JP2013140575A - Rfid tag and rfid system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an RFID tag achieving downsizing and cost reduction without decreasing a communication range.SOLUTION: An RFID tag 500 comprises: a chip module; and a retaining member and is mounted across a slit SLT of a metal plate P. The chip module has an IC chip and two terminal members, each terminal member having a metal foil laminated with a resin film. The RFID tag satisfies the relationship of Wmin≤Wa-4πf×S×ε×ε×V/d, where f represents a frequency of radio waves used for communication; Wa and V represent electromotive force and voltage, respectively, induced between one side and the other side of the slit when the tag receives the radio waves; S represents an area of each metal foil; d represents a thickness of an insulating member; εrepresents a dielectric constant of the insulating member; εrepresents a dielectric constant of vacuum; and Wmin represents a minimum value of power required for the operation of the IC chip.

Description

  The present invention relates to an RFID tag and an RFID system, and more particularly to an RFID tag corresponding to metal and an RFID system including the RFID tag.

  An RFID (Radio Frequency Identification) system is known as one system that transmits information without contact.

  The RFID system generally includes an RFID tag (also referred to as a “wireless tag”) and a reader / writer (RW) device. Information is read from and written to the RFID tag from the RW device by wireless communication.

  The RFID tag includes a so-called active type tag that is mounted with a battery and driven by the electric power, and a so-called passive type tag that receives electric power from the RW device and drives it using it as a power source.

  Active tags have a battery compared to passive tags, so there are advantages in terms of communication distance and communication stability, but the structure is complicated and the size is increased and the cost is increased. There are also disadvantages.

  In addition, with recent improvements in semiconductor technology, IC tags for passive tags have become smaller and higher in performance, and the use of passive tags in a wide range of fields has become possible due to the expansion of communication distance and the improvement of communication stability. Expected.

  Various frequency bands are used in the RFID system.

  In an RFID system using a passive tag as an RFID tag, when the frequency band is a long wave band or a short wave band, a voltage is induced in the RFID tag due to electromagnetic induction between the transmission antenna coil of the RW device and the antenna coil of the RFID tag. Then, the IC chip is activated by this voltage, and communication becomes possible. That is, communication is performed by an electromagnetic induction method.

  Therefore, in this case, the RFID tag operates only within the induction electromagnetic field generated by the reader / writer device, and the communication distance becomes about several tens of centimeters.

  On the other hand, when the frequency band is the UHF band and the microwave band, electric power is supplied to the IC chip of the RFID tag by radio waves. That is, communication is performed using a radio wave communication method.

  Therefore, in this case, the communication distance is greatly improved to about 1 to 8 m.

  Therefore, in the case of the radio wave communication method, it becomes possible to collectively read a plurality of RFID tags, which are difficult to realize by the electromagnetic induction method, and to read a moving RFID tag, and the range of use will be greatly expanded in the future. It is considered a thing.

  By the way, when a general RFID tag is attached to the surface of a metal object or when moisture exists in the vicinity, communication may be difficult.

  Therefore, various metal-compatible RFID tags that can be attached to the surface of a metal object have been devised (see, for example, Patent Document 1 and Patent Document 2).

  Patent Document 3 discloses an RFID tag having a passive RFID chip that is arranged on an insulating film and does not require a power supply, and antenna pattern portions arranged on both sides of the RFID chip. A protective film formed on the entire surface of the conductive flat plate, including the conductive flat plate partially formed with the cut portion, the filled portion made of a non-conductive material filled in the cut portion, and the upper surface of the filled portion The RFID tag is disposed on the back side of the conductive flat plate so as to straddle the cut portion, and the insulating film is disposed toward the back surface of the conductive flat plate, and the total length L of the cut portion is an RFID chip. When the wavelength of the radio signal transmitted from λ is λ, it is expressed by L = λ / n (n is an integer of 1 or more), and the width of the cut portion is 7 to 8 when transmitting and receiving UHF band radio signals. Within 9mm An in-vehicle license plate is disclosed that is set to a length within a range of 2 to 3 mm when transmitting and receiving radio signals in the 2.45 GHz band.

  However, it has been difficult to reduce the size and cost of a conventional RFID tag without reducing the communication distance.

The present invention is an RFID tag attached to a metal member in which a slit or a groove is formed, and insulates the surface of the metal member on one side and the other side of the slit or groove with respect to the width direction of the slit or groove, respectively. Two conductive members attached via members, and an IC chip to which electric power is supplied via the two conductive members, the frequency f of the radio wave used for communication, the slit or Electromotive force Wa and voltage V generated between one side and the other side of the groove, area S of each of the two conductive members, thickness d of the insulating member, dielectric constant ε _{r of} the insulating member, dielectric constant ε of vacuum ₀ and a minimum value Wmin of electric power necessary for the operation of the IC chip, the RFID tag satisfies a relationship of Wmin ≦ Wa−4πf · S · ε ₀ · ε _r · V ² / d .

