Method for detecting state of oil film, state detection device, and program

Abstract

A state detection method detects a state of an oil film formed by a lubricant in an apparatus configured to lubricate a plurality of sites with the lubricant, the state detection method having: a measurement step of measuring an impedance and a phase angle of a circuit composed of the plurality of sites by applying an alternating voltage to the circuit while varying a frequency; and a derivation step of deriving an oil film thickness formed by the lubricant and a parameter representing an electrical characteristic at the oil film thickness, based on a relative dielectric constant of the lubricant at a high frequency limit and the measured impedance and phase angle.

Description

Technical Field

[0001] This invention relates to a method, apparatus, and procedure for detecting the condition of an oil film. Background Technology

[0002] In the past, structures that use lubricants (e.g., lubricating oil, grease) to lubricate the rotation of bearings in bearing assemblies have been widely adopted. On the other hand, for rotating components such as bearing assemblies, periodic condition diagnostics are performed to detect damage and wear in advance, thereby preventing the occurrence of failures in rotating components.

[0003] In bearing assemblies that use lubricants, it is necessary to properly inspect the internal condition in order to diagnose their operating status. For example, Patent Document 1 discloses a method for detecting the thickness of the lubricating oil film and the metal-to-metal contact ratio in a rolling mechanism.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-211317 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] In devices such as bearing assemblies, understanding the state of the lubricant's surroundings is very useful in preventing damage to the device. While the method in Patent Document 1 can derive the thickness of the lubricant film and the metal-to-metal contact ratio, it does not derive parameters related to the electrical characteristics of the rolling bearing. Originally, it was difficult to derive the electrical characteristics at that lubricant film thickness because it was difficult to measure the actual thickness of the lubricant film within a rotating rolling bearing.

[0009] In view of the above-mentioned problems, the object of the present invention is to provide a method for deriving the film thickness of a lubricant in a device such as a rolling bearing and parameters related to the electrical properties determined by the film thickness.

[0010] Technical means for solving problems

[0011] To solve the above problems, the present invention has the following structure. That is, a state detection method for detecting the state of an oil film formed by a lubricant within an apparatus configured to lubricate multiple parts using a lubricant, the state detection method comprising:

[0012] The measurement process involves applying an alternating voltage to a circuit comprised of multiple said components while simultaneously varying the frequency, thereby measuring the impedance and phase angle of the circuit; and

[0013] The derivation process derives the oil film thickness formed by the lubricant and parameters representing the electrical properties at the oil film thickness, based on the relative permittivity of the lubricant at the high-frequency limit as specified according to the composition of the lubricant, and the impedance and phase angle measured in the measurement process.

[0014] Furthermore, other embodiments of the present invention have the following structure. That is, a state detection device detects the state of an oil film formed by a lubricant within a device configured to lubricate multiple parts using a lubricant, the state detection device comprising:

[0015] A measurement unit that measures the impedance and phase angle of a circuit by applying an alternating voltage to a circuit composed of multiple said components while changing the frequency; and

[0016] The derivation unit derives the oil film thickness formed by the lubricant and parameters representing the electrical properties at the oil film thickness based on the relative permittivity of the lubricant at the high-frequency limit as specified according to the composition of the lubricant, the impedance measured by the measuring unit, and the phase angle.

[0017] Furthermore, other embodiments of the present invention have the following structure. That is, a program for causing a computer to perform the following steps:

[0018] The measurement process involves applying an alternating voltage to a circuit comprised of multiple parts, configured to lubricate multiple components using a lubricant, while simultaneously varying the frequency, thereby measuring the impedance and phase angle of the circuit; and

[0019] The derivation process derives the oil film thickness formed by the lubricant and parameters representing the electrical properties at the oil film thickness, based on the relative permittivity of the lubricant at the high-frequency limit as specified according to the composition of the lubricant, and the impedance and phase angle measured in the measurement process.

[0020] Invention Effects

[0021] According to the present invention, a method is provided for determining the thickness of a lubricant film within an apparatus and parameters relating to the electrical properties determined by the film thickness. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating an example of the structure of a diagnostic apparatus according to the present invention.

[0023] Figure 2 This is a graph illustrating the physical model of the bearing device involved in this invention.

[0024] Figure 3 This is a graph illustrating the geometric model involved in this invention.

[0025] Figure 4 This is a circuit diagram illustrating the equivalent circuit of the bearing device involved in this invention.

[0026] Figure 5 This is a circuit diagram illustrating the equivalent circuit of the bearing device involved in this invention.

[0027] Figure 6 It is a graph used to illustrate the relationship between frequency, relative permittivity, and relative permittivity.

[0028] Figure 7 It is a diagram used to illustrate how parameters are derived by applying theoretical formulas.

[0029] Figure 8 This is a diagram used to illustrate an example of deriving parameters by applying theoretical formulas.

