Gear Fault Detection System

Abstract

To provide a technique that can accurately detect an abnormality in a gear despite low performance of a sensor.SOLUTION: A gear failure detection system comprises: a pulse generation unit that generates one pulse every time a shaft provided with a gear makes one rotation; an acceleration sensor that is provided on a bearing part rotatably supporting the shaft, and after the pulse generation unit generates the pulse, measures an instantaneous value of acceleration resulting from vibration of the bearing part for a predetermined time shorter than the time required for one rotation of the shaft from a measurement starting time point; a measurement starting time point changing unit that changes the measurement starting time point every measurement of the acceleration for the predetermined time conducted by the acceleration sensor; a storage unit that stores a plurality of instantaneous values of the acceleration measured by the acceleration sensor while the shaft rotates multiple times; and a failure determination unit that determines a failure of the gear based on the plurality of instantaneous values of the acceleration measured by the acceleration sensor while the shaft rotates multiple times.SELECTED DRAWING: Figure 13

Description

Technical Field

[0001] The present invention relates to a gear fault detection system for detecting faults in gears.

Background Art

[0002] Various types of fatigue can occur in gears, and natural wear corresponding to the usage time and the like can also occur. Generally, even without damage, gears generate vibrations due to changes in meshing stiffness and other reasons over time. The occurrence of vibrations increases due to the presence of damage.

[0003] In a gear transmission mechanism, the vibrations of the gears are transmitted to the case of the gear transmission mechanism through the shafts and bearings that support the gears. As a device for detecting abnormalities in the gears of a gear transmission mechanism, there is the device of Patent Document 1. The device of Patent Document 1 has an acceleration sensor that detects vibrations generated when two gears mesh. The acceleration sensor is fixed to the casing of the transmission.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When gears mesh, part of the vibration energy generated is radiated to the outside as audible noise from the case that houses the gears. Along the transmission path of this audible noise, the vibration originally excited by the meshing is affected by the vibration transmission path specific to the case as it travels from the vibration excitation point to the pickup point (the installation position of the acceleration sensor). Therefore, the vibration characteristics measured at the pickup point are different from those of the vibration at the excitation point. This is due to the rigidity and mass characteristics of the objects present in the transmission path and attenuation, which change the vibration time series with respect to the changed amplitude and phase across the entire frequency band.

[0006] In the configuration disclosed in Patent Document 1, since the acceleration sensor is attached to the casing of the speed increaser, the vibration generated when two gears (gear pair) mesh is transmitted to the acceleration sensor via the casing of the speed increaser. The vibration reaching the acceleration sensor is affected by the vibration transmission path specific to the casing, so the vibration measured by the acceleration sensor may have different vibration characteristics compared to the vibration at the vibration generation location (meshing gear pair). Also, with the configuration of Patent Document 1, it is not possible to detect abnormalities in individual teeth of the gears. Also, it is expected that the higher the performance of the sensor, the higher the diagnostic accuracy, but high-performance sensors are expensive.

[0007] Therefore, an object of the present invention is to provide a technique capable of accurately detecting gear abnormalities even with a low-performance sensor.

Means for Solving the Problems

[0008] According to an aspect of the present invention, there is provided a gear fault detection system for detecting a fault of a gear. This gear fault detection system includes a pulse generation unit that generates one pulse every time the shaft provided with the gear makes one revolution, a bearing unit that rotatably supports the shaft, and after the pulse generation unit generates a pulse, an acceleration sensor that measures an instantaneous value of acceleration caused by vibration of the bearing unit for a predetermined time shorter than the time required for one revolution of the shaft from the start of measurement, a measurement start time change unit that changes the measurement start time every time the acceleration sensor measures the acceleration for a predetermined time, a storage unit that stores a plurality of instantaneous values of the acceleration measured by the acceleration sensor while the shaft rotates a plurality of times, and a fault determination unit that determines a fault of the gear based on the plurality of instantaneous values of the acceleration measured by the acceleration sensor while the shaft rotates a plurality of times.

Advantages of the Invention

[0009] In one aspect of the present invention, a large number of instantaneous values of the acceleration measured by the acceleration sensor are accumulated while the shaft rotates a plurality of times. The fault location of the gear is detected as an abnormality in acceleration at any angular position within the angular range of 360°, and in multiple rotations of the shaft, the abnormality in acceleration corresponding to the fault location of the gear is repeatedly measured. In one aspect of the present invention, by changing the measurement start time of the acceleration sensor every time the acceleration sensor measures the acceleration for a predetermined time, the acceleration sensor measures instantaneous values corresponding to different angles of the shaft every time the acceleration is measured for a predetermined time. By doing so, overlapping of the measurement start points can be prevented, and instantaneous values of the measured acceleration corresponding to a large number of angles of the shaft can be accumulated while the shaft rotates a plurality of times. By using such a large number of instantaneous values of the measured acceleration, the fault of the gear can be accurately determined.

Brief Description of the Drawings

[0010]

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DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, various embodiments of the present invention will be described with reference to the accompanying drawings. The scales of the drawings are not necessarily accurate, and some features may be exaggerated or omitted.

[0012] The gear fault detection system of this embodiment monitors the state of gears and detects gear faults. The gear fault detection system of this embodiment is configured to monitor gears using a self-powered bearing with a sensor (bearing device) and evaluate the vibration signal of each tooth of the gear. The bearing device used in this embodiment has functions of self-power generation, sensing, and wireless transmission in addition to the original function of the bearing to rotatably support a shaft. That is, the bearing device is a device that supports a shaft and also has a function as a sensor device (measurement device). Since the sensor device can also be referred to as a measurement device, the rolling bearing with a sensor may be referred to as a bearing with a measurement device.

[0013] In the following description, the gear transmission mechanism may be referred to as a gearbox. Also, in this embodiment, for simplicity of explanation, a gear transmission mechanism of a simple single-stage gear mechanism is exemplified as the gear transmission mechanism. The scope of the present invention is not limited to the following embodiments, and changes and modifications can be made within the scope of the technical idea of the present invention.

[0014] FIG. 1 shows a gear fault determination device 10 and a gear transmission mechanism 20 according to an embodiment of the present invention. The gear transmission mechanism 20 has a housing 21, a first gear 22 and a second gear 23 provided in the housing 21. The housing 21 has a first wall 21a and a second wall 21b that face each other with a space therebetween. The first gear 22 and the second gear 23 mesh with each other. Further, the gear transmission mechanism 20 has a first shaft 24a to which the first gear 22 is attached, and a first bearing 25 and a second bearing 26 that support both ends of the first shaft 24a. The first bearing 25 is provided on the first wall 21a of the housing 21. The second bearing 26 is provided on the second wall 21b of the housing 21.

[0015] Further, the gear transmission mechanism 20 has a second shaft 24b to which a second gear 23 is attached, and a third bearing 27 and a fourth bearing 28 that support both ends of the second shaft 24b. The third bearing 27 is provided on a first wall 21a of the housing 21 below the first bearing 25. The fourth bearing 28 is provided on a second wall 21b of the housing 21 below the second bearing 26. In the present embodiment, the first bearing 25 to the fourth bearing 28 may be rolling bearings, for example, tapered roller bearings or deep groove ball bearings.

[0016] In the present embodiment, among the four bearings 25 to 28, only one bearing (for example, the first bearing 25) is a bearing device with a measuring device incorporating the measuring device 100 (FIG. 3). The measuring device 100 measures vibrations generated by the meshing of the first gear 22 and the second gear 23. Further, the measuring device 100 also detects the rotational angle position of the first bearing 25 (the rotational angle position of the first shaft 24a). The measuring device 100 has a communication function and can perform wireless communication with the gear failure determination device 10. Furthermore, the measuring device 100 also includes a power generation unit 149 (FIG. 8). The gear failure determination device 10 detects a failure of the first gear 22 based on the signal received from the measuring device 100 of the first bearing 25. In the present embodiment, the gear failure detection system 30 is constituted by the gear failure determination device 10 and the measuring device 100. Since the first bearing 25 includes the measuring device 100, it may also be referred to as a bearing device.

[0017] FIG. 2 is a block diagram showing the configuration of the gear failure determination device 10. As shown in FIG. 2, the gear failure determination device 10 has an input unit 11, a control unit 12, a storage unit 13, a display unit 14, and a communication unit 15. The gear failure determination device 10 may be, for example, a personal computer. The input unit 11 includes buttons, switches, a mouse, a touch panel, etc., and the user performs various inputs (for example, inputs the number of teeth of the first gear 22) via the input unit 11. The user uses the input unit 11 when operating the gear failure determination device 10. The input unit 11 may also be referred to as an operation unit.

[0018] The control unit 12 is composed of one or more CPUs (Central Processing Units) and MPUs (Microprocessor Units), and controls the operations of the input unit 11, the storage unit 13, the display unit 14, and the communication unit 15 of the gear failure determination device 10. The control unit 12 processes the signals received from the measurement device 10 to determine the failure of the gear (execute the failure determination process). The control unit 12 controls the gear failure determination device 10 or executes the gear failure determination process by executing the control program stored in the storage unit 13.

[0019] The storage unit 13 is composed of an HDD (Hard Disk Drive), a ROM (Read Only Memory), a RAM (Random Access Memory), and / or an IC (Integrated Circuit) memory card, etc., and stores various information such as the control program executed by the control unit 12 and the algorithm for generating a map (described later) representing the relationship between the angle and teeth of the first gear 22. The generation of the map is performed by the control unit 12 executing the control program stored in the storage unit 13. The storage unit 13 can store the data received from the measurement device 100. The display unit 14 is composed of a liquid crystal display, etc., and displays various data, numerical values, characters, images, etc. The display unit 14 can display the data received from the measurement device 100 on the display unit. Also, the display unit 14 can display the processing result of the gear failure determination process under the control of the control unit 12. The communication unit 15 performs wireless communication with the measurement device 100.

[0020] Figs. 3 and 4 are exploded perspective views showing the configuration of the first bearing 25. Fig. 3 is an exploded perspective view of the first bearing 25 as viewed from the left side. Fig. 4 is an exploded perspective view of the first bearing 25 as viewed from the right side. As shown in Fig. 3, the first bearing 25 has a measuring device 100 and a bearing portion 250. The measuring device 100 is attached to the left side surface of the bearing portion 250. The measuring device 100 includes a cover 110, a coil substrate 120 (Fig. 4), a rotating portion 130, a circuit board group 140 (Fig. 4), a storage battery (capacitor) 150, a retainer (not shown), and a Z-phase magnet unit 160. The retainer is a thin annular member and is located between the cover 110 and the Z-phase magnet unit 160. The circuit board group 140 is composed of a plurality of boards as will be described later.

[0021] The rotating portion 130 is attached to the first shaft 24a and rotates together with the first shaft 24a. When the cover 110 is attached to the bearing portion 250, the cover 110 is attached to the outer ring 250A of the bearing portion 250. Therefore, the cover 110 does not rotate. The retainer is attached to the inner ring 250B of the bearing portion 250. By the retainer, the Z-phase magnet unit 160 is fixed to the inner ring 250B of the bearing portion 250. Therefore, the Z-phase magnet unit 160 rotates together with the inner ring 250B (and thus the first shaft 24a) of the bearing portion 250.

[0022] The cover 110 is an annular flat plate member and is formed of a magnetic material such as, for example, silicon steel sheet, carbon steel (JIS SS400 or S45C), martensitic stainless steel (JIS SUS420), or ferritic stainless steel (JIS SUS430). Since a sensor is attached to the cover 110, the cover 110 may be referred to as a sensor case.

[0023] On the surface of the cover 110 facing the bearing portion 250, as shown in FIG. 4, a coil substrate 120, a circuit board group 140, and a storage battery 150 are attached. The circuit board group 140 includes a power control board 141, an angle sensor board 142, and a control board 143. The power control board 141, the angle sensor board 142, and the control board 143 are fixed to the cover 110 by fastening bolts made of a non-magnetic material such as brass to female screw holes formed in the cover 110, for example. The bolts have a length that does not protrude from the cover 110 when attached to the cover 110.

[0024] The power control board 141 has a voltage sensor 152, a rectifying circuit 261, a smoothing circuit 262, a power management IC 263, and an FET 264 (Field Effect Transistor) as shown in FIG. 6. The circuits 261 to 263 and the FET 264 of the power control board 141 will be described later with reference to FIG. 6.

