CN203933231U - Motor, load combination and the air conditioner that possesses load combination - Google Patents

Abstract

The utility model relates to an electric motor, a load combination and an air conditioner equipped with the load combination. The electric motor of the utility model has a stator, a rotor and a pair of bearings. The stator includes a stator core and a stator winding wound around the stator core. The rotor includes a rotor core located inside the stator core and a rotating shaft penetrating through the axis of the rotor core. A pair of bearings rotatably supports the rotating shaft. One of the pair of bearings is a ball bearing and the other bearing is a plain bearing. A ball bearing has an inner ring, an outer ring, and rolling elements located between the inner ring and the outer ring. It also has a connection path portion for electrically connecting the outer ring and the sliding bearing. With this configuration, a motor with high resistance to galvanic corrosion can be realized.

Description

Motor, load combination, and air conditioner with load combination

technical field

The utility model relates to a motor and load combination used in air conditioners and the like.

Background technique

Conventionally, in a symmetrical three-phase AC circuit based on a sine wave, the neutral point of the Y-connection line has always been shown as a constant value when the conditions constituting the loop circuit of each phase are the same. No potential difference occurs between the neutral point of the Y-connection line on the power supply side and the neutral point of the Y-junction line on the load side. At this time, as the sine wave of the three-phase power supply, a distortion-free sine wave containing no harmonic components is applied.

In addition, in a symmetrical three-phase AC circuit, when the conditions constituting the loop circuits of the respective phases are unbalanced, the following cases are known. That is, the neutral point of the Y-junction line on the load side is not a zero potential but a potential of a certain value. The above situation is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-340637.

In addition, the observation of the shaft voltage requires some time, for example, as shown below. That is, the observation of the shaft voltage is to measure the potential difference of a certain circuit part of the symmetrical three-phase AC circuit and the midpoint of the voltage dividing circuit temporarily set according to the situation as a virtual neutral point.

In a practical symmetrical three-phase AC circuit, the three-phase power supply sometimes becomes unbalanced for various reasons. Or, in a symmetrical three-phase AC circuit, the sine wave supplied by the three-phase power supply sometimes contains several higher harmonic components. In addition, it can be observed that a slight potential is generated at the neutral point of the Y-junction line on the power supply side and the neutral point of the Y-junction line on the load side. And, due to the change in the potential of the neutral point, a voltage is induced in the rotating shaft included in the generator and the rotating shaft included in the motor. The induced voltage is observed as a so-called shaft voltage. This shaft voltage is sometimes applied to an inner ring of a bearing for rotatably supporting a rotating shaft.

On the other hand, the outer ring of the bearing is electrically connected to the outer shell of the generator, the motor, or the ground. Therefore, the outer ring of the bearing has a potential different from that of the inner ring of the bearing. That is, a potential difference is generated between the inner ring of the bearing and the outer ring of the bearing. Therefore, when the outer ring and the inner ring are electrically connected via the rolling elements of the bearing, electric discharges are generated between the outer ring, the rolling elements, and the inner ring. When a discharge occurs, a discharge trace is left at the place where the discharge occurred. This electric discharge mark is called electrocorrosion. When discharge marks, that is, electrical corrosion, occur, problems occur when the bearing rotates.

For example, as disclosed in the following patent documents, in a generator of a three-phase power supply, the magnetic circuit may become unbalanced due to errors, misalignment, etc., which occur when assembling the generator. If the magnetic circuit is unbalanced, a symmetrical three-phase AC circuit cannot be obtained, so an unbalanced three-phase AC is produced. When an unbalanced three-phase AC is generated, a potential is generated at the neutral point, and thus a shaft voltage is generated.

Patent documents include JP-A-47-41121, JP-A-50-76547, JP-A-57-16549, and the like.

In addition, the field power supply supplies power to the field winding of the generator. As an excitation power source, an excitation device using a thyristor or the like may be used. In this case, a voltage of a non-sinusoidal waveform including a large number of harmonics is applied to the field winding. The generator has an equivalent impedance component of the generator components including the field winding. The applied voltage with a non-sinusoidal waveform generates a shaft voltage caused by the excitation power supplied by the excitation device through an equivalent impedance component.

In addition, as disclosed in the above-mentioned patent documents and the like, the following peculiar phenomenon occurs in the generator. That is, the steam collides with the blades of the steam turbine included in the generator. Part of the vapor after the collision is ionized and charged. The charge generated by the ionization of the vapor is transferred to the rotating shaft by means of the equivalent impedance component. The charge transferred to the rotating shaft appears as a shaft voltage of the generator. It is well known that shaft voltages of generators lead to galvanic corrosion of bearings.

On the other hand, Japanese Patent Application, JP-A-10-32953 discloses the following. That is, in the motor on the load side in a symmetrical three-phase AC circuit, a shaft voltage is generated due to an unbalance generated in the three-phase AC circuit. The motor on the load side develops galvanic corrosion on the bearings due to the generated shaft voltage. In addition, Japanese Patent Application, Unexamined Patent Publication No. 10-32953 discloses that an inverter device is used to drive a motor. That is, in the motor, momentary voltage imbalance occurs every time the power supply is switched. In other words, the potential of the neutral point of the motor fluctuates at a very high frequency. The frequency sometimes reaches several MHz. Therefore, since the potential of the neutral point fluctuates, an axial voltage is generated and an axial current flows. As a result, electrical corrosion occurs on the bearings of the motor.

