Condition measurement method, condition measurement device, and program

Abstract

This condition measuring method for measuring a condition between a first member and a second member that are lubricated using a lubricating agent involves: measuring an impedance by applying an alternating-current voltage to the first member and the second member while sweeping the alternating-current voltage; fitting a measurement result to an equivalent circuit defined in accordance with the configurations of the first member and the second member; and deriving the condition using the fitting result, and a predetermined mathematical formula including a parameter indicating the condition between the first member and the second member.

Description

Technical Field

[0001] The present invention relates to a state measurement method, a state measurement apparatus, and a program.

Background Art

[0002] Conventionally, in mechanical devices such as bearing devices and sliding devices, a configuration in which the contact surfaces between members are lubricated using a lubricant (for example, lubricating oil or grease) has been widely spread. For such mechanical devices, by periodically monitoring the states such as the surface roughness and oil film thickness of the members, damage and wear are detected at an early stage to suppress the occurrence of failures of rotating parts and the like.

[0003] In a mechanical device using a lubricant, when diagnosing the oil film state between members, measurement of the dielectric breakdown of the oil film is performed. For example, in Patent Document 1, a method of detecting the dielectric breakdown of an oil film between two objects by applying a voltage is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Dielectric breakdown can be affected by the surface roughness and oil film thickness of members lubricated with a lubricant. In other words, it is considered that by appropriately capturing the occurrence of dielectric breakdown, parameters around the lubricant such as the surface roughness and oil film thickness of the members can be estimated. In the method of Patent Document 1, a method of monitoring the surface roughness and oil film thickness of members lubricated with a lubricant by paying attention to such points is not considered.

[0006] In view of the above problems, an object of the present invention is to provide a method capable of monitoring the state around a lubricant, such as the surface roughness and oil film thickness of a member lubricated by the lubricant, in a mechanical device.

Means for Solving the Problems

[0007] In order to solve the above problems, the present invention has the following configuration. That is, a method for measuring the state between a first member and a second member lubricated by a lubricant, a measurement step of measuring impedance by applying an alternating voltage while sweeping it between the first member and the second member; a fitting step of fitting the measurement result obtained in the measurement step based on an equivalent circuit defined corresponding to the configurations of the first member and the second member; a derivation step of deriving the state using the result obtained in the fitting step and a predetermined mathematical formula including parameters indicating the state between the first member and the second member; having the predetermined mathematical formula is specified based on the relationship between the surface roughness of the first member and the second member, the oil film thickness of the lubricant, and the applied voltage, and uses the ratio of the region where dielectric breakdown occurs between the first member and the second member, the equivalent circuit defines a capacitor and a resistor caused by the lubricant based on the ratio, and is a state measurement method characterized by this.

[0008] Further, another form of the present invention has the following configuration. That is, a state measurement device for the state between a first member and a second member lubricated by a lubricant, measurement means for measuring impedance by applying an alternating voltage while sweeping it between the first member and the second member; fitting means for fitting the measurement result obtained by the measurement means based on an equivalent circuit defined corresponding to the configurations of the first member and the second member; A derivation means for deriving the state using the results obtained by the fitting means and a predetermined mathematical formula that includes parameters indicating the state between the first member and the second member, It has, The predetermined formula is determined based on the relationship between the surface roughness of the first member and the second member, the oil film thickness of the lubricant, and the applied voltage, and uses the percentage of the region where dielectric breakdown occurs between the first member and the second member. The equivalent circuit is characterized in that the capacitor and resistance due to the lubricant are defined based on the ratio.

[0009] Another embodiment of the present invention has the following configuration: namely, a program, On the computer, A measurement step in which impedance is measured by applying an AC voltage while sweeping through a first member and a second member that are lubricated with a lubricant, A fitting step in which the measurement results obtained in the measurement step are fitted based on an equivalent circuit defined in correspondence with the configuration of the first member and the second member, A derivation step of deriving the state using the results obtained in the fitting step and a predetermined mathematical formula that includes parameters indicating the state between the first member and the second member, Make it run, The predetermined formula is determined based on the relationship between the surface roughness of the first member and the second member, the oil film thickness of the lubricant, and the applied voltage, and uses the percentage of the region where dielectric breakdown occurs between the first member and the second member. The equivalent circuit is a program in which the capacitor and resistor due to the lubricant are defined based on the ratio. [Effects of the Invention]

[0010] This invention makes it possible to monitor the surface roughness and oil film thickness of components that are lubricated with a lubricant. [Brief explanation of the drawing]

