JPH0423505B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a permanent magnet type DC machine, and more particularly to a permanent magnet type DC machine having a field formed by using an anisotropic permanent magnet as a main pole and auxiliary magnetic poles arranged in parallel with the main pole. Regarding DC machines.

Conventionally known permanent magnet type DC machines such as starters are provided with a commutating pole on the side of the armature that increases magnetization due to armature reaction, as disclosed in Japanese Patent Publication No. 48-35721, for example.

In other words, an anisotropic permanent magnet (main magnetic pole) with both ends cut parallel to the center line extending radially from the rotor center.
There is a structure in which this magnet and an auxiliary magnetic pole (iron core) are adjacent to each other with an air gap, or a structure in which the opposing surfaces of the main magnetic pole and auxiliary magnetic pole are in close contact with each other over the entire surface, but as is well known, there are different types. Since magnetic flux passes in the radial direction of a directional permanent magnet, if auxiliary magnetic poles are placed closely in parallel in the rotation direction, a leakage magnetic path φ _P will occur between them.
is formed. Therefore, in the latter case, the effective magnetic flux decreases, resulting in a decrease in rotational torque. On the other hand, in the former case, the leakage magnetic flux decreases, but because there is a gap over the entire length between the two magnetic poles, a steep drop occurs between the two magnetic flux distribution waveforms seen from the armature side at high loads, as shown by the dotted line in Figure 5. , smooth operation cannot be expected, output decreases and magnetic noise occurs,
Vibration occurs. Incidentally, the above output reduction is approximately 5% output reduction with a 0.8kw starter.

An object of the present invention is to provide a permanent magnet DC machine with a smooth magnetic flux distribution waveform and improved rotational torque.

The present invention provides a permanent magnet DC machine comprising a main magnetic pole made of an anisotropic permanent magnet arranged on the inner circumferential surface of a yoke, and an auxiliary magnetic pole adjacent to and arranged in parallel with the main magnetic pole in the circumferential direction. , the two adjacent magnetic poles are in contact with each other on the inside in the radial direction of the magnetic poles and are separated on the outside in the radial direction to form a leakage magnetic path blocking part, so that the magnetic flux distribution is smooth and magnetic noise and vibration are reduced; Moreover, leakage magnetic flux can be reduced and rotational torque can be improved.

Embodiments of the present invention will be described below based on the drawings.
FIG. 1 shows a case where a permanent magnet type DC machine is used as a starter, and the explanation will mainly be given to the electric motor section. In the figure, four arc-shaped anisotropic permanent magnets 2 made of ferrite are arranged at equal intervals on the inner circumferential surface 1a of a yoke 1, and are fixed with an adhesive. As shown in FIG. 2, the end face of this permanent magnet is cut on a radial line that spreads out in a fan shape from the axis 0, and an auxiliary magnetic pole 3 made of an iron core is arranged on the side where an increased magnetic field is generated due to magnetic reaction. A part is fixed tightly to the side of the
Reference numeral 4 denotes a gap portion forming a leakage magnetic path blocking portion, which is formed to block magnetic flux leaking to the auxiliary magnetic pole with the radial center of the magnet as a boundary, which is unique to anisotropic magnets. This gap is drawn in the permanent magnet 2 whose both end faces are cut on a radial line, parallel to the center line connecting the center 0 of the rotation axis and the center in the rotation direction of the permanent magnet, and passes through a point 1/2H width of the magnet. It is formed by cutting the outside of a line segment. That is, since the neutral point of the N and S poles of the permanent magnet 2 is at the 1/2H point, if the neutral point is set to the minimum neutral point, leakage of magnetic flux can be prevented and the rotational torque can be increased by 3 to 5%.

On the other hand, the relationship between the pole enclosures will be explained with reference to FIG. Since the above embodiment is a so-called 4-pole system, if the angle at which the permanent magnet 2 and the auxiliary pole 3 are combined is θ, then θ/90° = 0.7 to 0.8 The θ width is approximately 70°, which is similar to a general rotating machine. It is.

As the pole enclosure becomes larger, the amount of no-load magnetic flux after magnetization increases, but the performance is susceptible to the demagnetizing field of armature reaction, resulting in a high demagnetization rate, making it impossible to improve performance. For this reason, even with anisotropic ferrite magnets, increasing the pole enclosure is ineffective, and it is economically advantageous to reduce the amount of magnets used, which is about 0.7 to 0.8. Therefore, in order to increase the effective magnetic flux within this range, it is most effective to block the leakage magnetic path as described above.

As mentioned above, the anisotropic permanent magnet has an S
If it is a pole, the outer diameter side becomes the north pole, and the center of the thickness of the permanent magnet becomes a neutral point where no polarity occurs.
Therefore, as shown in FIGS. 1 and 2, the magnetic circuit through which the main magnetic flux passes is permanent magnet 2 → air space g1 → armature A.
→ Empty part g1 → Auxiliary magnetic pole 3 → Yoke 1 → Permanent magnet 2
The side surface where the permanent magnet 2 and the auxiliary magnetic pole 3 are in contact should be as far as possible below the neutral point of the permanent magnet 2, and the tip should be placed around the outer periphery of the permanent magnet so that there is a space larger than the air gap g ₁ with the armature. A parallel surface cut parallel to the radiation passing through the center of the magnetic flux or a surface that creates a larger space is provided at the corner to reduce leakage magnetic flux from the side surface of the permanent magnet.

