JP3240761B2 - Tension servo circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tension servo circuit for controlling a tension during operation of a magnetic tape set in a magnetic recording / reproducing apparatus to a predetermined value.

[0002]

2. Description of the Related Art In a magnetic recording / reproducing apparatus, in order to obtain a reproduction signal of a normal magnitude from a head in contact with a magnetic tape or to record with a signal of a normal magnitude,
It is conventionally known that the magnetic tape must be pressed against the recording / reproducing head with a predetermined tension. For this purpose, a magnetic recording / reproducing apparatus is generally provided with a tension servo circuit so as to press the magnetic tape against the head with a predetermined tension. FIG. 6 shows an example of such a conventional tension servo circuit.

In this figure, a magnetic tape 55 is wound around a reel 53 driven by a reel motor 51, and the magnetic tape 55 pulled out of the reel 53
Is wound around a roller guide 54 and a post 56 provided at one end of a tension arm 57. A tension arm 57 having one end provided with the post 56 is rotatably supported about a rotation shaft 58, and an angle sensor 59 for detecting the rotation angle of the rotation shaft 58 is connected to the rotation shaft 5.
8 attached. In addition, tension arm 5
A spring 60 that urges the magnetic tape 7 against the tension of the magnetic tape 55 is attached to one end of the tension arm 57.

Then, for example, when the tension of the magnetic tape 55 becomes loose, the tension arm 57 is urged by the spring 60 and rotates in the B direction. In this case, in order to restore the loosened tension, if the torque in the C direction supplied to the reel motor 51 is controlled to increase, the tension applied to the tape 55 increases, and the tension returns to the original tension. Become. Conversely, when the tension of the tape 55 increases, the tension arm 57 rotates in the A direction against the urging force of the spring 60. In this case, in order to return to the original tension, when the drive current supplied to the reel motor 51 is controlled so that the torque in the D direction increases, the tension applied to the tape 55 is reduced,
It returns to the original tension.

[0005] In order to perform such control to keep the tension constant, the angle data output from the angle sensor 59 is supplied to a servo circuit 63, and the target tension output from the system control circuit 62 is supplied to the servo circuit 63. And the difference is applied to an integral control circuit, a proportional control circuit and a differential control circuit to calculate a servo output signal. The calculated servo output signal is supplied to the reel motor 51 via the driver 64, and controls the number of rotations of the reel motor 51 to control the tape tension to the target tension.

The integral control circuit 63-1 of the servo circuit 63 is provided for removing an offset remaining due to the proportional operation of the proportional control circuit 63-2. The differential control circuit 63-3 is provided with an integral control circuit. 63-1 is provided to compensate for the degradation of stability due to the integration operation of 63-1.
Stability is achieved by adding a differential operation. As described above, in this conventional tension servo circuit, the angle of the tension arm 57 is controlled to be constant in order to keep the tension constant. However, the tension is controlled by keeping the angle of the tension arm 57 constant. To make it constant
It is assumed that the magnetic tape 55 is normally wound on the reel 53 and that the traveling system is operating normally.

However, in the magnetic recording / reproducing apparatus, the tape running system may get caught, the tape may be loosely wound on the reel, or the tape may be wound upside down, or an external force may be applied to the tension arm. Disturbance may occur. In such a case, the tension servo circuit recognizes only that the tension fluctuates abruptly, and the tape is instantaneously fed to the reel motor in order to keep the tension constant despite the assumption being broken. Alternatively, control for performing a winding operation is performed. Then, a large tension is applied to the tape and the tape is strongly tensioned, or a small tension is applied and the tape is loosened, which may cause tape damage to the tape.

[0008] Therefore, the tension servo circuit so as to limit the torque of the reel motor to prevent tape damage from Applicants have already been published, filed (see Japanese Patent Laid-Open No. 4 30 2838). The outline of this prior art tension servo circuit will be described with reference to FIG.

