JPH11299150A - Permanent-magnet motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To largely increase the torque of a permanent-magnet motor, by constituting the motor to have both a large main magnetic flux torque component and a reluctance torque component. SOLUTION: A permanent-magnet motor is constituted in such a way that its rotor 11a is rotationally driven when a winding is energized through an inverter by facing the rotor 11a mounted with a plurality of permanent magnets 2a oppositely to a rotor core 19 on the inside of a stator provided with a plurality of phases of windings wound around a stator core. The outer peripheral section of the rotor core 1a is formed of a plurality of sides forming a polygon and, at the same time, a radial projection 18 is provided to each apex of the polygon. Each permanent magnet 2a, in addition, is formed in a semicylindrical shape having a straight line section which comes into contact with the sides of the rotor core 1a and a circular-arcuate section forming the outer periphery of the rotor 11a, and a cylindrical nonmagnetic sleeve 3 is put on the outer peripheries of the permanent magnets 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous motor having an adduction type rotor equipped with a permanent magnet (hereinafter, referred to as a magnet) typified by a motor for driving a compressor of a refrigerator or an air conditioner. It is.

[0002]

2. Description of the Related Art As the above-mentioned electric motor, those having the structure shown in FIGS. 5 and 6 are known. In the figure, reference numeral 11b denotes a rotor generally called a surface magnet structure (hereinafter, referred to as SPM), which has a configuration disclosed in, for example, Japanese Patent Application Laid-Open No. 5-15092. In this rotor, a plurality of tile-shaped magnets 2b are arranged on the outer periphery of a thick-walled cylindrical rotor core 1b, and a thin metal sleeve 3 is fitted on the outer periphery of the magnet 2b. End plates 4 and 5 are attached to both ends in the direction.

[0003] The rotor core 1b is formed by laminating a number of thin iron plates punched out of a silicon steel plate, and protrudes into the gap between the magnets 2b on the outer peripheral portion to position the magnets 2b in the circumferential direction. 8 is provided. As the magnet 2b, a ferrite magnet is mainly used, and the magnet 2b is equidistantly mounted on the outer peripheral portion of the iron core 1b. Have been.

[0004] The metal sleeve 3 covers and seals the outer periphery of the magnet 2b, and the magnet 2b is rotated by centrifugal force.
Is a protective member for preventing scattering and movement, and is required to be excellent in tensile strength and corrosion resistance, and is also required to be a non-magnetic material so as not to cause leakage of magnetic flux of the magnet. Therefore, a non-magnetic stainless steel material such as SUS304 is generally used, and is fitted by tight fitting means such as shrink fitting. The end plates 4 and 5 cover both ends in the axial direction of the magnet 2b and are hermetically sealed. A non-magnetic circular plate such as brass is used, and the end plates 4 and 5 are attached by a plurality of caulking pins 7 penetrating through the iron core 1b in the axial direction. ing.

[0005] The rotor 11b is supported by a shaft 6 fitted in the center thereof, and is disposed so as to face the inner periphery of the iron core 13 of the stator 12 with a predetermined air gap 10 therebetween. To constitute a permanent magnet type electric motor. The stator core 13 is formed by laminating a number of thin iron plates in the same manner as the rotor core 1b. The stator core 13 includes a plurality of teeth 14 on the inner periphery thereof and slots 15 between the teeth. Three-phase winding 1 through the material
6 is mounted. The winding 16 is energized by a three-phase trapezoidal wave of 120 ° through an inverter to rotate the rotor 11b.

In the electric motor shown in FIGS. 5 and 6, a rotor 11c as shown in FIG. 7 can be used instead of the rotor 11b. The rotor shown in FIG. 7 shows an example of an embedded magnet structure (hereinafter referred to as IPM), and has a configuration disclosed in, for example, Japanese Patent Application Laid-Open No. 9-247880. In the case of this configuration, the magnet 2c having a shape substantially similar to the accommodation hole 9 is inserted into a plurality of accommodation holes 9 for accommodating magnets provided in the iron core 1c. It is characterized by being housed inside. Therefore, in addition to the main magnetic flux torque obtained by the current of the current-carrying winding and the magnetic flux of the magnet interlinking with the current, the reluctance torque obtained by the difference of the magnetic resistance depending on the rotor position can be used.

