Bearing, motor, and state detection system

Abstract

To detect deterioration of a state of a lubricant in a bearing properly.SOLUTION: A bearing (1) includes: a plurality of rolling elements (13) positioned between an outer ring (11) and an inner ring (12); a lubricant (15) enclosed between the outer ring and the inner ring; first electrodes (21, 25) provided at the outside of the lubricant; and a second electrode (22) located close to the first electrode through the lubricant. Change of a dielectric constant of the lubricant located between the first electrodes and the second electrode can be detected.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to bearings, motors, and condition detection systems. [Background technology]

[0002] A bearing is provided between a fixed part and a rotating part that rotates relative to the fixed part, and reduces friction during rotational motion. A lubricant is used in the bearing to lubricate the rotation of the rolling elements within the bearing.

[0003] In recent years, electric vehicles have become popular, and electrolytic corrosion of bearings used in motors due to shaft voltage has become a problem. If the bearings are damaged by this electrolytic corrosion, the motor will also fail, so there is a need to detect the condition of the bearings, i.e., whether or not electrolytic corrosion is occurring. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-293776 A Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 discloses a device that uses an electrode placed inside a bearing as a detector and monitors changes in the electrical characteristics of the detector to detect the condition of the bearing, in particular wear debris that has become mixed into the lubricant.

[0006] However, in Patent Document 1, since the change in electrical characteristics caused by wear debris mixing into the lubricant after a certain amount of wear of the bearing is detected, it is not possible to detect the condition before the wear debris gets mixed in, i.e., the deterioration of the bearing condition, and therefore it may be difficult to prevent failure of the motor, etc.

[0007] Therefore, an object of one aspect of the present invention is to appropriately detect deterioration of the condition of the lubricant in a bearing. [Means for solving the problem]

[0008] A bearing according to one embodiment of the present invention comprises a plurality of rolling elements located between a first wheel and a second wheel, a lubricant sealed between the first wheel and the second wheel, a first electrode provided on the outside of the lubricant, and a second electrode adjacent to the first electrode via the lubricant, and is configured to be capable of detecting a change in the dielectric constant of the lubricant located between the first electrode and the second electrode.

[0009] A bearing according to one embodiment of the present invention comprises a plurality of rolling elements located between a first wheel and a second wheel, a lubricant sealed between the first wheel and the second wheel, a first electrode provided on the outside of the lubricant, and a second electrode which is the first wheel, and is configured such that the impedance or capacitance between the first electrode and the second electrode can be measured.

[0010] A bearing according to one embodiment of the present invention comprises a plurality of rolling elements located between a first wheel and a second wheel; a lubricant sealed between the first wheel and the second wheel; a first electrode divided into two or more in a circumferential direction centered on the central axis of the first wheel and having a plurality of first divided regions in contact with the lubricant; and a second electrode divided into two or more in the circumferential direction and having a plurality of second divided regions in contact with the lubricant, wherein the first divided regions and the second divided regions are alternately and evenly arranged around one circumference in the circumferential direction, and impedance or capacitance between the first electrode and the second electrode is measurable. Effect of the Invention

[0011] According to one aspect of the present invention, it is possible to detect deterioration of the condition of the lubricant in a bearing. [Brief description of the drawings]

[0012] [Figure 1]1 is a partial cross-sectional view of a bearing according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a front view of a ring according to an embodiment of the present invention. [Diagram 3] 4 is a diagram showing electric field lines generated by a first divided region, a second divided region, and a rolling element when a voltage is applied to a first electrode and a second electrode. FIG. [Figure 4] FIG. 2 is a partial cross-sectional view of a test bearing according to an embodiment of the present invention. [Diagram 5] 6 is a diagram showing the relationship between the impedance between the first electrode and the second electrode and the moisture contamination rate in the lubricant. FIG. [Figure 6] 10 is a diagram showing the relationship between the capacitance between the first electrode and the second electrode and the moisture contamination rate in a lubricant. FIG. [Figure 7] FIG. 4 is a diagram showing the relationship between the impedance between the first electrode and the second electrode and the temperature of the lubricant. [Figure 8] FIG. 4 is a diagram showing the relationship between the capacitance between the first electrode and the second electrode and the temperature of the lubricant. [Figure 9] 1 is a partial cross-sectional view of a bearing according to an embodiment of the present invention. [Figure 10] FIG. 13 is a diagram showing changes in impedance over time when the frequency of an AC voltage applied to the ring is 100 Hz. [Figure 11] FIG. 13 is a diagram showing changes in impedance over time when the frequency of an AC voltage applied to the ring is 1 kHz. [Figure 12] FIG. 13 is a diagram showing the change in capacitance over time when the frequency of the AC voltage applied to the ring is 100 Hz. [Figure 13] FIG. 13 is a diagram showing the change in capacitance over time when the frequency of the AC voltage applied to the ring is 1 kHz. [Figure 14] FIG. 11 is a diagram showing changes in impedance over time when a bearing is stopped or rotating. [Figure 15] FIG. 13 is a diagram showing the change in capacitance over time when the bearing is stopped or rotating. [Figure 16] FIG. 1 is a perspective view of a pipe according to an embodiment of the present invention. [Figure 17] 1 is a block diagram showing a configuration of a main part of a state detection system; [Figure 18] FIG. 11 is a partial cross-sectional view of a bearing according to a modified example. [Figure 19] 1 is a partial cross-sectional view of a bearing according to an embodiment of the present invention. [Figure 20] FIG. 2 is a front view of a first electrode according to one embodiment of the present invention. [Figure 21] FIG. 4 is a diagram showing the change over time in capacitance between the outer ring and the first electrode in a bearing according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [Embodiment 1] Hereinafter, an embodiment according to one aspect of the present invention (hereinafter, also referred to as "the present embodiment") will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0014] (Structure of bearing 1) 1 is a partial cross-sectional view of a bearing 1 according to embodiment 1. Bearing 1 is a so-called bearing that is provided between a fixed part and a rotating part, holds the rotating part in a correct position relative to the fixed part, and reduces friction in the rotational motion of the rotating part relative to the fixed part.

