JPH0682452B2 - Rotating drum device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] This invention is, for example, a video tape recorder (hereinafter referred to as VTR
Abbreviated), which was made especially to improve the playback image quality of the VTR.
The present invention relates to a rotary drum device in which a head can be moved in the width direction of a magnetic tape to faithfully trace a magnetic recording trace.

[Prior Art] FIG. 2 is a sectional view showing a main part of a conventional rotary drum device,
3 is a plan view thereof, FIG. 4 is a detailed plan view of the head driving device thereof, FIG. 5 is a sectional view of FIG. 4, and FIG. 6 is a front view of FIG.

In FIGS. 2 and 3, (4a) is a drive unit for fixing the head (5) to the tip and for moving the head (5) in the width direction of the tape. Reference numeral (50) is a recess provided in a part of the upper drum (3) for accommodating the head drive section (4a), and is formed slightly larger to adjust the position of the drive section (4a). The head is positioned using the position adjusting hole (51), and the yoke (47) is fixed with the screw (48). In addition, (14) is a non-rotating contactor for supplying a control current to the drive part (4a), and (15) is a rotating part provided in a part of the pedestal (9) so as to make sliding contact with the contactor (14). The electrodes (16) are connected to the drive section (4a) from the electrode (15) via the connection section (12) and the wiring board (11). The head (5) is electrically connected to the upper transformer (7) via the connecting portion (10), the wiring board (11) and the connecting portion (12).

4, 5 and 6 show the above-mentioned drive unit (4a) in more detail, (41) is a non-magnetic plate spring having a head (5) attached to the tip thereof, and (43) is a plate. A coil bobbin attached to the spring (41), (44) a driving cylindrical coil wound around the coil bobbin (43), and (42) a coil bobbin that supports the coil bobbin (43) and is deformed together with the leaf spring (41). (43) leaf springs to enable linear movement,
(45) is a cylindrical permanent magnet, (46) is a cylindrical permanent magnet (4
5) A cylindrical permanent magnet having the same magnetic poles as that of the oppositely arranged, (46a) is a ferromagnetic center pole provided between a pair of cylindrical permanent magnets (45), (46), (47) Is York. This yoke (47) has leaf springs (41), (4
2), the cylindrical coil (44), the coil bobbin (43), the pair of cylindrical permanent magnets (45), (46) and the center pole (46a) are stored and held, and are divided for easy storage and assembly. Part (47a), (47b), (47c). (48a) is a screw hole for attaching and fixing the yoke (47) to the upper drum (3).

Further, (49) is a window provided in a part of the yoke (47). The head (5) projects through the window (49) and is arranged on the upper drum so as to make a sliding contact with the tape (13).
The cylindrical coil (44) and coil bobbin (43)
Are vertically movably arranged in an annular gap formed between the yoke and the pair of cylindrical permanent magnets (45) and (46) and the center pole (46a). Also, leaf springs (41)
Is sandwiched between portions (47a) and (47b) of the yoke (47), and the leaf spring (42) is sandwiched between portions (47b) and (47c).

Next, the operation will be described. Referring to FIG. 5, the magnet (4
In 5), the magnetic flux (D) is radially generated from the center pole (46a) toward the yoke due to the closed magnetic circuit formed by the portions (47a) and (47b) of the yoke (47). Magnets as well (46)
Generates a magnetic flux (E) by forming a closed magnetic path in the opposite direction with the portions (47b) and (47c), and both the magnetic fluxes (D) and (E) cross the annular gap in the same direction. Thus, the combined magnetic flux of the magnets (45) and (46) traverses the cylindrical coil (44). If a current is applied to the coil (44) from the contact (14) through the electrode (15), the connecting portions (12) and (16), the coil (44)
The coil bobbin (43) and the head (5) integrally move vertically in a straight line. Thus, the head (5) is displaced in the tape width direction.

In detail, when an electric current is applied to the coil (44), the force F acting on the coil (44) and the coil bobbin (43) is F = BIl (A) where B: the center pole (46a) and the yoke ( 47) Magnetic flux generated in the gap between: I: Coil current l: Effective length of coil (length of coil wound in gap with magnetic flux of B) (Fleming's left-hand rule) Hooke's law holds between the springs consisting of leaf springs (41) and (42).

F = kx (B) However, k: Composite spring constant consisting of leaf springs (41) and (42) x: Displacement amount of leaf spring Therefore, since both equations (A) and (B) are equal, displacement x X = BIl / k (C) B, l, k has a fixed value. Therefore, depending on I, that is, the current value of the coil, the leaf springs (41), (42), the bobbin (43), and the head ( The amount of displacement of the position of 5) can be controlled.

