JPS5885950A - Automatic reversing circuit of tape recorder - Google Patents

Abstract

PURPOSE:To prevent a malfunction at the leader tape part, by using a delaying circuit to a circuit that detects the change of the reflection light at the leader tape part, a joint and the recording part respectively of a recording tape and performs an automatic reversing action. CONSTITUTION:A delaying circuit is provided to stop the working of a switch circuit by the output of another switch circuit for a period equivalent to the time longer than the driving time of a reverse driving mechanism. The reflected light is detected by a photocoupler at the joint between the leader tape part and the recording part of a recording tape. The voltage is compared 4 after the DC detection 2 and the reverse amplification 3. A current is amplified 5 by the output of the voltage comparison. Thus a plunger 6 is actuated to drive an automatic reversing mechanism (not shown in the diagram). While the output of the current amplifier 5 drives a bias switch circuit 12 via an inhibiting circuit 10 and a delaying circuit 11. The circuit 12 switches the bias of a DC detecting circuit 2, an inverse amplifying circuit 3, a comparator 4 and the current amplifying circuit 5 respectively and controls the start/stop of the circuits 2-5.

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention relates to an automatic reversing circuit for a tape recorder having a built-in automatic reversing mechanism, and in particular, to an automatic reversing circuit for a tape recorder that optically detects the end of a recording tape and drives a reversing drive mechanism. This invention relates to an automatic reversing circuit for a tape recorder.

(Technical Background of the Invention) In recent tape recorders, such as cassette decks, in order to omit the loading operation of flipping the cassette when recording and playing back from side A to side 8 of the cassette, the direction in which the cassette tape runs is A so-called automatic reversal mechanism (auto-reverse mechanism) is incorporated, which automatically reverses the rotation from forward to reverse.

This automatic reversing mechanism detects the end of the running tape and automatically reverses the running direction of the tape.

One of the conventional methods for detecting the end of this type of tape is as follows:
A method of optical detection using the transmittance or reflectance of light in the running tape has been considered.

This method of utilizing the reflectance of the tape utilizes the difference in the reflection coefficient of light in the leader tape section, splicing chive section, and magnetic tape section in the tape. Then, a detection section of the automatic reversing circuit detects a decrease in reflectance of the leader tape section at the end of the running tape, and the reversing drive mechanism is driven by the detection signal,
Move the recording/playback head J3 and the detection unit up and down in accordance with the tape track, or once remove it from the tape, rotate it half a turn, and bring it into contact with -j-1 again, and reverse the rotation direction of the cassette deck hub drive shaft. let

(Problems with the Background Art) However, in the automatic reversing method that uses the difference in the light reflectance of the running tape as described above, since the light reflectance of the leader tape is detected and driven, the end of the running cassette tape When the reversing drive mechanism is driven by detecting the leader tape section of the tape, the detection section is temporarily separated from the tape and the detection signal changes.

Therefore, there is a drawback that the automatic inverting circuit is likely to malfunction.

・'(Objective of the invention) The present invention was made to improve the above-mentioned drawbacks.
An object of the present invention is to provide an automatic reversing circuit for a tape recorder that enables reliable and smooth automatic reversal at the end of a running tape loaded in the tape recorder.

(Summary of the Invention) To achieve this object, the present invention provides a switch circuit for operating the reversing drive mechanism in an automatic reversing circuit for a tape recorder that detects changes in light from the tape and drives the reversing drive mechanism. a switching circuit for operating/stopping the switching circuit; and a delay circuit for stopping the operation of the switching circuit for a time corresponding to a time period exceeding the drive time of the reversing drive mechanism by the output of the switching circuit; The present invention is characterized in that the inverting drive mechanism is driven and the operation of the switch circuit is delayed.

(Example of the invention) Embodiments of the present invention will be described in detail below with reference to the drawings.

First, in order to facilitate understanding of the present invention, FIG. 1 shows a schematic block diagram of an automatic reversing circuit for a tape recorder according to the present invention.

In the figure, a photocoupler 1 is a detection unit that converts reflected light from a leader tape section, a splicing tape section, and a magnetic tape section of a running tape into a current, and the output thereof is applied to a DC detection circuit 2.

An inverting amplifier circuit 3, a comparator circuit 4, and a current amplifier circuit 5 are connected in series to the output terminal of the DC detection circuit 2. When the output of the current amplifying circuit 5 is completed, a plunger 6 for driving an inversion drive mechanism (not shown) is connected, and the plunger 6 is connected to a power source 8 via a switch 7. Note that the reference numeral 9 is a motor.

Furthermore, an inhibition circuit 10, a delay circuit 11, and a bias switching circuit 12 are connected in series to the output terminal of the current amplification circuit 5. This bias switching circuit 12 includes a DC output circuit 2,
The bias of the inverting amplifier circuit 3, the comparator circuit 4, and the current amplifier circuit 5 is switched, and the operation and stop of each circuit 2, 3, 4, and 5 is controlled.

