Heat sensor

Abstract

To improve assembling performance and visibility of an actuation pilot lamp in a heat sensor having a heat sensitive element.SOLUTION: In a heat sensor, a circuit board mounting a heat sensitive element and components constituting a detection circuit is stored inside a housing including a body case and a body cover for covering an opening side of the body case. In the body cover, an opening part is formed at a center part and a protector part is arranged to cover the opening part from a lower side. The heat sensitive element is a thermistor. An actuation pilot lamp includes: an insertion hole having an inner diameter larger than a diameter of a distal end part of the thermistor; and a cone-shaped tapered part extending downward and outward from an edge part of the insertion hole, and formed of a light transmission material. The insertion hole is arranged on the lower side of the circuit board so as to be positioned around the heat sensitive element. Then, the whole tapered part of the actuation pilot lamp positioned on an inner side of the opening part of the body cover shines by light from a light emitting element mounted on the circuit board.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fire detector, and particularly to a technique effective for application to a heat detector using a thermistor as a heat-sensitive element (sensor).

Background Art

[0002] A heat detector using a thermistor generally has a thermistor as a heat-sensitive element disposed at the center of a dome-shaped housing, and the housing is attached to the ceiling surface of a building so that the thermistor faces downward to detect the occurrence of a fire. In addition, some covers of fire detectors are provided with an operating indicator lamp that can be lit so that it can be visually determined from the outside whether the detector is detecting a fire. Conventionally, many operating indicator lamps have a point light-emitting type LED installed on the surface of the fire detector. In that case, a structure in which the point light-emitting indicator lamp is installed at a position deviated from the center of the detector is common, but such an operating indicator lamp has a problem of visual recognition directivity. Therefore, for a fire detector installed on the ceiling surface, when looking up from below to check the state of the operating indicator lamp, if the operating indicator lamp is not installed so that it faces the entrance side at a position where it can be seen when, for example, an entrance door is opened, it will be troublesome to check the operation of the detector at the time of fire detection.

[0003] Therefore, in order to eliminate the directivity of the operating indicator lamp, a plurality of point light-emitting type LEDs are provided on the cover of the detector, a point light-emitting type LED is installed on the top of the detector, or a display lamp that lights in a ring shape is provided on the flat part of the cover of the detector. On the other hand, in the case of a general heat detector, in the manufacturing process, after soldering the heat-sensitive element to the electronic substrate, when assembling the electronic substrate into the detector housing, the element is inserted through an opening in the housing that is just the size of the diameter of the heat-sensitive element, so there is a problem of poor assemblability. In addition, since there is no structure for protecting the heat-sensitive element in the state of being mounted on the electronic substrate, there is also a problem that it may be damaged during assembly and requires skill in assembly.

[0004] In addition, as a heat sensor having a structure in which a thermistor is mounted on a printed wiring board constituting a fire detection circuit and an insertion hole through which the thermistor protrudes is formed at the center of a cover covering the board, there are, for example, those described in Patent Documents 1 and 2. Moreover, as a sensor provided with an indicator lamp that lights up in a ring shape on a flat portion of the cover, there is, for example, one described in Patent Document 3. Furthermore, a heat sensor in which a protector covering the head of the thermistor is formed of a translucent resin material, and a confirmation lamp is disposed at the base of the protector so as to illuminate the entire protector is described as Embodiment 2 in Patent Document 4.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the case of a heat sensor, it is difficult to install an operation indicator lamp because the top of the sensor is where the heat-sensitive element is located. If a ring-shaped indicator lamp is arranged on the sensor cover as in the sensor described in Patent Document 3, there are problems such as an increase in cost due to an increase in the number of parts and difficulty in miniaturization. In particular, since the electronic substrate has become smaller due to the miniaturization of electronic components in the heat sensor, and as a result, the sensor housing has also been miniaturized, it is difficult to arrange a ring-shaped operation indicator lamp with the structure described in Patent Document 3.

