Method for Measuring Revolution Period of Rolling Elements of Rolling Bearing, Method for Detecting State of Rolling Bearing, Measuring Device, Condition Monitoring Device, and Program

Abstract

A measuring device for measuring the revolution period of rolling elements of a rolling bearing, comprising: an acquisition means for acquiring waveform data of a current and a voltage applied to the rolling bearing; a calculation means for calculating an instantaneous amplitude and an instantaneous phase from the waveform data using a Hilbert transform; a derivation means for deriving an impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; and a specifying means for specifying the period of the impedance using an autocorrelation function and specifying it as the revolution period of the rolling elements of the rolling bearing.

Description

Technical Field

[0001] The present invention relates to a method for measuring the revolution period of rolling elements of a rolling bearing, a method for detecting the state of a rolling bearing, a measuring device, a state detecting device, and a program.

Background Art

[0002] Conventionally, in a rolling bearing, abnormal conditions such as seizure may occur as a result of its rotational operation. Seizure affects the operation of the rolling bearing, and as the condition progresses, it may cause the device to stop or malfunction. For the proper operation of a rolling bearing, it is effective to detect a sign of the occurrence of seizure. One of the causes of seizure is the occurrence of revolution slip around the rolling elements in the rolling bearing. In conventional methods, for example, methods for detecting revolution slip by focusing on strain gauges, vibration, ultrasonic waves, overcurrent, etc. are known.

[0003] For example, Patent Document 1 discloses a method for monitoring the state of a rolling bearing by detecting the number of revolutions by ultrasonic waves and monitoring the revolution slip based on the number of revolutions. Further, Patent Document 2 discloses a method for diagnosing abnormalities in a rolling bearing based on the peak value of frequency spectrum data based on the detected vibration of the rolling bearing.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Strain gauges, ultrasonic sensors, etc. used in the above-described conventional technologies have certain constraints for installation. Also, in a configuration where high-speed rotation is performed by a rolling bearing, a higher sampling period of the detection value is required to perform more accurate measurement. Therefore, for example, a method for accurately measuring the revolution period of rolling elements in a rolling bearing with a simple configuration is required for the condition monitoring of the rolling bearing.

[0006] In view of the above problems, an object of the present invention is to provide a method for measuring the revolution period of rolling elements in a rolling bearing that performs high-speed rotation with a simple configuration.

Means for Solving the Problems

[0007] To solve the above problems, the present invention has the following configuration. That is, a measuring device for measuring the revolution period of rolling elements of a rolling bearing, acquisition means for acquiring waveform data of current and voltage applied to the rolling bearing; calculation means for calculating instantaneous amplitude and instantaneous phase from the waveform data using Hilbert transform; derivation means for deriving impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; specification means for specifying the period of the impedance using an autocorrelation function and specifying it as the revolution period of the rolling elements of the rolling bearing; A measuring device having

[0008] Also, another form of the present invention has the following configuration. That is, a state detection device for a rolling bearing, acquisition means for acquiring waveform data of current and voltage applied to the rolling bearing; calculation means for calculating instantaneous amplitude and instantaneous phase from the waveform data using Hilbert transform; derivation means for deriving impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; Specific means for identifying the period of the impedance using an autocorrelation function and identifying it as the revolution period of the rolling elements of the rolling bearing; Detection means for detecting revolution slip in the rolling bearing in response to the revolution period falling below a predetermined threshold value; Notification means for notifying the state of the rolling bearing based on the detection result by the detection means; A state detection device having the above.

[0009] Another aspect of the present invention has the following configuration. That is, a measurement method for measuring the revolution period of the rolling elements of a rolling bearing, comprising: An acquisition step of acquiring waveform data of current and voltage applied to the rolling bearing; A calculation step of calculating the instantaneous amplitude and the instantaneous phase from the waveform data using Hilbert transform; A derivation step of deriving impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; A specific step of identifying the period of the impedance using an autocorrelation function and identifying it as the revolution period of the rolling elements of the rolling bearing; A measurement method having the above.

[0010] Another aspect of the present invention has the following configuration. That is, a state detection method for a rolling bearing, comprising: An acquisition step of acquiring waveform data of current and voltage applied to the rolling bearing; A calculation step of calculating the instantaneous amplitude and the instantaneous phase from the waveform data using Hilbert transform; A derivation step of deriving impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; A specific step of identifying the period of the impedance using an autocorrelation function and identifying it as the revolution period of the rolling elements of the rolling bearing; A detection step of detecting revolution slip in the rolling bearing in response to the revolution period falling below a predetermined threshold value; A notification step of notifying the state of the rolling bearing based on the detection result by the detection step; A state detection method having

[0011] Another aspect of the present invention has the following configuration. That is, a program that causes a computer to perform an acquisition step of acquiring waveform data of current and voltage applied to a rolling bearing; perform a calculation step of calculating an instantaneous amplitude and an instantaneous phase from the waveform data using a Hilbert transform; perform a derivation step of deriving impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; perform an identification step of identifying the period of the impedance using an autocorrelation function and identifying it as the revolution period of the rolling elements of the rolling bearing; A program for causing the above to be executed.

