Tire noise evaluation method and tire noise evaluation device

Abstract

To provide a tire noise evaluation method and apparatus that can accurately and precisely evaluate acceleration noise. [Solution] The tire noise evaluation method evaluates the noise emitted from a tire 2 having one or more blocks 30 and running on a simulated road surface 22. The tire noise evaluation method includes the steps of: installing first accelerometers 6 and 7 at the circumferential ends of the blocks 30; installing second accelerometers 8 and 9 inside the tire 2; running the tire 2 under conditions in which noise from two or more blocks 30 does not mix and collecting first output data from the first accelerometers 6 and 7; identifying a period based on the first output data that is related to at least one of the time when the blocks 30 make contact with the ground and when the blocks 30 push off, and in which the contribution of sliding noise to the noise is large; and evaluating the noise based on second output data from the second accelerometers 8 and 9 during that period.

Description

Technical Field

[0001] The present disclosure relates to a tire noise evaluation method and a tire noise evaluation device.

Background Art

[0002] It is known that tire noise increases during acceleration when a driving force acts. Also, it is said that the contribution of the sliding sound of the block is large in acceleration noise. Therefore, in order to improve the reduction of acceleration noise, it is necessary to evaluate the sliding sound. In this background, conventionally, there is a tire noise evaluation method described in Patent Document 1. This tire noise evaluation method specifies the period from when the block touches the ground to when it kicks out in the output data of an accelerometer arranged at the circumferential end of the block where the displacement is intense in the block of the tire. Then, based on that period, data of the period during which the block slides in the output data of the accelerometer arranged at the circumferential end is cut out, and the sliding sound is evaluated based on the frequency analysis of the cut-out output data.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the above tire noise evaluation method, after accurately specifying the period from when the block touches the ground to when it kicks out during which the block slides, the noise during that period can be objectively and accurately analyzed. Therefore, according to the above tire noise evaluation method, the sliding sound of the block, and thus the evaluation of acceleration noise, can be accurately performed, but it would be preferable if acceleration noise could be evaluated with even higher accuracy. Therefore, an object of the present disclosure is to provide a tire noise evaluation method and a tire noise evaluation device that can accurately and highly accurately evaluate acceleration noise. [Means for solving the problem]

[0005] To solve the above problems, the tire noise evaluation method according to the present disclosure is a method for evaluating noise emitted from a tire having one or more blocks and running on a simulated road surface, comprising the steps of: installing a first accelerometer at the circumferential end of the block in the tire; installing a second accelerometer on the inside of the tire; running the tire under conditions in which noise from two or more blocks does not mix and collecting first output data from the first accelerometer; identifying a period based on the first output data that is related to at least one of the time when the block is in contact with the ground and the time when the block is kicked off, and in which the contribution of sliding noise to the noise is large; and evaluating the noise based on second output data from the second accelerometer during the period.

[0006] According to this disclosure, based on a first accelerometer grounded around the block, a period is identified that is related to at least one of the time the block is grounded or the time the block is pushed off, and in which the contribution of sliding noise to the noise is large. This makes it easier to accurately identify the period during which the block is sliding, and enables noise evaluation that is specifically targeted at sliding noise.

[0007] Furthermore, as will be described later, when the blocks vibrate, that vibration is transmitted to the tire body, and the vibration of the tire body is transmitted to the air, generating noise. However, the inventors of this invention have found that analyzing the vibration of the tire body that accompanies the vibration of the blocks is more accurate and objective in evaluating acceleration noise (slip noise) than analyzing the vibration of the blocks. Against this backdrop, according to this disclosure, since the noise is evaluated based on the output data of a second accelerometer placed inside the tire during periods when the contribution of slip noise is large, the vibration of the tire body during periods when the contribution of slip noise is large can be evaluated. Therefore, acceleration noise can be evaluated more accurately and objectively.

[0008] The second accelerometer may be positioned inside the tire such that at least a portion of it is inside the tire and radially faces the front edge of the block in the circumferential direction.

[0009] As described later, the inventors have found that by positioning the second accelerometer inside the tire such that at least a portion of it is on the inside of the tire and radially facing the front edge of the circumferential direction of the block, vibrations of the tire body can be detected more easily and accurately. Therefore, with this configuration, acceleration noise can be evaluated more accurately.

[0010] Furthermore, the tire noise evaluation device according to this disclosure comprises: a simulated road surface on which a tire travels; a first accelerometer installed at the circumferential end of the tire block; a second accelerometer installed inside the tire; a data acquisition unit that collects first output data from the first accelerometer and second output data from the second accelerometer when the tire is traveling on the simulated road surface; a period identification unit that identifies a period based on the first output data that relates to at least one of the time when the block makes contact with the ground and the time when the block pushes off, and during which the contribution of slip noise to the noise emitted by the tire is large; and a noise evaluation unit that evaluates the noise based on the second output data during the period.

[0011] According to this disclosure, by using the first output data from a first accelerometer installed at the circumferential end of the block, the period during which slippage occurs in the flock (for example, the period during which a stick-slip phenomenon occurs or the period during which a stick-snap phenomenon occurs) can be accurately identified. Furthermore, by using the second output data from a second accelerometer installed inside the tire to evaluate the acceleration noise (slip noise) during that period, the acceleration noise can be accurately evaluated. In other words, by combining the first and second accelerometers to evaluate the acceleration noise, the acceleration noise can be evaluated accurately and with high precision.

[0012] Furthermore, at least a portion of the second accelerometer may be positioned on the inside of the tire and radially opposite the front edge of the block in the circumferential direction.

