JPH0421938B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a tape drive control device for a magnetic recording/reproducing device using a magnetic tape as a recording medium.

Conventional configuration and its problems Conventional cassette video tape recorder (hereinafter referred to as
FIG. 1 shows a schematic diagram of a tape drive control device for a VTR (VTR).

In FIG. 1, 1 indicates a tape cassette;
2 indicates a magnetic tape. 3 and 4 are reels on the supply side and take-up side of the tape cassette. Reference numerals 7 and 8 are supply side and take-up side reel motors. Reference numeral 9 denotes a rotating head cylinder, which is provided with a pair of rotating magnetic heads. Then, the magnetic tape 2 is wound around the rotating head cylinder 9 at an angle of about 180 degrees and is run, and the rotating magnetic head records the video signal so as to form a recording track oblique to the longitudinal direction of the magnetic tape. It is recorded and then played back. 10 is a capstan, 11 is a pinch roller, and magnetic tape 2
is transferred at a predetermined speed by the pressure bond between the capstan 10 and the pinch roller 11. 12 is a full width erase head, 13 is an audio erase head, 14
is the audio control head. 15
is a fixed torque generation circuit on the supply side, the output of which is input to the supply reel motor drive circuit 16, which drives the supply reel motor 7, generates a predetermined torque on the supply reel motor 7, and generates a fixed torque on the tape. It is controlled so that a predetermined tape tension is generated. On the other hand, on the take-up side, the output of the take-up side fixed torque generation circuit 17 is input to the take-up side reel motor drive circuit 18, and the output drives the take-up side reel motor 8. The torque is generated and the tape tension is controlled to occur.

According to the above conventional example, since a constant torque is generated in the supply reel motor, the torque fluctuation generated by the supply reel motor becomes a tape tension fluctuation, and the wah value of the audio signal reproduced from the audio head changes. The problem is that it doesn't get better.

Furthermore, as a conventional example that improves the stability of the tape running speed, the movable end of the brake band wound around the supply reel in a U-shape is connected between the fulcrum of the tension arm and the tape contact part. Some are equipped with a servo. In this tension servo, the tape contact part contacts the stretched tape,
When the tape is too tensioned (that is, when the tape tension is too high), the tape contacts the tape and displaces the movable end of the brake band, loosening the brake band on the supply reel and making it easier to unwind the tape. to control the tape tension in the direction of decreasing it. On the other hand, if the tape becomes too loose (i.e., the tape tension is too low), the tape abutting part will move in the direction of pushing the tape more, displacing the movable end of the brake band in the opposite direction, and tightening the brake band of the supply reel. control to increase the tape tension. The tension servo described above suppresses fluctuations in tape tension and stabilizes the running speed of the tape.

Furthermore, variations in tape tension due to changes in the tape winding diameter of the supply reel can be compensated for by changes in frictional force by changing the angle at which the tape is wrapped around the fixed pole in the cassette.
(Katsuya Yokoyama, "Introduction to Home VTR," published by Corona Publishing, 1981, etc.) In the conventional example improved as described above, the design reference value of the tape tension can be almost stably controlled (the value on the cylinder entry side). For example, 25~30gw)
However, it is not possible to remove so-called AC-like fluctuation components that fluctuate at a frequency of 20 Hz or less for a certain value among the above, and the wah value of the reproduced audio signal still does not improve. There was a problem.

OBJECTS OF THE INVENTION The present invention solves these conventional problems, and aims to improve the wah value of an audio signal during tape playback, which is caused by tape tension fluctuations.

Structure of the Invention The present invention detects tape tension fluctuations due to torque fluctuations of the supply side (or take-up side) reel motor with a tape tension detector, performs differential voltage amplification on the output, and further performs a limiter function. A tape drive control device that improves the wow value of an audio signal during tape playback by increasing the current width and controlling the supply side (or take-up side) reel motor current to reduce tape tension fluctuations. This is what we provide.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Figure 2 shows a cassette type device which is an embodiment of the present invention.
1 is a schematic configuration diagram of a tape drive control device of a VTR.

