JPH10242893A - Tag information reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the influence of magnetic flux of an exciting coil and to improve the signal-to-noise ratio as the time of reading tag information by composing a receiving coil of a couple of differentially connected coils and arranging them so that pieces of magnetic flux applied to the respective coils from the exciting coil become equal in the absolute value. SOLUTION: The couple of coils 3A and 3B which are connected differentially to constitute the receiving coil are formed to 1/2 as large as the area of the surface that the exciting oil 1 forms, and arranged at positions where magnetic fields from the exciting coil 1 become equal without making the surfaces overlap with each other in the surface of the exciting coil 1. A radio tag 21 attached to an article 30 moving on a conveyor 22 one receiving an exciting signal from the exciting coil 1 sends tag information stored in the memory through a tag coil at, for example, a transmit signal frequency 1/2 as high as the exciting signal frequency. Either of the coils 3A and 3B when approaching the radio tag 21 can receive the tag information without being disturbed by the exciting signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tag information reading apparatus for reading and recognizing tag information as desired information stored in a tag IC carried by a person or attached to an object from outside without contact. .

[0002]

2. Description of the Related Art FIG. 19 is a view showing a tag information transmitting / receiving system. The tag information transmitting / receiving system shown in FIG. That is, in the tag information reading device 20,
The wireless tag 21 is excited by electromagnetic induction, receives desired tag information transmitted from the excited wireless tag 21, and demodulates the tag information into data.

The tag information reading device 20 includes an exciting coil 1, an exciting circuit unit 2, a receiving coil 3 and a reading circuit unit 4. The wireless tag 21 includes a memory 5, a tag coil 6, and an IC (Integrated Circuit). ) 7. That is, the excitation circuit unit 2 controls the excitation coil 1 by supplying an electric signal for exciting the excitation coil 1, and is configured by, for example, an AC power supply.

The receiving coil 3 receives a magnetic flux including the tag information generated by the wireless tag 21 as an electric signal, and the tag information received by the receiving coil 3 is amplified by the reading circuit unit 4. , Are demodulated and converted into data. Further, the memory 5 of the wireless tag 21 stores desired information as tag information (information for identifying the article to which the wireless tag 21 is attached, etc.). This is for obtaining energy for starting the wireless tag 21 by a signal using an electromagnetic induction technique and transmitting the tag information stored in the memory 5.

Therefore, the tag coil 6 has two functions as a coil for receiving energy from the exciting coil 1 and a coil for transmitting data to the receiving coil 3. The IC 7 controls the tag information stored in the memory 5 to be transmitted via the tag coil 6 when the wireless tag 21 is activated by the energy obtained by the tag coil 6.

In the tag information transmission / reception system shown in FIG. 19, for example, as shown in FIG. 20A, the excitation coil 1 and the reception coil 3 of the tag information reading device 20 and the tag coil 6 of the wireless tag 21 are separated. The three coils are arranged substantially coaxially and arranged so that the coils face each other. In particular, the exciting coil 1 and the receiving coil 3 are arranged substantially on the same plane. The reading device 20 and the wireless tag 21
Energy and signal transmission efficiency between the two.

That is, by arranging the tag information reading device 20 and the wireless tag 21 as described above, FIG.
As shown in (b), an excitation signal (magnetic flux for supplying power to the wireless tag 21) 8 generated by the excitation coil 1 to the tag coil 6 can be efficiently passed through the tag coil 6, while the tag coil 6 The magnetic flux (including the tag information to be transmitted to the tag information reading device 20) 9 generated at the above can be efficiently penetrated into the receiving coil 3.

[0008]

However, in the tag information transmitting / receiving system shown in FIG. 19, the exciting coil 1 and the receiving coil 3 are arranged on substantially the same plane. Thus, the unnecessary magnetic flux 8 from the exciting coil 1 penetrates the receiving coil 3,
There is a problem that a signal of the weak magnetic flux 9 may not be demodulated and read.

In other words, in the tag information reading device 20, since the exciting coil 1 and the receiving coil 3 are formed on substantially the same plane, the magnetic flux 8 as an exciting signal from the exciting coil 1 is applied to the receiving coil 3. Are linked according to the coil area ratio. Since the excitation signal 8 is usually stronger than the signal 9 from the tag coil 6 to be received, the reception coil 3
, The detection of the excitation signal 8 causes a reduction in the signal-to-noise ratio of the reception signal detected by the reception coil 3.

On the other hand, a magnetic flux having a frequency of 125 kHz is used for energy transmission by the excitation coil 1, while a magnetic flux having a frequency of 62.5 kHz is used for signal transmission from the tag coil 6 to the receiving coil 3. And set the frequency to 125 kHz and 6
It is conceivable that a filter circuit (for example, a low-pass filter or a band-pass filter) that removes a 125-kHz signal from a 2.5-kHz signal and extracts a 62.5-kHz signal is read and mounted in the memory circuit unit 4.

However, when a filter circuit is applied to remove the excitation signal 8 contained in the reception signal of the reception coil 3, the frequency transmission characteristic of the filter circuit is limited. When the frequency is about 125 kHz: 62.5 kHz (= 2: 1) as described above, it is not possible to sufficiently remove the signal in the 125 kHz band.

In other words, in the reading circuit section 4,
When amplifying the reception signal from the reception coil 3, the frequency component of the excitation signal 8, which is a disturbance, may be removed by a filter circuit. However, the frequency component is usually about twice as high as the frequency of the signal 9 from the wireless tag 21. There is a limit to the characteristics of the filter circuit in removing the excitation signal 8 by the filter circuit.

Further, as described above, in the tag information transmitting / receiving system shown in FIG. 19, in order to read information from the wireless tag 21 efficiently, the tag coil 6 of the wireless tag 21 is connected to the receiving coil of the tag information reading device 20. 3, the direction of which is almost the same as that of the tag information reading device 20.
The condition that the wireless tag 21 is fixed to the article is restricted because the condition that the wireless tag 21 is on the extension of the central axis of the two coils 1 and 3 is used. There is also a problem that it takes time and effort to rearrange the articles so that the 21 faces the optimal direction with respect to the tag information reading device 20.

