JPH03111996A - Photoelectric smoke sensor - Google Patents

Abstract

PURPOSE:To reduce the influence of external noise by integrating a photodetector and a smoke sensing circuit into one integrated circuit. CONSTITUTION:Light projected from a projecting element 3 is dispersed by smoke and condensed through a photodetection lens 8 onto an integrated circuit 7. In addition to the photodetector which is a photodiode, a smoke detecting circuit to detect the existence of the smoke based on the output of the photodetector, projecting element driving circuit and power supply circuit are integrated. On a circuit board 5, the other circuit parts are loaded in addition to the integrated circuit 7 and the projecting element 3. This circuit board 5 is composed of a bendable printed circuit board equipped with flexibility and the optical axis of the projecting element and the optical axis of the photodetector are coupled to an optical pedestal 2 in a bent form so as to form a prescribed angle between the optical axes.

Description

[Detailed description of the invention] [Industrial application field]

TECHNICAL FIELD The present invention relates to a photoelectric smoke sensor that detects smoke by using a light receiving element to detect light scattered by smoke particles in a light beam irradiated onto a smoke monitoring area from a light projecting element.

[Conventional technology]

Generally, in this type of photoelectric smoke detector, as shown in FIG.
The light emitting element 3 and the light receiving element 4 are placed in the lower smoke monitoring room 11, and the smoke monitoring room 12 is placed in the upper circuit storage chamber 12 to detect smoke based on the drive circuit of the light emitting element 3 and the output of the light receiving element 4. The bag is supplied with a circuit board 5 on which a smoke detection circuit for detecting smoke is mounted. As shown in FIG. 5, the light emitting element 3 and the light receiving element 4 are arranged so that their optical axes intersect with each other, and as shown in FIG. 4, direct light from the light emitting element 3 is received. A light shielding plate 13 is arranged so that the light does not enter the element 4. Smoke particles are introduced into the smoke monitoring chamber 11 through a smoke inlet (not shown) formed in the lower peripheral wall of the housing 1, and the light beam from the light emitting element 3 is introduced into the smoke monitoring chamber 11. When the scattered light is received by the light receiving element 4, the presence of the smoke particles is detected. Here, the output of the light receiving element 4 is a weak signal,
Since the circuit board 5 is easily affected by external noise, the current situation is to surround both sides and the surrounding area of the circuit board 5 with a shield plate 6 (Japanese Patent Publication No. 63-34520). In some cases, copper foil is left over the entire surface without forming a pattern on the negative side, and this negative side is used as a part of the shield member. Even in the case of this configuration, as shown in FIG. 6, a shield plate 6 is provided on the other side and around the circuit board 5 (Japanese Unexamined Patent Publication No. 163698/1983).

[Question H that the invention attempts to solve]

The conventional configuration described above requires a shield plate to prevent malfunctions caused by external noise, so there is a problem in that the overall size tends to increase. Furthermore, since the shield plate is provided separately, there is a problem in that the number of parts increases, leading to high costs. The present invention aims to solve the above-mentioned problems, and aims to provide a photoelectric smoke detector that does not require a shield plate, is smaller in size, and reduces costs by reducing the number of parts. .

[Means to solve the problem]

In order to achieve the above object, the present invention provides a photoelectric sensor for detecting smoke by detecting, with a light receiving element, light scattered by smoke particles of a light beam irradiated from a light projecting element onto a smoke monitoring area formed in a housing. In the type smoke detector, the light receiving element is incorporated into one integrated circuit along with a smoke detection circuit section that outputs a smoke detection signal corresponding to the presence or absence of smoke in the smoke monitoring area based on the output of the light receiving element, and this integrated circuit is mounted on a bendable circuit board on which a light emitting element is mounted, and the circuit board is bent so that the optical axis of the light emitting element and the optical axis of the light receiving element form a predetermined angle. It is coupled to the optical base, and the optical base holds a light projecting element and a light receiving lens that condenses scattered light from the smoke monitoring area onto the light receiving element.

