Condition inspection methods, inspection equipment and inspection procedures for bearing assemblies
Patent Information
- Authority / Receiving Office
- TW · TW
- Patent Type
- Patents
- Current Assignee / Owner
- NSK LTD
- Filing Date
- 2023-03-13
- Publication Date
- 2026-08-01
Smart Images
Figure TWG2TB001903444_002
Abstract
Description
Technical Field
[0001] The invention of this application relates to a method, a detection device and a program for detecting the status of a bearing device. Prior Art
[0002] Previously, bearings were widely used to lubricate their rotation using lubricants (e.g., oil or grease). Meanwhile, regular diagnostics of the status of rotating parts in bearings and other similar devices are required to detect damage and wear early and prevent failures.
[0003] In bearing devices that use lubricants, appropriate detection of lubricant-related conditions is required to diagnose their operating conditions. For example, Patent Document 1 discloses a method for diagnosing the bearing's oil film condition based on the measured voltage by applying a low DC voltage to the bearing. Furthermore, Patent Document 2 discloses a method for estimating the bearing's oil film condition based on the measured capacitance by modeling the oil film as a capacitor and applying an AC voltage to the bearing's rotating ring in a non-contact manner. [Prior Art Literature] [Patent Document]
[0004] [Patent Document 1] Japanese Utility Model Publication No. 05-003685 [Patent Document 2] Japanese Patent No. 4942496 Summary of the Invention
[0005] [Problems to be solved by the invention]
[0006] In recent years, there has been a demand for further reductions in torque in bearing devices. In response to this reduction in torque, efforts are underway to reduce the viscosity or oil content of lubricants used in bearing devices. Meanwhile, bearing devices used in large-scale devices such as windmills carry heavier loads. Under such circumstances, the possibility of oil film rupture within the bearing device and the proportion of contact between parts increase. Therefore, in addition to oil film thickness, appropriate detection of the contact state between parts within the bearing device is also sought. Furthermore, there are various types of bearing devices, such as sliding bearings. Within such bearing devices, line contact can occur between the rotating shaft and its surrounding parts as the device moves. For example, the method described in Reference 2 measures only the oil film thickness, making it difficult to determine the proportion of metal contact. Furthermore, because the electrostatic capacitance outside the contact area is not considered, the measurement accuracy is low. Furthermore, measurements assuming line contact are not performed.
[0007] In view of the above problems, the purpose of the invention of this application is to imagine the line contact generated inside the bearing device and to detect the oil film thickness inside the bearing device and the metal contact ratio between parts with high precision. [Technical means to solve the problem]
[0008] In order to solve the above-mentioned problems, the present invention has the following structure. That is, a detection method is characterized in that the state of a bearing device including a sliding bearing is detected. Applying AC voltage to the circuit formed by the sliding bearing and the rotating shaft, Measure the impedance and phase angle of the aforementioned circuit when the aforementioned AC voltage is applied. Based on the impedance and the phase angle, the oil film thickness and the metal contact ratio between the sliding bearing and the rotating shaft are derived. The oil film thickness and the metal contact ratio are derived using the following calculation formula, which corresponds to an electric circuit formed by line contact between the sliding bearing and the rotating shaft generated in the bearing device.
[0009] Another aspect of the present invention has the following configuration. Specifically, a detection device is characterized in that it detects the state of a bearing device including a sliding bearing and includes: an acquisition mechanism for acquiring, when an AC voltage is applied to the circuit formed by the sliding bearing and the rotating shaft, the impedance and phase angle of the circuit when the AC voltage is applied; and a derivation mechanism for deriving the oil film thickness and the metal contact ratio between the sliding bearing and the rotating shaft based on the impedance and the phase angle; and The derivation mechanism derives the oil film thickness and the metal contact ratio using a calculation formula corresponding to an electric circuit formed by line contact between the sliding bearing and the rotating shaft generated in the bearing device.
[0010] Another aspect of the present invention has the following configuration. Specifically, a program that enables a computer to function as: an acquisition mechanism for acquiring, for a bearing device including a sliding bearing, an impedance and a phase angle of the circuit formed by the sliding bearing and the rotating shaft when an AC voltage is applied to the circuit; and a derivation mechanism for deriving the oil film thickness and the metal contact ratio between the sliding bearing and the rotating shaft based on the impedance and the phase angle; and The derivation mechanism derives the oil film thickness and the metal contact ratio using a calculation formula corresponding to an electric circuit formed by line contact between the sliding bearing and the rotating shaft generated in the bearing device.
[0011] In order to solve the above-mentioned problems, the present invention has the following structure. That is, a detection method is characterized in that the state of a bearing device composed of an outer member, an inner member, and a plurality of rollers is detected. While applying a predetermined radial load to the bearing device, an AC voltage is applied to the circuit consisting of the outer member, the inner member, and the plurality of rollers. Measure the impedance and phase angle of the aforementioned circuit when the aforementioned AC voltage is applied. Based on the impedance and the phase angle, an oil film thickness and a metal contact ratio of at least one of the inner member and the plurality of rollers or the inner member and the plurality of rollers are derived.
[0012] Another aspect of the present invention has the following configuration. Specifically, a detection device is characterized in that it detects the state of a bearing device comprising an outer member, an inner member, and a plurality of rollers, and includes: An acquisition mechanism obtains the impedance and phase angle of the aforementioned circuit when an AC voltage is applied to a circuit composed of the aforementioned outer member, the aforementioned inner member, and the aforementioned plurality of rollers under a state in which a prescribed radial load is applied to the aforementioned bearing device; and a derivation mechanism derives the oil film thickness and metal contact ratio of at least one of the inner member and the aforementioned plurality of rollers or the inner member and the aforementioned plurality of rollers based on the aforementioned impedance and the aforementioned phase angle.
[0013] Another aspect of the present invention has the following configuration. Specifically, a program that enables a computer to function as: an acquisition mechanism for acquiring, when a predetermined radial load is applied to a bearing device comprising an outer member, an inner member, and a plurality of rollers, the impedance and phase angle of the circuit when an alternating voltage is applied to the circuit comprised of the outer member, the inner member, and the plurality of rollers; and A derivation mechanism derives the oil film thickness and metal contact ratio of at least one of the inner member and the plurality of rollers or the inner member and the plurality of rollers based on the impedance and the phase angle. [Effects of the Invention]
[0014] According to the invention of this application, it is possible to imagine line contact generated inside the bearing device, and to detect the oil film thickness inside the bearing device and the contact ratio between parts with high precision. Simple diagram description
[0015] FIG1 is a schematic diagram showing an example of the configuration of a device for diagnosis according to the first embodiment of the present invention. FIG. 2 is a diagram showing a solid model of a bearing device according to the first embodiment of the present invention. FIG3 is a circuit diagram for explaining an equivalent circuit of the bearing device according to the first embodiment of the present invention. FIG. 4 is a diagram for explaining rolling elements (balls) of a bearing device. FIG5 is a diagram for explaining a rotation axis. FIG6 is a diagram for explaining a sliding bearing and a rotating shaft. FIG. 7 is a diagram for explaining the verification results of the first embodiment of the invention of this application. FIG8 is a flowchart of the processing during measurement in the first embodiment of the present invention. FIG9 is a schematic diagram showing an example of the configuration of a device for diagnosis according to the second embodiment of the present invention. FIG. 10 is a circuit diagram for explaining an equivalent circuit of a bearing device according to a second embodiment of the present invention. FIG. 11 is a diagram for explaining a load ring and a non-load ring according to a second embodiment of the present invention. FIG. 12A is a diagram for explaining the electrostatic capacitance of the load coil according to the second embodiment of the present invention. FIG. 12B is a diagram for explaining the electrostatic capacitance of the load coil according to the second embodiment of the present invention. FIG. 13 is a circuit diagram for explaining an equivalent circuit of the second embodiment of the invention of this application. FIG. 14A is a diagram showing the measurement results of the second embodiment of the invention of this application. FIG. 14B is a diagram showing the measurement results of the second embodiment of the present invention. FIG. 14C is a diagram showing the measurement results of the second embodiment of the present invention. FIG. 15A is a diagram showing the measurement results of the second embodiment of the invention of this application. FIG. 15B is a diagram showing the measurement results of the second embodiment of the present invention. FIG. 15C is a diagram showing the measurement results of the second embodiment of the present invention. Implementation Method
[0016] The following describes embodiments for implementing the present invention with reference to the drawings and other figures. The embodiments described below are intended to illustrate one embodiment of the present invention and are not intended to limit the present invention. Furthermore, not all components described in each embodiment are necessarily required to achieve the objectives of the present invention. In the drawings, identical components are designated by the same reference numerals to indicate corresponding relationships.