To enable reading by the tag information reading device 20 irrespective of the orientation of the surface of the wireless tag 21, a plurality of excitation coils 1 may be arranged three-dimensionally. In this case, the individual receiving coils 3 receive the excitation signals from all the adjacent excitation coils 1, and there is also a problem that the disturbance may be further increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and improves the accuracy of read data by improving the signal-to-noise ratio when reading tag information. It is an object of the present invention to provide a tag information reading device capable of reading a signal from a wireless tag without any restriction.

[0016]

Therefore, a tag information reading apparatus according to the present invention includes an exciting coil for exciting a tag coil in a wireless tag, and tag information transmitted from the wireless tag by exciting the tag coil by the exciting coil. In a tag information reading device provided with a receiving coil for receiving, the receiving coil is characterized in that it is configured to cancel an induced voltage due to a magnetic flux from an exciting coil, and thereby, tag information from the tag coil can be obtained. When reading a weak signal including the signal, the effect of the magnetic flux generated by the exciting coil is eliminated.

Furthermore, the receiving coil can be constituted by a pair of coils connected differentially, and the absolute values of the magnetic flux entering each of the pair of coils from the exciting coil can be equalized. While reading a weak signal including tag information from the tag coil, the influence of the magnetic flux generated by the exciting coil can be eliminated (claim 2).

Further, the receiving coil is formed by a single figure-eight coil, and a magnetic flux having an absolute value equal to each other is formed on each of two surfaces through which the magnetic flux from the exciting coil can pass in the figure-eight coil. Can be configured to enter
Even in this case, it is possible to eliminate the influence of the magnetic flux generated by the excitation coil when reading a weak signal including the tag information from the tag coil.

Furthermore, the above-mentioned pair of coils can be arranged in or near the plane formed by the exciting coil so that the planes formed by the pair of coils do not overlap each other. The effect of the magnetic flux generated by the exciting coil when reading a weak signal including the tag information can be eliminated (claim 4). Further, at least two sets of the above-described excitation coil and the pair of coils can be arranged on the outer periphery of the passage of the wireless tag.
Directional restriction of the tag IC to excite the tag coil and reliably read the signal including the tag information while eliminating the influence of the magnetic flux generated by the excitation coil when reading the weak signal including the tag information from the tag coil. Can be reduced (claim 5).

Further, a pair of coils may be arranged so as to face each other with a surface formed by the exciting coil therebetween, and the wireless tag may be configured to pass through the inside of the exciting coil and the pair of coils. Also, it is possible to eliminate the influence of the magnetic flux generated by the excitation coil when reading a weak signal including the tag information from the tag coil (claim 6).

Further, the tag information reading device of the present invention
In a tag information reading device that excites a tag coil of a wireless tag and receives tag information from the wireless tag, a first excitation coil that excites the tag coil and a wireless tag that cancels an induced voltage due to a magnetic flux from the first excitation coil. And a first receiving coil composed of a pair of coils that are differentially connected to each other to receive the tag information described above, and the absolute value of the magnetic flux entering each of the pair of coils from the first excitation coil is configured to be equal. A pair of coils are disposed so as to face each other with a surface formed by the first excitation coil therebetween, and a first coil unit configured so that the wireless tag passes through the inside of the first excitation coil and the pair of coils is provided. In order to receive the tag information from the wireless tag while canceling out the induced voltage due to the magnetic flux from the second exciting coil and the second exciting coil for exciting the tag coil, And a second reception coil comprising a pair of coils operatively connected to each other, wherein the second reception coil is configured such that the absolute values of magnetic fluxes entering each of the pair of coils of the second reception coil from the second excitation coil become equal. A pair of coils is provided in or near the plane formed by the second excitation coil,
At least two pairs of second coil units are arranged on the outer periphery of the first coil unit so as to prevent the surfaces formed by the pair of coils from overlapping each other, and the second excitation coil is a pair of coils of the first reception coil. It is characterized by being arranged so as to be close to each of the boundary positions, thereby eliminating the influence of the magnetic flux generated by the excitation coil when reading a weak signal including the tag information from the tag coil, It is possible to eliminate the directional restriction of the tag IC for exciting the tag coil and reliably reading the signal including the tag information (claim 7).

[0022]

Embodiments of the present invention will be described below with reference to the drawings. (A) Description of First Embodiment FIGS. 1 to 3 show a first embodiment of the present invention.
1 is a schematic perspective view showing a tag information transmitting / receiving system to which a tag information reading device according to a first embodiment of the present invention is applied, and FIG. 2 is a diagram illustrating a tag information reading device and a wireless tag according to the first embodiment of the present invention. FIGS. 3A and 3B are diagrams illustrating a main part of the tag information reading apparatus according to the first embodiment of the present invention. FIG. FIG. 3A is a schematic diagram showing the main part, and FIG. 3B is an equivalent circuit diagram of the main part.

Here, the tag information transmitting / receiving system according to the first embodiment shown in FIG. 1 or FIG. 2 is for reading the tag information stored in the wireless tag 21 attached to the article 30 traveling on the conveyor 22. And a tag information reading device 20A. That is, the tag information transmitting / receiving system as shown in FIG. 1 or FIG. By receiving the information wirelessly, it is possible to identify the package, which is expected to simplify subsequent distribution journals and the like.

The tag information transmitting / receiving system can be applied to a system in which a person has the wireless tag 21 and identifies each person. Here, the tag information reading device 20A according to the first embodiment includes an exciting coil 1;
It has a pair of coils 3A and 3B as the receiving coil 3, and has an exciting circuit section 2 and a reading circuit section 4 having substantially the same functions as those shown in FIG. 19 (see FIG. 1). , The excitation circuit section 2 and the reading circuit section 4 are not shown). Note that a coil set 23 is formed by the above-described excitation coil 1 and the pair of coils 3A and 3B.

