JPH02192009A - Rotary drum controller - Google Patents

Abstract

PURPOSE:To control the vibration of a head against the sharp displacement of the head and to correctly trace a recording locus by controlling the switching of the transmission characteristic of a control circuit to make the head locus at the time of recording correspond to the head locus at the time of reproducing at a cycle related to a head switching signal. CONSTITUTION:By controlling a head 5 so as to be displaced in the width direction of a tape 13, the head 5 can be always correctly traced along the recording locus at an arbitrary tape 13 sending speed, and a regenerative signal at a prescribed level can be obtained regardless of the tape 13 sending speed. Further by controlling the switching of the transmission characteristic of the control circuit at the period related to the switching of the head 5, the vibration after the sharp head displacement such as the flyback or jump of the head 5 can be suppressed. Consequently prescribed tracking can be always stably executed, and the excellent reproduction without a noise nor picture blurring can be realized.

Description

[Detailed Description of the Invention] - [Field of Tabletop Application] This invention is applicable to, for example, a video tape recorder (hereinafter referred to as
It is applied to improve the playback quality of a VTR (VTR), and allows the head installed on a rotating drum to be moved in the width direction of the magnetic tape, so that the trajectory of the head during playback is faithful to the trajectory during recording. The present invention relates to a rotating drum control device configured to perform tracing.

[Prior Art] Fig. 7 is a vertical cross-sectional view of a rotating drum in a conventional rotating drum control device, in which (1) is a rotating shaft;
2) is a fixed lower drum, (3) is a rotating upper drum, (
4) is a head stand that is removably screwed to the upper drum (3), (5) is a head fixed to the tip of the head stand (4), and (6) is a head that is attached to the lower drum (2). Axis of rotation(
1) is a bearing that freely rotates, (7) is an upper transformer that rotates together with the upper drum (3), (8)
is a fixed lower transformer, (9) is a pedestal supported by the rotating shaft (1) and supports the above-mentioned upper drum (3), and (13) is a magnetic tape.

A more detailed explanation of the configuration of each of the above parts is as follows.

The head (5) is fixedly held at a fixed position with respect to the upper drum (3), and its tip is slightly protruding from the outer periphery of the upper drum (3), and the connecting portion (lO) and the wiring board (1
1), it is electrically connected to the upper transformer (7) via the connection part (12). The upper drum (3) is driven to rotate at a constant high speed, and the magnetic tape (13) is wound slightly diagonally around the outer peripheral surfaces of the upper drum (3) and the lower drum (2) and runs at a predetermined speed. . The head (5) contacts the magnetic tape (13) to magnetically record or reproduce video and audio signals.

The upper transformer (7) is attached to the pedestal (9) and rotates together with the pedestal (9). The lower transformer (8) faces the upper transformer (7) with a small interval therebetween, whereby the upper and lower transformers (7) and (8) are magnetically coupled to mutually transmit signals. The lower transformer (8) is connected to an externally provided control circuit which will be described later.

Also, in Fig. 7, (75) is a magnet attached to the upper drum (3), and (18) is the rotational position at which the rotational position of the upper drum (3) is detected by sensing the lines of magnetic force of this magnet (75). It is a detector.

Next, the operation of the above configuration will be explained.

By running the magnetic tape (13) and rotating the head (5), the head (5) diagonally crosses the magnetic tape (13).

These transverse lines are parallel to each other, as shown in FIG. In Fig. 8, (13a) is the trajectory of the magnetic tape (13), (vl) is the normal feeding speed of the magnetic tape (13), (5A) is the trajectory of the head (5), (VO)
is the rotational speed of the head (5) and the magnetic tape (13)
The trajectory (13a) of the head (5) intersects with the trajectory (5A) of the head (5) as shown.

Therefore, the relative locus drawn on the magnetic tape (13) by the head (5), that is, the above-mentioned transverse line is as shown in FIG.
), the interval (P) is the track pitch. By the way, when the feed speed of the magnetic tape (13) changes from (Vl) to (Vl), for example during slow playback,
VS), the relative trajectory of the head (5) with respect to the magnetic tape (13) becomes (B) as shown in FIG. 8(b).
) becomes.

In this way, when the magnetic tape (13) is played back at a different speed from the normal feed speed (vl), for example, in static playback, slow playback, high-speed search playback, etc.
The head (5) may come off without accurately tracing the recording trajectory, resulting in a low signal level picked up by the head (5), making it difficult to obtain clear playback images and playback audio, and causing noise and blurring. .

To solve this problem, the normal feed rate (V
Displace the head (5) in the tape width direction in response to changes in the magnetic tape feed speed during playback with respect to the recording trace on the magnetic tape recorded in step 1), that is, the relative trajectory 111i (A). Accordingly, the present applicant has previously proposed a rotating drum control device that allows the head (5) to accurately trace the relative trajectory (A).

