TECHNICAL FIELD
[0001] The present invention relates to an oil film state detection method, a state detection
device, and a program.
10 BACKGROUND ART
[0002] 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 suppress failures of the rotating parts
15 from occurring.
[0003] The bearing device using a lubricant is required to appropriately detect the internal
state for diagnosing 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.
20 CITATION LIST
PATENT LITERATURE
[0004] Patent Literature 1: JP2019-211317A
SUMMARY OF INVENTION
25 TECHNICAL PROBLEM
[0005] It is very useful to grasp conditions around a lubricant in a device such as a bearing
device to suppress damage to the device. In a method of Patent Literature 1, although a film
thickness of a lubricant and a metal contact ratio can be derived, parameters related to
electrical characteristics of the rolling bearing are not derived. In the first place, since it is
30 difficult to actually measure an oil film thickness of a lubricant in a rolling bearing during
rotation, it is also difficult to derive electrical characteristics according to the oil film
thickness.
[0006] In view of the above-described problems, the present invention is to provide a
2
method for deriving a film thickness of a lubricant and a parameter related to an electrical
characteristic according to the film thickness in a device such as a rolling bearing.
SOLUTION TO PROBLEM
5 [0007] To solve the above-described problems, the present invention has the following
configuration. That is, there is provided a state detection method for detecting an oil film state
according to a lubricant in a device configured to lubricate a plurality of parts with the
lubricant, the method including:
a measurement step of measuring impedance and a phase angle of an electric circuit
10 by applying an AC voltage to the electric circuit configured with the plurality of parts while
changing a frequency; and
a derivation step of deriving an oil film thickness according to the lubricant and a
parameter indicating an electrical characteristic according to the oil film thickness, based on a
relative dielectric constant at a high frequency limit of the lubricant defined based on a
15 composition of the lubricant, and the impedance and the phase angle measured in the
measurement step.
[0008] Another aspect of the present invention has the following structures. That is, there is
provided a state detection device configured to detect an oil film state according to a lubricant
in a device configured to lubricate a plurality of parts with the lubricant, the device including:
20 a measurement unit configured to measure impedance and a phase angle of an
electric circuit by applying an AC voltage to the electric circuit configured with the plurality
of parts while changing a frequency; and
a derivation unit configured to derive an oil film thickness according to the
lubricant and a parameter indicating an electrical characteristic according to the oil film
25 thickness, based on a relative dielectric constant at a high frequency limit of the lubricant
defined based on a composition of the lubricant, and the impedance and the phase angle
measured in by the measurement unit.
[0009] Another aspect of the present invention has the following structures. That is, there is
provided a program for causing a computer to execute:
30 a measurement step of measuring impedance and a phase angle of an electric circuit
by applying an AC voltage to the electric circuit configured with a plurality of parts while
changing a frequency for a device configured to lubricate the plurality of parts with a
lubricant; and
3
a derivation step of deriving an oil film thickness according to the lubricant and a
parameter indicating an electrical characteristic according to the oil film thickness, based on a
relative dielectric constant at a high frequency limit of the lubricant defined based on a
composition of the lubricant, and the impedance and the phase angle measured in the
5 measurement step.
ADVANTAGEOUS EFFECTS OF INVENTION
[0010] According to the present invention, it is possible to provide a method for deriving a
film thickness of a lubricant in a device and a parameter related to an electrical characteristic
10 according to the film thickness.
BRIEF DESCRIPTION OF DRAWINGS
[0011] [FIG. 1] FIG. 1 is a schematic diagram illustrating an example of a configuration
of an apparatus for diagnosis according to the present invention.
15 [FIG. 2] FIG. 2 is a graph illustrating a physical model of a bearing device
according to the present invention.
[FIG. 3] FIG. 3 is a graph illustrating a geometric model according to the present
invention.
[FIG. 4] FIG. 4 is a circuit diagram illustrating an equivalent circuit of the bearing
20 device according to the present invention.
[FIG. 5] FIG. 5 is a circuit diagram illustrating an equivalent circuit of the bearing
device according to the present invention.
[FIG. 6] FIG. 6 is a diagram illustrating a relationship between frequency, a
relative dielectric constant, and a relative dielectric loss factor.
25 [FIG. 7] FIG. 7 is a diagram illustrating derivation of parameters by fitting to a
theoretical formula.
[FIG. 8] FIG. 8 is a diagram illustrating an example of parameter derivation by
fitting to a theoretical formula.
[FIG. 9] FIG. 9 is a diagram illustrating an example of parameter derivation by
30 fitting to a theoretical formula.
[FIG. 10] FIG. 10 is a diagram illustrating a relative dielectric constant and a
relative dielectric loss factor for each oil film thickness.
[FIG. 11] FIG. 11 is a diagram illustrating an example of oil film thickness and
4
parameter derivation.
[FIG. 12] FIG. 12 is a diagram illustrating an example of oil film thickness and
parameter derivation.
[FIG. 13] FIG. 13 is a flowchart of processing during measurement according to the
5 present invention.
DESCRIPTION OF EMBODIMENTS
[0012] Hereinafter, an aspect for implementing the present invention is described with
reference to drawings. Note that the embodiment described below is one embodiment for
10 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 each drawing, the same component is denoted by the same reference number to
indicate correspondence.
15 [0013]
Hereinafter, a first embodiment according to the present invention will be described.
Note 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
20 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.
[0014] [Device Configuration]
FIG. 1 is a schematic configuration diagram illustrating an example of the overall
configuration when performing diagnosis with a diagnosis device 1 according to the present
25 embodiment. In FIG. 1, a bearing device 2 to which a state detection method according to the
present embodiment is applied and the diagnosis device 1 performing state detection and
diagnosis, are illustrated. Note that the configuration illustrated in FIG. 1 is an exemplary one,
and a different configuration may be used according to a configuration of the bearing device 2
and the like. Although FIG. 1 illustrates a configuration in which the bearing device 2
30 includes one rolling bearing, the present invention is not limited thereto, and one bearing
device 2 may include a plurality of rolling bearings.
[0015] In the bearing device 2, the rolling bearings rotatably support a rotating shaft 7. The
rotating shaft 7 is supported by a housing (not illustrated) that covers an outside of the
5
rotating shaft 7 via the rolling bearing that is a rotating component. The rolling bearing
includes an outer ring (outer member) 3 which is a fixing ring fitted inside the housing, an
inner ring (inner member) 4 which is a rotating ring fitted on the rotating shaft 7, a plurality of
balls (rollers) which are a plurality of rolling elements 5 arranged between the inner ring 4
5 and the outer ring 3, and a holder (not illustrated) holding the rolling elements 5 so that rolling
elements can roll. Herein, although the outer ring 3 is fixed in the above-described
configuration, the inner ring 4 may be fixed, and the outer ring 3 may be rotated in the other
configurations. A seal 6 is provided as a peripheral member for suppressing dust from
entering the vicinity of the rolling elements 5 and lubricant from leaking. Friction between the
10 inner ring 4 and the rolling elements 5 and friction between the outer ring 3 and the rolling
elements 5 are reduced by a predetermined lubrication method inside the rolling bearing.
Although the lubrication method is not particularly limited, for example, grease lubrication,
oil lubrication, or the like is used and is supplied to the inside of the rolling bearing. The type
of lubricant is not particularly limited.