JPH0743815B2 - Magnetic head degausser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a degaussing device for a magnetic head such as a tape recorder for video, audio, data, etc., and more particularly to a device having a timer circuit incorporated therein.

[Background of the Invention] A recording / reproducing magnetic head such as a tape recorder is magnetized by a long-term use, resulting in deterioration of recording / reproducing characteristics.
Since it is necessary to regularly perform degaussing of the magnetic head, a cassette type degaussing device having a magnetic head built in a cassette case has been widely implemented as a device that can perform degaussing easily.

By the way, a tape recorder normally projects a magnetic head to the tape path and abuts the tape after inserting the tape cassette. Recently, this projecting operation takes a relatively long time (0.5 seconds) by using the power of a motor or the like. The number of types that protect the tape and the magnetic head by increasing the smoothness and making the contact between the tape and the head gentle are increasing.

[Conventional example]

In the conventional cassette type degaussing device, it takes about 0.3 seconds until the switch is turned on and the degaussing is started. Therefore, when the conventional degaussing device is used for the tape recorder, as shown in FIG. Degaussing may start in a state where the degaussing head 28 is not in good contact (FIG. 2 (b)), and the degaussing effect becomes insufficient.

Therefore, the applicant has previously found that an oscillation circuit connected to a power supply battery and a capacitor charged through a switching circuit from 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 including 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 portion is made steep, the degaussing effect is enhanced, and after a certain time (about 1 second) has elapsed since the head was contacted and the switch was turned on, that is, the magnetic head and the degaussing head. We proposed a method that starts demagnetization after the contact of the is stabilized.

However, in this case, as shown in FIG.
A timer circuit 24 is provided between the booster circuit 23 and the switching circuit 25, and the boosted voltage is used as a driving power supply for the timer circuit by applying the voltage of the booster circuit 23 to both ends of the timer circuit 24. Therefore, the time t required for the capacitor 29 in the timer circuit 24 to reach a predetermined value (voltage value for operating the switching circuit 25) has a relatively high voltage, and the voltage may be changed depending on the ambient temperature, quality accuracy, and the like. This is inconvenient because the curve depends on the booster circuit 23, which tends to vary. That is, the predetermined value of the capacitor 29 is several hundred mV, while the voltage applied from the booster circuit 23 is 0 to
The voltage is as high as about 16V, and the capacitor 29 is charged by this high voltage via the resistor 30, so that the setting values of the booster circuit 23 and the resistor 30 vary even if they are slight due to quality accuracy or environmental conditions such as ambient temperature. And the charging time t (time until demagnetization start) of the capacitor 29 becomes unstable,
Not only will the user feel uneasy, but if the time t of the timer circuit 24 is longer than necessary, the current flowing into the constant voltage circuit 26 will be wasted that much, which is uneconomical.

Therefore, according to the present invention, by providing this timer circuit between the power supply battery and the booster circuit, a stable power supply battery voltage is applied to both ends of the timer circuit until the switch is turned on and the demagnetization action starts. An object is to provide a degaussing device with stable time.

〔Example〕

The embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an electric circuit diagram of a degaussing device incorporated in a cassette case, in which 1 is a power supply battery or a switch circuit, 4 is a DC-DC converter circuit as a DC step-up circuit, and switch circuit 2 is a converter circuit. It consists of a variable contact 2a on the 4th side, a fixed contact 2b on the negative side of the power supply battery 1 and a fixed contact 2c on the side of the capacitor C3 which will be described later. When the cassette case is set on the tape recorder, the variable contact 2a is turned on to the contact 2b side. Then, when the tape recorder is removed from the tape recorder, it is inserted to the contact 2c side. The converter circuit 4 includes a resistor R1, coils L1 and L2, capacitors C1 and C2, a diode D1, transistors Q1 and Q2, etc., and boosts the terminal voltage of the power supply battery 1.

Also, in the output stage of the power supply battery 1, a resistor R2 and a capacitor C3
Is connected to the timer circuit 3, and the switching unit 5 is connected to the timer circuit 3. The switching unit 5 includes a drive display circuit 51 and a switching circuit 52. The drive display circuit 51 includes a light emitting diode D2 as a light emitting element,
It is composed of a transistor Q3, resistors R3, R4, etc., a light emitting diode D2 is in parallel with the capacitor C3, and resistors R3, R
4 is connected to the base side of the transistor Q1 and the resistor R2 side of the capacitor C3 is connected to the fixed contact 2c of the switch circuit 2 and is also connected to the base side of the transistor Q5 described later via the diode D3. Has been done.

The switching circuit 52 includes transistors Q4, Q5, a resistor R5,
R6, R7, R8, the base side of the transistor Q4 is connected to the base side of the transistor Q3 via the resistor R6, R7, the resistor R6, R7 is connected to the collector side of the transistor Q5. There is. The base side of the transistor Q5 is connected to the collector side of the transistor Q3 via the resistor Q8, and is also connected to the capacitor C3 via the diode D3 as described above.

Reference numeral 6 denotes a constant voltage circuit connected to the switching unit 5, which is composed of a Zener diode D4, and a large capacity capacitor C4 is connected to the constant voltage circuit 6.

