JP2010166689A - Electric motor and electric apparatus including the motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of electric corrosion of a bearing in an electric motor driven by an inverter in a PWM system. <P>SOLUTION: The electric motor is provided with: a stator which includes a stator core wound with windings; a rotating body 30 which holds a plurality of magnets 32 facing the stator in the circumferential direction; a shaft 16 coupled to the rotating body so as to penetrate the center of the rotating body 30; an outer core 31a which constitutes the outside circumferential part of the rotating body 30; an inner core 31b, which constitutes the inside circumferential part coupled to the shaft 16; a dielectric layer 50 arranged between the outer core 31a and inner core 31b, a bearing 15, which supports the shaft 16; and a bracket which fixes the bearing. The outer core 31a and inner core 31b are formed by stacking steel plates. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric motor and an electric device including the electric motor. In particular, the present invention relates to an electric motor improved so as to suppress the occurrence of electrolytic corrosion of a bearing and an electric device including the electric motor.

  In recent years, electric motors are often used in a system driven by an inverter of a pulse width modulation system (hereinafter referred to as a PWM system). In such PWM inverter drive, the neutral point potential of the winding does not become zero, and therefore a potential difference (hereinafter referred to as shaft voltage) is generated between the outer ring and the inner ring of the bearing. The shaft voltage includes a high-frequency component due to switching. When the shaft voltage reaches the dielectric breakdown voltage of the oil film inside the bearing, a minute current flows inside the bearing and electric corrosion occurs inside the bearing. When electrolytic corrosion progresses, a wavy wear phenomenon may occur in the bearing inner ring, the bearing outer ring or the bearing ball, resulting in abnormal noise, which is one of the main causes of problems in the motor.

  Note that a power supply circuit of a drive circuit (including a control circuit) that drives an electric motor with an inverter by a PWM method and a ground on the primary side circuit and the ground on the primary side of the power supply circuit are electrically Insulated configuration.

Conventionally, the following countermeasures have been considered to suppress electric corrosion.
(1) Bring the bearing inner ring and bearing outer ring into a conductive state.
(2) Insulate the bearing inner ring and the bearing outer ring.
(3) Reduce the shaft voltage.

  As a specific method of the above (1), it is possible to make the bearing lubricant conductive. However, the conductive lubricant has problems such as deterioration of conductivity with time and lack of sliding reliability. Moreover, although the method of installing a brush in a rotating shaft and making it a conduction | electrical_connection state is also considered, this method also has subjects, such as a brush abrasion powder and space being required.

  As a specific method of the above (2), the iron ball in the bearing is changed to a non-conductive ceramic ball. This method has a very high effect of suppressing electrolytic corrosion, but has a problem of high cost, and cannot be used for a general-purpose electric motor.

  As a specific method of (3) above, a method of reducing the axial voltage by changing the capacitance by short-circuiting the stator iron core and the conductive bracket is conventionally known (for example, , See Patent Document 1).

  By the way, the impedance when the capacitance and the resistance are connected in parallel is expressed by a relational expression of Z = 1 / jωC + R. Here, Z is an impedance, j is an imaginary number, ω is an angular frequency, C is a capacitance, and R is a resistance. As can be seen from this equation, the impedance decreases as the capacitance increases or the resistance decreases. On the other hand, when the capacitance is small or the resistance is large, the impedance is high.

  In Patent Document 1, the impedance on the stator side is lowered by short-circuiting the fixed iron core and the bracket, thereby suppressing the electrolytic corrosion of the bearing.

  That is, in general, an electric motor that is used around water such as a washing machine or a dishwasher and has a risk of an electric shock has added independent insulation in addition to insulation of the charging part (basic insulation) (hereinafter referred to as additional insulation). )There is a need to. On the other hand, motors used for other air conditioner indoor units, air conditioner outdoor units, hot water heaters, air purifiers, and the like do not need an additional insulation because there is no risk of electric shock. Therefore, since the motor used for the air conditioner indoor unit, the air conditioner outdoor unit, the water heater, the air purifier, etc. does not have an insulating structure, the rotor side (bearing inner ring side) has a low impedance. . On the other hand, since the stator side (bearing outer ring side) has an insulating structure, the impedance is high. In this case, since the potential on the bearing inner ring side is high while the potential on the bearing outer ring side is low, an unbalanced state occurs and a high shaft voltage is generated. In addition, such high shaft voltage may cause electric corrosion in the bearing.

  In order to avoid such a state, Patent Document 1 eliminates the capacitance component between the stator core and the bracket by short-circuiting, and the impedance on the stator side (bearing outer ring side) as described above. A method of lowering and approximating the impedance on the rotor side (bearing inner ring side) is adopted.

