JP6545597B2 - Displacement measuring device - Google Patents

Description

  The present invention relates to a displacement measuring device that measures displacement to a displacement sensor and an object to be measured (made of metal). In particular, in a machine tool equipped with an automatic tool changer such as a machining center (hereinafter abbreviated as "MC"), a tool for automatically changing the tool holder with respect to the spindle by a robot arm or the like. The present invention relates to a displacement measuring device that measures displacement of a flange periphery of a tool holder in order to confirm whether the holder is set at the rotation center of the spindle.

  Eddy current type displacement sensors are used in many rotating machines in various industrial fields, and important ones among them are regularly monitored and constantly monitored the condition of the machine, especially vibration, and efficient maintenance And are used for analysis and diagnosis.

  Shinkawa Electric Co., Ltd., "Web Magazine, SHINKAWA Times", "Vol.2 No. 1 Jan. 13, 2010", "Column", "Principle of state monitoring of rotating machinery vol.2 principle of eddy current displacement sensor" Page, [online], January 13, 2010 [search May 11, 2015], Internet <U R L: http://www.shinkawa.co.jp/ magazine / vol. 2_column_sst. html> (Non-patent Document 1) shows the principle of an eddy current displacement sensor as shown in FIG. Basically, the eddy current displacement sensor is a displacement sensor that measures the displacement (gap) between the sensor and the target. The reason that vibration measurement can be performed with this displacement gauge is that the frequency response of the eddy current displacement sensor is as wide as DC to 10 kHz, and gaps in the range of several tens Hz to several hundreds Hz, which are targets in normal rotating shaft vibration measurement This is because the output of the converter with respect to the change of (sensor input) follows one to one. The static characteristic of the eddy current displacement meter outputs a voltage proportional to the displacement within the range used as shown in FIG. 2 (A). When the target oscillates in the range of x1 to x3 around x2, the displacement with respect to time is shown as shown in FIG. 2 (B). Also, the output voltage of the converter appears as a waveform of the output voltage with respect to time as shown in FIG. 2 (C). At this time, displacements (gaps) x1, x2, x3 with respect to the output voltages y1, y2, y3 are approximately proportional to known values. Therefore, the vibration amplitude can be calculated by arithmetically processing the deviation (y3-y1) of y3 and y1 using a vibration monitor or the like. Furthermore, since the output waveform of the displacement gauge shows a vibration waveform, it is possible to observe the waveform or analyze the vibration.

As shown in FIG. 3, an eddy current displacement sensor in which the inductance changes in accordance with the displacement with respect to the measurement object (metal) as shown in FIG. 3 is disclosed in JP 2006-317387 A (patent document 1). It has been described that the mounting condition abnormality of the tool holder 302 in a machine tool having a rotation axis is determined. At that time, it is described that the equivalent circuit of the eddy current displacement sensor is assumed to be a series circuit of an inductance L, a capacitance C, and a resistance R. As shown in FIG. 3, in order to measure the displacement of the tool flange 303 and the eddy current displacement sensor 312, the eddy current displacement sensor 312 and the alternating current of various frequencies (f _{1 to} f _i ) are eddy current equations The oscillating circuit 321 which supplies the displacement sensor 312, the rectifying circuit 322 which rectifies the alternating current voltage which appears in the eddy current displacement sensor 312, the filter circuit 323 which takes out the direct current component of the rectified voltage waveform, and the digital current component It comprises an analog-to-digital converter 324 (hereinafter referred to as “ADC”) for converting into a signal, and a functional module 330 consisting of a microcomputer 326 and a memory 325 for calculating the inductance L based on the digital signal. There is. As shown in FIG. 4, in the microcomputer 326, based on the calculated inductance, a frequency conversion unit 400 for instructing the oscillation frequency, an inductance calculation unit 410 for calculating an inductance based on the signal from the detection circuit 320, and A displacement calculating unit 420 that calculates displacement, and an abnormality determining unit 430 that determines abnormality based on the calculated displacement. In the function module 330, a digital signal indicating the amplitude (V _{1 to} V _i ) of the AC voltage appearing from the detection circuit 320 to the eddy current displacement sensor 312 is supplied to the inductance calculation unit 410. The displacement (gap) of the tool flange 303 and the eddy current displacement sensor 312 is measured based on the inductance L calculated by solving n simultaneous equations as shown in Equation 1 with i = 1 to n, It is described that the abnormality of the mounting state of the holder to the spindle is determined.
(1)
V _i = | jω _i L + 1 / (jω _i C) + R | × E _i (i = 1 to n)
In addition, while changing the step of changing the frequency of the alternating current signal applied to the eddy current displacement sensor 312 finely and sweeping the frequency of the alternating current signal almost steplessly, the amplitude V of the signal appearing in the eddy current displacement sensor 312 is detected Do. Then, when the sweep is completed in all of the sweep range (f _{s to} f _e ), the inductance calculation 410 changes the signal level V appearing in the eddy current displacement sensor 312 with respect to the change of the frequency of the AC signal, that is, the differential value dV. Calculate / dω (ω = 2πf). Subsequently, a vortex is obtained by substituting the differential value dV / dω into a calculation equation derived by differentiating the signal appearing in the eddy current displacement sensor 312 as shown in the above equation with respect to the angular frequency ω. The inductance component L of the current displacement sensor 312 can be calculated. Finally, it is described that the displacement calculation unit 420 determines the displacement (gap) with the outer peripheral surface of the tool flange 303 from the eddy current displacement sensor 312 corresponding to the inductance component L.

  In JP-A-2004-276145 (Patent Document 2), in a chuck error device incorporated in a machine tool, an eddy current is used to detect displacement to the outer peripheral surface of a flange portion of a tool holder mounted on a spindle as an electric signal. It is described that a data processing apparatus is provided which stores the displacement measured by the equation displacement sensor and the eddy current displacement sensor in a memory and calculates the amount of eccentricity of the tool holder based on the displacement. Then, the CPU in the data processing apparatus performs Fast Fourier Transform (FFT) analysis on the displacement of each one turn of the tool holder, decomposes it into components of each frequency, and decenters the amplitude value of the fundamental frequency component by twice. If it is acquired as an amount and if the difference between the first eccentricity T1 for the first rotation and the eccentricity T2 for the second rotation is greater than or equal to a predetermined threshold, it is determined as a chuck error (abnormal mounting state) and the difference is It is described that it is determined to be normal if it is less than a predetermined value.

