Sensor

Abstract

To provide a sensor that can suppress unexpected operations.SOLUTION: A sensor 5 includes: a first electrode 6; a second electrode 8; an adsorption unit 10 arranged between the first electrode 6 and the second electrode 8, the adsorption unit changing the electric resistance between the first electrode 6 and the second electrode 8 by adsorbing conductive particles; and a short-circuit suppression unit 10a for suppressing the short-circuit between the first electrode 6 and the second electrode 8 due to a large-diameter conductor piece having a larger size than the interval between the first electrode 6 and the second electrode 8.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to sensors. [Background technology]

[0002] Mechanical devices such as reducers are housed in a housing that stores lubricating oil to prevent damage to gears and other mechanical components. When the mechanical components wear during operation of such a mechanical device, wear particles (e.g., conductive materials such as iron powder) become mixed into the lubricating oil. This wear particle is, for example, a conductive material such as iron powder. As the wear of the mechanical components progresses and they enter the wear-out failure period on the failure rate curve (bathtub curve), the amount of wear particles mixed into the lubricating oil increases. Therefore, a sensor that detects the amount of wear particles in the lubricating oil can be used to accurately perform preventive maintenance of the mechanical components.

[0003] As an example of such a sensor, Patent Document 1 discloses an oil check sensor that is attached to an automobile transmission or the like to check the deterioration of oil in an oil container, the degree of wear of machine parts lubricated by oil, etc. This sensor has a pair of electrodes and a magnet that attracts conductive substances such as iron powder contained in the oil, and detects the amount of conductive substances in the oil based on the resistance value between the pair of electrodes, which changes depending on the attracted conductive substances. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-286697 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the amount of wear debris detected in reducers and the like increases due to initial wear, and then after a period of approximately constant normal operation, increases rapidly before a failure occurs. The sensor of the present invention detects this increase in the amount of wear debris before a failure, but if the amount of wear debris generated by initial wear is large, such as in the case of a large reducer, the sensor may malfunction and fail to detect the increase in the amount of wear debris before a failure that it should have detected. There is also a demand for preventing sensor malfunctions and detecting failures before they occur, so that reducers and other equipment can be stopped and replaced reliably.

[0006] Furthermore, during the manufacture of mechanical devices such as reducers, large particles of foreign matter (e.g., chips) generated by cutting processes may adhere to the components of the mechanical devices and become mixed into the lubricating oil. If such large particles of foreign matter adhere to the sensor, a short circuit will occur between the pair of electrodes even if almost no wear debris is generated. In this way, sensors that detect the amount of wear debris may unexpectedly activate even when the amount of wear debris is small.

[0007] The present invention has been made in consideration of the above circumstances, and aims to achieve the object of providing a sensor that can suppress unexpected operation due to the inclusion of foreign matter or a difference between the amount of wear powder generated and the operating setting amount. [Means for solving the problem]

[0008] The sensor according to the first aspect of the present invention comprises: It has a cylindrical shape a first electrode on a circular end face of the cylinder as viewed in the axial direction; a cylindrical second electrode having an end flush with a surface of the first electrode at a radially outer side of the cylinder of the first electrode; an adsorption section that is disposed between the first electrode and the second electrode, has insulating properties, has the same surface as a detection surface that connects end portions of the first electrode and the second electrode, and adsorbs conductive particles that are smaller than the gap between the first electrode and the second electrode, thereby changing the electrical resistance between the first electrode and the second electrode along the detection surface; a short-circuit prevention portion that prevents a short circuit between the first electrode and the second electrode due to a large-diameter conductor piece having a dimension larger than the gap between the first electrode and the second electrode; Equipped with the short circuit prevention portion is a protruding portion that protrudes from the detection surface in the axial direction along a periphery of the first electrode and is provided on at least one of the first electrode and the second electrode and has insulating properties; When viewed from the axial direction, the adsorption portion and the protrusion are arranged side by side in the radial direction of the cylinder. a detection unit that detects a change in electrical resistance between the first electrode and the second electrode. 。 Book The sensor of the invention is The short circuit prevention portion has a cylindrical width in a radial direction that is the same as the distance between the first electrode and the second electrode. It is possible. The sensor of the present invention comprises: When viewed in the axial direction of the cylinder, the short circuit prevention portion has an annular shape and is formed so as to surround the entire periphery of the first electrode. It is possible.

[0009] The sensor according to the first aspect of the present invention comprises: a first electrode; a second electrode; an adsorption unit disposed between the first electrode and the second electrode, which adsorbs conductive particles that are smaller than the gap between the first electrode and the second electrode, thereby changing the electrical resistance between the first electrode and the second electrode; a short-circuit prevention portion that prevents a short circuit between the first electrode and the second electrode due to a large-diameter conductor piece having a dimension larger than the gap between the first electrode and the second electrode; Equipped with. This sensor is equipped with a short-circuit suppression unit that suppresses a short circuit between the first and second electrodes caused by a large-diameter conductor piece (i.e., a foreign object) that has a dimension larger than the distance between the first and second electrodes. This suppresses a short circuit between the first and second electrodes caused by the large-diameter conductor piece, making it possible to suppress unexpected sensor operation.

[0010] The sensor of the present invention may include a detection unit that detects a change in electrical resistance between the first electrode and the second electrode.

[0011] In the sensor of the present invention, the short circuit prevention portion may be an insulating protrusion provided on at least one of the first electrode and the second electrode. With this configuration, even if the large-diameter conductor piece is attracted, the protrusion prevents electrical contact with at least one of the first and second electrodes, thereby preventing a short circuit between the first and second electrodes due to the large-diameter conductor piece and preventing unexpected sensor activation.

[0012] The sensor of the present invention may be a convex portion provided on the suction portion. In this way, the provision of the protrusion between the first electrode and the second electrode prevents electrical contact with at least one of the first and second electrodes even when the large-diameter conductor piece is attracted, thereby preventing a short circuit between the first and second electrodes due to the large-diameter conductor piece and preventing unexpected sensor activation.

[0013] In the sensor of the present invention, the short circuit prevention portion and the suction portion may have a one-piece structure.

[0014] In the sensor of the present invention, the short circuit prevention portion and the suction portion may be separate members.

[0015] In the sensor of the present invention, the short circuit prevention portion may have insulating properties.

[0016] In the sensor of the present invention, the short circuit prevention portion may be a wire extending in a direction intersecting the direction in which the first electrode and the second electrode face each other. With this configuration, even if the large-diameter conductor piece is attracted, the wire prevents electrical contact with at least one of the first and second electrodes, thereby preventing a short circuit between the first and second electrodes due to the large-diameter conductor piece and preventing unexpected sensor activation.

[0017] A sensor according to a first aspect of the present invention includes a plurality of detection units, each including a pair of electrodes and an adsorption portion disposed between the pair of electrodes and configured to adsorb conductive particles to change the electrical resistance between the pair of electrodes; and a detection section that outputs a signal when the electrical resistance changes in any of the set arbitrary number of the detection units.

[0018] This sensor has multiple detection units, and the detection unit outputs a signal when the electrical resistance drops in any number of the detection units. This allows the detection unit to be configured so that it does not output a signal even if the electrical resistance of one detection unit changes due to a large-diameter conductor piece. This makes it possible to prevent unexpected sensor activation due to a large-diameter conductor piece.

[0019] In the sensor of the present invention, when the conductive particles are not adsorbed, the electrical resistance in each of the plurality of sensing units can be the same. According to this configuration, the same voltage can be applied to each of the plurality of detection units, so that the voltage applied to the sensor can be reduced.

[0020] In the sensor of the present invention, the plurality of detection units can be connected in parallel to one another. According to this configuration, the voltage applied between the pair of electrodes of each detection unit can be made lower than when a plurality of detection units are connected in series.

[0021] The sensor according to the first aspect of the present invention includes a first electrode; a second electrode; an adsorption unit disposed between the first electrode and the second electrode, which adsorbs conductive particles to change the electrical resistance between the first electrode and the second electrode; a detection unit that detects that a predetermined amount of the conductor wear powder has been adsorbed; a sensitivity adjusting means for adjusting the adsorption state of the conductor wear powder to change the detection sensitivity; The above problem has been solved by having the above.

