Bearing device

Abstract

To provide a bearing device capable of performing radio communication of detection information of a sensor even in low-speed rotation.SOLUTION: The bearing device includes a bearing, a generator 16 provided in the bearing and generating AC power by rotation of the bearing, and a circuit board 12 provided in the bearing. The circuit board 12 has a sensor 22 for detecting the state of the bearing, a radio communication circuit 24 for transmitting the state of the bearing obtained by the sensor 22 to the outside by radio, and a power supply circuit 23 for converting the AC power into DC power. A pulse conversion circuit 25 which is a speed detection means for detecting the rotation speed of the bearing is further provided, and the transmission radio wave intensity of the radio communication circuit 24 is switched based on the rotation speed obtained from the pulse conversion circuit 25. The pulse conversion circuit 25 converts the AC output of the generator 16 into a pulse signal, and calculates the rotational speed from the period or frequency of the pulse signal.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a bearing device including a bearing, a generator, and a circuit board, and relates to a technique used in applications such as industrial machinery. [Background technology]

[0002] A bearing device is known that is a sensor-equipped bearing incorporating a generator, a sensor, and a wireless communication circuit. The sensor-equipped bearing wirelessly transmits information detected by the sensor to a receiving device via the wireless communication circuit. In this sensor-equipped bearing, power generated by the generator is supplied to the sensor and the wireless communication circuit. If the power supplied to the sensor and the wireless communication circuit is insufficient, the sensor or the wireless communication circuit may malfunction or stop operating at an unintended time. For this reason, it is necessary to keep power consumption low in the sensor-equipped bearing.

[0003] For example, in Patent Document 1, when the power supply is unstable, the device transitions to a sleep mode in which the power consumption per unit time is lower than in normal mode, thereby keeping power consumption low and stabilizing the power supply. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7031447 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the case of a generator that uses electromagnetic induction and is made up of a magnet, a yoke, and a coil, it is not possible to secure sufficient power in the low-speed rotation range, resulting in a loss of wireless communication.

[0006] An object of the present invention is to provide a bearing device that is capable of wirelessly communicating sensor detection information even when rotating at low speeds. [Means for solving the problem]

[0007] The bearing device 1 of the present invention is a rolling bearing 2; a generator 16 provided in the rolling bearing 2 to generate AC power by rotation of the bearing 2; a circuit board (12) provided on the rolling bearing (2), The circuit board 12 is a bearing device having a sensor 22 that detects the state of the rolling bearing 2, a wireless communication circuit 24 that wirelessly transmits the state of the rolling bearing 2 obtained by the sensor 22 to an external device, and a power supply circuit 23 that converts the AC power into DC power, Further provided is a speed detection means 25 for detecting the rotation speed of the outer ring 6 or the inner ring 7 of the rolling bearing 2, Based on the rotation speed obtained from the speed detection means 25, the intensity of the radio wave transmitted from the wireless communication circuit 24 is changed. The "condition of the rolling bearing" refers to the parameters of the bearing that are considered necessary to maintain the function of the bearing and extend the bearing life, such as temperature, vibration, load, preload, torque, etc. The "rotational speed" is synonymous with the number of rotations per unit time.

[0008] With this configuration, the generator 16 generates AC power through the rotation of the rolling bearing 2. This AC power is rectified by the power supply circuit 23 and converted into DC power that drives the circuit board 12. The wireless communication circuit 24 wirelessly transmits the state of the rolling bearing 2 obtained by the sensor 22 to the outside. The amount of power generated by generator 16 increases as the rotation speed increases, and once the rotation speed exceeds a certain level, the power increase decreases. Therefore, circuit board 12 is in a reset state and wireless communication is stopped until the generated power consumed by circuit board 12 is obtained. Among the components of circuit board 12, wireless communication circuit 24 consumes a large amount of power, and if the power consumption of wireless communication circuit 24 can be reduced, the rotation speed at which circuit board 12 starts can be lowered.

[0009] Therefore, the intensity of the radio wave transmitted by the wireless communication circuit 24 is switched based on the rotational speed of the rolling bearing 2 obtained from the speed detection means 25. In this way, by setting the intensity of the radio wave transmitted according to the rotational speed of the rolling bearing 2, it is possible to reduce the power consumption of the wireless communication circuit 24 and to lower the rotational speed at which wireless communication is possible.

