JP3013976B2 - How to fast forward or rewind magnetic tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape device (for example, a video cassette recorder, a video cassette player, a DAT, etc.) for controlling a rotational speed of a drive motor for rotating a take-up reel of a magnetic tape to a target value. More specifically, when the winding is near the end, the target value is continuously changed from a value corresponding to the high-speed winding to a value corresponding to the low-speed winding according to a predetermined characteristic, and the fast-forwarding of the magnetic tape. Or, it relates to a rewinding method.

[0002]

2. Description of the Related Art In a magnetic tape device such as a video cassette recorder using a video tape which is a magnetic tape as a recording or reproducing medium, the time required for fast-forwarding and rewinding is reduced, and the fast-forwarding and rewinding may cause damage to the video tape. A control method has been adopted to prevent the cause of the problem.
That is, when the remaining amount of the video tape on the supply reel is large, the winding is performed at a high speed to shorten the time required for the winding. When the remaining amount of the video tape on the supply reel becomes small, the winding speed is changed from high speed to low speed, and when the end of the video tape is detected in the low speed winding state, the winding is stopped. Also, when changing the winding speed from high speed to low speed, if the winding speed is suddenly reduced, the wound video tape will be slackened, so the winding speed is controlled to be gradually reduced. .

[0003]

However, in the prior art, the target value of drive motor control in fast-forward or rewind is defined as an integral multiple of the reference value with respect to the control target value of the drive motor during normal reproduction. Is treated as a value.
Therefore, even when the control target value is gradually changed to a smaller value in order to gradually reduce the winding speed, as shown by reference numeral 91 in FIG. It is given as a continuously decreasing value. As a result, the rotation speed of the drive motor decreases while waving as shown by the curve 92. Therefore, 93
As shown in (1), the tension of the winding also undulates, causing a problem that the wound video tape becomes slack.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. It is an object of the present invention to set a target value for controlling the drive motor from a value corresponding to high-speed winding when winding is nearing completion. By continuously changing the value to a value corresponding to low-speed winding in accordance with predetermined characteristics, a magnetic tape capable of winding a magnetic tape such as a video tape without causing slack even when the winding speed is reduced. It is to provide a method for fast-forwarding or rewinding a tape.

[0005]

According to the present invention, there is provided a method for fast-forwarding or rewinding a magnetic tape, comprising the steps of:
A magnetic tape that controls the rotational speed of the drive motor to match the target value by driving the drive motor based on the difference between the rotational speed of the drive motor that rotates the take-up reel of the magnetic tape and the target value. Applied to the apparatus, in a state where the remaining amount of the magnetic tape on the supply reel is small, when the tensile force of the magnetic tape is set to 0 during high-speed winding in fast-forward or rewind, the magnetic tape supplied from the supply reel is When the deceleration characteristic having a lower degree of deceleration than the deceleration characteristic is set as the target deceleration characteristic, and when the remaining amount of the magnetic tape on the supply reel is larger than a predetermined remaining amount, which is a preset remaining amount, the target value is set to the high speed. Set to a value corresponding to the winding, when the remaining amount of the magnetic tape of the supply reel is less than the specified remaining amount, the target value, From a value corresponding to a serial high-speed winding to a value corresponding to the low-speed winding, and a method of varying in accordance with said target deceleration characteristic.

[0006]

When the tension of the magnetic tape is set to 0 at the time of high-speed winding in fast-forward or rewind with the remaining amount of magnetic tape on the supply reel being small, the supply speed of the magnetic tape supplied from the supply reel is The tape is decelerated according to the deceleration characteristics determined by the influence of the inertia and the frictional force on the tape supply side. If this deceleration characteristic is referred to as a tape deceleration characteristic, when the winding speed is reduced according to the tape deceleration characteristic, the magnetic tape wound on the take-up reel is wound with a tension of substantially zero. .
For this reason, when the winding speed is reduced according to the target deceleration characteristic in which the degree of deceleration is smaller than the tape deceleration characteristic, the magnetic tape to be wound has both the degree of deceleration of the tape deceleration characteristic and the degree of deceleration of the target deceleration characteristic. Winding is performed with a tension determined by the difference in the degree of deceleration. The value of the tension at this time is a substantially constant value.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an electrical configuration of an apparatus to which an embodiment of a video tape fast-forward or rewind method according to the present invention is applied.

