Method for Detecting Rotation Speed Fluctuation of Rotating Shaft and Device for Detecting Rotation Speed Fluctuation of Rotating Shaft

Abstract

To provide a rotation number variation detection method for a rotation shaft, and a rotation number variation detection device for a rotation shaft, which are capable of accurately detecting variation of a rotation number of the rotation shaft, without adding a new component to the object rotation shaft.SOLUTION: A method for detecting variation of a rotation number of a rotation shaft 100 comprises: a preparing step; a rotation step; and a detection step. The preparing step is configured to prepare at least one detection unit which includes: a roller 10 and a rotary encoder 20 which rotates in synchronization with the roller 10. The rotation step is configured to press the roller 10 of the at least one detection unit to the outer peripheral face of the rotary shaft 100, and rotate the rotary shaft 100, the roller 10, and the rotary encoder 20 in synchronization. The detection step is configured to process a signal output from the rotary encoder 20 for detecting the variation of the rotation number of the rotary shaft 100.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for detecting fluctuations in the rotational speed of a rotating shaft and a device for detecting fluctuations in the rotational speed of a rotating shaft.

Background Art

[0002] Conventionally, methods for detecting fluctuations in the rotational speed of a rotating shaft are known. Patent Document 1 discloses a technique for detecting torsional vibration of a rotating shaft by fixing a gear to the rotating shaft, irradiating detection light onto the unevenness of the gear when the rotating shaft rotates, and receiving the reflected light.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technique described in Patent Document 1, it is necessary to attach new parts such as a gear to the rotating shaft, and there is a problem that it is difficult to easily detect the vibration of the rotating shaft provided in a machine that has already been manufactured and installed.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for detecting fluctuations in the rotational speed of a rotating shaft and a device for detecting fluctuations in the rotational speed of a rotating shaft that can accurately detect fluctuations in the rotational speed of the rotating shaft without attaching new parts to the target rotating shaft.

Means for Solving the Problems

[0006] Provided by the present invention is a method for detecting fluctuations in the rotational speed of a rotating shaft. The method includes a preparation step of preparing at least one detection unit including a roller and a rotary encoder that rotates synchronously with the roller, a rotation step of pressing the roller of the at least one detection unit against the outer peripheral surface of the rotating shaft and rotating the rotating shaft, the roller, and the rotary encoder synchronously, and a detection step of detecting fluctuations in the rotational speed of the rotating shaft by processing a signal output from the rotary encoder.

[0007] According to this method, it is possible to easily detect fluctuations in the rotational speed including torsional vibration in existing rotating machinery, industrial machinery, etc. without attaching new parts to the rotating shaft.

[0008] In the above method, the preparation step includes preparing, as the at least one detection unit, a first detection unit including a first roller and a first rotary encoder, and a second detection unit including a second roller having the same outer diameter as the first roller and a second rotary encoder. The rotation step includes pressing the first roller and the second roller against the outer peripheral surface such that the second roller is disposed on the opposite side of the first roller with the center of the rotating shaft therebetween, and rotating the rotating shaft, the first roller, the second roller, the first rotary encoder, and the second rotary encoder synchronously. The detection step may include detecting fluctuations in the rotational speed of the rotating shaft by removing a translational vibration component generated in the rotating shaft by processing signals output from the first rotary encoder and the second rotary encoder, respectively.

[0009] According to this method, by paying attention to the fact that the influence of shaft vibration and eccentricity of the rotating shaft is reversed between rollers disposed on opposite sides of each other, it is possible to easily and accurately detect fluctuations in the rotational speed focusing on torsional vibration by removing the translational vibration component generated in the rotating shaft.

[0010] In the above method, the preparation step includes preparing, as the at least one detection unit, a first detection unit including a first roller and a first rotary encoder, and a second detection unit including a second roller having an outer diameter different from that of the first roller and a second rotary encoder. The rotation step includes pressing the first roller and the second roller against the outer peripheral surface and synchronously rotating the rotary shaft, the first roller, the second roller, the first rotary encoder, and the second rotary encoder. The detection step may include removing the rotation frequency components of the first roller and the second roller to detect the rotational speed variation of the rotary shaft.

[0011] According to this method, when two rollers with different outer diameters rotate synchronously with the rotary shaft, attention is paid to the fact that the rotation frequency components of each roller are included in two regions other than the frequency of the rotational speed variation of the rotary shaft. By replacing the data of the two rotary encoders with each other, it becomes possible to separate these rotation frequency components from the frequency of the desired rotational speed variation such as torsional vibration.

[0012] In the above method, the rotation step includes pressing the first roller and the second roller against the outer peripheral surface such that the second roller is disposed on the opposite side of the first roller with the center of the rotary shaft interposed therebetween, and synchronously rotating the rotary shaft, the first roller, the second roller, the first rotary encoder, and the second rotary encoder. The detection step may include further removing the translational vibration component generated in the rotary shaft to detect the rotational speed variation of the rotary shaft.