[0011] [Figure 1] A diagram illustrating dielectric breakdown around a lubricant according to the present invention. [Figure 2] A diagram illustrating dielectric breakdown around a lubricant according to the present invention. [Figure 3] A schematic diagram showing an example configuration of a measuring device according to one embodiment of the present invention. [Figure 4A] A graph showing an example of measurement results related to a certain model. [Figure 4B] A graph showing an example of measurement results related to a certain model. [Figure 4C] A graph showing an example of measurement results related to a certain model. [Figure 5] A conceptual diagram illustrating the surface roughness distribution in one embodiment of the present invention. [Figure 6] A conceptual diagram illustrating the voltage dependence of dielectric breakdown in one embodiment of the present invention. [Figure 7] A diagram showing an equivalent circuit around a lubricant according to one embodiment of the present invention. [Figure 8] A conceptual diagram illustrating the voltage dependence of dielectric breakdown in one embodiment of the present invention. [Figure 9] A diagram showing the equivalent circuit of the entire bearing device according to one embodiment of the present invention. [Figure 10A] A graph showing an example of measurement results related to a certain model. [Figure 10B] A graph showing an example of measurement results related to a certain model. [Figure 10C] A graph showing an example of measurement results related to a certain model. [Figure 11] Flowchart of the measurement process related to Embodiment 1. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings and other documents. The embodiments described below are merely examples for illustrating the present invention and are not intended to be interpreted as limiting the invention. Furthermore, not all configurations described in each embodiment are necessarily essential for solving the problems of the present invention. In addition, in each drawing, the same components are given the same reference numeral to indicate their correspondence.

[0013] <First Embodiment> The first embodiment of the present invention will be described below. In this embodiment, a rolling bearing that performs rolling behavior while being lubricated by a lubricant will be used as an example. For example, types of rolling bearings to which the state measurement method of the present invention can be applied include deep groove ball bearings, angular contact ball bearings, tapered roller bearings, cylindrical roller bearings, and self-aligning roller bearings. However, the present invention is not limited to these, and can be applied to any mechanical device that operates by lubricating the contact positions between members with a lubricant.

[0014] [Dielectric breakdown] First, we will describe the dielectric breakdown between components lubricated by a lubricant according to this embodiment. The lubricant in this embodiment includes, but is not particularly limited to, lubricating oil or grease.

[0015] Figure 1 shows a schematic configuration of a rolling bearing 100 in which lubricant 103 is filled between the rolling elements 101 and the outer ring 102, and its equivalent circuit. Here, an example of an outer ring 102 is shown, but the same applies to an inner ring with a rolling surface. Surface roughness is formed on the surface of the rolling elements 101 and the surface of the outer ring 102 due to irregularities. Here, for the sake of simplicity, the combined surface roughness is shown collectively on the rolling element 101 side.

[0016] The region lubricated with a lubricant as shown in Figure 1(a) can be defined as an equivalent circuit of a parallel circuit in which a capacitor 111 and a resistor 112 are connected in parallel. In this embodiment, in order to measure the state of the rolling bearing, for example, impedance measurements using known methods such as EIM or EIS are performed. When a predetermined voltage is applied for measurement, if dielectric breakdown does not occur, current flows to the capacitor 111 side and almost none flows to the resistor side, as shown in Figure 1(b). When such dielectric breakdown does not occur, for example, an impedance |Z| = 10kΩ and a phase angle θ = -90° are obtained.

[0017] Figure 2 shows the case where dielectric breakdown occurs inside the rolling bearing 100 when a predetermined voltage is applied for measurement. As shown in Figure 2(a), when dielectric breakdown occurs, current 104 is conducted between the components (in this case, between the rolling elements 101 and the outer ring 102). In this state, as shown in Figure 2(b), current flows to the side of the resistance 112 due to the lubricant 103. As a result, the impedance |Z| decreases and the phase angle θ approaches 0°. For example, impedance |Z| = 100Ω and phase angle = 0°.

[0018] The degree of dielectric breakdown described above is assumed to be due not only to the applied voltage but also to the surface roughness of the components. In other words, even with the same applied voltage, dielectric breakdown is more likely to occur if there are areas where the surface roughness is rough and the distance between components is close.

[0019] [Device configuration] Here, an example of the apparatus configuration according to this embodiment will be described. Figure 3 is a schematic diagram showing an example of the overall configuration of System 1 to which the condition measurement method according to this embodiment can be applied. In Figure 3, System 1 using the condition measurement method according to this embodiment shows a measuring device 10, an LCR meter 20, and a bearing device 30 which is the object of measurement. Note that the configuration shown in Figure 3 is just one example, and different configurations may be used depending on the object of measurement, etc.

[0020] The bearing device 30 is composed of two rolling bearings. In the example shown in Figure 3, an example of two ball bearings 31a and 31b is shown. The ball bearings 31a and 31b are provided around the rotating shaft 40 and are configured to allow the rotating shaft 40 to rotate. Inside the ball bearings 31a and 31b, friction within each rolling bearing is reduced by a predetermined lubrication method. The lubrication method is not particularly limited, but for example, grease lubrication or oil lubrication can be used and supplied inside each rolling bearing. The type of lubricant is also not particularly limited.

[0021] Each of the ball bearings 31a and 31b is composed of an outer ring, multiple balls that act as rolling elements, and an inner ring. The ball bearings 31a and 31b are described as having the same configuration. In the example shown in Figure 3, the inner ring of each rolling bearing is described as a rolling ring and the outer ring as a stationary ring, but the reverse configuration is also possible. Although this embodiment shows an example where the bearing device 30 includes two ball bearings, the same can be applied to a bearing device composed of a single rolling bearing. Furthermore, the bearing device 30 is configured to be subjected to loads in predetermined directions (radial load, axial load).