In addition, in the prior art for suppressing / suppressing the electric corrosion of the motor bearing, many configurations for electrically connecting the stator core of the motor to the earth ground are also disclosed.
JP 2007-159302 A

  However, the conventional method as disclosed in Patent Document 1 has the following problems. That is, since this conventional method is a method of short-circuiting, the impedance cannot be adjusted, and the shaft voltage may increase depending on the magnet material and structure of the rotor. Another problem is that since the impedance is lowered, the balance is always maintained between the bearing inner ring and the bearing outer ring with a high potential. In such a state, if the balance of impedance is lost due to the usage environment of the motor or variations in the assembly accuracy of the stator and rotor, the shaft voltage becomes high and electric corrosion tends to occur. The case was also considered as a possibility.

  In addition, as described above, the configuration of the subject of the present application includes a power supply circuit of a drive circuit (including a control circuit) that drives an electric motor in an inverter by a PWM method, a primary side circuit and a primary circuit of the power supply circuit. It is an electrically insulated configuration from the ground on the side circuit side. Therefore, adopting a configuration in which the stator core of the motor is electrically connected to the earth ground in the prior art and taking this into account will solve the problem from the viewpoint of the specifications and characteristics of the motor. Other issues were also considered and some were difficult.

  The electric motor of the present invention has been made in view of the above problems, and an object thereof is to provide an electric motor in which the occurrence of electrolytic corrosion in a bearing is suppressed and an electric device including the electric motor.

  In order to achieve the above object, an electric motor according to the present invention includes a stator including a stator core wound with a winding, a rotating body holding a permanent magnet in a circumferential direction facing the stator, and a center of the rotating body An electric motor including a rotor including a shaft fastened with a rotating body so as to pass through the shaft, a bearing that rotatably supports the shaft, and a bracket that fixes the bearing. The rotating body includes an outer iron core that forms an outer peripheral portion of the rotating body, an inner iron core that forms an inner peripheral portion fastened to the shaft, and a dielectric layer disposed between the outer iron core and the inner iron core, The outer iron core and the inner iron core are formed by stacking steel plates.

  With such a configuration, the dielectric layer provided between the shaft and the outer periphery of the rotor has a configuration in which the capacitance of the dielectric layer is equivalently connected in series in the rotor of low impedance. The impedance on the side can be increased. When the impedance on the rotor side is increased in this way, the impedance on the stator side, which is a high impedance, can be approximated, and as a result, the high-frequency potentials on the bearing inner ring side and the bearing outer ring side become equal. Balance can be taken. Since the potential difference between the bearing inner ring and the outer ring can be reduced in this way, it is possible to suppress the occurrence of electrolytic corrosion of the bearing caused by a high frequency due to PWM or the like. In addition, since the capacitance can be varied by changing the width and material of the dielectric layer, the rotor-side impedance can be set optimally. The dielectric layer refers to a layer that intentionally changes the dielectric constant and thickness of the dielectric and the surface area of the conductive material (electrode) in contact with the dielectric, as if a dielectric element is interposed between the shaft and the rotating body. Is intended to be

  The rotating body includes an outer iron core constituting the outer peripheral portion, an inner iron core constituting the inner peripheral portion fastened to the shaft, and a dielectric layer, and the outer iron core and the inner iron core are interposed via the dielectric layer. Thus, the rotor can be easily manufactured, so that the productivity of the rotor can be improved.

  Since the outer iron core and the inner iron core are each formed by laminating steel plates, the bonding strength is increased at the bonding surface between the outer iron core and the dielectric layer and the bonding surface between the inner iron core and the dielectric layer. And sufficient reliability can be secured.

  The electric motor of the present invention has a structure in which the outer iron core and the inner iron core have a plurality of convex portions in the radial direction, and a protrusion is formed between the dielectric layer and the iron core, so that the dielectric during rotation The idling of the layer can be suppressed.

  Moreover, the electric motor of this invention is good also as a structure arrange | positioned in the position where the convex part of an outer side iron core and the convex part of an inner side iron core oppose in a radial direction.

  Further, in the electric motor of the present invention, the contact area between the dielectric layer and the outer iron core in the portion where the radial distance between the outer iron core and the inner iron core is the minimum is the outer contact area, and the radial direction between the outer iron core and the inner iron core When the contact area between the dielectric layer and the inner iron core is the inner contact area and the contact area between the shaft and the inner iron core is the shaft contact area, at least one of the outer contact area and the inner contact area. In this configuration, the rotating body is formed such that one of the areas is substantially equal to the shaft contact area.

  Moreover, the electric motor of this invention is good also as a structure by which the convex part of the outer iron core and the convex part of an inner iron core are arrange | positioned in the position where an unevenness | corrugation opposes to radial direction.

