State diagnosis method, state diagnosis device, and program

Abstract

In a method for diagnosing the state of a bearing device provided with a plurality of electrically connected rolling bearings, a voltage is applied to the plurality of rolling bearings while changing the frequency by means of an AC power source, thereby measuring the impedance of the entire plurality of rolling bearings, and the state of the bearing device is diagnosed on the basis of an equivalent circuit in which the plurality of rolling bearings are connected in series. And a diagnosis unit for determining the impedance of each of the plurality of rolling bearings by fitting the measured impedance to derive the impedance of each of the plurality of rolling bearings, and diagnosing the state of each of the plurality of rolling bearings on the basis of the derived impedance of each of the plurality of rolling bearings.

Description

Technical Field

[0001] The present invention relates to a state diagnosis method, a state diagnosis device and a program. Background Art

[0002] In the past, in rolling devices such as bearing devices, structures that use lubricants (e.g., lubricating oil, grease) to lubricate their rotation have been widely popularized. On the other hand, for rotating parts such as bearing devices, damage and wear are detected early by regularly performing status diagnosis to suppress the occurrence of failures of rotating parts.

[0003] In rolling devices using lubricants, it is required to appropriately detect the internal state in order to diagnose the operating state. On the other hand, depending on the type of device, multiple bearing devices are sometimes used to support the rotational motion. For example, Patent Document 1 shows the following structure: for a device having a structure in which a rotating shaft is supported by two rolling bearings, the state of the lubricating film of the rolling bearing is determined in a non-contact state with the rotating ring and the rolling element.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-239779 Summary of the invention

[0007] Problems to be solved by the invention

[0008] On the other hand, the method of Patent Document 1 uses the total value of the electrostatic capacitance of two rolling bearings for measurement. However, the method of Patent Document 1 cannot grasp the state of each rolling bearing. However, for a device having multiple rolling bearings, there is a demand to grasp the state of each rolling bearing with fewer measurements.

[0009] In view of the above problems, an object of the present invention is to provide a method capable of diagnosing the state of each rolling bearing based on the measurement results of the plurality of rolling bearings in a device including a plurality of rolling bearings.

[0010] Means for solving problems

[0011] In order to solve the above-mentioned problem, the present invention has the following configuration. That is, a state diagnosis method is a state diagnosis method of a bearing device, wherein the bearing device has a plurality of rolling bearings that are electrically connected,

[0012] The state diagnosis method comprises:

[0013] A measuring step of applying a voltage to the plurality of rolling bearings by using an AC power source while changing the frequency, thereby measuring the impedance of the plurality of rolling bearings as a whole;

[0014] a deriving step of fitting the impedance measured in the measuring step based on an equivalent circuit formed by connecting the plurality of rolling bearings in series, thereby deriving the impedance of each of the plurality of rolling bearings; and

[0015] The diagnosis step diagnoses the state of each of the plurality of rolling bearings based on the impedance of each of the plurality of rolling bearings derived in the deriving step.

[0016] In addition, another embodiment of the present invention has the following configuration. That is, a state diagnosis device is a state diagnosis device for a bearing device, wherein the bearing device includes a plurality of rolling bearings that are electrically connected,

[0017] The state diagnosis device comprises:

[0018] a measuring unit that applies a voltage to the plurality of rolling bearings by using an AC power source while changing a frequency, thereby measuring the impedance of the plurality of rolling bearings as a whole;

[0019] a deriving unit that derives the impedance of each of the plurality of rolling bearings by fitting the impedance measured by the measuring unit based on an equivalent circuit in which the plurality of rolling bearings are connected in series; and

[0020] A diagnosis unit is provided for diagnosing a state of each of the plurality of rolling bearings based on the impedance of each of the plurality of rolling bearings derived by the deriving unit.

[0021] In addition, another embodiment of the present invention has the following configuration. That is, a program that causes a computer to execute the following steps:

[0022] A measuring step of applying a voltage to a plurality of electrically connected rolling bearings using an AC power supply while changing the frequency, thereby measuring the impedance of the plurality of rolling bearings as a whole;

[0023] a deriving step of fitting the impedance measured in the measuring step based on an equivalent circuit in which the plurality of rolling bearings are connected in series, thereby deriving the impedance of each of the plurality of rolling bearings; and

[0024] The diagnosis step diagnoses the state of each of the plurality of rolling bearings based on the impedance of each of the plurality of rolling bearings derived in the deriving step.

[0025] Effects of the Invention

[0026] According to the present invention, in a device including a plurality of rolling bearings, the state of each rolling bearing can be diagnosed based on the measurement results of the plurality of rolling bearings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a diagram showing a configuration example of a device to which a state diagnosis method according to an embodiment of the present invention can be applied.

