JP4747750B2 - Environmental change detection system - Google Patents

Description

  The present invention relates to a system that detects an environmental change of an article or the like using a wireless IC tag that is set so that a resonance frequency changes with an environmental change such as temperature and humidity.

  Conventionally, a tag has been used exclusively to detect the presence of an article or identify an article, and has not been used to grasp environmental changes such as temperature and humidity during the transportation or storage of an article. Recently, there has been a demand for a method that can easily grasp environmental changes of articles using tags.

  For example, in order to easily grasp changes in the environment such as the temperature of an article, a tag having a resonance circuit set so that the resonance frequency is changed when there is an environment change, and when there is a change A system has been proposed in which communication is attempted at the same frequency as the resonance frequency of each case, and a predetermined environmental change is detected depending on whether or not communication has been made (for example, Patent Document 1).

In this patent document 1, a reader that communicates at the same frequency as a predetermined resonance frequency when the resonance frequency changes, and a reader that communicates at the same frequency as the predetermined resonance frequency when the resonance frequency does not change. Are prepared, and the former is used as an abnormal article detection reader and the latter is used as a normal article management reader.
JP 2005-135132 A

  However, a reader corresponding to the resonance frequency before the change and a reader corresponding to the resonance frequency after the change are prepared separately, or a frequency scan type reader that performs communication while switching a plurality of frequencies is prepared. Compared with the case where a system is constructed using a general IC tag reader (including an IC tag reader / writer) that communicates with a wireless IC tag at a predetermined frequency in conformity with the standard for wireless IC tags. There is a problem that the range of design selection is narrowed and the cost is increased.

  The present invention has been made to cope with such a situation, and in a system in which the resonance frequency of the tag changes in accordance with a change in the environment of the tag, it is not necessary to prepare a reading device having a frequency corresponding to the change in the frequency. It is an object of the present invention to provide an environment change detection system that can be constructed and operated more easily by using a general IC tag reader that communicates with a tag at a specific frequency.

  In order to achieve the above object, an environment change detection system according to an aspect of the present invention includes a resonance circuit configured to change a resonance frequency from a first resonance frequency to a second resonance frequency in accordance with an environment change, and the resonance circuit. A system comprising an environmental change sensing tag having an IC chip connected to a circuit, and a reading device that reads data from the tag in a non-contact manner, and the reading power level of the reading device is When a radio wave of a predetermined frequency is transmitted from a position at a predetermined interval, a first power level that can communicate with a tag that resonates at the first resonance frequency and a second that can communicate with the tag of the second resonance frequency And a first determination unit that determines whether or not there is an environmental change in accordance with a transmission power level communicable with the tag.

  In the present invention, the reader can be configured to use a set of tag readers capable of setting and changing the transmission power level according to an instruction from the outside.

  The reading device has a tag reader having a predetermined transmission power level, an antenna connected to the tag reader and capable of transmitting / receiving to / from the tag, and disposed between the antenna and the tag reader. A configuration using a variable power attenuator or variable power amplifier capable of attenuating or amplifying may be used. Of course, it is also possible to configure the reading apparatus using two sets of tag readers having different transmission power levels.

  In order to achieve the above object, an environment change detection system according to another aspect of the present invention includes a resonance set so that the resonance frequency changes from the first resonance frequency to the second resonance frequency in accordance with the environment change. A system comprising an environment change sensing tag having a circuit and an IC chip connected to the resonance circuit, and a reading device for reading data from the tag in a non-contact manner, wherein the reading position of the reading device is When the transmission power level and the frequency are constant, a first position that can communicate with a tag that resonates at the first resonance frequency, and a second position that can communicate with a tag that resonates at the second resonance frequency And a second determination means for determining whether or not there is an environmental change in accordance with a position where communication with the tag is possible.

  In order to enable installation at the first position and the second position, the reading device can switch between two antennas by using two antennas for one tag reader communicating at a predetermined frequency and at a predetermined transmission power level. Can be configured. It may be mobile with one antenna. Of course, two sets of antennas and tag readers may be prepared and arranged at respective positions.

  According to the present invention, in a system in which the resonance frequency of the tag changes with the environmental change of the tag, there is no need to prepare a reader having a frequency corresponding to the frequency change, and the IC that communicates with the IC tag at a predetermined frequency. It is possible to detect the presence or absence of a change in tag frequency using a tag reader. Therefore, according to the present invention, it is possible to provide an environment change detection system that allows a wider range of system design choices and can be more easily constructed and operated.

  The present invention is a wireless IC tag (hereinafter referred to as an environmental change detection tag) having a resonance circuit set so that the resonance frequency changes from a predetermined first resonance frequency f1 to a second resonance frequency f2 in accordance with an environmental change. In other words, the present invention relates to a system for detecting an environmental change by using the tag to determine whether the resonance frequency has changed or not as an environmental change of the tag. Here, “environmental change” means that the predetermined index of the environment where the tag is placed has changed so as to deviate from the predetermined allowable range. Examples of the index include temperature and humidity. Water, pressure, gas concentration, acceleration, impact, etc. are appropriately selected. The index does not need to be one and may be composite.

  Here, the resonance frequency f1 before the change and the resonance frequency f2 after the change are predetermined frequencies that are different from each other so that they can be distinguished from each other (for example, about 3 to 5 MHz). Either f1 or f2 may be a higher frequency, but one of f1 and f2 is a predetermined frequency in a frequency band (for example, 13.56 MHz band, 900 MHz band, 2.45 GHz band, etc.) that complies with the wireless IC tag standard. The frequency is the same as or close to the frequency of the frequency of. The frequency fr of the reading device that reads the data of the wireless IC tag is also a frequency that complies with the standard. Therefore, for example, when the frequency f1 before the change is set to be the same as or close to the frequency fr of the reader, the reader can communicate with the tag before the change even with a relatively small transmission power. The tag after the change cannot be communicated unless the transmission power is increased or the distance is shortened. When the frequency f2 after the change is set to be the same as or close to the frequency fr of the reading device, conversely, the reading device cannot communicate with the tag before the change unless the transmission power is increased or the distance is shortened. However, the tag after the change can be communicated far away even with relatively small transmission power. The present invention utilizes such a natural law.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings and the following description, the same components are generally denoted by the same reference numerals and words, and description thereof is omitted.

(Outline of environmental change detection system)
FIG. 1 is a diagram illustrating an appearance of a configuration of an example of an environment change detection system to which the present invention is applied. As shown in the figure, in this example, a large number of articles 31 such as fresh foods, which are individually packaged in a box or the like and attached with an environmental change detection tag 10, are stored in a storage 310 that is a freezer. When using it, put it on the conveyor belt 360, take it out one by one, pass it through the gate 210 in order, read the identification information of the tag 10 with the reading device 20, determine the presence or absence of the change of the resonance frequency, necessary The related processing and the processing result are displayed according to the above, and the article with the tag 10A having no change in the resonance frequency is selected as a non-defective product 31A, and the article with the tag 10B having a change in the resonance frequency is not specified. This is a system for sorting as non-defective product 31B.

[First Embodiment]
(Functional configuration of environmental change detection system)
FIG. 2 is a diagram showing an outline of the functional configuration of the first embodiment of the present invention. In FIG. 2, reference numeral 10 indicates an environmental change detection tag, and reference numeral 20 indicates a reader. The broken line with the code | symbol 350 shows an electromagnetic wave. The reason why “f1 or f2” is written in the rectangle 10 is that the environment change detection tag 10 (hereinafter also simply referred to as tag 10) is configured to resonate at the frequency f1 or f2. Is shown. P_High and P_Low indicate that the reader 20 is configured to be able to switch its transmission power level between a high level P_High and a low level P_Low. Here, the transmission power level is high level P_High means that when the tag 10 and the reading device 20 are arranged at a predetermined interval and a radio wave having a predetermined frequency fr is transmitted from the reading device 20 to the tag 10, f1, The power level is set to a large power level that enables communication even with a tag that resonates at a frequency that is significantly different from fr of f2, and the transmission power level is low P_Low is close to fr of f1 and f2. The power level is set so as to be low enough to communicate with a tag that resonates at one frequency but cannot communicate with a tag that resonates at the other frequency. In this manner, the strength of the electric field and magnetic field of the radio wave 350 emitted from the reading device 20 is switched by switching the transmission power level of the reading device 20 between high and low. Then, the reading device 20 of the present embodiment attempts to determine the presence or absence of a change in the frequency of the tag 10 by switching the power level and transmitting radio waves and checking the presence or absence of a response from the tag 10. . The relationship between these frequencies and transmission power levels and their settings will be described later.

