JPH04353612A - rotating head device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary head device used in a video tape recorder (hereinafter referred to as a VTR).

0002

2. Description of the Related Art In recent years, VTRs using rotary head devices have been made smaller and thinner as well as higher in performance and quality. In addition, a video tape recorder (hereinafter referred to as a VTR) using the VHS system ("VHS" is a registered trademark of Victor Japan) consists of a fixed head called an A/C head for linear audio and tape speed control. As devices become smaller and thinner, leakage magnetic flux from the motor section of the rotary head device tends to leak into the A/C head, resulting in an increase in audio noise. As a countermeasure against this problem, a rotary head device has been developed in which a shielding material such as a silicon steel plate or permalloy is provided inside the rotary head device.

An example of a conventional rotary head device will be described below with reference to the drawings. FIG. 8 is a side sectional view of a conventional rotary head device. In FIG. 8, the fixed drum 4
1 has a shaft 42 fixed at its center. A rotatable hydrodynamic fluid bearing 44 is press-fitted into the center of the rotating drum 43 with a predetermined gap between it and the shaft 42 . The thrust bearing 45 is slidably abutted on the tip of the shaft 42 and fastened to the rotating drum 43. The rotary transformers 47a and 47b on the rotating side and fixed side are respectively fixed to the rotating drum 43 and the fixed drum 41 with a predetermined gap (approximately 50 to 70 μm). The rotor part 48 has a plurality of annular magnets 49 magnetized in the axial direction,
It is rotatably supported on a rotating drum 43. The rotating yoke 50 is disposed facing the magnetized surface of the magnet 49 with a predetermined gap in the axial direction, and is fixed to the rotor portion 48 so that it can rotate integrally with the rotor portion 48 . The stator section 51 is made of a non-magnetic material, is disposed in a gap between the rotor section 48 and the rotating yoke 50 with a predetermined gap therebetween, and has an armature coil. . The shield ring 53 is made of a magnetic material such as a silicon steel plate or permalloy, and is disposed all around the inside of the outer circumference of the fixed drum 41 and is fixed to the fixed drum 41 via the stator section 51. Further, the fixed yoke 52 is made of an annular magnetic material,
Through a predetermined gap between the magnetized surface of the magnet 49 and the axial direction,
The rotor part 48 is coaxially fixed to the stator part 51 and is urged toward the fixed drum 41 in the axial direction by a magnetic attraction force generated between the rotor part 48 and the magnet 49 . Further, the height of the head 46 and the height of the magnetized surface of the magnet 49 are determined by the press-fitting height of the tip of the shaft 42 and the accuracy of individual processing of other constituent members.

The operation of the rotary head device constructed as described above will be explained below. First, stator section 5
When a predetermined current is passed through a coil of a magnetic circuit consisting of a coil arranged at 1 and a magnet 49 fixed to the rotor section 48, a magnetic field is generated, thereby causing the rotor section 48 and the rotating drum 43 to rotate.

[0005] Also, the shield ring 53 is connected to the magnet 4.
9 and the rotating yoke 50 shield leakage magnetic flux from the opposing gap, thereby reducing the influence on the A/C head.

[0006]

However, the conventional configuration has a problem in that audio noise cannot be sufficiently reduced. In other words, when it comes to downsized equipment such as camera-integrated VTRs, rotating head devices and A/
As the distance from the C head becomes shorter, leakage magnetic flux from the motor section of the rotary head device inevitably tends to flow into the A/C head. Further, it would be more effective to make the shielding material constructed inside the fixed drum as large as possible and as thick as possible, but due to space issues, an optimal construction could not be achieved and the effect was insufficient. FIG. 9 shows the leakage magnetic flux 55 in a conventional configuration. Magnet 49 and rotating yoke 50
The leakage magnetic flux 55 generated from the gap between the shield ring 53 leaks from the upper end of the shield ring 53 to the outer periphery of the rotating drum 43. Furthermore, FIG. 10 shows a frequency analysis of the level of audio noise generated from the motor section of the conventional rotary head device configured as described above, and shows the frequency analysis of the 45Hz (fundamental frequency of the rotary head device) and 90Hz components. It can be seen that the level is very high.

The present invention solves the above-mentioned conventional problems, and aims to provide a high-quality, small and thin rotary head device with little audio noise.

