State diagnosis method, state diagnosis device, and storage medium

Abstract

The state diagnosis method includes a measurement step of measuring a relative dielectric constant of a lubricant by applying a voltage to the lubricant while changing a frequency using an alternating current power supply, a derivation step of deriving a parameter indicating an electrical characteristic of the lubricant by applying the relative dielectric constant measured in the measurement step to a theoretical formula, and a diagnosis step of diagnosing a state of the lubricant using the parameter.

Description

TECHNICAL FIELD

[0001] The present application relates to a state diagnosis method, a state diagnosis apparatus, and a storage medium. BACKGROUND

[0002] In the past, when diagnosing the state of a material, methods such as physical property analysis of apparent viscosity and the like, chemical component analysis of deterioration degree and the like, and structural analysis using a microscope have been used. Such methods generally require complicated operations. In addition, the above-described methods are difficult to perform non-destructively on the object, and in most cases, the diagnosis object is discarded.

[0003] On the other hand, there is a method of performing impedance analysis using an alternating current power source. By using impedance analysis, it is possible to derive the electrical characteristics of the material.

[0004] For example, in Patent Literature 1, a method of measuring the dielectric constant of blood while changing the frequency, and measuring the damage of blood corpuscles is disclosed, with blood as the analysis object. In addition, in Patent Literature 2, a method of evaluating the change in the composition of an extraction solvent based on the frequency characteristics of the relative dielectric constant and the relative dielectric constant loss rate is disclosed.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent Application Laid-Open No. 2008-215901

[0008] Patent Literature 2: Japanese Patent Application Laid-Open No. H7-239316 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] As a material used in an actual device, for example, a lubricant can be cited. It is also very useful to grasp the state of such a lubricant in preventing damage to a device using the lubricant and the like. On the other hand, there are difficulties in non-destructively taking out the lubricant and the like as the object from the device and observing it.

[0011] In view of the above-described problems, an object of the present application is to provide a method capable of easily diagnosing the state of a lubricant without destroying the diagnosis object.

[0012] MEANS OF SOLVING THE PROBLEM

[0013] In order to solve the above-described problems, the present application has the following structure. That is, a state diagnosis method has:

[0014] a measurement step of measuring the relative dielectric constant of the lubricant by applying a voltage to the lubricant while changing the frequency using an alternating current power source;

[0015] deriving a parameter indicating an electrical characteristic of the lubricant by applying the relative dielectric constant measured in the measuring step to a theoretical formula; and

[0016] diagnosing a state of the lubricant using the parameter.

[0017] Further, another aspect of the present application has the following structure. That is, a state diagnosing apparatus has:

[0018] a measuring unit that measures a relative dielectric constant of a lubricant by applying a voltage to the lubricant while changing a frequency using an alternating current power supply;

[0019] a deriving unit that derives a parameter indicating an electrical characteristic of the lubricant by applying the relative dielectric constant measured by the measuring unit to a theoretical formula; and

[0020] a diagnosing unit that diagnoses a state of the lubricant using the parameter.

[0021] Further, another aspect of the present application has the following structure. A program for causing a computer to execute the following steps:

[0022] a measuring step of measuring a relative dielectric constant of a lubricant by applying a voltage to the lubricant while changing a frequency using an alternating current power supply;

[0023] a deriving step of deriving a parameter indicating an electrical characteristic of the lubricant by applying the relative dielectric constant measured in the measuring step to a theoretical formula; and

[0024] a diagnosing step of diagnosing a state of the lubricant using the parameter.

[0025] Effects of Invention

[0026] According to the present application, it is possible to easily diagnose a state of a lubricant without damaging a diagnosis object. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a conceptual diagram showing the structure of a lubricant, which is a diagnosis object, and an alternating current power supply, which are related to the present application.

[0028] Figure 2 is a diagram for explaining an equivalent circuit constituted by a lubricant, which is a diagnosis object, and an alternating current power supply, which are related to the present application.

[0029] Figure 3 is a schematic structure diagram showing an example of the structure of an apparatus, which is related to the present application.

[0030] Figure 4 is a graph for explaining the relationship of frequency and relative dielectric constant and relative dielectric loss rate.

[0031] Figure 5 is a graph for explaining the derivation of parameters by fitting to a theoretical formula (Debye model).

[0032] Figure 6 is a graph for explaining the derivation of parameters by fitting to a theoretical formula (Cole-Cole model).

[0033] Figure 7 is a graph for explaining the derivation of parameters by fitting to a theoretical formula (Cole-Cole improved model).

[0034] Figure 8 is a flowchart of a state diagnosis process according to an embodiment of the present application.

[0035] Figure 9 is a graph for explaining the relationship of the state of a lubricant and parameters.

[0036] Figure 10 is a graph for explaining the relationship of the state of a lubricant and parameters.

[0037] Figure 11 is a graph for explaining the relationship of thickener and relaxation strength.

[0038] Figure 12 is a graph for explaining the roll state of a thickener.

[0039] Figure 13 is a graph for explaining the relationship of frequency and parameters corresponding to the fiber state of a thickener.

[0040] Figure 14 is a graph for explaining the relationship of frequency and parameters corresponding to the fiber state of a thickener.

[0041] Figure 15 is a graph for explaining the relationship of deterioration of a base oil and relative dielectric constant.

[0042] Figure 16 is a graph for explaining the relationship of deterioration of a base oil and relative dielectric loss rate.

[0043] Figure 17 is a graph for explaining the relationship of deterioration of a grease and parameters.