In FIG. 2, 1 indicates a tape cassette;
2 indicates a magnetic tape. 3 and 4 are reels on the supply side and take-up side of the tape cassette. Reference numerals 7 and 8 are supply side and take-up side reel motors. Reference numeral 9 denotes a rotating head cylinder, which is provided with a pair of rotating magnetic heads. Then, the magnetic tape 2 is wound around the rotating head cylinder 9 at an angle of about 180 degrees and is run, and the rotating magnetic head records the video signal so as to form a recording track oblique to the longitudinal direction. It is also made to be regenerated. 10 is a capstan, 11 is a pinch roller, and the magnetic tape 2 is transferred at a predetermined speed by pressure contact between the capstan 10 and the pinch roller 11. 12 is a full width erase head;
13 is an audio erase head, and 14 is an audio control head. Reference numeral 21 denotes a tension sensor post, which is biased in the direction of arrow 22 by a spring body (not shown), and the magnetic tape 2
The position of the tension sensor post 21 is changed by the tape tension, and when the tape tension is small, it moves in the direction of arrow 22, and when the tape tension is large, it moves in the direction of arrow 23. A position signal output corresponding to the movement position of the tension sensor post 21 is input to a conversion circuit 24, which converts the mechanical position signal into an electrical signal. FIG. 3 shows one embodiment of the conversion circuit 24. A current is applied to the light emitting diode 32 from the power supply V _CC through the resistor 31 to cause it to emit light, and a light receiving transistor 34 is connected from the power supply V _CC through the resistor 33 to cause the light emitting diode 32 to emit light in response to changes in the position of the tension sensor post 21. By moving the plate 35 and controlling the amount of light emitted from the light emitting diode 32 reaching the base of the light receiving transistor 34, a change in the mechanical position of the tension sensor post is converted into an electrical signal. Figure 4 shows the electrical signal output characteristics with respect to changes in the position of the tension sensor post. The output of the conversion circuit 24 is input to a voltage amplification circuit 25. Voltage amplification circuit 25
uses an amplifier including a filter circuit for use as a means for adjusting the gain and phase characteristics that determine the response characteristics of the entire tape tension control system. Fifth
An embodiment of the voltage amplification circuit 25 is shown in the figure. When the input signal is input, the series circuit of the resistor R ₂ 42 and the capacitor C ₁ 43 and the parallel circuit of the resistor R ₁ 41 become the impedance on the input circuit side, and the resistor R ₄ 45 and the capacitor C ₂ 4
The operational amplifier 4 is connected so that the series circuit of 6 and the parallel circuit of the resistor R ₃ 44 becomes the impedance on the feedback circuit side.
7, and a constant voltage source 48 is connected to the positive input terminal. FIG. 6 shows the frequency characteristics of the voltage amplification circuit 25 shown in FIG. The amplification degree A _o of the voltage amplification circuit 25 is An=R ₃・1+SC ₂ R ₄ /1+SC ₂ (R ₃ +R ₄ )/R ₁・1+SC
₁ R ₂ /1 + SC ₁ (R ₁ + R ₂ )...(1) (S: Laplace operator). The degree of amplification A _o1 in the DC region is A _o1 = −R ₃ /R ₁ (2). The degree of amplification A _o2 in the midrange region is A _o2 = −R ₃ /R ₁ ·R ₂ /R ₁ +R ₂ (3). The degree of amplification A _o3 in the high frequency region is A _o3 =-R ₃ · R ₄ /R ₃ +R ₄ /R ₁ ·R ₂ /R ₁ +R ₂ (4). The output of the voltage amplification circuit 25 is input to a current amplification circuit 26, which is configured to control the supply side reel motor current according to input voltage changes, and is a limiter circuit that limits the maximum value of the reel motor current. have. FIG. 7 shows an embodiment of the current amplification circuit 26. The input voltage is input to a differential amplifier composed of transistors 51 and 52,
This is achieved by comparing the reference voltage V _REF 53 and controlling the current flowing through the collector of the transistor 51 out of the current value I ₀ of the constant current source 54 . The current value I ₀ of this constant current source 54 is determined as follows. The supply side reel motor generated torque _s is _s = K _Ts · I _s ... (5) K _Ts : Supply side reel motor torque generation constant, I _s : Supply side reel motor current. On the other hand, if the tape tension T _s at the outlet from the supply reel 5 is the radius R _s of the tape wound on the supply reel 5, then T _s = _s /R _s (6). Therefore, if the maximum radius of the tape wound on the supply reel 5 is R _{s nax} , then I ₀ = k・R _{s nax}・T _s /K _Ts ……(7) (k: constant of proportionality) determined. The output of the current amplification circuit 26 is input to the supply reel motor drive circuit 16, which drives the supply reel motor 7 to generate a predetermined back tension on the magnetic tape 2. On the other hand, on the take-up side, the output of the take-up side fixed torque generation circuit 17 is input to the take-up side reel motor drive circuit 18, and the output drives the take-up side reel motor 8, and the take-up side reel motor 8 is given a predetermined value. The torque is generated and the tape tension is controlled to occur.