[Effect]

According to the above configuration, the light receiving element and the smoke detection circuit that outputs a smoke detection signal corresponding to the presence or absence of smoke based on the output of the light receiving element are incorporated into one integrated circuit. The path until the detection signal is obtained passes through the integrated circuit, so it is not affected by external noise. In other words, as a result of eliminating the need for a shielding member, the overall size is reduced, and since the shielding member is not required, the number of parts is reduced compared to the conventional configuration, leading to lower costs. . Furthermore, the integrated circuit incorporating the light-receiving element is mounted on a bendable circuit board E on which the light-emitting element is mounted, and the circuit board is arranged so that the optical axis of the light-emitting element and the optical axis of the light-receiving element are in a predetermined position. Since they are bent at an angle and connected to the optical base, a circuit is required to set the positional relationship between the light emitting element and the light receiving element so that the light scattered by smoke particles can be efficiently received. All that is needed is to adjust the bending angle of the substrate, and the positional relationship between the light emitting element and the light receiving element can be easily adjusted. Furthermore, since a light receiving lens is provided to condense scattered light from the monitoring area onto a light receiving element, there is an advantage that light receiving efficiency is increased.

【Example】

As shown in FIG. 1, the housing 1 includes a bottomed cylindrical body 10 with an open bottom, a cylindrical labyrinth body 20 attached to the opening of the body 10 and forming a smoke monitoring chamber 11, and a labyrinth body 20. It is formed by a cover 30 that covers the lower end surface of. The labyrinth body 20, as shown in FIG.
, and a roughly shaped smoke introduction path is formed between adjacent partition walls 2. One end of the smoke introduction path opens on the outer peripheral surface of the housing 1 to serve as a smoke introduction port, and the other end of the smoke introduction path opens into a circular smoke monitoring chamber 1 formed in the center of the labyrinth body 20.
Connects to 1. The partition wall 21 is black to prevent reflection, and the smoke introduction path is curved.
This is to prevent outside light from entering the smoke monitoring room 11. An insect repellent #I22 is attached to the circumferential surface of the labyrinth body 20 to prevent insects from entering the smoke monitoring room 11. On the other hand, an optical base 2 and a circuit board 5 are packed in the body 10, and the circuit board 5, which has a circuit storage chamber 12 above the optical base 2, is folded so that it can be seen. An integrated circuit 7 is mounted on the circuit board 5 made of a flexible printed circuit board, and the integrated circuit 7 includes a light receiving element, which is a photodiode, as well as a smoke detection circuit that detects the presence or absence of smoke based on the output of the light receiving element. , a light emitting element drive circuit, and a power supply circuit are incorporated. The smoke detection circuit includes an analog signal processing circuit that processes the output of the light receiving element, and a digital circuit that controls the switching circuit based on the output of the analog signal processing circuit. That is, this integrated circuit 7 has all the circuits necessary for the smoke detector built in, except for parts that cannot be built into the integrated circuit or parts that are undesirable to be built into the integrated circuit. The light emitting element 3 is mounted on the inner bottom surface of the body 10 on the circuit board 5 on which the light emitting element 3, the surge protection element ZNR5, the variable resistor VR for sensitivity adjustment, the capacitor C, etc. are also mounted. The portion where the integrated circuit 7 incorporating the light-receiving element is mounted is bent. The light emitting element 3 is positioned by being inserted into a holding tube 14 provided at one end (the right end in FIG. 1) of the optical base 2 connected to the circuit board 5. Further, a light receiving lens 8 is held at the other end (left end in FIG. 1) of the optical character base 2 so that its optical axis coincides with the optical axis of the light receiving element. The light emitting element 3 and the light receiving element are arranged so that the optical axes of the light emitting element 3 and the light receiving element are directed diagonally downward so that the optical axes pass near the center of the upper surface of the labyrinth body 20, and the optical axes of the light emitting element 3 and the light receiving element intersect with each other. Placed. The light receiving lens 8 is an aspherical lens and is designed to have a shorter focal length than a five-spherical lens. That is, as shown in FIG. 3, the focal length can be set short relative to the aperture of the light-receiving lens 8, and the F-number can be made small, resulting in high light-receiving efficiency. For example, it is possible to set the front shape to a 6×8 square ellipse and set the focal length to 511, thereby making it possible to obtain the light-receiving lens 8 with less aberration. Therefore, O0F3w
Although it is small, it is possible to obtain high light receiving efficiency. In addition, as a result of the aberration of the light-receiving lens 8 being reduced, the blurring of the boundary of the field of view of the light-receiving element is reduced.
It also has the effect of reducing the influence of stray light. With the above structure, when smoke particles are introduced into the smoke monitoring chamber 11 from the outer peripheral surface of the labyrinth 2o, the smoke monitoring area in the smoke monitoring chamber 11 (the light beam from the light projecting element 3) , the scattered light is generated in the area (overlapping the field of view of the light-receiving element), so the light-receiving element detects this and the integrated circuit 7
A smoke detection signal is output from the Also, the light receiving element is used together with the smoke detection circuit! Since it is incorporated in the A product circuit 7, it is less susceptible to external noise, and a good signal-to-noise ratio can be achieved without providing a shielding member as in the conventional case.

