JPS6367253B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fine movement device for a rotating magnetic head, and more particularly to a fine movement device suitable for finely moving a rotating magnetic head such as a VTR in the direction of the rotation axis during rotation.

Conventionally, in helical scan VTRs, etc.
In order to perform special reproduction or automatic tracking of recorded traces, a rotating magnetic head is slightly moved in the direction of the rotation axis. By the way, in this type of conventional fine movement device, a rotating magnetic head is placed on a piezoelectric bimorph to deform the piezoelectric bimorph, but in order to deform the piezoelectric bimorph, a high voltage is applied. It is expensive to use as a home VTR, etc.
The drawback was a lack of reliability.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a rotating magnetic head that does not require high voltage for operation, is compact, has high precision, can easily move the head over a wide range, and is highly reliable. The purpose of the present invention is to provide a fine movement device.

A feature of the present invention is that a cylindrical or columnar movable member to which a rotating magnetic head is attached and which contains an electromagnetic coil or a magnetic material is spaced apart from each other in the direction of the center axis of the movable member in a magnetic circuit member consisting of a permanent magnet or a yoke. A predetermined current is controlled and supplied to the electromagnetic coil provided in the movable member or the electromagnetic coil provided on the magnetic circuit member side, and the electromagnetic force By moving and displacing the movable member in the direction of its central axis against the rigidity of the spring member, the rotating magnetic head is moved and displaced integrally with the movable member to automatically track the track on the recording medium ( The feature is that the system is configured to allow automatic tracking.

The present invention will be explained below using FIGS. 1 to 6 on a VTR.
The case of a fine movement device for a rotating magnetic head will be explained in detail.

FIG. 1 is a diagram illustrating the basic structure of a fine movement device in which an electromagnetic coil is fixed to a magnetic circuit member, and shows a state where it is mounted on a cylinder of a VTR, and FIG. 2 is a bottom view of the device shown in FIG. 1. This configuration is for explaining the moving operation of the rotating magnetic head due to the electromagnetic force generated by controlling power supply to the electromagnetic coil, and some of the spring members are omitted in the configuration. In FIG. 1, reference numeral 1 denotes a rotating cylinder. The rotating cylinder 1 is fixed to a rotating disk 2, and rotates together with a rotating shaft 3. 4 is a fixed lower cylinder. Reference numeral 5 denotes a fine movement device according to the present invention, and the fine movement device 5 is fixed to the rotating cylinder 1 and rotates together with it. 6 is the head support plate 7
A rotating magnetic head fixed to the head support plate 7
is fixed to the shaft 8 of the fine movement device 5, and by finely moving the shaft 8 in the axial direction of the shaft 8 by electromagnetic force, the rotating magnetic head 6 is finely moved in the same direction. That is,
In this configuration, the shaft 8 constitutes a movable member, and is capable of slightly displacing the rotating magnetic head 6 in a direction perpendicular to the scanning direction of the rotating magnetic head 6.

In this configuration, the electromagnetic coil 10 is not provided on a movable member such as the shaft 8, but is provided on a magnetic circuit member fixed to the rotating cylinder 1 side. Reference numeral 9 denotes a slip ring provided on the rotating shaft 3 for supplying current to the electromagnetic coil 10 of the fine movement device 5, and is configured to allow current to flow from the brush 11 through the slip ring 9 to the rotating electromagnetic coil 10.

