JP2009210301A - Rolling device and method of detecting abnormality of rolling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling device and a method of detecting the abnormality of the rolling device which enable detection of the abnormality of a monitoring object with high accuracy. <P>SOLUTION: The rolling device includes an acceleration sensor 11 which is attached to either a first raceway member or a second raceway member and outputs voltage based on the acceleration in vibrations, an amplifier 12 which amplifies an output voltage value of the acceleration sensor 11, and a low-pass filter 13 which attenuates a set frequency component as to the output voltage of the amplifier 12. The low-pass filter 13 attenuates frequencies exceeding eight or preferably six times higher than a specific frequency calculated geometrically when a rolling body moves along a rolling body circulation path, accompanying the relative movement of the first and second raceway members. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rolling device in which a plurality of rolling elements are arranged on a rolling path provided between track members to relatively move the track members, and an abnormality detection method for detecting an abnormality of such a rolling device.

  For example, when a defect occurs on the raceway surface of a rolling bearing for some reason, an impact is generated each time a rolling element passes through the portion, and vibration is generated. Various methods have been proposed in the past for measuring vibrations from the devices and rolling elements that occur in this way, and determining abnormalities based on the changes in the measured vibrations. However, in any case, the abnormality is determined within a general measurement frequency range, and thus the abnormality cannot be detected with high accuracy.

  For example, in Patent Document 1, in order to detect an abnormality in a rolling bearing, the lower limit side of the measurement frequency range is set to 9 kHz to 10 kHz, and the upper limit side of the measurement frequency range is set to 25 kHz to 30 kHz based on the characteristics of the acceleration detector. Yes. Then, the measured vibration acceleration is subjected to frequency analysis, and an abnormality is detected based on the peak value of the frequency spectrum obtained from the analysis result. Moreover, as a method which does not require such frequency analysis, in patent document 2, the measurement frequency range of general mechanical equipment is set to 20 kHz to 50 kHz. Then, the cumulative frequency distribution of the absolute value of the vibration waveform is obtained, and abnormality is diagnosed based on the equivalent effective value, the maximum value of the vibration waveform, and the magnitude of the peak ratio.

Here, there is a vibration sensor as a sensor for detecting vibration. Patent Document 3 discloses such a vibration sensor. Patent Document 3 discloses a technique for detecting vibration in a ball screw with a vibration sensor. As such vibration sensors, piezoelectric acceleration sensors (acceleration pickups) that are small and easy to handle and have a wide detection frequency band and dynamic range are widely used. This vibration sensor converts vibration (acceleration, speed, displacement) into an electric signal, and is roughly classified into a charge output type acceleration pickup and an amplifier built-in type piezoelectric acceleration pickup. The charge output type acceleration pickup is a charge output type pickup that outputs a detected vibration as a charge, and converts the output charge into a voltage by a charge amplifier. The piezoelectric acceleration pickup with a built-in amplifier outputs the detected vibration as a voltage.
Japanese Patent Laid-Open No. 61-288126 JP 2001-304954 A JP 2001-349407 A

By the way, as described in Patent Document 1 and Patent Document 2, when an abnormality is detected in a general measurement frequency range, even if an abnormality (vibration indicating an abnormality) occurs, There was a problem of being overlooked by noise and overlooking the abnormalities that occurred.
In particular, in the case of a rolling device such as a ball screw or a linear motion guide bearing device, the rolling element is different from a rolling device such as a rotating rolling bearing in which the rolling elements are arranged at almost constant intervals and are always in a substantially constant restrained state. Such a tendency was prominent because of the unique problems.

  An object of the present invention is to detect an abnormality of a rolling device with high accuracy.

  In order to solve the above-mentioned problem, a rolling device according to a first aspect of the present invention includes a first race member, a second race member, and a plurality of rolling elements, the first race member and the first race member. By inserting the rolling element in a freely rolling manner in at least one rolling element circulation path constituted by a raceway groove provided in each of the two raceway members and a return path provided in one of the raceway members. In the rolling device for moving the first track member and the second track member relative to each other, a voltage is attached to either the first track member or the second track member and corresponds to the acceleration during vibration. An amplifying means for amplifying the output voltage of the acceleration sensor, and a filter means for attenuating a set frequency component with respect to the output voltage of the acceleration sensor or the output voltage of the amplifying means. means More than eight times the specific frequency geometrically calculated when the rolling element moves in the rolling element circulation path with relative movement between the first and second race members. The frequency is attenuated.

The rolling device according to a second aspect of the present invention is the rolling device according to the first aspect, wherein the filter means has an attenuation characteristic of 20 dB / dec or more.
The rolling device according to a third aspect of the present invention is the rolling device according to the first aspect, wherein the filter means has a calculated passing frequency of the rolling element and a calculated passing frequency of the rolling element. On the other hand, it is characterized in that at least one of the 4 times, 6 times and 8 times frequencies is attenuated with an attenuation characteristic of 6 dB / oct or more.

