Physical quantity measurement system and physical quantity detection device

Abstract

[Problem] To remotely measure, with a simple configuration, a physical quantity such as the weight (load) of an object placed on a sensor or a pressure applied to the sensor. [Solution] In the present invention, a movable electrode installation member 113A and a fixed electrode installation member 114A are installed so that a movable electrode 113 and a fixed electrode 114 oppose each other between an upper plate 112 and a lower plate 115 connected by a leaf spring LS. The movable electrode installation member 113A is connected to the upper plate 112 by a connection member 116, and is connected to a pulling spring fixation member 115A of the lower plate 115 by a pulling spring 117. When the plate spring LS is deformed by a placed object and the upper plate 112 sinks, the movable electrode 113 moves following such sinking, thus changing the area of a region in which the two electrodes 113,114 oppose each other. An information processing device 30 measures the weight of a measurement object MO placed on a placement part 111 on the basis of a capacitance value of a variable capacitor 110 which depends on the area of such region, and executes processing based on the measurement result.

Description

Physical quantity measurement system and physical quantity detection device

[0001] The present invention relates to a physical quantity measurement system that detects load or pressure, and more particularly to a physical quantity measurement system that remotely detects and measures load or pressure.

[0002] Conventionally, various devices have been proposed that detect physical quantities such as load and pressure based on changes in capacitance caused by changes in the distance between two opposing electrodes, such as electronic scales that have a movable electrode disposed opposite a fixed electrode and an elastic body such as a leaf spring between the fixed electrode and the movable electrode, and detect the weight of an object placed on the movable electrode based on changes in capacitance caused by the distance between the electrodes, which changes depending on the weight (load) of the object placed on the movable electrode (e.g., Patent Documents 1 and 2).

[0003] Recently, a sensor has been proposed that is equipped with switches that have different load or pressure values ​​that serve as thresholds for on / off control, and that combines multiple RFIDs (Radio Frequency Identification) that have pre-stored data indicating the load or pressure values ​​that serve as the thresholds.When an RFID is turned on, data corresponding to the threshold is wirelessly transmitted, and the range of load or pressure applied to the sensor can be displayed at a location away from the sensor (for example, Patent Document 3).

[0004] Furthermore, recently, RFID tags equipped with an IC with a capacitance sensor function that can measure capacitance values ​​with very low power consumption have also been proposed (for example, Patent Document 4). Because RFID tags equipped with this capacitance sensor can detect capacitance with very low power consumption, they can accurately detect capacitance values ​​even when using passive drive and communication modes.

[0005] Japanese Patent Laid-Open No. 7-270219 Japanese Patent Laid-Open No. 63-2203530 Japanese Patent Laid-Open No. 2005-158018 Japanese Patent Laid-Open No. 2020-134354

[0006] However, the inventions described in Patent Documents 1 and 2 are configured to display the load and pressure detected by a sensor composed of electrodes on a display device electrically connected to the sensor, making it difficult to check physical quantities such as load and pressure at a location distant from where the sensor is installed. Furthermore, the invention described in Patent Document 3 is capable of remotely displaying and checking the load and pressure applied to the sensor, but is configured to display the range of the load and pressure applied to the sensor by combining multiple RFID tags having switches with different on / off thresholds. This not only makes the sensor more complex and larger, but also makes it difficult to properly measure the load and pressure.

[0007] The present invention has been made in consideration of the circumstances described above, and one object of the present invention is to provide a physical quantity measurement system or the like that can detect physical quantities such as the weight (load) of an object placed on a sensor or the pressure applied to the sensor with a simple configuration and perform measurement remotely.

[0008] (1) In order to solve the above-mentioned problems, the physical quantity measuring system according to the present invention is constructed by two members connected by a first elastic member in a state where they face each other, (1) a first member that is installed so as to be movable in accordance with the elastic deformation of the first elastic member when a load or pressure is applied, (2) a second member that has a fixed electrode installed at a predetermined position and is fixed so as not to move even when the load or pressure is applied to the first member, and (3) a movable electrode installation member that is connected to the first member by a connection member and has a movable electrode installed at a position opposite to the fixed electrode, and when the first elastic member elastically deforms in accordance with the state of application of the load or pressure to the first member and the first member moves, the first member The device includes: a variable capacitor whose capacitance value changes as the movable electrode installation member moves as the first member moves, causing the area of ​​the area where the movable electrode and the fixed electrode face each other and overlap to change according to the amount of movement of the first member; a capacitance sensor electrically connected to the variable capacitor and detecting the capacitance value of the variable capacitor and wirelessly transmitting corresponding detection data; and (1) a physical quantity measuring device that pre-stores reference data that defines the relationship between the value of the load or pressure applied to the first member and the capacitance value of the variable capacitor, measures the value of the load or pressure applied to the first member based on the reference data and (2) the detection data wirelessly transmitted by the capacitance sensor, and performs processing based on the measurement results.

[0009] With this configuration, in the variable capacitor constituting the physical quantity measurement system of the present invention, when a load or pressure is applied to the first member (corresponding to upper plate 112 described later) and the first elastic member (e.g., leaf springs LS1-LS4 or a coil spring described later) connecting the first member and the second member elastically deforms, the first member moves accordingly, while the second member (corresponding to lower plate 115 described later) does not move and remains fixed. As a result, the fixed electrode fixed to the second member does not move, while the movable electrode installation member connected to the first member by the connecting member moves in accordance with the movement of the first member. Therefore, the area of ​​the overlapping region between the fixed electrode fixed to the second member and the movable electrode 113 while facing each other changes according to the amount of movement of the first member. The capacitance value "C" of the variable capacitor as a parallel plate capacitor composed of the movable electrode and the fixed electrode is calculated based on Equation 1 described later and changes in proportion to the area of ​​the overlapping region between the two electrodes ("S" in Equation 1). Therefore, when a load or pressure is applied to the first member and the area "S" of the region where the two electrodes face each other and overlap changes in accordance with the amount of movement of the first member, the capacitance value "C" of the variable capacitor changes accordingly. In the physical quantity measurement system of the present invention, the capacitance sensor detects the capacitance value "C" of the variable capacitor and wirelessly transmits detection data corresponding to the detection result to the physical quantity measuring device. Meanwhile, in the present invention, the physical quantity measuring device measures the value of the load or pressure applied to the first member based on (1) reference data that is stored in advance in the device and defines the relationship between the value of the load or pressure applied to the first member and the capacitance value of the variable capacitor, and (2) the detection data wirelessly transmitted by the capacitance sensor, and executes processing based on the measurement result.

[0010] As a result, the physical quantity measurement system of the present invention can remotely measure physical quantities such as the weight of an object placed on the first member of the variable capacitor functioning as a sensor (i.e., the load applied to the first member) and the pressure applied to the first member of the variable capacitor using a physical quantity measurement device, and can perform various processes using the measurement results. Furthermore, the variable capacitor functioning as a sensor can be constructed very simply and at low cost by simply connecting the first member and a second member having a fixed electrode disposed thereon with a first elastic member, connecting a movable electrode mounting member, which is installed so that the fixed electrode and the movable electrode face each other, to the first member with a connecting member, and configuring the variable capacitor so that when the first member moves, the movable electrode mounting member moves in conjunction with this. Specific configuration examples of the variable capacitor will be described in detail later. Furthermore, in the present invention, the capacitance sensor can be configured, for example, as an RFID that can be manufactured at low cost, or as a capacitance tester with a wireless communication function, so that the capacitance value "C" of the variable capacitor, which is obtained by converting the value of the load or pressure applied to the first member of the variable capacitor (sensor), can be detected at low cost, and detection data corresponding to the detection result can be transmitted wirelessly to the physical quantity measuring device. Note that it is desirable to use reference data that has been appropriately calibrated in accordance with the characteristics of the variable capacitor, and this point will be described in detail later.

[0011] As described above, the physical quantity measurement system of the present invention has a very simple configuration and is low-cost. The physical quantity measurement device is installed at a location away from the variable capacitor functioning as a sensor. The physical quantity measurement device converts the value of a load or pressure applied to a first member into a capacitance value of the variable capacitor and acquires the value from the capacitance sensor. The physical quantity measurement device then appropriately measures the value of the load or pressure applied to the first member based on reference data previously stored therein, which defines the relationship between the capacitance value "C" of the variable capacitor and the load or pressure applied to the first member, and on detection data acquired from the capacitance sensor, and executes processing based on the measurement results. The specific processing executed by the physical quantity measurement device is arbitrary. For example, the physical quantity measurement device can (1) display the measurement results or notify the user of the measurement results using at least one of audio and / or visual information, (2) execute processing for product inventory management, or (3) execute processing for measuring the pressure values ​​applied to the first member of variable capacitors functioning as pressure sensors installed at different locations in real space and monitoring the changes in pressure at each location. This will be described in more detail below.

[0012] (2) Furthermore, in the above configuration, the movable electrode installation member may be connected by the connecting member to the first member, which is in a position where no elastic deformation occurs in the first elastic member, and may be connected to a predetermined position of the second member by a second elastic member, so that when the first elastic member elastically deforms and the first member moves, the movable electrode installation member is pulled by the second elastic member, and the area of ​​the region where the movable electrode and the fixed electrode face each other and overlap changes depending on the amount of movement of the first member.

[0013] With this configuration, the movable electrode installation member is connected to the first member by the connecting member, and is connected to a predetermined position of the second member (for example, the pull spring fixing member 115A described below) by a second elastic member (corresponding to the pull spring 117 described below), and the movable electrode installation member can be pulled by the second elastic member. Therefore, the movable electrode installation member can be moved in conjunction with the movement of the first member, and the area of ​​the region where the movable electrode and the fixed electrode face each other and overlap can be reliably changed according to the amount of movement of the first member. As a result, with this configuration, the capacitance value "C" of the variable capacitor can be reliably changed according to the amount of movement of the first member, and the value of the load or pressure applied to the first member can be measured based on the capacitance value "C."

[0014] (3) In the configuration according to claim 1 or 2, a plurality of physical quantity detection devices each composed of the variable capacitor and the capacitance sensor may be installed at different positions in real space, and the physical quantity measuring device may have a storage means for storing the reference data corresponding to each of the plurality of physical quantity detection devices in association with identification information for identifying the physical quantity detection device. The physical quantity measuring device may wirelessly acquire, from each of the capacitance sensors constituting the plurality of physical quantity detection devices, (a1) the detection data corresponding to the capacitance value of the variable capacitor constituting the corresponding physical quantity detection device, and (a2) the identification information corresponding to the physical quantity detection device, while associating the data with each other. The physical quantity measuring device may individually measure a value of the load or pressure applied to the first member of each of the physical quantity detection devices based on (b1) the detection data acquired in association with the identification information and (b2) the reference data stored in the storage means in association with the acquired identification information, and perform processing based on the measurement results.

[0015] With this configuration, when the physical quantity detection devices each composed of a variable capacitor and a capacitance sensor are installed in different positions in a real space, such as a warehouse, a store, or an indoor / outdoor exhibition hall (for example, various positions in a warehouse or various positions in a store), the physical quantity measurement system of the present invention can measure the weight or pressure applied to the first member constituting the variable capacitor of each physical quantity detection device individually with the physical quantity measurement device, and can perform centralized management. For example, when a plurality of physical quantity detection devices are installed in a facility such as a warehouse or a store (for example, installed on each shelf of a storage shelf for product inventory management or on a product pallet (also simply referred to as a "pallet") within the facility), and the inventory status of each different product is managed by each physical quantity detection device, the inventory of multiple types of products managed by each physical quantity detection device can be managed centrally with a single physical quantity measurement device.

[0016] (4) In the configuration described in claim 3, the storage means may store commodity attribute information indicating attributes of commodities whose inventory is managed using the corresponding physical quantity detection device, in association with the identification information and the reference data, and the physical quantity measuring device may measure the load applied to the first member as a weight value of the commodities whose inventory is managed using the physical quantity detection device based on the acquired detection data and the reference data corresponding to the physical quantity detection device that is the source of the detection data, and may execute a process of managing the inventory of the commodities managed using each physical quantity detection device based on the measured load and the commodity attribute information of the corresponding commodities stored in the storage means.

[0017] With this configuration, in the case where a plurality of physical quantity detection devices are installed in a facility such as a warehouse, a store, or an indoor / outdoor exhibition hall (for example, on each shelf of a storage shelf for product inventory management or on a product pallet within the facility, as described above), and the inventory of each different product is managed by each physical quantity detection device, the physical quantity measurement system of the present invention can accurately and appropriately manage the inventory status of multiple types of products using a single physical quantity measurement device, and can realize an operation form in which, for example, (a) an alert is issued when an additional order is required, or (b) an automatic ordering process is executed for the required products.

[0018] (5) In the configuration described in claim 1 or 2, the capacitance sensor may be configured as an RFID tag, and may generate an electromotive force based on electromagnetic waves transmitted by the physical quantity measuring device or another device, or a magnetic field generated by the information processing device or another device, and may detect the capacitance value of the variable capacitor using the electromotive force, and may wirelessly transmit the detection data corresponding to the detection result to the physical quantity measuring device.

[0019] With this configuration, the physical quantity measurement system of the present invention does not require a power source for the capacitance sensor, making it possible to monitor the weight or pressure value applied to the first member of the variable capacitor over a very long period of time without replacing the battery in the capacitance sensor, thereby significantly reducing the initial cost of building the system and the running cost of operating the system.

[0020] (6) In the configuration of claim 1 or 2, the variable capacitor is rotatably connected to (a1) the first member and (a2) the second member, or is rotatably connected to (b1) a first frame link fixed to the first member and (b2) a second frame link fixed to the second member, and is provided in parallel with the first elastic member, and two connecting arm links having the same length connect (a) the first member and the second member to each other, or (b) the first frame link and the second frame link to each other, so that (A) the first and second members, or (B) the first and second frame links and the two connecting arm links A parallel link mechanism is constructed in which a parallelogram is formed by four connection points to which the frame links are connected and members that constitute the sides formed by each connection point, and when the first elastic member elastically deforms in accordance with the state of the load or pressure applied to the first member or the first frame link, the first member or the first member fixed to the first frame link moves while remaining parallel to the second member, causing the movable electrode installation member to move, and the area of ​​the region where the movable electrode and the fixed electrode face each other and overlap changes in accordance with the amount of movement of the first member or the first member fixed to the first frame link, thereby changing the capacitance value.

[0021] With this configuration, the variable capacitor in the physical quantity detection system of the present invention (a) directly connects the first member and the second member in a rotationally movable state via two connecting arm links, thereby forming a parallel link mechanism between the first and second members and the two connecting arm links, or (b) constructs a parallel link mechanism between the first and second frames and the two connecting arm links. In the variable capacitor in the physical quantity detection system of the present invention, even when a load or pressure is applied to the first member or the first frame link fixed thereto, the second member or the second frame link fixed thereto does not move. Meanwhile, the first member connected thereto via two connecting links, or the first member fixed to the first frame link, moves while remaining parallel to the second member when the first elastic member elastically deforms in response to the applied load or pressure. As a result, the movable electrode constituting the variable capacitor moves in accordance with the movement of the first member, changing the area of ​​the overlapping region between the fixed electrode and the movable electrode while facing each other, thereby changing the capacitance value.