  In the electric motor according to the present invention, the outer iron core and the inner iron core are divided into a plurality of parts in the axial direction, and the outer iron cores divided into a plurality of parts adjacent to each other in the axial direction or the inner iron cores face each other. It is good also as a structure arranged in this way.

  Thus, by dividing the iron core into a plurality of parts in the axial direction, a protrusion is formed between the dielectric layer and the iron core in the axial direction, and the strength against the force applied in the axial direction can be increased. .

  In the electric motor of the present invention, the dielectric layer may include a plurality of hole portions.

  By forming holes as holes in part of the dielectric layer in this manner, resin sinks during molding can be suppressed when integrally molded with the outer iron core and the inner iron core, and the rotor Productivity can be improved. Further, the dielectric constant can be lowered, and the impedance on the rotor side can be further increased.

  Moreover, the electric device of the present invention is equipped with the above-described electric motor.

  As described above, according to the electric motor of the present invention, the impedance on the rotor side (bearing inner ring side) is increased to approximate the impedance on the stator side (bearing outer ring side), and the bearing inner ring side and the bearing outer ring side are A high-frequency potential can be balanced, the occurrence of electrolytic corrosion in a bearing can be suppressed, and a highly reliable and highly reliable electric motor and an electric device including the electric motor can be provided.

  Hereinafter, an electric motor of the present invention and an electric device including the electric motor will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a structural diagram showing a cross section of a brushless motor according to Embodiment 1 of the present invention. In the present embodiment, an example of a brushless motor that is mounted for an air conditioner as an electric device and that is an electric motor for driving a blower fan will be described. Further, in the present embodiment, an example of an inner rotor type electric motor in which a rotor is rotatably arranged on the inner peripheral side of the stator will be described.

  In FIG. 1, a stator winding 12 is wound around a stator core 11 with a resin 21 serving as an insulator for insulating the stator core 11 interposed therebetween. Such a stator core 11 is molded with an insulating resin 13 as a molding material together with other fixing members. In the present embodiment, the stator 10 whose outer shape is substantially cylindrical is formed by integrally molding these members in this way.

  A rotor 14 is inserted inside the stator 10 through a gap. The rotor 14 includes a disk-shaped rotating body 30 including the rotor core 31 and a shaft 16 to which the rotating body 30 is fastened so as to penetrate the center of the rotating body 30. The rotating body 30 holds a magnet 32 that is a permanent magnet such as a ferrite resin magnet in the circumferential direction facing the inner peripheral side of the stator 10. The rotor core 31 is formed by stacking steel plates. As will be described in detail below, the rotating body 30 constitutes the outer peripheral portion of the rotor core 31 from the outermost peripheral magnet 32 toward the inner peripheral shaft 16 as shown in FIG. The outer iron core 31a, the dielectric layer 50, and the inner iron core 31b constituting the inner periphery of the rotor iron core 31 are arranged in this order. FIG. 1 shows a configuration example in which the rotor core 31, the dielectric layer 50, and the magnet 32 are integrally formed as the rotor 30. In this manner, the inner peripheral side of the stator 10 and the outer peripheral side of the rotating body 30 are arranged to face each other.

  Two bearings 15 that support the shaft 16 are attached to the shaft 16 of the rotor 14. The bearing 15 is a bearing having a plurality of iron balls. One of the two bearings 15 is fixed to an insulating resin 13 that is integrally molded with the mold, and the other is fixed to a metal bracket 17. With the configuration as described above, the shaft 16 is supported by the two bearings 15, and the rotor 14 rotates freely.

  Further, the brushless motor incorporates a printed circuit board 18 on which a drive circuit is mounted. After the printed board 18 is built in, the brushless motor is formed by press-fitting the bracket 17 into the stator 10. Further, a connection line 20 such as a lead wire for applying a power supply voltage for the winding, a power supply voltage for the control circuit and a control voltage for controlling the number of revolutions, or a ground line for the control circuit is connected to the printed circuit board 18.

  In addition, a power supply circuit for supplying a power supply voltage for windings connected to the printed circuit board 18 on which the drive circuit is mounted, a power supply circuit for supplying a power supply voltage for the control circuit, a lead wire for applying the control voltage, a ground line for the control circuit, etc. Is connected to the primary side (power supply) circuit for the power supply circuit for supplying the power supply voltage of the winding, the primary side (power supply) circuit for the power supply circuit for supplying the power supply voltage of the control circuit, and the primary side (power supply) circuit. Grounded earth ground and independently grounded earth ground are both electrically isolated.