[0010] The speed detection means 25 may convert the AC output of the generator 16 into a pulse signal and calculate the rotation speed from the period or frequency of the pulse signal. The period or frequency of the pulse signal changes depending on the rotation speed of the rotating ring of the bearing 2. The speed detection means 25 can calculate the rotation speed of the rotating ring, for example, by measuring the period of the pulse signal.

[0011] The intensity of the radio wave transmitted from the wireless communication circuit 24 may be set lower as the rotation speed decreases. Lowering the intensity of the radio wave transmitted from the wireless communication circuit 24 reduces the power consumption, i.e., current, of the wireless communication circuit 24, and reduces the rotation speed required to start up the circuit board 12. If the rotation speed required to start up the circuit board 12 is reduced in this way, the speed range that can be sensed by the sensor 22 is expanded.

[0012] Acceleration / deceleration information may be further obtained from the rotation speed obtained from the speed detection means 25, and the transmission radio wave intensity may be switched by a relationship setting means Tb that compiles settings for the transmission radio wave intensity selected from the rotation speed and the acceleration / deceleration information. In this case, by finely setting the transmission radio wave intensity, it is possible to reduce the power consumption of the wireless communication circuit 24, and to further lower the rotation speed at which wireless communication is possible. [Effects of the Invention]

[0013] The bearing device of the present invention comprises: a rolling bearing; a generator provided in the rolling bearing and generating AC power by rotation of the rolling bearing; a circuit board provided in the rolling bearing, the circuit board is a bearing device having a sensor that detects the state of the rolling bearing, a wireless communication circuit that wirelessly transmits the state of the rolling bearing obtained by the sensor to an external device, and a power supply circuit that converts the AC power into DC power, Further provided is a speed detection means for detecting the rotation speed of the outer ring or the inner ring of the rolling bearing, The intensity of the radio wave transmitted from the wireless communication circuit is changed based on the rotation speed obtained from the speed detection means. This allows the bearing device to wirelessly communicate information detected by the sensor even when rotating at low speeds. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view of a bearing device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a side view of the bearing device as seen from the sensor unit side. [Figure 3] FIG. 2 is a vertical cross-sectional view of the bearing device. [Figure 4] FIG. 4 is a partially enlarged view of the sensor unit and the like in FIG. 3. [Figure 5] FIG. 2 is a block diagram showing the system configuration of the bearing device. [Figure 6] FIG. 10 is a diagram showing the relationship between the rotation speed of a rotating ring in a bearing and the generated power. [Figure 7] 10 is a diagram showing the relationship between the intensity of a transmitted radio wave and the current consumption of a wireless communication circuit. [Figure 8] 10 is a diagram showing a bearing device according to a second embodiment of the present invention, illustrating a method for setting the intensity of transmitted radio waves taking into consideration acceleration and deceleration. FIG. [Figure 9] FIG. 9 is a diagram showing a discrimination table in which the setting methods of FIG. 8 are summarized in a table. DETAILED DESCRIPTION OF THE INVENTION

[0015] [First embodiment] A bearing device according to an embodiment of the present invention will be described with reference to Figures 1 to 7. This bearing device is used in applications such as various industrial machines, machine tools, and transport machines, but is not limited to these applications. This bearing device can also be applied to vehicles, for example.

[0016] As shown in Figure 1, the bearing device 1 comprises a bearing 2, a sensor unit 3, and a magnetic ring 4. The sensor unit 3 and the magnetic ring 4 are attached to the bearing 2. The sensor unit 3 and the magnetic ring 4 can each be traded independently on the market. As shown in Figures 2 and 3, the bearing device 1 monitors the condition of the bearing 2 by wirelessly transmitting information about the bearing 2 detected by a sensor in the sensor unit 3, which will be described later, to a receiver not shown. Note that part of the lid 5, which will be described later, has been omitted from Figure 2 so that the interior of the sensor unit 3 can be seen.

