JP2000287393A - Rotor for motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the total torque of magnet torque and reactance torque by simple rotor structure by arranging a plurality of permanent magnets at regular intervals so that an angle formed between a (d) axis as the center of the magnetic force of the magnets and a (q) axis as the center of a core is less than 90 deg. at an electrical angle. SOLUTION: Four pairs of rmanent magnets 13 arranged in a fan shape towards the center of a rotor core 11 and flux barriers (flux interrupting sections) 14 are disposed. According to such arrangement, an angle formed between a (d) axis (the center of the magnetic force of magnets) and a (q) axis (the center of a core) is less than 90 deg. at an electrical angle. That is, the permanent magnets 13 are arranged near the (q) axis in the direction that the (d) axis is advanced in the rotor rotational direction R. Accordingly, since current phase in which magnet torque is maximized is shifted in the direction of current phase in which reluctance torque is maximized and the maximum point of magnet torque and the maximum point of reluctance torque are brought near, total torque is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor structure of a motor in which permanent magnets are embedded in a rotor, and more particularly to an improvement in the total torque of a magnet torque and a reluctance torque.

[0002]

2. Description of the Related Art As a magnet type synchronous motor, there is an IPM motor (embedded magnet type motor) in which a permanent magnet is embedded in a rotor. Since this motor has features of high efficiency, downsizing, and high rotation, it is currently widely used as a motor suitable for electric vehicles and the like.

FIG. 3 is a sectional view showing an example of the configuration of this motor. This motor has a permanent magnet 1 embedded inside
Reference numeral 3 denotes a magnetic pole of a rotor (rotor) 10a. A stator (stator) 20 is disposed around the rotor 10a, and a plurality of teeth 21 are formed on the stator 20 so as to face the rotor 10a. I have. Then, a coil (not shown) inserted into the slot 22 between the teeth 21
, A repulsive force and an attractive force are generated between the stator 20 and the rotor 10a by the rotating magnetic field generated by the current, and the rotor 10a rotates in the R direction in the drawing. The torque generated at this time is the magnet torque caused by the coil of the stator 20 and the permanent magnet 13 of the rotor 10a repelling and attracting, and the coil of the stator 20
a) (the reluctance torque generated by attracting the iron (a) (rotor core 11a). That is, in this type of motor, the magnet torque and the reluctance torque are used in combination, and the total torque of both is the output torque of the motor. In order to reduce the leakage magnetic flux of the permanent magnet 13 and to form an optimal passage of the magnetic flux lines in the iron core (rotor core 11a), the both sides of the permanent magnet 13 are provided with a magnetic flux blocking portion for blocking the passage of the magnetic flux in the radial direction. (Flux barrier) 1
4a and 14b are formed.

[0004]

However, in the above-described conventional electric motor (IPM motor), the center of the d-axis which is the magnetic force center of the magnet 13 and the center of the iron core (that is, the place where iron is the most). Since the angle formed with the q-axis was 90 ° in electrical angle, the total torque of the magnet torque and the reluctance torque was not so high.

That is, when the angle between the d-axis and the q-axis is an electrical angle of 90 °, as shown in FIG. 4, the magnet torque TM is maximum when the current phase α is 0 °, and when the current phase α is 90 °. And the reluctance torque TR becomes maximum when the current phase α is 45 °, and becomes 0 when the current phase α is 0 ° and 90 °.
Becomes Therefore, the total torque T is 0 ° <α <45.
It is maximum in the range of °. As described above, the point at which the total torque T is maximum is the point at which the magnet torque TM is maximum (α = 0).
°) and the point of maximum reluctance torque TR (α = 45)
°) and the point of maximum magnet torque TM (α = 0 °) and the point of maximum reluctance torque TR (α
(= 45 °) is shifted by 45 ° in the current phase, so it cannot be said that the magnet torque TM and the reluctance torque TR are effectively used, and the total torque T is not so high.

For example, as shown in FIG. 3, the angle between the d-axis and the q-axis is less than 90 ° in electrical angle, and the rotor structure is such that the magnet torque and the reluctance torque become maximum at the same current phase. In some cases, the total torque is improved (see JP-A-10-112945).

