Smoke detector

Abstract

To prevent first irradiation light from directly reaching a light receiving element from a first light emitting element in a smoke detector, which includes: the light receiving element, the first light emitting element whose forward scattering is received by the light receiving element; and a second light emitting element whose backward scattering is received by the light receiving element.SOLUTION: A smoke detector includes: a smoke detection part surrounded by a peripheral wall from the lateral side; and a first light emitting element, a second light emitting element, and a light receiving element arranged in the periphery of the smoke detection part. The light receiving element and the first light emitting element are arranged so as to allow the light receiving element to receive forward scattering light formed when first irradiation light transmitted from the first light emitting element is applied to smoke in the smoke detection part. The smoke detector also includes a light shielding plate which is arranged between a first optical axis being the optical axis of the first light emitting element and a second optical axis being the optical axis of the second light emitting element, which has a plane along a direction in which the second light emitting element is oriented.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a photoelectric smoke detector that detects smoke by scattered light. [Background technology]

[0002] Photoelectric spot-type smoke detectors detect smoke by utilizing light scattering. In this smoke detector, a light receiving element is disposed at a position offset from the optical axis of the light emitting element. When smoke is present in the smoke detection section around the optical axis, scattered light is generated and enters the light receiving element, thereby detecting the smoke. Patent Document 1 describes a smoke detector that detects smoke by forward scattered light and backward scattered light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-191462 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has an objective of preventing first irradiation light from reaching the light receiving element directly from the first light emitting element in a smoke detector having a light receiving element, a first light emitting element that receives forward scattered light at the light receiving element, and a second light emitting element. In addition, the optical bench surrounding the smoke detector that detects scattered light is made of black resin, etc. This is to prevent external light from passing through the optical bench, and to prevent stray light and the like from reflecting off the inner surface of the optical bench and entering the light receiving element by painting the inside of the optical bench black, thereby increasing light absorption and preventing erroneous detection. On the other hand, there is a technology that uses reflected light that is not absorbed by the inside of the optical bench and is emitted from the light emitting element to detect whether the light emitting element and the light receiving element are functioning normally. In this case, if the reflected light inside the optical bench is too little or too much, the optical bench will not function normally. An object of the present invention is to achieve an appropriate amount of reflected light inside the optical bench. [Means for solving the problem]

[0005] The present invention is a smoke detector comprising a smoke detection section surrounded from the sides by a peripheral wall, a first light-emitting element, a second light-emitting element, and a light-receiving element arranged around the smoke detection section, wherein the light-receiving element and the first light-emitting element are arranged so that the light-receiving element receives forward scattered light when a first irradiation light emitted from the first light-emitting element is irradiated onto smoke in the smoke detection section, and a light-shielding plate is provided between a first optical axis which is the optical axis of the first light-emitting element and a second optical axis which is the optical axis of the second light-emitting element, with a flat surface along the direction in which the second light-emitting element is facing. In the present invention, the light shielding plate has a flat surface along the direction in which the second light emitting element faces, and blocks the first irradiation light from the first light emitting element from reaching the light receiving element directly.

[0006] (1) The present invention also provides a smoke detector comprising: a smoke inlet section; a smoke detection section provided above the smoke inlet section and laterally surrounded by a peripheral wall; a first light-emitting element; and a light-receiving element, wherein the light-receiving element and the first light-emitting element are arranged at a position where the light-receiving element receives forward scattered light when a first irradiation light emitted from the first light-emitting element is irradiated onto smoke in the smoke detection section, and a secondary reflector is provided on the side of the first light-emitting element inside the peripheral wall, which forms a secondary reflected light when the first irradiation light is irradiated onto the smoke detection section where there is no smoke, and the secondary reflector receives and reflects the primary reflected light of the first irradiation light reflected by the peripheral wall, and allows the resulting secondary reflected light to enter the light-receiving element. According to the present invention, the reflected light entering the light receiving element when there is no smoke in the smoke detection section is increased, and it is possible to check for defects in the first light emitting element and the light receiving element.

