JPS6070955A - Magnetizing device - Google Patents

Abstract

PURPOSE:To enable to perform a fine magnetization in a simple step by forming slots for forming a frequency detecting pole of fine pitch in the entire end of a cylinder, and winding an exciting coil in the slots. CONSTITUTION:A magnetizing yoke 14' has a cylinder 15' made of a ferromagnetic material. Thick four slots 17' which perpendicularly crosses at the center are inserted at an equal interval to the ends 16' of the cylinder 15', and exciting coil of thick diameter is wound in the slots 17'. Slots 19, 19' for forming the many frequency detecting pole of a fine interval pitch are formed over the entirety, and exciting coils are spirally wound in the slots 19, 19'.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetizing device that can easily form a frequency detection magnetic pole overlapping the magnetic pole of a main magnet of a disc-type brushless motor. In a disc type brushless motor used in a direct drive type cassette tape recorder or the like, it is necessary to obtain a detailed rotational speed signal.

As such a disk type brushless motor, one having a structure as shown in FIG. 1 is known. To explain this motor, a disk-shaped rotor yoke 3 is fixed to the motor shaft 2, and a ring-shaped field magnet 4 is adhesively fixed to the lower surface of this four-way yoke B as shown in FIG. .

A center spindle 5 is formed at the front end of the motor shaft 2, and a rotatable shaft is supported at the lower end by a bearing 6. A stator yoke 7 is fixed to the bearing 6, and on this stator yoke 7, as shown in FIG. 3, three fan frame-shaped armature coils 8tP are adhesively fixed at equal intervals so as not to overlap in plane. . The white paper inside the frame of the armature coil 8 is a Hall element and Hall IC for detecting the rotational position.
, a magnetoelectric transducer 9 such as a magnetoresistive element is housed.

A disk-shaped printed circuit board 10 is fixed to the upper surface of the H coil 8, and a tooth-shaped conductive pattern 11 for detecting the rotational speed of the rotor (forming a frequency generator) is formed on the surface of the printed circuit board 1o. ing.

The printed circuit board 10 and the field magnet 4 face each other with a small gap in between.

FIG. 2 is a bottom 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 around the periphery there are approximately 18
A zero-pole frequency detection magnet 411!13 is formed.

The north and south poles are N'ffi.

It is more strongly magnetized than the S' pole. Therefore, N'% is S
The S' pole of the poles functions as a north pole, so it is a north pole.

This means that the S-pole frequency detection mf5s are alternately magnetized and formed at a fine pitch.

FIG. 5 is a perspective view of the magnetizing device 14 for explaining a conventional method of magnetizing the main pole 12. As shown in FIG. This entrance device 14
In this method, a groove 17 is formed perpendicularly at the center in the end face 16 of a cylindrical body 15 made of a ferromagnetic material such as pure iron, and a groove 1117 is formed in this groove.
．． Excitation coil 18 for forming the main magnetic pole 12 for operation
It is wrapped in . By bringing this into contact with a magnet and energizing the excitation coil 18, the four main magnetic poles 12 are magnetized.

In this way, after first magnetizing the main magnetic pole 12, the frequency detecting magnetic pole 13 is relatively weakly magnetized using a special magnetizing device (not shown) for magnetizing the frequency detecting magnetic pole 13. do.

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 on the magnetic flux density waveform formed by the frequency detection magnetic pole 13, so the magnetic flux formed by the main magnetic pole 12 A finely uneven waveform is formed at the peaks or valleys of the density waveform.

FIG. 4 is a plan view of the printed circuit board 10 of FIG. 1. A comb-shaped conductive pattern 11 as shown in FIG. 4 is formed on the surface of the printed circuit board 10 in a portion facing the frequency detection magnetic pole 13 of the field magnet 4. As shown in FIG. The pitch of this conductive pattern 11 is the same as the pitch of the frequency detection magnetic poles 13 shown in FIG. Conductive pattern 11
When every other line segment group in the radial direction faces, for example, the N or S pole of the frequency detection magnetic pole, the line segments between them are opposite to each other. As a result, an electromotive force is generated in the same direction in each line segment according to the rotational speed of the frequency detection magnetic pole 13, and a detection output of a frequency corresponding to the rotational speed of the rotor is obtained from an output terminal (not shown) of the conductive pattern 11.

