Sensor

Abstract

To protect a detection element of a sensor and an amplifier circuit for amplifying a signal of the detection element from an electromagnetic wave environment.SOLUTION: The detection device includes a shield case made of a conductive resin material, the shield case being disposed between the second case and the first case, having a container shape with one surface opened, and holding the detection element inside, and a substrate assembly disposed on one surface of the shield case, the substrate assembly holding an amplifier circuit that amplifies a signal of the detection element, a control unit that controls the detection element, a transmission unit that transmits a notification signal to the outside, and an output antenna. The substrate assembly includes a conductive ground conductor film that closes one surface of the shield case, the ground conductor film is electrically connected to the shield case, and the output antenna is electrically connected to the ground conductor film. Since the shield space is formed by the shield case and the ground conductor film, and the detection element and the amplifier circuit are disposed in this space, the electromagnetic wave resistance performance can be enhanced, and the ground conductor film of the substrate assembly and the shield case can be used for the ground of the output antenna.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a detector, which is useful as a smoke detector to be installed near electrical wiring or transformers in factories where there is a high risk of fire, for example. [Background technology]

[0002] Smoke detectors equipped with an output antenna are disclosed in Patent Documents 1 and 2. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-59947 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-170274 Summary of the Invention [Problem to be solved by the invention]

[0004] The smoke detector disclosed in Patent Document 1 uses a metal conductor to ensure the ground of the output antenna. The smoke detector disclosed in Patent Document 2 uses a metal insect screen to ensure the ground of the output antenna. However, both of these documents simply ensure the ground of the output antenna. Therefore, neither document considers the electromagnetic wave resistance of electronic components.

[0005] In view of the above, an object of the present disclosure is to protect a detection element, which is a sensor of a detector, and an amplifier circuit that amplifies a signal detected by the detection element, from an electromagnetic wave environment. [Means for solving the problem]

[0006] The sensor of the present disclosure includes a first case (120) made of a non-conductive resin material that is attached to the detection site, and a second case (130) made of a non-conductive resin material that is attached to the first case. The sensor of the present disclosure also includes a shield case (150) made of a conductive material that is disposed between the second case and the first case, has a container shape with one side open, and holds a detection element inside the container shape. The sensor also includes a board assembly (140) that is disposed on one side of the shield case and holds an amplifier circuit (170) that amplifies a signal detected by the detection element, a control unit (141) that controls the detection element, a transmission unit (142) that transmits an alarm signal determined by the control unit based on the signal detected by the detection element to the outside, and an output antenna (143).

[0007] The circuit board assembly of the sensor of the present disclosure has a conductive ground conductor film (1402) that extends over one surface of the shielding case and is electrically connected to the shielding case. The amplifier circuit is located on the shielding case side of the ground conductor film. The output antenna uses the ground conductor film and the shielding case as grounds.

[0008] According to the present disclosure, a shielded space is formed by a shielding case made of a conductive resin material and a conductive ground conductor film. A sensing element and an amplifier circuit are disposed within this shielded space. This allows the sensor of the present disclosure to have enhanced electromagnetic wave resistance. For example, even when the sensor is mounted near electrical wiring or a transformer, it can still have sufficient electromagnetic wave resistance.

[0009] Furthermore, according to the present disclosure, the ground conductor film and the shielding case of the circuit board assembly can be used as the ground for the output antenna, thereby improving the radiation efficiency of the output antenna in the sensor of the present disclosure.

[0010] When the detector of the present disclosure is used as a smoke detector (100), it further includes a base (110) that is fixed to the detection site of a building. The first case is attached to the base. The second case forms a smoke detection space (132) therein and is configured to introduce smoke into the smoke detection space and block external light. The detection element includes a light-emitting element (151) that projects light toward the smoke detection space and a light-receiving element (152) that detects the light projected from the light-emitting element and scattered in the smoke detection space. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view of a smoke detector according to an embodiment of the present invention. [Figure 2] FIG. 2 is an exploded perspective view of the smoke detector. [Figure 3] FIG. 2 is a front view showing a board assembly and a shield case of the smoke detector. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 2 is a perspective view showing a board assembly and a shield case of the smoke detector. [Figure 6] FIG. 2 is a circuit diagram showing an amplifier circuit of a smoke detector. [Figure 7] FIG. 2 is a front view showing the mounting surface of the smoke detector circuit board assembly disassembled. [Figure 8] FIG. 2 is a front view showing the ground conductor film when the substrate assembly of the smoke detector is disassembled. [Figure 9] FIG. 2 is a front view showing the circuit surface of the smoke detector circuit board assembly disassembled. [Figure 10] FIG. 2 is a perspective view of a substrate assembly of the smoke detector. [Figure 11] FIG. 10 is a front view showing an amplifier circuit configured on the circuit surface shown in FIG. [Figure 12] FIG. 2 is a perspective view showing the arrangement of smoke detectors. [Figure 13] FIG. 10 is an exploded perspective view showing another example of a smoke detector. [Figure 14] FIG. 13 is a perspective view showing a third case of the example shown in FIG. [Figure 15] FIG. 2 is a diagram illustrating the directivity of an antenna. [Figure 16] 10A and 10B are diagrams illustrating the relationship between the presence or absence of a metal plate and antenna performance. DETAILED DESCRIPTION OF THE INVENTION

[0012] FIG. 1 shows an example of a detector according to the present disclosure used as a smoke detector 100. The smoke detector 100 is installed, for example, near electrical wiring or transformers in a factory where there is a high risk of fire. Therefore, the smoke detector 100 is installed in a location where electromagnetic wave resistance is required. The smoke detector 100 is small enough to be held by a worker in one hand. The smoke detector 100 has a cylindrical shape with a diameter of approximately 50 millimeters and a height of approximately 45 millimeters. The total weight is approximately 50 grams.

