JP4913418B2 - Simulation method for radiation noise from tires - Google Patents

Description

  The present invention relates to a simulation method for simulating radiated noise generated during rolling of a tire and a program therefor, and more particularly to a method for simulating radiated noise based on a pattern impact sound.

  Recently, as attention to environmental problems has increased, efforts to reduce radiated noise (external noise) generated from vehicles have progressed, and reduction of noise radiated from tires has become an urgent task. Noise sources related to radiated noise during tire rolling include pumping noise caused by tire grooves and road clearances, resonance noise of tire cavities, pattern impact sound generated between the pattern placed on the tire surface and the road surface, and slippage. There are sound and vibration noise generated when the tire surface is vibrated by the unevenness of the road surface and the tire surface vibrates.

  Of the radiated noise from these tires, pattern impact sound (sometimes called pattern excitation sound) collides with the road surface when the tread pattern touches down, and the tire vibrates due to the impact force at that time. It is a sound of about 500 Hz to 1 kHz generated by doing this, and is one of the main factors of tire radiation noise.

  Conventionally, in order to improve the noise performance based on such pattern impact sound, the frequency band of the generated noise is predicted using a simple calculation formula, or the noise level is predicted using an estimation formula obtained by an experimental approach. We are carrying out.

  Further, in Patent Document 1 below, the ground contact pattern with respect to the road surface of the tire is scanned along the circumferential direction of the tread pattern to obtain variation data of the contact area of the tread portion, and by frequency analysis based on the variation data. A simulation method for evaluating pattern impact noise has been proposed.

In Patent Document 2 below, an amplitude waveform corresponding to the frequency of noise caused by the tire pitch arrangement is obtained by a noise simulation method, and between the amplitude waveform and a quaternary expression obtained by regression from the amplitude waveform. There has been proposed a method for evaluating whether or not the pitch arrangement is a low pattern noise pitch arrangement from the value of the correlation coefficient.
JP 2003-136926 A International Publication No. WO 97/14946

  In the above-described prior art, simple prediction is limited with respect to the frequency and level of radiation noise of the tire, and there is a problem in prediction accuracy. For example, a tire has a horn shape (a trumpet shape) from the contact end with the road surface, which affects the radiation noise characteristics, and in the case of a pattern impact sound, the tire tread pattern extends in the width direction. Although there is a spread, there is a problem that it is difficult to consider the influence of the width direction in the simple calculation.

  For example, in the case of the above-mentioned Patent Document 1, noise evaluation is performed based on the area variation data of the contact surface. However, since the sub-groove that intersects the main groove generally has variations in depth, the area variation data is accurate. It is difficult to predict. Further, since the noise level is immediately converted from the frequency analysis, it is necessary to obtain the relationship between the frequency analysis result and the noise level in advance.

  This invention is made in view of the above point, and provides the simulation method which can predict the pattern impact sound which is one of the main factors of tire radiation noise accurately, and the program for it. Objective.

  In the method for simulating radiation noise from a tire according to the present invention, the tire circumferential direction includes a plurality of main grooves extending in the tire circumferential direction, and blocks divided by the main grooves and divided by sub-grooves intersecting the main grooves. A pneumatic tire having a tread pattern including a row of blocks arranged along the line simulating radiation noise due to pattern impact sound, the method including the following steps.

(A) a step of obtaining a ground contact shape with respect to a road surface of the tire;
(B) obtaining volume fluctuation data in the tire circumferential direction for each block row using the ground contact shape;
In (c) the volume variation data after converting to impart virtual rolling speed of the tire vibration data to obtain the frequency analysis data representing the volume velocity change due to the frequency to implement the frequency analysis, the frequency analysis data From the contact surface element in the contact end corresponding block of each block row at the time of rolling equivalent, the area of the contact surface element in the contact end corresponding block calculated for each block row, Obtaining the surface velocity from the volumetric velocity of frequency analysis ; and
(D) The surface velocity is given as input information of the sound source in the acoustic analysis to the contact surface element in the block corresponding to the grounding end of each block row in the boundary element model, and the radiation noise from the tire by the acoustic analysis by the boundary element method Step to ask for.

