Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
2003-03-10
2004-11-16
Nghiem, Michael (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
Reexamination Certificate
active
06820015
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention concerns a method of predicting the maximum running distance in degraded mode, without substantial deterioration in the running conditions, of a mounted assembly comprising a wheel rim, a safety support mounted on the rim, and a tire cover mounted on the rim, with the support supporting the tread of the cover during such running. (Running “in degraded mode” means running at reduced or zero inflation pressure.) The invention also concerns an installation for implementing this method.
2. The Related Art
It is known that the safety supports for vehicle tires are intended to be mounted on a rim inside a tire, with a view to being able to support the tread of the tire in the event of loss of inflation pressure. These supports comprise, notably, a base which is intended to be mounted on the rim, and a crown which is intended to come into contact with the tread in the aforementioned case (loss of inflation pressure) and which leaves clearance with respect to it at nominal pressure.
The international patent document WO-A-00/76791 (United States Published Application US 2002/0124924 A1, the disclosure of which is hereby incorporated herein for all purposes) presents such a support, in which the base and crown are substantially cylindrical, and which also comprises an annular body connecting the base and the crown. This annular body comprises a support element which is continuous circumferentially with a circumferential mid-plane. The support element comprises a plurality of partitions extending axially on each side of the circumferential mid-plane and distributed over the circumference of the support.
The tests or methods used at the present time for predicting the maximum running distance in degraded mode, without substantial deterioration of the running conditions, of a mounted assembly comprising a wheel rim provided with such a safety support and a tire cover mounted on the rim consist generally of:
running a motor vehicle equipped with such mounted assemblies in degraded mode on a circuit of the road or motorway type, at a predetermined constant speed (for example around 100 km/h) and at a given external temperature, and then
interrupting the running when the driver of the vehicle detects such a substantial deterioration of the running conditions that continued running in degraded mode is very difficult, a deterioration which is due to significant damage to the mounted assemblies and which results, for example, in a substantial increase in the vibration originating at the steering wheel, or following an examination of each mounted assembly following running flat over predetermined distances.
Generally, the criterion for stopping the running test in degraded mode, which is chosen by the operator in charge of the test, corresponds to the appearance of one or more specific items of damage concerning both the safety support and the tire cover.
The damage concerning the support can, for example, consist of cracks or breaks at the partitions of the support because of significant internal heating and buckling stresses to which the running support is subjected in degraded mode.
The damage concerning the tire cover can, for example, consist of cuts at the sidewalls of the tire cover, notably because of the camber stresses to which the tire cover is subjected on a more or less winding circuit, or by a burst pure and simple thereof, making it impossible to continue any running in degraded mode.
However, experience shows that these stoppage criterion or criteria are parameters that can have a determining effect on the result with regard to the maximum running distance in degraded mode without substantial deterioration in the running conditions, which is obtained at the end of the test on a circuit.
The same applies to the parameters characterizing the running which are peculiar to the vehicle, such as the speed chosen for the running or the load to which each mounted assembly is subjected during running.
Naturally, the parameters relating to the ambient air (temperature) and to the surface of the circuit used (roughness, dry or wet ground) may also have an influence on the maximum running distance obtained in degraded mode.
A major drawback of these prediction tests on a circuit lies in the difficulty of keeping the aforementioned parameters identical from one test to another because of their variability, and in the more or less constraining character of these parameters for the support and tire cover during running in degraded mode. This may result, in particular, in difficulties in comparing the respective running endurances of various mounted assemblies in degraded mode.
SUMMARY OF THE INVENTION
An object of the present invention is to propose a method of predicting the maximum running distance in degraded mode, without substantial deterioration of the running conditions (that is to say without loss of control of the vehicle), of a mounted assembly comprising a wheel rim, a safety support mounted on the rim, and a tire cover mounted on the rim around the support, with the support supporting the tread of the cover during the running, which makes it possible reliably and reproducibly to predict the maximum running distances in degraded mode of various mounted assemblies and to compare them with each other under identical experimental conditions.
To this end and according to a first embodiment of the invention, the prediction method comprises running the mounted assembly at a reduced or zero inflation pressure, from a time t
0
, at a given temperature, at a given mode and at a constant speed V, on at least one running surface so that the center of the wheel rim is a substantially invariant point during the running (i.e. on a rolling road test drum, typically), monitoring the variation in a variable R representing the radial loading of the support as a function of the reduced or zero pressure running time t, and, during such running, implementing the following sequence of steps (i) to (iii):
(i) determining a value R
1
attained by the variable R at the end of a predetermined stabilization time t
1
which is such that the direction of variation of the variable R represents a radial loading of the support increasing overall beyond the stabilization time t
1
, then
(ii) determining a critical running time t
2
(t
2
>t
1
) at the end of which the variable R reaches a critical value R
2
such that R
2
=R
1
+&Dgr;R, where &Dgr;R is a value representing a critical increase in the loading of the support with respect to the value R
1
at the end of the stabilization time t
1
, and then
(iii) making the running time t
2
correspond to a distance d
2
, with d
2
=V(t
2
−t
0
), representing a prediction of the maximum running distance without substantial deterioration in the running conditions.
It should be noted that the value &Dgr;R which is adopted at step (ii) constitutes a criterion for stopping the running, beyond which the support is subjected to stresses and heating liable to make it unsuitable for use.
It should also be noted that it would be possible to choose at least one new critical value &Dgr;R′ greater than or less than &Dgr;R according to the absence or presence of substantial damage in the support at the end of the time t
2
, and once again to implement the sequence of steps (i) to (iii) by replacing &Dgr;R with &Dgr;R′, so as to obtain, at the end of n iterations, a still further improved prediction of the maximum running distance of the support without substantial deterioration in the running conditions.
According to a second embodiment of the invention, the method of predicting the maximum running distance of the mounted assembly at a reduced or zero inflation pressure, without substantial deterioration in the running conditions, comprises running the support mounted on the wheel rim, also at a given temperature, at a given load and with a constant speed V, directly in contact with the running surface so that the center of the rim is a substantially invariant point d
Ferres Laurent
Thiallier Daniel
Michelin & Recherche et Technique S.A.
Nghiem Michael
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