Measuring device and gear failure detection device

Abstract

To provide a measuring device that can accurately detect abnormalities of a gear.SOLUTION: The measuring device is provided on one side of a bearing portion that rotatably supports a rotary shaft provided with a gear. The measuring device includes: a cover that is attached to an outer ring of the bearing portion and covers the one side of the bearing portion, an acceleration sensor provided on an inner surface of the cover to measure vibrations of the bearing portion in each of 3 axes (X-, Y-, and Z-axes); an angle sensor provided on the inner surface of the cover to measure an angle between the outer ring and an inner ring of the bearing portion; and an acquiring unit that is provided on the inner surface of the cover to acquire acceleration measurement values respectively on the 3 axes obtained by the acceleration sensor and angle measurement values obtained by the angle sensor, associated with each other sharing one common time reference.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a measuring device and a gear failure detection device, and more particularly to a measuring device for measuring the vibration and angular position of a bearing provided in a gear transmission mechanism, and a gear failure detection device for determining a gear failure provided in a gear transmission mechanism. [Background technology]

[0002] Gears can experience various forms of fatigue, and spontaneous damage can occur depending on usage time and other factors. Generally, even without damage, gears generate vibrations due to changes in meshing rigidity and other reasons over time. The occurrence of vibrations varies depending on the presence of damage. In the case of a gear transmission mechanism, the vibrations described above are transmitted to the case of the gear transmission mechanism through the gear body (parts other than the teeth), shaft, and bearings. Patent Document 1 describes a device for detecting abnormalities in the gears of a gear transmission mechanism.

[0003] The device described in Patent Document 1 has an acceleration sensor that detects vibrations generated when two gears mesh. The acceleration sensor is fixed to the transmission casing. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-181282 [Overview of the project] [Problems that the invention aims to solve]

[0005] A portion of the vibration energy generated when gears mesh is released externally as audible noise from the case housing the gears. Along the transmission path of this audible noise, the vibrations originally excited by the meshing are affected by the case's inherent vibration transmission path as they travel from the vibration excitation point to the pickup point (the installation location of the acceleration sensor). Consequently, the vibration characteristics measured at the pickup point are different from those at the excitation point. This is due to the stiffness and mass characteristics of the objects present in the transmission path, as well as damping, which alters 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, the acceleration sensor is mounted on the casing of the speed increaser, so vibrations generated when the two gears (gear pair) mesh are transmitted to the acceleration sensor via the speed increaser casing. The vibrations that reach the acceleration sensor are affected by the vibration transmission path inherent to the casing, so the vibrations measured by the acceleration sensor may have different vibration characteristics compared to the vibrations at the vibration source (the meshing gear pair). Furthermore, the configuration in Patent Document 1 cannot detect abnormalities in individual teeth of the gears. Therefore, the present invention aims to provide a technology (device) that can more accurately detect abnormalities in gears. [Means for solving the problem]

[0007] To solve the above problems, a measuring device according to one aspect of the present invention is a measuring device provided on one side surface of a bearing portion that rotatably supports a shaft on which a gear is provided, and comprises: a cover attached to the outer ring of the bearing portion and covering the one side surface of the bearing portion; an acceleration sensor provided on the inner surface of the cover for measuring the vibration of the bearing portion in each of the three axes (X axis, Y axis, Z axis); an angle sensor provided on the inner surface of the cover for measuring the angle between the outer ring and the inner ring of the bearing portion; and an acquisition unit provided on the inner surface of the cover for acquiring the acceleration measurement values ​​for each of the three axes obtained by the acceleration sensor and the angle measurement values ​​obtained by the angle sensor, by linking them together using a common time reference.

Advantages of the Invention

[0008] According to one aspect of the present invention, since the acceleration sensor is attached to the bearing portion, the path through which the vibration of the gear is transmitted to the acceleration sensor becomes extremely short. Further, by diagnosing the abnormality of the gear from the acceleration values obtained in each of the three axes (three directions), the diagnostic sensitivity is increased. Therefore, it becomes possible to detect the abnormality of the gear earlier and more accurately.

Brief Description of the Drawings

[0009] [Figure 1] FIG. 1 is a diagram showing a gear fault judgment device and a gear transmission mechanism according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the configuration of the gear fault judgment device of FIG. 1. [Figure 3] FIG. 3 is an exploded perspective view of the first bearing of FIG. 1. [Figure 4] FIG. 4 is an exploded perspective view of the first bearing of FIG. 1 viewed from another direction. [Figure 5A] FIG. 5A is a plan view showing a cover, a coil substrate, a circuit board group, and a storage battery. [Figure 5B] FIG. 5B is a plan view showing details of the coil substrate. [Figure 6] FIG. 6 is a block diagram for explaining a self-power generation mechanism. [Figure 7] FIG. 7 is a graph for explaining the operation of the power management IC. [Figure 8] FIG. 8 is a block diagram showing the configuration of the measuring device. [Figure 9] FIG. 9 is a timing chart for explaining the processing of the measuring device. [Figure 10] FIG. 10 is a diagram for explaining a pair of acceleration measurement values and angle measurement values. [Figure 11] FIG. 11 is a flowchart for explaining the processing of the measuring device. [Figure 12] FIG. 12 is a diagram for explaining a method of obtaining an acceleration curve for each tooth. [Figure 13] FIG. 13 is a diagram for explaining a failure detection process executed by the gear failure determination device. [Figure 14] FIG. 14 is a map of angles and teeth when the angle offset value is not used. [Figure 15] FIG. 15 is a map of angles and teeth when the angle offset value is used. [Figure 16] FIG. 16 is a diagram showing an example of acceleration data for three axes. [Figure 17] FIG. 17 is a diagram showing experimental results for confirming the effects of the embodiment. **Embodiments for Carrying Out the Invention**

[0010] The gear failure detection system of the present embodiment monitors the state of gears provided in a gear transmission mechanism and detects gear failures. The gear failure detection system of the present embodiment is configured to monitor the gear transmission mechanism using a self-powered bearing with a sensor (bearing device) and to evaluate the vibration signal for each tooth of the gear. The bearing device used in the present embodiment has functions of self-power generation, sensing, and wireless transmission in addition to the original function of the bearing that rotatably supports 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.

[0011] In the following description, the gear transmission mechanism may be referred to as a gearbox. Also, the gear may be referred to as a gear. Further, for the sake of simplicity of explanation, the gear transmission mechanism of the present embodiment is assumed to be a simple single-stage gear gear transmission mechanism. The scope of the present invention is not limited to the following embodiments, and changes and modifications can be made within the scope of the technical idea of the present invention.

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 shows a gear failure detection device 10 and a gear speed change mechanism 20 according to an embodiment of the present invention. The gear speed change mechanism 20 has a housing 21 and a first gear 22 and a second gear 23 provided inside the housing 21. The housing 21 has a first wall 21a and a second wall 21b facing each other at a predetermined interval. The first gear 22 and the second gear 23 mesh with each other. The gear speed change mechanism 20 also has a first shaft 24a to which the first gear 22 is attached, and a first bearing 25 and a second bearing 26 supporting 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.

[0013] Furthermore, the gear transmission mechanism 20 includes a second shaft 24b to which a second gear 23 is attached, and a third bearing 27 and a fourth bearing 28 supporting both ends of the second shaft 24b. The third bearing 27 is located below the first bearing 25 and is provided on the first wall 21a of the housing 21. The fourth bearing 28 is located below the second bearing 26 and is provided on the second wall 21b of the housing 21. In this embodiment, the first bearings 25 to the fourth bearings 28 are rolling bearings. Each of the bearings 25, 26, 27, and 28 is, for example, a tapered roller bearing or a deep groove ball bearing.

