JPH08315460A - Tape slackening preventing device - Google Patents

Abstract

PURPOSE: To quickly reduce the speed without producing slackening of a tape when the tape speed is reduced during a high-speed movement. CONSTITUTION: When a speed reduction command is received during the high- speed movement of a tape 1 by a tape speed control circuit 10, the slackening condition of the tape 1 is detected based on the cycle ratio of a frequency generator and the winding diameter ratio of the tape 1. In a driving force setting means (11), a driving force is outputted according to the slackening condition. During a speed reduction, a motor 6 is driven by a tape speed judging circuit 25 according to the output of the driving force setting means (11) and the speed is reduced without any slackening. When a target low speed is reached, the motor 6 is driven according to the tape speed judging circuit 25 and thus the tape 1 is transferred at a fixed low speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tape slack preventing device for an apparatus using a tape-shaped recording medium such as an audio tape recorder and a video tape recorder.

[0002]

2. Description of the Related Art In recent years, a device using a tape-shaped recording medium typified by a video tape recorder is required to have a high winding speed with an increase in the amount of tape wound on a reel. The performance of high-speed tape transfer depends on the tape transfer speed and start / stop time.

Conventionally, in these devices, the number of revolutions of a winding motor is increased in order to increase the tape transfer speed, and the deceleration of gears for transmitting rotational force is changed,
The transfer speed was increasing. Also, when the tape wound on one reel rushes to the end, unless the tape transfer speed is sufficiently reduced, abnormal tension is applied to the tape at the end of transfer and the tape is damaged, At the end, the tape speed needs to be reduced even though there is transport capacity. Further, even during the high-speed transfer of the tape, the transfer speed may be reduced in order to make it easier to read the data recorded on the tape. In this way, when the transfer speed is changed from high speed to low speed, if the rotation speed of the reel on the take-up side is simply abruptly decreased, the rotation speed of the reel on the delivery side does not follow up, causing slack in the tape, resulting in equipment reliability. You will lose your sex. Therefore, conventionally, the tape speed is reduced by a sufficiently gentle inclination (Japanese Patent Laid-Open No. 2-157946).
In addition, the rotational torque of a motor provided on the supply side is controlled to shorten the deceleration time (Japanese Patent Publication No.
-48565).

[0004]

However, in the above-described conventional tape slack prevention device, it is necessary to slow down the tape speed from a position sufficiently before the tape position where deceleration is desired to be completed, or 2 There is a problem in that the cost increases because it is necessary to provide a motor for each reel.

In view of the above problems, an object of the present invention is to speedily decelerate a single reel driving motor without causing slack.

[0006]

In order to achieve the above-mentioned object, a tape slack preventing device having a first structure of the present invention comprises a reel on a winding side and a reel on a feeding side wound from both ends of a tape, and the winding. Drive means for generating a winding torque on the side reel,
First and second frequency generators that output frequency signals proportional to the rotation speeds of the take-up reel and the delivery reel, respectively, and the tape is wound around the take-up reel at a plurality of speeds according to an external command. A tape speed control means for outputting a drive signal, a tape speed discriminating means for detecting a state of reaching a tape speed corresponding to the external command, a cycle of output signals of the first and second frequency generators, or A period ratio calculating means for calculating a frequency ratio, the winding side reel,
A tape slack state is detected by comparing the output value of the winding ratio calculation means with the winding diameter ratio calculation means for calculating the ratio of the winding diameters of the tape including the delivery side reel. A comparing means; a driving force setting means for outputting a driving signal according to the output of the comparing means; an output of the tape speed controlling means and an output of the driving force setting means based on the output of the tape speed determining means. And a driving force transmitting means for synthesizing and transmitting to the driving means.

