Measurement system, measurement method, and jig

Abstract

We provide a measurement system for acquiring the resonant frequency of a wheel. [Solution] The measurement system comprises a jig 50 having a support shaft 52 that fixes the wheel 5 so that it cannot be displaced, an excitation block 60 fixed to the outer surface of the wheel 5, a hammer device 30 having a hammer body 32 that excites the excitation block 60 in a left-right direction parallel to the central axis of the wheel 5, and a first sensor 31 for detecting the excitation by the hammer body 32, a second sensor 22 attached to the support shaft 52 for detecting one or both of the vibration components around the axis in a direction perpendicular to the left-right direction and the vibration components in the left-right direction, and a calculation unit 15 that performs calculation processing to obtain one or both of the lateral bending primary resonance frequency and the left-right translation resonance frequency of the wheel 5 based on the signals from the first sensor 31 and the second sensor 22.

Description

Technical Field

[0001] The present invention relates to a measurement system for obtaining the resonance frequency of a wheel, a measurement method executed by the measurement system, and a jig used in the measurement system and the measurement method.

Background Art

[0002] In an automobile, when the resonance frequency of a wheel is close to the resonance frequency of other devices (for example, a steering system device) installed around it, problems such as abnormal noise generation occur. Therefore, in the development of wheels, as a method for detecting vibration and evaluating vibration characteristics, for example, the method disclosed in Patent Document 1 has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As the resonance frequency of a wheel, there are resonance frequencies of various vibration modes. An object of the present invention is to provide a new technical means for obtaining the resonance frequency of a wheel. In addition to pneumatic tires mounted on a rim, airless tires are known as wheels.

Means for Solving the Problems

[0005] The measurement system according to the present invention is a measurement system for acquiring the resonant frequency of a wheel. The measurement system comprises a jig having a support shaft for fixing the wheel so that it cannot be displaced, an excitation block fixed to the outer surface of the wheel, a hammer device having a hammer body for excitation of the excitation block in a left-right direction parallel to the central axis of the wheel, and a first sensor for detecting excitation by the hammer body, a second sensor attached to the support shaft for detecting one or both of the vibration components around an axis in a direction perpendicular to the left-right direction and the left-right vibration components, and a calculation unit that performs calculation processing to acquire one or both of the lateral bending primary resonant frequency and the left-right translational resonant frequency of the wheel based on the signals from the first sensor and the second sensor.

[0006] The measurement method according to the present invention is a measurement method for acquiring the resonant frequency of a wheel. The measurement method comprises: a preparation step of fixing the wheel to a support shaft so that it cannot be displaced; an excitation step of exciting an excitation block fixed to the outer surface of the wheel in a left-right direction parallel to the central axis of the wheel using a hammer device; a first acquisition step of acquiring the vibration of the hammer device during the excitation of the excitation block as an input signal; a second acquisition step of acquiring one or both of the vibration components around the axis in a direction perpendicular to the left-right direction and the left-right vibration components caused by the excitation of the hammer device as output signals; and a measurement step of acquiring one or both of the lateral bending primary resonant frequency and the left-right translational resonant 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 to obtain one or both of the lateral bending primary resonance frequency and the left-right translational resonance frequency of a wheel. The jig comprises 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 in a manner that prevents displacement. The support shaft has a fixing portion that fixes the wheel in a manner that prevents displacement in the direction of three orthogonal axes including the axial direction of the support shaft which is the left-right direction, and in the rotational direction around the three orthogonal axes, and a mounting portion for attaching a sensor that obtains vibrations acting on the support shaft. [Effects of the Invention]

[0008] According to the measurement system and measurement method of the present invention, it is possible to obtain one or both of the lateral bending primary resonance frequency and the left-right translational resonance frequency of the wheel. The jig of the present invention, when used in the measurement system and measurement method, allows for the acquisition of one or both of the lateral bending primary resonance frequency and the left-right translational resonance frequency of the wheel. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram to explain wheel resonance. [Figure 2] This is a diagram to explain wheel resonance. [Figure 3] This is a schematic diagram of a jig used in a measurement system. [Figure 4] This is a schematic diagram of a jig used in a measurement system. [Figure 5] Figures 3 and 4 are explanatory diagrams showing a tire supported by the jig, viewed from a direction along the central axis. [Figure 6] This is an explanatory diagram showing the configuration of the measurement system. [Figure 7] This is a flowchart of a measurement method for obtaining the resonant frequency of a tire. [Figure 8] This is an explanatory diagram showing the output obtained by wavenumber analysis. [Modes for carrying out the invention]

[0010] [Details of Embodiments of the Present Invention] The present invention will now be described in detail, with reference to the drawings, based on preferred embodiments.

