Method, device, and program for detecting the condition of a bearing device

Abstract

To detect an oil film thickness in a bearing device and a ratio of metal contact between components simultaneously while taking a load direction into consideration.SOLUTION: The present invention relates to a detection method that detects a state of a bearing device 2 comprising an outward member 3, an inward member 4 and a plurality of rolling bodies 5, and comprises: applying an electric voltage to an electric circuit consisting of the outward member 3, the inward member 4, and the plurality of rolling bodies 5 with a predetermined load placed on the bearing device 2; measuring impedance and a phase angle of the electric circuit during the application of the AC voltage; and deriving, based upon the impedance and the phase angle, an oil film thickness and a ratio of metal contact at least one of between the inward member 4 and the plurality of rolling bodies 5 and between the inward member 4 and the plurality of rolling bodies 5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method, a device, and a program for detecting the state of a bearing device. [Background technology]

[0002] Conventionally, bearing devices have been widely configured to use lubricants (e.g., lubricating oil or grease) to lubricate their rotation. Meanwhile, rotating parts such as bearing devices are routinely diagnosed for their condition to detect damage or wear at an early stage and prevent failure of the rotating parts.

[0003] In bearing devices that use lubricants, it is necessary to properly detect the state of the lubricant in order to diagnose the operating state of the device. For example, Patent Document 1 discloses a method of applying a low DC voltage to a bearing and diagnosing the oil film state in the bearing from the measured voltage. Furthermore, Patent Document 2 discloses a method of modeling the oil film as a capacitor, applying an AC voltage to the rotating ring of the bearing in a non-contact state, and estimating the oil film state of the bearing device based on the measured capacitance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese National Law Publication No. 05-003685 [Patent Document 2] Japanese Patent No. 4942496 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been a demand for even lower torque in rolling bearings. In response to this trend toward lower torque, the viscosity and amount of lubricants used in rolling bearings have been reduced. Under these circumstances, the possibility of oil film rupture inside the rolling bearing and the contact rate between parts increases. Therefore, in addition to the oil film thickness, it is necessary to properly detect the contact state between parts inside the rolling bearing. The method in Patent Document 2 measures only the oil film thickness, making it difficult to grasp the metal-to-metal contact rate. Furthermore, since the electrostatic capacitance outside the contact area is not taken into consideration, the measurement accuracy is not high. Furthermore, measurements focusing on the load direction are not performed.

[0006] In view of the above problems, an object of the present invention is to simultaneously detect the oil film thickness inside a bearing device and the proportion of metal contact between parts, taking into account the load direction. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention has the following configuration: That is, a detection method for detecting the state of a bearing device that includes an outer member, an inner member, and a plurality of rolling elements, the method comprising: applying an AC voltage to an electric circuit formed by the outer member, the inner member, and the plurality of rolling elements while a predetermined load is applied to the bearing device; measuring the impedance and phase angle of the electric circuit when the AC voltage is applied; and deriving an oil film thickness and a metal contact ratio between at least one of the inner member and the plurality of rolling elements or the inner member and the plurality of rolling elements based on the impedance and the phase angle.

[0008] Another aspect of the present invention has the following configuration: A detection device for detecting the state of a bearing device including an outer member, an inner member, and a plurality of rolling elements, the detection device comprising: an acquisition means for acquiring an impedance and a phase angle of an electric circuit formed by the outer member, the inner member, and the plurality of rolling elements when an AC voltage is applied to the electric circuit while a predetermined load is applied to the bearing device; and deriving means for deriving an oil film thickness and a metal contact ratio at least between the inner member and the plurality of rolling elements or between the inner member and the plurality of rolling elements based on the impedance and the phase angle.

[0009] Another aspect of the present invention has the following configuration: an acquisition means for acquiring the impedance and phase angle of an electric circuit when an AC voltage is applied to an electric circuit formed by an outer member, an inner member, and a plurality of rolling elements, while a predetermined load is being applied to a bearing device formed by the outer member, the inner member, and a plurality of rolling elements; a deriving means for deriving an oil film thickness and a metal contact ratio between at least one of the inner member and the plurality of rolling elements or the inner member and the plurality of rolling elements based on the impedance and the phase angle; A program to function as a [Effects of the Invention]

[0010] The present invention makes it possible to simultaneously detect the oil film thickness inside a bearing device and the contact ratio between parts, taking into account the load direction. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing an example of an apparatus configuration during diagnosis according to a first embodiment of the present invention. [Figure 2] FIG. 3 is a graph showing a physical model of the bearing device according to the first embodiment of the present invention. [Figure 3] FIG. 2 is a graph showing a geometric model according to the first embodiment of the present invention. [Figure 4]FIG. 1 is a circuit diagram for explaining an equivalent circuit of a bearing device according to a first embodiment of the present invention. [Figure 5] FIG. 1 is a circuit diagram for explaining an equivalent circuit of a bearing device according to a first embodiment of the present invention. [Figure 6] FIG. 2 is a diagram for explaining a load zone and a non-load zone according to the first embodiment of the present invention. [Figure 7A] FIG. 2 is a diagram for explaining capacitance in a load region according to the first embodiment of the present invention. [Figure 7B] FIG. 2 is a diagram for explaining capacitance in a load region according to the first embodiment of the present invention. [Figure 8] FIG. 1 is a circuit diagram for explaining an equivalent circuit according to a first embodiment of the present invention. [Figure 9] FIG. 2 is a graph illustrating capacitance according to the first embodiment of the present invention. [Figure 10] 3 is a flowchart of a process during measurement according to the first embodiment of the present invention. [Figure 11A] FIG. 2 is a graph showing measurement results according to the first embodiment of the present invention. [Figure 11B] FIG. 2 is a graph showing measurement results according to the first embodiment of the present invention. [Figure 12A] FIG. 10 is a graph illustrating the influence of a seal according to a second embodiment of the present invention. [Figure 12B] FIG. 10 is a graph illustrating the influence of a seal according to a second embodiment of the present invention. [Figure 13] FIG. 4 is a diagram for explaining an equivalent circuit according to a second embodiment of the present invention. [Figure 14] FIG. 10 is a graph illustrating capacitance according to a second embodiment of the present invention. [Figure 15A] FIG. 10 is a graph showing measurement results according to the second embodiment of the present invention. [Figure 15B] FIG. 10 is a graph showing measurement results according to the second embodiment of the present invention. [Figure 16A] FIG. 10 is a graph illustrating measurement accuracy according to the second embodiment of the present invention. [Figure 16B]FIG. 10 is a graph illustrating measurement accuracy according to the second embodiment of the present invention. [Figure 17A] FIG. 10 is a graph illustrating measurement accuracy according to the second embodiment of the present invention. [Figure 17B] FIG. 10 is a graph illustrating measurement accuracy according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. Note that the embodiment described below is one embodiment for explaining the present invention and is not intended to be interpreted as limiting the present invention. Furthermore, not all of the configurations described in each embodiment are necessarily essential configurations for solving the problems of the present invention. Furthermore, in each drawing, the same components are assigned the same reference numerals to indicate correspondence.