In the rotating drum control device proposed earlier, the head (5
) is configured such that a control current to a control circuit for controlling the trajectory of the head (5) is supplied based on a periodic waveform signal generated to give a predetermined displacement to the head (5).

[Problems to be Solved by the Invention] According to the conventional rotating drum control device configured as described above, since the periodic waveform signal and the control current have linearity, it is possible to prevent head flyback, jump, etc. When the periodic waveform changes rapidly, the control current also changes rapidly, resulting in sudden displacement of the head. Therefore, due to the large inertia of the head and the parts that cooperate with this head,
There is a problem in that the head vibrates even after a predetermined displacement, and as a result, the head no longer accurately traces the recording locus, causing noise.

This invention was made to solve the above-mentioned problems, and provides a rotating drum control device that can control the vibration of the head and accurately trace the recording trajectory even when the head is suddenly displaced. The purpose is to

[Means for Solving the Problems] A rotating drum control device according to the present invention switches the transfer characteristic of a control circuit for matching the head trajectory during recording and the head trajectory during playback at a cycle related to a head switching signal. It is characterized by being configured to control.

[Function] According to the present invention, in the field where the head is in contact with the tape, by ensuring the linearity of the head switching cycle signal and the control current to the control circuit, the displacement of the head in the tape width direction is It is possible to match the head trajectory during playback with the recording trajectory.

In addition, during flybacks in which the head changes rapidly from the end of the tape track to the beginning, and jumps in which the head changes rapidly over multiple track pitches, the transfer characteristics of the control circuit can be switched to have high-frequency cut-off characteristics. By making the displacement of the head gentle and controlling the vibration of the head after the displacement, it is possible to perform stable tracking of the recording locus.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a longitudinal sectional view showing the main parts of a rotating drum in a rotating drum control device according to an embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a longitudinal sectional view showing the main parts in more detail. Figure 4 is a bottom view of Figure 3, and in each of these figures, (1) to (3) and (5) to (13) have the same configuration as the conventional device shown in Figure 7. , are given the same reference numerals.

In FIGS. 1 and 2, (4a) is a drive unit that supports the head (5) and displaces the head (5) in the width direction of the tape, and (14) is a drive unit that applies a control current to the drive unit (4a). A non-rotating contactor (15) for supplying the contactor (14)
) is provided on a part of the pedestal (9) so as to be in sliding contact with the rotating electrode (16), which connects the electrode (15) to the wiring board (11).
This is a connection part that is electrically connected to the drive part (4a) via.

In the main parts shown in Figures 3 and 4, (41) is a non-magnetic leaf spring with a head (5) attached to its tip;
) is a cylindrical coil attached to a leaf spring (41), (
43) is a cylindrical permanent magnet that generates a magnetic reaction to move the cylindrical coil (42) up and down, (44)
(45) is a ferromagnetic yoke that carries a cylindrical permanent magnet (43) and is attached to the upper drum (3).
) is a ferromagnetic plate that is attached to a cylindrical permanent magnet (43) to form a magnetic closed circuit. This ferromagnetic plate (45) extends in a direction away from the head (5), and forms a mounting portion (45a) in its extension. (
46) is a screw for attaching the leaf spring (41) to the mounting part (45a), (47) is a spacer, (48) is a washer, (
49) is a screw for attaching the yoke (44) to the upper drum (3), and (50) is a recess formed in the rotating upper drum (3) to accommodate the drive part (4a).

The free end of the leaf spring (41) is movable up and down, and the cylindrical coil (42) supported by the leaf spring (41) has a cylindrical permanent magnet (43) and a ferromagnetic plate (45). It is disposed in an annular gap formed between the cylindrical coils (42) and is movable up and down, and by passing a control current through the cylindrical coil (42), an appropriate magnetic flux is generated in the coil (42), and the permanent magnet (43) ) displaces the coil (42) up and down. As the coil (42) moves up and down, the leaf spring (41) deforms, allowing the head (5) to move in the width direction of the tape.

There is a centering round hole (52) approximately in the center of the leaf spring (41).
is formed, and a cylindrical jig (53) is inserted into this round hole (52).
The cylindrical coil (42) is centered in the annular gap formed between the cylindrical permanent magnet (43) and the ferromagnetic plate (45) by inserting and aligning it with the cylindrical permanent magnet (43). and positioning. In this state, the drive part (4a) is assembled as a unit by tightening the screw (46).