[0008]

[Means for Solving the Problems] In order to achieve this object, the rotary head device of the present invention includes a fixed drum having a lead groove on its outer circumferential surface for guiding a tape-shaped recording medium, and a fixed drum for transmitting and receiving signals to and from the tape-shaped recording medium. a rotary drum that carries and rotatably supports the head; a rotor portion configured in an area where a fixed drum and a rotary drum face each other on the same axis and that can rotate integrally with the rotary drum; It is composed of an annular magnet fixed to the rotor and magnetized into multiple poles, and an annular magnetic shielding member made of a magnetic material fixed to the rotating drum.

[0009]

[Operation] With the above structure, interference occurs between the magnetic shielding member and the leakage magnetic flux from the motor section, and the flow of the leakage magnetic flux changes. Therefore, the amount of change in leakage magnetic flux from the motor section that jumps into the A/C head is reduced, and audio noise can be reduced.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a rotary head device according to a first embodiment of the present invention. In FIG. 1, a fixed drum 41 has a shaft 42 fixed at its center. A rotatable hydrodynamic fluid bearing 44 is press-fitted into the center of the rotating drum 43 with a predetermined gap between it and the shaft 42 . The thrust bearing 45 is slidably abutted on the tip of the shaft 42 and fastened to the rotating drum 43. The rotary transformers 47a and 47b on the rotating side and fixed side are respectively fixed to the rotating drum 43 and the fixed drum 41 with a predetermined gap (approximately 50 to 70 μm). The rotor portion 48 has a plurality of annular magnets 49 magnetized in the axial direction fixed thereto, and is rotatably supported by the rotating drum 43 . The rotating yoke 50 is arranged to face the magnetized surface of the magnet 49 with a predetermined gap in the axial direction, and is fixed to the rotor portion 48 so that it can rotate integrally with the rotor portion 48 . The stator section 51 is made of a non-magnetic material, is disposed in a gap between the rotor section 48 and the rotating yoke 50 with a predetermined gap therebetween, and has an armature coil. . The shield ring 53 is made of a magnetic material such as a silicon steel plate or permalloy, and is arranged all around the inside of the outer periphery of the fixed drum 41.
It is fixed to the fixed drum 41 via the stator section 51. Further, the fixed yoke 52 is made of an annular magnetic material, and is fixed to the stator section 51 coaxially with the rotor section 48 with a predetermined gap in the axial direction from the magnetized surface of the magnet 49.
The rotor portion 48 is urged toward the fixed drum 41 in the axial direction by the magnetic attraction force generated between the rotor portion 48 and the magnet 49 . Also, the height of the head 46 and the magnet 49
The height of the magnetized surface is determined by the press-fitting height of the tip of the shaft 42 and the accuracy of individual processing of other constituent members. Further, the magnetic shielding member 54 is made of a magnetic material such as a silicon steel plate or permalloy, and is fixed to the rotating drum 43.

The operation of the rotary head device of this embodiment constructed as described above will be explained below.

First, when a predetermined current is passed through the coil of a magnetic circuit consisting of a coil disposed in the stator section 51 and a magnet 49 fixed to the rotor section 48, a magnetic field is generated, which causes the rotor section 48 and the rotating drum to 43 rotates. The shield ring 53 is connected to the magnet 49 and the rotating yoke 5.
A/C
This reduces the impact on the head. Further, by configuring the magnetic shielding member 54, leakage magnetic flux that could not be suppressed by the shield ring 53 is attracted to the magnetic shielding member 54. In other words, the flow of magnetic flux will change (Figure 2
). Therefore, the amount of change in leakage magnetic flux from the motor section that jumps into the A/C head is reduced, and the shielding effect can be enhanced. FIG. 3 shows the level of audio noise generated from the motor section of the rotary head device of this embodiment. 45H
It can be seen that there is an improvement effect of about 5 dB regarding the z component.

As described above, according to this embodiment, audio noise can be reduced by providing the magnetic shielding member 54 on the rotating drum 43.

FIG. 4 is a diagram for explaining the relative positional relationship between the rolling direction of the magnetic shielding member and the partially magnetized portion of the magnet in the second embodiment of the present invention based on claim 2. In the figure, reference numeral 49 denotes a magnet that is magnetized with eight poles in the axial direction, and a predetermined region of one of the magnets has a partially magnetized portion 49a that is partially magnetized to an S pole or an N pole. Reference numeral 54 denotes a magnetic shielding member made of an annular magnetic material, which is oriented in the rolling direction. The difference from the first embodiment is that the rolling direction of the magnetic shielding member 54 is different from the partially magnetized portion 49 as shown in FIG.
In the vicinity of a, perpendicular to the rotation axis, and partially magnetized part 4
This is because the magnetic shielding member 54 is arranged perpendicular to the line segment connecting the rotation center on the rotation plane of 9a and the partially magnetized portion 49a. Note that the other configurations of the rotary head device are similar to those of the first embodiment.