[0022] In this configuration, the physical quantity measuring device can measure the value of the load or pressure applied to the first member or the first frame link fixed to the first member based on pre-stored (1) reference data defining the relationship between the value of the load or pressure applied to the first member and the capacitance value of the variable capacitor, or calibrated reference data obtained by calibrating the reference data in accordance with the characteristics of the variable capacitor when the variable capacitor is installed, and the detection data wirelessly transmitted by the capacitance sensor. In particular, the parallel link mechanism constructed in this configuration, like a Roberval mechanism, moves while maintaining parallelism with the second member or the second member fixed to the second frame link regardless of where a load or pressure is applied to the first member or the first frame link. Therefore, with this configuration, even if a load or pressure is concentrated near an end of the first member or the first frame link fixed thereto, and the load or pressure is concentrated only on some of the first elastic members that make up the variable capacitor, the load or pressure can be applied evenly to all of the first elastic members, and the value of the load or pressure applied to the first member or the first frame link can be measured with high accuracy. Note that when the first member is fixed to the first frame link, the value of the load or pressure applied to the first frame link is equal to the load or pressure applied to the first member itself, so the two can be treated equally.

[0023] (7) The physical quantity detection device of the present invention is constructed of two members connected by a first elastic member in a state where they face each other, the first member being movable in response to elastic deformation of the first elastic member when a load or pressure is applied to the first member, (2) a fixed electrode being installed at a predetermined position and being fixed so as not to move even when the load or pressure is applied to the first member, and (3) a movable electrode installation member being connected to the first member by a connecting member and having a movable electrode installed at a position opposite to the fixed electrode, and when the first elastic member is elastically deformed in response to the state of application of the load or pressure to the first member and the first member moves, the movable electrode installation member moves in response to the movement of the first member. The capacitance sensor is a variable capacitor in which the area of ​​the overlapping region between the movable electrode and the fixed electrode facing each other changes according to the amount of movement of the first member, thereby changing the capacitance value, and is electrically connected to the variable capacitor and detects the capacitance value of the variable capacitor to generate corresponding detection data, and the capacitance sensor comprises: (1) reference data that defines the relationship between the value of the load or pressure applied to the first member and the capacitance value of the variable capacitor, and the reference data is stored in advance; and (2) the capacitance sensor measures the value of the load or pressure applied to the first member based on the detection data generated by the capacitance sensor and wirelessly transmits the generated detection data to a physical quantity measuring device that performs processing based on the measurement results.

[0024] With this configuration, the physical quantity detection device of the present invention can convert a load or pressure applied to the first member of the variable capacitor functioning as a sensor into a capacitance value using the variable capacitor and wirelessly transmit the corresponding detection data to the physical quantity measuring device using the capacitance sensor. Meanwhile, the physical quantity measuring device can measure the value of the load or pressure applied to the first member based on the detection data wirelessly transmitted from the physical quantity detection device, while using reference data that is stored in advance in the device and defines the relationship between the value of the load or pressure applied to the first member and the capacitance value of the variable capacitor. Note that, as in the case of a physical quantity measurement system, it is desirable to use reference data that has been appropriately calibrated in accordance with the characteristics of the variable capacitor; this point will be described in detail later.

[0025] As a result, the physical quantity detection device of the present invention can remotely measure physical quantities such as the weight (load) of an object placed on the first member of the variable capacitor functioning as a sensor or the pressure applied to the first member of the variable capacitor using a physical quantity measuring device, and can perform various processes using the measurement results in the physical quantity measuring device. Furthermore, the variable capacitor functioning as a sensor can be constructed very simply and inexpensively by connecting the first member and a second member having a fixed electrode via a first elastic member, connecting a movable electrode mounting member, which is installed so that the fixed electrode and the movable electrode face each other, to the first member via a connecting member, and configuring the variable capacitor so that the movable electrode mounting member moves in conjunction with movement of the first member. Furthermore, the capacitance sensor can be configured, for example, as an RFID (preferably a passive type) that can be manufactured at low cost, or as a capacitance tester with wireless communication capabilities. Therefore, the capacitance value "C" of the variable capacitor, which is obtained by converting the value of the load or pressure applied to the first member of the variable capacitor (sensor), can be detected at low cost and the detection result can be wirelessly transmitted to the physical quantity measuring device. Therefore, the physical quantity detection device of the present invention can measure the value of the load or pressure applied to the first member of the variable capacitor functioning as a sensor using a physical quantity measuring device installed at a location away from the installation location of the variable capacitor functioning as a sensor, with a very simple configuration and at low cost, and can perform processing using the measurement results.

[0026] The physical quantity measurement system according to the present invention can detect physical quantities such as the weight (load) of an object placed on a sensor or the pressure applied to a sensor with a simple configuration, and can measure these quantities remotely.

[0027] 1 is a system configuration diagram illustrating an example of the configuration of a weight measurement system according to a first embodiment; FIG. 2 is a diagram illustrating the principle of detecting the weight of a measurement object in the weight detection device according to the first embodiment, in which (A) shows the weight detection device and the variable capacitor when no measurement object is placed (i.e., when the placed weight is "0 kg"), as viewed from the "X" direction in FIG. 3; (B) shows the weight detection device and the variable capacitor when a small measurement object (e.g., weighing "1 kg") is placed, as viewed from the same direction; and (C) shows the weight detection device and the variable capacitor when a large measurement object (e.g., weighing "2 kg") is placed, as viewed from the same direction. This is a perspective view of the weight detection device according to the first embodiment, as viewed from the "X" direction in FIG. 3; and FIG. 3 is a side view of the weight detection device according to the first embodiment, as viewed from the "X" direction in FIG. 3, similar to FIG. 2. This is a perspective view of the weight detection device according to the first embodiment, as viewed from the bottom side. 1 is an enlarged view of an electrode portion constituting a variable capacitor of a first embodiment, in which (A) is a perspective view of the electrode portion as seen from the top side of a weight detection device, and (B) is a perspective view of the electrode portion as seen from the bottom side of the weight detection device. FIG. 2 is a diagram showing an example of data storage in a product inventory management database (hereinafter also referred to as "DB") stored in a storage unit of an information processing device of a second embodiment. FIG. 3 is a flowchart showing processing executed by the information processing device of the second embodiment. FIG. 4 is a device configuration diagram showing the configuration of a weight detection device according to a fifth variation of the physical quantity weight detection device of the present invention, in which (A) shows the state of the weight detection device when no measurement object is placed thereon, and (B) shows the state of the weight detection device when a measurement object of a predetermined weight is placed thereon.

[0028] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are examples in which a physical quantity measurement system according to the present invention is applied to a system for measuring the weight (i.e., load) of an object to be measured. However, the embodiments described below do not unduly limit the scope of the present invention as defined in the claims, and not all of the configurations described in the following embodiments are necessarily essential components of the present invention. Furthermore, while the embodiments described below will be described using an example in which the weight of a measurement object is measured, the physical quantity measured by the physical quantity measurement system of the present invention is arbitrary, and the system can also be applied to measuring physical quantities other than the weight of a measurement object, such as pressure. Strictly speaking, "weight" and "mass" are essentially different concepts. However, mass and weight can be converted by multiplying or dividing by the gravitational acceleration. Therefore, in this application, measuring "weight" and measuring "mass" are considered equivalent. Furthermore, the units of weight are normally "N (Newton)", "gf (gram force)", "kgf (kilogram force)", etc., but in this specification, to make the invention easier to understand, they will be simply expressed as "g (gram)" and "kg (kilogram)".

[0029] [A] First Embodiment [A1] Overall Configuration and Overview of Weight Measurement System 1 First, the configuration and overview of a weight measurement system 1 of this embodiment will be described with reference to Fig. 1. Fig. 1 is a system configuration diagram showing an example of the configuration of the weight measurement system 1 of this embodiment.

[0030] 1 , a weight measurement system 1 of this embodiment includes: (a1) a weight detection device 10 having a mounting portion 111 for mounting an object (hereinafter also referred to as a “measurement object MO”) whose weight is to be measured; (a2) a capacitance sensor tag 120 electrically connected to the variable capacitor 110 and detecting the capacitance value of the variable capacitor 110; (b) an RFID reader / writer 20; and (c) an information processing device 30 such as a PC (personal computer), smartphone, or tablet-type information communication terminal device. The weight measurement system 1 of this embodiment converts the weight (load) of the measurement object MO mounted on the mounting portion 111 into a capacitance value using the variable capacitor 110, measures the weight of the measurement object MO using the information processing device 30 based on the capacitance value, and notifies or manages the measurement result to a user using at least one of audio and images. For example, the weight detection device 10 and the information processing device 30 of this embodiment constitute the "physical quantity detection device" and the "physical quantity measurement device" of the present invention, respectively.

[0031] Here, in the conventional capacitance-type electronic scales and sensors (e.g., Patent Documents 1 and 2), weight and pressure detected by a parallel-plate capacitor sensor composed of a fixed electrode and a movable electrode arranged opposite to each other are displayed on a display device electrically connected to the sensor. This makes it difficult to confirm or manage physical quantities, such as the weight of a measurement object or the pressure applied to the sensor, at a location distant from the sensor's installation location. On the other hand, the configuration described in Patent Document 3 wirelessly transmits physical quantities, such as load and pressure applied to the sensor, for remote display, confirmation, and management. However, the sensor is configured by combining multiple RFID tags equipped with switches with different on / off thresholds, and detects the range of load and pressure applied to the sensor. Therefore, the method described in Patent Document 3 not only requires a complex and large sensor, but also requires an increased number of switches and RFID tags to measure loads and pressures precisely, further increasing the complexity and size of the device, making it difficult to manufacture the device at low cost.

[0032] Therefore, in the weight measurement system 1 of this embodiment, a mounting section 111 is provided, and one capacitance sensor tag 120 configured as a passive RFID is electrically connected to a variable capacitor 110 that functions as a load sensor to configure the weight detection device 10. Then, an electromagnetic wave, for example, in the UHF (Ultra High Frequency) band, is supplied from the RFID reader / writer 20 to the capacitance sensor tag 120, and the capacitance sensor tag 120 generates an electromotive force based on the electromagnetic wave, detects the capacitance value of the variable capacitor 110 using the electromotive force, and wirelessly transmits the corresponding detection data to the RFID reader / writer 20. In addition, if the capacitance sensor tag 120 and the RFID reader / writer 20 transmit and receive signals in the HF (High Frequency) band, for example, the capacitance sensor tag 120 generates an electromotive force based on the magnetic field generated by the RFID reader / writer 20, measures the capacitance value of the variable capacitor 110 using the electromotive force, and transmits corresponding detection data to the information processing device 30.

[0033] In the present embodiment, the information processing device 30 measures the weight of the measurement object MO placed on the mounting unit 111 based on the detection data acquired from the capacitance sensor tag 120 via the RFID reader / writer 20 and the measurement reference data previously stored in the device, and notifies the user of the measurement result using at least one of audio and images, or executes processing to manage the measurement result. Note that, for example, the measurement reference data in this embodiment corresponds to the "reference data" of the present invention, and this measurement reference data will be described in detail later. With this configuration, the user can check the weight of the measurement object MO using the information processing device 30 installed at a location remote from the weight detection device 10, and the information processing device 30 installed at a location remote from the weight detection device 10 can also manage weight changes of the measurement object MO placed on the mounting unit 111. As a result, this configuration can realize a usage scenario in which the inventory count of products placed on inventory management shelves, etc., installed in a facility such as a warehouse, a store, or an indoor or outdoor exhibition hall can be managed by the information processing device 30 installed in a control room or office inside or outside the warehouse or store. In this embodiment, the information processing device 30 is installed in a control room or office inside or outside the warehouse, and weight detection devices 10 are installed on inventory management shelves, inventory management pallets, storage boxes, storage baskets, etc., installed in the facility such as a warehouse, store, or exhibition hall, thereby realizing a function of managing product inventory stored and managed in the facility such as a warehouse. However, the specific processing content executed by the information processing device 30 based on the measurement results is arbitrary. For example, the information processing device 30 may simply display the measurement results of the weight of the measurement object MO, or may notify the user of the measurement results using at least one of audio and images.Furthermore, the number of weight detection devices 10 managed by the information processing device 30 is arbitrary, and a configuration in which multiple weight detection devices 10 are centrally managed by a single information processing device 30 to centrally manage the inventory of multiple types of products may be adopted. However, in this embodiment, to facilitate understanding of the invention, an example is described in which only one weight detection device 10 is managed by the information processing device 30 and the weight detection device 10 is used to manage the inventory of only one type of product. A method in which multiple weight detection devices 10 are managed by a single information processing device 30 and the inventory of multiple types of products managed in a facility is centrally managed by a single information processing device 30 will be described in the second embodiment. Furthermore, the capacitance sensor tag 120 may be of any of the active, passive, semi-active, and semi-passive drive types. However, in this embodiment, a passive drive type is described as being used, and cases in which an active or semi-active drive type is used will be described in the modified examples. This configuration eliminates the need to provide a power source to the capacitance sensor tag 120, allowing the weight of the measurement object MO placed on the placement unit 111 to be measured, managed, and monitored over a very long period of time without the need to replace the battery in the capacitance sensor tag 120. As a result, the weight measurement system 1 of this embodiment can significantly reduce the initial cost of building the system and the running cost of operating the system. Furthermore, this configuration eliminates the need to provide a power source to the capacitance sensor tag 120, allowing the weight of the measurement object MO to be measured without being affected by the ambient temperature during use (also referred to as the "usage environment temperature"). As a result, the weight measurement system 1 of this embodiment can perform inventory management of products in a freezer warehouse at very low cost, even in situations where the weight detection device 10 is installed in a freezer warehouse at a temperature of approximately -22°C to manage the inventory of products stored there.

