Radio communication device

Abstract

To provide a configuration capable of appropriately updating the display status of a display unit of an RFID tag which operates upon receiving power supply by radio waves during transportation.SOLUTION: A control unit 21 performs tag information update processing for updating the display status of a display unit 11 of an RFID tag 10 using the antenna 31 installed along a transport path 1 in response to the detection results of a passage sensor 41 which can detect the transport status of a returnable box 2 to which the RFID tag 10 is attached. RSSI transition information acquisition processing performed by the control unit 21 makes it possible to preliminarily acquire the time variation of the received signal strength indicator (RSSI) of the radio signal received via an antenna 31 from the RFID tag 10 being transported as RSSI transition information. The control unit 21 controls the timing for initiating display update processing according to the acquisition results (a predetermined threshold value set relative to a peak value) of RSSI transition information.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wireless communication device capable of updating the display state of a display unit of an RFID tag that operates by receiving power supply by radio waves.

Background Art

[0002] Among battery-less RFID tags (passive tags) that operate by receiving power supply by radio waves, there are tags provided with a non-volatile display unit (hereinafter also referred to as an RFID tag with a display unit), and the display state of the display unit can be controlled by power supply by radio waves from an RFID reader / writer or the like.

[0003] In a manufacturing site, a logistics site, etc., in order to increase the flow rate as much as possible, it is desired to eliminate the residence time of articles. For an RFID tag with a display unit attached to a storage box that is transported while accommodating each component, it is also desired to change the display state of the display unit by power supply by radio waves during the transportation.

[0004] As a technology for securing a power supply area (communication area) for an RFID tag during transportation, for example, a non-contact ID tag writing device disclosed in Patent Document 1 below is known. In this non-contact ID tag writing device, a plurality of antennas are arranged along the transportation direction of the non-contact ID tag, and while a plurality of non-contact ID tags pass through the communication range of one antenna, writing is performed on one of them, and each of the plurality of antennas performs writing on different non-contact ID tags, thereby performing writing on all non-contact ID tags.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Incidentally, when updating the display state of an RFID tag with a display unit, a wireless communication device such as an RFID reader / writer performs transmission processing of display image data to the RFID tag with a display unit and display update processing for updating the display state according to the display image data. The RFID tag with a display unit during this display update processing requires more power than other processes such as when receiving display image data. For this reason, at least during the above display update processing, it is necessary to continuously supply power by radio waves to the RFID tag with a display unit by the wireless communication device.

[0007] However, when updating the display state of an RFID tag with a display unit during conveyance, if it moves outside the area where power can be supplied by radio waves during the above display update processing, there is a possibility that the display update processing may fail due to power shortage depending on the timing and the like. In the first place, since radio waves cannot be visually recognized, there is a problem that the user cannot easily determine which timing during conveyance is the optimal timing for starting the display update processing. In particular, since the timing suitable for starting the display update processing varies depending on the type of RFID tag, the conveyance speed, etc., the above problem becomes prominent.

[0008] The present invention has been made to solve the above-described problems, and an object thereof is to provide a configuration capable of appropriately updating the display state of a display unit of an RFID tag that operates by receiving power supply by radio waves during conveyance.

Means for Solving the Problems

[0009] To achieve the above object, one aspect of the present invention is a wireless communication device (20) capable of updating the display state of a display unit (11) of an RFID tag (10) that operates by receiving power supply by radio waves, with the RFID tag as a wireless communication target, an antenna (31) installed along a conveyance path (1) along which an article (2) with the RFID tag attached is conveyed, A detection unit (41) capable of detecting the conveyance state of the article; A control unit (21) that performs a tag information update process for updating the display state of the display unit using the antenna according to the detection result of the detection unit; A received radio wave information acquisition unit (21, 31, 32) capable of acquiring in advance received radio wave information regarding the received signal strength of a radio wave signal received from the RFID tag during conveyance via the antenna; Comprising: The tag information update process includes a display image data transmission process for transmitting display image data to the RFID tag, and a display update process for supplying power for display update to the RFID tag that has received the display image data by radio waves; The control unit is characterized by controlling the start timing of the display update process according to the acquisition result of the received radio wave information acquisition unit.

[0010] Another aspect of the present invention is: A wireless communication device (20) capable of updating the display state of a display unit (11) of an RFID tag (10) that operates by receiving power supply by radio waves and that is a wireless communication target, A plurality of antennas (33, 34, 35, 33a, 34a, 30a) arranged side by side along a conveyance path (1) along which an article (2) with the RFID tag attached is conveyed; A detection unit (41) capable of detecting the conveyance state of the article; A control unit (21) that performs a tag information update process for updating the display state of the display unit by sequentially switching the plurality of antennas used according to the detection result of the detection unit; Comprising: The tag information update process includes a display image data transmission process for transmitting display image data to the RFID tag, and a display update process for supplying power for display update to the RFID tag that has received the display image data by radio waves; The control unit controls such that the start timing of the display update process uses a downstream antenna (35, 34, 30a) installed on the downstream side of the antenna used at the completion of the display image data transmission process among the plurality of antennas. Note that the reference signs in each of the parentheses above indicate the correspondence with the specific means described in the embodiments to be described later.