[0014] In this embodiment, of the four bearings 25 to 28, only the first bearing 25 is a bearing device with a built-in measuring device 100 (Figure 3). The measuring device 100 detects and measures vibrations generated by the meshing of the first gear 22 and the second gear 23. 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 detection device 10. Furthermore, the measuring device 100 also includes a power generation unit 149 (Figure 8). The gear failure detection device 10 detects a failure in the first gear 22 based on the signal received from the measuring device 100 of the first bearing 25. In this embodiment, the gear failure detection system 30 is configured by the gear failure detection device 10 and the measuring device 100. Since the first bearing 25 is equipped with the measuring device 100, it may also be referred to as a bearing device.

[0015] Figure 2 is a block diagram showing the configuration of the gear failure detection device 10. As shown in Figure 2, the gear failure detection 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 detection device 10 is, for example, a personal computer. The input unit 11 consists of buttons, switches, a mouse, a touch panel, etc., and the user performs various inputs via the input unit 11 (for example, inputting the number of teeth of the first gear 22). The user uses the input unit 11 when operating the gear failure detection device 10. The input unit 11 can also be called the operation unit.

[0016] The control unit 12 is composed of one or more CPUs or MPUs and controls the operation of each part 11 and 13-15 of the gear failure detection device 10. The control unit 12 processes signals received from the measuring device 10 to determine if a gear is faulty (executes fault detection processing). The control unit 12 controls the gear failure detection device 10 and executes gear fault detection processing by executing control programs stored in the memory unit 13. CPU stands for Central Processing Unit. MPU stands for Microprocessor Unit.

[0017] The memory unit 13 is composed of an HDD, ROM, RAM, IC memory card, etc., and stores various information such as the control program executed by the control unit 12 and an algorithm for generating a map (described later) that represents the relationship between the angle of the first gear 22 and its teeth. The map is generated when the control unit 12 executes the control program stored in the memory unit 13. The memory unit 13 can store data received from the measuring device 100. HDD stands for Hard Disk Drive. ROM stands for Read Only Memory. RAM stands for Random Access Memory. IC stands for Integrated It is an abbreviation for Circuit. The display unit 14 consists of a liquid crystal display or the like, and displays various data, numbers, characters, and images. The display unit 14 can display data received from the measuring device 100. The communication unit 15 communicates wirelessly with the measuring device 100.

[0018] 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 viewed from the left side. Figure 4 is an exploded perspective view of the first bearing 25 viewed from the right side. As shown in Figure 3, the first bearing 25 has a measuring device 100 and a bearing section 250. The measuring device 100 is attached to the left side of the bearing section 250. The measuring device 100 includes a cover 110, a coil substrate 120 (Figure 4), a rotating section 130, a group of circuit boards 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 located between the cover 110 and the Z-phase magnet unit 160. The group of circuit boards 140 is composed of multiple substrates, as will be described later.

[0019] The rotating part 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 part 250, the cover 110 is attached to the outer ring 112 of the bearing part 250. Therefore, the cover 110 does not rotate. The retainer is attached to the inner ring 113 of the bearing part 250. The retainer fixes the Z-phase magnet unit 160 to the inner ring 113 of the bearing part 250. Therefore, the Z-phase magnet unit 160 rotates together with the inner ring 113 of the bearing part 250 (i.e., the first shaft 24a).

[0020] The cover 110 is an annular flat plate member and is formed from a magnetic material such as silicon steel sheet, carbon steel (JIS standard SS400 or S45C), martensitic stainless steel (JIS standard SUS420), or ferritic stainless steel (JIS standard SUS430). Since a sensor is attached to the cover 110, the cover 110 may also be called a sensor case.

[0021] As shown in Figure 4, a coil substrate 120, a group of circuit boards 140, and a storage battery 150 are mounted on the side of the cover 110 facing the bearing portion 250. The group of circuit boards 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, for example, by fastening bolts made of a non-magnetic material such as brass to female screw holes drilled in the cover 110. In this case, the bolts have a length that does not protrude from the cover 110 when attached to the cover 110.

[0022] The power control board 141 includes a rectifier circuit 261 (Figure 6), a smoothing circuit 262 (Figure 6), a power management IC 263 (Figure 6), and an FET 264 (Figure 6). Circuits 261-263 and FET 264 of the power control board 141 will be described later with reference to Figure 6. FET stands for Field Effect Transistor.

[0023] Furthermore, the cover 110 has a through hole 111, which is sealed by a lid 117 made of a non-magnetic material such as resin. As will be described later, an antenna 147 (Figure 5A) is mounted on the control board 143. Since the cover 110 is magnetic, it has the effect of shielding electromagnetic waves from the antenna 147. However, the antenna 147 is positioned opposite the lid 117, so the electromagnetic waves from the antenna 147 can reach the external gear failure detection device 10 through the non-magnetic lid 117. The coil substrate 120 is fixed to the cover 110, for example, with adhesive.

[0024] Figure 5A is a plan view showing an example configuration of the cover 110, coil substrate 120, circuit board group 140, and storage battery 150. Figure 5B shows only the cover 110 and coil substrate 120. As shown in Figure 5B, the coil substrate 120 has 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. 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 axis Ax. The coil pattern 123 has a plurality of planar coils stacked in the thickness direction of the flexible substrate 121. A planar coil is a pattern of a conductor that is patterned and provided on a predetermined surface of an insulator. In this embodiment, the conductor pattern is formed on multiple surfaces of the insulator. However, it is not limited to this, and the conductor pattern may be formed on a single surface of the insulator. The number of turns of the coil pattern 123 is proportional to the number of stacked planar coils. The amount of power generated can be adjusted by changing the number of layers of planar coils.

[0025] Furthermore, the coil pattern 123 is arranged in a plan view such that the bumps and dips are arranged alternately along the circumference of a circle centered on the rotation axis Ax. One yoke 125 is placed in each of the dips. The coil pattern 123 may have a shape in which a circular section is missing in order to place an angle sensor at a position where the magnetic change of the encoder magnet, which will be described later, can be detected.

[0026] As shown in Figure 5A, the power control board 141, angle sensor board 142, control board 143, and battery 150 are mounted radially outward from the coil board 120 in a plan view. The power control board 141 (more specifically, the power management IC 263 described later) is equipped with two DC-DC converters (one for stepping down and one for stepping up) that step down the DC voltage supplied from the battery (capacitor) 150 and supply this DC voltage to the angle sensor board 142 and the control board 143.

[0027] The angle sensor board 142 is equipped with an angle sensor 443 and a Z-phase detector 444. The Z-phase detector 444 is, for example, a Hall IC. The Z-phase detector 444 generates one pulse each time the Z-phase magnet 162 (described later) passes near it. In other words, the Z-phase detector 444 generates one pulse each time the first bearing 25 rotates once. The control board 143 is equipped with a control circuit 145, an antenna 147, an acceleration sensor 441, and a temperature sensor 442. The acceleration sensor 441, temperature sensor 442, angle sensor 443, control circuit 145, and antenna 147 may be composed of separate IC chips, or some or all of them may be composed of a single IC chip. The temperature sensor 442 is provided to detect the temperature when acceleration and angle are detected (or before detection). The acceleration sensor 441 used in this embodiment is, for example, a MEMS acceleration sensor. Furthermore, as shown in Figure 5A, the acceleration sensor 441 used in this embodiment is configured to measure acceleration values ​​(acquire acceleration measurement values) in each of the three axes (X / Y / Z axes) (i.e., it is a 3-axis acceleration sensor).

[0028] Both ends of the coil pattern 123 are connected to the power control board 141 via extensions 116 provided at predetermined positions on the outer circumference of the coil substrate 120. Alternatively, the coil substrate 120 and the power control board 141 may be connected by lead wires instead of the extensions 116. Or, instead of the extensions 116, the coil substrate 120 and the power control board 141 may be connected by an FPC (Flexible Printed Circuit) connector. Using an FPC connector eliminates the need for soldering, thus increasing the productivity of the measuring device 100.