[0030] Figure 9 This is a diagram used to illustrate an example of deriving parameters by applying theoretical formulas.

[0031] Figure 10 It is a graph used to illustrate the relative permittivity and relative permittivity at various oil film thicknesses.

[0032] Figure 11 This is a diagram used to illustrate an example of deriving oil film thickness and parameters.

[0033] Figure 12 This is a diagram used to illustrate an example of deriving oil film thickness and parameters.

[0034] Figure 13 This is a flowchart of the measurement process involved in this invention.

[0035] Symbol Explanation

[0036] 1. Diagnostic device

[0037] 2. Bearing assembly

[0038] 3. Outer ring (outer component)

[0039] 4. Inner ring (inner component)

[0040] 5. Rolling element

[0041] 6. Seals

[0042] 7 Rotation axis

[0043] 8 LCR tester

[0044] 9 Rotary Connector

[0045] 10 motors Detailed Implementation

[0046] Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. Furthermore, the embodiments described below are merely illustrative of one embodiment of the present invention and are not intended to limit or explain the invention. Additionally, not all structures described in each embodiment are necessary to solve the problems of the present invention. Furthermore, in the accompanying drawings, the same reference numerals are used to indicate the correspondence of the same constituent elements.

[0047] <First Implementation>

[0048] The first embodiment of the present invention will be described. It should be noted that, in the following description, a ball bearing is used as an example of a rolling bearing, but the invention is not limited to this; the present invention can also be applied to rolling bearings of other structures. For example, types of rolling bearings to which the present invention can be applied include deep groove ball bearings, angular contact ball bearings, tapered roller bearings, cylindrical roller bearings, and self-aligning roller bearings.

[0049] [Device Structure]

[0050] Figure 1 This is a schematic structural diagram illustrating an example of the overall structure of the diagnostic device 1 according to this embodiment during diagnosis. Figure 1 The system includes a bearing device 2 that can apply the condition detection method described in this embodiment, and a diagnostic device 1 for performing condition detection and diagnosis. Additionally, Figure 1 The structure shown is an example; different structures can be used depending on the structure of bearing assembly 2, etc. Furthermore, in Figure 1 In the diagram, bearing assembly 2 shows a structure with one rolling bearing, but it is not limited to this; multiple rolling bearings may also be present in one bearing assembly 2.

[0051] In bearing assembly 2, a rolling bearing rotatably supports a rotating shaft 7. The rotating shaft 7 is supported by a housing (not shown) covering the outer side of the rotating shaft 7 via the rolling bearing, which is a rotating component. The rolling bearing includes: a fixed ring, i.e., an outer ring (outer component) 3, embedded in the housing; a rotating ring, i.e., an inner ring (inner component) 4, embedded in the rotating shaft 7; a plurality of rolling elements 5, i.e., a plurality of balls (rollers), disposed between the inner ring 4 and the outer ring 3; and a retainer (not shown) that rotatably holds the rolling elements 5. Here, a structure in which the outer ring 3 is fixed is used, but a structure in which the inner ring 4 is fixed and the outer ring 3 rotates is also possible. In addition, a seal 6 is provided, which serves as a peripheral component to prevent debris from entering the periphery of the rolling elements 5 and to prevent lubricating oil leakage. Inside the rolling bearing, friction between the inner ring 4 and the rolling elements 5, and between the outer ring 3 and the rolling elements 5, can be reduced by a prescribed lubrication method. The lubrication method is not particularly limited; for example, grease lubrication or oil lubrication is supplied to the inside of the rolling bearing. The type of lubricant is also not particularly limited.

[0052] Motor 10 is a drive motor that supplies rotational power to the rotating shaft 7. The rotating shaft 7 is connected to the LCR tester 8 via a rotary connector 9. The rotary connector 9 can be made of carbon brushes, for example, and is not limited to this. In addition, the bearing assembly 2 is also electrically connected to the LCR tester 8, in which case the LCR tester 8 also functions as an AC power source for the bearing assembly 2.

[0053] The diagnostic device 1 operates as a detection device capable of performing the detection method according to this embodiment. During diagnosis, the diagnostic device 1 inputs the angular frequency ω and AC voltage V of the AC power supply to the LCR meter 8 as an indication, and as corresponding outputs, acquires the impedance |Z| (where |Z| represents the absolute value of Z) and phase angle θ of the bearing assembly 2 from the LCR meter 8. Furthermore, the diagnostic device 1 uses these values ​​to detect information related to the state of the lubricant in the bearing assembly 2. Details regarding the detection method will be explained later.

