JPH0536043A - Fine adjustment for rotary magnetic head - Google Patents

Abstract

PURPOSE:To facilitate the displacement of a head movement by forming a magnetic field with a permanent magnet as a magnetic flux source by a magnetic circuit member, generating an electromagnetic force in the magnetic field for a movable member, and displacing the movable member through spring members. CONSTITUTION:A shaft 21 being one part of the movable member, is supported by plural plate springs 23 and 24 whose outer peripheral edges are fixed to the middle part and top end part of the height direction of a yoke 22 at a constant interval in a direction in parallel to a central axis, so as to be freely movable to the direction in parallel to the central axis. A head supporting plate 7 to which a rotary magnetic head 6 is attached, and a winding frame 2 whose outer periphery a electromagnetic coil 26 is wound around, are respectively attached to the top end and the lower edge of the shaft 21 made of light materials. Then, the coil 26 is inserted into a void 29 in a magnetic circuit part formed of a permanent magnet 27 fixed to the bottom face of the cylindrical yoke 22, and a yoke 28. Now, when currents are running through the electromagnetic coil 26, the electromagnetic force works at the coil 26, the shaft 21 is moved in parallel to the shaft, and the head 6 is displaced to the same direction only in a linear proportion to the current flowing through the coil 26.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine moving device for a rotary magnetic head, and more particularly to a rotary magnetic head for a magnetic recording / reproducing device such as a VTR, which is parallel to the rotary shaft during its rotation. The present invention relates to a fine movement device suitable for fine movement in various directions. 2. Description of the Related Art Conventionally, in a helical scan VTR or the like, a rotary magnetic head is mounted on a piezoelectric bimorph, and the piezoelectric bimorph is controlled and deformed to perform special reproduction or recording on the rotary magnetic head. Fine movements are being performed to perform automatic trace tracking. In the conventional fine movement device of this type, a high voltage must be applied in order to deform the piezoelectric bimorph, and it is also used in a home VTR or the like. Has the drawback of being expensive and lacking reliability. The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art,
It is an object of the present invention to provide a fine movement device for a rotary magnetic head which does not require a high voltage for operation, is compact and highly accurate, can easily move a wide range of heads, and is highly reliable and easy to assemble. In order to achieve the above object, in the present invention, (a) a flat plate-shaped yoke portion (corresponding to one embodiment reference numeral 40) and a cylindrical yoke portion (corresponding to one embodiment reference numeral). Two
2) and a magnetic circuit member (corresponding one embodiment reference numeral 22, 40, 27, 2) having a permanent magnet (corresponding one embodiment reference numeral 27).
8), a movable member (corresponding to one embodiment reference numeral 21, 25, 26) inserted in the magnetic circuit member, a rotary magnetic head (corresponding to one embodiment reference numeral 6) attached to the movable member, and a bending displacement. A plurality of spring members (corresponding to one embodiment reference numerals 23 and 24) that support the movable member at positions separated from each other in the direction parallel to the central axis by the elastic restoring force of The permanent magnet, the movable member, the rotary magnetic head, and the plurality of spring members are all arranged on the side of the plate-shaped yoke portion where the cylindrical yoke portion is provided. The magnetic circuit member forms a magnetic field using at least a permanent magnet as a magnetic flux source, and the electromagnetic field causes an electromagnetic force to the movable member. The tubular yoke portion forms at least a magnetic path. The spring member elastically supports the movable member at positions separated from each other in a direction parallel to the central axis thereof. The movable member is controlled and displaced in the direction parallel to the central axis by the electromagnetic force, thereby moving and displacing the rotary magnetic head together in the same direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A case where the present invention is applied to a fine moving device of a rotary magnetic head for a VTR will be described in detail below with reference to FIGS. FIG. 1 is a principle configuration diagram of a fine movement device in which an electromagnetic coil is fixedly provided on a magnetic circuit member side, showing a state of being mounted on a rotary cylinder device of a VTR, and FIG. 2 is a bottom view of the configuration of FIG. This configuration is a configuration for explaining the moving operation of the rotary magnetic head by the electromagnetic force generated by the control power supply to the electromagnetic coil, and in the configuration diagram, a part of the spring member is omitted. In FIG. 1, reference numeral 1 is a rotary cylinder, which is fixed to a rotary disk 2 and rotates together with a rotary shaft 3. Reference numeral 4 is a fixed lower cylinder. 5 is a fine movement device according to the present invention. The fine movement device 5 is fixed to the rotary cylinder 1 and rotates together with the rotary cylinder 1. 6 is a rotary magnetic head fixed to the head support plate 7,
The head support plate 7 is fixed to the shaft 8 of the fine movement device 5, and the rotary magnetic head 6 is finely moved in the same direction as this by finely moving the shaft 8 in the axial direction of the shaft 8 by an electromagnetic force. I am doing it. That is,
