Condition diagnostic methods, condition diagnostic devices, and programs

Abstract

The condition diagnosis method of the present invention is used in a bearing device having a plurality of rolling bearings electrically connected. By using an alternating current power supply to apply voltage to the plurality of rolling bearings while changing the frequency, the impedance of the plurality of rolling bearings as a whole is measured. By fitting the measured impedance to an equivalent circuit formed by connecting the plurality of rolling bearings in series, the impedance of each of the plurality of rolling bearings is derived. Based on the derived impedance of each of the plurality of rolling bearings, the condition of each of the plurality of rolling bearings is diagnosed.

Description

Technical Field

[0001] This application relates to a condition diagnosis method, a condition diagnosis device, and a program. Prior Technology

[0002] Previously, in rolling devices such as bearing assemblies, the use of lubricants (e.g., lubricating oil or grease) to lubricate their rotation was widespread. On the other hand, the condition of rotating parts such as bearing assemblies was regularly checked to detect damage or wear at an early stage and to prevent failures of rotating parts.

[0003] In rolling devices that use lubricants, it is desirable to accurately detect the internal condition in order to diagnose their operational status. On the other hand, depending on the type of device, some use multiple bearing devices to support the rotational movement. For example, Patent Document 1 shows a configuration in which a device consisting of two rolling bearings supporting a rotating shaft is used to determine the condition of the lubricating film on the rolling bearings without contact with the rotating wheel or rolling elements. [Previous Technical Documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2007-239779 Summary of the Invention

[0005] [The problem that the invention aims to solve]

[0006] On the other hand, in the method of Patent Document 1, the sum of the electrostatic capacitances of the two rolling bearings was used for measurement. However, the method of Patent Document 1 cannot determine the state of each rolling bearing. However, for devices containing a plurality of rolling bearings, there is a desire to determine the state of each rolling bearing with fewer measurements.

[0007] In view of the above-mentioned problems, the purpose of this application is to provide a method that, in a device containing a plurality of rolling bearings, can diagnose the condition of each rolling bearing based on the measurement results of the plurality of rolling bearings. [Technical means to solve the problem]

[0008] To address the aforementioned issues, the invention of this application has the following structure: a condition diagnosis method for a bearing assembly having a plurality of electrically connected rolling bearings, comprising the following steps: The measurement procedure involves applying voltage to the aforementioned plurality of rolling bearings by varying the frequency of an AC power supply, thereby measuring the overall impedance of the plurality of rolling bearings. The derivation sequence is achieved by fitting the impedances measured in the aforementioned measurement sequence to an equivalent circuit formed by connecting the aforementioned plurality of rolling bearings in series, thereby deriving the impedance of each of the aforementioned plurality of rolling bearings; and The diagnostic procedure is based on deriving the impedance of each of the aforementioned plurality of rolling bearings in the aforementioned derivation procedure, and diagnosing the condition of each of the aforementioned plurality of rolling bearings.

[0009] Furthermore, another aspect of the invention in this application has the following configuration: a condition diagnostic device for a bearing device having a plurality of electrically connected rolling bearings, and comprising the following mechanism: The measuring mechanism applies voltage to the aforementioned plurality of rolling bearings by varying the frequency of an alternating current power supply, thereby measuring the overall impedance of the plurality of rolling bearings. The impedance derivation mechanism derives the impedance of each of the aforementioned rolling bearings by fitting the impedance measured by the aforementioned measuring mechanism to an equivalent circuit formed by connecting the aforementioned plurality of rolling bearings in series; and The diagnostic mechanism diagnoses the condition of each of the aforementioned plurality of rolling bearings based on the impedances derived from the aforementioned derivation mechanism.

[0010] Furthermore, another aspect of the invention in this application has the following structure: a program, It is used to make the computer perform the following steps: The measurement procedure involves applying voltage to a plurality of electrically connected rolling bearings by varying the frequency of an alternating current power supply, thereby measuring the overall impedance of the plurality of rolling bearings. The derivation sequence is achieved by fitting the impedances measured in the aforementioned measurement sequence to an equivalent circuit formed by connecting the aforementioned plurality of rolling bearings in series, thereby deriving the impedance of each of the aforementioned plurality of rolling bearings; and The diagnostic procedure is based on deriving the impedance of each of the aforementioned plurality of rolling bearings in the aforementioned derivation procedure, and diagnosing the condition of each of the aforementioned plurality of rolling bearings. [Effects of the Invention]

