JP2024081334A - Noise prediction method - Google Patents

Abstract

To accurately predict in-vehicle noise derived from a tire.SOLUTION: A noise prediction method for predicting in-vehicle noise derived from a tire includes: obtaining a first transfer function indicating a relationship between tire axis vibration and in-vehicle noise and a second transfer function indicating a relationship between a tire sound around the tire and in-vehicle noise by a test; calculating in-vehicle noise due to structure propagation from the tire axis vibration obtained by numerical analysis and the first transfer function; calculating in-vehicle noise due to air propagation from a tire sound around the tire obtained by numerical analysis and the second transfer function; and calculating the in-vehicle noise derived from the tire from the in-vehicle noise due to structure propagation and the in-vehicle noise due to air propagation.SELECTED DRAWING: Figure 1

Description

The present invention relates to a noise prediction method.

Human sensory evaluation is used as a method for evaluating tire-induced noise heard inside a vehicle (car). However, sensory evaluation has problems such as the need to run an actual vehicle, the need to manufacture the tires to be evaluated, and the need to create a mold to manufacture the tires.

Therefore, as described in Patent Document 1, it is proposed to predict interior noise based on tire axle force from tire axle force predicted by finite element analysis and selected transfer characteristics, and to predict interior noise based on exterior noise from exterior noise predicted by boundary element analysis and selected vehicle body sound insulation characteristics.

Patent No. 4087193

In order to accurately predict noise using methods that use finite element analysis or boundary element analysis, it is necessary to use accurate transfer characteristics, etc. However, a specific noise prediction method that uses accurate transfer characteristics, etc. has not been proposed until now.

The present invention was made in consideration of these circumstances, and aims to provide a method for accurately predicting interior noise caused by tires.

The present invention includes the following embodiments:

[1] A noise prediction method for predicting tire-induced interior noise, which involves determining by testing a first transfer function that indicates the relationship between tire axle vibration and interior noise, and a second transfer function that indicates the relationship between tire sound around the tire and interior noise, calculating interior noise due to structure propagation from the tire axle vibration determined by numerical analysis and the first transfer function, calculating interior noise due to air propagation from the tire sound around the tire determined by numerical analysis and the second transfer function, and calculating interior noise due to tire propagation from the interior noise due to structure propagation and the interior noise due to air propagation.

[2] The noise prediction method described in [1], in which the first transfer function is calculated from tire axle vibration measurement data and vehicle interior sound measurement data when the tire axle is vibrated and the vehicle interior sound is measured.

[3] The noise prediction method described in [1], in which the first transfer function is calculated from data on sound inside the vehicle and measurement data on tire axle vibration when sound is generated inside the vehicle.

[4] A noise prediction method according to any one of [1] to [3], in which the first transfer function is calculated for five directions, including the extension directions of three axes: an X-axis extending in the vehicle's longitudinal direction, a Y-axis coinciding with the tire axis, and a Z-axis extending in the vertical direction, and two directions rotating around the X-axis and the Z-axis, respectively.

[5] The noise prediction method described in [4], in which a vibration jig having an axial member extending in the tire axial direction and a vibration surface perpendicular to the axial member is attached to a tire mounting surface of a vehicle, and tire axial vibrations are generated in each of the five directions by vibrating the axial member and the vibration surface, respectively, and the first transfer function is obtained for each of the five directions from measurement data of the tire axial vibration at each vibration and measurement data of the sound inside the vehicle at each vibration.

[6] A noise prediction method according to any one of [1] to [5], in which transfer functions for tire sound at multiple positions around the tire are calculated as the second transfer function.

[7] The noise prediction method described in [6], in which the multiple positions include three positions: the leading side of the tire, the trailing side, and the outer lateral side of the vehicle.

[8] The noise prediction method described in [7], wherein the multiple positions further include a position on the inside of the vehicle in the lateral direction.

This embodiment makes it possible to accurately predict interior noise caused by tires.

FIG. 2 is a diagram for explaining the transmission path of sound from a tire to the interior of a vehicle. 1 is a flowchart of a noise prediction method. FIG. 2 is a diagram showing a vehicle in a test for obtaining a first transfer function. 1A is a top view of the tire mounting surface, and FIG. 1B is a top view of the tire and wheel mounted on the tire mounting surface. 1 is a perspective view of a vibration jig used in a test to obtain a first transfer function, (a) is a diagram showing orthogonal XYZ directions as vibration directions, (b) is a diagram showing the direction of a moment that causes rotation around the X-axis as the vibration direction, and (c) is a diagram showing the direction of a moment that causes rotation around the Z-axis as the vibration direction. FIG. 4 is a diagram showing a vehicle in a test for obtaining a second transfer function. A diagram explaining the direction of a tire. (a) is a diagram of a tire seen from the front. (b) is a diagram of the tire contact surface seen from above. FIG. 13 is a diagram showing a vehicle in a test of a modified example for obtaining a first transfer function.

The embodiment will be described with reference to the drawings. Note that the embodiment described below is merely an example, and any modifications that do not deviate from the spirit of the present invention are considered to be within the scope of the present invention.

In this embodiment, we predict the interior noise caused by a pneumatic tire (hereinafter simply referred to as "tire") rolling on the road surface. In the following, interior noise refers to noise at the position of the passenger's ears inside the vehicle.

First, the transmission path of sound from the tire to the interior of the vehicle will be explained with reference to Figure 1. When a tire rolls on the road surface, two types of tire vibrations (hereinafter referred to as "tire vibrations") occur as a result of this: tire pattern vibrations and tire body vibrations. Tire pattern vibrations are vibrations of the parts of the tire tread that are in contact with the road surface. Tire body vibrations are vibrations of the parts of the tire that are not in contact with the road surface (including the sidewalls and parts of the tread that are not in contact with the road surface). Tire pattern vibrations and tire body vibrations are transmitted to the vehicle body and become vehicle body vibrations. Vehicle body vibrations are transmitted to the ears of passengers inside the vehicle as noise.