[0044] Figure 18 is a graph for explaining the relationship of the amount of moisture in a grease and parameters.

[0045] Figure 19 is a graph for explaining the relationship of the amount of moisture in a grease and average relative dielectric constant.

[0046] Figure 20 is a graph for illustrating the relationship between the amount of iron powder in the grease and the relative dielectric loss factor.

[0047] Explanation of symbols

[0048] 10 AC power supply

[0049] 11 electrode

[0050] 12 grease

[0051] 30 state diagnosis device

[0052] 31 measurement device

[0053] 32 material content DETAILED DESCRIPTION

[0054] Hereinafter, a mode for carrying out the present application will be described with reference to the drawings and the like. Furthermore, the following described embodiments are for illustrating one embodiment of the present application, and are not intended to limit the explanation of the present application, and furthermore, all the structures described in each embodiment are not necessarily structures that are essential for solving the problems of the present application. Furthermore, in each drawing, for the same constituent elements, the correspondence is indicated by annotating the same reference numerals.

[0055] [diagnostic object]

[0056] In the present embodiment, as the diagnostic object, a lubricant for component lubrication is described as an example. The lubricant here is a grease having a dielectric relaxation generating characteristic. More specifically, a 12-OH Li stearate grease or the like can be taken as an object. Generally, a grease is configured to contain a base oil, a thickener, and an additive. Details will be described later, and the value of a parameter indicating an electric characteristic varies depending on the configuration and state of the grease.

[0057] In the present embodiment, as the case where the grease is in a block state, a parameter indicating an electric characteristic corresponding to the internal state is derived, and the diagnosis of the state of the grease is performed using the parameter. Figure 1 is a conceptual diagram indicating the structure of a lubricant (here, a grease) and an AC power supply when evaluating (measuring) the electric characteristic of the lubricant involved in the present embodiment. The lubricant 12 filled between the electrodes 11 is supplied with electric power by the AC power supply 10. Furthermore, the distance between the electrodes 11 here can be constituted by, for example, mm order.

[0058] Figure 2 is a conceptual diagram indicating Figure 1A diagram of an electrical equivalent circuit around the grease 12. The circuit E has a structure in which a capacitor C constituted by the grease 12 and a resistance R caused by the elements around it are connected in parallel. In addition, Z represents the impedance of the circuit E. Here, the alternating voltage V applied to the circuit E, the current I flowing through the circuit E, and the complex impedance Z of the entire circuit E are represented by the following equations (1) to (3).

[0059] V = |V| exp(jωt) (1)

[0060] I = |I| exp(jωt - jθ) (2)

[0061] Z = V / I = |V / I| exp(jθ) = |Z| exp(jθ) (3)

[0062] j: imaginary number

[0063] ω: angular frequency of voltage

[0064] t: time

[0065] θ: phase angle (phase deviation of voltage and current)

[0066] [Apparatus structure]

[0067] Figure 3 is a schematic configuration diagram indicating an example of the overall configuration of a system to which the state diagnosis method according to the present embodiment can be applied. In Figure 3 , a state diagnosis apparatus 30 using the state diagnosis method according to the present embodiment, a measurement apparatus 31, and a material containing object 32 containing the grease 12 as a diagnosis object are shown. In addition, Figure 3 The configuration shown is an example, and different configurations can be used depending on the diagnosis object and the like.

[0068] The measurement apparatus 31 is configured to include Figure 1 The alternating current power supply 10 shown applies electric power to the grease 12 contained in the material containing object 32 at the time of diagnosis.

[0069] The state diagnosis apparatus 30 instructs the measurement apparatus 31 to apply the alternating voltage V of the angular frequency ω of the alternating current power supply 10 as the input value of the electric power applied to the grease 12, and acquires the impedance |Z| of the grease 12 (|Z| represents the absolute value of Z) and the phase angle θ as the output (measurement value) therefrom. Then, the state diagnosis apparatus 30 derives a parameter indicating an electrical characteristic related to the grease 12 using these values, and performs diagnosis on the basis thereof. The details of the kind of the parameter and the derivation method are described later.

[0070] The state diagnosis device 30 can be realized by an information processing device including a control device, a storage device, and an output device, which are 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, or the like. The storage device is constituted by a volatile and non-volatile storage medium such as an HDD (Hard Disk Drive), a ROM (Read Only Memory), a RAM (Random Access Memory), or the like, and can perform input and output of various information according to an instruction from the control device. The output device is constituted by a speaker, a lamp, or a display device such as a liquid crystal display, and performs reporting to an operator according to an instruction from the control device. The output method of the output device is not particularly limited. In addition, the output device can be a network interface having a communication function, or can perform an output action by transmitting data to an external device (not shown) via a network (not shown).

[0071] In addition, the state diagnosis device 30 and the measurement device 31 are not particularly limited in form. For example, the state diagnosis device 30 and the measurement device 31 can be connected by any one of wired / wireless. In addition, the state diagnosis device 30 and the measurement device 31 can be integrated. Alternatively, a user can be in charge of data input and output between the state diagnosis device 30 and the measurement device 31.

