Tire state estimation device, tire state estimation method, and program

Abstract

A tire state estimation device (1) comprises: an opening amount / deviation amount derivation unit (121) for calculating the opening amount and the deviation amount of a crack that has occurred in the surface of a target tire of which the state is to be estimated; a crack progression pattern determination unit (122) that determines, on the basis of the opening amount and deviation amount and with respect to the depth direction, whether the crack is in a crack progression pattern in which the crack will progress in a straight line or in a crack progression pattern in which the crack will progress so as to bifurcate; a crack progression rate derivation unit (123) for calculating a crack progression rate corresponding to the crack progression pattern; and a service life prediction unit (124) for calculating, from the crack progression rate and in accordance with the crack progression pattern, the service life of the target tire based on the crack.

Description

TITLE TIRE STATE ESTIMATION APPARATUS, TIRE STATE ESTIMATION METHOD, AND PROGRAM TECHNICAL FIELD

[0001] The present disclosure relates to a tire state estimation apparatus, a tire state estimation method, and a program. BACKGROUND

[0002] Conventionally, techniques for evaluating the crack growth of cracks occurring on the surface of a tire are known. For example, PTL 1 discloses a technique in which a mark element, in which marks are arranged in a matrix in a region including the vicinity of a crack tip, is formed, the local strain generated at the crack tip is measured as strain based on the displacement of the intervals between the mark elements, and a stretching test of a rubber test piece is performed by a tensile stroke so as to achieve the measured strain, thereby evaluating the crack growth. CITATION LIST Patent Literature

[0003] PTL 1: JP 2013-72794 A SUMMARY (Technical Problem)

[0004] However, in the technique disclosed in PTL 1, it is necessary to form mark elements arranged in a matrix, which increases cost. In addition, it is not possible to evaluate the crack growth in the depth direction of the crack.

[0005] In view of these circumstances, an object of the present disclosure is to provide a tire state estimation apparatus, a tire state estimation method, and a program capable of evaluating the crack growth in the depth direction of cracks occurring on the surface of a tire at low cost. (Solution to Problem)

[0006] The gist of the present disclosure for solving the above problems is as follows.

[0007] (1) A tire state estimation apparatus comprising: an opening amount and displacement amount derivation unit configured to determine an opening amount and a displacement amount of a crack generated on a surface of a target tire to be subjected to state estimation; a crack growth pattern determination unit configured to determine, from the opening amount and the displacement amount, whether the crack grows in a straight-line crack growth pattern or in a bifurcated crack growth pattern with respect to a depth direction; a crack growth rate derivation unit configured to determine a crack growth rate corresponding to the crack growth pattern; and a service life prediction unit configured to determine, from the crack growth rate, a service life of the target tire due to the crack in accordance with the crack growth pattern.

[0008] (2) The tire state estimation apparatus according to (1), wherein the opening amount and displacement amount derivation unit refers to a database associating a strain of a surface of a tire without a crack, calculated using a finite element method, with opening amounts and displacement amounts measured for a plurality of tires having cracks with different crack states, and determines the opening amount and the displacement amount.

[0009] (3) A tire state estimation method to be executed by a tire state estimation apparatus, comprising: determining an opening amount and a displacement amount of a crack generated on a surface of a target tire to be subjected to estimation; determining, from the opening amount and the displacement amount, whether the crack grows in a straight-line crack growth pattern or in a bifurcated crack growth pattern with respect to a depth direction; determining a crack growth rate corresponding to the crack growth pattern; and determining, from the crack growth rate, a service life of the target tire due to the crack in accordance with the crack growth pattern.

