JP7413110B2 - Truing completion determination device - Google Patents

Description

The present invention relates to a truing completion determination device for determining the completion of truing for reshaping the grinding surface of a grinding wheel, and a truing device equipped with the truing completion determination device.

In a grinding machine that processes a workpiece using a grinding wheel, in order to continuously maintain the accuracy of the grinding process, for example, by performing truing using a tool such as a diamond dresser as a truing tool, the grinding wheel It is known that the shape of the grinding surface of the grinding surface is periodically reshaped. For example, the grinding device described in Patent Document 1 is one such example. In such a grinding device, the entire grinding surface of the grinding wheel is shaped into a perfect circle by periodic truing, so that grinding accuracy is maintained in subsequent grinding operations.

Among the above truings, in truing in which the truing tool is scanned (traversed) 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 that performs truing, and The number of scans for relatively moving the truing tool is set in advance, and the truing tool for performing truing with the preset depth of cut is scanned for the preset number of scans, thereby completing the truing. Furthermore, among the above truings, when truing is performed by plunging the truing tool to cut in a direction perpendicular to the rotation center line of the grinding wheel, the cutting speed of the truing tool with respect to the grinding wheel that performs truing is set in advance, and the cutting speed depends on the cutting speed. When the depth of cut reaches a preset total depth of cut, truing is completed.

Japanese Patent Application Publication No. 2018-167331 Japanese Patent Application Publication No. 2000-233369

Incidentally, the depth of cut, the number of scans, and the total depth of cut of the truing tool are set in advance with a margin in consideration of various variations so that sufficient truing can be performed. As a result, the grinding surface of the grinding wheel is ground more than necessary, resulting in a problem that the life of the grinding wheel is shortened.

On the other hand, Patent Document 2 discloses a method for detecting an AE signal (acoustic emission signal: a vibration wave in the ultrasonic range with a frequency of, for example, 100 kHz or more) representing crushing vibrations generated in connection with crushing of abrasive grains. A device has been proposed that uses the AE signal to monitor the dressing state of a grinding wheel. In this dressing condition monitoring device, with respect to a vitrified grinding wheel, the grinding wheel side AE signal output from the grinding wheel side AE sensor detects interface peeling between the abrasive grains and inorganic binder (100 kHz to 2 MHz), cracks in the abrasive grain itself ( 100kHz to 2MHz), cracks in the inorganic bonding material itself (100kHz to 2MHz), and the workpiece side AE signal output from the workpiece side AE sensor indicates plastic deformation of the workpiece (100kHz to 800kHz), It is said to represent the brittle fracture (200kHz to 700kHz) of the cutting material, and the original AE signal obtained by frequency analysis from the grinding wheel side AE signal and the workpiece side AE signal is input into the neural network. For example, the dressing state of a grinding wheel is determined.

However, when the conventional dressing condition monitoring device is applied to the truing of a grinding wheel, the crushing of the abrasive grain itself and the crushing of the inorganic binder itself occur at the same frequency component (100 kHz to 2 MHz) in the AE signal on the grinding wheel side. Therefore, it is not possible to accurately detect the fracture of the abrasive grains themselves and the fracture of the inorganic binder itself, and it is difficult to accurately determine the truing state of the grinding surface of the grinding wheel and the completion of truing. I couldn't do that.

The present invention has been made against the background of the above circumstances, and its purpose is to provide a truing completion determination device that enables truing without impairing the life of a grinding wheel as much as possible.

As a result of various studies against the background of the above circumstances, the present inventors have determined that the AE signal output from the AE sensor during truing can be converted into an A/R with a sampling period of approximately 10 μsec or less, which is faster and has higher resolution than conventional methods. After digitization using a D converter, frequency analysis (FFT) reveals that in a frequency band lower than 100kHz in the power spectrum, a group of relatively low peak signals in the first frequency band and a group of peak signals in the first frequency band are detected. A group of peak signals in the second frequency band, which is relatively higher in frequency than the above, 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 due to frictional vibrations caused by contact (rubbing) between the abrasive grains and the dresser. It was discovered that the vibrations originate from elastic vibrations. Furthermore, it has been found that the signal strength integral value of the peak signal group in the first frequency band or the peak signal group in the second frequency band exhibits a phenomenon in which the increase saturates in synchronization with the completion of truing.

That is, the gist of the first invention is (a) a grinding wheel truing completion determination device that determines the completion of truing for shaping the grinding surface of a grinding wheel using a truing tool, and (b) a an AE sensor that detects an AE signal generated during truing of a grindstone; (c) an A/D converter that converts the AE signal output from the AE sensor into a digital signal; and (d) the A/D converter. (e) a frequency analysis section that frequency-analyzes the AE signal converted into a digital signal to obtain a power spectrum; A signal strength integral value of at least one of a first signal strength and a second signal strength of a second frequency band having a higher frequency than the first frequency band is sequentially calculated, and based on the fact that the signal strength integral value is saturated; , and a truing completion determination section for determining completion of truing of the grinding wheel.