[0013] FIG. 2 shows an exploded view of the components of the smoke detector 100. Arranged from top to bottom are a base 110, a first case 120, and a second case 130. The base 110 is made of a non-conductive resin material, such as ABS resin (acrylonitrile butadiene styrene resin). The base 110 is formed into a disk shape by injection molding the ABS resin. As mentioned above, its diameter is approximately 50 millimeters. The base 110 is fixed to the detection target using screws or double-sided tape. The detection target is usually the ceiling of a building. However, in factory buildings, ventilation openings are often installed in the ceiling, and air is often blown downward through these openings. Therefore, even in the event of a fire, smoke does not reach the ceiling easily. If smoke fills the area around the ceiling, the fire may have progressed significantly.

[0014] The smoke detector 100 of this example is placed on the production line, not on the ceiling of a factory building. Specifically, as shown in FIG. 12, it is placed inside a control box 200 where electrical wiring is concentrated, or a transformer box that houses a transformer. Alternatively, it is placed inside a safety case that houses cutting machines and soldering machines on the production line. Both are closed spaces that quickly fill with smoke in the event of a fire. Therefore, the base 110 is fixed to a top plate 201 of the space, such as the control box 200, rather than to the ceiling. Therefore, the detection area in this example is near the expected source of smoke. Since screwing requires additional processing of the top plate 201, the base 110 of this example is mainly fixed to the top plate 201 with double-sided tape.

[0015] 12 shows an example where the smoke detector 100 is fixed to the side wall 202 in addition to an example where the smoke detector 100 is fixed to the top panel 201. However, two smoke detectors 100 are not usually installed in one control box 200. FIG. 13 shows fixing to the side wall 202 to explain an example of placement. As shown in FIG. 13, when fixing the smoke detector 100 to the side wall 202, it is desirable to fix it in an upper position. Furthermore, since a fan 203 is usually provided in the control box 200 for exhausting heat, it is desirable to place the smoke detector 100 in a position near the fan 203 where it is affected by the air flow caused by the fan 203.

[0016] Typically, several tens to around 200 smoke detectors 100 are installed on one production line. Each smoke detector 100 is equipped with a transmitter 142, which will be described later. Signals from each smoke detector 100 are transmitted wirelessly to a receiver installed on the production line. The signals from each smoke detector 100 received by the receiver are sent to a management server installed at a location away from the production line via a communication line such as the Internet and / or an intranet cloud system. The communication line of the cloud system or the like may be wired and / or wireless.

[0017] Like the base 110, the first case 120 is made of a non-conductive resin material. The first case 120 is also formed by injection molding of ABS resin. The first case 120 holds a battery 121 inside. Specifically, battery fixing tabs formed on the first case 120 are elastically deformed to hold the battery 121 by their own elasticity. The battery 121 is electrically connected to a power connector 145 formed on the board assembly 140, which will be described later. The power connector 145 electrically connects the negative terminal to the ground conductor film 1402 and the positive terminal to the power conductor film 1403. In this example, a 3-volt battery 121 is used. The first case 120 is fitted into snap-fit ​​tabs 111 of the base 110. The first case 120 can be attached to or detached from the base 110 by rotating it relative to the base 110.

[0018] The second case 130 is also made of a non-conductive resin material and is formed by injection molding of ABS resin. The second case 130 is fixedly connected to the first case 120 by fixing claws. Therefore, when the first case 120 is attached to the base 110 as described above, all components of the smoke detector 100 held between the first case 120 and the second case 130, including the battery 121, are attached to or detached from the base 110.

[0019] The second case 130 has a cylindrical shape with a closed bottom end, which is hemispherical. Multiple inlet windows 131 are formed at equal intervals around the periphery on the cylindrical side of the second case 130 to introduce smoke that has flowed near the top plate of the closed space. In this example, 14 inlet windows 131 are formed. A smoke detection space 132 is formed at the center of the hemispherical bottom end of the second case 130. The inlet windows 131 and the smoke detection space 132 are connected so that smoke introduced through the inlet windows 131 flows into the smoke detection space 132. However, multiple labyrinth walls 133 are disposed between the inlet windows 131 and the smoke detection space 132. In this example, 16 labyrinth walls 133 are formed. Therefore, the labyrinth walls 133 prevent external light from reaching the smoke detection space 132. In other words, the labyrinth walls 133 block external light. However, blocking external light does not necessarily mean blocking 100% of the external light. In this disclosure, blocking external light means preventing the entrance of an amount of external light that would adversely affect the light receiving element 152.

[0020] The circuit board assembly 140, the shield case 150, and the insect screen 160 are disposed between the first case 120 and the second case 130. The shield case 150 is made of a conductive resin material. The shield case 150 is injection-molded from a resin material, for example, a blend of PA6 resin (6-nylon resin) and CF30 resin (carbon fiber reinforced resin). The shield case 150 has a container shape with one side open, and holds a light-emitting element 151 and a light-receiving element 152 inside the container shape. More specifically, as shown in FIG. 4, the shield case 150 holds the light-emitting element 151 and the light-receiving element 152 in positions where the light-emitting element 151 and the light-receiving element 152 face the smoke detection space 132. In the smoke detector 100, the light-emitting element 151 and the light-receiving element 152 function as the detector's detection element. The detection element of the smoke detector 100 may be a chemical gas sensor that detects gas components.

