State measurement method, state measurement device, and program

Abstract

In the method for measuring the state between a first member and a second member lubricated by a lubricant, the impedance is measured by applying an AC voltage to the first member and the second member while scanning the AC voltage, and the measurement results are fitted on the basis of an equivalent circuit defined in accordance with the configuration of the first member and the second member. The state is derived using the fitting result and a prescribed formula including parameters indicating the state between the first member and the second member.

Description

Technical Field

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

[0002] Conventionally, in mechanical devices such as bearing devices and sliding devices, a structure in which a lubricant (e.g., lubricating oil, grease) is used to lubricate the contact surfaces between components has been widely popularized. For such mechanical devices, the states such as the surface roughness and oil film thickness of the components are regularly monitored, thereby early detecting damages and wear and suppressing the occurrence of failures of rotating components.

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

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2008-241383 Summary of the Invention

[0007] Technical Problem to be Solved by the Invention

[0008] The dielectric breakdown may be affected by the surface roughness and oil film thickness of the components lubricated by the 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 components can be estimated. In the method of Patent Document 1, a method of monitoring the surface roughness, oil film thickness, etc. of the components lubricated by the lubricant by focusing on this point is not considered.

[0009] 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 components lubricated with the lubricant in a mechanical device.

[0010] Technical Means for Solving the Problem

[0011] In order to solve the above problems, the present invention has the following configuration. That is, a state measurement method, characterized in that it is a state measurement method between a first component and a second component lubricated by a lubricant, and has:

[0012] A measurement step of applying an alternating voltage to the first component and the second component while scanning the alternating voltage, thereby measuring an impedance;

[0013] A fitting process of fitting the measurement result of the measurement process according to an equivalent circuit defined corresponding to the structures of the first component and the second component; and

[0014] A derivation process of deriving the state by using the result obtained in the fitting process and a prescribed formula including a parameter representing the state between the first component and the second component,

[0015] wherein the prescribed formula uses a ratio of a region where dielectric breakdown occurs between the first component and the second component, which is determined based on the relationship among the surface roughness of the first component and the second component, the oil film thickness of the lubricant, and the applied voltage,

[0016] and the equivalent circuit defines a capacitor and a resistor caused by the lubricant based on the ratio.

[0017] In addition, another aspect of the present invention has the following structure. That is, a state measurement device, characterized in that

[0018] it is a state measurement device between a first component and a second component lubricated by a lubricant, and includes:

[0019] a measurement unit that measures impedance by applying an alternating voltage to the first component and the second component while scanning the alternating voltage;

[0020] a fitting unit that fits the measurement result of the measurement unit according to an equivalent circuit defined corresponding to the structures of the first component and the second component; and

[0021] a derivation unit that derives the state by using the result obtained in the fitting unit and a prescribed formula including a parameter representing the state between the first component and the second component,

[0022] wherein the prescribed formula uses a ratio of a region where dielectric breakdown occurs between the first component and the second component, which is determined based on the relationship among the surface roughness of the first component and the second component, the oil film thickness of the lubricant, and the applied voltage,

[0023] and the equivalent circuit defines a capacitor and a resistor caused by the lubricant based on the ratio.

[0024] In addition, another aspect of the present invention has the following structure. That is, a program, characterized in that it causes a computer to execute the following processes:

[0025] A measurement process of measuring impedance by applying an alternating voltage to a first component and a second component lubricated by a lubricant while scanning the alternating voltage;

[0026] A fitting process of fitting the measurement result of the measurement process according to an equivalent circuit defined corresponding to the structures of the first component and the second component; and

[0027] A derivation process of deriving the state using the result obtained by the fitting process and a prescribed formula including a parameter representing the state between the first component and the second component,

[0028] The prescribed formula uses the ratio of the region where dielectric breakdown occurs between the first component and the second component, which is determined based on the relationship between the surface roughness of the first component and the second component, the oil film thickness of the lubricant, and the applied voltage,

[0029] The equivalent circuit defines a capacitor and a resistor caused by the lubricant based on the ratio.

[0030] Advantages of the Invention

[0031] According to the present invention, it is possible to monitor the surface roughness and the oil film thickness of components lubricated with a lubricant. Brief Description of the Drawings

[0032] Figure 1 is a diagram for explaining dielectric breakdown around the lubricant of the present invention.

[0033] Figure 2 is a diagram for explaining dielectric breakdown around the lubricant of the present invention.

[0034] Figure 3 is a schematic diagram showing a structural example of a measurement device according to an embodiment of the present invention.

[0035] Figure 4A is a graph showing an example of a measurement result according to an embodiment of the present invention.

[0036] Figure 4B is a graph showing an example of a measurement result according to an embodiment of the present invention.

[0037] Figure 4C is a graph showing an example of a measurement result according to an embodiment of the present invention.

[0038] Figure 5 is a conceptual diagram for explaining the distribution of surface roughness according to an embodiment of the present invention.

[0039] Figure 6 is a conceptual diagram for explaining the voltage dependence of dielectric breakdown according to an embodiment of the present invention.

