This invention relates to a photoelectric tilt-detecting sensor for detecting the presence or absence of tilting of an object to be detected, and a method of fabricating the same.
There have been known photo-interrupters for use in various applications of optical sensors. The photo-interrupter generally includes a light-emitting element for emitting light, and a light-receiving element for receiving the light emitted therefrom. The photo-interrupter is utilized to determine whether or not a certain object is present between these two optical elements, by detection of an electric current generated from reception of light by the light-receiving element.
The conventionally known photoelectric tilt-detecting sensor, as shown in FIG. 13, comprising a photo-interrupter 31 formed by a light-emitting element 31a and a light-receiving element 31b. The photo-interrupter 31 is built in a lower case 32 for the sensor formed of a resin, with an upper case 33 fitted over the lower case 32. The upper case 33 has opposite bearing supports 33a extending therefrom toward the inner side of the lower case 32. A fan-shaped light-shielding plate 34 is pivotally supported on bearings 33b for swinging between the light-emitting element 31a and the light-receiving element 31b.
In the tilt-detecting sensor thus constructed, the light-shielding plate 34 ordinarily rests at its lowest position due to the action of gravity. To use the tilt-detecting sensor, it is mounted or fixed on an object to be detected, not shown. While the tilting angle is smaller than a certain value, the light emitted from the light-emitting element 31a is shielded by the light-shielding plate 34 and no light is transmitted to the light-receiving element 31b. However, if the angle of tilting exceeds the above angle, the light-shielding plate 34 goes out between the light-emitting element 31a and the light-receiving element 31b. As a result, the light emitted is transmitted to the light-receiving element 31b. The light-receiving element 31b, upon reception of light, generates an electric current to supply the same through lead terminals thereof, making possible detection of the tilting for the object to be detected.
Meanwhile, there is increase in demands of offering sensors integral with a photo-interrupter, as the technology in the art of semiconductor or optical devices advances. On the other hand, it is strongly demanded that the number of parts be reduced for making such devices, together with simplification of fabrication processes.
However, the conventional tilt-detecting sensor necessitates bearings 33b on the upper case 33 for assembling a light-shielding plate 34 therein. Besides the light-shielding plate 34 has to be assembled by inserting its support axis into the respective bearings 33b. This light-shielding plate 34 must be formed relatively complicated in shape, or otherwise assembled with a separate support shaft, thus incurring complexity in fabrication processes. In practical, there is difficulty of reducing the number of parts used and simplifing the fabrication processes.
Further, in the conventional tilt-detecting sensor, there is a problem left in smoothness of movement of the light-shielding plate which is in pivotal support by the opposite bearings. The light-shielding plate thus mechanically structured is apt to lose its smoothness in movement, particularly where an external impact force be applied or tilting is in other direction than the direction being detected.