[0021] Light emitting element 151 is an LED that projects light toward smoke detection space 132, and projects light with an intensity of, for example, about 20 milliwatts. As shown in Fig. 4, a light projecting holding groove 156 through which the light projected from light emitting element 151 passes is formed in a portion of shielding case 150 between light emitting element 151 and smoke detection space 132. Light emitting holding groove 156 is about 4 millimeters wide, and the light from light emitting element 151 reaches smoke detection space 132 through light emitting holding groove 156.

[0022] Light receiving element 152 is a photodiode that detects scattered light when smoke is introduced into smoke detection space 132 and light projected from light emitting element 151 is diffused by the smoke. As shown in FIG. 4 , a light receiving groove 1542 is formed in shielding case 150 between light receiving element 152 and smoke detection space 132, through which light emitted in smoke detection space 132 passes toward light receiving element 152. Like light projecting groove 156, light receiving groove 1542 has a groove width of approximately 4 millimeters. Note that light receiving element 152 is positioned away from the optical axis of light emitting element 151. In other words, light receiving element 152 does not directly detect light projected from light emitting element 151, but rather detects scattered light diffused by smoke. Because the scattered light diffused by smoke is weak, the output signal from light receiving element 152 is a weak current of approximately several nanoamperes.

[0023] As described above, since the shield case 150 is made of a conductive resin material, the light emitting element 151 is held in a light emitting element holder 153 made of ABS resin, a non-conductive resin material. The light emitting element 151 is electrically insulated from the shield case 150 and the board assembly 140 by this light emitting element holder 153. Similarly, the light receiving element 152 is held in a light receiving element holder 154 made of ABS resin, a non-conductive resin material, and is electrically insulated from the shield case 150 and the board assembly 140. The light emitting element holder 153 is held in the light emitting holding groove 156 described above. Furthermore, the light receiving element holder 154 is held in the light receiving holding groove 1542. The light emitting element holder 153 has a light projection hole 1531 through which light projected from the light emitting element 151 passes toward the smoke detection space 132. The light projection hole 1531 is a circular hole with a diameter of approximately 3 millimeters. Similarly, light receiving element holder 154 also has a light receiving hole 1541 that allows scattered light to pass through toward light receiving element 152. Light receiving hole 1541 is also a circular hole with a diameter of about 3 mm.

[0024] The light emitting element 151 and the light receiving element 152 are available in two types of packages: a conductive metal package and an electrically insulating resin package. In this example, the light emitting element 151 and the light receiving element 152 are used in metal packages, which are superior in performance and reliability. For this reason, an ABS resin light emitting element holder 153 and a light receiving element holder 154 are used to ensure electrical insulation. However, it is also possible to use a resin package for the light emitting element 151 and the light receiving element 152. When a resin package is used, the ABS resin light emitting element holder 153 and the light receiving element holder 154 are not necessary because the resin package is inherently electrically insulating.

[0025] The board assembly 140 is disposed on one side of the shield case 150 as an opening. As shown in FIGS. 3, 5, and 10, the board assembly 140 holds a control unit 141, a transmitting unit 142, an output antenna 143, an alarm LED 146, and a power connector 145. The control unit 141 is a one-chip microcomputer including a CPU that controls the light-emitting element 151 and the light-receiving element 152, and is equipped with an internal temperature sensor. The control unit 141 also monitors the remaining charge of the battery 121. The transmitting unit 142 is a communication module that transmits signals to the outside and is equipped with an internal transmission circuit. The transmitted signals include a steady-state signal and an alarm signal. The alarm signal is a signal transmitted by the control unit 141 to indicate the possibility of a fire if the signal detected by the light-receiving element 152 is equal to or greater than a predetermined threshold. The alarm LED 146 lights up when an alarm signal is output. As described above, the smoke detector 100 of this example is placed in a closed space, but the safety cover and the like are visible from the outside, so the occurrence of a fire can be notified to those around by lighting up the notification LED. As shown in Fig. 10, the notification LED 146 is mounted on the same surface as the control unit 141. On the other hand, the light emitting element 151 and the light receiving element 152 are mounted on the surface opposite to the surface on which the control unit 141 is mounted. The output antenna 143 is a monopole antenna made of copper wire insulated with polyethylene resin. The length of the output antenna 143 is determined according to the output frequency. For factory wireless communication, a lower transmission frequency is used compared to the frequency (2.4 GHz) used for Wi-Fi and Bluetooth (registered trademark) to improve diffraction and reach. The frequency used in this example is, for example, 920 MHz. As the frequency decreases, the wavelength of the radio wave increases, and the length and surface area of ​​the output antenna 143 must be increased accordingly. In this example, the length of the output antenna 143 is approximately 80 millimeters. Note that the output antenna 143 is a monopole antenna because it can be made smaller than a dipole antenna. However, in this disclosure, as described below, a sufficient ground is provided for the output antenna 143. Therefore, in this example, the ground can function as a second antenna in a dipole antenna. Therefore, although the output antenna 143 in this example is a monopole antenna, it is designed to have performance approaching that of a dipole antenna.