[0025] A through hole 111 is formed in the cover 110, and the through hole 111 is sealed with a cover 117 made of a non-magnetic material such as resin. As will be described later, an antenna 147 (FIG. 5A) is mounted on the control board 143. Since the cover 110 has magnetism, it has the effect of shielding electromagnetic waves from the antenna 147. However, the antenna 147 is disposed at a position facing the cover 117, whereby the electromagnetic waves of the antenna 147 can reach the external gear failure determination device 10 through the non-magnetic cover 117. The coil substrate 120 is fixed to the cover 110 by an adhesive, for example.

[0026] FIG. 5A is a plan view showing a configuration example of a cover 110, a coil substrate 120, a circuit board group 140, and a storage battery 150. FIG. 5B is a view showing only the cover 110 and the coil substrate 120. As shown in FIG. 5B, the coil substrate 120 includes a flexible substrate 121, a coil pattern 123 provided on the flexible substrate 121, and a plurality of yokes 125 provided on the flexible substrate 121. Note that the installation of the yokes 125 is optional. The shape of the flexible substrate 121 in a plan view is a circular ring shape centered on the rotation center axis Ax. The coil pattern 123 includes a plurality of planar coils laminated in the thickness direction of the flexible substrate 121. A planar coil is a pattern of a conductor provided by patterning on a predetermined surface of an insulator. In the present embodiment, the pattern of the conductor is formed on a plurality of surfaces of the insulator. Note that the present invention is not limited to this, and the pattern of the conductor may be formed on one surface of the insulator. The number of turns of the coil pattern 123 is proportional to the number of layers of the planar coils. By changing the number of layers of the planar coils, the power generation amount can be adjusted.

[0027] Further, the coil pattern 123 is provided such that concavities and convexities are alternately arranged along the circumferential direction of a circle centered on the rotation center axis Ax in a plan view. One yoke 125 is disposed in each of the concave portions of the concavities and convexities. The coil pattern 123 may have a shape in which a part of the circle is missing in order to dispose an angle sensor at a position where a magnetic change of an encoder magnet described later can be detected.

[0028] As shown in FIG. 5A, the power supply control board 141, the angle sensor board 142, the control board 143, and the storage battery 150 are attached to the radially outer side of the coil substrate 120 in a plan view. The power supply control board 141 (more specifically, a power management IC 263 described later) includes two DC-DC converters (for step-down and step-up), steps down the DC voltage supplied from the storage battery (capacitor) 150, and supplies the DC voltage to the angle sensor board 142 and the control board 143.

[0029] An angle sensor substrate 142 is mounted with an angle sensor 443 and a Z-phase detector (pulse generation unit) 444. As will be described later, the angle sensor 443 used in the present embodiment is a low-performance acceleration sensor with low resolution and low sampling frequency. The Z-phase detector 444 is, for example, a Hall IC. The Z-phase detector 444 generates one pulse every time a Z-phase magnet 162 that is stationary with respect to the inner ring 250B of the first bearing 25 and rotates together with the inner ring 250B passes near the Z-phase detector 444. That is, the Z-phase detector 444 generates one pulse every time the inner ring 250B of the first bearing 25 makes one rotation (every time the first axis 24a makes one rotation). A control board 143 is mounted with a control circuit 145, an antenna 147, an acceleration sensor 441, and a temperature sensor 442. Note that the acceleration sensor 441, the temperature sensor 442, the angle sensor 443, the control circuit 145, and the antenna 147 may be composed of separate IC chips, or some or all of them may be composed of one IC chip. The temperature sensor 442 is provided to detect the temperature at the time (or before detection) when the acceleration and the angle are detected. The acceleration sensor 441 used in the present embodiment is, for example, a MEMS (Micro Electro Mechanical Systems) acceleration sensor. Also, as shown in FIG. 5A, the acceleration sensor 441 used in the present embodiment is configured to measure acceleration values (acquire measured acceleration values) for each of the three axes (X / Y / Z axes) (that is, it is a three-axis acceleration sensor). As will be described later, the acceleration sensor 441 used in the present embodiment is a low-performance acceleration sensor with low resolution and low sampling frequency.

[0030] Both ends of the coil pattern 123 are connected to the power control board 141 via the extending part 116 provided at a predetermined position on the outer periphery of the coil board 120. Note that instead of the extending part 116, the coil board 120 and the power control board 141 may be connected by a lead wire. Alternatively, instead of the extending part 116, the coil board 120 and the power control board 141 may be connected by an FPC (Flexible Printed Circuit) connector. In the connection using the FPC connector, soldering is not required, so the productivity of the measuring device 100 can be improved.

[0031] Returning to FIGS. 3 and 4, the rotating part 130 includes an annular magnetic track 131, an annular base material 133, and an annular mounting jig 135. The base material 133 and the mounting jig 135 are preferably made of a magnetic metal material. The magnetic track 131 is provided on the left surface of the base material 133. The base material 133 has an opening. The mounting jig 135 is fixed to the right surface of the base material 133. The mounting jig 135 protrudes from the right surface of the base material 133 through the opening of the base material 133 to the left surface side of the base material 133. The left surface of the base material 133 is the surface facing the cover 110. Note that the magnetic track 131 may be configured to be detachable from the base material 133.

[0032] In the present embodiment, the magnetic track 131 and the base material 133 together are referred to as an encoder magnet. For example, the encoder magnet is formed by forming a plastic magnet on one surface of a metal base material 133, and alternately magnetizing N poles and S poles on the surface of the formed plastic magnet. The mounting jig 135 is a jig for attaching the encoder magnet (rotating part 130) to the first shaft portion 24a.

[0033] The magnetic track 131 has a plurality of magnetic pole pairs 311 each composed of an N pole 131N and an S pole 131S. The plurality of magnetic pole pairs 311 are arranged in the circumferential direction of the magnetic track 131. The N pole 131N and the S pole 131S are arranged alternately. The distance between the centers of adjacent N poles 131N and S poles 131S in the magnetic track 131 is the same as the distance between the centers of adjacent yokes 125 in the coil substrate 120 (see FIG. 5B).

[0034] In this embodiment, when the magnetic track 131 rotates relative to the coil substrate 120 about the rotation center axis Ax (FIG. 5B), when one of the adjacent yokes 125 faces the N pole, the other yoke 125 faces the S pole. Also, when one of the yokes 125 faces the S pole, the other yoke 125 faces the N pole. That is, the adjacent yokes 125 of the coil substrate 120 do not face the same magnetic pole of the magnetic track 131. As a result, the phase of the change in the magnetic flux density passing through one yoke 125 and the phase of the change in the magnetic flux density passing through the other yoke 125 are shifted by 180°.

[0035] In this way, when the magnetic track 131 rotates relative to the coil substrate 120, the magnetic poles facing the yoke 125 alternate. As a result, the magnetic flux density passing through the yoke 125 changes periodically. In response to this periodic change in the magnetic flux density, a voltage change (for example, an alternating voltage of a sine wave) is generated in the coil pattern 123 located around the yoke 125. That is, in this embodiment, when the inner ring 250B of the first bearing 25 rotates together with the first shaft 24a, power generation by electromagnetic induction is performed within the first bearing 25. This power generation is self-power generation. The combination of the encoder magnet (magnetic track 131) and the coil substrate 120 may be referred to as a power generation unit 149. The power generation unit 149 generates power based on the relative rotation between the outer ring 250A and the inner ring 250B of the first bearing 25. The DC voltage generated by the power generation unit 149 is stored in the storage battery 150.

[0036] The Z-phase magnet unit 160 has a Z-phase magnet holder 161 and a Z-phase magnet 162. The Z-phase magnet holder 161 is an annular member, and the Z-phase magnet 162 is embedded in a hole formed in the Z-phase magnet holder 161. The Z-phase magnet holder 161 is made of metal (for example, aluminum). When the Z-phase magnet unit 160 rotates once together with the first axis 24a, the Z-phase magnet 162 crosses the Z-phase detector 444 once. At this time, the Z-phase detector 444 generates one pulse.

[0037] FIG. 6 is a diagram schematically showing the above-described self-power generation mechanism. In FIG. 6, the coil C corresponds to a coil pattern 123 attached to a cover (metal case) 110, and the magnet M corresponds to an encoder magnet provided on the inner ring 250B of the first bearing 25. As shown in FIG. 6, electromagnetic induction occurs due to the relative rotation of the coil C and the magnet M, and power generation is performed. Since the generated current is alternating current, it is converted to direct current through a rectifier circuit 261. The rectifier circuit 261 is, for example, a diode bridge. Since the current converted by the rectifier circuit 261 may contain pulsating current, in the present embodiment, in order to be in a state closer to direct current, the output of the rectifier circuit 261 is connected to a smoothing circuit 262.

[0038] The direct current passing through the smoothing circuit 262 is input to a power management IC (battery control unit, charge completion detection unit) 263 and stored in a battery (capacitor) 150. The power management IC 263 includes two DC-DC converters (for step-down and step-up), and the minute power generated by a generator (the coil C and the magnet M in FIG. 6) is stepped up by the step-up DC-DC converter of the power management IC 263 and stored in the battery 150. The charging of the battery 150, the discharge during overcharging, and the power supply at the voltage Vcc to a load L (acceleration sensor 441, angle sensor 443, Z-phase detector 444, antenna 147) are managed by the power management IC 263. In order to prevent the control board 143 from running wild due to the inflow of an indefinite voltage, an FET 264 is provided between the power management IC 263 and the load L. Also, the power management IC 263 can switch between supplying and cutting off power to the load L by controlling the FET 264.

[0039] Since the power obtained by the rotation of the first axis 24a (relative rotation between the coil board 120 and the magnetic track 131) is extremely small, as the power management IC 263, for example, a power management IC used for energy harvesting that can store electricity even with a small amount of power is adopted (for example, the ultra-low power harvester power management IC - BQ25570 manufactured by Texas Instruments).

[0040] The storage battery 150 can store an amount of charge sufficient for at least one operation of the measuring device 100. One operation of the measuring device 100 is an operation from measuring the angular position and acceleration of the teeth of the gear for a predetermined time (for example, 25 ms) to transmitting the measurement result to the gear failure determination device 10. When the charging of the storage battery 150 is completed, the power management IC 263 detects the completion of the charging of the storage battery 150 and sends a charging completion signal notifying the FET 264 of the charging completion. Then, the storage battery 150 resumes power supply to the angle sensor board 142 and the acceleration sensor 441. Since the lower the ESR (Equivalent Series Resistance) of the storage battery 150, the greater the current that can be instantaneously extracted, it is preferable to adopt a storage battery with a low ESR. If a storage battery with a low ESR is not adopted, a capacitor or an all-solid-state battery that can be connected in parallel to the storage battery 150 may be provided. In this case, parallel connection may be made.

[0041] The voltage sensor 152 measures the voltage of the storage battery 150. When the voltage of the storage battery 150 measured by the voltage sensor 152 is lower than a predetermined threshold value, the power management IC 263 cuts off the power supply to the angle sensor substrate 142 having the Z-phase detector 444 and the angle sensor 443 and the acceleration sensor 441. Cutting off the power supply to the angle sensor substrate 142 and the acceleration sensor 441 is called "Sleep". During the sleep state, the power management IC 263 charges the storage battery 150. When the voltage of the storage battery 150 measured by the voltage sensor 152 exceeds the threshold value by charging, the power management IC 263 resumes the power supply to the angle sensor substrate 142 having the Z-phase detector 444 and the angle sensor 443 and the acceleration sensor 441. Resuming the power supply to the angle sensor substrate 142 and the acceleration sensor 441 is called "Wake-up". The threshold value for sleep and the threshold value for Wake-up are different. Note that the voltage sensor 152, the rectifier circuit 261, the smoothing circuit 262, the power management IC 263, and the FET 264 may be collectively referred to as a circuit group 431 (FIG. 8).

