JP3185066B2 - Ball screw life monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a ball screw, a ball bearing,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for monitoring the life of a roller bearing or the like, and more particularly to a device for monitoring the life of a ball screw which displays a remaining life while actually measuring a ball screw or a bearing at predetermined intervals.

[0002]

2. Description of the Related Art Conventionally, the life, which is one of the most important factors as a selection criterion for a ball screw, a bearing, and the like, is calculated and selected at the design stage, but how long the operation has been performed since the start of operation and the rated value. Since it is not known how much the remaining life is relative to the fatigue life, it was impossible to instruct an appropriate replacement time. That is, the rated fatigue rotation speed R
[Rev] is obtained as being proportional to the m-th power of a value obtained by dividing the basic dynamic load rating C [kg] by the operating equivalent load P [kg]. However, the basic dynamic load rating C is
The exponent m is 3 in the case of a ball screw and a ball bearing, and 10 / in the case of a roller bearing.
It is set to 3. Further, the rated fatigue life L [h] is obtained by dividing the rated fatigue rotation speed R [rev] by the average rotation speed N [rev / min] during the period in question. Further, the operation equivalent load P is a load at the average rotation speed N.

[0003]

However, let us see how such a calculation formula is used. First, in the design stage, for example, when the operating equivalent load P of the ball screw is estimated to be の of the true value, the rated fatigue life L obtained by calculation becomes eight times the true value, and the life limit is reduced. It will be used greatly beyond. Next, looking at the operation stage, even if the rated fatigue life L is given and the actual operation time is measured and recorded, a somewhat conceptual operation equivalent load P is obtained.
It is almost impossible to record while calculating the average rotation speed N. At best, it can only be expected to estimate the remaining life while sequentially subtracting the actual operating time from the given rated fatigue life L. Thus, in the first place, it was not possible to grasp the exact rated fatigue life, and moreover, it had to repeat the estimation twice,
In addition, since the actual operating time, the load, and the number of rotations cannot be easily and constantly monitored, an appropriate remaining life at each time cannot be estimated. Therefore, it can be presented only at a level of about several years as a guide, and therefore, actually increase torque, generate noise,
The fact is that the replacement procedure is started due to a failure such as inoperability.

[0004] In view of the drawbacks of the prior art, the present invention provides
An object of the present invention is to provide a life monitoring device capable of displaying an accurate remaining life of a ball screw, a ball bearing, a roller bearing, and the like.

[0005]

[0006]

SUMMARY OF THE INVENTION The present invention relates to a rotation transmission device and the like.
In the axial direction of the ball screw used for
Relationship between the load and the current value of the motor that drives the ball screw
And means for pre-storing the basic dynamic load rating of the ball screw.
Steps, the sampling time interval and the sampling interval
Means for setting the divided unit minute time, and the unit minute time
Measure the rotation speed of the ball screw shaft and motor current value
Means, a value measured by the measuring means,
Between the read axial load and the motor current value.
Based on the basic dynamic load rating of the ball screw.
Calculation means for calculating the rated fatigue life value for each
The rated fatigue life value calculated for each sampling interval
Can be rewritten, and the ball screw
Display means for each rewriting of the remaining life with reduced usage of
Is configured to be able to be displayed. More preferably, the usage amount may be always subtracted from the remaining life during the sampling interval, and the remaining life at each time may be displayed.
Here, the used amount of the ball screw means the number of rotations of the ball screw, and the variation coefficient means the motor current value and the number of rotations of the ball screw shaft. Also, the ball screw
Relationship between axial load and motor current value, and the ball screw
Means for pre-storing the basic dynamic load rating of the
Means for setting the interval and time of use, and the use of said ball screw
Means for recording the amount, which changes at each sampling interval.
Coefficient of dynamics and the rated fatigue calculated based on the measured values.
And the remaining life for each interval
It is characterized by displaying. Still more preferably, the usage amount is always subtracted from the remaining life during the sampling interval,
The remaining life at that time may be displayed. Here, the used amount of the ball screw means the number of rotations of the ball screw, and the variation coefficient means the motor current value and the number of rotations of the ball screw shaft.