When a tire rolls on the road surface, two types of tire noise ("tire noise" refers to noise generated from the tire as a result of the tire rolling) are generated around the tire outside the vehicle: tire pattern noise and tire body noise. Tire pattern noise is noise generated when the parts of the tire tread that are in contact with the road surface vibrate. Tire body noise is noise generated when the parts of the tire that are not in contact with the road surface (including the sidewall and parts of the tread that are not in contact with the road surface) vibrate. Tire pattern noise and tire body noise penetrate the air into the vehicle and are transmitted to the ears of passengers inside the vehicle as noise.

When tire pattern vibrations and tire body vibrations are transmitted as noise to the ears of passengers inside the vehicle, this is called structure-borne noise. When tire pattern sound and tire body sound are transmitted as noise to the ears of passengers inside the vehicle, this is called air-borne noise. The noise that reaches the ears of passengers inside the vehicle is a combination of structure-borne noise (referred to as "structure-borne noise") and air-borne noise (referred to as "air-borne noise").

The noise prediction method of this embodiment is carried out according to the flowchart of FIG. 2. First, a first transfer function, which is a transfer function of structure propagation, is obtained by testing (step S1). Here, the tire pattern vibration and tire body vibration are transmitted to the tire rotation axis (hereinafter also referred to as the "tire axis"), and can be measured as the vibration of the tire rotation axis (hereinafter referred to as the "tire axis vibration"). Therefore, the transfer function of structure propagation in this embodiment is a function that indicates the relationship between the tire axis vibration and the noise at the position of the passenger's ears in the vehicle. Also, obtaining by testing means obtaining by measuring actual sounds, etc. using actual tires and vehicles.

Next, a second transfer function, which is a transfer function of air propagation, is obtained by testing (step S2). Here, the transfer function of air propagation is a function that indicates the relationship between the tire sound around the tire outside the vehicle and the noise at the position of the passenger's ears inside the vehicle.

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 is obtained by vibration due to tire body vibration and vibration due to tire pattern vibration. In addition, finite element analysis is performed as the numerical analysis to obtain the tire axle vibration.

Next, tire sounds around the tire outside the vehicle when the tire rolls on the road surface are acquired by numerical analysis (step S4). In this embodiment, tire body sounds and tire pattern sounds are acquired as tire sounds. In addition, finite element analysis and boundary element analysis are performed as numerical analyses to acquire tire sounds.

Next, the structure-borne noise is calculated by multiplying the tire axle vibration acquired in step S3 by the first transfer function acquired in step S1 (step S5). As described above, in step S3, the tire body vibration and the tire pattern vibration are acquired as the tire axle vibration. Using these, the interior noise caused by the tire body vibration and the interior noise caused by the tire pattern vibration are calculated as the structure-borne noise, and the structure-borne noise is calculated by adding these interior noises.

Next, the tire sound acquired in step S4 is multiplied by the second transfer function acquired in step S2 to calculate airborne noise (step S6). As described above, in step S4, the tire body sound and the tire pattern sound were acquired as tire sounds. Using these, the interior noise resulting from the tire body sound and the interior noise resulting from the tire pattern sound are calculated as airborne noise, and the airborne noise is calculated by adding these interior noises.

Next, the structure-borne noise calculated in step S5 is added to the air-borne noise calculated in step S6 to calculate the interior noise caused by the tires (step S7).

The details of each of steps S1 to S7 will now be explained in order.

In step S1, as described above, a first transfer function, which is a transfer function indicating the relationship between tire axle vibration and interior noise and is a structure-propagated transfer function, is obtained by testing.

As shown in FIG. 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 placed at the position of the passenger's ear inside the vehicle 10, and an analysis device (not shown) for determining a transfer function based on the recorded data.

The vehicle 10 is preferably a vehicle on which the tire to be evaluated is actually to be mounted, or a vehicle structurally similar to such a vehicle. The vehicle 10 has a tire mounting surface 15 as shown in FIG. 4(a). When the vehicle 10 is moving, a tire 16 and a wheel 17 are mounted on this tire mounting surface 15 as shown in FIG. 4(b). In addition, as shown in FIG. 3, multiple seats 18 equipped with headrests 19 are arranged inside the vehicle 10.

As shown in FIG. 5, the vibration jig 11 is composed of a disk 11a and a shaft member 11b that protrudes from the center of the disk 11a on one side of the disk 11a. The shaft member 11b extends perpendicular to the surface of the disk 11a (the vibration surface described below). The disk 11a has a number of holes 11c formed around the shaft member 11b.

The vibration jig 11 is attached in place of the tire 16 and wheel 17 to the tire mounting surface 15 that appears when the tire 16 and wheel 17 are removed from the vehicle 10. In detail, the vibration jig 11 is provided so that the surface of the disk 11a without the shaft member 11b contacts the tire mounting surface 15 of the vehicle 10, and the bolt 15a (the bolt around the hub) protruding from the tire mounting surface 15 of the vehicle 10 enters the hole 11c of the disk 11a. Then, the vibration jig 11 is fixed to the tire mounting surface 15 by tightening a nut on the bolt 15a to hold down the disk 11a.

