JPH0341387A - Detection coil of article discrimination instrument - Google Patents

Abstract

PURPOSE:To enable a detection coil to be arranged so that a stable output voltage can be taken out by calculating and setting the diameter of the detection coil such that maximum output can be obtained. CONSTITUTION:The integral value phi of the normal component of a magnetic field vector in the direction of the center line of a detection coil 7 is represented by the function of the diameter (r) of the coil 7, that is, phi=F(r) can hold. Since the peak value of an output voltage is proportional to the value phi, the diameter (r0) of the coil 7 at which the output voltage takes the maximum value can be calculated from an expression phimax=F(r0) (phimax: maximum value of phi). Taking a fact into consideration that, when only one pair of the coils 7 with the diameters (r0) are used, the diameter (r0) of the coil 7 is too small as compared with the width of a belt and the output voltage is not generated depending on the passing position of a magnet marker 1, a plurality of pairs of the coils 7 should be arranged in the direction of the belt width. Thus, even when the marker 1 passes an AC magnetic field in any position above the belt, a stable and large output can be secured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a detection coil used in a device for attaching a marker to an article and identifying the quantity and type of the article.

[Conventional technology]

It is known to attach a marker to an article and use the marker to detect the quantity or type of the article or to prevent the article from being stolen. For example, a device is used that passes an alternating current magnetic field through an article to which an amorphous magnetic ribbon or thin wire is attached as a marker, and detects the fluctuations in the magnetic field that occur. Figure 8 shows the main components of this device. It is a schematic diagram. In FIG. 8, an article 2 to which an amorphous magnetic ribbon or thin wire magnetic marker 1 is attached is placed on a heald 4 stretched between two pulleys 3, and as the belt 4 runs due to the rotation of the pulleys 3, it moves in the direction of the arrow. Moving.

The magnetic marker 1 is made of a magnetic ribbon or thin wire made of, for example, a Co-based amorphous alloy, and its B-H curve has a rectangular characteristic as shown in FIG. 9. One or more magnetic markers 1 are attached to an article 2 as a detection object, but depending on the situation, the magnetic marker 1 can also be used as a detection element fixed to a plastic material or the like.

? An excitation coil 5 that generates an alternating magnetic field is connected to an alternating current oscillator 6, and a detection coil 7 that detects as an induced electromotive voltage a change in magnetic flux accompanying magnetization reversal of the magnetic marker 1 caused by the alternating magnetic field is connected to a measuring device 8. ing. Excitation coil5.
AC oscillator6. The detection coil 7 and the measuring device 8 are also shown as enlarged views in FIG. 10 (81, (b)).The detection coil 7 is
Twin coils are used to cancel the induced electromotive force generated within the coil itself. The measuring device 8 identifies the pulse voltage train generated in the detection coil 7 by pattern recognition.

11(a) and 11(b) are pulse voltage waveform diagrams induced in the detection coil 7, and FIG. 11(a) shows one magnetic marker 1. FIG. 11 (bl shows the case where a plurality of magnetic markers 1 are used.

[Problem to be solved by the invention]

However, the device shown in FIG. 8 has the following problem regarding the detection coil 7.

That is, in the apparatus shown in FIG. 8, the detection coil 7 is a twin coil, and only one set is provided below the belt 4 through which the article 2 passes, and its diameter is set to an arbitrary size. The excitation coil 5
When the magnetic marker 1 passes through an alternating current magnetic field region generated in the magnetic field, the output from the detection coil 7 becomes unstable depending on its position and direction.

The present invention has been made to eliminate the above-mentioned drawbacks, and its purpose is to determine the diameter of the detection coil in such a way that maximum output is obtained and the position at which the magnetic marker is placed on the belt of the article affixed to it. It is an object of the present invention to provide a detection coil for an article identification device that is arranged so that a stable output voltage can be extracted regardless of the direction or orientation.

[Means to solve the problem]

In order to solve the above problems, the article identification device of the present invention includes:
Detection coils whose diameters are calculated so as to obtain maximum output are used in pairs, and a plurality of pairs are arranged in the width direction of the belt.

