EP-4224136-B1 - TEMPERATURE DERIVATION METHOD FOR OIL FILM, TEMPERATURE DERIVATION DEVICE, AND PROGRAM

Inventors

• IWASE, SHUNSUKE
• MARUYAMA, TAISUKE

Dates

Publication Date

20260506

Application Date

20210924

Claims (4)

1. A temperature derivation method for deriving an oil film temperature of a lubricant in a rolling bearing (2), the temperature derivation method comprising: a measurement step of measuring a dielectric constant of the lubricant by applying an alternating voltage while changing a frequency to an electric circuit configured by the rolling bearing (2); a derivation step of applying the dielectric constant measured in the measurement step to a theoretical formula to derive a relaxation time of the lubricant; and a calculation step of calculating the oil film temperature by using the relaxation time, wherein in the calculation step, the oil film temperature is calculated using T = Δ H ‡ R / W Δ H ‡ k B τ Rh exp Δ S ‡ R wherein an activation enthalpy ΔH ‡ and an activation entropy ΔS ‡ are values of the lubricant in a bulk state, and wherein the theoretical formulas are represented by ε r ′ = 1 2 ε r 0 − ε r∞ 1 − sinh βX cosh βX + cos βπ 2 + ε r∞ ε r " = σ 0 2 πfε 0 + 1 2 ε r 0 − ε r∞ sinh βπ 2 cosh βX + cos βπ 2 , and X = ln ωτ = ln 2 πfτ .
2. The temperature derivation method according to claim 1, further comprising a diagnosis step of diagnosing a state of the rolling bearing (2) using the oil film temperature calculated in the calculation step.
3. A temperature derivation device (1) for detecting an oil film temperature of a lubricant in a rolling bearing (2), the temperature derivation device (1) comprising: a measurement unit measuring a dielectric constant of the lubricant by applying an alternating voltage while changing a frequency to an electric circuit configured by the rolling bearing (2); a derivation unit applying the dielectric constant measured in the measurement unit to a theoretical formula to derive a relaxation time of the lubricant; and a calculation unit calculating the oil film temperature by using the relaxation time, wherein in the calculation unit, the oil film temperature is calculated using T = Δ H ‡ R / W Δ H ‡ k B τ Rh exp Δ S ‡ R wherein an activation enthalpy ΔH ‡ and an activation entropy ΔS ‡ are values of the lubricant in a bulk state, and wherein the theoretical formulas are represented by ε r ′ = 1 2 ε r 0 − ε r∞ 1 − sinh βX cosh βX + cos βπ 2 + ε r∞ , ε r " = σ 0 2 πfε 0 + 1 2 ε r 0 − ε r∞ sinh βπ 2 cosh βX + cos βπ 2 , and X = ln ωτ = ln 2 πfτ
4. A program causing a computer to execute with the temperature derivation device (1) according to claim 3: a measurement step of measuring a dielectric constant of a lubricant in a rolling bearing (2) by applying an alternating voltage while changing a frequency to an electric circuit configured by the rolling bearing (2); a derivation step of applying the dielectric constant measured in the measurement step to a theoretical formula to derive a relaxation time of the lubricant; and a calculation step of calculating an oil film temperature of the lubricant by using the relaxation time, wherein in the calculation step, the oil film temperature is calculated using T = Δ H ‡ R / W Δ H ‡ k B τ Rh exp Δ S ‡ R wherein an activation enthalpy ΔH ‡ and an activation entropy ΔS ‡ are values of the lubricant in a bulk state, and wherein the theoretical formulas are represented by ε r ′ = 1 2 ε r 0 − ε r∞ 1 − sinh βX cosh βX + cos βπ 2 + ε r∞ , ε r " = σ 0 2 πfε 0 + 1 2 ε r 0 − ε r∞ sinh βπ 2 cosh βX + cos βπ 2 , and X = ln ωτ = ln 2 πfτ .

