Gear failure 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: an acceleration sensor that is provided on a bearing part rotatably supporting a shaft provided with a gear, and 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 every time the shaft rotates; an acceleration profile creation unit that rearranges a plurality of instantaneous values of the acceleration measured by the acceleration sensor while the shaft rotates multiple times, and connects the rearranged instantaneous values of the acceleration to create an acceleration profile representing a change in the acceleration per one rotation of the shaft; and a failure determination unit that determines a failure of the gear based on the acceleration profile created by the acceleration profile creation unit.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 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] Part of the vibration energy generated when gears mesh 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 unique 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, and it changes 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 unique 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 (the 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, a gear fault detection system for detecting a fault in a gear is provided. This gear fault detection system is provided in a bearing portion that rotatably supports a shaft on which the gear is provided, and for a predetermined time shorter than the time required for one rotation of the shaft each time the shaft rotates, an acceleration sensor that measures an instantaneous value of acceleration caused by vibration of the bearing portion, and a plurality of instantaneous values of acceleration measured by the acceleration sensor while the shaft rotates a plurality of times are rearranged, and by connecting the rearranged instantaneous values of acceleration, an acceleration profile generation unit that generates an acceleration profile representing the change in acceleration per rotation of the shaft, and a fault determination unit that determines a fault in the gear based on the acceleration profile generated by the acceleration profile generation unit.

Advantages of the Invention

[0009] In one aspect of the present invention, a large number of instantaneous values of acceleration measured by the acceleration sensor are accumulated while the shaft rotates a plurality of times. The faulty portion of the gear is detected as an abnormality in acceleration at any angular position within a 360° angular range, and in multiple rotations of the shaft, the abnormality in acceleration corresponding to the faulty portion of the gear will be repeatedly measured. In one aspect of the present invention, by rearranging a large number of instantaneous values of acceleration accumulated during multiple rotations of the shaft and connecting the rearranged instantaneous values of acceleration, it is possible to generate an acceleration profile representing the change in acceleration per rotation of the shaft even if the performance of the acceleration sensor is low, so that a fault in 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 scale of the drawings is not necessarily accurate, and some features may be exaggerated or omitted.

[0012] The gear fault detection system of this embodiment monitors the state of the gear and detects gear faults. The gear fault detection system of this embodiment is configured to monitor the gear using a self-powered bearing with a sensor (bearing device) and be able to evaluate the vibration signal for 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 the shaft. That is, the bearing device is a device that supports the 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 also be referred to as a bearing with a measurement device.

[0013] In the following description, the gear transmission mechanism may sometimes be referred to as a gearbox. Also, in this embodiment, for the sake of simplicity of explanation, a simple single-stage gear mechanism as the gear transmission mechanism is exemplified. 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 the gear fault determination device 10 and the gear transmission mechanism 20 of the 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 facing 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 the first wall 21a of the housing 21 below the first bearing 25. The fourth bearing 28 is provided on the 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 that incorporates the measuring device 100 (FIG. 3). The measuring device 100 measures the vibration 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 communicate wirelessly 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 is composed of 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] Figures 3 and 4 are exploded perspective views showing the configuration of the first bearing 25. Figure 3 is an exploded perspective view of the first bearing 25 as seen from the left side. Figure 4 is an exploded perspective view of the first bearing 25 as seen from the right side. As shown in Figure 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 (Figure 4), a rotating portion 130, a circuit board group 140 (Figure 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 plate, 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 also 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 such that they do not protrude from the cover 110 when attached to the cover 110.

[0024] The power control board 141 has a rectifying circuit 261, a smoothing circuit 262, a power management IC 263, and a 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 lid 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 lid 117, whereby the electromagnetic waves of the antenna 147 can reach the external gear failure determination device 10 through the non-magnetic lid 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 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 laminated planar coils. By changing the number of laminated 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 plan view. One yoke 125 is arranged 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 arrange 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 radially outside the coil substrate 120 in 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 angular sensor substrate 142 has an angular sensor 443 and a Z-phase detector (pulse generation unit) 444 mounted thereon. As will be described later, the angular sensor 443 used in this 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 has a control circuit 145, an antenna 147, an acceleration sensor 441, and a temperature sensor 442 mounted thereon. Note that the acceleration sensor 441, the temperature sensor 442, the angular sensor 443, the control circuit 145, and the antenna 147 may be composed of separate IC chips, or a part 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) the acceleration and the angle are detected. The acceleration sensor 441 used in this embodiment is, for example, a MEMS (Micro Electro Mechanical Systems) acceleration sensor. Also, as shown in FIG. 5A, the acceleration sensor 441 used in this 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 this 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 extension part 116 provided at a predetermined position on the outer periphery of the coil board 120. Note that, instead of the extension part 116, the coil board 120 and the power control board 141 may be connected by a lead wire. Alternatively, instead of the extension 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 an FPC connector, soldering is not required, so the productivity of the measuring device 100 can be increased.