[0007] In addition, a thermistor is often used as the heat-sensitive element in a heat sensor. However, since a thermistor is an element with a thin and delicate structure and is supported by soldering two lead terminals of the element to an electronic substrate, it may be damaged during the assembly operation. Moreover, the thermistor is erected on the electronic substrate and the heat-sensitive element is inserted through an opening on the surface of the sensor body for assembly. If the opening is small, the assemblability is poor. If the opening is enlarged, dust and moisture are likely to enter the sensor, which may have an adverse effect on the electronic circuit.

[0008] Note that Patent Document 4 describes a heat sensor having a structure in which a mortar-shaped support member is provided at the base of a thermistor and the head of the thermistor is covered with a protector. However, as described above, this heat sensor is intended to form the protector with a translucent resin material, arrange a confirmation lamp at the base of the protector, and guide and emit light to the entire protector. However, there is no suggestion regarding the circulation of light, and there is also a problem that the light emission may not be good only by using two light-emitting elements.

[0009] The present invention has been made paying attention to the above problems, and an object thereof is to improve the assemblability and the visibility of the operation indicator lamp in a heat sensor using a thermistor as the heat-sensitive element. Another object of the present invention is to provide a heat sensor that can be miniaturized and reduce the number of parts to achieve cost reduction.

Means for Solving the Problems

[0010] To achieve the above object, the present invention provides In a heat sensor in which a circuit board on which components constituting a heat-sensitive element and a detection circuit are mounted is housed inside a housing composed of a main body case and a main body cover that covers the opening side of the main body case, The main body cover has an opening formed in the central portion and has a protector portion provided so as to cover the opening from below. The heat-sensitive element is a thermistor, An operation indicator lamp formed of a light-transmitting material, which has an insertion hole with an inner diameter larger than the diameter of the tip of the thermistor and a mortar-shaped tapered portion that extends outward downward from the edge of the insertion hole, is disposed below the circuit board such that the insertion hole is positioned around the heat-sensitive element. It is configured such that the entire tapered portion located inside the opening is illuminated by light from a light-emitting element mounted on the circuit board.

[0011] According to the heat sensor having the above configuration, since the operation indicator lamp has an insertion hole with an inner diameter larger than the diameter of the heat-sensitive element and a mortar-shaped tapered portion, it is easy to insert the thermistor mounted on the circuit board, and the assemblability can be improved. Also, since the entire tapered portion of the operation indicator lamp located inside the opening of the main body cover is illuminated, the light emission of the tapered portion can be visually recognized from any direction of 360°, and the visibility can be improved. Furthermore, the size of the sensor can be reduced, and the number of parts can be reduced to reduce costs.

[0012] Here, preferably, the operation indicator lamp is a separate member from the main body cover and is configured to be joined to the main body cover. Also, preferably, the operation indicator lamp is configured to be joined to the main body case. According to the above configuration, the assemblability of the heat sensor can be improved.

Advantages of the Invention

[0013] According to the heat sensor according to the present invention, in a heat sensor using a thermistor as a heat-sensitive element, the assemblability can be improved, and the visibility of the operation indicator lamp can be improved. Also, according to the present invention, there is an effect that a heat sensor can be realized that can be miniaturized, reduce the number of parts, and reduce costs.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments of a heat sensor according to the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 shows a front cross-sectional explanatory view of a heat sensor of the first embodiment, and FIG. 2 shows a specific example of an element support constituting the heat sensor of the first embodiment. The heat sensor 10 of the present embodiment uses a thermistor 11 as a heat-sensitive element and is a sensor capable of detecting a change in electrical resistance caused by hot air generated by a fire coming into contact with the thermistor 11 to detect a fire. The tip of the thermistor 11 is configured to be installed and used on the ceiling surface of a building or the like in a posture facing downward.

[0016] As shown in Fig. 1, the heat sensor 10 of this embodiment includes a bottomed cylindrical main body case 12 having a housing recess for housing components that sense heat and being insertable into a mounting opening provided on the ceiling surface of a building, and a main body cover 13 coupled to the main body case 12 so as to cover the opening on the lower side of the main body case 12 and having a protector portion 13A at the center for covering the tip of the thermistor 11. The main body case 12 and the main body cover 13 form a housing having an accommodation space inside. Although not shown, a terminal block for electrically connecting wiring disposed on the back surface of the ceiling and an internal circuit board is provided on the upper part of the main body case 12.