  As shown in FIGS. 1 and 2, the environment change detection processing system 1 according to the present embodiment includes an environment change detection tag 10 and a reading device 20. The tag 10 is a wireless IC tag including a resonance circuit 110 that is also an antenna, and is configured to resonate at a first frequency f1 during normal times and to change to a second resonance frequency f2 after sensing an environmental change. ing. An IC chip is mounted on the tag 10, and at least identification information unique to the tag is stored in the memory of the IC chip, and can be read from the reading device 20 by wireless communication without contact. Has been. Details of the environment change detection tag 10 will be described later.

  As shown in FIG. 1 and FIG. 2, in this example, the antenna 21 of the reading device 20 has a substantially constant distance d from the tag 10 mounted on the article 31 passing through the gate 210. Is installed. Note that it is not essential to provide a gate, and the antenna 21 of the reading device 20 may be directly installed on both sides of the transport belt 360 or the like. The distance d between the antennas of the tag 10 and the reading device 20 is adjusted in advance in consideration of antenna characteristics, allowable transmission power level, installation location, operating conditions, and other conveniences.

(Configuration example of reader)
Next, an example of the configuration of the reading device 20 in the present embodiment will be described with reference to FIG.

  As shown in FIG. 2, the reading device 20 includes an antenna 21 that transmits and receives a radio wave having a predetermined frequency fr, a tag reader 22, and a detection processing unit 23, which can function as a set of reading devices 20. Connected and set up. As described above, the reading device 20 can switch the transmission power level, more specifically, the power level supplied from the tag reader 22 to the antenna 21 between two power levels, a high level P_High and a low level P_Low. It is configured as follows.

  The tag reader 22 is a wireless transmitter capable of transmitting a radio wave having a predetermined frequency fr conforming to the standard for IC tags to the tag 10 via the antenna 21 based on an instruction from the detection processing unit 23. . The tag reader 22 is also a wireless receiver that receives radio waves from the tag 10 via the antenna 21, converts the received signal into a predetermined format that can be read by the detection processing unit 23, and passes the signal to the detection processing unit 23. The tag reader 22 has a function capable of setting the power supplied to the antenna 21 (also referred to as the transmission power of the tag reader 22) to an instructed value based on an instruction from the detection processing unit 23. By switching the transmission power level of the tag reader 22 between high and low, the strength of the electric field and magnetic field of the radio wave emitted from the antenna 21 of the reader 20 can be switched. The tag reader 22 may have a function of writing to the tag 10, but may not have a writing function.

  As the tag reader 22, a commercially available reader / writer or reader / writer module for a wireless IC tag, which can arbitrarily set a transmission power level from an external program or the like, can be used. The tag reader 22 may be stored in an independent housing, may be of a substrate type that can be mounted on a host computer, or is housed in a single chip and incorporated into a substrate or the like. It may be provided in any form. Further, the antenna 21 and the tag reader 22 may be integrated.

  The detection processing unit 23 is a device that performs various processes necessary for the environment change detection processing system 1. The detection processing unit 23 can instruct the tag reader 22 to set the power level of the transmission power to the high level P_High or the low level P_Low. The detection processing unit 23 can issue a reading instruction toward the tag 10 via the tag reader 22. If there is a response from the tag 10, the detection processing unit 23 responds to a reading instruction such as identification information from the tag 10 via the tag reader 22. Data (response) can be received. The detection processing unit 23 can know at least the presence / absence of a response from the tag 10 via the tag reader 22. Based on the presence / absence of a response from the tag 10, the detection processing unit 23 can determine the presence / absence of a change in the resonance frequency of the tag 10, thereby detecting the presence / absence of an environmental change in the article to which the tag 10 is attached. Can be processed. Necessary information can be extracted from the received response, saved, and saved information and processing results can be displayed.

  The detection processing unit 23 is composed of, for example, a computer main body provided with a memory, a hard disk or the like in which a program or data for processing for this system is stored, a display capable of displaying the result, and an MPU capable of executing the program. be able to. If the tag reader 22 is sufficiently small, such as being housed in one chip, the tag reader 22 can be incorporated into the detection processing unit 23 to integrate the device, and the whole can be made portable enough to be held with one hand. .

  As shown in FIG. 1, the reading device 20 may be provided with a display for displaying the result. However, a display is not provided, and a lamp is turned on only when there is an abnormality (environmental change) It may be a simple configuration such as ringing.

(Relationship between resonance frequency of tag and transmission power level)
Here, the resonance frequency f1 before the change, the resonance frequency f2 after the change, the frequency fr of the reader 20 (tag reader 22), and the transmission power levels P_High and P_Low of the reader 20 will be described with reference to FIGS. explain.

  FIG. 3 shows the minimum necessary for receiving a response from the tag when the antenna 21 connected to the tag reader 22 is arranged at a constant interval d toward the antenna of the tag and a radio wave of frequency fr is emitted. It is the graph which showed the transmission power level (minimum communicable power). In FIG. 3, the horizontal axis represents the center of the resonance frequency of the tag, and the vertical axis represents the minimum communicable power with the tag that resonates at the frequency fr in dB (decibel) with reference (0 dB). In the figure, P1 is the power level corresponding to the intersection of the lines Pf and f1, and therefore indicates the minimum power level that can be communicated with the tag that resonates at the frequency f1, and P2 is the tag that resonates at the frequency f2. The minimum communicable power level is shown. As shown in the figure, if the resonance frequency of the tag is close to the frequency fr of the tag reader 22, communication with the tag is possible with a small transmission power level. However, the resonance frequency of the tag is as large as the frequency fr of the tag reader 22. If the frequency is different, communication with the tag is not possible unless the transmission power level is high.

  Thus, when the transmission frequency and the communication distance are kept constant and the frequency on the tag reader side is set to a predetermined frequency, the minimum communicable power and the resonance frequency of the tag are approximately as shown by the line Pf in the graph of FIG. It has become a relationship. Therefore, in order to distinguish the tag frequency based on the communicable power level, either the resonance frequency f1 before the change or the resonance frequency f2 after the change is set to be the same as or close to the transmission / reception frequency fr of the tag reader 22. Is preferred. Either f1 or f2 may be set to be the same as or near fr, but FIG. 3 shows a case where f2 is set near fr. As shown in FIG. 3, it is necessary that f1 and f2 have different frequencies so as not to be within the error range. By doing so, it is possible to determine whether or not there is a change in the resonance frequency of the tag based on the difference in the transmission power level that can be communicated. Either f1 or f2 may be larger. For example, f1 may be a value on the left side of the drawing, or may be a value ((f1) on the right side of the drawing) that is a substantially line-symmetrical position with respect to fr.

  As shown in FIG. 3, when the frequency f2 is set close to fr and f1 is greatly different from f2, the minimum power P1 that can communicate with the tag that resonates at the frequency f1 is the same as the tag that resonates at the frequency f2. The value is an order of magnitude greater than the minimum communicable power P2. In order to communicate with a tag that resonates at frequency f2, it is possible to transmit radio waves with a transmission power greater than or equal to P2, but to communicate with a tag that resonates at frequency f1, P1 It is necessary to transmit radio waves with a transmission power of the above magnitude. In other words, the reading device 20 in the present embodiment may set the transmission power of the high level P_High to a magnitude greater than or equal to P1, and set the transmission power of the low level P_Low to a magnitude greater than or equal to P2 and smaller than P1. In consideration of variations in the actual tag resonance frequency, errors, etc., as shown in FIG. 3, P_Low is set to be slightly larger than P2 and significantly smaller than P1, and P_High is slightly larger than P1. It is preferable to set to. By doing so, even if there is some variation or error in the resonance frequency of the actual tag, it is possible to reliably distinguish whether there is a change in the resonance frequency of the tag due to the difference in the power level that can be communicated with the tag. it can.

  4 sets the resonance frequency f1 of the tag before the change, the resonance frequency f2 of the tag after the change, the frequency fr of the reader 20, the high level P_High and the low level P_Low of the transmission power in the relationship shown in FIG. Then, when the reading device 20 transmits a radio wave to the tag 10, “○” indicates that the reading device 20 can receive the response of the tag 10 (can communicate), and cannot receive the response of the tag 10 (cannot communicate). The case is indicated by “x”. As shown in FIG. 4, a radio wave having a transmission power P_High level can communicate with a tag 10 that resonates at either frequency f1 or f2, but a radio wave having a transmission power P_Low level can resonate at a frequency f1. 10 and cannot communicate with only the tag 10 that resonates at the frequency f2.

