JP4891150B2 - Vibration suppressor for machine tools - Google Patents

Vibration suppressor for machine tools Download PDF

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JP4891150B2
JP4891150B2 JP2007135896A JP2007135896A JP4891150B2 JP 4891150 B2 JP4891150 B2 JP 4891150B2 JP 2007135896 A JP2007135896 A JP 2007135896A JP 2007135896 A JP2007135896 A JP 2007135896A JP 4891150 B2 JP4891150 B2 JP 4891150B2
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chatter
vibration
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rotation speed
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JP2008290164A (en
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浩 稲垣
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オークマ株式会社
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本発明は、工具又はワークを回転させながら加工を行う工作機械において、加工中に発生する振動を抑制するための振動抑制装置に関するものである。   The present invention relates to a vibration suppressing device for suppressing vibration generated during machining in a machine tool that performs machining while rotating a tool or a workpiece.
従来より、たとえば回転可能な主軸にワークを支持させ、ワークに対して工具を送りながら、ワークに加工を施すといった工作機械がある。該工作機械においては、切削加工における切り込み量を必要以上に大きくすると、加工中に所謂「びびり振動」が発生して、加工面の仕上げ精度を悪化させてしまうという問題がある。このとき、特に問題となるのは、工具とワークとの間に生じる自励振動である「再生型びびり振動」と、工具を備える工作機械が振動源となる「強制びびり振動」である。このうち再生型びびり振動については、特許文献1、2に記載されているように、加工を行うにあたって、工具やワーク等のびびり振動が生じる系の固有振動数や加工中におけるびびり振動数を求め、固有振動数又はびびり振動数を60倍して工具刃数及び所定の整数で除した値を回転速度とすればよいことが知られている。一方、強制びびり振動の場合は、回転速度をずらす、送り速度を下げる、ワークへの切り込みを小さくする、といった対応が有効であることがわかっている。   2. Description of the Related Art Conventionally, for example, there is a machine tool that supports a workpiece on a rotatable main shaft and processes the workpiece while feeding a tool to the workpiece. In the machine tool, if the depth of cut in the cutting process is increased more than necessary, there is a problem that so-called “chatter vibration” occurs during the process, and the finished accuracy of the processed surface is deteriorated. Particularly problematic at this time are “regenerative chatter vibration” that is self-excited vibration generated between the tool and the workpiece, and “forced chatter vibration” in which the machine tool including the tool is a vibration source. Of these, with regard to regenerative chatter vibration, as described in Patent Documents 1 and 2, when processing, the natural frequency of the system in which chatter vibration of tools and workpieces occurs and the chatter frequency during machining are obtained. It is known that a value obtained by multiplying the natural frequency or chatter frequency by 60 and dividing by the number of tool blades and a predetermined integer may be used as the rotation speed. On the other hand, in the case of forced chatter vibration, it has been found that countermeasures such as shifting the rotation speed, lowering the feed speed, and reducing the cut into the workpiece are effective.
特開2003−340627号公報JP 2003-340627 A 特表2001−517557号公報JP-T-2001-517557
しかし、びびり振動数は、数10Hzから10kHzと広範囲に及ぶにもかかわらず、単一のサンプリング振動数によってフーリエ解析を行う等してびびり振動数を求めていたため、測定分解能に限界があり、全ての範囲で短時間且つ高精度にびびり振動数を検出することができない。従って、回転速度の変更が常に的確とは言えず、びびり振動の効果的な抑制に繋がらないという問題があった。   However, although the chatter frequency ranges from several tens of Hz to 10 kHz, the chatter frequency is obtained by performing Fourier analysis with a single sampling frequency, etc., so there is a limit to the measurement resolution. The chatter frequency cannot be detected for a short time and with high accuracy in the range of. Accordingly, there has been a problem that the change of the rotation speed is not always accurate and does not lead to effective suppression of chatter vibration.
そこで、本発明は、上記問題に鑑みなされたものであって、びびり振動数を広範囲で短時間且つ高精度に求めることができ、正確な最適回転速度を計算してびびり振動を効果的に抑制可能な工作機械の振動抑制装置を提供しようとするものである。   Therefore, the present invention has been made in view of the above problems, and can determine chatter frequency over a wide range in a short time and with high accuracy, and can accurately suppress chatter vibration by calculating an accurate optimum rotation speed. An object of the present invention is to provide a vibration suppressing device for a machine tool that can be used.