[0017] Further, the heat sensor 10 includes a circuit board 14 housed in the housing recess of the main body case 12 and fixed to a boss portion at the bottom of the main body case 12 by screws (not shown). The thermistor 11 is mounted substantially at the center of the circuit board 14, and an inverted bell-shaped element support member 15 having a cylindrical portion 15a through which the thermistor 11 can be inserted and joined in a state where the base of the thermistor 11 is inserted through the surface of the circuit board 14 is provided. Note that the thermistor 11 is mounted on the circuit board 14, and resin 16 is filled and solidified in the cylindrical portion 15a at the upper part of the element support member 15 through which the base of the thermistor 11 is inserted, so as to support the base of the thermistor 11.

[0018] The main body cover 13 has a main body portion that is generally flat and disc-shaped as a whole. An opening is formed at the center of this main body portion, and a protector portion 13A is provided so as to cover this opening from the lower side. The circuit board 14 is composed of a printed wiring board on which electronic components such as resistors, capacitors, and ICs (semiconductor integrated circuits) that constitute an electronic circuit for fire detection are mounted on the upper surface and the lower surface. The tips of the two lead terminals of the thermistor 11 penetrate the circuit board 14 and protrude from the upper surface substantially at the center of the circuit board 14, and are connected to the circuit board 14 by soldering or the like. Also, a light-emitting element 17 such as an LED (light-emitting diode) is surface-mounted at a predetermined portion of the circuit board 14.

[0019] The above-described element support member 15 is formed of a light-transmissive material such as a polycarbonate resin. As shown in Fig. 2(A), it includes a cylindrical portion 15a for inserting the thermistor 11, a tapered portion 15b that extends obliquely downward from the cylindrical portion 15a, a flange portion 15c that extends horizontally outward from the lower end of the tapered portion 15b, and a plurality (e.g., three) of locking pieces 15d for attachment that are erected upward from the outer peripheral surface of the tapered portion 15b and have outward-facing claws at their tips. At corresponding positions on the circuit board 14, engagement holes through which the claws of the locking pieces 15d can be inserted are formed in a number corresponding to the number of locking pieces 15d, and the element support member 15 is mounted on the circuit board 14 by the locking pieces 15d. In Figs. 1 and 2, only one of the plurality (three) of locking pieces 15d is shown for the sake of illustration. However, only one locking piece 15d may be provided.

[0020] As described above, since the element support member 15 has a mortar-shaped tapered portion 15b, the assemblability when mounting the element support member 15 to the circuit board 14 on which the thermistor 11 is mounted is good. After mounting the element support member 15 to the circuit board 14 by inserting the thermistor 11 into the cylindrical portion 15a, resin can be easily filled into the cylindrical portion 15a for inserting the thermistor by facing the nozzle of the dispenser inside the tapered portion 15b.

[0021] Furthermore, a stepped portion (recess) 13b is provided on the upper surface of the opening edge of the disc-shaped main body portion of the main body cover 13, and the lower surface of the flange portion 15c of the element support member 15 is configured to be joined to this stepped portion 13b. A film or layer with good light reflectivity, such as aluminum, may be formed on the inner surface of the stepped portion 13b of the main body cover 13 to which the flange portion 15c is joined. Also, a cylindrical light guide portion 15e is provided on the flange portion 15c of the element support member 15 corresponding to the position of the light-emitting element 17 mounted on the circuit board 14, and a light reflection portion 15f is provided on the surface portion (the lower surface portion in the figure) corresponding to the light guide portion 15e. The end face of the light guide portion 15e, i.e., the face facing the light-emitting element 17, is formed in a concave shape so as to be able to sufficiently introduce the light from the light-emitting element 17.

