Diagnostic device and diagnostic method

Abstract

A diagnostic device (1) for diagnosing the state of a bearing is provided with a relative rotation speed acquisition unit (21), a vibration signal acquisition unit (22), and a diagnostic unit (24). The relative rotation speed acquisition unit (21) acquires the relative rotation speed between an inner ring and an outer ring of the bearing. The vibration acquisition unit (22) acquires a vibration sensor signal output by a vibration sensor (92) that measures the magnitude of vibration of the bearing. The diagnostic unit (24) determines that an abnormality has occurred in the bearing if it is detected, from the vibration sensor signal, that the magnitude of rotation synchronous vibration is equal to or greater than a threshold value within a range in which the relative rotation speed is less than a reference rotation speed and that the magnitude of the rotation synchronous vibration is less than the threshold value when the relative rotation speed is equal to or greater than the reference rotation speed in a case where the rotation synchronous vibration, the frequency of which increases as the relative rotation speed increases, has been detected.

Description

Diagnostic device and diagnostic method

[0001] The present disclosure relates to diagnostic devices and methods.

[0002] A rolling bearing that supports a rotating body so that it can rotate around a central axis includes an inner ring and an outer ring, one of which rotates as the rotating body rotates, multiple rolling elements that roll between the inner ring and the outer ring, and a cage that maintains the spacing between adjacent rolling elements. When the cage wears due to friction between the rolling elements and the cage, the gap between the rolling elements and the cage expands. This increases the cage's range of movement in the radial direction relative to the central axis, and centrifugal force acts on the cage when the rotating body rotates, causing the cage to whirl. When the cage whirls, it may collide with at least one of the inner ring, outer ring, and rolling elements.

[0003] Repeated collisions of the cage with at least one of the inner ring, outer ring, and rolling elements can damage the bearing. Patent Document 1 discloses an abnormality diagnosis device as an example of a method for determining whether a bearing is damaged. The abnormality diagnosis device disclosed in Patent Document 1 is provided on the annular portion of the cage and diagnoses the condition of the bearing from vibrations generated by collisions between a fixed ring and a convex portion that protrudes radially.

[0004] JP 2014-052346 A

[0005] When the rotation speed of the cage is low, the centrifugal force acting on the cage is small, so the cage may not whirl. Even when the rotation speed of the cage is high, if the amount of wear on the cage is small, the range of movement of the cage is narrow, in other words, the whirling diameter is small, so the vibration caused by collision between the cage and the fixed ring is small. For this reason, in cases like the above example, it is difficult for the abnormality diagnosis device disclosed in Patent Document 1 to accurately diagnose the condition of the bearing.

[0006] The present disclosure has been made in consideration of the above circumstances, and an object of the present disclosure is to provide a diagnostic device and diagnostic method that can accurately diagnose the condition of a bearing.

[0007] To achieve the above object, a diagnostic device disclosed herein diagnoses the condition of a rolling bearing that rotatably supports a shaft around a central axis that intersects the vertical direction, the bearing comprising: an inner ring; an outer ring disposed radially outward of the inner ring relative to the central axis; a plurality of rolling elements that roll between the inner ring and the outer ring while abutting against the inner ring and the outer ring; and a cage disposed between the inner ring and the outer ring and having a plurality of columns each positioned between adjacent rolling elements at a distance from each other. The diagnostic device comprises a relative rotation speed acquisition unit, a vibration signal acquisition unit, and a diagnostic unit. The relative rotation speed acquisition unit acquires the relative rotation speed between the inner ring and the outer ring. The vibration signal acquisition unit acquires a vibration sensor signal output by a vibration sensor that measures the magnitude of bearing vibrations generated when the shaft rotates. When the diagnostic unit detects from the vibration sensor signal that rotation-synchronous vibration, the frequency of which increases as the relative rotation speed increases, that the magnitude of the rotation-synchronous vibration is above a threshold value when the relative rotation speed is below a predetermined reference rotation speed, or that the magnitude of the rotation-synchronous vibration is below the threshold value when the relative rotation speed is above the reference rotation speed, the diagnostic unit determines that an abnormality has occurred in the bearing.

[0008] When the diagnostic device according to the present disclosure detects from the vibration sensor signal that rotation-synchronous vibration, the frequency of which increases as the relative rotation speed increases, that the magnitude of the rotation-synchronous vibration is equal to or greater than a threshold value when the relative rotation speed is below a reference rotation speed, or that the magnitude of the rotation-synchronous vibration is less than the threshold value when the relative rotation speed is equal to or greater than the reference rotation speed, the diagnostic device determines that an abnormality has occurred in the bearing, thereby enabling accurate diagnosis of the condition of the bearing.

[0009] FIG. 1 is a cross-sectional view of a bearing to be diagnosed by the diagnostic device according to the first embodiment; FIG. 1 is a cross-sectional view of a bearing to be diagnosed by the diagnostic device according to the first embodiment; FIG. 2 is a diagram showing an example of a movable range of a cage in a bearing to be diagnosed by the diagnostic device according to the first embodiment; FIG. 3 is a diagram showing an example of wear of a cage in a bearing to be diagnosed by the diagnostic device according to the first embodiment; FIG. 4 is a diagram showing an example of a fallen cage in a bearing to be diagnosed by the diagnostic device according to the first embodiment; FIG. 5 is a diagram showing an example of a fallen cage in a bearing to be diagnosed by the diagnostic device according to the first embodiment;

[0010] A diagnostic device and a diagnostic method according to an embodiment of the present disclosure will be described in detail below with reference to the drawings, in which the same or equivalent parts are designated by the same reference numerals.

[0011] (Embodiment 1) A diagnostic device according to embodiment 1 will be described using, as an example, a diagnostic device that diagnoses the condition of a bearing that rotatably supports the shaft of an electric motor. The electric motor is, for example, a traction motor mounted on a railway vehicle to generate propulsive force for the railway vehicle. As shown in Fig. 1 , a bearing 10, which is an example of an object to be diagnosed by the diagnostic device, rotatably supports a shaft 90 of the electric motor about a central axis AX1 that intersects the vertical direction. The bearing 10 includes an inner ring 11 that rotates integrally with the shaft 90, an outer ring 12 that is disposed radially outward of the inner ring 11 relative to the central axis AX1, a plurality of rolling elements 13 that roll between the inner ring 11 and the outer ring 12 while abutting against the inner ring 11 and the outer ring 12, and a cage 14 that is disposed between the inner ring 11 and the outer ring 12.

[0012] Figure 1 is a cross-sectional view of a bearing 10 taken along a cross section perpendicular to a central axis AX1. In Figure 1, the axis extending parallel to the central axis AX1 is the X-axis. The Z-axis indicates the vertical direction. The Y-axis is perpendicular to both the X-axis and the Z-axis. This also applies to subsequent figures.

[0013] The bearing 10 is a rolling bearing such as a roller bearing or a ball bearing. As an example, the inner ring 11 has a cylindrical shape and is fitted onto the shaft 90 to rotate integrally with the shaft 90. The central axis of the inner ring 11 coincides with the central axis AX1 of the shaft 90.

[0014] The outer ring 12 has a cylindrical shape and is provided radially outward of the inner ring 11 relative to the central axis AX1. A raceway surface 12a facing radially inward of the outer ring 12 and a raceway surface 11a facing radially outward of the inner ring 11 face each other radially with a gap between them. The central axis of the outer ring 12 coincides with the central axis AX1 of the shaft 90. The outer ring 12 is held in a housing (not shown) and is maintained stationary even when the shaft 90 is rotating.

[0015] The plurality of rolling elements 13 are provided between the raceway surface 11 a of the inner ring 11 and the raceway surface 12 a of the outer ring 12, and are arranged at intervals from one another in the circumferential direction about the central axis AX1. Each of the rolling elements 13 rolls in accordance with the relative rotation of the inner ring 11 and the outer ring 12. In detail, each rolling element 13 revolves around the inner ring 11 while rotating on its own axis while abutting against the raceway surfaces 11 a, 12 a.

[0016] The cage 14 maintains the spacing between adjacent rolling elements 13. More specifically, as shown in FIG. 1 and FIG. 2, which is a cross-sectional view of the bearing 10 at a position shifted in the negative X-axis direction from FIG. 1, the cage 14 has a cylindrical annular portion 14a and a plurality of pillar portions 14b extending from the annular portion 14a in the X-axis direction and positioned between adjacent rolling elements 13 at a distance from each other. As an example, the cage 14 has a pair of annular portions 14a facing each other in the X-axis direction and a plurality of pillar portions 14b connected to each annular portion 14a and positioned between the rolling elements 13. The pillar portions 14b are positioned between two adjacent rolling elements 13, thereby maintaining equal spacing between the rolling elements 13.