[0072] [Relative dielectric constant and relative dielectric loss rate]

[0073] Figure 4 is a graph for explaining a change tendency of a relative dielectric constant and a relative dielectric loss rate corresponding to a frequency change. Here, as described above, as the grease 12, a 12-OH Li-based grease is exemplified. Using the structure shown in Figure 3 , a relative dielectric constant εr′ and a relative dielectric loss rate εr″ of the grease 12 are measured by performing a frequency sweep with respect to the frequency, and thus a dielectric relaxation phenomenon is confirmed. r r

[0074] In Figure 4 (a), the horizontal axis represents a frequency [Hz], and the vertical axis represents a relative dielectric constant εr′. Figure 4 (a) represents an experimental value obtained from the grease 12. As shown in Figure 4 (a), the relative dielectric constant εr′ has a tendency to decrease (monotonically decrease) as the frequency increases. ​​

[0075] In Figure 4 (b), the horizontal axis indicates frequency [Hz], and the vertical axis indicates relative dielectric loss rate εr" r . Figure 4 (b) indicates experimental values obtained from the grease 12. As shown in Figure 4 (b), the relative dielectric loss rate εr" has a tendency to temporarily decrease with an increase in frequency, then increase, and then decrease again.

[0076] In the present embodiment, as parameters indicating the electrical characteristics of the grease 12, the following seven parameters are taken as derivation targets.

[0077] ε r0 : relative dielectric constant at low frequency limit

[0078] ε r∞ : relative dielectric constant at high frequency limit

[0079] ε r0 - ε r∞ : relaxation strength

[0080] ε r : average relative dielectric constant

[0081] τ: relaxation time [s]

[0082] β: constant indicating distribution of relaxation time

[0083] σ0: direct current conductivity [S / m]

[0084] Details will be described later, but the above parameters vary depending on the internal state of the grease 12. Therefore, by deriving the parameters, it is possible to utilize in diagnosing the internal state of the grease.

[0085] [fitting to theoretical formula]

[0086] The electrical characteristics based on the dielectric relaxation phenomenon of the grease 12 have a change tendency as shown in Figure 4 . In order to determine the change tendency, various theoretical formulas are fitted, and various parameters are derived. Here, three theoretical formulas are described as examples, but are not limited to these. For example, other theoretical formulas can also be used as long as the above seven parameters can be derived with higher accuracy, respectively. Note that, unless specifically described, the symbols used in each theoretical formula indicate the same meaning in the case of indicating the same symbol.

[0087] (Debye model)

[0088] Fitting to the Debye model theoretical formula will be described. The theoretical formula of the Debye model is represented by the following expression.

[0089] [Num 1]

[0090]

[0091] [Num 2]

[0092]

[0093] ω: angular frequency of voltage

[0094] Figure 5 is a graph obtained by comparing a curve obtained by applying a theoretical formula of a Debye model with values obtained by experiment. In addition, Figure 5 (a) and Figure 5 (b) are the same as Figure 4 (a) and Figure 4 (b), respectively. As shown in Figure 5 (b), the relaxation time τ (peak position) is consistent. On the other hand, a result showing that parameters other than this are inconsistent is shown.

[0095] (Cole-Cole model)

[0096] Fitting to a theoretical formula of a Cole-Cole model will be described. The theoretical formula of the Cole-Cole model is shown below.

[0097] [Num 3]

[0098]

[0099] [Num 4]

[0100]

[0101] [Num 5]

[0102] X = ln(ωτ) = ln(2πfτ)... (8)

[0103] π: circular constant

[0104] f: frequency

[0105] ln: logarithmic function

[0106] Figure 6 is a graph obtained by comparing a curve obtained by fitting to a theoretical formula of a Cole-Cole model with values obtained by experiment. In addition, Figure 6 (a) and Figure 6 (b) are the same as Figure 4 (a) and Figure 4 (b), respectively. As shown in Figure 6(a) and (b) show the results of fitting the theoretical formula to the Cole-Cole model. The theoretical formula of the Cole-Cole model is shown below. Note that the formulas (9) and (11) are the same as the formulas (6) and (8) shown in the Cole-Cole model. Figure 6 (b) shows the results of fitting the theoretical formula to the Cole-Cole model. The theoretical formula of the Cole-Cole model is shown below. Note that the formulas (9) and (11) are the same as the formulas (6) and (8) shown in the Cole-Cole model.

[0107] (Cole-Cole improved model)

[0108] The fitting of the theoretical formula to the Cole-Cole improved model based on the Cole-Cole model will be described. The theoretical formula of the Cole-Cole improved model is shown below. Note that the formulas (9) and (11) are the same as the formulas (6) and (8) shown in the Cole-Cole model.

[0109] [Equation 6]

[0110]

[0111] [Equation 7]

[0112]

[0113] ε0: vacuum permittivity

[0114] [Equation 8]

[0115] X = ln(ωτ) = ln(2πfτ)... (11)

[0116] Figure 7 is a graph in which the curve obtained by fitting the theoretical formula to the Cole-Cole improved model is compared with the values obtained by the experiment. In addition, Figure 7 (a) and (b) show the results of fitting the theoretical formula to the Cole-Cole improved model. The experimental values of (a) and (b) are the same as those of (a) and (b) shown in FIG. 6, respectively. As shown in Figure 7 (a), with respect to the relative permittivity, the theoretical formula can express the trend of the experimental values by fitting, as in the Cole-Cole model. In addition, referring to Figure 4 (b), with respect to the relative dielectric loss in the low frequency region, the theoretical values can express the trend of the experimental values by fitting, in addition to the relaxation time τ (peak position). Figure 4 Figure 7 (a) and (b) show the results of fitting the theoretical formula to the Cole-Cole improved model. The experimental values of (a) and (b) are the same as those of (a) and (b) shown in FIG. 6, respectively. As shown in Figure 7 (b), with respect to the relative dielectric loss in the low frequency region, the theoretical values can express the trend of the experimental values by fitting, in addition to the relaxation time τ (peak position).