  According to the RFID tag of the present invention, size reduction and cost reduction can be achieved without causing a reduction in communication distance.

It is a figure for demonstrating schematic structure of the RFID system which concerns on one Embodiment of this invention. It is a figure for demonstrating the slit of a metal plate. It is a figure for demonstrating the RFID tag attached to the metal plate. It is FIG. (1) for demonstrating operation | movement of a RFID system. It is a figure for demonstrating an example of detection information. FIG. 6 is a second diagram for explaining the operation of the RFID system; FIG. 6 is a diagram (part 3) for explaining the operation of the RFID system; FIG. 6 is a diagram (part 4) for explaining the operation of the RFID system; FIG. 9A and FIG. 9B are diagrams for explaining the RFID tag. It is FIG. (1) for demonstrating a chip module. It is FIG. (2) for demonstrating a chip module. It is FIG. (3) for demonstrating a chip module. FIG. 13A to FIG. 13D are views (No. 1) for explaining the holding member, respectively. FIGS. 14A and 14B are views (No. 2) for explaining the holding member, respectively. It is FIG. (3) for demonstrating a holding member. FIG. 16A to FIG. 16C are diagrams for explaining the dimensions of the holding member. It is a figure for demonstrating the dimension of metal foil. FIGS. 18A and 18B are views (No. 1) for explaining a state where the chip module is attached to the holding member. FIGS. 19A and 19B are views (No. 2) for explaining a state where the chip module is attached to the holding member, respectively. It is FIG. (1) for demonstrating the attachment method of a RFID tag. It is FIG. (2) for demonstrating the attachment method of a RFID tag. It is FIG. (3) for demonstrating the attachment method of a RFID tag. It is FIG. (4) for demonstrating the attachment method of a RFID tag. It is FIG. (5) for demonstrating the attachment method of a RFID tag. It is FIG. (6) for demonstrating the attachment method of a RFID tag. It is a figure for demonstrating the electric field around a slit when an electromagnetic wave is radiated | emitted from the RW apparatus. It is a figure for demonstrating the modification 1 of a holding member. It is a figure for demonstrating the dielectric material sheet which covers a slit. It is a figure for demonstrating the modification 2 of a holding member. FIG. 30 (A) and FIG. 30 (B) are diagrams for explaining a medicine package, respectively. It is a figure for demonstrating the chip | tip module affixed on the slit provided in the chemical | medical agent package, and the chemical | medical agent package. It is FIG. (1) for demonstrating the chip module affixed on a chemical | medical agent package. It is FIG. (2) for demonstrating the chip module affixed on a chemical | medical agent package. FIG. 34A and FIG. 34B are diagrams for explaining how the chip module is attached to the medicine package. It is a figure for demonstrating the modification of the chip module affixed on a chemical | medical agent package. It is a figure for demonstrating the groove | channel of a metal plate. It is a figure for demonstrating the state by which the RFID tag was attached to the metal plate of FIG. It is a figure for demonstrating the groove | channel formed by press work. It is a figure for demonstrating groove formation of a slit. FIG. 40A to FIG. 40D are diagrams for describing modifications of the holding member. It is a figure for demonstrating the state by which the RFID tag using the holding member of a modification was attached to the metal plate.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of an RFID system 10 according to an embodiment.

  This RFID system 10 is an RFID system using a passive tag, and corresponds to the UHF band (860 MHz to 960 MHz).

  Here, the RFID system 10 is used in an assembly line for assembling the industrial product M. The assembly line has a transport system T and five stations (ST1 to ST5) in which primary to fifth order assembly is performed.

  Hereinafter, for the sake of convenience, an assembly assembled at the station ST1 is referred to as an “assembly M1”, an assembly assembled at the station ST2 is an “assembly M2”, an assembly assembled at the station ST3 is an “assembly M3”, and the station ST4. The assembled product is referred to as “assembled product M4”, and the product assembled at station ST5 is referred to as “assembled product M5”.

  The RFID system 10 includes a control device 100, nine RW devices (200a to 200i), a plurality of RFID tags (referred to as “RFID tags 500”), a data transmission path, and the like.

  The plurality of RFID tags are RFID tags having the same configuration, but each stores a unique ID number. Here, since it is not necessary to distinguish a plurality of RFID tags, hereinafter, each RFID tag is collectively referred to as “RFID tag 500”. Details of the RFID tag 500 will be described later.

  The RFID tag 500 is attached to the metal plate P of the assembly M1 at the station ST1. As shown in FIG. 2 as an example, the metal plate P is formed with a slit SLT having a length Ly and a width Lx, and two screw holes for attaching the RFID tag 500.

  When the length (dimension in the longitudinal direction) Ly of the slit SLT is ½ times the wavelength λ of the radio wave used in the RFID system 10, the X direction of the slit SLT when the radio wave is received The voltage generated between both ends of the is maximized. For example, when the wavelength λ is 950 MHz, Ly = 160 mm.