  The present invention also provides a program for executing a simulation method for simulating radiation noise caused by a pattern impact sound for the pneumatic tire having the tread pattern, and the program causes a computer to execute the above steps. Is for.

  The present invention also provides a method for manufacturing a pneumatic tire, wherein the tire is designed and manufactured using the simulation method.

In the present invention, the ground contact shape of the tire is a ground line at the start of tire ground contact. In the step (b), the ground line is scanned along the circumferential direction of the tread pattern, and each block row is scanned. The volume fluctuation data may be obtained .

  According to the present invention, the surface speed at the ground end element of each block row at the time of rolling equivalent is calculated by the ground contact fluctuation analysis, and the surface speed is used as input information for the analysis by the boundary element method. Excellent noise simulation becomes possible. In other words, the present invention focuses on the surface speed at the contact end element of each block row corresponding to rolling, and uses this as a pattern impact sound source to perform simulation by the boundary element method, so that the pattern impact can be achieved with excellent accuracy. Sound can be predicted.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a flowchart showing the flow of a tire pattern impact noise simulation method according to an embodiment of the present invention, which can be implemented using a computer. In this simulation method, tire volume variation data is obtained by ground contact variation analysis using a ground contact shape obtained by a finite element method (FEM) ground contact analysis, a surface speed is calculated from the data, and this is used as a virtual vibration speed. It is used as input information for analysis by the boundary element method (BEM) to simulate radiation noise, and is a simulation method combining FEM and BEM.

  The ground contact fluctuation analysis is performed by modifying the image processing method described in Patent Document 1, and is specifically performed as follows.

  First, as shown in FIG. 1, in step A1, a tread pattern is imaged. More specifically, a tread pattern is created by CAD, and the grounding part and the non-grounded groove part are color-coded. At the time of color classification, color information corresponding to the groove depth is assigned in order to acquire volume fluctuation data in step A3 described later. FIG. 2 is a plan view of a part of a tread pattern of a pneumatic tire to be analyzed, and FIG. 3 is an image of the tread pattern. In FIG. 3, the darkly colored part is the grounding part, and the other part is the non-grounding part, and the closer to white, the deeper the groove depth. Image data representing the tread pattern is stored in the hard disk.

  Here, the tread pattern of the pneumatic tire to be analyzed will be described. As shown in FIG. 2, the tread pattern is formed with a plurality of (four in this example) main grooves 12 extending in the tire circumferential direction and a number of sub grooves 14 crossing the main grooves 12. A block 16 is defined by the groove 12 and the sub-groove 14. The blocks 16 are arranged along the tire circumferential direction to constitute a block row 18, and the block row 18 is divided into a plurality of portions in the tire width direction by the main grooves 12.

  More specifically, in this example, a center rib 20 defined by two main grooves 12 is provided in the center portion in the width direction of the tread, and block rows 18A of mediate portions are provided on both sides on the outer side in the width direction. Further, block rows 18B of shoulder portions are provided on both sides on the outer side in the width direction. In each block row 18, the blocks 16 are formed to have a predetermined pitch length, and the pitch length is set to three or more different lengths. In this example, blocks 16 having three types of pitch lengths of S (small), M (medium), and L (large) are arranged side by side in a predetermined pitch arrangement, and these three types of pitch length are equal to one tire circumference. The average pitch length is set to M which is an intermediate pitch length.

  By imaging the tread pattern, as shown in FIG. 3, the block 16 portion which is a grounding portion is darkly colored, and the groove portion which is a non-grounding portion has a white main groove 12 portion having a deep groove depth. In addition, the sub-groove 14 portion having a shallow groove depth is lightly colored.

  Next, in step A2, a ground shape is obtained by FEM ground analysis. In addition, this step A2 can be implemented by changing the order of the above step A1. Here, FEM (Finite Element Method) is a technique for dividing a structure into finite elements (Finite Elements) in order to investigate the physical properties of the structure, and obtaining a motion equation described by each element by a calculus operation. .

  For FEM ground contact analysis in tires, first, a tire finite element model (tire FEM model) is created by dividing the tire into a finite number of elements, and boundary conditions such as tire internal pressure and load acting on the tire are set. The ground contact simulation by FEM for the virtual road surface is performed using the tire FEM model. For example, ABAQUS Inc. “ABAQUS” of the company, “MARC” of MS Software Co., Ltd., ANSYS Inc. It can be performed using commercially available FEM analysis software such as “ANSYS” of the company.