The rolling device according to a fourth aspect of the present invention is the rolling device according to any one of the first to third aspects, wherein the frequency characteristic of the acceleration sensor is substantially linear over 10 KHz. The amplifying means performs nonlinear output based on the output voltage from the acceleration sensor.
Moreover, the rolling device according to claim 5 according to the present invention is the rolling device according to any one of claims 1 to 4, wherein the filter means is a mechanical filter formed of an elastic body. It is characterized by being.

A rolling device according to a sixth aspect of the present invention is the rolling device according to any one of the first to fifth aspects, wherein the raceway groove and the second raceway member of the first raceway member. Any one of the track grooves has a Gothic arch shape.
The rolling device according to a seventh aspect of the present invention is the rolling device according to any one of the first to sixth aspects, wherein the first and second race members and the rolling element are It is formed of metal or ceramic.

  Moreover, the abnormality detection method of the rolling device of Claim 8 which concerns on this invention is a said 1st track member and 2nd track member of the rolling device of any one of Claims 1-7. In the abnormality detection method for a rolling device that detects vibration when any of the above linearly moves and detects the abnormality of the rolling device from the detected value, the vibration of a specific frequency is monitored, An abnormality is detected.

According to the first and eighth aspects of the present invention, in the rolling device, the vibration of the monitoring target is accurately detected by attenuating the frequency exceeding eight times the specific frequency, and the abnormality of the monitoring target is accurately detected. Can be detected.
Moreover, according to the invention which concerns on Claim 3, since an individual event is considered and filtering can be performed, the vibration of a monitoring object can be detected more correctly.
Moreover, according to the invention which concerns on Claim 5, a filter means can be comprised easily.

In addition, when the raceway groove is formed in a Gothic arch shape, it is inevitable that vibration will occur due to the unevenness when the rolling element rolls on the raceway groove because the grinding wheel cannot be superfinished to the left and right. . According to the invention which concerns on Claim 6, the output voltage according to the vibration of the frequency which becomes the monitoring object of the vibration detection which generate | occur | produces in such a case can be reduced, ie, a detection sensitivity can be reduced.
Further, when the race member and the rolling element are formed of metal or ceramic, it is inevitable that vibration is generated by the unevenness when the rolling element rolls on the raceway groove. According to the invention which concerns on Claim 7, the output voltage according to the vibration of the frequency outside the monitoring object of the vibration detection which generate | occur | produces in such a case can be reduced, ie, a detection sensitivity can be reduced.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described in detail with reference to the drawings.
(First embodiment)
First, the first embodiment will be described.
(Constitution)
The first embodiment is an acceleration pickup that constitutes a vibration sensor. FIG. 1 shows the configuration of the acceleration pickup 10. As shown in FIG. 1, the acceleration pickup 10 is a piezoelectric acceleration pickup with a built-in amplifier. That is, the acceleration pickup 10 includes a piezoelectric acceleration sensor 11 that outputs a voltage corresponding to acceleration during vibration, an amplifier 12 that amplifies the output voltage value of the acceleration sensor, and a low-pass filter 13 that is an electrical filter. . Here, the acceleration sensor 11 is a so-called bimorph type piezoelectric acceleration sensor in which two piezoelectric elements that expand and contract in the length direction are joined and one of them expands and the other contracts. As the characteristics of the acceleration sensor 11, for example, a maximum output voltage range or an output voltage range at an acceleration of 1G when the vibration frequency is 1 KHz is determined. For example, the output voltage range is ± 5V.

The low-pass filter 13 filters (filters) a vibration frequency band (vibration frequency component) equal to or higher than the natural frequency of the object to be measured to which the acceleration pickup 10 is attached or the monitoring target (the track member or the rolling element member of the rolling device). Is set to Specifically, the low pass filter 13 filters a frequency band that is n times the specific frequency obtained by the object to be measured to which the acceleration pickup 10 is attached. Here, the specific frequency is, for example, a calculated passing frequency of the rolling element calculated by the following equations (1) to (3). Moreover, n times is 8 times, preferably 6 times. The formulas (1) to (3) are formulas in which the rolling device corresponds to a ball screw.
_{z · f c = z · (} 1- (D w · cosα · cos 2 β / d m)) · f r / 2 [Hz] ··· (1)
z · f _i = z · (1+ (D _w · cos α · cos ² β / d _m )) · f _r / 2 [Hz] (2)
2 · f _b = 2 · (d _m / (D _w · cos ² α · cos ² β) − (D _w · cos ² α · cos ² β / d _m )) · f _r / 2 [Hz]・ (3)

Here, z is the number of load balls per lead _{(z = π · d m /} (D w · cosβ)). _Fc is the revolution frequency [Hz] of the ball. That, f _c is the frequency in which one rolling element revolves 1 lead content, showing the movement of the rolling elements relative to the nut. F _i is the relative rotational frequency [Hz] of the screw shaft with respect to the revolution frequency of the ball. That is, f _i is a frequency at which the screw shaft revolves by one lead with reference to the revolution frequency f _{c of the} ball, and indicates the movement of the shaft relative to the rolling element. Further, f _b is the ball rotation frequency [Hz], and _fr is the shaft rotation frequency [Hz]. Further, _{D w} is the ball diameter [mm], _{d m} is a ball pitch diameter [mm], alpha is the contact angle [°], β is a lead angle [°].