[0022] According to the sensor of the present invention, the state of adsorption of conductor wear powder is adjusted by the sensitivity adjustment means. As a result, even when a large amount of wear powder is adsorbed, the detection sensitivity of the sensor can be adjusted according to the amount of adsorption of conductor wear powder, thereby enabling reliable detection. In particular, when the reducer or other device on which the sensor is installed is large and a large amount of initial wear powder is generated, the sensor can limit the adsorption of initial wear powder or change the detection state when the amount of adsorption is large, enabling reliable detection.

[0023] In the sensor of the present invention, the sensitivity adjusting means may be means for adjusting the distance between the first electrode and the second electrode.

[0024] In the sensor of the present invention, the sensitivity adjustment means can be a group of insulator walls arranged between the first electrode and the second electrode, the insulator walls having different heights.

[0025] In the sensor of the present invention, the sensitivity adjustment means may be a group of insulators arranged between the first electrode and the second electrode, the insulators having different thicknesses between the first electrode and the second electrode.

[0026] In the sensor of the present invention, the first electrode may have an end portion on the same plane as the second electrode.

[0027] In the sensor of the present invention, the sensitivity adjusting means may be a separate suction portion other than the suction portion that attracts the conductor wear powder.

[0028] In the sensor of the present invention, the sensitivity adjusting means may have a surface treatment layer on the first electrode and the second electrode.

[0029] The sensor according to a first aspect of the present invention comprises: a cylindrical outer electrode with a bottom; an insulator disposed on the outer electrode as a bottomed inner cylinder; a magnet disposed inside the insulator; an inner electrode disposed inside the insulator and positioned closer to the opening of the outer electrode than the magnet in the axial direction; a detection unit that detects that a predetermined amount of conductor wear powder has been attracted by the magnet so as to short-circuit the outer electrode and the inner electrode; a sensitivity adjusting means for adjusting the adsorption state of the conductor wear powder to change the detection sensitivity; The above problem has been solved by having the above.

[0030] According to the sensor of the present invention, the state of adsorption of conductor wear powder is adjusted by the sensitivity adjustment means. As a result, even when a large amount of wear powder is adsorbed, the detection sensitivity of the sensor can be adjusted according to the amount of adsorption of conductor wear powder, thereby enabling reliable detection. In particular, when the reducer or other device on which the sensor is installed is large and a large amount of initial wear powder is generated, the sensor can limit the adsorption of initial wear powder or change the detection state when the amount of adsorption is large, enabling reliable detection.

[0031] In the sensor of the present invention, the insulator comprises a cylindrical portion, a sheet-like bottom portion, and It can have or be.

[0032] The sensor of the present invention may have a fastening portion that passes through the inner electrode, the magnet, the bottom of the insulator, and the bottom of the outer electrode in the axial direction. [Effects of the Invention]

[0033] According to the present invention, it is possible to provide a sensor that can suppress unexpected operation and improve operational reliability. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a cross-sectional view showing an example of a mechanical device including a sensor according to a first embodiment of the present invention. [Figure 2] 1A and 1B are a top view and a cross-sectional view of a sensor according to a first embodiment of the present invention. [Figure 3] 10A and 10B are a top view and a cross-sectional view showing a sensor having a short circuit prevention unit according to a modified example. [Figure 4] 10A and 10B are a top view and a cross-sectional view showing a sensor having a short circuit prevention unit according to a modified example. [Figure 5] 10A and 10B are a top view and a cross-sectional view showing a sensor having a short circuit prevention unit according to a modified example. [Figure 6] 10A and 10B are a top view and a cross-sectional view showing a sensor having a short circuit prevention unit according to a modified example. [Figure 7] FIG. 6 is a diagram illustrating a sensor according to a second embodiment of the present invention. [Figure 8] FIG. 10 is a cross-sectional view showing a third embodiment of a sensor according to the present invention. [Figure 9] FIG. 10 is a top view showing a fourth embodiment of a sensor according to the present invention. [Figure 10] FIG. 10 is a cross-sectional view showing a fifth embodiment of a sensor according to the present invention. [Figure 11] FIG. 10 is a diagram illustrating a sensor according to a sixth embodiment of the present invention. [Figure 12] FIG. 10 is a diagram illustrating a sensor according to a seventh embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] A first embodiment of a sensor according to the present invention will be described below with reference to the drawings. In addition, components common to multiple drawings are designated by the same reference numerals throughout the multiple drawings, and it should be noted that the drawings are not necessarily drawn to scale for the sake of convenience.

[0036] 1 is a cross-sectional view showing an example of a mechanism 1 including a sensor 5 according to an embodiment of the present invention. The mechanism 1 is a movable part such as a robot arm, and includes a reducer 2, a flange 3 provided on the input side, a servomotor 4, and a device A1 on the output side.

[0037] The reducer 2 includes a case 21 attached to the flange 3, an input shaft 23 connected to the output shaft 22 of the servomotor 4, and an output shaft 24 connected to the output-side device A1. The input shaft 23 and the output shaft 24 are supported on the case 21 so as to be rotatable about an axis AX. The output of the servomotor 4 is input to the reducer 2 via the input shaft 23, reduced in speed by the reducer 2, and then transmitted to the output-side device A1 via the output shaft 24. This allows the output-side device A1 and the flange 3 to rotate relative to each other.

[0038] The flange 3 is a cylindrical member that houses at least a part of the reducer 2. A servo motor 4 is also attached to the flange 3. An opening at one end of the flange 3 in the direction along the axis AX is closed by the reducer 2, and an opening at the other end is closed by the servo motor 4. This forms a sealed hollow portion (space S) in the flange 3. Lubricating oil is contained within the space S, and the flange 3 also functions as an oil bath.

[0039] A gear mechanism, for example, is housed inside the case 21 of the reducer 2. The space inside the case 21 is continuous with the space S inside the flange 3. When the reducer 2 operates, the gear mechanism inside the case 21 rotates, causing lubricating oil to circulate between the space inside the case 21 and the space S inside the flange 3. This circulation of lubricating oil causes conductive materials such as wear particles (conductor wear particles) generated inside the reducer 2 to be discharged into the space S inside the flange 3.

[0040] A sensor 5 for detecting the amount of conductive material contained in the lubricating oil is attached to the space S. The sensor 5 is fixed to the flange 3 via, for example, a support member 25. The sensor 5 uses a magnet to accumulate the conductive material contained in the lubricating oil between a pair of electrodes, and detects the amount of conductive material in the lubricating oil based on a change in the electrical resistance between the pair of electrodes. The sensor 5 may be located, for example, inside the case 21, or anywhere in the mechanism 1 as long as it is within the space containing the lubricating oil.

[0041] Next, the structure of the sensor 5 will be described in detail with reference to Fig. 2. Fig. 2 is a diagram schematically showing the configuration of a sensor according to a first embodiment of the present invention. Fig. 2 shows a top view of the sensor 5 and a cross section taken along line AA of the top view.

[0042] 2, the sensor 5 has a substantially cylindrical outer shape and includes a first electrode 6, a magnet 7, a second electrode 8, a fastening member 9, and an adsorption portion 10. As shown in FIG. 2, the first electrode 6 is circular when viewed from above the sensor 5 and is disposed at the center of the sensor 5. The second electrode 8 is a cylindrical member with a bottom, and includes a bottom 8a extending substantially parallel to the first electrode 6, and a wall portion (tubular portion) 8b that is continuous with the bottom 8a and extends substantially perpendicular to the bottom 8a.

[0043] The magnet 7 has a substantially cylindrical shape and is disposed between the first electrode 6 and the bottom 8a of the second electrode 8. The first electrode 6, the magnet 7, and the bottom 8a of the second electrode 8 each have a through-hole through which a fastening member 9 (a bolt in the illustrated embodiment) is inserted. The first electrode 6, the magnet 7, and the second electrode 8 are fixed to one another by inserting the fastening member 9 into the through-hole. The first electrode 6 and the second electrode 8 are fixed while being spaced apart from one another. The first electrode 6 and the second electrode 8 are made of a conductive magnetic material, such as iron, a ferrite core, or silicon steel. The magnet 7 is, for example, a permanent magnet; however, the first electrode 6 may serve as both a magnet and an electrode without using a permanent magnet.