Further, the present invention is characterized in that the bearing is configured similarly to the case of the ball screw, and the remaining life at each sampling interval is displayed. Specifically, a rotation transmitter, etc.
Bearings, the axial load of the bearing and the bearing
Relationship with the current value of the shaft drive motor and the basic operation of the bearing
Means to pre-store rating load and sampling time interval
And a unit minute time obtained by dividing the sampling time interval.
Means for determining the shaft rotation speed and
Means for measuring the data current value, and the measured value from the measuring means
And an axial load and a motor read from the storage means.
Of the bearing and the basic dynamic load rating of the bearing
To calculate the rated fatigue life value for each sampling interval.
Calculating means for calculating at every sampling interval.
The rated fatigue life value can be rewritten,
The remaining life obtained by subtracting the amount of bearing used from the value
The display is configured to be able to be displayed on the display means. Preferably, similarly to the case of the ball screw, during the period of the sampling interval, the usage amount may be always subtracted from the remaining life, and the remaining life at each time may be displayed. However, depending on the type of the bearing, the rated fatigue speed, the power in the calculation formula for calculating the rated fatigue life is different, so either use an algorithm properly, or according to the model, the power multiplier,
Enter the exponent.

Further, the present invention provides a means for storing in advance the numerical value and the basic dynamic load rating of the ball screw when the axial load of the ball screw / bearing is known, It is provided with a means for recording, and is configured such that a rated fatigue life value calculated based on a rotational speed constantly measured and a used rotational speed obtained by decoding the rotational speed can be rewritten every moment, and the remaining life is displayed. It may be.
Specifically, ball screws used in rotation transmitters, etc.
And the average axial load of a known ball screw and the ball
Means for storing the basic dynamic load rating of the ball screw,
Means for recording the number of rotations used, wherein the storage means and
Average axial load and basic dynamic load rating obtained from recording means
Fatigue life based on the operating speed of the ball screw and ball screw
Calculation means for calculating rewritably every moment,
The remaining value obtained by subtracting the amount of the bearing used from the rated fatigue life value
A board equipped with display means for displaying the life for each rewrite
Characterized by life monitoring device ball screw, also the rotating transfer machine or the like
For the bearing used, the average axial load of the known bearing
Means for storing the basic load rating of the bearing, and use of the bearing.
Means for recording the number of rotations for use.
Average load and basic dynamic load rating obtained from recording means
The rated fatigue life based on the operating speed of the bearing
Equipped with calculation means for calculating rewritably, calculated rating
The remaining life obtained by subtracting the amount of the bearing used from the fatigue life value
Bearing life monitoring with display means for displaying each time of rewriting
It features a visual device.

[0009]

According to this technical means, the relational expression between the axial load applied to the ball screw in question and the current value of the motor driving the ball screw is determined in advance, and the basic dynamic load rating C is determined. On the other hand, if the rotation speed of the ball screw shaft and the motor current value in the unit minute time actually obtained by dividing the predetermined time are measured, the average value and the average rotation speed N of the operation equivalent load P in the predetermined time are calculated. Can be calculated,
The rated fatigue rotation speed R and the rated fatigue life L, which are the remaining life of the ball screw, can be calculated and displayed. Thereafter, the sampling measurement is periodically continued, the average value of the operation equivalent load P and the average rotation speed N are calculated and updated, and the remaining lives R and L can be updated and displayed. Preferably, the number of revolutions of the ball screw shaft is constantly measured and accumulated and recorded, and the number of revolutions is subtracted from the once determined remaining lives R and L, and the remaining life can be displayed every moment.

Further, even in the case of bearings, the exponentiation of the calculation formula may differ depending on the type of the bearing. Therefore, by selecting and inputting the exponentiation, the remaining life R and L can be reduced just like the ball screw. You can ask.

