Measuring system, measuring method, jig, and excitation block

Abstract

To provide a measuring system for acquiring the in-plane torsional resonance frequency of a wheel.SOLUTION: The measuring system has: a jig 50 that has a support shaft 52 that fixes a wheel 5 in a non-displaceable manner; an excitation block 60 that is fixed to an outer peripheral surface 8 of the wheel 5; a hammer device 30 that has a hammer body 32 that excites the excitation block 60 in a tangential direction of the outer peripheral surface 8 of the wheel 5, and a first sensor 31 for detecting the excitation by the hammer body 32; a second sensor 22 that is attached to the support shaft 52 for detecting a vibration component around a central axis C2 of the support shaft 52; and an operation unit 15 that executes arithmetic processing for acquiring the resonance frequency of the wheel 5 on the basis of a signal from the first sensor 31 and a signal from the second sensor 22.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a measurement system for acquiring the in-plane torsional resonance frequency of a wheel, a measurement method performed by the measurement system, a jig, and a vibration block. [Background technology]

[0002] In an automobile, if the resonant frequency of a wheel is close to the resonant frequency of other devices (such as steering system devices) installed around the wheel, problems such as abnormal noise can occur. In the development of wheels, the resonant frequency of the wheel must be obtained in advance, and as a method for obtaining the resonant frequency of the wheel, for example, a method disclosed in Patent Document 1 has been proposed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-141244 A Summary of the Invention [Problem to be solved by the invention]

[0004] There are various modes of resonance frequencies of a wheel. 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 in-plane torsional resonance frequency of a wheel. [Means for solving the problem]

[0005] A measurement system according to the present invention is a measurement system for acquiring an in-plane torsional resonance frequency of a wheel, the measurement system including a jig having a support shaft for fixing the wheel so as to be immovable, a vibration block fixed to an outer peripheral surface of the wheel, a hammer device including a hammer body for vibrating the vibration block in a tangential direction to the outer peripheral surface of the wheel and a first sensor for detecting the vibration caused by the hammer body, a second sensor attached to the support shaft for detecting a vibration component about a central axis of the support shaft, and a calculation unit for executing a calculation process for acquiring the in-plane torsional resonance frequency of the wheel based on a signal from the first sensor and a signal from the second sensor.

[0006] A measurement method according to the present invention is a method for acquiring an in-plane torsional resonance frequency of a wheel, the method comprising the steps of: 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 a vibration block fixed to the outer peripheral surface of the wheel in a tangential direction to the outer peripheral surface of the wheel, a first acquisition step of acquiring, as an input signal, a vibration in the hammer device when the vibration block is excited, a second acquisition step of acquiring, as an output signal, a vibration component about the central axis of the support shaft caused by the vibration of the hammer device, and a measurement step of acquiring the in-plane torsional resonance frequency of the wheel from a transfer function based on the input signal and the output signal.

[0007] The jig according to the present invention is used for acquiring the in-plane torsional resonance frequency of a wheel. 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 to be immovable, the support shaft having a fixing portion that fixes the wheel so as not to be displaceable in three orthogonal axis directions including the axial direction of the support shaft and in rotational directions about the three orthogonal axes, and a mounting portion for mounting a sensor that acquires vibration acting on the support shaft.

[0008] The present invention relates to a vibration block used for obtaining an in-plane torsional resonance frequency of a wheel, the vibration block having a fixed part fixed to an outer peripheral surface of the wheel and a vibration part integral with the fixed part, the fixed part having a dimension larger than that of the vibration part in a tangential direction of the tire, and the vibration part protruding from the fixed part in a radial direction of the wheel. Effect of the Invention

[0009] According to the measurement system and measurement method of the present invention, it is possible to obtain the in-plane torsional resonance frequency of a wheel. The jig and vibration block of the present invention are used in the measurement system and measurement method to obtain the in-plane torsional resonance frequency of the wheel. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is an explanatory diagram of in-plane torsion of a wheel. [Diagram 2] FIG. 2 is a schematic diagram of a jig used in the measurement system. [Diagram 3] FIG. 2 is a schematic diagram of a jig used in the measurement system. [Figure 4] FIG. [Diagram 5] FIG. 1 is an explanatory diagram showing a configuration of a measurement system. [Figure 6] FIG. 1 is a flow diagram of a measurement method for obtaining the in-plane torsional resonance frequency of a wheel. [Figure 7] FIG. 13 is an explanatory diagram showing an output obtained by wave number analysis. [Figure 8] FIG. 13 is an explanatory diagram showing an output obtained by wave number analysis. [Figure 9] FIG. 2 is an explanatory diagram showing outputs for six types of wheels (tires). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [Details of the embodiment of the present invention] Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings.