The drive section assembled as a unit in this way (4a
) is mounted in the recess (50) of the upper drum (3) with screws (49). At this time, the amount and attitude of the head (5) that protrudes from the outer peripheral surface of the upper drum (3) must be adjusted correctly. For this purpose, three head position adjustment holes (51a) and (51b) are provided in the upper drum (3).

(51c) is provided. These three holes (51a),
(51b).

The four points including (51c) and the head (5) are arranged in a cross shape. Distance (i
) and the drive unit mounting hole (49a
) is formed, and a screw (49) is passed through this hole (49a) to attach the yoke (44) to the upper drum (3) in a predetermined state. After that, head position adjustment holes (51a) to (5)
Insert a wedge for position adjustment into hole (51a) and (5).
1b) generates a rotational force to adjust the posture, and the hole (51c)
) to adjust the emptying amount of the head (5). This makes the position of the drive part (4a) with respect to the upper drum (3) accurate. If necessary, tighten the screw (49) in this state.
Tighten further.

As described above, in the high magnetic flux magnetic closed circuit consisting of the permanent magnet (43), yoke (44), and ferromagnetic plate (45), the gap between the permanent magnet (43) and the ferromagnetic plate (45) A cylindrical coil (42) located within the annular gap exerts a magnetic force on the permanent magnet (43) by means of its control current, displacing the leaf spring (41). At this time, in order to prevent magnetic flux leakage toward the head (5), a ferromagnetic plate (
The attachment part (45a) which is an extension of the head (5)
placed far away from.

Next, the operation of the above configuration will be explained.

For example, if the tape feed speed (VS) is different from the normal feed speed (v
l) When the magnetic head (5) is moved slower than the fixed position, the magnetic head (5) is displaced from the fixed position in the direction of the arrow (T), that is, in the width direction of the tape, and the trajectory of the head (5) is changed from (5A) to (5B).
By changing to , the relative trajectory between the tape and the head becomes (C) as shown in FIG. 6(C), and this relative trajectory (C) matches the relative trajectory (A). Even at other tape feeding speeds, the relative trajectory (A) can be similarly achieved by moving the head correspondingly.

FIG. 5 is a control circuit diagram of the rotating drum control device having the above configuration, and in the same figure, the head (5) is
', (5b), and accordingly, all the components of each part are given subordinate symbols (a) and (b).

In FIG. 5, (61a) and (elb) are periodic signal generators controlled by switching signals. The switching signal is generated by detecting the mechanical position of the movable part (74) using a magnet (75) attached to the movable part (74) and a position detection head (76).
) created by

The outputs of the periodic signal generators (81a) and (61b) are connected to low-pass filters (63a) and (63b) and a switch (64a).

(6'4b) a transfer characteristic switch (62a),
(62b), differential amplifier (85a), (65b)
It is supplied to a drive circuit consisting of. The output of this drive circuit, that is, the control current is transmitted to each control side contactor (14-1
), (14-3), electrode (15-1), (t5-
3) to the coils (42a) and (42b). The non-control side terminals of the individual coils (42a) and (42b) are made common, and the common side electrode (
15-2) and a reference potential via a common side contact (14-2). The control current is connected to the individual coils (42
The magnetic field generated by being supplied to a) and (42b) generates a magnetic reaction with the cylindrical permanent magnet (43), causing mechanical displacement in the individual heads (5a) and (5b). The amount of displacement is controlled such that the head trajectory during reproduction matches the recording trajectory on the magnetic tape. In addition, the control current is applied to the head (5a), (5
Even when the coil (42a) is not in contact with the magnetic tape, the coil (42a
).

(42b). individual head (5a),
The signal reproduced by (5b) is transferred to the upper transformer (7a)
, (7b), and lower transformers (8a) and (8b), the movable part (74) is supplied to the head amplifiers (72a) and -(72b), and the output is switched by the switch (73) which is switched by the switching signal. ) and then output as a reproduced video signal via a signal processor (78).

Next, the transfer characteristic switching device (62a), (62b
) will be explained using slow playback as an example.

In a rotating drum control device where the head is controlled so that the head trajectory during recording and the head trajectory during playback match even under any tape feed speed, when slow playback is performed, the same track is repeatedly trained multiple times. □-Zing is performed. When scanning the same track, it is necessary to rapidly change the head from the end to the start point each time one trace is completed, that is, flyback is required.

Furthermore, each time the track being scanned changes, the head must be abruptly changed by a maximum of two track pitches, that is, it is necessary to jump.

When the head flies back or jumps as described above, the vibrations do not converge even if the head completes the flyback or jump and starts tracing. As a result, the reproduction envelope vibrates as shown by the solid line in FIG. 6(d).

Here, the control current is as shown by the solid line in FIG. 6(c).

