Block for excitation, measurement system, and measurement method

Abstract

To efficiently analyze resonance frequencies in a plurality of vibration modes.SOLUTION: The block 60 for excitation is used to acquire the resonance frequency of the wheel 5. The block 60 for excitation has an attachment surface 61 attached to the wheel 5 and an excitation surface 62. The attachment surface 61 is a surface along one surface of the virtual hexahedron K. The excitation surface 62 is a flat surface, and the flat surface intersects with a plurality of adjacent surfaces of the virtual hexahedron K.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a vibration block used to obtain the resonance frequency of a wheel, and a measurement system and a measurement method using the vibration block. [Background technology]

[0002] In an automobile, if the resonance frequency of a wheel is close to the resonance frequency of other devices (such as steering devices) installed around the wheel, the problem of abnormal noise occurs. Therefore, in the development of a wheel, it is necessary to obtain the resonance frequency in advance. As a method for obtaining the resonance frequency of a wheel, for example, a method disclosed in Patent Document 1 has been proposed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-141244 Summary of the Invention [Problem to be solved by the invention]

[0004] The resonance frequencies of a wheel exist in various vibration modes. In addition to pneumatic tires mounted on rims, airless tires are also known as wheels. An object of the present invention is to provide a new technical means for acquiring the resonance frequency of a wheel. [Means for solving the problem]

[0005] The vibration block according to the present invention has a mounting surface that is attached to a wheel and a vibration surface, the mounting surface being a surface that follows one of the faces of a virtual hexahedron, and the vibration surface being a plane that intersects with multiple adjacent faces of the virtual hexahedron.

[0006] The present invention is a measurement system for obtaining the resonant frequency of a wheel, comprising: a jig having a support shaft that fixes the wheel so that it cannot be displaced; a vibration block fixed to the outer peripheral surface of the wheel; a hammer device having a hammer body that applies a vibration force to the vibration surface of the vibration block and a first sensor for detecting vibration by the hammer body; a second sensor attached to the support shaft that detects vibration components based on an axis included in the three orthogonal axes of the support shaft; and a calculation unit that performs calculations to obtain the resonant frequency of the wheel based on the signal from the first sensor and the signal from the second sensor.

[0007] The present invention is a measurement method for acquiring the resonant frequency of a wheel, comprising: a preparation step of fixing the wheel to a support shaft so that it cannot be displaced; a vibration step of using a hammer device to vibrate the vibration block fixed to the outer peripheral surface of the wheel; a first acquisition step of acquiring, as an input signal, the vibration in the hammer device when the vibration block is vibrated; a second acquisition step of acquiring, as an output signal, the vibration caused by the vibration of the hammer device and based on an axis included in the three orthogonal axes of the support shaft; and a measurement step of determining the resonant frequency of the wheel from a transfer function based on the input signal and the output signal. [Effects of the Invention]

[0008] According to the present invention, it is possible to efficiently analyze the resonance frequencies of a wheel in a plurality of vibration modes. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram illustrating an example of a measurement system according to the present invention. [Figure 2] 1 is an explanatory diagram of a wheel from which a resonant frequency is to be acquired, viewed from a direction along the center axis of the wheel; [Figure 3] FIG. 2 is an explanatory diagram of the measurement system with a part of the wheel cut away. [Figure 4] FIG. 1 is an explanatory diagram showing the configuration of a measurement system. [Figure 5] FIG. [Figure 6] FIG. 10 is a flow chart of a measurement method for acquiring the resonance frequency in each vibration mode of a wheel. [Figure 7] FIG. 10 is an explanatory diagram showing an output obtained by frequency analysis. [Figure 8] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Details of the embodiment of the present invention] Fig. 1 is an explanatory diagram showing an example of a measurement system of the present invention. The measurement system 10 shown in Fig. 1 is a system for acquiring the resonance frequency of a wheel 5. Fig. 2 is an explanatory diagram showing the wheel 5, the object of which resonance frequency is to be acquired, viewed from a direction along its central axis C1. The wheel 5 in this embodiment is a wheel having a pneumatic tire 7 mounted on a rim 6. Note that the wheel the object of which resonance frequency is to be acquired may also be an airless tire.

[0011] The tire 7 is made of rubber and is supported by a metal rim 6. The central axis of the tire 7 coincides with the central axis of the rim 6, and these central axes are the central axis C1 of the wheel 5. The direction along an imaginary circle centered on the central axis C1 of the wheel 5 is the circumferential direction of the wheel 5, and the direction perpendicular to the central axis C1 is the radial direction of the wheel 5.

[0012] The directions in the measurement system 10 are defined as follows: The measurement system 10 has a jig 50 to which the wheel 5 is fixed (see Figure 1). The wheel 5 is fixed to the jig 50 with its central axis C1 horizontal. When the wheel 5 is fixed to the jig 50, the direction along the central axis C1 is the "left-right direction." The vertical up-down direction perpendicular to the left-right direction is the "up-down direction." The direction perpendicular to both the left-right direction and the up-down direction is the "front-rear direction."

