JP2015023751A - Electric motor and electrical machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric motor capable of preventing generation of electric corrosion on bearing and electrical machine including the same.SOLUTION: The stator core 11 has a stator winding 12 wound being interposed by a resin 21 as an insulator for insulating the stator core 11. A stator 10 which has a generally cylindrical outer shape is formed by integrally molding these members. The stator core 11 is molded with a resin outer casing 13 which is integrally formed an insulation resin as a mold material together with other fixing members. A rotor 14 is disposed inside the stator 10 being interposed by a space. The rotor 14 includes a disk-like rotor 30 with a rotor core 31 and a shaft 16 fastened with the rotor 30 penetrating at the center of the rotor 30. The rotor 30 includes a magnet 32 of a ferrite resin which is a permanent magnet in a periphery direction facing inward of the stator 10.

Description

  The present invention relates to an electric motor, and more particularly to an electric motor improved to suppress the occurrence of electrolytic corrosion of a bearing.

  As is well known, when the circuit conditions of each phase are equalized in a sine wave symmetrical three-phase AC circuit, the neutral point of the Y connection always shows a constant value, and the neutral point of the Y connection on the power source side and the load point side There is no potential difference between the neutral point of the Y connection. In addition, it cannot be overemphasized that the sine wave of the three-phase power supply in this case is an undistorted sine wave which does not contain a harmonic component.

  Further, when the condition of the circuit loop of each phase of the three-phase circuit is unbalanced, the neutral point on the load side of the Y connection shows not a zero potential but a certain potential. These are well known as disclosed in Patent Document 1, for example. Note that the shaft voltage is measured with some contrivance, such as measuring the potential difference from any circuit location of the three-phase AC circuit or the pseudo neutral point at the midpoint of the voltage divider circuit provided for convenience. It is necessary.

  In an actual symmetric three-phase AC circuit, due to various factors, the three-phase power supply is unbalanced and the sine wave of the three-phase power supply contains some harmonic components. Some potential is observed at the neutral point of the Y connection. Furthermore, due to this potential change at the neutral point, a voltage value induced on the rotating shaft of the generator and the rotating shaft of the motor, so-called shaft voltage, is observed. This shaft voltage is also applied to the inner ring of the bearing that rotatably supports the rotating shaft.

  On the other hand, since the outer ring of the bearing is electrically connected to the outer shell of the generator or motor and the grounding part, the potential of the inner ring of the bearing is different from that of the inner ring and the outer ring of the bearing. Occurs. When the outer ring and the inner ring are electrically connected via the rolling elements of the bearing, discharge occurs between the outer ring, the rolling elements, the inner ring, and these. A discharge mark is generated at the location of this discharge, and this discharge mark is called electric corrosion. This discharge mark, that is, electric corrosion, causes a problem in the rotation of the bearing.

  For example, as described in Patent Documents 2 to 4 and the like, a symmetric three-phase alternating current is not obtained in a three-phase power generator due to an unbalance of a magnetic circuit caused by improper assembly of the generator. An unbalanced three-phase alternating current is generated, and a shaft voltage is generated due to generation of a neutral point potential.

  Further, when the excitation power source of the excitation winding of the generator is an excitation device such as a thyristor, a non-sinusoidal waveform voltage containing a large amount of harmonics is applied to the excitation winding. The voltage having the non-sinusoidal waveform is generated as a shaft voltage due to the excitation power of the above-described excitation device via an equivalent impedance component due to the excitation winding and other components of the generator.

  Further, as described in the above-mentioned patent documents and the like, as a phenomenon peculiar to the generator, a part of the steam colliding with the steam turbine blade is ionized and charged. Then, it is known that the electric charge due to the ionization of the vapor is transmitted to the rotating shaft through an equivalent impedance component by the constituent members of the generator and appears as a shaft voltage of the generator, leading to electrolytic corrosion of the bearing.

  On the other hand, in the electric motor on the load side in the three-phase AC circuit, as described in Patent Document 5, for example, the occurrence of electrolytic corrosion of the bearing due to the shaft voltage due to the three-phase AC imbalance is known. . Further, as described in the same literature, etc., when an electric motor is driven using an inverter device, neutrality of a very high frequency component (several MHz) is caused by voltage imbalance that occurs instantaneously every time the power supply is switched. A shaft voltage (shaft current) resulting from the fluctuation of the point potential is generated, and electric corrosion of the bearing of the motor occurs.