  The frequency calculated by the equations (1), (2), and (3) has a high correlation with a site where damage occurs in the ball screw. From this, it can be seen which part has been damaged by the increase of the spectrum peak of the frequency calculated by each equation. Specifically, in equation (1), the damage to the nut by the ball (frequency at the time of damage) can be found, and in equation (2), the damage to the shaft by the ball (frequency at the time of damage) can be found. ) Shows the damage of the ball (frequency at the time of damage). The largest one among those obtained by the equations (1) to (3) is set as a specific frequency.

  The low-pass filter 13 filters and outputs a frequency band that is 8 times, preferably 6 times the calculated passing frequency of the rolling element calculated based on the equations (1) to (3). The low-pass filter 13 has an attenuation characteristic of 20 dB / dec or more. FIG. 2 shows the attenuation characteristics. FIG. 3 shows an example of the configuration of the low-pass filter 13 that realizes such attenuation characteristics.

  4 to 7 show examples of mounting the acceleration pickup 10 (vibration sensor). As shown in FIG. 4, the acceleration pickup 10 is attached to the outer peripheral surface of the flange portion 32 a of the nut 32 in the ball screw 30. As shown in FIG. 5, the acceleration pickup 10 is attached to a side surface facing the moving direction of the flange portion 32 a of the nut 32. As shown in FIG. 6, the acceleration pickup 10 is attached to a side surface of a linear guide (linear motion guide device) 90 including a guide rail 91 and a slider 92 that is parallel to the moving direction of the slider 92. Further, as shown in FIG. 7, the acceleration pickup 10 is attached to a side surface facing the moving direction of the slider 92.

(Operation, action and effect)
The operation, action and effect are as follows.
As shown in the examples of FIGS. 4 to 7, the acceleration pickup 10 is attached to the track member (the nut 32 and the slider 92). Thereby, in the acceleration pickup 10, the acceleration sensor 11 outputs a signal according to the vibration (acceleration) generated in the track member by the movement of the track member. Then, the amplifier 12 amplifies the output signal of the acceleration sensor 11 and outputs it to the low-pass filter 13. The low-pass filter 13 filters the signal from the amplifier 12 and outputs it externally.

  Here, in such a ball screw or linear guide, the circulating rolling element collides with the raceway surface when entering the load zone from the non-load zone, and the free vibration of the raceway member on the raceway side due to the collision is excited. Thus, vibration having the natural frequency of the race member as a frequency is generated. When the acceleration pickup 10 is attached to such a track member, the acceleration pickup 10 detects the natural frequency of the track member due to free vibration excited by the collision between the rolling element and the track surface with high sensitivity. For this reason, in the present embodiment, the low-pass filter 13 filters a vibration frequency band equal to or higher than the natural frequency of the track member to which the acceleration pickup 10 is attached. That is, the low pass filter 13 filters a frequency band that is 8 times, preferably 6 times the calculated passing frequency of the rolling element. Here, when the object to be measured is a ball screw, the calculated passing frequency of the rolling element is calculated based on the equations (1) to (3).

Here, for the following reasons, the low-pass filter 13 filters the frequency band of 8 times, preferably 6 times the calculated passing frequency of the rolling element.
FIG. 8 shows the result of frequency analysis of the vibration acceleration of the ball screw. This result is obtained when an abnormality occurs such that the rolling element peels off in the ball screw, and shows vibration frequency analysis results before and after the occurrence of the abnormality. In the figure, the thick line is the result before the occurrence of the abnormality, and the thin line is the result after the occurrence of the abnormality. As shown in the figure, the free vibration of the nut, which is the track member to which the acceleration pickup is attached, is excited by the collision between the transfer body and the track surface in the frequency band near 5 kHz both before and after the occurrence of the failure. Thus, it can be seen that vibration having the natural frequency of the raceway member as a frequency is generated. However, in the frequency band of 6 kHz or higher, a clear difference between before and after the occurrence of abnormality is not recognized. On the other hand, in the frequency band of 3 kHz or less, vibrations of frequency components that are in a geometrically proportional relationship with the rotation speed clearly appear. Therefore, if the vibration acceleration signal detected by the acceleration pickup before and after the occurrence of abnormality is filtered in a frequency band of 5 kHz, preferably 6 kHz or more, a clear difference appears in the peak value or rms value of the vibration acceleration signal. It becomes.

  At this time, with respect to the ball screw having such vibration characteristics, the calculated passing frequency of the rolling element obtained by the equations (1) to (3) is 500 Hz to 750 Hz. Therefore, the peak value or rms value of the vibration acceleration signal is obtained by filtering the frequency band of 5 kHz, preferably 6 kHz or more, which is 8 times or more of the calculated passing frequency of 500 Hz to 750 Hz with the low-pass filter 13. A clear difference can be obtained. Alternatively, the low-pass filter may be set so that the largest frequency among the frequencies obtained by the equations (1) to (3) is set as a reference (specific frequency) and the frequency is 8 times or more.