[0013] A three-dimensional Cartesian coordinate system with X, Y, and Z axes is set in the jig 50 to which the wheel 5 is fixed. The left-right direction is the direction of the Z axis, the front-back direction is the direction of the Y axis, and the up-down direction is the direction of the X axis.

[0014] The measurement system 10 has a vibration block 60 fixed to the outer peripheral surface 8 of the wheel 5 in order to acquire the resonance frequency. In this embodiment, the vibration block 60 is fixed at a rear position of the wheel 5 (a position on the right side in FIG. 2). The vibration position at which vibration is input to the wheel 5 is the rear position of the wheel 5. Note that the vibration block 60 may be fixed at a position other than the rear, such as the front, top (above), or bottom (below).

[0015] [Regarding the resonance frequency of wheel 5] Known resonance modes of the wheel 5 include eccentric primary resonance, cavity resonance (cavity resonance), left-right translational resonance, lateral bending primary resonance, and in-plane torsional resonance. Known resonance frequencies of the wheel 5 include an eccentric primary resonance frequency, a cavity resonance frequency, a left-right translational resonance frequency, a lateral bending primary resonance frequency, and an in-plane torsional resonance frequency.

[0016] Eccentric primary resonance is a resonance that occurs when the tread 71 of the tire 7 vibrates in the radial direction of the wheel 5. In this embodiment, the vibration position is at the rear of the wheel 5, and the vibration direction has a component that runs from top to bottom. Therefore, the axis related to the vibration direction is the "vertical axis (hereinafter referred to as the vertical axis)." In other words, eccentric primary resonance occurs in a vibration mode in which the tread 71 moves in a direction along the X-axis, which is the vertical axis. The eccentric primary resonance frequency is the resonance frequency when the tire 7 vibrates along the vertical axis. In this embodiment, an excitation force component is also generated in the direction along the Y-axis, which is the axis in the front-rear direction, and therefore eccentric primary resonance occurs in the front-rear direction. The resonance frequency is measured as the same value for both the vertical axis and the front-rear axis. Therefore, it is sufficient to utilize either the vertical axis or the front-rear axis for the eccentric primary resonance.

[0017] Cavity resonance is a resonance that occurs when the air (gas) vibrates in the annular space 9 formed between the tire 7 and the rim 6. There is no axis related to the vibration direction of the air. The cavity resonance frequency is the resonance frequency at which air vibrates in the annular space 9 .

[0018] Lateral translational resonance occurs when the tread 71 vibrates in a rigid-body motion manner in the tire width direction. In this embodiment, the tire width direction is the left-right direction, which is a direction parallel to the center axis C1. The axis relating to the direction of vibration is the "left-right axis (hereinafter referred to as the left-right axis)." In other words, lateral translational resonance occurs in a vibration mode in which the tread 71 moves in a direction along the Z axis, which is the left-right axis. The lateral translational resonance frequency is the resonance frequency when the tire 7 vibrates along the lateral axis.

[0019] The primary lateral bending resonance is a resonance that occurs when the tread 71 vibrates in a rigid-body motion around an axis in the vertical direction when the excitation position is behind the wheel 5 and the excitation direction has a lateral component. The axis relating to the direction of the vibration is the "vertical axis." Note that, because the primary lateral bending resonance is a vibration around the vertical axis, the axis relating to the direction of the vibration is distinguished by being called the "vertical rotation axis." In other words, the primary lateral bending resonance occurs in a vibration mode in which the tread 71 moves around the vertical rotation axis (around the X axis). The lateral bending primary resonance frequency is a resonance frequency when the tire 7 vibrates around the vertical rotation axis.

[0020] In-plane torsional resonance is a resonance that occurs when the tread 71 vibrates in a rigid-body manner around the central axis C1. As a result of this vibration, the sidewall 72 is twisted in a plane perpendicular to the central axis C. The axis related to the direction of this vibration is the "lateral axis." Note that, because in-plane torsional resonance is a vibration about the lateral axis, the axis related to the direction of this vibration will hereinafter be distinguished by being referred to as the "lateral rotation axis." In other words, in-plane torsional resonance occurs in a vibration mode in which the tread 71 moves about the lateral rotation axis (about the Z axis). The in-plane torsional resonance frequency is the resonance frequency when the tread 71 vibrates in a direction centered on the lateral rotation axis of the tire 7.

[0021] [Findings that form the basis of the present invention] Generally, to obtain the resonant frequency of a wheel, the wheel is placed in a rolling state and vibration data is obtained from the wheel. Until now, it has not been necessary to obtain the resonant frequency when the wheel is not in a rolling state and not on the ground. Note that the resonant frequency may differ between when the wheel is in a rolling state and when it is not in a rolling state and when it is not on the ground and not on the ground.