  Japanese Patent Laid-Open Publication No. 2005-333426 (Patent Document 3) uses an inductor 560 oscillating by using a self-oscillation type displacement detection sensor 570 whose oscillation frequency is determined based on the product of an inductance and a capacitance of a capacitor. A displacement detection system (displacement detection device for detecting a change in displacement (gap) with an object from an oscillation intensity caused by an eddy current generated in the object or a change in oscillation frequency by applying an output magnetic flux to the object ) Is described. FIG. 5 is an explanatory view schematically showing a configuration example of a displacement detection system (displacement detection device). The displacement detection device includes a storage unit 510 in the control circuit 500 connected to the variable oscillator 520 and the detection unit 580, and causes the storage unit 510 to store the resonant frequency detected for the resonant circuit 570. The control circuit 500 detects the displacement of the displacement detection target T by using the stored resonance frequency as the drive frequency. A technique is described in which the drive frequency is estimated to match the changed resonant frequency by this detection method, and the decrease in oscillation intensity caused by the change in resonant frequency is suppressed.

JP, 2006-317387, A Unexamined-Japanese-Patent No. 2004-276145 JP 2005-333426 A

Shinkawa Electric Co., Ltd., "Web Magazine, SHINKAWA Times", "Vol.2 No. 1 Jan. 13, 2010", "Column", "Principle of state monitoring of rotating machinery vol.2 principle of eddy current displacement sensor" Page, [online], January 13, 2010, [search May 11, 2015], Internet <URL: http://www.shinkawa.co.jp/magazine/vol.2_column_sst. html>

  Although the principle of a general eddy current displacement sensor is shown in Non-Patent Document 1, the relationship between the resonance frequency and the displacement between the sensor and the target, and the method and configuration for measuring the resonance frequency are not disclosed.

  Patent Document 1 describes a machine tool that uses an eddy current displacement sensor whose inductance changes in accordance with a displacement from a measurement object, and determines a mounting abnormality of a tool holder in a machine tool having a rotation axis. However, when determining the inductance of the eddy current displacement sensor, there is a problem that the process of solving simultaneous equations based on the circuit equations is complicated, and a microcomputer for the process is required.

  In Patent Document 2, in a chuck error device incorporated in a machine tool, displacement d up to the outer peripheral surface of a flange portion of a tool holder mounted on a spindle is measured by an eddy current displacement sensor, and based on the displacement Although it is described that a data processor is provided to calculate the amount of eccentricity of the tool holder, it is noted that what kind of response of the eddy current displacement sensor is focused on, and what kind of response is correlated to calculate the displacement. Disclosure is lacking.

Patent Document 3 discloses a displacement detection device for detecting a change in displacement (gap) with an object from changes in oscillation intensity and oscillation frequency caused by eddy currents generated in the object in a self-oscillation type displacement detection sensor. It is described that, as shown in FIG. 6, when the gap between an inductor (coil) functioning as a displacement detection unit and an object decreases, the resonance frequency increases and the resonance voltage decreases. However, there is no disclosure about increasing the measurement accuracy or sensitivity of the oscillation frequency.

  The present invention has been made based on the above circumstances, and the object of the present invention is to measure the displacement between an eddy current displacement sensor and an object to be measured. An eddy current displacement sensor and an object to be measured by providing a displacement measuring device having accuracy and sensitivity, in particular, by improving measurement accuracy or sensitivity of oscillation frequency of a voltage waveform supplied by the eddy current displacement sensor. It is an object of the present invention to provide a displacement measurement device that improves measurement accuracy or measurement sensitivity for displacement with (for example, a tool flange).

  The object of the present invention is to provide an eddy current displacement sensor for supplying a first voltage waveform whose oscillation frequency changes in accordance with a voltage value of a control voltage and a displacement of an object to be measured; A frequency conversion that generates a second voltage waveform modulated using a first reference voltage waveform having a frequency different from that of the first voltage waveform, and supplies a third voltage waveform that is a low-frequency component of the second voltage waveform. A portion, which is achieved by calculating the displacement between the eddy current displacement sensor and the object to be measured based on the frequency of the third voltage waveform.

The above object of the present invention is that the frequency conversion unit includes a first conversion circuit including a first modulator and a first band pass filter, and the first modulator is generated based on a first clock waveform of a predetermined frequency. Generating a second voltage waveform that is a voltage waveform including a frequency component corresponding to a frequency difference between the first reference voltage waveform and the first voltage waveform, and the first band pass filter generates the second voltage waveform By supplying the third voltage waveform based on
Alternatively, the frequency conversion unit includes a second conversion circuit including a second modulator and a second band pass filter, and the second modulator generates a second clock waveform having a frequency lower than that of the first clock waveform. And a fourth voltage waveform which is a voltage waveform including a frequency component corresponding to a difference between the second reference voltage waveform generated at a frequency lower than the frequency of the first reference voltage waveform and the third voltage waveform. Generating a second voltage pass filter by supplying a fifth voltage waveform based on the fourth voltage waveform;
Alternatively, the frequency conversion unit includes a third conversion circuit including a third modulator and a third band pass filter, and the third modulator generates a third clock waveform having a frequency lower than that of the second clock waveform. And a sixth voltage waveform which is a voltage waveform including a frequency component corresponding to a difference between the third reference voltage waveform generated at a frequency lower than the frequency of the second reference voltage waveform and the fifth voltage waveform. Generating a third voltage pass filter by supplying a seventh voltage waveform based on the sixth voltage waveform;
Alternatively, the frequency conversion circuit generates a second low-pass filter that generates the first reference voltage waveform based on the first clock waveform, and generates the second reference voltage waveform based on the second clock waveform. By providing a second low pass filter and a third low pass filter that generates the third reference voltage waveform based on the third clock waveform,
Alternatively, the period of the voltage waveform converted to the frequency according to the frequency of the first voltage waveform by the frequency conversion unit by counting with the second reference clock waveform of the predetermined frequency generated by the counting unit reference clock oscillator By providing a periodic time counting unit that counts a count number corresponding to the number, and a displacement calculation unit that calculates the displacement that corresponds to the count number,
Alternatively, it is a machine tool comprising a displacement measuring device, a rotationally driven spindle, and a tool holder to which a cutting tool is attached, and rotationally driving the spindle on which the tool holder is mounted to process a workpiece, the displacement By measuring the displacement of the tool holder mounted on the spindle to the flange outer peripheral surface by a measuring device to determine whether the mounting state of the tool holder on the spindle is normal or abnormal
Alternatively, the processing apparatus includes a displacement measuring device and an object to be measured which moves in parallel, and the displacement measuring device measures the displacement to the displacement measuring device and the object to be measured to thereby measure the object to be measured. It is more effectively achieved by determining the state of spatial installation of objects.