[0040] Figure 7 is a diagram showing an equivalent circuit around the lubricant according to an embodiment of the present invention.

[0041] Figure 8 It is a conceptual diagram for explaining the voltage dependence of dielectric breakdown in one embodiment of the present invention.

[0042] Figure 9 It is a diagram showing the equivalent circuit of the entire bearing device in one embodiment of the present invention.

[0043] Figure 10A It is a chart showing an example of the measurement result in one embodiment of the present invention.

[0044] Figure 10B It is a chart showing an example of the measurement result in one embodiment of the present invention.

[0045] Figure 10C It is a chart showing an example of the measurement result in one embodiment of the present invention.

[0046] Figure 11 It is a flowchart of the measurement process in one embodiment of the present invention. Detailed Embodiment

[0047] Hereinafter, a mode for implementing the present invention will be described with reference to the drawings and the like. In addition, the embodiments described below are for explaining one embodiment of the present invention, and are not intended to limit the interpretation of the present invention. In addition, all the structures described in each embodiment are not limited to the structures necessary for solving the problems of the present invention. In addition, in each drawing, the same reference numerals are used to indicate the corresponding relationship for the same constituent elements.

[0048] <First Embodiment>

[0049] Hereinafter, a first embodiment of the present invention will be described. In addition, in the present embodiment, a rolling bearing that performs a rolling motion while being lubricated with a lubricant will be described as an example. For example, as the types of rolling bearings to which the state measurement method of the present invention can be applied, deep groove ball bearings, angular contact ball bearings, tapered roller bearings, cylindrical roller bearings, self-aligning roller bearings, etc. can be cited. However, it is not limited thereto, and the present invention can be applied to any mechanical device that lubricates the contact position between components with a lubricant.

[0050] [Dielectric Breakdown]

[0051] First, dielectric breakdown between components lubricated with a lubricant in the present embodiment will be described. As the lubricant in the present embodiment, lubricating oil, grease, etc. are included, but there is no particular limitation.

[0052] Figure 1Schematic structure of a lubricant 103 filled between rolling elements 101 and an outer ring 102 that constitute a rolling bearing 100 and its equivalent circuit are shown. Here, an example of the outer ring 102 is shown, but the same applies to an inner ring having a rolling surface. Surface roughness caused by unevenness is formed on the surface of the rolling element 101 and the surface of the outer ring 102. Here, for simplicity of explanation, it is shown as a combined surface roughness on the rolling element 101 side.

[0053] Figure 1 (a) The lubricated region shown can define a parallel circuit in which a capacitor 111 and a resistor 112 are connected in parallel as an equivalent circuit. In the present embodiment, in order to measure the state of the rolling bearing, for example, impedance measurement based on EIM and EIS, which are well-known methods, is performed. When a prescribed voltage is applied for measurement, in the case where insulation breakdown does not occur, as Figure 1 (b) shows, current flows on the capacitor 111 side and almost no current flows on the resistor side. When such insulation breakdown does not occur, for example, impedance |Z| = 10 kΩ and phase angle θ = -90° are obtained.

[0054] Figure 2 Shows the case where insulation breakdown has occurred when a prescribed voltage is applied for measurement inside the rolling bearing 100. As Figure 2 (a) shows, in the case where insulation breakdown has occurred, conduction 104 is generated between components (here, between the rolling element 101 and the outer ring 102). This state is as Figure 2 (b) shows, current flows on the resistor 112 side of the lubricant 103. As a result, the impedance |Z| decreases and the phase angle θ approaches 0°. For example, impedance |Z| = 100 Ω and phase angle = 0°.

[0055] The degree of generation of such insulation breakdown is assumed to be caused not only by the applied voltage value but also by the surface roughness of the components. That is, it is considered that even with the same applied voltage, insulation breakdown is likely to occur in the case where the surface roughness is rough and the distance between components is close.

[0056] [Device Structure]

[0057] Here, an example of the device structure of the present embodiment will be described. Figure 3 Is a schematic structural diagram showing an example of the overall structure of a system 1 to which the state measurement method of the present embodiment can be applied. In Figure 3 it, a system 1 using the state measurement method of the present embodiment shows a measurement device 10, an LCR meter 20, and a bearing device 30 as a measurement object. In addition, Figure 3 The structure shown is an example, and different structures can be used depending on the measurement object and the like.

[0058] The bearing device 30 is configured to include two rolling bearings. In Figure 3 the example of Figure 3 , examples of two ball bearings 31a and 31b are shown. The ball bearings 31a and 31b are disposed around the rotating shaft 40 and are configured to enable the rotating shaft 40 to rotate. Inside the ball bearings 31a and 31b, friction within each rolling bearing is reduced by a prescribed lubrication method. The lubrication method is not particularly limited. For example, grease lubrication, oil lubrication, etc. are used and supplied to the inside of each rolling bearing. The type of lubricant is also not particularly limited.

