JP2011147313A - Electric motor, compressor, and refrigeration cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor which can suppress an iron loss even if pseudo slots are formed at tips of teeth of a stator, can smooth a distribution of the density of magnetic flux, and can further reduce cogging torque. <P>SOLUTION: The electric motor includes: the cylindrical stator 3 having the teeth 33 formed between the slots 32 arranged in the circumferential direction, and coils wound around the teeth 33; and a rotor 4 which is installed with an axial center of the stator 3 as its center, with air gaps between tips of the teeth 33 of the stator 3, and has permanent magnet insertion holes arranged in the circumferential direction and permanent magnets 42 inserted in the permanent magnet insertion holes. The pseudo slots 34 are formed at the tips of the teeth 33 of the stator 3, radially extending slits 44 are formed between the permanent magnet insertion holes of the rotor 4 and the external periphery of the rotor 4 opposing the permanent magnet insertion holes, and the lengths from the tips of the slits 44 at the external peripheral side of the rotor 4 to the external periphery of the rotor 4 are nonuniform. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a permanent magnet type motor that is an electric motor, a compressor including the permanent magnet type motor, and a refrigeration cycle apparatus including the compressor.

2. Description of the Related Art Conventionally, a permanent magnet motor for driving a compressor that suppresses cogging torque that causes vibration and noise and that is highly efficient is known.
The cogging torque is a force that is always generated in a permanent magnet type motor having saliency, and is a magnetic force against the rotor position (rotation angle) that acts between the stator teeth and the permanent magnet placed on the rotor when no current is applied. This is a torque pulsation caused by a change in suction force. That is, the position where the magnetic resistance between the stator and the rotor is minimum is magnetically most stable, and the rotor tries to stop at that position. Furthermore, in order to rotate the rotor from that position, a torque sufficient to overcome the magnetic attractive force is required. However, once the rotation is performed at a certain speed, since the positive and negative torques become alternating vibration torques, the average value of the cogging torque becomes zero.

  When the cogging torque is generated, speed fluctuation occurs, which causes vibration and noise to be transmitted along the rotor shaft, and acts like a static torque to increase the starting torque of the motor. At the same time, the magnetic flux changes due to the rotation of the rotor, and when there is hysteresis loss and eddy current loss, it acts like solid friction and viscous friction. Therefore, reduction of cogging torque is required. This cogging torque is generated because the magnetic resistance between the stator and the rotor changes depending on the rotation angle, and is caused by Maxwell's stress proportional to the square of the magnetic flux density. This change in the magnetic resistance largely depends on the harmonic component of the stator slot space and the harmonic component of the magnetic flux of the permanent magnet disposed in the rotor. Therefore, in order to reduce the cogging torque, it is desirable to smooth the distribution of the magnetic flux density in the gap portion in the circumferential direction to reduce the harmonic component.

Conventionally, as a permanent magnet type motor that suppresses cogging torque, for example, with respect to the pole center of the permanent magnet provided in the rotor, the magnet curvature is reduced so that the air gap length at both ends of the magnet is increased, and the stator Some teeth have a pseudo slot at the tip.
With such a structure, in addition to the effect that the spatial harmonics of the slots are dispersed by the pseudo slot at the teeth tip of the stator and the frequency band of the cogging torque can be dispersed and shifted to the higher order side, the permanent magnet can be By reducing the curvature of the magnet so that the air gap length at both ends of the magnet increases with respect to the pole center, the change in the magnetic force between the poles of the permanent magnet can be smoothed, and the sudden change in magnetic force can be suppressed. Therefore, the cogging torque is reduced as compared with the case where each effect is applied alone (see, for example, Patent Document 1).

  In addition, as a conventional permanent magnet type motor, a stator-side pseudo slot, which is one or a plurality of grooves, is provided along the axial direction at the inner peripheral end of the stator teeth, and the rotor is centered on the rotating shaft. A plurality of pole pieces are arranged radially at equal intervals, and one or more rotor-side pseudo slots, which are one or a plurality of grooves, are provided along the axial direction at the outer peripheral side of the pole piece. By providing grooves at the tips of the stator teeth and rotor pole pieces, the number of slots can be increased in a pseudo manner, and slot harmonics can be dispersed. That is, the order of the harmonics of the slot is shifted to the high frequency region so that the harmonics of a specific slot are not duplicated (see, for example, Patent Document 2).

