Method for evaluating carcass line and method for manufacturing tire

Abstract

To provide a method for evaluating a carcass line that can properly evaluate accuracy of a carcass shape of a product tire, and to provide a method for manufacturing a tire.SOLUTION: A method for evaluating a carcass line includes: a reference carcass line acquisition step of acquiring an actual value or prediction value of a carcass line of a carcass layer, as a reference carcass line Lr; a reference point selection step of selecting coordinates of at least two reference points PA, PC that are present on the reference carcass line Lr; a shape parameter value setting step of setting a numerical value of a shape parameter of a specific theoretical expression that defines a theoretical carcass line Lt; a theoretical carcass line calculation step of calculating a theoretical carcass line Lt by substituting the coordinates of at least two reference points and the numerical value of the shape parameter into the theoretical expression; and an evaluation value calculation step of calculating a specific evaluation value on the basis of a comparison result between the reference carcass line Lr and the theoretical carcass line Lt.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a carcass line evaluation method and a tire manufacturing method, and more particularly to a carcass line evaluation method and a tire manufacturing method that can appropriately evaluate the accuracy of the carcass shape of a product tire. [Background technology]

[0002] In recent years, a method for designing a tire carcass shape using a theoretical equation that defines the carcass line shape in a natural equilibrium state has been known. As such a conventional technique, the technique described in Patent Document 1 is known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-066953 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the carcass shape of a finished tire in an inflated state does not match the carcass shape at the design stage (i.e., before vulcanization molding), there is a problem in that the accuracy of the carcass shape of the finished tire cannot be properly evaluated.

[0005] Therefore, the present invention has been made in consideration of the above, and an object of the present invention is to provide a carcass line evaluation method and a tire manufacturing method that can properly evaluate the accuracy of the carcass shape of a product tire. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the carcass line evaluation method of the present invention is a carcass line evaluation method for evaluating the carcass line of a tire having a pair of bead cores, a carcass layer spanned between the pair of bead cores, and a belt layer arranged around the outer periphery of the carcass layer, and is characterized in that it includes a reference carcass line acquisition step for acquiring an actual value or a predicted value of the carcass line of the carcass layer as a reference carcass line, a reference point selection step for selecting the coordinates of at least two reference points on the reference carcass line, a shape parameter value setting step for setting numerical values ​​of shape parameters of a predetermined theoretical formula that defines a theoretical carcass line, a theoretical carcass line calculation step for calculating the theoretical carcass line by substituting the coordinates of the at least two reference points and the numerical values ​​of the shape parameters into the theoretical formula, and an evaluation value calculation step for calculating a predetermined evaluation value based on a comparison result between the reference carcass line and the theoretical carcass line.

[0007] In addition, a tire manufacturing method according to the present invention is a tire manufacturing method for manufacturing a tire having a pair of bead cores, a carcass layer spanned between the pair of bead cores, and a belt layer arranged around the outer periphery of the carcass layer, and includes a reference carcass line acquisition step for acquiring an actual value or a predicted value of the carcass line of the carcass layer as a reference carcass line, a reference point selection step for selecting coordinates of at least two reference points on the reference carcass line, a shape parameter value setting step for setting numerical values ​​of shape parameters of a predetermined theoretical formula that defines a theoretical carcass line, a theoretical carcass line calculation step for calculating the theoretical carcass line by substituting the coordinates of the at least two reference points and the numerical values ​​of the shape parameters into the theoretical formula, and an evaluation value calculation step for calculating a predetermined evaluation value based on a comparison result between the reference carcass line and the theoretical carcass line, and is characterized in that the theoretical carcass line is determined so that the evaluation value is equal to or less than a predetermined threshold value. Effect of the Invention

[0008] In the carcass line evaluation method and tire manufacturing method of the present invention, a predetermined evaluation value is calculated based on the results of a comparison between a reference carcass line and a theoretical carcass line, which has the advantage of being able to quantitatively evaluate the accuracy of the theoretical carcass line, or more specifically, the accuracy of the setting values ​​of the shape parameters in the theoretical formula. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a functional block diagram showing a carcass line evaluation device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view in the tire meridian direction showing a tire that serves as an evaluation standard for the carcass line evaluation device 1. As shown in FIG. [Diagram 3] FIG. 3 is a flowchart showing a carcass line evaluation method. [Figure 4] FIG. 4 is an explanatory diagram showing the carcass line evaluation method shown in FIG. [Diagram 5] FIG. 5 is an explanatory diagram showing the carcass line evaluation method shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the embodiments. The components of the embodiments include those that can be substituted and are obvious substitutes while maintaining the identity of the invention. The multiple modified examples described in the embodiments can be arbitrarily combined within the scope of what is obvious to those skilled in the art.

