ABNORMALITY DETECTING DEVICE

An abnormality detecting device relating to the present disclosure includes at least two first cover parts arranged next to each other in a circumferential direction; a plurality of electrode parts respectively supported by the first cover parts; a plurality of magnet parts provided inside of the first cover parts in the radial direction, where each magnet part is in contact with a corresponding one of the electrode parts; and at least two second cover parts provided between adjacent ones of the first cover parts in the circumferential direction. Each electrode part has an oil-repellent surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority from Japanese

Patent Applications Serial Nos. 2022-108740 (filed on Jul. 6, 2022) and 2023-026351 (Feb. 22, 2023), the contents of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to an abnormality detecting device.

BACKGROUND

For example, speed reducers and other mechanical mechanisms are contained in mechanical devices, where the casing of the mechanical devices is filled with lubricant in order to prevent the mechanical mechanisms from wearing out. As such mechanical devices are used over a certain period of time, their mechanical parts may wear off or get damaged. If such occurs, metal powder particles may mix into the lubricant (hereinafter, the metal powder particles in the lubricant will be referred to simply as the metal powder particles). This may compromise the ability of the lubricant to save the mechanisms from being abraded. To address this issue, various abnormality detecting devices have been proposed to detect if the amount of metal powder particles reaches or exceeds a predetermined level.

For example, an abnormality detecting device is disclosed that includes a rod member formed of a conductive material, a holder member holding the rod member, a magnet part provided on the outer periphery of an end of the rod member, a first cover part (an insulating cover) covering the outer periphery of the magnet part, a first electrode part attached to the outer periphery of the first cover part while being in conduction with the rod member, and a second electrode part attached to the outer periphery of the first cover part while being in conduction with the rod member (See Patent Literature 1: Japanese Patent Application Publication No. 2005-331324). The first and second electrode pats are spaced away from each other in the axial direction. The magnet part is configured to magnetically attract metal powder particles, so that the metal powder particles adhere to the electrode parts. The adhering metal powder particles may cause a short circuit between the first and second electrode parts. This can result in detecting that the amount of metal powder particles reaches or exceeds a predetermined level.

The conventional technology described above is effective when oil is used as the lubricant. Contamination of the oil caused by metal powder particles can be checked real time. When grease, which has a higher viscosity than oil, is used, however, the new and highly viscous grease may adhere to the electrode parts. Here, the new grease does not contain a large amount of metal powder particles. The grease may deteriorate as metal powder particles mix, and experience a drop in viscosity The deteriorated grease having the lowered viscosity can not reach the electrode parts. This may undermine the abnormality detection based on the real-time contamination observation.

SUMMARY

An object of the present disclosure is to provide an abnormality detecting device that is capable of detecting abnormalities real time even when grease, which has a higher viscosity than oil, is used as the lubricant.(1) An aspect of the present disclosure provides an abnormality detecting device including at least two first cover parts arranged next to each other in a circumferential direction; a plurality of electrode parts respectively supported by the first cover parts, each electrode part having a portion being externally exposed beyond a surface of a corresponding one of the first cover parts; a plurality of magnet parts provided inside of the first cover parts in a radial direction, each magnet part being in contact with a corresponding one of the electrode parts; and at least two second cover parts each provided between adjacent ones of the first cover parts in the circumferential direction. At least a portion of a surface of the each electrode part that is externally exposed beyond a surface of the corresponding first cover part is oil repellent.