In this figure, a magnetic tape 73 is wound around a reel 71 driven by a reel motor 72, and the magnetic tape 73 pulled out from the reel 71
Is wound around a roller guide 79 and a post 74 provided at one end of the tension arm 75. Post 74
A tension arm 75 provided at one end is provided with a rotating shaft 76.
And is rotatably supported about the
An angle sensor 77 for detecting the rotation angle of the rotation shaft 6 is attached to the rotation shaft 76. Further, a spring 78 for urging the tension arm 75 against the tension of the magnetic tape 73 is attached to one end of the tension arm 75.

Further, a signal from a rotary encoder provided on the roller guide 79 is applied to a tape travel detector 84 to detect the tape travel. Further, an output signal of a frequency generator (FG) provided on the reel motor 72 is applied to a reel rotation detector 83 so that the reel motor 7
2 is detected. Then, the reel diameter detector 85 calculates the diameter of the tape wound on the reel 71 from the tape running distance and the rotation speed of the reel motor 72. Data of the winding diameter of the calculated tape is inputted to the transducer 86, the proportional control feedback gain G _P according to the data, differential control feedback gain G _D and the limit torque T _L is read from converter 86 operation It is input to the means 81.

By the way, if the diameter of the tape wound on the reel 71 is R and the tension applied to the tape at this time is N, the torque T of the reel motor 72 can be expressed as T = RN in a steady state. That is, it is understood that the torque of the reel motor 72 must be changed in proportion to the tape diameter in order to keep the tension N constant.
For this, the gain G _P, I'm reading from the transducer 85 in proportion to the winding diameter, as shown in FIG. 8 G _D. Further, a limiting torque _TL for limiting the torque of the reel motor 72 is set so as not to cause tape damage even if the disturbance occurs. This limit torque is also read from the converter 86 in proportion to the reel diameter as shown in the figure.

[0012] Then, read from transducer 86 proportional control foot back gain G _P, differential control feedback gain G _D and the limit torque T _L from the target tension data and the angle sensor 77 is outputted from the target tension generator 87 Calculation means 81 together with the output angle data
Are input to the motor driver 82 and are subjected to a predetermined calculation.
Is applied to the reel motor 72.

[0013] calculation by the calculation means 81, first angle data D ₁ and the difference between the target tension D _R (D ₁ -D
It calculates the _R), to calculate a proportional control servo data E _P is multiplied by the proportional control feedback gain G _P to the difference. That is, E _P = (D ₁ −D _R ) × G _P (1) Further, a differential value dD ₁ / dt of the angle data is calculated, and the differential control feedback gain G _D
The multiplied to calculate the differential control servo data E _D. That is, E _D = (dD ₁ / dt) × G _D (2)

[0014] Here, the servo data output from the operation unit 81 becomes the servo data E _P and servo data E _D and the added data _{E = (E P + E D} ). The calculating means 81 determines that the added value data E is equal to the limit torque T.
_When it exceeds _L , it operates to output the limit torque _TL to prevent tape damage. These E _P , E _D
Is changed as shown in FIGS. 9A and 9B, for example, the addition data E changes as shown in FIG. 9C, and the addition data E exceeds the limit torque _TL . when the positive side of the limit torque T _L + or the negative side limit torque T _L - is made so is output. Since the tension servo circuit shown in FIG. 7 is configured as described above, it is possible to prevent a tension that may damage the tape from being applied to the tape even when disturbance occurs.

Next, an application filed by the present applicant (Japanese Unexamined Patent Publication No.
FIG. 10 shows another example of a tension servo circuit that can prevent tape damage according to Japanese Patent Application Laid-Open No. 480/480. The tension servo circuit shown in this figure has a certain reel rotation speed in a mode such as a loading / unloading mode, a pinch mode, and a stop mode, in which the reel rotation speed is predicted not to exceed a certain rotation speed. When the rotation speed becomes equal to or more than the rotation speed, the control is switched to a control for keeping the rotation speed of the reel constant, thereby preventing an excessive tension from being applied to the tape.