[0017] The operation of the bearing 10 having the above configuration will be described below. As an example, the operation of the bearing 10 when the shaft 90 rotates around the central axis AX1 in the rotational direction D1 as shown in Figure 2 will be described. The shaft 90 rotates counterclockwise as viewed in the negative direction of the X axis. At this time, the inner ring 11 rotates integrally with the shaft 90 around the central axis AX1 in the rotational direction D1. In other words, the inner ring 11 rotates counterclockwise as viewed in the negative direction of the X axis.

[0018] As described above, the inner ring 11 rotates in rotational direction D1, while the outer ring 12 does not rotate because it is held in the housing. As a result, each rolling element 13 rotates around the central axis AX2 in a rotational direction D2 opposite to rotational direction D1. In other words, the rolling elements 13 rotate clockwise when viewed in the negative direction of the X-axis. While rotating in rotational direction D2 as described above, each rolling element 13 rolls around the central axis AX1 in a rotational direction D3. In other words, each rolling element 13 revolves in rotational direction D3 while rotating on its own axis in rotational direction D2. The rolling of each rolling element 13 as described above enables the bearing 10 to rotatably support the shaft 90.

[0019] 3, as the rolling elements 13 roll, the cage 14 rotates around the central axis AX3 in a rotational direction D3. When the cage 14 rotates, centrifugal force acts on the cage 14, causing the central axis AX3 of the cage 14 to deviate from the central axis AX1. When the cage 14 rotates, the column portions 14b come into contact with the rolling elements 13, causing wear to the column portions 14b.

[0020] As the bearing 10 continues to be used, the columnar portion 14b gradually wears away. The wear depth of the columnar portion 14b, specifically, the amount of wear in the circumferential direction of the columnar portion 14b, increases due to factors such as an increase in the rotation speed of the shaft 90, use of the bearing 10 in a high-temperature environment, and deterioration of the grease used in the bearing 10. As a result, as shown in FIG. 4, the columnar portion 14b wears away, and the length W2 of the columnar portion 14b in the circumferential direction, which is the direction around the central axis AX3, becomes shorter than the circumferential length W1 of the columnar portion 14b shown in FIG. 3. The wear depth of the columnar portion 14b, in other words, the amount of reduction in the circumferential length of the columnar portion 14b due to wear, is expressed as W1 - W2.

[0021] As described above, when the retainer 14 rotates, centrifugal force acts on the retainer 14, causing the central axis AX3 of the retainer 14 to deviate from the central axis AX1. As shown in FIG. 3 , when the circumferential length of the column portions 14b is W1, the distance in the YZ plane between the central axis AX3 and the central axis AX1 when the central axis AX3 of the retainer 14 is located farthest from the central axis AX1 in the radial direction is defined as the movable radius h1. In other words, while rotating around the central axis AX3, the retainer 14 moves within a range where the distance in the YZ plane between the central axis AX3 and the central axis AX1 is equal to or less than h1. If the wear depth of the column portions 14b is short, the movable radius h1 is sufficiently small, and the central axis AX3 can be considered to coincide with the central axis AX1.

[0022] As shown in Fig. 4, when the circumferential length of the column portions 14b is W2, the distance in the YZ plane between the central axis AX3 and the central axis AX1 of the retainer 14 when the central axis AX3 is located at its farthest radial distance from the central axis AX1 is defined as the movable radius h2. That is, while rotating around the central axis AX3, the retainer 14 moves within a range where the distance in the YZ plane between the central axis AX3 and the central axis AX1 is equal to or less than h2. As the wear depth of the column portions 14b increases, the movable radius increases. In other words, the retainer 14 included in the bearing 10 shown in Fig. 4 moves within a wider radial range than the retainer 14 included in the bearing 10 shown in Fig. 3.

[0023] In the bearing 10 shown in Figure 4 where the column portion 14b is worn, when the inner ring 11 rotates at high speed, the centrifugal force acting on the cage 14 increases, causing the cage 14 to rotate around the central axis AX3 that moves in an orbit around the central axis AX1. This type of movement of the cage 14 is called whirling. When the cage 14 whirls, the cage 14 collides with at least one of the inner ring 11, the outer ring 12, and the rolling elements 13.

[0024] While the inner ring 11 is rotating at a low speed, the cage 14 does not whirl, but as the cage 14 moves vertically downward, it falls, colliding with at least one of the inner ring 11, the outer ring 12, and the rolling elements 13. The falling of the cage 14 will be described in detail below. In FIG. 5 , the range vertically below the central axis AX1 and sandwiched between the dotted line segments is the loaded zone. In detail, the loaded zone is a sector-shaped range centered on the point on the YZ plane through which the central axis AX1 passes, with a central angle of 45 degrees or more and 90 degrees or less, and symmetrical with respect to an axis extending parallel to the Z axis that passes through the center.

[0025] The rolling elements 13 located in the loaded zone are subjected to the loads of the inner ring 11 and shaft 90. For this reason, a contact load is generated between the inner ring 11 and the rolling elements 13 in the loaded zone, and as the inner ring 11 rotates, a frictional force in the rotational direction D1 of the inner ring 11 is generated between the inner ring 11 and the rolling elements 13. In the loaded zone, the rolling elements 13 move in a rotational direction D3 around the central axis AX1 while rotating in a rotational direction D2 around the central axis AX2.

[0026] In the non-load zone, which is outside the loaded zone, it can be assumed that no contact load occurs between the inner ring 11 and the rolling elements 13. In the non-load zone, the frictional force generated between the inner ring 11 and the rolling elements 13 as the inner ring 11 rotates is sufficiently small. For this reason, in the non-load zone, the rolling elements 13 do not roll between the inner ring 11 and the outer ring 12, but slide while moving in the rotational direction D3 around the central axis AX1.

[0027] As the rolling element 13 moves from the non-load zone into the load zone and into the load zone, the gap between the rolling element 13 and the column portion 14b located adjacent to the rolling element 13 narrows. As a result, when the rolling element 13 moves out of the load zone, the column portion 14b with which the rolling element 13 is in contact is pushed up in the rotational direction D3, as shown by the dotted arrow in Figure 5. This pushes up the cage 14 in the positive direction of the Y axis and the positive direction of the Z axis.

[0028] Subsequently, when the rolling elements 13, which had been pushing up the column portions 14b as described above, move from the loaded zone to the unloaded zone, the rolling elements 13 slide and lose the force pushing up the column portions 14b. As a result, the cage 14 drops vertically downward, as shown in FIG. 6. In the example of FIG. 6, the cage 14 drops, and the inner peripheral surface of the upper vertical portion of the cage 14 hits the raceway surface 11a of the inner ring 11. As the wear depth of the column portions 14b increases, the movable radius of the cage 14 increases, and the drop width of the cage 14 increases. As a result, vibrations caused by the cage 14 colliding with at least one of the inner ring 11, outer ring 12, and rolling elements 13 when the cage 14 drops increase. The above-mentioned drop of the cage 14 occurs each time each rolling element moves from the loaded zone to the unloaded zone. A diagnostic device that diagnoses the condition of a bearing 10 using the vibrations caused by the drop of the cage 14 each time a rolling element 13 leaves the loaded zone is described below.

[0029] 7 determines whether or not there is an abnormality in the bearing 10, specifically, whether or not there is wear on the bearing 10, as an example of diagnosing the condition of the bearing 10. The diagnostic device 1 includes a relative rotation speed acquisition unit 21 that acquires the relative rotation speed between the inner ring 11 and the outer ring 12, a vibration signal acquisition unit 22 that acquires a vibration sensor signal from a vibration sensor signal 92 that measures the magnitude of vibration of the bearing 10, a peak detection unit 23 that detects peaks in spectrum data that indicate the distribution of vibration of the bearing 10 for each frequency, and a diagnostic unit 24 that diagnoses the condition of the bearing 10 from the vibration sensor signal, including determining whether or not there is wear on the bearing 10.

[0030] The relative rotation speed acquisition unit 21 acquires, from the rotation sensor 91, a rotation sensor signal that changes in accordance with the rotation of each of the inner ring 11 and the outer ring 12. The rotation sensor 91 has, for example, a PG (Pulse Generator) provided near the shaft 90 and near the outer ring 12. The relative rotation speed acquisition unit 21 obtains the relative rotation speed between the inner ring 11 and the outer ring 12 from digital data obtained by sampling the signals output by each PG. The relative rotation speed acquisition unit 21 sends the obtained relative rotation speed to the vibration signal acquisition unit 22 and the diagnosis unit 24.