[0007] (2) The present invention also provides a smoke detector according to (1), characterized in that the second light-emitting element is disposed at a position where the light-receiving element receives backscattered light when the second irradiation light emitted from the second light-emitting element is irradiated onto smoke in the smoke-detecting section, the primary reflection area of ​​the peripheral wall where the second irradiation light emitted by the second light-emitting element is reflected when the second irradiation light is irradiated onto the smoke-detecting section where there is no smoke is a polarized reflection wall that reflects the second irradiation light in a direction different from the direction in which the second irradiation light entered, the light-receiving element is accommodated in a light-receiving element accommodating wall that protrudes inward from the peripheral wall, and the second irradiation light is reflected by the polarized reflection wall and guided to a side of the light-receiving element accommodating wall opposite to the second light-emitting element. Here, the phrase "the light-receiving element is accommodated in a light-receiving element accommodating wall that protrudes inward from the peripheral wall" also includes a case where the light-receiving element accommodating wall does not surround the light-receiving element in any part other than the peripheral wall.

[0008] According to the present invention, the reflected light entering the light receiving element when there is no smoke in the smoke detection section can be reduced, and the signal-to-noise ratio can be improved, thereby making it possible to achieve high-precision, high-quality smoke detection.

[0009] (3) The present invention also provides a smoke detector as described in (2), characterized in that the deflection reflection wall is provided with a portion close to the light receiving element protruding outward.

[0010] According to the present invention, it is possible to guide reflected light to a position where it does not enter the light receiving element, without narrowing the smoke detecting section.

[0011] (4) The present invention also relates to a smoke detector as described in (2) or (3), characterized in that it has a light-shielding plate between the first light-emitting element and the second light-emitting element, and the light-shielding plate has a flat surface along the direction in which the second light-emitting element is facing.

[0012] According to the present invention, it is possible to prevent the light emitted from the first light-emitting element from directly entering the light-receiving section without interfering with the irradiation of light to the smoke detection section and the entry of scattered light into the light-receiving section. Effect of the Invention

[0013] In the present invention, the first irradiation light is blocked so as not to directly reach the light receiving element from the first light emitting element. In addition, by optimizing the amount of reflected light entering the light receiving element, it is possible to detect whether the light emitting element and the light receiving element are functioning normally. Furthermore, by preventing excessive reflected light from entering the light receiving element, the signal-to-noise ratio is improved, making it possible to improve the accuracy and quality of smoke detection. [Brief description of the drawings]

[0014] [Figure 1] 1 is an exploded perspective view of a smoke detector 1 according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a cross-sectional view for explaining a smoke detector 1 according to an embodiment of the present invention. [Diagram 3] FIG. 4 is a diagram for explaining forward scattering in one embodiment of the present invention. [Figure 4] 5A and 5B are diagrams showing amounts of emitted light and received light in one embodiment of the present invention. [Diagram 5] FIG. 2 is a diagram showing an optical bench 71 in one embodiment of the present invention. [Figure 6] FIG. 2 is a diagram showing a sensor base 2 according to an embodiment of the present invention as viewed obliquely from below. [Figure 7] FIG. 4 is a diagram for explaining backscattering in one embodiment of the present invention. [Figure 8] 5 is a diagram showing the amount of emitted light and the amount of received light due to forward scattered light and backward scattered light in one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described. Note that the up and down directions are shown with the smoke detector 1 installed on a horizontal ceiling. The same applies to the horizontal and vertical directions.

