JPH04295992A - Photoelectric type sensor - Google Patents

Abstract

PURPOSE:To prevent malfunction and an erroneous alarm, etc., by fully shielding a photodetector and a printed board. CONSTITUTION:A shield plate 10 with the same size as that of the printed board 3 is arranged at the lover side of the printed board 3. Also, a shield plate 9 with the same size as that of the printed board 3 is arranged at the upper side of the printed board 3. A shield plate 15 is arranged so as to cover the photodetector 13 of an optical system block 5. A shield plate 16 is also arranged at the lover plane of the optical system block 5. By arranging the shield plates 9, 10, 15, and 16 in such way, an electromagnetic wave/noise from the outside can be cut off, which prevents the malfunction and the erroneous alarm from occurring.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric sensor that detects smoke using a photoelectric method using a light emitting element and a light receiving element.

0002

2. Description of the Related Art Electromagnetic waves generated from inverter lighting, hair dryers, vacuum cleaners, etc. may interfere with reception of televisions, etc. Similarly, it may have an adverse effect on the sensor, causing the circuit to not operate properly, resulting in malfunctions, missed alarms, etc. It is necessary to absorb or reflect this electromagnetic wave noise to prevent electromagnetic wave energy from being transmitted.

In the case of a photoelectric sensor, the circuit and the light-receiving element that detects smoke are particularly sensitive, so it is necessary to prevent electromagnetic noise from entering this area. FIG. 3 shows an exploded perspective view of a conventional photoelectric sensor. A printed circuit board 3 on which an electronic circuit is mounted on a body 1 attached to the lower surface of the ceiling via a rubber packing 2, a spacer 4 made of vinyl chloride,
An optical system block 5 containing a light emitting element and a light receiving element, a cover 6, etc. are provided.

Smoke flows into the optical system block 5, and the light from the light emitting element is diffused and received by the light receiving element.
Smoke is detected. A signal from this light receiving element is processed by an electronic circuit mounted on the printed circuit board 3, and a fire is reported.

[0005]

In this conventional example, the shield plate 7 is used to shield the electronic circuit constructed on the printed circuit board 3. Further, a shield plate 8 is used to shield the light receiving portion of the light receiving element. However, since the shield plate 7 shields only the IC components of the electronic circuit, it is formed small and therefore does not provide sufficient protection. Furthermore, the shield plate 8 that shields the light receiving section does not sufficiently cover the light receiving section or the optical system block 5, causing a problem of malfunction due to electromagnetic noise.

The present invention has been provided in view of the above-mentioned points, and provides a photoelectric sensor whose purpose is to sufficiently shield the light-receiving element and the printed circuit board to eliminate malfunctions, missed alarms, etc. It is something.

[0007]

[Means for Solving the Problems] The present invention provides first and second shield plates that shield the upper and lower surfaces of a printed circuit board, a third shield plate that shields a light receiving element portion of an optical system block, and an optical system block. A fourth shield plate is provided to shield parts of the system block other than the light receiving element.

[0008]

[Function]The first and second shield plates sufficiently shield the printed circuit board, and the third and fourth shield plates protect the optical system block and the light receiving element. It is sufficiently shielded to prevent malfunctions, missed alarms, etc.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an exploded perspective view of the photoelectric sensor of the present invention. Incidentally, the same parts as in the prior art are given the same numbers and the explanation is omitted. A shield plate 10 of approximately the same size as the printed circuit board 3 is disposed on the lower side in the figure, which is the component side of the printed circuit board 3, and a shield plate 10 of approximately the same size as the printed circuit board 3 is disposed on the upper side of the printed circuit board 3. A shield plate 9 is arranged.

FIG. 2 shows the optical system block 5, with the base 1
A light-emitting element 12 and a light-receiving element 13 are disposed inside the base 11, and a notch 14 is formed in the outer portion of the base 11 where the light-receiving element 13 is disposed, as shown in FIG. A shield plate 15 is attached to the portion 14 so as to cover the light receiving element 13.
is now set up. A shield plate 16 having the same size as the base 11 is also provided on the lower surface of the base 11.

In this way, the shield plates 9, 10, 15, 1
6, it is possible to block electromagnetic noise from the outside and prevent malfunctions and missed alarms.

0012

Effects of the Invention As described above, the present invention includes first and second shield plates that shield the upper and lower surfaces of a printed circuit board, a third shield plate that shields the light receiving element portion of the optical system block, and an optical Since a fourth shield plate is provided to shield the parts of the system block other than the light-receiving element, the printed circuit board can be sufficiently shielded by the first and second shield plates, and the third shield plate can be By sufficiently shielding the optical system block and light receiving element with the fourth shield plate, it is possible to block electromagnetic wave noise from the outside, which has the effect of preventing malfunctions, missed alarms, etc. It is something to play.

[Brief explanation of drawings]

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

FIG. 2(a) is a plan view of an optical system block. (b) is a side view. (c) is a sectional view.

FIG. 3 is an exploded perspective view of a conventional example.

[Explanation of symbols]

3 Printed circuit board 5 Optical system block 9 First shield plate 10 Second shield plate 13 Photo receiving element 15 Third shield plate 16 Fourth shield plate

Claims (1)

[Claims] Claim 1: In a photoelectric sensor comprising an optical system block incorporating a light-receiving element for detecting smoke, and a printed circuit board mounting an electronic circuit for processing output from the optical system block, the upper and lower surfaces of the printed circuit board first and second shield plates that shield the optical system block, a third shield plate that shields the light receiving element of the optical system block, and a fourth shield plate that shields the optical system block other than the light receiving element. A photoelectric sensor characterized by: