JP5312520B2 - Electric motors and air conditioners - Google Patents

Description

  The present invention relates to an electric motor and an air conditioner using the same.

  Many blower motors (hereinafter simply referred to as “motors”) installed in an air conditioner have built-in inverters from the viewpoint of structural convenience. When this motor is driven by an inverter, a voltage is induced between the rotor shaft ends or between the winding wound around the stator (stator) and the stator core (stator core) as the inverter is switched. It is known that Here, when the bearing that supports the rotating shaft is a bearing composed of an inner ring, an outer ring, and a rolling element, the voltage is applied between the inner ring and the outer ring, causing discharge inside the bearing, There is a risk of causing a problem called food. For this reason, various structural measures for preventing such electric corrosion have been proposed for inverter-driven electric motors.

  For example, the technology described in Patent Document 1 below is configured to electrically connect the outer rings of two bearings mounted on a frame and not to transmit the voltage generated between the winding and the stator core to the bearings. Yes.

JP 2010-158152 A

  However, the technique disclosed in Patent Document 1 requires a change in the structure of the bracket and the frame, which makes it difficult to share equipment for manufacturing a conventional electric motor. It was.

  This invention is made | formed in view of the above, Comprising: It aims at obtaining the electric motor and air conditioner which can suppress the electrolytic corrosion of a bearing cheaply.

  In order to solve the above-described problems and achieve the object, the present invention includes a stator disposed in a frame, and a rotor having a permanent magnet disposed around a rotation shaft so as to face the stator. A pair of brackets disposed at both ends of the frame and supporting the rotating shaft, a pair of bearings mounted on the bracket and supporting the rotating shaft, and provided between the rotor and the bearing, And a magnetic member that is provided around a rotation axis and includes a magnetic material that is softer than the magnetic material of the permanent magnet.

  According to the present invention, since the discharge current is suppressed only by changing the material of the support member, there is an effect that the electrolytic corrosion of the bearing can be suppressed at a low cost.

FIG. 1 is a cross-sectional view of an electric motor according to an embodiment of the present invention. FIG. 2 is a diagram for explaining a path of a discharge current flowing through the bearing. FIG. 3 is a model diagram of an annular magnetic material. FIG. 4 is a frequency characteristic diagram of the complex permeability of soft ferrite. FIG. 5 is a diagram showing a waveform of a discharge current flowing through the bearing.

  Embodiments of an electric motor and an air conditioner according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a cross-sectional view of an electric motor according to an embodiment of the present invention. An electric motor 1 shown in FIG. 1 mainly includes a stator 2, a rotor 5, a rotating shaft 9, a bearing 13, a bearing 15, an inverter 8 for generating a rotating magnetic field in the stator 2, and a mold frame. 10, a mold bracket 11, a metal bracket 12, a magnetic member 16, and a magnetic member 17.

  The stator 2 has a structure in which the stator core 4 is covered with an insulator 14 and the winding 3 is wound, and a rotating magnetic field is generated when the inverter 8 is switched.

  The rotor 5 includes a permanent magnet 6 that is provided around the rotary shaft 9 so as to face the stator 2, and an annular support member 7 that is disposed between the rotary shaft 9 and the permanent magnet 6 and is formed of resin. It is configured. The rotor 5 obtains a rotational force by the rotating magnetic field from the stator 2 and transmits torque to the rotating shaft 9, and a load (not shown) provided on the rotating shaft 9 (for example, a fan built in an indoor unit of an air conditioner). Drive.

The permanent magnet 6 is made of a magnetic material having a predetermined coercive magnetic force (e.g., a hard magnetic material). The support member 7 mechanically fixes the permanent magnet 6 to the rotating shaft 9. The mold frame 10 is formed integrally with the inverter 8 and includes the stator 2 and the rotor 5.

  The mold frame 10 is formed integrally with the inverter 8 and includes the stator 2 and the rotor 5. The mold bracket 11 is formed integrally with the mold frame 10 on the upper side of the mold frame 10 (upper side in FIG. 1), and surrounds and supports the outer ring a of the bearing 13. The metal bracket 12 is formed integrally with the mold frame 10 on the lower side (lower side in FIG. 1) of the mold frame 10 and surrounds and supports the outer ring a of the bearing 15.