That is, generally, the torque T of such an electric motor
Is T = T1 + T2 (1) where T1 is the main magnetic flux torque and T2 is the reluctance torque. 5 and 7, the direction connecting the center of the magnetic pole of the magnet and the rotation axis is the d-axis, the electric angle 90 ° phase with respect to the d-axis is the q-axis, the amount of magnetic flux by the magnet is Φ, and the d-axis current is Id , Q-axis current is Iq, d-axis inductance is L
Assuming that the d and q axis inductances are Lq, T1 = Φ · Iq (2) T2 = (Ld−Lq) Id−Iq (3)

[0008]

In the case of the SPM rotor shown in FIG. 5, since Ld = Lq and non-salient polarity, there is almost no component of the reluctance torque T2. Instead, the feature is that the main flux torque T1 is large because the leakage of the magnetic flux amount Φ by the magnet is relatively small. However, in general, in the control of an electric motor such as an air conditioner, a double-rectified AC commercial power supply is used as a link power supply for an inverter. As a result, the motor is driven by a voltage with a small duty width,
A large eddy current is generated in the metal sleeve 3 by the time harmonic component included in the voltage applied to the stator winding, and the loss due to the eddy current causes the motor efficiency to decrease.

On the other hand, the rotor 11c of the IPM shown in FIG.
In this case, Ld <Lq, and the motor becomes a reverse salient pole machine. This is because the q-axis inductance Lq is increased by the iron core portion 17 interposed between the magnets 2c in the circumferential direction. Therefore, since there is a component of the reluctance torque T2, this reluctance torque can be used. However, since the N-pole and the S-pole of the magnet 2c are short-circuited due to the presence of the iron core portion 17 and the iron core portion 21 on the outer periphery of the magnet, the leakage of the magnetic flux amount Φ by the magnet increases, and the main magnetic flux torque T1 greatly decreases. . As a result, the motor torque T does not significantly improve, and there is a limit to the improvement of the motor efficiency.

[0010]

In a permanent magnet type electric motor according to the present invention, in a cross section perpendicular to a rotation axis, a rotor core is formed by a plurality of sides having a polygonal outer peripheral portion. Each of the vertices has a radial projection, and the magnet is formed in a substantially semi-cylindrical shape having a linear portion abutting on the side of the rotor core and an arc portion forming an outer peripheral portion. It is characterized in that a cylindrical non-magnetic sleeve is fitted.

In the present invention, the curvature of the outer periphery of the magnet is formed larger than the curvature of the inner diameter of the sleeve.

Further, in the present invention, the voltage applied to the stator winding via the inverter is PAM wave or P-wave using a link power obtained by full-wave rectification of AC commercial power.
A WM wave, a PWM wave using a link power supply via an active power factor correction circuit using a boost chopper circuit after full-wave rectification of an AC commercial power supply, or a composite of the above waves Features.

[0013]

The polygonal corners forming the rotor core protrude toward the outer periphery of the rotor and are provided with radial projections, so that the q-axis inductance increases and the salient pole ratio increases. Lq / Ld increases.

Further, when a magnet is mounted on the side of the outer peripheral portion of the rotor core, the outer peripheral portion of the magnet fits within a predetermined circle regardless of variations in the grinding accuracy of the magnet. It will be easier.

[0015]

An embodiment of the present invention will be described with reference to the drawings.
In the rotor 11a shown in FIG. 1, reference numeral 1a denotes a rotor core, which is a well-known clamp means for laminating a number of thin iron plates formed by punching a silicon steel plate into a predetermined shape in the axial direction, cutting and raising the thin iron plates, and caulking them with projections. Fixedly formed. The outer peripheral portion of the rotor core 1a is formed by four sides forming a square, and a radial projection 18 is integrally formed at each apex of the square. A shaft 6 is fitted in the center, and end plates are fixed to both ends of the rotor in the axial direction by four caulking pins 7 penetrating in the core in the axial direction.

The magnet 2a is formed in a substantially semi-cylindrical cross-section having an inner straight portion abutting on the side of the outer peripheral portion of the rotor core 1a and an outer arc portion on which the sleeve 3 is fitted.
It is positioned by the projection 18 and is arranged on the outer peripheral portion of the rotor core 1a in an evenly distributed manner. As the magnet 2a, a ferrite magnet or the like is used, and magnets adjacent in the circumferential direction are magnetized such that one magnet forms one pole so that they have different polarities, thereby forming a field. The Kamaboko shape has a feature that the thickness in the radial direction is large, so that the amount of magnetic flux can be increased and the demagnetization resistance is excellent.

