Bearing condition detection device, rotating electrical machine, and bearing condition detection method

Abstract

The bearing condition detection device (200) of the present disclosure includes a sensor (50) that measures at least one of a magnetic field and an electric field around a bearing (20) that has a cylindrical shape and supports a shaft (12) of a rotor (10) of a rotating electric machine (100) on an inner peripheral surface, and a shaft current detection unit (70) that detects a shaft current flowing through the bearing (20) based on a signal from the sensor (50). The sensor (50) is arranged to face at least one end surface (20fe) of both end surfaces in the axial direction of the bearing (20).

Description

Technical Field

[0001] The present disclosure relates to a bearing condition detection device, a rotating electric machine, and a bearing condition detection method.

Background Art

[0002] In a rotating electric machine driven by a power conversion circuit using an inverter, electric erosion of bearings occurs due to the switching operation of semiconductor elements included in the inverter. Such electric erosion causes wear and damage of the bearings, and reduces the reliability of the rotating electric machine.

[0003] It is known that electric erosion of bearings is caused by shaft current, which is a discharge current flowing between the rigid balls and the inner and outer rings constituting the bearings. However, since the shaft current propagates from the bearings to the housing that holds the bearings, there is a problem that direct measurement is difficult. On the other hand, a technique for indirectly measuring the shaft current by arranging a magnetic field sensor in the vicinity of a magnetized bearing and detecting a change in the magnetic field caused by the shaft current has been disclosed (see, for example, Patent Document 1). In addition, a technique for highly sensitively detecting the shaft current by combining a magnetic field sensor and an acoustic sensor has also been disclosed (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, additional equipment is required to magnetize the bearing, which increases the number of components and cost. In addition, simply arranging a magnetic field sensor in the vicinity of the bearing reduces the detection sensitivity for the shaft current propagating from the bearing to the housing. Also, when combining an acoustic sensor, additional equipment such as the acoustic sensor is required, increasing the number of components and cost.

[0006] This disclosure discloses a technique for solving the above problems, and aims to detect shaft current with high sensitivity without increasing the number of components.

Means for Solving the Problems

[0007] The bearing condition detection device of this disclosure is cylindrical and supports the shaft of the rotor of a rotating electrical machine on its inner peripheral surface. Not magnetized It includes a sensor for measuring at least one of the magnetic field and the electric field around the bearing, and a shaft current detection unit for detecting the shaft current flowing through the bearing based on the signal from the sensor. The sensor is arranged to face at least one of the both end faces in the axial direction of the bearing.

[0008] The bearing condition detection method of this disclosure includes a step of arranging a sensor for measuring at least one of the magnetic field and the electric field to face at least one of the both end faces in the axial direction of the bearing that supports the shaft of the rotor of a rotating electrical machine, and a step of detecting the shaft current flowing in the radial direction of the bearing based on the signal from the sensor. Not magnetized It is characterized by including the above steps.

Advantages of the Invention

[0009] According to the bearing condition detection device or the bearing condition detection method of this disclosure, since the sensor is opposed to the axial end face of the bearing, the shaft current can be detected with high sensitivity without increasing the number of components.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiment for Carrying Out the Invention

[0011] Embodiment 1. FIGS. 1 to 9 are for explaining the configuration of a bearing state detection device and a rotating electrical machine equipped with the bearing state detection device according to Embodiment 1, and a bearing state detection method. FIG. 1 is a block diagram showing a rotating electrical machine equipped with a bearing state detection device together with a cross-sectional view including the shaft of the rotating electrical machine. FIG. 2A is a top view when the axial direction of the bearing to be detected is the vertical direction, and FIG. 2B is a cross-sectional view taken along line B-B of FIG. 2A including the shaft.

[0012] Further, FIG. 3 is a cross-sectional view taken along line A-A of FIG. 1 perpendicular to the shaft of the rotating electrical machine to which the bearing state detection device is to be mounted. FIG. 4 is a block diagram showing the rotating electrical machine to which the bearing state detection device is to be mounted and the drive circuit of the rotating electrical machine. FIG. 5 is an equivalent circuit diagram showing the principle of shaft voltage generation in the rotating electrical machine.

[0013] FIG. 6 is a cross-sectional view corresponding to FIG. 1 including the shaft showing an example of the shaft current path in the rotating electrical machine. FIG. 7 is a cross-sectional view including the shaft showing an example of the shaft current path when a load is connected to the motor which is the rotating electrical machine. Further, FIG. 8 is a partially enlarged cross-sectional view obtained by enlarging a part of FIGS. 6 and 7 including the shaft showing an example of the arrangement of sensors with respect to the bearing in the bearing state detection device. FIG. 9A is a top view showing a preferred form when a conductor sealing plate is provided on the bearing. FIG. 9B is a schematic cross-sectional view including the shaft corresponding to line C-C of FIG. 9A. FIGS. 9A and 9B are schematic cross-sectional views corresponding to FIG. 2B showing two preferred forms of the sealing plate respectively when a conductor sealing plate is provided on the bearing. Further, FIG. 10 is a partially enlarged cross-sectional view corresponding to FIG. 8 including the shaft showing another example of the arrangement of sensors.

