JP2023179328A - Grinding stone upper slip detection method and device - Google Patents

Abstract

To provide a grinding stone upper slip detection method and device which can correctly detect the occurrence of upper slip of a grinding stone by using an AE signal being the vibration generated due to crushing of abrasive grains and a vitrified bond in grinding processing.SOLUTION: A grinding stone upper slip detection device comprises: a frequency analysis unit 50 which frequency-analyzes an AE signal SAE generated in the time of grinding to a grinding object material 12 from a grinding wheel 20; and an upper slip detection unit 56 which detects upper slip of the grinding wheel 20 on the basis of the magnitude of a periodical change amount synchronized with rotation of the grinding object material 12 of the signal intensity of a prescribed frequency band of the signal intensities of the frequency spectra that are frequency-analyzed by the frequency analysis unit 50. With this, the device can correctly detect the occurrence of upper slip of the grinding wheel 20 on the basis of the magnitude of the periodical change amount synchronized with rotation of the grinding object material 12 of the signal intensity SP of the prescribed frequency band obtained by frequency-analyzing the AE signal SAE.SELECTED DRAWING: Figure 1

Description

The present invention relates to a grinding wheel top slip detection method and apparatus for detecting a grinding wheel top slip from an AE signal obtained during a grinding process for grinding the outer peripheral surface of a workpiece.

For example, in the process of grinding the outer circumferential surface of a cylindrical workpiece using a grinding wheel, there is a phenomenon in which the abrasive grains of the grinding wheel slide upward on the surface of the workpiece without cutting the workpiece. For example, when grinding difficult-to-cut materials that easily trap heat, such as titanium alloys, when grinding with a high hardness grinding wheel at a low polishing efficiency with a minute depth of cut, such a grinding wheel top-slip phenomenon occurs. Easy to do. When top slip occurs, a pattern indicating a change in the metallographic structure of the surface of the workpiece is observed at the top slip location on the ground surface.

To detect such top slip, for example, estimation is performed using changes in the power consumption value of the electric motor that rotates the grinding wheel or changes in the grinding resistance value measured by a dynamometer. There was a problem in that it was not possible to accurately determine the timing and magnitude of the occurrence.

On the other hand, Patent Document 1 discloses a cutting table movement amount detection means for determining the amount of movement of the cutting table during grinding, and an in-process gauge change for determining the amount of change in the in-process gauge for detecting the amount of remaining grinding of the workpiece. and a cutting amount calculation means for calculating the cutting amount based on the obtained cutting table movement amount and the change amount of the in-process gauge, and the variation amount associated with one rotation of the workpiece detected by the in-process gauge is When the value becomes smaller than the predetermined value compared to the value at the initial stage of machining, the cutting table movement amount and in-process gauge change amount are reset to zero, and the switching amount (= cutting table movement amount - in-process gauge change amount) is A device for measuring the amount of hooks to be determined has been proposed.

Japanese Patent Application Publication No. 2008-119803

However, the amount of change in the remaining amount of grinding determined by the grinding amount measuring device described in Patent Document 1 cannot be distinguished from the effect of the sharpness of the tool, and it is not possible to accurately detect the upward slippage of the grinding wheel. There was a problem.

The present invention has been made against the background of the above circumstances, and its purpose is to use an AE signal, which is a vibration generated due to the crushing of abrasive grains and vitrified bond during grinding, to An object of the present invention is to provide a method and device for detecting top slip of a grinding wheel, which can accurately detect the occurrence of top slip of a grinding wheel.

Against the background of the above circumstances, the present inventors conducted frequency analysis of the AE signal obtained during the process of grinding the workpiece by cylindrical plunge grinding, and found that the When frequency analysis is performed on the digitized AE signal using an A/D converter that performs A/D conversion at a short sampling period, the first signal intensity estimated to be derived from the occurrence of fracture is found in the frequency-analyzed frequency spectrum. A second peak of signal strength in a predetermined frequency band, for example, a frequency band of 45 to 75 kHz, following the peak of , is observed, and the time change of the integrated value of the signal strength constituting the second peak of signal strength is expressed as a waveform. , there are periodically multiple valley waveforms that become locally low, and the multiple valley waveforms correspond to the rotation period of the workpiece, and the consumption of the electric motor that rotates the grinding wheel. It was noticed that such a valley-shaped waveform does not exist in the time-lapse waveform indicating the power value, and that the depth of the valley-shaped waveform becomes smaller when the rotational speed of the grinding wheel is decreased. Considering these three facts, we came to the conclusion that the size of the valley waveform described above indicates the degree of the top-slip phenomenon of the grinding wheel. The present invention has been made based on this knowledge.

That is, the gist of the first invention is (a) a method for detecting the top slip of a grinding wheel that grinds the outer circumferential surface of a workpiece, and (b) a method for detecting the top slip of a grinding wheel that grinds the outer peripheral surface of a workpiece. (c) a frequency analysis step of frequency-analyzing the AE signal generated during grinding of the work material; and (c) determining the integrated value of the signal intensity in a predetermined frequency band of the signal intensity of the frequency spectrum frequency-analyzed in the frequency analysis step. The method further includes a top-slip detection step of detecting top-slip of the grinding wheel based on the magnitude of a periodic variation that is synchronized with the rotation of the workpiece.