[0015] 1, the bearing 1 includes an outer ring (first ring) 11, an inner ring (second ring) 12, a plurality of rolling elements 13, a lubricant 15, and a ring 20. The bearing 1 may also include a cage 14 and a sealing portion 16.

[0016] The outer ring 11 and the inner ring 12 share a central axis C and rotate relative to each other. One of the outer ring 11 and the inner ring 12 is provided on a fixed part, and the other is provided on a rotating part. The diameter of the outer ring 11 is larger than the diameter of the inner ring 12. Both the outer ring 11 and the inner ring 12 have a ring-like shape.

[0017] The rolling elements 13 are spheres, and rotate while in contact with a recess formed on the inner circumference of the outer ring 11 and a recess formed on the outer circumference of the inner ring 12. That is, a plurality of rolling elements 13 are located between the outer ring 11 and the inner ring 12. A plurality of rolling elements 13 are provided in the bearing 1. In order to arrange the rolling elements 13 at equal intervals, a cage 14 is provided that maintains the relative positions of the rolling elements 13.

[0018] The rolling elements 13 are in contact with the outer ring 11 and the inner ring 12 and are kept rotating. Therefore, frictional contact occurs between the outer ring 11 and the rolling elements 13, and between the inner ring 12 and the rolling elements 13. In order to reduce this frictional contact, a lubricant 15 is added. That is, the lubricant 15 is enclosed between the outer ring 11 and the inner ring 12. In order to prevent the lubricant 15 from leaking out, a sealing portion 16 and / or a ring 20 are provided.

[0019] The sealing portion 16 is slidably fitted into the outer ring 11 and the inner ring 12. In other words, lubricant 15 is filled between the rolling element 13 and the sealing portion 16, and the lubricant 15 ensures the smooth rotation of the rolling element 13. The sealing portion 16 prevents the lubricant 15 filled between the outer ring 11 and the inner ring 12 from leaking out and preventing foreign matter from entering from the outside.

[0020] (Ring 20) FIG. 2 is a front view of the ring 20 according to the first embodiment. The ring 20 is fixed to the outer ring 11 and rotates with a small gap with respect to the inner ring 12. That is, the lubricant 15 is filled between the rolling element 13 and the ring 20, and the lubricant 15 ensures smooth rotation of the rolling element 13. The ring 20 prevents leakage of the lubricant 15 filled between the outer ring 11 and the inner ring 12 and the intrusion of foreign matter from the outside. That is, the ring 20 may perform a function similar to that of the sealing portion 16 and act as a sealing portion. The ring 20 is fixed to the inner ring 12 and may rotate with a small gap with respect to the outer ring 11.

[0021] In the ring 20, a first electrode 21 and a second electrode 22 are formed on a polyimide film 24. The polyimide film 24 is formed on a stainless steel substrate 23. The first electrode 21 has a plurality of first divided regions 21a in contact with the lubricant 15, which are divided into two or more in the circumferential direction about the central axis C. The second electrode 22 has a plurality of second divided regions 22a in contact with the lubricant 15, which are divided into two or more in the circumferential direction about the central axis C.

[0022] The first divided regions 21a and the second divided regions 22a are alternately arranged and evenly arranged around one circumference in the circumferential direction centered on the central axis C. As a result, the number of first divided regions 21a in the first electrode 21 (the number of divisions of the first electrode 21) is equal to the number of second divided regions 22a in the second electrode 22 (the number of divisions of the second electrode 22). Here, for example, when the number of divisions is two, the first first divided region 21a, the first second divided region 22a, the second first divided region 21a, and the second second divided region 22a complete one circumference in the circumferential direction. In other words, when the number of divisions is two, the electrode is divided into a total of four divided regions.

[0023] The first divided regions 21a are connected to each other and connected to the output terminal 21b at one point. The second divided regions 22a are connected to each other and connected to the output terminal 22b at one point. That is, the first electrode 21 and the second electrode 22 can be electrically measured by the output terminals 21b and 22b. That is, the impedance or capacitance between the first electrode 21 and the second electrode 22 can be measured.

[0024] Both the first divided region 21a and the second divided region 22a include a region enclosed by two arcs with different radii and two radial line segments connecting the arcs. The shapes of the first divided region 21a and the second divided region 22a are not limited to this shape and may be any shape, such as a circle.

[0025] (Electric field lines) Here, the number of divisions of the first electrode 21, the number of divisions of the second electrode 22, and the number of rolling elements 13 are equal. Fig. 3 is a diagram showing electric lines of force generated by the first divided region 21a, the second divided region 22a, and the rolling elements 13 when a voltage is applied to the first electrode 21 and the second electrode 22. Note that Fig. 3 is a diagram in which the arc shapes are approximated to linear shapes.

[0026] The electric field lines emerging from the second divided region 22a enter the first divided region 21a while being influenced by the rolling elements 13. The electric field lines may be influenced by the cage 14 in addition to the influence of the rolling elements 13.

[0027] When the lubricant 15 deteriorates and decomposes, the relative dielectric constant of the lubricant 15 changes. Therefore, the impedance and capacitance, which can be measured by the voltage applied between the first electrode 21 and the second electrode 22, change. The impedance and capacitance were measured by applying an AC voltage using an LCR meter.

[0028] (Test bearing 2) A verification experiment was carried out to confirm whether the deterioration of the lubricant 15 can be measured by the ring 20 in the bearing 1. In the verification experiment, a test bearing 2 was used instead of the bearing 1. The reason for this is to simplify the phenomenon and more clearly clarify only the moisture dependency and temperature dependency of the lubricant 15.