[0054] The diagnostic device 1 can be implemented, for example, by an information processing device comprising a control device, a storage device, and an output device (not shown). The control device can be composed of a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a DSP (Digital Single Processor), or dedicated circuitry. The storage device can be composed of volatile and non-volatile storage media such as HDD (Hard Disk Drive), ROM (Read-Only Memory), and RAM (Random Access Memory), and can input and output various information according to instructions from the control device. The output device can be composed of a speaker, a light, or a display device such as an LCD, and can report to the operator according to instructions from the control device. The reporting method of the output device is not particularly limited; for example, it can be an auditory report based on sound or a visual report based on screen output. Furthermore, the output device can be a network interface with communication capabilities, and can also perform reporting actions by sending data to an external device (not shown) via a network (not shown). The content of this report is not limited to reports of anomalies detected when an anomaly diagnosis is performed based on the test results, but may also include reports indicating that bearing assembly 2 is normal.

[0055] [Physical Model]

[0056] use Figure 2 The contact state between the rolling element 5 and the outer ring 3 (or inner ring 4) in the bearing assembly 2 is described. Figure 2 This is a graph illustrating the physical model of the contact between the ball and the disc. The ball corresponds to the rolling element, and the disc corresponds to the outer ring 3 (or inner ring 4). The h-axis represents the oil film thickness direction, and the y-axis represents the direction orthogonal to the oil film thickness direction. Additionally, Figure 2 The variables shown are as follows.

[0057] S1: Hertzian contact area (Hertzian contact region)

[0058] c: Radius of the Hertzian contact circle (=√(S1 / π))

[0059] α: Oil film breakage rate (metal contact ratio) (0≤α<1)

[0060] r b : Radius of the sphere

[0061] αS1: Actual contact area (the area where the oil film breaks down)

[0062] h: Oil film thickness

[0063] h1: Oil film thickness in the Hertz contact area

[0064] In the Hertzian contact region, the ratio of the area of ​​contact to the area of ​​non-contact metal is α:(1-α). Furthermore, in the ideal state where the sphere and disk are not in contact, α = 0, and when y = 0, h > 0.

[0065] Figure 2 The oil film thickness h shown is expressed by the following formula.

[0066] h = 0 (-αS1 / 2 ≤ y ≤ αS1 / 2)

[0067] h = h1(-c≤y<-αS1 / 2, or αS1 / 2<y≤c)

[0068] h = h1 + √(rb) 2 -c 2 )-√(rb 2 -y 2 ) (-r b ≤y<-c, or c <y≤r b (1)

[0069] It should be noted that in actual rolling bearings, the rolling element 5 undergoes elastic deformation under load, and therefore is not strictly speaking a sphere. However, in this embodiment, it is treated as a sphere and the above formula (1) is used. Therefore, the formula used to calculate the oil film thickness is not limited to formula (1), and other calculation formulas can also be used.

[0070] Figure 3 This is a diagram showing the geometric model of a rolling bearing. The x-axis represents the axial direction orthogonal to the y-axis and h-axis, respectively. Figure 3 The variables shown are described below. Additionally, with... Figure 2 The same symbols represent the corresponding content.

[0071] R x Effective radius (x-axis)

[0072] R y Effective radius (y-axis)

[0073] h1: Oil film thickness in the Hertz contact area

[0074] r b : Radius of the sphere

[0075] like Figure 3 As shown, the case where the rolling element 5 rotates around the y-axis and a load (axial load) is applied in the y-axis direction is explained.

[0076] [Equivalent Circuit]

[0077] Figure 4 It is represented using an electrical equivalent circuit (equivalent circuit). Figure 2 The diagram is derived from the physical model shown. The equivalent circuit E1 consists of resistors R1 and R2, capacitor C1, and capacitor C2. Resistor R1 corresponds to the resistance in the fracture region (=αS1). Resistor R2 corresponds to the resistance around the fracture region. Capacitor C1 corresponds to the capacitor formed by the oil film in the Hertz contact region, denoted as electrostatic capacitance C1. Capacitor C2 corresponds to the capacitor formed by the oil film around the Hertz contact region ( ). Figure 2 -r b ≤y<-c and c<y≤r b The capacitor formed by the oil film in the oil film is designated as electrostatic capacitance C2. The Hertzian contact region (=S1) is formed. Figure 4 The equivalent circuit E1 consists of a parallel circuit of resistor R1 and capacitor C1. Additionally, a Hertzian contact region is formed around... Figure 4 The equivalent circuit E1 consists of a parallel circuit of resistor R2 and capacitor C2. Furthermore, by connecting these parallel circuits in parallel, the equivalent circuit E1 is formed. At this time, around the Hertzian contact region ( Figure 2 -r b ≤y<-c and c<y≤r b It is filled with lubricant.

[0078] Let Z represent the impedance of the equivalent circuit E1. Here, the AC voltage V applied to the equivalent circuit E1, the current I flowing through the equivalent circuit E1, and the complex impedance Z of the equivalent circuit E1 as a whole are represented by the following equations (2) to (4).

