JP6586845B2 - Tire wear evaluation method - Google Patents

Description

  The present invention relates to a tire wear evaluation method.

  As a form of uneven wear of a tire, heel and toe wear in which a land portion of a tread portion of a tire is worn unevenly in a tire circumferential direction is known. When heel and toe wear occurs in the tread portion, a step is generated in the tread portion in the tire circumferential direction. When a step is generated in the tread portion, a trouble event such as abnormal noise or vibration occurs in running of the tire. As the level difference generated in the tread portion increases, the malfunction phenomenon increases.

  As a method of measuring the state of uneven wear of a tire, a method using a step wear amount measuring device as disclosed in Patent Document 1 and an uneven wear amount measuring device as disclosed in Patent Document 2 are used. A method and a method using an apparatus as disclosed in Patent Document 3 are known. Further, as a method for evaluating uneven wear resistance, a method for evaluating heel and toe wear as disclosed in Patent Document 4 is known. By evaluating a failure phenomenon due to heel and toe wear, it is possible to determine the superiority or inferiority of tires having different specifications.

Japanese Utility Model Publication No. 61-139404 Japanese Patent No. 5552925 Japanese Patent No. 3274729 JP 2013-221847 A

  The amount of step formed in the tread portion by heel and toe wear changes in a complicated process involving the generation, growth and disappearance of the step due to heel and toe wear. That is, the progress of wear in the tread (the amount of wear, the amount of remaining groove, or the travel distance correlated with the amount of wear or the amount of remaining groove) changes in a simple process, whereas the step formed in the tread due to heel and toe wear The amount varies in a complex process with the progress of wear. By forming a step in the tread portion due to heel and toe wear, noise or vibration is induced, and the level of a malfunction event such as noise or vibration increases as the step amount increases. Therefore, it is important in evaluating the heel-and-toe wear performance to accurately grasp the maximum step amount in the transition of the step amount that changes in a complicated manner with the progress of wear.

  An object of an aspect of the present invention is to provide a tire wear evaluation method capable of accurately grasping the maximum level difference generated in the tread portion by heel and toe wear and accurately evaluating the heel and toe wear performance.

  According to the aspect of the present invention, at least the first measurement point and the second measurement point are set in the tire circumferential direction in the tread portion of the tire, the reference point for measurement is set, and at least three stages of the tread different from each other. Measuring the distance between the first measurement point in the tire radial direction and the reference point at each of the wear progress degrees of the portion, and the second measurement point in the tire radial direction at each of the wear progress degrees. Measuring the distance from the reference point; and based on the difference between the distance between the first measurement point and the reference point and the distance between the second measurement point and the reference point. Calculating a step amount between the first measurement point and the second measurement point in the step and estimating a maximum step amount in the wear history based on step amount data indicating the calculated step amount. DOO DOO, wear evaluation method of the tire comprising, the method comprising evaluating the Hiruandotu wear performance of the tire on the basis of the maximum step amount estimated is provided.

  According to the aspect of the present invention, at least the first measurement point and the second measurement point are set in the tire circumferential direction in the tread portion, the distance between the reference point and the first measurement point, and the distance between the reference point and the second measurement point. Since the step amount between the first measurement point and the second measurement point is calculated, the step amount generated in the tread portion due to the heel and toe wear can be known. The amount of difference in level between the first measurement point and the second measurement point is calculated at each of at least three different degrees of progress of wear. By acquiring step amount data indicating the step amount of at least three different stages of wear progress, it is possible to know the tendency of the change in the step amount according to the degree of wear progress based on the step amount data. Therefore, the maximum step amount indicating the maximum step amount can be estimated accurately and easily. Since the maximum level difference generated in the tread portion due to the heel and toe wear can be accurately grasped, the heel and toe wear performance can be accurately evaluated.

  In an aspect of the present invention, the tread portion includes a plurality of groove patterns provided in the tire circumferential direction, and is defined by a pitch defined by one groove pattern and two lug grooves adjacent in the tire circumferential direction. Defining an evaluation section in the tread portion based on at least one of the blocks, wherein the first measurement point and the second measurement point may be set in the tire circumferential direction in the evaluation section.

  An evaluation section is defined in the tread portion of the tire based on at least one of the pitch and the block, and the first measurement point and the second measurement point are set by setting the first measurement point and the second measurement point in the evaluation section. Based on the step amount, the heel and toe wear performance in the evaluation section is accurately evaluated, and the maximum step amount can be estimated with high accuracy.

  In an aspect of the present invention, the tread portion includes a first tread surface and a second tread surface disposed next to the first tread surface in the tire circumferential direction via a lug groove or a sipe, The first measurement point may be set on the first tread surface, and the second measurement point may be set on the second tread surface.

  By setting the first measurement point on the first tread surface and setting the second measurement point on the second tread surface, the first tread surface is based on the level difference between the first measurement point and the second measurement point. And after evaluating the heel and toe wear performance in the 2nd tread surface exactly, the maximum level | step difference amount can be estimated accurately. In addition, the wear form in which the step amount between the two predetermined sections of the tread portion separated by the lug groove or sipe is larger than the step amount in the predetermined section of the tread portion defined by the lug groove or sipe is accurately evaluated. can do.

  In the aspect of the present invention, at least one stage of the wear progression degree of the wear progression degree, except when the tire is new, and the cumulative value of the travel distance of the tire from the new article is 3000 [km] or less. The degree of wear progression at this time may be used.

  The timing at which the maximum step amount is reached is often when the wear rate of the tread portion is 30% or more and 50% or less. Therefore, in order to accurately estimate the maximum step amount, it is necessary to calculate the step amount before the wear rate reaches 30 [%]. When the tire is run under the running condition that the tire is most worn out in the general market, the wear rate may reach 30 [%] for a tire that progresses rapidly when it is run for 3000 [km]. Therefore, by calculating the step amount at least once when the cumulative value of the travel distance of the tire from a new article is 3000 km or less, the step amount at the initial stage of wear before the maximum step amount is calculated. be able to. Thereby, the heel and toe wear performance can be accurately evaluated.

  In the aspect of the present invention, the step amount indicating the maximum value among the calculated step amounts may be set as the maximum step amount.

  Thereby, the maximum step amount can be easily grasped.

  In the aspect of the present invention, the maximum step amount may be estimated by interpolating the calculated step amount.

  Thereby, the maximum level difference can be estimated with high accuracy. Function interpolation by the least square method may be used as the step amount interpolation. Alternatively, spline interpolation using a secondary spline or a tertiary spline may be used as the step amount interpolation. As the spline curve, a B-spline, a C-spline, a natural spline, or the like may be used.

  In an aspect of the present invention, the maximum step amount includes measuring the depth of the lug groove or sipe adjacent to the first and second measurement points, and based on the calculated step amount and the groove depth. May be estimated.

  By measuring the depth of the lug groove or sipe groove close to the measurement point, the degree of wear progress can be obtained with high accuracy. Therefore, the step amount between the first measurement point and the second measurement point can be calculated and the maximum step amount can be estimated with high accuracy.

  In the aspect of the present invention, the maximum step amount may be estimated using a polynomial including a growth term that is a function of the groove depth and a suppression term that is a function of the step amount at the groove depth.

  As the groove depth increases, the block tends to collapse, and the amount of the step is likely to grow. On the other hand, when the step amount increases, the contact pressure distribution of the block fluctuates, and the block is worn so that the step returns flat, and the growth of the step amount is suppressed or the step disappears. That is, the generation, growth, and disappearance of the step due to the heel and toe wear are determined by the balance between the groove depth and the step amount. The maximum step amount can be estimated with high accuracy by using a polynomial including the step growth term as a function of the groove depth and the step suppression term as a function of the step amount.

  According to the aspect of the present invention, there is provided a tire wear evaluation method capable of accurately grasping the maximum level difference generated in the tread portion due to heel and toe wear and accurately evaluating the heel and toe wear performance.

FIG. 1 is an enlarged cross-sectional view of a part of the tire according to the first embodiment. FIG. 2 is a schematic diagram illustrating an example of a processing apparatus according to the first embodiment. FIG. 3 is a flowchart illustrating an example of a procedure of the tire wear evaluation method according to the first embodiment. FIG. 4 is a diagram illustrating an example of a tread portion of the tire according to the first embodiment. FIG. 5 is a diagram illustrating an example of a tread portion of the tire according to the first embodiment. FIG. 6 is a schematic diagram for explaining measurement points according to the first embodiment. FIG. 7 is a schematic diagram for explaining measurement points according to the first embodiment. FIG. 8 is a schematic diagram for explaining measurement points according to the first embodiment. FIG. 9 is a schematic diagram for explaining measurement points according to the first embodiment. FIG. 10 is a diagram schematically illustrating an example of a measurement apparatus according to the first embodiment. FIG. 11 is a schematic diagram for explaining an example of a method for measuring the distance between the measurement point and the reference point according to the first embodiment. FIG. 12 is a schematic diagram for explaining an example of a method for measuring the distance between the measurement point and the reference point according to the first embodiment. FIG. 13 is a diagram schematically illustrating an example of an evaluation result of heel and toe wear according to the first embodiment. FIG. 14 is a diagram schematically illustrating an example of an evaluation result of heel and toe wear according to the first embodiment. FIG. 15 is a diagram schematically illustrating an example of an evaluation result of heel and toe wear according to the first embodiment. FIG. 16 is a diagram schematically illustrating an example of an evaluation result of heel and toe wear according to the first embodiment. FIG. 17 is a diagram for explaining processing for estimating the maximum level difference according to the first embodiment. FIG. 18 is a diagram for explaining processing for estimating the maximum level difference according to the first embodiment. FIG. 19 is a diagram schematically showing the relationship between the degree of progress of the heel and toe wear and the level difference between two measurement points. FIG. 20 is a diagram for explaining the wear rate. FIG. 21 is a diagram illustrating an operation when the maximum step amount is estimated based on the step amount calculated at the end of wear. FIG. 22 is a diagram showing a change in the level difference due to heel and toe wear. FIG. 23 is a schematic diagram for explaining measurement points according to the first embodiment. FIG. 24 is a schematic diagram for explaining an example of the reference height according to the first embodiment. FIG. 25 is a schematic diagram for explaining an example of the reference height according to the first embodiment. FIG. 26 is a diagram schematically illustrating an example of a reference point according to the first embodiment. FIG. 27 is a diagram schematically illustrating an example of a reference point according to the first embodiment. FIG. 28 is a schematic diagram for explaining measurement points according to the first embodiment. FIG. 29 is a diagram schematically illustrating an example of an evaluation section according to the second embodiment. FIG. 30 is a schematic diagram for explaining measurement points according to the second embodiment. FIG. 31 is a schematic diagram for explaining measurement points according to the second embodiment. FIG. 32 is a schematic diagram for explaining measurement points according to the second embodiment. FIG. 33 is a diagram schematically illustrating an example of an evaluation result of heel and toe wear according to the second embodiment. FIG. 34 is a diagram showing a tire wear evaluation method according to a third embodiment. FIG. 35 is a flowchart illustrating an example of a procedure of the tire wear evaluation method according to the fourth embodiment. FIG. 36 is a view for explaining the depth of the lug groove or sipe according to the fourth embodiment. FIG. 37 is a view for explaining the groove depth of the lug groove or sipe according to the fourth embodiment. FIG. 38 is a view for explaining the depth of the lug groove or sipe according to the fourth embodiment. FIG. 39 is a diagram for explaining processing for estimating the maximum level difference according to the fourth embodiment. FIG. 40 is a diagram for explaining processing for estimating the maximum level difference according to the fourth embodiment.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings, but the present invention is not limited thereto. The components of the embodiments described below can be combined as appropriate. Some components may not be used.

<First Embodiment>
A first embodiment will be described. FIG. 1 is an enlarged cross-sectional view of a part of a tire 1 according to this embodiment. FIG. 1 shows a meridional section passing through the rotation axis AX of the tire 1.

  The tire 1 is a passenger tire. The passenger car tire refers to a tire defined in Chapter A of JATMA YEAR BOOK 2015 (Japan Automobile Tire Association Standard). The tire 1 may be a small truck tire defined in Chapter B, or a truck and bus tire defined in Chapter C.