Here, the exciting coil 1 of the first embodiment is
The tag coil of the wireless tag 21 is excited, and is arranged to generate an exciting magnetic flux in a direction substantially orthogonal to the traveling direction of the wireless tag 21. The wireless tag 21 can be the same as that shown in FIG. 19 described above, and a detailed description thereof will be omitted.

Further, the receiving coil 3 composed of a pair of coils 3A and 3B excites the tag information transmitted from the wireless tag 21 by exciting the tag coil 6 (see FIG. 19) of the wireless tag 21 by the exciting coil 1. This is to cancel the induced voltage due to the exciting magnetic flux from the exciting coil 1. Specifically, the coils 3A,
Each of the coils 3B has a size sufficiently larger than that of the wireless tag 21 and is sequentially arranged in the traveling direction of the wireless tag 21 so that the surfaces of the coils 3A and 3B do not overlap with each other.

Further, the coils 3A, 3B are arranged in the plane formed by the exciting coil 1, and the coils 3A, 3B
The coils B and B are arranged so that the surfaces of the coils 3A and 3B do not overlap with each other while the area of the surface formed by B is の of that of the exciting coil 1. Thereby, the absolute values of the magnetic flux 8 (see FIG. 3A) from the exciting coil 1 entering each of the coils 3A and 3B are made equal.

In other words, the coils 3A and 3B are located in the plane defined by the exciting coil 1 so that the absolute values of the magnetic fluxes 8 entering the respective coils 3A and 3B from the exciting coil 1 are equal, and the coils 3A and 3B are equal to each other. 3B are arranged so as not to overlap with each other. In addition, these 2
The three coils 3A and 3B are arranged at the same position with the magnetic field from the exciting coil 1 and are differentially connected.

Here, the coil has a polarity that depends on the direction (or winding direction) of the magnetic pole when current flows, but the differential connection of the coil means that the two coils have the same polarity. It connects them. Accordingly, since the pair of coils 3A and 3B as the receiving coil are differentially connected, the output signal (the induced voltage at both ends of the coils 3A and 3B) is the output voltage of the induced voltage generated in the two coils 3A and 3B. The difference is output.

In the above-described differential connection, at least two coils 3A and 3B may be connected on the same side with the same polarity, as shown in FIG. 1 or FIG.
As shown in (b), the pair of coils 3A and 3B may be arranged so that the winding directions are opposite to each other, or may be arranged so that the winding directions are the same. In addition, coil 3
When the induced voltages are canceled by A and 3B, based on Lenz's law that a current flows in a direction that prevents the magnetic flux from changing, even if the pair of coils 3A and 3B have the same position, the polarities are reversed (for example, the windings are wound). The direction is right-handed to left-handed)
It takes advantage of the fact that the direction of the induced current changes when it is set to.

For example, when the magnetic flux penetrating through the coil 3A or the coil 3B among the magnetic fluxes 8 generated by the excitation coil 1 is φ, the excitation signal e received by the coil 3A or the coil 3B
Is represented by Faraday's law as shown in equation (1). e = −N (dφ / dt) (1) where N is the number of turns of the coils 3A and 3B, and e is a signal having the same frequency as the excitation signal from the excitation coil 1 but having a different phase. Further, when the pair of coils 3A and 3B are differentially connected, even if the same magnetic flux φ penetrates from the same direction, the voltages induced in the individual coils 3A and 3B have opposite phases. It becomes zero theoretically.

That is, if the absolute values of the magnetic flux from the exciting coil 1 entering the coils 3A and 3B are made equal, the output signals of the differentially connected coils 3A and 3B will
The induced voltage due to is canceled out. With the above configuration, in the tag information reading device 20A according to the first embodiment of the present invention, as shown in FIGS. 1 and 2, the article 30 with the wireless tag 21 travels on the conveyor 22, When the tag 21 approaches one of the pair of coils 3A and 3B, the tag 21 is excited by receiving an excitation signal from the excitation coil 1 to activate the wireless tag 21. In the activated wireless tag 21, the IC 7 (FIG. 1)
9), the tag information stored in the memory 5 is transmitted via the tag coil 6.

At this time, the magnetic flux 9 emitted from the wireless tag 21
Can be received by the coil 3A, 3B that is closer to the wireless tag 21 of the pair of coils 3A, 3B. That is, the magnetic flux 9 emitted from the wireless tag 21 can be read when approaching any one of the pair of coils 3A and 3B. For example, as shown in FIG. 2, when the wireless tag 21 passes through the position P on the conveyor 22, the tag information transmitted from the wireless tag 21
When the wireless tag 21 passes through the position R while being received by one of the coils 3A and 3B, the tag information transmitted from the wireless tag 21 is the other of the pair of coils 3A and 3B. Received by coil 3B.

When the wireless tag 21 passes through any of the positions P and R on the conveyor 22, the pair of coils 3A and 3B receive the same amount of magnetic flux φ from the exciting coil 1 but are differentially connected. In the output signals from the coils 3A and 3B, the induced voltage due to the magnetic flux from the exciting coil 1 is cancelled. That is, a pair of coils 3
A and 3B receive the same exciting magnetic flux from the exciting coil 1, but since the pair of coils 3A and 3B are differentially connected, the coils 3A and 3B are output as the receiving coil 3 outputs.
In the reception signals output from the output terminals A and B of FIG. 3B (see FIG. 3B), the excitation magnetic flux from the excitation coil 1 is canceled. Therefore, the receiving coil 3 can output the tag information read signal while improving the signal-to-noise ratio.

