JPH06150456A - Tape tension controller - Google Patents

Abstract

PURPOSE:To prevent a fluctuation of tape tension and a slack of tape by suppressing the fluctuation of take-up speed of a reel. CONSTITUTION:A calculated value of the current I corresponding to the tape winding diameter R for making the tape tension constant is supplied to an adding device 29 as a control signal SCi. A frequency signal RFG from an FG 21 is supplied to a microcomputer 11 to detect the rotational speed of a reel motor 15, and this speed is compared with a reference rotational speed fR and supplied to the adding device 29 as a correction signal SCOMP corresponding to the comparison difference signal. A PWM signal corresponding to the added signal SCi+SCOMP, is obtained from a PWM modulation circuit 12, and this PWM signal is smoothed by an LPF 13 and supplied to a constant current drive circuit 14, to drive the motor 15. Since the correction signal SCOMP is added to the control signal SCi to control so that the rotational speed of the motor 15 becomes equal to the reference rotational speed fR, the fluctuation of take-up speed of the reel is suppressed, then the fluctuation of tape tension F and the slack of tape are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention is applicable to, for example, VTRs and DAs.
The present invention relates to a tape tension control device suitable for application to a tape transport system using a helical scan such as T.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a tape traveling system of a known VTR and shows a loading state. In the figure, 1 is a supply reel, 2 is a take-up reel, 3 is a drum, 4 is a capstan, 5 is a pinch roller, and 6 is a tape.

By keeping the tape tension F of the P portion constant while the tape is running, it is possible to obtain a good head output and prevent the tape from being damaged by the tape guide or the like to improve the reliability of the tape path. it can.

Conventionally, in order to keep the tape tension F constant, the tape tension control of the forward (FWD) system is performed by a mechanical tension regulator, and the tape tension control of the reverse (RVS) system drives the reel stand. It has been proposed to use a current servo system that controls the current supplied to the reel motor according to the tape winding diameter.

As is well known, since the current I flowing through the reel motor and the torque generated by the motor are in a proportional relationship, if the tape winding diameter (radius) is R, the tape tension is F, and the torque generated by the reel stand is Tr, The relationship of Formula 1 will be satisfied.

[0006]

[Equation 1]

Considering mechanical loss and electrical loss, it can be expressed as shown in Equation 2. Where K1, K
2, A and B are constants, and A = K1 × F and B = K2. As a mechanical loss, the loss of the reel motor, the loss of the swing gear that transmits the driving force from the reel motor to the reel stand,
There is a loss of the reel stand, etc., and there is an error etc. generated in the current detection circuit as an electrical loss.

[0008]

[Equation 2]

As is clear from the equation (2), in order to keep the tape tension F constant, the motor current should be changed according to the tape winding diameter R. It should be noted that A and B in Equation 2 are adjusted for each set by measuring the tape tension F on the production line.

By the way, the tape winding diameter R is as follows.
It is obtained from the reel rotation period and the tape speed as described in Japanese Patent Publication No. 17992. That is, the tape winding diameter of the supply reel 1 is RS, the tape winding diameter of the take-up reel 2 is RT, the rotation cycle of the supply reel 1 is TS, the rotation cycle of the take-up reel 2 is TT, the tape speed is v, and the tape 6 is. If the total area of the reel hub is AA, then the relational expression of Formula 3 can be obtained. Although detailed description is omitted, the tape winding diameters RS and RT can be calculated from these relational expressions if the reel rotation period and the tape speed are known.

[0011]

[Equation 3]

FIG. 5 shows a tape tension control device for controlling the tape tension F to a constant value by controlling the current flowing through a reel motor for driving a reel base in a reverse system according to the tape winding diameter.

