EP1050855A1 - Method for detecting a magnetic identifier of a test object - Google Patents

Abstract

The device detects a magnetic identification for a test object (3) transported along a transport path (2) using a number of magnetic field sensors extending across the full width (B) of the transport path, combined with at least one magnetization devic (10,11), also extending across the full width of the transport path, in a common module (1). An Independent claim for an automatic banknote checking device is also included.

Description

Technical field

The invention relates to a device for detecting a with a magnetic identifier provided test object guided on a transport track with several magnetic field sensors and at least one magnetizing agent. The invention further relates on a banknote checking machine with such a device.

State of the art

EP 0 640 841 A1 describes a device for checking the magnetic property an American banknote. There are four magnetic heads used, which are connected in series in the transport direction of the banknote. The first Head applies a saturation field. If the banknote is out of the sphere of influence away from this head, a magnetic saturation remanence is maintained, which is from the second head, which can be combined with the first to form a structural unit, is read. The third head turns a non-saturating field of opposite polarity on and the fourth head reads the magnetic remanence field. If the banknote is true, the remanence field signals read by the second and fourth head are opposite the same, i.e. out of phase by 180 °. Counterfeit with high coercivity show different behavior and can be recognized.

The method known from EP 0 640 841 A1 therefore measures the magnetic behavior (Hysteresis curve) of a magnetizable layer with low particle density.

Sensor arrangements are also known with which the different strip spacings a US banknote can be detected. The WO is an example 94/12952 cited. There are two for each magnetic stripe pattern to be recognized or more sensors placed next to each other in one of the periods of the respective Strip pattern corresponding distance. So e.g. three different stripe patterns To differentiate, three different sensor arrangements are typically one behind the other Three magnetoresistive sensors arranged next to each other are required.

The known devices are specific to the identification features present in US banknotes aligned and cannot easily be used for other currencies deploy.

Presentation of the invention

The object of the invention is to provide a device of the type mentioned, which without the need for a structural change to test a variety of different ones magnetic characteristics is suitable.

The solution to the problem is defined by the features of claim 1. As a result the largest possible number of magnetic field sensors in one over the entire width the transport path of the banknote (test object) extending unit. The As an integral part, the structural unit also includes parts that extend across the entire width Means for magnetizing a test area.

The invention makes it possible to use automatic test machines for different currencies with a standardized unit for the review of whatever magnetic identifier. The differentiation related to the test object can be achieved purely in software. In other words, the hardware is with everyone Applications are the same, only different (specific) software is loaded.

The magnetizing means preferably comprise one that extends over the entire width Permanent magnet. To this magnetic field in the surface of the test object to bring, two can also extend across the entire width of the transport path Pole shoes with a gap in between may be provided.

The field for biasing or saturating the layer can also be electromagnetic Funds are generated.

The Hall element sensors of the type as they are preferred as magnetic field sensors are described in EP 0 772 046 A2 (Sentron AG). These can be in integrate a chip and have a small space requirement. You can use low field strengths Detect parallel to the chip surface and are relatively insensitive to the outside Interference fields (e.g. also against stray fields of the magnetizing agent).

A magnetic field sensor of the type described has two flux concentrators with one air gap in between and at least one Hall element outside the air gap on. At least part of that from the first flow concentrator to the second flow concentrator leading field lines of the magnetic field flood the Hall element. The above Sensors can be integrated on a chip using the known techniques of microelectronics become. Such a so-called cylindrical Hall element is sensitive to the magnetic field, parallel to the surface in which the magnetic flux concentrators are integrated. Overall, such an element is particularly good at the direction of magnetization Customized banknote.

To improve the geometric resolution, the sensors can be offset in two from each other arranged rows must be built. So the sensors are in the back row in the spaces between those in the front row. The two rows will be arranged as close together as possible. The distance between the rows is e.g. in the order of magnitude the distance of the sensors within a row. Will the banknotes Transversely to their longitudinal direction, are typically per row according to the invention several dozen sensors are provided. A geometric resolution in the Range of a few millimeters can be achieved.

The magnetic field sensors are advantageously arranged on a plate-shaped carrier element, which is on the end face and essentially perpendicular to a circuit board is attached for signal processing. The carrier element (with all Hall sensors) is considerably smaller than the circuit board mentioned (which are equipped on both sides can). The result is a compact T-shaped construction.