[0016] FIG. 1 is an exploded perspective view of a smoke detector 1 according to an embodiment of the present invention. The smoke detector 1 is exploded and viewed from diagonally below. The smoke detector 1 is a photoelectric spot type, and detects smoke by capturing scattered light of light irradiated on smoke. The smoke detector 1 comprises a detector base 2, a first optical base cover 3, a second optical base cover 4, and a cover body 5. In the detector base 2, an optical base plate 7 is fixed under a back plate 6, and a circuit board 8 (see FIG. 2(b)) is sandwiched between the back plate 6 and the optical base plate 7. The optical base plate 7 is formed by integrally molding an optical base 71 and a plate portion 72 around it with black resin. The optical base 71 has a top plate 710 provided on the upper side, and a peripheral wall including a side wall 711, a first light-emitting element housing wall 712, a second light-emitting element housing wall 713, and a light-receiving element housing wall 714 in the horizontal direction. Snap protrusions 715 are provided on the outer sides of the peripheral wall and the first light-emitting element accommodating wall 712 and the light-receiving element accommodating wall 714. The first light-emitting element 91 is accommodated in the first light-emitting element accommodating wall 712, the second light-emitting element accommodating wall 713 is accommodated in the second light-emitting element accommodating wall 714, and the light-receiving element 93 is accommodated in the light-receiving element accommodating wall 714. The plate portion 72 is provided with a screw hole 721 (covered by a screw 731 in FIG. 2), a light-transmitting hole 722, and a positioning cylindrical portion 723. The light-transmitting hole 722 transmits light from a confirmation light 81 provided on the circuit board 8.

[0017] The first optical bench cover 3 is provided with a horizontally disposed cover disk 31, smoke introduction fins 32 disposed downward, positioning legs 33 protruding laterally, and snap pieces 34. The center of the cover disk 31 is open to provide a cover opening 35, and the cover disk 31 on the outside of the cover opening 35 slopes down toward the inside to form a thick portion 36 that is thicker. With the positioning legs 33 inserted into the positioning cylindrical portions 723 , the snap protrusions 715 of the first optical bench cover 3 fit into the snap pieces 34 at three points, and the first optical bench cover 3 is locked to the sensor base 2 .

[0018] The second optical bench cover 4 comprises a bottom 41 with annular projections and recesses, side ventilation holes 42 and connecting posts 43, a circular portion 44 above the ventilation holes 42, and a locking piece 45 connected to the circular portion 44. The bottom 41 is connected to the circular portion 44 by six connecting posts 43, and the circular portion 44 is locked to the cover body 5 via the two locking pieces 45. A circular insect screen (not shown) is fitted inside the ventilation holes 42 and connecting posts 43.

[0019] The cover main body 5 has six support posts 52 erected below an annular cover outer ring part 51, and a protective plate 53 connected below the support posts 52. Six openings 54 are provided, surrounded by the cover outer ring part 51, the support posts 52, and the protective plate 53. A confirmation light window 55 fitted with transparent resin is also provided in the cover outer ring part 51. The smoke introduction fins 32 of the first optical base cover 3, the connecting posts 43 of the second optical base cover 4, and the support posts 52 of the cover main body 5 are arranged in the same positions.

[0020] The smoke detection mechanism has a two-layer structure consisting of a lower layer of a smoke inlet section that introduces smoke while blocking external light between the first optical bench cover 3 and the second optical bench cover 4, and an upper layer that has a smoke detector 10 and detects smoke between the optical bench 71 and the first optical bench cover 3. The upper and lower layers are separated by the first optical bench cover 3, and are connected by a cover opening 35.

[0021] FIG. 2 is a diagram for explaining a cross section of a smoke detector 1 in one embodiment of the present invention. FIG. 2(a) is a view of the smoke detector 1 seen from below, and FIG. 2(b) shows a cross section taken along line AA in FIG. 2(a). A circuit board 8 is provided on the optical base plate 7. The circuit board 8 is provided with a circuit for smoke detection, a circuit for communication with a receiver (not shown), and a confirmation light 81, the illumination of which is confirmed through a confirmation light window 55 of the cover body 5 via a light-transmitting hole 722 in the plate portion 72 (see FIG. 1). The first optical base cover 3 is provided between the optical base plate 7 and the second optical base cover 4, and has a cover opening 35 in the center. The second optical base cover 4 has a bottom 41 with an annular protrusion, and a cross protruding plate 46 protruding in a cross shape when viewed from above at the center of the bottom 41.