[0042] FIG. 7 shows two graphs for explaining the operation of the power management IC 263. The vertical axis of the upper graph in FIG. 7 indicates the voltage of the storage battery 150 measured by the voltage sensor 152, and the horizontal axis indicates time. The vertical axis of the lower graph indicates the charge completion signal. The vertical axis of this graph indicates the intensity (High or Low) of the signal, and the horizontal axis indicates time. When the charge completion signal is Low (low), the charging of the storage battery 150 is not completed (charging). When the charge completion signal is High (high), the storage battery 150 is in a state of supplying power. When the charge completion signal transitions from High to Low, it represents that the storage battery 150 has stopped (ended) power supply and has entered a charging state. The charge completion signal is a signal generated by the power management IC 263. By combining the two graphs in FIG. 7, it can be seen what kind of management (control) the power management IC 263 performs on the voltage of the storage battery 150.

[0043] As shown in Fig. 7, when the charge completion signal is Low, as time elapses, the charge amount of the storage battery 150 increases, and the charge completion signal becomes High at time t1. The voltage of the storage battery 150 at time t1 is V2. The voltage V2 is a threshold value for restarting power supply to the angle sensor substrate 142 and the acceleration sensor 441, that is, a threshold value for Wake-up. After time t1 (after starting power supply to the load L), when the power consumption of the load L is greater than the power generation amount, the voltage decreases from V2 (solid line J1). When the voltage decreases and reaches V1, the power management IC 263 stops power supply to the angle sensor substrate 142 and the acceleration sensor 441. That is, V1 is a threshold value for sleep. During the sleep state, the power management IC 263 charges the storage battery 150. V1 has a value equal to or slightly larger than Vcc. This is because if V1 is smaller than Vcc, the boost DC-DC converter of the power management IC 263 will stop functioning.

[0044] After time t1, when the power consumption of the load L is equal to the power generation amount, the voltage maintains V2 (two-dot chain line J2). After time t1, when the power consumption of the load L is smaller than the power generation amount, the voltage rises from V2 (one-dot chain line J3). When the power rises and reaches V3, the power management IC 263 stops charging the storage battery 150. This is to prevent overcharging.

[0045] In this embodiment, the storage battery 150 can store the charge amount required for one operation of the measuring device 100. Under normal conditions, the voltage of the storage battery 150 changes as shown by the solid line J1 in Fig. 7. And during the time from time t1 when the voltage drops from V2 to V1 to time t2, the measuring device 100 can perform one operation. The time from time t1 to time t2 is the time when the storage battery 150 can supply power to the load L (acceleration sensor 441, angle sensor 443, Z-phase detector 444, and antenna 147), and the measurement of acceleration and angle and the transfer of the measured data are performed during the time from time t1 to time t2.

[0046] FIG. 8 is a block diagram showing the configuration of the measuring device 100. As described above, the measuring device 100 includes a power control board 141, an angle sensor board 142, and a control board 143. The angle sensor board 142 includes a sensor board 170 and a Z-phase detector board 171. The power control board 141 includes a circuit group 431. The circuit group 431 includes the voltage sensor 152, the rectifier circuit 261, the smoothing circuit 262, the power management IC 263, and the FET 264 shown in FIG. 6. The circuit group 431 is connected to the storage battery 150 and the power generation unit 149.

[0047] The power generation unit 149 includes a magnetic track 131 (FIG. 4) and a coil board 120 (FIG. 5B). The power generation unit 149 generates power based on the relative rotation between the outer ring 250A and the inner ring 250B of the bearing unit 250, and supplies power to the angle sensor board 142 and the like. The power generation unit 149 generates single-phase AC power and outputs it to the circuit group 431. The rectifier circuit 261 of the circuit group 431 full-wave rectifies the single-phase AC power generated by the power generation unit 149 and converts it into DC power. The DC power output from the rectifier circuit 261 is smoothed by the smoothing circuit 262 into stable power. The power is then stored in the storage battery 150 via the power management IC 263 (boosted by the boost DC-DC converter of the power management IC 263). The DC power stored in the storage battery 150 is supplied to the angle sensor board 142 and the control board 143 via the power management IC 263 (stepped down by the buck DC-DC converter of the power management IC 263) at the timing of measurement.

[0048] An angle sensor 443 is mounted on the sensor board 170. A Z-phase detector 444 is mounted on the Z-phase detector board 171. An acceleration sensor 441, a temperature sensor 442, a microcomputer (hereinafter referred to as "microcontroller") 451, an external memory 452, and a wireless module (transmission unit) 453 are mounted on the control board 143. The microcontroller 451, the external memory 452, and the wireless module 453 are included in the control circuit 145 (FIG. 5).

[0049] The acceleration sensor 441, the temperature sensor 442, and the angle sensor 443 detect acceleration, temperature, and rotation angle (position), respectively, using the DC power supplied from the power control board 141. For example, the angle sensor 443 is mounted on the sensor board 170 so as to be located on the side of the magnetic track 131. The rotating part 130 having the magnetic track 131 is fixed to the inner ring 250B of the bearing part 250, and the angle sensor 443 detects the magnetic flux density that changes as the magnetic track 131 rotates together with the inner ring 250B of the bearing part 250, thereby detecting the rotation angle of the inner ring 250B with respect to the outer ring 250A of the bearing part 250. The angle sensor 443 is a magnetic rotary encoder. The angle sensor 443 may have one reader for reading the rotation of the magnetic track 131, or may have a plurality of readers each of which reads the rotation of the magnetic track 131. In the present embodiment, the angle sensor 443 has 25 readers arranged at equal angular intervals around the axis of the shaft 24a, and each reader reads the rotation of the magnetic track 131. Therefore, the readers output similar reading values that are 14.4° apart from the reading values of the adjacent readers. The angle sensor 443 may be an absolute type, but in the present embodiment, an incremental type and a pseudo-absolute method using the Z-phase detector 444 are used.

[0050] The microcomputer 451 includes a CPU 455, a DMA (Direct Memory Access) controller 456, and an internal memory 457. The microcomputer 451 writes the measurement values acquired from the acceleration sensor 441 and the angle sensor 443 into the internal memory 457 and the external memory 452. The DMA controller is described as DMAC in the drawings. The external memory 452 is used as an auxiliary when the storage capacity of the internal memory 457 is insufficient for the data of the measurement values acquired from the acceleration sensor 441 and the angle sensor 443. Therefore, the external memory 452 is not absolutely necessary. Hereinafter, the internal memory 457 and the external memory 452 may be referred to as the storage unit 230.

[0051] Also, when the acceleration sensor 441 has a large-capacity FIFO (first in, first out) buffer and the angle sensor 443 has a large-capacity FIFO buffer, the DMA controller 456, the internal memory 457, and the external memory 452 may be omitted. In this case, the data of the measured values of the acceleration sensor 441 can be accumulated in the FIFO buffer of the acceleration sensor 441, and the data of the measured values of the angle sensor 443 can be accumulated in the FIFO buffer of the angle sensor 443. The clock for data transfer to the internal memory 457 and the external memory 452 and the DMA controller 456 are not required, and the power consumption can be reduced.

[0052] The CPU 455 initializes the storage unit 230, the acceleration sensor 441, the temperature sensor 442, and the angle sensor 443, and performs the initial setting of the DMA controller 456. When a DMA trigger (INT signal from the acceleration sensor 441) is input, the DMA controller 456 starts a DMA transfer. Specifically, when a DMA trigger is input, the DMA controller 456 transfers the latest measured values (a plurality of discrete instantaneous values described later) held by the acceleration sensor 441 and the angle sensor 443 to the storage unit 230 (the internal memory 457 and the external memory 452 as necessary) without conversion as raw data, bypassing the CPU 455. The acceleration sensor 441 and the angle sensor 443 update and hold the measured values (a plurality of discrete instantaneous values) at predetermined update periods, respectively. When the acceleration sensor 441 is a MEMS acceleration sensor, the update period is the ODR (Output Data Rate) of the MEMS acceleration sensor. The acceleration sensor 441 generates an INT signal (interrupt signal) each time it becomes capable of data output, and the INT signal is input to the DMA controller 456 as a trigger. The update period (sampling period) will be described later with reference to FIG. 10.

[0053] The wireless module 453 transmits the data stored in the storage unit 230 to the gear fault determination device 10 under the control of the CPU 455. The wireless module 453 includes an antenna 147 (Fig. 5A). For example, the wireless module 453 transmits data to the gear fault determination device 10 by wireless communication such as BLE. BLE is the abbreviation of Bluetooth (registered trademark) Low Energy. The transmitted data is received by the communication unit 15 of the gear fault determination device 10 and processed by the control unit 12 of the gear fault determination device 10. When using BLE, the data is transmitted, for example, one packet at a time. If you want to increase the throughput, you may use More data or Data Length Extension. Alternatively, the throughput can also be increased by adopting PHY 2Mbps defined in BLE 5.x.

[0054] When the first bearing 25 and the gear fault determination device 10 perform wireless communication, wireless communication conforming to a communication standard other than BLE may be performed. For example, Zigbee (registered trademark) or Thread may be adopted. Alternatively, a frequency band different from BLE (for example, 920 MHz band specific low power radio) may be used.

[0055] Each time the acceleration measurement by the acceleration sensor 441 for a predetermined time and the angle measurement by the angle sensor 443 for a predetermined time are completed, the power management IC 263 in the circuit group 431 cuts off the power supply to the acceleration sensor 441, the angle sensor 443, and the Z-phase detector 444, and puts them into a sleep state. Preferably, after the wireless module 453 performs BLE wireless communication of the instantaneous value measured by the acceleration sensor 441 and the instantaneous value measured by the angle sensor 443, the power management IC 263 cuts off the power supply to the load L (acceleration sensor 441, angle sensor 443, Z-phase detector 444, and antenna 147), and puts them into a sleep state. However, even in the sleep state, the power management IC 263 continues to supply power to the microcomputer 451, the external memory 452, and the wireless module 453. Therefore, while the power management IC 263 stops supplying power to the load L by the battery 150 and charges the battery 150, the wireless module 453 holds the pairing information for wireless communication between the communication unit 15 of the gear failure determination device 10, and the CPU 455 of the microcomputer 451 holds various setting information (for example, the supply time point of the immediately preceding measurement start signal described later). Further, when the power management IC 263 detects the completion of charging the battery 150 (when the voltage measured by the voltage sensor 152 exceeds the threshold value V2), it resumes power supply to the load L.

[0056] FIG. 9 is a timing chart for explaining the operation of the measuring device 100. FIG. 9(A) shows the period of power supply by the power management IC 263, and FIG. 9(B) shows the period during which the measuring device 100 connects to the gear failure determination device 10 via a wireless network (BLE). FIG. 9(C) shows the pulse output by the Z-phase detector 444, and FIG. 9(D) shows the measured acceleration value output by the acceleration sensor 441, which is the measured acceleration value stored from the acceleration sensor 441 in the storage unit 230. FIG. 9(E) shows the measured angle value output by the angle sensor 443, which is the measured angle value stored from the angle sensor 443 in the storage unit 230. When the power is turned on, the power management IC 263 starts supplying power from the battery 150 to the microcomputer 451 and the antenna 147 of the wireless module 453. Then, the CPU 455 of the measuring device 100 controls the wireless module 453 to exchange information necessary for wireless communication with the communication unit 15 of the gear failure determination device 10 and establish a connection. That is, the measuring device 100 pairs with the gear failure determination device 10. The "pairing time" is the time required for the measuring device 100 to establish communication (connection) with the gear failure determination device 10. The pairing time is, for example, 5 seconds. "Pairing completion" indicates the time point when the BLE connection is established. After pairing completion, the power management IC 263 also starts supplying power from the battery 150 to the acceleration sensor 441, the angle sensor 443, and the Z-phase detector 444.

[0057] In this embodiment, the output of the Z-phase detector 444 is active low. When the Z-phase detector 444 detects the Z-phase magnet 162, it outputs a low signal. However, in FIG. 9(C), the pulse output when the Z-phase detector 444 detects the Z-phase magnet 162 is shown at a high level. In FIG. 9, the "sensor preparation time" is the time to wait until the Z-phase detector 444, the acceleration sensor 441, and the angle sensor 443 can accurately measure after the power supply to the acceleration sensor 441, the angle sensor 443, and the Z-phase detector 444 starts. For example, it is 50 ms. The "processing waiting time" is set to be longer than the time required for the CPU 455 to complete a predetermined monitoring process. The processing waiting time is, for example, 30 seconds. After pairing is completed and after the sensor preparation period and the processing waiting time have ended, when the Z-phase detector 444 first detects the Z-phase magnet 162, the CPU 455 supplies a measurement start signal to the acceleration sensor 441 and the angle sensor 443. After the supply of the measurement start signal, the acceleration sensor 441 and the angle sensor 443 are initialized (acceleration sensor / angle sensor initialization time). The initialization of the acceleration sensor 441 and the angle sensor 443 means that power is supplied to the acceleration sensor 441 and the angle sensor 443 so that the angle sensor 443 can operate correctly. When the initialization of the acceleration sensor 441 and the angle sensor 443 is completed, after a measurement start delay (for example, about 480 ms), the acceleration sensor 441 and the angle sensor 443 start measurement. The acceleration sensor / angle sensor initialization time is, for example, 100 ms.