In this configuration, the shaft 8 constitutes a movable member, and the rotary magnetic head 6 can be finely displaced in a direction perpendicular to the scanning direction of the rotary magnetic head 6. In this configuration, the electromagnetic coil 10 is not provided on the shaft 8 as a movable member, but is provided on the magnetic circuit member side fixed to the rotary cylinder 1 side. Reference numeral 9 denotes a slip ring provided on the rotary shaft 3 for supplying a current to the electromagnetic coil 10 of the fine movement device 5, and supplies a current from the brush 11 to the electromagnetic coil 10 rotating through the slip ring 9. FIG. 3 and FIG. 4 are views showing an example of a unitary structure of a fine movement device in which a permanent magnet is further added to the structure of FIG. 1 and FIG. In this configuration diagram, a part of the spring member is shown and the rest is omitted. In this configuration, with respect to the flat plate-shaped yoke portion in the magnetic circuit member,
A permanent magnet, a movable member, a spring member for supporting the movable member, and a rotary magnetic head attached to the movable member are arranged on the same side as the side where the outer wall-shaped yoke portion is formed.
3 is a bottom view and FIG. 4 is a sectional view. In FIG. 4, 12 is a leaf spring as a spring member for elastic support, the inner peripheral portion of which is fixed to the shaft 8 side as a movable member,
The outer peripheral portion is a yoke 1 as an outer wall-shaped yoke of a magnetic circuit member.
It is fixed at 3. The leaf spring 12 is made of, for example, an elastic material such as phosphor bronze, and as shown in FIG.
The rotary magnetic head 6 attached to the end of the head support plate 7 fixed to the shaft is supported together with the shaft 8 with appropriate rigidity, and the rotary magnetic head 6 records a signal on a recording medium or reproduces a signal from the recording medium. At this time, the rotary magnetic head 6 is prevented from being undesirably displaced by a force received by the head end, and the shaft 8 and the rotary magnetic head 6 are axially moved by a required distance by an electromagnetic force received by the shaft 8. It is designed so that it can be moved and displaced in parallel directions. Reference numeral 14 denotes a yoke fixed to a bottom surface portion (flat plate-shaped yoke portion) 40 of the yoke 13, and an upper end surface thereof faces the lower end surface of the shaft 8 with a gap 15 therebetween. Reference numerals 16 and 17 are permanent magnets fixed in the yoke 13, and 18 is a holder made of a magnetic material.
The shaft 8 is also made of a magnetic material such as iron. A magnetic circuit is configured by the permanent magnets 16 and 17, the holder 18, the yokes 13 and 14, and the shaft 8, and the electromagnetic coil 10 fixed in the yoke 13 excites this. Permanent magnets 16 and 17 apply a fixed bias magnetic field to this magnetic circuit. A spacer 19 made of a non-magnetic material serves as a guide for the axial movement of the shaft 8, and is made of a material that allows the shaft 8 to slide with low friction against the spacer. A lubricant is also used on the surface. When 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 contact in a normal state. It is also possible to eliminate the spacer 19 in some cases. 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. Attraction force and leaf spring 12
The position where the shaft 8 stops can be adjusted by balancing the restoring force due to the rigidity of the shaft. Then, when the shaft 8 is displaced by a slight disturbance in the axial direction, the restoring force of the leaf spring 12 is larger than the increase in the suction force due to the decrease in the gap 15 gap. By doing so, the shaft 8 and the rotary magnetic head 6 can be stably held against disturbance. In the event that a very large disturbance occurs, the attraction force may overcome the restoring force of the leaf spring 12 and the gap 15 becomes zero, and the yoke 14 and the shaft 8 may be attracted to each other to prevent separation. There is. for that reason,
In order to prevent this, the stopper 20 is fixed to the shaft 8 and the stopper 20 is brought into contact with the spacer 19 or the holder 18 (when there is no spacer) against the displacement of the shaft 8 in the direction in which the gap 15 becomes extremely small. The shaft 8 is not displaced until it comes into contact with the yoke 14. When the electromagnetic coil 10 is energized in the state of FIG. 4, the magnetic field generated in proportion to the current value at that time is superimposed on the fixed bias magnetic field, and the combined magnetic field increases or decreases depending on the direction of the current. Therefore, the magnetic flux density of the air gap 15 is controlled centering on the magnetic flux density of the bias magnetic field by passing a control current in the electromagnetic coil 10 in the positive or reverse direction, and the attractive force between the yoke 14 and the shaft 8 is controlled. This causes the shaft 8 to slightly move in a direction parallel to the axis. As a result, the rotary magnetic head 6 is finely displaced together with the shaft 8 in the same direction. As is clear from FIG. 1, this causes the rotary magnetic head 6 to be finely displaced in the direction perpendicular to the scanning direction. As a result, the recording track of the helical scan type VTR is correctly traced during reproduction
A so-called auto-tracking or variable speed reproduction function can be realized. As described above, according to the fine movement apparatus having the above-described structure, the outer wall-shaped yoke portion 13, the permanent magnets 16, 17, and the outer wall-shaped yoke portion 13 are provided on one surface side of the flat plate-shaped yoke portion 40 of the magnetic circuit member.