[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 part 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 alternately arranged. 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 yoke 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 yokes 125 alternate. As a result, the magnetic flux density passing through the yokes 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 in 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 this 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, and control board 143) are managed by the power management IC 263. In order to prevent the runaway of the control board 143 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 the supply and cut-off of 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 minute 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 measurement device 100. One operation of the measurement device 100 refers to the 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 charge completion signal notifying the FET 264 of the completion of charging. Then, the storage battery 150 resumes power supply to the load L. 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 with the storage battery 150 may be provided. In this case, parallel connection may be made. Note that 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).

[0041] 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 battery 150, 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 signal strength (High or Low), and the horizontal axis indicates time. When the charge completion signal is Low, the battery 150 is not fully charged (charging). When the charge completion signal is High, the battery 150 is supplying power. When the charge completion signal transitions from High to Low, it indicates that the battery 150 has stopped supplying power and entered the charging state. The charge completion signal is generated by the power management IC 263. By combining the two graphs in FIG. 7, it can be seen how the power management IC 263 manages (controls) the voltage of the battery 150.

[0042] As shown in FIG. 7, when the charge completion signal is Low, as time passes, the charge amount of the battery 150 increases, and the charge completion signal becomes High at time t1. The voltage of the battery 150 at time t1 is V2. The voltage V2 is a threshold value for restarting power supply to the load L. After time t1 (after starting power supply to the load L), if 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 to reach V1, the power management IC 263 stops power supply to the load L. That is, V1 is a threshold value for stopping power supply. During the power supply stop, the power management IC 263 charges the battery 150. V1 has a value equal to or slightly greater 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.

[0043] After time t1, if 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, if the power consumption of the load L is smaller than the power generation amount, the voltage increases from V2 (one-dot chain line J3). When the power increases to reach V3, the power management IC 263 stops charging the battery 150. This is to prevent overcharging.

[0044] In this embodiment, the storage battery 150 can store the amount of charge 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 period from time t1 when the voltage drops from V2 to V1 to time t2, the measuring device 100 can perform one operation. During the time period from time t1 to time t2, it is the time when the storage battery 150 can supply power to the load L (the angle sensor substrate 142, the control substrate 143, and the acceleration sensor 441, angle sensor 443, Z-phase detector 444, antenna 147, etc. thereon). The measurement of acceleration and angle and the transfer of the measured data are performed during the time period from time t1 to time t2.

[0045] 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 substrate 141, an angle sensor substrate 142, and a control substrate 143. The angle sensor substrate 142 includes a sensor substrate 170 and a Z-phase detector substrate 171. The power control substrate 141 includes a circuit group 431. The circuit group 431 includes the rectifier circuit 261, smoothing circuit 262, power management IC 263, and FET 264 shown in FIG. 6. The circuit group 431 is connected to the storage battery 150 and the power generation unit 149.

[0046] The power generation unit 149 includes a magnetic track 131 (FIG. 4) and a coil substrate 120 (FIG. 5B). The power generation unit 149 generates electricity based on the relative rotation of the outer ring 250A and the inner ring 250B of the bearing unit 250, and supplies power to the angle sensor substrate 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.

[0047] 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).

[0048] The acceleration sensor 441, the temperature sensor 442, and the angle sensor 443 detect acceleration, temperature, and rotational 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 substrate 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 for reading 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 of the absolute type, but in the present embodiment, an incremental type and a pseudo-absolute method using a Z-phase detector 444 are used.

[0049] 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.

[0050] 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.

[0051] The CPU 455 initializes the storage unit 230, the acceleration sensor 441, the temperature sensor 442, and the angle sensor 443, and performs initial settings for 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 as raw data (unconverted data) to the storage unit 230 (the internal memory 457 and the external memory 452 as necessary) without going through the CPU 455. The acceleration sensor 441 and the angle sensor 443 update and hold 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.

[0052] The wireless module 453 transmits the data stored in the storage unit 230 to the gear fault judgment 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 judgment 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 judgment device 10 and processed by the control unit 12 of the gear fault judgment device 10. When using BLE, 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 the PHY 2Mbps defined in BLE 5.x. When the first bearing 25 and the gear fault judgment device 10 perform wireless communication, wireless communication compliant with 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.

[0053] Each time the power management IC 263 in the circuit group 431 finishes measuring the acceleration for a predetermined time by the acceleration sensor 441 and measuring the angle for a predetermined time by the angle sensor 443, it cuts off the power supply to the load L. Preferably, after the wireless module 453 wirelessly communicates the instantaneous value measured by the acceleration sensor 441 and the instantaneous value measured by the angle sensor 443 via BLE, 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 control board 143). In addition, when the power management IC 263 detects the completion of charging of the storage battery 150 (when the voltage of the storage battery 150 exceeds the threshold value V2), it resumes the power supply to the load L.

[0054] Figure 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 storage 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 completed" indicates the time point when the BLE connection is established. After the pairing is completed, the power management IC 263 also starts supplying power from the storage battery 150 to the acceleration sensor 441, the angle sensor 443, and the Z-phase detector 444.

[0055] In the present embodiment, the output of the Z-phase detector 444 is active low (Low), and 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 the 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 start of power supply to the acceleration sensor 441, the angle sensor 443, and the Z-phase detector 444, and is, for example, 50 ms. The "processing wait time" is set to be longer than the time required for the CPU 455 to complete a predetermined monitoring process. The processing wait 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.