  In recent years, in the field of electric motors, drive technology using an inverter device has been very popular. The drive by the inverter device is completely different from the drive by the undistorted sinusoidal voltage source, and a pseudo three-phase drive is achieved by forming a rectangular wave voltage source. In the drive by the inverter device, as described in Patent Document 5 described above, shaft current (shaft voltage) due to fluctuation of the neutral point potential is generated, and electric corrosion of the motor bearing is likely to occur.

  As is well known, driving by an inverter device is not driving by a symmetrical three-phase alternating current using an undistorted sine wave. Therefore, at the neutral point of the Y connection of the electric motor, the voltage values of the respective phases cancel each other and do not always become zero level, and it is obvious that some voltage value is generated.

  For example, as described in Non-Patent Document 1 and the like, the neutral value of the Y connection of the motor driven by the inverter device is caused by a convex waveform wave and a square wave whose maximum value also reaches the power supply voltage value of the inverter device. A periodic large amplitude voltage change is shown. And as described in the said nonpatent literature etc., due to the potential change of this neutral point, axial voltage is observed in a rotating shaft.

  As described in Non-Patent Document 1 and the like, the driving voltage of each phase from the inverter device is electrically transferred from the stator winding of the stator of the motor to the outside of the stator through the impedance component of the stator constituent member. Propagates as energy. The propagation of this electrical energy propagates to the rotor of the motor via the distributed capacity component between the stator and rotor of the motor, and further to the rotating shaft via the impedance component of the rotor component. To reach. Here, since the rotation axis is located at the neutral point of the equivalent Y-connection of the three-phase AC circuit, some potential change is observed on this rotation axis. As described above, this change in potential is referred to as an axial voltage.

  As is well known, the third harmonic component of each phase in the three-phase AC circuit is not canceled out and can be observed at the neutral point of the Y connection. As is well known, an unbalanced component of each phase can also be observed at the neutral point of the Y connection.

  Although inverter driving is used, specifically, there are many cases in which a driving method using a pulse width modulation (hereinafter referred to as PWM) inverter is employed. In the case of such PWM type inverter driving, the potential at the neutral point of the winding does not become zero and the reason why some voltage is generated is as described above.

  In addition, regarding the potential change at the neutral point described above, when the equivalent circuit based on the electrical equivalent impedance component of each component of the motor is analyzed from the viewpoint of a three-phase AC circuit, the rotating shaft of the motor is Needless to say, this is considered as the neutral point of the equivalent Y-connection in the circuit, and some potential change occurs on the rotation axis.

  For example, an attempt has been made to calculate a shaft voltage by extracting an equivalent impedance component of each component of the motor and analyzing an equivalent circuit of the motor including each component of the motor.

  As described above, from the viewpoint of an equivalent circuit based on an electrical equivalent impedance component of each component of the electric motor, analysis of generation of shaft voltage and suppression of electric corrosion are described in Patent Document 5 described above or non-patent It can be found in known documents such as Document 1. There are various types of equivalent circuits for electric motors, such as analysis based on the viewpoint of a distributed constant circuit, and analysis by modeling a lumped constant element for each major circuit element of the distributed constant circuit.

  In addition, the equivalent circuit of the motor including each component of the motor varies depending on the type and structure of the motor. Specifically, an electric motor that covers the stator winding and the stator core with an insulating resin, and an electric motor that covers the stator winding and the stator core with a metal casing are equivalent circuits of the motor. Is clearly different.

  Also, the equivalent circuit of the electric motor varies depending on the structure of the rotor of the electric motor. For example, it is clear that the equivalent circuit of the electric motor differs depending on the combination of the presence / absence of the rotor core forming the back yoke of the rotor and whether the resistance value of the magnet constituting the magnetic pole is high or low.