[0017] <Bearings> As shown in Figure 3, in this example, a rolling bearing consisting of a deep groove ball bearing is used as bearing 2. Bearing 2 has outer ring 6, which is a fixed ring, inner ring 7, which is a rotating ring, multiple rolling elements 8 interposed between the raceways of inner and outer rings 6, 7, a cage 9 that holds these rolling elements 8, and a seal 10. Inner and outer rings 6, 7 are made of high-carbon chromium bearing steel such as SUJ2 or martensitic stainless steel. Rolling elements 8 are balls made of steel or ceramics. Cage 9 is a crown-shaped resin cage with one axial end open. Seal 10 seals one axial end of the bearing space between inner and outer rings 6, 7, facing the other axial end of cage 9.

[0018] The direction along the bearing center line C1 of the bearing 2 or the direction parallel to the bearing center line C1 is defined as the "axial direction." The direction perpendicular to the "axial direction" is defined as the "radial direction." The direction around the center axis is defined as the "circumferential direction."

[0019] <Sensor unit> The sensor unit 3 is fixed to the outer ring 6, which is a fixed ring. As shown in FIG. 4, the sensor unit 3 includes a holding member 11, a circuit board 12, a stator 13, and a lid 14. The holding member 11 is a member that holds the circuit board 12 and the stator 13 and is formed of a ferromagnetic material in a bottomed, annular shape. The holding member 11 has a standing plate portion 11a, an outer cylindrical portion 11b, and an inner cylindrical portion 11c, which are integrally formed. The standing plate portion 11a is an annular portion that holds the circuit board 12 and the stator 13 and is formed in a standing plate shape that is perpendicular to the axial direction. The outer cylindrical portion 11b is connected to the outer diameter edge of the standing plate portion 11a and extends outward in the axial direction. The inner cylindrical portion 11c is connected to the inner diameter edge of the standing plate portion 11a and extends outward in the axial direction.

[0020] A first cutout portion 6a having an annular step is formed on the inner peripheral surface on one axial side of the outer ring 6. The outer peripheral surface of the outer cylindrical portion 11b is fitted and fixed to the inner peripheral surface of the first cutout portion 6a. This fixes the retaining member 11 concentrically with the outer ring 6. Furthermore, the outer diameter side portion of one side of the upright portion 11a abuts against the step portion of the first cutout portion 6a. The retaining member 11 is fixed to the outer ring 6 so that the axial tip edges of the outer cylindrical portion 11b and the inner cylindrical portion 11c do not protrude from the end face 6b of the outer ring 6. Furthermore, when the retaining member 11 is fixed to the outer ring 6, a constant axial gap δ1 is secured between the rolling elements 8 and the retaining member 11.

[0021] Of the other side surface of the standing portion 11a, i.e., the axially outer surface, the circuit board 12 is held on the outer diameter side portion, and the stator 13 is held on the inner diameter side portion. The lid 14 is a resin member that protects the inside of the sensor unit 3, i.e., the circuit board 12. The lid 14 is fitted onto the inner circumferential surface of the outer cylindrical portion 11b and the outer circumferential surface of a soft magnetic member 15 (described later) of the stator 13. The lid 14 covers the circuit board 12. The entire sensor unit 3 including the lid 14 is arranged so as not to protrude from the end face 6b of the outer ring 6. The circuit board 12 may be sealed using a resin sealing material instead of the lid 14.

[0022] The stator 13 and a magnetic ring 4 (described later) constitute a generator 16. The generator generates AC power by rotating the bearing. The generator is a claw-pole type generator, but may be a generator of other structures.

[0023] The stator 13 includes two soft magnetic members 17 and 15, a bobbin 18, and a coil 19. Of the holding member 11, a portion consisting of the inner diameter side portion of the standing portion 11a and the inner diameter cylindrical portion 11c is used as one soft magnetic member 17 of the stator 13. In other words, the portion consisting of the inner diameter side portion of the standing portion 11a and the inner diameter cylindrical portion 11c also serves as one soft magnetic member 17 of the stator 13. The other soft magnetic member 15 is formed from a magnetic material to have an L-shaped cross section.

