Electric motor and electrical equipment equipped with the same

Abstract

To suppress the generation of an electric corrosion of a bearing in a dynamo-electric motor.SOLUTION: A dynamo-electric motor according to the present disclosure, comprises: a stator containing a stator iron core to which a stator winding is wound; a rotator that holds a plurality of magnets to a peripheral direction so as to be opposite to the stator or holds a plurality of magnets in a spork shape from a center; a rotator that contains the rotator and a shaft binding the rotator so as to penetrate the center of the rotator; a first bearing and a second bearing supporting the rotator; a first metal bracket that fixes the first bearing; and a second metal bracket that fixes the second bearing. In the dynamo-electric motor, a capacitance member of an electrostatic capacity Cnb1 is provided between any one of the first metal bracket and the second metal bracket and a zero reference potential of a driving circuit applying a voltage to the fixing winding.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an electric motor and an electric device equipped with the electric motor, and more particularly to an electric motor improved to suppress the occurrence of electrolytic corrosion of bearings and an electric device equipped with the electric motor. [Background technology]

[0002] In recent years, brushless motors have increasingly been driven by inverters that use the pulse width modulation (PWM) method. In such PWM inverter drives, the neutral point potential of the stator winding fluctuates due to the switching of the power elements. This fluctuation in neutral point potential is divided into voltages on the outer ring side and inner ring side of the bearing due to the electrostatic capacitance distribution of the motor.

[0003] Because the capacitance distribution on the stator side between the stator winding and the outer ring of the bearing differs from the capacitance distribution on the rotor side between the stator winding and the inner ring of the bearing, a potential difference (hereinafter referred to as shaft voltage) occurs between the outer ring of the bearing and the inner ring of the bearing. The shaft voltage contains high-frequency components due to switching, and it is known that when this shaft voltage reaches the breakdown voltage of the grease film inside the bearing, a minute current flows inside the bearing due to breakdown of the grease film, causing roughness on the metal surface inside the bearing and resulting in electrolytic corrosion (see, for example, Non-Patent Document 1 and Patent Documents 1-4). Furthermore, if electrolytic corrosion progresses, corrugated wear may occur in the inner ring of the bearing, the outer ring of the bearing, or the balls of the bearing, resulting in abnormal noise, which is one of the main causes of malfunctions in electric motors. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-158152 [Patent Document 2] Patent No. 4935934 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-159302 [Patent Document 4] WO2015 / 001782 [Non-patent literature]

[0005] [Non-Patent Document 1] "Shaft Voltage Suppression Based on Ungrounded Common-Mode Equivalent Circuit for Inverter-Fed Brushless DC Motors," IEEJ Transactions on Power Systems, Vol. 132, No. 6, pp. 666-672, 2012 Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure aims to suppress the occurrence of electrolytic corrosion in bearings in electric motors and electrical equipment equipped with the electric motors. [Means for solving the problem]

[0007] An electric motor according to one aspect of the present disclosure includes: a stator including a stator core wound with a stator winding; a rotor that faces the stator and holds a plurality of magnets in a circumferential direction, or that holds a plurality of magnets in a spoke-like manner from the center; a rotor including the rotating body and a shaft to which the rotating body is fastened so as to pass through the center of the rotating body; a first bearing and a second bearing that support the rotating body; An electric motor comprising a first metal bracket that fixes the first bearing and a second metal bracket that fixes the second bearing, A capacitance C is provided between either the first metal bracket or the second metal bracket and the zero reference potential of a drive circuit that applies voltage to the stator winding. nb1 a capacitive member of The capacitance between the stator winding on the stator side and one of the brackets is C sb1 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 The rotor side capacitance including the above is defined as the composite capacitance B1. The capacitance between the zero reference potential of the drive circuit and the shaft is C ns and The capacitance between the stator winding on the stator side and the other of the first metal bracket and the second metal bracket is defined as C sb2 and The capacitance between the other bracket and the zero reference potential of the drive circuit that applies voltage to the stator winding is C nb2 When we define The capacitance C sb1 and the capacitance C nb1 Ratio of X1 (C sb1 / C nb1 ) and the combined capacitance B1 and the capacitance C ns Ratio of Y1 (B1 / C ns ) are similar or identical to The capacitance C sb2 and the capacitance C nb2 Ratio of X2 (C sb2 / C nb2 ) and the capacitance C sb1 and the capacitance C nb1 Ratio of X1 (C sb1 / C nb1 ) are similar or identical. [Effects of the Invention]

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

[0009] [Figure 1] 1 is a schematic cross-sectional view of a motor according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a model diagram of capacitance distribution of the electric motor of the first embodiment. [Figure 3] 10 is a graph showing the relationship between the capacitance of a capacitive member of the electric motor of embodiment 1, the axial voltage, the ratio (RX1 / RY1) of the voltage division ratio RX1 to the voltage division ratio RY1, and the ratio (RX2 / RX1) of the voltage division ratio RX2 to the voltage division ratio RX1. [Figure 4] FIG. 4 is a schematic cross-sectional view of a motor showing a modified example of the first embodiment. [Figure 5] 1 is a perspective view of an embodiment of an electric device using the electric motor of the first embodiment. [Figure 6] FIG. 10 is a perspective view of another aspect of an electric device using the electric motor of the first embodiment. [Figure 7] FIG. 10 is a perspective view of another aspect of an electric device using the electric motor of the first embodiment. [Figure 8] FIG. 3 is a schematic cross-sectional view of a motor according to a first embodiment of the present disclosure. [Figure 9] FIG. 1 is a schematic cross-sectional view of a conventional electric motor. [Figure 10] FIG. 10 is a model diagram of capacitance distribution of the electric motor of FIG. 9. [Figure 11] FIG. 10 is a schematic cross-sectional view of another conventional electric motor. [Figure 12] FIG. 12 is a model diagram of capacitance distribution of the electric motor of FIG. [Figure 13] FIG. 10 is a schematic cross-sectional view of another conventional electric motor. [Figure 14] FIG. 10 is a model diagram of capacitance distribution in another conventional electric motor. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Findings that formed the basis of this disclosure) Before describing the embodiments of the present disclosure, the findings on which the present disclosure is based will be described. Conventionally, the following documents have devised measures to prevent dielectric breakdown of the grease film inside the bearing by reducing the shaft voltage to keep the grease film inside the bearing below the breakdown voltage in order to suppress electrolytic corrosion of the bearing.The following documents also devise measures to reduce damage to the metal surface inside the bearing by reducing the shaft voltage to reduce the discharge energy caused by dielectric breakdown of the grease film inside the bearing.