[Effect]

The integral value Φ of H, which is the vertical component of the magnetic field vector in the direction of the center line of the detection coil, is expressed as a function of the diameter r of the detection coil, and can be set as Φ - F (r), and this Φ and the output voltage Since the peak value of is in a proportional relationship, if the diameter r0 of the detection coil where the output voltage is the maximum value is the maximum value of Φ, -X = F
It can be calculated from (ro). Mote r. Simply using a pair of detection coils with a diameter of
Diameter r of detection coil. becomes smaller relative to the belt width,
Considering that the output voltage may not be generated depending on the position where the magnetic marker passes, by arranging multiple pairs of detection coils in the width direction of the belt, it is possible to detect whether the magnetic marker passes through the alternating current magnetic field at any position on the belt. It is possible to always ensure a stable and large output even when the output is high.

〔Example〕

Hereinafter, the present invention will be explained based on examples with reference to the drawings.

First, in order to describe the procedure for determining the diameter of the detection coil 7, a schematic diagram showing the relationship between the magnetic flux generated from the magnetic marker 1 and the detection coil 7 is shown in FIG. Although FIG. 1 shows only one detection coil 7 as a perspective view cut parallel to the floor, as described in FIG.
The magnetic marker 1 traveling above is magnetized by the excitation coil 5 and generates a magnetic force m9. The vector drawn on the detection coil 7 is the magnetic field strength H, and the component H□ in the direction perpendicular to the floor surface of the detection coil 7 is integrated over the shaded area, and the value Φ is generated in the detection coil 7. The induced electromotive voltage e can be expressed by the following equation.

dΦ e= -N tl) dt However, N is the number of turns of the detection coil. Therefore, the induced electromotive force e, that is, the absolute value of the pulse voltage generated in the detection coil 7 by the magnetic marker 1, will increase as dΦ increases, assuming that dt is constant. growing. As mentioned above, Φ is the value obtained by integrating the vertical component H of the magnetic field strength H at the point The peak value of the pulse wave pressure differs depending on the diameter.

FIG. 2 is a schematic perspective view showing the positional relationship between the magnetic marker 1 on the belt 4 (the article 2 is not shown) and one detection coil 7. The center of the detection coil 7a is located at that position.
When the diameter of
) used for H I+ H! +H vector diagram is shown, and Fig. 3 (1)) is shown as an enlarged view.

φ=μf f HA ds -----
・−・・・−(2) H=H+ Xcos θ, +Hz
Xcos θz '-'-------' (31l, μ: magnetic permeability, m,: magnetic charge r,: A, distance between x + rz: B1 distance between X, θ,
: Angle θ2 between Hl and the normal to the shaded area in Figure 1 : Angle kI between H2 and the normal to the shaded area in Figure 1 : Constant Figure 4 is calculated using equations (2) to (5) It is a diagram showing the relationship between Φ and the diameter of the detection coil 7, and it can be seen that there is an optimum detection coil diameter r0 at which Φ is maximum.

Therefore, in order to obtain a pulse voltage with a large output,
By calculating Φ, the optimum value r0 of the detection coil diameter can be determined.

FIG. 5 (111-(C1 is a vertical cross-sectional view of the detection coil 7,
2 is a schematic diagram showing a magnetic marker 1 and lines of magnetic force 9 generated from the magnetic marker 1. FIG. FIG. 5(a) shows a case where the detection coil 7 is too large for the magnetic marker 1,
Since there are places where the lines of magnetic force 9 cross each other in directions opposite to the cross-sectional view of the detection coil 7, Φ becomes smaller than its maximum value Φ, □. In FIG. 5), the detection coil 7 has a diameter of approximately the optimum size, and Φ becomes Φ□. In FIG. 5fc), the detection coil 7 is too small relative to the magnetic marker 1, and the cross section of the detection coil 7 is also small, so Φ is smaller than Φ and X. Therefore, in the present invention, as shown in FIG. This makes it possible to increase and stabilize the output of the device.

However, even if the diameter of the detection coil 7 can be set to an optimal value as described above, the belt 4 of the magnetic marker 1
Depending on the position over which the coil passes, there may be cases where no output can be obtained by using only one pair of twin coils. Next, we will discuss ways to deal with this.

