JP2928891B2 - Tape drive controller - Google Patents

Description

The present invention relates to a tape drive control device in a magnetic tape running system of a video tape recorder (hereinafter, referred to as a VTR), for example.

[Prior Art] FIG. 2 shows a schematic configuration diagram of a conventional tape drive control device such as a VTR.

In FIG. 2, 1 is a rotary head drum, 2 is a supply side reel, 3 is a take-up side reel, 4 is a magnetic tape, 5, 6
Is a tension detector for detecting the tape tension on the tape entrance side and the tape exit side with respect to the rotary head drum, respectively, and 18 is a speed detector for detecting the running speed of the tape.

In the above configuration, the magnetic tape 4 is wound from the supply reel 2 to the take-up reel 3 during fast-forward.
Reference numerals 17 and 14 denote supply-side and take-up-side reel motors for directly driving the axes of the supply-side reel 2 and the take-up-side reel 3, respectively. The tensions of the tapes on the supply side and the winding side are detected by tension detectors 5 and 6, respectively.

Outputs from the tension detectors 5 and 6 are input to a and b ends of a changeover switch 7. The changeover switch 7 is interlocked with changeover switches 10 and 11, which will be described later, and when the magnetic tape runs in the forward direction, that is, when the supply reel 2 sends out the tape and the take-up reel 3 winds the tape. The signal at the end a is selected, and when the tape is run in the reverse direction, the signal at the end b is selected.

The output from the changeover switch 7 is compared with a tension reference value 9 by a subtractor 8, and an error from the tension reference value is input to a terminal b of the changeover switch 10 and an terminal a of the changeover switch 11.

As described above, when the tape is caused to travel in the forward direction, the changeover switch selectively outputs the end a, so that the tension error signal from the subtractor 8 is input to the loop filter 15. Conversely, when running in the rewind direction,
As for the changeover switch, the end b is selected and input to the loop filter 12. The loop filters 12 and 15 respectively perform phase and gain compensation so that the servo loop operates stably. Outputs of the loop filters 12 and 15 are input to reel motor drivers 13 and 16, respectively, and the drivers 13 and 16 drive the reel motor.

The output of the speed detector 18 is output from the speed reference value 20 by the subtractor 19.
And the speed error is input to the terminal a of the changeover switch 10 and the terminal b of the changeover switch 11.

With the above configuration, the supply-side reel 2 is controlled such that the tension on the supply side becomes the reference tension value, and the winding-side reel 3 is controlled such that the tape runs at the reference speed, and changes the reference value. This allows the tape to be fed at a desired speed.

FIG. 3 shows a magnetic pattern on a tape of a general helical scan VTR. In the figure, 4a indicates the lower end of the tape, 4b indicates the upper end of the tape, and 4c indicates the video track recorded and reproduced by the head on the rotating drum. As shown by arrows in the drawing, if the tape and the head advance during normal reproduction, the hatched portion in the drawing comes into contact with the entrance where the head enters the tape, and in FIG. It is at a certain P position.

In general, a synchronization signal, an ID signal, and a clock signal for pulling in a PLL in the case of digital recording are recorded at a tape entrance portion indicated by oblique lines in FIG. These signals are signals that have an important meaning in the subsequent signal processing unit.
The synchronization signal indicates the vertical synchronization of the video or the position identification of the data. If this portion is missing, the vertical synchronization of the video is disturbed, resulting in an unsightly video.

As the ID signal, a signal that supports each function such as a recording mode and a time code of the tape is generally used.

Similarly, due to lack of digital recording, PLL
However, it cannot be pulled in promptly, it takes a long time to pull it in, and data is greatly lost or broken.

As described above, the information at the tape entrance is particularly important, and the omission of this part should be controlled so as to be avoided as much as possible.

[Problems to be Solved by the Invention] However, in the above-described conventional example, when the tape feeding direction is changed, the tension control loop and the speed control loop are switched between the supply side and the winding side, so that the state is temporarily reduced. Abnormally high or abnormally low tension may be applied to the tape, damaging the tape. Also,
At the time of rewinding and deceleration, the supply-side tension is reduced, and it may not be possible to read out the information at the tape entrance normally, thereby causing the above-described inconvenience of the reproduced image.

