JPS59884B2 - tape recorder - Google Patents

Description

[Detailed description of the invention] The magnetic tape has a magnetic surface made of gamma hematite γ-F.
One is made of e2o3 (hereinafter referred to as ordinary tape), the other is made of chromium dioxide cro2 (hereinafter referred to as chromium tape), and gamma hematite γ-Fe2o.
3 and chromium dioxide cro2 (hereinafter referred to as a two-layer tape).

In tape recorders, the bias circuit and equalizer circuit are switched depending on which of the above magnetic tapes is used.

By the way, the conventional method for automatically identifying whether a magnetic tape is one of the above types is to feed the magnetic tape in the forward direction, record a certain signal on it, then rewind it, and then is fed in the forward direction again to reproduce the recorded signal, and the tape is identified by detecting the level of the reproduced signal, which switches the circuit.
Thereafter, the tape is rewound again and put into recording mode. However, this method identifies the tape by running it, and requires repeating the forward feeding and rewinding operations twice before it can be recorded, making it complicated and difficult to configure. The disadvantage is that it is complicated.

In view of this, the present invention is designed to automatically identify which tape it is when the tape is stopped, and in particular, to easily identify whether it is a two-layer tape or not. A magnetic head having an excitation coil and a detection coil is placed in direct contact with the magnetic tape, and a varying current is supplied to the excitation coil, so that
The present invention provides a tape recorder in which a bias circuit or an equalizer circuit is switched by identifying the type of tape based on the number of peaks in an output signal from a detection coil.

Hereinafter, an example of a tape recorder equipped with a magnetic medium identification function according to the present invention will be explained with reference to the drawings.

The relationship between the magnetic field H and the magnetic flux density B of a magnetic tape exhibits a hysteresis characteristic, as shown in Figure 1A, and the coercive force HA of a normal tape is relatively small, about 324 Oe, as shown by the solid line. As shown by the broken line, the chrome tape has a relatively large coercive force HB of about 4690e. The double-layer tape is a composite of both characteristics. In the present invention, paying attention to this point, as shown in FIG. 2, a magnetic head for detection is constructed by winding an excitation coil 3 and a detection coil 4A around a magnetic core 2A having an air gap IA,
The air gap IA is brought into contact with the magnetic surface 5a of the magnetic tape 5,
For example, a triangular wave-shaped changing current is passed through the excitation coil 3, and the tape 5 is identified by the number of peaks in the output voltage e obtained from the detection coil 4A at this time. That is, when the current flowing through the coil 3, and thus the generated magnetic field H, is changed from negative to positive through zero, and vice versa, the magnetic flux density B is When it is a tape, the voltage e changes as shown by the solid line and the broken line in FIG. 1A, and the voltage e obtained from the coil 4A at this time is proportional to the rate of change of the magnetic flux density B.

Therefore, if the tape 5 is a normal tape, the voltage e is
As shown in FIG. 1B, when the current 1 changes from negative to positive through zero, the positive current value 1 becomes such that the magnetic field H becomes HA.
When the current 1 changes from positive to negative through zero, it takes on a negative peak value at a negative current value of -1A, where the magnetic field H becomes -HA, and the tape 5 In the case of Tarom tape, the voltage e is equal to the magnetic field H when the current 1 changes in the positive direction, as shown in Figure 1C.
It exhibits a positive peak value at a positive current value of 1B, where the value becomes HB, and when the current 1 changes in the negative direction, it exhibits a negative peak value at a negative current value of -1B, where the magnetic field H becomes -HB. They will each change to form a mountain so as to exhibit different values. When the tape 5 is a double-layer tape, the voltage e is a positive current value IA at which the magnetic field H becomes HA and HB when the current 1 changes in the positive direction, as shown in FIG. 1D. , IB, and when the current 1 changes in the negative direction, the magnetic field H becomes -HA, -HB at negative current values -A, -B. Incidentally, the values change so as to form a mountain, each exhibiting a negative peak value. Therefore,
It can be determined whether the tape 5 is a double-layer tape or not by the number of peaks appearing in the output voltage e when the current 1 is varied.

