JP2996537B2 - Measurement method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring method and an apparatus for measuring the thickness of a sheet material such as a glass sheet, an iron sheet and an aluminum sheet.

[0002]

2. Description of the Related Art Conventionally, as a device for measuring the thickness of a plate material, in addition to a simple measuring device for actually measuring the thickness using a micrometer, a caliper, or the like, using a laser or the like,
A measuring device that optically measures the thickness, a device that measures the thickness by using ultrasonic waves, and the like are known.

[0003]

However, these conventional measuring devices have the following drawbacks. First, with a device that measures using a micrometer or caliper, it is possible to accurately measure only the portion around the plate that is the object to be measured, for example, in the case of a plate material with a large area,
The measurement of the thickness of the central part has to rely on a relative measurement. That is, in such a measurement with a micrometer or the like, first, a reference surface is defined, a plate material to be measured is placed on the reference surface, and the distance between the upper surface of the plate and the reference surface is measured. Thereby measuring the thickness of the plate material. In this case, if the plate as the object to be measured is distorted or warped, a gap is generated between the lower surface of the plate and the reference plane depending on the location of the plate. When such a gap occurs, the measured plate thickness differs from the actual plate thickness, resulting in poor reliability.

On the other hand, an optical measuring device using a laser or the like is expensive and the handling thereof is complicated. Further, in a device that calculates the plate thickness based on the difference in the path of reflected light between the upper surface and the lower surface of the plate using a laser, the object to be measured must be transparent, as a matter of course, and its use is limited. There is also a method in which a non-transparent plate is irradiated with a laser from each of its upper and lower surfaces, and the thickness of the plate is measured based on the reflected light from each surface, but operations such as adjusting the optical axis are complicated. There is a problem that it cannot be easily measured.

In the method of measuring the thickness of a plate using ultrasonic waves, the time required for a sound wave incident from a signal source to a plate to be measured to be reflected by the bottom surface of the plate and returned. Is measured to calculate the plate thickness. However, in this method, the time required for the incident ultrasonic signal to be reflected by the bottom surface and returned is reduced as the thickness becomes thinner. It is difficult to measure accurately. In order to solve this problem, a method of increasing the resolution by setting the frequency of the incident ultrasonic signal to be sufficiently high is adopted, but in any case, there is a limit that the cost of the apparatus itself is increased. . The present invention has been made in view of the above conventional example,
Arbitrarily set the distance between the vibration application position and the point of detection of the plate wave.
It is an object of the present invention to provide a measuring method and an apparatus which can measure the thickness of a plate material at a low cost and easily.

[0006]

In order to achieve the above object, a measuring apparatus according to the present invention has the following arrangement. That is, a measuring device for measuring the thickness of the plate material, wherein the plate material
Vibration that generates a plate wave by applying vibration at any position above
And generating means is placed at an arbitrary position of the plate, the vibration
Detecting means for detecting a plate wave propagating through the plate material by applying vibration by the motion generating means; and detecting at least two frequency components contained in the plate wave detected by the detecting means.
Extracting means for extracting a corresponding group velocity and its frequency ; and a signal before the signal indicating the group velocity extracted by the extracting means.
Measuring means for measuring the arrival time from the position where the vibration is applied by the vibration generating means to the detecting means, each arrival time measured by the measuring means, and the group velocity and frequency corresponding to each arrival time. Computing means for computing the plate thickness of the plate material based on the above.

[0007] In order to achieve the above object, the measuring method of the present invention comprises the following steps. That is, a measuring method for measuring the thickness of a plate material, which is an arbitrary method on a plate material to be measured.
Generating a plate wave by applying vibration at the position, and being included in the plate wave detected by a sensor mounted on an arbitrary position on the plate material and detecting the plate wave transmitted through the plate material.
Group velocity corresponding to at least two frequency components and its circumference
The wave number extraction process and each of these extracted group velocities are shown.
Measuring the arrival time of the vibration signal from the time of application of the vibration, and calculating the arrival time measured based on the measured arrival time, and the group velocity and the frequency corresponding to the arrival time. And a step of determining

[0008]

