JPH06339238A - Permanent magnet type motor - Google Patents

Abstract

(57) [Summary] [Purpose] In a permanent magnet type motor, the magnetic flux density distribution in the air gap between the stator and rotor can be made to have as few harmonic components as possible to reduce cogging torque, and Reduce vibration and noise. [Structure] Each of the permanent magnets 28 incorporated in the rotor 24 is formed to have an arc-shaped cross section, and each of the permanent magnets 28 is arranged on the rotor core 26 so that the convex portion 28a side faces inward. Further, the permanent magnet 28 is magnetized so that the magnetic flux B of each part thereof is concentrated at one point.
The distance L from the magnetic center C to the average arc line D of the permanent magnet 28 and the average radius R of the permanent magnet 28 are 0.4
It is configured such that × R ≦ L ≦ 0.9 × R.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet type motor having a rotor constructed by incorporating a plurality of permanent magnets inside a rotor core.

[0002]

2. Description of the Related Art Recently, as a permanent magnet type motor, a motor having a structure shown in FIG. 5 has been developed as a motor having high torque and high efficiency. This product has the following configuration.

That is, the stator 1 has U-phase stator windings 1U and 2U and V-phase stator windings 1V and 2V in twelve slots 3 formed in an annular stator core 2. ,
In addition, the W-phase stator windings 1W and 2W are inserted and arranged. Each slot 3 is provided on the inner circumference of the stator core 2.
The opening 3a is formed corresponding to the.

On the other hand, as shown in FIG. 6, the rotor 4 has a rotor shaft 6 to which a rotor core 6 is fitted and fixed, and a section of a storage portion 7 formed in the rotor core 6 has a cross section. It is configured by inserting and incorporating four arc-shaped permanent magnets 8 from the axial direction, and the stator core 2 is provided inside the stator 1.
It is rotatably arranged in a state where there is a predetermined gap 9 with the inner peripheral portion. Each of the permanent magnets 8 is arranged so that the convex portion 8a side faces the outside (air gap 9 side), and the four permanent magnets 8 have N poles and S poles alternately in FIGS. 5 and 6. Is magnetized so that

FIG. 7 and FIG. 8 show the magnetic anisotropy (direction of magnetic alignment) of a permanent magnet. 7 shows a known radial anisotropy in which the center A of the rotor 4 and the center (magnetic center) of the magnetic flux B of each part of the permanent magnet 8 are the same, and FIG. The magnetic anisotropy in the magnetic pole axis direction with the center at infinity is shown, and these anisotropies are selected and used according to the application.

On the other hand, FIG. 9 shows a so-called inverter power source used for driving a motor. This Figure 9
In, the switching main circuit 11 is connected to the DC power supply 10. The switching main circuit 11 is configured by connecting six transistors 12 and a free wheeling diode 13 in a three-phase bridge connection. In this switching main circuit 11, the three-phase arm units 11U, 11V, 1
The common connection points of the transistors 12 included in 1W are connected to the output lines U, V, and W to the corresponding motors. These output lines U, V, W are the stator windings 1U, 2U of each phase of the stator 1 and 1V, 2V and 1W,
It is connected to 2W.

The control circuit 14 includes a switching main circuit 11
By controlling each transistor 12 of, the stator windings 1U, 2U and 1V, 2V and 1W, 2W corresponding to the stator windings for two adjacent phases are, for example, 120 degrees (electrical angle). It is configured to energize by shifting the phase one by one, that is, to energize the well-known 120 degrees (electrical angle). The control circuit 14 is also connected to the output lines U, V, W, and the rotation of the rotor 4 causes the stator windings 1U, 2U,
The induced voltage induced in 1V, 2V, 1W, 2W is detected, and the motor drive signal according to the rotational position of the rotor 4 is obtained.

[0008]

However, the conventional structure as described above has the following problems. (1) The magnetic flux density of the air gap 9 by the permanent magnets 8 for one pole in the rotor 4 has a substantially trapezoidal distribution as shown in FIG. 10, and the magnetic flux in the air gap 9 has a third order and a fifth order. ,
It contains harmonic components such as the 7th order. Since the shape of the rotor iron core 6 for reducing these harmonics is limited, the degree of freedom in design is reduced, and the application is limited, it is generally not easy to reduce the harmonics, and it is usually difficult to reduce the harmonics. Contains many harmonic components.

(2) Many energy components are present in the void 9 due to these harmonic components. Cogging torque is generated by the interaction between such an energy component and the opening 3a of the slot 3 in the stator core 2.