[0017] <First embodiment> The following describes the first embodiment of the present invention. Furthermore, while the following description of the device configuration uses a sliding bearing as an example, the present invention is not limited to this embodiment and is applicable to devices with other configurations. For example, it is also applicable to rolling devices having components that generate sliding motion, as described later.
[0018] [Device Configuration] FIG1 schematically illustrates an example of the overall configuration of a diagnostic device 1 according to this embodiment. FIG1 shows a bearing device 2 to which the diagnostic method of this embodiment is applicable, and the diagnostic device 1 performing the diagnosis. The configuration shown in FIG1 is merely an example; different configurations may be employed depending on the configuration of the bearing device 2. FIG1 also illustrates a bearing device 2 comprising a single sliding bearing 3, but this is not limiting and may also comprise a plurality of sliding bearings.
[0019] The bearing device 2 includes a sliding bearing 3. In the bearing device 2, the sliding bearing 3 is disposed around the rotating shaft 7 and is configured to rotate while in line contact with the rotating shaft 7. Within the sliding bearing 3, friction between the rotating shaft 7 and the sliding bearing 3 is reduced by a predetermined lubrication method. The lubrication method is not particularly limited; for example, grease or oil lubrication is supplied to the interior of the sliding bearing 3. The type of lubricant is also not particularly limited.
[0020] Motor 10 is a driving motor that supplies power to the rotating shaft 7 through rotation. The rotating shaft 7 is connected to the LCR meter 8 via a rotary connector 9. The rotary connector 9 can be constructed using, but is not limited to, carbon brushes. Furthermore, the sliding bearing 3 of the bearing assembly 2 is also electrically connected to the LCR meter 8. In this case, the LCR meter 8 also functions as an AC power source for the bearing assembly 2.
[0021] Diagnostic device 1 operates as a detection device capable of executing the detection method of this embodiment. During diagnosis, diagnostic device 1 receives the angular frequency ω and AC voltage V of the AC power supply from LCR meter 8 as inputs. LCR meter 8 then obtains the impedance |Z| (|Z| represents the absolute value of Z) and phase angle θ of bearing assembly 2 as corresponding outputs. Diagnostic device 1 then uses these values to detect the oil film thickness or metal contact ratio of bearing assembly 2. Details of the detection method will be described later.
[0022] The diagnostic device 1 is implemented, for example, using an information processing device comprising a control device (not shown), a memory device, and an output device. The control device may be composed of a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a DSP (Digital Single Processor), or a dedicated circuit. The memory device is composed of volatile and non-volatile storage media such as an HDD (Hard Disk Drive), ROM (Read Only Memory), or RAM (Random Access Memory), and can input and output various information in response to instructions from the control device. The output device is composed of a speaker, a lamp, or a display device such as a liquid crystal display, and notifies the operator in response to instructions from the control device. The notification method performed by the output device is not particularly limited and may be, for example, an auditory notification via sound or a visual notification via screen output. Furthermore, the output device may be a network interface with communication capabilities, and may also transmit data to an external device (not shown) via a network (not shown) to perform a notification. The notification content herein is not limited to notifications when an abnormality is detected, for example, when performing abnormality diagnosis based on the detection results, and may also include notifications indicating that the bearing device 2 is normal.
[0023] [Solid Model] Figure 2 will be used to explain the contact state between the sliding bearing 3 and the rotating shaft 7 of the bearing device 2. Figure 2 shows a solid model of the roller and bearing ring in contact (here, line contact). The roller corresponds to the rotating shaft 7, and the bearing ring corresponds to the sliding bearing 3. The h-axis represents the oil film thickness direction, and the y-axis represents the direction perpendicular to the oil film thickness direction. The variables shown in Figure 2 are described below. Furthermore, in the various equations used in the following description, identical variables are assigned the same symbols to establish a corresponding relationship.
[0024] S: Hertzian contact area a: Contact width of the roller (rotation axis) in the short direction (here is the x-axis direction) α: Oil film rupture rate (metal contact ratio) (0≦α<1) r: roller radius αS: Actual contact area (oil film rupture area) h: Oil film thickness h 1: Oil film thickness in the Hertzian contact area O: Rotation center of the roller
[0025] In the Hertzian contact region, the ratio of the area in contact with metal to the area not in contact is α:(1-α). Furthermore, in the ideal state where the roller does not contact the bearing ring, when α = 0 and x = 0, h > 0.
[0026] The oil film thickness h shown in FIG2 is expressed by the following formula (1). In addition, the value of S shown here corresponds to the range of the x-axis direction of FIG1. h=f(x)=h 1+√(r 2-a 2)-√(r 2-x 2) (-r≦x<-a, or a <x≦r) …(1)
[0027] Furthermore, within the Hertzian contact region, there is a thin oil film region called a horseshoe. However, in this embodiment, the average oil film thickness within the Hertzian contact region, i.e., the average oil film thickness ha, is used. Therefore, when an oil film break occurs within the Hertzian contact region, ha is calculated using the following formula (2). ha=(1-α)h 1…(2)
[0028] In Figure 2, O is x=0, and the coordinate system of O in Figure 2 is represented by O(0,h 1+√(r 2-a 2)).
[0029] Furthermore, since the rotating shaft 7 may undergo elastic deformation during the actual operation of the sliding bearing 3, strictly speaking, its cross-section may sometimes not be a perfect circular shape. However, in this embodiment, it is assumed to be a perfect circular shape 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 (for example, involute curve in the case of gears) can also be used.
[0030] [Equivalent Circuit] Figure 3 is a diagram showing the physical model shown in Figure 2 using an electrically equivalent 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 of the fracture region (= αS). The capacitor C1 corresponds to the capacitor formed by the oil film in the Hertz contact region and is set as the electrostatic capacitance C1. The capacitor C2 corresponds to the capacitor formed by the oil film around the Hertz contact region (-r ≤ x < -a and a < x ≤ r in Figure 2) and is set as the electrostatic capacitance C2. The Hertz contact region (= S) forms a parallel circuit of the resistor R1 and the capacitor C1 in the equivalent circuit E1 of Figure 3. Furthermore, for the circuit composed of the resistor R1 and the capacitor C1, the capacitor C2 is connected in parallel. At this time, it is assumed that a lubricant is filled around the Hertz contact region (-r ≤ x < -a and a < y ≤ r in Figure 2).