[0117] By performing the fitting to the above-described theoretical formula, as the parameters of the electrical properties related to the grease 12, the relative permittivity in the low frequency limit and the high frequency limit, the relaxation strength, the average relative permittivity, the relaxation time, the distribution of the relaxation time, and the direct current conductivity can be derived.

[0118] ​[Processing flow]

[0119] Figure 8 is a flowchart of the state diagnosis processing involved in the present embodiment. The processing is executed by the state diagnosis device 30, and for example, a control device (not shown) possessed by the state diagnosis device 30 can be realized by reading a program for realizing the processing involved in the present embodiment from a storage device (not shown) and executing it.

[0120] In S801, the state diagnosis device 30 controls the measuring device 31 so that the power of the alternating voltage V of the angular frequency ω is supplied to the grease 12 with the alternating power source 10 possessed by the measuring device 31. Thereby, the alternating voltage V of the angular frequency ω is applied to the grease 12.

[0121] In S802, the state diagnosis device 30 acquires the impedance |Z| and the phase angle Θ from the measuring device 31 as the output corresponding to the input indicated in S801. That is, the measuring device 31 outputs the impedance |Z| and the phase angle Θ as the measurement result of the grease 12 corresponding to the alternating voltage V of the angular frequency ω as the input to the state diagnosis device 30.

[0122] In S803, the state diagnosis device 30 derives the relative dielectric constant and the relative dielectric loss rate corresponding to each frequency based on the information of the impedance |Z| and the phase angle Θ acquired in S802 and the alternating voltage V of the angular frequency ω indicated in S801. The derivation method here can use a known method. In addition, it can be a structure in which the measuring device 31 performs the derivation of the relative dielectric constant and the relative dielectric loss rate and outputs the relative dielectric constant and the relative dielectric loss rate as the measurement result to the state diagnosis device 30 together with the impedance |Z| and the phase angle Θ.

[0123] In S804, the state diagnosis device 30 fits the obtained measurement result to the theoretical formula described above. For example, the state diagnosis device 30 performs fitting to the theoretical formula of the Cole-Cole modified model shown in the formula (9) to the formula (11).

[0124] In S805, the state diagnosis device 30 derives various parameters from the result of the fitting in S804. In addition, it is not necessary to derive all of the above-mentioned 7 parameters at the same time, and for example, only the required parameters can be derived depending on the item of the diagnosis object. The required parameters here can be arbitrarily set by the user who performs the diagnosis. In addition, the relationship of each parameter to the diagnosis item will be described later.

[0125] In S806, the state diagnosing device 30 performs the state diagnosis of the grease 12 based on the parameters derived in S805. The content of the diagnosis here is not particularly limited, and for example, a structure can be employed in which thresholds are set in advance for the parameters, and the diagnosis of normality or abnormality is performed by comparison with the thresholds. Alternatively, a structure can be employed in which a plurality of thresholds corresponding to degrees of emergency of abnormality are set in advance, and the degree of emergency is diagnosed by comparison with these thresholds.

[0126] In S807, the state diagnosing device 30 reports the diagnosis result obtained in S806 to the user. The reporting method here is not particularly limited, and for example, a structure can be employed in which a parameter or item judged to be abnormal is displayed on a screen or notified by sound. Then, the processing flow is ended.

[0127] [Relationship between various parameters and state of lubricant]

[0128] Hereinafter, the relationship between the various parameters derived by the above-described method and the state of the lubricant (here, the grease 12) will be described.

[0129] [Relationship between amount of thickener and parameter]

[0130] Using Figure 9 and Figure 10 , the relationship between the amount of thickener in the grease 12 and the parameter will be described. Here, an example of a grease of the following composition is shown. Further, the amount of thickener (ratio in the grease [%]) is shown as an example of three kinds of thickener.

[0131] Base oil: ester + mineral oil

[0132] Thickener: 12OH (lithium 12-hydroxystearate: 12-OH St Li) (short fiber)

[0133] Amount of thickener: 3%, 7.5%, 15%

[0134] In Figure 9 (a), the horizontal axis represents the frequency [Hz], and the vertical axis represents the relative dielectric constant ε r '. As shown in Figure 9 (a), the relative dielectric constant has a tendency to decrease (monotonically decrease) with an increase in frequency, regardless of the amount of thickener. The tendency is the same as that described using Figure 4 (a). On the other hand, the relative dielectric constant ε r0 varies depending on the amount of thickener. Further, the degree of change in the relative dielectric constant accompanying the change in frequency varies depending on the amount of thickener. On the other hand, in the high-frequency region, the influence of the variation in the amount of thickener on the relative dielectric constant is small.

[0135] By containing a thickener in the grease 12, a reverse electric field is generated relative to the external electric field applied to the grease 12 in the low-frequency region. As a result, in the low-frequency region, depending on the amount of thickener, the dielectric constant (relative dielectric constant ε in the low-frequency limit) is... r0 The dielectric constant (relative permittivity ε at the high-frequency limit) increases due to the amount of thickener. On the other hand, in the high-frequency region, no reverse electric field is generated relative to the external electric field applied to the grease 12. Therefore, in the high-frequency region, the dielectric constant (relative permittivity ε at the high-frequency limit) increases due to the amount of thickener. r∞ The changes are minimal. Based on this reason, such as... Figure 9 As shown in (a), the relative permittivity ε in the low-frequency limit corresponds to the change in the amount of thickener. r0 The differences.