  That is, since the drive circuit mounted on the printed circuit board 18 is electrically insulated from the primary side (power supply) circuit potential and the ground potential, the potential is floated. Yes. This is also expressed as a state where the potential is floating, and is well known. For this reason, the configuration of the power supply circuit that supplies the power supply voltage of the winding connected to the printed circuit board 18 and the power supply circuit that supplies the power supply voltage of the control circuit is also called a floating power supply, which is also well known. It is an expressed expression.

  FIG. 2 is a diagram schematically showing a main part of the brushless motor shown in FIG. As shown in FIG. 2, the rotating body 30 has a magnet 32 disposed on the outermost peripheral portion, and further toward the inner peripheral side, an outer iron core 31 a constituting the rotor iron core 31, a dielectric layer 50, and a rotor iron core. The inner iron cores 31b constituting the 31 are arranged in this order. The dielectric layer 50 is a layer formed of an insulating resin. In the present embodiment, such a dielectric layer 50 is provided for suppressing electrolytic corrosion. Thus, the rotating body 30 has a configuration in which the magnet 32, the outer iron core 31a, the insulating resin forming the dielectric layer 50, and the inner iron core 31b are integrally formed. In addition, the rotating body 30 is fastened to the shaft 16 at the fastening portion 51 on the inner periphery of the inner iron core 31b. Thereby, the rotor 14 supported by the bearing 15 is configured.

  In the rotating body 30, the dielectric layer 50 is a layer formed of an insulating resin that is an insulator, and insulates and separates the outer iron core 31a and the inner iron core 31b in series. On the other hand, the dielectric layer 50 is formed of an insulating resin having a predetermined dielectric constant, and a high-frequency current can flow between the outer iron core 31a and the inner iron core 31b.

  By the way, when such a dielectric layer 50 is not provided, as described above, the impedance between the brackets based on the stator core is high, and conversely, the impedance between the shafts electrically connected to the rotating body is Low. A pulse width modulated high frequency current generated from a stator core or the like flows into an equivalent circuit having such an impedance component. For this reason, a potential difference due to the high-frequency current is generated between the outer ring of the bearing electrically connected to the bracket and the shaft on the bearing inner ring side.

  In the present embodiment, by providing a dielectric layer 50 as shown in FIG. 2 for a low impedance rotor formed only of an iron core, the rotor 14 is approximated to the impedance on the bracket 17 side. Impedance is high. That is, by providing the dielectric layer 50 between the outer iron core 31a and the inner iron core 31b, the rotor 14 is equivalently configured in such a manner that the electrostatic capacitance of the dielectric layer 50 is connected in series. Impedance can be increased. By increasing the impedance of the rotor 14, the high-frequency voltage drop flowing from the rotor 14 to the shaft 16 is increased, so that the potential generated in the shaft 16 by the high-frequency current can be lowered. Based on such a principle, the brushless motor of the present embodiment reduces the potential difference due to the high-frequency current between the outer ring of the bearing 15 electrically connected to the bracket 17 and the shaft 16 on the inner ring side of the bearing 15. is doing. For this reason, the potential is always low between the bearing inner ring and the bearing outer ring, and the balance is maintained so as to reduce the potential difference, thereby suppressing the occurrence of electrolytic corrosion in the bearing.

  In addition, since the capacitance can be varied by changing the width and material of the dielectric layer 50, the impedance on the rotor 14 side can be set optimally. That is, by reducing the dielectric constant of the insulating resin forming the dielectric layer 50, increasing the thickness of the insulating resin (distance between the electrodes), or reducing the electrode area, the electrostatic capacity of the dielectric layer 50 is increased. Can be lowered. In this way, the impedance of the rotor 14 can be increased by reducing the capacitance of the dielectric layer 50.

  Further, as shown in FIG. 2, the rotor core 30 is configured such that the dielectric layer 50 is separated into the outer iron core 31a and the inner iron core 31b. It is possible to integrally mold the insulating resin. For this reason, compared to a structure in which a dielectric layer is provided between the shaft and the rotor core, the structure as shown in FIG. 2 can form the rotor 30 without the shaft. Productivity can be increased. Further, with the structure shown in FIG. 2, even if the type of the shaft 16 is changed, the shaft 16 can be fixed by caulking or press-fitting, so that the type change can be easily handled. Even productivity can be improved.

  Further, the outer iron core 31a and the inner iron core 31b are each formed by laminating steel plates. In the present embodiment, with such a configuration, the bonding strength is increased at the bonding surface between the outer iron core 31 a and the dielectric layer 50 and the bonding surface between the inner iron core 31 b and the dielectric layer 50.

