JP6616964B2 - State display method and apparatus of rolling bearing in machine tool - Google Patents

Description

  The present invention relates to a method and an apparatus for displaying the state of a rolling bearing that supports a spindle or the like in a machine tool.

Conventionally, an abnormality diagnosis of a rolling bearing (hereinafter abbreviated as “bearing”) used for a main shaft of a machine tool has been mainly used a method using vibration.
For example, in Patent Document 1, as a method for detecting a bearing abnormality, vibration acceleration is detected using an acceleration sensor fixed to a rotating device or a bearing, and the degree of damage or remaining life of the bearing is determined based on the strength. doing.
In Patent Document 2, the life of the bearing is accurately predicted based on the actual life of the bearing. That is, the dynamic equivalent load is calculated from the specification information of the bearing, and then the lubrication parameter corresponding to the lubricant to be used is calculated. Further, the contamination coefficient is determined in consideration of the material coefficient, and based on the specification information. The fatigue limit load is calculated, and based on these, the life correction coefficient is calculated with reference to the life correction coefficient calculation map to correct the bearing life.
In Patent Document 3, the deterioration state of the lubricating oil due to mixing of dust and water is preliminarily determined based on the basic data using the resonance frequency band and high frequency band signals of the acceleration sensor for each bearing specification such as the model number and manufacturer name of each bearing. Measurements are made, and the basic data is used to estimate the dust contamination state of the bearing and the deterioration state of the lubricating oil to calculate the remaining life of the bearing.

Japanese Examined Patent Publication No. 2-59420 JP 2002-148148 A JP 2010-190901 A

In the technique of Patent Document 1, damage to the bearing is detected at a level that appears in vibration and sound. However, since the spindle of a machine tool is required to have a high rotational accuracy of several microns, even if this technology is applied to a machine tool having such a high rotational accuracy, the rotational accuracy is already present when it appears in vibration or sound. May be worse and unsuitable.
In the technique disclosed in Patent Document 2, a technique for accurately predicting the remaining life from the contamination state of the lubricating oil due to the intrusion of foreign matter or the like or wear powder from the bearing is shown. However, in the main spindle of a machine tool, the bearing may be damaged due to the collision between the main spindle and a workpiece. In such a case, it cannot be determined by contamination of the lubricating oil.
The technique disclosed in Patent Document 3 combines the penetration of foreign matter into the lubricating oil, the deterioration of the lubricating oil, and the bearing vibration. However, when oil-air lubrication is adopted in the spindle of the machine tool, new and clean lubricating oil is always supplied to the bearing. In addition, as described above, the bearing may be damaged by the collision between the main shaft and the workpiece without being contaminated by the lubricating oil. Therefore, in a machine tool in which the state of the lubricating oil is rarely changed, there is a possibility that the life cannot be judged only by the bearing vibration investigated by changing the state of the lubricating oil.

  Therefore, the present invention can accurately determine the state of the bearing and notify the operator even if the machine tool has high rotational accuracy and the bearing may be damaged regardless of the lubricating oil. An object of the present invention is to provide a state display method and apparatus for a rolling bearing.