FIG. 5 shows the level of audio noise generated from the motor section of the rotary head device configured as described above.
Shown below. It can be seen that there is an improvement effect of about 13 dB regarding the 45 Hz component.

As described above, according to this embodiment, the rolling direction of the magnetic shielding member 54 is perpendicular to the rotation axis in the vicinity of the partially magnetized portion 49a, and the rolling direction of the magnetic shielding member 54 is perpendicular to the rotation axis of the partially magnetized portion 49a. By arranging the magnetic shielding member 54 perpendicularly to the line segment connecting the center and the partially magnetized portion 49a, the audio noise reduction effect can be further enhanced.

Note that in this embodiment, the magnetic shielding member 54
is fixed on the back surface of the mounting surface of the head 46 supported on the rotating drum 43, but it may also be fixed on the inside of the outer periphery of the rotating drum 43 (FIG. 6). Alternatively, it may be fixed to the rear surface of the mounting surface of the head 46 and the entire area inside the outer periphery of the rotating drum 43 (FIG. 7).

[0019]

As described above, the present invention provides a fixed drum having a lead groove on its outer circumferential surface for guiding a tape-shaped recording medium;
A head that sends and receives signals to and from a tape-shaped recording medium, a rotating drum that carries the head and is rotatably supported, a fixed drum, and a rotating drum that are arranged in an area facing each other on the same axis, and are integrated with the rotating drum. Audio noise is reduced by providing a rotor part that can be rotated, a circular magnet fixed to the rotor part and magnetized with multiple poles, and a circular magnetic shielding member made of magnetic material fixed to the rotating drum. can do. In addition, the rolling direction of the magnetic shielding member is near the partially magnetized part, is perpendicular to the rotation axis, and is perpendicular to the line segment connecting the rotation center on the rotation plane of the partially magnetized part and the partially magnetized part. The effect becomes even greater by arranging the magnetic shielding member so that

As described above, the present invention can realize an excellent rotary head device that is small, thin, and high quality with little audio noise.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a rotary head device in a first embodiment of the present invention.

FIG. 2 is a partial side view illustrating the flow of leakage magnetic flux in the first embodiment of the present invention.

FIG. 3: Characteristic diagram of audio noise in the first embodiment of the present invention

FIG. 4 is a plan view illustrating the relative positional relationship between the rolling direction of the magnetic shielding member and the partially magnetized portion of the magnet in the second embodiment of the present invention.

FIG. 5: Characteristic diagram of audio noise in the second embodiment of the present invention

FIG. 6 is a sectional view of a rotary head device according to a third embodiment of the present invention.

FIG. 7 is a sectional view of a rotary head device in a fourth embodiment of the present invention.

[Fig. 8] Cross-sectional view of a conventional rotating head device

[Fig. 9] Partial side view showing the flow of leakage magnetic flux in the conventional configuration

[Figure 10] Characteristic diagram of audio noise in conventional configuration

[Explanation of symbols]

41 Fixed drum 42 axis 43 Rotating drum 44 Dynamic pressure type fluid bearing 45 Thrust bearing 46 Head 47a Rotating side rotary transformer 47b Fixed side rotary transformer 48 Rotor section 49 Magnet 49a Partially magnetized part 50 Rotating yoke 51 Stator part 52 Fixed yoke 53 Shield ring 54 Magnetic shielding member 55 Leakage magnetic flux

Claims (2)

[Claims] 1. A fixed drum having a lead groove on its outer circumferential surface for guiding a tape-shaped recording medium, a head for transmitting and receiving signals to and from the tape-shaped recording medium, and a rotating drum that supports and rotatably supports the head. a rotor part configured in a region where the fixed drum and the rotating drum coaxially face each other and can rotate integrally with the rotating drum; and a circle fixed to the rotor part and magnetized with multiple poles. A rotating head device comprising an annular magnet and an annular magnetic shielding member made of a magnetic material fixed to the rotating drum. 2. A plurality of N magnetized on the magnet.
A partially magnetized portion is formed in a predetermined region of at least one of the poles or the south pole, and the magnetic shielding member is made of a rolled magnetic material, and the magnetic shielding member is made of a rolled magnetic material. The rolling direction is near the partially magnetized part, perpendicular to the rotation axis, and perpendicular to a line segment connecting the rotation center on the rotation plane of the partially magnetized part and the partially magnetized part. 2. The rotary head device according to claim 1, wherein said magnetic shielding member is disposed at said magnetic shielding member.