JP2003196760A - Fire detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fire detector which has high responsiveness to temperature variation due to the thermal current of a fire and can be made small. <P>SOLUTION: This fire detector is provided with a substrate 1 the outer side of which is a thermosensitive surface for receiving the thermal current, a temperature detection element 2 for coming into thermal contact with the inner side of the substrate 1 to detect the temperature of the substrate, and a detector main body 3 which is in contact with the outer circumferential part of the inner side of the substrate 1 to form an enclosed space with the substrate and includes the temperature detection element 2 in the enclosed space. The substrate 1 has the temperature detection element 2 almost at the center of the inner side of the substrate, and has a shape and material which satisfy the relationship that a product of the thickness d of the substrate 1 and heat conductivity λ<SB>disk</SB>is not larger than 1.1×10<SP>-4</SP>(W/K). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire detector for detecting a temperature change of an air flow due to a fire by using a temperature detecting element.

[0002]

2. Description of the Related Art Conventionally, as a fire detector of this type, there is one shown in, for example, FIG.
0). In this fire detector, a temperature detection element 103 housed in a metal protective case 102 is arranged so as to project from a sensor body 101 having a built-in circuit board 105. A heat collecting plate 104 is provided to increase the response speed. A transistor is used as the temperature detecting element 103.

FIG. 18 shows another example of a conventional fire heat detector. In this fire detector, a thermistor in which a resin coating 106 is applied to a sensor body 101 having a built-in circuit board 105 is used as a temperature detecting element 103. A protective structure 107 is provided around the temperature detecting element 103.
Is provided.

In this case, since the temperature detecting element 103 is in contact with the outside air via the resin coating 106, the temperature detecting element 103 shown in FIG.
Even if there is no special heat collecting structure such as a heat collecting plate, a sufficient response speed can be obtained.

[0005]

However, such a conventional fire detector has the following problems. First, in the fire detector of FIG. 17, the protective case 1
In order to prevent heat from escaping to the sensor body 101 through the wall of 02, it is necessary to dispose the sensor body 101 and the temperature detecting element 103 apart from each other, which causes a problem that miniaturization becomes difficult.

Further, in the fire detector of FIG. 18, it is necessary to dispose the detector main body 101 and the temperature detecting element 103 apart from each other so that the heat energy does not escape through the portion of the wiring 108. Since the mechanical strength of the portion 108 is low, the protective structure 107 is required, and thus there is a problem that miniaturization is difficult.

It is an object of the present invention to provide a fire detector which has a high temperature responsiveness due to the heat flow of a fire and can be miniaturized.

[0008]

In order to achieve this object, the fire detector of the present invention has a substrate having a heat sensitive surface on the outside for receiving a hot air flow and a substrate which is in thermal contact with the inside of the substrate. A temperature detecting element for detecting a temperature, and a protective case which is in contact with an outer peripheral portion inside the substrate to form a closed space between the substrate and the temperature detecting element is included in the closed space are provided.

According to the structure of the fire detector of the present invention as described above, since the heat sensitive portion composed of the substrate and the temperature detecting element is flat, it is easy to make the device thinner and smaller.

Here, the substrate has a temperature detecting element substantially at the center inside the substrate, and the thickness d of the substrate and the thermal conductivity λ.
_The shape and the material satisfy the requirement that the product of _disks is 1.1 × 10 ⁻⁴ [W / K] or less.

Therefore, when the heat flow of a fire is received by the substrate, the amount of heat Q escaping through the substrate as seen from the temperature detecting element.
_The amount of heat that the _disk escapes through the air in the enclosed space is less than or equal to Q _air, and the substrate can be equated with the air in terms of the flow of thermal energy, so that the temperature detecting element is substantially suspended in the air. A close thermal response, that is, a fast thermal response and a large temperature rise can be obtained.

Further, in the fire detector of the present invention, the closed space formed by the substrate and the protective case may be filled with a resin material or a heat insulating material.

[0013]

1 is a basic structure of a fire detector according to the present invention. This basic structure comprises a substrate 1, a temperature detecting element 2, and a sensor body 3 that functions as a protective case. The outside of the substrate 1 is a heat-sensitive surface that receives a hot air flow, and the temperature detecting element 2 is installed near the center of the back surface of the substrate 1, that is, on the back surface that is not in contact with the joint between the substrate 1 and the sensor body 3, and inside the substrate 1. The temperature of the substrate 1 is detected by making thermal contact.

