JP2019045259A - Lubrication state diagnostic apparatus and lubrication state diagnostic method of bearing of rotation shaft device - Google Patents

Abstract

To appropriately and inexpensively determine the quality of a lubrication state of a bearing whose lubrication state periodically varies.SOLUTION: In a lubrication state diagnostic apparatus 100, a main shaft 1 is rotated at a diagnosis rotational speed, and, at an inertia operation start time, the rotational speed is controlled to an inertia operation start speed and an inertia operation is started. During the inertia operation, the rotational speed is recorded in the time sequence, and, when the speed becomes an inertia operation end speed, the rotational speed is controlled to a diagnosis rotational speed. Then, an operation unit 9 calculates a feature quantity representing the magnitude of the rotational resistance of the main shaft 1, calculates a feature-quantity-calculation-time lubrication phase indicating the timing to which the representative time for calculating the feature quantity corresponds in the discharge period of a lubricant, and determines the lubrication state of a bearing 2a on the basis of a plurality of feature quantities having different feature-quantity-calculation-time lubrication phases.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a diagnostic device and a diagnostic method for diagnosing the lubricating state of a bearing in a rotary shaft device in which a rotary shaft is supported by a bearing such as a spindle device of a machine tool.

Bearings are used in many rotating shaft devices such as spindle devices of machine tools. In such bearings, it is desirable to reduce the amount of oil supplied to the bearings as much as possible for reasons such as environmental considerations, cost reduction, friction heat generation and power loss suppression. As such an extremely small amount of oil lubrication method, oil air lubrication in which lubricating oil is transported by compressed air is known, and is adopted for lubricating high speed spindle bearings of machine tools. In a rotary shaft device adopting oil-air lubrication, in order to avoid problems such as seizure due to insufficient lubrication, a technique for grasping the supply state of the lubricant and the lubrication state is required.
With regard to this technology, for example, Patent Document 1 discloses a lubricant that monitors the flow rate of oil particles in a lubricant supply path by a sensor that can set the monitoring sensitivity according to oil particles and generates a signal when the flow exceeds a predetermined flow rate. A feeder is shown.
Patent Document 2 discloses a bearing lubrication mechanism that prevents damage to a bearing caused by a lubrication failure by monitoring the amount of lubricant particles flowing through the supply path with a sensor.
Patent Document 3 shows a flow rate measuring device for calculating the flow rate from the volume and the flow rate of a passing oil droplet by a space filter by a standing wave of microwaves.
Patent Document 4 discloses a method of detecting the flow of lubricating oil by an electromagnetic wave of a specific frequency in a pipe line after a mixing valve.
Patent Document 5 calculates the representative value by extracting the cycle data for each operation cycle from continuous data including physical quantity and measurement time in the lubrication state of the movable member in which the machine operation is a constant cycle. An apparatus for diagnosing the absence of lubrication based on the series transition is shown.
Patent Document 6 discloses a method of determining the deterioration state of a spindle by comparing the inertial rotation time and the rotational resistance when the spindle of the machine tool is operated by inertia.
Patent Document 7 discloses a method of detecting whether a grease discharge has been performed by detecting an increase in rotational torque after grease replenishment for a main shaft of grease lubrication.

Unexamined-Japanese-Patent No. 2006-258263 Japanese Patent Application Publication No. 2008-304036 Patent No. 4106075 Patent No. 4920518 gazette Patent No. 4956261 Unexamined-Japanese-Patent No. 2016-200523 JP, 2005-344784, A