The above-described abnormality detecting device may be used in, for example, a speed reducer. When highly viscous grease is used in the speed reducer, the grease can be easily removed from the electrode parts during the initial phase of the lifetime of the speed reducer. According to the above-described invention, the highly viscous grease can be prevented from adhering to the electrode parts. The speed reducer may deteriorate over time and start malfunctioning or breaking down, but, when such happens, no highly viscous grease will be found on the electrode parts. The grease may also deteriorate over time and experience a drop in viscosity. The deteriorated and less viscous grease often contain metal powder particles, which result from the deterioration of the speed reducer over the time. According to the present disclosure, the deteriorated and less viscous grease can directly touch the electrode parts of the abnormality detecting device, which has been continuously used. Accordingly, the above-described abnormality detecting device is capable of detecting abnormalities real time even when grease is used.(2) The first and second cover parts may each have an oil-repellent surface.(3) The first and second cover parts may be made of an oil-repellent resin. The electrode parts may have an oil-repellent and conductive plating layer formed on a surface thereof.(4) The abnormality detecting device may include a first case having the first cover parts, the first case forming an outer shell; and a second case having the second cover parts, the second case forming the outer shell. The first and second cases may be made of the oil-repellent resin.(5) Another aspect of the present disclosure provides an abnormality detecting device including a first case having at least two first cover parts arranged next to each other in a circumferential direction, the first case forming an outer shell; a plurality of electrode parts respectively supported by the first cover parts, each electrode part having a portion externally exposed beyond a surface of a corresponding one of the first cover parts; a plurality of magnet parts provided inside of the first cover parts in a radial direction, each of the magnet parts being in contact with a corresponding one of the electrode parts; a second case having at least two second cover parts, each second cover part being provided between adjacent ones of the first cover parts in the circumferential direction, the second case forming the outer shell; and a detecting unit for detecting a resistance between two of the electrode parts via the magnet parts to determine whether an abnormality occurs based on the detected resistance. At least a portion of a surface of the each electrode part that is externally exposed beyond a surface of the corresponding first cover part has an oil-repellent and conductive plating layer formed thereon. The first and second cases are made of an oil-repellent resin.

The above-described abnormality detecting device may be used in, for example, a speed reducer. When highly viscous grease is used in the speed reducer, the grease can be easily removed from the electrode parts during the initial phase of the lifetime of the speed reducer. According to the above-described invention, the highly viscous grease can be prevented from adhering to the first and second cover parts. In this manner, a spacious oil-repellent region can be provided so as to surround the electrode parts of the abnormality detecting device. An oil-repellent material may be sprayed or applied in other manners later. In this case, the oil-repellent material may be applied unevenly. The present disclosure, however, can avoid such drawbacks. The highly viscous grease can be thus prevented from adhering to the electrode parts and cases. The speed reducer may deteriorate over time and start malfunctioning or breaking down, but, when such happens, no highly viscous grease will be found on the electrode parts or cases. The grease may also deteriorate over time and experience a drop in viscosity. The deteriorated and less viscous grease often contains metal powder particles, which result from the deterioration of the speed reducer over the time. According to the present disclosure, the deteriorated and less viscous grease can directly touch the electrode parts of the abnormality detecting device, which has been continuously used. Accordingly, the above-described abnormality detecting device is capable of detecting abnormalities real time even when grease is used.

The abnormality detecting device relating to the present disclosure is capable of detecting abnormalities real time even when grease, which has a higher viscosity than oil, is used as the lubricant.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the present disclosure will be hereinafter described with reference to the drawings.

Speed Reducer

FIG.1schematically shows an example of a speed reducer100having an abnormality detecting device1relating to the present disclosure provided therein. The speed reducer100shown inFIG.1is an example of a mechanical device. The speed reducer100is used in, for example, the joints of industrial robots used in the production lines of plants. As shown inFIG.1, the speed reducer100includes a casing101and a speed reducing mechanism102housed in the casing101. The speed reducing mechanism102reduces the speed of the rotation input from a power source, which is not shown, at a predetermined reduction ratio.

The casing101is filled with a non-conductive lubricant103. The speed reducing mechanism102is immersed in the lubricant103. In other words, the speed reducing mechanism102employs grease or oil bath lubrication.

The following describes in detail a case where grease lubrication is employed. When grease fills the casing101, the flowability inside the casing101is lower than when oil bath is employed due to the nature of the grease. The grease exhibits a high viscosity immediately after filling the casing101. The grease, however, progressively deteriorates as the speed reducer100is driven and the grease is thus agitated. This resultantly lowers the viscosity of the grease.

Therefore, when grease is used as the lubricant103to fill the internal space within the casing101, the grease is aggressively agitated so that the grease may deteriorate and partly experience a drop in viscosity. Part of the grease, however, is not agitated very much, and another part of the grease may keep the initial viscosity, which is exhibited immediately after the grease fill the casing101. This means that the lubricant103also has a part of high viscosity. The lubricant103thus has a low-viscosity part and a high-viscosity part. The highly viscous part of the lubricant103is likely to adhere to the speed reducer100and the abnormality detecting device1. The low-viscosity part of the lubricant103, on the other hand, has a large amount of conductive particles such as metal powder particles (for example, metal powder particles (initial abrasion powder particles and over-time metal powder particles described below).