[0056] As shown in FIG. 9(D), after the measurement start delay, the acceleration sensor 441 measures the acceleration for each of the three axes (X / Y / Z axes) for a predetermined measurement time. 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. In this way, the acceleration sensor 441 measures the instantaneous value of the acceleration caused by the vibration of the bearing portion 250 for a certain measurement time from the measurement start point after the Z-phase detector 444 generates a pulse. During the measurement start delay, the CPU 455 performs three processes (1) to (3). In process (1), the CPU 455 acquires the temperature data before the start of measurement from the temperature sensor 442. Based on the temperature measured by the temperature sensor 442, the CPU 455 can determine whether abnormal heat generation occurs inside the first bearing 25. 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 has received the signal displays a message indicating abnormal heat generation on the display unit 14. Also, based on the temperature measured by the temperature sensor 442, the CPU 455 can correct the angle measured by the angle sensor 443. Since the angle sensor 443 is a magnetic sensor, the influence on magnetism due to temperature changes may appear as a measurement error of the angle sensor 443. Regarding this angle error, it is necessary to confirm in advance what kind of influence and error will appear in the measured value of the angle sensor 443 for each temperature, and create a correction table for performing correction to cancel the influence and 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. In process (3), the CPU 455 activates a Wake-up timer for determining the end of measurement (timer timeout).

[0057] The measurement start delay is, for example, about 480 ms. After the above three processes are performed, the CPU 455 enters the Sleep state. The measurement of acceleration and angle is performed by activating only the minimum necessary functional blocks such as the DMA controller 456, the acceleration sensor 441, and the acceleration sensor 443 while the CPU 455 is in the Sleep state. The measurement of acceleration and angle ends when the Wake-up timer expires. When the measurement of acceleration and angle ends, the sleep of the CPU 455 is released, and the CPU 455 returns to the operating state. By doing so, only the minimum functional blocks operate, and a measurement system with low power consumption can be realized.

[0058] 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 corresponds to a time less than one rotation of the axis 24a. During the predetermined measurement time, the angle sensor 443 repeats the measurement at a sampling period, so the measurement results are a plurality of discrete instantaneous values. In this way, 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 after the Z-phase detector 444 generates a pulse. In the present 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 fault determination device 10 during the "data transfer time". The data transfer time is, for example, 1 second. One operation of the measuring device 100 is from power-on to the end of the data transfer time.

[0059] When the data transfer is completed, the power management IC 263 stops power supply to the load L and starts charging the storage battery 150. When the charging of the storage battery 150 is completed, the power management IC 263 sends a charge completion signal notifying the FET 264 of the charge completion, and enables power supply to the load L (the angle sensor substrate 142, the control substrate 143, and the acceleration sensor 441, the angle sensor 443, the Z-phase detector 444, the antenna 147, etc. thereon) again.

[0060] After this, after the pairing time, 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, while the supply timing of the immediately previous measurement start signal is immediately after the generation of the Z-phase detection pulse (detection of the Z-phase magnet 162 by the Z-phase detector 444), 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 by the acceleration sensor 441 for a predetermined time and the angle is measured by the angle sensor 443. Therefore, the acceleration sensor 441 and the angle sensor 443 measure instantaneous values corresponding to different mechanical angles (the actual angle around the axis 24a) every time a measurement for a predetermined time is performed. By doing so, overlapping of the measurement start timing can be prevented. 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 previous supply timing.

[0061] 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 power supply to the load L and starts charging the storage battery 150. When the charging of the storage battery 150 is completed, the power management IC 263 sends a charge completion signal notifying the charge completion to the FET 264, making it possible to supply power to the load L again. After that, after the pairing time, 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. Thereafter, such operations are repeated. Therefore, every time the power management IC 263 finishes measuring the instantaneous value of acceleration for a predetermined time (corresponding to less than one rotation of the shaft 24a) by the acceleration sensor 441 and the instantaneous value of angle for a predetermined time (corresponding to less than one rotation of the shaft 24a) by the angle sensor 443, it stops power supply to the acceleration sensor 441, the angle sensor 443, etc. by the storage battery 150 and charges the storage battery 150 with the electricity generated by the power generation unit 149.

[0062] FIG. 10 shows the update cycles 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 cycle (sampling cycle) of the acceleration sensor 441 is equal to the update cycle (sampling cycle) 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 the acceleration and the instantaneous value of the 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 axis 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 the acceleration and the instantaneous value of the 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 selected (set) in advance, for example, based on the meshing frequency of the gears.

[0063] 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(A)). 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.

[0064] In S3, the CPU 455 determines whether the processing waiting 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 time point 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 time point 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.

[0065] 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), and 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 three processes (1) to (3) and enters the sleep state.

[0066] Next, in S7, the CPU 455 determines whether it is the transmission time point of the measured value. If the determination result is Yes, the operation proceeds to S8. If the determination result is No, S7 is repeated. The determination result of S7 being Yes means that the CPU 455 returns from the sleep state to the operating state due to the expiration of the above Wake-up timer. In S8, the CPU 455 transmits (transfers) the instantaneous value measured by the acceleration sensor 441 stored in the storage unit 230 and the instantaneous value measured by the angle sensor 443 from the measuring device 100 to the gear fault determination device 10 by BLE wireless communication. In this way, one measurement of the measuring device 100 is performed by S2 to S8.