Although the pulsed magnetic flux generated by the frequency detection magnetic pole 13 appears intermittently, since the conductive pattern 11 is formed around the entire circumference as shown in FIG. is obtained with continuous waves. Furthermore, even if the frequency detection magnetic poles 13 have pitch irregularities, the plurality of conductive patterns 11
The pitch unevenness is averaged by a group of line segments in the radial direction of
When the rotation speed of the rotor is constant, a detection output of a constant frequency is obtained. The variation in the rotor rotational speed is extracted as the frequency (5) wave number variable temperature component of the detection output.

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

However, in the past, the main magnetic pole 12. Also, it took a lot of effort to form the field magnet 4 having the frequency detection magnetic pole 13. That is, this is because the magnetization of the main magnetic pole 12 and the magnetization of the frequency detection magnetic pole 13 had to be performed separately. For this purpose, a magnetizing device for forming the main magnetic pole 12 and a magnetizing device for forming the frequency detecting magnetic pole 13 are required, resulting in a very expensive device.

Further, referring to FIG. 4, one conductive pattern 11 is normally formed in the radial direction, but the conductive pattern 11 in the radial direction
Reducing the width of 1a' is extremely troublesome with current technology. Therefore, a more accurate rotational speed signal cannot be obtained, making it impossible to control the rotational speed with better performance. The present invention has been developed based on the above circumstances.6) It is possible to simultaneously magnetize the main magnetic pole and the frequency detection magnetic pole using a magnetizing device, thereby simplifying the magnetizing process and reducing the cost. This was done for the purpose of making it possible to construct a magnetic device and also to be able to obtain more frequency signals in order to obtain finer and more accurate rotational speed signals.

An object of the present invention is to provide a magnetizing device in which a groove orthogonal to the center is provided in the end face of a cylindrical body made of a magnetic material for winding an excitation coil for forming a main magnetic pole for driving. In order to form frequency detection magnetic poles with a fine pitch over the entire end face, the frequency structure 1 is made perpendicular to each other at the center with a fine pitch.
Ship! In a magnetizing device characterized in that a large number of pole forming grooves are formed and an excitation fill is wound around the grooves, the magnetic pole forming groove for frequency phantom number formation is formed with a magnetic pole section for frequency detection of 2 minutes. This is achieved by providing a magnetizing device characterized in that two stages are provided on the inner and outer peripheries of the end face with the phase shifted by one pitch in the circumferential direction.

Embodiment (7) of the magnetizing device of the present invention will be described below with reference to FIG. 8 and subsequent figures. Note that parts that are common to those in FIG. 5 are marked with dashes.

FIG. 8 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. In the magnetizing yoke 14', an excitation coil 18 with a thick wire diameter is wound around the groove 17' as in the case of FIG. magnet, and the ninth groove is placed in the grooves 19A and 19b.
As shown in the figure, excitation coils 21-1 and 21-2 for forming the frequency detecting magnetic pole 13 having a thin wire diameter are wound in a spiral manner. The grooves 19a and 19b provided in two stages in the radial direction of the end surface 16' (the grooves 19a and 19b in the circumferential direction
A and 19b are formed with a phase shift of one-half width. This was done because of the magnetizing yoke 1 having the above-mentioned shape.
4' (see FIGS. 8 and 9) (8), for example, an annular field magnet having a frequency detection magnetic pole 13 and a main magnetic pole (driving magnetic pole) 12 as shown in FIG. 14'.

Therefore, when the magnetizing yoke 14' is first used to apply current to the excitation coil 181 to magnetize it, it is natural that four main magnetic poles having magnetic poles numbers ζN and S as shown in FIG. 12 is formed. After that, the excitation coil 21
1.21-2, two frequency detecting magnetic poles 13-1 whose phase is shifted in the circumferential direction from each other by one-half magnetic pole of the frequency detecting magnetic pole 16 in two steps in the radial direction
13-2 is formed in the main pole 12, and a field magnet 4' shown in FIG. 10 is obtained. In addition, excitation coil 2
Since the wire 1 has a small diameter, the frequency detection magnetic pole 13 is magnetized relatively weakly compared to the main magnetic pole 12. Therefore, the pulsed magnetic flux generated by the frequency detection magnetic pole 13 hardly affects the armature coil 8.