[0044] The attraction portion 10 is provided to fill the space between the first electrode 6 and the second electrode 8 and is interposed between the first electrode 6 and the second electrode 8. The distance X1 between the first electrode 6 and the wall portion 8b of the second electrode 8 is larger than the dimensions of the conductive material contained in the lubricating oil. For example, the dimensions of the conductive material are approximately 1.0 μm to 100 μm, and the distance X1 is preferably set to a distance that does not cause a short circuit due to initial wear iron powder. In the illustrated embodiment, the magnet 7 contacts the first electrode 6 and is surrounded by the attraction portion 10. The attraction portion 10 is made of an insulating non-magnetic material such as resin. The magnet 7 forms magnetic flux lines between the first electrode 6 and the second electrode 8. As a result, the conductive material contained in the lubricating oil accumulates around the attraction portion 10.

[0045] The sensor 5 is equipped with a short-circuit suppression unit 10a that suppresses a short circuit between the first electrode 6 and the second electrode 8 due to the large diameter conductor piece. Here, the large diameter conductor piece refers to foreign matter such as chips generated by cutting or the like during the manufacturing of the mechanism 1 (see FIG. 1), and is a conductive particle having a dimension larger than the distance X1 between the first electrode 6 and the second electrode 8. As an example, the size of the large diameter conductor piece is approximately 2 mm to 5 mm.

[0046] In the embodiment shown in FIG. 2, the short-circuit prevention unit 10a is a protrusion provided on the attraction unit 10 and is configured integrally with the attraction unit 10. That is, the short-circuit prevention unit 10a and the attraction unit 10 have a one-piece structure. Therefore, like the attraction unit 10, the short-circuit prevention unit 10a is configured of an insulating non-magnetic material such as resin. Note that the attraction unit 10 and the short-circuit prevention unit 10a may be separate bodies. In the cross-sectional view of FIG. 2, the width of the short-circuit prevention unit 10a is approximately the same as the distance X1 between the first electrode 6 and the wall portion 8b of the second electrode 8. When viewed from above the sensor 5, the short-circuit prevention unit 10a is annular and is formed to surround the entire periphery of the first electrode 6.

[0047] An output line (not shown) is connected to each of the first electrode 6 and the second electrode 8, and the first electrode 6 and the second electrode 8 are electrically connected to the detection unit 50 (see Figure 1) via the output line.

[0048] The detection unit 50 detects a change in the electrical resistance between the first electrode 6 and the second electrode 8. The detection unit 50 includes a sensor drive circuit that predicts failure of components of the mechanism 1 based on, for example, a change in electrical resistance due to the accumulation of conductive materials around the suction unit 10. When conductive materials contained in the lubricant accumulate around the suction unit 10, the electrical resistance between the first electrode 6 and the second electrode 8 to which a voltage is applied decreases (or a short circuit occurs), causing a change in the output level of the output line. The detection unit 50 detects this change in electrical resistance to predict failure of components of the mechanism 1.

[0049] The decrease in electrical resistance also includes on / off signals due to de-energization and energization, and the two states of de-energization and energization may be detected (hereinafter referred to as "digital detection"). The detection unit 50 may be connected to a higher-level control device (not shown) such as a manipulator by wire or wirelessly. Upon receiving a signal from the detection unit 50, the higher-level control device may be configured to issue a warning to prompt maintenance of the reducer 2, etc., using a predetermined notification means (for example, a display device or an audio output device).

[0050] As described above, the sensor 5 includes the short-circuit suppression unit 10a that suppresses a short circuit between the first electrode 6 and the second electrode 8 caused by a large-diameter conductor piece having a dimension larger than the distance X1 between the first electrode 6 and the second electrode 8. The short-circuit suppression unit 10a is a protrusion provided on the suction unit 10. By providing the protrusion between the first electrode 6 and the second electrode 8 in this manner, electrical contact between the large-diameter conductor piece and at least one of the first electrode 6 and the second electrode 8 is suppressed even when the large-diameter conductor piece is attracted to the periphery of the suction unit 10. Therefore, a short circuit between the first electrode 6 and the second electrode 8 caused by the large-diameter conductor piece is suppressed, and unexpected operation of the sensor 5 can be suppressed.

[0051] Furthermore, the short circuit prevention portion 10a and the suction portion 10 of the sensor 5 have a one-piece structure, which reduces the number of parts that make up the sensor 5, making it easier to manufacture the sensor 5.

[0052] Next, a modified example of the short circuit prevention section of the sensor 5 will be described with reference to FIG. As shown in FIG. 3 , the short-circuit prevention unit 11 according to the modified example is a protrusion provided on the attraction unit 10, similar to the short-circuit prevention unit 10a, and is configured integrally with the attraction unit 10. Similar to the short-circuit prevention unit 10a, the short-circuit prevention unit 11 is configured from an insulating non-magnetic material, such as resin. When viewed from above the sensor 5, the short-circuit prevention unit 11 has an annular shape and is formed to surround the entire periphery of the first electrode 6. The short-circuit prevention unit 11 differs from the short-circuit prevention unit 10a in that the width of the short-circuit prevention unit 11 is smaller than the distance X1 between the first electrode 6 and the wall portion 8b of the second electrode 8.

[0053] As described above, even in the sensor 5 having the short circuit prevention part 11 having a width smaller than the interval X1, electrical contact between the large diameter conductor piece and at least one of the first electrode 6 and the second electrode 8 is prevented. Therefore, a short circuit between the first electrode 6 and the second electrode 8 due to the large diameter conductor piece is prevented, and unexpected operation of the sensor 5 can be prevented.

[0054] Next, another modified example of the short circuit prevention section of the sensor 5 will be described with reference to FIG. As shown in FIG. 4, the short-circuit prevention unit of the sensor 5 may be divided into multiple units. In the embodiment shown in FIG. 4, the sensor 5 has three short-circuit prevention units 12a, 12b, and 12c. Each of the multiple short-circuit prevention units 12a, 12b, and 12c is a protrusion provided on the attraction unit 10 and is configured integrally with the attraction unit 10. Like the attraction unit 10, the short-circuit prevention units 12a, 12b, and 12c are configured from an insulating non-magnetic material such as resin. When viewed from above the sensor 5, the multiple short-circuit prevention units 12a, 12b, and 12c are arranged at equal intervals around the first electrode 6.

[0055] As described above, even if the short circuit prevention unit is divided into multiple parts, electrical contact between at least one of the first electrode 6 and the second electrode 8 and the large diameter conductor piece is prevented in the locations where the short circuit prevention units 12a, 12b, and 12c are provided. Therefore, a short circuit between the first electrode 6 and the second electrode 8 is prevented, and unexpected activation of the sensor 5 can be prevented.

[0056] Next, with reference to FIG. 5, a further modification of the short circuit prevention section of the sensor 5 will be described. 5, the short circuit prevention portion of the sensor 5 may be a wire 14 extending in a direction intersecting with the direction in which the first electrode 6 and the wall portion 8b of the second electrode 8 face each other. The wire 14 is supported by a plurality of supports 13 and is provided on the suction portion 10 at a distance from the suction portion 10.

[0057] In the embodiment of FIG. 5 , each of the multiple support parts 13 is a stake-shaped member, one end of which is fixed in a state where it is embedded inside the suction part 10. A through-hole is provided at the other end of each support part 13, through which a wire 14 is inserted. By inserting the wire 14 into this through-hole, the wire 14 is fixed in a state where it is spaced apart from the suction part 10. When viewed from above the sensor 5, the multiple support parts 13 are arranged spaced apart from each other at equal intervals in the circumferential direction of the first electrode 6, and the wire 14 is provided so as to surround the entire circumference of the first electrode 6. There are no particular limitations on the material constituting the wire 14, and it may be a conductive material such as metal, or an insulating material such as resin.