[0028] Figure 2 This is a conceptual diagram for explaining an equivalent circuit around a lubricant in a rolling bearing according to one embodiment of the present invention.

[0029] Figure 3 This is a schematic diagram for explaining an equivalent circuit of a rolling bearing according to one embodiment of the present invention.

[0030] Figure 4 This is a flowchart of a status diagnosis process according to one embodiment of the present invention.

[0031] Figure 5A This is a graph for explaining the result of the status diagnosis process according to one embodiment of the present invention.

[0032] Figure 5B This is a graph for explaining the result of the status diagnosis process according to one embodiment of the present invention.

[0033] Figure 5C This is a graph for explaining the result of the status diagnosis process according to one embodiment of the present invention.

[0034] Fig. 6A This is a graph for explaining the result of the status diagnosis process according to one embodiment of the present invention.

[0035] Figure 6B This is a graph for explaining the result of the status diagnosis process according to one embodiment of the present invention.

[0036] Figure 6C This is a graph for explaining the result of the status diagnosis process according to one embodiment of the present invention.

[0037] Fig. 7A This is a graph for explaining the result of the status diagnosis process according to one embodiment of the present invention.

[0038] Figure 7B This is a graph for explaining the result of the status diagnosis process according to one embodiment of the present invention. DETAILED DESCRIPTION

[0039] Hereinafter, the mode for implementing the present invention will be described with reference to the accompanying drawings and the like. In addition, the embodiment described below is an embodiment for describing the present invention and is not intended to limit the interpretation of the present invention. In addition, not all structures described in each embodiment are necessary structures for solving the problems of the present invention. In addition, in each of the accompanying drawings, the same reference numerals are used to indicate the corresponding relationship for the same constituent elements.

[0040] <First Embodiment>

[0041] The first embodiment of the present invention is described below. It should be noted that the measuring method of the present invention can be applied to a device having a plurality of rolling bearings that are lubricated with a lubricant while rolling. For example, as types of rolling bearings to which the diagnostic method of the present invention can be applied, deep groove ball bearings, angular contact ball bearings, tapered roller bearings, cylindrical roller bearings, self-aligning roller bearings, etc. can be listed.

[0042] [Device structure]

[0043] Figure 1 1 is a schematic structural diagram showing an example of the overall structure of a system to which the state diagnosis method involved in this embodiment can be applied. Figure 1 , a diagnosis device 1, an LCR meter 8, and a bearing device 10 as a diagnosis target using the state diagnosis method according to the present embodiment are shown. Figure 1 The structure shown is an example, and a different structure may be used depending on the diagnosis object and the like.

[0044] The bearing device 10 is constructed to include two rolling bearings. Figure 1 In the example of , an example of a combination of a roller bearing 2 and a ball bearing 3 is shown. The roller bearing 2 and the ball bearing 3 are arranged around the rotating shaft 5 and are configured to enable the rotating shaft 5 to rotate. Inside the roller bearing 2 and the ball bearing 3, the friction in each bearing is reduced by a predetermined lubrication method. The lubrication method is not particularly limited, and for example, grease lubrication, oil lubrication, etc. are used to supply lubricants to the inside of each rolling bearing. There is no particular limitation on the type of lubricant. In addition, the lubricants used in each rolling bearing may be different.

[0045] The roller bearing 2 is composed of an outer ring 2a, a plurality of rollers 2b as rolling elements, and an inner ring 2c. The ball bearing 3 is composed of an outer ring 3a, a plurality of balls 3b as rolling elements, and an inner ring 3c. In the present embodiment, the inner ring of each rolling bearing is described as a rolling ring and the outer ring is described as a fixed ring, but the opposite structure may also be used.

[0046] The linear guide 4 is used to guide the movement of the roller bearing 2 in the rotation axis direction. In the present embodiment, the roller bearing 2 receives an axial load in the rotation axis direction, and the roller bearing 2 can move along with the linear guide 4 according to the axial load.

[0047] The motor 6 is a driving motor and supplies power by rotation to the rotating shaft 5. The LCR meter 8 is electrically connected to the roller bearing 2 and the ball bearing 3. In this case, the LCR meter 8 also functions as an AC power source for the roller bearing 2 and the ball bearing 3.

[0048] The diagnostic device 1 operates as a detection device capable of executing the detection method involved in the present embodiment. During diagnosis, the diagnostic device 1 uses the angular frequency ω and the AC voltage V of the AC power supply as inputs to indicate the LCR meter 8, and obtains the impedance |Z| (|Z| represents the absolute value of Z) and the phase angle θ of the roller bearing 2 and the ball bearing 3 from the LCR meter 8 as corresponding outputs. In addition, the diagnostic device 1 uses these values ​​to monitor the oil film of the lubricant in the roller bearing 2 and the ball bearing 3. The details of the state diagnosis method will be described later.

