JPS60115042A - Control system of magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain the common use of a reference voltage with motor drive circuits having different control objects by having a fixed relation between a trapezoidal wave signal for control of revolution of a video head and another trapezoidal wave signal for control of tape speed. CONSTITUTION:A rotary head motor 33 is driven by a motor drive circuit 32 of a control system 41, and the revolving state of the motor 33 is detected by a detector 34 and fed to a wave detector 35. The detector 35 obtains the DC wave detection output and supplies it to the other input terminal of the circuit 32. Thus the revolving speed of the motor 33 is controlled to a target level. A control system 42 controls the tape speed, and a motor drive circuit 36 drives a reel drive motor 37. The control signals are recorded on a tape 38 which is driven via reels and then detected by a head 39 to be supplied to a wave detector 40. Thus the motor 37 is controlled to maintain the tape speed at a desired level. In such a way, a fixed relation is secured between two trapezoidal wave signals. Thus the reference voltage of the drive circuit can be used in common.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a control system for a magnetic recording and reproducing apparatus, and is an improvement of a control circuit that controls tape fast forwarding and rewinding functions.

[Technical background of the invention]

There is a video tape recorder (hereinafter referred to as a VTR) that is capable of fast-forwarding and rewinding a tape. In this type of VTR, a control pulse recorded on the tape is detected so that the tape speed is kept at a certain speed, and a reel motor is controlled to set the frequency to a desired frequency. The rotary video head motor is also controlled so that the relative speed between the tape track and video track is the desired speed.

FIG. 1 shows a control system for controlling the relative speed of tape and video. In FIG. 1, a switch 1 is a switch that selects either the reference voltage (RgFJ) or (RgF 2 ) and inputs it to one input terminal of the motor drive circuit 12. The motor drive circuit J2 is a circuit that drives the rotary rotor motor J3. The rotation status of the rotary gear motor J3 is detected by a rotation detector 14, and a rotation detection pulse PI whose frequency and phase vary depending on the rotation speed is input to a detector 15. This detector 15 detects the frequency and phase of the rotation detection pulse PI,
The DC detection output is input to the other input terminal of the motor drive circuit J2.

Switch 1 is set when the VTR is in fast forward playback mode.
It is switched to select the reference voltage REF J and select the reference voltage RgF 2 during high-speed reverse playback. The motor drive circuit 2 controls the rotational speed of the motor 3 so that the relationship between the detected voltage and the reference voltage REF 7 or REF 2 is always maintained constant.

In the above control system, the reference voltage is switched between fast-forward playback and high-speed playback because the inclination direction of the recording track recorded on the tape is relative to the rotational direction of the video head. There is a difference between forward feeding and reverse feeding.
This is because it is necessary to greatly change the speed of the rotating video.

FIG. 2 is a control system for maintaining constant tape speed.

The switch slope is set to the reference voltage RE when in fast forward playback mode.
F 3 is selected, and the reference voltage REF 4 is selected and applied to one input terminal of the motor drive circuit 17 in the high-speed reverse regeneration mode. A motor drive circuit 17 drives a reel drive motor 18. When the reel is driven by the reel drive motor 18, the tape 9 is fast forwarded or fast reversed. On this tape J9, a control track is recorded on a control track for each frame, and this control file is fed to the control at Pff01/ml. The detection pulse P2 detected by this control head 20 is
The signal is input to detector 2. This detector 2 detects the frequency and phase of the detection pulse P2, and inputs the DC detection output to the other input terminal of the motor drive circuit 2. Thereby, the motor drive circuit J7 controls the rotational speed of the reel drive motor J8 so that the relationship between the detected voltage and the reference voltage RBF 3 or iF 4 is always maintained constant.

In the above control system, the reference voltage is switched between fast-forward playback and high-speed reverse playback depending on whether the rotational speed of the rotating video head is fast-forward or high-speed reverse playback. This is because tape speeds have to be changed accordingly.

Figure 3 shows the 11. This is a signal waveform for explaining the basic operation of the speed detection system used in the control system shown in FIG. 2. The speed detection signal 3a shown in FIG. 3 corresponds to the detection signals PI and P2. Further, the trapezoidal wave signal 3b is a signal generated inside the detector 5°2. The trapezoidal wave signal 3b rises at the first pulse a, and gradually falls by the time the next pulse a2 arrives, repeating such changes.

