Detector

Abstract

To ensure that the aperture diameter of a detection window does not increase even when sensor heights are difference in a detector having multiple types of sensors built-in.SOLUTION: Provided is a detector comprising: a housing having a circuit board built-in where a detection circuit having the function to detect an event as a detection object is formed; multiple types of light-receiving elements for detection that are disposed so as to face an opening provided on the front side of the housing and receive light of a prescribed wavelength emanated from the detection object; and a transparent protective cover provided between the opening and the light-receiving elements for detection. A first type of light-receiving element for detection whose height is low among the multiple types of light-receiving elements for detection is mounted on the circuit board so as to be minimal in fitting height, and an opening or a recess of the size corresponding to the light-receiving elements for detection is formed in the mounting region of other types of light-receiving elements for detection than the first type among the multiple types of light-receiving elements for detection, with some of the other types of light-receiving elements for detection than the first type mounted by being inserted into the opening or the recess of the circuit board.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a detector that detects abnormal events such as flames, and in particular to a technology that is useful when applied to a detector that incorporates multiple types of sensors at different heights for detecting flames and the like. [Background technology]

[0002] Flame detectors are one type of fire detector used in fire alarm systems installed inside and outside buildings. Flame detectors use ultraviolet and infrared sensors that can detect specific types of flames and have limited wavelengths of light they can receive so as not to detect sunlight or other heat sources. Considering their outdoor use, flame detectors are dustproof and waterproof, with a cover glass in front of the sensor located in the center of the case. The ultraviolet and infrared sensors that detect flames are located inside the cover glass so that they can detect flames through the cover glass. BACKGROUND ART Conventionally, an invention relating to a flame detector incorporating a plurality of sensors is disclosed in, for example, Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-71775 Summary of the Invention [Problem to be solved by the invention]

[0004] The flame detector described in Patent Document 1 has three flame detection elements that detect different wavelengths arranged inside a light-transmitting window (cover glass), but all of them are designed to be sensors using photodiodes, so they have the same shape. The inventors investigated the use of sensors suited to each wavelength to improve the detection accuracy of light of the desired wavelength. As a result, they concluded that it would be desirable to use a photocell-type UV sensor for the ultraviolet sensor and a semiconductor sensor using a photodiode for the infrared sensor. However, in this case, they found that the shapes and sizes of the UV sensor and the semiconductor sensor are significantly different, and that if these different types of sensors were mounted on the same circuit board, the heights of the sensors would differ.

[0005] Therefore, if the distance between the cover glass and the circuit board is set to match the height of the taller sensor, the detection range (field of view) of the lower sensor will be narrowed. Therefore, it is conceivable to increase the height of the lower sensor 52, as shown in Figure 6(A). However, this increases the length of the lead terminals exposed from the circuit board 214, which creates the problem of the lead terminals acting as antennas and becoming more susceptible to the effects of electromagnetic noise. Furthermore, as shown in FIG. 6(B), it was found that if an attempt is made to achieve the required field of view (e.g., 120°) while keeping the sensors 51 and 52 firmly attached to the circuit board 214, the diameters of the detection window 211A and the cover glass 213 would become large, resulting in an increase in the size of the detector housing 211.

[0006] The present invention was made with an eye on the above-mentioned problems, and its purpose is to provide a detector that incorporates multiple types of sensors, in which the diameter of the detection window opening does not become large even when the sensors are at different heights, and which is less susceptible to the effects of electromagnetic noise. Another object of the present invention is to ensure a required viewing angle in a detector incorporating a plurality of types of sensors when the heights of the sensors are different, without increasing the size of the housing. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides: a housing incorporating a circuit board on which a detection circuit having a function of detecting an event to be detected is formed; a plurality of types of light-receiving elements for detection, each having a different height from the other, that are disposed inside the housing so as to face an opening provided on the front side of the housing and that receive light of a predetermined wavelength emitted by a detection target; a transparent protective cover provided between the opening and the plurality of types of detection light-receiving elements; A detector comprising: a first type of detection light-receiving element having the lowest height among the plurality of types of detection light-receiving elements is mounted on the circuit board at a minimum mounting height; an opening or a recess having a size corresponding to the detection light receiving element is formed in a mounting portion of the detection light receiving element other than the first type among the plurality of types of detection light receiving elements on the circuit board; The light-receiving elements for detection other than the first type are configured to be mounted in a state where a part of each element is inserted into the opening or recess of the circuit board.