Note that the wireless tag 21 has two coils 3A,
When passing through an intermediate position (position Q in FIG. 2) of the coil 3B, the magnetic flux 9 emitted from the wireless tag 21 is also canceled, but at least the front position of one of the coils 3A and 3B (FIG. 2).
At the positions P, R). As described above, according to the tag information reading device 20A according to the first embodiment of the present invention, the coils 3A and 3B can cancel out the induced voltage due to the magnetic flux from the exciting coil 1; It is possible to improve the signal-to-noise ratio when receiving and reading the signal including the tag information, to improve the accuracy of the read data, and to increase the area in which communication with the wireless tag 21 is possible. .

In the above-described first embodiment, the excitation signal from the excitation coil 1 is canceled by differentially connecting the pair of coils 3A and 3B. However, the present invention is not limited to this. For example, even if a figure-eight coil configured so that magnetic fluxes having the same absolute value enter each of two surfaces through which the magnetic flux from the excitation coil 1 can pass is used, the two coils are differentially connected. Since a coil equivalent to this case can be configured, the same advantages as in the case of the above-described first embodiment can be obtained in this case as well.

In the above-described first embodiment, at least two sets of the exciting coil 1 and the pair of coils 3A and 3B constituting the coil set 23 can be arranged on the outer periphery of the passage of the wireless tag 21. That is, for example, as shown in FIG. 4, two sets of left and right coil sets 23-1 and 23-2 can be provided so as to face each other along the conveyor 22. Here, as shown in FIG.
1 and the coil set 23-2 are respectively
1, 1-2 and receiving coils 3-1 and 3-2. Each of the receiving coils 3-1 and 3-2 is constituted by a pair of differentially connected coils 3A and 3B.

The excitation coils 1-1 and 1-2 are connected in series to the same AC power supply (excitation circuit section) 2, so that the excitation coils 1-1 and 1-2 are connected to each other. A magnetic flux of the same phase that is substantially orthogonal to the traveling direction of the wireless tag 21 is generated. Further, each receiving coil 3-
Reference numerals 1 and 3-2 denote two excitation coils 1-1 and 1-2.
, The excitation signals generated by the two receiving coils 3-1 and 3-2 are output from a signal combiner as a reading circuit unit (see reference numeral 4 in FIG. 19). At 10, the signal from the wireless tag 21 is added.

Therefore, by providing the two coil sets 23-1 and 23-2 so as to face each other along the conveyor 22, the induced voltage due to the magnetic flux from the exciting coils 1-1 and 1-2 is offset. Therefore, the same advantages as those of the first embodiment can be obtained, and the wireless tag 21 can be obtained.
The tag information can be received regardless of whether the tag is facing left or right with respect to the traveling direction, and there is an advantage that the restriction on the direction of the wireless tag 21 attached to the article 30 can be reduced.

As shown in FIG. 6, for example, coil sets 23-1 to 23-4 are provided on the four outer surfaces of the passage of the wireless tag 21 (the upper and lower surfaces as well as the left and right sides of the conveyor 22).
Can also be provided. That is, the coil sets 23-1 to 23-1
23-4 are each provided with an exciting coil and a receiving coil (not shown) having the same functions as those shown in FIG. 1 described above (in FIGS. 7 to 10 described later,
Only the receiving coil 3-2 of the coil set 23-2 and the exciting coils 1-1 to 1-4 of the coil sets 23-1 to 23-4 are shown).

Here, when the coil sets 23-1 to 23-4 are arranged on the four surfaces on the outer periphery of the passage of the wireless tag 21, the influence of the two exciting coils facing each other on the receiving coil facing in the same direction. 7 and 8
This will be described below with reference to FIG. In this case,
As shown in FIG. 7, the figure-shaped coil 3-2 as a receiving coil of the coil set 23-2 is provided with exciting coils 1-1 and 1-1 oriented in the same direction as the figure-shaped coil 3-2.
2 focuses on the effects of the other receiving coils 3
The same applies to -1,3-3,3-4.

Here, in FIG. 7 and FIG. 8, assuming that two kinds of magnetic flux penetrating the figure-eight coil 3-2 are φa and φb, the relationship between these φa and φb is as shown in the equation (2). Become equal. Therefore, the output of the figure-eight coil 3-2 equivalent to the two differentially connected coils is as shown in Expression (3), and cancels the magnetic flux from the excitation coils 1-1 and 1-2. . As a result, the figure-8 coil 3-2 becomes the exciting coil 1
It can be said that there is no influence from the magnetic flux generated in -1 and 1-2.

Φa = φb (2) φa−φb = 0 (3) Also, regarding the influence of the receiving coil due to the magnetic flux from the exciting coil adjacent to (or close to) the direction by 90 ° with respect to the receiving coil, This will be described below with reference to FIGS.

Also in this case, as shown in FIG. 9, the figure-shaped coil 3-2 as the receiving coil of the coil set 23-2 is oriented 90 degrees with respect to the figure-shaped coil 3-2. ° Exciting coils 1-3 and 1 that are different and adjacent
The focus is on the effect of -4. Here, the values of the two types of magnetic fluxes φa and φb generated in the exciting coils 1-3 and 1-4 and intersecting with the receiving coil 3-2 are small, and are approximated as shown in Expression (4). can do. Therefore, the output of the figure-eight coil 3-2 equivalent to the two coils connected differentially becomes as shown in the equation (5), and cancels the magnetic flux from the exciting coils 1-3 and 1-4. Can be.
As a result, the figure-8 coil 3-2 becomes the exciting coil 1-3,
It can be said that there is no influence by the magnetic flux generated in 1-4.

Φa = φb ≒ 0 (4) φa−φb = 0 (5) That is, even when the four opposed coil sets 23-1 to 23-4 are arranged on the upper, lower, left, and right sides of the conveyor 22, respectively. The penetration of the magnetic flux from the exciting coil into the receiving coil can be canceled.