[0012] Another aspect of the present invention has the following configuration. That is, a program that causes a computer to perform an acquisition step of acquiring waveform data of current and voltage applied to a rolling bearing; perform a calculation step of calculating an instantaneous amplitude and an instantaneous phase from the waveform data using a Hilbert transform; perform a derivation step of deriving impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; perform an identification step of identifying the period of the impedance using an autocorrelation function and identifying it as the revolution period of the rolling elements of the rolling bearing; perform a detection step of detecting revolution slip in the rolling bearing in response to the revolution period falling below a predetermined threshold; perform a notification step of notifying the state of the rolling bearing based on the detection result of the detection step; A program for causing the above to be executed.

Advantages of the Invention

[0013] According to the present invention, it is possible to measure the revolution period of rolling elements in a rolling bearing that rotates at high speed with a simple configuration.

Brief Description of the Drawings

[0014]

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Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings and the like. Note that the embodiments described below are one embodiment for explaining the present invention and are not intended to be construed as limiting the present invention, and not all the configurations described in each embodiment are essential configurations for solving the problems of the present invention. Also, in each drawing, the same reference numerals are given to the same components to indicate the correspondence.

[0016] <First Embodiment> Hereinafter, the first embodiment of the present invention will be described. Examples of the types of rolling bearings to which the method for measuring the revolution period of the rolling elements of the rolling bearing according to the present invention and the method for detecting the state of the rolling bearing are applicable include deep groove ball bearings, angular ball bearings, tapered roller bearings, cylindrical roller bearings, self-aligning roller bearings, and the like. However, the present invention is not limited to these, and any rotating device such as other bearings and gear devices can be applied as long as the waveform data of the current and voltage described later can be acquired.

[0017] FIG. 1 is a diagram showing a configuration example of a measurement system 1 to which the measurement method and the state detection method according to the present embodiment can be applied. The measurement system 1 includes a rolling bearing 10 to be measured, an information processing device 20, and an oscilloscope 30. Although not an essential element in the method according to the present embodiment, the measurement system 1 in FIG. 1 is shown including an LCR meter 40 used in the test described later.

[0018] The rolling bearing 10 is connected to a rotating shaft 15 and is configured to be rotatable. Here, the inner ring is described as a rotating ring and the outer ring is described as a fixed ring. A configuration example of the rolling bearing 10 will be described with reference to FIG. 2. The rotating shaft 15 is connected to a motor (not shown) and is rotated while applying a load (radial load, axial load) in a predetermined direction to the rolling bearing 10. In the present embodiment, it is assumed that the information processing device 20 controls the rotation of the motor (not shown) and the load applied to the rolling bearing 10, but a separate control device (not shown) may be used to control the rotation operation of the rolling bearing 10.

[0019] The information processing device 20 includes a control unit 21, a storage unit 22, an IF (Interface) unit 23, a UI (User Interface) unit 24, and a communication unit 25. The information processing device 20 may be configured by a general-purpose information processing device such as a PC (Personal Computer), or may be configured as a dedicated device.

[0020] The control unit 21 of the information processing apparatus 20 may be composed of a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a DSP (Digital Single Processor), or a dedicated circuit, etc. The storage unit 22 is composed of volatile and non-volatile storage media such as an HDD (Hard Disk Drive), a ROM (Read Only Memory), and a RAM (Random Access Memory), and can input and output various information according to instructions from the control unit 21.

[0021] The IF unit 23 is an interface for connecting to an external device. In this embodiment, it is configured to be able to transmit and receive data with an oscilloscope 30 and an LCR meter 40. The UI unit 24 receives operations from the user and displays various information such as measurement results. For example, the UI unit 24 is composed of a display device such as a speaker, a light, or a liquid crystal display, etc., and outputs to the user according to instructions from the control unit 21. The output method by the UI unit 24 is not particularly limited, but for example, it may be a visual output by screen output or an auditory output by sound. The communication unit 25 is a network interface for communicating with an external device.

[0022] The oscilloscope 30 is electrically connected to the rolling bearing 10 and the rotating shaft 15, and measures the current and voltage applied thereto. In this embodiment, the oscilloscope 30 uses an AC power supply and regards the rolling bearing 10 as an electric circuit for measurement. The oscilloscope 30 appropriately provides the measurement results to the information processing apparatus 20. The LCR meter 40 is electrically connected to the rolling bearing 10 and the rotating shaft 15, applies an AC power supply thereto, and measures impedance and phase. The LCR meter 40 appropriately provides the measurement results to the information processing apparatus 20. The measurement results of the oscilloscope 30 and the LCR meter 40 are managed by the information processing apparatus 20 in association with the measurement timing (such as time information).

[0023] (Load range of the rolling bearing) Figure 2 is a schematic diagram for explaining the change of rolling elements in the load zone of the rolling bearing 10 during the rotation operation. The rolling bearing 10 includes an outer ring 11, a plurality of rolling elements 12 such as balls, a cage 13 for holding the rolling elements 12, and an inner ring 14. A lubricant (not shown) is filled around the rolling elements 12 to lubricate between the members. The outer ring 11 is a fixed ring and is fixed to a housing (not shown). Further, the inner ring 14 is a rotating ring, is connected to the rotating shaft 15, and is configured to be rotatable integrally with the rotating shaft 15. The rotating shaft 15 is transmitted with a driving force from a motor (not shown) and performs a rotation operation. Here, as an example, nine ball rolling elements 12 are shown, but it is not limited thereto.

