JPS61265691A - Magnetic detector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magnetic detection device used in a bill discriminating device that discriminates, for example, the type, authenticity, etc. of a bill.

[Technical background of the invention 1] For example, some banknotes have a printed pattern printed with magnetic ink, and a banknote discrimination device detects the presence or absence of a magnetic component to determine the type of banknote, authenticity, etc. is used in various banknote handling equipment. Conventionally, in such a banknote discriminating apparatus, there has been a magnetic detection device for detecting the magnetic component of a banknote using a magnetoresistive element such as INSb, and FIG. 5 shows an example thereof. That is, 1 is the main body of the device, and the detection surface 2 is on the top surface.
is formed, and the banknote P slides on this detection surface 2 by a conveyance means (not shown) and is conveyed (moved) in the direction of the arrow shown in the figure.
be done. In this case, the transport row 53 is opposite to the detection surface 2.
is provided, and the bill P is conveyed while being pressed onto the detection surface 2 by the conveyance roller 3. A magnetoresistive element 4 that converts changes in the magnetic field into changes in resistance is provided in the main body 1 adjacent to the detection surface 2, and a magnetoresistive element 4 is provided below the magnetoresistive element 4. A permanent magnet 5 as a magnetic field generating means for generating a bias magnetic field is disposed on the magnet 4 . Thus, a change in the magnetic field generated by the magnetic component of the banknote P moving on the detection surface 2 is detected by the magnetoresistive element 4 as a change in resistance value.

It converts it into an electrical signal.

The magnetoresistive element 4 is internally divided into two resistance elements 4A and 4B, which are internally connected in series, as shown in FIG. 6, for example. These resistive elements 4A and 4B are bridge-connected together with resistors 6 and 7 as shown in FIG. 6, and the output thereof is amplified by a differential amplifier 8 to be converted into an electrical signal.

[Problems with Background Art] As is clear from FIG. 5, there is only one permanent magnet that generates a bias magnetic field, and the generated magnetic flux distribution is as shown in FIG. 7. Further, the change ΔB in the magnetic flux density in the vertical direction of the detection surface 2 is inversely proportional to the distance d between the magnetoresistive element 4 and the banknote P, as shown in FIG. therefore,
As the distance d between the magnetoresistive element 4 and the banknote P increases, the change in the output of the magnetoresistive element 4 becomes smaller. Conventionally, in order to stably detect minute magnetic components of banknotes P, efforts have been made to keep this distance d constant. For example, the aforementioned conveyance roller 3 is also used for such purpose. but,
There are problems such as jams, heat, and so-called piezo noise caused by the collision of the banknotes P conveyed at a speed of In addition, the detection surface 2 and the conveyance roller 3
There was a problem in that it was very difficult to adjust the gap (up to 100 μm).

[Purpose of the Invention] The present invention has been made in view of the above circumstances, and its purpose is to eliminate all the problems of the prior art described above;
An object of the present invention is to provide a magnetic detection device that can always perform stable and accurate magnetic detection.

[Summary of the Invention 1 In order to achieve the above object, the present invention includes magnetic field generating means for generating a bias magnetic field so as to have a uniform magnetic flux density in a direction perpendicular to the detection surface, which is disposed opposite to the detection surface. This makes it possible to always perform stable and accurate magnetic detection even if the distance between the object having a magnetic component and the magnetoresistive element varies.

Embodiment of the invention Hereinafter, an embodiment of the invention will be described with reference to the drawings. Note that the same parts as in FIG. 5 are denoted by the same reference numerals, and the explanation thereof will be omitted, and only the different parts will be explained. That is, as shown in FIG. 1, a permanent magnet 9 as a magnetic field generating means for generating a bias magnetic field so as to have a uniform magnetic flux density in a direction perpendicular to the detection surface 2 is provided at an upper portion facing the detection surface 2. is further arranged. The magnetic flux distribution due to such bidirectional bias is shown in Figure 2,
Further, the change ΔB in the magnetic flux density in the vertical direction of the detection surface 2 is as shown in FIG. In addition, in FIG. 3, the solid line A shows the change in magnetic flux density when the width of the permanent magnets 5 and 9 is sufficiently large with respect to the magnetoresistive element 4, and the broken line B shows the change in magnetic flux density when the width of the permanent magnet 5 and 9 is small. ing.

With such a configuration, as is clear from the characteristics shown in FIG. 3, a constant output can always be detected even if the distance d between the banknote P and the magnetoresistive element 4 varies. Furthermore, there is no need to convey the bill P in sliding contact with the detection surface 2, and the bill P can remain in a non-contact state, and the conventional conveyance roller 3 can be omitted. Therefore, all of the above-mentioned conventional problems can be eliminated, and stable and accurate magnetic detection can be performed at all times.

In addition, instead of the permanent magnets 5 and 9, a fourth magnet that integrates them is used.
By using an integrated permanent magnet 10 as shown in the figure, it is also possible to prevent changes in the magnetic field due to vibrations or the like.

Further, in the above embodiment, the case where the magnetic component of the banknote is detected in the banknote discriminating device has been described, but the present invention is not limited to this. It can be applied to magnetic detection of objects that have objects.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to eliminate all the conventional problems and provide a magnetic detection device that can always perform stable and accurate magnetic detection.

[Brief explanation of the drawing]

Figures 1 to 3 are for explaining one embodiment of the present invention. Figure 1 is a schematic configuration diagram, Figure 2 is a diagram showing magnetic flux distribution, and Figure 3 is a diagram showing changes in magnetic flux density. Characteristic diagram showing 4th
The figure shows a modification of the present invention, Figures 5 to 8 are for explaining a conventional magnetic detection device, Figure 5 is a schematic configuration diagram, Figure 6 is an electric circuit diagram, FIG. 7 is a diagram showing magnetic flux distribution, and FIG. 8 is a characteristic diagram showing changes in magnetic flux density. P... Banknote (object with magnetic component), 1...
...Device body, 2...Detection surface, 4...
. . . Magnetoresistive element, 5 . . . Permanent magnet (first magnetic field generation means), 9 . . . Permanent magnet (211th field generation means). Agent Patent attorney Kensuke Chika (and 1 other person) Figure 11 Figure 2 Figure 3 □d Figure 4 Figure 5 Figure 6

Claims (3)

[Claims] (1) A detection surface on which an object having a magnetic component moves, a magnetoresistive element that is installed close to this detection surface and converts changes in the magnetic field into changes in resistance value, and generates a bias magnetic field on this magnetoresistive element. A magnetic detection device comprising: a first magnetic field generating means for generating a bias magnetic field so as to have a uniform magnetic flux density in a direction perpendicular to the detection surface; and a second magnetic field generating means for generating a bias magnetic field so as to have a uniform magnetic flux density in a direction perpendicular to the detection surface. (2) The magnetic detection device according to claim 1, wherein each of the first and second magnetic field generating means is a permanent magnet. (3) The magnetic detection device according to claim 1, wherein the object having a magnetic component is a banknote having a print pattern printed with magnetic ink.