JPH07118065B2 - Magnetic head cassette type degaussing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cassette-type degaussing device for a magnetic head such as a tape recorder for audio and data, and relates to the drive start timing of the degaussing head and the output of a constant voltage circuit. It is set by a timer circuit which starts operation by a signal.

(Background of the Invention) Since a recording / reproducing magnetic head such as a tape recorder is magnetized by long-term use, the recording / reproducing characteristics are deteriorated.
Since it is necessary to regularly perform the degaussing, a cassette type degaussing device in which a degaussing head is built in a cassette case is 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).

(Conventional example) By the way, when the cassette type degaussing device is set on a tape recorder or the like to degauss the bed, it is necessary to drive the degaussing head after the head has been 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. 3, there is a case where the degaussing head 7 starts driving in a state where the head 9 that has entered toward the degaussing head 7 is not yet in good contact with the degaussing head 7 (FIG. 3B). Therefore, there is a problem that the demagnetization of the head 9 is not always completely performed.

Therefore, the applicant has previously found an oscillation 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 abuts, and after a certain amount of time has elapsed since the switch was turned on, that is, the abutment of 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 degaussing circuit is boosted to a good constant voltage value are likely to vary depending on the ambient temperature and the quality accuracy of each element. Before the voltage is boosted to the constant voltage value, the output signal of the timer circuit may start oscillation.

(Summary of the Invention) The present invention has been made in consideration of the above circumstances, and the present invention not only surely obtains a good initial voltage for degaussing, but also applies the magnetic head to a degaussing head in a good state. It is an object of the present invention to provide a cassette type degaussing device in which the degaussing head is driven to make it possible to completely degauss the magnetic head after contact. To this end, the present invention provides a capacitor for driving the oscillation circuit of the degaussing head with the discharge current thereof, and a constant voltage circuit for detecting that the capacitor has reached a predetermined voltage. Driving the timer to operate the timer circuit after the capacitor is charged to a predetermined voltage, and after the set time of the timer circuit has elapsed, the switching circuit is inverted by the output signal of the timer circuit to cause the oscillation circuit to operate. Is oscillated to generate an alternating gradually decreasing magnetic field in the degaussing head. With this configuration, it is possible to prevent the timer circuit from operating and the oscillation circuit from oscillating insufficiently before the capacitor is charged to the predetermined voltage.
As shown in FIG. 6C, after the magnetic head comes into contact with the degaussing head to a good state, the oscillation circuit is sufficiently oscillated so that the magnetic head is completely demagnetized.

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, 3 is a booster circuit composed of a DC-DC converter circuit connected to a power supply battery 1 through a power switch 2. 4 is a switching circuit, 5 is a constant voltage circuit, 6
Is an oscillation circuit, and 7 is a degaussing head. Power switch 2
Set the cassette on a tape recorder or the like, press the play button to close it, and remove it from it to open it. Step-up circuit 3 is a resistor R1, capacitors C1, C2, coil
It is composed of L1, L2, transistors Q1, Q2, diode D1, etc., and boosts the terminal voltage of the power supply battery 1 to a predetermined voltage.

The switching circuit 4 is connected to the output stage of the booster circuit 3, and includes a light emitting diode D2 as a drive display element, transistors Q3, Q4, Q5, low antibodies R2, R3, R4, R5, R6, R7.
Etc., and the resistors R2 and R3 are connected to the base side of the transistor Q1. The base side of the transistor Q4 is connected to the base side of the transistor Q3 via the low antibodies R6 and R4.

The constant voltage circuit 5 is composed of a constant voltage element D3 and a diode D4. 8 is a timer circuit, a resistor R8, a capacitor
Made of C3. The diode D4 applies a constant voltage to the timer circuit 8 when a breakdown current flows through the constant voltage element D3, that is, when the large-capacity capacitor C4 is charged with a predetermined voltage, as described later in detail. . Resistor
R8 is connected to the constant voltage element D3 and the diode D4, and the resistor R8 and the capacitor C3 are connected to the base side of the transistor Q5 via the diode D5. C4 is a large-capacity capacitor connected in parallel to the constant voltage circuit 5,
It is charged by the booster circuit 3 via the switching circuit 4.

The oscillating circuit 6 is connected to the capacitor C4 and oscillates by its discharge current. The oscillating circuit 6 is composed of capacitors C5, C6, transistors Q6, Q7, resistors R9, R10, etc. The head 7 is connected. The degaussing head 7 is composed of coils L3, L4, a capacitor C7 and the like. The emitter sides of the transistors Q6 and Q7 are connected to the collector side of the transistor Q5.

