Electric motor and electric equipment equipped with the same

Abstract

To suppress the occurrence of electric corrosion of a bearing of a motor.SOLUTION: A motor according to the present disclosure comprises: a stator including a stator core around which a stator winding is wound; a rotor including a rotary body for holding a plurality of magnets in the circumferential direction while facing the stator or holding a plurality of magnets like the spokes of a wheel from the center and a shaft penetrating the center of the rotary body; two bearings for supporting the rotary body; a first metal bracket for fixing one of the two bearings; a second metal bracket for fixing the other of the two bearings; and a housing made of resin for holding the first metal bracket and the second metal bracket. A capacitive member and a first conduction member are arranged between the first metal bracket and the housing.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an electric motor and an electric apparatus including the electric motor, and more particularly to an electric motor improved to suppress the occurrence of electric erosion of a bearing and an electric apparatus including the electric motor.

Background Art

[0002] In recent years, many brushless motors have adopted a driving method using an inverter of a pulse width modulation (PWM) method (hereinafter, appropriately referred to as a PWM method). In the case of driving by such a PWM method inverter, the neutral point potential of the stator winding varies due to the switching of the power element. This variation in the neutral point potential is divided between the outer ring side of the bearing and the inner ring side of the bearing according to the capacitance distribution of the electric motor.

[0003] Since the capacitance distribution on the stator side on the outer ring side of the bearing including the stator winding is different from the capacitance distribution on the rotor side of the capacitance on the inner ring side of the bearing including the stator winding, a potential difference (hereinafter, referred to as shaft voltage) is generated between the outer ring of the bearing and the inner ring of the bearing. The shaft voltage includes a high-frequency component due to switching. When this shaft voltage reaches the breakdown voltage of the grease oil film inside the bearing, a minute current flows inside the bearing due to the breakdown of the grease oil film, causing roughness on the metal surface inside the bearing and resulting in electric erosion (see, for example, Patent Documents 1-4 and Non-Patent Document 1). In addition, when electric erosion progresses, a wavy wear phenomenon may occur on the inner ring of the bearing, the outer ring of the bearing, or the ball of the bearing, leading to abnormal noise, which is one of the main causes of problems in electric motors.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] [Non-Patent Document 1] "Suppression of Axial Voltage Based on Ungrounded Common-Mode Equivalent Circuit of Inverter-Driven Brushless DC Motor", Transactions of the Institute of Electrical Engineers of Japan, D, 2012, Vol. 132, No. 6, pp. 666-672 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] This disclosure aims to suppress the occurrence of electrolytic corrosion of bearings in an electric motor and an electric device equipped with the electric motor. [Means for Solving the Problems]

[0007] An electric motor according to one aspect of this disclosure includes a stator including a stator core wound with a stator winding, a rotor including a rotating body that holds a plurality of magnets in the circumferential direction facing the stator or holds a plurality of magnets in a spoke shape from the center, and a shaft that penetrates the center of the rotating body, a first bearing and a second bearing that support the rotating body, a first metal bracket that fixes the first bearing and a second metal bracket that fixes the second bearing, a housing made of resin that holds the first metal bracket, and is an electric motor provided with a capacitive member of capacitance C sb1sb2 electrically connected to the first metal bracket and the second metal bracket, and the capacitive member is disposed between the first metal bracket and the housing, With the capacitive member, the capacitance distribution on the stator side and the capacitance distribution on the rotor side coincide or are approximated.

Advantages of the Invention

[0008] According to one aspect of the present disclosure, it is possible to suppress the occurrence of electrolytic corrosion of bearings in an electric motor and an electrical device including the electric motor.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Embodiments for Carrying Out the Invention

[0010] (Knowledge on which the present disclosure is based) Before explaining the embodiments of the present disclosure, the knowledge on which the present disclosure is based will be explained. Conventionally, in the following documents, in order to suppress electrolytic corrosion of bearings, measures have been devised to reduce the shaft voltage so that the oil film of the grease inside the bearing is below the breakdown voltage and the breakdown of the oil film of the grease in the bearing does not occur. Also, measures have been devised in the following documents to reduce the discharge energy due to the breakdown of the oil film of the grease inside the bearing by reducing the shaft voltage and to reduce the damage to the metal surface inside the bearing.

[0011] , Hereinafter, the above documents will be described in detail. FIG. 10 is a schematic configuration diagram of a cross section of an inner rotor type and brushless radial type motor 50 of Patent Document 1. Patent Document 1 and Non-Patent Document 1 have the same configuration. As shown in FIG. 10, the motor 50 includes a first metal bracket 1 and a second metal bracket 2 disposed at both ends of the motor 50, a pair of bearings (a first bearing 5a and a second bearing 5b), a shaft 4, a rotor 10, and a stator 18. The rotating body 9 includes a rotor core 8 and a magnet 11 which is a permanent magnet. The rotor 10 includes the rotating body 9 and the shaft 4. The stator 18 includes a stator core 6 and a stator winding 3.

[0012] As shown in Fig. 10, the outer ring of the first bearing 5a is connected to the first metal bracket 1, and the outer ring of the second bearing 5b is connected to the second metal bracket 2. The inner ring of the first bearing 5a and the inner ring of the second bearing 5b are connected by a shaft 4 and are electrically conductive. The first metal bracket 1 and the second metal bracket 2 are electrically short-circuited by a conductive member 13.

[0013] Patent Document 1 electrically shorts the first metal bracket 1 and the second metal bracket 2 with a conductive member 13 to make the capacitances of the first metal bracket 1 and the second metal bracket 2 coincide. Further, Patent Document 1 is a method of providing a dielectric layer 20 on a rotating body 9 and changing the capacitance of the rotating body 9 to reduce the shaft voltage.

[0014] Fig. 11 is a model diagram of the capacitance distribution of the motor 50 of Patent Document 1. In the motor 50 of Patent Document 1, when considering the capacitance distribution based on the stator core 6, since the voltage distribution of the motor 50 is dominated by the capacitive reactance which is the reciprocal in impedance, as described in Fig. 5 of Non-Patent Document 1, it will be described with a capacitance distribution model. The capacitance C between the stator winding 3 and the first metal bracket 1 sb1 schematically represents that the charge of the first bearing 5a accumulates and the first shaft voltage V sh1 rises. When the first shaft voltage V sh1 rises and reaches the breakdown voltage of the grease oil film inside the bearing, breakdown occurs. The capacitance C between the stator winding 3 and the second metal bracket 2 sb2 is also the capacitance C sb1 Similarly, it schematically represents that the charge of the second bearing 5b accumulates and the second shaft voltage V sh2 rises. When the second shaft voltage V sh2 rises, breakdown occurs.