上記目的を達成するために、請求項1に記載の発明は、工具又はワークを回転させるための回転軸を備えた工作機械において、前記回転軸を回転させた際に生じるびびり振動を抑制するための振動抑制装置であって、回転中の前記回転軸の時間領域での振動加速度を検出する検出手段と、検出手段により検出された時間領域の振動加速度を予め設定された夫々異なるサンプリング振動数で解析してびびり振動数とその加速度とを得る複数の信号解析手段と、何れかの信号解析手段で算出したびびり振動数の加速度が所定の基準値を超えた場合、所定のパラメータに基づき、びびり振動を抑制可能な前記回転軸の最適回転速度を算出する演算手段と、その演算手段により算出された最適回転速度にて前記回転軸を回転させる回転速度制御手段と、を備え、前記演算手段は、前記複数の信号解析手段で得られた複数のびびり振動数を所定の閾値と夫々比較し、前記複数のびびり振動数が前記所定の閾値よりも低い場合には、前記複数の信号解析手段のうち前記サンプリング振動数の低い信号解析手段が解析して得たびびり振動数を、前記複数のびびり振動数が前記所定の閾値よりも高い場合には、前記複数の信号解析手段のうち前記サンプリング振動数の高い信号解析手段が解析して得たびびり振動数を夫々選択して最適回転速度を算出することを特徴とするものである。 In order to achieve the above object, the invention according to claim 1 is a machine tool having a rotating shaft for rotating a tool or a workpiece, in order to suppress chatter vibration generated when the rotating shaft is rotated. of a vibration suppressing device, a detecting means for detecting the vibration acceleration in the time domain of the rotary shaft during rotation, the vibration acceleration of the detected time domain preset respectively at different sampling frequencies by the detection means A plurality of signal analyzing means for analyzing and obtaining chatter frequency and its acceleration, and when the acceleration of chatter frequency calculated by any of the signal analyzing means exceeds a predetermined reference value, the chatter frequency is determined based on a predetermined parameter. Calculation means for calculating the optimum rotation speed of the rotation shaft capable of suppressing vibration, and rotation speed control means for rotating the rotation shaft at the optimum rotation speed calculated by the calculation means; Wherein the calculating means, the plurality of the plurality of chatter frequencies obtained by the signal analyzing means to a predetermined threshold value and each comparison, if the plurality of chatter frequency is lower than the predetermined threshold, The chatter frequency obtained by analysis by the signal analysis means having a low sampling frequency among the plurality of signal analysis means, and when the plurality of chatter frequencies are higher than the predetermined threshold, the plurality of signals Among the analysis means, the signal analysis means having a high sampling frequency selects the chatter frequency obtained by analysis and calculates the optimum rotational speed.
請求項2に記載の発明は、請求項1に記載の発明において、演算手段は、所定のパラメータとなる下記の演算式(1)〜(3)に基づいて最適回転速度の演算を行うようにしたものである。
k’値=60×びびり振動数/(工具刃数×回転軸回転速度) ・・・(1)
k値=k’値の整数部 ・・・(2)
最適回転速度=60×びびり振動数/(工具刃数×k値)・・・(3)
According to a second aspect of the present invention, in the first aspect of the present invention, the calculation means calculates the optimum rotational speed based on the following calculation formulas (1) to (3) which are predetermined parameters. It is a thing.