JP 2002-136001 A (page 3-4, FIG. 1 to FIG. 3) JP 2006-67708 A (page 4-6, FIGS. 1 to 3)

The conventional permanent magnet type motor described above is configured as described above to reduce vibration and noise caused by the harmonics of the slot. However, there is a problem in the structure of the permanent magnet type motor described above in order to further reduce the vibration and noise caused by the harmonics of the slot.
In the permanent magnet type motor described in Patent Document 1, when the number of pseudo slots is increased in order to enhance the effect of the pseudo slot, the width of the pseudo slot is narrowed, thereby narrowing the magnetic path and increasing the iron loss. is expected.
Further, in the permanent magnet type motor described in Patent Document 2, since the number of pseudo slots is increased by providing grooves on both the stator and the rotor, the magnetic path is prevented from becoming narrower than providing grooves on one side. be able to. However, in the structure, only the order of the harmonics of the slot is shifted to the high frequency region, and the smoothing of the magnetic flux density distribution in the air gap is insufficient.

  The present invention has been made to solve the above-described problems. Even if a pseudo slot is provided at the tip of the stator teeth, iron loss can be suppressed, the distribution of magnetic flux density can be smoothed, and more cogging can be achieved. An object is to provide an electric motor, a compressor, and a refrigeration cycle apparatus capable of reducing torque.

  An electric motor according to the present invention includes a cylindrical stator having a slot provided in a circumferential direction, teeth formed between adjacent slots and a coil wound around the teeth, and an axial center of the stator. A stator having a permanent magnet insertion hole provided in the circumferential direction and a permanent magnet inserted into the permanent magnet insertion hole, and a stator having a permanent magnet inserted in the circumferential direction. A pseudo slot is provided, and a slit extending in the radial direction is provided between the permanent magnet insertion hole of the rotor and the outer peripheral portion of the rotor facing the permanent magnet insertion hole, and from the tip on the outer peripheral side of the rotor to the outer peripheral portion of the rotor. It is characterized by non-uniform length.

  In the present invention, a pseudo slot is provided at the tip of the teeth of the stator, a slit extending in the radial direction is provided between the permanent magnet insertion hole of the rotor and the outer peripheral portion of the rotor facing the permanent magnet insertion hole, Since the length from the tip on the outer peripheral side to the outer peripheral part of the rotor is made non-uniform, in addition to the effect that the spatial harmonics of the slot are dispersed and the frequency band of the cogging torque can be dispersed and shifted to the higher order side, The effect of being able to smooth the change in the magnetic force between the poles of the permanent magnet and suppressing the sudden change in magnetic force is superimposed, so that the cogging torque is even greater than when each effect is applied alone. Can be reduced. In addition, since the pseudo slot is provided on the stator side and the slit is provided on the rotor side, the effect of the pseudo slot can be obtained while suppressing iron loss by suppressing magnetic flux saturation.

FIG. 3 is a cross-sectional view showing a side surface of the compressor according to Embodiment 1 by cutting. 1 is a cross-sectional view showing a structure of an electric motor according to Embodiment 1. FIG. It is an enlarged view of the permanent magnet and slit shown in FIG. It is sectional drawing which shows the structure of the electric motor in which cogging countermeasures are not implemented. It is sectional drawing which shows the structure of the electric motor which provided the pseudo slot in the front-end | tip part of the teeth of a stator. It is sectional drawing which shows the structure of the electric motor which provided the slit for a cogging countermeasure in the rotor, and the pseudo slot in the stator side. It is a figure which shows the result of having analyzed the waveform of the cogging torque with respect to the angle change of the rotor of the electric motor in Embodiment 1, and the frequency analysis of the waveform. It is a figure which shows the result of having frequency-analyzed the waveform of the cogging torque with respect to the angle change of the rotor of the electric motor in which cogging countermeasures are not implemented. It is a figure which shows the result of having analyzed the frequency of the waveform of the cogging torque with respect to the angle change of the rotor of the electric motor which provided the pseudo slot in the front-end | tip part of the teeth of a stator, and the waveform. It is a figure which shows the result of having analyzed the waveform of the cogging torque with respect to the angle change of the rotor of the electric motor which provided the slit for a cogging countermeasure in a rotor, and the pseudo slot in the stator side, and the waveform. 6 is a schematic diagram showing a refrigerant circuit of a refrigeration cycle apparatus according to Embodiment 2. FIG.

