JP6204719B2 - Tire design method - Google Patents

Description

  The present invention relates to a tire design method capable of efficiently designing spike pins and holes in a tread portion of a tire into which spike pins are fitted.

  Patent Document 1 below proposes a tire that has improved running performance on icy and snowy roads by attaching spike pins to the tread portion. A plurality of holes for fitting spike pins are provided in the tread rubber tread of such a tread portion.

JP 2012-001120 A

  In order to fully exhibit the running performance on icy and snowy roads, it is important to fit them so that the gap between the spike pin and the hole is small. In a conventional design method, a spike pin and a tire hole actually manufactured are fitted together, and the fitting state is evaluated from, for example, a cross-sectional image captured by a CT scanning device or the like. For this reason, in the conventional design method, the cost required for the trial production of spike pins and tires and the evaluation of the fitting state increased, and there was a problem that the design could not be performed efficiently.

  Also, using a spike pin model and a rubber model, each model of tread rubber including spike pins and holes, modeled with a finite number of elements, the fitting state between the spike pin model and the holes is evaluated using a computer. It is also possible. However, when the spike pin model is inserted into the hole of the rubber model as it is, there is a problem that element collapse occurs in which the volume of the element of the rubber model becomes negative, and calculation loss is likely to occur.

  The present invention has been devised in view of the above circumstances, and provides a tire design method capable of efficiently designing spike pins and holes in a tread portion of a tire into which the spike pins are fitted. The main purpose is to do.

  The present invention is a method for designing a spike pin and a hole in a tread portion of a tire into which the spike pin is fitted using a computer, and the size of the hole is larger than the size of the spike pin. A spike pin model in which the spike pin is modeled by a finite number of elements is input to the computer, and at least a part of the tread rubber of the tread portion including the hole is input to the computer. A step of inputting a rubber model modeled by a finite number of elements, a step of fitting the spike pin model into a hole of the rubber model, and a step of fitting the spike pin model to the hole of the rubber model; A fitting state with a hole, and the fitting step includes the spike pin model and the rubber module. Disabling deformation calculation due to contact with the screw, aligning the center axis of the spike pin model with the center axis of the hole, and overlapping the spike pin model and the rubber model, The first step of shrinking the spike pin model or expanding the rubber model to eliminate the overlap between the spike pin model and the rubber model, enabling effective calculation of deformation due to contact between the spike pin model and the rubber model And a second step of returning the spike pin model or the rubber model to an original magnification and fitting the spike pin model into the hole.

  In the tire designing method according to the present invention, the spike pin model and the rubber model are preferably a two-dimensional model based on a cross-sectional shape including the central axis.

In the tire designing method according to the present invention, the first step is to inflate the rubber model, the thermal expansion coefficient of the tread rubber is defined in the rubber model, and the first step includes: The rubber model is expanded by increasing the temperature of the rubber model based on the thermal expansion coefficient, and the second step returns the temperature of the rubber model based on the thermal expansion coefficient. It is desirable to shrink the model .

  In the tire designing method according to the present invention, the rubber model includes an inner surface which is a surface opposite to the hole, and the fitting step includes a position of the inner surface of the rubber model after the second step. Preferably, the method further includes a step of calculating the deformation of the rubber model so as to coincide with the position of the inner surface of the rubber model before the first step.

  In the tire designing method according to the present invention, the computer calculates the deformation of the rubber model by moving the spike pin model fitted in the hole in the fitting step so as to be pulled out from the hole. Preferably, the method further includes a step of evaluating the anti-pinning performance of the spike pin model and the hole based on the deformation calculation of the rubber model.

  The tire designing method of the present invention includes a fitting step in which a computer fits a spike pin model into a hole of a rubber model, and a step of evaluating a fitting state between the spike pin model and the hole. For this reason, the design method of the present invention can evaluate a fitting state using a computer without making a prototype of a spike pin or a tire, so that the spike pin and the tread rubber hole can be efficiently designed. .