[0008] With a detector configured as described above, the height when mounted on the circuit board can be adjusted depending on the type of light-receiving element (sensor) used for detection, preventing significant differences in the field of view even when sensors of different heights are used. Furthermore, because the lowest-height sensor is mounted flush with the circuit board, the lead terminals are not exposed from the circuit board, making it less susceptible to electromagnetic noise. Furthermore, because taller sensors are mounted with a portion inserted into an opening or recess in the circuit board, the distance from the circuit board to the protective cover is shortened, ensuring the desired field of view without requiring a large opening in the front of the protective cover, i.e., without increasing the size of the housing.

[0009] Here, it is preferable to include a holder capable of holding a detection light-receiving element other than the first type, The light-receiving elements for detection other than the first type are mounted in a state where they are held by the holder and partly inserted into the opening or recess of the circuit board. With this configuration, a taller detection light receiving element can be mounted at a predetermined position on the circuit board with its height set so that its field of view is approximately the same as that of the shortest detection light receiving element.

[0010] Preferably, the holder is provided with a locking piece having a claw at its tip, a small hole through which the claw at the tip of the locking piece can be inserted is formed in the circuit board near the opening; The claw at the tip of the locking piece is inserted into the small hole, thereby mounting the holder to the circuit board. According to this configuration, the holder for holding the tall detection light-receiving element can be easily mounted on the circuit board.

[0011] Furthermore, preferably, the holder has a pair of side walls that come into contact with the sides of the detection light-receiving elements other than the first type, The pair of side walls of the holder are provided at their upper portions with notches for increasing the viewing angle of the detection light-receiving elements other than the first type. With this configuration, even if both side walls of the holder are made high in order to hold the detection light receiving element in a stable state, it is possible to avoid the field of view of the detection light receiving element becoming narrow.

[0012] Furthermore, preferably, an operation indicator light is mounted on the circuit board to notify that the detection circuit has detected an event to be detected based on signals from the plurality of types of detection light-receiving elements, a light guide plate is disposed between the protective cover and the circuit board, and allows light from the operation indicator lamp to be emitted from the protective cover; The light guide plate is formed with a protrusion at a location corresponding to the small hole in the circuit board, the protrusion coming into contact with or close to the claw at the tip of the locking piece inserted into the small hole. With this configuration, the claw at the tip of the locking piece is less likely to come out of the small hole in the circuit board, preventing the holder, which is attached while holding the detection light-receiving element, from falling off the circuit board. [Effects of the Invention]

[0013] According to the present invention, in a detector incorporating multiple types of sensors, even if the heights of the sensors are different, the diameter of the detection window opening does not become large and the detector is less susceptible to the effects of electromagnetic noise. Furthermore, even if the heights of the sensors are different, the detector can ensure the required viewing angle (for example, 120°) without increasing the size of the housing. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view showing an embodiment of a flame detector according to the present invention. [Figure 2] 1A is a central cross-sectional perspective view showing the internal structure of a flame detector according to an embodiment, and FIG. 1B is an enlarged cross-sectional view showing a part of the internal structure (a portion surrounded by a dashed line) in an enlarged manner. [Figure 3] 1A is a plan view showing the shape of the light guide plate and the arrangement of sensors inside the main body case of the flame detector of the embodiment, and FIG. 1B is a cross-sectional side view showing the cross-sectional structure of the light guide plate and the circuit board along line B-B' in FIG. [Figure 4] FIG. 2 is a cross-sectional front view showing the internal structure of the upper part of the main body case of the flame detector according to the embodiment. [Figure 5] FIG. 2 is a perspective view showing a specific example of a holder for holding an ultraviolet sensor in the flame detector of the embodiment. [Figure 6] FIG. 10 is an explanatory diagram showing the relationship between the range of the viewing angle and the opening (detection window) of the main body case when the mounting height of two types of sensors mounted on a circuit board is changed. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the present invention applied to a flame detector for detecting hydrogen flames will be described below with reference to the drawings. Fig. 1 is a perspective view of flame detector 10 of this embodiment, and Fig. 2 is a central cross-sectional perspective view and a partially enlarged cross-sectional view showing its internal structure. For convenience of explanation, in the following description, the side facing the front when the flame detector is installed in a building will be referred to as the upper side, and the rear side will be referred to as the lower side. Flame detectors are generally installed with their backs facing the mounting surface, either directly on the wall of a building or fixed to a base such as an angle adjuster, and detect flames in the area directly in front of them. Such flame detectors are connected via wiring (sensor lines) to a receiver (not shown) that centrally manages multiple flame detectors within the detection area, and when they detect a flame, they send a detection signal (alarm signal) to the receiver.

