Communications: electrical – Land vehicle alarms or indicators – Internal alarm or indicator responsive to a condition of the...
Patent
1996-01-17
1999-10-05
Wu, Daniel J.
Communications: electrical
Land vehicle alarms or indicators
Internal alarm or indicator responsive to a condition of the...
340440, 3406861, 731465, B60C 2300
Patent
active
059631287
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a remote tire pressure monitoring system for vehicles. The system provides temperature-compensated and, in one embodiment, altitude-compensated tire pressure indications through transmission of radio frequency (RF) signals from tire mounted sensors to a central location on the vehicle. The system also incorporates the assignee's technology, as described in copending application No. PCT/US93/01995, filed Mar. 11, 1993, related, among other things, to a technique which enables the system to learn tire identification and position on a vehicle, without confusion from other vehicles that may be nearby. The disclosure of that copending application is expressly incorporated herein by reference.
BACKGROUND OF THE INVENTION
In the past there have been many attempts to provide tire pressure monitoring in vehicles. Numerous patents have issued which disclose various approaches. Earlier designs tended to be of an electromechanical nature, with large inductive coil mechanisms attached to the wheel and brake drum. These systems provided a high level of information, as to both tire pressure and tire temperature, on a continuous basis. However, high cost and installation difficulties made such systems unacceptable to the majority of mainstream car companies.
More recently, lower cost systems have been developed which provide a simple threshold pressure warning by means of a pressure switch, an internal power source, and a radio wave communication link from each wheel to a dashboard receiver and display. These systems are more attractive to car companies because of their low cost and ease of installation. However, these systems have a number of problems, including, inter alia, the ability to provide a long-lasting and reliable power source, the size and weight of the wheel unit, and mounting of the unit inside the wheel. Moreover, the information available in such systems has been limited to a single pressure threshold, typically 25 psi, which may or may not be compensated for changes in temperature which occur inside the tire. Also, such systems, some of which are not mounted internally of the tire, have been unable to compensate for changes in altitude, which can affect the performance of tire pressure monitoring systems.
SUMMARY OF THE INVENTION
In view of the foregoing, it is one object of the present invention to provide a system which gives continuous tire pressure information on a real time basis, as in the earlier coil type systems, but which utilizes the low-cost radio wave communication system of the more recent threshold based systems. As a result, the inventive system provides a high level of information, while maintaining low cost and relative simplicity, and thus will be more attractive to car manufacturers.
In one embodiment of the inventive system, each wheel unit is constituted by of a low profile enclosure mounted on the back of a conventional clamp-in tire valve on the inside of the wheel and tire. The enclosure houses an electronic unit comprising a battery, a pressure sensor, a roll (motion) switch, control electronics, and a radio transmitter. The entire assembly preferably is fully potted to protect the electronics from the environment. The overall size and weight are kept to a minimum; the entire enclosure is located inside the wheel drop center well, thus preventing tire fitting and tire removal problems.
The wheel units measure tire pressure and report the information to a dashboard receiver via radio wave communication. To conserve battery power, the pressure is sampled periodically, typically once every 10 seconds, while the vehicle is in motion. In addition, the RF signals are transmitted periodically, typically once every minute, again while the vehicle is in motion, provided the tire pressure is not changing rapidly. Rapid tire pressure changes (e.g. greater than 1 psi in 10 seconds) are detected in the course of the pressure measurements, and are reported immediately to the dashboard receiver via an RF transmission. This immediat
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Schrader-Bridgeport International, Inc.
Wu Daniel J.
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