[0029] Returning to Figures 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 side of the base material 133. The base material 133 has an opening. The mounting jig 135 is fixed to the right side of the base material 133. The mounting jig 135 protrudes from the right side of the base material 133, through the opening in the base material 133, to the left side of the base material 133. The left side of the base material 133 is the side facing the cover 110. The magnetic track 131 may be configured to be detachable from the base material 133.

[0030] In this embodiment, the magnetic track 131 and the base material 133 together are referred to as the encoder magnet. For example, the encoder magnet is formed by forming a plastic magnet on one side of a metal base material 133, and then alternately magnetizing the surface of the formed plastic magnet with north and south poles. The mounting jig 135 is a jig for attaching the encoder magnet (rotating part 130) to the first shaft part 24a.

[0031] The magnetic track 131 has multiple magnetic pole pairs 311, each consisting of a north pole 131N and a south pole 131S. The multiple magnetic pole pairs 311 are arranged in the circumferential direction of the magnetic track 131. The north poles 131N and south poles 131S are arranged alternately. The distance between the centers of adjacent north poles 131N and south poles 131S on the magnetic track 131 is the same as the distance between the centers of adjacent yokes 125 on the coil substrate 120.

[0032] In this embodiment, when the magnetic track 131 rotates relative to the coil substrate 120 around the rotation axis Ax (Figure 5B), when one of two adjacent yokes 125 faces the north pole, the other yoke 125 faces the south pole. Conversely, when one yoke 125 faces the south pole, the other yoke 125 faces the north pole. In other words, adjacent yokes 125 on the coil substrate 120 never face the same magnetic pole of the magnetic track 131. As a result, the phase of the change in magnetic flux density passing through one yoke 125 and the phase of the change in magnetic flux density passing through the other yoke 125 are shifted by 180°.

[0033] In this way, as the magnetic track 131 rotates relative to the coil substrate 120, the magnetic poles facing the yoke 125 alternate. This causes the magnetic flux density passing through the yoke 125 to change periodically. In response to this periodic change in magnetic flux density, a voltage change (for example, a sinusoidal AC voltage) is generated in the coil pattern 123 located around the yoke 125. In other words, in this embodiment, when the inner ring 113 of the first bearing 25 rotates together with the first shaft 24a, power generation occurs within the first bearing 25 by electromagnetic induction. This power generation is self-generated. The combination of the encoder magnet (magnetic track 131) and the coil substrate 120 is sometimes referred to as the power generation unit 149. The power generation unit 149 generates power based on the relative rotation of the outer ring 112 and inner ring 113 of the first bearing 25. The DC voltage generated in the first bearing 25 is stored in the storage battery 150.

[0034] The Z-phase magnet unit 160 includes a Z-phase magnet holder 161 and a Z-phase magnet (not shown). The Z-phase magnet holder 161 is an annular member, and the Z-phase magnet 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 with the first axis 24a, the Z-phase magnet passes the Z-phase detector 444 once. At this time, the Z-phase detector 444 generates one pulse.

[0035] Figure 6 is a schematic diagram illustrating the self-generation mechanism described above. In Figure 6, coil C corresponds to a coil pattern 123 attached to the cover (metal case) 110, and magnet M corresponds to an encoder magnet provided on the inner ring 113 of the first bearing 25. As shown in Figure 6, electromagnetic induction occurs when coil C and magnet M rotate relative to each other, generating electricity. 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, the output of the rectifier circuit 261 is connected to a smoothing circuit 262 to make it closer to direct current.

[0036] The DC current that passes through the smoothing circuit 262 is input to the power management IC 263 and stored in the battery (capacitor) 150. The power management IC 263 is equipped with two DC-DC converters (one for step-down and one for step-up), and the small amount of power generated by the generator (C and M in Figure 6) is boosted 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 in case of overcharging, and the output Vcc to the load L (sensor, circuit board) are all managed by the power management IC 263. To prevent the control board 143 from malfunctioning due to the inflow of an undefined voltage, an FET 264 is provided between the power management IC 263 and the load L. The FET 264 can completely cut off the power supply to the load L.

[0037] Since the power obtained by the rotation of the first axis 24a (relative rotation between the coil substrate 120 and the magnetic track 131) is extremely small, a power management IC for energy harvesting that can store even minute amounts of power is used as the power management IC 263 (for example, Texas Instruments' ultra-low power harvester power management IC-BQ25570).

[0038] The storage battery 150 has a storage capacity that is sufficient to perform at least one operation of the measuring device 100. One operation of the measuring device 100 refers to the operation from measuring the angular position and acceleration of the gear teeth for a predetermined time (for example, 1 second) to transmitting the measurement results to the gear fault detection device 10. When the battery 150 is fully charged, the power management IC 263 sends a charge completion signal to the FET 264 to indicate that charging is complete. Since a lower ESR (Equivalent Series Resistance) of the battery 150 increases the instantaneous current that can be drawn, it is preferable to use a battery with a low ESR. If a battery with a low ESR is not used, a capacitor or solid-state battery that can be connected in parallel to the battery 150 may be provided. In this case, parallel connection is preferable. The rectifier circuit 261, smoothing circuit 262, power management IC 263, and FET 264 are sometimes collectively referred to as circuit group 431 (Figure 8).

[0039] Figure 7 shows two graphs illustrating the operation of the power management IC 263. In the upper graph of Figure 7, the vertical axis represents the voltage of the battery 150, and the horizontal axis represents time. In the lower graph, the vertical axis represents the charge completion signal. In this graph, the vertical axis represents the signal strength (High or Low), and the horizontal axis represents time. When the charge completion signal is Low, it indicates that the battery 150 is not yet fully charged (charging in progress). When the charge completion signal is High, it indicates that the battery 150 is supplying power. When the charge completion signal changes from High to Low, it indicates that the battery 150 has stopped supplying power (ended) and entered a charging state. The charge completion signal is a signal generated by the power management IC 263, and by looking at the two graphs in Figure 7 together, it is possible to see how the power management IC 263 manages (controls) the voltage of the battery 150.

[0040] As shown in Figure 7, when the charge completion signal is Low, the charge level of the battery 150 increases over time, and the charge completion signal becomes High at time t1. The voltage of the battery 150 at time t1 is V2. Voltage V2 is the voltage at which power is supplied to the load L. After time t1 (after power supply to load L begins), if the power consumption of load L is greater than the amount of power generated, the voltage will decrease from V2 (solid line J1). When the voltage drops to V1, the power management IC263 stops supplying power to load L. V1 is equal to or slightly greater than Vcc. This is because if V1 is less than Vcc, the converter will no longer function.

[0041] After time t1, if the power consumption of load L is equal to the power generated, the voltage remains V2 (dotted line J2). After time t1, if the power consumption of load L is less than the power generated, the voltage will rise from V2 (dotted line J3). When the power rises to V3, the power management IC 263 stops charging the battery 150. This is to prevent overcharging.

[0042] In this embodiment, the battery 150 has a capacity to store the power required for one operation of the measuring device 100. In other words, even if the voltage drops from V2 to V1 between time t1 and time t2 in Figure 7, the measuring device 100 can perform one operation between time t1 and time t2. The period between time t1 and time t2 is the time during which power can be supplied, and the measurement of acceleration and angle, and the transfer of the measured data are performed between time t1 and time t2.

[0043] Figure 8 is a block diagram showing the configuration of the measuring device 100. As described above, the measuring device 100 comprises a power control board 141, an angle sensor board 142, and a control board 143. The angle sensor board 142 comprises a sensor board 170 and a Z-phase detector board 171. The power control board 141 includes a circuit group 431. The circuit group 431 includes the rectifier circuit 261, smoothing circuit 262, power management IC 263, and FET 264 shown in Figure 6. The circuit group 431 is connected to the storage battery 150 and the power generation unit 149.