[0031] The vibration signal acquisition unit 22 acquires a vibration sensor signal, which is an analog data signal whose amplitude changes depending on the magnitude of the vibration of the measurement target, from the vibration sensor 92. The vibration sensor 92 is, for example, an acceleration sensor, a displacement sensor, or a velocity sensor attached to the outer surface of a housing that houses the outer ring 12 of the bearing 10. The vibration signal acquisition unit 22 generates spectral data, which is frequency domain data, from the vibration sensor signal, which is a time domain signal. More specifically, the vibration signal acquisition unit 22 generates the spectral data by performing an FFT (Fast Fourier Transform) on digital data obtained by sampling the vibration sensor signal while the shaft 90 is rotating. The vibration signal acquisition unit 22 sends the generated spectral data to the peak detection unit 23.

[0032] The peak detection unit 23 detects peaks in the spectrum data. Specifically, the peak detection unit 23 detects a maximum value equal to or greater than the detection threshold as a peak. When there are multiple maximum values ​​equal to or greater than the detection threshold, the peak detection unit 23, for example, detects the largest one of the multiple maximum values ​​equal to or greater than the detection threshold as the peak. The detection threshold is set based on tests, simulations, etc., to a value corresponding to the magnitude of vibration caused by the fall of the cage 14 when the column portion 14b is worn. The peak detection unit 23 outputs the frequency corresponding to the peak to the diagnosis unit 24. If a peak is not detected, the peak detection unit 23 notifies the diagnosis unit 24 that a peak was not detected.

[0033] When the diagnosing unit 24 detects, based on the spectrum data obtained from the vibration sensor signal, rotation-synchronous vibration whose frequency increases as the relative rotation speed increases, the diagnosing unit 24 determines that an abnormality has occurred in the bearing 10, such as wear of the bearing 10, if it detects that the magnitude of the rotation-synchronous vibration is equal to or greater than a threshold value when the relative rotation speed is below a predetermined reference rotation speed, and that the magnitude of the rotation-synchronous vibration is less than the threshold value when the relative rotation speed is equal to or greater than the reference rotation speed. The threshold value may be set to, for example, a value smaller than the possible value of the rotation-synchronous vibration in the low-speed range when an abnormality has occurred in the bearing 10.

[0034] The hardware configuration of the diagnostic device 1 having the above configuration is shown in Fig. 8. The diagnostic device 1 includes a processor 81, a memory 82, and an interface 83. The processor 81, the memory 82, and the interface 83 are connected to one another via a bus 80. The processor 81 includes any electronic circuit including a transistor, and is considered to be a circuit or a processor circuit.

[0035] The functions of the diagnostic device 1 are realized by software, firmware, which is software built into an electronic device, or a combination of software and firmware. The software is written as a program and stored in the memory 82. The processor 81 reads and executes the program stored in the memory 82, thereby realizing the functions of the above-mentioned parts. In other words, the memory 82 stores a program for executing the processing of the diagnostic device 1.

[0036] The memory 82 includes, for example, non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read-Only Memory), flash memory, EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable and Programmable Read-Only Memory), magnetic disk, flexible disk, optical disk, compact disk, mini disk, DVD (Digital Versatile Disc), etc. Although FIG. 8 illustrates one processor 81 and one memory 82, the diagnostic device 1 may be realized by a plurality of processors 81 and a plurality of memories 82. In this case, the plurality of processors 81 and the plurality of memories 82 may cooperate to execute each function of the diagnostic device 1.

[0037] The diagnostic device 1 is connected to a rotation sensor 91 and a vibration sensor 92 via an interface 83. The interface 83 has interface modules that comply with one or more standards depending on the connected device.

[0038] The diagnostic device 1 having the above configuration continuously performs the diagnostic process shown in Fig. 9 during operation. The relative rotation speed acquisition unit 21 included in the diagnostic device 1 obtains the relative rotation speed between the inner ring 11 and the outer ring 12 from the rotation sensor signal acquired from the rotation sensor 91 (step S11).

[0039] The vibration signal acquirer 22 determines whether the shaft 90 is rotating (step S12). Specifically, the vibration signal acquirer 22 determines whether the shaft 90 is rotating based on whether the relative rotation speed calculated in step S11 is equal to or greater than a rotation speed lower limit value. The rotation speed lower limit value is set to a small value that is sufficiently close to 0.

[0040] If the shaft 90 is not rotating, i.e., if the relative rotation speed calculated in step S11 is less than the lower limit (step S12; No), the above-described process is repeated from step S11. If the shaft 90 is rotating, i.e., if the relative rotation speed calculated in step S11 is equal to or greater than the lower limit (step S12; Yes), the vibration signal acquisition unit 22 acquires a vibration sensor signal from the vibration sensor 92 and generates spectrum data from the acquired vibration sensor signal (step S13). The peak detection unit 23 detects peaks from the spectrum data calculated in step S13 (step S14). The diagnosis unit 24 associates the relative rotation speed with the peaks and diagnoses the condition of the bearing 10 based on changes in the peaks in response to changes in the relative rotation speed (step S15). After the process of step S15 is completed, the diagnosis device 1 repeats the above-described process from step S11.

[0041] The shaft 90 is, for example, the shaft of an electric motor that rotates upon receiving a supply of electric power from a power converter (not shown). A control device that controls the power converter gradually brings the value of the current supplied from the power converter to the electric motor closer to a target value, and the rotation speed of the shaft 90 gradually increases from a stopped state to the target rotation speed. As the rotation speed of the shaft 90 changes, the relative rotation speed between the inner ring 11 and the outer ring 12 changes. This changes the interval at which the cage 14 falls.

[0042] The diameter of the rolling element 13 is d (unit: mm), the diameter of the path around the central axis AX1 through which the center of the rolling element 13 passes is D (unit: mm), the contact angle of the rolling element 13 is α (unit: rad), and the relative rotation speed between the inner ring 11 and the outer ring 12 is f ｓ (unit: rps), the rotation period T ０ is expressed by the following formula (1). The diameter D corresponds to the sum of the outer diameter of the inner ring 11 and the diameter of the rolling element 13. The contact angle α is determined in advance in the design for each bearing 10. The rotation period T of the cage 14 expressed by the following formula (1) ０ (unit: seconds) is considered to coincide with the revolution period of the rolling element 13 around the central axis AX1.

[0043]

[0044] Rotational speed f of the cage 14 ０ (unit: rps) is the rotation period T ０ The rotational speed f of the cage 14 is the reciprocal of ０ is considered to be equal to the revolution speed of the rolling element 13 around the central axis AX1.

[0045]

[0046] If the number of rolling elements 13 included in the bearing 10 is Z, the interval Tr between the timings at which the rolling elements 13 leave the loaded zone and enter the unloaded zone is ０ (unit: seconds) is the rotation period T of the cage 14 as expressed by the following equation (3): ０ is calculated by dividing by the number Z of rolling elements.

[0047]

[0048] As described above, the interval Tr between the timings at which the rolling element 13 leaves the loaded zone and enters the non-loaded zone is ０ is the relative rotation speed f ｓ Therefore, the interval between the timing of the cage 14 dropping, which occurs every time the rolling element 13 leaves the loaded area and enters the non-loaded area, is the relative rotation speed f ｓ In other words, the period of the vibration caused by the dropping of the cage 14 changes depending on the relative rotation speed. This vibration is called rotation-synchronous vibration. As the relative rotation speed increases, the frequency of the rotation-synchronous vibration increases. As an example, the frequency of the rotation-synchronous vibration increases in proportion to the increase in the relative rotation speed. An example of rotation-synchronous vibration is shown in FIG. 10. As shown in FIG. 10, when the relative rotation speed f ｓ In accordance with the change in frequency, the frequency at which a peak due to the dropping of the cage 14 appears in the spectrum data changes. The horizontal axis of FIG. 10 represents frequency (unit: Hz), and the vertical axis represents the magnitude of vibration as the amplitude of acceleration (unit: m / s ２ ) is expressed as

[0049] In FIG. 10, the solid line indicates the relative rotation speed f ０＿１ The dashed line shows the spectrum data when the relative rotation speed is f ０＿２ The dashed double-dashed line shows the spectrum data when the relative rotation speed is f ０＿３The spectrum data for each relative rotation number is shown below. ０＿１ <f ０＿２ <f ０＿３ The relative rotation speed is f ０＿１ The frequency corresponding to the peak when the relative rotation speed is f ０＿２ The frequency corresponding to the peak when the relative rotation speed is f ０＿３ When the peak is detected, the frequency corresponding to the peak is F1<F2. The frequency F1 is calculated by the above equations (1)-(3) using the relative rotation speed f ０＿１ The interval Tr obtained from ０ The frequency F2 is calculated by using the above equations (1)-(3) and the relative rotation speed f ０＿２ The interval Tr obtained from ０ It corresponds to the reciprocal of

[0050] As described above, when the relative rotation speed is low, the cage 14 falls, but when the relative rotation speed is high, the cage 14 does not fall. Therefore, when the relative rotation speed is low, the magnitude of the rotation-synchronous vibration is equal to or greater than the threshold value, and when the relative rotation speed is high, the magnitude of the rotation-synchronous vibration is less than the threshold value. Specifically, when the relative rotation speed is low and the cage 14 falls, a peak is present in the spectrum data, but when the relative rotation speed is high and the cage 14 does not fall, no peak is present in the spectrum data. The target rotation speed range, which indicates the range of relative rotation speed values ​​when the cage 14 falls, will be described below.