Therefore, by providing the coil sets 23-1 to 23-4 on the four surfaces on the outer periphery of the passage of the wireless tag 21,
Not only has the same advantages as the above-described first embodiment, but also when the wireless tag 21 is facing up, down, left, or right with respect to the traveling direction, the tag information can be received. The tag information can be reliably received without restriction on the direction of the wireless tag 21.

(B) Description of the Second Embodiment FIG. 11 is a schematic perspective view showing a tag information transmitting / receiving system to which the tag information reading device according to the second embodiment of the present invention is applied, and is shown in FIG. The tag information transmission / reception system is for reading tag information stored in the wireless tag 21 attached to the article 30 traveling on the conveyor 22, as in the case of the first embodiment described above. A tag information reading device 20B different from that in the first embodiment is provided.

In FIG. 11, the same reference numerals as those in FIG. 1 indicate the same parts. Here, the tag information reading device 20B shown in FIG. 11 also includes the exciting coil 11 and a pair of coils 13A and 13B as the receiving coil 13, and the same exciting circuit unit as that in the first embodiment described above. 2 and a reading circuit unit 4 (in FIG. 11, the reading circuit unit 4
Is not shown).

In the tag information transmitting / receiving system according to the second embodiment, the exciting coil 11 and the pair of coils 13A, 13A constituting the tag information reading device 20B are provided.
The conveyor 22 as a passage for the article 30 passes through the opening B. That is, the pair of coils 13A, 13A of the tag information reading device 20B according to the second embodiment.
The wireless tag 3B is disposed so as to face the surface formed by the exciting coil 11, and the wireless tag 21 passes through the inside (opening) of the exciting coil 11 and the pair of coils 13A and 13B.

Specifically, three coils (the excitation coil 1
1 and the pair of coils 13A, 13B) have substantially the same dimensions, so that the areas of the surfaces formed by the three coils 11, 13A, 13B are substantially the same size.
A pair of coils 3A and 3B are arranged at a point where the magnetic flux from the excitation coil 11 becomes the same before and after along the traveling direction of the conveyor 22 with the excitation coil 11 at the center. Note that the coil set 24 is configured by the excitation coil 11 and the pair of coils 13A and 13B arranged as described above.

Here, the exciting coil 11 is
, And is arranged to generate an exciting magnetic flux in a direction substantially parallel to the traveling direction of the wireless tag 21. Further, the pair of coils 13A and 13B as the receiving coil 13 receive the tag information transmitted from the wireless tag 21 by exciting the tag coil 6 (see FIG. 19) of the wireless tag 21 by the exciting coil 1. Thus, as in the first embodiment described above,
The differential connection is made so as to cancel the induced voltage due to the exciting magnetic flux from the exciting coil 1.

That is, the pair of coils 13A, 13B
As shown in FIG. 12, the pair of coils 13A and 13B are differentially connected to each other, so that the coils 13A and 13B are output as the output of the receiving coil 13 as shown in FIG. In the received signals output from the output terminals A and B, the exciting magnetic flux from the exciting coil 11 is canceled.

The pair of coils 13A and 13B according to the second embodiment are connected in series with their winding directions being opposite to each other as shown in FIGS. 11 and 12, but according to the present invention. For example, if at least the differential connection is made, the winding directions may be the same. With the configuration described above, in the tag information reading device 20B according to the second embodiment of the present invention, as shown in FIGS. 11 and 12, the article 30 with the wireless tag 21 proceeds on the conveyor 22, The wireless tag 21 passes inside each of the excitation coil 11 and the pair of coils 13A and 13B.

Here, the wireless tag 21 is connected to the pair of coils 13
A, 13B, and the surface formed by the wireless tag 21 is the excitation coil 11 and the pair of coils 13.
At the same time as the plane formed by the A and 13B, the wireless tag 21 is excited by receiving an excitation signal from the exciting coil 11.
Is started. Further, the activated wireless tag 21 transmits the tag information stored in the memory 5 to the receiving coil 13 via the tag coil 6 based on the control by the IC 7 (see FIG. 19).

At this time, the magnetic flux 9 emitted from the wireless tag 21
Is the wireless tag 21 of the pair of coils 13A and 13B.
Can be received by the coils 13A and 13B that are closer to. That is, the magnetic flux 9 emitted from the wireless tag 21 can be read when approaching any one of the pair of coils 13A and 13B. Here, a pair of coils 1
3A and 13B receive the same exciting magnetic flux from the exciting coil 11, but the pair of coils 13A and 13B
Are connected differentially, the received signals output from the output terminals A and B of the coils 13A and 13B as the output of the receiving coil 13 cancel out the exciting magnetic flux from the exciting coil 11. Therefore, the receiving coil 13 can output the tag information read signal while improving the signal-to-noise ratio.

When the wireless tag 21 passes through the exciting coil 11, the magnetic flux generated from the wireless tag 21 is also canceled, but the tag information is surely obtained at least at a position close to one of the coils 13 A and 13 B. Can be read. Thus, according to the tag information reading device 20B according to the second embodiment of the present invention, the pair of coils 13A,
13B are arranged to face each other with the surface formed by the exciting coil 11 therebetween, and the wireless tag 21 is configured to pass through the inside of the exciting coil 11 and the pair of coils 13A and 13B. In addition to canceling out the induced voltage due to the magnetic flux from the wireless tag 11, the signal-to-noise ratio when receiving and reading the signal including the tag information from the wireless tag 21 can be improved, and the accuracy of the read data can be improved. There is also an advantage that the communicable area with the tag 21 can be expanded.

(C) Description of Third Embodiment FIG. 13 is a schematic perspective view showing a tag information transmitting / receiving system to which the tag information reading device according to the third embodiment of the present invention is applied, and is shown in FIG. The tag information transmitting / receiving system includes a tag information reading device 20C different from those in the above-described embodiments, and also includes a conveyor 22 having functions substantially similar to those of the embodiments.