[0013] First Embodiment A first embodiment of the present invention will be described below. In the following description, a ball bearing will be used as an example of a rolling bearing, but the present invention is not limited to this and can be applied to rolling bearings of other configurations. 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.

[0014] [Device configuration] FIG. 1 is a schematic diagram showing an example of the overall configuration when a diagnosis is performed by a diagnostic device 1 according to this embodiment. In FIG. 1, a bearing device 2 to which the diagnostic method according to this embodiment is applied and a diagnostic device 1 that performs the diagnosis are provided. Note that the configuration shown in FIG. 1 is just one example, and a different configuration may be used depending on the configuration of the bearing device 2, etc. Also, in FIG. 1, the bearing device 2 is shown as having a configuration including one rolling bearing, but this is not limited to this, and one bearing device 2 may be equipped with multiple rolling bearings.

[0015] In the bearing device 2, a rolling bearing rotatably supports a rotating shaft 7. The rotating shaft 7 is supported by a housing (not shown) that covers the outside of the rotating shaft 7 via a rolling bearing, which is a rotating component. The rolling bearing includes an outer ring (outer member) 3, which is a fixed ring fitted inside the housing; an inner ring (inner member) 4, which is a rotating ring fitted around the rotating shaft 7; a plurality of balls (rollers), which are a plurality of rolling elements 5, arranged between the inner ring 4 and the outer ring 3; and a cage (not shown) that rotatably holds the rolling elements 5. Here, the outer ring 3 is configured to be fixed, but the inner ring 4 may be configured to be fixed and the outer ring 3 to rotate. In addition, a seal 6, which is a peripheral component, is provided to prevent the intrusion of dust around the rolling elements 5 and the leakage of lubricating oil. A predetermined lubrication method is used inside the rolling bearing to reduce friction between the inner ring 4 and the rolling elements 5 and between the outer ring 3 and the rolling elements 5. The lubrication method is not particularly limited, but for example, grease lubrication or oil lubrication is used and supplied to the inside of the rolling bearing. The type of lubricant is also not particularly limited.

[0016] The motor 10 is a driving motor that supplies rotational power to the rotating shaft 7. The rotating shaft 7 is connected to an LCR meter 8 via a rotary connector 9. The rotary connector 9 may be configured using, for example, but is not limited to, a carbon brush. The bearing device 2 is also electrically connected to the LCR meter 8, and in this case, the LCR meter 8 also functions as an AC power source for the bearing device 2.

[0017] The diagnostic device 1 operates as a detection device that can execute the detection method according to this embodiment. During diagnosis, the diagnostic device 1 instructs the LCR meter 8 to input the angular frequency ω of the AC power supply and the AC voltage V, and obtains the impedance |Z| (|Z| indicates the absolute value of Z) and phase angle θ of the bearing device 2 from the LCR meter 8 as the corresponding output. The diagnostic device 1 then uses these values ​​to detect the oil film thickness and metal contact ratio in the bearing device 2. Details of the detection method will be described later.

[0018] The diagnostic device 1 may be realized, for example, by an information processing device including a control device, a storage device, and an output device (not shown). The control device may be configured with a central processing unit (CPU), a microprocessing unit (MPU), a digital single processor (DSP), or a dedicated circuit. The storage device is configured with volatile and nonvolatile storage media such as a hard disk drive (HDD), a read-only memory (ROM), or a random access memory (RAM), and is capable of inputting and outputting various information in response to instructions from the control device. The output device is configured with a speaker, a light, or a display device such as an LCD display, and notifies the operator in response to instructions from the control device. The notification method used by the output device is not particularly limited, and may be, for example, an auditory notification using voice or a visual notification using a screen output. The output device may also be a network interface with a communication function, and may perform the notification operation by transmitting data to an external device (not shown) via a network (not shown). The notification content here is not limited to a notification when an abnormality is detected, for example, when an abnormality diagnosis is performed based on the detection results, but may also include a notification that the bearing device 2 is normal.