The sleeve 3 covers the outer periphery of the magnet 2a and protects the magnet 2a from centrifugal force during rotation. The sleeve 3 has excellent tensile strength and corrosion resistance and is a non-magnetic material.
A stainless steel tube such as 04 is used. The sleeve 3 is fitted to the outer peripheral arc surface of the magnet 2a by interference fitting means such as shrink fitting.

The rotor 11a constructed as described above is supported by the shaft 6, and is disposed so as to be opposed to the inner peripheral portion of the stator via an air gap as in the examples of FIGS. Construct a magnet type electric motor. This situation is shown in FIG. Since the sleeve 3 is a non-magnetic material, the magnetic flux short-circuit between the N pole and the S pole in each magnet 2a is very small, and the amount of magnetic flux Φ by the magnet becomes large, so that the main magnetic flux torque T1 shown in the equation (2) is Largely composed.

On the other hand, when the stator winding 16 is energized, the stator magnetic flux 20 flows into and out of the rotor through the air gap 10, but each of the quadrangular corner portions 19 forming the rotor core 1a. Has a shape protruding toward the outer periphery of the rotor as compared with the central portion of each pole. Therefore, unlike the rotor having the arc-shaped core outer periphery shown in FIG. 5, Ld <L
q is a reverse salient pole machine. Further, since the corner portion 19 is provided with the radial projection 18, the stator magnetic flux 20 is efficiently induced, the q-axis inductance is increased, and the salient pole ratio Lq / Ld is increased. As a result, the reluctance torque can be utilized, and (3)
T2 shown in the equation is configured to be large.

As described above, the electric motor shown in FIG. 2 has a large main magnetic flux torque T1 and also has a reluctance torque T2. Therefore, when compared with a conventional motor at the same torque, the copper loss of the motor is reduced, and the motor efficiency can be greatly improved.

However, in the above-described motor, as described in the example of FIG. 5, there is a problem that the eddy current loss generated in the sleeve 3 lowers the motor efficiency, so that the efficiency is not drastically improved. . Therefore, in the present invention, the voltage applied to the stator winding 16 via the inverter is changed to a PAM wave, a PWM wave using a link power obtained by full-wave rectification of an AC commercial power supply, or an AC commercial power supply. PWM using link power supply through active power factor correction circuit using boost chopper circuit after wave rectification
It consists of waves or a composite of each of the above waves. As a result, compared to the conventional double voltage rectified link voltage,
The motor is driven by the voltage having a large duty width, and the time harmonic component contained in the voltage applied to the stator winding 16 is significantly reduced, thereby reducing the eddy current loss. It is possible to provide an even more efficient motor utilizing the features of the configuration.

In the rotor 11a shown in FIG. 1, the magnet 2a
When the sleeve 3 is fitted to the outer peripheral portion of the device, the following failure occurs.

As is well known, magnets such as ferrite and neodymium rare earths are formed by performing dimensional adjustment by grinding in a final step when used in an electric motor. In other words, in the case of a kamaboko-shaped magnet, one of the inner peripheral straight portion abutting on the rotor core and the outer peripheral arc portion fitted to the sleeve is first ground, and then the ground surface is removed. The other is ground based on the standard. In FIG. 4, when grinding the straight portion on the inner circumference side with reference to the grounded arc portion on the outer circumference side of the magnet M1 shown by the solid line, the magnet M1 is inclined at the angle A in this grinding die and is shown by M2 shown by the broken line. The magnet is ground by the grinding line L,
It will be finished in the magnet shape as shown by the grid-like hatching. Since the finished magnet is arranged with the line L in contact with the side of the outer peripheral portion of the rotor core, the outer peripheral portion should be formed by the design ideal radius R1 having the center at the axis. A portion B protruding from the outer peripheral portion is generated.

When the sleeve is to be fitted to the outer peripheral portion of the magnet having the above inclination by interference fit,
In many cases, the protrusion B makes the fitting impossible.
If the inner diameter of the sleeve is designed to be large in consideration of this fact, the magnet may be finished in a normal grinding state without inclination, so in such a case, the fitting of the sleeve becomes loose, and the sleeve and the magnet However, there is a problem that it cannot be fixed firmly.

In view of the above problems, the present invention employs a magnet 2d as shown in FIG. In FIG. 3, R
Reference numeral 1 denotes a design ideal arc radius of a magnet outer peripheral portion having a center at an axis, and is an arc surface on which the sleeve inner diameter is fitted. The radius R2 of the arc surface of the outer peripheral portion of the magnet 2d is formed to have a larger curvature than the radius R1. As a result, the ideal arc surface of the magnet 2d and the inner peripheral portion of the sleeve come into contact at the central portion of the magnet 2d and are separated at both ends.
Therefore, even if the grinding line L is inclined and ground as shown in FIG. Does not protrude. In addition, it is not necessary to form the entire outer circumference with the same curvature in the arc surface of the outer circumference of the magnet 2d.
The curvature may be partially changed as appropriate.

