JP2020038158A - Tire vibration characteristic evaluation method - Google Patents

Abstract

To provide a method capable of evaluating the vibration characteristic of a rotating tire more accurately.SOLUTION: A tire vibration characteristic evaluation method for additionally vibrating a tire T with additional vibration means 11 to detect the vibration of a tire T, comprises: additionally vibrating a rotating tire T with the additional vibration means 11; detecting the additional vibration with a vibration sensor 12 provided in the additional vibration means 11; detecting the vibration of the surface of the tire T in a non-contact manner with a non-contact sensor 20 away from the tire T; and calculating a frequency response function as a ratio of the Fourier spectrum of the vibration of the surface of the tire to the Fourier spectrum of the additional vibration.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for evaluating tire vibration characteristics.

  As described in Patent Literature 1 and Patent Literature 2, evaluation of vibration characteristics of a stationary tire has been conventionally performed. In Patent Document 1, a structure support that supports a stationary tire is vibrated to detect the vibration of the tire and the vibration of the structure support, and the vibration of the tire and the vibration of the structure support are detected. It describes that the vibration transmission rate of the tire is calculated based on the ratio. Patent Document 2 describes that a stationary tire is vibrated by a hammer, and a transfer function is calculated based on a vibration signal of the hammer and an output signal of a tread portion or the like. However, with these methods, the vibration characteristics of the tire during rolling are not known, and as a result, it is not possible to evaluate the change in the vibration characteristics of the tire at rest and during rolling.

  On the other hand, as described in Non-Patent Documents 1 to 3, evaluation of the vibration characteristics of a rotating tire has also been performed. Non-Patent Document 1 describes that a tire is vibrated with a hammer to measure a force transmission coefficient with respect to a tire axis. In addition, Non-Patent Documents 2 and 3 disclose that a tire is pressed against a drum and rotated, an input is applied to the tire by a protrusion attached to the drum surface, and the vibration of the tire surface resulting from the input is measured by a laser Doppler vibrometer. Is described.

JP 2008-39510 A JP 2012-141244 A

Takanari Saguchi, "On the effect of rolling on the natural frequency of tires", Symposium text of the Society of Automotive Engineers of Japan, 9808 (1998) Kensuke Bito et al., "Experimental Elucidation of Tire Lateral Vibration Characteristics", The Society of Automotive Engineers of Japan, 2014 Spring Science Lecture Preprints, 325-201424587 Takayuki Koizumi et al., “Analysis of Vibration Behavior during Rolling of Tire Focusing on Rotation Effect”, Transactions of the Japan Society of Mechanical Engineers (C), Vol. 77, No. 777 (2011-5). 10-0183

  However, in the method of measuring the force on the tire shaft as in Non-Patent Document 1, the vibration of the tire shaft is affected by the vibration of an object other than the tire, so that the vibration characteristics of the tire cannot be accurately evaluated. There was a problem.

  On the other hand, in the method of measuring the vibration of the tire surface as described in Non-Patent Documents 2 and 3, the problem of measuring the vibration of the tire shaft does not occur and the vibration characteristics of the tire are accurately evaluated. Seems to be able to do it. However, when trying to evaluate the vibration characteristics of a tire by obtaining the Fourier spectrum waveform of the vibration of the tire surface, the difference in the magnitude of each input frequency affects the waveform. Could not be evaluated. Further, when the rotation of the drum is stopped, the rotation of the tire is also stopped. However, in this state, it is not possible to evaluate the vibration characteristics of the tire at rest because the projection on the drum surface does not allow input to the tire. As a result, it was not possible to evaluate changes in the vibration characteristics of the tire at rest and rolling. Further, since the input changes when the rotation speed of the tire changes, the change in the vibration characteristics due to the change in the rotation speed of the tire cannot be accurately evaluated.

  In Non-Patent Documents 2 and 3, a large number of measurements are performed at many measurement points on the tire surface, respectively, but such a method takes time. Therefore, such a method is not suitable for evaluating the vibration characteristics of many tires or evaluating the vibration characteristics many times while changing the rotation speed of the tire.

  The present invention has been made in view of the above circumstances, and has as its object to provide a method capable of more accurately evaluating the vibration characteristics of a rotating tire.

