Safety sensor

Abstract

An actuator (3) for a safety sensor 1 includes an RFID tag (31). A sensor head (2) includes an RFID reader (21) and a memory unit. The RFID reader (21) reads tag information stored in the RFID tag (31) when the actuator (3) approaches. The memory unit stores sensor information. Each of the tag information and the sensor information includes product information about the safety sensor (1). Only when the product information included in the tag information read by the RFID reader (21) matches the product information included in the sensor information, ON output processing in the sensor head (2) becomes executable. Erroneous detection of the actuator (3) and intentional invalidation of the safety sensor (1) can thereby be suppressed.

Description

Safety sensor

[0001] The present invention relates to a safety sensor. [Reference to related applications] This application claims the benefit of priority from Japanese Patent Application JP2024-208676 filed on November 29, 2024, and all disclosures of the said application are incorporated herein.

[0002] Conventionally, a safety sensor (also called a safety switch) is provided at the entrance and exit of a room where industrial machinery or the like is installed. When the door at the entrance and exit is closed, the safety sensor detects the closing of the door, enabling the supply of power to industrial machinery or the like. On the other hand, when the door at the entrance and exit is opened, the supply of power to industrial machinery or the like becomes impossible.

[0003] As one of the above safety sensors, an RFID type non-contact safety sensor is used. In this non-contact safety sensor, for example, a sensor head having an RFID reader is attached to the periphery of the entrance and exit of the room, and an actuator having an RFID tag is attached to the door. When the door closes the entrance and exit and the actuator approaches the sensor head, the RFID tag of the actuator is read by the RFID reader of the sensor head, and the safety output is turned on at the sensor head, enabling the supply of power to industrial machinery or the like.

[0004] For example, in the safety switch of Japanese Unexamined Patent Application Publication No. 2021-173062 (Document 1), when the actuator approaches the sensor body, the unique ID of the RFID tag of the actuator is read by the sensor body, and when the unique ID matches the unique ID previously stored in the sensor body, the safety output is turned on at the sensor body. Before the said safety switch is used, a pairing mode for associating the actuator and the sensor body is executed, and the unique ID of the RFID tag of the actuator is read and stored by the sensor body.

[0005] Incidentally, in the safety switch described in Reference 1, in the pairing mode described above, there is a risk that the safety switch may be intentionally disabled by using an item other than the actuator that should be paired with the sensor body, such as a transportation IC card or access control card, and storing the unique ID of the RFID tag embedded in the other item in the sensor body.

[0006] Furthermore, in safety switches that do not pair the sensor body with the actuator, if an object other than the actuator is brought close to the sensor body, the RFID tag embedded in that object may be mistakenly detected by the sensor body, potentially causing the safety switch to malfunction. In particular, if the wireless communication frequency band used in the safety switch is the HF band, many other devices also utilize HF band wireless communication.

[0007] This invention is directed towards safety sensors and aims to suppress false detections by actuators and intentional deactivation of safety sensors.

[0008] One aspect of the present invention is a safety sensor comprising an actuator having an RFID tag, and a sensor head having an RFID reader that reads tag information stored in the RFID tag when the actuator is in close proximity, and a memory unit that stores sensor information. The tag information and the sensor information each include product information of the safety sensor. Authorized processing in the sensor head is only possible when the product information contained in the tag information read by the RFID reader matches the product information contained in the sensor information.

[0009] According to the present invention, false detection of actuators and intentional disabling of safety sensors can be suppressed.

[0010] Aspect 2 of the present invention is a safety sensor according to aspect 1, wherein the tag information includes a unique identifier specific to the actuator. The sensor head determines whether the safety sensor is used in high-code or low-code mode, using the unique identifier. The authorized processing is an initial teaching process that is only executable when the usage information is high-code, which involves storing the unique identifier in the sensor head and including it in the sensor information.

[0011] A third aspect of the present invention is the safety sensor of the second aspect, wherein the application information is determined based on a signal input to a predetermined terminal provided on the sensor head.

[0012] A fourth aspect of the present invention is a safety sensor according to aspect 2 (or aspect 2 or 3), wherein the initial teaching process comprises: a) the process of continuing the initial teaching process only if the duration of reading the tag information of the RFID tag by the RFID reader is within a first time condition, the unique identifier included in the tag information is stored in the sensor head as a temporary unique identifier; b) the process of continuing the initial teaching process only if, following step a), the state of being unable to read the tag information of the RFID tag by the RFID reader continues within a second time condition, and c) the process of including the unique identifier included in the tag information in the sensor information only if, after step b), the tag information of the RFID tag is read by the RFID reader, the product information included in the tag information matches the product information included in the sensor information, and the unique identifier included in the tag information matches the temporary unique identifier stored in the sensor head.

[0013] Aspect 5 of the present invention is a safety sensor according to aspect 2 (which may be any one of aspects 2 to 4), wherein, after the completion of the initial teaching process, the re-teaching process in the sensor head can be performed only if the product information contained in the tag information read by the RFID reader matches the product information contained in the sensor information, the application information is high-code, and the unique identifier contained in the tag information read by the RFID reader does not match the unique identifier contained in the sensor information. The reteaching process includes the steps of: d) continuing the reteaching process only if the duration of reading the tag information of the RFID tag by the RFID reader is within the range of the third time condition; e) continuing the reteaching process only if, following step d), the state of being unable to read the tag information of the RFID tag by the RFID reader continues within the range of the fourth time condition; and f) following step e), reading the tag information of the RFID tag by the RFID reader, and only if the duration of reading the tag information is within the range of the fifth time condition, the unique identifier included in the tag information is stored in the sensor head as a provisional unique identifier and the reteaching process continues. The process includes: g) continuing the teaching process; g) continuing the re-teaching process only if, following step f), the RFID reader remains unable to read the tag information of the RFID tag within the range of the sixth time condition; and h) after step g), reading the tag information of the RFID tag by the RFID reader, and only if the product information contained in the tag information matches the product information contained in the sensor information, and the unique identifier contained in the tag information matches the temporary unique identifier stored in the sensor head, the unique identifier contained in the sensor information is rewritten to the unique identifier contained in the tag information.

[0014] Embodiment 6 of the present invention is a safety sensor according to any one of embodiments 1 to 5, wherein the frequency band used for wireless communication between the RFID reader and the RFID tag is the HF band.

[0015] The aforementioned objectives, as well as other objectives, features, embodiments, and advantages, will be revealed by the detailed description of the present invention below, with reference to the attached drawings.

[0016] This is a plan view of the restricted area where the safety sensor according to the first embodiment is provided. This is a plan view showing a magnified view of the vicinity of the safety sensor. This is a diagram of the tag memory area. This is a diagram of the sensor memory area. This is a diagram of the operation of the safety sensor. This is a diagram of the operation of the safety sensor. This is a diagram of the operation of the safety sensor. This is a diagram of the flow of the initial teaching process. This is a diagram of the flow of the initial teaching process. This is a diagram of the flow of the reteaching process. This is a diagram of the flow of the reteaching process. This is a plan view of the safety sensor according to the second embodiment.

