JP3066549B2 - Photoelectric type smoke detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light transmitter and a light receiver which are opposed to each other at a predetermined distance, emit a signal light from the light emitter to the light receiver, and when smoke enters between them, a signal caused by the smoke is emitted. TECHNICAL FIELD The present invention relates to a photoelectric separation type smoke sensing device that detects the occurrence of a fire by detecting light attenuation, and more particularly to an improvement in a light receiver thereof.

[0002]

2. Description of the Related Art As shown in FIG. 3, a photoelectric-separated smoke detector usually includes a light-emitting device 1 having a light-emitting element at a monitoring distance of 5 to 100 m and a light-receiving device having a light-receiving element such as a photodiode. The light receiver 2 is disposed opposite to the light receiver 2 so that the signal light (pulse signal) 10 from the light transmitter 1 can be received by the light receiver 2. If smoke enters between the two, the signal light 10 received by the light receiver 2 is attenuated. Therefore, the occurrence of a fire is detected by detecting this.

FIG. 4 is a schematic diagram showing an example of a conventional photodetector in cross section, and FIG. 5 is a schematic diagram showing an outline of an output circuit thereof. Reference numeral 3 denotes a substantially funnel-shaped optical table housed in a case (not shown). A lens 4 is mounted on a front opening, and a holder 6 on which a light receiving element 5 is mounted on a rear reduced diameter portion.
Is housed. Reference numeral 7 denotes a printed circuit board to which a lead wire of the light receiving element 5 is connected and on which a load resistor 8, an amplifier 9, and the like are provided.

[0004] The signal light 10 from the light projector 1 is projected to the light receiver 2, condensed by the lens 4 and incident on the light receiving element 5. The signal light 10 incident on the light receiving element 5 is converted into a current corresponding to the intensity and output to the load resistor 8, and the output voltage is applied to the amplifier 9 to be amplified and output as a detection signal.

[0005]

In the photoelectric separation type smoke sensing device constructed as described above, as shown in FIG. 3, light (hereinafter referred to as "interfering light") 11 such as the sun or an electric light is received at a certain angle. 2 may be incident. When such interfering light 11 enters the light receiver 2, as shown in FIG. 5, the light is reflected by the inner surface of the optical bench 3 and irradiates the light receiving element 5, so that the performance of the optical element 5 is reduced or saturated. Signal light 10
May not be received. In order to solve such a problem, it is conceivable to protrude the front edge of the optical bench 3 long or provide a hood on the outer periphery of the front opening. However, in this case, the light receiver 2 becomes large. Is not preferred.

In particular, when the distance between the light projector 1 and the light receiver 2 is long, the signal light 10 from the light projector 1 is weakened and the amplification degree of the amplifier 9 needs to be increased. Becomes more susceptible to noise,
Problems such as deterioration of temperature characteristics occur.

Further, the load resistance 8 for converting the output current of the light receiving element 5 into a voltage can capture a small change in the current as the resistance value increases. There are various problems, for example, the higher the value, the more susceptible to the interference light 11.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a photoelectric-separated smoke detector having a light-receiving element whose light-receiving element is not likely to be affected by sunlight or the like. It was done.

[0009]

According to the present invention, there is provided a photoelectric separation type smoke sensing device according to the present invention, in which a light emitting device having a light emitting element and a light receiving device having a light receiving element are arranged to face each other, and signal light is emitted from the light emitting device to the light receiving device. However, when smoke enters between the two and the signal light emitted to the light receiver is attenuated, the photoelectric separation type smoke sensing device which detects the occurrence of a fire by this is almost funnel-shaped, An optical table provided with the light receiving element in a reduced diameter portion,
A light receiving device provided with a shielding cylinder on an outer periphery of the light receiving element for preventing sunlight or the like reflected on an inner surface of the optical bench from entering the light receiving element;

[0010]

The sunlight and the like incident on the optical receiver are reflected by the inner surface of the optical bench and are blocked by the shielding cylinder and do not enter the light receiving element.

[0011]

【Example】

Embodiment 1 FIG. 1 is a schematic view of a first embodiment of a light receiver as a main part of the present invention. 4 and 5 are denoted by the same reference numerals, and description thereof is omitted. Reference numeral 12 denotes a shielding cylinder mounted on the light receiving table 3 on the outer periphery of the light receiving element 5 so as to cover the periphery of the light receiving element 5.

In this embodiment constructed as described above,
The signal light 10 from the projector 1 is refracted by the lens 4 and enters the light receiving element 5, where it is converted into a current corresponding to the intensity and output. On the other hand, even if the interfering light 11 refracted by the lens 4 and entered the optical bench 4 is reflected by the inner surface of the optical bench 3, the shielding tube 1
2 and does not enter the light receiving element 5. For this reason,
There is no possibility that the light receiving element is deteriorated or saturated, and the amplifier is not affected by noise.

Embodiment 2 FIG. 2 is a schematic view of a second embodiment of the light receiving device. This embodiment focuses on the fact that the outer peripheral side of the lens 4 has a large refractive index of light and a large chromatic aberration. A donut-shaped shielding plate 13 for shielding a portion 11a of the light 11 having a large chromatic aberration is provided.

In this embodiment, the signal light 10 refracted by the lens 4 passes through the transmission hole 14 of the shielding plate 13 through the light receiving element 5.
Although the amount of light slightly decreases due to the incident light, a portion 11a of the interfering light 11 having a large chromatic aberration and a large refractive index is shielded by the shielding plate 13 and is prevented from entering the optical bench 3. Therefore, only a part of the portion 11b that is refracted by the lens 4 and does not directly enter the light receiving element 5 enters the optical bench 3 through the transmission hole 14, and there is no possibility that the light enters the light receiving element 5 directly. In addition, the shielding plate 13 is not limited to a donut shape, and may have another shape according to an installation location.

[0015]

As described above in detail, the present invention provides a shield for preventing sunlight or the like from entering the light receiving element on the outer periphery of the light receiving element provided at the reduced diameter portion of the funnel-shaped optical bench of the light receiving device. Since the tube is provided, there is no possibility that sunlight or the like enters the light receiving element.

As a result, the light receiving element does not deteriorate or saturates to prevent signal light from being received, and the amplifier is not easily affected by noise or the temperature characteristics are not deteriorated. And a photoelectric separation type smoke sensing device having a high sensitivity can be obtained. Furthermore, since there is no need to provide a hood projecting forward from the light receiver, the light receiver can be downsized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a first embodiment of a light receiver forming a main part of the present invention.

FIG. 2 is a schematic view of a second embodiment of the light receiver.

FIG. 3 is an explanatory diagram of a photoelectric separation type smoke sensing device.

FIG. 4 is a cross-sectional view of an example of a conventional light receiver.

FIG. 5 is a schematic diagram illustrating an example of an output circuit of a conventional light receiver.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light emitter 2 light receiver 3 optical bench 4 lens 5 light receiving element 8 load resistance 9 amplifier 10 signal light 11 interfering light 12 shielding cylinder 13 shielding plate 14 transmission hole

Claims (1)

(57) [Claims] 1. A light emitting device having a light emitting element and a light receiving device having a light receiving element are arranged to face each other, and a signal light is emitted from the light emitting device to the light receiving device. In a photoelectric separation-type smoke sensing device which detects the occurrence of a fire when the signal light is attenuated, an optical base having a funnel shape and having the light receiving element in a reduced diameter portion.
And a photodetector provided on the outer periphery of the light receiving element with a shielding cylinder for preventing sunlight or the like reflected on the inner surface of the optical bench from entering the light receiving element. Smoke sensing device.