JP2018040594A - Rotary shaft device and method of determining presence/absence of bearing anomaly in the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect bearing anomalies at a low cost.SOLUTION: A main shaft device 1 comprising a main shaft 3 rotatably supported by bearings 4 has a control unit 7 including; measurement means (vibration sensor 5) for measuring vibration of the bearings 4 while the main shaft 3 is rotating; waveform extraction means (computation unit 8) configured to apply signal processing to a measured signal waveform to extract a waveform in a frequency band pre-specified in accordance with rotation speed of the main shaft 3; definite integration means (computation unit 8) configured to definitely integrate the extracted waveform to derive area between the waveform and a lateral axis; and determination means (computation unit 8) configured to compare the derived area with a preset threshold to determine the presence/absence of anomalies in the bearings 4.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rotary shaft device in which a rotary shaft is supported by a bearing, such as a main spindle device of a machine tool, and more specifically, a rotary shaft device capable of determining a bearing abnormality without disassembly, and the rotary shaft The present invention relates to a bearing abnormality determination method in an apparatus.

The bearing is used in many rotating shaft devices such as a main shaft device of a machine tool. Among them, the rolling bearing is generally composed of an inner ring, an outer ring, a plurality of rolling elements, a cage for keeping the rolling elements at equal intervals, the inner ring rotates together with the rotating shaft, and the outer ring is incorporated in the housing. It is fixed.
Such bearing abnormalities include poor lubrication, contamination of foreign materials, wear, excessive load, etc., and in production sites using rotary shaft devices, to prevent a decrease in productivity due to sudden equipment failure, Monitoring is required. In order to determine the abnormality of this bearing, for example, in Patent Document 1, the frequency component of the measured data is obtained by analyzing the frequency of the vibration signal generated from the rotating part, and the abnormal frequency of the vibration caused by the abnormality of the rotating part is obtained. An invention is disclosed in which the frequency component of the measured data corresponding to the abnormal frequency is calculated and the frequency component of the measured data is extracted, and the presence / absence of the abnormality is determined by comparing and comparing the extracted frequency component with a threshold value.

Japanese Patent No. 5146008

  In the conventional method, a very high-performance measuring instrument is required to accurately determine an abnormality. However, since a high-performance measuring instrument is expensive, a machine can be determined only with limited equipment. Moreover, since vibration may suddenly increase, there is a risk of misdiagnosis only by determination based on the threshold value of the vibration value.

  Accordingly, an object of the present invention is to provide a rotary shaft device capable of determining the presence or absence of a bearing abnormality with low cost and high accuracy, and a method for determining a bearing abnormality in the rotary shaft device.

In order to achieve the above object, the invention according to claim 1 is a rotating shaft device in which a rotating shaft is supported by a bearing,
A measuring means for measuring vibration or sound of the bearing during rotation of the rotating shaft, a signal processing is performed on the measured signal waveform, and a waveform in a frequency band specified in advance corresponding to the rotational speed of the rotating shaft A waveform extracting means for extracting the calculated waveform, a definite integrating means for calculating the area between the horizontal axis by deintegrating the extracted waveform, and comparing the calculated area with a preset threshold value to determine whether the bearing is abnormal. And determining means for determining whether or not there is any.
According to a second aspect of the present invention, in the configuration of the first aspect, the waveform extraction unit obtains an absolute value of the signal waveform, performs a filtering process of the frequency band, performs frequency analysis, and performs the frequency analysis. Envelope processing is performed at a cycle that is an integral multiple of the frequency caused by a bearing abnormality, and the waveform is extracted again by performing frequency analysis.
According to a third aspect of the present invention, in the configuration of the second aspect, the waveform extracting unit calculates a predetermined number of peak frequencies after performing the first frequency analysis, and sets each peak frequency in advance. In comparison with the frequency caused by the bearing abnormality, the envelope processing is performed only when the error between the frequencies is equal to or less than a predetermined value, and the waveform is extracted again by performing frequency analysis. Features.
According to a fourth aspect of the present invention, in the configuration according to any one of the first to third aspects, the definite integration unit divides the calculated area for each frequency interval set in advance for each part of the bearing, When determining that the bearing is abnormal, the determination means calculates the rate of change by comparing the divided area for each frequency interval with the area divided for the threshold value for each frequency interval, When the change rate is compared with each lower limit change rate set in advance for each frequency interval, and the change rate exceeds the lower limit change rate, the bearing portion including the frequency interval of the change rate is abnormal. It is characterized by specifying.
According to a fifth aspect of the present invention, in the configuration according to any one of the first to fourth aspects, the display device displays a determination result by the determination unit.
A sixth aspect of the present invention is the configuration of the fifth aspect, further comprising storage means for storing the waveform extracted by the waveform extraction means, wherein the display means includes the past waveform stored in the storage means. The current waveform extracted by the waveform extraction means is displayed together.
In order to achieve the above object, an invention according to claim 7 is a method of determining an abnormality of the bearing in a rotating shaft device in which the rotating shaft is supported by a bearing,
A measurement step of measuring vibration or sound of the bearing during rotation of the rotating shaft by a sensor, and applying signal processing to the measured signal waveform, in a frequency band specified in advance corresponding to the rotation speed of the rotating shaft A waveform extracting step for extracting the waveform of the bearing, a constant integration step for calculating the area between the horizontal axis by deintegrating the extracted waveform, and comparing the calculated area with a preset threshold value. A determination step of determining whether or not there is an abnormality.

