Thermal measuring and testing – Temperature measurement – Combined with diverse art device
Patent
1990-01-29
1991-12-10
Cuchlinski, Jr., William A.
Thermal measuring and testing
Temperature measurement
Combined with diverse art device
374185, 374183, 73146, 731465, G01K 114, G01K 700, B60C 2320, B60C 2304
Patent
active
050712594
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a sensor for determining the pressure and temperature of the air in a vehicle tire and which comprises at least one pressure and temperature sensor element arranged in a front opening of a sensor housing communicating with a tire interior, and connected with an electrical circuit.
WO 87/035 45 discloses a diaphragm box carrying an electrical contact inserted in an insulating housing screwed in a threaded hole of a wheel rim. The diaphragm box is accordingly thermally decoupled from the wheel rim, so that it takes on the temperature of the tire air, and the reference pressure in the diaphragm box is not influenced by the rim temperature. In monitoring the tire pressure, a temperature-dependent change in the tire pressure is compensated for by a corresponding change in the reference pressure in the diaphragm box by coupling the latter with the temperature of the tire air, so that when the tire pressure is too low, the electrical contact triggers a switching process and, accordingly, a warning signal which is transmitted in a wireless manner from the revolving sensor to an evaluating circuit which is stationary with respect to the vehicle.
WO 87/001.28 discloses semiconductor sensors which measure the absolute air pressure in the tire and the temperature independently of one another, arranged on an insulating plate which is received in the center of a metallic sensor housing. The housing is to be inserted into a corresponding opening of the wheel rim. In so doing, the temperature of the rim is transmitted to the sensor housing and reaches the sensors partially because of heat conduction via the insulating plate and partially due to heat radiation. Since the temperature of the wheel rim can diverge considerably from the temperature in the tire because of the proximity of the brake, but also because of the head wind, falsified values can be determined because of this thermal coupling of the sensors with the wheel rim and can trigger a false alarm and, in critical cases, can even suppress a necessary warning.
SUMMARY OF THE INVENTION
The object of the invention is a temperature sensor having a good thermal coupling with the temperature of the tire air. The object of the invention is achieved by arranging at least one temperature sensor element on an insulating foil for monitoring the mass of the tire inflating gas and which is surrounded with tire air, and connecting the sensor element with the sensor circuit via conductor path of the foil, the sensor element being insulated from the sensor housing. The mass of the tire inflation gas present in the tire is monitored in that the tire pressure and the inflation gas temperature are continuously measured independently of one another. An advantage of the sensor according to the invention consists in that the thermal resistance of the temperature sensor for the tire inflation gas is smaller by several orders of magnitude than that for the rim with the sensor according to the invention. Accordingly, the sharp differences in temperature which can occur between the wheel rim and the tire air no longer lead to the falsification of the measurements, as was previously the case. Thus, it is possible to effect a correction of the measured value of the tire pressure from the exact temperature measurement with the electronic circuit in the sensor in such a way that the mass of the tire inflation gas is continuously monitored and a warning signal is triggered when the inflation of the tire is too low.
In order to communicate the tire air temperature with the temperature sensor, it is particularly advantageous if the foil with the temperature sensor is stretched over a perforation or a central opening on the inside of a cover cap which closes the housing opening toward the tire and at which a particularly favorable whirling of the tire air occurs during travel. In order to prevent damage to the foil with the temperature sensor when mounting or removing the tire, the foil is advisably clamped between two profiled sheet metal
REFERENCES:
patent: 3807226 (1974-04-01), Williams
patent: 4597286 (1986-07-01), Aguglia
patent: 4703650 (1987-11-01), Dosjoub et al.
patent: 4723445 (1988-02-01), Ripley et al.
patent: 4891973 (1990-01-01), Bollweber et al.
patent: 4893110 (1990-01-01), Hebert
patent: 4918423 (1990-04-01), Fukuyama et al.
Dorfler Reiner
Hettich Gerhard
Metzger Kurt
Cuchlinski Jr. William A.
Gutierrez Diego F. F.
Robert & Bosch GmbH
Striker Michael J.
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