Further, the tape slack preventing device having the second structure of the present invention comprises a winding side and a sending side reel wound from both ends of the tape, and a drive means for generating a winding torque on the winding side reel. And a frequency signal that is proportional to the rotation speed of the take-up reel and the delivery reel, respectively.
A second frequency generator, tape speed control means for outputting a drive signal for winding the tape around the take-up reel at a plurality of speeds according to an external command, and reaching a tape speed corresponding to the external command. Tape speed discriminating means for detecting the state, first and second winding diameter detecting means for respectively detecting the winding diameters of the tape including the winding side reel and the sending side reel, and the external command as a deceleration command. Immediately after the change, the first and second counting means for respectively counting the pulse numbers of the first and second frequency generators, the output value of the first counting means, and the first winding diameter detection means A first multiplication means for multiplying the output value; a second multiplication means for multiplying the output value of the second counting means by the output value of the second winding diameter detection means; and the first multiplication means. The output value and the output value of the second multiplication means are compared and the Comparing means for detecting the slack state, driving force setting means for outputting a driving signal according to the output of the comparing means, output of the tape speed control means and the driving force based on the output of the tape speed discriminating means. And driving force transmitting means for synthesizing the output of the setting means and transmitting the synthesized output to the driving means.

[0008]

According to the first structure of the present invention described above, the driving force transmitting means outputs only the output signal of the tape speed controlling means and the driving means outputs the driving force transmitting means in the high speed transfer state by the external command. Based on this, the take-up reel is driven, and the tape is taken up at high speed. Next, when the tape is transferred to the low speed state by an external command, the target tape speed of the tape speed control means is set to a low speed, and the comparing means compares the output of the winding diameter ratio calculating means and the output of the period ratio calculating means to determine the looseness of the tape. To detect. The driving force setting means outputs a driving signal according to the slack detection output of the comparing means, and the driving force transmitting means synthesizes the output of the tape speed control means and the output of the driving force setting means and outputs. The drive means drives the take-up side reel based on the output of the drive force transmission means, and the tape is decelerated in a short time without causing slack. When the tape speed determination means detects that the tape speed reaches the low target tape speed, the driving force transmission means outputs only the output signal of the tape speed control means, and the driving means winds up based on the output of the driving force transmission means. The side reel is driven, and the tape is wound at a low speed.

Further, according to the above-mentioned second configuration, when the high speed transfer state is performed by the external command, the driving force transmitting means outputs only the output signal of the tape speed controlling means, and the driving means is based on the output of the driving force transmitting means. The reel on the take-up side is driven to wind the tape at high speed. Then, when the low speed transfer state is changed by an external command, the target tape speed of the tape speed control means is set to a low speed, and the first and second counting means count the number of pulses of the first and second frequency generators, respectively. Begin to.
The first multiplication means multiplies the output of the first winding diameter detection means and the output of the first counting means and outputs the result. The second multiplication means is the second
The output of the winding diameter detecting means and the output of the second counting means are multiplied and output. The comparing means outputs the error between the output of the first multiplying means and the output of the second multiplying means as the tape slack amount. The driving force setting means outputs a driving signal according to the tape slack amount of the comparing means, and the driving force transmitting means synthesizes the output of the tape speed control means and the output of the driving force setting means and outputs the combined result. The drive means drives the take-up side reel based on the output of the drive force transmission means, and the tape is decelerated in a short time without causing slack. When the tape speed determination means detects that the tape speed reaches the low target tape speed, the driving force transmission means outputs only the output signal of the tape speed control means, and the driving means winds up based on the output of the driving force transmission means. The side reel is driven, and the tape is wound at a low speed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the structure of a tape slack preventing device according to the first embodiment of the present invention.

