METHOD AND TEST BENCH FOR PREDICTING PRESSURE OSCILLATIONS IN A VEHICLE TIRE

Abstract

A test bench and a method to predict pressure oscillations in a vehicle tire. The tire is rotatably positioned, via a bearing on a test bench rim, the tire is pressurized with fluid, a load is applied on the tire, the tire is accelerated according to pre-determinable speed ramp to a final speed, the fluid in accordance with the tire speed, undergoes an oscillation excitation, and reacts to the oscillation excitation with a pressure oscillation. The method is characterized in that an effective force of the tire, due to the pressure oscillation, at the bearing is continuously detected, and that a descriptive data set is determined for the tire speed over the frequency, a timing signal of the speed ramp undergoes a Fourier transformation and, in an analogous manner, a reference data set is created through the use of a vehicle rim instead of the test bench rim.

Claims

1-13. (canceled)

14. A method for predicting pressure oscillations in a vehicle tire (1), the vehicle tire (1) is rotatably mounted on a test bench rim (2) via a wheel bearing, an interior of the vehicle tire (1) is pressurized with fluid pressure, the vehicle tire (1) is applied with a wheel load, the vehicle tire (1) is accelerated in accordance with a pre-determinable speed ramp up to final speed, the fluid in accordance with a tire speed undergoes an oscillation excitation, and the fluid reacts to the oscillation excitation with a pressure oscillation, the method comprising: continuously detecting, at the wheel bearing, an effective force acting on the vehicle tire (1) due to the pressure oscillation, and generating a data set describing the force over the tire speed and over a frequency by subjecting a time signal of the speed ramp to a Fourier transformation and, in an analogous manner, a reference data set is generated using a vehicle rim instead of the test bench rim.

15. The method according to claim 14, further comprising determining amplitudes and positions of resonances of the fluid (5) in the data set and in the reference data set by two lines (23, 24) which intersect when the vehicle tire is at standstill.

16. The method according to claim 15, further comprising placing the straight lines (23, 24) by forces of different oscillation orders starting from the standstill of the vehicle tire (1) through V-shaped maxima forces (15′-22′, 16″-22″).

17. The method according to claim 14, further comprising exclusively considering maxima (15′-22′, 16″-22″) of oscillation orders larger than the tenth order.

18. The method according to claim 14, further comprising that exclusively considering maxima (15′-22′, 16″-22″) in a frequency range of 140 Hz to 300 Hz.

19. The method according to claim 14, further comprising that from amplitudes of the resonances of the fluid (5, 15′ to 22′, 16″-22″), and amplitudes of resonances of the structure of the vehicle tire (1, 4, 15′″-19′″) of the same order, a first relative ratio is generated and/or that from resonances of the fluid (5, 15′-22′, 16″-22″) in positions of resonances of the vehicle tire (1, 6, 15′″-19′″) of the same order a second relative ratio is generated.

20. The method according to claim 19, further comprising, as contained in the data set, the amplitudes of resonances of the structure of the vehicle tire (1, 6, 15′″-19′″) and the first relative ratio, the resonances of the fluids (5, 15′-22′, 16″-22″) are determined and/or, contained in the data set, with positions of resonances of the vehicle tire (1, 6, 15′″-19′″) and the second relative ratio, the positions of the resonances of the fluids (5, 15′-22′, 16″-22″) are determined.

21. The method according to claim 15, further comprising classifying the vehicle tire (1) by comparing the amplitudes of the resonances of the fluids (5. 15′-22′, 16″-22″) with the reference amplitudes in a pre-determinable established window and over a frequency spectrum and a tire speed spectrum.

22. The method according to claim 21, further comprising predetermining the window in accordance with an intended use of the vehicle tire (1).

23. The method according to claim 14, further comprising that the Fourier transformation is a fast Fourier transformation.

24. The method according to claim 19, further comprising that the data set and the reference data set comprise a tire force value for each value pair of tire speed and tire frequency.