[0013] According to this method, it becomes possible to accurately detect the rotational speed variation due to torsional vibration after removing the influences of the shaft vibration and eccentricity of the rotary shaft and the frequencies of the two rollers.

[0014] Also provided by the present invention is an apparatus for detecting fluctuations in the rotational speed of a rotating shaft. The apparatus includes at least one detection unit including a roller and a rotary encoder that rotates synchronously with the roller, and a rotational speed fluctuation detection unit that processes a signal output from the rotary encoder when the roller of the at least one detection unit contacts an outer peripheral surface of the rotating shaft and the rotating shaft, the roller, and the rotary encoder rotate synchronously to detect fluctuations in the rotational speed of the rotating shaft.

[0015] According to this configuration, it becomes possible to easily detect fluctuations in the rotational speed including torsional vibration even in a rotating machine or industrial machine that is already installed without attaching new parts to the rotating shaft.

[0016] In the above configuration, the at least one detection unit may include a first detection unit including a first roller and a first rotary encoder, and a second detection unit including a second roller having the same outer diameter as the first roller and a second rotary encoder disposed on the opposite side of the first roller across the center of the rotating shaft. The rotational speed fluctuation detection unit may process signals respectively output from the first rotary encoder and the second rotary encoder when the first roller and the second roller contact the outer peripheral surface and the rotating shaft, the first roller, the second roller, the first rotary encoder, and the second rotary encoder rotate synchronously, to remove a translational vibration component generated in the rotating shaft and detect fluctuations in the rotational speed of the rotating shaft.

[0017] According to this configuration, paying attention to the fact that the influence of shaft vibration and eccentricity of the rotating shaft is reversed between the rollers disposed on opposite sides of each other, it becomes possible to easily and accurately detect fluctuations in the rotational speed focusing on torsional vibration by removing the translational vibration component generated in the rotating shaft.

[0018] In the above configuration, the at least one detection unit may include a first detection unit including a first roller and a first rotary encoder, and a second detection unit including a second roller having an outer diameter different from that of the first roller and a second rotary encoder. The rotation speed fluctuation detection unit may detect the rotation speed fluctuation of the rotating shaft by removing the rotation frequency components of the first roller and the second roller by processing the signals respectively output from the first rotary encoder and the second rotary encoder when the first roller and the second roller are in contact with the outer peripheral surface and the rotating shaft, the first roller, the second roller, the first rotary encoder, and the second rotary encoder rotate synchronously.

[0019] According to this configuration, paying attention to the fact that when two rollers with different outer diameters rotate synchronously with the rotating shaft, the components of the rotation frequencies of the two rollers are included in two regions other than the frequency of the rotation speed fluctuation of the rotating shaft, and by replacing the data of the two rotary encoders with each other, it becomes possible to separate these rotation speed components from the frequency of the desired rotation speed fluctuation such as torsional vibration.

[0020] In the above configuration, the second roller may be disposed on the opposite side of the first roller with the center of the rotating shaft interposed therebetween, and the rotation speed fluctuation detection unit may further remove the translational vibration component generated in the rotating shaft to detect the rotation speed fluctuation of the rotating shaft.

[0021] According to this configuration, it becomes possible to accurately detect the rotation speed fluctuation due to torsional vibration after removing the influence of the shaft vibration and eccentricity of the rotating shaft and the influence of the frequencies of the two rollers.

Effect of the Invention

[0022] According to the present invention, it is possible to provide a method for detecting the rotation speed fluctuation of a rotating shaft and a device for detecting the rotation speed fluctuation of a rotating shaft that can accurately detect the rotation speed fluctuation of the target rotating shaft without attaching new parts to the rotating shaft.

Brief Description of the Drawings

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Embodiments for Carrying Out the Invention

[0024] <First Embodiment> Hereinafter, with reference to the drawings, a rotational speed fluctuation detection device according to each embodiment of the present invention will be described. FIGS. 1 and 2 are a front view and a side view of a rotational speed fluctuation detection device 1 according to the first embodiment of the present invention. The rotational speed fluctuation detection device 1 is a device for detecting fluctuations in the rotational speed of a rotating shaft that is a problem in rotating machinery such as a rolling mill or a resin machine. Conventionally, in such rotating machinery, detecting fluctuations in the rotational speed caused by torsional vibration of the rotating shaft has been a problem. In the present invention, it is possible to easily and accurately detect such fluctuations in the rotational speed.

[0025] Referring to FIGS. 1 and 2, the rotational speed fluctuation detection device 1 detects fluctuations in the rotational speed of the rotating shaft 100. Note that the rotating shaft 100 is rotated at a predetermined rotational speed by a drive source such as a motor (not shown). The rotating shaft 100 is supported by bearings (not shown).

