JP2000065740A - Photoelectric detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric detector with further improved sensitivity without deteriorating the optical S/N ratio. SOLUTION: In the photoelectric detector for detecting particles, a light- emitting device 4 and a photo detector 5 being arranged in an optical chamber 2 so that the light axes cross each other are provided and scattered light of light from the light-emitting device 4 due to such particles as smoke and dust at a detection region that is a region where the light projection region of the light-emitting device 4 and the light reception region of the photo detector 5 overlap each other is received by the photo detector 5. In the photoelectric detector, a light trap T with labyrinth structure for breaking external light but not preventing the inflow of particles is provided at a position that opposes at least one of the light-emitting device 4 and the photo detector 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a photoelectric sensor used for detecting smoke particles and the like.

[0002]

2. Description of the Related Art A conventional photoelectric sensor will be described with reference to FIGS. FIG. 2 is a perspective view showing an appearance of the photoelectric sensor, and FIG. 3 is a sectional view showing an optical chamber of the photoelectric sensor.

[0003] This type of photoelectric sensor is disclosed in JP-A-63-1.
63695 and the like. That is, the light emitting device includes a light projecting element 4 and a light receiving element 5 arranged in the optical chamber 2 in such a manner that their optical axes cross each other. In the detection area, which is a region, particles are detected by receiving light scattered from the light projecting element 4 by light receiving elements 5 due to particles such as smoke and dust. The case 1 forming the optical chamber 2 has a labyrinth structure in which particles such as smoke and dust easily flow in, but hardly receive external light. In the photoelectric sensor shown in FIG. 3, a labyrinth structure is formed by the wall 12.

[0004]

However, in the photoelectric sensor having the above-described structure, the light from the light projecting element 4 is reflected by the inner wall of the optical chamber 2 or dust accumulated on the inner wall. There is a problem that the light becomes stray light and reaches the light receiving element 5 to deteriorate the optical S / N ratio.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide an optical S / N.
It is an object of the present invention to provide a photoelectric sensor with higher sensitivity without deteriorating the ratio.

[0006]

According to the first aspect of the present invention,
A light-emitting element and a light-receiving element arranged in an optical chamber so that the optical axes cross each other, and smoke and dust in a detection area where a light-emitting area of the light-emitting element and a light-receiving area of the light-receiving element overlap. In a photoelectric sensor that detects particles by receiving light scattered from the light emitting element due to particles by the light receiving element, external light is blocked at a position facing at least one of the light emitting element and the light receiving element However, an optical trap having a labyrinth structure that does not hinder the flow of particles is provided.

According to a second aspect of the present invention, in the photoelectric sensor of the first aspect, an inflow port through which particles can flow is provided at an end of the wood light trap as the light trap. It is assumed that.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 is a plan view showing a photoelectric sensor according to an embodiment of the present invention. The same parts as those of the photoelectric sensor described in the section of the related art are denoted by the same reference numerals, and detailed description thereof will be omitted.

The photoelectric sensor according to the present embodiment differs from the conventional photoelectric sensor in the following points. That is, an optical trap T having a labyrinth structure is provided at a position facing at least one of the light projecting element 4 and the light receiving element 5 so as to block external light but not to prevent inflow of particles. Here, the optical trap T is to attenuate the light incident into the optical trap T by reflecting the light on the inner wall a plurality of times, thereby preventing stray light from entering the light receiving element 5.

According to the photoelectric sensor according to the present embodiment, stray light entering the light projecting element 4 in the optical chamber 2 can be reduced by the optical trap T, and
Since it is possible to reduce the hindrance of particles from entering the optical chamber 2 by the optical trap T, it is possible to provide a high-sensitivity photoelectric sensor.

For example, in the photoelectric sensor shown in FIG. 1, an inflow port through which particles can flow is provided at the tip of a light trap T 'made of wood, the opening area of which gradually decreases from the opening. The above constitutes the photoelectric sensor described above. The light trap T 'made of wood has a structure in which the invading light is reflected on the inner wall as the number of times per unit time increases as it travels inside, so that the invading light can be efficiently attenuated. It is. In addition, since particles can be made to flow from the inflow port provided at the distal end portion, it is possible to provide a photoelectric sensor excellent in sensitivity as compared with a case where an apparatus without an inflow port is arranged.

[0012]

As described above, according to the first aspect of the present invention, there are provided a light projecting element and a light receiving element which are arranged in the optical chamber so that the optical axes cross each other. A photoelectric sensor that detects particles by receiving light scattered from the light emitting element by the light emitting element due to particles such as smoke and dust in a detection area where the light area and the light receiving area of the light receiving element overlap. In the device, an optical trap having a labyrinth structure is provided at a position facing at least one of the light projecting element and the light receiving element, which blocks external light but does not prevent the inflow of particles, so that stray light in the optical chamber is reduced by the optical trap. In addition to the above, the photoelectric trap can be further improved in sensitivity without deteriorating the optical S / N ratio because the inflow of particles flowing into the optical chamber is not hindered by the optical trap. There is an effect that can be provided.

According to the second aspect of the present invention, the first aspect is provided.
In the photoelectric sensor described above, an inflow port is provided at the end of the wood light trap as the above-described light trap so that particles can flow therein, so that the stray light can be efficiently attenuated efficiently by the light trap having a simple configuration. This makes it possible to prevent the inflow of particles from being hindered by the inflow port provided at the end of the optical trap.

[Brief description of the drawings]

FIG. 1 is a plan view showing a photoelectric sensor according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the appearance of a conventional photoelectric sensor.

FIG. 3 is a sectional view showing an optical chamber of a conventional photoelectric sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case 2 Optical room 4 Light emitting element 5 Light receiving element 12 Wall H Inflow port T Optical trap

Continuing from the front page (72) Inventor Naoyuki Nishikawa 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. 2G059 AA05 BB02 CC19 EE02 JJ30 KK01 LL04 NN01 NN07 5C085 AA03 AB01 BA33 CA07 FA10

Claims (2)

[Claims] 1. A detection device comprising: a light projecting element and a light receiving element arranged in an optical chamber so as to intersect an optical axis, wherein a light projecting area of the light projecting element and a light receiving area of the light receiving element overlap. In a photoelectric sensor that detects particles by receiving light scattered light from the light emitting element due to particles such as smoke and dust in the area by the light receiving element, a position facing at least one of the light emitting element and the light receiving element A photoelectric trap having a labyrinth structure that blocks external light but does not prevent the inflow of particles. 2. The photoelectric sensor according to claim 1, wherein an inflow port through which particles can flow is provided at an end of the wood light trap as the light trap.