JPH03150056A - Motor - Google Patents

Abstract

PURPOSE:To reduce a torque ripple by forming the axial distance of poles of a field in a shape including a sine or cosine harmonic wave in a 3-phase coreless motor. CONSTITUTION:A pair of poles N, S of a motor having poles made of m pieces of permanent magnets, and p pieces of air core coils are set to one period T with respect to the rotating direction of the motor, and the relationship between the lateral distance h(theta) of the poles and the rotational angle theta is specified as an equation. n=1-infinity , and when n = i + or - 1, n is so selected that coefficients an, bn which are not zero exist with one or more n. i is an integer number represented by p/q, when the q is greatest common divisor of m/2 and p. The field 1 represented by the equation becomes a shape as indicated, for example, by 1-3. Thus, a torque ripple is reduced.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The invention of Part B is a three-phase core smoke in which the torque ripple is extremely small.

[Prior Art] Three-phase coreless motors are used as capstan motors for VTRs and the like. As equipment becomes smaller, torque ripple is more likely to occur in these low-speed, low-inertia motors, and its reduction has become an important issue. As a method for reducing the torque ripple of the motor, as shown in Japanese Patent Application Laid-Open No. 5-206267 and Japanese Patent Application Laid-Open No. 58-22574, a non-magnetic part or a part of each magnetic pole of a multi-pole magnet is provided. A method of providing magnetized portions of opposite polarity, and a method of providing five sub magnetic poles on the outer periphery of a permanent magnet, as disclosed in Japanese Patent Application Laid-Open No. 63-257445, are known.

[Problem to be solved by the invention]

However, JP-A No. 5-206267, JP-A-58
-The method of Publication No. 22574 has a large torque loss;
Further, the method disclosed in Japanese Patent Application Laid-Open No. 63-257445 has problems in that magnetization is difficult and mass productivity is lacking.

The present invention aims to solve these drawbacks and provide a coreless motor with extremely low ripple.

[Means to solve the problem]

The motor according to the present invention is a motor consisting of magnetic poles made of m permanent magnets and p air-core coils, and the pair of magnetic poles N and S has one period T with respect to the angular direction of the motor, and the magnetic poles When the width direction distance h(θ) is expressed with respect to the rotation angle θ by the following formula (% formula %), when n=i±1, at least one value of n has a non-zero coefficient. The magnetic poles have a distribution of distances in the width direction of the magnetic poles such that a1 or s exists. However, hori, =H(0
≦θ〈π), h, = -H (π〈θ≦2K), H: Standard distance in the width direction of the magnetic pole. In the above equation, when π≦θ〈2π, the sign becomes negative because the sign is a change in polarity. , and the distance in the width direction is considered to be its supply value. Further, when the greatest common divisor of iLtm/2 and p is q, it is an integer expressed as P/q.

[Effect]

In this invention, the distance in the width direction of the magnetic pole, which is the field part, has a special shape that includes harmonics of a sine wave or a cosine wave, so that torque ripple is extremely small.

〔Example〕

Figure 12 (a) is the most common type of coreless motor.
An explanation will be given by taking as an example a motor with an axial gap type quadrupole magnet, three coils, and Yv; wire shown in (b).

In FIG. 12 (-), 1 is a field part made of a permanent magnet, 2 is a rotor yoke, to which the field part 1 is attached, and the rotor shaft 3 is fixed. 4 is an air-core coil, and three coils are Y-connected.

Reference numeral 5 denotes a back yoke to which an air-core coil 4 is attached, and supports the rotor shaft 3 by a bearing 6 at the center. A plan view of the field section 1 is shown in FIG. 12(b). 12th
As shown in Figure (b), two magnetic poles made of permanent magnets, a north pole 1N and a south pole 1S, are alternately arranged to constitute the field section 1.

Before describing an example in which the present invention is applied to such a motor, the sixth
This will be described first with reference to FIGS.

FIG. 7 shows a field section 1 consisting of four-pole permanent magnets in which the distance in the width direction of the permanent magnets is sinusoidal.

If the gap between the permanent magnet and the back yoke 5 on the back surface of the air-core coil 4 is made very small, the magnetic flux distribution in the gap caused by the permanent magnet will become a sinusoidal magnetic flux distribution in the rotation direction.

