JP2017020961A - Tire noise display method, and noise performance evaluation method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To represent the transition of pitch sound and main groove air column resonance sound due to speech change to be utilized for evaluation of a tire noise characteristic and design change of a tread pattern.SOLUTION: A noise performance evaluation method includes a measurement process, an analysis process and a display process. In the measurement process, tire noise is measured while changing a travel speed of a tire to acquire noise information. In the analysis process, the noise information undergoes a frequency analysis in each travel speed to acquire noise data B composed of a frequency of sound volume in each travel speed. In the display process, travel speed data A and the noise data B are displayed in one graph. The travel speed is displayed in one axial direction of the graph, the frequency is displayed in the other axial direction, and also, the sound volume is displayed at a position at which the travel speed and the frequency cross each other by a change of a color element including saturation, hue, and brightness.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a tire noise display method useful for evaluation of tire noise characteristics and tread pattern design change, and a noise performance evaluation method using the same.

  As a tire noise test method, for example, a method in which a tire is rotated at a steady speed on a drum and noise generated at that time is measured with a microphone is known (for example, see Patent Documents 1 and 2).

  Conventionally, frequency analysis of the measured noise is performed to graph the frequency distribution of the sound pressure level, and the noise performance of the tire is evaluated based on this graph. Specifically, as illustrated in FIG. 6, frequency analysis (for example, 1/3 octave analysis) of tire noise is performed, the frequency is plotted on the horizontal axis, and the sound pressure level (dB) is plotted on the vertical axis. Is graphed. The noise performance is evaluated based on the sound pressure level and frequency at the peak point a in this graph, the overall level (O.A.), and the like.

  Here, main causes of tire noise include main groove air column resonance sound caused by the circumferential main groove in the tread pattern and pitch sound caused by the lateral groove. The main groove air column resonance is air column resonance generated from an air column tube formed by a circumferential main groove and a road surface, and the frequency thereof is the length of the circumferential main groove in the ground plane. Affected. The pitch sound is an impact sound when the horizontal groove contacts the road surface, and its frequency is influenced by the running speed, the tire circumferential length, and the number of pitches of the horizontal groove.

  However, the conventional graph is obtained from noise information measured at only one traveling speed (steady speed), and is only a frequency distribution of the sound pressure level. Therefore, just looking at this graph, what frequency sound is the pitch sound and main groove air column resonance sound, or how much the pitch sound overlaps with the main groove air column resonance sound and other sounds? I do n’t know if.

  For this reason, it is difficult to sufficiently evaluate the noise characteristics of the tire, and it has not been possible to sufficiently utilize the design change of the tread pattern.

JP2013-86656A JP 2013-134213 A

  Therefore, the present invention is directed to the transition of pitch sound and main groove air column resonance sound accompanying speed change, and which sound is pitch sound or main groove air column resonance sound, or pitch sound is main groove air column resonance sound. It is possible to express how much it overlaps with other sounds, such as the tire noise display method that is useful for evaluating the tire noise characteristics and changing the tread pattern design, and the noise performance evaluation method using it. The issue is to provide.

1st invention of this application is a display method which displays the noise of a tire,
A measurement process for obtaining noise information by measuring the noise of a tire rotating on a road surface while changing the running speed of the tire, using at least one microphone;
Analyzing the frequency of the noise information for each traveling speed to obtain the traveling speed data A and noise data B including the frequency and sound pressure level or sound energy at each traveling speed;
And a display step of displaying the travel speed data A and the noise data B in one graph,
In the display step, the travel speed is displayed in one axial direction of the graph, the frequency is displayed in the other axial direction, and the volume, saturation, hue, and brightness are displayed at a position where the travel speed and the frequency intersect. It is characterized by being displayed with changes in color elements including

  In the tire noise display method according to the present invention, the traveling speed is partitioned into a plurality of small speed regions, the frequency is partitioned into a plurality of small band regions, and the small speed region and the small band region include It is preferable that the intersecting position is one dot and each dot is displayed by the change of the color element.

  In the tire noise display method according to the present invention, the frequency analysis is preferably octave analysis or narrowband analysis.