[0014] The bearing state detection device 200 according to Embodiment 1 is configured to detect the shaft current flowing through a bearing 20A that rotatably supports a rotor 10 of a rotating electrical machine 100, as shown in FIG. 1. Here, before a detailed description of the bearing state detection device 200, the structure of the bearing 20 (when not distinguishing between the two bearings 20A and 20B, referred to as the bearing 20) to be detected will be described.

[0015] As shown in FIGS. 2A and 2B, the bearing 20 has an inner ring 21, a plurality of rigid balls 22 as rolling elements, and an outer ring 23. The plurality of rigid balls 22 are loaded between the inner ring 21 and the outer ring 23. The bearing 20 has a cylindrical shape, and has an outer peripheral surface 20fo, an inner peripheral surface 20fi, and a pair of end surfaces 20fe at both ends in the axial direction (the direction along the axis Xr). The inner peripheral surface 20fi is closely fixed to the shaft 12 of the rotating electric machine 100, and the plurality of rigid balls 22 roll around the axis Xr. Further, together with lubricating oil (not shown) filled between the inner ring 21 and the outer ring 23, the plurality of rigid balls 22 roll with less friction.

[0016] At this time, an oil film made of lubricating oil, which is an insulator, is formed between the inner ring 21 and the rigid ball 22, and between the rigid ball 22 and the outer ring 23. In the present embodiment, the rolling bearing uses the rigid ball 22 as a ball, but this is not the only case, and other rolling elements such as cylindrical rollers and needle rollers may be used. Further, a bearing other than the rolling bearing such as a sliding bearing may be used.

[0017] Based on the configuration of the bearing 20 described above, the configuration of the rotating electric machine 100, which is a rotating electric machine, and the bearing state detection device 200 will be described with reference to FIGS. 1 and 3. The rotating electric machine 100 depicted in FIGS. 1 and 3 has a configuration of a so-called brushless motor. The rotating electric machine 100 has a housing 40, a stator 30, a rotor 10 disposed radially inside the stator 30, and bearings 20A and 20B that are fixed to the housing 40 and rotatably support the rotor 10.

[0018] Of the end surfaces 20fe of each of the bearings 20, the one facing the inside of the housing 40 is referred to as the inner end surface 20fei, and the one facing the outside is referred to as the outer end surface 20fex. The bearing state detection device 200 has a sensor 50 opposed to the end surface 20fe of the bearing 20, and a shaft current detection unit 70 that receives a signal from the sensor 50 via a transmission unit 200w and detects the presence or absence of a shaft current. Before the details are described, the rotating electric machine 100 will be explained.

[0019] The stator 30 is composed of a stator core 31 and a stator winding 32. The stator core 31 includes an annular core back portion 31b, teeth portions 31t extending radially inward from the inner peripheral surface side of the core back portion 31b, and flange portions 31g protruding in the circumferential direction from the tips of the teeth portions 31t. The radial direction refers to the direction that is perpendicular to the axis Xr with the axis Xr as the origin and radiates outward, and the circumferential direction refers to the direction along the circumference of a concentric circle with the axis Xr as the origin.

[0020] The stator core 31 is obtained, for example, by laminating thin plates of electromagnetic steel sheets in the axial direction and integrating them. The stator winding 32 is wound around the teeth portions 31t and is housed in slot portions 31s formed between adjacent teeth portions 31t. Among the stator windings 32, the portion protruding axially from the outermost layer of the stator core 31 is referred to as the coil end portion. As the winding method of the stator winding 32, there are a winding method called concentrated winding in which the stator winding 32 is wound around each teeth portion 31t, and a winding method called distributed winding in which it is wound across a plurality of teeth portions 31t. In any winding method, the effect of detecting the axial current described later with high sensitivity can be obtained in the same manner.

[0021] The housing 40 is composed of a housing 41 and brackets 42A and 42B. The housing 41 has a cylindrical shape, and the inner peripheral surface of the housing 41 and the outer peripheral surface of the core back portion 31b of the stator core 31 face each other and are fixed to each other integrally. The housing 41 and the core back portion 31b of the stator core 31 are electrically conductive.

[0022] The brackets 42A and 42B are fastened to both ends of the housing 41, that is, the openings on the load connection side and the non - load connection side, respectively, with bolts or the like. Also, the brackets 42A and 42B are fixed to the outer peripheral surfaces of the outer rings 23 of the bearings 20A and 20B, respectively. These integrated housing 41, brackets 42A, and 42B serve as the housing 40 of the rotating electrical machine 100 and house the rotor 10, the bearings 20, and the stator 30 inside.