In FIG. 1, 1 is a tape, 2 and 3 are reels on the take-up side and reels of the tape 1, and 4 and 5 are tapes 1.
Forming a traveling path of the motor, 6 is a motor for rotating the take-up reel 2 or the delivery reel 3, and 7 and 8 are signals FG having frequencies proportional to the rotation speeds of the reels 2 and 3, respectively.
A frequency generator that outputs S and FGT, a drive circuit 9 that generates a winding torque on the motor 6, and a tape 1 based on the output signals FGS and FGT of the frequency generators 7 and 8.
, A tape speed control circuit for outputting a drive signal for controlling the speed constant, 11 is a drive means composed of a motor 6 and a drive circuit 9, 12 and 13 are frequency generators 7, respectively.
A winding diameter detection circuit for detecting the winding diameter of the tape 1 wound on the reels 2 and 3 from the output signals FGS and FGT of 8 and the tape speed, and 14 and 15 are output signals FGS and FGT of the frequency generators 7 and 8, respectively. Cycle detection circuit that detects the cycle of
Rs and Rt are the values of the output signals of the winding diameter detection circuits 12 and 13, respectively, and Ts and Tt are the cycle detection circuits 14 and 15, respectively.
Output signal value, 16 is a winding diameter ratio calculating circuit for calculating the ratio of Rs and Rt, 17 is a cycle ratio calculating circuit for calculating the ratio of Ts and Tt, and 18 is a winding diameter detecting circuit 12, 13 and winding diameter ratio A winding diameter ratio calculating means composed of the calculating circuit 16, 19 is a cycle ratio calculating means composed of the cycle detecting circuits 14 and 15 and a cycle ratio calculating circuit 17, and 20 is a margin for outputting a value A of a predetermined winding diameter ratio. Reference numeral 21 is a circuit, 21 is an addition circuit for adding the output value of the winding diameter calculation circuit 16 and the output value A of the margin circuit 20, 22 is a comparison between the output value of the addition circuit 21 and the output value of the period ratio calculation circuit 17, and the tape 1 Of the slack, a comparison circuit 23 includes a margin circuit 20, an adder circuit 21, and a comparison circuit 22, and a reference numeral 24 indicates a fixed torque command Q1 when the comparison circuit 22 determines the slack state. Output, or zero torque otherwise Torque selection circuit for outputting a decree Q0,
25 is a tape speed discriminating circuit for monitoring the signals FGS and FGT of the frequency generators 7 and 8 and discriminating whether or not the vehicle is decelerating.
Is a driving force setting means composed of a plurality of torque setting commands and a torque selection circuit 24, and 27 is an output signal of the torque selection circuit 24 if the output of the tape speed determination circuit 25 indicates that the tape is decelerating. It is a driving force transmission circuit that outputs the output signal of the speed control circuit 10 to the drive circuit 9.

The operation of the tape slack preventing device of the first embodiment constructed as described above will be described below.

First, the winding operation of the tape 1 during high speed transfer will be described. When the high speed transfer command is received by the external command signal, the tape speed control circuit 10 causes the frequency generator 7,
The drive signal is output so that the total value of the values obtained by squaring the cycles of the output signals of 8 becomes a constant value corresponding to the high transfer speed, and the tape speed determination circuit 25 outputs the non-deceleration signal so that the drive force is transmitted. The circuit 27 outputs the output signal of the tape speed control circuit 10. The drive circuit 9 drives the motor 6, and the tape 1 is wound around the reel 2 at a high constant speed. At this time, the winding diameter detection circuit 13 controls the tape speed and the frequency generator 8
The winding diameter Rt of the tape wound on the reel 3 is detected from the cycle of the output signal of. Similarly, the winding diameter detection circuit 12 detects the winding diameter Rs of the tape wound on the reel 2 from the tape speed and the cycle of the output signal of the frequency generator 7.

Next, the winding operation of the tape 1 when shifting to the low speed transfer state will be described.

When the tape speed forcing circuit 10 receives the low speed transfer command from the external command signal, the tape speed forcing circuit 10 sums the values obtained by squaring the periods of the output signals of the frequency generators 7 and 8 to a constant value corresponding to the low speed transfer speed. Although the drive signal is output as described above, the tape speed determination circuit 25 outputs the deceleration signal, so that the drive force transmission circuit 27 does not output the output signal of the tape speed control circuit 10. Therefore, the drive circuit 9 cannot apply the drive force required for tape speed control to the motor 6, and the rotation of the reel 2 is gradually reduced by the rotation load.
Move to low speed transfer state. On the other hand, the cycle detection circuits 14 and 1
5 detects the cycles Ts and Tt of the frequency generators 7 and 8, respectively, and the cycle ratio calculation circuit 17 calculates the ratio of the cycles Ts and Tt. The winding diameter detection circuits 12 and 13 continue to output the winding diameter information Rs and Rt at the time of high speed transfer, and the winding diameter ratio calculation circuit 16 calculates the ratio of Rs and Rt. The margin circuit 20 outputs a value A of a predetermined winding diameter ratio, and the adder circuit 21 adds the output value of the winding diameter ratio calculation circuit 16 and the output value A of the margin circuit 20. The comparison circuit 22 outputs the output value of the addition circuit 21 and the period ratio calculation circuit 17
Of the tape 1 to determine whether or not there is slack, and the torque selection circuit 24 outputs the fixed torque command Q1 when the comparison circuit 22 determines that there is slack, or otherwise the zero torque command Q0. Is output. Driving force transmission circuit 2
7 outputs the output signal of the torque selection circuit 24 to the drive circuit 9. The drive circuit 9 causes the motor 6 to generate a winding torque according to the input signal. That is, when the rotation of the reel 2 is gradually decelerated by the rotational load, the deceleration of the reel 3 cannot be followed and the tape is loosened. When the looseness of the tape 1 is detected by the comparison circuit 22, the fixed torque is applied to the motor 6 by the fixed torque command Q1. Therefore, a predetermined accelerating force acts on the reel 2 on the take-up side to prevent the reel 2 on the take-up side from rapidly decelerating, thereby eliminating looseness. In this way, the reels 2 and 3 are gradually decelerated, and when the tape speed discriminating circuit 25 detects that the tape speed has reached the target speed, a non-deceleration signal is output, so that the driving force transmission rotation 2
7 outputs the output signal of the tape speed control circuit 10. That is, the tape 1 is wound around the reel 2 at a constant low speed.