Advantages of the Invention

[0011] In the present invention, the control unit performs tag information update processing for updating the display state of the display unit of the RFID tag using an antenna installed along the conveyance path according to the detection result of a detection unit capable of detecting the conveyance state of an article with an RFID tag attached thereto. The received radio wave information acquisition unit can acquire in advance received radio wave information regarding the received signal strength of a radio wave signal received from the RFID tag in transit via the antenna, and the control unit controls the start timing of the display update process according to the acquisition result of the received radio wave information acquisition unit.

[0012] Thereby, for the RFID tag in transit, the display update process can be started in accordance with the timing at which the received signal strength becomes the highest, that is, the timing at which power supply by radio waves can be received most efficiently. Therefore, the display state of the display unit can be appropriately updated during the conveyance of the RFID tag that operates by receiving power supply by radio waves.

[0013] The received radio wave information acquisition unit may acquire in advance received radio wave information using an upstream antenna installed on the upstream side of the conveyance path with respect to the antenna.

[0014] Thereby, even when a change in the type of the RFID tag attached to the article or a change in the conveyance speed of the article with the RFID tag attached thereto occurs, the received radio wave information after the change can be easily acquired.

[0015] The control unit may control the start timing of the display update process to be a time before the display update time required for the display update process from the time when the received signal strength acquired by the received radio wave information acquisition unit reaches a peak.

[0016] Depending on the location of the RFID tag attached to the article and the installation position of the antenna with respect to the conveyance path, the received signal strength of the radio wave signal received from the RFID tag during conveyance via the antenna may rapidly decrease from the peak value.

[0017] Therefore, by controlling the start timing of the display update process to be a time before the display update time from the time when the received signal strength reaches a peak, the display update process is completed when the received signal strength reaches a peak, and the update process is not performed during the time when the received signal strength rapidly decreases thereafter. Therefore, it is possible to eliminate the failure of the update process due to the rapid decrease in the received signal strength as described above.

[0018] In the present invention, a plurality of antennas are arranged side by side along the conveyance path along which the article with the RFID tag is conveyed, and the control unit, according to the detection result of the detection unit capable of detecting the conveyance state of the article with the RFID tag, sequentially switches the plurality of antennas to be used and performs a tag information update process for updating the display state of the display unit of the RFID tag. The control unit controls the start timing of the display update process to use the downstream antenna installed on the downstream side of the antenna used at the completion of the display image data transmission process among the plurality of antennas.

[0019] When supplying power to the RFID tag by radio waves by sequentially switching a plurality of antennas, since the radio wave output stops at the time of antenna switching, if this antenna switching timing occurs at the start of the display update process or during the display update process, there is a possibility that the update process may fail due to power shortage.

[0020] Therefore, by using the downstream antenna installed on the downstream side of this antenna for the display update process without using the antenna used at the completion of the display image data transmission process, the antenna switching timing does not occur at the start of the display update process or during the display update process. Therefore, it is possible to appropriately update the display state of the display unit during the conveyance of the RFID tag that operates by receiving power supply by radio waves.

[0021] When the remaining operation time of the antenna used at the completion of the display image data transmission process among the plurality of antennas is equal to or longer than the display update time, the control unit immediately starts the display update process. When the remaining operation time is less than the display update time, the control unit may control the start timing of the display update process to use the downstream antenna.

[0022] As a result, in the construction of the conveyance line for which the RFID tag that can perform the display image data transmission process and the display update process using the same antenna is the conveyance target, compared with the construction of the conveyance line for which the RFID tag that performs the display update process using the next downstream antenna is the conveyance target, the number of antennas can be reduced by one. By reducing the number of antennas in this way, it is possible to save space in the conveyance line and shorten the processing time.

[0023] The lowermost downstream antenna installed at the lowermost downstream among the plurality of antennas is the antenna used for the display update process, and the received signal strength from the RFID tag during conveyance may be higher than that of other antennas.

[0024] In the tag information update process for updating the display state of the display unit, after the display image data transmission process of transmitting the display image data to the RFID tag, a display update process of supplying power for display update to the RFID tag that has received this display image data by radio waves is performed. For this reason, the antenna used in the display update process becomes the antenna installed most downstream (the most downstream side antenna) and a high gain is required. On the other hand, for other antennas, a gain as high as that of the most downstream side antenna is not required. That is, for antennas other than the most downstream side antenna, an antenna that prioritizes miniaturization and cost reduction can be adopted, so that space saving and cost reduction of the conveyance line can be achieved.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

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Figure 11

Figure 12

Figure 13

[0026] [First Embodiment] Hereinafter, a first embodiment in which a wireless communication device according to the present invention is embodied will be described with reference to the drawings. The wireless communication device 20 according to the present embodiment is configured as a device capable of updating the display state of the display unit 11 of the RFID tag 10, which operates by receiving power supply by radio waves (radio wave power supply), as a wireless communication target. In the present embodiment, as shown in FIG. 1, the RFID tag 10 is attached to the side surface of the passing box 2, and the antenna 31 of the wireless communication device 20 is installed along the conveyance path 1 on the conveyance line that sequentially conveys a plurality of passing boxes 2. Note that the passing box 2 can correspond to an example of an "article" with an RFID tag attached.