  The tire 1 is mounted on a rim of a vehicle wheel. The tire 1 rotates on the rotation axis AX and travels on the road surface while being mounted on the vehicle.

  In the following description, a direction parallel to the rotation axis AX of the tire 1 is appropriately referred to as a tire width direction, and a radial direction with respect to the rotation axis AX of the tire 1 is appropriately referred to as a tire radial direction. The rotation direction around AX is appropriately referred to as the tire circumferential direction.

  In the following description, the center of the tire 1 in the tire width direction is appropriately referred to as a tire center CL. The tire center CL includes a tire equator plane and a center line (tire equator line) where the tire equator plane and the surface of the tread portion 10 intersect on the surface of the tread portion 10 of the tire 1. The tire equator plane refers to a plane that passes through the center of the tire 1 in the tire width direction and is orthogonal to the rotation axis AX.

  Further, in the following description, a position far from or away from the tire center CL in the tire width direction is appropriately referred to as an outer side in the tire width direction, and a position close to or approaching the tire center CL in the tire width direction is appropriately determined as the tire width. In the tire radial direction, the position far from or away from the rotation axis AX is appropriately referred to as the tire radial direction outside, and in the tire radial direction, the position close to or approaching the rotation axis AX is appropriately adjusted in the tire radial direction. .

  The tire 1 includes a carcass part 2, a belt layer 3, a belt cover 4, a bead part 5, a tread part 10, and a side part 9. The tread portion 10 includes a tread rubber 6. The side portion 9 includes a side rubber 8.

  The carcass portion 2 is a strength member that forms the skeleton of the tire 1. The carcass part 2 functions as a pressure vessel when the tire 1 is filled with air. The carcass part 2 is supported by the bead part 5. The bead portions 5 are arranged on one side and the other side of the carcass portion 2 in the tire width direction. The carcass portion 2 is folded back at the bead portion 5. The carcass portion 2 includes a carcass cord and rubber that covers the carcass cord.

  The belt layer 3 is a strength member that maintains the shape of the tire 1. The belt layer 3 is disposed between the carcass portion 2 and the tread rubber 6. The belt layer 3 includes a belt cord and rubber covering the belt cord. The belt layer 3 includes a first belt ply 3A and a second belt ply 3B. The first belt ply 3A and the second belt ply 3B are laminated so that the cord of the first belt ply 3A and the cord of the second belt ply 3B intersect.

  The belt cover 4 is a strength member that protects and reinforces the belt layer 3. The belt cover 4 is disposed outside the belt layer 3 with respect to the rotation axis AX of the tire 1. The belt cover 4 includes a cover cord and rubber covering the cover cord.

  The bead portion 5 is a strength member that fixes both ends of the carcass portion 2. The bead portion 5 fixes the tire 1 to the rim. The bead portion 5 is a bundle of steel wires or a bundle of carbon steel.

  The tread rubber 6 forms a tread portion 10. The tread portion 10 includes a land portion 19 and a groove 20 disposed around the land portion 19. The land portion 19 includes a tread surface 24 (a contact surface) in contact with the road surface.

  The side rubber 8 forms the side portion 9. The side rubber 8 is disposed on each of one side and the other side of the tread rubber 6 in the tire width direction.

  FIG. 2 is a diagram illustrating an example of a processing device 50 capable of evaluating wear of the tire 1 according to the present embodiment. The processing device 50 includes a computer.

  The processing device 50 is connected to a measuring device 57 that can measure the wear state of the tire 1. The processing device 50 evaluates the wear performance of the tire 1 based on the wear state of the tire 1 measured by the measuring device 57.

  The processing device 50 includes a processing unit 50p, a storage unit 50m, and an input / output unit 53. The processing unit 50p and the storage unit 50m are connected via the input / output unit 53.

  The processing unit 50p includes a CPU (Central Processing Unit) and a memory such as a RAM (Random Access Memory). The processing unit 50p includes a calculation unit that performs calculation based on the measurement result of the measurement device 57, and an analysis unit that evaluates wear of the tire 1. The processing unit 50p is connected to the input / output unit 53.

  The storage unit 50m includes at least one of a volatile memory such as a RAM (Random Access Memory), a nonvolatile memory, a fixed disk device such as a hard disk device, a storage device such as a flexible disk and an optical disk. The storage unit 50m stores information for evaluating the wear of the tire 1. The storage unit 50m stores an evaluation result of wear of the tire 1. The storage unit 50m stores a computer program for evaluating the wear of the tire 1. The computer program can cause the processing device 50 to execute the method for evaluating the wear of the tire 1.

  The input / output unit 53 is connected to the measuring device 57 and the terminal device 54. The terminal device 54 is connected to the input device 55 and the output device 56. The input device 55 includes at least one of a keyboard, a mouse, and a microphone. The output device 56 includes at least one of a display device such as a display and a printer.

  The measurement result of the measuring device 57 is output to the processing unit 50p via the input / output unit 53. The processing unit 50p acquires the measurement result of the measurement device 57. The processing unit 50p evaluates the wear performance of the tire 1 using the measurement result of the measuring device 57. Note that at least part of the data for evaluating the wear of the tire 1 may be input from the input device 55.

  The evaluation result of the wear of the tire 1 performed in the processing unit 50p is output to the output device 56 via the input / output unit 53 and the terminal device 54. The output device 56 can output the evaluation result of the wear of the tire 1. When the output device 56 includes a display device, the display device can display an evaluation result of wear of the tire 1.

  Next, an example of the wear evaluation method for the tire 1 according to the present embodiment will be described. FIG. 3 is a flowchart showing a processing procedure of the wear evaluation method for the tire 1 according to the present embodiment. As shown in FIG. 3, the method for evaluating wear of the tire 1 includes a step of setting at least the first measurement point 43A and the second measurement point 43B in the tire circumferential direction in the tread portion 10 of the tire 1 (step SP10), and measurement. The distance between the first measurement point 43A and the reference point 44 in the tire radial direction is measured in each of the step of setting the reference point 44 (step SP20) and the degree of wear progress of the tread portion 10 in at least three different stages. The step of measuring the distance between the second measurement point 43B and the reference point 44 in the radial direction (step SP50), the distance between the first measurement point 43A and the reference point 44, and the distance between the second measurement point 43B and the reference point 44. The step of calculating the step amount between the first measurement point 43A and the second measurement point 43B in each of the degree of progress of wear based on the difference between (step SP60) A step of estimating the maximum step amount in the wear history based on the step amount data indicating the calculated step amount (step SP80), and a step of evaluating the heel and toe wear performance of the tire 1 based on the estimated maximum step amount ( Step SP90).

  The heel and toe wear means that the tread surface 24 of the land portion 19 of the tire 1 is worn unevenly in the tire circumferential direction. Heel and toe wear occurs due to the difference between the wear amount of the first and second wear parts of the tread surface 24. The first landing portion refers to a portion of the tread surface 24 that comes into contact with the road surface first when the tire 1 travels on the road surface while rotating about the rotation axis AX. The rear landing portion refers to a portion of the tread surface 24 that contacts the road surface later when the tire 1 travels on the road surface while rotating about the rotation axis AX.

  FIG. 4 is a diagram illustrating an example of the tread portion 10 of the tire 1 according to the present embodiment. As shown in FIG. 4, the tread portion 10 includes a land portion 19 and a groove 20 adjacent to the land portion 19. The groove 20 includes a main groove 21 extending in the tire circumferential direction, a lug groove 22 extending at least partially in the tire width direction, and a sipe 23 extending at least partially in the tire width direction. A land portion 19 is provided around the groove 20. The land portion 19 is provided between the groove 20 and the groove 20 adjacent to the groove 20.

  The main groove 21 is formed in the tire circumferential direction. At least a part of the main groove 21 is provided in the center portion 11 of the tread portion 10. The main groove 21 has a tread wear indicator inside. The treadwear indicator indicates the end of wear. The main groove 21 has a width of 4.0 [mm] or more and may have a depth of 5.0 [mm] or more. In the example shown in FIG. 4, the tire 1 has four main grooves 21.

  At least a part of the lug groove 22 is formed in the tire width direction. At least a part of the lug groove 22 is provided in the shoulder portion 12 of the tread portion 10. The shoulder portion 12 is disposed on each of one side and the other side of the center portion 11 in the tire width direction. The lug groove 22 has a width of 1.5 [mm] or more. The lug groove 22 may have a depth of 4.0 [mm] or more, and may partially have a depth of less than 4.0 [mm].

  At least a part of the sipe 23 is formed in the tire width direction. The sipe 23 is formed in the land portion 19. At least a part of the sipe 23 is provided on the shoulder portion 12 of the tread portion 10. The sipe 23 has a width of less than 1.5 [mm].

  The tread portion 10 has a plurality of groove patterns of the same or similar design provided in the tire circumferential direction. A region formed by one groove pattern is called a pitch 31 or a pattern element 31. That is, the pitch 31 refers to the minimum unit of pattern components when the same or similar groove pattern is repeated along the tire circumferential direction. In other words, the pitch 31 refers to a portion defined in the tread portion 10 of the tire 1 by one groove pattern when a plurality of groove patterns having the same or similar design are provided in the tire circumferential direction. The pitch 31 may be defined by two lug grooves 22 arranged in the tire circumferential direction. The pitch 31 may be partitioned by two sipes 23 arranged in the tire circumferential direction. The pitch 31 may be defined by a lug groove 22 having a first width arranged in the tire circumferential direction and a lug groove 22 having a second width different from the first width. The pitch 31 may be partitioned by lug grooves 22 and sipes 23 arranged in the tire circumferential direction.

  Further, the tread portion 10 has a plurality of blocks 32. The block 32 refers to a portion defined in the tread portion 10 of the tire 1 by two lug grooves 22 adjacent in the tire circumferential direction. The block 32 may be defined by lug grooves 22 having the same width adjacent to each other in the tire circumferential direction. The block 32 may be defined by a lug groove 22 having a first width adjacent to the tire circumferential direction and a lug groove 22 having a second width different from the first width.

  In the example shown in FIG. 4, one pitch 31 is defined by two lug grooves 22 arranged in the tire circumferential direction. The pitch 31 includes a part of the sipe 23 and the main groove 21. One block 32 is arranged for one pitch 31 in the tire circumferential direction.

  FIG. 5 is a diagram illustrating an example of the tread portion 10 of the tire 1 according to the present embodiment. In the example shown in FIG. 5, a main groove 21, a lug groove 22, and a sipe 23 are provided in the tread portion 10 of the tire 1. The tire 1 has two main grooves 21. The lug groove 22 includes a lug groove 22A and a lug groove 22B provided in the shoulder portion 12 on one side in the tire width direction, a lug groove 22C, a lug groove 22D, and a lug groove 22E provided in the center portion 11, and a tire. It includes a lug groove 22F and a lug groove 22G provided in the shoulder portion 12 on the other side in the width direction. The lug grooves 22A, lug grooves 22B, lug grooves 22C, lug grooves 22D, lug grooves 22E, lug grooves 22F, and lug grooves 22G have different designs. The design of the lug groove 22 includes at least one of the width, length, extending direction, number of corners, and angle of the corners of the lug groove 22. In the shoulder portion 12 on one side in the tire width direction, the lug grooves 22A and the lug grooves 22B are alternately arranged in the tire circumferential direction. In the center portion 11, the lug grooves 22C and the lug grooves 22D are alternately arranged in the tire circumferential direction. In the shoulder portion 12 on the other side in the tire width direction, three lug grooves 22G are arranged between the lug grooves 22F and the lug grooves 22F. The sipe 23 is provided on the shoulder portion 12 on the other side in the tire width direction. The sipe 23 is not provided on the shoulder portion 12 on one side in the tire width direction.