[0059] The ball bearings 31a and 31b are each configured to include an outer ring, a plurality of balls as rolling elements, and an inner ring. A case where the ball bearings 31a and 31b have the same structure will be described. In Figure 3 the example of Figure 3 , the inner ring of each rolling bearing is used as the rolling ring and the outer ring is used as the fixed ring for description, but the opposite structure is also possible. In addition, in the present embodiment, an example where the bearing device 30 is configured to include two ball bearings is shown, but a bearing device composed of one rolling bearing can also be applied in the same manner. Further, a load (radial load, axial load) in a prescribed direction is applied to the bearing device 30.

[0060] The motor 50 is a driving motor and supplies rotational power to the rotating shaft 40 via a rotating belt or the like. The heater 60 is used to maintain the temperature around the bearing device 30, which is the object to be measured, at a prescribed temperature. The LCR meter 20 is electrically connected to the bearing device 30 and the rotating shaft 40. At this time, the LCR meter 20 also functions as an AC power supply for the bearing device 30.

[0061] The measuring device 10 operates as a measuring device capable of executing the state measuring method of the present embodiment. When measuring, the measuring device 10 instructs the LCR meter 20 with the angular frequency ω and the AC voltage V of the AC power supply as inputs, and obtains the impedance |Z| (|Z| represents the absolute value of Z) and the phase angle θ of the bearing device 30 from the LCR meter 20 as an output thereof. Then, the measuring device 10 uses these values to monitor the state of the bearing device 30. Details of the state measuring method will be described later.

[0062] The measuring device 10 can be implemented, for example, by an information processing device configured to include a control device, a storage device, and an output device (not shown). The control device can be constituted by a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a DSP (Digital Single Processor), or a dedicated circuit, etc. The storage device is constituted by volatile and non-volatile storage media such as an HDD (Hard Disk Drive), a ROM (ReadOnly Memory), and a RAM (Random Access Memory), and can input and output various information according to instructions from the control device. The output device is constituted by display devices such as a speaker, a lamp, or a liquid crystal display, etc., and outputs to the operator according to instructions from the control device. The output method of the output device is not particularly limited. For example, it can be a visual output based on screen output, or an auditory output based on sound. In addition, the output device can be a network interface with a communication function, or can perform an output operation by sending data to an external device (not shown) via a network (not shown). The output content here is not limited to, for example, outputting a status measurement based on a measurement result and outputting when an abnormality is detected, and can also include an output indicating that the bearing device 30 is normal.

[0063] [Pre-verification]

[0064] Figures 4A - 4C Indicates the use of Figure 3 An example of the measurement result obtained when applying a voltage to a rolling bearing while scanning the voltage using the device structure shown. The conditions in this measurement are as follows.

[0065] (Measurement conditions)

[0066] Bearing used: Deep groove ball bearing (No.: 608)

[0067] Temperature (outer ring): 27 °C

[0068] Rotation speed: 1000 [min -1

[0069] Axial load: 32 [N]

[0070] Radial load: 0 [N]

[0071] Maximum contact pressure: 1.0 [GPa]

[0072] AC frequency: 1000000 [Hz]

[0073] ​AC voltage: 0.5 → 3.5 → 0.5 [V]

[0074] Scanning speed: 5 / 60 [mV / s]

[0075] (Using lubricant)

[0076] Base oil: Polyalphaolefin oil (PAO)

[0077] Filling amount: 40 [mg]

[0078] Kinematic viscosity: 17 [mm 2 / s] (at 40 °C)

[0079] Relative permittivity: 2.1

[0080] (Measurement results)

[0081] 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 part of the impedance Z re [Ω], and the vertical axis represents the imaginary part of the impedance Z im [Ω]. Here, the results when the applied voltage is gradually increased (boosted) are shown.

[0082] In Figures 4A - 4C 's example, as a result of boosting the applied voltage, the impedance changes (decreases) around 1.6 V. In addition, the phase angle θ changes (increases) around 1.6 V. In addition, referring to Figure 4C for explanation, the following results are obtained: As the voltage increases, the lubricant changes from the state where it functions as a capacitor ( Figure 1 's state) to the state where it functions as a resistor ( Figure 2 's state). At this time, Figure 1 's state corresponds to the plot of the higher value of -Z Figure 4C in im , and Figure 2 's state corresponds to the plot of the value of -Z Figure 4C in im that is close to 0.

[0083] Based on the above measurement results, as shown in Figure 1 and Figure 2 , it is considered that dielectric breakdown occurs with the boosting of the applied voltage, and the lubricant changes from the state where it functions as a capacitor to the state where it functions as a resistor. In addition, the inventors of the present application recognized by observing the measurement as shown in Figures 4A - 4C that Figure 4CThe curve shape of the drawing as shown depends on the surface roughness between components. Additionally, the resistance of the lubricant caused by the transition voltage and insulation breakdown depends on the oil film thickness.

[0084] [Modeling]

[0085] In the present embodiment, considering the above measurement results, in order to derive the surface roughness and oil film thickness of the components, modeling corresponding to the conditions for insulation breakdown is performed.