[0034] [A2] Specific Configuration of Weight Detection Device 10 and Weight Measurement Principle Next, the specific configuration and weight measurement principle of the weight detection device 10 of this embodiment will be described with reference to Figures 1 to 7. Note that Figure 2 is a diagram illustrating the principle of detecting the weight of a measurement object MO in the weight detection device 10 of this embodiment, where (A) shows the weight detection device 10 and variable capacitor 110 when no measurement object MO is placed (i.e., when the placed weight is "0 kg"), as viewed from the direction "X" in Figure 3; (B) shows the weight detection device 10 and variable capacitor 110 when a small measurement object MO (e.g., weighing "1 kg") is placed, as viewed from the same direction; and (C) shows the weight detection device 10 and variable capacitor 110 when a large measurement object MO (e.g., weighing "2 kg") is placed, as viewed from the same direction. Furthermore, the weight detection device 10 shown in each figure in Figure 2 has the same configuration as that in Figure 1, but to prevent the figures from becoming too complicated, components that are not necessary for explaining the measurement principle (for example, some of the leaf springs LS1 to LS4 described later) have been omitted from those shown in Figure 1. 3 to 7 are diagrams each showing the configuration of the weight detection device 10 of this embodiment, (1) FIG. 3 is an oblique view of the weight detection device 10 as seen from the top side (i.e., the side of the upper plate 112 described later), (2) FIG. 4 is a top view of the weight detection device 10, (3) FIG. 5 is a side view of the weight detection device 10 as seen from the direction of "X" in FIG. 3, similar to FIG. 2, (4) FIG. 6 is an oblique view of the weight detection device 10 as seen from the bottom side (i.e., the side of the lower plate 115 described later), and (5) FIG. 7 is an enlarged view of the electrode portion constituting the variable capacitor 110 of this embodiment, with (A) being an oblique view of the electrode portion as seen from the top side of the weight detection device 10, and (B) being an oblique view of the electrode portion as seen from the bottom side of the weight detection device 10. In Figures 3 to 7, in order to simplify the drawings and make them easier to understand, an example configuration of the weight detection device 10 and variable capacitor 110 is shown in a state in which the mounting portion 111 is not provided, but the mounting portion 111 will be provided on the upper plate 112 of the weight detection device 10 and variable capacitor 110 that are actually manufactured and operated.In this case, the shape of the mounting portion 111 is arbitrary, and in addition to the shapes shown in Figures 1 and 2, a box-shaped or basket-shaped mounting portion may also be used. Furthermore, the mounting portion 111 may be configured in the shape of a box or basket for product inventory management, and the weight detection device 10 may be configured in the shape of a pallet to serve as a mounting base for the box or basket.

[0035] 1 to 3, the weight detection device 10 of this embodiment has a configuration in which four metal Z-shaped leaf springs LS1 to LS4 (hereinafter, referred to as "leaf springs LS" unless otherwise specified) that function as first elastic members are sandwiched in parallel between an upper plate 112 that is provided with a mounting portion 111 for mounting a measurement object MO whose weight is to be measured, and a lower plate 115 that is fixed to a floor, a desk, the side panel of a shelf, etc. The specific materials for the upper plate 112 and the lower plate 115 are arbitrary, and for example, synthetic resins such as PP (polypropylene) and PE (polyethylene) can be used, as well as insulating substrates such as FR4 (Flame Retardant Type 4). However, in the weight detection device 10 of this embodiment shown in FIGS. 3 to 7, a configuration example is shown in which the upper plate 112 and the lower plate 115 are made of transparent acrylic resin (PMMA: Polymethyl methacrylate) so that the device configuration can be clearly seen.

[0036] 3, 4, and 6, the leaf springs LS1 to LS4 installed between the upper plate 112 and the lower plate 115 in the weight detection device 10 of this embodiment are arranged so as to be located in areas near the four corners of the upper plate 112 and the lower plate 115, respectively, and are fixed to the upper plate 112 and the lower plate 115 by fixing means such as double-sided tape or adhesive (not shown). As a result, in this embodiment, the upper plate 112, which corresponds to the first member, and the lower plate 115, which corresponds to the second member, are mutually connected by the four leaf springs LS1 to LS4, and a configuration is achieved in which the upper plate 112 is prevented from shifting during measurement, resulting in inaccurate measurement results. With this configuration, in the weight detection device 10 of this embodiment, when a measurement object MO is placed on the placement portion 111, (a) the lower plate 115, which is fixed to an immovable object such as the floor, the top of a desk, or the side panel of a storage shelf, does not move, while (b) the leaf springs LS1-4 sandwiched between the upper plate 112 and the lower plate 115 contract (i.e., elastically deform) in accordance with the weight of the measurement object MO placed on the placement portion 111, and the upper plate 112 moves toward the lower plate 115 (i.e., sinks downward in the drawings in FIGS. 1 and 2 ) in accordance with the weight of the measurement object MO placed on the placement portion 111. Note that, for example, the upper plate 112 and the lower plate 115 of this embodiment respectively constitute the "first member" and the "second member" of the present invention, and the leaf spring LS constitutes the "first elastic member."

[0037] Here, as a characteristic feature of this embodiment, the weight detection device 10 of this embodiment is provided, in a region near the center thereof, with (1) a fixed electrode mounting member 114A on which a fixed electrode 114 made of a metal (e.g., copper) and approximately several tens of micrometers (μm) thick, and configured from a copper-clad substrate such as FR4, and (2) a movable electrode mounting member 113A on which a movable electrode 113, configured from the same metal as the fixed electrode 114, is mounted, as shown in Figures 1 to 7. Note that Figure 7 shows an enlarged view of the periphery of the two mounting members 113A and 114A to facilitate understanding of the configurations of the movable electrode mounting member 113A on which the movable electrode 113 is mounted and the fixed electrode 114 on which the fixed electrode 114 is mounted. In the weight detection device 10 and variable capacitor 110 of this embodiment, the fixed electrode mounting member 114A and the movable electrode mounting member 113A are mounted so that the fixed electrode 114 and the movable electrode 113 face each other, as shown in Figures 1 and 2. The fixed electrode installation member 114A is fixed to a predetermined position on the lower plate 115 by a fixing means (not shown), such as an adhesive or double-sided tape, and is configured not to move even when the measurement object MO is placed on the mounting portion 111 and the upper plate 112 moves downward in the drawing. Note that the fixed electrode 114 may be configured such that the fixed electrode installation member 114A is provided separately from the lower plate 115 and this fixed electrode installation member 114A is fixed to a predetermined position on the lower plate 115, as in the weight detection device 10 and variable capacitor 110 of this embodiment shown in Figures 1 to 7 , or the fixed electrode 114 may be formed directly in a predetermined area on the lower plate 115 without providing the fixed electrode installation member 114A, or may be installed by a method such as attaching a metal fixed electrode 114 directly to the lower plate 115. However, in this embodiment, the description will be given assuming a configuration in which the fixed electrode installation member 114A on which the fixed electrode 114 is installed is installed at a predetermined position on the lower plate 115, as exemplified in Figures 1 to 7 .

[0038] Meanwhile, in the weight detection device 10 or the variable capacitor 110 of this embodiment, the movable electrode installation member 113A is connected near one end (i.e., the left end in FIGS. 1 and 2 , the upper end in FIG. 4 ) to a pull spring fixing member 115A provided near the left end of the lower plate 115 by a pull spring 117, and is installed in a state in which it can move (slide) freely in the left-right direction in FIGS. 1 and 2 (up-down direction in FIG. 4 ). One end of a flexible string- or ribbon-shaped connecting member 116 such as a fishing line or polyimide ribbon is fixed to the end of the movable electrode installation member 113A opposite to the end (the left end in FIGS. 1 and 2 , the upper end in FIG. 4 ) where the pull spring 117 is fixed (see FIGS. 7A and 7B ). The other end of the connecting member 116 is connected to the upper plate 112 as illustrated in FIGS. 4 , 5 , and 7A . 3, 4, 5, and 7A, the vicinity of one end of this connecting member 116 is fixed to the upper plate 112 and is installed in a state of hanging down vertically from the upper plate 112, and the orientation of the member is changed horizontally (specifically, left-right direction in FIGS. 1 and 2, and up-down direction in FIG. 4) by changing the orientation of the member along the direction changing member 115B, and the vicinity of the end opposite the side fixed to the upper plate 112 is fixed to the vicinity of the right end of the movable electrode installation member 113A in FIGS. 1 and 2 as described above. In addition, the length of the connecting member 116 is set so that the position of the movable electrode 113 is at a predetermined initial position (see FIG. 2A) when the connecting member 116 is in a state where there is no slack in the upper plate 112 when the upper plate 112 is in a position (hereinafter also referred to as the "upper plate initial position") when the measurement object MO is not placed on the placement part 111 (see FIG. 2A). For example, the pull spring 117 of this embodiment corresponds to the "second elastic member" of the present invention, and the pull spring fixing member 115A corresponds to the "predetermined position of the second member."

[0039] In this embodiment, the spring constant of the tension spring 117 is set to be sufficiently small relative to the composite spring constant of the leaf springs LS1 to LS4. Therefore, even when the measurement object MO (for example, in this embodiment, a product whose inventory is managed using the weight detection device 10) is not placed on the placement unit 111 and the upper plate 112 is in its initial position, the tension spring 117 pulls the upper plate 112, causing the leaf springs LS1 to LS4 to contract, and the influence of the tension spring 117 causing the upper plate 112 to sink downward in FIGS. 1 and 2 is negligibly small. For this reason, in the weight detection device 10 or variable capacitor 110 of this embodiment, when the measurement object MO is not placed on the mounting portion 111, the upper plate 112 has its initial position determined based on the average spring length "x1" of the leaf springs LS1 to LS4 when the mounted weight is "0 kg," which is determined by a combination of factors such as the effect of the leaf springs LS1 to LS4 slightly shortening from their initial lengths due to the weight of the upper plate 112 including the mounting portion 111, and the spring constant of the tension spring 117 relative to the composite spring constant of the leaf springs LS1 to LS4. As a result, when the measurement object MO is not placed on the mounting portion 111, the upper plate 112 does not move from its initial position, and only when the measurement object MO is placed does the leaf springs LS1 to LS4 elastically deform, causing the upper plate 112 to sink downward as shown in FIGS. 1 and 2 , changing its position. Furthermore, in the weight detection device 10 or variable capacitor 110 of this embodiment, as described above, the spring constant of the pull spring 117 is sufficiently small compared to the composite spring constant of the leaf springs LS1 to LS4. Therefore, even if the movable electrode installation member 113A is pulled to the left in Figures 1 and 2 by the pull spring 117, the leaf springs LS1 to LS4 will not be elastically deformed due to the influence of the pulling force, causing the upper plate 112 to sink downward in the figure, and the movable electrode installation member 113A will not move to the left in Figures 1 and 2 from its initial position. Only when the measurement object MO is placed on the mounting portion 111, the leaf springs LS1 to LS4 will be elastically deformed, causing the upper plate 112 to sink downward in Figures 1 and 2 will the movable electrode installation member 113A be pulled to the left in Figures 1 and 2 by the pull spring 117.

[0040] Specifically, when the measurement object MO is placed on the mounting portion 111, the leaf springs LS1 to LS4 elastically deform, causing the upper plate 112 to sink downward in FIGS. 1 and 2. At this time, the connecting member 116 slackens by the amount that the upper plate 112 sinks. For example, assume that a light measurement object MO is placed on the mounting portion 111 as shown in FIG. 2B, causing the leaf springs LS1 to LS4 to contract and the average spring length to become "x2." In this case, the connecting member 116, which connected the upper plate 112 and the movable electrode mounting member 113A without slack when the average spring length of the leaf springs LS1 to LS4 was "x1," slackens by "Δx1 = x1 - x2." For example, suppose weight detection device 10 is configured using four leaf springs LS1-LS4 with an initial length of 20.00 mm. When the average spring length "x1" is 19.00 mm when a 0 kg load is placed on the device, the average spring length "x2" becomes 12.00 mm when a 1 kg product or weight is placed on the device. In this case, the average spring length of leaf springs LS1-LS4 changes from 19.00 mm to 12.00 mm, resulting in a change in the average spring length "Δx1" of approximately 7 mm (i.e., Δx1 = x1 - x2 = 19.00 mm - 12.00 mm). At this time, upper plate 112 sinks downward by approximately 7 mm from its initial position, creating approximately 7 mm of slack in connecting member 116. 1 and 2 by the pull spring 117, the movable electrode installation member 113A moves (slides) leftward by approximately "7 mm." As a result, in this example, the region where the fixed electrode 114 and the movable electrode 113 face each other and overlap changes by approximately "7 mm," and the area of ​​the facing and overlapping region changes from the initial area "S1" (i.e., the area value of the region where the movable electrode 113 and the fixed electrode 114 face each other and overlap when the average spring length of the leaf springs LS1 to LS4 is "x1" and the movable electrode installation member 113A is in the initial position) to "S2."In the actual weight detection device 10, factors such as the weight of the mounting portion 111 and the upper plate 112 and the influence of the tension spring 117 act in combination, causing the leaf springs LS1-LS4 to slightly shorten from their initial lengths (e.g., 20.00 mm), as in the above example, and the average spring length "x1" of the leaf springs LS1-LS4 to be slightly smaller than the initial length of the leaf springs LS1-LS4 (in the above example, "x1 = 19.00 mm" for an initial length of "20.00 mm"). In this embodiment, the length of the connecting member 116 is adjusted so that the upper plate 112 in this initial position (upper plate initial position) and the movable electrode installation member 113A are connected together without slack. The specific method for installing the movable electrode installation member 113A having the movable electrode 113 provided thereon, the fixed electrode installation member 114A having the fixed electrode 114 provided thereon, the pull spring 117, and the direction change member 115B on the variable capacitor 110 between the upper plate 112 and the lower plate 115 is arbitrary. The fixed electrode installation member 114A may be fixed to a predetermined position on the lower plate 115 using adhesive, double-sided tape, or the like, and the movable electrode installation member 113A may be installed so that it can move (slide) in the left-right direction in Figures 1 and 2 using a guide rail or the like, with the pull spring 117 fixed near one end and the connecting member 116 fixed near the other end, and the fixed electrode installation member 114A may be connected to the pull spring fixing member 115A provided on the lower plate 115 by the pull spring 117, while the fixed electrode installation member 114A may be connected to the upper plate 112 by the connecting member 116 and installed so as not to shift between the lower plate 115. The direction-changing member 115B may be fixed to the lower plate 115, but in this embodiment, the following method is adopted for the description.