  In the fitting step, the deformation calculation due to the contact between the spike pin model and the rubber model is invalidated, the center axis of the spike pin model and the center axis of the hole are matched, and the spike pin model and the rubber model are Including overlapping steps. Further, in the fitting step, the first step of contracting the spike pin model or expanding the rubber model to eliminate the overlap between the spike pin model and the rubber model, the deformation calculation by contact between the spike pin model and the rubber model is performed. And a second step of returning the spike pin model or rubber model to its original magnification and fitting the spike pin model into the hole.

  Such a fitting step does not need to reproduce the actual process of driving the spike pin model into a hole smaller than that of the spike pin model, for example, and can prevent local large deformation of the rubber model. For this reason, in the fitting step of the present invention, it is possible to prevent calculation loss due to element collapse, and to reliably calculate the fitting state between the spike pin model and the hole.

It is a perspective view of the computer which performs the design method of this embodiment. It is sectional drawing of the hole of a spike pin and a tread part. It is a flowchart which shows an example of the design method of this embodiment. It is a figure which visualizes and shows a spike pin model. It is a figure which visualizes and shows a rubber model. It is a flowchart which shows an example of the fitting step of this embodiment. It is the figure which arranged the spike pin model and the rubber model overlappingly. It is a figure explaining the 1st step which expands a rubber model. It is a figure explaining the 2nd step which shrinks a rubber model. It is a figure which expands and shows the rubber model and spike pin model after a 2nd step. It is a figure which shows the rubber model which made the position of the inner surface after a 2nd step correspond to the position of the inner surface before a 1st step. It is a flowchart which shows the design method of other embodiment. It is a figure explaining the state which moved the spike pin model in the direction pulled out from the hole of a rubber model. It is a graph which shows the relationship between the movement distance of a spike pin model, and the extraction force F of a spike pin model.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The tire design method of the present embodiment (hereinafter sometimes simply referred to as “design method”) is for designing spike pins and holes in the tread portion of the tire into which the spike pins are fitted using a computer. Is the method.

  As shown in FIG. 1, the computer 1 includes a main body 1a, a keyboard 1b, a mouse 1c, and a display device 1d. The main body 1a is provided with an arithmetic processing unit (CPU), a ROM, a working memory, a storage device such as a magnetic disk, and disk drive devices 1a1, 1a2. Note that a processing procedure (program) for executing the design method of the present embodiment is stored in the storage device in advance.

  As shown in FIG. 2, the spike pin 2 includes a base portion 5 that is fitted into the hole 4 of the tread portion 3 of the tire, and a spike portion 6 that protrudes outward in the tire radial direction from the base portion 5.

  The base 5 has a conical surface between a large diameter portion 5A disposed on the outer side in the tire radial direction, a small diameter portion 5B disposed on the inner side in the tire radial direction of the large diameter portion 5A, and between the large diameter portion 5A and the small diameter portion 5B. 5C and a flange 5D fixed to the inner end of the small diameter portion 5B.

  The outer diameter D1a of the large diameter portion 5A of the present embodiment is set larger than the outer diameter D1b of the small diameter portion 5B. Further, the outer diameter D1d of the flange 5D is set to be larger than the outer diameter D1b of the small diameter portion 5B. As a result, a constricted portion 5E is formed in the base portion 5 between the large diameter portion 5A and the flange 5D. In this manner, the constricted portion 5E can cause the tread rubber 3G to bite in greatly by fitting the base portion 5 into the hole 4, and can improve anti-pinning resistance.

  The spike portion 6 protrudes in the tire radial direction from the outer end of the large diameter portion 5A in the tire radial direction and the tread surface 3s of the tread portion 3. Furthermore, the spike portion 6 is formed in a columnar shape whose outer diameter D2 is smaller than the outer diameter D1b of the small diameter portion 5B of the base portion 5. Such a spike portion 6 can contact the road surface and obtain a large frictional force.

