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

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

[0001] The present disclosure relates to a tire condition estimation device, a tire condition estimation method, and a program.

[0002] Conventionally, there are known techniques for evaluating the growth potential of cracks occurring on the surface of a tire. For example, Patent Document 1 discloses a technique for evaluating the crack growth potential by forming mark elements in a matrix arrangement in an area including the area near the crack tip, measuring the local strain occurring at the crack tip based on the displacement of the spacing between the mark elements, and conducting an extension test on a rubber test piece with a tensile stroke so as to achieve the measured strain.

[0003] JP 2013-72794 A

[0004] However, the technique disclosed in Patent Document 1 requires forming mark elements arranged in a matrix, which is costly, and it is not possible to evaluate the growth of cracks in the depth direction.

[0005] An object of the present disclosure, made in consideration of the above circumstances, is to provide a tire condition estimation device, a tire condition estimation method, and a program that are capable of evaluating the depth-wise growth tendency of cracks that occur on the surface of a tire at low cost.

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

[0007] (1) A tire condition estimation device comprising: an opening amount / shift amount derivation unit that calculates the opening amount and shift amount of a crack that has occurred on the surface of a target tire whose condition is to be estimated; a crack growth pattern determination unit that determines, from the opening amount and the shift amount, whether the crack has a crack growth pattern in which the crack grows in a straight line in the depth direction or a crack growth pattern in which the crack grows in two directions; a crack growth rate derivation unit that calculates a crack growth rate according to the crack growth pattern; and a life prediction unit that calculates, from the crack growth rate, the lifespan of the target tire due to the crack according to the crack growth pattern.

[0008] (2) The tire condition estimation device described in (1), wherein the opening amount / deviation amount deriving unit determines the deviation amount and the opening amount by referring to a database that links the strain on the surface of a crack-free tire calculated using the finite element method with the opening amounts / deviation amounts measured for multiple tires with cracks in different crack states.

[0009] (3) A tire condition estimation method in which a tire condition estimation device executes the steps of: determining the opening amount and shift amount of a crack that has occurred on the surface of a target tire to be estimated; determining, from the opening amount and the shift amount, whether the crack has a crack growth pattern in which the crack grows in a straight line in the depth direction or a crack growth pattern in which the crack grows in two directions; determining a crack growth speed according to the crack growth pattern; and determining, from the crack growth speed, the lifespan of the target tire due to the crack according to the crack growth pattern.

[0010] (4) A program for causing a computer to function as the tire condition estimation device according to (1) or (2).

[0011] According to the present disclosure, it is possible to evaluate the depth-wise growth of cracks that occur on the surface of a tire at low cost.

[0012] FIG. 1 is a diagram showing an example of the configuration of a tire condition estimation device according to an embodiment. FIG. 2 is a schematic diagram showing crack generation due to tensile stress. FIG. 3 is a schematic diagram showing crack generation due to out-of-plane shear. FIG. 4 is a graph showing an example of derived results of crack opening amount and deviation amount. FIG. 5 is a schematic diagram showing a crack growth pattern in which a crack grows in one direction. FIG. 6 is a schematic diagram showing a crack growth pattern in which a crack grows in two directions. A method for calculating tire life by a tire condition estimation device according to an embodiment will be described. FIG. 7 is a flowchart showing an example of the procedure of a tire condition estimation method according to an embodiment.

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

[0014] Figure 1 shows an example configuration of a tire condition estimation device according to one embodiment. Tire condition estimation device 1 shown in Figure 1 includes an input unit 11, a control unit 12, a storage unit 13, and an output unit 14. Tire condition estimation device 1 may further include a communication I / F such as a LAN (Local Area Network) I / F to enable communication with external devices. Tire condition estimation device 1 is a device that estimates the condition of a tire related to cracks (side cuts).