[0012] [On the in-plane torsional resonance frequency of wheels] The in-plane torsional resonance frequency is known as the resonance frequency of a wheel. Fig. 1 is an explanatory diagram of the in-plane torsion of a wheel. In the following embodiment, a wheel 5 having a pneumatic tire 7 mounted on a rim 6 will be described. As will be described later, the wheel may be an airless tire. The in-plane torsional resonance frequency is the resonance frequency of vibration in a direction along an imaginary circle centered on the central axis C1 of the tire 7 (wheel 5). In Figure 1, an image of the torsional deformation of the tire 7 is shown by a dashed line, and the vibration is indicated by an arrow V.

[0013] The tire 7 is made of rubber and is supported by a metal rim 6. A central axis C1 of the tire 7 coincides with the central axis of the rim 6. In the following description, the direction along an imaginary circle centered on the central axis C1 of the tire 7 (wheel 5) is the circumferential direction of the tire 7 (wheel 5), and this direction is also called the "in-plane torsion direction."

[0014] [Findings on which the present invention is based] Generally, to obtain the in-plane torsional resonance frequency of a wheel, the wheel is placed in contact with the ground and in a rolling state, and vibration and other data are obtained from the wheel. Until now, there has been no need to obtain the in-plane torsional resonance frequency when the wheel is not in contact with the ground and is not rolling. The resonance frequency differs greatly between when the wheel is in contact with the ground and rolling and when the wheel is not in contact with the ground and not rolling.

[0015] In recent years, model-based development has been progressing in the development of automobiles. In light of this trend, the present inventors have noticed the need to measure the in-plane torsional resonance frequency of a single wheel (single tire). In order to obtain the in-plane torsional resonance frequency of the tire 7 (wheel) (see FIG. 1), it is necessary to apply a torsional force around the central axis C1 of the tire 7. For this purpose, for example, two points on the tread that are 180 degrees apart around the central axis C1 of the tire 7 are excited in opposite directions. This is to prevent the tire 7 from translating, but such an operation is difficult. Alternatively, it is possible to apply a torsional force if the tire 7 is in a ground contact state. However, this does not satisfy the requirement of being "not on the ground."

[0016] As described above, the present inventor focuses on the in-plane torsional resonance frequency of a tire (wheel) in a non-grounded and non-rolling state, but a specific means for acquiring this frequency has not yet been established. Therefore, we have now completed the invention of a measurement system, a measurement method that can be performed by the measurement system, and a jig and vibration block used in the measurement system and measurement method, as new technical means for obtaining the in-plane torsional resonance frequency of a wheel that is not on the ground and not rolling, as described below.

[0017] Preferred embodiments of the measurement system, the measurement method, the jig, and the vibration block will be described below.

[0018] 〔jig〕 Figures 2 and 3 are schematic diagrams of a jig used in the measurement system. Figure 2 shows a tire 7 in a partially cut-away state. A jig 50 shown in Figures 2 and 3 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. The support shaft 52 is supported by the support block 51 in a cantilever shape. Hereinafter, the high-rigidity support block 51 may be simply referred to as the "support block 51."

[0019] The support block 51 is made of a metal member. The support block 51 is heavy and has high rigidity, and the support block 51 will not be displaced even if an external force (excitation force by a hammer device 30 shown in FIG. 5, which will be described later) acts on the rim 6 and tire 7 (wheel 5) fixed to the support shaft 52. The base 59 is the ground or a strong support base installed on the ground. When the base 59 is a support base, the support base is firmly fixed to the ground so as not to be displaced in the horizontal and vertical directions.

[0020] The support shaft 52 is fixed to the support block 51 so as to be immovable. The support shaft 52 is supported by the support block 51 so as to be immovable 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) to which the tire 7 is attached. The attachment portion 54 is a portion for attaching the sensor 41 for acquiring vibrations acting on the support shaft 52. 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 cross section of the support shaft 52 in this embodiment is circular. The support shaft 52 shown in Figures 2 and 3 is cylindrical, but may have a shape with a partially expanded diameter.

[0021] The jig 50 and the tire 7 attached to the jig 50 will be described below. A three-dimensional Cartesian coordinate system is set in the jig 50. The jig 50 of this embodiment is installed on the base 59 so that the direction of the central axis C2 of the support shaft 52 coincides with the horizontal direction. The direction along the central axis C2 of the support shaft 52 is defined as the Z-axis direction. The vertical up-down direction perpendicular to the Z-axis direction is the X-axis direction, and the direction perpendicular to both the Z-axis direction and the X-axis direction is the Y-axis direction. The Y-axis direction is also referred to as the front-back direction, and the Z direction is also referred to as the left-right direction.