[0026] The rotational speed fluctuation detection device 1 includes a roller 10, an encoder 20, and an arithmetic processing unit 30.

[0027] As shown by the thick arrows in FIGS. 1 and 2, the roller 10 is pressed against the outer peripheral surface of the rotating shaft 100 with a predetermined load and rotates in synchronization with the rotating shaft 100. Note that the roller 10 is rotatably supported by bearings (not shown). Also, in FIGS. 1 and 2, the rotational directions of the roller 10 and the rotating shaft 100 are indicated by thin arrows (the same applies to the subsequent figures).

[0028] The encoder 20 is a known rotary encoder and is connected to the roller 10 via a coupling or the like (not shown) so as to rotate in synchronization with the roller 10. The encoder 20 outputs a pulse signal corresponding to the rotation of the roller 10. Note that the roller 10 and the encoder 20 constitute the detection unit of the present invention.

[0029] The arithmetic processing unit 30 receives the pulse signal (signal) output from the encoder 20 when the roller 10 contacts the outer peripheral surface of the rotary shaft 100 and the rotary shaft 100, the roller 10, and the encoder 20 rotate synchronously, and detects fluctuations in the rotational speed of the rotary shaft 100 by processing the pulse signal. In the present embodiment, a personal computer functions as the arithmetic processing unit 30 by executing a predetermined program. The arithmetic processing unit 30 constitutes the rotational speed fluctuation detection unit of the present invention. Note that the arithmetic processing unit 30 may be other arithmetic devices.

[0030] Next, a method for detecting fluctuations in the rotational speed of the rotary shaft 100 using the rotational speed fluctuation detection device according to the present embodiment will be described in detail. This method includes a preparation step, a rotation step, and a detection step. In the preparation step, the detection unit including the roller 10 and the encoder 20 is prepared. In the rotation step, the roller 10 of the detection unit is pressed against the outer peripheral surface of the rotary shaft 100, and the rotary shaft 100, the roller 10, and the encoder 20 are rotated synchronously by the driving force of the motor. At this time, the rotational speed of the motor is set so that the rotary shaft 100 rotates at a target rotational speed used in the rotating machine. In the detection step, the arithmetic processing unit 30 detects fluctuations in the rotational speed of the rotary shaft 100 by processing the signal output from the encoder 20.

[0031] The arithmetic processing of the arithmetic processing unit 30 will be specifically described. Assuming that the radius of the rotary shaft 100 is R10 and the radius of the roller 10 is R, N10' is obtained by performing the operation of the following formula 1 on the time history signal N10 of the rotational speed of the roller 10. N10’=R / R10×N10 ···(Formula 1) Here, N10' is the result of correcting the time history signal N10 of the roller 10 with the ratio of the radii as data of the rotary shaft 100, and is the result of being corrected to the time history signal of the rotary shaft 100 with a radius of R10.

[0032] Next, by performing a fast Fourier transform (FFT) on N10' obtained above to obtain a spectrum, data on the rotational unevenness of the measurement target rotary shaft 100 can be obtained.

[0033] In this way, in the present embodiment, since measurement can be performed without attaching new parts to the rotating shaft 100, it becomes possible to easily detect rotational speed fluctuations including torsional vibration in already installed rotating machines, industrial machines, etc.

[0034] <Second Embodiment> Next, a second embodiment of the present invention will be described. FIGS. 3 and 4 are a front view and a side view of a rotational speed fluctuation detection device according to this embodiment. In this embodiment, as shown in FIGS. 3 and 4, two detection units are used. That is, one roller 10 (first roller) is pressed against the outer peripheral surface of the rotating shaft 100 above the rotating shaft 100, and the other roller 10 (second roller) is pressed against the outer peripheral surface of the rotating shaft 100 below the rotating shaft 100. Note that the two rollers 10 have the same outer diameter. The lower roller 10 is arranged on the opposite side of the upper roller 10 across the center of the rotating shaft 100 (a position 180 degrees apart in the circumferential direction). The encoder 20 that rotates in synchronization with the upper roller 10 constitutes the first rotary encoder of the present invention, and the encoder 20 that rotates in synchronization with the lower roller 10 constitutes the second rotary encoder of the present invention. The upper roller 10 and the encoder 20 connected thereto constitute the first detection unit of the present invention, and the lower roller 10 and the encoder 20 connected thereto constitute the second detection unit of the present invention.

[0035] In this embodiment, first, two detection units shown in FIGS. 3 and 4 are prepared (preparation step). When the rotating shaft 100 is rotated by the motor, the rotating shaft 100, the rollers 10 and the encoders 20 of each detection unit rotate in synchronization (rotation step). Then, the arithmetic processing unit 30 processes the signals output from the two encoders 20 respectively, removes the vibration component in the translational direction (the direction orthogonal to the axial direction of the rotating shaft 100) generated in the rotating shaft 100, and detects the rotational speed fluctuation of the rotating shaft 100 (detection step). The method will be described in detail below.