If one between the magnetizing means and the carrier element or the sensors magnetic shielding (partition) is provided, the dimensions of the Unit in the direction of the note transport direction can be minimized.

To protect against dust and damage, the magnetic field sensors can be behind a Cover (z. B. a copper-coated epoxy resin plate) may be arranged. This is in accordance with the basic idea of the invention, a self-contained unit to create, which is used as a finished module in a holder of a testing machine and can be connected in terms of data via a standardized interface.

As already mentioned, the unit according to the invention is specifically for banknote recognition, in combination e.g. suitable with optical test units. After this The same principle can also be used for other test objects with a geometric magnetic Marking to be examined.

From the following detailed description and the entirety of the claims there are further advantageous embodiments and combinations of features of the invention.

Brief description of the drawings

Fig. 1

eine schematische Darstellung eines erfindungsgemässen Moduls in der Draufsicht;

Fig. 2

eine schematische Darstellung des Moduls im Querschnitt.

The drawings used to explain the exemplary embodiment show:

Fig. 1

a schematic representation of a module according to the invention in plan view;

Fig. 2

a schematic representation of the module in cross section.

In principle, the same parts are provided with the same reference symbols in the figures.

Ways of Carrying Out the Invention

1 shows a top view of a module 1 according to the invention. It is on a transport track 2 arranged, which runs here in the plane of the drawing and symbolized by two lines is. Its width is greater than the width B of the transport track 2.

Banknotes 3 are unreferenced on the transport track 2 at a relatively high speed promoted in transport direction 4. Unreferenced means that the lateral position with respect to the track boundaries is not fixed. A first banknote can therefore be more left and a subsequent second is located on the right on the transport track 2. It’s even possible that banknote 3 arrives with a slight inclination. In the example according to Fig. 1 the banknote 3 is conveyed in the transverse direction, d. H. the long side of banknote 3 stands perpendicular to the direction of transport 4.

According to the invention, module 1 has a large number of Hall sensors 5.1, ..., 5.N, 6.1, ..., 6.N. They are preferably in two (transverse to the transport direction 4) Rows 7, 8 arranged. On each row 7, 8 there are e.g. N = 40 to N = 50 Hall sensors with the smallest possible mutual distance. The Hall sensors 6.1. ..., 6, N the second row 8 are in the spaces between the Hall sensors 5.1, ..., 5.N of the first Row 7 set. The resolution (viewed transversely to the direction of transport 4) can thus be several Lines are brought per centimeter.

The sensor arrangement described is one that extends over the entire width of the module 1 Small magnetizing gap 9 upstream. It is between the two pole pieces 10, 11 formed. It brings a saturating magnetic field into the transport path (and thus into the test object).

If the bank note 3 with its magnetic identifier 12 is guided past the module 1, the magnetizing gap first pre-magnetizes the identifier 12 (which e.g. a number printed with magnetic ink has been reached). If the identifier 12 afterwards past the Hall sensors, these are activated. That means, those in the affected Hall sensors located in the area signal a magnetic field. By a clocked Activation of the sensors can additionally trigger a resolution in the transport direction from the bank note 3 and thus generate a magnetic pixel image. In principle, this can processed digitally like an optical image. For referencing the magnetic If necessary, the pixel image can be based on the result of a (with an upstream in the Module derived) optical orientation can be used.

It should be noted that the magnetic identifier, wherever it is on the test object and what dimensions it has, with the device according to the invention can be.

In order to achieve a good signal-to-noise ratio, the bandwidth of the Amplifier to the speed of the banknote and the desired spatial resolution be adjusted. (With a banknote speed of e.g. v = 800 mm / s and one desired resolution of Lmin = 2 mm, Lmax = 10 mm is the required frequency band between Fmin = v / Lmax = 80 Hz and Fmax = v / Lmin = 400 Hz.)

2 shows an example of the cross section of a specific embodiment. On the front side a carrier 13 (which, for example, can be an integral part of the module housing can) a rod-shaped permanent magnet 14 is attached. (The longitudinal axis of the permanent magnet 14 is perpendicular to the plane of the drawing.) To the side of the permanent magnet 14 are the (magnetically conductive) pole shoes 10 and 11, which are where they connect to the transport path 2 border, form a magnetizing gap 9.