[0051] Centrifugal force and gravity act on the column portions 14b of the cage 14. When the centrifugal force acting on the cage 14 is equal to or greater than gravity, the cage 14 will whirl, and when the centrifugal force acting on the cage 14 is smaller than gravity, the cage 14 will fall. If the mass of the cage 14 is m (unit: kg), the movable radius of the cage 14 is h (unit: mm), the angular velocity of the cage 14 is ω (unit: rad / s), and the gravitational acceleration is g, the cage 14 will fall when the following formula (4) is true:

[0052]

[0053] If the wear depth of the bar portions 14b is Wa (unit: mm), the movable radius h of the cage 14 is expressed as a function of the wear depth Wa of the bar portions 14b, as shown in the following equation (5). As an example, there is a positive linear relationship between the movable radius h of the cage 14 and the wear depth Wa of the bar portions 14b. Specifically, when the bar portions 14b wear, in other words, when the wear depth Wa of the bar portions 14b increases, the movable radius h of the cage 14 increases. The angular velocity ω of the cage 14 is expressed as a function of the rotation period T of the cage 14. ０ Using the above formula (1) which expresses this, the following formula (6) is obtained. By substituting the following formulas (5) and (6) into the above formula (4), the condition for the relative rotation speed to be included in the target rotation speed range is obtained by the following formula (7). The range of relative rotation speed values ​​when the cage 14 falls is a range less than the upper limit value expressed on the right side of the below formula (7) and a range equal to or greater than 0.

[0054]

[0055]

[0056]

[0057] The upper limit of the target rotation speed range represented by the right-hand side of equation (7) is shown by a solid line graph in FIG. 11 . In other words, the graph shown by the solid line in FIG. 11 shows the relationship between the upper limit of the target rotation speed range and the wear depth of the column portion 14b. The horizontal axis of FIG. 11 represents the wear depth of the column portion 14b (unit: mm), and the vertical axis represents the upper limit of the target rotation speed range represented by the right-hand side of equation (7) (unit: rps). As described above, as the wear depth of the column portion 14b increases, the movable radius h increases, and therefore the value of the right-hand side of equation (7) decreases. Therefore, as shown in FIG. 11 , as the wear depth of the column portion 14b increases, the upper limit of the target rotation speed range decreases.

[0058] As described above, if the relative rotation speed is less than the upper limit of the target rotation speed range, which changes depending on the wear depth of the column portion 14b, the peak detection unit 23 detects a peak, and if the relative rotation speed is equal to or greater than the upper limit, the peak detection unit 23 does not detect a peak. The diagnosis unit 24 determines that wear is occurring in the bearing 10 if the frequency corresponding to the peak increases as the relative rotation speed increases in the low-speed region of the relative rotation speed, and if the peak detection unit 23 does not detect a peak in the high-speed region of the relative rotation speed. The low-speed region is a range of relative rotation speeds lower than the value indicated by the solid line in FIG. 11, and the high-speed region is a range of relative rotation speeds equal to or greater than the value indicated by the solid line in FIG. 11. The branch point between the low-speed region and the high-speed region changes depending on the wear depth of the column portion 14b, as shown by the solid line in FIG. 11.

[0059] The diagnosing unit 24 associates the relative rotation speed acquired from the relative rotation speed acquisition unit 21 and the frequency acquired from the peak detection unit 23 at the same timing and stores them in a memory (not shown). The diagnosing unit 24 diagnoses the state of the bearing 10 from changes in the peak according to changes in the relative rotation speed. In detail, the diagnosing unit 24 determines that wear has occurred in the bearing 10 if the frequency corresponding to the peak increases as the relative rotation speed increases in the region where the rotation speed of the inner ring 11 is low, and if no peak is detected in the region where the rotation speed of the inner ring 11 is high.

[0060] As an example, the diagnoser 24 repeatedly associates the relative rotation speed acquired from the relative rotation speed acquirer 21 with the frequency corresponding to the peak detected by the peak detector 23 during a target period from when the shaft 90 is stopped until the rotation speed of the shaft 90 reaches the target rotation speed. From the associated relative rotation speed and frequency, the diagnoser 24 determines that wear is occurring in the bearing 10 when the frequency increases as the relative rotation speed increases and when a peak is no longer detected when the relative rotation speed reaches a high-speed range. In other words, if the minimum relative rotation speed when no peak is detected is defined as the reference rotation speed, it can be determined that wear is occurring in the bearing 10 when the frequency corresponding to the peak increases as the relative rotation speed increases in a range where the relative rotation speed is below the reference rotation speed and when a peak is not detected in a range where the relative rotation speed is equal to or greater than the reference rotation speed.

[0061] If the relative rotation speed is in a range equal to or greater than the reference rotation speed and the magnitude of the rotation-synchronous vibration is equal to or greater than a threshold value, specifically if a spectrum is detected, the diagnostic unit 24 determines that the occurring vibration, specifically the detected spectrum, is not caused by the retainer 14 falling, and therefore no wear has occurred in the bearing 10.

[0062] When the pillars 14b are not worn, the vibration caused by the cage 14 falling is sufficiently small, so that the rotation-synchronous vibration is not detected. Specifically, when the pillars 14b are not worn, no peak is detected in the spectrum data, regardless of the relative rotation speed. Therefore, the diagnosis unit 24 determines that the bearing 10 is not worn, because no peak is detected in the low relative rotation speed region.

[0063] As described above, the diagnostic device 1 according to the first embodiment diagnoses the condition of the bearing 10 based on the rotation-synchronous vibration, the frequency of which increases as the relative rotation speed between the inner ring 11 and the outer ring 12 increases. This makes it possible to accurately diagnose the condition of the bearing 10.

[0064] Vibrations caused by scratches, peeling, etc. on the bearing 10 increase as the relative rotation speed increases, and do not occur only in the target frequency range, as is the case with rotation-synchronous vibration caused by the dropping of the cage 14. Therefore, the diagnostic device 1 according to the first embodiment is able to accurately diagnose the condition of the bearing 10 based on the vibration sensor signal output by the vibration sensor 92, without being affected by vibrations caused by scratches, peeling, etc.

[0065] By determining whether or not the column portions 14b of the bearing 10 are worn, it becomes possible to prevent excessive loads from being applied to the rolling elements 13, which would otherwise occur due to the wear depth of the column portions 14b becoming larger, causing the spacing between the rolling elements 13 to become irregular and the inclination of the rolling elements 13 to become greater. This prevents the rolling elements 13 from seizing, or the inner ring 11, outer ring 12, and / or cage 14 from seizing or breaking, which would otherwise occur due to the excessive load being applied to the rolling elements 13, and prevents damage to the bearing 10 and to the shaft 90 or other bearings, joints, etc. connected to the shaft 90.

[0066] (Embodiment 2) The method of diagnosing the condition of the bearing 10 is not limited to the above example. A diagnostic device 1 that diagnoses the condition of the bearing 10 using a method different from that of Embodiment 1 will be described in Embodiment 2. The configuration of the diagnostic device 1 according to Embodiment 2 is similar to that of the diagnostic device 1 according to Embodiment 1.

[0067] As shown in Fig. 12, the diagnosis unit 24 uses a first reference rotation speed Ft1 that is higher than the upper limit of the target rotation speed range and a second reference rotation speed Ft2 that is lower than the first reference rotation speed. Fig. 12 can be interpreted in the same way as Fig. 11. The first reference rotation speed Ft1 is set to a value that is higher than the upper limit of the target rotation speed range expressed by the right side of the above equation (7) when the column portion 14b is not worn.

