JPS6120666Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a magnetic recording/reproducing device.

An example of a magnetic recording/reproducing device is shown in FIG. 1 is a video head cylinder in which a video head 2 is built-in. 3 is a supply reel, and 4 is a take-up reel. 5 is a full-width erase head, 6 is a magnetic tape, and 7 is a full-width erase head.
8 is a voice control head, 8 is a capstan shaft, 9 is a pinch roller, and 10 is a flywheel, which is connected to a capstan motor 13 via a belt 11 and a motor pulley 12.

FIG. 2 shows the magnetization pattern of a magnetic tape recorded at normal speed. Part 30 is the audio track, 3
The part 1 is a control track, and the part 32 is a video track section.To simplify the explanation, the fields a to j and the horizontal synchronization signal shown by broken lines are used instead. If the length of one pitch of the control signal is l as shown in FIG. 2, then in the case of an NTSC signal, the tape speed per second is υ ₀ =30×l. If the rotation of the capstan shaft 8 during playback is normal playback, the tape speed is υ ₀ , but if the rotation of the capstan is set to 1/5, for example, the trajectory of the video head 2 on the tape 6 will be A in FIG. The slope becomes steeper as shown in the figure. In this case, video head 2
Since the playback output does not completely trace the tape pattern, it contains noise, but the playback image is in 1/5 slow motion. Conversely, if the rotation speed of the capstan shaft 8 is increased by five times, for example,
The tape speed becomes _5υ0 , and the trajectory of the video head 2 on the tape 6 begins to slope as shown at B in FIG. The playback output at this time picks up noise when crossing each track, but the playback image is in a mode of 5 times faster playback. Normally, switching between slow mode and high speed mode was performed using separate switches.

This invention reduces the number of mode change switches by making it possible to operate slow mode and high speed mode with the same switch, and at the same time, it also makes it possible to reduce the number of remote control cables when performing remote control operations. It is something to do.

An embodiment of the present invention will be described below based on the drawings. FIG. 3 shows the running circuit and drive section of the capstan. 14 is an FG gear fixed to the rotating shaft of the capstan motor 13, and 15 is an FG head that detects a pulse output proportional to the rotation speed of the FG gear 14. The output of the FG head 15 is input to a waveform shaping circuit 21, and the output of the circuit 21 is input to a 1/2 frequency divider flip-flop 22. The output whose frequency has been divided by 1/2 and shaped to have a duty of 50% by the 1/2 frequency divider flip-flop 22 triggers the speed monomulti 24 having a time constant that determines the rotation speed, and the 1/2 frequency divider flip-flop 22 and the output of the speed monomulti 24 are input to the gate 23. The output of the gate 23 is input to a drive circuit 27 via an integrator 25 and a compensation filter 26, and the output of the drive circuit 27 drives the capstan motor 13. The loops 13 to 27 are the speed system of a so-called capstan servo system. In the case of normal reproduction, the output of the control track 31 recorded on the magnetic tape 6 is detected by the control head 7, and is input from the control amplifier 17 to the phase comparator 19 via the tracking adjustment monomulti 18. 16 is a 30Hz reference oscillator, for example,
Its output is input to a phase comparator 19. The phase comparison output of the phase comparator 19 is sent to the phase compensation filter 20.
and modulates the time constant of the speed monomulti 24. As a result, phase locking of the normal reproduction system is performed.

A specific circuit example of the drive circuit 27 is shown in FIG.
Q ₁ is a DC amplifier composed of transistors, the collector output of which is input to a Darlington circuit composed of transistors Q ₂ and Q ₃ , and applied to the motor 13 from the emitter of transistor Q ₃ . FIG. 5 shows an example of the characteristic of υin- _VM when the power supply voltage is 15V, the voltage applied to the motor is _VM , and the input voltage of the drive circuit 27 is υin.

Assume that the voltage applied to the motor is approximately 2.5 V (a in FIG. 5) when the tape speed is υo, which is the normal reproduction mode. At this time, when υin is forced to earth potential during playback, transistor Q ₁ is cut off, and the power supply voltage of 15V is applied to resistor R ₂ , transistor Q ₂ ,
Since the voltage is applied to the motor 13 via _Q3 , the voltage applied to the motor is approximately 13.5V (b in FIG. 5), and the motor rotation speed is approximately five times the normal speed, resulting in a five times high speed mode.

To set the slow mode, it is possible to set the voltage lower than the 2.5V applied during normal driving, but for example, to reduce the voltage to 1/5, the motor applied voltage must be 1V.
The rotational operation is unstable at such a low voltage. However, as shown in FIG. 7C, by applying a pulse voltage and changing the ratio of the application time t to the pulse period T, the motor 13 can be driven relatively stably at a low speed.