  FIG. 3 is a diagram schematically showing a partial cross section of the rotator 30. FIG. 3 is a diagram schematically showing the state of the rotating body 30 for easy understanding, and dimensions and the like are different from actual ones. As shown in FIG. 3, the outer iron core 31a is configured by laminating a plurality of steel plates 311a. The inner iron core 31b is configured by laminating a plurality of steel plates 311b. The dielectric layer 50 is disposed between the outer iron core 31a and the inner iron core 31b. In such a configuration, by laminating the steel plates 311a and 311b, minute concavities and convexities are formed on the joint surface 41 on the iron core side for each of the steel plates 311a and 311b. On the other hand, since the dielectric layer 50 is formed of resin, it has a certain degree of elasticity compared to the steel plates 311a and 311b. And when such an iron core and the dielectric layer 50 are joined, as shown in FIG. 3, the dielectric layer 50 bites into the recesses between the steel plates at the joint surface 41 between the iron core and the dielectric layer 50. . For this reason, the adhesion between the outer iron core 31a and the inner iron core 31b and the dielectric layer 50 is improved, so that the bonding strength can be increased, and in particular, the strength against the pull-out strength and the force applied in the axial direction can be increased. it can. Thus, even if it is the structure which provides the dielectric material layer 50 in the rotary body 30, sufficient intensity | strength can be obtained, generation | occurrence | production of electrolytic corrosion can be prevented, and sufficient reliability can also be ensured. In addition, when further bonding strength is required, the bonding surface may be bonded more firmly using an adhesive or the like.

  4 and 5 are diagrams showing a specific configuration example of the rotating body 30 of the brushless motor in the present embodiment. 4 is an external perspective view of the rotating body 30, and FIG. 5 is an exploded perspective view of the rotating body 30 shown in FIG. In the rotating body 30 shown in FIGS. 4 and 5, the outer iron core 31a and the inner iron core 31b have a plurality of convex portions in the radial direction. Specifically, the outer iron core 31a has a substantially annular shape. More specifically, the outer peripheral side is circular, and the convex portions in the radial direction are equally spaced on the inner peripheral side. Further, the inner core 31b is also substantially annular, and more specifically, the inner peripheral side is circular, and the outer peripheral side has convex portions in the radial direction at equal intervals. And the convex part of the outer side iron core 31a and the convex part of the inner side iron core 31b are arrange | positioned in the position which mutually opposes. Furthermore, between the radial directions of the outer iron core 31a and the inner iron core 31b, the dielectric layer 50 integrally formed with the rotor iron core 31 has a shape that repeatedly circulates between a convex protrusion shape and a concave protrusion shape. It exists.

  When the dielectric layer 50 has a perfect ring shape, there is a risk of idling during rotation. On the other hand, by adopting the shape of the dielectric layer 50 as shown in FIGS. 4 and 5, a structure for preventing idling is inserted between the dielectric layer 50 and the iron core. Rotational strength can be increased.

  4 and FIG. 5 shows a configuration example in which the dielectric layer 50 includes a hole portion 40 that is a substantially circular hole in a partial region thereof.

  In order to increase the impedance of the rotating body 30, it is preferable to increase the thickness of the dielectric layer 50 in the radial direction. However, in order to suppress sink marks when forming the dielectric layer 50 that is integrally formed with the rotor core 31, it is necessary to make the thickness of the dielectric layer 50 in the radial direction small and uniform. On the other hand, in the present embodiment, by providing the hole portion 40 in the thick portion of the dielectric layer 50, sink marks at the time of molding are suppressed. Note that sink marks are a phenomenon in which a resin taken out after being cooled contracts compared to a melted resin at the time of molding.

  Moreover, since the dielectric constant of air is about 1, it is very small compared with insulating resin. That is, the electrostatic capacity can be reduced by forming an air layer or a hole in a part of the insulating resin. Therefore, the upper limit of the thickness of the insulating resin is structurally restricted, and even if a resin with a low dielectric constant is used, the impedance on the rotor side (bearing inner ring side) is low, the shaft voltage is high, or the amount of insulating resin used is low. In the case where the cost is increased in many cases, the provision of the hole portion 40 has an advantage that the impedance on the rotor side (bearing inner ring side) can be further increased.

  In FIG. 5, the outer contact area Sa is the area of the contact portion between the dielectric layer 50 and the outer iron core 31a where the radial distance between the outer iron core 31a and the inner iron core 31b is minimized. The inner contact area Sb is the area of the contact portion between the dielectric layer 50 and the inner iron core 31b where the radial distance between the outer iron core 31a and the inner iron core 31b is minimized. The shaft contact area Si is the area of the contact portion between the shaft 16 and the inner iron core 31b. In the present embodiment, the rotating body 30 is formed so that at least one of the outer contact area Sa and the inner contact area Sb is substantially equal to the shaft contact area Si. In other words, by adopting a configuration in which at least one of the outer contact area Sa and the inner contact area Sb is slightly larger than or equal to or less than the shaft contact area Si, the shaft and the rotor core are disposed. The impedance of the rotating body can be increased in the same manner as the structure in which the dielectric layer is provided.