[0022] In recent years, model-based development has been progressing in the development of automobiles. In light of this trend, the present inventors have focused on the need to measure the resonance frequency of a single wheel (single tire). As a result, they have completed the invention of a measurement system 10, a measurement method that can be performed by the measurement system 10, and a vibration block 60 used in the measurement system 10 and the measurement method, all of which are described below, as new technical means for acquiring the resonance frequency of a wheel that is not in contact with the ground and is not rolling.

[0023] In particular, to obtain the resonance frequency, it is necessary to vibrate the wheel with a hammer or the like in a direction parallel to the vibration direction of the vibration mode of interest. If the vibration modes are different, that is, if the axes related to the vibration direction are different, it is necessary to perform measurements multiple times for each vibration mode. Specifically, to obtain the resonance frequencies in multiple vibration modes, it was necessary to vibrate and measure the wheel 5 separately in each direction parallel to each of the three orthogonal axes (X-axis, Y-axis, and Z-axis).

[0024] In contrast, by using the vibration block 60 described below, it becomes possible to analyze resonance frequencies in multiple vibration modes based on multiple orthogonal axes with a single input using a hammer or the like. Preferred embodiments of the measurement system 10, the measurement method, and the vibration block 60 will now be described.

[0025] [Measurement System 10] Fig. 3 is an explanatory diagram of the measurement system 10, showing a part of the wheel 5 in a cutaway view. Fig. 4 is an explanatory diagram showing the configuration of the measurement system 10. The measurement system 10 is equipment for acquiring the resonance frequency in each vibration mode of the wheel 5 (tire 7). The measurement system 10 includes a jig 50 having a support shaft 52 for fixing the wheel 5, a vibration block 60 fixed to the outer peripheral surface 8 of the wheel 5, a hammer device 30, a second sensor 22, and a calculation unit 15.

[0026] The hammer device 30 has a hammer body 32 that applies a vibration force to the vibration block 60, and a first sensor 31. The hammer body 32 has a metal striking member that vibrates a vibration surface 62 (see FIG. 5) of the vibration block 60. The first sensor 31 is a sensor device that detects vibration caused by the hammer body 32.

[0027] The second sensor 22 is attached to the support shaft 52 and is a sensor unit for detecting vibration components based on axes included in the three orthogonal axes of the support shaft 52. More specifically, the second sensor 22 is a sensor unit for detecting vibration components in the axial direction of each of the three axes (X-axis, Y-axis, Z-axis) included in the three orthogonal axes of the support shaft 52, and vibration components around each of the axes (X-axis, Y-axis, Z-axis) included in the three orthogonal axes. The second sensor 22 functions as a six-component force meter.

[0028] [Jig 50] The jig 50 has a high-rigidity support block 51 fixed to a base 59, and a support shaft 52 extending from the high-rigidity support block 51. Hereinafter, the high-rigidity support block 51 may be simply referred to as the "support block 51." The support shaft 52 is supported by the support block 51 in a cantilever shape.

[0029] The support block 51 is made of a metal member. The support block 51 is heavy and has high rigidity, so that the support block 51 will not be displaced even if an external force such as the excitation force from the hammer device 30 acts on the wheel 5 fixed to the support shaft 52. The base 59 is the ground or a strong support stand installed on the ground.

[0030] The support shaft 52 is fixed to the support block 51 so as not to be displaceable. The support shaft 52 is supported by the support block 51 so as not to be displaceable in the axial direction along the central axis C2 of the support shaft 52 and in the rotational direction around the central axis C2. The support shaft 52 has a fixing portion 53 and an attachment portion 54. The fixing portion 53 is a portion for fixing the rim 6 (wheel 5) on which the tire 7 is mounted. The attachment portion 54 is a portion for attaching the sensor 41 that acquires vibrations acting on the support shaft 52.

[0031] The support shaft 52 is made of metal and has high rigidity. Vibrations of the wheel 5 having the tire 7 and the rim 6 are transmitted to the support shaft 52. The jig 50 is installed on a base 59 so that the direction of the central axis C2 of the support shaft 52 coincides with the horizontal direction. The cross section of the support shaft 52 in this embodiment is circular. The support shaft 52 shown in FIG. 3 is cylindrical, but may have a shape with a partially expanded diameter.

[0032] The fixing portion 53 of the support shaft 52 fixes the rim 6 (wheel 5) on which the tire 7 is mounted so that it cannot be displaced in the directions of three orthogonal axes including the axial direction of the support shaft 52 and in the rotational directions around the three orthogonal axes. The three orthogonal axes are the X-axis, Y-axis, and Z-axis of the three-dimensional Cartesian coordinate system. The axial direction of the support shaft 52 is the direction along the Z-axis. In other words, the fixing portion 53 fixes the wheel 5 so that it cannot be displaced in the directions of the X-axis, Y-axis, and Z-axis and cannot be rotated around the X-axis, Y-axis, and Z-axis.

