WO2023063435A1 - Working machine bearing quality determining method and system - Google Patents

Working machine bearing quality determining method and system Download PDF

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Publication number
WO2023063435A1
WO2023063435A1 PCT/JP2022/039805 JP2022039805W WO2023063435A1 WO 2023063435 A1 WO2023063435 A1 WO 2023063435A1 JP 2022039805 W JP2022039805 W JP 2022039805W WO 2023063435 A1 WO2023063435 A1 WO 2023063435A1
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bearing
srf
vibration
frequency
quality
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PCT/JP2022/039805
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French (fr)
Japanese (ja)
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保宏 駒井
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エヌティーエンジニアリング株式会社
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Publication of WO2023063435A1 publication Critical patent/WO2023063435A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
    • B23Q17/00—Arrangements for observing, indicating or measuring on machine tools
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
    • B23Q17/00—Arrangements for observing, indicating or measuring on machine tools
    • B23Q17/12—Arrangements for observing, indicating or measuring on machine tools for indicating or measuring vibration
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H17/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves, not provided for in the preceding groups
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M13/00—Testing of machine parts
    • G01M13/04—Bearings
    • G01M13/045—Acoustic or vibration analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M99/00—Subject matter not provided for in other groups of this subclass

Definitions

  • the present invention relates to a bearing quality determination method and system for a machine tool for determining the quality of bearings that rotatably support a spindle.
  • a boring tool is attached to the main shaft (spindle) of a machine tool, and by rotating the boring tool at high speed and feeding it out sequentially along a prepared hole, the machining diameter of the cutting edge is precisely positioned at a predetermined position. It processes the hole.
  • an abnormal frequency is calculated in advance for each part of the bearing, specifically, for each inner ring, outer ring, rolling element, and cage, and the calculated abnormal frequency corresponds to Techniques are disclosed for extracting spectral data levels and comparing them to thresholds.
  • the abnormal frequency calculated in advance using a predetermined relational expression for each part of the bearing and the level of the frequency spectrum of the digital signal obtained by detecting the vibration generated from the bearing are compared and collated. are doing. For this reason, the process of comparison and collation becomes complicated, and an expensive FFT analyzer is required for vibration measurement, which is not economical. Moreover, unless there is obvious damage to the bearing, there is no vibration frequency that indicates an abnormality in a specific part. It cannot be used well when desired.
  • the present invention relates to a machine tool bearing quality determination method and system for determining the quality of a bearing that rotatably supports a spindle in a machine tool that processes a workpiece via a rotary tool attached to the spindle. be.
  • This method for judging whether the bearing is good or bad includes the steps of detecting rotational vibration of the bearing when the spindle is idling; analyzing the rotational vibration by Fourier series expansion to obtain the vibration frequency; A total SRF that is the sum of the spindle rotation frequency (SRF) calculated from and its harmonics (integer multiples of the spindle rotation frequency), and a residual frequency (Non-SRF) obtained by removing the total SRF from all the vibration frequencies , and a step of determining whether the bearing is good or bad by comparing the total sum SRF and the residual frequency.
  • SRF spindle rotation frequency
  • Non-SRF residual frequency
  • a vibration detection mechanism detects rotational vibration of the bearing
  • a calculation mechanism analyzes the rotational vibration by Fourier series expansion and obtains the vibration frequency
  • the vibration frequency is The total SRF, which is the sum of the spindle rotation frequency (SRF) calculated from the spindle rotation speed/60 and its harmonics (integer multiples of the spindle rotation frequency), and the residual frequency obtained by removing the total SRF from all the vibration frequencies (Non-SRF), and a frequency dividing mechanism for dividing into (Non-SRF), and a comparing and judging mechanism for judging the quality of the bearing by comparing the total SRF and the residual frequency.
  • SRF spindle rotation frequency
  • the vibration frequency of the bearing when the spindle is idling is divided into the total SRF (spindle rotation frequency) and the remaining residual frequency (Non-SRF),
  • SRF spindle rotation frequency
  • Non-SRF residual frequency
  • FIG. 1 is a schematic explanatory diagram of a machine tool to which a bearing quality determination system according to an embodiment of the present invention is applied;
  • FIG. 3 is an explanatory diagram of a controller that constitutes the bearing quality determination system;
  • FIG. 4 is an explanatory diagram of a display unit that constitutes the bearing quality determination system; It is explanatory drawing of various dimensions of a bearing. It is explanatory drawing which shows the vibration data of the said bearing before exchange. It is explanatory drawing which shows the vibration data of the said bearing after exchange.
  • a bearing quality determination system 10 is applied to a machine tool 12.
  • the machine tool 12 includes a spindle (main shaft) 18 rotatably provided in a housing 14 via a pair of front bearings 16f and a pair of rear bearings 16b.
  • a tool holder (rotary tool) 20 is detachably attached to the spindle 18 , and a cutter 22 is attached to the tip of the tool holder 20 .
  • the bearing quality determination system 10 includes an acceleration sensor (vibration detection mechanism) ( Alternatively, a microphone) 24 for acquiring vibration sound by sound waves is provided. This is because in the case of the front bearing 16f and the rear bearing 16b that support the spindle 18, usually the front bearing 16f is likely to malfunction. Note that the acceleration sensor 24 may be arranged adjacent to the rear bearing 16b.
  • the acceleration sensor 24 is connected to a rotational vibration measuring instrument (hereinafter referred to as controller) 28 via a signal line 26, and the controller 28 is connected to a machine tool control panel 30 as shown in FIG.
  • the machine tool control panel 30 has a function of controlling the machine tool 12 .
  • the controller 28 includes a computation unit (computation mechanism) 34 that amplifies the rotational vibration (idling vibration) of the front bearing 16f detected by the acceleration sensor 24 using an amplifier and filter circuit 32 and captures the amplified vibration.
  • the arithmetic unit 34 is connected to an input setting unit 36 for inputting the inner and outer ring dimensions of the front bearing 16f, the number of balls of the rolling elements, the ball diameter, the contact angle, and the like (to be described later).
  • the input setting unit 36 can set thresholds for monitoring and identification determination, signal processing procedures when vibration exceeding the thresholds occurs, and the like.
  • a rotational vibration judgment unit 38 and an input/output unit 40 for outputting a signal subjected to arithmetic judgment processing are connected to the arithmetic unit 34 .
  • a display unit 42 is connected to the calculation unit 34 to display the calculation result, the detection result, and the like on the screen. Updated data is typically sent from the arithmetic unit 34 to the rotational vibration determination unit 38 every second.
  • Arithmetic unit 34 functions as a frequency division mechanism that divides the frequency spectrum into summed SRF and residual frequency (Non-SRF), as will be described later.
  • the display unit 42 includes a total power display window 44, a frequency spectrum display window 46, a non-SRF/SRF comparison display window 48, and a history display window 50. Above the display unit 42, a Measuring lamp 52a, a Watching lamp 52b, and a spindle rotation speed display 52c are provided.
  • the total power display window 44 is a vibration amount monitoring unit that is turned on by a measurement start button of the controller 28 or a signal from the device.
  • the total power display window 44 displays the total power (G 2 ) of rotational vibration that changes with the idling of the spindle 18 (and, if necessary, machining). , is displayed as total power in real time.
  • the sum of the squared acceleration values is displayed on the vertical axis, and the elapsed time (seconds) is displayed on the horizontal axis.
  • acquired data for 20 seconds from the start of measurement (Measuring lamp 52a turns ON) is displayed.
  • the period from the start of measurement to 7 seconds is the time zone for obtaining the idling signal, and the period from 2 seconds to 5 seconds after the start of measurement is the time period for monitoring vibration (the Watching lamp 52b is ON).
  • the period from 7 seconds to 17 seconds after the start of measurement is machining vibration, and the period from 17 seconds to 20 seconds is idle vibration.
  • a sign threshold 54 for displaying a sign that the total power enters the warning range, an alarm threshold 56 for displaying that the total power has increased abnormally, and a vibration monitoring time zone. are separately set by the input setting unit 36 .
  • the signal is transmitted to the outside via the input/output unit 40 .
  • the frequency spectrum display window 46 displays the frequency spectrum obtained by Fourier transforming the rotational vibration during idling.