Further, the sensor body 4 is in contact with the temperature detecting element 2 and the outer peripheral portion inside the substrate 1 to form a closed space between the substrate 1 and the temperature detecting element 2 in the closed space. .

Here, the substrate 1, the temperature detecting element 2, and the sensor main body 3 are set to satisfy the following conditions. First, substrate 1
The thickness d is 0 .. from the viewpoint of mechanical strength and thermal response.
It is desirable that it is 1 [mm] or more and 0.8 [mm] or less (0.1 [mm] ≤ d ≤ 0.8 [mm]).

The material of the substrate 1 is preferably plastic or glass having a small thermal conductivity and a certain strength. Desirably, the thickness d of the substrate 1 and its thermal conductivity λ
The product and shape of _disk satisfy the following conditions.

D · λ _disk ≦ 1.1 × 10 ⁻⁴ [W / K] (1) where d: thickness of the substrate [m] λ _disk : thermal conductivity of the substrate [W / (m · K) FIG. 2 is an explanatory diagram of symbols used in the conditional expression (1), where r ₀ is the radius or average radius of the temperature detecting element,
r is the radius or average radius of the substrate, d is the thickness of the substrate, λ
_disk is the thermal conductivity of the substrate R _disk is the thermal resistance through the substrate between the temperature detecting element and the main body, and R _air is the thermal resistance through the air between the temperature detecting element and the main body.

The functions of the respective parts will be described with reference to the symbols in FIG. FIG. 3A is an explanatory diagram showing the thermal relationship of each part. The thermal energy given to the temperature detecting element 2 from the hot airflow via the thin substrate 1 escapes to the sensor body 3 via the substrate 1 and air.

Assuming that the thermal energy applied to the temperature detecting element 2 is Q _in and the total thermal energy escaping to the sensor body 3 is Q _loss , the temperature rise ΔT _s of the temperature detecting element 2 is
It is proportional to the difference between Q _in and Q _loss .

[0020]

[Equation 1]

Q_inIs determined by external conditions, so this
Assuming the same, the temperature rise ΔT _sTo maximize
Q_lossIt is effective to make
It

Therefore, assuming that the thermal energy flow rate escaping from the temperature detecting element 2 via the substrate 1 is Q _disk , and the thermal energy flow rate escaping via _air is Q _air , the heat flow rate Q _disk ,
Q _air is inversely proportional to the respective thermal resistances R _disk and R _air , and the following relational expressions (2) and (3) are established therebetween.

[0023]

[Equation 2]

If the heat flow rate Q _disk is equal to or less than Q _air , that is, Q _disk ≤Q _air , the substrate 1 can be regarded as air with respect to the flow of heat energy.

Therefore, the substrate 1 can be identified with air, and the total amount of heat energy that escapes to the sensor body 3 is small.
As shown in (B), a thermal response close to a state in which the temperature detecting element 2 is floated in the air, that is, a fast thermal response and a large temperature rise can be obtained. In addition, since the heat-sensitive portion composed of the substrate 1 and the temperature detecting element 2 is flat, it is easy to make the fire detector thin and compact.

In the above description, the thermal resistance in the direction perpendicular to the surface of the substrate 1 can be neglected if the substrate 1 is made sufficiently thin with a thickness of 0.8 [mm] or less, and is not considered.

Next, the basis of the substrate condition given by the equation (1) will be described with reference to the symbols in FIG. The radius of the heat-sensitive portion that is the heat-sensitive portion of the temperature detection element 2 is r ₀ , the radius of the substrate 1 is r,
Assuming that the thermal conductivity of the substrate is λ _disk and the thermal conductivity of _air is λ _air , the thermal resistance R _{disk of the} substrate and the thermal resistance R _air of _air are approximated by the following equations (4) and (5). It becomes a value.

[0028]

[Equation 3]

The derivation of equations (4) and (5) will be described in more detail as follows. Figure 4 shows the thermal resistance of the substrate R _disk
It is explanatory drawing for calculating | requiring.

In FIG. 4, the thickness of the substrate 1 is set to d [m
m] and the radius r ₀ [mm] of the cylinder side surface to the thickness d [mm] with the same center and the radius r [mm] of the cylinder side surface, the thermal resistance is R [K / W], and the area of the cylinder side surface is The thermal resistance R is obtained as S. The temperature difference dT [K] between the minute radii dr is caused by the thermal resistance dR [K / W] when the heat flux q _r [W / m ² ] in the radial direction is about to flow.
When this is expressed in a formula, it becomes like a formula (6).