According to the truing completion determination device of the first invention, the signal strength integral value of at least one of the first signal strength in the first frequency band and the second signal strength in the second frequency band having a higher frequency than the first frequency band. A truing completion determination unit is provided that sequentially calculates the signal strength integral value and determines completion of truing of the grinding wheel based on saturation of the signal strength integral value. As a result, the depth of cut, number of scans, and total depth of cut of the truing tool are set to necessary and sufficient values to complete truing, so that the grinding surface of the grinding wheel is not ground more than necessary. This prevents the life of the grinding wheel from being impaired by truing.

Here, preferably, the first frequency band is a frequency band that includes at least a part of a frequency band of 25 to 40 kHz, and the second frequency band includes at least a part of a frequency band of 45 to 65 kHz. The reason is that it is a frequency band. As a result, a first signal intensity in a first frequency band originating from the abrasive grain crushing on the truing surface of the grinding wheel, and a second signal strength originating from the contact (rubbing) between the abrasive grains on the truing surface of the grinding wheel and the truing tool. By using at least one of the second signal strengths in the frequency band, the truing of the grinding wheel can be appropriately and accurately completed.

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. Thereby, a first signal intensity in a first frequency band originating from the abrasive grain crushing on the truing surface of the grinding wheel, and a second frequency band originating from the contact between the abrasive grains on the truing surface of the grinding wheel and the truing tool. Using at least one of the second signal strengths, it is possible to appropriately and accurately determine whether truing of the grinding wheel has been completed.

Further, preferably, the sampling period of the A/D converter is 10 μsec or less, preferably 5 μsec or less, and more preferably 1 μsec or less. By frequency-analyzing the A/D-converted AE signal using the A/D converter with increased resolution, we can detect the first frequency originating from the abrasive fragmentation on the truing surface of the grinding wheel in the region of 100 kHz or less. At least one of the first signal intensity of the band and the second signal intensity of the second frequency band derived from the contact between the abrasive grains of the grinding wheel and the truing tool is obtained, and a signal intensity integral value of the first signal intensity and It is possible to determine the completion of truing based on a change in at least one of the signal strength integral values of the second signal strength.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating the configuration of a grinding device including a truing completion determination device according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a generation mechanism of an AE signal obtained from a vitrified grindstone in a state of a grinding surface by the grinding apparatus of FIG. 1. FIG. FIG. 2 is a diagram showing a display example in which a signal strength ratio SR (=SP1/SP2) indicating a ground surface state is displayed on the surface state display device of FIG. 1; 2 is a diagram showing a display example in which the signal strength integral value of the first signal strength SP1 and the signal strength integral value of the second signal strength SP2, which increase as truing progresses, are displayed on the surface state display device of FIG. 1. FIG. FIG. 2 is a diagram showing a power spectrum obtained in a truing test in which the circumferential velocity ratio Vd/Vg is 1.0 and down cut, among three types of truing tests with different circumferential velocity ratios conducted by the present inventor. . FIG. 2 is a diagram showing a power spectrum obtained in a truing test in which the circumferential velocity ratio Vd/Vg is 0.3 and down-cut among three types of truing tests with different circumferential velocity ratios conducted by the present inventor. . FIG. 2 is a diagram showing the power spectrum obtained in the truing test when the circumferential velocity ratio Vd/Vg is 1.0 and up-cut among three types of truing tests with different circumferential velocity ratios conducted by the present inventor. . A predetermined judgment threshold is set for each peak waveform of the three types of power spectra shown in FIGS. 5, 6, and 7 to judge the occurrence of each peak waveform, and among the generated peak waveforms, the peak waveform that exceeds the judgment threshold FIG. 3 is a diagram showing an occurrence map in which it is determined that the occurrence has occurred. FIG. 6 is a diagram illustrating truing performed by moving the dresser in a direction parallel to the rotational center line of the grinding wheel with respect to the grinding wheel portion of the grinding wheel that has a certain deflection with respect to the center of the grinding wheel axis during installation. 10 is a diagram showing the output signal output from the AE sensor in the truing of FIG. 9, in which (a) shows the output signal when the runout of the grinding wheel is not removed, and (b) shows the output signal after the runout of the grinding wheel is removed. shows the output signal of In the truing shown in FIG. 9, the signal strength integral value of the first signal strength SP1 and the signal strength integral value of the second signal strength SP2 increase as the truing depth of cut increases, but when a predetermined depth of cut is reached. It is a figure which shows the property which saturates to a constant value after that. FIG. 3 is a diagram illustrating plunge truing using a full-length dresser for a grindstone portion of a grinding wheel. FIG. 13 is a diagram illustrating a damaged area D formed on a part of the grinding surface of the grindstone portion of the grinding wheel. 13 is a diagram showing an output signal output from an AE sensor during plunge truing in FIG. 12. FIG. In the plunge truing shown in FIG. 12, the signal strength integral value of the first signal strength SP1 and the signal strength integral value of the second signal strength SP2 increase as the depth of cut of truing increases, but reach a predetermined depth of cut. FIG. 3 is a diagram showing the property of saturating to a constant value after reaching a certain value. 2 is a flowchart illustrating a main part of a truing control operation by traverse of the arithmetic and control unit and truing control unit of FIG. 1. FIG. 2 is a flowchart illustrating a main part of a plunge-based truing control operation of the arithmetic and control unit and truing control unit of FIG. 1. FIG.