A shield 15 is provided laterally next to the pole piece 11 in the carrier 13. It is, for example, a partition made of a suitable material. It is vertical to transport track 2 (front of the module) and should be the stray field of the above Keep magnetizing agents away from the sensor part of module 1.

The sensor part is towards the transport path 2 through an epoxy resin plate 16 e.g. with copper coating 17 (spring bronze) completed as a cover. The coated side of the Epoxy resin plate 16 and the front of the pole shoes 10,11 form a continuous smooth plane along which the banknote (driven by suitably arranged rollers) glides can. On the back of the epoxy resin board 16 is a ceramic circuit board 19 attached. It carries the Hall sensors 5.1, 6.1 designed as chip elements.

So that the distance of the Hall sensors 5.1, 6.1 to the transport track 2 (and thus to the banknote) can be kept as small as possible, the epoxy resin plate 16 is in the corresponding Provide area 18 with a recess (e.g. milling).

The ceramic printed circuit board 19 is on the front side of a printed circuit board via two angle pin strips 20, 21 22 attached for the sensor electronics. The latter is therefore perpendicular to the front of module 1. The sensor electronics performs the processing (amplification, multiplexing) of the sensor signals so that they can be sent to a Evaluation unit (not shown) can be passed on.

The linear arrangement of the Hall sensors creates a magnetic field for each pixel proportional analog voltage.

The module 1 has a housing made of aluminum and is preferably with mounting elements or mechanical couplings, so that it can be easily gripped into one Banknote recognition machines can be installed.

The invention is not limited to the described embodiments. Basically Although one or two rows of sensors are preferred, they can be used in special circumstances but also more (e.g. three) rows can be provided. The sensor elements of the different Rows should be placed offset to each other in order to achieve the greatest possible resolution to reach.

Instead of Hall sensors, other components can also be used. In each It is the case, however, that the distance between the sensors does not depend on a periodicity of a certain one Magnetic structure of the test object, but to the desired image resolution is aligned. Usually the sensors are placed as close to each other as possible. The electronics can also be at least partially integrated on the magnetic field sensor chip his.

The structural design according to FIG. 2 allows a compact construction but in its nature not essential for the objective of the invention. In particular there is other options for designing the front end or for accommodation the sensor electronics.

In summary, it should be noted that the invention is a versatile and manufacturing technology has created advantageous unit to detect magnetic patterns and to consider.

Claims (10)

Device for detecting a magnetic identification (12) test object (3) guided on a transport track (2) with several magnetic field sensors and at least one magnetizing agent, characterized in that that the largest possible number of magnetic field sensors (5.1, ..., 5.N; 6.1, ..., 6.N) in a structural unit which extends over an entire width of the transport path) (1) together with the magnetization means, which also extend over the entire width are accommodated. Device according to claim 1, characterized in that the magnetizing means comprise a rod-shaped permanent magnet (14). Device according to one of claims 1 or 2, characterized in that the Magnetic field sensors cylindrical Hall elements with sensitivity to a field parallel to a surface of the test object and that they are in regular Distances are arranged on at least one straight line (7, 8). Device according to one of claims 1 to 3, characterized in that the Magnetic field sensors on two straight lines immediately one behind the other (7, 8) are arranged offset. Device according to one of claims 1 to 4, characterized in that the Magnetic field sensors (5.1, ..., 5.N; 6.1, ..., 6.N) on a ceramic carrier plate (19) on the face and essentially perpendicular to one with signal conditioning electronics assembled circuit board (22) are attached. Device according to one of claims 1 to 5, characterized in that between the magnetization means and the magnetic field sensors (5.1, ..., 5.N; 6.1, ..., 6.N) a magnetic shield is provided. Device according to one of claims 1 to 6, characterized in that the Magnetic field sensors (5.1, ..., 5.N; 6.1, ..., 6.N) to the transport path (2) through a metal-coated epoxy resin plate (16) are covered. Device according to one of claims 1 to 7, characterized in that more than 20 magnetic field sensors (5.1, ..., 5.N; 6.1, ..., 6.N) are provided to Detect banknote identifier. Banknote checking machine with at least one device according to claim 1. Banknote checking machine according to claim 9, characterized in that also optical Detectors for determining the position and location of the funded banknote are provided are.

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