In addition, the frequency band to be filtered by the low-pass filter 13 can be determined in consideration of the following individual events.
FIG. 9 shows the peak-to-peak value change rate of the vibration acceleration signal (acceleration pickup output signal) before and after the occurrence of abnormality. In the same figure, the ratio of the peak after the occurrence of abnormality and the peak before the occurrence of abnormality (peak after occurrence of abnormality / peak before occurrence of abnormality) is taken as the peak-peak value change rate on the vertical axis. When the filter is not applied (marked with ● in the figure), it is not possible to obtain a clear difference between the peak-to-peak value change rate before and after the occurrence of the abnormality. That is, the abnormality cannot be detected. Also, the peak-to-peak value change rate of the vibration acceleration signal obtained by applying a 6 kHz low-pass filter and filtering a frequency band of 6 kHz or higher, which is a range in which there is no clear difference before and after the occurrence of an abnormality (■ in the figure) With regard to ()), a clear difference is less likely to appear before and after the occurrence of an abnormality. This is because the frequency component of the natural vibration generated near 5 kHz cannot be removed. On the other hand, when a low-pass filter of 3 kHz is applied, a natural vibration frequency band of 5 kHz or more composed of natural vibration frequency components or the like can be sufficiently filtered, and the difference appears clearly.

  Generally, the natural frequency of the raceway member excited by the collision between the rolling element and the raceway surface is in the range of 4 kHz to 100 kHz (see FIG. 10 below), and is geometrically proportional to the rotational speed. The frequency range in which the influence of the vibration of the related frequency component appears remarkably is up to about 3 kHz. Therefore, by setting the low-pass filter 13 to 3 kHz and filtering the frequency component of the natural vibration, it is possible to measure both vibrations in a frequency range in which the influence of geometric vibrations is noticeable. The objective can be achieved. In addition, when the frequency component of the natural vibration of the raceway member can be confirmed in advance, a low-pass filter can be set so that a vibration frequency band equal to or higher than the natural frequency can be sufficiently filtered.

  Further, a very low frequency band (a frequency band surrounded by a circle in FIG. 8) may be filtered by the low-pass filter 13. That is, a frequency that is less than the calculated passing frequency of the rolling element is attenuated. For example, the frequency that is less than the calculated passing frequency of the rolling element includes the resonance frequency of the screw shaft of the ball screw or vibration from the outside of the rolling device. Thereby, these vibrations can be cut off, and the peak value or rms value of the vibration acceleration signal can be obtained as a clearer difference.

In order to filter a plurality of frequency bands as described above, it is effective to use a filter having a different attenuation frequency or a notch filter that attenuates only a specific frequency.
FIG. 10 shows the relationship between frequency and vibration strength (db) for a ball screw. The figure (a) is the result of the ball screw of φ50, and the figure (b) is the result of the ball screw of φ32. As described above, in the ball screw, the circulating rolling element collides with the raceway surface when entering the load zone from the non-load zone, and free vibration of the element member on the raceway surface side due to the collision is excited, and the element member A vibration having a natural frequency as a frequency is generated. The frequency band of the natural vibration due to the collision between the rolling element and the raceway is slightly different depending on the size of the nut of the ball screw, but generally 4 kHz to 100 kHz as shown in a circle in FIG. It will exceed.

  In addition, since the amplitude of vibration generated by the collision between the rolling elements and the raceway surface changes depending on the collision energy, for example, it easily changes or reciprocates due to the difference in the angle of entry of each rolling element to the raceway surface. The linear motion element or the like easily changes depending on the difference between the outward travel (FIG. 11 (a)) and the backward travel (FIG. 11 (b)). For this reason, in a rolling element having a circulating portion, there is a high possibility that an abnormality is erroneously detected by the conventional method. However, by applying the present invention, even under such conditions, it is possible to detect anomalies with high accuracy by filtering a specific frequency, for example, a frequency band that is eight times or more the calculated passing frequency of a rolling element. It becomes like this.

FIG. 12 is a usage example of the output signal of the acceleration pickup 10. Here, a configuration of an abnormality detection system 130 that detects an abnormality of the rolling device (specifically, the race member, in this example, the ball screw 30 or the linear guide 90) 120 based on the output signal of the acceleration pickup 10 is shown.
As shown in FIG. 12, the abnormality detection system 130 is stored in the storage unit 131 that stores the output signal of the acceleration pickup 10 attached to the rolling device 120 (for example, the nut 32 or the slider 92), and the storage unit 131. A vibration acceleration display unit 132 that externally outputs (displays) vibration acceleration based on the output signal, and an abnormality determination unit 133 that performs abnormality determination based on the output signal stored in the storage unit 131 are provided. The abnormality determination unit 133 determines the peak value of the output signal or the rms value of the output signal based on the signal stored in the storage unit 131, that is, the time series signal of the output signal (vibration acceleration signal) of the acceleration pickup 10. The abnormality of the rolling device 120 is determined based on the peak value or the rms value. For example, the abnormality of the rolling device 120 is determined in comparison with a predetermined threshold value.

  Thereby, it is possible to determine an abnormality with high accuracy using the output signal (vibration acceleration vibration) of the acceleration pickup 10. Further, since the abnormality of the track member is determined based on the time series change of the output signal, the abnormality can be detected with high accuracy. In addition, since it is possible to detect an abnormality only with a filter and a peak value display device (vibration acceleration display device) without using a frequency analysis device or a plurality of arithmetic devices, the abnormality is high even though the configuration is simple. It can be detected with accuracy.