The outline will be described with reference to FIG. An output from a rotation speed detector 110 such as a frequency generator attached to the reel motor 101 is applied to a reel rotation speed constant control circuit 113 and a control switching circuit 114. In the mode in which the rotation speed of the reel is not expected to exceed a certain rotation speed, and the rotation speed of the reel motor 101 is a certain rotation speed or less, the control switching circuit 114 sets the movable contact 114c to the fixed contact. It is controlled to connect to 114b. Then, since the output of the tension servo circuit 112 is supplied to the reel motor 101, the reel motor 101 is controlled by the servo circuit 112. The tension servo circuit 112 includes a tension arm 1
07 angle sensor 109 attached to the rotation shaft 108
Is applied. Therefore, the tension servo circuit 112 is connected to the tension arm 1 as described above.
The reel motor 101 is controlled via the reel driver 116 so that the angle of the tape 07 becomes constant.
The tension applied to 05 is controlled to be constant.

The output of the angle sensor 109 is also applied to a reel rotation direction determining circuit 111. The reel rotation direction determination circuit 111 determines a direction approaching the target tension stored in advance based on the angle data from the angle sensor 109, and supplies a direction signal to the reel rotation speed constant control circuit 113. The reel rotation speed constant control circuit 113 outputs a control signal for keeping the rotation speed of the reel 103 constant based on the direction signal from the reel rotation direction determination circuit 111 and the rotation speed signal from the rotation speed detector 110.

The mode signal from the system controller 115 is a signal of a mode in which the rotation speed of the reel is predicted not to exceed a certain rotation speed. When the detection signal is equal to or higher than a certain rotation speed, the operation is performed to connect the movable contact 114c to the fixed contact 114a. Then, the control signal from the reel rotation constant control circuit 113 is supplied to the reel motor 101 via the reel driver 116, and even if the error continues for a certain reason, the reel rotation speed is kept at a constant value. Reel motor 1 to hold down
Since 01 is controlled, it is possible to prevent the magnetic tape 105 from being damaged.

[0019]

When a disturbance is applied to the running system and a large error signal is applied to the tape tension servo circuit, the effect appears not only in the tape tension servo circuit but also in the magnetic recording / reproducing apparatus. Depending on the diagnosis function, when a disturbance occurs, a stop operation may be performed. The stop operation by such a diagnostic function is not performed instantaneously, but is performed when the abnormal state continues for a certain period of time, so the conventional tape damage prevention method can damage the tape before stopping. There is. Furthermore, when the disturbance is removed, the conventional tape damage prevention method has a large deviation between the target tension and the angle of the tension arm.

For this reason, a large error is supplied to the tape tension servo circuit, and the servo circuit reaches the target tension while repeatedly responding excessively. There was a problem that it became long. Therefore, according to the present invention, the stop operation can be performed without damaging the tape even when the stop operation is performed, and when the disturbance is removed, the error signal input to the tension servo circuit is small, and the state quickly returns to the stable state. It is intended to provide a tape tension servo circuit.

[0021]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a target tension changing speed which is lower than a response speed of a tape tension servo circuit. Further, when the tape tension becomes excessive and an abnormal state occurs, the target tension input to the tape tension servo circuit is switched to the angle data of the tension arm, so that the output of the servo circuit is reduced to zero for a certain period of time, and the servo is turned off. In this case, the integral control means, which is a part of the circuit configuration, is reset.

[0022]

According to the present invention, the tape tension becomes excessive.
By switching the target tension input to the tape tension servo circuit when an abnormal condition occurs ,
Since the output of the servo circuit is set to zero for a certain period of time, the reel motor continues to rotate by inertia at this time, thereby preventing the tape from being damaged. In addition, when the tape tension returns from the abnormal state, the error between the target tension and the angle of the tension arm is small, and the speed at which the target tension returns to the original state is slow. You will be able to follow. Therefore, even if there is a disturbance, the tape quickly returns to a stable state, and the tape can be run as if nothing had happened.