Figures 3 and 4 are diagrams showing an example of a single structure of a fine movement device in which a permanent magnet is further added to the configuration shown in Figures 1 and 2 above, and a part of the spring member is shown, and the rest is It has been omitted. Of these, FIG. 3 is a bottom view, and FIG. 4 is a sectional view. In FIG. 4, reference numeral 12 denotes a leaf spring as a spring member for elastic support, the inner circumferential part of which is fixed to the shaft 8 side, and the outer circumferential part fixed to a yoke 13 made of a magnetic material, which is one of the magnetic circuit members. ing. The plate spring 12 is made of an elastic material such as phosphor bronze, and is used as shown in FIG. Head support plate 7 fixed to shaft 8 as shown
Appropriate rigidity is given to the rotating magnetic head 6 attached to the tip of the shaft to prevent undesirable displacement of the rotating magnetic head 6 due to the force applied to the tip of the head, and to prevent the shaft from being displaced by the electromagnetic force applied to the shaft 8. 8 is shaped to be displaced in the axial direction by the required amount. 14 is a yoke fixed to the yoke 13 so that its upper surface faces the lower end surface of the shaft 8 with a gap 15 in between; 16 and 17 are the yoke 1;
The permanent magnet fixed in 3, 18 is a holder made of a magnetic material, the shaft 8 is made of a magnetic material such as iron, and fixed to the permanent magnets 16, 17 and yoke 13 by yokes 13, 14, shaft 8, and holder 18. A magnetic circuit of the electromagnetic coil 10 is constructed using the above-described structure. Permanent magnets 16 and 17 are connected to this magnetic circuit.
gives a fixed bias magnetic field. Reference numeral 19 denotes a spacer made of a non-magnetic material, which serves as a guide for the shaft 8 to move in the axial direction.The material of the spacer 19 is selected so that the shaft 8 slides with low friction against the spacer 19, and , a lubricant is also used. If the leaf spring 12 has sufficient rigidity, the gap between the spacer 19 and the shaft 8 can be made sufficiently large so that the spacer 19 and the shaft 8 do not come into contact with each other under normal conditions. In some cases, it is also possible to eliminate the spacer 19.

An attractive force acts between the yoke 14 and the shaft 8 due to the fixed bias magnetic field generated by the permanent magnets 16 and 17, but by appropriately selecting the length of the air 15 and the rigidity of the leaf spring 12, the attractive force due to the bias magnetic field can be reduced. The shaft 8 stops at a position where the restoring force due to the rigidity of the leaf spring 12 and the restoring force are balanced. When the shaft 8 is displaced due to a small disturbance in the axial direction, the restoring force of the leaf spring 12 is made larger than the increase in the suction force due to the decrease in the gap between the air holes 15. By doing so, the shaft 8, that is, the rotating magnetic head 6 can be stably held against minute disturbances. In addition, in the unlikely event that a very large disturbance occurs, the suction force will be reduced by the leaf spring 12.
There is a possibility that the restoring force of the yoke 14 and the shaft 8 will be overcome and the distance between the air holes 15 will become zero, and the yoke 14 and the shaft 8 will become stuck together and become unable to separate. Therefore, in order to prevent this, a stopper 20 is fixed to the shaft 8, and when the shaft 8 is displaced in a direction in which the empty space 15 becomes extremely small, the stopper 20 hits the spacer 19 or the holder 18 if there is no spacer. , the shaft 8 is prevented from being displaced until it comes into contact with the yoke 14.

When the electromagnetic coil 10 is energized in the state shown in FIG. 4, a magnetic field generated in proportion to the current value is superimposed on the fixed bias magnetic field, and the combined magnetic field increases or decreases depending on the direction of the current. Therefore, by passing current in the forward and reverse directions through the electromagnetic coil 10, the air
The magnetic flux density of the yoke 14 and the shaft 8 increases and decreases around the magnetic flux density caused by the bias magnetic field as a center value, and the attraction force between the yoke 14 and the shaft 8 increases and decreases, thereby causing the shaft 8 to move slightly in the axial direction. As a result, the rotating magnetic head 6 is slightly displaced in the axial direction of the shaft 8. As is clear from FIG. 1, this causes the rotating magnetic head 6 to be slightly displaced in a direction perpendicular to the scanning direction. As a result, it is possible to realize a so-called auto-tracking or variable-speed playback function that correctly traces the recording track of a helical scan VTR during playback.

