JPH05266447A - Movable head device and drum device - Google Patents

Abstract

PURPOSE:To provide a movable head device and a drum device having a head position detecting mechanism improving attaching workability and reducing the influence of internal magnetic field to a position senser. CONSTITUTION:In an electromagnetic driving type, the movable head device of a voice coil type in particular, in the movable head device 1 consisting of a head loading body 100 consisting of a magnetic head 12 and gimbals springs 16a and 16b attaching the head, a driving coil 6 wound around a bobbin 11 and a magnet 3 and a yoke 4 forming a magnetic circuit between the magnet 3, a penetration hole 32 is provided on the yoke 4 and a part 33 of the bobbin 11 is prolonged and the head position detection mechanism 200 is provided on the outside of the yoke.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a movable head device (rotary magnetic head device for dynamic tracking) of a rotary head type magnetic recording / reproducing device and a drum device equipped with the movable head device, and more particularly to a magnetic head position detecting mechanism. It is a thing.

[0002]

2. Description of the Related Art FIG. 19 shows a conventional movable head device disclosed in Japanese Patent Application Laid-Open No. 2-304711. In FIG. 19, 1
Is a movable head device, 2 is a pole piece sandwiched by a pair of cylindrical magnets, 4 is a soft magnetic yoke formed of an upper portion 4a, a body portion 4b and a lower portion 4c.
To form a cylindrical magnetic gap 5. 6 is a drive coil placed in the magnetic gap 5, 7a and 7b are leaf springs, and their circular outer peripheral portions are held parallel to each other in the mounting portions 8 and 9, and further, an adhesive agent
It is fixed to the bobbin 11 at the inner circumference of the bobbin by 10 and the bobbin 11
Are held coaxially with the magnetic gap 5. A magnetic head 12 is fixed to the tip of the leaf spring 7b with an adhesive (not shown) to form a head mounting body 100. A hall element 13 detects the strength of the magnetic field, and is fixed inside the yoke 4a. Further, 14 is a through hole, which is formed in a punched-out portion 15 integrated with the yoke 4c.

FIGS. 20 (a), 20 (b) and 21 show a gimbal type spring which is an elastic body of a conventional movable head device and a drum device shown in JP-A-63-173217. 20 (a) and 20 (b) are the leaf springs 7 shown in FIG.
It is a top view of the gimbal type | mold spring corresponding to a and 7b. In the figure, the gimbal type springs 16a and 16b correspond to the leaf springs 7a and 7b shown in FIG. In FIG. 20, 17a, 17
b is an arcuate intermediate portion of the gimbal springs 16a, 16b, 18a, 18
b is an arcuate outer peripheral portion of the gimbal springs 16a, 16b, 19a,
Reference numeral 19b denotes a mounting hole for mounting the bobbin 11 provided at the center of the gimbal spring, and 20a and 20b denote arcuate notches of the gimbal springs 16a and 16b.

FIG. 21 is a sectional view showing a state in which the movable head device is attached to the rotary drum. In FIG. 21, 21
Is a rotary drum, 22 is a screw for attaching the movable head device 1 to the rotary drum 21, and 23 is a wiring board attached to the rotary drum 21. Reference numeral 24 is a screw for attaching the rotary drum 21 to the flange 25, 26a and 26b are rotary transformers, and 27 is a signal line from the rotary transformers 26a and 26b. 28 is a rotary shaft integrally attached to the flange 25, 29a, 29
Reference numeral b indicates a bearing that rotatably supports the rotating shaft 28 with respect to the fixed drum 30. Reference numeral 300 denotes a drum device composed of the rotary drum 21 to the fixed drum 30. Reference numeral 31 denotes a magnetic tape wound around the outer peripheral surfaces of the rotary drum 21 and the fixed drum 30.

Next, the operation will be described. The conventional movable head device and drum device are configured as described above, and the current is supplied to the drive coil 6 to move the magnetic head. Further, as a magnetic head position control method, for example, a head position detection signal is supplied by being superimposed on a coil drive signal, and a magnetic field generated by this signal is detected by a head position detection mechanism 200 composed of a Hall element 13. By doing so, the position information is fed back. Then, the relationship between the coil drive signal and the head movement amount is adjusted with respect to characteristic changes such as temperature change, non-linearity of magnetic characteristics, and hysteresis, and position control is attempted in a sufficiently low frequency band below the resonance frequency of the system. Is.