[0013] This configuration allows for more accurate evaluation of acceleration noise. [Effects of the Invention]

[0014] According to the tire noise evaluation method and tire noise evaluation apparatus described herein, acceleration noise can be evaluated accurately and with high precision. [Brief explanation of the drawing]

[0015] [Figure 1] This is a block diagram illustrating the main configuration of a tire noise evaluation device according to one embodiment of the present disclosure. [Figure 2] This is a schematic diagram illustrating the placement of the first and second accelerometers. [Figure 3] This is a schematic diagram illustrating in more detail the method of mounting the first accelerometer on the tire. [Figure 4] This is a schematic diagram illustrating how the acceleration data measured by the second accelerometer is acquired. [Figure 5] This is a schematic diagram illustrating the structure of the pulse signal acquisition unit. [Figure 6] This is a schematic diagram illustrating the method of installing the second accelerometer on a tire, and shows the tire viewed from the radially inward direction. [Figure 7] This diagram illustrates pattern noise in tire noise. [Figure 8] This graph shows an example of voltage data from the pulse signal acquisition unit acquired by the control device, and an example of acceleration data from the second accelerometer acquired by the control device. [Figure 9] The graph in Figure 8 shows an enlarged view of the area enclosed by the frame, representing the period from just before kick-off to the time when the vibrations after kick-off subside. [Figure 10]A graph showing voltage data from a pulse signal acquisition unit acquired by a control device and acceleration data from a second first accelerometer acquired by the control device, and including data during the period from the timing when the front end of the block touches the ground until the rear end of the block is kicked out and the vibration converges. [Figure 11] A graph showing acceleration data after removing signals with frequencies of 1000 [Hz] or higher from the acceleration data shown in FIG. 10. [Figure 12] A graph showing acceleration data including one cycle period from when the block touches the ground until it touches the ground next time, and which is acceleration data subjected to low-pass filter processing. [Figure 13] A graph showing the tire radial output of the second second accelerometer when no driving force is applied to a tire with only one block provided, and the tire radial output of the second second accelerometer when no driving force is applied to a slick tire which only differs in the configuration where there is no block in comparison with that tire. [Figure 14] A graph showing the tire radial output of the second second accelerometer when a driving force of 767 N is applied to a tire with only one block provided, and the tire radial output of the second second accelerometer when a driving force of 767 N is applied to the above-mentioned slick tire. [Figure 15] A bar graph showing the relationship between the driving force applied to a tire with only one block provided and the PP value in the tire radial output of the second second accelerometer, and the relationship between the driving force applied to the above-mentioned slick tire and the PP value in the tire radial output of the second second accelerometer. [Figure 16] A bar graph showing the relationship between the driving force applied to a tire with only one block provided and the PP value in the tire radial output of the second first accelerometer. [Figure 17] A bar graph showing the relationship between the driving force applied to a tire with only one block provided and the PP value in the tire radial output of the second second accelerometer.

Embodiments for Carrying Out the Invention

[0016] The embodiments relating to this disclosure will be described in detail below with reference to the attached drawings. Note that if multiple embodiments or modifications are included below, it is intended from the outset that new embodiments may be constructed by appropriately combining their characteristic features. Furthermore, in the following embodiments, the same reference numerals are used for the same components in the drawings, and redundant explanations are omitted. Also, multiple drawings include schematic diagrams, and the dimensional ratios such as length, width, and height of each component do not necessarily match between different drawings. Additionally, among the components described below, those not described in the independent claim indicating the highest-level concept are optional components and not essential components.

[0017] Figure 1 is a block diagram illustrating the main components of a tire noise evaluation device 1 according to one embodiment of the present disclosure. As shown in Figure 1, the tire noise evaluation device 1 includes a simulated road surface 22 on which a tire 2 travels, a first accelerometer 6, a second accelerometer 7, a first second accelerometer 8, a second second accelerometer 9, a data acquisition unit 70 that collects first output data output from at least one of the two first accelerometers 6 and 7 and second output data output from at least one of the two second accelerometers when the tire 2 is traveling on the simulated road surface 22, a pulse signal acquisition unit 15 that acquires pulse signals capable of identifying the circumferential position of blocks 30 (see Figure 2, etc.) on the tire 2 while it is traveling, and a data analysis device 10 that evaluates noise based on the first output data and the second output data.

[0018] Accelerometers 6, 7, 8, and 9 are composed of MEMS (Micro Electro Mechanical Systems) acceleration sensors fabricated using MEMS technology, for example. Accelerometers 6 and 7 may be composed of capacitive acceleration sensors that detect slight positional changes in minute movable parts supported by a beam structure as changes in capacitance, and amplify and measure them using an electrical circuit. Alternatively, accelerometers 6 and 7 may be composed of piezoresistive acceleration sensors that detect positional changes of a diaphragm formed by silicon semiconductor manufacturing technology using a piezoresistive element, and amplify and measure the detected physical quantity using an electrical circuit.

[0019] The tire noise evaluation device 1 includes a bench test apparatus configured, for example, in accordance with the JASO standard. The bench test apparatus includes a drum 21 that is circumferentially rotatable, a rotating shaft (not shown) for rotating the drum 21, and an electric motor or the like (not shown) for driving the rotating shaft. The tire noise evaluation device 1 includes a support shaft that holds the tire 2 in a rotatable and cantilevered manner, with the outer surface of the tire 2 in contact with the outer surface of the drum 21. The support shaft is rotatably fixed to a stationary shaft (not shown) with a bearing (not shown). The support shaft rotates synchronously with the tire 2 when the tire 2 rotates due to the force from the drum 21. Although the case in which the drum 21 is rotated by an electric motor or the like has been described, the drum may be stationary and the rotating shaft on which the tire is mounted may be rotated by an electric motor or the like (not shown). Alternatively, the rotating shaft of the drum may be rotated by a first electric motor or the like, and the rotating shaft on which the tire is mounted may be rotated by a second electric motor or the like.

[0020] A simulated road surface 22 is provided on the outer surface of the drum 21. The simulated road surface 22 is composed of SW (Safety Walk). The simulated road surface 22 is formed by mixing aggregate and a binder made of resin to bind the aggregate, for example, according to the particle size curve of the ISO road surface standard (see the tolerance range of the particle size curve for asphalt mixtures described in Annex C of ISO 10844, design guidelines). The aggregate may consist of, for example, crushed river pebbles, crushed mountain pebbles collected from quarry sites, etc., with a particle size of 4 to 5 mm, and a second aggregate made of sand such as river sand or mountain sand, with a particle size smaller than the first aggregate. The binder may be made of epoxy resin or the like. The simulated road surface 22 can be any road surface that can simulate a road surface, and may be composed of the same road surface as one of the many asphalt road surfaces that are actually used.