[0015] The voltage generated between the outer ring side of the first bearing 5a (location 1 in Fig. 11) and the zero potential reference N (12) of the drive circuit is the voltage V generated between the zero reference potential N (12) of the drive circuit and the neutral point potential S of the stator winding 3. comIt becomes a value divided by the capacitance distribution on the stator side. Also, the voltage generated between the outer ring side of the second bearing 5b (at position 2 in Fig. 11) and the zero potential reference N (12) of the drive circuit is the voltage V generated between the zero reference potential N (12) of the drive circuit and the neutral point potential S of the stator winding 3. com It becomes a value divided by the capacitance distribution on the stator side. The voltage generated between the inner ring side of the first bearing 5a and the inner ring side of the second bearing 5b (at position 4 in Fig. 11) and the zero potential reference N (12) of the drive circuit is the voltage V generated between the zero potential reference N (12) of the drive circuit and the neutral point potential S of the stator winding 3. com It becomes a value divided by the capacitance distribution on the rotor side.

[0016] By considering the capacitance distribution in Fig. 11, the present inventors found the following findings. The first shaft voltage V sh1 and the second shaft voltage V sh2 are the difference between the voltage generated on the outer ring side of the first bearing 5a and the outer ring side of the second bearing 5b and the voltage generated on the inner ring side. Therefore, to reduce the first shaft voltage V sh1 and the second shaft voltage V sh2 it was found that it is necessary to make the capacitance distribution on the stator side and the capacitance distribution on the rotor side coincide or approximate.

[0017] The voltage generated between the outer ring side of the first bearing 5a and the outer ring side of the second bearing 5b and the zero potential reference N (12) of the drive circuit is the capacitance C between the zero reference potential N (12) of the drive circuit and the first metal bracket 1 nb1 and the capacitance C between the stator winding 3 and the first metal bracket 1 sb1 and the capacitance C between the stator winding 3 and the second metal bracket 2 sb2 and the synthetic capacitance A2 of the voltage division ratio A2 (C nb1 / synthetic capacitance A2). Also, the voltage generated between the inner ring side of the first bearing 5a and the inner ring side of the second bearing 5b and the zero potential reference N (12) of the drive circuit is the capacitance C between the zero reference potential N (12) of the drive circuit and the shaft 4 ns and the capacitance C between the stator winding 3 and the stator core 6i 1. The capacitance C between the stator core 6 and the magnet 11 g 2. The capacitance C between the stator winding 3 and the magnet 11 sm 3. And the capacitance C of the magnet 11 m The voltage division ratio B2 of the combined capacitance B2 and C ( ns C / combined capacitance B2) is obtained.

[0018] As a result of intensive studies, the inventors have found that in order to reduce the first axial voltage V sh1 and the second axial voltage V sh2 it is necessary to make the voltage division ratio A2 (C nb1 / combined capacitance A2) and the voltage division ratio B2 (C ns / combined capacitance B2) coincide or approximate. Making the voltage division ratio A2 and the voltage division ratio B2 coincide or approximate is hereinafter simply referred to as matching. In Patent Document 1, since the capacitances C nb1 C sb2 C ns are smaller than the combined capacitance B2, it has been found that in order to match the capacitances, a method of reducing the capacitance of the combined capacitance B2 is adopted.

[0019] As shown in FIG. 10, in Patent Document 1, a dielectric layer 20 is provided on the rotating body 9 to form the capacitance C d . This capacitance C of the dielectric d in the model diagram of the capacitance distribution in FIG. 11 is such that the capacitance C m of the magnet has a capacitance C d inserted in series, and by reducing the combined capacitance B2, matching is achieved with the capacitance distribution on the stator side, and it has been found that this is a method of reducing the first axial voltage V sh1 and the second axial voltage V sh2 .

[0020] The capacitance C d of the dielectric layer 20 is inversely proportional to the width which is the distance in the thickness direction of the dielectric layer 20 (the short direction distance of the dielectric layer 20 in FIG. 10) and proportional to the length (the longitudinal direction distance of the dielectric layer 20 in FIG. 10). Therefore, the capacitance C dTo lower it, it is necessary to increase the width of the dielectric layer 20.

[0021] However, in Patent Document 1, as shown in FIG. 10, since stress is applied to the dielectric layer 20 as rotational torque, there are cases where the width of the dielectric layer 20 is restricted in order to ensure its strength. In that case, it was considered that the required capacitance could not be obtained and the shaft voltage could not be lowered. Also, in Patent Document 1, in the motor 50 using the rotating body 9 that holds a plurality of permanent magnets (magnets) in a spoke shape from the center in the radial direction, it is necessary to shorten the length of the permanent magnet (magnet) 11 by increasing the width of the dielectric layer 20, and there is a problem that the performance of the motor 50 deteriorates.

[0022] Next, Patent Document 2 will be described. FIG. 12 is a schematic configuration diagram of a cross-section of the motor 50 of Patent Document 2. FIG. 13 is a model diagram of the capacitance distribution of the motor 50 shown in FIG. 12. As shown in FIG. 12, the first metal bracket 1 and the second metal bracket 2 are short-circuited by the conducting member 13. It is a configuration in which an impedance adjusting member 14 is inserted between the stator core 6 and either the first metal bracket 1 or the second metal bracket 2.

[0023] As shown in FIG. 13, when a capacitor having capacitance is used as the impedance adjusting member 14, for the combined capacitance of C i , C sb1 and C sb2 , the impedance adjusting member 14, which is the capacitance for impedance adjustment, is connected in parallel. And, by increasing the combined capacitance of C i , C sb1 and C sb2 , consistency is achieved with the capacitance on the rotor side. As a result, in Patent Document 2, the first shaft voltage V sh1 and the second shaft voltage V sh2 can be reduced.

[0024] However, it is difficult to establish a method for connecting the impedance adjustment member 14 to the stator core 6. Further, since it is molded after the above connection, a problem that the above connection portion comes off during the production process was considered. Next, Patent Document 3 will be described. FIG. 14 is a schematic configuration diagram of a cross section of the motor 50 of Patent Document 3. In Patent Document 3, the stator core 6 is short-circuited with either the first metal bracket 1 or the second metal bracket 2 by a short-circuit member 25. In FIG. 14 of Patent Document 3, the stator core 6 and the first metal bracket 1 are short-circuited to reduce the first axial voltage V sh1 thereby reducing it.