In the vibration jig 11 fixed to the tire mounting surface 15, the disk 11a and the shaft member 11b are the vibration parts that the tester hits with a vibration tool such as a hammer. For the disk 11a, the surface on which the shaft member 11b is provided is the vibration surface that the tester hits with a vibration tool such as a hammer. When the tester hits the vibration jig 11 to generate vibration, tire axle vibration is generated.

Tire axle vibration has five degrees of freedom: three translational degrees of freedom and two rotational degrees of freedom. 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 tire axial direction) 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 perpendicularly with each other at the contact position between the disk 11a and the shaft member 11b.

The tester can apply vibrations in the X, Y, and Z directions by tapping the shaft member 11b in each of the X, Y, and Z directions as shown by the arrows in Figure 5(a). These vibrations generate translational tire axle vibrations in the X, Y, and Z directions as tire axle vibrations with three degrees of freedom.

Also, by the tester hitting the top and bottom parts of the disk 11a as shown by the arrows in FIG. 5(b), vibration can be applied in the direction of a moment that causes rotation around the X-axis. Also, by the tester hitting the front and back parts of the disk 11a as shown by the arrows in FIG. 5(c), vibration can be applied in the direction of a moment that causes rotation around the Z-axis. These vibrations generate tire axle vibrations with two degrees of freedom, namely, tire axle vibrations with rotation around the X-axis and Z-axis.

In this embodiment, the interior noise is evaluated when the vehicle 10 runs straight at a constant speed. When the vehicle 10 runs straight at a constant speed, the input in the tire rotation direction, i.e., the rotational moment around the Y axis, can be assumed to be constant. Therefore, the moment that causes rotation around the Y axis does not need to be taken into account when calculating the first transfer function or structure-borne noise.

The microphone 12 has a detection section that detects sound (more specifically, a section that vibrates in response to sound). The microphone 12 is positioned and fixed so that the detection section 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.

The number of microphones 12 may be one or two. When there is one microphone 12, it is preferable that the microphone 12 is placed closer to the window than the center of the headrest 19 in the left-right direction so that the microphone 12 is positioned at the position of the passenger's left or right ear, whichever is closer to the window. When there are two microphones 12, it is preferable that the two microphones 12 are placed at the same height on both sides of the center of the headrest 19 in the left-right direction so that the microphones 12 are positioned at the position of the passenger's left or right ear.

The analysis device is a device that can determine 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). In detail, the analysis device breaks down the input data and output data into frequency components using a Fast Fourier Transformation (FFT), and determines the transfer function between the input and output as a function with frequency as an independent variable.

After completing the above preparations, the tester applies vibrations that generate five degrees of freedom of tire axle vibrations (i.e., translational tire axle vibrations with three degrees of freedom and rotational tire axle vibrations with two degrees of freedom). Then, every time one degree of freedom of vibration is applied, the tire axle vibrations are recorded and the sound is recorded (sounded) by microphone 12. Here, the tire axle vibrations during vibration are recorded by measuring the vibration of the vibration device with a vibration meter (force sensor, etc.) attached to the vibration device.

The recorded data is sent to an analysis device. The analysis device inputs the tire axle vibration data recorded by the vibration meter and outputs the sound data recorded by the microphone 12, and determines the transfer function between the input and output. At this time, the analysis device breaks down the input data and output data into frequency components using FFT (Fast Fourier Transformation) as described above, and determines the transfer function between the input and output as a function with frequency as an independent variable. In this way, the first transfer function is determined, which indicates the relationship between tire axle vibration and interior noise.

Since the first transfer function is obtained for each degree of freedom of the tire axial vibration, five first transfer functions are obtained for one tire mounting surface 15. The five first transfer functions are three translational first transfer functions and two rotational first transfer functions. In addition, the vehicle 10 has four tire mounting surfaces 15, and the tester performs tests to obtain first transfer functions for all of these tire mounting surfaces 15, so a total of 20 first transfer functions are obtained.

In step S2, as described above, a second transfer function, which is a transfer function indicating the relationship between the tire sound around the tire outside the vehicle and the noise inside the vehicle, and is an air-propagated transfer function, is obtained by testing.

As shown in FIG. 6, this test involves preparing a vehicle 10 such as a passenger car, a sound source 13 placed around the tires of the vehicle 10, a microphone 12 placed inside the vehicle 10 at the position of the passenger's ear, and an analysis device (not shown) for determining a transfer function based on the recorded data.

The sound source 13 emits a sound of a predetermined frequency, for example a volume velocity sound source. The sound source 13 is arranged around the tire. The surroundings of the tire means the area around the tire that is in contact with the ground outside the vehicle.

The specific positions of the sound source 13 (hereinafter referred to as "sound source positions") are four positions on the tire's leading side, trailing side, front side, and rear side. As shown in FIG. 7, the leading side is the forward direction of the vehicle 10, the trailing side is the opposite side of the leading side, the front side is the outer side in the lateral direction of the vehicle, and the rear side is the inner side in the lateral direction of the vehicle (the side of the center line in the left-right direction of the vehicle 10).

All four sound source positions are located on the road surface where the shortest distance from the tire contact edge is less than the tire radius (i.e. half the tire's outer diameter) and is on the same plane as the tire's contact surface. The four detailed sound source positions are explained by considering the traveling direction of the vehicle 10 as the X direction (forward direction is +, backward direction is -), the tire axial direction as the Y direction (the outer side of the vehicle in the lateral direction is +, the inner side of the vehicle in the lateral direction is -), and the vertical direction as the Z direction (upper is +, lower is -).

First, the sound source position on the leading side of the tire is a position that is a predetermined distance away in the X direction (but in the positive direction) from the ground contact edge of the leading side of the tire. The predetermined distance is a length that is equal to or less than the tire radius (half the outer diameter of the tire). In addition, the sound source position on the leading side of the tire is the center of the tire ground contact part in the Y direction, and is 0 in the Z direction.