Here, the tag information reading device 20C according to the third embodiment excites the tag coil 6 (see FIG. 19) of the wireless tag 21 to receive the tag information from the wireless tag 21. A coil set 23-1 to 23-4 similar to that shown in FIG. 6 and a coil set 24 similar to that shown in FIG. 11 are provided. That is, the tag information reading device 20 </ b> C includes four coil sets (second coil units) 2 arranged on the outer periphery of the conveyor 22 in the upper, lower, left and right directions
In addition to 3-1 to 23-4, a coil set (first coil unit) 24 in the tag information reading device 20B according to the second embodiment is arranged, whereby the wireless tag 21 faces in all directions. However, it is possible to reliably receive the tag information.

The coil set 24 includes a first exciting coil 11 and a first receiving coil 13 substantially similar to those in the second embodiment (see FIG. 11).
The coil sets 23-1 to 23-4 respectively include the second excitation coils 1-1 to 1-4 and the second reception coils 3-1 to 3-4 having substantially the same functions as those shown in FIG. The detailed description of these components is omitted.

That is, the first receiving coil 13 of the coil set 24 also includes a pair of coils 13A and 13B similar to the case of the above-described second embodiment, and the first receiving coil 13 of the coil set 23-1 to 23-4 has the same configuration. 2 receiving coils 3-1 to 3-4
Also includes a pair of coils 13A and 13B similar to those shown in FIG. Here, the second excitation coils 1-1 to 1-4 are disposed so as to be close to (adjacent to) the respective boundary positions of the pair of coils 13A and 13B in the first reception coil 13, and the first excitation coil 11
Are arranged along the boundary between the pair of coils 3A and 3B in the coil sets 23-1 to 23-4.

In the tag information reading device 20C according to the third embodiment, the coil sets 23-1 to 23-2
As the receiving coil of 3-4, for example, a figure-eight coil configured so that magnetic fluxes having the same absolute value enter each of two surfaces through which the magnetic flux from the exciting coil 1 can pass can be used. By the way, the second receiving coil 3-1
3-4, the pair of coils 3A and 3B are differentially connected to each other, so that the second excitation coils 1-1 to 1-4 are formed.
14 to 16, the second receiving coils 3-1 to 3-4 are formed by the first excitation coil 11 of the coil set 24, as shown in FIGS. Also, the induced voltage due to the magnetic flux can be canceled.

14 to 16, the magnetic flux from the first exciting coil 11 causes the coil set 23
The description is given focusing on the influence of the second receiving coils 3-1 and 3-2 of -1, 23-2. FIG. 14 is a schematic perspective view showing an arrangement relationship between the first excitation coil 11 and the second reception coils 3-1 and 3-2 of the tag information reading device 20C, and FIG. FIG. 16 is a diagram showing a state in which a magnetic flux that flows is entering the second receiving coils 3-1 and 3-2. FIG. 16 is a diagram showing that the receiving coils 3-1 and 3-2 are connected in series (equivalent circuit diagram). It is.

Here, the second receiving coils 3-1 and 3-2 facing (opposing) with the conveyor 22 interposed therebetween are arranged at symmetrical positions with respect to the exciting coil 11, so that the -1, 3-2, a pair of coils 3A, 3
The relationship of the magnetic flux received from the exciting coil 11 for each of B
Equations (6) to (10) are as follows. In Expressions (6) to (10), among the magnetic fluxes generated by the exciting coil 11, the magnetic fluxes entering the pair of coils 3A and 3B of the second receiving coil 3-1 are φd and φc, respectively. A pair of coils 3 in the two receiving coils 3-2
The magnetic fluxes entering A and 3B are φb and φa, respectively.

| Φa | = | φb | = | φc | = | φd | (6) φa = −φb (7) φc = −φd (8) φa = −φc (9) φb = −φd (10) A pair of coils 3 in the second receiving coils 3-1 and 3-2
Since A and 3B are differentially connected, each of the above equations (6)
To (10), each second receiving coil 3-1 and 3-2
, The magnetic flux component by the exciting coil 11 as shown in the following equations (11) and (12) is detected.

Φa−φb = 2φa> 0 (11) φc−φd = 2φc> 0 (12) By the way, as described above, the opposing second receiving coil 3
Since the outputs of -1 and 3-2 are added, the result of the addition (the outputs of the terminals A and B in FIG. 16) is as shown in the following equation (13).

2φa + 2φc = 2φa−2φa = 0 (13) That is, in each output of the second receiving coils 3-1 and 3-2 (output by differential connection of the pair of coils 3A and 3B), the first excitation is performed. Although the magnetic flux from the coil 11 cannot be canceled, when the opposing second receiving coils 3-1 and 3-2 are connected in series, the tag information reading in which the magnetic flux from the first exciting coil 11 is canceled. It can output a signal.

This is because, as shown in FIG. 15, a clockwise magnetic flux enters the second receiving coil 3-2 of the opposed coil set 23-2, while the second receiving coil 3-2 of the opposed coil set 23-1.
It can also be seen from the fact that counterclockwise magnetic flux enters the receiving coil 3-1 and the output voltages induced by these second receiving coils 3-1 and 3-2 are in opposite phases. Note that FIG.
As in the case of FIG. 16, the tag information reading signal in which the induced voltage due to the magnetic flux generated in the first exciting coil 11 is canceled from the second receiving coils 3-3 and 3-4 connected in series is output. can do.

Therefore, at least the second receiving coils 3-1 and 3-2 (or the second receiving coils 3-3 and 3-
4) are connected in series, so that the second receiving coil 3-
1 to 3-4 can also cancel out the induced voltage due to the magnetic flux from the first excitation coil 11. Further, as in the case of the above-described second embodiment, the pair of coils 13A and 13B of the first receiving coil 13 are differentially connected to cancel out the induced voltage due to the magnetic flux from the first exciting coil 11. However, as shown in FIGS. 17 and 18, the first receiving coil 13 is connected to the second exciting coils 1-1 to 1-1-1.
Thus, the induced voltage due to the magnetic flux from No. 4 can be canceled.