Hereinafter, embodiments 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 12 that also functions as a truing device and includes a truing completion determination device 10 that also functions as a grinding surface evaluation device according to an embodiment of the present invention. In FIG. 1, the grinding device 12 includes vitrified abrasives, including 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. Grinding wheels such as whetstones, resinoid whetstones, metal bond whetstones, and electroplated whetstones 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 grindstone portion 16 fixed to the outer peripheral surface of a cylindrical or drum-shaped metal core, that is, a main body 18, and is attached to a rotating shaft rotationally driven by a main shaft drive motor 62. The grinding wheel 14 is driven at a relatively high circumferential speed of, for example, about 80 m/sec or more, and grinds the surface of a columnar workpiece 44, for example. Truing is performed on this grinding wheel 14 using a rotary dresser 46 shown in FIG. 1 as a truing tool.

The truing completion determination device 10 includes an AE sensor 22, a preamplifier 24, a transmitting circuit 26 that transmits the AE signal SAE amplified by the preamplifier 24 using a predetermined carrier wave, and an AE signal SAE transmitted from the transmitting 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 and control device 36. 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 38 contained in the grinding wheel 16 are crushed and propagated within the grinding wheel 16 . 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 has a predetermined frequency band that allows the carrier wave received by the receiving circuit 30 to pass therethrough. The A/D converter 34 converts the AE signal SAE demodulated from the carrier wave into a digital signal. The arithmetic and control unit 36 processes the AE signal SAE converted into a digital signal.

The AE sensor 22, preamplifier 24, and transmission circuit 26 described above are provided within the main body 18 of the grinding wheel 14. The A/D converter 34 has a high resolution and converts the AE signal with a sampling period of, for example, 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. Convert SAE to digital signal. The shorter the sampling period of the A/D converter 34 (the higher the speed), the more the first frequency band B1 related to crushing the abrasive grains of the grinding wheel 14 and the contact between the abrasive grains 38 of the grinding wheel 14 and the rotary dresser 46. The second frequency band B2 related to the origin becomes clear. Note that in this embodiment, 1 μsec is used as the sampling period of the A/D converter 34.

The grinding wheel portion 16 of the grinding wheel 14 is, for example, a well-known vitrified grinding wheel, as shown in FIG. Vibration in the first frequency band B1 resulting from the occurrence of cracks Ca or fractures in the abrasive grains 38 itself due to sliding contact with the cut material (work) 44 or the rotary dresser 46, the abrasive grains 38 and Vibrations in the second frequency band B2 are generated due to frictional vibrations or elastic vibrations generated by contact with the workpiece 44 or the rotary dresser 46, that is, friction Cb, and grinding vibrations including these vibrations, that is, AE waves, are detected by the AE sensor. 22.

The arithmetic and control unit 36 in FIG. 1 is a so-called microcomputer including a CPU, ROM, RAM, interface, etc., and the CPU processes input signals according to a program stored in the ROM in advance while utilizing the temporary storage function of the RAM. By doing so, numerical values, graphs, figures, etc. representing the condition of the ground surface for determining the condition of the truing surface are calculated and outputted from the surface condition display device 48 which also functions as a surface condition display device, and the grinding control device Send to 72.

The arithmetic and control device 36 of the truing completion determination device 10 functionally includes a frequency analysis section 50, a grinding surface state output section 51, and a truing surface state output section 52. The frequency analysis unit 50 performs frequency analysis (FFT) of the AE signal SAE input from the A/D converter 34 during grinding of the workpiece 44 or truing of the grinding wheel 14 to indicate the signal power. In a two-dimensional coordinate system with a vertical axis and a horizontal axis representing frequency, a power spectrum is generated that shows various signal powers representing the magnitude of frequency components as peak waveforms on the frequency axis (horizontal axis) for each frequency.

