WO2004055489A1 - Obstacle for running bench test - Google Patents

Abstract

The invention concerns an obstacle for running tests of at least one vehicle wheel, said wheel rotating about an axis of rotation Y, said obstacle co-operating with a running surface whereon is defined a direction along a running axis X of the wheel, said obstacle comprising at least one useful surface for which a normal to said useful surface has a non-null component along the axis Y. Such an obstacle can be used to induce noises or vibration for measurements, for example directly on the wheel (at the hub for instance) or on the vehicle itself.

Description

 OBSTACLE FOR TRAVEL TEST BENCH

The invention relates to an obstacle capable of being used in a method for predicting the acoustic and vibration levels inside a vehicle traveling on ground having one or more obstacles.

The discomfort perceived by the driver and passengers of a vehicle when driving over one or more obstacles (such as manholes, bitumen connections, various joints, gravel, etc.) has two distinct aspects. A first aspect is of a vibratory nature and manifests itself by vibrations of the vehicle floor, the seats, the steering wheel. A second aspect is of an acoustic nature, and is manifested by the noise created inside the vehicle by the vibrations of different parts of said vehicle. The level of discomfort felt by the occupants of a vehicle depends in particular on the body, the mechanical system of connection to the ground, the speed of travel and of course the type of obstacle on the roadway.

Definition of terms used in the following:

• "comfort performance" corresponds to the acoustic and / or vibration level measurable inside a vehicle traveling on a roadway (or a test facility) provided with at least one obstacle of determined dimensions;

• "ground connection system": set of elements of the vehicle providing the link between one or more of the contact surfaces between the vehicle and the ground and one or more points of said vehicle; in all cases, the ground connection system comprises at least one tire and its mounting wheel; • "body": all the elements of the vehicle complementary to the ground connection system;

• "attachment points": points which link the ground connection system to the body; • "global transfer function": function which comprises two parts, a first part concerns the noise in the passenger compartment of the vehicle and a second part the vibrations at certain predetermined points in the same passenger compartment;

• "ground link reference system": ground link system fitted to the vehicle and available to obtain the overall transfer function;

• "prototype ground link system": ground link system which is sought to predict the impact on comfort performance on the same vehicle equipped with this prototype system instead of the reference system without having said vehicle. • “X direction” or “X axis”: direction corresponding substantially to the direction of advancement of the wheel (and / or the tire) during tests.

• "Y direction" or "Y axis": substantially transverse direction or direction of the axis of rotation of the tire.

• "Z direction" or "Z axis": substantially vertical direction.

Several methods are known to those skilled in the art in order to evaluate the comfort performance of a new ground connection system for a given vehicle and enabling it to optimize said ground connection system. The optimization of obtaining characteristics of a connection system which provide a significantly improved level of comfort.

For example, in order to evaluate and optimize the comfort performance of a vehicle equipped with a new ground connection system, a person skilled in the art can implement an experimental method consisting in making noise and vibration measurements. in the passenger compartment of a vehicle traveling on a portion of road or track making it possible to reveal discomfort of a vibratory and / or acoustic nature in said vehicle, this portion of road or track comprising on its surface one or more obstacles. However, this method requires having the vehicle at your disposal to evaluate different ground connection systems; furthermore, it does not can be driven only in favorable weather conditions which induces a vehicle immobilization time which is sometimes excessively long and consequently an additional cost in the development phase of a ground connection system since numerous iterations are often necessary. It is also long and tedious for the operator and subject to large measurement variations.

European patent application No. 886130 describes a method for predicting the noise level in the passenger compartment of a vehicle fitted with tires and driving on uneven ground with a plurality of roughness. According to this method, a transfer function of a vehicle equipped with tires is determined by applying directly to each axle (at the wheel center) of the vehicle when the forces directed in a predetermined direction are stopped (in the form of shocks). A sound recording is carried out for each impact inside said vehicle and this operation is repeated successively for each of the front and rear positions and for each side of the vehicle. In another step, an identical tire rolls on a steering wheel provided on its rolling surface with a plurality of roughness simulating uneven ground. In this test, the tire is mounted on a fixed axis and the resulting forces at the wheel center are recorded. Finally, these resulting measured forces are used as input to a model involving the transfer function determined as mentioned above so as to obtain the resulting noise level inside the vehicle. This method, which is certainly interesting, nevertheless has limits which can, for example for tires of the same size but with different structures, provide different noise levels than those obtained from tests carried out with the same vehicle equipped with these different tires. and rolling on uneven ground.