[0049] The diagnostic device 1 can be realized, for example, by an information processing device that includes a control device, a storage device, and an output device (not shown). The control device can be composed of a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a DSP (Digital Single Processor), or a dedicated circuit. The storage device is composed of volatile and non-volatile storage media such as HDD (Hard Disk Drive), ROM (Read Only Memory), and RAM (Random Access Memory), and can input and output various information according to instructions from the control device. The output device is composed of a display device such as a speaker, a lamp, or a liquid crystal display, and notifies the operator according to instructions from the control device. The notification method of the output device is not particularly limited, for example, it can be an auditory notification based on sound, or it can be a visual notification based on screen output. In addition, the output device can be a network interface with a communication function, and can also perform a notification action by sending data to an external device (not shown) via a network (not shown). The content of the notification here is not limited to notification when an abnormality is detected, for example, when a state diagnosis is performed based on the detection result, and may include notification indicating that the bearing device 10 is normal.

[0050] [Circuit]

[0051] Figure 2 This is a diagram showing an electrically equivalent circuit around the lubricant in a rolling bearing. Circuit E has a structure in which a capacitor C formed by the lubricant is connected in parallel with a resistor R caused by its surrounding elements. The surrounding elements here include rolling elements (rollers, balls, etc.), inner rings, outer rings, etc. that constitute the rolling bearing. In addition, the impedance of circuit E is represented by Z. Here, the AC voltage V applied to circuit E, the current I flowing through circuit E, and the complex impedance Z of the entire circuit E are represented by the following equations (1) to (3).

[0052] V=|V|exp(jωt) (1)

[0053] I=|I|exp(j(ωt-θ)) (2)

[0054] Z=V / I=|V / I|exp(jθ)=|Z|exp(jθ) (3)

[0055] j: imaginary number

[0056] ω: angular frequency of voltage

[0057] t: time

[0058] θ: Phase angle (phase shift between voltage and current)

[0059] In addition, in the present embodiment, electrochemical impedance spectroscopy is used for diagnosis. Electrochemical impedance spectroscopy is a well-known method, and therefore detailed description thereof is omitted here. The electrochemical impedance spectroscopy is a method for distinctively capturing the impedance behavior of the solution·electrode / solution interface.

[0060] like Figure 1 As shown in FIG. 1 , two rolling bearings are used in this embodiment. From the perspective of the LCR meter 8 , this can be regarded as a circuit connected in series. Figure 3 The figure shows an electrically equivalent circuit of the roller bearing 2 and the ball bearing 3. In the present embodiment, the surface roughness of the rolling element and the inner and outer rings is assumed, and CPE (Constant Phase Element; pseudo-capacitance) is adopted.

[0061] Here, the resistance of the roller bearing 2 is represented by R1, and CPE is represented by CPE1. Similarly, the resistance of the ball bearing 3 is represented by R2, and CPE is represented by CPE2.

[0062] CPE is a circuit element that has both capacitor and resistor elements caused by the unevenness and non-uniformity of the electrode surface. In CPE, the time constant is not fixed to one. The impedance of CPE is expressed by the following equation (4). In the case of p = 1, it becomes based on the CPE constant T CPE The capacitor has a resistance value of 1 / T when p = 0. CPEIn addition, the R-CPE parallel circuit represents a flattened semicircle, the flattening of which depends on p.

[0063] [Number 1]

[0064]

[0065] Z CPE :impedance

[0066] j: imaginary number

[0067] π: Pi

[0068] f: frequency

[0069] T CPE : CPE constant

[0070] p: CPE index

[0071] In this embodiment, based on Figure 3 The equivalent circuit shown is used to determine the oil film behavior in each rolling bearing separately by applying impedance spectroscopy. In addition, for each rolling bearing, the LCR meter 8 is electrically connected to the outer ring as a fixed ring and is not in contact with the rotating shaft 5.

[0072] [Processing Flow]

[0073] Figure 4 : is a flowchart of the state diagnosis process involved in this embodiment. This process is executed by the diagnostic device 1, for example, by causing the control device (not shown) provided in the diagnostic device 1 to read the program for implementing the process involved in this embodiment from the storage device (not shown) and execute it. In addition, the fitting and parameter derivation in the following process can be configured to implement part of it using the function of general-purpose software.

[0074] In S401, the diagnostic device 1 controls the LCR meter 8 to supply power of an AC voltage V of an angular frequency ω to the bearing device 10 (i.e., the roller bearing 2 and the ball bearing 3) using an AC power source (not shown) provided in the LCR meter 8. As a result, the AC voltage V of the angular frequency ω is applied to the lubricant in each rolling bearing.

