JPS5986465A - Magnetized yoke - Google Patents

Abstract

PURPOSE:To enable to readily magnetize a sinusoidal wave at the pole by forming grooves perpendicular to the central hole on the end face of a cylinder which is formed of a magnetic material, and winding an exciting coil in the grooves. CONSTITUTION:Four grooves 17 perpendicular to a hole 19 are formed on the end face 16 of a cylinder 15 so as to wind an exciting coil by forming the hole 19 at the center of the end face 16 of the cylinder 15 formed of a magnetic material and forming 4-pole field magnet alternately having N- and S-main poles for driving. In this manner the opposed surfaces 16 are divided equally into four sections to form crest-shaped portions 15a, and the exciting coils are wound in the grooves 17.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetizing yoke that allows the magnetic poles of the main magnet of a motor to be easily magnetized in a sine wave.

A disk type brushless motor used in a direct drive type cassette tape recorder etc. needs to have smooth rotational drive, that is, with less torque ripple. Such a disk type brushless motor 1 is shown in Fig. 1. A motor with a structure like this is known.To explain this motor 1, a disk-shaped rotor yoke 3 is fixed to the motor shaft 2, and a ring-shaped rotor yoke 3 is fixed to the lower surface of the rotor yoke 3 as shown in FIG. A field magnet 4 is fixed with adhesive.A center spindle 5 is formed at the tip end of the motor shaft 2, and its lower end side is rotatably supported by a bearing 6.

A stator yoke 7 is fixed to the bearing 6, and on the stator yoke 7, as shown in FIG. 3, three fan frame-shaped armature coils 8 are adhesively fixed at equal intervals so that the planes do not overlap. There is. The opening angle of the conductor portion contributing to the generated torque in the radial direction of the armature coil 8 is formed by winding to have an opening angle width approximately equal to the magnetic pole width of the field magnet 4. A magnetic core conversion element 9 (for example, a Hall element) for detecting a rotational position is housed in a hollow portion within the frame of the armature coil 8. The magnetoelectric conversion element 9 is disposed in a hollow portion within the frame of the armature coil 8, which is in an equal relationship with the conductor portion that contributes to the generated torque. A disk-shaped printed circuit board IO is fixed to the upper surface of the armature coil 8, and the surface of this printed circuit board 10 is provided with a toothed conductive pattern 1 for detecting the rotational speed of the rotor.
1 is formed (see Figure 4). Printed circuit board 1
0 and the field magnet 4 are opposed to each other with a minute gap in between.

FIG. 2 is a plan view of the field magnet 4 of FIG. 1. As shown in FIG. 2, the main magnetic pole 12 of the field magnet 4 is
It is magnetized into a 4-pole structure with N and S magnetic poles alternately spaced at equal intervals, and the periphery is magnetized with 2M to create a frequency of about 180 N and S poles for rotor rotational speed detection. A detection magnetic pole 13 is formed. In this case, N and N' poles are formed as N poles, and s and s' poles are formed as S poles.

N and S must be made stronger than N/ and s/ (so that they are magnetized).

It should be noted that the direct drive disc type brushless motor 1 also has other drawbacks as will be described later.

FIG. 5 shows a conventional field magnet 4 (main magnetic pole 12
) is a perspective view of a magnetizing yoke 14 for explaining the magnetizing force method. This magnetized yoke 14 has a hole 19 in the center of the end surface 16 of a cylindrical body 15 made of a ferromagnetic material such as pure iron, and has 2P (P is 2 or more) alternately having N and S magnetic poles for driving. In order to wind the excitation coil 18 for forming the field magnet 4 of 4 poles (P=2 in this embodiment), the hole J9 is formed in the end face 16 of the cylindrical body 15.
Four orthogonal grooves 17 are formed 7, the end face 16 is divided into four parts, and an excitation coil 18 is installed in the grooves 17. By bringing this into contact with a magnet and energizing the excitation coil 18, a four-pole field magnet 4 can be fully magnetized.

In this way, first, after the main magnetic pole 12 is magnetized, a special magnetizing yoke (not shown) for magnetizing the frequency detection magnetic pole 13 is used to magnetize the frequency detection magnetic pole 13 relatively weakly. Magnetize.

