JPH0356060A - Motor - Google Patents

Abstract

PURPOSE:To decrease cogging torque torque by putting the distance in the thickness direction of a permagnet being the field part, in special shape which includes higher harmonies. CONSTITUTION:In case that the distance d(o) in the thickness direction of magnetic poles is expressed by formula I with respect to an AC servo motor which has four poles of permanent magnets and fifteen pieces of salient poles, m=4 (number of magnetic poles), p=15 (number of salient poles), q=1 (the greatest common measure between m/2 and p, i=15 (p/q), and j=2 (2 is taken for simplification among j=2,4, 6,...20). Accordingly, n=(iXj)+ or -1=(15X2)+ or -1=31 or 29. Finally, the distance d (o) in the thickness direction of magnetic poles becomes the one shown in formula II. What percent of the distance do in the standard thickness direction to set b29 and d31 to is determined from the property figure so that the cogging torque may by the minimum.

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]

Figure 14(a). (b) is 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 equipped with a coil 4 and is arranged to face the magnet 1i1 with a gap g therebetween. 5 is the rotation axis,
Armature 3 and Ii are supported by supporting members (not shown).
It is supported together with n-pole 1.

[Problem to be solved by the invention]

In order to reduce cogging torque, which is a major problem of torque ripple in such conventional motors, l+fi
Methods have been considered to make the magnetization distribution of pole 1 sinusoidal or to control the magnetization angle (see Japanese Patent Application Laid-Open No. 61-254045), but none of them completely eliminates the cogging torque. It wasn't the kind of technology that would do that.

This invention was made in order to solve such problems, and when the distance in the thickness direction of the permanent magnet is expressed as a Fourie series in accordance with the number of salient poles and the number of poles of the permanent magnet, ,
It is an object of the present invention to provide a motor that has almost no cogging torque by having a shape that includes a specific Fourier coefficient.

[Means to solve the problem]

The motor according to the present invention is a motor having a permanent magnet having m magnetic poles and P salient poles that are substantially magnetically equivalent to the permanent magnet, and a pair of N and S poles of the magnetic poles are connected to the motor. One period T in the direction of the rotation angle, and the distance Md (θ) in the thickness direction of the magnetic pole is expressed by the following Fourier series d (θ)=d. +Σ a. COS(2 πnθ
/T), when n=(iXj)shicho, j
=2.At least 1 out of 4, 6, ..., 20
non-zero Fourier coefficients for values of n greater than or equal to b.
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 thickness direction of the permanent magnet, which is the field part, has 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): radial magnetic flux amount in the gap Fe (θ): rotational direction magnetic flux amount R in the gap; radius ν at the position of the gap g. : is the 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 0 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 iF, (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 the combined value of the fundamental wave and harmonics of a sine wave. N
, S$i11 pairs are 2π and one period T, so 2πnθ
By expressing /2π=nθ, it can be expressed by the following equation.

F, (θ) = Fo (sin θ + Σ β.・sin
nθ)nm2 (3) However, FO is a constant. In addition, F.
．． In the distribution equation of (θ), the amount of magnetic flux at the N pole and s8i is equal, so the DC component is expressed as zero, and n is 2, 3
, 4, ..., an integer of β. represents the mixing ratio of the n-order component to the first-order component. In equation (3), β. ” (bn /b+), Fo=b, the form matches the equation when the DC component d0 and cosine component are zero in Equation (1).In other words, in this invention, the magnetic flux amount F(θ ) is the distance d in the thickness direction of the permanent magnet
We believe that there is a linear relationship with (θ).

Magnetic flux in the rotation direction Fe (θ) is F, rotation of (θ) = -
Fo(cosθ+Σβ,・n cosnθ)・・
...(4) becomes. In the term F, (θ)・Fe (θ) of equation (2), if we focus on the fundamental wave and one specific n component, +sin (n-1) θ}◆βn ' sin n
θ"cosnθko... (5) The ratio β of the n-order component to the fundamental wave is usually small.《1
Considering this, the last term can be ignored.

Next, when the magnetic flux component F, (θ) generated by the magnetic pole 1 is only the k-order component, the terms F, (θ) and F(θ) in equation (2) are as follows: 6) It becomes.

Cogging torque is calculated when magnetic pole 1 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). Since it is zero, cogging torque occurs when n±1 becomes an integer multiple of 3 in equation (5). Section (5), (8
), it is clear that 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=
5, the fifth-order mode alone does not generate cogging torque, but when the fifth-order mode is slightly added to the fundamental mode, (5+1)/2=3, and the independent third harmonic Ii
ii A cogging torque pattern created by the east component occurs.

Conversely, even if a mode generates cogging torque by itself, if it is combined with the fundamental wave, β in equation (5)
It only affects the term n', and rather cogging torque does not occur much. That is, when a higher-order mode is mixed with the fundamental wave, if a cogging torque pattern of the higher-order mode alone is generated, 11 <, the cogging torque pattern 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 as shown in FIG. In a motor that is provided with distributed windings and has a large number of salient poles, it is not the number of coils 4 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 radial thickness d of the permanent magnet is made into a shape in which the harmonic components are added. Note that d is a distance in the radial direction in a radial gap type motor, and a distance in the rotation axis direction in an axial gap type motor.