[0027] The RFID tag 10 is a passive wireless tag that operates by receiving power supply via radio waves. As shown in FIG. 2, in addition to the above-described display unit 11, it is configured to include an antenna 12, a power supply circuit 13, a demodulation circuit 14, a control circuit 15, a memory 16, a modulation circuit 17, and the like. The power supply circuit 13 rectifies and smoothes the transmission signal (carrier signal) from a wireless communication device 20 or the like received via the antenna 12 to generate an operating power supply, and is configured to supply the operating power supply to each component including the control circuit 15. The demodulation circuit 14 is configured to demodulate the data superimposed on the transmission signal (carrier signal) and output it to the control circuit 15. The memory 16 is composed of various semiconductor memories such as ROM and EEPROM, and a UII (Unique Item Identifier) for storing a tag ID and a user area where the user can freely read and write data are constructed. The control circuit 15 reads and writes to a predetermined area of the memory 16 in response to the execution of a predetermined program stored in the memory 16, and when information corresponding to a request is read from the memory 16, it functions to output it to the modulation circuit 17 as transmission data. The modulation circuit 17 is configured to load-modulate the response signal (carrier signal) with the above transmission data and transmit it as a reflected wave from the antenna 12.

[0028] In this embodiment, the display unit 11 is an electrophoretic or electronic powder particle type electronic paper, and is configured to be able to maintain the display state even after the power supply is stopped and the display state is controlled by the control circuit 15.

[0029] In the RFID tag 10 configured as described above, the recorded information recorded in the memory 16 is updated and the display information displayed in the display area of the display unit 11 is updated by the tag information update process performed by the wireless communication device 20 in order to update the display state of the display unit 11. Specifically, in response to the display image data transmission process and the display update process in the tag information update process, after the display image data is received via the antenna 12, the power supply by radio waves for display update is continuously received via the antenna 12 for a certain period of time, so that the display state of the display unit 11 is updated according to the received display image data. As a result, the display state of the display unit 11 is updated from the display state illustrated in FIG. 3(A), for example, to the display state illustrated in FIG. 3(B).

[0030] The wireless communication device 20 is a so-called stationary RFID tag reader / writer, and as shown in FIG. 2, includes a control unit 21, a storage unit 22, a notification unit 23, an operation unit 24, a communication processing unit 25, an external interface 26, an antenna 31, a passage sensor 41, and the like. In the present embodiment, a controller 30 is configured by the control unit 21 and the communication processing unit 25 other than the antenna 31 and the passage sensor 41, and the wireless communication device 20 is installed with the controller 30, the antenna 31, and the passage sensor 41 being separate from each other.

[0031] The control unit 21 is mainly configured by a microcomputer, has a CPU, a system bus, an input / output interface, etc., and constitutes an information processing device together with the storage unit 22 composed of a semiconductor memory or the like.

[0032] The notification unit 23 is for notifying a user of predetermined information, and is configured by a display, an LED, a buzzer, etc. controlled by the control unit 21. The operation unit 24 is provided with a trigger switch, a numeric keypad, etc. and is configured to output an operation signal corresponding to the operation to the control unit 21, and the control unit 21 performs an operation according to the content of the operation signal in response to this operation signal.

[0033] The communication processing unit 25 includes a transmission circuit, a reception circuit, and the like. The transmission circuit is composed of, for example, a carrier oscillator, an encoding unit, a modulation unit, an amplifier, and the like. The carrier oscillator outputs a carrier (carrier wave) of a predetermined frequency. The encoding unit is connected to the control unit 21 and encodes the transmission data output from the control unit 21 and outputs it to the modulation unit. The modulation unit receives the carrier (carrier wave) from the carrier oscillator and the transmission data from the encoding unit. For the carrier (carrier wave) output from the carrier oscillator, an ASK (Amplitude Shift Keying) modulated modulated signal is generated by the encoded transmission code (modulation signal) output from the encoding unit when transmitting a command to the communication target, and is output to the amplifier. The amplifier amplifies the input signal (the modulated signal modulated by the modulation unit) at a set amplification rate, and the amplified signal is output to the antenna 31 as a transmission signal. An input terminal of the reception circuit is connected to the antenna 31, and the radio wave signal (reception signal) received by the antenna 31 is input to the reception circuit. The reception circuit is composed of, for example, an amplifier, a demodulation unit, a binarization processing unit, a decoding unit, and the like. The reception signal received by the antenna 31 is amplified by the amplifier, and the amplified signal is demodulated by the demodulation unit. Further, the demodulated signal waveform is binarized by the binarization processing unit and decoded by the decoding unit, and the decoded signal is output to the control unit 21 as reception data.

[0034] The external interface 26 is configured as an interface for data communication with external devices such as a host terminal, and is configured to perform communication processing in cooperation with the control unit 21.

[0035] As shown in FIG. 1, the antenna 31 is installed along the conveyance path 1 along which the tote box 2 with the RFID tag 10 attached is conveyed, such that its radio wave radiation direction is substantially orthogonal to the conveyance direction (the right direction in FIG. 1). For this reason, a narrow wireless communication area S1a in the vicinity of the antenna 31 schematically illustrated in FIG. 1 becomes an area that can receive sufficient power supply by radio waves. Also, a wireless communication area S1b surrounding the wireless communication area S1a becomes a wireless communication possible area although the power supply by radio waves becomes relatively weak.

[0036] The passage sensor 41 is a transmissive or reflective photo - electric sensor, and is installed at a position separated by a predetermined distance upstream from the antenna 31. By detecting the passage of the tote box 2 that has been conveyed on the conveyance path 1 up to a predetermined conveyance detection position, it is configured to output a predetermined detection signal to the control unit 21. The above - mentioned predetermined distance is set such that the RFID tag 10 attached to the tote box 2 at the above - mentioned predetermined conveyance detection position is outside the wireless communication area S1b of the antenna 31. Note that the passage sensor 41 may correspond to an example of a “detection unit” that can detect the conveyance state of an article such as the tote box 2.