[0025] The configuration of Patent Document 3 has a similar configuration shown in FIG. 10 of Patent Document 2. And it is disclosed that the configuration of Patent Document 3 has a problem that waveform distortion occurs in the axial voltage in Comparative Example 3 of Patent Document 2. This is presumably because the capacitance between the stator core 6 and the short-circuited first metal bracket 1 increases, but the capacitance between the stator core 6 and the non-short-circuited second metal bracket 2 does not change. Therefore, it was considered that the axial voltage of the second bearing V sh2 does not decrease and the effect of suppressing electrolytic corrosion is small.

[0026] Patent Document 4 will be described. FIG. 15 is a diagram of a model of the capacitance distribution of the motor 50 of Patent Document 4. As shown in FIG. 15, the first metal bracket 1 and the second metal bracket 2 are electrically insulated, and the capacitance C sb1 between the stator core 6 and the first metal bracket 1 and the capacitance C sb2 between the stator core 6 and the second metal bracket 2 are set to be approximate or equal to reduce the axial voltage.

[0027] However, in the embodiment of Patent Document 4, the capacitance C sb1 and the capacitance C sb2When adjusting the ratio to [object], there is a concern that the external dimensions and shape of the motor will increase because it is necessary to adjust the dimensions of the members and the distance between the members. In addition, the capacitance matching adjustment function is insufficient for the capacitance distribution on the rotor side, and the first shaft voltage V sh1 and the second shaft voltage V sh2 It was considered that there is a problem that it cannot be lowered sufficiently. Therefore, the first shaft voltage V, which is an insulation breakdown phenomenon of the grease of the first bearing 5a and the second bearing 5b sh1 and the second shaft voltage V sh2 Waveform distortion occurs, and it was considered that there is a problem with the electric erosion life in long-term operation.

[0028] Figure 16 is a schematic configuration diagram of a cross-section of the motor 50 of Patent Document 5. As shown in FIG. 16, the motor 50 includes a first metal bracket 1 and a second metal bracket 2 disposed at both ends of the motor 50, a pair of bearings (first bearing 5a and second bearing 5b), a shaft 4, a rotor 10, and a stator 18. The stator 18 includes a stator core 6 and a stator winding 3.

[0029] As shown in FIG. 16, the outer ring of the first bearing 5a is connected to the first metal bracket 1, and the outer ring of the second bearing 5b is connected to the second metal bracket 2. The inner ring of the first bearing 5a and the inner ring of the second bearing 5b are connected by a shaft 4 and are electrically conductive. The shaft 4 protrudes from the first bearing 5a and the second bearing 5b. Loads 91 and 92 are disposed at both ends of the shaft 4. The motor 50 has a resin part 23 between the first metal bracket 1 and the second metal bracket 2, and the first metal bracket 1 and the second metal bracket 2 are fixed by the resin part 23. The resin part 23 insulates the first metal bracket 1 and the second metal bracket 2.

[0030] The mounting member 61 includes an insulator 611, mounting portions 612 and 613, and mounting legs 614. The first metal bracket 1 and the second metal bracket 2 are held while being insulated by the mounting member 61. Since the distance of the resin portion 23 between the first metal bracket 1 and the second metal bracket 2 is long, the resin portion 23 does not function as a capacitive member used for storing electric charges between the first metal bracket 1 and the second metal bracket 2. Therefore, the resin portion 23 is merely for insulating the first metal bracket 1 and the second metal bracket 2. Therefore, in Patent Document 5, since the capacitance distribution on the stator side and the capacitance distribution on the rotor side are not made to coincide or approximate with each other by the resin portion 23, it is considered that there is a problem that the first axial voltage and the second axial voltage do not decrease and there is almost no effect of suppressing electrolytic corrosion.

[0031] The inventors of the present invention have found the above problems and have intensively studied to solve the problems, leading to the following disclosure. FIG. 2 is a schematic configuration diagram of a cross section of the motor 50 of the present disclosure. As shown in FIG. 2, the motor 50 has a first metal bracket 1 and a second metal bracket 2 disposed at both ends thereof, a first bearing 5a and a second bearing 5b, a shaft 4, a rotor 10, and a stator 18. The rotating body 9 has a rotor core 8 and a magnet 11 which is a permanent magnet. The rotor 10 has the rotating body 9 and the shaft 4. The motor 50 has a housing 20 made of resin that holds the first metal bracket and the second metal bracket. The stator 18 has a stator core 6 and a stator winding 3. A capacitive member 15 with a capacitance C is disposed between the first metal bracket 1 and the second metal bracket 2 so as to be in contact with the first metal bracket 1. sb1sb2 is disposed. The motor 50 has a capacitive member 15 in contact with the first metal bracket 1 and a first conduction member 31 electrically connected to the capacitive member 15 disposed between the first metal bracket 1 and the housing 20, and the first conduction member 31 and the second metal bracket 2 are electrically connected. The motor 50 makes the capacitance distribution on the stator 18 side and the capacitance distribution on the rotor 10 side coincide or approximate by the capacitive member 15.

[0032] FIG. 5 is a diagram showing a model of the capacitance distribution of the motor 50 of the present disclosure. A capacitive member 15 with a capacitance C is inserted between the first metal bracket 1 and the second metal bracket 2, so that the capacitance C between the stator winding 3 and the second metal bracket 2 sb1sb2 and the capacitance C of the capacitive member 15 sb2 form a series circuit. Further, a parallel circuit of this series circuit and the capacitance C between the stator winding 3 and the first metal bracket 1 sb1sb2 is formed. By adjusting the capacitance C of this capacitive member 15 sb1 , the combined capacitance A1 can be adjusted. Here, the combined capacitance A1 is the combined capacitance of the capacitance C sb1sb2 , the capacitance C sb1 , and the capacitance C sb2 . The combined capacitance B1 is the combined capacitance of the capacitance C between the stator winding 3 and the stator core 6 sb1sb2 , the capacitance C between the stator core 6 and the magnet 11 i , the capacitance C between the stator winding 3 and the magnet 11 g , and the capacitance C of the magnet 11 sm . m Specifically, the inventors have increased the combined capacitance A1 by increasing the capacitance C sb1sb2 , and found that the voltage division ratio A1 (C nb1 / combined capacitance A1) and the voltage division ratio B1 (C ns / combined capacitance B1) are made to coincide or approximate. As a result, they came up with a method of matching the capacitance distribution on the stator side and the capacitance distribution on the rotor side to reduce the shaft voltage. Based on the above considerations, the inventors came up with the aspects of the present disclosure described below.