[0011] [Carcass line evaluation device] FIG. 1 is a functional block diagram showing a carcass line evaluation device 1 according to an embodiment of the present invention.

[0012] The carcass line evaluation device 1 is a device that compares and evaluates a reference carcass line Lr and a theoretical carcass line Lt of a tire 10 described later, and includes a processing device 2, an input device 3, and a display device 4.

[0013] The processing device 2 is, for example, a PC (Personal Computer), and has a CPU (Central Processing Unit) 21, a RAM (Random Access Memory) 22, and a ROM (Read-Only Memory) 23. The processing device 2 is also connected to an external input device 3 and a display device 4 via an input / output unit 24. The ROM 23 stores various programs 23a to 23g, which will be described later. The input device 3 is a device for inputting input data such as necessary conditions to the processing device 2, and is composed of, for example, a keyboard and a mouse. The display device 4 is a device for displaying a condition input screen, generated data, and the like, and is composed of, for example, a PC monitor.

[0014] In this carcass line evaluation device 1, the CPU 21 of the processing device 2 temporarily stores input data from the input device 3, various data read from the ROM 23, and the like in the RAM 22. The CPU 21 also reads and executes various programs 23a to 23g stored in the ROM 23 while referring to these data as necessary. The CPU 21 also displays the generated data and the like on the display device 4. In this way, various functions of the carcass line evaluation device 1 are realized.

[0015] [tire] 2 is a cross-sectional view in the tire meridian direction showing a tire 10 that is an evaluation standard for the carcass line evaluation device 1. The figure shows a cross-sectional view of one side region in the tire radial direction. In this embodiment, a pneumatic radial tire for passenger cars will be described as an example of a tire.

[0016] In the figure, the tire meridian cross section is defined as a cross section of the tire cut by a plane including the tire rotation axis (not shown). The tire equatorial plane CL is defined as a plane that passes through the midpoint of the tire section width defined by JATMA and is perpendicular to the tire rotation axis. The tire width direction is defined as a direction parallel to the tire rotation axis, and the tire radial direction is defined as a direction perpendicular to the tire rotation axis.

[0017] The tire 10 has an annular structure centered on the tire rotation axis, and includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, 16, and a pair of rim cushion rubbers 17, 17 (see Figure 2).

[0018] The pair of bead cores 11, 11 are formed by winding one or more steel bead wires in an annular manner in multiple layers, and are embedded in the bead portions to form the cores of the left and right bead portions. The pair of bead fillers 12, 12 are disposed on the outer periphery of the pair of bead cores 11, 11 in the tire radial direction, respectively, to reinforce the bead portions.

[0019] The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass plies stacked together, and is toroidally stretched between the left and right bead cores 11, 11 to form the tire framework. Both ends of the carcass layer 13 are wrapped around and secured to the outside in the tire width direction so as to envelop the bead cores 11 and the bead fillers 12. The carcass ply of the carcass layer 13 is formed by covering multiple carcass cords made of steel or organic fiber material (e.g., aramid, nylon, polyester, rayon, etc.) with coating rubber and rolling them, and has a cord angle (defined as the inclination angle of the carcass cords in the longitudinal direction with respect to the tire circumferential direction) of 80 degrees or more and 100 degrees or less.

[0020] 2, the carcass layer 13 has a single-layer structure made of a single carcass ply. However, the carcass layer 13 is not limited to this, and may have a multi-layer structure made of a plurality of carcass plies stacked together (not shown).

[0021] The belt layer 14 is formed by laminating a plurality of belt plies 141 to 143, and is disposed by being wound around the outer periphery of the carcass layer 13. The belt plies 141 to 143 each include a pair of cross belts 141, 142 and a belt cover 143.

