JPH08321023A - Rotary magnetic head device - Google Patents

Abstract

PURPOSE: To reduce the adverse effect of the leaked magnetic flux on a magnetic head, in a rotary magnetic head device of integrated magnetic shieldless drum motor. CONSTITUTION: The device is provided with a fixed drum 1, a rotary drum 3 pivotally supported freely rotatably by a shaft 2 stuck to the fixed drum, a magnetic head 6 attached to the rotary drum, and the drum motor 11 consisting of a rotor magnet 16 rotating integrally with the rotary drum and a stator coil 12 stuck to the shaft while facing to the rotary magnet. A boundary part 21 of magnetic poles of the rotor magnet is arranged so as to almost match the part on a line 22 connecting a magnetic gap 7a of the magnetic head and a rotational center 2a of the rotary drum, and a brass or non-magnetic material of resin is selected for a screw for adjusting the height of the magnetic head.

Description

Detailed Description of the Invention

[0001]

[Industrial application] Video tape recorders (hereinafter referred to as V
(Referred to as TR) and the like, and relates to a rotary magnetic head device in a magnetic recording / reproducing apparatus, and particularly to a mounting arrangement of a rotor magnet and a magnetic head.

[0002]

2. Description of the Related Art FIG. 5 is a sectional view of a conventional rotary magnetic head device. In the figure, 1 is a fixed drum provided with a magnetic tape guide portion on its outer peripheral surface, 2 is a shaft fixed to the fixed drum 1, 3 is attached to a disk 4 and is rotatable about a shaft 2 via a bearing 5. A rotary drum pivotally supported on the magnetic head 6 is a magnetic head to which a head chip 7 is adhered. The head chip 7 has a magnetic gap (not shown) for exchanging signals with the magnetic tape.

Reference numeral 8 is a rotary transformer comprising a rotor 8a and a stator 8b, 9 is a magnetic head fixing screw, and 10 is a magnetic head height adjusting screw. 11 is a motor stator 12
And a motor rotor 13, and the motor stator 12 includes a motor coil (not shown) and an F motor.
A G coil (not shown) pattern is printed and fixed to the shaft 2 via the boss 14. The motor rotor 13 includes a rotor case 15 and a rotor magnet 16, and is attached to the rotary drum 3. Reference numeral 17 denotes a rotor yoke fixed to the rotary drum 3. Reference numeral 18 is a magnetic shield plate for reducing adverse effects on the magnetic head 6 due to the leakage magnetic flux of the rotor magnet 16.

[0004]

The outer diameter of the rotary cylinder of a digital VTR is about φ due to the miniaturization and high performance of the device.
Since the distance between the magnetic head 6 and the rotor magnet 16 is only a few millimeters and both are extremely close to each other, even if the leakage magnetic flux has a magnetic flux density of only a few gausses, a large C / N is achieved. This causes deterioration of the ratio and increase of noise, which causes deterioration of the performance of the device. Therefore, the magnetic shield plate 18 is adopted as shown in the figure. However, the interposition of such a magnetic shield member not only causes an increase in the number of parts, an increase in cost, and a decrease in reliability, but also requires a space in response to a request for downsizing of the device, particularly for downsizing in the axial direction. There is no room for it, which is a design bottleneck.

[0005]

Therefore, in the present invention, a fixed drum for guiding the running of the magnetic tape wound around the outer peripheral surface, and a rotary drum rotatably supported by a shaft fixed to the fixed drum. A magnetic head attached to the rotary drum, a rotary transformer attached between the fixed drum and the rotary drum, a rotor magnet that rotates integrally with the rotary drum, and a shaft facing the rotor magnet. In a rotary magnetic head device including a drum motor composed of a fixed stator coil, the magnetic pole boundary portion of the rotor magnet is arranged substantially in line with a line connecting the magnetic gap of the magnetic head and the rotation center of the rotary drum, and The material of the height adjusting screw of the magnetic head is selected from brass or non-magnetic material such as resin.

[0006]

As described above, the N of the rotor magnet of the motor is
Since the boundary of the S magnetic pole is substantially aligned with the line connecting the magnetic gap of the magnetic head and the center of rotation of the rotary drum, and the height adjusting screw of the magnetic head is made of a non-magnetic material, the magnetic head caused by the leakage flux of the rotor magnet is used. The effect on the magnetic field is reduced to a minimum, and even if the magnetic shield plate is not provided, substantially the same performance as when the magnetic shield is provided can be obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described below with reference to the drawings. 1 and 2 are partial plan views showing a main part in a state where the positional relationship between the magnetic gap of the magnetic head and the magnetic poles of the rotor magnet is different, and FIG. 3 is a partial cross-sectional view showing the positional relationship between the magnetic head fixing screw and the height adjusting screw. 4 and 5 are sectional views of the rotary magnetic head device. In the figure, the same parts as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted. A sectional view of the rotary magnetic head device of FIG. 4 is shown in FIG.
The magnetic shield plate 18 in the cross-sectional view of is removed, and other than that is exactly the same.