[0026] 7, 8, 9, and 11, the substrate assembly 140 has a four-layer structure separated by three insulating substrates: a first insulating substrate 1405, a second insulating substrate 1406, and a third insulating substrate 1407. Fig. 7 shows the first layer, which is the upper surface of the first insulating substrate 1405. The first layer is a mounting surface 1401 on which the control unit 141 (CPU, etc.), the transmission unit 142 (communication module), the notification LED 146, and the power connector 145 are mounted.

[0027] The second layer of the substrate assembly 140 is a power supply conductor film sandwiched between a first insulating substrate 1405 and a second insulating substrate 1406 on the top and bottom. Although not shown, the back surface in FIG. 7 and the back surface in FIG. 8 are the second layer. On this second layer, a power supply conductor film is formed of copper foil with a thickness of about 18 micrometers, and the power supply conductor film is formed in approximately the same position as a ground conductor film 1402 (described below). As described above, the power supply conductor film is electrically connected to the positive terminal of the battery 121 via the power connector 145, and positive power is supplied from the battery 121. The light-emitting element 151, the light-receiving element 152, and the notification LED 146 are also electrically connected to this power supply conductor film 1403 and receive a supply of electricity.

[0028] The third layer of the substrate assembly 140 is a ground conductor film 1402 sandwiched between a second insulating substrate 1406 and a third insulating substrate 1407 on the top and bottom. This ground conductor film 1402 is made of a conductive metal material such as copper foil, and its thickness is approximately 18 micrometers, similar to that of the power conductor film. As shown in FIG. 8, the ground conductor film 1402 is formed over substantially the entire surface of the substrate assembly 140. More specifically, the ground conductor film 1402 is divided into multiple island-shaped areas, each having linear slit-like gaps. The reason for dividing it into multiple island-shaped areas is to separate the ground conductor film 1402 for the analog circuit from the ground conductor film 1402 for the digital circuit, thereby reducing the transmission of noise.

[0029] Because the ground conductor film 1402 is formed over substantially the entire surface of the board assembly 140, the board assembly 140 has the ground conductor film 1402 that extends over one side of the shielding case 150. As a result of the ground conductor film 1402 extending over the entire surface of the shielding case 150, one side of the shielding case 150 is blocked by the ground conductor film 1402. As shown in FIG. 5 , the board assembly 140 is fixed to the shielding case 150 at two locations using fasteners 144 made of conductive metal. The fasteners 144 are screws made of an iron-based material, and the ground conductor film 1402 is electrically connected to the shielding case 150 via these fasteners 144. In other words, the ground conductor film 1402 and the shielding case 150 form a closed space, which serves as a shielded space and shields the interior from electromagnetic waves. The ground conductor film 1402 is electrically connected to the negative terminal of the battery 121 via the power connector 145. The "one surface of shield case 150" is also referred to as the open end surrounded by the open edge of shield case 150, which may be called a container-shaped or bottomed cylindrical shape.

[0030] The fourth layer of the substrate assembly 140 is a circuit surface 1404 on which an amplifier circuit 170 (shown in FIG. 6) that amplifies a signal detected by the light-receiving element 152 is mounted. Therefore, this circuit surface 1404 is also a mounting surface. However, in this example, the first layer on which the control unit 141 and the like are mounted is referred to as the mounting surface 1401, and the fourth layer on which the amplifier circuit is mounted is referred to as the circuit surface 1404. As shown in FIG. 9, the circuit surface 1404 is located on the underside of the third insulating substrate 1407. In addition to the amplifier circuit 170, positive wiring connecting a power supply conductor film to the positive terminals of the light-emitting element 151 and the light-receiving element 152 is printed on the circuit surface 1404. Negative wiring connecting a ground conductor film 1402 to the negative terminals of the light-emitting element 151 and the light-receiving element 152 is also printed on the circuit surface 1404. Furthermore, the signal line of the light-receiving element 152 is also printed on the circuit surface 1404.

[0031] FIG. 11 shows a circuit side 1404 similar to that shown in FIG. 9, but the light-emitting element 151 and the light-receiving element 152 have been removed. Therefore, the amplifier circuit 170 is mounted in the area surrounded by the dashed line in FIG. 11. The circuit side 1404 on which the amplifier circuit 170 is formed is disposed on the shielding case 150 side of the ground conductor film 1402. More specifically, it is located in a shielded space enclosed by the above-mentioned ground conductor film 1402 and the shielding case 150. The signal lines of the amplifier circuit 170 and the light-receiving element 152 formed on the circuit side 1404 are sensitive to electromagnetic noise. By locating them in a closed space as in this example, electromagnetic wave shielding is ensured.

[0032] As shown in FIG. 6 , the amplifier circuit 170 of this embodiment includes a current-voltage conversion circuit 171 and a voltage amplifier circuit 175. The current-voltage conversion circuit 171 includes a first capacitor 172, a first resistor 173, and a first operational amplifier 174. The current-voltage conversion circuit 171 amplifies the output current of approximately several nanoamperes from the light-receiving element 152 to a voltage of approximately 1,000,000 times the original voltage. The voltage amplifier circuit 175 also includes a second capacitor 176, a second resistor 177, and a second operational amplifier 178. The voltage from the current-voltage conversion circuit 171 is amplified approximately 300 times. For example, the output current of approximately several millivolts from the current-voltage conversion circuit 171 is amplified to a voltage of approximately 1 volt by the voltage amplifier circuit 175. Therefore, the control unit 141 determines whether to transmit a notification signal based on the signal from the light-receiving element 152 amplified by the amplifier circuit 170.

