JPH0528914B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a semiconductor sensor using a light emitting element and a light receiving element, and can be used particularly in a bad environment with a lot of dust. It is about a sensor.

(Prior Art) A semiconductor sensor detects the presence or absence of an object to be detected in a detection space using a light emitting element and a light receiving element.

Conventionally, in this semiconductor sensor, in order to prevent malfunctions caused by external light and improve detection accuracy, the light emitting element and the light receiving element are each covered with opaque resin, and a small slit (window) is provided in this resin. There is something that inputs and outputs light.

However, such a sensor is difficult to use in a dusty environment because dust tends to accumulate in the slit.

For this reason, we considered using a dustproof cover case to cover this sensor.

(Problem to be solved by the invention) However, when this cover case was used,
Even in a light-blocking state in which light from the light-emitting element does not enter the light-receiving element, an output current is generated in the light-receiving element, resulting in malfunction. Further, even when a phototransistor is used as a light receiving element, a collector current (output current) is generated and the S/N ratio is lowered.

This is because the cover case itself becomes a light path and guides light to the light receiving element.

The purpose of the present invention is to provide a semiconductor sensor that can be used satisfactorily even in a dusty and harsh environment.Furthermore, it is possible to provide a semiconductor sensor that can be easily used in a light-blocking state at low cost and without the need for processing a normal sensor body. The purpose is to provide a semiconductor sensor with low leakage output current.

[Structure of the invention]

(Means to solve the problem) When a dust cover case is used for a semiconductor sensor, a light path (light path) is installed in this cover case.
is inevitably formed.

On the other hand, if the light path is completely blocked by an opening etc., dust may enter through this blocking part.
Dust reaches the slit and deteriorates the light transmission characteristics.

The present invention forms a reflective scattering wall by forming a groove with a vertical side surface without dividing the part of the cover case that becomes the light path, and reduces the light that passes through this light path and reaches the light receiving element. It is something.

(Function) In the semiconductor sensor of the present invention, a groove with a vertical side surface is formed in a portion of the cover case that serves as a light path.

The peripheral wall of this groove constitutes a light reflection and scattering wall for light passing through the light path.

Therefore, the light that has passed through the light path from the light emitting element is reflected and scattered by the reflection and scattering wall and is reduced, so that the amount of light that enters the light receiving element is extremely small.

(Example) A first example apparatus of the present invention will be described with reference to the drawings.

FIG. 1 shows a perspective view of the sensor body and cover case of the device of this embodiment.

A light emitting element and a light receiving element (not shown) are housed in an opaque light emitting element housing part 1 and an opaque light receiving element housing part 2 which are arranged at a predetermined interval so as to constitute the detection space X. A slit (window) 3 is formed in each of the opposing surfaces of each housing section 1 and 2 so that the light emitted by the light emitting element is incident on the light receiving element.

Note that the lower portions of the storage sections 1 and 2 are connected by a connection section 4, and the sensor body has a substantially U-shape with the storage sections 1 and 2 and the connection section 4. Furthermore, leads 5, 5 of a light emitting element and a light receiving element protrude from the bottom surface of each storage part 1, 2.

The cover case 6 made of transparent resin has this abbreviation U.
It has a substantially U-shape similar to the main body so as to cover the top and side surfaces of the main body and form a detection space X.

The part of the cover case 6 that covers the connecting part 4 has one in the center of the outer surface and one in each corner of the inner surface, as shown in the cross-sectional view in FIG.
A groove M whose side surfaces are vertical is formed. Note that 7 and 8 in the figure indicate a light emitting element and a light receiving element.

Next, the operation of the apparatus of this embodiment will be explained using FIG. 2.

First, a voltage is applied to the light emitting element 7. The element 7 to which the voltage is applied emits light, and this light passes through the slit in the light emitting element storage section 1 and is irradiated into the space X.

If there is no object to be detected in the space X, this light passes through the slit in the light receiving element storage section 2 and enters the light receiving element 8.

Further, if there is a detected object in the space X, this light is blocked by the detected object and does not enter the light receiving element 8.

As described above, the presence or absence of the object to be detected is detected.

However, even in the case of the light blocking state where a detected object exists in the space X, the light from the light emitting element 7 is transmitted to the light receiving element 8 using the cover case itself as a light path (light path).

However, in the device of this embodiment, the light transmitted through the cover case 6 is reflected and scattered by the peripheral walls of the grooves M, M, M, which have three vertical sides.

Therefore, the amount of light reaching the light receiving element 8 is significantly reduced.

When a phototransistor was used as a light receiving element and the collector current (output current) was measured in a light-blocking state, this collector current was reduced by 40% to 50% compared to a case using a cover case without grooves.

Further, when the surface of a groove with a vertical structure is roughened, the light scattering effect increases, and this collector current further decreases by several percent.

The present invention is not limited to the one embodiment described above; for example, the cover case 6 may have a plurality of grooves each having a vertical side surface.

Moreover, when using an infrared light emitting LED as a light emitting element, a visible light blocking resin may be used.

Further, when carbon-containing polycarbonate is used for the cover case, dust is less likely to adhere to the cover case. For this reason, this may occur when used for a long time.
The problem of "deterioration of light transmission characteristics due to dust adhesion to the cover case" can be prevented.

Note that even when a normal resin is used, deterioration of light transmission characteristics can be similarly prevented by applying antistatic treatment to the surface of the cover case.

(Effects) According to the semiconductor sensor of the present invention, light reaching the light receiving element through the cover case can be significantly reduced with a simple configuration. Therefore, there is an advantage that it can be used without malfunctioning even in a bad environment with a lot of dust.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an apparatus according to an embodiment of the present invention, and FIG.
The figure is a sectional view of an embodiment of the device. 1... Light-emitting element storage section, 2... Light-receiving element storage section, 3
...Slit, 4...Connection part, 6...Cover case, 7
...Light emitting element, 8... Light receiving element, M... Groove.

Claims (1)

[Scope of Claims] 1. An opaque light-emitting element housing part and an opaque light-receiving element housing part arranged at a predetermined interval, slits formed in the surfaces of these housing parts facing the object to be detected, and each of the above-mentioned housing parts. a connecting part that connects lower parts of the parts, a light emitting element and a light receiving element housed in each of the storage parts, and a cover case that covers the surfaces of each of the storage parts and the connecting part, the connecting part of the cover case A semiconductor sensor characterized by a groove with a vertical structure formed on the side surface. 2. The cover case is characterized in that one groove is formed near the center of the outer surface of the portion covering the connecting portion, and one groove is formed at each corner of the inner surface. semiconductor sensor. 3. Each of the storage parts and the connecting part form a substantially U-shape, and the cover case also has a corresponding substantially U-shape.
The semiconductor sensor according to claim 1, characterized in that it has a letter shape. 4. The semiconductor sensor according to claim 1, wherein the cover case is made of antistatic resin or has been subjected to antistatic processing. 5. The semiconductor sensor according to claim 1, wherein at least the groove surface of the cover case is roughened.