Recently, in the field of electric motors, a driving technique using an inverter device is very popular. Drive technology using an inverter device is completely different from that using a voltage source that generates an undistorted sine wave. That is, a virtual three-phase drive is performed by configuring a rectangular-wave voltage source using the driving technique of the inverter device. In Japanese patent application, Japanese Patent Application Laid-Open No. 10-32953, the following matters are disclosed. That is, in the driving technology using the inverter device, the shaft voltage is generated due to the fluctuation of the potential of the neutral point. When a shaft voltage is generated, a shaft current flows in the motor. As a result, electrical corrosion easily occurs on the bearings of the motor.

As is well known, the drive technology using an inverter device is not based on a symmetrical three-phase AC drive using a distortion-free sine wave as a power source. Therefore, there is no possibility that the voltages of the respective phases cancel each other out and always reach a zero level. That is, a voltage having a certain value is generated at the neutral point of the Y-junction of the motor.

For example, the following cases are disclosed in the non-patent literature mentioned later. That is, the motor driven by the inverter device has a neutral point of the Y-junction. At the neutral point of the Y-junction line, voltage changes with large amplitudes such as convex waveforms and square waves are periodically generated. The maximum value of convex wave and square wave sometimes reaches the power supply voltage value of the inverter device.

In the non-patent literature, there is "Shaft voltage of an inverter-driven induction motor (shaft voltage of an inverter-driven induction motor)" published in "Fuji Times Vol. 72, No. 2 (February 1999)" ( P.144～P.149).

As shown in this non-patent document, the potential change at the neutral point is observed as the shaft voltage of the rotating shaft.

Also as disclosed in the non-patent literature, etc., the driving voltage of each phase supplied from the inverter device is transmitted to the outside of the stator through the following path as electric energy. That is, the drive voltage of each phase is transmitted from the stator winding of the stator included in the motor to the outside of the stator via the impedance components of the members constituting the stator.

Electric energy is transmitted to the rotor of the motor by means of the distributed capacitance of the motor between the stator and the rotor. And, electric energy reaches the rotating shaft via the impedance component of the members constituting the rotor. The axis of rotation is located at the neutral point of the Y junction line equivalent to a symmetrical three-phase AC circuit. Therefore, some potential changes are observed on the axis of rotation. As mentioned above, this potential is called shaft voltage.

In a symmetrical three-phase AC circuit, a third harmonic component such as a triple wave exists in each phase. The 3rd harmonic components do not cancel each other out. It is known that the third harmonic component is observed at the neutral point of the Y junction line. In addition, it is known that an unbalanced component of each phase is also observed at the neutral point of the Y-junction line.

In addition, as a driving method of a motor, inverter driving using a pulse width modulation (Pulse Width Modulation) method (hereinafter referred to as "PWM method") is often used. In the case of inverter driving using the PWM method, the potential of the neutral point of the winding does not become zero. As mentioned above, some potential is developed at the neutral point of the winding.

The rotation axis of the motor can also be considered as the neutral point of the Y junction line equivalent to the symmetrical three-phase AC circuit. Similar to the potential change that occurs at the neutral point of the winding, some potential changes also occur on the rotating shaft of the motor.

If a shaft voltage is generated due to inverter driving, a potential difference will be generated between the outer ring of the bearing and the inner ring of the bearing. High-frequency components generated by switching are included in the shaft voltage. An oil film exists inside the bearing. When the potential difference caused by the shaft voltage reaches a voltage at which the insulation of the oil film is destroyed, a high-frequency current flows inside the bearing. Since a high-frequency current flows inside the bearing, electrical corrosion occurs inside the bearing. When the galvanic corrosion progresses, a wavy wear phenomenon occurs inside the inner ring of the bearing or inside the outer ring of the bearing, which may cause abnormal noise. In electric motors, galvanic corrosion is a representative undesirable phenomenon that needs to be solved.

As described above, galvanic corrosion is a phenomenon in which members constituting a bearing are damaged by arc discharge. Due to the shaft voltage, a potential difference is generated between the inner ring of the bearing and the outer ring of the bearing. The discharge current generated by the shaft voltage flows along the path of the inner ring of the bearing - the balls as rolling elements - the outer ring of the bearing. Therefore, in order to suppress the occurrence of galvanic corrosion, the following countermeasures have been proposed.

(1) Make the inner ring of the bearing and the outer ring of the bearing in a conduction state.

(2) Make the inner ring of the bearing and the outer ring of the bearing in an insulating state.

(3) Reduce the shaft voltage.

As a specific method for realizing the above (1), for example, the lubricant used for the bearing is a lubricant having conductivity. However, there are problems such as that the conductivity of the conductive lubricant deteriorates over a period of time or lacks reliability when rubbing and sliding against each other.

As another specific method for realizing the above (1), it is also conceivable to provide a brush on the rotating shaft to make it in a conduction state. However, this method has problems such as generation of abrasive powder of the brush or requiring a space for installing the brush.

As a specific method for realizing the above (2), for example, changing the iron balls positioned inside the bearing to non-conductive ceramic balls is exemplified. This method is very effective in suppressing the occurrence of electrical corrosion. However, this method has a problem of high cost, so it cannot be adopted for general-purpose motors.

As a specific method for realizing the above (3), the method disclosed in JP 2010-121807 A is known. That is, a fan formed in a cylindrical shape along an axis is attached to the indoor unit body of the air conditioner. The fan is made of conductive material. The fan has a motor mounted on one side of the shaft. The fan is attached to the output side of the rotating shaft of the motor. The fan is fitted with plain bearings on the other side of the shaft. The fan is rotatably supported by the indoor unit main body via sliding bearings. Plain bearings are electrically conductive. The sliding bearings are grounded by means of grounding devices.

With this configuration, the shaft voltage generated on the rotating shaft of the motor is discharged to the ground via the grounding device. Therefore, a method for preventing the occurrence of galvanic corrosion in an electric motor has been proposed.