Embodiment 1 FIG.
Hereinafter, an electric motor of the present invention and a compressor including the electric motor will be described with reference to the drawings.
1 is a cross-sectional view showing a side surface of a compressor according to Embodiment 1 by cutting.
The compressor 1 includes a sealed container 2, a compression unit 200 and an electric motor 100 housed in the sealed container 2, refrigeration oil (not shown) stored in the bottom of the sealed container 2, and the like. The refrigerating machine oil mainly lubricates the sliding part of the compression part 200.

  The electric motor 100 is formed of, for example, a permanent magnet type motor, and will be described later. As will be described later, a cylindrical stator 3 having slots provided in the circumferential direction, teeth formed between adjacent slots, and coils wound around the teeth, and The stator 3 includes a permanent magnet insertion hole provided in the circumferential direction and a permanent magnet inserted in the permanent magnet insertion hole, with the tip of the teeth of the stator 3 being centered on the stator 3 and an air gap. And a rotor 4. The compression unit 200 includes a cylinder 5, an upper bearing 6, a lower bearing 7, a rotating shaft 8, a rolling piston 9, a discharge muffler 10, a vane (not shown), and the like.

The configuration of the compression unit 200 is the same as that of a general compressor except for the rotating shaft 8, and the schematic configuration will be described below.
The cylinder 5 in which the compression chamber is formed has a substantially circular outer periphery in plan view, and a cylinder chamber that is a substantially circular space in plan view is provided inside. The cylinder chamber is open at both ends in the axial direction. The cylinder 5 has a predetermined axial height in a side view. The cylinder 5 communicates with the cylinder chamber described above, and is provided with parallel vane grooves (not shown) extending in the radial direction and penetrating in the axial direction. Further, a back pressure chamber (not shown) that is a substantially circular space in plan view communicating with the vane groove is provided on the back surface (outside) of the vane groove.

  An intake port (not shown) through which the intake gas from the refrigeration cycle passes through the cylinder 5 passes through the cylinder chamber from the outer peripheral surface of the cylinder 5. The cylinder 5 is provided with a discharge port (not shown) in which the vicinity of the circular edge forming the cylinder chamber (the end surface on the electric motor 100 side) is cut out. The rolling piston 9 is formed in a ring shape, and an eccentric shaft portion 8a of the rotary shaft 8 is slidably fitted into the hole. Thereby, the rolling piston 9 rotates eccentrically in the cylinder chamber.

  The vane is housed in the vane groove of the cylinder 5 and is always pressed against the rolling piston 9 by a vane spring (not shown) provided in the back pressure chamber. Since the compressor 1 has a high pressure inside the sealed container 2, when the operation is started, a force due to the differential pressure between the high pressure in the sealed container 2 and the pressure in the cylinder chamber acts on the back surface (back pressure chamber side) of the vane. The vane spring is mainly used for the purpose of pressing the vane against the rolling piston 9 when the rotary compressor is started up (when there is no difference in pressure between the sealed container 2 and the cylinder chamber). The shape of the vane is flat (the thickness in the circumferential direction is smaller than the length in the radial direction and the axial direction) and is formed in a substantially rectangular parallelepiped shape.

  The upper bearing 6 is slidably fitted to the main shaft portion 8b (a portion above the eccentric shaft portion 8a) of the rotary shaft 8, and is also one end surface (the electric motor 100) of the cylinder chamber (including the vane groove) of the cylinder 5. Block the side). The lower bearing 7 is formed in a substantially T shape in a side view, and is slidably fitted to the auxiliary shaft portion 8c (a portion below the eccentric shaft portion 8a) of the rotating shaft 8, and the cylinder chamber ( The other end face (including the vane groove) (refrigerating machine oil side) is closed.