As described above, according to the fine movement device having the above configuration, the shaft 8 is slightly displaced by passing current in the forward and reverse directions through the electromagnetic coil 10, and the rotating magnetic head 6 is finely displaced in a direction perpendicular to the scanning direction. Therefore, it is possible to provide a small fine movement device for a rotating magnetic head that can be operated at a low voltage and has high precision and reliability. Along with this, it is possible to achieve variable speed playback of helical scan VTR recording traces and to reduce the time axis error (jitter) of the generated signal, making it possible to achieve high recording density and high image quality for home use.
It becomes possible to produce VTRs.

In the above configuration, the permanent magnets 16 and 17 are inserted into the magnetic circuit member to generate a fixed bias magnetic field, but instead of this, a direct current bias current that generates a bias magnetic field in the electromagnetic coil 10 is used. You may also leave it to flow. In this case, a disadvantage is that power consumption increases because a bias current is allowed to flow, but there is a new advantage in that a permanent magnet is not required and the structure is simplified. Other effects are the same as above.

Further, in the above configuration, the electromagnetic coil 10
Although the relationship between the current applied to the bias magnetic field and the displacement of the shaft 8 becomes non-linear, the magnetic field due to the current applied to the bias magnetic field is made sufficiently small, and the displacement of the shaft 8 is made sufficiently small with respect to the spacing of the air 15. If designed in this way, it is possible to create an almost linear relationship.

In addition, in the above principle configuration diagram, a magnetic material such as a piece of iron is used as a movable member that slightly moves the rotating magnetic head. (which may include a bobbin) is included in the movable member or is movably supported as the entire movable member in an empty magnetic field in a magnetic circuit member, and this movable electromagnetic coil is controlled to supply power to the movable electromagnetic coil. The structure that allows movement and displacement in the direction of the central axis has high-speed response.
This is particularly effective in terms of controllability such as linearity of displacement characteristics. The present invention is also based on a configuration using the above movable electromagnetic coil.

A first embodiment of the present invention is shown in FIGS. 5 and 6.
5 is a bottom view, and FIG. 6 is a sectional view thereof. In FIGS. 5 and 6, the shaft 21 has a first shaft 21 whose outer peripheral edge is fixed to a yoke 22 at a certain distance in the axial direction. The leaf spring 23, which is a spring member, has a second
It is supported movably in the axial direction by a leaf spring 24, which is a spring member. In this case, shaft 2
1 is preferably made of a light material such as plastic. A head support plate 7 with a rotating magnetic head 6 attached to the tip thereof is fixed to the shaft 21, and a winding frame 25 is attached to the lower end of the shaft 21, and an electromagnetic coil 26 is wound around the outer circumference of the winding frame 25. It's attached. And the electromagnetic coil 26
is located in the space 29 of the magnetic circuit member made of the yoke 22, the permanent magnet 27 fixed to the yoke 22, and the yoke 28. Therefore, using exactly the same principle as the voice coil of a speaker, the electromagnetic coil 26
When a current is applied to the electromagnetic coil 26, an axial electromagnetic force acts on the electromagnetic coil 26, the shaft 21 moves in the axial direction, and the rotating magnetic head 6 moves in the axial direction accordingly. According to this embodiment, a linear relationship is established between the current applied to the electromagnetic coil 26 and the displacement of the shaft 21, and there is also an advantage that the mass of the movable part can be reduced and the frequency characteristics can be improved. . Other effects are similar to those of the configurations shown in FIGS. 3 and 4.