In the figure, 11 is a microcomputer (hereinafter referred to as "microcomputer"). This microcomputer 1
1 is a frequency signal SF from a frequency generator (not shown) attached to the supply reel 1 and the take-up reel 2.
G and TFG are supplied, and a frequency signal CFG from a frequency generator (not shown) attached to the capstan 4 is supplied. And in the microcomputer 11,
The rotation periods TS and TT of the supply reel 1 and the take-up reel 2 are obtained from the frequency signals TFG and SFG, and
The tape speed V is obtained from the frequency signal CFG, and the tape winding diameters RS and RT are calculated.

In the microcomputer 11, the tape winding diameter Rs of the supply reel 1 is used as the tape winding diameter R to calculate the current I according to the tape winding diameter R by the equation 2, and the calculated value is used as the control signal SCi. It is supplied to the PWM modulation circuit 12 in 11. A PWM signal corresponding to the control signal SCi is output from the PWM modulation circuit 12, and the PWM signal is smoothed by the low pass filter 13 and then supplied to the constant current drive circuit 14. As a result, the supply reel 1
A current I corresponding to the tape winding diameter R is made to flow through the reel motor 15 that drives the tape motor F, and the tape tension F is controlled to be constant.

[0015]

If the system is close to the ideal,
A current I flowing through the reel motor 15 as in the example of FIG.
The tape tension F can be stably controlled only by controlling the tape tension F according to the tape winding diameter R.

However, the winding speed of the supply reel 1 may fluctuate due to load fluctuations and disturbances in the drive system of the reel motor 15, etc., and as a result, the tape tension F may fluctuate and the tape 6 may sag.

When the tape tension F is controlled only by controlling the current I flowing through the reel motor 15 as shown in FIG. 5, if the tape 6 has a slack at the time of start-up, the load on the reel motor 15 is lightened. However, there is a possibility that the tape 6 may be excessively loaded at the moment the tape 6 is rapidly wound up due to the increase in the rotation speed thereof and then the slack in the tape 6 is eliminated.

An object of the present invention is to suppress the fluctuation of the reel winding speed and prevent the fluctuation of the tape tension and the slack of the tape. Another object of the present invention is to prevent excessive transit tension from being applied to the tape even if the tape has a slack at the time of starting.

[0019]

According to a first aspect of the present invention, in a tape tension control device for controlling a tape tension to a constant value by causing a current corresponding to a tape winding diameter to flow through a reel motor for driving a reel stand, the reel motor is rotated. Depending on the comparison result of the rotation speed detection means for detecting the speed, the rotation speed comparison means for comparing the rotation speed detected by the rotation speed detection means with the reference rotation speed according to the tape winding diameter, and the comparison result of the rotation speed comparison means. And a current value correction means for correcting the value of the current passed through the reel motor, and the value of the current passed through the reel motor is corrected so that the rotation speed of the reel motor becomes equal to the reference rotation speed.

According to a second aspect of the present invention, a current servo system for controlling the tape tension to a constant value by causing a current corresponding to the tape winding diameter to flow through a reel motor for driving the reel base, and the rotation speed of the reel motor correspond to the tape winding diameter. And a speed servo system that controls the current flowing through the reel motor to achieve the specified rotation speed,
Servo switching means for switching between the current servo system and the speed servo system, and a current value detection means for detecting the value of the current flowing through the reel motor are provided, and the speed servo system is switched at startup, and the current flowing through the reel motor thereafter. When the voltage exceeds a predetermined value, the current servo system is switched.

According to a third aspect of the present invention, a current corresponding to the tape winding diameter is supplied to the reel motor for driving the reel base to control the tape tension constant, and the rotation speed of the reel motor is a reference rotation corresponding to the tape winding diameter. A current servo system that corrects the value of the current that flows in the reel motor so that it becomes equal to the speed, and a speed servo system that controls the current that flows in the reel motor so that the rotation speed of the reel motor corresponds to the tape winding diameter. A servo switching means for switching between the current servo system and the speed servo system, and a current value detection means for detecting the value of the current flowing through the reel motor. At the time of startup, the speed servo system is switched over, and then the current flows through the reel motor. The current servo system is switched to when the current exceeds a predetermined value.