[0067] Next, in S9, the CPU 455 instructs the power management IC 263 to stop power supply. As a result, the power management IC 263 stops power supply to the acceleration sensor 441, the angle sensor 443, etc. from the storage battery 150, and charges the electricity generated by the power generation unit 149 into the storage battery 150. As described above, when the charging of the storage battery 150 is completed, the power management IC 263 sends a charging completion signal notifying the charging completion to the FET 264, and resumes power supply to the acceleration sensor 441, the angle sensor 443, etc. from the storage battery 150. When the charging of the storage battery 150 is completed, the power management IC 263 also sends a charging completion signal to the CPU 455. In S10, the CPU 455 determines whether it has received a charging completion signal from the power management IC 263. If the determination result is Yes, the operation proceeds to S11. If the determination result is No, S8 is repeated. In S11, 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, the operation proceeds to S12. If the determination result is No, the operation ends. In S12, the CPU 455 determines the supply timing (measurement start command timing) of the next measurement start signal with respect to the Z-phase detection pulse based on the supply timing (measurement start command timing) of the measurement start signal immediately before the stop of power supply. The next measurement start command timing can be determined, for example, by adding or subtracting a predetermined time to the immediately previous measurement start command timing. In this way, the CPU 455 changes the measurement start timing every time it measures acceleration and angle for a predetermined time. After this, the operation returns to S1.

[0068] 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 with respect to one axis output by the three-axis acceleration sensor 441. The illustration of the change in acceleration with respect to 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 related to the central graph). The illustration of the change in the angle output by the other 23 readers is omitted. As described above, during the predetermined measurement time, since the acceleration sensor 441 repeats the measurement at the sampling period, the measurement results are a plurality of discrete instantaneous values. Also, during the predetermined measurement time, since each reader of the angle sensor 443 repeats the measurement at the sampling period, the measurement results are a plurality of discrete instantaneous values. As described above, each time the acceleration and angle are measured for a predetermined time (the 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 adjacent readers.

[0069] 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 from the wireless module 453 via BLE 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.

[0070] The control unit 12 of the gear fault 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 association with each other. Therefore, the generated angle profile is synchronized with the acceleration profile.

[0071] 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 fault 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 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.

[0072] 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 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.

[0073] FIG. 15 shows graphs of an acceleration profile and an angle profile obtained from results continuously measured during one rotation (360°) of axis 24a by a high-cost 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 FIG. 14 and FIG. 15, the acceleration profile and the angle profile obtained by repeatedly measuring with the low-performance acceleration sensor and angle sensor with low resolution and low sampling frequency according to the present embodiment have accuracy comparable to that of the acceleration profile and the angle profile obtained by measuring with the high-cost acceleration sensor and angle sensor with high resolution and high sampling frequency.

[0074] 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 faults 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 angles 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.

[0075] 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.

[0076] The control unit (map generation unit) 12 creates a map of angles and teeth (angle-to-tooth mapping function) (process 520). FIGS. 17 and 18 are diagrams showing examples of the map of angles and teeth. The vertical axis of the map in FIG. 17 indicates 22 teeth, and the horizontal axis indicates 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 shaft angle = 0° position at the time of map creation is regarded as the first tooth. The vertical axis of the map in FIG. 18 indicates 22 teeth, and the horizontal axis indicates 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 shaft angle = 0° position 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° (absolute angle), when using the map of FIG. 18, the user inputs 44.6° as the angle offset value to the input unit 11 in process 510.

[0077] As shown in FIGS. 17 and 18, since the gear rotates 360 degrees in one revolution, 22 line segments S obtained by dividing 360 degrees by 22 can be formed. FIGS. 17 and 18 show that when the axial 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.

[0078] After generating the map of the angle and the teeth (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 according to the Per-tooth method using Equation (1).

Equation

[0079] 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 the condition (*) (the number of samples of the measured acceleration value corresponding to the k-th tooth).

[0080] 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 acceleration signal intensity values P for 22 teeth can be created. That is, through Process 530, the acceleration signal intensities for 22 teeth can be obtained. Reference numeral 540 in FIG. 16 shows the values used in Equation (1) for each tooth.

[0081] In this 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 comes to 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

[0082] Therefore, when 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

[0083] 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 value serves as an index representing tooth damage. When teeth mesh with each other, vibrations occur 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. [Number] Here, Z represents the number of samples of the acceleration signal intensity, that is, the number of teeth of the gear.

[0084] Next, the control unit (third calculation unit) 12 calculates the relative signal power coefficient P rel (k) for each tooth using Equation (5). [Number]

[0085] 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, the value of P rel (k) can take a value smaller than 0 (that is, P rel (k) is not 0 but P rel (k) < 0 can occur). Therefore, if it is normalized so that the average vibration reference becomes zero, P rel (k) can be used as a numerical value for easily evaluating the normality / abnormality of each tooth. This 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 intensity coefficient is used as an index value of damage indicating the state of each individual tooth, enabling per-tooth evaluation of the acceleration signal intensity.