[0075] In S402, the diagnostic device 1 obtains the impedance |Z| and the phase angle θ from the LCR meter 8 as outputs for the input indicated in S101. That is, the LCR meter 8 outputs the impedance |Z| and the phase angle θ to the diagnostic device 1 as the measurement results of the AC voltage V of the angular frequency ω of the bearing device 10 as the input.

[0076] In S403, the diagnostic device 1 performs a diagnostic operation based on the impedance |Z| and the phase angle θ acquired in S402 and the information of the AC voltage V of the angular frequency ω indicated in S401. Figure 3 Fitting (substitution) of the equation of the equivalent circuit shown.

[0077] In S404, the diagnostic device 1 can determine the Figure 3 The parameters in equation (1) corresponding to the equivalent circuit shown are R, T CPE (CPE constant), p (CPE index). At this time, the above parameters corresponding to each rolling bearing connected in series are derived.

[0078] In S405, the diagnostic device 1 uses the parameters derived in S404 to derive the frequency dependency of the impedance Z of each of the plurality of rolling bearings. An example of deriving the frequency dependency of the impedance Z will be described later.

[0079] In S406, the diagnostic device 1 performs a state diagnosis of the lubricant in each rolling bearing based on the result of the frequency dependence of the impedance Z derived in S405. The diagnostic content here is not particularly limited. For example, the lubricant film thickness h and the metal contact ratio α can be derived by the method described in Japanese Patent No. 6729633 of the present patent applicant. In addition, it can also be configured to set a predetermined threshold value for the lubricant film thickness h and the metal contact ratio α, and diagnose normality or abnormality by comparison with the threshold value. In addition, it can also be configured to pre-set multiple threshold values ​​corresponding to the urgency of the abnormality, and diagnose the urgency by comparison with these threshold values. In addition, it can also be configured to pre-set threshold values ​​and evaluation criteria for multiple rolling bearings, respectively, and diagnose the state of each rolling bearing by comparison with them. The measurement accuracy involved in this embodiment when deriving the lubricant film thickness h and the metal contact ratio α will be described later as an experimental example.

[0080] In S407, the diagnostic device 1 notifies the user of the diagnostic result obtained in S406. The notification method is not particularly limited, and may be, for example, displaying the parameter or item determined to be abnormal on the screen, or notifying with sound. Then, this process flow ends.

[0081] [test]

[0082] The following is an explanation of the results of tests conducted using the above-mentioned diagnostic method. Here, the results of two different test conditions are explained. The test conditions are as follows. In Test 1, two rolling bearings, a tapered roller bearing and a ball bearing, were set as a series circuit and the test was conducted using the same lubricant (viscosity). On the other hand, in Test 2, two identical ball bearings were used and the test was conducted using lubricants with different viscosities.

[0083] (Test condition 1)

[0084] Bearings used: tapered roller bearings (No.: HR32206), ball bearings (No.: 6306)

[0085] Axial load: 300[N]

[0086] Radial load: 0[N]

[0087] Base oil viscosity: 47 [cSt] (at 40°C)

[0088] Grease: Urea

[0089] Enclosed amount: 3.6[g]

[0090] Rotation speed: 400[min -1 ]

[0091] AC frequency: 20~1000000[Hz]

[0092] AC voltage: 0.2[V]

[0093] (Test result 1)

[0094] Figure 5A to Figure 5C is a graph showing the measurement results under test condition 1. Figure 5A In the figure, the horizontal axis represents the logarithm of the frequency f[Hz], and the vertical axis represents the logarithm of the impedance |Z|[Ω]. Figure 5B In FIG. 1 , the horizontal axis represents the logarithm of the frequency f [Hz], and the vertical axis represents the phase angle θ [°]. Figure 5A Data point 501 and Figure 5B The information of data point 511 is obtained through the above Figure 4 The actions of steps S401 and S402 shown are determined.

[0095] exist Figure 5A In the example, data point 502 represents the result of testing a single tapered roller bearing used in Test 1. In addition, curve 503 represents the result obtained based on the data point 501 by comparing with Figure 3 The circuit configuration shown is fitted and estimated as the result of the estimated value for the tapered roller bearing. Figure 4Similarly, data point 504 represents the result of the test using the single ball bearing used in test 1. In addition, curve 505 represents the result obtained based on the result obtained as data point 501 by comparing with Figure 3 The circuit structure shown is fitted to estimate the estimated value for a single ball bearing. Figure 4 The results of S404 and S405 shown are obtained.

