JP2016200979A - smoke detector - Google Patents

Abstract

The present invention provides a smoke detector that reduces the amount of light reflected on the incident surface of a prism used in a chip LED and efficiently takes a light-emitting beam into the prism to irradiate a smoke detection space. A chip LED 24 and a chip PD 26 are surface-mounted on a circuit board 22, diffused light from the chip LED 24 is converted into parallel light by a light-emitting side prism 28, and irradiated to a smoke detection space 20. Light scattered by the smoke is reflected and collected by the light receiving side prism 30 and enters the chip PD 26. The incident surface of the light emitting side prism 28 is a concavely curved incident surface 36 for reducing the incident angle of light, for example, a part of a spherical surface centered on the light emitting point Q, and the reflecting surface is a parabolic reflecting surface 38 having the light emitting point Q as a focal point. And The reflecting surface of the light receiving side prism 30 is a parabolic reflecting surface 44 with the light receiving point as a focal point, and the exit surface is a concave exit surface 46 that condenses light on the chip PD 26, for example, a part of a spherical surface centered on the light receiving point R And [Selection] Figure 2

Description

  The present invention relates to a smoke detector using a chip-type light emitting element surface-mounted on a circuit board.

  The light emitting element used in the conventional smoke detector is a so-called bullet-shaped discrete LED with a lead wire, and irradiates a light beam toward the smoke detection space in the smoke detector, and the scattered light by the smoke. Is received by a photodiode (PD) that is also provided as a discrete element, so that a fire is detected and an alarm is issued.

  However, in smoke detectors that use discrete LEDs as light-emitting elements, smoke detector units incorporating discrete LEDs and circuit boards are made separately. After components are mounted on the circuit boards and soldered, smoke detection is performed. The operation of soldering the discrete LED lead wires of the unit to the circuit board is required, the soldering work is increased, the production efficiency is low, and the component size of the discrete LED is large. .

  Therefore, by using a small chip LED that can be surface-mounted on the circuit board, the soldering work after the circuit board is incorporated in the sensor is not required, and the production efficiency can be improved.

  Thus, when the chip LED is used for the light emitting element, since the light emitting axis faces directly above the circuit board, it is not possible to irradiate the light beam toward the smoke detection space in the smoke detector, so by bending the optical axis with a prism, It can be directed to the smoke detection space.

  A smoke detector is known in which a light receiving element is surface-mounted on a circuit board and scattered light from a smoke detection section is made incident by a prism lens (Patent Document 3).

Japanese Patent Laid-Open No. 7-103892 JP-A-9-231485 JP-A-9-231484

  However, in the structure of the light emitting unit that combines a chip LED and a prism that are surface-mounted on a circuit board, the chip LED emits a light beam that diffuses over a wide range, and the incident light increases as the incident angle increases. As a result, the degree of reflection is increased, and there is a problem that light cannot be efficiently taken into the prism.

  It is an object of the present invention to provide a smoke detector that reduces the amount of light reflected on the incident surface of a prism used in a chip LED and efficiently takes a light-emitting beam into the prism to irradiate the smoke detection space. .

(Light emission side structure of smoke detector)
The present invention provides a smoke detector,
A chip-shaped light emitting element surface-mounted at a predetermined position on the circuit board;
A light emitting side prism that converts diffused light incident from the light emitting element into parallel light and irradiates a predetermined smoke detection space;
With
The light-emitting prism is
When the incident surface on which diffused light from the light emitting element is incident is a flat incident surface, it is a concave incident surface that reduces the incident angle of the light,
The reflecting surface that internally reflects the light incident from the concave incident surface is a parabolic reflecting surface that focuses on the light emitting point of the light emitting element,
The diffused light from the light emitting element is incident from the concave curved incident surface, is internally reflected in the axial direction by the parabolic reflecting surface, and emits parallel light from the flat emitting surface toward the smoke detection space.

(Concave entrance surface of light-emitting prism)
The concave curved incident surface of the light emitting side prism is a part of a spherical surface centered on the light emitting point of the light emitting element.