  FIG. 5 is a graph showing a result of an experiment of the minimum communicable power using a 13.56 MHz band tag, a reader / writer, and a set of antennas, with a constant distance between the antenna of the tag and the reader / writer. In FIG. 5, the horizontal axis indicates the center of the resonance frequency of the tag, and the vertical axis indicates the minimum power (minimum communicable power) when communication with the tag is possible. The vertical axis on the left is expressed in dB (decibel) with the minimum communicable power with the tag resonating at 13.56 MHz as the reference (0 dB), and the vertical axis on the right is how many times the reference It is a representation. FIG. 5 does not show a frequency higher than 14.5 MHz, but it is a matter of course that a substantially bilaterally symmetric relationship is established about 13.56 MHz as in FIG.

  As shown in FIG. 5, when the distance between the antenna of the reading device 20 and the antenna surface of the tag 10 is constant, the reading device 20 including an antenna that emits a 13.56 MHz radio wave toward the tag. To communicate with a tag that resonates at 5 MHz, power that is 1000 times (30 dB) the minimum communicable power with the tag that resonates at 13.56 MHz is required. Therefore, in the same condition as this experiment, for example, if the frequency f1 before the change is 10.5 MHz and the frequency f2 after the change is 13.56 MHz, P1 is about 30 dB, so P_High is, for example, 32 dB, and P2 is Since it is 0 dB, it can be seen that P_Low may be set to 10 dB, for example. The same applies when f1 is set to 16.5 MHz instead of 10.5 MHz. In an actual system, the frequency and power level are not limited to these values, and can be determined in consideration of various operating conditions of the system and other various situations. 3 to 5 are not limited to the 13.56 MHz band, and the same holds true for other frequency bands. For example, other frequency bands used for IC tags include the 900 MHz band and the 2.45 GHz band. The same applies to these frequency bands.

  In the present embodiment, the supply power level to the antenna of the reading device 20 (the transmission power of the reading device 20) is determined as described above using such a relationship between the resonance frequency of the tag and the minimum communicable power. Whether the frequency of the tag is the frequency f1 before the change or the frequency f2 after the change depending on the power level at which the communication can be performed, which can be set and switched between the two levels of the high level P_High and the low level P_Low. That is, it is determined whether or not there has been an environmental change.

(Example of operation of the environmental change detection system)
In FIG. 6, when the values of f 1, f 2, fr, P_High, and P_Low are determined so as to have the relationships as shown in FIGS. 3 to 4, the reading device 20 for the article 31 to which one tag 10 is attached. The main processing flow is shown. That is, the frequency f2 after the change is matched to the vicinity of fr, the frequency f1 before the change is set to a value separated from the resonance frequency fr of the reading device 20, and P_High is the minimum with the tag 10 that resonates at the frequency f1 before the change. When the tag 10 is set to a value slightly larger than the communicable power P1, and P_Low is set to a value slightly larger than the minimum communicable power P2 with the tag 10 that resonates at the frequency f2 after the change and significantly smaller than P1, one tag 10 FIG. 6 shows an outline of a processing flow of the reading device 20 that detects whether or not the attached article 31 has an environmental change.

  As shown in FIG. 6, the reading device 20 first attempts to read identification information such as an IC tag identification code of the environment change detection tag 10 by setting the transmission power level to P_High and emitting a radio wave with a frequency fr. (Step S101). In the configuration example of the reading device 20 shown in FIG. 2, this step is performed when the detection processing unit 23 instructs the tag reader 22 to set the transmission power level to P_High, and then the detection processing unit 23 instructs the tag reader 22. This can be realized by instructing to read identification information such as an IC tag identification code of the tag 10. Next, if there is no response from the tag 10 (No in step S102), the reading device 20 assumes that the tag 10 does not exist at a predetermined position, and tries reading again after a predetermined time (step S101). If there is a response from the tag 10 (Yes in step S102), the identification information is extracted from the received response and stored in the internal memory or the like so that it can be referred to in later processing (step S103).

  As shown in FIGS. 3 to 4, if the tag 10 is present at a predetermined distance d from the antenna 21 of the reading device 20, if a transmission power level is set to P_High and a radio wave with a frequency fr is emitted, f 1 , F2 should be able to read the identification information of the tag 10 which resonates at any frequency. That is, in this way, by first setting the transmission power to a large value and transmitting a strong radio wave, the identification information of the tag 10 can be reliably read if the tag 10 exists at a predetermined position.

  Although not shown, after the identification information is read and stored in the internal memory or the like in step S103, the database stored inside or outside the reading device 20 is read / written based on the identification information, and the related information It is also possible to perform reference and update processing. By doing so, the related information can be processed in the same way for the article 31 with the tag 10 that has changed and the article 31 with the tag 10 that has not changed. High service can be provided.

  Next, the reading device 20 attempts to read the identification information of the tag 10 by setting the transmission power to a low level P_Low and emitting a radio wave with the frequency fr (step S104). Also in this step, after the detection processing unit 23 of the reading device 20 instructs the tag reader 22 to set the transmission power level to P_Low, the detection processing unit 23 instructs the tag reader 22 to use the IC tag identification code of the tag 10, etc. This can be realized by instructing to read the identification information. If there is a response from the tag 10 (Yes in step S105), the detection processing unit 23 of the reading device 20 determines that the tag 10 is resonating at the changed frequency f2 based on the relationship of FIG. (Step S106). Then, the detection processing unit 23 determines that the environment of the tag 10 has changed, and determines that the article 31 to which the tag 10 is attached is an abnormal article (step S107). If there is no response from the tag 10 (No in step S105), the detection processing unit 23 determines that the tag 10 is resonating at the frequency f1 before the change based on the relationship of FIG. 4 (step S108). . The detection processing unit 23 determines that the environment of the tag 10 has not changed, and determines that the article 31 to which the tag 10 is attached is a normal article (step S109). Based on the determination result, the detection processing unit 23 displays the presence / absence of an environmental change or the like as the detection result together with the identification information of the article 31 (step S110).

  As described above, according to the present embodiment, the reading device 20 has a predetermined position at two transmission power levels, a high level P_high and a low level P_Low, which are different to the extent that the change in the resonance frequency of the tag 10 can be distinguished. , A determination unit that emits a radio wave of a certain frequency fr toward the tag 10 to confirm the presence / absence of the response and determines the presence / absence of a change in the resonance frequency according to the communicable power level. Therefore, the present system can detect the presence or absence of an environmental change of the article based on the determination result.

  Thereafter, as shown in FIG. 1, the article 31 determined to have no environmental change is used as the normal article 31A for the original purpose, and the article 31 determined to have an environmental change is recovered as the abnormal article 31B. Is done. This part is the same as the process described in Patent Document 1.

  Then, as shown in FIG. 1, the reading device 20 repeats the same processing as in FIG. 6 for the next tag 10.

(Effects of the first embodiment)
In this way, according to the first embodiment, even with a commercially available tag reader and antenna that transmit and receive at a predetermined frequency such as 13.56 MHz band or 2.45 GHz band, a commercially available transmission power level can be controlled from the outside. The tag 10 and the antenna are selected, a program for performing necessary processing is created and mounted on a commercially available computer or the like to configure a detection processing unit, and these are connected and set appropriately, so that the resonance of the tag 10 The reading device 20 that can be switched to a power level corresponding to a change in frequency can be easily configured. Therefore, an environment change detection system can be constructed and operated without using a tag reader that communicates at different frequencies.

(Modification of the first embodiment)
The example shown in FIGS. 3 to 4 and 6 is a case where the resonance frequency f2 of the tag 10 after the change is matched with the vicinity of the transmission / reception frequency fr of the reader 20, but on the contrary, the change before the change is shown. The resonance frequency f1 of the tag 10 may be matched with the vicinity of the transmission / reception frequency fr of the reader 20. 7 to 9 show this case by the same method as that shown in FIGS. In this way, when the resonance frequency f1 of the tag 10 before the change is matched with the vicinity of the transmission / reception frequency fr of the reading device 20 and the resonance frequency of the tag 10 after the change is set to a value greatly different from fr, 7, P1 is smaller than P2, so P_Low may be set to a value greater than or equal to P1 and smaller than P2, and P_High may be set to a value greater than or equal to P2. With this setting, as shown in FIG. 8, a transmission radio wave whose transmission power is set to the P_High level can communicate with both the tag 10 resonating at the frequency f1 and the tag 10 resonating at the frequency f2. A transmission radio wave whose power is set to the P_Low level cannot communicate with the tag 10 that resonates at the frequency f1, but can communicate with the tag 10 that resonates at the frequency f2. A processing flow of the reading device 20 in this case is shown in FIG. As shown in the figure, since f1 and f2 are reversed, steps S206 to S209 are opposite to steps S106 to S109 in FIG. 6, but steps S201 to S205 are followed by steps S101 to S105 in FIG. And no different.

