JPS601671B2 - Magnetic signal verification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic signal matching device that matches a magnetic signal written on a permanent magnet sheet such as a rubber ferrite magnet sheet with a preset signal.

Magnetic card verification devices, which are generally used in electronic key lock systems, are made by mixing barium ferrite powder with high coercive force into the resin because they need to be unaffected by the environment and the signal will not fade easily. A magnetic force code collation device has been put into practical use, which uses a rubber ferrite sheet produced by a saturable coil to read the magnetic signal in a stationary state.

This device performs verification by superimposing a fixed bias magnetic field higher than the saturation magnetic field of the coil core from one side of the saturable coil, and canceling the magnetic field applied to the saturable coil to a value lower than the core saturation magnetic field. However, there are limits to the magnetization state of the magnetic card because it can only match signals of up to three values, and because it uses fluctuations in the magnetic field near the core's saturation magnetic field.For example, if the canceling magnetic field is too strong, However, there are disadvantages such as the generation of a bias magnetic field higher than the saturation magnetic field, which causes inconvenience. The present invention eliminates the above drawbacks by using two magnetoresistive elements with the same characteristics and a bias magnetic field generator in the detection section, and also makes it possible to verify the 400 million code signals written on the magnetic card. The present invention provides a new magnetic signal matching device that can

According to the present invention, there is no restriction on the magnetization state of the magnetic card, and it is possible to stably operate the card from a relatively weak magnetization state to a strong magnetization state. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross-sectional view of a magnetic detection section and a magnetic sheet 2, and shows 1. , 12, 13 are magnetic detection sections each having a set of two permanent magnets 3, 3, 4, 4, 5, 5, which are arranged in a line inside the main body of the detection section made of resin. .
The permanent magnets 3, 3, 4, 4, 5, 5 of each set are arranged in the same polarity relationship or in the opposite polarity relationship, and this polarity relationship is set in advance as a signal to be verified. Here, electromagnets can be used instead of the permanent magnets in each set, and in this case,
The magnetization direction can be easily determined by the direction of the current. M,, M2 are magnetoresistive elements fixed on the magnetic pole faces of a set of magnets 3, 3, 4, 4, 5, 5 in each magnetic detection unit 11, 12, 13, as shown in FIG. They are connected in series, a DC voltage Vin is applied to both ends, and an output terminal 6 is taken out from the intermediate connection point. Here element M,
, M2 is indium antimonide lnSb,
A high mobility semiconductor such as indium arsenide lnAs is used. In FIG. 2, 7 is a comparator circuit to which the intermediate output signals of the elements M, . . . M2 are added and converts this into a digital signal, and 8 is its output terminal. Figure 3 shows
A plan view of the magnetic sheet 2 is shown, which is made of a hard magnetic material such as a rubber ferrite magnet sheet, and has magnetic signal portions 9, 9, . . . at each magnetic spot magnetized in its thickness direction.
is formed.

The magnetic signal portions 979 are composed of a pair of magnetized portions 10, 10 of the same or opposite polarity to which a binary code signal is assigned in accordance with the magnetization direction. With such a structure, the bias magnetic field applied to the magnetoresistive elements M, , M2 has a strength superimposed on the magnetic field of the magnetic signal section 9 of the magnetic sheet poison, and each element M, , M2 responds accordingly. It shows the resistance value, and the output terminal 6 outputs a signal corresponding to the resistance change.

Now, the output signal when the resistance of element M increases and the resistance of element M2 decreases is V+, and the output signal in the opposite case is V.
-, the signal when both elements M, , M2 increase or decrease is Vo, and if we consider the output due to the combination of the direction of the bias magnetic field and the direction of the magnetic field of the magnetic signal section 9, it will be as shown in the following table. As is clear from the above, there is only one type of magnetic bias that can obtain V+ for one type of magnetic signal section 9. For example, when the magnetic signal section 9 is S pole with respect to elements M, , M2, the bias The magnetic field is
However, only in the case of N pole and S pole.

In other words, the comparator circuit 7 produces an output only when an output of V+ is obtained, and does not produce an output when an output of Vo and V- is obtained.
By giving a hysteresis characteristic to 0 (FIG. 4), it becomes possible to discriminate between the four-value codes NS, SN, NN, and SS of the magnetic signal section 9. In this case, the value of V+ is determined by the variation width of the bias magnetic field, and can operate with a variation of several Gauss, which is smaller than in the case of a conventional saturable coil, and no disadvantages will occur due to too large a variation. As described above, the magnetic signal matching device of the present invention combines two series-connected magnetoresistive elements into one
A large number of magnetic detection sections are provided as a set, and a preset magnetic bias is applied to them as a signal, and only when the magnetic signal section consisting of a pair of magnetized sections that have a constant zero relationship with this magnetization direction come close to each other. , it is possible to determine the four-value code of this signal part.

Furthermore, compared to a conventional AC-driven detector using a saturable coil, an oscillation circuit, a detection circuit, etc. are not required, and costs can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view of an embodiment of the present invention, Fig. 2 is a circuit block diagram of the same example, Fig. 3 is a front view of a magnetic card used in the same example, and Fig. 4 is a sectional view of an embodiment of the present invention. FIG. 3 is an input-output signal characteristic diagram for explaining the operation of the comparator circuit.

1, 12, 13... Magnetic detection unit, 2... Magnetic sheet, 3, 3, 4, 4, 5, 5... Permanent magnet, 7...
Comparator circuit, 9...magnetic signal section, M,, M2...
... Magnetoresistive element.

Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1 A set of two magnetic pole faces having the same polarity or opposite polarity, and a plurality of sets are set in a predetermined polarity relationship,
It includes a magnetic detection section in which two magnetoresistive elements connected in series are placed on two magnetic pole faces of each set, and a magnetic signal section magnetized in the thickness direction and given this magnetization direction as a signal. a magnetic sheet, the magnetic signal section of the magnetic sheet is moved in the vicinity of the magnetic detection section, and a four-value code signal is obtained by a combination of the magnetization direction of the magnetic detection section and the magnetization direction of the magnetic signal section. Features of magnetic signal matching device.