[0019] [Physical Model] The contact state between the rolling element 5 and the outer ring 3 (or inner ring 4) in the bearing device 2 will be explained using Figure 2. Figure 2 is a graph showing a physical model when a ball fragment and a disk fragment come into contact. The ball fragment corresponds to the rolling element, and the disk fragment corresponds to the outer ring 3 (or inner ring 4). The h-axis indicates the oil film thickness direction, and the y-axis indicates the direction perpendicular to the oil film thickness direction. The variables shown in Figure 2 are as follows: S1: Hertzian contact area (Hertzian contact area) c: Hertzian contact circle radius (=√(S1 / π) α: Oil film rupture rate (metal contact rate) (0≦α<1) r b : radius of ball piece αS1: Actual contact area (oil film rupture area) h: Oil film thickness h1: Oil film thickness in the Hertzian contact area

[0020] In the Hertzian contact region, the ratio of the area where the metals are in contact to the area where they are not in contact is α:(1-α). In an ideal state where the ball and disk pieces are not in contact, α=0, and when y=0, h>0.

[0021] The oil film thickness h shown in Fig. 2 is expressed by the following formula. h=0 (-αS1 / 2≦y≦αS1 / 2) h=h1(-c≦y<-αS1 / 2, or αS1 / 2 <y≦c) h=h1+√(r b 2 -c 2 )-√(r b 2 -y 2 ) (-r b ≦y<-c, or c <y≦r b ) …(1)

[0022] In an actual rolling bearing, the rolling elements 5 undergo elastic deformation when subjected to a load, and therefore are not strictly spherical, but in this embodiment, the above formula (1) is used assuming that the rolling elements are spherical. Therefore, the formula used to calculate the oil film thickness is not limited to formula (1), and other calculation formulas may be used.

[0023] Figure 3 is a diagram showing a geometric model of a rolling bearing. The x-axis indicates an axial direction perpendicular to the y-axis and h-axis. The variables shown in Figure 3 are as follows. The same symbols as in Figure 2 correspond to each other. R x : Effective radius (x axis) R y : Effective radius (y-axis) h1: Oil film thickness in the Hertzian contact area r b : radius of ball piece

[0024] As shown in FIG. 3, the description will be given assuming that the rolling element 5 rotates around the y-axis and that a load (radial load) is applied in the h-axis direction.

[0025] [Equivalent Electric Circuit] Figure 4 shows the physical model shown in Figure 2 in the form of an electrically equivalent electrical circuit (equivalent circuit). The equivalent circuit E1 is composed of a resistor R1, a capacitor C1, and a capacitor C2. The resistor R1 corresponds to the resistance in the fracture region (=αS1). The capacitor C1 corresponds to the capacitor formed by the oil film in the Hertzian contact area, and has a capacitance of C1. The capacitor C2 corresponds to the capacitor formed around the Hertzian contact area (-r in Figure 2). b ≦y<-c, and c <y≦r b ) corresponds to a capacitor formed by the oil film at the Hertzian contact area, and its capacitance is C2. The Hertzian contact area (=S1) forms a parallel circuit of the resistor R1 and capacitor C1 in the equivalent circuit E1 of Figure 4. Furthermore, the capacitor C2 is connected in parallel to the electrical circuit consisting of the resistor R1 and capacitor C1. At this time, the area around the Hertzian contact area (-r b ≦y<-c, and c <y≦r b ) is assumed to be filled with lubricant.

[0026] The impedance of the equivalent circuit E1 is represented by Z. 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 entire equivalent circuit E1 are expressed by the following equations (2) to (4). V = |V|exp(jωt) …(2) I = |I|exp(jωt) …(3) Z=V / I=|V / I|exp(jθ)=|Z|exp(jθ) …(4) j: imaginary number ω: Angular frequency of AC voltage t: time θ: Phase angle (phase difference between voltage and current)

[0027] FIG. 5 is a diagram showing an electrically equivalent electrical circuit around the rolling element 5 of 1, based on the equivalent circuit E1 shown in FIG. Focusing on the rolling element 5 of 1, 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 will be described as an electrical circuit formed by the outer ring 3 and the rolling element 5, and the lower side will be described as an electrical circuit formed by the inner ring 4 and the rolling element 5, but the reverse is also possible. Around the rolling element 5 of 1, these electrical circuits are connected in series to form the equivalent circuit E2.

[0028] [Capacitance due to radial load] FIG. 6 is a diagram illustrating the loaded and unloaded zones when a radial load is applied to a rolling bearing. Here, it is assumed that a radial load Fr is applied to the rolling bearing via a rotating shaft 7. In this case, the range in which the Hertzian contact zone as shown in FIG. 2 occurs among the multiple rolling elements 5 is called the loaded zone, and the other range is called the unloaded zone. Note that the range of the loaded zone can vary depending on the magnitude of the radial load, the configuration of the rolling bearing, etc.

[0029] First, we will explain the capacitance of capacitor C1 in the load zone. Figures 7A and 7B are diagrams for explaining the concept of capacitor C1 formed by rolling elements 5 located in the load zone. Here, we will explain using an example in which five rolling elements are included in the load zone, and capacitors C1(1) to C1(5) are formed by each rolling element. In the load zone, the size of the Hertzian contact area varies depending on the position of the rolling element. In this case, as shown in Figure 7A, it is also assumed that the capacitance decreases the further away from the center in the load zone.

[0030] However, as shown in Figures 2 and 3, the oil film thickness h1 in the Hertzian contact area is assumed to be less affected by radial load, and in this embodiment, the oil film thickness within the load zone is assumed to be constant. Based on this, as shown in Figure 7B, the Hertzian contact area S1 is averaged, and the capacitance of the capacitor C1 formed by each of the multiple rolling elements 5 within the load zone is treated as uniform. Therefore, the capacitance of the capacitor C1 formed by the multiple rolling elements 5 located in the load zone can be derived using the following equation (5).

