Noise prediction method

Abstract

It accurately predicts in-car noise originating from tires. [Solution] A noise prediction method for predicting in-vehicle noise originating from tires, wherein a first transfer function showing the relationship between tire axle vibration and in-vehicle noise is determined by testing, in-vehicle noise due to structural propagation is calculated from the tire axle vibration obtained by numerical analysis and the first transfer function, and the tire axle vibration is determined in the numerical analysis by performing a rolling analysis in which a tire model assembled on a wheel model is rolled.

Description

Technical Field

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[0001] The present invention relates to a noise prediction method.

Background Art

[0002] ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0007] This invention was made in view of the above circumstances, and aims to provide a method for accurately predicting in-vehicle noise originating from tires. [Means for solving the problem]

[0008] The present invention includes embodiments shown below.

[0009] [1] A noise prediction method for predicting in-vehicle noise originating from tires, wherein a first transfer function showing the relationship between tire axle vibration and in-vehicle noise is determined by test, in-vehicle noise due to structural propagation is calculated from the tire axle vibration obtained by numerical analysis and the first transfer function, and the tire axle vibration is determined in the numerical analysis by performing a rolling analysis in which a tire model assembled on a wheel model is rolled.

[0010] [2] A noise prediction method according to [1], wherein a second transfer function showing the relationship between tire noise around the tires and interior noise is determined by test, interior noise due to air propagation is calculated from the tire noise around the tires obtained by numerical analysis and the second transfer function, and the interior noise due to structural propagation and the interior noise due to air propagation are added together to obtain the interior noise.

[0011] [3] The noise prediction method according to [2], wherein the tire noise is determined by performing a rolling analysis in which a tire model assembled on a wheel model is rolled in the numerical analysis for determining the tire noise.

[0012] [4] The noise prediction method according to any one of [1] to [3], wherein the rolling analysis is performed with the contact portion between the tire model and the wheel model coupled and constrained.

[0013] [5] The noise prediction method according to any one of [1] to [4], wherein in the numerical analysis, the first step is to assemble the tire model onto the wheel model, the second step is to apply internal pressure to the tire model, the third step is to connect and restrain the contact portion between the tire model and the wheel model, the fourth step is to perform a contact analysis to bring the tire model into contact with the road surface model, and the fifth step is to perform a rolling analysis to roll the tire model on the road surface model, the steps being performed in the order of the first to fifth steps. [Effects of the Invention]

[0014] According to this embodiment, it is possible to accurately predict in-vehicle noise originating from tires. [Brief explanation of the drawing]

[0015] [Figure 1] A diagram illustrating the sound transmission path from the tires to the interior of the vehicle. [Figure 2] A flowchart for noise prediction methods. [Figure 3] A diagram showing the vehicle in a test to obtain the first transfer function. [Figure 4] (a) is a top view of the tire mounting surface. (b) is a top view of the tire and wheel mounted on the tire mounting surface. [Figure 5] Perspective view of the vibration jig used in the test to obtain the first transfer function. (a) shows the XYZ directions orthogonal to the vibration direction. (b) shows the direction of the moment that produces rotation around the X axis as the vibration direction. (c) shows the direction of the moment that produces rotation around the Z axis as the vibration direction. [Figure 6] A diagram showing the vehicle in a test to obtain the second transfer function. [Figure 7] A diagram illustrating the direction of a tire. (a) is a view of the tire from the front. (b) is a view of the contact surface of the tire in (a) from above. [Figure 8] A flowchart for numerical analysis. [Figure 9]A diagram showing a vehicle in a test of a modification example for obtaining a first transfer function.

Embodiments for Carrying Out the Invention

[0016] Embodiments will be described based on the drawings. Note that the embodiments described below are merely examples, and those appropriately modified without departing from the gist of the present invention are included in the scope of the present invention.

[0017] In the present embodiment, the in-vehicle noise caused by the rolling of a pneumatic tire (hereinafter simply referred to as "tire") on a road surface is predicted. Hereinafter, the in-vehicle noise means the noise at the position of the ears of the passengers in the vehicle.

[0018] First, the sound transmission path from the tire to the vehicle interior will be described based on FIG. 1. When the tire rolls on the road surface, two types of vibrations of the tire occur as a result of this, namely, tire pattern vibration and tire body vibration. The tire pattern vibration is the vibration of the part of the tire tread that is in contact with the road surface. Also, the tire body vibration is the vibration of the part of the tire that is not in contact with the road surface (including parts such as the sidewall and the part of the tread that is not in contact with the road surface). The tire pattern vibration and the tire body vibration are transmitted to the vehicle body and become vehicle body vibrations. The vehicle body vibrations become noise and are transmitted to the ears of the passengers in the vehicle interior.

[0019] When the tire rolls on the road surface, two types of sounds occur as tire noise around the tire outside the vehicle due to this (the "tire noise" refers to the sound generated from the tire due to the rolling of the tire): tire pattern noise and tire body noise. The tire pattern noise is the sound generated by the vibration of the portion of the tire tread that is in contact with the road surface. Also, the tire body noise is the sound generated by the vibration of the portion of the tire that is not in contact with the road surface (including the sidewall and the portion of the tread that is not in contact with the road surface, etc.). The tire pattern noise and the tire body noise are transmitted through the air and penetrate into the vehicle interior, becoming noise and reaching the ears of the passengers inside the vehicle.

[0020] The transmission of tire pattern vibration and tire body vibration to the ears of the passengers inside the vehicle as noise is called structure-borne transmission. Also, the transmission of tire pattern noise and tire body noise to the ears of the passengers inside the vehicle as noise is called air-borne transmission. The noise reaching the ears of the passengers inside the vehicle is the combined result of structure-borne noise (referred to as "structure-borne noise") and air-borne noise (referred to as "air-borne noise").