[0017] Figure 1 is a plan view of a restricted area 90 in which a safety sensor 1 according to the first embodiment of the present invention is installed. The restricted area 90 is, for example, a part of a factory. The restricted area 90 is an area separated from the surroundings by a fence or wall (hereinafter also referred to as "partition 91"), and access by workers is restricted. Industrial machinery 8 is installed in the restricted area 90, and workers enter the area when performing maintenance on the industrial machinery 8, etc.

[0018] An entrance / exit 92 is provided in the partition 91 surrounding the restricted area 90. The entrance / exit 92 is provided with a door 93 for opening and closing the entrance / exit 92. In other words, the restricted area 90 is surrounded by the partition 91, except for the entrance / exit 92 which is provided with a door 93. A safety sensor 1 is provided near the entrance / exit 92. The safety sensor 1 is an RFID (Radio Frequency Identification) type non-contact safety sensor. The safety sensor 1 is a device that detects the opening and closing of the door 93 and allows the industrial machine 8 to be driven only when the door 93 is closed. The safety sensor 1 is also called a safety switch or interlock device. In the example shown in Figure 1, the safety sensor 1 is located outside the restricted area 90. The installation position of the safety sensor 1 can be changed in various ways. For example, the safety sensor 1 may be installed inside the restricted area 90.

[0019] Figure 2 is a plan view showing an enlarged view of the vicinity of the safety sensor 1. Figure 2 also shows the components other than the safety sensor 1. In Figure 2, the state in which the door 93 is slightly open is shown by a dashed line, and the state in which the door 93 is closed is shown by a solid line.

[0020] The safety sensor 1 comprises a sensor head 2 and an actuator 3. The sensor head 2 is fixed, for example, to a portion of the partition 91 near the side edge of the entrance / exit 92, outside the restricted area 90. The actuator 3 is fixed, for example, to a portion near the side edge of the door 93.

[0021] The actuator 3 includes an RFID tag 31. The RFID tag 31 is built into the main body of the actuator 3. The RFID tag 31 includes an antenna and an IC chip (not shown). As shown in Figure 3, the IC chip of the RFID tag 31 is provided with a tag memory area 34 for storing tag information. The tag memory area 34 includes a first tag memory area 35, a second tag memory area 36, ​​and a third tag memory area 37.

[0022] The first tag memory area 35 is pre-stored with a unique identifier (hereinafter also referred to as "unique ID 41") that uniquely identifies the RFID tag 31 of the actuator 3. The second tag memory area 36 is pre-stored with product information 42, which is information relating to the manufacturer and type of the safety sensor 1. The product information 42 includes, for example, the name of the manufacturer that produced the safety sensor 1 and the product model number of the safety sensor 1. The information included in the product information 42 may be changed in various ways. For example, the product information 42 may include information other than the manufacturer name and product model number (for example, the name of the manufacturing department). Also, the product information 42 does not necessarily have to include the manufacturer name and product model number.

[0023] The third tag memory area 37 has pre-stored usage information 43 for the safety sensor 1. The usage information 43 indicates whether the safety sensor 1 is for high-code or low-code use. High-code is a mode in which the unique ID 41 described above is used when the sensor head 2, which will be described later, detects the actuator 3. Low-code is a mode in which the unique ID 41 is not used when the sensor head 2 detects the actuator 3. In other words, the usage information 43 indicates whether the actuator 3 is used in high-code or low-code mode.

[0024] Thus, in the safety sensor 1, the tag information stored in the tag memory area 34 includes a unique ID 41 specific to the actuator 3, product information 42 for the safety sensor 1, and application information 43 for the safety sensor 1.

[0025] The sensor head 2 comprises an RFID reader 21, an antenna 22, and a controller 23. The RFID reader 21, antenna 22, and controller 23 are built into the main body of the sensor head 2. The sensor head 2 is connected to a control device (not shown) of the industrial machine 8 via wiring 28. This control device includes, for example, a PLC (Programmable Logic Controller).

[0026] As will be described later, the RFID reader 21 reads the tag information stored in the RFID tag 31 of the actuator 3 and transmits the tag information to the controller 23. The memory section (not shown) of the IC chip of the controller 23 is provided with a sensor memory area 24 for storing sensor information, as shown in Figure 4. The sensor memory area 24 includes a first sensor memory area 25 and a second sensor memory area 26.

[0027] As described later, the unique ID 41 of the actuator 3 is written to the first sensor memory area 25 as a unique ID 51 as needed. The product information 52 of the safety sensor 1 is pre-stored in the second sensor memory area 26. That is, the sensor information stored in the sensor memory area 24 includes the product information 52 of the safety sensor 1. The product information 52 includes, for example, the name of the manufacturer that produced the safety sensor 1 and the product model number of the safety sensor 1. The information included in the product information 52 may be changed in various ways. For example, the product information 52 may include information other than the name of the manufacturer and the product model number (for example, the name of the manufacturing department). Also, the product information 52 does not necessarily have to include the name of the manufacturer and the product model number.

[0028] When the door 93 of the entrance / exit 92 is closed, the actuator 3 approaches the sensor head 2, as shown by the solid line in Figure 2. When the distance between the actuator 3 and the sensor head 2 becomes less than or equal to a predetermined communication range (for example, about 10 mm), wireless communication is performed between the antenna 22 of the sensor head 2 and the RFID tag 31 of the actuator 3. This communication information is transmitted to the controller 23 via the RFID reader 21, allowing the sensor head 2 to detect the actuator 3. The frequency used for this wireless communication is, for example, the HF (High Frequency) band.

[0029] When the sensor head 2 detects the actuator 3, it is determined that the door 93 is closed, and information enabling the industrial machine 8 to be driven is output from the controller 23 of the sensor head 2 to the control device of the industrial machine 8. In other words, the sensor head 2 performs an ON output process that turns on the safety output to the industrial machine 8. This enables power to be supplied to the industrial machine 8. On the other hand, when the door 93 of the entrance / exit 92 is open and the sensor head 2 cannot detect the actuator 3 (i.e., the actuator 3 is farther away from the sensor head 2 than the communication range), the safety output output from the controller 23 of the sensor head 2 is OFF, and power cannot be supplied to the industrial machine 8.

[0030] Next, we will explain the operation examples of the safety sensor 1 with reference to Figures 5 to 8B. Below, we will first explain the operation example of the safety sensor 1 for low-code systems with reference to Figure 5, and then explain the operation example of the safety sensor 1 for high-code systems.

[0031] In the low-code safety sensor 1, the application information 43 stored in the third tag memory area 37 of the actuator 3 is "low-code". Also, no information such as a unique ID 51 is written in the first sensor memory area 25 of the sensor head 2, and the first sensor memory area 25 is blank.

[0032] In the example shown in Figure 5, when the power to the safety sensor 1 is first turned ON, the first sensor memory area 25 is checked in the sensor head 2. If it is confirmed that the first sensor memory area 25 is blank (step S11), the operations from step S12 onward are performed. Note that if a unique ID 51 is stored in the first sensor memory area 25 in step S11, the safety sensor 1 is for high-code use, and the operations described later in Figures 6A and 6B are performed.

