JP2709195B2 - Rotary drum control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention for example, a video tape record <br/> code Da (hereinafter abbreviated as VTR) applied to, and rotates while contacting moving the tape to a portion of the peripheral surface, the tape Drum control device for recording an image on the tape or reproducing the recorded image from the tape, in particular, a rotary drum control for accurately controlling a drive unit for moving a head housed and arranged in the rotary drum in a tape width direction It concerns the device.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing a main part of a rotary drum device, FIG. 4 is a plan view thereof, and FIG. 5 is an enlarged sectional view of a part of the main part. 3 to 5, the rotation axis (1)
Is mounted with a lower drum (2) via a bearing (6).
An upper drum (3) is attached via a pedestal (9).

A driving unit (4) that enables the head (5) to move in the width direction of the tape (13) includes a cylindrical coil (42).
And a leaf spring (41) as an elastic body for supporting the head (5), and the upper and lower drums (3),
It is housed and arranged in the space between (2).

The upper and lower transformers (7) and (8)
It is housed in a space (50) between the lower drums (3) and (2) and is connected to the head (5). On the upper surface of the upper drum (3), a connecting portion (10), a switchboard (11), and a connecting portion (12) are provided. An electrode (15) that rotates in contact with the fixed contact (14) is provided on the upper surface of the pedestal (9).
The electrode (15) is connected to the coil (42) of the drive section (4) via the switchboard (11) via the connection section (16).

The cylindrical permanent magnet (43) is a circular coil (4).
2) A magnetic reaction is generated to move up and down. The ferromagnetic yoke (44) carries the columnar permanent magnet (43) and is housed in a space 50 between the upper and lower drums (3) and (2) and is screwed to the upper drum (3). (4
It is attached in 9). The ferromagnetic plate (45) is attached to the yoke (44) and forms a magnetically closed circuit together with the columnar permanent magnet (43). This ferromagnetic plate (4
One end of 5) extends in a direction away from the head (5) to form a mounting portion (45a), and the mounting portion (45a) is provided with a leaf spring (41) via a spacer (47) and a washer (48). Are attached with screws (46).

The free end of the leaf spring (41) is movable, and the cylindrical coil (42) carried by the leaf spring (41) has a cylindrical permanent magnet (43) and a ferromagnetic plate (4).
5), that is, it is arranged in the magnetic circuit and can be displaced up and down. Therefore,
By flowing a control current (85) to the cylindrical coil (42) through the contact (14) and the electrode (15), the interaction between the magnetic flux generated in the coil (42) and the magnetic flux of the cylindrical permanent magnet (43). As a result, the coil (42) is vertically displaced.
Accordingly, the leaf spring (41) is deformed, and the head (5) is displaced in the tape width direction. (51) is a head position adjusting hole provided in the upper drum (3).

Next, the operation will be described. For example, when the tape feeding speed is made faster than the normal speed (V1) such as the speed (V2), the control current (85) flowing through the coil (42) is changed, and as shown in FIG.
Is moved from the fixed position in the direction of the arrow (T) (that is, the width direction of the tape), and the trajectory of the head (5) is changed from (5a) to (5b), the tape (13) and the head (5) are changed.
Is (A). This relative locus (A) matches the relative locus at the time of recording. If the corresponding head movement is performed at other tape feed speeds, the relative trajectory at the time of recording can be matched. In FIG. 6,
(V0) is the rotational speed of the head (5), (P)) is the preparative rack <br/> Kupitchi.

FIG. 7 is a control circuit diagram for supplying a control current (85) to the cylindrical coil (42). In FIG. 7, the periodic signal generator (61) is controlled by a switching signal. This switching signal is detected by a magnet (77) attached to the movable part (76) and a rotational position detector (18) to detect the mechanical position of the movable part (76). Switching signal generator (73)
Created by (72) is a head amplifier, (75)
Is a signal processing circuit. The switching signal is also used for switching the circuit of the two heads (5) and (5 ') housed at positions 180 degrees apart from the rotary drum by switching the changeover switch (74). The head (5 ')
Is the same as the circuit configuration of the head (5), the same portions are denoted by the same reference numerals with dashes, and the description thereof will be omitted.