Spring member 12, movable members 18, 20, rotary magnetic head 6
Since all of the above are arranged, the entire fine movement device can be made small, compact and easy to assemble. Further, since the control current in the forward direction or the reverse direction is passed through the electromagnetic coil 10 to cause the shaft 8 to be finely displaced so that the rotary magnetic head 6 is finely displaced in the direction perpendicular to the scanning direction, a low voltage is applied. Further, it is possible to obtain a fine movement device which can be operated with a small current and has high accuracy and high reliability. Along with this, it is possible to achieve automatic tracking of the recording trace of the helical scan VTR (auto tracking), reduction of fluctuations in the time axis (jitter) of a variable speed reproduction or generated signal, and a home with high recording density and high image quality. It also becomes possible to easily manufacture VTRs for use. In the above configuration, the permanent magnets 16 and 17 are inserted in the magnetic circuit member to generate the fixed bias magnetic field, but instead of this,
A DC bias current for generating a bias magnetic field may be passed through the electromagnetic coil 10. in this case,
Although it has a drawback of increasing power consumption, it has a new effect that the permanent magnet is not required and the structure is simplified.
Other effects are similar to the above. Further, in the above configuration, the relationship between the current supplied to the electromagnetic coil 10 and the displacement of the shaft 8 has a non-linear characteristic, but the magnetic field due to the current supplied to the bias magnetic field is sufficiently small, and the gap 15 On the other hand, if the shaft 8 is designed so that the displacement thereof is sufficiently small, it is possible to obtain almost linear characteristics. Further, in the above principle configuration diagram, a magnetic material such as an iron piece is used as a movable member for finely moving the rotary magnetic head, but an air-core electromagnetic coil (a winding material (bobbin) of a non-magnetic material may be included). Is supported in a movable state in the air gap magnetic field in the magnetic circuit member by including this in the movable member or as a whole of the movable member, and the movable electromagnetic coil is fed in a direction parallel to the central axis thereof by control power feeding thereto. It may be configured to move and displace. This structure is advantageous in terms of high-speed response, controlled characteristics such as linearity of displacement characteristics, and the like. The structure of an embodiment of the present invention is shown in FIGS. Figure 5
5 is a bottom view, and FIG. 6 is a cross-sectional view thereof. In FIGS. 5 and 6, the shaft 21, which is a part of the movable member, has a yoke 22 as a cylindrical yoke portion which is spaced at a constant distance in a direction parallel to the central axis. It is movably supported in a direction parallel to the central axis by a plurality of leaf springs 23 and 24 whose outer peripheral edges are fixed to an intermediate portion and a tip portion in the height direction. In this case, the shaft 21 is preferably made of a light material such as plastic from the viewpoint of control response. A head support plate 7 having a rotary magnetic head 6 attached to the tip is fixed to the shaft 21, and a winding frame 25 is attached to the lower end. An electromagnetic coil 26 is wound around the winding frame 25. It is attached. The electromagnetic coil 26 includes a cylindrical yoke 22, a permanent magnet 27 fixed to the bottom surface (flat plate-shaped yoke portion 40) of the cylindrical yoke 22, and a yoke 28 coupled to the permanent magnet 27. It is inserted in the space 29 in the formed magnetic circuit portion. When a current is applied to the electromagnetic coil 26, an electromagnetic force in a direction parallel to the axis acts on the electromagnetic coil 26, and the shaft 21 is moved in a direction parallel to the axis. Accordingly, the rotary magnetic head 6 moves in the same direction. Is moved and displaced. According to this embodiment, the electromagnetic coil 26
It is said that the current supplied to the shaft and the displacement of the shaft 21 can be made to have a linear proportional characteristic relationship, and the magnetic material can be eliminated in the movable member, so that the mass of the movable member can be reduced and the frequency characteristic can be improved. There are also advantages. In addition, the electromagnetic coil 26