  The width (dimension in the short direction) Lx of the slit SLT is related to the frequency width at which a desired gain (good antenna performance) as an antenna can be obtained. That is, as the width Lx is reduced, the frequency width is reduced. Conversely, as the width Lx is increased, the frequency width is increased. However, as the width Lx is increased, the impedance increases and the efficiency of the antenna decreases.

  Generally, the slit SLT is formed by punching using a mold, and is shaped by secondary processing as necessary. In this case, if the width Lx is too narrow, it is difficult to obtain a desired width with a predetermined accuracy. Therefore, it is conceivable to form the slit SLT by laser processing, but this leads to an increase in cost. On the other hand, if the width Lx is too narrow, a foreign object such as a metal piece may get caught in the slit SLT and the antenna performance may be deteriorated. Therefore, when the wavelength λ is 950 MHz, the width Lx is set to 2 to 3 mm. In the present embodiment, when the wavelength λ is 950 MHz, slits with Ly = 160 mm and Lx = 2 mm are formed.

  In this specification, in the XYZ three-dimensional orthogonal coordinate system, the length direction (longitudinal direction) of the slit SLT is described as the Y-axis direction, and the width direction (short direction) of the slit SLT is described as the X-axis direction. Therefore, the direction orthogonal to the surface of the metal plate P is the Z-axis direction.

  One of the two screw holes is formed on the −X side of the slit SLT, and the other is formed on the + X side of the slit SLT. The two screw holes are formed at the same position in the Y-axis direction.

  By the way, the metal plate P may be a casing of the industrial product M or a metal plate used inside the industrial product M.

  A state where the RFID tag 500 is attached to the metal plate P is shown in FIG. The attachment position in the Y-axis direction is a position where impedance matching can be taken, and is shifted from the center of the slit SLT.

  Returning to FIG. 1, the RW apparatus 200a is arranged in the vicinity of the exit of the station ST1. The RW device 200b is disposed near the entrance of the station ST2, and the RW device 200c is disposed near the exit of the station ST2.

  The RW device 200d is disposed near the entrance of the station ST3, and the RW device 200e is disposed near the exit of the station ST3.

  The RW device 200f is disposed near the entrance of the station ST4, and the RW device 200g is disposed near the exit of the station ST4.

  The RW device 200h is disposed in the vicinity of the entrance of the station ST5, and the RW device 200i is disposed in the vicinity of the exit of the station ST5.

  Each RW device has a unique device number. In the following, the device number of each RW device is referred to as “own device number”.

  When each RW device reads the ID number from the RFID tag 500, the RW device notifies the control device 100 as “detection information” via the data transmission path together with the reading date / time and its own device number. Hereinafter, the reading date and time is referred to as “detection date and time”.

  Each RW device writes the detection date and time and its own device number to the RFID tag 500 as “history information”.

  That is, each RW device is a reader / writer device of the RFID tag 500. A space area in which the RW device and the RFID tag 500 can communicate with each other is also referred to as an “effective communication area”.

  The control device 100 includes a CPU, a ROM, a RAM, a hard disk device, an input device, a display device, and the like.

  The hard disk device has a hard disk in which information is recorded, and a drive device that reads and writes the hard disk according to instructions from the CPU.

  The input device includes, for example, at least one input medium of a keyboard, a mouse, a tablet, a light pen, a touch panel, and the like, and notifies the CPU of various types of information input from an operator via the input medium. Note that information from the input medium may be input in a wireless manner.

  The display device includes a display unit using, for example, a CRT, a liquid crystal display (LCD), a plasma display panel (PDP), and the like, and displays various information instructed by the CPU. As an integrated display device and input device, for example, there is an LCD with a touch panel.

  The ROM is a memory in which a plurality of programs described by codes decodable by the CPU and a plurality of data used for executing the programs are stored. The RAM is a working memory.

  An interrupt is generated when a notification is received from each RW device.

  A personal computer can be used as the control device 100.

  The control device 100 is connected to a host device (for example, a host computer), and transmits various information to the host device in response to a request.

  Here, the operation of the RFID system 10 will be described. Each RW device transmits a command signal at every predetermined timing. When there is a response from the RFID tag 500 to the command signal, the RW device shifts to a communication mode with the RFID tag 500.

  First, primary assembly is performed at the station ST1. When the assembly at the station ST1 is completed, the assembly M1 is sent out toward the station ST2 by the transport system T.

  As shown in FIG. 4, when the RFID tag 500 of the assembly M1 enters the effective communication area of the RW device 200a, the RFID tag 500 transmits a signal including an ID number.

  When receiving a signal from the RFID tag 500, the RW device 200a extracts an ID number included in the signal, notifies the control device 100 of detection information (see FIG. 5), and writes history information to the RFID tag 500. .