[0021] The noise prediction method of this embodiment is implemented according to the flowchart of FIG. 2. First, a first transfer function, which is a transfer function of structure-borne transmission, is obtained through testing (step S1). Here, since the tire pattern vibration and the tire body vibration are transmitted to the rotation axis of the tire (hereinafter also referred to as the "tire axis"), they can be measured as the vibration of the vibration of the rotation axis of the tire (hereinafter referred to as "tire axis vibration"). Therefore, the transfer function of structure-borne transmission in this embodiment is a function showing the relationship between the tire axis vibration and the noise at the position of the ears of the passengers inside the vehicle. Also, obtaining through testing means obtaining through measuring actual sounds and the like using actual tires and vehicles.

[0022] Next, a second transfer function, which is a transfer function of air-borne transmission, is obtained through testing (step S2). Here, the transfer function of air-borne transmission is a function showing the relationship between the tire noise around the tire outside the vehicle and the noise at the position of the ears of the passengers inside the vehicle.

[0023] Next, the tire axle vibration when the tire rolls on the road surface is obtained by numerical analysis (step S3). In this embodiment, the tire axle vibration includes vibrations originating from the tire body and vibrations originating from the tire pattern. Furthermore, finite element analysis is performed as the numerical analysis to obtain the tire axle vibration.

[0024] Next, the tire noise around the tire outside the vehicle as the tire rolls on the road surface is acquired by numerical analysis (step S4). In this embodiment, tire body noise and tire pattern noise are acquired as tire noise. Furthermore, finite element analysis and boundary element analysis are performed as numerical analyses to acquire the tire noise.

[0025] Next, the structural propagation noise is calculated by multiplying the tire axle vibration obtained in step S3 by the first transfer function obtained in step S1 (step S5). As described above, in step S3, tire body vibration and tire pattern vibration are obtained as tire axle vibration. Using these, the interior noise generated from tire body vibration and the interior noise generated from tire pattern vibration are calculated as structural propagation noise, and the structural propagation noise is calculated by adding these interior noises together.

[0026] Next, the airborne noise is calculated by multiplying the tire noise obtained in step S4 by the second transfer function obtained in step S2 (step S6). As described above, in step S4, tire body noise and tire pattern noise were obtained as tire noise. Using these, the in-cabin noise generated from the tire body noise and the in-cabin noise generated from the tire pattern noise are calculated as airborne noise, and the airborne noise is calculated by adding these in-cabin noises together.

[0027] Next, the structural noise calculated in step S5 and the airborne noise calculated in step S6 are added together to calculate the in-cabin noise originating from the tires (step S7).

[0028] The details of each step, from Step S1 to S7, will be explained in order above.

[0029] In step S1, as described above, the first transfer function, which is a transfer function showing the relationship between tire axle vibration and in-vehicle noise and is a structural propagation transfer function, is obtained through testing.

[0030] As shown in Figure 3, this test involves preparing a vehicle 10 such as a passenger car, a vibration jig 11 attached to the tire mounting surface (also called the wheel mounting surface) of the vehicle 10, a microphone 12 positioned at the ear level of the occupant inside the vehicle 10, and an analysis device (not shown) for determining the transfer function based on the recorded data.

[0031] Vehicle 10 is preferably a vehicle on which the tire under evaluation is actually to be mounted, or a vehicle structurally similar to such a vehicle. Vehicle 10 has a tire mounting surface 15 as shown in Figure 4(a). When vehicle 10 is in motion, the tire 16 and wheel 17 are mounted on this tire mounting surface 15, as shown in Figure 4(b). Also, as shown in Figure 3, the interior of vehicle 10 is arranged multiple seats 18 equipped with headrests 19.

[0032] As shown in Figure 5, the vibration jig 11 consists of a disc 11a and a shaft member 11b that protrudes from the center of the disc 11a on one side of the disc 11a. The shaft member 11b extends perpendicularly to the surface of the disc 11a (the vibration surface described later). The disc 11a has a plurality of holes 11c formed therein, centered on the shaft member 11b.

[0033] The vibration jig 11 is attached to the tire mounting surface 15, which becomes visible when the tires 16 and wheels 17 are removed from the vehicle 10, in place of the tires 16 and wheels 17. Specifically, the vibration jig 11 is positioned such that the side of the disc 11a without the axle member 11b contacts the tire mounting surface 15 of the vehicle 10, and that bolts 15a (bolts around the hub) protruding from the tire mounting surface 15 of the vehicle 10 enter the holes 11c in the disc 11a. The vibration jig 11 is then fixed to the tire mounting surface 15 by tightening nuts on the bolts 15a so as to press down on the disc 11a.

[0034] In the vibration jig 11 fixed to the tire mounting surface 15, the disc 11a and the shaft member 11b are the vibration-generating parts that the tester strikes with a vibration-generating tool such as a hammer. For the disc 11a, the side on which the shaft member 11b is attached is the vibration-generating surface that the tester strikes with a vibration-generating tool such as a hammer. By striking the vibration jig 11, the tester generates tire shaft vibration.

[0035] The tire axle vibration has 5 degrees of freedom: 3 degrees of freedom in translation and 2 degrees of freedom in rotation. Here, as shown in Figures 4 and 5, the longitudinal direction of the vehicle 10 is the X direction, the lateral direction of the vehicle 10 (i.e., the direction of the tire axis) is the Y direction, and the vertical direction is the Z direction. The X-axis extending in the X direction, the Y-axis extending in the Y direction, and the Z-axis extending in the Z direction intersect orthogonally with each other at the contact point between the disk 11a and the axle member 11b.

[0036] The tester can perform vibrations in the X, Y, and Z directions by striking the shaft member 11b in the X, Y, and Z directions, as indicated by the arrows in Figure 5(a). These vibrations generate three-degree-of-freedom tire shaft vibrations, specifically translational tire shaft vibrations in the X, Y, and Z directions.

[0037] Furthermore, the tester can perform vibrations in the direction of a moment that generates rotation around the X-axis by striking the upper and lower parts of the disk 11a, as indicated by the arrows in Figure 5(b). Also, the tester can perform vibrations in the direction of a moment that generates rotation around the Z-axis by striking the front and rear parts of the disk 11a, as indicated by the arrows in Figure 5(c). These vibrations result in tire axle vibrations with two degrees of freedom, specifically rotations around the X-axis and Z-axis, respectively.