[0022] The pair of cross belts 141, 142 are formed by covering a plurality of belt cords made of steel or organic fiber material with coating rubber and rolling them, and have a cord angle (defined as the inclination angle of the belt cords in the longitudinal direction with respect to the tire circumferential direction) of 15 degrees or more and 55 degrees or less in absolute value. The pair of cross belts 141, 142 have cord angles of opposite signs to each other, and are layered with the longitudinal directions of the belt cords crossing each other (so-called cross-ply structure). The pair of cross belts 141, 142 are layered and arranged on the outer side of the carcass layer 13 in the tire radial direction.

[0023] The belt cover 143 is configured by covering a belt cover cord made of steel or organic fiber material with coating rubber, and has a cord angle of 0 degrees or more and 10 degrees or less in absolute value. The belt cover 143 is, for example, a strip material configured by covering one or more belt cover cords with coating rubber, and is configured by winding this strip material spirally multiple times in the tire circumferential direction around the outer circumferential surfaces of the cross belts 141, 142. The belt cover 143 is disposed to cover the entire area of ​​the cross belts 141, 142.

[0024] The tread rubber 15 is disposed on the outer periphery of the carcass layer 13 and the belt layer 14 in the tire radial direction to form a tread portion of the tire 10. A pair of sidewall rubbers 16, 16 are disposed on the outer sides of the carcass layer 13 in the tire width direction to form left and right sidewall portions. A pair of rim cushion rubbers 17, 17 extend from the inner side in the tire radial direction of the left and right bead cores 11, 11 and the turned-up portions of the carcass layer 13 to the outer side in the tire width direction to form a rim fitting surface of the bead portion.

[0025] [Carcass line evaluation method] Fig. 3 is a flowchart showing a carcass line evaluation method. Fig. 4 and Fig. 5 are explanatory diagrams showing the carcass line evaluation method described in Fig. 3. Here, a method of evaluation by comparing the reference carcass line Lr of the tire 10 described in Fig. 2 with the theoretical carcass line Lt used in tire design using the carcass line evaluation device 1 described in Fig. 1 will be described.

[0026] In the reference carcass line obtaining step ST01, the reference carcass line obtaining unit 23a (see FIG. 1) reads and obtains data of the reference carcass line Lr of the tire 10 shown in FIG.

[0027] The carcass line is a so-called carcass profile, and is defined as the center line of the carcass layer 13 in a cross-sectional view in the tire meridian direction. In addition, in a configuration in which the carcass layer 13 is formed by laminating a plurality of carcass plies, the carcass line is defined as the average curve of the center lines of the plurality of carcass plies. In addition, in a configuration in which the carcass layer 13 has an asymmetric shape on the left and right sides of the tire, the carcass line is defined in each of the left and right regions of the tire, with the tire centerline described later as the boundary.

[0028] The reference carcass line Lr is defined as an actual measured value or a predicted value of the carcass line of the carcass layer 13 when the tire 10 is mounted on a specified rim, a specified internal pressure is applied, and the tire is in an unloaded state.

[0029] The specified rim refers to the "standard rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. The specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "inflation pressures" specified by ETRTO. The specified load refers to the "maximum load capacity" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "load capacity" specified by ETRTO. However, in JATMA, for passenger car tires, the specified internal pressure is 180 kPa, and the specified load is 88% of the maximum load capacity at the specified internal pressure.

[0030] The actual or predicted values ​​of the carcass line can be obtained based on the cross-sectional information of the tire or the surface shape of the tire. For example, the actual measured values ​​of the carcass line in the inflated state can be obtained by scanning the inflated tire with CT (Computed Tomography), specifically, by irradiating the inflated tire with electromagnetic waves such as X-rays or gamma rays and observing the change in intensity of the electromagnetic waves that pass through the tire. The cross-sectional shape of the carcass layer can be obtained by using a cut sample of the tire or by using an ultrasonic sensor or an eddy current sensor to measure the distance from the inner surface of the tire to the carcass layer. The predicted values ​​of the carcass line can be obtained from other than the actual tire, such as FEM (Finite Element Method) or a numerical model. The actual measured values ​​of the carcass line in the inflated state can be obtained by making a mold of the outer surface of the tire in the inflated state with plaster, and then arranging the tire cut in the radial direction along the mold. In addition, the inner surface shape of the tire in an inflated state can be measured using a laser profile, the distance from the inner surface of the tire to the carcass line can be measured using a cut sample of the tire, and the measured distance can be applied to the measured inner surface shape of the tire to obtain the actual measurement value of the carcass line in an inflated state.