  The hole 4 is a circular hole with a bottom extending from the tread surface 3s of the tread portion 3 inward in the tire radial direction. The hole 4 of the present embodiment includes an outer portion 4A disposed on the outer side in the tire radial direction and an inner portion 4B disposed on the inner side in the tire radial direction of the outer portion 4A.

  The outer diameters D3a and D3b of the outer portion 4A and the inner portion 4B are formed smaller than the outer diameter D1b of the small diameter portion 5B of the spike pin 2. Furthermore, the length L3 of the hole 4 in the tire radial direction is set to be smaller than the length L1 of the base portion 5 of the spike pin 2 in the tire radial direction. Since such a hole 4 can press-fit the spike pin 2, it can improve anti-pinning performance. Further, the outer diameter D3b of the inner portion 4B is set larger than the outer diameter D3a of the outer portion 4A. For this reason, the hole 4 can be deformed along the constricted portion 5E of the base portion 5 of the spike pin 2, and the base portion 5 can be prevented from being pulled out.

  FIG. 3 shows a specific procedure of the design method of the present embodiment. In the present embodiment, first, a spike pin model obtained by modeling the spike pin 2 is input to the computer 1 (step S1).

  As shown in FIG. 2, the spike pin 2 has rotational symmetry about the central axis 2c. Therefore, as shown in FIG. 4, the spike pin model 7 of the present embodiment is set as a two-dimensional model based on a cross-sectional shape including the central axis 2 c (shown in FIG. 2) of the spike pin 2. Since such a spike pin model 7 is defined by a half area with respect to the central axis 7c, for example, the calculation time can be shortened compared to a three-dimensional model.

  The spike pin model 7 of the present embodiment is modeled by limiting only the base portion 5 fitted into the hole 4 among the base portion 5 and spike portion 6 of the spike pin 2 shown in FIG. This is because the spike portion 6 does not affect the fitting with the hole 4 of the tread rubber 3G. Therefore, since the spike pin model 7 is modeled by limiting only the base portion 5, the time required for modeling and the calculation time can be shortened.

  The spike pin model 7 of this embodiment is modeled only on the outer surface of the base 5 of the spike pin 2 shown in FIG. For this reason, the spike pin model 7 can further reduce the time required for modeling and the calculation time. The spike pin model 7 is provided with a large-diameter portion 8A, a small-diameter portion 8B, a joint portion 8C, and a flange 8D that model the large-diameter portion 5A, the small-diameter portion 5B, the joint portion 5C, and the flange 5D. Furthermore, each dimension of the spike pin model 7 is set based on each dimension of the spike pin 2.

  A fixed boundary condition is set for the center axis 7 c of the spike pin model 7. In the spike pin model 7, a contact condition for preventing other models from slipping through the spike pin model 7 is defined in the contour excluding the central axis 7 c.

  The spike pin model 7 is modeled (discretized) with a finite number of elements 10 that can be handled by a numerical analysis method. As a numerical analysis method, a finite element method is employed in this embodiment.

  The element 10 of the present embodiment is a quadrilateral element having four nodes 10s, but other than this, for example, a triangular element having three nodes 10s, a beam element having two nodes 10s, or the like. May be used. Such a triangular element and a beam element are suitable for expressing a complicated shape as compared with a quadrilateral element. Each element 10 includes numerical data such as an element number, a node 10s number, a coordinate value of the node 10s, and material characteristics (for example, density, Young's modulus or damping coefficient) of the spike pin 2 (shown in FIG. 2). Is defined. These numerical data are stored in the computer 1.

  Next, a rubber model in which at least a part of the tread rubber 3G including the hole 4 shown in FIG. 2 is modeled with a finite number of elements is input to the computer 1 (step S2).

  As shown in FIG. 2, the hole 4 has rotational symmetry about the central axis 4 c of the hole 4, similar to the spike pin 2. Therefore, as shown in FIG. 5, the rubber model 11 including the hole 12 is set as a two-dimensional model based on a cross-sectional shape including the central axis 4 c of the hole 4. A fixed boundary condition is set for the central axis 12 c of the hole 12. Further, in the rubber model 11, a contact condition for preventing other models from slipping through the rubber model 11 is defined on the contour excluding the central axis 12 c.

