Bearing damage detection system and bearing damage detection method

Abstract

To provide a bearing damage detection system and a bearing damage detection method capable of detecting damage to each part of a rolling bearing, such as a raceway surface at an early stage.SOLUTION: A bearing damage detection system includes: a rotation sensor which detects rotation of a rolling bearing and outputs a rotation signal; a rotational fluctuation extraction part 24A which extracts rotational fluctuation of the rolling bearing from the rotation signal to generate a rotational fluctuation signal; a frequency analysis part 24B which performs frequency analysis on a waveform of the rotational fluctuation signal to obtain a frequency characteristic; a peak intensity calculation part 24C which determines peak intensity corresponding to bearing damage from the frequency characteristic; and a damage detection part 24D which detects bearing damage of the rolling bearing according to the peak intensity. The rotational fluctuation extraction part 24A obtains the waveform of the rotational fluctuation signal after removing various noise.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a bearing damage detection system and a bearing damage detection method.

Background Art

[0002] A wheel constituting a wheel of an automobile and a disk rotor constituting a disk brake or a drum brake as a braking device are rotatably supported by a suspension device of a vehicle body via a vehicle wheel bearing unit (hereinafter referred to as a hub unit). The outer ring and the hub ring of this hub unit bearing are manufactured by hot forging medium carbon steel having a carbon content of 0.5 to 0.6% by mass and then heat-treating the raceway surface. However, although the inner ring raceway surface portion of the hub ring is relatively thick, the outer ring raceway surface portion is thin, so damage to the raceway surface such as flaking often occurs on the outer ring raceway surface. In addition, when a strong external force acts on the hub unit, the rolling element may form an indentation on the outer ring raceway surface.

[0003] In addition, since the above-mentioned medium carbon steel has higher toughness than bearing steel (C: 1% by mass), cracks at the dynamic maximum shear stress position are difficult to extend toward the raceway surface and progress parallel to the raceway surface. In the case of such cracks, the surface does not peel off initially, and only the portion from the crack to the raceway surface is engaged by the rolling element and indented, so there is little deterioration in vibration and sound. However, when the crack appears on the raceway surface as the crack progresses, the peeling progresses rapidly. Similarly, the indentation also affects vibration and sound. Such a failure mode in which peeling progresses rapidly from a certain point is not preferable, for example, in the case of a vehicle such as a large truck where the distance from the driver to the wheel bearing is long and it is difficult for the driver to detect small damage. Also, considering future driverless vehicles and platoon driving, it is desirable to detect damage such as the above-mentioned peeling and indentation at a stage where the damage to the hub unit bearing is small.

[0004] For example, as shown in Fig. 43, the hub unit bearing 300 of Patent Document 1 includes an outer ring 301 having a double row of outer ring raceways 301a, a hub 302 having a double row of inner ring raceways 302a, and a plurality of rolling elements 303 rotatably provided between the outer ring raceway 301a and the inner ring raceway 302a. Encoders 304 are provided on both axial sides of the hub 302 of the hub unit bearing 300, and based on the phase difference between the detection signals of sensors (not shown) facing the respective encoders 304, the torque applied to the hub 302 can be detected.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Damage to the outer ring and hub of the hub unit bearing as described above, particularly damage to the outer ring raceway surface, is a cause of deterioration of vibration and noise, and it is desirable to detect it at an early stage. However, in the hub unit of Patent Document 1, although torque can be detected, damage that occurs cannot be detected. Further, detection of such damage is not limited to the hub unit bearing of a vehicle, and the same applies to other bearing mechanisms using rolling bearings, and early detection is desired.

[0007] Therefore, an object of the present invention is to provide a bearing damage detection system and a bearing damage detection method capable of early detecting damage to each part such as the raceway surface of a rolling bearing.

Means for Solving the Problems

[0008] The present invention has the following configuration. (1) A rotation sensor that detects the rotation of a rolling bearing and outputs a rotation signal, A rotation variation extraction unit that extracts the rotation variation of the rolling bearing from the rotation signal and generates a rotation variation signal, A frequency analysis unit that performs frequency analysis on the waveform of the rotational fluctuation signal to obtain frequency characteristics; A peak intensity calculation unit that obtains the peak intensity corresponding to bearing damage from the frequency characteristics; A damage detection unit that detects bearing damage of the rolling bearing based on the peak intensity; A bearing damage detection system comprising the above. (2) Detect the rotation of the rolling bearing to generate a rotation signal, Extract the rotational fluctuation of the rotation from the rotation signal to generate a rotational fluctuation signal, Perform frequency analysis on the waveform of the rotational fluctuation signal to obtain vibration peaks, Obtain the peak intensity corresponding to bearing damage from the vibration peaks, Detect bearing damage of the rolling bearing based on the peak intensity, A bearing damage detection method comprising the above.

Advantages of the Invention

[0009] According to the present invention, damage to each part such as the raceway surface of the rolling bearing can be detected early.

Brief Description of the Drawings

[0010]

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BEST MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, a hub unit bearing is taken as an example of the bearing, but the application target of the present invention is not limited thereto. <First Embodiment> (Configuration of Damage Detection System) FIG. 1 is a schematic configuration diagram of a bearing damage detection system 100 for a hub unit bearing according to the first embodiment. In this specification, the “axially inner side” with respect to the hub unit bearing means the vehicle body side of the hub unit bearing when attached to the vehicle body, and means the right side indicated by the arrow Ax_in in FIG. 1. Further, the “axially outer side” means the wheel side of the hub unit bearing when attached to the vehicle body, and means the left side indicated by the arrow Ax_out in FIG. 1. Therefore, the bearing portion, outer ring raceway, and inner ring raceway arranged on the inner side are also referred to as the bearing portion of the inner row, the outer ring raceway of the inner row, and the inner ring raceway of the inner row, and the bearing portion, outer ring raceway, and inner ring raceway arranged on the outer side are also referred to as the bearing portion of the outer row, the outer ring raceway of the outer row, and the inner ring raceway of the outer row.

[0012] The hub unit bearing 11 shown in FIG. 1 is a hub unit bearing for a driven wheel, and includes an outer ring 13 as a fixed-side member, a hub 15 as a rotating-side member, a plurality of rolling elements 17, and a rotation detection device 19. In FIG. 1, the hub 15 of the hub unit bearing 11 and a sensor 21 described later are shown in a horizontal cross section. The bearing damage detection system 100 for the hub unit bearing 11 includes the hub unit bearing 11, a pulse signal generation unit 23 that converts a detection signal from a sensor 21 (described later) of the rotation detection device 19 of the hub unit bearing 11 into a pulse signal and outputs it, and a control unit 24. Here, a hub unit bearing for a driven wheel is shown, but it is similarly possible to detect bearing damage for a hub unit bearing for a driving wheel.

[0013] The outer ring 13 has a stationary-side flange 25 on its outer peripheral surface, and has an outer ring raceway 27 of the outer row and an outer ring raceway 29 of the inner row on its inner peripheral surface, respectively. During use, the outer ring 13 is fixed by connecting the stationary-side flange 25 to a knuckle of a suspension device (not shown), and rotation is blocked while being supported by this suspension device.

[0014] The hub 15 is composed of a hub shaft 31 and an inner ring 33 that fits onto the hub shaft 31 and is fixed by caulking, and is arranged coaxially (concentrically) with the outer ring 13 on the radially inner side of the outer ring 13.

[0015] On the hub shaft 31, at a portion protruding axially outward from the axially outer opening of the outer ring 13, an annular mounting flange 35 is provided that extends radially outward to fix braking rotating members such as a wheel (driven wheel) and a disk rotor (none of which are shown).

[0016] The mounting flange 35 is provided with a plurality of insertion holes 35a, and hub bolts 37 are serration-fitted into the respective insertion holes 35a. Note that by using the plurality of insertion holes 35a as female screw holes and screwing in the hub bolts, the mounting flange 35 can also be fixed to braking rotating members such as a wheel and a disk rotor.

[0017] On the outer peripheral surface of the hub shaft 31, at a portion facing the outer ring raceway 27 of the outer row, an inner ring raceway 39 of the outer row is provided. Also, at the axially inner end portion of the outer peripheral surface of the hub shaft 31 that faces the outer ring raceway 29 of the inner row, a small-diameter stepped portion 41 is provided. The hub shaft 31 partially constitutes the outer peripheral surface of the small-diameter stepped portion 41 and has a caulking portion 43 in which the axially inner end portion is deformed radially outward to fix the inner ring 33 by caulking.

[0018] On the outer peripheral surface of the inner ring 33, at a portion facing the outer ring raceway 29 of the inner row, an inner ring raceway 45 of the inner row is provided. The inner ring 33 is externally fitted onto the small-diameter stepped portion 41 of the hub shaft 31 with its axially outer end face abutting against the stepped surface of the small-diameter stepped portion 41, and is caulked and fixed to the hub shaft 31 by the caulking portion 43 in which the axially inner end portion of the small-diameter stepped portion 41 is deformed radially outward.

[0019] The rolling elements 17 are provided between the outer ring raceway 27 of the outer row and the inner ring raceway 39 of the outer row, and between the outer ring raceway 29 of the inner row and the inner ring raceway 45 of the inner row, so as to be freely rotatable while being held by the respective cages 47.

[0020] Note that the outer ring raceway 27 of the outer row, the inner ring raceway 39 of the outer row, and the rolling elements 17 form the bearing portion 49A of the outer row, and the outer ring raceway 29 of the inner row, the inner ring raceway 45 of the inner row, and the rolling elements 17 form the bearing portion 49B of the inner row.

[0021] A seal ring 51 is fixed to the axially outer end of the inner peripheral surface of the outer ring 13. The seal ring 51 closes the axially outer end opening of the internal space 53 in which a plurality of rolling elements 17 are provided, which exists between the inner peripheral surface of the outer ring 13 and the outer peripheral surface of the hub shaft 31. The seal ring 51 is in sliding contact with the large-diameter stepped portion on the axially outer side of the inner ring raceway 39 of the outer row, of the outer peripheral surface of the hub shaft 31.

[0022] The rotation detection device 19 is an axial type sensor that is disposed in the vicinity of the inner row bearing portion 49B, that is, at the axially inner end of the hub unit bearing 11, and detects the rotational speed of the hub 15. The rotation detection device 19 includes a magnetic encoder 55 and a sensor 21.

[0023] The magnetic encoder 55 is composed of a support ring 55a and an encoder body 55b. The support ring 55a is formed into an L-shaped cross-section and is integrally formed in an annular shape by performing press working on a magnetic metal plate such as a ferrite stainless steel plate such as SUS430 or a rolled steel plate such as SPCC. The axially outer portion of the support ring 55a is externally fitted and fixed to the inner ring 33.

