JP2939011B2 - Whetstone inspection 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 method and an apparatus for detecting cracks in a grindstone using ultrasonic waves.

[0002]

2. Description of the Related Art FIGS. 5A and 5B are a plan view and a front view schematically showing an example of a grindstone. This whetstone 10 has an outer diameter d1
= 610 mm, inner diameter d2 = 305 mm, thickness t = 205
It has a donut shape with a size of mm, and is formed into a grindstone by forming a grindstone raw material into such a shape and then firing.

[0003] Ceramic whetstones may crack during the drying and firing steps. On the other hand, since the grindstone is used at a high rotation speed, it may be broken even if a minute crack is present. Therefore, it is an essential condition that cracks are surely found by the time of shipment, and the grindstone with the cracks is removed. When this crack has grown to the surface, it can be found by an appearance inspection after firing or an appearance inspection in a finish inspection. Further, even when the crack is minute or stopped inside, the grindstone having a small thickness can determine the presence or absence of the crack by the hammering inspection.

[0004]

However, when an internal crack exists in a grindstone having a large thickness as shown in FIG.
It could not be determined by the hammering test, and there was no effective determination method.
Until now, only a full rotation test was performed at 1.5 times the used peripheral speed in the shipping inspection to ensure the strength.
As a result, the whetstone could be broken during use.

[0005] In order to solve this problem, it is conceivable to perform inspection using ultrasonic waves. However, there is a problem how to use ultrasonic waves so that anyone can make objective judgments without requiring skill. The present invention has been made in view of the above circumstances, and has as its object to provide a method and an apparatus for non-destructively and objectively inspecting cracks in a grindstone without requiring skill.

[0006]

According to a first aspect of the present invention, there is provided a method for inspecting a grindstone, wherein an ultrasonic transmitter and an ultrasonic receiver are disposed with a reference grindstone interposed therebetween. 1
, And the ultrasonic transmitter and the ultrasonic receiver are arranged with an inspection grindstone interposed therebetween to obtain a second reception signal, and the first reception signal and the second reception signal are respectively obtained. Fourier transform, and at least in a part of the frequency domain, for each frequency component corresponding to each other, generate the first spectrum generated by Fourier transform of the first received signal and the Fourier transform of the second received signal by Fourier transform Determine the difference or ratio with the second spectrum obtained, determine the total value of the difference or ratio in the at least a part of the frequency domain, based on the total value to determine the presence or absence of cracks in the inspection whetstone. It is characterized by determining.

According to a second whetstone inspection method of the present invention for achieving the above object, an ultrasonic transmitter and an ultrasonic receiver are arranged with a reference whetstone interposed therebetween, and a first reception signal serving as a reference is generated. Fourier transforming the first received signal, arranging the ultrasonic transmitter and the ultrasonic receiver with an inspection grindstone therebetween to obtain a second received signal, and performing Fourier transform on the second received signal. In at least a part of the frequency domain, the first spectrum generated by the Fourier transform of the first received signal and the second
Find the difference or ratio with the second spectrum generated by Fourier transform of the received signal of the above, determine the difference or the total value of the difference in the at least a part of the frequency domain,
It is characterized in that the presence or absence of cracks in the inspection whetstone is determined based on the total value.

[0008] Further, the grindstone inspection apparatus of the present invention is characterized in that:
An apparatus for performing a second whetstone inspection method, comprising: an ultrasonic transmitter, an ultrasonic receiver, a Fourier transform unit for performing a Fourier transform on a reception signal received by the ultrasonic receiver, at least a part of the frequency. By placing the ultrasonic transmitter and the ultrasonic receiver across a reference grindstone for each frequency component corresponding to each other, a first reception signal received by the ultrasonic receiver is Fourier-converted. The first spectrum generated by the conversion and the second reception signal received by the ultrasonic receiver are arranged in a Fourier manner by arranging the ultrasonic transmitter and the ultrasonic receiver across an inspection grindstone. Calculating means for calculating a difference or ratio with the second spectrum generated by conversion, adding means for calculating a total value of the difference or ratio in the at least a part of the frequency domain, and It is characterized in that it comprises determination means for determining presence or absence of cracks in the test grindstone on the basis of the total value.

[0009]

According to the present invention, a standard grindstone (a grindstone without cracks) is used.
And a second reception signal obtained from an inspection grindstone (a grindstone whose presence or absence of a crack is unknown) characterized by at least a part of the frequency domain. , A difference or a ratio between a first spectrum obtained by Fourier transform of the first received signal and a second spectrum obtained by Fourier transform of the second received signal for each of the corresponding frequency components. Is determined, and the total value of the difference or the ratio is calculated. Therefore, the presence or absence of a crack in the inspection grindstone is easily and objectively determined based on the total value.