In order to achieve the above object, the invention according to claim 1 is a machine tool including a rotating shaft or a linear shaft supported by a rolling bearing, and processing the workpiece by rotating a tool or a workpiece. A method for displaying the state of a bearing,
A bearing state detection step for detecting a bearing state associated with the operation of the rolling bearing;
An operation information calculation step for calculating the cumulative operation time of the rolling bearing;
An information acquisition step of acquiring a predetermined bearing state of the detected rolling bearing together with the accumulated operating time at that time point;
A life calculating step for calculating a life time of the rolling bearing;
The predetermined bearing state in each cumulative operating time, a threshold value for determining the bearing state as abnormal, a life time of the rolling bearing, and the current bearing state at present, the predetermined bearing state as the vertical axis, A display step of creating a graph with the accumulated operation time as a horizontal axis and displaying the graph in a state where the graph is divided into predetermined regions by the threshold value and the life time is executed.
According to a second aspect of the present invention, in the configuration of the first aspect, in the bearing state detecting step, vibrations associated with operation of the rolling bearing are detected to analyze the vibrations, and a vibration value having a predetermined frequency is determined as the rolling value. It is detected as a bearing state accompanying the operation of the bearing.
According to a third aspect of the present invention, in the configuration of the first or second aspect, the operation information calculation step calculates an average rotation speed of the rolling bearing, and the information acquisition step also acquires the average rotation speed. In the life calculation step, the life time of the rolling bearing is also calculated using the average rotational speed.
In order to achieve the above object, the invention according to claim 4 is a machine tool comprising a rotating shaft or a linear shaft supported by a rolling bearing, and processing the workpiece by rotating a tool or a workpiece. A device for displaying the state of a bearing,
Bearing state detecting means for detecting a bearing state associated with operation of the rolling bearing;
Operating information calculating means for calculating the cumulative operating time of the rolling bearing;
Information acquisition means for acquiring a predetermined bearing state together with the cumulative operating time at that time;
A life calculating means for calculating a life time of the rolling bearing;
The predetermined bearing state at each of the cumulative operating times, a threshold value for determining the bearing state as abnormal, a life time of the rolling bearing, and the current bearing state at present, the predetermined bearing state on the vertical axis, And a display unit that creates a graph with the accumulated operation time as a horizontal axis and displays the graph in a state where the graph is divided into predetermined regions by the threshold value and the life time.
According to a fifth aspect of the present invention, in the configuration of the fourth aspect, the bearing state detecting means detects vibrations of the rolling bearing, and the detected vibrations are expressed as a frequency and a vibration value corresponding to the frequency. Vibration analysis means for analyzing the relationship, and the information acquisition means acquires a vibration value of a predetermined frequency of the analyzed relationship between the frequency and the vibration value together with the accumulated operation time at that time. It is characterized by.
According to a sixth aspect of the present invention, in the configuration of the fourth or fifth aspect, the operation information calculation unit calculates an average rotation speed of the rolling bearing, and the information acquisition unit acquires the average rotation speed together. The life calculation means calculates the life time of the rolling bearing also using the average rotation speed.

According to the present invention, the calculation life and the bearing state of the bearing can be grasped simultaneously. There is a possibility that the bearing will be replaced at an early stage in spite of the fact that the calculated life alone is sufficient for the true life. On the other hand, if it is determined only by the bearing state, there is a possibility that the bearing life is already at the end when the timing starts to increase. By displaying these values together, it is possible to accurately determine the state of the bearing even in a machine with high rotational accuracy such as a machine tool that may damage the bearing regardless of the lubricant. The operator can be notified.
Therefore, it is possible to improve the accuracy of the life diagnosis by entrusting the final judgment to a person, making it easier to make a maintenance plan, and eliminating production stop due to a sudden failure. Further, since the determination can be made based on the bearing state, there is an effect of reducing the maintenance cost.

It is a block block diagram of NC apparatus of the machine tool provided with the status display apparatus of the rolling bearing. It is a side view of a spindle housing. It is a front view (bottom view) of a spindle housing. It is a flowchart of recording control of vibration information. It is a flowchart of calculation control of accumulated operation time. It is explanatory drawing of the data of the recorded bearing state. It is explanatory drawing which shows the display screen of a monitor.

Hereinafter, embodiments in which the present invention is applied to a spindle bearing of a machine tool using a vibration value as a bearing state will be described with reference to the drawings.
FIG. 1 is a block configuration diagram showing an example of an NC device provided with a spindle bearing state display device in a machine tool, FIG. 2 is a side view of the spindle housing of the machine tool, and FIG. 3 is a front view of the spindle housing. It is the figure shown from the axial direction lower side.
Reference numeral 1 denotes a spindle housing having a spindle 3 in a machine tool, which processes a workpiece placed on a lower table by rotating a tool held by the spindle 3. The main shaft housing 1 includes vibration sensors 2a to 2c, which are acceleration sensors, as bearing state detection means for detecting time domain vibration (vibration on the time axis) generated in the main shaft 3 rotatably provided around the C axis. Is provided. The vibration sensors 2a to 2c are arranged in the spindle housing 1 in a state in which vibration information in the time domain in the X-axis, Y-axis, and Z-axis directions orthogonal to each other can be detected so as to detect vibration information in directions perpendicular to each other. It is attached.