[0024] The encoder body 55b is formed into an annular shape as a whole by a permanent magnet formed by mixing a magnetic material such as ferrite powder into rubber or a thermoplastic resin, and is attached and fixed to the inner side surface of the annular portion of the support ring 55a that is bent radially inward. The inner side surface of the encoder body 55b is magnetized with S poles and N poles alternately and at equal pitches in the circumferential direction.

[0025] The sensor 21 is a magnetic sensor that detects the rotation of the hub 15, particularly the rotation of the inner portion of the hub 15. The sensor 21 is disposed with the detection surface 21a facing the magnetic encoder 55, and is fixed to the side cover 59 that closes the inner opening of the outer ring 13. The sensor 21 detects the rotation of the hub 15 by detecting a change in magnetism in the detection region DR of the magnetic encoder 55 facing the detection surface 21a as the hub 15 rotates. That is, the sensor 21 and the magnetic encoder 55 function as a rotation sensor, and this rotation sensor and the pulse signal generation unit 23 constitute the rotation detection device 19.

[0026] The rotation sensor is not limited to the above configuration, and may be a combination of a cylindrical encoder and a radial sensor. Further, it is not limited to a magnetic encoder, and other types such as an optical encoder, a proximity sensor, etc., or a gear-shaped encoder, a gear-shaped excitator used in a track, etc. may be used to detect rotation.

[0027] The sensor 21 may be, for example, an active wheel speed sensor provided in the hub unit bearing 11. In that case, a detection element such as a Hall IC element or an MR element whose electrical characteristics change in response to magnetism can be used as the sensor 21. The active wheel speed sensor faces the magnetic encoder, outputs a voltage on the HIGH side when the magnetic flux density is below the threshold value, and outputs a voltage on the LOW side when the pole of the encoder approaches and the magnetic flux density exceeds the threshold value. The active wheel speed sensor generates a pulse wave corresponding to the rotational speed of the tire. Generally, this pulse wave is sent to an in-vehicle controller and used for ABS (Anti-lock Braking System) and traction control. By using this pulse wave for damage detection, there is no need to separately add a rotation sensor.

[0028] The sensor 21 outputs a rotation detection signal to the pulse signal generation unit 23. The pulse signal generation unit 23 generates a pulse signal based on the input detection signal and outputs the generated pulse signal to the control unit 24.

[0029] Figure 2 is a functional block diagram of the control unit 24. The control unit 24 includes a rotation variation extraction unit 24A, a frequency analysis unit 24B, a peak intensity calculation unit 24C, and a damage detection unit 24D. The rotation variation extraction unit 24A extracts the rotation variation of the rolling bearing from the rotation signal output from the rotation sensor and generates a rotation variation signal. The frequency analysis unit 24B performs frequency analysis on the waveform of the rotation variation signal to obtain frequency characteristics. The peak intensity calculation unit 24C obtains the peak intensity corresponding to bearing damage from the frequency characteristics. The damage detection unit 24D detects the bearing damage of the rolling bearing based on the peak intensity.

[0030] The control unit 24 executes a procedure for determining damage to the hub unit bearing 11 based on the pulse signal input from the pulse signal generation unit 23. This control unit 24 is configured as a computer including a processor such as a CPU, and storage devices such as a ROM (Read Only Memory), a RAM (Random Access Memory), an HDD (Hard Disk Drive), and an SSD (Solid State Drive). In this case, the functions of the rotation detection device 19, the pulse signal generation unit 23 shown in FIG. 1, and each unit shown in FIG. 2 can be realized by the processor executing a predetermined program stored in the storage device. Further, the control unit 24 is not limited to a form directly or wirelessly connected to the hub unit bearing 11 and the rotation detection device 19, and may be connected via communication such as a network. In that case, the determination of damage to the hub unit bearing 11 can be performed from a remote location, improving the convenience of management. Also, it becomes easy to comprehensively manage a plurality of hub unit bearings 11.

[0031] In the bearing damage detection system 100 of the hub unit bearing 11 of the present embodiment configured as described above, the control unit 24 highly accurately detects damage occurring in the outer ring raceway or the inner ring raceway based on the pulse signal generated by the rotation detection device 19. In general, this pulse signal includes not only a frequency change depending on the rotation speed of the tire, but also uneven rotation of the tire, and magnetization errors due to the magnetization pitch and magnetization eccentricity of the encoder. Further, when the bearing raceway surface is damaged, errors due to relative displacement between the outer and inner rings generated by the damage and relative displacement due to impact when the rolling element enters and exits the damaged area are also included in the pulse signal. When these various types of information are included in the pulse signal, it becomes difficult to extract only the damage information. However, in this bearing damage detection system 100, by removing the above-mentioned various noises included in the pulse signal, the damage information can be extracted with high accuracy and an accurate evaluation can be performed.

[0032] Next, the process of generating the above-mentioned pulse signal based on the detection signal from the sensor 21 will be described. FIG. 3 is an explanatory diagram schematically showing the arrangement position of the sensor 21. FIG. 3 shows the acting direction of the radial load applied from the inner ring 33 to the outer ring 13 (vertically in the vertical direction Z which is generally the direction of gravity) in the vertical direction. The sensor 21 is preferably arranged in the vertical intermediate region Wa, particularly at the central position, of the annular encoder body 55b. When a radial load is applied from the inner ring 33 to the outer ring 13 and the rolling elements roll between the outer ring raceway and the inner ring raceway, the radial vibration that occurs when damage occurs on the raceway surface is likely to occur significantly in the vertical direction Z in which the radial load acts. Therefore, when rotation is detected within the intermediate region Wa close to the center in the vertical direction Z of the inner ring 33 and the outer ring 13, the vertical displacement can be detected with high sensitivity. In FIG. 3, the part where rotation is detected by the sensor 21 is schematically shown by a rectangular detection region DR, but the actual detection region DR is a minute region.

[0033] For example, when a radial load is applied from the inner ring 33 to the outer ring 13 and the rolling elements roll between the outer ring raceway and the inner ring raceway, the radial vibration caused by damage to the raceway surface becomes significant in the vertical direction Z in which the radial load acts. Therefore, when rotation is detected within the intermediate region Wa close to the center in the vertical direction Z of the inner ring 33 and the outer ring 13, the vertical displacement can be detected with high sensitivity. The above-described intermediate region Wa can be exemplified by the range radially inside the outer ring raceway surface or the inner ring raceway surface.

[0034] However, the detection region DR by the sensor 21 is not limited to being arranged in the above-described intermediate region Wa, and may be set at an arbitrary position such as the upper and lower ends in the vertical direction. Even in that case, rotation can be detected, and the installation freedom of the sensor 21 is not reduced.

[0035] FIG. 4 is a schematic circuit diagram of the pulse signal generation unit 23. The pulse signal generation unit 23 outputs, as a pulse signal, the output signal from the sensor 21 when a drive voltage E adjusted by a resistance value R is applied to the sensor 21, for example. Specifically, when the sensor 21 is of the current output type, the current value output from the sensor 21 is switched by the magnetic flux, and the voltage E based on the relationship between the voltage value E, the current value I, and the resistance value R is output as a pulse signal.

[0036] FIG. 5 is an explanatory diagram schematically showing how vibration occurs when peeling occurs in a part of the outer raceway 27. For example, consider a situation where a radial load Pr directed vertically upward from the inner ring 33 to the outer ring 13 is applied, and there is a defective region Ad where peeling has occurred on the upper side in the vertical direction of the outer raceway 27. In that case, when the rolling element 17 that rolls between the inner ring 33 and the outer ring 13 enters the defective region Ad, the internal clearance between the outer raceway 27 and the inner raceway 45 expands due to the peeling, so the rolling element 17 moving on the peeling surface becomes a floating state. When the floating rolling element 17 moves along the inner ring rotation direction Ro in the defective region Ad and reaches the end of the defective region Ad and enters again between the outer raceway 27 and the inner raceway 45 without peeling, the rolling element 17 collides with the inner ring 33 and the outer ring 13, generating an impact load that pushes the inner ring 33 downward. Note that the load on the inner ring also occurs in the horizontal direction in addition to the downward load, but here the load in the downward direction will be particularly described. By repeating such collisions of the rolling element 17, vibrations in the vertical direction (and horizontal direction) are generated. That is, as the inner ring 33 rotates, the inner ring 33 and the outer ring 13 move relatively up and down in the defective cycle, so damage can be detected by detecting the vertical relative displacement with the sensor 21.

[0037] FIG. 6 is an explanatory diagram showing the change in the relative displacement between the inner ring 33 and the outer ring 13 due to peeling of the outer raceway on the sensor output. In FIG. 6, among the outer bearing portion 49A having the outer raceway 27 and the inner raceway 39 and the inner bearing portion 49B having the outer raceway 29 and the inner raceway 45, the case where peeling has occurred in the outer raceway 27 of the outer bearing portion 49A is shown. Note that this hub unit bearing is shown in the configuration of a hub unit bearing for a driving wheel.

[0038] Here, a case where a radial load Pr (preload) directed upward in the vertical direction is applied from the hub shaft 31, which becomes the inner ring of the bearing portion 49A, to the outer ring 13 will be described as an example. However, damage can be detected by the same procedure even when no preload is applied. When the rolling element 17A is in a floating state within the defective region Ad where peeling has occurred on the outer ring raceway 27, the relative velocity VR0 in the vertical direction between the hub shaft 31 and the outer ring 13 in the detection region DR on one side in the horizontal direction where the sensor (not shown) is disposed, and the relative velocity VL0 in the vertical direction on the other side, which is the opposite side in the horizontal direction, are equal.

[0039] Next, when the rolling element 17A reaches the end of the defective region Ad and rides on the non-peeled outer ring raceway 27 and inner ring raceway 39, an impact load Pinp is applied to the hub shaft 31. Then, the relative velocity between the hub shaft 31 and the outer ring 13 in the detection region DR becomes a velocity VR1 smaller than the relative velocity VR0 in the upward floating state, as a downward velocity Vp due to the displacement caused by the impact load Pinp is added to the upward relative velocity VR0 in the floating state. On the other hand, on the other side in the horizontal direction of the detection region DR, a velocity Vp due to the impact load Pinp in the same direction as the relative velocity VL0 is added, resulting in a velocity VL1 larger than the relative velocity VL0 in the floating state.

[0040] Then, as the hub shaft 31 further rotates and the rolling element 17A returns to its original rolling state between the outer ring raceway 27 and the inner ring raceway 39 during the transition, a return load Pbk acts on the hub shaft 31. Then, the relative velocity between the hub shaft 31 and the outer ring 13 in the detection region DR becomes a velocity VR2 larger than the relative velocity VR0 in the upward floating state, as an upward velocity Vq due to the displacement caused by the return load Pbk is added to the upward relative velocity VR0 in the floating state. On the other hand, on the other side in the horizontal direction of the detection region DR, a velocity Vq due to the return load Pbk in the upward direction opposite to the relative velocity VL0 is added, resulting in a velocity VL2 smaller than the relative velocity VL0 in the floating state.

