JP5637840B2 - Vibration detection method - Google Patents

Description

The present invention relates to vibration detection method for detecting chattering of a machine tool odor for machining while rotating the tool or work Te occur during pressurization Engineering.

2. Description of the Related Art Conventionally, for example, in a machine tool that cuts the surface of a workpiece by rotating a tool, chatter vibration may occur during machining due to the low rigidity of the tool. Thus, as a technique for detecting this chatter vibration, for example, there is a technique described in Patent Document 1. This is to detect chatter vibration and its frequency (chatter frequency) using a microphone (hereinafter referred to as a microphone) capable of detecting sound pressure. It is also known that the following formulas (1) and (2) as disclosed in Patent Document 2, for example, may be used when obtaining the stable rotational speed using the detected chatter frequency in this way. Yes.
Stable rotational speed = {60 × chat frequency / number of tool blades × (k value + 1)} (1)
k value = 60 × chatter frequency / integer part of (current rotation speed × number of tool blades) (2)
The number of tool blades is, for example, the number of blades of a tool mounted on a main shaft as a rotation axis.

JP-T-2001-517557 JP 2007-44852 A

  Generally, during processing, a sound similar to vibration sound may be generated due to vibration or noise different from chatter vibration. However, with the technique described in Patent Document 1, it cannot be determined whether the detected vibration and frequency are due to chatter vibration (that is, chatter frequency) or due to vibration or noise other than chatter vibration. For this reason, when using the equations (1) and (2) disclosed in Patent Document 2, an accurate stable rotation speed may not be obtained.

The present invention has been made in view of the above, it can capture the chatter frequency accurately, and thus even accurate vibration that can also be made calculation of stable rotational speed motion detection method It is something to be offered.

To achieve the above object, the invention according to claim 1 of the present invention is a machine tool having a rotary shaft for rotating the factory tools or work, for detecting the chatter vibration occurring in the rotary shaft The vibration detection method of the first step of arbitrarily setting the detection range on the frequency axis , outputting a sound of a predetermined frequency, and changing the lower limit of the detection range based on the output sound, A second step of detecting vibration on the time axis generated on the rotation axis, a third step of obtaining the vibration on the frequency axis by performing FFT analysis on the vibration on the time axis, and the vibration on the frequency axis Among the fourth step of outputting a sound having a frequency at which the vibration is maximum within the detection range, and whether or not the vibration sound resulting from chatter vibration generated from the rotating shaft matches the output sound. And if they match Is characterized by performing a fifth step of identifying as a chatter frequency for the frequency of the output sounds to the chatter vibration.
The invention according to claim 2 is the invention according to claim 1, wherein, in the fifth step, when the vibration sound is higher than the output sound, the lower limit of the detection range is set to the lower limit of the output sound. On the other hand, when the output sound is lower than the output sound, the upper limit of the detection range is changed to a frequency lower than the frequency of the output sound when the output sound is lower than the output sound. Thereafter, a sound having a frequency included in the detection range after the change is newly output.

According to the present invention , the detection range is arbitrarily set on the frequency axis, a sound having a predetermined frequency is output, and the lower limit of the detection range is changed based on the output sound, and the rotation axis is generated. The second step of detecting vibration on the time axis, the third step of obtaining the vibration on the frequency axis by performing FFT analysis on the vibration on the time axis, and within the detection range among the vibrations on the frequency axis The fourth step of outputting the sound of the frequency at which the vibration is maximum in the process, and whether or not the vibration sound resulting from chatter vibration generated from the rotating shaft and the output sound match, In this case, the operator sets the detection range arbitrarily and performs detection based on the output sound in order to execute the fifth step of specifying the frequency of the output sound as the chatter frequency related to chatter vibration. after you change the lower limit of the range, actually occurs By comparing the output sound output from the vibration sound and sound generation control apparatus Irubibiri vibration, it is possible to catch a precise chatter frequency. Therefore, by calculating the stable rotational speed based on the chatter frequency accurately in this way, it is possible to obtain a stable rotational speed that has a higher chatter vibration suppressing effect than in the prior art.

It is explanatory drawing which showed the block structure of the vibration detection apparatus. It is the flowchart figure which showed vibration detection control. It is explanatory drawing which showed the display mode of the sound pressure (vibration) on the frequency axis in a display apparatus. It is explanatory drawing which showed the state by which the detection range was set by the operator. It is explanatory drawing which showed the state from which the minimum of the detection range was changed. It is explanatory drawing which showed the state by which the upper limit of the detection range was changed and the chatter frequency was specified.