[0011] According to the invention of this application, in a device comprising a plurality of rolling bearings, the condition of each rolling bearing can be diagnosed based on the measurement results of the plurality of rolling bearings. Simple Explanation of the Diagram

[0012] Figure 1 is a diagram showing an example of the configuration of an apparatus applicable to one embodiment of the invention of this application for state diagnosis. Figure 2 is a conceptual diagram illustrating the equivalent circuit around the lubricant in a rolling bearing according to one embodiment of the invention of this application. Figure 3 is a schematic diagram illustrating the equivalent circuit of a rolling bearing according to one embodiment of the invention of this application. Figure 4 is a flowchart of the state diagnosis process of one embodiment of the invention of this application. Figure 5A is a diagram illustrating the result of state diagnosis processing in one embodiment of the invention of this application. Figure 5B is a diagram illustrating the result of state diagnosis processing in one embodiment of the invention of this application. Figure 5C is a diagram illustrating the result of state diagnosis processing in one embodiment of the invention of this application. Figure 6A is a diagram illustrating the results of state diagnosis processing in one embodiment of the invention of this application. Figure 6B is a diagram illustrating the result of state diagnosis processing in one embodiment of the invention of this application. Figure 6C is a diagram illustrating the result of state diagnosis processing in one embodiment of the invention of this application. Figure 7A is a diagram illustrating the result of state diagnosis processing in one embodiment of the invention of this application. Figure 7B is a diagram illustrating the result of state diagnosis processing in one embodiment of the invention of this application. Implementation

[0013] The following description, with reference to figures, illustrates the embodiments used to implement the invention of this application. Furthermore, the embodiments described below are merely illustrative of one embodiment of the invention of this application and are not intended to limit the scope of the invention. Also, not all components described in each embodiment are necessarily necessary to solve the problems of the invention of this application. In each drawing, the same reference numerals are used to indicate the correspondence of the same constituent elements.

[0014] <First Implementation Form> The first embodiment of the present invention will now be described. Furthermore, the measurement method of the present invention is applicable to devices comprising a plurality of rolling bearings, one side of which is lubricated by a lubricant and the other side performs rolling motion. Examples of rolling bearings to which the diagnostic method of the present invention is applicable include deep groove ball bearings, angular contact ball bearings, tapered roller bearings, cylindrical roller bearings, and self-aligning roller bearings.

[0015] [Device Composition] Figure 1 is a schematic diagram showing an example of the overall configuration of a system for which the condition diagnosis method of this embodiment can be applied. Figure 1 shows the diagnostic device 1, the LCR meter 8, and the bearing device 10, which is the object of diagnosis, using the condition diagnosis method of this embodiment. Furthermore, the configuration shown in Figure 1 is an example, and different configurations can be used depending on the object of diagnosis, etc.

[0016] The bearing assembly 10 comprises two rolling bearings. Figure 1 shows an example of a combination of roller bearing 2 and ball bearing 3. The roller bearing 2 and ball bearing 3 are positioned around the rotating shaft 5, configured to rotate about the shaft. Inside the roller bearing 2 and ball bearing 3, friction within each bearing is reduced by a prescribed lubrication method. The lubrication method is not particularly limited; for example, grease lubrication or oil lubrication is supplied to the interior of each rolling bearing. There is also no particular limitation on the type of lubricant. Furthermore, the lubricants used in each rolling bearing can be different.

[0017] Roller bearing 2 comprises an outer ring 2a, rolling elements (i.e., a plurality of rollers 2b), and an inner ring 2c. Ball bearing 3 comprises an outer ring 3a, rolling elements (i.e., a plurality of balls 3b), and an inner ring 3c. In this embodiment, the inner ring of each rolling bearing is described as the rolling ring, and the outer ring as the stationary ring, but the configuration can be reversed.

[0018] The linear guide 4 is used to guide the movement of the roller bearing 2 in the direction of its rotation axis. In this embodiment, the roller bearing 2 is assumed to be under an axial load along the direction of its rotation axis, and the roller bearing 2 can move with the linear guide 4 accordingly to the axial load.

[0019] Motor 6 is a drive motor that supplies power to the rotating shaft 5 through rotation. LCR tester 8 is electrically connected to roller bearing 2 and ball bearing 3. At this time, LCR tester 8 can also function as an AC power source for roller bearing 2 and ball bearing 3.

[0020] The diagnostic device 1 operates as a detection device capable of performing the detection method of this embodiment. During diagnosis, the diagnostic device 1 indicates the angular frequency ω of the AC power supply and the AC voltage V as inputs to the LCR meter 8, and obtains the impedance |Z| (where |Z| represents the absolute value of Z) and phase angle θ of the roller bearing 2 and the ball bearing 3 from the LCR meter 8 as its output. Then, 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. Details regarding the condition diagnosis method will be described later.

[0021] The diagnostic device 1 is implemented, for example, using an information processing device comprising a control device, a memory device, and an output device (not shown). The control device may be composed of a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a DSP (Digital Single Processor), or dedicated circuitry. The memory device is composed of volatile and non-volatile memory media such as an HDD (Hard Disk Drive), ROM (Read Only Memory), or RAM (Random Access Memory), and can perform various information input and output via instructions from the control device. The output device is composed of a speaker, a lamp, or a display device such as an LCD, and provides notification to the operator via instructions from the control device. The notification method performed by the output device is not particularly limited; for example, it can be an auditory notification via sound or a visual notification via screen output. Furthermore, the output device can be a network interface with communication capabilities, or it can perform a notification action by sending data to an external device (not shown) via a network (not shown). The notification content here is not limited to notification when an abnormality is detected, for example, in the case of status diagnosis based on the detection results, but can also include notification that the bearing device 10 is normal.

[0022] [Circuit] Figure 2 shows the electrically equivalent circuit around the lubricant in a rolling bearing. The circuit E is composed of a capacitor C made of lubricant and a resistor R caused by its surrounding elements connected in parallel. Examples of the surrounding elements include the rolling elements (rollers or balls, etc.), inner ring, and outer ring that make up the rolling bearing. Furthermore, Z represents the impedance of the circuit E. Here, the AC voltage V applied to the circuit E, the current I flowing in the circuit E, and the complex impedance Z of the circuit E as a whole are represented by the following equations (1) to (3). V=|V|exp(jωt) …(1) I=|I|exp(j(ωt-θ)) …(2) Z=V / I=|V / I|exp(jθ)=|Z|exp(jθ) …(3) j: Imaginary number ω: Angular frequency of voltage t: time θ: Phase angle (the phase shift between voltage and current)

[0023] Furthermore, in this embodiment, electrochemical impedance spectroscopy is used for diagnosis. Since electrochemical impedance spectroscopy is a well-known method, a detailed explanation is omitted here. It is a method for distinguishing and processing the impedance behavior of the solution and the electrode / solution interface.

[0024] As shown in Figure 1, in this embodiment, two rolling bearings are used. When observed using an LCR tester 8, they can be considered as a circuit connected in series. Figure 3 shows the electrically equivalent circuit of the roller bearing 2 and the ball bearing 3. In this embodiment, the surface roughness of the rolling elements and the inner and outer rings is assumed to be achieved using a CPE (Constant Phase Element; pseudocapacitor).

[0025] Here, the resistance of roller bearing 2 is represented as R1, and CPE is represented as CPE1. Similarly, the resistance of ball bearing 3 is represented as R2, and CPE is represented as CPE2.

[0026] A CPE is a circuit element that simultaneously possesses the elements of both capacitor and resistor due to the unevenness or non-uniformity of the electrode surface. The time constant in a CPE is indeterminate and is 1. The impedance of a CPE is expressed by the following equation (4). When p=1, it is a capacitor based on the CPE constant TCPE; when p=0, it is a resistor with a resistance of 1 / TCPE. Furthermore, the R-CPE parallel circuit represents a collapsed semicircle, the collapse condition of which depends on p.

[0027] [Number 1]

[0028] Z CPE: Impedance j: Imaginary number π: Pi f: Frequency T CPE: CPE constant p:CPE index

[0029] In this embodiment, the oil film movement of each rolling bearing is determined separately by applying impedance spectroscopy based on the equivalent circuit shown in Figure 3. Furthermore, the LCR tester 8 is electrically connected to the outer ring, which serves as the fixed ring, for each rolling bearing and is non-contact with the rotating shaft 5.

[0030] [Processing Flow] Figure 4 is a flowchart of the state diagnosis process of this embodiment. This process is executed using the diagnostic device 1. For example, the control device (not shown) included in the diagnostic device 1 can read the program for implementing the process of this embodiment from the memory device (not shown) and execute it. Furthermore, the fitting or parameter derivation in the following processes can be implemented as part of the function using general-purpose software.

[0031] In S401, the diagnostic device 1 controls the LCR tester 8 to apply an AC voltage V with an angular frequency ω to the bearing assembly 10 (i.e., the roller bearing 2 and the ball bearing 3) using the AC power supply (not shown) provided by the LCR tester 8. This applies an AC voltage V with an angular frequency ω to the lubricant within each rolling bearing.