[0041] FIG. 7 is an explanatory diagram schematically showing changes in the sensor output signal from the sensor 21 when transitioning to the floating state, the riding state, and the original rolling state of the rolling elements. The speeds detected in the detection region DR change in the order of VR0, VR1, and VR2. By capturing the change in the sensor output signal due to the speed change from VR0 to VR1 and VR2, the presence of damage can be identified.

[0042] (Procedure for damage determination) FIG. 8 is a flowchart showing the procedure for determining damage to the hub unit bearing 11. Each of the following procedures is carried out based on a command from the control unit 24 shown in FIGS. 1 and 2. First, the rotation of the hub shaft 31 that is rotationally driven by the hub unit bearing 11 is detected by the sensor 21, and a sensor output signal that is a rotation signal output from the sensor 21 is acquired (S11). This sensor output signal is converted into a pulse signal by the pulse signal generation unit 23.

[0043] FIG. 9 is an explanatory diagram showing a pulse signal corresponding to the sensor output signal and a spatial waveform plotting the period of each pulse of this pulse signal. Here, an example of a pulse signal when the rotation of the hub 31 is detected by a magnetic encoder and a magnetic sensor is illustrated. The two pulse signals shown on the upper side of FIG. 9 represent the magnetic changes of the magnetic encoder 55 passing through the detection region DR of the sensor 21 as the hub 31 rotates. One of the pulse signals is an example of two-pole detection where the signal rises when detecting a magnetic field of the N pole or the S pole, and the other shows an example of alternating detection where the signal rises when detecting a magnetic field of the N pole or the S pole and then falls when subsequently detecting a magnetic field of the S pole or the N pole.

[0044] In the case of two-pole detection, when the poles of the magnetic encoder 55 reach the detection region DR, the sensor output signal changes from LOW voltage to HIGH voltage. Therefore, the timing of the transition from LOW voltage to HIGH voltage is used as the rising timing described above. On the other hand, in the case of alternating detection, when the poles of the magnetic encoder 55 reach the detection region DR, the sensor output signal changes from HIGH voltage to LOW voltage. Therefore, the timing of the transition from HIGH voltage to LOW voltage is used as the rising timing described above.

[0045] For example, in the case of two-pole detection, a set of HIGH voltages by the same type of poles is regarded as one pulse, and in the case of alternating detection, a set of one HIGH voltage and the subsequent LOW voltage is regarded as one pulse. When uneven rotation occurs in the hub 31, the pulse periods (for example, T1 to T7) of each pulse will fluctuate.

[0046] Generally, in semiconductor design, the rising accuracy of a signal is high, but the falling accuracy of the signal is often low. Therefore, by using only the rising timing of the signal as described above, the error in the falling time can be eliminated from the spatial waveform. Depending on the characteristics of the signal, it is desirable to use the transition with higher accuracy between the transitions from HIGH to LOW and from LOW to HIGH as the rising edge.

[0047] The result of representing the change in the pulse period of each pulse of the above-described pulse signal in time series is the lower spatial waveform in FIG. 9. The spatial waveform shown here is a spatial waveform plotted with the horizontal axis representing the i-th (i = 1 to n (n is an integer)) pulse starting from an arbitrary point (starting point) of the pulses for one rotation of the rotating body 12, and the vertical axis representing the period (time) per pulse.

[0048] This spatial waveform shows the uneven rotation of the hub 31 and the magnetization error (pitch error and eccentricity error) of the magnetic encoder 55 as an increase or decrease over time. By correcting the pulse signal using this spatial waveform, a more accurate rotational speed of the hub 31 with reduced errors can be obtained.

[0049] FIG. 10 is an explanatory diagram showing an example of another definition of a pulse of a pulse signal. The definition of the pulse of the pulse signal described above is an example, and each of the repeatedly generated HIGH voltages may be defined as a pulse (T a1 , T a2 , ···). Also, each of the repeatedly generated LOW voltages may be defined as a pulse (T b1 , T b2 , ···). In that case, the period of one pulse can be shortened, and finer control becomes possible.

[0050] FIG. 11 is an explanatory diagram schematically showing the period of an arbitrary pulse PL i (i is an integer) of a pulse signal and the pulses for one rotation of the hub shaft 31 centered on the pulse PL i . Let the pulse period of a set of a pair of HIGH voltage and LOW voltage of the pulse PL i shown in FIG. 11 be Tp. Also, let the period of one rotation of the hub shaft 31 centered on the pulse PL i be T.

[0051] Based on the above-described spatial waveform, a pulse period waveform WF1 representing the transition of the pulse period Tp of each pulse is generated as damage detection data (S13). Also, for each pulse of the pulse signal, a rotation period waveform WF2 representing the transition of the period T of one rotation centered on the pulse is generated (S14).

[0052] FIG. 12 is an explanatory diagram showing an example of waveforms from when a pulse output signal is extracted to generate a rotational fluctuation signal of the hub shaft 31. Note that the waveform data described below is for explaining the content of signal processing, and is not necessarily information obtained from an actual hub unit bearing of an automobile. The horizontal axis of each waveform is, as an example, a spatial value corresponding to the number of pulses for five rotations of the hub shaft 31. After generating the above-described pulse period waveform WF1 and rotation period waveform WF2, a period ratio waveform WF3 (= WF1 / WF2) representing the ratio Tp / T of the pulse period Tp and the rotation period T is obtained (S15).

[0053] In the above-described pulse period waveform WF1 and rotation period waveform WF2, the vertical axis represented time, but the vertical axis of the period ratio waveform WF3 represents the ratio value per rotation. Therefore, in the period ratio waveform WF3, the influence of the rotational speed error is removed as described above.

[0054] Next, the period ratio waveform WF3 is smoothed to obtain a period ratio smoothed waveform WF4 (S16). For smoothing, it can be calculated, for example, by moving average of the seven points before and after. This period ratio smoothed waveform WF4 has a smoothed waveform, similar to applying a low-pass filter process to the period ratio waveform WF3, and low-frequency fluctuations such as rotational unevenness can be extracted.

[0055] Generally, low-pass filters (LPF) include IIR (Infinite Impulse Response) and FIR (Finite Impulse Response). However, since IIR has a delay element, there is a possibility that a phase delay occurs in the averaged data. Also, although the processing result of FIR is stable, the calculation amount is large, and there is a possibility that a phase delay occurs in the averaged data unless a high-performance arithmetic element (expensive CPU etc.) is used. Therefore, here, data smoothing processing is performed by moving average with a small calculation amount and capable of high-speed processing, but various smoothing processing methods may be appropriately used according to the situation.

[0056] Then, the difference between the period ratio waveform WF3 and the period ratio smoothed waveform WF4 is obtained, and a period ratio difference waveform WF5 (= WF3 - WF4) with fluctuations extracted is obtained (S17). This period ratio difference waveform WF5 becomes a waveform from which low-frequency fluctuations such as rotational unevenness are removed, but displacement accompanying the change in the rolling element position and magnetization error of the encoder still remain. Also, errors due to bearing damage when the bearing raceway surface etc. is damaged also remain. Note that, depending on the conditions, instead of subtracting the period ratio smoothed waveform WF4 from the period ratio waveform WF3, the period ratio waveform WF3 may be used as the period ratio difference waveform WF5 as it is.

[0057] Further, when the computer has sufficient arithmetic processing capabilities, a type of low-pass filter (LPF) that does not cause a phase delay in the period ratio waveform WF3 may be applied to calculate the period ratio smoothed waveform WF4. Also, a type of high-pass filter (HPF) that does not cause a phase delay in the period ratio waveform WF3 may be applied to calculate the period ratio difference waveform WF5.

[0058] Next, an average value is calculated for each rotational position, that is, for each pole of the magnetic encoder 55, from the period ratio difference waveform WF5 (S18). That is, although the period ratio difference waveform WF5 shown in FIG. 12 shows a range of five rotations of the hub shaft 31, in the case of a magnetic encoder 55 having, for example, 48 poles in one rotation, the values of the period ratio difference waveform WF5 are extracted and averaged for each pole, and a period ratio average value distribution WF6 representing the distribution of the average values for each rotational speed of each pole is obtained.

[0059] FIG. 13 is an explanatory diagram showing an example of the period ratio average value distribution WF6 which is the average value of the period ratio differences for each pole of the magnetic encoder. The deviation from the 0 level on the vertical axis in the period ratio average value distribution WF6 represents the magnetization error. In FIG. 13, a line (not shown) connecting the average values for each pole of the period ratio average value distribution becomes the period ratio average value waveform.

[0060] Next, a period ratio fluctuation waveform WF7 representing the difference between the above-described period ratio difference waveform WF5 and the period ratio average value waveform WF6 is obtained (S19). The period ratio fluctuation waveform WF7 is obtained by subtracting the value for each pole indicated by the period ratio average value waveform WF6 from the value for each pole of the period ratio difference waveform WF5 for corresponding poles. Hereinafter, the period ratio difference waveform WF5 is also referred to as the "detection waveform", the period ratio average value waveform WF6 is also referred to as the "reference waveform", and the period ratio fluctuation waveform WF7 is also referred to as the "rotation fluctuation waveform".

[0061] FIG. 14 is an explanatory diagram schematically showing the period ratio fluctuation waveform WF7. In this period ratio fluctuation waveform WF7, the magnetization error of the magnetic encoder 55 is removed. That is, since the period ratio fluctuation waveform WF7 removes the fluctuations due to the rotational speed change, rotational unevenness, and magnetization error, the fluctuations appearing here can be said to be caused by the displacement accompanying the change in the rolling element position and the displacement accompanying the damage of the bearing when the bearing is damaged.

[0062] Note that the period ratio fluctuation waveform WF7 may be a waveform obtained by geometrically converting the vertical axis from the period ratio to speed fluctuation (S20). In this case, the level of fluctuation can be more intuitively grasped as the magnitude of speed. The processes from S12 to S19 and S20 above are performed by the rotation fluctuation extraction unit 24A of the control unit 24 shown in FIG. 2.

[0063] Next, the frequency analysis unit 24B performs frequency analysis on the above-described period ratio fluctuation waveform WF7 to obtain frequency characteristics (S21). For frequency analysis, various analysis methods such as a discrete Fourier transform method like FFT (Fast Fourier Transform) and a maximum entropy method can be used.

[0064] FIG. 15 is an explanatory diagram schematically showing frequency characteristics WF8 obtained by performing FFT processing on the period ratio fluctuation waveform WF7. When the bearing raceway surface is damaged, the period ratio fluctuation waveform WF7 includes speed fluctuations associated with the damage. When damage such as peeling or indentation occurs on the above-described raceway surface or the like, the frequency characteristics WF8 include the spatial frequency of the defect (how many times the defect impacts per rotation) calculated by each variable including the diameter d (mm) of the bearing rolling element, the pitch circle diameter D (mm) of the rolling element, the number Z of rolling elements, and the contact angle α (rad). When a peak corresponding to such a bearing damage-caused peak is equal to or higher than the threshold value, it is determined that the bearing is damaged (S22). Note that the same frequency characteristics WF8 can be obtained even when the vertical axis of the period ratio fluctuation waveform WF7 is converted to speed fluctuation.