[0022] 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 about the three orthogonal axes. The three orthogonal axes are the X-axis, Y-axis, and Z-axis of the three-dimensional orthogonal 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 rim 6 (wheel 5) on which the tire 7 is mounted so that it cannot be displaced in the directions of the X-axis, Y-axis, and Z-axis, and cannot be rotated about the X-axis, Y-axis, and Z-axis.

[0023] The fixing portion 53 fixes the rim 6 so that the central axis C2 of the support shaft 52 and the central axis C1 of the tire 7 are coaxial. The fixing portion 53 in this embodiment has a flange 55 as a configuration for fixing the rim 6. In other words, the fixing portion 53 has the flange 55 that fixes the rim 6 to which the tire 7 is mounted. The rim 6 is fastened to the flange 55 with bolts.

[0024] The attachment portion 54 of the support shaft 52 is a portion for attaching the four sensors 41 at equal intervals along the circumferential direction centered on the central axis C2 of the support shaft 52. The attachment portion 54 is located near the tip of the support shaft 52. The sensors 41 are located in the vicinity of the flange 55. In this embodiment, the four sensors 41 are located at the intersections (two points, top and bottom) between the outer peripheral surface of the support shaft 52 and a virtual line parallel to the X-axis, and at the intersections (two points, front and back) between the outer peripheral surface of the support shaft 52 and a virtual line parallel to the Y-axis.

[0025] The sensor 41 is, for example, a load sensor, and acquires, as a waveform signal, vibration of the support shaft 52 caused by a force acting on the support shaft 52. The four sensors 41 may be one unit, and the mounting portion 54 may be configured to mount the one unit.

[0026] In this embodiment, a sensor unit is configured by four sensors 41. This sensor unit corresponds to a second sensor 22 described below. The second sensor 22 has a predetermined wiring structure for the lead wires extending from each of the four sensors 41, and outputs a six-component force signal. In other words, the second sensor 22 has a function 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 a six-component force signal. 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 about the X-axis, Y-axis, and Z-axis.

[0027] According to the jig 50 having the above-described configuration, when a vibration component (moment) about the central axis C1 acts on the tire 7 and the rim 6 supporting the tire 7, the vibration component becomes a vibration about the central axis C2 of the support shaft 52 and is transmitted to the support shaft 52. A unit (second sensor 22) of the sensor 41 attached to the support shaft 52 detects vibration components about the central axis C2 of the support shaft 52. As a result, as will be described later, the in-plane torsional resonance frequency of the tire 7 is obtained. In this manner, the jig 50 shown in Figs. 2 and 3 is used to obtain the in-plane torsional resonance frequency of the tire 7.

[0028] As described above, the vibration component around the central axis C1 of the tire 7 becomes vibration around the central axis C2 of the support shaft 52 and is transmitted to the support shaft 52. The mounting portion 54 of the support shaft 52 is a portion for mounting the four sensors 41 at equal intervals along the circumferential direction centered on the central axis C2 of the support shaft 52. With this configuration, the calculation unit 15 of the measurement system 10, which will be described later, processes signals from the four sensors 41 according to a publicly known six-component calculation algorithm. With this calculation, the vibration component around the central axis C2 of the support shaft 52 (the vibration component around the central axis C1 of the tire 7) is acquired.

[0029] [Vibration block] The vibration block 60 is fixed to the outer peripheral surface 8 of the tire 7 (see FIG. 3). The vibration block 60 is used to acquire the in-plane torsional resonance frequency of the tire 7. The vibration block 60 is fixed to the tread center of the tire 7 at one location in the Y-axis direction, which is the front-rear direction (see FIG. 1). 4 is a perspective view of the vibration block 60. The vibration block 60 has a fixing part 61 fixed to the outer peripheral surface 8 of the tire 7, and a vibration part 62. The fixing part 61 is fixed to the tire 7 by adhesion (adhesive). The fixing part 61 can be directly adhered to the tread surface (outer peripheral surface 8) of the tire 7. Note that the fixing part 61 may also be adhered to the tread surface via an adhesive sheet (not shown).