  The tire vibration characteristic evaluation method of the embodiment is a tire vibration characteristic evaluation method in which a tire is vibrated by a vibration means and a tire vibration is detected, wherein the rotating tire is vibrated by the vibration means, The vibration of the vibration is detected by a vibration sensor provided in the means, the vibration of the surface of the tire is detected in a non-contact manner by a non-contact sensor separated from the tire, and the vibration of the tire surface relative to the Fourier spectrum of the vibration of the vibration is detected. The frequency response function is calculated as the ratio of the Fourier spectrum of

  According to the tire vibration characteristic evaluation method of the embodiment, by calculating the frequency response function from the vibration of the excitation and the vibration of the tire surface detected by the non-contact sensor, the vibration characteristics of the rotating tire can be more accurately evaluated. can do.

The figure of the vibration characteristic evaluation device in the case of performing the test of the vibration of a radial direction mode. The figure of the vibration-characteristics evaluation apparatus at the time of performing the test of the vibration of a lateral bending mode. The figure which shows the mode of the vibration of the tire of a radial direction mode. It is a figure when a tire is seen from the width direction. The figure which shows the mode of the vibration of the tire of a radial direction mode. The figure which shows a mode of the vibration of the tire of a side bending mode. It is a figure when a tire is seen from a radial direction. 7 is a waveform of a frequency response function of vibration in a radial direction obtained by the method of the embodiment. 7 is a waveform of a frequency response function of vibration in a radial direction mode obtained by the method of the comparative example. 5 is a waveform of a frequency response function of vibration in a lateral bending mode obtained by the method of the embodiment. 7 is a waveform of a frequency response function of vibration in a lateral bending mode obtained by the method of the comparative example. The figure which shows the rate of change of the natural frequency by rotation.

  An embodiment will be described with reference to the drawings. It should be noted that the embodiments described below are merely examples, and those that are appropriately changed without departing from the spirit of the present invention are included in the scope of the present invention.

1. Vibration Characteristics Evaluation Apparatus (1) Overall Structure of Evaluation Apparatus As shown in FIG. 1, a vibration characteristics evaluation apparatus 10 of the present embodiment includes a drum D as a rotating device for rotating a pneumatic tire (hereinafter, “tire”) T. A hammer 11 as a vibration means for vibrating the rotating tire T, a vibration sensor 12 for detecting vibration of the vibration, a non-contact sensor 20 for detecting vibration of the surface of the tire T in a non-contact manner, An analysis device 21 is provided that collects information on the vibration detected by the excitation sensor 12 and information on the vibration detected by the non-contact sensor 20 to obtain a frequency response function.

  The tread portion of the tire T is pressed against the outer peripheral surface of the drum D. When the drum D rotates in this state, the tire T rotates in the opposite direction to the drum D. The rotating device for rotating the tire T is not limited to the drum D. For example, instead of the drum D, a motor that rotates a rotation axis of a wheel on which the tire T is mounted may be provided.

  The hammer 11 as a vibration means is held by a hammering device 13 using a power source such as electromagnetic force or fluid pressure. The hammering device 13 is, for example, a rotary actuator. When the hammering device 13 is operated, the hammer 11 is swung down toward the tire T to vibrate the tire T.

  A vibration sensor 12 is attached to the tip of the hammer 11. The vibration sensor 12 may be anything as long as it can detect vibration of the vibration. For example, a force sensor (load sensor) is used. The vibration sensor 12 is connected to the analysis device 21, and information on the vibration detected by the vibration sensor 12 is sent to the analysis device 21.

  The vibrating means is not limited to the hammer 11, but may be another type capable of vibrating the rotating tire T. However, it is preferable that the vibrating means is not fixed to the rotating device (the drum D in the present embodiment). Further, it is preferable that the vibrating means is held by an object that is not in contact with the tire T (the hammering device 13 in the present embodiment). Each of the vibration means is provided with a vibration sensor 12 for detecting vibration of the vibration.

