smoke sensor

Abstract

To suppress entries of airflow, dust, insects and the like into between a main body base and a circuit board.SOLUTION: A smoke detector for detecting smoke by taking ambient air thereinto comprises: a main body base; a circuit board mounted on the main body base; and a smoke inlet cover for covering the circuit board. The smoke inlet cover includes hook holes through which hooks for fixing an optical bench cover pass. The circuit board includes openings at positions corresponding to the hook holes. Cylindrical bodies protrude from the main body base at positions surrounding the openings so that the cylindrical bodies support the circuit board.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a smoke detector. [Background technology]

[0002] Patent Document 1 describes a smoke detector in which an optical bench cover is attached to an antenna positioning plate inside the main body cover. Figure 1 shows the internal structure of a conventional smoke detector 9 with the main body cover (not shown) removed.

[0003] 1, a smoke intake cover 95 covers a circuit board 92 (not shown) attached to a main body base 91. Smoke intake cover 95 has a plurality of protrusions 951 arranged radially, and outside air passes through a flow path formed by the gaps between the protrusions 951 and is guided toward an insect screen 97. The outside air passes through the insect screen 97 and enters a smoke detector (not shown) provided on main body base 91, where smoke is optically detected.

[0004] The optical bench cover 98 has two cover legs 981. Hooks (not shown) are provided at the tips of the cover legs 981, and are engaged with the edges on the back side of the hook holes 952 in the smoke intake cover 95. An opening is provided in the circuit board 92 covered by the smoke intake cover 95 to prevent the hooks from colliding with it. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-5844 Summary of the Invention [Problem to be solved by the invention]

[0006] To allow the hooks to pass through, the hook holes 952 are formed larger than the cross section of the cover legs 981 of the optical bench cover 98, and a gap is created after the optical bench cover 98 is attached. If airflow is generated through this gap past the circuit board 92, it will affect and obstruct the airflow to the smoke detection unit 911. There is also the possibility that dust or small insects may pass through the gap and enter the space behind the circuit board 92. An object of the present invention is to suppress the airflow between the main body base and the circuit board, and the intrusion of dust, insects, etc. [Means for solving the problem]

[0007] In one embodiment of the present invention, a smoke detector that takes in outside air and detects smoke comprises a main body base, a circuit board installed on the main body base, and a smoke intake cover that covers the circuit board, wherein the smoke intake cover has hook holes through which hooks that secure an optical base cover pass, the circuit board has an opening at a position corresponding to the hook holes, and a cylindrical body protrudes from the main body base at a position surrounding the opening, and the cylindrical body supports the circuit board. [Effects of the Invention]

[0008] This invention prevents airflow disturbances near the optical bench cover, which can impede smoke detection, and also makes it difficult for dust and small insects to enter the space between the main body base and the circuit board through the hook holes. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a conventional smoke detector with the main body cover removed. [Figure 2] FIG. 2 is an exploded perspective view of the smoke detector according to the embodiment. [Figure 3] FIG. 2 is a top view of the smoke detector according to the embodiment with the main body cover, optical base cover, and insect screen removed. [Figure 4] FIG. 2 is a top view of the smoke detector according to the embodiment with the main body cover removed. [Figure 5] FIG. 2 is a top view of the smoke detector according to the embodiment, with a circuit board attached to the main body base. [Figure 6] FIG. 2 is a top view of the main body base of the smoke detector according to the embodiment. [Figure 7] FIG. 2 is a partially enlarged perspective view of a main body base of the smoke detector according to the embodiment. [Figure 8] FIG. 3 is a partially enlarged cross-sectional view of the vicinity of a hook of the smoke detector according to the embodiment. [Figure 9] 1 is a bottom view of a smoke intake cover of a smoke detector according to an embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Smoke detectors and the like are often assembled with the bottom facing up when attached to a ceiling. In this embodiment, a smoke detector 1 that takes in outside air and detects smoke will be described according to the up-down orientation when assembled. The smoke detector 1 of this embodiment has a wireless device and is linked to other smoke detectors. The smoke detector takes in outside air and, when it detects smoke, activates its speaker and transmits a smoke detection signal to the other smoke detectors via wireless transmission, activating their speakers. It also receives smoke detection signals from the other smoke detectors and activates its speaker.