The sound source position on the trailing edge of the tire is a position a predetermined distance away in the X direction (but in the negative direction) from the ground contact edge of the trailing edge of the tire. The predetermined distance is a length equal to or less than the tire radius (half the outer diameter of the tire). The sound source position on the trailing edge of the tire is the center of the tire ground contact part in the Y direction and 0 in the Z direction.

The sound source position on the front side of the tire is a position that is a predetermined distance away in the Y direction (but in the positive direction) from the tire's front side ground contact edge. The predetermined distance is a length that is equal to or less than the tire radius (half the tire's outer diameter). The sound source position on the front side of the tire is the center of the tire ground contact part in the X direction and 0 in the Z direction.

The sound source position on the rear side of the tire is a position a predetermined distance away in the Y direction (but in the negative direction) from the ground contact edge on the rear side of the tire. The predetermined distance is a length equal to or less than the tire radius (half the outer diameter of the tire). The sound source position on the rear side of the tire is the center of the tire ground contact part in the X direction and 0 in the Z direction.

In the test to obtain the second transfer function, sounds are emitted from the four sound source positions in order. Then, each time a sound is emitted from a sound source position, the sound is recorded by the microphone 12.

The recorded data is sent to an analysis device. The analysis device used in step S2 is the same as that used in step S1. The analysis device inputs sound data emitted from the sound source 13 and outputs sound data recorded by the microphone 12, and determines 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 determines the transfer function between the input and output as a function with frequency as an independent variable. In this way, the second transfer function is determined, which indicates the relationship between the tire sound around the tire and the noise inside the vehicle.

Since the second transfer function is obtained for each sound source position, four second transfer functions are obtained for each tire. In addition, the vehicle 10 has four tires, and the tester performs tests to obtain the second transfer functions for all of these tires, so a total of 16 second transfer functions are obtained.

In step S3, as described above, tire axle vibrations as the tire rolls on the road surface are obtained by numerical analysis.

For this purpose, first, a simulation device is prepared. The simulation device is realized by a computer including a processing unit, a storage unit, an input unit, and a display unit. As the storage unit, a RAM (Random Access Memory), a ROM (Read Only Memory), a HDD (Hard Disk Drive), etc. are provided. The storage unit stores a program for performing finite element analysis, a program for performing boundary element analysis, a program for predicting interior noise using a transfer function, a tire model to be analyzed, etc.

The processing unit is composed of a CPU (Central Processing Unit) and the like. The processing unit reads out a program stored in a ROM or the like onto a RAM and executes it to perform finite element analysis, boundary element analysis, and the like. 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, and the like.

A patterned tire model and a non-patterned tire model are acquired by this simulation device. 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.

The patterned tire model and non-patterned tire model are finite element models that are the subject of analysis using the finite element method, and are models that are divided into multiple mesh elements and have nodes at the vertices of these elements. Each element and node is assigned an element number, node number, node coordinates, physical property values (e.g. density, Young's modulus, Poisson's ratio, rigidity, etc.).

For both the patterned tire model and the non-patterned tire model, the position at the center of rotation of the tire mounting surface 15 on the vehicle 10 is defined as the position at which the tire axle vibration is calculated.

Next, a simulation is performed by finite element analysis in the simulation device to simulate the rolling of the patterned tire model on the road surface. This calculates the tire pattern vibration during rolling and the tire axle vibration caused by the tire pattern vibration being transmitted to the tire axle. The tire axle vibration calculated at this time is the same five degrees of freedom as in the test. This allows the five degrees of freedom tire axle vibration derived from the tire pattern vibration to be obtained. The vehicle 10 is fitted with four tires, and the tire axle vibration derived from the tire pattern vibration is obtained for each tire.

Furthermore, a simulation is performed by finite element analysis in the simulation device, in which the non-pattern tire model is rolled on a road surface. Then, the tire body vibration during rolling and the tire axle vibration caused by the tire body vibration being transmitted to the tire axle are calculated. The tire axle vibration calculated at this time is the same five degrees of freedom as in the test. In this way, the five degrees of freedom tire axle vibration derived from the tire body vibration is obtained. The vehicle 10 is fitted with four tires, and the tire axle vibration derived from the tire body vibration is obtained for each tire.

The tire axle vibrations resulting from tire pattern vibrations and tire body vibrations obtained in this manner are decomposed into frequency components by FFT in the simulation device for use in calculating the first transfer function.

In step S4, as described above, tire noise around the tire outside the vehicle as the tire rolls on the road surface is obtained by numerical analysis.

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

Next, a simulation is performed by finite element analysis in the simulation device, in which the patterned tire model is rolled on a road surface. This calculates the vibration of each of the four ground contact ends of the rolling patterned tire: the leading end (the line from position 1 to position 2 in FIG. 7(b)), the trailing end (the line from position 3 to position 4 in FIG. 7(b)), the front end (the line from position 4 to position 1 in FIG. 7(b)), and the rear end (the line from position 2 to position 3 in FIG. 7(b)).

Next, the simulation device performs boundary element analysis to calculate the sound at four virtual sound source positions on the leading edge, trailing edge, front side, and rear side around the tire. As described above, the four virtual sound source positions are the same as the sound source positions during the test in step S2 to obtain the second transfer function.

Specifically, the air vibration caused by the vibration of the leading-side ground end calculated by finite element analysis is calculated by boundary element analysis, and the sound at the leading-side virtual sound source position is calculated. Similarly, the sound at the trailing-side virtual sound source position caused by the vibration of the trailing-side ground end, the sound at the front-side virtual sound source position caused by the vibration of the front-side ground end, and the sound at the rear-side virtual sound source position caused by the vibration of the rear-side ground end are each calculated.