[0024] The soft magnetic member 15 has an L-shaped cross section and is made up of a cylindrical portion 15a that is fixed to the upright portion 11a and into which the inner peripheral surface of the lid 14 is fitted, and a stator upright portion 15b that is connected to the axial tip edge of the cylindrical portion 15a and extends a predetermined distance radially inward. A coil 19 is housed via a bobbin 18 in an annular space with a rectangular cross section that is surrounded by the one and the other soft magnetic members 17, 15.

[0025] <Magnetic ring> An annular stepped second notch 7a is formed in the outer peripheral surface of one axial side of the inner ring 7 so as to radially face the first notch 6a. A magnetic ring 4 is fixed to the outer peripheral surface of the inner ring 7 by press fitting or the like. The magnetic ring 4 includes a core 20 and a multi-pole permanent magnet 21. The multi-pole permanent magnet 21 is formed by, for example, bringing a hard magnetic material, made by kneading hard magnetic powder and rubber, into vulcanized contact with the core 20, and then magnetizing the multi-pole permanent magnet 21 so that north and south poles are alternately arranged in the circumferential direction of the bearing.

[0026] The core 20 has a cylindrical core body 20a and a flange portion 20b that increases the rigidity of the core 20. The axial base end of the inner circumferential surface of the core body 20a is press-fitted onto the outer circumferential surface of the inner ring 7. The flange portion 20b is integrally connected to the axial tip edge of the core body 20a, extends radially inward, and fits into the second notch portion 7a. As a result, the magnetic ring 4 faces the stator 13 across a predetermined radial gap δ2, and the magnetic ring 4 and the stator 13 form the generator 16. When the core 20 is fixed to the inner ring 7, the magnetic ring 4 is arranged so as not to protrude from the end face 7b of the inner ring 7.

[0027] <System configuration> As shown in Figure 5, circuit board 12 is electrically connected to generator 16. Circuit board 12 has a sensor 22, a power supply circuit 23, a wireless communication circuit 24, and a pulse conversion circuit 25 as speed detection means. Sensor 22 detects the state of bearing 2 (Figure 3). Examples of sensor 22 include an acceleration sensor 22a and a temperature sensor 22b, and these multiple sensors 22a, 22b are provided on circuit board 12. Power supply circuit 23 converts AC power generated by generator 16 into DC power.

[0028] 2 and 5, the pulse conversion circuit 25 converts the AC output of the generator 16 into a pulse signal, and calculates (detects) the rotational speed of the bearing 2 from the period or frequency of the pulse signal. The pulse conversion circuit 25 is an example of a speed detection means, and other speed detection means may also be used. The wireless communication circuit 24 wirelessly transmits the state of the bearing 2 obtained by the sensor 22 to the outside, and includes a processing function (CPU function) and an antenna 24a.

[0029] The AC output of generator 16 is rectified by power supply circuit 23, which generates DC power to drive circuit board 12. The AC output of generator 16 is converted into a pulse (rectangular) output by pulse conversion circuit 25. The pulse output is input to wireless communication circuit 24, which calculates the rotational speed of the rotating ring of bearing 2 through arithmetic processing.

[0030] The number of pulse outputs is the same as the number of magnetized pole pairs in the magnetic ring 4 per rotation of the rotating wheel. For example, if the multi-pole magnet 21 (Figure 3) has 36 pole pairs, 36 pulses are output per rotation. The frequency or period of the pulse output changes depending on the rotational speed of the rotating wheel. For example, by measuring the period of the pulse output, the rotational speed, which is the speed of the rotating wheel, can be calculated.

[0031] Figure 6 shows the relationship between the rotational speed of the rotating ring in the bearing and the generated power, i.e., DC power. As shown in Figures 5 and 6, the amount of power generated by generator 16 increases as the rotational speed increases, and once the rotational speed exceeds a certain value, the power increase decreases. Therefore, rotating substrate 12 is in a reset state and wireless communication is stopped until the generated power consumed by circuit board 12 is obtained. Among the components of the circuit board 12, the wireless communication circuit 24 consumes a large amount of power. If the power consumption of the wireless communication circuit 24 can be reduced, the rotation speed at which the circuit board 12 starts can be lowered.