  Further, the configuration of the reading device 20 of the first embodiment is not limited to that of FIG. 2, and may be modified as shown in FIGS. 10 to 12.

  FIG. 10 shows a modified example of the configuration of the reading device 20 of the first embodiment. In the figure, what is indicated by reference numeral 24A is a variable power attenuator such as a programmable attenuator that can arbitrarily set the amount of attenuation by an external instruction. As shown in the figure, the reader 20 of this example includes an antenna 21A, a fixed transmission power tag reader 22A, a detection processing unit 23A, and a variable power attenuator 24A. The variable power attenuator 24A It is provided between 21A and the tag reader 22A. The detection processing unit 23A is configured to instruct the variable power attenuator 24A to set the power attenuation amount to a predetermined value or 0 necessary for attenuating the power attenuation amount from P_High to P_Low as necessary. The 24A may be configured such that a path passing through a power attenuator capable of attenuating a predetermined level of power and a path not passing through the power attenuator can be switched by a switch.

  In the configuration of FIG. 10, it is not necessary to make the tag reader 22A and the antenna 21A controllable, and it is possible to use a reader / writer module and a set of antennas with a fixed transmission power that can be easily obtained. The distance d between the tag 10 and the antenna 21A is appropriately adjusted according to the transmission power level of the tag reader 22A to be used.

  Reference numeral 24A may be a variable power amplifier such as a programmable amplifier that can arbitrarily set the amount of amplification, as opposed to a power attenuator, or a combination of an attenuator and an amplifier. Of course. By doing so, even if there is a limit in relation to the output power level of the tag reader 22A to be used, the installation location, and the like, and even if the power supply level to the antenna 21A cannot be adjusted by the attenuator alone, the desired power level is achieved. It becomes possible to adjust to. That is, a variable power attenuator and a variable power amplifier that can be instructed from the outside are appropriately combined to constitute 24A, and the detection processing units 23A to 24A instruct the power attenuation amount or the power amplification amount, whereby the antenna 21A is connected. The reading device 20 can be easily configured so that the power level of the supplied power or the transmission power from the reading device 20 can be switched between the above-described P_High and P_Low.

  In the case of the configuration example in FIG. 10, the method for setting the power level is slightly different from that in FIG. 2, but is the same in that the power level of the power supplied to the antenna 21A can be switched between high and low. Therefore, the outline of the processing flow for detecting the environmental change is the same as that shown in FIG. Other matters are substantially the same as those described in the first embodiment.

  FIG. 11 shows another modification of the configuration of the reading device 20 of the first embodiment. As shown in the figure, the reading device 20 in this example includes an antenna 21B1 and a set of tag reader 22B1, an antenna 21B2 and a set of tag reader 22B2, and a detection processing unit 23B. The detection processing unit 23B includes: It is connected to both tag readers 22B1 and 22B2. The supply power (transmission power) from the tag reader 22B1 to the antenna 21B1 is high level P_High, and the transmission power from the tag reader 22B2 to the antenna 21B2 is low level P_Low. In this example, the detection processing unit 23B is configured to be able to communicate by switching between the tag readers 22B1 and 22B2 as necessary. The configuration example of FIG. 11 is the same in that the transmission power level of the reading device 20 can be switched between high and low, and therefore the basic flow of processing for environmental change detection is shown in FIG. 6 or FIG. Same as 9. In this configuration, two sets of tag readers and antennas having different transmission power levels are used, so there is a demerit that the apparatus becomes large, but there is an advantage that the range of selection of tag readers (reader / writer modules) is widened.

  FIG. 12 shows still another modified example of the configuration of the reading device 20 according to the first embodiment. As shown in the figure, the reader 20 of this example includes two types of antennas, an antenna 21C1 whose transmission power is set to a high level P_High and an antenna 21C2 whose transmission power is set to a low level P_Low, and a tag reader. The two types of antennas 21C1 and 21C2 that are configured by 22C and the detection processing unit 23C and have different transmission power levels are connected to one tag reader 22C. The power supplied from the tag reader 22C to the antenna 21C1 is set to a high level P_High, and the power supplied from the tag reader 22C to the antenna 21C2 is set to a low level P_Low. In this configuration, switching of the two antennas is performed by the tag reader 22C based on an instruction from the detection processing unit 23C. Even in this configuration, the reader 20 can communicate with the tag 10 by switching the transmission power between the high level P_High and the low level P_Low, and the change in the resonance frequency of the tag based on the presence or absence of the response. The presence / absence of the environmental change can be determined. The configuration example of FIG. 12 is the same in that the transmission power level of the reading device 20 can be switched between high and low, and therefore the basic flow of processing for environmental change detection is shown in FIG. 6 or FIG. Same as 9. In this configuration, the configuration of the tag reader 22C is slightly complicated. However, since it is not necessary to prepare a tag reader having a different transmission power level, it is possible to save space compared to the case of FIG. In the case of this configuration as well, as described in FIG. 2, the tag reader 22C and the detection processing unit 23C may of course be incorporated in the same casing.

(Tag configuration example)
Next, an example of the environment change detection tag 10 used in the present embodiment will be described.

  FIG. 13 is a block diagram showing a functional configuration of the environment change detection tag 10. As shown in the figure, the environment change detection tag 10 includes a resonance circuit 110, an environment change detection unit 120, and an IC chip 130. The resonance circuit 110 is a resonance circuit configured such that the resonance frequency changes from the first resonance frequency f1 to the second resonance frequency f2 when the environment change sensing unit 120 detects the environment change. The normal resonance frequency f1 is, for example, 10.5 MHz, and the changed resonance frequency f2 is, for example, 13.56 MHz. The resonance circuit 110 is also an antenna for communicating with the reading device 20, and is also a circuit that converts a radio wave emitted from the antenna of the reading device 20 toward the tag 10 into electric power by electromagnetic induction. The environment change sensing unit 120 has a function of sensing that the environment has changed when a predetermined temperature has been reached and a predetermined time has elapsed. The IC chip 130 is mainly composed of an arithmetic unit (CPU), a read-only memory (ROM), and a random access memory (RAM) (not shown), and the CPU uses a program or data stored in the ROM or RAM. Various arithmetic processes such as communication control with the reader / writer and response processes are executed. The ROM stores an IC tag identification code, which is identification information uniquely assigned to each IC tag when the tag 10 is manufactured, and the IC tag identification code cannot be rewritten.

  One specific example of the environmental change detection tag 10 will be described with reference to FIGS. In the tag 10, a temperature fuse is used as the environment change sensing unit 120 that is blown when a predetermined temperature is reached and a predetermined time elapses. The tag 10 has a flat plate shape with a width of about 45 mm and a length of about 76 mm, for example.

  FIG. 14 is a schematic plan view showing an example of the configuration of the tag 10 in a perspective view from the surface on which the thermal fuse 120 is mounted. In FIG. 14, the region with the left-down parallel diagonal lines indicates the conductor pattern 10 a formed on the front (front) surface, and the region with the right-down parallel diagonal lines is formed on the back surface. The conductor pattern 10b is shown. FIG. 15 is a diagram showing the conductor pattern 10a formed on the front surface (the surface on which the thermal fuse 120 is mounted) of the tag 10 of FIG. 14 in a black area, and FIG. 16 is the tag of FIG. 10 is a diagram showing an electrical functional configuration of a conductor circuit constituting the circuit 10. FIG.

  As shown in FIGS. 14 and 15, the tag 10 includes a thermal fuse 120 mounted on one surface of an insulating base material 11, an antenna coil 113 formed as a coiled conductor pattern on the same surface, and this An IC chip 130 electrically connected to the antenna coil 113; and adjustable capacitance portions (capacitance adjustable capacitors) 115 and 116 each including a conductor pattern formed on both sides of the insulating base material 11 that is also a dielectric. The connection portions 117 and 118 electrically connect the conductor patterns on both the front and back surfaces. The adjustable capacity sections 115 and 116 can be adjusted in capacity by cutting off a part thereof. Note that the connecting portions 117 and 118 can be constituted by caulking connecting portions that are crushed and electrically connected from both sides, but may be constituted by well-known through holes. The capacity unit may be a fixed capacity unit having a capacity set in advance by calculation or experiment.