FIG. 2 is a circuit diagram showing in detail the automatic inversion circuit shown in FIG. 1.

The photocoupler 1 in the figure has one end connected to the power switch 7.
It consists of a light-emitting diode D+ connected to the switch 7 and its other end forwardly grounded via a current limiting resistor R1, and a phototransistor Q1 whose collector is also connected to the switch 7 and whose emitter is grounded via a load resistor R2. The reproducing head is placed on a slide substrate (not shown) on which the reproducing head is mounted.

A series circuit of a resistor R3 and a resistor R4 that divides the voltage between the emitter and ground is connected to the emitter of the transistor Q1 in parallel with a load resistor R2.

The collective circuit Q2 is an active circuit element, for example, an integrated circuit, which includes a DC detection circuit 2, an inverting amplifier circuit 3, and a voltage comparison circuit 4. Power is supplied to the power supply terminal (■) via the switch 7, and the power is supplied to the bias terminal (■). The built-in DC detection circuit 2, inverting amplifier circuit 3, and voltage comparison circuit 4 can be switched on and off at the same time by applying a bias current.

The DC detection circuit 2 consists of a two-stage amplifier circuit made up of two transistors, with the terminal ■ as the input terminal and the terminal ■ as the output terminal. When an input voltage is applied, the potential at the output terminal 2 becomes a low (L) level, and when an input voltage lower than the base-emitter voltage (VBE) is applied, the potential at the output terminal 2 becomes a high (1-1) level.

The inverting amplifier circuit 3 is composed of a conventionally known OP amplifier circuit, and amplifies the input voltage applied to the input terminal (2) in opposite phase, and outputs the amplified voltage to the output terminal (2).

The voltage comparator circuit 4 is a transistor circuit that detects the magnitude of the input signal voltage with respect to the reference voltage. When the input voltage is lower than the base-emitter voltage of the input transistor, it outputs a voltage approximately equal to the power supply voltage from the output terminal This is a circuit whose output is approximately 0 when the voltage is high.

The connection point between resistors R3 and R4 is the input terminal of DC detection circuit 2.
The output terminal (2) is grounded via a load resistor R6, and a bias resistor R5 is inserted between the input/output terminals (2) and (2).

Furthermore, the output terminal (■) of the current detection circuit 2 is connected to the input terminal (■) of the inverting amplifier circuit 3, and the output terminal (■) is connected to the load resistor R7.
and is grounded via a parallel circuit of capacitor C1. Note that the resistor R8 is the input/output terminal of the inverting amplifier circuit 3,
This is the resistance inserted between 0 and 0.

The output terminal ■ of the inverting amplifier circuit 3, that is, the connection point with the resistor R7 and the capacitor C1, is connected to the input terminal of the voltage comparator circuit 4 via the resistor R9, and the output terminal ■ of the voltage comparator circuit 4 is Transistor Q3 of current amplification circuit 5
is connected to the base of the resistor R10 via a resistor R10. The emitter of this transistor Q3 is grounded, and the collector is connected to a switch 7 via a plunger 6.

Further, the output terminal (2) of the voltage comparator circuit 4 is connected to the base of the transistor Q4 of the inhibition circuit 10 via a diode D2 and a resistor R11 in series. transistor Q
The emitter of 4 is grounded.

The collector is connected to the base of a transistor Q5 that constitutes the delay circuit 11.

The base of this transistor Q5 is connected to the switch 7 by a resistor R.
12, and a capacitor C2 is inserted and connected between the ground and the resistor R12 and the capacitor C2 constitute an OR time constant circuit. The time constant of this time constant circuit is set, for example, to a time that exceeds the running time of the leader tape section and the splicing chive section.

The emitter of the transistor Q5 is grounded, and the collector is connected via a resistor 13 to the base of a transistor Q6 constituting the piezo switching circuit 12. The emitter of the transistor Q6 is connected to the switch 7, and the collector is connected to the bias terminal (2) of the collective circuit Q2.

Note that the reference numeral 9 is a motor inserted between the switch 7 and the ground, and the reference numeral 8 is a power supply.

Next, the operation of the automatic reversing circuit of the present invention configured as described above will be explained.
The operation will be explained with reference to the waveform diagram in FIG.

Note that A in FIG. 3 shows the running order of the leader tape section A1, splicing chive section A2, and magnetic tape section A3 passing near the photocoupler 1. In addition, 8 to I in Figure 3 indicate the voltage waveforms at 8 points or 1 point in the circuit shown in Figure 2, and the solid line indicates when normal tape is used, and the broken line indicates when chrome tape or metal tape is used. It is shown in

First, an example of using normal tape will be explained.