During the grinding process of the workpiece 44, the grinding surface state output unit 51 outputs a preset first frequency band B1 containing, for example, 32.5 kHz at the center, for example, a first frequency from 25 to 40 kHz, from the power spectrum. a first signal strength SP1 for band B1; and a second signal strength SP2 for a preset second frequency band B2 centered around, for example, 55 kHz, for example from 45 to 65 kHz; The ratio SR (=SP1/SP2) is calculated and output to the surface state display device 48. FIG. 3 shows a display example of the signal strength ratio SR representing the condition of the ground surface of the workpiece 44 when the surface condition display device 48 is a liquid crystal screen or a level meter displayed on a meter.

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

Furthermore, during truing of the grinding wheel 14 using the rotary dresser 46 as a truing tool, the truing completion determination unit 53 determines the signal strength integral value of the first signal strength SP1 from the truing surface state output unit 52 and/or the signal strength integral value of the first signal strength SP1 from the truing surface state output unit 52. Based on the property that the signal strength integral value of the second signal strength SP2 is saturated when approaching the completion of truing, 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. The completion of truing is determined 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 TF1 is a value corresponding to, for example, about 90% of the saturation value of the signal strength integral value of the first signal strength SP1, or the saturation value of the signal strength integral value of the second signal strength SP2 of the second frequency band B2. It is set in advance 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, which is converted from the AE wave detected by the AE sensor 22 into a digital signal using the high-speed, high-resolution A/D converter 34, the first frequency band is Tests conducted by the inventor on a given grinding wheel regarding the generation of peak waveform signals within B1 and peak waveform signals within 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, which are composed of a group of peak waveform signals, in the power spectrum obtained during truing of the grinding wheel 14 using a vitrified grindstone. .

(Test 1)
5, 6, and 7 show the circumferential speed ratio Vd/Vg and the rotation direction of the rotary dresser 46 (down cut is rotation in the opposite direction to the rotation direction of the grinding wheel 14) under the following truing condition 1. A truing test was conducted on the grinding wheel 14 using three types of vitrified grindstones with different rotations (up cut in the same direction as the rotation direction of the grinding wheel 14) (down cut with Vd/Vg=1.0, down cut with Vd/Vg=0. FIG. 3 is a diagram showing power spectra obtained by a down cut of Vd/Vg=1.0 and an up cut of Vd/Vg=1.0. In addition, in FIG. 8, a predetermined judgment threshold is provided for each peak waveform of the three types of power spectra to judge the occurrence of each peak waveform, and among the generated peak waveforms, those exceeding the judgment threshold are generated. It is a figure which shows the occurrence map which was determined to be.

(Trueing condition 1)
Grinding wheel: Grinding wheel with built-in AE sensor Grinding wheel part: CB 80 N 200 V
(CBN abrasive grains with a particle size of 80 are bonded by a vitrified bonding material, and have a bonding degree N and a concentration degree of 200)
Grinding machine: General-purpose cylindrical grinding machine Grinding wheel circumferential speed Vg: 45 m/sec (clockwise)
Truing tool: Diamond rotary dresser Rotary dresser circumferential speed/Vd: 45 m/sec (counterclockwise down cut)
Circumferential speed ratio Vd/Vg=1.0
・Vd: 13.5m/sec (counterclockwise down cut)
Circumferential speed ratio Vd/Vg=0.3
・Vd: 45m/sec (clockwise up cut)
Circumferential speed ratio Vd/Vg=1.0

FIG. 5 shows the power spectrum obtained under the truing condition with a down cut of Vd/Vg=1.0 of the above truing condition 1. As shown in FIG. 1, the truing conditions in FIG. 5 are such that the circumferential speed Vg of the clockwise grinding wheel 14 and the circumferential speed Vd of the counterclockwise rotary dresser 46 match in opposite rotation directions, This is a truing condition in which the relative circumferential speed of the grinding wheel 14 and the rotary dresser 46 at the contact point becomes zero, and the crushing of the abrasive grains 38 and the inorganic binder 40 of the grinding wheel 14 becomes significant. In the power spectrum of FIG. 5, a plurality of peak waveforms occur intensively in the first frequency band B1 from 25 to 40 kHz and the second frequency band B2 from 45 to 65 kHz, excluding low-frequency noise such as mechanical vibration. A phenomenon was observed in which the peak waveform height (signal strength) in the first frequency band B1 was greater than the peak waveform height (signal strength) in the second frequency band B2.

