JP2996538B2 - 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 its handling is complicated. Further, in a device that calculates the plate thickness based on a path difference between reflected light from 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, as the thickness of the plate becomes thinner, the time difference until the incident ultrasonic signal is reflected by the bottom surface and returns becomes shorter, so when measuring a thin plate thickness, the time until the return is reduced. 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, and makes the distance from the vibration application position to the detection position arbitrary.
Te, and an object thereof is to provide a measuring method and apparatus capable of measuring the thickness of even simple plate at low cost.

[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 a plate material, wherein vibrations of at least two types of frequencies are applied in a time series at arbitrary positions on the plate material, and a plate of at least two types of frequencies is applied to the plate material. Vibration generating means for generating a wave, detecting means for detecting a plate wave placed at an arbitrary position on the plate material and propagating through the plate material, and detecting a small amount of the plate wave detected by the detecting means.
A signal indicating the group velocity of each of at least two frequencies
Measurement means for measuring the arrival time and group velocity of the, arrival time corresponding to each frequency measured by the measurement means,
A calculating means for calculating the plate thickness of the plate material based on the group velocity corresponding to each frequency and each of the frequencies . In order to achieve the above object, the measuring method of the present invention includes 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 vibrations of at least two types of frequencies in a time series at the position of; and a plate placed on the plate material and propagating through the plate material by applying the vibration. Detecting the waves, measuring the arrival time and group velocity of the signal indicating the group velocity corresponding to the vibration of each frequency, and the arrival time and group velocity corresponding to each of these measured frequencies , and the respective <br / > and having a step of calculating the basis of the frequency determining the thickness of the plate, the.

[0007]

In the above arrangement, vibrations of at least two types of frequencies are applied in a time series at arbitrary positions on the plate to generate plate waves of at least two types of frequencies on the plate, and arbitrary waves on the plate are generated. The plate wave placed at the position and propagating through the plate material is detected from the detection means well. The arrival time and group velocity of a signal indicating each group velocity of at least two kinds of frequencies of the detected plate wave are measured, and the arrival time corresponding to each measured frequency and the group velocity corresponding to each frequency are measured. And the respective frequencies are used to calculate the plate thickness of the plate material.

[0008]

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 is a block diagram showing a specific configuration of the vibrator driving circuit 2 for driving the vibrator 4 in the vibrating pen 3, and FIG. 3 is a timing chart thereof. In FIG. 2, an oscillator (O
SC) 201, the clock signal is frequency-divided by the frequency dividing circuit 202 and converted into a frequency signal of frequency fb (212 in the timing chart of FIG. 3).
The signal is input to the b and fc switching circuit 204. OSC
The clock signal fb output from 201 is frequency-divided by another frequency dividing circuit 203 and converted into a clock signal indicated by 213 in the timing chart of FIG. The switching circuit 204 is switched by the clock signal 213, and the clock signals of the frequencies fb and fc are alternately selected and output to the shift register 205. The shift register 205 is configured to output a pulse train of several cycles (five cycles in this embodiment) immediately after the clock signal 213 changes, and the frequency of the pulse train 214 is the frequency of fb and fc. Depends on.

As a result, from the shift register 205,
As shown in the timing chart of FIG.
Immediately after the change of 13, the clocks of the frequencies f1 and f2 indicated by the clock signal 214 are output alternately. Reference numeral 206 denotes a drive circuit which converts the clock signal 214 output from the shift register 205 to the vibrator 4
It is converted to the optimal electric signal level for driving. In the present embodiment, the clock signal 214 drives the vibrator 4 as a pulse train of a rectangular wave, but there is no problem even if the waveform of the drive signal is a sine wave or the like.

The oscillator 201 starts oscillating by a signal 11 input from the arithmetic and control circuit 1.
The signal 213 output from the frequency dividing circuit 203 is output to the arithmetic and control circuit 1. As a result, the arithmetic and control circuit 1 can detect the signal output timing from the drive circuit 206 shown in the timing chart of FIG. 3, and thus instructs the counter 83 of the waveform detection circuit 8 described later to start timing. Can be.

