JPH08124240A - Fast winding or rewinding method for magnetic tape - Google Patents

Abstract

PURPOSE: To wind a tape without slackening the tape, by changing the winding speed to low in accordance with a predetermined characteristic when the winding approaches the final stage. CONSTITUTION: During winding at high speeds, a deceleration control part 7 generates and outputs a value of 0. When a signal 11 generated by a rotation speed ratio of a feed reel and a wind reel indicates that the remaining amount of a tape is not larger than a regulated value, the control part 7 sends to an operational part 5 a value which continuously increases in accordance with a predetermined characteristic from a starting value of 0. The operational part 5 subtracts the value of the control part 7 from an output value from a target value generation part 4, and inputs the obtained value to a subtraction part 6. The subtraction part 6 sends to a multiplication part 8 a value obtained by subtracting the output value of the operational part 5 from a rotation speed detected by a cycle detection part 3. The multiplication part 8 multiplies the value of tone operational part 6 by an integral multiple in accordance with a mode output 12, thereby driving a motor 1 via a PWM 9 and a driving circuit 10. Since the wind speed is decelerated in accordance with a target deceleration characteristic, the tension of the tape can be maintained generally constant, so that the tape can be wound around the wind reel without being slackened.

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, DAT, etc.) for controlling the rotation speed of a drive motor for rotating a take-up reel of a magnetic tape to match a target value. More specifically, when the winding is near the end, the target value is continuously changed from the value corresponding to the high-speed winding to the value corresponding to the low-speed winding according to a predetermined characteristic. Or regarding the rewind 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 shortened, and the fast-forwarding and rewinding damages the video tape. The control method is adopted so as not to cause the above.
That is, when the remaining amount of the video tape on the supply reel is large, the winding time is shortened by performing winding at high speed. When the remaining amount of the video tape on the supply reel becomes low, the winding speed is changed from high speed to low speed, and the winding is stopped when the end of the video tape is detected in the low speed winding state. When the winding speed is changed from a high speed to a low speed, if the winding speed is suddenly reduced, slackening or the like occurs in the wound video tape, so that the winding speed is controlled to be gradually reduced. .

[0003]

However, in the prior art, the target value for controlling the drive motor during fast-forwarding and rewinding is an integer multiple of the reference value with the control target value for the drive motor during normal reproduction as the reference value. It is treated as a value.
For this reason, since the winding speed is gradually reduced, even when the control target value is gradually changed to a small value, as shown by 91 in FIG. It is given as a continuously decreasing value. As a result, the rotational speed of the drive motor is decelerated with a large undulation, as indicated by the curve 92. Therefore, 93
As shown in FIG. 3, the winding tension is also wavy, which causes a problem that the wound video tape is slack.

The present invention was devised to solve the above-mentioned problems, and an object thereof is to set a target value for controlling a drive motor from a value corresponding to high-speed winding when the winding is almost completed. By continuously changing to a value corresponding to low-speed winding according to a predetermined characteristic, it is possible to wind a magnetic tape such as a video tape without causing slack even when the winding speed is reduced. It is to provide a method of fast-forwarding or rewinding a tape.

[0005]

In order to solve the above problems, a magnetic tape fast-forwarding or rewinding method according to the present invention comprises:
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. When the tensile force of the magnetic tape applied to the apparatus is set to 0 during high-speed winding in fast-forwarding or rewinding in a state where the remaining amount of the magnetic tape on the supply reel is small, the magnetic tape supplied from the supply reel is When the deceleration characteristic having a lesser 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 preset remaining amount which is a preset remaining amount, the target value is set to the high speed. When the remaining amount of the magnetic tape on the supply reel becomes less than the specified remaining amount, the target value is set to a value corresponding to winding. 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 pulling force of the magnetic tape is set to 0 during high-speed winding in fast-forwarding or rewinding when the remaining amount of the magnetic tape on the supply reel is 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 of the tape supply side and the frictional force. When this deceleration characteristic is referred to as 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 in a state where the tension is substantially zero. .
Therefore, when the winding speed is reduced in accordance with the target deceleration characteristic having a smaller deceleration degree than the tape deceleration characteristic, the magnetic tape to be wound has both the deceleration degree of the tape deceleration characteristic and the deceleration degree of the target deceleration characteristic. It will be wound up with the tension determined by the difference in the degree of deceleration. Further, the tension value 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 the fast forward or rewind method of a video tape according to the present invention is applied.