[0031] Let the impedance of the equivalent circuit E1 be represented by Z. Here, the AC voltage V applied to the equivalent circuit E1, the current I flowing in the equivalent circuit E1, and the complex impedance Z of the entire equivalent circuit E1 are represented by the following formulas (3) to (5). V = |V|exp(jωt) …(3) I = |I|exp(j(ωt - θ)) …(4) Z = V / I = |V / I|exp(jθ) = |Z|exp(jθ) …(5) j: Imaginary number ω: Angular frequency of the AC voltage t: Time θ: Phase angle (offset between the phases of the voltage and the current)
[0032] As shown in formula (5), the complex impedance Z is represented by two independent variables, the absolute value |Z| of Z and the phase angle θ. This means that by measuring the complex impedance Z, two independent parameters (in this embodiment, ha and α shown below) can be measured. The complex impedance Z of the entire equivalent circuit shown in Figure 3 is represented as follows in formula (6). Z -1=R 1 -1+jω(C 1+C 2) …(6) R1: Resistance value of resistor R1 C1: electrostatic capacitance of capacitor C1 C2: electrostatic capacitance of capacitor C2 |Z|: Impedance in dynamic contact state
[0033] Furthermore, the following equations (7) and (8) can be derived from equation (6). R 1=|Z| / cosθ …(7) ω(C 1+C 2)=-sinθ / |Z| …(8)
[0034] Here, R1 in formula (7) has an inversely proportional relationship with the contact area, and can therefore be expressed as the following formula (9). R 1=R 10 / α …(9) R 10: Resistance value at rest (i.e. α=1)
[0035] R 10 can be represented by the following formula (10). R 10=|Z 0| / cosθ 0…(10) |Z 0|: Impedance in static contact state θ 0: Phase angle in static contact state
[0036] Therefore, the fracture rate α can be expressed as the following formula (11) based on formulas (7), (9), and (10). Furthermore, as described above, when θ 0 is set as the phase angle in the static contact state, θ can be regarded as the phase angle in the dynamic contact state.
[0037] [Number 1]
[0038] On the other hand, C1 in equations (6) and (8) can be expressed as in equation (12). Furthermore, assuming line contact, with the length of the rotating shaft 7 (here, the contact width in the longitudinal direction) set to L, the contact area of the Hertzian contact region S is S = 2aL.
[0039] [Number 2]
[0040] ε: Dielectric constant of lubricant
[0041] Furthermore, C 2 in formula (6) and formula (8) can be expressed as in the following formula (13).
[0042] [Number 3]
[0043] [Electrostatic capacitance corresponding to contact state] Here, we will explain C2 under point contact. Figure 4 illustrates the case where the rolling elements are balls (e.g., a ball bearing). While h1 is shown as large for ease of explanation, it is actually small enough to produce contact (in this case, point contact), as shown in Figure 2. In this case, point contact may occur between the rolling element and the raceway. As in FIG2 , when the radius of the rolling element is set to r and the oil film thickness is set to h1, the electrostatic capacitance of the capacitor C2 in the equivalent circuit shown in FIG3 can be calculated using the following formula (14).
[0044] [Number 4]
[0045] π: pi r: ball radius ε: Dielectric constant of lubricant ln: logarithmic function
[0046] Next, the situation in which line contact occurs, as addressed in this embodiment, will be described. Figure 5 illustrates the situation between the rotating shaft 7 and the sliding bearing 3. As in Figure 4, the value of h1 is shown as large for ease of explanation. However, as shown in Figure 2, it is actually small enough to produce contact (in this case, line contact). In this situation, line contact may occur between the rotating shaft 7 and the sliding bearing 3. As shown in Figure 6, when the radius of the rotating shaft 7 is r1 and the radius of the inner diameter of the sliding bearing 3 is r2, r can be calculated using r1 and r2 as the equivalent radii of curvature. In this case, the surface of the sliding bearing 3 that produces line contact with the rotating shaft 7 has a negative curvature. Furthermore, the oil film thickness at the position where the rotating shaft 7 and the sliding bearing 3 come into line contact is set to h1. In this case, the electrostatic capacitance of the capacitor C2 in the equivalent circuit shown in FIG3 can be calculated using the formula shown in the above formula (13).
[0047] Furthermore, as shown in Figure 5 , the rotating shaft 7 may be formed with a chamfered end. In this case, the straight portion where line contact may occur can be treated as L. Furthermore, if the length ΔL in the longitudinal direction due to the chamfer is extremely small relative to L, the length L' (=L+2ΔL) including the chamfered portion can be used to calculate the capacitor C2.
[0048] At this time, when using the symbols shown in Figures 2 and 5, the contact area caused by line contact (that is, the contact area of the Hertzian contact region S) can be represented by 2aL.
[0049] Furthermore, for the portion that is not chamfered, point contact rather than line contact may occur. Therefore, for this portion, the calculation formula for C2 under point contact (for example, the above formula (14)) can be further used to add capacitor C2 to the calculation formula (13).
[0050] This example shows a verification of the calculation results for capacitor C2 using the theoretical formula defined by the above formula (13). Here, a comparison is shown with the results of a simulation analysis using the finite element method, a well-known electromagnetic field analysis method. Furthermore, the following formula (15) based on the well-known calculation formula of Jackson is shown as a comparison object. Furthermore, Jackson's formula assumes that h1 is extremely large compared to r.
[0051] [Number 5]
[0052] FIG7 is a graph showing the verification results, with the horizontal axis representing the oil film thickness h1 [m] and the vertical axis representing the electrostatic capacitance C2 [F]. Line 701 shows the result of calculating the electrostatic capacitance C2 using the calculation formula of this embodiment, namely, equation (13). Line 702 shows the result of calculating the electrostatic capacitance C2 using the calculation formula based on Jackson, namely, equation (15). Furthermore, symbol 703 (○) shows the result obtained by simulation using the finite element method.
[0053] As shown by line 701 and symbol 703 in Figure 7 , the value of capacitance C2 calculated using equation (13) yields a value substantially identical to the simulation result within the range of 1.0 - 2 ≧ h. This range corresponds to the dimensions of the sliding bearing 3 assumed in the present invention (h1 is extremely small compared to r). Compared with line 702 obtained using Jackson's equation (15), a higher degree of accuracy is achieved.
[0054] [Derivation of oil film thickness and oil film rupture rate] In this embodiment, the lubrication state is detected using the lubricant film thickness h1 and the oil film rupture rate α as described above. The following equation (16) is derived from the above equations (8), (11) to (13).
[0055] [Number 6]
[0056] At this time, ψ is defined as follows:
[0057] [Number 7]
[0058] L: Length of the rotation axis
[0059] Then, based on equations (2) and (16), the average oil film thickness ha is derived as shown in the following equation (18).
[0060] [Number 8]
[0061] That is, according to equations (11) and (18), by measuring the complex impedance and phase angle at rest and when the oil film is formed, ha and α can be monitored simultaneously.
[0062] Furthermore, the above formula (18) is a theoretical formula when the contact area is 1.
[0063] [Processing Flow] FIG8 is a flowchart of the diagnostic processing of this embodiment. This processing is performed by diagnostic device 1. For example, it can be implemented by a control device (not shown) included in diagnostic device 1 reading and executing a program for implementing the processing of this embodiment from a memory device (not shown).
