JPH07118066B2 - Magnetic head cassette type degaussing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cassette type degaussing device for a magnetic head such as a tape recorder for audio and data, and a degaussing head drive start timing for a constant voltage circuit and a timer circuit. It is controlled by the output signal of the determination unit that determines that both outputs of

(Background of the Invention) A recording / reproducing magnetic head such as a tape recorder is magnetized by a long-term use and deteriorates recording / reproducing characteristics.
Since it is necessary to periodically perform the degaussing, a cassette type degaussing device of a type in which a degaussing head is built in a cassette case has been widely implemented as a device that can easily perform the degaussing.

By the way, the tape recorder normally projects the magnetic head to the tape path portion and makes contact with the tape after the tape cassette is set on the deck. There is an increasing number of auto-drive systems that use the power of a motor or the like to slowly and smoothly take a relatively long time (about 0.5 seconds).

(Example) By the way, when the cassette type degaussing device is set on a tape recorder or the like to degauss the head, it is necessary to drive the degaussing head after the head is in good contact with the degaussing head. In the case of the expression type, since the protruding speed of the head is slow as described above,
As shown in FIG. 2, there is a case where the degaussing head 7 starts driving in a state where the head 9 approaching the degaussing head 7 is not yet in good contact with the degaussing head 7 (FIG. 2B). Therefore, there is a problem that the demagnetization of the head 9 is not always completely performed.

Therefore, the applicant has previously proposed an oscillator circuit connected to a power supply battery and a capacitor charged through a switching circuit by a booster circuit connected to the power supply battery to raise the voltage as seen in Japanese Patent Application No. 58-21158. , A degaussing head, and a timer circuit composed of a resistor and a capacitor supplied with power by the booster circuit is provided between the booster circuit and the switching circuit, and the switching circuit is controlled by the output signal of the timer. By doing so, the oscillation rise of the oscillation circuit part is made steep, the degaussing effect is enhanced, and the head comes into contact with the head, and after a certain amount of time has passed since the switching was turned on, that is, the contact between the magnetic head and the degaussing head I proposed a method to start demagnetization after stabilizing.

However, even in this case, the set time of the timer circuit and the time until the voltage is boosted to a good constant voltage value for starting demagnetization are likely to vary depending on the ambient temperature, the quality accuracy of each element, and the power supply voltage. Therefore, there is a problem that oscillation may be started by the output signal of the timer circuit before the voltage is boosted to a good constant voltage value for starting demagnetization.

(Summary of the Invention) The present invention has been made in consideration of the above circumstances, and it is possible not only to reliably obtain a good initial voltage for degaussing, but also after the magnetic head contacts the degaussing head to a good state. SUMMARY OF THE INVENTION It is an object of the present invention to provide a cassette type degaussing device capable of completely degaussing a magnetic head by driving the degaussing head. To this end, the present invention provides a large-capacity capacitor for driving the degaussing head with a constant voltage circuit that detects when this capacitor has reached a predetermined voltage, and the output of this constant voltage circuit and the predetermined time can be set. The output of this timer circuit is connected to a determination unit for determining that the output has been obtained, and the switching circuit for starting the driving of the degaussing head is controlled by the output signal of this determination unit. . With this configuration, the switching capacitor is not activated until the large-capacity capacitor that supplies current to the degaussing head reaches the predetermined voltage value defined by the constant voltage circuit and the set time of the timer circuit elapses. The degaussing head is driven by reversing the magnetic field. By doing so, the degaussing is prevented from being started before the large-capacity capacitor reaches a predetermined voltage, and the magnetic head is moved to the position shown in FIG. As shown in (4), the degaussing head is prevented from being incompletely degaussed by being driven by the degaussing head before being sufficiently brought into contact with the degaussing head.

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

FIG. 1 is an electric circuit diagram of a cassette type degaussing device according to the present invention, in which 1 is a power supply battery, 2 is a timer circuit connected to the power supply battery 1 through a power switch section sw, and a resistor
It consists of R1 and capacitor C1. The switch part sw is composed of a variable contact a on the timer circuit side, a fixed contact b on the side of the power supply battery 1 and a fixed contact c on the side of the judgment part 8 (described in detail later), and when the cassette case is set on the tape recorder, the variable contact a. Is applied to the contact b side, and when removed from the tape recorder, it is applied to the contact c side.