Therefore, at the timing of the signal a2, the trapezoidal wave signal 3b
By sampling and holding the slope part of , an average DC voltage proportional to the period of Noculus a2 can be obtained. Normally, when the period of the pulse a2 reaches the phase position t1 of the trapezoidal wave signal 3b, the average voltage is set to be equal to the reference voltage, and this is set as the control target value.

[Problems with background technology]

During fast-forward playback and high-speed reverse playback of a VTR, both control systems shown in FIGS. 1 and 2 are operated simultaneously. Therefore, a total of four types of reference voltage power supplies are required for setting the control target value. Furthermore, since strict accuracy is required for these reference voltages, adjustment may be necessary in some cases, leading to an increase in the number of parts and an increase in price.

[Purpose of the invention]

This invention was made in view of the above-mentioned circumstances, and is a fast-forwarding system necessary for a control system that stably controls the relative speed between a tape and a video tape P, and a control system that maintains a constant tape speed. It is an object of the present invention to provide a control system for a recording and reproducing apparatus in which a reference voltage power source in a reproduction mode and a reference voltage power source in a high-speed transmission reproduction mode can be used in common in each system.

[Summary of the invention]

This invention applies equation (8), which will be described later, to a signal corresponding to the trapezoidal wave 4M generated in the detectors 35 and 40 as shown in FIG.

The above objective is achieved by establishing equation (9).

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

First, to explain the basic principle of this invention, in this invention, a certain relationship is created between the trapezoidal wave signals generated in each control system during fast forward playback and high speed reverse playback. It is intended to achieve the desired purpose.

FIG. 4 shows a trapezoidal wave signal generated by a detector detecting a detection pulse in a system for controlling a rotating video rad motor in order to maintain the relative speed of the tape and video head at a desired speed. There is.

First, when playing fast-forward and high-speed reverse playback, set the control/base pulse frequency to fcTL, and set the rotational speed of the video head to f.
If D and the ratio is N, then 'CTL = "/D
... (1) holds true.

In FIG. 4, m is the number of detection pulses P1 obtained during one rotation of the rotating video head. Also, ■, (c),
(2) and (R) are reference voltage values, so-called target values, during fast-forward playback and high-speed reverse playback, respectively.

Here Chi, 'VBC), Vl(R), fD(.)
: Number of rotations of the video head during fast forwarding 'D(R): Number of revolutions ΔT of the video head during high speed reverse playback, ; Slope time To of the trapezoidal wave signal, : Measurement start, constant trapezoidal wave signal The time from 9 o'clock to the start of the slope section is the trapezoidal wave signal amplitude.

FIG. 5 shows a trapezoidal wave signal generated by a detector in a control system to maintain a constant tape speed at a desired speed. In the figure, v2(C) l ■
2(R) is a reference voltage value, a so-called target value, at the time of fast-forward playback and high-speed reverse playback, respectively.

Here -■2cc)lv2(R)c, fCTL(C); Fast forward') Time (D Control pulse frequency fCTL(R); Control pulse frequency during high-speed reverse playback ΔT2: Slope time of trapezoidal wave signal T02: Time from start of measurement to start of inclination ■A: Trapezoidal wave signal amplitude.

Next, by substituting equation (1) into equations (4) and (5), we get the following.

Here, the relationship m'ΔT=N-ΔT2・(8) m-To,=N-T02...(9) is established between the trapezoidal wave signal in FIG. 4 and the trapezoidal wave signal in FIG. If you have it, ■t(c) = v2(c) Vfu(R) : ■2(R)@Tsumashi, create the relationship between equations (8) and (9) between the trapezoidal wave signals. By doing so, it is possible to share a reference voltage source used in each control system that controls different objects.

Figure 6 shows a control system for a VTR configured based on the above principle. Switch 3 selects the reference voltage REF (A) during fast forward playback of the VTR, and selects the reference voltage REF (A) during fast reverse playback of the VTR. Is base II! Select voltage REF(B). The output of the switch 3 is the motor drive circuit 32. ．． 36 input terminals. 41 is a first control system that controls the relative speed of the tape and video head 9;
2 is a second control system for keeping the tape speed constant.

