Detector

Abstract

To provide technology that suppresses power consumption of a heater and improve power efficiency in a detector equipped with a heater for elimination of condensation.SOLUTION: Provided is a detector comprising: a housing having within it a circuit board having the function to detect an event as a detection object; one or more light-receiving elements for detection that are disposed inside the housing 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; a transparent protective cover provided between the opening and the one or more light-receiving elements for detection; and heating means provided so as to be in contact the inside surface of the protective cover. A control circuit for generating a signal to actuate the heating means is mounted on the circuit board, and one or more grooves forming an annular shape in the circumferential direction along an edge of the opening are formed in a section of the inner surface of the housing that is in contact with the protective cover and close to the edge of the opening.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a detector that detects abnormal events such as flames, and in particular to a technology for improving power efficiency in a detector that is equipped with a heater that removes condensation on a cover glass that covers the front side of the sensor. [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, which are capable of detecting specific types of flames and have limited wavelengths of light they can receive so as not to detect sunlight or other heat sources. Flame detectors are designed to be dustproof and waterproof for outdoor use, and a cover glass is placed in front of the sensor, which is located in the center of the case, and a sealant is sometimes placed between the cover glass and the main case. Furthermore, the main case of a flame detector may be made of metal, such as aluminum or stainless steel.

[0003] In flame detectors that have a cover glass in front of the sensor, changes in temperature and humidity in the installation environment can cause condensation on the surface of the cover glass, hindering light reception and preventing normal detection functions.To prevent this, a heater is installed on the inside of the cover glass to remove the fogging caused by condensation, and by passing electricity through the heater, the cover glass is heated and the water on the surface evaporates, preventing interference with light reception.

[0004] Conventionally, there is an invention relating to a fire detector that is provided with a sensor for detecting condensation, and when condensation is detected, a moisture detection signal is used to prevent the output of a fire detection signal or to display a condensation detection indication (Patent Document 1). Patent Document 2 describes a flame detector in which a light-transmitting window member (cover glass) is disposed on the front side of an infrared detection element (infrared sensor), and a sealant is provided between the light-transmitting window member and the main body case. Patent Document 2 also describes that the main body case is made of a metal such as aluminum or stainless steel. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 57-123490 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-71775 Summary of the Invention [Problem to be solved by the invention]

[0006] Because heaters consume a large amount of electricity, there is a demand for minimizing their operating time to reduce power consumption, and there is also a demand for the heater's heat to be transferred to the cover glass in a short time so that the heating effect can be achieved quickly. However, in the case of flame detectors whose main body case is made of metal such as aluminum or stainless steel, the metal case comes into contact with the cover glass, causing the heat from the heater to be transferred to the case and escape to the outside, slowing down the rate at which the temperature of the cover glass rises, lengthening the period during which the detector is unable to perform normal detection (off-alarm time), and increasing power consumption.

[0007] In recent years, demand for hydrogen energy has increased, and hydrogen vehicles are now being used on city streets. Hydrogen vehicles are refueled at hydrogen stations, but there is a risk of hydrogen leaks during the refueling process. However, because both gaseous hydrogen and the hydrogen flames that appear when hydrogen is applied are invisible, it can take a while to detect a leak, which can lead to a hydrogen fire or explosion. For this reason, flame detectors that can detect hydrogen flames are becoming increasingly important in order to detect and warn of flames caused by ignition of leaked hydrogen.

[0008] The present invention was made with an eye on the above-mentioned problems, and its purpose is to reduce the power consumption of the heater and improve power efficiency in a detector equipped with a heater to remove fogging caused by condensation on the cover glass covering the front side of the sensor. Another object of the present invention is to prevent a detector equipped with a heater for removing condensation from having a state in which normal detection function cannot be performed (off-alert time) that is prolonged due to a slow rate of temperature rise of the cover glass caused by heat conduction to the case. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides: a housing incorporating a circuit board having a function of detecting an event to be detected; one or more light-receiving elements for detection, which are disposed inside the housing so as to face an opening provided on the front side of the housing and receive light of a predetermined wavelength emitted by a detection target; a transparent protective cover provided between the opening and the one or more detection light receiving elements; a heating means provided in contact with the inner surface of the protective cover; In a detector comprising: a control circuit for generating a signal to activate the heating means is mounted on the circuit board; The housing is configured so that one or more grooves are formed along the edge of the opening near the edge of the opening and in the area on the inner surface of the housing that comes into contact with the protective cover.

[0010] In a detector having the above configuration, the grooves provided on the inner surface of the housing where it comes into contact with the protective cover reduce the contact area between the protective cover and the metal housing (case), thereby suppressing the transfer of heat applied to the protective cover from the heating means to the housing to remove condensation, allowing the protective cover to be heated efficiently, thereby reducing the power consumption of the heater and improving power efficiency.In addition, the rate at which the temperature of the cover glass rises due to heat conduction to the case slows down, preventing a prolonged period during which the detector is unable to perform normal detection (off-alarm period).