  FIG. 4 is a main part front view showing a shape when the tire FEM model 22 is grounded on a virtual road surface, and FIG. 5 is a main part plan view of the FEM model 22 showing a tire ground contact shape with respect to the virtual road surface. . Of the ground contact area 24 (the portion colored in gray) when the tire contacts the virtual road surface, the ground line 26 when the tire starts to ground is defined as a ground shape. The data of the ground line 26 is stored in the hard disk.

  Next, in step A3, scanning analysis is performed to acquire volume variation data of the tread pattern. In the scanning analysis, the ground line 26 is scanned along the circumferential direction of the tread pattern (see FIG. 6), and volume fluctuation data in the tire circumferential direction is obtained for each block row 18. The volume variation is obtained from the volume of the space portion existing between the virtual road surface on the contact line 26 and the tire surface. That is, the number of pixels of the grounding part and the non-grounding part existing on the grounding line 26 is counted, the volume is set to 0 in the grounding part, and each pixel is multiplied by the volume determined according to the groove depth in the non-grounding part. The space volume is obtained by summing up each block row 18, and the variation of the space volume in the tire circumferential direction is obtained. The reason why the volume variation data is obtained in this way is that sound is generated by the expansion and compression of air, so that the volume variation in the space between the ground contact portion and the virtual road surface can be regarded as a noise source.

  FIG. 7 is a graph showing volume variation data for the serial and anti-serial side mediate block row 18A and the serial and anti-serial side shoulder row block 18B in the tread pattern shown in FIG. The horizontal axis represents the position in the tire circumferential direction from a certain reference point, and the vertical axis represents the space volume. FIG. 7 shows a part of the data in the tire circumferential direction, but actually, the volume fluctuation data is acquired over the entire circumference of the tire.

  Next, in step A4, frequency analysis is performed using the volume fluctuation data. The frequency analysis is performed after the virtual fluctuation speed (for example, 60 km / h) of the tire is applied to the volume fluctuation data and converted into vibration data, thereby representing the volume speed change depending on the frequency as shown in FIG. Frequency analysis data is obtained. FIG. 8 shows frequency analysis data of the four volume fluctuation data shown in FIG. 7. In FIG. 8, the horizontal axis indicates the frequency and the vertical axis indicates the volume velocity. Here, the said virtual rolling speed is defined according to the measurement conditions of the radiation noise made into the object of simulation.

Thereafter, in step A5, the surface speed of the contact surface element in the block corresponding to the ground end of each block row at the time of rolling is calculated from the frequency analysis data. The surface speed is obtained by calculating the area of the contact surface element in the block corresponding to the ground end for each block row and dividing the volume speed of the frequency analysis data by the area. Specifically, in the case of the tread pattern shown in FIG. 2, the area of the contact surface element in the block corresponding to the ground end is 33.1 mm × 18.3 mm = 605.7 mm ² in the shoulder block row 18B, and the mediate block block row. in 18A 928.3Mm is ^2, the surface speed of the ground terminal element is obtained by dividing the volume velocity shown in FIG. 8 at these areas. At that time, normally, the surface speed of each frequency band is calculated, and for example, the surface speed averaged in increments of 20 Hz is obtained. The area is the area for the block having the pitch length M.

  Next, in step A6, as a preparation for analysis by the boundary element method, a tire boundary element model (tire BEM model) is created by dividing the tire surface and the virtual road surface on which the tire comes into contact with a number of elements. Here, the Boundary Element Method is a computer solution that selects a boundary integral equation as a basic expression and numerically analyzes it through element division of the integration region. In contrast, the boundary element method takes unknowns only on the boundary.