[0065] In the frequency characteristic WF8 shown in FIG. 15, the main peaks resulting from bearing damage appear as, for example, the first-order defect peak Pk1 and the second-order defect peak Pk2. The frequencies at which the peaks appear can be generally determined by calculation according to the content of the defects. Although a large number of peaks appear in the low-frequency region (for example, the spatial band BD0), these are due to the system's inherent frequencies and not due to bearing damage. When determining bearing damage based on the peaks Pk1 and Pk2 resulting from bearing damage, for example, since the first-order outer-race defect peak Pk1 is relatively close to the system's inherent frequency, it is likely to be mixed with the peak of the system's inherent frequency. On the other hand, if the second-order defect peak Pk2 is far away and not easily mixed, the second-order defect peak Pk2 may be used for determination. Also, modulation with the system's low-frequency inherent vibration and sidebands (sidebands) resulting from factors other than the other detection targets may occur around the first-order defect peak Pk1 and the second-order defect peak Pk2. Therefore, for determining the peak intensity due to bearing damage, specific-length spatial bands BD1 and BD2 may be set for each of the peaks Pk1 and Pk2, and bearing damage may be determined according to the total value of the peak intensities within each spatial band BD1 and BD2. Since the contact angle of the rolling elements changes slightly due to the above-described preload and load conditions, etc., the theoretical defect frequency and the peak frequency measured may deviate by a few percent. Even in such a case, by setting the spatial bands BD1 and BD2 of the above-described specific length, detection omission can be surely prevented. In addition to the above-described determination examples, extraction and determination of desired peaks and their intensities can be appropriately performed using an appropriate algorithm according to the situation.

[0066] FIG. 16 is an explanatory diagram showing the frequency characteristics of the pulse period waveform WF1 shown as a reference example. The pulse period waveform WF1 includes defect information other than bearing damage, such as rotation unevenness and magnetization error, so when the pulse period waveform WF1 is frequency analyzed, many peaks of the Nth rotation order (N is an integer) and system-specific vibration frequencies appear. In this case, it is more difficult to select and extract peaks due to defects of bearing damage compared to the case shown in FIG. 15, and a decrease in the accuracy of bearing damage determination is unavoidable. Therefore, by removing defect information other than bearing damage from the pulse period waveform WF1 as in this method, bearing damage information can be easily extracted from the frequency analysis result, and the accuracy of damage determination can be improved. The process of calculating the peak intensity from the above frequency characteristics is performed by the peak intensity calculation unit 24C shown in FIG. 2, and the process of determining bearing damage according to the peak intensity is performed by the damage detection unit 24D.

[0067] The above-described damage determination procedure can be modified as appropriate. Fig. 17 is a flowchart showing another procedure 1 of damage determination, which is a partial modification of the procedure in the flowchart shown in Fig. 8. In the other procedure shown in Fig. 17, the above-mentioned steps S11 to S14 and S18 to S22 are common, and the pulse period (Tp) waveform WF1 generated in S13 is smoothed before being converted into a period ratio to remove errors due to rotation unevenness.

[0068] That is, the pulse period waveform WF1 generated in S13 is smoothed by a method such as the moving average described above to obtain a pulse period smoothed waveform WF1A (S31). Then, the pulse period smoothed waveform WF1A is divided by the rotation period waveform WF2 generated in S14 to obtain a period ratio waveform WF3A (=WF1A / WF2) which is the period ratio described above, and a period ratio waveform WF3 is obtained by dividing the pulse period (Tp) waveform WF1 by the rotation period (T) waveform WF2 as described above (S32). Furthermore, a period ratio difference waveform WF5 (=WF3-WF3A) which is the difference between the period ratio waveform WF3 and the period ratio waveform WF3A is obtained (S33). The subsequent processing is the same as described above.

[0069] This procedure is the same as the flowchart shown in FIG. 8, except that smoothing processing is performed before obtaining the period ratio. As in this procedure, the timing of non-dimensionalization as the period ratio is arbitrary, and substantially the same results can be obtained at any timing.

[0070] FIG. 18 is a flowchart showing another procedure 2 for damage determination in which part of the procedure of the flowchart shown in FIG. 8 is changed. In the other procedure 2 shown in FIG. 18, instead of the period ratio smoothed waveform WF4 obtained in S16 described above, a constant offset value is set as WF4 (S36). WF4 as this offset value may be, for example, 1 / number of poles n (n = 48) ≈ 0.02083.

[0071] FIG. 19 is a flowchart showing another procedure 3 for damage determination in which part of the procedure of the flowchart shown in FIG. 8 is changed. In the other procedure 3 shown in FIG. 19, the period ratio smoothed waveform WF4 obtained in S16 and the period ratio difference waveform WF5 obtained in S17 described above are omitted, and from the period ratio waveform WF3 obtained in S15, a period ratio average value distribution WF6 that is the average value for each pole of the period ratio is obtained (S35). Then, the value of the period ratio average value distribution WF6 is subtracted from the period ratio waveform WF3 to obtain a period ratio fluctuation waveform WF7 (S36).

[0072] FIG. 20 is a flowchart showing another procedure 4 for damage determination in which part of the procedure of the flowchart shown in FIG. 8 is changed. In the other procedure 4 shown in FIG. 20, the period ratio smoothed waveform WF4 obtained in S16 described above is obtained by performing a 7-term moving average process of moving average of data for 7 poles of the period ratio waveform WF3 (S37). By performing the moving average between terms corresponding to a part of the total number of poles (n = 48) of the magnetic encoder, an appropriate noise reduction effect can be obtained. The number of terms of the moving average may be set to, for example, 1 / 5 to 1 / 10 of the total number of poles of the magnetic encoder.

[0073] <Second Embodiment> (Configuration of Damage Detection System) Figure 21 is a schematic configuration diagram of a bearing damage detection system 200 for a hub unit bearing according to the second embodiment. In Figure 21, the hub 15 of the hub unit bearing 11A and the sensors 21 and 22 are shown in a horizontal cross section. In the first embodiment shown in Figure 1, the rotation of the hub shaft 31 was detected by one sensor 21, but the second embodiment has the same configuration of the hub unit bearing as the first configuration example except that the rotation is detected by two sensors 21 and 22.

[0074] When there is one sensor, an error due to the displacement of the raceway ring accompanying the change in the rolling element position is superimposed on the output signal from the sensor. Therefore, the fluctuations of each of the waveforms described above include the displacement accompanying the change in the rolling element position, and peaks due to this influence also appear in the frequency characteristics.

[0075] On the other hand, in the bearing damage detection system 200 shown in Figure 21, at an intermediate position in the vertical direction of the hub unit bearing 11A, a sensor (first rotation sensor) 21 that detects rotation at one end in the horizontal direction and a sensor 22 (second rotation sensor) that detects rotation at the other end in the horizontal direction are provided. And data processing is performed using the phase difference of the output signals from the respective sensors 21 and 22. The sensor 22 is arranged with its detection surface 22a facing the magnetic encoder 55. In the sensor output signals from the two sensors 21 and 22 arranged at positions facing each other in the horizontal direction, a phase delay or advance due to the displacement of the rolling ring accompanying the change in the rolling element position appears in opposite directions to each other. Therefore, by using the difference signal of the sensor output signals from the two sensors 21 and 22, the above-described phase delay or advance is canceled, and the displacement in the vertical direction is calculated. When data processing is performed based on this difference signal to obtain the frequency characteristics, the frequency characteristics have reduced noise, and when the bearing is damaged, peaks occur at the period calculated from the rolling element pitch and the revolution speed of the rolling element, and in the case of inner ring damage, at the period calculated from the rotation speed, and the detection accuracy of the damage is improved.

[0076] FIG. 22 is an explanatory diagram schematically showing the arrangement relationship between the inner ring 33, the outer ring 13, and the magnetic encoder 55 of the hub unit bearing 11A, and the detection regions DRa of the sensor 21 and the detection region DRb of the sensor 22. FIG. 23 shows the acting direction of the radial load applied from the inner ring 33 to the outer ring 13 (vertically in the vertical direction Z which is generally the direction of gravity) in the vertical direction.

[0077] It is preferable that both the detection region DRa of the sensor 21 and the detection region DRb of the sensor 22 are set at positions where their center positions Pc are shifted downward by a distance δ from the horizontal line Lh passing through the central axis O of the hub unit bearing 11A. In that case, although details will be described later, it becomes easy to detect the shift by the phase difference signal. Also, the center positions Pc of the detection regions DRa and DRb may be arranged on the above-described horizontal line Lh.

[0078] FIG. 24 is a schematic circuit diagram of the pulse signal generation unit 23A. In this case, the pulse signal generation unit 23A, for example, sets the output signal from the sensor 21 (sensor A) as the pulse signal PL_A and the output signal from the sensor 22 (sensor B) as the pulse signal PL_B. Also, the difference signal between the pulse signal A and the pulse signal B is output as the phase difference signal PD (=PL_A - PL_B).

[0079] FIG. 24 is an explanatory diagram showing waveform examples of the pulse signals PL_A, PL_B, and the phase difference signal PD. The pulse period of the pulse signal PL_A is T A , the pulse period of the pulse signal PL_B is T B , and the phase difference between the pulse signals PL_A and PL_B is T PD . The phase difference signal PD has, for example, a waveform that changes in the range of +V to -V when the voltages of the pulse signals PL_A and PL_B are +V and +2V, and the period during which it becomes -V corresponds to the phase difference T PD .

[0080] The above-described pulse signals PL_A, PL_B, and phase difference signal PD change due to damage to the hub unit bearing 11A. Fig. 25 is an explanatory diagram showing the effect on the sensor output of the relative displacement of the inner and outer rings caused by flaking of the outer ring raceway. Here, similar to the case shown in Fig. 6, the hub axle 31 moves up and down due to flaking or indentations on the outer ring raceway 27 of the outer row bearing part 49A.

[0081] It is assumed that a radial load Pr (preload) is applied from the hub axle 31 to the outer ring 13 in the vertically upward direction in the bearing portion 49A. When the rolling element 17, which is floating in a defective area where flaking has occurred in the outer ring raceway 27, rides up from the end of the defective area to an area without flaking, the hub axle 31 is subjected to the above-mentioned impact load larger than the radial load Pr, and the hub axle 31 is displaced downward. If the hub axle 31 subsequently rotates further and an impact load is generated in the opposite direction, the hub axle 31 is displaced upward. Then, the magnetic encoder 55 fixed to the hub axle 31 is displaced in a downward and then upward direction in response to the displacement of the hub axle 31. Even if the above-mentioned preload is not applied to the hub axle 31, the behavior of the magnetic encoder 55 is the same as above, and it is displaced downward and upward in response to the displacement of the hub axle 31.