[0033] The fixing portion 53 fixes the wheel 5 so that the central axis C2 of the support shaft 52 and the central axis C1 of the wheel 5 are coaxial. The fixing portion 53 of this embodiment has a flange 55 as a structure for fixing the rim 6. The rim 6 is fastened to the flange 55 with bolts. With the above structure, the support shaft 52 fixes the wheel 5 so that it cannot be displaced.

[0034] The mounting portion 54 of the support shaft 52 is a portion where the four sensors 41 are mounted at equal intervals in the circumferential direction centered on the central axis C2 of the support shaft 52. The mounting portion 54 is located near the tip of the support shaft 52. The sensors 41 are located near the flange 55. In this embodiment, the four sensors 41 are located at the intersections (two points, top and bottom) between the outer surface of the support shaft 52 and an imaginary line parallel to the X-axis, and at the intersections (two points, front and back) between the outer surface of the support shaft 52 and an imaginary line parallel to the Y-axis.

[0035] The sensor 41 is, for example, a load sensor, and acquires vibration of the support shaft 52 caused by a force acting on the support shaft 52 as a waveform signal. Four sensors 41 may form one unit, and the mounting part 54 may be configured to mount the one unit. The four sensors 41 form a sensor unit, and the sensor unit corresponds to the second sensor 22.

[0036] The second sensor 22 has a predetermined wiring structure for the lead wires extending from each of the four sensors 41, and outputs six-component force signals. In other words, the second sensor 22 functions as a six-component force meter. The second sensor 22 has a circuit section including an amplifier and the like (not shown), and is capable of outputting six-component force signals. The six component forces are a total of six types of forces: forces in the directions of the X-axis, Y-axis, and Z-axis of the three-dimensional orthogonal coordinate system, and moments around the X-axis, Y-axis, and Z-axis.

[0037] According to the jig 50 having the above configuration, when a force acts on the wheel 5, the force becomes a vibration of the support shaft 52 and is transmitted to the support shaft 52. For example, when a force (force component) on the vertical axis acts on the wheel 5, the force (force component) becomes a vibration in a direction along the vertical axis of the support shaft 52 and is transmitted to the support shaft 52. When a vibration component (moment) about one of the three orthogonal axes acts on the wheel 5, the vibration component becomes a vibration of the support shaft 52 about the one axis and is transmitted to the support shaft 52. For example, when a vibration component (moment) about the left-right rotation axis acts on the wheel 5, the vibration component becomes a vibration of the support shaft 52 about the left-right rotation axis and is transmitted to the support shaft 52.

[0038] As described above, the mounting portion 54 of the support shaft 52 is a portion where the four sensors 41 are mounted at equal intervals in the circumferential direction around the central axis C2 of the support shaft 52. With this configuration, the calculation unit 15 performs arithmetic processing of signals from the four sensors 41 in accordance with a well-known six-component calculation algorithm. This arithmetic processing acquires force components and vibration components in directions along each axis of the support shaft 52, as well as force components and vibration components about each axis. Based on the results of this arithmetic processing, the resonance frequency of the wheel 5 in each vibration mode is acquired.

[0039] [Vibration block 60] The vibration block 60 is fixed to the outer peripheral surface 8 of the wheel 5 (tire 7) (see FIGS. 1 and 2). The vibration block 60 is used to obtain the resonance frequency in each vibration mode of the wheel 5. In the present embodiment, the vibration block 60 is fixed to the tread center of the tire 7 at one location (rear position) in the Y-axis direction, which is the fore-and-aft direction.

[0040] 5 is a perspective view of the vibration block 60. The vibration block 60 is made of a metal block. The vibration block 60 has an attachment surface 61 that is attached to the outer peripheral surface 8 of the tire 7, and a vibration surface 62 that is struck (striked) by the hammer body 32 (see FIG. 4).

[0041] The overall shape of the vibration block 60 will be explained based on one imaginary hexahedron K. The mounting surface 61 is a surface that follows one of the rectangular faces of the imaginary hexahedron K. The mounting surface 61 is fixed to the tire 7 by adhesive. In this embodiment, the imaginary hexahedron K is a virtual cube. Therefore, the mounting surface 61 has a square shape. The vibration block 60 is fixed to the tire 7 in such a manner that one side of the square is parallel to the tangent direction of the tire 7 (parallel to the X-axis in this embodiment) and the other side of the square is parallel to the axis in the left-right direction (Z-axis).

[0042] The excitation surface 62 is a plane. This plane is not a plane along one of the rectangular faces of the imaginary hexahedron K, but a plane that intersects with multiple adjacent faces of the imaginary hexahedron K. To explain the excitation surface 62 in more detail, as shown in FIG. 5, the plane that constitutes the excitation surface 62 intersects with three mutually adjacent faces (faces P1, P2, and P3) of the imaginary hexahedron K. Note that in FIG. 5, the excitation surface 62 is cross-hatched for ease of explanation. The three faces (faces P1, P2, and P3) are the three faces excluding the face that becomes the mounting face 61.

