JP2021146490A - Truing completion verification device - Google Patents

Abstract

To provide a truing completion verification device that can perform truing by which a service life of a grinding stone is not spoiled as much as possible.SOLUTION: A truing completion verification device is provided with a truing completion verification part 53 that sequentially calculates signal intensity integral values of at least either of first signal intensities SP1 in a first frequency band B1 relevant to fracture of abrasive grain 38 of a grinding wheel 14 and second signal intensities SP2 in a second frequency band B2 higher than the first frequency band, and verifies truing completion of the grinding wheel 14, on the basis of saturation of the signal intensity integral values. Therefore, cut-in amounts of a rotary dresser 46, frequencies of scanning, and total cut-in amounts are supposed to be necessary and sufficient values to complete truing, so that a grinding surface of the griding wheel 14 is prevented from being ground uselessly beyond necessity, which can suppress the truing from spoiling a service life of the grinding wheel 14.SELECTED DRAWING: Figure 1

Description

The present invention relates to a truing completion determination device for determining the completion of truing for reforming the ground surface of a grinding wheel, and a truing device including the truing completion determination device.

In a grinding machine that processes a work material using a grinding wheel, in order to continuously maintain the accuracy of grinding, for example, by performing trueing using a tool such as a diamond dresser as a grinding tool, the grinding wheel is used. It is known that the shape of the ground surface of the above is periodically reshaped. For example, the grinding apparatus described in Patent Document 1 is that. In such a grinding apparatus, the entire grinding surface of the grinding wheel is adjusted to a perfect circular shape by periodic grinding, so that the grinding accuracy in the subsequent grinding process is maintained.

Among the above-mentioned truing, in the truing in which the truing tool is scanned (traverse) along the rotation center line of the grinding wheel, the depth of cut is set in advance for the grinding wheel of the truing tool for truing, and the depth of cut is set in advance for the grinding wheel. The number of scans for relatively moving the grindstone is set in advance, and the grindstone for performing the grindstone with the preset depth of cut is scanned for the preset number of scans to complete the truing. Further, among the above-mentioned truing, when truing by a plunge that cuts the truing tool in a direction orthogonal to the rotation center line of the grinding wheel, the cutting speed of the truing tool for truing with respect to the grinding wheel is set in advance, and the cutting speed depends on the cutting speed. When the cut reaches the preset total cut amount, the growing is completed.

JP-A-2018-167331 Japanese Unexamined Patent Publication No. 2000-23336

By the way, the cutting amount, the number of scanning times, and the total cutting amount of the truing tool are set in advance with a margin so that the truing can be sufficiently performed in consideration of various variations. For this reason, the ground surface of the grinding wheel is unnecessarily scraped, which causes a problem that the life of the grinding wheel is impaired.

On the other hand, in Patent Document 2, an AE signal (acoustic emission signal: a vibration wave having a frequency of, for example, 100 kHz or more, which is an ultrasonic region) representing crushing vibration generated in connection with crushing of abrasive grains is detected. , A device for monitoring the dressing state of the grinding wheel using the AE signal has been proposed. In this dressing state monitoring device, regarding the vitrified grinding grindstone, the grinding grindstone side AE signal output from the grinding grindstone side AE sensor is the interface peeling between the abrasive grains and the inorganic binder (100 kHz to 2 MHz) and the cracks of the abrasive grains themselves (100 kHz to 2 MHz). 100 kHz to 2 MHz), cracks of the inorganic binder itself (100 kHz to 2 MHz), and the work material side AE signal output from the work material side AE sensor is the plastic deformation of the work material (100 kHz to 800 kHz) and the work material. It is said to represent brittle fracture (200 kHz to 700 kHz) of the cutting material, and the original AE signal obtained by frequency analysis from the grinding wheel side AE signal and the work material side AE signal is input to the neural network. For example, it is said that the dressing state of the grinding wheel is determined.

However, in the above-mentioned conventional dressing condition monitoring device, when applied to the trueing of the grinding wheel, the crushing of the abrasive grains themselves and the crushing of the inorganic binder itself are the same frequency components (100 kHz to 2 MHz) in the AE signal on the grinding wheel side. Therefore, it is not possible to accurately detect the crushing of the abrasive grains themselves and the crushing of the inorganic binder itself, and the grinding state of the grinding surface of the grinding wheel and the determination of the completion of the grinding are performed with high accuracy. I couldn't.

The present invention has been made in the background of the above circumstances, and an object of the present invention is to provide a growing completion determination device capable of growing without impairing the life of the grinding wheel as much as possible.

As a result of various studies against the background of the above circumstances, the present inventor has a sampling period of about 10 μsec or less, which is faster and has higher resolution than the conventional AE signal, for the AE signal output from the AE sensor during truing. After digitizing using a D converter, frequency analysis (FFT) shows that in the frequency band lower than 100 kHz in the power spectrum, the peak signal group of the relatively low frequency first frequency band and the first frequency band. A group of peak signals in the second frequency band, which is relatively higher in frequency, clearly appeared on the frequency axis. The peak signal group in the first frequency band is derived from the crushing of the abrasive grains of the grinding wheel, and the peak signal group in the second frequency band is frictional vibration generated by contact (rubbing) between the abrasive grains and the dresser. And found the fact that it is derived from elastic vibration. It was also found that the integrated signal intensity of the peak signal group in the first frequency band or the peak signal group in the second frequency band shows a phenomenon in which the increase is saturated in synchronization with the completion of turwing.

That is, the gist of the first invention is (a) a tool for determining the completion of turwing of a grinding wheel, which determines the completion of turwing for shaping the ground surface of the grinding wheel using a turwing tool, and (b) the grinding. An AE sensor that detects an AE signal generated during truing of a grindstone, (c) an A / D converter that converts an AE signal output from the AE sensor into a digital signal, and (d) the A / D converter. Of the frequency analysis unit that obtains a power spectrum by frequency-analyzing the AE signal converted into a digital signal by (e) and the frequency band of 100 kHz or less of the power spectrum obtained by the frequency analysis unit, the first frequency band Based on the sequential calculation of at least one signal strength integrated value of the first signal strength and the second signal strength of the second frequency band having a frequency higher than that of the first frequency band, and the saturation of the signal strength integrated value. It is intended to include a truing completion determination unit for determining the completion of the truing of the grinding wheel.