[0036] When two types of vibrations, torsional vibration and axial vibration (vibration of the rotating shaft 100 in the left - right direction in FIG. 4), occur on the rotating shaft 100, the rotational unevenness input to the two detection units is the sum of the above - mentioned two vibrations. Here, assuming that the direction in which the rotating shaft 100 rotates in FIG. 4 is positive, the rotational speed fluctuation caused by torsional vibration acts on the two detection units in the same direction. On the other hand, the axial vibration acts on the two detection units in opposite directions. Specifically, in FIG. 4, assuming that the rotating shaft 100 moves to the right due to the occurrence of axial vibration, this movement acts to promote the rotation of the upper roller 10. On the other hand, the movement acts to prevent the rotation of the lower roller 10. Therefore, by taking the sum of the signals measured by the two detection units, only the torsional vibration component can be extracted, and the component of the axial vibration can be canceled and removed.

[0037] The above - mentioned method will be described in detail with reference to FIGS. 5 to 10. FIG. 5 is a graph showing the time - history signal N1 (a signal obtained by converting the pulse signal of the encoder 20 into the rotational speed) of the upper roller 10 of the rotational speed fluctuation detection device 1 according to the present embodiment. FIG. 6 is a graph showing the amplitude spectrum obtained by performing FFT analysis on the data of FIG. 5. FIG. 7 is a graph showing the time - history signal N2 of the lower roller 10 of the rotational speed fluctuation detection device 1 according to the present embodiment. FIG. 8 is a graph showing the amplitude spectrum obtained by performing FFT analysis on the data of FIG. 7.

[0038] In FIG. 6 obtained by performing a fast Fourier transform on the time history signal N1 in FIG. 5, a peak S60 corresponding to the rotation of the upper roller 10 appears in the DC component, that is, the region of frequency zero. In a frequency region larger than this peak S60, a peak S61 corresponding to the shaft vibration of the rotating shaft 100, a peak S62 corresponding to the torsional vibration, and a peak S63 corresponding to the rotation unevenness of the upper roller 10 appear respectively. Similarly, in FIG. 8 obtained by performing a fast Fourier transform on the time history signal N2 in FIG. 7, a peak S80 corresponding to the rotation of the lower roller 10 appears in the DC component, that is, the region of frequency zero. In a frequency region larger than this peak S80, a peak S81 corresponding to the shaft vibration of the rotating shaft 100, a peak S82 corresponding to the torsional vibration, and a peak S83 corresponding to the rotation unevenness of the lower roller 10 appear respectively.

[0039] By using the time history signals N1 and N2 (FIGS. 5 and 7) of each roller 10 detected by the above two detection units, the time history signal N3 is obtained from the following formula 2, and thus the shaft vibration component can be canceled out as described above. N3 = (N1 + N2) / 2 ···(Formula 2) The time history signal N3 corresponds to the variation in the rotational speed of the roller 10 with radius R. Therefore, in order to correct the variation in the rotational speed of the rotating shaft 100 with radius R0, the time history signal N4 (FIG. 9) can be obtained from the time history signal N3 by the following correction formula of formula 3. N4 = R / R0 × N3 ···(Formula 3) FIG. 9 is a graph showing the time history signal N4 of the rotating shaft 100. FIG. 10 is a graph showing the amplitude spectrum obtained by performing FFT analysis on the data in FIG. 9.

[0040] Then, by performing a fast Fourier transform on this time history signal N4, as shown in FIG. 10, it is possible to obtain the relationship between the frequency and amplitude of the rotational speed fluctuations occurring on the rotating shaft 100. In FIG. 10, a peak S100 corresponding to the rotation of the rotating shaft 100 appears in the DC component region, i.e., the region of zero frequency, and peaks S101 corresponding to torsional vibrations and S102 corresponding to rotational unevenness of the upper and lower rollers 10 appear in frequency regions greater than this peak S100. That is, it becomes possible to remove the peaks S61 and S81 corresponding to the axial vibrations of the rotating shaft 100 in FIGS. 6 and 8. As a result, it becomes possible to accurately detect the rotational speed fluctuations of the torsional vibration of the rotating shaft 100. In FIG. 10, the rotational speed of the roller 10 can be obtained from the central value of the data in FIG. 9 and can be easily measured by other measuring instruments. Therefore, in FIG. 10, since it can be easily determined that the peak S102 is caused by the rotational unevenness of the roller 10, it can be determined that the remaining peak S101 is caused by torsional vibration.