[0037] In the control unit 21 of the wireless communication device 20 configured as described above, based on an update instruction from a host terminal or the like, a tag information update process for updating the display state of the display unit 11 of the RFID tag 10 attached to the tote box 2 conveyed on the conveyance path 1 is performed.

[0038] In this embodiment, even when the RFID tag 10 is being conveyed (in motion), in order to ensure the power supply by radio waves necessary for the display update process in the tag information update process, the start timing of the display update process is controlled such that the display update process is completed while passing through the wireless communication area S1a.

[0039] Specifically, through the RSSI transition information acquisition process performed by the control unit 21, the time change of the received signal strength (radio wave strength: hereinafter also referred to as RSSI) of the radio wave signal received from the RFID tag 10 via the antenna 31 during the conveyance of the passing box 2 is acquired in advance as RSSI transition information. From this RSSI transition information, the peak value of the RSSI value is obtained, and a value slightly lower than the peak value is set as a predetermined threshold value (for example, a value about 80 to 90% of the peak value) so that the display update process is performed before and after this peak value, and the timing when the RSSI value measured to increase becomes equal to or higher than the predetermined threshold value is set as the start timing of the display update process. The RSSI transition information, peak value, predetermined threshold value, etc. obtained as described above are stored in advance in the storage unit 22 together with the tag ID of the RFID tag 10 and the like. Note that the RSSI transition information corresponds to an example of "received radio wave information", and the control unit 21 and the antenna 31 that perform the RSSI transition information acquisition process may correspond to an example of a "received radio wave information acquisition unit". Also, without the RSSI transition information and the peak value being stored in the storage unit 22, the predetermined threshold value may be acquired in advance as "received radio wave information" and stored in the storage unit 22 in advance.

[0040] Hereinafter, the tag information update process performed by the control unit 21 of the wireless communication device 20 will be described in detail with reference to the flowchart shown in FIG. 4. When the tag information update process is started by receiving the predetermined detection signal from the passage sensor 41 that has detected the passage of the passing box 2 (see t11 in FIG. 1), the tag reading process shown in step S101 of FIG. 4 is performed. Immediately after the start of the tag information update process, since the RFID tag 10 is outside the wireless communication area S1b by the antenna 31, the state where the tag reading fails is repeated (No in S102), and it enters the process waiting state (see process P11 in FIG. 1).

[0041] After that, when the RFID tag 10 of the conveyed passing box 2 enters the wireless communication area S1b by the antenna 31 (see t12 in FIG. 1), since the reading of the RFID tag 10 is successful (Yes in S102), the wireless communication process with the RFID tag 10 is started (S103, see process P12 in FIG. 1).

[0042] When it becomes possible to communicate wirelessly with the RFID tag 10, the display image data transmission process shown in step S104 is performed, and the process for transmitting the display image data based on the above update instruction to the RFID tag 10 is started (see t13 and process P13 in FIG. 1).

[0043] When the transmission of the display image data is completed (see t14 in FIG. 1), the RSSI value from the RFID tag 10 is measured (S105). If the measured RSSI value is not equal to or greater than the predetermined threshold (No in S106), the RSSI measurement state is continued and the process waits (see process P14 in FIG. 1).

[0044] Thereafter, since the RFID tag 10 of the passing box 2 to be conveyed enters the wireless communication area S1a, when the measured RSSI value that gradually increases becomes equal to or greater than the predetermined threshold (Yes in S106), the display update process for supplying power for display update by radio waves is started (S107, see t15 and process P15 in FIG. 1).

[0045] When the above display update process is completed (see t16 in FIG. 1), this tag information update process ends. As described above, by starting the display update process at the timing when the measured RSSI value becomes equal to or greater than the predetermined threshold, the display update process is completed while the RFID tag 10 passes through the wireless communication area S1a, so that the power supply by radio waves required for this display update process can be surely ensured.

[0046] As described above, in the wireless communication device 20 according to the present embodiment, the control unit 21 performs tag information update processing for updating the display state of the display unit 11 of the RFID tag 10 by using the antenna 31 installed along the transport path 1 according to the detection result of the passage sensor 41 capable of detecting the transport state of the passing box 2 with the RFID tag 10 attached. By the RSSI transition information acquisition processing performed by the control unit 21, the time change of the received signal strength (RSSI) of the radio wave signal received from the RFID tag 10 during transport via the antenna 31 can be acquired in advance as RSSI transition information, and the control unit 21 controls the start timing of the display update processing according to the acquisition result of the RSSI transition information (a predetermined threshold set based on the peak value).

[0047] Thereby, for the RFID tag 10 during transport, the display update processing can be started in accordance with the timing when the received signal strength (RSSI) becomes the highest, that is, the timing when the power supply by radio waves can be received most efficiently. Therefore, during the transport of the RFID tag 10 that operates by receiving power supply by radio waves, the display state of the display unit 11 can be appropriately updated.

[0048] [Second Embodiment] Next, the wireless communication device according to the second embodiment will be described with reference to the drawings. In the second embodiment, the main difference from the first embodiment is that RSSI transition information is acquired in advance by using an antenna installed upstream of the transport path 1 with respect to the antenna 31. Therefore, the same reference numerals are given to substantially the same components as those in the first embodiment, and the description thereof is omitted.