Description

TECHNICAL FIELD The present invention relates to an oil film temperature derivation method, a temperature derivation device, and a program. BACKGROUND ART In the related art, in bearing devices, a configuration in which a lubricant (for example, lubricating oil or grease) is used to lubricate rotation has been widely used. On the other hand, by periodically diagnosing a state of rotating parts such as bearing devices, damage and wear can be detected at an early stage to prevent failures of the rotating parts from occurring. The bearing device using a lubricant is required to appropriately detect the state related to the lubricant in order to diagnose the operating state. For example, Patent Literature 1 discloses a method for detecting an oil film thickness of a lubricant and a metal contact ratio in a rolling device. CITATION LIST PATENT LITERATURE Patent Literature 1: JP-A-2019-211317. Hakim Raymond M.: "Distribution of Relaxation Times in an Insulating Oil",IEEE Transactions on Electrical Insulation, vol. EI-6, no. 4, 1 December 1971 (1971-12-01), pages 158-164, XP093130245, US ISSN: 0018-9367, DOI: 10.1109/TEI.1971.299171 discloses an investigation of the dielectric properties of an insulating oil. The dielectric constant of the oil is studied as a function of the frequency of the applied excitation signal. SUMMARY OF INVENTION TECHNICAL PROBLEM It is very useful to grasp conditions around a lubricant in a device such as a bearing device to prevent damage to a device. The conditions around the lubricant include a temperature of an oil film due to the lubricant. In a method of Patent Literature 1, although a film thickness of a lubricant and a metal contact ratio can be derived, the temperature of the lubricant is not measured. When measuring the temperature of an oil film due to a lubricant whose temperature is expected to change, there are restrictions according to the installation position of a temperature sensor and control during measurement based on the measurement principle of the temperature sensor. For example, infrared methods such as thermography require constant thermal radiation of the object. In addition, in the temperature diagnosis method by means of thermochromism, or the like, the object needs to exist in a place where the object can be diagnosed. In view of the above problems, an object of the present invention is to provide a method for easily deriving an oil film temperature of a lubricant in a device. SOLUTION TO PROBLEM According to the invention, there is provided a temperature derivation method as defined in claim 1. According to the invention, there is provided a temperature derivation device as defined in claim 3. ADVANTAGEOUS EFFECTS OF INVENTION According to the present invention, it is possible to provide a method for easily deriving the oil film temperature of a lubricant in a device. BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a schematic diagram illustrating an example of a configuration of a device according to one embodiment of the present invention.Figs. 2A and 2B are diagrams illustrating a relationship between a frequency and a dielectric constant.Fig. 3 is a diagram illustrating a relationship between a relaxation time and an absolute temperature.Fig. 4 is a diagram illustrating derivation of parameters by fitting to a theoretical formula.Fig. 5 is a diagram illustrating a correlation between a temperature and a relaxation time.Fig. 6 is a diagram illustrating an example of a derivation result of an oil film temperature according to the present embodiment.Fig. 7 is a flowchart of processing when deriving a temperature according to one embodiment of the present invention. DESCRIPTION OF EMBODIMENTS Hereinafter, an aspect for implementing the present invention is described with reference to drawings. It is noted that the embodiment described below is one embodiment for describing the invention of the present application, and is not intended to be construed as limiting the invention of the present application, and all configurations described in the embodiments are not essential configurations for solving the problems of the present invention. In addition, in each drawing, the same component is denoted by the same reference number to indicate a correspondence. <First Embodiment> Hereinafter, a first embodiment according to the present invention will be described. It is noted that, in the following description, a ball bearing is used as an example of a rolling bearing, but the present invention is not limited thereto, and can be applied to rolling bearings having other configurations. For example, as types of the rolling bearings to which the present invention can be applied, there are exemplified deep groove ball bearings, angular contact ball bearings, tapered roller bearings, cylindrical roller bearings, and self-aligning roller bearings. [Device Configuration] Fig. 1 is a schematic configuration diagram illustrating an example of the overall configuration when performin