k ′ value = 60 × chat vibration frequency / (number of tool blades × rotational axis rotation speed) (1)
k value = integer part of k ′ value (2)
Optimal rotation speed = 60 x chatter frequency / (number of tool blades x k value) (3)
本発明によれば、実際に回転している回転軸に生じるびびり振動に基づいて最適回転速度を算出するため、より正確な最適回転速度を直ちに算出することができると共に、算出した最適回転速度を直ちに回転軸の回転に活かすことができる。特にここでは、サンプリング振動数が異なる信号解析手段を複数備えて、演算手段は、各信号解析手段で得られた解析結果から最適な精度を持つびびり振動数を選択して最適回転速度を算出するので、びびり振動数を広範囲で短時間且つ高精度に求めることができ、正確な最適回転速度を計算してびびり振動を効果的に抑制可能となる。従って、加工面の仕上げ精度を高品位に保つことができ、工具摩耗の抑制、工具欠損の防止も期待できる。
According to the present invention, since the optimum rotation speed is calculated based on chatter vibration generated in the rotating shaft that is actually rotating, it is possible to immediately calculate a more accurate optimum rotation speed and to calculate the calculated optimum rotation speed. Immediately, it can be used to rotate the rotating shaft. In particular, here, a plurality of signal analysis means having different sampling frequencies are provided, and the calculation means selects the chatter frequency having the optimum accuracy from the analysis result obtained by each signal analysis means and calculates the optimum rotation speed. Therefore, the chatter frequency can be obtained in a wide range in a short time and with high accuracy, and an accurate optimum rotational speed can be calculated to effectively suppress chatter vibration. Therefore, the finishing accuracy of the machined surface can be maintained at a high quality, and it can be expected to suppress the tool wear and prevent the tool from being lost.
以下、本発明の一実施形態となる振動抑制装置について、図面をもとに説明する。   Hereinafter, a vibration suppression device according to an embodiment of the present invention will be described with reference to the drawings.
図1は、振動抑制装置10のブロック構成を示した説明図である。図2は、振動抑制の対象となる回転軸ハウジング1を側面から示した説明図であり、図3は、回転軸ハウジング1を軸方向から示した説明図である。
振動抑制装置10は、回転軸ハウジング1にC軸周りで回転可能に備えられた回転軸3に生じるびびり振動を抑制するためのものであって、回転中の回転軸3に生じる時間領域の振動加速度を検出するための振動センサ(検出手段)2a〜2cと、該振動センサ2a〜2cによる検出値をもとにして回転軸3の回転速度を制御する制御装置5とを備えてなる。
FIG. 1 is an explanatory diagram showing a block configuration of the vibration suppressing device 10. FIG. 2 is an explanatory view showing the rotary shaft housing 1 to be subjected to vibration suppression from the side, and FIG. 3 is an explanatory view showing the rotary shaft housing 1 from the axial direction.
The vibration suppressing device 10 is for suppressing chatter vibration generated in the rotating shaft 3 provided in the rotating shaft housing 1 so as to be rotatable around the C axis, and is vibration in the time domain generated in the rotating rotating shaft 3. Vibration sensors (detecting means) 2a to 2c for detecting acceleration and a control device 5 for controlling the rotation speed of the rotary shaft 3 based on the detection values by the vibration sensors 2a to 2c are provided.
振動センサ2a〜2cは、図2及び3に示す如く回転軸ハウジング1に取り付けられており、一の振動センサは、他の振動センサに対して直角方向への時間領域の振動加速度(時間軸上の振動加速度を意味する)を検出するようになっている(たとえば、振動センサ2a〜2cにて、それぞれ直交するX軸、Y軸、Z軸方向での時間領域の振動加速度を検出するようにする)。   The vibration sensors 2a to 2c are attached to the rotary shaft housing 1 as shown in FIGS. 2 and 3, and one vibration sensor is a time domain vibration acceleration (on the time axis) in a direction perpendicular to the other vibration sensors. (For example, the vibration sensors 2a to 2c detect vibration accelerations in the time domain in the X-axis, Y-axis, and Z-axis directions orthogonal to each other, respectively). To do).
一方、制御装置5は、振動センサ2a〜2cから検出される時間領域の振動加速度をもとにした解析を、夫々異なるサンプリング振動数で行う信号解析手段としての複数のFFT演算装置6,6・・と、該FFT演算装置6の何れかで算出された値に基づいて最適回転速度の算出等を行う演算手段としてのパラメータ演算装置7と、回転軸ハウジング1における加工を制御する回転速度制御手段としてのNC装置8とを備えており、FFT演算装置6における後述の如き解析、及び回転軸3の回転速度のモニタリングを行っている。   On the other hand, the control device 5 includes a plurality of FFT operation devices 6, 6... As signal analysis means for performing analysis based on vibration acceleration in the time domain detected from the vibration sensors 2 a to 2 c at different sampling frequencies. A parameter calculation device 7 as calculation means for calculating the optimum rotation speed based on a value calculated by any one of the FFT calculation devices 6, and a rotation speed control means for controlling machining in the rotary shaft housing 1. And an analysis as described later in the FFT arithmetic unit 6 and monitoring of the rotational speed of the rotary shaft 3.