However, the method of grounding the rotating shaft disclosed in JP 2010-121807 A has the following problems. That is, the impedance components of the components constituting the motor can be converted into equivalent circuits. Specifically, in the motor, the rotating shaft and the outer ring of the ball bearing are converted into an equivalent circuit. At this time, it is considered that the potential of the rotating shaft, that is, the shaft voltage becomes higher than the potential of the outer ring by the grounding device between the potential of the rotating shaft and the potential of the outer ring of the ball bearing. It was found that galvanic corrosion occurs in the electric motor as a result.

In addition, in order to discharge the shaft voltage of the motor from the output shaft to the ground via the grounding device, the fan has the following configuration. That is, the fan attached to the output shaft has a double support structure in which the main body including the blades is supported on both sides in the axial direction. The grounding device is connected to the bearing on one side of the fan forming a double bearing configuration.

In addition, this structure cannot be applied to a cantilever structure in which a fan is supported by a shaft on only one side.

In addition, in recent years, a configuration using ball bearings on both sides of a rotor has become mainstream in electric motors controlled by inverter drive by a PWM method. However, conventional motors generally have a structure in which sliding bearings are used on both sides of the rotor.

The reason for changing the bearing from a plain bearing to a ball bearing is as follows. That is, when both sides of the rotor are supported by a pair of bearings, an alignment function is required. That is, the sliding bearing also requires an alignment function. In order for the sliding bearing to have an aligning function, it is necessary to make the bearing into a spherical shape and to require parts for supporting the bearing, etc. Therefore, material costs become high. Therefore, ball bearings are gradually adopted because they are relatively cheap.

For such reasons, the use of plain bearings in general-purpose motors is not supported from an economical point of view, so it has not been adopted.

Utility model content

The electric motor of the utility model has a stator, a rotor and a pair of bearings.

The stator includes a stator core and a stator winding wound around the stator core.

The rotor includes a rotor core located inside the stator core and a rotating shaft penetrating through the axis of the rotor core.

A pair of bearings rotatably supports the rotating shaft.

In the above technical solution, one bearing in the pair of bearings is a ball bearing, and the other bearing is a sliding bearing. A ball bearing has an inner ring, an outer ring, and rolling elements located between the inner ring and the outer ring. It also has a connection path portion for electrically connecting the outer ring and the sliding bearing.

In particular, the technical solution which exhibits a remarkable function and effect is as follows.

That is, the motor further includes a resin case that covers at least a part of the stator core and the stator winding.

In addition, the sliding bearings used in electric motors are made conductive.

In addition, sliding bearings used in electric motors are porous metal bodies impregnated with lubricating oil.

Also, one end of the rotating shaft for the motor is used as an output shaft for connecting a load. In this technical solution, among the pair of bearings, the ball bearing is located on the output shaft side. Of the pair of bearings, the slide bearing is located on the side opposite to the output shaft side.

The electric motor further has an output shaft-side end cover located on the output shaft side with respect to the rotor core in the direction of the shaft center. The output shaft side cover includes a ball bearing housing for housing the ball bearings.

The motor further includes an output shaft opposite end cover located on the opposite side to the output shaft side with respect to the rotor core in the direction of the shaft center. The end cover on the opposite side of the output shaft includes a sliding bearing housing portion for housing the sliding bearing.

The load combination of the present invention has the above-mentioned motor and a load connected to the motor. The load includes a main body and a load shaft, and the load shaft runs through the load axis of the main body. The load shaft has a load bearing that rotatably supports the load on the side opposite to the motor connection side. The electric motor has a sintered and oil-impregnated sliding bearing as one of a pair of bearings on the opposite side of the output shaft.

In particular, the load is a cross flow fan.

The air conditioner of this invention has the said load combination body, and the drive part for driving a load combination body.

The utility model adopts the above-mentioned technical solution to make the two bearings conductive, thereby making the outer ring of the ball bearing and the sliding bearing have the same potential. In addition, by mounting a conductive sliding bearing as one bearing, it is possible to reduce the axial voltage generated between the outer ring of the ball bearing and the inner ring of the ball bearing. Accordingly, it is possible to realize a motor with high resistance to galvanic corrosion.

In addition, the utility model can enjoy the centering function of the ball bearing by making the bearing on the other side a ball bearing. That is, the sliding bearing does not need to have an aligning function. Therefore, the sliding bearing is not limited to a specific shape such as a spherical shape, and the sliding bearing can be selected from a wide range. As a result, the present invention can also be applied to general-purpose electric motors, so the industrial value is also large.

In addition, the utility model uses the bearing on the output shaft side as a ball bearing. By employing this aspect, it is possible to prevent lubricant oil from leaking from the sliding bearing to the outside of the motor. Therefore, the electric motor of the present invention has long service life, high reliability and great industrial value.

Description of drawings

FIG. 1 is a cross-sectional view of a motor according to Embodiment 1 of the present invention.

Fig. 2 is an enlarged view of main parts in Fig. 1 .

Fig. 3 is a sectional view of a motor for comparison with the present invention.

Fig. 4 is a schematic diagram of a load combination in Embodiment 2 of the present invention.

It is explanatory drawing of the main part of the air conditioner in Embodiment 2 of this invention.

Detailed ways

This utility model utilizes the electric motor shown in Embodiment 1 mentioned later, reduces shaft voltage, and suppresses generation|occurrence|production of electric corrosion on a bearing. Moreover, as shown in each embodiment mentioned later, this invention provides the electric motor which suppresses generation|occurrence|production of electro-corrosion, and has long life and high reliability, a load combination, and the air conditioner which has a load combination.

