JP2011205724A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner having a built-in motor to be driven by an inverter in a PWM system, wherein the occurrence of electrolytic corrosion of a bearing of the motor is prevented.SOLUTION: The air conditioner 100 includes a heat exchanger 102, a fan 103, and a motor 104 for driving and rotating the fan 103 by a rotary shaft 16, and has a grounding part 110 for grounding at least the heat exchanger 102. The motor 104 includes a stator having a winding 12 wound around a stator core 11, a rotor including a rotary body 30 centered at the rotary shaft 16, bearings 15a, 15b for supporting the rotary shaft 16, and two conductive brackets 17, 19 for fixing the bearings 15a, 15b. Further, a dielectric layer 50 is provided between the rotary shaft 16 and the outer circumference of the rotary body 30, and the stator core 11 is electrically connected to the grounding part 110.

Description

  The present invention relates to an air conditioner including an electric motor for blowing air, and more particularly, to an air conditioner improved so as to suppress the occurrence of electrolytic corrosion in a built-in motor bearing.

  An air conditioner that performs air conditioning such as cooling and heating generally includes a fan for blowing air and an electric motor for rotationally driving the fan. In recent years, there have been an increasing number of cases in which electric motors employ so-called brushless motors. Such a brushless motor uses an inverter of a pulse width modulation type (hereinafter, referred to as a PWM type as appropriate). On the other hand, in the PWM method, since switching is performed using high-frequency pulses, unnecessary high-frequency signals are easily radiated from the brushless motor.

  For this reason, the air conditioner which aimed at reduction of the high frequency noise radiated | emitted from such an electric motor is proposed conventionally (for example, refer patent document 1). In such an air conditioner, a method is used in which a portion where noise is easily radiated is covered with a shield case, and the shield case is connected to a ground wire inside the air conditioner.

  Further, when the motor is driven by a PWM inverter, the neutral point potential of the winding does not become zero, so that 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 has progressed, a wavy wear phenomenon may occur in the bearing inner ring, bearing outer ring or bearing ball, resulting in abnormal noise, which has been one of the main causes of problems in motors.

  As described above, the motor using the PWM method has a problem that it is easy to generate an unnecessary high-frequency signal that causes noise, and further, electric corrosion is likely to occur in the bearing due to such unnecessary electromagnetic radiation.

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 the above (3), a method of changing the electrostatic capacity by electrically short-circuiting the stator iron core and the conductive metal bracket to reduce the shaft voltage is conventionally known. Is known (see, for example, Patent Document 2).

  In Patent Document 2, the stator iron core and the bracket are short-circuited to reduce the impedance on the stator side, 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, since the electric motor used for the air conditioner has no fear of electric shock, no additional insulation is required.

  Therefore, since the motor used for the air conditioner does not normally have a rotor having an insulating structure, the impedance on the rotor side (bearing inner ring side) is low. On the other hand, since the stator side (bearing outer ring side) has an insulating structure, the impedance is high. In this case, a difference in voltage drop due to impedance occurs, and the potential on the bearing inner ring side is high, while the potential on the bearing outer ring side is low, so that 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 2 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 particular, in the case of a general brushless motor structure, when considering the impedance from the stator core to the outer ring of the bearing as the impedance on the stator side, the two are usually not electrically connected, and to some extent Therefore, it can be said that the impedance during this period is high. Further, since the impedance during this period is high, the high-frequency signal generated from the stator core is attenuated and reaches the outer ring of the bearing, and as a result, a low-frequency high-frequency voltage is generated in the outer ring of the bearing.

  On the other hand, when considering the impedance on the rotor side from the stator core to the inner ring of the bearing, the stator core and the rotor face each other through a slight gap, and the normal rotor and rotating shaft are Since it is a metal of a conductor, the impedance during this period can be said to be low. Further, since the impedance during this period is low, the high frequency signal generated from the stator core reaches the inner ring of the bearing without being attenuated, and as a result, a high potential high frequency voltage is generated in the inner ring of the bearing.