[0029] Fig. 4 is a partial cross-sectional view of the test bearing 2 according to the embodiment 1. As shown in Fig. 4, the test bearing 2 includes an outer ring 11, an inner ring 12, a plurality of rolling elements 13, a cage 14, a lubricant 15, a pair of sealing portions 16, a ring 20, and a lubricant 15a. The pair of sealing portions 16 prevent the lubricant 15 from leaking out.

[0030] Unlike the bearing 1, the ring 20 of the test bearing 2 is provided on the outside of the sealing portion 16. Furthermore, lubricant 15a is filled between the ring 20 and one of the sealing portions 16. The lubricant 15a may be the same as the lubricant 15. In other words, the test bearing 2 is used to test whether the degree of deterioration of the lubricant 15 can be measured by the ring 20.

[0031] In the test bearing 2, by making the sealing portion 16 out of stainless steel, the electric field lines emerging from the second divided region 22a of the ring 20 are less affected by the rolling elements 13 and enter the first divided region 21a while being affected by the sealing portion 16. Since the sealing portion 16 is formed continuously in an annular shape, it is believed that the measurement results of the ring 20 in the test bearing 2 will be more continuous than those of the ring 20 in the bearing 1.

[0032] (moisture dependent) Fig. 5 is a diagram showing the relationship between the impedance between the first electrode 21 and the second electrode 22 and the moisture mixing rate in the lubricant 15a. Fig. 6 is a diagram showing the relationship between the capacitance between the first electrode 21 and the second electrode 22 and the moisture mixing rate in the lubricant 15a. Note that Figs. 5 and 6 were measured with AC voltage frequencies of 100 Hz and 1 kHz. Here, the moisture mixing rate was adjusted by directly mixing moisture into the lubricant 15a.

[0033] 5 and 6, it can be seen that when the moisture mixing rate is 0 to 2%, the impedance drops sharply and the capacitance increases sharply. This is because water is a substance with an extremely high relative dielectric constant. Therefore, the moisture mixing rate for the lubricant 15a can be estimated by measuring the impedance or capacitance between the first electrode 21 and the second electrode 22.

[0034] In addition, the lubricant 15a reacts with moisture and decomposes by oxidation. Therefore, moisture mixed into the lubricant 15a accelerates the deterioration of the lubricant. In other words, when the amount of mixed moisture is large, it is understood that the deterioration of the lubricant 15a has started, and the condition of the test bearing 2 has deteriorated.

[0035] (temperature dependence) Fig. 7 is a diagram showing the relationship between the impedance between the first electrode 21 and the second electrode 22 and the temperature of the lubricant 15a. Fig. 8 is a diagram showing the relationship between the capacitance between the first electrode 21 and the second electrode 22 and the temperature of the lubricant 15a. Note that Figs. 7 and 8 were measured with AC voltage frequencies of 100 Hz and 1 kHz. Here, the temperature rise of the lubricant 15a was performed by placing the test bearing 2 in a high-temperature environment.

[0036] 7 and 8, as the temperature of the lubricant 15a increases, the impedance decreases and the capacitance increases. The lubricant 15a is heated by frictional heat in the test bearing 2. Therefore, it is believed that the temperature increase caused by the frictional heat promotes the decomposition reaction of the lubricant 15a.

[0037] (Distance between first divided region 21a and second divided region 22a) A gap for insulation is provided between the first divided region 21a and the second divided region 22a. The gap is 50 μm or more. In other words, a gap of 50 μm or more is provided between the first electrode 21 and the second electrode 22. If the gap is too large, the capacitance decreases rapidly and the impedance increases, deteriorating the measurement accuracy, so the gap is preferably 500 μm or less.

[0038] This is because it is known that the size of wear debris that generally gets mixed into lubricant 15 is less than 50 μm, and the purpose of this is to prevent the first electrode 21 and the second electrode 22 from being short-circuited by the wear debris even if the wear debris gets mixed in.

[0039] (summary) 5 to 8 reveal the moisture dependency and temperature dependency of lubricant 15a in test bearing 2. This tendency is common not only to lubricant 15a but also to lubricant 15. In other words, it is considered that the same results as those in Figs. 5 to 8 will be obtained not only for test bearing 2 but also for bearing 1.

[0040] Therefore, the impedance and / or capacitance of the ring 20 changes due to moisture being mixed into the lubricant 15. The impedance and / or capacitance of the ring 20 changes due to an increase in temperature of the lubricant 15. As a result, it is possible to detect a deterioration in the condition of the bearing 1, i.e., a deterioration in the condition of the lubricant 15.

[0041] 5 to 8, the impedance at 1 kHz is sufficiently smaller than the impedance at 100 Hz. This is because the AC voltage applied to ring 20 has a sufficiently high frequency, so the impedance is reduced.

[0042] At low frequencies, it is easy to measure the change in impedance and / or capacitance, but the variation is large. At high frequencies, the variation in impedance and / or capacitance is small, but the amount of change is small. Therefore, it is necessary to apply an AC voltage of an appropriate frequency to the ring 20.

[0043] Furthermore, the impedance and / or capacitance may be measured by applying AC voltages at multiple frequencies, which improves the accuracy of the state of the lubricant 15 derived from the impedance and / or capacitance measurement results.

[0044] [Embodiment 2] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals are given to members having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0045] (Structure of bearing 3) Fig. 9 is a partial cross-sectional view of a bearing 3 according to embodiment 2. As shown in Fig. 9, the bearing 3 includes an outer ring 11, an inner ring 12, a plurality of rolling elements 13, a cage 14, a lubricant 15, a conductive part 31, and a ring 20. That is, compared to the bearing 1, the bearing 3 includes the conductive part 31 instead of the sealing part 16.

[0046] Conductive part 31 is a member that can establish electrical continuity between outer ring 11 and inner ring 12 and seals lubricant 15. Conductive part 31 may be, for example, a structure in which a conductive member fixed to outer ring 11 and a conductive member fixed to inner ring 12 slide against each other. Conductive part 31 may also be a sealing part such as conductive rubber, or may rotate while in contact with outer ring 11 and inner ring 12. In other words, conductive part 31 may be any structural member that can establish electrical continuity between outer ring 11 and inner ring 12.

