Measuring and testing – Tire – tread or roadway
Reexamination Certificate
1998-11-23
2001-09-25
McCall, Eric S. (Department: 2855)
Measuring and testing
Tire, tread or roadway
Reexamination Certificate
active
06293140
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for detecting the rotational behavior of a vehicle wheel, which includes an encoder rotating with the wheel and having permanent magnet areas that are evenly distributed in a circumferential direction and follow one another with alternating polarity, and a stationary measurement transducer sensitive to magnetic fields which furnishes an output signal representative of the rotational movement, and an electric circuit to evaluate the output signals of the measurement transducer.
A device for detecting rotational or angular movements is disclosed in WO 95/17680. The measurement device includes a measurement transducer in the shape of an encoder which rotates with the wheel and has a plurality of permanent magnet areas that are arranged so as to be evenly distributed in the direction of rotation over the entire periphery of the encoder. As a measurement transducer, an active measuring element is arranged stationarily at the periphery of the encoder in such a manner that the variations of the magnetic field which are due to the rotation produce signals at the output of the measuring elements or measurement transducer which indicate the rotation.
Passive and active measurement devices for detecting the rotational behavior of vehicle wheels are numerous and manifold in the state of the art. An electric signal representative of the rotational movement is, among others, required as an input quantity of automotive vehicle control systems, such as antilock systems (ABS), traction slip control systems (TCS), driving stability control systems (DSC, ASMS), etc. The necessary effort in manufacture beside a reliable mode of operation is of major significance for these cases of application, even more so because most of the systems require several sensors, i.e., one individual rotational speed sensor for each vehicle wheel. Therefore, the search for an especially inexpensive sensor is the objective of intensive development work.
An object of the present invention is to develop a measurement device of the type mentioned hereinabove which involves, above all, reduced efforts in manufacture and assembly and ensures a high degree of reliability.
SUMMARY OF THE INVENTION
It has been found that this object can be achieved by a device providing that the permanent magnet areas are made of a material on a barium-ferrite basis which is embedded into the tire wall or applied to the tire wall, that the measurement transducer includes two or more measuring elements which are offset in the direction of rotation of the wheel and arranged at a different radial distance from the axis of rotation, namely in such a manner that upon distortion of the tire as a result of forces acting upon the tire or due to the drive or brake torques transmitted, there is a shift of the phase position between the measurement signals issued by the measuring elements, and in that the shift of the phase position can be evaluated as a measure of the torques transmitted from the wheel and the tire to the road surface and/or as a measure of the instantaneous coefficient of friction.
Thus, the present invention is based on the knowledge that, as a measurement transducer, it is possible to use a magnetized track embedded into the tire wall or applied to this wall, on the one hand, and that, on the other hand, when two or more offset sensors or measuring elements are used, the torsional stress of the tire or the tire wall can be evaluated in addition to the measurement of the rotational or angular movements in order to measure the transmitted torques and/or the instantaneous coefficient of friction.
Further details, advantages and possible applications of the present invention can be seen on the following description making reference to the accompanying drawings.
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patent: 4570152 (1986-02-01), Melton et al.
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62-177453, Jan. 23, 1988, Patent Abstracts of Japan.
61-198063, Jan. 24, 1987, Patent Abstracts of Japan.
07-2 80 821, Oct. 27, 1995, Japan.
Stöcker, Jörg, u.a.: Der“Intelligente Reifen”—In: ATZ Automobiltechnische Zeitschrift 97, 1995, 12, S.824-832; Bild 5,6.
Continental Teves AG & Co. oHG
McCall Eric S.
Rader & Fishman & Grauer, PLLC
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