[0006]

Since the conventional movable head device and drum device are configured as described above,
It was necessary to attach a Hall element, which is a head position detection unit, in the vicinity of the drive coil where the magnetic field generated by the drive coil changes. Therefore, there are two major problems: the mounting workability is poor, and the head position detection unit is affected by the magnetic field generated by the coil drive signal, resulting in poor accuracy.

The present invention has been made in order to solve the above two problems, and improves the workability of mounting and has a movable head having a head position detecting mechanism which is not easily affected by the magnetic field generated by the coil. The purpose is to obtain a device and a drum device.

[0008]

In a movable head device according to the present invention, as a first means, a through hole is provided in a yoke for accommodating a drive coil, and a part of a bobbin is extended axially outside the yoke. A head position detection mechanism is provided outside the yoke. Further, as a second means, a part of the elastic body to which the magnetic head is not attached is projected to the outside from an opening provided in the yoke, and a head position detecting mechanism is provided outside the yoke. Further, the drum device of the present invention is provided with a mounting position adjusting means for the head position detecting mechanism.

[0009]

Since the movable head device according to the present invention is constructed as described above, the work of mounting the head position detecting portion can be performed outside the yoke. Further, a head position detection signal in which the influence of the magnetic field generated by the head driving signal is reduced can be obtained. Further, since the drum device according to the present invention is configured as described above, the head position detecting section can be set to the optimum position by the mounting position adjusting means of the head position detecting section.

[0010]

【Example】

Example 1. Embodiments of the present invention will be described below with reference to the drawings. 1 is a sectional view showing a movable head device according to a first embodiment of the present invention, FIG. 2 is a perspective view showing the movable head device shown in FIG. 1, and FIG. 3 is a special view of the movable head device shown in FIG. 4A and 4B are schematic diagrams of a head locus showing a head moving effect during reproduction, FIGS. 4A and 4B are schematic diagrams showing a reproducing envelope showing a head moving effect of the movable head device, and FIG. 5 is a movable head shown in FIG. Head locus schematic diagram during compatible playback of the device,
6 is a schematic diagram showing a reproduction envelope at the time of the head locus shown in FIG. 5, FIG. 7 is a characteristic diagram showing an open loop characteristic of the movable head device shown in FIG. 1, and FIG. 8 is a movable head shown in FIG. FIG. 9 is a block diagram for performing active damping control of the apparatus, and FIG. 9 is a characteristic diagram showing open loop characteristics of the movable head apparatus to which the active damping control shown in FIG. 8 is added, which is the same as or equivalent to FIGS. The reference numerals are given and the description is omitted.

In FIG. 1, reference numeral 32 is a through hole provided in the yoke 4a, 33 is an extended portion obtained by extending a part of the bobbin 11 in the axial direction, and 34 is a magnetic field generating means attached to the bobbin 11 for head position detection. Is a magnet, 35 is a holder for attaching the Hall element 13 as magnetic field detecting means to the yoke 4, and 36 is a screw for fastening the holder 34 to the yoke 4. In FIG. 2, reference numeral 14 is a hole provided in the punching portion 15 for fastening the movable head device 1 to a rotary drum (not shown).

Next, the operation will be described in detail with reference to the drawings. In FIG. 1, the yoke 4 of the movable head device 1 is provided with a through hole 32 to extend the bobbin 11 to the outside of the yoke 4, a magnet 34 is attached to the extended portion 33, and the magnet 34
Since the head position detecting mechanism is configured by fixing the Hall element 13 at a position opposed to the Hall element 13, the mounting work can be performed outside the yoke 4, and the influence of the magnetic field generated in the driving coil by the driving signal is reduced. The output of the device was obtained.

Hall element 13 for detecting the head position
If a head position detection mechanism consisting of is provided and head position information is detected and active diping control shown in FIG. 8 is applied, a control band can be widened and precise tracking can be realized. This description will be given below.

In FIG. 3, 37 is a signal track recorded on the magnetic tape 31 by the magnetic head 12, 38 is an off-track head locus when the magnetic head 12 is not moved, and 39 is the magnetic head following the signal track 37. The on-track head locus at the time of recording, 40 is the off-track amount indicating the movement amount of the magnetic head 12, 41 is the feeding speed of the magnetic tape 29 during special reproduction, and this feeding speed 41 is the speed ratio n. It is the product of the standard speed Vt.