[0058] As described above, even when the short circuit prevention unit is wire 14, wire 14 prevents electrical contact between at least one of first electrode 6 and second electrode 8 and the large diameter conductor piece. Therefore, a short circuit between first electrode 6 and second electrode 8 is prevented, and unexpected operation of sensor 5 can be prevented.

[0059] Next, with reference to FIG. 6, a further modification of the short circuit prevention section of the sensor 5 will be described. 6, the short-circuit prevention unit 15 according to the modified example may be an insulating protrusion provided on at least one of the first electrode 6 and the second electrode 8. In the illustrated embodiment, the short-circuit prevention unit 15 is provided on the wall 8b of the second electrode 8 along the inner edge where the wall 8b contacts the chucking unit 10. The short-circuit prevention unit 15 may be provided on the first electrode 6, or on both the first electrode 6 and the second electrode.

[0060] As described above, even when short circuit prevention unit 15 is provided on at least one of first electrode 6 and second electrode 8, similar to short circuit prevention unit 10a, electrical contact between at least one of first electrode 6 and second electrode 8 and the large diameter conductor piece is prevented. Therefore, a short circuit between first electrode 6 and second electrode 8 is prevented, and unexpected operation of sensor 5 can be prevented.

[0061] A second embodiment of the sensor according to the present invention will be described below with reference to the drawings. FIG. 7 is a diagram illustrating the sensor in this embodiment. The sensor 30 according to this embodiment is a sensor for detecting the amount of conductive material contained in lubricating oil, similar to the sensor 5 according to the first embodiment described above.

[0062] The sensor 30 has a substantially cylindrical outer shape and includes a plurality of detection units and a detection section 50 that outputs a signal when the electrical resistance of the detection unit changes. More specifically, the sensor 30 has a center electrode 31, a plurality of outer electrodes 32, an attraction portion 33 disposed between the center electrode 31 and the outer electrodes 32, and a magnet 34. The outer electrodes 32 are insulated from one another, and one detection unit is formed by a pair of electrodes consisting of the center electrode 31 and one outer electrode 32, and the attraction portion 33 disposed between the pair of electrodes.

[0063] In the illustrated embodiment, the sensor 30 has four outer electrodes 32A, 32B, 32C, and 32D, and four detection units are configured. The number of outer electrodes 32 and the number of detection units are not particularly limited. The magnet 34 of the sensor 30 forms magnetic flux lines between the pair of electrodes, so that conductive substances contained in the lubricant are attracted to the attraction portion 33. In this way, when conductive substances accumulate near the attraction portion 33, the electrical resistance of the detection unit changes. When no conductive particles are attracted, the electrical resistance of each of the multiple detection units is the same.

[0064] An output line is connected to each of the central electrode 31 and the outer electrodes 32, and each of the detection units is electrically connected to the detection section 50 via the output line. In this embodiment, the multiple detection units are connected in parallel with each other, and a voltage from the same voltage source is applied between the center electrode 31 and each outer electrode 32. The detection unit 50 outputs a signal when the electrical resistance changes in any number of detection units that have been set. For example, the detection unit 50 may be set to output a signal to a higher-level control device such as a manipulator when the electrical resistance decreases in two or more detection units, or may be set to output a signal when the electrical resistance decreases in all detection units.

[0065] As described above, the sensor 30 includes multiple detection units, and the detection unit 50 outputs a signal when the electrical resistance of any number of the detection units decreases. This allows the detection unit 50 to be configured so that it does not output a signal even if the electrical resistance of one detection unit changes due to a large-diameter conductor piece. This makes it possible to prevent unexpected sensor activation due to a large-diameter conductor piece. Furthermore, the sensor 30 allows the conditions for the detection unit 50 to output a signal to be set, allowing the timing at which a signal is output from a single sensor 30 to be adjusted to the optimal timing for failure prediction, which varies depending on the needs of each user.

[0066] Furthermore, when no conductive particles are adsorbed, the electrical resistance of each of the plurality of detection units is the same, which allows the voltage applied to the sensor 30 to be reduced.

[0067] Furthermore, the plurality of detection units are connected in parallel with one another, which allows the voltage applied between the pair of electrodes of each detection unit to be reduced.

[0068] A third embodiment of the sensor according to the present invention will be described below with reference to the drawings. Fig. 8 is a cross-sectional view showing a sensor in this embodiment, and this embodiment differs from the above-described embodiments in terms of the suction part. Note that some components are omitted from Fig. 8.

[0069] As shown in FIG. 8, the sensor 60 in this embodiment has an approximately cylindrical outer shape and includes a first electrode (inner electrode) 61, a magnet 64, a second electrode (outer electrode) 62, a fastening member (fastening portion) 69, an adsorption portion (insulator) 63, and a case 65. The first electrode (inner electrode) 61 has a circular shape when viewed from the top of the sensor 60, and is disposed at the center of the sensor 60. The second electrode (outer electrode) 62 is a cylindrical member with a bottom, and has a bottom 62a extending substantially parallel to the first electrode (inner electrode) 61, and a wall portion (tubular portion) 62b continuing from the bottom 62a and extending substantially perpendicular to the bottom 62a. The first electrode (inner electrode) 61 is located in an opening of the second electrode (outer electrode) 62.

[0070] The magnet 64 has a substantially cylindrical shape (substantially disk shape) and is disposed between the first electrode (inner electrode) 61 and the bottom 62a of the second electrode (outer electrode) 62. The first electrode (inner electrode) 61, the magnet 64, and the bottom 62a of the second electrode (outer electrode) 62 each have a through-hole through which a fastening member (fastening portion) 69 (a bolt in the illustrated embodiment) is inserted. The first electrode (inner electrode) 61, the magnet 64, and the second electrode (outer electrode) 62 are fixed to one another by inserting the fastening member (fastening portion) 69 into the through-hole. The outer diameter of the magnet 64 is smaller than the outer diameter of the second electrode (outer electrode) 62.

[0071] The first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 are fixed and spaced apart from each other. The first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 are made of a conductive magnetic material, such as iron, a ferrite core, or silicon steel. The magnet 64 is, for example, a permanent magnet, but the first electrode (inner electrode) 61 may serve as both a magnet and an electrode without using a permanent magnet.

[0072] The adsorption portion (insulator) 63 is arranged to fill the space between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62, and is interposed between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62. The adsorption portion (insulator) 63 has a bottom portion 63a along the bottom portion 62a of the second electrode (outer electrode) 62, and a tubular portion 63b along the wall portion (tubular portion) 62b of the second electrode (outer electrode) 62. The bottom portion 63a and the tubular portion 63b are separate bodies. The bottom portion 63a is sheet-shaped.

[0073] The bottom 63a of the suction portion (insulator) 63 may be made of insulating paper with a thickness of 0.05 to 1 mm, for example. The bottom 63a of the suction portion (insulator) 63 may be made of a circular piece of paper with an outer diameter substantially the same as the inner diameter of the cylindrical portion 63b. Furthermore, the bottom portion 63a may be a circular piece of paper with an outer diameter larger than the inner diameter of the cylindrical portion 63b. In this case, the bottom portion 63a may be a circular piece of paper with an outer diameter smaller than the outer diameter of the cylindrical portion 63b. Furthermore, the bottom portion 63a may be a circular piece of paper with an outer diameter the same as the outer diameter of the cylindrical portion 63b.

[0074] A step 63c is formed on the inner surface of the cylindrical portion 63b of the attracting portion (insulator) 63. The cylindrical portion 63b of the attracting portion (insulator) 63 has an inner diameter dimension equal to the outer diameter of the first electrode (inner electrode) 61 on the first electrode (inner electrode) 61 side relative to the step 63c. The cylindrical portion 63b of the attracting portion (insulator) 63 has an inner diameter dimension equal to the outer diameter of the magnet 64 on the magnet 64 side relative to the step 63c.