[0033] A motor according to one aspect of the present disclosure A stator including a stator core around which a stationary winding is wound, a rotor including a rotating body that holds a plurality of magnets in the circumferential direction facing the stator or holds a plurality of magnets in a spoke shape from the center, and a shaft that penetrates the center of the rotating body, a first bearing and a second bearing that support the rotating body, a first metal bracket that fixes the first bearing and a second metal bracket that fixes the second bearing, a housing made of resin that holds the first metal bracket, and an electric motor comprising: a capacitive member having a capacitance C electrically connected to the first metal bracket and the second metal bracket, the capacitive member being disposed between the first metal bracket and the housing, sb1sb2 wherein the capacitive member makes the capacitance distribution on the stator side and the capacitance distribution on the rotor side coincide or approximate. According to the above aspect, a capacitive member in contact with the first metal bracket and a first conduction member electrically connected to the capacitive member are disposed between the first metal bracket and the housing, the first conduction member and the second metal bracket are electrically connected, and by making the voltage division ratio A1 (C / synthetic capacitance A1) and the voltage division ratio B1 (C nb1 / synthetic capacitance B1) approach each other, the occurrence of electric erosion of the bearings in the electric motor can be suppressed. ns According to the above aspect, since the capacitive member in contact with the first metal bracket is disposed between the first metal bracket and the housing, it is not necessary to dispose the capacitive member inside the electric motor other than the housing, so that miniaturization of the electric motor can be achieved. Further, since the capacitive member is disposed between the first metal bracket and the housing, the capacitive member does not shift in position even if the rotor 10 vibrates. By changing the area or thickness of the capacitive member in contact with the first conduction member, the capacitive member can easily set an arbitrary capacitance. According to the above aspect, since the capacitive member in contact with the first metal bracket is disposed between the first metal bracket and the housing, it is not necessary to dispose the capacitive member inside the electric motor other than the housing, so that miniaturization of the electric motor can be achieved. Further, since the capacitive member is disposed between the first metal bracket and the housing, the capacitive member does not shift in position even if the rotor 10 vibrates. By changing the area or thickness of the capacitive member in contact with the first conduction member, the capacitive member can easily set an arbitrary capacitance. Further, even if a capacitive member 15 is provided on the surface of the U-shaped portion (concave portion) of the first metal bracket 1 and the capacitive member 15 and the first conductive member 31 are electrically connected, an effect similar to the above effect can be obtained.

[0034] Hereinafter, more specific embodiments of the present disclosure will be described. However, detailed descriptions may be omitted more than necessary. For example, detailed descriptions of well-known matters and duplicate descriptions of substantially the same configurations may be omitted. This is to avoid making the following description unnecessarily redundant and to facilitate understanding by those skilled in the art. The inventors provide the accompanying drawings and the following description for those skilled in the art to fully understand the present disclosure, and do not intend to limit the subject matter described in the claims thereby. In the following description, the same or similar components are denoted by the same reference numerals.

[0035] (Embodiment 1) Hereinafter, a motor showing one aspect of the present disclosure will be described with reference to the drawings.

[0036] FIG. 1 is an external view of an inner rotor type brushless radial type motor 50 showing one aspect of the present disclosure. The motor 50 has a lid member 21, a housing 20, and a shaft 4. The lid member 21 includes a first metal bracket 1, and the housing 20 includes a second metal bracket 2. FIG. 2 is a schematic configuration diagram of a cross section of an inner rotor type brushless radial type motor 50 showing one aspect of the present disclosure. As shown in FIG. 2, a first metal bracket 1 having conductivity and a second metal bracket 2 having conductivity are arranged at both ends of the motor 50. The outer diameter of the first metal bracket 1 is the same as or larger than the outer diameter of the second metal bracket 2. Thereby, the bearing can be stably supported and the shaft 4 can be rotated. At the center of the first metal bracket 1, a first bearing 5a fixed to the first metal bracket 1 is arranged. At the center of the second metal bracket 2, a second bearing 5b fixed to the second metal bracket 2 is arranged. The shaft 4 is supported and rotated by the first bearing 5a and the second bearing 5b. The shaft 4 protrudes from the first metal bracket 1. The stator 18 generates a rotating magnetic field and rotates the rotor 10 by the rotating magnetic field. Inside the stator 18, the rotor 10 is inserted via a gap with the stator 18. The stator 18 has a stator core 6 and a stator winding 3 which is a winding. The stator winding 3 is wound around the stator core 6 with a resin 7 interposed therebetween for insulating the stator core 6. Also, the first metal bracket 1 and the second metal bracket 2 may be insulated from the stator core 6 by a space. The rotor 10 rotates in the electric motor 50 and has a shaft 4 and a rotating body 9. The rotating body 9 has a rotor core 8 and magnets 11 which are permanent magnets made of ferrite. The rotor 10 holds a plurality of magnets 11 on the outer periphery of the rotor core 8 and has a shaft 4 penetrating through the center of the rotor core 8. Also, the rotor 10 may hold a plurality of magnets 11 in a spoke shape from the center facing the stator 18.

[0037] Attached to the shaft 4 are a first bearing 5a and a second bearing 5b for supporting the shaft 4. The first bearing 5a and the second bearing 5b are cylindrical bearings having a plurality of iron balls, and the inner ring sides of the first bearing 5a and the second bearing 5b are fixed to the shaft 4. As a result, the inner ring of the first bearing 5a, the inner ring of the second bearing 5b, and the shaft 4 are electrically conductive.

[0038] In these first bearing 5a and second bearing 5b, the outer ring sides of the first bearing 5a and the second bearing 5b are fixed by a first metal bracket 1 and a second metal bracket 2 each having conductivity. In FIG. 2, the first bearing 5a is fixed to the first metal bracket 1, the second bearing 5b is fixed to the second metal bracket 2, the shaft 4 is supported by the two bearings, and the rotor 10 rotates rotatably.

[0039] Furthermore, inside this motor 50, a printed circuit board 12 on which a drive circuit for generating a rotating magnetic field is mounted is disposed between the rotor 10 and the first metal bracket 1. For example, an inverter circuit or the like is mounted on the drive circuit to apply a voltage to the stator winding 3.

[0040] With respect to the motor 50 configured as described above, by applying a voltage from the drive circuit to the stator winding 3, a current flows through the stator winding 3, and a magnetic field is generated from the stator core 6. Then, due to the rotating magnetic field from the stator core 6 and the magnetic field from the magnet 11, attractive forces and repulsive forces are generated according to the polarities of these magnetic fields, and the rotor 10 rotates about the shaft 4 by these forces.

[0041] In FIG. 2, the first metal bracket 1 and the second metal bracket 2 are held by a housing 20 made of resin. In FIG. 2, the second metal bracket 2, the stator winding 3, and the stator core 6 are integrally molded by resin molding to form the housing 20. The housing 20 has a protrusion 22 at the end on the first metal bracket 1 side.