[0044] The power generation unit 149 includes a magnetic track 131 (Figure 4) and a coil substrate 120 (Figure 5B). The power generation unit 149 generates electricity based on the relative rotation of the outer ring 112 and inner ring 113 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 to obtain stable power. This power is then stored in the battery 150 via the power management IC 263 (boosted by the power management IC 263's boost DC-DC converter). The DC power stored in the battery 150 is output to the angle sensor board 142 and the control board 143 via the power management IC 263 (stepped down by the power management IC 263's step-down DC-DC converter) at the timing of measurement.

[0045] 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 (transmitter) 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 (Figure 5).

[0046] The acceleration sensor 441, temperature sensor 442, and angle sensor 443 use DC power supplied from the power control board 141 to detect acceleration, temperature, and rotation angle (position), respectively. For example, the angle sensor 443 is mounted on the sensor board 170 so as to be located to the side of the magnetic track 131. The rotating part 130 having the magnetic track 131 is fixed to the inner ring 113 of the bearing part 250, and the angle sensor 443 detects the rotation angle of the inner ring 113 relative to the outer ring 112 of the bearing part 250 (the angle between the outer ring 112 and the inner ring 113 of the bearing part 250) by detecting the change in magnetic flux density as the magnetic track 131 rotates together with the inner ring 113 of the bearing part 250. The angle sensor 443 is a magnetic sensor. The angle sensor 443 may be of the incremental or absolute type.

[0047] The microcontroller 451 comprises a CPU 455, a DMA controller 456, and internal memory 457. The microcontroller 451 writes the measured values ​​obtained from the acceleration sensor 441 and the angle sensor 443 to the external memory 452. DMA stands for Direct Memory Access. The DMA controller may be referred to as DMAC in the following description. The internal memory 457 and the external memory 452 may be collectively referred to as the storage unit 230.

[0048] The CPU 455 initializes the memory unit 230, the acceleration sensor 441, the temperature sensor 442, and the angle sensor 443, and also performs the initial setup of the DMA controller 456. When the DMA controller 456 receives a DMA trigger (INT signal from the acceleration sensor 441), it starts a DMA transfer. Specifically, when the DMA controller 456 receives a DMA trigger, it transfers the latest measured values ​​(measurement data) held by the acceleration sensor 441 and the angle sensor 443 to the memory unit 230 (internal memory 457 or external memory 452) as unconverted data (raw data), without going through the CPU 455. The acceleration sensor 441 and the angle sensor 443 update and retain the measured values ​​(measured values ​​acquired through measurement) at predetermined update cycles. If the acceleration sensor 441 is a MEMS acceleration sensor, the update cycle is the MEMS acceleration sensor's ODR (Output Data Rate). The acceleration sensor 441 generates an INT signal (interrupt signal) each time it becomes capable of outputting data, and this INT signal is input to the DMA controller 456 as a trigger. The update cycle (sampling cycle) will be described later using Figure 10.

[0049] The wireless module 453 transmits data stored in the internal memory 457 and external memory 452 to the gear failure detection device 10 under the control of the CPU 455. The wireless module 453 is equipped with an antenna 147. For example, the wireless module 453 transmits data to the gear failure detection device 10 via wireless communication such as BLE. BLE stands for Bluetooth® Low Energy. The transmitted data is received by the communication unit 15 of the gear failure detection device 10 and processed by the control unit 12 of the gear failure detection device 10. When using BLE, data is transmitted, for example, one packet at a time. If you want to increase throughput, you can use More data or Data Length Extension. Alternatively, you can increase throughput by adopting the 2Mbps PHY specified in BLE 5.x.

[0050] When the first bearing 25 and the gear failure detection device 10 communicate wirelessly, wireless communication compliant with a communication standard other than BLE may be used. For example, Zigbee® or Thread may be used. Alternatively, a different frequency band from BLE (for example, 920MHz band low-power radio) may be used.

[0051] Although the description above describes writing the measured values ​​obtained from the acceleration sensor 441 and the angle sensor 443 to the external memory 452, the measured values ​​obtained from the acceleration sensor 441 and the angle sensor 443 may also be written to the internal memory 457, or the internal memory 457 and the external memory 452 may be used in combination. Furthermore, the internal memory 457 and the external memory 452 may be a single memory.

[0052] Figure 9 is a timing chart illustrating the operation and processing of the measuring device 100. Figure 9(A) shows the timing of power supply (power ON) to the load L (accelerometer 441, angle sensor 443, circuit board group 140). The power ON timing indicates the point in time when the power management IC 263 starts supplying power to the load L, which corresponds to time t1 in Figure 7 (start of power supply). Figure 9(B) shows the timing of the measurement device 100 connecting to the gear failure detection device 10 via a wireless network (BLE). "Pairing time" is the time required for the measurement device 100 to establish communication (connection) with the gear failure detection device 10. The pairing time is, for example, 3.5 to 5 seconds. "Pairing complete" indicates the point at which the BLE connection is established.

[0053] Figure 9(C) shows the pulse output by the Z-phase detector 444. In this embodiment, the output of the Z-phase detector 444 is active low, and the Z-phase detector 444 outputs a low signal when it detects a Z-phase magnet. The "processing wait time" is set to a time longer than the time required for the CPU 455 to complete a predetermined monitoring process. The processing wait time is, for example, 30 seconds. When the processing wait time is over, the angle sensor 443 is activated. After the angle sensor 443 is activated, the angle sensor 443 is initialized (angle sensor initialization time). Initialization of the angle sensor 443 means that power is supplied to the angle sensor 443 so that the angle sensor 443 can operate correctly. When the initialization of the angle sensor 443 is complete, the CPU 443 starts preparing for measurement. The angle sensor initialization time is, for example, 100 ms.

[0054] Figure 9(D) shows the pulses (acceleration measurements) output by the acceleration sensor 441, which are stored in the external memory 452. The output pulses of the acceleration sensor 441 represent the vibrations generated in the first gear 22 due to the meshing of the first gear 22 and the second gear 23. Here, the output pulses (acceleration measurements) from the acceleration sensor 441 are shown for one of the three axes (X / Y / Z axes). The acceleration sensor 441 detects the acceleration for each of the three axes for a predetermined measurement time and stores the acceleration. The predetermined measurement time is longer than the time required for the first axis 24a to complete one rotation. During the "measurement start delay" shown in Figure 9(D), CPU 455 performs three processes (1) to (3). In process (1), the CPU 455 acquires temperature data from the temperature sensor 442 before the start of measurement. Based on the temperature measured by the temperature sensor 442, the CPU 455 can determine whether abnormal heat generation is occurring inside the first bearing 25. If the temperature measured by the temperature sensor 442 is above a predetermined value, the CPU 455 sends a signal indicating abnormal heat generation to the gear failure detection device 10. Upon receiving this signal, the gear failure detection device 10 displays a message indicating abnormal heat generation on the display unit 14. The CPU 455 can also correct the angle measured by the angle sensor 443 based on the temperature measured by the temperature sensor 442. Since the angle sensor 443 is a magnetic sensor, the effect of temperature changes on magnetism may appear as a detection error (measurement error) of the angle sensor 443. For this angle error, it is confirmed in advance what kind of effects and errors appear in the detected value (measured value) of the angle sensor 443 for each temperature, and a correction table is created to perform a correction to cancel out these effects and errors. The CPU 455 then 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 involves triggering an INT signal from the acceleration sensor 441 to acquire measurement data from the acceleration sensor 441 and the angle sensor 443, and storing this measurement data in the external memory 452. Process (3) involves CPU455 setting a wake-up timer to determine when the measurement is finished (timer out).