[0041] (1) First, a hole for forming the cavity region 115C is bored in a predetermined area near the center of a thick acrylic plate, for example, approximately 3 to 5 mm thick. A groove for accommodating the extension spring 117 is also bored in part of the cavity region 115C. This hole is created by processing the thick acrylic plate while adjusting its position to match the desired installation positions of the movable electrode installation member 113A and the fixed electrode installation member 114A. This thick acrylic plate is sandwiched between two thin acrylic plates, for example, approximately 0.5 mm thick, to form the triple-layered lower plate 115. The movable electrode installation member 113A and the fixed electrode installation member 114A are then placed inside the cavity region 115C, which is formed by the two thin acrylic plates and the hole corresponding to the cavity region 115C (see Figures 3, 4, 6, and 7). In this case, the size of the hole in the thick acrylic plate is set so that the size of the hollow region 115C can accommodate both (a) the fixed electrode installation member 114A installed inside the hollow region 115C and (b) the movable electrode installation member 113A, and so that the movable electrode installation member 113A can move within the hollow region 115C even when the movable electrode installation member 113A moves (slides) a maximum amount in the left-right direction in the drawing depending on the weight of the measurement object MO placed on the mounting portion 111. (2) In the hollow region 115C formed by sandwiching the thin acrylic plates, the fixed electrode installation member 114A is fixed with adhesive or double-sided tape to the thin acrylic plate that forms the bottom side of the weight detection device 10 (i.e., the surface of the lower plate 115 that is fixed to a fixed object). Furthermore, a pull spring fixing member 115A is installed at the end of the area of ​​the thin acrylic plate on the bottom side that overlaps the groove that accommodates the pull spring 117, and the end of the pull spring 117 opposite the end that is fixed to the movable electrode installation member 113A is fixed to this pull spring fixing member 115A. In this way, the pull spring 117 connects the movable electrode installation member 113A to the pull spring fixing member 115A of the lower plate 115. (3) With the fixed electrode 114 and the movable electrode 113 facing each other, the movable electrode installation member 113A is installed on the fixed electrode installation member 114A (see Figures 1, 2 and 7), and another thin acrylic plate is adhered to the top of it to form the lower plate 115.With this configuration, the movable electrode installation member 113A provided with the movable electrode 113 and the fixed electrode installation member 114A provided with the fixed electrode 114 are sealed and installed within the hollow region 115C with the electrodes 113 and 114 facing each other. (4) A hole for passing the connecting member 116 is previously formed in the thin acrylic plate on the upper surface of the lower plate 115, and the connecting member 116 fixed to the right end of the movable electrode installation member 113A is pulled out to the upper side of the lower plate 115 through this hole and fixed to the upper plate 112 (see FIG. 7A). With this configuration, the direction changing member 115B is formed by this hole and the thin acrylic plate on the upper surface of the lower plate 115. (5) The vertical height of the hollow region 115C is set to a value obtained by adding the thickness (approximately 3 to 4 mm) of the movable electrode installation member 113A and the fixed electrode installation member 114A, including both electrodes 113 and 114, plus the thickness of an adhesive or the like (approximately 100 μm), plus the inter-electrode distance "d" (for example, approximately 1 mm), and the thin acrylic plate on the upper surface is bonded to the thick acrylic plate with an adhesive or by heat so that the thin acrylic plate does not shift. With this method, the variable capacitor 110 can be constructed by enclosing the movable electrode installation member 113A and the fixed electrode installation member 114A inside the hollow region 115C with both electrodes 113 and 114 facing each other so that the inter-electrode distance "d" remains constant even when the movable electrode installation member 113A moves (slides) in the left-right direction in Figures 1 and 2.

[0042] 2C , assume that a heavy weight measurement object MO (e.g., a measurement object MO weighing approximately 2 kg) is placed on the mounting portion 111, and the average spring length "x3" of the leaf springs LS1-LS4 at this time is 5.00 mm. In this case, the average spring length of the leaf springs LS1-LS4 changes from 19.00 mm to 5.00 mm, and the change in the average spring length "Δx2" of the leaf springs LS1-LS4 is approximately 14 mm (i.e., Δx2 = x1 - x3 = 19.00 mm - 5.00 mm). At this time, the upper plate 112 sinks downward by approximately 14 mm from its initial position in FIGS. 1 and 2, and the connecting member 116 sags by approximately 14 mm. 1 and 2 by the pull spring 117, the movable electrode installation member 113A moves (slides) leftward by approximately 14 mm. As a result, in this example, the area of ​​the region where the fixed electrode 114 and the movable electrode 113 face each other and overlap changes from the initial value "S1" to "S3."

[0043] On the other hand, when the measurement object MO is removed from the mounting portion 111, the average spring length of the leaf springs LS1 to LS4 returns to its original length "x1", and the upper plate 112 returns to its initial position, the movable electrode installation member 113A is also pulled to the right in Figures 1 and 2 and returns to its initial position, and the area of ​​the overlapping region of both electrodes 113 and 114 also returns from "S2" or "S3" to "S1".

[0044] In the weight detection device 10 having the above configuration, the fixed electrode 114 installed on the fixed electrode installation member 114A and the movable electrode 113 installed on the movable electrode installation member 113A are positioned opposite each other with a distance "d" as shown in Figures 1 and 2, and the two electrodes 113 and 114 function as a parallel plate capacitor. Meanwhile, the electrostatic capacitance value "C" of the parallel plate capacitor can generally be calculated based on the following (Equation 1).

[0045]

[0046] In (Equation 1), "d" is the inter-electrode distance between the movable electrode 113 and the fixed electrode 114, and "S" is the area of ​​the overlapping region of the movable electrode 113 and the fixed electrode 114, which function as a parallel plate capacitor. In the above example, the value of the area "S" will vary from "S1" to "S3" depending on the weight of the measurement object MO placed on the placement portion 111 as described above (for example, in this embodiment, the total weight of the products whose inventory is managed using the weight detection device 10). Furthermore, depending on the setting values ​​of parameters such as (a) the position at which the fixed electrode mounting member 114A is installed on the lower plate 115, (b) the length of the connecting member 116, and (c) the average spring length "x1" which is determined depending on the initial length of the leaf springs LS1 to LS4, it is also possible to set "S1", which is the area of ​​the overlapping region of both electrodes 113 and 114 when the loaded weight is "0 kg", to be the maximum value of the area of ​​the overlapping region of both electrodes 113 and 114, and "S3", which is the area of ​​the overlapping region of both electrodes 113 and 114 when a heavy measurement object MO (e.g., "2 kg") is placed, to be the minimum value of the area of ​​the overlapping region of both electrodes 113 and 114. However, in this embodiment, as shown in Figure 2, when the loaded weight is "0 kg", the area "S1" of the overlapping region of both electrodes 113 and 114 is the minimum value of the area "S", and as the weight of the measurement object MO placed on the loading section 111 increases, the area "S" of the overlapping region of both electrodes 113 and 114 increases, and the parameters such as the installation position of the fixed electrode installation member 114A will be described. Also, in (Equation 1), "ε" represents the dielectric constant of the dielectric filled between both electrodes 113 and 114, and when air is filled between both electrodes 113 and 114, the dielectric constant of a vacuum, "ε" ０ = 8.85 x 10 －１２ (F / m) (i.e., the relative dielectric constant is 1.0006, which is approximately 1).

[0047] On the other hand, as shown in Equation 1, the capacitance value "C" of the variable capacitor 110 is affected by the inter-electrode distance "d" between the two electrodes 113 and 114. Therefore, even a slight change in the inter-electrode distance "d" during system operation will result in a change in the capacitance value "C" of the variable capacitor 110. As described above, by sandwiching the lower plate 115 to form a hollow region 115C within the lower plate 115 and installing the movable electrode installation member 113A and the fixed electrode installation member 114A therein, it is possible to prevent the inter-electrode distance "d" from changing significantly during system operation. However, it is more preferable to sandwich a member with a uniform thickness and good slipperiness, such as fluororesin tape, between the movable electrode 113 and the fixed electrode 114 to prevent the inter-electrode distance "d" from changing. In this case, a dielectric material other than air, such as a polyimide ribbon, is filled between the electrodes 113 and 114. Therefore, in this case, the value of "ε" in Equation 1 changes from the value when air is filled between the electrodes. For this reason, when actually constructing the variable capacitor 110, it is necessary to correctly set the value of "ε" depending on the dielectric to be used and the way in which the dielectric is sandwiched. Note that if a configuration is adopted in which fluororesin tape is sandwiched in a portion of the area between the electrodes 113 and 114, materials with different dielectric constants (i.e., air and fluororesin tape) will be interposed between the electrodes 113 and 114. In this case, the variable capacitor 110 will be equivalent to a configuration in which multiple capacitors with dielectrics with different dielectric constants "ε" sandwiched between them are connected in parallel. In this case, a configuration in which fluororesin tape is sandwiched parallel to the movement (sliding) direction of the movable electrode installation member 113A can be adopted, and the capacitance value "C" can be calculated while treating the variable capacitor 110 as a capacitor in which capacitors filled with dielectrics with different dielectric constants are connected in parallel.

[0048] In the weight detection device 10 or variable capacitor 110 of this embodiment having the above configuration, the area "S" of the overlapping region between the electrodes 113 and 114 changes according to the amount of movement of the upper plate 112, which is in accordance with the weight of the measurement object MO placed on the placement portion 111. When the area "S" of the overlapping region changes, the capacitance value "C" of the variable capacitor 110 changes based on (Equation 1).

[0049] In this embodiment, the first and second input terminals 120A and 120B of the capacitance sensor tag 120 are electrically connected to a fixed electrode 114 and a movable electrode 113, respectively, and a variable capacitor 110 serving as a parallel plate capacitor is electrically connected between the first and second input terminals 120A and 120B. The capacitance sensor tag 120 detects the capacitance value of the variable capacitor 110 connected between the first and second input terminals 120A and 120B, and transmits detection data corresponding to the detection result to the information processing device 30. As described above, the area "S" of the region where the movable electrode 113 and the fixed electrode 114 face each other and overlap changes depending on the weight of the measurement object MO placed on the placement section 111, and the capacitance value "C" of the variable capacitor 110 changes accordingly. For this reason, a weight or product having a known weight is placed on the placement unit 111, the capacitance value of the variable capacitor 110 at that time is detected by the capacitance sensor tag 120, and the detected data is transmitted to the information processing device 30. Measurement reference data is generated while plotting the relationship between the placed weight and the capacitance value. This measurement reference data is then stored in advance in a storage unit (not shown) of the information processing device 30. When the information processing device 30 acquires detection data from the capacitance sensor tag 120, the information processing device 30 can measure the weight (or total weight) of the product as the measurement object MO placed on the placement unit 111 based on the detection data and the measurement reference data stored therein. Specifically, the capacitance value "C" of the variable capacitor 110 indicated by the detection data can be applied to the relationship between the capacitance value "C" of the variable capacitor 110 indicated by the measurement reference data and the placed weight, thereby calculating the placed weight at that time. In this embodiment, the information processing device 30 uses the above relationship to measure the weight of the measurement object MO placed on the placement section 111 based on (i) the detection data obtained from the capacitance sensor tag 120 via the RFID reader / writer 20 and (ii) the measurement standard data previously stored in the device using the above method, and notifies the user of the measurement results or performs processing to manage the inventory of the products placed on the placement section 111.

[0050] Here, the change characteristics of the capacitance value "C" of the variable capacitor 110 during manufacture (also referred to herein as "initial characteristics") vary depending on the spring constants of the leaf spring LS and pull spring 117 actually used, and individual differences due to manufacturing errors in the movable electrode 113 and fixed electrode 114. Therefore, the initial characteristics of the variable capacitor 110 will differ for each individual variable capacitor 110 manufactured. Furthermore, if (a1) an unexpected external force is applied to the variable capacitor 110 when the manufactured weight detection device 10 is installed in a facility such as a warehouse, store, or exhibition hall, or if (a2) a considerable period of time (e.g., approximately six months to one year) passes between the manufacture and installation of the variable capacitor 110, the characteristics of the leaf spring LS, movable electrode 113, fixed electrode 114, pull spring 117, etc. may change due to factors such as external force or aging deterioration of the leaf spring LS, and as a result, the characteristics of the variable capacitor 110 may change from their initial characteristics. Therefore, when a weight detection device 10 is newly installed in a facility, it is necessary to generate measurement standard data that is suitable for the actual characteristics of the variable capacitor 110 at the time of new installation, including not only the initial characteristics of the variable capacitor 110 that constitutes the weight detection device 10, but also any changes in characteristics that have occurred between manufacture and installation, and use this measurement standard data; otherwise, it will be difficult to properly measure the weight of the measurement object MO placed on the mounting section 111 based on the capacitance value "C" of the variable capacitor 110.

[0051] Furthermore, (b1) there is a possibility that the leaf springs LS and the like may deteriorate over time after the variable capacitor 110 is installed in a facility, and (b2) there is also a possibility that a measurement object MO exceeding a predetermined weight limit may be placed on the mounting portion 111. In such a case, there is a possibility that permanent changes in the characteristics, including plastic deformation, may occur in the leaf springs LS1 to LS4 (e.g., changes in initial length or spring constant). In order to prevent such changes in characteristics, including plastic deformation, of the leaf springs LS, the variable capacitor 110 of this embodiment is provided with a stopper 112B for preventing plastic deformation of the leaf springs LS, made of, for example, rubber, between the upper plate 112 and the lower plate 115. However, even with the stopper 112B for preventing plastic deformation, there is a possibility that plastic deformation may occur in some or all of the leaf springs LS that constitute the variable capacitor 110, causing changes in the characteristics, when a measurement object MO exceeding the weight limit is placed on the mounting portion 111. It is also anticipated that at least some of the leaf springs LS1-LS4 may need to be replaced to eliminate the effects of characteristic changes, including aging and plastic deformation. If such a situation occurs, the characteristics of the installed variable capacitor 110 will change. Therefore, if a change in the characteristics of the variable capacitor 110 occurs after the weight detection device 10 is installed in a facility, the measurement reference data generated at the time of new installation must be appropriately calibrated to generate calibrated measurement reference data (hereinafter also referred to as "calibrated measurement reference data") according to the characteristics of the variable capacitor 110 after the change occurs. The measurement reference data generated at the time of new installation and stored in the memory unit of the information processing device 30 or the calibrated measurement reference data generated through subsequent calibration work must be sequentially overwritten and updated with the newly generated calibrated measurement reference data. Therefore, it is difficult to achieve appropriate weight measurement unless the measurement reference data or calibrated measurement reference data appropriate for the current characteristics of the variable capacitor 110 is always used, and the weight of the measurement object MO placed on the mounting unit 111 is measured based on the data and the detection data acquired from the capacitance sensor tag 120.

[0052] Typically, when generating measurement reference data that matches the characteristics of a newly installed variable capacitor 110, or when calibrating the measurement reference data to match the characteristics of the variable capacitor 110 after a characteristic change to generate calibrated measurement reference data, it is necessary to place a plurality of measurement objects MO having different known weights on the mounting portion 111, obtain measurement results for approximately 10 points, and generate measurement reference data that matches the characteristics at the time of new installation, including the initial characteristics of the newly installed weight detection device 10 or variable capacitor 110, or generate and use calibrated measurement reference data that matches the characteristics of the variable capacitor 110 after a characteristic change. Meanwhile, as shown in (Equation 1), the capacitance value "C" of the variable capacitor 110 is proportional to the area "S" of the region where the two electrodes 113 and 114 face each other and overlap. Therefore, in the case of the variable capacitor 110 of this embodiment, the capacitance value "C" is proportional to the placed weight and is aligned in a straight line. Therefore, when generating measurement standard data suitable for the characteristics of a newly installed variable capacitor 110, or when generating calibrated measurement standard data suitable for the characteristics of a variable capacitor 110 after a change in characteristics, the capacitance sensor tag 120 detects the capacitance value "C" of the variable capacitor 110 when the loaded weight is "0 kg" and the capacitance value "C" of the variable capacitor 110 when a measurement object MO having a known weight (for example, "1 kg") is placed on the loading section 111, and these two measurement points are connected by a straight line to generate measurement standard data suitable for a newly installed variable capacitor 110, or to appropriately generate calibrated measurement standard data suitable for the characteristics of a variable capacitor 110 after a change in characteristics.

