Measuring and testing – Speed – velocity – or acceleration – Acceleration determination utilizing inertial element
Patent
1992-05-08
1995-03-28
Chapman, John E.
Measuring and testing
Speed, velocity, or acceleration
Acceleration determination utilizing inertial element
73DIG3, G01P 1511
Patent
active
054006546
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an acceleration sensor. More particularly, it relates to an acceleration sensor which has a deflection spring fixed at one end and arranged in a casing, at the free end of which at least one sensor element is attached which is in active connection with a Hall element. In such a sensor, a permanent magnet is attached to the deflection spring as a seismic mass and is in an active connection with a Hall element for the generation of a measuring signal. The Hall element is fixed to a hybrid circuit which is arranged on the base plate of the acceleration sensor. The deflection spring is configured perpendicular to the hybrid circuit and has a sloping longitudinal edge, whereby it is intended to prevent twisting of the spring. However, this arrangement of the deflection spring and its design makes the acceleration sensor relatively high. Moreover, the spring can be easily broken or plastically deformed, should the acceleration sensor be dropped, which would falsify the measured values and make the sensor no longer operable.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an acceleration sensor of the above mentioned type which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in an acceleration sensor of the above mentioned general type in which the deflection spring together with the sensor element is arranged in a recess of a plate, and a hybrid circuit with the Hall element is located on the plate.
An acceleration sensor in accordance with the invention has the advantage that it is of very small height, that is, it has a very small volume. The spring with the seismic mass is arranged protected in the recess of a plate. This ensures that it can be safely dropped from at least 1 meter height onto concrete. The plate itself and the hybrid circuit arranged on the plate will serve as overload protection. This arrangement furthermore shrouds the deflection spring and the sensor magnets, so that the measuring equipment is protected from soiling. The resonance frequency of the deflection spring can be easily influenced by the choice of material for the spring. If tombac is selected for the deflection spring, then the deflection spring is no longer deformed in the sensing direction and in the bowed direction. Due to the stops for the seismic mass being geometrically optimally arrangeable, an approximately straight line is obtained for the progression of the measuring signal. Since the sensor magnets also represent the seismic mass, this may be kept as small as possible, whereas the magnetic induction is relatively large, due to the choice of permanent magnets. Due to its connection with the mounting plate and the base plate of the housing, the hybrid circuit rearside is connected to vehicle earth. This results in a relatively low EMC sensitivity (EMC=electromagnetic compatibility). The number of the individual parts used is relatively small. The sensor can also be made in a small number of mounting and assembly steps. Mounting of the sensor can be carried out almost fully automatically. After fitting the connector housing, the hybrid circuit can be balanced in a simple manner, with the housing itself not yet slid into position. By using the bonding technique for connection between the hybrid circuit and the connector plug, this step of manufacture can be automated and it can be carried out in a safe manner, i.e. without high failure rates.
The permanent magnets attract each other, so that only simple gluing is required. Gluing is required primarily only in order to prevent displacement of the permanent magnets relative to each other in the event of any knock. The base plate used with its connection flanges provides high accuracy of fitting within the vehicle. Based on the simple symmetrical design and the solid, sturdy measuring element of the acceleration sensor, good tempe
REFERENCES:
patent: 4825697 (1989-05-01), Huber
patent: 4870864 (1989-10-01), Io
Kaiser Harry
Willig Rainer
Chapman John E.
Robert & Bosch GmbH
Striker Michael J.
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