  The non-contact sensor 20 may be any sensor that can detect the vibration of the surface of the tire T in a non-contact manner. For example, any one of a laser displacement meter, a laser Doppler vibrometer, an ultrasonic sensor, an eddy current sensor, and an image sensor is used. Is done. The non-contact sensor 20 is connected to the analysis device 21, and information on the vibration detected by the non-contact sensor 20 is sent to the analysis device 21.

  The analysis device 21 includes, for example, an information acquisition unit 22 that acquires information sent from the vibration sensor 12 and information sent from the non-contact sensor 20, and a frequency that obtains a frequency response function based on the acquired information. A response function calculation unit 23, an evaluation unit 24 for evaluating vibration characteristics based on the frequency response function, a storage unit 25 for storing acquired information and the like, and a display unit 26 for displaying the frequency response function and the like are provided. As such an analyzer 21, for example, an FFT (Fast Fourier Transform) analyzer is used. However, the information acquisition unit 22, the frequency response function calculation unit 23, the evaluation unit 24, the storage unit 25, and the display unit 26 do not necessarily need to be incorporated in one device. For example, a part including the information acquisition unit 22 may be incorporated in the analyzer, and the functions of the remaining part may be realized by a computer connected to the analyzer. The evaluation of the vibration characteristics based on the frequency response function may be performed by a person.

  Further, an input unit (not shown) may be provided in the vibration characteristic evaluation device 10 so that conditions such as a rotation speed given to the tire T can be input from the input unit.

(2) Mode of Vibration The vibration characteristic evaluation device 10 of the present embodiment can test at least the vibration in the radial mode and the vibration in the lateral bending mode.

  Here, the radial mode is a mode in which the tire vibrates in the radial direction. Modes from the first order to the higher order can be recognized as radial modes. The primary mode is a mode in which the tire vibrates in the radial direction without deformation when it is assumed that the tire is not in contact with the ground. However, when the tire is in contact with the ground, even in the first mode, the annular tread portion is deformed under the influence of the contact with the ground. The second and subsequent modes are modes in which the annular tread portion is deformed in the radial direction. In the second and subsequent modes, the tread portion is deformed so as to have the same number of peaks in the tire radial direction as the order of the mode. For reference, FIG. 3 schematically shows an exaggerated deformation of the tread portion in the first to fourth mode vibrations. FIG. 3 is a diagram on the assumption that the tire is not in contact with the ground. The vibration in each mode is a vibration in which the tread portion alternates between a solid line and a broken line.

  FIG. 4 is a graph in which the horizontal axis represents the angle from the excitation position and the vertical axis represents the amount of movement of the outer peripheral surface of the tread during vibration. In FIG. 4, the positions at 0 ° and 360 ° are vibration positions. The position of 0 ° in FIG. 4 corresponds to the position of 0 ° in FIG. On the vertical axis, the amount of movement outward in the tire radial direction during vibration is represented as a positive amount, and the amount of movement inward in the tire radial direction is represented as a negative amount with respect to the outer peripheral surface of the tread portion when not vibrating. ing. FIG. 4 shows a deformation of the tread portion for one rotation during vibration. The tread portion vibrates by alternately repeating the deformation of the thick solid line and the deformation of the thin solid line in the figure. In this figure, the same number of cosine waves as the order of the vibration mode appears in the range of one round of the tread portion.

  The lateral bending mode is a mode in which the tread vibrates in the lateral direction (tire width direction). Modes from the first order to the higher order can be recognized as the lateral bending mode. The primary mode is a mode in which the tread swings without being deformed. The secondary and subsequent modes are modes in which the tread portion deforms in the horizontal direction. In the second and subsequent modes, the tread portion is deformed so as to have the same number of peaks in the tire width direction (for example, the right side) as the mode order. For reference, FIG. 5 schematically shows exaggerated deformation of the tread portion in primary and secondary mode vibrations. FIG. 5 is a diagram in the case where it is assumed that the tire is not in contact with the ground. The vibrations in each mode are vibrations in which the tread portion alternates between a solid line and a broken line.

  Also for the lateral bending mode, if the amount of movement to one side in the tire width direction during vibration is a positive amount and the amount of movement to the other side in the tire width direction during vibration is a negative amount based on the surface of the tread portion when not vibrating. 4 can be drawn.

