JPH0670847B2 - Rotating magnetic head fine movement device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine movement 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 a rotary shaft during rotation. The present invention relates to a fine movement device suitable for fine movement in a direction or the like. 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 so that the rotary magnetic head is specially reproduced or recorded. Fine movements are being used to perform automatic trace tracking. By the way, in the conventional fine movement device of this kind, a high voltage has to be applied for the deformation of the piezoelectric bimorph, and it is also used in a home VTR or the like. Therefore, there is a drawback that it is expensive and lacks reliability. The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to require a high voltage for operation, to be small in size, to be highly accurate, to be able to easily move a wide range of heads, and to have a highly reliable rotary magnetic head. To provide a fine movement device. In order to achieve the above object, in the present invention, (a) the magnetic circuit member (corresponding to one embodiment reference numeral 22, 40, 27, 28) is inserted into the magnetic field. A rotary magnetic head for supporting the movable member (corresponding to one embodiment reference numeral 21, 25, 26) by a spring member and moving and displacing the movable member by an electromagnetic force to control the position of the rotary magnetic head attached to the movable member ( In the fine movement device of the corresponding embodiment code 6),
(B) The spring member is configured to generate an elastic restoring force by bending displacement, and the longitudinal directions of the spring members intersect with each other at a predetermined angle between different planes parallel to the central axis of the movable member. A plurality of spring members (corresponding to one embodiment reference numerals 23 and 24) arranged in the above are provided. The magnetic circuit member forms a magnetic field and applies an electromagnetic force to the movable member. The spring member elastically supports the movable member in a plurality of stages (two stages). The movable member is moved and displaced in a direction parallel to the central axis of the movable member to move and displace 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 movement device for a rotary magnetic head for a VTR will be described below with reference to FIGS. FIG. 1 is a principle configuration diagram of a fine movement device provided with an electromagnetic coil fixed to a magnetic circuit member side, showing a state of being mounted on a cylinder of a VTR, and FIG. 2 is a bottom view of FIG.
This configuration is 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 a part of the spring member is omitted in the configuration.
In FIG. 1, reference numeral 1 is a rotary cylinder. The rotary cylinder 1 is fixed to a rotary disc 2, and the rotary shaft 3
It is designed to rotate together with. Reference numeral 4 denotes 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 head support plate 7
The head support plate 7 is fixed to the shaft 8 of the fine movement device 5 by a rotary magnetic head fixed to the. The shaft 8 is finely moved in a direction parallel to the axis of the shaft 8 by an electromagnetic force, so that the rotary magnetic head 6 is also finely moved in the same direction. That is, in this configuration, the shaft 8 constitutes a movable member, and the rotary magnetic head 6 is finely displaced in the 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 a current is passed from the brush 11 through the slip ring 9 to the electromagnetic coil 10 in the fine movement device on the rotary cylinder. Is configured to flow. FIGS. 3 and 4 are views showing an example of a single structure of a fine movement device in which a permanent magnet is further added to the structure of FIGS. 1 and 2, and a part of the spring member is shown and the rest is omitted. Has been done. Of these, FIG. 3 is a bottom view thereof, and FIG.
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 and the outer peripheral portion of which is fixed to the yoke 13 of the magnetic circuit member. The leaf spring 12 is made of an elastic material such as phosphor bronze, and as shown in FIG. 3, the rotary magnetic head 6 attached to the tip of a head support plate 7 fixed to a shaft 8.