[0011] [Regarding the resonant frequency of the wheel] Wheel resonances include primary lateral bending resonance and lateral translational resonance. Figures 1 and 2 illustrate wheel resonances. In the following embodiments, a wheel 5 in which a pneumatic tire 7 is mounted on a rim 6 will be described. As will be explained later, the wheel may also be an airless tire.

[0012] The tire 7 is made of rubber and is supported by a metal rim 6. The central axis C1 of the tire 7 coincides with the central axis of the rim 6. In the following explanation, the direction along the central axis C1 of the tire 7 (wheel 5), and the direction parallel to the central axis C1, are defined as the "left-right direction." The direction along a virtual circle centered on the central axis C1 is defined as the "circumferential direction."

[0013] Assuming that the wheel 5 is mounted on the body of a vehicle (automobile) and rolls, the direction perpendicular to the left-right direction, and in which the vehicle moves linearly forward and backward, is defined as the "forward-backward direction" of the tire 7 (wheel 5). The direction that is perpendicular to both the left-right and front-back directions is defined as the "up-down direction."

[0014] Figure 1 shows the vibration modes of the first lateral bending resonance. The first lateral bending resonance is a resonance that occurs when the tread 71 vibrates in a manner in which it undergoes rigid motion around a vertical axis (X-axis). When the excitation position relative to the wheel 5 is, for example, the rear position of the wheel 5, and the excitation direction has a component in the left-right direction, the axis relating to the direction of vibration caused by that excitation becomes the "vertical axis". Since the first lateral bending resonance is a vibration around the vertical axis, the axis relating to the direction of that vibration is called the "vertical rotation axis". In other words, the first 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 the resonance frequency when the tire 7 vibrates around the vertical rotation axis.

[0015] FIG. 2 shows the vibration mode of the lateral translation resonance. The lateral translation resonance is the resonance when the tread 71 vibrates in a mode of rigid body motion in the tire width direction. The tire width direction is the left-right direction and is a direction parallel to the central axis line C1. The axis regarding the direction of that vibration becomes the "axis in the left-right direction (also referred to as the left-right axis)". The lateral translation resonance occurs in a vibration mode in which the tread 71 moves in a direction along the Z axis that is the left-right axis. The lateral translation resonance frequency is the resonance frequency when the tire 7 vibrates along the left-right axis.

[0016] In the case of this embodiment, regarding the lateral translation resonance, the excitation position with respect to the wheel 5 is the rear position of the wheel 5, and the excitation direction has a component in the left-right direction. Regarding the excitation position and the excitation direction, it is the same as in the case of the lateral bending primary resonance. That is, by making both the excitation position and the excitation direction the same, it becomes possible to simultaneously generate the vibration modes of both the lateral bending primary resonance and the lateral translation resonance.

[0017] Note that regarding the lateral bending primary resonance, the position for exciting the wheel 5 may be the front position of the wheel 5. However, the excitation direction has a component in the left-right direction. Even in this case, the tread 71 vibrates in a mode of rigid body motion around the vertical axis, and the vibration mode of the lateral bending primary resonance can be obtained. Also, regarding the lateral translation resonance, the excitation position for exciting the wheel 5 may be the front position of the wheel 5. However, the excitation direction has a component in the left-right direction. Even in this case, the tread 71 vibrates in the tire width direction, and the vibration mode of the lateral translation resonance can be obtained.

[0018] Conventionally, for the analysis of the lateral bending primary resonance, it has been necessary to grasp the vibration of the tire as a whole, and for that purpose, it has been necessary to measure the vibration at a plurality of locations, for example, 8 locations along the circumferential direction of the tire. Also, regarding the lateral translation resonance, means for its analysis have not been established.

[0019] In recent years, model-based development has been advancing in automobile development. Following this trend, the inventor focused on the need to measure the resonant frequency of a wheel (tire) alone. Therefore, as a new technical means for obtaining the lateral bending primary resonance frequency and the left-right translational resonance frequency of a wheel, we have now completed the invention relating to the measurement system, the measurement method that can be performed by the measurement system, and the jig used in the measurement system and the measurement method, as described below.