[0010] (4) A program configured to cause a computer to function as the tire state estimation apparatus according to (1) or (2). (Advantageous Effect)

[0011] According to the present disclosure, it becomes possible to evaluate the crack growth in the depth direction of cracks occurring on the surface of a tire at low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In the accompanying drawings: FIG. 1 is a diagram illustrating an example configuration of a tire state estimation apparatus according to one embodiment; FIG. 2A is a schematic diagram depicting the occurrence of a crack due to tensile stress; FIG. 2B is a schematic diagram depicting the occurrence of a crack due to out-of-plane shear; FIG. 3 is a graph presenting an example of derivation results of the opening amount and displacement amount of a crack; FIG. 4A is a schematic diagram illustrating a crack growth pattern in which a crack grows in one direction; FIG. 4B is a schematic diagram illustrating a crack growth pattern in which a crack grows in a bifurcated direction; FIG. 5 demonstrates a method for calculating tire life by the tire state estimation apparatus according to one embodiment; FIG. 6 is a flowchart illustrating an example procedure of the tire state estimation method according to one embodiment. DETAILED DESCRIPTION

[0013] Hereinafter, an embodiment will be described in detail with reference to the drawings.

[0014] FIG. 1 illustrates an example configuration of a tire state estimation apparatus according to one embodiment. The tire state estimation apparatus 1 illustrated in FIG. 1 includes an input unit 11, a controller 12, a storage unit 13, and an output unit 14. The tire state estimation apparatus 1 may further include a communication interface such as a LAN (Local Area Network) I / F to enable communication with external devices. The tire state estimation apparatus 1 is an apparatus that estimates a state related to a crack (side cut) in a tire.

[0015] The input unit 11 is, for example, a physical key, a capacitive key, a pointing device, or a touchscreen provided integrally with a display. The input unit 11 receives operations for inputting data used in the operation of the tire state estimation apparatus 1. The input unit 11 may be provided as an external input device connected to the tire state estimation apparatus 1 instead of being incorporated therein. As a connection interface, any interface conforming to standards such as USB (Universal Serial Bus), HDMI® (High-Definition Multimedia Interface; HDMI is a registered trademark in Japan, other countries, or both), or Bluetooth® (Bluetooth is a registered trademark in Japan, other countries, or both) may be used.

[0016] The storage unit 13 includes at least one semiconductor memory, at least one magnetic memory, at least one optical memory, or any combination thereof. The semiconductor memory may be, for example, a RAM (random access memory), ROM (read only memory), or flash memory. The RAM may be, for example, an SRAM (static random access memory) or DRAM (dynamic random access memory). The ROM may be, for example, an EEPROM (electrically erasable programmable read only memory). The flash memory may be, for example, an SSD (solid-state drive). The magnetic memory may be, for example, an HDD (hard disk drive). The storage unit 13 functions, for example, as a main storage device, auxiliary storage device, or cache memory.

[0017] The controller 12 may be constituted by dedicated hardware such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field-Programmable Gate Array), by a processor, or by a combination of both. The controller 12 controls each unit of the tire state estimation apparatus 1 and executes processing related to the operation of the tire state estimation apparatus 1.

[0018] The controller 12 illustrated in FIG. 1 includes an opening amount and displacement amount derivation unit 121, a crack growth pattern determination unit 122, a crack growth rate derivation unit 123, and a service life prediction unit 124.

[0019] The opening amount and displacement amount derivation unit 121 uses a finite element method (FEM) to determine an opening amount and a displacement amount of a crack generated on the surface of a tire to be subjected to state estimation (hereinafter referred to as the “target tire”). The opening amount and displacement amount derivation unit 121 outputs the determined opening amount and displacement amount to the crack growth pattern determination unit 122.

[0020] Since the finite element method has a high computational cost, the opening amount and displacement amount may be determined as follows. The measurer preliminarily calculates, using the finite element method, a strain (representative strain) of the surface of a tire without a crack. Further, for a plurality of tires having cracks with different crack states such as length, depth, and angle, the opening amount and displacement amount due to the cracks are preliminarily measured by indoor testing. A representative tire size is used for the calculation of the representative strain and the measurement of the opening amount and displacement amount. The measurer stores, via the input unit 11, a first database associating the representative strain with the opening amount and displacement amount in the storage unit 13. The opening amount and displacement amount derivation unit 121 inputs information indicating the tire size, crack position, and crack state of the target tire, and refers to the first database stored in the storage unit 13 to convert (estimate) the opening amount and displacement amount of the target tire. The opening amount and displacement amount derivation unit 121 may also acquire the tire size, crack position, and crack state of the target tire by performing image processing on an image of the target tire.