[0024] A load in a predetermined direction is applied to the rolling bearing 10 via the rotating shaft 15. In the example of FIG. 2, the radial load applied to the rolling bearing 10 is indicated by an arrow. During the rotation operation of the rolling bearing 10, according to the positions of the plurality of rolling elements 12 and the load direction, the contact state between the rolling elements 12 and the outer ring 11 and the inner ring 14 and the number of rolling elements 12 included in the load zone change. FIG. 2(a) shows a state in which two (i.e., an even number) of rolling elements 12 are included in the load zone 201 of the radial load. FIG. 2(b) shows a state in which one (i.e., an odd number) of rolling elements 12 is included in the load zone 202 of the radial load.

[0025] Due to the rotation operation of the rolling bearing 10, the state as shown in FIG. 2 is periodically repeated. By grasping this periodicity, it is possible to specify the revolution period of the rolling element 12. In the present embodiment, based on the current and voltage measured by the oscilloscope 30, the revolution period of the rolling element 12 is grasped.

[0026] [Sign of Seizure] Here, the relationship between the revolution period of the rolling element 12 accompanying the rotation operation of the rolling bearing 10 and the sign of seizure in the rolling bearing 10 will be described. There is a certain correlation between the revolution period of the rolling element 12, that is, the frequency of the period during which the rolling element 12 passes through the load zone, and the sign of seizure.

[0027] For example, assuming that the timing when the rotational operation of the rolling bearing 10 starts is t0 and the rotational operation continues. And it is assumed that seizure has occurred inside the rolling bearing 10 at the timing t2 when a certain period of time has elapsed. In this case, for example, when revolution slip occurs inside the rolling bearing 10, it is known that a decrease in frequency (downward peak value) occurs at the timing t1 (<t2) before the timing t2. Such an event regarding the relationship between damage inside the rolling bearing and the measured value is also disclosed in Japanese Patent Application Laid-Open No. 2006-17291 by the applicant of the present application. That is, by paying attention to the decrease in frequency of the revolution slip that occurs before seizure, it is possible to capture it as a sign of the occurrence of seizure inside the rolling bearing 10. In the present embodiment, when the frequency of the revolution period of the rolling element 12 falls below a previously defined threshold value, that is, when it is detected that revolution slip has occurred, it is treated as a sign of seizure. Note that in the present embodiment, an example is shown in which when revolution slip is detected once based on the frequency of the revolution period of the rolling element, it is treated as a sign of seizure, but the present invention is not limited to this. For example, when multiple occurrences of revolution slip are detected within a predetermined period, it may be specified as a sign of seizure.

[0028] [Waveform data] FIG. 3 shows the raw waveform data of the signal detected from the rolling bearing 10 by the oscilloscope 30 according to the present embodiment. In FIG. 3, the horizontal axis represents time [s], the left vertical axis represents voltage [V], and the right vertical axis represents current [A]. FIG. 3(b) is an enlarged view of the region 301 shown in FIG. 3(a). Also, the waveform 302 in FIG. 3 indicates the current value, and the waveform 303 indicates the voltage value.

[0029] As an example, the sampling frequency is 50 [MS / s] and the AC frequency is 1 MHz. Also, an FIR (Finite Impulse Response) filter is applied to the raw waveform data.

[0030] Figure 4 shows an example of performing a Hilbert transform on waveform data of current and voltage. The horizontal axis in Figure 4 indicates time [s], and it is assumed to correspond respectively. Also, in Figure 4(a), waveform 401 represents the current value, and waveform 402 represents the voltage value. By performing the Hilbert transform, the waveform is captured as a complex number, and the instantaneous amplitude and instantaneous phase are obtained as instantaneous information regarding the change in the waveform. Since the Hilbert transform is a known method, detailed explanation thereof is omitted.

[0031] In the Hilbert transform, the instantaneous amplitude A(t) and the instantaneous phase θ(t) are obtained using the following equations (1) to (3).

[0032]

Equation

[0033] Figure 4(a) shows the values of current and voltage measured with the oscilloscope 30. The left vertical axis indicates voltage [V], and the right vertical axis indicates current [A]. Figure 4(b) shows the instantaneous amplitude A(t) obtained based on the waveform data in Figure 4(a). The left vertical axis in Figure 4(b) indicates voltage [V], and the right vertical axis indicates current [A]. Waveform 411 represents the current value, and waveform 412 represents the voltage. Figure 4(c) shows the instantaneous phase θ(t) obtained based on the waveform data in Figure 4(b). The vertical axis indicates phase [°]. Waveforms 421 and 422 represent the phases of the current and voltage. At this time, the phase difference between the current and voltage is indicated by θ.

[0034] Figure 5 is a graph showing an example of deriving the impedance |Z| and the phase θ from the waveform data detected with the oscilloscope 30. In Figure 5, the horizontal axis indicates time [s], and it is assumed to correspond. Figure 5(a) is the waveform data detected with the oscilloscope 30. The left vertical axis indicates voltage [V], and the right vertical axis indicates current [A].

[0035] Figure 5(b) shows the impedance |Z| [Ω] calculated based on the waveform data in Figure 5(a). Also, Figure 5(c) shows the phase θ [°] calculated based on the waveform data in Figure 5(a). The Z shown in Figure 5(b) and Figure 5(c)LCR and θ LCR are the results measured by the LCR meter 40 respectively.