[0082] In other words, in the floating state, the hub axle 31 is displaced upward and the center O of the outer ring 13 out Center of hub axle 31 relative to O in is displaced upward. At that time, the pulse signals PL_A, PL_B detected from the detection regions DRa, DRb have a phase lead or lag from the neutral position. Specifically, in the detection region DRa, the hub axle 31 is displaced upward in the same direction as the rotation direction Ro, so that the phase of the pulse signal PL_A is advanced. In the detection region DRb, the hub axle 31 is displaced upward in the opposite direction to the rotation direction Ro, so that the phase of the pulse signal PL_B is delayed. As a result, the phase difference signal PD, which is the difference signal between the pulse signals PL_B and PL_A, has a phase difference T PD A period of time will occur.

[0083] On the other hand, when the hub shaft 31 is displaced downward, in the detection region DRa, since the hub shaft 31 is displaced downward in the direction opposite to the rotation direction Ro, a delay occurs in the phase of the pulse signal PL_A. In the detection region DRb, since the hub shaft 31 is displaced downward in the same direction as the rotation direction Ro, an advance occurs in the phase of the pulse signal PL_B. As a result, in the phase difference signal PD which is the difference signal between the pulse signal PL_B and the pulse signal PL_A, there is a phase difference T PD for a period different from the case where the hub shaft 31 is displaced upward.

[0084] That is, since the value of the phase difference T PD of the phase difference signal PD changes according to the amount of movement of the hub shaft 31 in the vertical direction, the relative displacement between the inner ring 33 and the outer ring 13 can be calculated from the phase difference of the pulse signals from the two sensors 21, 22. The phase difference T PD changes depending on the positions of the detection regions DRa, DRb, and the phase difference T PD appearing in the phase difference signal PD can be easily detected by obtaining the pulse length of a specific pulse. As described above, by setting the center positions Pc of the detection regions DRa, DRb to positions shifted downward from the horizontal line Lh passing through the central axis O of the hub unit bearing 11A, the pulse length of the above-described specific pulse does not become 0 and detection is not impossible.

[0085] The above-described phase difference and pulse period are not limited to being calculated from the waveform obtained by the pulse signal generation unit 23A subtracting the pulse signals PL_A and PL_B in real time, and may also be calculated from each pulse signal after individually monitoring the waveforms of the pulse signals PL_A and PL_B and then calculating the phase difference and pulse period.

[0086] The above description schematically shows the behavior of the signal change, and the state of the signal change closer to the actual signal will be described below. FIG. 26 is an explanatory diagram showing the relationship between the displacement of the encoder and the phase difference of the detected pulse signal. FIG. 27 is an explanatory diagram showing an example of changes in the pulse signals PL_A, PL_B, and the phase difference signal PD. FIGS. 26 and 27 show, in chronological order, the states of displacement when peeling occurs on the outer ring raceway shown in FIG. 6 described above, in the order of sections SC1, SC2, SC3, and SC4. In SC1 in the initial state, the speeds (VR0, VL0: also referred to as relative speeds) detected in the detection regions DRa and DRb shown in FIG. 26 are equal to each other. Then, in SC2 where the hub shaft 31 rotates, the rolling element reaches the end of the defect region of the outer ring raceway, and the rolling element enters again between the outer ring raceway without peeling and the inner ring raceway. At this time, as described in FIG. 6 for the case of the single sensor described above, the hub shaft 31 is displaced downward. Therefore, the speed (VR1) detected in the detection region DRa decreases, and the speed (VL1) detected in the detection region DRb increases.

[0087] In SC3 where the hub shaft 31 further rotates and the rolling element transitions back to the original rolling state between the outer ring raceway and the inner ring raceway, the speed (VR2) detected in the detection region DRa increases, and the speed (VL1) detected in the detection region DRb decreases. Then, in SC4 where the hub shaft 31 further rotates, it returns to the same state as SC1 in the initial state.

[0088] The pulse signals PL_A, PL_B, and the phase difference signal PD (=PL_A - PL_B) in each section SC1, SC2, SC3, SC4 generate the respective distributions of the speed, the pulse width of the phase difference signal, and the pulse period shown in FIG. 27. For example, the amount of displacement up and down is obtained from the pulse width of the phase difference signal, and the displacement speed is obtained from the pulse periods of the pulse signals PL_A, PL_B. Note that although the actual displacement of the hub shaft 31 occurs between SC1 and SC4, the detection of the displacement is between SC2 and SC4.

[0089] Figure 28 is an explanatory diagram schematically showing waveforms of specific pulse signals PL_A, PL_B, and a phase difference signal PD. In the pulse signals PL_A and PL_B, there are phase delays and advances corresponding to the height positions of the detection regions DRa and DRb. Also, in the aforementioned section SC2, the period of the pulse signal PL_A becomes long, and the period of the pulse signal PL_B becomes short. In section SC3, the period of the pulse signal PL_A becomes short, and the period of the pulse signal PL_B becomes long. Therefore, the phase difference T PD appearing in the phase difference signal PD between sections SC3 and SC4 PD is shorter than that in other sections. This change in the phase difference T PD is quantitatively obtained during the frequency analysis of the waveforms described later and is used for damage determination.

[0090] (Procedure for damage determination) Figure 29 is a flowchart showing a procedure for determining damage to the hub unit bearing 11A using the above two sensors 21 and 22. Each of the following procedures is carried out based on a command from the control unit 24 shown in Figure 21.

[0091] First, the rotation of the rotationally driven hub unit bearing 11A is detected by the sensors 21 and 22, and sensor output signals, which are rotation signals output from the sensors 21 and 22, are acquired (S41). These sensor output signals are each converted into pulse signals PL_A and PL_B by the pulse signal generation unit 23.

[0092] Figure 30 is an explanatory diagram showing waveforms of the pulse signal PL_A and the pulse signal PL_B. The control unit 24 obtains the pulse period T i of the pulse signal PL_B and the phase difference PD i (where i is an integer representing the order of the pulses) between the pulse signal PL_B and the pulse signal PL_A. The phase difference PD i may be obtained using the phase difference signal PD generated by the pulse signal generation unit 23A shown in Figure 23, or may be obtained by individually AD-converting each of the pulse signals PL_A and PL_B and converting them into a phase difference.

[0093] Figure 31 shows a space where the horizontal axis represents the order of the pulses of the pulse signal PL_B and the vertical axis represents time, Cycle T i and phase difference PD i is an explanatory diagram showing changes. In this procedure, the phase difference PD i is obtained for the spatial waveform of (S42), and damage is determined based on the waveform. That is, instead of the sensor output signal from one sensor 21, data processing is performed using the phase difference between the sensor output signals from the two sensors 21 and 22. The subsequent procedures are the same as those in the first embodiment except that the "pulse period" described above is changed to "phase difference", and since the basic processing content is common to the first embodiment, detailed descriptions of each procedure are omitted.

[0094] FIG. 32 is an explanatory diagram showing an example of waveforms from extracting the rotational fluctuation of the hub shaft 31 from the pulse output signal to generating the rotational fluctuation signal. The phase difference waveform WF11 shows the phase difference PD i in FIG. 31 (S43), and the rotational period waveform WF12 is a waveform obtained by obtaining the transition of the period T of one rotation centered on each pulse of the pulse signal PL_B (it may also be obtained by PL_A) as shown in FIG. 23 described above (S44).

[0095] Next, a phase difference ratio waveform WF13 (= WF11 / WF12) obtained by dividing the phase difference waveform WF11 by the rotational period waveform WF12 is obtained (S45). In this phase difference ratio waveform WF13, the influence of the rotational speed error is removed.

[0096] Then, the phase difference ratio waveform WF13 is smoothed in the same manner as described above to obtain a phase difference ratio smoothed waveform WF14 (S46), and a phase difference ratio difference waveform WF15 (= WF13 - WF14) representing the difference between the phase difference ratio waveform WF13 and the phase difference ratio smoothed waveform WF14 is obtained (S47). Note that depending on the conditions, instead of subtracting the phase difference ratio smoothed waveform WF14 from the phase difference ratio waveform WF13, the phase difference ratio waveform WF13 may be directly used as the phase difference ratio difference waveform WF15.

[0097] Next, a phase difference ratio average value distribution WF16, which is the average value for each pole of the magnetic encoder, is obtained from the phase difference ratio difference waveform WF15 (S48). FIG. 33 is an explanatory diagram showing an example of the phase difference ratio average value distribution WF16. In the phase difference ratio average value waveform WF16, the deviation from the 0 level on the vertical axis represents the magnetization error of the magnetic encoder. In FIG. 33, a line (not shown) connecting the average values of each pole of the phase difference ratio average value distribution becomes the phase difference ratio average value waveform.

[0098] Next, a phase difference ratio fluctuation waveform WF17 representing the difference between the above-described phase difference ratio difference waveform WF15 and the phase difference ratio average value waveform WF16 is obtained (S19). The phase difference ratio fluctuation waveform WF17 is obtained by subtracting the value of each pole indicated by the phase difference ratio average value waveform WF16 from the value of each pole of the phase difference ratio difference waveform WF15 for corresponding poles. Hereinafter, the phase difference ratio difference waveform WF15 is also referred to as a "detection waveform", the phase difference ratio average value waveform WF16 is also referred to as a "reference waveform", and the phase difference ratio fluctuation waveform WF17 is also referred to as a "rotation fluctuation waveform".

[0099] FIG. 34 is an explanatory diagram schematically showing the phase difference ratio fluctuation waveform WF17. In this phase difference ratio fluctuation waveform WF17, the magnetization error of the magnetic encoder 55 is removed. That is, since the rotation speed change, rotation unevenness, and magnetization error are removed in the phase difference ratio fluctuation waveform WF17, the fluctuations appearing here can be said to be caused by the displacement accompanying the change in the rolling element position and the displacement accompanying the damage when the bearing raceway surface is damaged.

[0100] Note that the phase difference ratio fluctuation waveform WF17 may be a waveform in which the vertical axis is converted from the period ratio to the displacement fluctuation by a geometric operation (S50). In that case, it becomes easier to intuitively grasp the level of the fluctuation as the magnitude of the displacement.

[0101] Next, the phase difference ratio fluctuation waveform WF17 is subjected to frequency analysis (S51). FIG. 35 is an explanatory diagram showing an example of the frequency characteristic WF18 obtained by subjecting the phase difference ratio fluctuation waveform WF17 to FFT processing. The phase difference ratio fluctuation waveform WF17 includes displacement fluctuations associated with changes in the rolling element position, and when the bearing is damaged, displacement fluctuations associated with the bearing damage. Therefore, in the frequency characteristic WF18, peaks of spatial frequencies calculated from the revolution speed of the balls (primary to several times), when the bearing is damaged, peaks generated at a period calculated from the ball pitch and the revolution speed of the balls, and in the case of outer ring damage, peaks generated at a period calculated from the rotation speed appear. When the peak caused by such bearing damage is equal to or greater than the threshold value, it is determined that the bearing is damaged. Note that the same frequency characteristic WF18 can be obtained even when the vertical axis of the phase difference ratio fluctuation waveform WF17 is converted into displacement fluctuations.