Further, in this case, since the integral control means which is a part of the tape tension servo circuit is reset, the output of the integral control means rises from zero. Accordingly, an output approaching the target tension is output from the servo circuit without being affected by the previous error signal, thereby preventing the tape from being over-tensioned.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment of Tape Tension Servo Circuit of the Present Invention
A block diagram of the embodiment is shown in FIG. 1 and will be described in detail below. In this drawing, a magnetic tape 5 is wound around a reel 3 driven by a reel motor 1, and the magnetic tape 5 pulled out from the reel 3 is provided at one end of a roller guide 4 and one end of a tension arm 7. It is hung over the post 6. A tension arm 7 having one end provided with a post 6 is rotatably supported around a rotation shaft 8, and an angle sensor 9 for detecting a rotation angle of the rotation shaft 8 is attached to the rotation shaft 8. . further,
A spring 10 for urging the tension arm 7 against the tension of the magnetic tape 5 is attached to one end of the tension arm 57.

Then, for example, when the tension of the magnetic tape 5 is loosened, the tension arm 7 is urged by the spring 10 to rotate in the direction B. In this case, in order to restore the tension, if the drive current supplied to the reel motor 1 is controlled to increase the torque in the C direction, the tension applied to the tape 5 increases, and the tension arm 7 moves in the A direction. To return to the original tension. Conversely, when the tension of the tape 5 increases, the tension arm 7 resists the tension of the spring 10.
Rotates in the A direction. In this case, in order to return the tension to the original tension, the drive current supplied to the reel motor 1 is controlled to increase the torque in the D direction.
, The tension applied to the tape 5 is reduced, and the tension arm 7 rotates in the direction B, thereby returning to the original tension.

Such control is performed by a servo loop including the angle sensor 9, the servo circuit 23, the driver 24, and the reel motor 1. The servo circuit 23 constitutes a part of the tension servo circuit 2, and the tension servo circuit 2 further includes an abnormal tension detector 21 and a target tension generator 22. The abnormal tension detector 21 monitors the output from the angle sensor 9 that outputs the angle data 11 of the rotating shaft 8 of the tension arm 7, and when the angle data 11 exceeds a certain angle range, the tension is abnormal. The detection output is applied to the target tension generator 22 and the servo circuit 23.

The target tension generator 22 has a target tension command 12 output from a system control 26 which controls the mode of the magnetic recording / reproducing apparatus.
Switching means 22-1 for switching between the rotation angle data 11 of the tension arm 7 output from the angle sensor 9 and a low-pass filter (LPF) 22 through which the output from the switching means 22-1 passes. -2 and switch means 2 for cutting off the output from LPF 22-2
2-3 and the output from the switch means 22-1 is LP
Switch means 22-3 for directly outputting without passing through F22-2
It is composed of

Further, the servo circuit 23 includes an integral control circuit 23-1, switch means 23-2 for cutting off the output from the integral control circuit 23-1, a proportional control circuit 23-3, a differential control circuit 23-4, It comprises an adder 23-5. This integral control circuit 23-1 is a proportional control circuit 23-3.
The differential control circuit 23-3 is provided to remove an offset remaining due to the proportional operation of the integral control circuit 23-1.
This is provided to compensate for the deterioration of the stability due to the integration operation described above, and is intended to stabilize the servo circuit 23 by adding a differentiation operation.