[0038] In this embodiment, the in-vehicle noise is evaluated when the vehicle 10 is traveling in a straight line at a constant speed. When the vehicle 10 is traveling in a straight line at a constant speed, the input in the direction of tire rotation, that is, the rotational moment about the Y-axis, can be assumed to be constant. Therefore, the moment that causes rotation about the Y-axis does not need to be considered when determining the first transfer function or structurally propagated noise.

[0039] The microphone 12 has a sound detection unit (more specifically, a part that vibrates in response to sound). The microphone 12 is positioned and fixed so that the position of its detection unit is at the position of the passenger's ear. For example, the microphone 12 is fixed to the headrest 19 of the seat 18 of the vehicle 10.

[0040] The number of microphones 12 can be one or two. If there is one microphone 12, it is preferable that the microphone 12 be positioned closer to the window than the left-right center of the headrest 19 so that it is positioned closer to the window-side ear of the passenger. If there are two microphones 12, it is preferable that the two microphones 12 be positioned at the same height on both sides of the left-right center of the headrest 19 so that they are positioned closer to the left and right ears of the passenger.

[0041] The analysis device is capable of determining the transfer function between input and output based on input data (for example, tire axle vibration data recorded by a vibration meter in this test) and output data (for example, sound data recorded by microphone 12 in this test). Specifically, the analysis device decomposes the input and output data into frequency components using Fast Fourier Transform (FFT), and determines the transfer function between input and output as a function with frequency as the independent variable.

[0042] After completing the above preparations, the tester performs excitation to generate five degrees of freedom tire axle vibrations (i.e., translational tire axle vibrations with three degrees of freedom and rotational tire axle vibrations with two degrees of freedom). Each time excitation is performed for one degree of freedom, the tire axle vibration is recorded and the sound is recorded using microphone 12. Here, the recording of the tire axle vibration during excitation is performed by measuring the vibration of the excitation device with a vibration meter (force sensor, etc.) attached to the excitation device.

[0043] The recorded data is sent to the analysis device. The analysis device takes the tire axle vibration data recorded by the vibration meter as input and the sound data recorded by microphone 12 as output, and calculates the transfer function between the input and output. At this time, as described above, the analysis device decomposes the input data and output data into frequency components using FFT (Fast Fourier Transformation), and calculates the transfer function between the input and output as a function with frequency as the independent variable. The first transfer function obtained in this way shows the relationship between tire axle vibration and in-vehicle noise.

[0044] Since the first transfer function is determined for each degree of freedom of the tire axle vibration, five first transfer functions are obtained for each tire mounting surface 15. These five first transfer functions consist of three translational first transfer functions and two rotational first transfer functions. Furthermore, the vehicle 10 has four tire mounting surfaces 15, and the tester performs tests to obtain the first transfer functions for all of these tire mounting surfaces 15, so a total of 20 first transfer functions are obtained.

[0045] In step S2, as described above, a second transfer function, which is the transfer function of air propagation and represents the relationship between tire noise around the tires outside the vehicle and noise inside the vehicle, is obtained through testing.

[0046] As shown in Figure 6, this test involves preparing a vehicle 10 such as a passenger car, sound sources 13 placed around the tires of the vehicle 10, microphones 12 placed at the ear positions of the occupants inside the vehicle 10, and an analysis device (not shown) for determining the transfer function based on the recorded data.

[0047] The sound source 13 emits sound at a predetermined frequency and is, for example, a volume velocity sound source. The sound source 13 is positioned around the tire. The area around the tire refers to the area around the contact point of the tire outside the vehicle.

[0048] The specific locations of the sound source 13 (hereinafter referred to as "sound source locations") are four positions: the tire's treading side, the tire's kicking side, the front side, and the rear side. As shown in Figure 7, the treading side is in the forward direction of the vehicle 10, the kicking side is on the opposite side of the treading side, the front side is on the outside in the lateral direction of the vehicle, and the rear side is on the inside in the lateral direction of the vehicle (towards the center line in the left-right direction of the vehicle 10).

[0049] All four sound source locations are on the road surface where the shortest distance from the tire's contact patch is less than or equal to the tire radius (i.e., half the tire's outer diameter), and which is on the same plane as the tire's contact patch. The four detailed sound source locations are described using the X direction as the direction of vehicle 10's movement (forward is +, backward is -), the Y direction as the tire axis (outside the vehicle's lateral direction is +, inside the vehicle's lateral direction is -), and the Z direction as the vertical direction (up is +, down is -).

[0050] First, the sound source on the tire's contact side is located at a predetermined distance in the X direction (but in the positive direction) from the tire's contact point on the contact side. This predetermined distance is less than or equal to the tire radius (half of the tire's outer diameter). Furthermore, the sound source on the tire's contact side is at the center of the tire's contact area in the Y direction, and 0 in the Z direction.

[0051] Furthermore, the sound source position on the tire's push-off side is located at a predetermined distance from the tire's push-off end in the X direction (however, in the - direction). This predetermined distance is less than or equal to the tire radius (half of the tire's outer diameter). Also, the sound source position on the tire's push-off side is at the center of the tire's contact area in the Y direction, and 0 in the Z direction.

[0052] Furthermore, the sound source position on the front side of the tire is located at a predetermined distance from the tire's front contact point in the Y direction (but in the positive direction). This predetermined distance is less than or equal to the tire radius (half of the tire's outer diameter). Additionally, the sound source position on the front side of the tire is at the center of the tire's contact point in the X direction, and zero in the Z direction.

[0053] Furthermore, the sound source on the rear side of the tire is located at a predetermined distance from the contact edge on the rear side of the tire in the Y direction (however, in the - direction). The predetermined distance is less than or equal to the tire radius (half of the tire's outer diameter). Also, the sound source on the rear side of the tire is at the center of the tire contact area in the X direction, and 0 in the Z direction.