  According to the present invention, the state of the bearing can be diagnosed with high accuracy at low cost, and the presence or absence of abnormality can be determined. Therefore, it is possible to prevent a decrease in productivity due to a sudden equipment failure.

It is the schematic of a main shaft apparatus. It is a flowchart of abnormality determination control. It is a figure which shows the outline of the waveform measured with the vibration sensor. It is a figure which shows the outline of the waveform which frequency-analyzed with the arithmetic unit. It is a graph which shows the waveform displayed on a display apparatus. It is a graph which shows the state which displayed on the display apparatus the waveform of the last time memorize | stored in the memory | storage device, and the waveform of this measurement result. In the waveform graph with frequency intervals set, the upper is the outer ring of the bearing, the inner is the inner ring of the bearing, and the lower is the rolling element.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram illustrating a spindle device of a machine tool that is an example of a rotary shaft device.
The spindle device 1 includes a housing 2 in which a spindle 3 as a rotating shaft that is driven to rotate by a motor (not shown) is supported by bearings 4, 4... That are rolling bearings, and a tool is attached to the tip of the spindle 3. It is removable.
A vibration sensor 5 as a measuring means for detecting vibration during rotation and a rotational speed detector 6 for detecting the rotational speed of the main shaft 3 are attached to the housing 2. The vibration sensor 5 is installed in a stationary part near the bearing 4. However, the number of vibration sensors 5 to be installed is not limited, and a single sensor can detect an abnormality, but by installing a plurality of sensors, the state of the bearing can be determined more accurately. A sensor for measuring sound may be used instead of the vibration sensor 5.

  Reference numeral 7 denotes a control device, and the control device 7 is provided with an arithmetic device 8, a storage device 9, a display device 10, and an input device 11. The main shaft 3 rotates at a rotational speed commanded from the control device 7, and the vibration during rotation detected by the vibration sensor 5 is input to the arithmetic device 8. The rotational speed of the main shaft 3 can be arbitrarily set by the input device 11, and the maximum rotation of the main shaft 3 can be set. The control device 7 performs processing by rotating the motor in accordance with the processing program stored in the storage device 9, and also performs abnormality determination of the bearing 4 described later. Here, the arithmetic unit 8 is a waveform extraction unit, a definite integration unit, and a determination unit related to abnormality determination, the storage device 9 is a storage unit, and the display unit 10 is a display unit.

The storage device 9 stores an abnormality determination program for the sequence shown in FIG. 2, and the control device 7 is operated by an operator input instruction or at predetermined time intervals when the spindle 3 rotates. The abnormality determination control of the bearing 4 is automatically executed based on the abnormality determination program. Hereinafter, the abnormality determination control will be described with reference to FIG.
First, in the calculation device 8 built in the control device 7 in advance, the outer ring, the inner ring, and the rolling element of the bearing 4 are calculated from the rotational speed, the number of rolling elements of the bearing 4, the diameter of the rolling element, and the rotational pitch circle diameter of the rolling element. The frequencies resulting from the scratches on the cage are calculated and stored in the storage device 9. Alternatively, the frequency resulting from the bearing abnormality at each rotational speed is calculated in advance and stored in the storage device 9.