[0011] The above document will be explained in detail below. 9 is a schematic cross-sectional view of an inner rotor, brushless radial type electric motor 50 of Patent Document 1. Patent Document 1 and Non-Patent Document 1 have the same configuration. As shown in FIG. 9, the electric motor 50 includes a first metal bracket 1, a second metal bracket 2, a first bearing 5a, a second bearing 5b, a shaft 4, a rotor 10, and a stator 18. Rotating body 9 has rotor core 8 and magnet 11, which is a permanent magnet. Rotor 10 has rotating body 9 and shaft 4. Stator 18 has stator core 6 and stator winding 3.

[0012] As shown in Figure 9, 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 the shaft 4 and are electrically conductive. A conductive member 13 electrically shorts the first metal bracket 1 and the second metal bracket 2.

[0013] In Patent Document 1 (Fig. 9), a conductive member 13 electrically shorts the first metal bracket 1 and the second metal bracket 2, thereby matching the capacitance of the first metal bracket 1 and the second metal bracket 2. Furthermore, Patent Document 1 (Fig. 9) describes a method in which a dielectric layer 20 is provided on the rotor 9, changing the capacitance of the rotor 9 and reducing the shaft voltage.

[0014] 9 has been considered in detail by the present inventors, and is a model diagram of capacitance distribution of the electric motor 50 of Patent Document 1. In the electric motor 50 of Patent Document 1, when considering capacitance distribution with the stator core 6 as a reference, the voltage distribution of the electric motor 50 is dominated by the influence of capacitive reactance, which is the reciprocal of the impedance, and therefore, as shown in FIG. 5 of Non-Patent Document 1, a description will be given using a capacitance distribution model. The capacitance C between the stator winding 3 and the first metal bracket 1 sb1 The charge of the first bearing 5a accumulates, and the first shaft voltage V sh1 The first shaft voltage V sh1 When the voltage rises and reaches the breakdown voltage of the grease film inside the bearing, breakdown occurs. sb2 The capacitance C sb1 Similarly, the charge in the second bearing 5b accumulates, and the second shaft voltage V sh2 The second shaft voltage V sh2 When this rises, breakdown occurs.

[0015] The voltage generated between the outer ring side of the first bearing 5a (point 1 in FIG. 10) and the zero potential reference N (12) of the drive circuit is the voltage V generated between the zero reference potential N of the drive circuit and the neutral point potential S of the stator winding 3. com The value is divided by the capacitance distribution on the stator side. In addition, the voltage generated between the outer ring side of the second bearing 5b (location 2 in FIG. 10) 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 The value is 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 (point 4 in FIG. 10) 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 The value is divided by the capacitance distribution on the rotor side.

[0016] The inventors have devised a model diagram of capacitance distribution shown in FIG. 10 and have discovered the following by examining it. sh1 and the second shaft voltage V sh2 is 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, the first shaft voltage V sh1 and the second shaft voltage V sh2 It was found that an effective way to reduce this is to make the capacitance distribution on the stator side match or approximate the capacitance distribution on the rotor side.

[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 calculated by 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 The combined capacitance A2 of the drive circuit and the capacitance C between the zero reference potential N(12) and the first metal bracket 1 nb2 Voltage division ratio R A2 (Combined capacitance A2 / C nb2 ) to the reciprocal of the voltage V com The voltage is multiplied by 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 calculated by the capacitance C between the stator winding 3 and the stator core 6. i , the capacitance C between the stator core 6 and the magnet 11 g , the capacitance C between the stator winding 3 and the magnet 11 sm and the capacitance C of magnet 11 m The combined capacitance B2 of the drive circuit and the capacitance C between the zero reference potential N and the shaft 4 ns Voltage division ratio R B2 (Composite capacitance B2 / C ns ) to the reciprocal of the voltage V com The voltage is multiplied by

[0018] As a result of careful consideration, the inventors of the present invention have found that the first shaft voltage V sh1 and the second shaft voltage V sh2 To reduce this, the voltage division ratio RA2 (Combined capacitance A2 / C nb2 ) and voltage division ratio R B2 (Composite capacitance B2 / C ns ) and the partial pressure ratio R A2 and voltage division ratio R B2 Hereinafter, the matching or approximation of these two will be simply referred to as "matching." In Patent Document 1, as a result, the capacitance C sb1 , C sb2 , C ns is smaller than the composite capacitance B2, so it was found that the capacitance of the composite capacitance B2 was reduced in order to match the capacitances.

[0019] In Patent Document 1, in FIG. 9, the capacitance distribution on the rotor 10 side is determined by providing a dielectric layer 20 on the rotor 9 and reducing the capacitance C d The capacitance of this dielectric is C d In FIG. 10, which is a model diagram of capacitance distribution, the capacitance C of the magnet 11 is m In series with the capacitance C d is inserted, and by reducing the combined capacitance B2, it is matched with the capacitance distribution on the stator side, and as a result, the first shaft voltage V sh1 and the second shaft voltage V sh2 was found to be lower.

