Method for measuring tire tread

Abstract

This invention provides a tire tread measurement method that allows for easy measurement within a measurement range set in the center region. [Solution] The method includes a processing step of partially removing the tread rubber 13 outside the tire width direction of the measurement range 20 set in the center region CA of the tire tread 3 to form a see-through portion 30 that allows the measurement range 20 to be seen from the side of the tire; a patterning step of forming a pattern on the side surface of the block 51 which is the land portion in the measurement range 20; a photography step of photographing the pattern through the see-through portion 30; and an analysis step of performing an analysis of the tire tread 3 based on the image including the photographed pattern.

Description

[Technical Field]

[0001] The present disclosure relates to a method for measuring a tire tread. [Background Art]

[0002] Patent Documents 1 and 2 each describe a method of capturing an image of a pattern formed on a surface of a sidewall portion of a tire, analyzing an image including the captured pattern, and measuring surface strain. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2017-1628 [Patent Document 2] Japanese Unexamined Patent Publication No. 2004-317316 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] When a tire tread is targeted, for example, in a test for measuring surface strain on a side surface of a block, it is conceivable to use a block piece cut out from an actual tire tread or a rubber sample produced by simulating a block. However, these methods cannot meet the demand for performing measurement based on the deformation behavior of the block when an actual tire is actually rolled.

[0005] On the other hand, when measurement is performed using an actual tire, the measurement range is set to the shoulder region of the tire tread. This is because the center region is blocked by the land portion of the shoulder region when viewed from the side of the tire, and the groove portion of the tire tread is too narrow for installing a camera, so that it is difficult to capture an image of the side surface of a block provided in the center region. No specific measurement method suitable for the measurement range set in such a center region has been known.

[0006] This disclosure has been made in view of the above circumstances, and its purpose is to provide a tire tread measurement method that can easily perform measurements within a measurement range set in the center region. [Means for solving the problem]

[0007] The tire tread measurement method of the present disclosure includes a processing step of partially removing the tread rubber outside the tire width direction of a measurement range set in the center region of the tire tread to form a see-through portion that allows the measurement range to be viewed from the side of the tire; a patterning step of forming a pattern on the side surface of the land portion in the measurement range; a photography step of photographing the pattern through the see-through portion; and an analysis step of performing an analysis of the tire tread based on the image including the photographed pattern. [Brief explanation of the drawing]

[0008] [Figure 1] A diagram showing an example of the configuration of a tire tread measurement system. [Figure 2] (A) Meridian section of the tire and (B) Bottom view of the tire tread [Figure 3] A flowchart illustrating an example of a procedure for measuring tire tread. [Figure 4] Bottom view showing key parts of the tire tread after the processing steps. [Figure 5] Side view showing the main part of the tire tread after processing and patterning steps. [Figure 6] This diagram illustrates one method of removing the side portion of a block. [Figure 7] A flowchart illustrating an example of a process for measuring the surface strain of a block. [Figure 8] (A) A schematic diagram showing the state of the blocks to be used as the reference image and (B) the modified image. [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described with reference to the drawings.

[0010] [Measurement System] Figure 1 shows an example of the configuration of a measurement system used in the tire tread measurement method of this embodiment. The measurement system 6 comprises a tire testing machine 7, a photography device 8, and an analysis device 9.

[0011] The tire testing machine 7 comprises a simulated road surface 71, a support device 72, and a drive device 73. The simulated road surface 71 is composed of a transparent plate 74 having a flat top surface. The transparent plate 74 is made of a light-transmitting material such as acrylic resin or glass. Lighting 82, described later, is installed below the transparent plate 74 and is configured to illuminate the tire 10 for photography. The light transmittance of the transparent plate 74 is not particularly limited as long as it does not interfere with photography. The simulated road surface 71 may be made of a material that does not transmit light, in which case the lighting 82 is installed in a different location that can illuminate the shooting range.

[0012] The support device 72 rotatably supports the tire 10. The support device 72 includes a rim 75 mounted on the tire 10 and a support shaft 76 connected to the rim 75. The rim 75 is configured to be displaceable relative to the support shaft 76. Therefore, the posture of the tire 10 relative to the transparent plate 74 can be adjusted to impart slip angle, camber angle, etc. The support shaft 76 is configured to have its height position adjustable. Therefore, the tire 10 can be pressed against the upper surface of the transparent plate 74 to apply a load.