As a feature of the configuration shown in FIG. 3, as described above, the contact portion between the arc surface of the magnet 2d and the arc surface of the inner diameter of the sleeve is reduced, so that the interference of this contact portion is slightly increased. Even so, there is no problem in shrink fitting and press fitting. For this reason, there is also a feature that the tolerance of the finished dimensions of the magnet and the sleeve is reduced.

[0027]

According to the present invention, since the outer peripheral portion of the magnet is made of a non-magnetic material, the amount of magnetic flux by the magnet is increased, so that the main magnetic flux torque component is increased. Since each corner of the rectangular shape projects toward the outer peripheral portion of the rotor and has radial projections at this portion, the q-axis inductance is increased and the reluctance torque component is also provided. Therefore,
It is possible to increase the torque of the motor, and when compared on the basis of the same torque, the copper loss of the motor can be reduced, and the motor efficiency can be greatly improved.

Further, the curvature of the outer peripheral portion of the magnet is made larger than the curvature of the inner diameter of the sleeve, so that when the magnet is mounted on the outer peripheral side of the rotor core, regardless of the variation in the grinding accuracy of the magnet, The outer peripheral portion is within a predetermined circle, so that there is no inferior fit with the sleeve, and the tolerance of the finished dimension is relaxed, so that the setting of the fit becomes easy.

Further, in the present invention, the voltage applied to the stator winding via the inverter is converted to a PAM wave or a PW using a link power source obtained by full-wave rectification of an AC commercial power source.
M wave, full-wave rectified AC commercial power, then PWM wave using a link power supply via an active power factor correction circuit using a boost chopper circuit, or a composite of the above waves As a result, the motor is driven by a voltage having a wide duty width and a small time harmonic component, and eddy current loss is reduced, so that a more efficient motor can be obtained.

[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 an enlarged plan sectional view showing a main part of the electric motor including the rotor shown in FIG. 1;

FIG. 3 is an explanatory plan view of a permanent magnet according to the present invention.

FIG. 4 is an explanatory view showing an example of grinding processing of a permanent magnet.

FIG. 5 is a plan sectional view of a motor showing a conventional example.

FIG. 6 is a front sectional view of the electric motor shown in FIG. 5;

FIG. 7 is a plan sectional view of a rotor of an electric motor showing another conventional example.

[Description of Signs] 1a, 1b, 1c: rotor cores, 2a, 2b, 2c, 2
d: permanent magnet, 3: sleeve, 6: shaft, 10: air gap, 11a, 11b, 11c: rotor, 12: stator, 13: stator core, 16: winding, 18: protrusion.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitsuhiko Sato 11-9 Shinkaicho, Mizuho-ku, Nagoya-shi 405 Shinkai Kapo (72) Inventor Seiichi Kaneko 68-4 Sakae, Kisosaki-cho, Kuwana-gun, Mie Prefecture

Claims (3)

[Claims] 1. A rotor having a plurality of permanent magnets mounted on a rotor core facing each other inside a stator having a plurality of windings on a stator core, and the rotor is connected to the winding via an inverter. In a permanent magnet motor configured to rotate the rotor by energizing, in a cross section perpendicular to a rotation axis, the rotor core is formed by a plurality of sides having an outer peripheral portion forming a polygon, Each of the polygons is provided with a radial projection at each vertex, and the permanent magnet is formed in a substantially semi-cylindrical shape having a linear portion abutting on a side of the rotor core and an arc portion forming an outer peripheral portion, A permanent magnet type electric motor characterized in that a cylindrical non-magnetic sleeve is fitted around the outer periphery of the permanent magnet. 2. The permanent magnet type electric motor according to claim 1, wherein a curvature of an outer peripheral portion of the permanent magnet is larger than a curvature of an inner diameter of the sleeve. 3. A voltage applied to the winding via the inverter is a PAM wave, a PWM wave using a link power source obtained by full-wave rectifying an AC commercial power source, or after a full-wave rectification of an AC commercial power source. PWM using link power supply via active power factor correction circuit using boost chopper circuit
The permanent magnet type electric motor according to claim 1, wherein the permanent magnet type electric motor is a wave or a composite of the waves.