[0042] The lower left figure in FIG. 2 is an enlarged view of the periphery of the capacitive member 15 in FIG. 2. The outer end of the first metal bracket 1 is recessed in a U-shape (recess). Between the U-shaped portion (recess) of the first metal bracket 1 and the protrusion 22 (protrusion), a capacitive member 15 in contact with the first metal bracket 1 and a first conductive member 31 in contact with the capacitive member 15 are arranged. The capacitive member 15 is arranged in the region surrounded by the recess of the first metal bracket 1. That is, the U-shaped portion (recess) of the first metal bracket 1 and the protrusion 22 (protrusion) are joined via the capacitive member 15 and the first conductive member 31. The upper and lower both sides of the capacitive member 15 and the first conductive member 31 are not in contact with the first metal bracket 1. With such a configuration, the first metal bracket 1 becomes the equivalent electrode of the capacitor, the capacitive member 15 becomes the equivalent dielectric layer of the capacitor, the first conductive member 31 becomes the equivalent electrode of the capacitor, and an equivalent capacitor is formed. The capacitance of this equivalent capacitor is, from the formula of the capacitance of the capacitor, C=ε0ε r S / d (Formula 1) S: The area [m 2 where the first metal bracket 1 faces the first conductive member 31 d: The thickness [m] of the capacitive member 15 ε0: The permittivity in vacuum, 8.85×10-12 [F / m] ε r : The relative permittivity of the capacitive member 15 and by changing the area S where the first conductive member 31 and the first metal bracket 1 face each other (the contact area between the first metal bracket 1 and the capacitive member 15, or the contact area between the capacitive member 15 and the first conductive member 31), the thickness d of the capacitive member 15, and the relative permittivity ε r of the capacitive member 15, it is possible to arbitrarily design the value of the capacitance. A portion other than the housing 20 where the capacitive member 15 is arranged is fitted with at least a part of the first metal bracket 1, and the housing 20 holds the first metal bracket 1. In addition, the capacitive member 15 may be provided first on the surface of the U-shaped portion (recess) of the first metal bracket 1, and the capacitive member 15 and the first conductive member 31 may be electrically connected. Alternatively, a convex portion may be provided on the first metal bracket 1, a concave portion may be provided on the housing 20, and the capacitive member 15 may be disposed in a region surrounded by the concave portion.

[0043] FIG. 3 is a perspective view of the periphery of the protrusion 22 of the housing 20. The first conductive member 31 is disposed on the flat portion at the tip of the protrusion 22. The capacitive member 15 is disposed on the first conductive member 31. The electric motor 50 has a second conductive member 32 that is electrically connected to the first conductive member 31. The first conductive member 31 and the second conductive member 32 are connected in an L shape, and the second conductive member 32 is disposed at the inner end of the protrusion 22. The first conductive member 31 may be bent in an L shape to form the second conductive member 32. The first conductive member 31 may be integrally formed with the tip of the protrusion 22. The first conductive member 31 and the second conductive member 32 are, for example, metal plates such as phosphor bronze and brass. As shown in the enlarged view of FIG. 2, the second conductive member 32 is electrically connected to one end of a third conductive member 33 protruding from the housing 20. The other end of the third conductive member 33 is electrically connected to the lower end portion of the second metal bracket 2 (FIG. 2). As shown in the enlarged view of FIG. 2, one end of the third conductive member 33 is a terminal made of a pin, and the pin and the second conductive member 32 are electrically connected. The portion of the third conductive member 33 other than the terminal is, for example, a metal wire.

[0044] In this way, the first conductive member 31, the second conductive member 32, and the third conductive member 33 are electrically connected to electrically connect the capacitive member 15 and the second metal bracket 2. The electrically connected first conductive member 31, second conductive member 32, and third conductive member 33 may be collectively referred to as the first conductive member 31.

[0045] With this configuration, inside the electric motor 50, the capacitive member 15 is disposed between the first metal bracket 1 and the second metal bracket 2, and the first metal bracket 1 and the second metal bracket 2 are electrically connected via the capacitive member 15. FIG. 4 is a schematic configuration diagram schematically showing a cross section of the motor 50 in FIG. 2. As shown in FIG. 4, a first metal bracket 1 having conductivity and a second metal bracket 2 having conductivity are arranged at both ends of the motor 50. At the center of the first metal bracket 1, a first bearing 5a fixed to the first metal bracket 1 is arranged. At the center of the second metal bracket 2, a second bearing 5b fixed to the second metal bracket 2 is arranged. The shaft 4 is supported and rotated by the first bearing 5a and the second bearing 5b. The shaft 4 protrudes from the first metal bracket 1.

[0046] With respect to the motor 50 configured as described above, by applying a voltage from the drive circuit to the stator winding 3, a current flows through the stator winding 3, and a magnetic field is generated from the stator core 6. Then, due to the rotating magnetic field from the stator core 6 and the magnetic field from the magnet 11, attractive and repulsive forces are generated according to the polarities of these magnetic fields, and the rotor 10 rotates about the shaft 4 by these forces.

[0047] As shown in FIG. 4, the first metal bracket 1 and the capacitive member 15 of the capacitance C sb1sb2 are electrically connected. One end of the conductive member 31 is electrically connected to the capacitive member 15, and the other end of the conductive member 31 is electrically connected to the second metal bracket 2.

[0048] With this configuration, inside the motor 50, the capacitive member 15 is arranged between the first metal bracket 1 and the second metal bracket 2, and the first metal bracket 1, the capacitive member 15, and the second metal bracket 2 can be electrically connected.

[0049] FIG. 5 is a model diagram of the capacitance distribution of Embodiment 1. Let the capacitance of the capacitive member 15 inserted between the first metal bracket 1 and the second metal bracket 2 be C sb1sb2 . The capacitance C sb1sb2 is the capacitance C sb2 between the stator winding 3 and the second metal bracket 2.constitutes a series circuit. Further, this series circuit has a capacitance C between the stator winding 3 and the first metal bracket 1 sb1 constitutes a parallel circuit, resulting in a series-parallel combined capacitance A1 (hereinafter referred to as combined capacitance A1). Also, the capacitance C between the stator winding 3 and the stator core 6 i and the capacitance C between the stator core 6 and the magnet 11 g and the capacitance C between the stator winding 3 and the magnet 11 sm and the capacitance C of the magnet 11 m are configured in series and / or parallel to form a series-parallel combined capacitance B1 (hereinafter referred to as combined capacitance B1).