[0013] The drive unit 73 applies driving force to the tire 10 supported by the support unit 72. The drive unit 73 includes a motor 77 that rotates the support shaft 76 and a motor control device 78 that controls the drive of the motor 77. The drive unit 73 rotates the rim 75 by driving the motor 77 with the motor control device 78. This reproduces the rolling state of the tire 10 during vehicle operation on the simulated road surface 71. Furthermore, various driving conditions can be set by appropriately adjusting the rotational speed, load, slip angle, camber angle, etc., applied to the tire 10.

[0014] The photographing device 8 includes a camera 81 serving as an imaging unit, and an illumination 82 that illuminates the imaging range of the camera 81. The camera 81 is arranged at a position where the tire tread 3 can be photographed from the outside in the tire width direction. The camera 81 photographs the tire tread 3 and generates an image (for example, digital image data). In FIG. 1 and other drawings, a line of sight 83, which is the photographing direction of the camera 81, is indicated by an alternate long and short dash line. In a state where the slip angle and the camber angle are set to 0 degrees, the line of sight 83 is parallel to the central axis (rotation axis) of the tire 10, but is not limited thereto. The illumination 82 irradiates the tire tread 3 with light through the transparent plate 74. For the illumination 82, for example, a lamp, a light bulb, an LED, or the like is used.

[0015] The analysis device 9 is constituted by one or more computers. A predetermined analysis program may be installed in the computer. The analysis device 9 includes a display unit 91 that displays various types of information on a screen, and an input unit 92 that receives input from a measurement operator. The input unit 92 is constituted by, for example, a touch panel or a keyboard. The analysis device 9 processes and analyzes the image of the tire tread 3 input from the photographing device 8, and performs measurement of surface strain and the like. A specific example of the processing flow will be described later.

[0016] Tire FIG. 2(A) is a tire meridional cross-sectional view schematically showing an example of the tire 10 to be subjected to measurement. In the present embodiment, the tire 10 is a pneumatic tire for an automobile. The tire 10 includes the tire tread 3 connected to outer ends in the tire radial direction of a pair of sidewall portions 2. The sidewall portions 2 extend outward in the tire radial direction from bead portions 1. Embedded in each bead portion 1 are a bead core 11 formed by coating a steel wire or the like with rubber, and a bead filler 12 positioned outward of the bead core 11 in the tire radial direction. A tread rubber 13 forming a tread surface is arranged on the tire tread 3.

[0017] Here, the tire radial direction is the direction along the diameter of the tire 10. The side closer to the central axis of the tire 10 is the inner side in the tire radial direction, and the side away from the central axis of the tire 10 is the outer side in the tire radial direction. The tire circumferential direction is the direction around the central axis of the tire 10. The tire width direction is the direction parallel to the central axis of the tire 10. The side closer to the center of the tire 10 in the tire width direction is the inner side in the tire width direction, and the side away from the center is the outer side in the tire width direction.

[0018] The tire 10 includes a carcass 14 extending in a toroidal shape across between a pair of bead portions 1. In the bead portion 1, a bead core 11 and a bead filler 12 are sandwiched by the carcass 14. The carcass 14 is formed of a carcass ply formed by covering a carcass cord with rubber. The carcass cords are aligned in a direction intersecting the tire circumferential direction. The inclination angle of the carcass cord with respect to the tire circumferential direction is, for example, 75 to 90 degrees. For the material of the carcass cord, metals such as steel and organic fibers such as polyester, rayon, nylon and aramid are preferably used.

[0019] The tire 10 includes a reinforcing cord member 15 embedded in a tire tread 3. The reinforcing cord member 15 is laminated on the outer side of the carcass 14 in the tire radial direction. The reinforcing cord member 15 includes a plurality of (two in the present embodiment) belt plies 16 and 17. The belt plies 16 and 17 are formed by coating belt cords, which are aligned in a direction inclined with respect to the tire circumferential direction (for example, a direction at an angle of about 20 degrees with respect to the tire circumferential direction), with topping rubber. The belt plies 16 and 17 are laminated such that the belt cords cross each other in opposite directions. A metal cord such as steel is preferably used for the belt cord.