[0030] The vibration block 60 is made of metal, and the fixed portion 61 and the vibration portion 62 are integrated. In other words, the fixed portion 61 is part of one metal member, and the vibration portion 62 is the other part of the metal member. The fixed portion 61 is a thin plate-like portion. The fixed portion 61 is thinner than the vibration portion 62. The fixed portion 61 has a larger dimension in the tangential direction at the outer peripheral surface 8 of the tire 7 than the vibration portion 62. In this embodiment, the tangential direction is the vertical direction (X-axis direction).

[0031] The vibration unit 62 is a rectangular parallelepiped or cubic part. The vibration unit 62 protrudes from the fixed part 61 to the outside in the radial direction of the tire 7. In the case of this embodiment, when the vibration block 60 is fixed to the tire 7, an upper surface 621 of the vibration unit 62 becomes a vibration surface that is struck (striked) by a hammer device 30 (see FIG. 5 ) described later. The tire 7 is vibrated in the up-down direction (downward) through the vibration block 60.

[0032] As described above, the fixed part 61 is fixed to the outer circumferential surface 8 of the tire 7, and the vibration part 62 protruding from the fixed part 61 is vibrated by the hammer device 30. As a result, the tire 7 is vibrated in the X-axis direction, that is, in the vertical direction (downward), and an in-plane torsional vibration (arrow V in FIG. 1) is applied to the tire 7. In other words, a vibration is applied about the central axis C1 of the tire 7.

[0033] If the adhesive strength between the vibration block 60 and the tire 7 is low, a strong vibration force cannot be applied to the tire 7, and as a result, sufficient vibration cannot be excited, which may reduce the accuracy of the measurement results. However, in the case of the vibration block 60 of this embodiment, the fixing portion 61 has a larger dimension than the vibration portion 62, so that the contact area with the tire 7 is increased and the fixing strength to the tire 7 is high. Therefore, a strong vibration force is applied to the tire 7. In this way, the fixing part 61 has a larger dimension than the excitation part 62, thereby increasing the fixing strength, and since the excitation part 62 is small, the influence of the existence of the excitation part 62 on the vibration of the tire 7 is suppressed. As a result, the measurement accuracy of the in-plane torsional resonance frequency of the tire 7 is improved.

[0034] [Measurement system] 5 is an explanatory diagram showing the configuration of a measurement system 10. The measurement system 10 is equipment for acquiring the in-plane torsional resonance frequency of a tire 7. The measurement system 10 includes a jig 50, a second sensor 22, a vibration block 60, a hammer device 30, and a calculation unit 15. The measurement system 10 of this embodiment further includes a third sensor 23.

[0035] As explained with reference to Figures 2 and 3, the jig 50 has a support shaft 52 that fixes the rim 6 on which the tire 7 is mounted so that it cannot be displaced. The support shaft 52 is fixed by the support block 51 so that it cannot be displaced. As described above, the support shaft 52 has a fixing portion 53 (flange 55). The fixing portion 53 fixes the rim 6 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 about these three orthogonal axes. The "three orthogonal axes" are the X-axis, Y-axis, and Z-axis of the three-dimensional orthogonal coordinate system.

[0036] 4, the vibration block 60 is a member fixed to the outer circumferential surface 8 of the tire 7. The vibration block 60 has a vibration part 62 as a part protruding from the outer circumferential surface 8 of the tire 7. The hammer device 30 has a hammer body 32 made of metal, and a first sensor 31. The hammer body 32 is a striking member that vibrates the vibration block 60 in a tangential direction of the outer circumferential surface 8 of the tire 7. In the case of this embodiment, the tire 7 is vibrated by the hammer body 32 in the X-axis direction, that is, in the up-down direction (downward).

[0037] The first sensor 31 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 one direction (one axis). The one direction is the vibration direction (strike 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.

[0038] The second sensor 22 (see FIG. 2) is composed of the four sensors 41 attached to the support shaft 52. As described above, the second sensor 22 has a function as a six-component force meter, but in order to obtain the in-plane torsional resonance frequency of the tire 7, the second sensor 22 only needs to be a sensor device that detects at least a vibration component about the central axis C2 of the support shaft 52. A signal (detection signal) of the second sensor 22 is transmitted to the calculation unit 15.

[0039] The third sensor 23 (see FIG. 5 ) is fixed to the outer peripheral surface 8 of the tire 7, for example, by adhesion. The third sensor 23 is, for example, an acceleration pickup. In the case of this embodiment, the third sensor 23 is installed near the vibration block 60. As described above, the vibration block 60 is fixed to one location in the Y-axis direction, which is the tread center of the tire 7. The third sensor 23 and the vibration block 60 are arranged side by side in the circumferential direction along the outer peripheral surface 8 of the tire 7.

