JPH0467678B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a scattered light type smoke detector equipped with a small and thin smoke detection section.

(Prior art) Conventionally, in this type of scattered light type smoke detector,
A relatively large cylindrical smoke detector is installed inside the sensor.
The light receiving element receives scattered light from the light emitting element due to smoke flowing into the smoke detection section, and is configured to generate a fire detection output when the received light output exceeds a threshold value corresponding to a predetermined smoke concentration.

On the other hand, in recent years, progress has been made in the development of small and thin scattered light detectors in which the diameter of the smoke detection part has been reduced and the height of the smoke detection part has been reduced to about one third of the conventional one. .

(Problems to be Solved by the Invention) However, in the case of a scattered light sensor in which the smoke detection part is small and thin, the smoke detection space is narrow, so the light emitted from the light emitting element into the smoke detection part is reflected. The increase in steady-state levels due to light becomes noticeable.

In other words, the smoke detection section is divided into upper and lower sections, and is surrounded by a plurality of partition walls known as a labyrinth structure arranged at intervals to allow smoke to flow in, while at the same time blocking the incidence of light from the outside. The light emitted from the light-emitting element does not directly enter the light-receiving element because the light-receiving element is placed at a position offset from the opposing position by, for example, about 135 degrees.
For a sensor with a small and thin smoke detection part,
Since the smoke detection section is narrow, the light reflected within the smoke detection section is not sufficiently attenuated and enters the light receiving element, making improvement of the S/N ratio due to internal reflection an important issue.

(Means for Solving the Problems) The present invention has been made in view of such conventional problems, and it reduces the steady level caused by internal light disturbance in the small and thin smoke detection unit, thereby achieving a high S/ It is an object of the present invention to provide a scattered light type smoke detector capable of obtaining an N ratio.

In order to achieve this objective, the present invention includes:
A first layer is provided near the optical axis intersection position of the light emitting element and the light receiving element to prevent light from the light emitting element from directly entering the light receiving element.
In addition, a second light shielding member is provided at a position corresponding to the light receiving element on the rear side of the light emitting element to prevent light reflected within the smoke detector from directly entering the light receiving element.

(Function) In the scattered light type smoke sensor having such a structure of the present invention, the light that is going to go around directly from the light emitting element to the light receiving element is reliably blocked by the first light shielding member, In addition, the light reflected within the smoke detection section, especially the light reflected at a position facing the light receiving element, is reflected in a direction other than the light receiving element by the second light shielding member, and the smoke detection section It is possible to significantly reduce the level of light received due to internal disturbance light, and achieve a high S/N ratio even with a small and thin smoke detection section.

(Embodiment) FIG. 1 is an explanatory plan view showing an embodiment of the smoke detection section in the scattered light type smoke detector of the present invention.

First, to explain the configuration, 1 is an upper wall that partitions the upper part of the smoke detection section, and a light emitting section holder 2 is mounted on the surface of the upper wall 1.
and a light-receiving section holder 3 are integrally formed, a light-emitting element 4 is incorporated into the light-emitting section holder 2, and a light-receiving element 5 is incorporated into the light-receiving section holder 3.

Here, the optical axis 4a of the light-emitting element 4 and the optical axis 5a of the light-receiving element 5 are arranged at a position shifted by a predetermined angle from the opposing position, θ=135° in this embodiment,
Light from the light emitting element 4 is prevented from directly entering the light receiving element 5.

A plurality of dogleg-shaped partition walls 6 are arranged at predetermined opening intervals on the circumference including the light emitting part holder 2 and the light receiving part holder 3 integrally formed on the upper wall 1, and the light emitting part holder 2 and a partition wall 6 including the light receiving section holder 3 form a peripheral wall of the smoke detection section.
In short, a capacitor accommodating portion 7 for accommodating a capacitor connected to a circuit board incorporated in the upper portion of the upper wall 1 is formed in the left peripheral wall forming portion of the light emitting portion holder 2 and the light receiving portion holder 3.

A light emitting element 4 in a smoke detection section surrounded by a plurality of partition walls 6
A first light shielding member 8 is provided on the left side of the intersection position A of the optical axis 4a of the light receiving element 5 and the optical axis 5a of the light receiving element 5.
The light shielding member 8 prevents light from the light emitting element 4 from directly entering the light receiving element 5 by going around. In this embodiment, a light shielding member 9 is further provided on the light receiving element 5 side of the first light shielding member 8, so that even if dew condensation or the like occurs on the tip 8a side of the light shielding member 8, the scattered light due to the condensation will be prevented. is prevented from entering the light receiving element 3.

On the other hand, a second
A light shielding member 10 is provided. In this embodiment, the second light shielding member 10 is formed by extending the tip of the dogleg-shaped partition wall 6 forming the peripheral wall.

This second light shielding member 10 has a reflective surface 10a on the optical axis 5a of the light receiving element 5, and has a reflective surface 10a on the optical axis 5a of the light receiving element 5.
has an angle inclined toward the outside of the light receiving element 5 by a predetermined angle α with respect to the direction perpendicular to the optical axis 5a.

Of course, the interior of the smoke detection section shown in FIG. 1 is coated with a matte black coating, for example.