Hereinafter, the electric motor, the load combination, and the air conditioner provided with the load combination according to each embodiment of the present invention will be described with reference to the drawings and tables.

In addition, the following embodiment is an example which actualized this invention, and does not limit the technical scope of this invention.

(Embodiment 1)

In Embodiment 1, a brushless motor mounted on an air conditioner as an electric device is taken as an example, and the motor will be described.

A brushless motor is used to drive the blower fan. In Embodiment 1, an inner rotor type motor in which the rotor is arranged on the inner peripheral side of the stator is illustrated and described.

Fig. 1 is a cross-sectional view of a motor according to Embodiment 1 of the present invention. FIG. 2 is an enlarged view of main parts of FIG. 1 . Fig. 3 is a sectional view of a motor for comparison with the present invention.

As shown in FIG. 1 , a brushless motor 21 as an electric motor has a stator 10 , a rotor 2 , and a pair of bearings, that is, an oil bearing 5 and a ball bearing 14 .

The stator 10 includes a stator core 9 and a winding 8 wound around the stator core 9 .

The rotor 2 includes a rotor core 15 located inside the stator core 9 and a rotating shaft 1 penetrating through an axis 1 a of the rotor core 15 .

A pair of bearings rotatably supports the rotating shaft 1 .

In the above structure, one of the pair of bearings is the ball bearing 14, and the other bearing is the oil-impregnated bearing 5 as a sliding bearing. As shown in FIG. 2 , the ball bearing 14 has an inner ring 14a, an outer ring 14b, and rolling elements 14c located between the inner ring 14a and the outer ring 14b.

Next, as shown in FIG. 1 , the brushless motor 21 has an end cap connection portion 3 as a connection path portion for electrically connecting the outer ring 14 b to the oil bearing 5 as a sliding bearing. The connection path part has the end cap connection part 3 as a main structural element.

In particular, the technical solution which exhibits a remarkable function and effect is as follows.

That is, the brushless motor 21 further includes an insulating resin 7 forming a resin case portion, and the insulating resin 7 covers the stator core 9 and at least a part of the winding 8 serving as the stator winding.

In addition, the oil impregnated bearing 5 as a sliding bearing used in the brushless motor 21 has electrical conductivity.

In addition, the oil-impregnated bearing 5 as a sliding bearing used in the brushless motor 21 is a porous metal body impregnated with lubricating oil.

Also, one end of the rotating shaft 1 for the brushless motor 21 is used as an output shaft 1b for connecting a load. In this structure, the ball bearing 14 among a pair of bearings is located in the output shaft 1b side. The oil-impregnated bearing 5 which is a sliding bearing among a pair of bearings is located in the side opposite to the output shaft 1b side.

Moreover, the brushless motor 21 has the end cover 13 as an output-shaft side end cover which is located on the output-shaft 1b side with respect to the rotor core 15 in the axial center 1a direction. The end cover 13 includes a ball bearing accommodating portion 13 a for accommodating the ball bearing 14 .

Furthermore, the brushless motor 21 has an end cover 6 as an end cover on the opposite side of the output shaft, and the end cover 6 is located on the side opposite to the output shaft side 1b with respect to the rotor core 15 in the direction of the axial center 1a. The end cover 6 includes a cylindrical portion 6 a serving as a sliding bearing housing portion for housing the oil-impregnated bearing 5 serving as a sliding bearing.

It demonstrates in more detail using FIGS. 1-3.

As shown in FIG. 1 , a coil 8 is wound around a stator core 9 . Between the stator core 9 and the winding 8, there is an insulator 11 formed of an insulating resin. Stator core 9 is molded together with other fixing members using insulating resin 7 as a molding material. In Embodiment 1, the above-mentioned members are integrally molded with insulating resin 7 . Thus, the brushless motor 21 is constituted by the stator 10 having an approximately cylindrical outer shape.

Inside the stator 10, the rotor 2 is inserted through a gap. The rotor 2 has a disc-shaped rotating body 17 including a rotor core 15 , and a rotating shaft 1 penetrating through an axis 1 a of the rotating body 17 . The rotating body 17 holds the magnet 16 of ferrite resin which is a permanent magnet in the circumferential direction facing the inner peripheral side of the stator 10 .

As shown in FIG. 1 , the rotating body 17 is an example of a structure in which a rotor core 15 and a magnet 16 made of ferrite resin are integrally molded. It is arranged such that the inner peripheral side of the stator 10 faces the outer peripheral side of the rotor 2 .

A ball bearing 14 and an oil bearing 5 for supporting the rotating shaft 1 are attached to the rotating shaft 1 included in the rotor 2 . A ball bearing 14 is attached to the output shaft 1 b side of the rotary shaft 1 . An oil-impregnated bearing 5 is attached to the output shaft opposite side of the rotary shaft 1 . As shown in FIG. 2, the ball bearing 14 on the side of the output shaft 1b is a cylindrical bearing having a plurality of iron balls as rolling elements 14c. The ball bearing 14 fixes the inner ring 14 a it has to the rotating shaft 1 . As shown in FIG. 1 , the rotary shaft 1 has an output shaft 1 b including a portion protruding from a main body of a brushless motor 21 as a motor. In this structure, the ball bearing 14 on the side of the output shaft 1 b supports the rotary shaft 1 . An oil-impregnated bearing 5 supports the rotary shaft 1 on the opposite side to the output shaft.

As shown in FIGS. 1 and 2 , the outer ring 14 b of the ball bearing 14 on the side of the output shaft 1 b is fixed by a conductive metal end cover 13 . The mounting position of the ball bearing 14 is determined by the ball bearing accommodating portion 13 a formed in the end cover 13 . The ball bearing accommodating portion 13 a is located at the center of the end cover 13 . The ball bearing accommodating portion 13a is formed with a concave portion opening toward the rotor core 15 in the direction of the axial center 1a.