In the tension servo circuit 2, when the angle data 11 is within a certain angle range, the abnormal tension detector 21 does not generate a detection output. Therefore, the switch means 22-1 in the target tension generator 22 has been switched to output the target tension command 12, and the switch means 22-3 is turned on and the switch means 22-4 is turned off. . Therefore, the target tension generator 22 outputs the system control 26
Is output from the LPF 22
Servo circuit 23 as target tension 25 through
Is output to

In this case, the abnormal tension detector 2
Since no detection output is applied from 1 to the servo circuit 23, the switch means 23-2 is turned on and the reset signal is not applied to the integration control circuit 23-1. Therefore, the servo circuit 23 outputs the error signal, which is the difference between the input angle data 11 output from the angle sensor 9 and the target tension 25, to the proportional control circuit 23-3, the integral control circuit 23-1, and the differential control circuit 23.
-4, and these outputs are added and output by the adder 23-5. The output of the servo circuit 23 is supplied to the reel motor 1 via a driver 24, and controls the tension applied to the tape 5 to be constant by keeping the angle of the tension arm 7 constant as described above.

FIG. 2 shows the waveforms of the angle data 11 and the target tension 25 at this time. In this figure, the horizontal axis is time, and the LPF output from the system control 26 is shown.
The target tension 25 via 22-2 is sometimes changed by the mode switching. Angle data 11 of the tension arm 7 repeats fine vibrations so as to sandwich the curve of the target tension. However, in this figure, it is emphasized so that it is easy to see, and it is not actually controlled by repeating the vibration as much as shown. Further, as shown in this figure, the target tension 25 is L
It can be understood that the servo circuit 23 can sufficiently follow the target tension 25 because the change speed is made gentle as shown by the PF 22-2.

If a disturbance occurs in the running system of the tape 5 for some reason, the tension arm 7 largely rotates in the direction A or B. Therefore, the abnormal tension detector 21 monitoring the angle data 11 output from the angle sensor 9 that the disturbance has occurred.
To be detected. The detection output of the abnormal tension detector 21 is applied to the target tension generator 22, and by switching the switch means 22-1,
The angle data 11 is output from the switch 22-1. Further, the switch 22-3 is turned off and the switch 22-4 is turned on by this detection output.
Is output from the target tension generator 22.

Further, a detection signal which continues for a certain period of time is applied to the servo circuit 23 to which the angle data 11 is inputted, via the timer circuit 21-1 of the abnormal tension detector 21. This detection signal resets the integration control means 23-1 in the servo circuit 23 and switches the integration means 23-.
2 is turned off. Then, the target tension generator 22
Is output to the servo circuit 23, and the difference from the angle data 11 is calculated. In this case, the target tension 25 is the angle data 1
Since it is 1, the difference is naturally zero. Therefore, the proportional control circuit 23-3 and the integral control circuit 23
-1, the output from the differential control circuit 23-4 becomes zero, the output of the adder 23-5 becomes zero, and no output is supplied to the reel motor 1. In this case, the reel motor 1 is in a state of continuing rotation by inertia. For this reason, no excessive tension is applied to the tape 5 and no tape damage occurs.

FIG. 3 shows the waveforms of the angle data 11 and the target tension 25 at this time. FIG. 3 shows a case where the tape tension is increased by disturbance. In this figure, it can be seen that when disturbance occurs, the angle data 11 of the tension arm 7 exceeds a predetermined maximum point. In this case, the target tension 25 is replaced with the angle data 11 as described above. Thereafter, after a certain period of time, the disturbance stops. Then, since the tension arm 7 operates to return to the original rotation angle, as shown in FIG.
1 falls within the tension maximum point, and the detection output generated by the abnormal tension detector 21 disappears.

Accordingly, the switch means 22-1, the switch means 22-3 and the switch means 22-4 in the target tension generator 22 are restored to the original state after being switched again. In this case, the target tension command 1 again
2 is supplied to the LPF 22-2.
Since the angle data 11 based on the abnormal tension was supplied to the PF 22-2 immediately before, the angle data 1 of the tension maximum point was supplied from the LPF 22-2 as shown in the figure.
From 1 to the target tension command 12, the change gradually falls. Therefore, since the difference between the target tension and the angle data 11, that is, the error is small and the response speed of the servo circuit 23 is fast, the servo circuit 23 performs a control operation so as to follow the change of the target tension 25, and quickly becomes stable It will return to the state. Then, the servo operation is continued as if nothing had happened as shown in the figure.

