Measuring and testing – Speed – velocity – or acceleration – Acceleration determination utilizing inertial element
Patent
1987-11-13
1989-05-02
Chapman, John
Measuring and testing
Speed, velocity, or acceleration
Acceleration determination utilizing inertial element
73517A, 73526, 73DIG3, G01P 1508
Patent
active
048256978
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is directed to an acceleration sensor. Known sensors use liquids, e.g. oil, as damping means; however, this has the disadvantage that the damping or the frequency response is dependent upon viscosity and, accordingly, vary dependent upon temperature. Accordingly, an additional measurement error results in the measurement of accelerations which change with respect to time. Moreover, sealing means are necessary in order to separate the electric or electronic signal processing device from the liquid in an absolutely leakproof manner and to prevent the leakage of liquid. This makes the acceleration sensor more expensive.
SUMMARY OF THE INVENTION
An acceleration sensor according to the invention provides for a damping or frequency response to have only a slight dependence on temperature and is designed so as to be very simple, inexpensive, and also light.
By means of using a leaf spring or spring band or a torsion spring and, for example, a Hall element as sensor, the device is constructed so as to be particularly compact and light. The sensor can also be constructed, in particular, as an angular acceleration sensor.
BRIEF DESCRIPTION OF THE DRAWING
Two embodiment examples of the invention are shown in the following drawing and are explained in more detail in the description.
FIG. 1 shows a side view of a first acceleration sensor;
FIG. 2 shows a top view;
FIG. 3 shows a view in the direction of the arrow;
FIG. 4 shows a diagram;
FIG. 5 shows a side view of an angular acceleration sensor;
FIG. 6 shows a view from the back; and
FIG. 7 shows a top view of an individual part of the sensor.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A base plate 10 of an acceleration sensor is shown and from which a web 11 extends upwardly at a right angle. A leaf spring 12, which is constructed so as to be approximately rectangular and extends so as to be parallel edgewise to the base plate 10, is fastened at the web 11, particularly by means of spot welding. An eddy current disk 13, which is likewise constructed so as to be approximately rectangular and extends in a horizontal manner transversely relative to the leaf spring 12, is fastened at the free end of the leaf spring 12, also paticularly by means of spot welding. The eddy current disk immerses in a cage-shaped flux conducting piece 15 which preferably consists of low-reluctance material. Two square brake magnets 16, 17, which extend toward the brake disk 13 but do not contact it, are arranged in the flux conducting piece 15 at a distance from one another. The width of the flux conducting piece 15 is somewhat greater than the width of the eddy current disk 13, so that the latter can oscillate without difficulty in the flux conducting piece.
At the free end of the leaf spring 12, that is, where the eddy current disk 13 begins, a prolongation 18 extends toward the base plate 10. A sensor magnet 19 is arranged at the lower end of the prolongation 18 and cooperates with a Hall element 20 which is located opposite it and which is fastened at the base plate 10. Evaluating circuits 21 are applied to the base plate adjacent to the Hall element by means of thick- or thin-film technology.
The eddy current disk 13, together with the flux conducting piece 15 and the brake magnets 16, 17, forms an eddy current brake. The brake magnets are magnetized in opposite directions. Because of this magnetization in opposite directions, the magnetic field in the air gap between the eddy current disk 13 and the brake magnets 16, 17 is very inhomogenous, so that the eddy current generation is benefited during the oscillation of the eddy current disk.
By way of example, the acceleration sensor is arranged so as to be perpendicular with respect to the traveling direction of a motor vehicle. The inertia mass in the form of the eddy current disk 13 at the end of the leaf spring 12 is deflected in proportion to the acceleration acting perpendicular relative to the leaf spring. The deflection is determined by means of the spring constant of the leaf spring
REFERENCES:
patent: 2656519 (1953-10-01), Sheppard
patent: 4065974 (1978-01-01), Euer et al.
patent: 4156366 (1979-05-01), Euer
patent: 4218614 (1980-08-01), Miller
patent: 4498341 (1985-02-01), Breitbach et al.
Chapman John
Robert & Bosch GmbH
Striker Michael J.
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