[0047] Since the outer ring 11 and the inner ring 12 are electrically connected by the conductive portion 31, the generation of shaft voltage can be reduced in a motor equipped with the bearing 3.

[0048] (Test conditions) The impedance and / or capacitance were tested for changes over time. The tests were performed under three conditions. In the bearing 1, the outer ring 11 was fixed, 5V was applied to the outer ring 11, and the inner ring 12 was rotated at 2000 rpm, which was the test result 1. In the bearing 3, the outer ring 11 was fixed, 5V was applied to the outer ring 11, and the inner ring 12 was rotated at 2000 rpm, which was the test result 2. In the bearing 1, the outer ring 11 was fixed, no voltage was applied to the outer ring 11, and the inner ring 12 was rotated at 2000 rpm, which was the comparative example. In other words, the test results 1 and 2 are pseudo-reproductions of the occurrence of shaft voltage, and the comparative example is data for comparison in which no shaft voltage is generated. When applying 5V to the outer ring 11, a 4.7 kΩ resistor was connected in series to limit the current.

[0049] (Change in impedance over time) Fig. 10 is a diagram showing the change in impedance over time when the frequency of the AC voltage applied to ring 20 is 100 Hz. Fig. 11 is a diagram showing the change in impedance over time when the frequency of the AC voltage applied to ring 20 is 1 kHz. Note that in Figs. 10 and 11, test result 2 was measured twice.

[0050] As shown in Figures 10 and 11, a change in impedance was observed immediately after the start of the test. This is thought to be due to the change occurring during the process of the lubricant 15 in each bearing becoming stable. Note that Figures 10 and 11 are graphs normalized based on the impedance at the time when the impedance became stable.

[0051] 10 and 11, it can be seen that only in Test Result 1, the impedance drops sharply from about 180 hours onwards. In contrast, in Test Result 2 and the Comparative Example, the impedance does not change. This is because shank voltage was generated only in the bearing 1 corresponding to Test Result 1, while in Test Result 2 the shank voltage was eliminated by the conductive part, and in the Comparative Example, shank voltage was not applied. As a result, it is believed that electrolytic corrosion occurred in the bearing 1 only in Test Result 1.

[0052] (Change in capacitance over time) Fig. 12 is a diagram showing the change in capacitance over time when the frequency of the AC voltage applied to ring 20 is 100 Hz. Fig. 13 is a diagram showing the change in capacitance over time when the frequency of the AC voltage applied to ring 20 is 1 kHz. Note that in Figs. 12 and 13, Test Result 2 was measured twice.

[0053] As shown in Figures 12 and 13, a change in capacitance was observed immediately after the start of the test. This is thought to be due to the change occurring during the process of the lubricant 15 in each bearing becoming stable. Note that Figures 12 and 13 are graphs normalized based on the capacitance at the time when the capacitance became stable.

[0054] 12 and 13, it can be seen that only in Test Result 1, the capacitance increases sharply from about 180 hours onwards. In contrast, in Test Result 2 and the Comparative Example, the capacitance does not change. This is because shaft voltage was generated only in Bearing 1 corresponding to Test Result 1, while in Test Result 2 the shaft voltage was eliminated by the conductive part, and in the Comparative Example, no shaft voltage was applied. As a result, it is believed that electrolytic corrosion occurred in Bearing 1 only in Test Result 1.

[0055] (Small summary) 10 to 13, it was possible to measure changes in impedance and / or capacitance only in test result 1, in which a pseudo axial voltage was applied (axial voltage relative to the potential of the fixed part was generated) in a bearing that had started to rotate and stabilized. Therefore, it is believed that by measuring the impedance and / or capacitance in bearing 1, it is possible to detect deterioration of lubricant 15 and the occurrence of electrolytic corrosion.

[0056] [Embodiment 3] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals are given to components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0057] (Rotating and stopped) Fig. 14 is a diagram showing the change in impedance over time when the bearing 1 is stopped or rotating. Fig. 15 is a diagram showing the change in capacitance over time when the bearing 1 is stopped or rotating. In Figs. 14 and 15, the changes over time in the stopped and rotating states were measured with the frequencies of the AC voltage applied to the ring 20 set to 100 Hz and 1 kHz. The measurements during rotation were taken at 2000 rpm.

[0058] 14 and 15, it can be seen that the measurement results for both impedance and capacitance vary when the bearing is stopped. This is thought to be because the lubricant 15 is unevenly positioned in the bearing 1, and the state of the electric field lines is not constant, resulting in unstable measurement results.

[0059] In contrast, it can be seen that the measurement results for both impedance and capacitance are stable in the rotating state. This is thought to be because, as the bearing rotates, the lubricant 15 diffuses (distributes) evenly inside the bearing 1, making the state of the electric field lines almost constant, and the measurement results are stable.

[0060] Therefore, the impedance and / or capacitance between the first electrode 21 and the second electrode 22 is preferably measured while the bearing 1 is rotating.

[0061] [Embodiment 4] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals are given to members having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0062] (Ring shape) Fig. 16 is a perspective view of a pipe 20a according to embodiment 4. In embodiments 1 to 3, the ring 20 has the first electrode 21 and the second electrode 22 formed on a flat surface. In contrast, in embodiment 4, the first electrode 21 and the second electrode 22 are formed on the inner surface of the pipe 20a.

[0063] The pipe 20a has a ring shape extending in the direction of the central axis C of the bearing 1, that is, has a pipe shape. The pipe 20a is fixed to the outer ring 11, for example, and is in contact with the lubricant 15.

[0064] A first electrode 21 and a second electrode 22 are formed on the inner surface of the pipe 20a. The first electrode 21 includes a plurality of first divided regions 21a connected to each other, as in the first embodiment. The second electrode 22 includes a plurality of second divided regions 22a connected to each other, as in the first embodiment. The first electrode 21 can be electrically measured by the output terminal 21b, and the second electrode 22 can be electrically measured by the output terminal 22b. The output terminal 21b and the output terminal 22b may be electrically connected to the first divided region 21a or the second divided region 22a inside the pipe 20a.