(Light receiving side structure)
A chip-type light receiving element surface-mounted at another predetermined position on the circuit board;
A light receiving side prism that collects scattered light from the smoke incident from the smoke detection space and enters the light receiving element;
With
The receiving prism is
The reflecting surface that reflects the scattered light from the smoke incident from the smoke detection space through the flat incident surface is a parabolic reflecting surface that focuses on the light receiving point of the light receiving element,
The exit surface that irradiates the light receiving element with the light internally reflected by the parabolic reflection surface is a concave exit surface that collects the light,
Scattered light incident from the smoke detection space is internally reflected by the parabolic reflection surface toward the concave exit surface, and is emitted from the concave exit surface and collected on the light receiving point of the light receiving element.

(Concavity exit surface of the light receiving prism)
The concave exit surface of the light emitting side prism is a part of a spherical surface centered on the light receiving point of the light receiving element.

(The three-dimensional shape of the light-emitting prism)
A part of a paraboloid formed by rotating the light-emitting side prism around the axis, or a parabola formed on the xy plane with the axis as the x-axis, in the z-axis direction orthogonal thereto It is formed as a part of a parabolic solid formed by translation.

(Three-dimensional shape of the light-receiving prism)
A part of a paraboloid formed by rotating the light receiving side prism about the axis of the parabola, or a parabola formed on the xy plane with the axis as the x axis, in the z-axis direction orthogonal thereto It is formed as a part of a parabolic solid formed by translation.

(Chip-type light emitting device)
As the chip-type light emitting element, a light emitting element including a lens that irradiates light to the range of the concave and convex incident surface of the light emitting side prism is used.

  According to the smoke detector of the present invention, the amount of reflection is reduced by reducing the incident angle by using the incident surface of the light emitting side prism of the light from the chip-shaped light emitting element as a concave incident surface, and the light from the light emitting element is reduced. Efficiently taking it into the prism and irradiating the smoke detection space allows it to be used without waste, improving the S / N ratio as a smoke detector and improving the quality.

  In addition, the shape of the parabolic reflecting surface of the light-emitting side prism is a three-dimensional shape obtained by rotating the parabola around its axis, or a parabola formed on the xy plane with the axis as the x-axis, and a z-axis orthogonal thereto By adopting a three-dimensional shape that moves in the direction, the irradiation area of the light beam can be set according to the smoke space, the smoke detector can be reduced in size and thickness, and design restrictions as a smoke detector can be reduced And

  Also on the light receiving side, the scattered light from the smoke detection space is collected and incident on a chip-type light receiving element that is surface-mounted on the circuit board as the same prism structure with the incident surface and the exit surface of the light emitting side prism interchanged. By doing so, the scattered light from the smoke detection space is efficiently incident on the light receiving element, the S / N ratio as a smoke detector is improved, and the quality can be improved.

  In addition, by using a light-emitting element with a lens as the chip-type light-emitting element, the condensed light beam is incident on the concave incident surface of the light-emitting side prism, and the light from the light-emitting element is taken into the prism more efficiently. The S / N ratio as a smoke detector is improved and the quality can be improved.

Explanatory drawing which showed embodiment of the smoke detector by this invention which uses chip LED and prism for the smoke detection structure which crossed the optical axis in the horizontal direction Explanatory drawing which extracted and showed the smoke detection structure of FIG. Explanatory drawing showing reflection of light incident on prism Explanatory drawing showing the optical function by changing the shape of the entrance and reflection surfaces of the light-emitting prism Explanatory diagram showing the outline of a three-dimensional prism moved in a direction perpendicular to the axis of the parabola and its smoke detection structure Explanatory drawing showing the optical function by changing the shape of the reflecting surface and the emitting surface of the light receiving side prism Explanatory drawing which showed other embodiment of the smoke detector by this invention using chip | tip LED and prism for the smoke detection structure which crossed the optical axis in the perpendicular direction. Explanatory drawing which extracted and showed the smoke detection structure of FIG. Explanatory diagram showing the outline of a three-dimensional prism rotated around a parabola and its smoke detection structure

[Embodiment of smoke detector crossing optical axis in horizontal direction]
(Structure of smoke detector)
FIG. 1 is an explanatory view showing an embodiment of a smoke detector according to the present invention in which a chip LED and a prism are used in a smoke detection structure crossing the optical axes in the horizontal direction, and FIG. The plane which looked at the smoke detection part from the lower side to 1 (B) is shown. Further, FIG. 1A is an X-X-X cross section of FIG.