[0096] exist Figure 5B In the example, data point 512 represents the result of testing a single tapered roller bearing used in Test 1. In addition, curve 513 represents the result obtained based on the data point 511 by comparing with Figure 3 The circuit structure shown is fitted and estimated as the result of the estimated value for the tapered roller bearing. Figure 4 Similarly, data point 514 represents the result of the test using the single ball bearing used in test 1. In addition, curve 515 represents the result obtained by comparing with the result obtained as data point 511. Figure 3 The circuit structure shown is fitted to estimate the estimated value for a single ball bearing. Figure 4 The results of S404 and S405 shown are obtained.

[0097] Figure 5C It means the above Figure 4 The results of the processing of S403 and S404 are shown in FIG. Figure 5C In the figure, the horizontal axis represents the real part of the impedance Z. re , the vertical axis represents the imaginary part Z of the impedance Z im The data point 521 is determined by the operation of step S402. The curve 522 represents the result of fitting using the data point 521. Figure 4 In addition, curve 524 is obtained by Figure 4 The curve obtained by processing S404 and S405 of FIG. 5 shows the frequency dependence of the impedance of the tapered bearing used in Test 1. In addition, data point 523 shows the measurement result when testing a single tapered bearing. Curve 526 is obtained by Figure 4 The curve obtained by the processing of S404 and S405 shows the frequency dependency of the impedance of the ball bearing used in the test 1. In addition, the data point 525 shows the measurement result when the test is performed with a single ball bearing.

[0098] exist Figure 5AIn the figure, the curve 503 derived by the present method is compared with the data point 502 obtained by the single test, and the curve 505 derived by the present method is compared with the data point 504 obtained by the single test. It can be seen that the method of this embodiment can derive estimated values ​​that are substantially the same as the data points in the single test.

[0099] Similarly, in Figure 5B In the figure, the curve 513 derived by the present method is compared with the data point 512 obtained by the single test, and the curve 515 derived by the present method is compared with the data point 514 obtained by the single test. It can be seen that the method of the present embodiment can derive estimated values ​​that are substantially the same as the data points in the single test.

[0100] Similarly, in Figure 5C , a comparison is made between the curve 524 derived by the present method and the data point 523 obtained by a single test, and a comparison is made between the curve 526 derived by the present method and the data point 525 obtained by a single test. It can be seen from this that in the case of measuring different types of rolling bearings as the measurement object with a tandem structure, the measurement method of the present embodiment can be used to perform the measurement with high accuracy.

[0101] (Test condition 2)

[0102] Bearings used: Ball bearing (model: 6306) × 2

[0103] Axial load: 436[N]

[0104] Radial load: 0[N]

[0105] Base oil viscosity: 17 [cSt] (at 40°C), 411 [cSt] (at 40°C)

[0106] Grease: Urea

[0107] Enclosed amount: 3.6[g]

[0108] Rotation speed: 500[min -1 ]

[0109] AC frequency: 20~1000000[Hz]

[0110] AC voltage: 0.2[V]

[0111] (Test result 2)

[0112] Figure 6A to Figure 6C is a graph showing the measurement results under test condition 2. Fig. 6A In the figure, the horizontal axis represents the logarithm of the frequency f[Hz], and the vertical axis represents the logarithm of the impedance |Z|[Ω]. Figure 6BIn FIG. 1 , the horizontal axis represents the logarithm of the frequency f [Hz], and the vertical axis represents the phase angle θ [°]. Fig. 6A Data point 601 and Figure 6B The information of data point 611 is obtained through the above Figure 4 The actions of steps S401 and S402 shown are determined.

[0113] exist Fig. 6A In the figure, data point 602 represents the result of testing a single ball bearing using a lubricant with a base oil viscosity of 17 cSt among the ball bearings used in Test 2. In addition, curve 603 represents the result obtained based on the data point 601 by comparing with Figure 3 The circuit structure shown is fitted to estimate the estimated value for a single ball bearing using a lubricant with a base oil viscosity of 17 cSt. Curve 603 is Figure 4 Similarly, data point 604 represents the result of testing a single ball bearing in which a lubricant with a base oil viscosity of 411 cSt was used in the ball bearing used in Test 2. In addition, curve 605 represents the result obtained by comparing the result obtained as data point 601 with the result obtained as data point 605. Figure 3 The circuit structure shown is fitted to estimate the estimated value for a single ball bearing using a lubricant with a base oil viscosity of 411 cSt. Curve 605 is Figure 4 The results of S404 and S405 shown are obtained.