[0043] 5 is a plane that passes through three vertices Q1, Q2, and Q3 of the virtual hexahedron K. Alternatively, the vibration plane 62 may be a plane that passes through the midpoints of three sides extending from one vertex Q4 of the virtual hexahedron K. The vibration plane 62 has a triangular shape, which is an equilateral triangle in this embodiment.

[0044] The vibration surface 62 is struck by the hammer body 32 in a direction perpendicular to the vibration surface 62, and a vibration force is applied in a direction perpendicular to the vibration surface 62. With one strike by the hammer body 32, the wheel 5 is vibrated in a direction having an up-down component, a front-rear component, and a left-right component through the vibration block 60. With one strike by the hammer body 32, vibrations having an up-down component, a front-rear component, and a left-right component are simultaneously applied to the wheel 5. With the vibration block 60 of this embodiment, vibrations due to one strike are simultaneous vibrations in three orthogonal axes.

[0045] As described above, when the hammer body 32 strikes the excitation surface 62, an excitation force is input to the excitation block 60. Because the excitation surface 62 is a plane having the above-described configuration, it is possible to resolve the excitation force from the hammer body 32 into force components in the directions of three orthogonal axes by calculation using Pythagoras's theorem. Therefore, using a measurement method described later, a single input from the hammer body 32 makes it possible to analyze the resonance frequencies in multiple vibration modes based on three orthogonal axes.

[0046] [Regarding the first sensor 31, the second sensor 22, and the calculation unit 15] The first sensor 31 (see FIG. 4) is a sensor for detecting vibration (input) to the tire 7 by the hammer body 32. The first sensor 31 may be a sensor whose detection direction is unidirectional (uniaxial). The unidirectional direction is the vibration direction (striking direction) of the hammer body 32. The first sensor 31 is, for example, an acceleration pickup. A signal (detection signal) of the first sensor 31 is transmitted to the calculation unit 15.

[0047] The second sensor 22 (see FIG. 3) is composed of four sensors 41 attached to the support shaft 52. As described above, the second sensor 22 functions as a six-component force meter. A signal (detection signal) of the second sensor 22 is transmitted to the calculation unit 15.

[0048] The calculation unit 15 is configured by a computer device. The computer device has a CPU (arithmetic processing unit) and a storage device that stores computer programs and various data. The CPU executes the computer program, and the computer device (calculation unit 15) has various processing functions. The computer device (calculation unit 15) has a calculation processing function and a frequency analysis function as functions achieved by the CPU and the computer program. A specific example of the processing executed by the calculation unit 15 will be described along the following measurement method.

[0049] [Measurement method] 6 is a flow diagram of a measurement method for acquiring the resonance frequency in each vibration mode of the wheel 5. The measurement method is performed using the measurement system 10. The measurement method includes a preparation step S10, a vibration application step S20, a first acquisition step S30, a second acquisition step S40, and a measurement step S50.

[0050] The preparation process S10 includes an assembly process in which the tire 7 is mounted on the rim 6 and air is filled into the tire 7, and a fixing process in which the wheel 5 having the tire 7 and rim 6 is fixed to a jig 50 (see Figure 4). A genuine rim is used as the rim 6. A genuine rim is a rim specified in the standard on which the tire is based. The "standard rim" in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are genuine rims.

[0051] During the assembly process, the internal pressure of the tire 7 is adjusted to a predetermined pressure. The state in which the tire 7 is mounted on the rim (regular rim) 6, the internal pressure of the tire 7 is adjusted to the regular internal pressure, and no load is applied to the tire 7 is called the regular state. The tire 7 and rim 6 are fixed to a jig 50 in the regular state, for example. The regular internal pressure means the internal pressure determined in the standard on which the tire is based. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are regular internal pressures.

[0052] Thus, the preparation step S10 is a step in which the wheel 5 is immovably fixed to the support shaft 52. The wheel 5 is fixed to the support shaft 52 so as to be immovable in the directions of three orthogonal axes including the axial direction of the support shaft 52 and in the rotational directions around the three orthogonal axes. The wheel 5 is completely constrained in all directions with six degrees of freedom.

[0053] The vibration step S20 is a step in which an operator vibrates the wheel 5 using a hammer device 30 (see FIG. 4). That is, the vibration step S20 is a step in which a vibration block 60 fixed to the outer peripheral surface 8 of the wheel 5 is vibrated by the hammer device 30. The vibration block 60 is vibrated by the hammer body 32 in a direction perpendicular to the vibration surface 62.

[0054] The first acquisition step S30 is a step in which the calculation unit 15 acquires a signal from the first sensor 31 of the hammer device 30 obtained by carrying out the vibration step S20. In other words, the first acquisition step S30 is a step in which the vibration (vibration component in the vibration direction) in the hammer device 30 when the vibration block 60 is vibrated is acquired as an input signal.

