Communications: electrical – Land vehicle alarms or indicators – Internal alarm or indicator responsive to a condition of the...
Patent
1994-12-19
1998-06-30
Hofsass, Jeffery
Communications: electrical
Land vehicle alarms or indicators
Internal alarm or indicator responsive to a condition of the...
340442, 340445, 731462, 731463, 731464, 731468, B60C 2300
Patent
active
057740488
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention is related to a valve having means for generating a wireless transmittable indicating signal in case of a pressure drop within vehicle tires. This valve is especially suited for tires of passenger cars, lorries, trucks and aircrafts.
In more detail, the invention is related to a valve having means for generating a wireless transmittable indicating signal due to a pressure drop (signal generating means) within vehicle tires, wherein the tire valve comprises a valve spud and a valve stem extending from said valve spud. The signal generating means is mounted on said valve spud at a valve spud side remote from said valve stem. Further, said signal generating means comprises a pressure sensing means, a transmitter means and a power supply means. A valve of said kind is known from U.S. Pat. No. 5,040,561. The pressure sensing means disclosed therewith comprises a reference pressure chamber being admittable with a desired tire pressure when the tire valve means is opened, and being closed pressure-tight when the tire valve means is closed. Said reference pressure chamber is partly defined by a deflectable diaphragm being provided with a movable switching member of a pneumatic-mechanic pressure switch. Whenever the switching contact is completed, the transmitter means will be activated and will emit an indicating signal indicating a pressure drop.
Typically the sensitivity of a pneumatic-mechanic pressure switch of said kind is not very high, because a deflection of the diaphragm requires significant pressure differences; typically a sensitivity lower than 0.3 or 0.4 bar may be not obtained. Whenever the diaphragm is made of a thin plastics or gum material, then there is a danger of a gradual gas diffusion through the diaphragm, which may cause a variation of the desired pressure adjusted within the reference pressure chamber. Further, there is a danger that the diaphragm may be displaced by substantial acceleration forces provided by the rotating wheel.
Recently miniaturized absolute-pressure sensors have been developed being formed like a semiconductor component and comprising a piezoresistive transducer or a transducer system having a capacitive bridge circuit. Absolute-pressure sensors of said kind generate an electric output (signal) which may be used for a modulation of a carrier frequency following an amplification and processing of said output signal. Absolute-pressure sensors of said kind may be held in an active status continuously or periodically or may be activated only in case of an inquiry signal or instruction. Frequently the reproducibility or consistency of an absolute tire pressure measuring by means of said absolute-pressure sensors provides problems, especially when considering the hard operating conditions of vehicle wheels, because said absolute-pressure sensors require a stabilized input voltage, a careful calibration of the off-set voltage and relatively constant operating conditions. Further, the telemetric transmission of a sensed absolute-pressure value requires some electronic expenditure.
Starting therefrom, it is a technical problem (object) of the present invention to provide a tire valve of the stated kind having a signal generating means including a pressure sensing means which senses the pressure within the vehicle tire by a miniaturized absolute-pressure sensor generating an electric output where the known problems regarding the reproducibility and the electronic expenditure have been reduced essentially. Especially, a tire valve of said kind is to be provided having a signal generating means being structured simple and robust, being adapted to sense the pressure within the tire at an accuracy of at least 0.1 bar and providing during a several years service time only a minimum power demand which may be provided easily by a conventional button cell.
SUMMARY OF THE INVENTION
Starting from a valve having means for generating a wireless transmittable indicating signal due to a pressure drop (signal generating means) within vehicle
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Alpha-Beta Electronics AG
Hofsass Jeffery
Mannaua Ashok
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