[0033] When step S11 is completed, the sensor head 2 begins searching for the actuator 3. When the door 93 described above is closed from the open state, wireless communication is performed between the antenna 22 of the sensor head 2 and the RFID tag 31 of the actuator 3, and the RFID tag 31 of the actuator 3 is detected. Then, the RFID reader 21 of the sensor head 2 reads the product information 42 stored in the second tag memory area 36 of the RFID tag 31 of the actuator 3 and transmits it to the controller 23 (step S12). The sensor head 2 compares the product information 42 of the RFID tag 31 read by the RFID reader 21 and transmitted to the controller 23 with the product information 52 that is pre-stored in the memory section (not shown) of the controller 23, and confirms whether the product information 42 and the product information 52 match (step S13).

[0034] In step S13, product information 42 and product information 52 may be judged to be a match only if they are a perfect match. Alternatively, product information 42 and product information 52 may be judged to be a match if a predetermined part of product information 42 and product information 52 (for example, the name of the manufacturer) matches according to a predetermined rule. In other words, the criterion for determining whether product information 42 and product information 52 are a match in step S13 may be set to either a perfect match or a partial match. Note that if the RFID reader 21 is unable to read the product information 42 of the RFID tag 31 in step S12, then in step S13, product information 42 and product information 52 are judged to be a mismatch (i.e., not a match).

[0035] If product information 42 and product information 52 match in step S13, the processing from step S14 onwards is performed. On the other hand, if product information 42 and product information 52 do not match in step S13, it is determined that an error has occurred in the safety sensor 1 and error processing is performed (step S17). Specifically, for example, the safety sensor 1 is locked out and requires a restart, and the operation of the safety sensor 1 is terminated. This error processing is performed, for example, when an actuator from another company whose product information is not stored is brought close to the sensor head 2.

[0036] In step S13, if it is determined that product information 42 and product information 52 match, the RFID reader 21 of the sensor head 2 reads the application information 43 stored in the third tag memory area 37 of the RFID tag 31 of the actuator 3 (i.e., the application information 43 is read and acquired) (step S14).

[0037] If the usage information 43 read by the RFID reader 21 is "low code" (step S15), the controller 23 performs an ON output process to turn on the safety output to the industrial machine 8 (step S16). This ON output process is called the "authorized process," and in the safety sensor 1, the authorized process (i.e., the ON output process) in the sensor head 2 is only executed if the product information 42 of the RFID tag 31 read by the RFID reader 21 matches the product information 52 pre-stored in the memory of the controller 23. This prevents or suppresses malfunctions or intentional deactivation of the safety sensor 1 by RFID tags of items other than the actuator 3 of the safety sensor 1 (for example, transportation IC cards, etc.).

[0038] When the door 93 is closed, the ON output from the safety sensor 1 continues. When the door 93 is opened and wireless communication between the sensor head 2 and the actuator 3 stops, the sensor head 2 performs an OFF output process to turn off the safety output to the industrial machine 8.

[0039] On the other hand, if the usage information 43 read by the RFID reader 21 is "high code" and not "low code" (step S15), the initial teaching process described later in Figures 7A and 7B is performed. If the usage information 43 read by the RFID reader 21 is neither "low code" nor "high code," or if the usage information 43 cannot be read, the safety sensor 1 determines that an error has occurred and the above-mentioned error processing is performed.

[0040] Next, an example of the operation of the safety sensor 1 for Hi-Code will be explained with reference to Figures 6A and 6B. In the safety sensor 1 for Hi-Code, the application information 43 stored in the third tag memory area 37 of the actuator 3 is "Hi-Code". In addition, the unique ID 41 of the actuator 3, which is associated with the sensor head 2 in a one-to-one relationship, is pre-written in the first sensor memory area 25 of the sensor head 2 and stored as unique ID 51.

[0041] In the example shown in FIGS. 6A and 6B, first, when the power supply of the safety sensor 1 is turned on, the first sensor memory area 25 in the sensor head 2 is checked. When it is confirmed that the unique ID 51 is stored in the first sensor memory area 25 (step S21), the operations after step S22 are performed. In step S21, if the first sensor memory area 25 is blank, the safety sensor 1 is for low code, and the operations illustrated in FIG. 5 described above are performed.

[0042] When step S21 ends, steps S22 to S24, which are substantially the same as steps S12 to S14 described above, are performed. Specifically, the RFID tag 31 of the actuator 3 is detected by the sensor head 2, and the product information 42 stored in the second tag memory area 36 of the RFID tag 31 is read by the RFID reader 21 (step S22). Then, the product information 42 of the RFID tag 31 read by the RFID reader 21 and transmitted to the controller 23 is compared with the product information 52 pre-stored in the memory unit of the controller 23, and it is confirmed whether the product information 42 and the product information 52 match (step S23).

[0043] If the product information 42 and the product information 52 match in step S23, the processing after step S24 is performed. On the other hand, if the product information 42 and the product information 52 do not match in step S23, it is determined that an error has occurred in the safety sensor 1, and error processing is performed substantially in the same manner as step S17 described above (step S29).

[0044] When it is determined that the product information 42 and the product information 52 match in step S23, the usage information 43 stored in the third tag memory area 37 of the RFID tag 31 is read by the RFID reader 21 (that is, the usage information 43 is read out and acquired) (step S24).

[0045] If the usage information 43 read by the RFID reader 21 is not "high code" (step S25), the safety sensor 1 determines that an error has occurred and performs error processing (step S29). Specifically, for example, the safety sensor 1 is locked out and requires a restart, and the operation of the safety sensor 1 is terminated. This error processing is performed, for example, when a low-code actuator 3 is brought close to the sensor head 2, or when an actuator from another company that does not have product information stored in it is brought close to the sensor head 2. In addition, if a low-code actuator 3 is detected, the detection result of this low-code actuator 3 may be ignored, and the safety sensor 1 may not be locked out, continuing normal operations such as tag searching.

[0046] On the other hand, if the usage information 43 read by the RFID reader 21 is a "high code" (step S25), the RFID reader 21 reads the unique ID 41 stored in the first tag memory area 34 of the RFID tag 31 (step S26). Then, the unique ID 41 of the RFID tag 31 read by the RFID reader 21 and transmitted to the controller 23 is compared with the unique ID 51 that is pre-stored in the memory section of the controller 23 to confirm whether the unique ID 41 and the unique ID 51 match (step S27).

[0047] If unique ID 41 and unique ID 51 match in step S27, the controller 23 performs an ON output process to turn on the safety output to the industrial machine 8 (step S28). On the other hand, if unique ID 41 and unique ID 51 do not match in step S27, the above-described error processing is performed (step S29). This error processing is performed, for example, when an actuator 3 of the same type but different from the actuator 3 that is pre-associated one-to-one with the sensor head 2 is brought close to the sensor head 2. As will be described later, by performing a predetermined operation between step S27 and step S29, error processing may be omitted and re-teaching processing (see Figures 8A and 8B) may be performed.