In particular, the transfer function of the vehicle being established from tests carried out at a standstill, it is clear that the characteristics are not taken into account tire running tires which, as a general rule, are significantly different from the same characteristics when stationary. It is notably known that the vertical rigidity under dynamic stress of a stationary tire is greater than the same vertical rigidity under dynamic stress of a rolling tire.

Furthermore, to apply forces to the axles, it is necessary to provide for the addition of a part fixed to the outside of the wheel, said part being intended to receive the impacts of a hammer for example, it is clear that the mass of this part is added to the unsprung masses and thereby disturbs the measurements made. It should also be noted that the noise of each impact of the hammer, and even if measures are taken to attenuate it, is transmitted by air in the passenger compartment and adds at least partially to the noise that one wishes to record inside the vehicle.

The document WO 01/04589 proposes a method for predicting noise and vibrations in the passenger compartment of a vehicle. Among the means used, an obstacle is used to generate noise and vibration when it comes into contact with at least one wheel of a vehicle. The obstacle used is a transverse bar, of the rectangular parallepiped type. This obstacle is used in a transverse or perpendicular arrangement to the direction of travel of the tire. In this way, no significant effort is induced in the direction Y. In fact, during taxiing, the obstacle acts obviously in the direction Z, by pushing the wheel upwards. It also acts in direction X, pushing the wheel in the direction opposite to the direction of travel of the vehicle. On the other hand, it is substantially neutral with respect to the direction Y, and the forces induced along this axis are insignificant.

To study the noise or vibration levels corresponding to all that is normally induced on a vehicle in normal operation, it is necessary to try, during tests or simiIations. to reproduce or generate all types of force likely to be induced on the vehicle via tires, wheels, ground contact means, etc. It is thus possible, for example using comparative tests, to compare different solutions making it possible for example to reduce certain noises at certain given frequencies. To be complete, the tests must include all the noises likely to occur during normal operation. However, efforts along the Y axis are regularly encountered. It is therefore desirable, in order to carry out noise or vibration measurement tests, to have an obstacle capable of generating frogs along the Y axis, and preferably in the other two directions (X and Z).

The object of the invention consists firstly in proposing an obstacle for a test bench or a vehicle running track which does not have the drawbacks of the obstacles which have just been mentioned; and on the other hand a rolling test bench comprising such an obstacle.

Thus, the invention provides an obstacle for rolling tests of at least one wheel of a vehicle, said wheel rotating around an axis of rotation Y, said obstacle cooperating with a rolling surface on which a direction is defined according to an axis X of rolling of the wheel, said obstacle comprising at least one useful surface for which a normal to said useful surface has a non-zero component along the Y axis.

Such an obstacle can be used to induce noise or vibration used for taking measurements, for example directly on the wheel (at the hub for example) or on or in the vehicle itself.

In the case where one wishes to use a transfer function, in order to predict the behavior of a given configuration, it is imperative that the function of transfer is as representative as possible. This aspect is all the more important as the noise levels and / or vibrations induced along the Y axis are appreciably important. Vehicles generally do not have any means allowing flexibility in this direction, as is the case in particular along the vertical axis, according to which a plurality of suspension and damping means are provided. This high rigidity along the Y axis is likely to be the source of many noises or vibrations. It is therefore essential to be able to generate such noises in order to establish a transfer function. The obstacle according to the invention is active or non-neutral with respect to the direction Y. It is also active in the directions X and Z, which makes it a particularly effective obstacle and representative of reality.

Said obstacle according to the invention makes it possible to generate in the wheel center an excitation along the three axes X, Y and Z, and in particular with a component along the Y axis, which can be presented in different forms, such as for example a force according to the direction Y (translation), a couple around the X and / or Z axis, etc.

According to an advantageous embodiment, at least one of the transverse profiles of the obstacle with respect to said running direction has a height Y which is not constant. Thus, the elevation of this profile (position along the Z axis) changes according to the position along the Y axis.