Reference numeral 3 denotes a booster circuit composed of a DC-DC converter circuit connected to the power supply battery 1, for boosting the terminal voltage of the power supply battery 1, and a switching circuit 4 is connected to the output stage of the booster circuit 3. Has been done. The switching circuit 4
Is composed of a light emitting diode D1 as a drive display element, transistors Q1, Q2, Q3, resistors R2, R3, R4, R5, R6, R7 and the like. The base side of the transistor Q3 is connected to the power supply battery 1 via resistors R4 and R6, and the base side of the transistor Q1 is connected to resistors R4 and R5. The collector of the transistor Q2 is connected to the base sides of the transistors Q1 and Q3, and the base side is connected to the collector side of the transistor Q1 via the resistor R7.

Reference numeral 5 is a constant voltage circuit connected to the switching circuit 4, and is composed of a constant voltage element D2 and a resistor R8. C2 is a large-capacity capacitor connected in parallel to the constant voltage circuit 5, and is charged by the booster circuit 3 via the switching circuit 4.

Reference numeral 6 denotes an oscillator circuit connected to the capacitor C2, which is oscillated by the discharge current of the capacitor C2, and is composed of capacitors C3 and C4, transistors Q4 and Q5, resistors R9 and R10, and the like. Reference numeral 7 denotes a degaussing head connected to the oscillator circuit 6, which is composed of coils L3, L4, a capacitor C5, etc. The emitter side of the transistors Q4, Q5 is connected to the collector side of the transistor Q2.

A reference numeral 8 designates a judgment unit for judging and outputting a coincidence signal such as an AND circuit or a NAND circuit, one input terminal of which is connected between the resistor R1 and the capacitor C1 of the timer circuit 2 and the switch unit. It is connected to the fixed contact c of sw. The other input terminal is connected to the constant voltage circuit 5.
Further, its output terminal is connected to the base side of the transistor Q2. This judging section 8 outputs an output signal from the output terminal to control the transistor Q2 when there is an input signal at both of its input terminals.

The present apparatus has the above-mentioned configuration, and the operation will be described next.

When the cassette case is set on the tape recorder and the play button is operated, the magnetic head 9 slowly advances toward the degaussing head 7, and the variable contact a of the power switch section sw is closed to the contact b side. Then, the capacitor C1 of the timer circuit 2 is gradually charged through the resistor R1 to start the time counting operation, the terminal voltage (for example, 1.5 V) of the power supply battery 1 is boosted by the booster circuit 3, and the transistor Q3 resistor R4 , R
The capacitor C2 is gradually charged by being biased via 6 and conducting.

The constant voltage circuit 5 is connected in parallel to the capacitor C2. Therefore, when the terminal voltage of the capacitor C2 reaches its constant voltage value, for example, 16V, a breakdown current flows in the constant voltage circuit 5, and thereafter the capacitor C2 becomes The constant voltage value is continuously maintained, and the input signal from the constant voltage circuit 5 is input to one input terminal of the determination unit 8. In addition, the timer circuit 2
The capacitor C1 is also fully charged after a predetermined time (eg, 0.6 seconds) has elapsed, and the input signal is also input from the timer circuit 2 to the other input terminal of the determination unit 8. Then, the determination unit 8 outputs an output signal from the output terminal, the transistor Q2 becomes conductive, the oscillation circuit 6 starts oscillation due to the discharge current of the capacitor C2, and the degaussing head 7 receives a gradually decreasing alternating magnetic field based on the discharge time constant. Then, the magnetic head 9 is demagnetized.

When the capacitor C2 is discharged and the degaussing operation is completed, remove the cassette case from the tape recorder.
Then, the variable contact a is closed to the contact c side, the power supply to the booster circuit 3 is stopped, and the capacitor C1 is quickly discharged.