[0010] As in the first whetstone inspection method,
After obtaining both the first received signal and the second received signal, the first and second received signals may be subjected to a Fourier transform, and as in the second grinding wheel inspection method, the first received signal may be obtained. And a second received signal may be obtained after Fourier transform.

[0011]

Embodiments of the present invention will be described below. FIG.
1 is a schematic configuration diagram of a grindstone inspection device according to one embodiment of the present invention. A grindstone 10 shown in FIG. 5 is rotatably mounted on the two rollers 12, and the grindstone 1 is placed below the grindstone 10.
0 is applied to the ultrasonic transmitter 13, and the ultrasonic receiver 1 is located at a position facing the ultrasonic transmitter 13 in the hollow portion of the grindstone 10.
4 is assigned. Here, the surface of the grindstone 10 is rough, and the ultrasonic transmitter 13 on the surface of the grindstone 10,
The portion where the ultrasonic receiver 14 is in contact is a curved surface,
Since rubber members 13a and 14a are attached to portions of the ultrasonic transmitter 13 and the ultrasonic receiver 14 that come into contact with the grindstone 10, the ultrasonic transmitter 13 and the ultrasonic transmitter 13 are connected via the rubber members 13a and 14a. The acoustic wave receiver 14 is in close contact with the grindstone 10, and the rubber bodies 13a and 14a serve as an acoustic impedance conversion element, whereby the ultrasonic waves emitted from the ultrasonic transmitter 13 are effectively transmitted into the grindstone 10. The ultrasonic wave propagating in the grindstone 10 is effectively received by the ultrasonic wave receiver 14. The ultrasonic transmitter 13 and the ultrasonic receiver 14 are connected to an ultrasonic transmission receiver 15, and the ultrasonic transmitter 13 is used for each measurement from the ultrasonic transmission receiver 15.
, One ultrasonic transmission pulse is transmitted toward the transmitter, an ultrasonic wave having a center frequency of 500 kHz is pulsated from the ultrasonic transmitter 13, and this ultrasonic wave is received by the ultrasonic receiver 14, and The obtained reception signal is input to the ultrasonic transmission receiver 15. The ultrasonic reception signal input to the ultrasonic transmission receiver 15 is appropriately amplified or the like and then A / D
The signal is input to the converter 16 and converted into a digital reception signal. The digital reception signal is input to the personal computer 17 for storage and analysis.

FIGS. 2 to 4 are diagrams showing the ultrasonic reception signal waveform (each figure (A)) and its Fourier transform waveform (each figure (B)) obtained as described above. Here, FIG. 2 shows the case where no crack exists in the portion of the grindstone 10 sandwiched between the ultrasonic transmitter 13 and the ultrasonic receiver 14, and FIGS. 3 and 4 show the case where the crack exists. 3 (A) and FIG. 4 (A), a slightly larger signal is seen in the portion of A2 following the larger received signal A1 than in the case of FIG. 2 (A). As it is, accurate and objective judgment is impossible. Therefore, the received signal waveform shown in FIG. 2A is Fourier-transformed and used as a reference waveform a. In the case of FIG. 2, the received signal of another part of the grindstone 10 without cracks is obtained and Fourier-transformed and compared. The waveform b1 is obtained, and in the case of FIGS. 3 and 4, the received signal (FIG. 3A, FIG. 4A) of the portion where the crack of the grindstone 10 exists is Fourier-transformed, and the respective comparison waveforms b2 and b3 250 kHz of two Fourier transform waveforms a, b1; a, b2; a, b3
The difference at each frequency within the range of
(B), FIG. 3 (B), and FIG. 4 (B) are logarithmic axes, and therefore, are ratios when comparing antilogarithms.
C2, C3), and the sums D1, D2, D3 of the differences in the frequency range of 250 kHz to 500 kHz were obtained. As a result, D = 36.1 in the comparison between the portions without cracks (in the case of FIG. 2) and D in the comparison with the portion with cracks (in the case of FIG. 3 and FIG. 4).
2 = 196.7, D3 = 167.0, and a remarkable difference occurred depending on the presence or absence of cracks. This sum is compared with, for example, a predetermined value, and it can be determined that a crack exists when the sum is equal to or more than the predetermined value, and that no crack exists when the sum is equal to or less than the predetermined value. This makes it possible to make objective and accurate determinations without special skill.

When the inspection of a certain portion of the grindstone 10 is completed as described above, the ultrasonic transmitter 13 and the ultrasonic receiver 14 are once separated from the grindstone 10, the grindstone is rotated, and the inspection is performed again in the same manner as described above. You. In the above embodiment, 250 kHz
The sum was determined within the range of z to 500 kHz.
The range of up to 250 kHz may be included in the above difference calculation and the calculation of the total value. However, the range of 0 to 250 kHz is a portion where there is a lot of noise such as noise when the grindstone inspection is performed in a noisy factory or the like, and the entire range of 0 to 500 kHz is subjected to the difference calculation and the calculation of the total value. 250k
Inspection accuracy was almost the same as in the case where the range of Hz to 500 kHz was set as a calculation target.