[0136] exist Figure 9 In (b), the horizontal axis represents frequency [Hz], and the vertical axis represents relative permittivity ε. r ".like Figure 9 As shown in (b), the relative permittivity exhibits a trend of temporarily decreasing with increasing frequency, then increasing, and then decreasing again. This trend is consistent with the use of... Figure 4 (b) The trends described are the same.

[0137] Figure 10 It is a summary of... Figure 9 The values ​​shown are derived from a graph of the parameters. For example... Figure 10 As shown, it can be seen that various parameters change with the amount of thickener. That is, it is clear that there is a correlation between the amount of thickener and the parameters representing electrical properties. Therefore, by referring to the parameters derived in this embodiment (especially the relative permittivity ε at the low-frequency limit), r0 This allows us to determine changes in the amount of thickener.

[0138] Figure 11 This is a graph used to illustrate the relationship between the type of base oil, the amount of thickener, and the relaxation strength. In Figure 11 In the diagram, the horizontal axis represents the amount of thickener (the percentage in the grease) [%], and the vertical axis represents the relaxation strength (ε). r0 -ε r∞ Furthermore, regarding the types of base oils, we will use two types of mineral oils, esters, and ester / PAO types as examples. For instance... Figure 11 As shown by the straight line, regardless of the type of base oil, the relaxation strength increases with the increase of the amount of thickener. Therefore, regardless of the type of base oil, the amount of thickener can be determined by referring to the relaxation strength.

[0139] (Relationship between the fiber state and parameters of thickener)

[0140] use Figure 12 to Figure 14The relationship between the fiber state of the thickener in the grease 12 and the parameters will be described.

[0141] Figure 12 is a graph for explaining the fiber state of the thickener contained in the grease 12. Here, the grease 12 was subjected to roll processing by the following conditions, whereby the grease containing the thickener whose fiber structure was destroyed was produced.

[0142] Base oil: mineral oil

[0143] Thickener: 12-OHStLi

[0144] Rolling pressure: 1 [MPa]

[0145] Rolling number: 5 times

[0146] Figure 12 (a) indicates an example of the state before the roll processing and the state where the fiber structure is maintained. Figure 12 (b) indicates an example of the state after the roll processing and the state where the fiber structure is destroyed. In addition, in Figure 12 , the unit of the scale is μm. Note that the fiber state here is an example and is not limited thereto.

[0147] In Figure 13 (a), the horizontal axis indicates the frequency [Hz] and the vertical axis indicates the relative dielectric constant ε r ". As shown in Figure 13 (a), regardless of the fiber state of the thickener, the relative dielectric constant has a tendency to decrease (monotonously decrease) as the frequency increases. The tendency is the same as that explained using Figure 4 (a). On the other hand, the relative dielectric constant ε r0 varies depending on the fiber state of the thickener. Further, the degree of change in the relative dielectric constant accompanying the change in the frequency varies depending on the fiber state of the thickener. On the other hand, in the high frequency region, the influence of the variation in the amount of the thickener on the relative dielectric constant is small.

[0148] In Figure 13 (b), the horizontal axis indicates the frequency [Hz] and the vertical axis indicates the relative dielectric loss ε r ". As shown in Figure 13 (b), the relative dielectric constant has a tendency to temporarily increase and then decrease as the frequency increases. The tendency is the same as that explained using Figure 4 (b). In the low frequency region, the difference due to the fiber state of the thickener is small, but the peak of the relative dielectric constant, the distribution, and the position of the peak (relaxation time τ) differ. For example, the constant β indicating the distribution of the relaxation time has a tendency to decrease if the fiber structure is destroyed.

[0149] Figure 14 is a graph of parameters derived from the values shown in Figure 13 Fig. 6. As shown in Figure 14 Fig. 6, it can be seen that various parameters vary with the change in the fiber state of the thickening agent. That is, it can be understood that the fiber state of the thickening agent is correlated with the parameters indicative of the electrical characteristics. Therefore, by referring to the parameters derived from the present embodiment (particularly, the constants indicative of the relaxation time, the distribution of the relaxation time), the change in the fiber state of the thickening agent can be determined.

[0150] (Relationship between the deterioration of the grease and the parameters)

[0151] Using Figure 15 to Figure 17 , the relationship between the deterioration (oxidative deterioration) of the grease 12 and the parameters is explained. Figure 15 and Figure 16 is a graph for explaining the relationship between the degree and the frequency of the deterioration (oxidative deterioration, that is, the increase in the oxygen consumption amount) of the base oil constituting the grease 12.

[0152] In Figure 15 (a), the horizontal axis represents the frequency [Hz], and the vertical axis represents the relative dielectric constant ε r ′. As shown in Figure 15 (a), the relative dielectric constant is substantially constant regardless of the change in the frequency. In addition, the more the oxygen consumption amount increases, the higher value the relative dielectric constant shows.

[0153] In Figure 15 (b), the horizontal axis represents the oxygen consumption amount [%], and the vertical axis represents the average relative dielectric constant ε r ′. As shown in Figure 15 (b), the more the oxygen consumption amount increases, the more the average relative dielectric constant increases.

[0154] The higher the polarity of the molecules in the base oil, the more the average relative dielectric constant increases. For the base oil, there is no polarity in the past (for example, in the new state), but the degree of the polarization increases due to the oxidative deterioration. Therefore, the base oil is subjected to the oxidative deterioration, and thus the average relative dielectric constant increases.

[0155] In Figure 16 (a), the horizontal axis represents the frequency [Hz], and the vertical axis represents the relative dielectric loss ε r ″. As shown in Figure 16 (a), the more the oxygen consumption amount increases, the more the relative dielectric loss in the low frequency region increases.