(3) Arrangement of Hammering Device and Non-Contact Sensor The hammering device 13 and the non-contact sensor 20 are different depending on whether the above-described radial mode vibration test is performed or the lateral bending mode vibration test. The arrangement is different.

  As shown in FIG. 1, when performing the test of the vibration in the radial direction mode, the hammering device 13 is arranged so that the hammer 11 can strike the tread portion, which is the outer diameter surface of the tire T, from a vertical direction or a direction close to vertical. Is done. Further, the non-contact sensor 20 is arranged so as to detect the vibration of the tread portion in a non-contact manner.

  Further, as shown in FIG. 2, when a test of vibration in the lateral bending mode is performed, the hammering device 13 is arranged so that the hammer 11 can strike a sidewall portion, which is a lateral surface of the tire T, from a vertical direction or a nearly vertical direction. Is arranged. Further, the non-contact sensor 20 is arranged so as to detect the vibration of the sidewall portion in a non-contact manner.

  In both cases of performing the vibration test in the radial mode and the lateral bending mode, the positions of the non-contact sensor 20 and the hammering device 13 are fixed during the test. However, the positions of the non-contact sensor 20 and the hammering device 13 can be changed so that the tests in both the radial direction mode and the lateral bending mode can be performed by one vibration characteristic evaluation device 10.

  As a preferred form, the hammering device 13 is attached to a moving device (not shown), and the position when the hammering device 13 hits the tread portion and the position when hitting the side wall portion by operating the moving device. Can be moved automatically. The moving device may operate based on an instruction from the input unit. In addition, it is preferable that the non-contact sensor 20 can be automatically moved similarly.

  In the radial mode vibration test, the vibration position by the hammer 11 and the detection position of the vibration of the surface of the tire T by the non-contact sensor 20 (hereinafter, “tire vibration detection position”) are the tire circumferential direction and the tire width direction. Or, it is shifted in a direction oblique to the tire width direction. In the lateral bending mode vibration test, the vibration position and the tire vibration detection position are shifted in the tire circumferential direction, the tire radial direction, or a direction oblique to the tire radial direction.

  In each test, the excitation position is the position of the antinode of the vibration. Therefore, in order to detect the vibration of the surface of the tire T at the position where the amplitude is large, it is preferable that the tire vibration detection position is close to the excitation position. Specifically, when the excitation position and the tire vibration detection position are displaced in the tire circumferential direction, the tire circumferential direction around the tire axis (that is, the tire rotation axis) between the excitation position and the tire vibration detection position is used. Is the angle difference θ (°) (see FIG. 1), where M is the order of the highest-order mode to be evaluated.

It is preferred that If the angle difference θ (°) is within this range, a region on the ventral side of the middle point between the antinode and the node of the vibration of the highest-order mode to be evaluated (for example, if the order of the highest-order mode to be evaluated is 4, Vibration on the surface of the tire T is detected in a region with a large amplitude indicated by oblique lines in FIG. 4). If the tire vibration detection position is in this region, the vibration of the surface of the tire T is detected at a position closer to the antinode of the vibration with respect to the vibration in the mode lower than the highest mode to be evaluated.

  Also, when the vibration position and the tire vibration detection position are displaced in a direction oblique to the tire width direction or in a direction oblique to the tire radial direction, the tire shaft between the vibration position and the tire vibration detection position is also displaced. Is preferably in the range of the above formula (I).

  In a preferred embodiment, as shown in FIG. 1, the non-contact sensor 20 is disposed behind the vibration position of the hammer 11 in the rotation direction of the tire T. Thereby, the non-contact sensor 20 can acquire the vibration at the position on the rear side in the rotation direction of the tire T from the vibration position by the hammer 11. However, the non-contact sensor 20 may be arranged on the front side in the rotation direction of the tire T from the vibration position, and may acquire the vibration at the position on the front side in the rotation direction of the tire T from the vibration position.

2. Vibration Characteristics Evaluation Method (1) Flow of Evaluation The tire vibration characteristics evaluation method of the present embodiment is performed by, for example, the vibration characteristic evaluation device 10 described above.