  In the example shown in FIG. 5, one pitch 31 is a part of the main groove 21, the lug groove 22A, the lug groove 22B, the lug groove 22C, the lug groove 22D, a part of the lug groove 22E, the lug groove 22F, and the lug groove 22G. , And Sipe 23. The pitch 31 includes the lug groove 22B, the lug groove 22C, and the lug groove 22F, and the lug groove 22B, the lug groove 22C, and the lug groove 22F that are adjacent to the lug grooves (22B, 22C, and 22F) in the circumferential direction. Stipulated in between. The block 32 includes a block 32A defined by lug grooves 22A and lug grooves 22B arranged in the tire circumferential direction, a block 32B defined by lug grooves 22B and lug grooves 22B arranged in the tire circumferential direction, and It includes a block 32C defined by lug grooves 22F and lug grooves 22G arranged in the tire circumferential direction, and a block 32D defined by lug grooves 22G and lug grooves 22G arranged in the tire circumferential direction.

  In the present embodiment, an evaluation section 41 is defined in the tread portion 10. The evaluation section 41 refers to a portion defined by the tread portion 10 of the tire 1 based on at least one of the pitch 31 and the block 32. The evaluation section 41 includes a heel and toe wear measurement target portion of the tire 1 and a heel and toe wear evaluation target portion of the tire 1.

  In the example shown in FIG. 4, the evaluation section 41 may be defined by one pitch 31. The evaluation section 41 may be defined by one block 32.

  In the example shown in FIG. 5, the evaluation section 41 may be defined by one pitch 31. The evaluation section 41 may be defined by the block 32A. The evaluation section 41 may be defined by the block 32B. The evaluation section 41 may be defined by the block 32C. The evaluation section 41 may be defined by the block 32D.

  In the present embodiment, a minimum section 42 is defined in the tread portion 10. The minimum section 42 is a portion defined inside the evaluation section 41 based on at least one of the lug groove 22 and the sipe 23. The minimum section 42 may be partitioned by two lug grooves 22 adjacent in the tire circumferential direction. The minimum section 42 may be partitioned by two sipes 23 adjacent in the tire circumferential direction. The minimum section 42 may be partitioned by the lug groove 22 and the sipe 23 that are adjacent to each other in the tire circumferential direction.

  In the example illustrated in FIG. 4, the minimum section 42 is defined between the lug groove 22 and the sipe 23 that are adjacent to each other in the tire circumferential direction inside the evaluation section 41.

  In the example illustrated in FIG. 5, the minimum section 42 is defined between the lug groove 22 </ b> A and the lug groove 22 </ b> B adjacent to each other in the tire circumferential direction inside the evaluation section 41. The minimum section 42 is defined between the lug groove 22 </ b> F and the sipe 23 that are adjacent to each other in the tire circumferential direction inside the evaluation section 41. The minimum section 42 is defined between the lug groove 22G and the sipe 23 adjacent to each other in the tire circumferential direction inside the evaluation section 41.

  A plurality of minimum sections 42 may be set in the tire circumferential direction in the evaluation section 41, or the same section as the evaluation section 41 may be used. In the example shown in FIG. 4, two minimum sections 42 are defined in the tire circumferential direction in the evaluation section 41. Note that three or more minimum sections 42 may be defined for one evaluation section 41. One minimum section 42 may be defined for one evaluation section 41.

  As shown in FIG. 4 or FIG. 5, a tire 1 is prepared in which a plurality of pitches 31 having the same or similar design are provided in the tire circumferential direction. The tire 1 is a test tire to be evaluated.

  The prepared tire 1 is a new tire. That is, the tire 1 to be prepared is a tire that has not yet traveled on the road surface and is not worn.

  Next, the evaluation section 41 of the tire 1 is defined based on at least one of the pitch 31 and the block 32. The definition of the evaluation section 41 is performed by the processing device 50.

  Next, a minimum section 42 is defined in the evaluation section 41. The definition of the minimum section 42 is performed by the processing device 50. A plurality of minimum sections 42 are defined in the tire circumferential direction in one evaluation section 41.

  Next, at least two measurement points 43 are set in the tire circumferential direction in the evaluation section 41 (step SP10). The measurement point 43 is set on the land portion 19 of the tread portion 10. As described above, the evaluation section 41 may include a plurality of minimum sections 42, and the evaluation section 41 and the minimum section 42 may be the same section.

  6, 7, 8, and 9 are diagrams illustrating an example of the measurement point 43 according to the present embodiment. FIG. 6 is a schematic diagram showing at least two measurement points 43 set in the tire circumferential direction in the evaluation section 41. FIG. 6 is a plan view of the evaluation section 41. FIG. 6 shows an example in which the evaluation section 41 and the minimum section 42 are the same section. The evaluation section 41 includes the tread surface 24 of the land portion 19. The positions of the plurality of measurement points 43 set in the tire circumferential direction in the evaluation section 41 are measured by the measurement device 57.

  The measurement points 43 include a first measurement point 43A set at one end of the evaluation section 41 in the tire circumferential direction and a second measurement point 43B set at the other end of the evaluation section 41. The first measurement point 43A is set at the first arrival part of the evaluation section 41. The second measurement point 43 </ b> B is set at the later part of the evaluation section 41.

  FIG. 7 is a schematic diagram showing the measurement points 43 set in each of the minimum sections 42 defined in the tire circumferential direction in one evaluation section 41. FIG. 7 is a plan view of the evaluation section 41. As shown in FIG. 7, the first measurement point 43A and the second measurement point 43B are set in the first minimum section 42A. The first measurement point 43A and the second measurement point 43B are set in the second minimum section 42B. In the example shown in FIG. 7, the positions of the measurement points 43 (43A, 43B) of the plurality of minimum sections 42 (42A, 42B) are measured.

  FIG. 8 is a schematic diagram showing measurement points 43 set in each of the three minimum sections 42 defined in the tire circumferential direction in one evaluation section 41. FIG. 8 is a plan view of the evaluation section 41. As shown in FIG. 8, the first measurement point 43A and the second measurement point 43B are set in the first minimum section 42A. The first measurement point 43A and the second measurement point 43B are set in the second minimum section 42B. The first measurement point 43A and the second measurement point 43B are set in the third minimum section 42C. In the example shown in FIG. 8, the positions of the measurement points 43 (43A, 43B) of the plurality of minimum sections 42 (42A, 42B, 42C) are measured.

  FIG. 9 is a schematic diagram showing an example in which the measurement point 43 is not set in at least one of the minimum sections 42 defined in the tire circumferential direction. FIG. 9 is a plan view of the evaluation section 41. As shown in FIG. 9, the first measurement point 43A and the second measurement point 43B are set in the first minimum section 42A. The first measurement point 43A and the second measurement point 43B are set in the third minimum section 42C. The measurement point 43 is not set in the second minimum section 42B. In the example shown in FIG. 9, the positions of the measurement points 43 (43A, 43B) of the first minimum section 42A and the third minimum section 42C are measured.

  Note that one minimum section 42 described with reference to FIGS. 7, 8, and 9 may be regarded as the evaluation section 41.

  Next, a reference point 44 for measurement is set (step SP20).

  Next, the counter k is set to “1” (step SP30).

  Next, the tire 1 mounted on the vehicle is caused to travel on the road surface (step SP40). By running on the road surface, the wear of the tire 1 proceeds. For example, the tire 1 may be mounted on a testing machine such as a drum testing machine and run.

  After the tire 1 has traveled a predetermined distance on the road surface, the position of the set measurement point 43 is measured by the measurement device 57. The predetermined distance is 2000 [km], for example. After the tire 1 is traveled until the travel distance from a new article reaches 2000 [km], the position of the measurement point 43 is measured by the measurement device 57.

  The measuring device 57 measures the distance between the set measurement point 43 and the reference point 44 (step SP50). The distance between the measurement point 43 and the reference point 44 is the distance between the measurement point 43 and the reference point 44 in the tire radial direction.

  FIG. 10 is a diagram schematically illustrating an example of the measurement device 57 according to the present embodiment. The measuring device 57 can measure the outer shape (profile) of the tire 1. The outer shape of the tire 1 includes the outer shape of the tread portion 10. The measuring device 57 optically measures the outer shape of the tire 1.

  The measurement device 57 includes a generation unit 571 that generates the measurement light ML, an emission unit 572 that emits the measurement light ML generated by the generation unit 571, and the measurement light ML that is irradiated to the tire 1 and reflected by the tire 1 is incident An incident part 573 that receives the measurement light ML from the incident part 573, and a support part 575 that supports the tire 1. The support portion 575 supports the tire 1 so as to be rotatable about the rotation axis AX. The positions of the generation unit 571 and the injection unit 572 are fixed. The positions of the incident portion 573 and the light receiving sensor 574 are fixed.

  The measurement light ML includes laser light. On the tread surface 24, the irradiation region of the measurement light ML has a spot shape. On the tread surface 24, the size of the irradiation region of the measurement light ML is substantially equal to the size of the measurement point 43.

  The measurement light ML emitted from the emission part 572 is applied to the measurement point 43 set on the tread surface 24 of the tread part 10. The measurement device 57 adjusts the relative position between the emission unit 572 and the tire 1 so that the measurement light ML emitted from the emission unit 572 is irradiated to the measurement point 43 of the tire 1. The measurement light ML is emitted from the emission unit 572 in a state where the relative position between the emission unit 572 and the tire 1 is adjusted. The measurement light ML emitted from the emission unit 572 is applied to the measurement point 43.

  The measurement device 57 adjusts the relative position between the emission portion 572 and the measurement point 43 of the tire 1 so that the measurement light ML irradiated to the measurement point 43 enters the tread surface 24 substantially perpendicularly. In addition, the measurement device 57 adjusts the relative position between the emission unit 572 and the measurement point ML so that the rotation axis AX is disposed on the extension line of the optical path of the measurement light ML emitted from the emission unit 572.

  At least a part of the measurement light ML irradiated to the measurement point 43 of the tire 1 is reflected at the measurement point 43. The measurement light ML reflected at the measurement point 43 enters the incident portion 573. The optical path of the measurement light ML emitted from the emission unit 572 and the optical path of the measurement light ML incident on the incident unit 573 substantially coincide with each other.

  The measuring device 57 has an optical member 576 including a half mirror (beam splitter). The emission part 572 and the incident part 573 include the surface of the optical member 576. In the present embodiment, the emission part 572 includes an incident part 573. The measurement light ML incident on the incident portion 573 is received by the light receiving sensor 574.

  The reference point 44 is set in the measuring device 57. The position of the reference point 44 is fixed. The reference point 44 is set at the incident portion 573. The reference point 44 may be set on the light receiving surface of the light receiving sensor 574.

  The measurement device 57 obtains the position of the measurement point 43 with respect to the reference point 44 based on the light reception result of the measurement light ML by the light reception sensor 574. The measuring device 57 obtains the relative position between the reference point 44 and the measuring point 43 using the measuring light ML.

  The measurement device 57 measures the distance between the measurement point 43 and the reference point 44 based on the light reception result of the light reception sensor 574. In the present embodiment, the distance between the measurement point 43 and the incident portion 573 is measured.

  The example in which the distance between one measurement point 43 set on the tire 1 and the reference point 44 is measured has been described above. As described above, at least two measurement points 43 are provided in the tire circumferential direction. The measurement device 57 sequentially arranges a plurality of measurement points 43 in the irradiation region of the measurement light ML, and measures the distance between each of the plurality of measurement points 43 and the reference point 44. The measurement device 57 uses the support portion 575 to rotate the tire 1 around the rotation axis AX, thereby sequentially arranging the plurality of measurement points 43 in the irradiation region of the measurement light ML.

  11 and 12 are schematic diagrams for explaining an example of a method for measuring the distance between the measurement point 43 (43A, 43B) and the reference point 44 according to the present embodiment. The position of the reference point 44 is fixed. On the tread surface 24, a first measurement point 43A and a second measurement point 43B are set.

  The tire 1 is supported by the support portion 575. The support portion 575 is driven so that the first measurement point 43A is arranged in the irradiation region of the measurement light ML. The measurement light ML is irradiated to the first measurement point 43A in a state where the first measurement point 43A is arranged in the irradiation region of the measurement light ML. Thereby, as shown in FIG. 11, the distance KA between the first measurement point 43 </ b> A and the reference point 44 is measured by the measurement device 57.