[0079] V=|V|exp(jωt) (2)

[0080] I=|I|exp(jωt-jθ) (3)

[0081] Z=V / I=|V / I|exp(jθ)=|Z|exp(jθ) (4)

[0082] j: Imaginary number

[0083] ω: Angular frequency of alternating current

[0084] t: time

[0085] θ: Phase angle (phase deviation between voltage and current)

[0086] Figure 5 Based on Figure 4The diagram shown is an equivalent circuit E1 representing the electrical equivalent circuit around a rolling element 5. Focusing on a single rolling element 5, an equivalent circuit E2 is formed between the outer ring 3 and the rolling element 5, and between the inner ring 4 and the rolling element 5. Here, the upper side is described as the circuit formed by the outer ring 3 and the rolling element 5, and the lower side as the circuit formed by the inner ring 4 and the rolling element 5, but the reverse is also possible. Around a rolling element 5, these circuits are connected in series to form the equivalent circuit E2.

[0087] [Oil film dielectric constant under axial load]

[0088] In this embodiment, the relative permittivity and relative permittivity loss rate under the condition that an axial load is applied to the rolling bearing via the rotating shaft 7 will be explained. Figure 5 The equivalent circuit E2 shown has the values ​​of each resistor and capacitor defined by the following formula.

[0089] [Number 1]

[0090]

[0091] [Number 2]

[0092]

[0093] [Number 3]

[0094]

[0095] [Number 4]

[0096]

[0097] [Number 5]

[0098]

[0099] [Number 6]

[0100]

[0101] ε: Dielectric constant of the oil film (lubricant)

[0102] ε′: Relative permittivity of the oil film

[0103] ε″: Relative dielectric loss rate of the oil film

[0104] Z: Overall impedance of the circuit

[0105] R1: Resistance in the Hertzian contact region

[0106] R2: Resistance around the Hertz contact region

[0107] C1: Electrostatic capacitance in the Hertzian contact region

[0108] C2: Electrostatic capacitance around the Hertzian contact area

[0109] S: Hertz contact area

[0110] k: Number of rolling bearings

[0111] n: Total number of rolling volumes

[0112] l: The number of contact areas for each rolling element

[0113] ω: Angular frequency of alternating current

[0114] θ: Phase angle

[0115] h: Oil film thickness

[0116] r: Effective radius of the rolling element

[0117] r x Effective radius of the rolling element (x-axis)

[0118] r y Effective radius of the rolling element (y-axis)

[0119] π: Pi

[0120] ln: Logarithmic function

[0121] Based on the above equations (5) to (10), the relative permittivity ε′ and relative permittivity ε″ are rearranged to obtain the following formulas.

[0122] [Number 7]

[0123]

[0124] [Number 8]

[0125]

[0126] In this embodiment, the above-described equations (11) and (12) are used in the derivation of the relative permittivity and relative permittivity of the rolling bearing under axial load.

[0127] [Relative permittivity and relative permittivity]

[0128] Figure 6 This is a graph used to illustrate the changing trends of relative permittivity and relative permittivity in relation to frequency variations. Here, in Figure 1 In the structure shown, the relative permittivity ε of the lubricant within the rolling bearing was determined by conducting experiments under the following conditions. r ′ and relative permittivity εr "This confirms the dielectric relaxation phenomenon caused by the lubricant in the rolling bearing. At this point, the relative permittivity ε is derived using equations (11) and (12) above." r ′ and relative permittivity ε r Here, as an example, the oil film thickness h in equations (7) and (8) is set to 250 nm.

[0129] (Experimental conditions)

[0130] Bearing: Deep groove ball bearing (nameplate: 6306)

[0131] Rotational speed: 997 [min] -1 ]

[0132] Axial load: 1000 [N]

[0133] Radial load: 0 [N]

[0134] Temperature: 23°C

[0135] Lubricant: 12-OH stearic acid grease

[0136] Lubricant base oil: ester oil

[0137] AC voltage: 1.0V

[0138] AC power frequency: 20–1 MHz

[0139] exist Figure 6 In (a), the horizontal axis represents the logarithm of the frequency [Hz], and the vertical axis represents the relative permittivity ε. r ′. Figure 6 (a) Shows the experimental values ​​obtained as a result of the above experiments. For example... Figure 6 As shown in (a), the relative permittivity ε r It has a tendency to decrease (monotonic decrease) as the frequency increases.

[0140] exist Figure 6 In (b), the horizontal axis represents the logarithm of the frequency [Hz], and the vertical axis represents the relative dielectric loss rate εr″. Figure 6 (b) Shows the experimental values ​​obtained as the results of the above experiments. For example... Figure 6 As shown in (b), the relative permittivity ε r "It exhibits a trend of temporarily decreasing as the frequency increases, then increasing again, and then decreasing again."

