JPH0449179B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a rotating magnetic head drum, and more particularly to a rotating magnetic head drum that prevents deterioration of the S/N ratio of rotation detection signals.

Fig. 1 is a partial sectional view showing an example of a conventional rotating magnetic head drum, Fig. 2 is a bottom view of its main parts, and Fig. 3 is a partial sectional view showing an example of a conventional rotating magnetic head drum.
This figure is a schematic plan view of the multipolar magnet shown in FIG. 1.

In the figure, 1 is a rotating drum, 2a and 2b are magnetic heads mounted on the lower periphery of the rotating drum 1, and 6 is fixed to the center of the rotating drum 1.
A rotating shaft 4 that rotates integrally with this is a fixed drum whose center portion is penetrated by the rotating shaft 6.

3 is a bearing of the rotary shaft 6 mounted on the fixed drum 4; 5 is a printed wiring board with printed wiring 21 provided on the bottom surface (see FIG. 2); 8 is a cylindrical rotor magnet yoke having a bottom. , 7 are bearing supports partially fixed to the bottoms of the rotating shaft 6 and the rotor magnet yoke 8, respectively.

9 is a rotor magnet fixed to a part of the inner surface of the side surface of the rotor magnet yoke 8; 10 is a stator core provided at a position facing the rotor magnet yoke 9 and fixed to the lower part of the fixed drum 4; 11; is a stator coil wound around the core.

Numeral 12 is provided at the upper end of the cylindrical portion of the rotor magnet yoke 8, and includes multi-pole magnets (third
(see figure).

As is well known, the printed wiring board 5 and the multipolar magnet 12 form a frequency generator (hereinafter referred to as FG).

Reference numerals 13a and 13b designate rotational phase detection magnets that are partially embedded and fixed in holes provided at diametrically opposed positions on the side surfaces of the rotor magnet yoke 8.

The magnets 13a, 13b are formed so as to pass through the side surface of the rotor magnet yoke 8, one end of which abuts the side surface of the rotor magnet 9, and the other end protrudes from the side surface.

A magnetic detector 14 is suspended from the printed wiring board 5 and provided at a position facing the magnets 13a and 13b.

The magnets 13a, 13b and the magnetic detector 1
4 forms a rotational phase detector.

The rotor magnet 9 and stator coil 11
and form the motor part. Therefore, when a current is applied to the coil 11, the rotor magnet 9, the rotor magnet yoke 8, the multipolar magnet 12, and the magnets 13a and 13b rotate integrally.

At the same time, the rotating shaft 6, which is connected to the rotor magnet yoke 8 by a bearing support 7, also rotates together with the rotating drum 1 and the magnetic heads 2a, 2b.

By performing the above-described operation, rotational phase detection signals of the magnetic heads 2a and 2b are obtained from the magnetic detector 14.

However, in the above-mentioned device,
As described above, holes are provided in the side surface of the rotor magnet yoke 8, and rotational phase detection magnets 13a and 13b are provided through the holes.

For this reason, magnetic leakage of the rotor magnet 9 of the motor section occurs through the hole, resulting in a disadvantage that the S/N ratio of the output signal from the magnetic detector 14 deteriorates.

Furthermore, there is a drawback that the magnets 13a and 13b cannot be made larger because of the risk of causing the above-mentioned drawbacks.

Also, since some of the magnets 13a and 13b protrude from the side of the rotor magnet yoke 8,
The drawback is that the parts are easily damaged during assembly and adjustment, making the work difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide a rotating magnetic head drum that eliminates the above-mentioned drawbacks, prevents deterioration of the S/N ratio of rotation detection signals, and facilitates assembly and adjustment operations.

In order to achieve the above object, the present invention is characterized in that the multipolar magnet constituting the FG of the rotating magnetic head drum and the magnet for detecting the rotational phase are fixedly integrated.