[0086] Figure 5 is a conceptual diagram for explaining the surface roughness of the components. Similar to Figure 1 the same, as components lubricated with a lubricant, the rolling elements and the outer ring are taken as examples for explanation. Additionally, there are irregularities (roughness) on the surface of the rolling elements and the surface of the outer ring, but it is shown that there are irregularities (synthetic surface roughness) on the surface of the rolling elements, and the surface of the outer ring is shown as a plane. In Figure 5 it, the dash-dot line represents the center line of the synthetic surface roughness.

[0087] In the present embodiment, as Figure 5 (a) shows, the irregularities on the surface of the rolling elements follow a normal distribution. Hereinafter, an explanation will be given using a formula assumed to be a normal distribution, but it is not limited to the normal distribution. As long as h described later can be represented by a probability density function, any probability density can be used. In this case, the roughness (height) of the surface of the rolling elements can be defined by the following formula (1).

[0088] [Equation 1]

[0089]

[0090] f(h): Probability density function (PDF) of the distribution of the interval h between two surfaces

[0091] h: Interval between two surfaces

[0092] μ: Distance between the center line of the roughness and the smooth surface

[0093] σ: Synthetic surface roughness

[0094] If formula (1) is transformed into Figure 5 (b) as shown, it can be expressed as the following formula (2). In Figure 5 (b), the horizontal axis represents the cumulative distribution probability F, and the vertical axis represents the interval h between components.

[0095] [Equation 2]

[0096]

[0097] F(h): Cumulative distribution function (CDF), probability that the interval between two surfaces is less than h

[0098] F: Cumulative distribution probability

[0099] In addition, in this embodiment, the dielectric breakdown voltage E limit , the critical oil film thickness h for dielectric breakdown limit and the ratio α of the dielectric breakdown area limit are used. The dielectric breakdown voltage E limit represents the voltage at which dielectric breakdown occurs in the lubricant. The critical oil film thickness h for dielectric breakdown limit represents the oil film thickness as the limit value at which dielectric breakdown does not occur. The ratio α of the dielectric breakdown area limit represents the ratio of the area where dielectric breakdown occurs in the contact area. The dielectric breakdown voltage E limit , the critical oil film thickness h for dielectric breakdown limit , and the ratio α of the dielectric breakdown area limit are defined as follows, respectively.

[0100] [Equation 3]

[0101]

[0102] [Equation 4]

[0103]

[0104] [Equation 5]

[0105]

[0106] E limit : Dielectric breakdown voltage

[0107] h limit : Critical oil film thickness for dielectric breakdown

[0108] α limit : Ratio of dielectric breakdown area (0 ≤ α limit ≤ 1)

[0109] V: Voltage

[0110] Figure 6 is used to illustrate Figure 5 the relationship between the cumulative distribution function shown in (b), the dielectric breakdown voltage E limit , the critical oil film thickness h for dielectric breakdown limit , and the ratio α of the dielectric breakdown area limit . First, for the applied voltage V, the ratio α of the dielectric breakdown area is determined by the above equations (3) to (5). limit With the ratio α of the dielectric breakdown area limitAs the boundary, within the range where the cumulative distribution probability F is lower than the insulation breakdown region ratio α limit it indicates that insulation breakdown occurs and the oil film functions as a resistor. On the other hand, within the range where the cumulative distribution probability F exceeds the insulation breakdown region ratio α limit it indicates that insulation breakdown does not occur and the oil film functions as a capacitor.

[0111] Here, as shown in Equations (3) to (5), the insulation breakdown region ratio α limit varies depending on the change in the applied voltage. In this embodiment, the contact area between the components lubricated by the lubricant is understood as a parallel circuit of a collection of minute resistors and a collection of minute capacitors. That is, the range below Figure 6 the indicated insulation breakdown region ratio α limit is set as the resistor R, and the range above the insulation breakdown region ratio α limit is set as the capacitor C to define the equivalent circuit.

[0112] Figure 7 is a conceptual diagram of the equivalent circuit of this embodiment. The equivalent circuit 700 has a structure in which a plurality of resistors 701 and a plurality of capacitors 702 are connected in parallel. At this time, the number of resistors 701 corresponding to the range where the cumulative distribution probability F is lower than the insulation breakdown region ratio α limit and the number of capacitors 703 corresponding to the range where the cumulative distribution probability F exceeds the insulation breakdown region ratio α limit vary according to the insulation breakdown region ratio α limit .

[0113] The equivalent circuit 700 can be defined by the following Equations (6) to (13). In addition, Figure 8 it represents the relationship between the equivalent circuit 700 and the Figure 6 cumulative distribution function shown, etc. Figure 8 The graph 801 shown is equivalent to the resistance ΔR of the minute region corresponding to one resistor 701 included in the range where the cumulative distribution probability F is lower than the insulation breakdown region ratio α limit . In addition, Figure 8 the graph 802 shown is equivalent to the capacitance ΔC of the minute region corresponding to one capacitor 702 included in the range where the cumulative distribution probability F exceeds the insulation breakdown region ratio α limit .

