Measuring and testing – Tire – tread or roadway
Reexamination Certificate
1999-05-07
2002-01-22
McCall, Eric S. (Department: 2855)
Measuring and testing
Tire, tread or roadway
C073S146400, C152S152100, C340S445000, C340S447000
Reexamination Certificate
active
06339956
ABSTRACT:
INTRODUCTION AND BACKGROUND
The present invention pertains to a pneumatic automobile tire (
1
) which contains beads (
2
) with bead cores (
3
) arranged therein, wherein at least one sensor (S) is arranged in the pneumatic automobile tire (
1
). This sensor delivers signals that are correlated to the forces transmitted by the tire during its operation. Such information on tire forces serves for controlling the brakes and the chassis.
It is known to arrange sensors in tires, e.g. from DE 39 37 966 A1, DE 43 35 938 A1 and EP 06 02 679 B1. In these instances, the sensors are inserted between the base of the tread groove and the top belt layer.
All known sensors arranged in tires have the disadvantage of requiring an electric supply voltage. The supply voltage may be transmitted from the non-rotating car battery/on-board network to the rotating wheel via brushes, generated by means of a generator arranged in the rotating wheel (e.g., according to DE-OS 34 07 254) or stored in a battery or the like which is arranged in the rotating wheel.
According to the current state of the art, the arrangement of a round cell battery in the tire or the wheel rim appears the most advantageous option for providing the energy supply. However, most drivers only consider this feasible if the battery has a service life of more than three years. The most important factors for ensuring such a long battery service life are
a low power consumption per transmission signal (i.e., a very short transmission period per signal or very low transmission power) which, however, contradicts another objective, namely an absolutely reliable signal identification in the receiver, due to the multitude of weak electromagnetic waves being dispersed,
a low frequency of transmission signals per time unit (which appears feasible for monitoring the air pressure, but can only be utilized for traction control purposes by limiting the control precision),
a high battery capacity (which increases the weight and cost of the system),
a very low self-discharge current, and
a low internal resistance and a low voltage drop at decreasing temperatures down to 40° C.
Although devices of this type were successfully tested in experimental automobiles, they have not been incorporated into a series production so far, wherein the incorporation into systems that also serve for traction control purposes, i.e., systems according to the present invention, currently appears improbable due to limitations of currently available batteries.
In addition, batteries of this type are difficult to exchange or can be easily stolen.
In order to solve this problem, EP-PA 03 63 570 already proposed to arrange the sensors that sense the longitudinal and/or lateral forces in a non-rotating system situated in the vicinity of the tire, e.g., on a transversal swinging arm of the wheel suspension, rather than in the tire. However, these measuring points are positioned relatively far from the tire contact area—at which the transmission of forces between the automobile and the road takes place—namely even farther than in a conventional ABS system.
The elasticities, masses and oscillatory pulses between the sensors and the tire contact area (caused by stiffness fluctuations of rolling bearings and driving elements) diminish the precision of the measurement. The lower the precision, the farther the nominal slip between the tire tread and the road which is predetermined for the ABS or ESP system needs to lie below the critical slip—for maximum brake maneuvers—in order to prevent overmodulation of deviation. This means that a correspondingly longer stopping distance must be accepted.
The principle of a non-rotating sensor arrangement is also utilized in DE-OS 44 35 160 A1 by the same applicant and the corresponding PCT/EP95/03864. However, the variable to be sensed, namely the side wall torsion, occurs in the rotating wheel. This principle makes it possible to determine deformations of the rotating wheel by means of non-rotating sensors arranged outside of the wheel. In this case, the forces are not directly measured, but rather the changes in time intervals, in which markings arranged on the tire pass by non-rotating sensors.
In comparison to ABS systems which were supplied with information via a magnet wheel until now, this system represents huge progress, namely because the mass of the wheel rim and the hub with its sleeve is no longer incorporated into the inertia calculation, i.e., this system allows faster control. However, applicants desired to broaden their knowledge and increase production by means of an internal development which resulted in a solution, in which the sensor is arranged in the rotating wheel.
The aforementioned measurement of the side wall torsion showed that torsional vibrations between the radially inner and the radially outer measuring track occur when continuously driving straight. Consequently, instantaneous torsion values showed intense fluctuations from the quotient longitudinal force/torsional rigidity. This influence can only be calculated by means of high resolution, i.e., a high pole number per magnetic track.
However, this effect also provides certain advantages, namely for detecting tread depth and aquaplaning, e.g., as described in the respective applications DE-OS 197 16 586.9 and 19 725 775.5. However, this effect also complicates the measurement of the longitudinal force which is of the utmost importance.
U.S. Pat. Nos. 4,625,207, 4,625,208 and 4,725,841 pertain to systems for obtaining signals from a passive transponder that carries phase-coded information.
EP 0 505 906 B1 discloses a pneumatic tire with an IC transponder that is arranged in the structure of the tire and used for tire identification, wherein an air pressure detector is incorporated into the transponder, and wherein said transponder is arranged on the axially inner side of the sealing inner liner together with its pressure detector.
DE-OS 41 12 738 discusses the fact that certain tire specifics vary from type to type. For example, tires of one manufacturer show a slightly different curve of the coefficient of friction &mgr; as a function of slip than tires by another manufacturer, namely even if the tires have the same dimensions. The critical slip of one tire type may, in particular, be higher than that of another tire type.
Manufacturers of ABS systems usually attempt to achieve an optimal slip that is as high as possible, but sufficiently low for preventing the dreaded overmodulation of the brakes with all tires. This measure serves for preventing that, after a slightly excessive brake pressure, the brake pressure is excessively decreased, whereafter excessive brake pressure is built up again, etc. This means that the deviation is increased.
In such automobiles, this results in the tires which have the steepest &mgr;-slip curve always performing best in brake tests, namely even if other tires reach a higher &mgr;; the higher slip required by these other tires is, however, not even reached due to the cautious nature of the controller which is based on the steepest &mgr;-slip curve stored in said controller.
The aforementioned DE 41 12 738 discloses a method for controlling and/or regulating automobile systems, wherein information on the properties of the actually mounted tires—e.g., the &mgr;-slip curve—is not stored in the controller, but rather in the tire so as to attain a superior tire identification system. In addition, this information is fed to the controller directly from the tire such that the controller bases the respective manipulations on the &mgr;-slip curve that fits the individual tire—namely even if different tires are used.
According to one embodiment of this invention, a data carrier is arranged on the axially inner side of the inner tire bead.
The progress reports of the VDI (Association of German Engineers), Volume 8, No. 515, contains a report on the colloquium “Contactless Transmission of Measurement Data and Power” of Nov. 30, 1995 which was held at the College of Technology in Darmstadt and organized by Special Research Branch 241 of the
Fries Volkmar
Huinink Heinrich
Kleinhoff Klaus
Köbe Andreas
Continental Aktiengesellschaft
McCall Eric S.
Smith , Gambrell & Russell, LLP
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