[0031]

number

[0032] m: A natural number indicating the rolling element located in the load zone (1≦m≦n1) n1: Number of rolling elements located in the load zone C1(m): Capacitance in the Hertzian contact area of ​​rolling element m C1: average value of C1(m)

[0033] Next, the capacitance of capacitor C3 in the non-load zone will be explained. In the non-load zone, there is a gap between the rolling element 5 and the outer ring 3, and a gap between the rolling element 5 and the inner ring 4. As shown in FIG. 6, among the rolling elements 5 located in the non-load zone, the gap between the central rolling element 5a and the outer ring 3 and the gap between the rolling element 5a and the inner ring 4 are referred to as radial gap h. gap In this case, the clearance between each of the rolling elements 5 located in the non-load zone and the outer ring 3 can be derived from the following formula (6). Note that the clearance between the rolling element 5a and the outer ring 3 and the clearance between the rolling element 5a and the inner ring 4 are the same (h gap / 2) The radial clearance h gap is the radial load F r This can be derived from the specifications of the rolling bearings.

[0034]

number

[0035] m: A natural number indicating the rolling element located in the non-load zone (1≦m≦(n-n1)) n: total number of rolling elements n1: Number of rolling elements located in the load zone

[0036] Then, based on equation (6), the capacitance C3 of the entire non-load zone can be derived from the following equation (7).

[0037]

number

[0038] m: A natural number indicating the rolling element located in the non-load zone (1≦m≦(n-n1)) n: total number of rolling elements n1: Number of rolling elements located in the load zone ε: Dielectric constant of the lubricant C3(m): Capacitance in the Hertzian contact area of ​​rolling element m S1: Hertzian contact area π: Pi r x ￣: average value of effective radius (x-axis) r y ￣: Average value of effective radius (y-axis) r h ￣: constant (=(r x ￣+r y ￣) / 2) h gap : Radial clearance ln: logarithmic function

[0039] Fig. 8 is a diagram showing an electrically equivalent circuit for the entire bearing device 2, taking into account the capacitors formed in the loaded and non-loaded zones described above. n equivalent circuits E2 are connected in parallel corresponding to the n rolling elements 5 located in the loaded zone. In this case, as explained using Fig. 7, C1 is used as the capacitance in the Hertzian contact area.

[0040] Additionally, (n-n1) equivalent circuits E3 are connected in parallel corresponding to the (n-n1) rolling elements 5 located in the non-load zone. As in the loaded zone, a capacitor is formed between the outer ring 3 and the rolling elements 5, and between the inner ring 4 and the rolling elements 5, so the equivalent circuit E3 has two capacitors C3 connected in series. Here, the upper side is the electrical circuit formed by the outer ring 3 and the rolling elements 5, and the lower side is the electrical circuit formed by the inner ring 4 and the rolling elements 5, but this may be reversed. During diagnosis, AC power is supplied from an LCR meter 8 to the equivalent circuit E4 formed by the entire bearing device 2 shown in Figure 8.

[0041] Figure 9 is a diagram showing an example of the relationship between oil film thickness h and capacitance C of capacitors C1, C2, and C3 included in the electric circuit shown in Figure 8. The horizontal axis represents oil film thickness h [m], and the vertical axis represents capacitance C [F]. Figure 9 also shows the relationship under the following conditions: Bearing: Deep groove ball bearing (product number: 6306) Number of rolling elements (n): 8 Number of rolling elements in the load zone (n1): 3 Radial load (F r ):147[N]

[0042] As shown in Fig. 9, the capacitance of capacitors C1￣ and C2 decreases (monotonically decreases) as the oil film thickness h increases. The slope of capacitor C1￣ is greater than that of C2. C3 remains constant regardless of the oil film thickness h. For the combination of capacitors C1￣, C2, and C3 (=C1￣ + C2 + C3), the capacitance decreases as the oil film thickness h increases, but the rate of change becomes more gradual as the oil film thickness h increases.

[0043] [Derivation of oil film thickness and oil film rupture rate] In this embodiment, the lubrication state is detected using the lubricant oil film thickness h and oil film rupture rate α under the radial load as described above. First, the lubricant oil film thickness h and oil film rupture rate α under the axial load can be derived using the following equation (8).

[0044]

number

[0045] h: Oil film thickness α: Oil film rupture rate (metal contact rate) δ: constant(=(1-α)r h ￣S1 / 2πr x ￣r y ￣) ω: Angular frequency of AC voltage W: Lambert W function ζ: constant (=lr h ￣ / 2πεkn1r x ￣r y ￣) θ0: Phase in static contact state θ: Phase in dynamic contact state |Z0|: Impedance in static contact state |Z|: Impedance in dynamic contact state r x ￣: average value of effective radius (x-axis) r y ￣: Average value of effective radius (y-axis) r h ￣: constant (=(r x ￣+r y ￣) / 2) k: Number of rolling bearings l: number of contact areas m: A natural number indicating the rolling element located in the non-load zone (1≦m≦(n-n1)) n: total number of rolling elements n1: Number of rolling elements located in the load zone C3(m): Capacitance in the Hertzian contact area of ​​rolling element m

[0046] Equation (8) is an equation constructed based on the equivalent circuit E2 explained using Figure 5. In other words, equation (8) takes into account the effects of capacitors C1 and C2. In this embodiment, in order to derive the oil film thickness h of the lubricant and the oil film rupture rate α under radial load, the following equation (9) is used, which combines the configuration of equations (5) to (7) with equation (8).

[0047]

number

[0048] C3(m): Capacitance in the Hertzian contact area of ​​the rolling element (m)

[0049] [Processing flow] 10 is a flowchart of the diagnostic processing according to this embodiment. This processing is executed by the diagnostic device 1, and may be realized, for example, by a control device (not shown) included in the diagnostic device 1 reading out a program for implementing the processing according to this embodiment from a storage device (not shown) and executing the program.