[0114] [Equation 6]

[0115]

[0116] [Equation 7]

[0117]

[0118] [Number 8]

[0119]

[0120] [Number 9]

[0121]

[0122] [Number 10]

[0123] C1 = ΔC1 + ΔC2 + ……(10)

[0124] [Number 11]

[0125]

[0126] [Number 12]

[0127]

[0128] [Number 13]

[0129]

[0130] R1: Resistance generated by the lubricant in the contact area

[0131] ΔR: Resistance of the micro-region

[0132] C1: Electrostatic capacitance generated by the lubricant in the contact area

[0133] ΔC: Electrostatic capacitance of the micro-region

[0134] ε: Dielectric constant of the lubricant

[0135] ρ: Volume resistivity of the lubricant

[0136] S: Contact area

[0137] That is, as shown in Equations (6) to (13), in the cumulative distribution function, by integrating the values of the minute resistance ΔR and capacitor ΔC within the range specified based on the insulation breakdown region ratio α limit it is possible to determine the resistance R1 and capacitor C1 caused by the lubricant in the contact area.

[0138] Furthermore, based on the resistance R1 and capacitor C1 obtained above, the impedance Z1 of the contact area can be defined by the following Equation (14).

[0139] [Number 14]

[0140]

[0141] ω: Angular frequency of the alternating voltage

[0142] Z1: Impedance in the contact area

[0143] [Application to rolling bearings]

[0144] Based on the above modeling, the application to rolling bearings will be further described. In the above modeling, it corresponds to one contact area, i.e., an area lubricated by lubricant. On the other hand, for example, inside a rolling bearing, there are multiple rolling elements, and each of the multiple rolling elements has a contact surface that contacts the outer ring and the inner ring. Therefore, in the case of a rolling bearing, it is necessary to expand the above modeling corresponding to the number of contact areas.

[0145] Figure 9 It is a diagram showing the equivalent circuit of a bearing device including the rolling bearing of the present embodiment. Each symbol is as described below.

[0146] Z1: Impedance of one contact area

[0147] R E : External resistance

[0148] C2: Electrostatic capacitance between the rolling element near the contact point and the raceway surface

[0149] C3: Electrostatic capacitance between the rolling element and the groove shoulder

[0150] C4: Electrostatic capacitance between the rolling element of the non-loaded coil and the raceway surface

[0151] C5: Electrostatic capacitance between the inner and outer rings

[0152] E1: Equivalent circuit in the contact area between the outer ring (or inner ring) and the rolling element

[0153] E2: Equivalent circuit in the contact area around one rolling element

[0154] Here, when only the axial load is applied, C4 = 0. In addition, Z1 and C2 are generated on the inner ring side and the outer ring side in one rolling element, so it becomes a structure in which two E1s are connected in series. In addition, E2 is connected in parallel by the number of rolling elements in the loaded coil under the axial load. C3 is set corresponding to the number of rolling elements, and they are connected in parallel. Apply a voltage V to the equivalent circuit of the entire bearing device including these rolling bearings and the external resistance R E and measure the impedance Z.

[0155] Based on Figure 9 the equivalent circuit, the impedance Z of a rolling bearing with n rolling elements bearingIt can be defined by the following formula (15). Here, as a method for measuring the EIM under a radial load, there is International Publication No. 2022 / 054352 of the applicant of the present application. Based on such a method, formula (16) and formula (17) can be defined.

[0156] [Equation 15]

[0157]

[0158] [Equation 16]

[0159]

[0160] [Equation 17]

[0161]

[0162] Z bearing : Impedance of the rolling bearing

[0163] n: Number of rolling elements

[0164] R tx : Equivalent curvature radius in the average rolling direction of the inner and outer rings

[0165] R ty : Equivalent curvature radius in the direction orthogonal to the rolling direction of the inner and outer rings on average

[0166] R b : Rolling element radius

[0167] h t1 : Sum of the oil film thicknesses generated by the inner and outer rings

[0168] γ: Groove angle

[0169] Average inner ring contact angle

[0170] C5: Electrostatic capacitance between the inner and outer rings (measured value)

[0171] Moreover, the impedance Z of the entire bearing device can be defined by the following formula (18).

[0172] [Equation 18]

[0173]

[0174] Z: Impedance of the bearing device

[0175] Based on the above formulas, various parameters during measurement, the specifications of the lubricant, and the specifications of the rolling bearing, the relationship between the impedance Z and the voltage V of the bearing device can be determined. Moreover, by performing fitting in a manner consistent with the measured values, unknown parameters treated as variables, such as the oil film thickness and surface roughness, can be estimated. As the method for fitting here, the method described in International Publication No. 2022 / 054352 of the applicant of the present application can be cited. In the present embodiment, an example of using such a method is shown.

[0176] [Application Example]

[0177] Figures 10A - 10C Indicates the result of fitting based on the above equivalent circuit for the result measured using the Figure 3 shown measuring device. In this example, an example of fitting using the following fixed values and estimating the breakdown voltage E limit , the composite surface roughness σ, and the volume resistivity ρ of the lubricant as variables is shown.

