Communications: electrical – Land vehicle alarms or indicators – Internal alarm or indicator responsive to a condition of the...
Reexamination Certificate
2002-07-24
2004-02-10
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Land vehicle alarms or indicators
Internal alarm or indicator responsive to a condition of the...
C340S442000, C340S444000, C340S445000, C340S446000, C073S146200, C073S146800
Reexamination Certificate
active
06690271
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a device for monitoring at least one parameter for a plurality of vehicle wheels.
The monitoring of parameters of a vehicle wheel, for example, of the tire pressure or the temperature of the tire, plays a decisive role for the safety of a vehicle or of the driver of a vehicle. To be able to dispense with manual checking of such parameters, devices have been developed with which it is possible to register important parameters of vehicle wheels automatically and display them, for example, by appropriate display devices on the dashboard. As it is generally desired not only to display the parameters but also to indicate a uniquely defined assignment between the displayed parameters and the position of the respective wheel, it is necessary to configure such a device to retain the assignment, or to re-initialize it, after a wheel is changed.
For such a purpose, existing in the prior art is an assignment of each detector device respectively disposed on a wheel to a receiver unit that is provided in the vicinity of the respective wheel position. As such, it is possible to detect the signal of the respectively adjacent detector device by reference to the intensity of the signals received through a receiver unit, by selecting the signal with the greatest intensity. It is assumed here that the detector devices of the wheels of a vehicle transmit with substantially the same transmitting power so that the signal of the respectively directly adjacent wheel or of the adjacent detector device has the greatest signal intensity at the reception location.
However, a disadvantage with such a device is that a receiver device is necessary for each wheel, the received signal of such a receiver device then having to be conducted in line-bound fashion to a central evaluation and control unit or directly to a display unit.
European Patent Application EP 0 806 306 A, corresponding to U.S. Pat. No. 5,808,190 to Ernst, discloses an air-pressure monitoring system in which the assignment of the wheel positions to the air-pressure monitoring devices that are disposed on the wheels is made possible by the fact that a further parameter is registered for each wheel with the air-pressure monitoring devices and with, in each case, a further measuring device assigned to the wheels. The parameter may be, for example, the rotational speed of the wheel. The air-pressure monitoring devices, thus, transmit not only measured values for the air pressure but also measured values for the further parameter to a central unit. As measured values are also transmitted from the further measuring devices to the central unit for the same further parameter, the central unit can make an assignment of an air-pressure monitoring device to a wheel position by comparing the measured values for the further parameter, if the measured value supplied by the respective air-pressure monitoring device for the further parameter coincides sufficiently precisely with the respective measured value of the parameter of a further measuring device. This is because the further measuring devices are disposed fixedly on the vehicle (not on the wheel), and, thus, remain continuously assigned to a specific wheel position.
A disadvantage with such a device is the additional expenditure on the two sensors for registering the further parameter. Even if the further parameter can be registered with the sensor that is provided in any case on the wheel for registering the air pressure, a further sensor that is provided fixedly on the vehicle is necessary for each wheel in order to register the further parameter.
Finally, European Patent Application EP 0 931 679 A discloses a method for assigning the wheel position of a motor vehicle in which the transmission signals of transmitter units assigned to the wheels are transmitted to a central receiver and evaluation unit, and in which the different characteristic influences of the individual transmission paths on the respective reception signal as the wheels rotate are widened in order to assign the signals to the wheel positions. For such a purpose, the envelope curve of the reception signal that is amplitude-modulated by the time variants including changes in the transmission properties is compared with stored signatures. However, the relatively complex registration and evaluation of the envelope curve is a disadvantage here.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a device for monitoring at least one parameter for a plurality of vehicle wheels that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that makes it easily possible to assign the detector units disposed on the wheels to the wheel positions with the necessary reliability and, at the same time, to achieve the lowest possible expenditure on hardware.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a device for monitoring vehicle wheels, including detector units disposed at the wheels, each detector unit having a sensor for registering at least one parameter of a wheel and a transmitter unit transmitting information regarding the at least one parameter, each of the detector units transmitting, with the transmitter unit, the information in a modulated signal over a wireless transmission path, a central evaluation and control unit having a receiver unit receiving the information from the transmitter unit and demodulating the signal, the control unit evaluating the information from the detector units, and generating signals dependent thereon, the control unit having a normal operating mode and an assignment mode and, in the normal operating mode each detector unit transmitting, as the information, an information item relating to the registered parameter and a wheel identifier uniquely defined for each of the wheels and the control unit evaluating the wheel identifier and the information relating to the registered parameter from the signal demodulated by the receiver unit and assigning a wheel position to each information item relating to the registered parameter from the identifier and from a stored assignment information item, in the assignment mode each the transmitter unit transmitting, as the information, at least the wheel identifier, the receiver unit generating a signature signal representing a measure for an average signal power of the received modulated signal, a duration of the signal transmitted by the transmitter unit of the detector units being shorter in comparison with a time required for a complete revolution of a wheel at a maximum speed of the wheel, the control unit registering the signature signal derived from each received signal and assigning an angle information item to the respective value of the signature signal, the control unit acquiring the angle information item from one of a time interval between one of the signature signals and the signature signals and a fixed time, and the group consisting of a velocity of the vehicle, a parameter proportional to the velocity of the vehicle, and an angle information item relating to an angular position of the respective wheel fed to the control unit, and the control unit assigning to the wheel position the wheel identifier transmitted by each of the detector units by comparing one of registered values and an information item determined therefrom with a stored signature information characteristic of each the wheel position, and storing the angle information item as an assignment information item.
The invention is based on the recognition that when data is transmitted by a preferably phase-modulated or frequency-modulated signal, the signal power occurring at the reception location of a central evaluation and control unit is influenced by the properties of the transmission path between the detector unit disposed on a wheel and the evaluation and control unit. The properties of the transmission path are determined here, on one hand, by the angular position of the wheel, and, t
Fischer Martin
Füssel Dominik
Prenninger Martin
Greenberg Laurence A.
Hofsass Jeffery
Locher Ralph E.
Previl Daniel
Siemens Aktiengesellschaft
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