[0049] As illustrated in FIG. 5, in the present embodiment, an antenna 32 is installed between the passage sensor 41 and the antenna 31. More specifically, the antenna 32 is installed such that the RFID tag 10 of the passing box 2 before detection by the passage sensor 41 is outside the wireless communication area, and the wireless communication area regarding the RFID tag 10 during transport does not overlap with the wireless communication area by the antenna 31.

[0050] Antenna 32 is an antenna having the same functions as antenna 31 and is used during the RSSI transition information acquisition process described above. That is, in the present embodiment, each time the passing box 2 is conveyed, a tag information update process is performed following the RSSI transition information acquisition process. Note that antenna 32 may correspond to an example of an "upstream side antenna".

[0051] Hereinafter, the RSSI transition information acquisition process and the tag information update process performed by the control unit 21 of the wireless communication device 20 will be described in detail with reference to the flowchart and the like shown in FIG. 6. When the RSSI transition information acquisition process is started by receiving the predetermined detection signal from the passing sensor 41 that has detected the passing of the passing box 2 (see t21 in FIG. 5), the tag reading process shown in step S201 of FIG. 6 is performed. Immediately after the start of the RSSI transition information acquisition process, since the RFID tag 10 is outside the wireless communication area by the antenna 32, the state where the tag reading fails is repeated (No in S202), and the process waits (see process P21 in FIG. 5).

[0052] Thereafter, when the RFID tag 10 of the passing box 2 being conveyed enters the wireless communication area by the antenna 32 (see t22 in FIG. 5), since the reading of the RFID tag 10 is successful (Yes in S202), the RSSI measurement process is performed (S203, see process P22 in FIG. 5). As a result, the temporal change in the received signal strength (RSSI) of the radio wave signal received from the RFID tag 10 via the antenna 32 is acquired as RSSI transition information until the tag reading fails. The acquired RSSI transition information is stored in the storage unit 22 of the RFID tag 10 together with the predetermined threshold value, the peak value, the tag ID, etc. set as described above.

[0053] When the acquisition and storage of the RSSI transition information are completed (see t23 in FIG. 5), the tag information update process after step S101 described above is performed. That is, after passing through the processing waiting state (see processing P11 in FIG. 5), the wireless communication process with the RFID tag 10 is started via the antenna 31 (see S103, t24 in FIG. 5, and processing P12). Then, the process of transmitting the display image data to the RFID tag 10 via the antenna 31 is started (see S104, t25 in FIG. 5, and processing P13).

[0054] When the transmission of the display image data is completed (see t26 in FIG. 5), until the measured RSSI value becomes equal to or greater than the above-mentioned predetermined threshold (No in S106), it enters the processing waiting state (see processing P14 in FIG. 5). Thereafter, when the measured RSSI value becomes equal to or greater than the above-mentioned predetermined threshold (Yes in S106), the display update process is started (see S107, t27 in FIG. 5, and processing P15). When this display update process is completed (see t28 in FIG. 5), this tag information update process ends.

[0055] As described above, in the RSSI transition information acquisition process in this embodiment, the RSSI transition information and the like are acquired in advance using the antenna 32 installed as the upstream antenna on the upstream side of the transport path 1 with respect to the antenna 31.

[0056] Thereby, even when there are changes such as a change in the type of the RFID tag 10 attached to the passing box 2 or a change in the transport speed of the passing box 2 to which the RFID tag 10 is attached, it is possible to easily acquire the RSSI transition information and the like after the change.

[0057] Note that each time the passing box 2 is transported, the tag information update process is not necessarily carried out following the RSSI transition information acquisition process. For example, when there is no change in the type of the RFID tag 10 or the transport speed, etc., the tag information update process may be carried out by diverting the RSSI transition information and the like previously acquired and stored in the storage unit 22 without performing the RSSI transition information acquisition process.

[0058] [Third Embodiment] Next, the wireless communication device according to the third embodiment will be described with reference to the drawings. In the third embodiment, the main difference from the first embodiment is that the start timing of the display update process is controlled based on the time when the RSSI value peaks and the display update time required for the display update process. Therefore, the same reference numerals are given to substantially the same components as those in the first embodiment, and the description thereof is omitted.

[0059] Depending on the location of the RFID tag 10 attached to the passing box 2 or the like and the installation position of the antenna 31 with respect to the conveyance path 1, the received signal strength (RSSI value) of the radio wave signal received from the RFID tag 10 during conveyance via the antenna 31 may rapidly decrease from the peak value. For example, as illustrated in FIG. 7, when the RFID tag 10 is attached to the front side in the conveyance direction of the passing box 2 and the antenna 31 is installed below the conveyance path 1, the RSSI value rapidly decreases from the peak value during the time period when the passing box 2 is interposed between the RFID tag 10 and the antenna 31.

[0060] If the RSSI value rapidly decreases from the peak value as described above, on the premise that the display update process is performed before and after the peak value, the power supply by radio waves may not be received before the display update process is completed, and thus the display update process may fail.