(Embodiment 2)
6 and 7 are diagrams showing a specific configuration example of the rotating body 30 of the brushless motor according to the second embodiment of the present invention. 6 is an external perspective view of the rotating body 30, and FIG. 7 is an exploded perspective view of the rotating body 30 shown in FIG. In the rotating body 30 shown in FIGS. 6 and 7, the outer iron core 31a and the inner iron core 31b have a plurality of convex portions in the radial direction. Specifically, the outer iron core 31a has a substantially annular shape. More specifically, the outer peripheral side has a circular shape, and radially has convex portions at regular intervals on the inner peripheral side. Further, the inner iron core 31b is also substantially annular, and more specifically, the inner peripheral side is circular, and the outer peripheral side has convex portions in the radial direction at equal intervals. And the convex part of the outer side iron core 31a is arrange | positioned in the position facing the recessed part of the inner side iron core 31b. Furthermore, between the radial direction of the outer iron core 31a and the inner iron core 31b, the dielectric layer 50 integrally formed with the rotor iron core 31 has a shape that repeatedly circulates between a convex protrusion shape and a concave protrusion shape. It exists.

  Even in the case of the configuration of the second embodiment, as in the configuration of the first embodiment, a protrusion for preventing idling is inserted between the dielectric layer 50 and the iron core, and the rotational strength is increased while preventing idling. Can do.

(Embodiment 3)
8 and 9 are diagrams showing a specific configuration example of the rotating body 30 of the brushless motor according to the third embodiment of the present invention. 8 is an external perspective view of the rotating body 30, and FIG. 9 is an exploded perspective view of the rotating body 30 shown in FIG. The rotating body 30 shown in FIGS. 8 and 9 has a structure in which the outer iron core 31a and the inner iron core 31b have a plurality of convex portions in the radial direction. Specifically, the outer iron core 31a has a substantially annular shape. More specifically, the outer peripheral side is circular, and the convex portions in the radial direction are equally spaced on the inner peripheral side. Further, the inner core 31b is also substantially annular, and more specifically, the inner peripheral side is circular, and the outer peripheral side has convex portions in the radial direction at equal intervals. Also, it is divided into a plurality (in this embodiment, three divisions) in the axial direction. And the convex part of the outer side iron core 31a1 adjacent to an axial direction and the recessed part of the outer side iron core 31a2 are arrange | positioned so that it may oppose alternately. Similarly to the outer iron core 31a, the inner iron core 31b is divided into a plurality of pieces in the axial direction, and the convex portions of the inner iron core 31b1 and the concave portions of the inner iron core 31b2 that are adjacent in the axial direction are alternately arranged. In addition, each division | segmentation iron core divided | segmented into the axial direction may be one steel plate, or may be a laminate formed by laminating a plurality of steel plates. The dielectric layer 50 is integrally formed with the rotor core 31 between the outer iron core 31a and the inner iron core 31b in the radial direction, and the convex protrusion shape and the concave protrusion shape repeatedly circulate in the radial direction. It exists in such a shape, and exists in a shape that is alternately stacked in the axial direction.

  By adopting such a configuration, in addition to preventing idling in the rotational direction and the rotational strength shown in the first and second embodiments, a protrusion for preventing slippage is also provided in the axial direction. A highly reliable electric motor can be provided even in a usage situation in which a load is applied in the axial direction.

(Embodiment 4)
10 and 11 are diagrams showing a specific configuration example of the rotating body 30 of the brushless motor according to the fourth embodiment of the present invention. 10 is an external perspective view of the rotating body 30, and FIG. 11 is a developed perspective view of the rotating body 30 shown in FIG. Similarly to the third embodiment, the rotating body 30 of the present embodiment is divided into a plurality of outer iron cores 31a and inner iron cores 31b in the axial direction (three divisions in the present embodiment). The outer iron core 31a includes an outer iron core 31a1 having a plurality of convex portions similar to those in the third embodiment in the radial direction and a substantially circular outer iron core 31a3. And the outer side iron core 31a has arrange | positioned the outer side iron core 31a1 and the outer side iron core 31a3 alternately by the axial direction. The inner iron core 31b includes an inner iron core 31b1 having a plurality of convex portions similar to those in the third embodiment in the radial direction and a substantially circular inner iron core 31b3. And the inner iron core 31b arrange | positions the inner iron core 31b1 and the inner iron core 31b3 alternately by the axial direction.

  Usually, the iron core of the rotor is generally punched out of a magnetic steel sheet with a press machine, laminated and caulked in the press machine.