[0033] The output antenna 143 has a linear portion 1431 extending perpendicularly from the transmitter 142 of the board assembly 140 and an arc portion 1432 that fits along the antenna fixing groove formed on the inner circumferential surface of the first case 120. Therefore, in this example, being arranged in an arc shape along the inner periphery refers to being arranged along the antenna fixing groove formed on the inner circumferential surface of the first case 120, which has a substantially circular shape. However, the arc shape does not have to be an exact circle; it can be any shape that is curved like a bow. The linear portion 1431 is connected to the transmitter 142. The ground of the transmitter 142 is electrically connected to the ground conductor film 1402 through via holes formed in the first insulating substrate 1405 and the second insulating substrate 1406 and is fixed to the first insulating substrate 1405 with solder. As described above, the ground conductor film 1402 is electrically connected to the shielding case 150. Therefore, the output antenna 143 is electrically connected to the ground conductor film 1402 of the board assembly 140 and the shielding case 150, and uses the ground conductor film 1402 and the shielding case 150 as a ground. This allows the ground to function as a second antenna, as described above, and can improve the radiation efficiency of the output antenna 143.

[0034] Furthermore, the fixing device 144 electrically connects the ground conductor film 1402 and the shielding case 150 at two locations, improving the electromagnetic wave shielding performance. Specifically, if the fixing device 144 were electrically connected at only one location, the ground conductor film 1402 and the shielding case 150 would behave as a slot antenna, potentially becoming a source of noise inflow. In contrast, if the fixing device 144 is electrically connected at two locations, the ground conductor film 1402 and the shielding case 150 form a closed ground surface, effectively preventing noise inflow. Furthermore, the increase in the number of grounding points reduces the impedance between the shielding case 150 and the ground conductor film 1402. This reduced impedance ensures a reliable current flow, which in turn helps improve the gain of the output antenna 143. The fixing device 144 may be electrically connected at two or more locations, and may be connected at three locations.

[0035] Furthermore, in this example, the straight portion 1431 ensures that the arc portion 1432 of the output antenna 143 is spaced a sufficient distance from the ground conductor film 1402 and the shielding case 150. The ground conductor film 1402 and the shielding case 150 act as an electromagnetic wave shield for the internal space, but this means that the ground conductor film 1402 and the shielding case 150 themselves are made of a conductive resin material and are therefore susceptible to electromagnetic influence. In contrast, in this example, the straight portion 1431 is used to separate the arc portion 1432 of the output antenna 143 from the ground conductor film 1402. In other words, a sufficient distance can be ensured between the arc portion 1432 and the ground conductor film 1402. This prevents the arc portion 1432 from being subjected to electromagnetic influence from the ground conductor film 1402 and the shielding case 150.

[0036] In this example, the insect screen 160 is disposed inside the second case 130 and outside the smoke detection space 132. The insect screen 160 prevents insects from entering the smoke detection space 132 and has a mesh size of about 0.5 millimeters. The insect screen 160 is made of a non-conductive resin material, like the first case 120 and the second case 130, and is formed by folding a thin sheet of net. Specifically, the net is folded into a cylindrical shape, and the end face is inserted into an insect screen 160 holding groove formed in the second case. As a result, the insect screen 160 is held between the second case 130 and the shield case 150 so as to surround the smoke detection space 132.

[0037] Next, the operation of the smoke detector 100 of this embodiment will be described. The smoke detector 100 of this embodiment is attached to the top panel 201 of the control box 200, which is a high-risk area in a factory due to fires. The control unit 141 periodically energizes the light-emitting element 151 to emit light. For example, the light-emitting element 151 is energized for approximately 20 milliseconds once every 10 seconds. This saves power from the battery 121. The light-receiving element 152 is also activated in synchronization with the timing at which the light-emitting element 151 emits light. When there is no fire, no smoke enters the smoke detection space 132, and the light from the light-emitting element 151 is not scattered. Furthermore, the labyrinth wall 133 blocks light from outside. Therefore, the light-receiving element 152, which is activated at the predetermined timing, does not detect light.

[0038] As described above, the light-emitting element 151 and the light-receiving element 152 periodically determine whether or not there is smoke. The control unit 141 periodically transmits information from the transmission unit 142, even when there is no fire. This periodically transmitted information includes a unique number assigned to each smoke detector 100, information indicating the remaining charge of the battery 121, temperature information from a temperature sensor provided in the CPU of the control unit 141, and signal information from the light-receiving element 152. When there is no fire, the signal from the light-receiving element 152 is below a predetermined threshold.

[0039] The control unit 141 transmits periodic information from the transmission unit 142 to an external receiver. Specifically, a signal is transmitted from the output antenna 143 to a receiver arranged on the production line. At this time, the ground conductor film 1402 of the board assembly 140 and the shielding case 150 function as a ground, thereby improving the antenna efficiency of the output antenna 143. Furthermore, the straight portion 1431 keeps the arc portion 1432 of the output antenna 143 away from (separated from) the ground conductor film 1402, making it difficult for electromagnetic coupling to occur between the ground conductor film 1402 and the shielding case 150 and the output antenna 143. This also improves the efficiency of the output antenna 143.