[0011] Fig. 2 is an exploded perspective view of the smoke detector 1 of the embodiment, seen from diagonally above during assembly. The main body cover 19, which is in the lowest position when attached to a ceiling, is shown at the top. Fig. 2 shows, from bottom to top, the main body base 11, the circuit board 12 to which conductor wires 141 and 142 are connected, the speaker 13, the smoke intake cover 15, the insect screen 17, the optical base cover 18, and the main body cover 19. The conductor wire 141 is located above the circuit board 12 in Fig. 2, and the conductor wire 142 is located below the circuit board 12.

[0012] The main body base 11 shown at the bottom of FIG. 2 is provided with a smoke detection unit 111, a battery housing unit 112, and a component housing wall 113. The smoke detection unit 111 is a location where outside air flows in and infrared light is irradiated into the smoke detection unit 111, where smoke is detected when scattered light is generated by the smoke that has flowed in. The smoke detection unit 111 is surrounded on all sides by a smoke detection unit wall 111a. In this embodiment, the smoke detection unit 111 has a shape surrounded by an isosceles trapezoidal cylinder formed by the smoke detection unit wall 111a. The isosceles trapezoidal cylinder is positioned so that the wall located near the outside of the main body base 11 is the longest.

[0013] A generally cylindrical peripheral wall 115 is provided around the main body base 11, with a flange portion 114 extending outward from the outside of the peripheral wall 115. The peripheral wall 115 has a shape where a cylinder is partially cut. A plurality of locking pieces 116 are provided on the outside of the peripheral wall 115. The component housing wall 113 is formed in a generally cylindrical shape, with a portion thereof protruding outward from the peripheral wall 115. A recess for accommodating a conductor wire 142 is provided below the protruding portion. Cylindrical bodies 117 are provided on both sides of the smoke detection unit 111.

[0014] Of the two parallel smoke detection wall sections 111a that form the isosceles trapezoidal cylinder of the smoke detection section 111, the longer smoke detection wall 111a is located outward and faces the peripheral wall 115. Another shorter smoke detection wall 111a is located toward the center of the main body base 11. The long smoke detection wall 111a and the short smoke detection wall 111a are connected by the two smoke detection wall sections 111a of the same length to form the isosceles trapezoidal cylinder.

[0015] A female screw cylinder 119 is provided on the outer side of the short smoke detection unit wall 111a, toward the center of the main body base 11. Further ahead, on the opposite side of the smoke detection unit 111, is a battery housing unit 112. A component housing wall 113 is provided on the side between the smoke detection unit 111 and the battery housing unit 112, and a cover base 118 is provided on the other side. The battery housing unit 112 houses a battery (not shown) below. Furthermore, the cover base 118 protrudes above the main body base 11.

[0016] The circuit board 12 shown second from the bottom in FIG. 2 is placed on the main body base 11. When placed, the circuit board 12 has openings 121 on both sides of the smoke detector 111. When placed, the circuit board 12 also has a screw passage hole 125 at a position toward the center of the main body base 11 of the smoke detector 111. The conductor wire 141 is connected to the circuit board 12 and is located above the circuit board 12. The conductor wire 142 is connected to the circuit board 12 and is located below the circuit board 12. When the circuit board 12 is placed on the main body base 11, the conductor wire 142 extends linearly outward along the side of the battery housing 112. It then bends in the opposite direction from the battery housing 112 and extends in an arc along the outside of the peripheral wall 115 to near the outside of the smoke detector 111. The arc-shaped conductor wire 142 is housed in a recess in the part of the component housing wall 113 that protrudes outward from the peripheral wall 115. The smoke detector 1 of the embodiment also includes a CO sensor 122.

[0017] Conductor wire 141 functions as an antenna. Conductor wire 142 is electrically connected to the ground of circuit board 12. When smoke detector 1 performs wireless transmission and reception, high-frequency potential fluctuations of conductor wire 141, which serves as an antenna, relative to the ground are used. By connecting conductor wire 142 to the ground, the ground area is widened, and the sensitivity of transmission and reception can be increased. Although conductor wire 142 is connected to the ground, it contributes to wireless transmission and reception and can be said to be a type of antenna.

[0018] Speaker 13, which sounds when a fire is detected, is housed with the sounding direction facing upward inside component housing wall 113 of main body base 11. After circuit board 12 is placed on main body base 11, speaker 13 is installed inside component housing wall 113 and connected to circuit board 12 by soldering.

