Heat sensor

Abstract

A heat sensor (1) comprises: a substrate (40); a heat detection element (30) that detects heat; and a housing (10) that accommodates the substrate (40). The substrate (40) includes a main body part (41) and an extension part (42) which extends from a peripheral edge (41a) of the main body part (41) to the outside of the main body part (41), and on which the heat detection element (30) is mounted. The extension part (42) has a mounting region (42a) on which the heat detection element (30) is mounted, and a pair of connection regions (42b) connected to the main body part (41). A hole (43) penetrating the substrate (40) is formed by the peripheral edge (41a) of the main body part (41) and the extension part (42). A first distance (L1) between the pair of connection regions (42b) is longer than a second distance (L2) from the center (O1) of the mounting region (42a) to the peripheral edge (41a) of the main body part (41).

Description

Thermal sensor

[0001] The present invention relates to a thermal sensor.

[0002] Conventionally, thermal sensors that detect heat generated by a fire or the like are known. For example, Patent Document 1 discloses a thermal sensor including a substrate body, a heat detection element mounted on the substrate body for detecting heat, and a housing for housing these components.

[0003] Japanese Unexamined Patent Application Publication No. 2019-212269

[0004] There is a desire for further improvement in the heat detection performance of thermal sensors.

[0005] The present invention provides a thermal sensor capable of improving heat detection performance.

[0006] The thermal sensor according to one aspect of the present invention includes a substrate, a heat detection element for detecting heat, and a housing for housing the substrate. The substrate has a main body portion and an extension portion that extends outward from the periphery of the main body portion and on which the heat detection element is mounted. The extension portion has a mounting region on which the heat detection element is mounted and a pair of connection regions connected to the main body portion. A hole penetrating the substrate is formed by the periphery of the main body portion and the extension portion, and a first distance between the pair of connection regions is longer than a second distance from the center of the mounting region to the periphery of the main body portion.

[0007] According to the present invention, a thermal sensor capable of improving heat detection performance can be provided.

[0008] FIG. 1 is a perspective view showing the structure of the thermal sensor according to the embodiment from below. FIG. 2 is a cross-sectional view showing the structure of the thermal sensor. FIG. 3 is a view showing the substrate and the heat detection element of the thermal sensor from below. FIG. 4 is a view showing the structure around the extension portion of the substrate of the thermal sensor from below. FIG. 5 is a view showing the structure around the extension portion of the substrate of the thermal sensor from above.

[0009] Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, arrangement positions of components, and connection configurations shown in the following embodiments are examples only and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, those not described in the independent claim representing the highest-level concept will be described as optional components.

[0010] Furthermore, each figure is a schematic diagram and not necessarily a strictly accurate representation. In addition, the same reference numerals are used for substantially identical components in each figure, and redundant explanations may be omitted or simplified.

[0011] Furthermore, coordinate axes may be shown in the drawings used to illustrate the following embodiments. In this embodiment, the Z-axis direction is the vertical direction. The X-axis and Y-axis directions are mutually orthogonal directions on a plane perpendicular to the Z-axis direction. The positive direction of the Z-axis is defined as the vertically upward direction. In the following embodiments, a plan view means viewing from the Z-axis direction.

[0012] (Embodiment) [Configuration of Heat Detector] The configuration of the heat detector according to the embodiment will be described with reference to Figures 1 to 5. Figure 1 is a perspective view from below showing the structure of the heat detector 1 according to the embodiment. Figure 2 is a cross-sectional view showing the structure of the heat detector 1.

[0013] As shown in Figures 1 and 2, the heat detector 1 according to this embodiment is a fire alarm that detects fires in a building and notifies the outside that a fire has occurred. The heat detector 1 is installed, for example, on the ceiling or wall (in this case, the ceiling) of a building such as an office building, factory, or house.

[0014] The heat detector 1 comprises a cylindrical housing 10 that forms the outer casing of the heat detector 1, a circuit board 40 provided inside the housing 10, a heat detection element 30, and a control unit 50 (see Figure 2). The heat detection element 30 and the control unit 50 are mounted on the circuit board 40.

[0015] The thermal sensing element 30 detects ambient heat. The thermal sensing element 30 primarily detects heat from the substrate 40. The thermal sensing element 30 is, for example, a chip thermistor. The thermal sensing element 30 is connected to the control unit 50 via wiring (not shown) formed on the substrate 40. One or more thermal sensing elements 30 are sufficient, but in this embodiment, multiple (six in this case) are provided.