DT = Sq _r dR (6) Here, the heat flow velocity q _r is expressed by the equation (7) from the definition of the thermal conductivity λ.

[0032]

[Equation 4]

(7) Substituting equation (7) into equation (6), the thermal resistance dR is expressed by equation (8).

[0034]

[Equation 5]

(8) The thermal resistance R to be obtained is the thermal resistance between the side surface of the cylinder having the radius r _{0 and} the side surface of the cylinder having the radius r ₀ .

[0036]

[Equation 6]

(9) is obtained. Further, since the area S of the side surface of the cylinder is S = 2πrd, the following equation is obtained by substituting this.

[0038]

[Equation 7]

From the above, the thickness of the substrate 1 is set to d [mm],
The thermal resistance R [K / W] from the side surface of the cylinder having the radius r ₀ [mm] to the side surface of the cylinder having the same center thickness d [mm] and radius r [mm] is expressed by the equation (4).

FIG. 5 is an explanatory diagram for _obtaining the thermal resistance R _air of _air . In FIG. 5, the thermal resistance from a hemisphere having a radius r ₀ [mm] to a hemisphere having the same center is represented by R [K
/ W], the thermal conductivity of the material filling the space between the hemispheres is λ, and the surface area of the hemisphere is S, and the thermal resistance R is determined.

The temperature difference dT [K] between the minute radii dr is, when the radial heat flux q _r [W / m ² ] is about to flow,
It is caused by the presence of thermal resistance dR [K / W]. When this is expressed in a formula, it becomes like a formula (6).

DT = Sq _r dR (10) Here, the heat flow rate q _r is expressed by the equation (11) from the definition of the thermal conductivity λ.

[0043]

[Equation 8]

(11) When the equation (11) is substituted into the equation (10), the thermal resistance R is represented by the equation (12).

[0045]

[Equation 9]

(12) Since the calculated thermal resistance R is the thermal resistance between the hemisphere with radius r _{0 and} the hemisphere with radius r, equation (12) is

[0047]

[Equation 10]

It becomes The area S of the side surface of the cylinder is S = 2
Since it is πr ² , the following equation is obtained by substituting this.

[0049]

[Equation 11]

As described above, the thermal resistance R [K / W] from the hemisphere having the radius r ₀ [mm] to the hemisphere having the same radius r [mm] is expressed by the equation (5).

Here, for r ₀ and r, realistic dimensions r ₀ = 2 [mm] and r = 15 for the heat-sensitive part of the fire detector.
Substituting [mm], the thermal conductivity of _air is λ _air = 0.
024 [W / (m · K)] is used. As a result, the equations (4) and (5) are changed to the equations (13) and (14), respectively.
Can be rewritten as

[0052]

[Equation 12]

Since the temperature detecting element is contained in the sensor body 3 as a protective case, air is treated as solid so that convection does not occur, but natural convection and the like are taken into consideration. It goes without saying that the analysis may be performed using the heat transfer coefficient.

On the other hand, in order to suppress Q _loss to a small value, it is desirable that the thermal energy flow rate Q _disk escaping via the substrate 1 be made approximately equal to the thermal energy flow rate Q _air escaping via _air (Q _disk ≤Q _air ). Replacing this condition with thermal resistance from the equation (3), it is expressed as the equation (15). R _disk ≧ R _air (15) By substituting the equations (13) and (14) into the equation (15), the condition of the equation (16) is obtained. d · λ _disk ≦ 1.1 × 10 ⁻⁴ [W / K] (16) An example is given by substituting the specific values of the substrate thickness d and the thermal conductivity λ _disk into the equation (15). . The thickness of the substrate is d = 0.1 [m
m], λ _disk ≦ 1.1 [W / (m · K)] is obtained as a condition of thermal conductivity from the equation (16).

Used as a material for the outer cover of the fire detector
Polycarbonate resin (λ_disk≈ 0.23 [W / (m
・ K)]) and epoxy resin used in printed circuit boards
(Λ _disk ≒ 0.30 [W / (m · K)]), Hokei
Acid glass (Pyrex (registered trademark) 7740 (R))
(Λ_disk ≈1.1 [W / (m · K)]) etc. meet the conditions
I know you can do it.