Abnormality Detecting Device

FIG.2is a perspective view of the abnormality detecting device1.FIG.3is a sectional view along the line III-III inFIG.2.FIG.4is an exploded perspective view showing a casing2constituting the abnormality detecting device1. As shown in FIGS.2to4, the abnormality detecting device1includes an externally threaded part70attached to the wall101aof the casing101, a support3shaped like a rectangular rod and inserted into the externally threaded part70, four magnet parts4supported on the support3, the tubular casing2surrounding and covering the support3and magnet parts4, and four electrode parts5provided on the casing2.

The wall101aof the casing101has an internally threaded part, which is not shown. The externally threaded part70is tightened into the internally threaded part. In this manner, the abnormality detecting device1can be mounted to the wall101aof the casing101. The externally threaded part70has a seal flange part (not shown) integrally formed therewith, which is positioned on the outside (on the right side inFIG.2) of the wall101a. The seal flange part abuts the wall101a, which reliably seals the wall101aof the casing101and the abnormality detecting device1. In the following description, the terms “axial direction,” “axially” and “axial” refer to the axial direction of the externally threaded part70. Similarly, the terms “circumferential direction,” “circumferentially” and “circumferential” refer to the circumferential direction of the externally threaded part70. The terms “radial direction,” “radially” and “radial” refer to the radial direction of the externally threaded part70, which is orthogonal to the axial and circumferential directions.

A through-hole, which is not shown, extends through the externally threaded part70in the axial direction. The support3is received in the through hole. The support3is made of, for example, a resin. The central axis of the externally threaded part70is aligned with the central axis of the support3. The end of the support3(the left end inFIG.2) protrudes beyond an end70aof the externally threaded part70toward and into the casing101. The protruding part of the support3beyond the end70aof the externally threaded part70has four surfaces, which respectively have magnet housing depressions6.

The four magnet housing depressions6are long in the axial direction and arranged at even intervals in the circumferential direction. Between every adjacent two of the magnet housing depressions6in the circumferential direction of the support3, in other words, corners3aof the support3that are adjacent to each other in the circumferential direction respectively have case receiving depressions7. The case receiving depressions7receive ridges24of the casing2, which will be described below.

In each of the magnet housing depressions6, a plate-shaped relay piece8is provided. The relay pieces8are formed of a metal magnetic material. The magnet parts4are provided on the relay pieces8. The magnet parts4are shaped like a bar long in the axial direction, which correspond to the shape of the magnet housing depressions6. The magnet parts4are conductive magnets and exhibit magnetic properties without magnetic field or current applied thereto from outside. The magnet parts4are fixedly attached to the relay pieces8through magnetic force.

The casing2is made of, for example, a resin. The casing2is cylindrically shaped so as to surround and cover the magnet parts4and support3protruding beyond the externally threaded part70. The casing2is configured such that it can be divided into a first case11and a second case12, which are arranged next to each other in the axial direction. The first case11is positioned closer to the externally threaded part70. The first case11has an oil-repellent surface. The first case11has a first cylindrical part13and four first cover parts14. The first cylindrical part13is designed to abut against the end70aof the externally threaded part70, and the first cover parts14extend in the axial direction from the first cylindrical part13toward the second case12.

The four first cover parts14are arranged at equal intervals in the circumferential direction. The four first cover parts14have an oil-repellent surface. The four first cover parts14are located radially outside the magnet parts4while the first case11is mounted onto the support3. The first cover parts14are shaped like a plate and arranged such that their thickness direction is aligned with the radial direction. The first cover parts14are elastically deformable in the radial direction, so that the first cover parts14slightly elastically presses the magnet parts4from radially outside. The side surfaces14aof the first cover parts14facing the circumferential direction (the circumferential ends) are sloped such that the width of the first cover parts14in the circumferential direction is smaller on the outer side in the radial direction than on the inner side. A recess15is formed in the inner peripheral surface14bof each first cover part14along its entire length in the axial direction and a large part of it in the circumferential direction.

A restraining projection16is formed in the recess15in each first cover part14. The restraining projection16is positioned in the recess15at the center in the axial direction. The restraining projection16extends along the entire length of the recess15in the circumferential direction. The restraining projection16is positioned on the end of the magnet part4that faces the externally threaded part70while the first case11is attached to the support3. In this manner, the restraining projections16can restrain the movement of the magnet parts4in the axial direction. The end of each first cover part14that faces the second case12has a retaining groove17formed therein. The retaining groove17is positioned in the first cover part14at the center in the circumferential direction. The retaining groove17of each first cover part14receives and retains the corresponding one of the electrode parts5. The electrode parts5will be described below in detail.