  When the combination of simple shapes is used as shown in the present embodiment, there is an advantage that the configuration of the press mold becomes easy and the productivity is improved. Even in the case of such a structure, as shown in the third embodiment, there are provided a protrusion for preventing slipping in the rotational direction, a protrusion for improving the rotational strength, and a protrusion for preventing the axial direction from coming off. Since it is provided, it is possible to provide a highly reliable electric motor by preventing idling in the rotational direction, improving rotational strength, and preventing axial disconnection.

(Embodiment 5)
In this embodiment mode, a configuration of an air conditioner indoor unit will be described as an example of an electric device in the present invention.

  FIG. 12 is a schematic diagram showing a configuration of an air conditioner indoor unit as an example of an electrical apparatus according to Embodiment 5 of the present invention.

  In FIG. 12, a brushless motor 201 is mounted in the casing 211 of the air conditioner indoor unit 200. A cross flow fan 212 is attached to the rotating shaft of the brushless motor 201. The brushless motor 201 is driven by a motor driving device 213. The brushless motor 201 is rotated by energization from the motor driving device 213, and the cross flow fan 212 is rotated accordingly. By the rotation of the cross flow fan 212, air conditioned by an indoor unit heat exchanger (not shown) is blown into the room. Here, for example, the brushless motor shown in the above embodiment can be applied to the brushless motor 201.

  The electric device of the present invention includes a brushless motor and a housing on which the brushless motor is mounted, and employs the brushless motor of the present invention having the above-described configuration as a brushless motor.

  In the above description, the brushless motor mounted on the air conditioner indoor unit is taken up as an embodiment of the electric device according to the present invention. However, the brushless motor mounted on the air conditioner outdoor unit and the brushless motor mounted on other electrical devices are described. For example, it is needless to say that the present invention can also be applied to brushless motors used in various home appliances, brushless motors mounted in various information devices, and brushless motors used in industrial devices.

  As described above, the electric motor of the present invention has a stator including a stator core wound with a winding, a rotating body that holds a permanent magnet in the circumferential direction facing the stator, and passes through the center of the rotating body. An electric motor including a rotor including a shaft fastened with a rotating body, a bearing that rotatably supports the shaft, and a bracket that fixes the bearing. The rotating body includes an outer iron core that forms an outer peripheral portion of the rotating body, an inner iron core that forms an inner peripheral portion fastened to the shaft, and a dielectric layer disposed between the outer iron core and the inner iron core, The outer iron core and the inner iron core are formed by stacking steel plates.

  For this reason, the dielectric layer provided between the shaft and the outer periphery of the rotor has a structure in which the capacitance of the dielectric layer is equivalently connected in series in the low impedance rotor, and the impedance on the rotor side Can be increased. As a result, the impedance between the bearing inner ring side and the bearing outer ring side can be approximated. As a result, it is possible to balance the high frequency potential between the bearing inner ring side and the bearing outer ring side, and to prevent the occurrence of electrolytic corrosion of the bearing caused by the high frequency due to PWM or the like. In addition, the outer iron core and the inner iron core are fixed to each other via a dielectric layer, and the structure of a rotor that can be easily manufactured can be obtained, thereby improving the productivity of the rotor. it can. Since the outer iron core and the inner iron core are each formed by laminating steel plates, the bonding strength is increased at the bonding surface between the outer iron core and the dielectric layer and the bonding surface between the inner iron core and the dielectric layer. And sufficient reliability can be secured.

  Further, the outer iron core and the inner iron core have a structure having a plurality of protrusions in the radial direction, and a protrusion is formed between the dielectric layer and the iron core to prevent idling of the dielectric layer during rotation. be able to.

  Further, by dividing the iron core into a plurality of parts in the axial direction, a protrusion is formed between the dielectric layer and the iron core in the axial direction, and the strength against a force applied in the axial direction can be increased.

  In addition, by forming a hole as a hole part in a part of the dielectric layer, when the outer iron core and the inner iron core are integrally formed, resin sink at the time of molding can be suppressed, and the rotor Productivity can be improved. Further, the dielectric constant can be lowered, and the impedance on the rotor side can be further increased.

  Therefore, according to the electric motor of this invention, the electric motor which suppressed generation | occurrence | production of the electric corrosion in a bearing can be provided. In addition, by incorporating the electric motor of the present invention into an electric device, it is possible to provide an electric device including the electric motor that suppresses the occurrence of electrolytic corrosion in the bearing.

  Further, the example of the inner rotor type electric motor in which the rotor is rotatably arranged on the inner peripheral side of the stator has been described, but the outer rotor type in which the rotor is arranged on the outer peripheral side of the stator, and further the inner and outer peripheral types A similar effect can be obtained by providing a dielectric layer as described above in a twin rotor type electric motor in which rotors are arranged on both sides.