In the inventions of Patent Documents 1 to 4, it is possible to judge the abnormality of the lubricant supply up to the detection position by detecting the passage of the lubricant particles in the flow path to which the lubricant is supplied. There is a problem that it can not be determined whether or not the lubricant is supplied to the bearing ahead of the detection position. In addition, since an additional sensor is required to determine the supply state of the lubricant, there is a problem that the manufacturing cost is increased. Furthermore, since the optimum lubricant supply amount differs depending on the built-in preload of the bearing and the spindle speed at the time of processing, it is difficult to judge the quality of the lubrication condition by monitoring the lubricant flow rate. There is.
In the invention of Patent Document 5, although it is possible to determine that the lubrication state deviates from the initial state with respect to a rotary shaft device that repeats a predetermined operation in a fixed cycle such as an injection molding machine, it is a relative determination. If the lubrication state is not proper from the initial state, there is a problem that it may not be detected as an abnormality.
In the invention of Patent Document 6, the degradation state of the machine tool spindle can be determined by setting the inertia rotation time and the threshold value of rotation resistance in advance, but in order to determine the threshold value, variations due to machine differences or seasons There is a problem that a lot of experiments are required to take account of fluctuations and the like. In addition, when the rotational speed changes, the lubricant discharges easily and the amount of heat generation differs, so that if the rotational speed changes significantly during inertial operation, even if the value of rotational resistance during inertial operation is calculated, it is constant. There is a problem that there is a possibility that the diagnosis can not be properly performed because the condition at the time of normal use operated at the rotation speed of the vehicle is not necessarily reflected.
In oil-air lubrication, since the lubrication state periodically changes, it is possible to detect that the oil-air lubrication is functioning by detecting that the rotational torque is increased as in the invention of Patent Document 7. However, there is a problem that it is not possible to determine whether or not the lubrication is insufficient even if it is detected that the rotation torque is increased, since the lubrication state periodically fluctuates as well as the excess and deficiency of the lubricant.

  Therefore, the present invention has been made in view of the above problems, and it is possible to appropriately determine at a low cost whether or not the lubrication state of the bearing in which the lubrication state changes periodically can be appropriately determined. It aims at providing a diagnostic device and a diagnostic method.

In order to achieve the above object, the invention according to claim 1 relates to a rotary shaft apparatus having a rotary shaft supported by a bearing that is lubricated by the periodically discharged lubricant being conveyed by compressed air. A device for diagnosing the lubrication condition of the bearing,
Feature amount calculation means for calculating a plurality of feature amounts representative of the magnitude of the rotational resistance of the rotation axis at different timings;
Lubricating phase calculating means for calculating a lubricating phase at the time of feature amount calculation indicating which timing of the discharge cycle of the lubricant is at a representative time when calculating the feature amount.
The invention according to claim 2 is the configuration according to claim 1, wherein the feature quantity calculation means is a section in which the quantity of the lubricant present on the rolling surface of the bearing decreases in the plurality of feature quantities. In the above.
The invention according to claim 3 is characterized in that, in the configuration according to claim 1 or 2, lubrication state determination means for determining the lubrication state of the bearing based on a plurality of feature amounts having different lubrication phases when calculating the feature amount is provided. Do.
In the invention according to claim 4, in the configuration according to claim 3, the lubrication state determination means calculates an index indicating whether or not the rotation resistance is increased in the lubricant reduction section from the plurality of feature amounts, and the index It is characterized in that when the reference value is exceeded, it is determined that the lubrication is insufficient.
According to a fifth aspect of the present invention, in the configuration according to any one of the first to fourth aspects, an inertial operation means for performing an inertial operation of the rotary shaft, and a rotational speed detection means for detecting a rotational speed of the rotary shaft. The feature amount calculating means is characterized in that the feature amount is calculated based on the change mode of the rotational speed during the inertia operation.
In the invention according to claim 6, in the configuration according to claim 5, in the rotational speed range from the start to the end of the inertial operation in the inertial operation, the fluctuation of the feature value in the rotational speed range during the inertial operation is less than the reference value. It is characterized by deciding.
The invention according to claim 7 displays, in the configuration according to any one of claims 1 to 6, a graph having one of the feature amount and the lubrication phase at the time of feature amount calculation on the vertical axis and the other on the horizontal axis. A display unit is provided.
In order to achieve the above object, the invention according to claim 8 relates to a rotary shaft apparatus having a rotary shaft supported by a bearing which is lubricated by the periodically discharged lubricant being conveyed by compressed air. A method of diagnosing the lubrication condition of a bearing,
A feature amount calculation step of calculating a plurality of feature amounts representative of the magnitude of the rotational resistance of the rotation axis at different timings;
A lubricant phase calculating step of calculating a lubricant phase at the time of feature amount calculation indicating which timing of the discharge cycle of the lubricant is the representative time at which the feature amount is calculated;
At the time of feature amount calculation, a lubrication state determination step of determining the lubrication state of the bearing based on a plurality of feature amounts different in lubrication phase is performed.