[0021] Figure 2 is a schematic diagram illustrating the placement of accelerometers 6, 7, 8, and 9. In Figure 2, arrow A indicates the direction of rotation of tire 2. As shown in Figure 2, the first accelerometer 6 is installed at the front (rotation direction side) end of the block 30 of tire 2 in the circumferential direction, and the second accelerometer 7 is installed at the rear (opposite side from the rotation direction) end of the block 30 of tire 2 in the circumferential direction. The first accelerometer 8 is positioned inside tire 2 such that it has a radially opposing portion to the front edge 30a of the block 30 in the circumferential direction. The second accelerometer 9 is installed at a circumferential position 45° forward of the block placement position (circumferential center position of block 30) inside tire 2.

[0022] Figure 3 is a schematic diagram illustrating in more detail the method of installing the first accelerometers 6 and 7 on the tire 2, and Figure 4 is a schematic diagram illustrating the method of acquiring acceleration data measured by the second first accelerometer 7. In this embodiment, as shown in Figure 3, the noise evaluation test is performed under the condition that only one block 30 of the tire 2 is in contact with the ground. If the tire has two or more blocks and it is desired to evaluate the noise from each block, the noise evaluation test should be performed under the condition that the noise generated by each block contacting the ground does not overlap with the noise generated by other blocks contacting the ground.

[0023] When a tire has multiple blocks, it is preferable to arrange these blocks at equal intervals in the circumferential direction so that the noise caused by the presence of each block does not overlap with the noise caused by the presence of other blocks, allowing for accurate noise evaluation of each block and enabling noise testing of multiple blocks at once. Furthermore, it is preferable to set the number of blocks on the tire to four or less, and to arrange the blocks at intervals of 90° or more in the circumferential direction, preferably at equal intervals, as this makes it easier to prevent the noise caused by the contact of each block with the simulated road surface from overlapping with the noise caused by the contact of other blocks with the simulated road surface.

[0024] When a tire has multiple blocks, the shape of the blocks can be varied, the presence or absence of chamfering on the edges can be changed, or the block material (block stiffness, friction coefficient) can be changed. If a low-noise block configuration can be identified based on the noise evaluation of a single block, the noise generated from the entire tire can also be reduced, making it possible to manufacture a low-noise tire.

[0025] More specifically, by analyzing noise data using the tire noise evaluation method disclosed herein, it is possible to identify which parts of the block need to be modified to achieve low noise, and to identify the configuration that should be modified to achieve low noise, such as the material, sipe structure, groove edge structure, etc. Furthermore, it is possible to find the tire with the least noise from among several tires with the same grip, and for example, when several candidate tires to be actually manufactured have been decided, it is possible to identify which of those tires is superior in terms of noise generation.

[0026] As shown in Figure 3, in this embodiment, in a plan view of the tire 2 viewed radially outward, the tire 2 has a rectangular block 30, a pair of first edges 32 of the block 30 extending in the circumferential direction of the tire 2, and a pair of second edges 33 of the block 30 extending in the axial direction of the tire 2. The tire 2 has a rectangular frame-shaped annular groove 35 provided along the entire circumference of the rectangular edge of the block 30. The circumferentially extending portion of the annular groove 35 may be a part of the main groove.

[0027] The first accelerometer 6 is fixed to the front (rotation direction side) end face 30b of the block 30 in the circumferential direction of the tire within the annular groove 35 using fixing means, such as double-sided tape, adhesive, or a welded joint. The second accelerometer 7 is fixed to the rear (opposite side from the rotation direction) end face 30c of the block 30 in the circumferential direction of the tire within the annular groove 35 using fixing means, such as double-sided tape, adhesive, or a welded joint. The case described above describes the case where the accelerometers 6 and 7 are fixed to the end faces 30b and 30c of the block 30 that extend axially. However, the accelerometers may also be fixed to the circumferential ends of the side surfaces of the block 30 that extend circumferentially within the annular groove 35.

[0028] As shown in Figures 3 and 4, each accelerometer 6 and 7 has wiring 42 and 43 for transmitting detected information. Figure 3(a) is a plan view of the circumferential location of the tire 2 where the block 30 is located, viewed from the radially outward direction, and Figure 3(b) is a plan view of the circumferential location of the tire 2 opposite to the circumferential location shown in Figure 3(a), viewed from the radially outward direction. Each wiring 42 and 43 passes through, for example, a rectangular frame-shaped annular groove 35, extends circumferentially within the main groove 31, and then extends axially outward. Then, it extends radially inward from the axially outward direction and connects to the wireless transmitter 34. The wireless receiver 36, electrically connected to the data analysis device 10, receives information based on the detection information detected by the accelerometers 6 and 7 transmitted by the wireless transmitter 34, so that the detection information detected by the accelerometers 6 and 7 can be analyzed by the data analysis device 10. The wireless transmitter 34 and the wireless receiver 36 constitute the data acquisition unit 70.

[0029] Next, the configuration of the pulse signal acquisition unit 15 will be described. Figure 5 is a schematic diagram illustrating the structure of the pulse signal acquisition unit 15. As shown in Figure 5, the pulse signal acquisition unit 15 includes a reflector 37, a laser oscillator 38, and a laser receiver 39. The reflector 37 is fixed to the side of the tire 2 at the same circumferential position as the circumferential center position of the block 30 with adhesive or the like. The laser oscillator 38 includes, for example, a semiconductor laser oscillator or a YAG laser oscillator. The laser oscillator 38 is positioned to emit laser light at the radial position on the side of the tire 2 where the reflector 37 is fixed.

[0030] The laser receiver 39 is composed of a light-receiving element such as a CCD (Charge Coupled Device). The laser receiver 39 is positioned to receive light emitted from the laser oscillator 38 and reflected by the reflector 37. The laser oscillator 38 is configured to emit laser light at a circumferential position on the bottom of the tire 2.

[0031] During noise measurement, the laser oscillator 38 continuously emits laser light. As a result, when the tire 2 rotates and the circumferential center of the block 30 reaches the bottom of the tire 2, the laser light emitted by the laser oscillator 38 is reflected by the reflector 37 and received by the laser receiver 39. Therefore, the timing when the circumferential center of the block 30 is at the bottom of the tire 2 coincides with the timing when the laser receiver 39 receives the laser light. The laser receiver 39 is electrically connected to the data analysis device 10. As a result, the data analysis device 10 can determine the timing when the circumferential center of the block 30 reaches the bottom of the tire 2.