  • the frequency spectrum display window 46 displays a spectrum with acceleration (G or m/s 2 ) or displacement ( ⁇ m) on the vertical axis and frequency (Hz) calculated by Fourier transform on the horizontal axis.
  • the display range of the horizontal axis of the spectrum is selected and set in advance from 10 Hz to 10,000 Hz, and generally selected ranges such as 10 Hz to 2,000 Hz and 10 Hz to 2,500 Hz.
  • the display on the vertical axis is the automatic gain method. Acceleration (m/s 2 ), velocity (m/s), or displacement ( ⁇ m) units can be selected for spectrum display.
  • the frequency spectrum display window 46 vertical lines indicating the spindle-revolving-frequency (hereinafter referred to as SRF) of the spindle 18 calculated from the spindle rotation speed rpm/60 (Hz) and its harmonics are displayed. be done. This is for facilitating determination of whether or not SRF is included in rotational vibration.
  • the spindle rotation speed rpm is taken into the arithmetic unit 34 via the input/output unit 40 in advance.
  • the frequency spectrum display window 46 data such as the inner and outer ring dimensions of the front bearing 16f, the number of balls of the rolling elements, the ball diameter, the contact angle, etc. separately set by the input setting unit 36, and the main shaft rotation speed rpm , vertical lines of frequencies that are likely to occur due to damage to the inner and outer rings and rolling elements are displayed.
  • the comparison display window 48 functions as a comparison and judgment mechanism for judging the quality of the front bearing 16f by displaying the relative ratio between the total SRF and the residual frequency as it changes over time.
  • the amount of change (comparison ratio ) is displayed as a dot graph over time (every second). In this dot graph, when the total amount of SRF during rotational vibration is large, it is displayed in the lower part, while when the total amount of Non-SRF is large, it is displayed in the upper part.
  • a sign threshold 58 for judging that the front bearing 16f has entered a pre-damage sign stage and an abnormality for judging that the front bearing 16f is damaged Threshold 60 and are separately set by the input setting unit 36 .
  • an alarm is output to the outside to alert an operator or the like.
  • the alarm display color and alarm flashing interval are changed to distinguish whether the alarm is caused by the total power display value or the comparison ratio display value. ing.
  • the total amount of rotational vibration is displayed as a bar graph in chronological order during the vibration monitoring time period in the process with the separately set sequence number.
  • the change over time of the bar graph makes it possible to confirm the change over time of the total amount of rotational vibration when the spindle 18 idles.
  • the history display window 50 is provided with arrow buttons 62a and 62b positioned on the left side of the bar graph, and by appropriately pressing the arrow buttons 62a and 62b, the total amount of past rotational vibrations can be confirmed.
  • a threshold value is separately set by the input setting unit 36 as necessary in the history display window 50, and an alarm is output to the outside when the total amount exceeds the threshold value.
  • the front bearing 16f (and the rear bearing 16b) that supports the spindle 18 for example, precision bearings set to the conditions (dimensions, etc.) shown in FIG. 4 are used. Then, precision machining is performed by the machine tool 12 using the front bearing 16f and the rear bearing 16b. Specifically, as shown in FIG. 1, a spindle 18 having a tool holder 20 having a cutter 22 attached to its tip is rotationally driven, and the tool holder 20 moves along a work (not shown). As a result, the cutter 22 rotates integrally with the tool holder 20, and the workpiece (not shown) is machined (precision machined) through the cutter 22. As shown in FIG.
  • the front bearing 16f and the rear bearing 16b that support the spindle 18 are particularly prone to damage, which may affect the machining accuracy. Therefore, the front bearing 16f and the rear bearing 16b are usually replaced with new bearings after the machining operation has been performed for a predetermined time (preferably before the front bearing 16f is damaged).
  • the applicant measured the vibration accompanying the main shaft rotation (2000 rpm) in the front bearing 16f after use (immediately before replacement), and the vibration data shown in FIG. 5 was obtained. . Specifically, significant frequency peaks appeared at 101 Hz, 198 Hz, 391 Hz, 587 Hz, 1256 Hz and 1504 Hz.
  • the applicant found that the front bearing 16f before and after replacement had a significant difference in the frequency of vibration due to rotation. That is, the difference depends on whether or not a significant vibration frequency appears in the signal of the spindle rotation frequency (SRF).
  • SRF spindle rotation frequency
  • the rotational vibration of the front bearing 16f that supports the spindle 18 is measured while the spindle 18 is idling before starting machining or during daily warm-up.
  • the acceleration sensor 24 acquires rotational vibration of the front bearing 16f during idling of the spindle 18 in the controller 28 during the vibration monitoring time period.
  • the acquired rotational vibration is taken into the arithmetic unit 34 via the amplifier and filter circuit 32 .
  • arithmetic analysis by Fourier transform is performed on the captured slip vibration. Specifically, the time oscillation f(t) is
  • f(t) ⁇ (a j cos2 ⁇ Jt+b j sin2 ⁇ Jt). Note that a j is the cosine harmonic component Fourier coefficient of frequency J, and b j is the sine harmonic component Fourier coefficient of frequency J.
  • the integration interval is from 0 to T, and the integration interval T is an integer multiple of the cycle 1/J.
  • the display unit 42 is provided with a total power display window 44, a frequency spectrum display window 46 and a non-SRF/SRF comparison display window 48, and the frequency spectrum calculated by Fourier analysis is displayed. , depending on the purpose, are displayed in these.
  • the magnitude of the vibration amount that changes as the spindle 18 idles is displayed as a real-time total power (G 2 ).
  • the vertical axis represents the total power (G 2 ) obtained by squaring the acceleration, and the increase/decrease ratio of the amount of idling vibration is represented as a large amount of change. That is, small vibrations are displayed smaller and large vibrations are displayed larger. For this reason, the total power energy, which is difficult to discern from the frequency spectrum, can be discriminated, thereby expressing rotational vibration (furthermore, machining vibration) during idling of the spindle 18, and increasing or decreasing the vibration, etc., can be sharply represented.
  • the rotational vibration of the front bearing 16f can be acquired at any time while the spindle 18 is idling. Acquiring and recording the data is easier to compare.
  • the frequency spectrum display window 46 displays the frequency spectrum obtained by Fourier transforming the rotational vibration.
  • the amount of change in the relative ratio between the total SRF in rotational vibration and the total non-SRF is displayed as a dot graph. Elapsed time (every second) is displayed. In this dot graph, when the total amount of SRF during rotational vibration is large, that is, when the front bearing 16f is in a good state, it is displayed at the bottom. It is displayed above that the front bearing 16f is in the no condition.
  • the controller 28 processes rotational vibration of the front bearing 16f when the spindle 18 idles.
  • the frequency spectrum display window 46 for example, a large amount of non-SRF total sum appears during rotational vibration, and the relative ratio in the comparison display window 48 may exceed the indication threshold 58 . Therefore, it is determined that the front bearing 16f has entered the premonitory stage of damage determination, and the replacement work of the front bearing 16f is started. Furthermore, in the total power display window 44, the total power value is large. As a result, it is determined that the front bearing 16f is worn, and it can be confirmed that the spindle 18 is rotating normally in the premonitory stage.
  • the front bearing 16f may have no damage to each part, or may have slight damage.
  • the operator can replace the front bearing 16f in a desired state. Also, the operator can arbitrarily set the abnormality threshold 60 .
  • the present embodiment it is possible to macroscopically detect the quality of the front bearing 16f in a list simply by observing the magnitude of the comparison ratio displayed in the comparison display window 48. That is, it is only necessary to use SRF vibration and non-SRF vibration with the main shaft rotation speed rpm as a parameter, and it is possible to perform a simple control to determine whether the front bearing 16f is good or bad, that is, to determine the replacement timing with high accuracy and efficiency. Become.
  • an omen threshold 58 is set in the comparison display window 48 .

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  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Acoustics & Sound (AREA)
  • Testing Of Devices, Machine Parts, Or Other Structures Thereof (AREA)

Abstract

[Problem] To enable the quality of a bearing to be determined accurately using a simple process and configuration. [Solution] This method includes: a step for detecting rotational vibration of a bearing; a step for obtaining a vibration frequency by analyzing the rotational vibration by means of Fourier series expansion; a step for dividing the vibration frequency into a total SRF and a residual frequency; and a step for determining the quality of the bearing by comparing the total SRF and the residual frequency.