  After the distance KA between the first measurement point 43A and the reference point 44 is measured, the support portion 575 that supports the tire 1 is driven so that the second measurement point 43B is disposed in the irradiation region of the measurement light ML. . The measurement light ML is irradiated to the second measurement point 43B in a state where the second measurement point 43B is arranged in the irradiation region of the measurement light ML. As a result, as shown in FIG. 12, the distance KB between the second measurement point 43 </ b> B and the reference point 44 is measured by the measurement device 57.

  As shown in FIGS. 7, 8, and 9, when a plurality of minimum sections 42 are defined in the tire circumferential direction in the evaluation section 41, the measurement points 43 and the reference set for each of the plurality of minimum sections 42 The distance from the point 44 is measured.

  In the example shown in FIG. 7, the distance between the first measurement point 43A of the first minimum section 42A and the reference point 44, the distance between the second measurement point 43B of the first minimum section 42A and the reference point 44, the second The distance between the first measurement point 43A of the smallest section 42B and the reference point 44 and the distance between the second measurement point 43B and the reference point 44 of the second smallest section 42B are measured by the measuring device 57.

  In the example shown in FIG. 8, the distance between the first measurement point 43A of the first minimum section 42A and the reference point 44, the distance between the second measurement point 43B of the first minimum section 42A and the reference point 44, the second The distance between the first measurement point 43A of the smallest section 42B and the reference point 44, the distance between the second measurement point 43B of the second smallest section 42B and the reference point 44, and the first measurement point 43A of the third smallest section 42C. The distance between the reference point 44 and the distance between the second measurement point 43B of the third smallest section 42C and the reference point 44 is measured by the measurement device 57.

  In the example shown in FIG. 9, the distance between the first measurement point 43A of the first minimum section 42A and the reference point 44, the distance between the second measurement point 43B of the first minimum section 42A and the reference point 44, the third The distance between the first measurement point 43A of the minimum section 42C and the reference point 44 and the distance between the second measurement point 43B of the third minimum section 42C and the reference point 44 are measured by the measurement device 57.

  After the distance between each of the plurality of measurement points 43 (43A, 43B) and the reference point 44 is measured by the measurement device 57, the measurement result is output to the processing device 50. The processing unit 50p of the processing device 50 is based on the difference between the distance between the first measurement point 43A and the reference point 44 and the distance between the second measurement point 43B and the reference point 44 among the at least two measurement points 43. Then, the step amount between the first measurement point 43A and the second measurement point 43B is calculated (step SP60).

  As shown in FIG. 6, when the first measurement point 43A and the second measurement point 43B are set in the minimum section 42, the distance between the first measurement point 43A and the reference point 44, the second measurement point 43B, Based on the difference from the distance from the reference point 44, the step amount between the first measurement point 43A and the second measurement point 43B is calculated.

  As shown in FIG. 7, when the evaluation section 41 has two minimum sections 42 (42A, 42B), the distance between the first measurement point 43A and the reference point 44 for the minimum section 42A, the second measurement point 43B, and Based on the difference from the distance from the reference point 44, the step amount between the first measurement point 43A and the second measurement point 43B for the minimum section 42A is calculated. Further, based on the difference between the distance between the first measurement point 43A and the reference point 44 for the minimum section 42B and the distance between the second measurement point 43B and the reference point 44, the first measurement point 43A for the minimum section 42B and A step amount with respect to the second measurement point 43B is calculated.

  As shown in FIG. 8, when the evaluation section 41 has three minimum sections 42 (42A, 42B, 42C), the distance between the first measurement point 43A and the reference point 44 and the second measurement point for the minimum section 42A. Based on the difference between the distance between 43B and the reference point 44, the step amount between the first measurement point 43A and the second measurement point 43B for the minimum section 42A is calculated. Further, based on the difference between the distance between the first measurement point 43A and the reference point 44 for the minimum section 42B and the distance between the second measurement point 43B and the reference point 44, the first measurement point 43A for the minimum section 42B and A step amount with respect to the second measurement point 43B is calculated. Further, based on the difference between the distance between the first measurement point 43A and the reference point 44 for the minimum section 42C and the distance between the second measurement point 43B and the reference point 44, the first measurement point 43A for the minimum section 42C and A step amount with respect to the second measurement point 43B is calculated.

  In the example shown in FIG. 9, based on the difference between the distance between the first measurement point 43A and the reference point 44 and the distance between the second measurement point 43B and the reference point 44 for the minimum section 42A, A step amount between the first measurement point 43A and the second measurement point 43B is calculated. Further, based on the difference between the distance between the first measurement point 43A and the reference point 44 for the minimum section 42C and the distance between the second measurement point 43B and the reference point 44, the first measurement point 43A for the minimum section 42C and A step amount with respect to the second measurement point 43B is calculated.

  FIG. 13 is a diagram schematically illustrating a state in which a step is generated in the evaluation section 41 of the tread portion 10 due to heel and toe wear. FIG. 13 is a side sectional view of a part of the tire 1 in the evaluation section 41. FIG. 13 shows a cross section of the tire 1 in a plane orthogonal to the rotation axis AX.

  The level difference of the evaluation section 41 refers to a difference between the distance between the reference point 44 and the first arrival part and the distance between the reference point 44 and the rear arrival part in the tire radial direction. In other words, the level difference of the evaluation section 41 refers to the difference between the height of the first arrival part and the height of the rear arrival part. The step amount of the evaluation section 41 refers to the value of the step of the evaluation section 41.

  In the present embodiment, the reference point 44 is set in the measuring device 57 disposed outside the tire 1. For example, the reference point 44 may be set to the rotation axis AX. In this case, the level difference of the minimum section 42 refers to a difference between the distance between the rotation axis AX and the first arrival part and the distance between the rotation axis AX and the rear arrival part in the tire radial direction.

  If the difference between the wear amount of the first arrival part and the wear amount of the rear arrival part of the evaluation section 41 is large, the step amount of the evaluation section 41 increases. If the difference between the wear amount of the first arrival portion and the wear amount of the rear arrival portion of the evaluation section 41 is small, the step amount of the evaluation section 41 becomes small.

  Therefore, the distance KA between the first measurement point 43A set at the first arrival part of the evaluation section 41 and the reference point 44 is measured, and the second measurement point 43B and the reference point 44 set at the rear arrival part of the evaluation section 41 The distance KB is measured, and the difference (difference) between the distance KA and the distance KB is derived, whereby the state of the heel and toe wear of the tire 1 in the evaluation section 41 can be grasped.

  FIG. 14 is a diagram schematically showing an example of heel and toe wear in the evaluation section 41 having two minimum sections 42 (42A, 42B) as shown in FIG. FIG. 14 shows a partial cross section of the tire 1 parallel to a plane orthogonal to the rotation axis AX. As shown in FIG. 14, since the plurality of minimum sections 42 are defined in the evaluation section 41, the local heel and toe wear state of each of the minimum sections 42 (42A, 42B) can be grasped. Further, the state of heel and toe wear in the entire evaluation section 41 can also be grasped.

  FIG. 15 is a diagram schematically illustrating an example of an evaluation result of heel and toe wear in the evaluation section 41 having the three minimum sections 42 (42A, 42B, and 42C) as illustrated in FIG. FIG. 15 shows a partial cross section of the tire 1 parallel to a plane orthogonal to the rotation axis AX. As shown in FIG. 15, since a plurality of minimum sections 42 are defined in the evaluation section 41, the local heel and toe wear state of each of the minimum sections 42 (42A, 42B, 42C) can be grasped. Further, the state of heel and toe wear in the entire evaluation section 41 can also be grasped.

  FIG. 16 shows the evaluation results of the heel and toe wear when the measurement point 43 is not set in the minimum section 42B in the evaluation section 41 having the three minimum sections 42 (42A, 42B, 42C) as shown in FIG. It is a figure which shows an example typically. FIG. 16 shows a partial cross section of the tire 1 parallel to a plane orthogonal to the rotation axis AX. By not setting the measurement point 43 in the minimum section 42B, the man-hour of the measurement device 57 is reduced, and the time required for measurement is shortened. In addition, as shown in FIG. 16, among the three minimum sections 42 (42A, 42B, 42C) defined in the evaluation section 41, the measurement point 43 and the reference point 44 in the two minimum sections 42 (42A, 42C) Is measured and the heel and toe wear is evaluated, whereby the form of the heel and toe wear in the entire evaluation section 41 can be grasped.

  After the step amount between the first measurement point 43A and the second measurement point 43B of the tire 1 after traveling 2000 [km] is calculated, it is determined whether or not the counter k is equal to or greater than a specified value Kr (step SP70). ). In the present embodiment, the specified value Kr is “3”.

  After the tire 1 travels 2000 [km], the counter k is “1”, and it is determined “No” in step SP70. “1” is added to the counter k (step SP75). As a result, the counter k is set to “2”.

  After the counter k is set to “2”, the process of step SP40 is performed. That is, the tire 1 is mounted on the vehicle and travels on the road surface. By running on the road surface, the wear of the tire 1 further proceeds.

  After the tire 1 has traveled a predetermined distance on the road surface, the position of the set measurement point 43 is measured by the measurement device 57. After the tire 1 is traveled until the cumulative value of the travel distance from the new article reaches 4000 [km], the position of the measurement point 43 is measured by the measurement device 57 (step SP50). The measuring device 57 measures the distance between the first measurement point 43A and the reference point 44 in the tire radial direction and measures the distance between the second measurement point 43B and the reference point 44 in the tire radial direction.

  Based on the difference between the distance between the first measurement point 43A and the reference point 44 and the distance between the second measurement point 43B and the reference point 44, the processing device 50 determines whether the first measurement point 43A and the second measurement point 43B are Is calculated (step SP60).

  After the step amount between the first measurement point 43A and the second measurement point 43B of the tire 1 after traveling for 4000 [km] is calculated, it is determined whether or not the counter k is equal to or greater than the specified value Kr (step SP70). ).

  After the tire 1 travels 4000 [km], the counter k is “2”, and it is determined “No” in step SP70. “1” is added to the counter k (step SP75). As a result, the counter k is set to “3”.

  After the counter k is set to “3”, the process of step SP40 is performed. That is, the tire 1 is mounted on the vehicle and travels on the road surface. By running on the road surface, the wear of the tire 1 further proceeds.

  After the tire 1 has traveled a predetermined distance on the road surface, the position of the set measurement point 43 is measured by the measurement device 57. After the tire 1 is traveled until the cumulative value of travel distance from new is 6000 [km], the position of the measurement point 43 is measured by the measurement device 57 (step SP50). The measuring device 57 measures the distance between the first measurement point 43A and the reference point 44 in the tire radial direction and measures the distance between the second measurement point 43B and the reference point 44 in the tire radial direction.

  The processing unit 50p of the processing device 50 uses the first measurement point 43A and the second measurement point based on the difference between the distance between the first measurement point 43A and the reference point 44 and the distance between the second measurement point 43B and the reference point 44. A step amount with respect to the measurement point 43B is calculated (step SP60).

  After the step amount between the first measurement point 43A and the second measurement point 43B of the tire 1 after traveling 6000 [km] is calculated, it is determined whether or not the counter k is equal to or greater than a specified value Kr (step SP70). ).

  After the tire 1 travels 6000 [km], the counter k is “3”, and it is determined as “Yes” in Step SP70.

  The distance between the first measurement point 43A and the reference point 44 in the tire radial direction is measured when the cumulative value of the travel distance of the tire 1 from the new time is 2000 [km], 4000 [km], and 6000 [km]. The process of measuring the distance between the second measurement point 43B and the reference point 44 in the tire radial direction, the distance between the first measurement point 43A and the reference point 44, and the second measurement point 43B and the reference point 44. After the processing for calculating the step amount between the first measurement point 43A and the second measurement point 44B based on the difference from the distance is performed, the processing device 50 is based on the step amount data indicating the calculated step amount. Then, the maximum step amount in the wear history is estimated (step SP80).

  FIG. 17 is a diagram for explaining processing for estimating the maximum level difference according to the present embodiment. FIG. 17 is a diagram illustrating a relationship between the cumulative value of the travel distance of the tire 1 from when it is new and the level difference S between the first measurement point 43A and the second measurement point 43B calculated based on the cumulative value of each travel distance. It is. In the graph shown in FIG. 17, the horizontal axis represents the cumulative value of the travel distance of the tire 1 from the new time, and the vertical axis represents the first measurement point 43A and the second measurement point calculated for the cumulative value of each travel distance. The step amount S with respect to 43B is shown.