[0075] The thickness of the end of the cylindrical portion 63b of the attracting portion (insulator) 63, i.e., the distance X1 between the wall portion 62b of the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62, is larger than the dimensions of the conductive material contained in the lubricating oil. As an example, the dimensions of the conductive material are approximately 1.0 μm to 100 μm, and it is preferable that the distance X1 be set to a distance that does not cause a short circuit due to initial wear iron powder. In the illustrated embodiment, the magnet 64 contacts the first electrode (inner electrode) 61 and is surrounded by the attracting portion (insulator) 63.

[0076] The attraction portion (insulator) 63 is made of a non-magnetic material having insulating properties, such as resin. The magnet 64 forms magnetic flux lines between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62. As a result, conductive substances contained in the lubricant are accumulated around the attraction portion (insulator) 63. The area in which the lubricant circulates is defined as the detection area.

[0077] In the sensor 60 of this embodiment, the detection surface 60a is a plane connecting the ends of the second electrode (outer electrode) 62, which is substantially flush with the surface of the first electrode (inner electrode) 61. That is, on the detection surface 60a, conductive wear powder is attracted between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 in response to magnetic flux lines, electrically connecting the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62, thereby detecting a change in the resistance value between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62. The openings of the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 do not have to be flush with each other.

[0078] As the creepage distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 increases, the amount of conductor wear powder that is attracted increases until the resistance value between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 decreases to a threshold value or a short circuit occurs. In addition, by shortening the creepage distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62, the amount of conductor wear powder that is attracted decreases until the resistance value between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 decreases to a threshold value or a short circuit occurs.

[0079] The sensor 60 of this embodiment has a sensitivity adjusting means for adjusting the state of adsorption of conductor wear powder to change the detection sensitivity. In this embodiment, the sensitivity adjustment means is the adsorption portion (insulator) 63. Furthermore, in this embodiment, the cylindrical portion 63b of the adsorption portion (insulator) 63 is the sensitivity adjustment means.

[0080] The adsorption portion (insulator) 63 of this embodiment can adjust the amount of conductor wear powder adsorbed by the adsorption portion (insulator) 63 by adjusting the surface distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62. Specifically, as shown in FIG. 8, the cylindrical portion 63b of the adsorption portion (insulator) 63 has a group of portions that protrude from the detection surface 60a at different heights. In the sensor 60A of FIG. 8, the height HA of the detection surface 60a is the same as that of the end of the cylindrical portion 63b of the adsorption portion (insulator) 63A, that is, the detection surface 60a and the cylindrical portion 63b of the adsorption portion (insulator) 63A are flush with each other.

[0081] In sensor 60B of Figure 8, the end of tubular portion 63b of adsorption portion (insulator) 63B is higher by height HB than detection surface 60a, that is, tubular portion 63b of adsorption portion (insulator) 63B protrudes by height HB from detection surface 60a. In the sensor 60C of Figure 8, the end of the cylindrical portion 63b of the adsorption portion (insulator) 63C is higher by a height HC than the detection surface 60a, that is, the cylindrical portion 63b of the adsorption portion (insulator) 63C protrudes by a height HC from the detection surface 60a. In the sensor 60D of Figure 8, the end of the cylindrical portion 63b of the adsorption portion (insulator) 63D is higher by a height HD than the detection surface 60a, that is, the cylindrical portion 63b of the adsorption portion (insulator) 63D protrudes by a height HD from the detection surface 60a.

[0082] Here, the relationship between the heights HA, HB, HC, and HD is: HA(=0) <HB<HC<HD is set as:

[0083] The sensor 60 of this embodiment has a group of cylindrical portions 63b of the suction portion (insulator) 63 set to such different values, and can be assembled by selecting from among these. That is, a group of cylindrical portions 63b of a plurality of suction portions (insulators) 63 having different heights (axial dimensions) constitutes a sensitivity adjustment means. This allows the creepage distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 to be selected from a plurality of values by selecting the sensitivity adjustment means.

[0084] Here, in the sensor 60A of Figure 8, the creepage distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 set at the end of the cylindrical portion 63b of the adsorption portion (insulator) 63A is used as a reference.

[0085] 8, the creepage distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62, which is set at the end of the cylindrical portion 63b of the attraction portion (insulator) 63B, is longer than the reference distance. Therefore, the amount of conductive wear powder that is attracted can be increased until the resistance value between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 decreases to the threshold value or a short circuit occurs. As a result, even if the reducer 2 is large, for example, fault detection of the reducer 2 can be reliably performed without being affected by an increase in the amount of initial wear powder in the reducer 2.

[0086] 8, the creepage distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62, which are set at the end of the cylindrical portion 63b of the attraction portion (insulator) 63C, is longer than that of the sensor 60B. Therefore, it is possible to increase the amount of conductive wear powder that is attracted until the resistance value between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 decreases to a threshold value or a short circuit occurs. As a result, even if the size of the reducer 2 is larger, it is possible to reliably detect a fault in the reducer 2 without being affected by an increase in the amount of initial wear powder in the reducer 2.

[0087] 8, the creepage distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62, which are set at the end of the cylindrical portion 63b of the attraction portion (insulator) 63D, is longer than that of the sensor 60C. Therefore, it is possible to increase the amount of conductive wear powder that is attracted until the resistance value between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 decreases to a threshold value or a short circuit occurs. As a result, even if the size of the reducer 2 is even larger, it is possible to reliably detect a fault in the reducer 2 without being affected by an increase in the amount of initial wear powder in the reducer 2.

[0088] In this way, by appropriately selecting from the group of suction parts (insulators) 63, it is possible to reliably detect faults in the reducer 2 without increasing the size of the sensor 60 or affecting other components. In other words, by using the same center electrode (inner electrode) 61, outer electrode (outer electrode) 62, magnet 64, case 65, and fastening member (fastening portion) 69, and replacing only the attraction portion (insulator) 63, a sensor 60 with different sensitivity can be produced.

[0089] In the above embodiment, the number of groups of the adsorption portions (insulators) 63 as the sensitivity adjusting means is four, but the number is not limited to four and can be set as appropriate.

[0090] The sensor 60 in this embodiment can be assembled as follows.

[0091] First, the outer electrode (outer electrode) 62 is set inside the case 65. Next, the bottom 63a of the attraction portion (insulator) 63 is placed on the bottom 62a of the outer electrode (outer electrode) 62. Next, the cylindrical portion 63b of the attraction portion (insulator) 63 having a selected height dimension is inserted into the outer electrode (outer electrode) 62. Next, the magnet 64 is inserted into the cylindrical portion 63b, and further, the center electrode (inner electrode) 61 is inserted. In this state, the sensor 60 is assembled by passing through and fastening / fixing the fastening member (fastening portion) 69.

[0092] The sensor 60 in this embodiment has a sensitivity adjustment means, which makes it possible to set the detection sensitivity to a predetermined state. Specifically, in response to the case where the expected amount of conductor wear powder to be generated is large, the sensitivity adjustment means can be selected to increase the creepage distance over which the wear powder is adsorbed between the electrodes 61 and 62, thereby setting the detection sensitivity of the sensor 60 to a predetermined state. In response to the case where the expected amount of conductor wear powder to be generated is small, the sensitivity adjustment means can be selected to decrease the length over which the wear powder is adsorbed between the electrodes 61 and 62, thereby setting the detection sensitivity of the sensor 60 to a predetermined state. This allows reliable detection of a fault in the reducer 2 without being affected by an increase in the amount of initial wear debris in the reducer 2.

[0093] The amount of iron powder (wear particles) generated by initial wear varies depending on the type (size) of the reducer, and in the case of large reducers, the amount of initial wear particles is large, which can fill the sensor's electrical gap between electrodes 61 and 62, causing a reaction and resulting in a malfunction. For this reason, it is necessary to design the sensor's electrical gap according to the reducer type, but this creates the problem of increasing the size of the sensor in the diametric direction. In contrast, the sensor 60 in this embodiment has a sensitivity adjustment means consisting of suction portions (insulators) 63 of different heights, which provides the same effect as stretching in the diameter direction, so the sensor 60 does not become larger.