  The bearing 13 is disposed while maintaining a predetermined interval in the rotation direction of the inner ring b, the inner ring b that rotates integrally with the rotating shaft 9, the outer ring a provided on the mold bracket 11, and between the inner ring b and the outer ring a. It is comprised with the some rolling element c arrange | positioned so that rolling is possible. Similarly, the bearing 15 includes an inner ring b, an outer ring a provided on the metal bracket 12, and a plurality of rolling elements c.

  Next, the generation principle of electrolytic corrosion and the mechanism for suppressing electrolytic corrosion will be described.

  FIG. 2 is a diagram for explaining a path of a discharge current flowing through the bearings 13 and 15, FIG. 3 is a model diagram of an annular magnetic material, and FIG. 4 is a frequency characteristic diagram of complex permeability of soft ferrite. FIG. 5 is a diagram showing a waveform of the discharge current flowing through the bearings 13 and 15.

  When the electric motor 1 is driven by the inverter 8, an imbalance occurs in the applied power source, or an imbalance occurs in the windings 3 of each phase applied to the stator 2. A voltage is induced between 9 shaft ends. When this voltage exceeds the dielectric breakdown voltage of the oil film inside the bearings 13 and 15, a minute current (discharge current) flows inside the bearings 13 and 15. This discharge current causes electrolytic corrosion inside the bearings 13 and 15. When electrolytic corrosion progresses, a wavy wear phenomenon occurs in the inner ring b, the outer ring a, or the rolling element c, and abnormal noise resulting from this wear phenomenon is one of the main causes of problems in the motor.

  FIG. 2 shows an example of a discharge current path. The discharge current flows through the electric motor 1 through a “path A” as shown by a solid line, and includes an inverter 8, a mold bracket 11, a bearing 13, a rotating shaft 9, and a bearing. 15, the metal bracket 12, the stator 2, and the conductor of the winding 3 are passed through. Note that a path in which the discharge current directly flows from the rotor 5 to the stator 2 can be considered, as in “path B” indicated by a dotted line. Therefore, the radial impedance in the rotor 5 is high and can be ignored as a discharge path. Therefore, in the following description, a path A indicated by a solid line is described as a discharge path.

  Since there are conductors such as the mold bracket 11, the bearing 13, the rotating shaft 9, the bearing 15, the metal bracket 12, the stator 2, and the winding 3 in the path A, the electric circuit corresponds to an RLC series circuit. At this time, if the discharge current flowing through the path A is i, the current i flows according to an equation such as the equation (1).

  In Equation (1), R represents resistance in the path, L represents inductance, C represents capacitance, and E represents axial voltage. At this time, the waveform of the discharge current is determined by the sign of the result of Expression (2).

  In a small blower motor applied to an air conditioner or the like, the materials such as the bearings 13 and 15 and the rotary shaft 9 are iron or copper, and the resistance R is extremely small. Therefore, since the inductance L and the capacitance C are dominant, Expression (2) <0. Therefore, the discharge current in the blower motor is observed as a current waveform of damped vibration as shown by a current curve A in FIG. Further, the damped vibration and the resonance frequency f in the equation (1) are as shown in the equations (3) and (4).

  Since the magnitude of the energy of the discharge current is affected by the exponential term −R / 2L of the exponential function in Expression (3), when the resistance R of the imaginary part is large, the discharge current is as shown by a current curve B in FIG. It decays quickly. That is, as the resistance R of the imaginary part increases, damage to the bearings 13 and 15 due to the discharge current decreases. In addition, since the resonance frequency f of the discharge current in a small blower motor is several tens to several hundreds of MHz, a material having a maximum iron loss in the vicinity of this resonance frequency should be inserted into the RLC series circuit. As a result, the discharge current can be quickly reduced, and electric corrosion can be suppressed.

  Next, a material that performs a resistance operation near the resonance frequency will be described.