Further, when the axial load of the ball screw / bearing is known, this numerical value and the basic dynamic rated load of the ball screw are stored in advance to calculate the remaining life, and the operating speed of the ball screw is simply calculated. By constantly measuring N and accumulating and recording / calculating it, the values of the rated fatigue rotational speed R and the rated fatigue life L can be rewritten instantaneously, and the remaining life can be displayed.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. Not just.

FIG. 2 is a schematic front view showing the configuration of a ball screw used in the embodiment of the present invention. Reference numeral 10 denotes a ball screw shaft, which is connected to a ball nut 11 fitted on the ball screw shaft. The ball screw shaft 10 is formed and supported by bearings 13 and 14 fixed to a base 12 at appropriate intervals, and one end thereof is connected to a motor 15 via a coupling 16. In such a configuration, if the motor 15 is driven, the rotation of the ball screw shaft 10 causes the ball nut 11 to move right and left together with the table 19 fixed to the ball nut 11. The configuration and operation of the ball screw is preferably applied particularly to positioning by numerical control of a machine tool, and in many cases,
The motor 15 is provided with a tachometer 17 coaxially with the motor 11, and the tachometer 17 outputs a follow-up value proportional to the rotation speed N and forms a part of the numerical control servo mechanism.

Now, in a ball screw incorporated in a specific machine tool, a load cell 18 is arranged on a bearing portion of a ball nut 11 on which a thrust acts. And the rotation speed N of the ball screw shaft 10 are measured and recorded. FIG. 3A is a characteristic diagram in which the motor current value I and the rotation speed N when the ball screw is rotated are recorded on the time axis. The broken line I indicates the motor current value, and the solid line N indicates the rotation speed. is there. FIG. 3B shows the motor current value | I when the absolute value conversion is performed for accumulation.
| And the shaft rotation speed | N | are shown by the broken line and the solid line, respectively, in the characteristic diagram of the ball screw. Separately, a relationship diagram (not shown) between the motor current value I and the axial load P by the load cell 18 is obtained at the same time.

When calculating the rated fatigue rotation speed R ₁ and the rated fatigue life L ₁ from the first actually measured values, first, the measurement time t [minutes] is divided into j, and the rotation speed N is calculated. ₁ , N
_{From the} axial loads P ₁ , P ₂ , ..., Pj at ₂ ,, ..., Nj
An average operation equivalent load Pm ₁ and an average rotation speed Nm ₁ are obtained. That is, Pm ₁ = [Σ (Pj ³ · Nj) / ΣNj] ^1/3 [kg] Equation (1) Nm ₁ = (ΣNj) / j [rev / min] Equation (2) Therefore, R ₁ = [C / (Pm ₁ · f ₁ )] ³ × 10 ⁶ [rev] Equation (3) L ₁ = R ₁ / (60 · Nm ₁ ) [h] Equation (4) where C is the model and size of the ball screw Is a basic dynamic load rating given as an eigenvalue by f, and f is an operation coefficient determined by an operation state, and is 1.3 in normal operation. Incidentally, f is about 1.8 in an operating state involving an impact.

That is, the rated fatigue rotational speed R _1, which means the total usable rotational speed of the ball screw under a specific load, is expressed by the following equation (3). According to equation (4), the rated fatigue life L ₁
It means that I was asked. Both values may be displayed as they are, but if the rotation speed | N | is continuously measured during the use period, and the use rotation speed r ₁ converted and accumulated into the rotation speed by the encoder is subtracted from the R ₁ , The remaining rotation speed R ₁ ′ and the remaining life L ₁ ′ at that time are obtained, and it is more specific if these countdown values are displayed.

Further, during actual operation, every predetermined period T [h],
The operation equivalent load P and the rotation speed N are reviewed and corrected. That it is, hit a second sampling, the rotation speed R ₁ of the remaining 'are consideration that is R ₁ -r _1, the basic dynamic load rating C ₂ remaining finding with reference to the equation (3) When, the _{C 2 = Pm 1 · f 1} [(R 1 -r 1) · 10- 6] 1/3 equation (5). Therefore, the average axial load Pm ₂ , which is the second measurement value,
Rated fatigue rotational speed R corrected by average rotational speed Nm _2
2 and the rated fatigue life L ₂ are given by the following equations (6) and (7). R ₂ = [C ₂ / (Pm ₂ · f ₂ )] ³ × 10 ⁶ [rev] Equation (6) L ₂ = R ₂ / (60 · Nm ₂ ) [h] Equation (7) where f ₂ is Is an operation coefficient when it is set in advance so that it can be automatically selected based on the magnitude of the fluctuation of the motor current value I.