The gist of the second invention is that in the first invention, the top slip detection step detects the magnitude of a periodic variation of the signal intensity integral value in synchronization with the rotation of the workpiece. The object of the present invention is to represent a moving standard deviation value of a plurality of signal strength integral values obtained within a moving section exceeding one rotation period of the signal strength.

The gist of the third invention is that, in the second invention, a top slip determination step of determining top slip of the grinding wheel based on the fact that the movement standard deviation value exceeds a preset determination threshold value is further provided. It consists in including.

The gist of the fourth invention is that in the third invention, when the top slip of the grinding wheel is determined in the top slip determination step, rotation speed reduction control that reduces the rotation speed of the grinding wheel by a predetermined value. The method further includes a step.

The gist of the fifth invention is (a) a grinding wheel top slip detection device for detecting top slip of a grinding wheel grinding the outer peripheral surface of a workpiece, (b) (c) a frequency analysis unit that frequency-analyzes an AE signal generated during grinding of a material to be cut; and a top-slip detection section that detects top-slip of the grinding wheel based on the magnitude of a periodic variation synchronized with the rotation of the material.

The gist of the sixth invention is that in the fifth invention, the top slip detection section detects the magnitude of a periodic variation of the signal intensity integral value in synchronization with the rotation of the workpiece. The object of the present invention is to represent a moving standard deviation value of a plurality of signal strength integral values obtained within a moving section exceeding one rotation period of the signal strength.

The gist of the seventh invention is that, in the sixth invention, a top slip determination unit that determines top slip of the grinding wheel based on the movement standard deviation value exceeding a preset determination threshold; It also includes:

The paper according to an eighth aspect of the invention is characterized in that, in the seventh aspect, when the top slip determination unit determines that the grinding wheel is top slip, the rotation speed reduction control reduces the rotation speed of the grinding wheel by a predetermined value. It further includes a section.

According to the top slip detection method of a grinding wheel of the first invention, there is provided a frequency analysis step of frequency-analyzing an AE signal generated from the grinding wheel when grinding the work material, and a frequency spectrum subjected to frequency analysis in the frequency analysis step. a top slip detection step of detecting top slip of the grinding wheel based on the magnitude of a periodic change in signal strength in a predetermined frequency band of the signal strength of the grinding wheel in synchronization with the rotation of the workpiece. ing. As a result, the occurrence of top slip of the grinding wheel can be accurately detected based on the magnitude of the periodic change in signal strength in a predetermined frequency band, which is obtained by frequency analysis of the AE signal, in synchronization with the rotation of the workpiece. can be detected.

According to the top slip detection method of the grinding wheel of the second invention, the top slip detection step detects the magnitude of a periodic change in the signal intensity that is synchronized with the rotation of the work material. Since it is expressed by the moving standard deviation value of the plurality of signal intensity values obtained within the movement section exceeding the rotation period, the occurrence of top slip of the grinding wheel can be accurately and quantified based on the magnitude of the moving standard deviation value. can be detected.

According to the grinding wheel top slip detection method of the third invention, the top slip determination step of determining the top slip of the grinding wheel based on the movement standard deviation value exceeding a preset determination threshold value further comprises: Therefore, the occurrence of top slip of the grinding wheel can be accurately determined in the top slip determination step.

According to the grinding wheel top slip detection method of the fourth invention, when the top slip of the grinding wheel is determined in the slip determination step, the rotation speed reduction control step of reducing the rotation speed of the grinding wheel by a predetermined value. is further included, so that when upward slip of the grinding wheel is determined, the rotational speed of the grinding wheel is reduced and upward slip is automatically eliminated.

According to the grinding wheel top slip detection device of the fifth invention, there is provided a frequency analysis section that frequency-analyzes an AE signal generated from the grinding wheel during grinding of the work material, and a frequency spectrum subjected to frequency analysis in the frequency analysis step. a top slip detection unit that detects top slip of the grinding wheel based on the magnitude of a periodic change in signal strength in a predetermined frequency band of the signal strength of the grinding wheel in synchronization with the rotation of the workpiece. ing. As a result, the occurrence of top slip of the grinding wheel can be accurately detected based on the magnitude of the periodic change in signal strength in a predetermined frequency band, which is obtained by frequency analysis of the AE signal, in synchronization with the rotation of the workpiece. can be detected.

According to the grinding wheel top slip detection device of the sixth aspect of the invention, the top slip detection section detects the magnitude of a periodic change amount of the signal intensity that is synchronized with the rotation of the workpiece material. Since it is expressed by the moving standard deviation value of the plurality of signal intensity values obtained within the movement section exceeding the rotation period, the occurrence of top slip of the grinding wheel can be accurately and quantified based on the magnitude of the moving standard deviation value. can be detected.

According to the grinding wheel top slip detection device of the seventh invention, the top slip determination section that determines the top slip of the grinding wheel based on the movement standard deviation value exceeding a preset determination threshold value further comprises: Therefore, the occurrence of top slip of the grinding wheel can be accurately determined by the top slip determining section.

According to the grinding wheel top slip detection device of the eighth aspect of the invention, when the top slip determining section determines that the grinding wheel is top slip, the rotation speed reduction control is performed to reduce the rotation speed of the grinding wheel by a predetermined value. Since the grinding wheel further includes a section, when upward slip of the grinding wheel is determined, the rotational speed of the grinding wheel is reduced and upward slip is automatically eliminated.