[0022] Motor 50 is a drive motor that supplies rotational power to the rotating shaft 40 via a rotating belt or the like. Heater 60 is used to maintain the ambient temperature around the bearing device 30, which is the object of measurement, at a predetermined temperature. The LCR meter 20 is electrically connected to the bearing device 30 and the rotating shaft 40, and in this case, the LCR meter 20 also functions as an AC power source for the bearing device 30.

[0023] The measuring device 10 operates as a measuring device capable of executing the state measurement method according to this embodiment. During measurement, the measuring device 10 instructs the LCR meter 20 to input the angular frequency ω of the AC power supply and the AC voltage V, and obtains the impedance |Z| (where |Z| represents the absolute value of Z) and the phase angle θ of the bearing device 30 from the LCR meter 20 as output. The measuring device 10 then uses these values ​​to monitor the state of the bearing device 30. Details of the state measurement method will be described later.

[0024] The measuring device 10 may be implemented as an information processing device comprising, for example, a control device, a storage device, and an output device (not shown). The control device may consist of a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a DSP (Digital Single Processor), or a dedicated circuit. The storage device consists of volatile and non-volatile storage media such as an HDD (Hard Disk Drive), ROM (Read Only Memory), or RAM (Random Access Memory), and is capable of inputting and outputting various types of information in response to instructions from the control device. The output device consists of a speaker, a light, or a display device such as an LCD, and outputs to the operator in response to instructions from the control device. The output method by the output device is not particularly limited, but for example, it may be a visual output via screen output, or an auditory output via sound. The output device may also be a network interface with communication capabilities, and may perform output operations by transmitting data to an external device (not shown) via a network (not shown). The output content here is not limited to, for example, the output when an abnormality is detected based on the measurement results, but may also include an output indicating that the bearing device 30 is functioning normally.

[0025] [Preliminary verification] Figures 4A to 4C show examples of measurement results obtained when applying voltage to a rolling bearing while sweeping, using the apparatus configuration shown in Figure 3. The conditions for the measurement here are as follows:

[0026] (Measurement conditions) Bearing used: Deep groove ball bearing (Model number: 608) Temperature (outer ring): 27°C Rotation speed: 1000 [min -1 ] Axial load: 32 [N] Radial load: 0 [N] Maximum contact pressure: 1.0 [GPa] AC frequency: 1000000[Hz] Alternating voltage: 0.5 → 3.5 → 0.5 [V] Scanning speed: 5 / 60 [mV / s] (Lubricant used) Base oil: Polyalphaolefin oil (PAO) Contents: 40 [mg] Kinematic viscosity: 17[mm 2 / s] (below 40℃) Relative permittivity: 2.1

[0027] (Measurement results) In Figure 4A, the horizontal axis represents the applied voltage V [V], and the vertical axis represents the magnitude of the impedance |Z| [Ω]. In Figure 4B, the horizontal axis represents the applied voltage V [V], and the vertical axis represents the phase angle θ [°]. In Figure 4C, the horizontal axis represents the real value of the impedance Z. re The graph shows [Ω], with the vertical axis representing the imaginary number Z of the impedance. im The value [Ω] is shown. Here, the results are shown when the applied voltage is gradually increased (boosted).

[0028] In the examples in Figures 4A and 4C, the impedance changes (decreases) around 1.6V as a result of increasing the applied voltage. Also, the phase angle θ changes (increases) around 1.6V. Furthermore, referring to Figure 4C, as the voltage increases, the lubricant transitions from a state where it behaves as a capacitor (state in Figure 1) to a state where it behaves as a resistor (state in Figure 2). At this time, the state in Figure 1 corresponds to -Z in Figure 4C. im The plot corresponds to a high value, and the state in Figure 2 is -Z in Figure 4C. im This corresponds to a plot where the value is close to 0.

[0029] Based on the above measurement results, as shown in Figures 1 and 2, it is considered that dielectric breakdown occurred as the applied voltage increased, causing the lubricant to transition from behaving as a capacitor to behaving as a resistor. Furthermore, by observing the measurements shown in Figures 4A to 4C, the inventors of this application observed that the curve shape of the plot shown in Figure 4C depends on the surface roughness between the components, and that the transition voltage and the resistance caused by the lubricant due to dielectric breakdown are due to the oil film thickness.

[0030] [Modeling] In this embodiment, taking into account the above measurement results, a model is created that corresponds to the conditions under which dielectric breakdown occurs in order to derive the surface roughness and oil film thickness of the component.

[0031] Figure 5 is a conceptual diagram illustrating the surface roughness of a component. Similar to Figure 1, rolling elements and outer rings are used as examples of components lubricated by a lubricant. Although both the surface of the rolling elements and the surface of the outer ring have irregularities (roughness), the surface of the rolling elements is represented by the combined surface roughness, while the surface of the outer ring is shown as flat. In Figure 5, the dashed line indicates the center line of the combined surface roughness.