When the switch 7 is turned on and power supply voltage is supplied to the collective circuit Q2 and the photocoupler 1, an output voltage is obtained from the photocoupler 1 in accordance with the running of the cassette tape. As shown in FIG. 3, the output voltage of the photocoupler 1 is high (
H) level, and low (L) level in the leader tape section.
) level.

Generally, the output voltage obtained from the photocoupler 1 by the light reflected by the splicing tape section A2 and the magnetic tape section A3 is about 1 volt. Then, the voltage generated at the emitter of the phototransistor Q1 of the photocoupler 1 is divided by resistors R3 and R4, outputted to both ends of the resistor R4, that is, point B and 0, and applied to the input terminal ■ of the DC detection circuit 2. .

When the switch 7 is turned on, the power supply voltage is applied to the CR time constant circuit inserted into the base of the transistor Q5 of the delay circuit 11, and the capacitor C2 is charged. The charging time is as shown in the third diagram.
1. Since the time is set to be sufficient to exceed the running time of the splicing tape section A2, it takes until the magnetic tape section A3 of the running tape runs over the photocoupler 1. Therefore, during the time T1 during which the capacitor C2 is charged, the transistor Q5 does not operate, and the transistor 16 of the bias switching circuit 12 also does not operate. Therefore, no bias current is applied to the bias terminal (2) of the aggregate circuit Q2, and the DC detection circuit 2, inverting amplifier circuit 3, and voltage comparison circuit 4 do not operate. Therefore, since the current amplification circuit 5 does not operate, the plunger 6 does not drive, and the reversal drive mechanism also does not operate.

Then, when the charging time T1 of the capacitor C2 elapses and the transistor Q6 operates in accordance with the operation of the transistor Q5, a bias current is applied to the bias terminal (2) of the collective circuit Q2, and the point E becomes the trubel.

However, when the magnetic tape part 3 of the cassette tape runs near the photocoupler 1, both ends of the resistor R4, that is, B,
Since a voltage is generated at point C, if the resistance values of resistors R3 and R4 are selected so that a voltage higher than the operating voltage of the DC detection circuit 2 is generated, the current detection circuit 2 will operate and the output terminal 01 point will become trubel. .

Further, the input of the inverting amplifier circuit 3 becomes a torque level, and the output terminal (2), that is, point G becomes a torque level as shown in FIG. 3G, and the capacitor C1 is charged.

When the G point reaches the torque level, no output appears at the output terminal (2) of the voltage comparator circuit 4, so the transistor Q3 of the current amplifier circuit 5 does not operate and the plunger 6 does not drive.

Thereafter, as the cassette tape travels and approaches the end and moves from the splicing chive section A2 to the leader tape section A1, the voltage at point B in FIG. 2 decreases to a trubel. Therefore, the output terminal (2) of the DC detection circuit 2 is inverted from trubel to torubel, and the output terminal (2) of the inverting amplifier circuit 3 becomes torubel. When the output terminal ■ becomes a torque level, the capacitor C1
starts discharging, and point G shifts to truvel as shown in Figure 3. Therefore, in the process where the voltage at the input terminal (■) of the voltage comparator circuit 4 reaches the positive level, the output from the output terminal (■) of the comparator circuit as shown in FIG.
Since the transistor Q3 operates, the plunger 6 is driven. As the plunger 6 is driven, a reversing drive mechanism (not shown) is operated.

This reversing drive mechanism moves the recording/playback head and photocoupler 1 up and down in accordance with the tape track by the switching action of the plunger 6, or once separates from the tape, rotates the recording/playback head 180 degrees, and then contacts the tape again. The cassette tape hub drive shaft rotates in a reverse direction.

When an output as shown in FIG. 3 is applied to the base of the transistor of the inhibition circuit 10 via the diode D 2 and the resistor 11 from the output terminal 2 of the voltage comparison circuit 4, the transistor Q4 is activated.

When the transistor Q4 operates, the base voltage of the transistor Q5 rapidly decreases, and the capacitor C2 is discharged, so that the transistor Q5 is cut off. Therefore, the transistor Q6 of the bias switching circuit 12 is also cut off, and no bias current is supplied to the collective circuit Q2, and each circuit 2.3.4 of the collective circuit Q2 is also cut off, so that the current limiting circuits 5 and 4 are also cut off. and the plunger 6 does not move.

When the voltage comparator circuit 4 is cut off, there is no output from the output terminal (2), so the transistor Q4 of the inhibiting circuit Q4 is also cut off, and the capacitor C2 is discharged and charged again according to the above-mentioned time constant. As mentioned above, the charging time is the leader tape part Δ1 of the cassette tape.
Since the travel time of the splicing tape portion A2 is set longer than the traveling time of the splicing tape portion A2, the driving of the reversing drive mechanism during operation is performed smoothly without malfunction.