Furthermore, FIG. 8 shows a sine harmonic that is four times as large as that in FIG. 7.

As described in Part B, we investigated how each harmonic component of magnetic flux contributes to the 1-lux characteristic of the motor.

In the experiment, the number of turns of the air-core coil 4 in Fig. 12(a) was 10.
The distance between the permanent magnet of the field section 1 and the back yoke 5 was made extremely small by rotating the permanent magnet, and the waveform of the back electromotive force generated in the air-core coil 4 was detected by rotating the permanent magnet.

FIG. 9 shows back electromotive force patterns when using permanent magnets with fundamental waves, quadruple sine harmonics, and double sine harmonics. In the motor B, the rotation angle for energization switching is 30 degrees, and in FIG. 9, the ratio of the minimum and maximum back electromotive force in this section is about 86%. The waveforms of the back electromotive force when permanent magnets having a shape of 4 and 2 times sinusoidal harmonics are concave and convex, respectively. Furthermore, when the 4th and 2nd sine harmonics were made negative, the waveforms had exactly the same shape but the positive and negative sides were reversed, making them convex and gate-like, respectively. From these results, it was predicted that the back electromotive force waveform would become flatter if the magnet shape was made such that a positive quadruple sine harmonic and a negative double sine harmonic were slightly added to the fundamental wave.

FIGS. 6(a), (b), and (e) schematically show a method for producing a magnet shape to which harmonics are added. That is, the waveform of the quadruple harmonic mode shown in FIG. 6(a) is changed to the fundamental sine wave mode shown in FIG. 6(b) (however,
(represented by a straight line), the N poles 1N and S of the magnetic poles of the desired shape shown in FIG.
A pole 1S is obtained. In an actual motor, an air-core coil 4 (Fig. 12(a)) with several hundred turns is used, so the field part 1
The distance between the back yoke 5 and the back yoke 5 is generally about the same as the height of the permanent magnet.

Figure 10 shows the distribution of magnetic flux density in the gap of an ordinary flat motor with a large gap, and
The figure also shows the relationship between the drive torque and rotor rotation angle of a normal flat motor. The permanent magnets have the usual shape shown in FIG. 12(b), and each permanent magnet is magnetized throughout. As is clear from FIG. 10, in a motor with such a large gap, the distribution of magnetic flux density changes from a sine wave to a shape close to a trapezoid, with a slight harmonic wave added to the fundamental wave.

Therefore, it is sufficient to change the permanent magnet shape of the magnetic pole so that the harmonic components necessary for reducing the torque ripple are included, and the shape of the fundamental wave may or may not be added.

Figures 1(a) and 1(b) show the magnetic pole shape of the field part 1 showing an embodiment of the invention of B, in which a positive quadruple sine harmonic is added to the permanent magnet shape used in a normal flat motor. This figure shows the shape of the magnet when 10% and -5% of the double sine harmonic are added to the width direction distance.

Figures 2 and 11 are similar to Figure 1 (a).

The torque ripple when using a permanent magnet having the shape shown in (b) is shown for comparison with a motor using a normal permanent magnet. The ratio of minimum and maximum torque is the first
It can be seen that while the normal motor shown in FIG. 1 has an improvement of about 87%, the motor according to the present invention has a significant improvement of about 94%.

Furthermore, the average decrease in 1-lux is as small as about 13%.

Figure 3 shows a magnet shape with 10% quadruple sine harmonics and 5% negative double sine harmonics; in this case, the minimum torque and Jl large ratios are further improved. As shown in FIG. 4, it was about 97%.

Next, although the structure was the same, a completely similar experiment was conducted in the case where the air-core coil 4 was connected in the Δ manner. In the case of B, the contribution of the harmonic components of the magnetic flux to the torque ripple is different from the Y-connection case, and the magnet shape has a positive quadruple cosine harmonic component of 10% and a negative double cosine harmonic component of 5%. The ratio of minimum to maximum torque is approximately 97%, resulting in a motor with extremely small torque ripple. FIG. 5 schematically shows the shape of the permanent magnet used in the motor of this embodiment.