The output of the periodic signal generator (61) is supplied to a drive circuit (200) composed of an operational amplifier (64) and resistors (62) and (63). The output of the driving circuit (200) is supplied to the coil (42) through the contact (14) and the electrode (15), and the magnetic flux generated by the control current (85) flowing through the coil (42) is a cylindrical permanent magnet. A magnetic reaction occurs with the magnetic flux of the magnet (43),
A mechanical displacement is generated in the head (5). The displacement is controlled so that the head trajectory during reproduction matches the trajectory during recording on the magnetic tape. The drive circuit (200) is configured to supply a current with a low output impedance, and is configured to short-circuit mechanical resonance.

[0010] As described above, the driving section (4) includes the coil (4).
2), a leaf spring (41) and a head (59) having a mechanical resonance frequency determined by them. FIG. 8 shows the mechanical resonance of the drive section (4). It is an electric equivalent circuit diagram of the drive unit for explaining the phenomenon, in which (81) is the DC resistance of the coil (42), (82) is the equivalent inductance at the time of mechanical resonance, and (83) is Equivalent resistance at the time of mechanical resonance, (84) is the equivalent capacitance at the time of mechanical resonance, and (85) is the DC resistance (8).
The control current flowing through 1), (86) is the equivalent current flowing through the equivalent inductance (82).

Here, the amount of mechanical displacement is proportional to the equivalent current flowing through the equivalent inductance (82), and when the drive unit (4) is driven with a low impedance and at a cycle related to the drum cycle, the mechanical displacement is reduced. The constant T is: contact resistance value between the contact (14) and the electrode (15) = Rc value of the DC resistance (81) of the coil (42) = Re value of the equivalent inductance (82) at resonance = Lm at resonance Value of equivalent resistance (83) = Rm Value of equivalent capacitance (84) at resonance = Cm Assuming that the attenuation time constant of mechanical resonance = T, the relationship of T = 2 × ((Re + Rc) // Rm) × Cm is obtained. Holds.

[0012]

Since the conventional rotary drum controller is constructed as described above, the decay time constant T of the mechanical resonance depends on the DC resistance Re of the coil (42), the contact resistance between the contact and the electrode. When the DC resistance Re of the coil (42) and the contact resistance Rc between the contacts and the electrodes are large, the braking effect is significantly insufficient.
When the DC resistance value Re of the coil changes due to heat generation of the coil or the contact resistance value Rc between the contactor and the electrode changes, the control current 85 does not reach a desired value. , Accurate tracking becomes impossible. For this reason, there is a problem that noise is generated and good reproduction image quality cannot be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems. Even when the DC resistance of the coil is large or the contact resistance between the contacts and the electrodes is large, the mechanical resonance is prevented. To obtain good reproduction quality without noise by performing accurate tracking even if the coil resistance value or the contact resistance value between the contact and the electrode changes. It is an object of the present invention to obtain a rotating drum control device capable of performing the following.

[0014]

SUMMARY OF THE INVENTION The rotary drum controller according to the present invention and current drive at least a driving fundamental frequency, and at least in the mechanical resonance frequency and the negative resistance driving, and when the current drive The configuration is such that a gain is substantially matched with respect to a resistance load at the time of negative resistance driving, and a driving circuit for driving the driving unit is provided.

[0015]

[Action] drive circuit in the present invention, current-driven at least driving fundamental frequency and at least the mechanical resonance <br/> frequency and negative resistance drive, when the current drive and when negative resistance driving By matching the gains with respect to the resistance load of the coil, a desired control current can be supplied even if the resistance value of the coil, the contact resistance between the contact and the electrode changes, and the resistance of the coil, the contact and the electrode Even when the contact resistance between them is large, not only a sufficient braking effect can be obtained, but also a control current with good linearity can be supplied. Therefore, accurate tracking can be obtained, and good reproduction image quality without noise can be obtained.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a control circuit diagram for supplying a control current (85) to the coil (42), and is different from the control circuit of the conventional device shown in FIG. 7 only in the configuration of the drive circuit (200). Are the same, and redundant description will be omitted.

The driving circuit (200) includes an operational amplifier (9)
4), (99), resistors (91), (92), (93),
(95), (96), (98), condenser (97),
The differential amplifier (100) includes a differential amplifier (100) and detects a voltage (that is, a control current) across the resistor (93). It has two feedback loops.