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 4 is a partial sectional view of the first embodiment of the present invention, and FIG. 5 is a plan view of the main part thereof. In the figures, the same reference numerals as in FIGS. 1 and 3 represent the same or equivalent parts.

23a and 23b are rotational phase detection magnets (first and second magnets) embedded in both ends of one diameter of the multipolar magnet 12 so that their outer surfaces are substantially flush with the outer surface of the multipolar magnet 12. 5), 24 is a magnetic detector suspended from the bottom surface of the printed wiring board 5 and provided at a position facing the magnets 23a, 23b.

In the rotation detector configured as described above, when a current is applied to the stator coil 11, the rotor magnet 9, the rotor magnet yoke 8, the multipolar magnet 12, and the magnets 23a and 23b rotate integrally.

At the same time, the rotating shaft 6, which is connected to the rotor magnet yoke 8 by a bearing support 7, also rotates together with the rotating drum 1 and the magnetic heads 2a, 2b.

At this time, the magnetic detector 24 obtains rotational phase detection signals of the magnetic heads 2a and 2b with little deterioration in the S/N ratio.

FIG. 6 is a partial sectional view of a second embodiment of the invention. In the figure, the same reference numerals as in FIG. 1 represent the same or equivalent parts.

Reference numeral 15 indicates multipolar magnets 22 in which the directions of lines of magnetic force are alternately arranged in opposite directions, and a printed wiring board provided oppositely to each other, and 25 indicates a fixed drum 4 whose upper end portion is fixed.
This is a magnetic shielding case fixed to the lower surface of the magnetic shielding board 15 and having a lower end portion coupled to the printed wiring board 15.

16 is a wiring board; 17 is a stator yoke fixed to the lower surface of the wiring board 16; 18 is a stator coil provided on the lower surface of the stator yoke 17;
A rotor magnet yoke 20 is partially fixed to the lower end of the bearing support 7, and a rotor magnet 19 is placed on the rotor magnet yoke 20, facing the stator coil 18.

Reference numerals 33a and 33b designate rotational phase detection magnets embedded in both ends of one diameter of the multipole magnet 22 so that their outer surfaces are substantially flush with the outer surface of the multipole magnet 22.

Further, 34 is a magnetic detector supported by the printed wiring board 15 and provided at a position facing the magnets 33a and 33b.

In the rotation detector configured as described above, when a current is applied to the stator coil 18, the rotor magnet 29, the rotor magnet yoke 20, the multipolar magnet 22, and the magnets 33a, 33b
rotates as a unit.

At the same time, the rotating shaft 6, which is connected to the rotor magnet yoke 20 by a bearing support 7, also rotates together with the rotating drum 1 and the magnetic heads 2a, 2b.

At this time, the magnetic detector 34 obtains rotational phase detection signals of the magnetic heads 2a and 2b with little deterioration in the S/N ratio.

In this embodiment, the rotation detector magnet 33
Since magnets 33a and 33b, including the motor section, are covered by the magnetic shielding case 25, there is no possibility that magnetic leakage from magnets 33a and 33b will affect the outside as noise.

FIG. 7 is a partial sectional view of a third embodiment of the present invention. In the figure, the same reference numerals as in FIG. 1 represent the same or equivalent parts.

36 is a wiring board fixed approximately parallel to the fixed drum 4 to the lower end portion of the magnetic shielding case 45 whose upper end portion is fixed to the lower surface of the fixed drum 4;
27 is a stator yoke provided on the upper surface of the wiring board 36, and 28 is a stator coil provided on the upper surface of the stator yoke 27.

29 is fixed to the bottom surface of the rotor magnet yoke 30 fixed to the bearing support 7, and the coil 2
The rotor magnets 32 provided opposite the rotor magnets 8 are multi-pole magnets placed on the upper surface of the rotor magnet yoke 30 and arranged alternately so that the lines of magnetic force are in opposite directions.