As described above, in the first embodiment, the slack state of the tape 1 can be detected by comparing the winding diameter ratio with the detected period ratio, and the driving force corresponding to the slack state is generated in the reel 2. Therefore, the tape speed deceleration time at the time of the low speed transfer command depends on the rotational load of the reels 2 and 3,
It is possible to prevent the tape from loosening due to the rapid deceleration of the reel 2, and it is possible to decelerate in a short time.

In the first embodiment, the comparison circuit 2
Although 2 is configured to detect only the presence or absence of slack and the torque selection circuit 24 outputs the fixed torque command only when there is slack, the comparison circuit 22 outputs the output of the adder circuit 21 and the output of the period ratio calculation circuit 17. Even if the configuration is such that an error is output and the torque selection circuit 24 outputs a torque command signal corresponding to the output of the comparison circuit 22, the same effect can be obtained, and the present invention is not limited to the embodiment.

Further, in the first embodiment, an example in which the cycle detecting circuits 14 and 15 for detecting the cycle of the output signals of the frequency generators 7 and 8 are used as means for detecting the rotation state has been described. If the configuration is such that the frequencies of the output signals of the machines 7 and 8 are detected and the ratio of the period ratio calculation circuit 17 is obtained in reverse, the same effect can be obtained, and the present invention is not limited to the embodiment.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing the configuration of the tape slack prevention device according to the second embodiment of the present invention. In FIG. 2, the same parts as those of the tape slack preventing device shown in FIG. Two
When the tape speed discriminating circuit 25 outputs a deceleration signal, the numbers 8 and 29 are the pulse numbers Ns and Nt of the frequency generators 7 and 8, respectively.
A counting circuit for starting counting of the output value Ns of the counting circuit 28 and the output value Rs of the winding diameter detection circuit 12, and 31 is an output value Nt of the counting circuit 29 and the winding diameter detection circuit 1.
A multiplication circuit for multiplying the output value Rt of 3 by 32;
The subtraction circuit that subtracts the output value of the multiplication circuit 30 from the output value of 1, 33 is a driving force setting circuit that outputs a torque command signal according to the output of the subtraction circuit 32, and 34 is the tape speed determination circuit 25 that outputs a deceleration signal. Driving force setting circuit 3 only while
A switch for outputting the output signal of No. 3, a deceleration force limiting circuit 35 for limiting the deceleration force command among the outputs of the tape speed control circuit 10, and an adder circuit 36 for adding the output of the switch 34 and the output of the deceleration force limiting circuit 35. , 37 are switches 34
Is a driving force transmission means composed of a deceleration force limiting circuit 35 and an adding circuit 36.

The operation of the tape slack preventing device of the second embodiment having the above-described structure will be described below.