[0022] FIG. 2(b) shows a state where smoke enters the smoke detector 10 from the right side of the drawing. The arrows indicate the progression of the smoke. The smoke passes through the opening 54 of the cover body 5, the vent 42 of the second optical base cover 4, and the smoke introduction section between the first optical base cover 3 and the second optical base cover 4. Then, it is blocked by the cross protruding plate 46 and passes through the cover opening 35 of the first optical base cover 3 to reach the smoke detector 10. In the smoke detector 10, the smoke is irradiated with light from the first light-emitting element 91 and the second light-emitting element 92, and the scattered light is received by the light-receiving element 93. The smoke introduction section has annular convex parts at the top and bottom to block external light, and the smoke rises and then falls, then rises again, enters the upper layer from the cover opening 35, and reaches the smoke detector 10.

[0023] The optical bench plate 7, the first optical bench cover 3, and the second optical bench cover 4 are made of black resin. External light is mainly blocked by the bottom 41 of the second optical bench cover 4, the cover disk 31 of the first optical bench cover 3, and the optical bench 71 of the optical bench plate 7, and does not reach the smoke detection unit 10.

[0024] FIG. 3 is a diagram for explaining forward scattering in one embodiment of the present invention. FIGS. 3, 5 to 7 show enlarged views of FIG. 2. FIG. 3 is a bottom view of the optical base plate 7 to which the first light emitting element 91, the second light emitting element 92, and the light receiving element 93 are attached. In the optical base 71 of the optical base plate 7, a side wall 711 hangs down from the bottom of the upper plate 710. The first light emitting element 91, the second light emitting element 92, and the light receiving element 93 are respectively accommodated in the first light emitting element accommodating wall 712, the second light emitting element accommodating wall 713, and the light receiving element accommodating wall 714, and are connected to the circuit board 8 via small holes provided in the optical base plate 7. The first light emitting element accommodating wall 712, the second light emitting element accommodating wall 713, and the light receiving element accommodating wall 714 are arranged from the position of the arc-shaped side wall 711 to the inside and outside. The part arranged on the inside constitutes a part of the peripheral wall. In addition, a deflection reflection wall 717 is provided from the circumference of the approximately circular side wall 711 toward the outside. The deflection reflection wall 717 has a portion close to the light receiving element 93 protruding outward, and the protruding end is connected to the side wall 711 by the connecting wall 718. The side wall 711, the first light emitting element housing wall 712, the second light emitting element housing wall 713, the light receiving element housing wall 714, the deflection reflection wall 717, and the connecting wall 718 form a peripheral wall of the optical stand 71. The side wall 711 is arc-shaped, and a portion of it has a plurality of small protrusions on the inside. The first light emitting element 91 transmits the first irradiation light, which is the irradiation light, and the second light emitting element 92 transmits the second irradiation light, which is the irradiation light, toward the smoke detection unit 10. The first light emitting element housing wall 712 is made up of side walls at the front, both sides, and the rear in the horizontal direction of the first light emitting element 91, and the front side wall has an opening for light transmission. Parts of the side walls on both sides and the front side wall form part of the peripheral wall. The same is true for the second light emitting element housing wall 713 and the light receiving element housing wall 714. The vertical positions of the top plate 710 and the plate portion 72 of the optical bench 71 are the same. In the first light-emitting element accommodating wall 712, the second light-emitting element accommodating wall 713, and the light-receiving element accommodating wall 714, the portions other than the peripheral walls have a small amount of protrusion from the plate portion 72. The lengths from the top plate 710 and the plate portion 72 to the lower ends of the peripheral walls are constant.