[0061] Therefore, in the tag information update process in the present embodiment, on the premise that the display update time Tu required for the display update process is acquired in advance from a host terminal or the like and stored in the storage unit 22, the start timing of the display update process is controlled so as to be Tu minutes before the time when the RSSI value peaks (see t16 in FIG. 7) in the RSSI transition information acquired as described above (see t15 in FIG. 7). Since the time Ta from the timing (see t11 in FIG. 7) when the predetermined detection signal is received from the passing sensor 41 that has detected the passing of the passing box 2 to the timing (see t16 in FIG. 7) when the RSSI value peaks can be measured in advance, the timing when the elapsed time T after receiving the predetermined detection signal reaches Ta - Tu is set as the start timing of the display update process.

[0062] Therefore, in the tag information update process, as shown in the flowchart illustrated in FIG. 8, after the display image data transmission process shown in step S104, in the determination process of step S301, if the elapsed time T since receiving the above-described predetermined detection signal has not reached Ta - Tu, it is determined that it is not the start timing of the display update process (No in S301). Thereafter, when the elapsed time T reaches Ta - Tu, it is determined that it is the start timing of the display update process (Yes in S301), and the display update process is started (see S107, t15 in FIG. 7, and process P15). At the timing when the above-described display update process is completed (see t16 in FIG. 7), since the RSSI value peaks, it is possible to reliably secure the power supply by the radio wave required for the display update process.

[0063] As described above, in the tag information update process according to the present embodiment, the start timing of the display update process is controlled so as to be Tu minutes before the time when the RSSI value peaks. Thereby, at the time when the RSSI value peaks, the display update process is completed, and the update process is not performed in the time zone where the subsequent RSSI value rapidly decreases. Therefore, it is possible to eliminate the failure of the update process caused by the rapid decrease of the RSSI value as described above.

[0064] [Fourth Embodiment] Next, the wireless communication device according to the present fourth embodiment will be described with reference to the drawings. In the present fourth embodiment, the main difference from the first embodiment is that the tag information update process is performed by sequentially switching a plurality of antennas arranged along the transmission path according to the elapsed time T. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[0065] In the present embodiment, as illustrated in FIG. 9, three antennas, i.e., a first antenna 33, a second antenna 34, and a third antenna 35, are arranged side by side along a transmission path 1 along which a passing box 2 with an RFID tag 10 attached is conveyed, and the tag information update process is performed by sequentially switching the antennas 33, 34, 35 according to the elapsed time T.

[0066] When power is supplied to the RFID tag 10 by radio waves by switching the antennas 33, 34, and 35 in order as described above, the radio wave output stops when the antennas are switched. For this reason, if the antenna switching timing occurs at the start or during the display update process, the update process may fail due to power shortage. In the display image data transmission process that requires relatively little power, even if the antenna switching timing occurs during the process, the display image data transmission process will not fail due to power shortage.

[0067] Therefore, in the tag information update process in this embodiment, without using the antenna used at the completion of the display image data transmission process, the downstream antenna installed on the downstream side of this antenna is used for the display update process.

[0068] Hereinafter, the tag information update process performed by the control unit 21 in this embodiment will be described in detail with reference to the flowcharts shown in FIGS. 9 and 10. When the tag information update process is started by receiving the predetermined detection signal from the passage sensor 41 that has detected the passage of the pass box 2 (see t41 in FIG. 9), the process waits as described above (see process P41 in FIG. 9). Thereafter, when the elapsed time T reaches the first switching time t42 set in advance (Yes in S401), the wireless communication process with the RFID tag 10 is started via the first antenna 33 (S402, see process P42 in FIG. 9). The first switching time t42 can be set based on the relative positional relationship between the detection range of the passage sensor 41 and the wireless communication range of the first antenna 33, the conveyance speed of the pass box 2, and the like.

[0069] Subsequently, the process of transmitting the display image data to the RFID tag 10 via the first antenna 33 is started (see S403, t43 in FIG. 9, and process P43). After that, when the elapsed time T reaches the preset second switching time t44 (Yes in S404), the antenna for transmitting the display image data is switched from the first antenna 33 to the second antenna 34 (S405), and the process of transmitting the display image data to the RFID tag 10 via the second antenna 34 is continued.

[0070] When the transmission of the display image data is completed (see t45 in FIG. 9), the process waits (see process P44 in FIG. 9) until the elapsed time T reaches the preset third switching time t46 (No in S406). After that, when the elapsed time T reaches the third switching time t46 (Yes in S406), the antenna for communicating with the RFID tag 10 is switched from the second antenna 34 to the third antenna 35 (S407), and the display update process is started via the third antenna 35 (see S408 and process P45 in FIG. 9). When this display update process is completed (see t47 in FIG. 9), this tag information update process ends. Note that the third antenna 35 may correspond to an example of the "downstream antenna".

[0071] The first switching time t42, the second switching time t44, and the third switching time t46 are set such that the operation time of the first antenna 33 (the time from the first switching time t42 to the second switching time t44) Tb1, the operation time of the second antenna 34 (the time from the second switching time t44 to the third switching time t46) Tb2, and the operation time of the third antenna 35 (the time from the third switching time t46 to the completion time t47 of the display update process) Tb3 are the same, and are set to be longer than the display update time Tu required for the display update process, and are stored in the storage unit 22 in advance.

[0072] As described above, in the tag information update process performed by the wireless communication device 20 according to the present embodiment, without using the antenna (the second antenna 34 in the example of FIG. 9) used at the completion of the display image data transmission process, the downstream antenna (the third antenna 35 in the example of FIG. 9) installed on the downstream side of this antenna is used for the display update process. As a result, the antenna switching timing does not occur at the start or during the display update process. Therefore, it is possible to appropriately update the display state of the display unit 11 during the conveyance of the RFID tag 10 that operates by receiving power supply by radio waves.