The first embodiment can also be realized by the following configuration.
That is, in the first embodiment, the equations (1) to (3) are for obtaining the calculated passing frequency of the rolling element of the ball screw. However, when obtaining the calculated passing frequency of the rolling element for another rolling device, for example, a linear guide, the above-mentioned formulas (1) to (3) according to various conditions such as the dimensions of the linear guide and the operating speed. Transform the formula. Thus, the calculated passing frequency of the rolling element is calculated for the linear guide, and the linear guide track member (guide rail or slider) is filtered by filtering the frequency band of 8 times, preferably 6 times the calculated passing frequency of the rolling element. Can be detected with high accuracy, and abnormalities can be detected with high accuracy.

Further, the low-pass filter 13 has an attenuation characteristic of 6 dB / oct or more at least one of a calculated passing frequency of the rolling element and a frequency that is four times, six times, and eight times the calculated passing frequency of the rolling element. Can also be attenuated. As a result, it is possible to appropriately select the frequency to be attenuated and the frequency to be detected as an abnormality detection, and to detect the abnormality with high accuracy. For example, when a frequency four times the calculated passing frequency of the rolling element matches a disturbance frequency other than the target, this is also attenuated, and an abnormality is detected at a frequency six times the calculated passing frequency of the rolling element. Detection accuracy can be improved.
In the first embodiment, the output voltage of the acceleration sensor 11 is output to the low-pass filter 13 via the amplifier 12. On the other hand, even if the output voltage of the acceleration sensor 11 is directly output to the low-pass filter 13 and filtered, an abnormality can be detected with high accuracy as the same effect as described above.

(Second Embodiment)
Next, a second embodiment will be described.
(Constitution)
The second embodiment is also a vibration sensor to which the present invention is applied.
FIG. 13 shows the configuration of the vibration sensor 20. As shown in FIG. 13, the vibration sensor 20 includes an elastic body 25 that forms mechanical filter means between an acceleration pickup 21 and an object to be measured (orbit member of a rolling device) 200. The acceleration pickup 21 is fixed to the device under test 200 via 25. The acceleration pickup 21 is an amplifier built-in type piezoelectric acceleration pickup. The acceleration pickup 21 is fixed to the device under test 200 via an elastic body 25 by screws.

FIG. 14 shows the configuration of the acceleration pickup 21. As shown in FIG. 14, the acceleration pickup 21 includes a piezoelectric acceleration sensor 22 that outputs a voltage corresponding to acceleration during vibration, and an amplifier 23 that amplifies the output voltage value of the acceleration sensor. For example, the acceleration sensor 22 is a so-called bimorph type piezoelectric acceleration sensor, as in the first embodiment.
FIG. 15 shows the characteristics of the acceleration pickup 21 (specifically, the acceleration sensor 22). As shown in FIG. 15, the frequency characteristic of the acceleration pickup 21 (specifically, the acceleration sensor 22) is substantially linear over 10 kHz. The amplifier 23 performs non-linear output based on the output voltage value from the acceleration sensor 22 having such characteristics.

  The elastic body 25 is made of rubber or an elastomer material. As shown in FIG. 13, a screw insertion hole 25 a is provided at the center of the elastic body 25, and a screw 26 is inserted into the hole 25 a to fasten the acceleration pickup 21 and the DUT 200. And the shape or physical property value of the elastic body 25 is determined so that the vibration outside the target measurement frequency range can be cut off. That is, a specific frequency, for example, the calculated passing frequency of the rolling element obtained for the rolling device (when the rolling device is a ball screw, refer to the above formulas (1) to (3)), preferably 8 times, preferably 6 The shape or physical property value of the elastic body 25 is determined so that the double frequency band can be mechanically filtered.

  A configuration example of a ball screw which is a rolling device including the vibration sensor 20 will be described with reference to FIGS. As shown in FIGS. 16 to 18, the ball screw 30 includes a screw shaft 31 that is one track member and a nut 32 that is another track member that relatively moves in the axial direction as the screw shaft 31 rotates. A large number of balls 33 are provided between the nut 32 and the screw shaft 31 so as to be freely rollable, and a side cap 34 as a ball circulation member for circulating the balls 33 is provided. The screw shaft 31 has a circular cross section perpendicular to the axial direction, and a spiral ball screw groove 41 that is a raceway groove is formed on the outer peripheral surface thereof. The ball screw groove 41 is opposed to a spiral ball screw groove 42 which is a raceway groove formed on the inner peripheral surface of the nut 32. When one of the screw shaft 31 and the nut 32 rotates around the axis, the ball screw groove 41 is synchronized with the spiral ball screw groove 42. Thus, the ball 33 rolls on a ball load rolling path 43 which is a rolling path formed between the ball screw grooves 41 and 42.