[0094] A fourth embodiment of the sensor according to the present invention will be described below with reference to the drawings. 9 is a top view showing the sensor of this embodiment, and this embodiment differs from the third embodiment in terms of the suction portion and the outer electrode. Note that some components are omitted from the illustration of FIG.

[0095] As shown in FIG. 9, the sensor 60 in this embodiment has an approximately cylindrical outer shape, and includes a first electrode (inner electrode) 61, a magnet 64, a second electrode (outer electrode) 62, a fastening member (fastening portion) 69, an adsorption portion (insulator) 63, and a case 65. When viewed from the top of the sensor 60, the first electrode (inner electrode) 61 has a circular shape and is disposed in the center of the sensor 60. The second electrode (outer electrode) 62 is a cylindrical member with a bottom, and has a bottom 62a extending substantially parallel to the (inner electrode) 61, and a wall (tubular portion) 62b that is continuous with the bottom 62a and extends substantially perpendicular to the bottom 62a.

[0096] The magnet 64 has a substantially cylindrical shape (substantially disk shape) and is disposed between the first electrode (inner electrode) 61 and the bottom 62a of the second electrode (outer electrode) 62. The first electrode (inner electrode) 61, the magnet 64, and the bottom 628a of the second electrode (outer electrode) 62 each have a through-hole through which a fastening member (fastening portion) 69 (a bolt in the illustrated embodiment) is inserted. The first electrode (inner electrode) 61, the magnet 64, and the second electrode (outer electrode) 62 are fixed to one another by inserting the fastening member (fastening portion) 69 into the through-hole. The outer diameter of the magnet 64 is smaller than the outer diameter of the second electrode (outer electrode) 62.

[0097] The first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 are fixed and spaced apart from each other. The first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 are made of a conductive magnetic material, such as iron, a ferrite core, or silicon steel. The magnet 64 is, for example, a permanent magnet, but the first electrode (inner electrode) 61 may serve as both a magnet and an electrode without using a permanent magnet.

[0098] The adsorption portion (insulator) 63 is arranged to fill the space between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62, and is interposed between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62. The adsorption portion (insulator) 63 has a bottom portion 63a along the bottom portion 62a of the second electrode (outer electrode) 62, and a tubular portion 63b along the wall portion (tubular portion) 62b of the second electrode (outer electrode) 62. The bottom portion 63a and the tubular portion 63b are separate bodies. The bottom portion 63a is sheet-shaped.

[0099] The bottom 63a of the suction portion (insulator) 63 may be made of insulating paper with a thickness of 0.05 to 1 mm, for example. The bottom 63a of the suction portion (insulator) 63 may be made of a circular piece of paper with an outer diameter substantially the same as the inner diameter of the cylindrical portion 63b. Furthermore, the bottom portion 63a may be a circular piece of paper with an outer diameter larger than the inner diameter of the cylindrical portion 63b. In this case, the bottom portion 63a may be a circular piece of paper with an outer diameter smaller than the outer diameter of the cylindrical portion 63b. Furthermore, the bottom portion 63a may be a circular piece of paper with an outer diameter the same as the outer diameter of the cylindrical portion 63b.

[0100] A step 63c is formed on the inner surface of the cylindrical portion 63b of the attracting portion (insulator) 63. The cylindrical portion 63b of the attracting portion (insulator) 63 has an inner diameter dimension equal to the outer diameter of the first electrode (inner electrode) 61 on the first electrode (inner electrode) 61 side relative to the step 63c. The cylindrical portion 63b of the attracting portion (insulator) 63 has an inner diameter dimension equal to the outer diameter of the magnet 64 on the magnet 64 side relative to the step 63c.

[0101] The thickness of the end of the cylindrical portion 63b of the attracting portion (insulator) 63, i.e., the distance X1 between the wall portion 62b of the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62, is larger than the dimensions of the conductive material contained in the lubricating oil. As an example, the dimensions of the conductive material are approximately 1.0 μm to 100 μm, and it is preferable that the distance X1 be set to a distance that does not cause a short circuit due to initial wear iron powder. In the illustrated embodiment, the magnet 64 contacts the first electrode (inner electrode) 61 and is surrounded by the attracting portion (insulator) 63.

[0102] The attracting portion (insulating body) 63 is made of a non-magnetic material having insulating properties, such as resin. The magnet 64 forms magnetic flux lines between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62. As a result, conductive materials contained in the lubricating oil are accumulated around the attracting portion (insulating body) 63.

[0103] In the sensor 60 of this embodiment, the detection surface 60a is a plane connecting the ends of the second electrode (outer electrode) 62, which is substantially flush with the surface of the first electrode (inner electrode) 61. That is, on the detection surface 60a, conductive wear powder is attracted between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 in response to magnetic flux lines, electrically connecting the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62, thereby detecting a change in the resistance value between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62.

[0104] As the creepage distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 increases, the amount of conductor wear powder that is attracted increases until the resistance value between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 decreases to a threshold value or a short circuit occurs. In addition, by shortening the creepage distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62, the amount of conductor wear powder that is attracted decreases until the resistance value between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 decreases to a threshold value or a short circuit occurs.

[0105] The sensor 60 of this embodiment has a sensitivity adjusting means for adjusting the state of adsorption of conductor wear powder to change the detection sensitivity. In this embodiment, the sensitivity adjustment means is the adsorption portion (insulator) 63. Furthermore, in this embodiment, the sensitivity adjustment means is the cylindrical portion 63b of the adsorption portion (insulator) 63, the outer electrode (outer electrode) 62, and the case 65.

[0106] The adsorption portion (insulator) 63 of this embodiment can adjust the amount of adsorbed conductor wear powder by adjusting the surface distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 formed by the large diameter conductor piece. Specifically, as shown in FIG. 9, the cylindrical portion 63b of the attraction portion (insulator) 63 has a group in which the radial thickness is changed. The sensor 60E in FIG. 9 has an adsorption portion (insulator) 63E that has a distance X1 between the first electrode (inner electrode) 61 and the wall portion 62b of the second electrode (outer electrode) 62 on the detection surface 60a, i.e., a thickness X1 of the end portion of the tubular portion 63b on the detection surface 60a. The sensor 60E also has an outer electrode (outer electrode) 62E having a diameter corresponding to the suction portion (insulator) 63E, and a case 65E.

[0107] The sensor 60F in Figure 9 has an adsorption portion (insulator) 63F that has a distance X2 between the first electrode (inner electrode) 61 and the wall portion 62b of the second electrode (outer electrode) 62 on the detection surface 60a, i.e., a thickness X2 of the end of the tubular portion 63b on the detection surface 60a. The sensor 60F also has an outer electrode (outer electrode) 62F having a diameter corresponding to the suction portion (insulator) 63F, and a case 65F. The sensor 60G in FIG. 9 has an adsorption portion (insulator) 63G that has a distance X3 between the first electrode (inner electrode) 61 and the wall portion 62b of the second electrode (outer electrode) 62 on the detection surface 60a, i.e., a thickness X2 of the end of the tubular portion 63b on the detection surface 60a. The sensor 60G also has an outer electrode (outer electrode) 62G having a diameter corresponding to the suction portion (insulator) 63G, and a case 65G.

[0108] Here, the relationship between thicknesses X1, X2, and X3 is: X1 <X2<X3 is set as:

[0109] The sensor 60 of this embodiment has a group of cylindrical portions 63b of the suction portion (insulator) 63 set to such different values, and can be assembled by selecting from among these. That is, a group of cylindrical portions 63b of a plurality of suction portions (insulators) 63 having different thicknesses (diameter dimensions) constitutes a sensitivity adjusting means. This allows the creepage distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62 to be selected from a plurality of values by selecting the sensitivity adjustment means.

[0110] Here, in the sensor 60E of Figure 9, the creepage distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62E set at the end of the cylindrical portion 63b of the adsorption portion (insulator) 63E is used as a reference.