[0022]

According to the first aspect of the invention, the value of the electric current supplied to the reel motor is corrected so that the rotation speed of the reel motor becomes equal to the reference rotation speed, so that fluctuations in the reel winding speed can be suppressed and the tape tension can be reduced. It is possible to prevent fluctuation and slack of the tape.

According to the second aspect of the invention, since the reel motor is switched to the speed servo system for controlling the current flowing through the reel motor so that the reel motor rotation speed corresponds to the tape winding diameter at the time of start-up, the tape sags at the start-up. Even if there is, the tape is not suddenly wound, and it is possible to prevent excessive transit tension from being applied to the tape.

In the third invention, since the speed servo system is switched at the time of starting, it is possible to prevent excessive transit tension from being applied to the tape even if the tape is slack at the time of starting, and the reel is used in the current servo system. Since the value of the current passed to the reel motor is corrected so that the motor rotation speed becomes equal to the reference rotation speed, fluctuations in the reel winding speed can be suppressed, and fluctuations in tape tension and tape slack can be prevented. Becomes

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the figure, reference numeral 21 is a frequency generator attached to the reel motor 15, and this frequency generator 2
The frequency signal RFG from 1 is amplified by the sensor amplifier 22 and waveform-shaped, and then supplied to the free running counter 23 of the microcomputer 11. The counter 23 sequentially outputs the count value for each rising edge of the frequency signal RFG whose waveform has been shaped by the amplifier 22.

The output signal of the counter 23 is supplied to the subtractor 24 and the delay circuit 25, and the output signal of the delay circuit 25 is supplied to the subtractor 24. The subtractor 24 subtracts the count value tn-1 one cycle before from the count value tn, and the subtractor 24 outputs a count value T = tn-tn-1 corresponding to each cycle of the frequency signal RFG. Value T
Is supplied to a subtractor 26 as a rotation speed comparison means.

The subtractor 26 is supplied with a reference count value Tref corresponding to one cycle of the frequency signal RFG when the reel motor 15 rotates at the reference rotation speed fR. Here, the reference rotation speed fR can be calculated from the tape winding diameter R and the tape speed V, and is expressed as in Equation 4.

[0029]

[Equation 4]

In the subtractor 26, the reference count value Tref is subtracted from the count value T, and the output signal T of this subtractor 26
-Tref is supplied as a correction signal SCOPM to the adder 29 via the amplifier 27 having the gain G and the connection switch 28 as an error signal of the rotation speed. The adder 29 is supplied with the calculated value of the current I calculated by the above-described equation 2 as the control signal SCi. In the adder 29, the correction signal SCOMP is added to the control signal SCi, and the added signal is supplied to the PWM modulation circuit 12. Then, the PWM signal corresponding to the addition signal is output from the PWM modulation circuit 12.

The present example is constructed as described above, and the others are constructed in the same manner as the example of FIG.

In this example, the correction signal Scomp is added to the control signal SCi and the current I flowing through the reel motor 15 is increased.
Is corrected. That is, the count value T is controlled to be equal to the reference count value Tref, and thus the rotation speed of the reel motor 15 is controlled to be equal to the reference rotation speed fR. It is possible to prevent the fluctuation of the tension F and the slack of the tape 6.

Although not described above, the changeover switch 28 has
It is turned on when ref, and turned off when T <Tref. That is, the correction signal Scom is added to the control signal SCi only when the rotation speed of the reel motor 15 is lower than the reference rotation speed fR.
By adding p, the rotation speed of the reel motor 15 is controlled to become the reference rotation speed fR. This is tape 6
In a system driven by the capstan 4 and the pinch roller 5 (see FIG. 4), if the tape winding diameter R is accurately calculated, T <Tref, that is, the rotation speed of the reel motor 15 becomes the reference rotation speed. This is because it cannot be faster than fR and there is no need for correction. Further, if the rotation speed of the reel motor 15 is corrected to a slower direction, the torque generated by the reel motor 15 may decrease, the tape tension F may decrease, and the tape 6 may sag.