  The control device 100 records the received information on the hard disk and displays the status on the display unit of the display device (see FIG. 6). Thereby, it can be seen that the industrial product M having the ID number “21584486” has finished the primary assembly.

  In the station ST1, the primary assembly of the next industrial product M is continuously performed. However, in order to avoid complexity, the description will be continued assuming that the primary assembly of the next industrial product M is not performed in the station ST1.

  When the RFID tag 500 of the assembly M1 enters the effective communication area of the RW device 200b, the RFID tag 500 transmits a signal including an ID number.

  When receiving the signal from the RFID tag 500, the RW device 200b extracts the ID number included in the signal, notifies the control device 100 of the detection information, and writes the history information to the RFID tag 500. The time at the detection date and time (hereinafter referred to as “detection time”) at this time means the assembly start time at the station ST2.

  The control device 100 records the received detection information on the hard disk and displays the status on the display unit of the display device (see FIG. 7). Thereby, it can be seen that the industrial product M having the ID number “2158486” is in the station ST2.

  Secondary assembly is performed at station ST2. When the assembly at the station ST2 is completed, the assembly M2 is sent out toward the station ST3 by the transport system T.

  When the RFID tag 500 of the assembly M2 enters the effective communication area of the RW device 200c, the RFID tag 500 transmits a signal including an ID number.

  When receiving a signal from the RFID tag 500, the RW device 200c extracts an ID number included in the signal, notifies the control device 100 of detection information, and writes history information to the RFID tag 500. The detection time at this time means the assembly end time at the station ST2. Therefore, the assembly time at the station ST2 can be obtained from the detection time of the RW device 200c and the detection time of the RW device 200b.

  The control device 100 records the received detection information on the hard disk and displays the status on the display unit of the display device (see FIG. 8). Thereby, it can be seen that the industrial product M having the ID number “2158486” has finished the secondary assembly.

  When the RFID tag 500 of the assembly M2 enters the effective communication area of the RW device 200d, the RFID tag 500 transmits a signal including an ID number.

  When receiving the signal from the RFID tag 500, the RW device 200d extracts the ID number included in the signal, notifies the control device 100 of the detection information, and writes the history information to the RFID tag 500. The detection time at this time means the assembly start time at the station ST3.

  The control device 100 records the received detection information on the hard disk and displays the status on the display unit of the display device. Thereby, it can be seen that the industrial product M having the ID number “2158486” is in the station ST3.

  Tertiary assembly is performed at station ST3. When the assembly at the station ST3 is completed, the assembly M3 is sent to the station ST4 by the transport system T.

  When the RFID tag 500 of the assembly M3 enters the effective communication area of the RW device 200e, the RFID tag 500 transmits a signal including an ID number.

  When receiving the signal from the RFID tag 500, the RW device 200e extracts the ID number included in the signal, notifies the control device 100 of the detection information, and writes the history information to the RFID tag 500. The detection time at this time means the assembly end time at the station ST3. Therefore, the assembly time at the station ST3 can be obtained from the detection time of the RW device 200e and the detection time of the RW device 200d.

  The control device 100 records the received detection information on the hard disk and displays the status on the display unit of the display device. Thereby, it can be seen that the industrial product M having the ID number “21584486” has finished the tertiary assembly.

  When the RFID tag 500 of the assembly M3 enters the effective communication area of the RW device 200f, the RFID tag 500 transmits a signal including an ID number.

  When receiving the signal from the RFID tag 500, the RW device 200f extracts the ID number included in the signal, notifies the control device 100 of the detection information, and writes the history information to the RFID tag 500. The detection time at this time means the assembly start time at the station ST4.

  The control device 100 records the received detection information on the hard disk and displays the status on the display unit of the display device. Thereby, it can be seen that the industrial product M having the ID number “2158486” is in the station ST4.

  The fourth order assembly is performed at the station ST4. When the assembly at the station ST4 is completed, the assembly M4 is sent out toward the station ST5 by the transport system T.

  When the RFID tag 500 of the assembly M4 enters the effective communication area of the RW device 200g, the RFID tag 500 transmits a signal including an ID number.

  When receiving the signal from the RFID tag 500, the RW device 200g extracts the ID number included in the signal, notifies the control device 100 of the detection information, and writes the history information to the RFID tag 500. The detection time at this time means the assembly end time at the station ST4. Therefore, the assembly time at the station ST4 can be obtained from the detection time of the RW device 200g and the detection time of the RW device 200f.

  The control device 100 records the received detection information on the hard disk and displays the status on the display unit of the display device. Thereby, it can be seen that the industrial product M having the ID number “2158486” has finished the fourth assembly.

  When the RFID tag 500 of the assembly M4 enters the effective communication area of the RW device 200h, the RFID tag 500 transmits a signal including an ID number.