  The state display device 10 includes an FFT calculation device 11 (vibration analysis means) that performs Fourier analysis based on vibrations detected by the vibration sensors 2a to 2c, and an NC device 12. The NC device 12 detects the rotation speed of the main shaft 3 by a main shaft rotation detector 13 provided in the main shaft housing 1, and the rotation speed of the feed shaft by a feed shaft rotation detector 14 provided in a servo motor of the feed shaft. A rotation detection unit 15 to detect, an operation time is calculated from the detection timing obtained from the rotation detection unit 15 and accumulated and recorded, and an accumulated operation time recording unit 16 (operation information calculation means) for calculating an average spindle rotation speed; Based on the analysis data obtained from the life calculation unit 17 (life calculation means) for calculating the bearing life from the cumulative operation time and the average spindle rotation speed recorded by the cumulative operation time recording unit 16 and the analysis data obtained from the FFT arithmetic unit 11 And the vibration value are calculated, and it is determined whether or not the machine is cutting based on the cutting execution information obtained from the rotation detection unit 15. A record determination unit 18 (information acquisition unit) that acquires the cumulative operating time and average spindle rotational speed from the recording unit 16 and a calculated bearing life from the life calculation unit 17, and the information acquired by the record determination unit 18 are recorded. A bearing state recording unit 19 that creates a graph and a monitor 20 that displays the data recorded by the bearing state recording unit 19 in a graph are provided. The bearing state recording unit 19 and the monitor 20 serve as display means. Here, the state display is performed by regarding the vibration, accumulated operation time, and average rotation speed obtained by the rotation of the main shaft 3 as the vibration, accumulated operation time, and average rotation speed of the bearing of the main shaft 3, respectively.

The recording determination unit 18 calculates a frequency band to be recorded from bearing specifications set by the manufacturer, and records a vibration value in the obtained frequency band. Generally, an outer ring wound, an inner ring wound, and a rolling element wound are known as in the following Expression 1, and this frequency is obtained by the recording determination unit 18. The number, diameter, pitch circle diameter, and contact angle of the rolling elements are input to the recording determination unit 18 in advance.
[Formula 1]
Inner ring wound: Zfi = fr · (1 + Da · cos α / dm) · Z / 2
Outer ring wound: Zfc = fr · (1−Da · cos α / dm) · Z / 2
Rolling body wound: 2fb = fr · (1-Da ² · cos ² α / dm ² ) · dm / Da
Z: Number of rolling elements fr: Inner ring rotation frequency [Hz]
fc: Cage rotation frequency [Hz]
fi: fr-fc
fb: rolling element rotation frequency [Hz]
dm: Pitch circle diameter (PCD) [mm]
Da: Rolling element diameter [mm]
α: Contact angle [°]

The calculated bearing life calculated by the life calculation unit 17 uses a formula for calculating the basic rated life. The basic rated life L [Hour] is expressed by the following formula 2.
[Formula 2]
L = (10 ⁶ / 60n) · (C / P) ^A
C: Basic dynamic load rating of rolling bearing [N]
P: Dynamic equivalent load acting on the bearing [N]
A: Load index (3 for ball bearings, 10/3 for roller bearings)
n: Average rotational speed [min ⁻¹ ]

Next, a procedure until the recording determination unit 18 acquires and records vibration information will be described based on the flowchart of FIG.
First, in the FFT arithmetic unit 11, the vibration detected by the vibration sensors 2a to 2c is Fourier-analyzed to the relationship between the frequency and the vibration value and is output to the recording determination unit 18 (signal detection step).
The recording determination unit 18 determines whether the spindle rotation speed obtained from the rotation detection unit 15 has changed (S11). When it changes here, it is determined by a feed rate whether the machine is cutting (S12). If the feed rate is 0 and it is determined that cutting is not in progress, the process proceeds to S13. If the spindle speed has not changed in S11 and if it is determined in S12 that cutting is in progress, the process returns to S11 again.
In S13, the acquisition time, the accumulated operation time, the average spindle rotation speed, the spindle rotation speed at the time of vibration acquisition, and the calculated bearing life are acquired from the rotation detection unit 15, the accumulated operation time recording unit 16, and the life calculation unit 17, respectively. Along with (life calculation step), a vibration value of a predetermined frequency is acquired from the analysis data from the FFT arithmetic unit 11 (information acquisition step). In S14, the acquired information is recorded in the bearing state recording unit 19. In this way, the bearing state recording unit 19 records data as shown in FIG.

