Measuring and testing – Tire – tread or roadway – Tire inflation testing installation
Reexamination Certificate
2000-05-08
2002-08-20
McCall, Eric S. (Department: 2855)
Measuring and testing
Tire, tread or roadway
Tire inflation testing installation
C340S445000, C340S446000, C340S447000
Reexamination Certificate
active
06435020
ABSTRACT:
BACKGROUND OF THE INVENTION
For reasons of safety, the tire pressure of motor vehicles must be checked regularly and this is often neglected by the driver of the motor vehicle for various reasons. For this reason, tire pressure control systems have already been developed which include a tire pressure control device on each wheel which automatically measures the tire pressure of the tires of the motor vehicle and announces to the driver of the motor vehicle at least a critical deviation from a desired tire pressure. The tire pressure control devices can, for example, be vulcanized into the tires or can be mounted with adhesive or can be attached on or in the valve or on or in the wheel rim. Appropriate configurations are known.
U.S. patent application Ser. No. 09/131,910, filed Aug. 10, 1998, discloses a tire pressure control system wherein a tire pressure control device is assigned to each tire of the motor vehicle. At regular intervals, a tire pressure control device transmits a measured pressure signal together with an individual identifier to a central unit. Because of the transmission of an individual identifier, the situation is avoided that the data, which are transmitted to the central unit, are, for example, mistaken for data which are transmitted by another motor vehicle. In the central unit, value pairs of the form (identifier of the tire pressure control device/wheel position) are stored for each wheel of the motor vehicle so that by a corresponding comparison in the central unit, a conclusion can be drawn as to which identifier with the pressure signal corresponding thereto is transmitted from which wheel position of the motor vehicle. A deviation of the transmitted pressure signal from a pregiven value at a wheel position is displayed to the driver of the motor vehicle by the central unit so that the driver can initiate suitable measures.
The embodiments show that the tire pressure control system, which is known from U.S. patent application Ser. No. 09/131,910, can only function without problems when the allocations (identifier of the tire pressure control device/wheel position) are correctly stored in the central unit. Correspondingly, a new allocation must be undertaken at least after each change of tires. In the above-identified patent application, this new allocation takes place in the known tire pressure control system as follows: each tire pressure control device is assigned an rpm sensor which is switched on for a first time interval. During the first time interval, a first defined angular position of the wheel (to which the rpm sensor is assigned) is determined from the signal of the rpm sensor. The individual identifier is transmitted by the tire control device to the central unit at a first time point t
1
at which the wheel assumes this first defined angular position. The same rpm sensor is later switched on for a second time interval during which the same defined angular position of the wheel is determined from the signal of the rpm sensor as in the first interval. The tire pressure control device transmits its individual identifier to the central unit at a second time point t
2
in which the wheel assumes this defined angular position. The central unit knows that the wheel (from which the individual identifier has been transmitted) has made an integer number of revolutions between the time points t
1
and t
2
. A check is now made in the central unit as to from which rpm sensor or from which wheel position an integer number of revolutions was transmitted between the time points t
1
and t
2
. The rpm sensors are sensors of a slip control system and are each fixedly mounted at a location. The corresponding wheel position is assigned in the central unit to the individual identifier transmitted from the tire pressure control device. The remaining tire pressure control devices of the motor vehicle are assigned to their wheel positions in the same manner.
A reliable allocation of the tire pressure control devices to the wheel positions in a tire pressure control system of a motor vehicle is possible with the method disclosed in U.S. patent application Ser. No. 09/131,910, filed Aug. 10, 1998. However, the tire pressure control system requires an rpm sensor in every tire pressure control device which drives up the cost of the system. Furthermore, the rpm sensors are a load on the batteries of the tire pressure control devices even though they are switched on only during short time intervals. In this way, the service life of the batteries is reduced so that the high service life of the batteries which is sought is realizable only with difficulty.
A tire pressure control system is disclosed in German patent publication 4,205,911 wherein a new allocation is carried out in that the intensity of the signals (transmitted by the individual tire pressure control devices) is measured by receivers with each receiver being permanently assigned to a corresponding one of the wheel positions and each signal transmitted from a pressure control device is allocated to the wheel position at which the highest signal intensity is generated. For example, the signal intensity of the tire pressure control device, which is located in the forward left tire, will be largest at the receiver which is allocated to the forward left wheel position so that a corresponding allocation can be determined. The respective allocations are stored in the central unit.
For the allocation method explained above, a receiver is needed at each wheel position of the motor vehicle whereby the costs of the tire pressure control system disclosed in German patent publication 4,205,911 are likewise increased.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method for allocating the tire pressure control devices to the wheel positions in a tire pressure control system of a motor vehicle which can be carried out with a cost-effective tire pressure control system.
The method of the invention is in the context of a tire pressure control system of a motor vehicle having a plurality of wheels at respective wheel positions. The method is for allocating tire pressure control devices of the tire pressure control system to the wheel positions of the motor vehicle during the operation of the motor vehicle. The system further includes: a central unit; the tire pressure control devices being assigned to corresponding ones of the wheels; each of the tire pressure control devices functioning to transmit an individual identifier to the central unit at time intervals; a plurality of rpm sensors assigned to corresponding ones of the wheels and the rpm sensors being fixedly mounted at respective ones of the wheel positions with the allocation of the rpm sensors to the wheel positions being known by the central unit; and, the central unit storing the allocation (identifier of the tire pressure control device/wheel position) for each of the wheels; the method including the steps of: causing one of the tire pressure control devices assigned to one of the wheels to transmit to the central unit, at any desired time point, its own individual identifier and a first lengthened high frequency signal, which extends over a first time interval I
1
; and, as a consequence of a rotation of the one wheel, the signal having an individual trace dependent upon the rotational angle of the one wheel and/or upon the time; causing the one tire pressure control device to transmit to the central unit, at any desired later time point, its own individual identifier and a second lengthened high frequency signal, which extends over a second time interval I
2
, the second lengthened high frequency signal having the same individual trace at least segmentwise as the first lengthened high frequency signal, the individual trace of the second lengthened high frequency signal being dependent upon time and/or the rotational angle of the one wheel; in the central unit, determining a first time point at which the one wheel assumes a desired relative angular position from the trace of the first lengthened high frequency signal; in the centra
Behrends Holger
Ernst Gerhard
Klodmann Wolfgang
Oldenettel Holger
Continental Aktiengesellschaft
McCall Eric S.
Ottesen Walter
LandOfFree
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