According to the truing completion determination device of the first invention, at least one signal strength integrated value of the first signal strength of the first frequency band and the second signal strength of the second frequency band having a frequency higher than that of the first frequency band. Is sequentially calculated, and based on the saturation of the signal intensity integrated value, a truing completion determination unit for determining the completion of the truing of the grinding wheel is provided. As a result, the depth of cut, the number of scans, and the total amount of depth of cut of the truing tool are set to necessary and sufficient values for the completion of truing, so that the grinding surface of the grinding wheel may be unnecessarily scraped. Therefore, it is possible to prevent the life of the grinding wheel from being impaired by trueing.

Here, preferably, the first frequency band is a frequency band including at least a part of the frequency band of 25 to 40 kHz, and the second frequency band includes at least a part of the frequency band of 45 to 65 kHz. It is in the frequency band. As a result, the first signal strength in the first frequency band derived from the crushing of the abrasive grains on the true surface of the grinding wheel and the second signal strength derived from the contact (rubbing) between the abrasive grains on the true surface of the grinding wheel and the true tool. At least one of the second signal intensities in the frequency band can be used to properly and accurately complete the truing of the grinding wheel.

Further, preferably, the first frequency band is a frequency band of 25 to 40 kHz, and the second frequency band is a frequency band of 45 to 65 kHz. As a result, the first signal strength of the first frequency band derived from the crushing of the abrasive grains on the true surface of the grinding wheel and the second frequency band derived from the contact between the abrasive grains on the true surface of the grinding wheel and the true tool. At least one of the second signal intensities of the above can be used to appropriately and accurately determine the completion of growing of the grinding wheel.

Further, preferably, the sampling period of the A / D converter is 10 μs or less, preferably 5 μs or less, and more preferably 1 μs or less. By frequency-analyzing the A / D-converted AE signal by the A / D converter with improved resolution in this way, the first frequency derived from the crushing of abrasive grains on the true-wing surface of the grinding wheel in the region of 100 kHz or less. At least one of the first signal strength of the band and the second signal strength of the second frequency band derived from the contact between the abrasive grains of the grinding wheel and the truing tool is obtained, and the signal strength integrated value of the first signal strength and the signal strength integrated value and the signal strength integrated value of those first signal strengths are obtained. Based on the change of at least one of the signal strength integrated values of the second signal strength, it is possible to determine the truthing completion.

It is a figure explaining the structure of the grinding apparatus provided with the turwing completion determination apparatus of one Example of this invention. It is a figure explaining the generation mechanism of the AE signal obtained from the vitrified grindstone in the state of the ground surface by the grinding apparatus of FIG. It is a figure which shows the display example which displayed the signal intensity ratio SR (= SP1 / SP2) which shows the ground surface state on the surface state display device of FIG. It is a figure which shows the display example which displayed the signal strength integrated value of the 1st signal strength SP1 and the signal strength integrated value of the 2nd signal strength SP2 which increase with the progress of turwing on the surface state display device of FIG. It is a figure which shows the power spectrum obtained in the truing test when the peripheral speed ratio Vd / Vg is 1.0 and is down cut among three kinds of truing tests which performed by the present inventor with different peripheral speed ratios. .. It is a figure which shows the power spectrum obtained in the truing test when the peripheral speed ratio Vd / Vg is 0.3 and is down cut among three kinds of truing tests which differed in the peripheral speed ratio performed by the present inventor. .. It is a figure which shows the power spectrum obtained in the truing test when the peripheral speed ratio Vd / Vg is 1.0 and up-cut among three kinds of truing tests which performed by the present inventor with different peripheral speed ratios. .. A predetermined determination threshold value for determining the occurrence of each peak waveform is provided for each peak waveform of the three types of power spectra of FIGS. 5, 6, and 7, and the generated peak waveforms exceeding the determination threshold value. It is a figure which shows the occurrence map which determined that it occurred. It is a figure explaining the tsuruing performed by moving a dresser in a direction parallel to the rotation center line of a grinding wheel with respect to the grindstone part of a grinding wheel which has a constant runout with respect to the center of the grindstone axis at the time of mounting. It is a figure which shows the output signal which is output from the AE sensor in the truing of FIG. 9, (a) shows the output signal when the runout of a grinding wheel is not removed, (b) is after the runout of a grinding wheel is removed. The output signal of is shown. In the truing of FIG. 9, the signal strength integrated value of the first signal strength SP1 and the signal strength integrated value of the second signal strength SP2 increase as the cutting amount of the truing increases, but reach a predetermined cutting amount. After that, it is a figure which shows the property of being saturated to a constant value. It is a figure explaining the plunge true looing using the total type dresser for the grindstone part of a grinding wheel. FIG. 13 is a diagram illustrating a damage region D formed on a part of the grinding surface of the grindstone portion of the grinding wheel. It is a figure which shows the output signal which is output from the AE sensor in the plunge truing of FIG. In the plunge truing of FIG. 12, the integrated signal strength of the first signal strength SP1 and the integrated signal strength of the second signal strength SP2 increase as the cutting amount of the truing increases, but reach a predetermined cutting amount. It is a figure which shows the property of being saturated to a constant value after that. It is a flowchart explaining the main part of the troughing control operation by traverse of the arithmetic control apparatus and the troughing control unit of FIG. FIG. 5 is a flowchart illustrating a main part of a truing control operation by a plunge of the arithmetic control device and the truing control unit of FIG. 1.

Hereinafter, examples of the present invention will be described in detail with reference to the drawings. In the following examples, the drawings are appropriately simplified or deformed, and the dimensional ratios and shapes of each part are not necessarily drawn accurately.