  Hereinafter, a vibration detection apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory diagram showing a block configuration of the vibration detection device 4 and peripheral devices.
The vibration detection device 4 is for detecting “chatter vibration” generated in the rotary shaft 3 provided in the rotary shaft housing 1 so as to be rotatable about the vertical direction, and is generated from the rotating rotary shaft 3 during rotation. A microphone 2 for detecting the sound pressure of the sound generated around the rotating shaft housing 1 including vibration sound and the microphone 2 are connected, and FFT analysis of the sound detected by the microphone 2 is performed, and the rotating shaft housing 1 The computing device 5 for obtaining the relationship between the sound pressure of the sound generated in the vicinity and the vibration frequency, and the relationship between the sound pressure and the vibration frequency obtained by the computing device 5 are displayed in a manner as shown in FIG. 3, for example. A display device 6, an input device 7 for inputting various numerical values to the computing device 5 and setting the computing device 5, and a sounding device for generating a predetermined vibration sound under the control of the computing device 5 With 8 Reference numeral 9 denotes an NC device that controls the machining of the rotary shaft housing 1 by changing the rotational speed of the rotary shaft 3, and 10 is an operating device for operating the NC device 9.

Here, the vibration detection work using “vibration vibration” using the vibration detection apparatus 4 and the vibration suppression work using the NC apparatus 9 will be described with reference to the flowchart of FIG.
First, before starting the processing, the operator performs an FFT analysis on the vibration sound detected by the microphone 2 in the arithmetic device 5 and then sets the frequency to be referred to when the sound generation device 8 generates a sound as described later. A detection range is arbitrarily set (S1). Thereafter, machining is started (S2), and when the generation of vibration sound due to chatter vibration is recognized, the operator operates the input device 7 to output a sound of 1 kHz from the sound generator 8 (S3). Then, the operator compares the vibration sound with the output sound of 1 kHz (S4). If the vibration sound is higher than the output sound (YES in S4), the operator operates the input device 7 to set the lower limit of the detection range to 1 kHz. Change (S5). On the other hand, when the vibration sound is lower than the output sound (NO in S4), the input device 7 is operated to change the lower limit of the detection range to 0.1 kHz (S6).

  On the other hand, the arithmetic unit 5 performs FFT analysis of the sound pressure detected by the microphone 2 (S7), and when the detection range is set as in S3 to S6, the sound is detected within the set detection range. A signal component having the maximum pressure is found, and a sound having a frequency corresponding to the signal component is output from the sound producing device 8 (S8). Then, the operator compares the vibration sound with the output sound output from the sound generator 8 in S8 (S9), and if they match (YES in S9), the output output from the sound generator 8 Since the frequency of the sound is the chatter frequency, the frequency of the output sound is set as the chatter frequency (S13), and the stable rotation speed is calculated using, for example, the above formulas (1) and (2). 10, the rotational speed of the rotary shaft 3 is changed to a stable rotational speed via the NC device 9 to suppress chatter vibration.

  In addition, when the operator compares the vibration sound and the output sound output from the sounding device 8 in S8 and the two are different (NO in S9), the vibration sound is higher or lower than the output sound. Is determined (S10). As a result, when the vibration sound is high (YES in S10), the input device 7 is operated to change the lower limit of the detection range to a frequency higher than the frequency of the output sound (S11), while the vibration sound is higher than the output sound. If it is low (NO in S10), the upper limit of the detection range is changed to a frequency lower than the frequency of the output sound (S12). Then, a sound is output from the sound generation device 8 in a new detection range, and S7 to S12 are repeated until the vibration sound and the output sound match (YES in S9).

  In the arithmetic unit 5, the result of the FFT analysis of the sound pressure detected by the microphone 2 performed in S7 is displayed as a peak hold waveform 21 on the display unit 6 in the manner shown in FIG. In FIG. 3, 22 indicates the lower limit of the detection range, and 23 indicates the upper limit of the detection range, and the sound of the frequency corresponding to the signal component 24 having the maximum sound pressure within the detection range is generated by the sound generator 8. Will be output. Reference numeral 25 denotes a marker for allowing the operator to visually recognize the signal component 24.

  More specifically describing the vibration detection operation and the vibration suppression operation based on FIGS. 4 to 6, for example, in S1, the lower limit of the detection range is set to 0.1 kHz and the upper limit is set to 10 kHz as shown in FIG. Suppose that the processing is started in S2. However, in this detection range, since low frequency background noise (26 in FIG. 4) becomes a signal component having the maximum sound pressure, a sound having a frequency corresponding to this signal component is output from the sound producing device 8. End up. Therefore, by outputting a 1 kHz sound (S3) and comparing it with the background noise 26 (S4), the lower limit of the detection range is changed to 1 kHz as shown in FIG. 5 (S5), and the background noise 26 is removed from the detection range. except. However, if the lower limit of the detection range is set to 1 kHz, noise (27 in FIG. 4) caused by chatter vibrations such as sirens becomes the maximum sound pressure. 8 and the vibration sound and the output sound are determined not to coincide with each other in S9. Therefore, in order to remove the noise 27 from the detection range, the upper limit of the detection range is changed to a frequency lower than the frequency of the noise 27 in S12. Then, the detection range becomes a range as shown in FIG. 6, and the frequency caused by chatter vibration, that is, the chatter frequency can be accurately obtained, and the sound of the chatter frequency is output from the sound producing device 8 in the second S8. become. Therefore, the coincidence between the vibration sound and the output sound is confirmed in S9, and the optimum stable rotation speed can be calculated based on the chatter frequency.