[0019] The smoke intake cover 15 shown second from the top in FIG. 2 has an air vent 153 that opens toward the smoke detection unit 111. A labyrinth wall 154 is provided around the air vent 153 to block light. The smoke intake cover 15 has multiple protrusions 151 on its top surface that point toward the air vent 153, and the gaps between adjacent protrusions 151 function as a flow path for outside air from the air vent 153. An insect screen 17 is placed between the labyrinth wall 154 and the protrusions 151, and an optical bench cover 18 is placed on top of it. The optical bench cover 18 has two cover legs 181 with hooks 182 at their tips. When attaching the optical bench cover 18, the hooks 182 are inserted into the hook holes 152 of the smoke intake cover 15 to lock it in place. With the optical bench cover 18 placed on the labyrinth wall 154, hooks 182 attached to the tips of the cover legs 181 are engaged with the lower ends of the hook holes 152 and fixed in place. The area around the ventilation hole 153 is formed one step lower by a step 158. The insect screen 17 is pressed against the inside of the step 158 by the optical bench cover 18 and fixed in place.

[0020] A light-transmitting cover 16 is arranged laterally above the smoke inlet cover 15. The light-transmitting cover 16 is pivotally supported on a cover base 118 of the main body base 11 that protrudes above the smoke inlet cover 15 after the smoke inlet cover 15 is assembled. A plurality of locking springs 157 are provided around the periphery of the smoke inlet cover 15. The locking springs 157 engage with the locking pieces 116 of the main body base 11 to secure the smoke inlet cover 15 to the main body base 11.

[0021] When the smoke detector 1 is installed on a ceiling, the lowest part, i.e., the main body cover 19 facing the floor, covers the main body base 11, circuit board 12, smoke intake cover 15, etc. The main body cover 19 is fixed with male screws (not shown) inserted from the underside of the main body base 11. The main body cover 19 has ventilation holes 191 around its periphery, and outside air is taken in through the ventilation holes 191 and between the protrusions 151 of the smoke intake cover 15. The taken-in outside air passes between the multiple protrusions 151 that function as a flow path, passes through the insect screen 17, passes between the labyrinth walls 154, passes through the ventilation holes 153, and reaches the smoke detection unit 111. The outside air also passes through the ventilation holes 153 again from the smoke detection unit 111 and passes between the labyrinth walls 154 in the opposite direction from which the outside air entered. The air then passes through the insect screen 17, passes between the plurality of ridges 151 which function as flow paths, and exits the smoke detector 1 through the ventilation opening 191 in the main body cover 19.

[0022] However, there is a possibility that this outside airflow will pass through the hook holes 152 and the openings 121 in the circuit board 12 and head toward the back of the circuit board 12. The smoke detector 1 eliminates this possibility. FIG. 3 shows a top view of the smoke detector 1 without the main body cover 19, the optical base cover 18, and the insect screen 17. The smoke intake cover 15 has hook holes 152 in two locations on the outside of the labyrinth wall 154. These hook holes 152 lead to the space between the circuit board 12 and the main body base 11 via the openings 121 in the circuit board 12 shown in FIG. 2. Note that when assembly is complete, a male screw (not shown) is fitted into the screw passage hole 155, so the screw passage hole 155 is blocked. The other openings in the smoke intake cover 15 are provided facing the circuit board 12 and the speaker 13, and do not lead to the space between the main body base 11.

[0023] 4 is a top view of the smoke intake cover 15 of FIG. 3 with the insect screen 17 and optical base cover 18 attached. The insect screen 17 is also fixed in place by being pressed down by the optical base cover 18. The cover legs 181 of the optical base cover 18 block the hook holes 152 to a certain extent. However, hooks 182 protrude outward from the cover legs 181 of the optical base cover 18. Because the hooks 182 must pass through the hook holes 152, the hook holes 152 are formed larger than the cross section of the hooks 182. Thus, a gap is created between the cover legs 181 and the hook holes 152 when the optical base cover 18 is attached.