以下、制御装置5におけるびびり振動の抑制制御について、図5のフローチャートに基づいて説明する。
まず、回転中に常時検出される振動センサ2a〜2cにおける時間領域の振動加速度の信号を各FFT演算装置6へ分配し、夫々のFFT演算装置6において設定されたサンプリング振動数でフーリエ解析を行い(S1)、図4の4に示すような最大加速度とその振動数(びびり振動数)とを夫々算出する(S2)。
次に、パラメータ演算装置7で、上記S2で算出された各最大加速度と予め設定された所定の基準値とを比較し(S3)、何れか一つの最大加速度が基準値を超えた場合には、回転軸3に抑制すべきびびり振動が生じているとして、S4において、算出されたびびり振動数の値と予め設定された振動数の閾値とを比較して、最適のサンプリング振動数で得たびびり振動数を選択する。
Hereinafter, the chatter vibration suppression control in the control device 5 will be described based on the flowchart of FIG. 5.
First, the vibration acceleration signals in the time domain of the vibration sensors 2a to 2c that are constantly detected during rotation are distributed to each FFT arithmetic unit 6, and Fourier analysis is performed with the sampling frequency set in each FFT arithmetic unit 6. (S1) and the maximum acceleration as shown by 4 in FIG. 4 and its vibration frequency (chatter frequency) are calculated (S2).
Next, the parameter calculation device 7 compares each maximum acceleration calculated in S2 with a predetermined reference value set in advance (S3), and when any one of the maximum accelerations exceeds the reference value, Assuming that chatter vibration to be suppressed occurs on the rotary shaft 3, in S4, the calculated chatter frequency value is compared with a preset frequency threshold value and obtained at the optimum sampling frequency. Select chatter frequency.
例えば、サンプリング振動数を1kHz、10kHzとする2つのFFT演算装置があるとする。夫々の解析点数を1024とすると、最小分解能は前者で約1kHz,後者で約10kHzとなり、サンプリングに要する時間は夫々約1秒、0.1秒となる。
ここで検出されたびびり振動数が50Hz程度と低域の場合、最適回転速度を求めると、後者の装置では計算誤差が20%程度となるが、前者の装置では2%程度と高精度となる。一方、検出されたびびり振動数が400Hz程度と高域の場合、最適回転速度を求めると、前者の装置では最大加速度の測定精度が大幅に低下するのに対し、後者の装置では十分な分解能を持つことになる。また、後者の装置ではびびり振動数の計算誤差も2.5%と高精度となる。
For example, suppose that there are two FFT arithmetic units with sampling frequencies of 1 kHz and 10 kHz. When the number of analysis points is 1024, the minimum resolution is about 1 kHz for the former and about 10 kHz for the latter, and the time required for sampling is about 1 second and 0.1 second, respectively.
When the chatter frequency detected here is in the low range of about 50 Hz, the calculation error is about 20% in the latter device when the optimum rotation speed is obtained, but the accuracy is as high as about 2% in the former device. . On the other hand, when the detected chatter frequency is as high as about 400 Hz, when the optimum rotational speed is obtained, the measurement accuracy of the maximum acceleration is greatly reduced in the former device, whereas the latter device has sufficient resolution. Will have. Further, in the latter device, the calculation error of chatter frequency is as high as 2.5%.
従って、この場合、閾値を100Hzとして、これより低域の場合は前者のサンプリング振動数に係るFFT演算装置で解析されたびびり振動数を選択し、高域の場合は後者のサンプリング振動数に係るFFT演算装置で解析されたびびり振動数を選択するようにすれば、加速度の大きさや振動数の精度を損なうことなく目的のびびり振動数が取得できる。
なお、閾値を境にして低域側や高域側にFFT演算装置が複数ある場合は、低域側ではより低いサンプリング振動数のFFT演算装置を、高域側ではより高いサンプリング振動数のFFT演算装置を選択すればよい。
Therefore, in this case, the threshold value is set to 100 Hz, and if it is lower than this, the chatter frequency analyzed by the FFT arithmetic unit related to the former sampling frequency is selected, and if it is higher, the latter relates to the latter sampling frequency. If the chatter frequency analyzed by the FFT arithmetic unit is selected, the target chatter frequency can be acquired without impairing the magnitude of the acceleration and the accuracy of the frequency.