  Thus, even with the structure of the brushless motor itself, the impedance between the rotor side and the stator side is likely to be in an unbalanced state, and a potential difference, that is, a shaft voltage is generated between the inner ring and the outer ring of the bearing. Is considered to occur. Further, as a generation source of a signal for generating such a shaft voltage, a stator core around which a winding driven by high frequency switching of a PWM system is wound is considered as a main generation source. That is, since the stator core is wound with a winding driven by a high-frequency current, the stator core also generates a high-frequency signal due to the drive high-frequency together with the magnetic flux generated by the drive current. It is considered that is induced to the bearing inner ring and the bearing outer ring through the space.

  In recent years, a mold motor has been proposed in which a fixing member such as a stator iron core on the stator side is molded with a molding material or the like to improve reliability. Therefore, it is considered to fix the bearing with such an insulating mold material instead of the metal bracket to suppress unnecessary high-frequency voltage generated on the bearing outer ring side and unnecessary high-frequency current flowing between the bearing inner and outer rings. It is done. However, such a molding material is a resin and has problems such as insufficient strength to fix the bearing, poor dimensional accuracy due to resin molding, and easy occurrence of a creep failure of the bearing. It was. That is, in general, in a bearing such as a bearing, when there is a gap between the outer ring and the inner peripheral surface of the housing, a radial force is generated on the rotating shaft by the transmission load. When such a force is generated, a slip phenomenon is likely to occur due to a relative difference in the radial direction, and such a slip phenomenon is called creep. Such creep can be generally suppressed by firmly fixing the outer ring to a housing such as a bracket. Further, with the recent increase in output of electric motors, it is necessary to more firmly fix the bearings. For this reason, for example, it is indispensable to take a countermeasure against creep, such as adopting a metal bracket that is processed in advance with a steel plate and has good dimensional accuracy for fixing the bearing. In particular, the bearings are generally received at two locations with respect to the rotating shaft, but for reasons such as the strength and ease of implementation described here, metal brackets are used for the two bearings. It is preferable to fix.

JP 2007-198628 A JP 2007-159302 A

  As a method for suppressing electrolytic corrosion, the conventional method such as Patent Document 2 has the following problems. That is, this conventional method is a method for changing the impedance on the stator side to maintain a potential balance between the bearing inner ring and the bearing outer ring and to suppress electrolytic corrosion. In the case of such a method, if the balance of the impedance is lost depending on the use environment of the motor, the case where the shaft voltage becomes higher and the electric corrosion tends to occur is considered as a possibility.

  In particular, in the case of an air conditioner as an indoor unit, the proportion of heat exchangers that are usually made of metal occupy the air conditioner is large. Furthermore, since the fan connected to the rotating shaft is disposed facing the heat exchanger, a large electrostatic capacity is easily formed between the heat exchanger and the fan. For this reason, in the case of such an air conditioner, there is a high possibility that the balance of impedance in the electric motor is lost due to the influence of the capacitance. That is, for example, a high-frequency signal radiated from the stator core flows as a high-frequency current into the rotating shaft via the heat exchanger and the fan, and the potential on the bearing inner ring side may be further increased.

  In addition, for reasons of strength as described above, when each of the two bearings is fixed with a metal bracket, since the shape and arrangement of one bracket and the other bracket are usually different, the impedance of both brackets is Different. For this reason, the potential induced in one bracket is different from the potential induced in the other bracket. For this reason, the shaft voltages are different between the two bearings, and there is a possibility that even if one of the bearings does not generate electrolytic corrosion, the other bearing may generate electrolytic corrosion.

  The air conditioner of this invention is made in view of the said subject, and it aims at providing the air conditioner which suppressed generation | occurrence | production of the electrolytic corrosion in the bearing of the built-in electric motor.

  In order to achieve the above object, an air conditioner of the present invention includes a heat exchanger that includes a conductive metal member and performs heat exchange, a fan that blows air conditioned by the heat exchanger, and a fan And an electric motor that rotationally drives the fan by a rotating shaft connected to the, and has a grounding portion for grounding at least the conductive metal member of the heat exchanger. This motor also has a stator that is wound around a stator iron core, a rotating body that holds a permanent magnet in the circumferential direction facing the stator, and a rotating body that passes through the center of the rotating body. A rotor including the rotating shaft, a bearing that supports the rotating shaft, and two conductive brackets that fix the bearing. And it is the structure which provided the dielectric material layer between the rotating shaft and the outer periphery of the rotary body, and electrically connected the stator core to the grounding part.