  The rubber model 11 includes a tread surface 11 u provided with a hole 12, an inner surface 11 d that is a surface opposite to the hole 12, and a side surface 11 s that is a surface opposite to the central axis 12 c of the hole 12. Is formed. Further, the hole 12 is provided with an outer part 12A and an inner part 12B based on the outer part 4A and the inner part 4B of the hole 4 shown in FIG. Each dimension of the hole 12 is set based on each dimension of the hole 4.

  Similar to the spike pin model 7, the rubber model 11 is modeled (discretized) with a finite number of elements 13. Each element 13 is similar to the element 10 of the spike pin model 7 such as an element number, the number of the node 13s, the coordinate value of the node 13s, and the material characteristics of the tread rubber 3G (for example, density, Young's modulus or damping coefficient). Numeric data is defined.

Furthermore, the thermal expansion coefficient of the tread rubber 3G is defined in the rubber model 11 of the present embodiment. Here, the coefficient of thermal expansion indicates the rate at which the length and volume of an object expand with increasing temperature. The thermal expansion coefficient of the present embodiment is defined as a surface expansion coefficient because the rubber model 11 is set as a two-dimensional model. Such a thermal expansion coefficient can define the area of the rubber model 11 by the following formula (1).
V = V ₀ (1 + αt) (1)
Here, each variable and constant are as follows.
V: Area of tread rubber at t ° C. V ₀ : Area of tread rubber at reference temperature (0 ° C.) α: Thermal expansion coefficient (surface expansion coefficient) of tread rubber
t: Temperature change from the reference temperature (0 ° C)

  In the above formula (1), the area V of the rubber model 11 can be linearly increased / decreased while maintaining the ratio of the X axis and the Y axis by increasing / decreasing the temperature change t. Further, since the rubber model 11 is numerical data, it can be expanded to a size that is impossible in reality by substituting a very large numerical value for the temperature change t. As the thermal expansion coefficient α, for example, a general rubber thermal expansion coefficient (for example, about 0.0002 to 0.0003 (1 / ° C.)) is desirable. In step S2, such a rubber model 11 is stored in the computer 1.

  Next, the spike pin model 7 is fitted into the hole of the rubber model 11 (fitting step S3). FIG. 6 shows a specific procedure of the fitting step S3 of the present embodiment.

  In the fitting step S3 of the present embodiment, first, deformation calculation due to contact between the spike pin model 7 and the rubber model 11 is invalidated (step S31). In step S31, the contact condition of the spike pin model 7 and the rubber model 11 is invalidated, and the spike pin model 7 and the rubber model 11 are defined so as to be able to slip through each other.

  Next, the spike pin model 7 and the rubber model 11 are overlapped with the central axis 7c of the spike pin model 7 and the central axis 12c of the hole 12 aligned (step S32). The contact condition of the spike pin model 7 and the rubber model 11 is set to invalid beforehand. For this reason, as shown in FIG. 7, the spike pin model 7 and the rubber model 11 can pass through each other. The coordinate values of the spike pin model 7 and the rubber model 11 are stored in the computer 1.

  Next, the rubber model 11 is inflated, and the spike pin model 7 and the rubber model 11 are not overlapped (first step S33). In the first step S33, the rubber model 11 is expanded (the area V is increased) by gradually increasing the temperature change t based on the thermal expansion coefficient α of the above formula (1). Thereby, in 1st step S33, as shown in Drawing 8, hole 12 of rubber model 11 can be made larger than spike pin model 7. The temperature change t of the present embodiment is appropriately set so that the hole 12 is larger than the spike pin model 7, but may be set to about 4000 to 6000 ° C., for example.