Here, looking back on the second measurement and calculation, the relationship between the motor current value I and the axial load P by the load cell 18 does not seem to change throughout the life of the ball screw. If this relational expression is stored in the calculation means in advance, the load cell 18 can be omitted from a ball screw incorporated in a machine tool, for example.

As described above, the motor current value I and the axial load P
When the numerical values to be stored in the calculation means in addition to the relational expression are arranged, the following parameters can be raised. C: Basic dynamic load rating T: Sampling interval t: Sampling time j: Number of divisions for dividing the measurement time t to obtain an average value m: Equation (3) determined by the type of ball screw and bearing,
(6) Exponentiation, etc. f: operating coefficient or fi: operating coefficient selected from the fluctuation value of motor current value I in the i-th sampling. Nij: rotation as a fluctuation coefficient obtained at every i-th sampling Speed and Pi at the rotation speed Nij
j: The measured value of the axial load is input to the calculating means, and the remaining life is updated and calculated.

FIG. 1 is a block diagram showing a configuration and a calculation procedure of a life monitor of a ball screw according to an embodiment of the present invention. Reference numeral 15 'denotes a motor 15 for driving the ball screw 10.
, 17 is a shaft tachometer, and 18 is a load cell disposed on the ball nut. The table 19 fixed to the ball nut 18 is mounted on a carriage of a machine tool, for example. The storage device 22 stores a relational expression between the current value | I | by the motor ammeter 19 and the axial load P measured by the load cell 18. The sampling device 26 stores, via the input device 20, the sampling interval T, the sampling time t, and various setting values of the number j of divisions for dividing the sampling time t to obtain an average value. Via the input device 21, the basic dynamic load rating C, the operation coefficient f, or the motor current value I
Coefficient fi selected according to the magnitude of the variation of the power, and the power m of the calculation formula selected according to the ball screw / bearing
Are stored in the calculation device 30. Further, the alarm generation value Lz ′ is stored in the alarm generation device 45 via the input device 23. Reference numeral 25 denotes a timer for accumulating a clock signal in the computing device 30, and a time from the start of operation is prepared. The usage metering device 27 is a device that decodes the rotation speed | N | from the tachometer 17 and continuously accumulates the operating rotation speed ri from the end of each sampling to the next sampling. A display device 40 displays the remaining life Li 'of the ball screw updated and calculated for each sampling.

The operation of the thus configured ball screw monitoring device will be described. After assembling the ball screw into, for example, a machine tool, the motor 15 is actually driven to perform the first sampling, and the motor current values I ₁₁ , I ₁₂ ,. ..,
I ₁ j and the rotation speeds N ₁₁ , N ₁₂ ,..., N ₁ j are read into the sampling device 26. Motor current values I ₁₁ , I ₁₂ , ..., I ₁ j
, The axial load P _11, P ₁₂ with reference to stored in the storage unit 22 the relational expression, ..., is converted into P ₁ j, the rotational speed _{N 11, N 12, ...,} N 1 After A / D conversion with j, the calculation device 3
Moved to 0.

In the calculating device 30, the average operating equivalent load Pm ₁ is calculated in step 31 based on the above equations (1) and (2).
[Kg] and average rotation speed Nm ₁ [rev / min]
In step 32, the rated fatigue rotation speed R ₁ [rev] and the rated fatigue life L ₁ [h] are calculated based on the equations (3) and (4). In the procedure 33 determines the remaining number of revolutions R 1 _'at that time subtracted the operating rotational speed ri, which is accumulated in the usage metering device 27 from the nominal fatigue rotational speed R _1,
Subsequently, the R ₁ ′ is divided by the average rotation speed Nm ₁ ,
The remaining life L ₁ ′ [h] at that time is obtained. As described above, the remaining life L ₁ ′ [h] is continuously obtained until the next sampling is performed.
Is displayed on the display device 40.