[0055] In the vibration step S20, the hammer device 30 strikes the vibration block 60, causing vibration in the tire 7, and the vibration is transmitted to the support shaft 52 through the rim 6. The vibration force of the wheel 5 produced by the hammer device 30 is transmitted to the support shaft 52 as forces in directions along each of the three orthogonal axes and moments around each of the three orthogonal axes.

[0056] The second acquisition step S40 is a step of acquiring the vibration of the support shaft 52 caused by the excitation of the tire 7 in the excitation step S20. Specifically, the second acquisition step S40 is a step in which the calculation unit 15 acquires a signal from the second sensor 22 attached to the support shaft 52.

[0057] The second acquisition step S40 is a step of acquiring, as output signals, vibrations relative to the axes included in the three orthogonal axes of the support shaft 52, which are caused by the excitation of the hammer device 30. More specifically, vibration components in directions along each of the three orthogonal axes of the support shaft 52, which are caused by the excitation of the hammer device 30, and vibration components around each of the three orthogonal axes, are acquired as output signals.

[0058] The measurement process 50 is a process for executing a process for acquiring the resonance frequency of the wheel 5 in each vibration mode. To this end, the calculation unit 15 executes a calculation process for acquiring the resonance frequency of the wheel 5 based on the signal of the first sensor 31 and the signal of the second sensor 22. As the calculation process, the calculation unit 15 executes a first process for acquiring a transfer function based on the signal of the first sensor 31 and the signal of the second sensor 22, a second process for correcting the gain of the transfer function obtained by the first process, and a third process for outputting a peak value of the frequency analysis result of the transfer function. The first process, the second process, and the third process will be described below.

[0059] The calculation unit 15 acquires a vibration waveform based on the excitation force of the hammer device 30 based on the signal from the first sensor 31. This vibration waveform becomes the “input signal” that the hammer device 30 applies to the wheel 5. The calculation unit 15 acquires a vibration waveform of the support shaft 52 based on the signal of the second sensor 22. This vibration waveform becomes an "output signal" generated when the wheel 5 is vibrated. The calculation unit 15 executes a calculation process to divide the "output signal" by the "input signal" to obtain a transfer function. The calculation unit 15 obtains a transfer function of the output of the support shaft 52 with respect to the vibration input to the wheel 5. This is the first process.

[0060] As described above (see FIG. 5), the excitation surface 62 of the vibration block 60 is a plane that intersects with three mutually adjacent surfaces (surfaces P1, P2, and P3) of the imaginary hexahedron K. The vibration block 60 has a shape that conforms to the imaginary hexahedron K, which is a cube, and has the vibration surface 62 configured as described above. Therefore, when the magnitude of the force input to the vibration surface 62 is "1", the force in the direction along each of the three orthogonal axes that is input to the wheel 5 through the vibration block 60 is "1 / √3".

[0061] As described above, a single strike on the vibration block 60 causes vibrations in three orthogonal axes simultaneously. As described above, the second sensor 22 functions as a six-component force meter. Therefore, the calculation unit 15 can obtain the transfer function of the vibration mode for each axis included in the three orthogonal axes.

[0062] Since the input in the direction along each of the three orthogonal axes is multiplied by 1 / √3, the resulting gain value (before dB conversion) is multiplied by 1 / √3. The value of each transfer function obtained by the first processing is multiplied by 1 / √3. Therefore, the calculation unit 15 performs a second process, which is a correction process, to obtain the target gain of the transfer function. That is, in the measurement step 50, when the vibration force of the hammer body 32 is resolved into force components in the directions of three orthogonal axes, the calculation unit 15 corrects the gain of the transfer function using "1 / √3" as the ratio between the vibration force and the force component in each of the three orthogonal axes. This correction is sometimes called conversion.

[0063] In this embodiment, the value of the ratio is "1 / √3." Note that if the shape of the vibration block 60 (virtual hexahedron K) is different, the value of the ratio will be different and is obtained based on the geometric shape.

[0064] The calculation including the specific correction process (conversion) is as follows. Here, a case will be described in which the gain of the transfer function of the eccentricity primary resonance occurring in the vibration mode in which the tire 7 moves in the direction along the X axis is acquired. Note that the same method is used to acquire the gain of the transfer function in the vibration mode in the direction along the other axes, and the same method is also used to acquire the gain of the transfer function in the vibration mode about each axis.

[0065] The parameters used in the description are defined as follows: H: Original transfer function. Transfer function obtained by conversion. H′: Transfer function before conversion. Transfer function obtained by excitation to the excitation surface 62 before conversion. F: hammer vibration force, a value measured by the first sensor 31 when the vibration is applied to the vibration surface 62. Fx: Excitation force applied by the hammer body 32 in the X-axis direction. X: Force response in the X-axis direction (axial force response). The force component in the X-axis direction measured by the second sensor 22 when the excitation surface 62 is vibrated.