In addition, the voltage obtained from the detection coil 4A is actually
The voltage Ec due to the hysteresis characteristic of the core 2A is superimposed on the voltage e due to the hysteresis characteristic of the tape 5 mentioned above, and the latter voltage EO cannot be ignored, so in practice, a dummy core is not used separately. A voltage E is provided due to the hysteresis characteristic of this core 2A. It is better to cancel the . That is, for example, as shown in FIG. 3, a dummy core 2 that configures exactly the same magnetic path as the core 2A
B is formed integrally with the core 2A, and the excitation coil 3 is wound around the common magnetic path of both, and the detection coils 4A and 4 are respectively wound.
B is wound, and the gap 1A of the core 2A is the magnetic surface 5 of the tape 5.
a, but the air gap 1B of the core 2B is not brought into contact with it, a changing current is passed through the excitation coil 3, and the voltage obtained from both detection coils 4A and 4B is supplied to the differential amplifier 6.

In this way, the voltage obtained from the detection coil 4A will be the above-mentioned voltage e due to the hysteresis characteristic of the tape 5 plus the voltage EO due to the hysteresis characteristic of the core 2A, while the voltage obtained from the detection coil 4B will be the same as that of the core 2A. Since only the voltage EO due to the hysteresis characteristic of the tape 2B is obtained, only the above-mentioned voltage e due to the hysteresis characteristic of the tape 5 is obtained at the output terminal 6a of the amplifier 6. Further, as shown in FIG. 4, cores 2A and 2B are formed separately and arranged side by side in the width direction of the tape 5, with the core 2A having its gap 1A facing the tape 5, and the core 2B having its gap 1A facing the tape 5. Air gap 1B
It may be arranged so that the tape 5 does not come into contact with the tape 5.

In this case, it does not take up space in the thickness direction of the tape 5, unlike when it is integrally formed as shown in FIG. It may also be used as a head, or it may be provided separately from these heads. If it is provided separately, in the case of a force setting type tape recorder, the air gap 1A may be connected from a small window of the force setting to the so-called green belt of the tape, for example. They can be made to face each other.

In actual operation, first the air gap 1A of the detection head is brought into contact with the tape 5 by operating the recording button, in this case tension is applied to the tape 5 to obtain sufficient contact pressure, and then the excitation coil 3 A variable current 1 is applied to the output voltage e to identify the tape 5, and the bias circuit and equalizer circuit are automatically switched based on the identification output. This can be done in the order of separating from the tape 5 and then switching to the recording state.

The identification circuit can be configured as shown in FIG. 5, for example.

That is, in the example shown in the figure, 7 is an astable multipipulator from which a rectangular wave signal SO (FIG. 6A) with a data factor of Σ is obtained, which is supplied to a flip-flop circuit 8 to be converted into one. minutes
A rectangular wave signal SF (Fig. 6B) which has been rotated twice is obtained, and this is supplied to the integrating circuit 9 to obtain a current that changes in a triangular wave shape in positive and negative directions with zero as the border (Fig. 6C), which is excited. Supplied to coil 3.