[0024] FIG. 5 is a top view of FIG. 3 with the smoke inlet cover 15 and speaker 13 removed. Circuit board 12, to which conductor wires 141 and 142 are connected, is installed on main body base 11. When smoke inlet cover 15 is attached and hooks 182 of optical base cover 18 are inserted and locked into hook holes 152, hooks 182 locked into hook holes 152 protrude toward circuit board 12. Circuit board 12 has two openings 121 corresponding to hook holes 152 and hooks 182 so that hooks 182 protruding from smoke inlet cover 15 do not come into contact with circuit board 12. Because hooks 182 are vertically elongated, openings 121 are formed vertically elongated in the direction from smoke detector 111 toward the center of main body base 11. A light-emitting element 123 and a light-receiving element 124 are attached to circuit board 12 on the rear side of the portion indicated by the arrow.

[0025] FIG. 6 is a top view of the main body base 11 in FIG. 5 with the circuit board 12 removed. FIG. 6 is a top view of the main body base 11. A cylindrical body 117 protrudes upward from the main body base 11 at a position surrounding the opening 121 of the circuit board 12 when the circuit board 12 is attached as shown in FIG. 5. The cylindrical body 117 is provided toward the center of the main body base 11 when viewed from the two vertices closest to the peripheral wall 115 of the isosceles trapezoidal tube formed by the smoke detection unit wall 111a. This isosceles trapezoid has the shape of an equilateral triangle with the vertex cut off to form the shorter of the two parallel sides. This side is located toward the center of the main body base 11 when viewed from the longer of the two parallel sides. A female screw cylinder 119 is provided further toward the center of the main body base 11 from the shorter side.

[0026] When the circuit board 12 is attached to the main body base 11, the light-emitting element 123 and the light-receiving element 124 provided on the circuit board 12 are located in the areas indicated by the arrows in Fig. 6. The cylindrical bodies 117 are provided on both sides of the smoke detection unit 111, and when the circuit board 12 is attached, one cylindrical body 117 is located near the light-emitting element 123, and the other cylindrical body 117 is located near the light-receiving element 124. The cylindrical bodies 117 are formed to be elongated vertically in the direction from the smoke detection unit 111 toward the center of the main body base 11 to match the shape of the opening 121. The smoke detection unit 111 is surrounded by an isosceles trapezoidal cylindrical smoke detection unit wall 111a, and two light-shielding walls 111c protrude inward from the shorter smoke detection unit wall 111a.

[0027] 7 is an enlarged perspective view of the vicinity of the smoke detection unit 111 in the main body base 11. The circuit board 12 is placed so as to contact board mounting surface 11a, which is the upper end surface of the surrounding wall 115; board mounting surface 11b, which is the upper end surface of the wall connecting the surrounding wall 115 and the smoke detection unit wall 111a; board mounting surface 11c, which is the upper end surface of a step provided around the smoke detection unit wall 111a; and board mounting surface 11d, which is provided on the connecting column. The vertically elongated cylindrical body 117 has a vertically elongated inner hole 117a on its inside. The cylindrical body 117 is at the same height as the board mounting surfaces 11a, 11b, 11c, and 11d, and contacts the circuit board 12 together with the board mounting surfaces 11a, 11b, 11c, and 11d to support the circuit board 12.

[0028] The positions of the light-emitting element 123 and the light-receiving element 124 when the circuit board 12 is attached are indicated by arrows. Light-transmitting holes 111b are provided in the smoke detection unit wall 111a at positions corresponding to the light-emitting element 123 and the light-receiving element 124 of the circuit board 12. A cylindrical body 117 is provided on the outside of the smoke detection unit 111, between the apex of the isosceles trapezoidal cylinder formed by the smoke detection unit wall 111a that is close to the surrounding wall 115 and the light-transmitting hole 111b. The cylindrical body 117 is provided in a direction away from the surrounding wall 115 as viewed from the apex that is close to the surrounding wall 115. In addition, a light-shielding wall 111c that blocks direct light is provided between the two light-transmitting holes 111b, extending from the shorter smoke detection unit wall 111a on the female thread cylinder 119 side toward the inside of the smoke detection unit 111.

[0029] 5, the opening 121 of the circuit board 12 is vertically long and extends in a direction perpendicular to the direction in which the cylindrical bodies 117 are arranged. Similarly, the cylindrical bodies 117 and the inner holes 117a are also formed to extend in a direction perpendicular to the direction in which the cylindrical bodies 117 are arranged. The cylindrical bodies 117 protrude in a position that surrounds the opening 121 of the circuit board 12. The cylindrical bodies 117 of the main body base 11 and the opening 121 of the circuit board 12 are provided in positions that correspond to the hooks 182 of the optical bench cover 18.