Reference numeral 7 denotes an oscillator circuit driven by the discharge current of the capacitor C4, which includes capacitors C5, C6, resistors R9, R10, and a transistor Q.
A demagnetization head 8 composed of demagnetization coils L3 and L4 and a capacitor C7 is connected to the oscillation circuit 7 and is composed of 6, Q7 and the like. The switching circuit 5 is connected to each emitter side of the transistors Q6 and Q7.
It is connected to the collector side of the second transistor Q5.

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, the variable contact 2a of the switch circuit 2 is turned on to the contact 2b side, the terminal voltage of the power supply battery 1, for example, 1.5V, is gradually boosted by the converter circuit 4, and the transistor Q4 becomes conductive. The capacitor C4 is charged.

Since the constant voltage circuit 6 is connected in parallel to the capacitor C4, when the constant voltage value, for example 16V, is reached, the charging current of the capacitor C4 is bypassed to the constant voltage circuit 6,
The capacitor C4 will continue to maintain a constant voltage value.

Further, the capacitor C3 of the timer circuit 3 is charged by the power supply battery 1 through the resistor R2, and when the terminal voltage thereof reaches a predetermined value, for example, 0.8V, that is, when a predetermined time elapses, its discharge current causes the switching circuit 52 to discharge. Tanista Q5
To be biased in the conduction direction, and with this conduction, the transistor Q3 is simultaneously biased, and both the transistors Q5 and Q3 are biased to each other to perform the inversion operation and have a perfect conduction state.

Here, if the time of the timer circuit 3, that is, the time until the degaussing starts is set longer than the time until the large-capacity capacitor C4 reaches 16V (about 300 mS), the degaussing head 8 is completely demagnetized. The degaussing is started after the contact with the contact point, and a good degaussing effect can be obtained. Further, since the voltage is directly supplied to the timer circuit 3 from the power supply battery 1 having a stable voltage, the time for the timer circuit 3 does not vary and a good time for starting demagnetization can be set accurately. It is possible to do so, and it is not affected by the rising characteristics of the latter stage after the transistor Q4.Therefore, the inversion operation period is the time required for the inversion operation of the transistors Q3, Q5, and both transistors Q3, Q5 are biased mutually. The oscillation circuit 7
The rising edge of is steep.

When the transmission circuit 7 supplied with power from the capacitor C4 thus starts to operate, a decelerating alternating magnetic field is generated in the degaussing head 8 based on the discharge time constant, and the recording / reproducing magnetic head of the tape recorder is degaussed. Also transistor Q3
Is turned on, a base current flows through the transistor Q1 to turn on the transistor Q1 and the output of the converter circuit 4 is almost
It is held down by the output of about 3V and drives the light emitting diode D2,
Power is supplied to maintain the operation of the switching unit 5.

Next, when the discharging of the capacitor C4 is completed and the degaussing operation is completed, the cassette case is removed from the tape recorder. Then, the variable contact 2a is switched to the contact 2c side, and the capacitors C2 and C3 end the discharge immediately and prepare for the next use.

〔The invention's effect〕

As described above, the degaussing device according to the present invention includes the power supply battery, the booster circuit connected to the power supply battery to increase the voltage, the capacitor charged by the booster circuit through the switching circuit, and the oscillator circuit connected to the capacitor. , Consisting of a degaussing head, between the power supply battery and the booster circuit,
Since the timer circuit including the resistor and the capacitor is provided and the switching circuit is controlled by the output signal of the timer circuit, the oscillation rising characteristic of the oscillation circuit can be made good, and the inverting operation of the switching circuit can be performed. To make the rise of the gradually decreasing alternating magnetic field generated in the degaussing head to be good in response, and to ensure that a stable, relatively low, constant voltage, that is, the voltage of the power supply battery, is applied between the terminals of the timer circuit. Therefore, the timer time can be set easily and consistently, without causing the user to feel uneasy, and the timer time must be longer than necessary so that the degaussing function does not start when the degaussing head and the degaussing head have a bad contact. It does not need to be set for a long time, which means that it is possible to avoid wasting power.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a degaussing device according to the present invention, FIGS. 2A to 2C are explanatory diagrams showing a degaussing start time of a conventional degaussing device, and FIG. 3 is a circuit portion of a conventional degaussing device. is there. 1 ... Power supply battery 3 ... Timer circuit 4 ... Booster circuit 7 ... Oscillation circuit 8 ... Degaussing head 52 ... Switching circuit C3 ... Capacitor C4 ... Capacitor R2 ..

Claims (1)

[Claims] 1. A power supply battery 1, a booster circuit 4 connected to the power supply battery 1 to raise a voltage, a capacitor C4 charged by the booster circuit 4 through a switching circuit 52, and a capacitor C4 connected to the capacitor C4. It consists of an oscillation circuit 7 and a degaussing head 8, and between the power supply battery 1 and the booster circuit 4,
A timer circuit 4 consisting of a resistor R2 and a capacitor C3 is provided,
A magnetic head degaussing device which controls the switching circuit 52 by an output signal of the timer circuit 3.