Description

作業機械のベアリング良否判定方法及びシステムBearing quality judgment method and system for working machine
　本発明は、主軸を回転自在に支持するベアリングの良否を判定するための工作機械のベアリング良否判定方法及びシステムに関する。 The present invention relates to a bearing quality determination method and system for a machine tool for determining the quality of bearings that rotatably support a spindle.
　一般的に、加工工具を介してワークに加工処理を施すために、各種の工作機械が使用されている。例えば、ボーリング加工は、ボーリングツールを工作機械の主軸（スピンドル）に取り付け、前記ボーリングツールを高速で回転させながら下穴に沿って順次繰り出すことにより、その刃先加工径で所定の位置に高精度な孔部を加工するものである。 In general, various machine tools are used to process workpieces through processing tools. For example, in the boring process, a boring tool is attached to the main shaft (spindle) of a machine tool, and by rotating the boring tool at high speed and feeding it out sequentially along a prepared hole, the machining diameter of the cutting edge is precisely positioned at a predetermined position. It processes the hole.
　この種の作業機械では、特に精密な加工に使用される場合、主軸を回転自在に支持するベアリングの精度を高く維持する必要がある。従って、ベアリングに損傷等の異常が発生した際、加工精度にも悪影響が及ぶため、この異常を迅速に検出することが望まれている。 With this type of work machine, it is necessary to maintain a high degree of precision in the bearings that rotatably support the spindle, especially when used for precision machining. Therefore, when an abnormality such as damage occurs in the bearing, the processing accuracy is also adversely affected, so it is desired to quickly detect this abnormality.
　例えば、特許文献１では、所定の関係式を用いて、ベアリングの部位毎、具体的には、内輪、外輪、転動体及び保持器毎の異常周波数を予め計算し、計算した異常周波数に対応するスペクトルデータのレベルを抽出して、閾値と比較照合する技術が開示されている。 For example, in Patent Document 1, using a predetermined relational expression, an abnormal frequency is calculated in advance for each part of the bearing, specifically, for each inner ring, outer ring, rolling element, and cage, and the calculated abnormal frequency corresponds to Techniques are disclosed for extracting spectral data levels and comparing them to thresholds.
特開２００９−２００９０号公報JP-A-2009-20090
　上記の従来技術では、ベアリングの部位毎に、所定の関係式を用いて予め計算した異常周波数と、前記ベアリングから発生する振動を検出して得られたデジタル信号の周波数スペクトルのレベルとを比較照合している。このため、比較照合の処理が煩雑化してしまうとともに、振動の測定に高価なＦＦＴアナライザが必要であり、経済的ではないという問題がある。しかも、ベアリングに明らかな損傷が発生しなければ、特定部位の異常を表す振動周波数が出ないため、特に精密スピンドルに使用されるベアリングのように、損傷が出る前の予兆段階での異常検出が望まれる際に、良好に用いることができない。 In the above-described prior art, the abnormal frequency calculated in advance using a predetermined relational expression for each part of the bearing and the level of the frequency spectrum of the digital signal obtained by detecting the vibration generated from the bearing are compared and collated. are doing. For this reason, the process of comparison and collation becomes complicated, and an expensive FFT analyzer is required for vibration measurement, which is not economical. Moreover, unless there is obvious damage to the bearing, there is no vibration frequency that indicates an abnormality in a specific part. It cannot be used well when desired.
　本発明は、上記の問題を解決するためになされたものであり、簡単な工程及び構成で、ベアリングの良否を正確に判定することが可能な作業機械のベアリング良否判定方法及びシステムを提供することを目的とする。 SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and system for determining the quality of a bearing in a working machine, which can accurately determine the quality of a bearing with a simple process and configuration. With the goal.
　本発明は、主軸に取り付けられた回転工具を介してワークに加工処理を施す工作機械において、前記主軸を回転自在に支持するベアリングの良否を判定する工作機械のベアリング良否判定方法及びシステムに関するものである。 The present invention relates to a machine tool bearing quality determination method and system for determining the quality of a bearing that rotatably supports a spindle in a machine tool that processes a workpiece via a rotary tool attached to the spindle. be.
　このベアリング良否判定方法は、主軸の空転時に、ベアリングの回転振動を検出する工程と、前記回転振動をフーリエ級数展開により解析し、振動周波数を得る工程と、前記振動周波数を、主軸回転数÷６０から算出される主軸回転周波数（ＳＲＦ）及びその高調波（該主軸回転周波数の整数倍）の総和である総和ＳＲＦと、全ての前記振動周波数から前記総和ＳＲＦを除去した残余周波数（Ｎｏｎ−ＳＲＦ）と、に分割する工程と、前記総和ＳＲＦと前記残余周波数とを比較することにより、前記ベアリングの良否を判定する工程と、を有している。 This method for judging whether the bearing is good or bad includes the steps of detecting rotational vibration of the bearing when the spindle is idling; analyzing the rotational vibration by Fourier series expansion to obtain the vibration frequency; A total SRF that is the sum of the spindle rotation frequency (SRF) calculated from and its harmonics (integer multiples of the spindle rotation frequency), and a residual frequency (Non-SRF) obtained by removing the total SRF from all the vibration frequencies , and a step of determining whether the bearing is good or bad by comparing the total sum SRF and the residual frequency.
　また、このベアリング良否判定システムでは、主軸の空転時に、ベアリングの回転振動を検出する振動検出機構と、前記回転振動をフーリエ級数展開により解析し、振動周波数を得る演算機構と、前記振動周波数を、主軸回転数÷６０から算出される主軸回転周波数（ＳＲＦ）及びその高調波（該主軸回転周波数の整数倍）の総和である総和ＳＲＦと、全ての前記振動周波数から前記総和ＳＲＦを除去した残余周波数（Ｎｏｎ−ＳＲＦ）と、に分割する周波数分割機構と、前記総和ＳＲＦと前記残余周波数とを比較することにより、前記ベアリングの良否を判定する比較判定機構と、を備えている。 Further, in this bearing quality judgment system, when the main shaft is idling, a vibration detection mechanism detects rotational vibration of the bearing, a calculation mechanism analyzes the rotational vibration by Fourier series expansion and obtains the vibration frequency, and the vibration frequency is The total SRF, which is the sum of the spindle rotation frequency (SRF) calculated from the spindle rotation speed/60 and its harmonics (integer multiples of the spindle rotation frequency), and the residual frequency obtained by removing the total SRF from all the vibration frequencies (Non-SRF), and a frequency dividing mechanism for dividing into (Non-SRF), and a comparing and judging mechanism for judging the quality of the bearing by comparing the total SRF and the residual frequency.
　本発明に係る工作機械のベアリング良否判定方法及びシステムでは、主軸の空転時におけるベアリングの振動周波数を、総和ＳＲＦ（主軸回転周波数）とそれ以外の残余周波数（Ｎｏｎ−ＳＲＦ）とに二分割し、前記総和ＳＲＦと前記残余周波数とを比較するだけで、前記ベアリングの良否を判定することができる。これにより、簡単な工程及び構成で、ベアリングの良否を正確に判定することが可能になる。しかも、ベアリングに明らかな損傷が発生する前の予兆段階においても、前記ベアリングの良否判定を確実に遂行することができる。 In the method and system for judging the quality of a bearing for a machine tool according to the present invention, the vibration frequency of the bearing when the spindle is idling is divided into the total SRF (spindle rotation frequency) and the remaining residual frequency (Non-SRF), The quality of the bearing can be judged only by comparing the sum SRF and the residual frequency. This makes it possible to accurately determine the quality of the bearing with a simple process and configuration. Moreover, it is possible to reliably determine whether the bearing is good or bad even at the symptom stage before the bearing is clearly damaged.