[0023] The rotor 10 includes a rotor core 11, a plurality of permanent magnets 13 embedded on the side closer to the outer periphery of the rotor core 11, and a shaft 12 fixed to a hole penetrating the radial center of the rotor core 11. The rotor core 11 is obtained, for example, by laminating thin plates of electromagnetic steel sheets in the axial direction and integrally forming them. The shaft 12 is fixed to the inner rings 21 (inner peripheral surfaces 20fi) of the bearings 20A and 20B on its load connection side (left side in FIG. 1) and load non-connection side (right side in FIG. 2), respectively, and the outer peripheral surfaces 20fo of the bearings 20A and 20B are fixed to the housing 40, so that the rotor 10 is rotatably supported with respect to the housing 40.

[0024] Next, the configuration of the drive circuit 500 that drives the rotating electrical machine 100 will be described with reference to FIG. 4. The drive circuit 500 includes a power supply unit 501, a power conversion circuit 502, a wiring 503 connecting them, and a wiring 504 connecting the power conversion circuit 502 and the rotating electrical machine 100. The power supply unit 501 is a DC power supply that supplies the power necessary to drive the rotating electrical machine 100, which is a brushless motor. As the DC power supply, for example, a secondary battery such as a lithium-ion battery, a nickel-metal hydride battery, or a lead-acid battery can be used.

[0025] The power conversion circuit 502 is composed of a semiconductor switching element and a circuit that drives it. As the switching element, for example, an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), etc. can be used. In the power conversion circuit 502, a converter circuit is configured to adjust the DC voltage supplied from the power supply unit 501 via the wiring 503 to DC power with a desired voltage, either stepped up or stepped down.

[0026] The DC power adjusted to the desired voltage is used to adjust the ratio of the on-time to the off-time of the semiconductor switching elements used in the inverter circuit configured separately from the converter circuit, thereby generating a three-phase alternating current necessary for driving the rotating electrical machine 100. This three-phase alternating current is supplied to the rotating electrical machine 100 via the wiring 504. That is, the power conversion circuit 502 functions as a so-called converter circuit, an inverter circuit, or either of them. Further, in order not to leak the high-frequency noise generated by the switching operation of the semiconductor switching elements to the power supply unit 501 side, the power conversion circuit 502 is provided with a noise filter composed of an inductor and a capacitor as necessary.

[0027] In addition, in the present embodiment, a configuration using a DC power supply for the power supply unit 501 is shown, but the power supply unit 501 does not necessarily have to be a DC power supply, and an AC power supply may be used. In this case, the power conversion circuit 502 may be provided with a rectifier circuit that takes an AC voltage as an input and converts it into a DC voltage of a different voltage instead of the converter circuit.

[0028] Here, the principle of the generation of the shaft voltage V2 in the rotating electrical machine 100 driven by the power conversion circuit 502 will be described using the equivalent circuit of FIG. 5. Here, the shaft voltage V2 is defined as the voltage of the shaft 12 measured with reference to the potential of the housing 40. In FIG. 5, the point G represents the potential of the housing 40, the point N represents the potential of the neutral point N of the stator winding 32, and the point S represents the potential of the shaft 12. The voltage V1, which is the potential difference between the points N and G, represents the voltage of the neutral point N of the rotating electrical machine 100, and the potential difference between the points S and G is represented as the shaft voltage V2 of the rotating electrical machine 100. Further, C1 represents the stray capacitance between the stator winding 32 and the rotor 10, and C2 represents the stray capacitance between the rotor 10 and the housing 40.

[0029] To drive the rotating electrical machine 100, the semiconductor switching element group included in the power conversion circuit 502 performs a switching operation at a carrier frequency fc based on PWM (Pulse Width Modulation) control. At this time, the magnitude of the voltage V1 of the neutral point N also varies stepwise with the period of the carrier frequency fc over time. The variation in the voltage V1 of the neutral point N generated between the housing 40 and the stator winding 32 is divided by the stray capacitance C1 and the stray capacitance distributed inside the rotating electrical machine 100, thereby inducing a finite potential difference with respect to the housing 40 on the shaft 12, that is, an axial voltage V2.

