JPH1028344A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the noise of a motor caused by a magnetic pulling force by adjusting the directivity of a field magnetic flux near the interpole section of each magnetic pole to a direction which deviates from the axial direction of the magnetic poles to the radial direction. SOLUTION: The magnetic orientation of a magnet 8b is adjusted so that part of the interpole section of each magnetic pole can become anisotropic in the axial direction of the magnetic pole which is parallel with the axis 12 of the magnetic pole, as shown by the arrows 11a and 11b, and at the same time, anisotropic in the radial direction from the center axis O of a rotating shaft. When a field is formed by magnetizing the magnet 8b, the magnet is magnetized in a direction along the directions 11a and 11b of the orientation. Consequently, the quantity of local magnetic fluxes generated in an interpole section decrease, because local magnetic fluxes generated in the interpole section from a long loop in a rotor, and the magnetic reluctance increases. Therefore, the magnetic pulling force accompanying the eccentricity of the rotor becomes weaker, and the noise of a motor can be suppressed to a low level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor constructed by mounting a permanent magnet on a rotor typified by a motor for driving a compressor of a refrigerator or an air conditioner.

[0002]

2. Description of the Related Art A general structure of a motor of this type is shown in FIG.
Shown in The stator 1 includes a number of teeth 3 on the inner periphery of an iron core 2, and a slot 4 is provided between the teeth 3.
A winding (not shown) is mounted in this slot via an insulator. The rotor 6 is composed of an iron core 7 and a tile-shaped magnet 8 equidistantly mounted on an outer peripheral portion of the iron core, and a predetermined air gap 5 is provided between the rotor 6 and an inner peripheral portion of the stator core 2. And supported by the shaft 9 so as to face each other. In the drawing, reference numeral 10 denotes a protective sleeve fitted on the outer periphery of the magnet, which is formed of a stainless steel tube or the like to prevent the magnet from scattering. As the plurality of magnets 8, ferrite magnets or rare magnets are used, and one piece of magnet 8 is magnetized so as to form one pole to form a field. Indicates a 4-pole motor.

[0003] In the case of an electric motor having a magnet field in the rotor as described above, a large loop is drawn as much as possible while the magnetic flux flowing from the N pole of the field to the stator again reaches the S pole of the field. It is preferable to link with the stator to obtain a large torque. For this reason, the magnet constituting the field is generally of a magnetic pole axis direction anisotropy, and is configured to concentrate the field magnetic flux in one direction of the stator to reduce the leakage of the magnetic flux. . That is, as shown in FIG. 16, in one piece of the tile-shaped magnet 8a constituting one pole of the field, the direction of the magnetic orientation indicated by the arrow 11 is parallel to the magnetic pole axis 12 in the whole area of the magnet. As a result, when the magnet 8a is magnetized with the magnetic pole axis 12 as the pole center, the magnet is magnetized in the direction along the orientation direction 11 so that the field magnetic flux is given directionality.

[0004]

FIG. 17 shows the flow of the field magnetic flux of the electric motor when the magnetic pole axial direction anisotropic magnet 8a is used. As shown by broken lines, a large loop is formed at each pole. , And a local magnetic flux 14 that draws a small loop in the gap between the magnetic poles. The details of the local magnetic flux 14 are shown enlarged in FIG. Since the magnet 8a is anisotropic in the magnetic pole axis direction, the local magnetic flux 14a, 14b, 14c has a short magnetic path length in the rotor 6, and as a result, the magnetic resistance is small, so that the amount of local magnetic flux is large. It is a feature.

[0005] For example, an electric motor used for a refrigerant compressor such as an air conditioner is always exposed to a fluctuating load caused by a compression mechanism, so that the rotor tends to run out during operation. Returning to FIG. 17, if the rotor is now eccentric in the direction A, the local magnetic flux 14
The magnetic pull force in the direction becomes stronger than the magnetic pull force due to the local magnetic flux 15 existing in the opposite direction, and the rotor 6 receives a force in the eccentric direction A. Local magnetic flux 1
4 and 15 are particularly strongly affected by the eccentricity of the rotor 6, so that even a slight eccentricity causes the magnetic flux of both the local magnetic fluxes 14 and 15 to be greatly different. When the period of the magnet pull force matches the natural frequency of the shaft system, the noise of the electric motor becomes extremely large.