[0054] In the test to obtain the second transfer function, sounds are emitted sequentially from the four sound source locations mentioned above. Each time a sound is emitted from a sound source location, the sound is recorded by microphone 12.

[0055] The recorded data is sent to the analysis device. The analysis device used in step S2 is the same as the one used in step S1. The analysis device takes the sound data emitted from the sound source 13 as input and the sound data recorded by the microphone 12 as output, and calculates the transfer function between the input and output. At this time, the analysis device decomposes the input data and output data into frequency components using FFT, and calculates the transfer function between the input and output as a function with frequency as the independent variable. The result obtained in this way is the second transfer function that shows the relationship between tire noise around the tires and in-vehicle noise.

[0056] Since the second transfer function is determined for each sound source location, four second transfer functions are obtained for each tire. In addition, vehicle 10 has four tires, and the tester performs the test to obtain the second transfer function for all of them, so a total of 16 second transfer functions are obtained.

[0057] In step S3, as described above, the tire axle vibration when the tire rolls on the road surface is obtained through numerical analysis.

[0058] To this end, a simulation device is first prepared. The simulation device is implemented by a computer that includes a processing unit, a memory unit, an input unit, and a display unit. The memory unit is equipped with RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), etc. The memory unit stores programs for performing finite element analysis, programs for performing boundary element analysis, programs for predicting in-vehicle noise using transfer functions, and tire models to be analyzed, etc.

[0059] The processing unit consists of a CPU (Central Processing Unit), etc. The processing unit performs finite element analysis, boundary element analysis, etc., by reading programs stored in ROM, etc., onto RAM and executing them. The input unit is, for example, a mouse and keyboard, and accepts input from the analyst. The display unit is, for example, a display, and displays the input screen, analysis results, etc.

[0060] This simulation device acquires a wheel model, a patterned tire model, and a non-patterned tire model (S3-1). The wheel model is a wheel model on which the patterned tire model and the non-patterned tire model are assembled, respectively. The patterned tire model is a tire model with a tread pattern consisting of numerous grooves, etc. The non-patterned tire model is a tire model in which the tread pattern is omitted. The outer diameter surface of the non-patterned tire model is a single curved surface.

[0061] Wheel models, patterned tire models, and non-patterned tire models are finite element models that are the subject of analysis using the finite element method. These models are meshed into multiple elements, with nodes at the vertices of those elements. Each element and each node has an element number, node number, node coordinates, and material properties (e.g., density, Young's modulus, Poisson's ratio, stiffness, etc.) assigned to it.

[0062] For each of the acquired patterned tire models and non-patterned tire models, a simulation (numerical analysis) is performed using finite element analysis in the simulation system. The simulation is performed according to the flow shown in Figure 8. First, we will explain the simulation of the patterned tire model.

[0063] After acquiring the patterned tire model, the patterned tire model is mounted onto the wheel model (S3-1). Mounting means that the patterned tire model is attached to the correct position on the wheel model.

[0064] Next, a predetermined internal pressure is applied to the patterned tire model assembled to the wheel model, and the resulting deformation of the patterned tire model is calculated (S3-2).

[0065] Next, the contact points between the patterned tire model and the wheel model are joined and constrained (S3-3). This fixes the patterned tire model and the wheel model in place, eliminating the need to calculate the contact problem between them.

[0066] Next, a contact analysis of the patterned tire model is performed (S3-4). Specifically, the patterned tire model is placed in contact with a pre-prepared road surface model, and the resulting deformation of the patterned tire model is calculated.

[0067] Next, a rolling analysis is performed in which the patterned tire model rolls on the road surface model (S3-5). When the patterned tire model rolls (rotates), the wheel model naturally rotates together with the patterned tire model.

[0068] This rolling analysis calculates the tire pattern vibration during rolling and the tire axle vibration caused by the transmission of that tire pattern vibration to the tire axle. The position for calculating the tire axle vibration (tire axle vibration calculation position) is located on the mounting surface of the wheel model to the vehicle (in the actual vehicle 10, the mounting surface of the wheel 17 to the vehicle 10 is in contact with the tire mounting surface 15 on the vehicle 10 side), and is also the center of rotation of the wheel model. The wheel model has holes around the center of rotation, and one node is provided at the tire axle vibration calculation position within one of these holes. By rigidly connecting this node to a node in the wheel model, the tire axle vibration at that node can be calculated.

[0069] The tire axle vibration calculated by rolling analysis is the same 5-degree-of-freedom vibration as in the test. This allows for the acquisition of the 5-degree-of-freedom tire axle vibration originating from the tire pattern vibration. Vehicle 10 has four tires, and the tire axle vibration originating from the tire pattern vibration is acquired for each tire.

[0070] Furthermore, a simulation is performed using finite element analysis in the simulation device to simulate the rolling of a non-patterned tire model on a road surface. To do this, the flow from S3-1 to S3-5 in Figure 8 is executed, similar to the case with the patterned tire model. The tire body vibration during rolling and the tire shaft vibration caused by the transmission of that tire body vibration to the tire shaft are then calculated. The tire shaft vibration calculated at this time is a 5-degree-of-freedom vibration, the same as in the test. In this way, the 5-degree-of-freedom tire shaft vibration originating from the tire body vibration is obtained. Vehicle 10 has four tires, and the tire shaft vibration originating from the tire body vibration is obtained for each tire.

[0071] The tire axle vibrations derived from the tire pattern vibration and tire body vibration, obtained in this manner, are decomposed into frequency components by FFT in a simulation device for use in calculations with the first transfer function.

[0072] In step S4, as described above, the tire noise around the tires outside the vehicle as the tires roll on the road surface is acquired through numerical analysis.

[0073] In step S4, first, the same simulation device used in step S3 is prepared. Then, the same patterned tire model and non-patterned tire model used in step S3 are acquired by the simulation device. In addition, the virtual sound source positions in the simulation of step S4 are set to the respective sound source positions used in the test in step S2 to acquire the second transfer function.