By the way, when the integration operation is turned off for a certain period of time, the tape may become loose when returning from the abnormal tension area to the normal tension area, and may return to the abnormal tension area immediately afterward. This is a process for preventing the occurrence and expansion of damage. Note that the fixed time of the detection signal applied to the servo circuit 23 for a certain time may be at least empirically set to a time at which the disturbance is settled. Further, when a disturbance occurs in which the tape tension becomes loose, the angle data 11 of the tension arm 7 suddenly changes to exceed the minimum tension point, and
The difference is that the LPF 22-2 changes gradually from the minimum tension point to the target tension command 12 when the disturbance is settled, but the other operations are the same as described above. Description is omitted. In the embodiment shown in FIG.
A switch means 22-3 for shutting off the output of 22-2 is provided, but this is not always necessary.
The feature that 2-2 is constituted by, for example, a digital filter can also be deleted.

The tension servo circuit 2 shown in FIG.
Although the operation of the servo circuit 23 is stopped by switching the target tension 25 to the angle data 11, the operation of the servo circuit 23 may be stopped by setting the feedback gain of the servo circuit 23 to zero. However, in this case, the servo circuit 23 operates in an unstable manner as shown in FIG. That is,
In this case, the target tension command 12 is continuously input to the servo circuit 23 as the target tension 25,
The difference between the target tension 25 input to the servo circuit 23 when the disturbance is settled and the angle data 11 of the maximum tension point is large as shown in the figure. Then, as shown in the drawing, the servo circuit 23 performs the control operation so as to repeat the transient vibration with the target tension interposed therebetween, so that the tension applied to the tape 5 greatly changes during this operation. There is a risk of damaging the tape. Therefore, such means cannot be adopted.

FIG. 5 is a block diagram showing a second embodiment of the tape tension servo circuit according to the present invention. In this embodiment, the tape tension servo circuit 2 shown in FIG. 1 is further provided with a torque limiting circuit 30 for limiting the torque of the reel motor in accordance with the reel winding diameter, so as to further prevent tape damage. is there. Since the embodiment shown in FIG. 5 has a structure in which the torque of the reel motor is limited by the reel diameter in this manner, the description of the same portions as those in the structure shown in FIG. 1 is omitted here, and the torque is limited. The configuration will be described.

In this figure, reference numeral 30 denotes a torque limiting circuit, which comprises a tape running amount detector 31, a reel rotation speed detector 32, a reel winding diameter detector 33, and a converter 34. The tape travel detector 31 detects the tape travel based on a signal from a rotary encoder provided on the roller guide 4. Further, a frequency generator (FG) provided on the reel motor 1
Is applied to the reel rotation speed detector 32 to detect the rotation speed of the reel motor 1. Then, the diameter of the tape wound on the reel 3 is calculated by the reel diameter detector 33 from the tape running distance and the rotation speed of the reel motor 1. Data of the winding diameter of the calculated tape is input to the converter 34, the feedback gain of the proportional control circuit 23-3 in accordance with the data G _P, the feedback gain G _D and the limit torque T of the differential control circuit 23-4 _L is read from the converter 86 and supplied to the servo circuit 23.

Assuming that the diameter of the tape wound on the reel 3 is R and the tension applied to the tape at this time is N, the torque T of the reel motor 1 in the steady state is T = R・ It can be expressed as N. That is, in order to keep the tension constant, the torque of the reel motor 1 must be changed in proportion to the tape diameter. Therefore, the gain G _P, reads data such as proportional to the winding diameter, as shown in FIG. 8 as G _D from the transducers 34, further reel motor so as not to cause tape damage even as the disturbance occurs Fig. 8 Limiting torque of 1
The limiting torque _TL proportional to the reel winding diameter shown in FIG.
4 is read.