  Therefore, since the equivalent circuit of the electric motor including each component of the electric motor differs depending on the type and structure of the electric motor, a suitable technique for reducing electric corrosion differs depending on the type and structure of the electric motor, and is applicable to all types of electric motors. On the other hand, it is extremely difficult to establish a technique for reducing electric corrosion that can be applied uniformly. Of course, it is more common to establish a technique for reducing electric corrosion for each type and structure of an electric motor, and many techniques for reducing electric corrosion have been proposed.

  As described above, a potential difference is generated between the outer ring and the inner ring of the bearing due to the generation of the shaft voltage by the inverter drive of the electric motor. This shaft voltage includes a high-frequency component due to switching. When the potential difference caused by the shaft voltage reaches the dielectric breakdown voltage of the oil film inside the bearing, a high-frequency current flows inside the bearing, and electrolytic corrosion occurs inside the bearing. When this electrolytic corrosion progresses, a wavy wear phenomenon may occur inside the bearing inner ring or the outer ring, resulting in abnormal noise, which is a typical malfunction phenomenon in an electric motor.

As described above, electrolytic corrosion is a phenomenon in which the bearing material is damaged by arc discharge, and due to the potential difference generated between the inner ring of the bearing and the outer ring of the bearing due to the shaft voltage, the inner ring of the bearing—the ball of the bearing— This is because the shaft current flows through the path of the outer ring. Therefore, in order to suppress electric corrosion of the electric motor, the following measures are proposed.
(1) Make the bearing inner ring and outer ring conductive.
(2) Insulate the bearing inner ring and outer ring.
(3) Reduce the shaft voltage.

  As a specific method of the above (1), there is a method of making the bearing lubricant conductive. However, the conductive lubricant has problems such as deterioration of conductive characteristics over 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.

  Further, as another method of the above (1), a configuration in which the bearing is a sliding bearing is also considered. For example, by employing a metal sintered oil-impregnated bearing, the bearing portion can be brought into a conductive state. As is well known, motors using a pair of ball bearings are the mainstream in recent PWM type inverter-driven motors, but in the past, motors using a pair of slide bearings have been seen.

  For example, those described in Patent Document 6, Patent Document 7, and the like are examples. Since the bearing is in a conductive state, no electric discharge is generated and no electric corrosion occurs. However, the rotation accuracy of the shaft is inferior to that using a ball bearing, and the bearing loss is large, so that a ball bearing is used. As is well known, the efficiency of the electric motor is reduced more than that.

  As a specific method of the above (2), the material of the rolling element inside the bearing may be replaced with a metal material such as iron as a conductive material and a ceramic material as an insulator. This method is very effective in preventing electrolytic corrosion, but in the case of a ceramic material, the cost is high and causes a problem of economic aspects.

  Further, as another method of (2) above, a configuration in which the bearing is an insulating sliding bearing is also considered. For example, by employing an insulating sliding bearing using a resin described in Patent Document 8 or the like, the bearing portion can be in an insulating state. Electric corrosion does not occur in the bearing portion having insulation. However, as described above, it is well known that the rotational accuracy of the shaft is inferior to that using a ball bearing, and the efficiency of the motor is lower than that using a ball bearing because the bearing loss is large. It is as follows.

  As a specific method of (3) above, a method is known in which a dielectric layer is provided on the rotor to lower the axial voltage and suppress the occurrence of electrolytic corrosion (see, for example, Patent Document 9). .

  In addition, as another method of (3) above, there is known a method of reducing the axial voltage by changing the capacitance by electrically short-circuiting the stator core and the metal bracket having conductivity. (For example, see Patent Document 10). In addition, a configuration in which a stator core of an electric motor or the like is electrically connected to the earth ground is also known (see, for example, Patent Document 11).

JP-A-8-340637 Japanese Examined Patent Publication No. 47-41121 JP 50-76547 A JP 57-16549 A Japanese Patent Laid-Open No. 10-32953 Japanese Examined Patent Publication No. 61-52618 JP-A-8-214488 JP 2011-47495 A JP 2010-166689 A JP 2007-159302 A JP 2004-229429 A

“Fuji Jiho Vol. 72, No. 2 (February 1999)”, Inverter-driven induction motor shaft voltage 144-P. 149

  However, since the conventional method like patent document 10 is the method of short-circuiting a stator iron core and metal brackets, the electrostatic capacity distribution in an electric motor becomes high overall, and a shaft voltage may become high. there were.