[0020] The capacitance C of the dielectric layer 20 d is inversely proportional to the distance in the thickness direction of the dielectric layer 20 (the distance in the short direction of the dielectric layer 20 in FIG. 9) and proportional to the length (the distance in the long direction of the dielectric layer 20 in FIG. 9). Therefore, the capacitance C d To reduce this, it is necessary to increase the width of the dielectric layer 20 (the distance in the thickness direction of the dielectric layer 20).

[0021] However, in Patent Document 1, as shown in Figure 9, because stress is applied to the dielectric layer 20 as a rotational torque, there are cases where the width of the dielectric layer 20 is restricted in order to ensure its strength. In such cases, it was considered that the required capacitance cannot be obtained and the shaft voltage does not decrease. Furthermore, in Patent Document 1, in an electric motor 50 using a rotor 9 that holds multiple permanent magnets (magnets) in a spoke-like shape from the center in the radial direction, increasing the width of the dielectric layer 20 requires shortening the length of the permanent magnets (magnets), which poses a problem of deteriorating the performance of the electric motor 50.

[0022] Next, Patent Document 2 will be described. Fig. 11 is a schematic cross-sectional view of the configuration of an electric motor 50 of Patent Document 2. Fig. 12 is a model diagram of capacitance distribution that the inventors of the present invention have devised for the electric motor 50 of Fig. 11 . 11, the first metal bracket 1 and the second metal bracket 2 are short-circuited by a conductive member 13. An impedance adjustment member 14 is inserted between the stator core 6 and either the first metal bracket 1 or the second metal bracket 2. FIG. 11 shows a configuration in which the impedance adjustment member 14 is inserted between the stator core 6 and the second metal bracket 2.

[0023] When a capacitor having a capacitance is used as the impedance adjusting member 14, the capacitance C i , C sb1 and C sb2 The impedance adjusting member 14, which is an impedance adjusting capacitance, is connected in parallel to the combined capacitance of the above. i , C sb1 and C sb2 By increasing the combined capacitance of the first shaft voltage V, the capacitance is matched with the capacitance of the rotor side. sh1 and the second shaft voltage V sh2 was found to be lower.

[0024] However, it is difficult to establish a method for connecting the impedance adjusting member 14 to the stator core 6. Furthermore, since molding is performed after the connection, there is a problem that the connection may come loose during the production process. Next, Patent Document 3 will be described. FIG. 13 is a schematic cross-sectional view of an electric motor 50 of Patent Document 3. In Patent Document 3, the stator core 6 is short-circuited to either the first metal bracket 1 or the second metal bracket 2 by a short-circuit member 25. In Fig. 13, the stator core 6 is short-circuited to the second metal bracket 2 to reduce the first shaft voltage.

[0025] The configuration of Patent Document 3 is similar to that described in Fig. 10 of Patent Document 2. Furthermore, it is disclosed that the configuration of Patent Document 3 has a problem in 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 second metal bracket 2 increases, but the capacitance between the stator core 6 and the unshort-circuited first metal bracket 1 remains unchanged. Therefore, it was considered that the axial voltage of the first bearing 5a does not decrease, and the effect of suppressing electrolytic corrosion is small.

[0026] Finally, Patent Document 4 will be described. FIG. 14 is a model diagram of capacitance distribution that the present inventors have devised for the electric motor 50 shown in Patent Document 4. As shown in FIG. 14, the first metal bracket 1 and the second metal bracket 2 are electrically insulated, and the capacitance C sb1 and the capacitance C between the stator core 6 and the second metal bracket 2. sb2 and the shaft voltage are set to be close to or equal to each other, thereby reducing the shaft voltage.

[0027] However, in Patent Document 4, the capacitance C sb1 and capacitance C sb2When adjusting the ratio, it was considered that there was a concern that the external dimensions and shape of the motor would become larger because it would be necessary to adjust the dimensions of the components and the distance between the components. Furthermore, the capacitance matching adjustment function is insufficient for the capacitance distribution on the rotor side, and the first shaft voltage and the second shaft voltage cannot be reduced completely. As a result, the waveforms of the first shaft voltage and the second shaft voltage, which are a dielectric breakdown phenomenon of the grease in the first bearing 5a and the second bearing 5b, are distorted, and it was considered that there is an issue with the electrolytic corrosion life in long-term operation.

[0028] The present inventors have found the above-mentioned problems, and have conducted extensive research into solving the problems, and have discovered the essence of solving the problems. FIG. 1 is a schematic cross-sectional view of an electric motor 50 according to the present disclosure. As shown in FIG. 1, the electric motor 50 includes a first metal bracket 1 and a second metal bracket 2 arranged at both ends of the electric motor 50, a first bearing 5a and a second bearing 5b, a shaft 4, a rotor 10, and a stator 18. A first bearing 5a fixed to the first metal bracket 1 is disposed in the center of the first metal bracket 1. A second bearing 5b fixed to the second metal bracket 2 is disposed in the center of the second metal bracket 2. The shaft 4 is supported and rotates by the first bearing 5a and the second bearing 5b. Rotating body 9 has rotor core 8 and magnet 11, which is a permanent magnet. Rotor 10 has rotating body 9 and shaft 4. Stator 18 has stator core 6 and stator winding 3. Between the first metal bracket 1 and the zero reference potential N(12) of the drive circuit that applies voltage to the stator winding 3, there is a capacitance C nb1 A capacitive member 15 is provided. Here, either the first metal bracket 1 or the second metal bracket 2 will be described as the first metal bracket 1, and the other bracket will be described as the second metal bracket 2.

