Communications: electrical – Land vehicle alarms or indicators – Internal alarm or indicator responsive to a condition of the...
Reexamination Certificate
1998-06-08
2001-02-27
Wu, Daniel J. (Department: 2736)
Communications: electrical
Land vehicle alarms or indicators
Internal alarm or indicator responsive to a condition of the...
C340S448000, C073S146500, C073S146800, C200S061220
Reexamination Certificate
active
06194999
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention deals with a device fitted on vehicles for monitoring the air pressure in the vehicle's tires.
2. Discussion of the Prior Art
In known devices for monitoring the air pressure in the tires of a vehicle, pressure sensors are arranged in the wheels and each pressure sensor is connected with a transmitter. Here, an antenna is positioned in the vicinity of each wheel and the antennas are connected with a common receiving and evaluating circuitry. The transmitters provided in the wheels are not synchronized with each other. Therefore, it is possible that the signal strings coming from the various wheels overlap at the input side of the receiving and evaluating circuitry, thereby preventing unambiguous evaluation. This difficulty has previously been resolved where the disclosed device for monitoring the tire pressure is provided with a pressure sensor and a transmitter, which are integrated in the valve cap of each wheel in the form of an electronic assembly. In order to obtain the measured tire pressure by remote scanning, a preferably portable remote control unit equipped with a transmitter/receiver combination is provided. This unit is deployed in the vicinity of the selected tire to activate and scan the electronic assembly. In this case the tire pressure can be monitored only from time to time when the vehicle is standing still, but not when it is moving. However, for the purpose of scanning the electronic assembly provided in the valve cap. It is known to provide transmitting and receiving devices which are not contained in a portable remote control unit but are fixed to the chassis of the vehicle in the vicinity of the wheel, as well as providing display devices on the dashboard. This is an expensive solution, since the signals which are emitted by the transmitter located in a particular wheel and which contain the air pressure determined by the pressure sensor, are each transmitted wirelessly to a separate transmitting and receiving device assigned to each wheel.
A similar device is disclosed has been disclosed where the pressure sensor and the transmitter are not located in the valve cap but at the valve spud.
It is also known to provide an assembly consisting of a pressure sensor and a transmitter at the valve spud of an air tire, whereby to each transmitter in a particular tire valve is assigned a tuned-in receiver in the vicinity of the vehicle's wheel.
SUMMARY OF THE INVENTION
The object of the invention on hand is to show that even a simple and easy to install device for monitoring tire pressure while the vehicle is moving as well as while standing still, is capable of evaluating signals unambiguously.
The rectifier provided according to the invention rectifies the branched-off signal. If the field strength of the signal is sufficiently strong, the rectified signal component is able to set an input of the microcomputer on HIGH which enables the microcomputer to assign the transmitted signal to a particular wheel. If signals transmitted from several wheels are overlapping or are transmitted simultaneously, several inputs are set on HIGH, in which case the signals are not evaluated, in order to avoid erroneous evaluation.
In the vicinity of each wheel, only an antenna is provided, and all antennas are connected with a common electronic receiving and evaluating circuitry. An antenna cable is required to connect the antenna in the wheel housing with the receiving circuitry which may be located anywhere in a central location in the vehicle chassis, for example, in the dashboard area. The antenna cables need not be installed individually, which would be an expensive undertaking, but instead can be combined with other cables which need to be installed in the vicinity of the wheel anyway, to form a cable harness which can be prefabricated.
It is especially advantageous if, instead of installing a dedicated antenna cable, an electric cable is used as an antenna which needs to be installed anyway and belongs to another monitoring device assigned to the same wheel, in particular, a device monitoring brake lining wear of the wheel in question, or an ABS system, or a type of control device which prevents driven wheels from slipping. This would minimize circuitry cost, susceptibility to breakdown, and reduce cabling cost, because of the multiple use of an electric cable installed to each wheel area. This latter point is particularly important, because in the past few years the number of vehicle functions monitored, controlled and operated has steadily increased making it more and more difficult to accommodate the ever increasing cable harness thickness in the chassis cavities. The multiple use of an electric line allows each wheel to have its own antenna without increasing the cabling cost for signal transmission from the transmitter to the receiving and evaluating circuitry.
Naturally the cable must be suitable as an antenna for the intended frequency range. The frequencies needed for transmission are in the range of several hundred MHz, especially 433 MHz. Since the frequencies customarily used for ABS and ASR applications are not more than a few kHz and the brake liner wear display is performed in the low frequency range or with direct current, the high frequency signals used for monitoring tire pressures and the low frequency signals used for other monitoring functions can be easily combined in and again separated from one common line.
A co-axial cable is preferably utilized as electric line. In the vicinity of each wheel this cable is stripped of the outer conductor over a portion of its length, in particular over the length corresponding to one quarter of the wave length of the signal transmitting the tire pressure; for a frequency of 433 MHZ, this length is 17 cm.
There is another possibility which is modifying the sensors utilized in the ABS system, in the in ASR control, or in the brake liner wear display, so that they become suitable as antennas for tire pressure monitoring. In this case the cables used for further processing are also made for dual use by utilizing them for tire pressure monitoring as well.
Cables other than those used in a monitoring function can also be used as antenna cables, provided they are installed in sufficient proximity to the particular wheel in question, for example, lines used to supply electricity to a light or any other electric device.
REFERENCES:
patent: 4947151 (1990-08-01), Rosenberger
patent: 5140851 (1992-08-01), Hettich et al.
patent: 5541574 (1996-07-01), Lowe et al.
patent: 5790016 (1998-08-01), Konchin et al.
patent: 5808190 (1998-09-01), Ernst
patent: 5825286 (1998-10-01), Coulthard
Kessler Ralph
Normann Norbert
Schrottle Michael
Schulze Gunter Lothar
Uhl Gunter
Dvorak & Orum
Wu Daniel J.
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