[0064] In S801, diagnostic device 1 controls bearing device 2 to apply a load in a predetermined direction. In the configuration shown in Figure 1 , the load is applied to rotating shaft 7. However, load application control can also be performed by a device separate from diagnostic device 1. At this time, the phase angle and impedance in the static contact state are measured.
[0065] In S802, diagnostic device 1 starts rotating shaft 7 via motor 10. This causes shaft 7 to rotate while creating line contact between shaft 7 and sliding bearing 3. Motor 10 may also be controlled by a device separate from diagnostic device 1.
[0066] In S803, the diagnostic device 1 controls the LCR meter 8 to apply an AC voltage V of angular frequency ω to the bearing device 2 using an AC power supply (not shown) included in the LCR meter 8. As a result, the AC voltage of angular frequency ω is applied to the bearing device 2.
[0067] In S804, diagnostic device 1 obtains impedance |Z| and phase angle θ from LCR meter 8 as outputs in response to the input in S803. Specifically, LCR meter 8 outputs impedance |Z| and phase angle θ to diagnostic device 1 as detection results of bearing device 2 in response to the inputs, namely, AC voltage V and its angular frequency ω.
[0068] In S805, the diagnostic device 1 derives the oil film thickness h (ha in this embodiment) and the rupture rate α by applying the impedance |Z| and phase angle θ obtained in S804 and the angular frequency ω of the AC voltage used in S803 to equations (11) and (18).
[0069] In S806, diagnostic device 1 uses the oil film thickness h and fracture rate α derived in S805 to diagnose the lubrication condition of bearing device 2. Furthermore, the diagnostic method herein may, for example, set a threshold value for the oil film thickness h or fracture rate α, and determine the lubrication condition by comparing the values with the threshold value. This process then terminates.
[0070] As described above, according to this embodiment, it is possible to imagine the line contact generated inside the rolling bearing, and to detect the oil film thickness inside the bearing device and the contact ratio between parts with high precision.
[0071] <Second embodiment> The second embodiment of the present invention will be described below. Furthermore, in the following description, a cylindrical roller bearing in which line contact may occur is used as an example of a rolling bearing, but the present invention is not limited thereto and can also be applied to rolling bearings of other structures. For example, the present invention can be applied to rolling bearings in which line contact occurs and to devices utilizing such rolling bearings. Furthermore, the present invention is not limited to bearings and can also be applied to devices that generate line contact between parts lubricated with a lubricant, such as those described below. Furthermore, descriptions of structures that overlap with those of the first embodiment will be omitted, and the description will focus on the differences.
[0072] [Device Configuration] FIG9 schematically illustrates an example of the overall configuration of a diagnostic device 1 according to this embodiment. FIG9 shows a bearing device 12 to which the diagnostic method according to this embodiment is applicable, and a diagnostic device 1 for performing a diagnosis. The configuration shown in FIG9 is merely an example, and a different configuration may be employed depending on the configuration of the bearing device 2. FIG9 also illustrates a configuration in which the bearing device 2 includes a single rolling bearing, but this is not limiting; a single bearing device 2 may include multiple rolling bearings. The configuration other than the bearing device 12 is identical to that shown in the first embodiment.
[0073] In the bearing device 12, a radial cylindrical roller bearing, or rolling bearing, rotatably supports the rotating shaft 7. The rotating shaft 7 is supported by a housing (not shown) covering the outside of the rotating shaft 7 via the rolling bearing, which serves as a rotating component. The rolling bearing comprises an outer ring (outer member) 13, which is a stationary ring fitted within the housing; an inner ring (inner member) 14, which is a rotating ring fitted onto the outside of the rotating shaft 7; a plurality of rolling elements 15, or rollers, disposed between the inner ring 14 and the outer ring 13; and a retainer (not shown) that rotatably retains the rolling elements 15. While the outer ring 13 is fixed here, a configuration in which the inner ring 14 is fixed and the outer ring 13 rotates is also possible. Seals 16, or peripheral components, are provided to prevent dust from entering the periphery of the rolling elements 15 and prevent lubricant oil from leaking. Within the rolling bearing, a prescribed lubrication method is used to reduce friction between the inner ring 14 and the rolling elements 15, and between the outer ring 13 and the rolling elements 15. The lubrication method is not particularly limited; for example, grease or oil lubrication can be supplied to the interior of the rolling bearing. The type of lubricant is also not particularly limited.
[0074] [Solid Model] Using Figure 2 shown in the first embodiment, the contact state between the rolling elements 15 and the outer ring 13 (or inner ring 14) of the bearing device 12 is described. In this embodiment, Figure 2 can be replaced with a solid model of the contact between the rollers and the ring segments. The rollers correspond to the rolling elements 15, i.e., rollers, and the ring segments correspond to the outer ring 13 (or inner ring 14). The h-axis represents the direction of the oil film thickness, and the y-axis represents the direction perpendicular to the oil film thickness. Furthermore, the variables shown in Figure 2 are described below. Furthermore, in the various formulas used in the following description, identical variables are assigned the same symbols to establish a corresponding relationship. S: Hertz contact area a: Contact width of the roller in the short direction (here is the x-axis direction) α: Oil film rupture rate (metal contact ratio) (0≦α<1) r: roller radius αS: Actual contact area (oil film rupture area) h: Oil film thickness h 1: Oil film thickness in the Hertzian contact area O: Rotation center of the roller
[0075] In the Hertzian contact region, the ratio of the area in contact with the metal to the area not in contact is α:(1-α). Furthermore, in the ideal state where the roller and the ring are not in contact, when α = 0 and x = 0, h > 0.
[0076] Next, the situation in which line contact occurs, which is handled in this embodiment, is described using FIG. 5 shown in the first embodiment. In this embodiment, the situation in which the rolling element is a roller (e.g., a cylindrical roller bearing) is described. Here, as in FIG. 4 shown in the first embodiment, the value of h1 is shown as large for ease of explanation, but in reality, as shown in FIG. 2 of the first embodiment, it is small enough to cause contact (in this case, line contact). In this case, line contact may occur between the rolling element and the track disk. As in FIG. 2 , when the radius of the rolling element is set to r and the oil film thickness is set to h1, the electrostatic capacitance of the capacitor C2 in the equivalent circuit shown in FIG. 3 can be calculated using the formula shown in the above formula (13).
[0077] FIG10 shows an electrically equivalent circuit around the rolling element 15 of FIG9 , based on the equivalent circuit E1 shown in FIG3 of the first embodiment. Focusing on one rolling element 15 among the plurality of rolling elements 15 , an equivalent circuit E2 is formed between the outer ring 13 and the rolling element 15 , and between the inner ring 14 and the rolling element 15 . Here, the upper side is described as the circuit formed by the outer ring 13 and the rolling element 15 , and the lower side as the circuit formed by the inner ring 14 and the rolling element 15 , but the reverse is also possible. Around a single rolling element 15 , these circuits, namely, the equivalent circuit E1 of FIG3 , are connected in series to form an equivalent circuit E2.
[0078] [Electrostatic capacitance due to radial load] Figure 11 illustrates the load zone and non-load zone when a radial load is applied to a rolling bearing. Here, the radial load F r is applied to the rolling bearing via the rotating shaft 7. In this case, the area of the rolling elements 15 that produces the Hertzian contact region shown in Figure 2 is referred to as the load zone, while the area outside of this area is referred to as the non-load zone. The load zone range may vary depending on the magnitude of the radial load and the configuration of the rolling bearing.