[0006] Since the above noise is caused by vibration in the first mode in which the stator and the rotor are attracted to each other, it cannot be solved by measures using a sound absorbing material or the like, and has been a very difficult problem. The natural frequency of the shaft system is 800 to 2
Since it exists near 000 Hz, there is a problem that particularly unpleasant noise is generated.

[0007]

SUMMARY OF THE INVENTION The present invention provides an electric motor in which a rotor having a plurality of magnetic poles formed by magnetized magnets is arranged to face a stator via an air gap. .

According to a first aspect of the invention, the direction of the field magnetic flux in the vicinity of the gap between the magnetic poles is formed so as to be deviated from the axial direction of the magnetic pole to the radial direction.

As a second invention, in the electric motor according to the first invention, a magnet having the same number of magnetic poles is provided, and the magnetic orientation of this magnet is formed in a pole central anisotropic direction in a magnetic pole axial direction. The portion located in the vicinity of the gap is formed to have radial anisotropy or pseudo-radial anisotropy. Here, the pseudo-radial anisotropy refers to a radiation direction having a center at a position shifted from the rotation axis which is the center of the magnetic pole.

According to a third aspect of the present invention, in the electric motor of the second aspect, the divided portions of the plurality of magnets are made to coincide with the gaps between the magnetic poles, and a diamagnetic material is provided in a gap between the magnets. You may make it intervene.

According to a fourth aspect, in the electric motor according to the first aspect, the magnet includes a magnet located at the center of the pole and a magnet located near the gap between the poles. The magnetic orientation of the latter is formed in either radial anisotropy, pseudo-radial anisotropy or anisotropy in the direction parallel to the pole gap. Here, the inter-pole axis refers to an axial line in the radial direction connecting the axis of the rotor and the inter-pole portion of the magnetic pole.

According to a fifth aspect of the present invention, in the electric motor of the first aspect, the same number of magnets as the number of magnetic poles are provided, and the magnetic orientation of the magnets is formed to be anisotropic in the magnetic pole axis direction. Are made to coincide with the gaps between the magnetic poles, and a diamagnetic material is interposed in a gap existing between the magnets.

[0013]

According to the present invention, the direction of the field magnetic flux in the vicinity of the gap between the rotors is formed in a direction deviated in the radial direction.
The magnetic path of the local magnetic flux generated between the poles forms a long loop in the rotor, and the amount of magnetic flux of the local magnetic flux decreases due to an increase in magnetic resistance. As a result, the magnet pull force due to the eccentricity of the rotor becomes weak.

[0014]

FIG. 1 is a plan sectional view of a rotor of an electric motor according to an embodiment of the present invention. This rotor is composed of an iron core 7 and a tile-shaped magnet 8b equidistantly mounted on the outer peripheral portion of the iron core. As shown in FIG. It is configured to be supported by a shaft 9 so as to be opposed via a predetermined air gap 5. The iron core 7 is generally formed by laminating a number of thin iron plates punched into a predetermined shape, and has a central portion fitted to the shaft 9. Magnet 8
A protective sleeve 10 made of a stainless steel tube or the like is fitted to the outer peripheral portion of the magnet 8b by shrink fitting or the like.
Is prevented from scattering.

The four pieces of magnets 8b are made of ferrite magnets or rare earth magnets, are formed in the same shape, are positioned by the projections 17 of the iron core 7, and are mounted in an equidistant manner. Magnetization is performed with the central portion in the direction as the magnetic pole axis 12, and one piece forms one pole to form an N, S alternating field as shown in the figure. In the drawing, reference numeral 16 denotes a gap axis of each magnetic pole.

The magnetic orientation of the magnet 8b is indicated by an arrow 1 in FIG.
As shown by 1a and 11b, the portion located at the center of the pole is formed in a so-called magnetic pole axis direction anisotropy parallel to the pole axis 12, and the portion located near the gap between the poles is the center of the magnetic pole, that is, the rotation axis O. Is formed in a so-called radial anisotropy, which is a radiation direction centered at. The portion of the radial anisotropy orientation 11b may be a so-called pseudo-radial anisotropy in a radial direction centered on a position shifted from the rotation axis O, as long as there is no trouble. When the magnet 8b is magnetized to form a field as shown in FIG. 1, the magnet 8b is magnetized in a direction along the orientation directions 11a and 11b.