  According to the displacement measuring apparatus using the eddy current displacement sensor of the present invention, the voltage waveform supplied by the eddy current displacement sensor and the voltage waveform supplied by the eddy current displacement sensor use voltage waveforms different in frequency. A change in frequency of the voltage waveform that responds to displacement between the eddy current displacement sensor and the object to be measured by providing a frequency conversion unit that extracts the low frequency side component of the modulated voltage waveform The ratio can be increased to improve the measurement accuracy or sensitivity for the displacement.

It is a schematic block diagram of the conventional high frequency oscillation type proximity sensor. (A) shows the relationship between the displacement of the sensor and the target and the output waveform in the conventional high frequency oscillation type proximity sensor. (B) shows how the displacement of the sensor and target changes with time. (C) shows how the output voltage changes with time corresponding to the displacement between the sensor and the target. It is a schematic block diagram of the machine tool provided with the tool shake (abnormality detection) displacement measuring device using the eddy current type displacement sensor of a prior art example. FIG. 4 is a block diagram of a functional module provided inside the microcomputer shown in FIG. 3 and determining the mounting state of the tool holder on the main spindle based on the displacement calculated from the inductance of the sensor (coil). It is an explanatory view showing typically the example of composition of the conventional displacement detection system (displacement detection device) It is explanatory drawing which shows the detection method of the displacement of a displacement detection target object based on the change of resonant frequency using the conventional displacement detection apparatus. (A) is an explanatory view showing a configuration in the vicinity of a spindle head of a machine tool provided with a displacement measuring instrument using an eddy current displacement sensor for detecting an amount of eccentricity of a tool holder in the first embodiment of the present invention. (B) is a bottom view of (A). BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of the machine tool provided with the displacement measuring device which used the eddy current type displacement sensor in 1st Embodiment of this invention. It is a block diagram to a frequency conversion part of a displacement measuring instrument using an eddy current type displacement sensor in a 1st embodiment of the present invention. It is a block diagram of a period time counting part using a counter in a 1st embodiment of the present invention. In the first embodiment of the present invention, it is a graph of the rate of change of the fundamental output frequency f _vo with respect to the fundamental frequency f _vi from eddy current displacement sensor. In the first embodiment of the present invention, linear interpolation is performed between A and B using point A (n _k , d _k ) and point B (n _{k + 1} , d _{k + 1} ) on the conversion table, it is a method of calculating a displacement d _m corresponding to the measured count value n _m. It is a flow chart which shows an example of processing which measures an amount of eccentricity of a tool holder in a 1st embodiment of the present invention, and judges a zipper error of a tool holder. It is a flowchart which shows the example of the subroutine process which measures the displacement d of the sensor head of a sensor part, and the outer peripheral surface of a tool holder in 1st Embodiment of this invention. It is a flow chart which shows an example of processing which computes each amount of eccentricity of the 1st rotation eye of a tool holder-the N-th rotation eye in a 1st embodiment of the present invention. It is a flowchart which shows the example of the process which determines the presence or absence of a chuck | zipper error in 1st Embodiment of this invention. In the second embodiment of the present invention, (A) is a configuration example of a band pass filter in which a differentiating circuit and an integrating circuit are connected in series. (B) is a configuration example of a band pass filter in which the input side impedance of the operational amplifier A is a CR series differential circuit and the CR side integral circuit is assigned to the feedback side impedance. It is a structural example of the low pass filter in 2nd Embodiment of this invention. (A) is an example realized by a multiplier configured by arranging a voltage control resistance element on the input side of an operational amplifier and arranging a feedback resistor Rf in a feedback loop for MOD in the present invention. (B) is a configuration example of a multiplier in which an n-type field effect transistor is disposed as a voltage control resistance element. (A) is in the VCO circuit is a diagram showing the relationship between the output frequency f _out with respect to the control voltage V _cont. (B) is a configuration example of a VCO circuit using an LC resonance circuit including a varicap. It is an example which installed the sensor part in the bottom of a headstock in the present invention. It is an example applied to the displacement measurement of the to-be-measured object which translates in this invention. (A) is an example applied to measurement of displacement of a target that moves in parallel in the lateral direction with respect to the eddy current displacement sensor in the present invention. (B) is an example applied to the displacement measurement of a target moving so as to approach or separate from the eddy current displacement sensor in the longitudinal direction in the present invention.

  In the displacement measuring device using the eddy current displacement sensor according to the present invention, the voltage waveform supplied by the eddy current displacement sensor and the voltage waveform supplied by the eddy current displacement sensor are modulated using voltage waveforms different in frequency. The displacement by amplifying the frequency change ratio in the voltage waveform with respect to the displacement between the eddy current displacement sensor and the object to be measured It is possible to provide a displacement measurement device that improves the measurement accuracy or measurement sensitivity of In particular, in a machine tool equipped with an automatic tool changer such as MC, it is effective in detecting eccentricity due to foreign matter adhesion between the spindle and the tool holder.

  Hereinafter, a first embodiment of a displacement measuring device according to the present invention will be described based on the drawings.

  FIG. 7A is a schematic configuration diagram of the vicinity of a spindle head of a machine tool to be measured by the displacement measuring apparatus according to the present invention and an eddy current displacement sensor (generally indicated by 720 in FIG. 7A). It is a figure which shows the attachment position of. FIG. 7B is a bottom view of FIG. 7A.

  The headstock 704 of the machine tool is attached to an appropriate saddle or the like, and moves relative to a table (not shown). The spindle 703 supported by the spindle stock 704 has a shank hole at its tip and is engaged with the tool holder 701 by two claws. The tool holder 701 has an appropriate outer diameter, and is replaced with the main shaft 704 by an automatic tool changer (not shown). The tool holder 701 has a cutting tool 700 and performs the necessary processing on the work on the table.

  The eddy current displacement sensor 720 has a sensor head 722 inserted into the main body 721. The main body 721 is supported by the holder arm 723 by nuts 726 a and 726 b, and the holder arm 723 is attached to the support structure 724. A signal detected by the sensor head 722 is sent to a frequency converter 812 described later via a signal line 725.