FIG. 1 is a diagram illustrating a configuration of a grinding apparatus 12 that also functions as a grinding apparatus and includes a grinding completion determination apparatus 10 that also functions as a grinding surface evaluation apparatus according to an embodiment of the present invention. In FIG. 1, the grinding apparatus 12 includes general abrasive grains such as molten alumina-based abrasive grains, silicon carbide-based abrasive grains, and ceramic abrasive grains, and super-abrasive grains such as CBN abrasive grains and diamond abrasive grains. Grinding stones such as grindstones, resinoid grindstones, metal bond grindstones, and electrodeposition grindstones are used. In this embodiment, the grinding wheel 14 shown in FIG. 1 is used as the grinding wheel. The grinding wheel 14 has a cylindrical or drum-shaped metal core, that is, a grindstone portion 16 fixed to the outer peripheral surface of the main body 18, and is mounted on a rotary shaft that is rotationally driven by a spindle drive motor 62. The grinding wheel 14 is driven at a relatively high peripheral speed of, for example, about 80 m / sec or more, and grinds the surface of a columnar work material 44, for example. The rotary dresser 46 shown in FIG. 1 is used as a truing tool to perform truing on the grinding wheel 14.

The truing completion determination device 10 transmits the AE sensor 22, the preamplifier 24, the transmission circuit 26 that transmits the AE signal SAE amplified by the preamplifier 24 using a predetermined carrier, and the AE signal SAE transmitted from the transmission circuit 26. It includes a receiving circuit 30 having an antenna 28 for receiving, a bandpass filter 32, an A / D converter 34, and an arithmetic control device 36. The AE sensor 22 transmits an extremely high frequency acoustic vibration, which is generated at the time of crushing the abrasive grains 38 included in the grindstone portion 16 and propagates in the grindstone portion 16, for example, in an ultrasonic region of 20 kHz or more. The AE signal SAE, which is an analog signal representing the crushing vibration, is output. The preamplifier 24 amplifies the AE signal SAE output from the AE sensor 22. The bandpass filter 32 includes a predetermined passing frequency band through which the carrier wave received by the receiving circuit 30 is passed. The A / D converter 34 converts the AE signal SAE demodulated from the carrier wave into a digital signal. The arithmetic control device 36 processes the AE signal SAE converted into a digital signal.

The AE sensor 22, the preamplifier 24, and the transmission circuit 26 are provided in the main body 18 of the grinding wheel 14. The A / D converter 34 has a high resolution, for example, with a sampling period of 10 μs (microseconds) or less, preferably a sampling period of 5 μs or less, and more preferably a sampling period of 1 μs or less. Converts SAE into a digital signal. The shorter the sampling cycle of the A / D converter 34 (the higher the speed), the more the first frequency band B1 related to the grinding of the abrasive grains of the grinding wheel 14 and the abrasive grains 38 of the grinding wheel 14 come into contact with the rotary dresser 46. The second frequency band B2 related to the origin is clarified. In this embodiment, 1 μsec is used as the sampling period of the A / D converter 34.

As shown in FIG. 2, for example, the grindstone portion 16 of the grinding wheel 14 is a well-known vibrated grindstone composed of abrasive grains 38, an inorganic binder (vitrified bond) 40 for binding the abrasive grains 38, and pores 42. It is composed of a structure, and due to frictional contact with the work material (work) 44 or the rotary dresser 46, the vibration of the first frequency band B1 resulting from the occurrence of crack Ca, that is, crushing of the abrasive grains 38 itself, and the abrasive grains 38 Vibration of the second frequency band B2 derived from frictional vibration or elastic vibration generated by contact with the work material 44 or the rotary dresser 46, that is, rubbing Cb is generated, and the grinding vibration including those vibrations, that is, the AE wave is the AE sensor. Detected by 22.

The arithmetic control device 36 of FIG. 1 is a so-called microcomputer including a CPU, a ROM, a RAM, an interface, and the like, and the CPU processes an input signal according to a program stored in the ROM in advance while using the temporary storage function of the RAM. As a result, numerical values, graphs, figures, etc. representing the ground surface state for determining the truing surface state are calculated and output from the surface state display device 48 that also functions as the ground surface state display device, and the grinding control device. Send to 72.

The arithmetic control device 36 of the growing completion determination device 10 functionally includes a frequency analysis unit 50, a grinding surface state output unit 51, and a tsuruing surface state output unit 52. The frequency analysis unit 50 performs frequency analysis (FFT) of the AE signal SAE input from the A / D converter 34 during the grinding process of the work material 44 or during the truing of the grinding wheel 14 to show the signal power. In the two-dimensional coordinates of the vertical axis and the horizontal axis indicating the frequency, a power spectrum is generated in which various signal powers indicating the magnitude of the frequency component are shown as peak waveforms for each frequency on the frequency axis (horizontal axis).

During the grinding process of the work material 44, the ground surface state output unit 51 has a preset first frequency band B1 including, for example, 32.5 kHz in the center, for example, a first frequency of 25 to 40 kHz from the power spectrum. A first signal strength SP1 for band B1 and a preset second frequency band B2 containing, for example, 55 kHz in the center, for example, a second signal strength SP2 for a second frequency band B2 of 45 to 65 kHz, and a signal strength. The ratio SR (= SP1 / SP2) is calculated and output to the surface condition display device 48. FIG. 3 shows a display example of a signal intensity ratio SR indicating the ground surface state of the work material 44 when the surface state display device 48 is a level meter displayed on a liquid crystal screen or an instrument.

During the truing of the grinding wheel 14 using the rotary dresser 46 as the truing tool, the truing surface state output unit 52 has a preset first frequency band B1 including, for example, 32.5 kHz in the center from the above power spectrum, for example. The integrated value of the signal intensity SP1 of the first signal strength SP1 for the first frequency band B1 of 25 to 40 kHz, and the preset second frequency band B2 including, for example, 55 kHz in the center, for example, the second frequency band of 45 to 65 kHz. The integrated signal strength of the second signal strength SP2 for B2 is calculated and output to the surface state display device 48. FIG. 4 shows the signal intensity integrated value of the first signal intensity SP1 and the second signal representing the true wing surface state of the work material 44 when the surface condition display device 48 is a level meter displayed on a liquid crystal screen or an instrument. Display examples of the signal intensity integrated value of the intensity SP2 are shown. Here, the above signal intensity integral value is a value obtained by integrating the effective value of the amplitude at each frequency with respect to the frequency axis.