[0032] The pulse signal acquisition unit 15 can have any configuration as long as it can identify the timing at which the circumferential center of the block 30 is located at the bottom of the tire 2. For example, the pulse signal acquisition unit 15 may include a ring attached to the rotation axis of the tire and a magnetic sensor that detects the magnetic force from the ring. For example, a magnet is attached to the ring at the same circumferential position as the circumferential center of the block 30. The magnetic sensor is installed in the stationary part of the tire noise evaluation device with its sensor surface facing vertically downward. In this case, the timing at which the magnetic sensor detects the greatest magnetic force can be identified as the timing at which the circumferential center of the block 30 is located at the bottom of the tire 2.

[0033] Figure 6 is a schematic diagram illustrating the installation method of the second accelerometers 8 and 9 on the tire 2, and is a schematic diagram of the tire 2 viewed from the radially inside. As shown in Figure 6, the second accelerometers 8 and 9 are installed at circumferential intervals in the center of the width direction on the inside (back surface) 2a of the tire 2. Each accelerometer 8 and 9 is fixed to the inside of the tire 2 by fixing means, such as double-sided tape, adhesive, or welding. Wiring 58 and 59 extending from each accelerometer 8 and 9 passes between the tire 2 and a wheel (not shown), and is then electrically connected to a wireless transmitter 34 (see Figures 1 and 4) installed on the side of the tire 2. A wireless receiver 36 (see Figure 1) electrically connected to the data analysis device 10 receives information based on the detection information detected by the accelerometers 8 and 9 transmitted by the wireless transmitter 34, so that the detection information detected by the accelerometers 8 and 9 can be analyzed by the data analysis device 10.

[0034] As this is a well-known technique, it will not be described in detail, but the signals from the first accelerometer 6 or 7 and the signals from the second accelerometer 8 or 9 can be transmitted and received simultaneously using a pair of wireless transceivers 34 and 36 in a well-known manner. Using an operational amplifier or the like, a single composite signal can be generated that includes first information based on first output data and second information based on second output data, based on the first signal from the wiring 42 or 43 electrically connected to the first accelerometer 6 or 7 and the second signal from the wiring 58 or 59 electrically connected to the second accelerometer 8 or 9. Subsequently, the wireless transmitter 34 transmits a wireless signal based on this composite signal to the wireless receiver 36. Next, the wireless signal received by the wireless receiver 36 is filtered by the data analysis device 10, so that the first and second information can be extracted by the data analysis device 10, and the second output data of the first accelerometer 6 or 7 and the second output data of the second accelerometer 8 or 9 can be restored.

[0035] Figure 7 illustrates pattern noise in tire noise. As shown in Figure 7, the tire 2 first has the front of the block 30 come into contact with the simulated road surface 22 (Timing A), and then the entire block 30 comes into contact with the simulated road surface 22 (Timing B). Then, the block 30 moves in translation while remaining in contact with the ground (Timing C), and the circumferential front end of the block 30 becomes non-contact with the simulated road surface 22 and is released from the simulated road surface 22 (Timing D), and the circumferential rear end of the block 30 becomes non-contact with the simulated road surface 22 and is released from the simulated road surface 22 (Timing E).

[0036] In this context, during the period A to D enclosed by the dotted line, it is known that after the front tip of block 30 touches the ground, the block rubs against the ground surface, causing a sliding phenomenon called the Stick-Slip phenomenon. On the other hand, during the period D to E enclosed by the dashed line, it is known that a sliding phenomenon called the Stick-Snap phenomenon occurs. At the timing when block 30 is released from the ground, as the front end of block 30 begins to separate from the ground surface, the radial force in that part disappears, and the rear of block 30 is pulled from the front and slides away sequentially.

[0037] It is known that tire noise increases during acceleration when driving force is applied. Furthermore, it is thought that the sliding noise of the tread blocks contributes significantly to acceleration noise. Therefore, evaluating sliding noise is necessary to improve the reduction of acceleration noise. In this embodiment, a method for evaluating sliding noise in the Stick-Snap phenomenon will be described below. However, in the evaluation method described below, the sliding noise in the Stick-Slip phenomenon can be easily evaluated simply by changing the period for evaluating the noise from the period of timing D to E to the period of timing A to D.

[0038] The tire noise evaluation device 1 includes a first accelerometer 6 positioned at the front end of the block 30 and a second first accelerometer 7 positioned at the rear end of the block 30. The front and rear ends of the block 30 in the circumferential direction experience large movement and significant slippage, while the central part of the block 30 in the circumferential direction experiences small movement and minimal slippage. Therefore, by installing the first accelerometers 6 and 7 at the front and rear ends of the block 30 in the circumferential direction, slippage can be reliably and accurately detected.

[0039] The following section describes the evaluation of sliding noise in the Stick-Snap phenomenon, which is a sliding phenomenon on the rear side of block 30. Therefore, in the noise analysis, only data from the second first accelerometer 7 located at the rear end of block 30 will be used. When evaluating sliding noise in the Stick-Slip phenomenon, either only data from the first first accelerometer 6 located at the front end of block 30 will be used, or both data from the first first accelerometer 6 and the second first accelerometer 7 will be used to evaluate the sliding noise.

[0040] Referring to Figure 1, the tire noise evaluation device 1 includes a noise analyzer 5 positioned in a stationary part that does not rotate with the tire 2. The noise analyzer 5 comprises a wireless receiver 36, a laser receiver 39, and a data analysis device 10. The data analysis device 10 is composed of an information terminal, such as a personal computer or workstation. The data analysis device 10 includes an input unit 61, a display unit 62, a transmitting / receiving unit 63, and a control device 64. The input unit 61 is used for data input and consists of, for example, a keyboard and a mouse. The display unit 62 is composed of a liquid crystal panel and displays an image. The display unit 62 may be composed of an organic EL panel. The input unit 61 and the display unit 62 may be composed of a touch panel in which a touch sensor and a display are integrated. The transmitting / receiving unit 63 receives information from the wireless receiver 36 and the laser receiver 39 via a network connected to the data analysis device 10 and transmits a signal to the laser oscillation power supply device 46 to drive or stop the laser oscillator 38. The transmitting / receiving unit 63 consists of an interface for sending and receiving data with the devices 36, 38 (46), 39, and 56. The noise analyzer 5 may also be equipped with an output unit 47, which consists of a printer or the like, in which case data during the analysis or the final analyzed data can be output as appropriate.