[0018] The current feedback loop and the voltage feedback loop, such that the current feedback loop is dominant at least driving fundamental frequency, also, at least the mechanical resonance frequency
So that the voltage feedback loop becomes dominant, the resistance (9
6), the value of the capacitor (97) is set.

[0019] Therefore, the output impedance of the driver circuit (200) (201) is very large at least in driving fundamental frequency (current drive), at least the mechanical resonance frequency
The resistance (91), (92), when each R1, R2, R3 the resistance value of (93), the output impedance Ro = - (R1 × R3) / R2 become (negative value) (negative resistance Drive).

When the gain for current driving and the gain for resistive load during negative resistance driving are different, the periodic signal output from the periodic signal generator (61) shown in FIG. The linearity cannot be maintained as shown by the dotted line in FIG.
Therefore, in order to make the gains for the resistive load in the current driving and the negative resistance driving substantially the same, the resistors (81) and (9) are used.
6) and (98) are set to R4, R5, R6,
Assuming that the gain of the differential amplifier (100) is Av, Av =
(R2 × R4-R1 × R3) / R3 (however, R5 >> R
6).

[0021] Thus, at least the drive fundamental frequency is
The DC resistance (8) of the coil (42) in the driving section (4)
A desired control current (85) can be supplied irrespective of the change in the resistance value Re of 1) or the change in the resistance value Rc of the contact resistance (203) between the electrode and the contact. Also, T = 2 × ((Re + R
c + Ro) since it is // Rm) × Ro <0 from the relationship of Cm, it is possible to reduce the mechanical damping time constant T, at least, and the resistance value Re of the coil (42) is a mechanical resonance frequency, Even if the resistance value Rc of the contact between the electrode and the contact is large, a sufficient braking effect can be obtained.

Further, by making the gains for the resistive load in the current driving and the negative resistance driving substantially the same, a control current with good linearity can be supplied to the coil (42). As a result, accurate tracking can be realized, and good reproduction image quality without noise can be obtained.

[0023]

As is evident from the foregoing description, according to the present invention, and the current driving at least the driving fundamental frequency, and since at least the mechanical resonance frequency was negative resistance driving, driving fundamental frequency changes in the resistance value due to the heat generation of the coil, the electrode can be supplied a desired control current regardless of the change in the contact resistance between the contacts and the resistance value and contact of the coil with the mechanical resonance frequency Even if the contact resistance between the electrodes is large, a sufficient braking effect can be obtained. Furthermore, since the gains during current drive and during negative constant drive are configured to be substantially the same, good linearity can be obtained. As a result, accurate tracking can be realized, and a good reproduced image without noise can be obtained.

[Brief description of the drawings]

FIG. 1 is a control circuit diagram of the device of the present invention.

FIG. 2 is an explanatory diagram illustrating linearity of a control current.

FIG. 3 is a cross-sectional view of a main part of a rotary drum device in which a head that can be displaced in a tape width direction is housed and arranged.

FIG. 4 is a plan view of FIG. 3;

FIG. 5 is an enlarged sectional view of a part of FIG. 3;

FIG. 6 is an explanatory diagram illustrating a relationship between a trajectory at the time of recording and a trajectory at the time of reproduction of the head.

FIG. 7 is a control circuit diagram in a conventional device.

FIG. 8 is an electrical equivalent circuit diagram of a driving unit.

[Explanation of symbols]

 DESCRIPTION OF REFERENCE NUMERALS 1 rotating shaft 4 drive unit 5 head 13 tape 42 coil 200 drive circuit

Claims (1)

(57) [Claims] 1. A control device for a rotary drum which moves a head in a width direction of a tape so that a head trajectory at the time of recording matches even under an arbitrary tape feed speed. a driving unit for moving the head by supplying a predetermined control current to have a driver circuit for controlling the supply of the control current to the driving unit, the driving circuit, at least in driving fundamental frequency current drive and and and wherein at least in the mechanical resonance frequency as well as negative resistance driving, it drives the driving unit gain for the resistive load during the negative resistance driving and when the current drive to match so Rotating drum control device.