[0058] As shown in FIG. 9(D), after the measurement start delay, the acceleration sensor 441 measures the acceleration for a predetermined measurement time for each of the three axes (X / Y / Z axes). The measured values of the acceleration sensor 441 represent the vibration generated in the first gear 22 and thus in the bearing portion 250 due to the meshing of the first gear 22 and the second gear 23. Note that FIG. 9(D) shows the measured acceleration value by the acceleration sensor 441 for any one of the three axes. The predetermined measurement time is, for example, 25 ms, which corresponds to a time less than one rotation of the shaft 24a. During the predetermined measurement time, the acceleration sensor 441 repeats the measurement at a sampling period, so the measurement results are a plurality of discrete instantaneous values. Thus, after the Z-phase detector 444 generates a pulse, the acceleration sensor 441 measures the instantaneous value of the acceleration due to the vibration of the bearing portion 250 for a certain measurement time from the measurement start point.

[0059] During the measurement start delay, the CPU 455 performs two processes (1) and (2). In process (1), the CPU 455 acquires the temperature data before the start of measurement from the temperature sensor 442. The CPU 455 can determine whether abnormal heat generation occurs inside the first bearing 25 based on the temperature measured by the temperature sensor 442. When the temperature measured by the temperature sensor 442 is equal to or higher than a predetermined value, the CPU 455 transmits a signal indicating abnormal heat generation to the gear fault determination device 10. The gear fault determination device 10 that receives the signal displays a message indicating abnormal heat generation on the display unit 14. Further, the CPU 455 can correct the angle measured by the angle sensor 443 based on the temperature measured by the temperature sensor 442. Since the angle sensor 443 is a magnetic sensor, the influence of temperature change on magnetism may appear as a measurement error of the angle sensor 443. Regarding this angle error, check in advance what kind of influence / error appears in the measured value of the angle sensor 443 for each temperature, and create a correction table for performing correction to cancel the influence / error. Then, the CPU 455 corrects the angle data based on the correction table. In process (2), the CPU 455 programs the DMA controller 456. Programming the DMA controller 456 means programming to acquire the measurement data of the acceleration sensor 441 and the angle sensor 443 triggered by the INT signal from the acceleration sensor 441 and store the measurement data in the storage unit 230.

[0060] Also, as shown in FIG. 9(E), after the measurement start delay, the angle sensor 443 measures the angular position of the first axis 24a for a predetermined measurement time. The predetermined measurement time is, for example, 25 ms, which is a time corresponding to less than one rotation of the axis 24a. During the predetermined measurement time, since the angle sensor 443 repeats the measurement at the sampling period, the measurement results are a plurality of discrete instantaneous values. In this way, after the Z-phase detector 444 generates a pulse, the angle sensor 443 measures the instantaneous value of the angle of the axis 24a for a certain measurement time from the measurement start point. In this embodiment, the 25 readers of the angle sensor 443 simultaneously measure the angular position of the axis 24a at the sampling period for the predetermined measurement time. The waveform of the angle sensor 443 is stored in the storage unit 230 with a delay corresponding to the "DMA delay" compared to the waveform of the acceleration sensor 441. Theoretically, the measured values of the acceleration sensor 441 and the angle sensor 443 are DMA transferred (sampled) using the INT signal from the acceleration sensor 441 as a common timing source (trigger). However, in reality, there is a nanosecond-level deviation in the transfer of the measured values of the acceleration sensor 441 and the angle sensor 443, and this deviation is referred to as the "DMA delay". After the measurement of acceleration and angle is completed, data (a set of the instantaneous value of acceleration measured by the acceleration sensor and the instantaneous value of angle measured by the angle sensor) is transferred from the measuring device 100 to the gear failure determination device 10 during the "data transfer time". The data transfer time is, for example, 1 second. The time from power-on to the end of the first data transfer time is the first operation of the measuring device 100.

[0061] When the data transfer is completed, the power management IC 263 cuts off the power supply to the load L (acceleration sensor 441, angle sensor 443, Z-phase detector 444, and antenna 147), puts them into the sleep state, and starts charging the rechargeable battery 150. As described above, while the power management IC 263 stops the power supply from the rechargeable battery 150 to the load L and charges the rechargeable battery 150, the wireless module 453 holds the pairing information for wireless communication between the communication unit 15 of the gear failure determination device 10, and the CPU 455 of the microcomputer 451 holds various setting information (for example, the supply timing of the immediately preceding measurement start signal described later).

[0062] When the charging of the rechargeable battery 150 is completed, the power management IC 263 sends a charge completion signal notifying the FET 264 of the charge completion, and resumes the power supply to the load L (acceleration sensor 441, angle sensor 443, Z-phase detector 444, and antenna 147) (wakes up the load L). Since the wireless module 453 holds the pairing information, the pairing is not executed after the power supply is resumed. After the power supply is resumed and after the sensor preparation period and the processing waiting time are completed, when the Z-phase detector 444 first generates a pulse detecting the Z-phase magnet 162, the CPU 455 supplies a measurement start signal to the acceleration sensor 441 and the angle sensor 443. However, the supply timing of the first measurement start signal after the power-on is immediately after the generation of the Z-phase detection pulse (detection of the Z-phase magnet 162 by the Z-phase detector 444), whereas the supply timing of the current measurement start signal is shifted by a certain time after the generation of the Z-phase detection pulse. This is to change the measurement start timing every time the acceleration is measured for a predetermined time by the acceleration sensor 441 and the angle is measured by the angle sensor 443. Therefore, the acceleration sensor 441 and the angle sensor 443 measure the instantaneous values corresponding to different mechanical angles (actual angles around the axis 24a) every time the measurement for a predetermined time is performed. By doing so, it is possible to prevent the duplication of the measurement start timing. The CPU 455 (measurement start timing change unit) determines the supply timing of the next measurement start signal with respect to the Z-phase detection pulse. The supply timing of the measurement start signal with respect to the Z-phase detection pulse can be determined, for example, to be delayed from the immediately preceding supply timing.

[0063] After the measurement start signal, when the initialization of the acceleration sensor 441 and the angle sensor 443 is completed, after a measurement start delay, the acceleration sensor 441 and the angle sensor 443 start measuring again. After the measurement of acceleration and angle is completed, the data is transferred from the measuring device 100 to the gear fault determination device 10. When the data transfer is completed, the power management IC 263 stops the power supply to the load L and starts charging the battery 150. When the charging of the battery 150 is completed, the power management IC 263 sends a charge completion signal notifying the FET 264 of the charge completion and resumes the power supply to the load L. After this, after the sensor preparation period and the processing waiting time are completed and the Z-phase detection pulse is generated, the CPU 455 supplies a measurement start signal to the acceleration sensor 441 and the angle sensor 443. The period from the first power supply restart to the end of the second data transfer time is the second operation of the measuring device 100.

[0064] Thereafter, the same operation as the second operation is repeated. Therefore, every time the measurement of the instantaneous value of acceleration by the acceleration sensor 441 for a predetermined time (a time corresponding to less than one rotation of the shaft 24a) and the measurement of the instantaneous value of the angle by the angle sensor 443 for a predetermined time (a time corresponding to less than one rotation of the shaft 24a) are completed, the power management IC 263 stops the power supply to the acceleration sensor 441, the angle sensor 443, etc. by the battery 150, and charges the electricity generated by the power generation unit 149 into the battery 150. Therefore, sleep and Wake-up are repeated. During sleep, only the minimum functional blocks operate, and the power consumption can be reduced. During sleep, the wireless module 453 holds the pairing information, and the pairing after the power supply restart can be omitted. The CPU 455 of the microcomputer 451 holds the supply timing (measurement start command timing) of the measurement start signal immediately before the power supply to the acceleration sensor 441 and the angle sensor 443 is stopped, and uses it to determine the supply timing (measurement start command timing) of the next measurement start signal.

[0065] FIG. 10 shows the update periods of the measured values of the acceleration sensor 441 and the measured values of the angle sensor 443. In the present embodiment, as shown in FIG. 10, the completion timing of the update of the measured values of the acceleration sensor 441 and the completion timing of the update of the measured values of the angle sensor 443 (sampling timing) are set to be synchronized. That is, the update period (sampling period) of the acceleration sensor 441 is equal to the update period (sampling period) of the angle sensor 443. Then, the measured values of the acceleration sensor 441 and the measured values of the angle sensor 443 are stored in the storage unit 230 in a synchronized form (sharing the same time reference or at least one time reference). That is, the storage unit 230 stores the instantaneous value of acceleration and the instantaneous value of angle measured simultaneously by the acceleration sensor 441 and the angle sensor 443 in association with each other. In the present embodiment, the 25 readers of the angle sensor 443 measure the angular position of the shaft 24a at a predetermined measurement time simultaneously. Therefore, the storage unit 230 of the measuring device 100 and the storage unit 13 of the gear failure determination device 10 store the instantaneous value of acceleration and the instantaneous value of angle measured simultaneously by the acceleration sensor 441 and the 25 readers in association with each other. Thus, in the present embodiment, angle-acceleration measurement synchronized in time is performed. The sampling frequencies (ODR) of the acceleration sensor 441 and the angle sensor 443 are pre-selected (set) based on, for example, the meshing frequency of the gears.

[0066] FIG. 11 is a flowchart for explaining the operation of the measuring device 100. This operation starts with the first power-on of the measuring device 100 (the first power-on in FIG. 9). In S1, the CPU 455 determines whether the pairing time (for example, 5 seconds) has elapsed. If the determination result is Yes, the operation proceeds to S2. If the determination result is No, S1 is repeated. In S2, the CPU 455 determines whether the sensor preparation period (for example, 50 ms) has elapsed. If the determination result is Yes, the operation proceeds to S3. If the determination result is No, S2 is repeated.

[0067] In S3, the CPU 455 determines whether the processing wait time (e.g., 30 seconds) has elapsed. If the determination result is Yes, the operation proceeds to S4. If the determination result is No, S3 is repeated. In S4, the CPU 455 determines whether the Z-phase detector 444 has detected the Z-phase magnet 162. If the determination result is Yes, the operation proceeds to S5. If the determination result is No, S4 is repeated. In S5, the CPU 455 determines whether it is the supply timing of the measurement start signal. If the determination result is Yes, the operation proceeds to S6. If the determination result is No, S5 is repeated. The initial value of the supply timing of the measurement start signal is zero. Therefore, in the case of the first measurement, immediately after S4, the determination result of S5 is Yes, and the operation proceeds to S6.

[0068] In S6, the CPU 455 supplies the measurement start signal to the acceleration sensor 441 and the angle sensor 443. When the measurement start signal is supplied, as shown in FIG. 9, the acceleration sensor 441 and the angle sensor 443 are initialized (the initialization time is, for example, 100 ms). After the measurement start delay (about 480 ms), the acceleration sensor 441 and the angle sensor 443 perform measurement for a predetermined measurement time (e.g., 25 ms), and the DMA controller 456 stores the instantaneous value of the acceleration measured by the acceleration sensor 441 and the instantaneous value of the angle measured by the angle sensor 443 in the storage unit 230 in a synchronized manner. As described above, during the measurement start delay, the CPU 455 performs two processes (1) and (2).

[0069] Next, in S7, the CPU 455 determines whether it is the transmission timing of the measurement value. If the determination result is Yes, the operation proceeds to S8. If the determination result is No, S7 is repeated. In S8, the CPU 455 transmits (transfers) the instantaneous value measured by the acceleration sensor 441 and the instantaneous value measured by the angle sensor 443 stored in the storage unit 230 from the measuring device 100 to the gear failure determination device 10 via BLE wireless communication. In this way, one measurement of the measuring device 100 is performed by S2 to S8.