[0032] <Actions, effects, etc.> Therefore, the intensity of the radio wave transmitted from the wireless communication circuit 24 is switched based on the rotation speed obtained from the pulse conversion circuit 25, which is a speed detection means. Specifically, when the rotation speed is low, the intensity of the radio wave transmitted from the antenna 24a of the wireless communication circuit 24 is kept low in order to reduce the power consumption of the wireless communication circuit 24. The means 24b for setting the intensity of the radio wave transmitted is built into the wireless communication circuit 24 and is capable of setting the intensity of the radio wave in three stages, for example. The low rotation speed state depends on the bearing size, but for example, is a rotation speed of several hundred rpm or less for a deep groove ball bearing with the bearing number "6308". However, the bearing number and rotation speed are not limited to these.

[0033] FIG. 7 is a diagram showing the relationship between the intensity of the transmitted radio wave and the current consumption of the wireless communication circuit. The antenna power, which is the intensity of the transmitted radio wave, is set by selecting one of three settings: A, B, and C. The higher the intensity of the transmitted radio wave, the higher the current consumption of the wireless communication circuit 24 (FIG. 5). Here, three settings are used: A, B, and C, but this is not limited to this and two or more settings may be used. Note that if the number of settings is n, the number of thresholds for rotation speed control is (n-1) × 2. Even if the number of settings changes, the same number of thresholds will be used for acceleration and deceleration.

[0034] 5 and 6, when the transmitted radio wave intensity is at its maximum and the generated power required to drive circuit board 12 is PC, the rotation speed must be at least XC. If the transmitted radio wave intensity is reduced, the power consumption (current) of wireless communication circuit 24 decreases, and the rotation speed required to drive circuit board 12 also decreases. For example, if the power consumption decreases to PB, the rotation speed decreases to XB.

[0035] If the power consumption is further reduced to PA, the rotation speed will drop to XA. Although it is expected that the communication distance will be shortened if the transmitted radio wave intensity is reduced, communication can be ensured by shortening the distance to the receiver RV. If the rotation speed required to activate the circuit board 12 is reduced, the speed range that can be sensed by the sensor 22 will be expanded. For example, when the temperature detected by temperature sensor 22b or the acceleration detected by acceleration sensor 22a exceeds a predetermined threshold value determined for each sensor, the control unit of the machine in which this bearing device 1 (Fig. 3) is incorporated can perform control such as limiting or stopping the rotation of bearing 2 (Fig. 3). Note that an operator may limit or stop the rotation of bearing 2 (Fig. 3) based on the data sent to receiver RV.

[0036] <Other embodiments> In the following description, parts corresponding to matters previously described in each embodiment are given the same reference numerals, and duplicated description will be omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those in the previously described embodiment unless otherwise specified. The same configuration produces the same effects. It is possible to combine not only the parts specifically described in each embodiment, but also partially combine embodiments as long as there is no particular problem with the combination.

[0037] [Second embodiment] The rotational speed at which the circuit board 12 (FIG. 5) can operate differs between when the rotational speed is increasing and when it is decreasing. For example, it is known that in a power supply circuit 23 (FIG. 5) that uses a DC-DC converter IC, the operating ON voltage is lower than the operating OFF voltage. Therefore, when the rotational speed is decreasing, the circuit board 12 (FIG. 5) can operate up to a lower speed range than when it is accelerating.

[0038] Fig. 8 is a diagram showing a method for setting the transmission radio wave strength taking acceleration and deceleration into consideration. In Fig. 8, the alphanumeric characters (A, B, C) within the arrows are the same as the transmission radio wave strength settings A, B, C shown in Fig. 7. In Fig. 8, the relationship is that the transmission radio wave strength of setting A < the transmission radio wave strength of setting B < the transmission radio wave strength of setting C. Fig. 9 is a discrimination table that compiles the setting methods of Fig. 8 in table Tb, which is a relationship setting means.