FIG. 2 is a diagram illustrating the configuration of a grinding device including a grinding wheel upward slip detection device for detecting upward slip of a grinding wheel during grinding according to an embodiment of the present invention. 2 is a diagram illustrating a generation mechanism of an AE signal generated from a grinding point of a grinding wheel during a grinding process by the grinding apparatus shown in FIG. 1. FIG. FIG. 2 is a diagram showing an example of a frequency spectrum obtained by frequency analysis of the AE signal SAE detected by the AE sensor of FIG. 1 by a frequency analysis section. 2 is a diagram illustrating an example of a temporal change in the power consumption value of an electric motor that rotationally drives a grinding wheel in the grinding apparatus of FIG. 1. FIG. 4 is a diagram showing an example of a waveform showing a signal strength (integral) value SPI within a predetermined frequency band B2 of the frequency spectrum of FIG. 3. FIG. FIG. 6 is an enlarged view of a time axis showing a plurality of consecutive mountain waveforms and valley waveforms included in a waveform showing a temporal change in the signal strength (integral) value SPI within a predetermined frequency band B2 in FIG. 5; 7 is a diagram illustrating cycles between chevron waveforms included in the waveforms of FIG. 6. FIG. The waveform of the signal strength (integral) value SPI obtained when the rotational speed of the grinding wheel is lowered than in the case of FIG. 6 in the grinding apparatus of FIG. 1 is shown with the time axis expanded more than in FIG. 6. 7 is a diagram corresponding to FIG. 6. A diagram showing, on the same time axis as FIG. 8, the waveform of the signal intensity (integral) value SPI obtained when the rotation speed of the grinding wheel is further lowered than in the case of FIG. 8 in the grinding apparatus of FIG. 1. 6 is a diagram corresponding to No. 6. 7 is a diagram showing a waveform showing a temporal change in a moving standard deviation value MSD of a signal strength (integral) value SPI within a predetermined frequency band B2 shown in FIG. 6. FIG. 9 is a diagram showing a waveform showing a temporal change in the moving standard deviation value MSD of the signal strength (integral) value SPI shown in FIG. 8. FIG. 10 is a diagram showing a waveform showing a temporal change in a moving standard deviation value MSD of the signal strength (integral) value SPI shown in FIG. 9. FIG. Abnormality level 1 and abnormality level 2 used as the upward slip judgment threshold are superimposed on the waveform showing the temporal change of the moving standard deviation value MSD in Fig. 10, and when abnormality level 2 is detected, the grinding wheel FIG. 6 is a diagram showing a waveform showing a temporal change in the moving standard deviation value MSD after the rotation speed is lowered. 2 is a flowchart illustrating a main part of the control operation of the electronic control device of FIG. 1. FIG. FIG. 15 is a diagram illustrating a main part of a flowchart illustrating a control operation of another example of the electronic control device in FIG. 14;

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. Note that in the following examples, the figures are simplified or modified as appropriate, and the dimensional ratios, shapes, etc. of each part are not necessarily drawn accurately.

FIG. 1 is a diagram illustrating the configuration of a grinding device 14 equipped with a top slip detection device 10 for a workpiece 12 according to an embodiment of the present invention. The grinding device 14 uses a grinding wheel 20 to grind a workpiece 12 made of a difficult-to-cut material such as a titanium alloy. The workpiece 12 is a cylindrical or shaft-shaped metal component made of a difficult-to-cut material such as titanium alloy (Ti-6Al-4V). Furthermore, the grinding wheel 20 may be made of general abrasive grains such as fused alumina abrasive grains, silicon carbide abrasive grains, and ceramic abrasive grains, and superabrasive grains such as CBN abrasive grains and diamond abrasive grains, as well as inorganic, organic, or organic abrasive grains. The grinding wheel is constructed by attaching a grindstone portion 20b, which is a plurality of segment-shaped grindstone pieces such as a vitrified grindstone connected by a binding material such as metal, to the outer peripheral surface of a main body (base metal) 20a.

In FIG. 1, the grinding device 14 includes a grinding wheel 20, a spindle drive motor 62 that rotationally drives a rotating spindle that rotatably supports the grinding wheel 20 around a rotation center line C1 of the grinding wheel 20, and A workpiece movement motor 66 that moves the workpiece 12 in the radial direction to change the machining allowance in order to press the workpiece 12 against the outer peripheral surface of the cylindrical workpiece 12, and a rotation center of the grinding wheel 20 that moves the workpiece 12. A grinding control device that controls a workpiece rotation drive motor 68 that rotates around a rotation center axis C2 parallel to a line C1, a main shaft drive motor 62, a workpiece movement motor 66, a workpiece rotation drive motor 68, etc. 72.

The grinding wheel 20 has a cylindrical or drum-shaped metal core (base metal), that is, a main body 20a, and a plurality of segment-shaped grindstone portions 20b fixed to the outer peripheral surface of the main body 20a by adhesive or the like. It is attached to the shaft end of a rotating main shaft (not shown) that is rotationally driven around the rotational center line C1 of the grinding wheel 20 by the main shaft drive motor 62.