The control circuit of this embodiment is intended to solve this problem, and uses a transfer characteristic switch (62a) to change the transfer characteristic between the periodic signal generators (61a), (61b) and the amplifiers (65a), (65b). , (62b).

That is, these transfer characteristic switchers (62a), (62
In order for b) to exhibit high-frequency cut-off performance in fields where the head performs flybacks or jumps, and in fields where the head traces the tape,
In order to ensure linearity between the periodic signal and the control current shown in FIG. 6(b), no frequency characteristics are provided.

As a result, the control current becomes as shown by the dotted line in Figure 6 (c), and in fields where the head does not trace the tape, such as for fly batters, the displacement of the head necessary for flybacks and jumps is ensured within that field. At the same time, the change is gradual and no vibration is generated at the start of tracing. In the field where the head traces the tape, the linearity of the periodic signal shown in Figure 6(b) and the control current shown by the solid line in Figure 6(c), that is, the linearity of the head displacement, is ensured. can. Therefore, Fig. 6 (d
), the playback envelope does not vibrate and tracking is stabilized, making it possible to obtain a stable playback image.

In addition, in the above embodiment, a cantilever beam type was used for the leaf spring (41), but a double-sided beam, a torsion spring, or a parallel spring may be used.

Also, extend the ferromagnetic plate (45) and attach it to the mounting part (45a).
However, the mounting part (
You can extend the connection as a yoke (45a) or use a yoke (44
) may be extended.

Moreover, although the yoke (44) is used in the above embodiment to attach the drive part (4a), it may be fixed to the upper drum (3) using a ferromagnetic plate (45). At that time, the ferromagnetic plate (
45) with a non-ferromagnetic extension connected thereto may also be used.

Further, although the electrode (15) is shown as being integrated with the pedestal (9), it does not have to be integrated.

In addition, head position adjustment holes (51a) and (51b)
, (51c) are three arranged in a cross shape including the head, but more can be used, and the screw (49) is connected to the rotation axis (1
), but it may be on the contrary closer to the head (5).

In Figures 1 to 4, only one head (5) is shown on the upper drum (3) in order to simplify the explanation; One magnetic head device is attached, and two of the four connectors each pass a control current to a cylindrical coil (42) of the drive section of the respective magnetic head device.

Also, although I have not mentioned the gear angle of the head (5), that is, the azimuth angle, in the VH3 system, a pair of heads are tilted in opposite directions, making it difficult for other heads to reproduce their own recorded traces. In this case, as shown in FIG. 6(b), since the signal level decreases for each recorded trace, the effect of displacing the head in the width direction of the tape is even greater.

[Effects of the Invention] As described above, according to the present invention, by controlling the head to be displaced in the width direction of the tape, the head can be accurately moved along the recording trajectory even at any tape feed speed. It is possible to obtain a reproduction signal of a predetermined level regardless of the tape feed speed.

Moreover, by switching and controlling the transfer characteristics of the control circuit at a cycle related to head switching, it is possible to suppress vibrations after rapid head displacement such as flyback or jump of the head. Therefore, it is possible to always perform predetermined tracking stably and to realize good playback without noise or screen blur.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing the main parts of a rotating drum in a rotating drum control device according to an embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a longitudinal sectional view showing the main parts in more detail. Fig. 4 is a bottom view of Fig. 3, Fig. 5 is a control circuit diagram of the rotating drum control device, Fig. 6 is a waveform diagram of each part, and Fig. 7 is a bottom view of Fig. 3.
This figure is a vertical cross-sectional view showing the main parts of a rotating drum in a conventional rotating drum control device, and FIG. 8 is a diagram for explaining the relative trajectory between a tape and a head in a VTR. (2), (3)...Upper and lower drums, (4a)...
Drive unit, (5). (5a), (5b)...Head, (7), (8) ・
・Upper and lower transformer, (13) ・Tape, (14)
, (14-1) , (14-2) , (14-3
)...contact, (15), (ts-t), (
15-2), (15-3)...electrode, (61a)
, (81b)---periodic signal generator, (52a)
, (62b)...'Transfer characteristic switch. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A drive unit consisting of a coil installed in a magnetic circuit and a head that can be displaced in the width direction of the tape in cooperation with the coil, a contact that supplies a control current to the drive unit, and the contact an electrode that contacts the coil and is electrically connected to the coil; an upper transformer to which the head is electrically connected; a lower transformer that faces the upper transformer and is magnetically coupled; In a rotating drum control device that includes a transformer and a rotating drum that accommodates the above-mentioned drive unit, the transmission characteristic of a control circuit for matching the head trajectory during recording and the head trajectory during playback is determined by the cycle related to the head switching signal. 1. A rotating drum control device comprising a transmission characteristic switch that performs switching control.