[0032] In S402, the diagnostic device 1 obtains the impedance |Z| and phase angle θ from the LCR tester 8 as the output for the input indicated in S101. That is, the LCR tester 8 outputs the impedance |Z| and phase angle θ as the measurement results of the bearing device 10 with an input of AC voltage V at angular frequency ω to the diagnostic device 1.

[0033] In S403, the diagnostic device 1 performs fitting to the equation based on the impedance |Z| and phase angle θ obtained in S402, the AC voltage V with angular frequency ω indicated in S401, and the information obtained in S402.

[0034] In S404, the diagnostic device 1 can specify the parameters in equation (1) corresponding to the equivalent circuit shown in Figure 3 based on the fitting result of S403. The parameters specified here are R, T, CPE (CPE constant), and p (CPE exponent). At this time, the above parameters corresponding to each rolling bearing connected in series are derived.

[0035] In S405, diagnostic device 1 uses the parameters derived in S404 to derive the frequency dependence of the impedance Z of each of the plurality of rolling bearings. An example of deriving the frequency dependence of impedance Z will be described later.

[0036] In S406, the diagnostic device 1 performs a lubricant condition diagnosis on each rolling bearing based on the frequency dependence of the impedance Z derived in S405. The diagnostic content is not particularly limited here; for example, the lubricating oil film thickness h or metal-to-metal contact ratio α can be derived using a method described in Patent No. 6729633 filed by the applicant of this patent application. Furthermore, it can be configured such that a predetermined threshold value is set for the lubricating oil film thickness h or metal-to-metal contact ratio α, and normal or abnormal condition is diagnosed by comparing it with that threshold value. Alternatively, it can be configured such that a plurality of threshold values ​​corresponding to the urgency of the abnormality are set in advance, and the urgency is diagnosed by comparing it with these threshold values. Furthermore, it can be configured such that a threshold value or evaluation standard is set in advance for each of the plurality of rolling bearings, and the condition diagnosis of each rolling bearing is performed by comparing it with these standards. The accuracy of the measurement of the lubricating oil film thickness h or the metal contact ratio α in this embodiment will be described later as an experimental example.

[0037] In S407, the diagnostic device 1 will notify the user of the diagnostic results obtained in S406. The notification method is not particularly limited; for example, it could be displaying the abnormal parameters or items on the screen or using sound to notify the user. Then, the processing flow ends.

[0038] [test] The results of the tests conducted using the diagnostic method described above will now be explained. Here, the results of two different test conditions will be explained. The test conditions are as follows: In Test 1, two rolling bearings, a tapered roller bearing and a ball bearing, were connected in series and tested using the same lubricant (viscosity). In Test 2, two identical ball bearings were used, but lubricants with different viscosities were tested.

[0039] (Experimental Condition 1) Bearings used: Tapered roller bearing (model: HR32206), ball bearing (model: 6306) Axial load: 300 N Radial load: 0 [N] Base oil viscosity: 47 [cSt] (at 40℃) Lubricating grease: urea-based Enclosed amount: 3.6[g] Rotational speed: 400 [min -1] AC frequency: 20~1000000 [Hz] AC voltage: 0.2V

[0040] (Experimental Result 1) Figures 5A-5C represent the measurement results under test condition 1. In Figure 5A, the horizontal axis represents the logarithm of frequency f [Hz], and the vertical axis represents the logarithm of impedance |Z| [Ω]. In Figure 5B, the horizontal axis represents the logarithm of frequency f [Hz], and the vertical axis represents the phase angle θ [°]. The information in plot 501 of Figure 5A and plot 511 of Figure 5B is specific using the actions of steps S401 and S402 shown in Figure 4 above.

[0041] In Figure 5A, plot 502 represents the results measured using the tapered roller bearing unit used in Experiment 1. Curve 503 represents the estimated value for the tapered roller bearing, derived from the results obtained as plot 501 and fitted to the circuit configuration shown in Figure 3. Curve 503 is obtained as the result of S404 and S405 shown in Figure 4. Similarly, plot 504 represents the results measured using the ball bearing unit used in Experiment 1. Curve 505 represents the estimated value for the ball bearing unit, derived from the results obtained as plot 501 and fitted to the circuit configuration shown in Figure 3. Curve 505 is obtained as the result of S404 and S405 shown in Figure 4.