[0036] As shown in Fig. 5(b) and Fig. 5(c), the impedance |Z| and phase θ calculated from the waveform data measured by the oscilloscope 30, and the impedance Z and phase θ measured by the LCR meter 40 LCR and phase θ LCR can obtain substantially equivalent values.

[0037] Furthermore, in the present embodiment, using the values of the impedance |Z| and phase θ as shown in Fig. 5(b) and Fig. 5(c), and the autocorrelation function, the number of revolutions and the number of rotations of the rolling element 12 are calculated. The theoretical value of the number of revolutions of the rolling element used for comparison is calculated using the known mathematical formula shown in Fig. 6. Here, as shown in Fig. 6(b), the calculation is performed assuming that the rotation angle β = contact angle α (inner and outer rings). The parameters shown in Fig. 6(b) are as follows. ω i : Inner ring rotation speed ω o : Outer ring rotation speed ω c : Revolution speed ω b : Rotation speed α: Contact angle of the bearing β: Rotation angle D pw : Pitch diameter of the rolling element D w : Diameter of the rolling element

[0038] [Test example] Figs. 7 to 9 show test examples for verifying the measurement method according to the present embodiment. Each test uses the system configuration example shown in Fig. 1. First, the common test conditions for each test are as follows.

[0039] (Common conditions) Model number: Deep groove ball bearing (6306) Rotation speed: 400 [min -1 Lubricant: PAO (polyalphaolefin) - based lubricating oil Kinematic viscosity: 128 [mm​2 / s](40 °C) Sine wave voltage: 0.5 - 0.8 [V] AC frequency: 1000000 [Hz]

[0040] And the test conditions that are different from those shown in FIGS. 7 to 9 were set as follows, respectively.

[0041] (Test condition 1) Radial load: 100 [N] Axial load: 0 [N] Measurement timing: 3 minutes after the start of rotation

[0042] (Test condition 2) Radial load: 100 [N] Axial load: 0 [N] Measurement timing: Immediately after the start of rotation

[0043] (Test condition 3) Radial load: 200 [N] Axial load: 0 [N] Measurement timing: 3 minutes after the start of rotation

[0044] FIG. 7(a) shows the raw waveform data of the voltage and current measured by the oscilloscope 30 under Test Condition 1. FIGS. 7(b) and 7(c) show the impedance |Z| and the phase θ calculated based on the raw waveform data shown in FIG. 7(a). The broken lines shown in FIGS. 7(b) and 7(c) indicate the values measured by the LCR meter 40. These have the same configuration as the graph shown in FIG. 5.

[0045] FIG. 7(d) shows the waveform data obtained by applying the impedance |Z| and the phase θ shown in FIGS. 7(b) and 7(c) to the autocorrelation function. In FIG. 7(d), the horizontal axis indicates time [s], and the vertical axis indicates the value of the autocorrelation function. The broken line in FIG. 7(d) indicates the theoretical value T theory of the revolution period of the rolling element. The theoretical value T theory can be calculated by the formula shown in FIG. 6 and the following formula (4). T theory= 60 / Revolution speed of rolling elements [min -1 / Number of rolling elements ···(4)

[0046] As shown in Fig. 7(d), the theoretical value T theory and the value of the peak position obtained by the autocorrelation function match. Based on the values obtained by the oscilloscope 30, it can be seen that the revolution period of the rolling elements can be accurately measured. In other words, the revolution period of the rolling elements coincides with the period of the impedance |Z|.

[0047] Fig. 8(a) shows the raw waveform data of the voltage and current measured by the oscilloscope 30 under Test Condition 2. Figs. 8(b) and 8(c) show the impedance |Z| and the phase θ calculated based on the raw waveform data shown in Fig. 8(a). The dashed lines shown in Figs. 8(b) and 8(c) indicate the values measured by the LCR meter 40. These have the same configuration as the graph shown in Fig. 5.

[0048] Fig. 8(d) shows the waveform data obtained by applying the impedance |Z| and the phase θ shown in Figs. 8(b) and 8(c) to the autocorrelation function. In Fig. 8(d), the horizontal axis represents time [s], and the vertical axis represents the value of the autocorrelation function. The dashed line in Fig. 8(d) indicates the theoretical value T theory of the revolution period of the rolling elements.

[0049] As shown in Fig. 8(d), the value of the peak position obtained by the autocorrelation function corresponding to the theoretical value T theory is slightly smoother compared to the value of the peak position in Fig. 7(d). In other words, it can be said that Test Condition 1 is more suitable for capturing the impedance period than Test Condition 2. The difference between Test Condition 1 and Test Condition 2 is the acquisition timing of the waveform data. As a result, waveform data acquired at a stable timing after rotation has been performed for a certain period, rather than immediately after the rolling bearing starts its rotational operation, enables more accurate measurement. In Test Condition 1, the acquisition timing is set to 3 minutes after the start of rotation, but this is just an example and may vary according to the configuration of the rolling bearing to be monitored.

[0050] Figure 9(a) shows the raw waveform data of voltage and current measured by the oscilloscope 30 under Test Condition 3. Also, Figures 9(b) and 9(c) show the impedance |Z| and phase θ calculated based on the raw waveform data shown in Figure 9(a). The dashed lines shown in Figures 9(b) and 9(c) indicate the values measured by the LCR meter 40. These have the same configuration as the graph shown in Figure 5.