[0040] The third sensor 23 detects vibration components in the X-axis direction, i.e., the up-down direction, on the outer peripheral surface 8 of the tire 7. The third sensor 23 detects vibration components at the tread center of the tire 7. In this way, the third sensor 23 is a sensor for detecting vibration components in the tangential direction of the outer peripheral surface 8 of the tire 7. A signal (detection signal) of the third sensor 23 is transmitted to the calculation unit 15.

[0041] 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 process executed by the calculation unit 15 will be described along the following measurement method.

[0042] [Measurement method] 6 is a flow diagram of a measurement method for acquiring the in-plane torsional resonance frequency of the tire 7. 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. The first acquisition step S30 and the second acquisition step S40 may be performed simultaneously.

[0043] The preparation process S10 includes an assembly process in which a tire 7 is mounted on a rim 6 and air is filled into the tire 7, and a fixing process in which a wheel having the tire 7 and the rim 6 is fixed to a jig 50 (see Figures 2 and 3). A genuine rim is used as the rim 6. A genuine rim means 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.

[0044] In the assembly process, the internal pressure of the tire is adjusted to a specified 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 the 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 the regular internal pressures.

[0045] Thus, the preparation step S10 is a step in which the rim 6 (wheel) on which the tire 7 is mounted is immovably fixed to the support shaft 52. The rim 6 (wheel) 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 about these three orthogonal axes. In other words, the rim 6 (wheel) is completely constrained in all directions with six degrees of freedom.

[0046] The vibration applying step S20 is a step in which an operator applies vibration to the tire 7 in an in-plane torsional direction by using a hammer device 30 (see FIG. 5). That is, the vibration applying step S20 is a step in which a vibration block 60 fixed to the outer peripheral surface 8 of the tire 7 is applied with the hammer device 30 in a tangential direction of the outer peripheral surface 8 of the tire 7.

[0047] 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. That is, the first acquisition step S30 is a step in which the vibration (vibration component in the vibration direction) of the hammer device 30 when the vibration block 60 is vibrated is acquired as an input signal.

[0048] In the vibration step S20, the hammer device 30 strikes the vibration block 60, generating vibration in an in-plane torsional direction (circumferential direction of the tire 7) in the tire 7, and the vibration is transmitted to the support shaft 52 through the rim 6. The vibration force of the tire 7 applied by the hammer device 30 is transmitted to the support shaft 52 as a moment about the central axis C2. This moment appears as vibration in the torsional direction of the support shaft 52.

[0049] The second acquisition step S40 is a step of acquiring vibration in the torsional direction 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. As described above, the second sensor 22 has a function as a six-component force meter. The second acquisition step S40 is a step of acquiring a vibration component about the central axis C2 of the support shaft 52 caused by the excitation of the hammer device 30 as an output signal.

[0050] The measurement process 50 is a process for executing a process for acquiring the in-plane torsional resonance frequency of the tire 7. To this end, the calculation unit 15 executes a calculation process for acquiring the in-plane torsional resonance frequency of the tire 7 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, and a second process for outputting a peak value of a frequency analysis result of the transfer function. The first process and the second process will be described below.

[0051] The calculation unit 15 obtains 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 tire 7. 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 is a waveform regarding a vibration component about the central axis C2 of the support shaft 52, and serves as an "output signal" generated when the tire 7 is excited. The calculation unit 15 executes a calculation process of dividing the "output signal" by the "input signal" to obtain a transfer function. That is, the calculation unit 15 obtains a transfer function of the output of the support shaft 52 with respect to the vibration input to the tire 7. This is the first process.

[0052] The calculation unit 15 has a frequency analysis function. The calculation unit 15 calculates the gain and phase in each frequency band from the acquired transfer function by frequency analysis. Fig. 7 and Fig. 8 are explanatory diagrams showing the output obtained by the frequency analysis. Fig. 7 is an example (graph) of an output result in which the horizontal axis is frequency and the vertical axis is gain. Fig. 8 is an example (graph) of an output result in which the horizontal axis is frequency and the vertical axis is phase.

[0053] In Fig. 7 (solid line in Fig. 7), in the output of the gain obtained by frequency analysis of the transfer function, the frequency of the peak of the first-order component is acquired as the in-plane torsional resonance frequency F1. In Fig. 7, the peak of the first-order component is shown as a "first peak P1". The frequency of the peak of the first-order component (in-plane torsional resonance frequency F1) is acquired by calculation of the calculation unit 15. 8, the phase at the resonance frequency F1 is plus 90 degrees. When resonance occurs, the phase appears as plus 90 degrees or minus 90 degrees. This is the second process.