[0016] 1, the flame detector 10 of this embodiment includes a housing made up of a main body case 210 having a front cover portion 211 and a cylindrical portion 212, and a lower case 220 having a cylindrical portion 221 and a base portion 222 and coupled to the rear side of the main body case 210 and fixed to an installation location. Although not particularly limited, in this embodiment, the main body case 210 and the lower case 220 are formed from aluminum castings.

[0017] A recess is provided toward the center on the top surface of the front cover portion 211 of the main body case 210, and as shown in FIG. 1, a circular opening 211A is formed in the center of the recess, and a glass cover 213 serving as a protective cover made of a translucent material such as quartz glass is arranged in this opening 211A so as to cover the upper part of the detection light receiving elements 51, 52A, and 52B described below.

[0018] 2(A), the lower part of cylindrical part 212 of main body case 210 is a cylinder having an outer diameter slightly larger than that of cylindrical part 221 of lower case 220, and the upper end part of lower case 220 is inserted into an opening in the lower part of main body case 210, and the upper end part of lower case 220 is fitted inside main body case 210. Then, as shown in FIG. 1, main body case 210 and lower case 220 are configured to be joined by bolts 231 inserted into protruding parts 210a and 220a formed so as to protrude laterally from the lower peripheral wall of main body case 210 and the upper peripheral wall of lower case 220.

[0019] In addition, wing-shaped flange portions 223 are formed at the four corners of the base portion 222 of the lower case 220, and screw insertion holes 223a are formed in the flange portions 223 so that the lower case 220 can be fixed to an installation surface such as a ceiling surface by inserting screws (not shown) into the screw insertion holes 223a. Furthermore, a cylindrical wiring port 224 is provided on the outer peripheral surface of cylindrical portion 221 of lower case 220, through which an end of a cable (not shown) having wiring such as a signal line or a power line is inserted. The end of the cable inserted into wiring port 224 is connected to a terminal on terminal board 215A which is internally wired to circuit board 214 (see FIG. 2) which is provided inside main body case 210, has elements and ICs mounted thereon that constitute a circuit having a flame detection function, and has wiring that connects the elements and ICs together.

[0020] Flame detector 10 of this embodiment is equipped with one ultraviolet sensor 51 and two infrared sensors 52A and 52B to detect a hydrogen flame. As shown in FIG. 2(A), ultraviolet sensor 51 is installed approximately in the center of the top surface of circuit board 214, and infrared sensors 52A and 52B are installed slightly off-center. Of these, infrared sensors 52A and 52B are arranged parallel to ultraviolet sensor 51, i.e., in a direction perpendicular to the plane of the paper in FIG. 2(A), as shown in FIG. 3(A). Circuit board 214 is also provided with a control circuit that, when it determines that a flame has been detected based on signals from sensors 51, 52A, and 52B, transmits a detection signal (alert signal) to a receiver (not shown) and turns on an operation indicator light (described below).

[0021] The ultraviolet sensor 51 and the infrared sensors 52A and 52B are sensors capable of detecting light in different wavelength bands that are appropriately selected so as to detect sunlight and other heat sources and to detect light with a wavelength specific to hydrogen flames. In this embodiment, a phototube-type UV sensor is used as the ultraviolet sensor 51, and semiconductor sensors with built-in photodiodes are used as the infrared sensors 52A and 52B.