[0029] FIG. 2 is a diagram showing a model of capacitance distribution of the electric motor 50 of FIG. On the left stator 18 side, a capacitance C is formed between the first metal bracket 1 and the zero reference potential N(12). nb1 The capacitance between the stator winding 3 and the first metal bracket 1 is C sb1 On the stator 18 side of the first bearing 5a, the capacitance C sb1 and capacitance C nb1 The voltage division ratio R of the series circuit XX1 on the stator 18 side is X1 is the capacitance C sb1 / Capacitance C nb1 The voltage division ratio R X1 This is simply referred to as capacitance C sb1 and capacitance C nb1 Ratio of X1 (C sb1 / C nb1 ) may also be called. The capacitance between the stator winding 3 and the second metal bracket 2 is C sb2 The capacitance between the second metal bracket 2 and the zero reference potential N(12) of the drive circuit that applies voltage to the stator winding 3 is C nb2 The capacitance C sb2 and capacitance C nb2 The voltage division ratio R of the series circuit XX2 on the stator 18 side is X2 is the capacitance C sb2 / Capacitance C nb2 The voltage division ratio R X2 This is simply referred to as capacitance C sb2 and capacitance C nb2 Ratio of X2 (C sb2 / C nb2 ) may also be called. On the stator 18 side, the series circuit XX1 and the series circuit XX2 form a parallel circuit. The series circuit XX1 and the series circuit XX2 are connected to each other through a voltage V applied to the stator winding 3. com will be added. On the right rotor 10 side, 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 smand the capacitance C of magnet 11 m These are configured in series and / or parallel to form a series-parallel composite circuit. The capacitance of the series-parallel composite circuit is a series-parallel composite capacitance B1 (hereinafter simply referred to as composite capacitance B1). The capacitance between the shaft 4 and the zero reference potential N(12) of the drive circuit is C ns On the rotor 10 side of the first bearing 5a and the second bearing 5b, a combined capacitance B1 and a capacitance C ns The voltage division ratio R of the series circuit YY1 on the rotor 10 side is Y1 is the combined capacitance B1 / capacitance C ns The voltage division ratio R Y1 This is simply a composite capacitance B1 and a capacitance C ns Ratio of Y1 (B1 / C ns ) may also be called. The series circuit YY1 forms a parallel circuit with the series circuits XX1 and XX2. The series circuit YY1 is connected to the stator winding 3 through a voltage V com will be added. As mentioned above, the inventors have determined that the first shaft voltage V sh1 and the second shaft voltage V sh2 It was found that an effective way to reduce this is to make the capacitance distribution on the stator side match or approximate the capacitance distribution on the rotor side. In the present disclosure, a capacitance C is provided between the first metal bracket 1 and the zero reference potential N(12) of the drive circuit that applies voltage to the stator winding 3. nb1 A capacitive member 15 having a ratio R X1 (C sb1 / C nb1 ) and the ratio R Y1 (B1 / C ns ) and approximate or match the ratio R X2 (C sb2 / C nb2 ) and the ratio R X1 (C sb1 / C nb1 ) is made to approximate or match the capacitance distribution on the stator side with the capacitance distribution on the rotor side, thereby matching (matching or approximating) the capacitance distribution on the stator side and reducing the shaft voltage. Based on the above considerations, the inventors have come up with the aspects of the present disclosure described below.

[0030] An electric motor according to one aspect of the present disclosure includes: a stator including a stator core wound with a stator winding; a rotor that faces the stator and holds a plurality of magnets in a circumferential direction, or that holds a plurality of magnets in a spoke-like manner from the center; a rotor including the rotating body and a shaft to which the rotating body is fastened so as to pass through the center of the rotating body; a first bearing and a second bearing that support the rotating body; An electric motor comprising a first metal bracket that fixes the first bearing and a second metal bracket that fixes the second bearing, A capacitance C is provided between either the first metal bracket or the second metal bracket and the zero reference potential of a drive circuit that applies voltage to the stator winding. nb1 a capacitive member of The capacitance between the stator winding on the stator side and one of the brackets is C sb1 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 The rotor side capacitance including the above is defined as the composite capacitance B1. The capacitance between the zero reference potential of the drive circuit and the shaft is C ns and The capacitance between the stator winding on the stator side and the other of the first metal bracket and the second metal bracket is defined as C sb2 and The capacitance between the other bracket and the zero reference potential of the drive circuit that applies voltage to the stator winding is C nb2 When we define The capacitance Csb1 and the capacitance C nb1 Ratio of X1 (C sb1 / C nb1 ) and the combined capacitance B1 and the capacitance C ns Ratio of Y1 (B1 / C ns ) are similar or identical to The capacitance C sb2 and the capacitance C nb2 Ratio of X2 (C sb2 / C nb2 ) and the capacitance C sb1 and the capacitance C nb1 Ratio of X1 (C sb1 / C nb1 ) are similar or identical. According to the above aspect, the capacitance C of the capacitive member nb1 By adjusting the ratio R X1 (C sb1 / C nb1 ) and the ratio R Y1 (B1 / C ns ) and the ratio R X2 (C sb2 / C nb2 ) and the ratio R X1 (C sb1 / C nb1 ) can be made to approximate or match the capacitance distribution on the stator side with the capacitance distribution on the rotor side, thereby suppressing the occurrence of electrolytic corrosion in the bearings of the electric motor.

[0031] More specific embodiments of the present disclosure will be described below. However, more detailed descriptions than necessary may be omitted. For example, detailed descriptions of well-known matters or redundant descriptions of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the inventors provide the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims. In the following description, identical or similar components are designated by the same reference numerals.

[0032] (Embodiment 1) Hereinafter, an electric motor according to one embodiment of the present disclosure will be described with reference to the drawings.