[0054] In this way, the vibration (vibration component in the excitation direction) of the hammer device 30 is regarded as an "input signal", and the vibration component about the central axis C2 of the support shaft 52 caused by the excitation of the hammer device 30 is regarded as an "output signal (first output signal)". In the measurement process 50, the in-plane torsional resonance frequency F1 of the tire 7 is obtained from a transfer function based on the "input signal" and the "output signal".

[0055] [Warranty Processing] In the present embodiment, a guarantee process is executed to confirm (guarantee) the in-plane torsional resonance frequency F1. To this end, the calculation unit 15 executes a calculation process to acquire the in-plane torsional resonance frequency of the tire 7 based on the signal of the first sensor 31 and the signal of the third sensor 23. The details of this process are described below.

[0056] The calculation unit 15 acquires a vibration waveform based on the excitation force of the hammer device 30 based on the signal of the first sensor 31 (first acquisition step S30). This vibration waveform becomes the “input signal” applied to the tire 7 by the hammer device 30. As described above (see FIG. 5), the third sensor 23 is a sensor that detects vibration components in the tangential direction of the outer peripheral surface 8 of the tire 7. When the hammer device 30 applies vibration, the third sensor 23 outputs a signal (vibration waveform) of the tangential vibration generated in the tire 7 in response to the vibration.

[0057] The calculation unit 15 acquires a vibration waveform in the tire 7 based on the signal output by the third sensor 23. This vibration waveform is a waveform regarding a vibration component in the tangential direction of the outer peripheral surface 8 of the tire 7, and is defined as a "second output signal" generated when the tire 7 is excited. The calculation unit 15 executes a calculation process of dividing the "second output signal" by the "input signal" to obtain a second transfer function. In other words, the calculation unit 15 obtains a transfer function (second transfer function) of the output of the tire 7 with respect to the vibration input to the tire 7.

[0058] As described above, the calculation unit 15 has a frequency analysis function. The calculation unit 15 obtains the second transfer function, and obtains the gain in each frequency band from the second transfer function by frequency analysis. The graph indicated by the dashed line in Fig. 7 indicates the gain output (second gain output) obtained by frequency analysis of the second transfer function. In this second gain output (dashed line in FIG. 7), the frequency of the peak of the first-order component is obtained as the in-plane torsional resonance frequency F1. In FIG. 7, the peak of the first-order component of the second gain output (dashed line in FIG. 7) is shown as a "second peak P2." The frequency of the peak of the first-order component (in-plane torsional resonance frequency F1) is obtained by calculation by the calculation unit 15.

[0059] 7, the value of the second peak P2 is different (smaller) from the value of the first peak P1, but it is confirmed that they are the same frequency. That is, it is confirmed that the in-plane torsional resonance frequency acquired based on the second output signal of the third sensor 23 is also "F1."

[0060] According to the jig 50 of this embodiment (FIGS. 2 and 3), the rim 6 on which the tire 7 is mounted is fixed so as not to be displaceable to the support shaft 52. Therefore, the resonance frequency based on the value acquired by the calculation unit 15 using the signal of the third sensor 23 (see FIG. 5) fixed to the outer circumferential surface 8 of the tire 7 becomes the in-plane torsional resonance frequency (F1) of the tire 7. In other words, the result based on the third sensor 23 is used to confirm the in-plane torsional resonance frequency F1 obtained when the signal of the second sensor 22 is used.

[0061] [Measurement system 10 of this embodiment] As described above, the measurement system 10 of this embodiment includes the jig 50, the vibration block 60, the hammer device 30, the second sensor 22, and the calculation unit 15. The jig 50 has a support shaft 52 that fixes the rim 6 on which the tire 7 is mounted so that it cannot be displaced. The vibration block 60 is fixed to the outer peripheral surface 8 of the tire 7 and has a portion (vibration part 62) that protrudes from the outer peripheral surface 8. The hammer device 30 has a hammer body 32 that vibrates the vibration block 60 in the tangential direction of the outer peripheral surface 8 of the tire 7, and a first sensor 31 for detecting the vibration caused by the hammer body 32. The second sensor 22 is attached to the support shaft 52 and is a sensor for detecting vibration components around at least the central axis C2 of the support shaft 52.