Here, the procedure (operation information calculation step) until the accumulated operation time recording unit 16 calculates the accumulated operation time of the spindle 3 and the average spindle rotation speed will be described based on the flowchart of FIG.
First, the flag f for acquiring the time S at which the operation is started at a certain rotational speed and the time E at which the operation is ended is initialized (S21). In S22, it is determined whether or not the rotational speed of the main shaft 3 has changed. If not, the process returns to S22 again. If it has changed, it is determined in S23 whether or not the flag f = 0. If f = 0, it is determined that the spindle 3 has started operation at a certain rotational speed, and the time S is acquired in S24. Then, the spindle rotational speed is acquired in S26, the flag is set to 1 in S27, and the process returns to S22.
On the other hand, if it is not f = 0 in S23, it is determined that the time S has already been acquired and the main shaft 3 has changed from a certain rotational speed to a different rotational speed. The time E at this time is acquired in S25. The operation time at a certain rotation speed can be obtained from the time S and the time E, and the accumulated operation time and the average spindle rotation speed are calculated by recording and adding the past operation time and the rotation speed at that time. (S28). If the flag is initialized in S29, and if it is determined in S30 that the main spindle 3 is stopped, the process ends. If it is in operation, the process returns to S22.

Then, the bearing state recording unit 19 displays on the monitor 20 the accumulated operating time of the data 1, data 2... Recorded as shown in FIG. Step). At this time, the vibration value acquired at a rotation speed close to the maximum rotation speed of the main shaft 3 and the vibration value acquired under other conditions are changed in color so as to be displayed in a graph as shown in FIG. This is because the higher the rotational speed, the larger the vibration value appears, indicating that the data is highly reliable and well represents the state of the rolling bearing.
Next, the calculated bearing life value (life calculation value) and the upper limit value (normal value) of normal vibration set by the manufacturer are drawn as a threshold value. Thereby, the inside of a graph can be divided into four areas of circle numbers 1 to 4. The circled number 1 is a danger zone 1 and is in a state that requires replacement because vibrations may greatly affect the machining accuracy. Circle number 2 indicates danger zone 2 and indicates that the urgency of replacement is higher than circle number 1. The circled number 3 is a safety zone and can be used continuously. The circled number 4 is a caution zone. If there is no abnormality in the machining, use it with caution, and replace the bearing at the next maintenance timing.
In this state, the final data is indicated by “◯”, and the operator can determine the current bearing state depending on which region “◯” is in. Since it is in danger zone 2 here, it turns out that replacement | exchange is required immediately. In addition, you may attach | subject the comment which shows the present state (it is located in which zone etc.) in the character below a graph.

Thus, according to the bearing state display device 10 of the above-described form, the vibration accompanying the operation of the bearing of the main shaft 3 is detected during non-cutting, and the detected vibration is related to the relationship between the frequency and the corresponding vibration value. Analyzing and calculating the cumulative operating time and average rotational speed of the bearing during non-cutting, and calculating the vibration value at a predetermined frequency of the analyzed frequency and vibration relationship with the cumulative operating time and average rotational speed at that time In addition, the bearing life is calculated using the average rotational speed, and the monitor 20 creates a graph with the vibration value of a predetermined frequency in each cumulative operating time as the vertical axis and the cumulative operating time as the horizontal axis. In addition, the current vibration value is displayed together with the threshold value (normal value) for determining the vibration value as abnormal and the bearing life time (life calculation value) divided into a predetermined area in the graph. The actual life of the bearing and the actual It is possible to grasp the dynamic state at the same time. There is a possibility that the bearing will be replaced at an early stage in spite of the fact that the calculated life alone is sufficient for the true life. On the other hand, when judging only by the vibration value, there is a possibility that the bearing life is already at the end when it starts to increase. By displaying these values together, it is possible to accurately determine the state of the bearing even in a machine with high rotational accuracy such as a machine tool that may damage the bearing regardless of the lubricant. The operator can be notified.
Therefore, it is possible to improve the accuracy of the life diagnosis by entrusting the final judgment to a person, making it easier to make a maintenance plan, and eliminating production stop due to a sudden failure. Further, since the determination can be made based on the bearing state, there is an effect of reducing the maintenance cost.

In addition, in the said form, although the state display is performed about the bearing of the main axis | shaft, you may implement | achieve by the rolling guide of a feed shaft (linear axis). In this case, the case where the main shaft is not rotating may be determined as non-cutting. Although the status display is performed by regarding the vibration and rotation speed of the main shaft as that of the bearing, it is of course possible to display the status by directly detecting the vibration and rotation speed by providing a sensor or detector on the bearing. .
Furthermore, the current of the vibration sensor, microphone, position / rotation detector, main shaft / feed shaft motor can be used as the bearing state detecting means. On the other hand, as the bearing state detection means, not only the vibration value but also the torque and current of the motor may be detected and used as they are.
In addition, the life time of rolling bearings is calculated based on other information such as load torque applied to the spindle, etc., based solely on the operating time without using anything other than the average rotational speed of the spindle, etc. May be. Further, the bearing state may be displayed at the time of cutting. In this case, a method of filtering the detected vibration by estimating the vibration due to the cutting based on the processing conditions in the processing program, etc. can be considered. .