In the above configuration, a plate wave is generated by applying vibration at an arbitrary position on a plate material to be measured, and is placed at an arbitrary position on the plate material and propagated through the plate material. A group velocity corresponding to at least two frequency components included in the plate wave detected by the detecting means for detecting the group velocity and its frequency are extracted, and the signals indicating each of the extracted group velocities reach from the vibration application time point. An operation is performed to measure the time and calculate the thickness of the plate material based on the measured arrival times, the group velocity corresponding to the arrival times, and the frequency.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a schematic configuration of the thickness measuring apparatus of the present embodiment. In FIG. 1, 1
Is an arithmetic and control circuit for controlling the entire measuring apparatus to measure the thickness of the plate 7 as the object 7 to be measured. Reference numeral 2 denotes a drive circuit that inputs a drive signal from an arithmetic and control circuit and drives a vibration output actuator 3 of the vibration pen 10.
The vibration output actuator 3 has a vibrator 4 made of a piezoelectric element or the like inside, and converts an electric drive signal input from the drive circuit 2 into mechanical ultrasonic vibration by the vibrator 4. Is done. The ultrasonic vibration is transmitted to the plate 7 as the object to be measured via the horn portion 5 having a sharp tip. Thus, the ultrasonic vibration propagated through the plate member 7 is detected by the vibration sensor 6 configured by a mechanical-electrical conversion element such as a piezoelectric element. The output signal of the vibration sensor 6 is input to the waveform detection circuit 8 and is converted into a detection signal that can be processed by the arithmetic and control circuit 1. Thus, the arithmetic and control circuit 1 calculates the thickness of the plate 7 based on the result processed by the waveform detection circuit 8. Reference numeral 9 denotes a display / output unit that displays or prints out the measurement result.

Hereinafter, a method of obtaining the plate thickness will be described in detail. FIG. 2 shows a transducer driving waveform for driving the transducer 4 in the vibration pen 3. As shown in FIG. 2, in this embodiment, the vibrator drive circuit 2 inputs a rectangular wave pulse train of a predetermined length to the vibrator 4 at a predetermined cycle, and the vibrator 4 is vibrated by the driving signal. It has been converted to mechanical energy. This vibration is transmitted as elastic wave vibration on the plate 7 and is detected by the vibration sensor 6 also provided on the plate 7. In this manner, the electric energy input to the vibrator 4 from the drive circuit 2 is converted into mechanical energy by the vibrator 4, converted again into electric energy by the vibration sensor 6 via the plate member 7, and output. This vibration sensor 6
FIG. 3 shows an example of the signal waveform detected in the step (a).

Now, such a signal converted into an electric signal-mechanical energy and a signal converted into a mechanical energy-electric signal, that is, a signal detected by the vibration sensor 6 is, as shown in FIG. No. This is because each part of the vibrating pen 10 including the vibrator 4, the horn part 5, and the like has a unique vibration frequency with respect to the electric drive frequency input to the vibrator 4, so This is because the response does not become a single frequency but responds in various vibration modes. Also, since the horn 5 and the like are loaded on the vibrator 4, the vibration of the vibrator 4 is damped, and mechanical energy having a wide band is output from the tip of the vibrating pen 4 as a whole. Therefore, the electric signal detected and output by the vibration sensor 6 is a composite wave in which various frequency components are mixed.

In FIG. 4, the frequency (KHz) is plotted on the horizontal axis and the gain (3 dB) is plotted on the vertical axis.
At 0 KHz, it is −40.83 dBV. FIG.
Is a diagram showing a general property of an elastic wave (plate wave) propagating on a plate material, where 51 indicates Vp (phase velocity), and 52 indicates V
g (group velocity). As is clear from FIG.
It is well known that if the material of the plate is the same, the phase velocity Vp and the group velocity Vg of the plate wave depend on the product of the thickness d of the plate and the frequency F of the wave.

Further, as described above, the plate wave propagating on the plate member 7 is damped with respect to the electric drive signal (FIG. 2) and becomes a signal having a wide frequency band.
Therefore, as shown in FIG. 4, the signal waveform detected by the vibration sensor 6 has a relatively high frequency wave with a fast propagation speed at the head of the signal waveform when compared on the time axis. It can be seen that the plate wave having a lower frequency gradually reaches the vibration sensor 6 as time passes, is electrically converted, and is output while being superimposed on the wave having a higher frequency that has arrived earlier.

Therefore, focusing on the difference between the frequencies of these plate waves, the waveforms of the detection signals detected by the vibration sensor 6 are processed through band filters having different center frequencies, so that the thickness of the plate material is reduced. I want to ask. This will be described in detail below.