[0062] The calculation unit 15 executes a calculation process to obtain the in-plane torsional resonance frequency of the tire 7 based on the signal of the first sensor 31 and the signal of the second sensor 22. According to the measurement system 10 of this embodiment and the measurement method executed by the measurement system 10, the hammer device 30 vibrates the vibration block 60 in the tangential direction of the outer circumferential surface 8 of the tire 7. The vibration in the hammer device 30 during the vibration is acquired as an "input signal", and the vibration component about the central axis C2 of the support shaft 52 caused by the vibration of the hammer device 30 is acquired as an "output signal". The in-plane torsional resonance frequency F1 of the tire 7 is acquired from a transfer function based on the "input signal" and the "output signal".

[0063] The calculation unit 15 executes, as the calculation process for acquiring the resonance frequency of the tire 7, 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, and a second process for outputting a peak value of a frequency analysis result of the transfer function. As the second process, a gain-frequency graph is created from the frequency analysis result of the transfer function, as shown in Fig. 7. In the graph, the peak value (P1) of the gain is acquired as the in-plane torsional resonance frequency F1.

[0064] The jig 50 fixes the tire 7 around its central axis C1, and the hammer device 30 vibrates one location on the outer circumferential surface of the tire 7, making it possible to excite in-plane torsional vibration in the tire 7. The calculation unit 15 obtains the force (moment) in the in-plane torsional direction, thereby making it possible to determine the in-plane torsional resonance frequency F1.

[0065] 9 is an explanatory diagram showing an output (graph) when the measurement method is performed to obtain the in-plane torsional resonance frequency for six types of tires 7. For each tire 7, the peak frequency of the first-order component is obtained as the in-plane torsional resonance frequency. As described above, according to the measurement system 10 and the measurement method of the present embodiment, the in-plane torsional resonance frequency when the tire 7 is not in contact with the ground and is not rolling is obtained as a characteristic of the tire alone. As a result, the accuracy of model-based development is improved.

[0066] In the case of the embodiment, the wheel 5 is a pneumatic tire 7 mounted on a rim 6. As described above, the measurement system and the measurement method can also be applied to an airless tire as the wheel 5. Although not shown, an airless tire has an annular tread ring having a contact surface, a hub fixed to an axle-side member, and spokes connecting the tread ring and the hub. The tread ring is made of a rubber material such as vulcanized rubber. The hub is made of, for example, metal. The spokes are made of a thermosetting polymer material such as a thermosetting resin or a thermosetting elastomer. The in-plane torsional resonance frequency of such an airless tire is found by the measurement system and measurement method. When the wheel 5 is an airless tire, its hub is fixed to the support shaft 52 (see FIG. 2) so as not to be displaceable. A vibration block 60 and the like are fixed to the outer circumferential surface of the tread ring. [Industrial Applicability]

[0067] The measurement system, measurement method, jig, and vibration block described above are used for the development of various tires.

[0068] [Additional Notes] The present invention includes the following aspects. (1) A measurement system for acquiring the in-plane torsional resonance frequency of a wheel, the measurement system comprising: a jig having a support shaft for fixing the wheel so as not to be displaceable, a vibration block fixed to the outer peripheral surface of the wheel, a hammer device having a hammer body for vibrating the vibration block in a tangential direction to the outer peripheral surface of the wheel and a first sensor for detecting the vibration by the hammer body, a second sensor attached to the support shaft for detecting a vibration component about a central axis of the support shaft, and a calculation unit for executing calculation processing to acquire the in-plane torsional resonance frequency of the wheel based on a signal from the first sensor and a signal from the second sensor.

[0069] (2) The measurement system of (1), wherein the support shaft has a fixing portion that fixes the wheel so that it cannot be displaced in directions of three orthogonal axes including the axial direction of the support shaft and in rotational directions about the three orthogonal axes, and a third sensor is fixed to the outer peripheral surface of the wheel for detecting vibration components in the tangential direction of the outer peripheral surface, and the calculation unit performs calculation processing to obtain the in-plane torsional resonance frequency of the wheel based on the signal of the first sensor and the signal of the third sensor.

[0070] (3) The measurement system of (1) or (2), wherein the calculation unit executes, as the calculation process, a process of acquiring a transfer function based on a signal of the first sensor and a signal of the second sensor, and a process of outputting a peak value of a frequency analysis result of the transfer function.

[0071] (4) A measurement method for acquiring an in-plane torsional resonance frequency of a wheel, the measurement method including 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 a vibration block fixed to the outer peripheral surface of the wheel in a tangential direction of the outer peripheral surface of the wheel, a first acquisition step of acquiring, as an input signal, a vibration in the hammer device when the vibration block is excited, a second acquisition step of acquiring, as an output signal, a vibration component about the central axis of the support shaft caused by the vibration of the hammer device, and a measurement step of acquiring the in-plane torsional resonance frequency of the wheel from a transfer function based on the input signal and the output signal.