Therefore, for example, the magnetic flux density waveform of the gap formed by the field magnet 4 is as shown in FIG.

As shown in FIG. 6, the magnetic flux density waveform formed by the frequency detection magnetic pole 13 is superimposed on the magnetic flux density waveform formed by the main magnetic pole 12. A waveform with seven different kana concavities and convexities is formed at the peaks or valleys.

FIG. 4 is a plan view of the printed circuit board 10 of FIG. 1. On the surface of the printed circuit board 10, in a portion facing the frequency detection magnetic pole 13 of the field magnet 4, comb-like conductive ξ turns 11 are formed as shown in FIG.

The pitch of the conductive chisel turf 11 is the same as the pitch of the frequency detection magnetic poles 13 shown in FIG. When every other line segment group in the radial direction of the conductive pattern 11 faces, for example, N or S of the frequency detection magnetic pole, the line segment group between these faces the other N' or N'. As a result, an electromotive force in the same direction according to the rotational speed of the frequency detection magnetic pole 13 is generated in each line segment 7, and the output terminal (not shown) of the conductive chisel turn 11 also outputs a frequency detection according to the rotational speed of the rotor. is obtained.

Incidentally, although the ξ-shaped magnetic flux generated by the frequency detection magnetic pole 13 appears intermittently, since the conductive pattern 11 is formed all around the circumference as shown in FIG. 4, the detection output is obtained as a continuous wave. Even if there is still pitch unevenness in the frequency detection magnetic pole 13, the pitch unevenness is averaged out by the plurality of conductive ξ turns 11, and when the rotational speed of the rotor is constant, a detection output of a constant frequency can be obtained.

A variation in the rotor rotational speed is captured as a frequency modulation component of the detection output.

The disk-type brushless motor 1, which has the above-mentioned rotational speed jW detection mechanism, has recently attracted much attention, and various companies are desperately trying to develop it.

However, in the past, the main magnet, i! 412 k 5th above
When the field magnet 4 is formed by the magnetizing yoke 14 shown in the figure, the air gap magnetic flux density waveform of the field magnet 4 becomes a trapezoidal air gap magnetic flux density waveform 20 shown in FIG.

Here, the L portion waveform 22 above the reference line 21 of the waveform 200 is a magnetic flux density waveform generated by the north pole of the field magnet 4, and the lower waveform 23 is a magnetic flux density waveform generated by the south pole of the field magnet 4. As is clear from FIG. 7, these two magnetic flux waveforms are trapezoidal waveforms, and the rising and falling waveform portions of waveforms 22 and 23 are sharp. That is, the rapid rise and fall of the waveforms 22 and 23 means that the energization to the armature coil 8 is abruptly switched, which causes rotational torque ripple.

This is fatal for audio equipment having the disk-type planless motor 1 described above. The same applies to other audio equipment. Therefore, if the field magnet 4 is magnetized with a sine wave instead of a trapezoidal wave, the torque ripple will be reduced and the rotor will rotate smoothly.
It is desirable to use sine wave magnetization.

However, in the past, there was no magnetizing yoke for this purpose (a metal plate such as an iron plate was attached to a trapezoidal wave magnetized field magnet in order to make the field magnet magnetized in the same way as a kesine wave magnetized field magnet), which reduced productivity. It was a meager thing.

The present invention has been made based on the above-mentioned circumstances, and has been made for the purpose of obtaining a magnetic yoke that allows easy sine wave magnetization of the magnetic pole of the main magnet of a motor.

The present invention will be described in detail below with full reference to FIG. 8 and subsequent figures.

8 and 9, a magnetizing yoke 14' according to the first embodiment of the present invention has a hole 19i provided in the center of the end surface 6 of a cylindrical body 15 made of a magnetic material, and a hole 19i for driving. N,
Main magnetic pole 12 of S (see Figure 2) f! : Excitation coils 18 (
5), the end surface 16 of the cylindrical body 15 is formed with four grooves 17'z perpendicular to the hole 19, thereby dividing the end surface 16 into four equal parts. The side surface portion 24 of the equally divided end surface 16 facing the hole 19 is formed into a chevron-shaped portion 25a facing the hole J9, and N and S magnetic poles are alternately formed by the divided end surface 16. As shown in FIG. 5, an excitation coil 18 is wound around the groove 17 so that the four field magnets (see FIG. 2) can be magnetized. By bringing the end face of the magnetizing yoke 14' into contact with, for example, a flat annular ferrite magnet and energizing the excitation coil 18, a four-pole field magnet 4 as shown in FIG. 2 is formed. , the field magnet 4 is magnetized in a sine wave as shown in the magnetic flux density waveform diagram shown in FIG.

