Measuring and testing – Speed – velocity – or acceleration – Acceleration determination utilizing inertial element
Patent
1990-01-03
1992-04-28
Chapman, John E.
Measuring and testing
Speed, velocity, or acceleration
Acceleration determination utilizing inertial element
338 5, G01P 1512
Patent
active
051077086
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on an acceleration pick-up. In acceleration pick-ups, it is known to clamp in the bending spring at one side along the entire width and to determine the deflection of the bending spring by means of piezo-resistive elements. These pick-ups are relatively highly sensitive transversely and have no warning device when the bending spring breaks or is damaged in some other way.
SUMMARY OF THE INVENTION
The acceleration pick-up, according to the invention, includes flat bending spring of a ceramic material, the spring having a recess defining with lateral edges of the spring two bending webs, elongation-sensitive resistors applied on the webs, additional resistors applied on the spring between the webs and close to the recess and being connected in a Wheatstone bridge. The invention has the advantage that it determines the acceleration in a particularly simple, accurate and reliable manner. The transverse sensitivity of the bending spring to acceleration in the plane of the bending spring is reduced. In addition, transverse signals brought about by torsion of the bending spring are suppressed by the suspension. The bending spring is accordingly only sensitive to bending. A simple testing of the functioning of the mechanical area of the pick-up, i.e. its bending spring, at all times is made possible by means of the special arrangement of the resistors of the Wheatstone bridge circuit. The electrically closed circuit of the Wheatstone bridge is interrupted by mechanical damage to the web. Accordingly, an electrical monitoring of the mechanical state of the pick-up is also possible in the installed state. The oscillating seismic mass can also be included in the electrical monitoring by means of the special arrangement of the resistors as close as possible to the recess. The evaluation circuit can be arranged on a lengthening of the bending spring. Accordingly, the evaluating circuit can be applied on a ceramic substrate in an area of high strength using hybrid technology. No interference signals are produced in the evaluating circuit by means of mechanical deformation in this area. In addition, the bending spring can accordingly be constructed so as to be relatively thin and sensitive.
BRIEF DESCRIPTION OF THE DRAWING
An embodiment example of the invention is shown in the drawing and explained in more detail in the following description. FIG. 1 shows a perspective view of a pick-up of the invention, and FIG. 2 shows a modification of the pick-up of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The stepped support of an acceleration pick-up 11, which can be produced from a relatively rigid material, is designated by 10 in FIG. 1. A bending spring 13 which serves as seismic mass and comprises ceramic material, e.g. aluminum oxide (Al.sub.2 O.sub.3), is arranged on the elevated portion 12 of the support 10. The bending spring 13 comprises a cut out portion 14 in the area of the step of the support, so that two bending webs 15, 16 which extend parallel to one another are accordingly formed with which the bending spring is fastened in an elastic manner on the step or elevated portion 12 of the support 10. The cut out portion 14 is dimensioned such that the bending webs 15, 16 are as far as possible from one another, in particular, the outer edges of the bending webs 15, 16 can extend so as to be aligned with the outer edges of the bending spring 13. As can be seen the bending webs 15, 16 are arranged at two opposite marginal areas of the support 10.
In order to determine the deflection, the four sensor resistors 19 to 22 of a Wheatstone bridge circuit, which are sensitive to elongation, are arranged on the bending spring 13. The oppositely located resistors 19, 21 are arranged on the bending webs 15, 16 respectively. The remaining two resistors 20 and 22, respectively, are located on the oscillatory area of the bending spring 13, namely in the area near to the cut out portion 14 on the free part of the bending spring 13 and in the area on the part of the spri
REFERENCES:
patent: 4488445 (1984-01-01), Aske
patent: 4955234 (1990-09-01), Marek
Holland Martin
Marek Jiri
Seipler Dieter
Ziegenbein Botho
Chapman John E.
Robert & Bosch GmbH
Striker Michael J.
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