[0141] [Application of theoretical formulas]

[0142] Next, the parameters related to the dielectric relaxation phenomenon caused by the lubricant within the rolling bearing are explained. Due to the dielectric relaxation phenomenon of the lubricant within the rolling bearing, the relative permittivity and relative dielectric loss rate exhibit the following characteristics: Figure 6 The trend of change is shown. To determine this trend, theoretical formulas are applied (fitting) to derive various parameters. In this embodiment, the relative permittivity ε at the low-frequency limit is used. r0 The relative permittivity ε in the high-frequency limit r∞ Relaxation strength (ε) r0 -ε r∞ The relaxation time τ, the constant β representing the distribution of the relaxation time, and the DC conductivity σ0 are described as parameters of the derived object. In this embodiment, the following theoretical formulas are used.

[0143] [Number 9]

[0144]

[0145] [Number 10]

[0146]

[0147] [Number 11]

[0148] X=ln(ωτ)=ln(2πfτ)…(15)

[0149] ε r0 Relative permittivity in the low-frequency limit

[0150] ε r∞ Relative permittivity in the high-frequency limit

[0151] τ: Relaxation time [s]

[0152] β: A constant representing the distribution of relaxation time.

[0153] σ0: DC conductivity [S / m]

[0154] ε0: Dielectric constant of vacuum

[0155] π: Pi

[0156] f: Frequency

[0157] Figure 7 This is a graph comparing the curve obtained by applying the above theoretical formula with the value obtained through experiments. Figure 7 In (a), the horizontal axis represents frequency [Hz], and the vertical axis represents the relative permittivity ε. r '.exist Figure 7 In (b), the horizontal axis represents frequency [Hz], and the vertical axis represents relative dielectric loss εr″. For example... Figure 7 As shown in (a), for the relative permittivity, the theoretical value can be applied to show the trend of the experimental value. Furthermore, as... Figure 7 As shown in (b), for relative permittivity, the theoretical value can also be used to show the trend of the experimental value.

[0158] By applying the above theoretical formulas as parameters of the electrical properties related to lubricants, the relative permittivity ε in the low-frequency limit can be derived. r0 The relative permittivity ε in the high-frequency limit r∞ Relaxation strength (ε) r0 -ε r∞ The formulas are: relaxation time τ, a constant β representing the distribution of relaxation time, and DC conductivity σ0. It should be noted that the above theoretical formula is based on a Cole-Cole type formula and is only one example. Therefore, it is not limited to this theoretical formula, and other theoretical formulas can also be used.

[0159] [Parameter Export]

[0160] (Parameters related to electrical characteristics)

[0161] An example is given to illustrate how the above method can be used to derive parameters related to electrical characteristics. Figure 8 The curve represents the experimental results measured under the above-described test conditions and the theoretical value obtained by applying them to the theoretical formula. Here, an example is shown where the oil film thickness h of the lubricant within the rolling bearing is assumed to be 250 nm. Figure 7 In (a), the horizontal axis represents the logarithm of the frequency [Hz], and the vertical axis represents the relative permittivity ε. r '.exist Figure 7 In (b), the horizontal axis represents the logarithm of the frequency [Hz], and the vertical axis represents the relative permittivity ε. r ″.

[0162] Figure 9 Indicates based on Figure 8 The relative permittivity, relaxation strength, relaxation time, relaxation time distribution, and DC conductivity are derived from the application results shown.

[0163] (oil film thickness)

[0164] exist Figure 8 , Figure 9 In the example, the oil film thickness h is set to 250 nm. That is, using equations (11) and (12) above, in order to calculate the relative permittivity ε r The relative permittivity εr requires setting the oil film thickness h. In other words, the relative permittivity εr... rThe value of the relative dielectric loss rate εr″ varies depending on the value of the oil film thickness h.

[0165] Figure 10 This represents the experimental values ​​obtained by setting the oil film thickness to different values. Here, three values, 200 nm, 250 nm, and 300 nm, are used for comparison as the oil film thickness h. Figure 10 In (a), the horizontal axis represents the logarithm of the frequency [Hz], and the vertical axis represents the relative permittivity ε. r '.exist Figure 10 In (b), the horizontal axis represents the logarithm of the frequency [Hz], and the vertical axis represents the relative permittivity ε. r ″.

[0166] like Figure 10 As shown, due to the variation in oil film thickness h, the relative permittivity ε r ′、Relative permittivity ε r The value of ″ changes. On the other hand, even when the setting of the oil film thickness h is changed, the trend of the experimental values ​​obtained by frequency sweep does not change. For example, as Figure 10 As shown in (a), the relative permittivity ε r The change in ′ with respect to oil film thickness h is constant at any frequency. Similarly, as Figure 10 As shown in (b), the relative permittivity ε r The change in ″ with respect to the oil film thickness h is constant at any frequency.