This apparatus is, in detail, a video cassette recorder, and has one drive motor 1 for running a video tape. Then, at the time of recording or reproduction, the drive motor 1 drives the capstan and the take-up reel. When fast-forwarding or rewinding,
The drive motor 1 drives the take-up reel. The frequency generator 2 is a block for converting the rotation speed of the drive motor 1 into an electric signal, and generates a signal having a cycle equal to the rotation cycle of the drive motor 1. Then, the generated signal is sent to the cycle detector 3.

The cycle detector 3 is a block for detecting the rotation speed of the drive motor 1 by detecting the cycle of the signal sent from the frequency generator 2, and subtracting the detected rotation speed from the subtractor. 6 to the plus input. The target value generator 4 is a block that generates a target value of the rotation speed of the drive motor 1. That is, a target value of the rotation speed required for the drive motor 1 at the time of recording or reproduction, or a target value of the rotation speed required for the drive motor 1 at the time of fast forward or rewind is generated. Then, the generated target value is sent to the plus input of the subtraction unit 5.

The deceleration control unit 7 is a block for performing control for reducing the video tape take-up speed in a fast-forward operation or a rewind operation. Alternatively, at the time of recording or playback, the value 0 is simply generated and output. However, when the remaining amount of the video tape wound on the supply reel becomes smaller than a preset value (specified remaining amount), the generated value is changed in order to reduce the winding speed. That is, when the output 11 generated based on the ratio of the rotation speeds of the supply reel and the take-up reel indicates that the remaining amount of the video tape on the supply reel is smaller than the specified remaining amount, the value 0 is set to the start value. As a result, a value that continuously increases in accordance with a predetermined characteristic (described in detail later) is generated, and the generated value is sent to the minus input of the subtraction unit 5.

The subtraction unit 5 is a block for subtracting the value sent by the deceleration control unit 7 from the value sent by the target value generation unit 4 and sending the subtraction result to the minus input of the subtraction unit 6. Reference numeral 6 denotes a block for subtracting the value output by the subtraction unit 5 from the rotation speed detected by the cycle detection unit 3 and sending the subtraction result to the multiplication unit 8. The multiplication unit 8
The block is a block for multiplying the subtraction result of the subtraction unit 6 by an integer according to the mode output 12 indicating the operation mode. When the mode output 12 instructs, for example, double speed reproduction, the output of the subtraction unit 6 is set to a value. Multiply by 2, and multiply the result by PWM
9

The PWM 9 performs a pulse width modulation that repeats ON and OFF at a ratio corresponding to the value sent from the multiplier 8 to convert the digital value output from the multiplier 8 into an analog value with high precision. It is a block to be converted to. Then, the converted analog value is sent to the drive circuit 10. The drive circuit 10 is a power amplifier that drives the drive motor 1 with an output corresponding to the analog value sent from the PWM 9.

As described above, the drive motor 1 includes the frequency generator 2, the cycle detector 3, the subtractor 6,
The servo control is performed by a loop including the multiplying unit 8, the PWM 9, and the driving circuit 10. Therefore, the rotation speed of the drive motor 1 is controlled so as to match the target value given to the minus input of the subtraction unit 6. That is, when the output value of the deceleration control unit 7 is 0, the rotation speed of the drive motor 1 is controlled to match the target value generated by the target value generation unit 4. When the deceleration control unit 7 sends a value other than 0, the rotation speed of the drive motor 1 matches the result obtained by subtracting the value sent by the deceleration control unit 7 from the target value sent by the target value generation unit 4. Is controlled as follows.

Hereinafter, the deceleration control unit 7 will be described with reference to FIG.
The characteristic of the change of the value sent from the STA will be described.

In FIG. 1, a speed S1 indicates a winding speed of a high-speed winding in fast-forward or rewind, and a speed S2 indicates a winding speed of a low-speed winding in the fast-forward or rewind. In a high-speed winding operation such as fast-forward or rewind, if the pulling force for winding the video tape is set to 0 by stopping the winding or the like, the speed of the supplied video tape is reduced by the inertia and frictional force on the supply side. The deceleration is started with the characteristic determined by the relationship with the above, and the speed eventually becomes zero. The deceleration characteristics at this time show different values depending on the remaining amount of the video tape wound on the supply reel.

The deceleration characteristic indicated by a broken line 31 shown in FIG. 2 is that when the video tape is wound on the supply reel at a high speed and the remaining amount of the video tape is small, when the pulling force for winding the video tape is set to zero, The graph shows a characteristic obtained by linearly approximating the characteristic that the running speed of the tape decreases. If this characteristic is referred to as a tape deceleration characteristic, when the winding speed is decelerated in accordance with the tape deceleration characteristic, it means that the tension of the video tape during winding becomes a value near zero. For this reason, when the winding deceleration characteristic is decelerated in accordance with a characteristic in which the degree of deceleration is smaller than that of the tape deceleration characteristic, the tension of the video tape in winding becomes a value corresponding to the degree of the deceleration.

A straight line 32 in FIG. 1 shows a linearly changing deceleration characteristic, and shows a deceleration characteristic in which the degree of deceleration is smaller than that of the tape deceleration characteristic. When this deceleration characteristic is referred to as a target deceleration characteristic, when the winding speed is reduced according to the target deceleration characteristic, it means that a substantially constant tension is secured during winding even when the winding speed is reduced. Therefore, when an instruction to reduce the winding speed is given, the deceleration control unit 7 generates a value that increases with a characteristic corresponding to the slope of the straight line 32 and sends it to the subtraction unit 5.

This will be described in detail with reference to FIG. 2. A broken line 33 indicates a change characteristic of a target value corresponding to the tape deceleration characteristic indicated by the broken line 31. Now
It is assumed that the inclination is indicated by -A. A straight line 34 indicates a change characteristic of the target value corresponding to the target deceleration characteristic indicated by the straight line 32. It is assumed that the inclination is indicated by-(Ad). That is, the degree of deceleration of the target deceleration characteristic is smaller than that of the tape deceleration characteristic by the value d. For this reason, the deceleration control unit 7 increases the slope at (Ad) during deceleration so that the target value given to the minus input of the subtraction unit 6 has a slope of-(Ad). Send the value to be sent.

An embodiment of the present invention executed in the apparatus having the above configuration will be described below.

When the mode output 12 indicates fast-forward or rewind, the multiplying unit 8 calculates
The multiplication result is multiplied by an integer value corresponding to the instruction of the mode output 12, and the multiplication result is sent to the PWM 9. Therefore, the loop gain of the servo control of the drive motor 1 is set to an optimum value corresponding to the fast-forward or rewind rotation speed. Also, a target value generation unit 4
Generates a target value (indicated by V1 in FIG. 2) of the rotation speed of the drive motor 1 at the time of high-speed winding, and sends it to the subtraction unit 5. Further, the deceleration control unit 7 generates a value 0 and sends it to the subtraction unit 5. Therefore, a value V1 equal to the target value generated by the target value generation unit 4 is given to the minus input of the subtraction unit 6. As a result, the rotation speed of the drive motor 1 becomes the target value V1
The video tape is controlled to rotate at a rotation speed equal to the speed of the video tape, and the video tape is wound at a high speed (the winding speed at this time is shown as a speed S1 in FIG. 2).

When the remaining amount of the video tape wound on the supply reel becomes smaller than the specified remaining amount (time T1),
The output 11 gives an instruction to start deceleration to the deceleration control unit 7.
Therefore, the deceleration control unit 7 temporarily increases the value starting from the value 0. As a result, assuming that the output value of the subtraction unit 5 indicates the elapsed period from the time T1 by t,

## EQU1 ## The value is determined as V1- (Ad) × t, and the value decreases along the straight line 34. For this reason, the drive motor 1 is controlled so that the rotation speed decreases as the value output by the subtraction unit 5 decreases. Therefore, the winding speed of the video tape is reduced along the straight line 32, that is, along the target deceleration characteristic.