本発明の実施形態に係るベアリング良否判定システムが適用される工作機械の概略説明図である。1 is a schematic explanatory diagram of a machine tool to which a bearing quality determination system according to an embodiment of the present invention is applied; FIG. 前記ベアリング良否判定システムを構成するコントローラの説明図である。FIG. 3 is an explanatory diagram of a controller that constitutes the bearing quality determination system; 前記ベアリング良否判定システムを構成する表示ユニットの説明図である。FIG. 4 is an explanatory diagram of a display unit that constitutes the bearing quality determination system; ベアリングの諸寸法の説明図である。It is explanatory drawing of various dimensions of a bearing. 交換前の前記ベアリングの振動データを示す説明図である。It is explanatory drawing which shows the vibration data of the said bearing before exchange. 交換後の前記ベアリングの振動データを示す説明図である。It is explanatory drawing which shows the vibration data of the said bearing after exchange.
　図１に示すように、本発明の実施形態に係るベアリング良否判定システム１０は、工作機械１２に適用される。工作機械１２は、ハウジング１４内に一対の前方ベアリング１６ｆ及び一対の後方ベアリング１６ｂを介して回転可能に設けられるスピンドル（主軸）１８を備える。スピンドル１８には、ツールホルダ（回転工具）２０が着脱自在に設けられるとともに、前記ツールホルダ２０の先端には、カッタ２２が装着される。 As shown in FIG. 1, a bearing quality determination system 10 according to an embodiment of the present invention is applied to a machine tool 12. The machine tool 12 includes a spindle (main shaft) 18 rotatably provided in a housing 14 via a pair of front bearings 16f and a pair of rear bearings 16b. A tool holder (rotary tool) 20 is detachably attached to the spindle 18 , and a cutter 22 is attached to the tip of the tool holder 20 .
　ベアリング良否判定システム１０は、スピンドル１８の空転時に、前方ベアリング１６ｆの回転振動を検出するために、前記前方ベアリング１６ｆに隣接してハウジング１４の側部に装着される加速度センサ（振動検出機構）（又は音波により振動音を取得するマイクロフォン）２４を備える。スピンドル１８を支持する前方ベアリング１６ｆ及び後方ベアリング１６ｂでは、通常、前記前方ベアリング１６ｆに異常が発生し易いからである。なお、後方ベアリング１６ｂに隣接して加速度センサ２４を配置してもよい。 The bearing quality determination system 10 includes an acceleration sensor (vibration detection mechanism) ( Alternatively, a microphone) 24 for acquiring vibration sound by sound waves is provided. This is because in the case of the front bearing 16f and the rear bearing 16b that support the spindle 18, usually the front bearing 16f is likely to malfunction. Note that the acceleration sensor 24 may be arranged adjacent to the rear bearing 16b.
　加速度センサ２４は、信号線２６を介して回転振動測定器（以下、コントローラという）２８に接続されるとともに、前記コントローラ２８は、図２に示すように、工作機械制御盤３０に接続される。工作機械制御盤３０は、工作機械１２を制御する機能を有する。 The acceleration sensor 24 is connected to a rotational vibration measuring instrument (hereinafter referred to as controller) 28 via a signal line 26, and the controller 28 is connected to a machine tool control panel 30 as shown in FIG. The machine tool control panel 30 has a function of controlling the machine tool 12 .
　コントローラ２８は、加速度センサ２４により検出された前方ベアリング１６ｆの回転振動（空転振動）を、アンプ及びフィルタ回路３２により増幅して取り込む演算ユニット（演算機構）３４を備える。演算ユニット３４には、前方ベアリング１６ｆの内外輪寸法、転動体の玉数、玉直径及び接触角等（後述する）を入力するための入力設定ユニット３６が接続される。入力設定ユニット３６では、監視や識別判定のための閾値や、閾値越えの振動が発生した際の信号の処理手順等が設定可能である。 The controller 28 includes a computation unit (computation mechanism) 34 that amplifies the rotational vibration (idling vibration) of the front bearing 16f detected by the acceleration sensor 24 using an amplifier and filter circuit 32 and captures the amplified vibration. The arithmetic unit 34 is connected to an input setting unit 36 for inputting the inner and outer ring dimensions of the front bearing 16f, the number of balls of the rolling elements, the ball diameter, the contact angle, and the like (to be described later). The input setting unit 36 can set thresholds for monitoring and identification determination, signal processing procedures when vibration exceeding the thresholds occurs, and the like.
　演算ユニット３４には、回転振動判断ユニット３８と、演算判断処理した信号を出力するための入出力ユニット４０とが接続される。演算ユニット３４には、演算結果や検出結果等を画面表示する表示ユニット４２が接続される。演算ユニット３４から回転振動判断ユニット３８には、更新されたデータが、通常、毎秒送られる。演算ユニット３４は、後述するように、周波数スペクトルを総和ＳＲＦと残余周波数（Ｎｏｎ−ＳＲＦ）とに分割する周波数分割機構として機能する。 A rotational vibration judgment unit 38 and an input/output unit 40 for outputting a signal subjected to arithmetic judgment processing are connected to the arithmetic unit 34 . A display unit 42 is connected to the calculation unit 34 to display the calculation result, the detection result, and the like on the screen. Updated data is typically sent from the arithmetic unit 34 to the rotational vibration determination unit 38 every second. Arithmetic unit 34 functions as a frequency division mechanism that divides the frequency spectrum into summed SRF and residual frequency (Non-SRF), as will be described later.
　図３に示すように、表示ユニット４２は、トータルパワー表示窓４４、周波数スペクトル表示窓４６、Ｎｏｎ−ＳＲＦ／ＳＲＦの比較表示窓４８、及びヒストリー表示窓５０を備える。表示ユニット４２の上部には、Ｍｅａｓｕｒｉｎｇランプ５２ａ、Ｗａｔｃｈｉｎｇランプ５２ｂ及び主軸回転数表示部５２ｃが設けられる。 As shown in FIG. 3, the display unit 42 includes a total power display window 44, a frequency spectrum display window 46, a non-SRF/SRF comparison display window 48, and a history display window 50. Above the display unit 42, a Measuring lamp 52a, a Watching lamp 52b, and a spindle rotation speed display 52c are provided.
　トータルパワー表示窓４４は、図示しないが、コントローラ２８の測定開始ボタンや機器からの信号でＯＮ（オン）する振動量の監視ユニットである。トータルパワー表示窓４４は、スピンドル１８の空転（さらに必要であれば、機械加工）と共に変化する回転振動のトータルパワー（Ｇ２）を表示するものであり、各時間帯における振動量の大きさを、リアルタイム性を有してトータルパワーとして表示する。 Although not shown, the total power display window 44 is a vibration amount monitoring unit that is turned on by a measurement start button of the controller 28 or a signal from the device. The total power display window 44 displays the total power (G 2 ) of rotational vibration that changes with the idling of the spindle 18 (and, if necessary, machining). , is displayed as total power in real time.
　トータルパワー表示窓４４では、加速度を二乗した値の和が縦軸に表わされ、経過時間（秒）が横軸に表わされる。トータルパワー表示窓４４では、例えば、測定開始（Ｍｅａｓｕｒｉｎｇランプ５２ａがＯＮ点灯する）から２０秒間の取得データが表示される。測定開始から、例えば、７秒までが空転信号の取得時間帯であり、該測定開始後、２秒~５秒までが振動監視時間帯（Ｗａｔｃｈｉｎｇランプ５２ｂがＯＮ点灯する）である。なお、測定開始後の７秒~１７秒までは、加工振動であり、さらに１７秒~２０秒までは、空転振動である。 In the total power display window 44, the sum of the squared acceleration values is displayed on the vertical axis, and the elapsed time (seconds) is displayed on the horizontal axis. In the total power display window 44, for example, acquired data for 20 seconds from the start of measurement (Measuring lamp 52a turns ON) is displayed. For example, the period from the start of measurement to 7 seconds is the time zone for obtaining the idling signal, and the period from 2 seconds to 5 seconds after the start of measurement is the time period for monitoring vibration (the Watching lamp 52b is ON). It should be noted that the period from 7 seconds to 17 seconds after the start of measurement is machining vibration, and the period from 17 seconds to 20 seconds is idle vibration.