Next, another embodiment of the present invention will be described with reference to FIG. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the figure, the frequency signal RFG output from the frequency generator 21 is amplified and waveform-shaped by the sensor amplifier 22, and then the speed servo circuit 3 of the microcomputer 11 is executed.
1 is supplied. The speed servo circuit 31 is for controlling the rotation speed of the reel motor 15 to be the rotation speed fR 'corresponding to the tape winding diameter R. The speed servo circuit 31 detects the rotation speed of the reel motor 15 from the frequency signal RFG, and this rotation speed is the rotation speed f.
A control signal SCs for controlling the current I flowing through the reel motor 15 is output so as to be equal to R '. The control signal SCs is supplied to the fixed terminal on the side a of the changeover switch 33. Here, the rotation speed fR 'is the reference rotation speed fR.
It is set to be slightly larger than (see Formula 4).

Reference numeral 32 is a current servo circuit for supplying a current corresponding to the tape winding diameter R to the reel motor 15 to control the tape tension F constant. From the current servo circuit 32, the calculated value of the current I (see the equation 2) according to the tape winding diameter R is output as the control signal SCi. The control signal SCi is supplied to the fixed terminal on the b side of the changeover switch 33.

The output signal of the changeover switch 33 is supplied to the PWM modulation circuit 12, and the PWM modulation circuit 12 outputs a PWM signal corresponding to the output signal of the changeover switch 33. The changeover switch 33 is switched to the a side at the time of start-up, and is switched to the b side when the current I flowing through the reel motor 15 exceeds the current IM (see Formula 2) according to the tape winding diameter R at that time. Whether or not the current I flowing through the reel motor 15 exceeds IM can be determined, for example, by the PWM modulation circuit 12 based on the control signal SCs, and the changeover switch 33 is switched by the control signal from the PWM modulation circuit 12.

The present example is constructed as described above, and the others are constructed in the same manner as the example of FIG.

FIG. 3 is a flowchart showing the switching operation of the servo system.

First, when the rotation of the reel motor 15 is started, the connection switch 33 is switched to the side a to start the control operation by the speed servo circuit 31 (step 4).
1). Next, it is judged whether or not the current I flowing through the reel motor 15 exceeds the current IM corresponding to the tape winding diameter R at that time, and when it exceeds, the connection switch 33 is switched to the b side and the control operation by the speed servo circuit 31 is performed. With the end
The control operation by the current servo circuit 32 is started (steps 43 and 44).

In this example, the changeover switch 3 is activated at the time of starting.
3 is switched to the a side, and the speed servo circuit 31 controls the current I flowing through the reel motor 15 so that the rotation speed of the reel motor 15 becomes equal to the rotation speed fR '. Therefore, even if there is slack in the tape 6 at startup,
It is possible to prevent excessive transit tension from being applied to the tape 6 at the moment when the tape 6 is not suddenly wound up and then the slack of the tape 6 disappears. As a result, the tape 6 can be started up smoothly and the reliability of the tape path can be improved.

Here, the rotation speed f of the reel motor 15 is slightly higher than the reference rotation speed fR (see equation 4).
The reason why the tape is controlled to be R'is that if the tape is controlled to have the reference rotational speed fR, the tape 6 cannot be slackened forever.

When the current I flowing through the reel motor 15 exceeds the current IM corresponding to the tape winding diameter R at that time, the changeover switch 33 is switched to the b side, so that the reel motor 15 is changed to the tape winding diameter R. It is controlled so that a corresponding current I (see equation 2) flows, and thereafter, the tape tension F is controlled to be constant.

In the example of FIG. 2, during the control operation by the current servo circuit 32, the rotation speed of the reel motor 15 becomes equal to the reference rotation speed fR corresponding to the tape winding diameter R, as in the example of FIG. It can also be configured to control. According to this, the same effect as the example of FIG. 1 can be obtained.