[0102] In the frequency characteristic WF18 shown in FIG. 35, the main peaks caused by bearing damage appear as, for example, the peak Pk1 of the first-order defect and the peak Pk2 of the second-order defect. Then, as described above, the bearing damage is determined according to the total value of the peak intensities within the set spatial bands BD1 and BD2.

[0103] In addition to the above procedure, the bearing damage may be determined by other procedures shown below. FIG. 36 is a flowchart showing another damage determination procedure 1 in which the procedure of the flowchart shown in FIG. 29 is partially changed. In the other procedure 1 shown in FIG. 36, the phase difference ratio waveform WF13 obtained in S45 described above is subjected to a 48-term moving average process of moving the data for all poles (48 poles) of the magnetic encoder with respect to the phase difference ratio waveform WF13 to obtain a phase difference ratio smoothed waveform WF14. This phase difference ratio smoothed waveform WF14 is generally a flat waveform and has a substantially constant offset value as a whole. In S47, the difference between the phase difference ratio waveform WF13 and the phase difference ratio smoothed waveform WF14 is obtained as a phase difference ratio difference waveform WF15.

[0104] FIG. 37 is a flowchart showing another procedure 2 for damage determination in which the procedure of the flowchart shown in FIG. 29 is partially changed. In another procedure 2 shown in FIG. 37, the phase difference ratio waveform WF13 obtained in S45 described above is averaged for each pole of the magnetic encoder with respect to the phase difference ratio waveform WF13 to obtain a phase difference ratio average value distribution WF16 (S52). Then, the value of the phase difference ratio average value distribution WF16 is subtracted from the phase difference ratio waveform WF13 to obtain a phase difference ratio fluctuation waveform WF17 (S53). In S51, frequency analysis is performed on this phase difference ratio fluctuation waveform WF17.

[0105] FIG. 38 is a flowchart showing another procedure 3 for damage determination in which the procedure of the flowchart shown in FIG. 29 is partially changed. In another procedure 3 shown in FIG. 38, the phase difference ratio waveform WF13 obtained in S45 described above is subjected to a 7-term moving average process in which the data for 7 poles of the phase difference ratio waveform WF13 are moving-averaged to obtain a phase difference ratio smoothed waveform WF14 (S54). By performing the moving average between terms corresponding to a part of the total number of poles (n = 48) of the magnetic encoder, an appropriate noise reduction effect can be obtained. The number of terms for the moving average may be set to, for example, 1 / 5 to 1 / 10 of the total number of poles of the magnetic encoder.

[0106] <Time sequence of control> Next, the time sequence of control in each of the above-described embodiments will be described. FIG. 39 is a control block diagram from obtaining a differential waveform from the detected pulse signal until obtaining a rotational fluctuation waveform. In this process, the control unit 24 obtains the detection waveform K described above based on the output signal from the sensor (sensor 21 in FIG. 1, sensors 21 and 22 in FIG. 21), integrates and averages the obtained detection waveform K for each rotation angle (pole), and stores the synthesized average waveform C as a reference waveform in the storage device. Then, the detection waveform K is obtained from the output signal newly output from the sensor, and the value of the reference waveform stored in the storage device is subtracted from this new detection waveform K for each rotation angle to obtain a differential waveform. The obtained differential waveform (rotational fluctuation waveform) is a waveform from which unnecessary fluctuations are removed, and when frequency analysis is performed, a frequency characteristic from which unnecessary peaks are removed is obtained.

[0107] In this control, the detection waveform K itself is subtracted using a reference waveform obtained from the detection waveform K based on the output signal from the sensor. That is, a reference waveform is generated from the detection waveform K including variations due to defects, and the original detection waveform K is processed using the obtained reference waveform to remove unnecessary variations from the detection waveform K in real time. For example, when processing measurement data using a reference waveform, if a reference waveform based on past measurement data, calculations, etc. is prepared in advance and used for processing, the reference waveform does not necessarily match the timing when the measurement data is actually acquired. Therefore, there is a possibility that the processing result will be distorted. On the other hand, in this control, the reference waveform used for the subtraction process of the detection waveform K is generated from the pulse signal that obtained the detection waveform K or a pulse signal consecutive to the pulse signal. That is, the rotation of the rolling bearing when the pulse signal used for generating the reference waveform or the pulse signal is output is continuously maintained as it is, and the reference waveform is obtained using the pulse signal continuously output following the above pulse signal. Therefore, since the measurement data to be evaluated and the reference waveform are information on timing that can be regarded as simultaneous or substantially simultaneous in time series, there is almost no change in the rotation conditions, and the above-mentioned incompatibility does not occur.

[0108] Hereinafter, a specific example of the control for performing damage determination of the rolling bearing will be described. FIG. 40 is an explanatory diagram showing a time chart 1 until damage determination of the rolling bearing is carried out from the detection waveform K. In the time chart of FIG. 40, the horizontal axis is the elapsed time, and the processing content for each elapsed time is shown along the vertical axis. In this control, damage detection target sections SC1, SC2, SC3, SC4, ··· for detecting damage are set intermittently and sequentially. First, the output signal from the sensor is acquired between the elapsed times t0 to t1. During the next elapsed period t1 to t2, the detection waveform K is generated, a reference waveform is generated from this detection waveform K, the reference waveform is subtracted from the detection waveform K to obtain a difference waveform (rotation fluctuation waveform), and damage determination is performed by frequency analyzing this rotation fluctuation waveform by FFT or the like. In the period from t0 to t2 (the period surrounded by the broken line TM) as described above, the damage determination of the damage detection target section SC1 at the elapsed time t0 to t1 is completed. Hereinafter, the same processing as this is sequentially repeated for SC2, SC3, SC4, ···.

[0109] FIG. 41 is an explanatory diagram showing a time chart 2 until damage determination of the rolling bearing is carried out from the detection waveform K. The time chart 2 of FIG. 41 is a control example that can be executed even when the arithmetic processing ability of the control unit 24 is relatively low. In this control, first, the output signal from the sensor is acquired between the elapsed times t0 to t1. During the next elapsed period t1 to t2, the detection waveform K is generated, and a reference waveform is generated from this detection waveform K. Next, while acquiring the output signal from the sensor between the elapsed times t2 to t3 and generating the detection waveform K, the reference waveform obtained during the previous elapsed period t1 to t2 is subtracted from the detection waveform K to obtain a difference waveform (rotation fluctuation waveform). Then, the rotation fluctuation waveform is frequency analyzed by FFT (Fast Fourier Transform) or the like between the elapsed times t3 to t4 to perform damage determination. In this way, in the period from t0 to t4, the abnormality determination of the damage detection target section SC1 at the elapsed time t2 to t3 is completed. In this case, for the damage determination of SC1, a reference waveform based on the information between the elapsed times t0 to t1 is used. However, since it is close to the period of SC1, no large change occurs and no nonconformity occurs.

[0110] Furthermore, while acquiring the output signal from the sensor between elapsed times t4 to t5 and generating the detection waveform K, the reference waveform obtained during the previous elapsed time t1 to t2 is subtracted from the detection waveform K to obtain a difference waveform (rotation fluctuation waveform). Then, the rotation fluctuation waveform is frequency-analyzed by FFT or the like between elapsed times t5 to t6 to perform damage determination. In this way, within the period from t4 to t6, the abnormality determination of the damage detection target section SC2 at the elapsed time t4 to t5 is completed. Similarly, within the period from t6 to t8, the damage determination of the damage detection target section SC3 at the elapsed time t6 to t7 is completed. Hereinafter, the same processing as this is sequentially repeated. Within the period from t0 to t8 (the period surrounded by the broken line TM) above, the damage determination of the damage detection target sections SC1, SC2, and SC3 that commonly use the reference waveform obtained during the elapsed time t1 to t2 is completed.

[0111] In this control, the damage determination for the periods of SC1, SC2, and SC3 is performed based on the result of commonly using the reference waveform obtained during the elapsed time t1 to t2. Thereby, damage determination can be performed while reducing the calculation load of the control unit.

[0112] FIG. 42 is an explanatory diagram showing a time chart 3 until damage determination of the rolling bearing is performed from the detection waveform K. The time chart 3 in FIG. 42 is a control example that can be executed even when the calculation processing ability of the control unit 24 is further lower. In this control, first, the output signal from the sensor is acquired between elapsed times t0 to t1. Next, during the elapsed time t1 to t2, the detection waveform K is generated, and a reference waveform is generated from this detection waveform K. Then, the output signal from the sensor is acquired between elapsed times t2 to t3, and the detection waveform K of the output signal is generated between elapsed times t3 to t4, and the reference waveform generated between t1 to t2 is subtracted from the detection waveform K to obtain a difference waveform (rotation fluctuation waveform). Also, the difference waveform between t1 to t2 is frequency-analyzed during this period.

[0113] Next, acquire the output signal from the sensor during the elapsed period t4 to t5, generate the detection waveform K of the output signal during t5 to t6, and subtract the reference waveform generated during t1 to t2 from the detection waveform K to obtain a difference waveform (rotation fluctuation waveform). Also, perform frequency analysis on the difference waveform during t4 to t5 in this period.

[0114] Similarly, acquire the output signal from the sensor during the elapsed period t6 to t7, generate the detection waveform K of the output signal during t6 to t7, and subtract the reference waveform generated during t1 to t2 to obtain a difference waveform (rotation fluctuation waveform). Also, perform frequency analysis on the difference waveform during t6 to t7 in this period. During the elapsed period t8 to t9, average the results of the frequency analysis obtained at t3 to t4 (corresponding to SC1), t5 to t6 (corresponding to SC2), and t7 to t8 (corresponding to SC3) to perform damage determination for the periods of SC1, SC2, and SC3.

[0115] In this control, the damage determination for the periods of SC1, SC2, and SC3 is performed based on the result of commonly using the reference waveform obtained during the elapsed period t1 to t2. Also, by performing frequency analysis separately for each period, damage determination can be performed while further reducing the computational burden on the control unit.

[0116] In each of the above control examples, by setting the subtraction process of the reference waveform with a large computational burden and the section of frequency analysis outside the damage detection target section, efficient calculations can be performed even when the computational ability of the control unit 24 is relatively low. Also, since the difference waveform (rotation fluctuation waveform) is obtained using the reference waveform generated based on the information under the same conditions as when measuring the detection waveform K, or the reference waveform generated under conditions close to the measurement time, the accuracy of the reference waveform is high and more accurate damage determination is possible.