[0030] The impedance Z of the stray capacitance C at a frequency f can be expressed as in Equation (1). Z(C) = 1 / (2πfC) ···(1) Therefore, the axial voltage V2 generated between the housing 40 and the shaft 12 can be expressed by Equation (2). V2 = {Z(C2) / (Z(C1)+Z(C2))}×V1 = {C1 / (C1+C2)}×V1 ···(2)

[0031] Next, in the rotating electrical machine 100 driven by the power conversion circuit 502, the principle of the generation of the axial current and an example of its propagation path will be described with reference to FIG. 6. When the axial voltage V2 exceeds the breakdown voltage of the bearing 20, or when breakdown occurs due to low-speed rotation of the bearing 20 or contact of the rigid body balls 22 with the outer ring 23 and the inner ring 21 due to the intrusion of foreign matter, the charges charged in the stray capacitance of the rotating electrical machine 100 and the bearing 20 are discharged, and an axial current I1 flows.

[0032] The axial current I1 is generated due to the variation in the neutral point voltage V1, propagates from the stator winding 32 through the rotor 10, bearings 20A and 20B, and the housing 40, and flows out to the outside of the rotating electrical machine 100 at the same potential as the housing potential (G point). Since there are innumerable stray capacitances in the rotating electrical machine 100, there are multiple paths for the axial current other than the one indicated by the axial current I1. However, when the axial current is generated, it is accompanied by the breakdown of the bearing 20. Therefore, regardless of the path, the axial current includes at least one of the multiple bearings 20 in the propagation path.

[0033] In addition, in this embodiment, although an example of the propagation path of the shaft current I1 generated due to the fluctuation of the voltage V1 of the neutral point N is shown, this is not the only case. For example, the bearing state detection device 200 is also effective for shaft currents generated due to other phenomena such as shaft currents caused by insulation breakdown of the bearing 20 due to triboelectrification, and shaft currents caused by shaft voltage V2 due to asymmetry of the magnetic flux distribution. Further, in this embodiment, although an example of the propagation path in which the shaft current I1 flows into the outside of the rotating electrical machine 100 having the same potential as the housing potential is shown, this is not the only case. For example, the bearing state detection device 200 is also effective even when the propagation path circulates inside the rotating electrical machine 100 as shown in FIG. 10 described later.

[0034] In the rotating electrical machine 100 driven by the power conversion circuit 502, a further example of the propagation path of the shaft current I1 will be described with reference to FIG. 7. The load device 900 is driven as a load of the rotating electrical machine 100 described in FIG. 1 and is connected via the load device connection portion 400. The load device 900 includes a shaft 912, a bearing 920, and a housing 940 as part of its components.

[0035] The housing 940 includes a housing 941 and a bracket 942A as part of its components. The bearing 920 has an outer peripheral surface fixed to the bracket 942A and an inner peripheral surface fixed to the shaft 912. The shaft 12 of the rotating electrical machine 100 and the shaft 912 of the load device 900 are electrically and mechanically connected via the load device connection portion 400. In such a configuration, the shaft current generated due to the fluctuation of the voltage V1 of the neutral point N described in FIG. 6 branches into the shaft current I1 propagating through the bearing 20 of the rotating electrical machine 100 and the shaft current I2 propagating through the bearing 920 of the load device 900.

[0036] Next, the configurations of the sensor 50 and the shaft current detection unit 70 will be described with reference to FIG. 7. The sensor 50 is disposed at a position facing the outer end surface 20fex of the bearing 20A, and is a magnetic field sensor that measures a change in the magnetic field generated due to the shaft current I1 flowing through the bearing 20A. The shaft current detection unit 70 is connected via a transmission unit 200w that transmits the signal measured by the sensor 50 to the shaft current detection unit 70. In the present embodiment, the transmission unit 200w is depicted in a wired format such as an electric cable or an optical fiber, but this is not restrictive, and wireless signal transmission means may also be included.

[0037] The shaft current detection unit 70 detects the shaft current (bearing state) from the signal measured by the sensor 50. Examples of the bearing state include functions such as detection of the occurrence timing of the shaft current, calculation of the shaft current value, number and frequency of occurrences of the shaft current, monitoring of the bearing state based on the information of the current value, or abnormality diagnosis. In the present embodiment, an example of the function of the shaft current detection unit 70 is shown, but the technical scope of the present disclosure is not limited by the function of the shaft current detection unit 70.

[0038] Subsequently, the arrangement of the sensor 50 will be described with reference to FIG. 8. The sensor 50 detects the magnetic flux φ1 generated due to the shaft current I1 propagating in the radial direction of the bearing 20A. Since the sensor 50 is disposed at a position facing the outer end surface 20fex of the bearing 20A, efficient detection of the magnetic flux φ1 is possible. Further, from the viewpoint of improving the detection sensitivity of the magnetic flux φ1, it is desirable that the sensor 50 be disposed close to the outer end surface 20fex of the bearing 20A and have maximum sensitivity to the magnetic field of the current flowing in the radial direction of the bearing 20A.

[0039] Here, the end surface 20fe may be covered with a conductor such as a metal plate or a non-conductor sealing plate such as a rubber seal in order to protect and seal the rigid balls 22 and the lubricant of the bearing 20. From the viewpoint of improving the detection sensitivity of the magnetic flux φ1, it is desirable that no conductor be interposed between the sensor 50 of the bearing 20 and the end surface 20fe.