[0033] FIG. 1 is a schematic cross-sectional view of an inner rotor brushless radial electric motor 50 according to one embodiment of the present disclosure. As shown in Figure 1, a first conductive metal bracket 1 and a second conductive metal bracket 2 are arranged on both ends of an electric motor 50. The outer diameter of the second metal bracket 2 is the same as or larger than the outer diameter of the first metal bracket 1. This allows the bearings to be stably supported and the shaft 4 to rotate. A first bearing 5a fixed to the first metal bracket 1 and a second bearing 5b fixed to the second metal bracket 2 are arranged in the center of the first metal bracket 1 and the second metal bracket 2. The shaft 4 is supported and rotates by the first bearing 5a and the second bearing 5b. The shaft 4 protrudes from the second metal bracket 2. The stator 18 generates a rotating magnetic field, which rotates the rotor 10. The rotor 10 is inserted inside the stator 18 with a gap between them. 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 to insulate the stator core 6. The stator 18 is molded with resin together with other fixing members such as the first metal bracket 1 and the second metal bracket 2. In the first embodiment, these members are integrally molded to form the stator 18, which has a generally cylindrical outer shape. The integrally molded member also functions as a housing for the electric motor 50. 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 permanent magnets 11, which are ferrite magnets. The rotor 10 holds a plurality of magnets 11 on the outer periphery of the rotor core 8 and has the shaft 4 passing through the center of the rotor core 8. Alternatively, the rotor 10 may face the stator 18 and hold a plurality of magnets 11 arranged in a spoke shape from the center.

[0034] A first bearing 5a and a second bearing 5b that support the shaft 4 are attached to the shaft 4. The first bearing 5a and the second bearing 5b are cylindrical bearings that have 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.

[0035] 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, respectively, which are electrically conductive. In Fig. 1, 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 first bearing 5a and the second bearing 5b, and the rotor 10 rotates freely. The shaft 4, the inner ring of the first bearing 5a, and the inner ring of the second bearing 5b are electrically conductive.

[0036] Furthermore, inside this electric motor 50, a printed circuit board 12 on which a drive circuit (not shown) that generates a rotating magnetic field is mounted is arranged between the rotor 10 and the second metal bracket 2. For example, the drive circuit includes an inverter circuit or the like for applying a voltage to the stator winding 3.

[0037] When a voltage is applied from a drive circuit to stator winding 3 of electric motor 50 configured as described above, a current flows through stator winding 3, and a magnetic field is generated from stator core 6. Then, the rotating magnetic field from stator core 6 and the magnetic field from magnet 11 generate attractive and repulsive forces according to the polarities of these magnetic fields, and these forces cause rotor 10 to rotate around shaft 4.

[0038] As shown in FIG. 1, a capacitance C is provided between the first metal bracket 1 and the zero reference potential N(12) of the drive circuit. nb1 A capacitive member 15 is provided. Both ends of the capacitive member 15 are connected to the conductive member 13 which is a conductor. One end of the conductive member 13 connected to the right side of the capacitive member 15 is electrically connected to the first metal bracket 1, and the other end of the conductive member 13 is electrically connected to the capacitive member 15. One end of the conductive member 13 connected to the left side of the capacitive member 15 is electrically connected to the capacitive member 15, and the other end of the conductive member 13 is electrically connected to the zero reference potential N(12) of the drive circuit.

[0039] The capacitive member 15 is, for example, a ceramic capacitor. The capacitive member 15 is, for example, a molded product in which electrodes are provided on both sides of a resin such as PBT. The capacitive member 15 is not particularly limited in form as long as it can store electric charge. The electrostatic capacitance of the capacitive member 15 is C nb1 is. The capacitive member 15 may be located anywhere inside the electric motor 50, for example, between the housing of the electric motor 50 and the stator 18, or on the inner wall of the housing.

[0040] FIG. 2 is a model diagram of capacitance distribution of the electric motor 50 of the first embodiment. In FIG. 2, with the first bearing 5a and second bearing 5b located in the center as the boundary, the left side shows the capacitance distribution on the stator 18 side, and the right side shows the capacitance distribution on the rotor 10 side. The voltage V applied to the stator winding 3 by the drive circuit com is the potential difference between the neutral point potential S(3) and the zero reference potential N(12). On the left stator 18 side, a capacitance C is formed between the first metal bracket 1 and the zero reference potential N(12). nb1 The capacitance between the stator winding 3 and the first metal bracket 1 is C sb1On the stator 18 side of the first bearing 5a, the capacitance C sb1 and capacitance C nb1 The voltage division ratio R of the series circuit XX1 on the stator 18 side is X1 is the capacitance C sb1 / Capacitance C nb1 is. The capacitance between the stator winding 3 and the second metal bracket 2 is C sb2 The capacitance between the second metal bracket 2 and the zero reference potential N(12) of the drive circuit that applies voltage to the stator winding 3 is C nb2 The capacitance C sb2 and capacitance C nb2 The voltage division ratio R of the series circuit XX2 on the stator 18 side is X2 is the capacitance C sb2 / Capacitance C nb2 is.

[0041] On the stator 18 side, the series circuit XX1 and the series circuit XX2 form a parallel circuit. The series circuit XX1 and the series circuit XX2 are connected to each other through a voltage V applied to the stator winding 3. com will be added. On the right rotor side, 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 magnet 11 m The series-parallel composite circuit has a capacitance of B1.

[0042] The capacitance between the shaft 4 and the zero reference potential N(12) of the drive circuit is C ns On the rotor 10 side of the first bearing 5a and the second bearing 5b, a combined capacitance B1 and a capacitance C ns The voltage division ratio R of the series circuit YY1 on the rotor 10 side is Y1 is the combined capacitance B1 / capacitance C ns is. The series circuit YY1 forms a parallel circuit with the series circuits XX1 and XX2. The series circuit YY1 is connected to the stator winding 3 through a voltage V com will be added.