  With such a configuration, the stator core is connected to the grounding portion with respect to the stator core that is considered to be the voltage source that induces high-frequency voltage in the bearing inner ring and the bearing outer ring, so the potential of the stator core is zero potential. It becomes. Furthermore, since the heat exchanger is also connected to the grounding portion, a high-frequency current that flows from the heat exchanger through the fan to the rotating shaft can be suppressed, and the influence on the potential on the bearing inner ring side can be suppressed. In addition, the same effect can be obtained by grounding the stator core directly to earth ground. Furthermore, by providing a dielectric layer on the rotor, it is possible to adjust the impedance on the rotor side, and by maintaining a balance with the impedance on the stator side, the shaft voltage between the bearing inner ring and the bearing outer ring can be adjusted. It becomes possible to reduce. As described above, the potential difference between the inner ring and the outer ring of the bearing can be reduced with respect to the two bearings fixed by the conductive brackets, so that the bearing generated by the high frequency by PWM or the like while ensuring the fixing strength of the bearing. It is possible to suppress the occurrence of electric corrosion.

  Moreover, the air conditioner of this invention is the structure which connected two brackets electrically.

  With such a configuration, both brackets are set to the same potential, and the flow of high-frequency current through the rotating shaft is suppressed. Furthermore, by setting both brackets to the same potential, the potential difference between one bearing inner ring and the outer ring and the potential difference between the other bearing inner ring and the outer ring can be approximated or the same.

  Moreover, the air conditioner of this invention is good also as a structure by which two brackets in an electric motor were electrically connected inside the electric motor.

  With such a configuration, the two conductive brackets are electrically connected to each other through a connection pin or the like inside the motor, thereby providing a highly reliable electrical connection with respect to the use environment or external stress. it can.

  Moreover, the air conditioner of this invention is good also as a structure which electrically connected two brackets mutually connected in the electric motor further to the earthing | grounding part.

  The air conditioner of the present invention has a configuration in which at least the stator core in the electric motor is electrically connected to the grounding part via the capacitor.

  With such a configuration, the stator core is connected to the ground via the capacitor, so that the high-frequency potential of the stator core becomes zero potential. For this reason, in addition to reducing the shaft voltage, the high-frequency noise voltage generated from the stator core is not transmitted to other electric circuits in the air conditioner through the capacitor, so that the air conditioner malfunctions. Can be prevented.

  The air conditioner of the present invention has a configuration in which at least one of the two brackets in the electric motor and the stator core around which the winding is wound are integrally formed of an insulating resin.

  Moreover, the air conditioner of this invention is the structure by which the coil | winding wound around the stator core in an electric motor is driven by the inverter of a pulse width modulation system.

  As described above, according to the air conditioner of the present invention, since the shaft voltage generated in the two bearings of the electric motor can be suppressed to a low level, an air conditioner that suppresses the occurrence of electric corrosion of the built-in electric motor is provided. be able to.

The block diagram of the air conditioner in embodiment of this invention Structural diagram showing a cross section of the motor of the air conditioner The figure which showed the structural example of the rotary body of the electric motor in the same air conditioner The figure which showed the other structural example of the rotary body of the electric motor in the air conditioner The figure which showed the composition of the air conditioner typically The figure which showed the other structural example of the air conditioner typically A diagram schematically showing still another configuration example of the air conditioner

  The present invention will be described below with reference to the drawings.

(Embodiment)
FIG. 1 is a configuration diagram of an air conditioner according to an embodiment of the present invention. In the present embodiment, an air conditioner installed indoors will be described as an indoor unit. As shown in FIG. 1, the air conditioner 100 includes a heat exchanger 102, a fan 103, an electric motor 104, and a power supply unit 105 in a housing 101.

