JPH0650075Y2 - Scattered light smoke detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a scattered light type smoke detector used in a fire alarm device and detecting smoke from a fire.

[Prior Art] Conventionally, scattered light smoke detectors used in fire alarm devices are
A light emitting element irradiates a light beam into a dark box into which outside air can flow, and the light receiving element detects scattered light emitted from the light beam to catch smoke from a fire.

This scattered light type smoke detector is, for example, as disclosed in Japanese Utility Model Publication No. 58-40477, a light emitting element and a light receiving element have a photoelectric element mounting tool so that their optical axes are in a predetermined direction of a dark box. It is supported by. The light rays of the light emitting element do not directly enter the light receiving element, and the diffused reflection on the inner surface of the dark box is prevented as much as possible.

[Problems to be Solved by the Invention] A conventional scattered light type smoke sensor has a structure in which an optical system such as a light emitting and receiving element is uneven in a dark box. This structure complicates the inflow of outside air, which causes directionality and delays in detection time. In addition, stray light due to external light deteriorates the S / N ratio, which increases the emission intensity of the light emitting element,
There has been a need for an amplifier having a large amplification factor for amplifying the detection signal of the light receiving element.

[Means for Solving the Problems] A scattered light type smoke detector according to the present invention is a dark box configured so that outside air can freely enter and blocks light from the outside, and a light source provided outside the dark box. Light emitting element, a smoke detecting light receiving element provided outside the dark box, a light emitting Fresnel lens adapted to irradiate the smoke detecting area in the dark box with the light beam of the light emitting element, and in the dark box And a light-receiving Fresnel lens for condensing scattered light due to smoke in the smoke detection area to the light-receiving element, and the light-emitting Fresnel lens and the light-receiving Fresnel lens are arranged on the same plane inside the dark box. It is characterized by.

[Operation] By forming a dark box configuration including an optical system using a Fresnel lens in the scattered light smoke detector, it is possible to reduce the size, improve the inflow characteristic of the outside air, and simplify the signal processing circuit.

[Embodiment] An embodiment of the scattered light type smoke detector of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment of the scattered light type smoke sensor of the present invention, and FIG. 2 is a sectional view taken along the line D-D of FIG. The scattered light type smoke detector of the present invention has a body 1, a dark box 2 in which a plurality of holes are provided in the body 1 so that the outside air can freely flow and the outside light does not enter, and one side of the dark box 2 is provided. The light emitting Fresnel lens 3 arranged flush with each other, the light receiving Fresnel lens 5 similarly arranged, the light emitting element 4 provided to face the light emitting Fresnel lens 3, and the light receiving Fresnel lens 5 to face each other. And a light receiving element 6 provided as a component, and a printed circuit board 7 electrically connected to the light emitting element 4 and the light receiving element 6, fixedly supported by the body 1, and having electric circuit parts mounted thereon.
The elements 4 and 6 are shielded so that the emitted light of the light emitting element 4 does not directly enter the light receiving element 5.

The light beam emitted from the light emitting element 4 is emitted by the Fresnel lens 3 for light emission to a predetermined smoke detection area in the dark box 2 as shown in the figure. When there is no smoke in the dark box 2, the light emitting element 4
The light beam emitted from is repeatedly reflected in the dark box 2. In the reflected light, the light rays reaching the light receiving element 6 are attenuated by reflection, and while entering the Fresnel lens 5 for light reception, the light rays in only a predetermined direction reach the light receiving element 6. Therefore, the noise light detected by the light receiving element 6 due to diffused reflection in the dark box 2 is at an extremely low level.

When smoke is generated by the fire and enters the dark box, scattered light is generated by the smoke in the smoke detection area irradiated with the light beam of the light emitting element 4. The scattered light is converged by the Fresnel lens 5 for light reception and is incident on the light receiving element 6, so that the density of smoke can be detected as the magnitude of the optical signal.

[Advantage of the Invention] In the scattered light type smoke detector of the present invention, since the light emitting portion and the light receiving portion side in the dark box 2 are arranged on the same plane, this optical system is parallel to the smoke inflow direction and Since it does not hinder the inflow, it has the effect of improving the directionality and time delay. Further, if the Fresnel lenses 3 and 5, the light emitting element 4 and the light receiving element 6 are fixedly supported on the body 1 by a mounting member or the like integrally formed, the assembly becomes extremely easy and the adjustment of the optical system is hardly required. End

Even if the light emitting element 4 and the light receiving element 6 are directly attached to the printed circuit board 7, an optical system can be formed in a predetermined smoke detection area in the dark box 2 by the Fresnel lenses 3 and 5, and the size of the sensor can be reduced. Can be measured. Further, since the structure inside the dark box is relatively simple, cleaning becomes easy.

The external light entering from the outside of the sensor and the diffuse reflection in the dark box 2 by the light emitting element 4 enter the light receiving element 6, only the light beam incident on the Fresnel lens 5 for receiving light at a predetermined angle. Is extremely small, that is, because the optical system has a beam characteristic, the S / N ratio can be improved and a smoke detection signal can be made large, and the emission intensity of the light emitting element 4 and the detection signal of the light receiving element 6 are amplified. It has an advantage that it is not necessary to increase the amplification factor of.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the scattered light type smoke sensor of the present invention, and FIG. 2 is a sectional view taken along the line D-D of FIG. 1 ... Body, 2 ... dark box, 3,5 ... Fresnel lens, 4
...... Light emitting element, 6 ...... Light receiving element, 7 ...... Printed circuit board.

Claims (1)

[Scope of utility model registration request] 1. A dark box constructed so that the outside air can freely enter and blocks light from the outside, a light emitting element for a light source provided outside the dark box, and smoke provided outside the dark box. A light receiving element for detection, a Fresnel lens for light emission that irradiates the light ray of the light emitting element to the smoke detection area in the dark box, and scattered light due to smoke in the smoke detection area in the dark box is converged on the light receiving element. And a Fresnel lens for receiving light
The scattered light smoke detector, wherein the Fresnel lens for light emission and the Fresnel lens for light reception are arranged on the same plane inside the dark box.