[0074] Next, a simulation is performed using finite element analysis in the simulation device to simulate the rolling of a patterned tire model on a road surface. This calculates the vibrations of each of the four contact points of the rolling patterned tire: the contact point on the footing side (the line from position 1 to position 2 in Figure 7(b)), the contact point on the push-off side (the line from position 3 to position 4 in Figure 7(b)), the front contact point (the line from position 4 to position 1 in Figure 7(b)), and the rear contact point (the line from position 2 to position 3 in Figure 7(b)).

[0075] This simulation may be performed using only the patterned tire model, or it may be performed using the patterned tire model mounted on a wheel model. If the patterned tire model mounted on a wheel model is used, the same flow as S3-1 to S3-5 in Figure 8 will be executed.

[0076] Next, boundary element analysis in the simulation device calculates the sounds at four virtual sound source positions around the tire: on the pressing side, the pushing side, the front side, and the rear side. As described above, the four virtual sound source positions are the same as the sound source positions during the test in step S2, when the second transfer function is obtained.

[0077] Specifically, the air vibrations caused by the vibration of the foot-side contact point, calculated by finite element analysis, are calculated by boundary element analysis, and the sound at the virtual sound source position on the foot-side is calculated. Similarly, the sound at the virtual sound source position on the kick-off side, caused by the vibration of the kick-off side contact point, the sound at the virtual sound source position on the front side, caused by the vibration of the front-side contact point, and the sound at the virtual sound source position on the back side, caused by the vibration of the rear-side contact point, are each calculated.

[0078] This allows the sound produced at four virtual sound source positions as the patterned tire model rolls to be calculated. The sounds calculated at this time are the tire pattern sounds for each of the four virtual sound source positions.

[0079] Furthermore, the simulation system performs finite element analysis to simulate the rolling of a non-patterned tire model on a road surface. The vibration of the entire surface of the non-patterned tire, excluding the contact patch, is then calculated. In other words, the vibration of the entire surface of the non-patterned tire above the contact patch is calculated during rolling.

[0080] This simulation may be performed using only the non-pattern tire model, or it may be performed using the non-pattern tire model integrated into the wheel model. If the non-pattern tire model integrated into the wheel model is used, the same flow as S3-1 to S3-5 in Figure 8 will be executed.

[0081] Next, boundary element analysis in the simulation device calculates the sounds at four virtual sound source positions around the tire: on the pressing side, the pushing side, the front side, and the rear side. As described above, the four virtual sound source positions are the same as the sound source positions during the test in step S2, when the second transfer function is obtained.

[0082] Specifically, the vibration of the air surrounding the non-patterned tire, caused by vibrations of the entire surface of the non-patterned tire other than the contact area, is calculated using finite element analysis. Then, the sound produced by these air vibrations at four virtual sound source positions—the side being pressed down, the side being pushed off, the front side, and the rear side—is calculated. This allows the sound produced at each of the four virtual sound source positions when the non-patterned tire model rolls. The sounds calculated at this time are the tire body sounds at each of the four virtual sound source positions.

[0083] The tire pattern sound and tire body sound obtained in this way are decomposed into frequency components using FFT in a simulation device for use in calculations with the second transfer function.

[0084] In step S5, the simulation device calculates the in-vehicle noise (structurally propagated noise) caused by structural propagation by multiplying the tire axle vibration acquired in step S3 by the first transfer function acquired in step S1. Here, since the tire axle vibration acquired in step S3 includes tire pattern vibration and tire body vibration, the calculation is performed by multiplying each by the first transfer function. That is, if the tire pattern vibration acquired in step S3 is Xvp and the tire body vibration is Xvb, the structurally propagated noise Qv is calculated using the first transfer function Hv by the following equation [Equation 1].

[0085]

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[0086] Here, the first transfer function, tire pattern vibration, and tire body vibration each have 5 degrees of freedom. The components of structurally propagated noise that originate from tire pattern vibration and those that originate from tire body vibration are calculated by adding the components calculated for each of the 5 degrees of freedom.

[0087] In other words, the first transfer functions for the five degrees of freedom are represented as Hvx, Hvy, Hvz, Hvmx, and Hvmz respectively (Hvx, Hvy, and Hvz are the first transfer functions for translation in the X, Y, and Z directions, and Hvmx and Hvmz are the first transfer functions for rotation around the X and Z axes), and the tire pattern vibrations for the five degrees of freedom are represented as Xvpx, Xvpy, Xvpz, Xvpmx, and Xvpmz (Xvpx, Xvpy, and Xvpz are the tire pattern vibrations for translation in the X, Y, and Z directions, and Xv If pmx and Xvpmz are tire pattern vibrations rotating around the X and Z axes, and the five degrees of freedom of the tire body vibrations are Xvbx, Xvby, Xvbz, Xvbmx, and Xvbmz (Xvbx, Xvby, and Xvbz are tire body vibrations translating in the X, Y, and Z directions, and Xvbmx and Xvbmz are tire body vibrations rotating around the X and Z axes), then the component of structurally propagated noise originating from the tire pattern vibrations is calculated by the following equation [Equation 2].

[0088]

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[0089] Furthermore, the component of structurally propagated noise originating from tire body vibration is calculated using the following formula [Equation 3].

[0090]

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[0091] The structurally propagated noise generated from a single tire is the sum of the component originating from tire pattern vibration (the component obtained by [Equation 2]) and the component originating from tire body vibration (the component obtained by [Equation 3]). As can be seen from [Equations 1] to [Equation 3], structurally propagated noise is the sum of noise components (structurally propagated noise components) calculated for each type of vibration (tire pattern vibration and tire body vibration) and for each direction of vibration. The structurally propagated noise components are the respective "Xvpx*Hvx" in [Equation 2] and "Xvbx*Hvx" in [Equation 3].

[0092] Furthermore, the total cabin noise originating from the axle vibration of each of the four tires mounted on a single vehicle 10 is calculated by performing calculations [Equation 1] to [Equation 3] for each of the four tires and summing up the resulting cabin noise Qv. That is, if the cabin noise originating from the axle vibration of each of the four tires are Qv1, Qv2, Qv3, and Qv4, then their sum Qvtotal is calculated by the following equation [Equation 4].

