JP2005168097A - Motor and rotary compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an electric motor and a rotary compressor of high efficiency, low vibration and low noise. <P>SOLUTION: The electric motor 10 comprises a stator 1 where winding 1h is applied to a plurality of teeth 1c and which is made in cylindrical form and a columnar rotor 2 which is installed in the above stator 1, being supported by a rotating shaft 45, and is provided with a slit 2c parallel with the rotating shaft 45, in a position near the periphery. Herein, the resonance frequency ω of a peripheral iron core 2e, which connects with the center of the rotor through two places of thin parts 2d made between both ends of the slit 2c and the periphery of the rotor 2, being made on the side of the periphery of the above slit 2c, is set to a value higher than the carrier frequency Ω of a power source for drive of the motor 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rotary compressor used in a cooling cycle such as a freezer or an air conditioner, and an electric motor that drives the rotary compressor, and relates to an apparatus that reduces vibration and noise.

  Conventionally, the rotor of this type of electric motor is one in which a plurality of slits for inserting permanent magnets parallel to the rotation axis are provided in a rotor core laminated with electromagnetic steel plates, and permanent magnets are inserted and embedded in the slits. The thickness of the thin portion between the slit end and the outer periphery of the rotor was formed as thin as possible in order to prevent leakage of magnetic flux (see, for example, Patent Document 1).

  The thickness of the thin portion between the slit end and the outer periphery of the rotor is determined in consideration of the punchability in the mold and the centrifugal force due to the rotation of the rotor. Since it is difficult if the thickness of the portion is equal to or less than the plate thickness, the punching is performed with a thickness of about the plate thickness. In recent years, in order to increase the efficiency of electric motors, the thickness of electromagnetic steel sheets has been reduced, and the plate thicknesses (0.35 mm, 0.27 mm, 0.2 mm, 0.15 mm,. 1 mm) is used.

  Further, in order to reduce iron loss, a high hardness material (for example, Hv 180 or more) having a high content such as Si is also used. Accordingly, the thickness of the thin portion between the slit end and the outer periphery of the rotor can be reduced even in consideration of the punchability of the mold and the resistance to centrifugal force.

  In addition, electric motors for rotary compressors such as refrigerators and air conditioners are usually supplied with drive power from a PWM control type inverter having a carrier frequency of 2.5 kHz to 5.0 kHz (for example, see Patent Document 2).

JP 10-4643 A (page 3) JP 2001-78375 A (pages 4-5)

  However, since the rigidity of the thin wall portion between the slit end and the outer periphery of the rotor is low in the conventional electric motor, the resonance frequency of the half-moon-shaped iron core portion located on the outer peripheral side is lower than the permanent magnet insertion slit of the rotor core. Therefore, there is a problem that the frequency becomes the same as or close to the carrier frequency of the driving power source and vibration and noise increase.

  This is because motors of the type in which permanent magnets are embedded in the rotor use reluctance torque that the stator current magnetic flux acts on the rotor core in addition to the magnet torque generated by the permanent magnets, so that high efficiency is achieved. When the rotor current flux passes through the semicircular outer core of the rotor, the carrier frequency component magnetic flux contained in the stator current resonates with the outer core of the rotor, resulting in increased vibration and noise. It is.

  The present invention has been made in view of the above, and an object of the present invention is to obtain an electric motor and a rotary compressor having high efficiency, low vibration, and low noise.

  In order to solve the above-described problems and achieve the object, an electric motor according to the present invention includes a stator formed by winding a plurality of teeth portions and formed in a cylindrical shape, and the stator supported by a rotating shaft. And a cylindrical rotor provided with a slit parallel to the rotation axis at a position near the outer periphery, and formed on the outer peripheral side of the slit, both ends of the slit and the rotor The resonance frequency of the outer peripheral iron core portion connected to the rotor central portion at two thin portions formed between the outer periphery and the outer periphery is set to a value higher than the carrier frequency of the driving power source of the electric motor.

  According to this invention, the outer peripheral core part of the rotor does not resonate with the carrier frequency of the drive power supply of the electric motor.