Advantageously, for all the cutting planes of said obstacle in the directions XZ corresponding to positions along the axis Y likely to be occupied by the tire, said profiles of the obstacle in said plane XZ retain substantially the same shape and are differentiated only by their position in the X direction. In this way, the obstacle retains its effectiveness regardless of the position of the wheel along the Y axis. Said obstacle advantageously comprises a portion of the useful surface having a non-zero inclination and preferably greater than 5 degrees relative to the axis Y.

The invention further provides a rolling test bench for a vehicle wheel comprising an obstacle as previously defined. A first type of test bench comprises a flywheel on which said obstacle is capable of being rotated in order to cooperate with at least one wheel during tests. Otherwise, according to another type, it comprises a rolling surface on which said obstacle is arranged so as to cooperate with at least one wheel tested during tests.

The obstacle according to the invention and its use for carrying out tests are illustrated by the following FIGS. 1 to 30 in which:

- Figure 1 shows a passenger vehicle, the rear left tire of which is placed on a steering wheel;

- Figure 2 shows a ground connection system mounted on a frame, this connection system comprising the tire of Figure 1 crushed under the same conditions on the steering wheel of Figure 1;

- Figure 3 shows, from another angle of view, the assembly of Figure 2;

- Figures 4 and 5 show a tire mounted on its mounting wheel and crushed on a running wheel to overcome an obstacle according to the invention;

- Figure 6 illustrates an example of tests carried out with an obstacle according to the invention;

- Figures 7 to 16 illustrate exemplary embodiments passable with an angle of incidence α, not zero; - Figures 17 to 20 illustrate exemplary embodiments passable with an angle of incidence α zero or any;

- Figure 21 illustrates an exemplary embodiment comprising successive multiple active surfaces; - Figure 22 illustrates an exemplary embodiment comprising opposite multiple active surfaces;

- Figure 23 illustrates another embodiment passable with an angle of incidence α zero or any;

- Figures 24, 25 and 26 illustrate the self-spectrums of force measurements, respectively in the directions X, Y and Z;

- Figures 27 to 29 illustrate the principle of the invention with examples of active surfaces, Normals and components of Normals along Y;

- Figure 30 illustrates an example of tests performed with an obstacle according to the invention;

In FIG. 1, there is a passenger vehicle 1, the rear left tire 2 of which rests on a steering wheel 3 of diameter 1.6 m coated with a surface coating of fine particle size. An obstacle 4 according to one of the exemplary embodiments as described later, is suitably disposed on the surface of the flywheel 3. Means not shown are provided to drive the flywheel 3 in rotation.

In the first example presented by means of FIGS. 1, 2, 3, the ground connection system comprises the following elements: a tire 2 mounted on a wheel 5; a hub-hub assembly; a braking system 6; a shock absorber 7; an upper attachment 8 of the damper 7; a spring 9; a filtering piece 10 of the spring 9; a longitudinal arm 11; a joint elastic 12 for connecting the longitudinal arm 11 to the body 50; a lower arm 13; an elastic articulation 14 for connecting the lower arm 13 to the body 50; an upper arm 15; an elastic articulation 16 for connecting the upper arm 15 to the body 50; a clamp link 28; a ball joint 29 providing the link between the link 28 and the body 50; various secondary parts not shown in the figures (screws, nuts, ball joint, bearings, elastic joints, etc.).

The vehicle 1 is equipped inside its passenger compartment with: - a microphone 17 located at the right ear of a driver of the vehicle for recording noise;

- A three-directional accelerometer 18 placed on the steering wheel 19 of the vehicle;

- A three-way accelerometer 20 placed on one of the slides of the driver's seat.

The obstacle according to the invention is capable of being used during vehicle or wheel rolling tests alone, in order to generate noise and vibrations capable of being the subject of measurements or recording or any other appropriate treatment. It can also be used with a method making it possible to predict, for a chosen speed V and under the driving conditions on the steering wheel 3 provided with an obstacle 4, the comfort performance of the vehicle 1 and to analyze the impact on this performance of the previously defined ground connection system. With such a method, sound pressure and vibration measurements are made in this position for several driving speeds of the steering wheel framing the reference speed V. For example, speeds equal to ± 20% of the speed V. The noise and vibration values obtained are the outputs of the system which make it possible to determine an overall transfer function of the vehicle equipped with its reference ground connection system.