On the other hand, the outer ring of the oil-impregnated bearing 5 on the opposite output side is fixed by a conductive metal end cover 6 . The attachment position of the oil impregnated bearing 5 is determined by the cylindrical part 6a which is a sliding bearing housing part formed in the end cover 6. As shown in FIG. A cylindrical portion 6 a serving as a sliding bearing housing portion is located at the center portion of the end cover 6 . The cylindrical part 6a is formed with the recessed part which has an opening toward the rotor core 15 in the axial center 1a direction.

With the above structure, the rotary shaft 1 is rotatably supported by the ball bearing 14 on the side of the output shaft 1b and the oil bearing 5 on the opposite side of the output shaft.

In addition, the ball bearing 14 on the side of the output shaft 1 b is filled with grease in a partial space inside the bearing. As the ball bearing 14 , for example, a ball bearing with two shields indicated by Japanese Industrial Standards (hereinafter referred to as “JIS”) or JIS B1513 can be used. The code of the bearing with two dust shields, that is, the "auxiliary symbol", is specified as "ZZ". The ball bearing 14 is also called "a ball bearing with shields on both sides".

Furthermore, as shown in FIG. 1 , the brushless motor 21 according to Embodiment 1 incorporates a circuit board 12 on which a drive circuit including a control circuit is mounted. In the brushless motor 21 , after incorporating the circuit board 12 , the end cover 13 on the side of the output shaft 1 b is press-fitted into the stator 10 . In this way, the brushless motor 21 is formed.

A plurality of connection lines 18 are connected to the circuit board 12 . The power supply voltage Vdc applied to the winding 8 , the power supply voltage Vcc of the control circuit, the control voltage Vsp for controlling the rotational speed, and the ground of the control circuit are supplied to the circuit board 12 via the connecting wire 18 .

In addition, the zero-potential point on the circuit board 12 on which the drive circuit is mounted is insulated from the earth ground and the primary-side power supply circuit. That is, the ground wire between the zero potential point and the earth and the primary side power supply circuit are in a floating state. Here, the zero potential point refers to a potential of 0 volts as a reference potential on the circuit board 12 . The zero potential point generally refers to a ground wiring called ground. The ground line included in the connection line 18 is connected to the zero potential point, that is, the ground wiring.

A power supply circuit for supplying a power supply voltage to the coil 8 is connected to the circuit board 12 on which the drive circuit is mounted. The power supply circuit is electrically insulated from the primary-side power supply circuit and the earth ground to which the primary-side power supply circuit is connected.

A power supply circuit for supplying a power supply voltage is connected to the control circuit. The power supply circuit is electrically insulated from the primary-side power supply circuit and the earth ground to which the primary-side power supply circuit is connected.

In addition, a control power supply is connected to the leads. In addition, the control circuit is connected to the ground. The lead wires, the ground wire and the ground wire of the independently grounded earth are electrically insulated.

That is, the drive circuit mounted on the circuit board 12 is electrically insulated from the potential of the primary-side power supply circuit and the potential of the earth ground. In other words, the drive circuit mounted on the circuit board 12 is in a potential floating state with respect to the potential of the primary side power supply circuit and the potential of the earth ground. This state is also called a potential floating state.

Therefore, the following power supply circuit is also called floating power supply. That is, among the target power supply circuits, there is a power supply circuit that supplies a power supply voltage to the coil 8 connected to the circuit board 12 . Alternatively, another power supply circuit includes a power supply circuit that supplies a power supply voltage to the control circuit.

The respective power supply voltages and control signals are supplied to the brushless motor 21 of the first embodiment configured as described above via the connecting wire 18 . When the respective power supply voltages and control signals are supplied, the drive circuit mounted on the circuit board 12 energizes the coil 8 wound and mounted on the stator 10 . When the winding 8 of the stator 10 is energized, a drive current flows in the winding 8 wound around the stator 10 . The magnetic field generated by winding 8 is converted into a concentrated magnetic field by means of stator core 9 .

Between the magnetic field generated by the stator core 9 and the magnetic field generated by the magnet 16 of ferrite resin, an attractive force and a repulsive force are generated according to the polarity of each magnetic field. The rotor 2 rotates around the rotating shaft 1 by the above-mentioned attractive and repulsive forces.

Next, a more detailed configuration of the motor according to Embodiment 1 will be described. As described above, the rotating shaft 1 of the brushless motor 21 is supported by the ball bearing 14 on the side of the output shaft 1 b and the oil bearing 5 on the opposite side of the output shaft. In addition, the ball bearing 14 and the oil-impregnated bearing 5 are also fixed by the respective end covers 13 and 6 . In Embodiment 1, the ball bearing 14 and the oil-impregnated bearing 5 are respectively fixed by the end cover 13 and the end cover 6 made of conductive metal.

That is, in the first embodiment, the end cap 6 and the end cap 13 are processed in advance from steel plates. Therefore, the dimensional accuracy of the end cap 6 and the end cap 13 is good. When higher motor output is required, the ball bearing 14 and the oil-impregnated bearing 5 can be fixed with high precision by using the metallic end cover 6 and the end cover 13 described above.

Specifically, it is formed by the following procedure. First, the end cover 6 is installed with respect to the oil impregnated bearing 5 on the opposite side of the output shaft.

The end cap 6 has a hollow cylindrical cup-shaped cylindrical portion 6a. The cylindrical portion 6a has an opening on one side. The end cap 6 has an annular flange portion 6b extending in the outer peripheral direction around the cylindrical portion 6a. The inner diameter of the cylindrical portion 6 a is smaller than the outer diameter of the oil bearing 5 . The oil-impregnated bearing 5 is press-fitted into the cylindrical portion 6a to be fixed.