FIG. 6 shows that the same electric output signal output from the vibration sensor 6 when the plate thickness is constant is processed through a band-pass filter (BPF) having a different center frequency, and the vibration pen 4 and the vibration sensor are processed. Group velocity V in each case based on the relationship between the distance between 6 and the arrival delay time of the wave.
g (thousand m / sec) is shown.

As is apparent from FIG. 6, the group velocity Vg increases as the center frequency of the bandpass filter increases.
As the center frequency of the bandpass filter decreases, the group velocity Vg decreases accordingly. Therefore, even if the signal detected and output by the vibration sensor 6 is the same, the signal is processed through a band-pass filter having a different center frequency, whereby a plate having a specific speed corresponding to the center frequency is processed. Waves can be detected.

Next, the configuration of the waveform detection circuit 8 for detecting the group velocity and measuring the plate thickness will be described. In FIG. 1 of the present embodiment, this measuring device processes a signal output from the vibration sensor 6 using a band-pass filter 82 and a band-pass filter 83 having a center frequency different from that of the band-pass filter. ing. Vibration sensor 6
Is amplified by the preamplifier circuit 81,
It is input to bandpass filters 82 and 83. Here, the group velocity of the wave calculated from the signal waveform processed using the band-pass filter 82 is Vg1, and the frequency is f
1, the group velocity of the wave calculated by the signal waveform processed by the bandpass filter 83 is Vg2, and the frequency is f2.

The ultrasonic vibration output from the vibration output actuator 3 and propagated through the plate 7 reaches the vibration sensor 6 and is processed by the band-pass filter 82 to be detected by the group delay time t g1. - the group delay time detected by the filter 83 and t g2. Here, when the group velocity is approximated from FIG. 6, Vgn = α (fn × d) + β (1) where n = 1, 2 d: plate thickness of plate 7 α, β:
Is a constant.

[0019] Now, if where the distance between the vibration output actuator 3 and the vibration sensor 6 is L, by using the group delay is measured the time (t g) and group velocity (Vg), L = Vg1 Tg1 = Vg2 · tg2 (2) From the relationship of equation (1), ｛α (f1 × d) + β｝ tg1 = ｛α (f2 × d) + β｝ tg2 (3) = (Β / α) × {(tg2−tg1) / (f1 · tg1−f2 · tg2)} (4) As described above, the speed of the wave (plate wave) propagating on the plate becomes the vibration frequency. By utilizing the dependence, by detecting the group delay time of the plate wave of different speed, respectively,
It can be seen that the thickness can be easily measured.

In addition to controlling the measuring device, the arithmetic control circuit 1 calculates the plate thickness of the object to be measured by performing these calculations, and displays and prints the result on the display / output unit 9. The result can be output to an external device.

FIG. 7 is a timing chart showing the timing of signal processing performed in the signal detection circuit 8. In the figure, reference numeral 41 denotes a drive waveform for driving the vibrator 4 in the vibrating pen 10, and reference numeral 42 denotes a plate 7
4 shows a detection signal waveform when the vibration sensor 6 detects the vibration transmitted through the vibration sensor 6. Reference numerals 42-A and 42-B denote signal waveforms processed by the band-pass filters 82 and 83, respectively.
43-B shows the envelope of each detection signal waveform. Reference numerals 44-A and 44-B indicate differential waveforms of the envelopes 43-A and 43-B, respectively.
It is differentiated to determine the delay time of the vibration wave detected by the vibration sensor 6, and the peak of each envelope is detected by the zero cross signal (corresponding to the peak of the envelope). The signal processing circuit 8 performs such processing.
At 4 and 85, when each signal processing circuit detects the peak of the envelope, it outputs a count stop signal to the counter 86.

The counter 86 is composed of two counters, and starts counting when the arithmetic and control circuit 1 outputs a drive signal to the drive circuit 2 and starts driving the vibrator 4. The counting is stopped by the peak detection signals from 84 and 85. Therefore, the operation / control circuit 1
By reading the count value of the counter 86, it is possible to determine the time until vibration is generated by the vibration pen 10 and the vibration sensor 6 detects the vibration.

In this manner, the waveform detection circuit 8 outputs each group delay time tgn to the arithmetic and control circuit 1 as a count value of the counter 86 based on the peak signal of the envelope of each detection signal waveform. ing. FIG. 8 is a flowchart showing the thickness measurement processing in the arithmetic and control circuit 1 of the present embodiment. A control program for executing this processing is stored in a ROM (not shown) of the arithmetic and control circuit 1 or the like.