  When receiving a signal from the RFID tag 500, the RW device 200h extracts an ID number included in the signal, notifies the control device 100 of detection information, and writes history information to the RFID tag 500. The detection time at this time means the assembly start time at the station ST5.

  The control device 100 records the received detection information on the hard disk and displays the status on the display unit of the display device. Thereby, it can be seen that the industrial product M having the ID number “2158486” is in the station ST5.

  The fifth order assembly is performed at the station ST5. When the assembly at the station ST5 is completed, the assembly M5 is sent out toward the next line by the transport system T.

  When the RFID tag 500 of the assembly M5 enters the effective communication area of the RW device 200i, the RFID tag 500 transmits a signal including an ID number.

  When receiving a signal from the RFID tag 500, the RW device 200i extracts an ID number included in the signal, notifies the control device 100 of detection information, and writes history information to the RFID tag 500. The detection time at this time means the assembly end time at the station ST5. Therefore, the assembly time at the station ST5 can be obtained from the detection time of the RW device 200i and the detection time of the RW device 200h.

  The control device 100 records the received detection information on the hard disk and displays the status on the display unit of the display device. Thereby, it can be seen that the industrial product M having the ID number “2158486” has finished the fifth assembly.

  Thus, in the RFID system 10, the in-process status of the industrial product M can be known in real time. In addition, the RFID system 10 can know the assembly time at each station in real time.

  In this case, by arranging the personnel so that the assembly time at each station is substantially equal, it is possible to prevent the in-process product from staying and to efficiently assemble the industrial product M.

  Next, details of the RFID tag 500 will be described.

  As an example, the RFID tag 500 includes a chip module 510 and a holding member 550 as shown in FIGS. 9A and 9B.

  The chip module 510 includes an IC chip 511 and two terminal members 520 as shown in FIG. 10 as an example.

  Each terminal member 520 has a metal foil (here, an aluminum foil) 521 and a resin film 522 that laminates both surfaces of the metal foil 521. The resin film 522 has a role as an insulator between the metal plate P and the metal foil 521 and has a role to protect the metal foil 521 from contamination and breakage.

  The metal foil 521 of each terminal member 520 is connected to the electrode 512 of the IC chip 511 as shown in FIG. 11 and FIG. 12 as an example.

  As an example, the holding member 550 is a substantially rectangular ceramic or resin plate-like member as shown in FIGS.

  The holding member 550 is formed with through holes 553 into which screws are inserted in the vicinity of both ends in the X-axis direction. As shown in FIG. 14B as an example, the end portion on the −Z side of the through-hole 553 is counterbored so as to embed the head portion of the screw. Note that FIG. 14B is a cross-sectional view taken along the line AA of FIG.

  The holding member 550 has a flat portion 551 to which the chip module 510 is attached at the center of the + Z side surface. As shown in FIG. 15 as an example, the flat portion 551 protrudes by about 0.2 mm from the surroundings.

  Protrusions 552 are respectively provided on the + Y side and the −Y side of the flat portion 551. The protrusion 552 has a positioning function when the RFID tag 500 is attached to the metal plate P. Further, the protrusion 552 has a function of preventing the metal plate P from being twisted when the RFID tag 500 is attached to the metal plate P. In particular, when the RFID tag 500 is attached to the metal plate P using a tapping screw, the effect is great. The protrusion 552 also has a role of protecting the IC chip 511 from being damaged by an object colliding with the IC chip 511.

  At the center of the surface on the −Z side of the holding member 550, a seal printed with a product name or the like is attached.

  Here, a specific example of the dimensions of the holding member 550 will be described with reference to FIGS. Note that the wavelength of radio waves used for communication is 950 MHz.

  The holding member 550 has a length L1 in the X-axis direction of 55 mm and a length L2 in the Y-axis direction of 20 mm. The distance L3 between the centers of the two through holes 553 in the X axis direction is 40 mm. The flat portion 551 has a length L4 in the X-axis direction of 35 mm and a length L5 in the Y-axis direction of 14 mm.

  The length L6 of the holding member 550 in the Z-axis direction is 5 mm. Each projection 552 has a length L7 in the X-axis direction of 1.8 mm, a length L8 in the Z-axis direction of 2 mm, and a length L9 in the Y-axis direction of 2 mm. The length L7 of each protrusion 552 in the X-axis direction is set to be slightly smaller than the width Lx of the slit SLT. Thereby, when attaching the RFID tag 500 to the metal plate P, positioning in the X-axis direction is facilitated. Note that the length L9 of each protrusion 552 in the Y-axis direction is not a strictly defined value, but if it is too small, the protrusion 552 may be lost.

  The diameter of each through hole 553 is 3.5 mm.

  By the way, the communicable distance is related to the size of the metal foil 521 in the terminal member 520 and the thickness of an insulator such as a protective film or an adhesive layer interposed between the metal plate P. That is, by adjusting the size of the metal foil 521 in accordance with the thickness of the insulator, the impedance Z in electrostatic coupling can be reduced and the communicable distance can be extended.