[0020] The reinforcing cord member 15 further includes a belt reinforcing ply 18. The belt reinforcing ply 18 is formed by covering a belt reinforcing cord, which is substantially aligned in the circumferential direction of the tire, with a topping rubber. The belt reinforcing ply 18 is formed, for example, by spirally winding one or more rubber-coated belt reinforcing cords along the circumferential direction of the tire. The organic fiber cord described above is preferably used for the belt reinforcing cord. In this embodiment, the belt prisms 16 and 17 are completely covered by the belt reinforcing ply 18, but a structure in which only both ends of the belt prisms 16 and 17 are covered is also possible. Alternatively, the belt reinforcing ply 18 may be omitted.

[0021] Figure 2(B) is a bottom view (or top view) of the tire tread 3, schematically showing an example of the tread pattern of the tire 10. The tire tread 3 is provided with grooves 4 and land areas 5 partitioned by the grooves 4. The grooves 4 have a plurality of longitudinal grooves 41 extending along the circumferential direction of the tire and transverse grooves 42 extending in a direction intersecting the longitudinal grooves 41. The longitudinal grooves 41 extend in a straight line, but are not limited to this, and may include bent or curved portions. Wear indicators may be provided in the longitudinal grooves 41. The number of longitudinal grooves 41 is not particularly limited, and may be, for example, 3 to 6. Although a block pattern is shown in this example, the tread pattern of the tire 10 used in the measurement method of this disclosure is not limited to a specific shape.

[0022] The center region CA is the region inside the tire width direction from the shoulder longitudinal groove 41s. The shoulder region SA is the region outside the tire width direction from the shoulder longitudinal groove 41s. The shoulder longitudinal groove 41s is the longitudinal groove located furthest out of a plurality (three in this embodiment) of longitudinal grooves 41 in the tire width direction. In this embodiment, each of the center region CA and the shoulder region SA is provided with a row of blocks 51 arranged repeatedly along the tire circumferential direction. In this example, the spaces between adjacent blocks 51 are completely separated by the transverse groove 42, but this is not limited to this configuration, and they may be partially connected.

[0023] The deformation behavior of the land portion 5 (specifically, the blocks 51) of the tire tread 3 has a significant impact on tire performance, and analyzing this is extremely important in tread pattern development. In particular, there is a demand to observe the behavior of the blocks 51 when the actual tire is rolled and to quantify its deformation, especially regarding braking performance, driving performance, and wear resistance. However, the center region CA is obstructed by the land portion 5 of the shoulder region SA when viewed from the side of the tire, making it difficult to photograph with the camera 81. On the other hand, it is not practical to install the camera 81 in the narrow groove 4. Therefore, in this embodiment, a method described later is used to enable easy measurement within the measurement range set in the center region CA.

[0024] [Method for measuring tire tread] An embodiment of the tire tread measurement method of the present disclosure will be described. In this embodiment, an example is shown in which the deformation behavior of the land portion 5 in the measurement range 20 (see Figure 2(B)) set in the center region CA is analyzed and its surface strain is determined. In this example, the measurement range 20 is set to the range corresponding to one of the blocks 51 that form the block row provided in the center region CA. This eliminates the need to form the see-through portion 30, which will be described later, over an excessively wide area, thus suppressing the influence on the ground pressure distribution. The measurement range 20 may also be set to a range corresponding to multiple blocks or to a range corresponding to a part of the rib that extends continuously in the circumferential direction of the tire.

[0025] Figure 3 is a flowchart showing an example of the procedure for measuring the tire tread 3 according to this embodiment. As shown in Figure 3, the measurement method includes a processing step (step S1), a patterning step (step S2), a photography step (step S3), and an analysis step (step S4). In this example, the patterning step (step S2) is performed after the processing step (step S1), but the order of these steps is not limited.

[0026] Figure 4 is a bottom view showing the main parts of the tire tread 3 after the processing step. Figure 5 is a side view showing the main parts of the tire tread 3 after the processing step and the patterning step. As shown in Figures 4 and 5, in the processing step (step S1), the tread rubber 13 outside the measurement range 20 set in the center region CA of the tire tread 3 in the tire width direction is partially removed, forming a see-through portion 30 that allows the measurement range 20 to be seen from the side of the tire. The removal of the tread rubber 13 can be done using a tool such as a grooving tool like a ril fitter.