[0040] When a fire breaks out, smoke rises inside the control box 200. The rising smoke flows along the top panel 201, approximately 2 centimeters away from the top panel 201. If a fan 203 is provided in the control box 200, the smoke is subjected to the suction force of the fan 203 and flows along the top panel 201 toward the fan 203. The smoke flows just past the position where the entrance window 131 is open and enters the smoke detection space 132 through the entrance window 131. When the smoke detection space 132 is filled with smoke, the light from the light-emitting element 151 is scattered by the smoke. This scattered light is detected by the light-receiving element 152, which is activated at the same time as the light-emitting element 151, and the light-receiving element 152 outputs a weak detection signal of approximately a few nanoamperes. This detection signal is amplified by the amplifier circuit 170 and input to the control unit 141.

[0041] In this case, if electromagnetic waves are applied to the light receiving element 152 or the amplifier circuit 170, this may cause electromagnetic noise, which may cause the smoke detector 100 to react incorrectly. However, in the smoke detector 100 of this example, a shielded space is formed by the shield case 150 made of a conductive resin material and the ground conductor film 1402. The light receiving element 152 and the amplifier circuit 170 are disposed within this shielded space. Therefore, the light receiving element 152 and the amplifier circuit 170 are less susceptible to disturbances caused by electromagnetic waves.

[0042] When the signal from the light receiving element 152 exceeds a predetermined threshold, the control unit 141 determines that a fire has occurred and transmits an alarm signal from the transmission unit 142. At the same time, it causes the alarm LED 146 to flash. However, the alarm signal may be made redundant to prevent the transmission of erroneous information. For example, since the presence or absence of smoke is periodically determined, it may be determined that an alarm signal has been received when a signal exceeding the threshold is received three or more times in succession. Furthermore, the alarm signal may be determined in combination with a signal from a temperature sensor provided in the CPU of the control unit 141.

[0043] Next, another example of the smoke detector 100 of this embodiment will be described with reference to Figures 13 and 14. Like Figure 2, Figure 13 shows the smoke detector 100 in an exploded view. As shown in Figure 13, the smoke detector 100 of this embodiment has an air guide section formed at a position facing the introduction window 131. Specifically, a first case air guide section 124 is formed at a position facing the first case 120 within the introduction window 131. A shield case air guide section 155 is formed at a position facing the shield case 150 within the introduction window 131. Furthermore, a second case air guide section (labyrinth wall 133) is formed at a position facing the smoke detection space 132 within the introduction window 131.

[0044] When first case 120 and shield case 150 are housed in second case 130, first case air guide section 124, shield case air guide section 155, and second case air guide section (labyrinth wall 133) are continuous. Therefore, air is well guided from introduction window 131, which is formed over substantially the entire axial length, from smoke detection space 132 at one axial end located at the bottom in FIG. 13 to the position of first case 120 at the other axial end located above, by second case air guide section (labyrinth wall 133), shield case air guide section 155, and first case air guide section 124. Furthermore, shield case air guide section 155 and second case air guide section (labyrinth wall 133) also function as a labyrinth wall that prevents external light from entering smoke detection space 132 through introduction window 131.

[0045] 14, shield case airflow guide section 155 also has the function of increasing the surface area of ​​the outer surface of shield case 150. Shield case 150 is formed from a conductive material, and functions as the ground for output antenna 143. Therefore, shield case airflow guide section 155 increases the outer surface area, improving its function as the ground and contributing to improving the output of output antenna 143.

[0046] The antenna performance of the smoke detector 100 shown in Figures 13 and 14 will now be described. Figure 15 is a diagram explaining the directivity of the output antenna 143, with the axial direction of the smoke detector 100 defined as the Z direction. The plane perpendicular to the axial direction Z is the XY plane. Therefore, the planes including the axial direction Z are the ZX plane and the YZ plane, and the plane not including the axial direction Z is the XY plane. The dashed line indicates horizontal polarization a, and the solid line indicates vertical polarization b. As described above, the smoke detector 100 is mounted on the top plate 201 or side wall 202 of the control box 200 or the like by the base 110. The control box 200 or the like is usually made of a metal plate. Therefore, when the smoke detector 100 is mounted on the top plate 201 or side wall 202, the metal plate is located in the axial direction Z.

[0047] Since the presence of the metal plate is thought to have an adverse effect on the performance of output antenna 143, we measured the effect of the metal plate on output antenna 143. Specifically, we measured the antenna performance in the ZX plane, YZ plane, and XY plane when no metal plate was placed, and when a metal plate was placed 5.7 mm away from arc portion 1432 of output antenna 143 in the axial direction Z.

[0048] Figure 16 shows the measurement results. The frequency emitted by the output antenna 143 was 920 MHz. There was concern that the performance of the output antenna 143 would be degraded in the ZX plane and the YZ plane, which include the axial direction Z. However, as shown in Figure 16, the impact was limited. Although a decrease in output was observed in the 180-degree direction where the metal plate was located, it was observed that there was almost no change in the 0-degree to 150-degree and 210-360-degree directions, centered on the 0-degree angle opposite the metal plate. The measurement results for the ZX plane were as follows: With no metal plate in place, the maximum gain for horizontal polarization was -8.23 dBi and the average gain was -11.98 dBi, and the maximum gain for vertical polarization was -10.28 dBi and the average gain was -14.73 dBi. In contrast, with the metal plate in place, the maximum gain for horizontally polarized waves was -5.11 dBi and the average gain was -10.11 dBi, while the maximum gain for vertically polarized waves was -10.32 dBi and the average gain was -15.59 dBi.