  A discharge muffler 10 is attached to the upper bearing 6 on the outer side (motor 100 side). The high-temperature and high-pressure discharge gas discharged from the discharge valve of the upper bearing 6 once enters the discharge muffler 10 and then is discharged into the sealed container 2 from a discharge hole (not shown) of the discharge muffler 10. A suction muffler 11 fixed to the side surface of the sealed container 2 by welding or the like is provided beside the sealed container 2. The suction muffler 11 is connected to the suction port of the cylinder 5 via the suction pipe 12, and sucks low-pressure refrigerant gas from the refrigeration cycle device, and when the liquid refrigerant returns, the liquid refrigerant directly flows into the cylinder of the cylinder 5. Suppresses inhalation into the chamber.

  The high-temperature and high-pressure gas refrigerant compressed by the compression unit 200 passes through the electric motor 100 from the discharge hole of the discharge muffler 10 and from the discharge pipe 13 provided at the top of the sealed container 2 to the refrigerant circuit (not shown) of the refrigeration cycle apparatus. Discharged).

Next, the structure of the above-described electric motor 100 will be described with reference to FIG.
2 is a cross-sectional view showing the structure of the electric motor according to Embodiment 1, and FIG. 3 is an enlarged view of the permanent magnet and the slit shown in FIG.
The stator 3 of the electric motor 100 includes a cylindrical stator core 31 in which thin electromagnetic steel plates are punched into a predetermined shape and stacked in the axial direction, and a coil wound around a tooth 33 between slots 32 provided in the stator core 31 (see FIG. Not shown). The aforementioned slots 32 are arranged in the circumferential direction of the stator core 31 and are provided on the inner circumferential surface so as to extend in the axial direction.

  The teeth 33 have a substantially parallel shape from the outer diameter side to the inner diameter side of the stator core 31, and both ends of the teeth 33 extend in the circumferential direction. Further, a concave pseudo slot 34 having an open axial center is provided at the tip of the tooth 33. The pseudo slot 34 has a width substantially equal to the slot opening. The pseudo slots 34 provided for each tooth 33 are provided at different pitches. In the first embodiment, the number of slots 32 is 18 and the number of pseudo slots 34 provided at the tip of each tooth 33 is 2. However, the number of slots 32 and the number of pseudo slots 34 are the same. This is not the case.

  The rotor 4 of the electric motor 100 is provided with an air gap of about 0.3 to 0.8 mm in the opening of the stator 3, and a steel plate having a thickness of 0.1 to 1.5 mm is punched into a predetermined shape. The rotor core 41 is laminated in the axial direction, and six permanent magnets 42 are arranged in the circumferential direction of the rotor core 41 and inserted in the axial direction of the rotor core 41, for example. The permanent magnet 42 is embedded in the rotor core 41 so that the N pole and the S pole are alternated. When the rotor 4 is mounted on the compressor 1 described above, the rotary shaft 8 of the compressor 1 is fixed by shrink fitting or press fitting into the shaft hole of the rotor 4.

  The rotor core 41 has a permanent magnet insertion hole 43 into which the permanent magnet 42 is inserted, and the permanent magnet insertion hole 43 between the permanent magnet insertion hole 43 and the outer periphery of the rotor core 41 facing the permanent magnet insertion hole 43. And a plurality of slits 44 extending in the radial direction of the rotor core 41. The lengths of the plurality of slits 44 from the front end portion on the outer peripheral side of the rotor core 41 to the outer peripheral portion of the rotor core 41 are not uniform in each slit 44. The slits 44 provided for each permanent magnet insertion hole 43 are formed for each electromagnetic steel sheet and are arranged at different pitches. As shown in FIG. 3, the permanent magnet insertion hole 43 is formed slightly longer than the longitudinal dimension of the permanent magnet 42. Although the number of slits 44 is nine, the number of slits 44 is not limited to this.

  Next, the cogging torque reduction effect of the first embodiment (see FIG. 4) in which the cogging torque reduction effect has not been implemented, the electric motor (see FIG. 5) provided with a pseudo slot at the tip of the stator teeth, and the rotor against cogging This will be described in comparison with the cogging torque of an electric motor (see FIG. 6) provided with pseudo slots on the slit and stator side. 4 to 6 are the same parts as those in the first embodiment described with reference to FIG.