This allows the sound at each of the four virtual sound source positions to be calculated when the patterned tire model rolls. The sounds calculated at this time are the tire pattern sounds at each of the four virtual sound source positions.

Finite element analysis in the simulation device is also used to perform a simulation of the rolling of the non-pattern tire model on a road surface. The vibration of the entire surface of the rolling non-pattern tire, excluding the contact area, is then calculated. In other words, the vibration of the entire surface above the contact area of the rolling non-pattern tire is calculated.

Next, the simulation device performs boundary element analysis to calculate the sound at four virtual sound source positions on the leading edge, trailing edge, front side, and rear side around the tire. As described above, the four virtual sound source positions are the same as the sound source positions during the test in step S2 to obtain the second transfer function.

Specifically, the vibration of the air around the non-pattern tire caused by the vibration of the entire surface of the non-pattern tire other than the contact area, calculated by finite element analysis, is calculated. Then, the sound at four virtual sound source positions on the leading-in side, trailing-out side, front side, and rear side caused by the air vibration is calculated. In this way, the sound at each of the four virtual sound source positions when the non-pattern tire model rolls is calculated. The sounds calculated at this time are the tire body sounds at each of the four virtual sound source positions.

The tire pattern sound and tire body sound obtained in this manner are decomposed into frequency components by FFT in the simulation device for use in calculations with the second transfer function.

In step S5, the simulation device multiplies the tire axle vibration acquired in step S3 by the first transfer function acquired in step S1 to calculate the vehicle interior noise caused by structure propagation (structure-borne noise). Here, the tire axle vibration acquired in step S3 includes tire pattern vibration and tire body vibration, and a calculation is performed to multiply each by the first transfer function. In other words, if the tire pattern vibration and tire body vibration of the tire axle vibration acquired in step S3 are Xvp and Xvb, respectively, the structure-borne noise Qv is calculated using the first transfer function Hv according to the following formula [Equation 1].

ここで、第１伝達関数、タイヤパターン振動及びタイヤボディ振動はそれぞれ５自由度である。そして、構造伝播騒音のうちタイヤパターン振動に由来する成分と、タイヤボディ振動に由来する成分は、それぞれ、５つの自由度ごとに算出された成分が加算されることにより算出される。

Here, the first transfer function, the tire pattern vibration, and the tire body vibration each have five degrees of freedom. The components of the structure-borne noise originating from the tire pattern vibration and the components originating from the tire body vibration are calculated by adding up the components calculated for each of the five degrees of freedom.

That is, the first transfer functions of the five degrees of freedom are represented as Hvx, Hvy, Hvz, Hvmx, and Hvmz (Hvx, Hvy, and Hvz are the first transfer functions of translation in the X, Y, and Z directions, and Hvmx and Hvmz are the first transfer functions of rotation around the X and Z axes), and the tire pattern vibration of the five degrees of freedom is represented as Xvpx, Xvpy, Xvpz, Xvpmx, and Xvpmz (Xvpx, Xvpy, and Xvpz are the tire pattern vibration of translation in the X, Y, and Z directions, and Xvp mx, Xvpmz are tire pattern vibrations of rotation around the X and Z axes), and the five degrees of freedom of the tire body vibrations are Xvbx, Xvby, Xvbz, Xvbmx, Xvbmz (Xvbx, Xvby, Xvbz are tire body vibrations of translation in the X, Y, and Z directions, and Xvbmx, Xvbmz are tire body vibrations of rotation around the X and Z axes), the components of the structure-borne noise originating from the tire pattern vibrations are calculated using the following formula [Mathematical Equation 2].

また、構造伝播騒音のうちタイヤボディ振動に由来する成分は次の［数３］の式により算出される。

Furthermore, the component of the structure-borne noise that originates from tire body vibration is calculated by the following formula (3).

１つのタイヤから生じる構造伝播騒音は、タイヤパターン振動に由来する成分（［数２］で求まる成分）とタイヤボディ振動に由来する成分（［数３］で求まる成分）とを足したものである。［数１］～［数３］からわかるように、構造伝播騒音は、振動の種類（タイヤパターン振動とタイヤボディ振動）ごとかつ振動の方向ごとに算出される騒音成分（構造伝播騒音成分）を足したものである。構造伝播騒音成分は、［数２］における「Ｘｖｐｘ＊Ｈｖｘ」等や、［数３］における「Ｘｖｂｘ＊Ｈｖｘ」等のそれぞれのことである。

The structure-borne noise generated from one tire is the sum of the components derived from tire pattern vibration (components calculated by [Equation 2]) and the components derived from tire body vibration (components calculated by [Equation 3]). As can be seen from [Equation 1] to [Equation 3], the structure-borne noise is the sum of noise components (structure-borne noise components) calculated for each type of vibration (tire pattern vibration and tire body vibration) and for each direction of vibration. The structure-borne noise components are "Xvpx*Hvx" in [Equation 2], "Xvbx*Hvx" in [Equation 3], etc.

The total interior noise caused by the tire axle vibration of each of the four tires mounted on one vehicle 10 is calculated by performing the calculations of [Equation 1] to [Equation 3] for each of the four tires and adding up the calculated interior noises Qv for each tire. In other words, if the interior noises caused by the tire axle vibration of each of the four tires are Qv1, Qv2, Qv3, and Qv4, the sum Qvtotal is calculated by the following equation [Equation 4].