[0025] An upper light-shielding plate 719 protrudes downward from the upper plate 710 on the light-emitting side of the first light-emitting element housing wall 712. The upper light-shielding plate 719 does not reach the first optical axis 911, which is the optical axis of the first light-emitting element 91. In addition, a light-shielding plate 7131 protrudes from the second light-emitting element housing wall 713. The light-shielding plate 7131 has a flat surface provided along the direction in which the second light-emitting element 92 faces, and blocks the first irradiation light from the first light-emitting element 91 from reaching the light-receiving element 93 directly.

[0026] A first optical axis 911, which is the optical axis of the first light-emitting element 91, and a light-receiving axis 931, which is the optical axis of the light-receiving element 93, intersect at an obtuse angle of φ1 in Fig. 3 in the area of ​​the smoke detection unit 10. Therefore, when there is smoke in the smoke detection unit 10, the light-receiving element 93 captures the forward scattered light of the first light-emitting element 91. In terms of their positional relationship, the light-receiving element 93 and the first light-emitting element 91 are arranged at a position where the light-receiving element 93 receives the forward scattered light when the first irradiation light emitted from the first light-emitting element 91 is irradiated onto the smoke in the smoke detection unit 10.

[0027] When there is no smoke in the smoke detector 10, forward scattering does not occur, but the first irradiated light is reflected multiple times on the inner surface of the peripheral wall of the optical base 71, and is finally received by the light receiving element 93. Therefore, a small amount of non-interfering received light (so-called noise) is detected. The optical base 71 is made of black resin, but does not completely absorb the first irradiated light, and reflects a part of it. In the present application, this reflected light is used to check whether the first light emitting element 91 and the light receiving element 93 are functioning normally. If an error occurs in the light emission or reception, the non-interfering received light amount is not detected, so the error can be detected. In a normal state when there is no smoke in the smoke detector 10, light emission and reception are always performed, and if such an error occurs, it can be detected without delay.

[0028] FIG. 4 is a diagram showing the amount of light emitted and the amount of light received in one embodiment of the present invention. The vertical axis indicates the amount of light emitted and the amount of light received, and the horizontal axis indicates time. FIG. 4(a) shows the amount of light emitted by the first light-emitting element 91, and FIG. 4(b) shows the amount of light received by the light-receiving element 93. The first light-emitting element 91 emits light at regular intervals as shown in FIG. 4(a). Accordingly, the light-receiving element 93 receives light at regular intervals as shown in FIG. 4(b). In FIG. 4, there is no smoke in the smoke detector 10 during the two pulses in the period shown on the left, and no forward scattered light is generated, resulting in a small amount of light received as shown in FIG. 4(b). On the other hand, there is sufficient smoke in the smoke detector 10 during the two pulses in the period shown on the right, and forward scattered light is generated, resulting in a large amount of light received. In FIG. 4(b), when the amount of light received exceeds the threshold b1, smoke is detected by forward scattered light. When the amount of light received is a non-obstructive amount between the thresholds b1 and b2 at the timing of light emission, it is detected that there is no smoke and that there is no obstruction to light emission and light reception. Also, if the amount of received light is an interference amount that does not reach the threshold value b2, it is detected that an interference has occurred.

[0029] Incidentally, the optical bench 71 is black in color with high light absorption, and as shown in FIG. 3, the first optical axis 911 of the first light emitting element 91 is misaligned with the light receiving axis 931 of the light receiving element 93. The first irradiated light is reflected multiple times on the inner surface of the optical bench 71 before reaching the light receiving element 93, so the amount of non-obstructive received light obtained from the first irradiated light is small. Therefore, the value of the threshold b2 must be made small, but in order to make the threshold b2 small, a light receiving element 93 capable of detecting a small amount of light must be used. Therefore, in the present invention, the structure of the optical bench 71 is designed to increase the amount of non-obstructive received light within a range where the difference is comparable to the amount of light received when smoke is generated.