[0070] Next, in S9, the CPU 455 commands the power management IC 263 to enter sleep. As a result, the power management IC 263 cuts off the power supply to the load L (acceleration sensor 441, angle sensor 443, Z-phase detector 444, and antenna 147), puts these into the sleep state, and starts charging the storage battery 150. In S10, the power management IC 263 monitors the voltage of the storage battery 150 measured by the voltage sensor 152. When the charging of the storage battery 150 is completed, the determination in S10 becomes Yes. In S11, the power management IC 263 sends a charge completion signal notifying the charge completion to the FET 264, and resumes the power supply from the storage battery 150 to the load L (acceleration sensor 441, angle sensor 443, Z-phase detector 444, and antenna 147). When the charging of the storage battery 150 is completed, the power management IC 263 also sends a charge completion signal to the CPU 455. Next, in S12, the CPU 455 determines whether to execute the next measurement. In other words, it determines whether the number of executed measurements has reached a predetermined number. If the determination result is Yes, it proceeds to S13. If the determination result is No, the operation ends. In S13, the CPU 455 determines the supply timing (measurement start command timing) of the next measurement start signal for the Z-phase detection pulse based on the supply timing (measurement start command timing) of the measurement start signal immediately before the power supply to the acceleration sensor 441 and the angle sensor 443 is stopped. The next measurement start command timing can be determined, for example, by adding or subtracting a predetermined time to or from the immediately previous measurement start command timing. In this way, the CPU 455 changes the measurement start timing every time the acceleration and angle are measured for a predetermined time. After this, the operation returns to S2.

[0071] Next, the principle of gear failure determination in this embodiment will be described. FIG. 12 shows the temporal changes in acceleration and angle measured by the measuring device 100. Specifically, the upper graph shows the change in acceleration regarding one axis output by the three-axis acceleration sensor 441. The illustration of the changes in acceleration regarding the other two axes is omitted. The central graph shows the change in the angle (electrical angle) output by one reader of the angle sensor 443, and the lower graph shows the change in the angle output by the other reader of the angle sensor 443 (the reader adjacent to the reader regarding the central graph). The illustration of the changes in the angles output by the other 23 readers is omitted. As described above, during the predetermined measurement time, since the acceleration sensor 441 repeats measurement at the sampling period, the measurement results are discrete instantaneous values. Also, during the predetermined measurement time, since each reader of the angle sensor 443 repeats measurement at the sampling period, the measurement results are discrete instantaneous values. As described above, each time acceleration and angle are measured for a predetermined time (a time corresponding to less than one rotation of the shaft 24a), the measurement start point changes. Therefore, there is a measurement start deviation with respect to the Z-phase detection point between the first measurement and the second measurement. The same applies to multiple subsequent measurements. As described above, since the 25 readers are arranged at equal angular intervals around the axis of the shaft 24a, the readers output similar read values that are 14.4° apart from the read values of the adjacent readers.

[0072] FIG. 13 shows the elements particularly related to gear fault determination in the gear fault detection system 30. As described above, in the measuring device 100, the DMA controller 456 stores the instantaneous value of the acceleration measured by the acceleration sensor 441 and the instantaneous value of the angle measured by the angle sensor 443 in the storage unit 230 in a synchronized manner. The instantaneous value of the acceleration measured by the acceleration sensor 441 and the instantaneous value of the angle measured by the angle sensor 443 stored in the storage unit 230 are wirelessly transmitted via BLE from the wireless module 453 and received by the communication unit 15 of the gear fault determination device 10. Since the BLE wireless transmission is repeated periodically, the communication unit 15 of the gear fault determination device 10 periodically receives the instantaneous value of the acceleration and the instantaneous value of the angle.

[0073] The control unit 12 of the gear failure determination device 10 accumulates the instantaneous values of the acceleration measured by the acceleration sensor 441 and the instantaneous values of the angle measured by the angle sensor 443 in the storage unit 13. In one accumulation, the instantaneous values of the acceleration and the angle for a predetermined time (a time corresponding to less than one rotation of the shaft 24a) are stored in the storage unit 13, and the accumulation is performed periodically while the shaft 24a rotates a plurality of times. Therefore, the storage unit 13 stores the instantaneous values of the acceleration measured by the acceleration sensor 441 and the instantaneous values of the angle measured by the angle sensor 443 while the shaft 24a rotates a plurality of times. The control unit (acceleration profile generation unit) 12 reads out a plurality of instantaneous values of the acceleration accumulated in the storage unit 13, rearranges the plurality of instantaneous values of the acceleration measured by the acceleration sensor 441 while the shaft 24a rotates a plurality of times, and connects the rearranged instantaneous values of the acceleration to generate an acceleration profile representing the change in acceleration per rotation of the shaft 24a. Further, the control unit (angle profile generation unit) 12 reads out a plurality of instantaneous values of the angle accumulated in the storage unit 13, rearranges the plurality of instantaneous values of the angle measured by the angle sensor 443 while the shaft 24a rotates a plurality of times, and connects the rearranged instantaneous values of the angle to generate an angle profile representing the change in the measured angle value per rotation of the shaft 24a. As described above, the sampling periods of the acceleration sensor 441 and the angle sensor 443 are the same, and the storage unit 230 stores the instantaneous values of the acceleration and the instantaneous values of the angle measured simultaneously by the acceleration sensor 441 and the angle sensor 443 in an associated manner. Therefore, the generated angle profile is synchronized with the acceleration profile.

[0074] FIG. 14 shows a graph of the acceleration profile and a graph of the angle profile generated by the control unit 12 of the gear failure determination device 10 that has received a plurality of discrete instantaneous values of the acceleration and a plurality of discrete instantaneous values of the angle from the measuring device 100. The gear 22 to be measured has 22 teeth, and the tooth numbers are depicted in FIG. 14 for reference. The horizontal axes of the graph of the acceleration profile and the graph of the angle profile are time, and can also be regarded as the mechanical angle (the actual angle around the shaft 24a). The graph of the acceleration profile shows the change in acceleration for one axis measured by the three-axis acceleration sensor 441. The control unit 12 generates acceleration profiles for the three axes of the three-axis acceleration sensor 441, but illustration of the graphs of the acceleration profiles for the other two axes is omitted. As shown in FIG. 12, the measurement results of the acceleration sensor 441 are a plurality of discrete instantaneous values. The measurement results of the acceleration sensor 441 are periodically transmitted wirelessly via BLE and received by the gear fault determination device 10. Therefore, the control unit 12 can generate an acceleration profile per one rotation (360°) of the shaft 24a by rearranging the measurement results of the acceleration sensor 441 while the shaft 24a rotates a plurality of times with reference to the reception time point of the measurement results and connecting the rearranged instantaneous values of the acceleration.

[0075] The graph of the angle profile in FIG. 14 shows the change in the angle (electrical angle) measured by 25 readers of the angle sensor 443. As shown in FIG. 12, the measurement results of the angle sensor 443 are a plurality of discrete instantaneous values. The measurement results of the angle sensor 443 are periodically transmitted wirelessly via BLE and received by the gear fault determination device 10. Therefore, the control unit 12 can generate an angle profile per one rotation (360°) of the shaft 24a by rearranging the measurement results of the angle sensor 443 while the shaft 24a rotates a plurality of times with reference to the reception time point of the measurement results and connecting the rearranged instantaneous values of the angle. Since the angle sensor 443 has 25 readers arranged at equal angular intervals around the axis of the shaft 24a, the angle profile generated from the measurement results of the 25 readers has 25 substantially linear diagonal segments during one rotation (angular displacement of 360° of mechanical angle) of the shaft 24a. Each segment has an angular displacement of the electrical angle (absolute angle) from 0° to 360° composed of the instantaneous values of the electrical angle measured by the 25 readers.

[0076] FIG. 15 shows graphs of an acceleration profile and an angle profile obtained from the results continuously measured during one rotation (360°) of axis 24a by an expensive acceleration sensor and an angle sensor with high resolution and high sampling frequency, which are not embodiments of the present invention. The gear 22 to be measured has 22 teeth, and the tooth numbers are depicted in FIG. 15 for reference. The angle sensor has one reader. As is clear from the comparison between FIGS. 14 and 15, the acceleration profile and the angle profile obtained by repeatedly measuring with a low-performance acceleration sensor and an angle sensor with low resolution and low sampling frequency according to the present embodiment have accuracy comparable to those obtained by measuring with an expensive acceleration sensor and an angle sensor with high resolution and high sampling frequency.

[0077] The control unit (fault determination unit) 12 of the gear fault determination device 10 determines the fault of the gear based on the acceleration profile and the angle profile. Next, the fault determination process executed by the control unit 12 of the gear fault determination device 10 will be described with reference to FIG. 16. In the present embodiment, a method called the Per-tooth method (Per-tooth evaluation method) is used to detect a fault for each tooth of the gear. First, the control unit 12 converts the measured angle (electrical angle) of the angle profile (FIG. 14) into the mechanical angle φ(t). This conversion is performed, although not limited thereto, by dividing the accumulated value of the difference in electrical angle by 360 and obtaining the remainder (process 490). The control unit 12 associates the measured acceleration value a(t) of the acceleration profile, the mechanical angle φ(t) obtained in process 490, and the time t of the acceleration profile and the angle profile, and stores them in the storage unit 13 (process 500). In the figure, only the acceleration value a(t) related to one axis is shown, and the illustration of the acceleration values related to the other two axes is omitted.

[0078] The user of the gear failure determination device 10 inputs the number of teeth of the gear using the input unit 11 (process 510). Although not essential, the user may also input the tooth angle offset value. The tooth angle offset value is a calibration value for indicating (grasping) the absolute angular position of a specific known tooth. The angle offset value will be described later with reference to FIGS. 17 and 18.

[0079] The control unit (map generation unit) 12 creates a map of angles and teeth (an angle-to-tooth mapping function) (process 520). FIGS. 17 and 18 are diagrams showing examples of maps of angles and teeth. The vertical axis of the map in FIG. 17 shows 22 teeth, and the horizontal axis shows the shaft angle position (relative value). FIG. 17 is a map created without using the angle offset value. Without using the angle offset value, the tooth at the position where the shaft angle = 0 degrees at the time of map creation is regarded as the first tooth. The vertical axis of the map in FIG. 18 shows 22 teeth, and the horizontal axis shows the shaft angle position (absolute value). That is, FIG. 18 is a map created using the angle offset value. When creating the map of FIG. 18, numbers (or marks) are attached to the teeth of the gear in advance (in the example of FIG. 18, tooth numbers: 1 to 22). The tooth at the position where the shaft angle = 0 degrees at the time of map creation is the 20th tooth in the example of FIG. 18. That is, since the first tooth starts meshing at 44.6 degrees (absolute angle), when using the map of FIG. 18, the user inputs 44.6 degrees as the angle offset value to the input unit 11 in process 510.

[0080] As shown in FIGS. 17 and 18, since the gear makes one full rotation of 360 degrees, 22 line segments S obtained by dividing 360 degrees by 22 can be formed. FIGS. 17 and 18 show that when the shaft angular position is determined, one tooth out of 22 teeth is determined, so it can be said that they represent a mapping function. That is, the mapping function is generated by process 520. The control unit 12 uses the map of FIG. 17 or the map of FIG. 18. When using the map of FIG. 17, it is not known which tooth of the gear is damaged, but it is known that the gear contains a damaged tooth. When using the map of FIG. 18, it is known which tooth of the gear is damaged. In the following description, it is assumed that the map of FIG. 18 is used.

[0081] After generating the angle-to-tooth map (mapping function), the control unit 12 calculates the average acceleration signal intensity for each tooth (process 530). The average acceleration signal intensity is hereinafter referred to as the acceleration signal intensity. The numerical values and information used as inputs in the calculation of the acceleration signal intensity are the mechanical angle φ(t) and the measured acceleration value a(t) stored in the storage unit 13 in process 500, and the map of FIG. 18. The calculation of the acceleration signal intensity of the k-th tooth is performed using Equation (1) according to the Per-tooth method.