When there are a plurality of FFT operation devices on the low frequency side and the high frequency side with the threshold as a boundary, an FFT operation device with a lower sampling frequency is set on the low frequency side, and an FFT with a higher sampling frequency is set on the high frequency side. What is necessary is just to select an arithmetic unit.
次に、S5では、S4で取得されたびびり振動数、工具刃数、回転軸3の回転速度から以下の演算式(1)〜(3)により、最適回転速度の演算を行う。   Next, in S5, the optimum rotational speed is calculated from the chatter vibration frequency, the number of tool blades, and the rotational speed of the rotary shaft 3 acquired in S4 by the following arithmetic expressions (1) to (3).
k’値=60×びびり振動数/(工具刃数×回転軸回転速度) ・・・(1)
k値=k’値の整数部 ・・・(2)
最適回転速度=60×びびり振動数/(工具刃数×k値)・・・(3)
k ′ value = 60 × chat vibration frequency / (number of tool blades × rotational axis rotation speed) (1)
k value = integer part of k ′ value (2)
Optimal rotation speed = 60 x chatter frequency / (number of tool blades x k value) (3)
ここで、演算式(1)における「工具刃数」は、先の閾値等と共に予めパラメータ演算装置7に設定されているものとする。また、演算式(1)における回転軸回転速度とは、現在(最適回転速度とする前)の回転速度である。
そして、S6では、算出された最適回転速度となるように、NC装置8にて回転軸3の回転速度を変更して、びびり振動の増幅の防止、すなわち抑制を行う。
以上のようにして、制御装置5におけるびびり振動の抑制制御は行われる。
Here, it is assumed that the “number of tool blades” in the calculation formula (1) is set in the parameter calculation device 7 in advance together with the previous threshold value and the like. Further, the rotation shaft rotation speed in the calculation formula (1) is the current rotation speed (before the optimum rotation speed).
In S6, the NC device 8 changes the rotation speed of the rotary shaft 3 so as to obtain the calculated optimum rotation speed, thereby preventing chatter vibration from being amplified, that is, suppressing it.
As described above, chatter vibration suppression control in the control device 5 is performed.
このように、上記形態の振動制御装置10によれば、振動センサ2a〜2c、FFT演算装置6、及びパラメータ演算装置7により回転軸3の回転中に生じるびびり振動をリアルタイムでモニタリングしており、びびり振動の発生が検出されると、上記演算式(1)〜(3)により直ちに最適回転速度を算出して、回転軸3の回転速度を該最適回転速度としてびびり振動の増幅を抑制する。すなわち、実際に回転している回転軸3に生じたびびり振動に基づいて最適回転速度を算出するため、より正確な最適回転速度を直ちに算出することができる。特にここでは、サンプリング振動数が異なるFFT演算装置6を複数備えて、パラメータ演算装置7は、各FFT演算装置6で得られた解析結果から最適な精度を持つびびり振動数を選択して最適回転速度を算出するので、びびり振動数を広範囲で短時間且つ高精度に求めることができ、正確な最適回転速度を計算してびびり振動を効果的に抑制可能となる。従って、加工面の仕上げ精度を高品位に保つことができ、工具摩耗の抑制、工具欠損の防止も期待できる。   Thus, according to the vibration control device 10 of the above embodiment, chatter vibration generated during the rotation of the rotary shaft 3 is monitored in real time by the vibration sensors 2a to 2c, the FFT calculation device 6, and the parameter calculation device 7. When occurrence of chatter vibration is detected, the optimum rotational speed is immediately calculated by the above-described arithmetic expressions (1) to (3), and amplification of chatter vibration is suppressed with the rotational speed of the rotating shaft 3 as the optimum rotational speed. That is, since the optimum rotation speed is calculated based on chatter vibration generated in the rotating shaft 3 that is actually rotating, a more accurate optimum rotation speed can be immediately calculated. In particular, here, a plurality of FFT operation devices 6 having different sampling frequencies are provided, and the parameter operation device 7 selects a chatter frequency having the optimum accuracy from the analysis result obtained by each FFT operation device 6 and performs the optimum rotation. Since the speed is calculated, the chatter frequency can be obtained in a wide range in a short time and with high accuracy, and an accurate optimum rotational speed can be calculated to effectively suppress chatter vibration. Therefore, the finishing accuracy of the machined surface can be maintained at a high quality, and it can be expected to suppress the tool wear and prevent the tool from being lost.