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

When this device is set in the tape recorder and the play button is operated, the magnetic head 9 slowly advances toward the degaussing head 7, and the power switch 2 is closed. Then, the terminal voltage (for example, 1.5 V) of the power supply battery 1 is boosted by the booster circuit 3, and the transistor Q4 is turned on so that the capacitor C4 is gradually charged.

The constant voltage circuit 5 is connected in parallel to the capacitor C4. Therefore, when the terminal voltage of the capacitor C4 reaches its constant voltage value, for example, 16V, a breakdown current as an output signal flows in the constant voltage circuit 5, After that, the capacitor C4 continues to maintain the constant voltage value. On the other hand, the capacitor C3 of the timer circuit 8 starts the time counting operation by the breakdown current and is gradually charged, and when the capacitor C3 reaches a predetermined voltage value after a set time (for example, 0.3 seconds) elapses, the base of the transistor Q5. A current flows, the transistor Q5 becomes conductive, the oscillation circuit 6 starts oscillating due to the discharge current of the capacitor C4, and the demagnetizing head 7 produces a gradually decreasing alternating magnetic field based on the discharge time constant, and the demagnetizing of the magnetic head 9 is performed. Done. When the capacitor C4 has been discharged and the degaussing operation has ended, remove the cassette case from the tape recorder. Then, the power switch 2 is opened, the power supply to the booster circuit 3 is stopped, and all the operations are completed.

In the above operation, the time required for the capacitor C4 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 C4 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. 3 (b). Although it is difficult to completely demagnetize the magnetic head 9 after the start, this device does not immediately oscillate the oscillation circuit 6 even if the capacitor C4 reaches a predetermined voltage value as described above, and the capacitor C4
When the voltage reaches a predetermined voltage value, the timer circuit 8 is activated, and after the time set by the timer circuit 8 has elapsed, the switching circuit 4 is inverted by the output signal of the timer circuit 8 to start the oscillation of the oscillation circuit 6. Therefore, at that time, the magnetic head 9 is in good contact with the degaussing head 7 as shown in FIG. 3 (c), and complete degaussing is performed. Further, the charging flow of the timer circuit 8 is supplied only after the capacitor C4 reaches the predetermined voltage value, so that the rising of the alternating magnetic field is not deteriorated. The timer circuit 8 may be, for example, a well-known timer circuit other than a digital timer circuit that divides and counts the oscillation frequency of the booster circuit 3.

The present invention also provides a diode as described above, for example, as shown in FIG.
Instead of D4, a light emitting diode D6 as a drive display element may be provided and the driving of the timer circuit 8 may be displayed by the light emitting diode D6.

(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 C4 charged through the capacitor C4, an oscillating circuit 6 that oscillates by the discharge current of the capacitor C4, and a degaussing head 7 connected to the oscillating circuit 6 are provided, and it is detected that the capacitor C4 has reached a predetermined voltage. A timer circuit 8 for starting operation by an output signal of a constant voltage circuit 5 which generates an output is provided, and the switching circuit 4 is turned off by the output signal of the timer circuit 8 and at the same time, the oscillation circuit 6 starts oscillation. Since the degaussing head 7 starts driving after the large-capacity capacitor C4 is surely charged to the predetermined voltage, the degaussing of the magnetic head 9 is excellent. Can be done, even more by the time setting of the timer circuit 8 can particularly advantageously applied to demagnetize the auto-drive-type magnetic head.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is an electric circuit diagram of a cassette type degaussing device, FIG. 2 is an electric circuit diagram of another embodiment, and FIGS. 3 (a) and 3 (b). , (C) are explanatory views showing the start of the degaussing operation. 1 ... Power supply battery, 3 ... Booster circuit, 4 ... Switching circuit, 5 ... Constant voltage circuit, 6 ... Oscillation circuit, 7 ... Degaussing head, 8 ... Timer circuit, C4 ... Capacitor, D6 ... Drive display element

Claims (1)

[Claims] 1. A power supply battery 1, a booster circuit 3 connected to the power supply battery 1, a capacitor C4 charged by the booster circuit 3 via a switching circuit 4, and oscillation by the discharge current of the capacitor C4. The oscillator circuit 6 and the degaussing head 7 connected to the oscillator circuit 6 are provided, and the operation is started by the output signal of the constant voltage circuit 5 which detects that the capacitor C4 has reached a predetermined voltage and generates an output. A cassette type degaussing device for a magnetic head, comprising a timer circuit 8 and controlled so that the switching circuit 4 is turned off by the output signal of the timer circuit 8 and at the same time the oscillation circuit 6 starts oscillation.