[0042] In Figure 5B, plot 512 represents the results measured using the tapered roller bearing unit used in Experiment 1. Curve 513 represents the estimated value for the tapered roller bearing, derived from the results obtained as plot 511 and fitted to the circuit configuration shown in Figure 3. Curve 513 is obtained as the results of S404 and S405 shown in Figure 4. Similarly, plot 514 represents the results measured using the ball bearing unit used in Experiment 1. Curve 515 represents the estimated value for the ball bearing unit, derived from the results obtained as plot 511 and fitted to the circuit configuration shown in Figure 3. Curve 515 is obtained as the results of S404 and S405 shown in Figure 4.

[0043] Figure 5C shows the results of the processing of S403 and S404 shown in Figure 4 above. In Figure 5C, the horizontal axis represents the real part Zre of the impedance Z, and the vertical axis represents the imaginary part Zim of the impedance Z. Plot 521 is specific to the actions of the steps in S402. Curve 522 shows the fitting result obtained using plot 521, which is obtained in S403 of Figure 4. Furthermore, curve 524 shows the frequency dependence curve of the impedance of the tapered bearing used in Experiment 1, obtained by processing S404 and S405 in Figure 4. Furthermore, plot 523 shows the measurement results when measuring using a single tapered bearing unit. Curve 526 shows the frequency dependence curve of the impedance of the ball bearing used in Experiment 1, obtained by processing S404 and S405 in Figure 4. Furthermore, plot 525 shows the measurement results when measuring using a single ball bearing unit.

[0044] In Figure 5A, a comparison is made between curve 503 derived by this method and plot 502 obtained using measurements under single-unit conditions, and between curve 505 derived by this method and plot 504 obtained using measurements under single-unit conditions. This demonstrates that the method in this embodiment can derive estimated values ​​that are substantially the same as those obtained using plots under single-unit conditions.

[0045] Similarly, in Figure 5B, a comparison is made between curve 513 derived by this method and plot 512 obtained using measurements under single-unit conditions, and between curve 515 derived by this method and plot 514 obtained using measurements under single-unit conditions. Thus, it can be seen that in this embodiment, the method can derive estimated values ​​that are substantially the same as those obtained using measurements under single-unit conditions.

[0046] Similarly, in Figure 5C, a comparison is made between curve 524 derived by this method and plot 523 obtained by measurement under single-unit conditions, and between curve 526 derived by this method and plot 525 obtained by measurement under single-unit conditions. This demonstrates that, when measuring different types of rolling bearings in a series configuration, the measurement method of this embodiment can achieve high accuracy.

[0047] (Experimental Condition 2) Bearings used: Ball bearings (model: 6306) × 2 Axial load: 436 N Radial load: 0 [N] Base oil viscosity: 17 cSt (at 40°C), 411 cSt (at 40°C) Lubricating grease: urea-based Enclosed amount: 3.6[g] Rotational speed: 500 rpm AC frequency: 20~1000000 [Hz] AC voltage: 0.2V

[0048] (Experimental Result 2) Figures 6A-6C show the measurement results under test condition 2. In Figure 6A, the horizontal axis represents the logarithm of frequency f [Hz], and the vertical axis represents the logarithm of impedance |Z| [Ω]. In Figure 6B, the horizontal axis represents the logarithm of frequency f [Hz], and the vertical axis represents the phase angle θ [°]. The information in plot 601 of Figure 6A and plot 611 of Figure 6B is specific to the actions of the steps S401 and S402 shown in Figure 4 above.

[0049] In Figure 6A, plot 602 represents the results measured using a ball bearing unit with a base oil viscosity of 17 cSt lubricant, as used in Experiment 2. Curve 603 represents the estimated result for a ball bearing unit using a base oil viscosity of 17 cSt lubricant, obtained by fitting the circuit configuration shown in Figure 3, based on the results obtained as plot 601. Curve 603 is obtained as the result of S404 and S405 shown in Figure 4. Similarly, plot 604 represents the results measured using a ball bearing unit with a base oil viscosity of 411 cSt lubricant, as used in Experiment 2. Curve 605 represents the estimated result for a ball bearing unit using a base oil viscosity of 411 cSt lubricant, obtained by fitting the circuit configuration shown in Figure 3, based on the results obtained as plot 601. Curve 605 is obtained as a result of S404 and S405 shown in Figure 4.