[0040] Also, when a sealing plate 25 of a metal plate is provided on the end face 20fe, as shown in FIGS. 9A and 9B, the sealing plate 25 is configured to be non-contact with at least one of the inner ring 21 and the outer ring 23 of the bearing 20, that is, not to short-circuit between the inner ring 21 and the outer ring 23. Although the figure shows an example in which a gap Sp is provided between the inner ring 21 and the sealing plate 25, an insulating material may be interposed between the inner ring 21 and the sealing plate 25. Then, as a configuration in which no conductor is interposed between the sensor 50 and the end face 20fe described above, an opening 25a may be provided so that an opening is formed between the detection area 50d of the sensor 50 and the end face 20fe. In addition, when the sealing plate 25 is a non-conductor, the same effect as that in the case where the opening 25a is provided is obtained.

[0041] As described above, there are a plurality of propagation paths of the shaft current, and each of the paths includes at least one of the plurality of bearings 20A and 20B in the propagation path. Since the sensor 50 is disposed at a position facing the end face 20fe of the bearing 20, efficient detection can be performed for any of the plurality of propagation paths of the shaft current.

[0042] In the present embodiment, the sensor 50 is a magnetic field sensor, but this is not the only case. It may also be an electric field sensor that measures a change in the electric field generated due to the shaft current. In the sensor 50, at least one of the magnetic field and the electric field caused by the shaft current may be measured. Further, in the present embodiment, the sensor 50 is disposed at a position facing the outer end face 20fex of the bearing 20, but this is not the only case. It may be disposed facing the inner end face 20fei, or may be disposed facing each of the outer end face 20fex and the inner end face 20fei. Furthermore, in the present embodiment, the sensor 50 is disposed with respect to the bearing 20A on the load connection side, but this is not the only case. It may be disposed with respect to the bearing 20B on the non-load connection side, or may be disposed with respect to a plurality of bearings 20.

[0043] Further, the sensor 50 may include not only a sensor element that detects magnetic flux in a certain direction but also another sensor element that detects magnetic flux in a direction having an inclination, for example, 45° with respect to a certain direction. In particular, when another sensor for detecting magnetic flux orthogonal to a certain direction is provided, as shown in FIGS. 7 and 8, the surface on which the detection area of one sensor element is provided faces the end face 20fe of the bearing 20, and the surface on which the detection area of the other sensor element is provided faces the outer peripheral surface of the shaft 12. By adopting such a configuration, the sensor 50 can detect not only the magnetic flux φ1 generated due to the shaft current propagating in the radial direction of the bearing 20 but also the magnetic flux φ2 generated due to the shaft current propagating in the axial direction of the shaft 12, and the detection sensitivity can be further improved.

[0044] At that time, from the viewpoint of improving the detection sensitivity of the magnetic flux φ2, it is desirable that the sensor 50 be arranged close to the outer peripheral surface of the shaft 12 and that the other sensor element be arranged so as to have the maximum sensitivity to the magnetic field with respect to the current flowing in the axial direction of the shaft 12. That is, by arranging the sensor 50 so as to have the maximum sensitivity to both the magnetic field with respect to the current flowing in the radial direction of the bearing 20 and the magnetic field with respect to the current flowing in the axial direction of the shaft 12, further improvement in the detection sensitivity is possible.

[0045] In the present embodiment, as an example of the shaft current that generates the magnetic flux φ2, the sensor 50 is arranged with respect to the shaft current I2 that propagates to the housing 940 of the load device 900 among the shaft currents flowing through the shaft 12, but this is not the only case. For example, as shown in FIG. 10, the sensor 50 may be arranged with respect to the shaft current I1 that propagates to the housing 40 of the rotating electrical machine 100.

[0046] As described above, the sensor 50 has a function of detecting the bearing state by measuring the shaft current, but may also have a function of detecting other signals. As an example, magnetic rotary angle sensors such as resolvers and encoders can be mentioned. Generally, the rotary angle sensor is arranged close to the bearing 20 on the non-load connection side. In this way, by providing the sensor 50 with the rotary angle detection function of the rotating electrical machine 100, it is possible to reduce the number of sensor components.

[0047] That is, by arranging the sensor 50 at a position facing the end face 20fe of the bearing 20 which is the location where the shaft current is generated, the detection sensitivity of the shaft current can be improved without increasing the number of components, and the bearing state can be detected with higher precision.