[0032] In this embodiment, the surface irregularities of the rolling element are assumed to follow a normal distribution, as shown in Figure 5(a). The following explanation will use formulas assuming a normal distribution, but is not limited to a normal distribution. Any probability density can be used as long as h, described later, can be expressed as a probability density function. In this case, the surface roughness (height) of the rolling element can be defined by the following equation (1).

[0033]

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[0034] f(h): Probability density function of the distribution of the inter-plane spacing h (PDF) h: Spacing between two surfaces μ: Distance between the center line of roughness and the smooth surface σ: composite surface roughness

[0035] When Equation (1) is transformed as shown in Fig. 5(b), it can be expressed as the following Equation (2). In Fig. 5(b), the horizontal axis represents the cumulative distribution probability F, and the vertical axis represents the interval h between members.

[0036]

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[0037] F(h): Cumulative distribution function (CDF), probability that the interval between two surfaces is h or less F: Cumulative distribution probability

[0038] Furthermore, in this embodiment, the breakdown voltage E limit , the critical oil film thickness h for breakdown limit , and the breakdown region ratio α limit are used. The breakdown voltage E limit represents the voltage at which breakdown occurs in the lubricant. The critical oil film thickness h for breakdown limit represents the oil film thickness as the limit value at which breakdown does not occur. The breakdown region ratio α limit represents the ratio of the region where breakdown occurs in the contact area. The breakdown voltage E limit , the critical oil film thickness h for breakdown limit , and the breakdown region ratio α limit are defined as follows, respectively.

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[0042] E limit : Breakdown voltage h limit : Critical oil film thickness for breakdown α limit : Dielectric breakdown region ratio (0≦α) limit ≤1) V: Voltage

[0043] Figure 6 shows the cumulative distribution function shown in Figure 5(b) and the dielectric breakdown voltage E limit , dielectric breakdown critical oil film thickness h limit , dielectric breakdown region ratio α limit This diagram illustrates the relationship. First, with respect to the applied voltage V, the dielectric breakdown region ratio α is calculated using equations (3) to (5) above. limit The dielectric breakdown region ratio α is identified. limit With this boundary, the cumulative distribution probability F is the dielectric breakdown region proportion α. limit Below this range, dielectric breakdown occurs, indicating that the oil film acts as a resistor. On the other hand, the cumulative distribution probability F is the dielectric breakdown region proportion α. limit This indicates that, above a certain range, dielectric breakdown does not occur, and the oil film acts as a capacitor.

[0044] Here, as shown in equations (3) to (5), the dielectric breakdown region ratio α limit This changes depending on the applied voltage. In this embodiment, the contact area between components lubricated by the lubricant is considered as a parallel circuit of a collection of minute resistances and a collection of minute capacitors. That is, the dielectric breakdown region ratio α shown in Figure 6. limit Let R be the resistance in the range lower than this, and let α be the dielectric breakdown region ratio. limit The equivalent circuit is defined as a capacitor C in a range higher than this.

[0045] Figure 7 is a conceptual diagram of the equivalent circuit according to this embodiment. The equivalent circuit 700 has a configuration in which a plurality of resistors 701 and a plurality of capacitors 702 are connected in parallel. In this case, the cumulative distribution probability F is the dielectric breakdown region ratio α limit The number of resistors 701 corresponding to the range below this, and the cumulative distribution probability F is the dielectric breakdown region ratio α limit The number of capacitors 703 corresponding to the range exceeding this is the dielectric breakdown region ratio α limit Handle it so that it changes accordingly.

[0046] The equivalent circuit 700 can be defined by the following equations (6) to (13). Figure 8 shows the relationship between the equivalent circuit 700 and the cumulative distribution function shown in Figure 6, etc. Graph 801 in Figure 8 shows that the cumulative distribution probability F corresponds to the dielectric breakdown region ratio α. limit This corresponds to the resistance ΔR of a small region corresponding to one resistor 701 that falls within the range below this value. Also, the graph 802 shown in Figure 8 shows that the cumulative distribution probability F is equal to the dielectric breakdown region ratio α. limit This corresponds to a small region of capacitor ΔC that corresponds to one capacitor 702 included in the range above this value.

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[0055] R1: Resistance caused by lubricant in the contact area ΔR: Resistance in a small region C1: Capacitance caused by lubricant in the contact area ΔC: Capacitance in a minute region ε: Dielectric constant of the lubricant ρ: Volume resistivity of the lubricant S: Contact area area

[0056] In other words, as shown in equations (6) to (13), in the cumulative distribution function, the dielectric breakdown region ratio α limit By integrating the small resistance ΔR and capacitor ΔC values ​​within the range defined by the formula, the resistance R1 and capacitor C1 caused by the lubricant in the contact area can be identified.

[0057] Furthermore, based on the resistance R1 and capacitor C1 obtained above, the impedance Z1 in the contact region can be defined by the following equation (14).