The second case12has an oil-repellent surface. The second case12has a second cylindrical part21and four second cover parts22. The second cover parts22extend in the axial direction from the second cylindrical part21toward the first case11. A sealing plate23is integrally formed with the second cylindrical part21at the center in the axial direction. A through hole23ais formed in the sealing plate23at the center in the radial direction and extends through the sealing plate23in the thickness direction. The through hole23areceives therein a support shaft3b(seeFIG.2), which is integrally formed with the support3at its end. This results in the second case12supporting the end of the support3.

The four second cover parts22are arranged at equal intervals in the circumferential direction. The four second cover parts22have an oil-repellent surface. The four second cover parts22are located to fill the spaces between adjacent ones of the first cover parts14in the circumferential direction while the second case12is mounted onto the support3. The second cover parts22are shaped like a plate and arranged such that their thickness direction is aligned with the radial direction. More specifically, the second cover parts22each have an outer peripheral surface22aand an inner peripheral surface22bformed in the shape of an arc around the central axis of the support3, and also have side surfaces22c(circumferential ends) connecting the outer and inner peripheral surfaces22aand22b.

To make the surface of the casing2oil-repellent, an oil-repellent coating agent may be sprayed or applied using a brush to the surface of the casing2. Alternatively, the casing2may be made of an oil-repellent resin. Such a resin includes a fluororesin and the like. When made of an oil-repellent material, the casing2can be more uniformly oil-repellent than when the casing2has an oil repellent coating agent applied thereon. This is because the coating agent may be unevenly applied.

Stated differently, to make the surface of the first and second cases11and12oil-repellent, an oil-repellent coating agent may be sprayed or applied using a brush to the surface of the first and second cases11and12. Alternatively, the first and second casings11and12may be made of an oil-repellent resin. Such a resin includes a fluororesin and the like. When made of an oil-repellent material, the first and second cases11and12can be more uniformly oil-repellent than when the first and second casings11and12have an oil repellent coating agent applied thereon. This is because the coating agent may be unevenly applied.

It is not necessary to make the entire surface of the first and second cases11and12oil repellent. It is acceptable as long as at least the surfaces surrounding the electrode parts5are oil repellent. Specifically, what is least required is that the first and second cover parts14and22have an oil-repellent surface.

The side surfaces22cface the circumferential direction and are curved such that they are swollen outwardly from the outer and inner peripheral surfaces22aand22bin the circumferential direction. The side surfaces22care located outside the side surfaces14aof the first cover parts14in the radial direction while the second case12is attached to the support3. Stated differently, when seen in the radial direction, the side surfaces14aof the first cover parts14overlap the side surfaces22cof the second cover parts22. The side surfaces22cof the second cover parts22each have a slope part22dthat is positioned close to the inner peripheral surface22b. In compliance with the shape of the side surfaces14aof the first cover parts14, the slope parts22dare sloped such that the width of the second cover parts22in the circumferential direction is larger on the outer side in the radial direction than on the inner side. The slope parts22dare overlaid on the side surfaces14aof the first cover parts14. The second cover parts22hold the first cover parts14of the first case11down from the outside in the radial direction.

The ridge24is formed on the inner peripheral surface22bof each second cover part22. The ridge24is positioned on the inner peripheral surface22bat the center in the circumferential direction and extends in the axial direction. The ridges24are housed in the case receiving depressions7in the support3. In this way, the second case12can be rightly positioned relative to the support3in the circumferential direction. Via the second case12, the first case11can be also rightly positioned relative to the support3.

The electrode parts5, which are retained in the retaining grooves17in the first cover parts14of the first case11, are made of a non-magnetic conductive material such as brass, aluminum and copper. The electrode parts5have an oil-repellent surface. When cut along the radial and circumferential directions, the electrode parts5have a T-shaped section. When seen in the section along the radial and circumferential directions, the electrode parts5each have an electrode body31and a magnet abutting plate32. The electrode body31extends along the radial direction, and the magnet abutting plate32is integrated with the radially inner end of the electrode body31and extends in the circumferential direction when seen in the section along the radial and circumferential directions.

To make the surface of the electrode parts5oil-repellent, an oil-repellent coating agent may be sprayed or applied using a brush to the surface of the electrode parts5. Alternatively, the electrode parts5may be subjected to surface treatment, so that an oil-repellent and conductive plating layer may be formed. The plating layer may be, for example, an electroless nickel plating containing a fluororesin. When the electrode parts5undergo surface treatment, the electrode parts5can be more uniformly oil-repellent than when the electrode parts5have an oil repellent coating agent applied thereon. This is because the coating agent may be unevenly applied.