[0050] In order to approximate the capacitance distribution on the stator 18 side and the capacitance distribution on the rotor 10 side, based on the inner and outer rings of the first bearing 5a and the second bearing 5b, the capacitance C between the zero reference potential N(12) of the drive circuit and the first metal bracket 1 nb1 and the ratio of the capacitance C nb1 to the combined capacitance A1 (C ns / combined capacitance A1), and the capacitance C between the zero reference potential N(12) of the drive circuit and the shaft 4 ns and the ratio of the capacitance C

[0051] Fig. 6 shows the experimental results of measuring the first shaft voltage V sb1sb2 of the first bearing 5a (hereinafter referred to as the first shaft voltage V sh1 (hereinafter referred to as the first shaft voltage V sh1 ) and the second shaft voltage V sh2 of the second bearing 5b (hereinafter referred to as the second shaft voltage V sh1 ) while changing the value of the capacitance C of the capacitive member 15 In the experiment, the capacitance C of the magnet 11 m was 21 pF, the diameter of the rotor 10 was 51 mm, and 608 made by Minebea was used for the first bearing 5a and the second bearing 5b. Grease with a consistency of 239 was used for the first bearing 5a and the second bearing 5b. The power supply voltage of the stator winding 3 was set to 391 V, and the rotor 10 was rotated at a rotational speed of 1000 r / min.

[0052] In FIG. 6, the horizontal axis represents the capacitance C of the capacitive member 15 sb1sb2 and the left vertical axis represents the first shaft voltage V sh1 and the second shaft voltage V sh2 . The right vertical axis in FIG. 6 represents the ratio (synthetic capacitance A1 / C nb1 ) which is the reciprocal of the ratio (C nb1 / synthetic capacitance A1), and the ratio (synthetic capacitance B1 / C ns ) which is the reciprocal of the ratio (C ns / synthetic capacitance B1), i.e., the voltage division ratio. The value of this voltage division ratio is shown. The measurement of the first shaft voltage V sh1 and the second shaft voltage V sh2 was performed by measuring the voltage of the inner ring with reference to the outer rings of the first bearing 5a and the second bearing 5b. When the voltage of the inner ring is higher than that of the outer ring, it is considered positive, and when the voltage of the inner ring is lower than that of the outer ring, it is considered negative.

[0053] As is clear from FIG. 6, when the value of the capacitance C sb1sb2 is small, the first shaft voltage V sh1 becomes a large positive voltage, and the second shaft voltage V sh2 becomes a large negative voltage. As the value of the capacitance C sb1sb2 increases, the first shaft voltage V sh1 gradually becomes a small value, and it can be seen that the first shaft voltage V sh1 gradually approaches the second shaft voltage V sh2 . Also, as the value of the capacitance C sb1sb2 increases, it can be seen that the second shaft voltage V sh2 also gradually becomes a small negative value. The first shaft voltage V sh1 and the second shaft voltage V sh2 are the voltage differences between the outer and inner rings of the first bearing 5a and the second bearing 5b, and these potential differences are gradually decreasing. As shown in FIG. 6, by adjusting the capacitance C sb1sb2 , the first shaft voltage V sh1 and the second shaft voltage V sh2It was found that it can be reduced to 5 V or less, which is regarded as the standard for the breakdown of grease insulation in a general bearing. Also, it was confirmed that the waveform collapse of the shaft voltage waveform, which is a breakdown phenomenon of the grease oil film of the first bearing 5a and the second bearing 5b, does not occur.

[0054] As shown in Fig. 6, when the ratio (synthetic capacitance A1 / C nb1 ) and the ratio (synthetic capacitance B1 / C ns ) are in the range of 0.7 to 1.1, it was found that the absolute values of the first shaft voltage V sh1 and the second shaft voltage V sh2 can be reduced to 5 V or less. That is, by approximating or matching the ratio (synthetic capacitance A1 / C nb1 ) and the ratio (synthetic capacitance B1 / C ns ), the first shaft voltage V sh1 and the second shaft voltage V sh2 can be reduced. Also, by approximating or matching the reciprocal of the ratio (synthetic capacitance A1 / C nb1 ), which is the ratio (C nb1 / synthetic capacitance A1), and the reciprocal of the ratio (synthetic capacitance B1 / C ns ), which is the ratio (C ns / synthetic capacitance B1), the first shaft voltage V sh1 and the second shaft voltage V sh2 can be reduced.

[0055] The capacitive member 15 is not limited as long as it can hold charge. For example, a dielectric such as a resin film or plating treatment is preferable. One aspect of the capacitive member 15 will be specifically described. For the capacitive member 15, for example, hot-dip galvanizing treatment and zinc phosphate treatment were performed on the surface of the first conductive member to form the capacitive member 15, which is a zinc phosphate crystal film, on the surface of the first conductive member, and the following two samples were prepared. At this time, the thickness d of the capacitive member 15 is 5×10 -6 m (5 μm), and the relative dielectric constant ε r of the capacitive member 15 is 3. (Sample 1) The area S of the capacitive member 15 is 0.33×10 -4 m 2 and the capacitance C of the capacitive member 15 is 175 pF according to Equation 1. (Sample 2) The area S of the capacitive member 15 is 0.57×10 -4 m 2 and the capacitance C of the capacitive member 15 is 303 pF according to Equation 1. From FIG. 6, when the capacitance of the capacitive member 15 of Sample 1 is 175 pF and when the capacitance of the capacitive member 15 of Sample 2 is 303 pF, in both cases, it can be seen that the absolute values of the first axial voltage V sh1 and the second axial voltage V sh2 can be reduced to 5 V or less.

[0056] The above mechanism will be described in detail with reference to FIG. 5. The capacitance C sb2 between the stator winding 3 and the second metal bracket 2 and the capacitance C sb1sb2 of the capacitive member 15 are in series. Therefore, the second voltage V sh2 of the second metal bracket 2 is the first axial voltage V sh1 between the stator winding 3 and the first metal bracket 1, to which the voltage divided at both ends of the capacitance C sb1sb2 of the capacitive member 15 is applied. When the capacitance C sb1sb2 of the capacitive member 15 increases, the voltage divided at both ends thereof decreases, and the second axial voltage V sh2 generated in the outer ring of the second bearing 5b approaches the value of the first axial voltage V sh1 . Therefore, the second axial voltage V sh2 can also be reduced. That is, the capacitance C sb1 between the stator winding 3 and the first metal bracket 1, the capacitance C sb2 between the stator winding 3 and the second metal bracket 2, and the capacitance C sb1sb2By increasing the combined capacitance A1 and achieving consistency between the combined capacitance distribution on the stator 18 side and the combined capacitance distribution on the rotor 10 side, the first axial voltage V sh1 and the second axial voltage V sh2 can be reduced.