[0048] Thus, in the safety sensor 1 for high codes, only when the product information 42 of the RFID tag 31 read by the RFID reader 21 and transmitted to the controller 23 matches the product information 52 pre-stored in the memory unit of the controller 23, the RFID reader 21 reads the unique ID 41 of the RFID tag 31. Then, only when the unique ID 41 of the RFID tag 31 read by the RFID reader 21 and transmitted to the controller 23 matches the unique ID 51 pre-stored in the memory unit of the controller 23, the ON output process (i.e., the approved process) in the sensor head 2 can be executed.

[0049] Thereby, when an RFID tag of an article different from the actuator 3 of the safety sensor 1 (e.g., a transportation system IC card, etc.) approaches the sensor head 2, error processing can be executed without reading the unique ID of the RFID tag. Also, even when another actuator of the same type as the actuator 3 of the safety sensor 1 approaches the sensor head 2, malfunction of the safety sensor 1 (i.e., false detection of the other actuator) by the RFID tag of the other actuator, and intentional invalidation of the safety sensor 1 are prevented or suppressed.

[0050] In the state where the door 93 is closed, the ON output by the safety sensor 1 continues. When the door 93 is opened and the wireless communication between the sensor head 2 and the actuator 3 stops, an OFF output process for turning off the safety output to the industrial machine 8 is performed in the sensor head 2.

[0051] Next, the flow of the initial teaching process for using the low-code safety sensor 1 as a high-code safety sensor 1 will be explained with reference to Figures 7A and 7B. The high-code safety sensor 1 refers to a sensor head 2 in which a unique ID 51 has been written to the first sensor memory area 25. The initial teaching process is performed when the safety sensor 1 is attached to a partition 91 and a door 93 (see Figure 1) and put into use. The initial teaching process is the process of writing the unique ID 41 of the actuator 3 that corresponds one-to-one with the sensor head 2 to the blank first sensor memory area 25 of the safety sensor 1. The initial teaching process is also called the pairing process.

[0052] As described above, the initial teaching process is initiated when, during steps S11 to S15, the first sensor memory area 25 is blank in step S11, and the usage information 43 of the RFID tag 31 is "high code" in step S15. When the initial teaching process is initiated, the safety sensor 1 notifies the user of the safety sensor 1 that the initial teaching process has started, for example, by lighting up an indicator (not shown) provided on the sensor head 2.

[0053] In the examples shown in Figures 7A and 7B, once the initial teaching process begins, the elapsed time from the start is continuously measured by the controller 23 of the sensor head 2. Then, at a predetermined timing, the door 93 is opened and closed again, causing the unique ID 41 of the RFID tag 31 to be written as a unique ID 51 to the first sensor memory area 25 of the sensor head 2.

[0054] Specifically, when the initial teaching process begins with the door 93 closed, the RFID reader 21 of the sensor head 2 reads the tag information from the RFID tag 31. However, this reading of the tag information must continue only within a predetermined first time condition. This first time condition is, for example, 5 seconds or more and less than 10 seconds. In this case, the door 93 must remain closed for 5 seconds or more from the start of the initial teaching process to continue reading the tag information, and the door 93 must be opened before 10 seconds have elapsed from the start of the initial teaching process to prevent the RFID reader 21 from reading the tag information.

[0055] In other words, the initial teaching process continues only if the duration of reading the tag information of the RFID tag 31 by the RFID reader 21 is within the range of the first time condition (for example, 5 seconds or more and less than 10 seconds) (step S31). In the sensor head 2, the unique ID 41 included in the tag information read by the RFID reader 21 is temporarily held (stored) in the controller 23's cache memory (not shown) as a provisional unique identifier (hereinafter also referred to as "provisional unique ID") (step S32).

[0056] On the other hand, if the duration of reading the tag information of the RFID tag 31 by the RFID reader 21 is outside the range of the first time condition, it is determined that an error occurred during the initial teaching process and error processing is performed (step S40). Specifically, if the door 93 is opened before 5 seconds have elapsed since the start of the initial teaching process, and if the door 93 remains closed even after 10 seconds have elapsed since the start of the initial teaching process, error processing is performed. In error processing, for example, the safety sensor 1 is locked out and requires a restart, and the initial teaching process ends in a failed state. The sensor head 2 may notify the elapsed time since the start of the initial teaching process by changing the blinking interval of the indicator mentioned above.

[0057] In the initial teaching process, following steps S31 to S32, the door 93 must remain open for a predetermined second time period, making it impossible for the RFID reader 21 to read the tag information. After this, the door 93 must be closed, making it possible to read the tag information. This allows the initial teaching process to continue. The second time period is, for example, 1 second or more and less than 5 seconds. In this case, the door 93 must remain open for at least 1 second from the end of steps S31 to S32 (i.e., the opening of the door 93) to continue the state in which the tag information cannot be read, and the door 93 must be closed before 5 seconds have elapsed from the end of steps S31 to S32, making it possible for the RFID reader 21 to read the tag information.

[0058] In other words, in the initial teaching process, following steps S31 to S32, the initial teaching process continues only if the RFID reader 21 remains unable to read the tag information within the range of the second time condition (step S33). To put it another way, the initial teaching process continues only if the duration of the state in which the RFID reader 21 is unable to read the tag information is within the range of the second time condition.

[0059] On the other hand, if the duration of the state in which the RFID reader 21 is unable to read the tag information is outside the range of the second time condition, it is determined that an error has occurred in the initial teaching process and the above-described error processing is performed (step S40). Specifically, the above-described error processing is performed if the door 93 is closed before 1 second has elapsed since the end of steps S31 to S32 (i.e., the door 93 is opened), and if the door 93 remains open even after 5 seconds have elapsed since the end of steps S31 to S32. The sensor head 2 may notify the elapsed time since the end of steps S31 to S32 by changing the blinking interval of the indicator mentioned above.

[0060] If the initial teaching process continues in step S33, the RFID reader 21 of the sensor head 2 reads the tag information of the RFID tag 31 (step S34). The sensor head 2 compares the product information 42 contained in the tag information with the product information 52 contained in the sensor information stored in the memory of the controller 23 (step S35). If the product information 42 contained in the tag information and the product information 52 contained in the sensor information match, the initial teaching process continues. On the other hand, if the product information 42 contained in the tag information and the product information 52 contained in the sensor information do not match, the above-described error processing is performed (step S40).

[0061] If the initial teaching process continues in step S35, the sensor head 2 checks the application information 43 included in the tag information (step S36). If the application information 43 is "high code", the initial teaching process continues. On the other hand, if the application information 43 is "low code" or if the application information 43 cannot be read, the above-mentioned error processing is performed (step S40).

[0062] If the initial teaching process continues in step S36, the sensor head 2 compares the unique ID 41 included in the tag information with the temporary unique ID stored in the controller 23's cache memory (step S37). If the unique ID 41 included in the tag information matches the temporary unique ID, the initial teaching process continues. On the other hand, if the unique ID 41 and the temporary unique ID do not match, the error processing described above is performed (step S40).

