Deformation estimation method for tread part

Abstract

To provide a method capable of easily estimating deformation of the tread part of a tire in a rolling state.SOLUTION: A deformation estimation method 100 for tread part includes: a first step S1 of specifying a point P on the outer peripheral surface of a tread rubber at an arbitrary distance Ds1 which is equal to or less than a half width of a belt layer from the tire equator in a tire axial direction; and a second step S2 of calculating shearing deformation of the tread rubber in the tire axial direction through a comparison between a trajectory T0 of the point P in a grounding plane when it is assumed that the coefficient of friction between the tread rubber and a road surface is zero and a trajectory T1 of the point P in the grounding plane when it is assumed that there is no slip between the tread rubber and road surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for estimating deformation in the tread of a tire. [Background technology]

[0002] Conventionally, techniques for estimating the behavior of a tire during rolling have been proposed (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-035413 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned Patent Document 1, an attempt is made to shorten the calculation time required to estimate the wear energy by using intermediate physical quantities including the tire's contact pressure, contact length, and pattern rigidity.

[0005] In the tread rubber of a tire during rolling, localized shear deformation in the contact area is one of the causes of heat generation and rolling resistance in the tread. Therefore, by establishing a method for easily estimating the deformation of the tread of a tire during rolling, it can be useful in designing tires with low heat generation and rolling resistance in the tread.

[0006] The present invention has been devised in view of the above circumstances, and has as its main object to provide a method for easily estimating deformation of a tread portion of a tire during rolling. [Means for solving the problem]

[0007] The present invention provides a method for estimating axial deformation of a tread portion of a tire during rolling, comprising: The tread portion includes a tread rubber and a belt layer, A first step of identifying a point P on an outer peripheral surface of the tread rubber that is an arbitrary distance Ds1 that is equal to or less than half the width of the belt layer from the tire equator in the tire axial direction; The method includes a second step of calculating the shear deformation of the tread rubber in the tire axial direction based on a comparison between a locus T0 of the point P in the contact patch when it is assumed that the friction coefficient between the tread rubber and the road surface is zero, and a locus T1 of the point P in the contact patch when it is assumed that no slippage occurs between the tread rubber and the road surface. Effect of the Invention

[0008] The tread deformation estimation method of the present invention calculates the shear deformation of the tread rubber in the tire axial direction based on a comparison between a locus T0 of the point P in the contact patch when the friction coefficient between the tread rubber and the road surface is assumed to be zero, and a locus T1 of the point P in the contact patch when it is assumed that no slippage occurs between the tread rubber and the road surface. This makes it possible to easily estimate the deformation of the tread portion of a tire during rolling in simple steps. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a perspective view showing a tire during rolling. [Diagram 2] FIG. 2 is a meridian cross-sectional view showing the configuration of a tread portion of FIG. 1. [Diagram 3] 3 is a flowchart showing the procedure of a method for estimating deformation of a tread portion according to the present embodiment. [Figure 4] 1 is a cross-sectional view of a tread portion assuming zero friction between the tread rubber and the road surface. [Diagram 5] 4 is a cross-sectional view of a tread portion assuming that no slippage occurs between the tread rubber and the road surface. FIG. [Figure 6] 1 is a diagram showing the trajectory of point P within the contact patch when there is zero friction between the tread rubber and the road surface and when no slippage occurs between the tread rubber and the road surface. FIG. [Figure 7]FIG. 2 is a diagram showing the tire of FIG. 1 and a cone for calculating the area S. [Figure 8] FIG. 8 is a diagram showing the relationship between the cone in FIG. 7 and the area S. [Figure 9] 4 is a flowchart showing an example of details of a second step in FIG. 3. [Figure 10] 10 is a flowchart showing an example of details of an eighth step in FIG. 9. [Figure 11] FIG. 1 is a diagram showing a concept for more simply calculating the shear deformation of a tread rubber in the tire axial direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 shows a tire T rolling on a flat road surface G. The tire T applied in this embodiment includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4.

[0011] 2 shows, in a meridian section, the configuration of a tread portion 2 of a tire T. The tread portion 2 includes a tread rubber 21, a belt layer 8, and a carcass 7.

[0012] The tread rubber 21 is disposed on the radially outer side of the belt layer 8. The tread rubber 21 comes into contact with the road surface G and transmits the force received from the road surface G to the carcass 7 via the belt layer 8.

[0013] The belt layer 8 is disposed between the tread rubber 21 and the carcass 7 and reinforces the tread rubber 21.

[0014] The carcass 7 is disposed on the inner side in the tire radial direction of the belt layer 8. The carcass 7 is formed across a pair of bead portions 4, and maintains the shape of the tire T.

[0015] 2, a line along which the belt layer 8 extends in the tire axial direction Dr1, i.e., a belt line 8L, can be identified. The belt line 8L is preferably defined as a line passing through the center of the thickness of the belt layer 8, but since the thickness of the belt layer 8 is usually almost constant, the belt line 8L may be defined as a line passing through the outermost part or the innermost part of the belt layer 8.