[0086] 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 are repeatedly measured. In this embodiment, by rearranging a large number of instantaneous values of acceleration accumulated during multiple rotations of the shaft 24a and connecting the rearranged instantaneous values of acceleration, an acceleration profile representing the change in acceleration per rotation of the shaft 24a can be generated even if the performance of the acceleration sensor 441 is low. Also, by rearranging a large number of instantaneous values of the angle accumulated during multiple rotations of the shaft 24a and connecting the rearranged instantaneous values of the angle, an angle profile representing the change in angle per rotation of the shaft 24a can be generated even if the performance of the angle sensor 443 is low. Based on the thus obtained angle profile and acceleration profile that are synchronized with each other, the failure of the gear can be accurately determined. That is, it is possible to appropriately grasp at which angle and what kind of vibration is occurring during the rotation of the shaft 24a, and the location (angle) where the abnormality occurs can be appropriately specified. Also, since the angle profile and the acceleration profile are synchronized, the location where the abnormality occurs can be specified even if the rotational speed of the shaft 24a fluctuates.

[0087] In the measuring device 100, every time the acceleration is measured by the acceleration sensor 441 for a predetermined time, the measurement start point is changed. Therefore, every 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 by 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, every time the angle is measured by the angle sensor 443 for a predetermined time, the measurement start point is changed. Therefore, every 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 angle accumulated by multiple rotations of the shaft 24a and connecting the arranged instantaneous values of the angle, an angle profile representing the change in angle per rotation of the shaft 24a can be easily generated.

[0088] 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 the acceleration and a plurality of discrete instantaneous values of the angle are associated on the time axis) is transferred to the gear fault judgment device 10 and accumulated in the storage unit 13 of the gear fault judgment device 10. Therefore, in the gear fault judgment device 10, the control unit 12 can easily generate a synchronized acceleration profile and angle profile.

[0089] In the present embodiment, the 3-axis acceleration sensor 441 that measures the acceleration of each of the X-axis, Y-axis, and Z-axis can accurately determine the fault location of the gear.

[0090] 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 individual reader is low.

[0091] The measuring device 100 (acceleration sensor 441, angle sensor 443, circuit board group 140, etc.) of the present embodiment is built into the first bearing 25. Further, since the electricity obtained by the power generation unit 149 that generates electricity using the relative rotation between the outer ring 250A and the inner ring 250B of the bearing unit 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 unit 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 measure for a predetermined period, the power supply from the 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 battery 150. Therefore, the chargeable amount of the battery 150 may be small. Furthermore, during the measurement by the acceleration sensor 441 and the angle sensor 443, the CPU 455 enters a sleep state, so the chargeable amount of the battery 150 may be small.

[0092] 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 raw data without conversion. 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.

[0093] 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 this embodiment can be configured with inexpensive MEMS sensors and low-power microcontrollers. Since the measuring device 100 can install the acceleration sensor 441 in the immediate vicinity of the vibration source (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 direction of the action line where the 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.

[0094] The gear diagnosis algorithm adopted in this embodiment is the Per-tooth method and has the following advantages. Abnormal teeth can be identified. Diagnosis can be performed with a low computational cost. Conventionally, without comparing with the vibration data of normal gears used in gear diagnosis, an abnormality determination can be made from a single evaluation result. The fact that diagnosis can be performed with 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 a small amount of mathematical calculation, enabling calculation with low power. Further, according to the present embodiment, gear judgment 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 single-axis data cannot detect an abnormality in the Peak-Peak value, the data of the other axes can complement it to achieve high diagnostic sensitivity.

[0095] Further, 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, and thus 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 vibration near 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 vibration, so that fault judgment can 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.

[0096] Further, 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 meshing portion of the gears, and the vibration that can be obtained may be called 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.

[0097] Next, a modification of the present embodiment will be described. FIG. 19 shows elements particularly related to gear fault judgment 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 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 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 an instantaneous value of an 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.

[0098] 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 are wirelessly transmitted from the wireless module 453 as BLE wireless while being associated with the acceleration timestamp and the angle timestamp, 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 acceleration and the instantaneous value of the angle. The control unit 12 of the gear failure determination 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 stores the instantaneous value of the angle measured by the angle sensor 443 in association with the angle timestamp. The accumulation is performed periodically while the shaft 24a rotates a plurality of times.

[0099] 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. 20, the sampling periods of the acceleration sensor 441 and the angle sensor 443 do not have to match.

[0100] As shown in FIG. 20, 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. 21, 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. 21, point A indicates two instantaneous values of the angle measured by the angle sensor 443, and point B indicates 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.

[0101] 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 obtained by linear interpolation and the angle timestamp in addition to the measured instantaneous value of the angle and the angle timestamp. Therefore, the generated angle profile is synchronized with the acceleration profile.