[0016] The control unit 50 is composed of IC chips such as a CPU (Central Processing Unit), RAM (Random Access Memory), and ROM (Read Only Memory). The control unit 50 determines whether or not there is a fire based on the results obtained from the thermal sensing elements 30. Specifically, the resistance value of the thermal sensing elements 30 changes with temperature changes, and the voltage changes with the change in resistance value. The control unit 50 determines whether or not there is a fire by reading this change in voltage. The control unit 50 may also determine whether or not there is a fire by comparing the maximum or minimum value of the voltage output from multiple thermal sensing elements 30 with a predetermined threshold. Alternatively, the control unit 50 may determine whether or not there is a fire based on whether or not the average value of the voltage output from multiple thermal sensing elements 30 is higher than a predetermined threshold. Furthermore, the control unit 50 may determine whether or not there is a fire based on the number of thermal sensing elements 30 whose detected values ​​exceed a certain threshold. Furthermore, the control unit 50 may determine the presence or absence of a fire based on the largest or smallest detected value among the detected values ​​acquired from the multiple heat sensing elements 30 at the same time. Alternatively, the control unit 50 may determine the presence or absence of a fire after excluding outliers from the detected values ​​of the multiple heat sensing elements 30. Outliers are abnormal values, such as values ​​that are extremely large or small compared to other detected values, or values ​​that remain constant without change.

[0017] Furthermore, the control unit 50 has an alarm circuit (not shown) for notifying the determination result when it determines that a fire has occurred. The alarm circuit is connected to, for example, an external management device, such as a server. The control unit 50 notifies the server of the occurrence of a fire via this alarm circuit. The alarm circuit may also be connected to a speaker or LED (Light Emitting Diode) to inform those nearby that a fire has occurred.

[0018] Furthermore, in this embodiment, the heat detector 1 is equipped with a smoke detection unit 60 for detecting smoke. The smoke detection unit 60 is located inside the housing 10 and mounted on the circuit board 40. The smoke detection unit 60 may be, for example, an optical smoke detection sensor, and may detect smoke by utilizing the diffuse reflection of light. For example, a smoke detection sensor is composed of a chamber, a light-receiving element (such as a photodiode), and a light-emitting element (such as an LED). The smoke detection sensor may be any other known smoke detection sensor.

[0019] The structure of the heat detector 1 will be described in detail below with reference to Figures 1 to 5. Figure 3 is a view from below showing the substrate 40 and heat detection element 30 of the heat detector 1. Figure 4 is a view from below showing the structure around the extension portion 42 of the substrate 40 of the heat detector 1. Figure 5 is a view from above showing the structure around the extension portion 42 of the substrate 40 of the heat detector 1.

[0020] As shown in Figures 1 and 2, the housing 10 is, for example, a bottomed cylindrical shape and has a bottom portion 11 and side portions 12. The side portions 12 have a cylindrical shape. The bottom portion 11 is provided at one end (in this case, the lower end) of the side portions 12. The housing 10 also has an opening 13 located at the top (opposite the bottom portion 11). The upper end of the housing 10 contacts the ceiling when the heat detector 1 is installed on the ceiling of a building. The housing 10 is made of, for example, a heat-resistant resin.

[0021] The side portion 12 has a plurality of openings 12a that allow air flowing along the ceiling, etc., to pass through. The plurality of openings 12a are formed around substantially the entire circumference of the side portion 12. In the event of a fire or the like, the hot air will, for example, rise from the heat source and then flow horizontally along the ceiling, etc. The air flowing along the ceiling, etc. will flow into the housing 10 through the openings 12a on one side and out to the outside of the housing 10 through the openings 12a on the other side.

[0022] The substrate 40 is placed inside the housing 10 and is fixed to the bottom 11 of the housing 10 using fastening members and / or support members (not shown). The substrate 40 is positioned so that its first surface 40a, which will be described later, is perpendicular to the central axis A1 of the housing 10, i.e., it is positioned along the horizontal direction.

[0023] The substrate 40 is, for example, a CEM-3 (Composite Epoxy Material-3) substrate made of a resin material, but it may be any other resin substrate, or a metal-based substrate made of a metal material, or a ceramic substrate made of a ceramic material. An example of another resin substrate is an FR-4 (Flame Retardant-4) substrate. Examples of ceramic substrates include an alumina substrate made of aluminum oxide (alumina) or an aluminum nitride substrate made of aluminum nitride. Examples of metal-based substrates include an aluminum alloy substrate, an iron alloy substrate, or a copper alloy substrate.