Since the present invention has the above configuration, the magnetizing device for forming the main magnetic pole and the magnetizing device for frequency detection are integrated, so that the main magnetic pole and the frequency detection magnetic pole can be easily magnetized. Therefore, the field magnet shown in FIG. 10 can be mass-produced at low cost. Furthermore, since the magnetizing device having such a function is integrated and made compact, there is an advantage that it can be manufactured at low cost. In addition, since the two frequency detection magnetic poles provided in two steps in the radial direction are formed with a phase shift in the circumferential direction, the two frequency detection magnetic poles in the disk type brushless motor to be formed are 13-1.13-2. Since the frequency for speed detection is twice as high due to the magnetic pole 13-1.13-2 and the two conductive patterns 11-1.11-2 facing each other, F-9 (frequency-voltage) By using a conversion circuit, it is possible to obtain a smooth and high rotational speed voltage that is easy to control the rotational speed, so a highly accurate disc-type brushless motor can be easily obtained at low cost. Drink. Furthermore, since the rotational speed signals obtained from each of the two conductive patterns 11-1 and 11-2 are formed with a phase shift of one-half pitch of the frequency detection magnetic pole 16, this can be used to ,
Since the rotational speed signals of two phases, A phase and B phase, can be obtained, the rotation direction of the disc type brushless motor can be known based on the A phase and B phase signals, which eliminates the need for particularly complicated and expensive means. There is an effect that the forward and reverse rotation directions of the brushless motor can be easily controlled without the need for such a configuration.

[Brief explanation of the drawing]

Figure 1 is a longitudinal cross-sectional view of a disc-type brushless motor, Figure 2
The figure is a bottom view of a field magnet that has a main magnetic pole and a 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 a printed circuit board with a conductive pattern. , FIG. 5 is a perspective view of a magnetizing yoke showing a conventional magnetization method for forming a main magnetic pole, FIG. 6 is a waveform diagram of the air gap magnetic flux density formed by the field magnet in FIG. 2, and FIG.
The figure is a plan view of a printed circuit board on which the conductive pattern of the present invention is provided in two stages in the radial direction, FIG. 8 is a perspective view of a magnetizing yoke showing an embodiment of the present invention, and FIG. FIG. 10 is a plan view of a magnetizing yoke in which an excitation coil for frequency detection is wound, and FIG. 10 is a perspective view of a field magnet having a main magnetic pole and a frequency detection magnetic pole obtained by the present invention. DESCRIPTION OF SYMBOLS 1... Disk type brushless motor, 2... Motor shaft, 3... Rotor yoke, 4.4'... Field magnet, 5... Center spindle, 6... Bearing,
7...Stator yoke, 8...-armature coil, 9...
... Magnetoelectric conversion element, 10... Printed circuit board, 11...
・Conductivity, <turn, 12...Main magnetic pole, 16...Magnetic pole for frequency detection, 14.14'...Magnetizing yoke, 15.
15'... Cylindrical body, 16.16'... End face, patent applicant Yoshiteru Takahashi @ Figure 5 Figure 6 Figure 7 II (1"" 17-1 7-2 〆Figure 8 ( C(：○力)! へ う -i. /4' Figure 9 Figure 1Q

Claims (1)

[Scope of Claims] A magnetizing device in which a groove orthogonal at the center is provided in the end face of a cylindrical body made of a magnetic material in order to wind an excitation coil for forming a main magnetic pole for driving. In order to form frequency detecting magnetic poles with a fine pitch, a large number of frequency detecting pole forming grooves are formed at a fine pitch, and an excitation coil is wound around the grooves. A magnetizing device characterized in that a magnetic yoke is provided with two stages in the radial direction of the inner and outer circumferences of the upper surface.