(3) Although this cogging torque is superposed on the torque generated by the motor, it does not act as an effective drive torque, but it is a torque that vibrates the rotor 4, so this vibration is generated by the motor. It is transmitted to the equipment driven by the frame and the motor and causes vibration and noise.

The present invention has been made in view of the above circumstances, and an object thereof is to make it possible to reduce the magnetic flux density distribution in the air gap between the stator and the rotor with as few harmonic components as possible, and to reduce the cogging torque. The purpose of this is to provide a permanent magnet type motor with less vibration and noise.

[0012]

According to the present invention, a stator having stator windings of a plurality of phases and a plurality of permanent magnets incorporated in a rotor iron core are fixed inside the stator. A permanent magnet type motor having a rotor and a rotor rotatably arranged in a state where a predetermined gap is present, and rotating the rotor by sequentially energizing the stator winding. Each permanent magnet is formed so that its cross section has an arc shape, and each of these permanent magnets is arranged on the rotor core so that the convex side faces inward, and the magnetic flux of each part of this permanent magnet is concentrated at one point. And the average radius R of the permanent magnet and the distance L from the magnetic center of the permanent magnet to the average arc line of the permanent magnet are 0.4 × R ≦
The feature is that L ≦ 0.9 × R.

[0013]

According to the above-mentioned means, each permanent magnet of the rotor is formed to have an arc-shaped cross section, and each of the permanent magnets is arranged on the rotor core so that the convex side faces inward.
And the permanent magnet is magnetized so that the magnetic flux of each part thereof is concentrated at one point, and the relationship between the distance L from the magnetic center of the permanent magnet to the average arc line of the permanent magnet and the average radius R of the permanent magnet is By setting 0.4 × R ≦ L ≦ 0.9 × R, as is clear from the experimental result (relationship between L / R and the content ratio of the third-order harmonic magnetic flux density in the void), which will be described later, As the magnetic flux density in the air gap between the stator and the rotor, particularly the third harmonic component is small, and the cogging torque can be reduced accordingly.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to a three-phase, four-pole permanent magnet type motor will be described below with reference to FIGS. First, in FIG. 2, the stator 21 has the same structure as the conventional one, and the U-phase stator windings 1U, 2 are provided in 12 slots 23 formed in the stator core 22 having an annular shape.
It is configured by inserting and arranging U- and V-phase stator windings 1V and 2V and W-phase stator windings 1W and 2W. An opening 23 a is formed in the inner peripheral portion of the stator core 22 so as to correspond to each slot 23.

On the other hand, the rotor 24 has a rotary shaft 25.
The rotor core 26 is fitted and fixed to the rotor core 26, and four permanent magnets 28 made of ferrite having an arc-shaped cross section in this case are inserted in the housing 27 formed in the rotor core 26 from the axial direction. Stator 2 which is constructed by incorporating
It is rotatably arranged in the inside of the stator 1 with the inner peripheral portion of the stator core 22 and a predetermined gap 29. The rotor core 26 is formed by laminating a large number of silicon steel plates having holes for forming the storage portion 27.

Each of the above-mentioned permanent magnets 28 is arranged so that the convex portion 28a side faces inward, and the four permanent magnets 28 are attached so that the N poles and the S poles alternate in FIG. It is magnetized. Further, as shown in FIG. 1, each permanent magnet 28 is magnetized so that the magnetic flux B of each portion is concentrated at one point, that is, the magnetic center C. And this permanent magnet 2
When the distance from the magnetic center C of 8 to the average arc line D of the permanent magnet 28 is L and the average radius of the permanent magnet 28 is R,
The distance L and the average radius R are 0.4 × R ≦ L ≦ 0.
It is set so that the relationship of 9 × R is established.

The motor thus constructed is supplied with power from the inverter power source (see FIG. 9) as in the conventional case, and the stator windings 1U, 2U and 1V, 2 are provided.
Corresponding to the stator windings for V and the adjacent two phases of 1W and 2W, for example, the phase is shifted by 120 degrees (electrical angle) and the current is applied, that is, 120 degrees (electrical angle) is applied to fix. A rotating magnetic field is generated by the child 21, and the rotor 24 is rotated by the magnetic attractive force and repulsive force that accompany this.

Here, in FIG. 3, in the permanent magnet 28 of the rotor 24, the average arc line D from the magnetic center C is shown.
Shows an experimental result of the relationship between L / R, which is the ratio of the distance L to the average radius R, and the content ratio of the third-order harmonic magnetic flux density in the air gap 29 (to the fundamental wave magnetic flux density in the air gap). ing. The minus region of the third harmonic magnetic flux density content indicates that the phase is opposite to the fundamental wave.