[0167] Based on the above characteristics, we consider deriving parameters related to the electrical characteristics of the rolling bearing during rotation and the oil film thickness simultaneously. Here, the relative permittivity ε at the high-frequency limit is... r∞ The relative permittivity ε, which is determined based on the amount of thickener in the lubricant and the type of base oil, can be determined first, according to the amount of thickener and the type of base oil in the lubricant used in rolling bearings. r∞ The value of ε. Here, the relative permittivity ε at the high-frequency limit. r∞ This can be a value for the lubricant in a bulk state. Furthermore, by using the relative permittivity ε of this high-frequency limit... r∞ The values ​​are used as boundary conditions to set equations (13) and (14), thereby uniquely determining the oil film thickness h. Furthermore, the curve corresponding to the experimental values ​​can be determined. That is, in Figure 10 In the example shown in (a), by determining the relative permittivity ε corresponding to the high-frequency limit. r∞ The position of the right end allows us to determine the relative permittivity ε at each frequency. r The value of ′.

[0168] Figure 11This represents the relative permittivity ε determined by the high-frequency limit. r∞ The experimental values ​​obtained from the values ​​and the theoretical values ​​obtained through application. Figure 11 In (a), the horizontal axis represents the logarithm of the frequency [Hz], and the vertical axis represents the relative permittivity ε. r '.exist Figure 11 In (b), the horizontal axis represents the logarithm of the frequency [Hz], and the vertical axis represents the relative permittivity ε. r ".in addition, Figure 12 Indicates according to Figure 11 The application results shown derive the relative permittivity, relaxation intensity, relaxation time, relaxation time distribution, and DC conductivity at the low-frequency limit. As mentioned above, the relative permittivity ε at the high-frequency limit... r∞ The value is determined based on the composition of the lubricant; here, the value for the bulk state is used.

[0169] As a result, it is possible to simultaneously derive the relative permittivity, relaxation intensity, relaxation time, relaxation time distribution, DC conductivity, and oil film thickness at the low-frequency limit.

[0170] [Processing Flow]

[0171] Figure 13 This is a flowchart of the state diagnosis process according to this embodiment. This process is executed by the diagnostic device 1. For example, the control device (not shown) provided by the diagnostic device 1 can be implemented by reading and executing a program for implementing the process according to this embodiment from a storage device (not shown).

[0172] In S1301, diagnostic device 1 controls the bearing assembly 2 to apply an axial load in a specified load direction. Alternatively, the application of the axial load can be controlled by a different device than diagnostic device 1. In this case, the phase and impedance under static contact conditions are measured.

[0173] In S1302, the diagnostic device 1 uses the motor 10 to start rotating the rotating shaft 7. This causes the inner ring 4, which is connected to the rotating shaft 7, to begin rotating. Alternatively, the motor 10 can be controlled by a different device than the diagnostic device 1.

[0174] In S1303, the diagnostic device 1 controls the LCR tester 8 to supply an AC voltage V with angular frequency ω to the bearing assembly 2 using the AC power supply (not shown) provided by the LCR tester 8. Thus, an AC voltage V with angular frequency ω is applied to the bearing assembly 2.

[0175] In S1304, the diagnostic device 1 obtains the impedance |Z| and phase angle θ from the LCR tester 8 as the output corresponding to the input in S1303. That is, the LCR tester 8 outputs the impedance |Z| and phase angle θ to the diagnostic device 1 as the detection result of the bearing device 2 corresponding to the input, i.e., the AC voltage V and the angular frequency ω of the AC voltage.

[0176] In S1305, the diagnostic device 1 obtains the value of the relative permittivity εr∞ at the high-frequency limit based on the composition of the lubricant used in the bearing assembly 2. It should be noted that the relative permittivity εr∞ at the high-frequency limit... r∞ The value of ε is predetermined according to the composition of the lubricant. The relative permittivity ε at the high-frequency limit... r∞ The information can be stored in the storage device (not shown) of the diagnostic device 1, or it can be configured so that the user can set it separately.

[0177] In S1306, the diagnostic device 1 uses the impedance |Z| and phase angle θ obtained in S1304, the AC voltage V at the angular frequency ω indicated in S1303, and the value of the relative permittivity εr∞ at the high-frequency limit obtained in S1305 to determine the oil film thickness h and the curve corresponding to the theoretical value. Specifically, by applying experimental values ​​using the above equations (13) to (15), the oil film thickness h and Figure 11 The curve shown.

[0178] In S1307, the diagnostic device 1 derives various parameters based on the curves obtained as application results in S1306. In this embodiment, the relative permittivity, relaxation intensity, relaxation time, relaxation time distribution, and DC conductivity at the low-frequency limit are determined.

[0179] In S1308, the diagnostic device 1 performs a lubricant condition diagnosis based on the oil film thickness determined in S1306 and various parameters derived in S1307. The diagnostic content is not particularly limited; for example, it could involve pre-setting thresholds for each parameter and diagnosing normal or abnormal structures by comparing them to these thresholds. Alternatively, it could be configured to pre-set multiple thresholds corresponding to the urgency of the abnormality, and diagnose the urgency by comparing it to these thresholds.