Equation

[0082] Here, P (tooth=k) is the acceleration signal power of the k-th tooth, s(φ(i)) is the measured acceleration value at a certain sample angular position φ(i). tooth(φ(i)) is the value of the mapping function at the sample angular position φ(i). When the sample angular position φ(i) does not correspond to the k-th tooth, tooth(φ(i)) is not equal to k, so s(φ(i)) becomes 0. When the sample angular position φ(i) corresponds to the k-th tooth, tooth(φ(i)) is equal to k, so s(φ(i)) becomes the measured acceleration value (a(i)). n samples,k indicates the number of samples of the measured acceleration value that meet condition (*) (the number of samples of the measured acceleration value corresponding to the k-th tooth).

[0083] According to Equation (1), all the measured acceleration values (sample values) corresponding to one tooth are squared and summed, and then divided by the number of samples of the measured acceleration values corresponding to one tooth, so that the acceleration signal intensity per tooth can be obtained. That is, the acceleration signal intensity of the k-th tooth can be obtained. Since this calculation is performed for each tooth of the gear, a list of 22 acceleration signal intensity values P of the teeth can be created. That is, by Process 530, the acceleration signal intensities of 22 teeth can be obtained. Reference numeral 540 in FIG. 16 shows the values used in Equation (1) for each tooth.

[0084] In the present embodiment, as described above, the acceleration sensor 441 is configured to acquire measured acceleration values for each of the three axes (X / Y / Z axes). Let the measured acceleration values acquired for the X-axis, Y-axis, and Z-axis be x(φ(i)), y(φ(i)), and z(φ(i)), respectively. When it is the k-th tooth (tooth(φ(i)) = k), s(φ(i)) in Equation (1) is defined as the synthesis (vector synthesis) of these measured acceleration values. At this time, s(φ(i)) is expressed as the following Equation (2). [Equation] x(φ(i)), y(φ(i)), and z(φ(i)) may be the measured acceleration values for each axis after being subjected to the filtering process, respectively.

[0085] Therefore, using the measured acceleration values x(φ(i)), y(φ(i)), and z(φ(i)) acquired for each of the three axes, the acceleration signal intensity of Equation (1) considering Equation (2) is expressed as the following Equation (3). [Equation] The control unit (first calculation unit) 12 calculates the acceleration signal intensity using Equation (3).

[0086] When the calculation of Equation (3) is completed, the process 550 in FIG. 16 is performed. By this process, relative signal power values are calculated. This signal power coefficient serves as an index indicating tooth damage. When teeth mesh, vibration occurs even if there is no damage to the teeth. In this embodiment, the process 550 is performed so that vibrations generated from normal teeth and vibrations generated from abnormal teeth can be easily distinguished. Specifically, in the process 550, first, the control unit (second calculation unit) 12 calculates Equation (4). That is, the average value P￣ of the acceleration signal intensities of all teeth is calculated.

Equation

[0087] Next, the control unit (third calculation unit) 12 calculates the relative signal power coefficient P rel (k) for each tooth using Equation (5).

Equation

[0088] The relative signal power coefficient P rel (k) is a coefficient representing the following characteristics. If the signal intensity of tooth k matches the average acceleration signal intensity, P rel (k) = 0. When the signal intensity of tooth k is twice the average acceleration signal intensity, P rel (k) = 1. When the signal intensity of tooth k is three times the average acceleration signal intensity, P rel (k) = 2. Hereinafter, similarly, P rel (k) becomes 3, 4, ···. When the signal intensity of tooth k is lower than the average acceleration signal intensity, P rel (k) can take a value smaller than 0 (that is, P rel (k) ≠ 0 and P rel (k) < 0 can occur). Therefore, if normalized so that the average vibration reference becomes zero, P rel (k) values can be used as numerical values for easily evaluating the normality and abnormality of each tooth. Such evaluation may be an evaluation based on the judgment of an operator or an automatic evaluation (for example, a threshold may be set, and if the value of P rel (k) is equal to or greater than the threshold, it may be evaluated as abnormal). Thus, according to this embodiment, the relative signal strength coefficient is used as an index value of damage indicating the state of each tooth, enabling per-tooth evaluation of the acceleration signal strength.

[0089] FIG. 19 is a graph showing the relative signal strength coefficients P rel calculated by the per-tooth method for each of the three axes in this embodiment using a three-axis acceleration sensor. As shown in FIG. 19, it is determined that there is damage to the 14th tooth of the gear in each of the three axes.

[0090] Next, the effects of the above-described embodiment will be described. In this embodiment, a large number of instantaneous values of acceleration measured by the acceleration sensor 441 and a large number of instantaneous values of the angle measured by the angle sensor 443 are accumulated while the shaft 24a rotates multiple times. The failure location of the gear is detected as an abnormality in acceleration at any angular position within the 360° angular range. In multiple rotations of the shaft 24a, the acceleration abnormality corresponding to the gear failure location and the angle corresponding to the gear failure location will be repeatedly measured. In this embodiment, by arranging a large number of instantaneous values of the acceleration accumulated during multiple rotations of the shaft 24a and connecting the arranged instantaneous values of the acceleration, even if the performance of the acceleration sensor 441 is low, an acceleration profile representing the change in acceleration per rotation of the shaft 24a can be generated. Also, by arranging a large number of instantaneous values of the angle accumulated during multiple rotations of the shaft 24a and connecting the arranged instantaneous values of the angle, even if the performance of the angle sensor 443 is low, an angle profile representing the change in angle per rotation of the shaft 24a can be generated. Based on the angle profile and the acceleration profile synchronized with each other obtained in this way, the gear failure can be accurately determined. That is, it is possible to appropriately grasp at what angle and what kind of vibration is occurring during the rotation of the shaft 24a, and to appropriately identify the location (angle) where the abnormality occurs. Also, since the angle profile and the acceleration profile are synchronized, even if the rotational speed of the shaft 24a fluctuates, the location where the abnormality occurs can be identified.

[0091] In the measuring device 100, each time the acceleration is measured by the acceleration sensor 441 for a predetermined time, the measurement start point is changed. Therefore, each time the measurement for the predetermined time is performed, the acceleration sensor 441 measures the instantaneous value of the acceleration at different angular positions on the shaft 24a. Therefore, by arranging a large number of instantaneous values of the acceleration accumulated during multiple rotations of the shaft 24a and connecting the arranged instantaneous values of the acceleration, an acceleration profile representing the change in acceleration per rotation of the shaft 24a can be easily generated. Also, in the measuring device 100, each time the angle is measured by the angle sensor 443 for a predetermined time, the measurement start point is changed. Therefore, each time the measurement for the predetermined time is performed, the angle sensor 443 measures the instantaneous value of the angle at different angular positions on the shaft 24a. Therefore, by arranging a large number of instantaneous values of the angles accumulated by multiple rotations of the shaft 24a and connecting the arranged instantaneous values of the angles, an angle profile representing the change in the angle per rotation of the shaft 24a can be easily generated.

[0092] In the measuring device 100, the sampling periods of the acceleration sensor 441 and the angle sensor 443 are the same, and the instantaneous value of the acceleration and the instantaneous value of the angle measured simultaneously by the acceleration sensor 441 and the angle sensor 443 are associated and stored in the storage unit 230. Then, the raw data of the measured values stored in the storage unit 230 (a plurality of discrete instantaneous values of acceleration and a plurality of discrete instantaneous values of angle are associated on the time axis) is transferred to the gear failure determination device 10 and accumulated in the storage unit 13 of the gear failure determination device 10. Therefore, in the gear failure determination device 10, the control unit 12 can easily generate a synchronized acceleration profile and angle profile.

[0093] In this embodiment, the three-axis acceleration sensor 441 that measures the accelerations of the X-axis, Y-axis, and Z-axis respectively can accurately determine the failure location of the gear.

[0094] Since the angle sensor 443 has a plurality of readers arranged at equal angular intervals around the axis of the shaft 24a, the gear failure determination device 10 can generate a highly accurate angle profile even if the resolution of each reader is low.

[0095] The measuring device 100 (acceleration sensor 441, angle sensor 443, circuit board group 140, etc.) of this embodiment is built into the first bearing 25. Further, since the electricity obtained by the power generation unit 149 that generates power using the relative rotation between the outer ring 250A and the inner ring 250B of the bearing portion 250 serves as an energy source for supplying power to the acceleration sensor 441, the angle sensor 443, the Z-phase detector 444, etc., there is no need to provide a large energy source in the bearing portion 250 or its vicinity. Therefore, miniaturization and power saving of the measuring device 100 can be achieved. In this way, the data wireless transmission type measuring device 100 having a self-power generation function can measure acceleration and angle and wirelessly transmit the measured data to the failure determination device 10 using the minute power generated by the self-power generation function. Due to the self-power generation function, the acceleration sensor 441 can be used for acceleration measurement over a long period (at least during multiple rotations of the shaft 24a). Also, every time the acceleration sensor 441 and the angle sensor 443 perform measurement for a predetermined period, the power supply from the storage battery 150 to the acceleration sensor 441, the angle sensor 443, the Z-phase detector 444, etc. is stopped, and the electricity generated by the power generation unit 149 is charged to the storage battery 150. Therefore, the charge capacity that can be stored in the storage battery 150 may be small. During the power supply stop (sleep) to the acceleration sensor 441, the angle sensor 443, the Z-phase detector 444, etc., the wireless module 453 can hold the pairing information and omit the pairing after the power supply resumes. The CPU 455 of the microcomputer 451 holds the supply timing (measurement start command timing) of the measurement start signal immediately before the power supply to the acceleration sensor 441 and the angle sensor 443 is stopped, and uses it to determine the supply timing (measurement start command timing) of the next measurement start signal.

[0096] The measuring device 100 contributes to the miniaturization of the entire configuration by connecting the acceleration sensor 441, the temperature sensor 442, and the angle sensor 443 to the microcomputer 451. Therefore, even if the cover (device housing) 110 is small, it is possible to store the measuring device 100 in the same housing. Furthermore, the measured values obtained from each sensor are stored in the storage unit 230 as un-converted data. Therefore, data processing such as conversion from hexadecimal notation to decimal notation is not required during data storage, enabling high-speed data storage. Also, the load due to data processing can be reduced, and power consumption can be decreased.

[0097] Since the measuring device 100 can acquire and store data by DMA transfer, the load on the CPU 455 can be reduced. That is, the measuring device 100 in the present embodiment can be configured by an inexpensive MEMS sensor and a low-power microcomputer. Since the measuring device 100 can install the acceleration sensor 441 close to the vibration source (it can be installed at a position physically close to the vibration excitation point), compared with the case of installing a vibration sensor (for example, a high-performance sensor that senses in the acting line direction where gears mesh) on the outer surface of the housing 21 of the gear transmission mechanism 20, a signal with a higher S / N ratio can be acquired. Therefore, reliable gear diagnosis can be performed even using an inexpensive MEMS acceleration sensor.

[0098] The gear diagnosis algorithm adopted in the present embodiment is the Per-tooth method and has the following advantages. Abnormal teeth can be identified. Diagnosis can be performed at a low computational cost. Conventionally, abnormal determination can be made from a single evaluation result without comparing with the vibration data of normal gears used in gear diagnosis. The fact that diagnosis can be performed at a low computational cost means that diagnosis can be performed by arithmetic operations. That is, it does not require a high computational cost such as FFT (Fast Fourier Transform). Also, the process in FIG. 16 requires only slight mathematical calculations, enabling low-power calculation. Further, according to the present embodiment, gear determination is performed by the Per-tooth method using the measured acceleration values measured for each of the three axes. By using the data of the three axes, even when the data of a single axis cannot capture the abnormality of the Peak-Peak value, the data of other axes can complement it to achieve high diagnostic sensitivity.