[0030] A structure for increasing the amount of non-obstructive light reception will be described with reference to FIG. 3. When the first irradiation light from the first light-emitting element 91 is irradiated to the smoke detector 10 without smoke, the first irradiation light hits the side wall 711 and is reflected. Although the side wall 711 is black, it cannot completely absorb the first irradiation light and reflects it. The first irradiation light spreads around the first optical axis 911, and when it reaches the side wall 711, a primary reflection area 912, which is a reflection area of ​​a certain size, is generated as shown in FIG. 3. The primary reflection area 912 is an area on the surface of the side wall 711, but is conveniently represented as an ellipse viewed from the bottom in FIG. 3. The primary reflection area 912 reflects the light in the direction of the primary reflection axis 913. A secondary reflection plate 716 is provided in the direction of the primary reflection axis 913. The secondary reflection plate 716 is located inside the peripheral wall, on the side of the first light-emitting element 91 far from the light-receiving element 93. Further, as viewed from the light receiving element 93, a small convex portion is provided on the side wall 711 behind the secondary reflector 716. The secondary reflector 716 is provided on the side farther from the light receiving element housing wall 714 in the peripheral wall portion of the first light emitting element housing wall 712 protruding inwardly of the optical bench 71. The secondary reflector 716 has a surface that reflects the primary reflected light toward the light receiving element 93. Therefore, the primary reflected light is reflected by the secondary reflector 716 in the direction of the secondary reflection axis 914, and becomes secondary reflected light that enters the light receiving element 93. The secondary reflector 716 increases the secondary reflected light of the first light emitting element 91, and the amount of non-obstructing light increases.

[0031] FIG. 5 is a diagram showing an optical bench 71 in one embodiment of the present invention. FIG. 5(a) shows the optical bench 71 as seen from below. FIG. 5(b) shows a cross section along line BB. Line BB passes between the first light-emitting element housing wall 712 and the second light-emitting element housing wall 713, the upper light-shielding plate 719, and the deflection reflection wall 717. In FIG. 5(b), the lower part corresponds to the top of the ceiling side. In FIG. 5(b), the upper light-shielding plate 719 protrudes short from the upper plate 710, and the secondary reflection plate 716 protrudes at a protrusion amount of about 60% of the height of the peripheral wall such as the side wall 711. By appropriately setting the protrusion amount from the upper surface side of this secondary reflection plate 716, the intensity of the secondary reflected light can be adjusted, but it is preferable to set the height to 30 to 90% of the peripheral wall. The upper light shielding plate 719 is located below the first optical axis 911 of the first light emitting element 91 housed in the first light emitting element housing wall 712 , and blocks the light emitted from the first light emitting element 91 toward the upper plate 710 .

[0032] Fig. 6 is a view of the sensor base 2 in one embodiment of the present invention seen from diagonally below. This is a different direction from the sensor base 2 in Fig. 1. The first light-emitting element accommodating wall 712 and the second light-emitting element accommodating wall 713 are provided with openings through which irradiated light passes in the direction of the smoke detection unit 10. Although not shown in Fig. 6, the light-receiving element accommodating wall 714 is also provided with an opening. A secondary reflector 716 and an upper light-shielding plate 719 are provided on the inside of the optical stand 71. One upper light-shielding plate 719 is provided on each of the openings in the first light-emitting element accommodating wall 712 and the second light-emitting element accommodating wall 713 on the side of the smoke detection unit 10.

[0033] Note that while a portion of the primary reflected light reaches the secondary reflector 716, another portion passes through the lower side and side (the right side in Figs. 3 and 5) of the secondary reflector 716 and is almost entirely absorbed by the small convex portion. This allows a sufficient amount of light to enter the light receiving element 93 to determine whether the first light emitting element 91 is emitting light, while ensuring a difference in the amount of light that is sufficiently smaller than the amount of forward scattered light at the time of fire recognition. This results in a high S / N ratio and a highly accurate smoke detector.