[0057] Thus, in Embodiment 1, by inserting the capacitive member 15 between the first metal bracket 1 and the second metal bracket 2 and achieving consistency between the capacitance distribution on the stator 18 side and the capacitance distribution on the rotor 10 side, the first axial voltage V sh1 and the second axial voltage V sh2 are reduced, and the effect of suppressing electrolytic corrosion is obtained.

[0058] In the motor 50 according to Embodiment 1, the capacitive member 15 can be easily attached to the protrusion 22 of the housing 20, so it is excellent in manufacturability. In the motor 50 according to Embodiment 1, a capacitive member 15 in contact with the first metal bracket 1 is arranged between the first metal bracket 1 and the protrusion 22. Therefore, since it is not necessary to arrange the capacitive member 15 inside the motor 50, the motor 50 can be downsized. Also, since the capacitive member 15 is arranged between the first metal bracket 1 and the protrusion 22, the capacitive member 15 does not shift in position even if the rotor 10 vibrates. Also, by changing the area or thickness of the capacitive member 15 on the surface of the first conductive member 31, the capacitive member 15 can easily set an arbitrary capacitance. (Embodiment 2) As an example of the electric device according to the present disclosure, the configuration of an air conditioner indoor unit will be described in detail as Embodiment 2. The electric device according to the present disclosure is not necessarily limited to these examples.

[0059] In FIG. 7, a brushless motor 101 is provided inside the housing 111 of the air conditioner indoor unit 110. A cross-flow fan 112, which is a blower fan, is attached to the rotating shaft of the brushless motor 101. The brushless motor 101 is driven by a motor drive device 113. When the brushless motor 101 rotates due to the energization from the motor drive device 113, the cross-flow fan 112 rotates accordingly. Due to the rotation of the cross-flow fan 112, air-conditioned air is blown into the room by an indoor unit heat exchanger (not shown). Here, for example, the electric motor 50 of the above-described Embodiment 1 can be applied to the brushless motor 101.

[0060] The electric device of the present disclosure includes a brushless motor and a housing on which the brushless motor is mounted, and the electric motor 50 of the above-described Embodiment 1 is adopted as the brushless motor. (Embodiment 3) As an example of the electric device according to the present disclosure, the configuration of the air conditioner outdoor unit will be described in detail as Embodiment 3.

[0061] In FIG. 8, the air conditioner outdoor unit 201 includes a brushless motor 208 inside the housing 211. The brushless motor 208 has a blower fan 212 attached to its rotating shaft.

[0062] The air conditioner outdoor unit 201 is partitioned into a compressor chamber 206 and a heat exchanger chamber 209 by a partition plate 204 erected on the bottom plate 202 of the housing 211. A compressor 205 is provided in the compressor chamber 206. A heat exchanger 207 and a brushless motor 208 are disposed in the heat exchanger chamber 209. An electrical component box 210 is provided above the partition plate 204.

[0063] The brushless motor 208 is driven by a motor drive device housed in the electrical component box 210. As the brushless motor 208 rotates, the blower fan 212 rotates and blows air into the heat exchanger chamber 209 through the heat exchanger 207. Here, for example, the electric motor 50 of the above-described Embodiment 1 can be applied to the brushless motor 208.

[0064] The electric device of the present disclosure includes a brushless motor 208 and a housing on which the brushless motor 208 is mounted, and the electric motor 50 of the above-described Embodiment 1 is adopted as the brushless motor 208. (Embodiment 4) As an example of the electric device according to the present disclosure, the configuration of a water heater will be described in detail as Embodiment 4.

[0065] In FIG. 9, a brushless motor 333 is provided in the housing 331 of the water heater 330. A blower fan 332 is attached to the rotating shaft of the brushless motor 333.

[0066] The brushless motor 333 is driven by a motor drive device 334. When the brushless motor 333 rotates due to energization from the motor drive device 334, the blower fan 332 rotates accordingly. The rotation of the blower fan 332 blows air necessary for combustion into a fuel vaporization chamber (not shown). Here, for example, the electric motor 50 of the above-described Embodiment 1 can be applied to the brushless motor 333.

[0067] The electric device of the present disclosure includes a brushless motor 333 and a housing on which the brushless motor 333 is mounted, and the electric motor 50 of the above-described Embodiment 1 is adopted as the brushless motor 333.

[0068] In FIG. 2 of Embodiment 1, the printed circuit board 12 provided with a drive circuit is provided inside the electric motor 50, but the printed circuit board 12 provided with a drive circuit may be provided outside the electric motor 50. In that case, the electric motor 50 can be made more compact. In addition, in Embodiments 2 to 4, a blower fan was used assuming that the motor rotates, but what is rotated is not particularly limited. In addition, the inventions according to Embodiments 1 to 4 can be replaced or combined as long as no contradiction occurs.

[0069] As described above, the present disclosure includes the electric motor described in the following items and the electric equipment including the electric motor. 〔Item 1〕 A stator including a stator core around which a stator winding is wound, A rotor including a rotating body that holds a plurality of magnets in the circumferential direction facing the stator or holds a plurality of magnets in a spoke shape from the center, and a shaft that penetrates the center of the rotating body, A first bearing and a second bearing that support the rotating body, A first metal bracket that fixes the first bearing and a second metal bracket that fixes the second bearing, An electric motor including a housing made of resin that holds the first metal bracket, A capacitive member having a capacitance C that is electrically connected to the first metal bracket and the second metal bracket, and the capacitive member is disposed between the first metal bracket and the housing, sb1sb2 An electric motor in which the capacitive member makes the electrostatic capacitance distribution on the stator side and the electrostatic capacitance distribution on the rotor side coincide or approximate. According to the above aspect, a capacitive member in contact with the first metal bracket and a first conduction member electrically connected to the capacitive member are disposed between the first metal bracket and the housing, the first conduction member and the second metal bracket are electrically connected, and by making the voltage division ratio A1 (C / synthetic capacitance A1) and the voltage division ratio B1 (C nb1 / synthetic capacitance B1) closer, the occurrence of electric erosion of the bearing in the electric motor can be suppressed. ns According to the above aspect, since the capacitive member in contact with the first metal bracket is disposed between the first metal bracket and the housing, it is not necessary to dispose the capacitive member inside the motor other than the housing, so that miniaturization of the motor can be achieved. Also, since the capacitive member is disposed between the first metal bracket and the housing, the capacitive member does not shift in position even if the rotor vibrates. By changing the area or thickness of the capacitive member in contact with the first conductive member, the capacitive member can easily set an arbitrary capacitance.

