JPH0356059A - motor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a core type motor, and its cogging torque is reduced to the utmost limit.

[Conventional technology]

FIGS. 14(a) and 14(b) are a schematic cross-sectional view showing an example of a conventional motor and a magnetic flux density distribution diagram on the surface of a permanent magnet. In this figure, 1 is a magnetic pole made of a ring-shaped permanent magnet, with an N pole and an S pole.
It has a pole and is fixed to the magnetic yoke 2. Reference numeral 3 designates an armature having a salient pole, which is provided with a coil 4 and is disposed opposite to the magnetic pole 1 with a gap g therebetween. 5 is a rotating shaft, which is connected to the armature 3 and the magnetic pole 1 by a support member (not shown).
It is also supported.

[Problems to be Solved by the Invention] In order to reduce cogging torque, which is a major problem of torque ripple, in such conventional motors, the magnetization distribution of the magnetic pole 1 is made sinusoidal, and the magnetization angle is changed. (see Japanese Patent Laid-Open No. 61-254045), but none of these techniques completely eliminates cogging torque.

This invention was made in order to solve such problems, and when the distance in the width direction of the permanent magnet is expressed in a Fourier series according to the number of salient poles and the number of poles of the permanent magnet, The purpose is to provide a motor with almost no cogging torque by creating a shape that includes specific Fourier coefficients. [Means for Solving the Problems] A motor according to the present invention has a permanent magnet having m magnetic poles and P salient poles that are actually magnetically equivalent to the permanent magnet, and the motor has m magnetic poles. One pair of N and S poles is set as one period in the motor rotation angle direction, and the distance h(θ) in the width direction of the magnetic poles is expressed as the following Fourier series with respect to the rotation angle θ: h (θ)=ho +Σ an cos (2πnθ
/T), when n=(ixj)±1, j
=2.4.6,..., at least 1 out of 20
Fourier coefficients bn non-zero at values of n or more
The permanent magnet is made into a special shape so that the permanent magnet has a shape in which .

However, i is an integer expressed as P/q, where q is the greatest common divisor of m/2 and P.

[Effect]

In this invention, since the distance in the width direction of the permanent magnet that is the field part is made into a special shape that includes harmonics, the cogging torque becomes extremely small.

〔Example〕

Embodiments of this invention will be described below, but before that, the principle of this invention will be described.

The torque TQ of the radial gap type motor is shown in (2) below.
It is given by Eq.

Here, F, (θ): Amount of radial magnetic flux in the gap Fe (θ): Amount of magnetic flux in the rotational direction in the gap R: Radius at the position of the gap g vo: Magnetic resistivity in the gap g.

The simplest motor with two magnetic poles is shown in Figure 14(a).
This will be explained using a three salient pole motor as an example. ψ is the angle of one salient pole, θ
. Let be the angle of the end of a certain salient pole from the reference position. As shown in equation (2), torque TQ is F, (θ)・F
Since it occurs as a product of e (θ), it can be considered that it occurs only in the gap between the salient pole with a large magnetic flux density and the permanent magnet, and the integration of equation (2) only needs to be performed in the portion where the salient pole is located.

Let the radial direction magnetic flux amount F, (θ)' be the magnetic flux distribution generated by the magnetic pole 1 in the radial direction, and the magnetic flux distribution generated by the permanent magnet is expressed by a composite value of the fundamental wave and harmonics of the sine wave.

Since one pair of N and S poles is 2π and one period T, 2πnθ/
By expressing 2π=nθ, it can be expressed by the following equation.

F, (θ)=Fo(stnθ+Σ β,・sin
nθ)n恕2 ...... (3) However, F. is a constant. In addition, F by a permanent magnet,
In the distribution formula of (θ), the N pole. Since the amount of magnetic flux at the S pole is equal, the DC component is expressed as zero, and n is 2, 3, 4.
,... is an integer of β. represents the mixing ratio of the n-order component to the first-order component. In equation (3),
β. = (bn/bl). If F0=b, then
In equation (1), the DC component h. and the form matches the expression when the cosine component is zero. In other words, in this invention, the magnetic flux FcF(θ) is the distance h(θ) in the width direction of the permanent magnet.
I believe that there is a first-order relationship.