[0102] Next, the preferable range of the performance of the acceleration sensor 441 will be described. FIG. 22 is a diagram showing an example of an acceleration profile regarding the Y-axis obtained in the present embodiment. This acceleration profile was obtained under the conditions that the number of teeth of the gear was 22, the rotational speed of the shaft was 3000 rpm, and the transmission torque was 1000 Nm. The gear had moderate damage. In the acceleration profile of FIG. 22, the normal vibration (vibration in a state where there is no damage to the gear) is within the acceleration range of -2G to +2G. The abnormal vibration due to moderate gear damage is from 2 times (-4G to +4G) to 3 times (-6G to +6G) the acceleration range of the normal vibration. The vibration acceleration of the gear is not much affected by the transmission torque and can vary depending on the rotational speed of the shaft, the meshing state of the gear, and the type of the gear. The acceleration profile of FIG. 22 corresponds to the condition where the vibration acceleration is low. Therefore, if the acceleration sensor 441 can measure the acceleration in the range of -4G to +4G, which is at least twice the acceleration range of the normal vibration, the moderate damage of the gear can be determined. However, when the measured value of the acceleration sensor 441 saturates for a long time, the output of the acceleration sensor 441 becomes unstable. Therefore, the preferable range of the measurable acceleration of the acceleration sensor 441 is at least -6G to +6G, which is three times the acceleration range of the normal vibration. In the case of high vibration acceleration conditions, normal vibration is within the acceleration range of -5.3G to +5.3G. Abnormal vibration due to moderate gear damage is from 2 times (-10.6G to +10.6G) to 3 times (-16G to +16G) the acceleration range of normal vibration. Therefore, if the acceleration sensor 441 can measure accelerations from -10.6G to +10.6G, moderate damage to the gear can be determined. However, if the measured value of the acceleration sensor 441 saturates for a long time, the output of the acceleration sensor 441 becomes unstable. Therefore, the measurable acceleration range of the acceleration sensor 441 is preferably from -16G to +16G, which is 3 times the acceleration range of normal vibration. Therefore, the measurable acceleration range of the acceleration sensor 441 is preferably at least from -6G to +6G and at most from -16G to +16G. Regarding a triaxial acceleration sensor, it is preferable that the measurable acceleration range for all three axes is at least from -6G to +6G and at most from -16G to +16G. In such a measurable acceleration range, depending on the meshing state of the gears and the type of gears, it may not be possible to identify gear failures based only on the acceleration measurement results of one axis, but with a triaxial acceleration sensor, gear failures can be accurately identified.

[0103] The resolution of the acceleration sensor 441 is preferably 1 / 10 or less of the measurable acceleration range. In the example of FIG. 22, since the measurable acceleration range is from -6G to +6G, it is preferably 1.2G or less. When the measurable acceleration range is from -16G to +16G, it is preferably 3.2G or less. FIG. 23 is a graph showing the relative signal strength coefficient P for each of the three axes calculated by the Per-tooth method using a triaxial acceleration sensor whose resolution is 1 / 5 of the measurable acceleration range. rel As shown in FIG. 23, even when the resolution is 1 / 5 of the measurable acceleration range, damage to the 14th tooth was determined for each of the three axes. In order to further improve the measurement accuracy, it is preferable that the resolution of the acceleration sensor 441 is 1 / 10 or less of the measurable acceleration range. In this case, by using the Per-tooth method, it is possible to surely detect a gear failure. The higher the resolution of the acceleration sensor 441, the more accurately a gear failure can be detected. However, a sensor with a high resolution is expensive. Therefore, it is preferable that the resolution of the acceleration sensor 441 is 1 / 4096 (1 / 12 bits) or more of the measurable acceleration range.

[0104] FIG. 24 is a graph showing the three-axis FFT results obtained by FFT (Fast Fourier Transform) from the three-axis acceleration profiles. The FFT result on the central Y-axis in FIG. 24 was obtained from the acceleration profile in FIG. 22. These FFT results were obtained under the conditions that the number of teeth of the gear was 22, the rotational speed of the shaft was 3000 rpm, and the transmitted torque was 1000 Nm. The gear had moderate damage. Since the number of teeth of the gear was 22 and the rotational speed of the shaft was 3000 rpm, the meshing frequency was 1100 Hz. Also in the three-axis FFT results of FIG. 24, the normal vibration component and the abnormal vibration component have local maximum values at integer multiples of the meshing frequency. In particular, at 1 times and 3 times the meshing frequency, the local maximum values are high. However, depending on the rotational speed of the shaft and / or the transmitted torque, there may be a case where the local maximum value is high at 2 times the meshing frequency. It should be noted that in all three axes, the abnormal vibration component exceeds the normal vibration component in the range from 1 times to 2 times the meshing frequency. This feature was the same even when the rotational speed of the shaft and / or the transmitted torque was changed. Therefore, the measurable frequency band (detection band) of the acceleration sensor 441 is preferably 0.9 times or more and 2.1 times or less of the meshing frequency of the gear, and more preferably 1 time or more and 2 times or less of the meshing frequency of the gear. As described above, the acceleration sensor 441 with low performance can be used in this embodiment.

[0105] The sampling frequency of the actually set acceleration sensor 441 is preferably ideally 1 time the meshing frequency. However, as long as it is within the above detection band, the sampling frequency of the acceleration sensor 441 is not important. In the present embodiment and the modified example described above with reference to FIGS. 19 to 21, the instantaneous value of the measured acceleration and the instantaneous value of the angle are synchronized, and each time the acceleration and the angle are measured, the measurement start point is changed, and the acceleration and the angle can be measured at many angular positions of the axis.