The retaining grooves17in the first case11receive the electrode bodies31. This allows the electrode bodies31to be in communication with the inside and outside of the first cover parts14in the radial direction. Accordingly, the radially inner and outer ends of the electrode bodies31protrude out of the first cover parts14. The magnet abutting plates32are housed in the recesses15in the first cover parts14. The magnet abutting plates32can prevent the electrode parts5from moving outward in the radial direction. Here, the surface of the electrode parts5represents a part of the entire surface of the electrode parts5that protrudes at least beyond the first cover parts14(protruding part). It is acceptable as long as at least the protruding part is oil repellent. The present embodiment, however, is not limited to such. For example, in addition to the surface of the electrode parts5, a part of the entire surface of the electrode parts5that is inside the first cover parts14may be also oil repellent.

The first cover parts14slightly elastically press the magnet parts4from the outside in the radial direction. This means that the magnet abutting plates32are elastically pressed by the first cover parts14against the magnet parts4. In this way, a sufficient contact can be established between the magnet parts4and the magnet abutting plates32, so that electrical communication can be achieved between the electrode parts5and the magnet parts4. Since the electrode parts5are non-magnetic, they are electrically connected to the magnet parts4without being magnetized. The first cover parts14, which hold the electrode parts5down, are arranged such that their side surfaces14aare overlaid on the side surfaces22cof the second cover parts22in the radial direction. The first cover parts14are thus held down by the second cover parts22from the outside in the radial direction. In this way, the first cover parts14can reliably keep the electrode parts5holding down the magnet parts4.

Since the side surfaces14aof the first cover parts14are overlaid on the side surfaces22cof the second cover parts22in the radial direction, the micro-gap S between the first and second cover parts14and22has a complicated shape. In other words, the micro-gap S between the first cover parts14and the second cover parts22has such a bent shape that, as it extends in the radial direction from the outer side toward the inner side, it extends along the side surfaces22cof the second cover parts22in the circumferential direction from the outer side toward the inner side. Accordingly, the creepage distance Ed between adjacent ones of the electrode parts5(electrode bodies31) in the circumferential direction (hereinafter referred to as the inter-electrode creepage distance Ed) is less than the creepage distance Md between adjacent ones of the magnet parts4in the circumferential direction (hereinafter referred to as the inter-magnet creepage distance Md), where the inter-electrode creepage distance Ed is directed along the outer peripheral surfaces14cof the first cover parts14and along the outer peripheral surface22aof the second cover part22, and the inter-magnet creepage distance Md is directed along the respective sides (side surfaces22c) of the second cover part22in the circumferential direction and along the outer peripheral surface22aof the second cover part22.

Here, the term “creepage distance” denotes the minimum distance between two members along the surface of an insulating material. In the present embodiment, specifically, the creepage distance denotes the minimum distance between adjacent ones of the electrode parts5(target members) in the circumferential direction and between adjacent ones of the magnet parts4(target members) in the circumferential direction along the surface of the casing2(insulating material). In other words, the creepage distance denotes the shortest distance along the surface of the insulating material between the two target members that need to be insulated from each other. The effects produced by the fact that the inter-electrode creepage distance Ed is less than the inter-magnet creepage distance Md will be described below.

The above-described abnormality detecting device1is electrically connected to a detection circuit40for detecting abnormalities using the abnormality detecting device1(see alsoFIG.5). The detection circuit40has a circuit board43, a resistance detecting unit41and a power supply42. The circuit board43is connected to the relay pieces8, and the resistance detecting unit41and power supply42are connected to the relay pieces8via the circuit board43.

The power supply42applies voltage to any one of the electrode parts5. The resistance detecting unit41is configured to detect the resistance between the electrode part5to which voltage is applied and an adjacent one of the other electrode parts5in the circumferential direction. The detection circuit40observes how the detected resistance changes and, based on it, can detect the amount of conductive particles such as metal powder particles in the lubricant103in the speed reducer100. Based on the result, the abnormality detecting device1is configured to detect abnormalities of the speed reducer100. The following specifically describes how the abnormality detecting device1detects abnormalities of the speed reducer100.