  FIG. 7A is a waveform of cogging torque with respect to a change in the angle of the rotor of the motor according to the first embodiment, FIG. 8A is a waveform of cogging torque with respect to a change in the angle of the rotor of the motor that has not been subjected to cogging countermeasures, and FIG. FIG. 10A is a waveform of cogging torque with respect to a change in the angle of the rotor of the motor provided with a pseudo slot at the tip of the stator teeth. FIG. 10A is a diagram of an electric motor provided with a slit for cogging measures in the rotor and a pseudo slot on the stator side. The waveform of the cogging torque with respect to the angle change of a rotor is shown.

  From this result, the electric motor of the first embodiment has a smoother cogging torque waveform than the conventional electric motor shown in FIGS. 8A, 9A, and 10A. It can be seen that the peak value of the cogging torque is also reduced.

Reduction effect of peak level of cogging torque (integer multiple of the least common multiple of the number of slots and the number of poles on the stator side) based on the analysis result of the frequency of cogging torque shown in FIG. Will be described in comparison with the above-described conventional electric motor.
FIG. 7B shows the result of frequency analysis of the waveform of the cogging torque shown in FIG. 7A. FIG. 8B shows the result of frequency analysis of the waveform of the cogging torque shown in FIG. ) Shows the result of frequency analysis of the waveform of the cogging torque shown in FIG. 9A, and FIG. 10B shows the result of frequency analysis of the waveform of the cogging torque shown in FIG.

  First, comparing FIG. 8B and FIG. 9B, by providing the pseudo slot 34 at the tip of the tooth 33 of the stator 3, the spatial harmonics of the slot 32 are dispersed, and the frequency band of the cogging torque is increased. The peak level of the electric motor 100 in FIG. 5 is lower than that of the electric motor 100 in FIG.

  Next, when FIG. 9B is compared with FIG. 10B, the peak levels of the harmonic orders 18, 36 are in addition to the effect of the pseudo slot 34 provided at the tip of the teeth 33 of the stator 3, and the rotor level. 6 is more peaked than the motor of FIG. 5 due to the effect of smoothing the magnetic flux density distribution of the air gap by providing the slit 44 between the permanent magnet insertion hole 43 of FIG. 4 and the outer periphery of the rotor 4. The level is decreasing. However, the peak level of the harmonic order 54 is worse than that of the electric motor of FIG. As shown in FIG. 6, the length (slit thin portion) from the tip of the slit 44 on the outer peripheral side of the rotor core 41 to the outer peripheral portion (slit thin portion) is configured to be thin and uniform. This is because a ripple that deteriorates the above-described order 54 peak occurs in the magnetic flux density distribution of the air gap due to saturation and a decrease in magnetic permeability.

  Next, when FIG. 7B and FIG. 10B are compared, the peak levels of the harmonic orders 18 and 36 are the same, and the peak level of the harmonic order 54 is the same as that of the electric motor 100 of the first embodiment. Is reduced. This is because ripples that alleviate the magnetic saturation of the slit thin portion and deteriorate the peak level of the above-mentioned order 54 by giving a part of the slit thin portion provided in the rotor 4 (thickness non-uniformity). This can be said to be a reduced effect. The peak at a specific order of the cogging torque is the number of slots of the stator 3, the number of pseudo slots 34 provided at the tip of the teeth 33 of the stator 3, the number of magnetic poles, and the slit 44 provided on the outer peripheral side of the rotor 4 of the permanent magnet insertion hole 43. In the present embodiment, the peak of the harmonic order 54 occurs in the present embodiment, but in the conventional electric motor 100, the peak may occur in a different order. However, in any case, the peak of the cogging torque at a specific order can be reduced by making the thickness of the thin slit portion provided in the rotor 4 non-uniform.