  The outer shape of the thermal fuse 120 is a substantially rectangular shape having four rounded corners as shown in FIG. 14, and has a width of about 5 to 10 mm, a length of about 20 to 35 mm, and a thickness of about 20 to 100 μm. The thermal fuse 120 includes conductive terminals 121 and 122 exposed on one surface and a connecting portion 123 that electrically connects these terminals, and the surface is covered with an insulating shrink film. It has been broken. The terminals 121 and 122 have at least the back surfaces exposed, and are electrically connected to terminal portions 121a and 121b formed as part of the conductor pattern shown in FIG. 15 by known means such as thermocompression bonding, respectively. It is configured. As shown in FIG. 14, in the initial state of the thermal fuse 120, the connecting portion 123 connects the terminals 121 and 122. When the temperature reaches a predetermined temperature (for example, 50 ° C.) and a predetermined time (for example, 10 minutes) elapses, When a part of the connecting portion 123 is melted, the connection between the terminals 121 and 122 is cut off and is not restored.

  In FIG. 15, what is indicated by reference numeral 120a is an area where the thermal fuse 120 is mounted. 121a is a terminal portion to which the connection terminal 121 of the thermal fuse 120 is connected, and 122a is a terminal portion to which the connection terminal 122 of the thermal fuse 120 is connected. Reference numeral 115 a denotes a conductor pattern constituting one surface of the adjustable capacitor portion 15, and reference numeral 116 a denotes a conductor pattern constituting one surface of the adjustable capacitor portion 16. As shown in FIG. 15, 121a and 116a, 122a and 115a are electrically connected to each other because they are continuous conductor patterns, but 121a and 122a are separated from each other so that they are electrically disconnected. Has been. When the conductor pattern 10a configured as described above is electrically connected with the thermal fuse 120 interposed between 121a and 122a, a conductor circuit whose electrical configuration is shown in FIG. 16 is configured.

As shown in FIGS. 14 to 16, the antenna coil 113 and the capacitor 115 and / or 116 constitute a resonance circuit. The antenna coil 113, the capacitor unit 115, and the capacitor unit 116 are connected in parallel. When the thermal fuse 120 is cut, the conduction with the capacitor unit 116 is cut off. That is, when the thermal fuse 120 is cut, the resonance frequency is changed because the capacitance of the capacitor 116 is reduced. That is, assuming that the inductance of the antenna coil 113 is L, the capacitance of the capacitor 115 is C1, and the capacitor of the capacitor 116 is C2, the resonance frequency f1 at the time of thermal fuse conduction is 1 / (2π (L (C1)) ^{1 / 2} ), the resonance frequency f2 when the thermal fuse is cut is 1 / (2π (L (C1 + C2)) ^1/2 ). Therefore, when the thermal fuse 120 is cut, the resonance frequency is Go up. Therefore, after mounting the tag configured in this way on an article and transporting / storage, etc., by checking whether the resonance frequency of the tag remains unchanged or not, it can be determined whether the thermal fuse has been blown, As a result, it can be seen whether or not a predetermined time has passed since reaching a predetermined temperature during transportation and storage. Since the thermal fuse 120 is an additional reversible electrical and electronic component that does not return to its original state when it is cut, it can prevent unauthorized means such as resetting the memory. Is suitable.

  The tag 10 with a thermal fuse, which is a wireless IC tag configured as described above, is a resonance circuit set so that the resonance frequency changes from the first resonance frequency to the second resonance frequency in response to sensing temperature abnormality. have.

  As the IC chip 130, an IC tag chip that is commercially available as an IC tag chip, such as an I-CODE SLI chip from Philips or a my-d chip from Infineon Technologies, may be used as appropriate according to the application. it can.

(Modification of tag embodiment)
In the embodiment of the tag, the resonance frequency is changed by changing the capacitance of the capacitor without changing the inductance L of the antenna coil before and after the fuse is cut, but by changing the inductance L of the antenna coil. The resonance frequency may be changed. Further, as described in paragraph 0011 of Patent Document 1, the resonance circuit may be configured using a ceramic capacitor or the like whose capacitance changes according to a temperature change.

  In the tag embodiment, an example of a tag in which the resonance frequency changes from 10.5 MHz to 13.56 MHz in accordance with the environmental change is shown. However, the resonance frequency is not limited to this. For example, the frequency band is not limited to the 13.56 MHz band, and can also be applied to an RFID system that performs wireless communication in a 900 MHz band or a 2.45 GHz band. The configuration on the tag side and the reading device side can be appropriately designed according to the wavelength of each frequency band, communication characteristics, communication method, communication standard, and the like. Further, the width of the frequency change is not limited to 3 MHz, and may be about 5 MHz. It is sufficient that the change width is within a range allowed in the frequency band and can be read as an obvious change that is not within the error range. In the above-described embodiment, an example in which the resonance frequency is increased (increased) with an environmental change has been described. However, the resonance frequency may be decreased (decreased) with an environmental change. In the 13.56 MHz band, the resonance frequency increased when the fuse was cut, but in the 900 MHz band and 2.45 GHz band, the resonance frequency did not necessarily increase when the fuse was cut, The resonance frequency may be lowered.

  In the above description, the 13.56 MHz band tag has been described as an example. Therefore, the electromagnetic wave received from the reading device is driven by electromagnetic induction to drive the tag. In this case, the driving may be performed by a general method in the frequency band, for example, a method of rectifying a received radio wave and converting it into electric power. Further, the tag 10 may be of a battery built-in type and driven by its own built-in power regardless of the received radio wave.

(Effect of 1st Embodiment and its modification)
As described above, according to the first embodiment and the modification thereof, the interval between the tag 10 and the antenna 21 of the reading device 20 is kept constant, and the power supply level to the antenna of the reading device 20 is switched between high and low, Attempts to communicate with the tag at the transmission / reception frequency fr, and determines the presence or absence of a change in the frequency of the tag 10 according to the presence or absence of the response, thereby detecting the presence or absence of an environmental change of the article to which the tag 10 is attached. Is.

  In this way, according to the present embodiment and the modification thereof, unlike the one described in Patent Document 1, it is not necessary to prepare two sets of reading devices having different frequencies. According to the present embodiment and its modification, the environment change detection system only needs to prepare a set of standard frequency readers 20, which are combined with a tag reader such as a commercially available reader / writer module and an antenna. Because it can be configured in various ways, the degree of freedom in system design is expanded, and an environmental change detection system can be constructed and operated at low cost.

[Second Embodiment]
FIGS. 17 to 26 are diagrams for explaining the second embodiment and its modifications. 17 to 19 are diagrams schematically illustrating the positional relationship between the environment change detection tag 10 and the reading device 20 (20D, 20E, 20F) and the configuration of the reading device 20 according to the present embodiment and its modifications. 20, FIG. 21 and FIG. 24 are diagrams showing the relationship between the resonance frequency of the tag and the maximum communication distance. 20, 22, and 23 are diagrams illustrating the case where the changed resonance frequency f <b> 2 is matched with the vicinity of the frequency fr of the reading device 20, and FIGS. 24 to 26 illustrate the resonance frequency f <b> 1 before the change of the reading device 20. It is a figure which shows the case where it matches with the frequency fr vicinity. Since the environmental change detection tag 10 is the same as that of the first embodiment, a detailed description of the tag is omitted. In FIGS. 17 to 26, the same components as those in the first embodiment are denoted by the same reference numerals in principle and description thereof is omitted.

(Overview)
As shown in FIGS. 17 to 26, in the second embodiment, the transmission power level P and the frequency fr of the reading device 20 are made constant, and the distance between the antenna 110 of the tag 10 and the antenna 21 of the reading device 20 is reduced. (Long and short) Communication is attempted differently, and the presence or absence of a change in the number of resonance changes of the tag 10 is determined according to the presence or absence of a response from the tag 10.

  Here, D_far shown in the drawing means that the transmission power level P and the frequency fr of the reading device 20 are constant, and one of the frequency f1 before the change and the frequency f2 after the change is the reading device 20. When the other frequency is greatly different from the frequency fr of the reading device 20, the tag that resonates at the frequency near fr can communicate with the tag that resonates at the other frequency. Is a distance (wide interval) far enough that communication is not possible, and D_near is a distance (narrow interval) close to the extent that it can communicate with a tag that resonates at any frequency of f1 and f2. These will be described later.