ステップＳ６では、シミュレーション装置において、ステップＳ４にて取得されたタイヤ音と、ステップＳ２にて取得された第２伝達関数とを乗じて、空気伝播により生じる車内騒音（空気伝播騒音）が算出される。ここで、ステップＳ４において取得されたタイヤ音としてタイヤパターン音とタイヤボディ音があるため、それぞれに第２伝達関数を乗じる計算が行われる。すなわち、ステップＳ４において取得されたタイヤ音のうち、タイヤパターン音をＸｎｐ、タイヤボディ音をＸｎｂとすると、空気伝播騒音Ｑｎは、第２伝達関数Ｈｎを用いて次の［数５］の式により算出される。

In step S6, the simulation device multiplies the tire sound acquired in step S4 by the second transfer function acquired in step S2 to calculate interior vehicle noise caused by air propagation (air-borne noise). Here, since the tire sounds acquired in step S4 include tire pattern sound and tire body sound, a calculation is performed to multiply each of them by the second transfer function. That is, if the tire pattern sound and the tire body sound among the tire sounds acquired in step S4 are Xnp and Xnb, respectively, the air-borne noise Qn is calculated by the following formula [Equation 5] using the second transfer function Hn.

第２伝達関数、タイヤパターン音及びタイヤボディ音はそれぞれ４つの（仮想）音源位置について取得されている。そして、空気伝播騒音のうちタイヤパターン音に由来する成分と、タイヤボディ音に由来する成分は、それぞれ、４つの（仮想）音源位置ごとに算出された成分が加算されることにより算出される。

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

In other words, if the second transfer functions of the leading side, trailing side, front side and rear side are respectively expressed as Hns, Hnk, Hnf and Hnb, the tire pattern sounds of the leading side, trailing side, front side and rear side are respectively expressed as Xnps, Xnpk, Xnpf and Xnpb, and the tire body sounds of the leading side, trailing side, front side and rear side are respectively expressed as Xnbs, Xnbk, Xnbf and Xnbb, the components of the airborne noise originating from the tire pattern sound are calculated by the following formula [Mathematical Expression 6].

また、空気伝播騒音のうちタイヤボディ音に由来する成分は次の［数７］の式により算出される。

Further, the component of the airborne noise that originates from the tire body sound is calculated by the following formula [7].

１つのタイヤから生じる空気伝播騒音は、タイヤパターン音に由来する成分（［数６］で求まる成分）とタイヤボディ音に由来する成分（［数７］で求まる成分）とを足したものである。［数５］～［数７］からわかるように、空気伝播騒音は、タイヤ音の種類（タイヤパターン音とタイヤボディ音）ごとかつ音源位置ごとに算出される騒音成分（空気伝播騒音成分）を足したものである。空気伝播騒音成分は、［数６］における「Ｘｎｐｓ＊Ｈｎｓ」等や［数７］における「Ｘｎｂｓ＊Ｈｎｓ」等のそれぞれのことである。

The airborne noise generated from one tire is the sum of the components originating from the tire pattern sound (components calculated using [Equation 6]) and the components originating from the tire body sound (components calculated using [Equation 7]). As can be seen from [Equation 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 position. The airborne noise components refer to "Xnps*Hns" in [Equation 6] and "Xnbs*Hns" in [Equation 7], etc.

The total interior noise caused by the tire sound of each of the four tires attached to one vehicle 10 is calculated by performing the calculations of [Equation 5] to [Equation 7] for each of the four tires and adding up the calculated interior noises Qn for each tire. In other words, if the interior noises caused by the tire sound of each of the four tires are Qn1, Qn2, Qn3, and Qn4, the sum Qntotal is calculated by the following equation [Equation 8].

ステップＳ７では、シミュレーション装置において、ステップＳ５にて算出された構造伝播騒音と、ステップＳ６にて算出された空気伝播騒音とを足して、タイヤ由来の車内騒音が算出される。タイヤ由来の車内騒音Ｑｔｏｔａｌは次の式［数９］により算出される。

In step S7, the simulation device calculates the tire-derived interior noise by adding the structure-borne noise calculated in step S5 and the air-borne noise calculated in step S6. The tire-derived interior noise Qtotal is calculated by the following equation [Equation 9].

この車内騒音Ｑｔｏｔａｌが、予測されるタイヤ由来の車内騒音である。［数１］～［数９］の計算は周波数領域において行われるが、実際に搭乗者に聞こえる車内騒音の再生は、算出された車内騒音のデータが逆高速フーリエ変換（Ｉｎｖｅｒｓｅ Ｆａｓｔ Ｆｏｕｒｉｅｒ Ｔｒａｎｓｆｏｒｍ：ＩＦＦＴ）により時間軸のデータに変換されることにより行われる。

This interior noise Qtotal is the predicted interior noise originating from the tires. The calculations of [Equation 1] to [Equation 9] are performed in the frequency domain, but the interior noise actually heard by the passengers is reproduced by converting the calculated interior noise data into time-axis data by Inverse Fast Fourier Transform (IFFT).

According to the method of the present embodiment described above, tire-derived interior noise can be predicted with high accuracy. In detail, a first transfer function showing the relationship between tire axial vibration and interior noise, and a second transfer function showing the relationship between tire sound around the tire and interior noise are obtained by testing, so that transfer functions close to reality can be obtained as the first transfer function and the second transfer function. Then, structure-borne noise and air-borne noise are calculated from the realistic transfer function and the results of the numerical analysis (specifically, the tire axial vibration and sound around the tire obtained by the numerical analysis), and tire-derived interior noise is calculated from the structure-borne noise and air-borne noise, so that tire-derived interior noise can be predicted with high accuracy.