Further, the truing completion determination unit 53 sets the integrated value of the signal strength of the first signal strength SP1 from the truing surface state output unit 52 and / or the first during the truing of the grinding wheel 14 using the rotary dresser 46 as the truing tool. 2 The signal strength integral value of the first signal strength SP1 or the signal strength integral value of the second signal strength SP2 is set in advance based on the property that the signal strength integral value of the signal strength SP2 is saturated when the truing is completed. It is determined that the truing is completed based on the fact that the truing completion determination threshold value TF1 has been exceeded, and the result is output. The truing completion determination threshold value TF1 is a value corresponding to, for example, about 90% of the saturation value of the signal strength integrated value of the first signal strength SP1, or the saturation of the signal strength integrated value of the second signal strength SP2 in the second frequency band B2. It is preset to a value corresponding to, for example, about 90% of the value.

Here, in the power spectrum obtained by frequency analysis of the AE signal SAE converted from the AE wave detected by the AE sensor 22 into a digital signal using a high-speed and high-resolution A / D converter 34, the first frequency band. The test performed by the present inventor on a predetermined grinding wheel for the generation of the peak waveform signal group in B1 and the peak waveform signal group in the second frequency band B2 will be described below. Test 1 is a verification test of the generation state of the first frequency band B1 and the second frequency band B2 composed of the peak waveform signal group in the power spectrum obtained at the time of growing the grinding wheel 14 using the vitrified grindstone. ..

(Test 1)
In FIGS. 5, 6 and 7, the present inventor shows that the peripheral speed ratio Vd / Vg and the rotation direction of the rotary dresser 46 (the downcut is the rotation in the direction opposite to the rotation direction of the grinding wheel 14) under the following trueing condition 1. The upcut is a truing test (downcut of Vd / Vg = 1.0, Vd / Vg = 0. It is a figure which shows the power spectrum obtained by the down cut of 3 and the up cut of Vd / Vg = 1.0, respectively. Further, in FIG. 8, a predetermined determination threshold value for determining the occurrence of each peak waveform is provided for each peak waveform of the three types of power spectrum, and among the generated peak waveforms, those exceeding the determination threshold value are generated. It is a figure which shows the occurrence map which was judged as.

(Truing condition 1)
Grinding wheel: Grinding wheel with built-in AE sensor Grinding wheel grindstone part: CB 80 N 200 V
(CBN abrasive grains having a particle size of 80 are bonded by a vitrified binder and have a bonding degree of N and a concentration of 200).
Grinding machine: General-purpose cylindrical grinding machine Peripheral speed of grinding wheel Vg: 45 m / sec (clockwise)
Truing tool: Diamond rotary dresser Circumferential speed of rotary dresser ・ Vd: 45 m / sec (counterclockwise downcut)
Peripheral velocity ratio Vd / Vg = 1.0
・ Vd: 13.5m / sec (counterclockwise downcut)
Peripheral velocity ratio Vd / Vg = 0.3
・ Vd: 45m / sec (clockwise upcut)
Peripheral velocity ratio Vd / Vg = 1.0

FIG. 5 shows the power spectrum obtained under the truing condition in the downcut of Vd / Vg = 1.0 in the truing condition 1. As shown in FIG. 1, the truing condition of FIG. 5 is such that the peripheral speed Vg of the clockwise grinding wheel 14 and the peripheral speed Vd of the rotary dresser 46 counterclockwise coincide with each other in opposite directions. This is a trueing condition in which the relative peripheral speed between the grinding wheel 14 and the rotary dresser 46 at the contact point becomes zero, and the abrasive grains 38 and the inorganic binder 40 of the grinding wheel 14 are crushed remarkably. In the power spectrum of FIG. 5, a plurality of peak waveforms are intensively generated in the first frequency band B1 of 25 to 40 kHz and the second frequency band B2 of 45 to 65 kHz, respectively, excluding low frequency noise such as mechanical vibration. Therefore, a phenomenon was observed in which the height of the peak waveform (signal intensity) in the first frequency band B1 was larger than the height (signal intensity) of the peak waveform in the second frequency band B2.

FIG. 6 shows the truing condition in the downcut of Vd / Vg = 0.3 in the truing condition 1, that is, the peripheral speed Vg of the grinding wheel 14 is in the rotation direction opposite to the peripheral speed Vd of the rotary dresser 46. It shows the power spectrum obtained under the trueing condition in which large crushing of the abrasive grains 38 of the grinding wheel 14 is unlikely to occur and the increase of the abrasive grains 38 in contact is remarkable at about 3 times. Even in this power spectrum, a plurality of peak waveforms are intensively generated in the first frequency band B1 of 25 to 40 kHz and the second frequency band B2 of 45 to 65 kHz, respectively, excluding low frequency noise such as mechanical vibration. A phenomenon was observed in which the height of the peak waveform (signal intensity) in the second frequency band B2 was larger than the height (signal intensity) of the peak waveform in the first frequency band B1.

In FIG. 7, the truing condition in the upcut of Vd / Vg = 1.0 in the truing condition 1, that is, the peripheral speed Vg of the grinding wheel 14 is the same as the peripheral speed Vd of the rotary dresser 46, but FIG. It shows the power spectrum obtained under the trueing condition in which large crushing of the abrasive grains 38 of the grinding wheel 14 is unlikely to occur and the increase of the abrasive grains 38 in contact is remarkable in the reverse rotation direction as in the case. Even in this power spectrum, a plurality of peak waveforms are intensively generated in the first frequency band B1 of 25 to 40 kHz and the second frequency band B2 of 45 to 65 kHz, respectively, excluding low frequency noise such as mechanical vibration. A phenomenon was observed in which the height of the peak waveform (signal intensity) in the second frequency band B2 was larger than the height (signal intensity) of the peak waveform in the first frequency band B1.