[0031] The reference carcass line Lr is obtained at least in the region from the tire centerline position PA to the maximum width positions PC, PC on the left and right sides of the tire (see FIG. 2). For example, in this embodiment, as shown in FIG. 4, the reference carcass line Lr is obtained in the region of the entire tire, that is, in the region from the tire centerline position PA to the bead core positions PB, PB on the left and right sides of the tire. However, without being limited to this, the reference carcass line Lr may be obtained in the region on one side of the tire bounded by the tire equatorial plane CL (see FIG. 2), that is, in the region from the tire centerline position PA to the position PB of one bead core 11 (not shown).

[0032] 4, the positions PA to PF on the reference carcass line Lr are defined as follows in a cross-sectional view in the tire meridian direction: First, one direction in the tire width direction (i.e., the tire rotational axis direction) is defined as the positive direction of the Z axis, and the outer side in the tire radial direction is defined as the positive direction of the Y axis (see FIG. 1).

[0033] In this case, the tire centerline position PA of the reference carcass line Lr is defined as the intersection point between the reference carcass line Lr and a straight line passing through the left and right maximum width positions PC and the midpoint of PC (not shown) of the reference carcass line Lr and perpendicular to the tire rotation axis. If the tire has a symmetrical structure, the tire centerline position PA is on the tire equatorial plane CL (see FIG. 2). In addition, without being limited to the above, the tire centerline position PA may be defined as the intersection point between the reference carcass line Lr and a straight line passing through the left and right inflection points PF and the midpoint of PF of the reference carcass line Lr and perpendicular to the tire rotation axis.

[0034] The bead core positions PB, PB of the reference carcass line Lr are defined as the intersection points of the reference carcass line Lr and a straight line that passes through the radially outer end faces of the bead cores 11, 11 and is parallel to the tire rotation axis.

[0035] The maximum width positions PC, PC of the reference carcass line Lr are defined as the points on the reference carcass line Lr having the maximum and minimum values ​​of the Z coordinate, respectively.

[0036] The positions PD, PD of the reference carcass line Lr at the measurement point of the effective belt width Wb (see FIG. 2) of the belt layer 14 are defined as the intersection points of the reference carcass line Lr and a straight line passing through the measurement point of the effective belt width Wb and perpendicular to the tire rotation axis.

[0037] The inflection points PF, PF of the reference carcass line Lr are inflection points of the reference carcass line Lr that extend from the tire side portion to the bead portion, and can be simply defined as the start and end points of the nominal rim width of the specified rim 20 (see FIG. 2).

[0038] In the reference point selection step ST02, the reference point selection unit 23b (see FIG. 1) selects the coordinates of at least two reference points on the reference carcass line Lr. These reference points are selected from the region (see FIG. 4) from the tire centerline position PA to one of the maximum width positions PC of the reference carcass line Lr. It is preferable that the first of the two reference points is selected from the tire tread region, and the second reference point is selected from the tire side region.

[0039] The tire tread area is defined as the area from the tire centerline position PA of the reference carcass line Lr to the measurement point of the effective belt width Wb (see FIG. 2) of the belt layer 14. The tire side area is defined as the area from the measurement point of the effective belt width Wb to the maximum width position PC of the reference carcass line Lr.

[0040] The effective belt width Wb of the belt layer 14 is defined as the belt width of the wider cross belt 142 of the pair of cross belts 142, 143 constituting the belt layer 14, and is measured with the tire mounted on a specified rim, a specified internal pressure applied, and in an unloaded state.

[0041] For example, in this embodiment, the point at the tire center line position PA of the reference carcass line Lr is selected as the first reference point, and the point at the maximum width position PC of the reference carcass line Lr is selected as the second reference point. This allows the theoretical carcass line Lt, which will be described later, to be calculated with high accuracy.

[0042] In the shape parameter value setting step ST03, the shape parameter value setting unit 23c sets the numerical values ​​of the shape parameters of a predetermined theoretical formula that defines the theoretical carcass line Lt. When the process returns to step ST03 due to a positive determination in step ST06 described later, the shape parameter value setting unit 23c changes the previous numerical value (first numerical value) of the shape parameter to a new numerical value (second numerical value).