The feedback gain G _P , feedback gain G _D and limiting torque _TL read from the converter 34 are the target tension 25 output from the target tension generator 22 and the angle output from the angle sensor 9. The data 11 is input to the servo circuit 23 to which the data is input, and an output for limiting the torque of the reel motor 1 is applied to the reel motor 1 via the driver 24. In the servo circuit 23, the angle data 11 and D _1, the target tension 25 when the D _R, first, calculates the difference between them (D ₁ -D _R), multiplied by the feedback gain G _P to the difference outputting a proportional control servo data E _P shown in the equation (1) by the proportional control circuit 23-3. Then, it calculates a differential value dD ₁ / dt of the angular data 11, the differential control servo data E _D shown in the equation (2) by multiplying the feedback gain G _D in the differential value from the differential control circuit 23-4 Output.

[0042] Then, the by adding the servo data E _P and the servo data E _V and the adder 23-5, E = (E
_P + E _D ) is output. However, when the data E added by the adder 23-5 exceeds the limit torque _TL , the servo circuit 23 operates to output the limit torque _TL . The operation waveform at this time is as shown in FIG.
The operation waveform is the same as the waveform shown in FIG. Tension servo circuit shown in FIG. 5 is provided with a torque limiting circuit 30 as described above, are set the feedback gain G _P, G _D and limit torque T _L in accordance with the diameter of the tape 5 wound on the reel 3 Therefore, even if there is a delay in the operation with respect to the abnormal tension, it is possible to prevent the tape from being tensioned so as to damage the tape. In the above description, the target tension is switched while the abnormal tension detector is detecting the abnormal tension. However, the present invention is not limited to this, and the target tension may be changed for a certain time from the time when the abnormal tension is detected. The tension may be switched.

[0043]

As described above, according to the present invention, when the tape tension becomes abnormal, the target tension input to the tape tension servo circuit is switched, and the output of the servo circuit is set to zero for a certain time. At the time of abnormal tension, the reel motor continues to rotate by inertia, thereby preventing the tape from being damaged. Further, when the tape tension returns from the abnormal state, the difference between the target tension and the angle data of the tension arm is small, and the tension servo circuit is changing because the change speed at which the target tension returns to the original state is slow. It becomes possible to sufficiently follow the target tension. Therefore, even if disturbance occurs, the tape quickly returns to a stable state, and the tape can be run as if nothing had happened.

Further, in this case, since the integral control means in the tape tension servo circuit is reset, the output of the integral control means rises from zero. Therefore, an output approaching the target tension without being affected by the previous data is output from the servo circuit, and it is possible to prevent an excessive tension from being applied to the tape. The operation of the tension servo circuit may be turned off depending on the mode of the magnetic recording / reproducing apparatus, and may be turned on when the mode is switched. Even in such a case, according to the present invention in which the operation of the tension servo circuit is turned off by switching the target tension to the angle data, when the tension servo circuit is turned on, the angle of the tension arm is quickly adjusted to become the target tension. , And can be controlled stably.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a tension arm angle and a target tension in the first embodiment.

FIG. 3 is a diagram showing a relationship between an angle of a tension arm and a target tension in the first embodiment at the time of abnormal tension.

FIG. 4 is a diagram showing the relationship between the angle of the tension arm and the target tension when the target tension is not switched.

FIG. 5 is a diagram showing a block diagram of a second embodiment of the present invention.

FIG. 6 is a diagram showing a conventional servo tension servo circuit.

FIG. 7 is a diagram showing a servo tension servo circuit conventionally proposed.

FIG. 8 is a graph showing the amount of gain and torque limitation with respect to the reel diameter.

9 is a diagram showing operation waveforms of the servo circuit shown in FIG.

FIG. 10 is a diagram showing another servo tension servo circuit conventionally proposed.