In FIG. 5, the two leaf springs 23 and 24 are each concentric with the electromagnetic coil 26 and symmetrical about its central axis. The longitudinal directions of the springs are arranged perpendicularly to each other, and the longitudinal direction of the leaf spring 23 is aligned with the direction of the support plate 7 to which the rotating magnetic head 6 is attached. This is the displacement of the rotating magnetic head 6 due to an external force received when the rotating magnetic head 6 scans over the recording medium (displacement in the radial direction of the rotation, displacement in the tangential direction of the rotation, displacement in the rolling direction with respect to the tangential direction of the rotation). etc.) with the aim of minimizing the External forces that the rotating magnetic head 6 receives include contact reaction force from the recording medium, rotational radial force such as centrifugal force generated on the head 6 (including the mounting base) itself, the support plate 7, etc., and rotation on the surface of the recording medium. Frictional force in the tangential direction of rotation generated by friction when the magnetic head 6 contacts and scans, acts on the movable part supported by the leaf springs 23 and 24 and consisting of the electromagnetic coil 26, the rotating magnetic head 6, the support plate 7, etc. There is a rolling force centered on the tangential direction of rotation, which is generated based on centrifugal force during rotation. Rotating magnetic head 6 against these external forces
The displacement can be significantly reduced by increasing the planar stiffness of each of the leaf springs 23 and 24 or the planar stiffness of the combination of springs. On the other hand, in the direction of the central axis of the electromagnetic coil 26, each leaf spring 23, 24 needs to have low rigidity because it is necessary to easily take a large displacement of the rotating magnetic head 6 in that direction. desired. Therefore, it is necessary that the plate springs 23 and 24 be combined with each other to increase the rigidity in the plane direction and to reduce the amount of displacement in the plane direction due to the above-mentioned external forces. For this purpose, the most effective support structure is to provide the leaf springs 23 and 24 in two stages in the axial direction and in directions orthogonal to each other, as shown in FIG.

Furthermore, a second embodiment of the present invention is shown in FIG. In this embodiment, a shaft 8 made of a magnetic material as a movable member is provided with a leaf spring 30 as a first spring member and a leaf spring as a second spring member at two locations on both upper and lower ends in the direction of its central axis. 12, and the electromagnetic coil 10 is fixed to the magnetic circuit member side. Each of the leaf springs 30 and 12 has its outer peripheral edge fixed to the end face of a cylindrical yoke 13 provided on the outer peripheral part as a magnetic circuit member, and both leaf springs 30 and 12 have the following shapes: It is axially symmetrical with respect to the center line of the shaft 8. York 13,
14, permanent magnets 16 and 17, and an electromagnetic coil 10 are also arranged concentrically with respect to the shaft 8. The structural features of this embodiment include a leaf spring 30 as a first spring member and a leaf spring 1 as a second spring member.
2, the magnetic air gap 15 in the magnetic circuit member and the electromagnetic coil 10 are placed on both sides of the magnetic circuit member, with the magnetic gap 15 and the electromagnetic coil 10 sandwiched between them in the direction of the central axis, and a large distance is maintained between both leaf springs. In the above configuration, the electromagnetic coil 10 is energized and the attraction force generated at the gap 15 causes the shaft 8 to move slightly in the direction of its central axis. 31 is a stopper, and leaf spring 30 and shaft 8
It also serves as a link between the two.

According to this embodiment, the distance between the leaf springs 30 and 12 is increased, and the shaft 8 as a movable member is
Since the support spacing of the shaft 8 is expanded, the shaft 8 becomes difficult to displace due to an external force perpendicular to the axial direction of the shaft 8, and therefore, the stability of the rotating magnetic head 6 fixed thereto against disturbances is greatly improved. can.
Furthermore, since each leaf spring 30, 12 is exposed and fixed to the end face of the yoke 13, operations such as assembly, internal inspection, adjustment, and parts replacement are facilitated.

Note that the fine movement device of the present invention has a rotating magnetic head 6.
In addition to so-called auto-tracking, in which the recording track on the recording medium is accurately traced by moving the magnetic head 6 in a direction perpendicular to the scanning direction, for example, the rotating magnetic head 6 is moved in the scanning direction, and playback caused by fluctuations in the rotational speed of the head, etc. It can also be used to compensate for signal jitter. However, in this case, the fine movement device 5 is fixed to the rotating cylinder 1 so that the axial direction of the shaft 8 of the fine movement device 5 shown in FIG. 1 is the same as the scanning direction of the rotating magnetic head 6.

