Measuring and testing – Speed – velocity – or acceleration – Acceleration determination utilizing inertial element
Patent
1990-06-04
1991-11-19
Powell, William A.
Measuring and testing
Speed, velocity, or acceleration
Acceleration determination utilizing inertial element
156648, 156651, 156656, 156657, 1566591, 156662, 29 2535, G01P 1508, H01L 21306, B44C 122
Patent
active
050656287
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an instrument for measuring accelerations, with which the effect of an acceleration on an inert mass is measured. In particular, it relates to an instrument, which can be produced with the aid of microstructure technology. In such instruments, the inert mass is prepared with conventional anisotropic etching processes customary in microstructure technology. The mechanical effect of the acceleration is converted into an electrical signal, which is transmitted to an evaluation circuit.
STATE OF THE ART
Micromechanically integrated acceleration sensors, with the aid of which accelerations between the three axes of space cannot be differenciated, are described in several publications. For example: Davison, J. L., Kerns, D. V. "Silicon Acceleration Technology", in: Proceedings of the 1986 International Conference on Industrial Electronics, Control and Instrumentation", IEEE, New York 1986, pp. 218-222. The individual sensors are made of silicon using planar technology. In order to be able to measure in the three axes of space, three individual sensors have to be arranged in hybrid assembly and atuned to one another, whereby the achievable mechanical precision and the degree of miniaturization are limited.
An instrument for measuring accelerations with discrimination in the three directions in space is known from the published British Patent Application GB 2 174 500 A. In this instrument, the sensor elements are not arranged in a common crystal surface, but on the front, respectively rear, side of the substrate. This presents the difficult task of electrically connecting the different sensor elements, which the aforegoing publication proposes to solve with wire connections, respectively etched through holes with conductor paths. In production, this requires many procedural steps.
DESCRIPTION OF THE INVENTION
The object of the present invention is to provide an instrument for measuring accelerations, with the aid of which it should be possible to differenciate between accelerations in the three axes of space, which has a highly selective sensitivity with regard to the three axes of space and which can be produced with as few procedural steps as possible.
This object is solved with an instrument of this class by means of the characterizing features of claim 1 hereto, and by means of a process for its fabrication, which is set forth in claim 9 hereto.
A high degree of miniaturization and high mechanical precision are obtained by the planar integration of three sensor elements for the three axes of space in a crystal surface layer. Simultaneously, this solution offers the possibility of connecting the sensor elements with an electronic evaluation circuit, which can be integrated on the same substrate.
Having high precision and small dimensions, the invented instrument can be utilized, in particular, for detecting multi-dimensional courses of motion in aviation, overland traffic, in robotry and in the field of bio-medicine.
Advantageous improvements of the present invention are set forth in the claims 2 to 8 and 10 to 12 hereto.
In the improvement of claim 2 hereto, the directions of sensitivity are practically perpendicular to one another. By this means, the acceleration force acting in a random direction in space is simply divided into the three vertical components of a predeterminable Cartesian coordinate system.
Especially advantageous, is an embodiment according to claim 3 hereto, in which the reset elements are designed as torsion bars as a torsion bar having the inert mass arranged eccentrically thereon fixes a preferred direction for the sensitivity of a sensor in a simple manner. Claims 4 and 5 describe an embodiment which yields a very cost-favorable fabrication of the accelerator meter by utilization materials very conventional in semiconductor production.
An acceleration force causes the inert mass to lurch and thereby produces mechanical tension in the torsion bar, which is taken as the measure of the acceleration force. According to claim 6 hereto,
REFERENCES:
patent: 4776924 (1988-10-01), Delapierre
patent: 4851080 (1989-07-01), Howe et al.
Henley, "Advances in VLSI Stimulate Solid-State Sensors Market", New Elecnics, Aug. 12, 1986, pp. 45, 47-50.
Fraunhofer Gesellschaft zur Forderung der angewandten Forschung
Powell William A.
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