  As described above, according to the first embodiment, in the electric motor 100 using the permanent magnet 42 in which the N pole and the S pole are alternately magnetized, the permanent magnet insertion hole 43 of the rotor core 41 and the outer peripheral portion of the rotor core 41 are arranged. The length between the front end portion of the slit 44 provided between them (the outer peripheral portion side of the rotor core 41) and the outer peripheral portion of the rotor core 41 is non-uniform, and a pseudo slot 34 is provided at the front end portion of the teeth 33 of the stator 3. It is configured. Thereby, in addition to the effect that the spatial harmonics of the slots 32 are dispersed and the frequency band of the cogging torque can be dispersed and shifted to the higher order side, the change in the magnetic force between the poles of the permanent magnet 42 can be smoothed, and the magnetic force Since the effect that it is possible to suppress the sharp change of the noise is superimposed, the cogging torque can be further reduced as compared with the case where each effect is applied alone. Further, since the pseudo slot 34 is provided on the stator 3 side and the slit 44 (groove) is provided on the rotor 4 side, the effect of the pseudo slot 34 can be obtained while suppressing iron loss by suppressing magnetic flux saturation.

Embodiment 2. FIG.
FIG. 11 is a schematic diagram showing a refrigerant circuit of the refrigeration cycle apparatus according to Embodiment 2. In addition, the same code | symbol is attached | subjected to the part like Embodiment 1. FIG.
The refrigeration cycle apparatus according to the second embodiment includes the hermetic compressor 1 described in the first embodiment.

  In FIG. 11, the refrigeration cycle apparatus is configured by sequentially connecting a hermetic compressor 1, a four-way valve 51, an outdoor heat exchanger 52, an expansion device 53, and an indoor heat exchanger 54 through refrigerant piping. The hermetic compressor 1 is mounted with the electric motor 100 described in the first embodiment, and is connected to the compression unit 200 via a rotating shaft. The four-way valve 51 switches the flow path so that the refrigerant flows in the direction of the arrow shown in the figure during the cooling operation, and switches the flow path so as to flow toward the indoor heat exchanger 54 during the heating operation. The outdoor heat exchanger 52 acts as a condenser during the cooling operation and as an evaporator during the heating operation. The indoor heat exchanger 54 functions as an evaporator during the cooling operation and as a condenser during the heating operation. The expansion device 53 decompresses the high-pressure and low-temperature refrigerant from the outdoor heat exchanger 52 or the indoor heat exchanger 54.

  In the second embodiment, since the hermetic compressor 1 in which the electric motor 100 of the first embodiment is mounted in the refrigeration cycle apparatus, a refrigeration cycle apparatus in which vibration and noise are suppressed can be provided.

  DESCRIPTION OF SYMBOLS 1 Sealing type compressor, 2 Sealing container, 3 Stator, 31 Stator core, 32 slot, 33 Teeth, 34 Pseudo slot, 4 Rotor, 41 Rotor core, 42 Permanent magnet, 43 Permanent magnet insertion hole, 44 Slit, 5 Cylinder, 6 Top Bearing, 7 Lower bearing, 8 Rotating shaft, 8a Eccentric shaft part, 8b Main shaft part, 8c Subshaft part, 9 Rolling piston, 10 Discharge muffler, 11 Suction muffler, 12 Suction pipe, 13 Discharge pipe, 100 Electric motor, 200 Compression part 51 Four-way valve, 52 Outdoor heat exchanger, 53 Throttle device, 54 Indoor heat exchanger.

Claims (4)

A cylindrical stator having circumferentially provided slots, teeth formed between adjacent slots and coils wound around the teeth;
A stator having a permanent magnet inserted in the permanent magnet insertion hole and a permanent magnet insertion hole provided in the circumferential direction, provided at the tip of the stator teeth and an air gap around the stator axis. Prepared,
A pseudo slot is provided at the tip of the stator teeth,
A slit extending in the radial direction is provided between the permanent magnet insertion hole of the rotor and the outer peripheral portion of the rotor facing the permanent magnet insertion hole,
An electric motor characterized in that the length of the slit from the tip on the outer peripheral side of the rotor to the outer peripheral portion of the rotor is made uneven.   2. The electric motor according to claim 1, wherein the pseudo slot provided at the tip of the teeth of the stator and the slit provided in the rotor are provided at different pitches.   A compressor comprising the electric motor according to claim 1.   A refrigeration cycle apparatus comprising the compressor according to claim 3.

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