  As the cumulative value of the travel distance from a new article increases, the wear of the tire 1 (heel and toe wear) proceeds. Therefore, the travel distance from the time of a new article is synonymous with the degree of progress of wear of the tread portion 10 of the tire 1. The cumulative value of the travel distance is the first distance (2000 [km] in this example) indicates that the wear progress is the first progress. The cumulative value of the travel distance is the second distance that is longer than the first distance (in this example, 4000 [km]) is the second degree of progress in which the degree of progress of wear is higher than the first degree of progress. Indicates that there is. The cumulative value of the travel distance is the third distance longer than the second distance (in this example, 6000 [km]) is the third progress degree in which the wear progress degree is progressing more than the second progress degree. Indicates that there is.

  In the present embodiment, a tire and a process for measuring the distance between the first measurement point 43 </ b> A and the reference point 44 in the tire radial direction at each of the three stages of wear progress of the tread portion 10 (cumulative value of travel distance). Processing for measuring the distance between the second measurement point 43B and the reference point 44 in the radial direction is performed. Based on the difference between the distance between the first measurement point 43A and the reference point 44 and the distance between the second measurement point 43B and the reference point 44, the first measurement point 43A in each of the three stages of wear progress of the tread portion 10. And a process of calculating a step amount S between the second measurement point 43B and the second measurement point 43B.

Step amount between the first measurement point 43A and the second measurement point 43B when (in this example 2000 [km]) accumulated value first distance is the running distance of the _{S a.} Step amount between the second measurement point 43A and the second measurement point 43B when the accumulated value (in this example 4000 [km]) the second distance is the running distance of the _{S b.} Step amount between the first measurement point 43A and the second measurement point 43B when (in this example 6000 [km]) accumulated value third distance is the running distance of the _{S c.}

FIG. 17 is a plot of the step amounts S (S _a , S _b , S _c ) for each of the three stages of wear progress of the tread portion 10.

The processing device 50 estimates the maximum step amount _Smax in the wear history based on the step amount data indicating the calculated three step amounts S _a , S _b , and S _c . In the present embodiment, the processing device 50 estimates the maximum step amount S _max by interpolating the calculated three step amounts S _a , S _b , and S _c . As the interpolation of the step amounts S _a , S _b , and S _c , function approximation by the least square method may be used. Alternatively, spline interpolation using a quadratic spline or a cubic spline may be used as the step amount interpolation of the step amounts S _a , S _b , and S _c . As the spline curve, a B-spline, a C-spline, a natural spline, or the like may be used.

For example, (1) as shown in the expression for the n-th order function indicating a step amount S (n = 2, 3, 4 ...), be calculated coefficients a _n, such as residual is minimized by the least square method Good. In the formula (1), x ^{i (} i = 1, 2,..., N) is a cumulative value of the travel distance of the tire 1 from the new time.

FIG. 18 is a view for explaining processing for estimating the maximum step amount _{Smax according} to the present embodiment. FIG. 18 is a diagram illustrating an approximate curve representing the step amount S obtained by interpolating the three step amounts S _a , S _b , and S _c . By obtaining the approximate curve, the maximum step amount S _max indicating the maximum value of the step amount S between the first measurement point 43A and the second measurement point 43B is estimated. Based on the estimated maximum step _Smax , the heel and toe wear performance of the tire 1 is evaluated (step SP90).

As an evaluation of the heel and toe wear performance of the tire 1, the reference maximum step amount obtained from the reference tire and the maximum step amount S _max of the tire 1 may be compared. Furthermore, specifications are evaluated each of the different tire 1, the maximum step of the first tire 1 S _max and the maximum step amount S _max of the second tire 1 may be compared. Thereby, it is possible to know which tire 1 of which specification reaches the maximum step amount S _max with which traveling distance.

By evaluating the heel and toe wear performance of the tire 1 based on the estimated maximum step amount _Smax , it is possible to estimate the level of a malfunction event such as abnormal noise (noise) or vibration.

Even if it is evaluated how the level of the failure event due to the heel and toe wear performance changes with the progress of wear based on the travel distance that reaches the maximum step amount _Smax and the transition of the estimated step amount. Good. In the example shown in FIG. 18, when the cumulative value of the travel distance of the tire 1 from the new article is about 4500 [km], the step amount S between the first measurement point 43A and the second measurement point 43B is the maximum step amount S. Estimated to be _max . When the cumulative value of the travel distance of the tire 1 from the new time when the maximum step amount S _max is about 4500 [km], the level of a malfunction event such as abnormal noise or vibration in the travel of the tire 1 becomes maximum. Can be evaluated. Further, when the cumulative value of the travel distance of the tire 1 from when it is new exceeds about 4500 [km], it can be evaluated that the step amount S is gradually reduced and the malfunction event is also gradually reduced.

As described above, according to the present embodiment, at least the first measurement point 43A and the second measurement point 43B are set in the tire circumferential direction in the tread portion 10, and the distance between the reference point 44 and the first measurement point 43A and Since the distance between the reference point 44 and the second measurement point 43B is measured and the step amount S between the first measurement point 43A and the second measurement point 43B is calculated, the step amount generated in the tread portion 10 due to heel and toe wear It is possible to accurately know the state of S and heel and toe wear. The calculation of the step amount S between the first measurement point 43A and the second measurement point 43B is performed at each of at least three different degrees of wear progress. By acquiring step amount data indicating the step amount S of at least three different levels of wear progress, knowing the tendency of the change in the step amount S according to the progress of heel and toe wear based on the step amount data. Can do. Therefore, the maximum step amount _Smax indicating the maximum value of the step amount S can be estimated accurately and easily. Since the maximum level difference _Smax generated in the tread portion 10 due to heel and toe wear can be accurately grasped, the heel and toe wear performance can be evaluated with high accuracy. As described above, the degree of progress of wear may be a wear amount or a travel distance.

Further, according to the present embodiment, the evaluation section 41 is defined in the tread portion 10 of the tire 1 based on at least one of the pitch 31 and the block 32, and the first measurement point 43A and the second measurement point 43B are set in the evaluation section 41. Is set. Accordingly, the state of the heel and toe wear performance in the evaluation section 41 is accurately evaluated based on the step amount S between the first measurement point 43A and the second measurement point 43B, and the maximum step amount _Smax is accurately estimated. be able to.

In the present embodiment, the maximum step amount S _max is estimated by interpolating the calculated at least three step amounts S. Thereby, the maximum step amount _Smax can be estimated with high accuracy.

Further, in this embodiment, at least one stage of the wear progression degree of the wear progression degree is excluding the time when the tire 1 is new, and the cumulative value of the travel distance of the tire from the new time is 3000 [km] or less. It is the degree of wear progress. In this example, the step amount _Sa is calculated when the cumulative value of the travel distance of the tire from the new article is 2000 [km].

  FIG. 19 is a diagram schematically illustrating a general relationship between the degree of progress of heel and toe wear and the amount of a step between two measurement points. As shown in FIG. 19, the step amount S increases rapidly at the initial stage of wear of the tread portion 10, the step amount S decreases substantially constant or gently at the middle stage of wear, and the step amount S decreases gradually at the end stage of wear. The growth rate of the step amount S in the early stage of wear is faster than the decrease rate of the step amount S in the middle stage and the last stage of wear. The growth rate of the step amount S is an increasing rate of the step amount S with respect to the progress degree of wear. The decrease rate of the step amount S is a decrease rate of the step amount S with respect to the degree of wear progress.

Further, the growing step amount S tends to reach the maximum step amount S _max in the middle stage of wear. This is because the groove depth D of the groove 20 of the tread portion 10 is deep at the initial stage of wear of the tire 1, so that the grounded block 32 is greatly deformed so that it falls down during the running of the tire 1, and the step is in the growth process. In the middle stage of wear of the tire 1, the groove depth D becomes shallow due to the progress of wear, and the collapse of the block 32 is reduced, so that the growth of the step converges and reaches the maximum step amount S _max . Thereby, it is considered that the maximum step amount _Smax is reached in the middle stage of wear.

Further, the growth rate of the step amount S and the maximum step amount S _max in the initial stage of wear of the tire 1 are affected by the specifications of the tire 1. The specifications of the tire 1 are factors that determine the tire structure related to cornering stiffness and braking / driving stiffness, and the ease of falling down (ease of deformation, rigidity) of the grounded block 32 in the running of the tire 1 such as a tread pattern. Including. In order to accurately estimate the maximum step amount _Smax and evaluate the heel and toe wear performance according to the specifications of the tire 1, the growth rate of the step amount S is fast, and the step amount at the initial stage of wear before reaching the maximum step amount _Smax. It is preferable to calculate S.

The timing at which the maximum step amount _Smax is reached is often when the wear rate of the tread portion 10 is not less than 30 [%] and not more than 50 [%]. Therefore, in order to accurately estimate the maximum step amount _Smax , it is necessary to calculate the step amount S before the wear rate reaches 30 [%]. Here, the wear rate, as shown in FIG. 20, the size of the H _n in the tire radial direction of the block 32 at the time of a new _tire radial dimension of a portion of the block 32 which has lost by wear (wear amount) H _e when it _was, refers to a value of _H e / H _n. Definition of wear amount H _e is based on the definition of the wear progress. If wear progress (the amount of wear of the evaluation section 41) is defined by the maximum wear amount of the evaluation zone 41 (block 32), the wear amount H _e for defining the wear rate, the maximum size of the lost block 32 It is defined by _Hemax . If wear progress (the amount of wear of the evaluation section 41) is defined by the minimum amount of wear of the block 32 (Evaluation section 41), the wear amount H _e for defining the wear rate, the minimum size of the lost block 32 It is defined by _Hemin . Wear progress (amount of wear evaluation section 41) is, as defined by the mean value between the maximum wear amount and minimum wear amount of the block 32 (Evaluation section 41), the wear amount H _e for defining a wear rate The average value of the maximum dimension H _emax and the minimum dimension H _emin of the lost block 32 is defined.

The present inventor possesses statistical data that the tire wear rate is often 30 [%] when the tire is run 3000 [km] under the most severe running conditions (the most worn running conditions) assumed in the general market. . Therefore, the step amount S is calculated at least once when the cumulative value of the travel distance of the tire 1 from the new time is 3000 [km] or less, so that at the initial stage of wear before the maximum step amount S _max is reached. The step amount S can be calculated. Thereby, the heel and toe wear performance can be accurately evaluated.

For example, even if the step amount S at the end of wear after the travel distance of the tire 1 has reached a long distance is calculated, if the step amount S at the initial stage of wear is not calculated, as shown in FIG. _Max cannot be accurately captured. That is, in order to accurately capture the maximum step amount S _max , at least one of the three calculation processes for calculating the step amount S is performed at a stage before the maximum step amount S _max is reached. Need to be implemented.

That is, as shown in FIG. 22, the transition of the step amount S due to the heel and toe wear is changed into three periods of “a step amount growth process before reaching the peak”, “near the peak”, and “a step amount decreasing process after reaching the peak”. When classified, in order to accurately estimate the maximum step amount S _max , it is necessary to use at least the step amount S calculated in the “step amount growth process before reaching the peak”.

It is more preferable to estimate the maximum step amount S _max by using the step amount S calculated in “near the peak” in addition to the step amount calculated in the “step amount growth process before reaching the peak”. As described above, “near the peak” can be regarded as a point in time when the wear rate reaches 30 [%] or more and 50 [%] or less.

Furthermore, in order to more accurately estimate the maximum step amount S _max , the step amount S is calculated at least twice at the timing of “near the peak”, and the maximum step amount S _max is estimated based on the calculated step amount S. More preferably.

Further, in addition to the step amount S calculated in the “step amount growth process before reaching the peak” and the step amount S calculated in “near the peak”, it was calculated in the “step amount decreasing process after reaching the peak”. The step amount S may also be used to estimate the maximum step amount S _max . The “step difference decreasing process after reaching the peak” can be regarded as a point in time when the wear rate reaches 60% or more and 80% or less.