How Abnormality Detecting Device Detects abnormalities of Speed Reducer

The following describes how the abnormality detecting device1detects abnormalities of the speed reducer100with reference toFIG.5.FIG.5illustrates the abnormality detecting method employed by the abnormality detecting device1and shows part of the view inFIG.3in an enlarged state. The following first describes initial abrasion powder particles (metal powder particles) having a fine particle size, which is produced when the speed reducer100is used for the first time (in other words, during the initial phase of operation). The initial abrasion powder particles are fine metal powder particles with a particle size of, for example, less than 10 μm (usually less than approximately 2 μm) and has little adverse effects on the operation of the speed reducer100.

As shown inFIG.1, the casing2shown inFIG.2protrudes into the casing101of the speed reducer100, so that the casing2is immersed in the lubricant103. As shown inFIG.5, the initial abrasion powder particles are magnetically attracted by the magnet parts4of the abnormality detecting device1to adhere to the surface of the casing2, specifically, to the outer peripheral surfaces14cof the first cover parts14and the outer peripheral surfaces22aof the second cover parts22in the form of a lower layer Ps. The adhering initial abrasion powder particles are surrounded by the lubricant103, which forms a non-conductive layer. During the initial phase of the lifetime, the resistance detecting unit41detects an infinite resistance since the lubricant103is non-conductive. In addition, since the initial abrasion powder particles adhere with a relatively weak force, only a small amount of initial abrasion powder particles is deposited between adjacent ones of the electrode parts5in the circumferential direction.

Since the electrode parts5are made of a non-magnetic conductive material, there is no chance that the electrode parts5are magnetized under the influence of the magnetic force produced by the magnet parts4. This prevents the initial abrasion powder particles from adhering to the protruding parts31aof the electrode bodies31of the electrode parts5that protrude outward in the radial direction beyond the first cover parts14. In this manner, during the initial phase of operation of the speed reducer100, the protruding parts31acan avoid being covered with the initial abrasion powder particles. If the protruding parts31aare buried in the initial abrasion powder particles, the detection circuit40is not capable of accurately detecting whether the over-time metal powder particles adhere, which may occur after a certain period of time after the initial abrasion powder particles are generated.

The following now describes the over-time metal powder particles. The over-time metal powder particles include metal powder particles (abrasion powder particles) and broken fragments (metal fragments) that are generated after a certain period of time elapses after the initial abrasion powder particles are generated, in other words, that are generated as the speed reducer100is used in an ordinary manner. The over-time metal powder particles have a large particle size, for example, 10 μm or more. Therefore, the over-time metal powder particles are easily affected by the magnetic force produced by the magnetic parts4. The over-time metal powder particles push away the non-conductive lubricant and attract each other.

As the amount of over-time metal powder particles in the lubricant103increases, the over-time metal powder particles are magnetically attracted to the magnet parts4. The over-time metal powder particles adhere to the outer peripheral surfaces14cof the first cover parts14and the outer peripheral surfaces22aof the second cover parts22between adjacent ones of the electrode parts5in the circumferential direction. The over-time metal powder particles are subject to the magnetic force produced by the magnet parts4and deposited as an upper layer Pn on top of the lower layer Ps, which adheres to the outer peripheral surfaces14cof the first cover parts14and the outer peripheral surfaces22aof the second cover parts22.

When the amount of over-time metal powder particles deposited on the outer peripheral surfaces14cof the first cover parts14and the outer peripheral surfaces22aof the second cover parts22reaches or exceeds a specified amount, the resistance detecting unit41detects a resistance equal to or less than a specified value. When the detected resistance reaches or falls below the specified value, the detection circuit40determines that the speed reducer100experiences abnormalities. In this manner, the abnormality detecting device1can detect abnormalities of the speed reducer100.

In the abnormality detecting device1, the micro-gap S is left between each first cover part14and the corresponding second cover part22. For example, the broken fragments (metal fragments) or the like may get into the micro-gap S and adhere directly to the magnet parts4. If such occurs, the broken pieces (metal fragments) may cause a short-circuit between adjacent ones of the magnet parts4in the circumferential direction. As shown inFIG.3, however, the inter-electrode creepage distance Ed is less than the inter-magnet creepage distance Md. This prevents a short circuit from being caused by the metal powder particles or the like between the adjacent magnet parts4in the circumferential direction at least until the resistance detected by the resistance detecting unit41reaches or falls below the specified value.

For the comparison purpose, the following describes an example case where grease is used as the lubricant103, the casing2does not have an oil-repellent surface, and the electrode parts5do not have an oil repellent surface. The inventors have conducted tests to discover whether the above-described abnormality detecting device1could be used to detect abnormalities real time even when the lubricant103was grease. More specifically, the casing101was filled only with, as the lubricant103, deteriorated grease, that is to say, grease that had metal powder particles mixed therein and thus exhibited a low viscosity. This means that the speed reduction mechanism102of a new speed reducer100was immersed in the deteriorated grease, which served as the lubricant103.