[0099] Also, since the acceleration sensor 441 is not attached to the surface of the housing 21, the system 30 can be adopted regardless of the shape of the housing 21, and the shape of the housing 21 is irrelevant to the accuracy of fault diagnosis. When an acceleration sensor is installed in the housing 21 of the gear transmission mechanism 20, since the housing 21 exists between the meshing point of the gears and the acceleration sensor, it is affected by the vibration path, so a high-performance sensor is required. In the present embodiment, since the acceleration sensor 441 is built into the first bearing 25, the acceleration sensor 441 can measure vibrations in the vicinity of the first gear 22. Since the acceleration sensor 441 is not affected by the vibration transmission path, it does not need to be a high-performance sensor. That is, an inexpensive acceleration sensor is sufficient. Even an inexpensive acceleration sensor can accurately detect vibrations, so fault determination can also be accurately performed. In the present embodiment, since a MEMS acceleration sensor is adopted as the inexpensive acceleration sensor, it is excellent not only in terms of the sensor position but also in terms of cost. Also, the acceleration sensor 441 is installed on the outer ring 250A of the first bearing 25. This location is usually one of the non-rotating mechanical elements closest to the gear meshing portion, and the vibration that can be obtained can be said to be the meshing vibration of the gears. By measuring the acceleration near the vibration source, it is not affected by the vibration transmission path such as the housing.

[0100] Next, a modification of the present embodiment will be described. FIG. 20 shows elements particularly related to gear fault determination in the gear fault detection system 30 according to the modification. In this modification, an FPGA (Field Programmable Gate Array) 456A is provided instead of the DMA controller 456. Whenever the acceleration sensor 441 measures the instantaneous value of acceleration, it sends the instantaneous value of acceleration to the FPGA 456A. When the FPGA (acceleration timestamp generation unit) 456A receives the instantaneous value of acceleration from the acceleration sensor 441, it generates an acceleration timestamp indicating the time when the acceleration sensor 441 measured the instantaneous value of acceleration. Then, the FPGA 456A associates the acceleration timestamp with the instantaneous value of acceleration and stores it in the storage unit 230. Whenever the angle sensor 443 measures the instantaneous value of the angle, it sends the instantaneous value of the angle to the FPGA 456A. When the FPGA (angle timestamp generation unit) 456A receives the instantaneous value of the angle from the angle sensor 443, it generates an angle timestamp indicating the time when the angle sensor 443 measured the instantaneous value of the angle. Then, the FPGA 456A associates the angle timestamp with the instantaneous value of the angle and stores it in the storage unit 230.

[0101] The instantaneous values measured by the acceleration sensor 441 and the angle sensor 443 stored in the storage unit 230 are BLE wirelessly transmitted from the wireless module 453 while being associated with the acceleration timestamp and the angle timestamp, and received by the communication unit 15 of the gear fault judgment device 10. Since the BLE wireless transmission is periodically repeated, the communication unit 15 of the gear fault judgment device 10 periodically receives the instantaneous value of acceleration and the instantaneous value of the angle. The control unit 12 of the gear fault judgment device 10 accumulates the instantaneous value of acceleration measured by the acceleration sensor 441 and the instantaneous value of the angle measured by the angle sensor 443 in the storage unit 13 while being associated with the acceleration timestamp and the angle timestamp. That is, the storage unit 13 associates the instantaneous value of acceleration measured by the acceleration sensor 441 with the acceleration timestamp, and associates and stores the instantaneous value of the angle measured by the angle sensor 443 with the angle timestamp. The accumulation is periodically performed while the shaft 24a rotates multiple times.

[0102] In this modification, even if the acceleration sensor 441 and the angle sensor 443 are not synchronized, a synchronized acceleration profile and angle profile can be easily generated based on the timestamp related to acceleration and the timestamp related to the angle. That is, as shown in FIG. 21, the sampling periods of the acceleration sensor 441 and the angle sensor 443 do not have to match.

[0103] As shown in FIG. 21, when the sampling period of the angle sensor 443 is longer than the sampling period of the acceleration sensor 441, there may be a moment when the instantaneous value of the angle is not measured by the angle sensor 443 at the moment when the instantaneous value of the acceleration is measured by the acceleration sensor 441. That is, the number of measured instantaneous values of the angle is less than the number of measured instantaneous values of the acceleration. Therefore, as shown in FIG. 22, the control unit (linear interpolation calculation unit) 12 of the gear failure determination device 10 preferably calculates the instantaneous value of the angle at the moment when the instantaneous value of the acceleration is measured by the acceleration sensor 441 and the instantaneous value of the angle is not measured by the angle sensor 443 by interpolating from two instantaneous values of the angle measured by the angle sensor 443. Since the angular change of the shaft 24a is substantially linear with respect to time, the interpolation may be linear interpolation. In FIG. 22, point A represents two instantaneous values of the angle measured by the angle sensor 443, and point B represents the instantaneous value of the angle obtained by interpolation. The control unit 12 generates an angle time stamp corresponding to the instantaneous value of the angle obtained by linear interpolation from the angle time stamps corresponding to the two instantaneous values of the angle measured by the angle sensor 443, associates the angle time stamp with the instantaneous value of the angle obtained by linear interpolation, and stores it in the storage unit 13.

[0104] The control unit (acceleration profile generation unit) 12 reads out a plurality of instantaneous values of the acceleration and the acceleration time stamps stored in the storage unit 13, and uses the acceleration time stamps to rearrange the plurality of instantaneous values of the acceleration measured by the acceleration sensor 441 while the shaft 24a rotates a plurality of times, and connects the rearranged instantaneous values of the acceleration to generate an acceleration profile representing the change in acceleration per rotation of the shaft 24a. Further, the control unit (angle profile generation unit) 12 reads out a plurality of instantaneous values of the angle and angle timestamps stored in the storage unit 13, and uses the angle timestamps to rearrange the plurality of instantaneous values of the angle measured by the angle sensor 443 while the shaft 24a rotates a plurality of times, and connects the rearranged instantaneous values of the angle to generate an angle profile representing the change in the measured angle value per rotation of the shaft 24a. Even when the sampling period of the angle sensor 443 is longer than the sampling period of the acceleration sensor 441, the control unit 12 uses the instantaneous value of the angle and angle timestamp obtained by linear interpolation in addition to the measured instantaneous value of the angle and angle timestamp, so the generated angle profile is synchronized with the acceleration profile.

[0105] FIG. 23 shows elements particularly related to gear fault determination in the gear fault detection system 30 according to still another modification of the embodiment. In this modification, the angle sensor 443 is not provided, the Z-phase detector 444 is used as a tachometer, and a virtual angle profile is generated based on the Z-phase detection pulse output by the Z-phase detector 444. Each time the acceleration sensor 441 measures an instantaneous value of acceleration, it sends the instantaneous value of acceleration to the FPGA 456A. When the FPGA (acceleration timestamp generation unit) 456A receives the instantaneous value of acceleration from the acceleration sensor 441, it generates an acceleration timestamp indicating the time when the acceleration sensor 441 measures the instantaneous value of acceleration. Then, the FPGA 456A associates the acceleration timestamp with the instantaneous value of acceleration and stores it in the storage unit 230. Each time the Z-phase detector 444 detects the Z-phase magnet 162 and generates a Z-phase detection pulse (each time the shaft 24a makes one rotation), it sends the Z-phase detection pulse to the FPGA 456A. When the FPGA 456A receives the Z-phase detection pulse, it generates a Z-phase timestamp indicating the time when the Z-phase detector 444 generates the Z-phase detection pulse. Then, the FPGA 456A stores the Z-phase timestamp in the storage unit 230.

[0106] The instantaneous value measured by the acceleration sensor 441 associated with the acceleration timestamp stored in the memory unit 230 and the Z-phase timestamp are wirelessly transmitted via BLE from the wireless module 453 and received by the communication unit 15 of the gear failure determination device 10. Since the BLE wireless transmission is repeated periodically, the communication unit 15 of the gear failure determination device 10 periodically receives the instantaneous value of the acceleration and the Z-phase timestamp. The control unit 12 of the gear failure determination device 10 accumulates the instantaneous value measured by the acceleration sensor 441 associated with the acceleration timestamp and the Z-phase timestamp in the memory unit 13. That is, the memory unit 13 stores the instantaneous value of the acceleration measured by the acceleration sensor 441 in association with the acceleration timestamp, and further stores the Z-phase timestamp. The accumulation is performed periodically while the shaft 24a rotates multiple times.

[0107] In this modification, even without the instantaneous value of the angle measured by the angle sensor, a synchronized acceleration profile and angle profile can be generated based on the acceleration-related timestamp and the Z-phase timestamp. The control unit (angle estimation unit) 12 of the gear failure determination device 10 estimates the instantaneous value of the angle of the shaft 24a from the time interval of the Z-phase timestamp (that is, the interval of the Z-phase detection pulses). Specifically, as shown in FIG. 24, the control unit 12 estimates the moment identified by the Z-phase timestamp as the electrical angle 360° at the end of a certain cycle of the mechanical angle and the electrical angle 0° at the start of the next cycle. Point A indicates the instantaneous value of the angle to which the Z-phase timestamp is thus applied. Further, the control unit 12 calculates the instantaneous value of the angle at the moment when the instantaneous value of the acceleration is measured by the acceleration sensor 441 (the moment identified by the acceleration timestamp) by interpolating from the two instantaneous values of the angle at the moment identified by the Z-phase timestamp. When the shaft 24a rotates at a constant speed, since the angle change of the shaft 24a is linear with respect to time, the interpolation may be linear interpolation. In FIG. 24, point B indicates the instantaneous value of the angle obtained by interpolation. The control unit 12 generates angle timestamps corresponding to the instantaneous values of all the estimated angles from the Z-phase timestamp corresponding to the instantaneous value of the angle corresponding to point A. The angle timestamp corresponding to the instantaneous value of the angle corresponding to point A may be the Z-phase timestamp itself. The control unit 12 generates an angle timestamp corresponding to the instantaneous value of the angle obtained by linear interpolation from the angle timestamps corresponding to the two instantaneous values of the angle corresponding to point A, associates the angle timestamp with the instantaneous value of the angle, and stores it in the storage unit 13.

[0108] The control unit (acceleration profile generation unit) 12 reads out a plurality of instantaneous values of acceleration and acceleration timestamps stored in the storage unit 13, uses the acceleration timestamps to rearrange the plurality of instantaneous values of acceleration measured by the acceleration sensor 441 while the shaft 24a rotates a plurality of times, and connects the rearranged instantaneous values of acceleration to generate an acceleration profile representing the change in acceleration per rotation of the shaft 24a. Further, the control unit (angle profile generation unit) 12 reads out a plurality of instantaneous values of angle and angle timestamps stored in the storage unit 13, uses the angle timestamps to rearrange the plurality of instantaneous values of angle measured by the angle sensor 443 while the shaft 24a rotates a plurality of times, and connects the rearranged instantaneous values of angle to generate an angle profile representing the change in the measured angle value per rotation of the shaft 24a.

[0109] When the shaft 24a rotates at a constant speed, the generated angle profile is synchronized with the acceleration profile.

[0110] In the above embodiments and modifications, the Per-tooth method is used to detect failures for each tooth of the gear, but the failure determination process may be performed by other methods. FIG. 25 is a flowchart showing the failure determination process executed by the control unit 12 (failure determination unit) of the gear failure determination device 10 of the gear failure detection system 30 according to a modification of the embodiment.

[0111] First, in S21, the control unit 12 determines whether the communication unit 15 has received the acceleration measurement values (a plurality of instantaneous values) and the angle measurement values (a plurality of instantaneous values) transmitted from the measurement device 100. If the determination result is Yes, the process proceeds to S22. If the determination result is No, S21 is repeated.

[0112] In S22, the control unit 12 sequentially absolute-values the received plurality of acceleration measurement values. In S23, the control unit 12 sequentially associates the received plurality of angle measurement values with the teeth of the gear.

[0113] In S24, the control unit 12 records the maximum value among the absolute values of the acceleration for each tooth of the gear. In S25, the control unit 12 determines whether the measurement time at the measurement device 100 has ended. The measurement time at the measurement device 100 is known in the gear failure determination device 10. If the determination result is Yes, the process proceeds to S26. If the determination result is No, the process returns to S21. In S24 after the second time and later, for each tooth, the maximum value among the previously recorded maximum value and the absolute value of the acceleration received in the immediately preceding S21 is recorded.

[0114] In S26, the control unit 12 compares the maximum value of the absolute value of the acceleration for each tooth with a predetermined threshold value. In S27, the control unit 12 determines whether there is a tooth for which the maximum value of the absolute value of the acceleration is greater than the threshold value. If the determination result is Yes, the process proceeds to S29. If the determination result is No, the process proceeds to S28.