Then, the output voltage e of the differential amplifier 6 is supplied to a differentiating circuit 10 for differentiation, and its output is supplied to a zero point detection circuit 11 to obtain pulse signals at the positive and negative heater values of the output voltage e described above. And Astable Multipipulator 7
A rectangular wave signal SO is supplied to the differentiating circuit 12 to obtain a trigger pulse at the falling edge of the signal SO, that is, when the current 1 becomes zero, and this and the pulse signal from the zero point detection circuit 11 are ORed. 13 through the flip-flop circuit 14
The pulse signal from the zero point detection circuit 11 is supplied to the set side of the flip-flop circuit 14. In this case, the flip-flop circuit 14 is configured to give priority to resetting. Therefore, when the tape 5 is a normal tape, the output voltage e is as shown in FIG. 6D when the current 1 is 1.
By exhibiting a peak value at the time of A and -A,
From the circuit 14, a pulse signal SA having a pulse width smaller than the pulse width of the signal SO is obtained as shown in FIG. By exhibiting a peak value when becomes B and -1B, the circuit 14 obtains a pulse signal SB having a pulse width smaller than the pulse width of the signal SO, as shown in H in the figure. On the other hand, when the tape 5 is a two-layer tape, the output voltage e and the current are A, IB and -1A as shown in F of the same figure.
, -1B, and the circuit 14 is reset when the current 1 reaches IA, -1A, and IB, -1B.
By being set at the time of IB, the circuit 14 obtains a pulse signal Sc having a pulse width larger than the pulse width of the signal SO, as shown in FIG. Therefore, this pulse signal SA, SB or Sc is supplied to the AND circuit 15, and the signal S from the astable multipipulator 7 is
If O is supplied to the AND circuit 15, the AND circuit 15 obtains a signal SD (FIG. 6J) which is the same as the signal SO only when the tape 5 is a two-layer tape. Therefore, if the output of the AND circuit 15 is supplied to the smoothing circuit 16, the output terminal 17
In this case, if the tape 5 is a normal tape or chrome tape, an output voltage that is zero is obtained, and if it is a double-layer tape, it is a constant positive value, and it is determined whether the tape 5 is a double-layer tape or not. can be identified. Further, the pulse signal SA or SB from the flip-flop circuit 14 is sent to another AND circuit 18.
On the other hand, the trigger pulse from the differentiating circuit 12 is supplied to 2
From the point in time when the current I is supplied to the mono-multivibrator 19 of the stage and becomes zero, the falling of the pulse signal SA and the pulse signal S
The signal S becomes [1] until the point in the middle of the fall of B.
If E (K in Figure 6) is obtained and supplied to the AND circuit 18, the AND circuit 18 will output a pulse signal SF with a constant pulse width (L in Figure 6) only when the tape 5 is chrome tape.
) is obtained. Therefore, if the output of this AND circuit 18 is supplied to the smoothing circuit 20, the output terminal 21 will have a value of zero if the tape 5 is a normal tape, and a constant positive value if it is a chrome tape. Output voltage is obtained and tape 5
It can be identified that the tape is chrome tape. Therefore, the bias circuit, equalizer circuit, etc. can be automatically switched using the output voltages from the output terminals 17 and 21. In addition to the above example, it is also possible to identify whether or not the tape is a two-layer tape, for example, by counting pulse signals from the zero point detection circuit 11.

Note that, instead of providing the integrating circuit 9 separately from the excitation coil 3, a resistor may be connected between the flip-flop circuit 8 and the coil 13, and the resistor and the coil 3 may constitute an integrating circuit.

Further, the current 1 flowing through the excitation coil 3 may change, for example, in a sinusoidal manner.

According to the present invention described above, since the tape can be identified while the tape is stopped without being run, the operation becomes extremely simple and the configuration can be extremely simplified.

Moreover, since automatic identification is performed and the bias circuit, equalizer circuit, etc. are automatically switched, malfunctions do not occur and the user does not need to be careful.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the present invention, FIG. 2 is a diagram showing the principle configuration of the detection head used in the tape recorder of the present invention, and FIGS. 3 and 4 show actual examples of the detection head. FIG. 2 is a diagram showing a system diagram of an example of a coater, and a waveform diagram of FIG. Fig. 5 shows a tape player according to the present invention. Fig. 6 shows, for explanation, 2A is a core, 1A is its air gap, 3 is an excitation coil, 4A is a detection coil, 5 is a magnetic tape, 5a is its magnetic surface, and 6 is a differential amplifier. It is.

Claims (1)

[Claims] 1. A magnetic head having a magnetic core having a gap in contact with a magnetic tape, an excitation coil and a detection coil wound around the magnetic core, current supply means for supplying a changing current to the excitation coil, and the detection coil. A tape recorder characterized in that a discrimination means is provided for discriminating the number of peaks in an output signal obtained from the above, and the type of the magnetic tape is identified based on the output of the discrimination means, and a bias circuit or an equalizer circuit is switched. .