[0079] First, the electrostatic capacitance of capacitor C1 within the load ring will be described. Figures 12A and 12B illustrate the concept of capacitor C1 formed by rolling elements 15 located within the load ring. Here, an example is used in which the load ring includes five rolling elements, each of which forms capacitors C1(1) to C1(5). In the load ring, the size of the Hertzian contact area varies depending on the position of the rolling elements. In this case, as shown in Figure 12A, it is assumed that the further away from the center of the load ring, the smaller the electrostatic capacitance.
[0080] However, as shown in Figure 2, the oil film thickness h1 within the Hertzian contact region is assumed to be less susceptible to radial load. In this embodiment, the oil film thickness within the load ring is assumed to be constant. Based on this, as shown in Figure 12B, the Hertzian contact region S is averaged, and the capacitance of the capacitor C1 formed by each of the plurality of rolling elements 15 within the load ring is treated as uniform. Therefore, the capacitance of the capacitor C1 formed by the plurality of rolling elements 15 located within the load ring can be derived using the following equation (19).
[0081] [Number 9]
[0082] m: represents the natural number of the rolling element located in the load circle (1≦m≦n 1) n 1: Number of rolling elements located in the load ring C1(m): electrostatic capacitance of the Hertzian contact area of rolling element m C 1 ▔: Average value of C 1(m)
[0083] Next, the electrostatic capacitance of capacitor C3 in the non-load ring is described. In the non-load ring, gaps are generated between the rolling element 15 and the outer ring 13, and between the rolling element 15 and the inner ring 14. As shown in Figure 11, when the gaps between the central rolling element 15a of the rolling element 15 in the non-load ring and the outer ring 13, and between the rolling element 15a and the inner ring 14 are defined as radial gap hgap, the gaps between each of the plurality of rolling elements 15 in the non-load ring and the outer ring 13 can be derived using the following formula (20). Furthermore, the description assumes that the gaps between the rolling element 15a and the outer ring 13 and the gaps between the rolling element 15a and the inner ring 14 are the same (hgap / 2). Furthermore, the radial gap hgap can be derived based on the radial load Fr and the specifications of the rolling bearing.
[0084] [Number 10]
[0085] m: represents the natural number of the rolling element located in the non-load ring (1≦m≦(nn 1)) n: total number of rolling elements n 1: Number of rolling elements located in the load ring
[0086] Then, based on formula (20), the electrostatic capacitance C3 of the entire non-load coil can be derived according to the following formula (21).
[0087] [Number 11]
[0088] m: represents the natural number of the rolling element located in the non-load ring (1≦m≦(nn 1)) n: total number of rolling elements n 1: Number of rolling elements located in the load ring ε: Dielectric constant of lubricant C 3(m): The electrostatic capacitance of the Hertzian contact area of rolling element m π: pi L: Length of rolling element (roller) R tx: Effective radius of rolling element (roller) h gap: radial gap
[0089] Figure 13 shows an electrically equivalent circuit for the entire bearing device 12, taking into account the capacitors formed in the load and non-load rings described above. N equivalent circuits E2 are connected in parallel for each of the n rolling elements 15 located in the load ring. As described using Figures 12A and 12B , the capacitance within the Hertzian contact region is represented by C 1 ▔.
[0090] Furthermore, corresponding to the (nn 1) rolling elements 15 located on the non-load ring, (nn 1) equivalent circuits E3 are connected in parallel. Furthermore, similar to the load ring, capacitors are formed between the outer ring 13 and the rolling elements 15, and between the inner ring 14 and the rolling elements 15, respectively. Therefore, the equivalent circuit E3 is composed of two capacitors C3 connected in series. Here, the upper side is the circuit formed by the outer ring 13 and the rolling elements 15, and the lower side is the circuit formed by the inner ring 14 and the rolling elements 15, but the reverse is also possible. Then, during diagnosis, the AC power of the LCR meter 8 is supplied to the equivalent circuit E4 formed by the entire bearing assembly 12 shown in Figure 13.
[0091] [Derivation of oil film thickness and oil film rupture rate] In this embodiment, the lubrication condition is detected using the lubricant film thickness h and the film rupture rate α under radial load. In this embodiment, the above-mentioned formula (21) and the following formulas (22) to (25) are used to derive the lubricant film thickness h and the film rupture rate α under radial load.
[0092] [Number 12]
[0093] [Number 13]
[0094] [Number 14]
[0095] [Number 15]
[0096] n: The number of all rolling elements (rollers) in the bearing n 1: Number of rolling elements (rollers) located in the load ring b ▔: Average contact width of rolling element (roller) L: Length of rolling element (roller) R tx: Effective radius of rolling element (roller) S t1 ▔: average contact area S i1(m): contact area between rolling element (roller) m and inner ring S o1(m): contact area between rolling element (roller) m and outer ring ω: angular frequency of AC voltage ε: Dielectric constant of lubricant k: number of bearings Ψ: dimensionless constant h gap: radial gap m: represents the natural number of the rolling element located in the non-load ring (1≦m≦(nn 1)) |Z 0|: Impedance in static contact state θ 0: Phase in static contact state |Z|: Impedance in dynamic contact state θ: Phase in dynamic contact state
[0097] In the description using FIG. 2 , 2a represents the contact width of the roller. However, since there are a plurality of rolling elements 15 , the average of these, 2b ▔, is used in the above formula (25).
[0098] The processing flow is the same as that of the first embodiment. However, in this embodiment, in S801 of Figure 8 , the diagnostic device 1 controls the bearing device 12 so that a radial load F r is applied in a predetermined load direction. Here, the radial load F r is applied to the inner ring 14. Furthermore, the control of applying the radial load F r can also be performed by a device different from the diagnostic device 1. At this time, the phase and impedance are measured in the static contact state.
[0099] [Test 1] The results of tests conducted using the above diagnostic method are described below. The test configuration was based on the configuration shown in Figure 9, and the test conditions were as follows. Furthermore, in this test 1, bearings from a wind turbine generator were used.
[0100] (Test conditions) Test bearing: Cylindrical roller bearing (NU330EM) Number of rolling elements (n): 14 (φ45×45) Support bearing: Ball bearing (NU2315EM (Model: 6315); Insulated with a resin sleeve to prevent any influence on the test results of the test bearing) Speed: 200~1800[min-1] Axial load: 0[N] Radial load (F r): P / C=0.1 Lubricant: Windmill GB gear oil VB320 Relative dielectric constant: 2.3 AC voltage: 1.1[V] AC power frequency: 10[kHz] External resistance: 51[Ω]
[0101] Figures 14A through 14C show the relationship between rotational speed N, oil film thickness h, fracture rate α, and temperature T, obtained from tests conducted under the aforementioned test conditions. In Figure 14A, the horizontal axis represents rotational speed N [min-1], and the vertical axis represents oil film thickness h [m]. In Figure 14B, the horizontal axis represents rotational speed N [min-1], and the vertical axis represents fracture rate α. The vertical axis represents oil film thickness h [m]. In Figure 14C, the horizontal axis represents rotational speed N [min-1], and the vertical axis represents temperature T. Each figure corresponds to the rotational speed N [min-1] indicated on the horizontal axis. As indicated by the aforementioned test conditions, the results obtained within the rotational speed range of 200 to 1800 [min-1] are plotted.