  In addition, 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, and a primary circuit of the power supply circuit and a ground to the ground on the primary circuit side are electrically If the configuration is such that the stator core of the motor is electrically connected to the earth ground as in Patent Document 11, it is difficult to reduce the shaft voltage.

  Also, if the shaft voltage is not sufficiently small compared to the dielectric breakdown voltage of the bearing alone, it is difficult to prevent the electrical short-circuit phenomenon that occurs in the bearing for a long period of time, thus suppressing electric corrosion. It was difficult. This is because, when a shaft voltage is applied to the bearing for a long period of time, the dielectric breakdown voltage of the bearing itself decreases due to grease deterioration or bearing surface damage.

  Therefore, the dielectric breakdown voltage of the bearing is higher than the shaft voltage at the beginning of motor driving, and even if no short-circuit phenomenon occurs, the dielectric breakdown voltage of a single bearing decreases when driven for a long period of time. When the dielectric breakdown voltage of the bearing unit is reduced, a short circuit phenomenon occurs, resulting in the occurrence of electrolytic corrosion.

  The dielectric breakdown voltage of the bearing can be increased by increasing the thickness of the oil film of grease, and a method of increasing the kinematic viscosity of the base oil of grease is generally used. However, when the kinematic viscosity of the base oil of grease is increased, bearing loss increases and the efficiency of the motor decreases, so there is a limit to increasing the oil film thickness.

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

1st invention fastened the said rotary body so that the stator which wound the coil | winding, the rotary body which hold | maintained the magnet in the circumferential direction facing the said stator, and the center of the said rotary body might be penetrated In an electric motor comprising a rotor including a shaft, two bearings for supporting the shaft, and two conductive brackets for fixing the bearing,
The electric motor includes a cylindrical portion that is electrically connected to one or each of the pair of brackets and is opposed to and spaced from the shaft.

  A second invention is an electric motor according to the first invention, wherein the electric motor includes a resin sheathing portion in which the stator is integrally formed of an insulating resin.

  3rd invention is an electric motor which comprises the electrically conductive body which electrically connects each of a pair of said bracket in 1st invention.

  A fourth invention is an electric device equipped with the electric motor of the first to third inventions.

  According to the electric motor of the present invention, it is possible to provide an electric motor that suppresses electric corrosion noise in a bearing and an electric device including the electric motor.

Sectional drawing of the electric motor which has the cylindrical part (collar shape part) of the bracket by the side of the output shaft in Example 1 of this invention. Sectional drawing of the electric motor which has a cylindrical part (collar shape part) of both the bracket by the side of an output shaft and the bracket by the side of a non-output shaft in Example 2 of this invention.

  The present invention will be described below with reference to the drawings and tables. In addition, this invention is not limited by the following examples.

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

  In FIG. 1, a stator winding 12 is wound around a stator core 11 with a resin 21 as an insulator for insulating the stator core 11 interposed therebetween. And such a stator core 11 has the resin exterior part 13 integrally molded with the insulating resin as a molding material 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 ferrite resin magnet 32 that is a permanent magnet in the circumferential direction facing the inner peripheral side of the stator 10.

  FIG. 1 shows a configuration example in which the rotor core 31 and the ferrite resin 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.

  An output shaft side bearing 15 a and a counter output shaft side bearing 15 b that support the shaft 16 are attached to the shaft 16 of the rotor 14. The output shaft side bearing 15 a and the counter output shaft side bearing 15 b are cylindrical bearings having a plurality of iron balls, and the inner ring side of the output shaft side bearing 15 a and the counter output shaft side bearing 15 b is fixed to the shaft 16. .

  In FIG. 1, the output shaft side bearing 15 a supports the shaft 16 on the output shaft side where the shaft 16 protrudes from the brushless motor body, and on the opposite side (counter output shaft side), the counter output shaft side bearing 15 b. Supports the shaft 16.

  The output shaft side bearing 15a and the counter output shaft side bearing 15b are fixed to the outer ring side of the output shaft side bearing 15a and the counter output shaft side bearing 15b by metal brackets having conductivity.