[0055] The processing start delay is approximately 480ms. After the three processes described above are completed, the CPU 455 enters a sleep state. Acceleration and angle measurements are performed while the CPU 455 is in sleep mode by activating only the minimum necessary functional blocks, such as the DMA controller 456, acceleration sensor 441, and acceleration sensor 443. Acceleration and angle measurements are terminated when the number of measurement data points reaches a specified number or when the timeout period is reached. Once acceleration and angle measurements are complete, the CPU 455 is released from sleep mode. Whether the timeout period has been reached is determined by the wake-up timer. In this way, only the minimum necessary functional blocks are operated, enabling a low-power measurement system.

[0056] The "data transfer time" shown in Figure 9(D) is the time required to transfer data (pairs of measurement values ​​from the acceleration sensor and angle sensor) from the measuring device 100 to the gear failure detection device 10. The data transfer time is, for example, 2 to 3 seconds. One operation of the measuring device 100 takes place from the time the power is turned on in Figure 9(A) until the end of the data transfer time.

[0057] Figure 9(E) shows the pulses (angle measurement values) output by the angle sensor 443, which are stored in the external memory 452. The angle sensor 443 detects (measures) the angle position for a predetermined measurement time. The waveform from the angle sensor 443 is stored in the external memory 452 with a delay of the amount of "DMA delay" shown in Figure 9(E) compared to the waveform from the acceleration sensor 441. Theoretically, the values ​​measured by the acceleration sensor 441 and the angle sensor 443 are transferred via DMA (sampled) using the INT signal from the acceleration sensor 441 as a common timing source (trigger). However, in reality, there is a nanosecond-level delay in the transfer of the values ​​measured by the acceleration sensor 441 and the angle sensor 443, and this delay is indicated as "DMA delay" in Figure 9(E).

[0058] Figure 10 shows the update cycles for the measured values ​​of the acceleration sensor 441 and the angle sensor 443. In this embodiment, as shown in Figure 10, the timing of the completion of updating the measured values ​​of the acceleration sensor 441 and the timing of the completion of updating the measured values ​​of the angle sensor 443 (sampling timing) are set to be synchronized. In other words, the update cycle (sampling cycle) of the acceleration sensor 441 and the update cycle (sampling cycle) of the angle sensor 443 are equal. The measured values ​​of the acceleration sensor 441 and the angle sensor 443 are then stored in the external memory 452 in a synchronized manner (sharing the same time reference or sharing at least one time reference). This makes it possible to obtain measurement data in which acceleration data and angle data correspond one-to-one (in the form of pairs sharing the same time reference). Thus, in this embodiment, time-synchronized angle and acceleration measurement is performed. The sampling frequency (ODR) of the acceleration sensor 441 is pre-selected (set) from, for example, within the range of 1 to 5376 Hz.

[0059] Once the first operation of the measuring device 100 is completed, the next operation (the second operation) begins. That is, after waiting for the "processing waiting time" shown in Figure 9(C) to elapse (during which time power is supplied to each sensor etc. from the power management IC 263), the angle sensor 443 is initialized and measurement begins. When the measured value is transferred to the judgment device 10, the second operation of the measuring device 100 is completed.

[0060] Figure 11 is a flowchart illustrating the operation and processing of the measuring device 100. S stands for Step. The measuring device 100 is assumed to be powered (power ON as shown in Figure 9(A)) and to have established a BLE communication connection (Figure 9(B)). In S1, it is determined whether the processing waiting time (e.g., 30 seconds) has elapsed (Figure 9(C)). If the result is Yes, proceed to S2. If the result is No, repeat S1.

[0061] In S2, it is determined whether the Z-phase detector 444 has detected the Z-phase magnet 162 (Figure 9(C)). If the result is Yes, proceed to S3. If the result is No, repeat S2. In S3, the angle sensor 443 is activated (initialized). This is done during the angle sensor initialization time (100ms) shown in Figure 9(C). Once the angle sensor initialization time has elapsed, the process proceeds to S4.

[0062] In S4, it is determined whether the Z-phase detector 444 has detected the Z-phase magnet 162. If the result is Yes, proceed to S5. In other words, if the Z-phase magnet is detected after the initialization of the angle sensor 443 (angle sensor initialization time) is completed, proceed to S5. If the result is No, repeat S4. In S5, the DMA synchronizes the measurement values ​​from the acceleration sensor 441 (Figure 9(D)) and the angle sensor 443 (Figure 9(E)) and stores them in the external memory 452. In S6, the measured values ​​from the acceleration sensor 441 and the angle sensor 443 are transmitted (transferred) from the measuring device 100 to the gear failure detection device 10 via BLE wireless communication. After data transmission, the process returns to S1. In this way, S1 to S6 perform one operation cycle of the measuring device 100.

[0063] Next, the principle of gear failure detection in this embodiment will be explained. In other words, the process performed by the gear failure determination device 10, which receives measurement values ​​from the acceleration sensor 441 and angle sensor 443 from the measuring device 100, will be explained. First, the method for obtaining the acceleration curve for each tooth will be explained using Figure 12. To simplify the explanation, the first gear 22 is assumed to have three teeth (teeth 1, 2, and 3) as shown in Figure 12(A). The second gear 23 that meshes with the first gear 22 is assumed to have four or more teeth. Figure 12(B) is a graph showing the acceleration measurement values ​​from the acceleration sensor 441 (Figure 9(D)) on the vertical axis and the measurement values ​​from the angle sensor 443 (Figure 9(E)) on the horizontal axis when the first gear 22 has three teeth (teeth 1, 2, and 3). Here, the acceleration measurement values ​​measured on any of the three axes (X / Y / Z axes) are shown. When the first gear 22 and the second gear 23 mesh and the first gear 22 rotates once, the teeth of the second gear 23 (not shown) come into contact with the teeth of the second gear 23 in the order of tooth 1 → tooth 2 → tooth 3, and as shown in Figure 12(B), the measurement values ​​from the acceleration sensor 441 are obtained in the order of vibration of tooth 1 → vibration of tooth 2 → vibration of tooth 3.

[0064] Once the waveform from the acceleration sensor 441 shown in Figure 12(B) is obtained, the line segments of tooth 1 are collected to generate the curve R1 of tooth 1, as shown in Figure 12(C). In other words, by connecting the line segments of sections P1, P4, P7 (not shown), and P10 (not shown) in Figure 12(B), the non-coherent curve R1 shown in Figure 12(C) can be obtained. The number of line segments of tooth 1 used when generating the curve R1 depends on the volume of the measured value transmitted from the measuring device 100 to the gear failure detection device 10. Similarly, by collecting only the line segments of tooth 2, the curve R2 of tooth 2 is generated as shown in Figure 12(C). In other words, by connecting the line segments of intervals P2, P5 (not shown), P8 (not shown), and P11 (not shown) in Figure 12(B), the curve R2 in Figure 12(C) can be obtained. Similarly, by collecting only the line segments of tooth 3, the curve R3 of tooth 3 is generated as shown in Figure 12(C). In other words, by connecting the line segments of intervals P3, P6 (not shown), P9 (not shown), and P12 (not shown) in Figure 12(B), the curve R3 in Figure 12(C) can be obtained. Furthermore, in this embodiment, the acceleration sensor 441 is configured to acquire acceleration measurements for each of the three axes (X / Y / Z axes). Curves such as the tooth-by-tooth acceleration curves R1, R2, and R3 shown in Figure 12(C) are acquired for each of the three axes. In this embodiment, acceleration curves for each of the three axes are obtained for each tooth.