[0053] Therefore, in the weight measurement system 1 of this embodiment, a method is adopted in which measurement reference data suitable for the characteristics of a newly installed variable capacitor 110 is generated while employing such a simple calibration method based on two-point measurement, or calibrated measurement reference data suitable for the characteristics of the variable capacitor 110 after a characteristic change is generated and stored in advance in the storage unit of the information processing device 30, or already stored measurement reference data or calibrated measurement reference data is sequentially overwritten and updated with the generated calibrated measurement reference data to make it available for weight measurement. In this embodiment, the information processing device 30 employs a method of measuring the weight of the measurement object MO placed on the placement unit 111 based on the measurement reference data stored in its storage unit, or calibrated measurement reference data obtained by calibrating the measurement reference data and overwritten and updated in the storage unit, or calibrated measurement reference data that has already been calibrated and overwritten at least once and further calibrated and overwritten, and detection data. The process for generating measurement standard data suitable for a newly installed variable capacitor 110 or calibrated measurement standard data suitable for the characteristics of the variable capacitor 110 after a characteristic change may be executed in the information processing device 30 while obtaining detection data from the capacitance sensor tag 120, and the generated measurement standard data or calibrated measurement standard data may be stored in the memory unit of the information processing device 30 for use in weight measurement, or the detection data may be supplied to an external PC, and the data may be generated on the external PC, and the generated measurement standard data or calibrated measurement standard data may be transferred from the external PC to the information processing device 30 for use in weight measurement; however, in this embodiment, the former method is adopted.

[0054] Using the above method, the weight measurement system 1 of this embodiment can always appropriately measure the weight of the object to be measured MO based on measurement standard data or calibrated measurement standard data that is suitable for the current characteristics of the variable capacitor 110 and the capacitance value ``C'' of the variable capacitor 110 detected by the capacitance sensor tag 120.

[0055] [A3] Configuration and operation of each part of weight measurement system 1 The capacitance sensor tag 120 has a built-in IC chip ICC that executes a process of detecting the capacitance value "C" of the variable capacitor 110 connected to the first and second input terminals 120A and 120B, and also has a built-in antenna such as a dipole antenna or slot antenna for transmitting and receiving electromagnetic waves in the UHF (Ultra High Frequency) band (frequency band of approximately 300 MHz to 3 GHz), or an antenna AN such as a loop coil antenna for transmitting and receiving electromagnetic waves in the HF (High Frequency) band (frequency band of approximately 3 to 30 MHz) or LF band (frequency band of approximately 30 kHz to 300 kHz). In this embodiment, as shown in FIGS. 1 to 7 , the capacitance sensor tag 120 is configured separately from the upper plate 112 and the lower plate 115, and the first and second input terminals 120A and 120B of the capacitance sensor tag 120 are connected to the movable electrode 113 and the fixed electrode 114 of the variable capacitor 110, respectively. However, the capacitance sensor tag 120 may be incorporated into a part of the upper plate 112 or the lower plate 115. In this embodiment, the capacitance sensor tag 120 is configured to generate an electromotive force based on electromagnetic waves supplied from the RFID reader / writer 20 or a magnetic field generated by the RFID reader / writer 20. The shape and arrangement of the antenna AN are arbitrary and are not limited to the bilaterally symmetrical antenna AN illustrated in FIGS. 1 and 2 . An antenna AN with a bilaterally skewed shape to either the left or right may also be used. Using a bilaterally symmetrical antenna AN as illustrated in FIGS. 1 and 2 improves the communication sensitivity of the capacitance sensor tag 120, thereby ensuring communication stability and improving communication distance and communication speed.

[0056] Furthermore, the capacitance sensor tag 120 executes a process for detecting the capacitance value "C" of the variable capacitor 110 using the generated electromotive force based on the electromagnetic waves received from the RFID reader / writer 20 or the magnetic field generated by the RFID reader / writer 20, and wirelessly transmits detection data indicating the detection result to the RFID reader / writer 20. Note that the specific configuration of the capacitance sensor tag 120 is similar to that of a conventional RFID tag having a capacitance sensor function (for example, Patent Document 4), and therefore details thereof will be omitted.

[0057] The RFID reader / writer 20 is an RFID reader / writer equipped with a wired interface such as USB (Universal Serial Bus, registered trademark) or a wireless communication interface such as Bluetooth (registered trademark) or Wi-Fi (registered trademark). The RFID reader / writer 20 is fixedly installed at a predetermined position within a facility such as a warehouse where managed goods are stored (a predetermined position within a distance range where communication with the weight detection device 10 installed within the facility such as a warehouse) or is configured as a handheld terminal device. The RFID reader / writer 20 transmits and receives electromagnetic waves under the control of the information processing device 30 or in response to an input operation by a user such as a warehouse manager. At this time, the RFID reader / writer 20 activates the capacitance sensor tag 120 and transmits and receives electromagnetic waves in any of the UHF, HF, and LF frequency bands used to acquire detection data. With this function, the RFID reader / writer 20 drives the capacitance sensor tag 120, acquires detection data corresponding to the capacitance value "C" of the variable capacitor 110 detected by the capacitance sensor tag 120, and supplies the data to the information processing device 30. The configuration of the RFID reader / writer 20 is the same as that of a conventional passive RFID reader / writer.

[0058] The information processing device 30 is a computer system for managing the inventory status of products stored in a warehouse where the weight detection device 10 is installed, and includes a display, keyboard, mouse, a touch panel arranged on the display, a speaker, a hard disk drive (HDD), a solid state drive (SSD), etc. (not shown), or a storage unit configured by combining these with a random access memory (RAM). When installing a new device or system in a facility such as a warehouse or store, a user such as a warehouse manager is required to use the information processing device 30 to generate measurement reference data using the above method and store it in the storage unit in advance, and to register product attribute information indicating the attributes of the products whose inventory is managed using the weight detection device 10. The specific content of the product attribute information is arbitrary. For example, information necessary and sufficient for inventory management of the product may be registered, such as the product name, GTIN (Global Trade Item Number), weight per unit (hereinafter also referred to as "unit weight"), product unit price, inventory quantity currently stored in the warehouse, and inventory quantity of products requiring additional ordering (see FIG. 8 described below). Furthermore, if a change occurs in the characteristics of the variable capacitor 110 after the weight detection device 10 is newly installed, the memory unit is configured to generate and overwrite calibrated measurement reference data appropriate for the characteristics of the variable capacitor 110 after the change using the above-described method, and the information processing device 30 is configured to measure the weight of the measurement object MO using the measurement reference data or calibrated measurement reference data appropriate for the current characteristics of the variable capacitor 110 stored in the memory unit. Furthermore, in this embodiment, the information processing device 30 stores the product attribute information registered by the warehouse manager in the memory unit and executes processing necessary for product inventory management based on the weight measurement results and the product attribute information.

[0059] The information processing device 30 also has an input / output interface that communicates according to the same communication protocol as the input / output interface installed in the RFID reader / writer 20. At a predetermined timing, the information processing device 30 outputs a control command to the RFID reader / writer 20, causing the RFID reader / writer 20 to transmit and receive electromagnetic waves and acquire detection data from the capacitance sensor tag 120. Based on the detection data, the information processing device 30 measures the total weight (i.e., the weight of the measurement object MO) of the products placed on the placement unit 111. Based on the total weight thus measured, the information processing device 30 manages the inventory of the products placed on the placement unit 111. The information processing device 30 may be configured to present the measurement results of the total weight of the products to a user, such as a warehouse manager, without performing inventory management. In this case, the weight measurement results may be displayed on a display or reported by voice, or the measurement results may be reported by voice along with the measurement results displayed on the screen. Furthermore, if the RFID reader / writer 20 is a handheld type, when a user such as a warehouse manager receives the detection data read from the capacitance sensor tag 120 by the RFID reader / writer 20, the user can measure the total weight of the goods placed on the placement section 111 based on the detection data.

[0060] At this time, the information processing device 30 of this embodiment measures the total weight of the products stored while placed on the placement unit 111 based on (a1) measurement reference data generated when the weight detection device 10 was newly installed and stored in the memory unit, or (a2) calibrated measurement reference data calibrated to suit the characteristics of the variable capacitor 110 or the weight detection device 10 after the characteristics have changed and overwritten in the memory unit, and (b) detection data acquired from the capacitance sensor tag 120 via the RFID reader / writer 20, and executes processing to manage the inventory of the products based on the measurement results. Note that the specific method for managing product inventory in the warehouse by the information processing device 30 is arbitrary, and for example, the following method can be adopted.

[0061] <Management Method A> This method manages the inventory quantity of products stored on the placement unit 111 based on the total weight of the products (i.e., the weight of the measurement object MO) measured based on the detection data and the measurement standard data or the calibrated measurement standard data. When this method is adopted, the measured total weight is divided by the unit weight of the products included in the product attribute information to calculate the number of products placed on the placement unit 111, and (1) the calculated number of products may be displayed on a display or notified to the warehouse manager by voice, or (2) the calculated number may be stored in a database (hereinafter referred to as "DB") that manages product inventory in association with the product attribute information as product inventory quantity information (see FIG. 8 described below). For example, assume that the weight measured based on the detection data is "1.5 kg" and the unit weight of the products included in the product attribute information is "300 g." In this case, the information processing device 30 calculates that the inventory quantity of the product placed on the placement section 111 is "5 units," and (1) notifies the warehouse manager of the calculated inventory quantity of the product using at least one of audio and images, or (2) stores the calculated inventory quantity in the above-mentioned DB in association with the product attribute information, thereby maintaining the inventory quantity of the product in a state that can be confirmed later by the warehouse manager.

[0062] At this time, the information processing device 30 preferably uses a timer or the like built into the device to identify date and time information indicating the measurement date and time, generates inventory history information while linking it to the calculated inventory quantity, and stores the information in the DB in association with product attribute information. It is also possible that a surplus may be generated when dividing the measured weight by the unit weight of the product. In this case, for products manufactured and sold in single units (e.g., home appliances), the surplus may be rounded down and the inventory quantity may be managed. For example, for products packed in multiple units per box (e.g., soft drinks packaged by the dozen or retort pouch foods sold in multiple units per box), the inventory may be managed as having a fractional part. For example, if the measured weight of a box of 12 300 ml (milliliter) soft drinks, with a unit weight of 3.6 kg per box, is 6 kg, the inventory quantity may be calculated as one box plus 8 remaining bottles as fractional inventory. In this case, a program for executing the process is stored in advance in the storage unit, and a database containing product attribute information registered by users is constructed in the storage unit. The information processing device 30 then executes the process in accordance with the program, sequentially adding inventory history information to the database in association with the product attribute information. This method allows the user to grasp and manage changes in product inventory quantity (i.e., product shipping frequency, shipment quantity over a specified period, sales quantity, etc.). As a result, this method allows the user to grasp product sales trends, the timing of product arrival, etc. In this case, the method and timing by which the information processing device 30 acquires detection data from the capacitance sensor tag 120 of the weight detection device 10 can be adapted to the format of the RFID reader / writer 20. (a) If the RFID reader / writer 20 is fixedly installed in a facility such as a warehouse, the information processing device 30 can output a control command to the RFID reader / writer 20 at a predetermined time interval (for example, every 5 to 10 minutes), and have the capacitance sensor tag 120 detect the capacitance value "C" of the variable capacitor 110 at that time at that time, and acquire the corresponding detection data.(b) Furthermore, if the RFID reader / writer 20 is a handheld type, a configuration may be adopted in which the RFID reader / writer 20 transmits the detection data to the information processing device 30 at the time the user uses the RFID reader / writer 20 to read the detection data from the capacitance sensor tag 120.

[0063] <Management Method B> This method issues an alert instructing the user to order additional products when the inventory quantity of products stored on the placement unit 111 (i.e., the inventory quantity of products placed on the placement unit 111) falls below a predetermined threshold. When this method is employed, a program for executing this process is stored in advance in a storage unit. In this case, the information processing device 30 determines the timing of issuing an alert based on information about the inventory quantity requiring an additional order, which is included in the product attribute information registered by a user such as a warehouse manager, and issues the alert as necessary. Furthermore, in this case, the information processing device 30 determines a weight threshold for issuing an alert based on information about the inventory quantity requiring an additional order, which is included in the product attribute information, and stores the weight threshold in the storage unit. For example, assume that products with a unit weight of "300 g (grams)" are placed on the placement unit 111 to store and manage inventory, and the information about the inventory quantity requiring an additional order is set to "30 units." In this case, the information processing device 30 sets the threshold weight to "9 kg" (i.e., "300 g x 30 pieces") and stores it in the storage unit. The threshold information may be calculated when registering the product attribute information and stored while associating the calculated value with the product attribute information. Similarly to the above-described "management method a," the information processing device 30 (a) outputs a control command to the RFID reader / writer 20 at predetermined time intervals (e.g., intervals of about 5 to 10 minutes) to transmit and receive electromagnetic waves, and causes the capacitance sensor tag 120 to detect the capacitance value "C" of the variable capacitor 110 at that time to acquire corresponding detection data, or (b) acquires detection data transmitted from the RFID reader / writer 20 in response to a user operation, based on the thus-acquired detection data and the measurement reference data or the calibrated measurement reference data. Based on the thus-acquired detection data and the measurement reference data or the calibrated measurement reference data, the information processing device 30 measures the total weight of the product inventory placed and stored on the placement unit 111 and compares the measurement result with the threshold. As a result of the comparison, if the measured total weight of the inventory of goods based on the capacitance measurement value "C" is equal to or less than the threshold value, the information processing device 30 may issue an alert.The method of issuing the alert is optional. For example, a message such as "The inventory of product XX has fallen below the specified quantity. Please order additional products." may be displayed on the display, while the warehouse manager is notified by voice. According to this method, (a) the total weight of the products placed on the placement unit 111 is periodically measured at regular intervals, and an alert is issued when the total weight falls below a threshold value. Alternatively, (b) when a user reads detection data from the capacitance sensor tag 120 using the RFID reader / writer 20 (e.g., when the warehouse manager checks inventory), the total weight of the product inventory is measured and compared with a threshold value, and an alert is issued. As a result, this method prevents lost sales opportunities due to product shortages, streamlines sales activities, and prevents sales declines.

[0064] <Management Method C> This method automatically orders products from the manufacturer of a product when the inventory quantity of the product stored in a facility such as a warehouse falls below a predetermined threshold. In this case, the information processing device 30 is communicatively connected to a product ordering system managed by the product manufacturer via a network (not shown). When the inventory quantity of the product stored on the placement unit 111 falls below a predetermined threshold, the information processing device 30 automatically places an order with the product manufacturer's product ordering system while specifying the GTIN, product name, and order quantity of the ordered product. The timing of the automatic ordering process is determined in the same manner as the timing of issuing an alert in "Management Method B." The automatic ordering process may be executed when it is detected that the total weight of the product inventory has fallen below a threshold. The timing and method of the information processing device 30 acquiring the detection data are also the same as those in "Management Method B." Furthermore, the quantity of the product to be ordered during the automatic ordering process may be specified in advance by a user, such as a warehouse manager. According to this method, when the inventory quantity of a product stored in a facility such as a warehouse falls below a predetermined quantity, the product can be automatically ordered. As a result, this method can prevent product shortages caused by users overlooking alerts or ordering errors, prevent the loss of product sales opportunities, facilitate sales activities, and prevent a decrease in sales.