Subsequently, the timer 25 and the sampling interval T
Are constantly compared, and the sampling device 26 that knows the next sampling time performs the second sampling,
The motor current values I ₂₁ , I ₂₂ ,..., I _2j and the rotational speeds N ₂₁ , N ₂₂ ,..., N _2j are read, and the motor current values I ₂₁ , I _{22 ,. Are} converted into directional loads P ₂₁ , P _{22 ,.}
Informed to 0. In the computing device 30, the procedure 31,
The remaining life L ₂ ′ [h] at that time is obtained from 32 and 33 and displayed on the display device 40 every moment. However, the basic dynamic load rating C ₂ remaining after the second sampling, procedure 34
In formula (5), Pm ₁ , f ₁ , and R ₁ −
r ₁ call to update. Therefore, in the procedures 31 and 32, the equations (6) and (7) are used.

The above procedure is repeated, i.e., sampling is performed i times to reach the rated life Li ', and when it becomes smaller than the alarm generation value Lz', the alarm generator 45 is activated to generate an alarm, and the maintenance time comes. Notify what you did.

As described above, according to the present embodiment, the remaining life prediction, which was only a guideline for selection at the design stage, is based on the assumption that the operating equivalent load P is mediated by the motor current value I and the rotation speed N is Since the actual life is measured while sampling and the remaining life is calculated and displayed, accurate design can be confirmed at the beginning of assembly and appropriate judgment criteria can be provided during operation. Will be. Therefore, in the design stage, it is possible to accumulate technologies while reviewing the selection criteria so that the selection of the ball screw can be performed more accurately and reliably. In addition, during operation, so-called pre-maintenance becomes possible instead of arranging repairs after a problem occurs, incorporating the ball screw.
For example, it is possible to improve the operation rate of a machine tool.

In the above embodiment, the apparatus for monitoring the life of a ball screw has been described. However, the present invention can be applied to other bearings as they are. The life of a roller bearing can be monitored by the same procedure simply by replacing the exponent m = 3 in the calculation formula with 10/3.

In the above-described embodiment, the average axial load (operating equivalent load) P was obtained by sampling through the motor current value. However, if the operation equivalent load P during the life of the ball screw / bearing is known, or if it can be estimated by accumulating the technology according to the present invention, or if the machine tool equipped with the actual equipment is shipped from the manufacturing plant before shipment. When the axial load P obtained at the time of the test operation can be constant over the entire life of the ball screw / bearing, no sampling measurement is performed during operation. Therefore, if a known average axial load of the ball screw / bearing and the basic dynamic load rating of the ball screw are stored in advance, and means for recording the number of rotations of the ball screw / bearing are provided,
In the above calculation procedure, the rated fatigue life value L can be calculated using only ri and Rmi as variation coefficients. In addition, since the coefficient of variation merely processes the signal from the tachometer, the coefficient of variation can be rewritten momentarily, and the remaining life can be displayed.

Further, if an excessive motor current is detected, it means a failure such as an overrun of a machine incorporating the ball screw / bearing, for example, a machine tool overrun or a breakage of a blade.
An alarm can be issued by the alarm device.

[0029]

As described above, according to the present invention, the operating equivalent load P and the rotational speed N of the ball screw / ball bearing / roller bearing are provided.
Was measured during actual operation, and the remaining life was calculated and displayed, so that at the beginning of the assembly, an accurate design was confirmed, and the selection of ball screws and bearings was performed more accurately and reliably. It will also be possible to accumulate technology so that things can be done.
In addition, the accumulation of the above-mentioned technology enables accurate prediction of the life of the ball screw / bearing, and enables a reliability design. Also, even during operation, the so-called pre-maintenance becomes possible because the measurement is performed while sampling and the remaining life is calculated and displayed, and the operation rate of the device incorporating the ball screw / bearing, for example, the machine tool is reduced. It can be improved. Further, when the operation equivalent load value is known, since the operation equivalent load value is given to the calculation means in advance,
Since the calculation is possible every moment, the remaining life at that time can be displayed without sampling measurement. Further, even in the case of a plurality of ball screws / bearings, the remaining life thereof can be displayed in the same manner as described above by performing time-division processing calculation with the processing capacity of the computer as a limit. Further, by configuring so that an excessive motor current is detected and an alarm is issued by an alarm device, it is possible to know the malfunction of the device incorporating the ball screw / bearing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration and a calculation procedure of a life monitor of a ball screw according to an embodiment of the present invention.