[0065] Next, the fault detection process performed by the gear fault detection device 10 will be explained using Figure 13. In Figure 13, a gear that is closer to a real gear is used. Specifically, we consider the case where the first gear 22 has 22 teeth. In this embodiment, a method called the per-tooth method (per-tooth evaluation method) is used to detect faults for each tooth of the gear. From the measuring device 100, data consisting of a measurement value a(t) from the acceleration sensor 441 and a measurement value φ(t) from the angle sensor 443 is transmitted to the gear failure detection device 10, and this data is stored in the storage unit 13 of the gear failure detection device 10 along with time t (reference numeral 500). The user of the gear failure detection device 10 inputs the number of teeth on the gear via the input unit 11 (reference numeral 510). While not mandatory, the user may also input the tooth angle offset value. The tooth angle offset value is a calibration value used to indicate (understand) the absolute angular position of a specific known tooth. The angle offset value will be explained later using Figures 14 and 15.

[0066] The gear failure detection device 10 creates an angle-to-tooth map (angle-to-tooth mapping function) (reference numeral 520). Figures 14 and 15 are the angle-to-tooth maps. In the map in Figure 14, the vertical axis shows 22 teeth, and the horizontal axis shows the axis angle position (relative value). Figure 14 is a map created without using an angle offset value. Without using an angle offset value, the tooth at the axis angle = 0 degrees is designated as tooth number 1 when the map is created. In the map in Figure 15, the vertical axis represents the 22 teeth, and the horizontal axis represents the axis angle position (absolute value). In other words, Figure 15 is a map created using angle offset values. When creating the map in Figure 15, the teeth of the gear are numbered (or marked) in advance (in the example of Figure 15, tooth numbers: 1 to 22). In the example of Figure 15, the tooth at the axis angle = 0 degrees when the map is created is tooth number 20. In other words, tooth number 1 starts meshing at 44.6 degrees (absolute angle), so in Figure 15, 44.6 degrees is input as the angle offset value to the gear fault detection device 10 (reference numeral 510).

[0067] As shown in Figures 14 and 15, since a gear completes one rotation in 360 degrees, 22 line segments S are created by dividing 360 degrees by 22. Figures 14 and 15 can be said to represent a mapping function, as determining the axis angle position determines one of the 22 teeth. In other words, the mapping function is generated by the processing of symbol 520. The gear failure detection device 10 uses either the map in Figure 14 or the map in Figure 15. When using the map in Figure 14, it is not possible to determine which tooth of the gear corresponds to tooth number 1 on the vertical axis in Figure 14, but it is possible to determine that the gear contains a damaged tooth. When using the map in Figure 15, it is possible to determine which tooth of the gear corresponds to tooth number 1 in Figure 15. In the following description, the map in Figure 15 will be used.

[0068] After generating an angle-to-tooth map (mapping function), the gear failure detection device 10 calculates the average acceleration signal strength for each tooth (reference numeral 530). The average acceleration signal strength will be referred to as acceleration signal strength below. The numerical values ​​and information used as input in calculating the acceleration signal strength are the measurement data received from the measurement device 100 and the map shown in Figure 15. The measurement data, as indicated by reference numeral 500, consists of angular position information (φ(t)) and acceleration measurement value (a(t)). The acceleration signal strength of the k-th tooth is calculated using equation (1) according to the per-tooth method.

number

[0069] Here, P(tooth=k) is the acceleration signal power of the k-th tooth, and s(φ(i)) is the measured acceleration value at the angular position of a sample i. tooth(φ(i)) is the value of the mapping function at the angular position of a sample i. If it is not the k-th tooth, tooth(φ(i)) is not equal to k, so s(φ(i)) is 0. If it is the k-th tooth, tooth(φ(i)) is equal to k, so s(φ(i)) becomes the measured acceleration value (a(i)). samples,k This indicates the number of tooth samples that meet the condition (*) (the number of acceleration measurements obtained for the k-th tooth).

[0070] According to equation (1), all acceleration measurements (sample values) are squared and summed, then divided by the number of samples per tooth to obtain the acceleration signal intensity value per tooth. In other words, 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, by processing code 530, the acceleration signal intensity values ​​for 22 teeth can be obtained. In Figure 13, the reference numeral 540 indicates the value used in equation (1) for each tooth.

[0071] In this embodiment, as described above, the acceleration sensor 441 is configured to acquire acceleration measurements for each of the three axes (X / Y / Z axes). The acceleration measurements acquired for the X, Y, and Z axes are denoted as x(φ(i)), y(φ(i)), and z(φ(i)), respectively. For the k-th tooth (tooth(φ(i))=k), s(φ(i)) in equation (1) is defined as the sum (vector sum) of these acceleration measurements. In this case, s(φ(i)) is expressed as shown in equation (2) below.

number

[0072] Therefore, using the acceleration measurements obtained for each of the three axes, the acceleration signal intensity in equation (1) can be expressed as shown in equation (3) below, using equation (2).

number

[0073] When the calculation of Equation (3) is completed, the process of reference numeral 550 in FIG. 13 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, vibration occurs even if there is no damage to the teeth. In this embodiment, the process of reference numeral 550 is performed so that vibrations generated from normal teeth and abnormal teeth can be easily distinguished. Specifically, in the process of reference numeral 550, first, the calculation of Equation (4) is performed. That is, the average value P￣ of the acceleration signal power of all the teeth of the gear is calculated.

Number

[0074] Next, the relative signal power coefficient is calculated for each tooth using Equation (5).

Number

[0075] The relative signal power coefficient P rel (k) is a coefficient representing the following characteristics. If the signal power of tooth k matches the average acceleration signal power, P rel (k) = 0. When the signal power of tooth k is twice the average acceleration signal power, P rel (k) = 1. When the signal power of tooth k is three times the average acceleration signal power, P rel (k) = 2. Hereinafter, similarly, P rel (k) becomes 3, 4, ···. In addition, when the signal power of tooth k is lower than the average acceleration signal power, P rel (k) can take a value smaller than 0 (that is, P rel (k) ≠ 0 and P rel (k) < 0 can occur). Therefore, if it is normalized so that the average vibration reference becomes zero, P relThe value of (k) is a numerical value used to easily evaluate whether each tooth is normal or abnormal. This evaluation may be based on the operator's judgment or may be an automated evaluation (for example, by setting a threshold and P rel (If the value of (k) is above the threshold, it is evaluated as abnormal.) Thus, according to this embodiment, it becomes possible to evaluate the acceleration signal intensity for each tooth (per-tooth evaluation) as an indicator of the condition of each tooth. This evaluation can be performed by periodically synchronously sampling acceleration data and angle data.

[0076] Next, the effects of the above-described embodiment will be explained. Figure 16 shows an example of acceleration measurements for three axes (X-axis, Y-axis, and Z-axis) acquired by the acceleration sensor 441. The acceleration sensor 441 used to acquire these acceleration measurements has a sampling frequency of 5 kHz and 8 bits of information. In the graphs showing the data for the X-axis, Y-axis, and Z-axis (acceleration measurements are processed using a 5-point moving average), the vertical axis represents the acceleration measurement value and the horizontal axis represents the machine angle. As can be seen from Figure 16, the acceleration measurements for the Z axis show similar peak-to-peak values ​​(maximum-to-minimum peak values) across all teeth, but the acceleration measurements for the X and Y axes show different peak-to-peak values ​​depending on the tooth. For example, the peak-to-peak values ​​of the acceleration measurements for the tooth numbers enclosed by the dotted line in Figure 16 (tooth numbers: 22, 1, 2, 3, 4) are similar to those of other tooth numbers (tooth numbers 5-21) in the Z-axis, but are larger in the X and Y axes than those other tooth numbers. As explained with reference to equations (1) to (5) above, the relative signal strength coefficient P is calculated using the acceleration measurements for the X, Y, and Z axes respectively. rel When (k) is calculated, the larger the acceleration measurement value in at least one of the three axes, the larger the coefficient will be. In other words, the degree of tooth damage is expressed numerically. Thus, while impacted tooth damage may be detected if acceleration values ​​are measured on only one of the three axes, by measuring acceleration values ​​on the other two axes as well and combining the acceleration values ​​from all three axes to determine the presence or absence of damage, it becomes possible to detect damage with high sensitivity. In other words, even if the data from a single axis cannot capture an abnormality in the peak-to-peak value, the data from the other axes can compensate for this, enabling high diagnostic sensitivity. In this way, by combining the acceleration values ​​from each of the three axes to determine the presence or absence of tooth damage, the diagnostic sensitivity for damage is increased.

