Machine element or mechanism – Rotary member or shaft indexing – e.g. – tool or work turret – Preselected indexed position
Patent
1989-01-20
1990-12-11
Ruehl, Charles A.
Machine element or mechanism
Rotary member or shaft indexing, e.g., tool or work turret
Preselected indexed position
73779, G01L 310
Patent
active
049761609
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on a device for measuring torsion or bending force exerted or an object. It is known that ferromagnetic materials change their permeability in the direction in which tensile or compressive forces act. This change in permeability is detected in a contactless manner by a sensor coil If amorphous metals are used as materials, they can be glued or welded on only in the form of foils In so doing, it is difficult to achieve a high adhesive strength or creep resistance of the material on the object to be measured In addition, the crystallization threshold is easily exceeded when the amorphous metals are welded on, so that its structural state changes in partial areas and there is no longer any accurately definable material state. In addition, a measurement curve extending in a linear manner along the entire measurement region can no longer be achieved, even when the coating is applied to the shaft with prestress in a relatively complicated manner for this purpose. Particularly in the edge areas, the measurement curve diverges sharply from a straight line, so that only a very small measurement region can be evaluated. Moreover, the finishing process necessary for this is costly and difficult to carry out. A first film must be applied to a shaft which is twisted to the left and the other film must be applied to a shaft twisted to the right, or vice versa. In so doing, the prestressed surface portions work linearly only in a narrow measurement region, so that only a relatively small portion of the available measurement region can be utilized.
SUMMARY OF THE INVENTION
In contrast, the device, according to the invention, has the advantage that the film can be applied to the object to be measured with high adhesive strength and creep resistance in a simple and inexpensive manner No prestressing is necessary A characteristic line extending linearly for the entire range of measurement can be obtained by means of an evaluating circuit. A relatively simple installation of the sensors is also possible on objects with a complicated and poorly accessible construction by means of coils covering the films on one side of the object to be measured until the edge areas. Since the coils detect relatively many formed anisotropic regions simultaneously, a so-called average value is formed already by means of the coils themselves. The winding shape can be adapted to the respective measurement problem in a simple and economical form. The economical film technique (thin-film or thick-film technique) can be used for applying the coil.
In keeping with these advantages and others which will become apparent hereafter, one feature of this invention resides in the provision of two coatings of magnetoelastic material applied side by side on surface regions of the object to be measured, the coatings being free of prestress and each consisting of parallel stripe-shaped zones whereby the zones of one coating are oriented substantially at right angles to the zones of the other coating, two parallel resonant circuits each including a coil wound on an assigned coating, and a capacitor, and means for exciting the resonant circuits to produce a measuring voltage when the object is subjected to a mechanical stress.
BRIEF DESCRIPTION OF THE DRAWING
An embodiment example of the invention is shown in the drawing and described in more detail in the following description.
FIG. 1 shows a magnetoelastic torsion sensor;
FIG. 2 shows a circuit arrangement, according to the invention, for operating the magnetoelastic sensors according to FIG. 1;
FIG. 3 shows a diagram which shows the measurement voltage over the applied torsion;
FIGS. 4 to 7 show a modification of a detail, in each instance; and
FIG. 8 shows a partial step of a production process.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1, a shaft is designated by 10, the twisting of the shaft 10 is to be determined by means of the torsion measuring device of this invention. Two coatings 11, 12 of highly magnetoelastic material, whose permeabil
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Dobler Klaus
Hachtel Hansjorg
Zimmermann Georg
Robert & Bosch GmbH
Ruehl Charles A.
Striker Michael J.
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