As described above, in the test to obtain the first transfer function, a vibration jig 11 having an axial member 11b extending in the tire axial direction and a vibration surface perpendicular to the axial member 11b is attached to the tire mounting surface 15 of the vehicle 10. Vibration is then applied by striking the axial member 11b and the vibration surface. This makes it easy to generate tire axial vibration in the above five directions, and makes it easy to obtain the first transfer function.

As described above, in the test to obtain the second transfer function, the transfer functions of the tire sound at four positions, the leading side, trailing side, front side (lateral outer side of the vehicle) and rear side (lateral inner side of the vehicle) of the tire, are obtained. Furthermore, the tire sound at a virtual sound source position that is in the same position as these four positions is calculated by numerical analysis. Then, airborne noise is calculated from the second transfer function and tire sound for each of the four positions. This makes it possible to predict airborne noise with high accuracy.

In addition, in the numerical analysis of tire axle vibration and tire sound, tire body sound and tire body vibration are calculated using a non-pattern tire model, so the calculation of tire body sound and tire body vibration can be performed in a short time. On the other hand, tire pattern sound and tire pattern vibration are calculated using a patterned tire model, so they can be calculated with high accuracy.

Various modifications can be made to the above embodiment. Any one of the modifications described below may be applied to the above embodiment, or any two or more of them may be combined and applied to the above embodiment.

<Modification 1>
The first transfer function and the second transfer function may be acquired only for the front wheels and the rear wheels on either the left or right side of the vehicle 10. In this case, the tire axle vibration and tire sound are acquired by numerical analysis only for the tire on either the left or right side for which the transfer function has been acquired.

Then, assuming that the first transfer function, second transfer function, tire axle vibration, and tire sound for the other left or right tire are the same as the first transfer function, second transfer function, tire axle vibration, and tire sound obtained by testing and calculation for the one tire, the structure-borne noise and air-borne noise in the vehicle are calculated.

The transfer functions, etc. are assumed to be approximately the same on the left and right sides of the vehicle 10, so the interior noise can also be estimated using this modified method.

<Modification 2>
In step S3, tire axle vibrations may be obtained by finite element analysis only for one front wheel and one rear wheel among the two front and two rear tires of the vehicle 10. In this case, the data obtained by finite element analysis is used for the remaining two tires.

<Modification 3>
A modified example of the method of obtaining the first transfer function will be described.

As shown in FIG. 8, in this modified example, a sound source 14 is disposed inside the vehicle 10. The sound source 14 emits a sound of 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 disposed in the above embodiment.

A vibration jig 11 is attached to the tire mounting surface 15 of the vehicle 10, and a vibrometer is attached to the vibration jig 11. The vibrometer measures the same five degrees of freedom vibration as the tire axle vibration in the above embodiment. To this end, one vibrometer for measuring translational tire axle vibration in each of the X, Y, and Z directions is attached to the shaft member 11b of the vibration jig 11. In addition, multiple vibrometers for measuring rotational tire axle vibration about the X-axis and Z-axis are attached to the disk 11a of the vibration jig 11.

Here, in order to measure the tire shaft vibration of rotation around the X-axis, it is preferable to provide two vibrometers, one above and one below the center of the disk 11a (or the center of the disk 11a and two above or below it). In addition, in order to measure the tire shaft vibration of rotation around the Z-axis, it is preferable to provide two vibrometers in front and behind the center of the disk 11a (or the center of the disk 11a and two before or after it). For this purpose, two vibrometers may be provided at different positions when measuring the tire shaft vibration of rotation around the X-axis and when measuring the tire shaft vibration of rotation around the Z-axis. Also, a vibrometer may be provided at four positions, above and below and before and after the center of the disk 11a. Also, a vibrometer may be provided at the center of the disk 11a and five positions above and below and before and after it. In this way, it is preferable that the number of vibrometers attached to the disk 11a is 2 to 5.

With the sound source 14 and the vibration meter thus installed, sound is emitted from the sound source 14, and the tire axle vibrations with five degrees of freedom at that time are measured. Then, the analysis device calculates a first transfer function that indicates the relationship between the tire axle vibration and the interior noise from the sound data emitted from the sound source 14 and the tire axle vibration data recorded by the vibration meter.

<Modification 4>
Since sound generated on the rear side of the tire (the inner side in the vehicle lateral direction) does not reach the vehicle interior very much and contributes little to vehicle interior noise, the airborne noise generated inside the vehicle may be calculated based on the sound generated on the leading side, trailing side, and front side of the tire.

In this modified example, first, the transfer functions from the sound sources 13 on the leading side, trailing side, and front side of the tire to the microphone 12 inside the vehicle are obtained as the second transfer functions.

Next, tire pattern sounds at three virtual sound source positions on the leading side, trailing side, and front side of the tire are calculated as tire pattern sounds. Also, tire body sounds at three virtual sound source positions on the leading side, trailing side, and front side of the tire are calculated as tire body sounds. Then, from the tire pattern sound, tire body sound, and second transfer function calculated in this way, the interior noise caused by air propagation is calculated.

This modified example makes it possible to omit the calculation of tire noise at the virtual sound source position on the rear side of the tire, thereby making it possible to efficiently calculate interior noise caused by air propagation.

<Modification 5>
To calculate the tire axle vibration, in the above embodiment, a non-pattern tire model is used to calculate the tire body vibration, and a patterned tire model is used to calculate the tire pattern vibration.

However, a single patterned tire model may be used to calculate both the tire body vibration and the tire pattern vibration. In this case, the tire body vibration and the tire pattern vibration may be calculated simultaneously or separately.

In this modified example, a patterned tire model is used to calculate tire body vibrations, which does not require consideration of the tread pattern, so it takes longer to calculate tire body vibrations than when a non-patterned tire model is used. However, this has the advantage that it is no longer necessary to prepare a non-patterned tire model to calculate tire body vibrations.