To obtain the inputs of the system (these inputs multiplied by the global transfer function which must provide the previously recorded data), we carry out, as shown in FIG. 2 and FIG. 3, force measurements at the attachment points at the body of the reference system for ground connection comprising the above-mentioned elements, said system being mounted by its attachment points on a frame 21, the tire 2 rolling on the same steering wheel 3 equipped with the same obstacle 4.

In FIGS. 2 and 3, a distinction is made between the reference system of ground connection fixed by its points of attachment to the frame 21 and supporting, at its contact surface of the tire 2 with the steering wheel, the load supported by this reference system when it is mounted on the vehicle 1 as shown in FIG. 1. The plane of FIG. 2 contains the directions denoted X and Z (the direction Y is perpendicular to the plane of this FIG. 2 and parallel to the direction of the axis of rotation of the handwheel 3, the plane of FIG. 3 contains the perpendicular directions Y and Z. The frame 21 is designed so that its first resonant frequency is not included in the range of the frequencies for carrying out the measurements. attachment points of the reference system for connection to the ground to the frame 21, force sensors 22, 23, 24, 25, 26, 27 are placed to record the forces in three perpendicular directions at these points.

The measurements on the reference system only are carried out at the same speed values as those used during the measurements on the vehicle 1 equipped with the reference system of ground connection. Using then the values measured on the vehicle equipped with the reference system of ground connection and the values measured on the reference system only, one calculates, for each speed framing the speed V, a global transfer function characteristic of the vehicle comprising a first transfer function allowing, taking into account the forces at the points of attachment to the body, to determine the acoustic pressure in the passenger compartment and a second transfer function allowing, taking into account the same efforts at the points of attachment to the body, to obtain the vibration levels on the steering wheel and on the vehicle floor.

Finally, the overall transfer function of the vehicle at speed V is established by averaging the various global transfer functions obtained for each speed. Having then obtained the overall transfer function of a vehicle equipped with the reference system of ground connection, it is easy to predict, for this same vehicle, the comfort performance level of a prototype system different from the reference system. For this, it is sufficient to repeat the operations previously described for the reference system mounted on the measurement frame 21 as shown in FIG. 2 in order to determine, for example by measurement, the forces at the points of attachment to the frame on which is assembled the prototype system whose performance level is sought to be characterized on the vehicle. These forces are treated in the same way as the forces obtained with the reference system and are then multiplied by the overall transfer function of the vehicle previously determined.

In order to optimize the measurements in general and the use of such a method, the present invention proposes an obstacle specifically designed so as to generate noise and / or vibration along the three axes X, Y and Z.

Three types of obstacles are present. FIGS. 7 to 15 show a series of exemplary embodiments according to a first type of obstacle, which can be crossed in a driving direction (shown along the axis X in the various figures) having a non-zero angle of incidence α, and preferably greater than 5 degrees. Obstacles can consist of a succession of planes arranged so as to generate a volume, as in the examples of FIGS. 7 to 12 and 15. In this way, geometric shapes are obtained such as triangles, trapezoids, etc. The obstacles can also consist of partially tubular or rounded profiles, as illustrated in the examples of FIGS. 13 and 14.

Figures 16 to 20 and 23 show a series of exemplary embodiments according to a second type of obstacle, which can be crossed in a preferred direction of travel (shown along the X axis in the various figures) at a substantially zero angle of incidence . These exemplary embodiments also make it possible to use for all practical purposes an infinity of possibilities of angles of incidence. FIGS. 16 to 20 and 23 show an obstacle comprising an active surface 30 inclined at least with respect to the Y axis. Any tire or mounted assembly of which at least a portion of the tread comes into contact with such a surface will have a pulse in the Y direction, capable of inducing noise and / or vibration. In FIGS. 18 to 20 and 23, the active surface comprises an inclined plane 31 which constitutes the element generating implusion. In FIG. 17, a frustoconical portion 32 having a non-constant inclination relative to the axis Y fulfills this function. The rolling surface 50 is arranged and dimensioned so that, during rolling, at least a portion of the tire (or of the wheel) cooperates with the active surface 30.