Inside the main body 20a, there are an AE sensor 22, a preamplifier 24, a transmitting circuit 26 that modulates the AE signal SAE amplified by the preamplifier 24 using a predetermined carrier wave, and transmits the modulated signal, and a storage battery 44 that functions as a power source for these. , is provided. Further, a receiving circuit 30 having an antenna 28 for receiving the AE signal SAE transmitted from the transmitting circuit 26, a bandpass filter 32, a demodulating circuit 33, an A/D converter 34, and an electronic control device 36 are processed by grinding. It is provided in a fixed position on the device 14. The above-mentioned AE sensor 22, transmission circuit 26, reception circuit 30, bandpass filter 32, demodulation circuit 33, A/D converter 34, a part of the electronic control device 36, etc. constitute the upslip detection device 10. There is.

The AE sensor 22 detects extremely high-frequency crushing vibrations (acoustic emissions) in the ultrasonic range of, for example, 20 kHz or higher, which are generated when the abrasive grains contained in the grinding wheel 20b are crushed and propagated within the grinding wheel 20b. It is detected from the inner peripheral surface and outputs an AE signal SAE which is an analog signal representing the crushing vibration. The preamplifier 24 amplifies the AE signal SAE output from the AE sensor 22. The bandpass filter 32 has a predetermined pass frequency band that exclusively passes the carrier wave received by the receiving circuit 30. The demodulation circuit 33 outputs the AE signal SAE demodulated from the carrier wave, and the A/D converter 34 converts the AE signal SAE into a digital signal.

The A/D converter 34 converts the AE signal SAE into a digital signal at a sampling period of, for example, 1/10 or less of the rotation period of the workpiece 12, for example, a sampling period of 65 ms. The shorter the sampling period of the A/D converter 34 is than the rotation period of the workpiece 12 (the faster it becomes), the clearer the waveform of the frequency spectrum obtained by frequency analysis of the AE signal SAE becomes, and the more the grinding wheel 20 is affected. The detection accuracy of upward slip on the cutting material 12 can be obtained.

The grinding wheel portion 20b of the grinding wheel 20 is, for example, a well-known vitrified grinding wheel made of abrasive grains 38, an inorganic bond (vitrified bond) 40 that binds the abrasive grains 38, and pores 42, as shown in FIG. It is made up of organizations. Due to the sliding contact between the grinding wheel portion 20b of the grinding wheel 20 and the workpiece 12, vibrations that are presumed to be caused by the occurrence of cracks Ca, that is, fractures in the abrasive grains 38 themselves, and vibrations between the abrasive grains 38 and the workpiece 12 are generated. Vibrations presumed to be derived from frictional vibrations or elastic vibrations generated by contact with, or rubbing Cb, occur, and grinding vibrations, ie, AE waves including these vibrations, are detected by the AE sensor 22.

As shown in FIG. 3, the frequency spectrum obtained by frequency analysis of the AE signal SAE detected by the AE sensor 22 includes a signal intensity that is estimated to originate from the occurrence of cracks Ca, that is, fractures, in the abrasive grains 38 themselves. A first peak P1 with a frequency of 25 to 40 kHz indicating a peak, and a second peak P2 in a frequency band B2 of 45 to 75 kHz, which includes a signal intensity that sensitively responds to the upward slip of the abrasive grains 38 on the workpiece 12. is included. Detection of upslip is possible by using part of the signal strength within the 45-75 kHz frequency band B2, so the signal strength does not necessarily have to be within the 45-75 kHz frequency band B2. For example, the center frequency band B1 of 55 to 60 kHz corresponds to the region where the signal strength at the center of the second peak P2 in the frequency band B2 is maximum. Signal strength within a predetermined frequency range that includes at least a portion of B1 may be used to detect upslip.

Here, in order to confirm the relationship between the upward sliding phenomenon of the grinding wheel 20 with respect to the workpiece 12 and the signal strength integral value SPI within a predetermined frequency in the frequency spectrum of the AE signal SAE, the present inventors conducted a The confirmation test will be explained below. First, the inventors conducted a grinding test under the following grinding test conditions, collected the power consumption value of the main shaft drive motor 62 that rotates the grinding wheel, and measured the A/D converted AE signal SAE. Frequency analysis was performed to calculate the signal strength integral value SPI in a predetermined frequency band (45 to 75 kHz). FIG. 4 shows changes in the power consumption value of the spindle drive motor 62 during grinding. FIG. 5 shows changes in the signal strength integral value SPI. In this grinding test, the ratio of the circumferential speed of the grinding wheel to the circumferential speed of the workpiece was set to be constant (approximately 200:1).

(Grinding test conditions)
FFT analysis data length: 65ms
Integral analysis pitch Δt: 65ms
Integral frequency range: 45-75kHz
Processing machine: Cylindrical grinder Grinding wheel: GC 150 H 12 V99
Outer diameter of grinding wheel: 405mmφ
Peripheral speed of grinding wheel: 42m/sec, 37m/sec, 33m/sec Outer diameter of workpiece: 58mmφ
Peripheral speed of workpiece: 0.21 m/sec, 0.18 m/sec, 0.16 m/sec Cutting speed: 0.13 mm/min Spark out: 10 rev.
Grinding oil: SEC-1500P (50x dilution rate)
Work material: Titanium alloy (Ti-6Al-4V)
Polishing efficiency Z': 0.2

The inventors found that in grinding where the circumferential speed of the grinding wheel was 42 m/sec and the circumferential speed of the workpiece was 0.21 m/sec, the power consumption value at the initial stage of the grinding process was as shown in Figure 4. Although no noticeable periodic pulsation could be found, in the signal intensity integral value SPI at the beginning of the grinding process in Fig. 5 using the same time axis as Fig. 4 and Fig. 6 using the same time axis as Fig. 4. It was discovered that a pulsating waveform consisting of a mountain waveform and a trough waveform occurs continuously. This trough waveform has decreased to its initial value. When the pulsating waveforms shown in FIGS. 5 and 6 are enlarged, as shown in FIG. 7, the pulsating period of the signal strength integral value SPI is 0.88 sec, which corresponds to the rotation period of the workpiece 12 of 0.86 sec. It was a value.