[0077] Figure 17 shows the relative signal intensity coefficient P, which is the result of a demonstration experiment conducted by the inventor to confirm the effect of the above-described embodiment. rel (k) is shown (where k is the tooth number). A helical gear was used as the first gear 22. The number of teeth is 22. Before the demonstration experiment, it was confirmed that there were no abnormal teeth in the second gear 23 that meshes with the first gear. The vertical axis of the graph in Figure 17 is the relative signal intensity coefficient P rel (k) is shown, and the horizontal axis indicates the gear number. In this demonstration experiment, the sampling frequency (period) for acceleration data and angle data was 5376 Hz, respectively. The shaft speed during this experiment was approximately 500 rpm, and the nominal pinion torque was 500 Nm. In Figure 17, for example, the threshold 173 is set to P rel If (k) is set to 2, then P at tooth number 2 (k=2) rel (2) is approximately 5.5 and (P rel (2)171) It is possible to assess that the tooth in question is abnormal. Note that in Figure 17, for comparison, P was calculated for the second tooth using acceleration measurements obtained by another method. rel The value of (2) is also shown. P rel(2)172 shows the relative signal strength coefficient calculated using acceleration measurements (so-called high-performance sensors) measured by a high-performance sensor (so-called advanced high-performance sensor) installed on the outer surface of the housing 21 of the gear transmission mechanism 20, which senses in the direction of the line of action where the gears mesh. The high-performance sensor has a sampling frequency of 51 kHz, an information bit count of 24 bits, a shaft speed of approximately 500 / min, and a nominal pinion torque of 500 Nm. As can be seen in Figure 17, P rel (2) 171 is a much higher value than the threshold of 173, which is 2, and the anomaly is easily detected, while P rel (2) 172 is smaller than the threshold value 173, which is 2, so no abnormality is detected. Thus, as can be seen from Figure 17, the method according to this embodiment is more sensitive. In other words, even when using an inexpensive MEMS sensor as the acceleration sensor 441, it is possible to detect tooth damage with about four times better sensitivity than when using a high-end, high-performance sensor.

[0078] The features and variations of the measuring device 100 and gear failure detection device 10 of this embodiment are described below. In this embodiment, the measuring device 100 (accelerometer 441, angle sensor 443, circuit board group 140, etc.) is built into the first bearing 25. Furthermore, the power used by the measuring device 100 is generated by the rotation of the first bearing 25 (the measuring device 100 is a self-generating device). Therefore, the gear fault detection system 30 can be made smaller and more power-efficient. Thus, the gear fault detection system 30, which is equipped with a data wireless transmission type measuring device 100 having a self-generation function, can use the small amount of power generated by the self-generation function to wirelessly transmit acceleration data corresponding to the rotational position (angle) of the first gear 22 to the fault judgment device 10.

[0079] Furthermore, the measuring device 100 acquires measurement data that associates the acceleration of the first gear 22 with the rotation angle of the first gear 22. The external memory 452 then associates the angle data and acceleration data one-to-one and stores it as measurement data. Since measurement data is acquired in which the acceleration data and angle data are associated one-to-one, it is possible to appropriately understand what kind of vibration is occurring at what angle during rotation, and to appropriately identify the location (angle) where the abnormality is occurring. In this embodiment, since measurement data with a one-to-one correspondence between acceleration data and angle data can be obtained, there is no need to worry about variations in rotational speed.

[0080] Furthermore, the measuring device 100 contributes to the overall miniaturization of its configuration by connecting an acceleration sensor 441, a temperature sensor 442, and an angle sensor 443 to the microcontroller 451. As a result, even if the cover (device housing) 110 is small, the measuring device 100 can be housed within the same housing. Furthermore, the measured values ​​acquired from each sensor are stored in the external memory 452 as unconverted data. Therefore, data processing such as conversion from hexadecimal to decimal notation is unnecessary during data storage, enabling high-speed data storage. In addition, the load caused by data processing can be reduced, and power consumption can be reduced.

[0081] Furthermore, since the measuring device 100 can acquire and store data using DMA transfer, the load on the CPU 455 can be reduced. In other words, the measuring device 100 in this embodiment can be constructed using inexpensive MEMS sensors and low-power microcontrollers. In this embodiment, a self-generating sensor-equipped rolling bearing can be used to monitor the gear shifting mechanism 20 and evaluate the signal for each tooth. The measuring device 100 allows the acceleration sensor 441 to be installed very close to the vibration source (physically close to the vibration excitation point), thus enabling the acquisition of a signal with a higher signal-to-noise ratio compared to installing a vibration sensor (for example, a high-performance sensor that senses in the direction of the line of action where the gears mesh) on the outer surface of the housing 21 of the gear transmission mechanism 20. Therefore, reliable gear diagnosis can be performed even when using an inexpensive MEMS acceleration sensor.

[0082] The gear diagnostic algorithm used in this embodiment is the per-tooth method, which has the following advantages. It can identify abnormal teeth. Diagnosis can be performed with low computational cost. It can determine abnormalities based on standalone evaluation results, without comparing them to vibration data from normal conditions, which is a conventional approach in gear diagnostics. Being able to diagnose with low computational cost means that the diagnosis can be performed using basic arithmetic operations. In other words, it does not require the high computational cost of FFT (Fast Fourier Transform). Furthermore, the process shown in Figure 13 requires only minimal mathematical calculations, enabling low-power computation. Furthermore, according to this embodiment, gear determination is performed using the per-tooth method with acceleration measurements taken for each of the three axes. By using data from all three axes, even if the data from a single axis cannot detect an anomaly in the peak-to-peak value, the data from the other axes can compensate for this, thereby achieving high diagnostic sensitivity.

[0083] Furthermore, since the acceleration sensor 441 is not mounted on the surface of the housing 21, the system 30 can be used regardless of the shape of the housing 21, and the shape of the housing 21 is irrelevant to the accuracy of fault diagnosis. Even without knowing what the normal state is, it is possible to diagnose a malfunction (gear abnormality). If an acceleration sensor is installed in the housing 21 of the gear shifting mechanism 20, the housing 21 is located between the gear meshing point and the acceleration sensor, and therefore it is affected by the vibration path, requiring a high-performance, expensive sensor. In this embodiment, since the acceleration sensor 441 is built into the first bearing 25, the acceleration sensor 441 can measure vibrations in close proximity to the first gear 22. Since the acceleration sensor 441 is not affected by the vibration path, it does not need to be a high-performance, expensive sensor. In other words, an inexpensive acceleration sensor will suffice. Even with an inexpensive acceleration sensor, vibrations can be detected accurately, allowing for accurate fault diagnosis. In this embodiment, a MEMS acceleration sensor is used as an inexpensive acceleration sensor, which is advantageous not only in terms of sensor position but also in terms of cost.

[0084] Furthermore, the acceleration sensor 441 is installed on the outer ring 112 of the first bearing 25. This location is typically one of the non-rotating mechanical elements closest to the gear meshing area, and the vibrations that can be obtained can be considered gear meshing vibrations. Measuring acceleration near the vibration source eliminates the influence of vibration transmission paths such as the housing. In this embodiment, as shown in Figure 15, an angle-to-tooth map using angle offset values ​​is employed, so when generating tooth-by-tooth acceleration curves as shown in Figure 12(C) from a curve as shown in Figure 12(B), the divisions into intervals P1, P2, P3, P4, ... can be accurately determined.