[0015] Input unit 11 is, for example, a physical key, a capacitance key, a pointing device, a touch screen integrated with a display, or the like. Input unit 11 accepts operations for inputting data used in the operation of tire condition estimation device 1. Input unit 11 may be connected to tire condition estimation device 1 as an external input device, instead of being provided in tire condition estimation device 1. The connection interface may be any interface compatible with standards such as USB (Universal Serial Bus), HDMI (High-Definition Multimedia Interface, registered trademark), or Bluetooth (registered trademark).

[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 is, for example, a random access memory (RAM), a read-only memory (ROM), or a flash memory. The RAM is, for example, a static random access memory (SRAM) or a dynamic random access memory (DRAM). The ROM is, for example, an electrically erasable programmable read-only memory (EEPROM). The flash memory is, for example, a solid-state drive (SSD). The magnetic memory is, for example, a hard disk drive (HDD). The storage unit 13 functions, for example, as a main storage device, an auxiliary storage device, or a cache memory.

[0017] Control unit 12 may be configured with dedicated hardware such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field-Programmable Gate Array), or may be configured with a processor, or may be configured to include both. Control unit 12 executes processes related to the operation of tire condition estimation device 1 while controlling the various parts of tire condition estimation device 1.

[0018] The control unit 12 shown in FIG. 1 includes an opening amount / shift amount deriving unit 121, a crack growth pattern determining unit 122, a crack growth rate deriving unit 123, and a life prediction unit 124.

[0019] The opening amount / shift amount deriving unit 121 uses the finite element method (FEM) to determine the opening amount and shift amount of a crack that has occurred on the surface of a tire whose condition is to be estimated (hereinafter referred to as the “target tire”). Then, the opening amount / shift amount deriving unit 121 outputs the determined opening amount and shift amount to the crack growth pattern determining unit 122.

[0020] Because the finite element method requires high calculation costs, the opening amount and the deviation amount may be calculated as follows. The measurer uses the finite element method to calculate in advance the strain (representative strain) on the surface of a crack-free tire. Furthermore, the measurer measures in advance the opening amount and the deviation amount due to the crack through indoor testing for multiple tires with cracks of different lengths, depths, angles, and other crack conditions. A tire of a representative size is used to calculate the representative strain and measure the opening amount and the deviation amount. The measurer then stores a first database linking the representative strain and the opening amount and the deviation amount in the memory unit 13 via the input unit 11. The opening amount and deviation amount deriving unit 121 inputs information indicating the tire size, crack position, and crack condition of the target tire and converts (estimates) the opening amount and the deviation amount of the target tire by referring to the first database stored in the memory unit 13. The opening amount and deviation amount deriving unit 121 may also acquire the tire size, crack position, and crack condition of the target tire by image processing an image of the target tire.

[0021] Figure 2 shows the occurrence of a crack on the tire surface S. Figure 2A is a schematic diagram showing the occurrence of a crack due to tensile stress, called Mode I (opening). In this specification, a crack due to this tensile stress is called "opening," and the opening component of the strain amount is called "opening amount." Figure 2B is a schematic diagram showing the occurrence of a crack due to out-of-plane shear, called Mode III (tearing). In this specification, a crack due to this out-of-plane shear is called "displacement," and the displacement component of the strain amount is called "displacement amount."

[0022] Figure 3 shows an example of the results of calculating the crack opening and displacement. The horizontal axis represents the rotation angle [deg] of the target tire, with 0 degrees representing the position where the crack is closest to the ground. The vertical axis represents the strain [mm], with a representing the opening and b representing the displacement. The crack opens and displaces depending on the rotation of the target tire. In other words, Figure 3 focuses on one crack and shows the changes in the opening and displacement as the target tire rotates once (-180 degrees to 180 degrees). In this example, the crack is in the radial direction.

[0023] Figure 4 shows the propagation pattern of a crack that has occurred on the tire surface S. Stress concentrates at the tip of the crack, and the crack propagates (grows) due to elongation crystallization. Figure 4A is a schematic diagram showing a crack propagation pattern in which the crack propagates in a straight line in the depth direction, as indicated by the dotted arrow. Figure 4B is a schematic diagram showing a crack propagation pattern in which the crack propagates by bifurcating in the depth direction, as indicated by the dotted arrow.