According to the present invention, the bearing rolling surface is characterized in that the amount of lubricant present in the bearing is increased when the amount is too large or too small, and decreases when approaching an appropriate amount. In order to determine whether or not the lubricant is insufficient by calculating multiple times at the timing when the lubricant present in the area decreases and determining whether the feature value is increasing, it is necessary to experiment to set the threshold value. Absent. In addition, if a control device and a speed detector provided in a general rotary shaft device are used, an additional sensor is not necessary, and it becomes possible to appropriately grasp and diagnose the lubrication state of the bearing at low cost. Furthermore, since the rotational speed range from the start to the end of the inertial operation is determined so that the rotational resistance does not significantly fluctuate during the inertial operation, the change in the rotational speed is too large and diagnosis is performed in a state significantly different from that in normal use. You can prevent that.
Then, by displaying the transition of the rotational resistance, it is possible to visually grasp the fluctuation of the lubrication state.

It is the schematic of a lubrication condition diagnostic apparatus. It is a flowchart of a lubrication state diagnosis method. It is a graph which shows the example of measurement of rotation resistance. It is a graph which shows the rotational speed waveform at the time of diagnostic operation.

Hereinafter, embodiments of the present invention will be described based on the drawings.
FIG. 1 shows the configuration of a lubrication state diagnostic device provided in a spindle device of a machine tool as a rotary shaft device, and this will be specifically described based on this drawing.
The spindle 1 is rotatably attached to the spindle housing 2 via bearings 2a, 2a which are rolling bearings, and a tool 3 for processing is fixed. The motor 4 drives the spindle 1. At the time of processing, the control device 6 controls the current supplied to the motor 4 so as to maintain the rotational speed of the motor 4 measured by the speed detector 5 as the rotational speed detecting means at the commanded rotational speed. The lubricating device 7 discharges a fixed quantity of lubricant at a set time interval (hereinafter referred to as a lubricant discharge cycle), mixes it with compressed air, passes a pipe not shown, and supplies the lubricant to the bearings 2a, 2a Do.

  Since the lubrication state of the bearing 2a fluctuates in the lubricant discharge cycle, the lubrication state of the bearing 2a can be regarded as the same even at different times if the elapsed time from the latest lubricant discharge is the same. Also, in order to generally discuss the same lubrication state regardless of the lubricant discharge cycle, a non-dimensional value obtained by dividing the elapsed time from the latest lubricant discharge by the lubricant discharge cycle is defined as the lubricant phase. . The lubricant phase takes a value of 0 or more and less than 1, and the lubricant is discharged when the lubricant phase becomes 0.

Reference numeral 100 denotes a lubrication state diagnosis device for the bearing 2 a, which includes a storage unit 8, a calculation unit 9, and a display unit 10. At the time of a diagnosis operation by the lubrication state diagnosis device 100, the control device 6 performs control to stop the power supply to the motor 4 to be in an inertial operation state, in addition to the control to keep the rotational speed of the motor 4 at the command rotational speed. That is, the control device 6 also functions as an inertial operation means.
The storage unit 8 includes the moment of inertia of the rotating body, the lubricant discharge cycle, the latest lubricant discharge time, the estimated time to start the inertia operation, the diagnostic rotation speed set in advance, the inertia operation start speed set in advance, the inertia operation end set in advance Speed, time-series data of rotational speed during inertial operation, whether or not inertial operation at the lubrication phase at the start of each inertial operation has been performed, lubrication phase at feature value calculation described later, rotational resistance at diagnostic rotational speed arrival time described later , Date of diagnosis, increase rate of rotational resistance, and determination result of lubrication state are stored.