(Configuration example of reader)
First, a configuration example of the reading apparatus according to the second embodiment will be described together with its modifications.

  FIG. 17 shows an example in which a reader 20D is configured using a reader / writer module (tag reader) that can connect two antennas. As shown in the figure, in this example, the reading device 20D includes two antennas 21D, one tag reader 22D, and one tag reader 22D that have the same power supply P for the antennas and can transmit radio waves of the same power level. It consists of a detection processing unit 23D, and these are connected and set so as to function as the reading device 20D.

  The two antennas 21D are connected to the same tag reader 22D. One antenna 21D is installed at a distance close to the antenna 110 of the tag 10 and at a position about D_near, and the other antenna 21D is installed at a distance far from the antenna 110 of the tag 10 and a position about D_far. Yes. The tag reader 22D can switch between the antenna 21D arranged at the position D_near and the antenna 21D arranged at the position D_far to communicate with each other according to an instruction from the detection processing unit 23D. Yes.

  The detection processing unit 23D is a device that performs various processes necessary for the environment change detection processing system 1. The detection processing unit 23D can instruct the tag reader 22D which of the two antennas is used for communication, and transmits radio waves from the antenna to the tag 10 via the tag reader 22D. The presence or absence of the response and the content of the response can be known.

  Radio waves are emitted from the two antennas 21D at the same frequency fr and the same transmission power P, but the electric and magnetic field strengths of the radio waves reaching the tag 10 are emitted from the antennas 21D arranged at a long distance D_far. The transmitted radio wave 352 is smaller (becomes weaker) than the radio wave 351 emitted from the antenna 21D arranged at the short distance D_near. Therefore, the detection processing unit 23D can switch between the two antennas 21D to try to communicate with the tag 10 and know the presence / absence of the response, thereby determining the presence / absence of a change in the resonance frequency of the tag 10 and the environmental change. Presence / absence can be determined.

  According to the configuration of FIG. 17, since the reading device 20D has two antennas, a larger space is required as compared with the case of one antenna. However, since only one tag reader 22D is required, the installation location is small. The cost is also reduced.

  FIG. 18 shows an example in which one antenna 21E can be moved, and by moving the antenna 21E, the distance from the tag 10 can be switched between near and far. As shown in the figure, in this example, the reading device 20E includes one antenna 21E and one tag reader 22E that can transmit a radio wave having a transmission power level P at a predetermined frequency fr, and one detection processing unit 23E. These are connected and set so as to function as the reading device 20E. One antenna 21E is connected to the tag reader 22E, and is configured to reciprocate between a position away from the antenna 110 of the tag 10 by a distance D_near and a position away from the antenna 110 of the tag 10 by a distance D_far. . The detection processing unit 23E is a device that performs various processes necessary for this system. The detection processing unit 23E can move the antenna 21E to the position of D_near or D_far via the tag reader 22E or the antenna moving mechanism 26E provided for moving the antenna 21E. The radio wave is transmitted to the tag 10 via the tag reader 22E, and the response can be received. As the mechanism 26E for moving the antenna 21E, for example, a mechanical or electric slide mechanism in which a stopper is provided at a position where predetermined D_near and D_far intervals are conceivable.

  That is, in this example, radio waves are emitted from one antenna 21E at the frequency fr and the transmission power P in both the case of being arranged at the short distance D_near and the case of being arranged at the long distance D_far. 10, the electric field 352 emitted from the antenna 21 </ b> E disposed at the long distance D_far is smaller than the electric wave 351 emitted from the antenna 21 </ b> E disposed at the short distance D_near. (become weak). Therefore, the detection processing unit 23E attempts to communicate with the tag 10 by moving one antenna 21E to switch the distance between the tag 21 and the tag 10, and knows whether there is a response, thereby determining whether the resonance frequency of the tag 10 has changed. It is possible to determine whether there is an environmental change.

  According to the configuration of FIG. 18, the configuration may be complicated in that it is necessary to prepare a mechanism 26E for moving the antenna 21E, but the antenna to be prepared and a tag reader (reader / writer module) are one set. There is an advantage of being good.

  In FIG. 19, two sets of tag readers 22F and antennas 21F are used, and one antenna 21F is disposed at a position close to the tag 10 and at a distance D_near, and the other antenna 21F is disposed at a position far from the tag 10 and a distance D_far from This is an example of arrangement at the position. As shown in the figure, in this example, the reading device 20F includes two sets of an antenna 21F capable of transmitting a radio wave having a frequency fr at a transmission power level P and a tag reader 22F connected thereto, and the two tag readers 22F. It consists of one connected detection processing unit 23F. The detection processing unit 23F is a device that performs various processes necessary for this system. The detection processing unit 23F switches between the two tag readers 22F as necessary, and transmits radio waves to the tag 10 from different distances via the tag reader 22F, and knows whether there is a response and the contents of the response. It is configured to be able to.

  In other words, radio waves are emitted from the two sets of tag reader 22F and antenna 21F at the same frequency fr and the same transmission power P, but the electric and magnetic field strengths of the radio waves reaching the tag 10 are arranged at a long distance D_far. The radio wave 352 emitted from the antenna 21F thus made becomes smaller (weaker) than the radio wave 351 emitted from the antenna 21F arranged at the short distance D_near. Therefore, the detection processing unit 23F can determine whether there is a change in the resonance frequency of the tag 10 by switching between the two sets of tag readers 22F and the antenna 21F and trying to communicate with the tag 10 and knowing whether there is a response. The presence or absence of environmental changes can be determined.

  According to the configuration of FIG. 19, although two sets of tag reader 22F and antenna 21F are required, there is an inconvenience that the installation place is bulky, but the system can be configured using an ordinary reader / writer and antenna. It is simple in that it does not require the antenna moving mechanism that was necessary in the system, and can reduce the cost of system construction and operation.

  17 to 19, the detection processing unit 23 (23D, 23E, 23F) is similar to that described in the first embodiment, for example, a memory or a hard disk in which a program or data for this system is stored. And a computer main body equipped with a display capable of displaying the result and an MPU capable of executing the program. The tag reader 22 (22D, 22E, 22F) may be stored in an independent housing, may be of a substrate type that can be attached to the computer main body of the detection processing unit 23, or may be one chip. And can be mounted on the computer main body or provided in any form. If the tag reader 22 is sufficiently small, such as being housed in one chip, the tag reader 22 can be incorporated into the detection processing unit 23 to integrate the device and be portable enough to hold the whole device with one hand. .

(Relationship between tag resonance frequency and communicable distance)
Here, the resonance frequency f1 before the change, the resonance frequency f2 after the change, the frequency fr of the reading device 20 (tag reader 22), and the distance interval between the antenna 110 of the tag 10 and the antenna 21 of the reading device 20 are shown in FIG. This will be described with reference to FIG.

  FIG. 20 shows that a response from the tag is received when the antenna 21 connected to the tag reader 22 is directed toward the tag antenna 110 and a radio wave having a frequency fr is emitted toward the tag at a constant transmission power level. It is the graph which showed the maximum communication distance which can be done. In FIG. 20, the horizontal axis indicates the center of the resonance frequency of the tag, and the vertical axis indicates the maximum communication distance.

  In general, the maximum communication distance and the resonance frequency of the tag have such a relationship. Therefore, it is preferable to set one of the resonance frequency f1 before the change and the resonance frequency f2 after the change to be the same as or close to the transmission / reception frequency fr of the tag reader 22. Either f1 or f2 may be set near fr, but FIG. 20 shows a case where f2 is set near fr. As shown in FIG. 20, f1 and f2 need to have frequencies that are greatly different to the extent that they are not within the error range. Either f1 or f2 may be larger. For example, f1 may be a value on the left side of the drawing, or may be a value ((f1) on the right side of the drawing) that is a substantially line-symmetrical position with respect to fr.