  As shown in FIG. 1, the smoke detector 10 opens a plurality of smoke inlets 14 on the lower outer periphery of the detector cover 12, and allows smoke from fire to flow into an internal smoke detection space 20. For the smoke detection space 20, a light emitting unit 16 and a light receiving unit 18 constituting a scattered light type smoke detection structure are arranged around the horizontal direction.

  The optical axis 16a of the light emitting unit 16 and the optical axis 18a of the light receiving unit 18 intersect at a smoke detection point P in the smoke detection space 20, and intersect at a predetermined intersection angle so that the light emitting unit 16 and the light receiving unit 18 do not face each other. The light scattered from the light emitted from the light emitting unit 16 to the smoke detection space 20 is incident on the light receiving unit 18 to detect the amount of scattered light.

  A circuit housing part 34 is formed in the upper part of the smoke detection space 20 by mounting a lid member 32, and the circuit board 22 is arranged in the circuit housing part 34. A chip LED 24 functioning as a chip-type light emitting element is disposed on the surface of the circuit board 22 corresponding to the light-emitting unit 16. The chip-shaped LED 24 is mounted on the circuit board 22 at a position corresponding to the light-receiving unit 18. A chip PD (chip photodiode) 26 functioning as a light receiving element is arranged by surface mounting.

  A light-emitting side prism 28 provided in the light-emitting unit 16 is disposed close to the chip LED 24 of the circuit board 22 so that light by intermittent driving of the chip LED 24 is incident and the light detection space 20 is irradiated with the light beam. .

  The light receiving side prism 30 provided in the light receiving unit 18 is arranged close to the chip PD 26 of the circuit board 22 so that the scattered light due to the smoke existing in the smoke detection space 20 is condensed and incident on the chip PD 26. .

(Smoke detection structure)
FIG. 2 is an explanatory view showing the smoke detection structure of FIG. As shown in FIG. 2, the light-emitting side prism 28 has a concave incident surface 36 that reduces the incident angle of light compared to the case where the incident surface on which diffused light from the light emission of the chip LED 24 is incident is a flat incident surface. For example, the concave curved incident surface 36 is a part of a spherical surface having a predetermined radius centered on the light emitting point R of the chip LED 24. The reflection surface that internally reflects the light incident from the concave incident surface 36 of the light-emitting prism 28 is a parabolic reflection surface 38 that is a paraboloid with the light emission point Q of the chip LED 24 as a focal point.

  Due to such a structure of the light emitting side prism 28, diffused light due to intermittent light emission driving of the chip LED 24 is incident on the prism from the concave curved incident surface 36, and the parabolic reflecting surface 38 internally in the parabolic surface axial direction. The light is reflected and parallel light is emitted from the flat emission surface 40 toward the smoke detection space 20.

  The light receiving side prism 30 uses a reflecting surface that reflects scattered light from the smoke incident from the smoke detection space 20 via the flat incident surface 42 as a parabolic reflection with a light receiving point R of the chip PD 26 as a focal point. The surface 44 is used. In addition, the exit surface that irradiates the chip PD 26 with the light internally reflected by the parabolic reflection surface 44 of the light receiving side prism 30 is a concave exit surface 46 that collects the light. For example, the concave exit surface 46 may be the tip. It is a part of a spherical surface centered on the light receiving point R of the PD 26.

  Due to the structure of the light receiving side prism 30, the scattered light from the smoke incident from the smoke detection space 20 is internally reflected by the parabolic reflection surface 44 toward the concave outgoing surface 46, and is emitted from the concave outgoing surface 46 to be chipped. The light is focused on the light receiving point R of the PD 26.