[0106] Next, the preferable range of the performance of the angle sensor 443 will be described. As shown in FIG. 25, the resolution of each reader of the angle sensor 443 is preferably 1 / 10 or less of the angular pitch of the gear. Also, the repeatability accuracy of each reader of the angle sensor 443 is preferably 1 / 10 or less of the angular pitch of the gear. The inventor conducted a simulation to examine the upper limits of the resolution and the repeatability accuracy. FIG. 26 is a graph showing an acceleration profile with respect to the Y-axis as a reference for the simulation. This acceleration profile was obtained under the conditions that the number of teeth of the gear is 22, the rotational speed of the shaft is 3000 rpm, and the transmission torque is 1000 Nm, similar to the acceleration profile of FIG. 22. The gear had moderate damage. The acceleration profile of FIG. 22 was obtained in the present embodiment, while the acceleration profile of FIG. 26 was obtained from the results of continuously measuring during one rotation (360°) of the shaft 24a with high-cost acceleration sensors and angle sensors with high resolution and high sampling frequency. In the simulation, a uniform distribution error of 1.8° was given to the mechanical angle in the actually measured high-precision acceleration profile shown in FIG. 26. Since the angular pitch of the gear with 22 teeth is 16.36°, 1.8° is 1 / 9.09 of the angular pitch. FIG. 27 is a graph showing the acceleration profile obtained by this simulation. As is clear from the comparison with FIG. 26, the simulation results are similar to the reference acceleration profile, and abnormal vibrations could be detected from these simulation results by the Per-tooth method.

[0107] In another simulation, a uniform distribution error of 2° was given to the mechanical angle of the actually measured high-precision acceleration profile shown in FIG. 26. Since the angular pitch of the gear with 22 teeth is 16.36°, 2° is 1 / 8.18 of the angular pitch. FIG. 28 is a graph showing the acceleration profile obtained from this simulation. As is clear from the comparison with FIG. 26, the simulation result deteriorated from the reference acceleration profile, and abnormal vibration could not be detected from this simulation result by the Per-tooth method. Therefore, it is preferable that the resolution and repeatability accuracy of each reader of the angle sensor 443 be 1 / 9.09 or less of the angular pitch of the gear, and more preferably 1 / 10 or less in order to further improve the measurement accuracy.

[0108] The higher the resolution, the more accurately the failure of the gear can be detected. However, a sensor with high resolution is expensive. Therefore, it is preferable that the resolution of each reader of the angle sensor 443 be 1 / 65536 (1 / 16 bits) or more of the angular pitch of the gear. Also, the higher the repeatability accuracy, the more accurately the failure of the gear can be detected. However, a sensor with high repeatability accuracy is expensive. Therefore, it is preferable that the repeatability accuracy of each reader of the angle sensor 443 be 1 / 256 (1 / 8 bits) or more of the angular pitch of the gear. As described above, the angle sensor 443 with low performance can be used in this embodiment.

[0109] FIG. 29 shows elements particularly related to gear failure determination in the gear failure 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 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. 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 generated the Z-phase detection pulse. Then, the FPGA 456A stores the Z-phase timestamp in the storage unit 230.

[0110] The instantaneous value measured by the acceleration sensor 441 associated with the acceleration timestamp stored in the storage 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 fault determination device 10. Since the BLE wireless transmission is repeated periodically, the communication unit 15 of the gear fault determination device 10 receives the instantaneous value of acceleration and the Z-phase timestamp periodically. The control unit 12 of the gear fault 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 storage unit 13. That is, the storage unit 13 stores the instantaneous value of 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 a plurality of times.

[0111] In this modification, even without the instantaneous value of the angle measured by the angle sensor, synchronized acceleration profiles and angle profiles 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. 30, 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. 30, point B indicates the instantaneous value of the angle obtained by interpolation. The control unit 12 generates angle timestamps corresponding to all the estimated instantaneous values of the angle 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.

[0112] The control unit (acceleration profile generation unit) 12 reads out a plurality of instantaneous values of the acceleration and the acceleration timestamps stored in the storage unit 13, and uses the acceleration timestamps to rearrange the plurality of instantaneous values of the acceleration measured by the acceleration sensor 441 during multiple rotations of the shaft 24a, 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 sort the plurality of instantaneous values of the angle measured by the angle sensor 443 while the shaft 24a rotates multiple times. By connecting the sorted instantaneous values of the angle, an angle profile representing the change in the measured angle value per rotation of the shaft 24a is generated.

[0113] When the shaft 24a rotates at a constant speed, the generated angle profile is synchronized with the acceleration profile. The preferable range of the performance of the acceleration sensor described above also applies to this modification example.

[0114] Other modification examples As described above, the present invention has been illustrated and described with reference to the preferable embodiments of the present invention. However, it will be understood by those skilled in the art that changes in form and details are possible without departing from the scope of the invention described in the claims. Such changes, modifications, and corrections should be included in the scope of the present invention.

[0115] 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 considerably reduced. This is because thousands of angular data and acceleration data for each measurement are condensed into one scalar value for each tooth (for each axis). The measurement time can be appropriately set according to the capacity and power consumption of the storage unit 230.

