Multiplex communications – Communication over free space – Signaling for performing battery saving
Reexamination Certificate
1998-08-27
2002-10-22
Chin, Wellington (Department: 2664)
Multiplex communications
Communication over free space
Signaling for performing battery saving
C370S347000, C455S343200
Reexamination Certificate
active
06469989
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for transmitting data in a data transmission system which includes a receiver which is from time to time in a stand-by mode and from time to time in a data-receive mode. The receiver can be switched by a switch-on signal from the stand-by mode into the data-receive mode. The data transmission system also includes at least one transmitter which transmits data to the receiver at time intervals. The receiver is in the data-receive mode during data transmission. The invention also is directed to a data transmission system for carrying out the method of the invention.
BACKGROUND OF THE INVENTION
Methods of the kind described above for transmitting data in a data transmission system are known and are applied, for example, in air pressure control systems. Such air pressure control systems are built into a motor vehicle and comprise essentially a central unit and air pressure control devices. Each of the pressure control devices is assigned to a corresponding one of the wheels of the motor vehicle. With the aid of the air pressure control devices, the air pressure in the corresponding tires of the motor vehicle is detected and the air pressure control devices transmit a data message to the central unit at time intervals. Each data transmission includes an individual identifier in addition to the measured air pressure. With the aid of the individual identifier, a check is made in the central unit as to from which wheel position the data transmission was transmitted. In the central unit, it is, for example, stored that the individual identifier III is transmitted from the wheel position “forward left”.
The central unit compares the transmitted air pressure values to stored desired air pressure values and a warning is transmitted to the driver of the vehicle when the measured air pressure deviates from the measured desired air pressure by an amount greater than a pregiven quantity. If no announcement is sent to the driver, then this is an indication that the correct air pressure is present in all tires of the motor vehicle.
The measurement of the tire air pressure and the announcement of an incorrect tire air pressure is especially important during travel of the motor vehicle. However, it is likewise important that an announcement is made to the driver when starting the vehicle that the correct air pressure is present in all tires and that the driver may commence driving without danger. The air pressure control devices also measure the air pressure in the tires at time intervals when the vehicle is at standstill and transmit this information to the central unit where the air pressure is checked as to correctness. When the motor vehicle is started, the central unit can reliably indicate to the driver, on the basis of the last-transmitted values, whether the air pressure in all tires of the motor vehicle assumes the correct value. From this, it follows that the central unit must be able to receive the data transmissions of the air pressure control devices even at standstill of the motor vehicle. For this purpose, the central unit must be supplied with energy. At standstill of the motor vehicle, this energy is made available by the vehicle battery which, as a consequence of a longer standstill, is possibly loaded until completely discharged.
Data transmission systems of the above-mentioned type are known wherein the energy consumption of the receiver can be minimized. These data transmission systems contain, for example, an electronic ignition key (transmitter) which sends out a signal having an individual identifier to the receiver in the door of the motor vehicle. The receiver initiates opening of the door if the individual identifier, which is transmitted from the key, belongs to the corresponding motor vehicle. In a data transmission system of this kind, the receiver is in general in a stand-by mode wherein it can receive a base signal from the transmitters, that is, from the ignition keys. When a base signal is received, an amplifier circuit is switched on in the receiver and this amplifier circuit checks whether the received base signal exhibits a vehicle-typical character. If this is the case, then a downstream data evaluation unit in the receiver is switched on which compares the individual identifier transmitted from the ignition key to the individual identifier stored in the receiver and, when there is coincidence, an opening of the door is initiated. The battery supplies the central unit with energy and is sparingly used because the energy-consuming amplifier circuit as well as the energy-consuming data evaluation unit are switched on only as needed.
The method explained in the last paragraph for transmitting data in a data transmission system is not transferrable to air pressure control systems because, as initially mentioned, data is continuously transmitted from the transmitters of an air pressure control system even at standstill of the motor vehicle. If a vehicle equipped with a corresponding air pressure control system is parked, for example, in a large parking lot, then at least the amplifier circuit in the central unit is switched on continuously when applying the above-mentioned method because the central unit would very often receive the base signal from the motor vehicles standing in the immediate area. The energy consumption of the central unit therefore cannot be significantly reduced. Furthermore, it can be determined that the base signal must be transmitted from the transmitters over a certain time span so that the amplifier circuit in the central unit can be switched on. In this way, the battery of the transmitters is, in turn, greatly loaded.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method for transmitting data in a data transmission system wherein the energy resources of the receiver as well as the energy resources of the transmitters are used sparingly. It is a further object of the invention to provide a data transmission system with which the method of the invention can be carried out. The data transmission system should especially, but not exclusively, be suitable for use in air pressure control systems.
The method of the invention is for transmitting data in a data transmission system which includes: a receiver which is intermittently in a stand-by mode and intermittently in a data-receive mode; at least one transmitter for making a data transmission to the receiver at time intervals; and, means for supplying a switch-on signal to switch the receiver from the stand-by mode to the data-receive mode; and, the receiver being in the data-receive mode during the data transmission. The method of the invention includes the steps of: inputting a message to the receiver as to the time intervals at which the data transmissions are to be expected from the transmitter; on the basis of the message, determining the time point in the receiver at which the next data transmission can be expected from the transmitter measured from after receipt of the last data transmission; and, generating the switch-on signal in the receiver shortly before the time point at which the next data transmission is to be expected.
In the following, the term “data-receive mode” is intended to mean that mode wherein the receiver can receive and completely process the data transmitted by the transmitters. The phrase “shortly before the time point at which the next data transmission is to be expected, the switch-on signal is generated” is understood to mean that the time span between the time point, at which the switch-on signal is generated, and the time point, at which the next data transmission is to be expected, is significantly less (that is, at least by one order of magnitude less) than the time span between two data transmissions of a transmitter. It is further noted that the method for transmitting data in a data transmission system and the data transmission system is explained in connection with an air pressure control system. However, the method as well as the data transmission system can be transferred
Chin Wellington
Continental Aktiengesellschaft
Duong Frank
Ottesen Walter
LandOfFree
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