[0049] The measurement results in the YZ plane were as follows: Without the metal plate in place, the maximum gain for horizontal polarization was -9.17dBi, the average gain was -12.96dBi, and the maximum gain for vertical polarization was -10.36dBi, the average gain was -12.02dBi. On the other hand, with the metal plate in place, the maximum gain for horizontal polarization was -4.96dBi, the average gain was -10.30dBi, and the maximum gain for vertical polarization was -13.99dBi, the average gain was -20.01dBi.

[0050] In the XY plane, where the metal plate is not included in the plane, the metal plate's effect on the performance of the output antenna 143 is even more limited. The effect of horizontal polarization is barely noticeable. Horizontal polarization is also radiated from 0 degrees to 360 degrees around the entire circumference. The measurement results in the XY plane were as follows: Without the metal plate, the maximum gain of horizontal polarization was -11.16 dBi and the average gain was -13.93 dBi, while the maximum gain of vertical polarization was -7.97 dBi and the average gain was -9.68 dBi. With the metal plate in place, the maximum gain of horizontal polarization was -11.21 dBi and the average gain was -15.33 dBi, while the maximum gain of vertical polarization was -9.14 dBi and the average gain was -10.18 dBi.

[0051] When placed in the space inside the control box 200, radio waves from the output antenna 143 are radiated to the outside from gaps in the control box 200, rubber packing, and fan 203. Therefore, the presence of the metal plate in the axial direction Z is not considered a disadvantage. Rather, radio waves reflected by the metal plate are radiated to the outside from the above-mentioned gaps, and it is considered that the efficiency of the output antenna 143 is improved.

[0052] Since the smoke detector 100 of this example is placed in a closed space such as the control box 200, it does not include a speaker, but a speaker could be used. If a speaker is included, the control unit 141 may activate the speaker while flashing the alarm LED 146. This allows the surrounding area to be notified of a fire. Furthermore, to achieve a compact and lightweight design, the smoke detector 100 of this example only includes a transmitter 142 that transmits signals and does not include a receiver. However, a receiving function is possible. If the smoke detector 100 includes a receiving function, it may be configured to receive alarm signals from other nearby smoke detectors 100. In this case, upon receiving an alarm signal from another smoke detector 100, the speaker may be activated or the alarm LED 146 may be flashed. Furthermore, the receiving function may be used to receive signals from an external management server. For example, the smoke detector 100 may receive a signal to switch the communication channel or the number of bands, allowing the settings of the smoke detector 100 to be changed. In this case, the control unit 141 will change the settings.

[0053] In the above example, the control unit 141 determines whether a fire has occurred and transmits an alarm signal when there is a risk of a fire. This is a desirable example because the alarm signal can be determined near the signal from the light-receiving element 152. However, it is also possible for the smoke detector 100 to always only transmit signals at predetermined times. In this case, the signals from each smoke detector 100 are received by a receiver located on the production line and sent to a management server located at a location separate from the production line via a communication line such as the Internet and / or an intranet cloud system. The management server then determines whether a fire has occurred. If the smoke detector 100 does not determine whether a fire has occurred, the alarm LED 146 is also unnecessary.

[0054] In the above-described embodiment, an example was described in which the detector of the present disclosure was used as a smoke detector 100 in a factory. This is an example of use requiring electromagnetic wave resistance, and is a desirable application of the detector of the present disclosure. However, the smoke detector 100 can also be used for other purposes. It can be used not only in factories but also for environmental monitoring in remote locations. For example, it can be used in substations, inside ship or truck containers, warehouses, and cubicles housing solar power storage batteries. Depending on the usage situation, the base 110 may be screwed to the ceiling of a building. Also, depending on the usage situation, the base 110 may be fixed to the wall of a building. Therefore, in the present disclosure, functioning as a smoke detector 100 means that it can be widely used as a smoke detection device, not limited to use in factories.

[0055] In the above-described embodiment, an example was described in which the detector of the present disclosure is used as a smoke detector 100. The smoke detector 100 is a desirable example of a detector. However, the detector element is not limited to the light-emitting element 151 and the light-receiving element 152. Other detector elements that perform equipment sensing of odors, vibrations, sounds, etc. may also be used. For example, a detector element that detects carbon dioxide or odors may be used to detect the smell of burning grease in a motor installed on a production line, thereby detecting a malfunction of the production line. Furthermore, when an abnormality occurs in a motor installed on a production line, vibrations increase or a loud abnormal noise is generated. By detecting these vibrations or abnormal noises with a detector element, it is possible to detect malfunctions in the production line in advance.

[0056] The sensor of the present disclosure can be used in a wide range of applications as a wireless IOT (Internet of Things) sensor, including home appliances and wearable devices.

[0057] Furthermore, the sizes and materials in the above-described embodiments are merely examples. The size and material of the shield case 150 and other components can be selected appropriately depending on the application of the sensor. For example, while the shield case 150 in the above-described example was injection-molded from a conductive resin material, it may also be formed from a conductive metal material. Examples of metal materials include copper, aluminum, and iron. Alternatively, the shield case 150 may be formed from a non-conductive resin material and then plated or spray-coated with a conductive metal on its surface. Therefore, the shield case 150 made of a conductive material may be made of either resin or metal as long as it is conductive. Furthermore, while the insect screen 160 in the above-described example was made from a non-conductive resin material, the insect screen 160 may also be made from non-conductive stainless steel wire.