[0116] 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. For this reason, 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 rotational 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 the measuring device 100 may be damaged. To avoid such damage, that is, to ensure that the measuring device 100 is not damaged even when 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.

Description of Symbols

[0117] 10 Gear fault judgment device 12 Control unit (acceleration profile generation unit, angle profile generation unit, fault judgment 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 fault detection system 100 Measuring device 150 Storage battery (capacitor) 142 Angle sensor board 149 Power generation unit 250 Bearing part 263 Power management IC (storage 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 change unit) 456A FPGA (acceleration timestamp generation unit, angle timestamp generation unit)

Claims

1. It is provided in a bearing portion that rotatably supports a shaft provided with a gear, and measures an instantaneous value of acceleration caused by vibration of the bearing portion for a predetermined time shorter than the time required for one rotation of the shaft every time the shaft rotates. An acceleration sensor, An acceleration profile generation unit that rearranges a plurality of instantaneous values of acceleration measured by the acceleration sensor while the shaft rotates a plurality of times, and connects the rearranged instantaneous values of acceleration to represent the acceleration per rotation of the shaft. Generate an acceleration profile of the change, A failure determination unit that determines a failure of the gear based on the acceleration profile generated by the acceleration profile generation unit A gear failure detection system characterized by comprising.

2. It further comprises a pulse generation unit that generates one pulse every time the shaft rotates, The acceleration sensor measures an instantaneous value of acceleration for a predetermined time shorter than the time required for one rotation of the shaft from the measurement start time after the pulse generation unit generates a pulse, It further comprises a measurement start time change unit that changes the measurement start time every time the acceleration sensor measures acceleration for a predetermined time. The gear failure detection system according to claim 1, characterized in that.

3. A power generation unit that generates power by utilizing the relative rotation between the outer ring and the inner ring of the bearing portion, 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 supplying power from the storage battery to the acceleration sensor every time the acceleration sensor measures acceleration for a predetermined time, and charges the storage battery with the electricity generated by the power generation unit, It further comprises 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 period of 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 2, characterized in that.

4. 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 failure detection system according to any one of claims 1 to 3, characterized in that.

5. An angle sensor provided in the bearing portion that measures an instantaneous value of the angle of the shaft for a predetermined time shorter than the time required for one rotation of the shaft every time the shaft rotates, By arranging a plurality of instantaneous values of the angle measured by the angle sensor while the shaft rotates a plurality of times, 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 any one of claims 1 to 3, characterized by the above.

6. The sampling periods of the acceleration sensor and the angle sensor are the same. It further includes a storage unit that associates and stores the instantaneous value of the acceleration and the instantaneous value of the angle measured simultaneously by the acceleration sensor and the angle sensor. The gear failure detection system according to claim 5, characterized by the above.

7. An acceleration timestamp generation unit that generates an acceleration timestamp indicating the time when the acceleration sensor measures the instantaneous value of the acceleration, An angle timestamp generation unit that generates an angle timestamp indicating the time when the angle sensor measures the instantaneous value of the angle, It further includes a storage unit that associates the instantaneous value of the acceleration measured by the acceleration sensor with the acceleration timestamp, and associates and stores the instantaneous value of the angle measured by the angle sensor with the angle timestamp. The gear failure detection system according to claim 5, characterized by the above.

8. The sampling period of the angle sensor is longer than the sampling period of the acceleration sensor. It further includes 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 failure detection system according to claim 7, characterized by the above.

9. A pulse generation unit that generates one pulse every time the shaft rotates once, An angle estimation unit that estimates the instantaneous value of the angle of the shaft from the interval between the pulses. The angle profile generation unit arranges a plurality of instantaneous values of the angle estimated by the angle estimation unit and combines the arranged instantaneous values of the angle, thereby representing the change in the angle measurement value per one rotation of the shaft and generating 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 any one of claims 1 to 3, characterized in that.

10. 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 is 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 the teeth using Equation (2), a third calculation unit that calculates the damage index value of each tooth using Equation (3), and is provided with 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, and 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 the 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】 where P rel (k) is the damage index value of the k-th tooth The gear failure detection system according to any one of claims 5 to 9, characterized in that.

11. The measurable acceleration range of the acceleration sensor is at least -6G to +6G and at most -16G to +16G. The gear failure detection system according to any one of claims 1 to 10, characterized in that.

12. The resolution of the acceleration sensor is 1 / 4096 or more and 1 / 10 or less of the measurable acceleration range. The gear failure detection system according to claim 11, characterized in that.

13. The measurable frequency band of the acceleration sensor is 0.9 times or more and 2.1 times or less of the meshing frequency of the gear. The gear failure detection system according to any one of claims 1 to 12, characterized in that.

14. The resolution of the angle sensor is 1 / 65536 or more and 1 / 10 or less of the angle pitch of the gear. The gear failure detection system according to any one of claims 5 to 8, characterized in that.

15. The repeatability accuracy of the angle sensor is equal to or greater than 1 / 256 and equal to or less than 1 / 10 of the angle pitch of the gear. The gear fault detection system according to any one of claims 5 to 8 and 14, characterized in that.

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