The vibration of the vibrator 4 thus generated is applied to the plate 7 via the horn 5, propagates on the plate 7 as elastic wave vibration, and is detected by the vibration sensor 6. In this manner, the electric energy input to the vibrator 4 is converted into mechanical energy by the vibrator 4, converted again into electric energy by the vibration sensor 6 via the plate 7 as the object to be measured, and output. .

In this embodiment, the plate delay is calculated by measuring the arrival delay time of the plate wave of the first frequency (f1) and the plate wave of the second frequency (f2) having different frequencies. FIG.
FIG. 4 is a view showing general properties of an elastic wave (plate wave) propagating on the plate material 7, wherein 41 indicates Vp (phase velocity), and 42 indicates Vg.
(Group velocity). As is clear from FIG. 4, it is well known that if the material of the plate 7 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. ing. Therefore, this relationship is linearly approximated in the predetermined region of the F × d value.

Here, the group velocity of the plate wave of the first frequency on the plate 7 as the object to be measured is Vg1, the frequency is f1, the group velocity of the plate wave of the second frequency is Vg2, The frequency is f2. When the group velocity is obtained by using the constants α and β of the approximation functions obtained in advance, Vgn = α (fn · d) + β (1) n = 1, 2 d: The thickness of 7 of the measured object , time to reach the plate wave in the vibration sensor 6 from the actuator 3 is a vibration input means (group delay time), when the plate wave of the first frequency t g1, in the case of the plate wave of the second frequency t g2, the vibration input actuator 3 and the sensor 6
Is L. By using the measured group delay time and group velocity, L = Vg1 · tg1 = Vg2 · tg2 (2) From the relationship of this equation (1), {α (f1 × d) + β} × tg1 = {Α (f2 × d) + β} × tg2 (3) When solving for the plate thickness d, d = (β / α) {(tg2-tg1) / (f1 × tg1-f2 × tg2)} (4) By utilizing the fact that the speed of the wave (plate wave) propagating on the plate 7 depends on the frequency, the group delay times of the waves having different speeds are detected, respectively, so that the thickness of the plate can be easily determined. It can be seen that can be measured.

The arithmetic control circuit 1 controls the measuring machine, calculates the thickness by performing these calculations, displays the result, or outputs the result to an external device. FIG. 5 is a time chart of the signal processing performed by the signal detection circuit 8. In FIG. 5 , reference numeral 41 denotes a drive waveform (reference numeral 214 in FIGS. 2 and 3) for driving the vibrator 4 of the vibration pen 10, and reference numeral 42 denotes the vibration transmitted through the vibration transmission plate detected by the vibration sensor 6. 3 shows a detection signal waveform at the time. Each of reference numerals 43 (A) and (B) indicates an envelope of the detection signal waveform 42. Further, each of the reference numerals 44 (A) and (B) is differentiated to determine the delay time of each wave of each of the envelopes 43 (A) and (B), and its zero-cross signal (corresponding to the peak of the envelope). Used to detect

As a result, the signal waveform detection circuit 8 outputs the group delay time tgn for each drive signal to the arithmetic and control circuit 1 as a signal indicating the peak value of the envelope of each detected signal waveform. That is, the waveform detection circuit 8
Has a counter 83, indicated by 41 in FIG. 5, which starts clocking at the same time as the output of clock signals having different frequencies. Then, the signal processing circuit 82 receives the detection signals 42 of the vibration sensor 6 for the clock signals having different frequencies, obtains the envelopes 43 (A) and 43 (B) of the detection signals 42, and obtains the zero-cross signal 44 (A ), 44 (B). Counter 8
When the zero cross signal is input, the timer 2 terminates the clocking and outputs the clocked value to the arithmetic and control circuit 1.