[0058] (Disclosure of technical ideas) This specification discloses multiple technical ideas described in the following multiple clauses. Some clauses may be written in a multiple dependent form, with the subsequent clause referring to the preceding clause as an alternative. Furthermore, some clauses may be written in a multiple dependent form, referring to another multiple dependent clause. These multiple dependent clauses define multiple technical ideas.

[0059] (Technical thought 1) a first case (120) made of a non-conductive resin material attached to the detection site; a second case (130) made of a non-conductive resin material attached to the first case; a shield case (150) made of a conductive material, which is disposed between the second case and the first case, has a container shape with one side open, and holds the detection element inside the container shape; The shielding case is provided with a circuit board assembly (140) that holds an amplifier circuit (170) that amplifies a signal detected by the detector element, a control unit (141) that controls the detector element, a transmitter (142) that transmits the signal detected by the detector element to the outside, and an output antenna (143), The substrate assembly has a conductive ground conductor film (1402) that extends over one surface of the shielding case, and the ground conductor film is electrically connected to the shielding case; the amplifier circuit is disposed on the shielding case side of the ground conductor film, The output antenna uses the ground conductor film and the shield case as a ground. sensor.

[0060] (Technical thought 2) The ground conductor film of the board assembly and the shield case are electrically connected at two points by fasteners (144) made of conductive metal. A detector according to technical idea 1.

[0061] (Technical Thought 3) The output antenna includes an arc portion (1432) that is arranged in an arc shape along the inner periphery of the first case, and a straight portion (1431) that moves the arc portion away from the ground conductor film. A detector according to technical idea 1 or technical idea 2.

[0062] (Technical Thought 4) Further provided is a base (110) fixed to the detection site, The first case is attached to the base, The second case forms a smoke detection space (132) therein, introduces smoke into the smoke detection space, and blocks external light. The detection element has a light-emitting element (151) that projects light toward the smoke detection space and a light-receiving element (152) that detects the light that is projected from the light-emitting element and scattered in the smoke detection space, Acts as a smoke detector (100) A detector according to technical idea 1.

[0063] (Technical Thought 5) The light emitting element is held by a light emitting element holder (153) made of a non-conductive resin material and is electrically insulated from the ground conductor film and the shield case. A detector according to technical idea 4.

[0064] (Technical Thought 6) The light receiving element is held in a light receiving element holder (154) made of a non-conductive resin material and is electrically insulated from the ground conductor film and the shield case. A detector according to Technical Idea 4 or Technical Idea 5.

[0065] (Technical Thought 7) An insect screen (160) made of a non-conductive resin material is disposed inside the second case and outside the smoke detection space to prevent insects from entering the smoke detection space. A detector according to any one of technical ideas 4 to 6. [Explanation of symbols]

[0066] 100 smoke detector 110 Foundation 120 Case 1 130 Case 2 140 PCB Assembly 1402 Ground conductor film 141 Control Unit 142 Transmitter 143 output antenna 150 Shield Case 151 Light-emitting element 152 Photodetector

Claims

1. a first case (120) made of a non-conductive resin material attached to the detection site; a second case (130) made of a non-conductive resin material attached to the first case; a shield case (150) made of a conductive material, which is disposed between the second case and the first case, has a container shape with one side open, and holds the detection element inside the container shape; The shield case is provided with a substrate assembly (140) that is arranged on one surface thereof and that holds an amplifier circuit (170) that amplifies a signal detected by the detector element, a control unit (141) that controls the detector element, a transmitting unit (142) that transmits a signal detected by the detector element to the outside, and an output antenna (143), The substrate assembly has a conductive ground conductor film (1402) that extends over one surface of the shielding case, and the ground conductor film is electrically connected to the shielding case; the amplifier circuit is disposed on the shielding case side of the ground conductor film, The output antenna uses the ground conductor film and the shield case as a ground. sensor.

2. The ground conductor film of the board assembly and the shield case are electrically connected at two points by conductive metal fixtures (144). The detector of claim 1 .

3. The output antenna includes an arc portion (1432) that is arranged in an arc shape along the inner periphery of the first case, and a straight portion (1431) that moves the arc portion away from the ground conductor film. The detector of claim 1 .

4. Further provided is a base (110) fixed to the detection site; The first case is attached to the base, The second case forms a smoke detection space (132) therein, introduces smoke into the smoke detection space, and blocks external light. The detection element has a light-emitting element (151) that projects light toward the smoke detection space and a light-receiving element (152) that detects the light that is projected from the light-emitting element and scattered in the smoke detection space, Acts as a smoke detector (100) The detector of claim 1 .

5. The light emitting element is held by a light emitting element holder (153) made of a non-conductive resin material and is electrically insulated from the ground conductor film and the shield case.

5. The detector of claim 4.

6. The light receiving element is held in a light receiving element holder (154) made of a non-conductive resin material and is electrically insulated from the ground conductor film and the shield case.

5. The detector of claim 4.

7. An insect screen (160) made of a non-conductive resin material is disposed inside the second case and outside the smoke detection space to prevent insects from entering the smoke detection space.

5. The detector of claim 4.

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