[0051] Figure 9(d) shows the waveform data obtained by applying the impedance |Z| and phase θ shown in Figures 9(b) and 9(c) to the autocorrelation function. In Figure 9(d), the horizontal axis represents time [s], and the vertical axis represents the value of the autocorrelation function. Also, the dashed line in Figure 9(d) indicates the theoretical value T theory of the revolution period of the rolling element.

[0052] As shown in Figure 9(d), the value of the peak position obtained by the autocorrelation function corresponding to the theoretical value T theory is slightly smoother compared to the value of the peak position in Figure 7(d). In other words, it can be said that Test Condition 1 is more suitable for capturing the period of impedance than Test Condition 3. The difference between Test Condition 1 and Test Condition 3 is the magnitude of the load, more specifically, the magnitude of the radial load. As a result, it becomes possible to perform more accurate measurement with the waveform data obtained in a state where the radial load on the rolling bearing is reduced. In Test Condition 1, the radial load is 100 N, but this is just an example and may vary according to the configuration of the rolling bearing to be monitored.

[0053] (Correlation between Radial Load and Periodicity of Impedance) Figure 10 is a graph for explaining the correlation between the radial load, the contact area of the rolling elements in the rolling bearing, and the number of rolling elements located in the load zone. As described with reference to FIG. 2, the number of rolling elements included in the load zone changes according to the rotation of the rolling elements and the degree of the load. That is, in the rotational operation, the number of rolling elements included in the load zone changes while the even / odd numbers are interchanged. In this example, as an index of the contact area of the rolling elements in the load zone, the ratio of even contact to odd contact as shown in the following formula (5) is used. (Contact area ratio) = (Total area in even contact (average of inner and outer rings)) / (Total area in odd contact (average of inner and outer rings)) ···(5)

[0054] The horizontal axis of FIG. 10 indicates the radial load Fr [N], the left vertical axis indicates the contact area ratio, and the right vertical axis indicates the number (average) of rolling elements in the load zone. In FIG. 10, the axial load Fa = 0. Graph 1001 shows the relationship between the contact area ratio and the radial load. Graph 1002 shows the relationship between the number of rolling elements in the load zone and the radial load. As shown in Graph 1002, as the radial load increases, the average number of rolling elements in the load zone increases. For Graph 1002, the value indicated by the broken line (contact area ratio = 1.0) is set. Here, the contact area ratio deviates from 1 as the radial load becomes smaller. Based on the test results and the like shown in FIGS. 7 to 9, the inventors have specified that the periodicity of the impedance |Z| is more easily captured as the contact area ratio deviates from 1.0.

[0055] For example, based on the graph shown in FIG. 10 and the above-described test conditions 1 (radial load: 100 [N]) and test condition 3 (radial load: 200 [N]), it can be said that the contact area ratio of test condition 1 is further away from 1.0 and is in a state where the periodicity is more easily captured. In the present embodiment, based on such a correlation, the magnitude of the radial load at the time of measurement is defined so that the contact area ratio deviates from 1.0.

[0056] (Correlation between the combined load and the periodicity of the impedance) FIG. 11 is a graph for explaining the correlation between the combined load, the contact area of the rolling elements in the rolling bearing, and the number of rolling elements located in the loaded zone. The contact area ratio and the number of rolling elements included in the loaded zone are the same as those described in FIG. 10.

[0057] FIGS. 11(a), 11(b), and 11(c) respectively show graphs when the combined load F is 100, 1000, and 10000 [N]. In FIG. 11, the horizontal axis represents the direction Df of the load, Df = 0 [°] corresponds to a pure radial load (Fa = 0 [N]), and Df = 90 [°] corresponds to a pure axial load (Fr = 0 [N]).

[0058] In FIGS. 11(a) to 11(c), graphs 1101, 1111, and 1121 show the relationship between the number of rolling elements in the loaded zone and the direction of the combined load. In any of the graphs 1101, 1111, and 1121, as the direction of the combined load approaches 90°, that is, as it approaches a pure axial load, the number of rolling elements in the loaded zone increases.

[0059] In FIGS. 11(a) to 11(c), graphs 1102, 1112, and 1122 show the relationship between the contact area ratio in the loaded zone and the direction of the combined load. In any of the graphs 1102, 1112, and 1122, as the direction of the combined load approaches 0°, that is, as it approaches a pure radial load, the contact area ratio tends to deviate from 1.0. In this embodiment, based on such a correlation, the direction of the combined load during measurement is defined so that the contact area ratio deviates from 1.0. More preferably, the combined load is defined so as to be a pure radial load.

[0060] (Application Range Based on Rotation Speed) The conditions for the rotation speed of the rolling bearing in the measurement method according to this embodiment will be described. In the measurement method according to this embodiment, the upper limit of the rotation speed that satisfies the conditions shown in the following formula (6) is taken as the application range of this method.

[0061]

Equation

[0062] The range defined by the above formula is, for example, in the example of FIG. 7, sampling at point p within the range of time 0 to T theory is defined. More specifically, when p = 100, N = 75000 [min -1 , and it can be applied up to a rotational speed of the rotating wheel of 200000 [min -1 .

[0063] [Processing Flow] FIG. 12 is a flowchart of the method for detecting the state of the rolling bearing according to the present embodiment. The state detection method here is based on a measurement method that takes into account the correlation between the period of impedance based on the waveform data of the current and voltage detected by the oscilloscope 30 as described above and the revolution period of the rolling elements of the rolling bearing. This process is executed by the information processing device 20. For example, the control unit 21 included in the information processing device 20 may read and execute a program for realizing the process according to the present embodiment from the storage unit 22. Further, this processing flow may be executed at an arbitrary timing based on a user's instruction. As described above, in this flowchart, the measurement by the LCR meter 40 may be omitted.