なお、本発明の振動抑制装置に係る構成は、上記実施の形態に記載した態様に何ら限定されるものではなく、検出手段、制御装置、及び制御装置における振動抑制の制御等に係る構成を、本発明の趣旨を逸脱しない範囲で、必要に応じて適宜変更することができる。   The configuration related to the vibration suppression device of the present invention is not limited to the mode described in the above embodiment, and the configuration related to vibration suppression control in the detection means, the control device, and the control device, The present invention can be changed as appropriate without departing from the spirit of the present invention.
たとえば、上記形態では、加速度センサからの信号を複数に分配し、夫々異なるサンプリング振動数で解析する方法となっているが、所定の方向を測定する加速度ピックアップを複数個設置して夫々の信号を解析する方法であっても本発明の採用は可能である。
また、演算式(1)〜(3)やここで用いるk値等は適宜変更しても差し支えない。
さらに、上記実施形態では、検出手段にて検出される時間領域の振動加速度のフーリエ解析を行った際、周波数領域の振動加速度が最大値を示す波形を使用して、びびり振動の抑制に係る制御を行うようにしているが、周波数領域の振動加速度の値が上位の複数(たとえば、3つ)の波形を用いて最適回転速度を算出するようにして、びびり振動の抑制効果の更なる向上を図ってもよい。
For example, in the above embodiment, the signal from the acceleration sensor is divided into a plurality of signals and analyzed at different sampling frequencies. However, a plurality of acceleration pickups for measuring a predetermined direction are installed and each signal is transmitted. The present invention can be adopted even with the analysis method.
In addition, the arithmetic expressions (1) to (3) and the k value used here may be appropriately changed.
Furthermore, in the above embodiment, when Fourier analysis of the vibration acceleration in the time domain detected by the detection means is performed, the control related to suppression of chatter vibration is performed using a waveform in which the vibration acceleration in the frequency domain shows the maximum value. However, the optimal rotational speed is calculated using a plurality of (for example, three) waveforms with the highest vibration acceleration value in the frequency domain, and the chatter vibration suppression effect is further improved. You may plan.
その他、上記実施形態では、工具を回転させる所謂マシニングセンタ等の工作機械の回転軸における振動を検出する構成としているが、回転しない側(固定側)であるワーク又はその近傍の振動を検出するようにしても良い。更には、旋盤などワークを回転させる工作機械にも適用可能であり、その場合には回転軸であるワークを保持する主軸側の振動を検出したり、固定側である工具の振動を検出したりすることができる。尚、検出手段の設置位置や設置数等を、工作機械の種類、大きさ等に応じて適宜変更してもよいことは言うまでもない。
In addition, in the above-described embodiment, the vibration is detected in the rotating shaft of a machine tool such as a so-called machining center that rotates the tool. May be. Furthermore, it can also be applied to a machine tool that rotates a workpiece such as a lathe. In that case, it detects vibrations on the spindle side that holds the workpiece that is the rotation axis, or detects vibrations on the tool that is on the fixed side. can do. Needless to say, the installation position, the number of installations, and the like of the detection means may be appropriately changed according to the type and size of the machine tool.
振動抑制装置のブロック構成を示した説明図である。It is explanatory drawing which showed the block structure of the vibration suppression apparatus. 振動抑制の対象となる回転軸ハウジングを側面から示した説明図である。It is explanatory drawing which showed the rotating shaft housing used as the object of vibration suppression from the side surface. 回転軸ハウジングを軸方向から示した説明図である。It is explanatory drawing which showed the rotating shaft housing from the axial direction. 時間領域の振動加速度のフーリエ解析結果の一例を示した説明図である。It is explanatory drawing which showed an example of the Fourier-analysis result of the vibration acceleration of a time domain. びびり振動の抑制制御に係るフローチャートである。It is a flowchart which concerns on suppression control of chatter vibration.