4 to 6, 42 is a reproduction envelope at the time of off-track, 43 is a reproduction envelope at the time of on-track, 44 is a signal track having a curve recorded on the magnetic tape 29, and 45 is a curve. FIG. 6 is a reproduction envelope when the signal track 44 having is traced without moving the magnetic head 12. In FIG. 7, f0 represents a mechanical primary resonance frequency that affects the control band of the movable head device 1. In FIG. 8, 46 is a track error corresponding to the off-track amount 40 of FIG.
A control circuit that outputs a drive signal 47, one to which the drive signal 47 is input, the other is a movable head mechanism, the other is a state observer that electrically simulates the movable head mechanism, and 48 is a movable head obtained by head position detection means. The position information, the drive signal 47 and the position information 48 of the movable head are used to estimate the operating speed of the movable head, and the estimated speed 49 is fed back to the control circuit.

Generally, when the feeding speed of the magnetic tape 31 is made variable, the magnetic head traces the signal track 37 recorded on the magnetic tape deviating from the regular track as shown in FIG. 3, and a track deviation occurs. Then, a cross-tracked reproduced waveform is obtained as seen in the reproduced envelope 42 shown in FIG. Since a special processing method is generally required to obtain a good reproduced image from this reproduced waveform, it is desirable to make the magnetic head 12 follow the signal track 37 and trace it correctly to obtain a good reproduced envelope 43. Further, in consideration of compatibility as shown in FIG. 5, the normal signal track 44 is curved, and a deviation occurs with respect to the traced path 38 traced without moving the magnetic head 12. Therefore, the reproduced waveform has a shape as shown in the reproduced envelope 45 in FIG. 6, and the SN ratio is lowered and the image quality is deteriorated in the small envelope portion. Therefore, in order to follow the curved signal track 44 and obtain a good reproduction envelope, a control band of at least 2 to 3 times the rotational speed of the rotary drum and accurate magnetic head position control are required. As shown in FIG. 7, the open-loop characteristic of the movable head device 1 is such that, in the case of the movable head device 1 of FIG. 1, the primary resonance frequency f0 appears in a relatively low frequency band, and in the prototype example, the control band is about 30 Hz. is there. In FIG. 8, a drive input signal and head position information are input to a state observer that electrically simulates the movable head mechanism, an estimated speed is calculated, and the estimated speed is fed back to the control circuit. By performing damping control from this speed information, the primary resonance frequency f0 could be completely suppressed as shown in FIG. 9, and a control band of 300 Hz could be obtained.

Further, in the above embodiment, the holding table 35 is attached to the yoke 4.
Although it is separate from the above, it may be an integral type, and the same effect as that of the above-described embodiment can be obtained.

Example 2. FIG. 10 is a sectional view showing a movable head device according to a second embodiment of the present invention. The same or corresponding parts as in FIG.
50 is a holder attached to the yoke 4a, 51 is the yoke 4
A part of the gimbal spring protrudes from the opening 52 and the magnet 34 is attached to the tip 53 of the spring. Reference numeral 13 denotes the Hall element described above, which is installed so as to face the magnet 34. FIG. 11 is a plan view showing the gimbal type spring 51 of FIG.
It is composed of a tip portion 53 that moves integrally with the inner peripheral portion engaged with the bobbin 11. Also in this embodiment, the position of the gimbal type spring 51 that moves integrally with the magnetic head 12 can be detected by the Hall element 13 as in the first embodiment.

Further, in the above embodiment, the holding table 50 is attached to the yoke 4.
Although it is separate from the above, it may be an integral type, and the same effect as that of the above-described embodiment can be obtained.

Example 3. FIG. 12 is a sectional view showing a movable head device according to a third embodiment of the present invention. The same or corresponding parts as in FIG.
Reference numeral 54 denotes a light emitting portion provided outside the yoke 4, and reference numeral 55 denotes a light receiving portion provided opposite the light emitting portion 54 with the extension 33 of the bobbin 11 protruding outside the yoke 4 interposed therebetween. The head position is detected from the amount of light reaching the light receiving portion that changes due to the movement of the bobbin end, and it is expected that the mounting workability is improved and the influence of the magnetic field generated in the drive coil 6 by the drive signal is reduced.
Also in this embodiment, the position of the bobbin 11 that moves integrally with the magnetic head 12 can be detected by the light receiving section 55, as in the previous embodiment.