FIG. 2 shows a cross-sectional view of a scattered light type smoke detector equipped with the smoke detector shown in FIG. 1. The detector shown in FIG. A smoke section 13 is incorporated, a printed circuit board 14 on which a sensor circuit is mounted is disposed above the upper plate 1 of the smoke detection section 13, and a shield case 15 is provided above the printed circuit board 14. Printed circuit board 1
For the lower shield of 4, a printed circuit board 14 having a double-sided board structure is used, and the lower surface of the printed circuit board 14 is provided with copper foil.

Next, the operation of the above embodiment will be explained.

Light emitting element 4 provided in the light emitting unit holder 2 of the smoke detection section
For example, the light is emitted intermittently at regular intervals, and irradiates light into the smoke detection section. In response to the light from this light emitting element 4, a light receiving element 5 incorporated in the light receiving unit holder 3
Since it is arranged at a position shifted by a predetermined angle θ from the opposing position, it does not receive direct light from the light emitting element 4, but it does not receive light from the circumferential side of the opening in the light emitting unit holder 2. will begin to receive On the other hand, since the first light shielding member 8 is disposed near the intersection point A of the optical axes 4a and 5a of the light emitting element 4 and the light receiving element 5, the tip 8a of the first light shielding member 8 passes through the Light is prevented from going around to the left side of the line 16, and direct light from the light emitting element 4 is prevented from entering the light receiving element 5. Further, even if dew condensation or the like occurs at the tip 8a of the first light shielding member 8 and scattered light due to this condensation or the like is directed toward the light receiving element 5, a light shielding member 9 is provided following the first light shielding member 8. Therefore, scattered light due to dew condensation or the like is blocked by the light shielding member 9, and does not directly enter the light receiving element 5 and cause malfunction.

On the other hand, the light irradiated onto the partition wall 6 forming the peripheral wall at a position facing the light emitting element 4 is attenuated by the irradiation onto the partition wall 6, and at the same time, a part of the light is reflected into the smoke detection section.

Of the light reflected by the partition wall 6 in this way, the light reflected by the partition wall 6 facing the light receiving element 5 is reflected by the light receiving element 5.
However, in the present invention, since the second light-shielding member 10 is provided at a position facing the light-receiving element 5 on the rear side of the light-emitting element 4, internal reflection The reflected light that is about to enter the light receiving element 5 from the direction of the optical axis 5a is reflected by the reflecting surface 10a of the second light shielding member 10.
As a result, the reflected light that is reflected in a direction other than the above and, as a result, directly enters the light receiving element 5 can be almost completely eliminated.

That is, the light from the light emitting element 4 hits the partition wall 6 of the optical axis 4a, 4b of the light emitting element 4, and then hits the second light shielding member 10 of the partition wall 6 facing the light receiving element 5 and escapes to the outside as shown in the figure. go.

Of course, light attempting to enter the smoke detection section from the outside is completely blocked and attenuated by the trap section formed by the dogleg-shaped partition wall 6 forming the peripheral wall, and does not enter the smoke detection section.

In the embodiment shown in FIG. 1, an example will be taken in which the second light shielding member 10 provided at a position facing the light receiving element 5 is formed integrally with the partition wall 6 forming the peripheral wall of the smoke detection section. However, the present invention is not limited to this, and the second light shielding member 10 may be provided independently from the partition wall 6.

(Effects of the Invention) As described above, according to the present invention, a first lens is provided near the optical axis intersection position of the light emitting element and the light receiving element to prevent light from the light emitting element from directly entering the light receiving element.
In addition to providing a light shielding member, a second light shielding member is provided at a position opposite to the light receiving element on the rear side of the light emitting element to prevent light reflected within the smoke detection section from directly entering the light receiving element. The light-shielding member prevents the light from going around from the light-emitting element and entering the light-receiving element directly, and the second light-shielding member prevents the reflected light inside the smoke detection section from directly entering the light-receiving element, making the smoke detection section more compact. Even in the case of a thin structure, it is possible to significantly reduce the steady level of the light receiving element due to internal disturbance light, and realize a scattered light type smoke sensor with a high S/N ratio.

[Brief explanation of drawings]

FIG. 1 is an explanatory plan view showing one embodiment of the smoke detection section of the present invention, and FIG. 2 is a sectional view of a sensor equipped with the smoke detection section of FIG. 1. 1: Upper wall, 2: Light emitting unit holder, 3: Light receiving unit holder, 4: Light emitting element, 5: Light receiving element, 4a, 5a:
Optical axis, 6: Partition, 7: Capacitor housing, 8: First light shielding member, 9: Light shielding member, 10: Second light shielding member, 11: Main body cover, 12: Outer cover, 1
3: Smoke detection section, 14: Printed circuit board, 15: Shield case.

Claims (1)

[Scope of Claims] 1. A light emitting element and a light receiving element are arranged in a smoke detecting section at a predetermined angle shifted from opposing positions, and the light receiving element detects scattered light from the light emitting element caused by smoke flowing into the smoke detecting section. In a scattered light type smoke detector that detects a fire by receiving light, the first sensor is provided near a position where the optical axes of the light emitting element and the light receiving element intersect and prevents direct incidence of light from the light emitting element to the light receiving element. and a second light shielding member installed opposite to the light receiving element on the rear side of the light emitting element to prevent light reflected within the smoke detection section from directly entering the light receiving element. Scattered light smoke detector.