[0050] In Figure 6B, plot 612 represents the results measured using a ball bearing unit with a base oil viscosity of 17 cSt lubricant, as used in Experiment 2. Curve 613 represents the estimated result for a ball bearing unit using a base oil viscosity of 17 cSt lubricant, obtained by fitting the circuit configuration shown in Figure 3, based on the results obtained as plot 611. Curve 613 is obtained as the results of S404 and S405 shown in Figure 4. Similarly, plot 614 represents the results measured using a ball bearing unit with a base oil viscosity of 411 cSt lubricant, as used in Experiment 2. Curve 615 represents the estimated result for a ball bearing unit using a lubricant with a base oil viscosity of 411 cSt, obtained by fitting the circuit configuration shown in Figure 3, based on the results obtained as plot 611. Curve 615 is obtained as a result of S404 and S405 shown in Figure 4.

[0051] Figure 6C shows the results of the processing of S403 and S404 shown in Figure 4 above. In Figure 6C, the horizontal axis represents the real part Zre of the impedance Z, and the vertical axis represents the imaginary part Zim of the impedance Z. Plot 621 shows the action specifics of the step sequence of S402. Curve 622 shows the fitting result using plot 621, obtained from S403 in Figure 4. Furthermore, curve 624 shows the frequency dependence curve of the impedance of the ball bearing using a lubricant with a base oil viscosity of 17 cSt, used in this experiment 2, obtained by processing S404 and S405 in Figure 4. Moreover, plot 623 shows the measurement results when measuring the ball bearing unit using a lubricant with a base oil viscosity of 17 cSt. Curve 626 represents the frequency dependence of the impedance of the ball bearing using a lubricant with a base oil viscosity of 411 cSt, obtained through the treatments shown in Figures S404 and S405 in Experiment 2. Furthermore, plot 625 represents the measurement results obtained using individual ball bearings.

[0052] In Figure 6A, a comparison is made between curve 603 derived by this method and plot 602 obtained using measurements under single-unit conditions, and between curve 605 derived by this method and plot 604 obtained using measurements under single-unit conditions. Thus, it can be seen that in this embodiment, the method can derive estimated values ​​that are substantially the same as those obtained using plots under single-unit conditions.

[0053] Similarly, in Figure 6B, a comparison is made between curve 613 derived by this method and plot 612 obtained using measurements under single-unit conditions, and between curve 615 derived by this method and plot 614 obtained using measurements under single-unit conditions. Thus, it can be seen that in this embodiment, the method can derive estimated values ​​that are substantially the same as those obtained using plots under single-unit conditions.

[0054] Similarly, in Figure 6C, a comparison is made between curve 624 derived by this method and plot 623 obtained using measurements under single-component conditions, and between curve 626 derived by this method and plot 625 obtained using measurements under single-component conditions. This demonstrates that in measuring objects where the same rolling bearings using different types of lubricants are arranged in a series configuration, the measurement method of this embodiment can perform measurements with good accuracy.

[0055] In this embodiment, after estimating the frequency dependence of the impedance Z of each bearing in S406 of Figure 4, the oil film thickness h and metal contact ratio α of each bearing are calculated using the estimated value. Figures 7A and 7B are used to illustrate the comparison between the calculated results and the measured results in each bearing. Here, the explanation is based on the conditions of Experiment 2.

[0056] In Figure 7A, the horizontal axis represents the theoretical oil film thickness htheory [m], and the vertical axis represents the oil film thickness hm. Here, the theoretical oil film thickness htheory represents the value calculated using the well-known Hamrock & Dowson formula. In Figure 7A, the dashed line 701 represents the theoretical oil film thickness htheory. The circles 702 and 703 represent the oil film thickness h derived from the estimated values ​​of ball bearings based on a lubricant with a base oil viscosity of 17 cSt and a ball bearing with a base oil viscosity of 411 cSt, respectively, using the method of this embodiment. The square 704 represents the oil film thickness h derived from measurements taken using a ball bearing unit with a base oil viscosity of 17 cSt. The triangle 705 represents the oil film thickness h derived from measurements taken using a ball bearing unit with a base oil viscosity of 411 cSt.

[0057] In Figure 7B, the horizontal axis represents the theoretical oil film thickness h (theory [m]), and the vertical axis represents the metal-to-metal contact ratio α. In Figure 7B, the circles 711 and 712 represent the metal-to-metal contact ratio α derived from the estimated values ​​of ball bearings using a lubricant with a base oil viscosity of 17 cSt and a ball bearing using a lubricant with a base oil viscosity of 411 cSt, respectively, using the method of this embodiment. The square 713 represents the metal-to-metal contact ratio α derived from measurements taken using a ball bearing unit with a base oil viscosity of 17 cSt. Furthermore, the triangle 714 represents the metal-to-metal contact ratio α derived from measurements taken using a ball bearing unit with a base oil viscosity of 411 cSt.