It is designed to give appropriate rigidity to. When recording a signal on the recording medium with the rotary magnetic head 6 or reproducing a signal from the recording medium, the rotary magnetic head 6 is prevented from being undesirably displaced by a force received by the tip of the head. Due to the electromagnetic force received, the shaft 8 is displaced by a required amount in a direction parallel to the axis. Reference numeral 14 is a yoke fixed to the yoke 13, and its upper end face is opposed to the lower end face of the shaft 8 with a gap 15 in between. 16, 1
Reference numeral 7 is a permanent magnet 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, and has permanent magnets 16 and 17, a holder 18,
A magnetic circuit is formed by the shaft 8 and the yokes 13 and 14, and the electromagnetic coil 10 fixed to the yoke 13 excites this magnetic circuit. Permanent magnets 16 and 17 apply a fixed bias magnetic field to this magnetic circuit. Numeral 19 is a spacer made of a non-magnetic material, which serves as a guide for the axial movement of the shaft 8, and the material is selected so that the shaft 8 can slide with low friction, and the sliding surface is Is used together with a lubricant. 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. In some cases, it is 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 by the permanent magnets 16 and 17, but the bias magnetic field can be obtained by appropriately selecting the length of the air gap 15 and the rigidity of the leaf spring 12. The shaft 8 is placed at a position where the suction force by the blade and the restoring force by the rigidity of the leaf spring 12 are balanced.
Can be stopped. 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 rotary magnetic head 6 can be stably held via the shaft 8 against a slight disturbance. In the unlikely 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 stick to each other and not separate. is there. In order to prevent this, when the stopper 20 is fixed to the shaft 8 and the displacement of the shaft 8 in the direction in which the gap 15 becomes extremely small, the stopper 20 is used.
9 or holder 18 if the spacer 19 is not present
, And 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 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 in the air gap 15 is controlled with the magnetic flux density due to the bias magnetic field as the central value by passing currents in both the forward and reverse directions through the electromagnetic coil 10, and the yoke 14
The suction force between the shaft 8 and the shaft 8 is controlled to increase or decrease, whereby the shaft 8 slightly moves in the direction parallel to the axis. As a result,
The rotary magnetic head 6 is finely displaced in a direction parallel to the axis of the shaft 8. As is clear from FIG. 1, this causes the rotary magnetic head 6 to be finely displaced in a direction perpendicular to the scanning direction. As a result, the helical scan V
It is possible to realize a so-called auto-tracking or variable-speed reproduction function of correctly tracing a TR recording track during reproduction. As described above, according to the fine movement apparatus having the above-described structure, the shaft 8 is finely displaced in the predetermined direction by causing the control current to flow in the electromagnetic coil 10 in the forward direction or the reverse direction to move the rotary magnetic head 6. Since the fine movement displacement is made in the direction perpendicular to the scanning direction, it is possible to operate with a low voltage, and it is possible to obtain a fine movement device for a small rotary magnetic head which is highly accurate and highly reliable. Along with this, it is possible to achieve automatic tracking (recording trace) of the helical scan VTR, variable speed reproduction or reduction of time axis fluctuation (jitter) of the generated signal.
It is possible to manufacture a home VTR with high recording density and high image quality. In the above structure, the permanent magnets 16 and 17 are inserted in the magnetic circuit member to generate the fixed bias magnetic field, but instead of this, the electromagnetic coil 10 is used.
Alternatively, a DC bias current for generating a bias magnetic field may be supplied. In this case, there is a drawback that the power consumption increases, but there is a new effect that the permanent magnets 16 and 17 can be eliminated and the overall structure is simplified. Other effects are similar to the above. Further, in the above structure, 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 If the displacement of the shaft 8 is designed to be sufficiently small with respect to the interval of 15,
This can be a nearly linear characteristic. 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. However, as in a normal speaker, an air-core electromagnetic coil (nonmagnetic material) is used. Winding material (which may include a bobbin) in a movable member, or is movably supported in the air gap magnetic field in the magnetic circuit member as the whole movable member, and this movable electromagnetic coil is The structure for moving and displacing in the direction parallel to the central axis by the control power feeding is particularly advantageous in terms of high-speed response, controllability such as linearity of displacement characteristics, and the like. The present invention also includes a configuration using the movable electromagnetic coil. An embodiment of the present invention is shown in FIGS. FIG. 5 is a bottom view and FIG. 6 is a cross-sectional view thereof. In FIGS. 5 and 6, the shaft 21 is provided with a yoke 2 with a certain distance in the axial direction.