[0068] The second reference rotation speed Ft2 is set to a value lower than the maximum allowable wear depth, for example, the upper limit of the target rotation speed range expressed by the right side of the above equation (7) when the wear depth is 2.0 mm. As a result, if the wear depth of the column portion 14b is within the allowable range, the second reference rotation speed Ft2 is included in the target rotation speed range.

[0069] When the diagnostic unit 24 detects, based on the spectrum data obtained from the vibration sensor signal, rotation-synchronous vibration whose frequency increases as the relative rotation speed increases, and detects that the magnitude of the rotation-synchronous vibration is less than a threshold value when the relative rotation speed is in a range equal to or greater than a first reference rotation speed, and that the magnitude of the rotation-synchronous vibration is greater than or equal to a threshold value when the relative rotation speed is less than a second reference rotation speed, the diagnostic unit 24 determines that an abnormality has occurred in the bearing 10.

[0070] As an example, if the peak detection unit 23 does not detect a peak when the relative rotation speed acquired by the relative rotation speed acquisition unit 21 is equal to or greater than the first reference rotation speed Ft1, and if the peak detection unit 23 detects a peak when the relative rotation speed acquired by the relative rotation speed acquisition unit 21 is equal to or less than the second reference rotation speed Ft2, the diagnosis unit 24 determines that wear has occurred in the bearing 10.

[0071] As described above, with the diagnostic device 1 according to the second embodiment, diagnosis can be performed based on the spectrum data when the relative rotation speed is equal to or greater than the first reference rotation speed Ft1 and when the relative rotation speed is equal to or less than the second reference rotation speed Ft2, making it possible to more easily diagnose the condition of the bearing 10.

[0072] (Embodiment 3) Diagnosis of the condition of the bearing 10 is not limited to determining the presence or absence of wear, which is an example of an abnormality, and may also include estimation of the wear depth of the post portion 14b. A diagnostic device 1 that estimates the wear depth of the post portion 14b will be described in embodiment 3. The wear depth of the post portion 14b is the amount of reduction in the circumferential length of the post portion 14b. The configuration of the diagnostic device 1 according to embodiment 3 is similar to that of the diagnostic device 1 according to embodiment 1.

[0073] The diagnosing unit 24 increases or decreases the relative rotation speed to obtain a rotation speed evaluation value, which is the boundary rotation speed at which the magnitude of vibration of a specific period, calculated by dividing the rotation period of the cage calculated from the relative rotation speed by the number of rolling elements, is equal to or greater than a threshold value at low rotation speeds and less than the threshold value at high rotation speeds. In other words, when the relative rotation speed is in a range below the rotation speed evaluation value, the magnitude of vibration of the specific period is equal to or greater than the threshold value, and when the relative rotation speed is in a range above the rotation speed evaluation value, the magnitude of vibration of the specific period is less than the threshold. Specifically, when the relative rotation speed is in a range below the rotation speed evaluation value, the peak detecting unit 23 detects a peak, and when the relative rotation speed is in a range above the rotation speed evaluation value, the peak detecting unit 23 does not detect a peak. The diagnosing unit 24 estimates the wear depth of the column portion 14b based on the rotation speed evaluation value. The specific period is calculated by dividing the interval Tr ０ is.

[0074] As an example, the diagnosis unit 24 estimates a rotation speed evaluation value from the relative rotation speed acquired by the relative rotation speed acquisition unit 21 when a peak is detected by the peak detection unit 23 and the relative rotation speed acquired by the relative rotation speed acquisition unit 21 when no peak is detected by the peak detection unit 23, and estimates the wear depth of the column portion 14 b from the estimated upper limit value based on the relationship between the rotation speed evaluation value and the wear depth of the column portion 14 b. The rotation speed evaluation value corresponds to the upper limit value of a target rotation speed range that indicates the range of relative rotation speed values ​​when the cage 14 will fall.

[0075] Fig. 13 is a plot of an example of the relative rotation speed acquired by the relative rotation speed acquisition unit 21 in Fig. 11. The black circles in Fig. 13 indicate the relative rotation speed acquired by the relative rotation speed acquisition unit 21 when a peak is detected by the peak detection unit 23. The crosses in Fig. 13 indicate the relative rotation speed acquired by the relative rotation speed acquisition unit 21 when no peak is detected by the peak detection unit 23.

[0076] The diagnoser 24 acquires the maximum value Fu1 of the target rotation speed when a peak is detected as the rotation speed evaluation value. The diagnoser 24 calculates the wear depth Wa1 corresponding to the estimated upper limit value Fu1 from the relationship between the rotation speed evaluation value and the wear depth of the column portion 14b shown by the solid line in Fig. 13. The diagnoser 24 is assumed to hold information about the relationship between the upper limit of the target rotation speed range shown by the solid line in Fig. 13 and the wear depth of the column portion 14b.

[0077] The method for determining the relationship between the upper limit of the target rotational speed range and the wear depth of the bar portions 14b will be described below. As shown in Fig. 14, the movable radius of the cage 14 and the circumferential length of the bar portions 14b have a negative correlation, specifically a negative linear relationship. The horizontal axis of Fig. 14 indicates the movable radius of the cage 14 (unit: mm), and the vertical axis indicates the circumferential length of the bar portions 14b (unit: mm). Fig. 14 shows the movable radius h when no wear occurs in the bar portions 14b. ｍｉｎ The movable radius h is the upper limit of the allowable movable radius. ｍａｘ The predetermined relationship between the movable radius of the cage 14 and the circumferential length of the bar portions 14b is shown in the following range: As shown in Figure 14, as the circumferential length of the bar portions 14b becomes shorter, the movable radius of the cage 14 becomes larger.

[0078] Movable radius h ｍｉｎ The circumferential length of the column portion 14b corresponding to ｍａｘ Let's say. W ｍａｘ is the circumferential length of the column portion 14b when no wear occurs in the column portion 14b, i.e., the maximum value of the circumferential length of the column portion 14b. ｍａｘ The circumferential length of the column portion 14b corresponding to ｍｉｎ Let's say. W ｍｉｎ is the minimum allowable circumferential length of the column portion 14b. ｍａｘand length W ｍｉｎ are determined by the design of the bearing 10, and the movable radius h ｍｉｎ and the movable radius h ｍａｘ The predetermined relationship between the movable radius of the cage 14 and the circumferential length of the column portions 14b may be determined in advance by a geometric method, a test, a simulation, or the like.

[0079] Based on the relationship between the movable radius of the cage 14 and the circumferential length of the column portion 14b shown by the solid line in FIG. 14, for example, the circumferential length W of the column portion 14b when no friction is generated is calculated. ｍａｘ A linear function for calculating the movable radius h is obtained by using the wear depth Wa, which is obtained by subtracting the circumferential length of the column portion 14b when friction is occurring from Wa, as a variable. By applying this linear function to the above equation (7), the relationship between the upper limit of the target rotation speed range and the wear depth, as shown by the solid line in Figure 13, is obtained. The diagnosis unit 24 may store array data representing the relationship between the upper limit of the target rotation speed range and the wear depth of the column portion 14b, as a table.

[0080] Based on the relationship between the upper limit value of the target rotation speed range obtained as described above and the wear depth, the diagnostic unit 24 obtains the wear depth from the upper limit value Fu1 of the target rotation speed range estimated from the target rotation speed when a peak is detected and when a peak is not detected.

[0081] As described above, the diagnostic device 1 according to the third embodiment is able to determine the rotation speed evaluation value that is the boundary between the region where the magnitude of vibration at the specific period is equal to or greater than the threshold value and the region where the magnitude of vibration at the specific period is less than the threshold value, and is able to determine the wear depth of the column portion 14 b based on the rotation speed evaluation value. As a result, the diagnostic device 1 can accurately diagnose the condition of the bearing 10.

[0082] (Fourth Embodiment) The method of estimating the wear depth of the bar portion 14b is not limited to the above-described example. A diagnostic device that estimates the wear depth of the bar portion 14b using a method different from that used in the third embodiment will be described in the fourth embodiment, focusing on the differences from the third embodiment. In addition to the configuration of the diagnostic device 1, the diagnostic device 2 shown in Fig. 15 includes a cage rotation speed acquisition unit 25 that acquires the rotation speed of the cage 14.

[0083] The cage rotation speed acquisition unit 25 applies the relative rotation speed acquired from the relative rotation speed acquisition unit 21 to the above formula (2) to obtain the rotation speed f of the cage 14. ０ The cage rotation speed acquisition unit 25 is assumed to have previously stored therein information on the diameter d of the rolling element 13, the diameter D of the trajectory of the rolling element 13 around the central axis AX1, and the contact angle α of the rolling element 13. The cage rotation speed acquisition unit 25 calculates the calculated rotation speed f of the cage 14. ０ is output to the peak detection unit 23.