First, the winding operation of the tape 1 during high speed transfer will be described. When the high speed transfer command is received by the external command signal, the tape speed control circuit 10 causes the frequency generator 7,
The drive signal is output so that the total value of the values obtained by squaring the cycles of the output signals of 8 becomes a constant value corresponding to the high transfer speed. Since the tape speed determination circuit 25 outputs the non-deceleration signal B, the switch 34 is turned off and the addition circuit 36 is provided.
Is the tape speed control circuit 10 through the deceleration force limiting circuit 35.
Outputs the drive command for high speed transfer. The drive circuit 9 drives the motor 6, and the tape is wound around the reel 2 at a high constant speed. At this time, the winding diameter detection circuit 13 detects the winding diameter Rt of the tape wound on the reel 3 from the tape speed and the cycle of the output signal of the frequency generator 8. Similarly, the winding diameter detection circuit 12 detects the winding diameter Rs of the tape wound on the reel 2 from the tape speed and the cycle of the output signal of the frequency generator 7.

Next, the winding operation of the tape 1 when shifting to the low speed transfer state will be described.

When the tape speed control circuit 10 receives the low speed transfer command from the external command signal, the tape speed control circuit 10 makes the sum of the values obtained by squaring the periods of the output signals of the frequency generators 7 and 8 become a constant value corresponding to the low speed transfer speed. To output the drive signal.
The output of the tape speed control circuit 10 at this time is a deceleration force command. The deceleration force limiting circuit 35 outputs a drive command in which the deceleration force command is limited. Since the adder circuit 36 does not output the drive command at the time of high-speed transfer, the drive force applied by the drive circuit 9 to the motor 6 becomes small, and the rotation of the reel 2 is gradually decelerated by the rotational load. On the other hand, the counting circuits 28 and 2
Reference numeral 9 indicates the frequency generators 7 and 8 immediately after the transition to the low speed transfer state by the output signal B of the tape speed determination circuit 25.
The pulse numbers Ns and Nt of are counted. Winding diameter detection circuit 12,
13 continues to output the winding diameter values Rs and Rt at the time of high speed transfer.
The multiplication circuit 30 outputs a multiplication value of the output value Ns of the counting circuit 28 and the output value Rs of the winding diameter detection circuit 12. Multiplication circuit 3
1 outputs the multiplication value of the output value Nt of the counting circuit 29 and the output value Rt of the winding diameter detection circuit 13. The subtraction circuit 32 outputs a value V obtained by subtracting the output value of the multiplication circuit 30 from the output value of the multiplication circuit 31. If the frequency generators 7 and 8 have the same specifications, the rotation angle θ per pulse is the same, so the subtraction circuit 3
The output value V of 2 is the value of the following equation corresponding to the slack length L of the tape 1.

V = (Nt × Rt) − (Ns × Rs) = L / θ The driving force setting circuit 33 outputs a torque command signal corresponding to the output of the subtraction circuit 32, and the switch 34 causes the tape speed determination circuit 25. The output signal of the driving force setting circuit 33 is output until the arrival at the target speed is detected by. Adder circuit 3
Reference numeral 6 adds the output signal of the switch 34 and the output signal of the deceleration force limiting circuit 35 and outputs the result. The drive circuit 9 is an adder circuit 36.
The motor 6 is caused to generate a winding torque according to the output signal of. That is, since a torque corresponding to the output value V of the subtraction circuit 32 that is proportional to the slack length L is generated in the motor 6, a predetermined acceleration force acts on the reel 2 on the winding side and only the reel 2 on the winding side suddenly increases. The operation prevents deceleration and eliminates slack. In this way, the reels 2 and 3 are gradually decelerated, and when the tape speed discriminating circuit 25 detects that the tape speed has reached the target speed, the non-deceleration signal B is output, so that the switch 34 is turned off and the adding circuit 36 decelerates. Force limiting circuit 3
An output signal of the tape speed control circuit 10 is outputted through 5. The drive circuit 9 drives the motor 6, and the tape 1 is wound around the reel 2 at a low constant speed.

As described above, in the second embodiment, by calculating the value V proportional to the slack length L, the deceleration force corresponding to the slack state is generated in the reel 2, so that the low speed transfer command is issued. Although the tape speed deceleration time depends on the rotational load of the reels 2 and 3, it is possible to prevent the tape from slackening due to the rapid deceleration of the reel 2 and to decelerate in a short time without causing slack.

In each of the embodiments, an example in which the transfer is performed in a single direction is shown, but it is obvious that the same effect can be obtained even if the winding side and the sending side are switched.