[0030] When assembling the smoke detector 1, the circuit board 12 is placed on the main body base 11 shown in FIG. 7 and held by the board mounting surfaces 11a, 11b, 11c, and 11d and the cylindrical body 117. After achieving the state shown in FIG. 5, the speaker 13 is connected, and then the smoke intake cover 15 is placed on top. Then, the insect screen 17 and the optical base cover 18 are attached to achieve the state shown in FIG. 4. As shown in FIG. 2, the smoke intake cover 15 is provided with multiple locking springs 157 having locking holes extending downward around its periphery. When the smoke intake cover 15 is placed on top, the multiple locking springs 157 are locked onto the multiple locking pieces 116 protruding from the periphery of the main body base 11. Then, a male screw (not shown) is inserted through the screw passage hole 155 of the smoke intake cover 15 shown in FIGS. 3 and 4 and screwed into the female threaded cylinder 119, thereby screwing the smoke intake cover 15 and other components to the main body base 11.

[0031] FIG. 8 shows an enlarged cross-sectional view of the vicinity of the cylindrical body 117. FIG. 8 is an enlarged cross-section of the portion AA in FIG. 4. The smoke detection unit wall 111a of the main body base 11 has a board mounting surface 11c outside the smoke detection unit 111. A cylindrical body 117 is provided at the same height as the board mounting surface 11c. A circuit board 12 having an opening 121 is mounted on the cylindrical body 117 and the board mounting surface 11c. A smoke intake cover 15 having a hook hole 152 is mounted on the upper surface of the smoke detection unit wall 111a. The height of the cylindrical body 117 is such that it comes into contact with the circuit board 12.

[0032] Ventilation holes 153 of smoke intake cover 15 are provided above smoke detection unit 111 on the left side in Fig. 8. Fig. 8 also shows a cross section of a portion of labyrinth wall 154 shown in Fig. 3. Optical bench cover 18 is placed on labyrinth wall 154 of smoke intake cover 15. Insect screen 17 is pressed against optical bench cover 18 and housed inside step 158 of smoke intake cover 15.

[0033] The cover legs 181 of the optical base cover 18 pass through the hook holes 152 of the smoke inlet cover 15, and the hooks 182 at the tips are engaged with the edges of the hook holes 152 on the underside of the smoke inlet cover 15. The hooks 182 protrude outward from the cover legs 181 of the optical base cover 18. When the hooks 182 pass through the hook holes 152, the tapered surfaces of the hooks 182 abut against the upper parts of the hook holes 152. When the optical base cover 18 is further pushed toward the smoke inlet cover 15, the cover legs 181 bend inward and the hooks 182 pass through the hook holes 152. Because the hooks 182 protruding outward from the cover legs 181 must pass through the hook holes 152, the hook holes 152 are larger than the cover legs 181, and a gap is created on the smoke detection unit 111 side of the cover legs 181, as shown in FIG. 8 .

[0034] Furthermore, an opening 121 is provided in the circuit board 12 to prevent the hook 182 from hitting the circuit board 12. Therefore, the top of the smoke inlet cover 15 communicates with the bottom of the circuit board 12 through the hook hole 152 and the opening 121. Various electrical elements, including the light-emitting element 123 and the light-receiving element 124, are attached to the circuit board 12 between the circuit board 12 and the main body base 11, and the space between the circuit board 12 and the main body base 11 is formed to be much wider than the space between the circuit board 12 and the smoke inlet cover 15. The cylindrical body 117 has the same height around its entire circumference and contacts the circuit board 12 outside the opening 121 around its entire circumference. As shown in FIG. 8 , the cylindrical body 117 prevents the bottom of the opening 121 from communicating with the outside of the inner hole 117a of the cylindrical body 117. This prevents airflow, dust, insects, and the like from entering between the circuit board 12 and the main body base 11 from the top of the smoke inlet cover 15.

[0035] 6 and 7, cylindrical bodies 117 are provided on both sides of smoke detection unit 111, with one cylindrical body 117 positioned near light-emitting element 123 provided on circuit board 12, and the other cylindrical body 117 positioned near light-receiving element 124 provided on circuit board 12. Because cylindrical bodies 117 support circuit board 12, light-emitting element 123 and light-receiving element 124 can be positioned more accurately.