  FIG. 9 is a view showing an example of the tire BEM model 28. The tire BEM model 28 may be created for the entire tire, but in the present embodiment, it is partially created in consideration of the calculation man-hours. Specifically, as shown in FIG. 10, the measurement of the pattern impact sound is performed on the assumption that the microphone 30 is located at a predetermined height at a predetermined distance in front of the tire. It creates about the front-and-rear vicinity region including the ground contact portion with respect to the road surface 32 and the tire portion on the microphone 30 side. In the example of FIG. 10, the tire portion on the microphone 30 side is a portion closer to the microphone 30 than the contact when the tangent line T is drawn from the microphone 30 to the outer peripheral surface of the tire BEM model 28.

  Next, in step A7, a simulation of radiated noise (pattern impact sound) is performed by the boundary element method using the BEM model to obtain a pattern impact sound radiated from the tire. Such acoustic analysis by BEM can be performed using commercially available software such as “SYSNOISE” from LMS International, “RAYON” from ESI.

  The present embodiment is characterized in that the surface speed (vibration speed) of the contact surface element in the corresponding block at the contact end obtained in step A5 is used as input information of the sound source in the BEM analysis. By giving to the contact surface element 34 in the block corresponding to the grounding end of each block row in the model 28 (see FIGS. 9 and 10), energy calculation (numerical calculation) by BEM is performed, so that the predetermined position (that is, the microphone 30) The sound level and frequency can be calculated. The contact surface elements 34 that give the surface speed are all contact surface elements that exist in the block 16 located at the contact end of the tire BEM model 28 (the contact end at the start of contact in front of the traveling direction). 9 is a colored element.

  As described above, the noise level can be accurately predicted for the pattern impact sound of the tire without incurring an excessive calculation cost.

  The simulation method described above can be realized using a computer such as a personal computer. Usually, a simulation program for executing each step of the simulation method is stored in a hard disk of a computer, and various data input from an input means such as a keyboard are appropriately read into a RAM when the program is executed. Is used to calculate by the CPU, and the result is displayed by display means such as a monitor.

  The program functions as follows: a pattern image generation unit that images a tread pattern; a ground shape acquisition unit that acquires a ground shape by FEM analysis; and volume fluctuation data by scanning analysis using the pattern image and the ground shape. The volume fluctuation data acquisition section for acquiring the frequency fluctuation, the frequency analysis section for frequency analysis of the volume fluctuation data, and the surface speed for calculating the surface speed of the grounded end element of each block row at the time of rolling from the obtained frequency analysis data Each function of the calculation unit, the BEM model creation unit that creates a BEM model for simulating a pattern impact sound, and the BEM analysis unit that performs a BEM analysis to obtain a pattern impact sound is realized. Such a simulation program may be recorded on a computer-readable recording medium (CD-ROM, DVD, etc.).

  The simulation method can be used for tire design, and noise evaluation is performed on the tire modeled based on a predetermined design value by the simulation method, and whether the obtained result achieves the target performance. If the design value is not achieved and the design value is changed and the simulation method is repeated until the target performance is achieved, a design value that satisfies the target performance can be obtained. And by manufacturing a tire based on the design value obtained by this design method, a pneumatic tire with reduced pattern impact sound can be designed and manufactured at low cost.

  In order to show the effect of the simulation method according to the embodiment, a comparison experiment with actual measurement values was performed. In the experiment, simulation methods (examples) according to the above-described embodiment and bench measurements (actual measurement values) using the tires were actually performed on three types of tires with a pattern of 195 / 65R15.

  The three types of tread patterns to be measured are the angle α with respect to the tire width direction of the sub-groove 14A that partitions each block in the block row 18A of the mediate portion, and the sub-groove 14B that partitions each block in the block row 18B of the shoulder portion. The angle β with respect to the tire width direction (see FIG. 2) was set as shown in Table 1 below, and the other configurations were the same.

  The pattern impact sound was measured at a tire speed of 60 km / h, measured with a microphone at a position 100 cm ahead of the tire in the traveling direction and a height of 25 cm from the road surface. In addition, in the BEM analysis of the example, when the surface speed was applied to each grounded end element, the surface speed averaged in increments of 20 Hz was applied.

The results are as shown in Table 1 below, and the noise level in the generated frequency band (375 to 625 Hz) was evaluated. According to this example, the noise level was accurately measured for all three types of tread patterns. Further, the noise level between the three types of tread patterns can be predicted, and in this embodiment, the same ranking as the actually measured values is made.