  According to the present invention, since the outer peripheral core portion of the rotor does not resonate with the carrier frequency of the drive power supply of the motor, there is an effect of obtaining a motor with high efficiency, low vibration, and low noise.

  Embodiments of an electric motor according to the present invention and a rotary compressor driven by the electric motor will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
1 is a cross-sectional view showing the main part of the electric motor according to Embodiment 1 of the present invention, FIG. 2-1 is a diagram showing a 120 ° energizing rectangular wave for driving the motor, and FIG. 2-2 is a 180 ° energizing sine wave. FIG. 3 is a view showing the relationship between the thickness t of the thin portion of the rotor core and the resonance frequency of the semicircular outer core portion, and FIG. 4 is a view showing the rotor having 6 poles. These are figures which show the rotor which provided the connection part in the middle of the slit.

  As shown in FIG. 1, the electric motor 10 of the first embodiment is supported by a stator 1 that is formed in a substantially cylindrical shape and fixed to a container (not shown), and a rotary shaft 45 inserted into the rotary shaft hole 2b. It is composed of a columnar rotor 2 that rotates within the child 1. The stator 1 includes a stator winding 1h (only one part is shown in the figure) on a tooth portion 1c of a stator core T-shaped block 1b in which stator core pieces 1a made of electromagnetic steel sheets formed in a T shape are stacked. The concave portion 1e and the convex portion 1f formed at the end of the yoke portion 1d are engaged with each other to connect the plurality of stator core T-blocks 1b, thereby forming a cylindrical shape as a whole.

  The rotor 2 is a cylindrical rotor in which a rotating shaft hole 2b is formed in the center and a rotor core piece 2a made of an electromagnetic steel plate in which four slits 2c are formed at axially symmetric positions in the periphery is laminated. It is formed as an iron core 2f. The permanent magnet 3 is inserted into the slit 2c parallel to the rotation axis so that the adjacent end portions are different from each other. In order to minimize the leakage of magnetic flux between the adjacent magnets, both ends of the slit 2c are rotated. Two thin-walled portions 2d are formed between the outer periphery of the child 2 and two portions. A gap 4 is provided between the outer peripheral portion of the rotor 2 and the inner peripheral portion of the teeth portion 1 c of the stator 1. On the outer peripheral side of the slit 2c of the rotor 2, a half-moon-shaped outer peripheral core portion 2e connected to the center portion through two thin portions 2d is formed.

  Next, the operation of the electric motor 10 of the first embodiment will be described. The electric motor 10 according to the first embodiment configured as described above includes the magnet torque generated by the action of the magnetic flux by the permanent magnet 3 and the magnetic flux 5 by the stator current, the magnetic flux 5 by the stator current, and the rotor core 2f. The rotational force of the rotor 2 is obtained by the reluctance torque generated by the difference in magnetic resistance depending on the position.

  At this time, a part of the magnetic flux 5 due to the stator current passes through the semicircular outer core portion 2e of the rotor 2 as a magnetic path, and the flow of the magnetic flux vibrates the outer core portion 2e. 2e vibrates with the two thin portions 2d as nodes.

  When the electric motor 10 is used for driving a compressor of a refrigerator or an air conditioner, the driving power source is a 120 ° to 150 ° energization rectangular wave generated by a PWM control type inverter as shown in FIG. A 180 ° energized sine wave as shown in FIG. This driving power source is generated by PWM with a carrier frequency of 2.5 kHz to 5.0 kHz, and a carrier component harmonic of a cycle Tc (= 1 / carrier frequency) in FIG. When the frequency of the carrier component harmonic and the resonance frequency of the outer peripheral core portion 2e match or approach each other, the outer peripheral core portion 2e is greatly vibrated, and the vibration and noise of the motor 10 increase.

  Therefore, in the electric motor 10 of the present invention, the resonance frequency of the outer peripheral core portion 2e is set to be higher than the carrier frequency. For example, if the carrier frequency is 5 kHz, the resonance frequency of the outer peripheral core portion 2e is set to 6 to 7 kHz or more. The resonance frequency is measured based on the response of the sensor at the time when a vibration acceleration sensor is attached to the center of the outer peripheral core portion 2e, the rotor 2 is placed on the sponge, the outer peripheral core portion 2e is struck with a hammer, and is vibrated. be able to.

