JPS5928865A - Magnetizing yoke - Google Patents

Abstract

PURPOSE:To simplify the magnetizing step and obtain a field magnet capable of detecting a frequency in high performance by forming grooves at a short pitch on the outer periphery of the end of a cylinder formed of a magnetic material to form poles for detecting the frequency of short pitches. CONSTITUTION:Grooves 17' which perpendicularly cross at the center are formed on the end surface 16' of a cylinder 15' formed or a ferromagnetic material in a magnetizing yoke 14', energizing coils are mounted in the grooves 17', and many grooves 19 of short equal pitch are formed to form poles for detecting the frequency on the outer periphery of the end surface 16'. Since a weak energizing current flows at the grooves 19, they are weakly magnetized like N', and the projections 20 are strongly magnetized like N. Accordingly, exclusive energizing coil can be eliminated, the poles of strong and weak energizations of N, N' and S, S' for detecting the frequency can be formed at the extremely short pitch, thereby obtaining a field magnet which can detect the frequency with high performance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetizing yoke that allows frequency detection magnetic poles to be easily formed overlapping a magnetic pole of a main magnet of a motor.

Disk-type brushless motors used in direct-drive cassette tape recorders and the like are required to obtain detailed rotational speed signals.

As such a disc-shaped pral smoke 1, the first
A structure as shown in the figure is known. To explain this motor 1 briefly, a disk-shaped rotor yoke 3 is fixed to the motor spider 2, and a ring-shaped field magnet 4 as shown in FIG. It's cool.

A center spindle 5 is formed at the tip end of the morph shaft 2, and the lower end thereof is rotatably supported by a bearing 6. The stator yoke 7 is a fixed type on the 1qll bridge 6, and on this stator yoke 7, as shown in the 31 concavity, the armature coil 8 in the shape of a fan frame of 31 is arranged at equal intervals so that the planes do not overlap. The contact layer is fixed. armature coil 80
A magneto-electric transducer 9 for detecting the rotational position is located inside the cavity within the frame.
are arranged for storage. A disk-shaped printed circuit board 10 is fixed to the upper surface of the armature coil.
A comb-like conductive pattern 11 for detecting the rotational speed of the rotor is generally formed on the surface of the rotor (see FIG. 4). The printed circuit board 10 and the field magnet 4 face each other with a small gap in between.

FIG. 2 is a plan view of the field magnet 4 shown in FIG. 41.

As shown in FIG. 2, the main (IB pole 1
2 is magnetized into a 4-pole type having N and S magnetic poles alternately spaced at equal intervals, and approximately 180 frequency detection magnetic poles 13 for the rotor rotational speed (output) are formed around it. N and S are more strongly magnetized than N' and s'.

FIG. 5 is a perspective view of the magnetizing yoke 14 for explaining the conventional fR magnetization method of the main magnetic pole 12.

This N-magnetic yoke 14 has a cylindrical body 15 made of a ferromagnetic material such as pure iron, and has 17 grooves perpendicular to each other in the end face 16 of the cylindrical body 15, in which 12 main magnetic poles for driving are formed. The excitation coil 18 is fully wound. By contacting this n-2 magnet and energizing the excitation coil 18, 12 4-pole main magnetic poles are magnetized.

In this way, after the main magnetic pole 12 is magnetized without being removed, the frequency detection magnetic pole 13 is relatively weakly magnetized using a special magnetizing yoke (not shown) for magnetizing the 13 frequency detection magnetic poles. Magnetize. Alternatively, this process may be reversed.

Therefore, the magnetic flux density waveform in 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 main magnetic pole 12 is superimposed with the magnetic flux density waveform f′ formed by the frequency detection magnetic pole 13.
A finely uneven waveform is formed at the peaks or troughs of the magnetic flux density waveform t'' formed by Gn.