  First, if necessary, a surface treatment according to the type of the non-contact sensor 20 may be performed on the tire T in order to accurately acquire the vibration of the surface of the tire T. For example, when a laser displacement meter or a laser Doppler vibrometer is used as the non-contact sensor 20, a reflective paint may be applied to the surface of the tire T. When an eddy current sensor is used as the non-contact sensor 20, a metal deposition process may be performed on the surface of the tire T or a metal foil may be attached. When an image sensor is used as the non-contact sensor 20, a colored paint may be applied to the surface of the tire T or a light source may be fixed.

  Next, the tire T is set in the vibration characteristic evaluation device 10. Further, the hammering device 13 and the non-contact sensor 20 are arranged at predetermined positions. After that, the rotation device starts operating and the tire T starts rotating.

Next, the hammering device 13 is operated, and the hammer 11 is swung down on the rotating tire T to vibrate the tire T. This vibration causes the tire T to vibrate. The vibration of the vibration is detected by the vibration sensor 12. What is detected by the vibration sensor 12 is, for example, a force (unit: N). The vibration of the surface of the tire T is detected by the non-contact sensor 20. What is detected by the non-contact sensor 20 is, for example, a speed (unit: m / s). However, what is detected by the non-contact sensor 20 may be a displacement (unit: m) or an acceleration (unit: m / s ² ).

  Here, based on the sampling theorem, the detected maximum frequency is set to be at least twice the frequency of the vibration to be evaluated. For example, since it is known that torsional resonance occurs around 30 Hz, the maximum frequency is set to a frequency of 60 Hz or more when evaluating torsional resonance. In addition, since it is expected that a third-order mode of vibration will occur at 120 to 150 Hz, the maximum frequency is set to a frequency of 300 Hz or more when evaluating the vibration from the first-order mode to the third-order mode. In a preferred embodiment, the maximum frequency to be detected is set to be at least 2.56 times the frequency of the vibration to be evaluated.

Further, the detection of the vibration of the excitation and the detection of the vibration of the surface of the tire T are continuously performed for a predetermined time (for example, a time until the vibration of the surface of the tire T stops). The actual detection time may be appropriately set according to the resolution required for the frequency response function.
Information on each detected vibration is sent to the analyzer 21. The information of each vibration sent to the analysis device 21 is acquired by the information acquisition unit 22, and the frequency response function is calculated by the frequency response function calculation unit 23 based on the information. As represented by the following equation (II), the frequency response function H (f) is obtained by inputting the Fourier spectrum B (f) of the output (ie, the vibration of the surface of the tire T) to the Fourier spectrum of the input (ie, the vibration of the excitation). Defined as divided by the spectrum A (f).

  Therefore, the waveform of the frequency response function is obtained by dividing the output Fourier spectrum by the input Fourier spectrum for each frequency, and plotting the absolute value of the number (complex number) obtained thereby.

However, in a normal test, while there is little noise on the input side, various noises enter on the output side. Then, in order to reduce the influence of noise on the output side, the denominator and numerator on the right side of the above equation (II) are multiplied by the complex conjugate A ^* (f) of A (f), and the following equation (III) May be calculated based on the frequency response function H (f).

Conversely, to reduce the effect of noise on the input side, the denominator and numerator on the right side of the above equation (II) are multiplied by the complex conjugate B ^* (f) of B (f) to obtain the following equation (IV) Is calculated based on the frequency response function H (f).

Where A (f) A ^* (f) is the power spectrum of A (f), B (f) B ^* (f) is the power spectrum of B (f), B (f) A ^* (f) or A (f) B ^* (f) is the cross spectrum of A (f) and B (f).

  In a preferred embodiment, the steps from the excitation of the tire T to the calculation of the frequency response function are performed a plurality of times, and the final frequency response function is calculated from the average of the results of the plurality of times. Of course, the process from the excitation of the tire T to the calculation of the frequency response function may be performed only once.

  Based on the frequency response function calculated in this way, the evaluation unit 24 evaluates the vibration characteristics. Examples of the vibration characteristics include a peak frequency and a damping characteristic of each mode.