Figure 6 (al is magnetic marker 1 on belt 4 (article 2)
(not shown) is a schematic diagram showing the positional relationship between a pair of detection coils 7, and the width direction of the belt 4 is indicated by an arrow X.
The position 0 of the center of the coordinates is added. FIG. 6(b), corresponding to FIG. 6(a), is a diagram showing changes in the pulse voltage peak value when the position of the magnetic marker 1 changes in the X direction on the belt 4, and The axis represents the pulse voltage peak value, and the horizontal axis represents the coordinate of the center of the magnetic marker 1 when the belt'AM direction is the X axis. When this X coordinate is 0, the true value of the center point of the detection coil 7 is shown. This is a case where the magnetic marker 1 is centered on the top. Figure 7 (al, (b) is a schematic diagram in which the output voltage waveform is added to Figure 6 FB+.
Figure (al indicates a pair of twin detection coils 7, in Figure 7)
indicates that a plurality of pairs of twin detection coils 7 are used. Fig. 7 (When trying to obtain an output voltage of a certain value or more from a pair of detection coils 7, for example, the magnetic marker 1 must pass through the range of line segment AB and line segment CD on the output voltage waveform. However, as shown in Fig. 7 (bl), if the twin detection coils 7
By using a plurality of pairs, no matter what position on the belt the magnetic marker 1 passes, a stable and large pulse output voltage will always be obtained in one of the detection coils 7 of the plurality of pairs.

As described above, the detection coil of the present invention used in the article identification device calculates the diameter size that generates the maximum pulse output voltage by receiving the magnetic flux from the magnetic marker, and also has two coils in the heald width direction. By arranging a plurality of pairs of detection coils, it is possible to obtain a high-output pulse voltage with no stability, no matter where the article passes on the belt.

〔Effect of the invention〕

Conventionally, the diameters of the twin detection coils used in article identification devices that use magnetic markers have not been determined appropriately, and only one pair of detection coils is provided, which makes it difficult to identify articles with magnetic markers attached. The output from the detection coil was unstable depending on the position and direction in which it was placed, but in the present invention, as described in the embodiment, the diameter of the detection coil is calculated so as to obtain the maximum output. and set
By using this detection coil and arranging multiple pairs of twin coils in the width direction of the belt, a region with large magnetic flux generated from a magnetic marker running in an alternating magnetic field will always intersect with one of the detection coils. As a result, regardless of the position or direction of the magnetic marker, a large induced electromotive force is always generated in the detection coil, and a stable output can be obtained, making it easier and more reliable to identify the quantity and identification of items. Benefits can be obtained.

[Brief explanation of the drawings] Figure 1 is a schematic diagram showing the relationship between the magnetic flux of a magnetic marker and a detection coil, and Figure 2 is a schematic perspective view showing the positional relationship between the magnetic marker on the belt and one detection coil. , Figure 3 (I
f) is a vector diagram of H,, H,, H A schematic diagram showing the relationship between the diameter of the detection coil and the lines of magnetic force of the magnetic marker, FIG. 6 (al.
6(b) is a schematic diagram showing the positional relationship between the magnetic marker on the heald and a pair of detection coils, FIG. 6(b) is a diagram showing the relationship between the change in the position of the magnetic marker and the change in the pulse voltage peak value, Figure fa+ is a schematic diagram that shows the output voltage waveform of a pair of detection coils added to Figure 6 fal, Figure 7 (b)
is also a schematic diagram when multiple pairs of detection coils are used, No. 8
The figure is a schematic diagram showing the main components of the article identification device, Figure 9 is a B-H curve diagram of the magnetic marker, and Figure 10 fa), (b
) is a partially enlarged view of the device in Fig. 9, Fig. 11(a), (
bl is a pulse voltage waveform diagram induced in the detection coil. 1: Magnetic marker, 2: Article, 4: Belt 5: Excitation coil. 7: Detection coil 9: Lines of magnetic force. 3 Toko ((1) JP-A-3 41387 (6) /! 2 Ge Figure 8 Figure 7 Figure 10 (Q) (b) Figure 11

Claims (1)

[Claims] 1) An article in which a plurality of magnetic ribbons or thin wires are used as magnetic markers and these are attached in parallel in the longitudinal direction is placed on a belt and passed through an alternating magnetic field while running, and the pulse voltage generated by the magnetic flux change of the magnetic markers is A detection coil for an article identification device that uses a pair of twin detection coils to offset the induced electromotive force from an excitation coil that generates an alternating magnetic field, the detection coil being capable of obtaining a maximum output pulse voltage with respect to the magnetic flux of the magnetic marker. 1. A detection coil for an article identification device, wherein a plurality of pairs are arranged across the width direction of the belt.