[0021] FIG. 2 illustrates the occurrence of a crack on the tire surface S. FIG. 2A is a schematic diagram illustrating the occurrence of a crack due to tensile stress, referred to as Mode I (opening). In this specification, a crack due to tensile stress is referred to as “opening,” and the opening component of the strain amount is referred to as the “opening amount.” FIG. 2B is a schematic diagram illustrating the occurrence of a crack due to out-of-plane shear, referred to as Mode III (tearing). In this specification, a crack due to out-of-plane shear is referred to as “displacement,” and the displacement component of the strain amount is referred to as the “displacement amount.”

[0022] FIG. 3 illustrates an example of derivation results of the opening amount and displacement amount of a crack. The horizontal axis represents the rotation angle [deg] of the target tire, with 0 degrees being the position where the crack location is closest to the ground. The vertical axis represents the strain amount [mm], where a is the opening amount and b is the displacement amount. As the target tire rotates, the crack opens and displaces. That is, FIG. 3 focuses on a single crack and illustrates the changes in the opening amount and displacement amount as the target tire makes one rotation (from -180 degrees to 180 degrees). In this example, the crack is in the radial direction.

[0023] FIG. 4 illustrates crack growth patterns of a crack generated on the tire surface S. Stress is concentrated at the crack tip, and the crack grows (propagates) due to strain-induced crystallization. FIG. 4A is a schematic diagram illustrating a crack growth pattern in which the crack grows in a straight line in the depth direction, as indicated by the dotted arrow. FIG. 4B is a schematic diagram illustrating a crack growth pattern in which the crack grows in a bifurcated manner in the depth direction, as indicated by the dotted arrow.

[0024] The crack growth pattern determination unit 122 determines, from the opening amount and displacement amount input from the opening amount and displacement amount derivation unit 121, whether the crack grows in a straight-line crack growth pattern or in a bifurcated crack growth pattern with respect to the depth direction. The crack growth pattern determination unit 122 outputs the determined crack growth pattern to the crack growth rate derivation unit 123 and the service life prediction unit 124.

[0025] For example, the measurer preliminarily determines the crack growth pattern by a drum test in which a plurality of tires having cracks with different opening amounts and displacement amounts are run on a rotating drum. The measurer stores, via the input unit 11, a second database associating the opening amount and displacement amount with the crack growth pattern in the storage unit 13. The crack growth pattern determination unit 122 inputs the opening amount and displacement amount from the opening amount and displacement amount derivation unit 121, refers to the second database, and determines the crack growth pattern of the target tire.

[0026] The crack growth rate derivation unit 123 determines a crack growth rate corresponding to the crack growth pattern input from the crack growth pattern determination unit 122. The crack growth rate derivation unit 123 outputs the determined crack growth rate to the service life prediction unit 124.

[0027] For example, the measurer preliminarily measures the crack growth rate by drum tests and laboratory tests for a plurality of tires having different crack growth patterns and rubber physical properties. The measurer stores, via the input unit 11, a third database associating the crack growth pattern, rubber physical properties, and crack growth rate in the storage unit 13. The crack growth rate derivation unit 123 inputs the crack growth pattern from the crack growth pattern determination unit 122 and the rubber physical properties of the target tire, refers to the third database, and converts (estimates) the crack growth rate of the target tire.

[0028] The service life prediction unit 124 determines, from the crack growth rate input from the crack growth rate derivation unit 123, a service life of the target tire due to the crack in accordance with the crack growth pattern input from the crack growth pattern determination unit 122.