An object of the present invention is to provide a tape drive control device that solves the above problem, and further provides a tape drive control device that can hold a tension value near a drum at an appropriate value by a simple mechanism. The purpose is to:

[Means for Solving the Problems] In order to achieve the above object, a tape drive control device according to the present invention is characterized in that, in claim (1), a tape fed from a supply side reel is loaded on a head means and wound. Means for forming a tape path to be wound around a side reel; tension control means for controlling a tape tension before and after the head means in the tape path; tape running speed detecting means for detecting a running speed of the tape; Correction means for applying a predetermined weight to each of the tape tensions before and after the head means based on an output of the tape running speed detection means to correct the tension, and the correction means according to claim (2), The weight of the tape tension correction value before and after the head means is determined by the tape running load before and after the head means. It is configured so as to be determined based on this.

[Operation] According to the present invention, the tape speed error signal is divided at a predetermined ratio, and the divided signal is added to the tape tension reference value of the supply-side and winding-side tape tension control mechanism,
By providing an arithmetic unit for subtraction, the tape speed control is performed without changing the tape tension near the drum.

Embodiment An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a schematic diagram showing the most distinctive features at the time of rapid traverse in one embodiment of the present invention.

In FIG. 1, the same parts as those in the conventional example in FIG. 2 are indicated by the same reference numerals, and the description thereof is omitted here.

In FIG. 1, reference numerals 30 and 31 denote coefficient units, and a coefficient unit 27 applies a predetermined coefficient to a tape speed error signal obtained by comparing the tape speed information output from the tape running speed detector 18 with a tape reference speed. The multiplied value is divided and supplied to the supply-side and winding-side tension control systems at a predetermined division ratio n: m. Arithmetic units 24 and 26 perform addition and subtraction, respectively, and perform subtraction-based correction on the supply-side tension reference value 25 based on the divided signal to obtain a winding-side tension reference value.
It has the role of adding to 23 for correction. However, it should be added that the relationship between the supply side and the winding side and the addition and the subtraction are opposite when the tape is rewound. These are switched by a system controller circuit (not shown) together with the control of the tape running method.

Next, the operation of the tape speed control will be described with reference to the drawings.

The output from the tape speed detector 18 is compared with a speed reference value, that is, a target speed value 20 by a subtractor 19, and a speed error signal is output. Is sent to the coefficient unit 31 on the winding side. Weights in the coefficient units 30 and 31, respectively Is multiplied by the tape speed error signal between the supply side and the take-up side.
m: n. The supply side tension reference value 25 is subtracted by the subtracter 26 together with the divided tape speed error signal.
And the adder 24 corrects the winding-side tension reference value 23.

For example, when the tape running speed is lower than the target tape speed reference value 20, a tape running speed error signal is generated via the comparator 19 and the coefficient unit 27, and the coefficient units 30 and 31
The division into m: n is performed, and the tension reference value 25 on the supply side is set low and the tension reference value 23 on the winding side is set high by the arithmetic units 26 and 24, respectively. That is, the difference between the winding-side tension and the supply-side tension increases, and the tape running speed increases.

Next, a method of determining the speed error signal division ratio m: n will be described.

Generally, in order to obtain a stable head touch in a VTR, it is necessary that the tape tension near the drum be stable. For the sake of simplicity, consider the case where a fixed post is used for the tape guide.