Effects of the Invention As described above, according to the present invention, by using the tape tension sensor, the tape tension value can be controlled to a constant value with so-called DC fluctuation components zero, and the reel motor It is possible to reduce the so-called alternating-current fluctuation component of the tape tension value due to the trick fluctuation occurring from the fixed head, and it is possible to improve the wah value of the reproduced audio signal from the fixed head. In addition, by limiting the maximum value of the reel motor current, the tape tension control loop can be pulled in smoothly at startup, and tape protection can be realized to prevent abnormally large tape tension from occurring on the tape. be.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional tape drive control device for a cassette-type VTR, FIG. 2 is a block diagram of a tape drive control device for a cassette-type VTR according to an embodiment of the present invention, and FIG. 3 is a diagram of the conversion in FIG. An electric circuit diagram showing an example of the circuit, FIG. 4 is an input/output characteristic diagram of the conversion circuit in FIG. 3, and FIG. 5 is an electric circuit diagram showing an example of the voltage amplification circuit in FIG. 2.
Fig. 6 is an input/output characteristic diagram in Fig. 5, Fig. 7 is an electric circuit diagram showing an example of the current amplification circuit in Fig. 2, and Fig. 8 is an input/output diagram of the current amplification circuit in Fig. 7. It is a characteristic diagram. 1... Tape cassette, 2... Magnetic tape, 3
...Supply side reel, 4...Take-up side reel, 7...
Supply side reel motor, 8... Winding side reel motor, 9... Rotating head cylinder, 10... Capstan, 11... Pinch roller, 12... Full width erasing head, 13... Audio erasing head, 14
...Audio control head, 15...
Supply side fixed torque generation circuit, 16... Supply side reel motor drive circuit, 17... Winding side fixed torque generation circuit, 18... Winding side reel motor drive circuit,
21...Tension sensor post, 22, 23
...Arrow, 24...Conversion circuit, 25...Voltage amplification circuit, 26...Current amplification circuit.

Claims (1)

[Scope of Claims] 1. A magnetic tape drive means for transporting a magnetic tape by pressure bonding between a capstan shaft and a pinch roller, a supply reel for supplying the magnetic tape, a take-up reel for winding the magnetic tape, and the supply side. A supply reel motor that drives the reel, a take-up reel motor that drives the take-up reel, and a tape tension detection means between the capstan shaft and the supply (or take-up) reel, The input characteristics of the filter circuit means which inputs the output of the tension detection means and the filter circuit means during normal tape running are V _put /V _io =K・1+BS/1+AS (However, A, B, and K are constants, and S is a Laplace operator), and a current amplification means receives the output of the filter circuit means as an input, and a current is caused to flow through the supply side (or take-up side) reel motor according to the output of the current amplification means, and the supply side ( or take-up side) A tape drive control device characterized by being provided with a current limiter circuit that limits the maximum value of a reel motor. 2 The maximum value of the reel motor current is determined by the maximum winding diameter of the tape wound on the supply side (or take-up side) reel, the torque generation constant of the reel motor, and the required tape tension value on the supply side (or take-up side). 2. The tape drive control device according to claim 1, wherein the tape drive control device is determined by: