JPS601672B2 - magnetic signal detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic signal detection device that uses a magnetoresistive element to read magnetic signals written on a permanent magnet sheet such as a rubber ferrite magnet sheet.

2. Description of the Related Art Conventionally, as a signal reading method for a magnetic card, a method is known in which signals from a magnetic tape attached to a part of the card are scanned by a magnetic head to be input/output.

This method has the advantage of a large recording capacity, but the magnetic tape has a weak holding power, and if used in a bad environment, there is a risk that the card's magnetic signal may disappear or an erroneous signal may be detected.
There are reliability issues. To compensate for this, a magnetic sheet made by mixing resin with barium ferrite magnet powder, which has a higher coercive force than magnetic tape, is used on the card. Signals are magnetized and recorded in the thickness direction of the card, and the saturable coil is moved according to the magnetization pattern. A method has been proposed and put into practical use in which the magnetic field emitted by the card is detected as a change in the impedance of a saturable coil. However, since this method operates the saturable coil using alternating current, the peripheral circuitry is complicated, such as requiring an oscillation circuit and a detection circuit.Also, there is a limit to the size of the detection coil, so the recording density cannot be increased. However, the magnetization state of the sheet must be used within a certain range in order to detect changes in the magnetic field near the saturation magnetic field of the core of the detection coil. The present invention provides a novel magnetic signal detection device that uses two magnetoresistive elements to which a DC bias magnetic field is applied when reading a magnetic signal.

According to the present invention, the peripheral circuitry is simplified, relatively high-density input/output is possible, and there is no particular restriction on the magnetization strength of the magnetic card, making it possible to significantly improve performance. Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 shows a cross section of the magnetic detection unit 1 and a cross section of the magnetic sheet 2, where 3, 3... are horseshoe-shaped permanent magnets, and each magnet 3, 3... is a pair of adjacent magnets on the same plane. They are arranged in a line within the main body of the detection section made of resin 4 so as to have opposing magnetic pole faces. M, , M2 are magnetoresistive elements fixed on the respective magnetic pole faces of the magnets 3, 3..., which are connected in series as shown in FIG.
n is added, and the output terminal 4 is taken out from the intermediate connection point. Here, as the magnetoresistive elements M, M2, indium antimonide lnSb, indium arsenide IM
s high mobility semiconductors are used. Normally, opposing bias magnetic fields of approximately the same strength are applied to the magnetoresistive elements M, M2, but since the resistance change of the magnetoresistive elements M, M2 is unrelated to the polarity of the magnetic field, The output of intermediate output terminal 4 is 1/2Vh. 2 is a magnetic card made of a permanent magnet sheet such as a rubber ferrite magnet sheet, which is magnetized in its thickness direction, and each magnetized portion has a magnetic signal section 5.
, 5... are formed, and a binary code signal is given corresponding to the magnetization direction.

FIG. 3 shows a plan view of this magnetic sheet 2, 5, 5...
・ is a magnetic signal section to which the code signal is given,
They are arranged at substantially equal intervals to the intervals between the magnets 3, 3, . . . . As shown in FIG. 1, let us now consider a case where the north pole is located at the part of the magnetic card 2 facing the detection part 5, and a case b where the south pole is located.

In case a, the resistance of magnetoresistive element M, decreases and the resistance of magnetoresistive element M2 increases. Therefore, the signal appearing at the intermediate output terminal 4 is VWVin, where the resistance value of each magnetoresistive element M, , M2 is R,
Reduction in resistance of element M, -△R. , the resistance increase ΔR2 of the element M2 is considered to be equal, and ΔR,=ΔR2=ΔR.

Similarly, in the case of b, the output signal is V+=R3'V
It is expressed as in.

These output signals V+ and V- are input to a comparator circuit 6 shown in FIG. 2 and converted into digital signals, and a binary code signal is obtained from its output terminal 7.