[0020] Preferred embodiments of the measurement system, measurement method, and jig will be described below.

[0021] 〔jig〕 Figures 3 and 4 are schematic diagrams of the fixture used in the measurement system. Figure 3 shows a portion of the tire 7 cut away. Figure 5 is an explanatory diagram of the tire 7 supported by the fixture 50 shown in Figures 3 and 4, viewed from a direction along the central axis C1. The jig 50 has a high-rigidity support block 51 fixed to the base 59 and a support shaft 52 extending from the high-rigidity support block 51. The support shaft 52 is cantilevered and supported by the support block 51. Hereinafter, the high-rigidity support block 51 may be simply referred to as "support block 51".

[0022] The support block 51 is made of a metal component. The support block 51 is heavy and highly rigid, so even if an external force (excitation force by the hammer device 30 shown in Figure 6, described later) is applied to the rim 6 and tire 7 (wheel 5) fixed to the support shaft 52, the support block 51 will not be displaced. The base 59 is the ground, or a sturdy support base installed on the ground. If 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.

[0023] The support shaft 52 is fixed to the support block 51 in a way that prevents it from being displaced. The support shaft 52 is supported by the support block 51 in a way that prevents it from being displaced in the axial direction along the central axis C2 of the support shaft 52, and in the rotational direction about the central axis C2. The support shaft 52 has a fixing part 53 and a mounting part 54. The fixing part 53 is the part that fixes the rim 6 (wheel 5) on which the tire 7 is mounted. The mounting part 54 is the part on which a sensor 41 that acquires vibrations acting on the support shaft 52 is attached. The support shaft 52 is made of metal and has high rigidity. Vibrations from the wheel 5, which has a tire 7 and a 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 3 and 4 is cylindrical, but it may have a shape in which a part of it expands in diameter.

[0024] The fixing portion 53 of the support shaft 52 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 a flange 55 that fixes the rim 6 on which the tire 7 is mounted. The rim 6 is bolted to the flange 55.

[0025] The jig 50 and the tire 7 attached to the jig 50 will be described in terms of their respective directions. A three-dimensional Cartesian coordinate system is set on the jig 50. In this embodiment, the jig 50 is installed on the base 59 such 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 and 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 the front-to-back direction of the tire 7, and the Z-axis direction is the left-to-right direction of the tire 7.

[0026] The fixing part 53 fixes the rim 6 (wheel 5) on which the tire 7 is mounted so that it cannot be displaced in the direction of the three orthogonal axes, including the axial direction of the support shaft 52 which is in the left-right direction, and in the rotational direction around the three orthogonal axes. The three orthogonal axes coincide with the X, Y, and Z axes of the three-dimensional orthogonal coordinate system. In other words, the fixing part 53 fixes the rim 6 (wheel 5) on which the tire 7 is mounted so that it cannot be displaced in the X, Y, and Z directions, and cannot be rotated around the X, Y, and Z axes.

[0027] The mounting portion 54 on the support shaft 52 is the part on which the four sensors 41 are mounted at equal intervals along 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 in the vicinity of the flange 55. In this embodiment, the four sensors 41 are located at the intersections of the outer surface of the support shaft 52 with a virtual straight line parallel to the X-axis (two locations, top and bottom), and at the intersections of the outer surface of the support shaft 52 with a virtual straight line parallel to the Y-axis (two locations, front and back).

[0028] Sensor 41 is, for example, a load sensor that acquires the vibration of the support shaft 52 caused by the force acting on the support shaft 52 as a waveform signal. Four sensors 41 may form a single unit, and the mounting part 54 may be configured to mount one of these units.

[0029] In this embodiment, the sensor unit is composed of four sensors 41. This sensor unit corresponds to the second sensor 22 described later. The second sensor 22 has a predetermined wiring structure for the lead wires extending from each of the four sensors 41 and outputs a signal of six components of force. 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, etc. (not shown), and is capable of outputting a signal of six components of force. The six force components are a total of six types of forces: the forces in the X, Y, and Z directions of the three-dimensional Cartesian coordinate system (axial forces), and the moments around the X, Y, and Z axes.

[0030] With the jig 50 having the above configuration, when a vibration component (moment) around the vertical axis (X-axis) acts on the tire 7 and the rim 6 that supports the tire 7, that vibration component becomes a vibration around the vertical axis of the support shaft 52 and is transmitted to the support shaft 52. When a vibration component in the vertical direction (X-axis direction) acts on the tire 7 and the rim 6 that supports the tire 7, this vibration component is transmitted to the support shaft 52 as a vertical vibration in the support shaft 52.