[0070] 〔Item 2〕 The motor according to item 1, wherein a convex portion or a concave portion is provided in a part of the housing, a concave portion or a convex portion is provided in the first metal bracket at a position corresponding to the convex portion or the concave portion of the housing, and the capacitive member is disposed in a region surrounded by any of the concave portions. According to the above aspect, the capacitive member can be disposed between the first metal bracket and the housing in a state where the first metal bracket and the housing are fitted and fixed at some place of the cylindrical housing.

[0071] 〔Item 3〕 The motor according to item 1 or 2, further comprising a first conductive member electrically connected to the capacitive member, wherein the first conductive member and the second metal bracket are electrically connected. According to the above aspect, the motor has a first conductive member electrically connected to the capacitive member, and by using the first conductive member, the first conductive member and the second metal bracket are electrically connected, so that the capacitive member can be disposed between the first metal bracket and the housing.

[0072] 〔Item 4〕 The motor according to any one of items 1 to 3, wherein the capacitive member is formed on the surface of the first conductive member. According to the above aspect, by forming the capacitive member on the surface of the first conductive member, the capacitive member and the first conductive member are firmly connected. Also, it becomes easy to form the capacitive member into a thin film by plating or the like.

[0073] 〔Item 5〕 The motor according to any one of Items 1 to 3, wherein the capacitive member is formed on the surface of the first metal bracket. According to the above aspect, by forming the capacitive member on the surface of the first metal bracket, the capacitive member and the first metal bracket are firmly connected. Also, the capacitive member can be formed in a space-saving manner.

[0074] 〔Item 6〕 The motor according to any one of Items 1 to 4, wherein a part of the first conductive member is integrally formed with the housing. According to the above aspect, by integrally forming a part of the first conductive member with the housing, the first conductive member is firmly fixed to the housing. Also, the first conductive member can be arranged in a space-saving manner.

[0075] 〔Item 7〕 The capacitance C of the capacitive member sb1sb2 and the capacitance C between the stator winding and the first metal bracket sb1 and the capacitance C between the stator winding and the second metal bracket sb2 to increase the value A1 of the combined capacitance on the stator side including these, and the capacitance C between the combined capacitance A1 on the stator side and the first metal bracket at the zero reference potential of the drive circuit that applies a voltage to the stator winding nb1 and the capacitance C between the stator winding and the stator core i and the capacitance C between the stator core and the magnet g and the capacitance C between the stator winding and the magnet sm and the capacitance C of the magnet m and the combined capacitance B1 on the rotor side including these, and the capacitance C between the zero reference potential of the drive circuit and the shaftns The electric motor according to any one of Items 1 to 6 that approximates or matches the ratio. According to the above aspect, by increasing the value A1 of the combined capacitance, the combined capacitance A1 and the capacitance C nb1 Ratio (combined capacitance A1 / C nb1 ), the combined capacitance B1, and the capacitance C ns Ratio (combined capacitance B1 / C ns ) are approximated or matched, and the occurrence of electric erosion of the bearing in the electric motor can be suppressed.

[0076] 〔Item 8〕 The electric motor according to any one of Items 1 to 7, wherein the first metal bracket and the second metal bracket are insulated from the stator core of the stator by an insulating resin. According to the above aspect, since it is insulated, it is easier to generate a rotor magnetic field.

[0077] 〔Item 9〕 An electric device equipped with the electric motor according to any one of Items 1 to 8 and a blower fan driven by the electric motor. According to the above aspect, the occurrence of electric erosion of the bearing of the electric motor of the electric device equipped with the blower fan can be suppressed.

Explanation of Signs

[0078] 1 First metal bracket 2 Second metal bracket 3 Stator winding 4 Shaft 5a First bearing 5b Second bearing 6 Stator core 7 Resin 8 Rotor core 9 Rotating body 10 Rotor 11 Magnet 12 Printed circuit board 13 Conductive member 14 Impedance adjusting member 15 Capacitive member 18 Stator 20 housing 21 lid member 22 protrusion 31 first conductive member 32 second conductive member 33 third conductive member 50 electric motor

Claims

1. A stator including a stator core around which a stator winding is wound, a rotor including a rotating body that holds a plurality of magnets in the circumferential direction facing the stator or holds a plurality of magnets in a spoke shape from the center, and a shaft that penetrates the center of the rotating body, a first bearing and a second bearing that support the rotating body, a first metal bracket that fixes the first bearing and a second metal bracket that fixes the second bearing, a motor including a housing made of resin that holds the first metal bracket, A capacitance C electrically connected to the first metal bracket and the second metal bracket ｓｂ１ｓｂ２ has a capacitive member, and the capacitive member is disposed between the first metal bracket and the housing, having a first conductive member electrically connected to the capacitive member, and the first conductive member and the second metal bracket being electrically connected, a motor in which the ratio of the capacitance distribution on the stator side to the capacitance distribution on the rotor side is in the range of 0.7 to 1.1 by the capacitive member.

2. The motor according to claim 1, wherein a convex portion or a concave portion is provided in a part of the housing, a concave portion or a convex portion is provided in the first metal bracket at a position corresponding to the convex portion or the concave portion of the housing, and the capacitive member is disposed in a region surrounded by any one of the concave portions.

3. The motor according to claim 1 or 2, wherein the capacitive member is formed on the surface of the first conductive member.

4. The motor according to claim 1 or 2, wherein the capacitive member is formed on the surface of the first metal bracket.

5. The motor according to any one of claims 1 to 3, wherein a part of the first conductive member is integrally formed with the housing.

6. The capacitance C of the capacitive member ｓｂ１ｓｂ２ and a capacitance C between the stator winding and the first metal bracket. ｓｂ１ and a capacitance C between the stator winding and the second metal bracket. ｓｂ２ The value A1 of the composite capacitance on the stator side including ｓｂ１ｓｂ２ The value of the composite capacitance A1 on the stator side and the capacitance C between the zero reference potential of the drive circuit that applies voltage to the stator winding and the first metal bracket are set to be larger than the value A1 of the composite capacitance when the value of ｎｂ１ and the capacitance C between the stator winding and the stator core. ｉ and the capacitance C between the stator core and the magnet ｇ and the capacitance C between the stator winding and the magnet ｓｍ and the electrostatic capacitance C of the magnet ｍ A composite capacitance B1 on the rotor side including the rotor side capacitance B2 and a capacitance C between the zero reference potential of the drive circuit and the shaft ｎｓ 6. The electric motor according to claim 1, wherein the ratio is in the range of 0.7 to 1.

1.

7. The motor according to any one of claims 1 to 6, wherein the first metal bracket and the second metal bracket are insulated from the stator core of the stator by an insulating resin.

8. An electrical device equipped with the motor according to any one of claims 1 to 7 and a blower fan driven by the motor.

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