[0043] The theoretical carcass line Lt is defined by a predetermined theoretical formula. As such a theoretical formula, a publicly known formula can be adopted. For radial tires, for example, Bohm's theory (Reference 1: Journal of the Society of Rubber Industry of Japan, Structural Mechanics of Radial Tires, by Takashi Akasaka, Vol. 51, No. 3 (1978); Reference 2: Journal of the Society of Rubber Industry of Japan, Regarding Tire Shape Mechanics, by Shinya Yoshimura, Vol. 50, No. 3 (1977)) and Frank's theory (reference 1 above) can be adopted. For bias tires, for example, membrane theory (reference 2 above), HOFFERBERTH's theory (reference 3: Grand Prix Publishing, Tire Engineering, by Hideo Sakai), and DAY & GEMMAN's theory (reference 3 above) can be adopted.

[0044] In this embodiment, as an example, a case will be described in which the theoretical carcass line Lt is defined using Bohm's theory.

[0045] Bohm's theory is a theoretical formula that defines the carcass line shape in a natural equilibrium state, and the equilibrium carcass line shape of the tread portion is defined as a continuum of arcs with a curvature radius r1 expressed by the following mathematical formulas (1) and (2). The function g(y) indicates the internal pressure distribution rate of the carcass layer 13 from the tread portion toward the side portion. In the range of yD≦y≦yA, the mathematical formulas (1) and (3) are used, and in the range of yB≦y≦yD, the mathematical formulas (2) and (3) are used. Here, yA is the y coordinate of the reference carcass line Lr at the tire centerline position PA, yB is the y coordinate of the reference carcass line Lr at the bead core position PB, yC is the y coordinate of the reference carcass line Lr at the maximum width position PC, and yD is the y coordinate of the position PD of the reference carcass line Lr at the measurement point of the effective belt width Wb. Moreover, the shape parameter α indicates a distribution shape exponent, and the shape parameter η indicates an initial distribution rate.

[0046]

number

[0047]

number

[0048]

number

[0049] In the initial state, the shape parameter value setting unit 23c sets the distribution shape exponent α in the above-mentioned Bohm's theory to an initial value α1, and sets the initial contribution rate η to an initial value η1. In addition, when returning to step ST03 due to a positive determination in step ST06 described later, the shape parameter value setting unit 23c changes and newly sets at least one of the numerical values ​​of the distribution shape exponent α and the initial contribution rate η.

[0050] In the theoretical carcass line calculation step ST04, the theoretical carcass line calculation unit 23d calculates the theoretical carcass line Lt by substituting the coordinates of at least two reference points and the numerical values ​​of the shape parameters described above into a theoretical formula.

[0051] In Fig. 5, the calculated theoretical carcass line Lt is shown superimposed on the above-mentioned reference carcass line Lr. In this embodiment, as shown in Fig. 5, the theoretical carcass line Lt is calculated in the region from the tire center line position PA to the maximum width position PC of the reference carcass line Lr. Specifically, the region for calculating the theoretical carcass line Lt is set so as not to include the inflection point PF of the reference carcass line Lr. This improves the accuracy of the theoretical carcass line Lt, especially when the theoretical carcass line Lt is calculated using Bohm's theory.

[0052] In the evaluation value calculation step ST05, the evaluation value calculation unit 23e calculates a predetermined evaluation value based on the comparison result between the reference carcass line Lr and the theoretical carcass line Lt. This allows the accuracy of the theoretical carcass line Lt, more specifically, the accuracy of the setting values ​​of the shape parameters in the theoretical formula (step ST03), to be quantitatively evaluated.

[0053] For example, in this embodiment, the deviation or error of the theoretical carcass line Lt from the reference carcass line Lr in a predetermined region is calculated as the evaluation value.

[0054] In this embodiment, the deviation amount of the theoretical carcass line Lt from the reference carcass line Lr is integrated in the region from the tire center line position PA of the reference carcass line Lr to the maximum width position PC (see FIG. 5) to calculate the evaluation value. This improves the accuracy of the setting value of the shape parameter in the theoretical formula (step ST03). However, without being limited to this, the deviation amount of the theoretical carcass line Lt from the reference carcass line Lr may be integrated in the region from the tire center line position PA of the reference carcass line Lr to the position PD of the reference carcass line Lr at the measurement point of the effective belt width Wb to calculate the evaluation value. Note that, when the region is set narrower than the above region (PA to PD), there may be a shape parameter that matches the theoretical carcass line Lt depending on the shape of the reference carcass line Lr. In that case, the region may be set narrower than the above region (PA to PD).