The calculation unit 9 calculates an inertial operation start scheduled time from the current time whether the lubricant ejection period, the latest lubricant ejection time, and the inertial operation at the lubrication phase at the start of each inertial operation have been performed. Further, the diagnostic rotational speed arrival time is calculated from the time-series data of the rotational speed during the inertial operation, and the time-series data of the diagnostic rotational speed and the rotational speed during the inertial operation. Furthermore, the lubricant phase at the time of feature amount calculation is calculated from the lubricant discharge period, the latest lubricant discharge time, and the diagnostic rotational speed arrival time. In addition, the rotational resistance at the diagnosis rotational speed arrival time is calculated from the moment of inertia of the rotating body, time-series data of the rotational speed during inertial operation, and the diagnostic rotational speed. Then, the increase rate of the rotational resistance is calculated from the lubricating phase at the time of feature amount calculation and the rotational resistance at the diagnosis rotational speed arrival time, and the determination result of the lubricating state is calculated from the increase rate of the rotational resistance. That is, it functions as the feature amount calculating means, the lubricating phase calculating means, and the lubricating state determining means of the present invention.
The display unit 10 displays the determination result of the lubrication state and a two-dimensional graph in which the lubrication phase is on the horizontal axis and the rotational resistance is on the vertical axis.

The amount of lubricant supplied to the bearing 2a becomes maximum at a timing delayed by the time when the lubricant is conveyed by compressed air and reaches the bearing 2a from the timing when the lubricant is quantitatively discharged (the lubricant phase is 0). Decrease with time. Therefore, the amount of lubricant present on the bearing rolling surface changes from decrease to increase to decrease from the timing of the lubricant phase 0 to the timing of the next 0.
On the other hand, the value of rotational resistance decreases when the amount of lubricant present on the bearing rolling surface approaches an appropriate state from an excessive state, and the amount of lubricant present on the bearing rolling surface is appropriate It has characteristics that increase as it approaches a shortage.
From the above, when the rotational resistance is regarded as a function of the lubricant phase, as shown in FIG. 3, the lubricant is discharged from the timing (in the vicinity of the phase 1⁄4 of FIG. Since the amount of the lubricant present on the bearing rolling surface is reduced at the timing (in the vicinity of the phase 3/8 in the same figure) at which the inclination of the rotational resistance becomes opposite sign immediately after that, this section or this If the value of rotational resistance increases in a narrower section ("lubricant decreasing section" shown in FIG. 3), it can be determined that the lubrication is in an insufficient state.

FIG. 2 shows a flowchart for diagnosing the lubrication state of the bearing 2a in the lubrication state diagnostic device 100. FIG. 4 shows changes in rotational speed at the time of diagnostic operation, inertial operation start speed, diagnostic rotation The relationship between the speed, the inertial operation end speed, the inertial operation start time, and the diagnostic rotational speed arrival time is shown. A concrete description will be given based on this flowchart and FIG.
First, at S1, the main shaft 1 is rotated at a diagnosis rotational speed (here, 4000 min ⁻¹ ) via the control device 6, and the inertial operation start time is waited (S2). When it is determined in S2 that the inertial operation start time comes (Y in S2: YES), in S3, the rotational speed is controlled to the inertial operation start speed (here, 4100 min ⁻¹ ) to start the inertial operation. During the inertial operation, the rotational speed is recorded in time series (S4), and it is waited to reach the inertial operation end speed (here, 3900 min- ¹ ) (S5).

  If it is determined in S5 that the velocity has reached the end of the inertia operation (Y in S5: YES), the rotational speed is controlled to the diagnostic rotational speed in S6. Then, in S7, from the time series data of the recorded rotational speed and the value of the moment of inertia of the rotating body, the time when the diagnostic rotational speed is reached during the inertial operation used as the feature amount in the present diagnostic device (hereinafter While calculating the value of the rotational resistance according to equation (1) according to the following equation (1), and the lubricant phase at Step and Lubrication phase calculation step). In this diagnosis apparatus, the diagnosis rotational speed arrival time is used as a representative time. The angular acceleration is a derivative of the rotational speed.

Rotational resistance = -1 × moment of inertia × angular acceleration · · · · (1)
Feature calculation time lubrication phase = (diagnosis rotation speed arrival time-latest lubricant discharge time at diagnosis rotation speed arrival time) 時刻 lubricant discharge cycle · · · (2)

  However, in S7, the ratio of the difference between the maximum value and the minimum value of the rotational resistance between the inertial operation start speed of one inertial operation and the inertial operation end speed to the average of the rotational resistance exceeds the reference value (for example 15%) In this case, since the change in rotational speed is too large, it is determined that the rotational resistance can not be estimated during normal use operating at a constant rotational speed, and the difference between the inertial operation start speed and the inertial operation end speed is reduced. Make a diagnosis from the beginning again.