25. A test bench for predicting pressure oscillations in a vehicle tire (1), comprising: a test bench rim (2), a vehicle rim, a wheel bearing, means for pressurizing the vehicle tire, means applying a wheel load on the vehicle tire, means for accelerating the vehicle tire (1), means for detecting a tire speed, means for detecting at least one of a force, a tire oscillation, and a pressure oscillation, the vehicle tire (1) being rotatably positioned on the wheel bearing by a test bench rim (2) or the vehicle rim, an interior of the vehicle tire being pressurized with a fluid by the means for pressurizing the vehicle tire, the vehicle tire (1) being loaded with the wheel load by the means for applying the wheel load on the vehicle tire, the vehicle tire (1) being accelerated according to pre-determinable speed ramp to a final speed by the means for accelerating the vehicle tire so that the fluid, in accordance with the tire speed, undergoes an oscillation excitement, and the fluid reacts to the oscillation excitement with a pressure oscillation, the tire speed being detected by the means for detecting the tire speed, and an effective force of the vehicle tire (1) on the wheel bearing, due to the pressure oscillation, being continuously detected by the means for the detecting the at least one of the force, the tire oscillation, and the pressure oscillation, and the test bench further comprising an electronic computation means, the electronic calculation means being designed to generate a descriptive data set, or reference data set, for the force over the tire speed and over the frequency, whereby they submit a time signal of the speed ramp to a Fourier transformation.

26. The test bench according to claim 25, further comprising that the test bench is designed to execute a method for predicting pressure oscillations in a vehicle tire (1), the method comprising: continuously detecting, at the wheel bearing, an effective force acting on the vehicle tire (1) due to the pressure oscillation, and generating a data set describing the force over the tire speed and over a frequency by subjecting a time signal of the speed ramp to a Fourier transformation and, in an analogous manner, a reference data set is generated using a vehicle rim instead of the test bench rim.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Hereafter, the invention is further explained based on the embodiments shown in the figures.

[0038] These show:

[0039] FIGS. 1a and 1b schematically an overview of the two, generally seen oscillation degrees of freedom of a fluid in the interior of a vehicle tire,

[0040] FIG. 2 exemplary and schematically a data set generated in accordance with the invention and

[0041] FIG. 3 exemplary and schematically a reference data set generated in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] The same objects, functional units and comparable components are denoted by the same reference symbols in all the figures. These objects, functional units and comparable components are designed identically with regard to their technical features, unless the description explicitly or implicitly states otherwise.

[0043] FIGS. 1a and 1b schematically show an overview of the two degrees of freedom of oscillation of a fluid that are usually seen in the interior of a vehicle tire 1 under the application of pressure. Presented in FIGS. 1a and 1b is a vehicle tire 1 which is installed on a rim and which moves over a ground 3. As a result of the movement over the ground 3, the vehicle tire 1 experiences a speed dependent oscillation excitation, which is also transmitted to the fluid in the interior of the vehicle tire 1. According to the example, the fluid is air. The oscillations of the fluid occur as periodically changing density differences of the fluid, meaning in the form of pressure oscillations of the fluid. FIG. 1a shows a pressure oscillation along a first degree of freedom. According to the example, the pressure oscillation (marked by a double arrow) occurs along the direction of movement of the vehicle tire 1. The pressure difference due to the pressure oscillation of the fluid in the vehicle tire 1 is illustrated by hatching: in the area 1′ of the vehicle tire 1 a minimum of the pressure oscillation is shown, whereas a maximum is shown in a hatched area 1″. FIG. 1b shows a pressure oscillation of the fluid along a second degree of freedom. In accordance with FIG. 1b, the fluid does not oscillate along the direction of movement of the vehicle tire 1 but perpendicular to it against the ground 3 (also presented by a double arrow). The pressure difference due to the pressure oscillation of the fluid in the vehicle tire 1 is also in FIG. 1b by hatching.