[0055] In the value change necessity determination step ST06, the value change necessity determination unit 23f determines whether or not the value of the shape parameter needs to be changed. If the determination is affirmative, the process returns to step ST03, and if the determination is negative, the process proceeds to step ST07.

[0056] Specifically, in the case of a positive determination, the previous numerical value (first numerical value) of the shape parameter is changed and a new numerical value (second numerical value) is set (step ST03). Then, a new theoretical carcass line Lt (a second theoretical carcass line Lt for the previous first theoretical carcass line: not shown) is calculated using the new numerical value (step ST04), and a new evaluation value (a second evaluation value for the previous first evaluation value) is calculated by comparing the new theoretical carcass line Lt with the reference carcass line Lr (step ST05). In addition, by sequentially changing the numerical values ​​of the shape parameters within a predetermined numerical range, multiple evaluation values ​​corresponding to each numerical value are obtained. Furthermore, by changing the numerical values ​​of each of the multiple types of shape parameters, multiple evaluation values ​​corresponding to combinations of the numerical values ​​of the multiple types of shape parameters are obtained.

[0057] For example, in this embodiment, the theoretical carcass line Lt is calculated using Bohm's theory as described above (step ST04). At this time, the respective values ​​(αi: i = 1, 2, ... m and ηj: j = 1, 2, ... n) of the distribution shape index α and the initial contribution rate η, which are shape parameters, are sequentially changed and set from the initial value (first value: α1, η1) to another value (second value) (positive judgment in step ST04 and step ST06). Then, a plurality of evaluation values ​​corresponding to the combination of the respective values ​​of the distribution shape index α and the initial contribution rate η are calculated (step ST05).

[0058] In the shape parameter identifying step ST07, the shape parameter identifying unit 23g compares the multiple evaluation values ​​to identify the shape parameters. This allows the shape parameters of the theoretical formula to be identified so that the theoretical carcass line Lt based on the theoretical formula accurately indicates the reference carcass line Lr of the product tire.

[0059] For example, in this embodiment, a plurality of evaluation values ​​corresponding to the respective combinations of the numerical values ​​of the distribution shape index α and the initial contribution ratio η are calculated as described above. Then, by comparing these evaluation values, it is possible to determine a combination of the numerical values ​​of the distribution shape index α and the initial contribution ratio η so that the error between the theoretical carcass line Lt used in tire design and the reference carcass line Lr in the product tire is minimized, or the error is equal to or smaller than a predetermined threshold value.

[0060] In this embodiment, the numerical values ​​of the multiple shape parameters (α, η) are changed as described above (positive determinations in steps ST04 and ST06), and multiple evaluation values ​​are calculated (step ST05). However, this is not limiting, and multiple evaluation values ​​may be calculated by changing a single shape parameter. For example, η can be fixed and only α can be changed, or α can be fixed and only η can be changed.

[0061] In this embodiment, the Bohm's theory is adopted as described above, and the distribution shape exponent α and the initial contribution rate η, which are shape parameters, are set (step ST04), and the evaluation value is calculated (step ST05). However, this is not limiting, and for example, the membrane theory may be adopted, and in this case, it is preferable to change the ratio of the circumferential force and the radial force acting on the membrane surface, which is the shape parameter, and calculate the evaluation value.

[0062] [effect] As described above, [1] this carcass line evaluation method evaluates the carcass line of a tire (see FIG. 1) including a pair of bead cores 11, 11, a carcass layer 13 stretched between the pair of bead cores 11, 11, and a belt layer 14 arranged on the outer periphery of the carcass layer 13. The method also includes a reference carcass line acquisition step ST01 (see FIG. 3) for acquiring an actual measurement value or a predicted value of the carcass line of the carcass layer 13 as a reference carcass line Lr, a reference point selection step ST02 for selecting coordinates of at least two reference points (points PA and PC in FIG. 4) on the reference carcass line Lr, a shape parameter value setting step ST03 for setting numerical values ​​of shape parameters of a predetermined theoretical formula that defines a theoretical carcass line Lt, a theoretical carcass line calculation step ST04 for calculating the theoretical carcass line Lt by substituting the coordinates of at least two reference points and the numerical values ​​of the shape parameters into the theoretical formula, and an evaluation value calculation step ST05 for calculating a predetermined evaluation value based on a comparison result between the reference carcass line Lr and the theoretical carcass line Lt.

