Detector of inflation pressure of tires of a vehicle

Details Detector of inflation pressure of tires of a vehicle Detector of inflation pressure of tires of a vehicle

1987-08-07

1988-12-13

Woodiel, Donald O.

Measuring and testing

Tire, tread or roadway

Tire inflation testing installation

340 58, B60C 2304

Patent

active

047901799

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a tire pressure detector for motor vehicles according to the generic part of the main claim. In a known tire pressure detector (DE-OS N 31 08 998), a reference pressure chamber comprising a diaphragm is sealed relative to the space in the vehicle tire which is under air pressure, wherein the diaphragm simultaneously forms the movable part of a mechanical switch which opens when the checked allowable minimum air pressure in the tire is exceeded. The switch is located in an oscillating circuit with a capacitor and a coil which is arranged at the outwardly directed end of the tire pressure detector on a coil body consisting of insulating material. The coil, which revolves with the tire pressure detector, cooperates with a stationary signal receiver, past which it revolves once in every complete revolution of the wheel, and, in so doing, is penetrated by a high-frequency oscillation of the receiver. When the oscillating circuit of the tire pressure detector is closed, i.e. when the tire pressure is sufficiently high, this oscillation is attenuated each time the tire pressure detector runs past. This attentuation is detected in an evaluating circuit, which is connected with the stationary signal receiver, and an alarm signal is triggered in the evaluating circuit only when it is absent during driving.
It is known, in addition, from DE-OS No. 34 13 209 to construct the stationary signal receiver from a shell-type core with a coil arranged therein, its open side being directed toward the coil of the revolving tire pressure detector.
Since, on the one hand, the energy of the high-frequency oscillation provided by the stationary signal receiver is limited and, on the other hand, the dimensioning of the tire pressure detector must be kept as small as possible, it was necessary in the known solutions to achieve the smallest possible air gap of a few millimeters between the signal receiver and the tire pressure detector. This means a high assembly cost with special adjustment of the individual signal receivers. Moreover, because of imbalance, manufacturing tolerances and the like, the desired small air gap cannot be achieved for longer operating periods with increasing wheel diameters in heavier vehicles.


SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved pressure detector for vehicle tires.
The present solution attempts to increase the distance of detection by means of an improved coupling of the highfrequency oscillation between the signal receiver and the revolving coil of the tire pressure detector.
The tire pressure detector according to the invention has the advantage that the magnetic coupling can be considerably improved over the known constructions with the same dimensioning of the tire pressure detector by means of the arrangement of the coil on a middle limb of a plate-shaped ferrite core. This results in the additional advantage of a larger possible air gap between the signal receiver and the revolving coil and, accordingly, a larger air gap tolerance and simpler assembly of the signal receiver.
It is particularly advantageous with respect to a good magnetic coupling if the stationary receiver coil is also arranged on a middle limb of a plate-shaped ferrite core. In order to fasten the ferrite core with the coil in the tire pressure detector it is also advantageous if the middle limb comprises an axially continuous opening at which the ferrite core is received by a magnetically inert supporting part in the housing of the tire pressure detector.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connecton with the accompanying drawings.


BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a tire pressure detec

REFERENCES:
patent: 4148008 (1979-04-01), Lusk et al.
patent: 4180795 (1979-12-01), Matsuda et al.
patent: 4254398 (1981-03-01), Matsuda et al.

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