  FIG. 4 shows characteristics relating to soft ferrite, which is a kind of soft magnetic material, as an example of frequency characteristics of magnetic permeability of a material that exhibits a resistance operation near the resonance frequency. The vertical axis represents magnetic permeability, and the horizontal axis represents frequency. When the complex permeability μ of soft ferrite is expressed by μ = μ′−iμ ″, the permeability μ ′ shown in FIG. 4 represents the real part (inductance component) of the complex permeability μ and is shown in FIG. The permeability μ ″ represents the imaginary part (resistance component) of the complex permeability μ. As apparent from FIG. 4, the magnetic permeability μ ″ increases gradually from several MHz and reaches a maximum at about 100 MHz, and thus acts as a resistance R against a high-frequency component included in the discharge current. Accordingly, the energy of the decay oscillation of the discharge current is changed to heat in the soft ferrite, and as a result, the discharge current can be effectively attenuated as shown by the current curve B shown in FIG. Examples of the soft ferrite include Mn—Zn ferrite and Ni—Zn ferrite.

  An effective shape of the magnetic member 16 capable of enhancing the discharge current attenuation effect by the soft magnetic material will be described.

  FIG. 3 shows a model of an annular magnetic material. In FIG. 3, for convenience of explanation, the magnetic members 16 and 17 shown in FIG. 1 are regarded as an annular magnetic material, and the rotary shaft 9 shown in FIG. 1 is a shaft that penetrates the inner periphery of the annular magnetic material. I think. Here, the distance from the center line 20 of the shaft (9) to the inner peripheral surface 30 of the magnetic members 16, 17 is r1, and the distance from the center line 20 of the shaft (9) to the outer peripheral surface 40 of the magnetic members 16, 17 is When r2 and the height of the magnetic members 16 and 17 are defined as h and the magnetic flux generated when the discharge current flows through the shaft (9) is defined as φr, the magnetic flux φr is expressed by the equation (5).

  As apparent from the equation (5), the magnetic flux φr increases as the height h is relatively larger than the distance r1. Since the iron loss increases as the value of the magnetic flux φr increases, the discharge current can be effectively attenuated as shown by the current curve B shown in FIG. Therefore, the electric motor 1 according to the present embodiment has a height h that is relatively larger than the distance r1 in a space provided between the rotor 5 and the bearings 13 and 15, and is a soft magnetic material. By providing the resin (magnetic member 16 and magnetic member 17) mixed with the above, the discharge current is effectively attenuated without changing the dimensions of the electric motor 1.

  The principle that the discharge current is attenuated by providing the magnetic members 16 and 17 between the rotor 5 and the bearings 13 and 15 will be described. In the RLC series circuit described above, the resistance R represents a loss (copper loss) caused by the discharge current passing through a resistance component on the path A (for example, the resistance of the bearings 13 and 15). On the other hand, when the magnetic member 16 is disposed between the bearing 13 and the rotor 5 and the magnetic member 17 is disposed between the bearing 15 and the rotor 5, the rotation is caused by the discharge current flowing through the path A. An alternating magnetic field is generated around the shaft 9, and this magnetic field acts on the magnetic members 16 and 17 to cause iron loss (hysteresis loss), which acts as a resistance. Therefore, the discharge current (high frequency component) flowing through the path A is quickly attenuated by the iron loss generated in the magnetic members 16 and 17.

  The operation will be described below. The discharge current generated by the voltage induced between the shaft ends of the rotating shaft 9 with the switching of the inverter 8 generates an alternating magnetic field around the rotating shaft 9. This magnetic field acts on the magnetic members 16 and 17 to cause iron loss. Since this iron loss acts as a resistance, the discharge current is changed to heat in the soft ferrite of the magnetic members 16 and 17 and attenuates as shown by the current curve B.

  In the above description, the case where the electric motor 1 is applied to an indoor unit of an air conditioner has been described. However, the present invention is not limited to this, and the electric motor 1 can also be applied to an outdoor unit.

  In the above description, the embodiment using the magnetic members 16 and 17 formed by mixing the resin and the soft magnetic material has been described. However, the magnetic members 16 and 17 made of only the soft magnetic material may be used. .