(Function of light-emitting side prism)
FIG. 3 is an explanatory diagram showing reflection of light incident on the prism, and FIG. 4 is an explanatory diagram showing optical functions by changing the shapes of the incident surface and the reflective surface of the light-emitting prism.

  In the smoke detection structure of the present embodiment, as shown in FIG. 2, the incident surface of the light emitting side prism 28 is used as a concave curved incident surface 36 to reduce the incident angle of the emitted beam from the chip LED 24 to the prism, As a result, the amount of light reflected on the incident surface can be reduced, and the emitted light beam can be efficiently taken into the prism.

Here, as shown in FIG. 3A, consider a light ray incident from a medium 1 (here, air) having a refractive index n1 into a medium (acrylic resin constituting a prism) having a refractive index n2. According to Snell's law, the relationship between the incident angle α and the angle β of the refracted light is n1 / n2 = sin β / sin α.
It becomes.

When a light beam is incident on a medium having an incident angle α and a refractive index n2, the reflectance at the incident surface is determined by the polarization plane, and the amplitude reflectance of P-polarized light is Rp and the amplitude reflectance of S change is Rs. Given in.
Rp = tan (α−β) / tan (α + β)
Rs = −sin (α−β) / sin (α + β)

  The graph of FIG. 3B shows changes in the amplitude reflectance Rp and the amplitude reflectance Rs with respect to the incident angle α, and shows that the reflectance increases as the incident angle α increases. As a result, when the amplitude reflectance Rs is seen, when the incident angle α to the prism exceeds approximately 20 degrees, the reflectance at the incident surface gradually increases, and when it exceeds approximately 50 degrees, it becomes extremely large and efficient. It can be seen that the emission beam cannot be used.

  That is, as shown in FIG. 4A, when the incident surface on which light from the chip LED of the light-emitting side prism 28 is incident is a flat incident surface 36a, the light is incident toward the periphery where the light from the chip LED 24 spreads. The angle becomes large and the emitted light beam cannot be used efficiently.

  Therefore, in the present embodiment, the incident surface of the light emitting side prism 28 is the concave curved incident surface 36, and the incident angle is reduced to reduce reflection at the incident surface, so that the amount of light incident on the light emitting side prism 28 is reduced. Can be increased.

  More specifically, as shown in FIG. 2, it is desirable that a part of the spherical surface centering on the light emitting point Q, which is the center of the light emitting portion of the chip LED 24, be the concave curved incident surface 36. When it is difficult to make the concave incident surface 36 part of a spherical surface with the light emission point Q as the center due to the arrangement of the chip LED 24 and the light-emitting side prism 28, the emitted light beam from the chip LED 24 is approximately 20 on the incident surface. A concave reflecting surface 36 is formed by an aspherical surface that does not exceed the degree.

  Next, consider the reflection surface of the light-emitting side prism 28 for turning the beam incident from the chip LED 24 through the concave reflection surface 36 in the direction of the desired smoke detection space.

  FIG. 4B shows a case where the reflecting surface of the light emitting side prism 28 is a flat reflecting surface 38b, and the light beam emitted from the light emitting point Q of the chip LED 24 passes through the concave incident surface 36 and is flat reflecting surface 38b. To reach. At this time, the light beam extends almost radially from the light emitting point Q of the chip LED 24, enters the flat reflecting surface 38b at any angle, and the reflected light also diffuses in all directions, so that smoke detection can be performed efficiently. The space cannot be irradiated with a light beam.

  Therefore, in the present embodiment, as shown in FIG. 4C, the reflecting surface of the light-emitting side prism 28 forms a part of a parabolic surface with the light emitting point Q of the chip LED 24 as a focal point. Let it be surface 38. The beam reflected by the parabolic reflecting surface 38 is reflected parallel to the parabolic axis direction, and can efficiently irradiate the smoke detection space.

Here, the parabola that forms the parabolic reflecting surface 38 has the origin O (0,0) on the xy coordinates as the apex, and focuses on the light emitting point Q (q, 0).
y = 4qx ⁴
It is represented by

  Further, when it is desired to increase the reflection efficiency on the parabolic reflection surface 38, a reflection film such as aluminum may be formed on the reflection surface. The aluminum film can be formed by plating or vapor deposition.