  The tool holder 701 comprises a flange portion 705 having a largest diameter. In the automatic tool change position, the sensor head 722 of the eddy current displacement sensor 720 is disposed at a position facing the flange portion 705 of the tool holder 701. At this time, the displacement d (gap) formed by the tip of the sensor head 722 and the flange portion 705 of the tool holder may be, for example, 3 mm. The flange 705 is a mounting tool such as a cutting tool having a removable structure, and a metal material having a strong magnetic response is used as the material.

  When the main shaft 703 is rotated in this state, the flange portion 705 of the tool holder rotationally moves with respect to the sensor head 722. When the displacement d changes according to this rotational movement, the impedance (inductance) formed between the flange portion 705 of the tool holder and the sensor head 722 changes, and the amount of eccentricity of the flange portion 705 is changed by the operation described later. It can be detected. Then, when the amount of eccentricity exceeds a predetermined value, it can be determined that a clamp abnormality has occurred due to biting of chips or the like between the tool holder 701 and the spindle 703. Furthermore, the rotation of the main shaft 703 may be stopped to perform necessary processing.

FIG. 8 is a schematic block diagram of a displacement measuring device 800 used in the present invention. The displacement measuring device 800 according to the present invention comprises a control voltage data transmission unit 810 for supplying digital data of the control voltage V _{cont to} the eddy current displacement sensor 720, and oscillation based on the control voltage V _cont . An eddy current displacement sensor 720 that supplies a frequency waveform having a resonance frequency corresponding to a change in impedance (inductance) due to eddy current generation of an object to be measured (in this case, the flange portion 705) as the fundamental frequency f _vi And a frequency converter 812 which supplies a voltage waveform having a basic output frequency f _vo to which the voltage waveform having the basic frequency f _vi has been subjected to filter processing and low frequency conversion processing to a period time counting unit 813; The displacement calculation unit 814 is provided to calculate the displacement d of the flange unit 705 and the eddy current displacement sensor 720 based on the determined basic output frequency f _vo. .

Furthermore, a block diagram of the control voltage data transmission unit 810, the eddy current displacement sensor 720, and the frequency conversion unit 812 is shown in FIG. The control voltage data transmission unit 810 converts digital data of parallel control values corresponding to the control voltage V _cont according to a command from the computer 815 by the digital circuit 911 which converts the parallel data into serial data. It is supplied to the interface 913 of the displacement sensor 720. The DAC 914 outputs a D / A converted control voltage V _cont based on the holding of the control value and the value. The control voltage V _cont is supplied to a voltage / frequency conversion circuit 915 (hereinafter referred to as “VCO circuit”). The VCO circuit is provided with a sensor coil for detecting a change in impedance due to the generation of an eddy current as described later.

An eddy current is generated in accordance with the displacement d between the sensor head 722 and the flange portion 705 which is the object to be measured made of metal, and the impedance (inductance) of the eddy current displacement sensor 720 is changed. The resonant frequency of 915 changes. This resonance frequency is called the fundamental frequency f _vi in the present invention, but the changing width is, for example, 11415.2 to 11416.3 [kHz], and the change ratio based on 11415.2 [kHz] is about 0.01% The physical quantities to be measured change little and it is difficult to ensure sufficient measurement sensitivity or accuracy.

Therefore, in the present invention, by providing the frequency converter 812 for frequency converting a fundamental frequency f _vi to a lower frequency, with respect to the change ratio of the fundamental frequency f _vi, the frequency after conversion, i.e. the fundamental output frequency f _vo To increase the change ratio of

A block diagram schematically showing the frequency converter 812 is shown in FIG. As shown in FIG. 9, a voltage waveform v _i having this fundamental frequency f _vi is input, and band pass filter ₀ 917, buffer 918, modulator ₁ 919, band pass filter ₁ 920, buffer 921, modulator ₂ 922, band pass The voltage waveform v _zc is configured to be output through the filter ₂ 923, the buffer 924, the modulator ₃ 925, the band pass filter ₃ 926, the buffer 927, and the zero cross circuit (ZERO CROSS) 928. In this embodiment, a block formed by a buffer (hereinafter referred to as "BF"), a modulator (hereinafter referred to as "MOD") and a band pass filter (hereinafter referred to as "BPF") is one conversion circuit. The frequency conversion is performed by three conversion circuits. As processing before the voltage waveform v _i having the fundamental frequency f _vi is input to the first conversion circuit, noise removal is performed via the BPF. And BF performs impedance conversion of the voltage waveform which passed BPF. Then, if A ₀ sin (ω ₁ ) t, which is the reference signal that has passed LPF _1, and A ₁ sin (ω ₂ ) t, which is the voltage waveform that has passed the first BF, are input to the first MOD 1, sin A composite waveform having a (ω ₁ + ω ₂ ) t component and a sin (ω ₁ −ω ₂ ) t component is generated. For example, a multiplier circuit may be used as such a conversion processing circuit. Then, when the composite waveform passes through the BPF 1 of the next stage of the conversion processing circuit, the high frequency component is cut off and filtering processing is performed so that only the low frequency component _vo1 passes. Thus, sequentially, in the first step, the voltage waveform of the fundamental frequency f _vi is converted to the voltage waveform of the first low frequency conversion frequency f _vo1 , and in the second step, the voltage waveform of the first low frequency conversion frequency f _vo1 is It is converted into a voltage waveform of the second low frequency conversion frequency f _vo2, in the third step the voltage waveform of the second low frequency converted frequency f _vo2 is converted to a voltage waveform of the third low-frequency converting the frequency f _vo3. The frequency f _vo3 voltage waveform v _o is the same as the fundamental output frequency f _vo in the present invention. In the embodiment, although the conversion circuit configured by BF, MOD, and BPF is used, an LPF may be used instead of BPF according to the characteristics and performance of the conversion circuit. In addition, although the conversion circuit composed of BF, MOD, and BPF is connected in three stages, for example, one stage or two stages may be connected, or four or more stages may be connected to form a frequency conversion unit. The number of stages is not limited.

  In each MOD, the clock generator 934 generates a fixed voltage waveform (for example, f1: 12 MHz, f2: 750 kHz, and f3: 187.5 kHz in FIG. 9) corresponding to the frequency used for frequency modulation. Is generated by extracting the fundamental sin wave component through each low-pass filter (corresponding to LPF1, LPF2 and LPF3 in FIG. 9) and supplied to each corresponding MOD. Be done.