FIG. 8 is a predetermined determination for determining the occurrence of each peak value for each peak value of the three types of power spectrums having different peripheral speed ratios Vd / Vg shown in FIGS. 5, 6, and 7, respectively. It is a figure which shows the peak waveform generation map which provided the threshold value, determined that the peak value which occurred exceeds the determination threshold value, and showed in the black region.

According to FIG. 8, a peak value having a magnitude exceeding the above determination threshold occurs mainly in the first frequency band B1 of 25 to 40 kHz in the downcut with a peripheral speed ratio Vd / Vg of 1.0, and the peripheral speed ratio. A downcut with a Vd / Vg of 0.3 and an upcut with a peripheral velocity ratio of Vd / Vg of 1.0 occur in the second frequency band B2 of 45 to 65 kHz. As a result, in the power spectrum obtained by frequency-analyzing the AE signal SAE, the height (signal intensity) of the peak waveform of at least a part of the frequencies in the first frequency band B1 is the crushing of the abrasive grains 38 on the surface of the grindstone of the grinding wheel 14. The height (signal intensity) of the peak waveform of at least a part of the frequencies in the second frequency band B2 is the frictional vibration generated by the contact between the abrasive grains 38 and the rotary dresser 46 on the surface of the grindstone of the grinding wheel 14. Alternatively, it was confirmed that it reflected elastic vibration. That is, the first frequency band B1 corresponds to the abrasive grain crushing frequency band, and the second frequency band B2 corresponds to the elastic vibration frequency band due to the contact between the abrasive grains 38 and the rotary dresser 46.

(Test 2)
The present inventor uses the following trueing condition 2 to shape the outer circumference runout (runout of the outer circumference of the grindstone due to the deviation between the rotation center line C1 and the center of the grindstone) that occurs when the grinding wheel 14 is attached, as shown in FIG. The traversal was performed, and the integrated value of the signal strength of the first signal strength SP1 of the first frequency band B1 and the integrated value of the signal strength of the second signal strength SP2 of the second frequency band B2 were observed.

(Truing condition 2)
Grinding wheel specifications: CB 80 N 200 VN1
Outer diameter 409 mm x width 30 mm x inner diameter 127 mm
Coolant flow rate: 20 L / min
Truing tool specifications: SD 40 Q 75 MW7
Diameter 100 mm x Abrasive material layer thickness 1 mm
Growing tool peripheral speed: Vg = 45m / s, Vd = 13.5m / s (Vd / Vg = 0.3)
Truing tool lead: 0.10 mm / r. o. w.
Cutting amount of truing tool: R0.004mm / pass

In FIG. 9, while reciprocating scanning a single stone or blade type dresser 80 as a truing tool in a direction parallel to the rotation center line C1 of the grinding wheel 14, the grinding wheel portion 16 of the grinding wheel 14 is cut at each scanning. The filling amount was increased and the truing was repeated. A rotary dresser 46 may be used instead of the dresser 80. The AE signal SAE, which is the output signal of the AE sensor 22, is the time-axis waveform shown in FIG. 10 (a), and is the time-axis waveform shown in FIG. 10 (b) even after the runout of the grinding wheel 14 is removed. Met. Therefore, in the past, it was difficult to distinguish the time-axis waveform of FIG. 10 (b) from the time-axis waveform of FIG. 10 (a), so that it was difficult to determine the end of growing.

On the other hand, FIG. 11 shows a change in the integrated signal strength value of the first signal strength SP1 and a change in the integrated signal strength value of the second signal strength SP2 in the traversing. As shown in FIG. 11, the signal strength integrated value of the first signal strength SP1 and the signal strength integrated value of the second signal strength SP2 are 80 to 100 μm, which is the amount of runout of the grinding wheel 14 measured in advance with a dial gauge. Until the region R is reached, the amount of trewing cut increases, that is, it increases with the passage of time, but after that, it has the property of being saturated at a constant value. Therefore, for example, regarding the signal strength integrated value of the first signal strength SP1, if 2.0 × 10 ⁹ is set as the truing completion determination threshold value TF1, it is automatically performed in the necessary and sufficient truing progress state in the truing control. It shows that it is possible to judge the completion of truing.

(Test 3)
In order to shape the damaged region D, which is a rough portion where a part of the outer peripheral surface of the grinding wheel 14 has fallen off due to the grinding process, the present inventor uses the following truing condition 3 to form the plunge shown in FIG. (Pushing) was performed, and the integrated value of the signal strength of the first signal strength SP1 and the integrated value of the signal strength of the second signal strength SP2 were observed, respectively.

(Truing condition 3)
Grinding wheel specifications: CB 80 N 200 VN1
Outer diameter 409 mm x width 30 mm x inner diameter 127 mm
Coolant flow rate: 20 L / min
Truing tool specifications: SD 40 Q 75 MW7
Diameter 100 mm x Abrasive material layer thickness 1 mm
Growing tool peripheral speed: Vg = 45m / s, Vd = 13.5m / s (Vd / Vg = 0.3)
Truing tool lead: 0.10 mm / r. o. w.
Cutting amount of truing tool: R0.004mm / pass

FIG. 13 shows a damage region D formed on a part of the grinding surface of the grindstone portion 16 of the grinding wheel 14, and for removing the surface layer SL having a necessary and sufficient depth so that the damage region D disappears. , The growing by the plunge using the total dresser 82 shown in FIG. 12 is performed. As shown in FIG. 12, a total dresser that rotates around a rotation center line C2 parallel to the rotation center line C1 in a direction perpendicular to the rotation center line C1 of the grinding wheel 14 with respect to the grindstone portion 16 of the grinding wheel 14. When the surface of the grinding wheel 14 is damaged in the case of performing truing by the plunge while moving the 82, the AE signal SAE, which is the output signal of the AE sensor 22, is damaged before the damage is removed and as shown in FIG. After removal, it was difficult to distinguish them from each other, and it was difficult to determine the end of the rolling.