[0180] In S1309, the diagnostic device 1 reports the diagnostic results obtained in S1308 to the user. The reporting method is not particularly limited; for example, it could be displaying the parameters or items deemed abnormal on a screen, or providing a notification via sound. Then, the processing flow ends.

[0181] According to this embodiment, even when the thickness of the lubricant film in rolling bearings or the like is difficult to measure, the thickness of the oil film can be determined. Furthermore, parameters related to the electrical characteristics of the oil film can be derived. Moreover, based on these, condition diagnosis can be easily performed.

[0182] Furthermore, in the above examples, various parameters are derived by setting the relative permittivity εr∞ at the high-frequency limit. However, this structure is not limited to this one. For example, in equations (7) and (8) above, the parameters include the oil film thickness h. Here, the oil film thickness h is a parameter that does not change with the angular frequency ω of the AC voltage, so formulas that derive the permittivity by setting dh / dω=0 can also be used. Alternatively, the oil film thickness h can be calculated based on the operating conditions and design parameters of the rolling bearing, and various parameters can be calculated using this value.

[0183] <Other Implementation Methods>

[0184] In the above embodiments, a bearing device was used as an example for explanation, but the description is not limited to this. For example, using... Figures 2 to 5 As shown, by setting up a geometric model and equivalent circuit, the present invention can also be applied to other devices. For example, it is conceivable that the oil film thickness of the lubricant in the rolling bearing described in the first embodiment is on the order of approximately μm to nm. Therefore, the method according to the present invention can be applied when measuring substances at such dimensions. Furthermore, the method according to the present invention can be applied to rolling devices that use lubricants, etc., as suitable devices.

[0185] In addition, in this invention, a program or application for implementing the functions of one or more of the above embodiments can be provided to a system or device through a network or storage medium, and one or more processors in the computer of the system or device can read and execute the program.

[0186] Alternatively, it can be implemented using a circuit that performs more than one function (e.g., an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array)).

[0187] Therefore, the present invention is not limited to the above-described embodiments. Those skilled in the art can combine the various structures of the embodiments with each other, make changes based on the description in the specification and known technologies, and apply them within the scope of the present invention and include them within the scope of protection claimed.

[0188] As stated above, the following information is disclosed in this specification.

[0189] (1) A state detection method, characterized in that,

[0190] The state of an oil film formed by a lubricant within a device that lubricates multiple parts using a lubricant is detected, the state detection method comprising:

[0191] The measurement process involves applying an alternating voltage to a circuit comprised of multiple said components while simultaneously varying the frequency, thereby measuring the impedance and phase angle of the circuit; and

[0192] The derivation process derives the oil film thickness formed by the lubricant and parameters representing the electrical properties at the oil film thickness, based on the relative permittivity of the lubricant at the high-frequency limit as specified according to the composition of the lubricant, and the impedance and phase angle measured in the measurement process.

[0193] According to this structure, a method can be provided to simultaneously extract the thickness of the lubricant film within the device and parameters related to the electrical properties determined by the film thickness.

[0194] (2) The state detection method according to (1) is characterized in that,

[0195] The relative permittivity of the lubricant at the high-frequency limit is the relative permittivity of the lubricant at the high-frequency limit when it is in a bulk state.

[0196] Based on this structure, by using the relative permittivity of the lubricant in bulk state at the high-frequency limit, it is possible to easily derive both the thickness of the lubricant film within the device and parameters related to the electrical properties determined by the film thickness.

[0197] (3) The state detection method according to (1) or (2) is characterized in that,

[0198] The parameters include at least one of the following: relative permittivity at the low-frequency limit, relaxation strength, relaxation time, relaxation time distribution, and DC conductivity.

[0199] Based on this structure, the relative permittivity, relaxation strength, relaxation time, relaxation time distribution, and DC conductivity at the low-frequency limit can be derived as parameters corresponding to the state of the lubricant within the device.

[0200] (4) The state detection method according to any one of (1) to (3), characterized in that,

[0201] The device is a rolling device.

[0202] Based on this structure, it is possible to take the rolling device as an object and simultaneously derive parameters related to the thickness of the lubricant film within the rolling device and the electrical properties determined by the film thickness.

[0203] (5) The state detection method according to any one of (1) to (3), characterized in that,

[0204] The device is a bearing device.

[0205] The multiple parts include an outer component, an inner component, and a rolling element.

[0206] Based on this structure, it is possible to take a rolling bearing as an object and simultaneously derive the thickness of the lubricant film within the rolling bearing and the parameters related to the electrical properties determined by the film thickness.