It is movably supported in the direction parallel to the axis by the leaf springs 23 and 24 whose outer peripheral edges are fixed to 2. In this case, the shaft 21 is preferably made of a light material such as plastic in terms 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, and an electromagnetic coil 26 is wound around the outer periphery of the winding frame 25. There is. The electromagnetic coil 26 is located in the void portion 29 of the magnetic circuit formed by the yoke 22, the permanent magnet 27 fixed to the bottom surface of the yoke 22, and the yoke 28. In this configuration, when a current is passed through the electromagnetic coil 26, an electromagnetic force in the axial direction acts on the electromagnetic coil 26, the shaft 21 moves in the axial direction, and the rotary magnetic head 6 moves in the axial direction accordingly. According to this embodiment, a linear proportional relationship is established between the current passed through the electromagnetic coil 26 and the displacement of the shaft 21, and the mass of the movable portion can be reduced to improve the frequency characteristics. There is. Other effects are the same as those in the configurations of FIGS. 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 the longitudinal directions thereof are orthogonal to each other, and the longitudinal direction of the leaf spring 23 is the rotary magnetic head 6.
Are aligned with the direction of the support plate 7 to which is attached. This is the displacement of the head 6 due to the 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 relative to the tangential direction of rotation). Etc.) is made for the purpose of minimizing. The external force received by the rotary magnetic head 6 is the contact reaction force from the recording medium or the rotary magnetic head 6.
Rotational radial force such as centrifugal force generated on itself (including the mounting base), support plate 7 and the like, tangential frictional force of rotation generated by friction when the rotary magnetic head 6 scans the recording medium in contact, plate For example, there is a rolling force centered on the rotational tangential direction generated by centrifugal force at the time of rotation that acts on a movable portion that is supported by the springs 23 and 24 and that includes the electromagnetic coil 26, the rotary magnetic head 6, the support plate 7, and the like. The displacement of the rotary magnetic head 6 with respect to these external forces is greatly reduced by increasing the planar rigidity of each of the leaf springs 23 and 24 or the planar rigidity of each combination of springs. 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, while the leaf springs 23 and 24 are made of a combination of soft materials, the rigidity in the direction parallel to the center axis is reduced, while the rigidity in the plane direction perpendicular to the center axis is increased, and the plane springs are displaced by the external forces. It is necessary to reduce the amount. For this purpose, as shown in FIG. 5, it is most effective to provide the leaf springs 23 and 24 in two stages in the axial direction and to make them orthogonal to each other. The fine movement apparatus of the present invention moves the rotary magnetic head 6 in the direction perpendicular to the scanning direction to correctly trace the recording track on the recording medium, so-called auto-tracking. It can also be moved in the scanning direction to be used for compensating for the jitter of the reproduced 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. As described above, according to the present invention,
It does not require high voltage and can easily move and displace the head over a wide range. It can be used as a highly reliable rotary magnetic head fine movement device, and it is possible to manufacture a home VTR with high recording density and high image quality. The effect is that it is possible easily. In particular, the spring can have a simple structure, can be easily incorporated, and can support the rotary magnetic head with high accuracy.

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 fine moving device of the rotary magnetic head 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.

Claims (1)

[Claims] 1. A rotary magnetic head that supports a movable member having a portion to be inserted into a magnetic field of a magnetic circuit member by a spring member, and moves and displaces the movable member by an electromagnetic force to control the position of a rotary magnetic head attached to the movable member. In the fine movement device, the spring member is configured to generate an elastic restoring force by a bending displacement, and the longitudinal directions of the spring members intersect with each other at a predetermined angle between different planes parallel to the central axis of the movable member. A fine movement device for a rotary magnetic head, comprising a plurality of spring members arranged to 2. The fine movement device for a rotary magnetic head according to claim 1, wherein the spring member is a leaf spring. 3. 3. The spring member according to claim 1, wherein a longitudinal direction of the spring member coincides with or substantially coincides with a mounting direction of the rotary magnetic head.
Item 7. A fine movement device for a rotating magnetic head according to item.