  The heat exchanger 102 is configured to include a conductive metal member, and performs heat exchange of air taken from the suction portion for heating and cooling. The fan 103 is a cross flow fan and blows air that has been conditioned by the heat exchanger 102. The electric motor 104 is connected to the fan 103 via the rotating shaft of the electric motor 104 and rotationally drives the fan 103. In addition, the power supply unit 105 supplies power for operating the electric motor 104 and other electric components. With such a configuration of the air conditioner 100, air conditioned by the heat exchanger 102 is blown into the room, for example, by the rotation of the fan 103.

  Next, the structure of the electric motor 104 built in the air conditioner 100 in this Embodiment is demonstrated. FIG. 2 is a structural diagram showing a cross section of the electric motor 104 of the air conditioner 100 according to the embodiment of the present invention. In this embodiment, an example of a brushless motor using a PWM method will be described as the electric motor 104. In the present embodiment, an example of an inner rotor type brushless motor in which a rotor is rotatably disposed on the inner peripheral side of a stator will be described.

  In FIG. 2, a stator winding 12 is wound around a stator core 11 with an insulator or the like 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 a metal rotor core 31 and a rotating shaft 16 that fastens the rotating body 30 so as to penetrate the center of the rotating body 30. The rotating body 30 holds the magnet 32 in the circumferential direction facing the inner peripheral side of the stator 10. The rotating body 30 includes an outer iron core 31a, a dielectric layer 50, and an inner rotor core 31 that constitute the outer peripheral portion of the rotor core 31 from the outermost peripheral magnet 32 toward the inner peripheral rotation shaft 16. It has a structure which arranges in order with the inner iron core 31b which comprises a surrounding part. FIG. 2 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 rotating shaft 16 are attached to the rotating shaft 16 of the rotor 14. The bearing 15 is a cylindrical bearing having a plurality of iron balls, and the inner ring side of the bearing 15 is fixed to the rotating shaft 16. In FIG. 2, the bearing 15a supports the rotating shaft 16 on the output shaft side where the rotating shaft 16 protrudes from the main body of the electric motor 104, and the bearing 15b on the opposite side (hereinafter referred to as the non-output shaft side). The rotating shaft 16 is supported. These bearings 15 are fixed on the outer ring side of the bearings 15 by metal brackets having conductivity. In FIG. 2, the bearing 15 a on the output shaft side is fixed by a bracket 17, and the bearing 15 b on the opposite output shaft side is fixed by a bracket 19. With the configuration as described above, the rotary shaft 16 is supported by the two bearings 15, and the rotor 14 rotates freely.

  Further, the electric motor 104 incorporates a printed circuit board 18 on which a control circuit and a drive circuit are mounted. In addition, the printed circuit board 18 is connected to a power source of a drive circuit, a connection line 20 such as a ground line and a control signal.

  In this embodiment, the conductive pin 22 is molded integrally with the bracket 19 in an electrically connected state in advance, and the tip of the conductive pin 22 is exposed on the output shaft side end surface of the stator 10. The tip is electrically connected to the bracket 17. With this configuration, the bracket 17 and the bracket 19 are electrically connected to each other inside the electric motor 104.

  Further, in the present embodiment, a through hole 23 is provided in a part of the insulating resin 13 that is a molding material, and one end of a connection pin 24 connected to the stator core 11 through the through hole 23 protrudes to the outside. As will be described in detail below, the connection pin 24 is electrically connected to a ground portion for grounding.

  By supplying each power supply voltage and control signal from the power supply unit 105 via the connection line 20 to the motor 104 configured as described above, a drive current is supplied to the stator winding 12 by the drive circuit of the printed circuit board 18. Flows, 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 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 rotating shaft 16 by these forces. The fan 103 is connected to the output shaft side of the rotary shaft 16, and the fan 103 is driven to rotate according to the rotation of the rotary shaft 16.

  Next, a more detailed configuration in the structure of the electric motor 104 will be described.

  First, as described above, in the electric motor 104, the rotating shaft 16 is supported by the two bearings 15, and the respective bearings 15 are also fixed and supported by the brackets. Furthermore, in order to suppress the above-described defects due to creep, the present embodiment is configured such that each bearing 15 is fixed by a metal bracket having conductivity. 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 bearing 15. In particular, when a high output of the electric motor 104 is required, such a configuration is more preferable.