【Effect of the invention】

As described above, the present invention is a photoelectric FI sensor that detects smoke by detecting, with a light receiving element, light scattered by smoke particles of a light beam irradiated from a light projecting element onto a smoke monitoring area formed in a housing. In. The light receiving element is incorporated into one integrated circuit along with a smoke detection circuit section that outputs a smoke detection signal corresponding to the presence or absence of smoke in the smoke monitoring area based on the outputs of the five light receiving elements, and this integrated circuit is
Mounted on a bendable circuit board with a light emitting element mounted on it,
The circuit board is bent to an optical base so that the optical axis of the light emitting element and the optical axis of the light receiving element form a predetermined angle, and the circuit board is coupled to the optical base, and the light emitting element is held on the optical base. A smoke detection circuit that holds a light receiving lens that focuses scattered light from the smoke monitoring area onto a light receiving element, and outputs a smoke detection signal corresponding to the presence or absence of smoke based on the light receiving element and the output of the light receiving element. Since these are incorporated into one integrated circuit, the path from the output of the light receiving element to obtaining the smoke detection signal passes through the integrated circuit, which has the advantage of not being affected by external noise. In other words, as a result of eliminating the need for a shield member,
The overall size is reduced, and since no shielding member is required, the number of parts is reduced compared to the conventional configuration, leading to cost reduction. Furthermore, an integrated circuit incorporating a light-receiving element is mounted on a bendable circuit board on which a light-emitting element is mounted,
In addition, since the circuit board is bent and connected to the optical base so that the optical axis of the light emitting element and the optical axis of the light receiving element form a predetermined angle, light scattered by smoke particles is efficiently absorbed. To set the positional relationship between the light emitting element and the light receiving element so that they can receive light, all you have to do is adjust the bending angle of the circuit board, which makes it easy to adjust the positional relationship between the light emitting element and the light receiving element. . Furthermore, since a light receiving lens is provided to condense scattered light from the monitoring area onto a light receiving element, there is an advantage that light receiving efficiency is increased.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing Embodiment 1 of the present invention, FIG. 2 is a bottom view showing the same with the cover removed, FIG. 3 is an operation explanatory diagram showing the light receiving lens used in the same, and FIG. 4 is FIG. 5 is a plan view of the main part of the same as above, and FIG. 6 is a sectional view showing another conventional example. DESCRIPTION OF SYMBOLS 1... Housing, 2... Optical base, 3... Light emitting element, 5... Circuit board, 7... Integrated circuit, 8...
Light receiving lens.

Claims (1)

[Claims] (1) In a photoelectric smoke detector that detects smoke by using a light receiving element to detect light scattered by smoke particles in a light beam irradiated from a light emitting element to a smoke monitoring area formed in a housing, the light receiving element is is incorporated into one integrated circuit together with a smoke detection circuit section that outputs a smoke detection signal corresponding to the presence or absence of smoke in a smoke monitoring area based on the output of the light receiving element, and this integrated circuit is equipped with a light emitting element. The circuit board is mounted on a bendable circuit board, and the circuit board is bent and coupled to the optical base so that the optical axis of the light emitting element and the optical axis of the light receiving element form a predetermined angle, A photoelectric smoke detector characterized in that the optical base holds a light projecting element and a light receiving lens that focuses scattered light from a smoke monitoring area onto a light receiving element.