When the abnormality determination control is started, the rotational speed of the main shaft 3 is acquired via the rotational speed detector 6 at S1, and the rotating vibration as shown in FIG. Are measured and stored in the storage device 9 (measurement step).
Next, in S3, an analog signal of vibration measured by an A / D converter (not shown) incorporated in the control device 7 is converted into a digital signal, and then rectified in S4 to obtain the absolute value of the waveform.
Next, in S5, band pass filter processing for extracting only a specific frequency band corresponding to the rotation speed is performed, and in S6, frequency analysis of the extracted waveform is performed. This frequency analysis is an FFT analysis process for acquiring a frequency spectrum as shown in FIG. 4, and the frequency at five peaks is calculated in S7 from the acquired spectrum waveform. However, the calculated peak is not limited to five points.

Next, in S8, the calculated frequency of the five points of the peak is compared with the frequency caused by the bearing abnormality stored in the storage device 9, and whether the error between them is equal to or less than a predetermined value (here, 10 Hz). Determine whether or not. If the frequency error is greater than 10 Hz, it is determined that there is no abnormality in the bearing 4 in S9. If the rotation stop command to the spindle 3 is not confirmed in the next determination of S10, the process returns to S1 to acquire the rotation speed again and perform the subsequent processing. If the rotation stop command is confirmed in S10, the control is terminated.
On the other hand, if the error between frequencies is 10 Hz or less in the determination of S8, in S11, the waveform of the absolute value of the vibration acquired in S4 is subjected to envelope processing at a cycle that is an integral multiple of the frequency caused by the bearing abnormality. After that, frequency analysis is performed again in S12 to obtain a waveform as shown in FIG. 5 (waveform extraction step).

Next, in S13, the acquired waveform is definitely integrated to calculate the area S of the graph surrounded by the horizontal axis (definite integration step).
In S14, it is determined whether or not the calculated area S of the graph is larger than a preset threshold. If the area S is larger than the threshold, it is determined in S15 that the bearing 4 is abnormal, and the determination result is displayed on the display device. 10 (determination step). The threshold value can be arbitrarily changed. The notification that there is an abnormality may be performed together with other notification means such as a lamp and a buzzer in addition to the display.

Here, in the frequency band corresponding to the rotational speed, as shown in FIG. 7, frequency intervals (see FIG. 7) are respectively obtained beforehand for the bearing outer ring (upper figure), the bearing inner ring (in the figure), and the rolling element (lower figure). When the area S ₁ , S ₂ , S ₃ ... Is calculated by dividing the threshold area for each frequency interval, the outer ring, the inner ring, and the rolling element are abnormal. Are stored in the storage device 9 and the frequency interval at which the rate of change increases.
Therefore, in S13, the waveform is definitely integrated, the area for each frequency interval is also calculated, and the change rate from the area divided from the threshold value is obtained in the frequency interval where the change rate becomes large. Next, in S14, the change rate at the obtained frequency interval is compared with the lower limit change rate stored in the storage device 9. If the lower limit change rate is exceeded, the frequency interval at which the change rate is obtained is determined. The place (outer ring, inner ring, rolling element) to be included can be specified as an abnormal part of the bearing 4.
Therefore, in S15, the abnormal part can be easily grasped by displaying the specified abnormal part together with the determination result of abnormality. The frequency interval and the lower limit change rate stored in the storage device 9 can be arbitrarily changed. The change rate comparison may also be performed at every frequency interval.

On the other hand, if the area S of the graph is equal to or smaller than the threshold value in the determination in S14, it is determined in S16 that there is no abnormality, the process proceeds to S10, and the presence / absence of a rotation stop command is confirmed.
Even if the determination result is normal, it may be displayed on the display device 10, or the waveform calculated in S13 is stored in the storage device 9, and the past measurement stored in the display device 10 as shown in FIG. The result and the current measurement result may be displayed on the same graph. The data that can be displayed on the graph is not limited to two, and three or more measurement results can also be displayed retroactively.