  Next, the deformation calculation by the contact between the spike pin model 7 and the rubber model 11 is validated (step S34). In step S34, the contact conditions of the spike pin model 7 and the rubber model 11 are set to be effective. Thereby, the spike pin model 7 and the rubber model 11 are defined so as not to slip through.

  Next, the rubber model 11 is returned to the original magnification, and the spike pin model 7 is fitted into the hole 12 (second step S35). In the second step S35, the temperature change t of the rubber model 11 is returned to the initial value based on the thermal expansion coefficient of the above formula (1), and the rubber model 11 is contracted to the original area.

  In the second step S35, as shown in FIG. 9, the hole 12 comes into contact with the spike pin model 7 due to the contraction of the rubber model 11. Further, the rubber model 11 is contracted in a state where the hole 12 is in contact with the spike pin model 7. As a result, the rubber model 11 is deformed along the contour of the spike pin model 7. Therefore, in the second step S35, it is possible to calculate the state in which the spike pin model 7 is fitted in the hole of the rubber model 11.

  In the deformation calculation of the rubber model 11, a mass matrix, a stiffness matrix, and a damping matrix of the element 13 are created based on the shape and material characteristics of each element 13 (shown in FIG. 5). In addition, these matrices are combined to create a matrix for the entire system. Then, the computer 1 creates equations of motion by applying various conditions, and performs deformation calculation of the rubber model 11 for each unit time Tx (x = 0, 1,...) (For example, every 1 μsec). . Such deformation calculation can be performed using commercially available finite element analysis application software such as LS-DYNA manufactured by JSOL.

  In this way, in the second step S35, the spike pin model 7 can be fitted into the hole 12 of the rubber model 11 as shown in FIG. For this reason, in the fitting step S3, for example, it is not necessary to reproduce the actual process of driving the spike pin model 7 into the hole 12 smaller than the spike pin model 7 from the tread surface 11u side. Large deformation can be prevented. For this reason, in fitting step S3 of this embodiment, calculation omission due to element collapse can be prevented, and the fitting state between spike pin model 7 and hole 12 can be reliably calculated.

  As shown in FIG. 9, in the second step S <b> 35, when the rubber model 11 is contracted, in the region 11 </ b> T on the outer side in the tire radial direction of the large diameter portion 8 </ b> A of the spike pin model 7, the rubber model 11 There is a case where it bites into the central axis 7c side. For this reason, in the present embodiment, prior to the second step S35, the boundary condition 14 that extends linearly outward in the tire radial direction along the outline of the large-diameter portion 8A of the spike pin model 7 and prevents the rubber model 11 from entering. Is preferably defined. Thereby, in the second step S35, the biting of the region 11T of the rubber model 11 can be prevented, so that the fitting state between the spike pin model 7 and the hole 12 can be reliably calculated.

  As shown in FIG. 2, the tread rubber 3G of the tire is provided with a highly rigid belt layer (not shown) on the inner side in the tire radial direction. For this reason, even if the spike pin 2 is fitted in the hole 4 inside the tread rubber 3G in the tire radial direction, the tread rubber 3G hardly deforms. On the other hand, in the rubber model 11 after the second step S35, as shown in FIG. 10, the position of the inner surface 11d is different from the position before the first step S33 (indicated by a two-dot chain line).

  For this reason, in this embodiment, the deformation of the rubber model 11 is performed so that the position of the inner surface 11d of the rubber model 11 after the second step S35 matches the position of the inner surface 11d of the rubber model 11 before the first step S33. Calculated (step S36).

  In step S36, the deformation of the rubber model 11 is calculated while gradually moving the position of the inner surface 11d of the rubber model 11 after the second step S35 to the position of the inner surface 11d before the first step S33 (shown in FIG. 10). Is done. Thereby, in step S36, as shown in FIG. 11, the inner surface 11d of the rubber model can be matched with the position of the inner surface 11d before the first step S33, and the spike pin 2 and the hole 4 (shown in FIG. 2). ) Can be approximated with high accuracy.

