3 side are small. Therefore, the reflected wave reflected at the end face 4 of the nut 3 becomes smaller. The piezoelectric film section 7 detects small reflected waves.

FIG. 1(c) shows the case where a nut tightening tool is used. In this case, the fastening torque is large, and the waves transmitted from the sensor base material 5 to the nut 3 side are large. Therefore, the reflected wave reflected at the end face 4 of the nut 3 becomes large. The piezoelectric film section 7 detects large reflected waves.

Therefore, a processing device included in the ultrasonic processing device 13 (an example of a "processing device" in the claims of the present application, such as a processor that operates under the control of a program) is a "processing unit" as a means in which software and hardware resources cooperate. ) receives the reflected wave that passes through the boundary between the sensor base material 5 and the nut 3 and is reflected at the end surface 4 of the nut 3, and determines the nut using an evaluation value that evaluates the magnitude of the reflected wave. 3. Looseness can be evaluated. The evaluation value is, for example, the amplitude of the reflected wave.

FIG. 2 is a flow diagram showing an example of the operation of the looseness detection system 1 of FIG. 1. An example of the operation of the looseness detection system 1 will be described with reference to FIG. 2. For example, the evaluation value of the reflected wave at the nut 3 whose tightening state at the first time is the first state is the first evaluation value, and the evaluation value of the reflected wave at the nut 3 whose tightening state at the second time is the second state. It is assumed that the evaluation value of the reflected wave is the second evaluation value.

At the first time, the transmitting device included in the ultrasonic processing device 13 applies an electric signal to the electrode section 9 and transmits an ultrasonic wave toward the nut 3 using the piezoelectric film section 7 in the sensor base material 5 . The receiving device included in the ultrasonic processing device 13 receives from the electrode section 9 the reflected wave that passes through at least the boundary surface of the sensor base material 5 and is generated at the end surface 4 of the nut 3 . The processing device included in the ultrasonic processing device 13 acquires a first evaluation value that is an evaluation value of the magnitude of the received reflected wave (step STA1).

At the second time, the transmitting device included in the ultrasonic processing device 13 applies an electric signal to the electrode section 9 and transmits an ultrasonic wave toward the nut 3 using the piezoelectric film section 7 in the sensor base material 5 . The receiving device included in the ultrasonic processing device 13 receives from the electrode section 9 the reflected wave that passes through at least the boundary surface of the sensor base material 5 and is generated at the end surface 4 of the nut 3 . The processing device included in the ultrasonic processing device 13 acquires a second evaluation value that is an evaluation value of the magnitude of the received reflected wave (step STA2).

The processing device included in the ultrasonic processing device 13 compares the first evaluation value and the second evaluation value and determines which one shows a larger reflected wave (step STA3).

If the second evaluation value indicates that the reflected wave is smaller than the first evaluation value, it can be evaluated that the amount of ultrasonic waves transmitted to the nut 3 side has become smaller, and the tightening torque of the nut 3 at the second time is can be evaluated as having become smaller (step STA4).

If the second evaluation value indicates that the reflected wave is the same as the first evaluation value, it can be evaluated that the fastening torque is the same in the second state and the first state (step STA5).

If the second evaluation value indicates that the reflected wave is larger than the first evaluation value, it can be evaluated that the amount of ultrasonic waves transmitted to the nut 3 side is greater in the second state than in the first state, For example, it can be evaluated that the tightening torque of the nut 3 at the second time has increased due to retightening on the way (step STA6).

In this way, the present invention can not only simply detect ON-OFF whether or not the bolt is loose, but also detect the fastening torque in a numerically continuous state.

Experiments conducted to confirm the correlation between fastening torque and reflected waves will be described with reference to FIGS. 3 to 13. In this experiment, the nut 3 is tightened with different tightening torques. After tightening to each torque, pulses are input to the sensor base material 5 and changes in the reflected waveform from the end surface 4 of the nut 3 are observed.

Figure 3 shows the sensor substrate used in this experiment.

FIG. 4 shows a structure in which a piezoelectric film (an example of the piezoelectric film part 7 in FIG. 1) and an electrode (an example of the electrode part 9 in FIG. 1) are formed on the sensor base material in FIG. 3 (an example of the sensor base material 5 in FIG. 1). The following shows the wiring.

FIG. 5 shows (a) an apparatus for generating and receiving ultrasonic waves, and (b) reflected waves observed in the sensor substrate of FIG. 4.

FIG. 6 shows the assembled state and Loctite applied as a sensor protection material.

FIG. 7 is a diagram for explaining the situation in which the experiment was conducted. In the experiment, the sensor 25 shown in FIG. 6 was attached to the nut 23 of the mold 21 of the heading machine. A pulser 27 is connected to the sensor 25 for emitting pulses and measuring the waveform of the received reflected wave.