[0031] When a vibration component (moment) around the longitudinal axis (Y-axis) acts on the tire 7 and the rim 6 that supports the tire 7, this vibration component is transmitted to the support shaft 52 as vibration around the longitudinal axis of the support shaft 52. When vibration components in the longitudinal direction (Y-axis direction) act on the tire 7 and the rim 6 that supports the tire 7, these vibration components are transmitted to the support shaft 52 as longitudinal vibrations in the support shaft 52.

[0032] When a vibration component (moment) around the left-right axis (Z-axis) acts on the tire 7 and the rim 6 that supports the tire 7, this vibration component is transmitted to the support shaft 52 as a vibration around the left-right axis of the support shaft 52. When vibration components in the lateral direction (Z-axis direction) act on the tire 7 and the rim 6 that supports the tire 7, these vibration components are transmitted to the support shaft 52 as lateral vibrations in the support shaft 52.

[0033] The sensor unit (second sensor 22) attached to the support shaft 52 detects vibration components around each axis of the support shaft 52, as well as vibration components in each axial direction. As a result, the primary lateral bending resonance frequency and the left-right translational resonance frequency of the tire 7 are obtained, as will be explained later. Thus, the jig 50 shown in Figures 3 and 4 is used to obtain the primary lateral bending resonance frequency and the left-right translational resonance frequency of the tire 7.

[0034] The mounting portion 54 of the support shaft 52 is the part on which the four sensors 41 are mounted 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 the signals from the four sensors 41 according to a known six-component calculation algorithm. Through this calculation process, the vibration components around each axis defined by the three orthogonal axes of the support shaft 52, and the vibration components in the direction along each axis defined by the three orthogonal axes are obtained.

[0035] [Vibration-generating blocks] The vibration-generating block 60 is fixed to the outer circumferential surface 8 of the tire 7 (see Figures 4 and 5). The vibration-generating block 60 is used to obtain the lateral bending primary resonance frequency and the left-right translational resonance frequency of the tire 7. The vibration-generating block 60 is fixed to one location in the Y-axis direction, which is the tread center of the tire 7 (see Figure 1). In this embodiment, the vibration-generating block 60 is fixed at the rear position. The vibration-generating block 60 is fixed to the tire 7 by adhesive. The vibration-generating block 60 may be directly bonded to the tread surface (outer circumference 8) of the tire 7, or it may be bonded to the tread surface via an adhesive sheet (not shown).

[0036] The vibration-generating block 60 is made of metal. The vibration-generating block 60 has the shape of a rectangular parallelepiped or a cube. With the vibration-generating block 60 fixed to the tire 7, one of the surfaces of the vibration-generating block 60 facing left and right becomes the vibration-generating surface that is struck (striked) by the hammer device 30 (see Figure 6), which will be described later. The tire 7 is vibrated in the left and right directions through the vibration-generating block 60.

[0037] In this manner, the vibration-generating block 60 is fixed to the outer surface 8 of the tire 7, and one surface of the vibration-generating block 60 is vibrated by the hammer device 30. As a result, the tire 7 is vibrated in the Z-axis direction, that is, in the left-right direction, and the tread 71 of the tire 7 is subjected to vibrations that cause it to move around the vertical rotation axis (around the X-axis). Furthermore, by being vibrated in the Z-axis direction, that is, in the left-right direction, the tread 71 of the tire 7 is subjected to vibrations that cause it to move in the direction along the Z-axis, which is the left-right axis. A single strike of the hammer device 30 against the vibration-generating block 60 simultaneously imparts vibrations to the tread 71, causing it to move around its vertical rotation axis (X-axis) and vibrations causing it to move along the Z-axis, which is its left-right axis.

[0038] [Measurement System] Figure 6 is an explanatory diagram showing the configuration of the measurement system 10. The measurement system 10 is equipment for acquiring the lateral bending primary resonance frequency and the left-right translational resonance frequency of the tire 7. The measurement system 10 includes a jig 50, a second sensor 22, an excitation block 60, a hammer device 30, and a calculation unit 15.