  Specifically, since a plurality of peaks having a magnitude equal to or greater than a predetermined value appear in the waveform of the frequency response function, the frequencies of the peaks are obtained. Then, the peak frequency of each mode is specified as the peak of the lowest mode is the peak of the primary mode, and the peak of the higher frequency is the peak of the higher mode. These peak frequencies are the natural frequencies of the tire T. Further, for example, an attenuation ratio is obtained as the attenuation characteristic. The attenuation ratio is obtained by, for example, a half width method or a curve fitting method.

  The evaluation result of the waveform of the frequency response function and the vibration characteristic thus obtained is displayed on the display unit 26. In addition, the information on the vibration, the frequency response function, the evaluation result of the vibration characteristic, and the like are stored in the storage unit 25.

(2) Development Example Although the method of evaluating the vibration characteristics of the tire T under one condition has been described above, the conditions given to the tire T may be changed, and the frequency response functions before and after the change may be calculated. . Then, based on the frequency response functions before and after the change, the change in the vibration characteristic due to the change in the condition given to the tire T may be evaluated.

  Here, the conditions given to the tire T include the rotation speed of the tire T, the load applied to the tire T, the internal pressure of the tire T, the attitude angle of the tire T (that is, the angle of inclination with respect to the vertical direction), and the like. In the present embodiment, since the hammer 11 vibrates the tire T instead of the protrusion attached to the drum D, vibration can be performed even when the tire T is stationary. Therefore, it is also possible to calculate the respective frequency response functions by performing a vibration test when the tire T is stationary and when the tire T is rotating.

  Further, as the change in the vibration characteristic when the above condition is changed, a change in the peak frequency of the frequency response function (that is, the natural frequency of the tire T), a change in the damping characteristic, and the like are evaluated. Since the past test results are stored in the storage unit 25, a change in the vibration characteristics is evaluated by comparing the test results with the results of the newly performed test.

  Alternatively, the type of tire may be changed, the frequency response function before and after the change may be calculated, and the difference in vibration characteristics depending on the type of tire may be evaluated. The types of tires are classified based on size, tread pattern, cross-sectional structure, and the like.

3. Effect In the present embodiment, since the vibration of the vibration is detected by the vibration sensor 12 provided in the vibration means, the magnitude of the input for each frequency is determined by obtaining the Fourier spectrum of the vibration (that is, the input) of the vibration. You can know. Then, the frequency response function is calculated by dividing the Fourier spectrum of the vibration (that is, output) of the surface of the tire T by the Fourier spectrum of the vibration of the excitation as in the above equation (II). It is the size of the output divided by the size of the input. As a result, the frequency response function is such that the influence of the variation in the magnitude of the input for each frequency is eliminated. Therefore, if the vibration characteristics of the tire T are evaluated based on this frequency response function, the evaluation can be performed without the influence of the variation in the magnitude of the input for each frequency.

  Further, in the present embodiment, since the vibration of the surface of the tire T is detected by the non-contact sensor 20 in a non-contact manner, the vibration detected by the object other than the tire T does not significantly affect the detected vibration.

  As described above, according to the method of the present embodiment, the vibration characteristics of the rotating tire T can be more accurately evaluated than before.

  Further, in the present embodiment, since the hammer 11 is used to excite the tire T, it is possible to excite not only when the tire T is rotating but also when the tire T is stationary. Therefore, it is possible to evaluate a change in the vibration characteristics when the tire is stationary and when the tire is rotating.

  By the way, even if the tire T is vibrated in the same manner, the input will be different if the condition given to the tire T or the type of the tire is different. For example, the input differs when the tire T is stationary and when the tire T is rotating, and the input also differs depending on the rotation speed of the tire T.

  However, as described above, in the present embodiment, the magnitude of the output is divided by the magnitude of the input for each frequency to obtain the frequency response function, so that the frequency response function from which the influence of the input difference is eliminated is obtained. Therefore, if the condition given to the tire T or the type of the tire T is changed and the frequency response function is calculated before and after the change to evaluate the vibration characteristics, the condition given to the tire T or the type of the tire T is obtained. The change in the vibration characteristics due to the change in the input can be accurately evaluated without the influence of the change in the input.