[0034] FIG. 7 is a diagram for explaining backscattering in one embodiment of the present invention. FIG. 7 is a bottom view of the optical base plate 7 to which the first light-emitting element 91, the second light-emitting element 92, and the light-receiving element 93 are attached, as in FIG. 3. The second optical axis 921, which is the optical axis of the second light-emitting element 92, and the light-receiving axis 931, which is the optical axis of the light-receiving element 93, intersect at an acute angle, as shown by φ2 in FIG. 6, in the area of ​​the smoke detection unit 10. Therefore, the light-receiving element 93 captures the backscattered light of the second irradiation light by the second light-emitting element 92. In terms of positional relationship, the second light-emitting element 92 is disposed at a position where the light-receiving element 93 receives the backscattered light when the second irradiation light sent from the second light-emitting element 92 is irradiated to the smoke in the smoke detection unit 10. As for the backscattering, the light-receiving element 93 receives a non-obstruction received light amount in the same manner as the forward scattering, and detects that there is no obstruction in the second light-emitting element 92 and the light-receiving element 93. The amount of light emitted and the amount of light received are as explained for forward scattered light in Fig. 4, and Fig. 4(a) shows the amount of light emitted by the second light-emitting element 92. In the case of backward scattering, the second light-emitting element 92 and the light-receiving element 93 face in approximately the same direction. Therefore, the primary reflected light of the second light-emitting element 92 easily enters the light-receiving element 93, and the amount of non-obstructive light received by the light-receiving element 93 increases. Therefore, in Fig. 4(b), the threshold b1 at which the light-receiving element 93 detects smoke and the value of the non-obstructive light amount become close to each other. Therefore, the difference in the amount of light received depending on whether or not there is smoke (SN ratio) becomes small, and the accuracy of the smoke detector decreases.

[0035] In the present invention, as shown in Fig. 7, a part of the peripheral wall of the optical bench 71 is a deflection reflection wall 717. The deflection reflection wall 717 is formed so that the vertical axis of the inner surface is offset from the second optical axis 921. The offset angle θ of the vertical axis from the second optical axis 921 is preferably 15 to 30°, and more preferably 20 to 25°. In this embodiment, the inner surface of the deflection reflection wall 717 is flat.

[0036] In FIG. 7, the second irradiation light from the second light-emitting element 92 reaches the primary reflection area 922 of the deflection reflection wall 717 and is reflected. The primary reflection light generated by the reflection travels in the direction of a primary reflection axis 923 different from the direction in which the second irradiation light entered, and reaches the secondary reflection area 924 and is reflected. The primary reflection area 922 and the secondary reflection area 924 are areas on the surface of the peripheral wall, but in FIG. 7, as in FIG. 3, they are conveniently represented as ellipses viewed from the bottom. The secondary reflection light generated by the reflection travels in the direction of a secondary reflection axis 925 and is guided to the side of the light-receiving element housing wall 714 opposite to the second light-emitting element 92. Therefore, at least the secondary reflection light is not received by the light-receiving element 93. Since the reflected light is absorbed by the black optical bench 71 every time it is reflected, the reflected light after the tertiary reflection becomes extremely weak, and the difference in the amount of received light (signal-to-noise ratio) depending on whether or not there is smoke can be sufficiently obtained.

[0037] As described above, in the present invention, fire detection and the like can be performed by the single emission of the first light-emitting element 91 and the single emission of the second light-emitting element 92 to the light-receiving element 93. In that case, the second light-emitting element 92 and the first light-emitting element 91 are not necessary. On the other hand, smoke detection can be performed using both the first light-emitting element 91 and the second light-emitting element 92. The light emitted from the first light-emitting element 91 and the second light-emitting element 92 has different angles of scattered light entering the light-receiving element 93. Then, whether the smoke is white or black is determined based on the ratio of the forward scattered light by the light of the first light-emitting element 91 and the backscattered light by the second light-emitting element 92. In the case of black smoke, there is less scattered light, so the value of the forward scattered light can be amplified to determine whether or not there is a fire.