[0039] As explained in Figures 3 and 4, the jig 50 has a support shaft 52 that fixes the rim 6 on which the tire 7 is mounted in a non-displaceable position. The support shaft 52 is fixed to the support block 51 in a non-displaceable position. 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 in a non-displaceable position in the direction of three orthogonal axes including the axial direction of the support shaft 52, and in the rotational direction around these three orthogonal axes. The "three orthogonal axes" are the X, Y, and Z axes of the three-dimensional orthogonal coordinate system.

[0040] The vibration-generating block 60 is a component fixed to the outer circumferential surface 8 of the tire 7. The vibration-generating block 60 is fixed to the tire 7 in such a manner that it protrudes from the outer circumferential surface 8 of the tire 7. The hammer device 30 includes 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 the left-right direction. In this embodiment, the tire 7 is vibrated by the hammer body 32 in the left-right direction, toward the support block 51.

[0041] The first sensor 31 is a sensor for detecting the vibration (input) to the tire 7 by the hammer body 32. The first sensor 31 can be any sensor whose detection direction is unidirectional (uniaxial). That unidirectional direction is the vibration direction (impact direction) of the hammer body 32. The first sensor 31 is, for example, an acceleration pickup. The signal (detection signal) from the first sensor 31 is transmitted to the calculation unit 15.

[0042] The second sensor 22 (see Figure 3) is composed of the four sensors 41 attached to the support shaft 52. As described above, the second sensor 22 functions as a six-component force meter, but in order to obtain the lateral bending primary resonance frequency of the tire 7, the second sensor 22 only needs to detect vibration components around the vertical axis (X axis) of the support shaft 52, and in order to obtain the left-right translational resonance frequency of the tire 7, the second sensor 22 only needs to detect vibration components around the left-right direction (Z axis direction) of the support shaft 52.

[0043] The second sensor 22 functions as a six-component force meter. In this embodiment, in order to obtain both the lateral bending primary resonance frequency and the left-right translation resonance frequency from a single strike of the hammer body 32 against the vibration block 60, the second sensor 22 only needs to detect the vibration component around the vertical axis of the support shaft 52 and the vibration component of the support shaft 52 in the left-right direction. The signal (detection signal) from the second sensor 22 is transmitted to the calculation unit 15.

[0044] The arithmetic unit 15 is composed of a computer device. This computer device has a CPU (arithmetic processing unit) and a storage device for storing computer programs and various data. The computer device (arithmetic unit 15) has various processing functions when the CPU executes the computer program. The computer device (arithmetic unit 15) has arithmetic processing functions and frequency analysis functions as functions achieved by the CPU and the computer program. A specific example of the processing performed by the arithmetic unit 15 will be explained according to the following measurement method.

[0045] [Measurement method] Figure 7 is a flowchart of a measurement method for acquiring the resonant frequency of the tire 7. This measurement method is performed using the measurement system 10. The measurement method includes a preparation step S10, an excitation 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.

[0046] Preparation step S10 includes an assembly step in which the tire 7 is mounted on the rim 6 and air is filled into the tire 7, and a fixing step in which the wheel having the tire 7 and rim 6 is fixed to the jig 50 (see Figures 3 and 4). For rim 6, a standard rim is used. A standard rim refers to a rim defined 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 standard rims.

[0047] During the assembly process, the internal pressure of the tire is adjusted to a predetermined pressure. The tire 7 is mounted onto the rim (regular rim) 6, and the internal pressure of the tire 7 is adjusted to the regular internal pressure. The state in which no load is applied to the tire 7 is referred to as the regular state. The tire 7 and rim 6 are fixed to the jig 50, for example, in the regular state. The regular internal pressure refers to the internal pressure specified 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 all regular internal pressures.

[0048] Thus, preparation step S10 is the process of fixing the rim 6 (wheel) on which the tire 7 is mounted to the support shaft 52 in a state where it cannot be displaced. The rim 6 (wheel) is fixed to the support shaft 52 in a state where it cannot be displaced in the directions of the three orthogonal axes including the axial direction of the support shaft 52, and in the rotational direction around these three orthogonal axes. In other words, the rim 6 (wheel) is completely constrained in all directions of its six degrees of freedom.

[0049] The vibration process S20 is a process in which an operator uses a hammer device 30 (see Figure 5) to vibrate the tire 7 in the left-right direction. In other words, the vibration process S20 is a process in which the vibration block 60 fixed to the rear of the outer circumferential surface 8 of the tire 7 is vibrated in the left-right direction by the hammer device 30.

