Communications: electrical – Land vehicle alarms or indicators – Internal alarm or indicator responsive to a condition of the...
Utility Patent
1998-04-20
2001-01-02
Pope, Daryl (Department: 2736)
Communications: electrical
Land vehicle alarms or indicators
Internal alarm or indicator responsive to a condition of the...
C340S438000, C340S445000, C073S146200
Utility Patent
active
06169480
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for monitoring the air pressure on the tires of a vehicle.
2. Discussion of the Prior Art
A device of this kind has been known from DE 41 33 993 C2. The known device comprises a pressure measurement sensor and a transmitter that are integrated in the valve cap of the associated wheel. The receiver preferably consists of a portable remote control which is taken to the respective wheel to activate the electronic circuit contained in the valve cap in order to carry out a remote inquiry for the tire pressure measured. In this case, the tire pressure can be monitored only at intervals, with the vehicle in a stationary condition; performing an inquiry while driving is not possible. However, DE 41 33 993 C2 already discloses the possibility, instead of arranging the transmitter and receiver devices in a portable remote control unit, to arrange them on the chassis of the vehicle, near the wheel, and to provide indication means on the instrument panel. In any case, signals representative of the air pressure determined by the pressure measurement sensor are sent by wireless means to an evaluation and indicating device by the transmitter arranged at the wheel.
A similar device has been known also from DE 41 33 999; however, in this case the pressure measurement sensor and the transmitter are not arranged in the valve cap, but rather on the valve base.
Mounting a transmitter and receiver device in the neighborhood of each wheel, for inquiring the air pressure prevailing in the tire, is rather costly.
SUMMARY OF THE INVENTION
Now, it is the object of the present invention to teach how the structure and installation of a device for monitoring the tire pressure of vehicles can be simplified and made less costly.
An antenna associated to each wheel is connected to an electronic receiver and evaluation circuit. According to the invention, no separate electric line has to be run for the antenna; rather, the antenna makes use of an electric wire belonging to another monitoring device allocated to the same wheel, specifically a device monitoring the brake lining wear on the respective wheel or an antilock system or a control device that serves to avoid wheel slip on the driven wheels. This has the effect to reduce the amount of circuitry, the susceptibility to failure, and reduces the installation and wiring expense because one electric line, which is anyway guided to the neighborhood of each wheel to be monitored, can be used for several purposes at the same time. This last-mentioned aspect is of particular importance because as the number of functions of the vehicle, that are monitored, controlled and activated by electric means, has risen considerably over the last few years, the amount of wiring increased in parallel so significantly that it is already now very difficult to accommodate the cabling harnesses, that get continuously thicker and thicker, in the cavities of the vehicle body. If one electric line is used for several purposes, as provided by the present invention, the amount of wiring is not increased by the transmission of the signal from the transmitter to the receiver and the evaluation circuit although a separate antenna is allocated to each wheel.
The line must of course be suited as antenna for the intended frequency range. The possible frequencies for the transmission of signals lie in the range of a few hundred mega-hertz, specifically 433 MHz. As the frequencies used for antilock systems and slip control systems normally do not exceed a few kilo-hertz, and as brake lining wear indicators also use low frequencies or direct current, the high-frequency signals of the tire pressure monitoring system and the low-frequency signals of the remaining monitoring systems can be transmitted, and later separated, via a common wire without any difficulty.
Preferably, the electric line consists of a coaxial cable, from which the outer conductor is removed in the neighborhood of the associated wheel over part of its length, specifically over a length corresponding to a quarter-wave length of the tire pressure signal to be transmitted—i.e. 17 cm (6.6 inches) for a frequency of 433 MHz.
Another possibility consists in modifying the sensors, that are used for the antilock system, the slip control system or for the brake lining wear indicator, in such a way as to render them serviceable as antenna for the tire pressure monitoring device. This also has the result that the feed lines leading to the other monitoring devices are used twice, being used simultaneously by the tire pressure monitoring system.
Particular advantages can be achieved in each of the before-described cases if instead of providing a separate receiver circuit for each wheel, a common receiver and evaluation circuit is provided at a central position in the chassis. This helps once more reduce the amount of circuitry, the susceptibility to failure and the cost.
However, there is also the possibility to use as antenna cables of any other lines, that do not lead to a monitoring device, provided they run sufficiently close to the respective wheel, for example, wires supplying a lamp or any other electric consumer.
REFERENCES:
patent: 5808190 (1998-09-01), Ernst
patent: 5924055 (1999-07-01), Hattori
Kessler Ralf
Normann Norbert
Schulze Gunter Lothar
Uhl G{umlaut over (u)}nter
Doduco GmbH
Orum & Roth
Pope Daryl
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