　トータルパワー表示窓４４には、必要に応じて、トータルパワーが警告域に入る予兆を表示する予兆閾値５４と、前記トータルパワーが異常に上昇したことを表示するアラーム閾値５６と、振動監視時間帯とが、入力設定ユニット３６により別途設定される。振動監視時間帯内に、トータルパワーが予兆閾値５４又はアラーム閾値５６を超えると判断されると、その信号が入出力ユニット４０を介して外部に発信される。 In the total power display window 44, if necessary, a sign threshold 54 for displaying a sign that the total power enters the warning range, an alarm threshold 56 for displaying that the total power has increased abnormally, and a vibration monitoring time zone. are separately set by the input setting unit 36 . When it is determined that the total power exceeds the sign threshold 54 or the alarm threshold 56 during the vibration monitoring time period, the signal is transmitted to the outside via the input/output unit 40 .
　周波数スペクトル表示窓４６には、空転時の回転振動をフーリエ変換して得られた周波数スペクトルが表示される。周波数スペクトル表示窓４６では、加速度（Ｇ又はｍ／ｓ２）又は変位（μｍ）を縦軸に、フーリエ変換により演算された周波数（Ｈｚ）を横軸にしたスペクトラムが表示される。スペクトラム横軸の表示範囲は、１０Ｈｚ~１０，０００Ｈｚの間から予め選択設定され、一般的には、１０Ｈｚ~２，０００Ｈｚや１０Ｈｚ~２，５００Ｈｚ等の範囲が選択される。縦軸の表示は、自動ゲイン方式である。スペクトラムの表示には、加速度（ｍ／ｓ２）、速度（ｍ／ｓ）又は変位（μｍ）の単位が選択可能である。 The frequency spectrum display window 46 displays the frequency spectrum obtained by Fourier transforming the rotational vibration during idling. The frequency spectrum display window 46 displays a spectrum with acceleration (G or m/s 2 ) or displacement (μm) on the vertical axis and frequency (Hz) calculated by Fourier transform on the horizontal axis. The display range of the horizontal axis of the spectrum is selected and set in advance from 10 Hz to 10,000 Hz, and generally selected ranges such as 10 Hz to 2,000 Hz and 10 Hz to 2,500 Hz. The display on the vertical axis is the automatic gain method. Acceleration (m/s 2 ), velocity (m/s), or displacement (μm) units can be selected for spectrum display.
　周波数スペクトル表示窓４６には、主軸回転数ｒｐｍ÷６０（Ｈｚ）から算出されるスピンドル１８の主軸回転周波数（Ｓｐｉｎｄｌｅ−Ｒｅｖｏｌｖｉｎｇ−Ｆｒｅｑｕｅｎｃｙ）（以下、ＳＲＦという）及びその高調波を示す縦ラインが表示される。回転振動中にＳＲＦが含まれているか否かの判別を容易にするためである。主軸回転数ｒｐｍは、予め入出力ユニット４０を介して演算ユニット３４に取り込まれている。 In the frequency spectrum display window 46, vertical lines indicating the spindle-revolving-frequency (hereinafter referred to as SRF) of the spindle 18 calculated from the spindle rotation speed rpm/60 (Hz) and its harmonics are displayed. be done. This is for facilitating determination of whether or not SRF is included in rotational vibration. The spindle rotation speed rpm is taken into the arithmetic unit 34 via the input/output unit 40 in advance.
　周波数スペクトル表示窓４６には、必要に応じて、入力設定ユニット３６により別途設定された前方ベアリング１６ｆの内外輪寸法、転動体の玉数、玉直径及び接触角等のデータと、主軸回転数ｒｐｍの情報とから、内外輪及び転動体の損傷に起因して発生し易い周波数の縦ラインが表示される。 In the frequency spectrum display window 46, data such as the inner and outer ring dimensions of the front bearing 16f, the number of balls of the rolling elements, the ball diameter, the contact angle, etc. separately set by the input setting unit 36, and the main shaft rotation speed rpm , vertical lines of frequencies that are likely to occur due to damage to the inner and outer rings and rolling elements are displayed.
　比較表示窓４８は、総和ＳＲＦと残余周波数との相対比を、経時変化して表示させることにより、前方ベアリング１６ｆの良否を判定する比較判定機構として機能する。比較表示窓４８には、前方ベアリング１６ｆの回転振動におけるＳＲＦの総和と、それ以外のＮｏｎ−ＳＲＦの総和との相対比（Ｎｏｎ−ＳＲＦの総和量／ＳＲＦの総和量）の変化量（比較比）が、ドットグラフとして経時（毎秒）表示される。このドットグラフでは、回転振動中にＳＲＦの総和量が多いと下方に表示される一方、Ｎｏｎ−ＳＲＦの総和量が多いと上方に表示される。 The comparison display window 48 functions as a comparison and judgment mechanism for judging the quality of the front bearing 16f by displaying the relative ratio between the total SRF and the residual frequency as it changes over time. In the comparison display window 48, the amount of change (comparison ratio ) is displayed as a dot graph over time (every second). In this dot graph, when the total amount of SRF during rotational vibration is large, it is displayed in the lower part, while when the total amount of Non-SRF is large, it is displayed in the upper part.
　比較表示窓４８には、必要に応じて、前方ベアリング１６ｆが損傷前の予兆段階に入ったと判断させるための予兆閾値５８と、前記前方ベアリング１６ｆに損傷が発生していると判別させるための異常閾値６０と、が入力設定ユニット３６により別途設定される。振動監視時間帯内に、予兆閾値５８や異常閾値６０を超える数値が出た際、外部にアラームが出力され、オペレータ等に喚起を行う。なお、外部にアラームが発せられた場合、このアラームがトータルパワー表示値に起因するものか、比較比表示値に起因するものか、を区別するために、アラーム表示色やアラーム点滅間隔を変更している。 In the comparison display window 48, if necessary, a sign threshold 58 for judging that the front bearing 16f has entered a pre-damage sign stage and an abnormality for judging that the front bearing 16f is damaged. Threshold 60 and are separately set by the input setting unit 36 . When a numerical value exceeding the sign threshold value 58 or the abnormality threshold value 60 is output within the vibration monitoring time period, an alarm is output to the outside to alert an operator or the like. When an external alarm is issued, the alarm display color and alarm flashing interval are changed to distinguish whether the alarm is caused by the total power display value or the comparison ratio display value. ing.
　ヒストリー表示窓５０には、別途に設定されたシーケンス番号の工程での振動監視時間帯において、回転振動の総和量が、経時順に棒グラフとして表示される。棒グラフの経時変化により、スピンドル１８の空転時における回転振動の総和量の経時変化が確認可能になる。ヒストリー表示窓５０には、棒グラフの左側に位置して矢印ボタン６２ａ、６２ｂが設けられ、前記矢印ボタン６２ａ、６２ｂが適宜押圧されることにより、過去の回転振動の総和量を確認することができる。ヒストリー表示窓５０には、必要に応じて、入力設定ユニット３６により別途、閾値が設定され、前記閾値を超える総和量が発生した際に、外部にアラームが出力される。 In the history display window 50, the total amount of rotational vibration is displayed as a bar graph in chronological order during the vibration monitoring time period in the process with the separately set sequence number. The change over time of the bar graph makes it possible to confirm the change over time of the total amount of rotational vibration when the spindle 18 idles. The history display window 50 is provided with arrow buttons 62a and 62b positioned on the left side of the bar graph, and by appropriately pressing the arrow buttons 62a and 62b, the total amount of past rotational vibrations can be confirmed. . A threshold value is separately set by the input setting unit 36 as necessary in the history display window 50, and an alarm is output to the outside when the total amount exceeds the threshold value.
　このように構成される工作機械１２の動作について、以下に説明する。 The operation of the machine tool 12 configured in this manner will be described below.
　先ず、スピンドル１８を支持する前方ベアリング１６ｆ（及び後方ベアリング１６ｂ）として、例えば、図４に示す諸条件（寸法等）に設定された精密なベアリングが使用されている。そして、上記前方ベアリング１６ｆ及び後方ベアリング１６ｂを用いた工作機械１２により精密加工が行われる。具体的には、図１に示すように、先端にカッタ２２が装着されたツールホルダ２０を取り付けたスピンドル１８が回転駆動されるとともに、前記ツールホルダ２０が図示しないワークに沿って移動する。このため、ツールホルダ２０と一体にカッタ２２が回転し、前記カッタ２２を介して図示しないワークに加工（精密加工）が施される。 First, as the front bearing 16f (and the rear bearing 16b) that supports the spindle 18, for example, precision bearings set to the conditions (dimensions, etc.) shown in FIG. 4 are used. Then, precision machining is performed by the machine tool 12 using the front bearing 16f and the rear bearing 16b. Specifically, as shown in FIG. 1, a spindle 18 having a tool holder 20 having a cutter 22 attached to its tip is rotationally driven, and the tool holder 20 moves along a work (not shown). As a result, the cutter 22 rotates integrally with the tool holder 20, and the workpiece (not shown) is machined (precision machined) through the cutter 22. As shown in FIG.