  In the above description, a configuration example in which the magnetic member 16 is disposed between the bearing 13 and the rotor 5 and the magnetic member 17 is disposed between the bearing 15 and the rotor 5 has been described. However, the present invention is not limited to this, and either the magnetic member 16 or the magnetic member 17 may be provided. Even in such a configuration, since it is not necessary to change the dimensions of the electric motor 1, the electric motor 1 can be manufactured at a low cost and the electrolytic corrosion of the bearings 13 and 15 can be suppressed.

  As described above, the electric motor 1 according to the present embodiment is provided around the stator (stator) 2 disposed in the mold frame (frame) 10 and the rotating shaft 9 so as to face the stator 2. A rotor 5 having permanent magnets 6, a pair of brackets (mold bracket 11, metal bracket 12) disposed at both ends of the mold frame 10 to support the rotating shaft 9, and the brackets (mold bracket 11, metal bracket 12). ) And a pair of bearings 13 and 15 that support the rotating shaft 9, and are provided between the rotor 5 and the bearings 13 and 15, and are provided around the rotating shaft 9. In addition, since the magnetic members 16 and 17 including the soft magnetic material are provided, it is possible to effectively attenuate the discharge current that causes electric corrosion. That. Conventionally, in order to improve the electric corrosion resistance, a method of changing the structure of the bracket and the frame, a method of interposing an insulating sleeve between the rotating shaft 9 and the inner ring b of the bearings 13 and 15, There is a technique using ceramic for the rolling element c. However, these methods have a problem that the manufacturing cost increases. Since the electric motor 1 according to the present embodiment can suppress the discharge current only by disposing the magnetic members 16 and 17, the manufacturing equipment for the electric motor 1 can be shared. As a result, it is possible to suppress the electrolytic corrosion of the bearings 13 and 15 at low cost.

Further, the electric motor 1 according to the present embodiment includes a stator (stator) 2 disposed in a mold frame (frame) 10, and a permanent magnet 6 provided around the rotating shaft 9 so as to face the stator 2. A rotor 5 having a pair of brackets (mold bracket 11, metal bracket 12) disposed on both ends of the mold frame 10 and supporting the rotation shaft 9; a pair of bearings 13 and 15 supporting the shaft 9, is provided between the rotor 5 and the bearing 13 and 15, it is circumferentially provided around the rotation shaft 9, a weak coercive force than coercive magnetic force of the permanent magnet 6 Since the magnetic members 16 and 17 including the magnetic material having the magnetic material are provided, the electrolytic corrosion of the bearings 13 and 15 can be suppressed at a low cost.

  Further, the magnetic material of the magnetic members 16 and 17 according to the present embodiment may be composed of only a soft magnetic material. When comprised in this way, it is possible to suppress a discharge current still more effectively.

  In addition, the magnetic material of the magnetic members 16 and 17 according to the present embodiment increases the value of the imaginary part of the complex permeability near the resonance frequency of the current flowing through the rotating shaft 9 when voltage is induced on the rotating shaft 9. Is configured to do. That is, since the value of the imaginary part of the complex permeability is increased in the region where the resonance frequency f of the discharge current is 10 MHz or more, the resonance frequency of the discharge current in the small blower motor (several tens of MHz to several This discharge current can be effectively attenuated at 100 MHz).

  Further, since the magnetic material of the magnetic members 16 and 17 according to the present embodiment is made of soft ferrite, it can be easily manufactured when the magnetic members 16 and 17 are manufactured by injection molding. . This is because soft ferrite has a smaller particle size than other metal-based soft magnetic materials (for example, iron, silicon steel, etc.) and is therefore suitable for injection molding of a resin mixed with soft ferrite.

  Further, since the mold bracket 11 according to the present embodiment incorporates an inverter 8 that generates a high-frequency voltage applied to the winding 3 provided in the stator 2, the wiring in the inverter 8 is a winding. 3 acts as a conductor between the bearing 3 and the bearing 13, the insulation distance between the winding 3 and the bearing 13 is reduced, and the current flowing through the rotating shaft 9 is increased. Thus, even when a large current flows through the rotary shaft 9, the magnetic members 16 and 17 can effectively attenuate the discharge current.