[0156] In Figure 16 (b), the horizontal axis represents the oxygen consumption amount [%], and the vertical axis represents the direct current conductivity σ0. As shown in Figure 16 (b), the more the oxygen consumption amount increases, the more the direct current conductivity increases.

[0157] From the above, it is understood that the deterioration state of the base oil constituting the grease 12 has a correlation with the parameter indicating the electric characteristics. Therefore, by referring to the change in the various parameters (particularly, the average relative dielectric constant, the direct current conductivity) derived from this embodiment, it is possible to determine the deterioration state of the base oil.

[0158] Figure 17 is a graph for illustrating the relationship between the relative dielectric constant and the frequency caused by the deterioration of the grease. Here, the results of comparing the new grease and the grease after being deteriorated by the oxidation stability tester are shown. In Figure 17 In (a), the horizontal axis indicates the frequency [Hz], and the vertical axis indicates the relative dielectric constant ε r The new grease and the deteriorated grease both have a tendency that the relative dielectric constant decreases with an increase in the frequency. This tendency is the same as the tendency illustrated in (a). On the other hand, in the case of comparing the average relative dielectric constant, the deteriorated grease has a higher value. Here, the average relative dielectric constant of the new grease is 3.6, and the average relative dielectric constant of the deteriorated grease is 3.8. Figure 4

[0159] In Figure 17 (b), the horizontal axis indicates the frequency [Hz], and the vertical axis indicates the relative dielectric loss rate. In this case, if the direct current conductivity σ0 is compared, the deteriorated grease has a higher value. Here, the direct current conductivity of the new grease is 1.4, and the direct current conductivity of the deteriorated grease is 42.

[0160] From the above, it is understood that the deterioration state of the grease 12 has a correlation with the parameter indicating the electric characteristics. Therefore, by referring to the change in the various parameters (particularly, the average relative dielectric constant, the direct current conductivity) derived from this embodiment, it is possible to determine the deterioration state of the grease 12.

[0161] (Relationship between the water content and the parameter)

[0162] The relationship between the water content in the grease 12 and the parameter is described using Figure 18 , Figure 19 . Figure 18 is a graph for illustrating the relationship between the water content in the grease 12 and the relative dielectric constant ε r ′ and the relative dielectric loss rate ε r ″. Here, based on the example in which the water content of 0 to 10% is contained in the grease 12, the voltage is 1.0 V, and the measurement is performed in the range of the frequency of 30 Hz to 1 MHz, the relationship is described.

[0163] In Figure 18 (a), the horizontal axis indicates the logarithm of the frequency [Hz], and the vertical axis indicates the relative dielectric constant ε​r As shown in Figure 18 (a), there is a tendency for the relative dielectric constant εr' to assume a substantially constant value regardless of the change in frequency. In addition, there is a tendency for the relative dielectric constant εr' to assume a higher value as the amount of water in the grease 12 increases. r As shown in

[0164] In Figure 18 (b), the horizontal axis represents the logarithm of the frequency [Hz], and the vertical axis represents the relative dielectric loss εr". r As shown in Figure 18 (b), even in the case where the amount of water in the grease 12 increases, no significant difference is found in the change tendency of the relative dielectric loss. That is, the change tendency of the relative dielectric loss εr" when the frequency varies is almost the same regardless of the amount of water. r As shown in

[0165] Figure 19 is a graph for illustrating the relationship between the amount of water contained in the grease 12 and the average relative dielectric constant εr. In Figure 19 , the horizontal axis represents the amount of water in the grease 12 [wt%], and the vertical axis represents the average relative dielectric constant εr. Note that, here, the water in the grease 12 is in a completely mixed state. As shown in Figure 19 , there is a tendency for the average relative dielectric constant εrto increase (monotonically) as the amount of water increases.

[0166] From the above, it is understood that there is a correlation between the amount of water contained in the grease 12 and the parameters indicative of the electrical characteristics, specifically, the relative dielectric constant εr', the average relative dielectric constant εr, and the direct current conductivity σ0. Therefore, by focusing on these parameters, it is possible to determine the mixing of water into the grease 12. In addition, the degradation of the grease 12 is explained using , but the change tendency of the parameters at this time (for example, the average relative dielectric constant εr Figure 15 to Figure 17 Figure 15 of (b)) is different from the change tendency of the parameters shown in Figure 16 , and Figure 18 , Figure 19 Therefore, by capturing the difference in these changes, it is possible to separately detect the degradation of the grease and the mixing of water into the grease.

[0167] (Relationship between the amount of iron powder and the parameters)

[0168] Using Figure 20 , the relationship between the amount of iron powder in the grease 12 and the parameters is explained. Figure 20 ​​is a graph for illustrating the relationship between the amount of iron powder contained in the grease 12 and the relative dielectric loss ε r Due to the inclusion of iron powder in the grease 12, the direct current conductivity σ0increases extremely. The change in the direct current conductivity due to other factors is on the order of 10 to 100 times, whereas the rise in the direct current conductivity due to the inclusion (increase) of iron powder exhibits a change on the order of 10 6 times or more. Here, detection is performed with focus on this change. Here, an example based on the case where 0 to 20% of moisture is contained in the grease 12, and measurement is performed in the range of a voltage of 1.0 V and a frequency of 30 Hz to 1 MHz is described.