In addition, you may use the following (2) Formula as an estimation method of the travel distance which reaches | attains a predetermined wear rate. Equation (2) represents the estimated travel distance M _p of the tire 1 from the new time for the wear rate to reach a [%].

In the equation (2), M _l represents the cumulative value of the travel distance from the new time when the latest step amount S in the travel history is calculated, and W _l represents the wear rate at that time.

From the above, when the estimated travel distance of the tire 1 from the new time to reach a predetermined wear rate a [%] or more and b [%] or less is M _p , the condition of equation (3) is satisfied.

The step amount S at the estimated travel distance M _p may be calculated, and the maximum step amount S _max may be estimated based on the calculated step amount S.

Even in the early stage of wear, when the step amount S is calculated when the travel distance of the tire is too short, there is a possibility that the maximum step amount S _max cannot be accurately estimated. For this reason, it is preferable that the step amount S is calculated when the cumulative value of the travel distance of the tire from a new article is 1000 [km] or more and 3000 [km] or less.

In the above-described embodiment, the calculation of the step amount S between the first measurement point 43A and the second measurement point 43B of the tire 1 when new is not performed. The level difference S between the first measurement point 43A and the second measurement point 43B of the tire 1 when new is calculated, and the maximum level difference is obtained using at least three level differences S including the calculated level difference S when new. The quantity S _max may be estimated. The same applies to the following embodiments.

In the above-described embodiment, the step amount S between the first measurement point 43A and the second measurement point 43B is calculated for each of the three different stages of wear progress. The step amount S between the first measurement point 43A and the second measurement point 43B may be calculated for each of at least five different degrees of wear progress. By calculating the step amount S between the first measurement point 43A and the second measurement point 43B at each of at least five different levels of wear progress, the maximum step amount _Smax can be estimated more accurately. The same applies to the following embodiments.

  In the above-described embodiment, the positions of the plurality of measurement points 43 are substantially the same in the tire width direction. As shown in FIG. 23, the positions of the plurality of measurement points 43 may be different in the tire width direction. When the positions of the plurality of measurement points 43 are different in the tire width direction, the distance between the measurement point 43 on the most side and the measurement point 43 on the other side is preferably 5 [mm] or less. The same applies to the following embodiments.

  In the above-described embodiment, the reference point 44 is set to the measuring device 57 or the rotation axis AX. As shown in FIG. 24, a reference point 44 in the tire radial direction in measurement may be set at the apex of the land portion 19 of the tread portion 10. When the tire 1 travels, a vertex (protrusion) as shown in FIG. 24 may be formed in the land portion 19 of the tire 1. The apex of the land portion refers to a point having the largest distance from the rotation axis AX in the tire radial direction on the tread surface 24 of the land portion 19.

  A reference point 44 is set at the apex of the land portion 19 of the tread portion 10, and the distance between the position of the reference point 44 in the tire radial direction and each of the first measurement point 43A and the second measurement point 43B is measured. A step amount S between the first measurement point 43A and the second measurement point 43B in the radial direction is clearly calculated. Therefore, the heel and toe wear performance in the evaluation section 41 of the tire 1 can be accurately evaluated.

  As shown in FIG. 25, a reference height may be set based on the vertices (reference points 44) of a plurality of land portions. In the example shown in FIG. 25, the reference height includes a virtual plane connecting the vertices (reference points 44) of a plurality (three) of land portions 19 arranged in the tire circumferential direction. The virtual surface of the reference height includes an arc-shaped surface arranged around the rotation axis AX.

  As shown in FIGS. 26 and 27, the reference point 44 may include a first reference point 44A and a second reference point 44B set at different positions in the tire radial direction. In the example shown in FIG. 26, the first reference point 44 </ b> A is set on the measuring device 57, and the second reference point 44 </ b> B is set on the rotation axis AX of the tire 1. In the example shown in FIG. 27, the first reference point 44A is set in the measuring device 57, and the second reference point 44B is set at a position corresponding to the surface of the tread portion 10 of the new tire 1. The position of the first reference point 44A and the position of the second reference point 44B are fixed. The relative position between the first reference point 44A and the second reference point 44B does not change.

  The measurement device 57 measures the distance between the measurement point 43 and the first reference point 44A in the tire radial direction in a state where the first reference point 44A, the measurement point 43, and the second reference point 44B are arranged on the same straight line. To do. The measurement result of the measurement device 57 is output to the processing device 50. The processing device 50 calculates the position of the measurement point 43 in the tire radial direction with respect to the first reference point 44A based on the difference in distance between the measurement point 43 and the first reference point 44A. The processing device 50 calculates the position of the measurement point 43 in the tire radial direction with respect to the second reference point 44B based on the difference in distance between the first reference point 44A and the second reference point 44B. For example, the measurement device 57 measures the distance L1 between the measurement point 43 and the first reference point 44A. Thereby, the position of the measurement point 43 in the tire radial direction with respect to the first reference point 44A is calculated. The position of the first reference point 44A and the position of the second reference point 44B are fixed. The distance L between the first reference point 44A and the second reference point 44B is known data. Data indicating the distance L between the first reference point 44A and the second reference point 44B is stored in the storage unit 50m. The processing device 50 includes a distance L between the first reference point 44A and the second reference point 44B stored in the storage unit 50m, and a distance between the measurement point 43 measured by the meter-side device 57 and the first reference point 44A. Based on L1, the distance L2 between the second reference point 44B and the measurement point 43 can be calculated. Thereby, the position of the measurement point 43 in the tire radial direction with respect to the second reference point 44B is calculated. Based on the difference between the position of the first measurement point 43A in the tire radial direction with respect to the second reference point 44B and the position of the second measurement point 43B in the tire radial direction with respect to the second reference point 44B, the processing device 50 A step amount between the measurement point 43A and the second measurement point 43B is calculated.

  According to the example described with reference to FIGS. 26 and 27, not only the positional relationship between the first reference point 44A and the measurement point 43 but also the positional relationship between the second reference point 44B and the measurement point 43 is obtained. Therefore, the heel and toe wear performance can be more accurately evaluated. For example, after quantifying the wear state at the measurement point 43, the relationship between the wear state and the step amount can be evaluated. Further, as shown in FIG. 26, the rotation axis AX and the tread portion of the tire 1 after the tread portion 10 of the tire 1 is worn by setting the second reference point 44B to the rotation axis AX of the tire 1. The distance to the 10 surfaces can be determined. Further, as shown in FIG. 27, the second reference point 44B is set at a position corresponding to the surface of the tread portion 10 of the new tire 1, whereby the actual amount of wear of the tire 1 since the new tire 1 is obtained. be able to. The relationship between the absolute value of the wear amount of the tire 1 and the step amount between the first measurement point 43A and the second measurement point 43B can be evaluated.

  In the above-described embodiment, two measurement points 43 (first measurement point 43A and second measurement point 43B) are set in the minimum section 42 (evaluation section 41). Further, the first measurement point 43A is set as the first arrival part of the minimum section 42 (evaluation section 41), and the second measurement point 43B is set as the last arrival part of the minimum section 42 (evaluation section 41).

  As shown in FIG. 28, even if three measurement points 43 (first measurement point 43A, second measurement point 43B, and third measurement point 43C) are set in the tire circumferential direction in the minimum section 42 (evaluation section 41). Good. The first measurement point 43A is set, for example, at the first arrival part of the minimum section 42. The second measurement point 43B is set at, for example, the rear arrival part of the minimum section 42. The third measurement point 43C is disposed between the first measurement point 43A and the second measurement point 43B in the tire circumferential direction.

  By setting the third measurement point 43C, the shape of the surface of the land portion after wear can be evaluated in more detail as indicated by the line Sa, the line Sb, and the line Sc in FIG. For example, even if the amount of step difference between the first measurement point 43A and the second measurement point 43B is the same, various forms of uneven wear can be evaluated by measuring the measurement height of the third measurement point 43C.

  For example, as shown by line Sa, there is an uneven wear form that linearly slopes from the first arrival side to the rear arrival side, and there is also an uneven wear form that is convex on the surface side of the tire 1 as shown by line Sb. There is also a partial wear form in which the surface of the tire 1 becomes concave as indicated by the line Sc. In addition to the first measurement point 43A and the second measurement point 43B, a third measurement point 43C is set, and the step amount is calculated based on the at least three measurement points 43 (43A, 43B, 43C). The wear form can be accurately grasped, and the step amount can be accurately evaluated. Note that three or more measurement points 43 may be set in order to capture the uneven wear mode in more detail.

  Of the first measurement point 43A, the second measurement point 43B, and the third measurement point 43C, the measurement point 43 having the highest measurement height (for example, the first measurement point 43A) and the measurement point having the lowest measurement height. By calculating the step amount with respect to 43 (for example, the second measurement point 43B), the step amount can be accurately evaluated based on the uneven wear mode in the minimum section 42. By calculating the step amount between the adjacent measurement points 43 (for example, the step amount between the third measurement point 43C and the second measurement point 43B), it is possible to grasp a local uneven wear portion, and to determine the step amount. Can be evaluated accurately.

<Second Embodiment>
A second embodiment will be described. In the following description, the same or equivalent components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is simplified or omitted.

  In the above-described embodiment, the first measurement point 43A and the second measurement point 43B are set in one evaluation section 41 or the minimum section 42. In the present embodiment, the first tread surface 24 of the first land portion 19 and the tread surface 24 of the second land portion 19 that are separated in the tire circumferential direction via the lug groove 22 or the sipe 23, respectively. An example in which the measurement point 43A and the second measurement point 43B are set will be described. In the following description, the lug groove 22 and the sipe 23 are collectively referred to as a lateral groove 202 as appropriate.

  FIG. 29 is a diagram schematically illustrating an example of two tread surfaces 24 and measurement points 43 separated by a lateral groove 202. As shown in FIG. 29, the two tread surfaces 24 are arranged in the tire circumferential direction. The transverse groove 202 is provided between the two tread surfaces 24. In the following description, of the two tread surfaces 24 separated by the lateral grooves 202, the tread surface 24 disposed adjacent to one of the lateral grooves 202 in the tire circumferential direction is appropriately referred to as a first tread surface 241 and the other The adjacent tread surface 24 is appropriately referred to as a second tread surface 242.

  The second tread surface 242 is disposed next to the first tread surface 241 in the tire circumferential direction via the lateral groove 202 including the lug groove 22 or the sipe 23. The lateral groove 202 is provided between the first tread surface 241 and the second tread surface 242.

  Each of the first tread surface 241 and the second tread surface 242 has an end portion 440 disposed on one side in the tire circumferential direction and an end portion 450 disposed on the other side. An end 450 of the first tread surface 241 forms a boundary with the lateral groove 202. The end 440 of the second tread surface 242 forms a boundary with the lateral groove 202. A lateral groove 202 is provided between the end 450 of the first tread surface 241 and the end 440 of the second tread surface 242.

  In the example shown in FIG. 29, the evaluation section 41 is defined by each of the first tread surface 241 and the second tread surface 242. The evaluation section 41 includes a first evaluation section 411 defined by the first tread surface 241 and a second evaluation section 412 defined by the second tread surface 242.

  The measurement point 43 is defined on each of the first tread surface 241 and the second tread surface 242. In the following description, the measurement point 43 set on the first tread surface 241 is appropriately referred to as a first measurement point 43A, and the measurement point 43 set on the second tread surface 242 is appropriately referred to as a second measurement point 43B. Called.

  The first measurement point 43 </ b> A is defined at the end 450 of the first tread surface 241. The second measurement point 43 </ b> B is defined at the end 440 of the second tread surface 242. In the present embodiment, the end portion 440 is a first arrival portion of the tread surface 24. The end portion 450 is a rear wearing portion of the tread surface 24.

  Each of the first measurement point 43 </ b> A defined at the end 450 which is the rear part of the first tread surface 241 and the second measurement point 43 </ b> B defined at the end 440 which is the first part of the second tread surface 242. Is measured by the measuring device 57.

  30, FIG. 31, and FIG. 32 are diagrams illustrating an example of the measurement point 43 according to the present embodiment.