[0063] If the initial teaching process continues in step S37, after a predetermined write waiting time (for example, 5 seconds) has elapsed with the door 93 closed since the end of step S33 (i.e., the closing of the door 93) (step S38), the aforementioned temporary unique ID is written to and stored in the first sensor memory area 25 of the controller 23 as the unique ID 51 of the sensor information (step S39). This completes the initial teaching process of the safety sensor 1.

[0064] If we refer to this initial teaching process as the "authorized process," then in the safety sensor 1, the authorized process (i.e., the initial teaching process) can only be executed if the product information 42 of the RFID tag 31 read by the RFID reader 21 matches the product information 52 pre-stored in the memory of the controller 23. This prevents or suppresses malfunctions or intentional deactivation of the safety sensor 1 by RFID tags of items other than the actuator 3 of the safety sensor 1 (for example, transportation IC cards).

[0065] Once the initial teaching process for the safety sensor 1 is complete, an ON output process is performed by the safety sensor 1 for the high code, as shown in Figures 6A and 6B. The sensor head 2 may notify the elapsed time of the write waiting period in step S38 by changing the blinking interval of the indicator, etc.

[0066] In step S39, it can also be understood that the unique ID 41 of the actuator 3, which was read by the RFID reader 21 in step S34, is included in the sensor information as the unique ID 51 mentioned above. Furthermore, if the door 93 is opened in step S38 before the aforementioned write waiting time has elapsed, the aforementioned error processing is performed.

[0067] In this way, by complicating the initial teaching procedure, the safety sensor 1 can prevent or deter the execution of the initial teaching process by persons who do not have the authority to perform the initial teaching process (i.e., persons who do not have the authority to access the safety sensor 1 manual). Furthermore, it can weaken the will of those who attempt to perform the initial teaching process illegally. As a result, it is possible to prevent or deter the intentional deactivation of the safety sensor 1.

[0068] The first and second time conditions described above may be the same or different. Furthermore, the first and second time conditions may be modified in various ways. For example, the first time condition may consist of only one of the two time limits (5 seconds or more in the above example) and the other (less than 10 seconds in the above example). The same applies to the second time condition.

[0069] Next, the flow of the reteaching process for the Hi-Code safety sensor 1 will be explained with reference to Figures 8A and 8B. The reteaching process is performed when replacing the actuator 3 in the Hi-Code safety sensor 1 that was being used due to loss or malfunction. The reteaching process is a process in which the unique ID 41 of the new actuator 3, which corresponds one-to-one with the sensor head 2, is written to the first sensor memory area 25 in the sensor head 2 of the Hi-Code safety sensor 1, where the unique ID 51 is already stored, thereby overwriting (i.e., rewriting) the unique ID 51 included in the sensor information.

[0070] As described above, the reteaching process is performed when, during steps S21 to S29, a unique ID 51 is stored in the first sensor memory area 25 in step S21, and in step S27, the unique ID 51 does not match (i.e., there is a mismatch) with the unique ID 41 of the actuator 3. The reteaching process is started when the user performs a predetermined action between steps S27 and S29. In the following description, this predetermined action will also be included in the reteaching process. If this predetermined action is not performed, the reteaching process cannot be executed, and the error processing described above (step S29) is performed.

[0071] In the examples shown in Figures 8A and 8B, if a mismatch in the unique ID is detected in step S27, the elapsed time from the time of detection is continuously measured by the controller 23 of the sensor head 2. Then, at a predetermined timing, the door 93 is opened and closed again, thereby performing a re-teaching process.

[0072] Specifically, first, when a mismatch in the unique ID is detected with the door 93 closed, the RFID reader 21 of the sensor head 2 reads the tag information of the RFID tag 31. However, this reading of the tag information must continue only within a predetermined third time condition. This third time condition is, for example, 5 seconds or more and less than 10 seconds. In this case, the door 93 must remain closed for 5 seconds or more after the unique ID mismatch is detected, allowing the reading of the tag information to continue. The door 93 must then be opened before 10 seconds have elapsed since the unique ID mismatch was detected, making it impossible for the RFID reader 21 to read the tag information.

[0073] In other words, the reteaching process continues only if the duration of reading the tag information of the RFID tag 31 by the RFID reader 21 is within the range of the third time condition (for example, 5 seconds or more and less than 10 seconds) (step S51).

[0074] On the other hand, if the duration of reading the tag information of the RFID tag 31 by the RFID reader 21 is outside the range of the third time condition, it is determined that an error has occurred in the re-teaching process and error processing is performed (step S62). Specifically, if the door 93 is opened before 5 seconds have elapsed since the unique ID mismatch was discovered, and if the door 93 remains closed even after 10 seconds have elapsed since the unique ID mismatch was discovered, error processing is performed. In error processing, for example, the safety sensor 1 is locked out and requires a restart, and the re-teaching process ends in a failed state. The sensor head 2 may notify the elapsed time since the unique ID mismatch was discovered by changing the blinking interval of the indicator mentioned above.

[0075] In the re-teaching process, following step S51, the door 93 must remain open for a predetermined fourth time period, making it impossible for the RFID reader 21 to read the tag information. After this, the door 93 must be closed, making it possible to read the tag information. This allows the re-teaching process to continue. The fourth time period is, for example, 1 second or more and less than 5 seconds. In this case, the door 93 must remain open for at least 1 second from the end of step S51 (i.e., the opening of the door 93) to continue the state in which the tag information cannot be read, and the door 93 must be closed before 5 seconds have elapsed from the end of step S51, making it possible for the RFID reader 21 to read the tag information.

[0076] In other words, in the re-teaching process, following step S51, the re-teaching process continues only if the RFID reader 21 remains unable to read the tag information within the range of the fourth time condition (step S52). To put it another way, the re-teaching process continues only if the duration of the RFID reader 21's inability to read the tag information is within the range of the fourth time condition.

[0077] On the other hand, if the duration of the state in which the RFID reader 21 is unable to read the tag information is outside the range of the fourth time condition, it is determined that an error has occurred in the initial teaching process and the above-described error processing is performed (step S62). Specifically, the above-described error processing is performed if the door 93 is closed before 1 second has elapsed since the end of step S51 (i.e., the door 93 is opened), and if the door 93 remains open even after 5 seconds have elapsed since the end of step S51. The sensor head 2 may notify the elapsed time since the end of step S51 by changing the blinking interval of the indicator, etc.

[0078] When step S52 is completed, the door 93 is opened and then closed again at a predetermined timing, in much the same manner as in steps S31 to S39 described above (see Figures 7A and 7B), and the unique ID 41 of the RFID tag 31 is written as a unique ID 51 to the first sensor memory area 25 of the sensor head 2 (steps S53 to S61).

[0079] Specifically, first, with the door 93 closed, the RFID reader 21 of the sensor head 2 reads the tag information of the RFID tag 31. This reading of the tag information must continue only within a predetermined fifth time condition. This fifth time condition is, for example, 5 seconds or more and less than 10 seconds. In this case, the door 93 must remain closed for 5 seconds or more from the end of step S52 (i.e., the door 93 is closed) to continue reading the tag information, and the door 93 must be opened before 10 seconds have elapsed from the end of step S52 to prevent the RFID reader 21 from reading the tag information.