On the other hand, FIG. 15 shows changes in the integrated signal strength of the first signal strength SP1 and the integrated signal strength of the second signal strength SP2 in the truing by the plunge. As shown in FIG. 15, the signal strength integrated value of the first signal strength SP1 and the signal strength integrated value of the second signal strength SP2 increase with increasing the amount of cutting, that is, with the passage of time, but thereafter remain constant. It has the property of being saturated. Therefore, for example, regarding the signal strength integrated value of the first signal strength SP1, if 2.0 × 10 ⁹ is set as the truing completion determination threshold value TF2, it is automatically performed in the necessary and sufficient truing progress state in the truing control. It shows that it is possible to judge the completion of truing.

Returning to FIG. 1, the grinding apparatus 12 includes a spindle drive motor 62 for rotationally driving a spindle (not shown) to which a grinding wheel 14 is attached, and a work material rotary drive motor 64 for rotationally driving a columnar work material 44. The work material moving motor 66 that moves the work material 44 in the radial direction in order to press the grinding wheel 14 against the outer peripheral surface of the columnar work material 44, and the rotary dresser 46 used as a truing tool are rotationally driven. It includes a truing tool rotation drive motor 68, a truing tool feed motor 70 that feeds the rotary dresser 46 in the direction of the rotation center line C2, and a grinding control device 72.

The grinding control device 72 is composed of a microcomputer similar to the arithmetic control device 36, and functionally includes an automatic grinding control unit 74 and a growing control unit 76. Upon receiving the grinding start command signal, the automatic grinding control unit 74 grinds the work material 44 by moving the grinding wheel 14 and the work material 44 relative to each other while rotationally driving them in a preset operation to grind the work material 44. When the grinding of the material 44 is completed, the rotation of the work material 44 is stopped and the material 44 is returned to the original position.

The automatic grinding control unit 74 has an actual first signal strength SP1, a second signal strength SP2, or a signal strength ratio SR (= SP1) output from the grinding surface state output unit 51 in the process of grinding the work material 44. Based on / SP2), the spindle drive motor 62 and the work material rotation drive motor so that the grinding surface state indicated by the actual evaluation value for the work material 44 becomes the grinding surface state indicated by the preset target evaluation value. 64 and the work material moving motor 66 are automatically controlled.

For example, the automatic grinding control unit 74 sets the target signal intensity ratio SRT to a value with a good balance of grinding balance, for example, blinding and spillage, and the actual signal intensity sequentially output from the grinding surface state output unit 51 in real time. Grinding conditions are automatically adjusted so that the ratio SR matches the target signal intensity ratio SRT set in advance to, for example, about 0.55. Then, for example, when the actual signal intensity ratio SR exceeds the preset target signal intensity ratio SRT, the abrasive grains tend to be crushed. Therefore, in order to suppress the abrasive grain crushing, the processing efficiency (cutting speed) Of Change towards. On the contrary, when the actual signal intensity ratio SR is lower than the preset target signal intensity ratio SRT, the abrasive grains 38 tend to rub against the work material 44 or the rotary dresser 46, so that the rub is suppressed. Therefore, at least one of an increase in machining efficiency (cutting speed), a decrease in the peripheral speed Vg of the grinding wheel 14 (a decrease in the rotation speed), and an increase in the peripheral speed of the work material 44 is executed, and the actual operation is performed. The signal strength ratio SR is changed toward the target signal strength ratio SRT.

For example, when the target signal intensity ratio SRT is set to 0.55 as a value having a good grinding balance, the grinding automatic control unit 74 sets the actual signal intensity ratio SR to a preset target signal intensity ratio SRT (= 0. An example of automatic grinding control that adjusts the grinding conditions so as to match 55) is executed. In the automatic grinding control by the automatic grinding control unit 74, the actual first signal strength SP1 or the second signal strength SP2 is set to a value with a good grinding balance, and the target first signal strength SP1T or the target second signal strength SP2T is set. The grinding conditions may be adjusted so as to match.

When the arithmetic control device 36 reaches the truing start condition, the arithmetic control device 36 outputs a command to start the truing to the truing control unit 76. The tsuruing start condition is, for example, that the ratio of the first signal strength SP1 to the second signal strength SP2 (= SP1 / SP2) exceeds a predetermined value.

In the case of traversing, the truing control unit 76 uses a dresser 80 used as a truing tool with a depth of cut set in advance on the outer peripheral surface of the cylindrical grindstone portion 16 of the grinding wheel 14, as shown in FIG. It is cut and scanned along the rotation center line C1 of the grinding wheel 14, and this operation is repeatedly executed until the truing completion determination output from the truing completion determination unit 53 is received.

Further, in the case of truing by plunge, the truing control unit 76 presets a total dresser 82 used as a truing tool on the outer peripheral surface of the cylindrical grindstone portion 16 of the grinding wheel 14, as shown in FIG. The grinding wheel 14 is moved in a direction orthogonal to the rotation center line C1 at the cutting speed, and this operation is continuously executed until the grinding completion determination unit 53 receives the trueing completion determination.

In this embodiment, the trueing completion determination device 10 includes an AE sensor 22, an A / D converter 34, a frequency analysis unit 50, and a trueing completion determination unit 53. The AE sensor 22 detects the AE signal SAE generated during the truing of the grinding wheel 14. The A / D converter 34 converts the AE signal SAE output from the AE sensor 22 into a digital signal. The frequency analysis unit 50 frequency-analyzes the AE signal SAE converted into a digital signal by the A / D converter 34 to obtain a power spectrum. The truing completion determination unit 53 has a signal strength of at least one of the first signal strength SP1 of the first frequency band B1 and the second signal strength SP2 of the second frequency band B2 in the power spectrum obtained by the frequency analysis unit 50. The integrated value is sequentially calculated, and based on the saturation of the signal strength integrated value, it is determined that the grinding wheel 14 has been trued.