Next, in S8, the rotational resistance at the diagnosis rotational speed arrival time, and the lubrication phase at the time of feature amount calculation are recorded, and the inertial operation at the lubrication phase at the start of the current inertial operation is recorded as implemented.
In S9, it is determined whether or not the inertia operation in all the lubrication phases at the start of the inertia operation has been performed, that is, whether or not the diagnosis is possible, and if there is a lubrication phase that has not been performed (N in S9: (NO), calculate the inertial operation start time, and return to S2. If it has already been implemented (Y in S9: YES), in S10, from the rotational phase resistance at the feature amount calculation time and the diagnostic rotational speed arrival time, the increase rate of the rotational resistance used as a diagnostic index in this diagnostic device is Calculated according to equation (3).

  Rate of increase of rotational resistance = average of inclination of rotational resistance in lubricant reduction section 平均 average of rotational resistance in lubricant reduction section · · · (3)

Then, in step S11, the lubrication state is determined (lubrication state determination step). Here, when the rate of increase in rotational resistance is greater than the reference value 0%, it can be determined that the rotational resistance is increasing in the lubricant decreasing section, so it is determined that the lubrication is insufficient.
At S12, a two-dimensional graph in which the lubrication phase indicating the transition of the lubrication state is taken along the abscissa and the rotational resistance is taken along the ordinate, and the diagnosis result of the lubrication state is displayed on the display unit 10.

As described above, according to the lubrication state diagnosis device 100 of the above embodiment, the calculation unit 9 calculates a plurality of feature quantities representative of the magnitude of the rotational resistance of the main spindle 1 at different timings and calculates the feature quantities. Lubrication phase is calculated at the time of feature quantity calculation which indicates which timing of representative cycle of lubricant is at the discharge cycle of lubricant, and at the time of feature quantity calculation, the lubrication state of the bearing 2a is judged by a plurality of feature quantities different in lubrication phase. . That is, the timing at which the amount of lubricant present on the bearing rolling surface decreases when the amount of lubricant present in the bearing 2a is increased when the amount is too large or too small, and decreases when approaching an appropriate amount. In order to determine whether or not the lubrication is insufficient by calculating a plurality of times and checking whether or not the rotational resistance is increasing, it is not necessary to perform an experiment to set the threshold value. Further, since the control device 6 and the speed detector 5 provided in the spindle device are used, an additional sensor is not necessary, and it becomes possible to appropriately grasp and diagnose the lubrication state of the bearing 2a at low cost. Furthermore, since the rotational speed range from the start to the end of the inertial operation is determined so that the rotational resistance does not significantly fluctuate during the inertial operation, the change in the rotational speed is too large and diagnosis is performed in a state significantly different from that in normal use. You can prevent that.
In particular, here, since the transition of the rotational resistance is displayed on the display unit 10, it is possible to visually grasp the fluctuation of the lubrication state.

In the above embodiment, the value of the rotational resistance during inertia operation, which is directly related to the lubrication state of the bearing, is used as the feature amount representing the magnitude of the rotational resistance, but the change in moment of inertia at diagnosis If it can be ignored, the absolute value of the angular acceleration at the time of inertial operation or the like may be used.
In addition, although an example of calculating the rotational resistance from the values of angular acceleration and moment of inertia during inertial operation has been shown as feature quantity calculation means, as long as sufficient measurement accuracy can be obtained to capture fluctuations in the rotational resistance, The rotational resistance may be calculated from the value of the power supplied to the motor and the value of the rotational speed in order to keep the rotational speed at a constant command rotational speed, or flowed to the motor to maintain the rotational speed at a constant command rotational speed The magnitude of the current may be used as the feature quantity. In this case, the feature quantities can also be measured not continuously but discretely with respect to the lubrication phase. The representative time for calculating the feature amount may be a time at which the magnitude of the power or current supplied to the motor is measured or commanded.