FIGS. 17 and 18 focus on the influence of the magnetic flux from the second excitation coils 1-1 and 1-2 on the first receiving coil 13 of the coil set 24. Here, FIG. 17 is a schematic perspective view showing an arrangement relationship between the second exciting coils 1-1 and 1-2 and the first receiving coil 13 of the tag information reading device 20C, and FIG. 18 is a diagram showing the second exciting coil 1-1. , 1-2 generate the first magnetic flux.
It is a figure showing signs that a pair of coils 13A and 13B in receiving coil 13 enter.

By the way, the second excitation coils 1-1 and 1-2
The magnetic flux generated by the pair of coils 1 adjacent to (adjacent to) the second excitation coils 1-1 and 1-2 in directions different from each other by 90 °.
The components φa and φb intersecting with 3A and 13B are small. This is, as shown in FIG.
A and 13B respectively have second excitation coils 1-1 and 1-1.
This is because the magnetic fluxes having the opposite directions and the same magnitude are intersected from 1-2, and both φa and φb can be approximated to 0 as shown in Expression (14).

Φa = φb ≒ 0 (14) Since the pair of coils 13A and 13B are differentially connected, the output of the first receiving coil 13 (A in FIG. 12) is obtained as shown in Expression (15). −B terminal output)
Equation (15) is obtained. φa−φb = 0 (15) Accordingly, the first receiving coil 13 is connected to the second exciting coil 1−
Also, the induced voltage due to the magnetic flux from 1, 1-2 can be canceled.

The influence of the magnetic flux from the second exciting coils 1-3 and 1-4 on the first receiving coil 13 is also described below.
This is the same as the case of FIGS. 17 and 18 described above. Therefore, the first receiving coil 13 can also cancel the induced voltage due to the magnetic flux from the second exciting coils 1-1 to 1-4. That is, the first receiving coil 13 and the second receiving coil 3-
In the tag information read signals output from 1-3 to 4-4, the induced voltage due to the magnetic flux from all of the excitation coils 1-1 to 1-4 and 11 can be canceled.

With the above configuration, the tag information reading device 20C according to the third embodiment of the present invention has the configuration shown in FIG.
As shown in FIG. 3, the article 30 to which the wireless tag 21 is attached advances on the conveyor 22, and the wireless tag 21 passes through the inside of each of the exciting coil 11 and the pair of coils 13A and 13B. Here, even if the tag coil 6 (see FIG. 19) of the wireless tag 21 faces in any direction on the conveyor 22, the first excitation coil 11 and the second excitation coil 1-1 can be used.
Are excited by at least one of the magnetic fluxes from.

When excited, the wireless tag 21 transmits the tag information stored in the memory 5 via the tag coil 6 under the control of the IC 7. At this time, the magnetic flux 9 emitted from the wireless tag 21 crosses at least one of the first receiving coils 3-1 to 3-4 and the second receiving coil 13. In other words, the tag information transmitted from the wireless tag 21 can be received by at least one of the first receiving coils 3-1 to 3-4 and the second receiving coil 13.

In the tag information read signals output from the first receiving coil 13 and the second receiving coils 3-1 to 3-4, all the exciting coils 1-1 to 1-4, 1
The induced voltage due to the magnetic flux from 1 is cancelled. Therefore, the first reception coil 13 or the second reception coils 3-1 to 3-3
-4 can be output while improving the signal-to-noise ratio.

As described above, according to the tag information reading apparatus 20C according to the third embodiment of the present invention, the second exciting coils 1-1 to 1-4 are formed by the pair of coils 13A and 13B in the first receiving coil 13. Of the tag information read signals output from the first receiving coil 13 and the second receiving coils 3-1 to 3-4. -1 to
Voltages induced by magnetic fluxes from 1-4, 11 can be canceled out, the signal-to-noise ratio when receiving and reading a signal including tag information from the wireless tag 21 can be improved, and the accuracy of read data can be improved. And wireless tag 2
In addition to the advantage that the communicable area with the wireless tag 21 can be expanded, the receiving coils 3-1 to 3-4 and 13 can reliably receive the tag information regardless of the direction of the wireless tag 21. There are also benefits that can be done.

[0077]

As described above in detail, according to the tag information reading apparatus of the present invention, the receiving coil is configured to cancel the induced voltage due to the magnetic flux from the exciting coil. Therefore, it is possible to improve the signal-to-noise ratio when receiving and reading a signal containing tag information from the wireless tag, thereby improving the accuracy of the read data, and expanding the communication area with the wireless tag. There are also advantages that can be.

According to the tag information reading device of the present invention, the exciting coil and the pair of coils are
Since at least two sets are arranged on the outer periphery of the passage of the wireless tag, there is also an advantage that the restriction on the installation direction of the wireless tag can be reduced. Further, according to the tag information reading device of the present invention, the pair of coils are arranged to face each other with the surface formed by the exciting coil therebetween, so that the wireless tag passes inside the exciting coil and the pair of coils. Since the receiving coil cancels out the induced voltage due to the magnetic flux from the exciting coil, the signal-to-noise ratio when receiving and reading the signal including the tag information from the wireless tag can be improved. In addition to improving the accuracy of the wireless tag, there is an advantage that the communicable area with the wireless tag can be expanded.

Further, according to the tag information reading apparatus of the present invention, the second excitation coil is disposed so as to be close to each boundary position of the pair of coils in the first receiving coil. In the tag information reading signals output from the first receiving coil and the second receiving coil, the induced voltage due to the magnetic flux from all the exciting coils can be canceled, and the signal including the tag information from the wireless tag is received. And improve the signal-to-noise ratio when reading, improving the accuracy of the read data,
In addition to the advantage that the communicable area with the wireless tag can be expanded, the tag information can be reliably received by the first receiving coil or the second receiving coil regardless of the direction of the wireless tag. There is also an advantage that can be.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a tag information transmitting / receiving system to which a tag information reading device according to a first embodiment of the present invention is applied.

