JPH077489B2 - AC erasing head - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an erasing head for an audio tape recorder, and more particularly to a dry battery driven low power consumption portable type erasing head for a tape recorder.
Alternatively, it is used as an erasing head for a cassette tape recorder with a radio receiver and a cassette tape deck to which a dubbing function is added at a tape speed higher than a constant speed.

(Conventional Example) Conventionally, methods of erasing information recorded on a magnetic tape are roughly classified into a DC erasing method and an AC erasing method.

The DC erasing method is a method of applying a strong DC magnetic field to a magnetic tape to magnetize and erase all the residual magnetization by a recording signal to a magnetic saturation point, in which a coil is wound around a high-permeability material core having a gap. There are a DC current type erasing head that uses a DC magnetic field that is mounted in the coil and causes a large DC current to flow through the gap, and a magnet type erasing head that uses a ferromagnetic magnet. This direct current erasing method consumes less power, and the magnet type has the advantage of not consuming power at all, but the saturated residual magnetism remains on the magnetic tape, which causes a large amount of noise in the subsequent recording / playback, and also the playback signal. It had a major drawback of being distorted.

On the other hand, in the AC erasing head, as shown in FIG. 1, a coil 15 is wound around a high-permeability material core 14 having two gaps 11 and 12, and an AC current is supplied to the coil 15 by an AC power source 16 to form a gap. The magnetic tape receives a strong AC magnetic field when passing through the gap, and the AC magnetic field acting on the magnetic tape collides while reversing in the positive and negative directions as it moves away from the gap. Therefore, the magnetic neutral point is reached and the residual magnetism is erased to a state of almost zero. In general, two or more gaps are provided to improve erasing efficiency. The erase frequency is set so that it is not played by the playhead.
Selected as 3 to 4 times or more of the audio signal band, usually 60kH
An exchange of z or more is used. Compared to the DC erasing method, this AC erasing head has the advantages of less noise during subsequent recording / playback and less distortion of the audio signal, but especially when erasing high coercive force tape (such as metal tape). It has a drawback that it consumes a large amount of power and is difficult to mount on a dry battery driven portable type tape recorder.

Further, it was impossible to mount the above AC erase head on a tape recorder with a radio receiver or a cassette tape recorder to which a function capable of dubbing at a speed faster than the constant speed was added. . That is, at the time of high-speed dubbing, the audio signal shifts to the sound range according to the dubbing speed. Therefore, it is necessary to shift the erasing frequency at the time of high-speed dubbing to the high range as well.
However, since the AC erasing head has a structure in which a coil is wound around a high-permeability material core, its impedance increases in proportion to the increase of the erasing frequency. Moreover, in order to obtain the same magnetomotive force as during constant-speed running, the applied current must be the same as during constant-speed running, which requires a high voltage and high power consumption power source for the AC erasing head. was there.

In addition, when the conventional AC erase head is used at a higher frequency, hysteresis loss and eddy current loss increase, and due to the heat generation phenomenon caused by this, this AC erase head becomes high temperature, the magnetic permeability of the core material decreases, It is impossible to install the conventional AC erasing head on a cassette tape recorder with a radio receiver or a cassette tape deck that can dubb the conventional AC erasing head at a speed four times faster than the constant speed because it causes a short circuit due to melting of the wire coating. It was

(Object of the Invention) In view of the problems of the conventional AC erasing head as described above, an object of the present invention is to provide a low power consumption AC erasing head, and an AC erasing head for a dry battery driven portable cassette tape recorder. An AC erasing head for a radio receiver tape recorder or cassette tape deck that enables high-quality audio recording and playback with less noise and distortion, and dubbing at 4 times the constant speed or more. To provide.

(Structure of the Invention) The features of the present invention are that the gap in which the erasing magnetic field is generated in the AC erasing head has an azimuth angle inclined with respect to the direction orthogonal to the traveling direction of the magnetic tape, and the erasing frequency is set to the audio frequency. That is, it has an erasing power source set in the signal band. Therefore, the small magnetization remaining in the erasing process is not reproduced by the azimuth loss that occurs because the crossing angle between the magnetization pattern and the reproducing head gap is inclined by a certain angle. This means that the erase frequency can be set within the audio band.

Generally, when the recording wavelength on the magnetic tape is λ, the track width is W, and the azimuth angle is θ, the azimuth loss L _A is expressed by the following equation.

This is shown in Figure 2 with L _A as the vertical axis and θ as the horizontal axis. The loss becomes infinite at the angle θ.

The curve connecting the peaks of each mountain, that is, The azimuth loss L _A ′ is given by Expression (3) is the minimum azimuth loss guarantee level when considering the azimuth loss in consideration of variations in the azimuth angle.

Now, letting the running speed of the magnetic tape be υ and the erase frequency be λ = υ / ... (4).