In the above operation, the time required for the capacitor C2 to reach the predetermined voltage value is generally shorter than the time required for the automatic drive type magnetic head to completely contact the degaussing head 7 (generally about 0.5 seconds as described above). Therefore, when the capacitor C2 reaches the predetermined voltage value and the oscillation circuit 6 is oscillated at the same time, the degaussing operation is performed in a state where the magnetic head 9 is not yet in good contact with the degaussing head 7 as shown in FIG. 2 (b). Although it is difficult to completely demagnetize the magnetic head 9 after the start, the present apparatus does not drive the degaussing head 7 only when the capacitor C2 reaches a predetermined constant voltage value as described above, and the capacitor C2 does not completely demagnetize. Only when the voltage value is reached and the time set by the timer circuit 2 has elapsed, the switching circuit 4 is inverted by the output signal of the determination unit 8 to start driving the degaussing head 7. Since it has to, the magnetic head 9 at that time is in contact with the demagnetizing head 7 in a good condition as shown in FIG. 2 (c), its complete degaussing is performed. Of course, even if the time required to charge the capacitor C2 becomes longer than the driving time of the timer circuit due to various conditions such as power supply voltage, each element, ambient temperature, etc., the degaussing head is not driven by the signal of the timer circuit only. Therefore, there is no inconvenience that demagnetization is started before the capacitor C2 reaches the predetermined voltage.

(Effect of the Invention) As described above, the cassette type degaussing device for the magnetic head according to the present invention includes the power supply battery 1, the booster circuit 3 connected to the power supply battery 1, and the switching circuit 4 by the booster circuit 3. A capacitor C2 charged through the capacitor C2, a constant voltage circuit 5 that detects that the capacitor C2 has reached a predetermined voltage and generates an output, an oscillator circuit 6 that oscillates by the discharge current of the capacitor C2, and the oscillator circuit. A degaussing head 7 connected to the output of the constant voltage circuit 5 and an output of a timer circuit 2 that detects the passage of a predetermined time and generates an output.
Since the switching circuit 4 is turned off by the output signal of the determination unit 8 which determines that both outputs are obtained, the oscillation of the oscillation circuit 6 is started at the same time, the magnetic head 9 is set by setting the timer time. The degaussing head 7 can start driving after it has been in good contact with the degaussing head 7. Furthermore, due to factors such as the power supply voltage, the quality accuracy of each element, and the ambient temperature, the predetermined voltage charging time of the capacitor Is longer than the timer setting time, there is no inconvenience that the demagnetization is started before the capacitor reaches the predetermined voltage, and the degaussing of the magnetic head 9 can be favorably performed. It can be advantageously applied to the demagnetization of a magnetic head of the formula.

[Brief description of drawings]

1 shows an embodiment of the present invention. FIG. 1 is an electric circuit diagram of a cassette type degaussing device, and FIGS. 2 (a), (b),
(C) is an explanatory view showing the start of degaussing operation. 1 ... Power supply battery, 2 ... Timer circuit 3 ... Booster circuit, 4 ... Switching circuit 5 ... Constant voltage circuit, 6 ... Oscillation circuit, 7 ... Degaussing head, 8 ... Judgment unit C1, C2 ... Capacitor R1 ... Resistor

Claims (1)

[Claims] 1. A power supply battery 1, a booster circuit 3 connected to the power supply battery 1, a capacitor C2 charged by the booster circuit 3 via a switching circuit 4, and the capacitor C2 has reached a predetermined voltage. The output of the constant voltage circuit 5 is provided with a constant voltage circuit 5 for detecting the above situation, generating an output, an oscillation circuit 6 for oscillating by the discharge current of the capacitor C2, and a degaussing head 7 connected to the oscillation circuit 6. Then, the switching circuit 4 is turned off by the output signal of the determination unit 8 that determines that both outputs, that is, the output of the timer circuit 2 that generates an output by detecting the lapse of a predetermined time after the power is turned on, and at the same time causes the oscillation. A cassette type degaussing device for a magnetic head which is controlled so as to start oscillation of the circuit 6.