The magnetic flux in the rotational direction Fe (θ) is Fr (θ) rotation =
-F. (cosθ+Σβ, ・n cosnθ)
...... (4) It becomes. In the terms of F, (θ) and Fθ (θ) in equation (2), if we focus on the fundamental wave and one specific n component, we find that +sin (n-1) θ+ βn' sin n
θ ・cos nθ ko (5) Ratio β of the n-th component to the fundamental wave. is usually small β. 《1
Considering this, the last term can be ignored.

Next, the magnetic flux component F, (θ) where liii occurs is k
In the case of only the next component, F, (θ)・F(θ
) is the term k. F, (θ)le (θ)− − Fo” − s
tn2 kθ2 (6).

Cogging torque is zero when liB8i1 has a magnetic flux distribution of a single high-order sine wave, except when the order is an integral multiple of the salient pole (3, 6, 9, etc. in the case of this motor). Therefore, cogging torque occurs when n±1 becomes an integral multiple of 3 in equation (5). Section (5).
As is clear from comparing equation (8), n±1 and 2k correspond.

That is, in this motor, cogging torque is generated when the fundamental wave includes a component such that (n±1)/2 is a multiple of 3 among the harmonic magnetic flux components of the n-th mode. For example, n=
In the case of 5, cogging torque does not occur in the 5th mode alone, but when the 5th mode is slightly added to the fundamental mode, (5 + 1) / 2 = 3, and a single 3rd harmonic magnetic flux component is created. A cogging torque pattern occurs. vice versa,
Even if a mode generates cogging torque by itself, if it is combined with the fundamental wave, it will only affect the term βn' in equation (5), and rather cogging torque will not be generated much. In other words, when a higher-order mode is mixed with the fundamental wave, a cogging torque pattern of the higher-order mode alone is not generated, but acts nonlinearly.

Note that the number m of salient poles in this invention corresponds to the number of coils 4 of each phase in a motor having a normal concentrated winding shown in FIG. 14(a), but In a motor with distributed winding and many salient poles, the coil 4
It is not the number of , but the number of salient poles itself. In addition, in a motor having auxiliary grooves on the main salient pole as shown in FIG. 17, the term refers to the number of small convex portions.

Examples of the present invention based on the above principle will be described below.

FIGS. 1(a), (b), and (c) show an embodiment of the present invention, in which the two magnetic poles and three salient poles shown in FIG. 14(a).
The present invention is applied to a motor having concentrated windings (not shown). Since this motor is a radial gap type motor, in order to control each harmonic component of the magnetic flux, the height h of the permanent magnet in the direction of the rotation axis is set to a shape in which the harmonic precepts are added. Note that h is the distance in the direction of the rotating shaft in the case of a radial gap type motor, and the distance in the radial direction in the case of an axial gap type motor.

FIGS. 2(a), (b), and (C) schematically explain a method of adding, for example, a fifth-order harmonic component. FIG. 2(a) shows the fifth-order mode, and FIG. 2(b) shows the fundamental mode. However, in this figure, the shape of the fundamental mode is not represented as a sine wave but as a rectangle for simplicity. Therefore, when Figure 2 (a) and (b) are combined, Figure 2 (
As shown in C), it can be seen that each higher-order mode can be introduced simply by changing the distance in the width direction of the magnetic pole 1.

The direction of magnetization of the permanent magnets of the conventional motor shown in FIG. 14(a) is usually the radial direction as shown in the same figure, or one direction as shown in FIG. 15(a). In this case, the distribution of magnetic flux on the surface of I+ii pole 1 is as shown in Fig. 14 (b
), as shown in FIG. 15(b), it is sinusoidal in one direction, and rectangular or trapezoidal in radial direction.

However, even if the magnetic flux distribution is rectangular or trapezoidal, when these are expanded into a Fourier series, the largest component is the first-order fundamental wave. Therefore, the study can be performed by adding each higher-order component to this fundamental wave.

FIG. 3 shows the magnetic flux distribution with respect to the rotating direction of the surface of the magnetic pole 1 of the conventional motor shown in FIG. 14(a), which includes higher-order odd modes in addition to the fundamental wave. The cogging torque of this motor is shown in FIG. Cogging torque is 60”,
30' Contains each cogging torque having a period of 15°. As mentioned above, a 60° period corresponds to 5.7 of the magnetic flux.
Next component, 30' is 11.13th component, 15° is 17,1
This is thought to be the influence of the 9th precept.