符号の説明Explanation of symbols
1・・回転軸ハウジング、2a、2b、2c・・振動センサ、3・・回転軸、5・・制御装置、6・・FFT演算装置、7・・パラメータ演算装置、8・・NC装置、10・・振動抑制装置。   1 ··· Rotating shaft housing, 2a, 2b, 2c ·· Vibration sensor, 3 ··· Rotating shaft, 5 ·· Control device, 6 ·· FFT computing device, 7 ·· Parameter computing device, 8 ·· NC device, 10 ..Vibration suppression devices

Claims (2)

  1. 工具又はワークを回転させるための回転軸を備えた工作機械において、前記回転軸を回転させた際に生じるびびり振動を抑制するための振動抑制装置であって、
    回転中の前記回転軸の時間領域での振動加速度を検出する検出手段と、検出手段により検出された時間領域の振動加速度を予め設定された夫々異なるサンプリング振動数で解析してびびり振動数とその加速度とを得る複数の信号解析手段と、何れかの信号解析手段で算出したびびり振動数の加速度が所定の基準値を超えた場合、所定のパラメータに基づき、びびり振動を抑制可能な前記回転軸の最適回転速度を算出する演算手段と、その演算手段により算出された最適回転速度にて前記回転軸を回転させる回転速度制御手段と、を備え、
    前記演算手段は、前記複数の信号解析手段で得られた複数のびびり振動数を所定の閾値と夫々比較し、前記複数のびびり振動数が前記所定の閾値よりも低い場合には、前記複数の信号解析手段のうち前記サンプリング振動数の低い信号解析手段が解析して得たびびり振動数を、前記複数のびびり振動数が前記所定の閾値よりも高い場合には、前記複数の信号解析手段のうち前記サンプリング振動数の高い信号解析手段が解析して得たびびり振動数を夫々選択して最適回転速度を算出することを特徴とする工作機械の振動抑制装置。
    In a machine tool provided with a rotating shaft for rotating a tool or a workpiece, a vibration suppressing device for suppressing chatter vibration generated when the rotating shaft is rotated,
    Detecting means for detecting the vibration acceleration in the time domain of the rotary shaft during rotation, frequency chatter by analyzing a preset respectively different sampling frequencies of vibration acceleration of the detected time domain by the detecting means and its A plurality of signal analysis means for obtaining acceleration, and the rotation shaft capable of suppressing chatter vibration based on a predetermined parameter when the acceleration of chatter frequency calculated by any of the signal analysis means exceeds a predetermined reference value Calculation means for calculating the optimum rotation speed of the rotation speed control means for rotating the rotation shaft at the optimum rotation speed calculated by the calculation means,
    The arithmetic means compares the plurality of chatter frequencies obtained by the plurality of signal analysis means with a predetermined threshold value, respectively, and when the plurality of chatter frequencies are lower than the predetermined threshold value, Of the signal analysis means, the chatter frequency obtained by the analysis by the signal analysis means having a low sampling frequency, and when the plurality of chatter frequencies are higher than the predetermined threshold, the plurality of signal analysis means Among them, the vibration suppression device for a machine tool is characterized in that the optimum rotational speed is calculated by selecting each chatter frequency obtained by analysis by the signal analysis means having a high sampling frequency .
  2. 演算手段は、所定のパラメータとなる下記の演算式(1)〜(3)に基づいて最適回転速度の演算を行うものである請求項1に記載の工作機械の振動抑制装置。
    k’値=60×びびり振動数/(工具刃数×回転軸回転速度) ・・・(1)
    k値=k’値の整数部 ・・・(2)
    最適回転速度=60×びびり振動数/(工具刃数×k値)・・・(3)
    The vibration suppression device for a machine tool according to claim 1, wherein the calculation means calculates the optimum rotation speed based on the following calculation formulas (1) to (3) serving as predetermined parameters.
    k ′ value = 60 × chat vibration frequency / (number of tool blades × rotational axis rotation speed) (1)
    k value = integer part of k ′ value (2)
    Optimal rotation speed = 60 x chatter frequency / (number of tool blades x k value) (3)
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