For example, a circuit as shown in FIG. 6 has conventionally been used for low-speed, high-speed reproduction using the above method. S ₁ is static mode switch, S ₂ is high speed mode switch, S ₃
is a slow mode switch. In the normal regeneration mode, switches S ₁ , S ₂ , and S ₃ are all open, and the motor 13 has a motor voltage V _M1 (approximately
2.5V) is applied. Switch S ₂ from this state
When the transistor _Q1 is short-circuited, the cassette is turned off, and the motor voltage V _M2 (approximately 13.5 V) shown in FIG. 7B is applied to the motor 13. This increases the motor rotation speed and puts it in high-speed mode. If switch _S1 is shorted from normal playback mode, the transistor
The base of Q ₁ is connected to the power supply through resistors R ₄ and R ₅ , transistor Q ₄ becomes conductive, and transistor Q ₂
The base of the transistor Q3 is grounded, the output of the transistor _Q3 becomes zero, and the motor 13 becomes stationary. In other words, it becomes a pause state. From this state, when switch _S3 is short-circuited and a signal of the opposite polarity shown in Fig. 7C is applied,
Transistor Q ₅ is conductive and transistor Q ₄ is cut off for a period of time t, while transistor Q ₁ is cut off by switch S ₃ , so that the emitter of transistor Q ₃ has V as shown in FIG. A pulse output with a width of t is obtained with an amplitude of _M2 , and the mode becomes slow mode. In the example shown in FIG. 6 above, separate switches are required for the high speed mode and the slow mode.

Next, a specific example of the present invention is shown in FIG. In normal playback mode, switches S ₁ and S ₄ are open. If switch S ₄ is shorted from this state, transistor Q ₁
The base of is grounded through diode _D1 , switch _S4 , transistor _Q1 is cut off,
Approximately 13.5V as shown in FIG. 5b is applied to the motor 13, and the motor enters the high speed mode.

Next, when switch S ₁ is short-circuited in the normal playback mode, the base current of transistor Q 6 flows through resistor r ₂ and the base of transistor Q ₆ , which makes transistor _{Q 6 conductive} , and the collector of transistor Q ₁ becomes conductive. Q ₆ is grounded through switch S ₁ , the motor applied voltage becomes zero, and motor 1
3 stops and goes into stationary mode. When switch S ₄ is short-circuited from this state, transistor Q ₁ is cut off as before, and at the same time, the base of transistor Q ₇ is grounded via resistor r ₆ and switch S ₄ . A rectangular wave (for example, a 30Hz head switching pulse) as shown in Figure 9A is connected to the emitter of the transistor _Q7 , and the switch _S4
is shorted and transistor Q ₇ is conducting, so the square wave is output to the collector of transistor Q ₇ and applied to the base of transistor Q ₆ via a differentiating circuit consisting of capacitor C ₁ and resistors r ₆ and r ₃ . be done. Therefore, the transistor _Q6 is cut off on the negative side of the differential pulse generated in the differentiating circuit, and the
A pulse output as shown in Figure B is obtained. Therefore, pressing switch _S4 from pause mode switches to slow mode.

As described above, according to the present invention, a pulse related to head switching can be applied to the base of the first transistor connected in series with the static mode switch via the second transistor, and Since a second switch is connected between the base of this second transistor and ground, closing the second switch when the quiescent mode switch is conductive (during quiescent mode) causes the head switching to occur. The capstan motor is intermittently driven in response to pulses related to The transistor does not operate, and a high voltage is applied to the capstan motor to achieve high-speed playback mode. In other words, the second
With a simple configuration of only two transistors, one switch (second switch) can switch between the original two modes (normal playback mode and static mode).
The capstan mode can be controlled to achieve two different modes (high-speed playback mode and slow mode), reducing the number of switches for switching tape running modes, realizing miniaturization and improving operability. This has great practical effects.

[Brief explanation of the drawing]

Figure 1 is an overall configuration diagram of the magnetic recording and reproducing device, Figure 2
The figure shows the magnetization pattern of the magnetic tape, Figure 3 is a block diagram explaining the capstan drive, Figure 4 is a concrete example of the drive circuit, Figure 5 is the input-output characteristic diagram of the drive circuit, and Figure 6 is the conventional one. Mode switching circuit diagram,
FIG. 7 is a waveform diagram of each part, FIG. 8 is a circuit diagram showing an embodiment of the present invention, and FIG. 9 is a broken diagram of each part. 13...Capstan motor, 24...Speed monomulti, 27...Motor drive circuit, _S1 ...Station mode switch, _S4 ...Slow high speed mode switch.

Claims (1)

[Scope of utility model registration request] A drive circuit having a capstan motor, a front stage and a rear stage, and a drive control means having two output terminals connected to respective input terminals of the front stage and the rear stage of the drive circuit, and the drive control means is connected to a power source. A first transistor whose base is connected and whose collector is connected to the input end of the latter stage of the drive circuit, and between the emitter of the first transistor and ground, and the capstan motor is stopped by electrical conduction. between the static mode switch, a second transistor whose collector side is connected to the base of the first transistor and whose emitter receives a pulse for head switching, and the input terminal of the previous stage of the drive circuit and ground. a second switch connected to the switch, a connection path between the base of the second transistor and the input terminal of the previous stage, and a connection section between this input terminal and a power supply; Close the second switch to turn off the front stage of the drive circuit, apply a high voltage to the capstan motor via the second stage to set the high-speed playback mode, and with the static mode switch closed, turn off the second stage of the drive circuit. When the switch is closed, the first transistor is intermittently turned off by the second transistor at the cycle of pulses related to head switching, and when the cassette is turned off, a voltage is applied to the capstan motor via the latter stage of the drive circuit. A magnetic recording/reproducing device characterized in that it is configured to operate in a slow mode.