Then, in the first embodiment of the present invention, each MOD 919, 922, 925 of the frequency conversion unit 812 is converted to the frequency of the voltage waveform and the basic output frequency f _vo based on the fundamental frequency f _vi. Table 1 shows the correspondence relationship between the frequency of the voltage waveform sequentially converted by the frequency conversion unit based on the fundamental frequency f _vi from the displacement sensor and the fundamental output frequency f _vo . The change ratio of the fundamental frequency f _vi is 0.001%, 0.005%, and 0.01% with respect to 11415.2 [kHz], while the change ratio of the fundamental output frequency f _vo , Corresponding to 0.523%, 2.627% and 5.395% based on 22.3 [kHz]. And when the corresponding change rates are compared, 515 times (0.515%: 0.001%), 525 times (2.627%: 0.005%) and 539 times (5.395%: 0. 5 respectively). The change rate is significantly increased to 01%. Furthermore, the change ratio of the basic output frequency _{fvo to} the change ratio of the basic frequency _fvi is approximately proportional to one another in the drawing (see FIG. 11).

Thus, in the frequency conversion section 812, with respect to the change of the fundamental frequency f _vi, such that the change in the change ratio of the fundamental output frequency f _vo is increased significantly, the measurement sensitivity is increased, a fundamental frequency f _vi Can be frequency converted to the low frequency side. As a result, the sensitivity for detecting the displacement d between the sensor head 722 and the flange portion 705 which is the object to be measured made of metal can be improved along with the improvement of the detection sensitivity of the basic output frequency _fvo .

As shown in FIG. 8, the periodic time counting unit 813 is disposed between the computer 815 or the displacement calculating unit 814 and the frequency converting unit 812. As shown in FIG. 10, the periodic time counting unit 813 is supplied with a rectangular wave signal v _zc having a clock pulse φ of 150 MHz and a basic output frequency f _vo output from the frequency conversion unit 812. The period time counting unit 813 supplies the count number obtained by counting the clock pulse φ by the counter 944 to the displacement calculating unit 814 in a period corresponding to one cycle of the signal _vzc .

Then, in the first embodiment of the present invention, the period time counting unit 813 counts the count value of the period of the voltage waveform having the basic output frequency f _vo converted by the frequency conversion unit 812 based on the basic frequency f _vi . Table 2 shows a correspondence table of the period and the number of counters and the basic output frequency f _vo based on the basic frequency f _vi from the eddy current displacement sensor. Here, the change in the fundamental frequency f _vi with reference to 11415.2 [kHz] and the increase in the count number corresponding to the period of the voltage waveform having the fundamental output frequency f _vo are 0.01%, The values of 363 counts, 2314 counts and 7054 counts correspond to 0.05% and 0.1%, respectively, and all have significantly changed or expanded the sensitivity.

The count number is inversely proportional to the basic output frequency _fvo, and the displacement d can be calculated by detecting the count number. In the first embodiment of the present invention, when performing the calculation, a conversion table for storing the correspondence between the count number and the displacement d is provided, and conversion is performed according to the conversion table to obtain a final measured quantity. The displacement d is obtained. Table 3 shows a conversion table showing the correspondence between the counter number n and the displacement d based on the basic output frequency _fvo .

As for the use of the conversion table, since the measured count value does not usually coincide with the count value prepared in advance in the conversion table, as shown in FIG. Two count values n _k and n _{k + 1} stored in advance in the conversion table are selected, and two counts n and displacement d, respectively, for the section [n _k , n _{k + 1} ]. That is, linear interpolation between A and B is performed using point A (n _k , d _k ) and point B (n _{k + 1} , d _{k + 1} ), and displacement d corresponding to the measured count number n _{m Although m} can be calculated, an interpolation method other than linear interpolation may be used.

  Next, processing for determining a chuck error of the tool holder 701 by measuring the eccentricity T of the tool holder 701 will be described with reference to the flowchart of FIG.

First, it starts by performing automatic tool change (AUTOMATIC TOOL CHANGE) (S100). Then, the number of rotations of the tool holder 701, how many times the measurement for one rotation of the tool holder is to be performed, that is, the number of times of measurement N is set (S200). The computer 815 instructs the tool holder 701 to rotate at the set rotation speed (S300). During the process of measuring the amount of eccentricity, a variable k storing the number k of times the tool holder 701 has been rotated is initialized to 1 (S400). Next, the subroutine jumps to a subroutine for measuring the displacement d of the sensor head 722 of the eddy current displacement sensor 720 and the outer peripheral surface of the tool holder 701, that is, the flange portion. After the measurement, the process returns to step 600, and the process proceeds to step 600 (S500), and the variable k is counted up (S600). If it is determined that the variable k has exceeded the set number of measurements N to determine the end of measurement, the process returns to step 500, and if it is determined whether the variable k has exceeded the set number of measurements N and exceeded, The process proceeds to step 800 (S700). The process jumps to a subroutine for calculating eccentricity amounts T _k corresponding to the first rotation to the Nth rotation of the tool holder 701, returns after calculation, and returns to step 900 (S800). Since the chuck error of the tool holder 701 is determined based on the maximum value, the average value, and the minimum value of the eccentricity amounts T _k for the first rotation to the Nth rotation, the process jumps to a subroutine (S800 to S810 described later) After the determination, the process returns and proceeds to step 1000 (S900). The determination result is displayed on the display unit of the computer 815 (S1000).