FIG. 6 shows the truing condition under the down cut of Vd/Vg=0.3 of the above-mentioned truing condition 1, that is, the circumferential speed Vg of the grinding wheel 14 is in the opposite rotation direction to the circumferential speed Vd of the rotary dresser 46. The graph shows a power spectrum obtained under truing conditions where the abrasive grains 38 of the grinding wheel 14 are less likely to be significantly broken and the number of abrasive grains 38 in contact with the grinding wheel 14 is significantly increased. In this power spectrum as well, a plurality of peak waveforms occur intensively in the first frequency band B1 from 25 to 40 kHz and the second frequency band B2 from 45 to 65 kHz, excluding low-frequency noise such as mechanical vibration. A phenomenon was observed in which the peak waveform height (signal strength) in the second frequency band B2 was greater than the peak waveform height (signal strength) in the first frequency band B1.

FIG. 7 shows the truing condition under the up-cut condition of Vd/Vg=1.0 of the above-mentioned truing condition 1, that is, the circumferential speed Vg of the grinding wheel 14 is the same as the circumferential speed Vd of the rotary dresser 46, but the condition shown in FIG. The graph shows a power spectrum obtained under truing conditions in which the abrasive grains 38 of the grinding wheel 14 are less likely to be broken into large pieces and the number of abrasive grains 38 in contact with the grinding wheel 14 is significantly increased in the opposite rotation direction. In this power spectrum as well, a plurality of peak waveforms occur intensively in the first frequency band B1 from 25 to 40 kHz and the second frequency band B2 from 45 to 65 kHz, excluding low-frequency noise such as mechanical vibration. A phenomenon was observed in which the peak waveform height (signal strength) in the second frequency band B2 was greater than the peak waveform height (signal strength) in the first frequency band B1.

FIG. 8 shows a predetermined judgment for determining the occurrence of each peak value for each peak value of the three types of power spectra with different circumferential speed ratios Vd/Vg shown in FIGS. 5, 6, and 7, respectively. FIG. 4 is a diagram illustrating a peak waveform generation map in which a threshold value is provided and peak values that exceed the determination threshold value are determined to have occurred and are shown in black areas.

According to FIG. 8, the peak value exceeding the determination threshold value occurs mainly in the first frequency band B1 from 25 to 40 kHz in the down-cut when the circumferential velocity ratio Vd/Vg is 1.0, and The down-cut where Vd/Vg is 0.3 and the up-cut where the peripheral speed ratio Vd/Vg is 1.0 occur in the second frequency band B2 from 45 to 65 kHz. As a result, in the power spectrum obtained by frequency analysis of the AE signal SAE, the height (signal intensity) of the peak waveform of at least some frequencies in the first frequency band B1 is determined by the crushing of the abrasive grains 38 on the grinding wheel surface of the grinding wheel 14. The height (signal intensity) of the peak waveform of at least part of the frequencies in the second frequency band B2 reflects the friction vibration generated by the contact between the abrasive grains 38 on the grindstone surface of the grinding wheel 14 and the rotary dresser 46. 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 caused by contact between the abrasive grains 38 and the rotary dresser 46.

(Test 2)
The present inventor used the following truing condition 2, as shown in FIG. Trueing by traverse was performed, and the signal strength integral value of the first signal strength SP1 in the first frequency band B1 and the signal strength integral value of the second signal strength SP2 in the second frequency band B2 were observed.

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

In FIG. 9, a single-stone or blade-type dresser 80 as a truing tool is reciprocated in a direction parallel to the rotation center line C1 of the grinding wheel 14, and the grinding wheel portion 16 of the grinding wheel 14 is cut at each scan. The truing was repeated by increasing the amount of inclusion. Note that the 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, has the time axis waveform shown in FIG. 10(a), and even after the runout of the grinding wheel 14 is removed, the time axis waveform shown in FIG. Met. For this reason, conventionally, the time-domain waveform in FIG. 10(b) was difficult to distinguish from the time-domain waveform in FIG. 10(a), making it difficult to determine the end of truing.

On the other hand, FIG. 11 shows changes in the signal strength integral value of the first signal strength SP1 and changes in the signal strength integral value of the second signal strength SP2 in the truing by traversing. As shown in FIG. 11, the signal strength integral value of the first signal strength SP1 and the signal strength integral value of the second signal strength SP2 are 80 to 100 μm, which is the amount of runout measured in advance with a dial gauge for the runout of the grinding wheel 14. Until reaching region R, the truing depth of cut increases, that is, increases as time passes, but after that, it tends to be saturated at a constant value. For this reason, for example, regarding the signal strength integral value of the first signal strength SP1, if 2.0× ¹⁰⁹ is set as the truing completion determination threshold TF1, the truing control can be automatically performed in a necessary and sufficient truing progress state. This shows that it is possible to determine whether truing is complete.

(Test 3)
The present inventor used the following truing condition 3 to shape the damaged area D, which is a roughened area caused by part of the outer circumferential surface of the grinding wheel 14 falling off due to the grinding process, using the plunger shown in FIG. 12 ( Trueing was carried out using a truing (push-in), and the signal strength integral value of the first signal strength SP1 and the signal strength integral value of the second signal strength SP2 were observed, respectively.