  In FIG. 1, the output shaft side bearing 15 a is fixed by an output shaft side bracket 17, and the counter output shaft side bearing 15 b is fixed by a bracket 19 on the counter output shaft side. With the configuration described above, the shaft 16 is supported by the output shaft side bearing 15a and the non-output shaft side bearing 15b, and the rotor 14 rotates freely.

  The output shaft side bearing 15a and the counter output shaft side bearing 15b are filled with grease that fills a part of the internal space inside the bearing. These output shaft side bearing 15a and anti-output shaft side bearing 15b are referred to as “double-side shielded ball bearings” and are widely known in the bearing field as “ZZ” in the “Nominal Symbol” item. It is what.

  Further, the brushless motor of this embodiment incorporates a printed circuit board 18 on which a drive circuit including a control circuit is mounted. After the printed board 18 is built in, the bracket 17 on the output shaft side is press-fitted into the stator 10 to form a brushless motor. Also connected to the printed circuit board 18 are connection wires 20 such as a lead wire for applying a winding power supply voltage Vdc, a control circuit power supply voltage Vcc and a control voltage Vsp for controlling the number of revolutions, and a ground wire for the control circuit. Yes.

  The zero potential point on the printed circuit board 18 on which the drive circuit is mounted is insulated from the earth ground and the primary side (power supply) circuit, and is floated from the earth ground and the potential of the primary side power supply circuit. It is in the state. Here, the zero potential point portion is a wiring of 0 volt potential as a reference potential on the printed circuit board 18, and indicates a ground wiring called a normal ground. The ground line included in the connection line 20 is connected to the zero potential point, that is, the ground wiring.

  In addition, a power supply circuit that supplies a power supply voltage of a winding connected to the printed circuit board 18 on which the drive circuit is mounted, a power supply circuit that supplies a power supply voltage of the control circuit, a lead wire that applies the control voltage, and a ground line of the control circuit Are the primary side (power supply) circuit for the power supply circuit that supplies the power supply voltage of the winding, the primary side (power supply) circuit for the power supply circuit that supplies the power supply voltage of the control circuit, and these primary side (power supply) circuits. It is electrically isolated from both the connected earth ground and the independently grounded earth earth.

  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.

  By supplying each power supply voltage and control signal to the brushless motor configured as described above via the connection line 20, the stator winding 12 is driven by the drive circuit of the printed circuit board 18. When the stator winding 12 is driven, a drive current flows through the stator winding 12 and a magnetic field is generated from the stator core 11. The magnetic field from the stator core 11 and the magnetic field from the ferrite resin magnet 32 generate an attractive force and a repulsive force according to the polarities of the magnetic fields, and the rotor 14 rotates about the shaft 16 by these forces. To do.

  Next, a more detailed configuration of the brushless motor will be described. First, in the brushless motor, as described above, the shaft 16 is supported by the output shaft side bearing 15a and the counter output shaft side bearing 15b, and the output shaft side bearing 15a and the counter output shaft side bearing 15b are also formed by brackets. Fixed and supported.

  Further, in order to suppress the above-described problems caused by creep, in the present embodiment, the output shaft side bearing 15a and the counter output shaft side bearing 15b are each fixed by a conductive metal bracket. It is configured. That is, in the present embodiment, a conductive bracket that has been processed in advance with a steel plate and has good dimensional accuracy is employed for fixing the output shaft side bearing 15a and the non-output shaft side bearing 15b. In particular, when a high output of the electric motor is required, such a configuration is more preferable.

  Specifically, first, the counter-output shaft side bearing 15b is fixed by the bracket 19 on the counter-output shaft side having an outer diameter substantially equal to the outer diameter of the counter-output shaft side bearing 15b. Further, the opposite output shaft side bracket 19 is integrally formed with the resin sheathing portion 13.

  Further, the brushless motor of this embodiment has a configuration in which a part of the conductive body 22c that electrically conducts between the brackets on the output shaft side and the non-output shaft side is embedded in the resin.

  Specifically, the first counter-output shaft side conduction pin 22a is electrically connected to the bracket 19 on the counter-output shaft side in advance. That is, as shown in FIG. 1, the first counter-output shaft side conduction pin 22a is connected to the collar portion 19b of the bracket 19 on the counter-output shaft side. The first anti-output shaft side conduction pin 22a is disposed inside the resin sheathing portion 13, and is molded integrally with the resin sheathing portion 13 in the same manner as the bracket 19 on the counter-output shaft side.