  In addition, according to the present embodiment, the tire vibration detection position may be at one place, and the vibration characteristics can be evaluated if the process from the vibration of the tire T to the calculation of the frequency response function is performed at least once. Evaluation of the vibration characteristics of one tire T under one condition can be performed in a short time. Therefore, the evaluation of each vibration characteristic can be performed in a short time while changing the condition given to the tire T or the type of the tire T one after another.

  If the angular difference θ (°) between the vibration position and the tire vibration detection position in the tire circumferential direction about the tire axis is within the range of the above-mentioned formula (I), all the orders to be evaluated are obtained. Mode vibration can be detected near the antinode of the vibration. Therefore, it is possible to reliably detect the vibrations of all the modes of the order to be evaluated, and to accurately evaluate the characteristics of the vibrations of the higher-order modes.

  In addition, if the tire vibration detection position is behind the vibration position in the tire rotation direction, vibration having a larger amplitude can be detected.

4. Example and Comparative Example A frequency response function was actually calculated. The example is an example in which the frequency response function is calculated by the method of the above embodiment. In this embodiment, a laser Doppler vibrometer was used as a non-contact sensor. The frequency response function at rest as well as during tire rotation was calculated. The tire to be evaluated had a size of 205 / 55R16, a rim to be attached of 16 × 6.5JJ, an internal pressure of 250 kPa, and a ground contact load of 4.4 kN. The comparative example differs from the example in that an axial force (force generated on the tire shaft) is detected as an output instead of the vibration of the tire surface.

  FIGS. 6 to 9 show waveforms of the obtained frequency response function. From FIGS. 6 and 8, it was confirmed that according to the method of the example, the peak of the vibration of the higher-order mode clearly appears. On the other hand, from FIGS. 7 and 9, it was confirmed that in the method of the comparative example, the peak of the vibration of the higher-order mode was unclear.

  6 to 9 show waveforms of the frequency response function when the rotational speed of the tire is 0 km / h (that is, at rest) and when the speed is 10 km / h. From FIGS. 6 and 8, which are the waveforms of the example, it was clearly confirmed that the natural frequency of the tire was reduced by rotation.

  FIG. 10 shows the rate of change of the natural frequency when the rotation speed of the tire changes. The rate of change is based on the natural frequency of the tire at rest. Also, the change rates for the primary mode and the secondary mode are shown. From FIG. 10, it was confirmed that the rate of decrease in the natural frequency increases as the rotation speed increases, and that the rate of decrease in the natural frequency decreases as the order of the mode increases.

  Thus, according to the method of the above embodiment, it was confirmed that the vibration characteristics of the rotating tire can be accurately evaluated, and further, the change of the vibration characteristic due to the change of the condition given to the tire can be evaluated.

  D: drum, T: tire, 10: vibration characteristic evaluation device, 11: hammer, 12: vibration sensor, 13: hammering device, 20: non-contact sensor, 21: analysis device, 22: information acquisition unit, 23 ... Frequency response function calculator, 24 ... Evaluator, 25 ... Storage, 26 ... Display

Claims (4)

In a tire vibration characteristic evaluation method of detecting the vibration of the tire by vibrating the tire by the vibration means,
The rotating tire is vibrated by the vibrating means, the vibration of the vibration is detected by a vibrating sensor provided in the vibrating means, and the vibration of the tire surface is non-contacted by a non-contact sensor separated from the tire. And calculating a frequency response function as a ratio of a Fourier spectrum of the vibration of the tire surface to a Fourier spectrum of the vibration of the excitation.   The tire vibration characteristic evaluation method according to claim 1, wherein a condition given to the tire or a type of the tire is changed, the frequency response functions before and after the change are calculated, and a change in the vibration characteristic according to the change is evaluated. The angle difference θ (°) in the tire circumferential direction about the tire axis between the position where the vibration is applied by the vibration means and the position where the non-contact sensor detects the vibration of the tire surface is the highest mode to be evaluated. If the order is M
The tire vibration characteristic evaluation method according to claim 1 or 2, wherein:   The tire vibration characteristic evaluation method according to any one of claims 1 to 3, wherein the non-contact sensor detects vibration at a position rearward in the tire rotation direction from a position where the vibration is performed by the vibration means.