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

FIG. 13 shows a damaged area D formed on a part of the grinding surface of the grinding wheel 16 of the grinding wheel 14, and it is necessary to remove the surface layer SL to a necessary and sufficient depth to eliminate the damaged area D. , truing is performed by plunging using a full-length dresser 82 as shown in FIG. As shown in FIG. 12, the complete dresser rotates 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, around a rotation center line C2 parallel to the rotation center line C1. When performing truing by plunge while moving the grinding wheel 82, if the surface of the grinding wheel 14 is damaged, the AE signal SAE, which is the output signal of the AE sensor 22, is different from before the damage is removed and after the damage is removed, as shown in FIG. After removal, it was difficult to distinguish them from each other, making it difficult to determine the end of truing.

On the other hand, FIG. 15 shows changes in the signal strength integral value of the first signal strength SP1 and the signal strength integral value of the second signal strength SP2 in the truing by the plunge. As shown in FIG. 15, the signal strength integral value of the first signal strength SP1 and the signal strength integral value of the second signal strength SP2 increase as the truing depth increases, that is, as time passes, but after that, they remain constant. It has the property of becoming saturated. Therefore, for example, regarding the signal strength integral value of the first signal strength SP1, if 2.0× ¹⁰⁹ is set as the truing completion determination threshold TF2, the truing control will automatically This shows that it is possible to determine whether truing is complete.

Returning to FIG. 1, the grinding device 12 includes a main shaft drive motor 62 that rotationally drives a main shaft (not shown) to which a grinding wheel 14 is attached, and a workpiece rotation drive motor 64 that rotationally drives a cylindrical workpiece 44. A work material movement 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 cylindrical work material 44, and a 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 its 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 section 74 and a truing control section 76. Upon receiving the grinding start command signal, the automatic grinding control unit 74 rotates and moves the grinding wheel 14 and the workpiece 44 relative to each other in a preset operation, thereby grinding the workpiece 44. When the grinding of the work material 44 is completed, the rotation of the work material 44 is stopped and returned to the original position.

In the process of grinding the workpiece 44, the automatic grinding control unit 74 calculates the actual first signal strength SP1, second signal strength SP2, or signal strength ratio SR (=SP1) output from the ground surface state output unit 51. /SP2), the main shaft drive motor 62 and the workpiece rotation drive motor are operated so that the ground surface state indicated by the actual evaluation value for the workpiece 44 becomes the ground surface state indicated by the preset target evaluation value. 64 and the workpiece movement motor 66 are automatically controlled.

For example, the automatic grinding control unit 74 sets the target signal strength ratio SRT to a value that is well-balanced for grinding, such as a good balance between blind spots and missed spots, and the actual signal strength that is sequentially output from the grinding surface state output unit 51 in real time. The grinding conditions are automatically adjusted so that the ratio SR matches the target signal strength ratio SRT, which is set in advance to about 0.55, for example. For example, if the actual signal strength ratio SR exceeds the preset target signal strength ratio SRT, there is a tendency for the abrasive grains to break. , increase the circumferential speed Vg of the grinding wheel 14 (increase the rotational speed), and decrease the circumferential speed of the workpiece 44, and convert the actual signal strength ratio SR to the target signal strength ratio SRT. change towards. On the other hand, if the actual signal strength ratio SR is lower than the preset target signal strength ratio SRT, this indicates a tendency for the abrasive grains 38 to rub against the workpiece 44 or the rotary dresser 46, and this rubbing is suppressed. In order to achieve this, at least one of increasing the machining efficiency (cutting speed), decreasing the circumferential speed Vg of the grinding wheel 14 (decreasing the rotational speed), and increasing the circumferential speed of the workpiece 44 is carried out, and the actual The signal strength ratio SR is changed toward the target signal strength ratio SRT.

For example, when the target signal strength ratio SRT is set to 0.55 as a value with good grinding balance, the automatic grinding control unit 74 sets the actual signal strength ratio SR to a preset target signal strength ratio SRT (=0. Execute an example of automatic grinding control in which the grinding conditions are adjusted to match 55). Note that the automatic grinding control by the automatic grinding control unit 74 changes the actual first signal strength SP1 or second signal strength SP2 to a target first signal strength SP1T or target second signal strength SP2T set to a value with good grinding balance. The grinding conditions may be adjusted so that they match.

When the truing start condition is reached, the arithmetic and control unit 36 outputs a command to the truing control unit 76 to start truing. This truing 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 truing by traverse, the truing control unit 76 applies a dresser 80 used as a truing tool to the outer peripheral surface of the cylindrical grindstone portion 16 of the grinding wheel 14 at a preset depth of cut, as shown in FIG. The grinding wheel 14 is made to cut and scan along the rotation center line C1 of the grinding wheel 14, and this operation is repeatedly performed until a truing completion judgment output is received from the truing completion judgment section 53.