　工作機械１２による加工が継続されると、スピンドル１８を支持する前方ベアリング１６ｆ及び後方ベアリング１６ｂの内、特に前記前方ベアリング１６ｆに損傷が発生し易く、これが加工精度に影響するおそれがある。そこで、通常、所定時間だけ加工作業が行われた後（好ましくは、前方ベアリング１６ｆに損傷が発生する前）に、前方ベアリング１６ｆ及び後方ベアリング１６ｂを新たなベアリングと交換している。 If the machining by the machine tool 12 continues, the front bearing 16f and the rear bearing 16b that support the spindle 18 are particularly prone to damage, which may affect the machining accuracy. Therefore, the front bearing 16f and the rear bearing 16b are usually replaced with new bearings after the machining operation has been performed for a predetermined time (preferably before the front bearing 16f is damaged).
　本出願人は、ＦＦＴアナライザ（図示せず）を用いて、使用後（交換直前）の前方ベアリング１６ｆにおける主軸回転（２０００ｒｐｍ）に伴う振動を測定したところ、図５に示す振動データが得られた。具体的には、１０１Ｈｚ、１９８Ｈｚ、３９１Ｈｚ、５８７Ｈｚ、１２５６Ｈｚ及び１５０４Ｈｚに顕著な周波数ピークが現れた。 Using an FFT analyzer (not shown), the applicant measured the vibration accompanying the main shaft rotation (2000 rpm) in the front bearing 16f after use (immediately before replacement), and the vibration data shown in FIG. 5 was obtained. . Specifically, significant frequency peaks appeared at 101 Hz, 198 Hz, 391 Hz, 587 Hz, 1256 Hz and 1504 Hz.
　次いで、スピンドル１８に新たな前方ベアリング１６ｆ及び後方ベアリング１６ｂを取り付けた。この状態で、同様に、スピンドル１８を回転（６０００ｒｐｍ）させて、前方ベアリング１６ｆにおける振動をＦＦＴアナライザ（図示せず）により測定した。その結果、図６に示す振動データが得られた。具体的には、１００Ｈｚ、４４２Ｈｚ、５９０Ｈｚ、８７６Ｈｚ、１５２８Ｈｚ及び１７５４Ｈｚに顕著な周波数ピークが現れた。なお、ベアリング交換前は、低速の回転（２０００ｒｐｍ）で振動データを測定し、ベアリング交換後は、常用回転（６０００ｒｐｍ）で振動データを測定した。 Next, a new front bearing 16f and a new rear bearing 16b were attached to the spindle 18. In this state, the spindle 18 was similarly rotated (6000 rpm), and the vibration in the front bearing 16f was measured with an FFT analyzer (not shown). As a result, the vibration data shown in FIG. 6 were obtained. Specifically, remarkable frequency peaks appeared at 100 Hz, 442 Hz, 590 Hz, 876 Hz, 1528 Hz and 1754 Hz. Vibration data was measured at low speed rotation (2000 rpm) before bearing replacement, and vibration data was measured at normal rotation (6000 rpm) after bearing replacement.
　図５及び図６を検証したところ、本出願人は、交換前後の前方ベアリング１６ｆでは、回転による振動の周波数に顕著な相違が発生していることを見出した。すなわち、主軸回転周波数（ＳＲＦ）の信号に、顕著な振動周波数が現れているか否かによる相違である。 Upon verifying FIGS. 5 and 6, the applicant found that the front bearing 16f before and after replacement had a significant difference in the frequency of vibration due to rotation. That is, the difference depends on whether or not a significant vibration frequency appears in the signal of the spindle rotation frequency (SRF).
　具体的には、交換前の前方ベアリング１６ｆの振動データでは、図５に示すように、スピンドル１８の回転数が２０００ｒｐｍであり、ＳＲＦである３３．３Ｈｚ（２０００ｒｐｍ／６０）に顕著なピーク信号が出ていない。一方、交換後の前方ベアリング１６ｆの振動データでは、図６に示すように、スピンドル１８の回転数が６０００ｒｐｍであり、ＳＲＦである１００Ｈｚ（６０００ｒｐｍ／６０）に顕著なピーク信号が出ていた。 Specifically, in the vibration data of the front bearing 16f before replacement, as shown in FIG. not out On the other hand, in the vibration data of the front bearing 16f after replacement, as shown in FIG. 6, the number of rotations of the spindle 18 was 6000 rpm, and a remarkable peak signal appeared at the SRF of 100 Hz (6000 rpm/60).
　また、他の複数台のスピンドルにおいて、ベアリング交換前後での各回転の振動周波数を測定したところ、上記と同様の結果が得られた。さらに、加工作業に使用されている複数のマシニングセンタにおいて、空転時のスピンドルを支持するベアリングの回転振動を測定したところ、ＳＲＦに顕著な振動周波数が発生した。ここで、回転振動の測定は、機械加工時に出る加工振動等の外乱振動を回避するために、スピンドル空転時に行うことが好ましい。従って、スピンドルを空転させた際に現れるＳＲＦの振動周波数を検証することにより、ベアリング良否の判断を正確に遂行可能であることが判明した。 In addition, when we measured the vibration frequency of each rotation before and after bearing replacement on multiple other spindles, we obtained the same results as above. Furthermore, when measuring the rotational vibration of the bearings that support the spindle during idling in a plurality of machining centers used for machining work, a remarkable vibration frequency was generated in the SRF. Here, it is preferable to measure the rotational vibration when the spindle is idling in order to avoid disturbance vibration such as machining vibration that occurs during machining. Therefore, it has been found that it is possible to accurately determine whether the bearing is good or bad by verifying the vibration frequency of the SRF that appears when the spindle is idling.
　次いで、上述した考察に基づき、本発明に係るベアリング良否判定システム１０によるベアリング良否判定方法について、以下に説明する。 Next, based on the above considerations, a bearing quality determination method by the bearing quality determination system 10 according to the present invention will be described below.
　スピンドル１８を支持する前方ベアリング１６ｆの回転振動の測定処理は、加工開始前の前記スピンドル１８が空転している間、又は毎日の暖機運転中に行われる。 The rotational vibration of the front bearing 16f that supports the spindle 18 is measured while the spindle 18 is idling before starting machining or during daily warm-up.
　工作機械１２を構成するスピンドル１８の空転が開始されると、コントローラ２８では、振動監視時間帯内に、スピンドル１８の空転時における前方ベアリング１６ｆの回転振動が加速度センサ２４により取得される。この取得された回転振動は、アンプ及びフィルタ回路３２を介して演算ユニット３４に取り込まれる。演算ユニット３４では、取り込まれた空転振動に、フーリエ変換（フーリエ級数展開）による演算解析が行われる。具体的には、時間振動ｆ（ｔ）は、 When the spindle 18 constituting the machine tool 12 starts idling, the acceleration sensor 24 acquires rotational vibration of the front bearing 16f during idling of the spindle 18 in the controller 28 during the vibration monitoring time period. The acquired rotational vibration is taken into the arithmetic unit 34 via the amplifier and filter circuit 32 . In the arithmetic unit 34, arithmetic analysis by Fourier transform (Fourier series expansion) is performed on the captured slip vibration. Specifically, the time oscillation f(t) is
　ｆ（ｔ）＝Σ（ａｊｃｏｓ２πＪｔ＋ｂｊｓｉｎ２πＪｔ）で表される。なお、ａｊは、周波数Ｊの余弦調和成分フーリエ係数であり、ｂｊは、周波数Ｊの正弦調和成分フーリエ係数である。 f(t)=Σ(a j cos2πJt+b j sin2πJt). Note that a j is the cosine harmonic component Fourier coefficient of frequency J, and b j is the sine harmonic component Fourier coefficient of frequency J.