Also, if the magnetic card 2 is not magnetized, or
If two magnetoresistive elements M, , M2 are connected in the same way, a signal will appear that will make them into output terminals, and if this value is also used, three values will be obtained from (V-, Vo, V +). It is possible to obtain a code signal. To write a signal to the magnetic sheet 2, as shown in FIG. 4, one end of the core of the electromagnet 8 is brought into contact with the writing position of the magnetic sheet 2, and a current is momentarily applied to the coil 9.

FIG. 5 shows another embodiment of the present invention, in which the bias magnetic fields of a plurality of detecting sections 1, 12, 13, for example, three detecting sections 1, 12, 13 are set in advance by electromagnets, and a corresponding predetermined signal is written. This device was used as a card verification machine that detects only the magnetic card 2 that has been inserted and outputs a matching signal.

In the figure, the detection unit 1 has an element M, and N and S for the ground, respectively.
Bias magnetic fields of S and N poles are applied to the poles and detection units 12 and 13, respectively. Therefore, only when the magnetic signal parts 5, 5, 5 formed on the magnetic card 2 are magnetized in the relationship of S, N, N, the detection parts 1, 12, 13
All of them become the output signal V+, and a coincidence signal is outputted via the AND gate 9 shown in FIG. With this kind of structure, compared to a device that sets a specific code in the diode matrix or ROM like a conventional verification machine and compares and verifies the code after reading the card code, the peripheral circuit parts such as the diode matrix and ROM are Not necessary. That is, in the above example, if the direction of the magnetic bias is determined in advance according to the verification code N, an output can be obtained from the AND gate 10 when the code of the card and the code of the detection unit match, which eliminates complicated judgments. No circuit required. Such an embodiment is practical in application to, for example, an electronic door lock. In summary, in the magnetic signal detection device of the present invention, a predetermined bias magnetic field is applied to two serially connected magnetoresistive elements, and a magnetic card having a pair of magnetic pole portions formed in the thickness direction corresponding to the elements is used as an element. By detecting changes in the strength of the bias magnetic field applied to both elements, the signal of the magnetization signal section is
Since it is read out as a value code signal, compared to conventional AC-driven detection devices using saturable coils, there is no need for oscillation circuits, detection circuits, etc. Also, when used as a verification device, it is possible to change the magnetization bias as appropriate. , and gate 1
Since the structure can be easily configured by simply providing two pieces, it is possible to significantly reduce costs.

[Brief explanation of the drawing]

Figure 1 is a sectional view of an embodiment of the present invention, Figure 2 is a circuit block diagram of the same example, Figure 3 is a front view of a magnetic card used in the same example, and Figure 4 is a magnetized magnetic sheet. A diagram showing the operations to be performed,
FIG. 5 is a schematic diagram for explaining another embodiment of the present invention, and FIG. 6 is a circuit block diagram of the same example. DESCRIPTION OF SYMBOLS 1... Magnetic detection part, 2... Magnetic card, 3... Permanent magnet, 4, 7... Output terminal, 5... Magnetic signal part, 6...
... Comparator, M,, M2... Magnetoresistive element. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1. A magnetic detection unit in which two magnetic resistance elements connected in series are respectively placed on the magnetic pole faces of a magnet having a pair of opposing magnetic pole faces adjacent to each other on the same plane. and a magnetic sheet including a magnetic signal part that is magnetized in the thickness direction and this magnetization direction is given as a code signal, and the magnetic signal part of this magnetic sheet is moved in the vicinity of the magnetic detection part to detect the magnetic A magnetic signal detection device characterized by reading signals. 2. In claim 1, a plurality of magnetic detection sections are provided, the direction of a bias magnetic field applied to each magnetic detection section is made different, and the output signal of each magnetic detection section is inputted to an AND gate, A magnetic signal detection device characterized in that a matching signal is output from an AND gate only when a magnetic card on which specific information corresponding to the detection section is written is detected.