FIG. 16 is a flowchart illustrating a main part of the troughing control operation by traversing (scanning) using the dresser 80 of the arithmetic control device 36 and the truthing control unit 76, and is repeatedly executed at a predetermined control cycle. In FIG. 16, in step S1 (hereinafter, step is omitted), it is determined whether or not the truing completion determination threshold value TF1 has been set.

If the judgment of S1 is affirmed, S4 or less is executed, but if it is denied, the frequency analysis of the AE signal SAE measured at the time of preliminary normal truing performed in advance is performed in S2. From the power spectrum obtained as a result, at least one of the first signal strength SP1 in the first frequency band B1 and the second signal strength SP2 in the second frequency band B2 is sequentially calculated.

In the following S3, the value corresponding to the ratio immediately before reaching the saturation, for example, 90%, of the saturation value of at least one of the first signal strength SP1 and the second signal strength SP2 is the truing completion determination threshold value. It is predetermined as TF1.

Next, in S4 corresponding to the truing control unit 76, the truing control operation by traverse is started. Subsequently, S5, S6, S7, and S8 corresponding to the truing surface state output unit 52 are executed.

In S5, the AE signal SAE detected by the AE sensor 22 and converted into a digital signal by the A / D converter 34 is sequentially read as the truing progresses, and in S6, the AE signal SAE read by S5 is sequentially read. The frequency is analyzed, and in S7, at least one of the first signal strength SP1 of the first frequency band B1 and the second signal strength SP2 of the second frequency band B2, that is, the signal strength of the specific frequency band is sequentially calculated. ..

Then, in S8, the average signal strength of at least one of the first signal strength SP1 and the second signal strength SP2 for each scan of the dresser 80, that is, for each pass is calculated, and the average signal strength is calculated from the start of twiling. The signal strength integral value is calculated.

Next, in S9 corresponding to the truing completion determination unit 53, the truing completion determination in which the integrated signal intensity accumulated for each pass of at least one of the first signal strength SP1 and the second signal strength SP2 is determined in advance. It is determined whether or not the threshold value TF1 has been exceeded.

If the judgment of S9 is denied, S5 and below are repeatedly executed. However, if the determination in S9 is affirmed, the output of the truing completion determination is executed in S10, and at the same time, the truing operation by the truing control unit 76 is terminated in S11.

FIG. 17 is a flowchart illustrating a main part of the truing control operation by the plunge using the total dresser 82 of the arithmetic control device 36 and the truing control unit 76, and is repeatedly executed in a predetermined control cycle.

In FIG. 17, in step S21 (hereinafter, step is omitted), it is determined whether or not the truing completion determination threshold value TF2 has been set. If the judgment of S21 is affirmed, S24 or less is executed, but if it is denied, the AE signal SAE measured in advance at the time of preliminary normal truing in S22 is used for frequency analysis. The integrated value of at least one of the first signal strength SP1 of the first frequency band B1 and the second signal strength SP2 of the second frequency band B2 is sequentially calculated from the power spectrum obtained by the above.

In the following S23, the value corresponding to the ratio immediately before reaching the saturation, for example, 90%, of the saturation value of at least one of the first signal strength SP1 and the second signal strength SP2 is the truing completion determination threshold value. It is predetermined as TF2.

Next, in S24 corresponding to the truing control unit 76, the truing control operation by the plunge is started. Subsequently, in S25, S26, and S27 corresponding to the truing surface state output unit 52, as in S5, S6, and S7, the digital signal is detected by the AE sensor 22 and is detected by the A / D converter 34 as the truing progresses. The AE signal SAE converted to is sequentially read, and the read AE signal SAE is sequentially frequency-analyzed.

Next, in S28, a moving average value of at least one of the first signal strength SP1 and the second signal strength SP2 for each unit time set to, for example, 1 second or less is calculated, and the moving average value of the moving average value is calculated. The signal strength integrated value from the start of tsuruing is calculated.

Next, in S29 corresponding to the truing completion determination unit 53, the truing completion determination threshold value TF2 in which the signal intensity integral value of the moving average value of at least one of the first signal intensity SP1 and the second signal intensity SP2 is determined in advance is set. It is judged whether or not it has been exceeded.

If the judgment of S29 is denied, S25 and below are repeatedly executed. However, if the determination in S29 is affirmed, the output of the truing completion determination is executed in S30, and at the same time, the truing operation by the truing control unit 76 is automatically stopped in S31.

As described above, according to the truing completion determination device 10 of the present embodiment, the truing completion determination for determining the completion of the truing for shaping the ground surface of the grinding wheel (grinding grindstone) 14 using the truing tools 46, 80, 82 is determined. The device 10 includes an AE sensor 22 that detects an AE signal SAE generated during the truing of the grinding wheel 14, an A / D converter 34 that converts an AE signal SAE output from the AE sensor 22 into a digital signal, and the like. Of the frequency analysis unit 50 that obtains a power spectrum by frequency-analyzing the AE signal SAE converted into a digital signal by the A / D converter 34 and the frequency band of 100 kHz or less of the power spectrum obtained by the frequency analysis unit 50. The integrated signal strength of at least one of the first signal strength SP1 of the first frequency band B1 and the second signal strength SP2 of the second frequency band B2 having a frequency higher than that of the first frequency band B1 is sequentially calculated, and the signal strength is calculated. It includes a truing completion determination unit 53 that determines the completion of truing of the grinding wheel 14 based on the saturation of the integrated value. As a result, the depth of cut, the number of scans, and the total amount of depth of cut of the truing tools 46, 80, 82 are set to necessary and sufficient values for the completion of truing, so that the grinding surface of the grinding wheel 14 is wasted more than necessary. It is suppressed that the life of the grinding wheel 14 is not impaired by the trueing without being scraped.

Further, according to the truing completion determination device 10 of the present embodiment, the first signal strength SP1 of the first frequency band B1 and the second signal strength of the second frequency band B2 related to the crushing of the abrasive grains 38 of the grinding wheel 14 are obtained. A truing completion determination unit 53 for sequentially calculating at least one signal intensity integrated value of SP2 and determining the truing completion of the grinding wheel 14 based on the saturation of the signal intensity integrated value is provided. As a result, the depth of cut, the number of scans, and the total amount of depth of cut of the truing tools 46, 80, 82 are set to necessary and sufficient values for the completion of truing, so that the grinding surface of the grinding wheel 14 is wasted more than necessary. It is suppressed that the life of the grinding wheel 14 is not impaired by the trueing without being scraped.