[0048] Note that the part that executes calculations, such as the shaft current detection unit 70, as shown in FIG. 11, can be configured by one piece of hardware 700 including a processor 701 and a storage device 702. Although not shown, the storage device 702 includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory. Further, an auxiliary storage device of a hard disk may be provided instead of the flash memory. The processor 701 executes the program input from the storage device 702. In this case, the program is input to the processor 701 from the auxiliary storage device via the volatile storage device. Also, the processor 701 may output data such as calculation results to the volatile storage device of the storage device 702, or may save the data to the auxiliary storage device via the volatile storage device.

[0049] Embodiment 2. In the above Embodiment 1, an example in which one bearing state detection device is provided for one rotating electric machine has been described. In this Embodiment 2, an example in which two bearing state detection devices are provided for one rotating electric machine will be described. FIG. 12 is a block diagram corresponding to FIG. 1 for explaining the configuration of the bearing state detection device according to Embodiment 2. Note that also in Embodiment 2, the configurations and operations of the rotating electric machine including the bearing, the drive circuit, etc. are the same as those in Embodiment 1, the description of the same parts is omitted, and FIGS. 2A to 5 of Embodiment 1 are incorporated.

[0050] As shown in Fig. 12, the bearing state detection device 200T according to Embodiment 2 includes, in addition to the first bearing state detection device 200A that detects the shaft current of the bearing 20A, a second bearing state detection device 200B that detects the shaft current of the bearing 20B, and a propagation path discrimination unit 60. Both the first bearing state detection device 200A and the second bearing state detection device 200B have the same configuration as the bearing state detection device 200 described in Embodiment 1, but those constituting the first bearing state detection device 200A are distinguished by adding "A" at the end of the reference numerals, and those constituting the second bearing state detection device 200B are distinguished by adding "B" at the end of the reference numerals.

[0051] The second bearing state detection device 200B has a shaft current detection unit 70B that detects a shaft current based on a sensor 50B disposed to face the outer end face 20fex of the bearing 20B and a signal output from the sensor 50B. Even with such a structure, the same effects as those of the bearing state detection device 200 shown in Embodiment 1 can be obtained. The sensor 50B is a magnetic field sensor that is disposed at a position facing the outer end face 20fex of the bearing 20B and measures a magnetic field generated due to the shaft current flowing through the bearing 20B.

[0052] And a propagation path discrimination unit 60 is provided for discriminating the propagation path of the shaft current based on the output from the shaft current detection unit 70A and the output from the shaft current detection unit 70B. That is, the first bearing state detection device 200A, the second bearing state detection device 200B, and the propagation path discrimination unit 60 construct a single bearing state detection device 200T. In Embodiment 2, the shaft current detection unit 70A and the shaft current detection unit 70 are expressed separately, but this is not the case, and at least some of the functions of a plurality of parts that perform arithmetic processing including the propagation path discrimination unit may be integrated.

[0053] Here, the axial current I1 described with reference to FIG. 6 and the axial current I3 shown in FIG. 12 have different current propagation paths. The axial currents flowing through the bearing 20A on the load connection side and the bearing 20B on the non-load connection side shown in FIG. 6 both flow from the inner ring 21 side to the outer ring 23 side. That is, the bearing 20A on the load connection side and the bearing 20B on the non-load connection side are both experiencing insulation breakdown at the same time. At this time, the signs of the detection signals of the sensor 50A provided on the bearing 20A side and the sensor 50B provided on the bearing 20B side are the same.

[0054] In contrast, the axial currents flowing through the bearing 20A on the load connection side and the bearing 20B on the non-load connection side shown in FIG. 12 flow in opposite directions to each other. Such a propagation path of the axial current occurs, for example, when insulation breakdown occurs in either the bearing 20A on the load connection side or the bearing 20B on the non-load connection side due to the influence of foreign matter or the like.

[0055] As an example, considering the case where insulation breakdown occurs in the bearing 20A on the load connection side, the axial current I3 propagates along a path connecting the shaft 12, the bearing 20A on the load connection side, the housing 40, and the bearing 20B on the non-load connection side. At this time, the signs of the detection signals of the sensor 50A provided on the bearing 20A side and the sensor 50B provided on the bearing 20B side are different. Thus, since the rotating electrical machine 100 is provided with sensors 50A and 50B for the plurality of bearings 20A and 20B that support the shaft 12 respectively, the propagation path determination unit 60 can determine the propagation path of the axial current from the processing results of the detection signals of each of the plurality of sensors 50.

[0056] Furthermore, since the bearing state detection device 200T of Embodiment 2 is provided with sensors 50A and sensor 50B for the plurality of bearings 20A and 20B respectively, it is possible to monitor the states of the plurality of bearings 20 and perform abnormality diagnosis. Also, similar to the bearing state detection device 200 of Embodiment 1, the bearing state detection device 200T of Embodiment 2 can improve the detection sensitivity of the axial current without increasing the number of parts, and can detect the bearing state with higher accuracy.