The impedance Z is expressed by the following equation (1).
Z = 1 / (ω · C) (1)

In the above equation (1), ω is an angular frequency, and C is a capacitance. ω is represented by the following equation (2), and C is represented by the following equation (3). Here, f is the frequency of radio waves used for communication, S is the area of the metal foil 521, ε ₀ is the dielectric constant of vacuum, ε _r is the dielectric constant of the insulator, and d is the thickness of the insulator.
ω = 2πf (2)
C = S · ε ₀ · ε _r / d (3)

Therefore, the above equation (1) can be rewritten as the following equation (4).
Z = d / (2πf · S · ε ₀ · ε _r ) (4)

The electric power W supplied from the terminal member 520 to the IC chip 511 can be expressed by the following equation (5).
W = Wa-2 · V · A = Wa-2 · V ² / Z (5)

  Wa in the above equation (5) is an electromotive force generated between both ends of the slit SLT in the X-axis direction during communication, and V is a voltage generated between both ends of the slit SLT in the X-axis direction during communication. A is a current supplied from the two terminal members 520 to the IC chip 511. That is, the power supplied to the IC chip 511 is obtained by subtracting the power consumed at the connection portion (insulator portion) from the electromotive force at the so-called antenna.

Here, if the minimum value of the power W necessary to obtain a desired communication distance is Wmin, the area S of the metal foil 521 may be set so that the relationship of the following equation (6) is satisfied. . Note that Wmin is a value that is uniquely determined when the type of IC chip to be used and the desired communication distance are determined.
Wmin ≦ Wa−2 · V ² / Z = W−4πf · S · ε ₀ · ε _r · V ² / d (6)

For example, when f = 950 MHz, the insulator is PET (polyethylene terephthalate), d = 20 μm, and the desired communication distance is 3 m, if S = 100 mm ² , the relationship of the above equation (6) can be satisfied. it can.

  Therefore, in this embodiment, a PET film having a thickness of 20 μm is used as the resin film 522, and each metal foil 521 has a substantially square shape with a side L10 of 10 mm as shown in FIG. In addition, when the insulating protective material is apply | coated or laminated | stacked on the surface of the metal plate P, the thickness of the resin film 522 is determined according to the material and thickness of this protective material. For example, when the protective material is a PET film, the total thickness of the protective material and the resin film 522 is 20 μm.

  18A to 19B show a state where the chip module 510 is attached to the holding member 550. FIG. Note that FIG. 19B is a cross-sectional view taken along line AA in FIG.

  Next, an attachment method when an operator attaches the RFID tag 500 to the metal plate P at the station ST1 will be described.

(1) The RFID tag 500 is provided so that the longitudinal direction of the RFID tag 500 is orthogonal to the longitudinal direction of the slit SLT of the metal plate P.
(2) The RFID tag 500 is brought close to the metal plate P so that the two protrusions 552 of the RFID tag 500 are inserted into the slit SLT (see FIG. 20).
(3) When the two protrusions 552 of the RFID tag 500 are inserted into the slit SLT, the RFID tag 500 is set to Y so that each through hole of the holding member 550 is positioned on the −Z side of each screw hole of the metal plate P. It is moved along the axial direction (see FIGS. 21 and 22).
(4) Insert a screw into each through hole of the RFID tag 500 (see FIG. 23).
(5) Using a tool (screw turning), each screw is pushed into the screw hole of the metal plate P (see FIG. 24). At this time, each screw is strongly pushed into the screw hole of the metal plate P so that the peripheral portion of the through hole 553 is in contact with the metal plate P (see FIG. 25). Thereby, the adhesiveness of each terminal member 520 and the metal plate P can be improved. Note that FIG. 25 exaggerates the deformation of the RFID tag 500 for easy understanding.

  When linearly polarized waves or circularly polarized radio waves are radiated from the RW device toward the slit SLT, an electric field is generated around the slit SLT (see FIG. 26). The electric field causes a reverse voltage (alternating current) across the slit SLT. Therefore, when the RFID tag 500 is attached so as to straddle the slit SLT, current flows and the IC chip 511 of the RFID tag 500 is activated.

  The communication distance between the RW device and the RFID tag 500 was 3 m.

  As described above, the RFID tag 500 according to this embodiment includes the chip module 510 and the holding member 550.

  The chip module 510 includes an IC chip 511 and two terminal members 520. Each terminal member 520 has a metal foil 521 whose both surfaces are laminated with a resin film 522. The metal foil 521 of each terminal member 520 is connected to the electrode 512 of the IC chip 511.

  In the chip module 510, the thickness d of the resin film 522 and the area S of the metal foil 521 are set so that the relationship of the above expression (6) is satisfied.

  In this case, since the minimum value of the area of the metal foil 521 can be known according to use conditions, the chip module 510 is not made larger than necessary, and the chip module 510 is reduced in size and cost. be able to.