  The nut 32 has a side cap attachment surface 51 on the outer peripheral surface. Ball circulation holes 52 and 52 for circulating the balls 33 are formed in the side cap attachment surface 51. The side cap 34 is formed, for example, by injection molding a molding material such as resin or metal into a predetermined shape. The side cap 34 is a ball communicating with a pair of columnar ball scooping portions 34a and 34b fitted in the ball circulation holes 52 and 52, and ball return guide paths 53 and 53 formed in the columnar ball scooping portions 34a and 34b. It is comprised from the plate-shaped side cap main-body part 34c which has the return path 54 inside. Here, as a structure including the ball load rolling path 43, the ball return guide path 53, and the ball return path 54, a rolling element circulation path for circulating the ball 33 is configured.

  The ball scooping portions 34a and 34b have a circular cross section, and therefore the cross section of the ball circulation hole 52 into which the ball scooping portions 34a and 34b are fitted is also circular. The ball scooping portions 34a and 34b each have a tongue portion (not shown), and the ball 33 rolling on the ball load rolling path 43 is a tongue portion of the ball scooping portion 34a or 34b as shown in FIG. Thus, the ball screw grooves 41 and 42 are scooped up in the lead angle direction and introduced into the ball return path 54.

  As shown in FIG. 5, the vibration sensor 20 is attached to the side cap 34 which is a member on the nut 32 side of the ball screw 30 configured as described above. At this time, the vibration sensor 20 is mounted so that the elastic body 25 is interposed between the acceleration pickup 21 and the nut 32. The vibration sensor 20 outputs a detection signal (voltage value) to the outside via the sensor cable 27.

(Operation, action and effect)
The operation, action and effect are as follows.
The vibration of the ball screw 30 when the nut 32 and the screw shaft 31 move relative to each other is detected by the vibration sensor 20 (specifically, the acceleration pickup 21). The vibration sensor 20 outputs a detection signal to the outside via the sensor cable 27. At this time, since the elastic body 25 exists between the acceleration pickup 21 and the DUT 200, the vibration signal of the DUT 200 is transmitted to the acceleration pickup 21 via the elastic body 25. Thereby, the elastic body 25 acts as a filter, and the vibration signal outside the target measurement frequency range is cut off before being input to the acceleration pickup 21. Therefore, the acceleration pickup 21 can measure vibration at a high level in a wide frequency range. Moreover, the filter means can be simply configured by using the elastic body 25 as the filter means.

  Here, when a charge output type acceleration pickup is used for vibration detection of a linear motion element that repeats reciprocating motion such as a ball screw, a linear guide, and a rack and pinion, noise due to bending of the cable rides on the vibration detection signal. there were. On the other hand, in the piezoelectric acceleration pickup with a built-in amplifier, the noise accompanying the bending of the cable hardly gets on the vibration detection signal. However, the piezoelectric acceleration pickup with a built-in amplifier has a problem that it has a narrow dynamic range and is easily overloaded as compared with the charge output type acceleration pickup. In other words, in the pickup with a built-in amplifier, vibration is directly input without filtering, so if the vibration is large, the built-in amplifier is overloaded (sensitivity of vibration at high frequency is higher than vibration at low frequency). growing). As a result, the use of the built-in amplifier type pickup is limited to vibration measurement within a vibration level range in which the built-in amplifier does not overload. Therefore, in the vibration of a linear element such as a ball screw, linear guide or rack and pinion, the high frequency component is strong due to the vibration of the ball running on the grinding mark. There arises a problem that the type acceleration pickup is easily overloaded.

  In charge output type accelerometers that use external amplifiers, the target measurement frequency range (frequency range to be monitored) can be narrowed by applying an external filter, so even vibration signals that are at a high level over a wide frequency range are input. It is possible to identify and measure vibrations in the target measurement frequency range. However, in the charge output type accelerometer, as described above, in the vibration detection of the linear motion element that repeats reciprocating motions such as the ball screw, the linear guide, and the rack and pinion, the noise accompanying the bending of the cable gets on the signal. Cannot be resolved.

  In response to the various problems as described above, vibrations composed of high-frequency components outside the target measurement frequency range are blocked before being input to the acceleration pickup 21, thereby being buried in high-frequency components outside the target measurement frequency range. It becomes possible to detect vibrations to be monitored (including vibrations of high frequency components). In addition, the vibration of the high frequency component outside the target measurement frequency range is cut off before the acceleration pickup 21 is input, thereby preventing the acceleration pickup 21 from being overloaded and reliably detecting the vibration of the monitoring target. become able to. Since the acceleration pickup 21 is a piezoelectric acceleration pickup with a built-in amplifier, the influence of noise due to cable bending can be reduced.

In addition, the frequency range to be filtered can be determined in consideration of the following individual events.
For example, in the case of a ball screw, the maximum speed of the linear motion rolling element reaches DN = 160,000 mm / min, and the relative speed between the rolling element and the raceway groove at this time is about 1.5 m / s. In addition, the raceway surface has grinding traces due to the abrasive grains because it is not superfinished, and the pitch of the irregularities in the rolling element rolling direction due to this is approximately 150 μm, although it depends on the processing conditions. Hereinafter, it is mainly about 50 μm. From this, when the rolling element rolls on the raceway groove at the maximum speed, the vibration frequency due to the unevenness in the raceway groove is 10 KHz (= 1.5 · E6 / 150), even if estimated to be small, , 30 kHz (= 1.5 · E6 / 50). If the sensitivity to such frequency vibrations can be reduced and monitored by the acceleration pickup 21, vibrations at lower frequencies that occur due to separation of the raceway surface or clogging of the balls can be detected.