[0058]

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[0059] ω: Angular frequency of AC voltage Z1: Impedance within the contact area

[0060] [Application to rolling bearings] Based on the above model, we will now explain its application to rolling bearings. The above model corresponds to one contact area, that is, one region lubricated by a lubricant. On the other hand, for example, within a single rolling bearing, there are multiple rolling elements, and each of these rolling elements has a contact surface with the outer ring and inner ring. Therefore, in the case of rolling bearings, it is necessary to extend the above model to correspond to the number of contact areas.

[0061] Figure 9 shows the equivalent circuit of a bearing device including a rolling bearing according to this embodiment. The symbols are as follows: Z1: Impedance of one contact area R E External resistance C2: Capacitance between the rolling element and the raceway surface near the contact point C3: Capacitance between rolling element and groove shoulder C4: Capacitance between rolling elements and raceway surface in the unloaded zone C5: Capacitance between inner and outer rings E1: Equivalent circuit in the contact area between the outer ring (or inner ring) and the rolling element. E2: Equivalent circuit in the contact area around one rolling element

[0062] Here, we assume that only axial load is applied, and C4 = 0. Furthermore, since Z1 and C2 occur on the inner and outer ring sides of a single rolling element, two E1 values ​​are connected in series. Additionally, E2 values ​​are connected in parallel for each rolling element located in the axial load zone. C3 values ​​are set for each rolling element, and these are connected in parallel. These rolling bearings and the external resistance R... E A voltage V is applied to the equivalent circuit of the entire bearing device, including the bearing components, and the impedance Z is measured.

[0063] Based on the equivalent circuit in Figure 9, the impedance Z of a rolling bearing with n rolling elements is bearing This can be defined by the following equation (15). Here, the present applicant has published International Publication No. 2022 / 054352 as a method for measuring EIM under radial load, and based on this method, equations (16) and (17) can be defined.

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[0067] Z bearing Impedance of rolling bearings n: Number of rolling elements R tx : Equivalent radius of curvature in the rolling direction, averaged over the inner and outer rings. R ty : Equivalent radius of curvature in the direction perpendicular to the rolling direction, averaged over the inner and outer rings. R b : Rolling element radius h t1 : The sum of the oil film thicknesses formed on the inner and outer rings. γ:Groove angle φ: Average inner ring contact angle C5: Capacitance between inner and outer rings (measured value)

[0068] The impedance Z of the entire bearing system can be defined by the following equation (18).

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[0070] Z: Impedance of bearing device

[0071] Based on the above formula, various parameters during measurement, lubricant specifications, and rolling bearing specifications, the relationship between the impedance Z and voltage V of the bearing device can be determined. Then, by performing fitting to match the measured values, it becomes possible to estimate unknown parameters treated as variables, such as oil film thickness and surface roughness. One method for this fitting is the method described in International Publication No. 2022 / 054352 by the present applicant. This embodiment shows an example using such a method.

[0072] [Examples of application] Figures 10A to 10C show the results of fitting based on the equivalent circuit described above, using the measurement device shown in Figure 3. In this example, the following fixed values ​​were used for fitting, and the dielectric breakdown voltage E limitThis shows an example of estimation using the composite surface roughness σ and the volume resistivity ρ of the lubricant as variables.

[0073] (Setting parameters) Contact ellipse area S=2.4e-8[m 2 ](Fixed) The dielectric constant of the lubricant is ε = 2.1[-] (fixed). Average oil film thickness μ=37[nm] (fixed, h H-D =44nm,h EIM (=37nm)

[0074] In Figure 10A, the horizontal axis represents voltage V [V], and the vertical axis represents the phase angle θ [°]. Plot 1001 shows the measurement results, and plot 1002 shows the fitting results.

[0075] In Figure 10B, the horizontal axis represents voltage V [V], and the vertical axis represents the absolute value of impedance |Z| [Ω]. Plot 1011 shows the measurement results, and plot 1012 shows the fitting results.

[0076] In Figure 10C, the horizontal axis represents the real impedance -Z. re The graph shows [Ω], with the vertical axis representing the imaginary number of impedance -Z. im [Ω] is shown. Plot 1021 shows the measurement results, and plot 1022 shows the fitting results.

[0077] The fitting results and the values ​​estimated using the above formulas are as follows. Dielectric breakdown voltage E limit = 45 [kV / mm] (Approximately equivalent to the physical properties of typical oils, which are 30-40 [kV / mm]) Synthetic surface roughness σ = 1 [nm] (Ra 12 nm before testing) The volume resistivity ρ of the lubricant when dielectric breakdown occurs is 200 [Ωm] (typical physical property value of oil at low frequency: 1 × 10⁻⁶). 10 [Ωm])h H-D :Calculation of oil film thickness h using the Hamrock-Dowson formula EIM : Oil film thickness measured by EIM

[0078] The AC voltage V applied to the electrical circuit E, the current I flowing through the electrical circuit E, and the complex impedance Z of the entire electrical circuit E are given by the following equations (19) to (21). V = |V| exp(jωt) …(19) I = |I|exp(j(ωt-θ)) …(20) Z=V / I=|V / I|exp(jθ)=|Z|exp(jθ) …(21) j: imaginary number ω: Angular frequency of voltage t: time θ: Phase angle (the phase difference between voltage and current)

[0079] [Processing flow] Figure 11 is a flowchart of the state measurement process according to this embodiment using the method described above. This process is performed by the measuring device 10, and may be implemented, for example, by the control device (not shown) of the measuring device 10 reading a program for implementing the process according to this embodiment from a storage device (not shown) and executing it. In addition, the fitting and parameter derivation in the following processes may be configured to be partially implemented using the functions of general-purpose software.