[0024] As shown in Figure 3, the substrate 40 has a main body portion 41 and an extension portion 42 that extends from the peripheral edge 41a of the main body portion 41 to the outside of the main body portion 41, on which the heat sensing element 30 is mounted. Specifically, the main body portion 41 has a substantially circular shape in plan view. The main body portion 41 may also have a substantially polygonal shape in plan view, for example. In addition, the main body portion 41 has a plurality of through holes 41b through which, for example, wiring members and fastening members (neither of which are shown) are inserted. In Figures 3 to 5, the peripheral edge 41a of the main body portion 41 is shown by a dashed line.

[0025] The extension portion 42 protrudes from the main body portion 41 toward the opening 12a (see Figure 2) of the housing 10, and the heat sensing element 30 faces the opening 12a.

[0026] Multiple extensions 42 are provided on the substrate 40 (six in this case). The multiple extensions 42 are arranged at equal angular intervals along the peripheral edge 41a of the substrate 40.

[0027] As shown in Figure 4, the extension 42 has a mounting area 42a on which the thermal sensing element 30 is mounted, and a pair of connection areas 42b connected to the main body 41. The mounting area 42a is separated from the main body 41. The mounting area 42a is the area that overlaps the thermal sensing element 30 in a plan view. The connection areas 42b are the area near the main body 41 and are the area along the periphery 41a.

[0028] In this embodiment, the first distance L1 between a pair of connection regions 42b is longer than the second distance L2 from the center O1 of the mounting region 42a (i.e., the center of the thermal sensing element 30 in a plan view) to the periphery 41a of the main body 41. In this embodiment, the first distance L1 is the distance between the centers O2 of each connection region 42b in the direction along the periphery 41a of the main body 41. That is, the first distance L1 is the distance between the center O2 of one connection region 42b in the direction along the periphery 41a of the main body 41 and the center O2 of the other connection region 42b in the direction along the periphery 41a of the main body 41. In this embodiment, the first distance L1 is approximately the same as the value obtained by dividing the total circumference of the main body 41 by twice the number of thermal sensing elements 30.

[0029] Furthermore, a hole 43 is formed through the substrate 40 by the peripheral edge 41a of the main body portion 41 and the extension portion 42. In other words, the substrate 40 has a hole 43 formed by the main body portion 41 and the extension portion 42.

[0030] In this embodiment, the length L11 of the hole 43 in the first direction A along the periphery 41a of the main body portion 41 is longer than the length L12 of the hole 43 in the second direction B which is perpendicular to the first direction A. In this embodiment, the second direction B is the radial direction of the main body portion 41.

[0031] Furthermore, the length L11 of the hole 43 in the first direction A is longer than the second distance L2 from the center O1 of the mounting area 42a to the periphery 41a of the main body portion 41.

[0032] Here, as shown in Figure 2, the bottom 11 of the housing 10 is provided with a projection 11a extending upward. The projection 11a has, for example, a cylindrical shape. The projection 11a is provided so as to follow the periphery 41a of the main body 41. Specifically, the outer surface of the projection 11a is formed to be substantially flush with the periphery 41a of the main body 41. The hole 43 of the substrate 40 is located radially outside the projection 11a in a plan view. As a result, when high-temperature air flows in from the bottom of the opening 12a hits the projection 11a, it passes upward through the hole 43. Therefore, the portion of the substrate 40 around the hole 43 is more likely to come into contact with the high-temperature air, thus suppressing a decrease in the temperature of the portion around the hole 43.

[0033] Furthermore, as shown in Figure 4, the extension portion 42 extends along the periphery 41a of the main body portion 41 and has an arc-shaped portion 421 having a mounting area 42a, and a pair of connecting portions 422 extending from the end 421a of the arc-shaped portion 421 toward the main body portion 41 and having a connecting area 42b. The arc-shaped portion 421 does not have to be strictly arc-shaped; it is sufficient if it is substantially arc-shaped by a plurality (in this case, six) of arc-shaped portions 421. In other words, one arc-shaped portion 421 may be substantially straight, for example.