[0039] As shown in Figures 8 and 9, whether the bearing is accelerating or decelerating is determined by the pulse conversion circuit 25 (Figure 5), which is a speed detection means. If the current rotation speed is higher than the most recent rotation speed, it is determined to be accelerating. If the current rotation speed is lower than the most recent rotation speed, it is determined to be decelerating. The means for determining whether the bearing is accelerating, decelerating, or at a constant speed is built into, for example, the wireless communication circuit 24 (Figure 5).

[0040] The timing for switching the transmission signal strength during acceleration is, for example, at rotation speeds X1 and X2. During acceleration, the transmission signal strength is set to A when the rotation speed is less than X1, to B when the rotation speed is between X1 and X2, and to C when the rotation speed exceeds X2. In other words, X1X2 are thresholds for switching the transmission signal strength, and if the number of settings is n, there are n-1 thresholds X1X2.

[0041] During deceleration, the transmission radio wave strength is switched at a timing when the rotation speed is slower than the rotation speeds X1 and X2. The timing for switching the transmission radio wave strength during deceleration is, for example, rotation speed X1-α and rotation speed X2-β. In other words, X1-α and X2-β are thresholds for switching the transmission radio wave strength during deceleration. α and β are set in advance by simulation or testing. Note that α and β may be the same value. If the rotation speed is constant, the current setting is maintained.

[0042] In this way, in the bearing device according to the second embodiment, acceleration / deceleration information is further obtained from the rotational speed obtained from the pulse conversion circuit 25 (Fig. 5) which is a speed detection means, and the transmission radio wave intensity is switched using table Tb which is a relationship setting means that collects together the settings of the transmission radio wave intensity selected from the rotational speed and the acceleration / deceleration information. By finely setting the transmission radio wave intensity in this way, it is possible to reduce the power consumption of the wireless communication circuit 24 (Fig. 5), and it is possible to further lower the rotational speed at which wireless communication is possible.

[0043] The bearing may be an outer ring rotating type, with the inner ring as the fixed ring and the outer ring as the rotating ring. In this outer ring rotating type, the sensor unit is fixed to the inner ring, which is the fixed ring, and the magnetic ring is fixed to the outer ring, which is the rotating ring. Either or both of the generator and the circuit board may protrude partially from the bearing.

[0044] As the generator, it is also possible to employ an axial gap type generator in which a magnetic ring faces a stator across a predetermined axial gap. The means for setting the intensity of the transmitted radio wave may be provided outside the wireless communication circuit. The bearing is not limited to a deep groove ball bearing, and various radial bearings such as an angular contact ball bearing, a cylindrical roller bearing, or a tapered roller bearing can also be used. Alternatively, the bearing may be a thrust bearing or a sliding bearing.

[0045] Although the embodiments of the present invention have been described above, the disclosed embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0046] 1... bearing device, 2... bearing (rolling bearing), 12... circuit board, 16... generator, 22... sensor, 23... power supply circuit, 24... wireless communication circuit, 25... pulse conversion circuit (speed detection means), Tb... table (relationship setting means)

Claims

1. A rolling bearing; a generator provided in the rolling bearing and generating AC power by rotation of the rolling bearing; a circuit board provided in the rolling bearing, the circuit board is a bearing device having a sensor that detects the state of the rolling bearing, a wireless communication circuit that wirelessly transmits the state of the rolling bearing obtained by the sensor to an external device, and a power supply circuit that converts the AC power into DC power, Further provided is a speed detection means for detecting the rotation speed of the outer ring or the inner ring of the rolling bearing, The bearing device switches the intensity of the radio wave transmitted from the wireless communication circuit based on the rotation speed obtained from the speed detection means.

2. 2. The bearing device according to claim 1, wherein said speed detection means converts the AC output of said generator into a pulse signal and calculates the rotational speed from the period or frequency of said pulse signal.

3. 3. The bearing device according to claim 1, wherein the intensity of the radio wave transmitted from the wireless communication circuit is set to a lower value as the rotational speed decreases.

4. 4. A bearing device according to claim 3, further comprising: a setting means for setting the rotation speed and the acceleration / deceleration information, the setting means further acquiring acceleration / deceleration information from the rotation speed obtained from the speed detection means, and the transmission radio wave intensity being switched by the setting means for setting the transmission radio wave intensity selected from the rotation speed and the acceleration / deceleration information.

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