[0057] Embodiment 3. In Embodiments 1 and 2 described above, an example of detecting the bearing state based on a signal from a sensor that detects a magnetic field or an electric field associated with an axial current has been described. In Embodiment 3, an example of detecting the bearing state by further adding a signal of the axial voltage will be described. FIG. 13 is a block diagram corresponding to FIG. 1 for explaining the configuration of the bearing state detection device according to Embodiment 3. Note that also in Embodiment 3, the configurations and operations of the rotating electrical machine including the bearing, the drive circuit, etc. are the same as those in Embodiment 1, the description of the same parts will be omitted, and FIGS. 2A to 5 of Embodiment 1 will be incorporated.

[0058] As shown in FIG. 13, the bearing state detection device 200 according to Embodiment 3 includes a voltage sensor 80 that measures the axial voltage V2 with respect to the bearing state detection device 200 in FIG. 1, and the axial current detection unit 70 detects the axial current based on the signals of the sensor 50 and the voltage sensor 80.

[0059] The voltage sensor 80 measures the voltage between the shaft 12 and the housing 40, that is, the axial voltage V2 of the rotating electrical machine 100. Even with such a structure, the same effects as the bearing state detection device 200 shown in Embodiment 1 and Embodiment 2 can be obtained. As the connection location of the voltage sensor 80 to the shaft 12, a member for transmitting a detection signal from a rotating body such as the shaft 12, such as a brush or a conductive microfiber, is used.

[0060] In this way, the signal measured by the voltage sensor 80 that detects the voltage between the inner ring 21 and the outer ring 23 in the bearing 20 is transmitted to the axial current detection unit 70. Therefore, not only the axial current but also the axial voltage V2 can be measured, the correlation relationship is derived by measuring both the axial current and the axial voltage V2, and the state monitoring and abnormality diagnosis of a plurality of bearings with higher accuracy can be performed using the derived correlation relationship. The data of the derived correlation relationship may be stored in a database (not shown) provided in the axial current detection unit 70. Further, similar to the bearing state detection devices 200 of Embodiment 1 and Embodiment 2, the bearing state detection device 200 of Embodiment 3 can improve the detection sensitivity of the axial current without increasing the number of parts and can detect the bearing state with higher accuracy.

[0061] Note that although the present disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more of the embodiments are not limited to the application of a particular embodiment, but are applicable to the embodiments alone or in various combinations. Therefore, numerous variations not illustrated are envisioned within the scope of the technology disclosed in this specification. For example, it is assumed to include cases where at least one component is deformed, added, or omitted, and further cases where at least one component is extracted and combined with components of other embodiments.

[0062] As described above, according to the bearing state detection device 200 of the present disclosure, a sensor 50 that measures at least one of a magnetic field and an electric field around a bearing 20 that supports a shaft 12 of a rotor 10 of a rotating electrical machine 100 with an inner peripheral surface 20fi in a cylindrical shape, and a shaft current detection unit 70 that detects a shaft current flowing through the bearing 20 based on a signal from the sensor 50 are provided, and the sensor 50 is arranged so as to face at least one end surface 20fe of both end surfaces in the axial direction of the bearing 20. Thereby, without increasing the number of parts, the shaft current in the rotating electrical machine 100 can be detected with high sensitivity.

[0063] If the sensor 50 is arranged so that the sensor element has maximum sensitivity to at least one of a magnetic field and an electric field caused by a current flowing through the bearing 20 in the radial direction, the shaft current can be detected more reliably.

[0064] If the sensor 50 is also arranged to face the outer peripheral surface of the shaft 12, the current flowing through the shaft 12 in the axial direction can also be detected.

[0065] At that time, if the sensor 50 is arranged such that the second sensor element has maximum sensitivity with respect to at least one of the magnetic field and the electric field caused by the current flowing in the axial direction of the shaft 12 (the detection target is orthogonal to the above-described sensor element that has maximum sensitivity with respect to at least one of the magnetic field and the electric field caused by the current flowing in the radial direction), the current flowing in the axial direction of the shaft 12 can be detected more reliably.

[0066] Further, if the sensor 50 has a function of detecting the rotation angle of the rotor 10, the number of parts can be reduced.

[0067] The sensors 50A and 50B are provided corresponding to the two bearings 20A and 20B that support the shaft 12, and are provided with a propagation path determination unit 60 that determines the propagation path of the shaft current according to the direction of the shaft current of each of the two bearings 20 detected by the shaft current detection units 70A and 70B. In this way, it becomes easy to monitor the state and diagnose abnormalities of the bearing 20.