  The RFID tag 500 is attached so as to straddle the slit SLT of the metal plate P that is a part of the industrial product M. The RFID tag 500 uses the metal plate P as an antenna. Therefore, the RFID tag 500 does not need to have an antenna, and can be reduced in size and cost. Even if there is a metal near the RFID tag 500, a desired communication distance can be secured.

  Therefore, the RFID tag 500 is metal-compatible and can be reduced in size and cost without causing a reduction in communication distance.

  Further, since the RFID tag 500 is screwed to the metal plate P, it can be reused easily.

  Further, since the RFID tag 500 is screwed to the metal plate P, the RFID tag 500 can be securely attached to the metal plate P even when oil is attached to the surface of the metal plate P.

  According to the RFID system 10 according to the present embodiment, since it is configured to include the RFID tag 500, the ID number can be read accurately and stably, and the reliability of the system can be improved. .

  In the above embodiment, as shown in FIG. 27 as an example, a long hole 554 whose longitudinal direction is the Y-axis direction may be provided instead of the through hole 553. In this case, when attaching to the metal plate P, the attachment position of the RFID tag 500 can be adjusted within the range of the length L20 (for example, L20 = 10 mm) in the Y-axis direction. Specifically, for example, the RFID tag 500 is moved in the Y-axis direction while measuring the resistance value with a network analyzer, and the position where the resistance value becomes equal to the resistance value specified for the IC chip 511 is impedance-matched. Search as a possible position. When a position where impedance matching can be obtained is found, screws are fixed at that position. Thereby, the RFID tag 500 can be attached at the most appropriate position.

  Moreover, although the said embodiment demonstrated the case where the RFID tag 500 was screwed to the metal plate P, it is not limited to this. For example, when it is not necessary to reuse, the RFID tag 500 may be bonded to the metal plate P.

Moreover, although the said embodiment demonstrated the case where the shape of the metal foil 521 was substantially square, it is not limited to this, In short, the area S should just be 100 mm < ² >.

  Moreover, although the said embodiment demonstrated the case where the RFID tag 500 was attached to the metal plate P which comprises some industrial products M, it is not limited to this.

In the above embodiment, the RFID tag 500 may further include a dielectric sheet 560 that covers the slit SLT, as shown in FIG. 28 as an example. The wavelength λ of the radio wave is expressed by c / f, where c is the speed at which the radio wave travels in vacuum (≈air). On the other hand, when the radio wave passes through the dielectric, the velocity c of the radio wave proceeds, the dielectric constant of the dielectric and _{ε r, 1 / (ε 0} · ε r) changes to ^1/2. The wavelength λ of the radio wave is (c / (ε ₀ · ε _r ) ^1/2 ) / f. In this case, the length of the slit SLT in the longitudinal direction can be made shorter than that in the above embodiment.

  Therefore, in this case, instead of using the dielectric sheet 560, the holding member 550 may have a shape covering the slit SLT as shown in FIG. 29 as an example.

  In the above embodiment, the case where the RFID tag 500 includes the chip module 510 and the holding member 550 has been described. However, only the chip module 510 may be used as the RFID tag.

  For example, as shown in FIG. 30 (A) and FIG. 30 (B), a medicine package in which tablets are placed in a plurality of recesses formed in a resin sheet, and the plurality of recesses are sealed with aluminum foil. In addition, the chip module 510 can be attached. Note that FIG. 30B is a cross-sectional view taken along the line AA in FIG.

  A slit SLT formed in the medicine package and a chip module 510 attached across the slit SLT are shown in FIG. 31 as an example.

Here, since the chip module 510 is attached to the surface of the resin sheet, the shape of each metal foil 521 in the chip module 510 is a shape that avoids the concave portion of the resin sheet as shown in FIG. 32 as an example. However, the area of each metal foil 521 is 100 mm ² .

  As shown in FIG. 33 as an example, the chip module 510 has an adhesive layer, and is attached to the resin sheet through the adhesive layer (see FIGS. 34A and 34B). ). Here, the resin film 522 for laminating both surfaces of the metal foil 521 is as thin as possible.

  Therefore, a resin sheet, an adhesive layer, and a resin film 522 exist between the aluminum foil of the medicine package and each metal foil 521 of the chip module 510. In this case, the layer formed of the resin sheet, the adhesive layer, and the resin film 522 becomes an insulator, and the area of each metal foil 521 is determined according to the material and thickness of each.

  In this case, in order to take out the tablet from the medicine package, even if the concave portion is crushed with a finger and the opposing aluminum foil is broken, the chip module 510 is not affected at all.

  In addition, when taking out a tablet from a medicine package, when the chip module 510 may be detached from the medicine package, the chip module 510 may be attached to the aluminum foil side. In this case, the shape of each metal foil 521 may be substantially square as in the above embodiment. At this time, an adhesive layer and a resin film 522 exist between the aluminum foil of the medicine package and each metal foil 521 of the chip module 510.