The end cover 6 into which the oil bearing 5 is press-fitted is covered with an insulating resin 7 . The end cap 6 is integrally molded with the insulating resin 7 . Oil-impregnated bearing 5 is also fixed to insulating resin 7 via end cover 6 .

That is, the outer peripheral diameter of the flange portion 6 b included in the end cover 6 is larger than the outer peripheral diameter of the oil bearing 5 . Moreover, the outer peripheral diameter of the flange part 6b which the end cover 6 has is smaller than the outer peripheral diameter of the rotating body 17 at least.

If the end cover 6 on the side opposite to the output shaft is configured in this way, metal materials can be reduced. Specifically, when the flange portion 6 b has a larger outer diameter than that of the rotor 17 and covers the stator 10 , a large amount of metal material is required. Therefore, as described above, if it is configured as the end cover 6 used in the brushless motor 21 of the first embodiment, the use of metal materials can be suppressed, and an increase in cost can be suppressed.

Next, the ball bearing 14 on the output shaft 1 b side is fixed by the end cover 13 having an outer peripheral diameter substantially equal to that of the stator 10 . The end cover 13 attached to the side of the output shaft 1b has a substantially disc shape. The end cover 13 is formed at a central portion with a protrusion having an inner peripheral diameter substantially equal to the outer peripheral diameter of the ball bearing 14 . The inner side of the protrusion is hollow. As will be described later, the protruding portion serves as the ball bearing accommodating portion 13a.

Circuit board 12 is mounted on stator 10 covered with insulating resin 7 . The ball bearing 14 is press-fitted into the protrusion formed on the end cover 13 . In addition, the end cover 13 is press-fitted into the stator 10 so that the connection end formed on the outer periphery of the end cover 13 fits with the connection end of the stator 10 . Thus, the brushless motor 21 of the first embodiment is formed.

According to this structure, an assembly operation becomes easy. In addition, the outer ring 14b of the ball bearing 14 located on the side of the output shaft 1b is press-fitted into the metal end cover 13 to be fixed. Therefore, the brushless motor 21 according to Embodiment 1 can also suppress troubles caused by creep.

In addition, the motor according to Embodiment 1 has an end cap connecting portion 3 which is a connection path portion for electrically conducting between the end cap 13 on the output shaft 1b side and the end cap 6 on the opposite side of the output shaft. The end cap connecting portion 3 is partially or entirely embedded in the insulating resin 7 .

Specifically, the metal end cap 6 on the opposite side of the output shaft is electrically connected to the first conduction terminal 19 in advance. The metal end cap 13 on the side of the output shaft 1 b is electrically connected to the second conduction terminal 20 in advance. That is, as shown in FIG. 1 , the flange portion 6 b of the end cover 6 on the opposite side of the output shaft is connected to one end of the first conduction terminal 19 . The first conduction terminal 19 is arranged inside the insulating resin 7 . The first conduction terminal 19 is molded integrally with the insulating resin 7 similarly to the end cover 6 on the opposite side of the output shaft.

Furthermore, the first conduction terminal 19 is connected to one end of the end cap connection portion 3 . The end cap connecting portion 3 extends from the flange portion 6 b toward the outer peripheral direction of the brushless motor 21 inside the insulating resin 7 . In addition, it further extends from the vicinity of the outer periphery of the brushless motor 21 to the output shaft 1 b side along the rotating shaft 1 . The other end of the end cap connection portion 3 is connected to the second conduction terminal 20 .

Here, the first conduction terminal 19 is arranged inside the insulating resin 7 as a component located inside the brushless motor 21 . According to this configuration, it is possible to prevent the first conduction terminal 19 from being troubled by rust, external force, and the like. Therefore, it is possible to ensure highly reliable electrical connection with respect to the use environment of the brushless motor 21 , external stress applied to the brushless motor 21 , and the like.

Similarly, the second conduction terminal 20 is arranged inside the insulating resin 7 as a component located inside the brushless motor 21 . According to this configuration, it is possible to prevent the second conduction terminal 20 from being troubled by rust, external force, and the like. Therefore, it is possible to ensure highly reliable electrical connection against the use environment of the brushless motor 21 , external stress applied to the brushless motor 21 , and the like.

With such a structure, the metal end cap 13 on the output shaft 1 b side and the metal end cap 6 on the opposite side of the output shaft are connected via the first conduction terminal 19 , the end cap connection portion 3 , and the second conduction terminal 20 . are electrically connected.

Then, the end cover 6 and the end cover 13 are electrically connected to each other while the end cover 13 and the end cover 6 are insulated from the stator core 9 by the insulating resin 7 .

In this way, the outer ring 14b of the ball bearing 14 is electrically connected to the oil-impregnated bearing 5 which is a sliding bearing. In addition, the oil-impregnated bearing 5 is electrically connected to the rotating shaft 1 . This constitutes a configuration equivalent to a state in which the outer ring 14b included in the ball bearing 14 and the inner ring 14a included in the ball bearing 14 are electrically short-circuited. As a result, the potential difference causing the axial voltage between the outer ring 14b included in the ball bearing 14 and the inner ring 14a included in the ball bearing 14 becomes extremely small. Specifically, the potential difference generated between the outer ring 14b and the inner ring 14a can be reduced to the level of the voltage generated at both ends of the electrical short circuit. Therefore, the brushless motor 21 can suppress the occurrence of galvanic corrosion.

(Example 1)

As a first embodiment, a single row deep groove ball bearing of JIS code 608 is used as the ball bearing 14 in the brushless motor 21 shown in FIG. 1 .