[0027] Length L30 is the minimum length of the see-through portion 30 in the tire circumferential direction. Length L51 is the maximum length of the object to be photographed (in this embodiment, the side surface 53 of the block 51) in the tire circumferential direction. Length L30 should be set to a size that allows the object to be photographed by the camera 81. Length L30 may be the same size as length L51, but it is preferable that it be larger than length L51, for example, set to 110% or more of length L51. On the other hand, from the viewpoint of suppressing the effect on the ground pressure distribution, it is preferable that length L30 be set to 150% or less of length L51. From the above viewpoint, and further from the viewpoint of preventing the upper part of the see-through portion 30 in Figure 5 from deforming due to load and obscuring the pattern 54 which is the object to be measured, it is preferable that length L30 be 100 mm or less.

[0028] As shown in Figure 4, when forming a see-through portion 30 in a range that crosses the land portion 5 of the shoulder region SA, it is preferable to provide a cross-section 52 that is substantially parallel to the shooting direction of the camera 81 (in this embodiment, the tire width direction) so that the range in which the tread rubber 13 is removed is appropriately limited. It is also possible to form a see-through portion 30 in a range from a lateral groove 42 to another lateral groove 42 adjacent to it in the tire circumferential direction, so that a cross-section 52 is not provided on the land portion 5 of the shoulder region SA.

[0029] In the processing step, it is preferable to remove the tread rubber 13 to a depth position along the bottom of the shoulder longitudinal groove 41s or to a depth position that is radially inward from the bottom of the groove. This method is convenient for capturing the portion of the measurement range 20 that includes the base of the block 51 within the imaging range.

[0030] In the processing step, the tread rubber 13 may be removed to the extent that the reinforcing cord members 15 (see Figure 2) embedded in the tire tread 3 are exposed in the see-through portion 30. For example, the tread rubber 13 may be removed to a depth where the belt reinforcing ply 18 (and its belt reinforcing cord) located furthest outward in the tire radial direction among the reinforcing cord members 15 is exposed. This method is convenient for photographing the relative deformation between the annular beam (corresponding to the reinforcing cord members 15) and the elastic tread (corresponding to the tire tread 3) as defined in the Fiala tire model, and for observing the deformation behavior in the vicinity of the groove bottom.

[0031] In the patterning process (step S2), a pattern 54 is formed on the side surface 53 of the land portion 5 within the measurement range 20. As shown in Figure 5, in this embodiment, the pattern 54 is formed on the side surface 53 of the block 51 that is on the outer side in the tire width direction. The side surface of the block 51 facing the tire circumferential direction may also be targeted, but in that case, due to the field of view of the camera 81, it would be necessary to form the see-through portion 30 over a relatively wide area. In Figure 5, the surface exposed when the tread rubber 13 is removed in the processing process is shown with fine wavy lines.

[0032] If the side surface 53 is not a flat surface, or if the side surface 53 is not perpendicular to the shooting direction of the camera 81, as shown in Figure 6, the lateral portion 51s of the land portion 5 (block 51 in this embodiment) in the measurement range 20 may be removed so that a surface perpendicular to the shooting direction in the shooting process is formed, and a pattern 54 may be formed on the side surface 53 on the outer side in the tire width direction of the block 51, including the exposed portion resulting from the removal.

[0033] In the patterning process of this embodiment, a grid pattern is formed as the pattern 54. Then, as will be described in detail later, in the analysis process, the surface distortion of the land portion 5 (block 51) is measured based on the image including the grid pattern. The method for forming such a pattern 54 (grid pattern) is not particularly limited, and for example, a method of directly drawing on the side surface 53 or a method of attaching a sheet having the pattern 54 to the side surface 53 can be employed.

[0034] In the shooting process (step S3), the pattern 54 is photographed through the see-through section 30. This allows the camera 81 to photograph the measurement range 20 set in the center area CA from the outside in the tire width direction without obstruction by the land portion 5 of the shoulder area SA. The image data generated by the shooting is sent to the analysis device 9.

[0035] In the analysis step (step S4), the tire tread 3 is analyzed based on the image including the captured pattern 54. This allows the surface strain of the block 51 to be measured, for example, using a process described later. Thus, according to the tire tread measurement method of this embodiment, measurements can be easily performed within the measurement range 20 set in the center region CA.

[0036] [Processing flow] Figure 7 is a flowchart showing an example of a process for measuring the surface strain of block 51. In this embodiment, the surface strain of the side surface 53 of block 51 is measured based on a comparison between an image of the pattern 54 when it is not deformed (hereinafter referred to as the reference image) and an image of the pattern 54 when it is deformed (hereinafter referred to as the deformed image). Of the steps S11 to S18 described later, at least steps S11 and S14 are included in the aforementioned imaging process, and at least step S18 is included in the aforementioned analysis process.