Next, the present inventors changed the circumferential speed of the grinding wheel from 42 m/s (peripheral speed of work material 0.21 m/s) to 37 m/s (peripheral speed of work material 0.18 m/s) and 33 m/s. /second (peripheral speed of the workpiece 0.16m/second) and observe the change waveform of the signal strength integral value SPI at the initial stage of grinding. As shown in FIGS. 8 and 9, the pulsation waveform is 6, it was found that as the circumferential speed of the grinding wheel decreases, the depression of the valley waveform becomes smaller and the amplitude of the pulsating waveform becomes lower. The reason why the amplitude of the pulsating waveform of the signal strength integral value SPI decreases as the circumferential speed of the grinding wheel decreases is that as the circumferential speed of the grinding wheel decreases, the cutting depth of the abrasive grains increases, and one revolution of the grinding wheel increases. This is thought to be because the increase in the depth of cut per contact reduced the upward slippage of the abrasive grains at the initial stage of the grinding process.

From these facts, in grinding difficult-to-cut materials, where the cutting speed is 0.13 mm/min and the polishing efficiency Z' is 0.2, which is lower efficiency than general grinding, the signal intensity shown in Fig. 6 It was estimated that the valley waveform of the pulsating waveform of the integral value SPI indicates that the grinding wheel upwardly slid in synchronization with the rotation of the workpiece.

Returning to FIG. 1, the electronic control device 36 is a so-called microcomputer including a CPU, ROM, RAM, interface, etc., and the CPU uses the temporary storage function of the RAM to process input signals according to a program stored in the ROM in advance. By processing, a frequency spectrum is generated by frequency analysis of the AE signal SAE, and a signal strength integral value (integrated value) SPI within a predetermined wavelength band including, for example, 55-60 kHz of the frequency spectrum is calculated, The moving standard deviation value MSD of the signal strength integral SPI is displayed on the display device 46, and it is determined whether or not the moving standard deviation value MSD exceeds a preset upward slip determination threshold HS, and the determination result is displayed. Displayed on the device 46. If the signal strength integral value SPI exceeds a preset upward slip judgment threshold HS, the judgment result is transmitted to the grinding control device 72, and the rotational speed of the grinding wheel 20 is set to a predetermined value in order to suppress upward slip. lower.

The signal strength integral SPI is calculated with an integral analysis pitch Δt of 65 msec, which is 1/13.4 of the rotation period T (0.87 seconds = 58 x π/210) of the workpiece 12, The integral analysis pitch Δt is sufficiently smaller than the pulsation period of 0.88 sec of the signal strength integral value SPI in FIG. Further, the moving standard deviation value MSD is calculated from the following equation 1. In formula 1, n is the number of analysis data (integer) within the moving section, x _i is the i-th signal strength integral value SPI, x _av is the average value of the signal strength integral value SPI within the moving section, and T is the workpiece material. The rotation period (seconds) and Δt are the analysis data length (ms).

The moving standard deviation value MSD has a larger value as the amplitude of the pulsating waveform of the signal strength integral value SPI is larger, since the moving section including n pieces of analysis data is equivalent to the rotation period T of the workpiece 12. That is, the moving standard deviation value MSD indicates a value corresponding to the magnitude of the periodic variation (amplitude) of the pulsating waveform of the signal strength integral value SPI. In this respect, the amplitude of the pulsating waveform of the signal strength integral value SPI, the moving average of the amplitude value of the pulsating waveform, is used as an amplitude evaluation value indicating the amplitude of the pulsating waveform of the signal strength integral value SPI, that is, the magnitude of the periodic variation amount. value, the depth value or area value of the trough waveform, the moving average value of the depth or area value of the trough waveform, etc. may be used instead of the moving standard deviation value MSD.

The electronic control device 36 functionally includes a frequency analysis section 50, a signal strength integral value calculation section 52, a moving standard deviation calculation section 54, and an upslip detection section 56 having an upslip determination section 58.

The frequency analysis unit 50 repeatedly and continuously performs frequency analysis (FFT analysis) of the AE signal SAE output from the A/D converter 34 at predetermined analysis cycles during the grinding process of the workpiece 12 by the grinding wheel 20. Then, in the two-dimensional coordinates of the vertical axis showing the signal strength integral value SPI (power) and the horizontal axis showing the analysis frequency, the frequency spectrum showing the magnitude of the frequency component of the AE signal SAE is shown in FIG. 3, for example. Generate as shown.