[0207] (6) The state detection method according to any one of (1) to (5), characterized in that,

[0208] It also includes a diagnostic step, which uses the oil film thickness and the parameters derived in the export step to diagnose the condition of the device.

[0209] Based on this structure, the condition diagnosis of the device can be performed based on the derived lubricant film thickness and parameters.

[0210] (7) A state detection device, characterized in that...

[0211] The state detection device is used to detect the state of an oil film formed by a lubricant within a device that lubricates multiple parts using a lubricant.

[0212] A measurement unit that measures the impedance and phase angle of a circuit by applying an alternating voltage to a circuit composed of multiple said components while changing the frequency; and

[0213] The derivation unit derives the oil film thickness formed by the lubricant and parameters representing the electrical properties at the oil film thickness based on the relative permittivity of the lubricant at the high-frequency limit as specified according to the composition of the lubricant, the impedance measured by the measuring unit, and the phase angle.

[0214] According to this structure, a method can be provided to simultaneously extract the thickness of the lubricant film within the device and parameters related to the electrical properties determined by the film thickness.

[0215] (8) A program, characterized in that,

[0216] Used to enable the computer to perform the following procedures:

[0217] The measurement process involves applying an alternating voltage to a circuit composed of multiple parts using a lubricant while simultaneously varying the frequency of the device, thereby measuring the impedance and phase angle of the circuit; and

[0218] The derivation process derives the oil film thickness formed by the lubricant and parameters representing the electrical properties at the oil film thickness, based on the relative permittivity of the lubricant at the high-frequency limit as specified according to the composition of the lubricant, and the impedance and phase angle measured in the measurement process.

[0219] According to this structure, a method can be provided to simultaneously extract the thickness of the lubricant film within the device and parameters related to the electrical properties determined by the film thickness.

[0220] Various embodiments have been described above with reference to the accompanying drawings; however, the present invention is not limited to the examples described above. Those skilled in the art will readily recognize that various modifications and alterations can be made within the scope of the appended claims, but it should be understood that these modifications also fall within the technical scope of the present invention. Furthermore, the constituent elements of the above embodiments can be combined arbitrarily without departing from the spirit of the present invention.

[0221] Furthermore, the contents of Japanese patent applications filed on September 29, 2020 (Japanese Patent Application No. 2020-163963) and August 25, 2021 (Japanese Patent Application No. 2021-137564) are incorporated herein by reference.

Claims

1. A state detection method, characterized in that, The state of the oil film formed by the lubricant within a device configured to lubricate multiple parts using the lubricant is detected. The state detection method has the following characteristics: The measurement process involves applying an alternating voltage to multiple locations while simultaneously changing the frequency, thereby measuring the impedance and phase angle of the circuit containing the multiple locations. as well as The derivation process derives the oil film thickness formed by the lubricant and parameters representing the electrical properties at the oil film thickness, based on the relative permittivity of the lubricant at the high-frequency limit as specified according to the composition of the lubricant, and the impedance and phase angle measured in the measurement process.

2. The state detection method according to claim 1, characterized in that, The relative permittivity of the lubricant at the high-frequency limit is the relative permittivity of the lubricant at the high-frequency limit when it is in a bulk state.

3. The state detection method according to claim 1 or 2, characterized in that, The parameters include at least one of the following: relative permittivity at the low-frequency limit, relaxation strength, relaxation time, relaxation time distribution, and DC conductivity.

4. The state detection method according to claim 1 or 2, characterized in that, The device is a rolling device.

5. The state detection method according to claim 1 or 2, characterized in that, The device is a bearing device. The multiple parts include an outer component, an inner component, and a rolling element.

6. The state detection method according to claim 1 or 2, characterized in that, The state detection method further includes a diagnostic step, which uses the oil film thickness and the parameters derived in the export step to diagnose the state of the device.

7. A state detection device, characterized in that, The state detection device is configured to detect the state of an oil film formed by a lubricant within a device that lubricates multiple parts using a lubricant. The measuring unit measures the impedance and phase angle of the circuit by applying an AC voltage to the circuit composed of the plurality of said parts while changing the frequency. as well as The derivation unit derives the oil film thickness formed by the lubricant and parameters representing the electrical properties at the oil film thickness based on the relative permittivity of the lubricant at the high-frequency limit as specified according to the composition of the lubricant, the impedance and the phase angle measured by the measuring unit.

8. A storage medium for storing programs, characterized in that, Used to enable the computer to perform the following procedures: The measurement process involves applying an alternating voltage to a circuit composed of the multiple parts of a device configured to lubricate multiple parts using a lubricant, while changing the frequency, thereby measuring the impedance and phase angle of the circuit. as well as The derivation process derives the oil film thickness formed by the lubricant and parameters representing the electrical properties at the oil film thickness, based on the relative permittivity of the lubricant at the high-frequency limit as specified according to the composition of the lubricant, and the impedance and phase angle measured in the measurement process.

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