Figure 5 is a schematic diagram of a magnet shape in which the 5th and 7th modes are inserted by -8% and -3% of the fundamental wave, respectively, in order to cancel the 5.7th mode of the permanent magnet.
6 shows the cogging torque at that time.

As is clear from FIG. 6, when the 5th and 7th order magnetic flux modes are reduced, the 60'' period cogging torque almost disappears, leaving a high-order cogging torque.

The cogging torque with a period of 30' is calculated using the same method as the 11th order, 1
The third order mode can be reduced by placing it in the magnet shape.

Figure 7 is a schematic diagram of the magnet shape with -5% added only to the 5th mode, so that the 5th and 7th order components of the magnetic flux components generated by magnetic pole 1 have approximately the same value. .

In this case as well, as shown in Fig. 8, the cogging torque with a period of 60'' is a very small value.In other words, the cogging torque generated by a certain portion of the 5th and 7th order magnetic fluxes has opposite phases, so Even if fifth-order and seventh-order components are included, if their values have the same sign and values, the cogging torque in that mode will be a very small value.

Figure 9 shows the conventional motor shown in Figure 14(a) with the 5th and 11th modes added to the magnet shape.
As shown in Figure 0, the cogging torque becomes extremely small.

Figure 16 shows a 48i permanent magnet with distributed windings that is often used in AC servo motors. A conventional motor with 15 salient poles is shown. The period of cogging torque in this case using a normal permanent magnet is 6°, 3°...
It becomes...

When applying this invention to the above motor, m=4
(Number of magnetic poles) P = 15 (Number of salient poles) q = 1 (Greatest common divisor of 1 and P) 2 P i = 15 (-) q j = 2 (j = 2.4, 6, ...・20
Therefore, n=(ixj)±1=(1 5)l)±1=31 or 29Finally, h(θ) is h(θ)”ha+bzgsin29θ+b31si
n 3 1θ. b29. What percentage should be set for b31 is determined from the cogging torque characteristic diagram so that the cogging torque is minimized.

Furthermore, FIG. 17 shows a conventional motor having auxiliary grooves on the salient poles. When this invention is applied to this conventional motor, the number of salient poles that affect the cogging torque is 6,
N. n=6j±1 (j=2.4,・
All you have to do is put the mode (...) into the magnet shape. Until now, the shape of a magnet with a magnetization distribution in the radial direction was changed, but this invention can also be applied to a motor using a permanent magnet with a magnetization component in one direction as shown in FIG. 15(a). You can eliminate ripples in a similar way. In this case, the width h(θ) of the permanent magnet is constant with respect to θ, and most of the components are already primary. Therefore, adding n-th harmonics to this permanent magnet by changing its shape, for example, means adding harmonics of βn sin nθlsinθ.

In FIG. 11, n=5. This shows what harmonics are actually added when β5=1 is added. As is clear from the figure, the added 5th order component is approximately 60% of the added value.
However, it remains as it is, and the negative seventh order component is approximately 20
%. In addition, a slight component of 3Xk (k=1.2, . . . ) is generated. Therefore, the value of the added component can be controlled by predicting this rate of decrease, and the same effect as using a permanent magnet having a magnetization component in the radial direction can be obtained.

FIG. 18 shows a conventional motor using a C-shaped magnet with magnetization in one direction and an angle of li less than 180°. A case in which the present invention is applied to such a conventional motor will be described.

FIG. 12 shows the magnetic flux distribution on the surface generated by a C-type magnet having an angle of 150°, broken down into harmonics of each order. When a permanent magnet with magnetization in one direction is used, the F and (θ) components in equation (3) are not zero even in areas without permanent magnets, and the overall result is that a slight harmonic component is added to the fundamental wave. It is shaped like this. When the shape of such a permanent magnet is changed and an n-th harmonic is added, it means that a harmonic of the magnetic flux represented by F, (θ)=βn' Sin nθ·lSinθ is added.