[0041] The control device 64 is preferably configured as a computer, such as a microcomputer, and includes a control unit 65 and a storage unit 67. The control unit 65, i.e., the processor, includes, for example, a CPU (Central Processing Unit). The storage unit 67 is composed of a hard disk drive (HDD), a solid-state drive (SSD), etc., and may include non-volatile memory such as ROM (Read Only Memory) and volatile memory such as RAM (Random Access Memory). The storage unit 67 may consist of only one storage medium or multiple different storage mediums. The CPU reads and executes programs, etc., that are pre-stored in the storage unit 67. The non-volatile memory pre-stores control programs, predetermined thresholds, etc. The volatile memory temporarily stores the read programs and processing data.

[0042] The control unit 65 includes a laser oscillation control unit 65a, a received signal separation unit 65b, a low-pass filter unit 65c, a period specification unit 65d, a PP value calculation unit 65e, and a noise evaluation unit 65f. Next, a data analysis method using the control unit 65 will be described. The data received by the wireless receiver 36 and the data received by the laser receiver 39 may be subjected to known processing to make the data easier to understand, such as amplification, and noise analysis may be performed based on the processed data.

[0043] The test begins when an electric motor or the like is driven to rotate the drum 21 and the tires 2, and DC power is supplied from the laser oscillation power supply device 46 to the laser oscillator 38 using the input unit 61. The laser oscillation power supply device 46 converts commercial power into DC power and transforms the voltage to generate the supplied power. The laser oscillation power supply device 46 includes a switching unit made up of transistors or the like. When the switching unit is turned on by a signal from the laser oscillation control unit 65a, the supplied power is supplied to the laser oscillator 38.

[0044] The received signal separation unit 65b, which receives a signal from the wireless receiver 36 containing the first information based on the first output data and the second information based on the second output data, generates two identical signals and passes each signal through bandpass filters of different frequency bands. Through this process, the first information and the second information are extracted, and the first output data of the first accelerometer 7 and the second output data of the second accelerometer 8 or 9 are restored.

[0045] Figure 8 is a graph showing an example of voltage data from the pulse signal acquisition unit 15 acquired by the control device 64, and an example of acceleration data from the second accelerometer 7 acquired by the control device 64. Figure 9 is an enlarged graph of the area enclosed by the frame in Figure 8, and shows the period from just before kick-off to the time when the vibration after kick-off subsides. The noise of the Stick-Snap phenomenon is evaluated using the acceleration data shown in Figure 9. The acceleration data from which the noise shown in Figure 9 is analyzed is basically data from a time after the timing when a pulse signal in which the pulse voltage rises sharply instantaneously is received, that is, after the timing when the circumferential center of block 30 is located at the lower end of tire 2.

[0046] The period shown in Figure 9 is determined as follows. Figure 10 is a graph showing voltage data from the pulse signal acquisition unit 15 acquired by the control device 64 and acceleration data from the second first accelerometer 7 acquired by the control device 64. The graph includes data from the time when the front end of block 30 touches the ground until the rear end of block 30 is kicked out and the vibration subsides. Because the acceleration data shown in Figure 10 includes high-frequency vibrations (noise vibrations), the acceleration data is band-shaped, making it difficult to pinpoint the exact timing of the front end of block 30 touching the ground.

[0047] Therefore, a process is performed to remove vibrations with frequencies above a predetermined frequency from the acceleration data using a low-pass filter. This process is performed by the low-pass filter unit 65c using the acceleration data and a program stored in the storage unit 67 that excludes vibrations with frequencies above a predetermined frequency. In this embodiment, the predetermined frequency was set to 1000 [Hz] for the analysis, but the predetermined frequency can be appropriately changed depending on the noise measurement conditions, such as the material of the simulated road surface 22, the rotation speed of the tire 2, the material of the blocks, etc. For example, the predetermined frequency may be set to any value of 800 [Hz] or higher, or to any value of 900 [Hz] or higher.

[0048] Figure 11 is a graph showing the acceleration data after removing signals with frequencies above 1000 Hz from the acceleration data shown in Figure 10. In the data shown in Figure 11, the waveform portion f1 at ground contact, where the acceleration rises instantaneously and sharply, and the waveform portion f2 at push-off, where the acceleration rises instantaneously and sharply, are clearly visible. Therefore, by performing low-pass filtering, the times (timing) of ground contact and push-off of block 30 can be precisely identified.

[0049] Figure 12 is a graph showing acceleration data that includes one cycle period from when block 30 touches the ground until the next time it touches the ground, and which has been subjected to a low-pass filter. As shown in Figure 12, in the test of this embodiment, the time of one cycle is 0.138 [s]. This value is determined based on the outer diameter of tire 2 and the rotational speed of tire 2 in the test. Also, 0.019 [s] indicated by arrow A is the period identified as the period during which the Stick-Snap phenomenon occurs.

[0050] The period identification unit 65d identifies the timing of the kick-off from the acceleration value after low-pass filtering, and also identifies the timing after the kick-off when the acceleration value converges to an acceleration value that is unrelated to the contact between the block 30 and the simulated road surface 22. Since the tire 2 is continuously rotating, the acceleration value will never be zero. The period identification unit 65d determines that convergence has occurred when the acceleration value falls below a threshold. If the tire 2 has only one block 30, the threshold may be the acceleration value at the timing when the circumferential point opposite the circumferential center of the block 30 makes contact with the ground. In the example shown in Figure 10, the period identification unit 65d determines that the acceleration value has converged when the tire 2 has rotated approximately 50° in a test in which the tire 2 was rotated at 50 [km / h].

[0051] Once the period during which the Stick-Snap phenomenon occurs can be identified, the next step is to perform a noise evaluation. The noise evaluation is performed using the output data of the second accelerometers 8 and 9. First, we will explain why the output data of the second accelerometers 8 and 9 can be used to accurately evaluate acceleration noise. Figure 13 is a graph showing the radial output of the second accelerometer 9 when no driving force is applied to the tire 2, which has only one block 30, and the radial output of the second accelerometer 9 when no driving force is applied to a slick tire, which differs from tire 2 only in that it does not have a block 30.