  FIG. 5 is an explanatory diagram showing an outline of a three-dimensional prism whose parabola is moved in a direction orthogonal to the axis (x-axis) and its smoke detection structure.

  In the embodiment of FIG. 1, the light emitting unit 16 and the light receiving unit 18 are arranged horizontally with respect to the smoke detection space 20, and the light emitting side prism 28 used in this case is shown in FIG. A parabola obtained by translating the parabola in the direction orthogonal to the x-axis, which is the axis, to translate the hatched part in the direction of the arrow (z-axis direction orthogonal to the xy plane) as shown in FIG. The light emitting side prism 28 is formed as a solid.

By using the prism formed as shown in FIG. 5A on the light emitting side and the light receiving side, as shown in FIG. 5B, the smoke detection space 20 is formed wide in the horizontal direction and narrow in the vertical direction. If the height of the smoke detection space 20 is H and the diameter is D, for example, D × H = 60 mm × 10 mm
A thin smoke detector can be realized.

(Reception side configuration)
The light receiving side prism 30 shown in FIG. 2 has the same shape as the light emitting side prism 28, the light emitting side prism 28 has an exit surface 40 as an incident surface 42, and the light emitting side prism 28 has a parabolic reflecting surface 38 as a parabolic reflecting surface. 44, and the concave incident surface 36 of the light emitting side prism 28 may be the concave outgoing surface 46.

  FIG. 6 is an explanatory view showing the optical function by changing the shapes of the reflecting surface and the emitting surface of the light receiving side prism. The light receiving side prism is corresponding to the light emitting side prisms of FIGS. 4 (A), 4 (B), and 4 (C). 6 (A), 6 (B), and 6 (C).

  In the light receiving side prism 30 of the present embodiment shown in FIG. 6C, the main scattered light from the smoke in the smoke detection space 20 incident on the incident surface 42 is reflected by the parabolic reflection surface 44. The light can be incident on the chip PD 26 through 46 without waste. On the other hand, the flat reflection surface 44b of the light-receiving side prism 30b shown in FIG. 6B cannot receive light efficiently because the reflected light deviates from the chip PD26.

  Here, the amount of signal as a smoke detector is determined by the amount of scattered light due to the smoke reaching the chip PD26. For example, if the size of a light receiving element chip provided on a discrete PD used in a conventional smoke detector is 3 mm square (rectangular 3 mm in length and width), a signal amount proportional to the element area is obtained, and 1.5 mm If it is a corner, the signal amount is 1/4 of a 3 mm square.

  In this embodiment, since the chip PD that is surface-mounted on the circuit board 22 is used, the chip PD 26 having a larger element area than the discrete PD can be used, and the light-receiving side prism 30 is, for example, a 6 mm square chip PD 26. In combination, a signal amount four times that of a discrete PD having an element area of 3 mm square can be obtained.

  In addition, the light receiving side prism 30 can limit the direction of the light beam reflected by the parabolic reflecting surface 44, thereby preventing the light reflected from the ceiling or floor of the smoke detection space 20 from being received, The effects of condensation can be eliminated.

  In general, the price of the chip PD 26 is increased in proportion to the size of the element area. However, in this embodiment, the chip PD 26 having a small element area can be used, so that the cost can be reduced.

  With such a structure of the light receiving side prism 30, the scattered light from the smoke detection space 20 is collected and incident on the chip PD 26 surface-mounted on the circuit board 22, so that the scattered light from the smoke detection space 20 is reflected. By efficiently entering the chip PD 26, the S / N ratio as a smoke detector is improved and the quality can be improved.

[Embodiment of smoke detector crossing optical axis in vertical direction]
(Structure of smoke detector)
FIG. 7 is an explanatory view showing another embodiment of a smoke detector according to the present invention in which a chip LED and a prism are used in a smoke detection structure which intersects the optical axis in the vertical direction, and FIG. FIG. 7B shows a plan view of the smoke detector section viewed from below. FIG. 7A is an X-X-X cross section of FIG.