[0068] A voltage sensor 80 that measures the voltage (shaft voltage V2) between the housing 40 of the rotating electrical machine 100 that holds the bearing 20 and the shaft 12 is provided. The shaft current detection unit 70 detects the shaft current flowing through the bearing 20 based on the signal from the sensor 50 and the signal from the voltage sensor 80. By taking the correlation between the shaft current and the shaft voltage V2, the state of the bearing 20 can be monitored and diagnosed with higher accuracy. At that time, it is desirable to detect the shaft current using the above-described correlation.

[0069] Further, according to the rotating electrical machine 100 of the present disclosure, it includes a rotor 10, a stator 30 arranged concentrically with a gap from the outer peripheral surface of the rotor 10, and a bearing 20 and a housing 40 that holds the stator 30 from the outside in the radial direction and houses the stator 30 and the rotor 10 inside. If the above-described bearing state detection device 200 is equipped, the state of the bearing 20 can be easily diagnosed and the reliability is improved.

[0070] Also, the end face 20fe facing the sensor 50 of the bearing 20 is covered with a conductive sealing plate 25 for protecting the lubricant filled between the inner ring 21 and the outer ring 23. If the sealing plate 25 is insulated from one of the inner ring 21 and the outer ring 23 and the region facing the detection surface of the sensor 50 is open, the detection sensitivity of the magnetic flux is improved.

[0071] As described above, according to the bearing state detection method of the present disclosure, a step of disposing a sensor 50 for measuring at least one of a magnetic field and an electric field so as to face at least one end face 20fe in the axial direction of both end faces of a bearing 20 that supports a shaft 12 of a rotor 10 of a rotating electrical machine 100, and a step of detecting an axial current flowing in the radial direction of the bearing 20 based on a signal from the sensor 50 are included. Thereby, the axial current in the rotating electrical machine 100 can be detected with high sensitivity without increasing the number of components.

Explanation of reference numerals

[0072] 10: Rotor, 100: Rotating electrical machine, 12: Shaft, 20: Bearing, 200, 200T: Bearing state detection device, 20fe: End face, 25: Sealing plate, 30: Stator, 40: Housing, 50: Sensor, 60: Propagation path determination unit, 70: Axial current detection unit, 80: Voltage sensor, 500: Drive circuit, 501: Power supply unit, 502: Power conversion circuit, 900: Load device, 912: Shaft, I1, I2, I3: Axial current, V2: Axial voltage, Xr: Axis, φ1, φ2: Magnetic flux.

Claims

1. A sensor that measures at least one of the magnetic field and electric field around an unmagnetized bearing that is cylindrical in shape and supports the rotor shaft of a rotating electric machine on its inner circumference, and The system includes an axial current detection unit that detects the axial current flowing through the bearing based on the signal from the sensor, The bearing condition detection device is characterized in that the sensor is positioned opposite at least one of the end faces of the bearing in the axial direction.

2. The bearing condition detection device according to claim 1, characterized in that the sensor is arranged such that the sensor element has maximum sensitivity to at least one of the magnetic field and electric field caused by the current flowing radially through the bearing.

3. The bearing condition detection device according to claim 1 or 2, characterized in that the sensor is also positioned opposite the outer circumferential surface of the shaft.

4. The bearing condition detection device according to claim 3, characterized in that the sensor is arranged such that the second sensor element has maximum sensitivity to at least one of the magnetic field and electric field caused by the current flowing axially through the shaft.

5. The bearing condition detection device according to claim 1 or 2, characterized in that the sensor has a function of detecting the rotation angle of the rotor.

6. The sensors are provided corresponding to each of the two bearings that support the shaft, A propagation path determination unit determines the propagation path of the axial current according to the direction of the axial current of each of the two bearings detected by the axial current detection unit. A bearing condition detection device according to claim 1 or 2, characterized by comprising the above.

7. The system includes a voltage sensor for measuring the voltage between the housing of the rotating electric machine that holds the bearing and the shaft, The bearing condition detection device according to claim 1 or 2, characterized in that the shaft current detection unit detects the shaft current flowing through the bearing based on the signal from the sensor and the signal from the voltage sensor.

8. The rotor, A stator concentrically arranged at a distance from the outer surface of the rotor, and The housing holds the bearing and the stator from the radial outside and houses the stator and the rotor inside, A rotating electric machine characterized by being equipped with a bearing condition detection device according to claim 1 or 2.

9. The end face of the bearing facing the sensor is covered with a conductive seal plate to protect the lubricant filled between the inner ring and the outer ring. The rotating electric machine according to claim 8, characterized in that the seal plate is insulated from one of the inner ring and the outer ring, and has an opening in the region facing the sensing surface of the sensor.

10. A step of positioning a sensor for measuring at least one of a magnetic field and an electric field opposite at least one of the axial end faces of an unmagnetized bearing supporting the rotor shaft of a rotating electric machine, and A step of detecting the axial current flowing radially through the bearing based on the signal from the sensor, A bearing condition detection method characterized by including the following.

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