RU1780109C - Tape-transport mechanism of video tape recorder - Google Patents

Abstract

Usage: the device relates to magnetic recording and can be used in apparatuses for recording information line by line, in particular in VCRs. SUMMARY OF THE INVENTION; the operation of the device is based on the analysis of the constant component of the signal of block 17, that is, the voltage at the output of the filter 22. If the tape in the VCR has moved exactly the step of the recording line, the output signal of the filter will be zero, otherwise, the voltage at the output of the filter has the + sign when the pull amount is larger, or the "-" sign in the opposite situation. The signal is evaluated by a comparator zone, consisting of thresholds of comparators 23 and 24. If the signal exceeds one of the two thresholds of the estimated zone, the device decides to correct the length of the discrete displacement following the just perfect one. Corrections! is carried out by connecting multiplexer 21 to one of three delLafters to block 13. Information on the magnitude and sign of correction is contained in each of the two decoders 19 and 20. The first decoder 12 contains information about the calculated displacement corresponding to the case when the signal at the output of filter 22 is to zero. 13-21-12-11-1-2-3-4-5-6-5-8-9, 14-9, 8-10-1, 15-16-2, 15-11, 11-19- 21, 21-23-22-17, 21-24-22, 17-18. 2 ill. | 1L («..nLN / puf-i (• c» Jl ^ '^ Jr: r - "^ o

Description

The invention relates to magnetic recording and can be used in apparatuses that record information line by line, in particular in a VCR.

A tape speed control device is known which comprises a driving motor that rotates the drive shaft, and also drives the pickup and pickup coils through temporary or friction gears both during recording or during image playback, and when the tape 1 is rewound.

A disadvantage of this device is the low stability of the belt pulling speed due to the fact that the load of the drive shaft of the engine is unstable due to large fluctuations in the torque on the shaft of the receiving and feeding units and time-varying losses.

The closest in technical essence and the achieved result is a tape drive device for a VCR containing an automatic tape speed control unit, the output of which is connected to the first input of the first summing unit, the output of which through the first power amplifier is connected to a driving motor, the shaft of which rotates drives a belt moving from the falling unit to the receiving unit. A tachometer is mounted on the shaft, consisting of a movable and stationary gears coaxially located Enets, In the groove of the fixed ring gear there is a winding connected to the output of the second summing unit and simultaneously with the input of the unit through the former. The output of the driver is also connected to the counting input of the counter, which is bit related to the decoder, the output of which through the second power amplifier is connected to the first input of the summing unit, the second input of which is connected to the current source. The pulse sensor is connected to the installation input of the counter and to the second input of the first summing block through the shaper pulse duration 2.

A disadvantage of the described device is the relatively low accuracy of its operation, due to the fact that at the time of braking, the motor moves inertia, as a result of which, with a large number of step movements of the belt, the motor error accumulates and can exceed the step of the recording line.

The aim of the invention is to improve the accuracy of the work.

This goal is achieved in that the device containing the unit for automatically adjusting the speed of the tape through the first summing unit and amplifier

. power connected to a driving motor equipped with a rotational speed sensor including a stationary crown and a movable crown connected to the shaft of the driving motor, coaxially

0 located relative to each other, and the stationary crown is provided with an annular groove in which the winding is located, connected to the output of the second summing unit and simultaneously with the input of the unit through a shaper, the output of which is also connected to the counter input of the counter, which is bit related to the decoder, the first input the second summing unit connected to the output of the second

0 power amplifier, and the second input to the current source, a pulse sensor connected to the installation input of the counter and to the second input of the first summing block through the pulse width former, the auto tracking unit connected to the movable magnetic head by the output, further comprises a second and third decoders, also bottom connected to the meter, multiplexer,

0, the first input of which is connected to the output of the decoder, the output of the multiplexer is connected to the input of the second power amplifier, the output of the autotracking unit is connected through a low-pass filter to B. OTsZ.-A of comparators, the outputs of which are connected to the control inputs of the multiplexer.

Figure 1 - shows a structural diagram of the proposed device; in Fig. 2 voltage diagrams, and in Figs. 2a-0, the output signal of the pulse sensor, in Fig. 26 - the output signal of the pulse width generator, in Fig. 2c - p counter pulses, in Fig. 2d - (nk) pulse counts , in FIG. 2d (yyyy |) pulse counter.

5 construction contains 5lsk i machine

ленты belt speed control (САР-СЛ), through the first summing unit 2 and power amplifier 3 connected to the driving motor 4, ;; 1-; ab: 0 0 m for the sensor; about t bi r, p i n n and l (tachometer), 1 which connects to the stationary crown 5 and the movable crown 6 connected to the E} al of the driving engine, are coaxially located relative to each other. They are stationary and; the zenith is provided with an annular groove 7, in which the winding 8 is located, connected to the output of the second summing unit 9 and simultaneously with the input of the unit 1 through) rm and r. T he 10.

the output of which is also connected to the counting input of the counter 11, which is bit related to the decoder 12, the first input of the second summing unit 9 is connected to the output of the second power amplifier 13, and the second input to the current source 14. The pulse sensor 15 is connected to the installation input of the counter 11 and to the second input of the first summing unit 2 through a pulse width former 16. The device has an autotracking unit 17 loaded on a movable piezoelectric head 18. The decoders 19 and 20 are bitwise connected to the counter 11 in the same way as the decoder 12, the multiplexer 21, three information inputs of which are connected to the outputs of the decoders 12, 19 and 20, each input with one of the outputs of the above decoders, respectively, and the output with the input of the second power amplifier 13, the output of the auto tracking unit 17 is connected through a low-pass filter 22 to the inputs of the comparators 23 and 24, the outputs of which are connected to the control inputs and the multiplexer 21.