[0011] Here, it is desirable that a sealing material be disposed between the inner surface of the housing and the outer surface of the protective cover, and that the groove be provided in a portion of the inner surface of the housing that contacts the protective cover and is close to the edge of the opening. With this configuration, the heat applied to the protective cover from the heating means to remove condensation can be prevented from being transferred to the housing, so that when a sealing material is arranged between the inner surface of the housing and the outer surface of the protective cover, the provision of a groove makes it difficult for heat from the heating means to be transferred to the sealing material, thereby slowing down deterioration of the sealing material. [Effects of the Invention]

[0012] According to the present invention, in a detector equipped with a heater for removing condensation, the power consumption of the heater can be reduced. Also, the rate at which the temperature of the cover glass rises due to heat conduction to the case is slowed down, which has the effect of preventing a prolonged state in which the detector is unable to perform its normal detection function (off-alarm time). [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view showing an embodiment of a flame detector according to the present invention. [Figure 2] 1A is a perspective view of a central cross section showing the internal structure of a flame detector according to an embodiment, and FIG. 1B is an enlarged cross section showing a portion surrounded by a dashed line B in FIG. 1A. [Figure 3]FIG. 2 is a cross-sectional plan view showing the internal structure of the flame detector according to the embodiment. [Figure 4] 1A 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, and FIG. 1B is an explanatory diagram showing the path of light emitted from a light-emitting element for detecting condensation. [Figure 5] 1 is a perspective view showing a state in which a cover piece covering a light guide member in the flame detector of the embodiment is removed. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present invention applied to a flame detector that detects hydrogen flames will be described below with reference to the drawings. Fig. 1 is a perspective view of flame detector 10 of this embodiment, Fig. 2 is a central cross-sectional perspective view and a partially enlarged cross-sectional view showing the internal structure, and Fig. 3 is a cross-sectional plan view showing the internal structure of the flame detector of this embodiment. For convenience of explanation, in the following description, the side that faces forward when the flame detector is installed on a building will be referred to as the upper side, and the back 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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, and 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 offset from the 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. Circuit board 214 is also provided with a circuit that has the function of transmitting a detection signal (alarm signal) to a receiver (not shown) when it is determined that a flame has been detected based on signals from sensors 51, 52A, and 52B.

[0020] 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 also detect light with wavelengths specific to hydrogen flames. 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 passes through 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 is provided separately from the power light 55 described below and guides light from operation indicator lights (LED lamps) 58A, 58B that indicate that the detector has detected a flame, and emits the light forward through the glass cover 213.

[0021] 2(B), the central side of light guide plate 217 is formed one step lower so as not to come into contact with glass cover 213, and corresponding to this one step lower portion, thin planar heater 218 is disposed so as to come into contact with the underside of glass cover 213. This 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 central side, removing condensation from the entire glass cover 213.

[0022] 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 from 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.

[0023] 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. 2 shows grooves 211a with semicircular cross sections, but the cross sections of grooves 211a may be inverted V-shaped, rectangular, or the like. The number of grooves 211a is not limited to three and may be one, two, four, or more. Grooves 211a may be continuous in the circumferential direction along the edge of opening 211A, or may be formed intermittently. Instead of providing grooves, multiple hemispherical or polygonal pyramidal depressions may be formed and arranged in a dot pattern.

[0024] 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. This shortens the time required to remove condensation from the surface of glass cover 213, preventing a prolonged state in which normal detection function cannot be performed (off-alert time) and reducing power consumption. Furthermore, if front cover part 211 is made of a metal with high thermal conductivity and has a recess that houses packing 219, it is possible to prevent heat from being transferred to packing 219 and causing deterioration. Furthermore, groove 211a for reducing heat transfer also contributes to reducing the weight of main body case 211.

[0025] Next, a means for detecting condensation that has formed on the surface using the dirt detection function that detects dirt adhering to the surface of glass cover 213 will be described with reference to Figures 4 and 5. Figure 4 shows the cross-sectional structure of the upper part of flame detector 10, i.e., the vicinity of front cover part 211. 4, a light-emitting element 53 and a light-receiving element 54 for detecting dirt are mounted on circuit board 214 at positions facing each other with ultraviolet sensor 51 and infrared sensors 52A and 52B in between. Also, a power light (LED lamp) 55 is provided near infrared sensors 52A and 52B on circuit board 214 to indicate that power is being supplied and the sensors are operating.

[0026] Light-emitting element 53 is mounted in a position facing slightly upward and to the side, and light-receiving element 54 is mounted in a position facing straight up. A light-guiding member 56 made of a light-transmitting material is disposed above light-receiving element 54 at the bottom of a notched recess 211b formed in the upper surface of front cover portion 211, and a cover piece 57 having a shape corresponding to notched recess 211b is fitted into notched recess 211b so as to cover the upper surface of light-guiding member 56.

[0027] In other words, the front cover portion 211 has a ring-shaped bulge portion that is formed so that the central side where the opening 211A is located is recessed and that bulges forward around it, and a part of this bulge portion is cut out to form the recess 211b, and the light-guiding member 56 is arranged at the bottom of the recess 211b, and the light-guiding member 56 is covered by a cover piece 57 that has a shape that complements the recess 211b of the bulge portion and is fitted into the recess 211b. With this configuration, even if the light-guiding member 56, which also functions as a condensation detection means, is provided on the front cover portion 211, the apparent shape of the front cover portion 211 does not change, and the light-guiding member 56 can be made inconspicuous, which has the advantage of not compromising the design of the detector.