[0111] 9, the creepage distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62F, which is set at the end of the cylindrical portion 63b of the attraction portion (insulator) 63F, is longer than the reference distance. Therefore, the amount of conductive wear debris that is attracted can be increased until the resistance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62F decreases to the threshold value or a short circuit occurs. This allows reliable fault detection of the reducer 2, for example, even if the reducer 2 is large in size, without being affected by an increase in the amount of initial wear debris in the reducer 2.

[0112] 9, the creepage distance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62G, which are set at the end of the cylindrical portion 63b of the attraction portion (insulator) 63G, is longer than that of the sensor 60F. Therefore, the amount of conductive wear powder that can be attracted can be increased until the resistance between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62G decreases to a threshold value or a short circuit occurs. As a result, even if the size of the reducer 2 is larger, fault detection of the reducer 2 can be reliably performed without being affected by an increase in the amount of initial wear powder in the reducer 2.

[0113] In this way, by appropriately selecting from the group of attraction portions (insulators) 63, it is possible to reliably detect faults in the reducer 2 without increasing the axial size of the sensor 60 and without affecting the center electrode (inner electrode) 61, magnet 64, or fastening member (fastening portion) 69. In other words, by replacing the suction portion (insulator) 63, the outer electrode (outer electrode) 62, and the case 65 while keeping these components common, it is possible to obtain sensors 60 with different sensitivities.

[0114] In the above embodiment, the groups of the adsorption portions (insulators) 63 as the sensitivity adjusting means are three types, but the present invention is not limited to this and can be set as appropriate.

[0115] The sensor 60 in this embodiment can be assembled as follows.

[0116] First, the outer electrode (outer electrode) 62 is set inside the case 65 having a selected diameter. Next, the bottom 63a of the attraction portion (insulator) 63 having a corresponding diameter is placed on the bottom 62a of the outer electrode (outer electrode) 62. Next, the cylindrical portion 63b of the attraction portion (insulator) 63 having the selected diameter is inserted into the outer electrode (outer electrode) 62. Next, the magnet 64 is inserted into the cylindrical portion 63b, and then the center electrode (inner electrode) 61 is inserted. In this state, the sensor 60 is assembled by passing through and fastening / fixing the fastening member (fastening portion) 69. The set of the case 65 having the selected diameter, the outer electrode (outer electrode) 62, and the suction portion (insulator) 63 can also be set in advance.

[0117] The sensor 60 in this embodiment has a sensitivity adjustment means, which makes it possible to set the detection sensitivity to a predetermined state. Specifically, in response to the case where the expected amount of conductor wear powder to be generated is large, the sensitivity adjustment means can be selected to increase the creepage distance over which the wear powder is adsorbed between the electrodes 61 and 62, thereby setting the detection sensitivity of the sensor 60 to a predetermined state. In response to the case where the expected amount of conductor wear powder to be generated is small, the sensitivity adjustment means can be selected to decrease the length over which the wear powder is adsorbed between the electrodes 61 and 62, thereby setting the detection sensitivity of the sensor 60 to a predetermined state. This allows reliable detection of a fault in the reducer 2 without being affected by an increase in the amount of initial wear debris in the reducer 2.

[0118] A fifth embodiment of the sensor according to the present invention will be described below with reference to the drawings. Fig. 10 is a cross-sectional view showing the sensor of this embodiment, and this embodiment differs from the third and fourth embodiments in terms of the electrodes. Note that some components are omitted from Fig. 10.

[0119] As shown in FIG. 10, the sensor 60 in this embodiment has substantially the same configuration as the sensor 60 in the third and fourth embodiments. The sensor 60 in this embodiment has a sensitivity adjusting means for adjusting the state of adsorption of conductor wear powder to change the detection sensitivity.

[0120] In this embodiment, the sensitivity adjustment means includes a first electrode (inner electrode) 61 and a second electrode (outer electrode) 62. In this embodiment, a surface treatment layer 61h is formed on the first electrode (inner electrode) 61. In this embodiment, a surface treatment layer 62h is formed on the second electrode (outer electrode) 62.

[0121] Both of the surface treatment layers 61h and 62h have good slipperiness and non-stickiness, and also have conductive properties, low adhesion, smoothness, and lubricity. The surface treatment layers 61h and 62h can be formed by, for example, fluororesin composite electroless nickel plating, etc. Here, the fluororesin can be polytetrafluoroethylene particles or the like.

[0122] The surface treatment layers 61h, 62h can prevent sludge, which may reduce the amount of wear powder that can be adsorbed by the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62, from adhering to the first electrode (inner electrode) 61, the second electrode (outer electrode) 62 and the detection surface 60a, thereby reducing the amount of wear powder that can be adsorbed between the first electrode (inner electrode) 61 and the second electrode (outer electrode) 62. This makes it possible to set a predetermined state of detection sensitivity of the sensor 60. In Fig. 10, the state where sludge has adhered is indicated by a broken line.

[0123] If the surface treatment layers 61h, 62h were not provided, sludge generated by the lubricant would accumulate on the sensor electrodes, forming an insulating film that could cause malfunction. In contrast, in this embodiment, the surface treatment layers 61h, 62h are formed, and the improved slipperiness provided by the surface treatment layers 61h, 62h, along with the resulting improved flow of the lubricant, prevent the accumulation of sludge, and stable failure prediction operation of the sensor 60 can be expected.

[0124] A sixth embodiment of the sensor according to the present invention will be described below with reference to the drawings. FIG. 11 is a diagram illustrating the sensor in this embodiment. The sensor 60 according to this embodiment is a sensor for detecting the amount of conductive material contained in lubricating oil, similar to the sensor 30 according to the second embodiment described above.

[0125] The sensor 60 has a substantially cylindrical outer shape and includes a plurality of detection units and a detection section 70 that outputs a signal when the electrical resistance of the detection unit changes and prevents leakage of electricity. More specifically, the sensor 60 has a center electrode 61, a plurality of outer electrodes 62, an attraction portion 63 disposed between the center electrode 61 and the outer electrodes 62, and a magnet 64. The outer electrodes 62 are insulated from one another, and one detection unit is formed by a pair of electrodes consisting of the center electrode 61 and one outer electrode 62, and the attraction portion 63 disposed between the pair of electrodes.

[0126] In the illustrated embodiment, the sensor 60 has four outer electrodes 62A, 62B, 62C, and 62D, constituting four detection units. The number of outer electrodes 62 and the number of detection units are not particularly limited. The magnet 64 of the sensor 60 forms magnetic flux lines between the pair of electrodes, so that conductive materials contained in the lubricant are attracted to the attraction portion 63. In this way, when conductive materials accumulate near the attraction portion 63, the electrical resistance of the detection unit changes. When conductive wear particles are not attracted, the electrical resistance of each of the multiple detection units is the same.

[0127] An output line is connected to each of the central electrode 61 and the outer electrodes 62, and each of the detection units is electrically connected to the detection section 70 via the output line.

[0128] In this embodiment, the multiple detection units are connected in parallel with each other, and a voltage from the same voltage source is applied between the center electrode 61 and each of the outer electrodes 62. The detection unit 70 outputs a signal when the electrical resistance changes in any number of detection units that have been set. For example, the detection unit 70 may be set to output a signal to a higher-level control device such as a manipulator when the electrical resistance decreases in two or more detection units, or may be set to output a signal when the electrical resistance decreases in all detection units.

[0129] Alternatively, the detection section 70 switches between any of the detection units that have been set in order, and outputs a signal when the electrical resistance of the detection unit changes. Furthermore, as described above, the detection section 70 is set to output a signal when the electrical resistance in the detection unit decreases, and then turn off the detection power to the sensor 60.

[0130] Specifically, as described above, the detection unit 70 is set to output a signal to turn on a fault indicator when the electrical resistance in the detection unit decreases, and then turn off the switch 71 to turn off the detection power to the sensor 60. In other words, after the sensor 60 detects an increase in iron powder (a decrease in the resistance value of the gap) and determines that the reducer 2 has failed, it does not pass current.