[0084] The peak detection unit 23 determines the magnitude of vibration of a specific period by dividing the rotation period of the cage 14 by the number of rolling elements 13. Specifically, the peak detection unit 23 detects peaks in the spectrum data in a frequency band including a reference frequency corresponding to the period of the fall of the cage 14. As an example, the peak detection unit 23 calculates the magnitude of vibration of a specific period by dividing the rotation period of the cage 14 by the number of rolling elements 13. ０ The reciprocal of the interval Tr is used as the reference frequency. ０ The reciprocal of is Z / T ０ = f ０ ・Z. In other words, the reference frequency f ０ Z is determined according to the rotation speed of the cage 14.

[0085] The peak detection unit 23 detects the rotational speed f of the cage 14 acquired from the cage rotational speed acquisition unit 25. ０ The peak of the spectrum data is detected in a frequency band including a reference frequency obtained by multiplying the rotational speed f by the number Z of the rolling elements 13. The peak detecting unit 23 is assumed to have information about the number Z of the rolling elements 13 stored in advance. As an example, the peak detecting unit 23 detects a peak of the spectrum data in a frequency band including a reference frequency obtained by multiplying the rotational speed f by the number Z of the rolling elements 13. ０ and the number Z, which is the reference frequency f ０ Detect peaks in the spectral data in a frequency band centered at Z. The bandwidth of the frequency band is, for example, less than 20 Hz.

[0086] The diagnosing unit 24 estimates the wear depth of the cage 14 from the magnitude of the vibration of the specific period. Specifically, the diagnosing unit 24 estimates the wear depth of the post portions 14b based on peaks of spectrum data detected in a frequency band including a reference frequency corresponding to the period of the fall of the cage 14. As an example, the diagnosing unit 24 estimates the wear depth of the post portions 14b from the magnitude of the peaks. At this time, when the peak detection unit 23 detects a peak, it detects the magnitude of the peak and outputs the magnitude of the peak to the diagnosing unit 24.

[0087] As shown in Fig. 16, the diagnosis unit 24 holds information indicating a predetermined relationship between the magnitude of the peak and the movable radius of the cage 14. The horizontal axis of Fig. 16 represents the magnitude of the peak as the amplitude of acceleration (unit: m / s ２ ), and the vertical axis indicates the movable radius (unit: mm) of the cage 14. As an example, the diagnostic unit 24 calculates the movable radius h ｍｉｎ The movable radius h is the upper limit of the allowable movable radius. ｍａｘ The data stores information indicating a predetermined relationship between the peak magnitude and the movable radius of the cage 14 within the following range. As the movable radius of the cage 14 increases, the impact caused by dropping the cage 14 increases, and the peak of the spectrum data therefore increases. As an example, there is a positive linear relationship between the peak magnitude and the movable radius of the cage 14.

[0088] The relationship between the magnitude of the peak and the movable radius of the cage 14 may be determined in advance by a geometrical method, a test, a simulation, or the like. ｍｉｎ and the movable radius h ｍａｘ is determined by the design of the bearing 10.

[0089] The diagnosis unit 24 obtains the movable radius of the cage 14 from the magnitude of the peak using the relationship shown in Fig. 16. As an example, when the magnitude of the peak acquired from the peak detection unit 23 is S1, the diagnosis unit 24 calculates the movable radius of the cage 14 as h2.

[0090] The diagnosing unit 24 also holds information indicating a predetermined relationship between the movable radius of the cage 14 and the circumferential length of the bar portions 14b shown in Fig. 14. The diagnosing unit 24 uses the relationship shown in Fig. 14 to determine the circumferential length of the bar portions 14b from the movable radius of the cage 14 determined using the relationship shown in Fig. 16. As an example, when the movable radius of the cage 14 determined using the relationship shown in Fig. 16 is h2, the diagnosing unit 24 calculates the circumferential length of the bar portions 14b as W2.

[0091] The diagnostic section 24 has a circumferential length W of the column section 14b. ｍａｘ , W2 difference ΔW=W ｍａｘ The wear depth of the column portion 14b is calculated as -W2. The diagnosis unit 24 outputs the calculated wear depth of the column portion 14b.

[0092] As explained above, the diagnostic device 2 according to the fourth embodiment can determine the wear depth of the column portions 14b from the magnitude of vibration at a specific period, which is determined by dividing the rotation period of the cage 14 by the number of rolling elements 13. As a result, the diagnostic device 2 can accurately diagnose the condition of the bearing 10.

[0093] (Embodiment 5) Diagnosis of the condition of the bearing 10 is not limited to the above-mentioned examples. As an example of diagnosing the condition of the bearing 10, a diagnosis device 1 that estimates the life of the bearing 10 will be described in embodiment 5. The configuration of the diagnosis device 1 according to embodiment 4 is the same as that of embodiment 1.

[0094] The diagnosing unit 24 determines the movable radius of the retainer 14 from the magnitude of the vibration of the specific period determined from the relative rotation speed and the vibration sensor signal, using a predetermined relationship between the magnitude of the vibration of the specific period and the movable radius of the retainer 14. The diagnosing unit 24 determines the circumferential length of the post portions 14b from the determined movable radius of the retainer 14, using a predetermined relationship between the movable radius of the retainer 14 and the circumferential length of the post portions 14b. More specifically, as shown in Embodiments 3 and 4, the diagnosing unit 24 determines the movable radius of the retainer 14, the circumferential length of the post portions 14b, and the wear depth of the post portions 14b. The diagnosing unit 24 estimates the life of the bearing 10 from changes over time in at least one of the movable radius of the retainer 14, the circumferential length of the post portions 14b, and the wear depth of the post portions 14b.

[0095] As an example, the diagnosing unit 24 estimates the life of the bearing 10 from changes over time in the movable radius of the cage 14. The diagnosing unit 24 maintains a timer and stores in memory the usage time of the bearing 10, specifically, the time since the bearing 10 was installed in, for example, a railway vehicle and started operation. In FIG. 17 , the movable radius of the cage 14 calculated at different times is indicated by black circles. The diagnosing unit 24 estimates the relationship between the usage time of the bearing 10 and the movable radius of the cage 14, shown by the solid line in FIG. 17 , from the change over time in the movable radius of the cage 14 based on, for example, the least squares method. In the example of FIG. 17 , the diagnosing unit 24 estimates the relationship between the usage time of the bearing 10 and the movable radius of the cage 14 from the movable radius of the cage 14 calculated over the usage time T1 from the start of use of the bearing 10 to the present time.

[0096] The diagnosis unit 24 determines the movable radius h , which is the upper limit of the allowable movable radius of the cage 14, from the relationship between the movable radius of the cage 14 estimated as described above and the usage time of the bearing 10. ｍａｘ The usage time T ｍａｘ The diagnosis unit 24 calculates the usage time T1 and the usage time T ｍａｘ Difference T ｍａｘ −T1 is determined as the life of the bearing 10. The diagnosis unit 24 outputs the determined life of the bearing 10.

[0097] Similarly, the diagnosing unit 24 may estimate the life of the bearing 10 from the change over time in the circumferential length of the post portion 14b. Note that as the usage time of the bearing 10 increases, the circumferential length of the post portion 14b decreases. From the relationship between the circumferential length of the post portion 14b and the usage time of the bearing 10, the diagnosing unit 24 determines whether the circumferential length of the post portion 14b is equal to or shorter than the length W ｍｉｎ The usage time T ｍａｘ All we need to do is find the answer.

[0098] The diagnostic unit 24 may also estimate the life of the bearing 10 from the change over time in the wear depth of the post portion 14b. Note that the wear depth of the post portion 14b increases as the usage time of the bearing 10 increases. From the relationship between the wear depth of the post portion 14b and the usage time of the bearing 10, the diagnostic unit 24 determines whether the wear depth of the post portion 14b reaches a wear depth Waｍａｘ =W ｍａｘ -W ｍｉｎ The usage time T ｍａｘ The wear depth Wa ｍａｘ is determined according to the design of the bearing 10.

[0099] As described above, the diagnostic device 1 according to the fifth embodiment can estimate the life of the bearing 10 from changes over time in at least one of the movable radius of the cage 14, the circumferential length of the column portions 14b, and the wear depth of the column portions 14b. This makes it possible to perform maintenance work on the bearing 10 before wear occurs.