[0073] Note that when performing other rewriting processes or the like on the RFID tag 10 before and after the display image data transmission process during the tag information update process, assuming that four or more antennas are arranged and installed along the conveyance path 1, the operations of the respective antennas may be switched in order according to the elapsed time T.

[0074] [Fifth Embodiment] Next, the wireless communication device according to the present fifth embodiment will be described with reference to the drawings. In the present fifth embodiment, the main difference from the fourth embodiment above is that when the remaining operation time of the second antenna 34 used when the display image data transmission process is completed is equal to or longer than the display update time, the display update process is performed with the second antenna 34 to abolish the third antenna 35. Therefore, the same reference numerals are assigned to substantially the same components as those in the fourth embodiment, and the description thereof is omitted.

[0075] In the present embodiment, on the premise that the display update time Tu required for the display update process is acquired in advance from an upper-level terminal or the like and stored in the storage unit 22, in the tag information update process, when the remaining operation time of the antenna used when the display image data transmission process is completed among a plurality of antennas is equal to or longer than the display update time Tu, the display update process is immediately started, and when the remaining operation time is less than the display update time Tu, the start timing of the display update process is set to use the downstream antenna.

[0076] Hereinafter, the tag information update process performed by the control unit 21 in the present embodiment will be described in detail with reference to the flowcharts shown in FIGS. 11 and 12. When the tag information update process is started by receiving the predetermined detection signal from the passage sensor 41 that has detected the passage of the pass box 2 (see t51 in FIG. 11), the process waits in the state as described above (see process P51 in FIG. 11). After that, when the elapsed time T reaches the first switching time t52 set in advance (Yes in S401), the wireless communication process with the RFID tag 10 is started via the first antenna 33 (S402, see process P52 in FIG. 11).

[0077] Subsequently, the process of transmitting the display image data to the RFID tag 10 via the first antenna 33 is started (S403, see t53 and process P53 in FIG. 11). After that, when the elapsed time T reaches the second switching time t54 set in advance (Yes in S404), the antenna for transmitting the display image data is switched from the first antenna 33 to the second antenna 34 (S405), and the process of transmitting the display image data to the RFID tag 10 via the second antenna 34 is continued.

[0078] When the transmission of the display image data is completed (see t55 in FIG. 11), if the display update time Tu is acquired and stored in the storage unit 22 (Yes in S501), and if the remaining operation time of the second antenna 34 is equal to or greater than the display update time Tu (Yes in S502), the display update process is immediately started via the second antenna 34 without entering the process waiting state (S408, see process P54 in FIG. 11).

[0079] If the remaining operating time of the second antenna 34 is less than the display update time Tu (No in S502), and there is a third antenna 35 that can operate on the downstream side as illustrated in FIG. 9 (Yes in S503), after the elapsed time T reaches the third switching time t46 through a waiting state for processing (Yes in S406), the antenna is switched from the second antenna 34 to the third antenna 35 (S407), and display update processing is started via the third antenna 35 (S408). Further, if the display update time Tu has not been acquired (No in S501), similar to the fourth embodiment, when the elapsed time T reaches the third switching time t46 (Yes in S406), display update processing is started via the switched third antenna 35 (S408).

[0080] On the other hand, if the remaining operating time of the second antenna 34 is less than the display update time Tu (No in S502) and there is no operable antenna on the downstream side (No in S503), error notification processing shown in step S504 is performed. In this processing, a predetermined notification indicating that there is a shortage of antennas required for display update processing is made by the notification unit 23, and the present tag information update processing ends without performing the display update processing.

[0081] As described above, in the tag information update processing performed by the wireless communication device 20 according to the present embodiment, in the construction of the conveyance line in which the RFID tag 10 for which the display image data transmission processing and the display update processing can be performed using the same antenna (the second antenna 34 in the example of FIG. 11) is the conveyance target, compared with the construction of the conveyance line in which the RFID tag 10 for which the display update processing is performed using the next downstream antenna (the third antenna 35 in the example of FIG. 9) is the conveyance target, the number of antennas can be reduced by one. By thus reducing the number of antennas by one, it is possible to save space in the conveyance line and shorten the processing time.

[0082] In particular, when the remaining operating time of the second antenna 34 is less than the display update time Tu and there is no operable antenna on the downstream side, the above-described predetermined notification is made by the notification unit 23. Therefore, at the time of constructing the transport line or the like, the required number of antennas can be easily confirmed.

[0083] [Sixth Embodiment] Next, the wireless communication device according to the sixth embodiment will be described with reference to the drawings. In the sixth embodiment, the main difference from the fourth embodiment is that an antenna having a higher power supply capacity than other antennas is adopted as the most downstream antenna installed most downstream among the plurality of antennas. Therefore, the same reference numerals are given to substantially the same components as those in the fourth embodiment, and the description thereof is omitted.

[0084] In the tag information update process performed by the control unit 21, after the display image data transmission process of transmitting the display image data to the RFID tag 10, a display update process of supplying power for display update to the RFID tag 10 that has received this display image data by radio waves is performed.

[0085] Then, the antenna used for the display update process becomes the antenna installed most downstream (the most downstream antenna), and a high gain is required. On the other hand, for other antennas, a gain as high as that of the most downstream antenna is not required.