[0041] Generally, vibrations in the rotational direction and axial vibrations, which are vibrations in the translational direction, occur on the rotating shaft 100. Conventionally, it has been difficult to easily separate these vibration components. According to the present invention, by processing the measurement data of the two detection units, the axial vibration component can be removed and only the component of the rotational speed fluctuation can be easily detected. When the rotating shaft 100 is eccentric, even if the rotating shaft 100 rotates at a constant rotational speed, the distance between the contact point of the roller 10 and the rotating shaft 100 and the center of rotation of the rotating shaft 100 changes periodically, causing an influence on the roller 10 as a rotational speed fluctuation. Even in such a case, in this embodiment, by paying attention to the fact that the influence of the rotational speed fluctuation of the rotating shaft 100 as described above is reversed in the two detection units and adding the two time history signals N1 and N2, the influence of the eccentricity of the rotating shaft 100 can be canceled. As a result, it becomes possible to easily and accurately detect the rotational speed fluctuation focusing on torsional vibration.

[0042] <Third Embodiment> Next, a third embodiment of the present invention will be described. FIGS. 11 and 12 are a front view and a side view of the rotational speed fluctuation detection device 1 according to the present embodiment. Also in the present embodiment, as shown in FIGS. 11 and 12, two detection units are used. That is, above the rotating shaft 100, a roller 11 (first roller) is pressed against the outer peripheral surface of the rotating shaft 100, and below the rotating shaft 100, a roller 10 (second roller) is pressed against the outer peripheral surface of the rotating shaft 100. Note that the two rollers 10 have different outer diameters, and the outer diameter of the roller 11 is set to be larger than the outer diameter of the roller 10. Also in the present embodiment, the encoder 20 that rotates in synchronization with the upper roller 11 constitutes the first rotary encoder of the present invention, and the encoder 20 that rotates in synchronization with the lower roller 10 constitutes the second rotary encoder of the present invention. The upper roller 11 and the encoder 20 connected thereto constitute the first detection unit of the present invention, and the lower roller 10 and the encoder 20 connected thereto constitute the second detection unit of the present invention.

[0043] Also in the present embodiment, two detection units shown in FIGS. 11 and 12 are prepared (preparation step). When the rotating shaft 100 is rotated by the motor, the rotating shaft 100, the rollers 10 and 11, and the encoder 20 of each detection unit rotate synchronously (rotation step). Then, the arithmetic processing unit 30 processes the signals output from the two encoders 20 respectively, removes the rotational frequency components of the rollers 10 and 11, and detects the rotational speed fluctuation of the rotating shaft 100 (detection step). The method will be described in detail below.

[0044] As in the previous second embodiment, when the spectrum of the time history signal N1 or N2 is calculated by fast Fourier transform, in addition to the frequencies of torsional vibration and shaft vibration, peaks occur at the frequency of the rotational speed of the roller 10 due to the influence of unevenness in the shape of the roller 10 itself (peak S63 in FIG. 6, peak S83 in FIG. 8, peak S102 in FIG. 10). In order to detect torsional vibration more accurately, it is desirable to remove these frequency components of the rotational speed of the roller 10.

[0045] Specifically, first, when calculating the spectra of the N1 time history signal and the N2 time history signal respectively, the value of the DC component at 0 Hz corresponds to the rotational speed of the roller 10 when there is no rotational unevenness. Therefore, in the time history signal of one roller, by replacing the values around the frequency that matches the value of the above DC component with the measurement data of the other roller, only the frequency components of the torsional vibration can be extracted. At this time, if the outer diameters of the rollers are set to be different in the two detection units, since the rotational speeds of the two rollers are different, it becomes possible to replace the region where the frequency of the rotational speed of the roller is removed in one detection unit with the measurement data of the other detection unit.

[0046] The above method will be further described in detail with reference to FIGS. 13 to 17. FIG. 13 is a graph showing the time history signal N1 of the upper roller 11 of the rotational speed fluctuation detection device 1 according to the present embodiment. FIG. 14 is a graph showing the amplitude spectrum obtained by performing FFT analysis on the data of FIG. 13. FIG. 15 is a graph showing the time history signal N2 of the lower roller 10 of the rotational speed fluctuation detection device 1 according to the present embodiment. FIG. 16 is a graph showing the amplitude spectrum obtained by performing FFT analysis on the data of FIG. 15. FIG. 17 is a graph of the amplitude spectrum showing the state in which the frequency components (rotational frequency components) of the rotational speeds of the respective rollers are removed from FIGS. 14 and 16.