[0022] As shown in Fig. 2(A), the above-mentioned light reflecting portion 15f has an inclined surface orthogonal to the tapered portion 15b when cut in the vertical direction, and is a concave portion (groove) with a V-shaped cross section when viewed from the direction of arrow C in Fig. 2(B). The light guided from the light guiding portion 15e is formed to be reflected in the inclined direction of the tapered portion 15b shown in Fig. 2(A) and in the circumferential direction of the flange portion 15c shown in Fig. 2(B). On the surface of the element support member 15 on the circuit board side, by performing microfabrication consisting of a large number of thin linear grooves, the inner peripheral surface of the tapered portion 15b may be configured to emit light more brightly by the reflection of the light hitting the grooves. Further, by performing microfabrication on the element support member 15, it becomes cloudy glass-like and has the effect of preventing the inside of the sensor from being seen through from the outside. Also, fine particles that diffusely reflect light may be mixed into the forming material of the element support member 15.

[0023] The protector portion 13A shown in Fig. 1 formed integrally with the main body cover 13 includes a plurality (for example, six) of rectifying fins 13c that radially expand in a plan view, and a disk-shaped head cover 13d that connects the tips (lower ends in Fig. 1) of these rectifying fins 13c. The tip of the thermistor 11 is located in the space surrounded by the plurality of rectifying fins 13c and the head cover 13d, and the air flow is configured to pass between the respective rectifying fins 13c. Note that the diameter of the head cover 13d is made smaller than the diameter of the base (upper part in the figure) of the protector portion 13A, and is formed to have an inverted trapezoidal shape when the sensor is viewed from the side. Also, in Fig. 1, the rectifying fins 13c are arranged vertically, but they may be arranged horizontally (not shown).

[0024] In the thermal sensor of this embodiment having the configuration as described above, when the light emitting element 17 is lit while being installed on the ceiling surface of the building, the entire tapered portion 15b of the element support member 15 emits light, and the light can be seen from any direction among the plurality of rectifying fins 13c, that is, 360°, so there is no directivity in visibility. Therefore, it is not necessary to worry about the angle during installation on the ceiling surface, and the installation work can be completed in a short time. Moreover, the light emitting area becomes larger than that of a conventional sensor equipped with a point light emitting indicator lamp, and the light emitted from the tapered portion 15b also hits the surface of the rectifying fins 13c and is reflected, so that the apparent light emitting surface becomes larger, improving visibility.

[0025] Also, in the thermal sensor 10 of this embodiment, since the element support member 15 also serves as an operation indicator lamp, compared with the configuration in which a ring-shaped operation indicator lamp is formed by a member separate from the member (element support) that forms the accommodation space of the thermistor 11 and is attached to the main body cover as in the sensor described in Patent Document 3, the entire sensor can be miniaturized, and compared with the configuration in which the element support, the protector as the indicator lamp, and the main body cover are configured by separate members as in the sensor described in Patent Document 4, the number of parts can be reduced, thereby achieving cost reduction.

[0026] Furthermore, since the thermal sensor 10 of this embodiment is configured to provide a mortar-shaped element support member 15 having a relatively large opening and insert the thermistor 11 therethrough, the assembly workability is improved. In addition, since the gap between the inner wall of the cylindrical portion 15a of the element support member 15 and the base portion of the thermistor 11 is filled with resin, the thermistor 11 can be supported in a stable state, and dust and moisture are less likely to enter the accommodation space of the circuit board, preventing dust and moisture from having an adverse effect on the circuit board.

[0027] (Second Embodiment) FIG. 3 shows a front cross-sectional explanatory view of the thermal sensor of the second embodiment, and FIG. 4 shows a specific example of the element support member 15 constituting the thermal sensor of the second embodiment. Similar to the thermal sensor of the first embodiment, the thermal sensor 10 of the second embodiment includes a thermistor 11 as a heat-sensitive element, a main body case 12 that houses the circuit board 14, a main body cover 13 having a protector portion 13A that covers the tip of the thermistor 11, and an inverted mortar-shaped element support member 15 joined to the surface of the circuit board 14. The differences from the thermal sensor of the first embodiment are that the shape of the element support member 15 is different and the shape of the main body cover 13 is changed along with the change in the shape of the element support member 15. Hereinafter, the second embodiment will be described with emphasis on such differences.