FIG. 4 is a plan view of the printed circuit board 10 of FIG. 1. On the surface of the printed circuit board 10, a portion facing the frequency detection magnetic pole 13 of the field magnet 4 is provided with a comb-shaped conductive pattern 11 like a bore as shown in FIG.
is formed. The pitch of this conductive pattern 11 is
The pitch 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 N' or S'. As a result, an electromotive force is generated in the same direction according to the rotational speed VC of the frequency detection magnetic pole 13 in each part), and the conductive pattern 11
A detection output of a frequency corresponding to the rotational speed of the rotor is obtained from an output terminal (not shown) of the rotor.

Although the pulsed magnetic flux caused by the frequency detection pole 13 appears intermittently, it is formed all around the conductive pattern 11751) as shown in Figure 4, so the detection output Ci can be obtained as a continuous wave. . Furthermore, even if there is pitch unevenness in the frequency detection magnetic pole 13, the pitch unevenness is averaged out by the plurality of conductive patterns 11, and when the rotational speed of the rotor is constant, a +■ output of a constant frequency is not obtained. A variation in the rotor rotational speed is extracted as a frequency modulation component of the detection output.

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

However, in the past, it took a lot of effort to form the field magnet 4 having the main magnetic pole 12 and the frequency detection magnetic pole 13. That is, this is because the N magnetization of the main magnetic pole 12 and the magnetization of the frequency detection magnetic pole 13 had to be separated. Furthermore, it is very expensive because it requires a magnetizing yoke for forming the main magnetic pole 12 and a magnetizing yoke tray for forming the frequency detecting magnetic pole 13. Furthermore, in forming the frequency detection magnetic pole 13i, similarly to the case of forming the main magnetic pole 12, it is necessary to form a large number of grooves and install thin conductors and glands, and as a result, N, N ',S
, I was unable to form PoI11 despite the strong and weak N stimulation of S'.

The present invention is based on such circumstances.
The main magnetic pole and the frequency detection magnetic pole can be simultaneously magnetized using the yoke, which simplifies the N magnetization process, reduces the cost of magnetization, and allows for a less expensive yoke configuration. N, N', S, of the frequency detection magnet
By forming the strongly and weakly magnetized portions of S' into extremely fine pinches, field magnets having a main magnetic pole and a frequency detection magnetic pole with good performance can be quickly mass-produced and provided at low cost. The overall purpose of this design was to make the magnetizing yoke smaller and to be able to provide it at a lower cost.

The objects of the present invention are as follows: 1. To form a driving main magnetic pole sound f
In order to wind the excitation coil (C-), a magnetic inertia coil for frequency detection with a fine pitch is formed in the M magnetic yoke, which has a groove orthogonal to the center on the end face of a cylindrical body made of magnetic material. This is achieved by providing an M magnetic yoke characterized by forming grooves with fine pinches on the outer periphery mi of the end face.

Embodiments of the N-magnetic yoke of the present invention will be described below with reference to FIG. 7 and all subsequent figures. Note that parts that are common to FIG. 5 are marked with a dash.

FIG. 7 is a perspective view of the magnetizing yoke 14' of the present invention, and the magnetizing yoke 14' is configured to form four main magnetic poles 12. The magnetizing yoke 14' has a groove 17' perpendicular to the end face 16' of a cylindrical body 15' made of a ferromagnetic material, and a groove 17' that is perpendicular to the center thereof, as shown in FIG.
However, the excitation coil 18 (not shown in FIG. 7) is fully wound, and a frequency detection magnetic pole 1 is attached to the outer periphery of the end face 16'.
A large number of grooves 19 are made with fine evenly spaced pinches to form 3 grooves.
It forms.

Therefore, by using this magnetizing yoke 14', the excitation coil 18
When a current is applied to magnetize the magnet, a four-pole main magnetic pole 12 having N and S magnetic poles is naturally formed as shown in FIG.