In addition, in the case of truing by plunge, the truing control unit 76 controls a full-form dresser 82 used as a truing tool, which is set in advance 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 at a cutting speed in a direction perpendicular to the rotation center line C1, and this operation is continued until the truing completion determination is received from the truing completion determination section 53.

In this embodiment, the truing completion determination device 10 includes an AE sensor 22, an A/D converter 34, a frequency analysis section 50, and a truing completion determination section 53. AE sensor 22 detects an AE signal SAE generated during truing of 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 section 50 performs frequency analysis on the AE signal SAE converted into a digital signal by the A/D converter 34 to obtain a power spectrum. The truing completion determination section 53 determines the 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 among the power spectra obtained by the frequency analysis section 50. The integral value is calculated one after another, and the completion of truing of the grinding wheel 14 is determined based on the signal strength integral value being saturated.

FIG. 16 is a flowchart illustrating a main part of the truing control operation by the arithmetic and control unit 36 and the truing control unit 76 by traversing (scanning) using the dresser 80, and is repeatedly executed at a predetermined control cycle. In FIG. 16, in step S1 (step will be omitted hereinafter), it is determined whether a truing completion determination threshold TF1 has been set.

If the judgment in S1 is affirmative, steps S4 and subsequent steps are executed, but if the judgment is negative, in S2, the frequency of the AE signal SAE measured during preliminary normal truing performed in advance is analyzed. The signal strength integral 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 this.

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

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

In S5, as truing progresses, 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, and in S6, the AE signal SAE read in 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 of the average signal strength from the start of truing is calculated. A signal strength integral value is calculated.

Next, in S9 corresponding to the truing completion determination section 53, a truing completion determination is performed based on a predetermined signal strength integral value accumulated for each pass of at least one of the first signal strength SP1 and the second signal strength SP2. It is determined whether the threshold value TF1 has been exceeded.

If the determination in S9 is negative, steps S5 and subsequent steps are repeatedly executed. However, if the determination in S9 is affirmative, the truing completion determination is outputted 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 plunge-based truing control operation of the arithmetic and control unit 36 and the truing control unit 76 using the full-type dresser 82, and is repeatedly executed at a predetermined control cycle.

In FIG. 17, in step S21 (hereinafter, the step is omitted), it is determined whether the truing completion determination threshold TF2 has been set. If the judgment in S21 is affirmative, the steps from S24 onwards are executed, but if the judgment is negative, in S22, the AE signal SAE measured during the preliminary normal truing performed in advance is analyzed by frequency analysis. The signal strength integral 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 this.

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

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

Next, in S28, a moving average value of the signal strength 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 is calculated. A signal strength integral value from the start of truing is calculated.

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

If the determination at S29 is negative, S25 and subsequent steps are repeatedly executed. However, if the determination in S29 is affirmative, the truing completion determination is outputted 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 is performed to determine the completion of truing for shaping the grinding surface of the grinding wheel (grinding stone) 14 using the truing tools 46, 80, and 82. The device 10 includes an AE sensor 22 that detects an AE signal SAE generated during truing of the grinding wheel 14, and an A/D converter 34 that converts the AE signal SAE output from the AE sensor 22 into a digital signal. A frequency analysis section 50 obtains a power spectrum by frequency-analyzing the AE signal SAE converted into a digital signal by the A/D converter 34, and a frequency band of 100 kHz or less of the power spectrum obtained by the frequency analysis section 50, A signal strength integral value of at least one of a first signal strength SP1 of a first frequency band B1 and a second signal strength SP2 of a second frequency band B2 having a higher frequency than the first frequency band B1 is calculated sequentially, and the signal strength and a truing completion determination section 53 that determines completion of truing of the grinding wheel 14 based on saturation of the integral value. As a result, the depth of cut, number of scans, and total depth of cut of the truing tools 46, 80, and 82 are set to necessary and sufficient values to complete truing, so that the grinding surface of the grinding wheel 14 is not wasted more than necessary. Therefore, the life of the grinding wheel 14 is prevented from being damaged by truing.

Further, according to the truing completion determination device 10 of the present embodiment, the first signal strength SP1 in the first frequency band B1 and the second signal strength in the second frequency band B2 related to the crushing of the abrasive grains 38 of the grinding wheel 14 A truing completion determination section 53 is provided that sequentially calculates the signal strength integral value of at least one of SP2 and determines the completion of truing of the grinding wheel 14 based on the saturation of the signal strength integral value. As a result, the depth of cut, number of scans, and total depth of cut of the truing tools 46, 80, and 82 are set to necessary and sufficient values to complete truing, so that the grinding surface of the grinding wheel 14 is not wasted more than necessary. Therefore, the life of the grinding wheel 14 is prevented from being damaged by truing.