The device operates as follows.

If the VCR is in recording or nominal playback mode, unit 1 (CAP-SL) generates an output voltage that changes so that the speed of engine 4 is kept stable. Information on the frequency of rotation of the engine 4 is received from the tachometer, the winding 8 of which generates a constant magnetically movable force due to the action of the current source 14. The number of teeth of the movable 6 and the stationary 5 rings is chosen the same. During the rotation of the engine, the magnetic conductivity of the working gap of the tachometer changes, as a result of which the flux linkage of the winding 8 changes, in which EMF pulses are generated by the block 10 (comparator). Their frequency is proportional to the engine speed.

When moving the tape step by step, the operation of the device is organized as follows.

There is no voltage at the output of unit 1. The pulse sensor 15 generates a short single pulse (figa) when you switch the toggle switch or any other switching device. This pulse sets the counter 11 to the zero state and simultaneously enters the block 16 forming the duration (the latter can be implemented on

base odionibrator). Impu / and-s on w.;, Block 16 is depicted in Fig.26. Under the system of this impulse, the power of the shaft of the motor A and the magnetic leite |. | (not shown). In this case, pulses from the engine tachometer to the counter 11 begin to arrive (Fig. 2c), the frequency of which is proportional to the instantaneous frequency of rotation of the engine 4. In order for the tape to move a distance equal to the pitch of the recording lines. It is necessary to rotate the drive shaft of the engine each time the tape is pulled 4 at the same angle a, and the same number of pulses p must also enter the counter. However, in practice, after the counter 11 sets the number of pulses p, an electrical signal is applied to the winding 8 and braking occurs motor shaft 4, which by inertia or

due to the instantaneous increase in current in the winding 8, it is also rotated by a certain additional angle Da (the motor can also be rotated by an angle a - Aa due to errors in the formation of tachometer pulses). The latter can accumulate with a large number of tape pulls (steps) and exceed the angle a, which is unacceptable under the operating conditions of the VCR.

Therefore, in the proposed device

three decoders 12, 19 and 20 are provided, the output of which is a signal in those cases when the number of pulses in the counter, 11, (decoder 12),

several units, for example, two or three (decoder 19), and several units (decoder 20).

The control of the decoders depends on the constant component of the signal of block 17, that is, the voltage at the output of filter 22. As you know, if the tape in the video recorder has advanced exactly the step of the recording line, then block 17 can be configured so that the output signal of the filter is zero otherwise, the voltage at the output of the filter has a + sign when the pull amount is larger, or a sign in the opposite situation. Thresholds for comparators 23 and 24

are selected in such a way (these thresholds can be selected arbitrarily) that at a voltage at the output of filter 22 close to zero, a logic 0 voltage is present at the outputs of both comparators.

If the output voltage of the filter 22 is positive, then the output of the comparator 23 is logical, and the output of the comparator 24 is logic 0. When the output voltage of the filter 22 is negative

the reverse: at the output of the comparator 23, logical 0. and at the output of the comparator 24, logical 1.

Depending on the code at the output of the comparators, using the multiplexer 21, the output of one of the three decoders 12.19 or 20 is connected to the power amplifier 13.

If the engine has turned through an angle a when the signals of sensor 15 appear, as evidenced by the zero level (or close to zero) of the output voltage of block 22, then decoder 12 is connected to block 13 after n pulses are written into the counter (Fig.2c) )

If the engine has rotated through the angle a + Ad, then in the next step the engine should, compensating for the error Yes, make a rotation by the angle a А “, therefore, using the comparators 23 and 24 and the multiplexer 21, the decoder 19 is connected to the block 13 after the counter is nk pulses were accumulated (FIG. 2d), where k is the number of correction pulses. In the case when the engine 15 is turned at an angle α when the sensor 15 is started, decoder 20 is connected to block 13 when the meter enters the number n + k (FIG. 2e ) and the next step advancement of the tape is achieved by turning the motor shaft to approximately equal to the angle a. -B Yes, i.e. the rotation error is compensated.

Claims (1)

SUMMARY OF THE INVENTION A tape drive device for a VCR, comprising an automatic tape speed control unit, through a first summing unit and a power amplifier connected to a driven motor equipped with a speed sensor including a movable a crown connected to the shaft of the driving motor and a stationary crown coaxially located relative to each other, the stationary crown being provided with an annular pazdm in which the winding is located, connected to the unit for automatically controlling the speed of the tape through a former, the output of which is connected to the counter input of the counter, the installation input which is connected to the sensor and through the pulse width former - with the second input of the summing unit, and the outputs are bit-wired to the first decoder, the power amplifier and in a second summing unit, its second input coupled to a current source connected to the input of the coil and, auto tracking unit, connected to the output of the moving magnetic head ,, exc ichayuschees in that, for the purpose To increase the accuracy of work, it introduced the second and third decoders, bitwise connected to the counter, the first and second comparators, a multiplexer, and the output of the auto tracking unit is connected through a low-pass filter to the inputs of the comparators, the outputs of which are connected to the control inputs of the multiplexer, the switching inputs of which are connected to the outputs of all decoders, and the output connected to a power amplifier. fPi / g. 2.