[0022] In addition, below the circuit board 214, a terminal board 215A and a back cover 215B are arranged parallel to each other with a predetermined distance between them, and a connection terminal 216 to which the end of the cable (wiring) is connected is mounted facing downward in the center of the underside of the terminal board 215A, and is exposed by penetrating the back cover 215B. On the other hand, above the circuit board 214, a light guide plate 217 made of a light-transmitting resin is arranged so as to contact the peripheral edge of the underside of the glass cover 213. The light guide plate 217 guides light from operation indicator lights (LED lamps) 58A, 58B (described later) which are provided separately from the power light 55 (described later) and which indicate that the detector has detected a flame, and emits the light forward through the glass cover 213.

[0023] 2(B), the central portion of light guide plate 217 is formed one step lower so as not to come into contact with glass cover 213, corresponding to the edge of opening 211A on the front surface of main body case 210, and corresponding to this lowered portion, thin, planar heater 218 is disposed so as to come into contact with the underside of glass cover 213. Heater 218 has an annular shape when viewed from above, and heats the peripheral portion of glass cover 213. The heat imparted from heater 218 to glass cover 213 is transferred from the peripheral portion of glass cover 213 to the center, removing condensation from the entire glass cover 213.

[0024] 2(B), a recess that houses packing (O-ring) 219 as a sealing material is provided on the underside of front cover portion 211 of main body case 210, and packing 219 is configured to prevent water from entering the case through a gap at the joint between the edge of opening 211A of front cover portion 211 and glass cover 213. A sealing material is also provided at the fitting portion between cylindrical portion 212 of main body case 210 and cylindrical portion 221 of lower case 220.

[0025] In the flame detector of this embodiment, glass cover 213 is formed to be slightly larger than opening 211A. Light guide plate 217 is formed to be slightly larger than glass cover 213. Then, with glass cover 213 and packing 219 sandwiched between light guide plate 217 and the edge of the opening of front cover portion 211, screws are inserted from below into multiple screw insertion holes 217d provided on the periphery of light guide plate 217, and screwed into screw holes provided in corresponding locations on front cover portion 211. As a result, when attaching the light guide plate 217 to the front cover part 211, the glass cover 213 can be fixed at the same time, which makes it easy to assemble the parts, and also the packing (O-ring) 219 is crushed, which allows it to adhere tightly to the glass and aluminum housing, providing excellent sealing properties.

[0026] Furthermore, in flame detector 10 of the present embodiment, three heat insulating grooves 211a are formed on the underside of the edge of opening 211A of front cover part 211. Grooves 211a are formed over the entire circumferential direction of front cover part 211 so as to form a circle when viewed from above. As described above, the formation of multiple grooves 211a reduces the contact area between front cover portion 211 and glass cover 213, reducing the transfer of heat from heater 218 to glass cover 213 to front cover portion 211, allowing glass cover 213 to be heated efficiently and preventing a slower rate of temperature rise and a longer time required to remove condensation.

[0027] Next, the configuration of the light guide plate 217, which functions as a light emitting member that emits light from the operation indicator light forward, and the circuit board 214 on which the flame detection sensor is mounted will be described with reference to Figures 3 to 5. Of these, Figure 3 is a plan view and a cross-sectional view showing the internal structure of the flame detector of this embodiment, Figure 4 is a cross-sectional front view showing the structure of the upper part of the detector, and Figure 5 is a perspective view showing the shape of a holder for attaching UV sensor 51, which serves as an ultraviolet sensor, to the board. Of these, Figure 3(A) shows the shape of the light guide plate 217 and the arrangement of sensors 51, 52A, and 52B inside the main body case 210, and Figure 3(B) shows the cross-sectional structure of the light guide plate 217 and circuit board 214 along line B-B' in (A).