<Modification 6>
In order to calculate the tire sound, in the above embodiment, the tire body sound is calculated using a non-pattern tire model, and the tire pattern sound is calculated using a patterned tire model.

However, the tire body sound and the tire pattern sound may each be calculated using a single patterned tire model. In this case, the tire body sound and the tire pattern sound may be calculated simultaneously or separately.

In this modified example, a patterned tire model is used to calculate tire body noise, which does not require consideration of the tread pattern, so it takes longer to calculate the tire body noise than if a non-pattern tire model were used. However, this has the advantage that it is no longer necessary to prepare a non-pattern tire model to calculate tire body noise.

<Modification 7>
In the above embodiment, the tire pattern sound at the virtual sound source position when the patterned tire model rolls is calculated based on the vibration of the portion of the tire ground edge close to the virtual sound source position. For example, the tire pattern sound at the leading-side virtual sound source position is calculated based on the vibration of the leading-side ground edge.

However, the tire pattern sounds at the four virtual sound source positions may each be calculated based on the vibration of the entire tire contact edge.

Specifically, first, a simulation is performed by finite element analysis in the simulation device to simulate the rolling of a patterned tire model on a road surface. Then, the vibrations of the leading edge, trailing edge, front edge, and rear edge of the rolling patterned tire model are calculated.

Next, the tire pattern sound is calculated at four virtual sound source positions around the tire: the leading edge, trailing edge, front side, and rear side, using boundary element analysis in the simulation device.

Specifically, the vibration of the air around the tire caused by the vibration of the entire tire contact edge (the tire contact edge consists of the leading edge, trailing edge, front edge and rear edge) calculated by finite element analysis is calculated by boundary element analysis. Then, tire pattern sounds at four virtual sound source positions on the leading edge, trailing edge, front edge and rear edge caused by the vibration of the air around the tire are calculated.

In this way, in this modified example, the tire pattern sound at each of the four virtual sound source positions is calculated based on the vibration of the entire tire contact edge. Therefore, for example, the tire pattern sound at the leading-side virtual sound source position is influenced by the vibration of not only the leading-side contact edge but also the front-side contact edge, etc. This improves the accuracy of the calculated tire pattern sound.

<Modification 8>
The interior noise calculated using [Equation 9] is the direct addition of structure-borne noise components, which are noise components for each type of vibration and each direction of vibration as described in [Equation 2] and [Equation 3], and air-borne noise components, which are noise components for each type of tire sound and each virtual sound source position as described in [Equation 6] and [Equation 7], and is the interior noise that is predicted to actually be heard by passengers.

However, the interior noise may be calculated by adding multiple noise components (all noise components excluding the eliminated noise components) while eliminating or adjusting the intensity of selected noise components.

For example, methods may be implemented in which the interior noise is calculated from only some of the noise components (for example, the interior noise is calculated by adding only some of the noise components of the tires, or the interior noise is calculated by adding only some of the noise components caused by the tire pattern sound, the tire body sound, the tire pattern vibration, and the tire body vibration), or the interior noise is calculated by increasing or decreasing some of the noise components.

These methods make it possible to accurately predict interior noise when a particular noise component is absent, high, or low, and various considerations can be carried out based on the predictions. For example, if the interior noise is calculated and reproduced excluding only a particular noise component, and the noise is tolerable, it is clear that it is preferable to design tires so that the "certain noise component" is reduced.

10: vehicle, 11: vibration jig, 11a: disk, 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 (8)

A noise prediction method for predicting interior noise caused by tires, comprising:
A first transfer function indicating the relationship between the tire axle vibration and the vehicle interior noise, and a second transfer function indicating the relationship between the tire sound around the tire and the vehicle interior noise are obtained by testing;
calculating interior noise caused by structure propagation from the tire axle vibration obtained by the numerical analysis and the first transfer function;
Calculating interior noise due to air propagation from the tire sound around the tire obtained by the numerical analysis and the second transfer function;
Calculate the tire-induced interior noise from the structure-borne noise and air-borne noise.
Noise prediction methods. The noise prediction method according to claim 1, in which the first transfer function is calculated from tire axle vibration measurement data and vehicle interior sound measurement data when the tire axle is vibrated and the vehicle interior sound is measured. The noise prediction method according to claim 1, in which the first transfer function is calculated from data on sound generated inside the vehicle and measurement data on tire axle vibration when sound is generated inside the vehicle. The noise prediction method according to claim 1, in which the first transfer function is calculated for five directions, including the extension directions of three axes, an X-axis extending in the vehicle longitudinal direction, a Y-axis coinciding with the tire axis, and a Z-axis extending in the vertical direction, and two directions rotating around the X-axis and the Z-axis, respectively. A vibration jig having a shaft member extending in the tire axial direction and a vibration surface perpendicular to the shaft member is attached to a tire mounting surface of a vehicle,
The shaft member and the vibration surface are respectively excited to generate tire shaft vibrations in the five directions,
5. The noise prediction method according to claim 4, wherein the first transfer functions are calculated for the five directions from measurement data of tire axle vibrations at the time of each excitation and measurement data of sound inside the vehicle at the time of each excitation. The noise prediction method according to claim 1, in which the second transfer function is calculated as a transfer function for tire sound at multiple positions around the tire. The noise prediction method according to claim 6, wherein the multiple positions include three positions: the leading side of the tire, the trailing side, and the outer lateral side of the vehicle. The noise prediction method according to claim 7 , wherein the plurality of positions further includes a position on an inner side in a lateral direction of the vehicle.

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