  In this case, as shown in FIG. 35 as an example, the chip module 510 may further include a dielectric sheet 560 that covers the slit SLT. In this case, the length of the slit SLT in the longitudinal direction can be made shorter than that in FIG.

  Moreover, in the said embodiment, it replaces with the said slit SLT and the groove | channel Gr may be formed in the metal plate P as an example shown in FIG.36 and FIG.37. Even in this case, the RFID tag 500 is metal compatible and can be reduced in size and cost without causing a reduction in communication distance.

  In this case, as shown in FIG. 38 as an example, the groove Gr may be a groove formed by pressing the metal plate P.

  As an example, as shown in FIG. 39, a thin metal plate P2 in which a screw hole corresponding to each screw is formed may be attached to the + Z side of the metal plate P, and the slit SLT may be formed in a groove shape.

  Moreover, in the said embodiment, as FIG. 40 (A)-FIG.40 (C) show as an example, it may replace with the said protrusion 552 and the screw protrusion 552 'may be formed. In this case, the through hole 553 in the holding member 550 is not necessary (see FIGS. 40A and 40D).

  As an example, as shown in FIG. 41, the RFID tag 500 can be fixed to the metal plate P by fitting a nut Nt to the tip portion of the screw projection 552 ′ penetrating the slit SLT. In this case, the screw hole in the metal plate P is unnecessary.

  In the above embodiment, the case where information is written to the RFID tag 500 has been described. However, the present invention is not limited to this. When information is not written to the RFID tag 500, the IC chip 511 does not require a memory area in which information is written. Further, instead of the RW device, a read-only device (reader) that only reads the ID number can be used.

  Moreover, although the said embodiment demonstrated the case where an assembly line consists of five stations, the number of stations is not limited to this.

  Moreover, the contents of the detection information and history information in the above embodiment are examples, and the present invention is not limited to this. Similarly, the number of digits of the device number and the ID number is not limited to the above embodiment.

  Moreover, the content displayed on the display part in the said embodiment is an example, and is not limited to this.

  Moreover, although the said embodiment demonstrated the case where RFID system 10 was used for an assembly line, it is not limited to this. The present invention can be applied to applications where RFID systems are currently used. In that case, the reliability of the system can be improved without increasing the cost. In addition, by separately preparing a metal plate corresponding to the metal plate P, it is possible to use a metal plate that does not include a metal member.

  Moreover, although the said embodiment demonstrated the case where the frequency was a UHF band, it is not limited to this.

  DESCRIPTION OF SYMBOLS 10 ... RFID system, 100 ... Control apparatus, 200a-200i ... RW apparatus (communication apparatus), 500 ... RFID tag, 510 ... Chip module, 511 ... IC chip, 512 ... Electrode, 520 ... Terminal member, 521 ... Metal foil ( Conductive member), 522 ... resin film, 550 ... holding member, 551 ... flat portion, 552 ... projection, 553 ... through hole, 554 ... long hole, 560 ... dielectric sheet, P ... metal plate, SLT ... slit, ST1 ST5 ... Station.

JP 2002-157565 A JP 2005-309811 A JP 2008-284967 A

Claims (7)

An RFID tag attached to a metal member having a slit or groove,
With respect to the width direction of the slit or groove, two conductive members attached to the surfaces of the metal member on one side and the other side of the slit or groove, respectively, via an insulating member;
An IC chip to which power is supplied via the two conductive members,
Frequency f of radio wave used for communication, electromotive force Wa and voltage V generated between one side and the other side of the slit or groove when receiving the radio wave, area S of each of the two conductive members, the insulating member Using the thickness d, the dielectric constant ε _{r of} the insulating member, the dielectric constant ε _{0 of the} vacuum, and the minimum value Wmin of the electric power necessary for the operation of the IC chip,
An RFID tag satisfying a relationship of Wmin ≦ Wa-4πf · S · ε ₀ · ε _r · V ² / d. A holding member that holds the two conductive members and is fixed to the metal member;
The RFID tag according to claim 1, wherein the holding member is provided with a plurality of through holes into which screws are inserted when the metal member is screwed.   The RFID tag according to claim 2, wherein the plurality of through holes are long holes whose longitudinal direction is a direction parallel to a length direction of the slit or groove.   4. The RFID tag according to claim 2, wherein the holding member is provided with a protrusion for positioning with respect to the slit or groove. 5.   The RFID tag according to claim 2, wherein the holding member can cover the slit or the groove.   The RFID tag according to any one of claims 1 to 4, further comprising a dielectric sheet covering the slit or groove. The RFID tag according to any one of claims 1 to 6,
A communication device that performs at least one of reading and writing of information with respect to the RFID tag by wireless communication;
And a control device for controlling the communication device.

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