43a and 43b are rotation detection magnets embedded in both ends of one diameter of the multipolar magnet 32 so that their outer surfaces are substantially flush with the outer surface of the multipolar magnet 32; This is a printed wiring board located inside the magnetic shielding case 45 and fixed to the lower part of the fixed drum 4.

Reference numeral 44 denotes a magnetic detector fixed to the printed wiring board 35 and provided at a position facing the magnets 43a and 43b.

In the rotation detector configured as described above, when a current is applied to the stator coil 28, the rotor magnet 29, the rotor magnet yoke 30, the multipolar magnet 32, and the magnets 43a, 43b
rotates as a unit.

At the same time, the rotating shaft 6 connected to the rotor magnet yoke 30 by the bearing support 7 also rotates together with the rotating drum 1 and the magnetic heads 2a, 2b.

At this time, the magnetic detector 44 obtains rotational phase detection signals of the magnetic heads 2a and 2b with little deterioration in the S/N ratio.

In this embodiment, the rotational phase detection magnet 43
a, 43b, including the motor part, are covered by the magnetic shielding case 45, so the sixth
As described above in the figure, the magnet 43
There is no possibility that magnetic leakage caused by a and 43b will affect the outside as noise.

In the above description, the magnet for detecting the rotational phase was provided so as to be embedded in the multipolar magnet, but it goes without saying that it may be provided by adhesive bonding or press-fitting.

As described above, in the present invention, the FG multipole magnet of the rotating magnetic head drum and the rotational phase detection magnet are fixedly integrated, thereby preventing deterioration of the S/N ratio of the rotation detection signal and reducing assembly work and adjustment. It has the advantage of making work easier.

[Brief explanation of drawings]

Fig. 1 is a partial sectional view showing an example of a conventional rotating magnetic head drum, Fig. 2 is a bottom view of its main parts, and Fig. 3 is a partial sectional view showing an example of a conventional rotating magnetic head drum.
The figure is a plan view of the main part of Fig. 1, and Fig. 4 is a plan view of the main part of Fig. 1.
A partial sectional view of the embodiment, FIG. 5 is a plan view of the main part,
FIG. 6 is a partial sectional view of the second embodiment of the present invention, and FIG.
The figure is a partial sectional view of a third embodiment of the present invention. 1... Rotating drum, 2a, 2b... Magnetic head, 4... Fixed drum, 5, 15, 35... Printed wiring board, 6... Rotating shaft, 8... Rotor magnetic yoke, 9, 19, 29 ... Rotor magnet, 11, 18, 28 ... Coil, 12, 22,
32...Multi-polar magnet, 13a, 13b, 23
a, 23b, 33a, 33b... Magnet for rotational phase detection, 14, 24, 34, 44... Magnetic detector, 25, 45... Case for magnetic shielding.

Claims (1)

[Scope of Claims] 1. A rotating drum, a magnetic head mounted on the rotating drum, a stationary drum, a rotating shaft that integrally rotates the rotating drum and the magnetic head, and applying rotational force to the rotating shaft. Detecting the rotational phase of the motor section, a frequency generator formed by a multi-pole magnet whose lines of magnetic force are alternately arranged in opposite directions, and a wiring board provided at a position facing the magnet, and the magnetic head. A rotating magnetic head drum having at least one rotational phase detection magnet provided for the rotational phase detection magnet, and a magnetic detector for detecting the magnetism of the rotational phase detection magnet, wherein the rotational phase detection magnet is integrated with the multipolar magnet. A rotating magnetic head drum characterized by a 2. Claim 1, characterized in that the surface of the rotational phase detection magnet facing the magnetic detector is provided so as to be substantially flush with the surface of the multipolar magnet facing the magnetic detector. The rotating magnetic head drum described in Section 1. 3. The rotating magnetic head drum according to claim 1, wherein the rotational phase detection magnet is covered with a magnetic shielding case having a radius larger than the rotational radius of the magnet.