In this process, first, in step S1, a drive signal for driving the vibrator 4 is output to the drive circuit 2, and at the same time, the counter 86 is activated in step S2 to start time measurement. Next, the process proceeds to step S3, and waits for the counter 86 to stop measuring time. When the counter 86 finishes measuring time, the process proceeds to step S4 to read the measured value. The time value read here is the time until the peak value of the signal passing through each of the band-pass filters 84 and 85 is detected, and is represented by tg1 and tg2, respectively.

In step S5, the difference (tg2-tg1) between these time data is obtained, and then in step S6, the center frequency (f) of each band-pass filter (82, 83) is determined.
1, f2), the corresponding elapsed time (tg1, tg)
g2) to obtain a group velocity (f1 ·
tg1, f2 · tg2). The time and the group velocity thus obtained are substituted into the above-mentioned equation (4) to obtain the thickness of the plate 7 as the object to be measured. Then, the process proceeds to step S8, in which the obtained thickness is output to the display / output unit 9 for display or printing.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. Needless to say, the present invention can also be applied to a case where the present invention is achieved by supplying a system or an apparatus with a program for executing the processing specified by the present invention.

As described above, according to the present embodiment, the distance between the vibration output actuator 3 and the vibration sensor 6 can be measured without calculating the plate thickness. Therefore, it is necessary to set the distance between the two precisely. Absent. Thus, the vibration output actuator 3 and the vibration sensor 6 can be installed at arbitrary positions on the object to be measured.

[0028]

As described above, according to the present invention, the vibration
Arbitrarily set the distance between the position where the motion is applied and the point where the plate wave is detected
Can, there is an effect that can measure the thickness of even simple plate at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a thickness measuring apparatus according to an embodiment.

FIG. 2 is a diagram illustrating an example of a driving waveform of a vibrator in the embodiment.

FIG. 3 is a diagram illustrating an example of a detection signal waveform of the vibration sensor according to the present embodiment.

FIG. 4 is a diagram illustrating an example of a signal spectrum of a detection signal detected by a vibration sensor.

FIG. 5 is a diagram for explaining general properties of a plate wave.

FIG. 6 is a diagram illustrating a relationship between a center frequency of a bandpass filter and a group velocity of a plate wave in the present embodiment.

FIG. 7 is a time chart illustrating signal processing in the waveform detection circuit of the present embodiment.

FIG. 8 is a flowchart showing a thickness measurement process by a calculation / control circuit of the thickness measuring apparatus of the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Operation control circuit 2 Oscillator drive circuit 3 Oscillation output actuator 4 Oscillator 5 Horn 6 Vibration sensor 7 Device under test (plate material) 8 Signal waveform detection circuit 9 Display / output unit 10 Vibration pen 81 Preamplifier circuit 82, 83 Band Pass filter 84, 85 Signal processing circuit 86 Counter

Continuing from the front page (72) Inventor Yuichiro Yoshimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masaki Tokioka 3-30-2, Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inc. (56) References JP-A-57-187609 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 17/00-17/04

Claims (2)

(57) [Claims] 1. A measuring device for measuring a thickness of a plate material, comprising: vibration generating means for applying vibration at an arbitrary position on the plate material to generate a plate wave; and being mounted at an arbitrary position on the plate material. The vibration generating means
Detecting means for detecting a plate wave that has propagated through the plate material by application of vibration, and at least the wave included in the plate wave detected by the detecting means.
Extracting means for extracting a group velocity corresponding to two frequency components and its frequency; and signals of the group velocity extracted by the extracting means ,
Measuring means for measuring the arrival time from the position at which the vibration is applied by the vibration generating means to the detecting means, each arrival time measured by the measuring means, and the group velocity and the frequency corresponding to each arrival time. And a calculating means for calculating the thickness of the plate material based on the measuring device. 2. A method of measuring the thickness of the plate material, a step of generating a plate wave by applying a vibration at an arbitrary position on the plate material to be measured, at any position on the plate Included in the plate wave detected by the sensor that detects the plate wave that has been placed and propagated through the plate material
Group velocity corresponding to at least two frequency components
Extracting the frequencies of the vibrations of the signals indicating the respective group velocities.
Measuring the arrival time from the time of addition, and calculating the thickness of the plate by calculating based on the measured arrival times and the group velocity and the frequency corresponding to the arrival times. A measuring method characterized by the above-mentioned.