As is apparent from FIG. 3, when the value of L / R is within the range of 0.4 to 0.9, the content ratio of the magnetic flux density of the third harmonic which is the main component of the harmonic. It turns out that can be made smaller. As a result, the L / R value is 0.4 to 0.
Setting within the range of 9, that is, L and R,
By setting such that the relationship of 0.4 × R ≦ L ≦ 0.9 × R is established, the magnetic flux density in the air gap 29 has a smaller number of harmonic components. That is, since the magnetic flux density in the air gap 29 is as close to a sine wave as possible, the cogging torque can be reduced.

As described above, the harmonic component of the magnetic flux density in the air gap 29 is reduced as much as possible so that the magnetic flux density in the air gap 29 is distributed as sinusoidally as possible. Less, stator core 2
Since the energy fluctuation due to the interaction with the opening 23a of the slot 23 in 2 also becomes small, the cogging torque is reduced, and consequently the vibration and noise of the motor can be suppressed.

FIG. 4 shows a second embodiment of the present invention. In the second embodiment, the permanent magnet 30 of the rotor 24 is formed in an arc shape having a semi-cylindrical section.
Such a permanent magnet 30 is arranged so that the convex portion 30a side is on the inside.

In this case as well, the magnetic center C of the permanent magnet 30 is used.
By setting the average radius R and the average radius D and the average radius R, and setting the relationship between the average radius R and the distance L from the magnetic center C to the average radius D as in the first embodiment, It is possible to obtain various effects.

In the present invention, the number of permanent magnets (number of poles)
May be other than 4 poles, and the number of slots in the stator is 12
It may be other than individual pieces. Further, the permanent magnet may be other than ferrite, or may be a part of an ellipse if it has an arc shape. The present invention can be variously modified and implemented without departing from the scope of the invention.

[0024]

According to the permanent magnet type motor of the present invention, each permanent magnet of the rotor is formed so as to have an arc-shaped cross section, and each of the permanent magnets is directed to the rotor core so that the convex side faces inward. And the permanent magnet is magnetized so that the magnetic flux of each part thereof is concentrated at one point, and the distance L from the magnetic center of the permanent magnet to the average arc line of the permanent magnet and the average radius R of the permanent magnet are By setting the relation of 0.4 × R ≦ L ≦ 0.9 × R, the magnetic flux density in the air gap between the stator and the rotor can be made to have less harmonic components. The cogging torque can be reduced, and the vibration and noise can be reduced, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention and showing a dimensional relationship of essential parts.

FIG. 2 is a sectional view of a motor

FIG. 3 is a diagram showing a relationship between L / R and a content ratio of a third harmonic magnetic flux density.

FIG. 4 is a side view of a rotor showing a second embodiment of the present invention.

FIG. 5 is a view corresponding to FIG. 2 showing a conventional configuration.

FIG. 6 is a side view of the rotor.

FIG. 7 is an explanatory view showing a case where the magnetic arrangement of the permanent magnets is radial anisotropy.

FIG. 8 is an explanatory diagram showing a case where the magnetic arrangement of the permanent magnets is anisotropic in the magnetic pole axis direction.

FIG. 9 is an electrical configuration diagram.

FIG. 10 is a diagram showing a distribution of air gap magnetic flux density.

[Explanation of symbols]

1U, 2U, 1V, 2V, 1W and 2W are stator windings, 21 is a stator, 24 is a rotor, 26 is a rotor core, 28 is a permanent magnet, 28a is a convex portion, 29 is a gap, 30
Is a permanent magnet, and 30a is a convex portion.

Claims (1)

[Claims] 1. A stator having stator windings of a plurality of phases,
The rotor core is configured by incorporating a plurality of permanent magnets inside, and the stator includes a stator and a rotor rotatably disposed in a state in which a predetermined gap is present. In a permanent magnet type motor for rotating and driving the rotor by sequentially energizing the wires, each permanent magnet of the rotor is formed to have an arc-shaped cross section, and each of the permanent magnets is projected on the rotor core. And the permanent magnet is magnetized so that the magnetic flux of each part thereof is concentrated at one point, and the distance L from the magnetic center of the permanent magnet to the average arc line of the permanent magnet,
A permanent magnet type motor characterized in that the relationship with the average radius R of the permanent magnet is 0.4 × R ≦ L ≦ 0.9 × R.