[0065] Furthermore, the pipe 20a is not limited to having the first electrode 21 and the second electrode 22 formed on the inner surface. For example, the pipe may have the first electrode 21 and the second electrode 22 formed on the outer surface. In this case, it is preferable that the pipe is fixed to the inner ring 12 so that the first electrode 21 and the second electrode 22 come into contact with the lubricant 15.

[0066] When the pipe 20a, on whose inner surface the first electrode 21 and the second electrode 22 are formed, is fixed to the outer ring 11, the centrifugal force caused by the rotation applies a force to the lubricant 15 in a direction away from the central axis C. In other words, the lubricant 15 comes into contact with the pipe 20a.

[0067] [Embodiment 5] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals are given to members having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0068] (Condition Detection System 5) Unlike the first to fourth embodiments, the fifth embodiment aims to detect the state of the bearing 1 by using the impedance and / or capacitance of the ring 20 of the bearing 1.

[0069] 17 is a block diagram showing the configuration of the main parts of the condition detection system 5. The condition detection system 5 includes the bearing 1 and a condition detection device 50. The condition detection device 50 includes a measurement unit 51 and a detection unit 52.

[0070] The measuring unit 51 applies an AC voltage to the first electrode 21 and the second electrode 22, and measures the impedance and / or capacitance between the first electrode 21 and the second electrode 22. Note that the measuring unit 51 may use any method for measuring the impedance and / or capacitance between the first electrode 21 and the second electrode 22.

[0071] The measuring section 51 may include a storage section that stores the time-series changes in impedance and / or capacitance.

[0072] The detection unit 52 detects the state of the lubricant 15 based on the impedance and / or capacitance between the first electrode 21 and the second electrode 22 measured by the measurement unit 51. That is, the detection unit 52 detects the state of the bearing 1 by monitoring changes in the impedance and / or capacitance. That is, the detection unit 52 detects the state of the bearing 1, in particular the state of the lubricant 15, based on the trends in the impedance and / or capacitance derived by the first to fourth embodiments.

[0073] That is, the detection unit 52 detects deterioration of the lubricant 15 from a decrease in the impedance between the first electrode 21 and the second electrode 22 measured by the measurement unit 51. The detection unit 52 also detects deterioration of the lubricant 15 from an increase in the capacitance between the first electrode 21 and the second electrode 22 measured by the measurement unit 51.

[0074] It should be noted that the object to be detected by the detection unit 52 is not limited to the deterioration state of the lubricant 15. For example, the number of revolutions may be input from an external device, and the number of revolutions may be further used to predict the life span.

[0075] Furthermore, the state detection device 50 may have a notification unit that receives the detection result of the detection unit 52 and notifies the user, or an output unit that outputs the result to an external device.

[0076] [Embodiment 6] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals are given to components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0077] (Motor) In the first to fourth embodiments, the tendency of the state change of the bearing 1 is shown by the ring 20 in the bearing 1. In the sixth embodiment, a motor equipped with the bearing 1 is shown.

[0078] The motor has a rotating shaft supported by the bearing 1, so that it is possible to detect electrical corrosion of the bearing 1 caused by shaft voltage generated on the rotating shaft, as well as its precursors. This makes it possible to prevent motor failures and perform predictive maintenance. The motor rotates about the central axis C of the bearing 1.

[0079] The motor driver or inverter that drives the motor may be the state detection device according to embodiment 5. That is, motor failures and signs of failure may be detected by the motor driver or inverter.

[0080] Also, instead of a motor driver or an inverter, the motor itself may measure the impedance and / or capacitance between the first electrode 21 and the second electrode 22. Thus, the motor may be provided with a detection unit that detects deterioration of the lubricant 15.

[0081] [Modifications] (Thrust bearing) Although the first to fourth embodiments have been described with reference to a radial bearing, the ring 20 is not limited to being provided on a radial bearing. For example, the ring 20 may be provided on a thrust bearing. The ring 20 may include a first electrode 21 and a second electrode 22 in a thrust bearing that includes a shaft washer (first ring) and a housing washer (second ring).

[0082] (Number of electrode divisions) In the first embodiment, the number of divisions of the first divided region 21a and the second divided region 22a is specified to be two or more. In this modification, a more preferable number of divisions is specified. Specifically, the number of divisions of the first divided region 21a and the second divided region 22a is preferably equal to or greater than the number of rolling elements 13. In this case, the impedance and capacitance that can be measured can be stably and uniformly measured.

[0083] The number of the first divided regions 21a and the second divided regions 22a may be an integer multiple of the number of the rolling elements 13 or a number obtained by dividing the number by an integer. In this case, uniform measurement is possible at any phase angle during rotation.

[0084] (Ring 20 with sealing part 16) In the first to fourth embodiments, the ring 20 is provided separately from the sealing portion 16, but this modification differs from the first embodiment etc. in that the ring 20 is formed integrally with the sealing portion 16. Figure 18 is a partial cross-sectional view of a bearing 6 according to this modification.

[0085] As shown in Fig. 18, a ring 20 is formed on the inside of the sealing portion 16. The ring 20 may be attached to the inside of the sealing portion 16. Alternatively, the sealing portion 16 itself may serve as the ring 20. In other words, the ring 20 may be configured to act as the sealing portion 16 that prevents leakage of the lubricant 15. In this way, deterioration of the lubricant 15 can be detected by the sealing portion 16 on which the ring 20 is formed.

[0086] [Embodiment 7] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals are given to components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0087] 1 and 3, the holder 14 is made of, for example, metal. In this case, the metal holder 14 faces the first electrode 21 and the second electrode 22, so that a relatively large capacitance is formed between the first electrode 21 and the second electrode 22.