FIG. 3 shows the flow of the field magnetic flux in the electric motor using the magnet 8b having the magnetic orientation as shown in FIG. FIG. 3 shows the state of the local magnetic flux in the gap between the poles, which greatly affects the magnet pull force. The local magnetic fluxes 14d, 14e, and 14f in FIG. 3 are, as apparent from comparison with the conventional local magnetic fluxes 14a, 14b, and 14c shown in FIG. Therefore, the magnetic path in the rotor 6 forms a long loop, and the magnetic resistance increases. The rotor core 7
Inside is a magnetic path of the main magnetic flux, so the magnetic flux density is high,
As the local magnetic flux is corrected so as to pass through the core 7, the magnetic resistance of the magnetic path is further increased. Therefore, these magnetic resistances increase, so that the local magnetic flux 14d,
The magnetic flux amounts of 14e and 14f are greatly reduced. As a result, the magnet pull force accompanying the eccentricity of the rotor becomes very weak.

The local magnetic flux in the above-described electric motor is generated by a search coil 1 wound around the teeth 3 of the stator core 2 as shown in FIG.
8, the amount of magnetic flux can be measured, and an example is shown in FIGS. In this example, in the electric motor set in the state shown in FIG.
The figure shows the frequency analysis result of the voltage induced in the search coil 18 by forcibly rotating from outside at 0 rotation.
FIG. 8 shows the case of the product of the present invention using the magnet shown in FIG.
Shows the case of a conventional product using the magnet shown in FIG. 8 and 9, each peak indicated by a, b, c... Represents a primary component (approximately 175 Hz at 5230/60 × 2 in the embodiment) obtained from the product of the number of rotations per second and the number of pole pairs. , And the primary, secondary, and
Each component of the third order is shown. A, b, c
.. Are peak components that are present between the harmonics of the search coil 18.
When viewed from the wound stator teeth 3, one rotation per rotation
It is a component that changes at the rate of times.

Considering the magnetic flux distribution of the component caused by the whirling in FIG. 9, 14a, 14b and 14 in FIG.
It is presumed that the distribution of the local magnetic flux is as shown by c, and the distribution is different from that of the main magnetic flux as indicated by reference numeral 13 in FIG.
In the case of four poles, the local magnetic fluxes 14a, 14b, and 14c exist at four positions between the poles of the magnet 8a, and as described above, generate magnet pull force due to the eccentricity of the rotor. When the natural frequency of the shaft system coincides with the natural frequency of the shaft system, the first mode vibration is generated in which the stator and the rotor are attracted, and annoying noise is generated. On the other hand, in the product of the present invention shown in FIG. 8, the 1.5 order, 2.5 order, 3..
It can be seen that the component peaks of the fifth order are drastically reduced, and the magnetic flux amounts of the local magnetic fluxes 14d, 14e, and 14f shown in FIG. 3 are greatly reduced.

FIGS. 10 and 11 show the results of frequency analysis of noise in the hermetic refrigerant compressor using the motor of the present invention and the conventional motor, respectively, and show the noise when operating at 5230 revolutions per minute. It is a comparison of data.
In this example, the eigenvalue of the shaft system exists at 1830 Hz, and the 10.5 order (175 Hz × 175) of the magnetic flux component generated by whirling existing between j and k in FIGS. 8 and 9.
10.5, about 1830 Hz), and noise is a problem in this area. When FIG. 10 and FIG. 11 are compared, in the case of the present invention, the noise around 1830 Hz is eliminated, which is due to the disappearance of the 10.5 order component between j and k as shown in FIG. 8 and FIG. doing.

The magnet 8b shown in FIG. 2 has a portion of the magnetic pole axial anisotropy 11a and a portion of the radial anisotropy 11b in a single magnet, but separate magnets for each type of magnetic orientation. FIG. 4 shows an example. The rotor shown in FIG. 4 has magnets twice as many as the number of magnetic poles mounted on the outer periphery of an iron core 7c having no positioning projections. 8c, and the magnetic pole axis 16 between the magnets 8c.
And a magnet 8d having radial anisotropy or pseudo-radial anisotropy or an anisotropy in a direction parallel to the axis 16 between the poles. If the magnet 8d is anisotropic in the direction parallel to the gap axis 16, the magnet 8d can be formed with the same magnetic orientation in the parallel direction as that of the magnet 8c, so that there is a feature that the magnet can be easily manufactured.