In each of the embodiments, the tape speed control circuit 10 is configured to keep the sum of the squares of the cycles of the output signals of the frequency generators 7 and 8 constant, but the signals recorded on the tape 1 are The speed of the tape 1 can be kept constant even by the constitution in which the period is reproduced and kept constant, or the rotation period of the timing roller rotating in synchronization with the tape 1 is kept constant, and the present invention is not limited to the embodiment. .

Further, in each embodiment, the winding diameter detection circuit 1
Reference numerals 2 and 13 show a configuration in which the winding diameter is obtained from the output signals of the frequency generators 7 and 8 and the tape speed, but a method of optically detecting the winding diameter can be considered and the invention is not limited to the embodiment.

[0030]

As described above, according to the present invention, by providing the comparing means for outputting the table slack information and the driving force setting means, the slack of the tape is generated by the single driving means when the tape speed is reduced. Since it can be decelerated in a short time without any damage, damage to the device and the tape can be prevented, and the effect of carrying out the tape at a high speed is very large.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a tape slack preventing device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a tape slack preventing device according to a second embodiment of the present invention.

[Explanation of symbols]

 1 Tape 2 Winding Side Reel 3 Delivery Side Reel 4,5 Post 6 Motor 7,8 Frequency Generator 9 Drive Circuit 10 Tape Speed Control Circuit 11 Drive Means 12,13 Roll Diameter Detection Circuit 14,15 Period Detection Circuit 16 Roll Diameter Ratio calculation circuit 17 Period ratio calculation circuit 18 Winding diameter ratio calculation means 19 Period ratio calculation means 20 Margin circuit 21, 36 Addition circuit 22 Comparison circuit 23 Comparison means 24 Torque selection circuit 25 Tape speed discrimination circuit 26 Driving force setting means 27 Driving force Transmission circuit 28, 29 Counting circuit 30, 31 Multiplication circuit 32 Subtraction circuit 33 Driving force setting circuit 34 Switch 35 Decelerating force limiting circuit 37 Driving force transmission means

Claims (2)

[Claims] 1. A take-up side reel and a take-up side reel wound from both ends of a tape, drive means for generating a take-up torque on the take-up reel, and rotation speeds of the take-up reel and the take-out reel. First and second frequency generators for respectively outputting frequency signals proportional to, and tape speed control means for outputting a drive signal for winding the tape around the winding reel at a plurality of speeds in response to an external command. A tape speed discriminating means for detecting a state of reaching a tape speed corresponding to the external command, and a cycle ratio computing means for calculating a cycle or a frequency ratio of output signals of the first and second frequency generators, The winding diameter ratio calculating means for calculating the ratio of the winding diameters of the tape including the winding side reel and the sending side reel is compared with the output value of the cycle ratio calculating means and the output value of the winding diameter ratio calculating means. Detect slack condition The output of the tape speed control means and the output of the drive force setting means are combined based on the output of the comparison means, the drive force setting means for outputting a drive signal according to the output of the comparison means, and the tape speed determination means. And a driving force transmitting means for transmitting the tape to the driving means, and the tape slack preventing device for promptly transferring the tape at a target speed without causing slack in the tape during deceleration. 2. A take-up side reel and a take-out side reel wound from both ends of a tape, drive means for generating a take-up torque on the take-up side reel, and rotation speeds of the take-up reel and the take-out side reel. First and second frequency generators for respectively outputting frequency signals proportional to, and tape speed control means for outputting a drive signal for winding the tape around the winding reel at a plurality of speeds in response to an external command. , Tape speed discriminating means for detecting a state of reaching the tape speed corresponding to the external command, and first and second windings for respectively detecting the winding diameters of the tape including the winding side reel and the sending side reel. The diameter detecting means, the first and second counting means for counting the number of pulses of the first and second frequency generators immediately after the external command is changed to the deceleration command, and the first counting means. Output value and the first A first multiplication means for multiplying the output value of the first winding diameter detection means; and a second multiplication means for multiplying the output side of the second counting means by the output value of the second winding diameter detection means, Comparing means for comparing the output value of the first multiplying means and the output value of the second multiplying means to detect a slack state; and driving force setting means for outputting a drive signal according to the output of the comparing means, Drive force transmitting means for synthesizing the output of the tape speed control means and the output of the drive force setting means on the basis of the output of the tape speed determining means and transmitting the combined output to the drive means. A tape slack preventive device that transfers the tape at a target speed promptly without causing it.