[0034] Furthermore, the arc-shaped portion 421 has a first portion 4211 that extends along the periphery 41a of the main body portion 41 with a substantially constant width, and a second portion 4212 that protrudes from the first portion 4211 on the opposite side from the main body portion 41 (i.e., radially outward from the main body portion 41). The mounting area 42a is located in the second portion 4212.

[0035] Furthermore, the substrate 40 has a first surface 40a having a mounting area 42a on which the thermal sensing element 30 is mounted, and a second surface 40b opposite to the first surface 40a. In this embodiment, the first surface 40a faces downward.

[0036] As shown in Figure 2, a control unit 50 is mounted in the center of the first surface 40a. The control unit 50 is electrically connected to a plurality (in this case, six) of thermal sensing elements 30 via wiring provided on the substrate 40.

[0037] A smoke detection unit 60 is mounted in the center of the second surface 40b. The smoke detection unit 60 is electrically connected to the control unit 50 via wiring provided on the substrate 40 and wiring members (not shown).

[0038] In this embodiment, as shown in Figure 5, a metal layer 44 is provided in at least the portion of the second surface 40b that corresponds to (opposes) the mounting area 42a. In other words, the portion of the second surface 40b that corresponds to (opposes) the mounting area 42a is a metal surface. In Figure 5, for ease of understanding, the region where the metal layer 44 is provided is enclosed by a thick dashed line.

[0039] In this embodiment, the metal layer 44 has a larger area than, for example, the mounting area 42a. The metal layer 44 is provided over substantially the entire area of ​​at least the second portion 4212 of the arc-shaped portion 421. In this embodiment, the metal layer 44 is provided over substantially the entire area of ​​at least the arc-shaped portion 421 (i.e., substantially the entire area of ​​the first portion 4211 and the second portion 4212). Specifically, the metal layer 44 is provided from the second portion 4212 to an area midway through the connecting portion 422. Furthermore, the metal layer 44 is separated from the connecting region 42b. Therefore, when the metal layer 44 becomes hot, it is possible to suppress the transfer (escape) of heat from the metal layer 44 to the main body portion 41.

[0040] The metal layer 44 is formed, for example, by a metal wiring layer provided on the substrate 40. In this embodiment, the metal layer 44 is formed by a metal wiring layer made of copper or the like, and a solder layer formed on the metal wiring layer. The metal layer 44 may also be formed by layers other than the metal wiring layer and the solder layer.

[0041] As described above, in the heat detector 1 of this embodiment, the substrate 40 has a main body portion 41 and an extension portion 42 that extends from the periphery 41a of the main body portion 41 to the outside of the main body portion 41 and on which the heat detection element 30 is mounted. The extension portion 42 has a mounting area 42a on which the heat detection element 30 is mounted and a pair of connection areas 42b that are connected to the main body portion 41. The first distance L1 between the pair of connection areas 42b is longer than the second distance L2 from the center O1 of the mounting area 42a to the periphery 41a of the main body portion 41.

[0042] With this type of heat detector 1, it is possible to suppress the transfer of heat from the extension portion 42 to the main body portion 41, even though the heat transferred from the high-temperature air to the extension portion 42 is transferred to the main body portion 41. Specifically, air that has become hot due to a fire or the like flows into the opening 12a of the housing 10. As a result, the temperature of the outer periphery of the substrate 40 (in this case, the extension portion 42) tends to rise. On the other hand, the temperature of the main body portion 41 of the substrate 40 (especially the central part of the main body portion 41) does not rise easily. Here, since heat moves from areas of high temperature to areas of low temperature, the heat from the extension portion 42 moves toward the central part of the main body portion 41. Therefore, it takes time for the temperature of the mounting area 42a to reach a certain value or higher. In this embodiment, by making the first distance L1 between a pair of connecting areas 42b longer than the second distance L2 from the center O1 of the mounting area 42a to the periphery 41a of the main body portion 41, it is possible to suppress the transfer of heat from the extension portion 42 to the main body portion 41, even though the heat transferred from the high-temperature air to the extension portion 42 is transferred to the main body portion 41. Therefore, since it is possible to suppress the temperature rise of the extension portion 42, the thermal detection performance of the thermal detection element 30 can be improved.

[0043] Furthermore, in this embodiment, as described above, the length L11 of the hole 43 in the first direction A is longer than the second distance L2 from the center O1 of the mounting area 42a to the periphery 41a of the main body portion 41. This makes it easy to make the first distance L1 longer than the second distance L2 from the center O1 of the mounting area 42a to the periphery 41a of the main body portion 41.