[0080] In other words, the reteaching process continues only if the duration of reading the tag information of the RFID tag 31 by the RFID reader 21 is within the range of the fifth time condition (for example, 5 seconds or more and less than 10 seconds) (step S53). In the sensor head 2, the unique ID 41 included in the tag information read by the RFID reader 21 is temporarily held (stored) in the cache memory of the controller 23 as a provisional unique identifier (i.e., provisional unique ID) (step S54).

[0081] If the duration of reading the tag information of the RFID tag 31 by the RFID reader 21 is outside the range of the fifth time condition, it is determined that an error has occurred during the reteaching process and error processing is performed (step S62). Specifically, if the door 93 is opened before 5 seconds have elapsed since the end of step S52, and if the door 93 remains closed even after 10 seconds have elapsed since the end of step S52, error processing is performed. In error processing, for example, the safety sensor 1 is locked out and requires a restart, and the reteaching process ends in a failed state. The sensor head 2 may notify the elapsed time since the end of step S52 by changing the blinking interval of the indicator mentioned above.

[0082] In the re-teaching process, following steps S53 to S54, the door 93 must remain open for a predetermined sixth time period, making it impossible for the RFID reader 21 to read the tag information. After this, the door 93 must be closed, making it possible to read the tag information. This allows the re-teaching process to continue. The sixth time period is, for example, 1 second or more and less than 5 seconds. In this case, the door 93 must remain open for at least 1 second from the end of steps S53 to S54 (i.e., the door 93 is opened) to continue the state in which the tag information cannot be read, and the door 93 must be closed before 5 seconds have elapsed from the end of steps S53 to S54, making it possible for the RFID reader 21 to read the tag information.

[0083] In other words, in the re-teaching process, following steps S53 to S54, the re-teaching process continues only if the RFID reader 21 remains unable to read the tag information within the range of the sixth time condition (step S55). To put it another way, the re-teaching process continues only if the duration of the RFID reader 21's inability to read the tag information is within the range of the sixth time condition.

[0084] On the other hand, if the duration of the state in which the RFID reader 21 is unable to read the tag information is outside the range of the sixth time condition, it is determined that an error has occurred in the re-teaching process and the above-described error processing is performed (step S62). Specifically, the above-described error processing is performed if the door 93 is closed before 1 second has elapsed since the end of steps S53 to S54 (i.e., the door 93 is opened), and if the door 93 remains open even after 5 seconds have elapsed since the end of steps S53 to S54. The sensor head 2 may notify the elapsed time since the end of steps S53 to S54 by changing the blinking interval of the indicator, etc.

[0085] When step S55 is completed, the RFID reader 21 of the sensor head 2 reads the tag information of the RFID tag 31 (step S56). The sensor head 2 compares the product information 42 contained in the tag information with the product information 52 contained in the sensor information stored in the memory of the controller 23 (step S57). If the product information 42 contained in the tag information and the product information 52 contained in the sensor information match, the re-teaching process continues. On the other hand, if the product information 42 contained in the tag information and the product information 52 contained in the sensor information do not match, the error processing described above is performed (step S62).

[0086] If the re-teaching process continues in step S57, the sensor head 2 checks the usage information 43 included in the tag information (step S58). If the usage information 43 is "high code", the re-teaching process continues. On the other hand, if the usage information 43 is "low code" or if the usage information 43 cannot be read, the above-described error processing is performed (step S62).

[0087] If the re-teaching process continues in step S58, the sensor head 2 compares the unique ID 41 included in the tag information with the temporary unique ID stored in the controller 23's cache memory (step S59). If the unique ID 41 included in the tag information matches the temporary unique ID, the re-teaching process continues. On the other hand, if the unique ID 41 and the temporary unique ID do not match, the error processing described above is performed (step S62).

[0088] If the reteaching process continues in step S59, after a predetermined write waiting time (for example, 5 seconds) has elapsed with the door 93 closed since the end of step S55 (i.e., the closing of the door 93) (step S60), the above-mentioned temporary unique ID is written to and stored in the first sensor memory area 25 of the controller 23 as the unique ID 51 of the sensor information (step S61). In step S61, the unique ID 51 that was stored in the first sensor memory area 25 before step S61 is overwritten with the above-mentioned temporary unique ID. This completes the reteaching process of the safety sensor 1.

[0089] If we refer to this re-teaching process as an "authorized process," the safety sensor 1 will only be able to execute the authorized process (i.e., the re-teaching process) if the product information 42 of the RFID tag 31 read by the RFID reader 21 matches the product information 52 pre-stored in the memory of the controller 23. This prevents or suppresses malfunctions or intentional deactivation of the safety sensor 1 by RFID tags of items other than the actuator 3 of the safety sensor 1 (for example, transportation IC cards).

[0090] Once the re-teaching process for safety sensor 1 is complete, steps S21 to S28 shown in Figures 6A and 6B are performed, and the safety sensor 1 for high code performs an ON output process. The sensor head 2 may notify the elapsed time of the write waiting period in step S60 by changing the blinking interval of the indicator, etc.

[0091] In step S61, it can also be understood that the unique ID 41 of the actuator 3, which was read by the RFID reader 21 in step S56, is included in the sensor information as the unique ID 51 mentioned above. Furthermore, if the door 93 is opened before the aforementioned write waiting time has elapsed in step S60, the aforementioned error processing is performed.

[0092] In this way, by complicating the reteaching procedure, the safety sensor 1 can prevent or deter the reteaching process from being performed by persons who do not have the authority to perform the reteaching process (i.e., persons who do not have the authority to access the safety sensor 1 manual). Furthermore, it can weaken the will of those who attempt to perform the reteaching process illegally. As a result, the intentional deactivation of the safety sensor 1 can be prevented or deterred.

[0093] Furthermore, the third and fourth time conditions described above may be the same or different from each other. Also, the third and fourth time conditions may be modified in various ways. For example, the third time condition may be defined by specifying only one of the lower limit time (5 seconds or more in the above example) and the upper limit time (less than 10 seconds in the above example), while leaving the other unspecified. The same applies to the fourth time condition.

[0094] The fifth and sixth time conditions described above may be the same or different from each other. Furthermore, the fifth and sixth time conditions may be modified in various ways. For example, the fifth time condition may have only one of the two limits specified: a lower limit (5 seconds or more in the above example) and an upper limit (less than 10 seconds in the above example), with the other not specified. The same applies to the sixth time condition.

[0095] As described above, the safety sensor 1 comprises an actuator 3 and a sensor head 2. The actuator 3 has an RFID tag 31. The sensor head 2 has an RFID reader 21 and a memory unit. The RFID reader 21 reads the tag information stored in the RFID tag 31 when the actuator 3 is in close proximity. The memory unit stores the sensor information. The tag information and sensor information each include product information 42 and 52 of the safety sensor 1. Only when the product information 42 contained in the tag information read by the RFID reader 21 matches the product information 52 contained in the sensor information is authorized processing in the sensor head 2 (in the above example, ON output processing, initial teaching processing, or re-teaching processing) possible. This makes it possible to suppress false detection of the actuator 3 and intentional deactivation of the safety sensor 1, as described above.