  Thus, according to the spindle device 1 of the above embodiment, the control device 7 performs signal processing on the measurement signal (vibration sensor 5) for measuring the vibration of the bearing 4 during rotation of the spindle 3 and the measured signal waveform. Then, a waveform extraction means (calculation device 8) for extracting a waveform in a frequency band specified in advance corresponding to the rotational speed of the main shaft 3, and an area S between the horizontal axis by definite integration of the extracted waveform And a determinator (arithmetic device 8) for determining whether or not there is an abnormality in the bearing 4 by comparing the calculated area S with a preset threshold value. The state of the bearing 4 can be diagnosed with high accuracy at low cost and the presence or absence of abnormality can be determined. Therefore, it is possible to prevent a decrease in productivity due to a sudden equipment failure.

  In the above embodiment, the peak five frequencies are calculated from the spectrum waveform obtained by the FFT analysis and compared with the frequency caused by the bearing abnormality to determine that there is no abnormality (S6 to S9). The processing may be omitted, and the waveform subjected to the filter processing may be envelope-processed in S11, the subsequent processing may be performed to calculate the area S of the graph, and the abnormality determination may be performed.

  In addition, the abnormality determination method of the rotating shaft device and the bearing according to the present invention is not limited to the main shaft device of a machine tool, but can be applied to other mechanical equipment such as an automobile, a railcar, and a ship.

  1 .... Spindle device, 2 .... Housing, 3 .... Spindle, 4 .... Bearing, 5 .... Vibration sensor, 6 .... Rotational speed detector, 7 .... Control device, 8 .... Calculation device, ... Storage device, 10 ... display device.

Claims (7)

A rotary shaft device having a rotary shaft supported by a bearing,
Measuring means for measuring vibration or sound of the bearing during rotation of the rotating shaft;
Waveform extraction means for performing signal processing on the measured signal waveform and extracting a waveform in a frequency band specified in advance corresponding to the rotation speed of the rotation shaft;
A definite integration means for calculating the area between the horizontal axis by deintegrating the extracted waveform;
A rotating shaft device comprising: a determining unit that compares the calculated area with a preset threshold value and determines whether or not there is an abnormality in the bearing.   The waveform extraction means acquires the absolute value of the signal waveform and performs the filter processing of the frequency band, and then performs frequency analysis, and performs envelope processing at a cycle that is an integral multiple of the frequency caused by the abnormality of the bearing. The rotary shaft device according to claim 1, wherein the waveform is extracted by performing frequency analysis again.   The waveform extracting means calculates a predetermined number of peak frequencies after performing the first frequency analysis, compares each peak frequency with a preset frequency caused by the bearing abnormality, 3. The rotating shaft device according to claim 2, wherein the envelope processing is performed only when an error between frequencies is equal to or less than a predetermined value, and the waveform is extracted by performing frequency analysis again. The definite integration means divides the calculated area for each frequency interval set in advance for each part of the bearing,
When determining that the bearing is abnormal, the determination means calculates the rate of change by comparing the divided area for each frequency interval with the area divided for the threshold value for each frequency interval, When the change rate is compared with each lower limit change rate set in advance for each frequency interval, and the change rate exceeds the lower limit change rate, the bearing portion including the frequency interval of the change rate is abnormal. The rotating shaft device according to any one of claims 1 to 3, wherein the rotating shaft device is specified.   The rotary shaft device according to claim 1, further comprising a display unit that displays a determination result by the determination unit.   Storage means for storing the waveform extracted by the waveform extraction means; and the display means combines the past waveform stored in the storage means and the current waveform extracted by the waveform extraction means. The rotating shaft device according to claim 5, wherein the rotating shaft device is displayed. In a rotary shaft device in which a rotary shaft is supported by a bearing, a method for determining an abnormality of the bearing,
A measurement step of measuring vibration or sound of the bearing during rotation of the rotating shaft with a sensor;
A waveform extraction step of performing signal processing on the measured signal waveform and extracting a waveform in a frequency band specified in advance corresponding to the rotation speed of the rotation shaft;
A definite integration step of calculating the area between the horizontal axis by deintegrating the extracted waveform;
A determination step of comparing the calculated area with a preset threshold value to determine the presence or absence of abnormality of the bearing, and a method of determining abnormality of the bearing in the rotary shaft device.

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