[0043] In order to match (approximate or coincide) the capacitance distribution on the stator 18 side with the capacitance distribution on the rotor 10 side, the capacitance C of the capacitive member 15 is set to satisfy the following conditions 1 and 2. nb1 Adjust. (Condition 1) Voltage division ratio R of series circuit XX1 X1 (C sb1 / C nb1 ) and the voltage division ratio R of the series circuit YY1 Y1 (B1 / C ns ) to approximate or match. (Condition 2) Voltage division ratio R of series circuit XX2 X2 (C sb2 / C nb2 ) and the voltage division ratio R of the series circuit XX1 X1 (C sb1 / C nb1 ) to approximate or match.

[0044] FIG. 3 shows the capacitance C of the capacitive member 15. nb1 By changing the value of the shaft voltage V of the first bearing 5a, sh1 (Hereinafter, the first shaft voltage V sh1 ) and the second shaft voltage V of the second bearing 5b sh2 (Hereinafter, the second shaft voltage V sh2 These are the experimental results of measuring the In the experiment, the capacitance C of magnet 11 m The rotor 10 had a diameter of 51 mm, and the first bearing 5a and the second bearing 5b were made of Minebea 608. The electrostatic capacitance of the rotor 9 at this time was 10 pF. The grease used for the first bearing 5a and the second bearing 5b had a consistency of 239. The power supply voltage of the neutral point potential S(3) of the stator winding 3 was set to 391 V, and the rotor 10 was rotated at a rotation speed of 1000 r / min.

[0045] In FIG. 3, the horizontal axis represents the capacitance C of the capacitive member 15.nb1 The vertical axis on the left side of Figure 3 is the value of the first shaft voltage V sh1 and the second shaft voltage V sh2 The vertical axis on the right side of Figure 3 is the voltage division ratio R X1 (C sb1 / C nb1 ) and voltage division ratio R Y1 (B1 / C ns ) ratio (R X1 / R Y1 ), and the voltage division ratio R X2 (C sb2 / C nb2 ) and voltage division ratio R X1 (C sb1 / C nb1 ) ratio (R X2 / R X1 ) First shaft voltage V sh1 and the second shaft voltage V sh2 The measurement was performed by measuring the voltage of the inner rings based on the outer rings of the first bearing 5a and the second bearing 5b, and a positive voltage was used when the voltage of the inner rings was higher than that of the outer rings, and a negative voltage was used when the voltage of the inner rings was lower than that of the outer rings. First shaft voltage V sh1 The graph of is a solid black circle graph, and the second axis voltage V sh2 The graph of is the solid black square graph. X1 / R Y1 ) is the graph of the dotted black squares, and the ratio (R X2 / R X1 ) is a graph of dotted black circles.

[0046] From Figure 3, the first shaft voltage V sh1 The graph (solid black circle graph) extends from the bottom left to the top right of Figure 3. The second axis voltage V sh2 The graph in (the graph with solid black squares) extends from the upper left to the lower right of Figure 3. As is clear from Figure 3, the capacitance C nb1 If the value of is small, the first shaft voltage V sh1 becomes a small negative voltage, and the second shaft voltage V sh2 becomes a large positive voltage. nb1 As the value of is increased, the first axis voltage Vsh1 gradually increases, and the second shaft voltage V sh2 It can be seen that gradually becomes a smaller value. First shaft voltage V sh1 and the second shaft voltage V sh2 is the potential difference between the voltages of the outer and inner rings of the first bearing 5a and the second bearing 5b. As shown in Figure 3, the capacitance C nb1 By adjusting the first shaft voltage V sh1 and the second shaft voltage V sh2 It was possible to reduce the voltage to ±5V or less (|5V| or less), which is the standard for dielectric breakdown of grease in general bearings. At this time, it was confirmed that the distortion of the axial voltage waveform, which is a phenomenon of dielectric breakdown of the grease oil film of the first bearing 5a and the second bearing 5b, did not occur.

[0047] In FIG. 3, for example, when the capacitance of the rotor 9 is 10 pF, the first shaft voltage V sh1 and the second shaft voltage V sh2 The capacitance C of the capacitive member 15 satisfies |5V| or less nb1 The range is 10.0 pF or more and 16.3 pF or less. At this time, the ratio (R X1 / R Y1 ) graph, the ratio (R X1 / R Y1 ) is in the range of 0.6 to 1.0. In other words, the capacitance C nb1 Adjust the ratio R X1 (C sb1 / C nb1 ) and the ratio R Y1 (B1 / C ns ) can be approximated or matched. X2 / R X1 ) graph, the ratio (R X2 / R X1 ) is in the range of 0.75 to 1.25. That is, the capacitance C nb1 Adjust the ratio R X2 (C sb2 / C nb2 ) and the ratio R X1 (C sb1 / C nb1) can be approximated or matched. The first shaft voltage V sh1 and the second shaft voltage V sh2 The capacitance C of the capacitive member 15 satisfies |5V| or less nb1 The range varies depending on the capacitance of the rotor 9.

[0048] The above mechanism will be explained in detail with reference to FIG. As shown in FIG. 2, the present disclosure provides a capacitance C between the first metal bracket 1 and the zero reference potential N(12) of the driving circuit. nb1 A capacitive member 15 having a The series circuits XX1, XX2, and YY1 constitute a parallel circuit, and a voltage V applied to the stator winding 3 is com will be added. As shown in Figure 3, the capacitance C nb1 As we increase the ratio (R X1 / R Y1 ) changes from the top left to the bottom right. And the first axis voltage V sh1 and the second shaft voltage V sh2 The ratio (R X1 / R Y1 ) is in the range of 0.6 to 1.0. Therefore, the capacitance C nb1 Adjust the voltage division ratio R X1 (C sb1 / C nb1 ) and voltage division ratio R Y1 (B1 / C ns ) can be reconciled. As shown in Figure 3, the capacitance C nb1 As we increase the ratio (R X2 / R X1 ) changes from the bottom left to the top right. And the first axis voltage V sh1 and the second shaft voltage V sh2 The ratio (R X2 / R X1 ) is between 0.75 and 1.25. Therefore, the capacitance C nb1 Adjust the voltage division ratio RX2 (C sb2 / C nb2 ) can be reconciled.