[0117] The bearing damage detection method described above is also applicable to single-row bearings. In addition, a hub unit bearing used as a vehicle support mechanism has components such as an encoder, a wheel speed sensor, and a signal processing circuit for its signals. In that case, by improving the performance of these hardware components, without adding a new system, the processing of the above-described bearing damage inspection method can be easily realized by changing the control content, that is, by changing and adding software, and improving the performance of the hardware (such as improving the processing speed). Also, in a multi-row bearing such as a hub unit bearing, even if the sensor and the encoder are provided only in one row without being provided individually in each row, it is possible to detect damage in either of the two rows.

[0118] Thus, the present invention is not limited to the above-described embodiments, and it is also contemplated by the present invention that those skilled in the art may make changes and applications based on combining each configuration of the embodiments with each other, the description in the specification, and well-known techniques, and such are included in the scope sought to be protected. For example, depending on the type of sensor, there may be cases where there are waveform disturbances, superposition of additional information, etc. in the output signal. Even in such cases, appropriate signal processing, a processing circuit, etc. may be added to generate the desired pulse waveform described above. That is, necessary processing may be appropriately added according to the waveform of the signal acquired from the sensor, and each step of the damage detection described above may be carried out.

[0119] As described above, the following matters are disclosed in this specification. (1) A rotation sensor that detects the rotation of a rolling bearing and outputs a rotation signal, A rotation variation extraction unit that extracts the rotation variation of the rolling bearing from the rotation signal and generates a rotation variation signal, A frequency analysis unit that performs frequency analysis on the waveform of the rotation variation signal to obtain frequency characteristics, A peak intensity calculation unit that obtains the peak intensity corresponding to bearing damage from the frequency characteristics, A damage detection unit that detects the bearing damage of the rolling bearing based on the peak intensity, A bearing damage detection system comprising the above. According to this bearing damage detection system, when the rolling bearing has bearing damage, by obtaining a rotational fluctuation signal that selectively extracts the rotational fluctuation due to the bearing damage, the peak intensity corresponding to the bearing damage can be easily obtained from the result of frequency analysis of the rotational fluctuation signal.

[0120] (2) It is provided with a pulse signal generation unit that converts the rotation signal into a pulse signal synchronized with the rotation of the rolling bearing. The rotational fluctuation extraction unit For each pulse of the pulse signal, a pulse period waveform representing the transition of the pulse period Tp of each individual pulse, and A rotation period waveform representing the transition of the rotation period T of one rotation of the rolling bearing centered on any one of the pulses of the pulse signal, and are obtained, The bearing damage detection system according to (1), wherein the waveform of the rotational fluctuation signal is obtained based on a period ratio waveform representing the ratio Tp / T of the pulse period Tp to the rotation period T. According to this bearing damage detection system, by using a period ratio waveform representing the ratio Tp / T of the pulse period Tp to the rotation period T, the influence of the rotational speed error can be removed from the rotational fluctuation signal.

[0121] (3) The rotational fluctuation extraction unit The bearing damage detection system according to (2), wherein the waveform of the rotational fluctuation signal is obtained based on a period ratio difference waveform representing the difference between the period ratio waveform and a period ratio smoothed waveform obtained by smoothing the period ratio waveform. According to this bearing damage detection system, by using the period ratio difference waveform, the influence of the rotational unevenness error can be removed from the rotational fluctuation signal.

[0122] (4) The rotational fluctuation extraction unit Obtain a period ratio average value waveform obtained by averaging the differences corresponding to the same rotation position of the rolling bearing in the period ratio difference waveform for each rotation position, The bearing damage detection system according to (3), wherein the waveform of the rotational fluctuation signal is obtained based on a period ratio fluctuation waveform obtained by obtaining the difference between the period ratio difference waveform and the period ratio average value waveform for each rotation position. According to this bearing damage detection system, by using the period ratio fluctuation waveform, the influence of the detection error of the rotational position of the rotation sensor can be removed from the rotational fluctuation signal.

[0123] (5) The bearing damage detection system according to (4), wherein the period ratio average value waveform is a waveform obtained by using the rotation signal for which the period ratio difference waveform has been obtained, or a rotation signal continuously output subsequent to the rotation signal. According to this bearing damage detection system, since the period ratio average value waveform is obtained by using the rotation signal for which the period ratio difference waveform has been obtained or a subsequent rotation signal, the difference between the period ratio difference waveform and the period ratio average value waveform, which are acquired simultaneously or at substantially the same timing in time series, can be obtained. Therefore, accurate damage detection is possible without being affected by changes in conditions over time.

[0124] (6) The bearing damage detection system according to (1), wherein the rotation sensor includes a first rotation sensor that detects rotation at an intermediate position in the vertical direction of the rolling bearing and at one end in the horizontal direction, and a second rotation sensor that detects rotation at the other end in the horizontal direction. According to this bearing damage detection system, since the difference signal of the sensor output signals from the two rotation sensors cancels out the delay or advance of the phase of each sensor output signal, a rotation signal waveform with less noise can be obtained.

[0125] (7) The rotation signal is a first pulse signal output from the first rotation sensor and a second pulse signal output from the second rotation sensor, for the pulse of the first pulse signal or the second pulse signal, a rotation period waveform representing the transition of the rotation period T for one rotation of the rolling bearing centered on the pulse, and a phase difference waveform representing the transition of the phase difference PD between the first pulse signal and the second pulse signal, are obtained, The bearing damage detection system according to (6), wherein the waveform of the rotational fluctuation signal is obtained based on a phase difference ratio waveform representing the ratio PD / T of the phase difference PD to the rotation period T. According to this bearing damage detection system, by using a phase difference ratio waveform representing the ratio PD / T of the phase difference PD to the rotation period T, the influence of the rotational speed error can be removed from the rotational fluctuation signal.

[0126] (8) The rotational fluctuation extraction unit obtains the waveform of the rotational fluctuation signal based on a phase difference ratio difference waveform representing the difference between the phase difference ratio waveform and a phase difference ratio smoothed waveform obtained by smoothing the phase difference ratio waveform, according to the bearing damage detection system of (7). According to this bearing damage detection system, by using the phase difference ratio difference waveform, the influence of the rotational unevenness error can be removed from the rotational fluctuation signal.

[0127] (9) The rotational fluctuation extraction unit obtains a phase difference ratio average value waveform obtained by averaging, for each rotation position, the differences corresponding to the same rotation position of the rolling bearing in the phase difference ratio difference waveform, and obtains the waveform of the rotational fluctuation signal based on a phase difference ratio fluctuation waveform obtained by obtaining, for each rotation position, the difference between the phase difference ratio difference waveform and the phase difference ratio average value waveform, according to the bearing damage detection system of (8). According to this bearing damage detection system, by using the phase difference ratio fluctuation waveform, the influence of the detection error of the rotation position of the rotation sensor can be removed from the rotational fluctuation signal.

[0128] (10) The phase difference ratio average value waveform is a waveform obtained by using the rotation signal for which the phase difference ratio difference waveform was obtained, or a rotation signal continuously output subsequent to the rotation signal, according to the bearing damage detection system of (9). According to this bearing damage detection system, since the phase difference ratio average value waveform is obtained by using the rotation signal for which the phase difference ratio difference waveform was obtained or a subsequent rotation signal, the difference between the phase difference ratio difference waveform and the phase difference ratio average value waveform obtained simultaneously or at substantially the same timing in time series can be obtained. Therefore, accurate damage detection is possible without being affected by changes in conditions over time.

[0129] (11) The rolling bearing is a single-row bearing or a multi-row bearing, and the bearing damage detection system according to any one of (1) to (10). According to this bearing damage detection system, damage that has occurred can be detected regardless of whether it is a single-row bearing or a multi-row bearing.

[0130] (12) The rolling bearing is a hub unit bearing including an inner ring member, an outer ring member, a plurality of rolling elements disposed between the inner ring member and the outer ring member, a flange provided on at least one of the inner ring member and the outer ring member, and a wheel speed sensor that detects the rotational speed of the inner ring member. The wheel speed sensor functions as the rotation sensor, and the bearing damage detection system according to (11). According to this bearing damage detection system, the wheel speed sensor provided in the hub unit bearing can be directly diverted as the rotation sensor.

[0131] (13) Detect the rotation of the rolling bearing to generate a rotation signal. Extract the rotational variation of the rotation from the rotation signal to generate a rotational variation signal. Perform frequency analysis on the waveform of the rotational variation signal to obtain vibration peaks. Obtain the peak intensity corresponding to bearing damage from the vibration peaks. Detect the bearing damage of the rolling bearing based on the peak intensity. A bearing damage detection method comprising the steps of: According to this bearing damage detection method, when the rolling bearing has bearing damage, by obtaining a rotational variation signal that selectively extracts the rotational variation due to the bearing damage, the peak intensity corresponding to the bearing damage can be easily obtained from the result of frequency analysis of the rotational variation signal.

[0132] (14) The rotation signal is a pulse signal synchronized with the rotation of the rolling bearing. For each pulse of the pulse signal, obtain a rotation period waveform representing the transition of the rotation period for one rotation of the rolling bearing centered on the pulse. Obtain a pulse period waveform representing the transition of the pulse period of each pulse in the pulse signal, The bearing damage detection method according to (13), wherein the waveform of the rotational fluctuation signal is obtained based on a period ratio waveform representing the ratio Tp / T of the pulse period Tp to the rotation period T. According to this bearing damage detection method, by using a period ratio waveform representing the ratio Tp / T of the pulse period Tp to the rotation period T, the influence of the rotational speed error can be removed from the rotational fluctuation signal.

[0133] (15) The bearing damage detection method according to (14), wherein the waveform of the rotational fluctuation signal is obtained based on a period ratio difference waveform representing the difference between the period ratio waveform and a period ratio smoothed waveform obtained by smoothing the period ratio waveform. According to this bearing damage detection method, by using the period ratio difference waveform, the influence of the rotational unevenness error can be removed from the rotational fluctuation signal.

[0134] (16) Obtain a period ratio average value waveform obtained by averaging, for each rotation position, the differences corresponding to the same rotation position of the rolling bearing in the period ratio difference waveform, The bearing damage detection method according to (15), wherein the waveform of the rotational fluctuation signal is obtained based on a period ratio fluctuation waveform obtained by obtaining, for each rotation position, the difference between the period ratio difference waveform and the period ratio average value waveform. According to this bearing damage detection method, by using the period ratio fluctuation waveform, the influence of the detection error of the rotation position of the rotation sensor can be removed from the rotational fluctuation signal.

[0135] (17) The bearing damage detection method according to (16), wherein the period ratio average value waveform is obtained by using the rotation signal for which the period ratio difference waveform is obtained, or a rotation signal continuously output subsequent to the rotation signal. According to this bearing damage detection method, since the period ratio average value waveform is obtained by the rotation signal for which the period ratio difference waveform is obtained or a subsequent rotation signal, the difference between the period ratio difference waveform and the period ratio average value waveform obtained simultaneously or at substantially the same timing in time series can be obtained. Therefore, accurate damage detection is possible without being affected by changes in conditions over time.