　そして、周波数Ｊに対するフーリエ係数は、ａｊ＝１／２Ｔ∫ｆ（ｔ）ｃｏｓ（２πＪｔ）ｄｔ、及びｂｊ＝１／２Ｔ∫ｆ（ｔ）ｓｉｎ（２πＪｔ）ｄｔに基づいて、フーリエ級数展開を行う。なお、積分区間は、０~Ｔであり、この積分区間Ｔは、周期１／Ｊの整数倍とする。 Then the Fourier coefficients for frequency J are Fourier series expansion I do. The integration interval is from 0 to T, and the integration interval T is an integer multiple of the cycle 1/J.
　図３に示すように、表示ユニット４２には、トータルパワー表示窓４４、周波数スペクトル表示窓４６及びＮｏｎ−ＳＲＦ／ＳＲＦの比較表示窓４８が設けられており、フーリエ解析により演算された周波数スペクトラムが、目的に応じて、これらに表示される。 As shown in FIG. 3, the display unit 42 is provided with a total power display window 44, a frequency spectrum display window 46 and a non-SRF/SRF comparison display window 48, and the frequency spectrum calculated by Fourier analysis is displayed. , depending on the purpose, are displayed in these.
　具体的には、トータルパワー表示窓４４には、スピンドル１８の空転と共に変化する振動量の大きさが、リアルタイム性を有するトータルパワー（Ｇ２）として表示される。その際、縦軸には、加速度を二乗したトータルパワー（Ｇ２）が表示され、空転振動量の増減比が大きな変化量として表わされる。すなわち、小さな振動はより小さく、大きな振動はより大きく表示される。このため、周波数スペクトルでは判別し難いトータルのパワーエネルギーが判別され、これによりスピンドル１８の空転時の回転振動（さらには、加工振動）を表し、振動の増減等を鋭敏に表すことができる。なお、前方ベアリング１６ｆの回転振動の取得は、スピンドル１８が空転している間であればいつでもよいが、ヒストリー表示窓５０において、経年変化を比較する場合は、例えば、始業時に同一回転数でのデータを取得して記録する方が比較し易い。 Specifically, in the total power display window 44, the magnitude of the vibration amount that changes as the spindle 18 idles is displayed as a real-time total power (G 2 ). At that time, the vertical axis represents the total power (G 2 ) obtained by squaring the acceleration, and the increase/decrease ratio of the amount of idling vibration is represented as a large amount of change. That is, small vibrations are displayed smaller and large vibrations are displayed larger. For this reason, the total power energy, which is difficult to discern from the frequency spectrum, can be discriminated, thereby expressing rotational vibration (furthermore, machining vibration) during idling of the spindle 18, and increasing or decreasing the vibration, etc., can be sharply represented. The rotational vibration of the front bearing 16f can be acquired at any time while the spindle 18 is idling. Acquiring and recording the data is easier to compare.
　周波数スペクトル表示窓４６には、回転振動をフーリエ変換して得られた周波数スペクトルが表示される。そして、比較表示窓４８には、回転振動におけるＳＲＦの総和と、それ以外のＮｏｎ−ＳＲＦの総和との相対比（Ｎｏｎ−ＳＲＦの総和量／ＳＲＦの総和量）の変化量が、ドットグラフとして経時（毎秒）表示される。このドットグラフでは、回転振動中にＳＲＦの総和量が多いと、すなわち、前方ベアリング１６ｆが良の状態であると、下方に表示される一方、Ｎｏｎ−ＳＲＦの総和量が多いと、すなわち、前記前方ベアリング１６ｆが否の状態であると、上方に表示される。 The frequency spectrum display window 46 displays the frequency spectrum obtained by Fourier transforming the rotational vibration. In the comparison display window 48, the amount of change in the relative ratio between the total SRF in rotational vibration and the total non-SRF (total amount of non-SRF/total amount of SRF) is displayed as a dot graph. Elapsed time (every second) is displayed. In this dot graph, when the total amount of SRF during rotational vibration is large, that is, when the front bearing 16f is in a good state, it is displayed at the bottom. It is displayed above that the front bearing 16f is in the no condition.
　ここで、本実施形態では、コントローラ２８により、スピンドル１８の空転時における前方ベアリング１６ｆの回転振動が処理されている。その際、周波数スペクトル表示窓４６において、例えば、回転振動中にＮｏｎ−ＳＲＦの総和量が多く出て、比較表示窓４８の相対比が、予兆閾値５８を上回って表示されている場合がある。従って、前方ベアリング１６ｆは、損傷判別の予兆段階に入ったと判断され、前記前方ベアリング１６ｆの交換作業に移行される。さらに、トータルパワー表示窓４４では、トータルパワーの値が大きくなっている。これにより、前方ベアリング１６ｆに摩耗が発生していると判断され、スピンドル１８は、予兆段階に入った状態で、正常に回転していることが確認できる。 Here, in this embodiment, the controller 28 processes rotational vibration of the front bearing 16f when the spindle 18 idles. At that time, in the frequency spectrum display window 46 , for example, a large amount of non-SRF total sum appears during rotational vibration, and the relative ratio in the comparison display window 48 may exceed the indication threshold 58 . Therefore, it is determined that the front bearing 16f has entered the premonitory stage of damage determination, and the replacement work of the front bearing 16f is started. Furthermore, in the total power display window 44, the total power value is large. As a result, it is determined that the front bearing 16f is worn, and it can be confirmed that the spindle 18 is rotating normally in the premonitory stage.
　ここで、相対比が予兆閾値５８を上方に超えた際、前方ベアリング１６ｆは、各部品に損傷が発生していなくてもよく、あるいは、僅かな損傷が発生していてもよい。オペレータは、予兆閾値５８を任意に設定することにより、所望の状態で、前方ベアリング１６ｆを交換することができる。また、オペレータは、異常閾値６０を任意に設定することが可能である。 Here, when the relative ratio exceeds the sign threshold value 58 upward, the front bearing 16f may have no damage to each part, or may have slight damage. By arbitrarily setting the warning threshold 58, the operator can replace the front bearing 16f in a desired state. Also, the operator can arbitrarily set the abnormality threshold 60 .
　一方、図３中、測定開始後の７秒~１７秒までの加工振動領域では、周波数スペクトル表示窓４６に示されるように、回転振動中にＳＲＦの総和量が多く出て、比較表示窓４８の比較比（相対比）が、予兆閾値５８を下回っている場合がある。しかしながら、これらは加工振動が主体であるため、前方ベアリング１６ｆの良否判定の対象外である。 On the other hand, in the machining vibration region from 7 seconds to 17 seconds after the start of measurement in FIG. The comparison ratio (relative ratio) of is below the sign threshold 58 in some cases. However, since these are mainly machining vibrations, they are out of the scope of the quality judgment of the front bearing 16f.
　この場合、本実施形態では、比較表示窓４８に表示される比較比の大小を観察するだけで、前方ベアリング１６ｆの良否をマクロ的に一覧で検知することができるという効果が得られる。すなわち、主軸回転数ｒｐｍをパラメータとしたＳＲＦ振動とＮｏｎ−ＳＲＦ振動を用いるだけでよく、簡単な制御で、前方ベアリング１６ｆの良否判断、すなわち、交換タイミング判断が高精度且つ効率的に遂行可能になる。 In this case, in the present embodiment, it is possible to macroscopically detect the quality of the front bearing 16f in a list simply by observing the magnitude of the comparison ratio displayed in the comparison display window 48. That is, it is only necessary to use SRF vibration and non-SRF vibration with the main shaft rotation speed rpm as a parameter, and it is possible to perform a simple control to determine whether the front bearing 16f is good or bad, that is, to determine the replacement timing with high accuracy and efficiency. Become.