  In some cases, the carrier frequency is changed depending on the number of rotations of the motor 10. In this case, the resonance frequency of the outer core 2e is set to a value exceeding the carrier frequency at the time of operation where noise is a problem (for example, at rated operation). Should be set. Further, in the case of control in which the carrier frequency is randomly changed even under the same operating condition, the resonance frequency of the outer peripheral core portion 2e may be set to a value exceeding the average carrier frequency.

  As a method of shifting the resonance frequency of the outer peripheral core portion 2e and the carrier frequency, it is conceivable to make the resonance frequency of the outer peripheral core portion 2e smaller than the carrier frequency. Noise of low-order frequencies is often an issue because it is difficult to isolate the sound, and is not an effective method.

  As a method of increasing the resonance frequency of the outer peripheral core portion 2e, it is effective to increase the thickness t of the thin portion 2d. If the thickness is too large, the leakage of magnetic flux between adjacent magnets increases and the motor efficiency decreases. For example, if the amount of magnetic flux is increased by using a rare earth magnet for the permanent magnet 3, the efficiency is improved. Is less affected.

The resonant frequency ω of the outer peripheral core portion 2e is t (mm) for the thickness of the thin portion 2d, L (mm) for the laminated thickness of the rotor core 2f, and the weight per location of the laminated outer peripheral core portion 2e is M ( g), where ½ of the arc distance along the outer periphery of the outer peripheral core portion 2e is S (mm) and the coefficient is k, it is expressed by the following equation.

  The weight M (g) is the weight of one permanent magnet 3 in consideration of the fact that the permanent magnet 3 is pressed against the outer peripheral iron core portion 2e by the rotational centrifugal force of the rotor 2 and becomes an integral state. Is included. When the flat permanent magnet 3 is arranged in the vicinity of the outer peripheral portion of the rotor 2 as in the electric motor 10 of the first embodiment shown in FIG. 1, when k = 600,000, the measured value agrees with the thin wall thickness. The relationship between the thickness t of the portion 2d and the resonance frequency ω is as shown in the diagram of FIG. If the carrier frequency is 5 kHz, the thickness t of the thin portion 2d may be 0.5 mm or more in order to make the resonance frequency of the outer peripheral core portion 2e exceed the value.

  Further, as another method for increasing the resonance frequency of the outer peripheral core portion 2e, it is effective to increase the number of poles of the rotor 2 as shown in FIG. The rotor 2 shown in FIG. 4 has six poles with respect to the four pole rotor 2 shown in FIG. 1, and six permanent magnets 3 are inserted and arranged in six slits 2c. In the case of a general rectangular 6-pole, the permanent magnet 3 can be arranged closer to the outer periphery of the rotor 2 with respect to the 4-pole. For this reason, the outer peripheral core portion 2e is reduced, the weight is reduced, and the S dimension is also reduced, so that the resonance frequency of the outer peripheral core portion 2e can be increased.

  As another method, as shown in FIG. 5, it is effective to provide a connecting portion 2g that connects the outer peripheral core portion 2e and the inside of the slit 2c at the center portion of the slit 2c. The connecting portion 2g also serves as a magnetic flux leakage path to lower the motor efficiency, and the connecting portion 2g obstructs the permanent magnet 3 from being inserted into the slit 2c. It is not provided in all the stacking directions of the iron core pieces 2a, but is provided only on several sheets outside the stacking direction. Since the outer peripheral core portion 2e is provided with crimping portions 2h that are formed with concavities and convexities on the front and back of the rotor core piece 2a and are connected in a laminated manner, the outer peripheral core portion 2e is an integral rigid body in the stacking direction. The connection part 2g can raise the resonant frequency of the outer periphery iron core part 2e only by providing in the lamination direction outer side several sheets.