[0065] As described above, the weight measurement system 1 of this embodiment converts the weight of the measurement object MO placed on the placement unit 111 (e.g., the total weight of product inventory) into the capacitance value "C" of the variable capacitor 110, measures the weight of the measurement object MO based on the measurement result of the capacitance value "C," and notifies the user. It is also possible to appropriately manage and replenish inventory of products stored in a facility such as a warehouse. Furthermore, the weight measurement system 1 of this embodiment can generate measurement reference data appropriate for the characteristics (including initial characteristics) of the variable capacitor 110 at the time of new installation of the weight detection device 10 and use this data for weight measurement. Furthermore, if the characteristics of the variable capacitor 110 change, the measurement reference data can be calibrated based on two-point measurement to suit the changed characteristics, generating calibrated measurement reference data, and using the calibrated measurement reference data to perform weight measurement based on the capacitance value "C" of the variable capacitor 110. As a result, the weight measurement system 1 of this embodiment can reliably reduce the influence of individual differences in the manufactured variable capacitor 110 on the weight measurement results, as well as the influence of changes in the characteristics of the variable capacitor 110 due to changes in the characteristics of the leaf springs LS1-4, etc., and the influence of replacing at least some of the leaf springs LS1-4, thereby enabling the weight of the measurement object MO to be measured appropriately. In particular, the variable capacitor 110 constituting the weight detection device 10 of this embodiment is configured to convert the weight of the measurement object MO placed on the mounting portion 111 into changes in the area "S" of the region where the movable electrode 113 and the fixed electrode 114 overlap each other, and measure the placed weight based on the capacitance value "C" of the variable capacitor 110, which changes in response to changes in the area "S," and the measurement reference data or calibrated measurement reference data. In this respect, compared to methods of measuring the placed weight based on the inter-electrode distance, such as those described in Patent Documents 1 and 2, the measurement reference data and calibrated measurement reference data can be easily and accurately generated based on the linear relationship shown in (Equation 1). Furthermore, the weight measurement system 1 of this embodiment can perform weight measurements based on the generated measurement standard data or calibrated measurement standard data, thereby reducing the processing burden during data generation and ensuring a large amount of change, unlike the distance between electrodes, thereby improving the weight measurement accuracy with simple calculations.

[0066] In the above embodiment, a flexible string- or ribbon-shaped connecting member 116 is used to tightly connect the upper plate 112 and the movable electrode mounting member 113A, but a rod-shaped or other inflexible connecting member 116 may also be used. In this case, the upper plate 112 and the movable electrode mounting member 113A may be directly connected by the connecting member 116 so that the movable electrode mounting member 113A moves (slides) in accordance with the movement of the upper plate 112. The movable electrode mounting member 113A moves in accordance with the amount of movement of the upper plate 112, and the area of ​​the overlapping region between the electrodes 113 and 114 changes accordingly. In this case, the length of the connecting member 116 may be set so that the movable electrode mounting member 113A is positioned at a desired initial position relative to the upper plate 112, with the upper plate 112 in its initial position.

[0067] [B] Second Embodiment Next, a second embodiment of a weight measurement system as a physical quantity measurement system according to the present invention will be described with reference to Figures 8 and 9. Note that Figure 8 is a diagram showing an example of data storage in a product inventory management DB stored in the storage unit of the information processing device 300 of this embodiment, and Figure 9 is a flowchart showing processing executed by the information processing device 300 of this embodiment.

[0068] [B1] Overview of the Weight Measurement System of the Present Embodiment In the first embodiment described above, a single information processing device 30 was used to manage inventory of one type of product placed and stored on the placement unit 111 of one weight detection device 10. In contrast, the weight measurement system of the present embodiment is configured to manage multiple weight detection devices 10 using a single information processing device 300, and to manage inventory of multiple types of products using the single information processing device 300. To achieve this function, the present embodiment employs the following method in general. Note that this embodiment is similar to the above embodiments except that the number of weight detection devices 10 managed by the information processing device 300 is greater than that of the weight measurement system 1 of the above embodiments. Therefore, illustrations and descriptions of the system configuration and the configuration of the weight detection device 10 will be omitted.

[0069] (1) First, a weight detection device 10 is installed on each of multiple shelves constituting a product storage shelf installed in a facility such as a warehouse, or multiple pallets each equipped with a weight detection device 10 are installed in the facility such as a warehouse. (2) Products to be placed and stored on each shelf or pallet are determined in advance. (3) A user such as a warehouse manager uses the predetermined shelves or pallets to store and manage inventory of the corresponding products. (4) A device ID, such as a serial number, is assigned in advance to each of multiple weight detection devices 10 managed by the information processing device 300. This device ID is also pre-stored in a memory (not shown) built into the IC chip ICC of the capacitance sensor tag 120 constituting the corresponding weight detection device 10. The device ID in this embodiment corresponds to, for example, "identification information" in the present invention. In this case, the capacitance sensor tag 120 may be incorporated into a part of the upper plate 112 or the lower plate 115, or may be configured as a separate entity, as in the above-described embodiments.

[0070] (5) Furthermore, the information processing device 300 is provided in advance with a product inventory management DB for product inventory management, as exemplified in Fig. 8. Specifically, as shown in Fig. 8, (a) a field for storing a device ID assigned to each weight detection device 10 managed by the information processing device 300, (b) a field for storing measurement reference data or calibrated measurement reference data corresponding to the weight detection device 10, (c) a field for storing product attribute information of a product placed on the placement unit 111 of the weight detection device 10 for inventory management, (d) a field for storing inventory information indicating the inventory quantity of the product, and (e) a field for storing inventory history information of the product, are provided in association with each other, and the product inventory management DB with necessary data stored in each field is stored in advance in the storage unit of the information processing device 300. In addition, the measurement standard data or calibrated measurement standard data to be stored in the field associated with each device ID in the product inventory management DB can be generated in advance by a computing device such as the information processing device 300 or an external PC in a manner similar to that of the first embodiment described above, depending on the characteristics of the corresponding weight detection device 10, and then stored in the corresponding field. For example, in the example shown in Figure 8, data "MRD001" is stored as the measurement standard data or calibrated measurement standard data of the weight detection device 10 identified by the device ID "WDD01", and the weight detection device 10 stores and manages inventory of a product identified by product attribute information with a GTIN of "JAN001", a product name of "XX beer", a unit weight of "2100g per pack, 350g per bottle", price information of "1200 yen per pack, 222 yen per bottle", a stock quantity requiring an additional order of "10 packs", and the user has set "10 packs" as the stock quantity requiring an additional order, and this example shows a data storage situation in which "30 packs" of this product are currently stored on the placement section 111 and "IHI001" is stored as inventory history information. Similarly, for other weight detection devices 10, the product attribute information, inventory information, and inventory history information of products whose inventory is managed using the weight detection device 10 are stored in correspondence with the device ID, measurement standard data, or calibrated measurement standard data corresponding to the weight detection device 10.Furthermore, the measurement standard data or calibrated measurement standard data stored in this product inventory management DB is generated to suit the characteristics of the variable capacitor 110 that constitutes the weight detection device 10 when the corresponding weight detection device 10 is newly installed and stored in the product inventory management DB, and each time a situation occurs in which the characteristics of the variable capacitor 110 change, calibrated measurement standard data that is suitable for the characteristics of the variable capacitor 110 after the characteristic change is generated based on the above two-point measurement, and the corresponding field is overwritten and updated with the calibrated measurement standard data generated as needed, thereby always maintaining a state in which measurement standard data or calibrated measurement standard data that is suitable for the current characteristics of the variable capacitor 110 that constitutes the corresponding weight detection device 10 is stored. Furthermore, in this embodiment, the product inventory management DB provided in the storage unit of the information processing device 300 constitutes, for example, the "storage means" of the present invention.

[0071] 9, in this embodiment, the information processing device 300 first acquires detection data from each weight detection device 10 installed in the warehouse (step S1). The acquisition method is the same as that in the first embodiment, and depends on the configuration of the RFID reader / writer 20. (a) If the RFID reader / writer 20 is a fixed installation type, a control command is periodically output to the RFID reader / writer 20 to transmit and receive electromagnetic waves, thereby collectively acquiring detection data from the capacitance sensor tag 120 of each weight detection device 10 in a state where the detection data is associated with the device ID. (b) If a handheld RFID reader / writer 20 is used, the RFID reader / writer 20 periodically outputs a control command to the RFID reader / writer 20 to transmit and receive electromagnetic waves, thereby collectively acquiring detection data from the capacitance sensor tag 120 of each weight detection device 10 in a state where the detection data is associated with the device ID. The RFID reader / writer 20 may transmit and receive electromagnetic waves to read out detection data collectively from the capacitance sensor tag 120 of each weight detection device 10 while associating it with the device ID, and transmit the read detection data to the information processing device 300, or the RFID reader / writer 20 may read out detection data individually from the capacitance sensor tag 120 of each weight detection device 10 while associating it with the device ID, and transmit the read detection data to the information processing device 300 while associating it with the device ID.

[0072] After acquiring the detection data associated with the device ID from the capacitance sensor tag 120 of each weight detection device 10 in this manner, the information processing device 300 measures the total weight of the products placed and stored on the placement unit 111 of each weight detection device 10 based on the detection data (step S2). At this time, the information processing device 300 searches the product inventory management DB based on the device ID associated with the detection data acquired from the capacitance sensor tag 120 of each weight detection device 10, and reads out the measurement reference data or calibrated measurement reference data corresponding to the weight detection device 10 from which the detection data was acquired. Then, the information processing device 300 measures the total weight of the products placed on the placement unit 111 of each weight detection device 10 based on the capacitance measurement value "C" of the variable capacitor 110 indicated by the detection data corresponding to the read measurement reference data or calibrated measurement reference data (step S2).

[0073] Once the total weight of the products placed on the placement unit 111 of each weight detection device 10 has been measured, the information processing device 300 executes an inventory management DB update process (step S3) and terminates the process. At this time, the information processing device 300 reads the product attribute information stored in the inventory management DB in association with the device ID of each weight detection device 10, divides the measured product weight by the unit weight, calculates the inventory quantity of the corresponding product, and stores the calculated inventory quantity in the inventory management DB's inventory information storage field, or overwrites and updates the inventory information already stored. At this time, the information processing device 300 also determines the current date and time using a timer (not shown) built into the device, generates inventory history information by associating the current date and time with the calculated inventory quantity, and stores the information in the inventory history information storage field. This process is essentially the same as "management method a" in the first embodiment, except that it is executed for each weight detection device 10 and stored in the corresponding field. This embodiment may also employ a method similar to "management method b" or "management method c" described above. In this case, for each product whose inventory is stored and managed by each weight detection device 10, a threshold for the total weight of the product that requires an additional order is calculated for each weight detection device 10 from the inventory quantity, the inventory quantity that requires an additional order included in the product attribute information, and the unit weight, and the calculated threshold is compared with the measured total weight of the product.When the total weight of the product falls below the threshold (i.e., when the inventory quantity falls below the quantity that requires an additional order), an alert is issued or processing is executed to automatically place an order with the order management system of the manufacturer of the product in question.

[0074] The information processing device 300 repeats this process at a predetermined time interval (for example, every 5 to 10 minutes), or a user such as a warehouse manager reads the detection data from the capacitance sensor tag 120 using a handheld RFID reader / writer 20, and executes this process when the detection data is transmitted to the information processing device 300.

[0075] As a result, the inventory management DB is sequentially overwritten with the inventory information of the products managed by each weight detection device 10, so that the current inventory quantities of the products managed by each weight detection device 10 are always reflected. It is desirable to create an additional field for the inventory history information storage field in the inventory management DB each time the above process is executed, and to store additional inventory history information. Even when adopting the configuration of the first embodiment, it is desirable to construct a DB having data storage fields similar to those shown in FIG. 8 in the storage unit of the information processing device 300 and manage data. Furthermore, it is desirable for the information processing device 300 to have the function of analyzing increases and decreases in product inventory (sales trends, shipping and receiving status, etc.) based on the inventory history information stored in the inventory management DB and presenting the results to the user. Furthermore, by including and managing odd lot inventory in the inventory information, more detailed inventory management can be achieved.

[0076] As described above, according to the configuration of this embodiment, multiple weight detection devices 10 installed in a facility such as a warehouse can manage and store different product inventories, while the multiple weight detection devices 10 can be centrally managed by a single information processing device 300. As a result, the inventory status of multiple types of products can be centrally managed by a single information processing device 300, reducing the initial cost of system construction. Furthermore, users such as warehouse managers can centrally manage and understand the inventory status of multiple types of products stored and managed in a facility such as a warehouse or store, thereby significantly reducing the workload of inventory management. Furthermore, since measurement reference data or calibrated measurement reference data corresponding to each weight detection device 10 can be generated based on two measurement results, as in the above-described embodiments, the work required to generate measurement reference data suitable for a newly installed weight detection device 10 or to generate calibrated measurement reference data when a condition occurs in which the characteristics of the variable capacitor 110 change is simplified, significantly reducing the burden on the user.

[0077] [C] Modifications [C1] Modification 1 In the above-described embodiments, a passive capacitance sensor tag 120 and an RFID reader / writer 20 are used. However, the capacitance sensor tag 120 may be equipped with a power source and employ an active or semi-active driving system. In this case, the capacitance sensor tag 120 may be equipped with an IC chip and antenna that achieve the same functions as a typical capacitance tester, and the capacitance value "C" of the variable capacitor 110 may be detected using an internal power supply. This configuration ensures a longer communication distance (e.g., several tens of meters) than when a passive driving system is used. Therefore, even when the weight detection device 10 and the RFID reader / writer 20 are installed far apart in a facility such as a large warehouse, store, or exhibition hall, the total weight of the products placed on the mounting portion 111 of the weight detection device 10 (the weight of the measurement object MO) can be reliably measured by the information processing device 30, and product inventory can be managed.