[0080] In S1101, the measuring device 10 controls the LCR meter 20 to supply power to the bearing device 30 with an AC voltage V of angular frequency ω using the AC power supply (not shown) provided by the LCR meter 20. As a result, an AC voltage V of angular frequency ω is applied to the lubricant in each rolling bearing.

[0081] In S1102, the measuring device 10 obtains the impedance |Z| and phase angle θ from the LCR meter 20 as the output for the input specified in S1101. In other words, the LCR meter 20 outputs the impedance Z and phase angle θ to the measuring device 10 as the measurement results of the bearing device 30 for the AC voltage V of angular frequency ω which is the input.

[0082] In S1103, the measuring device 10 sets the values ​​of various parameters in the above formula based on the specifications of the lubricant, the specifications of the bearing device, the measurement conditions, etc. It is assumed that the formulas based on the equivalent circuit corresponding to the object being measured are predefined and registered for use by the measuring device 10.

[0083] In S1104, the measuring device 10 performs a fitting (application) to the equation based on the equivalent circuit shown in Figure 9, based on the impedance Z and phase angle θ obtained in S1102 and the AC voltage V of angular frequency ω indicated in S1101. For example, the method described in International Publication No. 2022 / 054352 by the present applicant can be used.

[0084] In S1105, the measuring device 10 estimates the variable parameters using the fitting results from S1104 and the mathematical formula whose parameters were set in S1103. The variable parameters here are, for example, the dielectric breakdown voltage E, as explained using Figures 10A to 10C. limit、 The composite surface roughness σ and the volume resistivity ρ of the lubricant may be used. Alternatively, the average oil film thickness μ may be estimated as a variable parameter.

[0085] In S1106, the measuring device 10 performs a condition diagnosis based on the results estimated in S1105. The content of the diagnosis here is not particularly limited, but for example, a predetermined threshold may be set for the estimated result, and the diagnosis of normal or abnormality may be made by comparing it with that threshold. Alternatively, multiple thresholds may be set according to the urgency of the abnormality, and the urgency may be diagnosed by comparing it with those thresholds.

[0086] In S1107, the measuring device 10 outputs the values ​​estimated in S1106 and the diagnostic results obtained in S1106 to the user. The output method here is not particularly limited, but for example, it may be configured to display the parameters or items that were judged to be abnormal on the screen or to notify the user by voice. Then, this processing flow ends.

[0087] As described above, this embodiment makes it possible to monitor the surface roughness and oil film thickness of components that are lubricated by a lubricant. For example, it can be applied to bearing devices equipped with rolling bearings as the measurement target.

[0088] <Other Embodiments> As mentioned above, it is also possible to use parameters other than the normal distribution for h. In such cases, another formula corresponding to the parameter is used instead of formula (5) above. Also, formula (4) is used for h limit =h(α limit It is used as a function.

[0089] Furthermore, in the present invention, the functions of one or more embodiments described above can also be realized by supplying a program or application to a system or device using a network or storage medium, and one or more processors in the computer of that system or device reading and executing the program.

[0090] Alternatively, it may be implemented by a circuit that performs one or more functions (for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array)).

[0091] Thus, the present invention is not limited to the embodiments described above. It is also intended and within the scope of protection to be provided for the combination of each configuration of the embodiments, as well as for modifications and applications by those skilled in the art based on the description in the specification and well-known technology.

[0092] As described above, the following matters are disclosed in this specification: (1) A method for measuring the condition between a first member (e.g., 101) and a second member (e.g., 102) that are lubricated by a lubricant (e.g., 103), A measurement step (for example, S1101, S1102) to measure impedance by applying an AC voltage to the first member and the second member while sweeping, A fitting step (for example, S1103, S1104) is performed to fit the measurement results obtained in the measurement step based on an equivalent circuit defined in correspondence with the configuration of the first member and the second member, A derivation step (for example, S1105) is performed to derive the state using the results obtained in the fitting step and a predetermined mathematical formula that includes parameters indicating the state between the first member and the second member. It has, The predetermined formula is determined based on the relationship between the surface roughness of the first member and the second member, the oil film thickness of the lubricant, and the applied voltage, and uses the percentage of the region where dielectric breakdown occurs between the first member and the second member. The equivalent circuit is characterized in that the capacitor and resistance caused by the lubricant are defined based on the ratio. This configuration makes it possible to monitor the surface roughness and oil film thickness of components lubricated by the lubricant. In particular, it makes it possible to monitor the condition around the lubricant based on the probability of dielectric breakdown occurring in the lubricant.