[0050] The first acquisition step S30 is a step in which the calculation unit 15 acquires the signal from the first sensor 31 of the hammer device 30 obtained by performing the vibration excitation step S20. In other words, the first acquisition step S30 is a step in which the vibration (vibration component in the excitation direction) of the hammer device 30 during the excitation of the excitation block 60 is acquired as an input signal.

[0051] In the vibration excitation process S20, the hammer device 30 strikes the excitation block 60, causing vibrations in the tire 7 in the left-right direction and vibrations around the vertical axis, and these vibrations are transmitted to the support shaft 52 through the rim 6.

[0052] The second acquisition step S40 is a step in which the vibration of the support shaft 52 caused by the vibration of the tire 7 in the vibration excitation step S20 is acquired. Specifically, the second acquisition step S40 is a step in which the calculation unit 15 acquires the signal from the second sensor 22 attached to the support shaft 52. As described above, the second sensor 22 has the function of a 6-component force meter. The second acquisition step S40 is a step in which the vibration components around the vertical axis and the left-right vibration components of the support shaft 52 caused by the vibration of the hammer device 30 are acquired as output signals.

[0053] Measurement step 50 is a step in which processing is performed to obtain the primary lateral bending resonance frequency and the left-right translational resonance frequency of the tire 7. To this end, the calculation unit 15 performs calculation processing to obtain the primary lateral bending resonance frequency and the left-right translational resonance frequency of the tire 7 based on the signals from the first sensor 31 and the second sensor 22. As part of the calculation processing, the calculation unit 15 performs a first process to obtain a transfer function based on the signals from the first sensor 31 and the second sensor 22, and a second process to output the peak value of the frequency analysis result of the transfer function. The first and second processes will be described below.

[0054] 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 provides to the tire 7. The calculation unit 15 acquires a vibration waveform around the vertical axis of the support shaft 52 based on the signal from the second sensor 22. This vibration waveform is the waveform of the vibration component around the vertical axis of the support shaft 52 and becomes the "first output signal" generated when the tire 7 is excited. Furthermore, the calculation unit 15 acquires the vibration waveform in the left-right direction at the support shaft 52 based on the signal from the second sensor 22. This vibration waveform is the waveform for the left-right vibration component and becomes the "second output signal" generated when the tire 7 is excited.

[0055] The calculation unit 15 obtains a first transfer function by performing an arithmetic operation that divides the "first output signal" by the "input signal". In other words, the calculation unit 15 obtains a first transfer function of the output of the support shaft 52 in response to vibration input to the tire 7. The calculation unit 15 obtains a second transfer function by performing an operation that divides the "second output signal" by the "input signal". In other words, the calculation unit 15 obtains a second transfer function of the output of the support shaft 52 in response to vibration input to the tire 7. The above is the first step.

[0056] The calculation unit 15 has a frequency analysis function. The calculation unit 15 obtains the gain and phase in each frequency band from the acquired first and second transfer functions by frequency analysis. Figure 8 is an explanatory diagram showing the output obtained by the frequency analysis. Figure 8 is an example (graph) of the output result where the horizontal axis is frequency and the vertical axis is gain.

[0057] In Figure 8, the frequency of the peak of the first-order component in the gain output obtained by frequency analysis of the first transfer function (solid line in Figure 8) is acquired as the transverse bending first-order resonance frequency F1. In Figure 8, this first-order component peak is shown as "first peak P1". The acquisition of the frequency of the first peak P1 of the first-order component (transverse bending first-order resonance frequency F1) is performed by calculation by the calculation unit 15.

[0058] Furthermore, in Figure 8, the frequency of the peak of the first-order component in the gain output obtained by frequency analysis of the second transfer function (dotted line in Figure 8) is acquired as the left-right translational resonance frequency F2. In Figure 8, this first-order component peak is shown as "second peak P2". The acquisition of the frequency of the second peak P2 of the first-order component (left-right translational resonance frequency F2) is performed by calculation by the calculation unit 15. The above is the second process.

[0059] Thus, the vibration in the hammer device 30 (vibration component in the excitation direction) is defined as the "input signal," and the vibration component around the vertical axis of the support shaft 52 caused by the excitation of the hammer device 30 is defined as the "first output signal." In the measurement process 50, the lateral bending primary resonance frequency F1 of the tire 7 is obtained from the transfer function based on the "input signal" and the "first output signal." The vibration in the hammer device 30 (vibration component in the excitation direction) is defined as the "input signal," and the vibration component in the left-right direction of the support shaft 52 caused by the excitation of the hammer device 30 is defined as the "second output signal." In the measurement process 50, the left-right translational resonance frequency F2 of the tire 7 is obtained from the transfer function based on the "input signal" and the "second output signal."