[0049] In summary, the capacitance C of the capacitive member 15 nb1 By adjusting the first shaft voltage V to satisfy the following conditions 1 and 2, the capacitance distribution on the stator 18 side and the capacitance distribution on the rotor 10 side can be matched (approximated or matched). As a result, sh1 and the second shaft voltage V sh2 This reduces the amount of corrosion, thereby suppressing electrolytic corrosion. (Condition 1) Voltage division ratio R of series circuit XX1 X1 (C sb1 / C nb1 ) and the voltage division ratio R of the series circuit YY1 Y1 (B1 / C ns ) to approximate or match. (Condition 2) Voltage division ratio R of series circuit XX2 X2 (C sb2 / C nb2 ) and the voltage division ratio R of the series circuit XX1 X1 (C sb1 / C nb1 ) to approximate or match.

[0050] The electric motor 50 according to the first embodiment is excellent in manufacturability because the capacitive member 15 can be easily attached to an empty space inside the electric motor 50. Furthermore, in the electric motor 50 according to the first embodiment, the capacitive member 15 is compact, so the outer diameter and shape of the electric motor 50 do not become large. (Variation) FIG. 4 is a schematic cross-sectional view of a modified electric motor 50. In FIG. 4, the difference from FIG. 1 is that a printed circuit board 12 is placed between the first metal bracket 1 and the stator winding 3. Then, a capacitance C nb2 The point is where the capacitive member 15 is placed. The capacitance distribution model of the electric motor 50 in FIG. 4 is the capacitance C nb2 is the capacitance C nb2 2 is replaced with the capacitive member 15. nb1 The capacitive member 15 has a simple capacitance C nb1 This becomes: (Embodiment 2) As an example of an electrical device according to the present disclosure, the configuration of an air conditioner indoor unit will be described in detail as embodiment 2. The electrical device according to the present disclosure is not necessarily limited to this example.

[0051] In FIG. 5, a brushless motor 101 is provided in a housing 111 of an air conditioner indoor unit 110. A crossflow 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 energized by the motor drive device 113, the brushless motor 101 rotates, which in turn rotates the crossflow fan 112. The rotation of the crossflow fan 112 blows conditioned air into the room via an indoor unit heat exchanger (not shown). The electric motor 50 of the first embodiment described above can be applied to the brushless motor 101.

[0052] The electric device of the present disclosure includes a brushless motor and a housing in which the brushless motor is mounted, and employs the electric motor 50 of the first embodiment described above as the brushless motor. (Embodiment 3) As an example of an electrical device according to the present disclosure, the configuration of an outdoor unit of an air conditioner will be described in detail as a third embodiment.

[0053] 6, air conditioner outdoor unit 201 includes brushless motor 208 inside housing 211. Brushless motor 208 has blower fan 212 attached to its rotation shaft.

[0054] Air conditioner outdoor unit 201 is divided into a compressor chamber 206 and a heat exchanger chamber 209 by a partition plate 204 erected on a bottom plate 202 of a housing 211. A compressor 205 is provided in the compressor chamber 206. A heat exchanger 207 and a blower fan motor are disposed in the heat exchanger chamber 209. An electrical component box 210 is provided above the partition plate 204.

[0055] The blower fan motor is driven by a motor drive device housed in an 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. The electric motor 50 of the first embodiment described above can be applied to the brushless motor 208.

[0056] The electric device of the present disclosure includes a brushless motor and a housing in which the brushless motor is mounted, and employs the electric motor 50 of the first embodiment described above as the brushless motor. (Embodiment 4) As an example of an electrical device according to the present disclosure, the configuration of a water heater will be described in detail as a fourth embodiment.

[0057] 7, a brushless motor 333 is provided in a housing 331 of a water heater 330. A blower fan 332 is attached to the rotating shaft of the brushless motor 333.

[0058] Brushless motor 333 is driven by motor drive device 334. Brushless motor 333 rotates when energized by motor drive device 334, which in turn rotates blower fan 332. The rotation of blower fan 332 blows air necessary for combustion into a fuel vaporization chamber (not shown). The electric motor 50 of the first embodiment described above can be applied to brushless motor 333.

[0059] The electric device of the present disclosure includes a brushless motor and a housing in which the brushless motor is mounted, and employs the electric motor 50 of the first embodiment described above as the brushless motor.

[0060] 1 of the first embodiment, the capacitive member 15 is disposed inside the electric motor 50, but as shown in FIG. 8, the capacitive member 15 may be disposed outside the electric motor 50. The capacitive member 15 may be disposed anywhere outside the electric motor 50, for example, on the outer wall of the housing of the electric motor 50. Furthermore, the capacitive member 15 may be provided at a position away from the electric motor 50, for example. 8, the conductive member 13 on the left side electrically connects the zero reference potential N(12) of the drive circuit provided on the printed circuit board 12 to the capacitive member 15. The conductive member 13 on the left side passes through an opening (not shown) provided in the housing of the electric motor 50, leading from the inside of the electric motor 50 to the outside of the electric motor 50. The conductive member 13 on the right side electrically connects the capacitive member 15 to the first metal bracket 1, and is disposed outside the housing of the electric motor 50. This makes it possible to further compact the electric motor 50. The aspect of FIG. 8 is not limited to the first embodiment, but can also be applied to the second to fourth embodiments. 1 of the first embodiment, the printed circuit board 12 equipped with the drive circuit is provided inside the electric motor 50, but the printed circuit board 12 equipped with the drive circuit may be provided outside the electric motor 50. In this case, the electric motor 50 can be made compact. In the second to fourth embodiments, a blower fan is used as the device rotated by the electric motor 50, but the device is not particularly limited as long as it is rotated by the electric motor 50. The inventions according to the first to fourth embodiments can be replaced or combined as long as no contradiction occurs.