  According to the vibration detection device 4 and the vibration detection method as described above, the sound generation device 8 capable of outputting sounds of various frequencies is provided, and the maximum sound is output from the sound generation device 8 within an arbitrarily set detection range. A sound having a frequency corresponding to the signal component that becomes the pressure is output, and the operator is made to compare the vibration sound with the output sound. Therefore, although the microphone 2 detects the sound pressure of the sound generated around the rotating shaft housing 1 including the vibration sound generated from the rotating rotating shaft 3, the operator removes various noises from the sound pressure. It is possible to accurately capture the chatter frequency of vibration sound caused by chatter vibration. Then, by calculating the stable rotation speed based on the chatter frequency, it is possible to obtain a stable rotation speed that has a higher chatter vibration suppression effect than before.

  In addition, the vibration detection apparatus according to the present invention is not limited to the aspect of the above-described embodiment, and the configuration relating to the vibration detection means, the vibration detection control in the arithmetic unit, the sound output form from the sound generator, and the like, The present invention can be changed as appropriate without departing from the spirit of the present invention.

For example, in the above embodiment, the microphone 2 is employed as a means for detecting vibration of the rotating shaft. However, an acceleration pickup or a displacement meter is employed instead of the microphone 2, and vibration acceleration or vibration displacement is used instead of sound pressure. It is also possible to detect vibration acceleration and vibration displacement on the frequency axis by FFT analysis, and output sound at a frequency at which vibration acceleration and vibration displacement are maximized, as described above.
In the above embodiment, the sound generator 8 is configured to output a sound of 1 kHz in S3. However, detection is performed without outputting a sound of 1 kHz in consideration of a case where the worker is an expert. The lower limit of the range may be set, or by providing an operation button for outputting a 1 kHz sound, it can be configured so that the operator can select whether or not to output a 1 kHz sound. It is. Needless to say, the sound output in S3 is not limited to 1 kHz, and it is possible to appropriately change how many kHz the lower limit of the detection range is set in S5 and S6.

Further, the NC device 9 or the like is incorporated into the vibration detection device 4 and, when the chatter frequency is specified, the stable rotation speed is automatically calculated, and the rotation speed of the rotary shaft 3 is changed to the stable rotation speed. That is, the vibration detection device 4 may include a rotation speed control function.
Furthermore, the sound output from the sound generator 8 does not need to be a single sound, and a bandpass filter is used to remove the sound outside the frequency range before and after the signal component having the maximum sound pressure. The generated sound may be output from the sound generator 8.
Furthermore, the processing from S3 to S6 may be omitted, and the signal component that maximizes the sound pressure may be determined based on the detection range preset by the operator (that is, at a predetermined frequency). The process of outputting the sound and changing the lower limit of the detection range may be omitted).
In addition, it is not necessary to perform the vibration detection control during actual machining, and there is no problem even if data is obtained in advance by performing test machining or the like and utilized for actual machining.

  1 .... Rotating shaft housing, 2..Microphone (vibration detecting means), 3 .... Rotating shaft, 4 .... Vibration detecting device, 5 .... Calculating device (vibration computing device, sound generation control device), 6 .... Display device , 7 .. Input device (range setting device), 8 .. Sound generation device (sound generation control device), 9 .. NC device, 10.

Claims (2)

In a machine tool having a rotating shaft for rotating a tool or a workpiece, a vibration detecting method for detecting chatter vibration generated on the rotating shaft,
A first step of arbitrarily setting a detection range on the frequency axis , outputting a sound of a predetermined frequency, and changing a lower limit of the detection range based on the output sound ;
A second step of detecting vibration on the time axis generated in the rotation axis;
A third step of obtaining the vibration on the frequency axis by performing FFT analysis on the vibration on the time axis;
A fourth step of outputting a sound having a frequency at which the vibration is maximum within the detection range among vibrations on the frequency axis;
It is determined whether or not the vibration sound caused by chatter vibration generated from the rotating shaft matches the output sound, and if they match, the frequency of the output sound is related to the chatter vibration. And a fifth step of identifying the chatter frequency. In the fifth step, when the vibration sound is higher than the output sound, the lower limit of the detection range is changed to a frequency higher than the frequency of the output sound, while the output sound is the vibration If the sound is lower than the output sound, the upper limit of the detection range is changed to a frequency lower than the frequency of the output sound, and then a new sound having a frequency included in the changed detection range is output. The vibration detection method according to claim 1, wherein:

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