Embodiment 2. FIG.
The electric motor according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 6 is a cross-sectional view showing a main part of the electric motor according to Embodiment 2 of the present invention. In FIG. 6, the same components as those in FIG.

  In the electric motor 10 of the first embodiment, the permanent magnet 3 is inserted into the slit 2c of the rotor 2 and is rotationally driven by the magnet torque and the reluctance torque. However, the electric motor 20 of the second embodiment is permanent in the slit. It is rotationally driven only by reluctance torque without inserting a magnet.

FIG. 6 is a cross-sectional view of the synchronous motor 20 that has been researched and developed in recent years. The rotor 22 is provided with a plurality of dish-shaped slits 22c ₁ , 22c ₂ , 22c ₃ , 22c ₄ , nothing is inserted into the slit 22c, and air flows if the installation environment of the synchronous motor 22 is in the air. However, the refrigerant circulates in the refrigerant compressor. Since the permanent magnet 3 is not provided as in the electric motor 10 of the first embodiment, the torque is generated only by the reluctance torque, and the electric motor efficiency is as much as the magnet torque is not generated as in the electric motor 10 of the first embodiment. Is low, but it is inexpensive because the permanent magnet 3 is not required.

Since the synchronous motor 20 according to the second embodiment is also driven by a drive power source using a PWM control type inverter, as with the electric motor 10 according to the first embodiment, in order to prevent resonance with the carrier frequency, the outer peripheral core portion 22e. The resonance frequencies of ₁ , 22e ₂ , 22e ₃ , and 22e ₄ are set to exceed the carrier frequency of the power source. Since this type of synchronous motor 20 has a plurality of slits 22c ₁ , 22c ₂ , 22c ₃ , 22c ₄ per pole and a plurality of outer peripheral core portions 22e ₁ , 22e ₂ , 22e ₃ , 22e ₄ , all The shape dimensions are set so that the outer peripheral core portions 22e ₁ , 22e ₂ , 22e ₃ , and 22e ₄ have a resonance frequency that exceeds the carrier frequency.

Embodiment 3 FIG.
The electric motor according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 7 is a cross-sectional view showing the main part of the electric motor according to Embodiment 3 of the present invention. In FIG. 7, the same components as those in FIG.

FIG. 7 is a cross-sectional view of a synchronous motor 30 that is also being researched and developed in recent years. The rotor 32 is provided with a plurality of dish-shaped slits 32c ₁ , 32c ₂ , 32c ₃ , 32c ₄ , and each slit 32c is filled with a conductive material 33 such as aluminum.

  The electric motor 30 according to the third embodiment is activated as an induction machine when a current flows through the conductive material 33 at the time of startup, and is driven as a synchronous motor at the time of steady operation. The synchronous motor 20 according to the second embodiment in which nothing is filled in the slit requires a special system for starting, but the electric motor 30 according to the third embodiment is a special system for starting as with the induction motor. Do not need. In addition, since no current flows through the conductive material 33 during steady synchronous operation, the conductive material such as an induction motor does not generate heat and can be operated with higher efficiency than the induction motor.

  The conductive material 33 can be operated in the same manner by using a material such as copper, copper alloy, brass, and stainless steel other than aluminum. For example, if copper is used as the conductive material 33, copper has a lower resistivity than aluminum, and therefore the resistance as a squirrel-cage secondary conductor is reduced, and the characteristics from the start to the synchronous pull-in can be improved.

Since the electric motor 30 of the third embodiment is also driven by the PWM control type inverter, the outer peripheral iron core portions 32e ₁ , 32e ₂ , 32e ₃ , 32e are prevented in order to prevent resonance with the carrier frequency in the same manner as the permanent magnet electric motor 10. The resonance frequency of ₄ is a value that exceeds the carrier frequency of the power supply. This type of electric motor has a plurality of slits 32c ₁ , 32c ₂ , 32c ₃ , 32c ₄ per pole and a plurality of outer peripheral iron core portions 32e ₁ , 32e ₂ , 32e ₃ , 32e ₄ , so that all the outer periphery The shape dimension is set so that the iron core portions 32e ₁ , 32e ₂ , 32e ₃ and 32e ₄ have a resonance frequency equal to or higher than the carrier frequency. At this time, the weight M (g) of the outer peripheral core portion 32e is determined by considering that the conductive material 33 is pressed against the outer peripheral core portion 32e by the rotational centrifugal force of the rotor 32, and becomes an integral state. The weight of the material 33 is included.