[0078] Furthermore, even when a handheld RFID reader / writer 20 is used, a long communication distance can be ensured. The detection result of the capacitance value "C" of the variable capacitor 110 can be read from a location remote from the installation location of the weight detection device 10 and reliably provided to the information processing device 30 or 300. This allows the total weight of the products placed on each weight detection device 10 to be easily measured from a remote location, enabling product inventory management. As a result, this modification improves the flexibility of system installation, allowing the total weight of the products placed on the placement unit 111 to be measured remotely in various locations, improving convenience for users such as warehouse managers. Note that, like conventional RFID systems, the communication method of the RFID reader / writer 20 must be changed to match the drive method of the capacitance sensor tag 120. Furthermore, the method of detecting capacitance using a power-supply-equipped RFID is similar to that of a conventional capacitance tester, and therefore details will be omitted. Furthermore, in this case, when the weight detection device 10 is installed in an extremely low-temperature environment, such as a refrigerated warehouse, a relatively high-performance power source capable of operating at low temperatures, such as a lithium polymer battery, can be used to reliably manage product inventory in the refrigerated warehouse. In this case, the capacitance sensor tag 120 including the power supply may also be incorporated into the upper plate 112 or the lower plate 115 .

[0079] [C2] Modification 2 In each of the above embodiments, four leaf springs LS1 to LS4 having similar initial lengths and spring constants are provided at the four corners of the upper plate 112 and the lower plate 115, and the upper plate 112 and the lower plate 115 are connected by the leaf springs LS1 to LS4. However, in addition to the leaf springs LS1 to LS4 provided near the four corners of the upper plate 112 and the lower plate 115, one leaf spring LS having the same initial length as the other springs may be added near the center of the upper plate 112 and the lower plate 115, so that five leaf springs LS are provided between the upper plate 112 and the lower plate 115, and the upper plate 112 and the lower plate 115 are connected by these five springs. In this case, (Configuration a) only the additional leaf spring LS may have a spring constant different from the other leaf springs LS, or (Configuration b) all five leaf springs LS, including the additional leaf spring LS, may have the same spring constant. By adopting "Configuration a," the natural frequency of only the leaf spring LS added to the center can be changed. Experiments by the inventors have shown that this prevents resonance and vibration of the upper plate 112 when the measurement object MO is placed on the mounting portion 111. Furthermore, experiments by the inventors have shown that vibration of the upper plate 112 during measurement can also be prevented when "Configuration b" is adopted. Therefore, according to this modification, vibration of the upper plate 112 can be prevented and measurement accuracy during weight measurement can be improved regardless of whether "Configuration a" or "Configuration b" is adopted. Note that the above-described embodiments have been described using four leaf springs LS1 to LS4 as elastic members. In this modification, one leaf spring LS is added near the center of the upper plate 112 and the lower plate 115. However, four or five coil springs may be used instead of the leaf spring LS. When using coil springs, by using five coil springs, it is possible to prevent the upper plate 112 from vibrating during weight measurement and reducing measurement accuracy, regardless of whether the above ``configuration a'' or ``configuration b'' is adopted.

[0080] [C3] Modification 3 In the above-described embodiments and modifications, examples have been described in which the capacitance sensor tag 120 as RFID is used as the capacitance sensor, but instead of the capacitance sensor tag 120 as RFID, a capacitance sensor may be formed by a capacitance tester equipped with an IC chip, antenna, and power supply that communicates according to a communication protocol such as Bluetooth (registered trademark) or Wi-Fi (registered trademark), and the capacitance sensor may detect the capacitance value "C" of the variable capacitor 110, while the information processing device 30 or 300 wirelessly acquires detection data corresponding to the detection result from the capacitance sensor. Other points are the same as those of the above-described embodiments.

[0081] [C4] Modification 4 In each of the above embodiments, an example has been described in which the mounting portion 111 is provided on the upper plate 112 of the variable capacitor 110, and the total weight of the products placed on the mounting portion 111 (i.e., the weight of the measurement object MO) is measured based on the capacitance measurement value "C" of the variable capacitor 110. However, a configuration may also be adopted in which the variable capacitor 110 is used as a pressure sensor to measure the pressure applied to the upper plate 112 and notify the user of the measurement result, or history information of the measurement result is generated based on the measurement result to monitor changes in the applied pressure.

[0082] In this case, a known pressure is applied to the upper plate 112 in advance, and the capacitance value "C" of the variable capacitor 110 at that time is measured by the capacitance sensor tag 120. Based on the measurement results, measurement reference data or calibrated measurement reference data is generated using a method similar to that of the above-described embodiments, and the data is stored in the information processing device 30 or 300 in advance. The information processing device 30 or 300 then measures the value of the pressure applied to the upper plate 112 based on the capacitance value "C" of the variable capacitor 110 indicated by the detection data acquired from the capacitance sensor tag 120 and the measurement reference data or calibrated measurement reference data stored therein. The measurement method used here is the same as that used in the above-described embodiments. Alternatively, the IC chip ICC and antenna AN may be incorporated into the upper plate 112 or the lower plate 115, and the capacitance sensor tag 120 may be built into the upper plate 112 or the lower plate 115.

[0083] Furthermore, in this case, pressure detection devices (corresponding to the weight detection device 10 in each of the above embodiments) each consisting of a variable capacitor 110 as a pressure sensor and a capacitance sensor tag 120 may be installed at multiple locations, and the pressure value applied to the upper plate 112 may be measured for each pressure detection device. In this case, as in the second embodiment, a device ID for identifying the pressure detection device is stored in advance in the capacitance sensor tag 120 of each pressure detection device. Furthermore, in this case, as in the information processing device 300 of the second embodiment, measurement reference data or calibrated measurement reference data corresponding to each pressure detection device is stored in advance in association with the device ID. The capacitance sensor tag 120 generates an electromotive force based on the electromagnetic waves received from the RFID reader / writer 20 or the magnetic field generated by the RFID reader / writer 20, detects the capacitance value "C" of the variable capacitor 110 connected to the device, and wirelessly transmits the corresponding detection data to the information processing device in association with the device ID.

[0084] On the other hand, in this case, the information processing device stores measurement reference data or calibrated measurement reference data corresponding to each pressure detection device in association with the corresponding device ID, similar to the information processing device 300 of the second embodiment. Then, based on the device ID wirelessly acquired in association with the detection data, the information processing device identifies the measurement reference data or calibrated measurement reference data corresponding to the pressure detection device, measures the pressure value applied to the upper plate 112 of the variable capacitor 110 constituting the corresponding pressure detection device based on the identified measurement reference data or calibrated measurement reference data and the detection data for each pressure detection device, and notifies the user of the measurement results. Alternatively, based on the measurement results for each pressure detection device, the information processing device generates pressure measurement history information for each pressure detection device and monitors changes in the pressure value applied to the upper plate 112 of the variable capacitor 110 for each pressure detection device. Other aspects are similar to those of the second embodiment, and therefore description thereof will be omitted.

[0085] [C5] Modification 5 Next, a weight detection device 100 corresponding to Modification 5 of the physical quantity detection device according to the present invention will be described with reference to Fig. 10. Fig. 10 is a device configuration diagram showing the configuration of the weight detection device 100 according to this modification, in which (A) shows the state of the weight detection device 100 in a state where no measurement object MO is placed (i.e., a state where the placed weight is "0 kg"), and (B) shows the state of the weight detection device 100 in a state where a measurement object MO of a predetermined weight (e.g., "1.0 kg") is placed. In addition, in Figure 10, to prevent the drawing from becoming too cluttered, the capacitance sensor tag 120 that constitutes the weight detection device 10 to be incorporated into the weight detection device 100 is omitted from the illustration. However, the capacitance sensor tag 120 may be incorporated into the upper plate 112 or lower plate 115 of the variable capacitor 110 that constitutes the weight detection device 10, as in the above-mentioned embodiments and modified examples, so that it is built into the upper plate 112 or lower plate 115 and the fixed electrode 114 and movable electrode 113 that constitute the variable capacitor 110 are electrically connected to each of the first and second input terminals 120A and 120B. Alternatively, the capacitance sensor tag 120 may be constructed separately from the upper plate 112 or lower plate 115 without being built into them, and the fixed electrode 114 and movable electrode 113 that constitute the variable capacitor 110 may be electrically connected to each of the first and second input terminals 120A and 120B. Furthermore, in Figure 10, in order to prevent the drawing from becoming too complicated, the movable electrode 113, movable electrode installation member 113A, fixed electrode 114, fixed electrode installation member 114A, pull spring fixing member 115A, direction change member 115B, connecting member 116, and pull spring 117 that constitute the variable capacitor 110 of the weight detection device 10 are not shown, but the weight detection device 10 shown in Figure 10 actually has each of these parts, has a configuration similar to that of the weight detection device 10 shown in Figure 1, etc., and is designed to achieve the same functions.In Figure 10, in order to prevent the drawing from becoming too complicated, an example is shown in which one leaf spring LS is provided between the upper plate 112 and the lower plate 115 of the variable capacitor 110 incorporated into the weight detection device 100. However, the number of leaf springs LS to be provided between the two plates 112 and 115 is arbitrary, and may be four as in the above embodiments, five as in variant 2, or one or two. However, in this variant, to make the explanation easier to understand, the explanation will be given assuming that four leaf springs LS1 to LS4 are sandwiched between the upper plate 112 and the lower plate 115 to form a variable capacitor 110 having a configuration similar to that of Figures 1 to 7.

[0086] As shown in FIG. 10, the weight detection device 100 of this modified example comprises: (1) a lower frame link LFL that is fixed to a fixed object such as a desk, floor, or shelf, and is made of a material such as metal, thermoplastic resin, or thermosetting resin; (2) an upper frame link UFL that has the same or a different length from the lower frame link LFL; (3) two connecting arm links CAL-L and CAL-R that are connected to the lower frame link LFL and the upper frame link UFL, respectively, and that connect the lower frame link LFL and the upper frame link UFL to each other, and that are set to the same length; 1 to 7 is sandwiched between the upper frame link UFL and the lower frame link LFL of a frame (hereinafter referred to as the "measurement object mounting frame") configured as above, with the Z-shaped leaf springs LS1 to LS4 of the weight detecting device 10 shown in Figures 1 to 7 being parallel to the two connecting arm links CAL-R and CAL-L. Specifically, (i) the center line CL of the lower frame link LFL and the upper surface of the lower plate 115 of the variable capacitor 110 are aligned, and the lower plate 115 is fixed to the lower frame link LFL with adhesive, double-sided tape, or the like, and (ii) the center line CL of the upper frame link UFL and the lower surface of the upper plate 112 are aligned, and the upper plate 112 is fixed to the upper frame link UFL with adhesive, double-sided tape, or the like. In this modified example, the upper and lower frame links UFL and LFL are shown as having the same length, but the lengths of the UFL and LFL do not necessarily have to be the same, and the UFL and LFL may be configured to have different lengths.

[0087] In the measurement object mounting frame constituting the weight detection device 100 of this modified example, (a1) the left connecting arm link CAL-L is connected to the upper frame link UFL in a state where rotational movement is possible around the connection point CP1 as the rotation axis, and (a2) is connected to the lower frame link LFL in a state where rotational movement is possible around the connection point CP2 as the rotation axis. In contrast, (b1) the right connecting arm link CAL-R is connected to the lower frame link LFL in a state where rotational movement is possible around the connection point CP3 as the rotation axis, and (b2) is connected to the upper frame link UFL in a state where rotational movement is possible around the connection point CP4 as the rotation axis. Furthermore, in the measurement object mounting frame that constitutes the weight detection device 100 of this modified example, (i) the distance from CP1 to CP4 and (ii) the distance from CP2 to CP3 are equal, and the connecting points CP1 to CP4 and the members that make up the sides connecting these four connecting points CP1 to CP4 (i.e., the upper and lower frame links UFL and LFL, or the upper plate 112 and lower plate 115 and the two connecting arm links CAL-R and CAL-L in the configuration described below) form a parallelogram. Note that even if the upper and lower frame links UFL and LFL are made up of members of different lengths, it is necessary to adjust the positions of each connecting point CP1 to CP4 so that a parallelogram is formed by the connecting points CP1 to CP4 and the members that make up the sides connecting these four connecting points CP1 to CP4.

[0088] If the upper plate 112 and lower plate 115 are fixed to the leaf springs LS1-LS4 without synchronizing with the two connecting arm links CAL-R and CAL-L, the horizontal displacement (amount of movement) of the upper and lower frame links UFL and LFL will not be the same as the horizontal displacement (amount of movement) of the upper and lower plate 112 and lower plate 115. This difference in displacement can be tolerated, for example, by allowing the upper plate 112 and the upper frame link UFL to slide rather than being glued. However, this method cannot eliminate the possibility of a decrease in weight detection accuracy due to friction, etc., when the upper frame link UFL moves downward in the drawing. Therefore, in the weight detection device 100 of this modified example, the size and installation position of the two connecting arm links CAL-R and CAL-L and the hypotenuses of the leaf springs LS1-LS4 are adjusted so that their lengths and angles are the same, thereby synchronizing them. In other words, when the two connecting arm links CAL-R and CAL-L rotate around the connection points CP1 to CP4 as the rotation axis, the hypotenuses of the leaf springs LS1 to LS4 and the two connecting arm links CAL-R and CAL-L become parallel to each other, and a parallelogram is formed by the two connecting arm links CAL-R and CAL-L and the hypotenuses of each leaf spring LS1 to LS4 that are sandwiched between them. With this configuration, when the weight detection device 100 of this modified example is constructed by fixing the leaf springs LS1 to LS4 to the upper plate 112 and the lower plate 115 and adhesively fixing the upper frame link UFL and the lower frame link LFL to the upper plate 112 and the lower plate 115, respectively, even if the object to be measured MO is placed on the upper frame link UFL and the upper frame link UFL sinks downward in the drawing, the parallelogram formed by the two connecting arm links CAL-R and CAL-L and each of the leaf springs LS1 to LS4 is crushed vertically without changing the length of each side, and the parallelism of (a) the lower plate 115 and the upper plate 112, or (b) the upper and lower frame links UFL and LFL fixed to the upper plate 112 and the lower plate 115 is maintained.With this configuration, the weight detection device 100 of this modified example minimizes the possibility of failure after the leaf springs LS1 to LS4 are distorted or bent due to lateral force being applied thereto, and can accurately measure the weight of the object to be measured MO and the pressure applied to the upper frame link UFL over a long period of time without causing failure.

[0089] In the weight detection device 100 of this modified example, the connection points CP1 to CP4 are configured such that, when viewed from the ends of the upper frame link UFL and the lower frame link LFL, (A1) connection point CP1 is set at a position distance "l2-1" from the end of the upper frame link UFL, while (A2) connection point CP2 is set at a position distance "l1-1" from the end of the lower frame link LFL on the same side. Also, (B1) connection point CP3 is set at a position distance "l2-2" from the end of the lower frame link LFL on the opposite side to the end on the connection point CP2 side, while (B2) connection point CP4 is set at a position distance "l1-2" from the end of the upper frame link UFL on the opposite side to the end on the connection point CP1 side. Note that (i) "l1-1" (L1-1) and "l1-2" (L1-2), and (ii) "l2-1" (L2-1) and "l2-2" (L2-2) may be the same value or different values.