[0044] Also, in the present embodiment, as described above, the length L11 of the hole 43 in the first direction A is longer than the length L12 of the hole 43 in the second direction B. Thereby, for example, while securing the heat transfer length from the mounting region 42a to the main body portion 41 (that is, approximately half the length of the extending portion 42), the amount by which the extending portion 42 protrudes radially from the main body portion 41 can be suppressed.

[0045] [Effects, etc.] Hereinafter, the invention obtained from the disclosure of this specification will be exemplified, and the effects, etc. obtained from the exemplified invention will be described.

[0046] Invention 1 includes a substrate 40, a heat detection element 30 that detects heat, and a housing 10 that houses the substrate 40. The substrate 40 has a main body portion 41 and an extending portion 42 that extends outward from the peripheral edge 41a of the main body portion 41 and on which the heat detection element 30 is mounted. The extending portion 42 has a mounting region 42a on which the heat detection element 30 is mounted and a pair of connection regions 42b connected to the main body portion 41. A hole 43 that penetrates the substrate 40 is formed by the peripheral edge 41a of the main body portion 41 and the extending portion 42. The first distance L1 between the pair of connection regions 42b is longer than the second distance L2 from the center O1 of the mounting region 42a to the peripheral edge 41a of the main body portion 41. It is a heat sensor 1.

[0047] According to such a heat sensor 1, the heat transmitted from the high-temperature air to the extending portion 42 can be suppressed from being transmitted from the extending portion 42 to the main body portion 41. Therefore, it is possible to suppress the temperature of the extending portion 42 from rising, so that the heat detection performance by the heat detection element 30 can be improved. Also, by making the first distance L1 longer than the second distance L2, the area of the portion that receives the high-temperature air can be increased. As a result, the temperature of the extending portion 42 is likely to rise, so that the heat detection performance by the heat detection element 30 can be further improved.

[0048] Invention 2 is the heat sensor 1 of Invention 1, in which the substrate 40 has a first surface 40a having a mounting region 42a on which the heat detection element 30 is mounted and a second surface 40b opposite to the first surface 40a, and a metal layer 44 is provided on at least a portion of the second surface 40b corresponding to the mounting region 42a.

[0049] With this type of heat sensor 1, heat is more easily transferred from the high-temperature air to the mounting area 42a via the metal layer 44. Therefore, the heat detection performance of the heat detection element 30 can be further improved.

[0050] Invention 3 is a heat detector 1 according to Invention 1 or 2, comprising a smoke detection unit 60 mounted on a substrate 40 for detecting smoke, wherein the substrate 40 has a first surface 40a having a mounting area 42a on which a heat detection element 30 is mounted, and a second surface 40b opposite to the first surface 40a, and the smoke detection unit 60 is mounted on the second surface 40b.

[0051] With this type of heat detector 1, in addition to detecting heat, smoke can also be detected. Furthermore, by arranging the heat detection element 30 on the first surface 40a and the smoke detection unit 60 on the second surface 40b, unlike, for example, when the heat detection element 30 and the smoke detection unit 60 are arranged on the same surface, it is possible to suppress changes in the airflow around the heat detection element 30 due to the influence of the smoke detection unit 60. This makes it possible to suppress a decrease in the heat detection performance of the heat detection element 30.

[0052] Invention 4 is a heat sensor 1 according to any of Inventions 1 to 3, wherein the first distance L1 is the distance between the centers O2 of each connection region 42b in a direction along the peripheral edge 41a of the main body 41.

[0053] With this type of heat sensor 1, compared to the case where the first distance L1 is the distance between the furthest points of the pair of connection regions 42b (for example, the distance from one end to the other of the extension portion 42 in the X-axis direction of Figure 4), the transfer of heat from the extension portion 42 to the main body portion 41 can be suppressed more effectively.

[0054] Invention 5 is a heat detector 1 according to any of Inventions 1 to 4, wherein the length L11 of the hole 43 in the first direction A along the periphery 41a of the main body 41 is longer than the length L12 of the hole 43 in the second direction B intersecting the first direction A.

[0055] With this type of heat detector 1, the heat transferred from the high-temperature air to the extension portion 42 can be easily suppressed from being transferred from the extension portion 42 to the main body portion 41. Therefore, the temperature of the extension portion 42 can be easily suppressed from rising, and the heat detection performance of the heat detection element 30 can be easily improved.