Here, the subroutine processing of step 500, that is, processing of measuring the displacement d of one rotation of the sensor head 722 of the sensor unit and the outer peripheral surface of the tool holder, that is, the flange portion 705 will be described with reference to the flowchart of FIG. The variable L is used to manage the number of data of the displacement d in one rotation of the tool holder (one rotation), and the variable L is initialized to 0 before measurement (S501). Then, in order to start measurement after detecting the reference of the rotation angle (azimuth angle) of the tool holder 701, when it is the first rotation of measurement (S502), until the reference of the rotation angle of the tool holder 701 is detected The process waits for the loop of step 503 without reading the displacement d from the displacement calculation unit 814 (S 503). In addition, about the said reference | standard, a recessed part or a convex part may be given to the flange part 705, and it may detect from the increase / decrease in the displacement d in a recessed part or a convex part, an optical sensor may be provided and the said reference may be detected. The detection method is not limited. Further, with regard to the detection of the reference, for example, the detection may be continued until the rotational speed becomes constant, and the detection may be omitted from the time when it is determined to be constant. In the detection order, the flowchart is modified so that the displacement d corresponding to the rotation angle is read from the displacement calculation unit 814 (S 504), and the timing of division (start or end) of one rotation of the tool holder 701 is detected. You may do it. Next, the reference of the rotation angle of the tool holder 701 is detected (S503), and displacement d corresponding to the rotation angle is sequentially read from the displacement calculation unit 814 (S504). The displacement d is stored in the array variable D (k, L) as the variable L measured during the rotation of the k-th rotation (S 505). A predetermined time is waited until the rotation angle changes to the next rotation angle, and the variable L is counted up (S506). If the reference of the rotation angle of the tool holder is not detected yet, the process returns to step 504 (S507). If the reference of the rotation angle of the tool holder 701 is detected again, the measurement of the data of the displacement d in one rotation of the tool holder is ended (S507), and the process proceeds to step 508 and an array corresponding to the number of displacement data of the kth rotation The variable L (k) = L−1 is stored, and the subroutine processing is ended and the process returns (S508). The step is to wait for a predetermined time, but by changing the predetermined time according to the rotational speed, the predetermined time is adjusted so that the number of data of displacement d per one rotation is adjusted to approximately the same number and it is easy to standardize. A configuration for controlling may be added, and the predetermined time is shortened from the start of the displacement measurement, and the predetermined time is extended after the predetermined time elapses, and the difference in the number of data of displacement d per one rotation is A configuration that can be controlled to be provided may be added, and a corresponding modification may be added to arrange the step of controlling the configuration in the flowchart.

  The subroutine processing of step 800, that is, the processing of calculating each eccentricity T of the first rotation to the Nth rotation of the tool holder 701 will be described with reference to the flowchart of FIG. As for the outline of this process, the measurement data of the displacement d output from the sensor unit is stored in the array variable D (k, L) in correspondence with the rotation angle θ of the tool holder 701. Since the (maximum value-minimum value) in the displacement d corresponding to the rotation, that is, the amplitude value can be regarded as twice the amount of eccentricity T of the tool holder 701, the computer 815 performs the first to Nth rotations The respective eccentricity values T (k) of the first to Nth rotations of the tool holder 701 are calculated.

  As this processing procedure, while the array variable D (k, L) and the adjacent array variable D (k, L + 1) are sequentially compared for the kth rotation to extract the maximum value and the minimum value, the array variable D (k , L) and finally dividing by the array variable L (k), which is the number of displacement data of the k-th rotation, to obtain an average value.

  The variable L is initialized (L = 0), and the variable Max = variable Min = array variable D (k, L) (S801). If the relation of array variable (k, L) <array variable (k, L + 1), the process proceeds to step 803 (S802), variable Max = array variable (k, L + 1), and the process proceeds to step 804 (S803). If the relationship of array variable (k, L) <array variable (k, L + 1) does not hold, the process proceeds to step 804 (S802).

  If the relation of array variable (k, L) <array variable (k, L + 1), step 805 (S804), variable Min = array variable (k, L + 1), and the process proceeds to step 806 (S805). If the relationship of array variable (k, L) <array variable (k, L + 1) does not hold, the process proceeds to step 806 (S804).

  If L> array variable L (k) is not satisfied (S 807), the process returns to step 802. In the case of L> array variable L (k) (S 807), that is, when comparison of data of all displacements d of the kth rotation is completed, array variable Min (k) = Min, array variable Max (k) = An array variable T (k) = (variable Max−variable Min) / 2 corresponding to the eccentricity of the k-th rotation is calculated as the variable Max, and stored (S808). In order to store the eccentricity of the next (k + 1) th rotation, the variable k is counted up (S809). If k> N is not satisfied, that is, if the variable k does not exceed the number of measurements N and the measurement is continued (S 810), the process returns to step 802. If k> N, that is, if measurement is completed, the subroutine processing of S901 to S912 is ended, and the process returns to step 900.

The subroutine processing of the next step 900, that is, the processing of determining the presence or absence of a chuck error will be described with reference to the flowchart of FIG. As a determination method in this processing, as one example, when there is an average value of each of the first to Nth rotation eccentricities of the tool holder that is equal to or larger than the threshold value, it is determined as a chuck error. In addition, if the difference between the maximum value (variable T _max ) and the minimum value (variable T _min ) in each eccentricity of the first rotation to the Nth rotation of the tool holder is equal to or larger than the threshold, the chuck error is also performed similarly. Although what can be judged can be mentioned, it is not limited to this judgment method. For example, each eccentricity may be compared with a predetermined threshold value, and the chucking error may be determined based on the number of eccentricity values exceeding the threshold, and statistical processing is performed for each eccentricity. A method may be employed in which a chuck error is determined on the basis of the statistical data obtained.

As an initial step in the subroutine 900, an initial value k = 1 is performed as initialization of variables and setting of initial values, and variable T _max = variable T _min = array variable T (1) The corresponding variable) is set (S901). The eccentric amounts are sequentially compared, and if the relation of T (k) <T (k + 1) is not satisfied (S 902), the process proceeds to step 904. If T (k) <T (k + 1) (S902), the variable T _max is updated to the array variable T (k + 1), and the process proceeds to step 904 (S903). Next, when it is not the relationship of T (k)> T (k + 1), it progresses to step 906 (S904). If T (k)> T (k + 1) (S904), T _min is updated to array variable T (k + 1), and the process proceeds to step 906 (S905). In order to calculate the average value of eccentricity amounts, the variable T _sum = variable T _sum + array variable T (k + 1) is calculated, and the array variable T (k) is sequentially added (S906). After that, the variable k is counted up to advance comparison between eccentricity amounts adjacent to each other and eccentricity amount totaling processing (S7).