The above explanation is for the operation when normal tape is used. However, as shown in Fig. 3C or the waveform diagram with broken lines, when using tape or metal tape (X), it is necessary to The output voltage of the photocoupler 1 becomes high, and the detected voltage at the leader tape section A1 becomes low.In the automatic reversing circuit of the present invention, the end leader tape section is detected and the reversing drive mechanism is driven, as in the case of a normal tape. and will not malfunction during operation of the reversing drive mechanism.

In this way, the automatic reversing circuit of the tape recorder of the present invention is
Since the automatic reversing circuit does not operate due to changes in the reflected light of the tape after automatic reversal at the end of the tape or changes in the output voltage at t8 when the photocoupler 1 is automatically advanced or retracted, malfunctions during reversal can be prevented.

Note that the DC detection circuit in the above-mentioned embodiment is a circuit that operates only by H level voltage among the voltages obtained from the running tape, and the reference voltage is set to a voltage higher than the voltage due to the reflected light from the beam tape section. It's good to do that.

Further, the voltage comparison circuit and the current limit circuit are switch circuits that invert the output of the DC detection circuit, compare fluctuations in the inverted output, and drive the inversion drive mechanism.

The bias switching circuit does not need to cut off all the circuits in the collective circuit Q2, but the present invention can be implemented by causing the switch circuit to stop its operation in order to cut off at least the operation of the current amplification circuit 5 that drives the plunger 6. It is possible to achieve the goal.

Also, the resistor R12 and capacitor C that constitute the time constant circuit
The time constant 2 can be arbitrarily set, and may be set to at least a time that exceeds the time it takes for the reversing drive mechanism to drive and for the photocoupler 1 to be located near the magnetic tape section, that is, usually about 5 seconds.

In the above-mentioned embodiment, a method was described in which the reversing drive mechanism is driven by detecting the reflected light from the tape, but the present invention has a method in which a light emitting element is arranged on a slide substrate on which a recording/playback head is mounted, and the cassette is It is also possible to implement a method in which a light receiving element is arranged in a guide bin to detect light transmitted through the tape.

(Effects of the Invention) As explained above, the automatic reversing circuit of the tape recorder of the present invention detects a change in light at the end of the tape to drive the reversing drive mechanism, and also connects the switch circuit that operates the reversing drive mechanism to the tape recorder. Since the tape is configured to be delayed by a time exceeding the drive time of the reversing drive mechanism during reversal, it has the advantage that malfunction of the automatic reversing mechanism when reversing the tape can be reliably prevented.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the automatic reversing circuit of a tape recorder according to the present invention, FIG. 2 is a circuit diagram showing the details of the first height indicator block diagram, and FIG. 3 is the circuit shown in FIG. 2. FIG. 3 is a voltage waveform diagram illustrating the operation shown in the figure. 1・・・・・・・・・・・・・・・・・・・・・Photocoupler 2・・・・・・・・・・・・・・・・・・・・・
DC detection port-3・・・・・・・・・・・・・・・・・・
・・・Inverting amplifier circuit 4・・・・・・・・・・・・・・・
・・・・・・Voltage comparison circuit 5・・・・・・・・・・・・
......Current amplification circuit 6...
・・・・・・・・・・・・Plunger 7・・・・・・・・・
・・・・・・・・・・・・・・・Switch 8・・・・・・
・・・・・・・・・・・・・Power supply 9・・・・・・・
......Motor 10...
・・・・・・・・・・・・Prohibition circuit 11...
・・・・・・・・・・・・・・・・・・Delay circuit 12...
・・・・・・・・・・・・・・・・・・Switching circuit D1
・・・・・・・・・・・・・・・・・・・・・Light-emitting diode D2・・・・・・・・・・・・・・・・・・・・・
・Diode Q1・・・・・・・・・・・・・・・・・・
・・・Phototransistor Q2・・・・・・・・・・・・
......Collective circuit 'Q3~Q6...
......Transistor CI, C2...
・・・・・・Capacitor R1~R13・・・・・・・・・
・Resistant agent patent attorney Sa Suyama −

Claims (1)

[Claims] , a switch for operating the reversing drive mechanism in an automatic reversing circuit of a tape recorder that detects changes in light due to the running of the leader tape section, splicing tape section, and magnetic tape section of the tape and drives the reversing drive mechanism; a switching circuit for operating/stopping the circuit, and a delay circuit for stopping the operation of the switching circuit for a time corresponding to a time period exceeding the drive time of the reversing drive mechanism by the output of the switching circuit, and the output of the switching circuit An automatic reversing circuit for a tape recorder, characterized in that the reversing drive mechanism is driven by the reversing mechanism and the operation of the switch circuit is delayed.