[0102] In FIG14A, dotted line 1101 represents the oil film thickness derived as a theoretical value. Plot 1102, indicated by a solid line (×), represents the result of deriving the oil film thickness h using the above-mentioned formula (22) taking into account capacitors C1, C2, and C3. Plot 1103, indicated by a dotted line (×), represents the result of deriving the oil film thickness h using the formula taking into account only capacitors C1 and C2. In other words, plot 1102 is the result of deriving the oil film thickness h taking into account capacitor C3 formed in the non-loaded ring under radial load. As shown in FIG14A, the result shown in plot 1102 is closer to the theoretical value than the result shown in plot 1103, and the oil film thickness h can be derived with higher accuracy. Furthermore, as shown in plot 1111 in FIG14B, the fracture rate α can be derived together with the oil film thickness h at any rotational speed. Furthermore, even when bearing temperature changes occur that are expected to affect the viscosity of the lubricant, this method suppresses the influence compared to previous methods, and the oil film thickness h or the rupture rate α can be calculated with high accuracy.
[0103] [Test 2] The results of other tests conducted based on the above-mentioned diagnostic method are described below. The test configuration was based on that shown in Figure 1, and the test conditions were as follows. Furthermore, in this test 2, the effects of a flange provided around the raceway surface for rolling elements 15 on the outer ring 13 (or inner ring 14, or both) were considered. Therefore, the following test results are presented for both the presence and absence of the flange.
[0104] (Test conditions) Test bearings: Cylindrical roller bearings (NU330EM; with flange), cylindrical roller bearings (N330EM; without flange (with a resin spacer)) Number of rolling elements (n): 14 (φ45×45) Support bearing: Ball bearing (NU2315EM (Model: 6315); Insulated with a resin sleeve to prevent any influence on the test results of the test bearing) Speed: 200~1800[min-1] Axial load: 0[N] Radial load (F r): P / C=0.1 Lubricant: Windmill GB gear oil VB320 Relative dielectric constant: 2.3 AC voltage: 1.1[V] AC power frequency: 10[kHz] External resistance: 51[Ω]
[0105] Figures 15A through 15C show the relationship between rotational speed N, oil film thickness h, fracture rate α, and temperature T, obtained from tests conducted under the aforementioned test conditions. In Figure 15A, the horizontal axis represents rotational speed N [min-1], and the vertical axis represents oil film thickness h [m]. In Figure 15B, the horizontal axis represents rotational speed N [min-1], and the vertical axis represents fracture rate α. The vertical axis represents oil film thickness h [m]. In Figure 15C, the horizontal axis represents rotational speed N [min-1], and the vertical axis represents temperature T. Each figure corresponds to the rotational speed N [min-1] indicated on the horizontal axis. As indicated by the aforementioned test conditions, the results obtained within the rotational speed range of 200 to 1800 [min-1] are plotted.
[0106] In FIG15A , the dashed line 1201 represents the oil film thickness derived as a theoretical value. The plot 1202, indicated by an x, represents the result of deriving the oil film thickness h for a flangeless bearing using the aforementioned equation (22) with capacitors C1, C2, and C3. The plot 1203, indicated by a circle, represents the result of deriving the oil film thickness h for a flanged bearing using the aforementioned equation (22) with capacitors C1, C2, and C3. Both of these are derived results taking into account capacitor C3 in the non-loaded ring under radial load. As shown in FIG15A , regardless of whether the bearing has a flange, the results are close to the theoretical value, allowing the oil film thickness h to be derived with higher accuracy. Furthermore, as shown in plots 1211 and 1212 in FIG15B , the fracture rate α can be derived together with the oil film thickness h at any rotational speed. Furthermore, even when the bearing temperature changes, which are thought to affect the viscosity of the lubricant, this method can calculate the oil film thickness h or the rupture rate α with high accuracy, regardless of the presence or absence of a flange.
[0107] As described above, according to this embodiment, the oil film thickness inside the roller bearing device and the contact ratio of the sliding portion can be detected simultaneously with good accuracy under radial load.
[0108] <Other embodiments> In the second embodiment described above, radial loads were specifically considered and described using radial bearings that generate radial loads. However, the above equations can also be applied to thrust bearings that generate axial loads by adjusting the parameters of the various variables. For example, the Ψ in equations (22) or (24) can be applied to bearings of other structures that generate line contact by adjusting the parameters based on the specifications of the bearing being tested.
[0109] Furthermore, in the invention of the present application, the following processing can be implemented, namely: a program or application for implementing the functions of one or more of the above-mentioned embodiments is provided to a system or device using a network or storage medium, and one or more processors in the computer of the system or device read and execute the program.
[0110] Furthermore, it can also be realized by a circuit that realizes more than one function (for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array)).
[0111] As mentioned above, the present invention is not limited to the above-mentioned embodiments. Combining the various components of the embodiments with each other, or making changes and applications by those skilled in the art based on the description in the specification and known technologies are also intended implementations of the present invention and are included in the scope of protection required.
[0112] As described above, this specification discloses the following matters. (1) A detection method, characterized in that the state of a bearing device including a sliding bearing is detected. Applying AC voltage to the circuit formed by the sliding bearing and the rotating shaft, Measure the impedance and phase angle of the aforementioned circuit when the aforementioned AC voltage is applied. Based on the impedance and the phase angle, the oil film thickness and the metal contact ratio between the sliding bearing and the rotating shaft are derived. The oil film thickness and the metal contact ratio are derived using the following calculation formula, which corresponds to an electric circuit formed by line contact between the sliding bearing and the rotating shaft generated in the bearing device. According to the above structure, it is possible to imagine line contact generated inside the bearing device and to detect the oil film thickness inside the bearing device and the contact ratio between parts with high precision.
[0113] (2) A detection method as in (1), wherein the circuit formed by the aforementioned wire contact includes a resistor generated by the aforementioned wire contact, a first capacitor formed by a lubricant located within a specified range from the aforementioned wire contact, and a second capacitor formed by a lubricant located outside the specified range. According to the above structure, the oil film thickness inside the bearing device and the contact ratio between parts can be detected with high precision based on the equivalent circuit corresponding to the structure of the bearing device.
[0114] (3) The detection method as in (2), wherein the electrostatic capacitance C1 of the first capacitor is given by
[0115] [Number 16]
[0116] express, The electrostatic capacitance C2 of the second capacitor is given by
[0117] [Number 17]
[0118] express. According to the above structure, the electrostatic capacitance of the capacitor in the equivalent circuit corresponding to the structure of the bearing device can be derived with good accuracy.
[0119] (4) The detection method as in (2) or (3), wherein the calculation formula for deriving the aforementioned oil film thickness h1 and the aforementioned metal contact ratio α is as follows:
[0120] [Number 18]
[0121] [Number 19]
[0122] [Number 20]
[0123] According to the above structure, it is possible to imagine line contact generated inside the bearing device and to detect the oil film thickness inside the bearing device and the contact ratio between parts with high precision.
[0124] (5) The detection method according to any one of (1) to (4), further comprising diagnosing the bearing device using the oil film thickness and the metal contact ratio. According to the above structure, it is possible to imagine line contact generated inside the bearing device, detect the oil film thickness inside the bearing device and the contact ratio between parts, and based on the results, diagnose the status of the bearing device with high precision.
[0125] (6) A detection device, characterized in that it detects the state of a bearing device composed of a sliding bearing, and comprises: an acquisition mechanism for acquiring, when an AC voltage is applied to the circuit formed by the sliding bearing and the rotating shaft, the impedance and phase angle of the circuit when the AC voltage is applied; and a derivation mechanism for deriving the oil film thickness and the metal contact ratio between the sliding bearing and the rotating shaft based on the impedance and the phase angle; and The derivation mechanism derives the oil film thickness and the metal contact ratio using a calculation formula corresponding to an electric circuit formed by line contact between the sliding bearing and the rotating shaft generated in the bearing device. According to the above structure, it is possible to imagine line contact generated inside the bearing device and to detect the oil film thickness inside the bearing device and the contact ratio between parts with high precision.