[Explanation of symbols]

1, 51, 72, 101 Reel motor 2, 52, 112 Tension servo circuit 3, 53, 71, 103 Reel 4, 54, 79, 104 Roller guide 5, 55, 73, 105 Tape 6, 56, 74, 106 Post 7, 57, 75, 107 Tension arm 8, 58, 76, 108 Rotation axis 9, 59, 77, 109 Angle sensor 10, 60, 78, 107a Spring 11, 61 Angle data 12 Target tension command 21 Abnormal tension detector 21 -1 Timer 22 Target tension generator 22-1, 22-3, 22-4 Switch means 22-2 LPF 23 Servo circuit 23-1, 63-1 Integration control circuit 23-2 Switch means 23-3, 63-2 Proportional control circuit 23-4, 63-3 Differential control circuit 23-5, 63-4 Adder 24, 6 4 Driver 25 Target tension 26, 62, 115 System control 30 Torque limiting circuit 31, 84 Tape running distance detector 32, 83, 110 Reel rotation speed detector 33, 85 Reel winding diameter detector 34, 86 Converter 35 Reel winding Diameter data 36 Torque limit data 37 Feedback gain G _D 38 Feedback gain _GP 81 Calculation means 82 Motor drive 87 Target tension generator 111 Reel rotation direction determination circuit 113 Reel rotation speed constant control circuit 114 Control switching circuit 114a, 114b Fixed contact 114c Movable contact 116 Reel driver

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-282959 (JP, A) JP-A-59-201256 (JP, A) JP-A-58-189852 (JP, A) JP-A 61-2012 196544 (JP, A) JP-A-2-257455 (JP, A) JP-A-2-276049 (JP, A) JP-A-3-280239 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 15/43

Claims (6)

(57) [Claims] 1. A reel for feeding or winding a magnetic tape, a reel motor for driving the reel, the magnetic tape drawn from the reel being wound, and according to the magnitude of the tension of the magnetic tape. A rotating tension arm, angle detection means for outputting a rotation angle of a rotation shaft of the tension arm, target tension output means for outputting a target tension signal, an angle signal output from the angle detection means, and the target A target tension signal output from the tension output means, and a servo control means for controlling the reel motor so as to eliminate the difference between the two signals, thereby making the angle of the tension arm constant. In the tension servo circuit, the target tension is calculated based on the response speed of the servo control means. Provided with a means to slow the rate of change of ® tone signal, the abnormality tension detecting means for detecting an excessive Ten <br/> Deployment by monitoring the output of the angle detection means is provided, excessive from the abnormal tension detecting means tension Wherein the target tension is switched from the output of the target tension output means to the angle signal output from the angle detection means when the signal is detected. 2. The tension servo circuit according to claim 1, wherein when the excessive tension is detected by the abnormal tension detecting means, the output of the servo control means is not output for a predetermined time. 3. The apparatus according to claim 1, wherein said servo means includes at least an integral control means, and shuts off an output of said integral control means when an excessive tension is detected, and resets said integral control means. Tension servo circuit. 4. A feedback gain of the servo circuit according to a winding diameter signal output from the winding diameter detecting means, wherein the winding diameter detecting means detects a winding diameter of the magnetic tape wound on the reel. 4. The tension servo circuit according to claim 1, wherein: 5. A winding diameter detecting means for detecting a winding diameter of the magnetic tape wound on the reel, wherein a torque of the reel motor is changed according to a winding diameter signal outputted from the winding diameter detecting means. 4. The tension servo circuit according to claim 1, wherein an output of said servo circuit is controlled so as to limit. 6. A winding gain detecting means for detecting a winding diameter of the magnetic tape wound on the reel, and a feedback gain of the servo circuit in accordance with a winding diameter signal output from the winding diameter detecting means. 4. The tension servo circuit according to claim 1, wherein the output of the servo circuit is controlled so as to limit the torque of the reel motor.