[0169] In Figure 20 , the horizontal axis represents the logarithm of the frequency [Hz], and the vertical axis represents the relative dielectric loss ε r . Here, four examples are shown in which the amount of iron powder contained in the grease 12 (relative to the weight of the grease) is 0%, 10%, 15%, and 20%. In the case where the amount of iron powder is 0%, 10%, 15%, and 20%, the direct current conductivity σ0is 2.0 x 10 -10 S, 5.4 x 10 -3 S, 1.9 x 10 -2 S, and 2.0 x 10S, respectively. That is, depending on the amount of iron powder in the grease 12, the value of the direct current conductivity σ0varies extremely. Therefore, by evaluating the value of the direct current conductivity σ0, it is possible to measure the amount of iron powder in the grease 12, that is, the inclusion of iron powder.

[0170] [Summary]

[0171] In the present embodiment, as the electrical characteristics for determining the state of the lubricant (in the present case, the grease), parameters related to dielectric relaxation are derived. Each parameter can be utilized in determining the state of the lubricant as follows.

[0172] Relative dielectric constant (ε r0 ) at low frequency limit: amount of thickener

[0173] Relative dielectric constant (ε r∞ ) at high frequency limit: kind of base oil

[0174] Relaxation strength (ε r0 - ε r∞ ): amount of thickener

[0175] Average relative dielectric constant Degree of degradation of base oil, amount of moisture in grease

[0176] Relaxation time (τ): fiber state of thickener, degree of degradation of grease

[0177] Constant (β) representing distribution of relaxation time: fiber state of thickening agent, degree of deterioration of lubricating grease

[0178] DC conductivity (σ0): amount of thickening agent, degree of deterioration of base oil, degree of deterioration of lubricating grease, amount of additive, amount of iron powder in lubricating grease

[0179] In addition, the correlation of each parameter with the state of the lubricant is one example and is not limited to the above. For example, one item of state can be diagnosed from a plurality of parameters, and a plurality of items of state can be diagnosed from one parameter. In addition, the state can be diagnosed on the basis of the correlation between the parameter and the state, according to the composition of the lubricant.

[0180] According to the present embodiment, the parameter representing the electrical characteristics of the lubricant can be determined without damaging the diagnosis target. Furthermore, the state of the lubricant can be easily diagnosed on the basis of the parameter representing the electrical characteristics.

[0181] <Other Embodiments>

[0182] In addition, in the present application, a program or an application for realizing the functions of one or more of the above-described embodiments can be provided to a system or an apparatus by using a network or a storage medium, and the functions can be realized by one or more processors in the computer of the system or the apparatus reading and executing the program.

[0183] In addition, the functions can be realized by a circuit (for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array)) that realizes one or more functions.

[0184] Thus, the present application is not limited to the above-described embodiments, and the skilled person in the art will implement the structures of the embodiments in combination with each other, make changes and applications according to the description and known technologies, which are also within the scope of the present application.

[0185] As described above, the following is disclosed in the present specification.

[0186] (1) A state diagnosis method characterized by comprising:

[0187] a measurement step of measuring the relative dielectric constant of the lubricant by applying a voltage to the lubricant while changing the frequency using an alternating current power supply;

[0188] deriving a parameter indicating an electrical property of the lubricant by applying the relative permittivity measured in the measuring step to a theoretical formula; and

[0189] diagnosing a state of the lubricant using the parameter.

[0190] According to this structure, it is possible to easily diagnose the state of the lubricant without destroying the diagnosis object.

[0191] (2) The state diagnosis method according to (1), characterized in that the parameter includes at least any one of a relative permittivity at a low frequency limit, a relative permittivity at a high frequency limit, a relaxation strength, an average relative permittivity, a relaxation time, a distribution of the relaxation time, and a direct current conductivity.

[0192] According to this structure, it is possible to derive a plurality of parameters for diagnosing the state of the lubricant.

[0193] (3) The state diagnosis method according to (1) or (2), characterized in that,

[0194] the theoretical formula is represented by the following formula:

[0195] [Num 9]

[0196]

[0197] [Num 10]

[0198]

[0199] [Num 11]

[0200] X = In (ωτ) = ln (2πfτ)

[0201] According to this structure, it is possible to derive a theoretical value of the relative permittivity and the relative dielectric loss rate with higher precision.

[0202] (4) The state diagnosis method according to any one of (1) to (3), characterized in that,

[0203] the lubricant is in a bulk state.

[0204] According to this structure, it is possible to diagnose the state of the lubricant in the bulk state.

[0205] (5) The state diagnosis method according to any one of (1) to (4), characterized in that,

[0206] the lubricant is lubricating oil.

[0207] According to this structure, it is possible to handle the lubricating oil as the diagnosis object.

[0208] (6) The state diagnosing method according to any one of (1) to (4), characterized in that

[0209] The lubricant is a grease.

[0210] According to this structure, it is possible to handle a grease as a diagnosis object.

[0211] (7) The state diagnosing method according to (6), characterized in that, in the diagnosing step, at least any one of the amount of thickener, the fiber state of thickener, the degree of deterioration of grease, the amount of moisture in grease, and the amount of iron powder in grease is diagnosed as the state of the grease.

[0212] According to this structure, it is possible to diagnose a plurality of states of a grease.

[0213] (8) A state diagnosing apparatus characterized by comprising:

[0214] a measuring unit that measures the relative dielectric constant of a lubricant by applying a voltage to the lubricant while changing the frequency using an alternating current power supply;

[0215] a deriving unit that derives a parameter indicating the electrical characteristics of the lubricant by applying the relative dielectric constant measured by the measuring unit to a theoretical formula; and

[0216] a diagnosing unit that diagnoses the state of the lubricant using the parameter.

[0217] According to this structure, it is possible to easily diagnose the state of a lubricant without destroying the diagnosis object.