[0085] Although the gear failure detection device 10 is described as a personal computer, it could also be a tablet device, smartphone, wearable watch, or other device. In the embodiment described above, the measuring device 100 transmitted the measured values ​​to the gear failure detection device 10 without processing them. However, the measuring device 100 may perform some of the processing that the gear failure detection device 10 would perform. In other words, the measuring device 100 may have some of the functions of the gear failure detection device 10. For example, the processing shown in Figure 13 may be performed by the microcontroller 451. The processing in Figure 13 involves little computation and therefore consumes little power. Consequently, the power generated by the first bearing 25 is sufficient for the microcontroller 451 to perform the processing. This configuration can be called on-bearing data processing. Adopting this configuration significantly reduces the amount of data transmitted from the measuring device 100 to the gear failure detection device 10. This is because thousands of angle and acceleration data points are condensed into a single scalar value for each tooth (for each axis) for each measurement. The measurement time can be set appropriately according to the capacity and power consumption of the memory unit 230. The temperature sensor 442 does not need to be provided. In Figure 6, a protection circuit may be provided between the smoothing circuit 262 and the power management IC 263. In Figure 6, electromagnetic induction power generation is performed by the relative rotation of the magnet M and the coil C. Therefore, as the rotational speed of the coil C increases, the electromotive force also increases proportionally. If the equipment connected to the first shaft 24a fails for any reason, and the first shaft 24a rotates at a rotational speed exceeding the expected speed, and the electromotive force of the magnet M and coil C increases proportionally to that rotation, an electromotive force exceeding the input limit of the power management IC 263 may be input to the power management IC 263, potentially damaging the measuring device 100. To avoid such damage, that is, to prevent damage to the measuring device 100 even if an electromotive force exceeding the expected speed 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 used. For example, a Zener diode can be provided between the smoothing circuit 262 and the power management IC 263 as a protection circuit. The Zener diode functions as a protection circuit that protects the measuring device 100 by converting and dissipating an input voltage exceeding a predetermined value into heat.

[0086] Furthermore, in the embodiment described above, as shown in Figure 10, the sampling timings of the acceleration sensor 441 and the angle sensor 443 were assumed to be the same. That is, when the acceleration sensor 441 takes 10 measurements, the angle sensor 443 also takes 10 measurements. Then, 10 pairs of measurement values ​​can be obtained from the 10 measurement values ​​of the acceleration sensor 441 and the 10 measurement values ​​of the angle sensor 443. However, this embodiment is not limited to obtaining such pairs of measurement values. That is, the sampling timings of the acceleration sensor 441 and the angle sensor 443 do not have to be the same. For example, the sampling timing of the acceleration sensor 441 may be twice that of the angle sensor 443. In this case, when the acceleration sensor 441 takes 10 measurements, the angle sensor 443 takes 5 measurements. When acquiring a pair of measurements from the acceleration sensor 441 and the angle sensor 443 (when transferring them to the external memory 452 via DMA), the DMA controller transfers the measurements from the acceleration sensor 441 and the angle sensor 443 to the external memory 452 so that the time at which the acceleration sensor 441 took a measurement and the time at which the angle sensor 443 took a measurement are the same. This acquisition of measurement value pairs is not synchronized with the sampling period, but rather the two measurements are linked (associated) using the time information of the acceleration sensor 441's measurement and the time information of the angle sensor 443's measurement to acquire the measurement value pair. More specifically, this is the association of two measurements so that they share one or a specific common time reference (common time information). In this invention, it is sufficient to acquire the measurements from the acceleration sensor 441 and the angle sensor 443 by associating them in some way. [Explanation of Symbols]

[0087] 10: Gear failure detection device 20: Gear transmission mechanism 21: Housing 22: First gear 25: First bearing 30: Gear failure detection system 100: Measuring device 110: Cover 120: Coil board 123: Coil Pattern 141: Power control board 142: Angle sensor board 143: Control board 149: Power Generation Department 160: Z-phase magnet unit 230: Storage section 250: Bearing part 261: Rectifier circuit 262: Smoothing circuit 263: Power management IC 441: Accelerometer 442: Temperature sensor 443: Angle sensor 444: Z-phase detector 452: External memory 455:CPU 456: DMA Controller

Claims

1. A measuring device provided on one side of a bearing portion that rotatably supports a shaft on which gears are attached, A fault detection device that determines a gear failure based on acceleration and angle measurements received from the measuring device, A system having, The aforementioned measuring device is A cover attached to the outer ring of the bearing portion and covering one side of the bearing portion, An acceleration sensor is provided on the inner surface of the cover to simultaneously measure the vibration of the bearing portion in each of the three axes (X axis, Y axis, Z axis), An angle sensor is provided on the inner surface of the cover to measure the angle between the outer ring and the inner ring of the bearing portion, An acquisition unit is provided on the inner surface of the cover, which acquires acceleration measurement values ​​for each of the three axes obtained by the acceleration sensor and angle measurement values ​​obtained by the angle sensor, linking them together using a single common time reference for each of the three axes. Equipped with, The fault detection device, An input means for inputting the number of teeth on the gear, A map generation unit that generates a map defining the relationship between the teeth and the rotation angle of the bearing portion, A first calculation unit calculates the acceleration signal intensity using equation (1), A second calculation unit calculates the average value of the acceleration signal intensity using equation (2), A third calculation unit calculates the tooth damage index value using formula (3), Equipped with, The above formula (1) is, Here, P(tooth=k) is the acceleration signal intensity of the k-th tooth, x(φ(i)), y(φ(i)), z(φ(i)) are the acceleration measurements of the X, Y, and Z axes, respectively, which have values ​​when the angular position of a sample i corresponds to the k-th tooth, and n samples,k is the number of acceleration measurements obtained for the k-th tooth. The above equation (2) is, Here, P is the average value of the acceleration signal intensity of all teeth of the gear, P(k) is the acceleration signal intensity of the k-th tooth, and Z is the number of acceleration signal intensity values ​​obtained, i.e., the number of teeth of the gear. The above equation (3) is, Here, P rel (k) is the damage index value of the k-th tooth. A system characterized by the following features.

2. The system according to claim 1, characterized in that the acceleration sensor measures vibrations transmitted from the teeth of the gear to the bearing for each of the three axes, and the angle sensor measures the relative rotation angle of the inner ring with respect to the outer ring of the bearing.

3. The acquisition unit is, A control unit that transfers the acceleration measurement value obtained by the acceleration sensor and the angle measurement value obtained by the angle sensor via DMA (Direct Memory Access), The system according to claim 1 or 2, further comprising a storage unit that stores the acceleration measurement value and the angle measurement value transferred via DMA by the control unit in association with each other.

4. The measuring device further comprises a pulse generation unit that generates one pulse each time the inner ring of the bearing part rotates once. The system according to any one of claims 1 to 3, characterized in that the acquisition unit acquires the acceleration measurement value obtained by the acceleration sensor and the angle measurement value obtained by the angle sensor in association with the pulse generated by the pulse generation unit.

5. The system according to any one of claims 1 to 4, further comprising a power generation unit that generates electricity based on the relative rotation of the outer ring and inner ring of the bearing and supplies power to the acceleration sensor, the angle sensor and the acquisition unit.

6. The system according to any one of claims 1 to 5, further comprising a transmission unit that transmits the acceleration measurement value and the angle measurement value acquired by the acquisition unit to the fault determination device.

7. The system according to claim 6, characterized in that the transmitting unit transmits the acceleration measurement value and the angle measurement value to the fault detection device via communication compliant with Bluetooth® Low Energy, ZigBee®, or Thread.

8. The system according to any one of claims 1 to 7, further comprising a determination unit that determines damage to the k-th tooth based on the damage index value.

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