[0114] exist Figure 6B In the figure, data point 612 represents the result of testing a single ball bearing using a lubricant with a base oil viscosity of 17 cSt among the ball bearings used in Test 2. In addition, curve 613 represents the result obtained based on the data point 611 by comparing with Figure 3 The circuit structure shown is fitted and estimated as the result of the estimated value for a single ball bearing using a lubricant with a base oil viscosity of 17 cSt. Figure 4 Similarly, data point 614 represents the result of testing a single ball bearing in which a lubricant with a base oil viscosity of 411 cSt was used in the ball bearing used in Test 2. In addition, curve 615 represents the result obtained by comparing the result obtained as data point 611 with the result obtained by comparing the result obtained as data point 615 with the result obtained by comparing the result obtained as data point 61 ... Figure 3 The circuit structure shown is fitted to estimate the estimated value for a single ball bearing using 411 cSt lubricant. Figure 4 The results of S404 and S405 shown are obtained.

[0115] Figure 6C It means the above Figure 4The results of the processing of S403 and S404 are shown in FIG. Figure 6C In the figure, the horizontal axis represents the real part of the impedance Z. re , the vertical axis represents the imaginary part Z of the impedance Z im The data point 621 is determined by the operation of step S402. Curve 622 represents the result of fitting using the data point 621. Figure 4 In addition, curve 624 is obtained by Figure 4 The curve obtained by processing S404 and S405 of the present invention is a curve showing the frequency dependence of the impedance of the ball bearing using the lubricant with a base oil viscosity of 17 cSt used in this experiment 2. It should be noted that data point 623 represents the measurement result when a single ball bearing is tested using a lubricant with a base oil viscosity of 17 cSt. Curve 626 is obtained by Figure 4 The curve obtained by the processing of S404 and S405 shows the frequency dependency of the impedance of the ball bearing of the lubricant with a base oil viscosity of 411 cSt used in Test 2. In addition, data point 625 shows the measurement result when a single ball bearing is tested.

[0116] exist Fig. 6A , a comparison is made between the curve 603 derived by the present method and the data point 602 obtained by a single test, and a comparison is made between the curve 605 derived by the present method and the data point 604 obtained by a single test. It can be seen that the method according to the present embodiment can derive an estimated value that is substantially the same as the data point when a single test is performed.

[0117] Similarly, in Figure 6B In the figure, the curve 613 derived by the present method is compared with the data point 612 obtained by a single test, and the curve 615 derived by the present method is compared with the data point 614 obtained by a single test. It can be seen that the method according to the present embodiment can derive an estimated value that is substantially the same as the data point when a single test is performed.

[0118] Similarly, in Figure 6C In the figure, the curve 624 derived by the present method is compared with the data point 623 obtained by a single test, and the curve 626 derived by the present method is compared with the data point 625 obtained by a single test. It can be seen that in the measurement object of the same rolling bearing using different types of lubricants as a series structure, it is possible to perform high-precision measurement by the measurement method of this embodiment.

[0119] In this embodiment, further Figure 4 After the frequency dependence of the impedance Z of each bearing is estimated in S406, the oil film thickness h and the metal contact ratio α of each bearing are calculated using the estimated value. Fig. 7A and Figure 7B The comparison results of the calculation results and the measurement results of each bearing will be described. Here, the description will be based on the conditions of Test 2.

[0120] exist Fig. 7A In the figure, the horizontal axis represents the theoretical oil film thickness h theory [m], the vertical axis represents the oil film thickness h[m]. The theoretical oil film thickness h theory represents the value calculated using the well-known Hamrock & Dowson formula. Fig. 7A In the figure, the dotted line 701 represents the theoretical oil film thickness h theory Data points 702 and 703 indicated by circles represent the oil film thickness h derived from the estimated values ​​of the ball bearings with a lubricant having a base oil viscosity of 17 cSt and the ball bearings with a lubricant having a base oil viscosity of 411 cSt, respectively, estimated by the method of this embodiment. Data point 704 indicated by a square represents the oil film thickness h derived from the result of measurement of a single ball bearing with a lubricant having a base oil viscosity of 17 cSt. In addition, data point 705 indicated by a triangle represents the oil film thickness h derived from the result of measurement of a single ball bearing with a lubricant having a base oil viscosity of 411 cSt.

[0121] exist Figure 7B In the figure, the horizontal axis represents the theoretical oil film thickness h theory [m], the vertical axis represents the metal contact ratio α. Figure 7B In the figure, the data points 711 and 712 indicated by circles represent the metal contact ratio α derived from the estimated values ​​of the ball bearings with a lubricant having a base oil viscosity of 17 cSt and the ball bearings with a lubricant having a base oil viscosity of 411 cSt, respectively, estimated by the method of this embodiment. The data point 713 indicated by a square represents the metal contact ratio α derived from the result of measurement in a single ball bearing with a lubricant having a base oil viscosity of 17 cSt. In addition, the data point 714 indicated by a triangle represents the metal contact ratio α derived from the result of measurement in a single ball bearing with a lubricant having a base oil viscosity of 411 cSt.