However, this structure is such that the permanent magnets 13b are arranged on the surface of the rotor core 11b (surface magnet type motor). Generally, the degree of freedom in the arrangement of the magnets and the shape and arrangement of the flux barrier is small, and the reluctance torque is large. And the skew effect and the cooling effect due to the flux barrier are structurally impossible. That is, the flux barrier is formed obliquely to the axis, and torque ripple (also called cogging torque)
It cannot be reduced or it cannot function as a fan.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and improves the total torque of the magnet torque and the reluctance torque with a simple rotor structure on the premise of an embedded magnet type motor. It is an object of the present invention to provide an electric motor rotor that can perform the above-described operations.

[0009]

The above object of the present invention is achieved by the following means.

(1) A rotor for an electric motor according to the present invention, wherein a plurality of permanent magnets are embedded in a rotor core and arranged, wherein the plurality of permanent magnets are the magnetic force centers of the magnets. It is characterized by being arranged at equal intervals so that the angle between the axis and the q-axis, which is the center of the iron core, is less than 90 electrical degrees.

(2) Each of the plurality of permanent magnets is paired with a magnetic flux interrupting portion, and each pair is arranged in a C-shape toward the center of the rotor core for each pair.

(3) The permanent magnet is a plate magnet.

(4) The magnetic flux blocking portion is a through hole.

(5) The magnetic flux blocking portion is formed obliquely with respect to the axis.

[0015]

Therefore, according to the present invention, in the interior magnet type motor, the angle between the d axis and the q axis is less than 90 ° in electrical angle, that is, the direction in which the d axis is advanced in the rotor rotation direction. Since the permanent magnet is arranged closer to the q-axis, the current phase at which the magnet torque becomes maximum shifts toward the current phase (α = 45 °) at which the reluctance torque becomes maximum, and the point at which the magnet torque is maximum and the reluctance torque Since the maximum point is approached, the total torque is improved.

At this time, when the permanent magnet and the magnetic flux interrupting portion are paired and the pair of permanent magnets and the magnetic flux interrupting portion are arranged in a C-shape toward the center of the rotor core, the C-shape is formed. Since a path easy to pass the magnetic force lines is formed in the iron cores on both sides of the pair of the permanent magnet and the magnetic flux cut-off portion arranged, a magnetic flux path is expanded with a simple rotor structure, and the q-axis inductance is increased. (Ease of passage of magnetic flux for generating reluctance torque) is set large. Therefore, the maximum value of the reluctance torque itself increases, and from this point as well, the total torque of the magnet torque and the reluctance torque improves.

In addition, as long as the C-shaped arrangement is maintained,
Because there is a great degree of freedom in the shape and arrangement of the magnets, it is possible to use flat magnets that are easy to manufacture as permanent magnets,
Together with the simple rotor structure described above, it is advantageous in terms of cost.

In the case where the magnetic flux interrupting portion is a through-hole, it can be dealt with as it is in a conventional processing step, so that there is no cost increase in this respect.

Also, as long as the C-shaped arrangement is maintained,
Because there is a great degree of freedom in the shape and arrangement of the magnetic flux cutoff,
The magnetic flux blocking portion can be formed obliquely with respect to the axis.
That is, the magnetic flux interrupting portion can be set so as to generate a skew effect and a cooling effect, and thus, reduction of torque ripple and cooling by a fan function can be achieved.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view showing a structure of an IPM motor having a motor rotor according to an embodiment of the present invention. 3 and 5 are denoted by the same reference numerals.

This motor is a 4-pole (2-pole pair) IPM motor (embedded magnet type motor) in which four permanent magnets are embedded in the rotor 10. The rotor 10 includes a rotor core 11 formed by laminating a plurality of thin (for example, 0.5 mm thick) silicon steel sheets, a motor shaft 12 press-fitted into a shaft hole at the center of the rotor core 11, and a rotor core 1.
It is composed of four pairs of permanent magnets 13 and a flux barrier (magnetic flux interrupting portion) 14 arranged in a C shape toward the center of 1. As the permanent magnet 13, a plate magnet which is easy to manufacture is used. The flux barrier 14 is a through hole that does not pass magnetic flux. By arranging the permanent magnets 13 (and the flux barriers 14) as described above, the angle between the d-axis (the center of the magnetic force of the magnet) and the q-axis (the center of the iron core, that is, the place where iron is the largest) becomes electric. The angle is less than 90 °. In other words, the permanent magnet 13 is arranged closer to the q-axis in a direction in which the d-axis is advanced in the rotor rotation direction R.