[0045]

According to the first aspect of the present invention, since the value of the electric current supplied to the reel motor is corrected so that the rotation speed of the reel motor becomes equal to the reference rotation speed, fluctuations in the reel winding speed can be suppressed. It is possible to prevent fluctuations in tape tension and tape slack.

According to the second aspect of the invention, the speed servo system for controlling the current flowing through the reel motor is switched so that the rotation speed of the reel motor corresponds to the tape winding diameter at the time of startup, so that the tape is switched at startup. Even if there is slack, the tape is not suddenly wound up, excessive transit tension can be prevented from being applied to the tape, and the tape can be started smoothly and the reliability of the tape path can be improved.

According to the third aspect of the invention, since the speed servo system is switched at the time of starting, it is possible to prevent excessive transit tension from being applied to the tape even if the tape is slack at the time of starting, and the current servo system allows the reel motor to operate. Since the value of the current supplied to the reel motor is corrected so that the rotation speed becomes equal to the reference rotation speed, fluctuations in the reel winding speed can be suppressed, and fluctuations in tape tension and slack in the tape can be prevented.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a tape tension control device according to the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the tape tension control device according to the present invention.

FIG. 3 is a flowchart showing a servo system switching operation in the example of FIG.

FIG. 4 is a diagram showing an example of a tape running system of a VTR.

FIG. 5 is a configuration diagram showing a conventional tape tension control device.

[Explanation of symbols]

 1 Supply reel 2 Take-up reel 3 Drum 4 Capstan 5 Pinch roller 6 Tape 11 Microcomputer 12 PWM modulation circuit 13 Low pass filter 14 Constant current drive circuit 15 Reel motor 21 Frequency generator 23 Free running counter 24, 26 Subtractor 25 Delay Circuit 27 Amplifier 28 Connection switch 29 Adder 31 Speed servo circuit 32 Current servo circuit 33 Changeover switch

Claims (4)

[Claims] 1. A tape tension controller for controlling a tape tension to a constant value by causing a current corresponding to a tape winding diameter to flow through a reel motor for driving a reel base, and a rotation speed detecting means for detecting a rotation speed of the reel motor. A rotation speed comparison means for comparing the rotation speed detected by the rotation speed detection means with a reference rotation speed according to the tape winding diameter, and a current flowing through the reel motor according to the comparison result of the rotation speed comparison means. A tape tension control device comprising: a current value correcting means for correcting a value, and correcting a value of a current supplied to the reel motor so that a rotation speed of the reel motor becomes equal to the reference rotation speed. 2. The tape tension control device according to claim 1, wherein the current value correction means performs the correction operation only when the rotation speed of the reel motor is lower than the reference rotation speed. 3. A current servo system for controlling a tape tension to a constant value by supplying a current corresponding to a tape winding diameter to a reel motor for driving a reel stand, and a rotation speed of the reel motor corresponding to the tape winding diameter. So as to control the current flowing through the reel motor, servo switching means for switching between the current servo system and the speed servo system, and current value detecting means for detecting the value of the current flowing through the reel motor. A tape tension control device comprising: a speed servo system at startup and a current servo system when a current flowing through the reel motor exceeds a predetermined value. 4. A reel motor for driving a reel base is supplied with an electric current corresponding to the tape winding diameter to control the tape tension constant, and the rotation speed of the reel motor becomes a reference rotational speed corresponding to the tape winding diameter. A current servo system that corrects the value of the current flowing through the reel motor so as to be equal, and a speed servo that controls the current flowing through the reel motor so that the rotation speed of the reel motor corresponds to the tape winding diameter. System, a servo switching means for switching the current servo system and the speed servo system, and a current value detection means for detecting the value of the current flowing in the reel motor, and at the time of startup, switching to the speed servo system, Thereafter, when the current flowing through the reel motor exceeds a predetermined value, the tape tension is switched to the current servo system. The control device.