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EP-4257973-B1 - ABNORMALITY DETECTING DEVICE AND MECHANICAL DEVICE

EP4257973B1EP 4257973 B1EP4257973 B1EP 4257973B1EP-4257973-B1

Inventors

  • SAKURAI, KAZUHIKO
  • HARADA, MASAKI

Dates

Publication Date
20260513
Application Date
20230123

Claims (7)

  1. An abnormality detecting device (1) for determining whether an abnormality of a mechanical mechanism (102) occurs by detecting conductive particles in a lubricant in a casing (101) in which the mechanical mechanism (102) is housed, the abnormality detecting device (1) comprising: a casing (2) including a first case (11) having a first cylindrical part (13) and a second case (12) having a second cylindrical part (21) which are arranged next to each other in an axial direction; at least two first cover parts (14) extending from the first cylindrical part (13) toward the second cylindrical part (21), the first cover parts (14) being arranged next to each other in a circumferential direction; a plurality of electrode parts (5) respectively supported by the first cover parts (14), the electrode parts (5) being in communication with inside and outside of the first cover parts (14) in a radial direction; a plurality of conductive magnet parts (4) provided inside of the first cover parts (14) in the radial direction, each of the plurality of magnet parts (4) being in contact with a corresponding one of the plurality of electrode parts (5); a plurality of second cover parts (22) extending from the second cylindrical part (21) toward the first cylindrical part (13), each of the second cover parts (22) being arranged between adjacent ones of the first cover parts (14) in the circumferential direction; and a detecting unit (40) configured to detect a resistance between two of the plurality of electrode parts (5) via the plurality of magnet parts (4), and to determine whether the abnormality of the mechanical mechanism (102) occurs by detecting an amount of conductive particles based on a change in the resistance, wherein an inter-electrode creepage distance (Ed) between adjacent ones of the electrode parts (5) in the circumferential direction is less than an inter-magnet creepage distance (Md) between adjacent ones of the magnet parts (4) in the circumferential direction, the inter-electrode creepage distance (Ed) being directed along outer peripheral surfaces (14c) of the first cover parts (14) and along an outer peripheral surface (22a) of the second cover parts (22), and the inter-magnet creepage distance (Md) being directed along respective sides (14a) of the second cover parts (22) in the circumferential direction and along the outer peripheral surface (22a) of the second cover parts (22).
  2. The abnormality detecting device (1) of claim 1, wherein circumferential ends (14a) of the first cover parts (14) are overlaid on circumferential ends (22c) of the second cover parts (22) in the radial direction.
  3. The abnormality detecting device (1) of claim 1, wherein the second cover parts (22) are configured to block a space between adjacent ones of the first cover parts (14) in the circumferential direction.
  4. The abnormality detecting device (1) of any one of claims 1 to 3, wherein four first cover parts (14), four second cover parts (22) and four magnet parts (4) are provided at even intervals in the circumferential direction.
  5. The abnormality detecting device (1) of any one of claims 1 to 4, wherein the plurality of electrode parts (5) are separately provided from the plurality of magnet parts (4), and wherein the first cover parts (14) are elastically deformable in the radial direction to energize the plurality of electrode parts (5) toward the plurality of magnet parts (4).
  6. The abnormality detecting device (1) of claim 1, comprising: four first cover parts (14); four electrode parts (5); four conductive magnet parts (4) provided separately from the electrode parts (5); and four second cover parts (22), wherein the first cover parts (14) are elastically deformable in the radial direction to energize the electrode parts (5) toward the magnet parts (4), and wherein circumferential ends (14a) of the first cover parts (14) are overlaid on circumferential ends (22c) of the second cover parts (22) in the radial direction.
  7. A mechanical device (100) comprising: a mechanical mechanism (102); a casing (101) housing the mechanical mechanism (102) and a lubricant therein; and the abnormality detecting device (1) of claim 6.

Description

TECHNICAL FIELD The present invention relates to an abnormality detecting device and a mechanical device. BACKGROUND For example, speed reducers and other mechanical mechanisms are contained in mechanical devices, where the mechanical mechanisms are prevented from wearing out by a lubricant filling the casing. 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. 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. Patent Literature 1 discloses an oil condition sensor comprising a sensor head with a permanent magnet and electrodes. The sensor detects the degree of contamination of oil by determining the amount of metallic particles. A plurality of conductors are arranged around the magnet, each electrically connectable to an electrode depending on the contamination level. The number of conductors electrically connected indicates the contamination degree. RELEVANT REFERENCES LIST OF RELEVANT PATENT LITERATURE Patent Literature 1: US 2005/212533 A1Patent Literature 2: JP 2005 331324 A SUMMARY The above-described conventional technique, however, may experience a difference from an expected value in electrical distance between the electrode parts if the metal powder particles directly adhere to the magnet part or metal fragments or the like adhere to the magnet parts. In such cases, short circuits between the electrode parts may be triggered by a different amount of metal powder particles from the predetermined amount. This may disadvantageously destabilize the accuracy of the abnormality detecting device. The object of the present invention is to provide an abnormality detecting device and a mechanical device capable of detecting abnormalities stably and accurately. According to the present invention, this object is achieved by an abnormality detecting device as defined in claim 1 and by a mechanical device as defined in claim 7. Claims 2 to 6 define preferred embodiments of the abnormality detecting device according to the present invention. ADVANTAGEOUS EFFECTS The abnormality detecting device and mechanical device relating to the present invention can stably perform accurate detection. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 schematically illustrates a configuration of a speed reducer relating to an embodiment of the present invention.Fig. 2 is a perspective view showing an abnormality detecting device relating to an embodiment of the invention.Fig. 3 is a sectional view along the line III-III in Fig. 2.Fig. 4 is an exploded perspective view showing a casing relating to an embodiment of the present invention.Fig. 5 illustrates an abnormality detecting method employed by an abnormality detecting device relating to an embodiment of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes embodiments of the present invention with reference to the drawings. <Speed Reducer> Fig. 1 schematically shows an example of a speed reducer 100 having an abnormality detecting device 1 relating to the present invention provided therein. The speed reducer 100 shown in Fig. 1 is an example of a mechanical device. The speed reducer 100 is used in, for example, the joints of industrial robots used in the production lines of plants. As shown in Fig. 1, the speed reducer 100 includes a casing 101 and a speed reducing mechanism 102 (an example of a mechanical mechanism recited in the claims) housed in the casing 101. The speed reducing mechanism 102 reduces the speed of the rotation input from a power source, which is not shown, at a predet