As the electrode parts5of the abnormality detecting device1, electrode parts5to which new grease, specifically speaking, grease having a high viscosity and no metal powder particles, was applied (adhered) and electrode parts5to which no grease was applied were provided. The tests were conducted such that the speed reducer100operated for a predetermined period of time and the abnormality detecting device1attempted to detect metal powder particles on the electrode parts5(see Table 1).

The results of the tests showed that no metal powder particles were detected on the electrode parts5to which the new grease was applied (adhered) even if the deteriorated grease was used as the lubricant103. On the other hand, metal powder particles were detected on the electrode parts5to which no grease was applied. From these findings, the inventors have identified the following problem. The abnormality detecting device1is incapable of detecting metal powder particles or the like if grease that has not deteriorated and still has a high viscosity (i.e., the state of the grease immediately after the grease fills the internal space and during the initial phase of the lifetime of the speed reducer100) adheres to the electrode parts5of the abnormality detecting device1.

When the tests were actually conducted, new grease that had a high viscosity and no metal powder mixed therein was applied to the entire casing2, which constituted the abnormality detecting device1.

The abnormality detecting device1is mounted to the wall101aof the casing101. The abnormality detecting device1is mounted at a site where the lubricant103is highly flowable. The abnormality detecting device1is configured to detect an abnormality of the speed reducer100by detecting the amount of conductive particles such as metal powder particles in the lubricant103(for example, metal powder particles described below).

Consequently, the above-described abnormality detecting device1can more reliably detect metal powder particles or the like than the device relating to the comparative example. In the abnormality detecting device1, at least a part of each electrode part5that outwardly protrude (is externally exposed) beyond the outer peripheral surface14cof the corresponding first cover part14has an oil-repellent surface. This allows the high-viscosity grease (lubricant103) to be easily removed from the electrode parts5during the initial stage of the lifetime of the speed reducer100. In this manner, the highly viscous grease can be prevented from adhering to the electrode parts5. The speed reducer100may deteriorate over time and start malfunctioning or breaking down. When such occurs, no high-viscosity grease will be found on the electrode parts5. The grease may also deteriorate over time and experience a drop in viscosity. The deteriorated and less viscous grease often contain metal powder particles, which result from the deterioration of the speed reducer100over time. The deteriorate and less viscous grease can directly touch the electrode parts5of the abnormality detecting device1, which has been continuously used. Accordingly, the above-described abnormality detecting device1is capable of detecting abnormalities real time even when grease is used.

The first and second cover parts14and22are made of an oil-repellent resin. The electrode parts5have an oil-repellent and conductive plating layer formed on a surface thereof. This prevents the highly viscous grease from adhering to the first and second cover parts14and22, which support the electrode parts5, so that the abnormalities can be detected more accurately. An oil-repellent material may be sprayed or applied onto the first and second cover parts14and22. In this case, the oil-repellent material may be applied unevenly. The present disclosure, however, can avoid such drawbacks.

In addition to the first and second cover parts14and22, the first and second cases11and12are also made of an oil-repellent resin. Therefore, a spacious oil-repellent region can be provided so as to surround the electrode parts5of the abnormality detecting device1. It is thus made sure that the highly viscous grease can be easily removed from the electrode parts5and prevented from adhering to the electrode parts5. An oil-repellent material may be sprayed or applied onto the first and second cases11and12. In this case, the oil-repellent material may be applied unevenly. The present disclosure, however, can avoid such drawbacks.

Therefore, the detection circuit40can detect that the amount of metal powder particles reaches or exceeds the specified amount, and the abnormality detecting device1described in the above can thus accurately determine whether abnormalities occur in the speed reducer100. In order to allow the inter-electrode creepage distance Ed to be less than the inter-magnet creepage distance Md, the side surfaces14aof the first cover parts14are overlaid on the side surfaces22cof the second cover parts22in the radial direction. According to the present embodiment, a long inter-magnet creepage distance Md can be achieved simply and easily, so that the inter-electrode creepage distance Ed can be less than the inter-magnet creepage distance Md.

In the abnormality detecting device1, the four first cover parts14are arranged at equal intervals in the circumferential direction, and so are the four second cover parts22. Corresponding to the electrode parts5provided in the first cover parts14, the four magnet parts4are provided at equal intervals in the circumferential direction. With such arrangement, the amount of metal powder particles can be detected anywhere over the entire circumference of the abnormality detecting device1, which can contribute to further improve the accuracy of detection performed by the abnormality detecting device1.