The ball bearing 14 has an inner ring 14a, an outer ring 14b, rolling elements 14c, and grease. Grease forms a grease film using preload from a preload spring. The inner ring 14a, the outer ring 14b, and the rolling elements 14c are lubricated by a grease film.

Grease is insulating. Grease utilizes the dielectric constant of the grease itself and also produces an equivalent capacitance component. That is, a capacitor generated by a grease film is formed. In the grease used in Example 1, ester-based oil was used as the base oil, and lithium soap was used as the thickener. Grease adjusts the capacitance value of the capacitor by adjusting the base oil and thickener. In this way, the grease adjusts the potential difference generated between the outer ring 14 b of the ball bearing 14 and the inner ring 14 a of the ball bearing 14 , which causes the shaft voltage to be generated.

In this way, the grease is selected according to the state of the motor equivalent circuit which differs according to the structure of each motor. By selecting the grease, it is possible to adjust the potential difference between the outer ring 14 b of the ball bearing 14 and the inner ring 14 a of the ball bearing 14 , which causes the shaft voltage to be generated.

Next, as the oil-impregnated bearing 5 on the opposite side to the output shaft, a cylindrical bearing made of sintered metal is used. The oil-impregnated bearing 5 is press-fitted into a metal end cover 6 . In the first embodiment, the sliding length of the oil-impregnated bearing 5 is set to 4.5 mm. In addition, if the oil-impregnated bearing 5 increases its sliding length, it can also be used for a motor that requires torque. In addition, the oil-impregnated bearing 5 can also be used as a high-efficiency motor if its sliding length is reduced.

Inside the metal end cover 6 , a resin-made oil slinger 4 is disposed between the oil-impregnated bearing 5 and the rotating body 17 . Apply oil repellent to the end face of end cap 6.

According to the above configuration, the oil impregnated bearing 5 pressed into the end cover 6 is less likely to be affected by the ambient air temperature around where the brushless motor 21 is used. The brushless motor 21 can prevent the outflow of oil by utilizing the Marangoni effect. Therefore, a long-life motor can be realized.

In Table 1, the measurement results of the above-mentioned Example 1 are shown. That is, the brushless motor 21 having the configuration of the first embodiment is driven at normal temperature. The brushless motor 21 was tested for 10000 hours at a speed of 1000 r/min. In Table 1, the results of measuring driving noise under the present conditions are shown.

[Table 1]

(comparative example)

As shown in FIG. 3 , in the comparative example, the ball bearing 14 and the ball bearing 22 were used for two bearings, the bearing on the side of the output shaft 1b and the bearing on the opposite side of the output shaft, respectively. The ball bearings 14 and 22 use ester-based oil as the base oil of the grease, and lithium soap as a thickener. The inner diameter of the end cover 6 is substantially equal to the outer diameter of the ball bearing 14 located on the output shaft 1b side. The ball bearing 22 is pressed into the end cover 6 . Other structures are the same as those of Embodiment 1.

The brushless motor 21a having the configuration of Comparative Example 1 was driven at normal temperature. The brushless motor 21a was tested for 10000 hours at a speed of 1000r/min. In Table 1, the results of measuring driving noise under the present conditions are shown.

As shown in Table 1, the driving noise under the condition of 1000 r/min after 10000 hours was optimized in Example 1, and deteriorated in Comparative Example. From this, it can be presumed that galvanic corrosion occurred in the comparative example.

It is presumed that this is because the surface roughness deteriorates due to the sliding of the rolling elements in the bearing through long-term driving. It is considered that the thickness of the oil film decreases due to deterioration of the surface roughness, and the dielectric breakdown withstand voltage of the bearing decreases. It is considered that the dielectric breakdown withstand voltage of the bearing decreases with the driving time of the brushless motor. Therefore, even if the breakdown withstand voltage of the bearing is higher than the shaft voltage initially, the breakdown voltage of the bearing may drop below the shaft voltage by driving the brushless motor for a long time. As a result, there is a problem that the reliability cannot be ensured because the noise generated by the galvanic corrosion lasts for a long time.

In Embodiment 1, the main factor for optimizing the driving noise is to use a sliding bearing as the bearing on the opposite side of the output shaft. As features of sliding bearings, noise can be optimized after driving compared to when sliding starts by adapting the bearing surface to the rotating shaft.

Furthermore, utilizing the characteristics of the present invention, that is, by providing conduction between the outer ring of the ball bearing and the sliding bearing, the following effects can be expected. That is, a shaft voltage is generated between the outer ring of the ball bearing and the inner ring of the ball bearing. The characteristic structure of this invention can suppress the potential difference which causes axial voltage generation, and can also suppress the generation|occurrence|production of electric corrosion. As a result, the electric motor of the present invention can reduce defects due to electrical corrosion, and thus become an electric motor with high industrial value.

In addition, the noise measurement was performed under the same operating conditions of an air temperature of 20° C. and a rotational speed of 1000 r/min. The posture of the motor during operation is set so that the axis of rotation is horizontal. The microphone was installed at a position 15 cm away from the motor, and the noise was measured by the A characteristic. In addition, regarding the measurement environment, the noise when the motor was not driven, that is, the dark noise was 13 dB.

(Embodiment 2)

Next, in the load combination shown in Embodiment 2, the motor described in Embodiment 1 is mounted with a cross-flow fan as a load.

In addition, the same code|symbol is attached|subjected to the structure similar to the structure shown in said Embodiment 1, and the description is used for it.

Fig. 4 is a schematic diagram of a load combination in Embodiment 2 of the present invention. It is explanatory drawing of the main part of the air conditioner in Embodiment 2 of this invention.

