Measuring and testing – Dynamometers – Responsive to torque
Patent
1990-03-02
1992-01-28
Ruehl, Charles A.
Measuring and testing
Dynamometers
Responsive to torque
G01L 310
Patent
active
050834681
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a measuring device for contact-free measuring of a rotation angle and/or torque of a shaft. In a known measuring device, the torque can be measured at the shaft by means of two cylindrical sleeves which are concentric to one another and to the shaft axis, rotatable relative to one another and divided at their circumferential surface into an equal number of a plurality of segment-like outer surface areas which are parallel to the shaft axis. The outer surface areas have high and low electrical conductivity alternating in the circumferential direction and are enclosed by at least one winding which is coaxial to the sleeves.
SUMMARY OF THE INVENTION
The object of the invention is a measuring device that has a high sensitivity, a relatively small temperature drift and a good measuring reliability. According to the invention, the sensitivity of the measuring device is improved by using four coils which are connected in a Wheatstone bridge circuit. An occurring temperature drift can accordingly be eliminated to a great extent. A relatively short overall length in spite of the incrased number of coils is achieved by arranging the coils side-by-side in abutting relationship with each other. In addition, the measuring reliability, and accordingly also the protection against failure of the device in which the measuring device is installed, is improved. An electronic arrangement for monitoring can determine immediately and unequivocally that a winding of the coils of the measuring device is short-circuited. At a so-called winding short circuit, one of the coils of the Wheatstone bridge is short circuited, so that the bridge circuit is detuned far beyond the limits of the measuring range, which is clearly detectable as an erroneous measurement signal.
The present invention both as to its construction so to its method of operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of specific embodiments when read in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a longitudinal cross-sectional view of a measuring device according to the invention;
FIG. 2 shows a longitudinal cross-sectional view of the inner sleeve;
FIG. 3 shows a longitudinal cross-sectional view of the outer sleeve;
FIG. 4 shows a circuitry of arrangement of coils of the measuring device according to the invention;
FIGS. 5 and 6 show a partial view of a modified embodiments of the measuring device according to the invention;
FIG. 7 shows a partial cross-sectional view of yet another embodiment of the measuring device according to the invention; and
FIGS. 8 and 9 show side views of disc-like bodies.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1, a torque rod 10 for detecting the rotation angle or torque is exposed to a torque between two shaft stubs 11 and 12. The shaft stub 11 on the right rotates relative to the shaft stub 12 on the left with a small angle of rotation. The shaft stubs 11, 12 are part of one shaft, e.g., a steering booster for motor vehicles. It is assumed in FIG. 1 that a torque Md acting in a clockwise direction is introduced into the shaft stub 11 via a square 13 and that a counter-torque, not shown, is acting at the square 14 connected with the shaft stub 12.
In order to determine the torque Md, the measuring arrangement, according to the invention, comprises two sleeves located in a tubular housing 16, namely an outer sleeve 18 and an inner sleeve 19 which are concentric to the mutual longitudinal axis 17 of the shaft and are made in each instance of electrically conducting, preferably non-magnetic material having a thickness of approximately 1 milliliter. The outer sleeve 18 is arranged on the shaft stub 11 on the right so as to be fixed against rotation relative to the stub 11, while the inner sleeve 19 is fastened in the same way on the shaft stub 12.
The outer sleeve 18 comprises a plurality of longitudinal slots 21, e.g., eight, which are unifor
REFERENCES:
patent: 2867118 (1959-01-01), Cavanagh
patent: 3858443 (1975-01-01), Roberts, III
patent: 4356732 (1982-11-01), Hachtel
patent: 4448084 (1984-05-01), Dobler et al.
Dobler Klaus
Hachtel Hansjorg
Robert & Bosch GmbH
Ruehl Charles A.
Striker Michael J.
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