In Figure 13, n=5. This study investigated what kind of harmonics are added when β5=1. In this case as well, it is similar to the conventional motor in which permanent magnets exist around the entire circumference as shown in Fig. 15(a), and in addition to the added components, 3k, 3k±1
Only higher-order components (k=1.2, . . . ) are generated. Therefore, even in such a motor where permanent magnets are not present around the entire circumference, the same effect can be obtained by adding a higher-order component to the part where permanent magnets are present. In this case, since the magnetic flux distribution contains many high-order components, it is important to control the amount of newly added high-order modes in consideration of the ratio of already existing high-order modes.

[Effects of the Invention] As explained in detail above, the present invention provides a motor having a field section consisting of m4f permanent magnets and P salient poles that are substantially magnetically equivalent and facing the field section. magnetic pole N
, Si 1 pair has one period T in the motor rotation angle direction,
The widthwise distance h(θ) of the magnetic pole is expressed as the rotation angle θ.
When expressed in the Foury series of equation (1), n=(iXj)±1 (j=2.4,...) for each N and S magnetic pole pair.
) in which one of the Fourier coefficients bn has a value other than zero, it has the advantage of being a high-quality motor with extremely low cogging torque.
This is of great industrial significance.

[Brief explanation of drawings]

FIGS. 1(a), (b), and (c) are a schematic cross-sectional view showing an embodiment of the present invention, a developed front view and a perspective view of a permanent magnet, and FIGS. 2(a), (b), and (c). is an explanatory diagram of how to add harmonic components according to this invention, FIG. 3 is a magnetic flux distribution diagram with respect to the rotation direction of the magnetic pole surface of a conventional motor, FIG. 4 is a cogging torque characteristic diagram, and FIG. 5 is also according to this invention. 5th order,
A schematic diagram showing the shape of a permanent magnet when the 7th mode is added, FIG. 6 is also a cogging torque characteristic diagram, FIG. 7 is a schematic diagram showing the shape of a permanent magnet when only the 5th mode is added, and FIG. The figure shows the cogging torque characteristics in that case, Figure 9 is a schematic diagram showing the shape of the permanent magnet when the 5th and 11th modes are added to the conventional motor, and Figure 10 shows the cogging torque characteristics in Figure 9. Figure 11 is a drive torque characteristic diagram when a 5th mode is added to a conventional motor, Figure 12 is a surface magnetic flux distribution diagram of a motor using a conventional C-shaped magnet, and Figure 13 is a diagram of this conventional motor. Figures 14 to 18 all show conventional motors, and Figure 14(a) shows a motor in which the magnetization direction of the permanent magnet is in the radial direction. Schematic cross-sectional view of FIG. 14 (b
) is a magnetic flux density distribution diagram on its surface, FIG. 15(a) is a schematic cross-sectional diagram of a motor with one direction of magnetization, and FIG. 15(b) is a diagram of the magnetic flux density distribution on its surface.
) is a magnetic flux density distribution diagram on its surface, and Figure 16 is a schematic cross-sectional diagram of a motor with a 48i permanent magnet and 15 salient poles.
Figure 7 is a schematic cross-sectional view of a motor having auxiliary grooves on salient poles, No. 18
The figure is a schematic cross-sectional view of a motor using C-shaped magnets. In the figure, 1Iif1 pole, 2 is the magnetic yoke, 3 is the armature. (Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 11, Fig. 12, Fig. 13, Fig. 14)] 5, Fig. 16, Fig. 16, ``Correcting hand sales'' Yohi (self-motivated), 1999, 12 28th of the month

Claims (1)

[Scope of Claims] In a motor having a field part made of a permanent magnet having m magnetic poles and P salient poles facing the field part, a pair of N and S poles of the magnetic poles are arranged in the motor rotation angle direction. If one period is T, and the distance h(θ) in the width direction of the magnetic pole is expressed as the following Fourier series ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ for the rotation angle θ, then n = (i x j) ± When set to 1, j=2,
A motor characterized in that the field portion has a shape in which a non-zero Fourier coefficient b_n exists for at least one value of n among 4, 6, . . . , 20. However, h_0 is the DC component, a_n is the Fourier coefficient, i
is an integer expressed as P/q, where q is the greatest common divisor of m/2 and P.