The value of the thickness d is within a desirable range (0.1 [m
m] ≤ d ≤ 0.8 [mm]) (d = 1.
0 [mm]) is illustrated. In Expression (16), d = 1.0 [m
[m] is substituted, λ _disk ≦ 0.11 [W / (m · K)] is obtained as a condition of thermal conductivity. Therefore, when the substrate 1 is thick, it has a mechanical strength of a certain level or more and λ _disk ≦ 0.11 [W / (m ·
K)] is difficult to obtain.

On the other hand, a desirable range (0.1 [mm] ≦ d
<0.8 [mm]) (d = 0.05 [m
m]), the condition of thermal conductivity is λ _disk ≦ 2.2 [W / (m · K)]. Almost all plastic materials and glass,
Although this condition is satisfied, if the thickness is less than 0.1 [mm], it is difficult to obtain sufficient mechanical strength.

An example of using a material having a higher thermal conductivity than plastic or glass will be described. When aluminum (metal) is used as the material, λ _disk ≈ 237 [W
/ (M · K)], the conditional expression becomes d ≦ 4.6 × 10 ⁻³ [mm]. In this case, since it is necessary to make the substrate 1 very thin, it is difficult to obtain sufficient mechanical strength.

Aluminum (ceramics) is used as the material.
Is used, λ _disk ≈ 36 [W / (m ·
K)], the conditional expression becomes d ≦ 3.1 × 10 ⁻² [mm]. In this case as well, it is difficult to obtain sufficient mechanical strength because the substrate 1 needs to be made very thin like aluminum.

FIG. 6 shows that the material of the substrate is λ _disk ≈0.2.
6 [W / (m · K)] plastic is used and thickness d
= 0.2, 0.3, 0.4, 0.8, 1.6 [mm]
In this case, the temperature rise of the temperature detecting element 2 is caused.

The product of the thickness d and the thermal conductivity λ _disk (d ·
It can be seen that the temperature rise is particularly high when λ _disk ) satisfies the conditional expression d · λ _disk ≦ 1.1 × 10 ⁻⁴ [W / K].

As described above, in the size of a general fire detector, the thickness d of the substrate 1 and the thermal conductivity λ _disk are d · λ _disk ≦ 1.1 × 10 ⁻⁴ [W / K]. When the conditions are satisfied, an optimum response can be obtained while maintaining sufficient mechanical strength.

In FIG. 7, the thermal resistances R _disk and R _air obtained from the equations (13) and (14) when the radius r _{0 of the} heat sensitive part and the radius r of the substrate 1 are changed are used in (15). The values of the coefficient α in the conditional expression d · λ _disk ≈α × 10 ⁻⁴ [W / K] satisfying the relationship are listed.

From a practical point of view, as described above, the coefficient α of r ₀ = 2.0 [mm] and r = 15 [mm] =
1.1 is preferable. Of course, when the radius r ₀ and the radius r of the substrate 1 take other values, the thickness d of the substrate 1 and its thermal conductivity coefficient λdisk satisfying the corresponding conditions.
The shape and material may be determined so that the product of

FIG. 8 shows an embodiment in which a thermocouple is used as the temperature detecting element. In FIG. 8, the fire detector according to this embodiment includes a substrate 1 having a material and a shape satisfying the condition of the expression (1), a thermocouple 2a arranged as a temperature detecting element on the back side of the center of the substrate 1, and a thermoelectric element. The sensor main body 3 is provided as a protective case surrounding the pair 2a, and the sensor main body 3 is installed on a mounting surface 4 such as a ceiling surface.

The thermocouple 2a used as the temperature detecting element in this embodiment is not a flat plate-shaped heat sensitive portion as shown in the basic configuration of FIG. 1, but its substantial radius r is, for example, r ₀ = The same configuration can be achieved by setting the distance to about 2 mm.

FIG. 9 is an explanatory view of an embodiment of the present invention in which a filler is provided in the space between the substrate and the sensor body. In this embodiment, in the space inside the sensor body 3 which covers the outside of the temperature detecting element 2 provided at the center of the back of the substrate 1, the air is not the air as in the embodiment of FIG. Instead of this, a filler 11 is provided. As the filler, a foaming resin or a heat insulating material having a sufficiently small thermal conductivity can be used.