Also, Fig. 8 is a longitudinal cross-sectional view taken along line X-Xa in Fig. 7, and at the same time, as is clear from Fig. 8, a weakening excitation current of 7#i is applied to the groove 19 portion, so as shown in [ma]. However, the convex portion 20 is strongly magnetized as shown by N, and as a result, the main magnetic pole 12 and the circumference are The field magnet 4 shown in FIG. 2 having the zero detection magnetic pole 13 can be easily obtained. In addition, since a dedicated excitation coil is not required for forming the frequency detection magnetic pole 13, the grooves 19 can be formed on the outer periphery of the end surface 16' by finely spaced pinches. , N', S, and S' strong and weak magnetic poles can be formed with very fine pinches.

FIG. 9 is a perspective view of an N magnetic yoke 14' illustrating a second embodiment of the present invention. The difference from the M magnetic yoke 14' shown in FIG. 7 is the shape of the groove 17'.

That is, in the case of the 6B yoke 14' shown in FIG. 7, as is clear from FIG. 8, the groove 17' has a groove 19 or a convex part 20 on the end surface 16' which forms the intermediate part between the N and S poles. cannot be formed.

Therefore, the second embodiment shows that grooves 19 and 20 protrusions can be formed in such positions.

That is, the groove 17' has a narrow slit groove 17'A formed on the surface of the end face 16', and a narrow slit groove 17'A formed on the inner surface thereof.
There is a wide groove 17'B at the end where the material is wound.

Incidentally, FIG. 10 is a longitudinal sectional view taken along the line X--X of FIG. 9.

Since the present invention has the above configuration, it has the following effects.

Since the main magnetic pole and the frequency detection magnetic pole can be N-magnetized at the same time, the magnetization process can be simplified and field magnet trays can be mass-produced at low cost.

In addition, the magnetizing yoke for the main magnetic pole and the magnetizing yoke for the frequency output magnetic pole can be integrated to make the device compact and inexpensive.

Even worse, excitation for forming magnetic poles for frequency detection (1-circle coil is not required, so strong and weak magnetic poles for frequency detection can be formed with a fine pinch, allowing for high-performance frequency detection. A field magnet is obtained.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a disc-type brushless smoke, Figure 2
The figure is a plan view of the field magnet that forms the main magnetic pole and the frequency detection magnetic pole, Figure 3 is an explanatory diagram showing how to arrange the armature coil group, and Figure 4 is a plan view of the printed circuit board with all the conductive patterns. , FIG. 5 is a perspective view of a magnetizing yoke fully illustrated by the conventional magnetizing force method for forming the main magnetic pole, FIG. 6 is a waveform diagram of the air gap magnetic flux density formed by the field magnet of FIG. 2, and FIG.
The figure is a perspective view of the magnetizing yoke according to the first embodiment of the present invention, FIG. 8 is a vertical cross-sectional view taken along the line X-X of FIG. 7, and FIG. 9 is a perspective view of the magnetizing yoke according to the second embodiment of the present invention. FIG. 1O is a longitudinal sectional view taken along the line X--X in FIG. 9. 1...Tisf 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 pattern, 12... Main magnetic pole,
13... Magnetic pole for frequency detection, 14... Magnetizing yoke, 15... Cylindrical body, 16... End face,
17... Groove, 1st... Excitation coil, 19...
Groove, 20... Convex portion. Patent pursuer Takayoshi Terusuke Hashi 1st figure 3rd 5th area 2nd Entai 4th figure 6th figure + 11

Claims (1)

[Scope of Claims] ] A magnetizing yoke in which a groove is provided in the end face of a cylindrical body made of a magnetic material with a groove extending directly in the center in order to wind an excitation coil for forming a main magnetic pole sound for driving. A magnetizing yoke characterized in that grooves are formed at a fine pitch on the outer periphery of the end face to form a frequency detection magnetic pole with a fine pinch. 2. Claim 1, characterized in that the 11 grooves that intersect at the center are narrow grooves on the surface portion of the end face, and wide grooves on the inner surface thereof. Magnetized yoke as described.