[0036] 8, main body base 11 supports circuit board 12 on board mounting surface 11c, the upper surface of cylindrical body 117, etc. Smoke intake cover 15 is placed on the upper surface of smoke detection section wall 111a. Smoke intake cover 15 has a protrusion 156 on its lower side, which presses circuit board 12 toward main body base 11.

[0037] Figure 9 shows a bottom view of smoke inlet cover 15. This is the back side of smoke inlet cover 15 shown in Figure 3. Smoke inlet cover 15 has ridges 156, as shown in Figure 8, that protrude all around vent hole 153. When smoke inlet cover 15 is attached, ridges 156 are positioned along the entire periphery of smoke detection unit wall 111a of main body base 11. This increases the airtightness of smoke inlet cover 15 and prevents air leakage from smoke detection unit 111.

[0038] Furthermore, protrusions 156 are positioned outside smoke detection section wall 111a and are provided so as to press down on the edge of circuit board 12 near smoke detection section wall 111a. This also makes it possible to prevent circuit board 12 from lifting up near smoke detection section 111a.

[0039] 9 shows hook holes 152 on the outside of ridges 156. Hooks 182 of optical bench cover 18 protrude from hook holes 152 in smoke intake cover 15 in FIG. 9 from the back to the front, and extend away from ventilation holes 153 in hook holes 152 to be engaged with smoke intake cover 15.

[0040] In addition, the specific configuration is not limited to the embodiments, and the present invention includes design changes within the scope of the gist of the present invention. Furthermore, the above-mentioned embodiments can be combined by utilizing each other's technologies as long as there are no particular contradictions or problems in the purpose, configuration, etc. [Explanation of symbols]

[0041] 1 smoke detector, 11 main body base, 11a board mounting surface, 11b board mounting surface, 11c board mounting surface, 11d board mounting surface, 111 smoke detection section, 111a smoke detection section wall, 111b light-transmitting hole, 111c light-shielding wall, 112 battery storage section, 113 component storage wall, 114 flange section, 115 surrounding wall, 116 locking piece, 117 cylindrical body, 117a inner hole, 118 cover base, 119 female screw cylinder, 12 Circuit board, 121 Opening, 122 CO sensor, 123 Light emitting element, 124 Light receiving element, 125 Screw passage hole, 13 speakers, 141 conductor wire, 142 conductor wire, 15 smoke intake cover, 151 ridge, 152 hook hole, 153 ventilation hole, 154 labyrinth wall, 155 screw passage hole, 156 ridge, 157 locking spring, 158 step 16 Translucent cover, 17 Insect screen, 18 Optical bench cover, 181 Cover legs, 182 Hooks, 19 Main body cover, 191 Ventilation hole, 9 smoke detector, 91 main body base, 911 smoke detector, 912 battery compartment, 92 circuit boards, 95 smoke intake cover, 951 protrusion, 952 hook hole, 97 Insect net, 98 Optical bench cover, 981 Cover legs, 982 Hooks

Claims

1. In smoke detectors that take in outside air and detect smoke, The main body base and a circuit board mounted on the main body base; a smoke intake cover covering the circuit board; The smoke intake cover has a hook hole through which a hook for fixing the optical bench cover passes, the circuit board has an opening at a position corresponding to the hook hole; The main body base has a cylindrical body protruding from it at a position surrounding the opening, A smoke detector characterized in that the circuit board is supported by the cylindrical body.

2. A smoke detector as described in claim 1, characterized in that the cylindrical bodies are provided on both sides of the smoke detection unit, one of the cylindrical bodies is located near a light-emitting element provided on the circuit board, and the other cylindrical body is located near a light-receiving element provided on the circuit board.

3. The opening is long in a direction perpendicular to the direction in which the cylindrical bodies are arranged, 3. The smoke detector according to claim 2, wherein the cylindrical bodies have an inner hole that is long in a direction perpendicular to the direction in which the cylindrical bodies are arranged.

4. 4. The smoke detector according to claim 1, wherein the smoke inlet cover is provided with a ridge that runs along the entire periphery of the smoke detection section wall of the main body base.

5. the circuit board is fitted to the outside of the smoke detection unit wall of the main body base, 5. The smoke detector according to claim 4, wherein the smoke inlet cover is provided with the protrusions so as to press against the edge of the circuit board near the wall of the smoke detection section.

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