Next, when the variable k does not exceed the set number of times of measurement N, that is, when the processing for calculating the maximum value, the minimum value, and the total of the eccentricity amount is not completed, the process returns to step 902 and the processing is continued using k counted up. . In the case of k> N, that is, when this process is ended, an average value T _ave (= Sum / N) of eccentricity amounts is calculated as a total (S909). Finally, T _ave and (T _max -T _min ) are compared with the corresponding threshold values to determine chuck errors. Specifically, if T _ave <first threshold (S910), or if T _max −T _min <second threshold (S911), it is determined that a chuck error has occurred, and the subroutine processing is terminated and returned. (S913). On the other hand, if T _ave <first threshold (S910), and if T _max −T _min <second threshold (S911), it is determined that the chuck error is not detected, and the subroutine processing is performed. And return to step 900 (S912). In the subroutine 900, the first threshold and the second threshold are set as fixed values, but may be variable. For example, it may be variable based on the type, material, age, etc. of the cutting tool 700 based on the attributes of the individual, or may be set and optimized based on the dimensions of the workpiece or the material, and is limited It is not a thing. Moreover, it is not limited to the example of the determination method shown in embodiment, You may employ | adopt another determination method.

  Next, a second embodiment of the displacement measuring device according to the present invention will be described based on the drawings. In the second embodiment, a configuration example using an operational amplifier for BPF, BF, MOD and LPF in the frequency converter 812 is shown, and the circuit constants of the resistor R and the capacitor C corresponding to the cutoff frequency of the BPF and each LPF An example of Further, an example in which a variable capacitance diode (varicap) is used for the VCO circuit 915 of the eddy current displacement sensor 720 is shown.

First, a configuration example of the BPF is shown in FIG. 17, and in FIG. 17A, the differentiating circuit and the integrating circuit are connected in series. In FIG. 17B, the input side impedance of the operational amplifier A in one stage is CR series. , And an integrating circuit of CR parallel is assigned to the feedback side impedance. The cut-off frequencies f _c1 and f _c2 have a relationship of f _c1 <f _c2 , and are calculated by f _c1 = (2πR ₁ C ₁ ) ⁻¹ and f _c2 = (2πR ₂ C ₂ ) ⁻¹ . That is, the BPF 1 passes a voltage waveform in a frequency band of f _c1 or more and f _c2 or less. Similarly, as shown in FIG. 18, the configuration example of the low pass filter is configured by providing an integration circuit in the feedback loop of the operational amplifier A, and the cutoff frequency is determined by f _c = (2πRC) ⁻¹ . Table 4 shows an example of the resistance R and the capacitance C corresponding to the cut-off frequency for BPF0 to BPF3 and LPF1 to LPF3 shown in FIG. 9 in the second embodiment of the present invention.

Next, although the multiplier using the operational amplifier A can be used in the MOD 919, 922, 925 as described above, for example, the configuration example of the multiplier 960 is the operational amplifier A as shown in FIG. On the input side of the circuit, a voltage control resistance element is disposed, and a feedback loop is disposed with a feedback resistor Rf. As shown in FIG. 19B, for example, an n-type field effect transistor or a MOS transistor may be _disposed as the voltage control resistance element Rv. In the multiplier 961, n-type field effect transistor voltage waveform v ₁ which is input to the drain side of Q is a voltage waveform v ₂ of the voltage level input to the gate side, receiving the amplitude modulation, V ₀ ~V ₁ * multiplication result such as V ₂ is output.

  Next, the VCO circuit 915 in the eddy current displacement sensor 720 can be configured using a variable capacitance diode (varicap). The varicap (variable capacity diode) controls the magnitude of the reverse bias voltage applied to the diode to change the reverse bias depletion capacity of the PN junction, thereby changing the capacitance VC at both ends of the varicap. An element that can The relationship of the capacitance VC to the reverse bias voltage is such that the capacitance VC increases as the reverse bias voltage applied across the varicap is small, and the capacitance VC decreases as the reverse bias voltage is large.

In the voltage / frequency conversion circuit 915, when the voltage (equal to the control voltage V _cont ) applied to the variable capacitance diode (varicap) changes, the capacitance of the diode changes, so the resonance frequency changes and the oscillation frequency changes. Changes. In the case of a normal voltage / frequency conversion circuit, the oscillation frequency also increases as the voltage increases.

The VCO circuit 915 of the eddy current displacement sensor 720 has a sensor coil L _VCO , and a high frequency magnetic field generated by the AC magnetic field lines generated by the sensor coil L _VCO is made of a metal target (flanged portion as an object to be measured) to generate eddy currents, Inpi possessed sensor coil L _VCO - Dance properties (especially, inductance characteristics) alter.

The characteristic L possessed by the sensor coil L _VCO inside the VCO circuit 915, the variable capacitance diode (varicap) VC and the characteristics C _{2 to} C ₅ of the respective capacitors form an LC resonant circuit, and this LC resonant circuit has a control voltage An AC signal having a resonant frequency based on V _cont and the impedance of the sensor coil L _VCO is provided.

The VCO circuit 915 is a circuit that controls the oscillation output frequency f _out with the control voltage V _{cont as} shown in FIG. It is desirable to use a VCO circuit having an input / output characteristic in which the characteristic of the oscillation output frequency f _{out with} respect to the control voltage V _cont is monotonous, that is, almost linear. As a circuit configuration example of the VCO circuit 915, a VCO circuit 970 including a variable capacitance diode (varicap) as shown in FIG. 20B can be mentioned. VCO circuit 970 utilizes the resonance circuit LC as described above, the inductance L corresponds to the sensor coil of the present invention, the capacitance C _VR of the variable capacitance diodes the capacitance C of the resonant circuit (varicap) The basic frequency f _vi is determined on the basis of the control voltage V _cont and the inductance of the sensor coil L _VCO since the capacitance C _VR can be varied on the basis of the control voltage V _cont as described above. The VCO circuit (voltage control oscillator) may control the oscillation frequency according to the input control voltage V _cont so that the circuit configuration is not limited as long as the sensor coil can be incorporated, and it is necessary to have a varicap There is no. Furthermore, since a quiet control voltage without noise is required as much as a high-performance VCO circuit, it is preferable to control the oscillation output frequency f _out with the control voltage V _cont of digital control. Further, the VCO circuit 970 shown in FIG. 20B does not specify the oscillation frequency.

  The position of the eddy current displacement sensor unit 720 may be installed on the bottom of the headstock 704 as shown in FIG. 21 or on the side (not shown), and the installation position is not particularly limited.