  Next, the computer 1 evaluates the fitting state between the spike pin model 7 and the hole 12 (step S4). In step S 4, the fitting state is evaluated based on the area of the gap between the spike pin model 7 and the hole 12 and the shape of the hole 12. If it is determined in step S4 that the fitting state between the spike pin model 7 and the hole 12 is good, the spike pin 2 and the tire are manufactured based on the spike pin model 7 and the hole 12 (step S5). On the other hand, when it is determined that the fitting state between the spike pin model 7 and the hole 12 is poor, various conditions such as the shape of the spike pin model 7 and the hole 12 are changed (step S6), and steps S3 to S4 are performed. Is executed again.

  Thus, since the design method of this embodiment can evaluate a fitting state using the computer 1 without making a prototype of a spike pin or a tire, the spike pin and the tread rubber hole are efficiently designed. be able to.

  In the first step S33 of the present embodiment, the rubber model 11 is expanded, but is not limited thereto. For example, the spike pin model 7 may be contracted, and the overlap between the spike pin model 7 and the rubber model 11 may be eliminated. In this case, in the second step S35, it is desirable that the spike pin model 7 is returned to the original magnification and the spike pin model 7 is fitted into the hole 12. In such a design method, since it is not necessary to bite the region 11T (shown in FIG. 9) of the rubber model 11 or move the inner surface 11d of the rubber model 11, the calculation time can be shortened.

In the design method of the present embodiment, the spike pin 2 and the tire are manufactured (step S5) after the fitting state of the spike pin model 7 and the hole 12 is evaluated (step S4). However, the present invention is not limited to this. For example, after step S4, the anti-pinning performance of the spike pin model 7 may be evaluated. FIG. 12 shows a specific procedure of the design method according to another embodiment of the present invention.

  In the design method of this embodiment, as shown in FIG. 13, the computer 1 pulls out the spike pin model 7 (shown in FIG. 11) fitted in the hole 12 from the hole 12 in the fitting step S3. And the deformation of the rubber model 11 is calculated (step S7). In step S7, first, the spike pin model 7 is moved at a constant speed outward in the tire radial direction. In step S7, a force F required to pull out the spike pin model 7 (hereinafter, referred to as “pull out force”) F is calculated by calculating deformation of the rubber model 11 accompanying the movement of the spike pin model 7. The FIG. 14 is a graph showing the relationship between the movement distance of the spike pin model 7 and the pulling force F of the spike pin model 7.

  By the way, as shown in FIG. 2, the tread rubber 3G of the tire is provided with a highly rigid belt layer (not shown). For this reason, even if the spike pin 2 is pulled out from the hole 4 on the inner side in the tire radial direction of the tread rubber 3G, it hardly deforms. Accordingly, in step S7, it is desirable that the spike pin model 7 is moved with the position of the inner surface 11d of the rubber model 11 fixed. Thereby, in step S7, the deformation calculation of the rubber model 11 accompanying the movement of the spike pin model 7 can be approximated to the actual deformation of the tread rubber 3G.

  Next, based on the deformation calculation of the rubber model 11, the anti-pinning performance of the spike pin model 7 and the hole 12 is evaluated (step S8). In step S8, the anti-pinning performance is evaluated based on the graph shown in FIG. In step S8, it is determined that the anti-pinning resistance performance is good enough to maintain the large pulling force F from the initial movement of the spike pin model 7.

  In step S8, when it is determined that the anti-pinning resistance is good, the spike pin 2 and the tire are manufactured based on the spike pin model 7 and the hole 12 (step S5). On the other hand, if it is determined that the anti-pinning resistance is poor, the design of the conditions such as the shape of the spike pin model 7 and the hole 12 is changed (step S9), and the steps S3, S4, S7 and S8 are performed again. Executed.