  Specifically, first, it is fixed to the bearing 15b on the side opposite to the output shaft by a bracket 19 having an outer diameter substantially equal to the outer diameter of the bearing 15b. The bracket 19 is integrally molded with the insulating resin 13. That is, as shown in FIG. 2, the shape of the insulating resin 13 on the side opposite to the output shaft is a shape having a main body protruding portion 13a that protrudes from the brushless motor main body in the direction opposite to the output shaft. A bracket 19 is disposed as an inner bracket on the inner side of the main body protruding portion 13a, and is integrally molded with the insulating resin 13. The bracket 19 has a cup shape having a hollow cylindrical shape, and more specifically, a cylindrical portion 19a that is open on one side, and an annular collar portion that slightly extends outward from the cylindrical end portion on the open side. 19b. The inner diameter of the cylindrical portion 19a is substantially equal to the outer diameter of the bearing 15b. By inserting the bearing 15b into the cylindrical portion 19a, the bearing 15b is fixed to the insulating resin 13 via the bracket 19. . By comprising in this way, since the outer ring | wheel side of the bearing 15b is fixed to the metal bracket 19, the malfunction by creep can be suppressed. The outer diameter of the collar portion 19b is slightly larger than the outer diameter of the bearing 15b. That is, the outer diameter of the collar portion 19 b is larger than the outer diameter of the bearing 15 b and at least smaller than the outer diameter of the rotating body 30. By using the bracket 19 in such a shape, for example, compared to a structure in which the flange portion extends beyond the outer periphery of the rotating body 30 to the stator core 11, the use of a metal material that increases the cost is suppressed. . In addition, since the area of the metal bracket 19 is suppressed and the mold is integrally formed so as to cover the outline of the bracket 19 with the insulating resin 13, noise generated from the bearing 15b can be suppressed.

  Next, the bearing 15a on the output shaft side is fixed by a bracket 17 having an outer peripheral diameter substantially equal to the outer peripheral diameter of the stator 10. The bracket 17 has a substantially disc shape, and has a protrusion having a diameter substantially equal to the outer diameter of the bearing 15a at the center of the disk, and the inside of the protrusion is hollow. After incorporating the printed circuit board 18, the bearing 15 a is inserted inside the protruding portion of the bracket 17, and the connection end provided on the outer periphery of the bracket 17 and the connection end of the stator 10 are fitted together. Thus, the electric motor 104 is formed by press-fitting the bracket 17 into the stator 10. By comprising in this way, since the outer ring | wheel side of the bearing 15a is fixed to metal bracket 17, the malfunction by creep can be suppressed.

  Next, the structure for suppressing the electric corrosion in this Embodiment is demonstrated. In the present embodiment, electrolytic corrosion is generally suppressed as follows. First, by providing the dielectric layer 50 in the rotating body 30 of the electric motor 104, the impedance on the rotor side is increased and approximated to the stator side having a high impedance. As a result, the potential difference between the inner ring and the outer ring of the bearing, that is, the shaft voltage is lowered. In addition, the configuration provided with the dielectric layer 50 suppresses transmission of high-frequency signals generated in the stator core 11 to the fan 103 and the heat exchanger 102, thereby reducing the shaft voltage due to unnecessary radiation from the fan 103 and the like. Reduced. Further, by electrically connecting the stator core 11 to the grounding part 110, the high frequency signal generated from the stator core 11 is attenuated, thereby reducing the shaft voltage. Moreover, the bracket 17 and the bracket 19 are configured to be electrically connected, so that both brackets have the same potential, and a problem that the axial voltage of one bracket becomes high is suppressed.

  Hereinafter, a detailed configuration for suppressing electrolytic corrosion will be described.

  FIG. 3 is a diagram illustrating a configuration example of the rotating body 30 of the electric motor 104 in the air conditioner 100 of the present embodiment. FIG. 3 shows a configuration in which the rotating body 30 is viewed from above. As shown in FIG. 3, the rotating body 30 has a configuration in which a dielectric layer 50 is provided between the rotating shaft 16 and the outer periphery of the rotating body 30.