  In the tire noise display method according to the present invention, a volume range that is an area range from the minimum value to the maximum value of the volume is equally divided into 6 to 18 small ranges, and each small range is distinguished by a color element. It is preferred that

  In the tire noise display method according to the present invention, in the measurement step, n microphones are installed at different positions, tire noise is simultaneously measured from each microphone to obtain noise information, and in the analysis step, It is preferable that the noise data B obtained from each noise information is integrated into one integrated data B0, and the travel speed data A and the integrated data B0 are displayed in one graph in the display step.

In the tire noise display method according to the present invention, a sound pressure level L is adopted as the volume,
In the integrated data B0, the average sound pressure level Lmean obtained by averaging the sound pressure levels L1 to Ln having the same traveling speed and the same frequency in each noise data B by the following equation (1) is set as the volume of the integrated data B0. Is preferred.

In the tire noise display method according to the present invention, a sound pressure level L is adopted as the volume,
In the integrated data B0, in each noise data B, the added sound pressure level Lsum obtained by adding the sound pressure levels L1 to Ln having the same traveling speed and the same frequency according to the following equation (2) is used as the volume of the integrated data B0. It is preferable to do this.

  In the tire noise display method according to the present invention, the number of the microphones is 2 to 5, and each microphone is forward, backward, and laterally perpendicular to the traveling direction with respect to the ground contact center of the tire. Installed at the same height and at the same distance from the ground contact center of the tire, at a position selected from diagonally forward between the front and side and diagonally rear between the rear and side. Is preferred.

  In the tire noise display method according to the present invention, the traveling speed continuously changes at a constant rate from the high speed side to the low speed side in a range of 120 to 40 km / h, and the rate of the change is It is preferably 0.1 to 5.0 km / h per second.

  The second invention of the present application is a tire noise performance evaluation method, wherein a tread groove including a circumferential main groove and a lateral groove is formed in the tread portion of the tire, and the tire noise display method of the first invention is used. The pitch noise caused by the lateral grooves and / or the air column resonance noise caused by the circumferential main grooves are evaluated.

  Since the present invention is configured as described above, only by looking at the graph, the transition of the pitch sound and the main groove air column resonance sound according to the change in travel speed, and which sound is the pitch sound and main groove air column resonance sound It can be easily understood by the change of the color element whether it is a sound or how much the pitch sound overlaps with the main groove air column resonance sound and other sounds.

  For this reason, it can be greatly useful for the evaluation of the noise characteristics of the tire and the design change of the tread pattern.

(A), (B) is the top view and side view which show the measurement process in the noise display method of the tire of this invention. It is a conceptual diagram of an analysis process. It is an example of the graph which displayed the noise by the noise display method of the tire of this invention. It is explanatory drawing which shows a volume range. It is explanatory drawing which shows the dot of a graph. It is the graph of the conventional tire noise which displayed the frequency distribution of the sound pressure level.

  Hereinafter, embodiments of the present invention will be described in detail. The tire noise display method of the present invention includes a measurement process, an analysis process, and a display process.

  As shown in FIG. 1, in the measurement step, noise information is obtained by measuring the noise of the tire T rotating on the road surface S while changing the traveling speed of the tire T using at least one microphone 2.

  A tread pattern including tread grooves 4 is disposed on the tread surface of the tire T. The tread groove 4 of this example includes a circumferential main groove 4A extending in the tire circumferential direction and a lateral groove 4B in a direction intersecting with the circumferential main groove 4A. Various tread grooves 4 can be employed.

  In this example, the outer peripheral surface of the drum 3 is employed as the road surface S. Specifically, by pressing the tread surface of the tire T against the outer peripheral surface of the drum 3 that is rotationally driven, the tire T is substantially the same as the drum 3 on the outer peripheral surface of the drum 3 that is the road surface S. Can rotate at speed. And the tire noise at that time is measured using the microphone 2.

  The number of the microphones 2 is one or more, and preferably 2 to 5 are used. In a plurality of cases, tire noise is simultaneously measured by each microphone 2. Each microphone 2 needs to be installed at an equal distance from the ground contact center J of the tire as a sound source and at the same height. Further, each microphone 2 has a front f1 and a rear f2 in the traveling direction with respect to the grounding center J, a side f3 perpendicular to the traveling direction, an oblique front f4 between the front f1 and the side f3, and a rear f2 and a side. It is preferable to arrange at a position selected from diagonally rear f5 between f3. Although not particularly restricted, the horizontal distance k from the ground center J of each microphone 2 is preferably in the range of 0.1 to 1.0 m, and the height h from the ground center J is 0.03 to 0.25 m. A range is preferred.