[0044] FIG. 2 shows exemplary and schematically a data set generated in accordance with the invention, which describes the force as a function of the tire speed and as a function of frequency. According to the example, the data set was generated by first rotating a vehicle tire 1 on a test bench rim 2 via a wheel bearing and pressurizing it inside by means of a fluid, for example air. Then, the vehicle tire 1 was accelerated in accordance with a pre-determinable speed ramp from the standstill to a final speed. While passing through the speed ramp, the vehicle tire 1 was also, in accordance with the invention, applied with a constant wheel load. As a result, the vehicle tire 1 was excited, in accordance with a tire speed, to a tire oscillation with a tire frequency. In the same way, the fluid in the interior of the vehicle tire 1 was, in accordance with the tire speed, excited to a pressure oscillation with a pressure frequency. The tire oscillation and the pressure oscillation both lead in each case to a force acting on the wheel bearing which was continuously detected during the entire passing through the speed ramp. Finally, the data set which is presented in FIG. 2 was generated, and where a timing signal of the speed ramp, for example a change in the detected tire force over the time during the passing through the speed ramp, was submitted to a Fourier transformation. The tire speed is in FIG. 2 presented on the y-axis and the frequency on the x-axis. The respective force can be recognized by means of a color or hatching. As can be seen in FIG. 2, in the representation of the force as a function of the tire speed and as a function of the frequency, highlighted lines are formed on which the detected force is greater than in the surrounding areas. These lines 3-16 show resonances of different orders. Where an excitation frequency meets a resonance of the vehicle tire 1 or a resonance of a fluid used for the pressure application of the vehicle tire 1, a clear increase of the detected force occurs. A multitude of resonances 4 can be seen in FIG. 2 which can be assigned to the vehicle tire 1. Also, a multitude of resonances 5 can be seen which can be assigned to the fluid, wherein the resonances 5 which are assigned to the fluid are at comparatively higher tire frequencies than the resonances 4 which are assigned to the tire. At even higher frequencies, a multitude of resonances 6 can be observed, which, however, can be assigned to the test bench used for carrying out the method according to the invention. These resonances 6 do not play a role in the determination of pressure oscillations of the vehicle tire 1 and can be disregarded accordingly in the inventive method.

[0045] FIG. 3 shows by way of example and schematically, a reference data set generated in accordance with the invention, which mainly corresponds to the data set in FIG. 2 but is limited to a frequency range which does not have resonances 6 that can be assigned to the test bench. Also, a vehicle rim was applied to generate the reference data set in FIG. 3, which means that resonances of the fluid can be monitored in those positions, i.e., at those tire speeds and frequencies where they would actually occur during operation of the vehicle tire 1 on a motor vehicle. A multitude of lines 7-22 can also be seen in the data set in FIG. 3, wherein the lines 7-22 having speed dependent or frequency dependent maxima or minima with regard to the force which is assigned to them (represented by coloring or hatching, respectively). Also, two straight lines 23 and 24 can be seen which intersect when the vehicle tire 1 is at the standstill, meaning they intersect at the speed zero in the data set. The straight lines 23 and 24 are, starting from the standstill of the vehicle tire 1, are placed by maxima 15′-22′, 16″-22″ of forces of different oscillation orders that fan out in a V-shape. The intersections of the straight lines 23 and 24 with the lines 15-22 or with their maxima 15′-22′, 16″-22″ represent the resonances of the fluids in the interior of vehicle tire 1. From the resonances of the fluid identified by means of the two straight lines 23 and 24 and the resonances 15′″, 17′″, 18′″, and 19′″ which are also contained in the data set of the vehicle tire 1 of the lines 15, 17, 18, and 19, a first relative ratio is now generated in accordance with the invention which describes the amplitude of each of the resonances 15′″, 17′″, 18′″, and 19′″ in the relation to the amplitude of the resonances 15′, 17′, 18′, 19′ of the same order, as well as a second relative ratio which describes the position of each of the resonances 15′″, 17′″, 18′″, and 19′″, each in relation to the position of the resonances 15′, 17′, 18′, 19′ of the same order. By means of the first and second relative ratio determined in this manner, the amplitudes and positions of resonances of the fluid can mathematically be computed in a simple way at the test bench on a test bench rim 2 which would occur in the actual operation of the vehicle tire 1 on a motor vehicle, meaning on a vehicle rim.

REFERENCE CHARACTERS

[0046] 1 Vehicle Tire [0047] 1′ Minimum of the pressure oscillation [0048] 1″ maximum of the pressure oscillation [0049] 2 Test Bench Rim [0050] 3 Ground [0051] 4 Resonances of the Vehicle Tire [0052] 5 Resonances of the Fluid [0053] 6 Resonances of the Test Bench [0054] 7-22 Lines, Resonances [0055] 15′-22′ Maxima, Resonances [0056] 16″-22″ Maxima, Resonances [0057] 15′″-19′″ Maxima, Resonances [0058] 23, 24 Straight Line