[0052] Figure 14 is a graph showing the tire radial output of the second accelerometer 9 when a driving force of 767N is applied to the tire 2, and the tire radial output of the second accelerometer 9 when a driving force of 767N is applied to the slick tire. In Figures 13 and 14, the data for tire 2 with block 30 is shown by a solid line, and the data for tire 2 without block 30 is shown by a dotted line.

[0053] In Figures 13 and 14, the direction indicated by arrow B is the direction in which the positive value of acceleration increases, and the direction indicated by arrow C is the direction in which the negative value of acceleration increases. Also, in Figures 13 and 14, the direction indicated by arrow D is the direction in which time progresses. Furthermore, in Figure 14, the rotational position of tire 2 indicated by α is the rotational position of tire 2 at time t1, and the rotational position of tire 2 indicated by β is the rotational position of tire 2 at time t2.

[0054] As shown in Figure 13, when no driving force was applied, no significant difference in noise was observed between the presence and absence of block 30. On the other hand, as shown in Figure 14, when a driving force of 767N was applied, a large amplitude vibration was observed in tire 2 with block 30 at time t1 after block 30 detached. This large vibration is presumed to be due to the Stick-Snap phenomenon. Therefore, it was confirmed that by installing an accelerometer inside tire 2, the sliding noise of block 30, i.e., acceleration noise, can be detected accurately and easily. The reason for this is that the vibrations that cause acceleration noise are radiated into the air from the tire body, so it is presumed that more accurate acceleration noise data can be obtained by detecting the vibration of the tire body.

[0055] Figure 15 is a bar graph showing the relationship between the driving force applied to the tire and the PP value of the tire radial output of the second accelerometer 9 for both tire 2 and the slick tire. The PP value is the PEAK to PEAK value, which is the difference between the maximum and minimum values ​​of the tire radial output of the second accelerometer 9. In Figure 15, the shaded values ​​are for the slick tire without block 30, and the white values ​​are for tire 2 with block 30.

[0056] As shown in Figure 15, in the case of a slick tire without blocks 30, the PP value did not change much even when the value of the driving force applied to tire 2 increased. On the other hand, in the case of tire 2 with blocks 30, when driving force was applied to tire 2, the PP value increased rapidly, and it was confirmed that the PP value increased as the value of the driving force applied to tire 2 increased.

[0057] Regardless of the applied driving force, the PP value of tire 2 with block 30 was higher than the noise level of the slick tire without block 30. More specifically, when no driving force was applied, the PP value of tire 2 with block 30 was approximately twice that of the slick tire. On the other hand, when driving force was applied, the PP value of tire 2 with block 30 increased sharply to approximately five times that of the slick tire.

[0058] From the above test results, it was confirmed that the vibration of the tire body significantly increased only when a block was present and driving force was applied, and that this vibration of the tire body was one of the factors that worsened tire noise during acceleration. In other words, it was confirmed that acceleration noise can be accurately and easily evaluated by evaluating the acceleration noise based on the readings of a second accelerometer installed inside tire 2 to detect the vibration of the tire body.

[0059] The inventors investigated the preferred installation position of the second accelerometer inside the tire by comparing the output of the first second accelerometer 8 with the output of the second second accelerometer 9. Figure 16 is a bar graph showing the relationship between the driving force applied to the tire 2 and the PP value of the tire radial output of the first second accelerometer 8, and Figure 17 is a bar graph showing the relationship between the driving force applied to the tire 2 and the PP value of the tire radial output of the second second accelerometer 9.

[0060] As shown in Figures 16 and 17, it was confirmed that the difference in the variation of the PP value with respect to the applied driving force difference was significantly larger for the first accelerometer 8 than for the second accelerometer 9. For example, when the driving force applied to the tire 2 was increased from 0N to 256N, the variation in the PP value in the output of the second accelerometer 9 was 27 [m / s²]. 2 While this is approximately [m / s], the variation in the PP value in the output of the second accelerometer 8 when the driving force applied to tire 2 is increased from 0N to 256N is 140[m / s] 2 The variation in PP value at the output of the first accelerometer 8 is approximately 5.2 times larger than the variation in PP value at the output of the second accelerometer 9.

[0061] This trend holds true regardless of the starting value from which the drive value is increased. From this, it was confirmed that acceleration noise can be evaluated more easily and accurately by using the output data of the first second accelerometer 8, specifically the output data of the second accelerometer positioned inside the tire 2 such that at least a portion of it is inside the tire 2 and radially opposite the front edge 30a of the block 30 in the circumferential direction.

[0062] Next, the noise evaluation in this embodiment will be described. When the period identification unit 65d identifies the period during which the Stick-Snap phenomenon occurs, the PP value calculation unit 65e acquires the second output data of the first second accelerometer 8 from the received signal separation unit 65b and calculates the PP value from the second output data. Subsequently, the noise evaluation unit 65f evaluates whether the acceleration noise of the tire 2 is appropriate based on the information from the input unit 61, the PP value from the PP value calculation unit 65e, and the information from the storage unit 67.

[0063] More specifically, the memory unit 67 has pre-stored maps that link driving forces and PP value thresholds for a large number of driving forces. The noise evaluation unit 65f identifies the driving force applied to the tire 2 based on the information from the input unit 61 and refers to the PP value threshold corresponding to the identified driving force from the stored data in the memory unit 67. The noise evaluation unit 65f then compares the PP value calculated by the PP value calculation unit 65e with the PP value threshold for the driving force in which that PP value was calculated. If the PP value calculated by the PP value calculation unit 65e is less than or equal to the PP value threshold for the driving force in which that PP value was calculated, the noise evaluation unit 65f determines that the acceleration noise of the tire 2 is low (determined to be appropriate). On the other hand, if the PP value calculated by the PP value calculation unit 65e exceeds the PP value threshold for the driving force in which that PP value was calculated, the noise evaluation unit 65f determines that the acceleration noise of the tire 2 is high (determined to be inappropriate).