[0028] 3(A), the elements denoted by the reference symbols 58A and 58B are LED lamps serving as operation indicators that emit visible light. These operation indicators 58A and 58B are mounted facing upward on circuit board 214 below light guide plate 217 and outside opening 211A of glass cover 213. Light guide plate 217 is configured so that light emitted from operation indicators 58A and 58B enters light guide plate 217 and spreads out in a planar form. The number of operation indicator lights is not limited to two, but may be one or three or more.

[0029] Also, in Figure 3, the symbols 53 and 54 are a light-emitting element (LED) and a light-receiving element for detecting dirt on the protective cover 213, and the light-emitting element 53 and the light-receiving element 54 are arranged in opposing positions across the sensors 51, 52A, and 52B. 4, light emitted obliquely upward from light-emitting element 53 passes through protective cover 213 and is introduced into incident surface 56a of light-guiding member 56 disposed on the edge of front cover portion 211, then changes direction downward, passes through leg portion 56b and is received by light-receiving element 54, and the degree of dirt on protective cover 213 is determined from the decrease in the amount of received light. Note that this dirt detection function is not essential to the present invention, so a detailed description will be omitted. The upper surface of light-guiding member 56 is covered by cover piece 57.

[0030] 3(B), light guide plate 217 is disposed parallel to and above circuit board 214 at a predetermined distance. To prevent light detection by sensors 51, 52A, and 52B and light emitted from light emitting element 53 for detecting dirt from being obstructed, light guide plate 217 has openings formed therein corresponding to sensors 51, 52A, and 52B and light emitting element 53, as shown in FIG. 3(A). Furthermore, power lights (LED lamps) 55 are provided near infrared sensors 52A and 52B on circuit board 214 to indicate that power is being supplied and the sensors are operating.

[0031] As described above, glass cover 213 is larger than the size of central opening 211A of front cover portion 211, and light guide plate 217 is formed to be even larger than glass cover 213. Therefore, when light incident from two fan-shaped light entrance portions 217a provided corresponding to operation indicator lights 58A, 58B spreads over the entire light guide plate 217, the light that reaches the area outside opening 211A is wasted because it cannot be seen from the front of the flame detector, and the amount of light emitted from opening 211A is reduced accordingly, resulting in poor efficiency.

[0032] Therefore, in this embodiment, as shown in FIG. 3(A), a plurality of (three in the figure) arc-shaped grooves 217b that follow the edge of the opening 211A, and two "L"-shaped slits 217c that connect the grooves 217b and surround the outside of the light incident portion 217a are formed in the light guide plate 217, so that the incident light does not spread to the outer edge. Groove 217b may be on the upper or lower surface of light guide plate 217. Alternatively, a groove may be formed in the portion of slit 217c shown in Figure 3(A), and a slit may be formed in the portion of groove 217b.

[0033] Next, a specific mounting structure of the ultraviolet sensor 51 and the infrared sensors 52A and 52B on the circuit board 214 will be described. As shown in Fig. 4, infrared sensors 52A and 52B are mounted flush on circuit board 214, i.e., the bottom surfaces of the sensor bodies are in contact with the top surface of circuit board 214 and do not float. On the other hand, ultraviolet sensor 51 is installed in a state where an opening is formed in circuit board 214 where the sensor is to be mounted, with part of the sensor body inserted into the opening. Note that ultraviolet sensor 51 used in the flame detector of this embodiment has lead terminals that extend in a direction perpendicular to the plane of the paper in Fig. 4, and are mounted with the lead terminals bent downward partway and their tips penetrating circuit board 214.

[0034] Furthermore, the diameter of ultraviolet sensor 51 is approximately twice the height of the main bodies of infrared sensors 52A and 52B, and in order to match the viewing angle of ultraviolet sensor 51 with the viewing angles of infrared sensors 52A and 52B, most of ultraviolet sensor 51 needs to be inserted into the opening in circuit board 214. For this reason, a holder 59 having a semi-cylindrical recess corresponding to the diameter of ultraviolet sensor 51 and a shape as shown in FIG. 5 is prepared to hold ultraviolet sensor 51, and ultraviolet sensor 51 is attached to circuit board 214 using this holder 59. This allows the height of ultraviolet sensor 51 relative to circuit board 214 to match the heights of infrared sensors 52A and 52B, preventing enlargement of opening 211A and an increase in the size of the housing (main body case 211). Also, tall ultraviolet sensor 51 can be mounted at a predetermined position on circuit board 214 with its height set so that its viewing angle is approximately the same as that of short infrared sensors 52A and 52B.