In the experiment, the nuts were installed with different tightening torques and changes in the waveform were observed. The measured tightening conditions were: without a nut (waveform when no nut is attached), hand tightening (without tools, waveform when using no tools), and 100N・m (tightening with a torque of 100N・m). 200N・m (waveform when tightened with a torque of 200N・m), 300N・m (waveform when tightened with a torque of 300N・m), limit (Full-Power, fully manually tightened) waveform when tightened).

The pulser 27 has transmission settings such that the number of channels used is 1, the frequency is 5 MHz, the gain is 40.5 dB, and the power is high, and transmit waves are suppressed.

Figure 8 shows the nuts used. It is a hexagonal nut with one side chamfer.

FIGS. 9(a) and 9(b) show the waveforms of the reflected waves when there is no nut and when the nut is manually tightened, respectively. FIGS. 10A and 10B show the waveforms of reflected waves in the case of 100 N·m and 200 N·m, respectively. FIGS. 11(a) and 11(b) show the waveforms of reflected waves in the case of 300 N·m and the limit, respectively. The horizontal axis is the time (μsec) when data was received, and the vertical axis is the amplitude (V). As the torque increases, more reflected waves are received.

FIG. 12 shows (a) a comparison of the waveforms in each graph of FIGS. 9 to 11, and (b) a comparison of the second reflected wave cut out for 10 to 15 μsec. The horizontal axis is the shift time (μsec), and the vertical axis is the amplitude (V).

FIG. 13 shows a comparison of the peak values of the second reflected waves. The horizontal axis shows the data number, and the vertical axis shows the peak value of amplitude (V). The data numbers are, in order from 1, no nut, manual tightening, 100 N·m, 200 N·m, 300 N·m, and limit. As the torque increases, the peak value increases. In this way, a correlation is recognized between the fastening torque and the peak value of the reflected wave. Therefore, in addition to realizing a simple sensor that outputs an ON-OFF signal indicating the presence or absence of looseness, it is also possible to realize a sensor that outputs a fastening torque value as a numerical value (for example, an analog value). Therefore, it is possible to determine not only the presence or absence of looseness, but also whether the fixation can be performed with a predetermined torque (for example, 559 N·m).

Note that in this experiment, the second reflected wave was used because the first reflected wave became large. Other reflected waves such as the first reflected wave may also be used.

FIG. 14 is a diagram for explaining an experiment conducted to confirm the correlation between fastening torque and tapping sound. Apply a shock after securing the sensor with a nut. The sensor captures the tapping sound at that time. Experiment by changing the tightening torque of the nut to see if there is a correlation between the tightening torque and the hammering sound shape.

The measured tightening conditions were 30 N·m, 50 N·m, 70 N·m, 90 N·m, 130 N·m, 150 N·m, and 170 N·m. Five measurements were taken at each torque.

FIG. 15 shows a comparison of one representative data point for each fastening torque. In this experiment, it was difficult to find a correlation between fastening torque and hammering sound. However, it is possible to acquire sound with sensors, and it is expected that it will be possible to monitor vibrations of vibration systems that include actually installed structures (equipment, etc.).

1 Looseness detection system 3 Nut 5 Sensor base material 7 Piezoelectric film part 9 Electrode part 11 Sensor protection material 13 Ultrasonic processing device 21 Mold 23 Nut 25 Sensor 27 Pulsar

Claims (4)

A loosening detection system for detecting loosening of fastening parts that fasten members,
comprising a sensor base material fastened together with the member by the fastening component,
The sensor base material has at least one surface in contact with the fastening component,
A loosening detection system comprising a sensor device that receives a reflected wave in which an ultrasonic wave that is transmitted to the sensor base material toward the fastening component and passed from the sensor base material to the fastening component is reflected at an end surface of the fastening component. The sensor device includes a piezoelectric film part ,
The loosening detection system according to claim 1, wherein the sensor device transmits an ultrasonic wave toward the fastening component in the sensor base material and receives a reflected wave reflected from an end surface of the fastening component. The piezoelectric film portion is present on a surface of the sensor base material that is different from a surface that is in contact with the fastening component,
3. The loosening detection system according to claim 2, wherein the piezoelectric film section transmits an ultrasonic wave toward a surface of the sensor base material that is in contact with the fastening component, and receives a reflected wave reflected from an end surface of the fastening component. . A loosening detection system for detecting loosening of fastening parts that fasten members,
a sensor base material fastened together with the member by the fastening component;
comprising a sensor device that receives a reflected wave in which an ultrasonic wave transmitted to the sensor base material and passed from the sensor base material to the fastening component is reflected at an end surface of the fastening component;
The evaluation values for evaluating the magnitude of the reflected wave received when the fastening component is in the first state and the second state are respectively defined as a first evaluation value and a second evaluation value, and the first evaluation value is the first evaluation value. Ultrasonic treatment comprising a processing device that evaluates that the fastening torque of the fastening component in the first state is greater than that of the fastening component in the second state when the reflected wave is larger than a second evaluation value. Looseness detection system with device.

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