[0037] First, a reference image is acquired (step S11). Specifically, a pattern 54 formed on the side surface 53 of the block 51 is photographed while no load is acting on the block 51. Figure 8(A) shows an example of the state of the block 51 used as the reference image. The block 51 may be in a contact state, but it is preferable that it be in a non-contact state, away from the simulated road surface 71. To make the block 51 non-contact, one can either raise the support shaft 76 to lift the tire 10, or rotate the support shaft 76 to shift the circumferential position of the block 51. In the latter case, a reference image in an inclined position can be obtained.

[0038] Next, the positions of the grid points in the reference image are set (step S12). Specifically, the positions of the grid points (intersections of the grid) of the grid pattern, which is the pattern 54, are obtained based on the reference image acquired in step S11. For example, the position of the grid points may be set by the measurement operator selecting the grid points on a screen displaying the reference image (for example, by pointing with a pointer and clicking). This operation can be performed using the display unit 91 and input unit 92 of the analysis device 9.

[0039] Next, the coordinates of the reference image are created (step S13). Specifically, the length per unit pixel is determined based on the grid size and the number of pixels in the image, and coordinates with units of length are created. For example, in a grid pattern made up of squares (grid meshes) with dimensions of 1.4 mm by 1.4 mm, it is possible to determine the length per unit pixel (unit: mm) and create the coordinates of the reference image.

[0040] Next, a deformed image is acquired (step S14). Specifically, the pattern 54 formed on the side surface 53 of the block 51 is photographed while a load is acting on it. Figure 8(B) shows an example of the state of the block 51 used as a deformed image, capturing a single moment while the tire 10 is rolling under load. Alternatively, the block 51 of the tire 10 when it is not rolling, such as during braking or driving, may be photographed and used as the deformed image.

[0041] Next, the positions of the grid points in the deformed image are set (step S15). The process for setting the grid points can be performed in the same way as in step S12 for the reference image, so a redundant explanation is omitted.

[0042] Next, coordinates of the deformed image are created (step S16). Specifically, coordinates of the deformed image with units of length are created based on the length per unit pixel obtained in step S13. This allows the size of the grid of the pattern 54 in the deformed block 51 to be determined in units of length.

[0043] If the coordinate orientations of the reference image and the deformed image differ, especially if a reference image with an inclined orientation was obtained in step S11, their orientations are made to match (step S17). For example, the reference image is rotated around the central axis of the tire 10 to make its coordinate axes match those of the deformed image. Step S17 may be performed as needed and may be omitted as appropriate.

[0044] After creating the coordinates for both the reference image and the deformed image, surface strain is measured based on them (step S18). Specifically, for each grid edge of the grid pattern (a line connecting adjacent grid points), the length in the reference image is compared with the length in the deformed image, and the surface strain is calculated based on the degree of change. The obtained surface strain distribution can be visualized using a contour plot or the like. Furthermore, by overlaying it on the deformed image, the strain distribution across the entire side surface of block 51 becomes immediately clear.

[0045] For example, to determine the compressive strain of block 51 along the vertical direction (tire radial direction), surface strain can be measured based on the grid edges included in the grid pattern that extend along the tire radial direction. To determine the tensile strain of block 51 along the longitudinal direction (tire circumferential direction), surface strain can be measured based on the grid edges included in the grid pattern that extend along the tire circumferential direction. Furthermore, if the coordinate axes of the reference image and the deformed image are aligned, the shear strain of block 51 can be determined based on the relative positional displacement of each grid point.

[0046] Those skilled in the art will understand that the embodiments described above are specific examples of the following embodiments.

[0047] [1] The tire tread measurement method of this disclosure includes a processing step of partially removing the tread rubber outside the tire width direction of a measurement range set in the center region of the tire tread to form a see-through portion that allows the measurement range to be viewed from the side of the tire; a patterning step of forming a pattern on the side surface of the land portion in the measurement range; a photography step of photographing the pattern through the see-through portion; and an analysis step of performing an analysis of the tire tread based on the image including the photographed pattern. With this method, measurements can be easily performed on a measurement range set in the center region.

[0048] [2] In the method described in [1] above, the measurement range may be the range corresponding to one of the blocks forming the block row provided in the center region. With this method, it is not necessary to form a see-through portion over an excessively wide area, and therefore the effect on the ground pressure distribution is suppressed.