[0122] Reference Fig. 7A and Figure 7B It can be seen that the oil film thickness h and the metal contact ratio α derived using the estimated values ​​for each bearing estimated by the method according to the present embodiment are derived with an accuracy substantially consistent with that of a single measurement result. That is, in the method according to the present embodiment, a plurality of bearings that must be tested separately in the conventional method can be tested collectively, and the same accuracy as that of a single test can be obtained.

[0123] In addition, in the above example, two rolling bearings are described as a series circuit, but the present invention is not limited to this. For example, even if there are three or more rolling bearings, the method involved in this embodiment can be applied according to the characteristics of each rolling bearing and the characteristics of the lubricant used in each rolling bearing.

[0124] As described above, according to this embodiment, in a device having a plurality of rolling bearings, the state of each rolling bearing can be diagnosed based on the measurement results of the plurality of rolling bearings. In particular, it is possible to determine the parameters representing the electrical characteristics of the lubricant of each of the plurality of rolling bearings. Furthermore, based on the parameters representing the electrical characteristics, it is possible to easily diagnose the state of the lubricant.

[0125] <Other Implementation Methods>

[0126] In addition, in the present invention, a program or application for implementing the functions of one or more of the above-mentioned embodiments may be supplied to a system or device using a network or storage medium, and the processing of the program may be implemented by causing one or more processors in a computer of the system or device to read and execute the program.

[0127] Alternatively, the present invention may be realized by a circuit that realizes one or more functions (for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array)).

[0128] Thus, the present invention is not limited to the above-mentioned embodiments, and combining the structures of the embodiments with each other, and changing and applying them by those skilled in the art based on the description in the specification and known technologies are also the intended contents of the present invention and are included in the scope of protection required.

[0129] As described above, the following matters are disclosed in this specification.

[0130] (1) A state diagnosis method, characterized in that:

[0131] A method for diagnosing the state of a bearing device, wherein the bearing device includes a plurality of rolling bearings that are electrically connected.

[0132] The state diagnosis method comprises:

[0133] A measuring step of applying a voltage to the plurality of rolling bearings by using an AC power source while changing the frequency, thereby measuring the impedance of the plurality of rolling bearings as a whole;

[0134] a deriving step of fitting the impedance measured in the measuring step based on an equivalent circuit formed by connecting the plurality of rolling bearings in series, thereby deriving the impedance of each of the plurality of rolling bearings; and

[0135] The diagnosis step diagnoses the state of each of the plurality of rolling bearings based on the impedance of each of the plurality of rolling bearings derived in the deriving step.

[0136] According to this configuration, in a device including a plurality of rolling bearings, the state of each rolling bearing can be diagnosed based on the measurement results of the plurality of rolling bearings.

[0137] (2) The state diagnosis method as described in (1), characterized in that:

[0138] The equivalent circuit is composed of pseudo-capacitors corresponding to the plurality of rolling bearings.

[0139] According to this configuration, the frequency dependency of the impedance of each rolling bearing can be determined based on the characteristics of the pseudo-capacitance of each of the plurality of rolling bearings.

[0140] (3) The state diagnosis method according to (1) or (2), characterized in that:

[0141] The plurality of rolling bearings are composed of different types of rolling bearings.

[0142] The plurality of rolling bearings use the same type of lubricant.

[0143] According to this configuration, it is possible to perform status diagnosis of each rolling bearing in a device composed of different types of rolling bearings.

[0144] (4) The state diagnosis method according to (1) or (2), characterized in that:

[0145] The plurality of rolling bearings are composed of the same type of rolling bearings,

[0146] The plurality of rolling bearings respectively use different types of lubricants.

[0147] According to this configuration, it is possible to perform a state diagnosis of each rolling bearing in a device including rolling bearings of the same type using different lubricants.

[0148] (5) A status diagnosis device, characterized in that:

[0149] A bearing device state diagnosis device is provided, wherein the bearing device includes a plurality of rolling bearings which are electrically connected.

[0150] The state diagnosis device comprises:

[0151] a measuring unit that applies a voltage to the plurality of rolling bearings by using an AC power source while changing a frequency, thereby measuring the impedance of the plurality of rolling bearings as a whole;

[0152] a deriving unit that derives the impedance of each of the plurality of rolling bearings by fitting the impedance measured by the measuring unit based on an equivalent circuit formed by connecting the plurality of rolling bearings in series; and

[0153] A diagnosis unit is provided for diagnosing a state of each of the plurality of rolling bearings based on the impedance of each of the plurality of rolling bearings derived by the deriving unit.

[0154] According to this configuration, in a device including a plurality of rolling bearings, the state of each rolling bearing can be diagnosed based on the measurement results of the plurality of rolling bearings.