FIGS. 11 and 12 show other magnetizing yokes 14"
, 14'#', and may be formed into chevron-shaped chevron-shaped portions 25b and 25c as shown in FIGS. 11 and 12. The magnetic flux density waveforms of the magnetizing yokes M' and '14' are as shown in FIGS. 13 and 14, respectively.

In the above embodiment, the magnetizing yokes 14', . Naturally, the present invention can also be applied to a device that forms a pole field magnet.

The present invention is also applicable to a magnetizing yoke in which the groove in which the excitation coil is completely wound is formed in a skewed manner to form a field magnet magnetized in a sine wave and in a skewed manner.

As is clear from the above, according to the magnetizing yoke of the present invention, the magnetic pole (main magnetic pole) of the main magnet of the motor can be easily formed with sine wave magnetization, so a sine wave magnetized 7 field magnet can be formed at a low cost. Moreover, since the torque ripple of the rotor is smoothed out by a brushless morph using such a field magnet, there is an effect that a brushless morph suitable for audio equipment can be obtained.

[Brief explanation of drawings]

Figure 1 is a longitudinal cross-sectional view of a disc-type planless motor, Figure 2
The figure is a plan view of a field magnet with a main magnetic pole and a frequency detection magnet IMk, Figure 3 is an explanatory diagram showing how to arrange the core armature coil group, and Figure 4 is a conductive pattern. 5 is a perspective view of a magnetizing yoke showing a conventional magnetizing method for forming a main magnetic pole, and FIG. 6 is a diagram showing the air gap magnetic flux density formed by the field magnet in FIG. 2. Waveform diagram, 7th
The figure is a waveform diagram of the air gap magnetic flux density formed by a conventional four-pole field magnet, FIG. 8 is a perspective view of the magnetizing yoke of the first embodiment of the present invention, and FIG. 9 is a plan view of FIG. 8. Figure 10 is a waveform diagram of the air gap magnetic flux density formed by the field magnet obtained by the magnetizing yoke of Figures 8 and 9;
Figure 2 is a plan view of the magnetizing yoke of the second and third embodiments of the present invention, and Figures 13 and 14 are Figures 11 and 14, respectively.
13 is a waveform diagram of the air gap magnetic flux density formed by the field magnet obtained by the magnetizing yoke of FIG. 12. FIG. ■... Disk type brushless motor, 2... Motor shaft, 3... Rotor yoke, 4... Field magnet, 5
... Center spindle, 6... Bearing, 7... Stator yoke, 8... Armature coil, 9... Magnetoelectric conversion element, 10... Printed circuit board, 11... Conductive chisel turn, 12... ...Main magnetic pole, I3...Magnetic pole for frequency detection, 14, 14', 14" 14m...Magnetizing yoke, 15...Cylindrical body, 16...End face, 17...
Groove, 18... Excitation coil, 19... Hole, 20...
Trapezoidal air gap magnetic flux density waveform, 21... Reference line, 22.
...Top waveform, n...Bottom waveform, 24...Side part,
25a, 25b, 2.5c... Yamagata part. Chrysanthemum 1 Illustration 3 Illustrations Most 5 Illustrations Shin 2 Illustration 4

Claims (1)

[Claims] A hole is provided in the center of the end face of a cylindrical body made of a magnetic material, and excitation is performed to form a 2P (P is a positive integer of 2 or more) pole field magnets, which have N and S main magnetic poles alternately for driving. In order to fully wind the coil, a groove is provided on the end face of the cylindrical body perpendicular to the hole, and the end face divided by the groove allows N, S
A magnetizing yoke characterized in that the excitation coil is wound around the groove so as to form a 2P-pole field magnet having alternating magnetic poles.