[0064] The tire noise evaluation method according to this disclosure is a method for evaluating noise emitted from a tire 2 having one or more blocks 30 and running on a simulated road surface 22, and includes the steps of: installing first accelerometers 6 and 7 at the circumferential ends of the blocks 30 on the tire 2; and installing second accelerometers 8 and 9 inside the tire 2. The tire noise evaluation method also includes the steps of: running the tire 2 under conditions in which noise from two or more blocks 30 does not mix and collecting first output data from the first accelerometers 6 and 7; identifying a period based on the first output data that is related to at least one of the time when the blocks 30 make contact with the ground and the time when the blocks 30 push off, and in which the contribution of sliding noise to the noise is large; and evaluating the noise based on second output data from the second accelerometers 8 and 9 during that period.

[0065] According to this disclosure, based on the first accelerometers 6 and 7 grounded around the block 30, a period is identified that is related to at least one of the time when the block 30 is grounded or when the block 30 is kicked off, and during which the contribution of sliding noise to the noise is large. This makes it easier to accurately identify the period during which the block 30 is sliding, and enables noise evaluation that focuses on sliding noise.

[0066] Furthermore, when block 30 vibrates, that vibration is transmitted to the tire body, and the vibration of the tire body is transmitted to the air, generating noise. However, as described above, the inventors of this invention have found that by analyzing the vibration of the tire body that occurs in conjunction with the vibration of block 30, acceleration noise (slip noise) can be evaluated accurately and objectively. Against this backdrop, according to this disclosure, since the noise is evaluated based on the output data of the second accelerometers 8 and 9 located inside the tire 2 during periods when the contribution of slip noise is large, the vibration of the tire body during periods when the contribution of slip noise is large can be evaluated. Therefore, acceleration noise can be evaluated more accurately and objectively.

[0067] Furthermore, the tire noise evaluation device 1 according to this disclosure comprises a simulated road surface 22 on which the tire 2 travels, first accelerometers 6 and 7 installed at the circumferential ends of the blocks 30 of the tire 2, second accelerometers 8 and 9 installed inside the tire 2, a data acquisition unit 70 that collects first output data from the first accelerometers 6 and 7 and second output data from the second accelerometers 8 and 9 when the tire 2 is traveling on the simulated road surface 22, a period identification unit 65d that identifies a period based on the first output data that is related to at least one of the time when the blocks 30 make contact with the ground and the time when the blocks push off, and in which the contribution of slip noise to the noise emitted by the tire is large, and a noise evaluation unit 65f that evaluates the noise based on the second output data during the period.

[0068] According to this disclosure, by using the first output data of the first accelerometers 6 and 7 installed at the circumferential ends of the block 30, the period during which slippage occurs in the block 30 (for example, the period during which a stick-slip phenomenon occurs or the period during which a stick-snap phenomenon occurs) can be accurately identified. Furthermore, by using the second output data of the second accelerometers 8 and 9 installed inside the tire 2 to evaluate the acceleration noise (slip noise) during that period, the acceleration noise can be accurately evaluated. In other words, by combining the first accelerometers 6 and 7 and the second accelerometers 8 and 9 to evaluate the acceleration noise, the acceleration noise can be evaluated accurately and with high precision.

[0069] Furthermore, the second accelerometer 8 may be positioned inside the tire 2 such that at least a portion of it is on the inside of the tire 2 and radially faces the front edge of the circumferential direction of the block 30. In this case, the evaluation of acceleration noise can be performed more accurately.

[0070] This disclosure is not limited to the embodiments and their modifications, and various improvements and modifications are possible within the scope of the claims of this application and their equivalents.

[0071] For example, a noise test may be conducted under conditions that eliminate air column resonance noise. More specifically, as in this embodiment, if the test tire has a main groove 31, the noise test may be conducted with the main groove 31 filled with an elastic material, such as urethane rubber. Alternatively, a tire may be manufactured in which only the main groove 31 exists without filling it with urethane rubber, and the noise from the main groove 31 may be measured separately. The noise from the main groove 31 may then be eliminated by subtracting that noise. When conducting a noise test under conditions that eliminate air column resonance noise, the circumferentially extending portion of the annular groove 35 may be a part of the main groove, and the portion of the main groove other than the circumferentially extending portion may be filled with an elastic material.

[0072] Furthermore, the noise evaluation unit 65f may determine that the acceleration noise of tire 2 is low (determined to be appropriate) if, in all of the tests conducted multiple times with multiple different driving forces, the PP value calculated by the PP value calculation unit 65e is less than or equal to the threshold value for the PP value at the driving force for which the PP value was calculated. Alternatively, if, in one or more of the tests conducted multiple times with multiple different driving forces, the PP value calculated by the PP value calculation unit 65e exceeds the threshold value for the PP value at the driving force for which the PP value was calculated, the noise evaluation unit 65f may determine whether the acceleration noise of the test tire is appropriate or not by comparing the maximum absolute value of the second output data output by the second accelerometer during the period in which the slip noise identified based on the data from the first accelerometer is high with the threshold value at that driving force.

[0073] Alternatively, the control unit of the control device may have a Fast Fourier Transform (FFT) unit, and after the control unit of the control device extracts acceleration data for the period specified by the period specification unit 65d from the acceleration data of the second accelerometer, the Fast Fourier Transform unit may perform a Fast Fourier Transform on the extracted acceleration data to perform frequency analysis (spectral analysis). Here, instead of applying a Fast Fourier Transform to the extracted acceleration data, the frequency analysis may be performed by applying a Fourier Transform.

[0074] The noise evaluation unit 65f may then compare acceleration data in the frequency range of 500 Hz to 2000 Hz, which is prone to producing noise that is unpleasant to people, with a threshold value stored in the storage unit 67. The noise evaluation unit 65f may then determine whether there are any frequencies in that range where the acceleration exceeds the threshold value, and if there are frequencies in that range where the acceleration is above the threshold value, it may determine that the sliding noise is loud, and if there are no frequencies where the acceleration is above the threshold value, it may determine that the sliding noise is quiet.

[0075] Here, the threshold value may be changed as appropriate based on the test conditions. Furthermore, it is preferable to calculate the data after frequency analysis by rotating the tire 2 multiple times, for example, three or more times, more preferably ten or more times, and averaging the processing data from multiple rotations. This allows the data to be leveled, enabling accurate noise evaluation.