[0060] [Measurement system 10 and measurement method of this embodiment] As described above, according to the measurement system 10 and measurement method of this embodiment, the lateral bending primary resonance frequency and the left-right translational resonance frequency are obtained as characteristics of the wheel itself in an ungrounded and non-rolling state. As a result, the accuracy in model-based development is improved.

[0061] In the above embodiment, the second sensor 22 attached to the support shaft 52 is a sensor for detecting both vibration components around the axis in a direction perpendicular to the left-right direction, and vibration components in the left-right direction. As a result, both the lateral bending primary resonance frequency and the left-right translation resonance frequency are obtained. In contrast, the second sensor 22 may be a sensor for detecting vibration components around an axis perpendicular to the left-right direction, or both vibration components in the left-right direction. In this case, the lateral bending primary resonance frequency or the left-right translation resonance frequency is obtained.

[0062] In other words, the second sensor 22 can be any sensor that detects either or both of the vibration components around an axis perpendicular to the left-right direction and the vibration components in the left-right direction. The calculation unit 15 then performs calculation processing to obtain either or both of the lateral bending primary resonance frequency and the left-right translation resonance frequency of the tire 7 based on the signals from the first sensor 21 and the second sensor 22.

[0063] In the above embodiment, the wheel 5 is a pneumatic tire 7 mounted on a rim 6. As described above, the measurement system and measurement method can also be applied to an airless tire as the wheel 5. An airless tire, although not shown in the diagram, has an annular tread ring with a contact surface, a hub fixed to a member on the axle side, 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 metal, for example. The spokes are made of a thermosetting polymer material such as a thermosetting resin or thermosetting elastomer. The lateral bending primary resonance frequency and the left-right translational resonance frequency of such an airless tire are determined 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 Figure 3) in a way that prevents displacement. A vibration-generating block 60 is fixed to the outer circumferential surface of the tread ring. [Industrial applicability]

[0064] The measurement systems, measurement methods, and jigs described above will be used for the development of various types of tires.

[0065] [Note] The present invention includes the following embodiments. (1) The measurement system is a measurement system for acquiring the resonant frequency of a wheel. The measurement system comprises a jig having a support shaft for fixing the wheel so that it cannot be displaced, an excitation block fixed to the outer surface of the wheel, a hammer device having a hammer body for excitation of the excitation block in a left-right direction parallel to the central axis of the wheel, and a first sensor for detecting excitation by the hammer body, a second sensor attached to the support shaft for detecting one or both of the vibration components around an axis in a direction perpendicular to the left-right direction and the left-right vibration components, and a calculation unit that performs calculation processing to acquire one or both of the lateral bending primary resonant frequency and the left-right translational resonant frequency of the wheel based on the signals of the first sensor and the second sensor.

[0066] (2) The measurement system according to (1), wherein the second sensor is a sensor for detecting both vibration components around an axis in a direction orthogonal to the left-right direction and vibration components in the left-right direction, and the calculation unit performs calculation processing to acquire both the lateral bending primary resonance frequency and the left-right translation resonance frequency of the wheel.

[0067] (3) The measurement system according to (1) or (2), wherein the support shaft has a fixing part for fixing the wheel, and the support shaft is immobile in the direction of three orthogonal axes including the axial direction of the support shaft which is the left-right direction, and in the rotational direction around the three orthogonal axes.

[0068] (4) The measurement system of any one of (1) to (3) above, wherein the calculation unit performs the following calculation processes: a process to acquire a transfer function based on the signal of the first sensor and the signal of the second sensor, and a process to output the peak value of the frequency analysis result of the transfer function.

[0069] (5) The measurement method is a measurement method for acquiring the resonant frequency of a wheel. The measurement method comprises: a preparation step of fixing the wheel to a support shaft so that it cannot be displaced; an excitation step of exciting an excitation block fixed to the outer surface of the wheel in a left-right direction parallel to the central axis of the wheel using a hammer device; a first acquisition step of acquiring the vibration of the hammer device during the excitation of the excitation block as an input signal; a second acquisition step of acquiring one or both of the vibration components around the axis in a direction perpendicular to the left-right direction and the vibration components in the left-right direction, which are caused by the excitation of the hammer device, as output signals; and a measurement step of acquiring one or both of the lateral bending primary resonant frequency and the left-right translational resonant frequency of the wheel from a transfer function based on the input signal and the output signal.