[0155] (6) A program, characterized in that:

[0156] Instruct the computer to perform the following steps:

[0157] A measuring step of applying a voltage to a plurality of electrically connected rolling bearings using an AC power supply while changing the frequency, thereby measuring the impedance of the plurality of rolling bearings as a whole;

[0158] a deriving step of fitting the impedance measured in the measuring step based on an equivalent circuit in which the plurality of rolling bearings are connected in series, thereby deriving the impedance of each of the plurality of rolling bearings; and

[0159] The diagnosis step diagnoses the state of each of the plurality of rolling bearings based on the impedance of each of the plurality of rolling bearings derived in the deriving step.

[0160] According to this configuration, in a device including a plurality of rolling bearings, the state of each rolling bearing can be diagnosed based on the measurement results of the plurality of rolling bearings.

[0161] In the above, various embodiments are described with reference to the accompanying drawings, but the present invention is certainly not limited to this example. As long as a person skilled in the art can think of various variations or modifications within the scope described in the claims, it is obvious that these variations or modifications also belong to the technical scope of the present invention. In addition, the various constituent elements in the above-mentioned embodiments may also be arbitrarily combined within the scope of the gist of the invention.

[0162] Various embodiments have been described above, but the present invention is certainly not limited to these examples. As long as one skilled in the art can think of various variations or modifications within the scope described in the claims, it is obvious that these variations or modifications also belong to the technical scope of the present invention. In addition, within the scope of not departing from the gist of the invention, the various constituent elements in the above-mentioned embodiments may also be arbitrarily combined.

[0163] In addition, the present application is based on the Japanese patent application (Japanese Patent Application No. 2022-041692) filed on March 16, 2022, the contents of which are incorporated herein by reference.

[0164] Description of Reference Numerals

[0165] 1 Diagnostic device

[0166] 2 Roller bearings

[0167] 2a Outer ring

[0168] 2b roller (rolling element)

[0169] 2c Inner circle

[0170] 3 Ball bearings

[0171] 3a Outer ring

[0172] 3b ball (rolling element)

[0173] 3c Inner Circle

[0174] 4 Linear guides

[0175] 5 Rotation Axis

[0176] 6 Motor

[0177] 8 LCR Meter

[0178] 10 Bearing assembly

Claims

1. A state diagnosis method, characterized in that: A method for diagnosing the state of a bearing device, wherein the bearing device includes a plurality of rolling bearings that are electrically connected. The state diagnosis method comprises: A measuring step of applying a voltage to the plurality of rolling bearings by using an AC power source while changing the frequency, thereby measuring the impedance of the plurality of rolling bearings as a whole; A deriving step of fitting the impedance measured in the measuring step based on an equivalent circuit formed by connecting a plurality of the rolling bearings in series, thereby deriving the impedance of each of the plurality of rolling bearings; as well as The diagnosis step diagnoses the state of each of the plurality of rolling bearings based on the impedance of each of the plurality of rolling bearings derived in the deriving step.

2. The state diagnosis method according to claim 1, characterized in that: The equivalent circuit is composed of pseudo-capacitors corresponding to the plurality of rolling bearings.

3. The state diagnosis method according to claim 1 or 2, characterized in that: The plurality of rolling bearings are composed of different types of rolling bearings. The plurality of rolling bearings use the same type of lubricant.

4. The state diagnosis method according to claim 1 or 2, characterized in that: The plurality of rolling bearings are composed of the same type of rolling bearings, The plurality of rolling bearings respectively use different types of lubricants.

5. A status diagnosis device, characterized in that: A bearing device state diagnosis device is provided, wherein the bearing device includes a plurality of rolling bearings which are electrically connected. The state diagnosis device comprises: a measuring unit that applies a voltage to the plurality of rolling bearings by using an AC power source while changing a frequency, thereby measuring the impedance of the plurality of rolling bearings as a whole; a deriving unit that derives the impedance of each of the plurality of rolling bearings by fitting the impedance measured by the measuring unit based on an equivalent circuit formed by connecting the plurality of rolling bearings in series; as well as A diagnosis unit is provided for diagnosing a state of each of the plurality of rolling bearings based on the impedance of each of the plurality of rolling bearings derived by the deriving unit.

6. A program, characterized in that Have your computer perform the following steps: A measuring step of applying a voltage to a plurality of electrically connected rolling bearings using an AC power supply while changing the frequency, thereby measuring the impedance of the plurality of rolling bearings as a whole; A deriving step of fitting the impedance measured in the measuring step based on an equivalent circuit in which the plurality of rolling bearings are connected in series, thereby deriving the impedance of each of the plurality of rolling bearings; as well as The diagnosis step diagnoses the state of each of the plurality of rolling bearings based on the impedance of each of the plurality of rolling bearings derived in the deriving step.

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