  As shown in FIG. 20, when the changed frequency f2 is adjusted to the vicinity of fr, the maximum communication distance D1 that can communicate with the tag that resonates at the frequency f1 before the change resonates at f2. It becomes smaller than the maximum communication distance D2 that can communicate with the tag (becomes a short distance). That is, in order to communicate with a tag that resonates at the frequency f2, the tag is set so that the distance interval D_far is less than the maximum communication distance D2 corresponding to the intersection of the polygonal line Df and the line f2 on the graph and is larger than D1. 10 and the antenna 21 may be installed. On the other hand, in order to communicate with the tag that resonates at f1, the tag 10 and the antenna 21 are arranged so that the distance interval D_near is equal to or less than the maximum communication distance D1 corresponding to the intersection of the polygonal line Df and the line f1 on the graph. Should be installed. In this case, the reader 20 installed so that the tag 10 and the antenna 21 have a distance interval D_near can naturally communicate with the tag that resonates at the frequency f1, but resonates at the frequency f2. You can also communicate with tags.

  In order to confirm an example that the relationship of FIG. 20 is established, FIG. 21 uses a 13.56 MHz band tag, reader / writer, and antenna set, and changes the distance between the tag antenna and the reader / writer antenna. It is the graph which showed the result of having conducted the experiment which investigated the maximum communication distance when the radio wave of frequency 13.56MHz was transmitted from the reader / writer with the fixed electric power level and it was able to communicate with the tag. In FIG. 21, the vertical axis represents the maximum communication distance (unit: mm), and the horizontal axis represents the tag resonance frequency (unit: MHz). FIG. 21 does not show a frequency greater than 14.5 MHz, but it is a matter of course that a substantially bilaterally symmetric relationship is approximately established around 13.56 MHz as in FIG.

  As shown in FIG. 21, when the power level and frequency of the radio wave transmitted from the reading device 20 to the antenna 21 are constant, the antenna 21 of the reading device 20 is installed at a distance of 10 mm, and the frequency is 10.5 MHz. If the antenna 21 of the reading device 20 is installed at a distance interval of 90 mm, communication with a tag resonated at 10.5 MHz is impossible. Can communicate with tags that resonate at .56 MHz. Therefore, for example, when the frequency f1 before the change is 10.5 MHz and the frequency f2 after the change is 13.56 MHz, it is understood that the distance interval D_near is set to 10 mm, for example, and the distance interval D_far is set to 90 mm. The value slightly smaller than the value of the intersection shown in the graph (maximum communication distance at that frequency) is due to consideration of the actual tag frequency and other variations. The same applies when f1 is set to 16.5 MHz instead of 10.5 MHz.

  In FIG. 22, when f1, f2, fr, D_near, and D_far are set as shown in FIG. 20 and radio waves are transmitted from the reader 20, the reader 20 can receive the response of the environment change detection tag 10 ( The case where communication is possible is indicated by “◯”, and the case where the response of the tag 10 cannot be received (communication is not possible) is indicated by “X”. As shown in FIG. 22, in the distance intervals D1 and D_near, it is possible to communicate with the tag resonating at the frequency f1 and the tag resonating at the frequency f2, but at the distance intervals D2 and D_far, the tag is resonating at the frequency f1. It cannot communicate with the tag, but can only communicate with the tag that resonates at the frequency f2. That is, a tag that resonates at a frequency f2 in the vicinity of the frequency fr of the reading device 20 if communication can be performed at both the D_near position and the D_far position. Can be determined.

  In an actual system, the frequency and distance interval are not limited to the values shown in FIG. 21, and can be determined in consideration of various operating conditions of the system and other various situations. 20 to 22 is not limited to the 13.56 MHz band, and it goes without saying that the same holds true for other frequency bands. For example, other frequency bands used for IC tags include the 900 MHz band and the 2.45 GHz band. The same applies to these frequency bands.

  In the present embodiment, the distance between the antenna 21 of the reading device 20 and the antenna 110 of the tag 10 is set to a long distance D_far and a short distance D_near using such a relationship between the resonance frequency of the tag and the maximum communication distance. Depending on where the antenna 21 can be installed at such a position and communication was possible, whether the tag frequency is the frequency f1 before the change or the frequency f2 after the change, that is, whether the environment has changed or not. It is something to try to determine.

(Example of processing flow of the reading apparatus in the second embodiment)
23, when f1, f2, fr, D_near, and D_far are determined as shown in FIGS. 20 to 22, the reading device 20 (20D, 20E, 20F) for the article 31 to which one tag 10 is attached. The main processing flow is shown. That is, the frequency f2 after the change is matched with the vicinity of the frequency fr of the reading device 20, the frequency f1 before the change is set to a value separated from fr, and D_near is the maximum communication distance with the tag that resonates at the frequency f1 before the change. When the value is set to a value slightly smaller than D1 and D_far is set to a value slightly smaller than the maximum communication distance D2 with the tag that resonates at the changed frequency f2, the environmental change of the article 31 to which one tag 10 is attached FIG. 23 shows an outline of a processing flow of the reading device 20 until it is determined whether or not there is.

  As shown in FIG. 23, the reading device 20 (20D, 20E, 20F) emits radio waves of the frequency fr by the antenna 21 installed at the position of the distance interval D_near, and the IC tag identification code of the environment change detection tag 10 Or the like (step S301). If there is no response from the tag 10 (No in step S302), the reading is attempted again after a predetermined time (step S301). If there is a response from the tag 10 (Yes in step S302), the identification information is extracted from the read response, and the identification information is stored.

  If a radio wave having a frequency fr is emitted when the tag 10 is present at a predetermined distance D_near from the antenna 21 of the reading device 20, the tag resonates at either f1 or f2, as shown in FIG. However, the identification information of the tag should be readable. That is, as described above, when the tag 10 is present at a predetermined position by first transmitting radio waves from a short distance, the tag 10 receives radio waves having sufficient strength to communicate with the reading device 20. Thus, the tag 10 can respond to the question from the reading device 20, and the reading device 20 can receive the response and reliably read the identification information of the tag 10.

  Although not shown, after the identification information is read and stored in an internal memory or the like, a database stored inside or outside the reading device 20 is read and written based on the identification information, and related information is referred to or updated. It is also possible to perform processing. By doing so, the related information can be processed in the same way for the article 31 with the tag that has changed and the article 31 with the tag that has not changed. Can be provided.

  Next, the reader 20 attempts to read identification information such as an IC tag identification code of the environment change detection tag 10 by emitting a radio wave having a frequency fr with the antenna 21 installed at the position of the distance interval D_far (step S304). ). If there is a response from the tag 10 (Yes in step S305), it is determined that the tag 10 is resonating at the changed frequency f2 based on the relationship of FIG. 22 (step S306). Then, the detection processing unit 23 determines that the environment of the tag 10 has changed, and determines that the article 31 to which the tag 10 is attached is an abnormal article (step S307). If there is no response from the tag 10 (No in step S305), it is determined that the tag 10 is resonating at the frequency f1 before the change based on the relationship of FIG. 22 (step S308). Then, the detection processing unit 23 determines that the environment of the tag 10 has not changed, and determines that the article 31 to which the tag 10 is attached is a normal article (step S309). Based on the determination result, the detection processing unit 23 displays the presence / absence of an environmental change or the like as the detection result together with the identification information of the article 31 (step S310).

  As described above, according to the present embodiment, the reading device 20 transmits radio waves by varying the distance between the reading device 20 and the tag 10 to such an extent that the change in the resonance frequency of the tag 10 can be distinguished. It has a determination means for checking the presence or absence of a response and determining the presence or absence of a change in the resonance frequency of the tag according to the communicable distance. Therefore, the present system can detect the presence or absence of an environmental change of the article based on the determination result.

  Thereafter, as shown in FIG. 1, the article 31 determined as having no environmental change is used as a normal article 31A for the original purpose, and the article 31 having been determined as having an environmental change is recovered as an abnormal article 31A. Is done. This part is the same as the process described in Patent Document 1.

  Then, the reading device 20 repeats the same processing as in FIG. 22 in order to detect an environmental change of the tag 10 attached to the next article 31.

(Another example of processing flow of the reading apparatus in the second embodiment)
Next, contrary to the above example, the frequency f1 before the change is the same as or close to the frequency fr of the reading device 20, and the frequency f2 after the change is greatly different from the frequency fr of the reading device 20. This will be described with reference to FIGS.