  As shown in FIG. 7, the smoke detector 10 opens a plurality of smoke inlets 14 on the lower outer periphery of the detector cover 12 so that smoke from a fire can flow into the smoke detection space 20 inside. A light emitting unit 16 and a light receiving unit 18 constituting a scattered light type smoke detecting structure are arranged above the smoke detecting space 20.

  The light emitting unit 16 is arranged so that the optical axis 16a is obliquely downward with respect to the smoke detection space 20, and the light receiving unit 18 is also arranged so that the optical axis 18a is obliquely downward with respect to the smoke detection space 20, The light axes 16a and 18a intersect at a smoke detection point P of the smoke detection space 20, and are arranged so as to intersect at a predetermined intersection angle so that the light emitting unit 16 and the light receiving unit 18 do not face each other. The light scattered from the smoke detection space 20 is incident on the light receiving unit 18 to detect the amount of scattered light.

  A circuit housing part 34 is formed in the upper part of the smoke detection space 20 by mounting a lid member 32, and the circuit board 22 is arranged in the circuit housing part 34. A chip LED 24 functioning as a chip-type light emitting element is disposed on the surface of the circuit board 22 corresponding to the light-emitting unit 16. The chip-shaped LED 24 is mounted on the circuit board 22 at a position corresponding to the light-receiving unit 18. The chip PD 26 functioning as a light receiving element is arranged by surface mounting.

  A light-emitting side prism 28 provided in the light-emitting unit 16 is disposed close to the chip LED 24 of the circuit board 22 so that light by intermittent driving of the chip LED 24 is incident and the light detection space 20 is irradiated with the light beam. .

  The light receiving side prism 30 provided in the light receiving unit 18 is arranged close to the chip PD 26 of the circuit board 22 so that the scattered light due to the smoke existing in the smoke detection space 20 is condensed and incident on the chip PD 26. .

(Smoke detection structure)
FIG. 8 is an explanatory view showing the smoke detection structure of FIG. As shown in FIG. 8, the light-emitting side prism 28 has a concave incident surface 36, for example, a concave curved incident surface 36 as an incident surface on which diffused light generated by light emission of the chip LED 24 is incident, and a light emitting point Q of the light emitting element as a center. A part of a spherical surface having a predetermined radius. In addition, the reflecting surface of the light emitting side prism 28 is a parabolic reflecting surface 38 that is a parabolic surface with the light emitting point Q of the chip LED 24 as a focal point. Such a light receiving side prism 30 is disposed with its flat emission surface 40 facing obliquely downward where the smoke detection space 20 is located. The function of the light-emitting side prism 28 is the same as that of the embodiment of FIG.

  The light receiving side prism 30 uses a reflecting surface that reflects scattered light from the smoke incident from the smoke detection space 20 via the flat incident surface 42 as a parabolic reflection with a light receiving point R of the chip PD 26 as a focal point. The exit surface that irradiates the chip PD 26 is a concave exit surface 46, for example, a part of a spherical surface that is centered on the light receiving point R of the chip PD 26. Such a light emitting side prism 28 is arranged with its flat incident surface 42 facing obliquely downward where the smoke detection space 20 is located. The function of the light receiving side prism 30 is the same as that of the embodiment of FIG.

  FIG. 9 is an explanatory view showing an outline of a three-dimensional prism rotated around a parabola and its smoke detection structure.

  In the embodiment of FIG. 7, the light emitting unit 16 and the light receiving unit 18 are arranged vertically around the smoke detection space 20, and the light emitting side prism 28 used in this case is shown in FIG. By rotating the illustrated parabola around the x axis, the light-emitting side prism 28 having a parabolic solid shape shown in FIG. 9A is formed. The light receiving side prism 30 is formed in the same manner.

By using the prisms formed as shown in FIG. 9A on the light emitting side and the light receiving side, as shown in FIG. 9B, the smoke detection space 20 can be formed narrow in the lateral direction. When the height of 20 is H and the diameter is D, for example, D × H = 40 mm × 15 mm
A small smoke detector can be realized.