[0029] With reference to FIG. 5, a method for calculating the tire service life by the service life prediction unit 124 will be described. The service life prediction unit 124 determines a distance D along the crack growth direction from the crack bottom P to the crack limit position Q. In this figure, the crack limit position Q is the position of the ply. When the determination result by the crack growth pattern determination unit 122 is a “straight-line crack growth pattern,” the distance D is the distance d1 along the direction perpendicular to the tire surface S from the crack bottom P to the crack limit position Q. When the determination result by the crack growth pattern determination unit 122 is a “bifurcated crack growth pattern,” the distance D is the distance d2 along the bifurcated direction from the crack bottom P to the crack limit position Q.

[0030] The service life prediction unit 124 inputs the crack growth rate V from the crack growth rate derivation unit 123, the crack growth pattern from the crack growth pattern determination unit 122, and the crack depth of the target tire, and, using the distance D along the crack growth direction from the crack bottom P to the crack limit position Q, predicts the service life L1 of the target tire due to the crack by the following formula (1). The crack limit position is, for example, the position of the ply (carcass) of the tire. The measurer may preliminarily store the crack limit position in the storage unit 13 via the input unit 11. L1 = D / V ... (1)

[0031] The service life prediction unit 124 may further input the remaining groove depth (RTD: remaining tread depth) of the target tire and predict a service life L2 due to wear of the target tire. For example, the service life prediction unit 124 may predict the service life L2 from the remaining groove depth using a machine-learned model of the relationship between the remaining groove depth and service life.

[0032] The service life prediction unit 124 may generate a replacement or repair schedule for the target tire based on the service life L1, or based on both service lives L1 and L2. When L2 < L1, the service life due to wear comes before the service life due to the crack, so the service life prediction unit 124 may determine that no action for the crack is necessary. Further, when the service lives L1 and L2 are greater than a threshold, the service life prediction unit 124 may determine that no action such as replacement or repair of the target tire is necessary.

[0033] The output unit 14 is, for example, a display, speaker, or printer, and presents data generated by the service life prediction unit 124 to the user. The display may be, for example, an LCD (liquid crystal display) or an organic EL (electro luminescent) display. The output unit 14 may be provided as an external output device connected to the tire state estimation apparatus 1 instead of being incorporated therein. As a connection interface, any interface conforming to standards such as USB, HDMI, or Bluetooth may be used.

[0034] (Tire State Estimation Method) Next, a tire state estimation method according to one embodiment will be described. FIG. 6 is a flowchart illustrating an example procedure of the tire state estimation method.

[0035] In step S101, the measurer stores, as necessary, measurement information such as the above-described first database, second database, third database, and crack limit position in the storage unit 13 of the tire state estimation apparatus 1.

[0036] In step S102, the opening amount and displacement amount derivation unit 121 of the tire state estimation apparatus 1 determines an opening amount and a displacement amount of a crack generated on the surface of the target tire to be subjected to estimation.

[0037] In step S103, the crack growth pattern determination unit 122 of the tire state estimation apparatus 1 determines, from the opening amount and displacement amount, whether the crack grows in a straight-line crack growth pattern or in a bifurcated crack growth pattern.

[0038] In step S104, the crack growth rate derivation unit 123 of the tire state estimation apparatus 1 determines a crack growth rate corresponding to the crack growth pattern.

[0039] In step S105, the service life prediction unit 124 of the tire state estimation apparatus 1 determines, from the crack growth rate, a service life of the target tire due to the crack in accordance with the crack growth pattern.

[0040] As described above, in the first embodiment, the opening amount and displacement amount of a crack generated on the surface of the target tire are determined, the crack growth pattern is determined from the opening amount and displacement amount, the crack growth rate corresponding to the crack growth pattern is determined, and the service life of the target tire due to the crack is determined from the crack growth rate in accordance with the crack growth pattern. Therefore, it is possible to evaluate the crack growth in the depth direction occurring on the surface of the tire at low cost. In the second embodiment, the opening amount and displacement amount are determined by referring to a database associating the strain of the surface of a tire without a crack, calculated using a finite element method, with the opening amounts and displacement amounts measured for a plurality of tires having cracks with different crack states. Since the calculation cost of the opening amount and displacement amount can be reduced in the second embodiment, it is possible to evaluate the crack growth in the depth direction occurring on the surface of the tire at even lower cost than in the first embodiment.