[0058] Referring to Figures 7A and 7B, it can be seen that the oil film thickness h and metal contact ratio α derived from the estimated values ​​of each bearing using the method of this embodiment are derived with an accuracy that is approximately consistent with the measurement results for individual bearings. That is, in the method of this embodiment, multiple bearings that had to be measured individually in previous methods can be measured collectively, and the same accuracy as individual measurements can be obtained.

[0059] Furthermore, in the example above, two rolling bearings were described as a series circuit, but this is not a limitation. For example, even with three or more rolling bearings, the method of this embodiment can be applied depending on the characteristics of each rolling bearing or the characteristics of the lubricant used in each rolling bearing.

[0060] According to this embodiment, in a device comprising a plurality of rolling bearings, the condition of each rolling bearing can be diagnosed based on the measurement results of the plurality of rolling bearings. In particular, parameters specifically representing the electrical characteristics of the lubricant for each of the plurality of rolling bearings can be defined. Then, the condition of the lubricant can be easily diagnosed based on these parameters representing the electrical characteristics.

[0061] <Other Implementation Forms> Furthermore, in the invention of this application, the following process can also be achieved: using a network or memory medium, a program or application program used to implement the functions of one or more of the above embodiments is supplied to a system or device, and the program is read and executed by one or more processors in the computer of the system or device.

[0062] Alternatively, it can be implemented by a circuit that performs more than one function (e.g., ASIC (Application Specific Integrated Circuit) or FPGA (Field-Programmable Gate Array)).

[0063] As described above, the present invention is not limited to the embodiments described above. Any combination of the components of the embodiments, or any modifications or applications made by those skilled in the art based on the description in the specification and well-known technologies, are also considered implementations of the present invention and are included within the scope of protection.

[0064] As stated above, this specification discloses the following matters. (1) A condition diagnosis method, characterized in that it is used for a bearing device having a plurality of electrically connected rolling bearings, and includes the following steps: The measurement procedure involves applying voltage to the aforementioned plurality of rolling bearings by varying the frequency of an AC power supply, thereby measuring the overall impedance of the plurality of rolling bearings. The derivation sequence is achieved by fitting the impedances measured in the aforementioned measurement sequence to an equivalent circuit formed by connecting the aforementioned plurality of rolling bearings in series, thereby deriving the impedance of each of the aforementioned plurality of rolling bearings; and The diagnostic procedure is based on deriving the impedance of each of the aforementioned plurality of rolling bearings in the aforementioned derivation procedure, and diagnosing the condition of each of the aforementioned plurality of rolling bearings. According to this configuration, in a device containing a plurality of rolling bearings, the condition of each rolling bearing can be diagnosed based on the measurement results of the plurality of rolling bearings.

[0065] (2) The state diagnosis method as in (1), wherein the aforementioned equivalent circuit is constructed by pseudocapacitors corresponding to each of the aforementioned plurality of rolling bearings. Based on this configuration, the frequency dependence of the impedance of each rolling bearing can be determined by the characteristics of the pseudocapacitance of each of the plurality of rolling bearings.

[0066] (3) The condition diagnosis method as in (1) or (2), wherein the aforementioned plurality of rolling bearings are composed of different types of rolling bearings. The aforementioned plurality of rolling bearings use the same type of lubricant. Based on this configuration, the condition diagnosis of each rolling bearing in a device composed of different types of rolling bearings can be performed.

[0067] (4) The condition diagnosis method as in (1) or (2), wherein the aforementioned plurality of rolling bearings are composed of the same type of rolling bearings. The aforementioned plurality of rolling bearings use different types of lubricants. Based on this configuration, the condition of each rolling bearing in a device consisting of rolling bearings of the same type using different lubricants can be diagnosed.

[0068] (5) A condition diagnostic device, characterized in that it is used in a bearing device having a plurality of electrically connected rolling bearings, and includes the following mechanism: The measuring mechanism applies voltage to the aforementioned plurality of rolling bearings by varying the frequency of an alternating current power supply, thereby measuring the overall impedance of the plurality of rolling bearings. The impedance derivation mechanism derives the impedance of each of the aforementioned rolling bearings by fitting the impedance measured by the aforementioned measuring mechanism to an equivalent circuit formed by connecting the aforementioned plurality of rolling bearings in series; and The diagnostic mechanism diagnoses the condition of each of the aforementioned plurality of rolling bearings based on the impedances derived from the aforementioned derivation mechanism. According to this configuration, in a device having a plurality of rolling bearings, the condition of each rolling bearing can be diagnosed based on the measurement results of the plurality of rolling bearings.