  In the first to third embodiments, the stator 1 has a stator winding 1h (see FIG. 5) on a tooth portion 1c of a stator core T-shaped block 1b in which stator core pieces 1a made of electromagnetic steel sheets formed in a T shape are stacked. In this example, only one part is shown), and a plurality of stator core T-shaped blocks 1b are joined together by fitting the concave part 1e and convex part 1f formed at the end of the yoke part 1d together to form a cylindrical shape as a whole. Even if a so-called “integrated core type” stator in which the yoke portion is not divided is employed, the same operation and effect can be obtained.

  In the case of the electric motor 10 of the first embodiment and the electric motors 20 and 30 of the second and third embodiments, the vibration prevention effect according to the present invention is more effective when the stator 1 is concentrated winding than distributed winding. large. The concentrated winding can make the coil circumferential length shorter than the distributed winding, so that a highly efficient electric motor can be obtained. However, as shown in FIG. 1, the magnetic flux 5 due to the stator current causes the outer peripheral core 2e to move. This is because the exciting force applied to the outer peripheral iron core 2e by the magnetic flux 5 is larger than that of the distributed winding. That is, according to the present invention, it is possible to obtain an electric motor that does not increase vibration and noise even if a concentrated winding stator is employed for high efficiency.

  As a drive power source, the sine wave as shown in FIG. 2-2 has less harmonics other than the carrier frequency than the rectangular wave as shown in FIG. 2-1, and noise and vibration other than the carrier frequency are related. Is an advantageous driving method, but the sinusoidal drive with a current-carrying width of 180 ° has more carrier component harmonics than the rectangular wave drive with a current-carrying width of less than 180 °, causing problems with carrier sound and vibration. It has become. The present invention in which the resonance frequency of the outer peripheral core 2e is higher than the carrier frequency is particularly effective in the case of sinusoidal driving.

Embodiment 4 FIG.
A rotary compressor according to the fourth embodiment of the present invention will be described with reference to FIG. FIG. 8 is a longitudinal sectional view showing a rotary compressor driven by the electric motor of the present invention.

  As shown in FIG. 8, a rotary compressor 400 for refrigerant such as a freezer or an air conditioner that is Embodiment 4 of the present invention is compressed with the electric motor 10 (20, 30) of Embodiment 1 (2, 3). And element 40. The compression element 40 includes a suction pipe 41 for sucking refrigerant, a cylinder 42, an upper bearing 43, a lower bearing 44, a crankshaft 45 as a rotating shaft, a rolling piston 46, a vane 47, and the like, and is lubricated by a lubricating oil 51. Yes. The electric motor 10 (20, 30) includes a stator 1, a stator winding 1h, a terminal block 1j, a rotor 2 (22, 32), a permanent magnet 3, and the like. The compression element 40 and the electric motor 10 (20, 30) are fixed in the sealed container 48 by a method such as welding or shrink fitting. The arrows in FIG. 8 indicate the flow of the refrigerant. The stator 1, which is a constituent element of the electric motor 10 (20, 30), includes a notch 1g on the outer periphery thereof.

  Next, the operation of the rotary compressor 400 will be described. The rotational motion generated from the electric motor 10 (20, 30) is transmitted to the compression element 40 by the crankshaft 45, and the compression element 40 performs compression work. The high-pressure refrigerant obtained by this compression work is discharged into the sealed container 48 from the refrigerant discharge port 49 of the compression element 40. The high-pressure refrigerant moves to the space above the electric motor 10 (20, 30) through the notch 1g and the gap 4 between the stator 1 and the rotor 2 (22, 32), and the sealed container 48. It is sent to the outside of the rotary compressor 400 by a discharge pipe 50 attached to the top of the compressor.