On the other hand, the stator 2 is provided around the rotor 10.
A plurality of teeth 21 are formed on the stator 20 so as to face the rotor 10, and slots 22 are formed between the teeth 21. A coil (not shown) is inserted into the slot 22. In this way, a rotating magnetic field is generated by passing a current through the coil wound around the stator 20, and a repulsive force and an attractive force are generated between the stator 20 and the rotor 10 by the rotating magnetic field.
The rotor 10 rotates in the R direction in the figure. As described above, the torque generated at this time depends on the magnet torque caused by the repulsion and attraction of the coil of the stator 20 and the permanent magnet 13 of the rotor 10 and the torque of the coil of the stator 20
And the reluctance torque generated by attracting the iron (rotor core 11).

FIG. 2 is a drawing showing the torque characteristics of this motor. Here, the difference in the operation and effect is clarified in comparison with the torque characteristics of a conventional motor. That is,
More specifically, FIG. 3A is a characteristic diagram showing the relationship between the torque and the current phase of the motor of the embodiment shown in FIG. 1, and FIG. 3B is the conventional motor shown in FIG. FIG. 4 is a characteristic diagram showing a relationship between torque and current phase. Note that FIG.
(B) is the same as FIG.

In this motor, as described above, the d-axis and q
Since the permanent magnet 13 is arranged close to the q axis so that the angle between the axes is less than 90 electrical degrees, the current phase at which the magnet torque TM becomes the maximum is the current phase at which the reluctance torque TR becomes the maximum ( α = 45 °) (amount of deviation = A), and the maximum point of the magnet torque TM and the maximum point of the reluctance torque TR are close to each other (B
<C), the total torque T is improved. Moreover, the permanent magnet 1
3 and the flux barrier 14 are paired, and the pair of permanent magnets 13 and the flux barrier 14 are arranged in a C shape toward the center of the rotor core 11, so that a pair of permanent magnets arranged in a C shape is formed. Magnet 13 and flux barrier 14
In the iron cores on both sides of the U-shape, there is a path P that is easy to pass the lines of magnetic force, so that the path of the magnetic flux is expanded, and the q-axis inductance (easiness of passing the magnetic flux for generating the reluctance torque) is set large. You. Therefore, the maximum value of the reluctance torque TR becomes large (increase amount =
D) Also from this point, the total torque T of the magnet torque TM and the reluctance torque TR is improved (increase =
E).

The flux barrier 14 can be set so as to generate a skew effect and a cooling effect by being formed obliquely with respect to the axis. That is, a skew is formed in the flux barrier 14 to make the distribution of magnetic flux uniform, thereby reducing the torque ripple (cogging torque) (skew effect), and at the same time, the flux barrier (through-hole) 14 having the skew formed. Can function as a fan, thereby achieving a cooling effect.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of an IPM motor including a motor rotor according to an embodiment of the present invention.

FIG. 2 is a diagram showing a torque characteristic of the motor of FIG. 1 in comparison with a torque characteristic of a conventional motor.

FIG. 3 is a cross-sectional view illustrating a configuration example of a conventional IPM motor.

FIG. 4 is a drawing showing torque characteristics of the motor of FIG. 3;

FIG. 5 is a cross-sectional view illustrating a configuration example of another conventional motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Rotor, 11 ... Rotor core, 12 ... Motor shaft, 13 ... Permanent magnet, 14 ... Flux barrier (magnetic flux interruption part), 20 ... Stator.

Continued on the front page (72) Inventor Makoto Abe 2 Takara-cho, Kanagawa-ku, Yokohama-shi, Kanagawa F-term in Nissan Motor Co., Ltd. (reference) 5H621 AA03 GA01 GA04 GA15 HH01 JK02 JK05 5H622 AA03 CA02 CA07 CA13 CB03 CB05 PP03 PP10 PP11 QB03 QB05

Claims (5)

[Claims] 1. A motor rotor having a plurality of permanent magnets embedded in a rotor core and arranged inside the rotor core, wherein the plurality of permanent magnets have a d-axis which is a magnetic force center of the magnet and a q-axis which is a center of an iron core. The electric motor rotor is arranged at equal intervals so that an angle formed by the electric motor is less than 90 degrees in electrical angle. 2. A plurality of permanent magnets, each paired with a magnetic flux interrupting portion, and each pair is arranged in a C-shape toward the center of the rotor core for each pair. 2. The rotor of the electric motor according to 1. 3. The motor rotor according to claim 1, wherein the permanent magnet is a plate magnet. 4. The rotor for an electric motor according to claim 2, wherein the magnetic flux interrupting portion is a through hole. 5. The rotor for an electric motor according to claim 2, wherein the magnetic flux interrupting portion is formed obliquely with respect to an axis.