FIG. 2 is a diagram for explaining a communication mode between the tag information reading device and the wireless tag according to the first embodiment of the present invention.

FIGS. 3A and 3B show main parts of the tag information reading apparatus according to the first embodiment of the present invention, wherein FIG. 3A is a schematic diagram showing the main parts, and FIG. 3B is an equivalent circuit diagram of the main parts. .

FIG. 4 is a schematic perspective view showing a tag information transmitting / receiving system to which a tag information reading device according to a modification of the first embodiment of the present invention is applied.

FIG. 5 is a diagram (equivalent circuit diagram) illustrating a main part of a tag information reading device according to a modification of the first embodiment of the present invention.

FIG. 6 is a schematic perspective view showing a tag information transmitting / receiving system to which a tag information reading device according to a modification of the first embodiment of the present invention is applied.

FIG. 7 is a diagram illustrating an operation of a modification of the first embodiment of the present invention.

FIG. 8 is a diagram illustrating an operation of a modification of the first embodiment of the present invention.

FIG. 9 is a diagram illustrating an operation of a modification of the first embodiment of the present invention.

FIG. 10 is a diagram for explaining an operation of a modification of the first embodiment of the present invention.

FIG. 11 is a schematic perspective view showing a tag information transmitting / receiving system to which a tag information reading device according to a second embodiment of the present invention is applied.

FIG. 12 is a diagram (equivalent circuit diagram) showing a main part of the tag information reading device according to the first embodiment of the present invention.

FIG. 13 is a schematic perspective view showing a tag information transmitting / receiving system to which the tag information reading device according to the third embodiment of the present invention is applied.

FIG. 14 is a diagram for explaining the operation of the third embodiment of the present invention.

FIG. 15 is a diagram for explaining the operation of the third embodiment of the present invention.

FIG. 16 is a diagram for explaining the operation of the third embodiment of the present invention.

FIG. 17 is a diagram for explaining the operation of the third embodiment of the present invention.

FIG. 18 is a diagram for explaining the operation of the third embodiment of the present invention.

FIG. 19 is a diagram showing a tag information transmission / reception system.

20 (a) and (b) are diagrams each showing an example of a coil arrangement in the tag information transmitting / receiving system shown in FIG. 19;

[Explanation of symbols]

 1, 1-1 to 1-4 Exciting coil 2 Exciting circuit unit 3, 3-1 to 3-4 Receiving coil 3A, 3B coil 4 Reading circuit unit 5 Memory 6 Tag coil 7 IC 8, 9 Magnetic flux 11 Exciting coil 13 Receiving coil 13A, 13B Coil 20, 20A to 20C Tag information reading device 21 Wireless tag 22 Conveyor 23-1 to 23-4 Coil set (second coil part) 24 Coil set (first coil part) 30 Article

Claims (7)

[Claims] 1. A tag information reading device comprising: an exciting coil for exciting a tag coil in a wireless tag; and a receiving coil for receiving tag information transmitted from the wireless tag by exciting the tag coil by the exciting coil. 2. The tag information reading device according to claim 1, wherein the receiving coil is configured to cancel an induced voltage due to a magnetic flux from the exciting coil. 2. The receiving coil according to claim 1, wherein said receiving coil is constituted by a pair of coils which are differentially connected, and wherein an absolute value of a magnetic flux entering each of said pair of coils from said exciting coil is equal. The tag information reading device according to claim 1, characterized in that: 3. The receiving coil is formed by a single figure-eight coil, and the absolute value of each of the two faces through which the magnetic flux from the exciting coil can pass in the figure-eight coil is different from each other. 2. The tag information reading device according to claim 1, wherein the tag information reading device is configured to receive an equal magnetic flux. 4. The apparatus according to claim 2, wherein the pair of coils are arranged in or near a plane defined by the exciting coil so that the planes defined by the pair of coils do not overlap each other. Tag information reading device. 5. The excitation coil and a pair of coils described above,
The tag information reading device according to claim 4, wherein at least two sets are arranged on the outer periphery of the passage of the wireless tag. 6. The wireless tag according to claim 1, wherein the pair of coils are disposed to face each other with a surface formed by the exciting coil therebetween, and the wireless tag is configured to pass through the inside of the exciting coil and the pair of coils. The tag information reading device according to claim 2, which performs the operation. 7. A tag information reading device for exciting a tag coil of a wireless tag and receiving tag information from the wireless tag, comprising: a first exciting coil for exciting the tag coil; and a magnetic flux induced from the first exciting coil. A first receiving coil comprising a pair of differentially connected coils for receiving the tag information from the wireless tag while canceling the voltage, and entering each of the pair of coils from the first exciting coil The magnetic flux is configured so that the absolute values of the magnetic fluxes are equal, the pair of coils are disposed opposite to each other across the surface formed by the first excitation coil, and the wireless tag passes inside the first excitation coil and the pair of coils. And a second coil for exciting the tag coil and a voltage induced by a magnetic flux from the second exciting coil. A second receiving coil composed of a pair of coils connected differentially to receive tag information from the wireless tag, and entering each of the pair of coils of the second receiving coil from the second exciting coil The pair of coils of the second receiving coil are configured so that the absolute values of the magnetic fluxes are equal, and the surfaces of the pair of coils do not overlap each other in or near the plane of the second excitation coil. At least two sets of the second coil portions are arranged on the outer periphery of the first coil portion so as to face each other, and the second excitation coil is located close to each boundary position of the pair of coils in the first receiving coil. A tag information reading device, characterized in that the tag information reading device is arranged so as to perform reading.