Further, in the truing completion determination device 10 of the present embodiment, the first frequency band B1 is a frequency band including at least a part of the frequency band of 25 to 40 kHz, preferably a frequency band of 30 to 40 kHz, and the second frequency. Band B2 is a frequency band including at least a part of the frequency band of 45 to 65 kHz, preferably 45 to 65 kHz. As a result, the first signal strength SP1 of the first frequency band B1 derived from the crushing of the abrasive grains on the true surface of the grinding wheel 14 and / or the abrasive grains 38 on the true surface of the grinding wheel 14 and the true tool 46, 80, 82. By using the time component value of the second signal strength SP2 of the second frequency band B2 derived from the contact with the grinding wheel 14, it is possible to appropriately and accurately determine the completion of the truing of the grinding wheel 14.

Further, in the truing completion determination device 10 of this embodiment, the sampling period of the A / D converter 34 is 10 μs or less, preferably 5 μs or less, and more preferably 1 μs or less. By frequency-analyzing the A / D-converted AE signal SAE by the A / D converter 34 whose resolution has been enhanced in this way, it is derived from the abrasive grain crushing of the truing surface of the grinding wheel 14 in the frequency region of 100 kHz or less. The first signal strength SP1 of the first frequency band B1 and / or the second signal strength of the second frequency band B2 derived from the contact between the abrasive grains 38 on the truing surface of the grinding wheel 14 and the truing tools 46, 80, 82. SP2 can be obtained, and the trueing completion determination can be made based on the change in the signal strength integrated value of the first signal strength SP1 and / or the signal strength integrated value of the second signal strength SP2.

Although one embodiment of the present invention has been described above with reference to the drawings, the present invention is also applicable to other aspects.

For example, in the above-described embodiment, the first signal strength SP1 of the first frequency band B1 and the second signal strength SP2 of the second frequency band B2 are used from the power spectrum generated from the AE signal SAE by the frequency analysis unit 50. ing. 25 to 40 kHz was used as the first frequency band B1, and 45 to 65 kHz was used as the second frequency band B2. However, since it is sufficient to use a frequency band in the power spectrum that mainly represents abrasive grain crushing and a frequency band that mainly represents elastic vibration due to contact between the abrasive grains 38 and the truing tools 46, 80, 82, the first frequency band B1 The signal strength of the frequency band included in the frequency range of 25 to 40 kHz or a part of the frequency band is used, and the second frequency band B2 is the frequency included in the frequency range of 45 to 65 kHz or the frequency band including a part of the frequency band. The signal strength of the band may be used. For example, the first frequency band B1 is a relatively narrow frequency band including a part of the frequency band of 25 to 40 kHz, for example, 32.5 kHz in the center, and the second frequency band B2 is a frequency band of 45 to 65 kHz. A relatively narrow frequency band including a part of, for example, 55 kHz in the central portion may be used. Even in this way, it is possible to quantitatively evaluate the state of the true wing surface such as the tendency of abrasive grain fracture and / or the tendency of rubbing of the grinding wheel 14.

In the above-described embodiment, the AE sensor 22 is built in the grinding wheel 14, but when the work material 44 is ground by the grinding wheel 14 in a non-rotating state because it has a rectangular parallelepiped shape, for example, the work material It may be provided on a support base that supports 44.

Further, in the above-described embodiment, a grinding wheel 14 in which a grindstone portion 16 made of a vitrified grindstone is fixed to the outer peripheral surface of the main body 18 is used, but instead of the grinding wheel 14, a metal core, that is, the main body 18 is used. When a general grindstone that does not use the above is used, the whole may be composed of a vitrified grindstone or the like as long as the AE sensor 22 is built in. Further, when the whole is composed of a vitrified grindstone, the AE sensor 22, the preamplifier 24, and the transmission circuit 26 are provided in the spacer sandwiched between the flange for fixing the general grindstone to the spindle and the general grindstone. It may have been done.

It should be noted that the above description is merely an embodiment of the present invention, and various modifications can be made to the present invention without departing from the spirit of the present invention.

10: Truing completion judgment device 14: Grinding wheel (grinding grindstone)
22: AE sensor 34: A / D converter 46: rotary dresser (truing tool)
50: Frequency analysis unit 53: Truing completion determination unit 80: Dresser (Truing tool)
82: Total dresser (truing tool)
SAE: AE signal SP1: 1st signal strength SP2: 2nd signal strength

Claims (4)

It is a true wing completion judgment device that judges the completion of true wing that shapes the grinding surface of the grinding wheel using a true wing tool.
An AE sensor that detects an AE signal generated during the truing of the grinding wheel, and an AE sensor.
An A / D converter that converts an AE signal output from the AE sensor into a digital signal,
A frequency analysis unit that obtains a power spectrum by frequency-analyzing an AE signal converted into a digital signal by the A / D converter.
Of the frequency bands of 100 kHz or less of the power spectrum obtained by the frequency analysis unit, the first signal strength of the first frequency band and the second signal strength of the second frequency band higher than the first frequency band. A truing completion determination unit, which sequentially calculates at least one signal intensity integrated value and determines the completion of the truing of the grinding wheel based on the saturation of the signal intensity integrated value, is included. Judgment device. The first frequency band is a frequency band including at least a part of the frequency band of 25 to 40 kHz.
The truing completion determination device according to claim 1, wherein the second frequency band is a frequency band including at least a part of a frequency band of 45 to 65 kHz. The first frequency band is a frequency band of 25 to 40 kHz.
The truing completion determination device according to claim 1 or 2, wherein the second frequency band is a frequency band of 45 to 65 kHz. The truing completion determination device according to any one of claims 1 to 3, wherein the sampling period of the A / D converter is 10 μsec or less.

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