[0050] In step S1001, the diagnostic device 1 applies a radial load F to the bearing device 2 in a predetermined load direction. r Here, the radial load F r is given. In addition, the radial load F r The control for providing this may be performed by a device separate from the diagnostic device 1. At this time, the phase and impedance in a static contact state are measured.

[0051] In S1002, the diagnostic device 1 starts the rotation of the rotating shaft 7 by the motor 10. This starts the rotation of the inner ring 4 connected to the rotating shaft 7. Note that the control of the motor 10 may be performed by a device separate from the diagnostic device 1.

[0052] In S1003, the diagnostic device 1 controls the LCR meter 8 to apply an AC voltage of angular frequency ω to the bearing device 2 using an AC power supply (not shown) provided in the LCR meter 8. As a result, an AC voltage of angular frequency ω is applied to the bearing device 2.

[0053] In S1004, the diagnostic device 1 acquires the impedance |Z| and the phase angle θ from the LCR meter 8 as the output in response to the input in S1003. That is, the LCR meter 8 obtains the following as the detection results of the bearing device 2 in response to the input AC voltage V and the angular frequency ω of the AC voltage: The impedance |Z| and the phase angle θ are output to the diagnostic device 1.

[0054] In S1005, the diagnostic device 1 derives the oil film thickness h and the rupture rate α by applying the impedance |Z| and phase angle θ acquired in S1004 and the angular frequency ω of the AC voltage used in S1003 to equation (9).

[0055] In S1006, the diagnostic device 1 diagnoses the lubrication state of the bearing device 2 using the oil film thickness h and the fracture rate α derived in S1005. Note that the diagnostic method here may, for example, set threshold values ​​for the oil film thickness h and the fracture rate α and determine the lubrication state by comparing with the threshold values. Then, this processing flow ends.

[0056] [test] The results of the test conducted based on the above-mentioned diagnostic method will be explained below. The configuration used during the test was the same as that shown in Figure 1, and the test conditions were as follows: (Test conditions) Bearing: Deep groove ball bearing (product number: 6306) Number of rolling elements (n): 8 Rotation speed: 50 to 1581 min -1 ] Axial load: 0 [N] Radial load (F r ):147[N] Temperature: 25[℃] Maximum contact pressure: 0.89 [GPa] Lubricant base oil: Polyalphaolefin Lubricant thickener: urea Worked penetration: 300 Kinematic viscosity: 74[mm 2 / s, 40℃] Pressure viscosity coefficient: 13.8 [GPa -1 , 25℃] Dielectric constant: 2.3 AC voltage: 0.2 [V] AC power frequency: 1.0 [MHz]

[0057] 11A and 11B are diagrams showing the relationship between the rotation speed N, the oil film thickness h, and the rupture rate α obtained from the results of tests conducted under the above test conditions. In FIG. 11A, the horizontal axis represents the rotation speed N [min -1 ], and the vertical axis represents the oil film thickness h [m]. In FIG. 11B, the horizontal axis represents the rotation speed N [min -1 As shown in the test conditions above, the rotation speed was 50 to 1581 [min -1 The results obtained within the range of [ ] are plotted.

[0058] In Figure 11A, the dashed line indicates the oil film thickness derived as a theoretical value. ● indicates the result of deriving the oil film thickness h using equation (8). ◯ indicates the result of deriving the oil film thickness h using equation (9). In other words, ◯ is the result derived taking into account the capacitor C3 configured in the non-load zone under radial load. As shown in Figure 11A, the results indicated by ◯ are closer to the theoretical value than the results indicated by ● at all rotational speeds, making it possible to derive the oil film thickness h with greater accuracy. Furthermore, as shown in Figure 11B, the breakage rate α can be derived in addition to the oil film thickness h at all rotational speeds.

[0059] As described above, this embodiment makes it possible to simultaneously detect the oil film thickness inside a bearing device and the contact ratio between components under a radial load.

[0060] Note that the formula (9) used in this embodiment is based on the formula (8) that takes into account the axial load, and therefore can be applied under an axial load as well, and can therefore be used universally under both axial and radial load conditions.

[0061] <Second embodiment> In the first embodiment, a configuration was described in which the oil film thickness inside the bearing device and the contact ratio between parts are simultaneously detected under a radial load, taking into account the configuration of the non-load zone of the bearing device 2. In the second embodiment of the present invention, a configuration for further improving measurement accuracy will be described. Note that a description of the configuration that overlaps with the first embodiment will be omitted, and the description will focus on the differences.

[0062] [Pre-verification] In order to improve the measurement accuracy as explained using Figures 11A and 11B, the inventors focused on the configuration (peripheral members) other than the periphery of the rolling element 5 that constitutes the bearing device 2. First, in order to verify the influence of the configuration other than the periphery of the rolling element 5, a test bearing device was prepared in which the influence of C1, C2, and C3 constituted by the rolling elements could be ignored, and a test was conducted. Specifically, the multiple rolling elements provided in the bearing device were constituted by ceramic rolling elements that have insulating properties that do not allow AC voltage to pass through. In addition, bearing devices with a seal 6 and bearing devices without a seal 6 were prepared. A radial load F was applied to these bearing devices. r After applying the voltage, measurements were taken using an LCR meter 8.

[0063] 12A and 12B show the radial load F obtained from the LCR meter 8 in a test performed on a test bearing device. r The relationship between the impedance |Z| and the phase angle θ is shown in Fig. 12A. In Fig. 12A, the horizontal axis is the radial load F r 12B, the horizontal axis represents the radial load Fr [N] and the vertical axis represents the phase angle θ.