[0028] As shown in Fig. 4(A), the element support member 15 in the thermal sensor 10 of this embodiment includes a cylindrical portion 15a, a tapered portion 15b, a flange portion 15c, a locking piece 15d, and a light guide portion 15e. Among them, it is different from the element support member 15 of the first embodiment in that a rib-shaped light-emitting portion 15g protruding downward along the outer peripheral edge of the flange portion 15c is provided. In addition, along with the provision of the light-emitting portion 15g, the light reflection portion 15f formed on the surface portion of the flange portion 15c corresponding to the light guide portion 15e is also formed in a V shape even when cross-sectioned in the vertical direction so as to reflect the light from the light guide portion 15e to the outside, that is, to the light-emitting portion 15g. This is also different from the element support member 15 of the first embodiment. As shown in Fig. 4(B), when viewed from below, the above-mentioned light-emitting portion 15g has a ring shape. The light reflection portion 15f is formed as a groove with a V-shaped cross-section also when viewed from the direction of arrow C in Fig. 4(B), similar to the first embodiment.

[0029] Furthermore, along with the provision of the rib-shaped light-emitting portion 15g protruding downward along the outer peripheral edge of the flange portion 15c, a slit 13e is formed in the main body cover 13 as shown in Fig. 3. The light-emitting portion 15g is fitted into this slit 13e, and its head faces the surface of the main body cover 13. The slit 13e forms a ring shape in plan view corresponding to the light-emitting portion 15g. Further, as shown in Fig. 4(A), the head of the light-emitting portion 15g is formed to have a shape that bulges downward, so that light is emitted while spreading from the light-emitting portion 15g due to the lens effect. Note that, similar to the back surface of the tapered portion 15b, fine processing consisting of a number of thin linear grooves may be applied to the back surface of the light-emitting portion 15g. Further, fine particles that diffusely reflect light may be mixed into the material forming the element support member 15.

[0030] Thus, in the second embodiment, by forming the ring-shaped slit 13e in the main body cover 13, the main body cover 13 is divided into an outer plate and an inner plate. However, the rectifying fins 13c of the protector portion 13A are made larger than those in the first embodiment, and the base of the rectifying fins 13c is formed to straddle the outer plate and the inner plate. Thereby, the outer plate and the inner plate of the main body cover 13 are connected to each other by the rectifying fins 13c and are not separated.

[0031] In the thermal sensor of the second embodiment configured as described above, when the light-emitting element 17 is lit while being installed on the ceiling surface of a building, the entire tapered portion 15b of the element support member 15 and the ring-shaped light-emitting portion 15g emit light, and the light can be seen from any direction among the plurality of rectifying fins 13c, that is, 360°. Therefore, there is no visual recognition directionality, and the total light-emitting area is larger than that of the thermal sensor of the first embodiment. Further, since the light emitted from the light-emitting portion 15g illuminates the side surfaces of the rectifying fins 13c, the visibility is further improved. Further, although the size of the rectifying fins 13c is slightly larger than that of the thermal sensor of the first embodiment, the size of the main body cover 13 can be made substantially the same as the main body cover of the thermal sensor of the first embodiment. It is possible to reduce the size compared to the conventional sensor and to reduce the number of parts as in the first embodiment.

[0032] (Modification 1) Figures 5(A) and 5(B) show a modified example of the thermal sensor of the second embodiment. Among these, Fig. 5(A) is a cross-sectional explanatory view of the element support member 15, and Fig. 5(B) is a view showing the state of the central portion (protector portion) of the main body cover 13 as seen from below. Incidentally, Fig. 5(A) shows a cross-section along the line A-A in Fig. 5(B).