More specifically, this apparatus is a video cassette recorder, which is equipped with one drive motor 1 for running a video tape. Then, at the time of recording or reproducing, 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 detection unit 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 the detected rotation speed is subtracted by the subtraction unit. Send to 6 plus inputs. The target value generation unit 4 is a block that generates a target value of the rotation speed of the drive motor 1. That is, the target value of the rotation speed required for the drive motor 1 at the time of recording or reproduction, or the target value of the rotation speed required for the drive motor 1 at the time of fast-forwarding or rewinding 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 controlling the video tape winding speed in the fast-forwarding or rewinding operation. When the fast-forwarding or rewinding is performed, high-speed winding is performed. Alternatively, at the time of recording or reproducing, 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 winding speed is reduced, and thus the generated value is changed. 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 less than the specified remaining amount, the value 0 is set as the start value. As a result, a value that continuously increases according to 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 that subtracts the value sent by the deceleration control unit 7 from the value sent by the target value generation unit 4 and sends the subtraction result to the minus input of the subtraction unit 6. Reference numeral 6 is a block that subtracts the value output by the subtraction unit 5 from the rotation speed detected by the cycle detection unit 3 and sends the subtraction result to the multiplication unit 8. The multiplication unit 8
This 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 value of the output of the subtraction unit 6 is set. Multiply by 2 and PWM the result
9 is sent.

The PWM 9 performs pulse width modulation in which ON and OFF are repeated at a ratio corresponding to the value output from the multiplication unit 8 so that the digital value output from the multiplication unit 8 is converted into an analog value with high accuracy. It is a block to be converted into. 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,
Servo control is performed by a loop including the multiplication unit 8, the PWM 9, and the drive 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 so as 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. Controlled as.

Hereinafter, with reference to FIG. 2, the deceleration control unit 7
The characteristics of the change in the value sent from the device will be described.

The speed S1 in the figure shows the winding speed of high speed winding in fast forward or rewind, and the speed S2 shows the winding speed of low speed winding in fast forward or rewind. Then, in high-speed winding such as fast-forwarding or rewinding, when the pulling force for winding the video tape is set to 0 by a method such as stopping the winding, the speed of the supplied video tape is equal to the inertia and frictional force on the supply side. The deceleration is started with a characteristic determined by the relationship with, and the speed becomes 0 eventually. Further, 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 of the broken line 31 shown in FIG. 2 is that when the tension force for winding the video tape is set to 0 in the state where the remaining amount of the video tape wound on the supply reel is small during high-speed winding, It shows a characteristic that linearly approximates the characteristic that the running speed of the tape decreases. When this characteristic is referred to as a tape deceleration characteristic, it means that when the winding speed is reduced according to the tape deceleration characteristic, the tension of the video tape during winding becomes a value near zero. Therefore, when the deceleration characteristic of the winding is decelerated according to the characteristic that the deceleration degree is smaller than the tape deceleration characteristic, the tension of the video tape in the winding takes a value corresponding to the small deceleration degree.

The straight line 32 in the figure shows the deceleration characteristic that changes linearly, and shows the deceleration characteristic that the degree of deceleration is smaller than the tape deceleration characteristic. When this deceleration characteristic is referred to as a target deceleration characteristic, it means that when the winding speed is reduced according to the target deceleration characteristic, a substantially constant tension is secured in the winding even when the winding speed is reduced. Therefore, when the deceleration control unit 7 is instructed to decelerate the winding speed, the deceleration control unit 7 generates a value that increases with the characteristic corresponding to the inclination of the straight line 32 and sends it to the subtraction unit 5.

This will be described in detail with reference to FIG. 2. The broken line 33 indicates the change characteristic of the target value corresponding to the tape deceleration characteristic indicated by the broken line 31. Now
The inclination is indicated by -A. Further, the straight line 34 shows the change characteristic of the target value corresponding to the target deceleration characteristic shown by the straight line 32. It is assumed that the inclination is indicated by-(A-d). That is, in the target deceleration characteristic, the degree of deceleration is reduced by the value d with respect to the tape deceleration characteristic. Therefore, the deceleration control unit 7 causes the target value given to the minus input of the subtraction unit 6 to have a slope of − (A−d). The value to be sent.