[0126] (7) A program that causes a computer to function as: an acquisition mechanism for acquiring, for a bearing device including a sliding bearing, an impedance and a phase angle of the circuit formed by the sliding bearing and the rotating shaft when an AC voltage is applied to the circuit; and a derivation mechanism for deriving the oil film thickness and the metal contact ratio between the sliding bearing and the rotating shaft based on the impedance and the phase angle; and The derivation mechanism derives the oil film thickness and the metal contact ratio using a calculation formula corresponding to an electric circuit formed by line contact between the sliding bearing and the rotating shaft generated in the bearing device. According to the above structure, it is possible to imagine line contact generated inside the bearing device and to detect the oil film thickness inside the bearing device and the contact ratio between parts with high precision.
[0127] As described above, this specification further discloses the following matters. (8) A detection method characterized by detecting the state of a bearing device comprising an outer member, an inner member, and a plurality of rollers. While applying a predetermined radial load to the bearing device, an AC voltage is applied to the circuit consisting of the outer member, the inner member, and the plurality of rollers. Measure the impedance and phase angle of the aforementioned circuit when the aforementioned AC voltage is applied. Based on the impedance and the phase angle, an oil film thickness and a metal contact ratio of at least one of the inner member and the plurality of rollers or the inner member and the plurality of rollers are derived. This configuration allows for simultaneous and precise detection of the oil film thickness and metal contact ratio of the sliding portion within a roller bearing under radial load. In particular, it allows for precise detection by taking into account the line contact generated within the roller bearing.
[0128] (9) The detection method as in (8) uses a calculation formula corresponding to the circuit formed in each of the load ring and the non-load ring in the aforementioned bearing device by specifying the aforementioned radial load to derive the aforementioned oil film thickness and the aforementioned metal contact ratio. This structure allows for accurate detection of the oil film thickness and sliding contact ratio inside the roller bearing device under radial load, taking into account the load ring and non-load ring under radial load.
[0129] (10) The detection method as in (9), wherein the calculation formula for deriving the aforementioned oil film thickness h and the aforementioned metal contact ratio α is as follows:
[0130] [Number 21]
[0131] [Number 22]
[0132] [Number 23]
[0133] [Number 24]
[0134] [Number 25] . This configuration enables simultaneous and highly accurate detection of the oil film thickness and metal contact ratio within a roller bearing assembly under radial load. In particular, this capability allows for measurement of the oil film thickness and metal contact ratio within the bearing assembly, taking into account the capacitance between the load and non-load rings of the rolling bearing, which creates line contact.
[0135] (11) The detection method according to any one of (8) to (10), further comprising diagnosing the bearing device using the oil film thickness and the metal contact ratio. According to this configuration, the condition related to the lubricant of the rolling bearing can be diagnosed based on the oil film thickness and metal contact ratio determined according to the radial load.
[0136] (12) A detection device, characterized in that it detects the state of a bearing device composed of an outer member, an inner member, and a plurality of rollers, and comprises: an acquisition mechanism for acquiring, when applying an AC voltage to a circuit formed by the outer member, the inner member, and the plurality of rollers, the impedance and phase angle of the circuit when the AC voltage is applied, while applying a predetermined radial load to the bearing device; and A derivation mechanism derives the oil film thickness and metal contact ratio of at least one of the inner member and the plurality of rollers or the inner member and the plurality of rollers based on the impedance and the phase angle. This configuration allows for simultaneous and precise detection of the oil film thickness and contact ratio of the sliding portion within a roller bearing under radial load. In particular, it enables precise detection by taking into account the line contact generated within the roller bearing.
[0137] (13) A program that causes a computer to function as: an acquisition mechanism for acquiring, when a predetermined radial load is applied to a bearing device comprising an outer member, an inner member, and a plurality of rollers, the impedance and phase angle of the circuit when an alternating voltage is applied to the circuit comprised of the outer member, the inner member, and the plurality of rollers; and A derivation mechanism derives the oil film thickness and metal contact ratio of at least one of the inner member and the plurality of rollers or the inner member and the plurality of rollers based on the impedance and the phase angle. This configuration allows for simultaneous and precise detection of the oil film thickness and contact ratio of the sliding portion within a roller bearing under radial load. In particular, it enables precise detection by taking into account the line contact generated within the roller bearing.
[0138] While various embodiments have been described above, the present invention is not limited to the examples described. A person skilled in the art will readily conceive of various variations and modifications within the scope of the claims, and these variations and modifications will naturally fall within the technical scope of the present invention. Furthermore, the various components of the above embodiments may be arbitrarily combined without departing from the spirit of the invention.
[0139] Furthermore, this application is based on the Japanese patent applications (invention patent application 2022-039416, invention patent application 2022-039417) filed on March 14, 2022, the contents of which are incorporated by reference in this application.
[0140] 1: Diagnostic device 2: Bearing device 3: Sliding bearings 7: Rotation axis 8:LCR meter 9: Rotary connector 10: Motor 12: Bearing device 13: Outer ring (outer member) 14: Inner ring (inner square component) 15,15a: rolling element 16: Seal 701,702: Line 703: Symbol 1101,1201: dotted line 1102,1103,1111,1202,1203,1211,1212: plotting a: Contact width of the roller (rotation axis) in the short direction (here is the x-axis direction) C1, C2: capacitor / capacitor C 3: Electrostatic capacitance / capacitor of the Hertzian contact area of the rolling element E1, E2, E3, E4: Equivalent circuit h,x,y: axis h 1: Oil film thickness in the Hertzian contact area h gap: radial gap L: The straight line portion of the rotating shaft that produces line contact / the length of the rotating shaft / the length of the rolling element (roller) L': Length of the rotating shaft including the chamfered part n: total number of rolling elements n 1: Number of rolling elements located in the load ring N: Speed r: roller radius r1: Radius of the rotation axis r2: The inner radius of the sliding bearing R1: resistor T: Temperature O: Rotation center of the roller S: Hertzian contact area Z: complex impedance |Z|: Impedance in dynamic contact state α: Oil film rupture rate (metal contact ratio) αS: Actual contact area (oil film rupture area) ΔL: The length of the rotating axis due to chamfering
Claims
1. A detection method, characterized in that the state of a bearing assembly comprising a sliding bearing is detected, an AC voltage is applied to a circuit comprising the aforementioned sliding bearing and a rotating shaft, the impedance and phase angle of the aforementioned circuit when the AC voltage is applied are measured, and based on the aforementioned impedance and the aforementioned phase angle, the oil film thickness and metal contact ratio between the aforementioned sliding bearing and the aforementioned rotating shaft are derived, the aforementioned oil film thickness and the aforementioned metal contact ratio are derived using the following formula, which corresponds to a circuit formed by line contact generated between the aforementioned sliding bearing and the aforementioned rotating shaft within the bearing assembly, the circuit formed by the aforementioned line contact comprising a resistance generated by the aforementioned line contact, a first capacitor formed by lubricant located within a predetermined range from the aforementioned line contact, and a second capacitor formed by lubricant located outside the predetermined range, the aforementioned formula used to derive the aforementioned oil film thickness h1 and the aforementioned metal contact ratio α is, [Number 1] [Number 2] [Number 3] |Z|: Impedance under dynamic contact state |Z0|: Impedance under static contact state θ: Phase angle under dynamic contact state θ0: Phase angle under static contact state ε: Dielectric constant of lubricant α: Oil film breakage rate (metal contact ratio) (0≦α<1) a: Contact width in the short direction of the rotating shaft L: Length of the rotating shaft h1: Oil film thickness in the Hertz contact area r: Radius of the roller ω: Angular frequency of the AC voltage 2. As in the detection method of Request 1, the electrostatic capacitance C1 of the first capacitor is represented by [number 4] ε: dielectric constant of lubricant α: oil film breakage rate (metal contact ratio) (0≦α<1) a: contact width in the short direction of the rotating shaft L: length of the rotating shaft h1: oil film thickness in the Hertz contact area, and the electrostatic capacitance C2 of the second capacitor is represented by [number 5] r: radius of the roller.