  The traveling speed of the tire T is preferably in a range of 120 to 40 km / h where noise is a problem, and is preferably continuously changed from a high speed side to a low speed side at a constant rate. The rate of speed change at this time is more preferably 0.1 to 5.0 km / h per second. The reason for changing the speed from the high speed side to the low speed side is that speed control is easier in deceleration.

  Next, in the analysis step, the tire noise information obtained in the measurement step is subjected to frequency analysis for each traveling speed, thereby obtaining traveling speed data A and noise data B comprising frequency and volume. The “volume” means a sound pressure level or sound energy.

  Specifically, as conceptually shown in FIG. 2, noise data B that is a frequency distribution of sound volume (for example, sound pressure level) is obtained at each traveling speed by frequency analysis for each traveling speed. .

  As frequency analysis, octave analysis and narrowband analysis can be employed. As the octave analysis, 1/3 octave analysis, 1/12 octave analysis, 1/24 octave analysis, or the like can be suitably employed. For example, in the case of octave analysis, the frequency is partitioned into 63 Hz, 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz,... Octave bands X based on 1000 Hz, and each octave band X is, for example, 1/3. It is further divided into three small band regions x in the octave analysis and 12 in the 1/12 octave analysis. Then, the sound pressure level at the center frequency of each small band region x is set as the sound pressure level of the small band region x.

As is well known, the sound pressure level L (unit: dB) is 20 times the common logarithm of the ratio between the sound pressure P and the reference sound pressure P0, and is expressed by the following equation. The reference sound pressure P0 is the minimum audible value at a frequency of 1000 Hz and is 20 μPa.
L = 20 Log ₁₀ (P / P0) = 20 Log ₁₀ P-20 Log ₁₀ P0

Further, since the sound energy E is proportional to the square of the sound pressure P, that is, can be expressed by E = P ² × C (C is a coefficient), when the sound energy E is displayed in decibels, it is expressed by the following equation.
E ′ = ₁₀ Log ₁₀ E = ₁₀ Log ₁₀ (P ² × C) = 20 Log ₁₀ P + ₁₀ Log ₁₀ C

  As described above, the sound energy E ′ in the decibel display is obtained by translating the sound pressure level, and the relative value is the same as the sound pressure level. Accordingly, either “sound pressure level” or “decibel-displayed sound energy E ′” can be adopted as the “volume”.

Further, as in this example, when a plurality (n) of microphones 2 are used, in the analysis step, the noise data B _{1 to} B _n obtained from each noise information are integrated into one integrated data B 0. The

Here, when the sound pressure level L is employed as the volume, the noise data B _{1 to} B _n can be integrated as follows. In the noise data B _{1 to} B _n , the sound pressure levels L _{1 to} L _n having the same traveling speed and the same frequency are averaged by the following equation (1), and the average sound pressure level Lmean obtained by this is calculated as the integrated data B 0. Adopt as volume. N in the equation is the number of microphones 2.

Alternatively, in the noise data B _{1 to} B _n , the sound pressure levels L _{1 to} L _n having the same traveling speed and the same frequency are added by the following equation (2), and the added sound pressure level Lsum obtained thereby is used as the integrated data. It can be adopted as the volume of B0.

Further, as described above, the sound energy E ′ in decibel display is the same as the sound pressure level as a relative value. Therefore, when the sound energy E ′ displayed in decibels is adopted as the volume, the sound pressure levels L _{1 to} L _n in the above formulas (1) and (2) are replaced with the sound energy E ₁ ′ to E _n ′ displayed in decibels. The average sound energy E′mean or the added sound energy E′sum replaced by can be adopted as the volume of the integrated data B0.

  Next, in the display step, the traveling speed data A and noise data B (or integrated data B0) are displayed as one graph 10.

  Specifically, as shown in FIG. 3, the traveling speed of the tire T is displayed in one axial direction of the graph 10 (in this example, the vertical axis direction). The frequency is displayed in the other axial direction (in this example, the horizontal axis direction). At each position where the traveling speed and the frequency intersect, the sound volume is displayed by changes in color elements including saturation, hue, and brightness. In this example, for the sake of convenience, different sound volumes are indicated by shading and different hatching. If the frequency range to be displayed is too narrow, the noise performance of the tire cannot be expressed sufficiently, and conversely, if it is too wide, work and time are wasted. Therefore, the range of the frequency to be displayed is preferably 100 to 2000 Hz.