[0064] In S1201, the information processing device 20 starts the rotation operation of the rolling bearing 10 to be detected. The rotation operation here may be started by the information processing device 20 transmitting a control signal to a motor (not shown), or may be started in cooperation with another control device (not shown) to rotate the rolling bearing 10. Also, the rotational speed of the rotation operation is within the range defined by the above formula (6).

[0065] In S1202, the information processing apparatus 20 applies a predetermined load to the rolling bearing 10 to be detected via the rotating shaft 15. The load here may be applied by the information processing apparatus 20 transmitting a control signal to a motor (not shown) or the like, or the load may be applied to the rolling bearing 10 in cooperation with another control apparatus (not shown). In the present embodiment, it is assumed that a combined load of a radial load and an axial load can be applied, and the load is applied based on the conditions described with reference to FIGS. 10 and 11. For example, a predetermined radial load is applied. The start of the rotation operation in S1201 and the start of the load application in S1202 may be performed substantially simultaneously and integrally.

[0066] In S1203, the information processing apparatus 20 acquires waveform data by measuring the current and voltage applied to the rolling bearing 10 with an oscilloscope 30 at a timing when a predetermined time has elapsed since the start of the rotation operation in S1201. The predetermined timing here is defined in advance based on the conditions described with reference to FIGS. 7 and 8, for example.

[0067] In S1204, the information processing apparatus 20 calculates the instantaneous amplitude and instantaneous phase of the current and voltage using Hilbert transform for the waveform data acquired in S1203. Note that the information processing apparatus 20 may apply a predetermined filtering process (for example, a FIR filter) to the waveform data before applying the Hilbert transform. Further, a decimation process or a filtering process (for example, a median filter) may be applied to the data after applying the Hilbert transform. The decimation interval and the window size of the median filter in this case may be set to arbitrary values.

[0068] In S1205, the information processing apparatus 20 derives the impedance |Z| using the current value and voltage value of the waveform data acquired in S1203 and the instantaneous amplitude and instantaneous phase calculated in S1204.

[0069] In S1206, the information processing apparatus 20 derives the period of the impedance |Z| derived in S1205 using the autocorrelation function.

[0070] In S1207, the information processing apparatus 20 determines whether or not the period of the impedance |Z| derived in S1206 is less than a predetermined threshold value. The predetermined threshold value here is defined in advance corresponding to the specifications of the rolling bearing 10 and is held in the storage unit 22. When the period is less than the predetermined threshold value (YES in S1207), the process of the information processing apparatus 20 proceeds to S1208. In this case, it means that revolution slip has occurred inside the rolling bearing 10. That is, it corresponds to the detection of the peak value corresponding to the occurrence of revolution slip. On the other hand, when the period is not less than the predetermined threshold value (NO in S1207), this processing flow is terminated.

[0071] In S1208, the information processing apparatus 20 notifies that there is a sign of seizure in the rolling bearing 10 which is the detection target. Then, this processing flow is terminated.

[0072] Note that, although an example where no special notification is made when the threshold value is not exceeded in the process of S1207 above has been shown, it may be notified that no revolution slip has occurred inside the rolling bearing 10 which is the detection target, that is, there is no sign of seizure.

[0073] As described above, according to the configuration of the present embodiment, for example, based on the waveform data of the current and voltage acquired by an oscilloscope, it becomes possible to measure the revolution period of the rolling elements of the rolling bearing. Furthermore, based on the revolution period, it becomes possible to detect a sign of seizure in the rolling bearing and detect it before an abnormality actually occurs.

[0074] <Other Embodiments> Also, in the present invention, a program or application for realizing the functions of one or more of the above-described embodiments is supplied to a system or apparatus using a network or a storage medium or the like, and a process in which one or more processors in the computer of the system or apparatus reads and executes the program can also realize it.

[0075] Alternatively, it may be implemented by a circuit (e.g., an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array)) that realizes one or more functions.

[0076] 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 the combination of the respective configurations of the embodiments, the description of the specification, and well-known techniques, which are included in the scope for which protection is sought.

[0077] As described above, the following matters are disclosed in this specification. (1) A measuring device (e.g., 20) for measuring the revolution period of a rolling element (e.g., 12) of a rolling bearing (e.g., 10), an acquisition means (e.g., 23) for acquiring waveform data of a current and a voltage applied to the rolling bearing, a calculation means (e.g., 21) for calculating an instantaneous amplitude and an instantaneous phase from the waveform data using a Hilbert transform, a derivation means (e.g., 21) for deriving an impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase, a specifying means (e.g., 21) for specifying the period of the impedance using an autocorrelation function and specifying it as the revolution period of the rolling element of the rolling bearing, and a measuring device having the above. According to this configuration, it becomes possible to measure the revolution period of the rolling element of the rolling bearing based on the waveform data of the current and the voltage.

[0078] (2) The measuring device according to (1), wherein the acquisition means acquires waveform data after a predetermined time has elapsed since the rolling bearing starts to rotate. According to this configuration, it becomes possible to measure the revolution period of the rolling element of the rolling bearing with higher accuracy.