  In addition, by disposing the first anti-output shaft side conduction pin 22a inside the resin sheathing 13 as an electric motor inside, the first anti-output shaft side conduction pin 22a can be prevented from rust, external force, etc. Highly reliable electrical connection against external stress. The first anti-output shaft side conducting pin 22a is connected to a conducting wire, and extends from the flange portion 19b of the bracket toward the outer periphery of the brushless motor inside the resin sheathing portion 13 and from the vicinity of the outer periphery of the brushless motor to the shaft 16. Is further extended in parallel to the output shaft side.

  The second output shaft side conduction pin 22b is exposed from the end surface on the output shaft side of the resin sheathing portion 13, and is electrically connected to the bracket 17 on the output shaft side. That is, when the output shaft side bracket 17 is press-fitted into the stator 10, the second output shaft side conduction pin 22b contacts the output shaft side bracket 17, and the output shaft side bracket 17 and the second output shaft side Electrical connection with the conductive pin 22b is ensured.

  With such a configuration, the two brackets of the output shaft side bracket 17 and the counter output shaft side bracket 19 are electrically connected via the counter output shaft side conductive pin 22a and the output shaft side conductive pin 22b. . Further, the bracket 17 on the output shaft side and the bracket 19 on the counter-output shaft side are electrically connected to each other in a state where they are insulated from the stator core 11 by the resin sheathing portion 13.

  The bracket 19 on the side opposite to the output shaft has a cup shape that becomes a hollow cylindrical shape. More specifically, the bracket portion 19a of the bracket that is open on one side and the cylindrical end portion on the opened side slightly outward. And a collar portion 19b of an annular bracket which is widened only.

  The inner peripheral diameter of the cylindrical portion 19a of the bracket is substantially equal to the outer peripheral diameter of the non-output shaft side bearing 15b. By pressing the anti-output shaft side bearing 15b into the cylindrical portion 19a of the bracket, the anti-output shaft side bearing 15b is anti-output. It is also fixed to the resin sheathing part 13 through the bracket 19 on the shaft side.

  By configuring in this way, the outer ring side of the non-output shaft side bearing 15b is fixed to the metal-side bracket 19 on the anti-output shaft side, so that it is possible to suppress problems due to creep. Further, the outer peripheral diameter of the flange portion 19b of the bracket is slightly larger than the outer peripheral diameter of the non-output shaft side bearing 15b.

  That is, the outer diameter of the flange portion 19 b of the bracket is larger than the outer diameter of the counter-output shaft side bearing 15 b and at least smaller than the outer diameter of the rotating body 30. By using the bracket 19 on the side opposite to the output shaft in such a shape, for example, a metal material that is costly is used as compared with a structure in which the collar portion extends beyond the outer periphery of the rotating body 30 to the stator 10. Suppressed.

  Next, the output shaft side bearing 15 a is fixed by an output shaft side bracket 17 having an outer diameter substantially equal to the outer diameter of the stator 10. The bracket 17 on the output shaft side has a protruding portion having a diameter substantially equal to the outer peripheral diameter of the output shaft side bearing 15a at the center, and the inside of this protruding portion is hollow.

  After the printed circuit board 18 is built in, the inner side of the protruding portion of the bracket 17 on the output shaft side is press-fitted into the output shaft side bearing 15a, and the connection end provided on the outer periphery of the bracket 17 on the output shaft side and the stator The brushless motor is formed by press-fitting the output shaft side bracket 17 into the stator 10 so that the connecting end portion 10 is fitted.

  With this configuration, the assembling work is facilitated, and the outer ring side of the output shaft side bearing 15a is fixed to the metal output shaft side bracket 17, so that problems due to creep are also suppressed.

  In the above configuration, in the present invention, the output shaft side bracket 17 has the cylindrical portion (collar shape portion) 40 of the output shaft side bracket facing the shaft 16. Specifically, the inner peripheral portion of the bracket 17 on the output shaft side has a shape that protrudes facing the shaft 16.