[0066] By applying vibration to the vibration surface 62, a transfer function H' is obtained as shown in the following equation (1). H′=X / F...Equation (1) According to the Square theorem, the excitation force can be decomposed as follows: F / √3=Fx ··· Formula (2) Due to the orthogonality of the vibrations, the excitation force Fx in the X-axis direction is dominant for vibrations in the X-axis direction, and therefore the following equation (3) is defined. H=X / Fx...Equation (3)

[0067] According to the equations (2) and (3), the following equation (4) is obtained. H=X√3 / F...Equation (4) From equations (1) and (4), the following equation (5) is obtained. H=H′√3...Equation (5) In this way, the gain of the transfer function H converted using the ratio value "1 / √3" is obtained. This completes the second process.

[0068] The calculation unit 15 has a frequency analysis function. The calculation unit 15 obtains the gain in each frequency band from the converted transfer function by frequency analysis. For example, FIG. 7 is an explanatory diagram showing the output obtained by frequency analysis. FIG. 7 is an example (graph) of the output result in which the horizontal axis represents frequency and the vertical axis represents gain.

[0069] In Fig. 7 (solid line in Fig. 7), in the gain output obtained by frequency analysis, the peak frequency of the first-order component is acquired as the eccentricity primary resonance frequency F1. In Fig. 7, the peak of the first-order component is shown as a "first peak S1." The peak frequency of the first-order component (eccentricity primary resonance frequency F1) is acquired by calculation by the calculation unit 15. This is the third process.

[0070] In this way, the vibrations in the hammer device 30 (vibration components in the excitation direction) are used as "input signals," and the vibration components in each axial direction and around each axis of the support shaft 52 caused by the vibrations of the hammer device 30 are used as "output signals." In the measurement process 50, the resonant frequency in each vibration mode of the wheel 5 is obtained from a transfer function based on the "input signals" and the "output signals."

[0071] According to the measurement method of this embodiment, a single input of the hammer body 32 to the vibration block 60 makes it possible to analyze the resonance frequencies in multiple vibration modes based on multiple orthogonal axes (three axes). In other words, with the vibration block 60 shown in Fig. 5, a single strike excites vibrations in the directions of the three orthogonal axes in the wheel 5. By using six component forces as the output of the support shaft 52, it becomes possible to simultaneously measure the resonance frequencies in multiple vibration modes.

[0072] According to the measurement method of this embodiment, it is possible to simultaneously obtain the resonance frequencies in multiple vibration modes by applying vibration once. Therefore, the number of steps required to obtain the resonance frequencies in multiple vibration modes is reduced. By obtaining the resonance frequencies in multiple vibration modes, it is expected that the accuracy of the model will be improved in the development of the wheel 5.

[0073] To verify the validity of the wheel 5 model, the absolute value of the gain of the resonant frequency obtained by frequency analysis is also important. In this embodiment, in the measurement process, when the excitation force from the hammer body 32 is resolved into force components in the directions of three orthogonal axes, the gain is corrected using the ratio (1 / √3) between these excitation forces and the force components. Correction based on the value of this ratio allows an accurate absolute value of the gain to be obtained.

[0074] The vibration block 60 may have a different form. For example, as shown in Fig. 8, the vibration surface 62 of the vibration block 60 may be a plane, and this plane may intersect with four adjacent faces of the virtual hexahedron K. In this case, the vibration surface 62 is rectangular. However, in the case of this vibration block 60, it is not possible to obtain the resonance frequencies in five (all) vibration modes at once, but it is possible to obtain the resonance frequencies in vibration modes related to two of the three orthogonal axes. [Industrial Applicability]

[0075] The measurement system, measurement method, and vibration block described above are used for the development of various tires.

[0076] [Note] The present invention includes the following aspects. (1) The vibration block has an attachment surface that is attached to the wheel and an excitation surface, the attachment surface being a surface that is along one of the faces of the virtual hexahedron, and the excitation surface being a plane that intersects with multiple adjacent faces of the virtual hexahedron. (2) The plane is a plane that intersects with three adjacent faces of the virtual hexahedron.

[0077] (3) A measurement system for acquiring the resonant frequency of a wheel includes a jig having a support shaft for immobilizing the wheel, a vibration block of (1) or (2) fixed to the outer peripheral surface of the wheel, a hammer device having a hammer body for applying a vibration force to the vibration surface of the vibration block and a first sensor for detecting the vibration applied by the hammer body, a second sensor attached to the support shaft for detecting vibration components based on an axis included in the three orthogonal axes of the support shaft, and a calculation unit for performing calculations to determine the resonant frequency of the wheel based on a signal from the first sensor and a signal from the second sensor.

[0078] (4) In the measurement system of (3), when the excitation force is decomposed into force components in the directions of three orthogonal axes, the calculation unit performs correction using the ratio between the excitation force and the force components to determine the gain of the transfer function. (5) In the measurement system of (4), the calculation unit performs the following calculation processes: obtaining a transfer function based on the signal of the first sensor and the signal of the second sensor; correcting the gain of the transfer function using the ratio; and outputting the peak value of the frequency analysis result of the transfer function.