[0035] As shown in Figure 5, the holder 59 has a pair of sensor-grasping claws 59a formed at the upper end facing inward into the semi-cylindrical recess, and a pair of L-shaped fixing locking pieces 59b with outward-facing claws at the tips on the outside of both side walls. On the other hand, a pair of small holes are formed on the edge of the opening for inserting the ultraviolet sensor in the circuit board 214, corresponding to the pair of fixing locking pieces 59b of the holder 59, and the holder 59 can be attached to the circuit board 214 by inserting the claws at the tips of the fixing locking pieces 59b into these small holes from below and fitting them together. In this embodiment, four protrusions 59c are provided on the outer surfaces of both side walls of the holder 59 to prevent tilt in the horizontal direction by contacting the underside of the circuit board 214. In addition, in order to increase the viewing angle of the ultraviolet sensor 51, notches 59d are formed in the upper ends of both side walls of the holder 59.

[0036] 3(B), a pair of inclined portions 217e are formed in the light guide plate 217 in correspondence with the fixing locking pieces 59b toward the claw portions at the tips of the fixing locking pieces 59b, and by arranging these inclined portions 217e so as to abut against or be close to the claw portions, the claw portions at the tips of the fixing locking pieces 59b come out of the small fitting holes in the circuit board 214, preventing the holder 59 from falling off from the circuit board 214. Note that a groove is formed on the upper surface of the inclined portion 217e that is closer to the dirt-detecting light-emitting element 53 to ensure a path for light emitted obliquely upward from the light-emitting element 53.

[0037] When using multiple types of sensors with different shapes and sizes, as in the flame detector of this embodiment, if the height of the lower sensor is increased to ensure the desired field of view, as shown in Figure 6(A), the length of the lead terminals exposed from the circuit board increases, and the lead terminals act as antennas, making them more susceptible to electromagnetic noise. Furthermore, if an attempt is made to achieve the required field of view while keeping the ultraviolet and infrared sensors directly attached to the circuit board, the diameters of the opening (detection window) 211A on the front of the case and the cover glass 213 become larger, as shown in Figure 6(B), resulting in an increase in the size of the detector housing.

[0038] In contrast, in the flame detector of this embodiment, the large ultraviolet sensor 51 is installed in an opening or recess formed in the circuit board 214, so as shown in Fig. 6(C), a desired viewing angle (e.g., 120°) can be secured without enlarging the opening (detection window) 211A, and an increase in the size of the housing can be avoided. In addition, the lead terminals of the infrared sensors 52A and 52B are not exposed from the circuit board 214, making it possible to reduce the influence of electromagnetic noise.

[0039] By mounting the ultraviolet sensor 51 on the circuit board 214 using the holder 59 as described above, the height of the ultraviolet sensor 51 can be made to match that of the infrared sensors 52A and 52B even if the infrared sensors 52A and 52B are mounted directly on the circuit board 214. Since the structure of the package varies depending on the type of sensor, it is advisable to set the height of the sensor using the holder 59 so that the height of each sensor is approximately the same.

[0040] While the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments and can be modified as appropriate without departing from the spirit of the present invention. For example, in the above embodiment, the holder 59 that holds the ultraviolet sensor 51 is provided with a pair of locking pieces 59b with claws at the tip to secure it to the circuit board 214. However, instead of providing the locking pieces 59b, the holder 59 may be secured to the circuit board 214 using screws or an adhesive. Furthermore, the sensor 51 may be secured to the circuit board 214 using a means such as a cable tie without using the holder 59.