  That is, the rotor 30 has the magnet 32 disposed on the outermost periphery, and further, toward the inner periphery, the outer iron core 31a, the dielectric layer 50, and the inner iron core 31 that constitute the rotor iron core 31. It arranges in order with the iron core 31b. The dielectric layer 50 is a layer formed of an insulating resin. FIG. 3 shows an example in which the dielectric layer 50 is formed in a ring shape that circulates around the rotation shaft 16 between the inner peripheral side and the outer peripheral side of the rotary body 30. 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. Further, the rotating body 30 is fastened to the rotating shaft 16 at the fastening portion 35 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. In the present embodiment, by providing such a dielectric layer 50, the impedance on the rotor side is increased so that the impedance on the rotor side approximates the impedance on the stator side. Here, the impedance on the stator side is the impedance between the stator core 11 and the outer ring of the bearing 15, and the impedance on the rotor side is the impedance of the bearing 15 from the stator core 11 through the rotor 14. It is the impedance between the inner ring.

  Thus, by providing the dielectric layer 50 in the middle part of the rotator 30, an equivalent circuit on the rotator side has a configuration in which the capacitance of the dielectric layer 50 is connected in series, and the impedance of the rotator 14 is reduced. Can be high. In the path where the high-frequency signal generated in the stator core 11 flows as a high-frequency current to the rotating shaft 16 via the rotor 30, the high-frequency voltage drop increases by increasing the impedance of the rotor 14. Such a high-frequency signal is a signal generated mainly from the stator core 11 by switching based on the PWM method.

  For this reason, the electric potential which generate | occur | produces in the rotating shaft 16 by a high frequency electric current, ie, the electric potential of the inner ring | wheel side of the bearing 15, can be made low. The potential on the inner ring side of the bearing 15 is lowered to approximate the potential on the outer ring side of the bearing 15, and the potential difference between the inner and outer rings of the bearing, that is, the shaft voltage is kept low. As a result, the bearing inner ring and the bearing outer ring are in a state where the potential is always low and the balance is maintained so that the potential difference is reduced. In the present embodiment, the shaft voltage is thus kept low, and the occurrence of electrolytic corrosion of the bearing due to the shaft voltage is prevented. In particular, in the present embodiment, since the shaft voltage is kept low when the potential of each of the bearing inner and outer rings is low, compared to a method that balances the shaft voltage when the potential of each of the bearing inner and outer rings is high. Easy to balance so that the potential difference is small. Moreover, even if the balance is lost, the voltage is low, so that the influence on the occurrence of electrolytic corrosion is small.

  The high-frequency signal generated in the stator core 11 is easily transmitted from the rotating body 30 to the fan 103 via the rotating shaft 16 and further transmitted from the fan 103 to the heat exchanger 102. In particular, in the case of the air conditioner 100 as an indoor unit such as the present embodiment, the fan 103 and the heat exchanger 102 have a large area and volume, so that the high-frequency signal transmitted to these is easily radiated as an unnecessary signal, There is a possibility that the radiated signal goes around the bearing 15 and affects the shaft voltage. In order to deal with such a problem, the dielectric layer 50 acts as an impedance component connected in series between the stator core 11 and the fan 103, so that the high-frequency signal transmitted to the fan 103 is attenuated by the dielectric layer 50. be able to. That is, generation of shaft voltage due to unnecessary radiation from the fan 103 and the heat exchanger 102 can also be suppressed.

  The dielectric layer 50 uses a thermosetting resin such as unsaturated polyester resin or epoxy resin, a thermoplastic resin such as polybutylene terephthalate or polyamide, or an elastic body such as an elastomer or vulcanized rubber. In addition to changing the material of the dielectric layer 50, the impedance can be arbitrarily adjusted by changing the shape, thickness, etc., so that the impedance on the rotor side can be set optimally. .

