Measuring and testing – Speed – velocity – or acceleration – Acceleration determination utilizing inertial element
Patent
1992-02-21
1994-08-09
Chapman, John E.
Measuring and testing
Speed, velocity, or acceleration
Acceleration determination utilizing inertial element
73862382, 73514, G01P 1508
Patent
active
053355440
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to an apparatus for measuring mechanical forces and force actions by means of a body, a restoring element and a movable mass, with elements for limiting the deflections of the movable mass. The movable mass is deflected against the resistance of the restoring element under the influence of a mechanical force. The mechanical elements of such an apparatus are manufactured by standard microstructural technology, isotropic and anisotropic etching processes, whilst the electronic elements for determining the measured values are manufactured with microelectronics production processes. With the aid of sensors the mechanical actions of a force are converted into electrical signals and supplied to an evaluation circuit.
Such devices are used, for example, for measuring accelerations, are described by J. L. Davison and D. V. Kerns in "Silicon Acceleration Technology", Proceedings of the 1'.about.86 International Conference on Industrial Electronics, Control and Instrumentation, IEEE, New York, 1986, pp. 218-222.
Apart from use-specific characteristics, when manufacturing devices for the measurement of forces and force actions account must also be taken of the requirements devolving from the general field of use of the apparatus. These requirements include insensitivity to mechanical overstressing. For example, a microgravimeter for satellites or space stations must be able to withstand accelerations which are orders of magnitude above its measuring range.
In all known solutions, overload protection is achieved by mechanical stops, which limit the deflection of the movable mass of an apparatus for measuring acceleration to certain maximum values. In monolithically integrated devices produced from a single semi-conductor chip, such elements for limiting the deflection of the movable mass are e.g. produced by the application of additional coatings. For this purpose at least one second semiconductor or glass plate must be connected to the monolithically integrated apparatus by adhesion or joining. This means that for the production of the stops, it is necessary to carry out additional operating steps not provided in the monolithic integration process. Moreover, joined devices suffer from additional sources of fault and error.
German patent document DE-OS 36 11 360 and U.S. Pat. No. 4,699,006 describe devices in which rotary pendulums are etched out of semiconductor crystals. A mechanical stop is formed in that the substrate is not completely removed below the rotary pendulum and instead pits are etched out, with the pit bottom being used as a mechanical stop during deflection of the rotary pendulum.
However, this type of mechanical limitation is not suitable for uses in which the deflection or amplitude must be limited to very small values, because a minimum etch pit depth is required for the complete undercutting of the rotary pendulum.
U.S. Pat. No. 4,653,326 discloses a micromechanical apparatus for measuring accelerations, which has a bender bar, which can perform deformations in the substrate plane. The bender bar is produced by clearance etching from the substrate. In order to obtain a deflection parallel to the substrate surface the substrate must be completely removed. The remaining limiting legs of the substrate form mechanical boundaries for the deflection of the bender bar in the substrate plane. Particularly if the leg faces of U.S. Pat. No. 4,653,326 are to be constructed as capacitor plates, they are not immediately suitable for limiting to very small deflections.
The object of the invention is therefore to provide a device for measuring mechanical forces and force actions with a mechanical overload protection, which can be made particularly easily adapted to the requisite use conditions and which is characterized by a very simple manufacturing process.
This object is achieved by the force measurement apparatus according to the invention, in which the element for limiting the deflection comprises at least two parallel tongues and a web,
REFERENCES:
patent: 4882933 (1989-11-01), Petersen et al.
patent: 5111693 (1992-05-01), Greiff
Benecke Wolfgang
Riethmuller Werner
Schnakenberg Uwe
Wagner Bernhard
Chapman John E.
Fraunhofer Gesellschaft zur Forderung der angewandten Forschung
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