[0079] (3) The acquisition means acquires waveform data in a state where a predetermined radial load is applied to the rolling bearing, and the measuring device according to (1) or (2). According to this configuration, it becomes possible to measure the revolution period of the rolling elements of the rolling bearing with higher accuracy.

[0080] (4) A state detection device (for example, 20) for a rolling bearing (for example, 10), acquisition means (for example, 23) for acquiring waveform data of current and voltage applied to the rolling bearing; calculation means (for example, 21) for calculating instantaneous amplitude and instantaneous phase from the waveform data using Hilbert transform; derivation means (for example, 21) for deriving impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; specification means (for example, 21) for specifying the period of the impedance using an autocorrelation function and specifying it as the revolution period of the rolling elements (for example, 12) of the rolling bearing; detection means (for example, 21) for detecting revolution slip in the rolling bearing in response to the revolution period falling below a predetermined threshold; notification means (for example, 24) for notifying the state of the rolling bearing based on the detection result by the detection means; A state detection device having the above. According to this configuration, based on the waveform data of current and voltage, the revolution period of the rolling elements of the rolling bearing can be accurately measured, and based on the revolution period, a sign of seizure in the rolling bearing can be detected before an abnormality actually occurs.

[0081] (5) A measuring method for measuring the revolution period of rolling elements (for example, 12) of a rolling bearing (for example, 10), an acquisition step (for example, S1201 to S1203) for acquiring waveform data of current and voltage applied to the rolling bearing; a calculation step (for example, S1204) for calculating instantaneous amplitude and instantaneous phase from the waveform data using Hilbert transform; A derivation step (for example, S1205) of deriving impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; A specifying step (for example, S1206) of specifying the period of the impedance using an autocorrelation function and specifying it as the revolution period of the rolling elements of the rolling bearing; A measuring method having: According to this configuration, it becomes possible to measure the revolution period of the rolling elements of the rolling bearing with higher accuracy.

[0082] (6) A method for detecting the state of a rolling bearing (for example, 10), comprising: An acquisition step (for example, S1201 to S1203) of acquiring waveform data of current and voltage applied to the rolling bearing; A calculation step (for example, S1204) of calculating an instantaneous amplitude and an instantaneous phase from the waveform data using a Hilbert transform; A derivation step (for example, S1205) of deriving impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; A specifying step (for example, S1206) of specifying the period of the impedance using an autocorrelation function and specifying it as the revolution period of the rolling elements of the rolling bearing; A detection step (for example, S1207) of detecting revolution slip in the rolling bearing in response to the revolution period falling below a predetermined threshold; A notification step (for example, S1208) of notifying the state of the rolling bearing based on the detection result of the detection step; A state detection method having: According to this configuration, based on the waveform data of current and voltage, it is possible to accurately measure the revolution period of the rolling elements of the rolling bearing, capture a sign of seizure in the rolling bearing based on the revolution period, and detect it before an abnormality actually occurs.

[0083] (7) A computer (for example, 20) is caused to perform: An acquisition step (for example, S1201 to S1203) of acquiring waveform data of current and voltage applied to a rolling bearing (for example, 10); A calculating step (e.g., S1204) of calculating the instantaneous amplitude and the instantaneous phase from the waveform data using Hilbert transform; A deriving step (e.g., S1205) of deriving impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; A specifying step (e.g., S1206) of specifying the period of the impedance using an autocorrelation function and specifying it as the revolution period of the rolling elements of the rolling bearing; A program for causing the above to be executed. According to this configuration, it becomes possible to measure the revolution period of the rolling elements of the rolling bearing with higher accuracy.

[0084] (8) A computer (e.g., 20) is caused to An acquisition step (e.g., S1201 to S1203) of acquiring waveform data of current and voltage applied to a rolling bearing (e.g., 10); A calculating step (e.g., S1204) of calculating the instantaneous amplitude and the instantaneous phase from the waveform data using Hilbert transform; A deriving step (e.g., S1205) of deriving impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; A specifying step (e.g., S1206) of specifying the period of the impedance using an autocorrelation function and specifying it as the revolution period of the rolling elements (e.g., 12) of the rolling bearing; A detecting step (e.g., S1207) of detecting revolution slip in the rolling bearing in response to the revolution period falling below a predetermined threshold; A notifying step (e.g., S1208) of notifying the state of the rolling bearing based on the detection result of the detecting step; A program for causing the above to be executed. According to this configuration, based on the waveform data of current and voltage, it becomes possible to accurately measure the revolution period of the rolling elements of the rolling bearing, capture a sign of seizure in the rolling bearing based on the revolution period, and detect it before an abnormality actually occurs.

[0085] The various embodiments have been described above with reference to the drawings. Needless to say, the present invention is not limited to such examples. It is obvious that those skilled in the art can conceive of various modifications or corrections within the scope described in the claims, and it is naturally understood that they also belong to the technical scope of the present invention. Also, within the scope not departing from the gist of the invention, the components in the above embodiments may be arbitrarily combined.

[0086] This application is based on a Japanese patent application (Japanese Patent Application No. 2023-177664) filed on October 13, 2023, the content of which is incorporated herein by reference.