  According to the rotary compressor 400 of the fourth embodiment, since any one of the motors of the first to third embodiments is provided, a rotary compressor that does not increase vibration and noise can be obtained.

  As described above, the electric motor and the rotary compressor according to the present invention are particularly suitable for a freezer or an air conditioner that requires high efficiency, low vibration, and low noise.

It is a cross-sectional view which shows the principal part of the electric motor of Embodiment 1 of this invention. It is a figure which shows the 120 degree electricity supply rectangular wave which drives an electric motor. It is a figure which shows the 180 degrees energization sine wave which drives an electric motor. It is a figure which shows the relationship between the thickness of the thin part of a rotor core, and the resonant frequency of a half-moon-shaped outer periphery core part. It is a cross-sectional view showing a rotor with 6 poles. It is a figure which shows the rotor which provided the connection part in the middle of the slit. It is a cross-sectional view which shows the principal part of the electric motor of Embodiment 2 of this invention. It is a cross-sectional view which shows the principal part of the electric motor of Embodiment 3 of this invention. It is a longitudinal cross-sectional view which shows the rotary compressor of Embodiment 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stator 1a Stator core piece 1c Teeth part 1d Yoke part 1h Stator winding 2, 22, 32 Rotor 2a Rotor core piece 2b Rotating shaft hole 2c, 22c, 32c Slit 2d Thin part 2e, 22e, 32e Outer circumference Iron core part 2f Rotor iron core 2g Connecting part 2h Caulking part 3 Permanent magnet 4 Air gap 5 Magnetic flux due to stator current 10, 20, 30 Electric motor 33 Conductive material 40 Compression element 45 Rotating shaft 48 Sealed container

Claims (12)

Winding is applied to a plurality of teeth, and a stator formed in a cylindrical shape;
In an electric motor comprising a columnar rotor supported by a rotating shaft and installed in the stator and provided with a slit parallel to the rotating shaft at a position near the outer periphery,
The resonance frequency of the outer peripheral iron core portion connected to the rotor central portion at two thin portions formed between the slit both ends and the rotor outer periphery is formed on the outer periphery side of the slit. An electric motor characterized by being set to a value higher than the carrier frequency of the driving power source. Winding is applied to a plurality of teeth, and a stator formed in a cylindrical shape;
In an electric motor comprising a columnar rotor supported by a rotating shaft and installed in the stator and provided with a slit parallel to the rotating shaft at a position near the outer periphery,
The resonance frequency of the outer peripheral iron core part connected to the rotor central part at two thin parts formed on the outer peripheral side of the slit and formed between both ends of the slit and the outer periphery of the rotor is ω. The stack thickness of the child is L (mm), the thickness of the thin portion is t (mm), the weight of the outer peripheral core portion is M (g), and 1/2 of the arc distance along the outer periphery of the outer peripheral core portion is S (mm), coefficient k = 600,000, when the carrier frequency of the driving power source of the motor is Ω,

An electric motor characterized in that the thickness t (mm) of the thin wall portion is set so as to satisfy the above relationship.   The electric motor according to claim 1, wherein a permanent magnet is inserted into the slit.   The electric motor according to claim 3, wherein the permanent magnet is a rare earth magnet.   3. The electric motor according to claim 2, wherein the weight is calculated by adding the weight of the permanent magnet inserted into the slit to the weight M (g) of the outer peripheral core portion.   The electric motor according to claim 1, wherein the slit is filled with a conductive material.   The electric motor according to claim 2, wherein the weight is calculated by adding the weight of the conductive material filled in the slit to the weight M (g) of the outer peripheral core portion.   The electric motor according to claim 1, wherein the winding applied to the teeth portion is a concentrated winding.   The electric motor according to claim 1, wherein the rotor has six or more poles.   The electric motor according to any one of claims 1 to 9, further comprising a connecting portion that connects the outer peripheral iron core portion and the inner side of the slit at a central portion of the slit.   The electric motor according to claim 1, wherein the waveform of the driving power source is a substantially sine wave.   The rotary compressor provided with the electric motor as described in any one of Claims 1-11.

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