Detector of the inflation pressure of motor vehicle tires

Details Detector of the inflation pressure of motor vehicle tires Detector of the inflation pressure of motor vehicle tires

1987-08-06

1988-12-27

Shoop, Jr., William M.

Signals and indicators

Vehicle

Tire inflation or deflation

307 10R, 340 58, 731465, 200 6122, 200 6125, 116246, H01H 3526, B60C 2304

Patent

active

047932775

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a tire pressure detector for motor vehicles.
In a known construction of a tire pressure detector (DE-OS No. 32 43 854), a reference pressure chamber, which is made from a metal housing, is received in a housing enclosure of insulating material which is screwed into a threaded borehole of the wheel rim by means of a threaded projection. The reference pressure chamber is closed in the front toward the tire by means of a switching diaphragm which cooperates with a contact pin in the reference pressure chamber and with an oscillating circuit in the housing enclosure which is connected to the contact pin. The fastening of the reference pressure chamber in the housing enclosure is effected by means of a metal sleeve which is inserted in the housing enclosure in a form-locking manner and which annularly encloses the reference pressure chamber in the area of the switching diaphragm by means of an inwardly curved rim. The housing enclosure of the tire pressure detector is meant to prevent the heat from reaching the reference pressure chamber when the wheel rim is heated and to prevent the gas which is enclosed in the reference pressure chamber from being heated to a greater extent than the compressed air in the tire.
The known solution has the disadvantage that the housing enclosure, which is made of insulating material, can easily be knocked off by the impact of a stone, which leads to a rapid loss of pressure in the tire and, accordingly, to an increased risk. Another disadvantage resides in that the metal sleeve in the housing enclosure clamps the switching diaphragm at the outer border so that tension can occur at the switching diaphragm, which impairs the switching accuracy of the tire pressure detector in an unwanted manner. It is known in another switch construction of the tire pressure detector (DE-OS No. 31 08 998) to weld the switching diaphragm on the outer rim of the reference pressure chamber so that it lies flat without tension; but the metallic reference pressure chamber in the housing enclosure of the tire pressure detector, which housing enclosure is made of insulating material, is held in this location only by means of a torus which can no longer withstand the centrifugal forces to a sufficient extent during temperature fluctuations and high speeds. Under unfavorable circumstances, the reference pressure chamber chan loosen and be thrown out of the housing enclosure into the interior of the tire, which can lead to a destruction of the tire.
The present solution attempts to achieve a secure mechanical fastening of the reference pressure chamber in the housing of the tire pressure detector while simultaneously achieving a favorable thermal communication with the air in the tire.


SUMMARY OF THE INVENTION

It is an object of the present invention to provide a tire pressure detector, which, has the advantage that by means of using a metallic detector housing and by means of enclosing the collar of the reference pressure chamber, the latter can no longer be pressed forward or back. Moreover, the housing chamber of the tire pressure detector, which housing chamber is open in the direction of the compressed air in the tire, is closed toward the back by the housing so as to be sealed against pressure in order to prevent the compressed air in the tire from escaping when the tire pressure detector is damaged by a blow from a stone. It is another advantage of this invention that a thermal uncoupling of the reference pressure chamber from the metallic detector housing, and accordingly from the temperature of the wheel rim, is achieved by means of enclosing the collar of the reference pressure chamber by means of the supporting ring and the spacing ring, each of which is made of insulating material. Moreover, the radial collar, which is formed on at the outer circumference of the reference pressure chamber, ensures that the switching diaphragm is no longer clamped and, accordingly, can be kept free of mechanical tensions; this leads to an increased accurac

REFERENCES:
patent: 3985984 (1976-10-01), Cappa
patent: 4211901 (1980-07-01), Matsuda et al.
patent: 4300118 (1981-11-01), Matsuda et al.
patent: 4435625 (1984-03-01), Buschmid et al.
patent: 4701742 (1987-10-01), Ruehr

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