[0131] This makes it possible to prevent electric leakage and electric shock even if wear debris continues to accumulate and the sensor 60 comes into contact with the reducer 2 or the mechanism 1. Therefore, even if the reducer 2 continues to be used after the sensor 60 notifies the reducer 2 of a fault, iron powder will continue to be generated inside the reducer 2 as it operates, and conductive wear powder will continue to accumulate on the sensor 60, causing the dimensions of the sensor 60 to expand due to the accumulation of iron powder. As a result, the sensor 60 and parts within the mechanism 1 will come into contact with each other and become electrically conductive due to the wear powder, which can prevent the risk of electric leakage or electric shock.

[0132] A seventh embodiment of the sensor according to the present invention will be described below with reference to the drawings. FIG. 12 is a diagram illustrating the sensor in this embodiment. The sensor 60 according to this embodiment is a sensor for detecting the amount of conductive material contained in lubricating oil, similar to the sensors 5, 30, and 60 in the above-described embodiments. 12, in the present embodiment, a cover 66 that covers the sensor 60 is provided in the space S. The sensor 60 is housed inside the cover 66, and a number of through holes 67 are formed in the cover 66 at positions facing the detection surface 60a of the sensor 60.

[0133] The through-hole 67 has an outer opening 67a on the space S side outside the cover 66 that is larger in diameter than an inner opening 67b on the surface side facing the sensor 60 inside the cover 66. In other words, when conductor wear powder enters the inside of the cover 66 from the space S, it passes through the through-hole 67 with a reduced diameter and reaches the sensor 60. The cover 66 is positioned so that the inner opening 67b of the through-hole 67 and the detection surface 60a of the sensor 60 are spaced apart. The interior of the cover 66 is sealed except for the through-hole 67.

[0134] As a result, even when the mechanism 1 and the reducer 2 are operating vigorously and the flow of lubricant is intense, the sensor 60 can be protected by the cover 66. This prevents conductor wear powder that has entered the cover 66 from being released again into the external space S, maintaining an accurate amount of adsorption and enabling reliable failure prediction. In addition, by preventing conductor wear powder from being released again from the cover 66, the impact on the mechanism 1 and the reducer 2 can also be reduced. The cover 66 may have an inner diameter that is approximately equal to the outer diameter of the sensor 60 when viewed in the axial direction of the sensor 60 .

[0135] Furthermore, according to this embodiment, in the early stages of operation of the reducer 2 when there is little wear powder, the cover 66 prevents a large amount of wear powder from being adsorbed to the sensor 60 at once, thereby preventing malfunction of the sensor 60. Furthermore, compared to the early stages of operation of the reducer 2 when there is little wear powder, if a large amount of wear powder is generated just before a failure of the reducer 2, sufficient wear powder will pass through the through-hole 67 and be adsorbed to the sensor 60, making it possible to detect this.

[0136] In the present invention, it is also possible to combine the individual configurations in the above-described embodiments as appropriate.

[0137] Furthermore, in the sensor of the present invention, the sensitivity adjusting means can have a group of the insulators having different axial heights relative to the opening of the outer electrode. This makes it possible to select from insulators having a plurality of axial heights and set the detection sensitivity of the sensor to a predetermined state in accordance with the expected amount of conductor wear powder to be generated. Specifically, when the expected amount of conductor wear powder is large, an insulator with a high axial height is selected to increase the length over which the wear powder is adsorbed between the electrodes, making it possible to set the sensor detection sensitivity to a predetermined state.Also, when the expected amount of conductor wear powder is small, an insulator with a low axial height or one flush with the electrodes is selected to reduce the length over which the wear powder is adsorbed between the electrodes, making it possible to set the sensor detection sensitivity to a predetermined state.

[0138] In the sensor of the present invention, the sensitivity adjustment means may have a group consisting of a set of insulators having different radial thicknesses adjacent to the opening of the outer electrode relative to the outer diameter of the inner electrode and outer electrodes corresponding to the outer diameters of the insulators. This makes it possible to select from insulators having a plurality of radial thicknesses and set the detection sensitivity of the sensor to a predetermined state according to the expected amount of conductor wear powder generated. Specifically, when the expected amount of conductor wear powder is large, an insulator with a large radial thickness is selected to increase the length over which the wear powder is adsorbed between the electrodes, thereby enabling the sensor detection sensitivity to be set to a predetermined state.Also, when the expected amount of conductor wear powder is small, an insulator with a small radial thickness is selected to decrease the length over which the wear powder is adsorbed between the electrodes, thereby enabling the sensor detection sensitivity to be set to a predetermined state.

[0139] In the sensor of the present invention, the outer electrode may have an open end that is flush with the inner electrode.

[0140] In the sensor of the present invention, the sensitivity adjusting means may have a separate magnet provided in addition to the magnet. Even in this case, it is possible to select from a group of separate magnets having a plurality of attraction amounts, or to not provide a separate magnet. This allows the amount of wear powder adsorbed between the electrodes to be reduced by using a separate magnet to adsorb the wear powder in accordance with the expected amount of conductor wear powder generated, thereby making it possible to set the detection sensitivity of the sensor to a predetermined state. Specifically, when the expected amount of conductor wear powder is large, a strong or large separate magnet is selected to reduce the amount of wear powder attracted between the electrodes, and the sensor detection sensitivity can be set to a predetermined state.Also, when the expected amount of conductor wear powder is small, a weak or small separate magnet is selected, or no separate magnet is provided, so that the amount of wear powder attracted between the electrodes is set to a predetermined amount, and the sensor detection sensitivity can be set to a predetermined state.

[0141] In the sensor of the present invention, the sensitivity adjusting means may have a surface treatment layer on the outer electrode and the inner electrode. This prevents sludge, which may reduce the amount of wear powder that can be adsorbed, from adhering to the adsorption surface of the electrodes, reducing the amount of wear powder adsorbed between the electrodes and resulting in a loss of the required detection sensitivity. Specifically, the surface treatment layer may have electrical conductivity, low adhesion, smoothness, and lubricity.

[0142] In the sensor of the present invention, the sensitivity adjusting means may be a cover that covers at least a pair of electrodes and the suction portion disposed between the pair of electrodes. [Explanation of symbols]

[0143] 2...Reducer 5, 30, 60...sensor 6, 61...First electrode (inner electrode) 8,62...Second electrode (outer electrode) 9,69... Fastening member (fastening part) 10,63...Adsorption part (insulator) 7,64...Magnet 10a, 11, 12a, 12b, 12c, 15...Short circuit suppression section 14...Wire 31...Center electrode 32(32A,32B,32C)...Outer electrode 50, 70...Detection unit 60a...Detection surface 61h, 62h...Surface treatment layer 66...Cover

Claims

1. It has a cylindrical shape a first electrode on a circular end face of the cylinder as viewed in the axial direction; a cylindrical second electrode having an end flush with a surface of the first electrode at a radially outer side of the cylinder of the first electrode; an adsorption section that is disposed between the first electrode and the second electrode, has insulating properties, has the same surface as a detection surface that connects end portions of the first electrode and the second electrode, and adsorbs conductive particles that are smaller than the gap between the first electrode and the second electrode, thereby changing the electrical resistance between the first electrode and the second electrode along the detection surface; a short-circuit prevention portion that prevents a short circuit between the first electrode and the second electrode due to a large-diameter conductor piece having a dimension larger than the gap between the first electrode and the second electrode; Equipped with the short circuit prevention portion is a protruding portion that protrudes from the detection surface in the axial direction along a periphery of the first electrode and is provided on at least one of the first electrode and the second electrode and has insulating properties; the adsorption portion and the protrusion are arranged side by side in a radial direction of the cylinder when viewed from a normal direction of an end face of the first electrode or the second electrode on which the protrusion is arranged. A sensor characterized by:

2. The sensor according to claim 1 , further comprising a detection unit that detects a change in electrical resistance between the first electrode and the second electrode.

3. The short circuit prevention portion has a cylindrical width in a radial direction that is the same as the distance between the first electrode and the second electrode. The sensor of claim 1 .

4. When viewed in the axial direction of the cylinder, the short circuit prevention portion has an annular shape and is formed so as to surround the entire periphery of the first electrode. The sensor of claim 1 .

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