[0072] (5) A jig is used to acquire the in-plane torsional resonance frequency of a wheel. 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 to be immovable, the support shaft having a fixing portion that fixes the wheel so as not to be displaceable in three orthogonal axis directions including the axial direction of the support shaft and in rotational directions about the three orthogonal axes, and a mounting portion for mounting a sensor that acquires vibration acting on the support shaft.

[0073] (6) The jig of (5) above, wherein the fixing portion 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 portion mounts the four sensors at equal intervals along the circumferential direction centered on the central axis of the support shaft.

[0074] (7) A vibration block is used to obtain the in-plane torsional resonance frequency of a wheel. The vibration block has a fixed part fixed to an outer circumferential surface of the wheel and a vibration part integral with the fixed part, the fixed part having a larger dimension in the tangential direction of the wheel than the vibration part, and the vibration part protrudes from the fixed part in the radial direction of the wheel. [Explanation of symbols]

[0075] 5...wheels 6. Rim 7. Tires 8...Outer surface 10. Measurement system 15... Arithmetic section 22 Second sensor 23 Third sensor 30. Hammer device 31 First sensor 32 Hammer body 41 Sensor 50... Jig 51 High-rigidity support block 52...Support shaft 53... Fixed part 54 Mounting part 59. Foundation 60...Vibration block 61...Fixed part 62...Vibration section C1: Center axis of tire C2: Central axis of support shaft F1: In-plane torsional resonance frequency

Claims

1. A measurement system for acquiring an in-plane torsional 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 fixed to an outer peripheral surface of the wheel; a hammer device having a hammer body for vibrating the vibration block in a tangential direction of an outer peripheral surface of the wheel, and a first sensor for detecting vibration caused by the hammer body; a second sensor attached to the support shaft for detecting a vibration component about a central axis of the support shaft; a calculation unit that executes a calculation process to obtain an in-plane torsional resonance frequency of the wheel based on a signal from the first sensor and a signal from the second sensor; A measurement system having the following features:

2. The support shaft has a fixing portion that fixes the wheel so as not to be displaceable in directions of three orthogonal axes including an axial direction of the support shaft and in rotational directions about the three orthogonal axes, a third sensor fixed to an outer peripheral surface of the wheel for detecting a vibration component in a tangential direction of the outer peripheral surface; The calculation unit performs a calculation process to obtain an in-plane torsional resonance frequency of the wheel based on a signal of the first sensor and a signal of the third sensor. The measurement system of claim 1 .

3. The calculation unit performs the calculation process as follows: obtaining a transfer function based on a signal of the first sensor and a signal of the second sensor; A process of outputting a peak value of a frequency analysis result of the transfer function; The measurement system according to claim 1 or 2, further comprising:

4. A measurement method for acquiring an in-plane torsional resonance frequency of a wheel, comprising the steps of: a preparation step of fixing the wheel to a support shaft so as to be immovable; a vibration applying step of applying vibration to a vibration block fixed to an outer peripheral surface of the wheel in a tangential direction of 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, a vibration component about a central axis of the support shaft caused by the vibration of the hammer device; a measurement step of acquiring an in-plane torsional resonance frequency of the wheel from a transfer function based on the input signal and the output signal; A measurement method comprising the steps of:

5. A jig used to obtain the in-plane torsional resonance frequency of a wheel, A high-rigidity support block fixed to the base; a support shaft extending from the high-rigidity support block and fixed to the high-rigidity support block so as not to be displaceable; having The support shaft is a fixing portion that fixes the wheel so as not to be displaced in directions of three orthogonal axes including an axial direction of the support shaft and in rotational directions about the three orthogonal axes; a mounting portion for mounting a sensor for acquiring vibration acting on the support shaft; A jig having the above structure.

6. The fixing portion has a configuration for fixing the wheel so that the central axis of the support shaft, which has a circular cross section, and the central axis of the wheel are coaxial with each other. The mounting portion mounts the four sensors at equal intervals along a circumferential direction centered on a central axis of the support shaft. The jig according to claim 5.

7. A vibration block used to obtain an in-plane torsional resonance frequency of a wheel, A fixing portion fixed to an outer peripheral surface of the wheel; A vibration unit that is integral with the fixed unit; having the fixed portion has a dimension larger in a tangential direction of the tire than the vibration portion, The vibration portion protrudes from the fixed portion in a radial direction of the wheel. Vibration block.

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