[0064] Referring to FIG. 12A, a difference occurs in impedance |Z| depending on whether or not there is a seal 6. At this time, the radial load F r Even if the radial load F changes, the difference remains almost constant, so the impedance |Z| r12B, there is a slight difference in the phase angle θ depending on whether or not the seal 6 is present, but in both cases it is approximately -90°. Since no AC voltage flows through the ceramic rolling elements, it can be seen that capacitance is generated between the outer ring 3 and the inner ring 4 and at the seal 6. In this embodiment, the capacitor formed between the outer ring 3 and the inner ring 4 and due to the seal 6 is treated as capacitor C4 (capacitance C4).

[0065] [Equivalent circuit] Figure 13 is a diagram showing an equivalent circuit E5 that is electrically equivalent to the entire bearing device 2, further including the above-mentioned capacitor C4, in addition to the equivalent circuit E4 described in the first embodiment using Figure 8. The equivalent circuit E5 is configured such that the equivalent circuit E4 and capacitor C4 are connected in parallel. During diagnosis, AC power is supplied from an LCR meter 8 to the equivalent circuit E5 formed by the entire bearing device 2 shown in Figure 13.

[0066] Figure 14 shows the relationship between the oil film thickness h and the capacitance C of the capacitors C1, C2, C3, and C4 included in the equivalent circuit shown in Figure 13. The horizontal axis represents the oil film thickness h [m], and the vertical axis represents the capacitance C [F]. Figure 13 also shows the relationship under the following conditions: Bearing: Deep groove ball bearing (product number: 6306) Number of rolling elements (n): 8 Number of rolling elements in the load zone (n1): 3 Radial load (F r ):147[N]

[0067] As shown in Figure 14, capacitors C1_, C2, and C3 are the same as those shown in Figure 9. Capacitor C4 remains almost constant regardless of oil film thickness h, but its capacitance is higher when seal 6 is present than when seal 6 is not present. For the combination of capacitors C1_, C2, C3, and C4 (=C1_+C2+C3+C4), the capacitance decreases as oil film thickness h increases, but the rate of change becomes more gradual as oil film thickness h increases. Although not shown in Figure 14, when comparing the combination of capacitors C1_, C2, C3, and C4 (=C1_+C2+C3+C4) with the combination of capacitors C1_, C2, and C3 shown in Figure 9 (=C1_+C2+C3), the curve for the combination of capacitors C1_, C2, C3, and C4 (=C1_+C2+C3+C4) shows a more gradual change (decrease).

[0068] [Derivation of oil film thickness and oil film rupture rate] In this embodiment, the lubricant oil film thickness h and oil film rupture rate α under radial load are derived using the following equation (10) based on the equivalent circuit E5 described with reference to Figure 13. In other words, equation (10) is obtained by further considering the influence of capacitor C4 in addition to equation (9) above. The value of C4 shown in equation (10) can be determined in advance depending on the configuration of the bearing device 2, as shown in Figure 14.

[0069]

number

[0070] C4: Capacitance generated between the outer ring and inner ring, and between the seal and inner ring

[0071] [test] The results of the test conducted based on the above-mentioned diagnostic method will be described below. The configuration and test conditions during the test are the same as those shown in the first embodiment.

[0072] 15A and 15B are diagrams showing the relationship between the rotation speed N, the oil film thickness h, and the rupture rate α obtained from the results of tests conducted under the above test conditions. In FIG. 15A, the horizontal axis represents the rotation speed N [min -1 ], and the vertical axis represents the oil film thickness h [m]. In Figure 15B, the horizontal axis represents the rotation speed N [min -1 As shown in the test conditions above, the rotation speed was 50 to 1581 [min -1 The results obtained within the range of [ ] are plotted.

[0073] In Figure 15(a), the dashed line, black circles, and circles are the same as in Figure 11. The triangles indicate the results of deriving the oil film thickness h using equation (10). In other words, the triangles indicate results that take capacitor C4 into account. As shown in Figure 15A, the results indicated by the triangles are closer to the theoretical value than the results indicated by the black circles and circles at all rotational speeds, making it possible to derive the oil film thickness h with greater accuracy. Furthermore, as shown in Figure 15B, the breakage rate α can be derived in conjunction with the oil film thickness h at all rotational speeds.

[0074] Next, the oil film thickness detection accuracy according to this embodiment will be explained. To determine the oil film thickness h and the fracture rate α in the loaded and unloaded zones according to this embodiment, the inventors prepared a test bearing device in which, among the multiple rolling elements, one rolling element was made of steel and the rest were made of ceramic. The steel rolling element functioned as a conductor, allowing current from an AC power source to flow through it. On the other hand, the ceramic rolling element functioned as an insulator, preventing current from flowing through it. When a radial load was applied to the steel rolling element and an AC voltage was applied to a bearing device with this configuration, the effect of capacitor C3 (i.e., capacitance C3 in the unloaded zone) described in the first embodiment could be ignored.

[0075] Using the above test bearing device, tests were carried out under the following conditions. (Test conditions) Bearing: Deep groove ball bearing (product number: 6306, rolling element configuration as above) Radial load (Fr ):147[N] Rotation speed: 50 min -1 ] Lubricant: Urea grease Kinematic viscosity: 74[mm 2 / s, 40℃]

[0076] 16A, 16B, 17A, and 17B are diagrams showing the relationship between the position φ and the oil film thickness h and the rupture rate α obtained from the results of tests conducted under the above test conditions. In FIGS. 16A and 16B, the oil film thickness h and the rupture rate α are plotted based on the results calculated using equation (8), which is a conventional method. In FIGS. 17A and 17B, the oil film thickness h and the rupture rate α are plotted based on the results calculated using equation (10) according to this embodiment. In FIGS. 16A and 17A, the horizontal axis represents the position φ [deg], and the vertical axis represents the oil film thickness h [m]. In FIGS. 16B and 17B, the horizontal axis represents the position φ [deg], and the vertical axis represents the rupture rate α. Here, the position φ is determined by the radial load F r The position in the direction in which the load is applied (the center position of the loaded zone) is set as the reference (φ=0), and positive values ​​are assumed in the counterclockwise direction along the rotational direction of the inner ring 4 (or outer ring 3). In the examples of Figures 16A and 16B, the position φ ranges from 0 to 1080, which corresponds to a range of three revolutions around the bearing device. The areas around φ=0, 360, 720, and 1080 correspond to the loaded zone, and the remaining ranges are the non-loaded zone.

