Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication
Reexamination Certificate
2003-06-30
2004-12-28
Zanelli, Michael J. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
C701S036000, C381S071400, C280S005515, C073S146000
Reexamination Certificate
active
06836706
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method of forecasting acoustic and vibrational levels which are obtained inside a vehicle travelling over smooth ground, this vehicle being equipped with mounted assemblies composed of tires mounted on their mounting wheels.
Despite all care taken in the manufacture of the different elements making up an assembly (tire and wheel) and in the assembly thereof before they are mounted on a vehicle, it is known that any mounted assembly has a greater or lesser number of irregularities or non-uniformities when the wheel turns. When the vehicle is travelling, these irregularities or non-uniformities cause vibrational excitation of the different components of a vehicle when the said vehicle is equipped with the said assembly, in ways which may be different and vary in dependence on the speed of the said vehicle.
By non-uniformity of a mounted assembly or a rotating assembly there is meant an irregularity which may be connected among other things with:
one or more faults or irregularities in the distribution of masses or rigidity in the mounted assembly;
eccentric mounting of the wheel on the vehicle;
geometric faults in the wheel;
poor mounting of the tire on its wheel.
These irregularities lead to cyclic variations in the forces on the wheel centers and/or at any other point of attachment of the system connecting the vehicle to the ground. By a system connecting to the ground there is meant a sub-assembly of elements of the vehicle ensuring that the vehicle body is connected to one or more surfaces of contact between the vehicle and the ground. This sub-assembly is determined in advance and comprises for example all the mechanical parts of the vehicle located between at least one fixing point on the body of the said vehicle and at least one footprint of each tire with which the said vehicle is equipped; in this example, at least one tire is included in the system connecting to the ground.
These cyclic variations of forces resulting from the non-uniformities become evident during travel in vibrations of the floor of the vehicle, the seats and the steering wheel. An acoustic disturbance may also occur with noise being created inside the vehicle by the vibrations of different parts of the said vehicle. The level of nuisance perceived depends on the vehicle and the speed of travel (there are also critical speeds, at which the nuisance perceived is at a maximum), but mainly on the level of non-uniformity of the rotating assemblies.
In the text below, “comfort performance” means the acoustic and vibrational level measured inside a given vehicle equipped with a set of mounted assemblies.
Those skilled in the art are familiar with a method of evaluating the comfort performance of a new tire for a given vehicle, in accordance with which noise and vibration measurements are made in the passenger compartment of a vehicle travelling over a section of smooth road, by working through different levels of non-uniformity (for example 10 grams, 20 grams, 30 grams of unbalanced load) for the four mounted assemblies of the vehicle over the entire range of speeds of the vehicle in order to be sure of having evaluated the maximum disturbance. This method requires the vehicle to be available, however, and can only be performed in favorable weather conditions, which gives rise to what is sometimes an excessively long immobilization period and consequently an additional cost. This method is moreover long and laborious for the operator, is subject to large variations in measurement, and is expensive in the implementation phase of a tire for a given vehicle.
SUMMARY OF THE INVENTION
The invention relates to a method of forecasting the comfort performance (level of noise and vibration) which does not have the disadvantages of the method which have just been mentioned.
With this object, there is proposed a method of forecasting the noise and vibrations in the passenger compartment of a vehicle equipped with test mounted assemblies and travelling at a given speed V over smooth ground, this method consisting in multiplying an overall transfer function of the vehicle equipped with reference mounted assemblies by forces resulting at the wheel center of the test mounted assembly, this mounted assembly bearing an identical load to that measured on the vehicle and travelling over the same ground. The method proposed includes a first step of determining an overall transfer function of the vehicle by using a reference mounted assembly and a second step in which forces are measured at the wheel center of the test mounted assembly.
By a reference mounted assembly there is meant a mounted assembly used to assess the overall transfer function, this reference mounted assembly being prepared such that it has a number N of irregularities of appropriate dimensions to excite the vehicle in a range of frequencies Fmin, Fmax within the spectrum of speeds selected (Vmin, Vmax). By a test mounted assembly there is meant a mounted assembly whereof the comfort performance is to be forecast for the vehicle, taking into account the non-uniformities this test mounted assembly may have. These mounted assemblies (test and reference) are composed of a wheel provided to be mounted on the vehicle (in accordance with the constructor's specifications) and a tire, also provided to be mounted on the vehicle. As a general rule, the mounting wheel has parts forming seats and parts forming edges, these parts being intended to cooperate with beads of the tire when the latter is mounted on this wheel. Moreover, the tire comprises a tread whereof the radially outer surface is intended to come into contact with the roadway during travel; sidewalls connect the tread to the beads.
Principle of the Method.
There is proposed a method of forecasting the comfort performance (noise and vibrations) in a vehicle equipped with a test mounted assembly in a selected position on a vehicle travelling at a given speed V on a travel medium of the smooth ground type, allowing an equivalent maximum speed Vmax of the vehicle to be attained (Vmax being greater than the given speed V), this test mounted assembly having a greater or smaller number of faults of non-uniformity as mentioned at the beginning of this description.
This method comprises the following steps:
(a)—preparing a reference mounted assembly comprising a tire and its mounting wheel, such that this reference mounted assembly of circumferential length &pgr;D has a number N of irregularities which are substantially identical and regularly distributed over the circumference of the mounted assembly, these irregularities being selected to excite the vehicle in a range of frequencies from a minimum frequency Fmin to a maximum frequency Fmax in the course of travel over smooth ground, this number N being determined by the formula:
N
=
integer
part
(
(
F
max
×
π
D
)
V
max
)
+
1
where: Fmax is in hertz, D is in meters and Vmax is in meters per second;
(b)—equipping the vehicle with the reference mounted assembly in the selected position on the vehicle;
(c)—positioning the vehicle such that the reference mounted assembly rests on the travel medium capable of causing the said reference mounted assembly to rotate;
(d)—recording the noise and vibrations at at least one point inside the vehicle by working through the speeds of rotation of the reference mounted assembly in a range of speeds of rotation (&ohgr;min, &ohgr;max) equivalent to the speeds (Vmin, Vmax) of the vehicle, the speed Vmin being defined by the following equation:
V
min
=
(
F
min
×
π
D
)
N
(e)—measuring the resulting forces exerted at the wheel center of the reference mounted assembly, this assembly being mounted to travel either on the travel medium used in step (c) or on a travel medium equivalent to that used in step (c) and put under the conditions of travel (direction of rotation, tire pressure, load, range of speeds of rotation) corresp
Dormegnie Eric
Fabry Pierre
Crecente Christopher P.
Csontos Alan
Furley Felipe J.
Gibson Eric M.
Michelin & Recherche et Technique S.A.
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