FIGS. 5 and 6 show still another embodiment of the magnet structure in the electric motor of the present invention, in which the functions of the magnets 8c and 8d shown in FIG. 4 are provided in a single magnet. . The magnet 8e shown in FIG. 5 includes a portion 21 of the magnetic pole axial anisotropy 11a on one side of the magnet, and a portion 22 of the radial or pseudo-radial anisotropy 11b on the opposite end of the magnet, These portions 21 and 22 are arranged so as to correspond to the portions where the magnets 8c and 8d are located in FIG. 4, respectively. By constituting the rotor with such a magnet 8e, a rotor having the same function as the rotor of FIG. 1 or 4 can be constituted by four identical magnets.

The magnet 8f shown in FIG. 6 has a portion 23 of the magnetic pole axis direction anisotropy 11a at the center of the magnet, and a portion 24 of the radial anisotropy or pseudo-radial anisotropy 11b at both ends of the magnet. The arrangement is such that these parts 23 and 24 correspond to the parts where the magnets 8c and 8d are located in FIG. 4, respectively. Half of the number of magnetic poles for one rotor are prepared for one rotor 8f, and the magnets 8f are arranged equally, and the magnet 8c in FIG. 4 is arranged between the magnets 8f. Therefore, a rotor having the same function as the rotor of FIG. 1 or 4 can be constituted by the two types of magnets 8f and 8c.

FIG. 7 shows still another embodiment of the motor of the present invention. The rotor 6 has the same number of magnets 8g as the number of magnetic poles, and the divided portions of the plurality of magnets 8g are made to coincide with the interpoles of each magnetic pole, similarly to the rotor shown in FIG. A projection 17 of the iron core 7 is provided between the poles of the magnetic poles, and the magnet 8g is divided and positioned to form a circumferential gap between the magnets. In the gap, a diamagnetic material such as a copper material is provided. 2
0 is inserted. With this configuration,
Since the local magnetic fluxes 14d, 14e, and 14f flow while avoiding the diamagnetic material 20, a magnetic path deviated from the magnetic pole axis direction to the radial direction is formed to form a loop similar to that shown in FIG.
As a result, the magnetic resistance increases and the amount of magnetic flux is greatly reduced. The magnet 8g used in the rotor shown in FIG. 7 is a conventional magnet 8a having a magnetic orientation in the conventional magnetic pole axis direction anisotropy shown in FIG.
However, if the magnet 8b shown in FIG.
0 can be reduced.

FIGS. 12 to 14 show different embodiments of the rotor in the electric motor of the present invention. Instead of having the protective sleeve 10 like the rotor shown in FIG. 1, the rotor is provided on the rotor core. 1 shows a rotor of a type configured to house a magnet in a bore. All of these rotors have the same number of magnets as the number of magnetic poles, and these magnets 8h,
8i and 8j, similarly to the magnet 8b shown in FIG. 2, the portion located at the pole center is formed in the magnetic pole axial direction anisotropy, and the portion located near the gap between the poles is radially anisotropic or pseudo-radial. The magnet is formed anisotropically and magnetized with the magnetic pole axis 12 at the center in the circumferential direction of each piece of the magnet to form a field. Therefore, these various rotors have the same function as the rotor shown in FIG.

A feature of the rotor shown in FIGS. 12 to 14 is that a magnetic resistance to a local magnetic flux is small because an iron core is interposed between poles between magnets. The problem of the noise caused by the magnet pull force is more serious than that of the rotor shown in FIG. 17, and the effect of reducing the magnet pull force and the noise by employing the magnet structure according to the present invention is very large.

The rotor shown in FIG. 12 has a tile core 8h housed in a core 7h. The magnet 8h has substantially the same shape as the magnet 8b shown in FIG.
Further, the rotor shown in FIG. 13 has a field formed by a semi-cylindrical magnet 8i instead of the tile-shaped magnet, and the hole for accommodating the magnet provided in the iron core 7i naturally has a magnet 8i.
Is provided in a substantially similar shape.

Further, the rotor shown in FIG. 14 has a configuration in which a plate-like magnet 8j is embedded in an iron core 7j, and this is a configuration that is frequently used mainly in motors using rare earth magnets. In the figure, reference numeral 19 denotes a space for preventing magnetic fluxes of different poles from being short-circuited. The effect becomes more remarkable if a diamagnetic material as described with reference to FIG. 7 is inserted into this space. As described above, the method of forming the directionality of the field magnetic flux in the present invention so as to be deviated from the magnetic pole axis direction to the radial direction in the vicinity of the gap between the magnetic poles is applicable to any type of rotor. It is also applicable.