[0178] (Set Parameters)

[0179] Contact ellipse area S = 2.4e-8 [m 2 (Fixed)

[0180] Dielectric constant ε of the lubricant = 2.1 [-] (Fixed)

[0181] Average oil film thickness μ = 37 nm (Fixed, h H-D = 44 nm, h EIM = 37 nm)

[0182] In Figure 10A , the horizontal axis represents the voltage V [V], and the vertical axis represents the phase angle θ [°]. Plot 1001 represents the measurement result, and plot 1002 represents the fitting result.

[0183] In Figure 10B , the horizontal axis represents the voltage V [V], and the vertical axis represents the absolute value of the impedance |Z| [Ω]. Plot 1011 represents the measurement result, and plot 1012 represents the fitting result.

[0184] In Figure 10C , the horizontal axis represents the real part of the impedance -Z re [Ω], and the vertical axis represents the imaginary part of the impedance -Z im [Ω]. Plot 1021 represents the measurement result, and plot 1022 represents the fitting result.

[0185] Moreover, the fitting results and the values estimated by the above various formulas are as follows.

[0186] Breakdown voltage E limit= 45 [kV / mm] (Physical property value of general oil 30 - 40 [kV / mm], about the same level)

[0187] Synthetic surface roughness σ = 1 [nm] (Ra 12 nm before the test)

[0188] Volume resistivity ρ of the lubricant when insulation breakdown occurs = 200 [Ωm] (Physical property value of oil at general low frequencies 1×10 10 [Ωm])h H-D : Calculated oil film thickness h according to the Hamrock - Dowson formula EIM : Oil film thickness measured by EIM

[0189] In addition, the alternating voltage V applied to circuit E, the current I flowing through circuit E, and the complex impedance Z of the entire circuit E are represented by the following equations (19) - (21).

[0190] V = |V| exp(jωt) … (19)

[0191] I = |I| exp(j(ωt - θ)) … (20)

[0192] Z = V / I = |V / I| exp(jθ) = |Z| exp(jθ) … (21)

[0193] j: Imaginary number

[0194] ω: Angular frequency of the voltage

[0195] t: Time

[0196] θ: Phase angle (Phase shift between voltage and current)

[0197] [Processing flow]

[0198] Figure 11 is a flowchart of the state measurement process of this embodiment using the above - mentioned method. This process is executed by the measurement device 10. For example, it can be realized by the control device (not shown) of the measurement device 10 reading a program for realizing the process of this embodiment from a storage device (not shown) and executing it. In addition, fitting and parameter derivation in the following processes can be configured to use the functions of general software to realize a part of them.

[0199] In S1101, the measurement device 10 controls the LCR meter 20 to supply power of an alternating voltage V with an angular frequency ω to the bearing device 30 using the alternating current power supply (not shown) of the LCR meter 20. Thereby, an alternating voltage V with an angular frequency ω is applied to the lubricant in each rolling bearing.

[0200] In S1102, the measuring device 10 obtains the impedance |Z| and the phase angle θ as the output for the input indicated in S1101 from the LCR meter 20. That is, the LCR meter 20 outputs the impedance Z and the phase angle θ as the measurement results of the bearing device 30 with respect to the AC voltage V of the angular frequency ω as the input to the measuring device 10.

[0201] 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. In addition, a formula based on the equivalent circuit corresponding to the measurement object is predefined and registered so as to be usable in the measuring device 10.

[0202] In S1104, the measuring device 10 performs fitting (application) to the formula of the equivalent circuit shown based on the impedance Z and the phase angle θ obtained in S1102 and the information of the AC voltage V of the angular frequency ω indicated in S1101. For example, the method described in International Publication No. 2022 / 054352 of the applicant of the present application can be used. Figure 9 In S1105, the measuring device 10 uses the fitting result in S1104 and the formula with the parameters set in S1103 to estimate the variable parameters. The variable parameters here can be, for example, the dielectric breakdown voltage E

[0203] as described, the composite surface roughness σ, the volume resistivity ρ of the lubricant. In addition, the average oil film thickness μ can also be estimated as a variable parameter. Figures 10A - 10C In S1106, the measuring device 10 performs a state diagnosis based on the result estimated in S1105. The diagnosis content here is not particularly limited. For example, it can be configured as follows: a predetermined threshold is set in advance for the estimated result, and normality or abnormality is diagnosed by comparing with this threshold. In addition, it can also be configured to set a plurality of thresholds corresponding to the urgency of the abnormality in advance, and diagnose the urgency by comparing with these thresholds. limit In S1107, the measuring device 10 outputs the value estimated in S1106 and the diagnosis result obtained in S1106 to the user. The output method here is not particularly limited. For example, it can be configured to display the parameters and items determined to be abnormal on the screen or to notify by voice. Then, this processing flow ends.

[0204] As described above, according to the present embodiment, it is possible to monitor the surface roughness and the oil film thickness of the components lubricated with the lubricant. For example, as a measurement object, it can be applied to a bearing device having a rolling bearing.

[0205]

[0206]

[0207] ​​<Other Embodiments>

[0208] In addition, as described above, for h, parameters other than the normal distribution can also be used. In such a case, instead of the above formula (5), other formulas corresponding to the parameters are used. In addition, formula (4) is used as h limit = h(α limit ).