Explanation of Reference Numerals

[0087] 1... Measurement system 10... Rolling bearing 11... Outer ring 12... Rolling element 13... Cage 14... Inner ring 15... Rotating shaft 20... Information processing device 21... Control unit 22... Storage unit 23... IF unit 24... UI unit 25... Communication unit 30... Oscilloscope 40... LCR meter

Claims

1. A measuring device for measuring the revolution period of a rolling element of a rolling bearing, comprising: The rolling bearing includes an outer ring, a plurality of the rolling elements, and an inner ring, and rotatably supports a rotating shaft connected to the inner ring, The measuring device is an acquisition means for acquiring waveform data of the current and voltage applied to the rolling bearing from a measuring device that is electrically connected to the outer ring and the rotating shaft and measures the current and voltage applied to the rolling bearing; a calculation means for calculating an instantaneous amplitude and an instantaneous phase from the waveform data using a Hilbert transform; a derivation means for deriving an impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; an identification means for identifying a period of the impedance using an autocorrelation function and identifying the period as a revolution period of the rolling elements of the rolling bearing; A measuring device having

2. The measuring device according to claim 1 , wherein the acquiring means acquires the waveform data after a predetermined time has elapsed since the rolling bearing started to rotate.

3. The measuring device according to claim 1 , wherein the acquiring means acquires the waveform data in a state where a predetermined radial load is applied to the rolling bearing.

4. A rolling bearing condition detection device, comprising: The rolling bearing includes an outer ring, a plurality of rolling elements, and an inner ring, and rotatably supports a rotating shaft connected to the inner ring, The state detection device is an acquisition means for acquiring waveform data of the current and voltage applied to the rolling bearing from a measuring device that is electrically connected to the outer ring and the rotating shaft and measures the current and voltage applied to the rolling bearing; a calculation means for calculating an instantaneous amplitude and an instantaneous phase from the waveform data using a Hilbert transform; a derivation means for deriving an impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; an identification means for identifying a period of the impedance using an autocorrelation function and identifying the period as a revolution period of the rolling elements of the rolling bearing; a detection means for detecting an orbital slip in the rolling bearing in response to the orbital period falling below a predetermined threshold value; a notification means for notifying a state of the rolling bearing based on a detection result by the detection means; A state detection device having the following:

5. A method for measuring the revolution period of a rolling element of a rolling bearing, comprising the steps of: The rolling bearing includes an outer ring, a plurality of the rolling elements, and an inner ring, and rotatably supports a rotating shaft connected to the inner ring, The measurement method includes: an acquiring step of acquiring waveform data of the current and voltage applied to the rolling bearing from a measuring instrument that is electrically connected to the outer ring and the rotating shaft and measures the current and voltage applied to the rolling bearing; a calculation step of calculating an instantaneous amplitude and an instantaneous phase from the waveform data using a Hilbert transform; deriving an impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; a step of identifying a period of the impedance using an autocorrelation function and identifying the period as a revolution period of a rolling element of the rolling bearing; A measurement method having the following characteristics.

6. A method for detecting a condition of a rolling bearing, comprising the steps of: The rolling bearing includes an outer ring, a plurality of rolling elements, and an inner ring, and rotatably supports a rotating shaft connected to the inner ring, The state detection method includes: an acquiring step of acquiring waveform data of the current and voltage applied to the rolling bearing from a measuring instrument that is electrically connected to the outer ring and the rotating shaft and measures the current and voltage applied to the rolling bearing; a calculation step of calculating an instantaneous amplitude and an instantaneous phase from the waveform data using a Hilbert transform; deriving an impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; a step of identifying a period of the impedance using an autocorrelation function and identifying the period as a revolution period of a rolling element of the rolling bearing; a detection step of detecting an orbital slip in the rolling bearing in response to the orbital period falling below a predetermined threshold value; a notification step of notifying a state of the rolling bearing based on a detection result by the detection step; A state detection method comprising:

7. A program for measuring the revolution period of a rolling element of a rolling bearing, comprising: The rolling bearing includes an outer ring, a plurality of the rolling elements, and an inner ring, and rotatably supports a rotating shaft connected to the inner ring, On the computer, an acquiring step of acquiring waveform data of the current and voltage applied to the rolling bearing from a measuring instrument that is electrically connected to the outer ring and the rotating shaft and measures the current and voltage applied to the rolling bearing; a calculation step of calculating an instantaneous amplitude and an instantaneous phase from the waveform data using a Hilbert transform; deriving an impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; a step of identifying a period of the impedance using an autocorrelation function and identifying the period as a revolution period of a rolling element of the rolling bearing; A program for executing.

8. A program for detecting the condition of a rolling bearing, comprising: The rolling bearing includes an outer ring, a plurality of rolling elements, and an inner ring, and rotatably supports a rotating shaft connected to the inner ring, On the computer, an acquiring step of acquiring waveform data of the current and voltage applied to the rolling bearing from a measuring instrument that is electrically connected to the outer ring and the rotating shaft and measures the current and voltage applied to the rolling bearing; a calculation step of calculating an instantaneous amplitude and an instantaneous phase from the waveform data using a Hilbert transform; deriving an impedance using the waveform data, the instantaneous amplitude, and the instantaneous phase; a step of identifying a period of the impedance using an autocorrelation function and identifying the period as a revolution period of a rolling element of the rolling bearing; a detection step of detecting an orbital slip in the rolling bearing in response to the orbital period falling below a predetermined threshold value; a notification step of notifying a state of the rolling bearing based on a detection result by the detection step; A program for executing.

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