In addition, 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 from 25 to 40 kHz, preferably a frequency band from 30 to 40 kHz, and the second frequency band B1 is a frequency band including at least a part of the frequency band from 25 to 40 kHz. Band B2 is a frequency band that includes at least part of the frequency band from 45 to 65 kHz, preferably from 45 to 65 kHz. Thereby, the first signal intensity SP1 of the first frequency band B1 derived from the abrasive grain crushing on the truing surface of the grinding wheel 14 and/or the abrasive grains 38 on the truing surface of the grinding wheel 14 and the truing tools 46, 80, 82 Using the time component value of the second signal strength SP2 in the second frequency band B2 derived from the contact with the grinding wheel 14, it is possible to appropriately and accurately determine whether truing of the grinding wheel 14 is complete.

Furthermore, in the truing completion determination device 10 of this embodiment, the sampling period of the A/D converter 34 is 10 μsec or less, preferably 5 μsec or less, and more preferably 1 μsec or less. By frequency-analyzing the AE signal SAE A/D-converted by the A/D converter 34 with increased resolution in this way, it is possible to detect the origin of abrasive grain fragmentation on the truing surface of the grinding wheel 14 in the frequency range of 100 kHz or less. a first signal strength SP1 in a first frequency band B1 and/or a second signal strength in a second frequency band B2 resulting from contact between the abrasive grains 38 on the truing surface of the grinding wheel 14 and the truing tools 46, 80, 82; SP2 is obtained, and truing completion can be determined based on changes in the signal strength integral value of the first signal strength SP1 and/or the signal strength integral 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 can also be applied to other aspects.

For example, in the above 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 caused by contact between the abrasive grains 38 and the truing tools 46, 80, 82, the first frequency band B1 As the second frequency band B2, the signal strength of a frequency band that includes a frequency included in 25 to 40 kHz or a part of the frequency band is used, and as the second frequency band B2, a frequency that includes a frequency included in 45 to 65 kHz or a part of the frequency band is used. The signal strength of the band may be used. For example, the first frequency band B1 is a relatively narrow frequency band that includes a part of the frequency band from 25 to 40 kHz, for example, 32.5 kHz at the center, and the second frequency band B2 is a frequency band from 45 to 65 kHz. A relatively narrow frequency band centered around a portion of, for example 55 kHz, may be used. Even in this manner, it is possible to quantitatively evaluate the state of the truing surface, such as the tendency of abrasive grain breakage and/or the tendency of rubbing of the grinding wheel 14.

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

Further, in the above-mentioned embodiment, the grinding wheel 14 of the type in which the grindstone part 16 made of a vitrified grindstone was fixed to the outer peripheral surface of the main body 18 was used, but instead of the grinding wheel 14, the metal core, that is, the main body 18 was used. In the case where a general grindstone that does not use a grindstone is used, as long as the AE sensor 22 is built-in, the entire grindstone may be composed of a vitrified grindstone or the like. In addition, when the entire grindstone is composed of a vitrified grindstone, an AE sensor 22, a preamplifier 24, and a transmission circuit 26 are installed in a spacer held between the flange that fixes the general grindstone to the main shaft and the general grindstone. It may be.

The above-mentioned embodiment is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

10: Truing completion determination device 14: Grinding wheel (grinding wheel)
22: AE sensor 34: A/D converter 46: Rotary dresser (truing tool)
50: Frequency analysis section 53: Truing completion determination section 80: Dresser (truing tool)
82: Full type dresser (truing tool)
SAE: AE signal SP1: First signal strength SP2: Second signal strength

Claims (4)

A truing completion determination device that determines the completion of truing for shaping the grinding surface of a grinding wheel using a truing tool,
an AE sensor that detects an AE signal generated during truing of the grinding wheel;
an A/D converter that converts the AE signal output from the AE sensor into a digital signal;
a frequency analysis unit that frequency-analyzes the AE signal converted into a digital signal by the A/D converter to obtain a power spectrum;
Among the frequency bands of 100 kHz or less of the power spectrum obtained by the frequency analysis section, a first signal strength in a first frequency band and a second signal strength in a second frequency band having a higher frequency than the first frequency band. a truing completion determination unit that sequentially calculates at least one signal strength integral value and determines completion of truing of the grinding wheel based on saturation of the signal strength integral value. Judgment device. The first frequency band is a frequency band including at least a part of a frequency band from 25 to 40 kHz,
The truing completion determination device according to claim 1, wherein the second frequency band is a frequency band that includes at least part of a frequency band from 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 from 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 microseconds or less.

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