The signal strength integral value calculation section 52 calculates a specific frequency, which is a small region in which the intensity changes relatively sensitively to the upward slip of the grinding wheel 20 against the workpiece 12, in the frequency spectrum subjected to frequency analysis by the frequency analysis section 50. Band B2 For example, by performing an integral calculation (integration) on the signal strength values SP included in the range of 45 to 70 kHz, the signal strength integral value SPI can be set to a period sufficiently shorter than the rotation period of the workpiece 12, for example, 1/10 or less. It is calculated sequentially at a period, preferably at the same period as the frequency analysis period by the frequency analysis section 50. For example, FIGS. 6, 7, and 8 show time-varying waveforms of the signal strength integral value SPI when the peripheral speed of the grinding wheel 20 is 42 m/sec, 37 m/sec, and 33 m/sec.

The moving standard deviation calculating section 54 calculates the moving standard deviation value MSD within the moving section including n pieces of analysis data of the signal strength integral value SPI sequentially calculated by the signal strength integral value calculating section 52, according to formula 1. The integral value SPI is repeatedly calculated every calculation period. For example, FIGS. 10, 11, and 12 show time-varying waveforms of the moving standard deviation value MSD when the peripheral speeds of the grinding wheel 20 are 42 m/sec, 37 m/sec, and 33 m/sec.

The top-slip detection section 56 detects a period in synchronization with the rotation of the workpiece 12 of a signal intensity integral value SPI in a predetermined frequency band, for example, a 45 to 75 kHz band, out of the signal intensity of the frequency spectrum frequency-analyzed by the frequency analysis section 50. An upward slip of the grinding wheel 20 is detected based on the magnitude of the amount of change in the target. Specifically, the top slip detection unit 56 determines the magnitude of the periodic variation of the signal strength integral value SPI that is synchronized with the rotation of the workpiece 12 within a movement section that includes one rotation period of the workpiece 12. It is expressed using the moving standard deviation value MSD of the plurality of n signal strength integral values SPI obtained. Then, the upward slip detection unit 56 detects whether the grinding wheel It further includes an upslip determining section 58 that determines an upslip of 20.

The upward slip determination unit 58 determines that the movement standard deviation value MSD and the movement standard deviation value MSD exceed either of a first upward slip determination threshold M1 and a second upward slip determination threshold M2 that are experimentally set in advance. is displayed on the display device 48. Just by displaying the numerical value of the moving standard deviation value MSD, it is possible to notify the occurrence of the upward slip phenomenon.

In the upward slip determination unit 58, as shown in FIG. 13, the first upward slip determination threshold M1 is a value for determining whether there is an abnormal upward slip, and is set to "50", for example. If the movement standard deviation value MSD is less than or equal to the first upward slip determination threshold M1, it is determined that there is no abnormality, but if the movement standard deviation value MSD exceeds the first upward slip determination threshold M1, it is determined that the abnormality level is 1. . The second upward slip determination threshold M2 is a value for determining whether an upward slip abnormality has occurred, and is set to "200", for example. If the movement standard deviation value MSD is less than or equal to the second upslip determination threshold M2, it is determined that the abnormality level is 1, but if the movement standard deviation value MSD exceeds the second upslip threshold M2, the upslip abnormality cannot be corrected. It is determined that the required abnormality level is 2.

When the top slip determination unit 58 determines that the top slip abnormality level 2 of the grinding wheel 20 is determined, the top slip detection unit 56 outputs the determination result to the rotational speed reduction control unit 74 of the grinding control device 72, The grinding control device 72 is caused to reduce the rotational speed of the grinding wheel 20 by a predetermined value.

The grinding control device 72 is an electronic control device that functionally includes a rotational speed reduction control section 74, and controls the main shaft drive motor 62, the workpiece movement motor 66, the workpiece rotation drive motor 68, and the like. When the grinding control device 72 receives the grinding start command signal, the grinding control device 72 rotates the grinding wheel 20 and the workpiece 12 in a preset operation, cuts at a preset cutting speed, and cuts the workpiece 12. When the grinding is completed, the rotation of the grinding wheel 20 and the workpiece 12 is stopped and returned to the original position. When abnormal level 2 of the top slip of the grinding wheel 20 is transmitted from the top slip detection section 56 of the electronic control device 36, the grinding control device 72 controls the rotation speed of the grinding wheel 20 so that the top slip is reduced. lower.

FIG. 14 is a flowchart illustrating the main part of the control operation of the electronic control device 36. In step S1 in FIG. 14 (hereinafter, steps will be omitted), prior to grinding, grinding conditions such as those shown in the above-mentioned grinding test conditions are input. Next, in S2, after the first upward slip determination threshold M1 and the second upward slip judgment threshold M2 are set, in S3, the grinding process on the workpiece 12 of the grinding device 14 is started, and the grinding wheel 20 is For example, it is rotated at a circumferential speed of 42 m/sec.

In S4, the AE signal SAE output from the AE sensor 22 and A/D converted by the A/D converter 34 during the grinding process is sequentially read. Next, in S5 corresponding to the function of the frequency analysis section 50 or a frequency analysis step, frequency analysis (FFT) is performed for each data length of, for example, 65 ms, and a frequency spectrum shown in, for example, FIG. 3 is generated.

Next, in S6 corresponding to the function of the signal strength integral value calculation unit 52 or the signal strength integral value calculation step, a specific frequency band B2 of the frequency spectrum subjected to frequency analysis in S5, for example, included within 45 to 70 kHz is determined. By performing an integral calculation (integration) on the signal strength value SP, the signal strength integral value is calculated at a sufficiently shorter period than the rotation period of the workpiece 12, for example, a period of 1/10 or less, for example, the same period as the frequency analysis period of S5. SPI is calculated sequentially.