Figure 2 (a), (b). (c) is a schematic explanation of 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 thickness 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 the magnetic pole 1 is as shown in FIG. 14(b). As shown in Figure 15(b), in the case of one direction, it is a sine wave,
In the radial direction, it is square or trapezoidal. 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°. It includes each cogging torque having a period of 15°. As mentioned above, the 60'' period is considered to be the effect of the 5.7th order component of the magnetic flux, the 30@ to the 11th and 13th order components, and the 15@ to the 17th and 19th order components.

Fig. 5 shows that in order to cancel the 5.7th mode of the permanent magnet, the 5th and 7th modes are each set to -8% relative to the fundamental wave. A schematic diagram of the shape in the thickness direction of a permanent magnet containing -3% and FIG. 6 show the cogging torque at that time.

As is clear from FIG. 6, when the fifth-order and seventh-order magnetic flux modes are reduced, the 60° cycle cogging torque almost disappears, leaving a high-order cogging torque.

The cogging torque of 30” period is calculated using the same method as 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 Figure 8, the cogging torque with a period of 60" is a very small value. In other words, the cogging torque generated by the 5th and 7th order magnetic flux components has opposite phases, so Even if second and seventh order components are included, if the values have the same sign and the same value, the cogging torque in that mode will be a very small value.

Fig. 9 shows the conventional motor shown in Fig. 14(a) in which the 5th and 11th modes are added to the shape of the permanent magnet in the thickness direction, and as shown in Fig. 10, the cogging torque is becomes extremely small.

FIG. 16 shows a conventional motor having a four-pole permanent magnet with distributed windings and 15 salient poles, which is often used in AC servo motors. The period of cogging torque in this case using a normal permanent magnet is 6°, 3°...
...becomes...

When this invention is applied to the above motor, m=4 P=1 5 (number of magnetic poles) (number of salient poles) P i=15(-) q j=2 (j=2. 4, 6.
・・・・・・Take 2 because there is only N out of 20) Therefore, n=(iXj)±1=(1 5X2)±1=31 or 29Finally, d(θ) is d(θ)= do+b29 sin29θ ten b nis
1n 3 1θ. What percentage should be set for b 29 and b 31 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, for 56fl pole pair n=6j±1 (j=2.
4,...) should be included in the shape of the permanent magnet in the thickness direction.

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 thickness d(θ) of the permanent magnet is constant with respect to θ, and the primary component is already the majority.

Therefore, for example, changing the shape and adding the n-th harmonic to this Miku bii stone is β. sin nθl sin
This means that harmonics of θ1 are added.

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.

Figure 18 has magnetization in one direction, and the angle of one pole is 180@
This figure shows a conventional motor using a C-shaped magnet with a diameter smaller than 1. A case in which the present invention is applied to such a conventional motor will be described.

Figure 12 shows the magnetic flux distribution on the surface generated by a C-shaped magnet with 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 the part without a permanent magnet, and the fundamental wave as a whole has a slight harmonic component. It has an added shape. When changing the shape of such a permanent magnet and adding n-th harmonics, F, (θ) = β. - sin nθl sinθ1F,
This means that a harmonic of the magnetic flux shown by (θ)=0 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 there are no permanent magnets around the entire circumference, the same effect can be obtained by adding a higher-order component to the part where the permanent magnet is present.In this case, the higher-order components in the magnetic flux distribution Therefore, it is important to control the amount of newly added higher-order modes by considering the ratio of already existing higher-order modes.

(Effects of the Invention) As explained in detail above, the present invention provides a motor having a field section consisting of m-pole permanent magnets and P salient poles that are actually mechanically equivalent to the field section. , said bni
N, S8i one pair in one period T in the motor rotation angle direction
When the thickness direction distance d(θ) of the magnetic pole is expressed by the Fourier series of equation (1) with respect to the rotation angle θ, N
, S for each magnetic pole pair n=(ixj)±1 (j=2.4,
), the Fourier coefficient b. Since the shape has a non-zero value, there is an advantage that a high-quality motor with extremely low cogging torque can be produced, and 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 rotating direction of the magnetic pole surface of a conventional motor, FIG. 4 is also a cogging torque characteristic diagram, and FIG. 5 is also a diagram of this invention. 5th order according to.
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, Figure 16 is a schematic cross-sectional diagram of a motor with 4-pole permanent magnets and 15 salient poles, and Figure 17 is a diagram of the magnetic flux density distribution on its surface.
The figure is a schematic cross-sectional view of a motor having auxiliary grooves on salient poles, and FIG. 18 is a schematic cross-sectional view of a motor using C-shaped magnets. In the figure, 1 is a magnetic pole, 2 is a magnetic yoke, 3 is an armature, 4 is a coil, and 5 is a rotating shaft. 2nd figure 5th mode cram school mode Figure 13 Figure 14 Figure 15 Figure 16 Figure Procedure Amendment (Voluntary) December 28, 1997

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 d(θ) in the thickness direction of the magnetic pole is expressed as the following Fourier series for the rotation angle θ, n = (1 x j) When ±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, d_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.