The example in which the bearing state is displayed on the monitor has been described as being divided into four regions. However, the region may be increased by dividing the vibration value into a plurality of levels such as normal, caution, and warning. Each area can be colored and displayed in an easy-to-understand manner. Moreover, it is also possible to display the state of a bearing only with a letter irrespective of a graph.
In addition, in the above embodiment, a machine tool that processes a workpiece by rotating a tool attached to the main shaft is described, but the workpiece attached to the rotating shaft is rotated and feed control is performed on the linear axis to process the workpiece. The present invention can also be applied to a combined processing machine or the like.

  1 ·· Tool housing, 2a to 2c ·· Vibration sensor, 3 ·· Main shaft, 10 ·· Status display device, 11 ·· FFT operation device, 12 ·· NC device, 13 ·· Main shaft rotation detector, 14 ·· Feed shaft rotation detector, 15 .... rotation detection unit, 16 .... cumulative operating time recording unit, 17 .... life calculation unit, 18 .... recording determination unit, 19 .... bearing state recording unit, 20 .... monitor.

Claims (6)

In a machine tool having a rotating shaft or a linear shaft supported by a rolling bearing, and processing the workpiece by rotating a tool or a workpiece, a method for displaying the state of the rolling bearing,
A bearing state detection step for detecting a bearing state associated with the operation of the rolling bearing ;
An operation information calculation step for calculating the cumulative operation time of the rolling bearing;
An information acquisition step of acquiring a predetermined bearing state of the detected rolling bearing together with the accumulated operating time at that time point;
A life calculating step for calculating a life time of the rolling bearing;
The predetermined bearing state in each cumulative operating time, a threshold value for determining the bearing state as abnormal, a life time of the rolling bearing, and the current bearing state at present , the predetermined bearing state as the vertical axis, A bearing state display step of creating a graph with the cumulative operating time as a horizontal axis, and displaying the graph in a state where the graph is divided into predetermined regions by the threshold value and the life time. How to display the state of rolling bearings in machinery. In the bearing state detection step, vibration associated with the operation of the rolling bearing is detected, the vibration is analyzed, and a vibration value at a predetermined frequency is detected as a bearing state associated with the operation of the rolling bearing. The state display method of the rolling bearing in the machine tool of claim | item 1. In the operation information calculation step, the average rotational speed of the rolling bearing is also calculated,
In the information acquisition step, the average rotation speed is also acquired,
The lifetime in the calculation step, the state display method of the rolling bearing in the machine tool according to claim 1 or 2, characterized in that to calculate the lifetime of the rolling bearing the average rotational speed be used. In a machine tool having a rotary shaft or a linear shaft supported by a rolling bearing, and processing the workpiece by rotating a tool or a workpiece, the device displays the state of the rolling bearing,
Bearing state detecting means for detecting a bearing state associated with operation of the rolling bearing;
Operating information calculating means for calculating the cumulative operating time of the rolling bearing;
Information acquisition means for acquiring a predetermined bearing state together with the cumulative operating time at that time;
A life calculating means for calculating a life time of the rolling bearing;
The predetermined bearing state in each cumulative operating time, a threshold value for determining the bearing state as abnormal, a life time of the rolling bearing, and the current bearing state at present , the predetermined bearing state as the vertical axis, A display means for creating a graph with the cumulative operating time as a horizontal axis, and displaying the graph in a state where the inside of the graph is divided into predetermined areas by the threshold value and the life time ,
A state display device for a rolling bearing in a machine tool. The bearing state detection means detects vibration of the rolling bearing,
Comprising vibration analysis means for analyzing the detected vibration into a relationship between a frequency and a vibration value corresponding to the frequency;
Said information obtaining means, according to claim 4, characterized in that the vibration value of the predetermined frequency of the relationship between the analyzed frequency and vibration values, acquires together with the cumulative operating time at that time Status display device for rolling bearings in machine tools. The operation information calculation means also calculates an average rotational speed of the rolling bearing,
The information acquisition means also acquires the average rotation speed together,
6. The state calculating device for a rolling bearing in a machine tool according to claim 4 , wherein the life calculating means calculates a life time of the rolling bearing using the average rotational speed.

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