[0056] Invention 6 is a heat detector 1 according to any one of Inventions 1 to 5, wherein the extension portion 42 has an arc-shaped portion 421 that extends along the periphery 41a of the main body portion 41 and has a mounting area 42a, and a pair of connecting portions 422 that extend from the end portion 421a of the arc-shaped portion 421 toward the main body portion 41 and have a connecting area 42b, and the arc-shaped portion 421 has a first portion 4211 that extends along the periphery 41a of the main body portion 41 and a second portion 4212 that protrudes from the first portion 4211 toward the opposite side from the main body portion 41, and the mounting area 42a is located in the second portion 4212.

[0057] With this type of heat sensor 1, the transfer of heat from the mounting area 42a to the main body 41 can be further suppressed.

[0058] (Other Embodiments) The heat detector 1 of the present invention has been described above based on the above embodiments, but the present invention is not limited to the above embodiments.

[0059] For example, in the above embodiment, an example was described in which the heat detector 1 is equipped with a smoke detection unit 60, but the present invention is not limited to this. The heat detector 1 does not need to be equipped with a smoke detection unit 60. Also, the heat detector 1 is not limited to the ceiling, but may be installed on a wall. The heat detector 1 may be powered by a commercial power supply, or by a battery provided inside the housing 10.

[0060] Furthermore, the shape of the housing 10 of the heat detector 1 is not limited to a cylindrical shape, but may also be rectangular.

[0061] Furthermore, the heat detection element 30 and the smoke detection unit 60 may be arranged on the same surface of the substrate 40 (either the first surface 40a or the second surface 40b).

[0062] Furthermore, the heat sensing element 30 may be mounted on the upper surface of the substrate 40 (the second surface 40b in the above embodiment) rather than the lower surface of the substrate 40 (the first surface 40a in the above embodiment).

[0063] Furthermore, the present invention also includes forms obtained by applying various modifications to the embodiments that a person skilled in the art could conceive, or forms realized by arbitrarily combining the components and functions of the embodiments without departing from the spirit of the present invention.

[0064] 1 Heat detector 10 Housing 30 Heat detection element 40 Substrate 40a First surface 40b Second surface 41 Main body 41a Periphery 42 Extension 42a Mounting area 42b Connection area 43 Hole 44 Metal layer 60 Smoke detection part 421 Arc-shaped part 421a End 422 Connection part 4211 First part 4212 Second part A First direction B Second direction L1 First distance L2 Second distance L11, L12 Length O1, O2 Center

Claims

1. A heat detector comprising: a substrate; a heat sensing element for detecting heat; and a housing for housing the substrate, wherein the substrate has a main body and an extension extending from the periphery of the main body to the outside of the main body and on which the heat sensing element is mounted, the extension has a mounting area on which the heat sensing element is mounted and a pair of connection areas connected to the main body, a hole penetrating the substrate is formed by the periphery of the main body and the extension, and the first distance between the pair of connection areas is longer than the second distance from the center of the mounting area to the periphery of the main body.

2. The heat detector according to claim 1, wherein the substrate has a first surface having the mounting area on which the heat sensing element is mounted, and a second surface opposite to the first surface, and a metal layer is provided on at least the portion of the second surface corresponding to the mounting area.

3. A heat detector according to claim 1 or 2, comprising a smoke detection unit mounted on the substrate for detecting smoke, wherein the substrate has a first surface having the mounting area on which the heat detection element is mounted, and a second surface opposite to the first surface, and the smoke detection unit is mounted on the second surface.

4. The heat detector according to claim 1 or 2, wherein the first distance is the distance between the centers of each of the connection areas in a direction along the periphery of the main body.

5. The heat detector according to claim 1 or 2, wherein the length of the hole in the first direction along the periphery of the main body is longer than the length of the hole in the second direction intersecting the first direction.

6. The heat detector according to claim 1 or 2, wherein the extension portion extends along the periphery of the main body and has an arc-shaped portion having the mounting area, and the extension portion extends from the end of the arc-shaped portion toward the main body and has a pair of connecting portions having the connecting area, the arc-shaped portion has a first portion extending along the periphery of the main body and a second portion projecting from the first portion toward the opposite side of the main body, and the mounting area is located in the second portion.

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