  As shown in FIG. 30, the measurement point 43 may be defined in a first arrival area 48 including an end 440 that is a first arrival portion. The measurement point 43 may be defined in a later arrival area 49 including the end 450 that is the later arrival part. The first arrival region 48 is defined between an end portion 440 of the tread surface 24 in the tire circumferential direction and a portion 46 on the center side of the tread surface 24 with respect to the end portion 440 in the tire circumferential direction. The rear landing area 49 is defined between an end portion 450 of the tread surface 24 in the tire circumferential direction and a portion 47 closer to the center of the tread surface 24 than the end portion 450 in the tire circumferential direction.

  In the tire circumferential direction, the distance between the end portion 440 and the portion 46 and the distance between the end portion 450 and the portion 47 are each set to 10 [mm] or less. That is, the measurement point 43 is defined in a first arrival region 48 of the tread surface 24 within 10 [mm] from the end 440 in the tire circumferential direction. Further, the measurement point 43 is defined in a part of the rear wearing region 49 of the tread surface 24 within 10 [mm] from the end 450 in the tire circumferential direction. The distance between the end portion 440 and the portion 46 and the distance between the end portion 450 and the portion 47 are preferably set to 5 [mm] or less. The distance between the end portion 440 and the portion 46 is the dimension of the first arrival region 48 in the tire circumferential direction. The distance between the end portion 450 and the portion 47 is a dimension of the rearward wearing region 49 in the tire circumferential direction.

  The measurement point 43 is determined in the first arrival area 48 and the measurement point 43 is determined in the rear arrival area 49, whereby the wear amount at the end portion 440 of the tread surface 24 or the vicinity thereof and at the end portion 450 of the tread surface 24 or the vicinity thereof. Can be measured. Therefore, it is possible to measure the respective wear amounts of the first arrival area 48 and the rear arrival area 49 separated by the lateral groove 202. Therefore, the form of the step between the first tread surface 241 and the second tread surface 242 generated by the heel and toe wear and the amount of the step can be accurately evaluated.

  Further, the amount of wear is measured while avoiding the central portion of the tread surface 24 in the tire circumferential direction. Thereby, it is suppressed that the level | step difference of the tread surface 24 and the tread surface 24 is underestimated.

  In the example shown in FIGS. 29 and 30, the position of the first measurement point 43A and the position of the second measurement point 43B are substantially the same in the tire width direction. As shown in FIG. 31, the position of the first measurement point 43A and the position of the second measurement point 43B may be different in the tire width direction. When the position of the first measurement point 43A and the position of the second measurement point 43B are different in the tire width direction, the distance between the first measurement point 43A and the second measurement point 43B in the tire width direction is 5 [mm. It is preferable that The same applies to the following embodiments.

  As shown in FIG. 32, a plurality of lateral grooves 202 and tread surfaces 24 are provided in the tire circumferential direction. For each of the plurality of tread surfaces 24, a measurement point 43 is defined at an end 440 that forms a boundary with the lateral groove 202 or in the vicinity thereof. For each of the plurality of tread surfaces 24, a measurement point 43 is defined at or near an end 450 that forms a boundary with the lateral groove 202. The positions (amount of wear) of the plurality of measurement points 43 are measured.

  Based on the difference between the wear amount at or near the end portion 440 of each of the plurality of tread surfaces 24 and the wear amount at or near the end portion 450, the step shape and the step amount of each of the plurality of tread surfaces 24 are evaluated. be able to. Based on the difference between the wear amount at or near the end portions 440 on both sides of each of the plurality of lateral grooves 202 and the wear amount at or near the end portions 450, the step form and the step amount of the adjacent tread surfaces 24 are evaluated. be able to.

  When calculating the step amount S between the first measurement point 43A and the second measurement point 43B, the reference point 44 in the measurement is set as in the above-described embodiment, and the degree of wear progress of the at least three different tread portions 10 is set. In each case, the distance between the first measurement point 43A and the reference point 44 in the tire radial direction is measured, and the distance between the second measurement point 43B and the reference point 44 in the tire radial direction is measured. Based on the difference between the distance between the first measurement point 43A and the reference point 44 and the distance between the second measurement point 43B and the reference point 44, the first measurement point 43A and the second measurement point at each of at least three stages of wear progress. A step amount S with respect to the measurement point 43B is calculated.

Based on the calculated step amount data indicating at least three step amounts S, the maximum step amount S _max in the wear history is estimated. Based on the estimated maximum step _Smax , the heel and toe wear performance of the tire 1 is evaluated. The evaluation of the heel and toe wear performance is performed by the processing device 50.

  FIG. 33 is a diagram schematically illustrating an example of an evaluation result of heel and toe wear on the first tread surface 241 and the second tread surface 242. FIG. 33 is a side sectional view of a part of the tire 1 on the first tread surface 241 and the second tread surface 242. FIG. 33 shows a cross section of the tire 1 in a plane orthogonal to the central axis AX.

  The level difference on the tread surface 24 refers to a difference between the distance between the rotation axis AX and the end 440 and the distance between the rotation axis AX and the end 450 in the tire radial direction. In other words, the step on the tread surface 24 refers to the difference between the height of the end portion 440 and the height of the end portion 450. The level difference on the tread surface 24 refers to the value of the level difference on the tread surface 24.

  If the difference between the wear amount of the end portion 440 of the tread surface 24 and the wear amount of the end portion 450 is large, the step amount of the tread surface 24 becomes large. When the difference between the wear amount of the end portion 440 of the tread surface 24 and the wear amount of the end portion 450 is small, the step amount of the tread surface 24 becomes small.

  The first measurement point 43A set at the end 450 of the tread surface 24 is measured, the second measurement point 43B set at the end 440 of the tread surface 24 is measured, and the first measurement point 43A and the second measurement point are measured. By calculating the step amount S with respect to 43B, the heel and toe wear performance of the tire 1 on the tread surface 24 is accurately evaluated.

  In the present embodiment, the step amount S between the first tread surface 241 and the second tread surface 242 separated by the lug groove 22 or the sipe 23 is calculated. The steps between the first tread surface 241 and the second tread surface 242 are the distance between the rotation axis AX and the first tread surface 241 and the distance between the rotation axis AX and the second tread surface 242 in the tire radial direction. Say the difference. In other words, the step between the first tread surface 241 and the second tread surface 242 refers to the difference between the height of the first tread surface 241 and the height of the second tread surface 242. The level difference S between the first tread surface 241 and the second tread surface 242 refers to the value of the level difference between the first tread surface 241 and the second tread surface 242.

  When the difference between the wear amount of the first tread surface 241 and the wear amount of the second tread surface 242 is large, the step amount between the first tread surface 241 and the second tread surface 242 becomes large. If the difference between the wear amount of the first tread surface 241 and the wear amount of the second tread surface 242 is small, the step amount between the first tread surface 241 and the second tread surface 242 becomes small.

  Therefore, the first measurement point 43A set on the first tread surface 241 is measured, the second measurement point 43B set on the second tread surface 242 is measured, and the first measurement point 43A and the second measurement point 43B are By deriving the difference, the step amount S between the first tread surface 241 and the second tread surface 242 is accurately evaluated. That is, the wear amount of the heel and toe wear of the first tread surface 241 and the wear amount of the heel and toe wear of the second tread surface 242 due to the difference between the wear amount of the first tread surface 241 and the wear amount of the second tread surface 242. Difference (non-uniformity) can be accurately evaluated.

As described above, according to the present embodiment, the first measurement point 43A is set on the first tread surface 241 and the second measurement point is set on the second tread surface 242 separated from the first tread surface 241 by the lateral groove 202. By setting 43B, the heel and toe wear performance on the first tread surface 241 and the second tread surface 242 is accurately evaluated based on the level difference S between the first measurement point 43A and the second measurement point 43B. The maximum step amount _Smax can be estimated with high accuracy. For example, it is possible to accurately evaluate the wear performance in which the step amount S of the two tread surfaces 24 separated by the lug groove 22 or the sipe 23 is larger than the step amount in the same evaluation section 41 (minimum section 42). .

<Third Embodiment>
A third embodiment will be described. In the following description, the same or equivalent components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is simplified or omitted.

  FIG. 34 is a diagram illustrating an example of a wear evaluation method for the tire 1 according to the present embodiment. FIG. 34 shows an example in which the step amount S between the first measurement point 43A and the second measurement point 43B is calculated for each of the four stages of wear progress of the tread portion 10. Note that the data of the calculated step amount S may be three, five, or six or more.

In the present embodiment, the step amount S indicating the maximum value among the plurality of calculated step amounts S is set as the maximum step amount _Smax .

According to this embodiment, without performing the arithmetic processing for estimating the maximum level difference S _max, it is possible to capture the maximum level difference S _max conveniently.

Similar to the above-described embodiment, the evaluation of the heel and toe wear performance of the tire 1 may include comparing the reference maximum step amount obtained from the reference tire with the maximum step amount S _max of the tire 1. maximum step of the tire 1 S _max and may include comparing the second largest step amount S _max of the tire 1.

<Fourth embodiment>
A fourth embodiment will be described. In the following description, the same or equivalent components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is simplified or omitted.

In the present embodiment, the groove depth D of the lug groove 22 or the sipe 23 adjacent to the measurement point 43 is measured. Based on the calculated step amount S between the first measurement point 43A and the second measurement point 43B and the measured groove depth D of the lug groove 22 or sipe 23, the maximum step amount _Smax is estimated.

FIG. 35 is a flowchart showing a processing procedure of the wear evaluation method for the tire 1 according to the present embodiment. Similar to the above-described embodiment, the method for evaluating the wear of the tire 1 according to this embodiment includes the step of setting at least two measurement points 43 (step SP10) and the step of setting a reference point 44 in measurement (step SP20). The tire radial direction in each of the step of setting the counter k to “1” (step SP30), the step of traveling the tire 1 by a predetermined distance (step SP40), and the degree of progress of wear of the tread portion 10 in at least three different stages. A step of measuring the distance between the first measurement point 43A and the reference point 44 in the tire, measuring the distance between the second measurement point 43B and the reference point 44 in the tire radial direction (step SP50), and the first measurement point 43A and the reference. Based on the difference between the distance between the point 44 and the distance between the second measurement point 43 </ b> B and the reference point 44, the first measurement point in each of the wear progress degrees A step of calculating the step amount S between 3A and the second measurement point 43B (step SP60), a step of comparing the counter k with the specified value Kr (step SP70), and a case where the counter k is smaller than the specified value Kr. The step of adding “1” to the counter k (step SP75) and the maximum step amount S _max in the wear history based on the step amount data indicating the step amount S calculated when the counter k is equal to or greater than the specified value Kr. A step of estimating (step SP80) and a step of evaluating the heel and toe wear performance of the tire 1 based on the estimated maximum step amount _Smax (step SP90) are included.

  In the present embodiment, a step (step SP55) of measuring the groove depth D of the lug groove 22 or the sipe 23 adjacent to the measurement point 43 is performed at each of at least three different degrees of progress of wear of the tread portion 10. The

  36, 37, and 38 are views for explaining the groove depth D of the lug groove 22 or the sipe 23 according to the present embodiment. Also in the following description, the lug groove 22 and the sipe 23 are collectively referred to as a lateral groove 202 as appropriate. The groove depth D can be measured using a measuring tool such as a caliper.

FIG. 36 is a diagram illustrating the groove depth D when the first measurement point 43A and the second measurement point 43B are set in one evaluation section 41 (minimum section 42). The first measurement point 43A is set at the first arrival part, and the second measurement point 43B is set at the rear arrival part. The groove depth D includes the groove depth _Dmax of the lateral groove 202 adjacent to the first measurement point 43A and the groove depth _Dmin of the lateral groove 202 adjacent to the second measurement point 43B. As the groove depth D, an average value of the groove depth _Dmax and the groove depth _Dmin is employed. As the groove depth D, the groove depth _Dmax may be employed, or the groove depth _Dmin may be employed. For example, as shown in FIG. 37, when heel and toe wear (so-called feather edge-like heel and toe wear) in which the leading portion becomes thin occurs, it is difficult to accurately measure the groove depth _Dmax using a measuring tool. . In such a case, the groove depth D _min may be adopted as the groove depth D.

