Measuring and testing – Tire – tread or roadway
Reexamination Certificate
2000-02-28
2003-07-15
Williams, Hezron (Department: 2855)
Measuring and testing
Tire, tread or roadway
C073S146500
Reexamination Certificate
active
06591668
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a system and a method for ascertaining the emergency running condition of a pneumatic tire for motor vehicle wheels. A permanently present first periodic oscillation in proportion to the wheel rotation speed is produced at least on each axle, preferably on each wheel, and is fed to a signal processing device as a speed output signal. The speed output signal is supplied by active or passive magnetic field sensors, in that magnetically active or passive devices, preferably encoders, rotating relative to the sensors and situated on parts of the vehicle that rotate with the wheel or are stationary, produce a periodic magnetic field change in proportion to the wheel rotation speed.
2. Discussion of Background Information
The constantly rising safety requirements for motor vehicles increasingly demand the most comprehensive detection possible of all parameters that represent and influence the driving and moving condition of a motor vehicle, for use in intelligent systems for chassis and vehicle control and regulation. In particular, typical hazardous situations which can occur, for instance, when there is a sudden loss of pressure in a tire, must be reliably recognized and must activate appropriate warning or control signals.
A number of developments are approaching the safety requirement in other ways, in that, e.g., in the particularly critical case of a sudden loss of pressure in a tire, the potentially fatal effects are to be alleviated using devices on the vehicle wheel or in the tire construction that maintain a stable driving condition and capability for emergency running over a certain distance or time, even under pressure loss. Such developments are also supported by the fact that, because the weight of vehicles is being continually reduced for the sake of energy conservation, spare wheels and/or the necessary tools to mount them are no longer to be carried.
The term ‘emergency running’ or ‘emergency running condition’ is understood in this context to mean the driving condition in which, owing to a sudden loss of pressure in a tire, for instance, caused by external damage, the normal steering, adhesion or traction, and stabilizing properties of the tire as a connecting link or interface between the vehicle and the road are no longer present to the original extent, in which, however, a running ability and usability are nonetheless retained to an extent such that the safety of a vehicle is not unreliably limited. The emergency running condition then makes it possible to continue the journey for a certain distance without problems, preferably at least to the next service station.
The modern forms of such emergency running systems, which have already been under discussion for decades, e.g., emergency running support elements mounted on the rim, or sidewall-reinforced tires, combined with today's customary vehicle and suspension comfort, have the general disadvantage that an emergency running condition is no longer noticed by the driver as a result of the behavior of the vehicle being markedly different from the normal condition, so that there is a danger that the emergency running ability which, as a rule, is limited with respect to time or distance driven, is overtaxed and can finally result in the total failure of a tire or wheel, which then can again be extremely hazardous to the vehicle and its occupants.
In order to meet or address this potential danger, for example, a number of mechanical/acoustic warning devices have already been conceived that warn the driver by producing strong vibrations or noises.
DE 25 38 948 A1 discloses a vehicle wheel with a pneumatic tire having an emergency running ring inside a tubeless tire, which ring is provided on its surface supporting the tire in the emergency running condition, i.e., on its emergency running surface, with one or more projections arranged distributed over the circumference to warn the driver which, in the case of a sudden loss of pressure in the tire and the resulting deposit of the inside of the tread region on the emergency ring, is intended to cause vibrations that draw the attention of the driver to the loss of air.
DE 25 09 939 A1 also discloses an emergency running support element, in this case an emergency running tube which, in its outer region, has a hollow cylindrical element of metal or hard plastic and has concavities in the shape of a universal ball joint distributed over the circumference on its outer surface which, when the emergency running tube is activated, produce an audible noise that is intended to indicate a defect in the pneumatic tire.
JP 91 69 203 A discloses annular pieces of rubber arranged inside the tire and on the rim, which support the inside of the tread region of the tire during emergency running. The annular pieces or annular sections disclosed here do not support the tire over the entire circumference of its rolling radius, but only partial regions, which may be staggered by up to 180°. Here as well, when there is a loss of air, a vibration is to be produced that informs the driver of a loss of air in the form of an audible noise or by transmission to steering elements.
The disadvantage of such mechanical/acoustic warning devices is essentially that in today's customary excellent damping and decoupling between the chassis and the bodywork in connection with a desired high level of suspension and driving comfort and good sound insulation of the interior of the vehicle, the resulting noises or vibrations are no longer reliably detected by the driver, or else would have to be so loud or severe that it would simply not be possible to continue driving.
Further development has therefore been concentrated on ascertaining an emergency running condition with measuring mechanisms and making the driver aware of it via optical and acoustic warning devices in the vehicle. Two basic methods are known essentially therefor, namely, on the one hand, direct measurement of the air pressure inside a tire and, on the other hand, the indirect determination of the air pressure of a tire, e.g., via a suspension behavior of the tire influenced by a change in air pressure or via a change in the rolling radius or the dynamic rolling circumference of a wheel caused by the change in air pressure, i.e., by a change in speed.
While it is true that a direct measurement of air pressure, for example, via aneroid boxes inside the tire, represents a reliable detection method, it results in a high expenditure on sensing, power supply, and transmission systems by which the changes in air pressure measured inside the rotating tire can be transmitted to the stationary sensors installed in the vehicle and thus to the processing electronics.
EP 630 769 A1 discloses a tire pressure detection device for truck tires in which a pressure sensor inserted inside a wheel bolt arranged in the rim, which is connected via hose lines to the tire valve, tests the air pressure in the tire and transmits these test results via rotating antennae, which are arranged adjacent to the wheel support and the axle, into the vehicle or to a processing unit.
The device conceived here for the large-scale mounting conditions of a truck tire requires a high expenditure on additional components that make the entire system more expensive, is extremely high-maintenance and susceptible to mechanical damage and soiling, makes it difficult to change the tire, and also, because it is necessary to arrange the system on all tires, represents a system that calls into question cost-effective production, even in series production and, in particular, for passenger automobile tires, owing to its high level of complexity for sensors, cabling, and other additional components.
On the other hand, pressure loss warning systems based on the detection of the dynamic rolling circumference, have a number of imponderabilities that lead to inaccurate measurements or decisions. Among other reasons, these imponderabilities arise because the dynamic rolling circumference can be strongly influenc
Becherer Thomas
Ernst Gerhard
Fennel Helmut
Huinink Heinrich
Köbe Andreas
Allen Andre
Continental Aktiengesellschaft
Greenblum & Bernstein P.L.C.
Latarnik Eva-Maria
Latarnik Sylvia Monika
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