  Since the present invention can accurately predict the pattern impact sound that is the main factor of the radiation noise of the tire, for example, when designing a pneumatic tire, the pattern impact sound of the tire can be predicted by simulation. Can be used effectively for tire design.

It is a flowchart which shows the flow of the simulation method which concerns on one Embodiment of this invention. It is a partial development figure of the tread pattern of the pneumatic tire which is an analysis object. It is the figure which imaged this tread pattern. It is a principal part front view which shows a shape when a tire FEM model is grounded. It is a principal part top view of the FEM model which shows the contact shape of the tire with respect to a virtual road surface. It is a figure which shows the place which is scanning-analyzing on a pattern image. It is a graph which shows volume fluctuation data. It is a graph which shows frequency analysis data. It is a perspective view of a BEM model. It is a side view of the BEM model.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 12 ... Main groove, 14 ... Sub groove, 16 ... Block, 18 ... Block row, 22 ... Tire FEM model, 24 ... Ground area, 26 ... Ground line, 28 ... Tire BEM model, 30 ... Microphone, 32 ... Virtual road surface, 34 ... Contact surface element in the block corresponding to the ground end

Claims (5)

A tread comprising a plurality of main grooves extending in the tire circumferential direction and a block row in which blocks divided by the main grooves and divided by sub-grooves intersecting the main grooves are arranged along the tire circumferential direction A method of simulating radiation noise caused by pattern impact sound for a pneumatic tire of a pattern,
(A) a step of obtaining a ground contact shape with respect to a road surface of the tire;
(B) obtaining volume fluctuation data in the tire circumferential direction for each block row using the ground contact shape;
In (c) the volume variation data after converting to impart virtual rolling speed of the tire vibration data to obtain the frequency analysis data representing the volume velocity change due to the frequency to implement the frequency analysis, the frequency analysis data From the contact surface element in the contact end corresponding block of each block row at the time of rolling equivalent, the area of the contact surface element in the contact end corresponding block calculated for each block row, Obtaining the surface velocity from the volumetric velocity of frequency analysis ;
(D) The surface velocity is given as input information of the sound source in the acoustic analysis to the contact surface element in the block corresponding to the grounding end of each block row in the boundary element model, and the radiation noise from the tire by the acoustic analysis by the boundary element method A step of seeking
For radiating noise from tires including   The ground contact shape of the tire is a ground line at the start of tire ground contact, and in the step (b), the ground line is scanned along the circumferential direction of the tread pattern, and the volume variation data is obtained for each block row. The simulation method according to claim 1, wherein the simulation method is obtained. In the step (d), assuming that there is a microphone at a predetermined height with a distance in front of the tire, the boundary element model of the tire includes a front and rear vicinity region including a ground contact portion with respect to the virtual road surface and the microphone side. The simulation method according to claim 1, wherein a radiation noise from the tire at the microphone position is obtained using the boundary element model. A tread comprising a plurality of main grooves extending in the tire circumferential direction and a block row in which blocks divided by the main grooves and divided by sub-grooves intersecting the main grooves are arranged along the tire circumferential direction A program for executing a simulation method for simulating radiation noise caused by a pattern impact sound for a pneumatic tire of a pattern,
(A) a step of obtaining a ground contact shape with respect to a road surface of the tire;
(B) obtaining volume fluctuation data in the tire circumferential direction for each block row using the ground contact shape;
In (c) the volume variation data after converting to impart virtual rolling speed of the tire vibration data to obtain the frequency analysis data representing the volume velocity change due to the frequency to implement the frequency analysis, the frequency analysis data From the contact surface element in the contact end corresponding block of each block row at the time of rolling equivalent, the area of the contact surface element in the contact end corresponding block calculated for each block row, Obtaining the surface velocity from the volumetric velocity of frequency analysis ;
(D) The surface velocity is given as input information of the sound source in the acoustic analysis to the contact surface element in the block corresponding to the grounding end of each block row in the boundary element model, and the radiation noise from the tire by the acoustic analysis by the boundary element method A step of seeking
A program that causes a computer to execute. Design a tire using the simulation method according to any one of claims 1 to 3, the pneumatic tire manufacturing method, characterized by manufacturing.