[0041] (Program) A computer capable of executing program instructions may be used to function as the above-described tire state estimation apparatus 1. Here, the computer may be a general-purpose computer, dedicated computer, workstation, PC (Personal Computer), electronic notepad, mobile terminal, or the like. The program instructions may be program code, code segments, or the like for executing necessary tasks.

[0042] The controller 12 is a processor such as a CPU (Central Processing Unit), MPU (Micro Processing Unit), GPU (Graphics Processing Unit), DSP (Digital Signal Processor), or SoC (System on a Chip), and may be constituted by a plurality of processors of the same or different types. The processor performs the above-described processing by reading and executing the program from the storage unit 13. Note that at least part of the processing content may be implemented by hardware.

[0043] The program may be recorded on a computer-readable recording medium. By using such a recording medium, the program can be installed on a computer. Here, the recording medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, but may be, for example, a CD-ROM, DVD-ROM, USB (Universal Serial Bus) memory, or the like. The program may also be provided in a form downloaded from an external device via a network.

[0044] The above-described embodiments have been described as representative examples, but it will be apparent to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present disclosure. Therefore, the present disclosure should not be construed as being limited by the above-described embodiments, and various modifications or changes can be made without departing from the scope of the claims. For example, it is possible to integrate a plurality of configuration blocks described in the configuration diagram of the embodiment, or to divide one configuration block. It is also possible to integrate a plurality of steps described in the flowchart of the embodiment, or to divide one step. [Contribution to the Sustainable Development Goals (SDGs) led by the United Nations]

[0045] The SDGs have been advocated for the realization of a sustainable society. An embodiment of the present disclosure is considered to be a technology that can contribute to, for example, “No. 9: Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation.” REFERENCE SIGNS LIST

[0046] 1    Tire state estimation apparatus 11 Input unit 12 Controller 13 Storage unit 14 Output unit 121 Opening amount and displacement amount derivation unit 122 Crack growth pattern determination unit 123 Crack growth rate derivation unit 124 Service life prediction unit

Claims

1. A tire state estimation apparatus comprising:an opening amount and displacement amount derivation unit configured to determine an opening amount and a displacement amount of a crack generated on a surface of a target tire to be subjected to state estimation;a crack growth pattern determination unit configured to determine, from the opening amount and the displacement amount, whether the crack grows in a straight-line crack growth pattern or in a bifurcated crack growth pattern with respect to a depth direction;a crack growth rate derivation unit configured to determine a crack growth rate corresponding to the crack growth pattern; anda service life prediction unit configured to determine, from the crack growth rate, a service life of the target tire due to the crack in accordance with the crack growth pattern.

2. The tire state estimation apparatus according to claim 1, wherein the opening amount and displacement amount derivation unit refers to a database associating a strain of a surface of a tire without a crack, calculated using a finite element method, with opening amounts and displacement amounts measured for a plurality of tires having cracks with different crack states, and determines the opening amount and the displacement amount.

3. A tire state estimation method to be executed by a tire state estimation apparatus, comprising:determining an opening amount and a displacement amount of a crack generated on a surface of a target tire to be subjected to estimation;determining, from the opening amount and the displacement amount, whether the crack grows in a straight-line crack growth pattern or in a bifurcated crack growth pattern with respect to a depth direction;determining a crack growth rate corresponding to the crack growth pattern; anddetermining, from the crack growth rate, a service life of the target tire due to the crack in accordance with the crack growth pattern.

4. A program configured to cause a computer to function as the tire state estimation apparatus according to claim 1 or 2.

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