[0093]

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[0094] In step S6, the simulation device calculates the in-vehicle noise (airborne noise) generated by air propagation by multiplying the tire noise acquired in step S4 by the second transfer function acquired in step S2. Here, since the tire noise acquired in step S4 includes tire pattern noise and tire body noise, the calculation is performed by multiplying each by the second transfer function. That is, if the tire pattern noise acquired in step S4 is Xnp and the tire body noise is Xnb, the airborne noise Qn is calculated using the second transfer function Hn by the following equation [Equation 5].

[0095]

number

[0096] The second transfer function, tire pattern noise, and tire body noise are each obtained for four (virtual) sound source positions. The components of airborne noise originating from the tire pattern noise and the components originating from the tire body noise are calculated by adding the components calculated for each of the four (virtual) sound source positions.

[0097] In other words, if the second transfer functions for the foot-down side, kick-off side, front side, and rear side are denoted as Hns, Hnk, Hnf, and Hnb respectively, and the tire pattern sounds for the foot-down side, kick-off side, front side, and rear side are denoted as Xnps, Xnpk, Xnpf, and Xnpb respectively, and the tire body sounds for the foot-down side, kick-off side, front side, and rear side are denoted as Xnbs, Xnbk, Xnbf, and Xnbb respectively, then the component of airborne noise originating from the tire pattern sound is calculated by the following equation [Equation 6].

[0098]

number

[0099] Furthermore, the component of airborne noise originating from tire body noise is calculated using the following formula [Equation 7].

[0100]

number

[0101] The airborne noise generated from a single tire is the sum of the component derived from the tire pattern sound (the component obtained by [Equation 6]) and the component derived from the tire body sound (the component obtained by [Equation 7]). As can be seen from [Equations 5] to [Equation 7], the airborne noise is the sum of the noise components (airborne noise components) calculated for each type of tire sound (tire pattern sound and tire body sound) and for each sound source location. The airborne noise components are the respective "Xnps*Hns" in [Equation 6] and "Xnbs*Hns" in [Equation 7].

[0102] Furthermore, the total in-vehicle noise originating from the tire noise of each of the four tires mounted on a single vehicle 10 is calculated by performing calculations [Equation 5] to [Equation 7] for each of the four tires and summing up the resulting in-vehicle noise Qn. That is, if the in-vehicle noise originating from the tire noise of each of the four tires are Qn1, Qn2, Qn3, and Qn4, then their sum Qntotal is calculated by the following equation [Equation 8].

[0103]

number

[0104] In step S7, the simulation device calculates the in-vehicle noise originating from the tires by adding the structural noise calculated in step S5 and the airborne noise calculated in step S6. The in-vehicle noise Qtotal originating from the tires is calculated by the following formula [Equation 9].

[0105]

number

[0106] This Qtotal represents the predicted in-car noise originating from the tires. Calculations [Equation 1] to [Equation 9] are performed in the frequency domain, but the actual in-car noise heard by the passengers is reproduced by converting the calculated in-car noise data into time-domain data using the Inverse Fast Fourier Transform (IFFT).

[0107] According to the method of this embodiment described above, it is possible to accurately predict in-vehicle noise originating from tires. Specifically, a first transfer function showing the relationship between tire axle vibration and in-vehicle noise is obtained through testing, so a transfer function close to reality can be obtained as the first transfer function. Then, since the in-vehicle noise due to structural propagation is calculated from the first transfer function close to reality and the tire axle vibration obtained by numerical analysis, it is possible to accurately predict in-vehicle noise originating from tires.

[0108] Furthermore, in the numerical analysis, a rolling analysis is performed on the tire model mounted on the wheel model, rather than the tire model alone. This allows for the determination of tire axle vibrations that take into account the influence of the wheel. Based on these tire axle vibrations, the in-vehicle noise due to structural propagation is calculated, enabling a more accurate prediction of in-vehicle noise originating from the tires.

[0109] Furthermore, a second transfer function showing the relationship between tire noise around the tires and interior noise is determined through testing. From the tire noise around the tires obtained by numerical analysis and the second transfer function, interior noise due to air propagation is calculated. Then, the interior noise due to structural propagation and the interior noise due to air propagation are added together to arrive at the total interior noise. As a result, the predicted interior noise now also takes into account the interior noise due to air propagation, further improving the accuracy of predicting interior noise originating from tires.

[0110] Furthermore, in the numerical analysis for determining tire noise, a rolling analysis is performed not on the tire model alone, but on the tire model mounted on the wheel model, so the tire noise is determined taking into account the influence of the wheel. Based on this tire noise, the in-vehicle noise due to air propagation is calculated, making it possible to predict in-vehicle noise originating from the tires with even greater accuracy.

[0111] Furthermore, in the numerical analysis, the following steps are executed in the order of the first to fifth steps: the first step of assembling the tire model onto the wheel model (S3-1 in Figure 8), the second step of applying internal pressure to the tire model (S3-2 in Figure 8), the third step of connecting and constraining the contact portion between the tire model and the wheel model (S3-3 in Figure 8), the fourth step of performing a contact analysis to bring the tire model into contact with the road surface model (S3-4 in Figure 8), and the fifth step of performing a rolling analysis to make the tire model roll on the road surface model.

[0112] In this way, the contact points between the tire model and the wheel model are bound together, eliminating the need to calculate the contact problem between the tire model and the wheel model, thus reducing computational costs.

[0113] Furthermore, when a ground contact analysis is performed, the contact portion of the tire model deforms significantly, while the other parts deform less. Therefore, if the contact portion between the tire model and the wheel model is coupled and constrained after the ground contact analysis, the tire model will be coupled and constrained in an irregularly deformed state. However, in this embodiment, the contact portion between the tire model and the wheel model is coupled and constrained before the ground contact analysis, so the aforementioned irregular deformation does not occur.