The load combination 43 of the present invention has the above-mentioned brushless motor 21 and a cross-flow fan 31 as a load, and the cross-flow fan 31 is connected to the brushless motor 21 . The cross-flow fan 31 serving as a load includes a main body and a load shaft 38 passing through the load shaft center of the main body. The main body has blades 32 , a support plate 33 , a motor-side end plate 34 , and a bearing-side end plate 35 . As described below using FIG. 5 , the load shaft 38 has a ball bearing 42 as a load bearing that rotatably supports the cross-flow fan 31 as a load on the opposite side to the side where the brushless motor 21 is connected. The brushless motor 21 has an oil-impregnated bearing 5 as a sintered and oil-impregnated sliding bearing as a bearing located on the opposite side of the output shaft 1 b among a pair of bearings.

In particular, the load is a cross-flow fan 31 .

The air conditioner 50 of this invention has the said load combination body 43 and the drive part 51 for driving the load combination body 43. As shown in FIG.

Further explain in detail using drawings.

As shown in FIG. 4 , the load combination 43 has the cross-flow fan 31 as a load.

As shown in FIG. 5 , a cross-flow fan 31 as a load has a plurality of blades 32 and a plurality of support plates 33 for supporting the blades 32 . The cross-flow fan 31 has a motor-side end plate 34 at one end and a bearing-side end plate 35 at the other end. The support plate 33 , the motor-side end plate 34 , and the bearing-side end plate 35 are connected to the blade 32 by ultrasonic welding or the like. The blade 32 , the support plate 33 , the motor-side end plate 34 , and the bearing-side end plate 35 are connected along the axial direction in which the cross-flow fan 31 rotates.

As shown in FIG. 5 , a rubber protrusion 36 for absorbing vibration is attached to the motor-side end plate 34 . An attachment shaft 37 for attaching the cross-flow fan 31 to the rotating shaft 1 of the brushless motor 21 is formed on the motor-side end plate 34 .

In addition, a load shaft 38 is formed on the bearing-side end plate 35 .

On the other hand, the cross-flow fan 31 is attached to the rotating shaft 1 of the brushless motor 21 . The mounting shaft 37 and the rotating shaft 1 are fixed by fixing screws 41 . On the other hand, the load shaft 38 of the cross flow fan 31 is supported by the ball bearing 42 . With this configuration, the cross-flow fan 31 is rotationally driven by the rotating shaft 1 included in the brushless motor 21 .

In addition, since the air conditioner 50 equipped with the load combination 43 of the present invention can suppress the occurrence of electrical corrosion on the bearings, it can also suppress noise due to electrical corrosion. Thereby, a higher-quality air conditioner can be provided.

The electric motor, the load combination and the air conditioner with the load combination of the utility model have the advantages of long life, miniaturization, high reliability and high quality, and have great industrial value.

Claims (10)

1. a motor, is characterized in that, has:

Stator, it comprises stator core and is installed on the stator winding of said stator iron core with reeling;

Rotor, its rotor core that comprises the inner side that is positioned at said stator iron core and the rotating shaft that runs through the axle center of above-mentioned rotor core; And

Pair of bearings, it supports above-mentioned rotating shaft rotation freely,

Wherein, a bearing in above-mentioned pair of bearings is ball bearing, and another bearing is sliding bearing, and this ball bearing has inner ring, outer ring and the rolling element between above-mentioned inner ring and above-mentioned outer ring,

Also have for by the access path portion being electrically connected between above-mentioned outer ring and above-mentioned sliding bearing.

2. motor according to claim 1, is characterized in that,

The resin enclosure portion also with at least a portion that covers said stator iron core and said stator winding.

3. motor according to claim 1, is characterized in that,

Above-mentioned sliding bearing has conductivity.

4. motor according to claim 1, is characterized in that,

The metallic object of the porous of above-mentioned sliding bearing is impregnation lubricating oil.

5. motor according to claim 1, is characterized in that,

One end of above-mentioned rotating shaft is as for connecting the output shaft of load,

In above-mentioned pair of bearings, above-mentioned ball bearing is positioned at above-mentioned output shaft side, and above-mentioned sliding bearing is positioned at a side contrary to above-mentioned output shaft side.

6. motor according to claim 5, is characterized in that,

Also have output shaft side end cap, this output shaft side end cap is positioned at above-mentioned output shaft side in the direction in above-mentioned axle center for above-mentioned rotor core,

Above-mentioned output shaft side end cap comprises for accommodating the ball bearing resettlement section of above-mentioned ball bearing.

7. motor according to claim 5, is characterized in that,

Also have output shaft opposition side end cap, this output shaft opposition side end cap is positioned at a side contrary to above-mentioned output shaft side in the direction in above-mentioned axle center for above-mentioned rotor core,

Above-mentioned output shaft opposition side end cap comprises for accommodating the sliding bearing resettlement section of above-mentioned sliding bearing.

8. a load combination, is characterized in that,

The above-mentioned load that there is motor claimed in claim 5 and be connected with above-mentioned motor,

Above-mentioned load comprises main part and bearing axle, and this bearing axle runs through the load axle center of aforementioned body portion,

Above-mentioned bearing axle has with the contrary side of above-mentioned motor connection side the load bearing that above-mentioned load rotation is supported freely,

Above-mentioned motor has the sliding bearing after sintering oil-containing, and this sliding bearing is as the bearing of the opposition side that is positioned at above-mentioned output shaft in above-mentioned pair of bearings.

9. load combination according to claim 8, is characterized in that,

Above-mentioned load is cross flow fan.

10. an air conditioner, is characterized in that,

There is claim 8 or load combination claimed in claim 9 and for driving the drive division of above-mentioned load combination.