Data processing: measuring – calibrating – or testing – Measurement system – Pressure
Reexamination Certificate
2000-04-17
2002-09-03
Hilten, John S. (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Pressure
C073S146500, C116S03400R, C340S442000, C340S444000
Reexamination Certificate
active
06446023
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for monitoring the air pressure of the tires of a motor vehicle utilizing a tire pressure control system. The control system has air pressure control devices on respective ones of the wheels of the motor vehicle and a central unit. The method includes method steps wherein each tire pressure control device measures the air pressure of the tire assigned thereto at time intervals; each tire pressure control device transmits a data transmission to the central unit at time intervals with the data transmission containing at least the measured air pressure and an individual identifier characterizing the tire pressure control device and a transmission pause takes place between two sequential data transmissions of a specific tire pressure control device; and, the central unit compares the transmitted air pressure with an air pressure stored therein and generates a warning signal when the transmitted air pressure deviates beyond the stored air pressure by a pregiven amount.
The invention also relates to a motor vehicle having a tire pressure control system with which the method can be carried out.
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.
German patent publication 4,205,911 discloses a method for carrying out the measurement of the air pressure of the tires of a motor vehicle utilizing a tire pressure control system of the kind mentioned above. The tire pressure control system includes tire pressure control devices assigned to corresponding ones of the tires of the motor vehicle and these control devices transmit a high-frequency signal at regular time intervals to a central unit. The high-frequency signal includes at least a measured pressure signal and an individual identifier. The data, which are transmitted to the central unit, cannot be mistaken for data which are, for example, transmitted from another motor vehicle because of the transmission of an individual identifier. 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 a conclusion can be drawn in the central unit via a corresponding comparison as to which identifier is transmitted with the corresponding pressure signal 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 by the central unit to the driver of the motor vehicle so that the driver can initiate appropriate measures.
The tire pressure control system disclosed in German patent publication 4,205,911 affords the advantage that the tire pressure control devices are mounted directly on the wheels of the motor vehicle and, in this way, the air pressure in the tires can be measured directly and can be transmitted contactlessly by a high-frequency signal to the central unit. A specific frequency of 434 MHz is used at the present time for the high-frequency signal. This frequency is also used by other transmitters such as weather stations which have, in part, a very high transmitting power. If a motor vehicle, which is equipped with a tire pressure control system of the above type, is in the vicinity of such a transmitter, then it can occur that the high-frequency signals, which are transmitted by the tire pressure control devices, are superposed with the high-frequency signals transmitted by the “disturbing” transmitter so that, in the central unit, the data, which are transmitted by the tire pressure control devices, can no longer be received without error or not at all. This causes the situation that the monitoring of the air pressure of the tires of the motor vehicle is no longer reliably possible in the region of the disturbing transmitter.
In addition to the above-described disturbance, additional disturbances can occur in the tire pressure control system. The tire pressure control devices are supplied by batteries whose service life is limited so that a tire pressure control device can become disabled after the service life of a battery has expired and the air pressure of the corresponding tire of the motor vehicle can no longer be monitored. Finally, component defects can occur in the tire pressure control system which lead to the disablement of one or more tire pressure control devices.
In summary, it can be seen that short-term disturbances (caused by a disturbance transmitter) as well as long-term disablements can occur which require maintenance (for example, caused by a run-down battery) in a tire pressure control system such as disclosed in German patent publication 4,205,911. A driver of a motor vehicle no longer takes a warning seriously if a disablement is displayed for each short-term disturbance of the tire pressure control system and the driver later determines that the system functions without error (for example, when the driver has left the region of the disturbing transmitter). If then a long-term disablement occurs in the tire pressure control system (for example, because of a run-down battery), the driver of the motor vehicle could fail to consider a corresponding warning and continue to drive over a long time span with a damaged tire pressure control system. In this case, the safety of the motor vehicle is reduced.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method for monitoring the air pressure of the tires of a motor vehicle utilizing a tire pressure control system wherein erroneous indications of a disturbance of the operation of the system can be avoided to the greatest extent possible. It is also an object of the invention to provide a motor vehicle having a tire pressure control system with which the method can be carried out.
The method of the invention is for monitoring the pressure of the tires of a motor vehicle utilizing a first tire pressure control system which includes a central unit and a plurality of tire pressure control devices on corresponding ones of the wheels of the motor vehicle for respective ones of the tires. The method includes the steps of: utilizing each one of the tire pressure control devices to measure the air pressure in the tire corresponding thereto at time intervals; causing each one of the tire pressure control devices to transmit a data transmission to the central unit at time intervals with the data transmission containing at least the measured air pressure and an individual identifier characterizing the one tire pressure control device and with a transmission pause being present between two sequential data transmissions of a specific one of the tire pressure control devices; monitoring each of the transmission pauses in the central unit which elapses after the receipt of a data transmission which is transmitted by a specific one of the tire pressure control devices; monitoring the air pressure of the tires of the motor vehicle utilizing a second tire pressure control system at least when at least one of the transmission pauses exceeds a pregiven first limit value; comparing the transmitted air pressure to an air pressure stored in the central unit; and, causing the central unit to generate a warning signal when the transmitted air pressure deviates from the stored air pressure beyond a pregiven amount.
A transmission pause, which is present between two sequential data transmissions of a specific tire pressure control device, is defined here
Cherry Stephen J.
Continental Aktiengesellschaft
Hilten John S.
Ottessen Walter
LandOfFree
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