[0061] As described above, the present disclosure includes the electric motors and electric devices equipped with the electric motors described in the following items.

[0062] [Item 1] a stator including a stator core wound with a stator winding; a rotor that faces the stator and holds a plurality of magnets in a circumferential direction, or that holds a plurality of magnets in a spoke-like manner from the center; a rotor including the rotating body and a shaft to which the rotating body is fastened so as to pass through the center of the rotating body; a first bearing and a second bearing that support the rotating body; An electric motor comprising a first metal bracket that fixes the first bearing and a second metal bracket that fixes the second bearing, A capacitance C is provided between either the first metal bracket or the second metal bracket and the zero reference potential of a drive circuit that applies voltage to the stator winding. nb1 a capacitive member of The capacitance between the stator winding on the stator side and one of the brackets is C sb1 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 The rotor side capacitance including the above is defined as the composite capacitance B1. The capacitance between the zero reference potential of the drive circuit and the shaft is C ns and The capacitance between the stator winding on the stator side and the other of the first metal bracket and the second metal bracket is defined as C sb2 and The capacitance between the other bracket and the zero reference potential of the drive circuit that applies voltage to the stator winding is C nb2 When we define The capacitance C sb1 and the capacitance C nb1 Ratio of X1 (C sb1 / C nb1 ) and the combined capacitance B1 and the capacitance C ns Ratio of Y1 (B1 / C ns ) are similar or identical to The capacitance C sb2 and the capacitance C nb2 Ratio of X2(C sb2 / C nb2 ) and the capacitance C sb1 and the capacitance C nb1 Ratio of X1 (C sb1 / C nb1 ) is similar to or coincides with the

[0063] [Item 2] Item 2. The electric motor according to item 1, wherein the one bracket is the first metal bracket and the other bracket is the second metal bracket.

[0064] [Item 3] The ratio R X2 (C sb2 / C nb2 ) and the ratio R X1 (C sb1 / C nb1 ) ratio (R X2 / R X1 3. The electric motor according to item 1 or 2, wherein the value of (a) is 0.75 or more and 1.25 or less.

[0065] [Item 4] 4. The electric motor according to any one of items 1 to 3, wherein the first metal bracket and the second metal bracket are insulated from the stator core by an insulating resin or a space.

[0066] [Item 5] 5. The electric motor according to any one of items 1 to 4, wherein the capacitive member is provided inside the electric motor.

[0067] [Item 6] 5. The electric motor according to any one of items 1 to 4, wherein the capacitive member is provided outside the electric motor.

[0068] [Item 7] 7. The electric motor according to any one of items 1 to 6, wherein a printed circuit board including the drive circuit is provided inside the electric motor.

[0069] [Item 8] 7. The electric motor according to any one of items 1 to 6, wherein a printed circuit board including the drive circuit is provided outside the electric motor.

[0070] [Item 9] 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. [Explanation of symbols]

[0071] 1 First metal bracket 2 Second metal bracket 3 Stator Winding 4 shafts 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 materials 14 Impedance adjustment material 15 Capacitive Members 18 Stator 20 dielectric layer 50 Electric motor

Claims

1. a stator including a stator core wound with a stator winding; a rotor that faces the stator and holds a plurality of magnets in a circumferential direction, or that holds a plurality of magnets in a spoke-like manner from the center; a rotor including the rotating body and a shaft to which the rotating body is fastened so as to pass through the center of the rotating body; a first bearing and a second bearing that support the rotating body; An electric motor comprising a first metal bracket that fixes the first bearing and a second metal bracket that fixes the second bearing, A capacitance C is provided between either the first metal bracket or the second metal bracket and the zero reference potential of a drive circuit that applies voltage to the stator winding. ｎｂ１ a capacitive member of The capacitance between the stator winding on the stator side and one of the brackets is C ｓｂ１ 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 The rotor side capacitance including the above is defined as a composite capacitance B1. The capacitance between the zero reference potential of the drive circuit and the shaft is C ｎｓ and The capacitance between the stator winding on the stator side and the other of the first metal bracket and the second metal bracket is defined as C ｓｂ２ and The capacitance between the other bracket and the zero reference potential of the drive circuit that applies voltage to the stator winding is defined as C ｎｂ２ When we define a value of a ratio (R X1 / R Y1 ) of a ratio R X1 (C sb1 / C nb1 ) of the capacitance C sb1 to the capacitance C nb1 to a ratio R Y1 (B1 / C ns ) of the combined capacitance B1 to the capacitance C ns is 0.6 or more and 1.0 or less; An electric motor in which the ratio (R X2 / R X1 ) of the ratio R X2 (C sb2 / C nb2 ) of the capacitance C sb2 to the capacitance C nb2 and the ratio R X1 (C sb1 / C nb1 ) of the capacitance C sb1 to the capacitance C nb1 is 0.75 or more and 1.25 or less.

2. 2. The electric motor according to claim 1, wherein said one bracket is said first metal bracket and said other bracket is said second metal bracket.

3. 3. The electric motor according to claim 1, wherein the first metal bracket and the second metal bracket are insulated from the stator core by an insulating resin or a space.

4. 4. The electric motor according to claim 1, wherein the capacitive member is provided inside the electric motor.

5. 4. The electric motor according to claim 1, wherein the capacitive member is provided outside the electric motor.

6. 6. The electric motor according to claim 1, wherein a printed circuit board having the drive circuit thereon is provided inside the electric motor.

7. 6. The electric motor according to claim 1, wherein the printed circuit board having the drive circuit thereon is provided outside the electric motor.

8. 8. An electric device equipped with the electric motor according to claim 1 and a blower fan driven by said electric motor.

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