[0114] Furthermore, as described above, in the test to obtain the first transfer function, an excitation jig 11 having a shaft member 11b extending in the tire axial direction and an excitation surface perpendicular to the shaft member 11b is attached to the tire mounting surface 15 of the vehicle 10. The shaft member 11b and the excitation surface are then excited by striking them. This makes it easy to generate tire shaft vibrations in the five directions described above, and thus easy to obtain the first transfer function.

[0115] Furthermore, as described above, in the test to acquire the second transfer function, the transfer function of tire noise is acquired at four positions: the tire's pressing side, the tire's pushing side, the front side (outer side of the vehicle), and the rear side (inner side of the vehicle). In addition, the tire noise at these four positions and at a virtual sound source position corresponding to these positions is calculated by numerical analysis. Then, airborne noise is calculated from the second transfer function and tire noise for each of the four positions. This makes it possible to predict airborne noise with high accuracy.

[0116] Furthermore, in the numerical analysis of tire axle vibration and tire noise, tire body noise and tire body vibration are calculated using a non-pattern tire model, allowing for quick calculation of tire body noise and vibration. On the other hand, tire pattern noise and tire pattern vibration are calculated using a patterned tire model, enabling accurate calculation.

[0117] Various modifications can be made to the above embodiments. Any one of the modification examples described below may be applied to the above embodiments, or two or more may be applied to the above embodiments in combination.

[0118] <Example of change 1> The first and second transfer functions may be obtained for only one of the front and rear wheels of the vehicle 10. In that case, tire axle vibration and tire noise are obtained by numerical analysis only for the tire for which the transfer function has been obtained.

[0119] Then, assuming that the first transfer function, second transfer function, tire axle vibration, and tire noise for the other tire are the same as those obtained by testing and calculation for the other tire, the in-vehicle noise due to structural propagation and in-vehicle noise due to air propagation are calculated.

[0120] Since the transfer functions and other parameters are estimated to be almost the same on the left and right sides of vehicle 10, the in-vehicle noise can also be estimated using the method of this modified example.

[0121] <Example of change 2> In step S3, tire axle vibration may be obtained by finite element analysis only for one front tire and one rear tire of the two front and two rear tires of the vehicle 10. In that case, the data obtained by finite element analysis for the remaining two tires will be reused.

[0122] <Example of change 3> This section explains an example of how to change the method for obtaining the first transfer function.

[0123] As shown in Figure 9, in this modified example, a sound source 14 is placed inside the vehicle 10. The sound source 14 emits sound at a predetermined frequency, and is, for example, a volume velocity sound source. The position of the sound source 14 is the same as the position where the microphone 12 is placed in the above embodiment.

[0124] Furthermore, a vibration jig 11 is attached to the tire mounting surface 15 of the vehicle 10, and a vibration meter is attached to the vibration jig 11. The vibration meter measures vibrations of the same five degrees of freedom as the tire shaft vibration in the above embodiment. For this purpose, one vibration meter for measuring the translational tire shaft vibration in the X, Y, and Z directions is attached to the shaft member 11b of the vibration jig 11. In addition, multiple vibration meters for measuring the rotational tire shaft vibration around the X axis and Z axis are attached to the disc 11a of the vibration jig 11.

[0125] Here, in order to measure the tire axle vibration of rotation around the X-axis, it is preferable to install vibration meters at two locations above and below the center of the disk 11a (or the center of the disk 11a and two locations above or below it). Also, in order to measure the tire axle vibration of rotation around the Z-axis, it is preferable to install vibration meters at two locations in front and behind the center of the disk 11a (or the center of the disk 11a and two locations in front of or behind it). For this purpose, the positions of the two vibration meters may be changed when measuring the tire axle vibration of rotation around the X-axis and when measuring the tire axle vibration of rotation around the Z-axis. Alternatively, vibration meters may be installed at a total of four locations above and below and in front of and behind the center of the disk 11a. Alternatively, vibration meters may be installed at a total of five locations: the center of the disk 11a and above and below and in front of and behind it. Thus, the number of vibration meters attached to the disk 11a is preferably 2 to 5.

[0126] With the sound source 14 and vibration meter set up as described above, sound is emitted from the sound source 14, and the vibration of the tire axle in each of the five degrees of freedom is measured. The analysis device then uses the sound data emitted from the sound source 14 and the tire axle vibration data recorded by the vibration meter to determine a first transfer function that shows the relationship between the tire axle vibration and the in-vehicle noise.

[0127] <Example of change 4> Sound generated on the rear side of the tire (the inner side in the lateral direction of the vehicle) does not reach the interior of the vehicle very well and contributes little to the interior noise. Therefore, the interior noise generated by air propagation may be calculated based on the sound generated from the tire's pressing side, pushing side, and front side.

[0128] In this modified example, first, the transfer functions from the sound sources 13 on the tire's pressing side, kicking side, and front side to the microphone 12 inside the vehicle are obtained as the second transfer function.

[0129] Next, tire pattern sounds are calculated for three virtual sound source positions: the tire on the pressing side, the tire on the pushing side, and the tire on the front side. Similarly, tire body sounds are calculated for the same three virtual sound source positions: the tire on the pressing side, the tire on the pushing side, and the tire on the front side. Finally, from the tire pattern sounds, tire body sounds, and the second transfer function calculated in this way, the in-vehicle noise generated by air propagation is calculated.

[0130] According to this example of modification, the calculation of tire noise at the virtual sound source location on the rear side of the tire can be omitted, allowing for more efficient calculation of in-vehicle noise generated by air propagation.

[0131] <Example of change 5> In the above embodiment, to calculate tire axle vibration, tire body vibration was calculated using a non-pattern tire model, and tire pattern vibration was calculated using a patterned tire model.

[0132] However, tire body vibration and tire pattern vibration may be calculated separately using a single patterned tire model. In this case, the calculation of tire body vibration and tire pattern vibration may be performed simultaneously or separately.

[0133] In this example of modification, the calculation of tire body vibration takes longer than when using a non-patterned tire model because a patterned tire model is used in the calculation of tire body vibration, which should not require consideration of the tread pattern. However, it has the advantage of eliminating the need to prepare a non-patterned tire model for calculating tire body vibration.