[0063] In this configuration, a predetermined evaluation value is calculated based on the comparison result between the reference carcass line Lr and the theoretical carcass line Lt, which has the advantage of allowing the accuracy of the theoretical carcass line Lt, more specifically, the accuracy of the setting values ​​of the shape parameters in the theoretical formula (step ST03), to be quantitatively evaluated.

[0064] [2] In the carcass line evaluation method described in [1] above, in the reference carcass line acquisition step ST01, an actual measurement value acquired by CT scanning an inflated tire is acquired as the reference carcass line Lr (see FIG. 4). This has the advantage of improving the accuracy of the reference carcass line Lr.

[0065] [3] In the carcass line evaluation method described in [1] or [2] above, in the reference point selection step ST02, a first reference point of the at least two reference points is selected from the area from the tire center line position PA of the reference carcass line Lr to the measurement point of the effective belt width Wb (see FIG. 1) of the belt layer 14, and a second reference point is selected from the area from the measurement point of the effective belt width Wb to the maximum width position PC of the reference carcass line Lr. This has the advantage of improving the accuracy of the reference carcass line Lr.

[0066] [4] In the carcass line evaluation method described in [3] above, the tire center line position PA (see FIG. 5) is defined as a point on the reference carcass line Lr that is the midpoint (not shown) of the maximum width position PC on the left and right of the reference carcass line Lr in the tire width direction, and the maximum width position PC is defined as either the maximum width position PC on the left or right of the reference carcass line Lr. This has the advantage of improving the accuracy of the reference carcass line Lr.

[0067] [5] In the carcass line evaluation method according to any one of the above [1] to [4], in the shape parameter value setting step ST03, the theoretical carcass line Lt (see FIG. 5) is defined based on the Bohm's theoretical formula, and at least one of the distribution shape index α and the initial contribution rate η of the Bohm's theoretical formula is set as the shape parameter value. This has the advantage of being able to quantitatively evaluate the accuracy of the theoretical carcass line Lt.

[0068] [6] In the carcass line evaluation method according to any one of the above [1] to [5], in the theoretical carcass line calculation step ST04, the theoretical carcass line Lt (see FIG. 5) is calculated in the region from the tire center line position PA to the maximum width position PC of the reference carcass line Lr. This has the advantage that the accuracy of the theoretical carcass line Lt is improved, particularly when the theoretical carcass line Lt is calculated using Bohm's theory.

[0069] [7] In the carcass line evaluation method according to any one of the above [1] to [6], in the evaluation value calculation step ST05, the evaluation value is calculated based on a comparison result between the reference carcass line Lr (see FIG. 5) and the theoretical carcass line Lt in the region from the tire center line position PA to the maximum width position PC of the reference carcass line Lr. This has the advantage of improving the accuracy of the setting values ​​of the shape parameters in the theoretical formula (step ST03).

[0070] [8] The carcass line evaluation method according to any one of the above [1] to [7] further includes a shape parameter identification step ST07 (see FIG. 3) for identifying the shape parameters based on a comparison result of a plurality of evaluation values ​​calculated using shape parameters set to mutually different numerical values. This has the advantage that the shape parameters of the theoretical formula can be identified so that the theoretical carcass line Lt based on the theoretical formula accurately indicates the reference carcass line Lr of the product tire.

[0071] [9] The tire manufacturing method manufactures a tire 10 (see FIG. 2) including a pair of bead cores 11, 11, a carcass layer 13 stretched between the pair of bead cores 11, 11, and a belt layer 14 disposed on the outer periphery of the carcass layer 13. The tire manufacturing method also includes a reference carcass line acquisition step (see FIG. 3) for acquiring an actual measurement value or a predicted value of the carcass line of the carcass layer 13 as a reference carcass line Lr, a reference point selection step ST02 for selecting coordinates of at least two reference points (points PA and PC in FIG. 4) on the reference carcass line Lr, a shape parameter value setting step ST03 for setting numerical values ​​of shape parameters of a predetermined theoretical formula that defines a theoretical carcass line Lt, a theoretical carcass line calculation step ST04 for calculating the theoretical carcass line Lt by substituting the coordinates of at least two reference points and the numerical values ​​of the shape parameters into the theoretical formula, and an evaluation value calculation step ST05 for calculating a predetermined evaluation value based on a comparison result between the reference carcass line Lr and the theoretical carcass line Lt. In addition, the theoretical carcass line Lt is determined so that the evaluation value is equal to or smaller than a predetermined threshold value. [Explanation of symbols]

[0072] 1 Carcass line evaluation device; 2 Processing device; 3 Input device; 4 Display device; 10 Tire; 11 Bead core; 12 Bead filler; 13 Carcass layer; 14 Belt layer; 15 Tread rubber; 16 Sidewall rubber; 17 Rim cushion rubber; 141, 142 Cross belt; 143 Belt cover

Claims

1. A carcass line evaluation method for evaluating a carcass line of a tire including a pair of bead cores, a carcass layer disposed between the pair of bead cores, and a belt layer disposed on an outer periphery of the carcass layer, comprising: A reference carcass line acquisition step of acquiring an actual measured value or a predicted value of the carcass line of the carcass layer as a reference carcass line; a reference point selection step of selecting coordinates of at least two reference points on the reference carcass line; a shape parameter value setting step for setting numerical values ​​of shape parameters of a predetermined theoretical formula that defines a theoretical carcass line; a theoretical carcass line calculation step of calculating the theoretical carcass line by substituting the coordinates of the at least two reference points and the numerical values ​​of the shape parameters into the theoretical formula; and calculating an evaluation value based on a comparison result between the reference carcass line and the theoretical carcass line.

2. The carcass line evaluation method according to claim 1 , wherein in the reference carcass line obtaining step, actual measurements obtained by CT scanning an inflated tire are obtained as the reference carcass line.

3. 2. The carcass line evaluation method according to claim 1, wherein in the reference point selection step, a first reference point of the at least two reference points is selected from a region from a tire center line position of the reference carcass line to a measurement point of an effective belt width of the belt layer, and a second reference point is selected from a region from the measurement point of the effective belt width to a maximum width position of the reference carcass line.

4. 4. The carcass line evaluation method according to claim 3, wherein the tire center line position is defined as a point on the reference carcass line that is a midpoint of the left and right maximum width positions of the reference carcass line in the tire width direction, and the maximum width position is defined as either one of the left and right maximum width positions of the reference carcass line.

5. 2. The carcass line evaluation method according to claim 1, wherein in the shape parameter value setting step, the theoretical carcass line is defined based on Bohm's theoretical formula, and at least one of the distribution shape index α and the initial contribution rate η of the Bohm's theoretical formula is set as the value of the shape parameter.

6. 2. The carcass line evaluation method according to claim 1, wherein in the theoretical carcass line calculation step, the theoretical carcass line is calculated in a region from a tire center line position to a maximum width position of the reference carcass line.

7. 2. The carcass line evaluation method according to claim 1, wherein in the evaluation value calculation step, the evaluation value is calculated based on a comparison result between the reference carcass line and the theoretical carcass line in a region from a tire center line position to a maximum width position of the reference carcass line.

8. The carcass line evaluation method according to claim 1 , further comprising a shape parameter identifying step of identifying the shape parameter based on a comparison result of a plurality of the evaluation values ​​calculated using the shape parameters set to mutually different numerical values.

9. A tire manufacturing method for manufacturing a tire including a pair of bead cores, a carcass layer disposed between the pair of bead cores, and a belt layer disposed on an outer periphery of the carcass layer, comprising: A reference carcass line acquisition step of acquiring an actual measured value or a predicted value of the carcass line of the carcass layer as a reference carcass line; a reference point selection step of selecting coordinates of at least two reference points on the reference carcass line; a shape parameter value setting step for setting numerical values ​​of shape parameters of a predetermined theoretical formula that defines a theoretical carcass line; a theoretical carcass line calculation step of calculating the theoretical carcass line by substituting the coordinates of the at least two reference points and the numerical values ​​of the shape parameters into the theoretical formula; an evaluation value calculation step of calculating a predetermined evaluation value based on a comparison result between the reference carcass line and the theoretical carcass line; and A tire manufacturing method, comprising: determining the theoretical carcass line so that the evaluation value is equal to or less than a predetermined threshold value.

Images