As explained above, according to the present invention, it is possible to provide a fine movement device for a rotating magnetic head that does not require high voltage, can easily move and displace the head over a wide range, and is highly reliable. This has the effect of making it easier to produce home-use VTRs with high recording density and high image quality.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the principle structure of a fine movement device for a rotating magnetic head, Fig. 2 is a bottom view of Fig. 1, Fig. 3 is a bottom view showing an improved structure of the fine movement device of Fig. 1, and Fig. 4 5 is a bottom view showing the first embodiment of the fine movement device for a rotating magnetic head of the present invention, and FIG. 6 is a sectional view thereof.
The figure is a sectional view thereof, and FIG. 7 is a sectional view showing a second embodiment of the apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Rotating cylinder, 5... Rotating magnetic head fine movement device, 6... Rotating magnetic head, 7... Head support plate, 8, 21... Shaft, 10, 26... Electromagnetic coil, 12, 23, 24, 30... leaf spring,
13, 22, 14, 28... York, 15, 29
...Sky, 16, 17, 27...Permanent magnet, 19
...Spacer, 20, 31...Stopper.

Claims (1)

[Scope of Claims] 1. A cylindrical or columnar movable member, a magnetic circuit member that includes the movable member therein and forms a magnetic circuit concentrically around the movable member, and a central axis direction of the movable member. a first spring member and a second spring member that are located apart from each other and support the movable member; and a rotation member that is connected and fixed to the movable member and that is integrally displaced with the movable member in the direction of its central axis. A rotating magnetic head fine movement device comprising a magnetic head. 2. The movable member is an air-core cylindrical electromagnetic coil around which a conductive wire is wound, and the magnetic circuit member is composed of a permanent magnet and a yoke arranged inside and outside the electromagnetic coil, and the magnetic circuit member is composed of a permanent magnet and a yoke arranged on the inside and outside of the electromagnetic coil. The fine movement device for a rotating magnetic head according to claim 1, which is a magnetic circuit member having a magnetic gap therein. 3. The electromagnetic coil is a cylindrical coil, and the magnetic circuit member includes a permanent magnet and a cylindrical yoke provided concentrically therewith, and the permanent magnet is located on the center line of the electromagnetic coil. The cylindrical yoke is a magnetic circuit member having a configuration in which the cylindrical yoke is arranged outside the electromagnetic coil in the radial direction, and the first spring member and the second spring member are arranged inside the electromagnetic coil. The rotating magnetic head according to claim 2, wherein the rotary magnetic head is a flat spring having an outer diameter smaller than the outer diameter of the magnetic circuit member and whose outer peripheral edge is fixed to the magnetic circuit member. Microtremor device. 4. The first spring member and the second spring member are spring members having a shape or arrangement that is axially symmetrical with respect to the center line of the electromagnetic coil. Fine movement device for rotating magnetic head. 5. According to claim 4, the first spring member and the second spring member are flat springs arranged orthogonally to each other in a plane perpendicular to the center line of the electromagnetic coil. The fine movement device for the rotating magnetic head described above. 6 The magnetic circuit member is a magnetic circuit member that has a magnetic gap therein that is concentric with the central axis of the movable member, and the first spring member and the second spring member arranged on both sides of the central axis, concentrically with the movable member,
2. The fine movement device for a rotating magnetic head according to claim 1, wherein the outer peripheral edge thereof is a flat spring fixed on the magnetic circuit member. 7. The movable member is a movable member including a member made of a magnetic material, and the magnetic circuit member has an axial magnetic gap concentric with the central axis of the movable member, and has a concentric electromagnetic coil. The fine movement device for a rotating magnetic head according to claim 1, wherein the fine movement device is a magnetic circuit member having a fixed magnetic circuit member.