Furthermore, although an example of 0% was shown as a reference value for the rate of increase in rotational resistance, it may be a value larger than 0% to avoid misjudgment due to measurement variation, or 0% to reliably avoid insufficient lubrication. It may be a smaller value.
On the other hand, although an example was shown using the increase rate of rotational resistance as an index for performing the lubrication state classification, any index that expresses increase or decrease of rotational resistance in the lubricant reduction section may be used. May be replaced with the ratio of the phase which increased, etc.
If the ratio of the difference between the inertial operation start time and the diagnostic rotational speed arrival time to the lubricant discharge cycle is smaller than the interval of the lubrication phase to start the inertial operation, the inertial operation start time is represented instead of the diagnostic rotational speed arrival time It may be time.
Furthermore, although the determination result of the lubrication state is calculated from the increase rate of the rotational resistance and the determination result is displayed, the increase rate of the rotational resistance and the display of the two-dimensional graph are limited and the operator determines from the display content You may do it.

  In addition, the bearing diagnosis apparatus and method of the present invention are applicable not only to the spindle device of the machine tool, but also to the rotary shaft device of other mechanical equipment such as an automobile, a railway vehicle, and a ship.

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Claims (8)

A rotary shaft device having a rotary shaft supported by a bearing that is lubricated by being conveyed by compressed air, a lubricant that is periodically discharged, and a device that diagnoses the lubricating state of the bearing,
Feature amount calculation means for calculating a plurality of feature amounts representative of the magnitude of the rotation resistance of the rotation axis at different timings;
Lubricating phase calculating means for calculating a lubricating phase at the time of feature amount calculation indicating which timing of the discharge cycle of the lubricant is the representative time at which the feature amount is calculated;
An apparatus for diagnosing a lubrication state of a bearing in a rotary shaft apparatus, comprising:   The feature quantity calculation means calculates the plurality of feature quantities in a lubricant reduction section, which is a section in which the amount of lubricant present on the rolling contact surface of the bearing decreases. Lubrication state diagnostic device of the bearing in a rotating shaft apparatus of a statement.   The bearing according to claim 1 or 2, further comprising: a lubrication state determination unit that determines the lubrication state of the bearing based on a plurality of the feature amounts different in lubrication phase when calculating the feature amount. Lubrication status diagnosis device.   The lubrication state determination means calculates an index indicating whether the rotational resistance is increasing in the lubricant reduction section from the plurality of feature amounts, and determines that the lubrication is insufficient when the index exceeds a reference value. The lubricating state diagnostic device of the bearing in the rotating shaft apparatus of Claim 3 characterized by the above-mentioned. Inertial operation means for performing an inertial operation of the rotary shaft;
And rotational speed detection means for detecting the rotational speed of the rotation shaft,
The lubrication state of the bearing in the rotary shaft device according to any one of claims 1 to 4, wherein the feature amount calculation means calculates the feature amount based on a change mode of the rotational speed during the inertial operation. Diagnostic device.   The rotational speed range from the start to the end of the inertial operation in the inertial operation is determined such that the fluctuation of the feature value in the rotational speed range during the inertial operation is less than or equal to a reference value. Lubrication status diagnosis device for bearings in the rotary shaft device of   The display device according to any one of claims 1 to 6, further comprising a display unit for displaying a graph having one of the feature amount and the lubricant phase at the time of the feature amount calculation on the vertical axis and the other on the horizontal axis. Lubrication state diagnostic device of the bearing in the rotating shaft apparatus of description. A rotary shaft device having a rotary shaft supported by a bearing that is lubricated by being conveyed by compressed air, a lubricant that is periodically discharged, and a method of diagnosing the lubrication state of the bearing,
A feature amount calculation step of calculating a plurality of feature amounts representative of the magnitude of the rotational resistance of the rotation axis at different timings;
A lubricant phase calculating step of calculating a lubricant phase at the time of feature amount calculation indicating which timing of the discharge cycle of the lubricant is the representative time at which the feature amount is calculated;
A lubrication state determination step of determining the lubrication state of the bearing based on a plurality of the feature amounts different in lubrication phase when calculating the feature amount;
A method of diagnosing the lubrication state of a bearing in a rotary shaft device, characterized in that:

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