[0088] However, in a bearing for high speed rotation, a lightweight plastic cage may be used. The plastic cage is shaped so that it does not cover one side of the rolling elements. Therefore, when a plastic cage is used, the distance between the first electrode 21 and the second electrode 22 and the opposing metal member (rolling elements) becomes large, and the measurable capacitance becomes small.

[0089] 19 is a partial cross-sectional view of a bearing 7 according to this embodiment. The bearing 7 includes an outer ring (first ring) 11, an inner ring (second ring) 12, a plurality of rolling elements 13, a cage 14, a lubricant 15, two sealing devices (sealing portions) 17, and a first electrode 25. The cage 14 may be omitted.

[0090] In this embodiment, the cage 14 is made of resin. The cage 14 covers one side (left side in the drawing) of the rolling elements 13 and does not cover the other side (right side in the drawing).

[0091] The sealing device 17 seals the lubricant 15 inside the bearing 7 and prevents the lubricant 15 from leaking. The two sealing devices 17 are provided on one side and the other side of the rolling element 13, respectively. Here, the two sealing devices 17 are fixed to the outer ring 11. The two sealing devices 17 are in sliding contact with the inner ring 12. The sealing devices 17 are made of resin, which is an insulating material. The sealing device 17 includes a metallic (conductive) support member 17a as a reinforcing backing. The support member 17a is not in contact with the outer ring 11 and the inner ring 12. The support member 17a may be omitted.

[0092] The sealing device 17 has a lip portion 17b that constitutes a portion that contacts the inner ring 12, and an installation area 17c having a flat inner surface. Since the lip portion 17b, which does not have a flat inner surface, is formed on the inner ring 12 side, the installation area 17c is formed so as to be biased toward the outer ring 11 side (the side opposite to the lip portion 17b).

[0093] The first electrode 25 is provided on the inside of one of the sealing devices 17. The first electrode 25 is provided on the outside of the lubricant 15 (outside in the rotation shaft direction). More specifically, the first electrode 25 is disposed in the installation region 17c so as to be close to the outer ring 11 and form a capacitance between the outer ring 11 and the first electrode 25.

[0094] 20 is a front view of the first electrode 25 according to this embodiment. The first electrode 25 is a ring-shaped electrode extending in a circumferential direction centered on the central axis C. The first electrode 25 has an isotropic shape with respect to the central axis C. A wire 25b is connected to the first electrode 25 so that impedance or capacitance can be measured. The wire 25b is led out to the outside by passing through the sealing device 17 or through a notch provided in the sealing device 17. The first electrode 25 and the wire 25b are insulated from the outer ring 11.

[0095] As shown in FIG. 19, the outer ring 11 is close to the first electrode 25 via the lubricant 15. Therefore, the outer ring 11 functions as a second electrode that forms a capacitance between the outer ring 11 and the first electrode 25. The measuring unit 51 described above measures the impedance and / or capacitance between the outer ring 11 and the first electrode 25. This allows the detecting unit 52 to detect a change in the dielectric constant of the lubricant 15 located between the outer ring 11 and the first electrode 25. Note that wiring (not shown) is connected to the outer ring 11 so that the impedance and / or capacitance can be measured.

[0096] According to the bearing 7 of this embodiment, the first electrode 25 is disposed close to the outer ring 11 via the lubricant 15. The rolling elements 13 are not present at some positions in the circumferential direction. On the other hand, the outer ring 11 is present around the entire circumference in the circumferential direction. Therefore, the capacitance formed between the first electrode 25 and the outer ring 11 is relatively large. Therefore, the state detection device 50 can easily detect the change in impedance or capacitance. Therefore, the state detection device 50 can more accurately detect the change in the dielectric constant of the lubricant 15 and appropriately determine the deterioration of the lubricant 15.

[0097] It is not necessary for the lubricant 15 to completely fill the inside of the sealing device 17. When the bearing 7 rotates, the lubricant 15 is biased toward the outer ring 11 due to centrifugal force. Therefore, by bringing the first electrode 25 close to the outer ring 11, the lubricant 15 can be positioned between them.

[0098] Since the first electrode 25 has an isotropic shape with respect to the central axis C, the position of the rolling element 13 is unlikely to affect the measurement of impedance and / or capacitance. Therefore, in the bearing 7, it is possible to measure the impedance and / or capacitance more stably. However, the first electrode 25 does not have to be isotropic with respect to the central axis C. The detection unit 52 can obtain a stable measurement value by performing the measurement while the bearing 7 is rotating. Note that the detection unit 52 may perform the measurement while the bearing 7 is not rotating.

[0099] (Modification) The outer ring 11 may be a rotating ring. When performing measurements using the rotating ring as the second electrode, a sliding contact or the like may be used. Similarly, the sealing device 17 and the first electrode 25 may rotate.

[0100] The measurement unit 51 may measure the impedance and / or capacitance between the first electrode 25 and the inner ring 12, with the inner ring 12 as the second electrode. The sealing device 17 may be fixed to the inner ring 12. The first electrode 25 may be arranged so as to be biased toward the inner ring 12. The inner ring 12 may be a rotating ring or a fixed ring.

[0101] The metal support member 17a may be used as the first electrode. The first electrode 25 may be disposed on the side where the cage 14 covers the rolling elements 13.

[0102] Although the seventh embodiment has been described with reference to a radial bearing, the first electrode 25 may be provided on a bearing other than the radial bearing. For example, the first electrode 25 may be provided on a thrust bearing.

[0103] (Change in capacitance over time) FIG. 21 is a diagram showing the change over time in capacitance between the outer ring 11 and the first electrode 25 in the bearing 7. The vertical axis shows the capacitance ratio, with the capacitance at the start of the test taken as 1. The horizontal axis shows the test time [h]. The solid line shows the results of two tests performed while flowing a current of about 1 A between the outer ring 11 and the inner ring 12. The dotted line shows the results of a test performed without flowing a current between the outer ring 11 and the inner ring 12. The bearing 7 was rotated at a rotation speed of 2000 rpm. The measurement was performed while rotating the bearing 7. The capacitance was measured using a capacitive touch sensor circuit. The shape of the first electrode 25 used in the test was not isotropic, but was divided in the circumferential direction.