[0136] (18) For the pulse of the first pulse signal based on the rotation signal detected at one end in the horizontal direction or the pulse of the second pulse signal based on the rotation signal detected at the other end in the horizontal direction at the intermediate position in the vertical direction of the rolling bearing, a rotation period waveform representing the transition of the rotation period T for one rotation of the rolling bearing centered on the pulse, and a phase difference waveform representing the transition of the phase difference PD between the pulses of the first pulse signal and the second pulse signal, are obtained, and the waveform of the rotational fluctuation signal is obtained based on the phase difference ratio waveform representing the ratio PD / T of the phase difference PD to the rotation period T. The bearing damage detection method according to (13). According to this bearing damage detection system, by using the phase difference ratio waveform representing the ratio PD / T of the phase difference PD to the rotation period T, the influence of the rotational speed error can be removed from the rotational fluctuation signal.

[0137] (19) The waveform of the rotational fluctuation signal is obtained based on the phase difference ratio difference waveform representing the difference between the phase difference ratio waveform and the phase difference ratio smoothed waveform obtained by smoothing the phase difference ratio waveform. The bearing damage detection method according to (18). According to this bearing damage detection method, by using the phase difference ratio difference waveform, the influence of the rotational unevenness error can be removed from the rotational fluctuation signal.

[0138] (20) An average value waveform of the phase difference ratio is obtained by averaging the differences corresponding to the same rotation position of the rolling bearing in the phase difference ratio difference waveform for each rotation position, and the waveform of the rotational fluctuation signal is obtained based on the phase difference ratio fluctuation waveform obtained by obtaining the difference between the phase difference ratio difference waveform and the phase difference ratio average value waveform for each rotation position. The bearing damage detection method according to (19). According to this bearing damage detection method, by using the phase difference ratio fluctuation waveform, the influence of the detection error of the rotation position of the rotation sensor can be removed from the rotational fluctuation signal.

[0139] (21) The method for detecting bearing damage according to (20), wherein the phase difference ratio average value waveform is obtained using the rotation signal for which the phase difference ratio difference waveform has been obtained, or a rotation signal that is continuously output following the rotation signal. According to this method for detecting bearing damage, the phase difference ratio average value waveform is obtained using the rotation signal for which the phase difference ratio difference waveform has been obtained or the subsequent rotation signal, so that the difference between the phase difference ratio difference waveform and the phase difference ratio average value waveform, which are acquired simultaneously or at approximately the same timing in a time series, can be obtained. Therefore, accurate damage detection can be achieved without being affected by changes in conditions over time.

Explanation of Signs

[0140] 11, 11A Hub unit bearing 13 Outer ring 15 Hub 17, 17A Rolling element 19 Rotation detection device 21, 22 Sensor 21a, 22a Detection surface 23, 23A Pulse signal generation unit 24 Control unit 24A Rotation variation extraction unit 24B Frequency analysis unit 24C Peak intensity calculation unit 24D Damage detection unit 25 Stationary side flange 27, 29 Outer ring raceway 31 Hub shaft 33 Inner ring 35 Mounting flange 35a Insertion hole 37 Hub bolt 39, 45 Inner ring raceway 41 Small diameter section 43 Crimping part 47 Cage 49A Bearing part of outer row 49B Bearing part of inner row 51 Seal ring 53 Internal space 55 Magnetic encoder 55a Support ring 55b Encoder body 59 Side Cover 100, 200 Bearing Damage Detection System

Claims

1. A rotation sensor that detects the rotation of a rolling bearing and outputs a rotation signal, a rotation variation extraction unit that extracts the rotation variation of the rolling bearing from the rotation signal and generates a rotation variation signal, a frequency analysis unit that performs frequency analysis on the waveform of the rotation variation signal to obtain frequency characteristics, a peak intensity calculation unit that obtains the peak intensity corresponding to bearing damage from the frequency characteristics, a damage detection unit that detects the bearing damage of the rolling bearing based on the peak intensity, A bearing damage detection system comprising:

2. A pulse signal generation unit that converts the rotation signal into a pulse signal synchronized with the rotation of the rolling bearing, The rotation variation extraction unit For each pulse of the pulse signal, a pulse period waveform representing the transition of the pulse period Tp of each pulse, and A rotation period waveform representing the transition of the rotation period T for one rotation of the rolling bearing centered on any one of the pulses of the pulse signal, are obtained, The waveform of the rotation variation signal is obtained based on the period ratio waveform representing the ratio Tp / T of the pulse period Tp to the rotation period T. The bearing damage detection system according to claim 1.

3. The rotation variation extraction unit The waveform of the rotation variation signal is obtained based on a period ratio difference waveform representing the difference between the period ratio waveform and a period ratio smoothed waveform obtained by smoothing the period ratio waveform. The bearing damage detection system according to claim 2.

4. The rotation variation extraction unit A period ratio average value waveform is obtained by averaging the differences corresponding to the same rotation position of the rolling bearing in the period ratio difference waveform for each rotation position, The waveform of the rotation variation signal is obtained based on a period ratio variation waveform obtained by obtaining the difference between the period ratio difference waveform and the period ratio average value waveform for each rotation position. The bearing damage detection system according to claim 3.

5. The period ratio average value waveform is a waveform obtained using the rotation signal for which the period ratio difference waveform was obtained, or a rotation signal continuously output following the rotation signal. The bearing damage detection system according to claim 4.

6. The rotation sensor includes a first rotation sensor that detects rotation at an intermediate position in the vertical direction of the rolling bearing and at one end in the horizontal direction, and a second rotation sensor that detects rotation at the other end in the horizontal direction. The bearing damage detection system according to claim 1.

7. The rotation signal is a first pulse signal output from the first rotation sensor and a second pulse signal output from the second rotation sensor. Regarding the pulse of the first pulse signal or the second pulse signal, a rotation period waveform representing the transition of the rotation period T for one rotation of the rolling bearing centered on the pulse, and a phase difference waveform representing the transition of the phase difference PD between the pulses of the first pulse signal and the second pulse signal, are obtained, the waveform of the rotational fluctuation signal is obtained based on the phase difference ratio waveform representing the ratio PD / T of the phase difference PD to the rotation period T, The bearing damage detection system according to claim 6.

8. The rotational fluctuation extraction unit obtains the waveform of the rotational fluctuation signal based on the phase difference ratio difference waveform representing the difference between the phase difference ratio waveform and the phase difference ratio smoothed waveform obtained by smoothing the phase difference ratio waveform, The bearing damage detection system according to claim 7.

9. The rotational fluctuation extraction unit obtains a phase difference ratio average value waveform obtained by averaging the differences corresponding to the same rotation position of the rolling bearing in the phase difference ratio difference waveform for each rotation position, and obtains the waveform of the rotational fluctuation signal based on the phase difference ratio fluctuation waveform obtained by obtaining the difference between the phase difference ratio difference waveform and the phase difference ratio average value waveform for each rotation position, The bearing damage detection system according to claim 8.

10. The phase difference ratio average value waveform is a waveform obtained using the rotation signal for which the phase difference ratio difference waveform was obtained, or a rotation signal continuously output following the rotation signal, The bearing damage detection system according to claim 9.

11. The rolling bearing is a single-row bearing or a multi-row bearing, The bearing damage detection system according to any one of claims 1 to 10.

12. The rolling bearing is a hub unit bearing including an inner ring member, an outer ring member, a plurality of rolling elements disposed between the inner ring member and the outer ring member, a flange provided on at least one of the inner ring member and the outer ring member, and a wheel speed sensor that detects the rotational speed of the inner ring member, The wheel speed sensor functions as the rotation sensor, The bearing damage detection system according to claim 11.

13. detecting the rotation of the rolling bearing to generate a rotation signal, extracting the rotational fluctuation of the rotation from the rotation signal to generate a rotational fluctuation signal, performing frequency analysis on the waveform of the rotational fluctuation signal to obtain vibration peaks, obtaining the peak intensity corresponding to bearing damage from the vibration peaks, and detecting bearing damage of the rolling bearing based on the peak intensity, A bearing damage detection method comprising.

14. The rotation signal is a pulse signal synchronized with the rotation of the rolling bearing, For each pulse of the pulse signal, obtain a rotation period waveform representing the transition of the rotation period for one rotation of the rolling bearing centered on the pulse. Obtain a pulse period waveform representing the transition of the pulse period of each pulse in the pulse signal. Obtain the waveform of the rotational fluctuation signal based on the period ratio waveform representing the ratio Tp / T of the pulse period Tp to the rotation period T. The bearing damage detection method according to claim 13.

15. Obtain the waveform of the rotational fluctuation signal based on the period ratio difference waveform representing the difference between the period ratio waveform and the smoothed period ratio waveform of the period ratio waveform. The bearing damage detection method according to claim 14.

16. Obtain a period ratio average value waveform obtained by averaging the differences corresponding to the same rotational position of the rolling bearing in the period ratio difference waveform for each rotational position. Obtain the waveform of the rotational fluctuation signal based on the period ratio fluctuation waveform obtained by obtaining the difference between the period ratio difference waveform and the period ratio average value waveform for each rotational position. The bearing damage detection method according to claim 15.

17. Obtain the period ratio average value waveform using the rotation signal for which the period ratio difference waveform was obtained, or a rotation signal continuously output following the rotation signal. The bearing damage detection method according to claim 16.

18. Regarding the pulse of the first pulse signal based on the rotation signal detected at one end in the horizontal direction or the pulse of the second pulse signal based on the rotation signal detected at the other end in the horizontal direction at the intermediate position in the vertical direction of the rolling bearing, a rotation period waveform representing the transition of the rotation period T for one rotation of the rolling bearing centered on the pulse, and A phase difference waveform representing the transition of the phase difference PD between the pulses of the first pulse signal and the second pulse signal, are obtained, and the waveform of the rotational fluctuation signal is obtained based on the phase difference ratio waveform representing the ratio PD / T of the phase difference PD to the rotation period T. The bearing damage detection method according to claim 13.

19. Obtain the waveform of the rotational fluctuation signal based on the phase difference ratio difference waveform representing the difference between the phase difference ratio waveform and the smoothed phase difference ratio waveform of the phase difference ratio waveform. The bearing damage detection method according to claim 18.

20. Obtain a phase difference ratio average value waveform obtained by averaging the differences corresponding to the same rotational position of the rolling bearing in the phase difference ratio difference waveform for each rotational position. Based on the phase difference variation waveform obtained by calculating the difference between the phase difference ratio differential waveform and the phase difference ratio average value waveform for each rotational position, the waveform of the rotational variation signal is determined. The bearing damage detection method according to claim 19.

21. The phase difference ratio average value waveform is determined using the rotation signal for which the phase difference ratio differential waveform is obtained, or a rotation signal that is continuously output following the rotation signal. The bearing damage detection method according to claim 20.

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