[0028] The light guide member 56 has a light incident portion 56a with a trapezoidal cross section joined to the bottom surface of the notched recess 211b of the front cover portion 211, and leg portions 56b protruding downward from the lower surface of the light incident portion 56a, with the leg portions 56b being inserted into through holes formed in the front cover portion 211 and with their lower end surfaces facing the light receiving surface of the light receiving element 54. The trapezoidal light incident portion 56a is disposed so that one inclined surface faces the center of the front cover portion 211. In addition, a notch (or groove) 57a (see FIG. 1) serving as a light receiving window is formed in the lower part of the surface of the cover piece 57 facing the center of the glass cover 213.

[0029] Therefore, light emitted from light-emitting element 53 on circuit board 214 obliquely upward toward the center passes through glass cover 213, passes through light-receiving window 57a of cover piece 57, and enters one of the slopes of trapezoidal light incident portion 56a of light-guiding member 56. The light is then reflected by the outer slope of light incident portion 56a, changes direction downward, passes through leg portion 56b, and is incident on light-receiving element 54 and detected. Since the top surface of light-guiding member 56 is covered by cover piece 57, the light incident on light-guiding member 56 is reflected by the top surface and the outer slope of light-guiding member 56 and guided to leg portion 56b, as indicated by dashed-dotted line P in FIG. 4(B). Although FIG. 4(B) depicts the light path as if it were a straight line passing through both the outside and the inside of glass cover 213, in reality, light is refracted when entering and exiting cover glass 213.

[0030] If the surface of glass cover 213 becomes cloudy due to condensation, the light emitted from light-emitting element 53 is diffused and dispersed by the cloudy surface of glass cover 213, resulting in a decrease in the amount of light reaching light-receiving element 54 compared to when there is no condensation. Therefore, by monitoring the signal from light-receiving element 54 with a control circuit comprising a microcomputer or the like on circuit board 214, it is possible to determine that condensation has occurred if the amount of light received decreases significantly over several hours. When the control circuit determines that condensation has occurred, it energizes the heater to generate heat, which in turn raises the temperature of glass cover 213, thereby removing the cloudiness caused by condensation.

[0031] It should be noted that the condensation detection device configured as described above can detect not only condensation but also dirt on the surface of the glass cover 213, but because it is not possible to distinguish between condensation and dirt from the signal of the light-receiving element 54 alone, it cannot immediately determine that condensation has occurred based on a decrease in the amount of light received by the light-receiving element 54. Therefore, if the amount of light received decreases, it may be determined that condensation has occurred and the heater may be made to generate heat, and if the decrease in the amount of light received does not resolve after a predetermined time has passed, it may be determined that dirt has occurred and a display or the like may be displayed to notify the user of the occurrence of dirt.

[0032] 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, a trapezoidal block-shaped light-guiding member 56 is provided to guide light emitted from the light-emitting element 53 in an oblique direction intersecting with the glass cover 213 toward the mounting position of the light-receiving element 54, but this light-guiding member 56 may be a single optical fiber or a bundle of multiple optical fibers.

[0033] Furthermore, in the above embodiment, the means for detecting dirt on the glass cover 213 inside the flame detector 10 is used as the condensation detection means as well, but it is also possible to provide a condensation detection device separate from the flame detector 10, and to send a signal from this condensation detection device directly or via a receiver (not shown) to the flame detector 10 informing that condensation has occurred, and the control circuit on the circuit board then operates a heater to remove the condensation. Furthermore, although the above embodiment describes the application of the present invention to a flame detector, the present invention can also be applied to human presence sensors and other detectors that use pyroelectric elements as infrared sensors to detect human bodies. [Explanation of symbols]

[0034] 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) 56 Light guide member 56a Light incidence part 56b Legs 57 Cover Piece 57a Light receiving window (notch) 210 Main unit case 210a Overhang 211 Front cover 211A opening 211a Groove 211b Notched recess 212 Cylindrical part 213 Glass Cover 214 Circuit Board 215A terminal board 215B Back cover 216 connection terminal 217 Light guide plate 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 having a function of detecting an event to be detected; one or more light-receiving elements for detection, which are disposed inside the housing so as to face an opening provided on the front side of the housing and receive light of a predetermined wavelength emitted by a detection target; a transparent protective cover provided between the opening and the one or more detection light receiving elements; a heating means provided in contact with the inner surface of the protective cover; A detector comprising: a control circuit for generating a signal to activate the heating means is mounted on the circuit board; A detector characterized in that one or more grooves are formed along the edge of the opening near the edge of the opening and in the area of ​​the inner surface of the housing that comes into contact with the protective cover.

2. 2. The detector according to claim 1, wherein a sealant is disposed between the inner surface of the housing and the outer surface of the protective cover, and the groove is provided in a region of the inner surface of the housing that contacts the protective cover and is close to the edge of the opening.

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