[0049] [3] In the method described in [2] above, the patterning step may involve forming the pattern on the outer side surface of the block in the tire width direction. This method is useful for observing the behavior of the block as seen from the side of the tire and for quantifying its deformation.

[0050] [4] In any one of the above methods [1] to [3], the lateral portion of the land portion in the measurement range may be removed so as to form a surface perpendicular to the shooting direction in the shooting step, and the pattern may be formed on the side surface of the land portion on the tire width direction, including the exposed portion resulting from the removal. Such a method is useful for observing the behavior of the land portion (e.g., blocks) as seen from the side of the tire and for quantifying its deformation.

[0051] [5] In any one of the above methods [1] to [4], the patterning step may involve forming a grid pattern as the pattern, and the analysis step may involve measuring the surface distortion of the land area based on an image including the captured grid pattern. According to this method, the surface distortion of the land area (e.g., a block) can be easily measured by utilizing the grid pattern.

[0052] [6] In any one of the above methods [1] to [5], the processing step may involve removing the tread rubber to a depth position along the bottom of the shoulder longitudinal groove or to a depth position that is radially inward from the bottom of the groove. This method is convenient for capturing the portion of the measurement range 20 that includes the base of the block 51 within the imaging range.

[0053] [7] In any one of the above methods [1] to [6], the processing step may involve removing the tread rubber to the extent that the reinforcing cord members embedded in the tire tread are exposed in the see-through portion. Such a method is convenient for photographing the relative deformation between the annular beam and the elastic tread as defined in the Fiala tire model, or for observing the deformation behavior in the vicinity of the groove bottom.

[0054] While embodiments of the tire tread measurement method relating to this disclosure have been described with reference to the drawings, it should be understood that the specific configuration is not limited to these embodiments. The scope of the present invention is indicated not only by the above-described embodiments but also by the claims, and furthermore, all modifications within the meaning and scope of equivalence to the claims.

[0055] The tire tread measurement method according to this disclosure is not limited in any way to the embodiments described above, nor is it limited to the effects described above. The tire tread measurement method according to this disclosure can be modified in various ways without departing from its spirit. Furthermore, the various configurations adopted in the embodiments described above can be arbitrarily combined and adopted. [Explanation of Symbols]

[0056] 3 Tire tread, 4 Groove section, 5 Land section, 6 Measurement system, 7 Tire testing machine, 8 Imaging device, 9 Analysis device, 10 Tire, 13 Tread rubber, 15 Reinforcement cord member, 20 Measurement range, 30 See-through section, 51 Block, 51s Side section, 53 Side view, 54 Pattern (Grid pattern), CA Center area, SA Shoulder area

Claims

1. A processing step involves partially removing the tread rubber outside the measurement range set in the center region of the tire tread in the tire width direction, thereby forming a see-through portion that allows the measurement range to be viewed from the side of the tire. A patterning step of forming a pattern on the side surface of the land portion within the measurement range, A photographing step of photographing the pattern through the see-through portion, A method for measuring a tire tread, comprising an analysis step of performing an analysis of the tire tread based on an image including the captured pattern.

2. The tire tread measurement method according to claim 1, wherein the measurement range is defined as the range corresponding to one of the blocks forming a row of blocks provided in the center region.

3. The tire tread measurement method according to claim 2, wherein the pattern is formed on the outer side surface of the block in the tire width direction during the patterning step.

4. A method for measuring a tire tread according to claim 1, comprising removing the lateral portion of the land portion in the measurement range so as to form a surface perpendicular to the shooting direction in the shooting step, and forming the pattern on the outer side surface in the tire width direction of the land portion, including the exposed portion resulting from the removal.

5. In the patterning process, a grid pattern is formed as the pattern. The tire tread measurement method according to claim 1, wherein the analysis step involves measuring the surface strain of the land portion based on an image including the captured grid pattern.

6. The tire tread measurement method according to any one of claims 1 to 5, wherein the processing step involves removing the tread rubber to a depth position along the bottom of the shoulder longitudinal groove or to a depth position that is radially inward of the bottom of the groove from the bottom of the tire.

7. The tire tread measurement method according to any one of claims 1 to 5, wherein the processing step involves removing the tread rubber to the extent that the reinforcing cord members embedded in the tire tread are exposed in the see-through portion.

Images