Next, in S7 corresponding to the function of the moving standard deviation calculation unit 54 or the moving standard deviation calculation step, the moving standard deviation value within the moving section including n pieces of analysis data of the signal strength integral value SPI sequentially calculated in S6 is calculated. The MSD is repeatedly calculated in accordance with Equation 1, for example, as shown in FIG. 10, every calculation cycle of the signal strength integral value SPI.

Next, in S8 corresponding to the function of the upward slip determination unit 58 or the upward slip determination process, the movement standard deviation value MSD calculated in S7 exceeds the first upward slip determination threshold M1 or the second upward slip determination threshold M2. A threshold value determination is performed based on whether or not. Next, in S9 corresponding to the function of the upward slip detection section 56 or the upward slip detection process, the display device 48 outputs the determination result of S8. For example, if the moving standard deviation value MSD is less than or equal to the first upward slip judgment threshold M1, no abnormality is output, but if the moving standard deviation value MSD exceeds the first upward slip judgment threshold M1, an abnormality level 1 is output. When the movement standard deviation value MSD exceeds the second upslip determination threshold M2, an abnormality level 2 that requires correction of the upslip abnormality is output.

Then, in S10, it is determined whether or not the grinding process on the workpiece 12 has been completed. If the determination in S10 is negative, the threshold value determination is updated in S11, and then steps S4 and subsequent steps are repeatedly executed, but if the determination in S10 is affirmative, this control routine is ended.

As described above, according to the top slip detection device 10 or the top slip detection method of the present embodiment, the frequency analysis unit 50 frequency-analyzes the AE signal SAE generated when grinding the workpiece 12 from the grinding wheel 20; The upward slip of the grinding wheel 20 is determined based on the magnitude of the periodic variation amount in synchronization with the rotation of the workpiece 12 in the signal strength of a predetermined frequency band of the signal strength of the frequency spectrum frequency-analyzed in the frequency analysis step 50. An upward slip detection section 56 is included. As a result, the top slip of the grinding wheel 20 is determined based on the magnitude of the periodic variation in synchronization with the rotation of the workpiece 12 of the signal strength SP in a predetermined frequency band obtained by frequency analysis of the AE signal SAE. Occurrence can be detected accurately.

According to the top slip detection device 10 or the top slip detection method of the present embodiment, the top slip detection unit 56 detects the magnitude of the periodic variation of the signal strength SP in synchronization with the rotation of the workpiece 12. Since it is expressed by the moving standard deviation value MSD of a plurality of signal strength integral values SPI obtained within a moving section exceeding one rotation period T of 12, the upper part of the grinding wheel 20 is expressed based on the magnitude of the moving standard deviation value MSD. The occurrence of slip can be detected accurately and quantitatively.

According to the upward slip detection device 10 or the upward slip detection method of the present embodiment, the upward slip determination threshold M (the first upward slip determination threshold M1 and the second upward slip determination threshold M2) has a moving standard deviation value MSD set in advance. Since the top slip determination unit 58 further includes a top slip determination unit 58 that determines the top slip of the grinding wheel 20 based on the fact that the grinding wheel 20 exceeds the above value, the top slip determination unit 58 accurately determines the occurrence of top slip of the grinding wheel.

According to the top slip detection device 10 or the top slip detection method of the present embodiment, when the top slip determination unit determines that the grinding wheel is top slip, the rotation speed is adjusted to reduce the rotation speed of the grinding wheel by a predetermined value. Since a lowering control section is further included, when upward slip of the grinding wheel is determined, the rotational speed of the grinding wheel is reduced to automatically eliminate upward slip.

Next, another embodiment of the present invention will be described. In the following description, parts common to those in the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 15 is a flowchart illustrating a main part of the control operation of the electronic control device 36, and mainly shows differences from FIG. 14.

In FIG. 15, in S8, when the threshold value determination is performed based on whether the movement standard deviation value MSD exceeds the first upward slip determination threshold M1 or the second upward slip determination threshold M2, the upward slip detection unit In S91, S92, and S93, in S91, if the movement standard deviation value MSD is less than or equal to the first upward slip determination threshold M1, it is output that there is no abnormality. In S92, when the movement standard deviation value MSD exceeds the first upward slip determination threshold M1, an abnormality level 1 is output. In S93, when the moving standard deviation value MSD exceeds the second upward slip determination threshold M2, an abnormality level 2 that requires correction of the upward slip abnormality is output. Then, in S94 following S93, a signal for reducing the circumferential speed of the grinding wheel 20 to correct the top slip abnormality is output to the rotational speed control section 74, and the rotational speed control section 74 outputs a signal to reduce the circumferential speed of the grinding wheel 20. is reduced by, for example, 5 m/sec. As a result, when the circumferential speed of the grinding wheel 20 is reduced from, for example, 42 m/sec to 37 m/sec, the moving standard deviation value MSD is reduced from "200" to "0" as shown in FIG. .

According to the top slip detection device 10 or the top slip detection method of this embodiment, when the top slip determination unit 58 determines that the grinding wheel 20 is top slip, the rotation speed of the grinding wheel 20 is reduced by a predetermined value. Since a speed reduction control section 74 is further included, when upward slip of the grinding wheel 20 is determined, the rotational speed of the grinding wheel 20 is reduced to automatically eliminate the upward slip.