[Problems to be Solved by the Invention] First, the head drive device has a problem of resonance. If the resonance frequency is However, k: spring constant consisting of leaf springs (41), (42) m: mass consisting of leaf springs (41), (42), coil bobbin (43), coil (44), head (5) This resonance circumferential current drive must be performed in the drive state.

On the other hand, the problem of using this current drive is that the counter electromotive force ee = vBl generated by energizing this coil, where v: the speed at which the coil bobbin (43) moves in the magnetic flux is On the other hand, it works as a power generation brake and gives the first reduction of the resonance level, that is, the damper effect, but in the case of current drive, the output impedance from the circuit side is high, and this counter electromotive force hardly works. For this reason, the resonance level becomes high, and it is very vulnerable to disturbance at the resonance frequency.

The present invention has been made to solve the above problems, and an object thereof is to sufficiently reduce the resonance level of a spring by using a counter electromotive force generated in a coil while using a current driving method. .

[Means for Solving Problems] A magnetic head drive device for a rotary drum device according to the present invention has a coil bobbin (43) around which a first coil (44) is wound.
The second coil (60) is further wound in a plurality of layers on the outer circumference thereof, and the ends of the start and end of the second coil are short-circuited.

[Operation] The second coil (60) in the present invention is the coil (44)
A counter electromotive force e'e '= vBl' is generated with the energization of the coil, and a current I'is generated from this e'in the direction opposite to that of the coil (44). Therefore, F'F '= BI'l' is generated in the direction opposite to the force F generated by the first coil, and the resonance level is sufficiently reduced.

The force F'of the damper can be adjusted depending on l ', that is, the number of turns and the number of layers of the second coil wound around the coil bobbin (43).

[Embodiment] An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, (43) is a coil bobbin, (44) is a conventional coil, and (60) is a second coil wound according to the present invention. The second coil (60) has a winding start portion a shorted to a winding end portion b.

Next, the operation will be described.

When a current I is applied to the coil (44), the coil bobbin (43),
The leaf spring (41) and the head (5) move integrally and the displacement amount x
Becomes If the moving speed at this time is v, the force F acting on the coil (44) is F = BIl, while the counter electromotive force e ′ generated in the coil (60) is e ′ = − vBl ′ = − vB · πrN · n coil ( If the resistance value of 60) is R ′, the current I ′ flowing in (60) is The force F ′ generated by the ∴ coil (60) is Therefore, the amount of the damper F ′ is the number of turns n, the number of winding layers N, and the resistance value R ′.
You can see that you can adjust it freely.

In the present invention, the second coil (60) is wound in order to generate the counter electromotive force, but even if the coil (60) is not used, a cylinder of a non-magnetic metal such as aluminum or copper is used as the first coil (4).
The same effect can be expected by inserting it in the outer circumference of 4).

The coil bobbin (43) is made of a non-magnetic metal cylinder,
The same effect can be expected by winding the first coil (44) around this.

[Effects of the Invention] As described above, according to the present invention, by using a simple measure of winding the second coil (60) around the first coil (44), a large resonance level, which is a problem of current driving, can be reduced. It can be made small enough.

[Brief description of drawings]

FIG. 1 is a sectional view of a head driving device according to an embodiment of the present invention, FIG. 2 is a sectional view showing a main part of a conventional rotary drum device, FIG. 3 is its plan view, and FIG. 4 is FIG. FIG. 5 is a detailed plan view of the head drive section of FIG. 5, FIG. 5 is a sectional view of FIG. 4, and FIG. 6 is a front view of FIG. In the figure, (5) is a magnetic head, (4a) is a drive unit, and (4a)
1) and (42) are leaf springs, (43) is a bobbin, (44) is a cylindrical coil, (45) and (46) are cylindrical permanent magnets, (46a).
Is the center pole and (60) is the second coil. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (5)

[Claims] 1. A permanent magnet, and a yoke that holds the permanent magnet by forming a magnetic gap around the permanent magnet,
In a rotary drum device having a coil arranged in the magnetic gap, a leaf spring held in the yoke for movably carrying the coil, and a magnetic head, a conductive layer is formed on the coil. The rotating drum device is characterized in that the conductor layer constitutes an electric closed circuit. 2. The rotary drum device according to claim 1, wherein the conductor layer is composed of a second coil concentrically arranged with respect to the coil. 3. The rotary drum device according to claim 1, wherein the conductor layer is composed of a cylinder of non-magnetic metal such as aluminum or copper arranged concentrically with the coil. 4. The rotary drum device according to claim 1, wherein the conductor layer is constituted by a bobbin supporting the coil being made of a non-magnetic metal such as aluminum or copper. 5. The rotary drum device according to claim 1, wherein the conductor layer is formed on the inner surface, the outer surface, or both surfaces of the coil.