  Further, as shown in a schematic view of FIG. 22, the displacement measuring device of the present invention can also be applied to the displacement measurement of an object to be measured which is moved in parallel. In an apparatus 980 in which the levelness of the stage shown in FIG. 22 affects the processing quality, for example, in a printing machine, a coating apparatus for applying a chemical solution to a substrate, or an apparatus for polishing or rubbing the surface of a substrate, eddy current displacement If the sensor 981 and metal xy stage 982 are provided, the distance d between the eddy current displacement sensor 981 and the xy stage 982 translates the xy stage 982 on the xy plane. However, it is also used to evaluate the distribution of the above-mentioned distance d in the xy plane by measuring with the eddy current displacement sensor 981 and to adjust the levelness of the xy stage 982 can do.

In addition, the displacement measuring device of the present invention is used to measure the displacement of a target 991 which moves in parallel in the left-right direction with respect to the eddy current displacement sensor 993 as shown in a schematic view of FIG. Can also be used to measure the displacement of the target 992 moving toward and away from the eddy current displacement sensor 994 as shown in the schematic diagram of FIG. 23B. Can.

100 target (metal)
101 sensor (coil)
102 oscillation circuit 103 resonance circuit 104 detection circuit 105 amplification circuit 106 linearizer circuit 200 target 201 sensor 302 tool holder 303 tool flange 304 fitting portion 306 head 310 main shaft 311 bracket 312 eddy current displacement sensor 320 detection circuit 321 oscillation circuit 322 rectifier circuit 323 filter circuit 324 ADC
325 Memory 326 Microcomputer 327 Machine tool NC
330 function module 400 frequency conversion unit 410 inductance calculation unit 420 displacement calculation unit 430 abnormality determination unit 500 control circuit 510 storage unit 520 variable oscillation circuit 530 drive circuit 540 resistance 550 capacitor 560 coil 570 resonance circuit 580 detection unit 700 cutting tool 701 tool holder 702 Two jaws 703 Spindle 704 Headstock 705 Flange 720 Eddy current type displacement sensor 721 Body 722 Sensor head 723 Holder arm 724 Support 725 Signal wire 726a, 726b Nut 800 Displacement measuring device 810 Control voltage data transmitter 812 Frequency converter 813 period time measurement unit 814 displacement calculation unit 815 computer 816 memory 817 machine tool NC
911 Digital circuit (convert parallel data to serial data)
912 interface 913 interface 914 D / A converter (with data holding function)
915 VCO circuit 916 buffer 917 band pass filter 0
918 Buffer 919 Modulator 1
920 band pass filter 1
921 Buffer 922 Modulator 2
923 band pass filter 2
924 Buffer 925 Modulator 3
926 Bandpass filter 3
927 Buffer 928 zero crossing circuit (pulse waveform output)
930 divider 931 low pass filter 1
932 low pass filter 2
933 low pass filter 3
934 Clock generator 940 Counting unit 941 Clock generator 942 Flip-flop (1/2 frequency divider)
943 edge detection 944 counter 945 latch circuit 950 band pass filter 951 band pass filter 952 low pass filter 960 multiplier 961 multiplier 970 VCO circuit 980 device 981 eddy current displacement sensor 982 x-y stage
991, 992 Target 993, 994 Eddy current displacement sensor

Claims (8)

An eddy current displacement sensor that supplies a first voltage waveform whose oscillation frequency changes according to the voltage value of the control voltage and the displacement of the object to be measured;
The first voltage waveform and the first voltage waveform generate a second voltage waveform modulated using a first reference voltage waveform having a different frequency, and the third voltage component is a low frequency side component of the second voltage waveform. And a frequency converter for supplying a voltage waveform,
A displacement measuring device, which calculates displacements of the eddy current displacement sensor and the object to be measured based on the frequency of the third voltage waveform. The frequency conversion unit includes a first conversion circuit including a first modulator and a first band pass filter,
The first modulator is a voltage waveform including a frequency component corresponding to a difference in frequency between a first reference voltage waveform generated based on a first clock waveform of a predetermined frequency and the first voltage waveform. Generate a voltage waveform,
The displacement measurement device according to claim 1, wherein the first band pass filter supplies the third voltage waveform based on the second voltage waveform. The frequency conversion unit includes a second conversion circuit including a second modulator and a second band pass filter,
A second reference voltage waveform that is generated based on a second clock waveform whose frequency is lower than that of the first clock waveform, and whose frequency is lower than that of the first reference voltage waveform; Generating a fourth voltage waveform that is a voltage waveform including a frequency component corresponding to a difference in frequency from the three voltage waveforms,
The displacement measurement device according to claim 2, wherein the second band pass filter supplies a fifth voltage waveform based on the fourth voltage waveform. The frequency conversion unit includes a third conversion circuit including a third modulator and a third band pass filter,
A third reference voltage waveform that is generated based on a third clock waveform whose frequency is lower than that of the second clock waveform, and whose frequency is lower than that of the second reference voltage waveform; Generating a sixth voltage waveform that is a voltage waveform including a frequency component corresponding to the frequency difference from the five voltage waveforms,
The displacement measuring device according to claim 3, wherein the third band pass filter supplies a seventh voltage waveform based on the sixth voltage waveform.   The frequency conversion circuit is configured to generate a first low-pass filter that generates the first reference voltage waveform based on the first clock waveform, and a second low-pass filter that generates the second reference voltage waveform based on the second clock waveform. The displacement measuring device according to claim 4, further comprising: a low pass filter; and a third low pass filter that generates the third reference voltage waveform based on the third clock waveform. It corresponds to the period of the voltage waveform converted into the frequency according to the frequency of the first voltage waveform by the frequency conversion unit by counting with the second reference clock waveform of the predetermined frequency generated by the counting unit reference clock oscillator. A periodic time counting unit that counts the number of counts
A displacement calculation unit that calculates the displacement corresponding to the count number;
The displacement measurement device according to any one of claims 2 to 5, comprising: A displacement measuring device according to any one of claims 1 to 6, a main shaft for rotational driving, and a tool holder to which a cutting tool is attached, the main shaft on which the tool holder is mounted is rotationally driven to work Machine tools that process
A machine tool which measures the displacement to the flange outer peripheral surface of the tool holder mounted on the spindle by the displacement measuring device, and determines normality or abnormality of the mounting state of the tool holder on the spindle. A processing apparatus comprising: the displacement measuring device according to any one of claims 1 to 6; and an object to be measured which translates in parallel,
A processing apparatus which measures displacement of the displacement measuring device and the object to be measured by the displacement measuring device to determine a state of spatial installation of the object to be measured.