[0104] In the case of no current (dotted line), the capacitance ratio rose to about 1.1 about 25 hours after the start of the test, and no significant change was observed thereafter. The lubricant 15 had not discolored after the test. The initial small increase in the capacitance ratio is thought to be a change in the process of the lubricant 15 inside the bearing stabilizing.

[0105] When there is a current (solid line), the capacitance ratio rises sharply to about 1.3 to 1.4 about 25 hours after the start of the test. This is thought to be because the current flowing between the outer ring 11 and the inner ring 12 causes electrolytic corrosion, which deteriorates the lubricant 15 and changes the dielectric constant of the lubricant 15. After the test, the lubricant 15 had turned black. Furthermore, when there is a current, physical vibrations increased 200 hours after the start of the test.

[0106] Thus, according to the bearing 7 of this embodiment, by measuring the capacitance between the outer ring 11 and the first electrode 25, it is possible to detect a change in the state of the lubricant 15 before an abnormality in the physical vibration of the bearing 7 is detected. Therefore, an abnormality occurring in the bearing 7 can be detected at an early stage. Therefore, the bearing 7 can appropriately detect that the state of the lubricant 15 has deteriorated.

[0107] 〔summary〕 The bearing of the first aspect of the present invention comprises a plurality of rolling elements located between a first wheel and a second wheel, a lubricant sealed between the first wheel and the second wheel, a first electrode provided on the outside of the lubricant, and a second electrode adjacent to the first electrode via the lubricant, and is configured to be capable of detecting a change in the dielectric constant of the lubricant located between the first electrode and the second electrode.

[0108] According to the above configuration, by detecting a change in the dielectric constant of the lubricant located between the first electrode and the second electrode, it is possible to detect a deterioration in the condition of the bearing, in particular the condition of the lubricant.

[0109] A bearing according to a second aspect of the present invention may be configured as in the first aspect, wherein the second electrode is the first wheel.

[0110] A bearing according to a third aspect of the present invention may be configured as in the second aspect, wherein the first ring is an outer ring, and the second ring is an inner ring.

[0111] A bearing according to a fourth aspect of the present invention may be configured as in any one of the first to third aspects above, further comprising a sealing portion fixed to the first wheel and containing the lubricant, and the first electrode being provided in the sealing portion.

[0112] A bearing according to a fifth aspect of the present invention is any one of the second to fourth aspects, wherein the first electrode extends in a circumferential direction about a central axis of the first wheel.

[0113] A bearing according to a sixth aspect of the present invention comprises a plurality of rolling elements located between a first wheel and a second wheel, a lubricant sealed between the first wheel and the second wheel, a first electrode provided on the outside of the lubricant, and a second electrode which is the first wheel, and is configured such that the impedance or capacitance between the first electrode and the second electrode is measurable.

[0114] A bearing according to a seventh aspect of the present invention may be configured in such a way that, in the above-mentioned first aspect, the first electrode has a plurality of first divided regions in contact with the lubricant, which are divided into two or more in a circumferential direction centered on the central axis of the first wheel, and the second electrode has a plurality of second divided regions in contact with the lubricant, which are divided into two or more in the circumferential direction, and the first divided regions and the second divided regions are arranged alternately and evenly around one circumference in the circumferential direction.

[0115] A bearing according to an eighth aspect of the present invention may be configured in such a way that in the seventh aspect, the number of divisions of the first electrode and the second electrode is equal to or greater than the number of the rolling elements.

[0116] According to the above configuration, the impedance or capacitance can be measured stably and uniformly.

[0117] A ninth aspect of the present invention relates to a bearing according to the seventh or eighth aspect, wherein the distance between the first and second divided regions is 50 μm or more.

[0118] According to the above configuration, even if wear debris gets mixed into the lubricant, it is possible to measure impedance or capacitance without causing a short circuit due to the wear debris.

[0119] A bearing according to a tenth aspect of the present invention is any of the bearings according to the seventh to ninth aspects above, and further comprises a substrate on which the first electrode and the second electrode are formed, and the substrate may be configured to act as a sealing portion to prevent leakage of the lubricant.

[0120] According to the above-mentioned configuration, the substrate can prevent leakage of the lubricant and the intrusion of foreign matter, thereby enabling impedance or capacitance to be measured with high accuracy.

[0121] A bearing according to an eleventh aspect of the present invention is any one of the bearings according to the first to tenth aspects, wherein the first wheel and the second wheel are electrically connected to each other.

[0122] According to the above configuration, by electrically conducting the first wheel and the second wheel, it is possible to prevent electrolytic corrosion.

[0123] A bearing according to a twelfth aspect of the present invention comprises a plurality of rolling elements located between a first wheel and a second wheel, a lubricant sealed between the first wheel and the second wheel, a first electrode divided into two or more in a circumferential direction centered on the central axis of the first wheel and having a plurality of first divided regions in contact with the lubricant, and a second electrode divided into two or more in the circumferential direction and having a plurality of second divided regions in contact with the lubricant, wherein the first divided regions and the second divided regions are arranged alternately and evenly around one circumference in the circumferential direction, and impedance or capacitance between the first electrode and the second electrode is measurable.

[0124] According to the above configuration, by measuring the impedance or capacitance between the first electrode and the second electrode, it is possible to detect deterioration in the condition of the bearing, in particular, the condition of the lubricant.

[0125] A motor according to aspect 13 of the present invention may be configured as a motor having the bearing of any of aspects 1 to 12 above, further comprising a measuring unit that measures impedance or capacitance between the first electrode and the second electrode, and a detecting unit that detects deterioration of the lubricant.

[0126] According to the above configuration, by using a motor having a bearing, it is possible to realize a motor in which deterioration of the lubricant can be detected before an abnormality occurs in operation.