[0047] In FIG. 14 obtained by performing fast Fourier transform on the time history signal N1 of FIG. 13, a peak S140 corresponding to the rotation of the upper roller 11 appears in the DC component, that is, the region of frequency zero, and in the frequency region larger than this peak S140, a peak S141 corresponding to the axial vibration of the rotating shaft 100, a peak S142 corresponding to the torsional vibration, and a peak S143 corresponding to the rotational unevenness of the upper roller 11 appear respectively. Similarly, in FIG. 16 obtained by performing fast Fourier transform on the time history signal N2 of FIG. 15, a peak S160 corresponding to the rotation of the lower roller 10 appears in the DC component, that is, the region of frequency zero, and in the frequency region larger than this peak S160, a peak S161 corresponding to the axial vibration of the rotating shaft 100, a peak S162 corresponding to the torsional vibration, and a peak S163 corresponding to the rotational unevenness of the lower roller 10 appear respectively.

[0048] In this embodiment, since the outer diameters of the rollers 10 and 11 are different, in FIGS. 14 and 16, the peaks S143 and S163 corresponding to the rotational unevenness of the rollers occur at different frequencies. Therefore, by replacing the frequency region around the peak S143 in FIG. 14 obtained based on the roller 11 with the data in the same frequency region in FIG. 16 obtained based on the roller 10, a spectrum distribution as shown in FIG. 17 can be obtained. That is, in FIG. 17, no peak occurs in the frequency region A1. Similarly, by replacing the frequency region around the peak S163 in FIG. 16 obtained based on the roller 10 with the data in the same frequency region in FIG. 14 obtained based on the roller 11, a spectrum distribution as shown in FIG. 17 can be obtained in the same manner. That is, in FIG. 17, no peak occurs in the frequency region A2 either. In addition, by removing (replacing) the data in a predetermined frequency region from the time history signals N1 and N2 in FIGS. 13 and 15 by the above method, and taking the sum of the two data and performing correction according to the radius as in the previous second embodiment, the rotational speed fluctuation of the rotating shaft 100 can be detected.

[0049] As described above, in this embodiment, when the rollers 10 and 11 rotate synchronously with the rotating shaft 100, attention is paid to the fact that the components of the rotational frequencies of the rollers 10 and 11 are included in the regions other than the frequency of the rotational speed fluctuation of the rotating shaft 100, and it becomes possible to separate these rotational speed components from the frequency of the desired rotational speed fluctuation such as torsional vibration. In particular, in the present invention, the frequency components corresponding to the rotational speeds of the rollers 10 and 11 can be removed by data processing, and only the vibration components of the rotating shaft 100 can be extracted. As a result, it becomes possible to detect the rotational speed fluctuation focusing on torsional vibration with higher accuracy.

[0050] <Fourth Embodiment> Next, a fourth embodiment of the present invention will be described. FIGS. 18 and 19 are a front view and a side view of the rotational speed fluctuation detection device 1 according to the present embodiment. Also in the present embodiment, two detection units are used, as in the previous third embodiment. That is, the roller 11 (first roller) is pressed against the outer peripheral surface of the rotating shaft 100 above the rotating shaft 100, and the roller 10 (second roller) is pressed against the outer peripheral surface of the rotating shaft 100 below the rotating shaft 100. Note that the present embodiment is different from the third embodiment in that the roller 10 is arranged on the opposite side of the roller 11 with the center of the rotating shaft 100 interposed therebetween. Other configurations are the same as those of the third embodiment.

[0051] Also in the present embodiment, two detection units shown in FIGS. 18 and 19 are prepared (preparation step). When the rotating shaft 100 is rotated by the motor, the rotating shaft 100, the rollers 10 and 11 of each detection unit, and the encoder 20 rotate synchronously (rotation step). Then, the arithmetic processing unit 30 processes the signals output from the two encoders 20 respectively, removes the rotational frequency components of the rollers 10 and 11 and the vibration components in the translational direction generated in the rotating shaft 100, and detects the rotational speed fluctuation of the rotating shaft 100 (detection step). The method will be described in detail below.

[0052] FIG. 20 is a graph showing the time history signal N1 of the upper roller 11 of the rotational speed fluctuation detection device 1 according to the present embodiment, and FIG. 21 is a graph showing the amplitude spectrum obtained by performing FFT analysis on the data of FIG. 20. FIG. 22 is a graph showing the time history signal N2 of the lower roller 10 of the rotational speed fluctuation detection device 1 according to the present embodiment, and FIG. 23 is a graph showing the amplitude spectrum obtained by performing FFT analysis on the data of FIG. 22.

[0053] In the present embodiment, let the radius of the roller 11 of the upper detection unit be R1, the time history signal of the measured rotational speed be N1, the radius of the roller 10 of the lower detection unit be R2, the time history signal of the measured rotational speed be N2, and the radius of the rotating shaft 100 be R0.