  FIG. 38 is a diagram illustrating the groove depth D when the first measurement point 43 </ b> A is set on the first tread surface 241 and the second measurement point 43 </ b> B is set on the second tread surface 242. In the example shown in FIG. 38, the groove depth D is the groove depth D of the lateral groove 202 that separates the first tread surface 241 and the second tread surface 242.

The measurement of the groove depth D of the lateral groove 202 is carried out in each of at least three different stages of progress of wear of the tread portion 10. In the present embodiment, the groove depth D _{0 in} the tire 1 when new, the first depth D ₁ when the accumulated distance of the tire 1 from the new time is the first distance, a second depth D ₂ of the cumulative values of the travel distance of the tire 1 is longer than the first distance second distance, the cumulative value of the travel distance of the tire 1 from when new is longer than the second distance 3 distance and third depth D ₃ when the is measured. In addition, it is preferable that a 1st distance is 3000 [km] or less.

  FIG. 39 is a diagram showing the relationship between the measured wear amount or groove depth D and the step amount S between the first measurement point 43A and the second measurement point 43B calculated at each wear amount or groove depth D. It is. In the graph shown in FIG. 39, the horizontal axis represents the measured wear amount or groove depth D, and the vertical axis represents the first measurement point 43A and the second measurement point calculated at each wear amount or groove depth D. The step amount S with respect to 43B is shown. On the horizontal axis, the groove depth D decreases as the wear amount increases, and the groove depth D increases as the wear amount decreases. When the wear amount is zero, the groove depth is maximum (new), and when the groove depth is zero, the wear amount is maximum (complete wear).

As the cumulative value of the travel distance from the new article increases, the heel and toe wear of the tire 1 proceeds, and the groove depth D gradually decreases (shallow). Therefore, the groove depth D is synonymous with the amount of wear of the tread portion 10 of the tire 1. Groove depth D is the first the depth D _1, indicating that the wear amount is the first progress. The groove depth D being the second depth D ₂ that is shallower than the first depth D ₁ indicates that the wear amount is a second degree of progress that is more advanced than the first degree of progress. Groove depth D is to be a third depth D ₃ shallower than the second depth D _2, indicating that the abrasion loss is the third degree of progress in progress than the second progress.

  In the present embodiment, the process of measuring the distance between the first measurement point 43A and the reference point 44 in the tire radial direction and the tire radial direction in each of the wear amounts or groove depths D of the three different tread portions 10 A process of measuring the distance between the second measurement point 43B and the reference point 44 is performed. Based on the difference between the distance between the first measurement point 43A and the reference point 44 and the distance between the second measurement point 43B and the reference point 44, the wear amount or the groove depth D of each of the three stages of the tread portion 10 A process of calculating the step amount S between the first measurement point 43A and the second measurement point 43B is performed.

A step amount between the first measurement point 43A and the second measurement point 43B when the groove depth D is first depth _{D 1} and _{S 1.} A step amount between the first measurement point 43A and the second measurement point 43B when the groove depth D is a second depth _{D 2} and _{S 2.} A step amount between the first measurement point 43A and the second measurement point 43B when the groove depth D is the third depth _{D 3} and _{S 3.} Incidentally, the step amount S ₀ of the first measurement point 43A and the second measurement point 42B when the groove depth D which wear is not in progress is the groove depth D ₀ is zero.

  When the step amount S in each of the four stages of the tread portion 10 is plotted, it is as shown in FIG.

The processing device 50 includes step amount data indicating the calculated four step amounts S ₀ , S ₁ , S ₂ , and S ₃ , and the measured four groove depths D ₀ , D ₁ , D ₂ , and D ₃ . Based on the above, the maximum step amount S _max in the wear history is estimated.

In the present embodiment, the processing apparatus 50 includes a growth term f (D _i ) as a function of the groove depth D and a suppression term f (S _(i−1) as a function of the step amount S at the groove depth D. ) Is used to estimate the maximum step amount _Smax . The growth term f (D _i ) is expressed by the following equation (4). The suppression term f (S _(i-1) ) is expressed by the following equation (5). A polynomial representing the step amount S _i is expressed by the following equation (6).

In the formulas (4) and (5), a _n and b _n are constants. In the formulas (4) and (5), n may not be an integer. In equation (6), intercept = 0 is given as a constraint.

FIG. 40 is a diagram showing a curve representing the step amount S _i obtained from the equation (6). By obtaining the curve, the maximum step amount S _max indicating the maximum value of the step amount S between the first measurement point 43A and the second measurement point 43B is estimated. In the example shown in FIG. 40, the accumulated value of the travel distance of the tire 1 from when new is between the first distance and the second distance, the groove depth D is first depth D ₁ and the second depth D when between _2, step amount S between the first measurement point 43A and the second measurement point 43B is estimated to be a maximum level difference S _max.

After the maximum step amount _Smax is estimated, the heel and toe wear performance of the tire 1 is evaluated based on the estimated maximum step amount _Smax .

As described above, according to the present embodiment, by using both the step amount S due to heel and toe wear and the groove depth D of the lug groove 22 or the sipe 23, the maximum step amount _Smax can be made more accurate. Can be estimated.

As a method for determining the degree of progress of the heel and toe wear, there are a method for estimating from the travel distance of the tire 1 described in the above embodiment and a method for measuring the groove depth D after travel described in the present embodiment. Can be mentioned. By measuring the groove depth D of the lug groove 22 or the sipe 23 adjacent to the measurement point 43, the degree of progress of wear can be obtained with high accuracy. Therefore, it is possible to accurately calculate the step amount S between the first measurement point 43A and the second measurement point 43B and estimate the maximum step amount _Smax .

Further, the growth of the step amount S depends on the ease with which the block 32 falls. Further, the ease of falling of the block 32 correlates with the groove depth D of the lateral groove 202 including the lug groove 22 or the sipe 23. When the groove depth D is deep, the block 32 easily falls down and the step amount S is likely to grow. If the groove depth D is shallow, it is difficult for the block 32 to fall down, and the growth of the step amount S is suppressed. Therefore, the maximum step amount _Smax can be estimated with higher accuracy by using both the step amount S and the groove depth D.

In the present embodiment, a growth term f (D _i ) as a function of the groove depth D and a suppression term f (S _(i−1) ) as a function of the step amount S at the groove depth D are included. The maximum step amount S _max is estimated using a polynomial.

As described above, when the groove depth D becomes deep, the block 32 is likely to fall down, and the step amount S is likely to grow. On the other hand, when the step amount S increases, the contact pressure distribution of the block 32 fluctuates and the block 32 is worn so that the step becomes flat, and the growth of the step amount S is suppressed or the step disappears. That is, the generation, growth, and disappearance of the step due to the heel and toe wear are determined by the balance between the groove depth D and the step amount S. By using a polynomial including a step growth term f (D _i ) as a function of the groove depth D and a step suppression term f (S _(i−1) ) as a function of the step amount S, the maximum step The quantity S _max can be estimated with high accuracy.

The growth term f (D _i ) is a component that grows a step, and indicates the ease with which the block 32 falls. The ease of falling of the block 32 indicates the ease of slipping of the rear wearing portion of the block 32 and is proportional to the magnitude of the friction energy. The suppression term f (S _(i-1) ) is a component that suppresses the growth of the step or a component that eliminates the step, and depends on the contact pressure distribution that varies depending on the step shape. The step amount S is determined by a combination (synthesis) of the groove depth D as a growth component and the step amount S as a suppression component. Therefore, the maximum step amount _Smax can be estimated with higher accuracy by using a polynomial including the growth term f (D _i ) and the suppression term f (S _(i−1) ).

  In each of the above-described embodiments, the difference between the distance between the first measurement point 43A and the reference point 44 (first distance) and the distance between the second measurement point 43B and the reference point 44 (second distance). When calculating the step amount S between the first measurement point 43A and the second measurement point 43B based on the above, the step amount may be calculated based on the difference between the first distance and the second distance. However, it may be calculated based on the ratio between the first distance and the second distance. That is, in each of the above-described embodiments, the difference between the distance between the first measurement point 43A and the reference point 44 (first distance) and the distance between the second measurement point 43B and the reference point 44 (second distance) is , A concept including one or both of a difference between the first distance and the second distance and a ratio between the first distance and the second distance.

In each of the above-described embodiments, an example of evaluating heel and toe wear has been described as one form of circumferential uneven wear. The circumferentially uneven wear is a concept including both heel and toe wear and polygonal wear, and refers to a wear form in which the land portion of the tire is worn unevenly in the tire circumferential direction. Therefore, polygonal wear may be evaluated in each of the above-described embodiments. Polygonal wear refers to a wear form in which the tread portion of the tire is worn so that a plurality of corners are formed in the tire circumferential direction. Based on the estimated maximum level difference _Smax , the polygonal wear performance of the tire 1 may be evaluated.

1 tire 2 carcass part 3 belt layer 4 belt cover 5 bead part 6 tread rubber 8 side rubber 9 side part 10 tread part 11 center part 12 shoulder part 19 land part 20 groove 21 main groove 22 lug groove 22A lug groove 22B lug groove 22C lug Groove 22D Lug groove 22E Lug groove 22F Lug groove 22G Lug groove 23 Sipe 24 Tread surface 31 Pitch 32 Block 32A Block 32B Block 32C Block 32D Block 41 Evaluation section 42 Minimum section 42A Minimum section 42B Minimum section 42C Minimum section 43 Measurement point 43A First 1 measurement point 43B second measurement point 44 reference point 44A first reference point 44B second reference point 46 part 47 part 48 first arrival area 49 last arrival area 50 processing device 50m storage unit 50p processing unit 53 input / output unit 54 terminal device 55 input Device 56 Output device 57 Measuring device 202 Horizontal groove 241 First tread surface 242 Second tread surface 411 First evaluation section 412 Second evaluation section 440 End 450 End 571 Generation section 572 Injection section 573 Incident section 574 Light receiving sensor 575 Support section 576 Optical member ML Measurement light

Claims (6)

Setting at least a first measurement point and a second measurement point in the tire circumferential direction in the tread portion of the tire;
Setting a reference point for measurement,
Measuring the distance between the first measurement point and the reference point in the tire radial direction at each of at least three different degrees of wear progress of the tread portion;
Measuring the distance between the second measurement point and the reference point in the tire radial direction for each of the progress degrees of wear;
Based on the difference between the distance between the first measurement point and the reference point and the distance between the second measurement point and the reference point, the first measurement point and the second measurement point in each of the wear progress degrees. Calculating the amount of step between and
Estimating the maximum step amount in the wear history based on the step amount data indicating the calculated step amount;
Evaluating the heel and toe wear performance of the tire based on the estimated maximum step amount;
Measuring the depth of the lug groove or sipes adjacent to the first and second measurement points;
Only including,
Estimating the maximum step amount based on the calculated step amount and the groove depth,
Estimating the maximum step amount using a polynomial including a growth term as a function of the groove depth and a suppression term as a function of the step amount at the groove depth;
Tire wear evaluation method. The tread portion includes a plurality of groove patterns provided in the tire circumferential direction,
Including defining an evaluation section in the tread portion based on at least one of a pitch defined by the one groove pattern and a block defined by two lug grooves adjacent in the tire circumferential direction,
The first measurement point and the second measurement point are set in the tire circumferential direction in the evaluation section.
The tire wear evaluation method according to claim 1. The tread portion includes a first tread surface, and a second tread surface disposed next to the first tread surface in the tire circumferential direction via lug grooves or sipes,
The first measurement point is set on the first tread surface, and the second measurement point is set on the second tread surface.
The tire wear evaluation method according to claim 1. The degree of progress of at least one stage of the degree of progress of wear is the degree of progress of wear except when the tire is new and when the cumulative value of the travel distance of the tire from the new is 3000 [km] or less. Is,
The tire wear evaluation method according to any one of claims 1 to 3. Among the calculated step heights, the step height showing the maximum value is set as the maximum step height.
The tire wear evaluation method according to any one of claims 1 to 4. Interpolating the calculated step amount to estimate the maximum step amount,
The tire wear evaluation method according to any one of claims 1 to 4.

Images