　さらに、比較表示窓４８には、予兆閾値５８が設定されている。これにより、Ｎｏｎ−ＳＲＦの総和量／ＳＲＦの総和量の比較比が上がって、予兆閾値５８を上回ると、前方ベアリング１６ｆが損傷前の予兆段階に入ったと判断されるため、例えば、機械オペレータ等に喚起を行うことができる。 Furthermore, an omen threshold 58 is set in the comparison display window 48 . As a result, when the comparative ratio of the total amount of Non-SRF/the total amount of SRF increases and exceeds the sign threshold 58, it is determined that the front bearing 16f has entered the sign stage before damage. can be called to
１０…ベアリング良否判定システム　１２…工作機械
１４…ハウジング　　　　　　　　　１６ｆ…前方ベアリング
１６ｂ…後方ベアリング　　　　　　１８…スピンドル
２０…ツールホルダ　　　　　　　　２２…カッタ
２４…加速度センサ　　　　　　　　２８…コントローラ
３０…工作機械制御盤　　　　　　　３４…演算ユニット
３６…入力設定ユニット　　　　　　３８…回転振動判断ユニット
４０…入出力ユニット　　　　　　　４２…表示ユニット
４４…トータルパワー表示窓　　　　４６…周波数スペクトル表示部
４８…比較表示窓　　　　　　　　　５０…ヒストリー表示窓
５４、５８…予兆閾値　　　　　　　５６…アラーム閾値
６０…異常閾値 DESCRIPTION OF SYMBOLS 10... Bearing quality determination system 12... Machine tool 14... Housing 16f... Front bearing 16b... Rear bearing 18... Spindle 20... Tool holder 22... Cutter 24... Acceleration sensor 28... Controller 30... Machine tool control panel 34... Operation unit 36... Input setting unit 38 Rotational vibration determination unit 40 Input/output unit 42 Display unit 44 Total power display window 46 Frequency spectrum display section 48 Comparison display window 50 History display windows 54, 58 Prediction threshold 56 Alarm threshold 60...Abnormality threshold

Claims (8)

  1. 　主軸に取り付けられた回転工具を介してワークに加工処理を施す工作機械において、前記主軸を回転自在に支持するベアリングの良否を判定する工作機械のベアリング良否判定方法であって、
    　前記主軸の空転時に、前記ベアリングの回転振動を検出する工程と、
    　前記回転振動をフーリエ級数展開により解析し、振動周波数を得る工程と、
    　前記振動周波数を、主軸回転数÷６０から算出される主軸回転周波数（ＳＲＦ）及びその高調波（該主軸回転周波数の整数倍）の総和である総和ＳＲＦと、全ての前記振動周波数から前記総和ＳＲＦを除去した残余周波数（Ｎｏｎ−ＳＲＦ）と、に分割する工程と、
    　前記総和ＳＲＦと前記残余周波数とを比較することにより、前記ベアリングの良否を判定する工程と、
    　を有することを特徴とする工作機械のベアリング良否判定方法。     A bearing quality determination method for a machine tool for determining the quality of a bearing that rotatably supports a spindle in a machine tool that processes a workpiece via a rotary tool attached to the spindle, comprising:
    a step of detecting rotational vibration of the bearing when the spindle idles;
    a step of analyzing the rotational vibration by Fourier series expansion to obtain a vibration frequency;
    The vibration frequency is calculated from the total SRF, which is the sum of the spindle rotation frequency (SRF) calculated from the spindle rotation number divided by 60 and its harmonics (integer multiples of the spindle rotation frequency), and the total SRF from all the vibration frequencies. and a residual frequency (Non-SRF) from which the is removed;
    a step of determining whether the bearing is good or bad by comparing the total SRF and the residual frequency;
    A bearing quality judgment method for a machine tool, comprising:
  2. 　請求項１記載のベアリング良否判定方法において、前記総和ＳＲＦと前記残余周波数との相対比を、経時変化する比較表示窓に表示させ、前記比較表示窓から前記ベアリングの良否を判別することを特徴とする工作機械のベアリング良否判定方法。 2. The bearing quality determination method according to claim 1, wherein the relative ratio between the total SRF and the residual frequency is displayed in a comparison display window that changes with time, and the quality of the bearing is determined from the comparison display window. A method for judging the quality of bearings in machine tools.
  3. 　請求項２記載のベアリング良否判定方法において、前記比較表示窓には、異常閾値が設定されており、前記相対比が、前記異常限閾値を上回る際に、前記ベアリングに損傷が発生していると判定されることを特徴とする作業機械のベアリング良否判定方法。 3. The bearing quality determination method according to claim 2, wherein an abnormality threshold is set in the comparison display window, and when the relative ratio exceeds the abnormality limit threshold, it is determined that the bearing is damaged. A method for judging quality of a bearing for a work machine, characterized by:
  4. 　請求項２記載のベアリング良否判定方法において、前記比較表示窓には、予兆閾値が設定されており、前記相対比が、前記予兆閾値を上回る際に、前記ベアリングが損傷前の予兆段階に入ったと判定されることを特徴とする作業機械のベアリング良否判定方法。 3. In the bearing quality determination method according to claim 2, a predictive threshold is set in the comparison display window, and when the relative ratio exceeds the predictive threshold, it is determined that the bearing has entered a pre-damage predictive stage. A method for judging quality of a bearing for a work machine, characterized by:
  5. 　主軸に取り付けられた回転工具を介してワークに加工処理を施す工作機械において、前記主軸を回転自在に支持するベアリングの良否を判定する工作機械のベアリング良否判定システムであって、
    　前記主軸の空転時に、前記ベアリングの回転振動を検出する振動検出機構と、
    　前記回転振動をフーリエ級数展開により解析し、振動周波数を得る演算機構と、
    　前記振動周波数を、主軸回転数÷６０から算出される主軸回転周波数（ＳＲＦ）及びその高調波（該主軸回転周波数の整数倍）の総和である総和ＳＲＦと、全ての前記振動周波数から前記総和ＳＲＦを除去した残余周波数（Ｎｏｎ−ＳＲＦ）と、に分割する周波数分割機構と、
    　前記総和ＳＲＦと前記残余周波数とを比較することにより、前記ベアリングの良否を判定する比較判定機構と、
    　を備えていることを特徴とする作業機械のベアリング良否判定システム。     A bearing quality determination system for a machine tool for determining the quality of a bearing that rotatably supports a spindle in a machine tool that processes a workpiece via a rotary tool attached to the spindle, comprising:
    a vibration detection mechanism that detects rotational vibration of the bearing when the main shaft idles;
    an arithmetic mechanism for analyzing the rotational vibration by Fourier series expansion and obtaining a vibration frequency;
    The vibration frequency is calculated from the total SRF, which is the sum of the spindle rotation frequency (SRF) calculated from the spindle rotation number divided by 60 and its harmonics (integer multiples of the spindle rotation frequency), and the total SRF from all the vibration frequencies. a residual frequency (Non-SRF) with the
    a comparing and judging mechanism for judging the quality of the bearing by comparing the total SRF and the residual frequency;
    A bearing quality judgment system for a work machine, comprising:
  6. 　請求項５記載のベアリング良否判定システムにおいて、前記総和ＳＲＦと前記残余周波数との相対比を、経時変化して表示させる比較表示窓を備えていることを特徴とする工作機械のベアリング良否判定システム。 The bearing quality determination system for a machine tool according to claim 5, further comprising a comparison display window that displays the relative ratio between the total SRF and the residual frequency as it changes over time.
  7. 　請求項６記載のベアリング良否判定システムにおいて、前記比較表示窓には、前記ベアリングに損傷が発生している判定させるための異常閾値が設定されていることを特徴とする作業機械のベアリング良否判定システム。 7. A bearing quality determination system for a working machine according to claim 6, wherein an abnormality threshold for determining that said bearing is damaged is set in said comparison display window. .
  8. 　請求項６記載のベアリング良否判定システムにおいて、前記比較表示窓には、前記ベアリングが損傷前の予兆段階に入ったと判定させるための予兆閾値が設定されていることを特徴とする作業機械のベアリング良否判定システム。 7. The bearing quality determination system according to claim 6, wherein a predictive threshold value for determining that the bearing has entered a predictive stage before damage is set in the comparison display window. judgment system.
PCT/JP2022/039805 2021-10-14 2022-10-14 Working machine bearing quality determining method and system WO2023063435A1 (en)

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JPS62193751A (en) * 1986-02-19 1987-08-25 Ichiro Inazaki Multi-blade tool damage detecting device
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