[0209] In addition, in the present invention, it is also possible to supply a program or application program for realizing the functions of the above-described one or more embodiments to a system or device through a network, a storage medium, etc., and read and execute the program by one or more processors in a computer of the system or device.

[0210] In addition, it can also be realized by a circuit (for example, ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate Array)) that realizes one or more functions.

[0211] Thus, the present invention is not limited to the above-described embodiments, and it is also the content of the present invention to combine the respective structures of the embodiments, and to make changes and applications by those skilled in the art based on the description of the specification and well-known technologies, which are included within the scope of protection.

[0212] As described above, the following matters are disclosed in this specification.

[0213] (1) A state measurement method, characterized in that

[0214] it is a state measurement method between a first component (for example, 101) and a second component (for example, 102) lubricated by a lubricant (for example, 103), and has:

[0215] a measurement step (for example, S1101, S1102), measuring impedance by applying an alternating voltage to the first component and the second component while scanning the alternating voltage;

[0216] a fitting step (for example, S1103, S1104), fitting the measurement result of the measurement step based on an equivalent circuit defined corresponding to the structures of the first component and the second component; and

[0217] a derivation step (for example, S1105), deriving the state using the result obtained in the fitting step and a prescribed formula including a parameter representing the state between the first component and the second component,

[0218] The specified formula uses the ratio of the regions that cause dielectric breakdown between the first component and the second component, which is determined based on the surface roughness of the first component and the second component, the oil film thickness of the lubricant, and the applied voltage.

[0219] The equivalent circuit specifies the capacitor and resistor caused by the lubricant based on the ratio.

[0220] According to this structure, it is possible to monitor the surface roughness and oil film thickness of the components lubricated with the lubricant. In particular, it is possible to monitor the state around the lubricant based on the occurrence probability of dielectric breakdown in the lubricant.

[0221] (2) The state measurement method according to (1), characterized in that

[0222] The specified formula is specified as follows:

[0223] [Equation 19]

[0224]

[0225] [Equation 20]

[0226] α limit = F(h limit )

[0227] [Equation 21]

[0228]

[0229] [Equation 22]

[0230]

[0231] [Equation 23]

[0232]

[0233] E limit : Dielectric breakdown voltage

[0234] h limit : Critical oil film thickness for dielectric breakdown

[0235] α limit : Proportion of dielectric breakdown region (0 ≤ α limit ≤ 1)

[0236] V: Applied voltage

[0237] R1: Resistance caused by the lubricant in the contact area

[0238] C1: Capacitance caused by the lubricant in the contact area

[0239] Z1: Impedance within the contact area

[0240] ε: Dielectric constant of the lubricant

[0241] ρ: Volume resistivity of the lubricant

[0242] S: Contact area

[0243] j: Imaginary number

[0244] ω: Angular frequency of the voltage

[0245] According to this structure, by defining the region where dielectric breakdown occurs based on the occurrence probability of dielectric breakdown of the lubricant, various parameters around the lubricant can be estimated. For example, the surface roughness of the components and the oil film thickness can be estimated.

[0246] (3) The state measurement method according to (1), characterized in that

[0247] The first component and the second component are included in a rolling device (e.g., 30),

[0248] The equivalent circuit is defined according to the structure of the rolling device.

[0249] According to this structure, it is possible to estimate the state around the lubricant, particularly the surface roughness of the components and the oil film thickness, for the rolling device.

[0250] (4) A state measurement device, characterized in that

[0251] It is a state measurement device (e.g., 1) for between a first component and a second component lubricated by a lubricant, and includes:

[0252] A measurement unit (e.g., 20) that measures impedance by applying an alternating voltage to the first component and the second component while scanning the alternating voltage;

[0253] A fitting unit (e.g., 10) that fits the measurement result of the measurement unit according to an equivalent circuit defined corresponding to the structures of the first component and the second component;

[0254] A derivation unit (e.g., 10) that derives the state using the result obtained by the fitting unit and a prescribed formula including parameters representing the state between the first component and the second component,

[0255] The prescribed formula uses the ratio of the region where dielectric breakdown occurs between the first component and the second component, which is determined based on the relationship between the surface roughness of the first component and the second component, the oil film thickness of the lubricant, and the applied voltage,

[0256] The equivalent circuit specifies capacitors and resistors caused by the lubricant based on the ratio.

[0257] According to this structure, it is possible to monitor the surface roughness and oil film thickness of components lubricated with a lubricant. In particular, it is possible to monitor the state around the lubricant based on the occurrence probability of dielectric breakdown in the lubricant.

[0258] (5) A program, wherein

[0259] causing a computer (e.g., 10) to execute the following steps:

[0260] a measurement step (e.g., S1101, S1102), applying an alternating voltage to a first component (e.g., 101) and a second component (e.g., 102) lubricated with a lubricant (e.g., 103) while scanning the alternating voltage, thereby measuring the impedance;

[0261] a fitting step (e.g., S1103, S1104), fitting the measurement result of the measurement step based on an equivalent circuit specified corresponding to the structures of the first component and the second component; and

[0262] a derivation step (e.g., S1105), deriving the state using the result obtained in the fitting step and a specified formula including a parameter representing the state between the first component and the second component,

[0263] the specified formula uses a ratio of a region where dielectric breakdown occurs between the first component and the second component, which is determined based on the relationship between the surface roughness of the first component and the second component, the oil film thickness of the lubricant, and the applied voltage,

[0264] The equivalent circuit specifies capacitors and resistors caused by the lubricant based on the ratio.