[0070] (6) The jig is used to obtain one or both of the lateral bending primary resonance frequency and the left-right translation resonance frequency of the wheel. The jig comprises 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 in a manner that prevents displacement. The support shaft comprises a fixing portion that fixes the wheel in a manner that prevents displacement in the direction of three orthogonal axes including the axial direction of the support shaft which is the left-right direction, and in the rotational direction around the three orthogonal axes, and a mounting portion for attaching a sensor that obtains vibrations acting on the support shaft.

[0071] (7) The fixing part has a configuration for fixing the wheel such that the central axis of the support shaft, which has a circular cross-section, and the central axis of the wheel are coaxial, The mounting portion is the jig of (6) for mounting the four sensors at equal intervals along the circumferential direction centered on the central axis of the support shaft. [Explanation of symbols]

[0072] 5...wheels 6..Rim 7... Tires 8...Outer surface 10. Measurement System 15... Arithmetic section 22...Second 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... Base 60... Vibration-generating blocks C1... Tire center axis C2...Central axis of the support shaft F1... Transverse bending primary resonance frequency F2...Left and right translational resonance frequency

Claims

1. A measurement system for obtaining the resonant frequency of a wheel, A jig having a support shaft that fixes the wheel in a position where it cannot be displaced, A vibration-generating block fixed to the outer surface of the wheel, A hammer device having a hammer body that vibrates the vibration-generating block in a left-right direction parallel to the central axis of the wheel, and a first sensor for detecting the vibration by the hammer body, A second sensor is attached to the support shaft and is used to detect vibration components around an axis perpendicular to the left-right direction, and one or both of the vibration components in the left-right direction. A calculation unit that performs calculation processing to acquire one or both of the lateral bending primary resonant frequency and the left-right translational resonant frequency of the wheel based on the signal from the first sensor and the signal from the second sensor, A measurement system having the following features.

2. The second sensor is a sensor for detecting both the vibration component around the axis in a direction perpendicular to the left-right direction and the vibration component in the left-right direction. The calculation unit performs calculation processing to obtain both the lateral bending primary resonance frequency and the left-right translational resonance frequency of the wheel. The measurement system according to claim 1.

3. The support shaft has a fixing portion that fixes the wheel in a manner that prevents displacement in the direction of the three orthogonal axes, including the axial direction of the support shaft which is the left-right direction, and in the rotational direction around the three orthogonal axes. The measurement system according to claim 1 or claim 2.

4. The calculation unit performs the calculation process as follows: A process for obtaining a transfer function based on the signal from the first sensor and the signal from the second sensor, A process to output the peak value of the frequency analysis result of the transfer function, A measurement system according to claim 1 or claim 2, which performs the following:

5. A measurement method for obtaining the resonant frequency of a wheel, A preparatory step of fixing the wheel to the support shaft in a way that prevents displacement, A vibration step is performed by using a hammer device to vibrate a vibration block fixed to the outer surface of the wheel in a left-right direction parallel to the central axis of the wheel. A first acquisition step involves acquiring the vibration of the hammer device during the excitation of the vibration-generating block as an input signal, A second acquisition step involves acquiring, as an output signal, one or both of the vibration components around the axis in a direction perpendicular to the left-right direction and the vibration components in the left-right direction, which are caused by the excitation of the hammer device. A measurement step of obtaining one or both of the lateral bending primary resonance frequency and the left-right translational resonance frequency of the wheel from a transfer function based on the input signal and the output signal, A measurement method having the following characteristics.

6. A jig used to obtain one or both of the lateral bending primary resonance frequency and the left-right translational resonance frequency of a wheel, A high-rigidity support block fixed to the base, A support shaft extending from the aforementioned high-rigidity support block and fixed to the aforementioned high-rigidity support block in a manner that prevents displacement, It has, The aforementioned support shaft is A fixing part that fixes the wheel so that it cannot be displaced in the direction of the three orthogonal axes including the axial direction of the support shaft which is in the left-right direction, and in the rotational direction around the three orthogonal axes, A mounting section for attaching a sensor that acquires vibrations acting on the support shaft, A jig having

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

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