Taking a cassette tape recorder as an example, υ = 4.75 cm / s,
If the erasing frequency is taken as a parameter and set to 5 kHz, 10 kHz, and 20 kHz, equation (3) is illustrated as shown in FIG.

That is, in the erasing process of the AC erasing head having an azimuth angle, even if residual magnetization remains on the magnetic tape, the erasing frequency component is not reproduced by the reproducing head due to azimuth loss.

Especially, if the azimuth angle is set to 10 degrees or more, the azimuth loss becomes 30 dB or more at any frequency. An erasing head with an azimuth angle set to 10 degrees was created, and according to an erasing experiment, the residual magnetization level of the erasing frequency component is about -30 dB at the maximum with respect to the saturation level. Therefore, the playback level of the erase frequency component by the playback head is -60
It will be below dB and will not cause any practical problems.

(Description of Embodiments) FIG. 4 shows the configuration of an AC erasing head according to the present invention. As shown in the figure, the AC erasing head of the present invention is
That is, the gaps 41 and 42 are inclined by an angle θ with respect to the direction orthogonal to the magnetic tape running direction 43. That is, an erasing current is applied from the erasing power supply 46 to the coil 45 wound around the high-permeability material core 44, and the magnetic tape (not shown) is erased by the erasing magnetic field leaking from the gaps 41 and 42. . In this erasing process, even if remnant magnetization due to the erasing current remains on the magnetic tape, the remanent magnetization pattern is also inclined by an angle θ with respect to the direction orthogonal to the running direction of the magnetic tape. It will not be played by the playhead due to loss.

As a result, as described above, the erase frequency is 5k.
It becomes possible to select within the audio signal band such as Hz to 20 kHz.

(Effects) (1) When the AC erasing head according to the present invention was used as an erasing head for a dry battery driven portable cassette tape recorder at an azimuth angle of 45 degrees and an erasing frequency of 10 kHz, the results shown in Table 1 were obtained.

As described above, in the AC erasing head according to the present invention, although the erasing rate, the S / N, and the distortion rate are about the same as those of the conventional AC erasing head, the power consumption is 3 minutes of that of the conventional AC erasing head. It can be reduced to 1. This is for the following reasons.

Generally, a magnetic tape has an easy axis of magnetization in its running direction. Therefore, when the magnetic tape is magnetized from a direction different from the easy axis of magnetization as in the present invention, it is necessary to increase the magnetomotive force for use. Therefore, the azimuth angle is 45
In the AC erasing head according to the present invention inclined by
The applied current must be increased about 1.4 times that of the conventional one. However, when the erase frequency is reduced from 60 kHz to 10 kHz, the hysteresis loss, which is the main cause of the erase head core loss, is approximately 1/6 in proportion to the erase frequency. That is, in the AC erase head according to the present invention, the power consumption is (1.4) ² × 1/6 as compared with the conventional AC erase head.
It has the effect of being reduced to 1/3.

According to the experiment, when the azimuth angle is set to 15 degrees or more and 60 degrees or less, the power saving effect of the power consumption is great.

Since the noise characteristic after erasure depends on the number of magnetic field reversals during the passage of the gap of the magnetic tape, the erasing frequency cannot be lowered so much. According to the experiments by the generators, there was no practical problem when the erase frequency was set to 5 kHz or higher.

(2) Since the erasing power supply may be of low voltage and low power consumption, it can be made smaller and less expensive than the conventional one.

(3) In a tape recorder with a radio receiver, a cassette tape deck, etc. to which a high-speed dubbing function is added, the AC erasing head according to the present invention can be used at an erasing frequency according to the dubbing speed. For example, 6
It can be used at 60 kHz for double-speed dubbing and 100 kHz for 10-fold dubbing, and it is sufficiently effective even if it is driven at a conventional erasing frequency.

In this case, as described above, the erasing current is slightly increased and the temperature of the AC erasing head is slightly increased due to heat generation, but the magnetic permeability is not lowered and the winding coating is not melted.

As described above, the erasing head according to the present invention is particularly useful as an erasing head for dubbing at a speed of 4 times or more, which is impossible with the conventional AC erasing head.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing the configuration of a conventional AC erase head,
FIG. 2 is a diagram showing the relationship between azimuth loss and azimuth angle, FIG. 3 is a diagram showing the envelope connecting the peaks of the peaks of FIG. 2 with the erasing frequency as a parameter, and FIG. It is a perspective view which shows the structure of one Example. 41, 42 ... Gap, 43 ... Magnetic tape running direction, 44 ...
… High permeability material core, 45 …… coil, 46 …… power supply.

Claims (1)

[Claims] 1. An AC erasing head for erasing information recorded on the magnetic tape by applying an AC magnetic field generated from the gap to the magnetic tape, wherein the gap is formed in a direction orthogonal to a traveling direction of the magnetic tape. An AC erasing head characterized by being provided with an erasing power source which is inclined at an angle of 15 degrees or more and 60 degrees or less and an erasing frequency is set within an audio signal band.