[0054] The above time history signals N1 and N2 are corrected according to the following formulas 4 and 5 in accordance with the radius of the rotating shaft 100 to obtain time history signals N3 and N4. N3 = R1 / R0 × N1 ··· (Formula 4) N4 = R2 / R0 × N2 ··· (Formula 5)

[0055] From the vibration spectra obtained by performing FFT analysis on the above time history signals N3 and N4 respectively, the DC component (DC1) of the time history signal N3 and the DC component (DC2) of the time history signal N4 are obtained respectively. Note that the DC component corresponds to the peak S210 with a frequency of zero in the time history signal N1 of FIG. 21 and corresponds to the peak S230 in the time history signal N2 of FIG. 23. The same applies to the time history signals N3 and N4.

[0056] Next, in the time history signal N3, the signal around the frequency f1 corresponding to DC1 obtained above is removed by a band - elimination filter to obtain a time history signal N5. Also, in the time history signal N4, the signal around the frequency f1 is extracted by a band - pass filter to obtain a time history signal N6. Next, the sum of the time history signals N5 and N6 is taken to obtain a time history signal N7. FIG. 24 is a graph showing the time history signal N7 in the rotational speed fluctuation detection device 1 according to the present embodiment. By deriving the time history signal N7, the rotational speed component of the roller 11 can be removed from the aforementioned time history signal N3. Note that in the example of FIG. 21, the peak S213 corresponds to the rotational speed component of the upper roller 11. Note that the above filter processing is not limited to the band - elimination filter and may be by other filter processing.

[0057] Similarly, in the time history signal N4, the signal around the frequency f2 corresponding to the DC2 obtained above is removed by a band elimination filter to obtain a time history signal N8. Also, in the time history signal N3, the signal around the frequency f2 is extracted by a band pass filter to obtain a time history signal N9. Next, the sum of the time history signals N8 and N9 is taken to obtain a time history signal N10. FIG. 25 is a graph showing the time history signal N10 in the rotational speed fluctuation detection device 1 according to the present embodiment. By deriving the time history signal N10, the rotational speed component of the roller 10 can be removed from the aforementioned time history signal N4. In the example of FIG. 23, the peak S233 corresponds to the rotational speed component of the lower roller 10.

[0058] Furthermore, as shown in Equation 6 below, the sum of the time history signals N7 and N10 obtained above is taken and divided by 2 to obtain a time history signal N11. N11 = (N7 + N10) / 2 ···(Equation 6) FIG. 26 is a graph showing the time history signal N11 in the rotational speed fluctuation detection device 1 according to the present embodiment. By taking the sum of the time history signals N7 and N10, the components of the axial fluctuations of both are canceled out, and the component of the axial vibration of the rotating shaft 100 can be removed in the time history signal N11. In FIG. 21, the peak S211 corresponds to the axial vibration component of the rotating shaft 100, and in FIG. 23, the peak S231 corresponds to the axial vibration component of the rotating shaft 100. These components also appear similarly in the FFT analysis results of the time history signals N7 and N10.

[0059] As described above, the time history signal N11 obtained according to this embodiment is a signal from which the frequency components of the shaft vibration of the rotating shaft 100 and the rotation frequency components of the two rollers 10 and 11 have been removed, and is a signal from which only the frequency components of the rotational speed variation caused by torsional vibration have been extracted. Therefore, by subjecting the time history signal N11 to fast Fourier transform processing, it is possible to know the frequency and magnitude of the rotational speed variation caused by torsional vibration. FIG. 27 is a graph showing the amplitude spectrum obtained by performing FFT analysis on the data of the time history signal N11 in FIG. 26. In the example of FIG. 27, a peak S270 corresponding to the rotation of the rotating shaft 100 appears in the DC component, that is, the region of frequency zero, and only a peak S271 corresponding to torsional vibration appears in a frequency region larger than this peak S270. As described above, in this embodiment, it is possible to accurately detect the rotational speed variation due to torsional vibration after removing the influence of the shaft vibration of the rotating shaft 100 and the influence of the rotational unevenness of the two rollers. In particular, it becomes possible to easily and accurately detect the components of torsional vibration, which are generally difficult to extract, and it becomes possible to easily take various improvement measures for the rotation system of the rotating shaft 100.

Explanation of Signs

[0060] 1 Rotational speed variation detection device 10, 11 Rollers (first roller, second roller) 20 Encoder (rotary encoder) 30 Arithmetic processing unit (rotational speed variation detection unit) 100 Rotating shaft

Claims

1. A method for detecting fluctuations in the rotational speed of a rotating shaft, comprising: a preparation step of preparing at least one detection unit including a roller and a rotary encoder that rotates in synchronization with the roller; a rotation step of pressing the roller of the at least one detection unit against the outer peripheral surface of the rotating shaft and rotating the rotating shaft, the roller, and the rotary encoder in synchronization; a detection step of detecting fluctuations in the rotational speed of the rotating shaft by processing a signal output from the rotary encoder; characterized by comprising: in the preparation step, as the at least one detection unit, preparing a first detection unit including a first roller and a first rotary encoder, and a second detection unit including a second roller having the same outer diameter as the first roller and a second rotary encoder; in the rotation step, pressing the first roller and the second roller against the outer peripheral surface such that the second roller is disposed on the opposite side of the first roller with the center of the rotating shaft therebetween, and rotating the rotating shaft, the first roller, the second roller, the first rotary encoder, and the second rotary encoder in synchronization; in the detection step, processing signals respectively output from the first rotary encoder and the second rotary encoder to remove a translational vibration component generated in the rotating shaft and detecting fluctuations in the rotational speed of the rotating shaft. A method for detecting fluctuations in the rotational speed of a rotating shaft.