Finally, Figures 21 and 22 show particular embodiments. In FIG. 21, a plurality of active surfaces follow one another along the rolling direction. In the example illustrated, the surfaces are substantially parallel to each other. They could also be arranged in separate directions. It is also possible to provide more than two active surfaces, parallel or not, or even only certain parallels and others not.

FIG. 22 shows a particular embodiment in which a succession of active surfaces 30, substantially arranged face to face, but offset from each other in the rolling direction X, generate substantially opposite Y forces, insofar as these surfaces are included in the rolling surface 50. The active surfaces 30 could also be inclined relative to the direction X.

FIGS. 27 to 30 illustrate the principle of the invention according to which, in order to generate a pulse along the Y axis, the obstacle comprises at least one active surface whose normal N comprises at least one non-zero component N _y .

In FIG. 27, the inclined plane 31 generates said component N _y .

In FIGS. 28 and 29, said component is due to the angle of incidence, or direction of travel along the X axis, which has an angle α relative to the normal N.

FIG. 30 illustrates well the inclination of the obstacle, the longitudinal axis of which is inclined relative to the direction Y, perpendicular to the driving direction X. The rolling surface 50 shows the lateral limits within which the wheel or tire tested should normally be understood during testing. Or it is a question of maximum preferential limits, as for example in figure 30, in order to be certain that one rolls well on the obstacle. They may also be minimum preferential limits, as for example in FIG. 23, making it possible to ensure that the wheel or tire cooperates effectively with an active surface 30 or 31.

FIGS. 24 to 26 respectively illustrate the self-spectrums of force measurements in the X, Y and Z directions, at the pin wheel center of a mounted assembly. These tests were carried out with a mounted assembly fitted with an MXGS2 type tire, manufactured by Michelin ®, of size 195 / 65R15 with a load of 380 Dan, inflated with a pressure of 2.1 bars. Different measurements carried out on the one hand with an obstacle of known type and on the other hand with an obstacle according to the invention make it possible to highlight the fact that the obstacle according to the invention makes it possible to generate noises and / or vibrations clearly. more important along the Y axis than the obstacle of known type. Note the logarithmic scale, due to considerable measurement differences. Furthermore, the results obtained along the X and Z axes clearly illustrate that the obstacle according to the invention is also effective in these directions.

Advantageously, the obstacle according to the invention, whether it is one or the other of the embodiments presented or another not shown, comprises adjustment means, making it possible for example to separately check the excitation levels of the tire along the X, Y and Z axes. By adjusting for example the height of the obstacle, or its depth, etc., one acts on one of the three axes. This can make it possible to carry out particularly interesting comparative tests.

Of course, according to another advantageous variant of the invention, what has been described in the present description on a rolling means of the flywheel type can be carried out on a rolling machine reproducing rolling conditions close to a level ground ( including "flat band" machine).

Claims

1. Obstacle for rolling tests of at least one wheel of a vehicle, said wheel rotating around an axis of rotation Y, said obstacle cooperating with a rolling surface on which a direction is defined along a rolling axis X of the wheel, said obstacle comprising at least one useful surface for which a normal to said useful surface has a non-zero component along the axis Y, and at least one of the transverse profiles of the obstacle relative to said driving direction having a non-constant height Y. 2. Obstacle for rolling tests of at least one wheel of a vehicle, said wheel rotating around an axis of rotation Y, said obstacle cooperating with a rolling surface on which a direction is defined along a rolling axis X of the wheel, said obstacle comprising at least one useful surface for which a normal to said useful surface has a non-zero component along the axis Y, in which for all the cutting planes of said obstacle in the directions XZ corresponding to positions according to the Y axis capable of being occupied by the tire, said profiles of the obstacle in said plane XZ retain substantially the same shape and are differentiated only by their position in the direction X. 3. Obstacle according to one of claims 1 or 2, comprising a portion of the useful surface having a non-zero inclination and preferably greater than 5 degrees relative to the axis Y. 4. Rolling test bench for vehicle wheel comprising an obstacle according to one of the preceding claims. 5. Rolling test bench for vehicle wheel according to claim 4, comprising a steering wheel on which said obstacle is capable of being rotated in order to cooperate with at least one wheel during tests. 6. Rolling test bench for vehicle wheel according to claim 4, comprising a rolling surface on which said obstacle is arranged so as to cooperate with at least one wheel tested during tests.