The optimal amount of harmonics to mix varies depending on the characteristics of the permanent magnet and the structure of the motor, but by examining the torque characteristics of each component and adding them linearly, it is possible to create a motor with almost no torque ripple.

In the formula (%) regarding the widthwise distance glh(θ) of the magnetic poles in this invention, a negative sign is treated as a change in polarity, and the widthwise distance is taken to be its absolute value. Further, i in n = i±1 is an integer represented by plq when it is the greatest common divisor of qem12 and p.

Further, the distance h(θ) in the width direction of the magnetic poles is the distance in the rotating shaft direction for a radial gap type motor, and the distance in the radial direction for an axial gap type motor.

〔Effect of the invention〕

As described in detail above, in the invention of B, in a motor consisting of In magnetic poles made of permanent magnets and p air-core coils, the pair of magnetic poles N and S are arranged in one period in the motor rotation angle direction. T, the distance in the width direction of the magnetic pole #h (θ) is given by the rotation angle θ, then h(θ) = h o + Σtt, c
os(2xnθ/T)+Σbw+sin(2πnθ/T
), at least 1 when n = i±1
iaa non-zero for values of n or more.

or the width direction distance gih of the magnetic pole so that b a exists.
Since the shape is changed in (θ), there is an advantage that a high-quality motor with extremely small 1-leak ripple can be obtained, which is of great industrial significance.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a magnetic pole showing one embodiment of the present invention, and FIG.
1 is a characteristic diagram showing the torque ripple of the motor of the embodiment shown in FIG. 1, FIG. 3 is a plan view of magnetic poles showing another embodiment of the present invention, and FIG. 4 is a first embodiment of the embodiment shown in FIG. Fig. 5 is a plan view of a magnetic pole showing yet another embodiment of the present invention; Figs. 6(a), (b), and (e) are diagrams showing the magnetic shape of the magnet according to the present invention; Figures 7 to 12 are diagrams schematically showing the method, and Figures 7 to 12 are diagrams for explaining the principle of the invention of B. Figure 7 is a plan view of a field section consisting of a sinusoidal four-pole permanent magnet; Figure 8 is a plan view of the field section with four times as many harmonics as in Figure 7, and Figure 9 is the fundamental wave. Figure 10 shows the back electromotive force pattern when using permanent magnets with 2nd harmonic and 4th harmonic. FIG. 11 is a diagram similarly showing the relationship between drive torque and rotor rotation angle, and FIG. 12(a). (b) is a side sectional view and a plan view of magnetic poles of an axial gap type motor shown as an example of the object of the present invention. In the figure, 1 is a field part, 1N is an N pole, 15 is an S pole, 2 is a rotor yoke, 3 is a rotor shaft, 4 is an air-core coil, 5 is a back yoke, and 6 is a bearing at the center. Fig. 1 15 Y-' IS:b To Fig. 2 ■-Go to [1 Fig. 3 6 and) 〒・ Fig. 4) lI Fig. 5... , , , , , , , , , , 815″′-
1 (i Papa-1s1N\17 Do' Figure 6 4 skin & one wave mode -V... 1 (C) l l 1 1N Is Figure 7 Figure 8 Figure 9-Y) \41M) / "Kuch~da W interpretation angle θdυ" Fig. 10, l = \, /1 Rhoda Kaiyou θ Rinfu Fig. 11 1 "11

Claims (1)

[Scope of Claims] In a motor having a field section having m magnetic poles made of permanent magnets and p air-core coils consisting of three phases opposing the field section, the pair of magnetic poles N and S is set at a motor rotation angle. one period T in the direction, and the distance h(θ) in the width direction of the magnetic pole is the rotation angle θ
, the following formula h(θ)=h_0+Σa_ncos(2
If not expressed as A motor characterized in that it consists of magnetic poles with a distance distribution. However, h_0 is h_0=H (0≦θ<π), h_0=
-H (π<θ≦2π), H: Standard distance in the width direction of magnetic poles. In the above equation, when π≦θ<2π, the sign becomes negative as a change in polarity, and the distance in the width direction is its absolute Considered as a value. Also, i is p when q is the greatest common divisor of m/2 and p
It is an integer represented by /q.