[0100] The present disclosure is not limited to the above-described exemplary embodiments. As an example, any combination of the above-described exemplary embodiments is possible. The diagnostic device 3 shown in FIG. 18 has the functions of the diagnostic device 1 according to the first or second exemplary embodiment, the diagnostic device 1 according to the third exemplary embodiment, and the diagnostic device 1 according to the fifth exemplary embodiment. Specifically, the diagnostic unit 24 included in the diagnostic device 3 includes a wear determination unit 26 that determines whether or not the column portion 14 b is worn, as shown in the first or second exemplary embodiment, a wear amount estimation unit 27 that estimates the wear depth of the column portion 14 b, as shown in the third exemplary embodiment, and a life estimation unit 28 that estimates the life of the bearing 10, as shown in the fifth exemplary embodiment.

[0101] As another example, the diagnostic unit 24 included in the diagnostic device 3 may include only the wear determination unit 26 and the wear amount estimation unit 27. As another example, the diagnostic device 3 may include the cage rotation speed acquisition unit 25 like the diagnostic device 2, and the peak detection unit 23 included in the diagnostic device 3 may detect peaks of the spectrum data in a frequency band including a reference frequency corresponding to the period of the fall of the cage 14.

[0102] As another example, the diagnostic device 1 may include the cage rotation speed acquisition unit 25 like the diagnostic device 2, and the peak detection unit 23 included in the diagnostic device 1 may detect peaks of the spectrum data in a frequency band including a reference frequency corresponding to the period of the drop of the cage 14. In this case, the range in which the peak detection unit 23 detects peaks is narrowed, thereby speeding up the processing of the peak detection unit 23.

[0103] The configuration of the bearing 10 is not limited to the above example. As one example, the bearing 10 may include an outer ring 12 that rotates integrally with the shaft 90, and an inner ring 11 that is held in a housing and does not rotate even when the shaft 90 rotates. As another example, the bearing 10 may include an inner ring 11 and an outer ring 12 that rotate independently of each other, with one rotating integrally with the shaft 90. The number, arrangement, and shape of the rolling elements 13 may be arbitrary as long as they are capable of rolling between the inner ring 11 and the outer ring 12. The shape of the cage 14 may be arbitrary as long as it can maintain the spacing between adjacent rolling elements 13.

[0104] The diagnosing unit 24 may determine whether the estimated wear depth of the pillar portion 14b is appropriate. As an example, as shown in the fourth embodiment, the diagnosing unit 24 estimates the wear depth of the pillar portion 14b from the magnitude of the peak detected by the peak detecting unit 23. The estimated wear depth of the pillar portion 14b is designated as Wa2. The diagnosing unit 24 determines an upper limit value Fu2 corresponding to the wear depth Wa2 of the pillar portion 14b from the relationship between the upper limit value of the target rotation speed range shown by the solid line in FIG. 13 and the wear depth of the pillar portion 14b.

[0105] The diagnosis unit 24 is assumed to hold information on the upper limit of the target rotation speed range, specifically, the rotation speed evaluation value shown by the solid line in Fig. 13. The diagnosis unit 24 determines that the wear depth Wa2 is an appropriate value if the peak detection unit 23 detects a peak in a range where the relative rotation speed is less than the rotation speed evaluation value, and if the peak detection unit 23 does not detect a peak in a range where the relative rotation speed is equal to or greater than the rotation speed evaluation value.

[0106] The diagnostic unit 24 included in the diagnostic device 1 according to the fifth embodiment may estimate the life of the bearing 10 from the amount of change per unit time in at least one of the movable radius of the cage 14, the circumferential length of the bar portions 14b, and the wear depth of the bar portions 14b. The relationship between the movable radius of the cage 14 and the magnitude of the peak is not limited to a linear relationship. For example, the movable radius of the cage 14 may be expressed by a quadratic function with the magnitude of the peak as a variable. The relationship between the circumferential length of the bar portions 14b and the movable radius of the cage 14 is not limited to a linear relationship. For example, the circumferential length of the bar portions 14b may be expressed by a quadratic function with the movable radius of the cage 14 as a variable. The diagnostic unit 24 may store array data representing the relationship between the movable radius of the cage 14 and the magnitude of the peak, and the relationship between the circumferential length of the bar portions 14b and the movable radius of the cage 14, as a table.

[0107] The rotation sensor 91 is not limited to the above example, and may be any sensor that measures data necessary for the relative rotation speed acquisition unit 21 to calculate the relative rotation speed between the inner ring 11 and the outer ring 12. As an example, the rotation sensor 91 may include a current sensor, a vibration sensor, or the like.

[0108] The vibration sensor 92 may be installed at any position. The diagnostic device 1-3 may acquire sensor signals from a plurality of vibration sensors 92. In this case, the vibration signal acquisition unit 22 may generate spectrum data from the vibration sensor signal output by each vibration sensor 92.

[0109] The above hardware configuration and flowchart are merely examples and can be changed and modified as desired. The hardware configuration of the diagnostic device 1-3 is not limited to the above example. As an example, a modified example of the hardware configuration of the diagnostic device 1-3 is shown in FIG. 19. As shown in FIG. 19, the diagnostic device 1-3 may be realized by a processing circuit 84. The processing circuit 84 is connected to a rotation sensor 91 and a vibration sensor 92 via an interface circuit 85.

[0110] When the processing circuitry 84 is dedicated hardware, the processing circuitry 84 includes, for example, a single circuit, a composite circuit, a processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. Each unit of the diagnostic devices 1-3 may be realized by an individual processing circuit 84, or each unit of the diagnostic devices 1-3 may be realized by a common processing circuit 84.

[0111] Some of the functions of the diagnostic devices 1-3 may be implemented by dedicated hardware, and other functions may be implemented by software or firmware. For example, in the diagnostic device 1, the relative rotation speed acquisition unit 21 may be implemented by a processing circuit 84 shown in Fig. 18, and the vibration signal acquisition unit 22, the peak detection unit 23, and the diagnosis unit 24 may be implemented by a processor 81 shown in Fig. 8 reading and executing programs stored in a memory 82.

[0112] The configuration of the diagnostic device 1-3 is not limited to the above-mentioned example. As an example, when the diagnostic unit 24 included in the diagnostic device 1 according to the third embodiment only estimates the wear depth of the column portion 14b, the diagnostic device 1 does not need to include the relative rotation speed acquisition unit 21. As another example, when the diagnostic unit 24 included in the diagnostic device 1 according to the fourth embodiment only estimates the life of the bearing 10, the diagnostic device 1 does not need to include the relative rotation speed acquisition unit 21.

[0113] The timing at which the diagnostic device 1-3 performs the diagnostic process is not limited to the above example and may be arbitrary. As one example, the diagnostic device 1 may repeat the diagnostic process shown in Fig. 9 at irregular intervals. As another example, the diagnostic device 1 may start the diagnostic process shown in Fig. 9 in response to an operation of an operation unit (not shown).

[0114] The diagnostic device 1-3 may be provided in a device that has the bearing 10 to be diagnosed as part of that device, or may be provided independently of the device. When the diagnostic device 1-3 is provided as part of a device that has the bearing 10 to be diagnosed, the diagnostic device 1-3 may be detachably provided in the device.

[0115] The present disclosure allows various embodiments and modifications without departing from the broad spirit and scope of the present disclosure. Furthermore, the above-described embodiments are intended to illustrate the present disclosure and do not limit the scope of the present disclosure. That is, the scope of the present disclosure is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and the meaning of equivalent disclosures are considered to be within the scope of the present disclosure.

[0116] 1, 2, 3 Diagnostic device, 10 Bearing, 11 Inner ring, 11a, 12a Raceway surface, 12 Outer ring, 13 Rolling element, 14 Cage, 14a Annular portion, 14b Column portion, 21 Relative rotation speed acquisition unit, 22 Vibration signal acquisition unit, 23 Peak detection unit, 24 Diagnostic unit, 25 Cage rotation speed acquisition unit, 26 Wear determination unit, 27 Wear amount estimation unit, 28 Life estimation unit, 80 Bus, 81 Processor, 82 Memory, 83 Interface, 84 Processing circuit, 85 Interface circuit, 90 Shaft, 91 Rotation sensor, 92 Vibration sensor, AX1, AX2, AX3 Central axis, D1, D2, D3 Rotation direction.