The explanation will be given from the first control system 4 side. The motor drive circuit 32 drives the rad motor 33 into rotation. The rotation status of the rotary rotor motor 33 is detected by a rotation detector 34, and the detected f-lus P1 is input to a wave detector 35. This detector 35 is constructed by the method explained in FIG.
A DC detection output is obtained and applied to the other input terminal of the motor drive circuit 32. As a result, the rotational speed of the rotary head motor and the rotational speed of the two-way video head are as follows.
Controlled to target speed.

The second control system 42 controls the tape speed, and the motor drive circuit 36 controls the reel drive motor 37.
drive. A control signal is recorded on a tape 38 that is run via a reel by a reel drive motor 37. The control signal is detected by the control head 39, and its detection/4' pulse is
The signal is input to the detector 40. Also in this detector 40,
A DC detection output is obtained by the method explained in FIG. 3, and is applied to the other input terminal of the motor drive circuit 36. Thereby, the reel drive motor 37 is controlled to maintain the tape speed at a desired speed.

However, it goes without saying that the relationship as explained in FIGS. 4 and 5 is established between the trapezoidal wave signals generated by the detectors 35 and 40.

Next, an example of the detectors 35 and 4Q will be explained, and a method for obtaining the conditions (8) and (9) between the trapezoidal wave signals will be explained.

FIG. 7 shows a digital detector, and the detection pulse is applied to the reset terminal of the first counter 5 via the input terminal 50. The first counter 5 counts the clock ('CKS) inputted through the input terminal 53, and resets the second counter 52 when a carry output is obtained. The second counter 52 also counts the clock (fcK8) input via the input terminal 53. 2nd counter 5
The count output of 2 is provided to the input terminal of memory 54. This memory 54 latches the output of the second counter 52 when a detection pulse is input through the input terminal 50. However, these configurations are not suitable for sampling
It forms one hole circuit. Here, the first counter 5
As shown in FIG. 8, 1. is a flat period of the trapezoidal wave signal 8d. , and the second counter 52 sets the slope period t2.

The sampling data latched in the memory 54 is compared with a Nockles width modulation counter 56 and a comparator 55. The pulse width modulation counter 56 counts a high-speed clock input through an input terminal 59 and is reset by a constant cycle reset signal input through an input terminal 60.

When the latch data of the memory 54 and the output data of the pulse width modulation counter 56 match, the comparator 55 outputs a matching pulse and applies it to the set terminal of the R-S free-lag flow double loop circuit 57. A reset pulse from the input terminal 60 is input to the reset terminal of the R-8 flip-flop circuit 57.

As a result, the pulse width of the output pulse of the Fritzno-Frog circuit 52 is varied depending on the value of the data latched in the memory 54, and the pulse width modulated output is applied to the low-pass filter 58 to provide a DC voltage. If converted into , the motor control voltage can be obtained. Figure 8 Detection
In the digital pulse 8a, if the phase of the digital pulse a2 changes, the value of the sampling data latched in the memory 54 will also change, and the pulse data of the digital pulse output from the fritsuno frog circuit 57 will also change.

The detector 35 shown in FIG. 6 is the detector shown in FIG.
．． 40, respectively, but here,
In order to obtain the conditions of equations (8) and (9) above between the detectors 35 and 40, the following settings may be made, for example.

m , / = N'f(!KI!2 K8 j fCKMl ''' /CKM2 f=fM2 1 fCK81 ; Clock frequency of the first and second counters of the detector 35 'CKS2 ; First and second of the detector 40 Clock frequency fcm of the counter; Clock frequency fCKM2 of the pulse width modulation counter of the wave detector 35; Clock frequency fMl of the pulse width modulation counter of the wave detector 40; Reset and pulse frequency 'M2 of the wave detector 35
:Reset of the wave detector 40) By setting the pulse frequency as above, equation (8) is obtained.

The condition of equation (9) can be satisfied.

m'ΔT,=N・ΔT2 r m'T0. =N'T02
From the equation (1), N used for this becomes N=fCT/fD, which gives the ratio of the number of rotations of the video head (per unit time) and the frequency of the control pulse.