[0093] (2) The predetermined formula is:

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[0098]

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[0099] E limit : Dielectric breakdown voltage h limit : Dielectric breakdown critical oil film thickness α limit : Dielectric breakdown region ratio (0≦α) limit ≤1) V: Applied voltage R1: Resistance caused by lubricant in the contact area C1: Capacitance caused by lubricant in the contact area Z1: Impedance within the contact area ε: Dielectric constant of the lubricant ρ: Volume resistivity of the lubricant S: Contact area area j: imaginary number ω: Angular frequency of voltage The method for measuring a state according to (1), characterized in that it is defined in [the relevant section]. This configuration allows for the estimation of various parameters surrounding the lubricant by defining the region where dielectric breakdown occurs, based on the probability of dielectric breakdown in the lubricant. For example, it becomes possible to estimate the surface roughness and oil film thickness of the component.

[0100] (3) The first member and the second member are included in the rolling device (for example, 30), The state measurement method according to (1), characterized in that the equivalent circuit is defined according to the configuration of the rolling device. This configuration makes it possible to estimate the condition of the lubricant around the rolling mechanism, particularly the surface roughness and oil film thickness of the components.

[0101] (4) A condition measuring device (for example, 1) for the relationship between a first member and a second member that are lubricated by a lubricant, A measuring means (for example, 20) for measuring impedance by applying an AC voltage to the first member and the second member while sweeping, A fitting means (e.g., 10) that fits the measurement results from the measuring means based on an equivalent circuit defined in correspondence with the configuration of the first member and the second member, A derivation means (for example, 10) for deriving the state using the results obtained by the fitting means and a predetermined mathematical formula that includes parameters indicating the state between the first member and the second member, It has, The predetermined formula is determined based on the relationship between the surface roughness of the first member and the second member, the oil film thickness of the lubricant, and the applied voltage, and uses the percentage of the region where dielectric breakdown occurs between the first member and the second member. The equivalent circuit is characterized in that the capacitor and resistance due to the lubricant are defined based on the ratio. This configuration makes it possible to monitor the surface roughness and oil film thickness of components lubricated by the lubricant. In particular, it makes it possible to monitor the condition around the lubricant based on the probability of dielectric breakdown occurring in the lubricant.

[0102] (5) A computer (for example, 10) A measurement step (e.g., S1101, S1102) is performed to measure impedance by applying an AC voltage while sweeping through a first member (e.g., 101) and a second member (e.g., 102) that are lubricated with a lubricant (e.g., 103), A fitting step (for example, S1103, S1104) is performed to fit the measurement results obtained in the measurement step based on an equivalent circuit defined in correspondence with the configuration of the first member and the second member, A derivation step (for example, S1105) is performed to derive the state using the results obtained in the fitting step and a predetermined mathematical formula that includes parameters indicating the state between the first member and the second member. Make it run, The predetermined formula is determined based on the relationship between the surface roughness of the first member and the second member, the oil film thickness of the lubricant, and the applied voltage, and uses the percentage of the region where dielectric breakdown occurs between the first member and the second member. The equivalent circuit is a program in which the capacitor and resistor due to the lubricant are defined based on the ratio. This configuration makes it possible to monitor the surface roughness and oil film thickness of components lubricated by the lubricant. In particular, it makes it possible to monitor the condition around the lubricant based on the probability of dielectric breakdown occurring in the lubricant.

[0103] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to these examples. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any way without departing from the spirit of the invention.

[0104] Although various embodiments have been described above, it goes without saying that the present invention is not limited to these examples. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention. Furthermore, the components in the above embodiments may be combined in any way without departing from the spirit of the invention.

[0105] This application is based on Japanese Patent Application No. 2022-178453 filed on November 7, 2022, and its contents are incorporated herein by reference. [Explanation of Symbols]

[0106] 1 System 10 Measuring device 20 LCR meter 30 Bearing device 31 (31a, 31b) Rolling bearings (ball bearings) 40 Rotation axis 50 motors 60 Heater

Claims

1. A method for measuring the condition between a first member and a second member that are lubricated by a lubricant, A measurement step of measuring impedance by applying an AC voltage to the first member and the second member while sweeping, A fitting step in which the measurement results obtained in the measurement step are fitted based on a predetermined mathematical formula defined by an equivalent circuit that corresponds to the configuration of the first member and the second member, A derivation step is performed to derive the state using the variable parameters included in the predetermined mathematical formula that indicates the state between the first member and the second member, based on the results obtained in the fitting step, It has, The aforementioned predetermined mathematical formula is: The aforementioned variable parameters are the surface roughness of the first member and the second member, the oil film thickness of the lubricant, and the dielectric breakdown voltage E. limit Includes, Based on the surface roughness, a probability density function f(h) and its cumulative distribution function F(h) are defined, which show the distribution of the inter-plane spacing h between the first member and the second member. The dielectric breakdown voltage E limit Based on the relationship between the oil film thickness and the applied voltage, the dielectric breakdown critical oil film thickness h is set as the upper limit of the gap h between the two surfaces at which dielectric breakdown can occur. limit Seeking, In the cumulative distribution function F(h), h = h limit The value at which this occurs is the ratio α of the region where dielectric breakdown occurs between the first member and the second member. limit Identified as, The equivalent circuit is, The contact area between the first member and the second member is divided into a plurality of minute regions, and in each minute region, according to the distance between the two surfaces, either a resistive element or a capacitive element due to the lubricant is assigned. The aforementioned proportion α limit Based on the above, the proportion α of the contact area limit A collection of capacitors caused by the lubricant, which is located in a minute region higher than the ratio α, and the ratio α limit A condition measurement method characterized in that the impedance of a contact area is defined by connecting in parallel a collection of resistances caused by the lubricant arranged in a minute region lower than a certain value.