FIG. 2 is a schematic front view showing a configuration of a ball screw used in an embodiment of the present invention.

3A and 3B are characteristic diagrams when a ball screw according to an embodiment of the present invention is operated. FIG. 3A is a characteristic diagram in which a motor current value and a rotation speed are recorded on a time axis, and FIG. (A) Characteristic diagram obtained by performing absolute value conversion on the diagram

[Explanation of symbols]

 Reference Signs List 10 Ball screw 20 Input device 21 Input device 26 Sampling device 27 Usage measuring device 30 Calculator 40 Display C Basic dynamic load rating I Variation coefficient (motor current value) L Rated fatigue life value N Variation coefficient (rotation speed) P axis Directional load T sampling interval t sampling time

Claims (4)

(57) [Claims] (1)For ball screws used in rotation transmitters, etc.
Drive the ball screw axial load and the ball screw
Between the current value of the rotating motor and the basic operation of the ball screw
Means to store the rated load in advance, and between sampling time
Set the unit minute time by dividing the interval and the sampling interval
Means to The rotation speed of the ball screw shaft and the motor
Means for measuring the current value; The measured value from the measuring means and the value read from the storage means.
Between the applied axial load and the current value of the motor and the ball
Each sampling interval based on the basic dynamic load rating of the screw
Calculating means for calculating a rated fatigue life value, Write the rated fatigue life value calculated for each sampling interval.
Replaceable, and use the ball screw from the rated fatigue life value.
The remaining life of the reduced dose is displayed on the display for each rewrite.
Configured to show Ball screw life monitoring device. (2)Bearing smell used in rotation transmission machines, etc.
The axial load of the bearing and the current value of the shaft drive motor of the bearing
And the basic dynamic load rating of the bearing are stored in advance.
Means, sampling time interval and the sampling time
Means for setting a unit minute time obtained by dividing the interval, Measures shaft rotation speed and motor current value every unit minute time
Means to The measured value from the measuring means and the value read from the storage means.
Between the axial load and the motor current value
Based on the basic dynamic load rating,
Calculating means for calculating a rated fatigue life value, Write the rated fatigue life value calculated for each sampling interval.
Replaceable, and use the bearing usage from the rated fatigue life value.
The reduced remaining life can be displayed on the display unit for each rewrite.
Configured Bearing life monitoring device. 3. A ball screw used for a rotation transmitter or the like.
The average axial load of a known ball screw and the ball
Means for storing a basic dynamic load rating of the screw, and the ball screw
Means for recording the number of rotations used in the storage means.
Average load and basic dynamic load rating obtained from
Rated fatigue life based on the operating speed of heavy and ball screws
Calculating means for calculating the value every time in a rewritable manner;
The used amount of the bearing was subtracted from the calculated rated fatigue life value
A device for monitoring the life of a ball screw , comprising a display means for displaying the remaining life for each rewrite . 4. Smell of a bearing used for a rotation transmission machine or the like.
The average axial load of a known bearing and the basic rated load of the bearing
Means for storing the weight of the bearing, and means for recording the number of rotations used by the bearing.
And a shaft obtained from the storage means and the recording means.
Direction average load, basic dynamic load rating, and operating speed of the bearing.
Calculate the rated fatigue life value based on the
Calculating means for calculating the shaft fatigue from the calculated rated fatigue life value.
The remaining life of the battery, which has been reduced, is displayed for each rewrite.
Life monitoring device provided with a display means .