[0086] For this reason, in this embodiment, as the most downstream antenna (the antenna used for the display update process) installed most downstream among the plurality of antennas, an antenna having a higher received signal strength from the RFID tag 10 in transit than other antennas is adopted.

[0087] Specifically, as illustrated in FIG. 13, instead of the third antenna 35 and the controller 30 in the fourth embodiment, a controller-integrated antenna 30a with high power supply capability by radio waves is adopted. Instead of the first antenna 33 and the second antenna 34, low-performance and low-cost external auxiliary first antenna 33a and second antenna 34a with relatively low power supply capability are adopted. As the antenna included in the controller-integrated antenna 30a, for example, a linearly polarized wave antenna adapted to the conveyance direction (the moving direction of the RFID tag 10) can be adopted. Therefore, as can be seen from FIG. 13, during the antenna operation of the controller-integrated antenna 30a, the RSSI value during the tag information update process is higher and the power supply capability by radio waves is also higher than during the operation of the first antenna 33a and during the operation of the second antenna 34a.

[0088] Therefore, for antennas other than the controller-integrated antenna 30a, which is the most downstream antenna (the first antenna 33a and the second antenna 34a), antennas prioritizing miniaturization and cost reduction can be adopted, so that space saving and cost reduction of the conveyance line can be achieved.

[0089] Note that the present invention is not limited to the above-described embodiments and the like, and may be embodied, for example, as follows. (1) The present invention is not limited to being applied to the wireless communication device 20 that updates the display state of the display unit 11 of the RFID tag 10 attached to the passing box 2. For example, it may be applied to a wireless communication device that updates the display state of the display unit of an RFID tag attached to an article being conveyed, such as a packing box or a pallet, and operates by receiving power supply by radio waves.

[0090] (2) As the "detection unit" capable of detecting the conveyance state of an article such as the passing box 2, not only the passing sensor 41 composed of a transmissive or reflective photoelectric sensor is adopted, but also sensors of other detection methods such as a laser sensor or a proximity sensor may be adopted. Further, the conveyance state of the article may be detected according to a signal received from an upper terminal or the like via the external interface 26. In this case, the external interface 26 and the control unit 21 that controls the communication of the external interface 26 may correspond to an example of the "detection unit".

Explanation of Signs

[0091] 1 Conveyor path 2 Passing box (article) 10 RFID tag 11 Display unit 20 Wireless communication device 21 Control unit (received radio wave information acquisition unit) 22 Storage unit 30 Controller 30a Controller integrated antenna 31 Antenna (received radio wave information acquisition unit) 32 Antenna (upstream side antenna) 33, 33a First antenna 34, 33b Second antenna 35 Third antenna (downstream side antenna) 41 Passing sensor (detection unit)

Claims

1. A wireless communication device capable of updating the display state of a display unit of an RFID tag that operates by receiving power supply by radio waves and is a wireless communication target, an antenna installed along a conveyance path along which an article with the RFID tag attached is conveyed, a detection unit capable of detecting the conveyance state of the article, a control unit that performs a tag information update process for updating the display state of the display unit using the antenna according to the detection result of the detection unit, a received radio wave information acquisition unit capable of acquiring in advance received radio wave information regarding the received signal strength of a radio wave signal received from the RFID tag during conveyance via the antenna, comprising: The tag information update process includes a display image data transmission process of transmitting display image data to the RFID tag and a display update process of supplying power for display update to the RFID tag that has received the display image data by radio waves. The control unit controls the start timing of the display update process according to the acquisition result of the received radio wave information acquisition unit. The wireless communication device is characterized by this.

2. The received radio wave information acquisition unit acquires the received radio wave information in advance using an upstream antenna installed on the upstream side of the conveyance path with respect to the antenna. The wireless communication device according to claim 1 is characterized by this.

3. comprising a storage unit that stores the display update time required for the display update process, The control unit controls the start timing of the display update process to be before the display update time from the time when the received signal strength acquired by the received radio wave information acquisition unit peaks. The wireless communication device according to claim 1 is characterized by this.

4. A wireless communication device capable of updating the display state of a display unit of an RFID tag that operates by receiving power supply by radio waves and is a wireless communication target, a plurality of antennas arranged and installed along a conveyance path along which an article with the RFID tag attached is conveyed, a detection unit capable of detecting the conveyance state of the article, a control unit that performs a tag information update process for updating the display state of the display unit by sequentially switching the plurality of antennas used according to the detection result of the detection unit, comprising: The tag information update process includes a display image data transmission process for transmitting display image data to the RFID tag, and a display update process for supplying power for display update to the RFID tag that has received the display image data by radio waves. The control unit controls the start timing of the display update process to use a downstream antenna installed on the downstream side of the antenna used at the completion of the display image data transmission process among the plurality of antennas. The wireless communication device is characterized by this.

5. It includes a storage unit that stores the display update time required for the display update process. When the remaining operating time of the antenna being used at the completion of the display image data transmission process among the plurality of antennas is equal to or greater than the display update time, the control unit immediately starts the display update process. When the remaining operating time is less than the display update time, the control unit controls the start timing of the display update process to use the downstream antenna. The wireless communication device according to claim 4 is characterized by this.

6. The most downstream antenna installed most downstream among the plurality of antennas is the antenna used for the display update process, and the received signal strength from the RFID tag during conveyance is higher than that of other antennas. The wireless communication device according to claim 4 is characterized by this.

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