Further, although the light receiving section 55 has been described in the above embodiment, a two-divided detector 56 shown in FIG. 13 may be used, and the same effect as in the above embodiment can be obtained.

Example 4. FIG. 14 is a sectional view showing a movable head device according to a fourth embodiment of the present invention. The same or corresponding parts as in FIG.
Reference numeral 57 is a photosensor in which a light emitting portion 54 and a light receiving portion 55 provided outside the yoke 4 are integrally formed. Bobbin 11 extension
The head position is detected from the amount of light reaching the light receiving part that changes due to the movement of the end of 33, the workability of mounting the head position detecting mechanism 200 is improved, and the drive coil 6
It is not affected by the magnetic field generated in the. Also in this embodiment, the position of the bobbin 11 that moves integrally with the magnetic head 12 can be detected as in the previous embodiment.

Example 5. FIG. 15 is a sectional view showing a movable head device according to a fifth embodiment of the present invention. The same or corresponding parts as in FIG.
A part of the bobbin 11 is axially extended through a through hole 32 provided in the yoke 4 of the movable head device 1, a first electrode 58 is attached to the tip of the extension 33, and a second electrode 58 is attached so as to face the second electrode 58. The capacitive displacement sensor 60 having the electrode 59 is fastened to the yoke 4 with a screw 61, and the head position is detected by the capacitive displacement sensor 60. This improves the workability of mounting the head position detection mechanism. The accuracy of displacement detection is improved by reducing the influence of the magnetic field generated in the drive coil 6. Also in this embodiment, the position of the bobbin 11 that moves integrally with the magnetic head 12 can be detected by the second electrode 59, as in the previous embodiment.

In the above embodiment, the first electrode is the bobbin.
Although it is provided at the tip of 11, a metal displacement sensor or an electrostatic capacitance displacement sensor that detects displacement based on changes in eddy current loss may be used.

Example 6. FIG. 16 is a sectional view showing a drum device according to a sixth embodiment of the present invention. The same or corresponding parts as those in FIGS. 1 and 21 are designated by the same reference numerals and the description thereof will be omitted. 62 is a holding table to which the hall element 13 is attached, 63 is an elastic body, and 64 is a screw. The holding base 64 is fastened to the rotary drum 21 with screws 64 via the elastic body 63. The position adjustment of the Hall element 13 and the magnet 34, especially the gap adjustment, is performed by the compression adjustment of the elastic body 63.

FIG. 17 is a sectional view of an essential part of FIG. 16 viewed from the direction A, and shows the mounting relationship more clearly.

FIG. 18 is a schematic diagram showing the relationship between the distance between the Hall element 13 and the magnet 34 and the Hall element output level. 65 indicates a substantially linear range, and as the initial setting of the movable head device, the Hall element is screwed by the screw 64 so that the maximum movable range of the head does not deviate from the linear range 65.
13 height adjustments were made. The displacement detection accuracy of the head position detection mechanism is particularly improved when the movable range of the head is wide. In a prototype example in which ferrite is used as the magnet 34, a wide range of characteristics of about 600 μm is obtained as the linear range.

In the above embodiment, the height adjustment is performed by compressing the elastic body 63, but a means such as a shim may be used and the same effect as the above embodiment can be obtained.

Further, in each of the above embodiments, the movable head device has been described as a single head, but it is obvious that it can be applied to a case where a plurality of heads such as segment recording are used.

Although the movable head position detecting device is fixed to the yoke in the first to fifth embodiments,
Obviously, a mounting position adjusting device may be added as shown in the sixth embodiment.

[0031]

As described above, according to the present invention, the workability of attaching the head position detecting mechanism to the movable head device can be improved, and the influence of the magnetic field generated in the coil by the drive signal on the position sensor can be reduced. Therefore, since the head position can be detected with high accuracy, more precise tracking becomes possible and the image quality during special reproduction becomes good.

[Brief description of drawings]

FIG. 1 is a sectional view showing a movable head device according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a movable head device shown in FIG.