[0038] Fig. 8 is a diagram showing the amount of light emitted and the amount of light received due to forward scattered light and backward scattered light in one embodiment of the present invention. Fig. 8(a) shows the light emitted by the first light-emitting element 91, Fig. 8(b) shows the light emitted by the second light-emitting element 92, and Fig. 8(c) shows the light received by the light-receiving element 93. As shown in Figs. 8(a) and 8(b), the first light-emitting element 91 and the second light-emitting element 92 have a phase difference in light emission. The light-receiving output of the light-receiving element 93 distinguishes whether the light is received from the first light-emitting element 91 or the second light-emitting element 92, depending on the light-emitting timing of each light-emitting element.

[0039] The angle φ1 between the first optical axis 911 for detecting forward scattering and the light receiving axis 931 is an obtuse angle, but is preferably 110 to 130°. The angle φ2 between the second optical axis 921 for detecting backward scattering and the light receiving axis 931 is an acute angle, but is preferably 50 to 70°. In this embodiment, the first light emitting element housing wall 712, the second light emitting element housing wall 713, and the light receiving element housing wall 714 are configured to surround the first light emitting element 91, etc., but as long as light blocking properties are obtained, a configuration in which there are no walls other than the peripheral walls may be used. The deflection reflection wall 717 exerts an effect depending on the angle of the inner surface in the horizontal direction, and the shape of the outer surface may be any shape. The side wall 711 does not have to be arc-shaped.

[0040] If the secondary reflected light is directed toward the side of the light receiving element wall, the inner surface of the deflection reflector wall 717 may be gently concave. Although the above describes an embodiment using both forward scattering and backward scattering, it is also possible to implement only one of them. [Explanation of symbols]

[0041] 1 smoke detector, 2 detector base, 3 first optical base cover, 4 second optical base cover, 5 cover body, 6 back plate, 7 optical base plate, 8 circuit board, 10 smoke detector, 31 cover disk, 32 smoke inlet fin, 33 legs, 34 snap piece, 35 cover opening, 36 thick part, 41 bottom, 42 vent, 43 connecting column, 44 annular part, 45 locking piece, 46 cross protruding plate, 51 cover outer ring part, 52 support, 53 protective plate, 54 opening, 55 confirmation light window, 71 optical base, 72 plate part, 81 confirmation light, 91 first light emitting element, 92 second light emitting element, 93 light receiving element, 710 upper plate, 711 side wall, 712 first light emitting element housing wall, 713 second light emitting element housing wall, 7131 light shielding plate, 714 Light receiving element housing wall, 715 snap protrusion, 716 secondary reflector, 717 deflection reflector wall, 718 connection wall, 719 upper light shielding plate, 721 screw hole, 722 light transmitting hole, 723 cylindrical portion, 731 screw, 911 first optical axis, 912 primary reflector area, 913 primary reflector axis, 914 secondary reflector axis, 921 second optical axis, 922 primary reflector area, 923 primary reflector axis, 924 secondary reflector area, 925 secondary reflector axis, 931 light receiving axis

Claims

1. a smoke detection section surrounded from the side by a peripheral wall; A first light emitting element, a second light emitting element, and a light receiving element are provided around the smoke detection unit, The light receiving element and the first light emitting element are arranged so that the light receiving element receives forward scattered light when the first irradiation light emitted from the first light emitting element is irradiated onto the smoke in the smoke detection unit, A smoke detector characterized in that it comprises a light-shielding plate between a first optical axis which is the optical axis of the first light-emitting element and a second optical axis which is the optical axis of the second light-emitting element, and a flat surface is provided along the direction in which the second light-emitting element is facing.

2. A smoke detector as described in claim 1, characterized in that the second light-emitting element is arranged at a position where the light-receiving element receives backscattered light when the second irradiation light emitted from the second light-emitting element is irradiated onto smoke in the smoke detection section.

3. The second light emitting element is accommodated in a second light emitting element accommodating wall that protrudes inward from the peripheral wall, 3. The smoke detector according to claim 1, wherein the light blocking plate protrudes from the second light emitting element housing wall substantially parallel to the second optical axis.

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