  FIG. 4 is a diagram illustrating another configuration example of the rotating body 30 of the electric motor 104 in the air conditioner 100 according to the present embodiment. FIG. 4 is a view showing an upper surface of a rotating body 30 as another configuration example and a cross section taken along the line AA. 3 shows a so-called SPM (Surface Permanent Magnet) type structure in which a magnet is provided on the outer peripheral surface of the rotating body 30, whereas FIG. 4 shows an IPM (Interior Permanent Magnet) type structure. The rotor 14. In the rotating body 30 shown in FIG. 4, an outer iron core 31a, a dielectric layer 50, and an inner iron core 31b, which are arranged on the outermost periphery and have a plurality of insertion holes 33, are arranged in order toward the inner circumference. Has been. Further, magnets 32 that are permanent magnets such as neodymium rare earth sintered magnets are inserted into the plurality of insertion holes 33, respectively. The electric motor 104 may have such a configuration.

  Furthermore, in this Embodiment, in order to suppress an electric corrosion, it has a structure which is demonstrated below.

  FIG. 5 is a diagram schematically showing the configuration of the air conditioner 100 according to the embodiment of the present invention. Hereinafter, the configuration for suppressing electrolytic corrosion in the present embodiment will be further described with reference to FIG.

  First, as shown in FIG. 5, the heat exchanger 102 has a grounding part 110 for grounding the earth. The grounding part 110 is electrically connected to a grounding rod or the like for grounding via a grounding wire. Specifically, for example, a grounding wire is extended to the outdoor unit, and grounded from the outdoor unit to the ground using a grounding rod.

  By grounding the heat exchanger 102 in this way, the high-frequency signal induced in the heat exchanger 102 flows into the ground, so that the potential of the heat exchanger 102 can be zero. Further, the high frequency voltage reaching the inner ring of the bearing 15 from the stator core 11 through the rotating body 30 is also transmitted from the rotating shaft 16 and the fan 103 to the heat exchanger 102 and, as a result, generated in the inner ring of the bearing 15. The potential to be suppressed can also be suppressed.

  In addition, as shown in FIG. 5, the stator core 11, which is a main generation source of the high-frequency signal that generates the shaft voltage, is electrically connected to the ground unit 110 via the connection pin 24. For this reason, since the high frequency signal generated from the stator core 11 also flows into the ground, the high frequency signal generated in the stator core 11 can be attenuated, and the potential generated in the inner ring and the outer ring of the bearing can be suppressed.

  Further, in the present embodiment, two brackets, that is, the bracket 17 and the bracket 19 are electrically connected by the conduction pin 22. By setting it as such a structure, both brackets are made into the same electric potential and the flow of the high frequency current through a rotating shaft is suppressed. Furthermore, by setting both brackets to the same potential, the potential difference between the inner and outer rings of the bearing 15a and the potential difference between the inner and outer rings of the bearing 15b can be approximated or the same. For this reason, the malfunction that electric corrosion concentrates and generate | occur | produces only in one bracket can be suppressed.

  As described above, the air conditioner 100 has the grounding part 110 for grounding the heat exchanger 102, the dielectric layer 50 is provided on the rotating body 30, and the stator core 11 is also connected to the grounding part 110. Electrically connected. Further, the bracket 17 and the bracket 19 are electrically connected to each other. For this reason, the shaft voltage of each of the bearing 15a and the bearing 15b can be suppressed low, and it becomes possible to suppress the occurrence of electrolytic corrosion. In addition, the same effect can be obtained by grounding the stator core directly to earth ground.

  In the above description, the example in which the stator core 11 is electrically connected to the ground part 110 has been described. However, the bracket 17 and the bracket 19 that are electrically connected to each other are further connected to the ground part 110. It is good also as a structure which connects electrically. FIG. 6 is a diagram schematically illustrating another configuration example of the air conditioner 100 according to the embodiment of the present invention. In the configuration shown in FIG. 6, the connection pin 24 and the conduction pin 22 are further electrically connected, and this connection is electrically connected to the ground part 110. By adopting such a configuration, the brackets 17 and 19 are also grounded, the high frequency voltage generated in the brackets 17 and 19 can be suppressed, and the shaft voltage can be lowered.