FIG. 10 is an explanatory view of an embodiment of the present invention in which a metal foil is sandwiched between the substrate and the temperature detecting element. In this embodiment, the metal foil 5 is sandwiched between the temperature detecting elements 2 arranged in the center of the back surface of the substrate 1. By sandwiching the metal foil between the substrate 1 and the temperature detecting element 2 in this way, the heat energy due to the heat flow received by the substrate 1 is stored in the metal foil 5, and an action of assisting the temperature rise of the temperature detecting element 2 is obtained. To be

FIG. 11 is an explanatory view of an embodiment of the present invention in which a metal foil is arranged as an electrode element of a temperature detecting element. In this embodiment, when the temperature detecting element 2 is arranged substantially in the center on the back surface side of the substrate 1, for example, two metal foils 5 are arranged on both sides as electrode terminals thereof and are placed between the substrate 1 and the metal foil 5. It's sandwiched. Wirings 6 are drawn out from the metal foil 5 on both sides.

Also in this embodiment, the metal foil 5 arranged as the electrode terminal stores the thermal energy when the substrate 1 receives the hot air flow, and has the function of assisting the temperature rise of the temperature detecting element 2. .

FIG. 12 shows an embodiment in which, in addition to the embodiment shown in FIG. 11, other electric components besides the temperature detecting element are arranged on the back surface of the substrate. In this embodiment, the temperature detecting element 2 is arranged in the center of the back surface of the substrate 1 as an electrode terminal via a pair of metal foils 5, and wirings 6 are drawn out from the metal foils 5 on both sides. An electric component 7 is provided in the middle of the wiring 6 as required. By using the back surface side of the substrate 1 as the mounting surface of the electric component 7 in this manner, it is possible to improve the mounting efficiency when a mounting substrate for an electric circuit is separately provided.

FIG. 13 shows an embodiment of the present invention in which an electric circuit is arranged between the substrate and the sensor body. In this embodiment, the sensor body 3 is provided so as to cover the temperature detecting element 2 provided substantially in the center of the back surface of the substrate 1, and the internal space between the sensor body 3 and the substrate 1 is provided. The electric circuit 8 is provided on the electric circuit 8, and the temperature detecting element 2 is connected to the electric circuit 8 by the wiring 6.
Is connected with.

Since the electric circuit 8 is provided in the sealed space between the substrate 1 and the sensor body 3 as described above, it is possible to shut off the outside air as in the case of the temperature detecting element 2 and the influence of moisture or corrosive gas. The durability can be improved because it is not subject to damage.

FIG. 14 is an explanatory view of an embodiment of the present invention in which the substrate has a heat collecting structure. In this embodiment, on the front surface side of the substrate 1 in which the temperature detecting element 2 is arranged in the center of the back surface,
A heat collecting structure 9 using a metal member, for example, a heat collecting plate is provided opposite to the temperature detecting element 2.

Thus, by providing the heat collecting structure 9 facing the temperature detecting element 2 substantially in the center of the surface of the substrate 1, the temperature rising of the temperature detecting element 2 when receiving the heat flow of a fire is collected. 9 can make it even faster.

FIG. 15 is an explanatory view of an embodiment of the present invention in which a metal member is arranged in the center of the substrate and a temperature detecting element is arranged on the back side thereof. In this embodiment, a metal member 10 having a high thermal conductivity such as aluminum is embedded in the center of the substrate 1, the temperature detecting element 2 is provided for the metal member 10 exposed on the back side, and the outside thereof is covered. A sensor body 3 is provided as a protective case.

When a heat flow due to a fire is received by the metal member 10 provided in the center of the substrate 1 as described above, the heat energy is directly applied to the temperature detecting element 2 through the metal member 10 and the temperature of the temperature detecting element 2 rises. The temperature can be raised faster without being hindered by the interposition of the substrate 1.

FIG. 16 shows an example in which a temperature detecting element is arranged substantially in the center of the front surface side of the substrate 1. In this example, the substrate 1
By arranging the temperature detecting element 2 so as to be exposed to the outside substantially in the center, and directly receiving the heat flow due to the fire at the temperature detecting element 2, the temperature rise can be accelerated. A protective film such as a resin coating is applied to the temperature detecting element 2 arranged outside the substrate 1 to prevent the influence of moisture or corrosive gas. Wiring for the temperature detecting element 2 is performed from inside the sensor body 3 by penetrating the substrate 1.

