Measuring and testing – Tire – tread or roadway – Tire inflation testing installation
Patent
1998-08-06
1999-10-12
Felber, Joseph L.
Measuring and testing
Tire, tread or roadway
Tire inflation testing installation
731463, 116 34R, 340447, B01C 2302
Patent
active
059658088
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for operating devices on wheels having pneumatic tires to signal the tire pressure. A method of this kind is known from DE 43 03 583 A1. This document discloses d device having a device, arranged in the valve of the pneumatic tire, for generating a wirelessly transmittable pressure decrease indication signal, having a battery as power source, having a preferably semiconducting piezoresistive pressure sensor, having an analog-digital converter for digitizing the pressure signal obtained from the pressure sensor, having a memory for storing the pressure signal, having a comparator which compares the pressure signal with a previously stored comparison pressure signal, having a transmitter, and having a timing switch which activates the device from time to time and otherwise keeps it switched off in order to save power. The analog-digital converter, the memory, the comparator, and the timing switch are preferably realized in a module with a microprocessor which compares the pressure signal supplied by the pressure sensor with the previously stored comparison pressure signal, generates a signal if the deviation of the pressure signal from the comparison pressure signal exceeds a threshold value, and then activates a transmitter which thereupon transmits by radio, to a receiver arranged in the vehicle (in particular in the region of the dashboard) and having an analysis circuit and indicating unit, an information element concerning the deviation that has been ascertained; said receiver processes the information element and indicates to the driver the pneumatic tire in which the air pressure deviates significantly from the comparison pressure. The reference pressure of the pneumatic tire is stored in stable fashion, as the comparison pressure, each time the air pressure is checked with the aid of an external gauge at a filling station, and is set to its reference pressure by means of a compressed air source. For this purpose, the movement of the valve plunger is automatically monitored, for example by means of a magnet attached to the valve plunger which in turn actuates a magnetic switch when the valve plunger moves. When the device detects a movement of the valve plunger, the tire pressure measured thereafter is stored as the comparison pressure (reference pressure). Prior to initial use in a pneumatic tire, a reference pressure can be defined for and entered into the monitoring device by the manufacturer.
The practical applicability of a device of this kind for tire pressure monitoring depends on the fact that the device uses so little power that it is can operate for several years without a battery change. The transmitter has the highest power consumption. In the case of the known device, it is activated only if the deviation of the measured tire pressure from the reference value exceeds a predefined threshold value. Otherwise the pressure is measured not continuously but rather only at regular intervals, for example every 3 or 4 seconds, and compared with the reference value which is an absolute value.
Automobile manufacturers require, for such electronic monitoring devices which are preferably provided on the valve of vehicle wheels, a service life of at least 5 years without battery replacement. A service life on this order can now be approximately attained with modem batteries and the use of integrated circuits having a power consumption of less than 1 microampere. Difficulties result, however, if the electronic tire pressure monitoring devices sit in storage for some time before they are used on a vehicle. The storage time can range from a few weeks to two years, in particular in the accessories and spare-parts market. Since the electronic tire pressure monitoring device nevertheless becomes active as soon as the battery is inserted by the manufacturer, the maximum possible operating time on the vehicle, as determined by the battery service life, is shortened by a time equivalent to the storage time.
It is the object of the present invention to counteract this shortening
REFERENCES:
patent: 5054315 (1991-10-01), Dosjoub
patent: 5109213 (1992-04-01), Williams
patent: 5231872 (1993-08-01), Bowler et al.
patent: 5285189 (1994-02-01), Nowicki et al.
patent: 5656993 (1997-08-01), Coulthard
Normann Norbert
Schulze Gunter
Uhl Gunter
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