  FIG. 7 is a diagram schematically showing still another configuration example of the air conditioner 100 according to the embodiment of the present invention. In the configuration shown in FIG. 7, the connection pin 24 and the conduction pin 22 are electrically connected, and this connection is electrically connected to the ground part 110 via a capacitor. By adopting such a configuration, only the high-frequency signal is grounded via the capacitor 111, so that it is possible to reduce electric noise and reduce noise. 5 may be configured such that only the stator core 11 is electrically connected to the grounding part 110 via the capacitor 111.

  As described above, the air conditioner of the present invention includes a heat exchanger that includes a conductive metal member and performs heat exchange, a fan that blows air that is air-conditioned by the heat exchanger, and a fan connected And an electric motor that rotationally drives the fan by the rotating shaft, and has a grounding portion for grounding at least the conductive metal member of the heat exchanger. Further, the electric motor includes a stator in which a winding is wound around a stator iron core, a rotor disposed opposite to the stator around the rotation axis, a rotation body provided with a dielectric layer, and a rotation shaft. And two conductive brackets for fixing the bearing. And it is the structure which provided the dielectric material layer between the rotating shaft and the outer periphery of the rotary body, and electrically connected the stator core to the grounding part.

  With such a configuration, since the stator core is connected to the grounding portion, the potential of the stator core becomes zero and the shaft voltage can be reduced. Furthermore, since the heat exchanger is also connected to the grounding portion, a high-frequency signal that circulates from the heat exchanger to the rotating shaft through the fan can be attenuated. Furthermore, the impedance balance between the stator side and the rotor side can be maintained, and the shaft voltage can be reduced. For this reason, the potential difference between the outer ring and the inner ring of the bearing, that is, the shaft voltage can be suppressed extremely low, and the occurrence of electrolytic corrosion can also be suppressed. Therefore, according to this invention, the air conditioner which suppressed generation | occurrence | production of the electric corrosion in the bearing of the built-in electric motor can be provided.

  The air conditioner of the present invention can reduce the shaft voltage of the built-in electric motor, and is optimal for suppressing the occurrence of electrolytic corrosion of the bearing. Therefore, it is effective for an indoor unit of an air conditioner.

DESCRIPTION OF SYMBOLS 10 Stator 11 Stator core 12 Stator winding 13 Insulation resin 13a Main body protrusion 14 Rotor 15, 15a, 15b Bearing 16 Rotating shaft 17, 19 Bracket 18 Printed circuit board 20 Connection line 22 Conduction pin 23 Through hole 24 Connection pin DESCRIPTION OF SYMBOLS 30 Rotating body 31 Rotor core 31a Outer iron core 31b Inner iron core 32 Magnet 35 Fastening part 50 Dielectric layer 100 Air conditioner 101 Housing | casing 102 Heat exchanger 103 Fan 104 Electric motor 105 Power supply part 110 Grounding part 111 Capacitor

Claims (7)

A heat exchanger that includes a conductive metal member that performs heat exchange, a fan that blows air that is air-conditioned by the heat exchanger, and an electric motor that rotationally drives the fan by a rotating shaft connected to the fan An air conditioner equipped with
A grounding portion for grounding at least the conductive metal member of the heat exchanger;
The motor is
A stator with windings wound around the stator core;
A rotor including a rotating body that holds a permanent magnet in a circumferential direction facing the stator, and the rotating shaft that fastens the rotating body so as to penetrate the center of the rotating body;
A bearing that supports the rotating shaft;
Two conductive brackets for fixing the bearing;
An air conditioner, wherein a dielectric layer is provided between the rotating shaft and the outer periphery of the rotating body, and the stator core is electrically connected to the grounding portion. The air conditioner according to claim 1, wherein the two brackets are electrically connected to each other. The air conditioner according to claim 2, wherein the two brackets are electrically connected inside the electric motor. The air conditioner according to claim 2, wherein the two brackets electrically connected to each other are further electrically connected to the grounding portion. The air conditioner according to any one of claims 1 to 4, wherein at least the stator iron core is electrically connected to the grounding portion via a capacitor. 2. The air conditioner according to claim 1, wherein at least one of the two brackets and the stator core around which the winding is wound are integrally formed of an insulating resin. The air conditioner according to any one of claims 1 to 6, wherein the winding wound around the stator core is driven by a pulse width modulation type inverter.

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