[0127] A condition detection system according to aspect 14 of the present invention is a condition detection system comprising a bearing according to any one of aspects 1 to 12 above and a condition detection device, wherein the condition detection device may be configured to comprise a measurement unit that measures impedance or capacitance between the first electrode and the second electrode, and a detection unit that detects the condition of the lubricant based on the measurement results by the measurement unit.

[0128] According to the above configuration, the impedance or capacitance between the electrodes can be measured to detect the condition of the lubricant, which makes it possible to detect signs of deterioration in the condition of the bearing and to encourage regular maintenance, etc.

[0129] A condition detection system according to a fifteenth aspect of the present invention may be configured in the above fourteenth aspect such that the detection unit detects deterioration of the lubricant based on a decrease in impedance measured by the measurement unit.

[0130] According to the above configuration, deterioration of the bearing condition can be detected by detecting deterioration of the lubricant from a drop in impedance.

[0131] A condition detection system according to a sixteenth aspect of the present invention may be configured in the above fourteenth aspect such that the detection unit detects deterioration of the lubricant based on an increase in capacitance measured by the measurement unit.

[0132] According to the above configuration, deterioration of the bearing condition can be detected by detecting deterioration of the lubricant from an increase in capacitance.

[0133] A state detection system according to a seventeenth aspect of the present invention may be configured in the above fourteenth aspect, such that the impedance or capacitance between the first electrode and the second electrode is measured during rotation.

[0134] According to the above configuration, the state can be detected stably by measuring the impedance or capacitance during rotation.

[0135] The bearing according to an eighteenth aspect of the present invention may be configured in accordance with the twelfth aspect above, further comprising a sealing portion for preventing leakage of the lubricant.

[0136] According to the above configuration, the sealing portion can prevent leakage of the lubricant and the intrusion of foreign matter, thereby enabling impedance or capacitance to be measured with high accuracy. [Explanation of symbols]

[0137] 1, 3, 6, 7 Bearings 2 Test bearings 5. Status Detection System 11 Outer ring (second electrode) 12 Inner ring (second electrode) 13 Rolling elements 14 Cage 15, 15a Lubricants 16 Sealing part 17 Sealing device (sealing part) 17a Support member 17b Lip 17c Installation area 20 Ring 20a pipe 21, 25 1st electrode 21a 1st divided area 21b, 22b output terminals 22 2nd electrode 22a 2nd divided area 23 Stainless steel substrate 24 Polyimide film 25b Wiring 31 Conductive part 50 Status detection device 51 Measurement section 52 Detection unit

Claims

1. A plurality of rolling elements positioned between the first wheel and the second wheel; a lubricant enclosed between the first wheel and the second wheel; A first electrode provided on the outside of the lubricant; a second electrode adjacent to the first electrode via the lubricant; A bearing capable of detecting a change in the dielectric constant of the lubricant located between the first electrode and the second electrode.

2. The bearing of claim 1 , wherein the second electrode is the first ring.

3. The first wheel is an outer wheel, The bearing of claim 2 , wherein the second race is an inner race.

4. a sealing portion fixed to the first wheel and sealing the lubricant therein; The bearing according to claim 3 , wherein the first electrode is provided in the sealing portion.

5. The bearing according to claim 2 , wherein the first electrode extends in a circumferential direction about a central axis of the first wheel.

6. A plurality of rolling elements positioned between the first wheel and the second wheel; a lubricant enclosed between the first wheel and the second wheel; A first electrode provided on the outside of the lubricant; a second electrode which is the first ring; A bearing, wherein the impedance or capacitance between the first electrode and the second electrode is measurable.

7. the first electrode has a plurality of first divided regions that are divided into two or more in a circumferential direction about a central axis of the first wheel and are in contact with the lubricant, the second electrode has a plurality of second divided regions that are divided into two or more in the circumferential direction and are in contact with the lubricant, 2. The bearing according to claim 1, wherein the first divided regions and the second divided regions are alternately and uniformly arranged around one circumference in the circumferential direction.

8. The bearing according to claim 7 , wherein the number of divisions of the first electrode and the second electrode is equal to or greater than the number of the rolling elements.

9. The bearing according to claim 7 , wherein the distance between the first divided region and the second divided region is 50 μm or more.

10. a substrate on which the first electrode and the second electrode are formed, The bearing of claim 7 , wherein the base plate acts as a seal to prevent leakage of the lubricant.

11. The bearing of claim 1 , wherein the first ring and the second ring are in electrical communication.

12. A plurality of rolling elements positioned between the first wheel and the second wheel; a lubricant enclosed between the first wheel and the second wheel; a first electrode having a plurality of first divided regions in contact with the lubricant, the first electrode being divided into two or more in a circumferential direction around a central axis of the first wheel; a second electrode having a plurality of second divided regions that are divided into two or more in the circumferential direction and are in contact with the lubricant, the first division regions and the second division regions are alternately and evenly arranged around one circumference in the circumferential direction, A bearing, wherein the impedance or capacitance between the first electrode and the second electrode is measurable.

13. A motor comprising a bearing according to any one of claims 1 to 12, A measurement unit that measures an impedance or a capacitance between the first electrode and the second electrode; a detection unit that detects deterioration of the lubricant.

14. A condition detection system comprising the bearing according to any one of claims 1 to 12 and a condition detection device, The state detection device is A measurement unit that measures an impedance or a capacitance between the first electrode and the second electrode; a detection unit that detects a state of the lubricant based on a measurement result by the measurement unit.

15. The condition detection system according to claim 14 , wherein the detection unit detects the deterioration of the lubricant based on a decrease in impedance measured by the measurement unit.

16. The condition detection system according to claim 14 , wherein the detection unit detects the deterioration of the lubricant based on an increase in capacitance measured by the measurement unit.

17. The condition detection system of claim 14 , wherein the impedance or capacitance between the first electrode and the second electrode is measured during rotation.

Images