  As described above, the design method of this embodiment can evaluate the fitting state using the computer 1 without trial manufacture of spike pins or tires, and can further evaluate the anti-pinning resistance performance. . Therefore, in the design method of this embodiment, the spike pin and the tread rubber hole, which are excellent in the fitting state and the anti-pinning performance, can be designed more efficiently.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  In accordance with the processing procedure shown in FIG. 3 and FIG. 6, the spike pin and the hole of the tread portion into which the spike pin is fitted were designed (Example 1). Furthermore, according to the processing procedure shown in FIG. 12 and FIG. 6, the spike pin and the hole of the tread portion into which the spike pin is fitted were designed (Example 2).

For comparison, the spike pin model was directly inserted into the hole of the rubber model without shrinking the spike pin model or expanding the rubber model, and the fitting state of the spike pin model was calculated (Comparative Example). ). The common specifications are as follows.
Spike pins:
Outer diameter D1a of large diameter part: 6.562 mm
Outer diameter D1b of small diameter part: 3.777 mm
Flange outer diameter D1d: 7.700 mm
Base tire radial length L1: 10.178 mm
Spike outer diameter D2: 2.356mm
Hole:
Outer diameter D3a: 2.356 mm
Inner diameter D3b: 3.000 mm
Tire radial length L3: 8.534 mm
Rubber model:
Thermal expansion coefficient α: 0.00026 (1 / ° C)
Temperature of the first step rubber model: 5000 ° C

  As a result of the test, in Example 1 and Example 2, it is possible to efficiently design the spike pin and the hole in the tread portion of the tire to which the spike pin is fitted without causing a calculation drop due to element collapse. It was.

On the other hand, in the comparative example, the rubber model was strongly pressed by the corners of the flanges of the spike pin model, and element crushing in which the volume of the rubber model element was negative occurred. Due to this element collapse, calculation loss occurred, and it was impossible to design the spike pin and the tread hole.

2 Spike pin 4 hole 7 Spike pin model 11 Rubber model 12 hole

Claims (5)

A method for designing a spike pin and a hole in a tread portion of a tire into which the spike pin is fitted, using a computer,
The size of the hole is smaller than the size of the spike pin;
Inputting into the computer a spike pin model obtained by modeling the spike pin with a finite number of elements;
Inputting a rubber model in which at least a part of the tread rubber of the tread portion including the hole is modeled by a finite number of elements to the computer;
A step of fitting the spike pin model into a hole of the rubber model;
The computer includes a step of evaluating a fitting state between the spike pin model and the hole;
The fitting step invalidates deformation calculation due to contact between the spike pin model and the rubber model;
Aligning the center axis of the spike pin model with the center axis of the hole, and arranging the spike pin model and the rubber model in an overlapping manner;
A first step of shrinking the spike pin model or expanding the rubber model to eliminate overlap between the spike pin model and the rubber model;
A step of enabling deformation calculation due to contact between the spike pin model and the rubber model; and returning the spike pin model or the rubber model to an original magnification and fitting the spike pin model into the hole. A tire design method comprising steps.   The tire design method according to claim 1, wherein the spike pin model and the rubber model are two-dimensional models based on a cross-sectional shape including the central axis. In the first step, the rubber model is expanded.
In the rubber model, the thermal expansion coefficient of the tread rubber is defined,
The first step expands the rubber model by increasing the temperature of the rubber model based on the thermal expansion coefficient,
The tire design method according to claim 1 or 2, wherein the second step shrinks the rubber model by returning the temperature of the rubber model based on the thermal expansion coefficient .
The rubber model includes an inner surface that is a surface opposite to the hole,
The fitting step is a step of deforming and calculating the rubber model so that the position of the inner surface of the rubber model after the second step matches the position of the inner surface of the rubber model before the first step. The tire design method according to claim 3, further comprising: The computer calculates the deformation of the rubber model by moving the spike pin model fitted in the hole in the fitting step in a direction of pulling out from the hole, and
The tire design method according to any one of claims 1 to 4, further comprising a step of evaluating anti-pinning performance of the spike pin model and the hole based on deformation calculation of the rubber model.

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