[0090] 10B , when the measurement object mounting frame constituting the weight detection device 100 of this modified example has the lower frame link LFL fixed to a fixed object and the measurement object MO placed on the upper frame link UFL, the right and left connecting arm links CAL-R and CAL-L rotate about the connecting points CP1-CP4 as the rotation axes, causing the upper frame link UFL fixed to the top plate 112 to sink downward in the drawing. At this time, the measurement object mounting frame of this modified example functions as a type of parallel link mechanism in which the upper frame link UFL remains parallel to the fixed lower frame link LFL as described above, regardless of where the measurement object MO is placed on the upper frame link UFL, like a Roberval mechanism. Also, at this time, in the weight detection device 100 of this modified example, the lower frame link LFL fixed to the fixed object does not move left or right in Figure 10, while (a) the two connecting arm links CAL-R and CAL-L, and (b) the upper frame link UFL connected to the lower frame link LFL fixed by the leaf springs LS1 to LS4 of the weight detection device 10, moves to the right of the drawing by a distance "Δl" (Delta El) while sinking downward in the drawing depending on the weight of the object to be measured MO or the magnitude of the applied pressure.

[0091] As a result, in the weight detection device 100 of this modified example, the lower frame link LFL fixed to a fixed object in the measurement object mounting frame and the lower plate 115 fixed thereto are maintained in an immovable state. On the other hand, the upper frame link UFL connected to the fixed lower frame link LFL by the two connecting arm links CAL-L and CAL-R and the upper plate 112 fixed thereto move in the vertical direction in the drawing depending on the average spring length of the leaf springs LS1 to LS4 constituting the variable capacitor 110 of the weight detection device 10, which is sandwiched and installed between the upper and lower frame links UFL and LFL. For example, as illustrated in Figure 10(A), when the measurement object MO is not placed on top of the upper frame link UFL (i.e., when the placed weight is "0 kg"), the average spring length of the leaf springs LS1 to LS4 that make up the variable capacitor 110 is maintained at "x1", which is approximately equal to the initial length of the average spring length of the leaf springs LS1 to LS4 (for example, approximately "19.00 mm" in the above example) (see Figure 10(A)), as in the case illustrated in Figure 2(A).

[0092] On the other hand, when a measurement object MO of a predetermined weight (e.g., 1 kg) is placed on the upper frame link UFL, the leaf springs LS1 to LS4 constituting the variable capacitor 110 elastically deform in accordance with the weight of the measurement object MO, and the average spring length contracts to x2 (e.g., approximately 12.00 mm). At this time, the upper frame link UFL and the upper plate 112 sink downward in FIG. 10 by Δx1 = x1 - x2. For example, if the initial lengths x1 and x2 are the values ​​in the above example, the upper frame link UFL and the upper plate 112 sink downward in the drawing by approximately 7 mm = 19.00 mm - 12.00 mm. At this time, similar to the variable capacitor 110 in the above embodiment, the movable electrode installation member 113A is pulled to the left in FIGS. 1 and 2 by the pull spring 117 by the distance the upper plate 112 sinks downward (i.e., 7 mm). As a result, the area of ​​the region where the movable electrode 113 and the fixed electrode 114 face each other and overlap changes by this distance, and the capacitance value "C" of the variable capacitor 110 changes. Note that this point is similar to the above-described embodiments and modifications, so details will be omitted. Also, similar to the above-described embodiment, the inter-electrode distance "x1" when the load weight is "0 kg" is determined by the combined influence of factors such as the weight of the load portion 111 and the upper plate 112 and the spring constants of the leaf springs LS1 to LS4. However, in the case of this modified example, the frictional force during rotational movement of the two connecting arm links CAL-R and CAL-L rotatably connected to the upper and lower frame links UFL and LFL, and the weight of the upper frame link UFL can also be factors in determining "x1".

[0093] Furthermore, in this modified example as well, when the load weight is "0 kg" (i.e., when the average spring length of the leaf springs LS1 to LS4 is "x1"), the upper plate 112 and the movable electrode installation member 113A are connected by the connecting member 116 without slack, and it is necessary to set the movable electrode 113 to be in a predetermined initial position when the load weight is "0 kg." When the measurement object MO is placed on the upper frame link UFL and the upper frame link UFL and the upper plate 112 move downward in the drawing, slack occurs in the connecting member 116, and the movable electrode installation member 113A is pulled by the pull spring 117 toward the pull spring fixing member 115A (e.g., to the left in FIGS. 1 and 2). As a result, the area of ​​the region where the movable electrode 113 and the fixed electrode 114 face each other and overlap changes, and the capacitance value "C" of the variable capacitor 110 changes. In this modification, the capacitance value "C" at this time is detected by the capacitance sensor tag 120, and the information processing device 30 reads detection data corresponding to the detection result from the capacitance sensor tag 120 via the RFID reader / writer 20. The information processing device 30 then measures the weight of the measurement object MO placed on the upper frame link UFL based on (a) the detection data and (b) measurement reference data suitable for the characteristics of the variable capacitor 110, which has been previously stored in the information processing device 30, or calibrated measurement reference data obtained by calibrating the measurement reference data. The upper frame link UFL and the lower frame link LFL in this modification correspond to the "first and second frame links" of the present invention, respectively. The specific operation at this time is similar to that of the above-described embodiments and modifications, and therefore will not be described in detail.

[0094] With this configuration, even when the measurement object MO is placed near the end of the upper frame link UFL, the weight detection device 100 of this modified example can distribute the weight uniformly across the entire upper plate 112 of the variable capacitor 110 because the upper frame link UFL moves downward in the drawing while remaining parallel to the lower frame link LFL. Generally, when the measurement object MO is placed near the end of the upper plate 112, the weight on the upper plate 112 becomes uneven, and only some of the leaf springs LS1-LS4 elastically deform. In this case, the correlation between the capacitance value "C" detected by the variable capacitor 110 and the weight of the object placed on the mounting portion 111 becomes poor. As a result, the measured weight may be heavier or lighter than the actual weight, making it difficult to accurately measure the weight of the object MO placed on the mounting portion 111. On the other hand, with the configuration of this modified example, the weight can be uniformly distributed across the entire upper plate 112, allowing the weight of the object MO to be measured accurately. While this modification has been described with reference to an example in which the weight of a measurement object MO is detected, product inventory may also be managed based on the measured weight. In this case, the management method is the same as in the above-described embodiments. Furthermore, a similar method can be used to measure the value of pressure applied to the upper frame link UFL, as in the above-described modification. In this case, even if pressure is concentrated near the end of the upper frame link UFL, the value of the applied pressure can be measured with high accuracy. Furthermore, in Figure 10, the weight detection device 100 is constructed by sandwiching the weight detection device 10 between the upper frame link UFL and the lower frame link LFL, but it is also possible to configure the upper plate 112 and the lower plate 115 to have the same length as above, and to connect the two connecting arm links CAL-R and CAL-L that connect the two plates 112 and 115 to be rotatably connected to both members 112 and 115, so that when the measurement object MO is placed on the mounting section 111, the upper plate 112 moves up and down while remaining parallel to the lower plate 115, regardless of where the measurement object MO is placed on the mounting section 111.However, in this case, it is necessary to provide connection points CP1 to CP4 on the upper plate 112 and the lower plate 115 at the same positions as when two connecting arm links CAL-R and CAL-L are connected to the upper and lower frame links UFL and LFL in Fig. 10. For this reason, in this case, it is preferable to set the upper plate 112 and the lower plate 115 to the same lengths as the upper and lower frame links UFL and LFL shown in Fig. 10. Also, in this case, it is necessary to adjust the installation positions of the connecting arm links CAL-R and CAL-L and the installation positions of the leaf springs LS1 to LS4 so that the left and right connecting arm links CAL-R and CAL-L sandwich the leaf springs LS1 to LS4. Furthermore, in this case, as in the above example, it is necessary to set (i) the distance from CP1 to CP4 and (ii) the distance from CP2 to CP3 equal, and form a parallelogram using the upper plate 112, the lower plate 115, and the two connecting arm links CAL-R and CAL-L.

[0095] On the other hand, if a configuration is adopted in which a separate measurement object mounting frame is provided and the weight detection device 10 is sandwiched between the upper and lower frame links UFL and LFL, the measurement object mounting frame can be constructed using a member that is larger and sturdier than the upper plate 112 and the lower plate 115. As a result, according to the configuration of this modification, the range of measurable weights can be expanded by appropriately setting the number, initial length, and spring constant of the leaf springs LS. Note that, although this modification has been described as using a weight detection device 10 that uses leaf springs LS1 to LS4, a weight detection device 10 that uses, for example, four or five coil springs as the "first elastic member" as in the second modification may also be used.

[0096] 1...Weight measurement system, 10...Weight detection device, 110...Variable capacitor, 111...Placement portion, 112...Upper plate, 113...Movable electrode, 113A...Movable electrode installation member, 114...Fixed electrode, 114A...Fixed electrode installation member, 115...Lower plate, 115A...Pulling spring fixing member, 115B...Direction conversion member, 115C...Hollow area, 116...Connecting member, 117...Pulling spring, 120...Capacitive sensor tag, 120A...First input terminal, 120B...Second input terminal, 20...RFID reader / writer, 30, 300...Information processing device, AN...Antenna, ICC...IC chip, LS1 to 4...Leaf spring, UFL...Upper frame link, LFL...Lower frame link, CAL-R, CAL-L...Connecting arm link, CP1 to 4...Connection point

Claims

a variable capacitor constructed of two members connected by a first elastic member in a mutually opposing state, the first member being movable in response to the elastic deformation of the first elastic member when a load or pressure is applied thereto; (2) a second member having a fixed electrode installed at a predetermined position and fixed so as not to move even when the load or pressure is applied to the first member; and (3) a movable electrode installation member connected to the first member by a connection member and having a movable electrode installed at a position opposite the fixed electrode, the first elastic member elastically deforming in response to the state of application of the load or pressure to the first member, and when the first member moves, the movable electrode installation member moves in response to the movement of the first member, so that the area of ​​the overlapping region between the movable electrode and the fixed electrode while facing each other changes in response to the amount of movement of the first member, thereby changing the capacitance value; a capacitance sensor electrically connected to the variable capacitor, detecting a capacitance value of the variable capacitor and wirelessly transmitting corresponding detection data; (1) a physical quantity measuring device that stores in advance reference data defining the relationship between the value of the load or pressure applied to the first member and the capacitance value of the variable capacitor, measures the value of the load or pressure applied to the first member based on the reference data and (2) the detection data wirelessly transmitted by the capacitance sensor, and executes processing based on the measurement results; A physical quantity measuring system comprising: 　 The movable electrode installation member is 2. The physical quantity measurement system according to claim 1, wherein the first elastic member is connected to the first member by the connecting member when the first elastic member is in a position where no elastic deformation occurs, and the second elastic member is connected to a predetermined position of the second member, and when the first elastic member elastically deforms and the first member moves, the movable electrode and the fixed electrode are pulled by the second elastic member, and an area of ​​the region where the movable electrode and the fixed electrode face each other and overlap changes according to the amount of movement of the first member. 　 a plurality of physical quantity detection devices each including the variable capacitor and the capacitance sensor are installed at different positions in real space; The physical quantity measuring device is a storage means for storing the reference data corresponding to each of the plurality of physical quantity detection devices in association with identification information for identifying the physical quantity detection device; 3. The physical quantity measurement system according to claim 1, wherein (a1) the detection data corresponding to a capacitance value of a variable capacitor constituting the corresponding physical quantity detection device and (a2) the identification information corresponding to the physical quantity detection device are wirelessly acquired from each of the capacitance sensors constituting the plurality of physical quantity detection devices while associating the detection data with the identification information; (b1) the detection data acquired in association with the identification information and (b2) the reference data stored in the storage means in association with the acquired identification information; and the physical quantity measurement system performs processing based on the measurement results. 　 The storage means includes: Product attribute information indicating attributes of a product whose inventory is managed using the corresponding physical quantity detection device is stored in association with the identification information and the reference data; The physical quantity measuring device is 4. The physical quantity measurement system according to claim 3, wherein the load applied to the first member is measured as a weight value of a commodity whose inventory is managed using the physical quantity detection device based on the acquired detection data and the reference data corresponding to the physical quantity detection device that is the source of the detection data, and a process of managing inventory of the commodity managed using each of the physical quantity detection devices is executed based on the measured load and commodity attribute information of the corresponding commodity stored in the storage means. 　 The capacitance sensor 3. The physical quantity measuring system according to claim 1, wherein the physical quantity measuring system is configured as an RFID tag, and generates an electromotive force based on electromagnetic waves transmitted by the physical quantity measuring device or another device, or on a magnetic field generated by the physical quantity measuring device or another device, and detects the capacitance value of the variable capacitor using the electromotive force, and wirelessly transmits the detection data corresponding to the detection result to the physical quantity measuring device. 　 The variable capacitor (a) the first member and the second member are connected to each other by two connecting arm links that are rotatably connected to (a1) the first member and (a2) the second member, or (b1) a first frame link fixed to the first member and (b2) a second frame link fixed to the second member, and that are arranged in parallel with the first elastic member and have the same length, and (a) the first member and the second member are connected to each other, or (b) the first frame link and the second frame link are connected to each other, and (A) the first and second members, or (B) the first and second frame links, and at each connecting point, 3. The physical quantity detection system according to claim 1, wherein a parallel link mechanism is constructed in which a parallelogram is formed by members constituting sides formed by the first elastic member and the first frame link, and when the first elastic member elastically deforms in accordance with the state of application of the load or pressure to the first member or the first frame link, the first member or the first member fixed to the first frame link moves while remaining parallel to the second member, causing the movable electrode installation member to move, whereby an area of ​​a region where the movable electrode and the fixed electrode face each other and overlap each other changes in accordance with an amount of movement of the first member or the first member fixed to the first frame link, thereby changing the capacitance value. 　 a variable capacitor constructed of two members connected by a first elastic member in a mutually opposing state, the first member being movable in response to the elastic deformation of the first elastic member when a load or pressure is applied thereto; (2) a second member having a fixed electrode installed at a predetermined position and fixed so as not to move even when the load or pressure is applied to the first member; and (3) a movable electrode installation member connected to the first member by a connection member and having a movable electrode installed at a position opposite the fixed electrode, the first elastic member elastically deforming in response to the state of application of the load or pressure to the first member, and when the first member moves, the movable electrode installation member moves in response to the movement of the first member, so that the area of ​​the overlapping region between the movable electrode and the fixed electrode while facing each other changes in response to the amount of movement of the first member, thereby changing the capacitance value; a capacitance sensor electrically connected to the variable capacitor, detecting a capacitance value of the variable capacitor and generating corresponding detection data, the capacitance sensor comprising: (1) pre-storing reference data defining a relationship between a value of a load or pressure applied to the first member and a capacitance value of the variable capacitor, and wirelessly transmitting the generated detection data to a physical quantity measuring device that measures the value of the load or pressure applied to the first member based on the detection data generated by the capacitance sensor and executes processing based on the measurement results; A physical quantity detection device comprising:

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