JPH0682450B2 - 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 trace a magnetic recording trace faithfully.

[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 FIG. 2 and FIG. 3, (4a) is a drive unit for fixing the head (5) to the tip and 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 for adjusting 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). (14)
Is a non-rotating contactor for supplying a control current to the drive section (4a), (15) is a rotating electrode provided on a part of the pedestal (9) so as to make sliding contact with the contactor (14), ( Reference numeral 16) is a connection portion that is electrically connected to the drive portion (4a) from the electrode (15) via the connection portion (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 ball (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. (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 be in sliding contact with the tape (13). The cylindrical coil (4
The coil bobbin (43) and the 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 ball (46a). The leaf spring (41) is sandwiched between the yoke (47) portions (47a) and (47a), and the leaf spring (42) is sandwiched between the 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). Similarly, a magnet (46
In a), portions (47b) and (47c) form a closed magnetic path in the opposite direction to generate magnetic flux (E), and both magnetic fluxes (D) and (E) cross the annular gap in the same direction. Thus, the magnetic flux synthesized by the magnets (45) and (46) crosses the cylindrical coil (44). From the contact (14) to the electrode (1
5) By passing an electric current through the connecting portions (12) and (16), the coil (44), the coil bobbin (43) and the head (5) integrally move in a vertical straight line. Thus, the head (5) is displaced in the tape width direction.

[Problems to be Solved by the Invention] The conventional head driving device has a problem that the linearity of the displacement amount of the magnetic head (5) with respect to the control signal cannot be sufficiently obtained. It is a cylindrical permanent magnet (45), (4
6) Magnetization is uneven and uneven, or bobbin (4
3) The number of turns of the coil (44) per unit length is not uniform, or the core (47b) and center pole (46a)
And due to an error in relative position accuracy when assembling the coil (44).

The present invention has been made to solve the above problems, and the head (5) attached to the coil (44).
The linearity of the head movement amount with respect to the control signal can be increased when driving the
The purpose of the present invention is to obtain a magnetic head drive device that can absorb b) and center pole (46a) mounting errors and is excellent in mounting and assembling.

[Means for Solving the Problems] In the magnetic head drive device according to the present invention, the coil length (a) provided between the core (47b) and the center pole (46a) arranged in a concentric cylinder is centered. The pole and core length (b) should be equal to or longer than the operating range (c + d), or the center pole and core length (b) should be equal to the coil length (a). (C + d)
The length is the same as or longer than the length added with.

[Operation] In the magnetic head drive device according to the present invention, since the amount of the coil that traverses the magnetic flux does not change in the required operating range of the head, the linearity of the moving amount of the head with respect to the control signal is enhanced, and the magnetic head of high accuracy can be obtained. Enables driving.

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

In FIG. 1, (4a) is a magnetic head drive unit, (41),
(42) is a leaf spring arranged in parallel vertically, (44) is a drive coil, (43) is a bobbin around which the coil (44) is wound, (46)
a) is a coil (4) that applies the magnetic field from the permanent magnets (45), (46).
It is a center pole made of a ferromagnetic material for radial penetration to 4) and constitutes a magnetic generator. (29
Reference numerals a) and (29b) denote attachment portions that fix the bobbin (43) and the leaf springs (41) and (42) and move the head (5) while keeping the head parallel.

By the way, here, the axial length of the coil wound around the bobbin is a, the relative operating ranges when the projections of the center pole (46a) and the yoke part (47b) are seen from the coil (44) are c and d, Center pole (46a) or yoke (47b)
When the longer dimension of the protruding portion is b, the dimensions are determined so that the following relationship holds: a ≧ b + (c + d) c + d: coil movement range. Thus, by making the length (a) of the coil longer than the operating range (c + d) of the coil in addition to the length (b) of the center pole (46a) and the yoke portion (46b),
Since the amount of magnetic flux that crosses the coil (44) does not change at any position within the range in which the coil (44) moves, the vertical displacement of the head (5) having high linearity with respect to the control signal sent to the coil (44). The amount is obtained. Further, this makes it possible to increase the loop gain of the control circuit and to bring about the positioning accuracy and sensitive movement of the magnetic head.

Although the leaf spring (41) carrying the magnetic head (5) is attached to the lower side of the coil bobbin (43) in the above embodiment, it is fixed to the upper side of the coil bobbin or a part of the coil winding portion. Good.

In the above embodiment, the coil is longer, but the length (b) of the center pole and the yoke is longer than the length (c + d) of the operating range in addition to the length (a) of the coil. Even if the lengths are the same, a similar effect is produced.

That is, when the axial length (a) of the coil and the length (b) of the yoke portion are substantially equal, when the coil is displaced up and down, the coil on the one hand protrudes from the range of the length (b) of the yoke portion. On the other hand, the length of the yoke portion falls within the range (b), and the amount of magnetic flux traversing the coil changes. By making this like the present invention, it is possible to prevent the amount of magnetic flux traversing the coil from changing even when the coil moves up and down.

[Effects of the Invention] As described above, according to the present invention, since the coil to which the head (5) is attached is made longer or longer than the driving range, the device can be made inexpensive and highly accurate. is there.

[Brief description of drawings]

FIG. 1 is a sectional side view showing 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. 2 is a detailed plan view of the head drive portion of FIG. 2, FIG. 5 is a sectional view of FIG.
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 a center pole, (47a), (47b) and (47c) are yoke portions, and (49) is a window. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (5)

[Claims] 1. A rotary drum device in which a head is moved in the width direction of a tape so that a head locus at the time of recording and a head locus at the time of reproduction coincide with each other even at an arbitrary tape feeding speed, and a permanent magnet, A yoke of a magnetic body which is arranged with a gap around the permanent magnet to form a magnetic path of magnetic force lines from the permanent magnet, and a direction which is arranged so as to cross the magnetic force lines in the gap and is substantially orthogonal to the magnetic force lines. A coil that is movably supported by the head, and the head moves in response to movement of the coil due to energization of the coil. The width of the coil in the moving direction and the operating range of the coil are equal to or more than the length, or the width of the magnetic gap in the moving direction of the coil is equal to or larger than the width of the coil. Rotary drum and wherein the LE of is length and operating range and the length and equal to or greater than the addition. 2. A magnetic pole piece is fixed to the permanent magnet, and a magnetic pole line is arranged around the pole piece with a gap, and magnetic force lines from the permanent magnet pass through the pole piece to a yoke of the magnetic body and a magnetic path. The rotary drum device according to claim 1, further comprising a coil formed and supported so as to be movable in a direction substantially orthogonal to the magnetic force lines. 3. The coil is supported by one or more supports, the head is provided on one of the supports, and the coil is translatable across the magnetic flux. The rotary drum device according to the item. 4. The rotary drum device according to claim 3, wherein the support is formed of a non-magnetic spring. 5. The permanent magnets are arranged such that the same pole faces the pole piece with the pole piece sandwiched therebetween, and each permanent magnet and the yoke form two closed magnetic paths in opposite directions through the pole piece. The rotary drum device according to claim 1, wherein the gap is formed as a magnetic path that the magnetic field lines cross in the same direction.