[0076] The case described above was where the frequency range for comparing acceleration data and a threshold is between 500 Hz and 2000 Hz. However, the frequency range for comparing acceleration data and a threshold can be any predetermined frequency range and is not limited to the range between 500 Hz and 2000 Hz. For example, the frequency range for comparing acceleration data and a threshold may be a range of frequencies greater than 2000 Hz, or a range of frequencies less than 500 Hz. It is preferable that at least a portion of the frequency range for comparing acceleration data and a threshold is included in the range between 500 Hz and 2000 Hz.

[0077] It is known that overall (OA) and partial overall (POA) can be calculated from the power spectrum obtained by FET analysis. Overall is the sum of power values ​​(squared values) up to the analysis frequency range, while partial overall is the value obtained by limiting the frequency range over which the sum is taken and calculating the sum within that range. Whether or not the noise is acceptable may be evaluated by comparing the overall with a threshold. Alternatively, whether or not the noise is acceptable may be evaluated by comparing the partial overall with a threshold for a predetermined frequency range. For example, if the partial overall is above the threshold, the noise may be judged as unacceptable, and if the partial overall is below the threshold, the noise may be judged as acceptable.

[0078] The method for identifying the period during which slip occurs was described, based on both filtered data from the output of the first accelerometer 7 and the acquisition of pulse signals. However, the method for identifying the period during which slip occurs does not necessarily have to be based on pulse signals, but rather on filtered data. The method for identifying the period during which slip occurs was described, based on removing vibrations with frequencies above a predetermined frequency from the acceleration data output by the first accelerometer 7 using a low-pass filter. However, the method for identifying the period during which slip occurs does not have to be performed by low-pass filtering on the acceleration data output by the first accelerometer 7.

[0079] The method for calculating frequency analysis data by averaging multiple processing steps was described, but the frequency analysis data may also be calculated from acceleration data for only one rotation of tire 2. Furthermore, the method for evaluating noise using a rectangular block 30 in a plan view from the radially outward direction of tire 2 was described. However, the block may have any shape in a plan view from the radially outward direction of tire; for example, it may have an isosceles trapezoidal shape or a circular shape in a plan view from the radially outward direction of tire.

[0080] The case described above involves transmitting detection data from the first accelerometers 6 and 7 and detection data from the second accelerometers 8 and 9 to the data analysis device 10 using a pair of wireless transceivers 34 and 36. However, the tire noise evaluation device may be equipped with two pairs of wireless transceivers, one pair of which may be used to transmit detection data from the first accelerometers 6 and 7 to the data analysis device 10, while the other pair of wireless transceivers may be used to transmit detection data from the second accelerometers 8 and 9 to the data analysis device 10.

[0081] A tire noise evaluation device may have only one first accelerometer installed at the circumferential end of a tire block, or only one second accelerometer installed inside the tire. However, having multiple first accelerometers installed at the circumferential end of a tire block makes it easier to analyze and evaluate acceleration noise with greater accuracy. Similarly, having multiple second accelerometers installed inside the tire also makes it easier to analyze and evaluate acceleration noise with greater accuracy.

[0082] This document describes how to perform noise evaluation without using a sound level meter. However, since there is a correlation between noise and acceleration, it is also acceptable to measure noise using a sound level meter, which allows for a more accurate noise evaluation. When using a sound level meter, it is preferable to place it near the tires at a distance from them and to continuously measure the noise. [Explanation of Symbols]

[0083] 1 Tire noise evaluation device, 2 Tire, 5 Noise analysis device, 6 First accelerometer, 7 Second accelerometer, 8 First accelerometer, 9 Second accelerometer, 10 Data analysis device, 15 Pulse signal acquisition unit, 21 Drum, 22 Simulated road surface, 30 Block, 30a Front edge of block in the circumferential direction, 30b, 30c End faces of block in the circumferential direction, 31 Main groove, 32 First edge, 33 Second edge, 34 Wireless transmitter, 35 Annular groove, 36 Wireless receiver, 37 Reflector, 38 Laser oscillator, 39 Laser receiver, 42, 43, 58, 59 Wiring, 46 Power supply device for laser oscillation, 47 Output unit, 61 Input unit, 62 Display unit, 63 Transceiver unit, 64 Control device, 65 Control unit, 65a Laser oscillation control unit, 65b Received signal separation unit, 65c Low-pass filter unit, 65d Period specification unit, 65e PP value calculation unit, 65f Noise evaluation unit, 67 Storage unit, 70 Data acquisition unit.

Claims

1. A method for evaluating noise emitted from a tire having one or more blocks and traveling on a simulated road surface, The steps include installing a first accelerometer at the circumferential end of the block in the tire, The steps include installing a second accelerometer inside the aforementioned tire, The steps include: driving the tire under conditions where noise from two or more of the aforementioned blocks does not mix and collecting first output data from the first accelerometer; A step of identifying a period that is related to at least one of the time when the block is grounded and the time when the block is kicked off, and during which the contribution of sliding noise to the noise is large, based on the first output data, A step of evaluating the noise based on the second output data from the second accelerometer during the aforementioned period, A tire noise evaluation method, including the above.

2. The tire noise evaluation method according to claim 1, wherein the second accelerometer is positioned inside the tire such that at least a portion of the second accelerometer is inside the tire and radially faces the front edge of the block in the circumferential direction.

3. The simulated road surface on which the tires travel, A first accelerometer is installed at the circumferential end of the tire block, A second accelerometer installed inside the aforementioned tire, A data acquisition unit collects first output data from the first accelerometer and second output data from the second accelerometer when the tire is traveling on the simulated road surface. A period identification unit that identifies a period based on the first output data that is related to at least one of the time when the block is in contact with the ground and the time when the block is being pushed off, and during which the contribution of slip noise to the noise emitted by the tire is large, A noise evaluation unit that evaluates the noise based on the second output data during the aforementioned period, A tire noise evaluation device equipped with the following features.

4. The tire noise evaluation device according to claim 1, wherein at least a portion of the second accelerometer is positioned on the inside of the tire and radially opposite the front edge of the circumferential direction of the block.

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