Claims

1. A diagnostic device for diagnosing the condition of a rolling bearing that supports a shaft rotatably around a central axis that intersects the vertical direction, the bearing comprising: an inner ring; an outer ring located outside the inner ring in a radial direction relative to the central axis; a plurality of rolling elements that roll between the inner ring and the outer ring while abutting against the inner ring and the outer ring; and a cage that is located between the inner ring and the outer ring and has a plurality of columns that are respectively located between adjacent rolling elements at a distance from each other, the diagnostic device comprising: a relative rotation speed acquisition unit that acquires the relative rotation speed between the inner ring and the outer ring; a vibration signal acquisition unit that acquires a vibration sensor signal output by a vibration sensor that measures the magnitude of vibration of the bearing that occurs when the shaft rotates; and a diagnostic unit that, when detecting from the vibration sensor signal, rotation-synchronous vibration, the frequency of which increases as the relative rotation speed increases, determines that an abnormality has occurred in the bearing if it detects that the magnitude of the rotation-synchronous vibration is equal to or greater than a threshold value when the relative rotation speed is less than a predetermined reference rotation speed, and if it detects that the magnitude of the rotation-synchronous vibration is less than the threshold value when the relative rotation speed is equal to or greater than the reference rotation speed. A diagnostic device comprising:

2. A diagnostic device for diagnosing the condition of a rolling bearing that rotatably supports a shaft around a central axis that intersects the vertical direction, the bearing comprising: an inner ring; an outer ring disposed radially outward of the inner ring relative to the central axis; a plurality of rolling elements that roll between the inner ring and the outer ring while abutting against the inner ring and the outer ring; and a cage disposed between the inner ring and the outer ring and having a plurality of pillar portions each located between adjacent rolling elements at a distance from each other, the diagnostic device comprising: a relative rotation speed acquisition unit that acquires the relative rotation speed between the inner ring and the outer ring; and a vibration signal acquisition unit that acquires a vibration sensor signal output by a vibration sensor that measures the magnitude of vibration of the bearing that occurs when the shaft rotates. and a diagnostic unit that, when detecting from the vibration sensor signal that rotation-synchronous vibration whose frequency increases as the relative rotation speed increases, determines that an abnormality has occurred in the bearing if it detects that the magnitude of the rotation-synchronous vibration is less than a threshold value when the relative rotation speed is in a range equal to or greater than a predetermined first reference rotation speed, and that the magnitude of the rotation-synchronous vibration is equal to or greater than the threshold value when the relative rotation speed is in a range less than a second reference rotation speed that is lower than the first reference rotation speed.

3. A diagnostic device for diagnosing the condition of a rolling bearing that rotatably supports a shaft around a central axis that intersects the vertical direction, the bearing comprising: an inner ring; an outer ring disposed radially outward of the inner ring relative to the central axis; a plurality of rolling elements that roll between the inner ring and the outer ring while abutting against the inner ring and the outer ring; and a cage disposed between the inner ring and the outer ring and having a plurality of pillar portions each located between adjacent rolling elements at a distance from each other, the diagnostic device comprising: a relative rotation speed acquisition unit that acquires the relative rotation speed between the inner ring and the outer ring; and a vibration signal acquisition unit that acquires a vibration sensor signal output by a vibration sensor that measures the magnitude of vibration of the bearing that occurs when the shaft rotates. and a diagnostic unit that, by increasing or decreasing the relative rotation speed, determines a rotation speed evaluation value, which is the boundary rotation speed at which the magnitude of vibration of a specific period, calculated by dividing the rotation period of the cage, calculated from the relative rotation speed, by the number of rolling elements, becomes equal to or greater than a threshold value at low rotation speeds and less than the threshold value at high rotation speeds, and estimates the wear depth of column portions extending in the axial direction of the cage based on the rotation speed evaluation value.

4. A diagnostic device for diagnosing the condition of a rolling bearing that rotatably supports a shaft around a central axis that intersects the vertical direction, the bearing comprising: an inner ring; an outer ring disposed radially outward of the inner ring relative to the central axis; a plurality of rolling elements that roll between the inner ring and the outer ring while abutting against the inner ring and the outer ring; and a cage disposed between the inner ring and the outer ring and having a plurality of pillar portions each located between adjacent rolling elements at a distance from each other, the diagnostic device comprising: a relative rotation speed acquisition unit that acquires the relative rotation speed between the inner ring and the outer ring; and a vibration signal acquisition unit that acquires a vibration sensor signal output by a vibration sensor that measures the magnitude of vibration of the bearing that occurs when the shaft rotates. and a diagnostic unit that, when detecting rotation-synchronous vibration whose frequency increases as the relative rotation speed increases from the vibration sensor signal, estimates the wear depth of a column portion extending in the axial direction of the cage from the magnitude of vibration of a specific period obtained from the relative rotation speed and the vibration sensor signal by dividing the rotation period of the cage, which is calculated from the relative rotation speed, by the number of rolling elements.

5. A diagnostic device according to claim 1 or 2, wherein the diagnostic unit detects the rotation-synchronous vibration in a frequency band that includes a reference frequency corresponding to the period of the cage falling, which is calculated by dividing the rotation period of the cage, calculated from the relative rotation speed, by the number of rolling elements.

6. The diagnostic device according to claim 4, wherein the diagnostic unit estimates the wear depth of the column portion from the magnitude of the vibration of the specific period determined from the relative rotation speed and the vibration sensor signal, based on a predetermined relationship between the magnitude of the vibration of the specific period and the movable radius of the cage and a predetermined relationship between the movable radius of the cage and the circumferential length of the column portion.

7. The diagnostic device according to claim 6, wherein the diagnostic unit determines the movable radius of the retainer from the magnitude of the vibration of the specific period determined from the relative rotation speed and the vibration sensor signal, using a predetermined relationship between the magnitude of the vibration of the specific period and the movable radius of the retainer, determines the circumferential length of the bar portion from the determined movable radius of the retainer, using a predetermined relationship between the movable radius of the retainer and the circumferential length of the bar portion, and estimates the life of the bearing from changes over time in at least one of the movable radius of the retainer, the circumferential length of the bar portion, and the wear depth of the bar portion.

8. The diagnostic device according to claim 6 or 7, wherein the diagnostic unit estimates the wear depth of the column portion from the relative rotation speed and the magnitude of the vibration of the specific period determined from the vibration sensor signal, determines the upper limit value from the estimated wear depth based on a predetermined relationship between the wear depth of the column portion and the upper limit value of a target rotation speed range that indicates the range of relative rotation speed values ​​when the cage will fall, and determines that the wear depth is an appropriate value if it detects that the magnitude of the rotation-synchronous vibration is equal to or greater than a threshold value when the relative rotation speed is in a range below the upper limit value, or that the magnitude of the rotation-synchronous vibration is less than the threshold value when the relative rotation speed is equal to or greater than the upper limit value.

9. A diagnostic method performed by a diagnostic device that diagnoses the condition of a rolling bearing that rotatably supports a shaft around a central axis that intersects the vertical direction, the bearing comprising: an inner ring; an outer ring located outside the inner ring in a radial direction relative to the central axis; a plurality of rolling elements that roll between the inner ring and the outer ring while abutting against the inner ring and the outer ring; and a cage that is located between the inner ring and the outer ring and has a plurality of columns located between adjacent rolling elements at a distance from each other, the diagnostic method comprising: obtaining the relative rotation speed of the inner ring and the outer ring; obtaining a vibration sensor signal output by a vibration sensor that measures the magnitude of vibration of the bearing that occurs when the shaft rotates; and, when detecting from the vibration sensor signal that rotation-synchronous vibration whose frequency increases as the relative rotation speed increases, determining that an abnormality has occurred in the bearing if it is detected that the magnitude of the rotation-synchronous vibration is equal to or greater than a threshold value when the relative rotation speed is less than a predetermined reference rotation speed, and if it is detected that the magnitude of the rotation-synchronous vibration is less than the threshold value when the relative rotation speed is equal to or greater than the reference rotation speed.

10. A diagnostic method performed by a diagnostic device that diagnoses the condition of a rolling bearing that rotatably supports a shaft around a central axis that intersects the vertical direction, the bearing comprising: an inner ring; an outer ring located outside the inner ring in a radial direction relative to the central axis; a plurality of rolling elements that roll between the inner ring and the outer ring while abutting against the inner ring and the outer ring; and a cage that is located between the inner ring and the outer ring and has a plurality of columns located between adjacent rolling elements at intervals from each other, the diagnostic method comprising: obtaining the relative rotation speed between the inner ring and the outer ring; obtaining a vibration sensor signal output by a vibration sensor that measures the magnitude of vibration of the bearing that occurs when the shaft rotates; and, when rotation-synchronous vibration whose frequency increases as the relative rotation speed increases, estimating the wear depth of the columns extending in the axial direction of the cage from the magnitude of vibration of a specific period calculated by dividing the rotation period of the cage, calculated from the relative rotation speed, by the number of rolling elements, from the relative rotation speed and the vibration sensor signal.

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