2. A method for detecting fluctuations in the rotational speed of a rotating shaft, comprising: a preparation step of preparing at least one detection unit including a roller and a rotary encoder that rotates in synchronization with the roller; a rotation step of pressing the roller of the at least one detection unit against the outer peripheral surface of the rotating shaft and rotating the rotating shaft, the roller, and the rotary encoder in synchronization; a detection step of detecting fluctuations in the rotational speed of the rotating shaft by processing a signal output from the rotary encoder; characterized by comprising: in the preparation step, as the at least one detection unit, preparing a first detection unit including a first roller and a first rotary encoder, and a second detection unit including a second roller having an outer diameter different from that of the first roller and a second rotary encoder; The rotation step includes pressing the first roller and the second roller against the outer peripheral surface and synchronously rotating the rotary shaft, the first roller, the second roller, the first rotary encoder, and the second rotary encoder. The detection step includes removing the rotation frequency components of the first roller and the second roller and detecting the rotational speed variation of the rotary shaft, which is a method for detecting the rotational speed variation of a rotary shaft.

3. The rotation step includes pressing the first roller and the second roller against the outer peripheral surface such that the second roller is disposed on the opposite side of the first roller across the center of the rotary shaft, and synchronously rotating the rotary shaft, the first roller, the second roller, the first rotary encoder, and the second rotary encoder. The detection step includes further removing the translational vibration component generated in the rotary shaft and detecting the rotational speed variation of the rotary shaft, which is the method for detecting the rotational speed variation of a rotary shaft according to Claim 2.

4. An apparatus for detecting the rotational speed variation of a rotary shaft, comprising: at least one detection unit including a roller and a rotary encoder that rotates synchronously with the roller; a rotational speed variation detection unit that detects the rotational speed variation of the rotary shaft by processing a signal output from the rotary encoder when the roller of the at least one detection unit contacts the outer peripheral surface of the rotary shaft and the rotary shaft, the roller, and the rotary encoder rotate synchronously; and is provided with: the at least one detection unit has a first detection unit including a first roller and a first rotary encoder, and a second detection unit including a second roller having the same outer diameter as the first roller and a second rotary encoder disposed on the opposite side of the first roller across the center of the rotary shaft; the rotational speed variation detection unit removes the translational vibration component generated in the rotary shaft by processing the signals respectively output from the first rotary encoder and the second rotary encoder when the first roller and the second roller contact the outer peripheral surface and the rotary shaft, the first roller, the second roller, the first rotary encoder, and the second rotary encoder rotate synchronously, and detects the rotational speed variation of the rotary shaft, which is an apparatus for detecting the rotational speed variation of a rotary shaft.

5. An apparatus for detecting the rotational speed variation of a rotary shaft, comprising: At least one detection unit including a roller and a rotary encoder that rotates in synchronization with the roller; a rotation speed fluctuation detection unit that detects a rotation speed fluctuation of the rotating shaft by processing a signal output from the rotary encoder when the roller of the at least one detection unit contacts an outer peripheral surface of the rotating shaft and the rotating shaft, the roller, and the rotary encoder rotate in synchronization; comprising; the at least one detection unit includes a first detection unit including a first roller and a first rotary encoder, and a second detection unit including a second roller having an outer diameter different from that of the first roller and a second rotary encoder; the rotation speed fluctuation detection unit removes a rotation frequency component of the first roller and a rotation frequency component of the second roller by processing signals respectively output from the first rotary encoder and the second rotary encoder when the first roller and the second roller contact the outer peripheral surface and the rotating shaft, the first roller, the second roller, the first rotary encoder, and the second rotary encoder rotate in synchronization, and detects a rotation speed fluctuation of the rotating shaft, a rotation speed fluctuation detection device for a rotating shaft.

6. the second roller is disposed on the opposite side of the first roller with the center of the rotating shaft interposed therebetween; the rotation speed fluctuation detection unit further removes a vibration component in the translational direction generated in the rotating shaft and detects a rotation speed fluctuation of the rotating shaft, the rotation speed fluctuation detection device for a rotating shaft according to claim 5.

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