  In addition, the contact area between the dielectric layer and the outer iron core, or between the dielectric layer and the inner iron core, where the radial distance between the outer iron core and the inner iron core is the smallest, is slightly smaller than the contact area between the shaft and the inner iron core. The impedance is large or equal to or less than that, and the impedance of the rotor can be increased.

  In addition, as described above, the configuration in the embodiment of the present application includes a power supply circuit of a drive circuit (including a control circuit and the like) that drives an electric motor with an inverter by a PWM method, a primary circuit of the power supply circuit, and The primary circuit side is electrically insulated from the earth ground. And the effect which suppresses the electric corrosion of a bearing is acquired even if it does not employ | adopt the structure which electrically connects the stator core of an electric motor etc. to the earth ground of the prior art.

  The electric motor of the present invention can reduce the shaft voltage and is optimal for suppressing the occurrence of electrolytic corrosion of the bearing. For this reason, it is useful mainly for electric devices that are required to reduce the price and increase the life of electric motors, for example, electric motors mounted in air conditioner indoor units, air conditioner outdoor units, water heaters, air purifiers, and the like.

Structure diagram showing a cross section of the brushless motor according to the first embodiment of the present invention Diagram showing the main part of the motor The figure which showed the partial cross section of the rotary body of the motor typically External perspective view showing a specific configuration example of the rotating body of the motor An exploded perspective view showing a specific configuration example of the rotating body of the motor External appearance perspective view showing a specific configuration example of a rotating body of a brushless motor in Embodiment 2 of the present invention An exploded perspective view showing a specific configuration example of the rotating body of the motor External perspective view showing a specific configuration example of a rotating body of a brushless motor in Embodiment 3 of the present invention An exploded perspective view showing a specific configuration example of the rotating body of the motor External perspective view showing a specific configuration example of a rotating body of a brushless motor in Embodiment 4 of the present invention An exploded perspective view showing a specific configuration example of the rotating body of the motor The schematic diagram which showed the structure of the air-conditioner indoor unit as an example of the electric equipment in Embodiment 5 of this invention

DESCRIPTION OF SYMBOLS 10 Stator 11 Stator iron core 12 Stator winding 13 Insulation resin 14 Rotor 15 Bearing 16 Shaft 17 Bracket 18 Printed circuit board 20 Connection line 21 Resin (insulator)
30 Rotor 31 Rotor core 31a, 31a1, 31a2, 31a3 Outer core 31b, 31b1, 31b2, 31b3 Inner core 32 Magnet 40 Hole 41 Joint surface 50 Dielectric layer 51 Fastening portion 200 Air conditioner indoor unit 201 Brushless motor 211 Housing Body 212 Cross flow fan 213 Motor drive device 311a, 311b Steel plate

Claims (8)

A stator including a stator core wound with a winding; a rotating body that holds a permanent magnet in a circumferential direction facing the stator; and a shaft that fastens the rotating body so as to pass through the center of the rotating body Including a rotor, a bearing that rotatably supports the shaft, and a bracket that fixes the bearing,
The rotating body is
An outer iron core constituting the outer periphery of the rotating body;
An inner iron core constituting an inner periphery fastened to the shaft;
A dielectric layer disposed between the outer iron core and the inner iron core,
The outer iron core and the inner iron core are formed by laminating steel plates. The electric motor according to claim 1, wherein the outer iron core and the inner iron core have a plurality of convex portions in a radial direction. The electric motor according to claim 1, wherein the convex portion of the outer iron core and the convex portion of the inner iron core are arranged at positions that oppose each other in the radial direction. A contact area between the dielectric layer and the outer iron core in a portion where a radial distance between the outer iron core and the inner iron core is minimized is defined as an outer contact area,
The contact area between the dielectric layer and the inner iron core in the portion where the radial distance between the outer iron core and the inner iron core is minimized is defined as the inner contact area,
When the contact area between the shaft and the inner iron core is the shaft contact area,
The electric motor according to claim 3, wherein the rotating body is formed so that at least one of the outer contact area and the inner contact area is substantially equal to the shaft contact area. 3. The electric motor according to claim 1, wherein the convex portion of the outer iron core and the convex portion of the inner iron core are arranged at positions where irregularities oppose each other in a radial direction. The outer iron core and the inner iron core are each divided into a plurality in the axial direction, and at least one of the outer iron cores and the inner iron cores divided into a plurality adjacent in the axial direction is in the axial direction. The electric motor according to any one of claims 1 to 5, wherein the electric motor is arranged so that the unevenness faces each other. The electric motor according to claim 1, wherein the dielectric layer has a plurality of hole portions. An electric device comprising the electric motor according to any one of claims 1 to 7.

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