[Modification of the present invention]
In the above embodiment, the light emitting side is constituted by a chip LED and a light emitting side prism, and the light receiving side is constituted by a light receiving side prism and a chip PD. However, the light emitting side is constituted by a chip LED and a light emitting side prism. The light receiving side may be the same discrete PD as the conventional one.

  Further, the arrangement of the light emitting unit and the light receiving unit is not limited to the above embodiment, and any arrangement can be adopted as long as it realizes a scattered light type smoke detection structure. For example, a structure in which the light emitting unit and the light receiving unit are arranged in a smoke detection space formed outside the smoke detector may be used.

  Further, as the chip LED provided on the light emitting side, a chip LED provided with a lens having directivity for irradiating light to the range of the concave incident surface of the light emitting side prism may be used. By using such a chip LED with a lens, the condensed light beam is incident on the concave incident surface of the light emitting side prism, so that the light can be more efficiently taken into the light receiving side prism and used without waste.

  The present invention is not limited to the above-described embodiment, includes appropriate modifications without impairing the object and advantages thereof, and is not limited by the numerical values shown in the above-described embodiment.

10: Smoke detector 12: Sensor cover 14: Smoke inlet 16: Light emitting unit 16a, 18a: Optical axis 18: Light receiving unit 20: Smoke detection space 22: Circuit board 24: Chip LED
26: Chip PD
28: Light-emitting side prism 30: Light-receiving side prism 34: Circuit housing portion 36: Concave entrance surface 38, 44: Parabolic reflection surface 40: Exit surface 42: Incident surface 46: Concave exit surface

Claims (7)

A chip-shaped light emitting element surface-mounted at a predetermined position on the circuit board;
A light emitting side prism that converts diffused light incident from the LED chip into parallel light and irradiates a predetermined smoke detection space;
With
The light emitting side prism is
The incident surface on which diffused light from the light emitting element is incident is a concave incident surface that reduces the incident angle of light with respect to a flat incident surface,
A reflecting surface that internally reflects light incident from the concave incident surface is a parabolic reflecting surface that focuses on the light emitting point of the light emitting element,
Diffusing light from the light emitting element is incident from the concave incident surface, internally reflected in the axial direction by the parabolic reflecting surface, and parallel light is emitted from the flat emitting surface toward the smoke detection space. Characteristic smoke detector.
2. The smoke detector according to claim 1, wherein the concave incident surface of the light-emitting side prism is a part of a spherical surface centering on a light emitting point of the light emitting element.
The smoke detector according to claim 1, wherein
A chip-shaped light receiving element surface-mounted at another predetermined position of the circuit board;
A light receiving side prism that condenses scattered light from the smoke incident from the smoke detection space and enters the light receiving element;
With
The light receiving side prism is
A reflection surface that reflects scattered light from smoke incident from the smoke detection space through a flat incident surface is a parabolic reflection surface that has a light receiving point of the light receiving element as a focal point,
The exit surface that irradiates the light receiving element with the light internally reflected by the parabolic reflection surface is a concave exit surface that collects the light,
Scattered light incident from the smoke detection space is internally reflected by the parabolic reflection surface toward the concave exit surface, and is emitted from the concave exit surface and condensed on a light receiving point of the light receiving element. A smoke detector.
4. The smoke detector according to claim 3, wherein a concave exit surface of the light receiving side prism is a part of a spherical surface centering on a light receiving point of the light receiving element.
The smoke detector according to claim 1, wherein the light-emitting side prism is formed on a part of a parabolic solid formed by rotating a parabola around an axis, or on an xy plane with an axis as an x-axis. A smoke sensor, wherein a parabola is formed as a part of a parabolic solid formed by translating in a z-axis direction orthogonal thereto.
4. The smoke detector according to claim 3, wherein the light receiving side prism is formed on a part of a parabolic solid formed by rotating a parabola around an axis, or on an xy plane with an axis as an x axis. A smoke sensor, wherein a parabola is formed as a part of a parabolic solid formed by translating in a z-axis direction orthogonal thereto.
  2. The smoke detector according to claim 1, wherein the light emitting element is a light emitting element including a lens that irradiates light to a range of a concavely incident surface of the light emitting side prism.

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