2. The aforementioned predetermined mathematical formula is: [Math 1] [Math 2] [Math 3] [Math 4] [Math 5] E limit : Dielectric breakdown voltage h limit : Dielectric breakdown critical oil film thickness α limit : Dielectric breakdown region ratio (0 ≤ α) limit ≤1) V: Applied voltage R １ : Resistance caused by lubricant in the contact area C １ : Capacitance caused by lubricant in the contact area Z １ : Impedance within the contact area ε: Dielectric constant of the lubricant ρ: Volume resistivity of the lubricant S: Contact area area j: imaginary number ω: Angular frequency of voltage The condition measurement method according to feature 1, as defined in [reference].

3. The first member and the second member are included in the rolling device. The state measurement method according to claim 1, characterized in that the equivalent circuit is defined according to the configuration of the rolling device.

4. A condition measuring device for the space between a first member and a second member that are lubricated by a lubricant, A measuring means for measuring impedance by applying an AC voltage to the first member and the second member while sweeping it, A fitting means that performs fitting of the measurement results obtained by the measurement means based on a predetermined mathematical formula defined by an equivalent circuit corresponding to the configuration of the first member and the second member, Based on the results obtained by the fitting means, a derivation means for deriving the state using variable parameters included in the predetermined mathematical formula that indicates the state between the first member and the second member, It has, The aforementioned predetermined mathematical formula is: The aforementioned variable parameters are the surface roughness of the first member and the second member, the oil film thickness of the lubricant, and the dielectric breakdown voltage E. limit Includes, Based on the surface roughness, a probability density function f(h) and its cumulative distribution function F(h) are defined, which show the distribution of the inter-plane spacing h between the first member and the second member. The dielectric breakdown voltage E limit Based on the relationship between the oil film thickness and the applied voltage, the dielectric breakdown critical oil film thickness h is set as the upper limit of the gap h between the two surfaces at which dielectric breakdown can occur. limit Seeking, In the cumulative distribution function F(h), h = h limit The value at which this occurs is the ratio α of the region where dielectric breakdown occurs between the first member and the second member. limit Identified as, The equivalent circuit is, The contact area between the first member and the second member is divided into a plurality of minute regions, and in each minute region, according to the distance between the two surfaces, either a resistive element or a capacitive element due to the lubricant is assigned. The aforementioned proportion α limit Based on the above, the proportion α of the contact area limit A collection of capacitors caused by the lubricant, which is located in a minute region higher than the ratio α, and the ratio α limit A condition measuring device characterized in that the impedance of a contact area is defined by connecting in parallel a collection of resistances caused by the lubricant arranged in a minute region lower than a certain value.

5. On the computer, A measurement step in which impedance is measured by applying an AC voltage while sweeping through a first member and a second member that are lubricated with a lubricant, A fitting step in which the measurement results obtained in the measurement step are fitted based on a predetermined mathematical formula defined by an equivalent circuit that corresponds to the configuration of the first member and the second member, A derivation step is performed to derive the state using the variable parameters included in the predetermined mathematical formula that indicates the state between the first member and the second member, based on the results obtained in the fitting step, Make it run, The aforementioned predetermined mathematical formula is: The aforementioned variable parameters are the surface roughness of the first member and the second member, the oil film thickness of the lubricant, and the dielectric breakdown voltage E. limit Includes, Based on the surface roughness, a probability density function f(h) and its cumulative distribution function F(h) are defined, which show the distribution of the inter-plane spacing h between the first member and the second member. The dielectric breakdown voltage E limit Based on the relationship between the oil film thickness and the applied voltage, the dielectric breakdown critical oil film thickness h is set as the upper limit of the gap h between the two surfaces at which dielectric breakdown can occur. limit Seeking, In the cumulative distribution function F(h), h = h limit The value at which this occurs is the ratio α of the region where dielectric breakdown occurs between the first member and the second member. limit Identified as, The equivalent circuit is, The contact area between the first member and the second member is divided into a plurality of minute regions, and in each minute region, according to the distance between the two surfaces, either a resistive element or a capacitive element due to the lubricant is assigned. The aforementioned proportion α limit Based on the above, the proportion α of the contact area limit A collection of capacitors caused by the lubricant, which is located in a minute region higher than the ratio α, and the ratio α limit A program that defines the impedance of a contact area connected in parallel with a set of resistances caused by the lubricant, which is located in a minute region lower than a certain value.

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