JPH02220250A - Reel driving mechanism - Google Patents

Abstract

PURPOSE:To prevent slack of a tape and the reduction of tape tension at the time of deceleration and acceleration by changing the magnitude of brake torque in accordance with the value of speed error calculated by a speed error detecting means. CONSTITUTION:A speed error detecting means 20 calculates the speed error in accordance with information obtained from the rotational speed of a take-up reel 12 or/and a supply reel 16 and target rotational speed information and feeds back it to a driving torque giving means 14. A brake torque varying means 50 changes to brake torque which is given from a brake torque giving means 18 to the supply reel 16 in accordance with the value of speed error calculated by the speed error detecting means 20. By this constitution, slack of the tape or the reduction of tape tension due to deceleration of the tape speed for the terminal of the tape and acceleration for start of fast forwarding or rewinding is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reel drive mechanism for feeding a tape by driving a reel around which the tape is wound in a magnetic tape recording/reproducing device.

[Prior Art] When fast-forwarding or rewinding a tape using only a reel in a magnetic tape recording/reproducing device such as a VTR, compact cassette, or DAT, the rotational speed of the reel is detected, and the take-up reel is driven using an error voltage calculated from the rotational speed of the reel. Control torque. At that time, in order to prevent the tape from coming off the tape guide due to slack, and to prevent the tape tension run from dropping and making it impossible to read the data recorded on the tape that is necessary for searching, etc. is designed to generate a constant loss torque or brake torque.

FIG. 7 is a diagram representing an example of such a device.

In this figure, it is assumed that the tape IO is fed in the direction of arrow A in the figure for fast forward (FF) and in the opposite direction for rewind (REW). The changeover switches 301 and 302 are switches for changing the tape feeding direction, and when switched to the FF side, driving torque is applied to the reel drive motor 141 on the right side of the figure, and torque is applied to the reel drive motor 142 on the left side of the figure. , a weak braking torque is applied in the rotational direction opposite to the rotational direction of the reel 122 due to the tape IO being fed in the direction of the arrow in the figure. Motors 141 and 14
2 rotations are detected by FG sensors 201 and 202, respectively, and a speed error detector 200 calculates the difference from a predetermined target speed, and the output is sent to an amplifier 14 via a switch 301.
3 is converted to motor control current and reel drive motor 1
41.

A control current proportional to a constant voltage set by the VRI is supplied to the reel drive motor 142 as a control current for applying brake torque.

When the changeover switches 301 and 302 are switched to the REW side, the control currents supplied to the redrive motors 141 and 142 are switched, and the tape 10 is sent in the opposite direction of the arrow A in the same manner as described above.

There are several methods for calculating the speed error in the speed error detector 200, such as calculating the difference between the rotational speed of one of the reels and the target value, and calculating the difference between the rotational speed of both reels and the target value. There is a method of calculating the difference between the two reels, and a method of calculating the difference between the sum of squares of the rotation periods of both reels and its target value. Then, the speed error detector 200 outputs an inverted version of the voltage corresponding to the above-mentioned difference value, and a torque proportional to the voltage is supplied to the take-up reel to control the tape speed to be constant.

[Problems to be Solved by the Invention] In the reel drive mechanism of the type described above, when the tape speed is reduced during running, such as when the tape speed is reduced at the end of the tape, due to the inertia of the supply reel, A situation occurs in which the tape becomes slack and the tape tensile strength decreases.

On the other hand, if control overshoot occurs during acceleration at the start of fast forwarding or rewinding, sag or a decrease in tape tension run occurs as described above.

If the brake torque is increased to prevent the occurrence of these phenomena, the tensile force applied to the tape during acceleration will become excessive, damaging the tape, or it will be necessary to increase the driving force of the reel on the take-up side.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a reel drive mechanism that overcomes the above-mentioned problems.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle configuration of a reel drive mechanism according to the present invention.
Driving torque applying means 14 for applying driving torque to 2
, a brake torque applying means 18 that applies a brake torque to the supply reel 16 around which the other end of the information recording tape IO is wound, and the rotational speed of the wire winding reel 12 or the supply reel 16, or both of them. In the reel drive mechanism, the reel drive mechanism includes a speed error detection means 20 that calculates a speed error from information obtained from the target rotational speed information and target rotational speed information and feeds it back to the drive torque applying means 14. The present invention is characterized by comprising a brake torque variable means 50 that changes the brake torque applied by the brake torque applying means 18 in accordance with the value of .

The brake torque variable means 50 includes a comparison means for comparing the speed error value with a predetermined value;
Depending on the comparison result of the comparison means, a brake torque value is selected such that if the speed error value is larger than a predetermined value, a larger brake torque value is selected, and if it is smaller, a smaller brake torque value is selected. It is preferable to have a brake torque switching means for switching the brake torque.

Alternatively, the brake torque variable means 50 may include means for linearly varying the brake torque so that the larger the speed error is with respect to the value of the speed error, the greater the brake torque is. It is also preferable to include a limit means for limiting the value of to a predetermined value or more.

As the speed error, if the difference between the rotational speed of one of the reels and the target value is calculated and fed back to the torque of the driving reel, the speed difference is
If it is due to the difference between the sum of the rotation periods of both reels and its target value, that difference is adopted, and if it is due to the difference between the sum of squares of the rotation periods of both reels and its target value, that difference is adopted.

[For production]

When decelerating or when overshoot occurs, the tape speed and the rotational speed of both reels are greater than the target values. At this time, the brake torque is increased by the action of the variable brake torque means 50.

By applying the torque to the supply reel 16, slack in the tape or decrease in tape tension is prevented.

