JPS6045965A - Control system of tape travelling speed of video tape recorder - Google Patents

Abstract

PURPOSE:To control the tape traveling speed of a VTR without using a timer roller by using tacho signals from tachometers fitted to both reels. CONSTITUTION:Pulses outputted from pulse generators 23, 24 in accordance with the timing of tacho pulses from the tachometers 15, 16 fitted to feeding and winding reel motors 13, 14 respectively are counted by counters 31, 32 and the counted values are added as outputs corresponding to the rotational frequency of the reels by an adder 39. The added value corresponding to the tape traveling speed is D/A converted, and as the result of comparison of the converted analog signal with a reference voltage, an error voltage is generated from an error voltage amplifier 41 and the feedback of a motor 14 is controlled to fix the tape speed. Thus, the tape traveling speed of the VTR can be controlled without using a timer roller and increasing the size of the constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a tape running speed control system in Vi''l (using a cassette tape).

(Prior art and its problems) Figure 1 shows a V i" It using a cassette tape.
A general example of a fast-forward mode in which tape running is driven by IJ-rumoque using a tape running speed control device with six steps is shown.

As shown in the figure, conventionally, a so-called timer roller whose rotation speed changes in proportion to the tape running speed is used as a signal detection means to keep the tape running speed constant.
I' A Cl l signal 4 is taken out by the tachometer 3 which is digitized by IIR (=1) on this timer roller 2.
A, Cl-1 signal 4 is amplified and waveform shaped by TACHAMP 5 and sent to frequency discriminator 6. Pictured).

This frequency discriminator 6 detects the error voltage according to the frequency change of the 'l' A CI 1 signal. 11. Tape.

1 and the timer roller 2 are ignored (to the extent of slippage) (therefore, an error voltage proportional to the running speed of the tape is obtained at the output of the frequency discriminator 6. This error voltage is amplified by the error voltage amplifier 7. Thereafter, it passes through the motor drive AMP 8 and is supplied to the take-up reel motor 9.

On the other hand, in order to generate a constant holdback torque for the reel motor on the supply side, the DC voltage from the holdback voltage generator 10 is supplied to the supply reel motor 12 via the motor drive amplifier 11 in order to generate a constant holdback torque during the fast-forward mode. Apply the necessary bold back torque to bring the tape tension to a predetermined value.

In other words, conventionally, the timer roller is installed because an i'' signal proportional to the tape running speed is required as a clock pulse for an electronic timer that is installed to know the running time of the tape. Generally, the tape speed can be kept constant by controlling the rotational speed of the reel motor so that the frequency of the timer 1'' becomes a constant value. In this case, the timer roller and tachometer are connected to the device 1ifi.
Since space is required for this purpose, the tape transport portion of the V i' LL becomes thick. Therefore, in 9% of the VTlts, the timer roller is omitted in order to reduce the size even slightly.

Therefore, without a timer roller like this, VT
With R, it is impossible to control the tape running speed using conventional methods.

(Purpose) This invention is a tape running speed control device for a VTR that uses cassette tapes, which can be used to control the speed of tape running by installing tachometers on the supply reel and take-up reel even if the timer roller is not installed. By using the TACII signal, the tape running speed can be kept almost constant.

(Example) An embodiment of the present invention will be explained below with reference to FIG.

The TACI+ signal 17.18, which is 11+r by the tachometer 15.16 attached to the supply reel motor 13 and the take-up reel motor 14, is the TACHAMP 19.2.
0 and 11 respectively. be provided. i'AcHAMP1
The output of 9.20 is a rectangular wave signal as shown in FIG. 3 ta+K. The T A CH signals 21.22 are fed to pulse generators 23.24, respectively (FIG. 3tb), tc
) Pulses 25 to 28 that occur at the timing shown in
is obtained. The pulses 27, 28 shown in FIG. 3 tc) are fed to the digital counters 31, 32, respectively, and the pulses 25, 26 shown in FIG. 3 tb) are fed to the launch circuit 35, 36. On the other hand, the signal 30 obtained by the clock pulse generator 29 is transmitted to the counter 31.
32 clock pulse inputs, this operation
As shown in Figure td), the period-side numerical value of the pulse width of the reset pulses 27 and 28 is a value of 0.

Next, counting is started from the time when the reset period ends, and the period until the next reset pulse is the counting period. The count contents of counters 31 and 32 are stored by latch circuits 35 and 36. That is, the argument value at the latch timing is stored as shown in FIG. 3(d).

Therefore, this operation is 1 of T A CH signal 21.22
The clock pulses are counted and stored in the period f7). In addition, in the two embodiments, the counter 31.3
2 uses its own binary counter (81), so 33.34 is also an 8-bit binary number. Latch circuit 35.
The divisor values of counters 31 and 32 stored by 36 are respectively supplied to a digital full adder 39 and the two word values are added.

Here, V is used to drive the tape by the reel motor.
Taking the TR fast forward mode as an example, the relationship between the tape winding diameter and the reel rotation speed changes as shown in FIG. 4, assuming that the tape running speed during tape fast forwarding is constant. The adder 39 adds the count value 'l' in FIG. 4 and the count value T2, and the value remains almost constant even if the tape winding diameter changes. The binary number (m is 1) added by the adder 39
)-A converter 40, and after being compared with a reference voltage, an error voltage amplifier 41. The signal is supplied to the take-up reel motor 14 via the Tanabata drive amplifier 42.

Therefore, the number of revolutions of the take-up reel motor 4 is controlled so that the sum of the number of revolutions of the take-up reel and the number of revolutions of the supply reel becomes a certain reference value. As a result, the tape running speed remains approximately constant. The supply reel motor 13 is supplied with a DC voltage obtained by a voltage generator 43 via a motor drive amplifier in order to maintain a constant tape tension during fast forwarding.

Note that the above explanation is for the example of the fast forward mode, but in the case of the 1 rewind mode, the switch 45, 46
By switching, the tape running speed can be similarly controlled to be constant.

(Effects) According to the present invention, the timer roller is not required because the reel 'I'AC1 signal is used instead of the timer '1' AC1-1 signal as the feed bank signal necessary to control the tape running speed. This is advantageous in terms of reducing the size of the VTR.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a conventional tape speed control system in fast-forward mode, Fig. 2 is a system diagram showing an embodiment of the present invention, Fig. 3 is an operation waveform diagram of the present invention, and Fig. 4 is a tape winding diameter. It is a relationship diagram between and reel rotation speed. 13: Supply reel motor, 14: Take-up reel motor. 15, 16: Tach Make, 23.24: Pulse Generator, 27.28: Recenotoharus, 29: Chronok Pulse Generator, 31° 32: Counter, : 35, 36:
Lanochi circuit, 39: Adder. 40: D-A converter, 41: Error voltage m width amplifier, 42: Motor drive amplifier.

Claims (1)

[Claims] In a VTR that uses a cassette tape and supplies a constant DC voltage for applying hold bank torque to the tape supply reel motor, a tachometer is installed on the tape supply reel motor and the tape take-up reel motor. Attach it and take out the two 'I' A CH signals, and sequentially count the clock pulses in one cycle period of the two 'I' ACH signals using a digital frequency discriminator consisting of a clock pulse generator, counter and latch circuit. and remember the argument value. Note 1. A digital adder adds the two numbers, converts the added value into a DC signal using a D-A converter, compares it with a reference voltage, and winds the tape so that the difference voltage is constant. Vi'R's tape running speed control method is characterized in that it controls the take-side reel motor.