[0024] The crack growth pattern determination unit 122 determines whether the crack grows in a straight line in the depth direction or in a bifurcated pattern, based on the opening amount and the shift amount input from the opening amount / shift amount derivation unit 121. Then, the crack growth pattern determination unit 122 outputs the determined crack growth pattern to the crack growth rate derivation unit 123 and the life prediction unit 124.

[0025] For example, the measurer determines in advance the crack propagation pattern of a plurality of tires having cracks with different opening and misalignment amounts by a drum test in which the tires are run on a rotating drum. Then, the measurer stores a second database linking the opening and misalignment amounts and the crack propagation patterns in the memory unit 13 via the input unit 11. The crack propagation pattern determination unit 122 inputs the opening and misalignment amounts input from the opening and misalignment amount derivation unit 121 and determines the crack propagation pattern of the target tire by referring to the second database.

[0026] The crack growth rate derivation unit 123 calculates the crack growth rate according to the crack growth pattern input from the crack growth pattern determination unit 122. Then, the crack growth rate derivation unit 123 outputs the calculated crack growth rate to the life prediction unit 124.

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

[0028] The life prediction unit 124 determines the life due to cracks of the target tire from the crack growth rate input from the crack growth rate derivation unit 123 according to the crack growth pattern input from the crack growth pattern determination unit 122.

[0029] A method for calculating the tire life by the life prediction unit 124 will be described with reference to Figure 5. The life prediction unit 124 calculates the distance D along the crack propagation 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. If the determination result by the crack propagation pattern determination unit 122 is a "crack propagation pattern that propagates in a straight line," 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. If the determination result by the crack propagation pattern determination unit 122 is a "crack propagation pattern that propagates in two directions," the distance D is the distance d2 along the direction of the two directions from the crack bottom P to the crack limit position Q.

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

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

[0032] The lifespan prediction unit 124 may generate a schedule for replacing or repairing the target tire based on the lifespan L1 or based on the lives L1 and L2. In the case of L2 minus L1, the lifespan prediction unit 124 may determine that no action is required to address the cracks because the lifespan due to wear comes before the lifespan due to cracks. Furthermore, the lifespan prediction unit 124 may determine that no action is required to replace or repair the target tire when the lives L1 and L2 are greater than a threshold value.

[0033] Output unit 14 is, for example, a display, a speaker, or a printer, and presents the data generated by life prediction unit 124 to the user. The display is, for example, an LCD (liquid crystal display) or an organic EL (electro luminescent) display. Instead of being provided in tire condition estimation device 1, output unit 14 may be connected to tire condition estimation device 1 as an external output device. The connection interface may be any interface compatible with standards such as USB, HDMI, or Bluetooth.

[0034] <Tire Condition Estimation Method> Next, a tire condition estimation method according to one embodiment will be described. Fig. 6 is a flowchart showing an example of the procedure of the tire condition estimation method.

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

[0036] In step S102, opening amount / deviation amount deriving section 121 of tire condition estimation device 1 finds the opening amount and deviation amount of a crack that has occurred on the surface of the target tire that is the estimation target.

[0037] In step S103, the crack propagation pattern determination unit 122 of the tire condition estimation device 1 determines, from the opening amount and the shift amount, whether the crack propagation pattern is one in which the crack propagates in one direction or one in which the crack propagates in two directions.

[0038] In step S104, crack growth rate derivation section 123 of tire condition estimation device 1 calculates the crack growth rate according to the crack growth pattern.

[0039] In step S105, life prediction unit 124 of tire condition estimating device 1 determines the life due to cracks of the target tire from the crack growth rate according to the crack growth pattern.

[0040] As described above, in the first embodiment, the opening amount and deviation amount of a crack occurring on the surface of a target tire are calculated, the crack growth pattern is determined from the opening amount and deviation amount, the crack growth rate corresponding to the crack growth pattern is calculated, and the lifespan of the target tire due to the crack is calculated from the crack growth rate according to the crack growth pattern. This makes it possible to evaluate the depth-wise growth potential of a crack occurring on the surface of a tire at low cost. In the second embodiment, the deviation amount and opening amount are calculated by referring to a database that links the strain of the surface of a crack-free tire calculated using the finite element method with the opening amount and deviation amount measured for multiple tires with cracks of different crack conditions. In the second embodiment, the cost of calculating the opening amount and deviation amount can be reduced, making it possible to evaluate the depth-wise growth potential of a crack occurring on the surface of a tire at even lower cost than in the first embodiment.

[0041] <Program> A computer capable of executing program instructions can be used to function as the above-described tire condition estimation device 1. Here, the computer may be a general-purpose computer, a dedicated computer, a workstation, a PC (Personal Computer), an electronic notepad, a mobile terminal, etc. The program instructions may be program code, code segments, etc. for performing the necessary tasks.

[0042] The control unit 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 configured with multiple processors of the same or different types. The processor performs the above-mentioned processing by reading and executing a program from the storage unit 13. Note that at least a part of the processing content may be realized by hardware.

[0043] The program may be recorded on a computer-readable recording medium. 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, and may be, for example, a CD-ROM, a DVD-ROM, or a USB (Universal Serial Bus) memory. Furthermore, the program may be downloaded from an external device via a network.

[0044] Although the above-described embodiments have been described as typical examples, it will be apparent to those skilled in the art that many modifications and substitutions are possible within the spirit and scope of the present disclosure. Therefore, the present disclosure should not be interpreted as being limited by the above-described embodiments, and various modifications and alterations are possible without departing from the scope of the claims. For example, multiple building blocks shown in the block diagrams of the embodiments may be integrated, or a single building block may be divided. Furthermore, multiple steps shown in the flowcharts of the embodiments may be integrated into one, or a single step may be divided. Contributing to the United Nations-led Sustainable Development Goals (SDGs)

[0045] The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is thought to be a technology that can contribute to "No. 9 - Building a foundation for industry and technological innovation."

[0046] REFERENCE SIGNS LIST 1 Tire condition estimation device 11 Input unit 12 Control unit 13 Storage unit 14 Output unit 121 Opening amount / deviation amount deriving unit 122 Crack growth pattern determining unit 123 Crack growth rate deriving unit 124 Life prediction unit

Claims

1. A tire condition estimation device comprising: an opening amount / shift amount derivation unit that calculates the opening amount and shift amount of a crack that has occurred on the surface of a target tire whose condition is to be estimated; a crack growth pattern determination unit that determines, from the opening amount and shift amount, whether the crack has a crack growth pattern in which it grows in a straight line in the depth direction or a crack growth pattern in which it grows in two directions; a crack growth rate derivation unit that calculates a crack growth rate according to the crack growth pattern; and a lifespan prediction unit that calculates, from the crack growth rate, the lifespan of the target tire due to the crack in accordance with the crack growth pattern.

2. A tire condition estimation device as described in claim 1, wherein the opening / deviation amount deriving unit determines the deviation amount and opening amount by referring to a database that links the strain on the surface of a crack-free tire calculated using the finite element method with the opening amounts and deviation amounts measured for multiple tires with cracks of different crack conditions.

3. A tire condition estimation method in which a tire condition estimation device executes the following steps: determining the amount of opening and displacement of a crack that has occurred on the surface of a target tire to be estimated; determining, from the amount of opening and the amount of displacement, whether the crack has a crack propagation pattern in which it propagates in a straight line in the depth direction or in which it propagates in two directions; determining a crack propagation speed according to the crack propagation pattern; and determining, from the crack propagation speed, the lifespan of the target tire due to the crack, according to the crack propagation pattern.

4. A program for causing a computer to function as the tire condition estimation device according to claim 1 or 2.

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