Here, if N is multiplied by an odd number, the noise generated when the video head crosses different azimuth angle recording sections of the recording track will come to rest on the screen, and if N is multiplied by an odd number, the number of noise pars will be halved. In this way, in order to make N an integral multiple or an odd multiple, the clock frequency fcxs+
For example, as shown in FIG. 9, when creating a clock with a frequency of "fCK82," N is a product or an odd number, and the frequency mfo is selected. To create a clock of 1, it is sufficient to divide the frequency using the rry'N frequency divider 6.

In the above explanation, for convenience of explanation, an analog trapezoidal wave signal is used in FIGS. 4 and 5, and a digital type one is used as the specific circuit of the detector, as shown in FIG. 7. It shows.

However, the present invention is applicable not only to digital detectors but also to systems that actually generate analog trapezoidal wave signals.

〔Effect of the invention〕

As described above, the present invention provides a signal corresponding to the first trapezoidal wave signal used to control the rotation of the video tape, and a second trapezoidal wave signal used to control the tape speed. By establishing a certain relationship between the voltage and the signal corresponding to the voltage, it is possible to use a common reference voltage for motor drive circuits that control different objects.

As a result, the entire control system can be simplified and the cost can be reduced. In addition, the adjustment work for the reference voltage can be performed at two locations, making management easier.

[Brief explanation of the drawing]

Figures 1 and 2 are configuration explanatory diagrams showing the control systems of a conventional rotary held motor and a reel drive motor, respectively.
The figures are signal waveform diagrams shown to explain the operation of the detector in FIGS. 1 and 2, and FIGS. 4 and 5 are signal waveform diagrams shown to explain the present invention in detail, respectively. 6th
7 is a configuration explanatory diagram showing an example of the detector of FIG. 6, and FIG. 8 is an explanatory diagram for explaining the operation of the detector of FIG. 7. The operating waveform diagram shown in FIG. 9 is a circuit diagram showing an example for obtaining the clock shown in FIG. 7. REF(A), R#(B)--base*voltage, 31
・、! , if, 32.36... motor drive circuit, 3
3...Rotation rad motor, 34...Rotation detector, 3
5.40...Detector, 32...Reel drive motor,
38...Chi f, s9...Control hep0 Applicant's agent Patent attorney name Takehiko E -□□-] Figure 3 vA4 Figure 5v! J ICTLRI 59 Fig. 8 (8d>f-ゝ\\-- Fig. 9 1

Claims (1)

[Claims] The rotation of the video head is detected, and the first detection pulse has a flat region of time (To, ) and a subsequent slope region of time (ΔT, ) at the first time of the first detection pulse. A signal corresponding to a trapezoidal wave signal is generated, a sampling signal corresponding to a signal obtained by sampling and holding the slope region at the second time of the first detection pulse is generated, and based on this sampling signal, the first detection signal 4 is generated. a first means for obtaining a first detection signal having a value proportional to the period of the pulse; a second means for controlling a rotary rad motor for rotationally driving the video head; and a second means for detecting rotation of the reel drive motor;
A signal corresponding to a second trapezoidal wave signal having a flat area of time (T02) and a subsequent slope area of time (ΔTヮ) is generated at the first time of the second detection/fourth ruth. Second
A sampling signal corresponding to the signal obtained by sampling and holding the slope region is generated at the second detection pulse, and a second detection pulse having a value proportional to the period of the second detection pulse is generated based on this sampling signal.
a third means for obtaining a detection signal; and a fourth means for comparing the value of the second detection signal with a reference voltage and controlling the reel drive motor so that the relationship between the two human forces maintains a predetermined relationship. and fifth means for commonly inputting the reference voltage to the second means and the fourth means, the number (m) of the first detection pulses occurring during one rotation of the video head. , the ratio (N ) and the value (N・ΔT2) obtained by dividing the time (ΔT2), and the value (mT.+) obtained by multiplying the number (m) by the time (To, ) and the ratio (N ) multiplied by the above time (T02) (N-T02)
1. A control method for a magnetic recording/reproducing device, characterized in that the control method is set to match the .