[0041] Furthermore, in the above embodiment, the size of the opening formed in the circuit board 214 is set to a size that allows the holder 59 that holds the ultraviolet sensor 51 to be inserted, and the ultraviolet sensor 51 is mounted on the circuit board 214 with the holder 59 inserted into the opening, but the size of the opening formed in the circuit board 214 may be set to a size that allows the entire ultraviolet sensor 51 to be inserted. The holder 59 that holds the ultraviolet sensor 51 may be configured to contact the underside of the circuit board 214, and the ultraviolet sensor 51 may be mounted on the circuit board 214 with only the ultraviolet sensor 51 inserted into the opening. In this case, a means for preventing the ultraviolet sensor 51 from floating up may be provided on the upper surface of the circuit board 214.

[0042] In addition, in the above embodiment, an example using two types of sensors with different shapes and sizes was described, but the present invention can also be applied to a detector using three or more types of sensors. In that case, it is recommended that the sensor with the lowest height is mounted directly on the circuit board, and the other sensors are mounted on separate holders 59 according to their height so that the viewing angles are approximately the same. Furthermore, in the above embodiment, the present invention is described as being applied to a flame detector, but the present invention can be widely applied to detectors that use multiple types of sensors with different shapes and sizes. [Explanation of symbols]

[0043] 10 Flame detector 51 Ultraviolet sensor (light-receiving element for flame detection) 52A, 52B Infrared sensor (light receiving element for flame detection) 53 Light-emitting element for detecting dirt 54 Dirt detection light receiving element 55 Power light (LED lamp) 58A, 58B Operation indicator light (LED lamp) 59 Holder 59a Sensor gripping claw 59b Locking piece 59d Notch 210 Main unit case 210a Overhang 211 Front cover 211A opening 211a Groove 212 Cylindrical part 213 Glass Cover 214 Circuit Board 215A terminal board 215B Back cover 216 connection terminal 217 Light guide plate for operation indicator light 217a Light incidence part 217b Groove 217c Slit 217d Screw insertion hole 217e Slope 218 Heater 219 Sealing material (O-ring) 220 Lower Case 220a Overhang 221 Cylindrical part 222 Base 223 Flange 223a Screw insertion hole 224 Wiring port 231 Connecting bolt

Claims

1. a housing incorporating a circuit board on which a detection circuit having a function of detecting an event to be detected is formed; a plurality of types of light-receiving elements for detection, each having a different height from the other, that are disposed inside the housing so as to face an opening provided on the front side of the housing and that receive light of a predetermined wavelength emitted by a detection target; a transparent protective cover provided between the opening and the plurality of types of detection light-receiving elements; A detector comprising: a first type of light-receiving element for detection, which has the lowest height among the plurality of types of light-receiving elements for detection, is mounted on the circuit board at a minimum mounting height; an opening or a recess having a size corresponding to the detection light receiving element is formed in a mounting portion of the circuit board for the detection light receiving element other than the first type among the plurality of types of detection light receiving elements; A detector characterized in that the light-receiving elements for detection other than the first type are mounted in a state in which a part of the elements is inserted into the opening or recess of the circuit board.

2. a holder capable of holding a detection light-receiving element other than the first type, The detector of claim 1, characterized in that the detection light receiving elements other than the first type are held in the holder and mounted with a portion inserted into the opening or recess of the circuit board.

3. The holder is provided with a locking piece having a claw at its tip, a small hole through which the claw at the tip of the locking piece can be inserted is formed in the circuit board near the opening; 3. The detector according to claim 2, wherein the holder is attached to the circuit board by inserting a claw at the tip of the locking piece into the small hole.

4. the holder has a pair of side walls that come into contact with sides of the detection light-receiving elements other than the first type, 4. The detector according to claim 3, wherein notches are formed in the upper portions of the pair of side walls of the holder to increase the viewing angle of the detection light receiving elements other than the first type.

5. an operation indicator light is mounted on the circuit board to notify that the detection circuit has detected a detection target event based on signals from the plurality of types of detection light-receiving elements; a light guide plate is disposed between the protective cover and the circuit board, and allows light from the operation indicator lamp to be emitted from the protective cover; A detector as described in claim 3 or 4, characterized in that the light guide plate has a protrusion formed at a position corresponding to the small hole in the circuit board, which abuts or is close to the claw at the tip of the locking piece inserted into the small hole.

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