  Strictly speaking, as shown in FIG. 5, in the graph 10, the traveling speed is divided into a plurality of small speed regions z, and the frequency is divided into a plurality of the small band regions x. Then, the position where each small speed region z and the small band region x intersect is set to 1 dot D, and each dot D is displayed by the change of the color element. The small band area x is set by frequency analysis. The small speed range z can be freely set, for example, 2 km / h width, 4 km / h width, and the like.

  As the change of the color element, as shown in FIG. 4, for example, a volume range Y that is an area range from a minimum value (58 dB in this example) to a maximum value (82 dB in this example) in the noise data B is set, for example. Divide equally into 6 to 18 small ranges y. In the case of this example, the volume range Y from 58 dB to 82 dB is equally divided into 12 small ranges y. And each small range y is distinguished by the difference in a color element. In this case, each small range y is distinguished by a difference in saturation, by a difference in hue, by a difference in brightness, or by a difference in saturation, a difference in hue, and a brightness. It is also possible to distinguish by combining the differences.

  Here, the small range y displayed on the dot D is determined by the volume obtained by the center speed of the small speed region z and the center frequency of the small band region x.

  Next, a tire noise performance evaluation method using the noise display method will be described. As described above, main causes of tire noise include main groove air column resonance sound caused by the circumferential main groove 4A in the tread pattern and pitch sound caused by the lateral groove 4B. The frequency of the main groove air column resonance sound is influenced by the length of the circumferential main groove 4A in the contact surface, but is not affected by the running speed of the tire. On the other hand, the frequency of the pitch sound is affected by the traveling speed, the tire circumference, and the number of pitches of the lateral grooves 4B.

  Therefore, in the graph using the noise display method, as shown in FIG. 3, the transition of the main groove air column resonance sound and the pitch sound can be easily understood by the change of the color element. Specifically, in the test tire T of this example, it can be evaluated that the main groove air column resonance sound Na (encircled by a broken line) is generated in the frequency band 516 to 649 Hz. In addition, the primary component Nb1, the secondary component Nb2, and the tertiary component Nb3 (enclosed by a one-dot chain line) of the pitch sound are generated, and the noise of the secondary component Nb2 is large, particularly at a speed of 60 to 80 km / h. It is possible to obtain an evaluation that the noise is increased by overlapping the main groove air column resonance sound Na and the secondary component Nb2 of the pitch sound.

  Therefore, based on this evaluation, for example, the generation frequency range of the main groove air column resonance is reduced to, for example, 460 Hz or less, the sound pressure level of the secondary component Nb2 of the pitch sound is lowered, and / or the secondary component of the pitch sound. It is possible to improve the noise performance of the test tire by changing the design of the tread pattern so as to shift the Nb2 generation frequency range to the high frequency side.

  On the other hand, in the conventional graph shown in FIG. 6, which frequency sound is the pitch sound or the main groove air column resonance sound, or the pitch sound is the main groove air column resonance sound or any other sound. I don't know if they overlap. For this reason, it is difficult to sufficiently evaluate the noise characteristics of the tire, and it is not possible to make full use of the tread pattern design change.

Note that FIG. 3 is a noise graph according to the display method of the present invention performed on the test tire of the tire size (275 / 80R22.5) based on the following specifications.
<Measurement process>
Tire internal pressure: 670 kPa
Longitudinal load: 25.8kN
Tire running speed: 100km / h → Deceleration to 40km / h Rate of speed change: 2.0km / h per second
Drum outer peripheral surface: replica road surface Number of microphones: 1 (installation position is side f3)
Measurement time: 1 second <analysis process>
Frequency analysis: 1/12 octave analysis Frequency: 103-1939Hz
<Display process>
Small band of 1 dot: 6 to 343 Hz
〃 Small speed range: 2.0km / h
Sound pressure level: Volume range 58-82dB is divided into 12 small ranges Small range width: 2dB
(The small range is determined by the sound pressure level determined by the center velocity of the small velocity region z and the center frequency of the small band region x.)