[0096] In the example above, the tag information includes a unique identifier specific to the actuator 3 (i.e., unique ID 41). The sensor head 2 determines whether the safety sensor 1 is used in high-code mode using unique ID 41 or low-code mode without unique ID 41. Greater effectiveness can be achieved if the authorized processing described above is an initial teaching process that stores the unique ID 41 in the sensor head 2 and includes it in the sensor information, which is only executable when the usage information 43 is high-code.

[0097] In the safety sensor 1, as described above, after confirming the match of product information 42 and 52, the unique ID 41 is read and written to the controller 23. Therefore, if the initial teaching process is started using an item different from the actuator 3 that is to be associated with the sensor head 2, the initial teaching process can be quickly stopped without performing operations such as reading the unique ID 41 and writing to the controller 23. In other words, the safety sensor 1 can quickly stop incorrect and fraudulent initial teaching processes.

[0098] As described above, the initial teaching process preferably includes the steps (S31 to S32) in which the unique ID 41 included in the tag information is stored in the sensor head 2 as a temporary unique ID and the initial teaching process continues only if the duration of reading the tag information of the RFID tag 31 by the RFID reader 21 is within the range of a first time condition; the step (S33) in which the initial teaching process continues only if the state of being unable to read the tag information of the RFID tag 31 by the RFID reader 21 continues within the range of a second time condition, and the steps (S34, S35, S37, S39) in which the unique ID 41 included in the tag information is included in the sensor information only if the tag information of the RFID tag 31 is read by the RFID reader 21, the product information 42 included in the tag information matches the product information 52 included in the sensor information, and the unique ID 41 included in the tag information matches the temporary unique ID stored in the sensor head 2. In this way, by complicating the initial teaching process, it is possible to prevent or suppress the intentional disabling of the safety sensor 1.

[0099] In the above example, in the safety sensor 1, after the initial teaching process is completed, the re-teaching process in the sensor head 2 is only possible if the product information 42 contained in the tag information read by the RFID reader 21 matches the product information 52 contained in the sensor information, the application information 43 is a high code, and the unique ID 41 contained in the tag information read by the RFID reader 21 does not match the unique ID 51 contained in the sensor information.

[0100] The reteaching process preferably includes the steps of: continuing the reteaching process only if the duration of reading the tag information of the RFID tag 31 by the RFID reader 21 is within the range of the third time condition (step S51); continuing the reteaching process only if the state of being unable to read the tag information of the RFID tag 31 by the RFID reader 21 continues within the range of the fourth time condition (step S52); and continuing the reteaching process only if the RFID reader 21 reads the tag information of the RFID tag 31 and the duration of reading the tag information is within the range of the fifth time condition, and the unique ID 41 included in the tag information is stored in the sensor head 2 as a temporary unique ID. The process includes steps S53 to S54, a step S55 in which the reteaching process is continued only if the RFID reader 21 remains unable to read the tag information of the RFID tag 31 within the range of the sixth time condition following steps S53 to S54, and a step S56, S57, S59, S61 in which the unique ID 51 included in the sensor information is rewritten to the unique ID 41 included in the tag information only if the RFID reader 21 reads the tag information of the RFID tag 31, the product information 42 included in the tag information matches the product information 52 included in the sensor information, and the unique ID 41 included in the tag information matches the temporary unique ID stored in the sensor head.

[0101] As described above, the frequency band used for wireless communication between the RFID reader 21 and the RFID tag 31 is preferably the HF band. Since the HF band is a widely used frequency band in RFID, the RFID reader 21 and RFID tag 31 can be easily obtained. Furthermore, even in the HF band, which is used in many products, the safety sensor 1 can prevent or suppress misuse or intentional deactivation, as described above.

[0102] Next, a safety sensor 1a according to a second embodiment of the present invention will be described with reference to Figure 9. The safety sensor 1a has substantially the same configuration as the safety sensor 1 shown in Figure 2, and stores substantially the same information, except that a sensor head 2a is provided instead of the sensor head 2, and the actuator 3 does not store application information 43 (see Figure 3). The sensor head 2a has the same structure as the sensor head 2, except that it is provided with terminals 29. In the following description, the same reference numerals are used for the components and stored information of the safety sensor 1a as for those of the safety sensor 1.

[0103] In the safety sensor 1a, the intended use of the safety sensor 1a is determined by a signal input to a predetermined terminal 29 of the sensor head 2a. As described above, this intended use information indicates whether the safety sensor 1a is for high-code or low-code use. The signal input to terminal 29 is, for example, a voltage. Specifically, if terminal 29 is electrically connected to a power supply and a voltage is applied to terminal 29, the safety sensor 1a is used for high-code use. On the other hand, if terminal 29 is not connected to a power supply and no voltage is applied to terminal 29, the safety sensor 1a is used for low-code use.

[0104] In the safety sensor 1a, the signal input to terminal 29 may be anything other than voltage. For example, terminal 29 may be connected to a control device via a changeover switch. In this case, for example, the signal input from the control device to terminal 29 can be switched by the changeover switch between a signal indicating a high code and a signal indicating a low code.

[0105] When safety sensor 1a is used for low-code applications, the operation of safety sensor 1a is substantially the same as steps S11 to S17 shown in Figure 5, except that the source of acquisition of application information in step S14 is different. With safety sensor 1a, the acquisition of application information in step S14 is not based on the RFID tag 31 of actuator 3, but on the signal input to terminal 29 as described above. With safety sensor 1a, just like safety sensor 1 described above, false detection by actuator 3 and intentional deactivation of safety sensor 1a can be suppressed.

[0106] When safety sensor 1a is used for Hi-Code, the operation of safety sensor 1a is substantially the same as steps S21 to S29 shown in Figures 6A and 6B, except that the source of acquisition of application information in step S24 is different. In safety sensor 1a, the acquisition of application information in step S24 is based on the signal input to terminal 29, not the RFID tag 31 of actuator 3. In safety sensor 1a, as with safety sensor 1 described above, false detection by actuator 3 and intentional deactivation of safety sensor 1a can be suppressed.

[0107] When the initial teaching process for safety sensor 1a is performed, the operation of safety sensor 1a is substantially the same as steps S31 to S39 shown in Figures 7A and 7B, except that the source of acquisition of application information from the tag information in step S34 is different. In safety sensor 1a, in parallel with reading the tag information in step S34, application information is acquired based on the signal input to terminal 29. In safety sensor 1a, as with safety sensor 1 described above, intentional deactivation of safety sensor 1a can be prevented or suppressed by complicating the initial teaching process procedure.

[0108] When the safety sensor 1a undergoes reteaching, the operation of the safety sensor 1a is substantially the same as steps S51 to S62 shown in Figures 8A and 8B, except that the source of the application information from the tag information in step S56 is different. In the safety sensor 1a, the application information is acquired based on the signal input to terminal 29 in parallel with the reading of the tag information in step S56. In the safety sensor 1a as well, similar to the safety sensor 1 described above, intentional deactivation of the safety sensor 1a can be prevented or suppressed by complicating the reteaching procedure.