In the abnormality detecting device1, the electrode parts5are separate from the magnet parts4. The first cover parts14are elastically deformable in the radial direction, to energize the electrode parts5toward the magnet parts4. The abnormality detecting device1can be readily manufactured without requiring complicatedly shaped electrode and magnet parts5and4while the electrode parts5can be reliably in electrical communication with the magnet parts4.

The embodiments described herein are not intended to necessarily limit the present disclosure to any specific embodiments. Various modifications can be made to these embodiments without departing from the true scope and spirit of the present disclosure.

For example, in the embodiment described above, the casing2is configured such that it can be divided into the first and second cases11and12. The four second cover parts22fill the spaces between the first cover parts14of the first case11that are adjacent to each other in the circumferential direction. According to the above-described embodiment, the micro-gap S is left between each first cover part14and the corresponding second cover part22. The present disclosure, however, is not limited to such, and the second cover parts22may entirely block the spaces between the first cover parts14adjacent to each other in the circumferential direction. To be specific, the first and second cover parts14and22may be integrally molded, and the first and second cases11and12may be integrally molded. In this case, no micro-gap S is left, which can in turn prevent broken fragments (metal fragments) or the like from directly adhering to the magnet parts4. In this manner, the abnormality detecting device1can stably perform accurate detection.

According to the above-described embodiment, in order to achieve as long an inter-magnet creepage distance Md as possible, the side surfaces14aof the first cover parts14are overlaid on the side surfaces22cof the second cover parts22in the radial direction. The present disclosure, however, is not limited to such, and any configuration is acceptable as long as the inter-electrode creepage distance Ed is less than the inter-magnet creepage distance Md. For example, a long inter-magnet creepage distance Md may be achieved by imparting a complicated shape to the side surfaces14aand22cof the first and second cover parts14and22.

According to the above-described embodiment, the electrode parts5are separate from the magnet parts4. The present disclosure, however, is not limited to such, and the electrode and magnet parts5and4may be integrally molded. For example, the electrode and magnet parts5and4may be formed by two-color molding, and only the portions corresponding to the magnet parts4may be magnetized. In the embodiment described above, the abnormality detecting device1includes four first cover parts14, four second cover parts22, four magnet parts4, and four electrode parts5. The present disclosure, however, is not limited to such, and any configuration is acceptable as long as the abnormality detecting device1at least includes two first cover parts14, two second cover parts22, two magnet parts4, and two electrode parts5. With such arrangement, the resistance detecting unit41can detect the resistance between the two electrode parts5.

In the embodiment described above, the resistance between two of the electrode parts5is detected via the magnet parts4. The detection circuit40is provided as a detecting unit for determining whether an abnormality occurs based on the detected resistance. When the resistance detected by the resistance detecting unit41reaches or falls below the specified value, the detection circuit40determines that the speed reducer100experiences abnormalities. The present disclosure, however, is not limited to such, and the detection circuit40may be simply configured such that it outputs a signal at the ON level (for example, light is turned on) when the resistance between the adjacent electrode parts5exceeds the specified value. This may indicate that the speed reducer100experiences abnormalities. In other words, the detected resistance may be output in various manners.

In the above-described embodiment, the metal powder particles are described as an example of the conductive particles. The present disclosure, however, is not limited to such, and the conductive particles can be any of other various conductive particles than metal powder particles. For example, other metal powder particles include particles of iron-based magnetic and conductive materials, but the abnormality detecting device1can also detect a conductive resin.

In the embodiment described above, the speed reducer100is described as an example mechanical device. The speed reducing mechanism102is described as an example mechanical mechanism. According to the above description, the abnormality detecting device1is provided in the speed reducer100. The present disclosure, however, is not limited to such, and the abnormality detecting device1can be used in gear devices, or other mechanical devices including various mechanical mechanisms. The above-described embodiment includes the first and second cylindrical parts13and21, which do not need to be shaped like a perfect cylinder but only need to be tubular. For example, the first and second cylindrical parts13and21may be shaped like a polygonal cylinder.

The foregoing embodiments disclosed herein describe a plurality of physically separate constituent parts. They may be combined into a single part, and any one of them may be divided into a plurality of physically separate constituent parts. Irrespective of whether or not the constituent parts are integrated, they are acceptable as long as they are configured to solve the problems.