The fact that the cut plane of the space is parallel to the radiation passing through the center of the magnetic flux allows the punching direction to be constant when ferrite powder is molded using a mold, which greatly contributes to productivity.

Next, the product of the present invention and the conventional product will be compared and explained with reference to FIGS. 4 and 5.

Figure 4 (b) shows a permanent magnet 2 and an auxiliary magnetic pole 3 whose inner periphery opposing surfaces are brought into close contact to form a leakage magnetic path gap 4 on the outer diameter.The magnetic flux distribution seen from the armature side under high load is It slopes gently and smoothly from the 3rd side to the main magnetic pole 2, increasing the effective magnetic flux within the limited magnetic pole width,
It is also effective against magnetic sound generation and vibration.

On the other hand, as shown in Figure 5B, it is also possible to taper inversely to the above embodiment and abut at the outer periphery, but in this case, the magnetic flux distribution waveform (solid line) shown in Figure 5A
As shown in the figure, there are parts where the magnetic flux is close to 0, and rotational torque, magnetic noise, and vibration are not improved. This is because the gap 41 creates a portion where the magnetic pole does not face the armature conductor portion. Although this drop in magnetic flux is smaller than when a space is completely formed between the magnetic poles as shown by the dotted line, it is not preferable.

According to the embodiments of the present invention, the permanent magnets and auxiliary magnetic poles can be effectively arranged in the minimum shape within the defined range of the pole enclosure in order to effectively block the leakage magnetic path, and the rotational torque can be reduced to the current level. It is possible to maintain the structural physique and improve it by about 5%. Furthermore, since the magnetic flux distribution becomes smooth, magnetic sound and signals are suppressed, and an electromagnetic machine with less noise can be obtained.

FIG. 6 shows another embodiment of the present invention, in which the joining surface side of the permanent magnet 21 is joined to the auxiliary magnetic pole 31 at the tip 21a of the magnet, and the taper is removed from the joining point upward on the magnet side. By doing so, a leakage magnetic path blocking air gap 41 is formed, and in this case as well, leakage magnetic flux can be effectively blocked.

FIG. 7 shows yet another embodiment in which a gap 42 is provided on the side of the auxiliary magnetic pole 32. In this case, the side end surface of the magnet 22 is cut along the radial line, and the side end face of the auxiliary magnetic pole opposite thereto is formed by cutting along the radial line. Although it is removed in a circular shape, since it is made of iron such as soft iron, it can be shaped extremely easily, and has the advantage that the width of the joint surface can be freely controlled.

In this way, the leakage magnetic path blocking gap is formed by cutting out either the main magnetic pole or the auxiliary magnetic pole, but the same effect can be expected in either case.

The fourth embodiment has a permanent magnet 23 and an auxiliary magnetic pole 3.
A gap 43 is formed by providing a notch in each of the magnets 3 and abutting them on the inner diameter side, and this case also has the advantage that the auxiliary magnetic pole can be freely formed to match the taper on the permanent magnet side.

As described above, according to the present invention, it is possible to provide a permanent magnet type DC machine with a smooth magnetic flux distribution waveform and a large rotational torque under high loads.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view of the main parts of a starter that employs the permanent magnet type DC machine of the present invention, Fig. 2 is a partial side view of Fig. 1, and Fig. 3 is a dimensional drawing of the enclosure of the magnet type DC machine. Figures 4A and 4B are magnetic flux distribution diagrams and magnetic pole structure diagrams as seen from the armature side during high loads in the present invention, and Figures 5A and 5B are magnetic flux distribution diagrams and magnetic pole structure diagrams as seen from the armature side during high loads in the conventional method. The structural diagrams of the magnetic poles, FIGS. 6 to 8 are partial views showing the relationship between the permanent magnet and the auxiliary magnetic pole in other embodiments. 1... Yoke, 2... Permanent magnet (main magnetic pole), 3...
...Auxiliary magnetic pole, 4...Leakage magnetic path gap.

Claims (1)

[Claims] 1. A permanent magnet comprising a main magnetic pole made of an anisotropic permanent magnet arranged on the inner circumferential surface of a yoke, and an auxiliary magnetic pole adjacent to and arranged in parallel with the main magnetic pole in the circumferential direction. A permanent magnet type DC machine, wherein the two adjacent magnetic poles are in contact with each other on the inside in the radial direction of the magnetic poles and are separated on the outside in the radial direction to form a leakage magnetic path blocking part. 2. The permanent magnet direct current according to claim 1, characterized in that the two magnetic poles are in surface contact on the radial inner side in the radial direction from the rotation axis, and are isolated on the radial outer side. Machine. 3. The permanent magnet DC machine as set forth in claim 1, wherein the leakage magnetic path blocking portion is formed outside the center position of both magnetic poles in the radial direction. 4. In the description of claim 3, the leakage magnetic path blocking portion is formed at an outer peripheral corner of the main magnetic path,
A permanent magnet type DC machine, wherein a cut surface of the corner portion is parallel to a radiation passing through the center of the main magnetic pole.