[0109] As described above, in the safety sensor 1a, the application information is determined based on a signal input to a predetermined terminal 29 provided on the sensor head 2a. As a result, whether the safety sensor 1a is used with low code or high code, there is no need to store the application information 43 in the actuator 3, and one actuator 3 can be used in common with both the low code and high code safety sensors 1a.

[0110] Various modifications are possible to the safety sensors 1 and 1a described above.

[0111] For example, in the operation of the low-code safety sensor 1 shown in Figure 5, the reading of the product information 42 of the RFID tag 31 and the confirmation of the match between the product information 42 of the RFID tag 31 and the product information 52 of the sensor head 2 (steps S12 to S13) may be performed after the reading and confirmation of the application information 43 (steps S14 to S15).

[0112] In the operation of the Hi-Code safety sensor 1 shown in Figures 6A and 6B, the reading of the product information 42 of the RFID tag 31 and the confirmation of the match between the product information 42 of the RFID tag 31 and the product information 52 of the sensor head 2 (steps S22 to S23) may be performed after the reading and confirmation of the application information 43 (steps S24 to S25), and may also be performed after the reading of the unique ID 41 and the confirmation of the match between the unique ID 41 of the RFID tag 31 and the unique ID 51 stored in the sensor head 2 (steps S26 to S27).

[0113] In the initial teaching process and re-teaching process described above, the method for determining whether to continue the process based on the opening and closing of the door 93 can be varied. For example, the number of times the door 93 is opened and closed, the time conditions described above, etc., can be varied. In addition, the decision on whether to continue the initial teaching process and re-teaching process may be made based on processes other than the opening and closing of the door 93.

[0114] For example, in steps S31 and S33 described above, the initial teaching process is permitted to continue by switching the RFID tag 31 between readable and unreadable states according to predetermined rules by opening and closing the door 93, but it is not necessarily limited to this.

[0115] In steps S51 and S52 described above, the re-teaching process is permitted to continue by switching the RFID tag 31 between readable and unreadable states according to predetermined rules by opening and closing the door 93, but it is not necessarily limited to this.

[0116] In steps S53 and S55 described above, the re-teaching process is permitted to continue by switching the RFID tag 31 between readable and unreadable states according to predetermined rules by opening and closing the door 93, but it is not necessarily limited to this.

[0117] In the error handling described above, for example, in addition to locking out safety sensor 1, the surroundings may be notified that safety sensor 1 has been intentionally disabled by illuminating a warning light or sounding an alarm. Alternatively, safety sensor 1 may output a monitor signal to a higher-level PLC to notify that safety sensor 1 has been intentionally disabled.

[0118] In the safety sensor 1, for example, an RFID reader 21 and an RFID tag 31 that use the LF (Low Frequency) band for wireless communication may be used. The same applies to the safety sensor 1a.

[0119] In steps S32 and S54 described above, the provisional unique identifier was temporarily stored in the cache memory of the controller 23, but this is not limited to that. For example, the provisional unique identifier may be stored in the sensor memory area 24 of the controller 23.

[0120] In safety sensors 1 and 1a, the shape and structure of the sensor heads 2 and 2a and the actuator 3 can be modified in various ways. For example, the sensor heads 2 and 2a may have two controllers 23 and two sensor memory areas 24 each, which are duplicated and mutually monitor each other's memory information. Alternatively, the memory portion of the sensor heads 2 and 2a may be an external memory located outside the IC chip. Furthermore, the object on which the safety sensors 1 and 1a are installed is not limited to the above example and can be modified in various ways.

[0121] The configurations in the above embodiments and each modified example may be combined as appropriate, as long as they do not contradict each other.

[0122] Although the invention has been described in detail, the above description is illustrative and not limiting. Therefore, it can be said that numerous modifications and embodiments are possible as long as they do not deviate from the scope of the present invention.

[0123] 1, 1a Safety sensor 2, 2a Sensor head 3 Actuator 21 RFID reader 29 Terminal 31 RFID tag 41, 51 Unique ID 42, 52 Product information 43 Application information S11-S17, S21-S29, S31-S40, S51-S62 Step

Claims

1. A safety sensor comprising: an actuator having an RFID tag; an RFID reader that reads tag information stored in the RFID tag when the actuator is in close proximity; and a sensor head having a memory unit that stores sensor information, wherein the tag information and the sensor information each include product information of the safety sensor, and authorized processing in the sensor head is only possible when the product information contained in the tag information read by the RFID reader matches the product information contained in the sensor information.

2. A safety sensor according to claim 1, wherein the tag information includes a unique identifier specific to the actuator, the sensor head determines whether the safety sensor is used in high-code or low-code using the unique identifier, and the authorized processing is an initial teaching process which is only executable when the application information is high-code, by storing the unique identifier in the sensor head and including it in the sensor information.

3. A safety sensor according to claim 2, wherein the application information is determined based on a signal input to a predetermined terminal provided on the sensor head.

4. A safety sensor according to claim 2, wherein the initial teaching process comprises: a) the process of storing the unique identifier included in the tag information as a temporary unique identifier in the sensor head and continuing the initial teaching process only if the duration of reading the tag information of the RFID tag by the RFID reader is within a first time condition; b) the process of continuing the initial teaching process only if, following step a), the state of being unable to read the tag information of the RFID tag by the RFID reader continues within a second time condition; and c) the process of including the unique identifier included in the tag information in the sensor information only if, after step b), the tag information of the RFID tag is read by the RFID reader, the product information included in the tag information matches the product information included in the sensor information, and the unique identifier included in the tag information matches the temporary unique identifier stored in the sensor head.

5. A safety sensor according to claim 2, wherein, after the completion of the initial teaching process, a reteaching process in the sensor head is only possible if the product information contained in the tag information read by the RFID reader matches the product information contained in the sensor information, the application information is high-code, and the unique identifier contained in the tag information read by the RFID reader does not match the unique identifier contained in the sensor information, and the reteaching process comprises: d) the reteaching process is continued only if the duration of reading the tag information of the RFID tag by the RFID reader is within the range of the third time condition; and e) following step d), the reteaching process is continued only if the state of being unable to read the tag information of the RFID tag by the RFID reader continues within the range of the fourth time condition. f) Following step e), the RFID reader reads the tag information of the RFID tag, and only if the duration of reading the tag information is within the range of the fifth time condition, the unique identifier included in the tag information is stored in the sensor head as a temporary unique identifier and the reteaching process continues; g) Following step f), the reteaching process continues only if the RFID reader remains unable to read the tag information of the RFID tag within the range of the sixth time condition; h) After step g), the RFID reader reads the tag information of the RFID tag, and only if the product information included in the tag information matches the product information included in the sensor information, and the unique identifier included in the tag information matches the temporary unique identifier stored in the sensor head, the unique identifier included in the sensor information is rewritten to the unique identifier included in the tag information.

6. A security sensor according to any one of claims 1 to 5, wherein the frequency band used for wireless communication between the RFID reader and the RFID tag is the HF band.

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