[0115] In S28, the control unit 12 displays on the display unit 14 that there is no abnormality in the gear. In S29, the control unit 12 displays on the display unit 14 that there is an abnormality in the tooth of the gear for which the maximum value of the absolute value of the acceleration is greater than the threshold value. After S28 or S29, the process ends.

[0116] In this flowchart, S26 and S27 are executed after S25. However, before the measurement time at the measuring device 100 ends, S26 and S27 may be executed, and if there are abnormal teeth, they may be displayed on the display unit 14.

[0117] As yet another method for the failure determination process, the control unit 12 may generate an acceleration profile from the acceleration measurement values (a plurality of instantaneous values) transmitted by the communication unit 15 from the measuring device 100, and execute FFT (Fast Fourier Transform) on the acceleration profile. The method for generating the acceleration profile is the same as described above. However, in this case, the acceleration profile may not correspond to a long time during which the shaft 24a rotates a plurality of times, and may be for a shorter time period. Then, the control unit 12 may monitor the FFT result, and when an FFT result deviating from the spectrum of a normal gear occurs, determine that the gear is abnormal. The control unit 12 may repeat executing FFT on the acceleration profile for a short time period and monitoring the FFT result.

[0118] Other Modifications As described above, the present invention has been illustrated and described with reference to the preferred embodiments of the present invention. However, it will be understood by those skilled in the art that changes in form and details can be made without departing from the scope of the invention described in the claims. Such changes, modifications, and corrections should be included within the scope of the present invention.

[0119] For example, although the gear failure determination device 10 is a personal computer, it may also be a tablet terminal, a smartphone, a wearable watch, or the like. In the above-described embodiment, the measuring device 100 transmits the measured values to the gear failure determination device 10 without processing them. However, a part of the processing performed by the gear failure determination device 10 may be executed within the measuring device 100. That is, the measuring device 100 may have a part of the functions of the gear failure determination device 10. For example, the processing shown in FIG. 16 may be performed by the microcomputer 451. Since the processing in FIG. 16 involves less computational processing, the power consumption is small. Therefore, if the power generated by the first bearing 25 by self-generation is sufficiently large, the microcomputer 451 may perform the processing in FIG. 16. Such a configuration can be referred to as on-bearing data processing. When such a configuration is adopted, the amount of data transmitted from the measuring device 100 to the gear failure determination device 10 is significantly reduced. This is because for each measurement, thousands of angle data and acceleration data are condensed into one scalar value for each tooth (for each axis). The measurement time can be appropriately set according to the capacity of the storage unit 230 and the power consumption.

[0120] The temperature sensor 442 may not be provided. In FIG. 6, a protection circuit may be provided between the smoothing circuit 262 and the power management IC 263. In FIG. 6, electromagnetic induction power generation is performed by the relative rotation of the magnet M and the coil C. Therefore, as the rotation speed of the coil C increases, the generated electromotive force also increases proportionally. If the device connected to the first shaft 24a fails for some reason, the first shaft 24a rotates at a rotation speed exceeding the assumption, and the electromotive force of the magnet M and the coil C increases proportionally to the rotation, an electromotive force exceeding the input limit of the power management IC 263 is input to the power management IC 263, and there is a possibility that the measuring device 100 may be damaged. In order to avoid such damage, that is, to prevent the measuring device 100 from being damaged even if an electromotive force exceeding the assumption is generated, a protection circuit may be provided between the smoothing circuit 262 and the power management IC 263. This protection circuit is an input protection circuit, and various types of protection circuits can be adopted. For example, a Zener diode is provided between the smoothing circuit 262 and the power management IC 263 as the protection circuit. The Zener diode functions as a protection circuit that protects the measuring device 100 by converting an input voltage exceeding a predetermined value into heat and consuming it.

Explanation of Symbols

[0121] 10 Gear failure determination device 12 Control unit (acceleration profile generation unit, angle profile generation unit, failure determination unit, map generation unit, first calculation unit, second calculation unit, third calculation unit, angle estimation unit) 13 Memory unit 20 Gear transmission mechanism 24a First shaft 25 First bearing 30 Gear failure detection system 100 Measuring device 150 Battery (capacitor) 142 Angle sensor board 149 Power generation unit 250 Bearing part 263 Power management IC (battery control unit, charge completion detection unit) 441 Acceleration sensor 443 Angle sensor 444 Z-phase detector (pulse generation unit) 455 CPU (measurement start time point change unit) 456A FPGA (acceleration timestamp generation unit, angle timestamp generation unit)

Claims

1. A pulse generation unit that generates one pulse every time a shaft provided with a gear rotates once; Provided in a bearing unit that rotatably supports the shaft, after the pulse generation unit generates a pulse, for a predetermined time shorter than the time required for one rotation of the shaft from the measurement start time, an acceleration sensor that measures an instantaneous value of acceleration caused by vibration of the bearing unit; A measurement start time change unit that changes the measurement start time every time the acceleration sensor measures acceleration for a predetermined time; A storage unit that stores a plurality of instantaneous values of the acceleration measured by the acceleration sensor while the shaft rotates a plurality of times; A failure determination unit that determines a failure of the gear based on a plurality of instantaneous values of the acceleration measured by the acceleration sensor while the shaft rotates a plurality of times A gear failure detection system, characterized by comprising:

2. Further comprising an acceleration profile generation unit that rearranges a plurality of instantaneous values of the acceleration measured by the acceleration sensor while the shaft rotates a plurality of times, and combines the rearranged instantaneous values of the acceleration to generate an acceleration profile representing the change in acceleration per rotation of the shaft, The failure determination unit determines a failure of the gear based on the acceleration profile generated by the acceleration profile generation unit The gear failure detection system according to claim 1, characterized in that:

3. A power generation unit that generates power using the relative rotation between the outer ring and the inner ring of the bearing unit; A storage battery that stores the electric charge generated by the power generation unit and supplies power to the acceleration sensor; A storage battery control unit that stops the power supply from the storage battery to the acceleration sensor every time the acceleration sensor finishes measuring acceleration for a predetermined time, and charges the storage battery with the electricity generated by the power generation unit; Further comprising a charge completion detection unit that detects the completion of charging of the storage battery, The acceleration sensor measures an instantaneous value of acceleration for a certain time from the measurement start time after the charge completion detection unit detects the completion of charging of the storage battery and after the pulse generation unit generates a pulse The gear failure detection system according to claim 1 or 2, characterized in that:

4. Comprising a wireless module that wirelessly transmits the instantaneous value of the acceleration measured by the acceleration sensor The storage unit and the failure determination unit are provided in a gear failure determination device provided remotely from the bearing unit, The gear failure determination device includes a communication unit that receives the instantaneous value of the acceleration transmitted from the wireless module, While the battery control unit stops power supply from the battery to the acceleration sensor and charges the battery, the wireless module holds pairing information for wireless communication between the wireless module and the communication unit, and the measurement start time change unit holds the measurement start command time immediately before the stop of power supply to the acceleration sensor. The gear fault detection system according to claim 3, characterized in that.

5. The acceleration sensor is a three-axis acceleration sensor that measures the acceleration of each of the X-axis, Y-axis, and Z-axis. The gear fault detection system according to any one of claims 1 to 4, characterized in that.

6. Further provided with an angle sensor provided in the bearing portion for measuring an instantaneous value of the angle of the shaft for a predetermined time shorter than the time required for one rotation of the shaft from the measurement start time. The measurement start time change unit changes the measurement start time every time the acceleration is measured for a predetermined time by the acceleration sensor and the angle is measured for a predetermined time by the angle sensor. The storage unit stores a plurality of instantaneous values of the angle measured by the angle sensor while the shaft rotates a plurality of times. The fault determination unit determines a gear fault based on a plurality of instantaneous values of the acceleration measured by the acceleration sensor and a plurality of instantaneous values of the angle measured by the angle sensor while the shaft rotates a plurality of times. The gear fault detection system according to any one of claims 1, 3 to 5, characterized in that.

7. The sampling periods of the acceleration sensor and the angle sensor are the same. The storage unit stores the instantaneous value of the acceleration and the instantaneous value of the angle measured simultaneously by the acceleration sensor and the angle sensor in association with each other. The gear fault detection system according to claim 6, characterized in that.

8. An acceleration timestamp generation unit that generates an acceleration timestamp indicating the time when the acceleration sensor measures the instantaneous value of the acceleration, and Further provided with an angle timestamp generation unit that generates an angle timestamp indicating the time when the angle sensor measures the instantaneous value of the angle. The storage unit stores the instantaneous value of the acceleration measured by the acceleration sensor in association with the acceleration timestamp, and stores the instantaneous value of the angle measured by the angle sensor in association with the angle timestamp. The gear fault detection system according to claim 6, characterized in that.

9. The sampling period of the angle sensor is longer than that of the acceleration sensor. A linear interpolation calculation unit that linearly interpolates and calculates the instantaneous value of the angle when the instantaneous value of the acceleration is measured by the acceleration sensor and the instantaneous value of the angle is not measured by the angle sensor from a plurality of instantaneous values of the angle measured by the angle sensor. The gear fault detection system according to claim 8, characterized in that.

10. An acceleration profile generation unit that rearranges a plurality of instantaneous values of the acceleration measured by the acceleration sensor while the shaft rotates a plurality of times, and connects the rearranged instantaneous values of the acceleration to generate an acceleration profile representing the change in acceleration per rotation of the shaft. An angle profile generation unit that rearranges a plurality of instantaneous values of the angle measured by the angle sensor while the shaft rotates a plurality of times, and connects the rearranged instantaneous values of the angle to represent the change in the angle measurement value per rotation of the shaft, and generates an angle profile synchronized with the acceleration profile. The fault determination unit determines a gear fault based on the acceleration profile generated by the acceleration profile generation unit and the angle profile generated by the angle profile generation unit. The gear fault detection system according to any one of claims 6 to 9, characterized in that.

11. Further comprising an angle estimation unit that estimates the instantaneous value of the angle of the shaft from the interval between the pulses generated by the pulse generation unit. The storage unit stores a plurality of instantaneous values of the angle estimated by the angle estimation unit while the shaft rotates a plurality of times. The fault determination unit determines a gear fault based on a plurality of instantaneous values of the acceleration measured by the acceleration sensor and a plurality of instantaneous values of the angle estimated by the angle estimation unit while the shaft rotates a plurality of times. The gear fault detection system according to any one of claims 1, 3 to 5, characterized in that.

12. An acceleration profile generation unit that rearranges a plurality of instantaneous values of the acceleration measured by the acceleration sensor while the shaft rotates a plurality of times, and connects the rearranged instantaneous values of the acceleration to generate an acceleration profile representing the change in acceleration per rotation of the shaft. By arranging a plurality of instantaneous values of the angle estimated by the angle estimation unit and connecting the arranged instantaneous values of the angle, it represents the change in the angle measurement value per rotation of the shaft, and further includes an angle profile generation unit that generates an angle profile synchronized with the acceleration profile. The failure determination unit determines the failure of the gear based on the acceleration profile generated by the acceleration profile generation unit and the angle profile generated by the angle profile generation unit. The gear failure detection system according to claim 11, characterized by the above.

13. The acceleration sensor is a three-axis acceleration sensor that measures the acceleration of each of the X-axis, Y-axis, and Z-axis. The failure determination unit A map generation unit that generates a map defining the relationship between the teeth of the gear and the rotation angle of the shaft. A first calculation unit that calculates the acceleration signal intensity of each tooth using Equation (1). A second calculation unit that calculates the average value of the acceleration signal intensities of all teeth using Equation (2). A third calculation unit that calculates the damage index value of each tooth using Equation (3). Comprising Equation (1) is 【Number 6】 where P （ｔｏｏｔｈ＝ｋ ) is the acceleration signal intensity of the k-th tooth, and x(φ(i)), y(φ(i)), z(φ(i)) are the acceleration values of the X-axis, Y-axis, and Z-axis, respectively, when the sample angular position φ(i) corresponds to the k-th tooth. n samples,k is the number of samples of the acceleration value corresponding to the k-th tooth. Equation (2) is 【Number 7】 where P￣ is the average value of the acceleration signal intensities of all teeth, P(k) is the acceleration signal intensity of the k-th tooth, and Z is the number of teeth of the gear. Equation (3) is 【Number 8】 and here, P rel (k) is the damage index value of the k-th tooth The gear failure detection system according to claim 10 or 12, characterized by the above.

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