Since the center frequency of the ultrasonic wave emitted from the ultrasonic transmitter 13 is 500 kHz in the above embodiment, the spectrum of the received signal has a component exceeding 500 kHz. The component exceeding 500 kHz may be included in the above calculation. However, in which frequency domain is to be calculated, the speed of the A / D converter, the speed of the Fourier transform operation, and the like are compared with the inspection accuracy. It is determined by consideration.

In the above embodiment, the donut-shaped grindstone was inspected. However, the shape of the grindstone to be inspected in the present invention is not limited to the donut shape.

[0016]

As described above, the method and the apparatus for inspecting a grindstone according to the present invention employ the first received signal obtained from a reference grindstone (a grindstone without cracks) and the grindstone for inspection (whether or not a crack exists). Fourier transform is performed on each of the second received signals obtained from the unknown whetstones), and the difference (ratio) between the first spectrum and the second spectrum obtained as a result is obtained at least in a part of the frequency domain. For each frequency,
Since the total value of the difference (ratio) is obtained, the presence or absence of a crack can be accurately and objectively determined based on the total value.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a grindstone inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a received signal waveform (A) obtained by using the apparatus shown in FIG. 1 and its Fourier transform waveform (B).

FIG. 3 is a diagram showing another example of a received signal waveform (A) obtained by using the apparatus shown in FIG. 1 and its Fourier transform waveform (B).

FIG. 4 is a diagram showing still another example of a received signal waveform (A) obtained by using the apparatus shown in FIG. 1 and its Fourier transform waveform (B).

5A and 5B are a plan view and a front view schematically showing an example of a grindstone.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Whetstone 11 Crack 13 Ultrasonic transmitter 14 Ultrasonic receiver 15 Ultrasonic transmitter 16 A / D converter 17 Personal computer

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Katsumi Saruwatari 1-16-1 Hakusan, Midori-ku, Yokohama-shi, Kanagawa Prefecture Inside Ono Sokki Technical Center (56) References JP 50-115384 (JP, A JP-A-3-72258 (JP, A) JP-A-2-57967 (JP, A) JP-A-64-91056 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 29/00-29/28

Claims (3)

(57) [Claims] An ultrasonic transmitter and an ultrasonic receiver are arranged with a reference grindstone interposed therebetween to determine a first reception signal serving as a reference, and the ultrasonic transmitter and the ultrasonic receiver are used as inspection grindstones. , A second received signal is obtained, and the first received signal and the second received signal are Fourier-transformed, respectively, and at least in a part of the frequency domain, for each corresponding frequency component, Calculating a difference or a ratio between a first spectrum generated by Fourier transform of the first received signal and a second spectrum generated by Fourier transform of the second received signal; A total value of the differences or ratios in the above, and the presence or absence of cracks in the inspection whetstone is determined based on the total value. 2. An ultrasonic transmitter and an ultrasonic receiver are arranged with a reference grindstone interposed therebetween to obtain a first reception signal serving as a reference. The first reception signal is subjected to Fourier transform, and the ultrasonic transmission is performed. A second receiving signal is obtained by arranging a probe and an ultrasonic receiver with an inspection grindstone interposed therebetween, and performing a Fourier transform on the second receiving signal. Calculating a difference or a ratio between a first spectrum generated by Fourier transform of the first received signal and a second spectrum generated by Fourier transform of the second received signal; A method for inspecting a grindstone, comprising: determining the difference in the frequency domain or the total value thereof; and determining whether or not a crack exists in the inspection grindstone based on the total value. 3. An ultrasonic transmitter, an ultrasonic receiver, a Fourier transform unit for performing a Fourier transform on a reception signal received by the ultrasonic receiver, and at least a part of frequency components corresponding to each other in at least a part of a frequency domain. A first spectrum generated by Fourier transforming a first reception signal received by the ultrasonic receiver by arranging the ultrasonic transmitter and the ultrasonic receiver with a reference grindstone interposed therebetween; A second spectrum generated by Fourier transforming a second reception signal received by the ultrasonic receiver by arranging the ultrasonic transmitter and the ultrasonic receiver with an inspection grindstone interposed therebetween; Calculating means for calculating a difference or ratio of the test wheel; adding means for calculating a total value of the difference or ratio in the at least a part of the frequency domain; and the grinding wheel for inspection based on the total value. Grinding wheel inspection apparatus characterized by comprising determination means for determining presence or absence of cracks.