Since the movable member including the shaft 21 and the shaft 21 are supported by the two spring members in two steps in the direction parallel to the central axis, the movable member can be easily supported with high precision. Other effects such as miniaturization, compact structure, and improvement of assembling property are the same as those described in the case of the structures of FIGS. 3 and 4. In FIG. 5, the two leaf springs 23 and 24 are concentric with the electromagnetic coil 26 and axially symmetrical with respect to the central axis thereof. The springs 23 and 24 are arranged so that their longitudinal directions are orthogonal to each other, and the longitudinal direction of the leaf spring 23 coincides with the direction of the support plate 7 to which the rotary magnetic head 6 is attached. .. This is the displacement of the head 6 due to an external force received when the rotary magnetic head 6 scans the recording medium (displacement in the radial direction of rotation of the head, displacement in the tangential direction of rotation, displacement in the rolling direction with respect to the tangential direction of rotation). Etc.) is made for the purpose of minimizing. The external force received by the rotary magnetic head 6 includes a contact reaction force from the recording medium, a radial radial force such as a centrifugal force generated on the head 6 (including the mounting base) itself, the support plate 7 and the like, and a rotating magnetic force on the recording medium. A tangential frictional force of rotation generated by friction when the head 6 is contact-scanned, and a rotational force acting on a movable portion composed of the electromagnetic coil 26 supported by the leaf springs 23 and 24, the rotary magnetic head 6, the support plate 7 and the like For example, there is a rolling force that is generated based on the centrifugal force and has a tangential direction of rotation as an axis. The displacement of the rotary magnetic head 6 with respect to these external forces is greatly reduced by increasing the plane rigidity of each of the leaf springs 23 and 24 or the plane rigidity of the combination of each spring. On the other hand, with respect to the direction parallel to the central axis of the electromagnetic coil 26, the leaf springs 23 and 24 need to be able to easily make a large displacement of the rotary magnetic head 6 in that direction. Low rigidity is desired. Therefore, the leaf springs 23 and 24 should be soft,
By combining these, it is necessary to reduce the rigidity in the direction parallel to the central axis while increasing the rigidity in the plane direction perpendicular to the central axis. For this purpose, as shown in FIG.
A support structure provided in steps and orthogonal to each other is excellent in stability and effective. The fine movement device of the present invention is not limited to so-called auto-tracking in which the rotary magnetic head 6 is moved in a direction perpendicular to the scanning direction to correctly trace the recording track on the recording medium. Move 6 in the same direction as the scan direction,
It can also be used for compensating for the jitter of the reproduction signal due to fluctuations in the head rotation speed. However, in this case, the fine movement device 5 is fixed to the rotary 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 rotary magnetic head 6. According to the present invention, a high voltage is not required,
Easy to assemble, compact, compact and highly precise structure. Moreover, it is possible to easily move and move the head in a wide range, and it can be used as a highly reliable rotary magnetic head fine movement device. There is an effect that it is possible to easily manufacture a VTR or the like. Further, it is possible to configure a fine movement device having no magnetic leakage.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing a principle configuration of a fine moving device of a rotary magnetic head. FIG. 2 is a bottom view of FIG. 3 is a bottom view showing an improved structure of the fine movement device of FIG. 1. FIG. 4 is a cross-sectional view of the configuration of FIG. FIG. 5 is a bottom view showing an embodiment of the device of the present invention. 6 is a cross-sectional view of the configuration of FIG. [Explanation of Codes] 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 ... Plate Spring, 13, 22, 14, 28 ... Yoke, 15, 29 ... Air gap, 16, 17, 27 ... Permanent magnet, 19 ... Spacer, 20 ... Stopper, 40 ... Flat yoke portion.

Claims (1)

[Claims] 1. A magnetic circuit member having a flat yoke portion, a tubular yoke portion, and a permanent magnet, a movable member having a portion to be inserted into the magnetic circuit member, a rotary magnetic head attached to the movable member, and a bending member. A fine movement device for a rotary magnetic head, comprising: a plurality of spring members that support the movable member at positions separated from each other by an elastic restoring force due to displacement, in a direction parallel to the central axis of the movable magnetic member; A fine movement device for a rotary magnetic head, characterized in that the permanent magnet, the movable member, the rotary magnetic head, and the plurality of spring members are arranged on the surface side on which the cylindrical yoke portion is provided.