1 to 3, 2a is a rotation center (center of the shaft 2) O of the rotary drum, 7a is a magnetic gap of the head chip 7, 16a is an N pole magnet of the rotor magnet 16, and 16b is an S pole magnet. Reference numeral 19 is a magnetic force line indicating a magnetic flux, 2
Reference numerals 1 and 21 'denote magnetic pole boundaries where the NS magnets are joined, and 22 denotes the center of the magnetic gap 7a and the rotation center 2a of the rotary drum 3.
It is a line that connects with (called the reference line). 3a is the lower surface of the rotary drum 3, that is, the mounting surface of the magnetic head 6.

As shown in FIG. 1, the rotor magnet 16
The magnetic pole boundary portion 21 of the magnetic gap 7a and the rotary drum 3
If they are arranged so as to substantially coincide with the line 22 connecting the rotation center 2a, the number of magnetic force lines 19 crossing over the head chip 7 is small. On the other hand, when the central portion of the N-pole magnet 16a (or the S-pole magnet 16b) of the rotor magnet 16 is located on the magnetic gap 7a as shown in FIG. More, head chip 7
The magnetic flux that crosses above is the maximum, and the influence of the leakage magnetic flux on the magnetic head 6 becomes large.

FIG. 3 shows the positional relationship between the fixing screw 9 for attaching the magnetic head 6 to the rotary drum 3 and the height adjusting screw 10 of the magnetic head 6, and the magnetic head located on the reference line 22. Since the height adjusting screw 10 is also located on the reference line 22 with respect to the fixing screw 9, when the height adjusting screw 10 is rotated, the magnetic head 6, that is, the head chip 7 is moved to the reference line 2.
The height is adjusted without moving the gap 7a of the head chip 7 to the left or right.

By the way, as shown in the figure, the rotor magnet 1
Since the height adjusting screw 10 is located on the outer peripheral surface of the rotor 6, depending on the material of the screw 10, the rotor magnet 16
A phenomenon that adversely affects the magnetic field lines 19 emitted from the device occurs. That is, when the screw 10 is an iron material, it acts so as to converge the magnetic force lines 19. As a result, more magnetic lines of force 19 are emitted to the head chip 7, which affects the recording / reproducing operation. Therefore, in the present invention, the material of the height adjusting screw 10 is selected so as not to affect the magnetic force lines 19, that is, non-magnetic material. For example, a brass screw or a resin screw such as a product name polycarbonate is used.

[0012]

With the above-mentioned structure, the structure suitable for downsizing of the rotary cylinder is maintained without providing the magnetic shield plate on the rotor magnet portion,
This has the effect of reducing the adverse effect on the magnetic head due to the leakage magnetic flux of the rotor magnet.

[Brief description of drawings]

[0013]

FIG. 1 is a partial plan view showing a relative positional relationship between a magnetic head and a rotor magnet.

[0014]

FIG. 2 is a partial plan view showing a relative positional relationship in a different case corresponding to FIG.

[0015]

FIG. 3 is a partial cross-sectional view showing a positional relationship between a magnetic head fixing screw and a height adjusting screw.

[0016]

FIG. 4 is a sectional view of a rotary magnetic head device.

[0017]

FIG. 5 is a sectional view of a conventional rotary magnetic head device.

[0018]

[Explanation of symbols]

1 Fixed Drum 2 Axis 3 Rotating Drum 6 Magnetic Head 7 Head Chip 7a Magnetic Gap 9 Magnetic Head Fixing Screw 10 Magnetic Head Height Adjusting Screw 16 Rotor Magnet 21 Magnetic Pole Boundary 22 Line Connecting Magnetic Gap and Rotation Drum Rotation Center (Reference line)

Claims (3)

[Claims] 1. A fixed drum for guiding the running of a magnetic tape wound around an outer peripheral surface, a rotary drum rotatably supported by a shaft fixed to the fixed drum, and attached to the rotary drum. Magnetic head, a rotary transformer mounted between the fixed drum and the rotary drum, a rotor magnet that rotates integrally with the rotary drum, and a stator coil fixed to the shaft so as to face the rotor magnet. And a magnetic pole boundary portion of the rotor magnet substantially aligned with a line connecting a magnetic gap of the magnetic head and a rotation center of the rotary drum, and the magnetic head. A magnetic head unit with a height adjustment screw selected from non-magnetic material screws. 2. The rotary magnetic head device according to claim 1, wherein the non-magnetic material screw is a brass screw. 3. The rotary magnetic head device according to claim 1, wherein the non-magnetic material screw is a resin screw.