  By doing so, an electrostatic capacity is generated between the bracket 17 on the output shaft side and the shaft 16, and the shaft voltage generated between the rotor and the stator is divided, so that the bearing is connected between the inner ring and the outer ring. The generated shaft voltage can be reduced.

  The distance between the output shaft side bracket 17 and the shaft 16 is preferably 1 mm or less. More preferably, it is 0.5 mm or less. However, when the distance is 0.05 mm or less, there is a possibility that the bracket and the shaft come into contact depending on the load applied to the shaft and the vibration applied to the electric motor.

  The longer the axial length of the collar shape is, the greater the capacitance between the bracket and the shaft, which is desirable. However, if the length is too long, there is a possibility of contact with a crossflow fan connected to the shaft. .

  In the present invention, since the output shaft side bracket 17 and the counter output shaft side bracket 19 are electrically connected, the effect of the cylindrical portion (collar shape portion) 40 of the output shaft side bracket 17 is achieved. The shaft voltage of the output shaft side bearing 15a and the non-output shaft side anti-output shaft side bearing 15b can be reduced on average.

When the output shaft side bracket 17 and the non-output shaft side bracket 19 are not electrically connected, in this embodiment, only the output shaft side bearing 15a divides the shaft voltage. Electric corrosion cannot be prevented.

  In the form of the first embodiment, the collar shape is formed on the bracket 17 on the output shaft side, but it is also possible to form the collar shape on the bracket 19 on the non-output shaft side. It is also possible to form a collar shape on both the output shaft side bracket 17 and the non-output shaft side bracket 19.

  FIG. 2 is a structural diagram showing a cross section of a brushless motor having the collar shapes of both the output shaft side bracket and the non-output shaft side bracket in the second embodiment.

  The second embodiment is a configuration in which the cylindrical portion (collar-shaped portion) 41 of the bracket on the counter-output shaft side is formed in the configuration of the first embodiment, and the shaft 16 is extended to the counter-output side. The same as in the first embodiment.

  In this way, in addition to the effect of the first embodiment, the capacitance generated between the cylindrical portion (collar shape portion) 41 of the bracket on the side opposite to the output shaft can be utilized, so that the shaft voltage is divided. The effect of pressing increases. However, since the structure which extended the shaft 16 to the non-output side is needed, it may be impossible depending on the shape of the electric equipment carrying an electric motor.

With the above configuration, the shaft voltage generated between the inner ring and the outer ring of the bearing can be reduced, and the discharge damage when discharge is generated in the bearing is reduced, so that electric corrosion noise can be prevented.

  The electric motor of the present invention suppresses the occurrence of electrolytic corrosion of the bearing, and is useful for an electric motor mounted on a device such as an air conditioner indoor unit that is mainly required to reduce the price and increase the life of the electric motor.

DESCRIPTION OF SYMBOLS 10 Stator 11 Stator core 12 Stator winding 13 Resin exterior part 14 Rotor 15a Output shaft side bearing 15b Anti-output shaft side bearing 16 Shaft 17 Output shaft side bracket 18 Printed circuit board 19 Anti-output shaft side bracket 19a Bracket Cylindrical part 19b collar part of bracket 20 connecting line 21 resin (insulator)
22a Non-output shaft side conducting pin 22b Output shaft side conducting pin 22c Conducting body 30 Rotating body 31 Rotor core 32 Magnet 40 Cylindrical portion (collar-shaped portion) of bracket on output shaft side
41 Non-output shaft side bracket cylindrical part (collar shape part)

Claims (4)

A rotor including a stator around which a winding is wound, a rotating body that holds a magnet in a circumferential direction facing the stator, and a shaft that fastens the rotating body so as to penetrate the center of the rotating body. And an electric motor comprising two bearings for supporting the shaft and two conductive brackets for fixing the bearings.
An electric motor comprising a cylindrical portion that is electrically connected to one or each of the pair of brackets and is opposed to and spaced from the shaft. 2. The electric motor according to claim 1, further comprising a resin sheathing part in which the stator is integrally formed of an insulating resin. The electric motor according to claim 1, further comprising a conductive body that electrically connects each of the pair of brackets. An electric device equipped with the electric motor according to any one of claims 1 to 3.

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