[0079] (6) In any one of the measurement systems (3) to (5), the jig has a high-rigidity support block fixed to a base, and a support shaft extending from the high-rigidity support block and fixed to the high-rigidity support block so as not to be displaceable, and the support shaft has a fixing portion that fixes the wheel so as not to be displaceable in the directions of three orthogonal axes including the axial direction of the support shaft and in the rotational directions around the three orthogonal axes, and an attachment portion for attaching a sensor that acquires vibrations acting on the support shaft.

[0080] (7) In the measurement system of (6), the fixing unit is configured to fix the wheel so that the central axis of the support shaft, which has a circular cross section, is coaxial with the central axis of the wheel, and the mounting unit mounts four second sensors at equal intervals along the circumferential direction centered on the central axis of the support shaft.

[0081] (8) A measurement method for acquiring the resonant frequency of a wheel, the measurement method comprising: a preparation step of fixing the wheel to a support shaft so as to be immovable; a vibration step of using a hammer device to vibrate the vibration block of (1) or (2) fixed to the outer circumferential surface of the wheel; a first acquisition step of acquiring, as an input signal, vibration in the hammer device when the vibration block is vibrated; a second acquisition step of acquiring, as an output signal, vibration caused by the vibration of the hammer device and based on an axis included in the three orthogonal axes of the support shaft; and a measurement step of determining the resonant frequency of the wheel from a transfer function based on the input signal and the output signal. [Explanation of symbols]

[0082] 5...wheels 8...Outer surface 10. Measurement System 15... Arithmetic section 22 Second sensor 30. Hammer device 31 First sensor 32 Hammer body 50... Jig 51 High-rigidity support block 52...Support shaft 53...Fixed part 54 Mounting part 60···Vibration block 61 Mounting surface 62...Excitation surface C1...Central axis line K···Virtual hexahedron P1,P2,P3...plane

Claims

1. The vehicle has a mounting surface that is attached to the wheel and a vibration surface, the mounting surface is a surface along one of the faces of the imaginary hexahedron, The excitation surface is a plane, and the plane intersects with a plurality of adjacent faces of the virtual hexahedron. Vibration block.

2. The plane is a plane that intersects with three mutually adjacent faces of the virtual hexahedron. The vibration block according to claim 1 .

3. A measurement system for obtaining a resonance frequency of a wheel, comprising: a jig having a support shaft that fixes the wheel so that it cannot be displaced; a vibration block according to claim 1 or 2, which is fixed to an outer peripheral surface of the wheel; a hammer device having a hammer body that applies a vibration force to the vibration surface of the vibration block, and a first sensor that detects vibration caused by the hammer body; a second sensor attached to the support shaft for detecting a vibration component based on an axis included in the three orthogonal axes of the support shaft; a calculation unit that executes a calculation process to determine a resonance frequency of the wheel based on the signal from the first sensor and the signal from the second sensor; A measurement system having:

4. the calculation unit, when the excitation force is resolved into force components in the directions of three orthogonal axes, performs correction using a ratio between the excitation force and the force components to determine a gain of the transfer function. The measurement system according to claim 3 .

5. The calculation unit performs the calculation process as follows: obtaining a transfer function based on a signal from the first sensor and a signal from the second sensor; correcting the gain of the transfer function using the ratio; a process of outputting a peak value of a frequency analysis result of the transfer function; To execute The measurement system according to claim 4 .

6. The jig is a highly rigid support block fixed to the base; the support shaft extending from the high-rigidity support block and fixed to the high-rigidity support block so as not to be displaceable; and The support shaft is a fixing portion that fixes the wheel so that the wheel cannot be displaced in directions of three orthogonal axes including the axial direction of the support shaft and in rotational directions around the three orthogonal axes; a mounting portion for mounting a sensor for acquiring vibration acting on the support shaft; The measurement system of claim 3 , comprising:

7. the fixing portion has a configuration for fixing the wheel so that a central axis of the support shaft, which has a circular cross section, and a central axis of the wheel are coaxial with each other, The mounting portion mounts the four second sensors at equal intervals along a circumferential direction centered on a central axis of the support shaft. The measurement system of claim 6 .

8. A measurement method for acquiring a resonance frequency of a wheel, comprising: a preparation step of fixing the wheel to the support shaft so that it cannot be displaced; a vibration applying step of applying vibration to the vibration block according to claim 1 or 2, which is fixed to the outer peripheral surface of the wheel, by a hammer device; a first acquiring step of acquiring, as an input signal, vibration in the hammer device when the vibration block is vibrated; a second acquiring step of acquiring, as an output signal, vibrations based on an axis included in the three orthogonal axes of the support shaft, the vibrations being caused by the excitation of the hammer device; a measuring step of determining a resonance frequency of the wheel from a transfer function based on the input signal and the output signal; A measurement method having the following features.

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