[0069] (6) A program that causes a computer to perform the following steps: The measurement procedure involves applying voltage to a plurality of electrically connected rolling bearings by varying the frequency of an alternating current power supply, thereby measuring the overall impedance of the plurality of rolling bearings. The derivation sequence is achieved by fitting the impedances measured in the aforementioned measurement sequence to an equivalent circuit formed by connecting the aforementioned plurality of rolling bearings in series, thereby deriving the impedance of each of the aforementioned plurality of rolling bearings; and The diagnostic procedure is based on deriving the impedance of each of the aforementioned plurality of rolling bearings in the aforementioned derivation procedure, and diagnosing the condition of each of the aforementioned plurality of rolling bearings. According to this configuration, in a device containing a plurality of rolling bearings, the condition of each rolling bearing can be diagnosed based on the measurement results of the plurality of rolling bearings.

[0070] The various embodiments have been described above with reference to the accompanying drawings. However, this invention is not limited to the examples described. Those skilled in the art will readily conceive of various modifications or alterations within the scope of the claims, and these will also fall within the technical scope of this invention. Furthermore, the constituent elements of the above embodiments can be combined arbitrarily without departing from the intent of the invention.

[0071] The various embodiments have been described above; however, the present invention is not limited to the examples described herein. Those skilled in the art will obviously conceive of various modifications or alterations within the scope of the claims, and these should also fall within the technical scope of the present invention. Furthermore, the constituent elements of the above embodiments can be arbitrarily combined without departing from the intent of the invention.

[0072] Furthermore, this application is based on Japanese patent application filed on March 16, 2022 (Invention Patent Application 2022-041692), the contents of which are incorporated herein by reference.

[0073] 1: Diagnostic device 2: Roller bearings 2a: Outer ring 2b: Roller (rolling element) 2c: Inner ring 3: Ball bearings 3a: Outer ring 3b: Ball bearing (rolling element) 3c: Inner ring 4: Linear Guide 5: Rotation axis 6: Motor 8: LCR tester 10: Bearing assembly 501,502,504,511,512,514,521,523,525,601,602,604,611,612,614,621,623,625,702,703,704,705,711,712,713,714: Plotting 503,505,513,515,522,524,526,603,605,613,615,622,624,626: Curves 701: Dashed line C: Capacitor CPE1, CPE2: Circuit components E: Circuit f: Frequency h: Oil film thickness h theory: Theoretical oil film thickness R, R1, R2: Resistors Z: Impedance Z im: imaginary number part Z re: Real part α: Metal contact ratio θ: Phase angle

Claims

1. A condition diagnosis method, characterized in that it is used for a bearing device having a plurality of rolling bearings electrically connected, and comprising the following steps: a measurement step, which measures the impedance of the plurality of rolling bearings as a whole by applying a voltage to the plurality of rolling bearings while varying the frequency using an AC power supply; a derivation step, which derives the impedance of each of the plurality of rolling bearings by fitting the impedance measured in the measurement step to an equivalent circuit formed by connecting the plurality of rolling bearings in series; and a diagnosis step, which diagnoses the condition of each of the plurality of rolling bearings based on the impedance of each of the plurality of rolling bearings derived in the derivation step.

2. The state diagnosis method as claimed in claim 1, wherein the aforementioned equivalent circuit is constructed by pseudocapacitors corresponding to each of the aforementioned plurality of rolling bearings.

3. The condition diagnosis method as requested in item 1 or 2, wherein the aforementioned plurality of rolling bearings are composed of different types of rolling bearings, and the aforementioned plurality of rolling bearings use the same type of lubricant.

4. The condition diagnosis method as requested in item 1 or 2, wherein the aforementioned plurality of rolling bearings are composed of the same type of rolling bearings, and the aforementioned plurality of rolling bearings use different types of lubricants.

5. A condition diagnostic device, characterized in that it is used for a bearing device having a plurality of electrically connected rolling bearings, and comprises the following mechanisms: a measuring mechanism that applies a voltage to the plurality of rolling bearings by varying the frequency using an alternating current power supply, and measures the overall impedance of the plurality of rolling bearings; a derivation mechanism that derives the impedance of each of the plurality of rolling bearings by fitting the impedance measured by the measuring mechanism to an equivalent circuit formed by connecting the plurality of rolling bearings in series; and a diagnostic mechanism that diagnoses the condition of each of the plurality of rolling bearings based on the impedance of each of the plurality of rolling bearings derived by the derivation mechanism.

6. A program for causing a computer to perform a status diagnostic method as requested in any one of items 1 to 4.

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