[0218] (9) A storage medium storing a program for causing a computer to execute the following steps:

[0219] a measuring step of measuring the relative dielectric constant of a lubricant by applying a voltage to the lubricant while changing the frequency using an alternating current power supply;

[0220] a deriving step of deriving a parameter indicating the electrical characteristics of the lubricant by applying the relative dielectric constant measured in the measuring step to a theoretical formula; and

[0221] a diagnosing step of diagnosing the state of the lubricant using the parameter.

[0222] According to this structure, it is possible to easily diagnose the state of a lubricant without destroying the diagnosis object.

[0223] The above describes various embodiments with reference to the drawings, but the present application is of course not limited to the above examples. Those skilled in the art can find various modifications or corrections within the scope recited in the claims, but it should be understood that they will naturally fall within the technical scope of the present application. Furthermore, the structural elements in the above embodiments can be arbitrarily combined within the scope of the gist of the present application.

[0224] In addition, the present application is based on Japanese Patent Application (Japanese Patent Application No. 2020-163961) filed on September 29, 2020, and Japanese Patent Application (Japanese Patent Application No. 2021-137562) filed on August 25, 2021, the contents of which are incorporated herein by reference.

Claims

1. A state diagnosing method characterized by comprising: has: a measurement step of measuring a relative dielectric constant of a lubricant by applying a voltage to the lubricant while changing a frequency using an alternating current power supply; a derivation step of deriving a parameter indicating an electrical characteristic of the lubricant by applying the relative dielectric constant measured in the measurement step to a theoretical formula; and a diagnosis step of diagnosing a state of the lubricant using the parameter, the parameter includes at least any one of a relative dielectric constant at a low frequency limit, a relative dielectric constant at a high frequency limit, a relaxation strength, an average relative dielectric constant, a relaxation time, a distribution of the relaxation time, and a direct current conductivity, the theoretical formula is represented by the following formula [Num 1] [Num 2] [Num 3] X = ln(ωτ) = ln(2πfτ) where: β: a constant indicating a distribution of the relaxation time ε r ′: relative dielectric constant ε r0 : relative dielectric constant at low frequency epsilon r∞ : relative dielectric constant at high frequency limit σ0: the direct current conductivity epsilon r "relative dielectric loss rate" ε0: a vacuum dielectric constant ω: an angular frequency of the voltage τ: the relaxation time ln: a logarithmic function π: a circular constant f: the frequency.

2. The state diagnosis method according to claim 1, wherein the lubricant is in a bulk state.

3. The state diagnosis method according to claim 1 or 2, wherein the lubricant is a lubricating oil.

4. The state diagnosis method according to claim 1 or 2, wherein the lubricant is a lubricating grease.

5. The state diagnosis method according to claim 4, wherein at least any one of an amount of a thickening agent, a fiber state of the thickening agent, a degree of deterioration of the lubricating grease, an amount of moisture in the lubricating grease, and an amount of iron powder in the lubricating grease is diagnosed as the state of the lubricating grease in the diagnosis step. has:

6. A state diagnosing apparatus characterized by comprising: a measurement unit that measures a relative dielectric constant of a lubricant by applying a voltage to the lubricant while changing a frequency using an alternating current power supply; a derivation unit that derives a parameter indicating an electrical characteristic of the lubricant by applying the relative dielectric constant measured by the measurement unit to a theoretical formula; and a diagnosis unit that diagnoses a state of the lubricant using the parameter, the parameter includes at least any one of a relative dielectric constant at a low frequency limit, a relative dielectric constant at a high frequency limit, a relaxation strength, an average relative dielectric constant, a relaxation time, a distribution of the relaxation time, and a direct current conductivity, the theoretical formula is represented by the following formula [Num 1] [Num 2] [Num 3] X = ln(ωτ) = ln(2πfτ) where: β: a constant indicating a distribution of the relaxation time σ0: the direct current conductivity ε r ′: relative dielectric constant ε r0 : relative dielectric constant at low frequency ε r∞ : relative dielectric constant at high frequency limit ε0: a vacuum dielectric constant ε r tan δ: relative dielectric loss ω: an angular frequency of the voltage τ: the relaxation time ln: a logarithmic function π: a circular constant f: the frequency.

7. A storage medium storing a program, wherein the program causes a computer to execute the following steps: a measurement step of measuring a relative dielectric constant of a lubricant by applying a voltage to the lubricant while changing a frequency using an alternating current power supply; a derivation step of deriving a parameter indicating an electrical characteristic of the lubricant by applying the relative dielectric constant measured in the measurement step to a theoretical formula; and a diagnosis step of diagnosing a state of the lubricant using the parameter. ​ ​ a diagnosing step of diagnosing a state of the lubricant using the parameter, the parameter includes at least any one of a relative dielectric constant at a low frequency limit, a relative dielectric constant at a high frequency limit, a relaxation strength, an average relative dielectric constant, a relaxation time, a distribution of the relaxation time, and a direct current conductivity, the theoretical formula is represented by the following formula [Num 1] [Num 2] [Num 3] X = ln(ωτ) = ln(2πfτ) wherein: ε r ′: relative dielectric constant ε r0 : relative dielectric constant at low frequency ε r∞ : relative dielectric constant at high frequency limit β: a constant representing a distribution of the relaxation time epsilon r "relative dielectric loss rate" σ0: a direct current conductivity ε0: a vacuum dielectric constant ω: an angular frequency of a voltage τ: a relaxation time ln: a logarithmic function π: a circular constant f: a frequency.

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