FIG. 3 is a schematic diagram of a head locus showing a head moving effect during special reproduction of the movable head device.

FIG. 4 is a schematic diagram showing a reproduction envelope showing a head movement effect during special reproduction of the movable head device.

FIG. 5 is a schematic diagram of a head locus when the magnetic head is not moved during compatible reproduction.

FIG. 6 is a schematic diagram showing a reproduction envelope when the magnetic head is not movable during compatible reproduction.

FIG. 7 is a characteristic diagram showing open loop characteristics of the movable head device shown in FIG.

FIG. 8 is a block diagram for explaining active damping control.

9 is a characteristic diagram showing open loop characteristics of the movable head device shown in FIG. 1 to which active damping control is added.

FIG. 10 is a sectional view of a movable head device according to a second embodiment of the present invention.

11 is a plan view of the gimbal type spring of the movable head device shown in FIG. 10 to which the magnetic head is not attached.

FIG. 12 is a sectional view of a movable head device showing a third embodiment of the present invention.

13 is a cross-sectional view of a main portion in which a two-divided detector is provided instead of the light receiving unit shown in FIG.

FIG. 14 is a sectional view of a movable head device showing a fourth embodiment of the present invention.

FIG. 15 is a sectional view of a movable head device according to a fifth embodiment of the present invention.

FIG. 16 is a sectional view of a drum device showing a sixth embodiment of the present invention.

FIG. 17 is a cross-sectional view of essential parts taken along the line A of FIG.

FIG. 18 is a characteristic diagram showing the relationship between the distance between the Hall element and the magnet in FIG. 16 and the output of the Hall element.

FIG. 19 is a sectional view showing a conventional movable head device.

20 is a plan view showing the gimbal type spring shown in FIG. 19. FIG.

FIG. 21 is a sectional view of a conventional drum device showing a state in which a movable head device is attached to a rotary drum.

[Explanation of symbols]

 1 movable head device 3 magnet 4 yoke 6 drive coil 11 bobbin 12 magnetic head 13 Hall element 16a, 16b gimbal type spring 32 through hole 33 extension part 34 magnet 35 holding base 36 screw 51 gimbal type spring 53 tip part 54 light emitting part 55 light receiving Part 56 2-division detector 57 Photo sensor 58 Electrode 59 Electrode 60 Capacitive displacement sensor 63 Elastic body 100 Magnetic head mounted body 200 Head position detection mechanism 300 Drum device

Claims (5)

[Claims] 1. A head drive unit comprising at least a magnet, a bobbin, a drive coil and a yoke for accommodating the magnet, the bobbin, and the drive coil, and a central portion attached to an outer peripheral surface of the bobbin, the outer peripheral portion being the yoke. An elastic body supported by a magnetic head and a head mounting body that is attached to a tip portion of the elastic body and includes a magnetic head protruding from an opening provided in the yoke, and energizes the drive coil to displace the bobbin. Thus, in a movable head device that moves a movable portion composed of the magnetic head, the elastic body, the bobbin, and the drive coil in the axial direction of the bobbin, the movable portion includes an extended portion at least partially extended. A hole is provided in the yoke for projecting the extension portion, and the axial direction of the bobbin is provided in the extension portion projecting from the hole. A movable head device comprising a direction displacement detection mechanism. 2. The movable head device according to claim 1, wherein a magnetic field generating means is provided at a part of an extended portion of the bobbin or the elastic body protruding outside the yoke as an axial displacement detection mechanism of the bobbin. A movable head device, wherein magnetic field detecting means is provided so as to face the magnetic field generating means in the axial direction. 3. The movable head device according to claim 1, wherein the bobbin axial displacement detection mechanism is arranged so as to sandwich a part of an extended portion of the bobbin or the elastic body protruding outside the yoke. A movable head device comprising: an optical unit including a light receiving unit and a light receiving unit. 4. The movable head device according to claim 1, wherein the bobbin axial displacement detection mechanism is provided with an electric field generating means at a part of a bobbin protruding outside the yoke or an extended portion of an elastic body. A movable head device, wherein an electric field detecting means is provided so as to face the electric field generating means in the axial direction. 5. A drum device in which a movable head device is mounted on a rotary drum, wherein the rotary drum is provided with a mounting position adjusting means for axial displacement detection means of a bobbin of the movable head device. ..