  For this reason, the shape, physical property values, etc. of the elastic body 25 are set so that the vibration of the high frequency component of 30 kHz or more due to the collision between the ball and the rolling path (track groove) becomes out of the target measurement frequency range. To decide. By doing so, the sensitivity to vibration due to the collision between the ball and the rolling path (track groove) is lowered, and the acceleration pickup 21 detects the lower frequency vibration generated due to the separation of the raceway surface or ball clogging. it can.

  Note that the reason why the raceway surface is not superfinished in the linear motion rolling element is as follows, for example. For linear motion rolling elements (hereinafter referred to as “bearings”), the raceway surface is generally superfinished. There is no choice but to produce other high-mix low-volume production, and it is difficult in terms of cost, and since the use speed is naturally limited due to the end of the raceway groove, it cannot exhibit the performance suitable for super finishing. In addition, the effect of superfinishing is masked by the vibration when the rolling element enters and exits the circulation path and the raceway groove.

  In particular, when the screw shaft and the ball screw groove of the nut are formed in a Gothic arch shape, super-finishing is not possible by shaking the grinding wheel to the left and right. Vibration is inevitable. For this reason, by lowering the sensitivity to vibrations at that frequency and monitoring with the acceleration pickup 21, it is possible to detect lower-frequency vibrations that occur due to the separation of the raceway surface of the ball screw groove or clogging.

  In particular, even when the screw shaft or nut (specifically, their ball screw groove), or the rolling element is formed of a metal (for example, steel) or ceramic with a grinding finish, the rolling element is a ball screw groove. It is inevitable that vibrations will occur due to the unevenness when rolling down. For this reason, by lowering the sensitivity to vibrations at that frequency and monitoring with the acceleration pickup 21, it is possible to detect lower-frequency vibrations that occur due to the separation of the raceway surface of the ball screw groove or clogging.

  In addition, when superfinishing is performed, although the level is lowered, the vibration of the high-frequency component that is approximately the same can be detected in the linear motion rolling element. This vibration is considered to be a vibration of a high-frequency component generated when the rolling element enters and exits the circulation path and the raceway groove. Even in such a case, by applying the present invention, the sensitivity to vibrations of such a frequency is lowered and monitored by the acceleration pickup 21, so that the lower frequency generated due to the separation of the raceway surface or clogging of the balls is caused. Can be detected.

The second embodiment can also be realized by the following configuration.
That is, in the second embodiment, the acceleration pickup 21 and the elastic body 25 are fixed to the device under test 200 with screws. On the other hand, it can also be fixed by other fixing means such as wax, adhesive, double-sided tape or magnet. For example, one or both of the acceleration pickup 21 and the elastic body 25, and the elastic body 25 and the measured object 200 are fixed with wax, an adhesive, a double-sided tape, a magnet, or the like.

(Third embodiment)
Next, a third embodiment will be described.
The third embodiment is also a vibration sensor, and FIG. 19 shows the configuration of the vibration sensor 60. As shown in FIG. 19, the vibration sensor 60 in the third embodiment includes a mass member 61 in the acceleration pickup 21. The mass member 61 is determined so that the vibration sensor 60 (particularly the acceleration pickup 21) has a predetermined natural frequency. In this way, by adjusting the natural frequency of the vibration sensor 60 (particularly the acceleration pickup 21) with the mass member 61, the range of the high-frequency vibration component to be blocked by the vibration sensor 60 can be adjusted.

Here, the following equation (4) represents the natural frequency f ₀ of the primary spring mass system.
f ₀ = 1 / (2π) · √ (k / M) (4)
k is the spring constant and M is the mass. When this equation (4) is applied to the configuration of the vibration sensor 60, k is the spring constant of the elastic body 25, and M is the mass of the acceleration pickup 21 including the mass member 61. Thus, as can be seen from equation (4), by adding the mass member 61 in the accelerometer 21, it is possible to vary the natural frequency f ₀ of the accelerometer 21, including the mass member 61, as a result The vibration sensor 60 can adjust the range of the high-frequency vibration component to be cut off (the frequency band of 8 times, preferably 6 times the calculated passing frequency of the rolling element).

  In the third embodiment, the natural frequency is changed by adding the mass member 61 to the acceleration pickup 21, but the natural frequency can be changed by other methods. That is, the natural frequency can also be changed by appropriately changing the method for fixing the acceleration pickup 21 and the elastic body 25 or the method for fixing the acceleration pickup 21 and the DUT 200. The natural frequency can also be changed by appropriately changing the weight of the acceleration pickup 21 itself, such as the thickness and material (physical property value) of the elastic body 25.

(Fourth embodiment)
Next, a fourth embodiment will be described. The fourth embodiment is also a vibration sensor, and FIG. 20 shows a configuration of the vibration sensor 70. As shown in FIG. 20, in the vibration sensor 70 according to the fourth embodiment, the acceleration pickup 21 and the elastic body 25, and the elastic body 25 and the DUT 200 are individually fixed by screws 71 and 72. For example, with such a configuration, the natural frequency of the vibration sensor 70 can be changed, and the range of the high-frequency vibration component to be blocked by the vibration sensor 70 can be adjusted.

