Metal working – Method of mechanical manufacture – Electrical device making
Patent
1992-11-30
1994-09-27
Echols, P. W.
Metal working
Method of mechanical manufacture
Electrical device making
296211, 338 4, 427103, 26427218, H01C 1706
Patent
active
053497465
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The invention relates to a process and a device for the manufacture of a sensor for the determination of forces acting on the surface of the sensor, with the sensor being constructed in thick-film technology and including at least one thick-film resistor which is preferably applied to an insulating layer disposed on a preferably metal pressure support which has a smooth surface facing the layer arrangement, with the resistor being electrically contacted at at least two spatially separated locations by means of conductor paths, and with the surfaces of the layer arrangement being treated such that they are plane parallel to one another.
A process of this type has been proposed in German Published Patent Application No. DE 3,912,280. This process initially applies a pressure sensor arrangement in thick-film technology onto a steel substrate. Thereafter, the layer arrangement is coated with a casting substance or with another suitable material and is polished in such a way that the sensor surface extends plane parallel to the bottom face of the substrate. In addition to producing plane parallelism, the polishing simultaneously is effected to produce the least possible surface roughness since good surface pressure is possible only with a completely smooth surface. Therefore, the polishing constitutes a complicated and cost intensive manufacturing step.
It is the object of the invention to provide a process which makes it possible to economically produce a pressure sensor with uniform surface pressure and without costly subsequent working.
SUMMARY ADVANTAGES OF THE INVENTION
The above object generally is achieved according to the present invention by a process for manufacturing a sensor constructed in thick-film technology for the determination of forces acting on the surface of the sensor, which sensor includes at least one thick-film resistor which is applied to an insulating layer disposed on a metal pressure support having a smooth surface facing the layer arrangement, with the resistor being electrically contacted at at least two spatially separated locations by means of conductor paths, and with the surfaces of the layer arrangement being treated such that they are plane parallel to one another; and wherein the pressure support surface to be provided with the layer arrangement is polished smooth and the pressure support is removed once the production of the layer arrangement is completed.
The sensor produced according to the invention in thick-film technology is distinguished by a very smooth surface which permits excellent surface pressure characteristics combined with an increase in sensitivity and low hysteresis. A costly subsequent treatment of the individual sensor in order to produce a smooth surface is no longer required. Instead, it is merely necessary to polish the pressure surface just once to make it smooth; it can then be re-used for any desired number of manufacturing processes. The active layer of a conductive plastic material exhibits a pressure resistance characteristic that is substantially linear over a large area. The sensors are mechanically very robust and independent of the temperature over a broad range. A plurality of geometric configurations is possible. For example, with appropriate configuration of pressing tool and pressure support, any exterior shaping is possible such as, for example, the shape of a plain washer or a rod shape. However, the thick-film technology also makes it possible to give the sensor, with a fixed exterior shape, various surface subdivisions. For example, for a disc-shaped sensor it is possible to configure the active layer either parallel to the edge of the disc or in a meander shape.
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention is illustrated in the drawing and will be described in greater detail below.
FIG. 1 is a sectional view of the pressure support that has been wetted with a release agent;
FIG. 2 is a sectional view of the pressure support after application of the sensor layer arrangement, with the cente
REFERENCES:
patent: 3298863 (1967-01-01), McCusker
patent: 3626256 (1971-12-01), Brown
patent: 5070596 (1991-12-01), Gaul et al.
Gruenwald Werner
Mast Martin
Schmid Kurt
Echols P. W.
Robert & Bosch GmbH
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