[0265] According to this structure, it is possible to monitor the surface roughness and oil film thickness of components lubricated with a lubricant. In particular, it is possible to monitor the state around the lubricant based on the occurrence probability of dielectric breakdown in the lubricant.

[0266] As described above, various embodiments have been described with reference to the drawings, but the present invention is of course not limited to this example. It is obvious that those skilled in the art can conceive of various modification examples or correction examples within the scope described in the claims, and these modification examples or correction examples also of course belong to the technical scope of the present invention. In addition, within the scope not departing from the gist of the invention, the constituent elements in the above embodiments can be arbitrarily combined.

[0267] The above describes various embodiments, but the present invention is of course not limited to this example. It is obvious that those skilled in the art can conceive of various modification examples or correction examples within the scope described in the claims, and these modification examples or correction examples of course also belong to the technical scope of the present invention. In addition, within the scope not departing from the gist of the invention, the constituent elements in the above embodiments can be arbitrarily combined.

[0268] In addition, this application is based on a Japanese patent application filed on November 7, 2022 (Japanese Patent Application No. 2022-178453), the content of which is incorporated herein by reference.

[0269] Explanation of Reference Numerals

[0270] 1 System

[0271] 10 Measuring Device

[0272] 20 LCR Meter

[0273] 30 Bearing Device

[0274] 31 (31a, 31b) Rolling Bearing (Ball Bearing)

[0275] 40 Rotating Shaft

[0276] 50 Motor

[0277] 60 Heater

Claims

1. A state determination method, characterized in that, A method for determining the state between a first component and a second component lubricated by a lubricant, comprising: A measuring step of applying an alternating voltage to the first component and the second component while scanning the alternating voltage, thereby measuring the impedance; A fitting step of fitting the measurement result of the measuring step according to an equivalent circuit defined corresponding to the structures of the first component and the second component; And A derivation step of deriving the state by using the result obtained from the fitting step and a specified formula including a parameter representing the state between the first component and the second component, wherein the specified formula uses a ratio of a region where dielectric breakdown occurs between the first component and the second component, which is determined based on the relationship between the surface roughness of the first component and the second component, the oil film thickness of the lubricant, and the applied voltage, and the equivalent circuit defines a capacitor and a resistor caused by the lubricant based on the ratio.

2. The state determination method according to claim 1, wherein the specified formula is defined as follows: [Equation 1] [Equation 2] α limit = F(h limit ) [Equation 3] [Equation 4] [Equation 5] E limit : Insulation breakdown voltage h limit : Critical oil film thickness for insulation breakdown α limit : Proportion of insulation breakdown area (0 ≤ α limi ≤ 1) V: Applied voltage R1: Resistance caused by the lubricant in the contact area C1: Capacitance caused by the lubricant in the contact area Z1: Impedance in the contact area ε: Dielectric constant of the lubricant ρ: Volume resistivity of the lubricant S: Contact area j: Imaginary number ω: Angular frequency of the voltage.

3. The state determination method according to claim 1, wherein the first component and the second component are included in a rolling device, and the equivalent circuit is defined according to the structure of the rolling device.

4. A state determination device, characterized in that it is a state determination device for between a first component and a second component lubricated by a lubricant, and includes: A measuring unit that applies an alternating voltage to the first component and the second component while scanning the alternating voltage, thereby measuring the impedance; A fitting unit that fits the measurement result of the measuring unit according to an equivalent circuit defined corresponding to the structures of the first component and the second component; And A derivation unit that derives the state by using the result obtained from the fitting unit and a specified formula including a parameter representing the state between the first component and the second component, wherein the specified formula uses a ratio of a region where dielectric breakdown occurs between the first component and the second component, which is determined based on the relationship between the surface roughness of the first component and the second component, the oil film thickness of the lubricant, and the applied voltage, and the equivalent circuit defines a capacitor and a resistor caused by the lubricant based on the ratio.

5. A program, characterized in that, Causing a computer to execute the following steps: A measuring step of applying an alternating voltage to a first component and a second component lubricated by a lubricant while scanning the alternating voltage, thereby measuring the impedance; A fitting step of fitting the measurement result of the measuring step according to an equivalent circuit defined corresponding to the structures of the first component and the second component; And Derivation process: Using the result obtained from the fitting process and a specified formula including parameters representing the state between the first component and the second component, derive the state. The specified formula uses the ratio of the area where dielectric breakdown occurs between the first component and the second component, which is determined based on the relationship among the surface roughness of the first component and the second component, the oil film thickness of the lubricant, and the applied voltage. The equivalent circuit defines the capacitor and resistor caused by the lubricant based on the ratio.

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