  Further, the magnetic members 16 and 17 according to the present embodiment are such that the height h from the upper end to the lower end of the magnetic members 16 and 17 in the extending direction of the rotating shaft 9 is from the center line 20 of the rotating shaft 9 to the magnetic member. Since it is configured to be larger than the distance r1 to the inner peripheral surface 30 of 16, 17, it is possible to effectively attenuate the discharge current.

  Moreover, since the air conditioner according to the present embodiment is provided with the electric motor 1 as an electric motor for driving the indoor unit fan, noise due to electric corrosion of the bearings 13 and 15 can be reduced. In particular, noise is a problem caused by the electric corrosion of the bearings 13 and 15, and the indoor unit of the air conditioner is required to be quiet in order to be used in a living space for a long time, and the resistance to electric corrosion can be improved. This is because it greatly contributes to product reliability.

  The electric motor and the air conditioner according to the embodiment of the present invention show an example of the content of the present invention, and can be combined with another known technique, and depart from the gist of the present invention. Of course, it is possible to change and configure such as omitting a part within the range.

  As described above, the present invention can be applied to an electric motor, and is particularly useful as an invention capable of suppressing electric corrosion of a bearing at a low cost without changing dimensions.

1 Electric motor 2 Stator (stator)
3 Winding 4 Stator core 5 Rotor (rotor)
6 Permanent magnet 7 Support member 8 Inverter 9 Rotating shaft 10 Mold frame 11 Mold bracket 11a Soft magnetic bracket 11b Inner peripheral surface 11c Outer peripheral surface 12 Metal bracket 13, 15 Bearing 14 Insulator 16, 17 Magnetic member 20 Center line 30 Inner peripheral surface 40 Outer surface A, B Discharge current path a Outer ring b Inner ring c Rolling element h Height of magnetic member r1 Distance from center line of axis 1 to inner surface of magnetic member r2 Center line of axis to outer surface of magnetic member Distance φr Magnetic flux μ ', μ''Permeability

Claims (8)

A stator disposed in the frame;
A rotor having a permanent magnet disposed around a rotation shaft facing the stator;
A pair of brackets disposed at both ends of the frame and supporting the rotating shaft;
A pair of bearings mounted on the bracket and supporting the rotating shaft;
A magnetic member that is provided between the rotor and the bearing, is provided around the rotation axis, and includes a magnetic material that is softer than the magnetic material of the permanent magnet;
Equipped with a,
In the rotating shaft, a current flows when a voltage is induced in the rotating shaft,
The motor according to claim 1, wherein the magnetic material of the magnetic member has a characteristic that the value of the imaginary part of the complex permeability near the resonance frequency of the current is increased by the alternating magnetic field generated by the current . A stator disposed in the frame;
A rotor having a permanent magnet disposed around a rotation shaft facing the stator;
A pair of brackets disposed at both ends of the frame and supporting the rotating shaft;
A pair of bearings mounted on the bracket and supporting the rotating shaft;
Provided between the rotor and the bearing, it is circumferentially provided around the rotation axis, and the magnetic member configured to include a magnetic material having a weak coercive force than coercive magnetic force of the permanent magnet,
Equipped with a,
In the rotating shaft, a current flows when a voltage is induced in the rotating shaft,
The motor according to claim 1, wherein the magnetic material of the magnetic member has a characteristic that the value of the imaginary part of the complex permeability near the resonance frequency of the current is increased by the alternating magnetic field generated by the current . The electric motor according to claim 1, wherein the magnetic material of the magnetic member is composed only of a soft magnetic material. The magnetic member, the electric motor according to claim 1 or 2, characterized that you have been made of resin mixed with magnetic material. The motor according to claim 1, wherein the magnetic material of the magnetic member is made of soft ferrite.   The electric motor according to any one of claims 1 to 5, wherein the bracket includes an inverter that generates a high-frequency voltage applied to a winding provided in the stator.   The height from the upper end to the lower end of the magnetic member in the extending direction of the rotating shaft is larger than the distance from the center line of the rotating shaft to the inner peripheral surface of the magnetic member. The electric motor according to any one of? An air conditioner comprising the electric motor according to any one of claims 1 to 7 as an electric motor for driving a fan of an indoor unit and / or an outdoor unit.

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