[0077] In Figures 16A and 17A, the dashed lines indicate the theoretical value of h, and the peaks are the gaps (h = h) between the rolling element 5 located in the center of the non-load zone and the outer ring 3 (or inner ring 4). gap / 2) (see Figure 6). Referring to Figure 16A, while the oil film thickness h was measured to be close to the theoretical value in the loaded zone, the oil film thickness h could not be accurately measured in the non-loaded zone. In other words, as shown in Figure 16A, with the conventional method, the oil film thickness h was detected as thin even in the non-loaded zone, which is a result that is significantly different from the theoretical value. Referring to Figure 16B, the breakage rate α was measured at all positions φ. On the other hand, referring to Figure 17A, the oil film thickness h was measured to be close to the theoretical value in both the loaded and non-loaded zones. Furthermore, referring to Figure 17B, the breakage rate α was measured at all positions φ.

[0078] In this embodiment, the seal 6 has been described as an example of a peripheral member that constitutes the bearing device 2. However, the capacitor C4 (the capacitance of C4 in equation (10)) may be set taking into consideration other peripheral members that constitute the bearing device 2. Furthermore, as shown in FIG. 14, the value of C4 in equation (10) may be adjusted depending on whether or not the seal 6 is present.

[0079] As described above, this embodiment makes it possible to simultaneously detect the oil film thickness inside the bearing device and the contact ratio between parts under radial load, while improving measurement accuracy even more than the first embodiment. Furthermore, it is possible to accurately measure the oil film thickness and contact ratio in both the loaded and unloaded zones under radial load.

[0080] Note that the formula (10) used in this embodiment is based on the formula (8) that takes into account the axial load, and therefore can be applied even under an axial load, and can therefore be used universally under both axial and radial load conditions.

[0081] <Other embodiments> Furthermore, the present invention can also be realized by supplying a program or application for realizing the functions of one or more of the above-described embodiments to a system or device via a network or storage medium, etc., and having one or more processors in the computer of that system or device read and execute the program.

[0082] Alternatively, it may be realized by a circuit that realizes one or more functions (for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array)).

[0083] As such, the present invention is not limited to the above-described embodiments, and the present invention also contemplates the mutual combination of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the description in the specification and well-known techniques, and these modifications and applications are included in the scope of protection sought.

[0084] As described above, the present specification discloses the following: (1) A detection method for detecting a state of a bearing device including an outer member, an inner member, and a plurality of rolling elements, comprising: applying an AC voltage to an electric circuit formed by the outer member, the inner member, and the plurality of rolling elements while a predetermined load is applied to the bearing device; measuring the impedance and phase angle of the electric circuit when the AC voltage is applied; and deriving an oil film thickness and a metal contact ratio between at least one of the inner member and the plurality of rolling elements or the inner member and the plurality of rolling elements based on the impedance and the phase angle. With this configuration, it is possible to simultaneously detect the oil film thickness inside the bearing device and the proportion of metal contact between parts, taking into account the load direction.

[0085] (2) The predetermined load includes at least a radial load, The detection method according to claim 1, characterized in that the oil film thickness and the metal contact ratio are derived using a first calculation formula corresponding to an electric circuit configured in each of a loaded zone and a non-loaded zone in the bearing device specified by the predetermined load. According to this configuration, it is possible to improve measurement accuracy while simultaneously detecting the oil film thickness inside the bearing device and the proportion of metal contact between components, taking the radial load into consideration.

[0086] (3) The first calculation formula for deriving the oil film thickness h and the metal contact ratio α is

[0087]

number

[0088] The detection method according to (2), wherein This configuration makes it possible to improve measurement accuracy while simultaneously detecting the oil film thickness inside the bearing device and the proportion of metal contact between components, taking into account the radial load. It is possible to detect the oil film thickness inside a bearing device and the proportion of metal contact between parts, taking into account the capacitance corresponding to the loaded and unloaded zones of the rolling bearing.

[0089] (4) The bearing device further includes a peripheral member, the predetermined load includes at least a radial load, The detection method described in (1) is characterized in that the oil film thickness and the metal contact ratio are derived using a second calculation formula corresponding to an electric circuit formed in each of the loaded and unloaded zones within the bearing device specified by the predetermined load, and an electric circuit formed by the peripheral components. With this configuration, it is possible to improve measurement accuracy while simultaneously detecting the oil film thickness inside the bearing device and the proportion of metal contact between components, taking into account the radial load and the axial load.

[0090] (5) The second calculation formula for deriving the oil film thickness h and the metal contact ratio α is

number

[0091] The detection method according to (4), wherein This configuration allows for improved measurement accuracy while simultaneously detecting the oil film thickness and the contact ratio between components within the bearing device, taking into account the radial and axial loads. In particular, it allows for detection of the oil film thickness and the metal-to-metal contact ratio between components within the bearing device, taking into account the capacitance corresponding to the rolling bearing members.

[0092] (6) The detection method according to (4) or (5), wherein the peripheral member is a seal. This configuration makes it possible to detect the oil film thickness and the metal contact ratio while taking into account the influence of the seal.

[0093] (7) The detection method according to any one of (1) to (6), further comprising diagnosing the bearing device using the oil film thickness and the metal contact ratio. According to this configuration, based on the oil film thickness and the metal contact ratio specified according to the load, The condition of the lubricant in the rolling bearing can be diagnosed.