[0134] <Example of change 6> In the above embodiment, to calculate tire noise, a non-pattern tire model was used to calculate tire body noise, and a patterned tire model was used to calculate tire pattern noise.

[0135] However, a single patterned tire model may be used to calculate both the tire body sound and the tire pattern sound. In this case, the calculation of the tire body sound and the tire pattern sound may be performed simultaneously or separately.

[0136] In this example of modification, the calculation of tire body noise takes longer than when using a non-patterned tire model because a patterned tire model is used, even though the tread pattern should not need to be considered. However, it has the advantage of eliminating the need to prepare a non-patterned tire model for calculating tire body noise.

[0137] <Example of change 7> In the above embodiment, the tire pattern sound at the virtual sound source position when the patterned tire model rolls was calculated based on the vibration of the part of the tire's contact edge closest to that virtual sound source position. For example, the tire pattern sound at the virtual sound source position on the pressing side was calculated based on the vibration of the contact edge on the pressing side.

[0138] However, the tire pattern sounds at each of the four virtual sound source positions may also be calculated based on the vibration of the entire tire contact patch.

[0139] Specifically, first, a simulation is performed using finite element analysis in the simulation device, in which a patterned tire model is rolled on a road surface. Then, the vibrations of the contact points on the pushing side, pushing side, front side, and rear side of the patterned tire model during rolling are calculated.

[0140] Next, boundary element analysis in the simulation device calculates tire pattern sounds at four virtual sound source positions around the tire: the side where the tire is pressed down, the side where it is pushed off, the front side, and the rear side.

[0141] Specifically, the vibration of the air surrounding the tire, caused by vibrations of the entire tire contact patch (consisting of the contact patch on the footing side, the contact patch on the push-off side, the contact patch on the front side, and the contact patch on the rear side), calculated by finite element analysis, is calculated by boundary element analysis. Then, the tire pattern sounds at four virtual sound source positions—footing side, push-off side, front side, and rear side—caused by the vibrations of the air surrounding the tire are calculated.

[0142] In this modified example, the tire pattern sound at each of the four virtual sound source locations is calculated based on the vibration of the entire tire contact patch. Therefore, for example, the tire pattern sound at the virtual sound source location on the pressing side will be affected not only by vibrations at the contact patch on the pressing side but also by vibrations at the contact patch on the front side, etc. This improves the accuracy of the calculated tire pattern sound.

[0143] <Example of change 8> The in-vehicle noise calculated by [Equation 9] is the sum of structurally propagated noise components, which are noise components for each type and direction of vibration as described in [Equation 2] and [Equation 3], and airborne noise components, which are noise components for each type of tire noise and virtual sound source location as described in [Equation 6] and [Equation 7]. This represents the in-vehicle noise that is predicted to be actually heard by passengers.

[0144] However, the in-vehicle noise may also be calculated by adding up multiple noise components (all noise components except those that have been removed) while performing processes such as eliminating or adjusting the intensity of selected noise components.

[0145] For example, methods such as calculating the in-vehicle noise from only some of the noise components (for example, calculating the in-vehicle noise by adding only the noise components of some of the tires, or calculating the in-vehicle noise by adding only the noise components caused by some of the tire pattern noise, tire body noise, tire pattern vibration, and tire body vibration) or calculating the in-vehicle noise by increasing or decreasing some of the noise components may be employed.

[0146] These methods allow for accurate prediction of in-vehicle noise levels when specific noise components are absent, high, or low, and various studies can be conducted based on these predictions. For example, if the in-vehicle noise is calculated and reproduced while excluding a specific noise component, and the noise level is deemed acceptable, it can be determined that it is preferable to design the tires in a way that reduces that "specific noise component."

[0147] <Example of change 9> In Figure 8, the coupling constraint between the tire model and the wheel model (S3-3) and the contact analysis of the tire model (S3-4) can also be swapped in order.

[0148] Furthermore, in Figure 8, the coupling constraint (S3-3) between the tire model and the wheel model can be omitted. However, if omitted, it will be necessary to calculate the contact problem between the tire model and the wheel model. [Explanation of Symbols]

[0149] 10...Vehicle, 11...Excitation jig, 11a...Disc, 11b...Shaft member, 11c...Hole, 12...Microphone, 13...Sound source, 14...Sound source, 15...Tire mounting surface, 16...Tire, 17...Wheel, 18...Seat, 19...Headrest

Claims

1. In a noise prediction method for predicting in-vehicle noise originating from tires, The first transfer function showing the relationship between tire axle vibration and in-vehicle noise was determined through testing. The in-vehicle noise due to structural propagation was calculated from the tire axle vibration obtained by numerical analysis and the first transfer function. In the aforementioned numerical analysis, the tire axle vibration is determined by performing a rolling analysis in which the tire model assembled on the wheel model is rolled. Noise prediction method.

2. A second transfer function showing the relationship between tire noise around the tires and interior noise was determined through testing. The in-vehicle noise due to air propagation is calculated from the tire noise around the tires obtained by numerical analysis and the second transfer function. The total interior noise is calculated by adding the noise transmitted through the structure of the vehicle and the noise transmitted through the air. The noise prediction method according to claim 1.

3. The noise prediction method according to claim 2, wherein the tire noise is determined by performing a rolling analysis in which a tire model assembled on a wheel model is rolled, in the numerical analysis for determining the tire noise.

4. The noise prediction method according to any one of claims 1 to 3, wherein the rolling analysis is performed with the contact portion between the tire model and the wheel model coupled and constrained.

5. In the aforementioned numerical analysis, The first step is to assemble the tire model onto the wheel model, A second step involves applying internal pressure to the aforementioned tire model, A third step involves connecting and restraining the contact portion between the tire model and the wheel model, A fourth step involves performing a contact analysis to bring the tire model into contact with the road surface model, A fifth step involves performing a rolling analysis in which the tire model is rolled on the road surface model. Execute in the order of Step 1 to Step 5. The noise prediction method according to claim 4.

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