3. The testing method of claim 1 or 2, which further uses the aforementioned oil film thickness and the aforementioned metal contact ratio to diagnose the aforementioned bearing device.
4. A detection device, characterized in that it detects the state of a bearing assembly comprising a sliding bearing, and comprises: an acquisition mechanism that acquires the impedance and phase angle of the circuit when an AC voltage is applied to a circuit comprising the aforementioned sliding bearing and a rotating shaft; and a derivation mechanism that derives the oil film thickness and metal contact ratio between the aforementioned sliding bearing and the aforementioned rotating shaft based on the aforementioned impedance and the aforementioned phase angle; and the aforementioned derivation mechanism derives the aforementioned oil film thickness and the aforementioned metal contact ratio using the following formula, which corresponds to a circuit formed by line contact generated between the aforementioned sliding bearing and the aforementioned rotating shaft generated in the aforementioned bearing assembly, wherein the circuit formed by the aforementioned line contact comprises a resistance generated by the aforementioned line contact, a first capacitor formed by lubricant located within a predetermined range from the aforementioned line contact, and a second capacitor formed by lubricant located outside the predetermined range, and the aforementioned formula for deriving the aforementioned oil film thickness h1 and the aforementioned metal contact ratio α is, [number 1] [number 2] [number 3] |Z|: Impedance under dynamic contact state |Z0|: Impedance under static contact state θ: Phase angle under dynamic contact state θ0: Phase angle under static contact state ε: Dielectric constant of lubricant α: Oil film breakage rate (metal contact ratio) (0≦α<1) a: Contact width in the short direction of the rotating shaft L: Length of the rotating shaft h1: Oil film thickness in the Hertz contact area r: Radius of the roller ω: Angular frequency of the AC voltage 5. A detection program characterized in that a computer functions as follows: an acquisition mechanism that, for a bearing assembly including a sliding bearing, acquires the impedance and phase angle of the circuit when an AC voltage is applied to a circuit consisting of the aforementioned sliding bearing and a rotating shaft; and a derivation mechanism that, based on the aforementioned impedance and phase angle, derives the oil film thickness and metal contact ratio between the aforementioned sliding bearing and the aforementioned rotating shaft; and the derivation mechanism derives the aforementioned oil film thickness and the aforementioned metal contact ratio using the following formula, which corresponds to a circuit formed by line contact generated between the aforementioned sliding bearing and the aforementioned rotating shaft within the bearing assembly, wherein the circuit formed by the aforementioned line contact includes a resistance generated by the aforementioned line contact, a first capacitor formed by lubricant located within a predetermined range from the aforementioned line contact, and a second capacitor formed by lubricant located outside the predetermined range, and the aforementioned formula for deriving the aforementioned oil film thickness h1 and the aforementioned metal contact ratio α is, [number 1] [number 2] [number 3] |Z|: Impedance under dynamic contact state |Z0|: Impedance under static contact state θ: Phase angle under dynamic contact state θ0: Phase angle under static contact state ε: Dielectric constant of lubricant α: Oil film breakage rate (metal contact ratio) (0≦α<1) a: Contact width in the short direction of the rotating shaft L: Length of the rotating shaft h1: Oil film thickness in the Hertz contact area r: Radius of the roller ω: Angular frequency of the AC voltage 6. A detection method, characterized in that the state of a bearing assembly comprising an outer square component, an inner square component, and a plurality of rollers is detected; under a specified radial load applied to the bearing assembly, an alternating voltage is applied to a circuit comprising the outer square component, the inner square component, and the plurality of rollers; the impedance and phase angle of the circuit are measured when the alternating voltage is applied; based on the impedance and phase angle, the oil film thickness and metal contact ratio between at least one of the inner square component and the plurality of rollers, or between the inner square component and the plurality of rollers, are derived; the oil film thickness and metal contact ratio are derived using a formula corresponding to the circuits comprising the load rings and non-load rings within the bearing assembly, which are identified by the specified radial load.
7. As in the detection method of Request 6, the formulas used to derive the aforementioned oil film thickness h and the aforementioned metal contact ratio α are as follows: [Number 6] [Number 7] [Number 8] [Number 9] [Number 10] n: Number of all rolling elements in the bearing n1: Number of rolling elements located in the load ring b▔: Average contact width of the rolling element L: Length of the rolling element Rtx: Effective radius of the rolling element St1▔: Average contact area Si1(m): Contact area between rolling element m and the inner ring So1(m): Contact area between rolling element m and the outer ring ω: Angular frequency of AC voltage ε: Dielectric constant of lubricant k: Number of bearings Ψ: Dimensionless constant hgap: Radial clearance m: Natural number representing the rolling element located in the non-load ring (1≦m≦(n-n1)) |Z0|: Impedance under static contact state θ0: Phase under static contact state |Z|: Impedance under dynamic contact state θ: Phase under dynamic contact state 8. The testing method of claim 6 or 7, which further uses the aforementioned oil film thickness and the aforementioned metal contact ratio to diagnose the aforementioned bearing device.
9. A detection device, characterized in that it detects the state of a bearing assembly comprising an outer square member, an inner square member, and a plurality of rollers, and comprises: an acquisition mechanism that, under a state in which a predetermined radial load is applied to the bearing assembly, acquires the impedance and phase angle of the circuit when an AC voltage is applied to a circuit comprising the outer square member, the inner square member, and the plurality of rollers; and a derivation mechanism that, based on the impedance and the phase angle, derives at least one of the oil film thickness and metal contact ratio between the inner square member and the plurality of rollers, or between the inner square member and the plurality of rollers, and derives the oil film thickness and the metal contact ratio using a formula corresponding to the circuits comprising the load rings and non-load rings within the bearing assembly, which are identified by the predetermined radial load.
10. A detection program that enables a computer to function as: an acquisition mechanism that, under a specified radial load applied to a bearing assembly comprising an outer member, an inner member, and a plurality of rollers, acquires the impedance and phase angle of the circuit when an AC voltage is applied to a circuit comprising the aforementioned outer member, the aforementioned inner member, and the aforementioned plurality of rollers; a first derivation mechanism that, based on the aforementioned impedance and the aforementioned phase angle, derives at least one of the oil film thickness and metal contact ratio between the aforementioned inner member and the aforementioned plurality of rollers, or between the aforementioned inner member and the aforementioned plurality of rollers; and a second derivation mechanism that uses a formula corresponding to the circuits comprising the load rings and non-load rings within the aforementioned bearing assembly, identified by the specified radial load, to derive the aforementioned oil film thickness and the aforementioned metal contact ratio.