[0029]

According to the present invention, the direction of the field magnetic flux in the vicinity of the gap between the rotors is formed in a direction deviated in the radial direction, so that the magnetic path of the local magnetic flux generated in the gap between the poles is reduced. By forming a long loop in the rotor and increasing the reluctance, the amount of local magnetic flux decreases. As a result, the magnet pull force due to the eccentricity of the rotor is weakened, and even if the period of the magnet pull force matches the natural frequency of the shaft system, the noise of the motor is suppressed to a low level, which has a remarkable effect on reducing the noise of the motor. To demonstrate.

[Brief description of the drawings]

FIG. 1 is a plan sectional view of a rotor of an electric motor according to an embodiment of the present invention.

FIG. 2 is a structural explanatory view showing an embodiment of the magnet of FIG. 1;

FIG. 3 is an enlarged explanatory view of a main part showing a flow of a local magnetic flux component of a field magnetic flux in the electric motor using the rotor of FIG. 1;

FIG. 4 is a cross-sectional plan view of a rotor of the electric motor according to the embodiment of the present invention.

FIG. 5 is a structural explanatory view showing an embodiment of a magnet in the electric motor of the present invention.

FIG. 6 is a structural explanatory view showing an embodiment of a magnet in the electric motor of the present invention.

FIG. 7 is an enlarged explanatory view of a main part of a motor showing an embodiment of the present invention.

FIG. 8 is a characteristic diagram showing a frequency analysis result of a search coil induced voltage in the electric motor of the present invention.

FIG. 9 is a characteristic diagram showing a frequency analysis result of a search coil induced voltage in a conventional motor.

FIG. 10 is a characteristic diagram showing a frequency analysis result of noise in the hermetic refrigerant compressor using the electric motor of the present invention.

FIG. 11 is a characteristic diagram showing a result of frequency analysis of noise in a hermetic refrigerant compressor using a conventional electric motor.

FIG. 12 is a plan sectional view showing an embodiment of a rotor in the electric motor of the present invention.

FIG. 13 is a plan sectional view showing an embodiment of a rotor in the electric motor of the present invention.

FIG. 14 is a plan sectional view showing an embodiment of a rotor in the electric motor of the present invention.

FIG. 15 is a plan sectional view showing a general configuration of an electric motor.

FIG. 16 is an explanatory view showing the magnetic orientation of a conventional magnet.

FIG. 17 is an explanatory diagram showing a flow of a field magnetic flux of a conventional electric motor.

18 is an enlarged explanatory view of a main part of FIG. 17;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stator 2 Stator iron core 3 Tooth part 4 Slot 5 Air gap 6 Rotor 7, 7c, 7h, 7i, 7j Rotor core 8, 8a-8j Magnet 9 Shaft 10 Protection sleeve 12 Magnetic pole axis 16 Interpole axis

Claims (5)

[Claims] 1. An electric motor in which a rotor having a plurality of magnetic poles formed by magnetized magnets is opposed to a stator via an air gap, and a directionality of a field magnetic flux in the vicinity of a space between the poles of each magnetic pole. The motor is formed so as to be deviated from the magnetic pole axis direction to the radial direction. 2. A magnet having the same number of magnetic poles as the magnetic poles, and the magnetic orientation of the magnet is formed in the pole central part in the magnetic pole axial direction anisotropy, and the part located in the vicinity of the pole part is radially anisotropic. The electric motor according to claim 1, wherein the electric motor is formed to have a characteristic or pseudo-radial anisotropy. 3. The electric motor according to claim 2, wherein the divided portions of the plurality of magnets coincide with the inter-pole portions of the magnetic poles, and a diamagnetic material is interposed between the magnets. 4. A magnet having a magnet located at a pole center and a magnet located near a pole gap, wherein the magnetic orientation of the former is formed in the magnetic pole axial direction anisotropy, the magnetic orientation of the latter is radial anisotropy, 2. The electric motor according to claim 1, wherein the motor is formed to have either pseudo-radial anisotropy or anisotropy in a direction parallel to a gap axis. 5. Magnets having the same number as the number of magnetic poles are provided, and the magnetic orientation of the magnets is formed to be anisotropic in the magnetic pole axis direction. The electric motor according to claim 1, wherein a diamagnetic material is interposed between the motors.