[0094] (8) A detection device for detecting the state of a bearing device including an outer member, an inner member, and a plurality of rolling elements, an acquisition means for acquiring an impedance and a phase angle of an electric circuit formed by the outer member, the inner member, and the plurality of rolling elements when an AC voltage is applied to the electric circuit while a predetermined load is applied to the bearing device; and deriving means for deriving an oil film thickness and a metal contact ratio at least between the inner member and the plurality of rolling elements or between the inner member and the plurality of rolling elements based on the impedance and the phase angle. With this configuration, it is possible to simultaneously detect the oil film thickness inside the bearing device and the proportion of metal contact between parts, taking into account the load direction.

[0095] (9) The computer an acquisition means for acquiring the impedance and phase angle of an electric circuit when an AC voltage is applied to an electric circuit formed by an outer member, an inner member, and a plurality of rolling elements, while a predetermined load is being applied to a bearing device formed by the outer member, the inner member, and a plurality of rolling elements; a deriving means for deriving an oil film thickness and a metal contact ratio between at least one of the inner member and the plurality of rolling elements or the inner member and the plurality of rolling elements based on the impedance and the phase angle; A program to function as a With this configuration, it is possible to simultaneously detect the oil film thickness inside the bearing device and the proportion of metal contact between parts, taking into account the load direction.

[0096] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0097] This application is based on a Japanese patent application (Patent Application No. 2020-153845) filed on September 14, 2020, the contents of which are incorporated herein by reference. [Explanation of symbols]

[0098] 1...Diagnostic equipment 2...Bearing device 3...Outer ring (outer member) 4...Inner ring (inner member) 5...Rolling element 6...Seal 7...Rotation axis 8...LCR meter 9...Rotating connector 10...Motor

Claims

1. A detection method for detecting a state of a bearing device including an outer member, an inner member, and a plurality of rolling elements, comprising: applying an AC voltage to an electric circuit formed by the outer member, the inner member, and the plurality of rolling elements while a predetermined load is applied to the bearing device; measuring the impedance and phase angle of the electric circuit when the AC voltage is applied at least in a static contact state before the rolling elements start to rotate and in a dynamic contact state after the rolling elements start to rotate; deriving an oil film thickness and a metal contact ratio between at least one of the inner member and the plurality of rolling elements or the inner member and the plurality of rolling elements based on the impedance and the phase angle measured in each of the static contact state and the dynamic contact state.

2. the predetermined load includes at least a radial load, 2. The detection method according to claim 1, wherein the oil film thickness and the metal contact ratio are derived using a first calculation formula corresponding to an electrical circuit configured in each of a loaded zone and a non-loaded zone in the bearing device specified by the predetermined load.

3. The first calculation formula for deriving the oil film thickness h and the metal contact ratio α is: [Equation 1] h: oil film thickness α: Oil film rupture rate (metal contact rate) δ: constant (=(1-α) r h ￣S1 / 2πr x ￣r y ￣) ω: Angular frequency of AC voltage W: Lambert W function ζ: Constant (=lr h ￣ / 2πεkn 1 r x ￣r y ￣) θ 0 : Phase in static contact state θ: Phase in dynamic contact state |Z 0 |: Impedance in static contact state |Z|: Impedance in dynamic contact state rx: average value of effective radius (x-axis) r y : Average value of effective radius (y-axis) r h : constant (= (r x ￣ + ry ￣) / 2) k: Number of rolling bearings l: number of contact areas m: a natural number indicating a rolling element located in the non-load zone (1≦m≦(nn 1 )) n: total number of rolling elements n1: Number of rolling elements located in the load zone C3(m): Capacitance in the Hertzian contact area of ​​rolling element m 3. The detection method according to claim 2, wherein

4. The bearing device further includes a peripheral member; the predetermined load includes at least a radial load, 2. The detection method according to claim 1, wherein the oil film thickness and the metal contact ratio are derived using a second calculation formula corresponding to an electric circuit formed in each of the loaded and unloaded zones within the bearing device specified by the predetermined load, and an electric circuit formed by the peripheral components.

5. The second calculation formula for deriving the oil film thickness h and the metal contact ratio α is: [0012] C4: Electrostatic capacitance generated between the outer ring and the inner ring and between the seal and the inner ring 5. The detection method according to claim 4, wherein

6. 6. The detection method according to claim 4, wherein the peripheral member is a seal.

7. 7. The detection method according to claim 1, further comprising diagnosing the bearing device using the oil film thickness and the metal contact ratio.

8. A detection device for detecting a state of a bearing device including an outer member, an inner member, and a plurality of rolling elements, an acquisition means for acquiring impedance and phase angle of an electric circuit formed by the outer member, the inner member, and the plurality of rolling elements when an AC voltage is applied, the impedance and phase angle being obtained when the AC voltage is applied, at least in a static contact state before the rolling elements start to rotate and in a dynamic contact state after the rotation starts; and deriving means for deriving an oil film thickness and a metal contact ratio at least between the inner member and the plurality of rolling elements or between the inner member and the plurality of rolling elements, based on the impedance and the phase angle measured in each of the static contact state and the dynamic contact state.

9. Computer, an acquisition means for acquiring the impedance and phase angle of an electric circuit formed by an outer member, an inner member, and a plurality of rolling elements when an AC voltage is applied to the electric circuit formed by the outer member, the inner member, and the plurality of rolling elements, in at least a static contact state before the rolling elements start to rotate and a dynamic contact state after the rotation starts; a deriving means for deriving an oil film thickness and a metal contact ratio between at least one of the inner member and the plurality of rolling elements or the inner member and the plurality of rolling elements based on the impedance and the phase angle measured in each of the static contact state and the dynamic contact state; A program to function as a

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