The deceleration control unit 7 generates a target value V2 for low-speed winding and a target value V1 for high-speed winding.
When the value becomes equal to the difference (time T2), the value is stopped from increasing, and the value is maintained at a constant value. Therefore, the output of the subtraction unit 5 is maintained at the value V2 after the time T2. As a result, the video tape winding speed is maintained at this speed S2 after the speed becomes S2.
That is, low-speed winding is performed. When the end of the video tape supplied from the supply reel is detected in the low-speed winding, the rotation of the drive motor 1 is stopped,
Winding ends.

As described above, when the take-up speed is reduced, the degree of deceleration is smaller than the deceleration characteristic of the supplied video tape, and the degree of reduction is substantially constant (target deceleration). Characteristic), the winding speed is reduced. For this reason, the tension of the video tape at the time of deceleration is maintained substantially constant as shown by 35 in FIG. As a result, the video tape to be wound is wound on the winding reel without sagging even during deceleration.

As described above, in this embodiment, the tape deceleration characteristic is represented by a characteristic obtained by a first-order approximation. The target deceleration characteristic having a lower degree of deceleration than the tape deceleration characteristic is also a characteristic that changes linearly. For this reason, the control of the reduction of the video tape winding speed can be performed by a simple method.

In the above embodiment, a video cassette recorder, which is one of the magnetic tape devices, was described. However, the present invention is not limited to this, and any magnetic tape device such as a video cassette player or DAT may be used.

[0026]

The method for fast-forwarding or rewinding a magnetic tape according to the present invention is applied to a magnetic tape device which performs control for making the rotation speed of a drive motor for rotating a take-up reel coincide with a target value. In a state where the remaining amount of the magnetic tape on the supply reel is small, the degree of deceleration is smaller than the deceleration characteristic of the magnetic tape supplied from the supply reel when the tensile force of the magnetic tape is set to 0 during high-speed winding in fast-forward or rewind. When using a small deceleration characteristic as the target deceleration characteristic,
When the remaining amount of the magnetic tape on the supply reel is larger than a predetermined remaining amount, which is a preset remaining amount, the target value is set to a value corresponding to high-speed winding, and the remaining amount of the magnetic tape on the supply reel becomes the specified remaining amount. When it becomes smaller, the target value is changed from a value corresponding to high-speed winding to a value corresponding to low-speed winding according to the target deceleration characteristic.
For this reason, the winding speed continuously changes from a speed corresponding to high-speed winding to a speed corresponding to low-speed winding according to predetermined characteristics, so that even when the winding speed is reduced, slack is generated. It is possible to take up a magnetic tape without any need.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration of an apparatus to which an embodiment of a video tape fast-forward or rewind method according to the present invention is applied.

FIG. 2 is an explanatory diagram showing changes in a target value, a winding speed, and a tape tension when the winding speed is reduced.

FIG. 3 is an explanatory diagram showing a change in a target value, a winding speed, and a tape tension when the winding speed is reduced in the related art.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 drive motor 2 frequency generator 3 cycle detection unit 4 target value generation unit 5 subtraction unit 6 subtraction unit 7 deceleration control unit 11 output instructing start of deceleration 12 mode output indicating operation mode 31 tape deceleration characteristics 32 target deceleration characteristics

Claims (1)

(57) [Claims] The drive motor is driven based on a difference between a rotation speed of a drive motor for rotating a take-up reel of a magnetic tape and a target value, so that the rotation speed of the drive motor matches the target value. In the magnetic tape device that performs control, when the remaining amount of magnetic tape on the supply reel is small,
When the tensile force of the magnetic tape is set to 0 during high-speed winding in fast-forward or rewind, when a deceleration characteristic having a smaller degree of deceleration than the deceleration characteristic of the magnetic tape supplied from the supply reel is set as a target deceleration characteristic, When the remaining amount of the magnetic tape on the supply reel is larger than a predetermined remaining amount, which is a preset remaining amount, the target value is set to a value corresponding to the high-speed winding, and When the remaining amount is smaller than the specified remaining amount, the target value is changed from a value corresponding to the high-speed winding to a value corresponding to the low-speed winding,
A method for fast-forwarding or rewinding a magnetic tape, wherein the method is changed according to the target deceleration characteristic.