FIG. 6 is a graph of noise by the conventional display method performed on the same test tire based on the following specifications.
<Measurement process>
Tire internal pressure: 670 kPa
Longitudinal load: 25.8kN
Tire running speed: 70km / h
Drum outer peripheral surface: replica road surface Number of microphones: 1 (installation position is side f3)
Measurement time: 1 second <analysis process>
Frequency analysis: 1/3 octave analysis Frequency: 63-6300Hz

  As the road surface S, in addition to the outer peripheral surface of the drum 3, for example, an outer peripheral surface of an endless belt that can be circulated, such as a flat belt type tire testing device, can be used. Moreover, the road surface S of an actual road may be sufficient. In this case, the vehicle travels on the road surface S using a vehicle equipped with test tires and, after reaching a predetermined set speed, is coasted with the engine off. And the measurement process can be performed by measuring the tire noise at that time using the microphone 2 fixed to the vehicle. In addition, the change in traveling speed can utilize the speed reduction during coasting traveling. However, the coasting can be repeated by changing the set speed sequentially.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

2 Microphone 4 Tread groove 4A Circumferential main groove 4B Horizontal groove 10 Graph D Dot E Sound energy J Ground center L Sound pressure level S Road surface x Small band area Y Volume range y Small range z Small speed area T Tire

Claims (10)

A display method for displaying tire noise,
A measurement process for obtaining noise information by measuring the noise of a tire rotating on a road surface while changing the running speed of the tire, using at least one microphone;
Analyzing the frequency of the noise information for each traveling speed to obtain the traveling speed data A and noise data B including the frequency and sound pressure level or sound energy at each traveling speed;
And a display step of displaying the travel speed data A and the noise data B in one graph,
In the display step, the travel speed is displayed in one axial direction of the graph, the frequency is displayed in the other axial direction, and the volume, saturation, hue, and brightness are displayed at a position where the travel speed and the frequency intersect. A method for displaying a noise of a tire, characterized by displaying a change in color elements including   In the display step, the traveling speed is divided into a plurality of small speed areas, the frequency is divided into a plurality of small band areas, and a position where the small speed area and the small band area intersect is defined as one dot. The tire noise display method according to claim 1, wherein each dot is displayed by a change in the color element.   The tire noise display method according to claim 1 or 2, wherein the frequency analysis is octave analysis or narrowband analysis.   The volume range which is a region range from the minimum value to the maximum value of the volume is equally divided into 6 to 18 small ranges, and each small range is distinguished by a color element. The tire noise display method according to any one of the above. In the measurement step, n microphones are installed at different positions, and noise information is obtained by simultaneously measuring tire noise from each microphone.
In the analysis step, the noise data B obtained from each noise information is integrated into one integrated data B0,
5. The tire noise display method according to claim 1, wherein in the display step, the travel speed data A and the integrated data B <b> 0 are displayed as one graph. A sound pressure level L is adopted as the volume,
In the integrated data B0, in each noise data B, and the sound pressure level L ₁ ~L _n the same speed and the same frequency, the average sound pressure level Lmean averaged by the following formula (1), the volume of the integrated data B0 The tire noise display method according to claim 5, wherein:
A sound pressure level L is adopted as the volume,
In the integrated data B0, in each noise data B, the added sound pressure level Lsum obtained by adding the sound pressure levels L1 to Ln having the same traveling speed and the same frequency according to the following equation (2) is used as the volume of the integrated data B0. The tire noise display method according to claim 5, wherein the tire noise is displayed.
The number of the microphones is 2 to 5,
Each microphone is selected from the front and rear in the traveling direction with respect to the ground contact center of the tire, the side perpendicular to the traveling direction, the diagonal front between the front and the side, and the diagonal rear between the rear and the side. The tire noise display method according to any one of claims 1 to 7, wherein the tire noise display method is installed at a position that is equidistant from the ground contact center of the tire and at the same height.   The traveling speed continuously changes at a constant rate from the high speed side to the low speed side in a range of 120 to 40 km / h, and the rate of change is 0.1 to 5.0 km / h per second. The tire noise display method according to claim 1, wherein the tire noise is displayed.   A tread groove including a circumferential main groove and a lateral groove is formed in a tread portion of the tire, and a pitch noise caused by the lateral groove is obtained using the tire noise display method according to claim 1. And / or evaluation of air column resonance caused by the circumferential main groove.