Although the embodiments of the present invention have been described above in detail based on the drawings, the present invention can also be applied to other aspects.

For example, in the above-mentioned embodiment, the AE sensor 22 was provided in the main body (base metal) 20a to which the grindstone portion 20b of the grinding wheel 20 was attached, but the When using a shaped grinding wheel, the grinding wheel may be provided in a flange that is fixed to the rotating main shaft with the grinding wheel sandwiched therebetween, or in a table to which the workpiece 12 is fixed.

Further, in the above-mentioned embodiment, the upward slip determination unit 58 determines that the movement standard deviation value MSD exceeds either the first upward slip determination threshold M1 or the second upward slip determination threshold M2 that is experimentally set in advance. However, the upward slip determination unit 58 may use a single upward slip determination threshold, for example, a second upward slip determination threshold M2.

Moreover, although the above-mentioned example top-slip detection section 56 was equipped with the top-slip determination section 58, it does not necessarily have to be provided. The top slip detection unit 56 causes the display device 48 to numerically display the maximum value of the moving standard deviation value MSD, which represents the magnitude of the periodic variation amount of the signal strength integral value SPI that is synchronized with the rotation of the workpiece 12. As shown in FIG. 10 or 13, the changing waveform of the moving standard deviation value MSD may be numerically displayed on the display device 48.

Further, the upward slip detection unit 56 of the above-described embodiment detects that the movement standard deviation value MSD exceeds either the first upward slip determination threshold M1 or the second upward slip determination threshold M2 that is experimentally set in advance. Based on this, the upward slip of the grinding wheel 20 is determined, but either one of the first upward slip determination threshold M1 and the second upward slip determination threshold M2 may be used.

The above-mentioned embodiment is merely one embodiment, and the present invention can be implemented with various changes and improvements based on the knowledge of those skilled in the art.

10: Top slip detection device 12: Work material 14: Grinding device 20: Grinding wheel (grinding wheel)
22: AE sensor 34: A/D converter 50: Frequency analysis section 52: Signal strength integral value calculation section 54: Movement standard deviation calculation section 56: Upslip detection section 58: Upslip determination section 74: Rotation speed reduction control section S5: Frequency analysis step S5: Frequency analysis step S6: Signal strength integral value calculation step S7: Moving standard deviation calculation step S8: Upslip determination step S9: Upslip detection step SAE: AE signal B2: Predetermined frequency band (45~ 75kHz frequency band)
M1: First upward slip determination threshold M2: Second upward slip determination threshold SP: Signal strength value SPI: Signal strength integral value MSD: Moving standard deviation

Claims (8)

A grinding wheel top slip detection method for detecting top slip of a grinding wheel that grinds the outer peripheral surface of a workpiece, the method comprising:
a frequency analysis step of frequency analyzing an AE signal generated from the grinding wheel when grinding the work material;
on the grinding wheel based on the magnitude of the periodic variation in synchronization with the rotation of the workpiece in the signal intensity integral value of a predetermined frequency band of the signal intensity of the frequency spectrum frequency-analyzed in the frequency analysis step. A method for detecting top slip of a grinding wheel, comprising: a top slip detection step for detecting slip. In the top slip detection step, the magnitude of a periodic variation of the signal intensity integral value that is synchronized with the rotation of the workpiece is determined by detecting a plurality of values obtained within a movement section exceeding one rotation period of the workpiece. The method for detecting top slip of a grinding wheel according to claim 1, characterized in that the above-mentioned signal strength integral value is expressed by a moving standard deviation value. The top of the grinding wheel according to claim 2, further comprising a top slip determination step of determining top slip of the grinding wheel based on the movement standard deviation value exceeding a preset determination threshold. Slip detection method. Grinding according to claim 3, further comprising a rotation speed reduction control step of reducing the rotation speed of the grinding wheel by a predetermined value when the top slip of the grinding wheel is determined in the top slip determination step. How to detect grinding wheel slippage. A grinding wheel top slip detection device for detecting top slip of a grinding wheel that grinds the outer peripheral surface of a workpiece,
a frequency analysis unit that performs frequency analysis of an AE signal generated from the grinding wheel when grinding the work material;
on the grinding wheel based on the magnitude of the periodic variation in synchronization with the rotation of the workpiece of the signal intensity integral value of a predetermined frequency band of the signal intensity of the frequency spectrum frequency-analyzed by the frequency analysis section. A top-slip detection device for a grinding wheel, comprising a top-slip detection section that detects slippage. The top slip detection unit detects a magnitude of a periodic change amount of the signal strength integral value that is synchronized with the rotation of the workpiece, and detects a plurality of magnitudes of the periodic change amount of the signal intensity integral value obtained within a movement section exceeding one rotation period of the workpiece. The top-slip detection device for a grinding wheel according to claim 5, wherein the top-slip detection device for a grinding wheel is expressed by a moving standard deviation value of the signal intensity integral value. The top of the grinding wheel according to claim 6, further comprising an upward slip determination section that determines upward slip of the grinding wheel based on the movement standard deviation value exceeding a preset determination threshold. Slip detection device. Grinding according to claim 7, further comprising a rotation speed reduction control section that reduces the rotation speed of the grinding wheel by a predetermined value when the top slip of the grinding wheel is determined by the top slip determination section. Grinding wheel top slip detection device.

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