Pressure probe

Details Pressure probe Pressure probe

1989-08-18

1990-08-28

Woodiel, Donald O.

Measuring and testing

Tire, tread or roadway

Tire inflation testing installation

73754, 73756, 340442, B60C 2304, G01L 916

Patent

active

049515020

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention is based on a pressure probe for detecting the air pressure in a tubeless tire mounted on the rim of a motor vehicle.


BACKGROUND OF THE INVENTION

In known pressure probe of this type (DE-OS No. 35 23 774) the sensing elements are arranged in a corresponding recess on the front side of the probe housing in the outer area of a ceramic substrate on the side remote of the tire interior, wherein the gap between the substrate with the sensing elements and the housing recess is filled with a silicone gel. The silicone gel protects the sensing elements and their connections on the one hand and, on the other hand, enables the transmission of the air pressure in the tire and to the sensing elements.
However, under certain conditions measurement falsifications can occur at the sensing elements which are brought about by the stress states in the gel. Such stress states occur because of thermal expansion, centrifugal forces, etc.
It is attempted with the present invention to improve the measuring accuracy of such a pressure probe in that falsifications of measured values can be prevented to a great extent by means of covering the sensing elements.


SUMMARY OF THE INVENTION

The solution, according to the invention, with the characterizing features of the main claim has the advantage that inner stress states of the material covering the sensing elements can be prevented by means of using magnetic fluid. The measuring accuracy as well as the reproducibility and the hysteresis response of the pressure probe can be improved accordingly. In addition, the magnet arrangement ensures that the fluid is secured in the probe area against gravitational and centrifugal forces as well as against acceleration forces generally occurring at the vehicle. Moreover, the transmission of the air pressure to the sensing elements is not impaired by means of this.
A particularly advantageous solution consists in that the permanent magnet is embedded in a ring-shaped manner in the base of the annular housing cut-out portion for the magnetic fluid. This promotes a simple manufacturing of the probe housing and a simple attachment of the permanent magnets as well as a uniform securing of the electrically insulating magnetic fluid in the annular housing cut-out portion.


BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment example is shown in the drawing and explained in more in the following description. The FIGURE shows a through a pressure probe which is inserted in a rim.


DESCRIPTION OF THE EMBODIMENT OF THE INVENTION

The pressure probe for determining the air pressure in a vehicle tire is designated by 10 in the FIGURE. Its connection lines 11, 12 are received in a high-grade steel pipe 13 whose upper end is laser welded with the housing 14 of the pressure probe 10 by means of a welding seam 15. The housing 14 of the pressure probe 10 comprises a circumferentially extending annular groove 16 on the outside. During assembly, the housing 14 is slid in from the outside through a bore hole 17 of a vehicle rim 18, whereupon annular half-disks 19 are inserted into the annular groove 16 from both sides and outwardly secured in the radial direction by means of a pocket bore hole 20 at the inside of the rim bore hole 17 and come to rest there in such a way that the upper side terminates in a flush manner with the outer surface of the rim 18. In an area of the pressure probe 10 projecting out of the rim bore hole 17, the housing 14 is provided with a threaded projection 21 which carries an external thread 22. A union nut 23 comprising an internal thread is screwed over this threaded projection 21, wherein the union nut 23 overlaps the rim bore hole 17 externally and in this way enables a clamping of the housing 14 in the rim bore hole 17 by means of the annular half-disks 19. The probe housing 14 with the threaded projection 21 is provided with a longitudinal bore hole 25 in which the pipe 13 engages.
The pressure probe 10 comprises two pressure-sensitive sensing elements 24 which are fastened in the area of the

REFERENCES:
patent: 4768375 (1988-09-01), Eckardt et al.

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