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

When the mode output 12 gives an instruction to fast forward or rewind, the multiplying section 8 compares the output value of the subtracting section 6 with
It multiplies the integer value corresponding to the instruction of the mode output 12 and sends the multiplication result 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 rotational speed of fast forward or rewind. In addition, the 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 subtracting unit 5. The deceleration control unit 7 also generates a value 0 and sends it to the subtraction unit 5. Therefore, the minus input of the subtraction unit 6 is given a value V1 equal to the target value generated by the target value generation unit 4. As a result, the rotation speed of the drive motor 1 is the target value V1.
It is controlled to rotate at a rotation speed equal to, and high-speed winding of the video tape is performed (the winding speed at this time is shown as the speed S1 in FIG. 2).

When the remaining amount of the video tape wound around the supply reel becomes less than the specified remaining amount (time T1),
The output 11 gives a deceleration start instruction to the deceleration control unit 7.
Therefore, the deceleration control unit 7 temporarily increases the value with the value 0 as the start value. As a result, if the output value of the subtraction unit 5 is represented by t indicating the elapsed time from the time T1,

## EQU1 ## The value is determined as V1- (A-d) * t, and the value decreases along the straight line 34. Therefore, 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 decelerated along the straight line 32, that is, along the target deceleration characteristic.

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

As described above, when decelerating the winding speed, the deceleration characteristic is such that the degree of deceleration is less than the deceleration characteristic of the supplied video tape, and the degree of deceleration is substantially constant (target deceleration). The winding speed is reduced according to the characteristics. Therefore, the tension of the video tape at the time of deceleration is maintained substantially constant as indicated by 35 in FIG. As a result, the video tape to be taken up is taken up by the take-up reel without slack even during deceleration.

As described above, in this embodiment, the tape deceleration characteristic is represented by the characteristic obtained by the first-order approximation. The target deceleration characteristic, which has a smaller deceleration degree than the tape deceleration characteristic, is also a characteristic that undergoes a primary change. Therefore, the control of reducing the winding speed of the video tape can be executed by a simple method.

In the above embodiment, the video cassette recorder, which is one of the magnetic tape devices, has been described, but 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 for controlling the rotational speed of a drive motor for rotating a take-up reel to match a target value. When the tension of the magnetic tape is set to 0 during high-speed winding in fast-forwarding or rewinding when the remaining amount of the magnetic tape on the supply reel is small, the degree of deceleration is higher than the deceleration characteristic of the magnetic tape supplied from the supply reel. When using a small deceleration characteristic as the target deceleration characteristic,
When the remaining amount of the magnetic tape on the supply reel is greater than the preset remaining amount which is the preset 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 is set to the prescribed 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.
Therefore, the winding speed continuously changes from the speed corresponding to the high-speed winding to the speed corresponding to the low-speed winding according to the predetermined characteristic.Therefore, even when the winding speed is reduced, slack is generated. It is possible to wind a magnetic tape without it.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an apparatus to which an embodiment of a fast forward or rewind method for a video tape 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 decelerated.

FIG. 3 is an explanatory diagram showing changes in the target value, the winding speed, and the tape tension when the winding speed is decelerated in the conventional technique.

[Explanation of symbols]

 1 Drive Motor 2 Frequency Generator 3 Cycle Detection Section 4 Target Value Generation Section 5 Subtraction Section 6 Subtraction Section 7 Deceleration Control Section 11 Output for Instructing to Start Deceleration 12 Mode Output Showing Operation Mode 31 Tape Deceleration Characteristics 32 Target Deceleration Characteristics

Claims (1)

[Claims] 1. The rotational speed of the drive motor is made to match the target value by driving the drive motor based on the difference between the rotational speed of the drive motor for rotating the take-up reel of the magnetic tape and the target value. In the controlling magnetic tape device, when the magnetic tape remaining on the supply reel is low,
When the pulling force of the magnetic tape is set to 0 during high-speed winding in fast-forwarding or rewinding, and when the target decelerating characteristic is a decelerating characteristic having a smaller deceleration degree than the decelerating characteristic of the magnetic tape supplied from the supply reel, When the remaining amount of the magnetic tape of the supply reel is larger than a prescribed remaining amount which is a preset remaining amount, the target value is set to a value corresponding to the high-speed winding, and the target value of the magnetic tape of the supply reel is set. When the remaining amount is less than the specified remaining amount, the target value from the value corresponding to the high-speed winding to the value corresponding to the low-speed winding,
A method for fast-forwarding or rewinding a magnetic tape, characterized in that the method is changed according to the target deceleration characteristic.