Further, if the brake torque variable means 50 has a means for linearly varying the brake torque according to the value of the speed error, the brake torque may be changed when the tape speed and the rotational speed of both reels are sufficiently lower than the target values at startup, etc. There is a possibility that it will be too low. Even in this case, the brake torque above the predetermined value is always ensured by the action of the limit means.

[Embodiment] FIG. 2 is a diagram showing an embodiment of the reel drive mechanism according to the present invention. Components that are the same as those in FIG. 7 are given the same reference numerals and their explanations will be omitted.

VH2 is a volume that adjustably sets a voltage corresponding to a speed error value when the brake torque is switched. The comparator 500 outputs a voltage of V corresponding to the reversed sign of the speed error value output from the speed error detector 200.
When the voltage is higher than the voltage set by H2, the switch 502
A signal is sent to switch the current to the bottom of the diagram, and when it is small, to the top of the diagram.

VRla is an adjustable voltage corresponding to the brake torque applied when the output voltage of the speed error detector 200 is greater than a predetermined value, and VRlb is the brake torque applied when the output voltage of the speed error detector 200 is small. This is a volume that sets the voltage corresponding to .

The voltage set by VRla needs to be set smaller than the voltage set by VRlb.

FIG. 3 is a diagram for explaining the operating state of the reel drive mechanism shown in FIG. 2. The tape speed is kept constant because the winding side torque represented by the solid line increases linearly as the speed error value increases toward the negative side. The supply side torque shown by the broken line has a predetermined value set by VH2 as a boundary, and if it is larger than that, a larger torque is given, and if it is smaller than that (larger on the negative side), a smaller torque is given. It will be done. By adjusting VRla, the smaller torque value changes as shown by the arrow A in Figure 3, and by adjusting VRlb, the larger torque value changes as shown by the arrow B, thereby increasing VH2. By adjusting these values, the values of these boundaries change as shown by the arrow C in the figure.

FIG. 4 is a diagram showing a second embodiment of the reel drive mechanism according to the present invention. Only the portion corresponding to the speed error detector 200 to the changeover switches 301 and 302 in FIG. 2 is shown in FIG. OP amplifier 506 and resistor R1
and R2 are for inverting and amplifying the output of the speed error detector 200, and are used to obtain a brake torque that changes linearly with the value of the speed error. The volume VR2 is adjustable to set a voltage corresponding to the brake torque when the output of the speed error detector is 0, that is, corresponds to the target speed.

In the figure, the part surrounded by a broken line is a diode D1 in which the output voltage of the OP amplifier 506 is changed from the voltage set by the volume VRI in order to always ensure a brake torque higher than a predetermined value.
When the voltage is less than the voltage after subtracting the forward voltage drop,
This is a circuit to limit the value above that value, and the OP amplifier 5
04 constitutes a voltage follower circuit.

FIG. 5 is a diagram similar to that of FIG. 3 for explaining the operating state of the reel drive mechanism of FIG. 4.

The supply side torque represented by a broken line changes linearly with respect to the speed error value on the right side of the diagram, and is kept constant on the left side of the diagram. As the speed error increases toward the positive side, the brake torque increases linearly. Conversely, as the speed error increases, the brake torque decreases linearly, but it never decreases below a certain value.
By adjusting I, the limit value changes as shown by the arrow in FIG. 5A, and by adjusting VR2, the linearly changing portion changes up and down as shown by the arrow in B.

FIG. 6 shows an example in which the portion indicated by the broken line in FIG. 4 is mechanically realized. The brake plate 5 is arranged so as to prevent rotation of either the left or right reel depending on the feeding direction of the tape lO.
08 is in contact and a brake torque above a certain level is obtained.

〔Effect of the invention〕

As described above, according to the present invention, by changing the magnitude of the brake torque according to the value of the speed error,
It is possible to prevent tape sag and decrease in tape tension during deceleration and acceleration.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle configuration of the present invention, FIG. 2 is a diagram showing a first embodiment of the invention, FIG. 3 is a diagram for explaining the operation of the mechanism shown in FIG. 4 is a diagram showing a second embodiment of the invention, FIG. 5 is a diagram for explaining the operation of the mechanism shown in FIG. 4, and FIG. 6 is a diagram showing a third embodiment of the invention. , FIG. 7 is a diagram showing a conventional reel drive mechanism. In the figure, IO...tape, 121.122... reel, 143, 144... amplifier, 201.202... FG sensor.

Claims (1)

[Claims] 1. A driving torque applying means (14) for applying driving torque to a take-up reel (12) around which one end of the information recording tape (10) is wound; and the information recording tape (10). A brake torque applying means (18) for applying a brake torque to the supply reel (16) wound at the other end, and rotation of the take-up reel (12) or the supply reel (16) or both thereof. A speed error is calculated from the information obtained from the speed and the target rotational speed information, and the drive torque applying means (1
4), in which the brake torque application means (18) applies the brake according to the value of the speed error calculated by the speed error detection means (20). Brake torque variable means (50
) A reel drive mechanism characterized by comprising: 2. The brake torque variable means (50) includes a comparison means for comparing the magnitude of the speed error value with a predetermined value, and a predetermined value of the speed error according to the comparison result of the comparison means. 2. The reel drive mechanism according to claim 1, further comprising brake torque switching means for switching the brake torque value such that a larger brake torque value is selected if the value is larger than the value, and a smaller brake torque value is selected if the value is smaller than the value. 3. The brake torque variable means (50) is a means for linearly varying the brake torque so that the larger the speed error is with respect to the value of the speed error, the larger the brake torque is. 2. The reel drive mechanism according to claim 1, further comprising a limit means for limiting the value of to a predetermined value or more.