(Fifth embodiment)
Next, a fifth embodiment will be described. The fifth embodiment is also a vibration sensor, and FIG. 21 shows a configuration of the vibration sensor 80. As shown in FIG. 21, the vibration sensor 80 individually fixes the acceleration pickup 21 and the elastic body 25, and the elastic body 25 and the DUT 200. In the fifth embodiment, unlike the case of the fourth embodiment, the elastic body 25 is fixed to the device under test 200 by using an attachment member 82 that surrounds the outer peripheral portion of the elastic body 25. For example, with this configuration, the natural frequency of the vibration sensor 80 can be changed, and the range of the high-frequency vibration component to be blocked can be adjusted by the vibration sensor 80.

It is a block diagram which shows the structure of the vibration sensor (acceleration pick-up) with which the rolling device of the 1st Embodiment of this invention is provided. It is a characteristic view which shows the attenuation characteristic of the low-pass filter of an acceleration pick-up. It is a circuit diagram which shows an example of a structure of a low-pass filter. It is a figure which shows the example of attachment of the acceleration pick-up to a ball screw. It is a figure which shows the other example of attachment of the acceleration pick-up to a ball screw. It is a figure which shows the example of attachment of the acceleration pick-up to a linear guide. It is a figure which shows the other example of attachment of the acceleration pick-up to a linear guide. It is a characteristic view which shows the result of the frequency analysis of the vibration acceleration of a ball screw. It is a characteristic view which shows the peak-peak value change rate of the vibration acceleration signal (output signal of an acceleration pick-up) before and after abnormality occurrence. It is a characteristic view which shows the relationship between a frequency and vibration strength (db) regarding a ball screw. It is a characteristic view used for description of the difference in vibration at the time of reciprocation in a linear motion element etc. It is a block diagram which shows the structure of the abnormality detection system provided with the speed pick-up. It is a figure which shows the structure of the vibration sensor with which the rolling device of the 2nd Embodiment of this invention is provided. It is a block diagram which shows the structure of the vibration sensor (acceleration pick-up) in 2nd Embodiment. It is a characteristic view which shows the characteristic of the acceleration pick-up in 2nd Embodiment. It is a top view which shows the structure of the ball screw provided with the vibration sensor. It is an axial direction sectional view showing the composition of a ball screw provided with a vibration sensor. It is radial direction sectional drawing which shows the structure of the ball screw provided with the vibration sensor. It is a figure which shows the structure of the vibration sensor with which the rolling device of 3rd Embodiment is provided. It is a figure which shows the structure of the vibration sensor with which the rolling device of 4th Embodiment is provided. It is a figure which shows the structure of the vibration sensor with which the rolling device of 5th Embodiment is provided.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Acceleration pick-up (vibration sensor), 11 Acceleration sensor, 12 Amplifier, 13 Low-pass filter, 20 Vibration sensor, 21 Acceleration pick-up, 25 Elastic body

Claims (8)

A first track member, a second track member, and a plurality of rolling elements, the track groove provided in each of the first track member and the second track member, and the return provided in one track member In the rolling device for relatively moving the first raceway member and the second raceway member by inserting the rolling body so as to roll freely in at least one rolling body circulation path constituted by a path,
An acceleration sensor that is attached to any one of the first track member and the second track member and outputs a voltage corresponding to acceleration during vibration, amplification means for amplifying the output voltage of the acceleration sensor, and the acceleration sensor A filter means for attenuating a set frequency component with respect to the output voltage or the output voltage of the amplification means,
The filter means is for a specific frequency that is geometrically calculated when the rolling element moves in the rolling element circulation path with relative movement of the first race member and the second race member. A rolling device characterized in that a frequency exceeding eight times is attenuated.   The rolling device according to claim 1, wherein the filter means has an attenuation characteristic of 20 dB / dec or more.   The said filter means attenuate | damps at least any one of the frequency of 4 times, 6 times, and 8 times with respect to the said specific frequency by the attenuation | damping characteristic more than 6 dB / oct. Rolling device.   The frequency characteristic of the acceleration sensor is substantially linear over 10 KHz or more, and the amplification means performs nonlinear output based on an output voltage from the acceleration sensor. The rolling device according to item.   The rolling device according to claim 1, wherein the filter means is a mechanical filter formed of an elastic body.   6. The rolling device according to claim 1, wherein one of the raceway groove of the first raceway member and the raceway groove of the second raceway member has a Gothic arch shape.   The rolling device according to any one of claims 1 to 6, wherein the first and second race members and the rolling element are made of metal or ceramic. The vibration when any one of the first track member and the second track member of the rolling device according to any one of claims 1 to 7 is linearly moved is detected, and the rolling is detected from the detected value. In the abnormality detection method of the rolling device for detecting the abnormality of the device,
An abnormality detection method for a rolling device, wherein vibration of a specific frequency is monitored to detect an abnormality of the rolling device.

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