  In this case, as shown in FIG. 24, D_near is set to a value slightly smaller than the maximum communication distance D2 with the tag that resonates at the frequency f2 after the change, and D_far is the maximum with the tag that resonates at the frequency f1 before the change. The value is set to be a little smaller than the communication distance D1. If so, as shown in FIG. 25, the tag that resonates at the frequency f1 before the change can communicate from the reading device 20 arranged at any interval of D_near and D_far (there is a response), but the change A tag that resonates at a later frequency f2 can only communicate (no response) from the reading device 20 arranged at an interval of D_near. That is, the reading device 20 in which the antennas are arranged at the positions of the D_near interval can communicate with the tag resonating at the frequency f1 and the tags resonating at the frequency f2, but the position antenna having the D_far interval The arranged reading device 20 cannot communicate with a tag that resonates at the frequency f1, but can communicate with a tag that resonates at the frequency f2. The processing flow of the reading device 20 in this case is shown in FIG. As shown in FIG. 23, since f1 and f2 are reversed, steps S406 to S409 are opposite to steps S306 to S309 in FIG. 23, but steps S401 to S405 are steps S301 to S305 in FIG. And no different.

(Effect of 2nd Embodiment)
As described above, according to the second embodiment and the modification thereof, the resonance of the tag based on the distance of the communicable distance with the tag while the transmission / reception frequency and the power level on the reader side are fixed. Since the presence or absence of a change in frequency is determined, a system can be configured using a general reader / writer for IC tags and an antenna. Compared with the first embodiment, the positioning and arrangement of the antenna is not easy, and there is a problem that the configuration of the reading device tends to be large. However, the range of selection of the system configuration is widened, and it is constructed and operated at low cost. The effect that the system configuration which can be performed becomes possible is acquired.

[Other Embodiments]
Although not shown, a detection device that instructs the detection processing unit to place a shield or the like between the reading device 20 and the tag 10 that can switch between partial shielding and transmission of radio waves. Then, this shield may be switched. In this case, even if the apparent transmission power from the reading device 20 is the same, it is possible to switch the actual transmission power from the reading device 20 to the tag 10. As a result, the strength of the electric field and magnetic field of the radio wave reaching the tag 10 can be switched, so that the presence / absence of an environmental change can be detected by the same determination means as described above.

The figure which shows the external appearance of an example of the environmental change detection system to which this invention is applied. The figure which shows the structure of 1st Embodiment typically. The graph which shows typically the relationship between the resonant frequency of a tag, and the minimum communicable electric power. FIG. 4 is a diagram illustrating a relationship between communication availability when the resonance frequency of the tag and the transmission power of the reading device are set as illustrated in FIG. 3. The graph which shows the experimental result of the relationship between the resonant frequency of a tag in 13.56MHz band, and the minimum communicable electric power. The figure which shows the flow of the process which determines the presence or absence of an environmental change based on the relationship of FIG. The graph which shows typically the relationship between a resonant frequency and the minimum communicable electric power. The figure which shows the relationship of the communication availability at the time of setting the resonant frequency of a tag and the transmission power of a reader like FIG. The figure which shows the flow of the process which determines the presence or absence of an environmental change based on the relationship of FIG. The figure which shows typically the structure of the one modification of 1st Embodiment. The figure which shows typically the structure of the other modification of 1st Embodiment. The figure which shows typically the structure of the other modification of 1st Embodiment. The block diagram which shows an example of a function structure of the environmental change detection tag used by one Embodiment of this invention. The figure which shows an example of the environmental change detection tag used by one Embodiment of this invention from one surface. The figure which shows the conductor pattern of the surface of the environmental change detection tag shown in FIG. FIG. 15 is an equivalent circuit diagram of the environment change detection tag shown in FIG. 14. The figure which shows the structural example of 2nd Embodiment typically. The figure which shows the other structural example of 2nd Embodiment typically. The figure which shows the further another structural example of 2nd Embodiment typically. The graph which shows typically the relationship between the resonance frequency of a tag, and the maximum communication distance. The graph which shows the experimental result of the relationship between the resonant frequency of a tag in 13.56MHz band, and the maximum communication distance. The figure which shows the relationship of the communication availability at the time of setting the resonant frequency of a tag and the arrangement | positioning space | interval of a reader like FIG. The figure which shows the flow of the process which determines the presence or absence of an environmental change based on the relationship of FIG. The graph which shows typically the relationship between the resonance frequency of a tag, and the maximum communication distance. FIG. 25 is a diagram showing the relationship between communication availability when the resonance frequency of the tag and the arrangement interval of the reader are set as shown in FIG. The figure which shows the flow of the process which determines the presence or absence of an environmental change based on the relationship of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Environmental change detection system, 10 ... Environmental change detection tag (tag with a thermal fuse), 110 ... Tag antenna, 113 ... Antenna coil, 120 ... Environmental change detection part (thermal fuse), 130 ... IC chip, 20 ... Reading Device: 21 ... Antenna of reader, 22 ... Tag reader (reader / writer module), 23 ... Detection processing unit, 24 ... Variable attenuator, 31 ... Article, 350 ... Radio wave.

Claims (8)

An environmental change sensing tag having a resonance circuit set to change the resonance frequency from the first resonance frequency to the second resonance frequency in accordance with an environmental change, and an IC chip connected to the resonance circuit;
A system comprising a reader that reads data from the tag in a non-contact manner,
The transmission power level of the reading device is a first power that can communicate with the tag that resonates at the first resonance frequency when the reading device transmits a radio wave of a predetermined frequency from a position spaced from the tag. A first determination that determines whether or not there is an environmental change according to a transmission power level communicable with the tag An environmental change detection system characterized by comprising means. The reader is
A tag reader that can change the transmission power level according to an external instruction;
Connected to the tag reader, changes the transmission power level to the first power level or the second power level through the tag reader, attempts to communicate with the tag, and sets the transmission power level to be communicable with the tag. A detection processing unit having first determination means for determining the presence or absence of the environmental change in response,
The environment change detection system according to claim 1, further comprising: The reader is
A tag reader of a predetermined transmission power level;
An antenna connected to the tag reader and capable of transmitting and receiving the tag;
A variable power attenuator or a variable power amplifier that is disposed between the antenna and the tag reader and can be attenuated or amplified to be the first power level and the second power level according to an instruction from the outside;
Means connected to the tag reader and the variable power attenuator or the variable power amplifier and instructing the variable power attenuator or the variable power amplifier to set the first power level or the second power level; A detection processing unit having a first determination unit that attempts to communicate with the tag via the tag reader and determines the presence or absence of the environmental change according to a transmission power level communicable with the tag;
The environment change detection system according to claim 1, further comprising: The reader is
A first tag reader whose transmission power level is the first power level;
A second tag reader whose transmission power level is the second power level;
Connected to the first tag reader and the second tag reader, switching between the first tag reader and the second tag reader to try to communicate with the tag, and according to the transmission power level communicable with the tag A detection processing unit having first determination means for determining the presence or absence of an environmental change;
The environment change detection system according to claim 1, further comprising: The reader is
A first antenna having a transmission power level as the first power level;
A second antenna having a transmission power level as the second power level;
A third tag reader to which the first and second antennas are connected and which can be switched between the first antenna and the second antenna based on an instruction from the outside;
Connected to the third tag reader, switches between the first antenna and the second antenna via the third tag reader, attempts to communicate with the tag, and according to a transmission power level communicable with the tag A detection processing unit having first determination means for determining the presence or absence of the environmental change,
The environment change detection system according to claim 1, further comprising: An environmental change sensing tag having a resonance circuit set to change the resonance frequency from the first resonance frequency to the second resonance frequency in accordance with an environmental change, and an IC chip connected to the resonance circuit;
A system comprising a reader that reads data from the tag in a non-contact manner,
When the reading position of the reading device makes the transmission power level and frequency of the reading device constant, the first position that can communicate with the tag that resonates at the first resonance frequency, and the second resonance frequency It is possible to install at a second position communicable with the tag that resonates at the second position, and has a second determination means for determining the presence or absence of the environmental change according to the position communicable with the tag. Environmental change detection system. The reader is
A first antenna installed at the first position;
A second antenna installed at the second position;
A third tag reader to which the first and second antennas are connected and which can be switched between the first antenna and the second antenna based on an instruction from the outside;
Connected to the third tag reader, switched between the first antenna and the second antenna via the third tag reader to try to communicate with the tag, and depending on the position of the antenna capable of communicating with the tag A detection processing unit having second determination means for determining presence or absence of the environmental change;
The environmental change detection system according to claim 6, further comprising: The reader is
A first tag reader installed with the reading position as the first position;
A second tag reader installed with the reading position as the second position;
Connected to the first tag reader and the second tag reader, switching between the first tag reader and the second tag reader and trying to communicate with the tag, and depending on the reading position where the tag can communicate with the environment A detection processing unit having second determination means for determining the presence or absence of a change;
The environmental change detection system according to claim 6, further comprising:

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