Since the tape running load is caused by the friction phenomenon of the tape guide, when the tape tension at the entrance and exit of the fixed post is Tin, Tout, the winding angle is θ, and the friction coefficient is μ, Tout / Tin = exp (μ × θ) (1) Since the tape running system is formed of a plurality of tape guides, it is assumed that the tape tension of the drum is T _D , the tape tension at the tension detector 5 on the supply side is T _S, and the friction coefficient of the tape guide is the same. If the tape winding angle of the tape guide between the supply-side tension detector 5 and the drum is θ ₁ , θ ₂ ,..., Θ _n , T _D / T _S = Exp (μ × (θ ₁ + θ ₂ +... + Θ _k )) where φ ₁ = exp (μ × (θ ₁ + θ ₂ +... +)
θ _k )), T _D / T _S = φ ₁ (2) holds. Similarly, when the tape tension at the tension detector 6 on the winding side is T _T between the drum and the tension detector 6 on the winding side, T _T / T _D = exp (μ × (θ _{k + 1)} + Θ _{k + 2} + ... +
θ _{k + i} )) where φ ₂ = exp (μ × (θ _{k + 1} + θ _{k + 2} +... + θ)
_{k + i} )), T _T / T _D = φ ₂ (3) holds. Therefore, the amount of change in the tension T _D in the drum due to a change in the tape tension T _S, T _T at each tension detectors 5 and 6 is as follows.

ΔT _D = φ ₁ ΔT _S , ΔT _D = (1 / φ ₂ ) ΔT _T (4) Here, the fluctuation amounts ΔT _S and ΔT _T of the tape tension of the tension detectors 5 and 6 are determined by the speed control by m: n ΔT _S = {m / (m + n)} ΔV, ΔT _T = {− n / (m + n)}
ΔV (5) On the other hand, when the average of the fluctuations of both reel tensions is obtained from the equation (4), the amount of change in the tape tension at the drum is ΔT _D = ｛φ ₁ ΔT _S + (1 / φ ₂ ) ΔT _T ｝ / 2 Here, considering equation (5), ΔT _D = ΔV (mφ ₁ −n / φ ₂ ) / 2 (m + n) Assuming that there is no variation in tape tension at the drum,
Since ΔT _D = 0, mφ ₁ −n / φ ₂ = 0, and m and n are determined as m: n (1 / φ ₂ ): φ ₁ .

FIG. 4 is a schematic diagram showing an example of the variation of the tape tension on the drum when the tension is varied by the tape speed control, and is a schematic diagram showing the relationship between the tape tension and the tape traveling path. The horizontal axis indicates the tape running path, and the vertical axis indicates the tape tension value. FIG.
In the case where the drum is located substantially at the center of the tape path (the tape path is a target system and φ ₁ : φ ₂ = 1: 1 (showing a so-called M load method), FIG. In the case where the reel is offset to the supply side reel of the path (φ ₁ : φ
₂ = 1: 4, the so-called U-load system belongs to this case). The above coefficients m and n are set according to the ratio of the tape running load before and after the drum, that is, m: n = 1: 1 in FIG. By selecting = 1: 4, even if the tension reference value in the tension detector fluctuates, the tape tension near the drum does not fluctuate, and a stable tape running state can always be obtained.

[Effects of the Invention] As described above, the present invention divides a tape speed error signal at a predetermined ratio, and adds the divided signal to a tape tension reference value of a supply-side and winding-side tape tension control mechanism. The provision of the arithmetic unit for subtraction has an effect that even when the tape speed control is performed by operating the tape tension reference value, the head touch can be stably obtained without changing the tape tension near the drum.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a tape drive control device according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a conventional tape drive control device, and FIG. FIG. 4 is a schematic diagram showing a load change when the present invention is implemented. In the figure. 1: Drum 2: Supply reel 3: Take-up reel 4: Magnetic tape 5, 6: Tension detector 18: Travel speed detector 30, 31: Coefficient unit 24, 26: Computing unit 23, 25: Tension reference value

Claims (2)

(57) [Claims] 1. A means for forming a tape path for loading a tape fed from a supply reel into a head means and winding the tape to a take-up reel, and controlling a tape tension before and after the head means in the tape path. Tension control means, a tape running speed detecting means for detecting the running speed of the tape, and a tape weighting correction before and after the head means based on the output of the tape running speed detecting means. A tape drive control device comprising a correction unit. 2. The apparatus according to claim 1, wherein said correction means is configured to determine weighting of a tape tension correction value before and after said head means based on a tape running load before and after said head means. Characteristic tape drive control device.