The present invention is not limited to the above embodiment, including appropriate modifications that do not impair the object and advantages thereof.
Further, the present invention is not limited by the numerical values shown in the above embodiments.

[0080]

As described above, according to the present invention, there is provided a temperature detecting element for detecting the temperature of the substrate by thermally contacting the inside of the substrate whose outside is a heat sensitive surface for receiving a heat flow. A heat-sensitive structure composed of the substrate and the temperature detecting element is formed by a structure including a closed space that is in contact with the outer peripheral portion inside the substrate Since the part has a flat shape, it is possible to easily achieve a thin and compact fire detector.

Further, in the present invention, the product of the thickness of the substrate and its thermal conductivity is 1.1 × 10 ⁻⁴ [W / K] or less with the temperature detecting element arranged substantially in the center of the substrate. By making the shape and material so that the flow of heat energy can be almost equated with the air in the substrate, the thermal response due to the fire is substantially the same as that of the temperature detection element floating in the air. A fast thermal response and a large temperature rise are obtained when subjected to flow.

[Brief description of drawings]

FIG. 1 is an explanatory view of a basic embodiment of the present invention.

FIG. 2 is an explanatory diagram of symbols of each part in FIG.

FIG. 3 is an explanatory diagram showing a thermal relationship of each part in FIG.

FIG. 4 is an explanatory diagram related to calculation of substrate thermal resistance in FIG.

5 is an explanatory diagram related to calculation of air heat resistance in FIG.

FIG. 6 is a characteristic diagram showing the temperature detected by the temperature detecting element when the thickness d of the substrate is changed in the present invention.

FIG. 7 is an explanatory diagram of conditional expressions when the radius r0 of the heat-sensitive part and the radius r of the substrate are changed.

FIG. 8 is an explanatory diagram of an embodiment of the present invention in which a thermocouple is used as a temperature detecting element.

FIG. 9 is an explanatory diagram of an embodiment of the present invention in which a space between a substrate and a sensor body is filled with a foaming resin or the like.

FIG. 10 is an explanatory diagram of an embodiment of the present invention in which a metal foil is sandwiched between a substrate and a temperature detection element.

FIG. 11 is an explanatory diagram of an embodiment of the present invention in which a metal foil is used as an electrode terminal of a temperature detection element.

FIG. 12 is an explanatory view of an embodiment of the present invention in which electric components other than the temperature detecting element are arranged on the back surface of the substrate.

FIG. 13 is an explanatory diagram of an embodiment of the present invention in which an electric circuit is arranged between a substrate and a sensor body.

FIG. 14 is an explanatory diagram of an embodiment of the present invention in which a substrate is provided with a heat collecting structure.

FIG. 15 is an explanatory diagram of an embodiment of the present invention in which a temperature detecting element is arranged on the surface of a substrate.

FIG. 16 is an explanatory diagram of an embodiment of the present invention in which a metal member is arranged in the center of the substrate and a temperature detecting element is arranged on the back side thereof.

FIG. 17 is an explanatory diagram of a conventional fire detector structure.

FIG. 18 is an explanatory view of another structure of the conventional fire detector.

[Explanation of symbols]

1: substrate 2: Temperature detection element 3: Sensor body 4: Mounting surface 5: Metal foil 6: Wiring 7: Electrical parts 8: Electric circuit 9: Heat collecting structure 10: Metal member

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroshi Shima             2-1043 Kamiosaki, Shinagawa-ku, Tokyo Ho             Chiki Co., Ltd. F-term (reference) 5C085 AA01 AB01 AC03 BA12 CA30                       DA10 FA02 FA20

Claims (3)

[Claims] 1. A substrate having a heat-sensitive surface on the outside that receives a heat flow, a temperature detection element that is in thermal contact with the inside of the substrate to detect the temperature of the substrate, and is in contact with an outer peripheral portion inside the substrate. A fire detector, comprising: a protective case that forms a closed space between the substrate and the closed space, and that includes the temperature detecting element. 2. The fire detector according to claim 1, wherein the substrate has the temperature detecting element substantially at the center inside the substrate, and the product of the thickness and the thermal conductivity of the substrate is 1.1.
A fire detector characterized by having a shape and a material satisfying the condition of ^{x10 -4} [W / K] or less. 3. The fire detector according to claim 1 or 2, wherein the closed space is filled with a resin material or a heat insulating material.