FIG. 6 is a flowchart showing the thickness measurement processing in the arithmetic and control circuit 1 of the present embodiment. The control program for executing this processing is a ROM of the arithmetic and control circuit 1.
(Not shown) or the like.

In this process, first, in step S1, a drive signal 11 for driving the oscillator 201 of the drive circuit 2 is output to the drive circuit 2, and at the same time, the counter 83 is output in step S2.
Is started, and time counting by the counter 83 is started. Next, the process proceeds to step S3, and waits for the counter 83 to stop the time counting operation. When the counter 83 finishes the time counting, the process proceeds to step S4 to read the time value. The time value read here is the time tg1 shown in FIG.

Next, in step S5, the signal 213 from the drive circuit 2 is input, and the timing when the signal 213 rises is detected. When the signal 213 rises, step S
6 and the output timing of the clock signal (f2) shown in FIG. Then, in step S7, the process waits for the counter 83 to stop counting. When the counter 83 stops counting, the process proceeds to step S8, and the counted value (tg2 in FIG. 5).
Enter

Next, in step S9, the difference (tg2-tg1) between these time data is obtained, and each of the predetermined frequencies (f1, f2) is multiplied by the corresponding elapsed time (tg1, tg2). Then, the group velocities (f1 · tg1, f2 · tg2) corresponding to each frequency are obtained. 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 S10, 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 constituted by a plurality of devices or to an apparatus constituted by a single 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 pen 10 and the vibration sensor 6 does not need to be determined in advance, so that the vibration pen 10 and the vibration sensor 6 can be positioned at any positions on the object to be measured. Put it down and measure its thickness. Moreover,
An excellent effect that allows the apparatus to be configured at low cost is obtained.

[0023]

As described above, according to the present invention, the vibration
There is an effect that the thickness of the plate material can be easily measured at low cost by making the distance from the motion application position to the detection position arbitrary .

[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 block diagram illustrating a configuration of a vibrator drive circuit according to the present embodiment.

FIG. 3 is a diagram illustrating an example of a detection signal waveform of each part of the drive circuit illustrated in FIG. 2;

FIG. 4 is a diagram for explaining general properties of a plate wave.

FIG. 5 is a time chart showing signal processing in the waveform detection circuit based on the relationship between the drive signal waveforms of different frequencies and the group velocity of the corresponding plate wave in this embodiment.

FIG. 6 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 Arithmetic control circuit 2 Oscillator drive circuit 3 Oscillation output actuator 4 Oscillator 5 Horn 6 Vibration sensor 7 DUT (plate material) 8 Signal waveform detection circuit 9 Display / output unit 10 Vibration pen 81 Preamplifier circuit 82 Signal processing circuit 83 counter

Continuing on the front page (72) Inventor Jun Tanaka 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (72) Inventor Kiyoshi 3-30-2 Shimomaruko, 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, wherein at least two types of vibrations are applied in a time series at arbitrary positions on the plate material, and at least two types of vibrations are applied to the plate material.
A vibration generating means for generating a plate wave frequency, is placed at an arbitrary position on the plate, a detecting means for detecting a Lamb wave propagated through the said plate, at least the plate wave detected by said detecting means Two types
Signal arrival time and indicating the respective group velocity of the frequency of the
Measurement means for measuring the group velocity , arrival time corresponding to each frequency measured by the measurement means, group velocity corresponding to each frequency, and calculation for calculating the plate thickness of the plate material based on each frequency And a measuring device. 2. A measuring method for measuring a thickness of a plate material , wherein at least two kinds of measurement methods are provided at arbitrary positions on a plate material to be measured.
Applying a vibration of a frequency in a time series to generate a plate wave, and detecting a plate wave placed on the plate material and propagating through the plate material by applying the vibration, corresponding to the vibration of each frequency a step of measuring the arrival time and the group velocity of the signal indicating the group velocity which is the arrival time corresponding to the respective frequencies are those measured Suk
Time, and the measuring method characterized by comprising a step of determining the thickness of the plate was calculated on the basis of the respective frequencies, the.