[0033] As shown in Fig. 5(A), in the thermal sensor of this modified example, the flange portion 15c of the element support member 15 is formed so as to project outward, and trapezoidal convex portions 15h, which are nearly rectangular in shape, are formed side by side in the circumferential direction at a predetermined pitch on the surface (the lower surface in the figure) of the flange portion 15c. Further, in the main body cover 13, as shown in Fig. 5(B), a plurality of windows 13f that can be fitted with the convex portions 15h are formed side by side in the circumferential direction. Fine processing consisting of a large number of thin linear grooves may be applied to the back surface of the convex portion 15h. Note that the shape of the convex portion 15h is not limited to a trapezoid (pseudo-rectangle), and any shape such as a rhombus, a circle, or an ellipse can be adopted. The thermal sensor of this modified example can also achieve almost the same effects as the thermal sensor of the second embodiment, and can enhance the design effect.

[0034] (Modified Example 2) Fig. 6 shows another modified example common to the above embodiments. In the modified example of Fig. 6, instead of providing the columnar light guide portion 15e on the flange portion 15c of the element support member 15, a light guide portion 15e', which is a concave portion, is provided on the back surface of the flange portion 15c, and a bullet-shaped light emitting element 17 is provided at a portion of the circuit board 14 facing the light guide portion 15e'. This light emitting element 17 is mounted by soldering the lead terminals to the circuit board 14. Further, on the flange portion 15c, a light reflecting portion 15f is provided on the surface (the lower surface in the figure) of the portion corresponding to the light guide portion 15e'. In the modified example of Fig. 6, the light reflecting portion 15f forms a rectangle when cross-sectioned in the vertical direction, but it may be formed to form a triangle in the same manner as in Fig. 2. Note that the light reflecting portion 15f is composed of a concave portion (groove) whose cross-section forms a V shape when viewed from the direction of arrow C, similar to the previous embodiments and modified examples.

[0035] As described above, the present invention has been described based on the embodiments, but the present invention is not limited to those of the above embodiments. For example, in the above embodiment, only one light guide portion 15e or 15e' is provided on the flange portion 15c of the element support member 15, but a plurality of light guide portions 15e or 15e' may be provided at a plurality of locations, and a plurality of light emitting elements 17 may be provided corresponding thereto. Further, in the above embodiment, a locking piece 15d for attaching the element support member 15 to the circuit board 14 is provided on the tapered portion 15b of the element support member 15, but the locking piece 15d may be provided on the flange portion 15c. Furthermore, in the heat sensor 10 of the above embodiment, resin is filled only inside the cylindrical portion 15a of the element support member 15, but it may be configured to enhance waterproofness by covering the entire back surface side and front surface side of the circuit board 14 with resin.

Explanation of Reference Numerals

[0036] 10 Heat sensor 11 Thermistor (heat-sensitive element) 12 Main body case 13 Main body cover 13A Protector portion 13b Step portion 13c Rectifying fin 13d Head cover 13e Slit 14 Circuit board 15 Element support member 15a Cylindrical portion 15b Tapered portion 15c Flange portion 15d Locking piece 15e, 15e' Light guide portion 15f Light reflecting portion 15g Light emitting portion 15h Convex portion 16 Insulating resin (filling material) 17 Light emitting element

Claims

1. A heat detector in which a circuit board on which a heat-sensitive element and components constituting a detection circuit are mounted is housed inside a housing consisting of a main body case and a main body cover that covers the open side of the main body case, the main body cover has an opening formed in a central portion and a protector portion provided so as to cover the opening from below, the thermal sensitive element is a thermistor, an operation indicator light made of a light-transmitting material and having an insertion hole with an inner diameter larger than the diameter of the tip of the thermistor and a cone-shaped tapered portion spreading downward and outward from the edge of the insertion hole is disposed below the circuit board such that the insertion hole is positioned around the heat-sensitive element; A heat detector characterized in that the entire tapered portion located inside the opening is illuminated by light from a light-emitting element mounted on the circuit board.

2. 2. The heat detector according to claim 1, wherein the operation indicator light is a separate member from the body cover and is joined to the body cover.

3. 3. The heat detector according to claim 1, wherein the operation indicator light is joined to the main body case.

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