[0016] FIG. 3 is a flowchart showing the procedure of the method 100 for estimating deformation of a tread portion according to this embodiment.

[0017] The method 100 for estimating deformation of the tread portion includes a first step S1 of identifying a point P on the outer peripheral surface 22 of the tread rubber 21, and a second step S2 of calculating the shear deformation of the tread rubber 21 in the axial direction Dr1 of the tire based on the trajectory of the point P within the contact patch during rolling.

[0018] In a first step S1, point P is defined as a point on the outer circumferential surface separated from the tire equator CL by an arbitrary distance Ds1 in the tire axial direction Dr1. Here, the position of point P is limited to a position inside the outer end of the belt layer 8 in the tire axial direction Dr1. In other words, the distance Ds1 is equal to or less than half the width of the belt layer 8.

[0019] In a second step S2, a locus T0 of the point P in the contact patch when it is assumed that friction between the tread rubber 21 and the road surface G is zero is compared with a locus T1 of the point P in the contact patch when it is assumed that no slip occurs between the tread rubber 21 and the road surface G. Then, based on the comparison between the locus T0 and the locus T1, the shear deformation of the tread rubber 21 in the tire axial direction is calculated.

[0020] According to the tread deformation estimating method 100, by performing the above-described simple first step S1 and second step S2, it becomes possible to easily estimate the deformation of the tread portion 2 of the tire T during rolling.

[0021] The first step S1 and the second step S2 are performed, for example, by a computer device.

[0022] A computer device, for example, has a CPU (Central Processing Unit) that executes various types of arithmetic processing, information processing, and the like, and a memory that stores programs that control the operation of the CPU and various types of information.

[0023] Fig. 4 shows cross sections of the non-ground contact area and ground contact area of ​​the tread portion 2 when friction between the tread rubber 21 and the road surface G is zero. The cross section of the non-ground contact area is a cross section directly above the tire axis Ax, and the cross section of the ground contact area is a cross section directly below the tire axis Ax (the same applies to Fig. 5 below).

[0024] In the figure, only one side of the tire equator CL is shown, and a cross section of the tread portion 2 in a non-ground contact area is shown by a dashed line, and a cross section of the tread portion 2 in a ground contact area is shown by a solid line. For ease of explanation, the thickness of the tread rubber 21 is assumed to be uniform in the tire axial direction Dr1 (the same applies hereinafter to FIG. 5).

[0025] Since the tread rubber 21 is reinforced by the belt layer 8 having a strong rigidity, the shape of the outer peripheral surface 22 of the tread rubber 21 depends on the shape of the belt line 8L. In other words, it is also considered that the position of the point P on the outer peripheral surface 22 depends on the position of the intersection point Q between the perpendicular line VL of the belt line 8L passing through the point P and the belt line 8L.

[0026] In the non-ground contact region shown by the dashed line in Fig. 4, the belt line 8L is usually symmetrical with respect to the tire equator CL and has an arc shape with its center inside the tire axial direction Dr1, so that the intersection point Q is located inside the tire axial direction Dr1 with respect to point P. As the tire T rolls, the belt line 8L, which was arc-shaped in the non-ground contact region, changes to a straight line parallel to the road surface G in the ground contact region as shown by the solid line. As a result, point P on the outer peripheral surface 22 of the tread rubber 21 moves to the position of point B0.

[0027] FIG. 5 shows cross sections of the tread portion 2 in the non-ground contact area and the ground contact area on the assumption that no slippage occurs between the tread rubber 21 and the road surface G.

[0028] When no slippage occurs between the tread rubber 21 and the road surface G, the point P on the outer peripheral surface 22 of the tread rubber 21 does not move in the tire axial direction Dr1 from the non-grounded area through the grounded area to the non-grounded area. Therefore, regardless of the deformation of the belt line 8L, the point P moves to the position of the point B1 while maintaining the distance Ds1 from the tire equator CL. That is, the point P tries to move to the position of the point B0 as shown in FIG. 4 in accordance with the deformation of the belt line 8L, but is held at the position of the point B1, which is a distance Ds1 away from the tire equator CL, by the frictional force between the tread rubber 21 and the road surface G. It can be understood that a shear strain in the tire axial direction Dr1 occurs in the tread rubber 21 between the belt layer 8 and the road surface G.

[0029] 6 shows a locus T0 of point P in the contact patch when it is assumed that there is zero friction between the tread rubber 21 and the road surface G, and a locus T1 of point P in the contact patch CP when it is assumed that no slippage occurs between the tread rubber 21 and the road surface G. Note that in the figure, the component of the locus T0 in the tire axial direction Dr1 is exaggerated.

[0030] The deviation between the locus T0 and the locus T1 can be considered as a shear deformation of the tread rubber 21 in the contact patch CP. Then, by calculating the area S of the region Ar surrounded by the locus T0 and the locus T1, the magnitude of the shear deformation of the tread rubber 21 in the contact patch CP can be obtained.

[0031] It is considered that a tire T in which the area S of the region Ar surrounded by the locus T0 and the locus T1 is large tends to have a large deformation of the tread portion 2 during rolling, and thus tends to have a large heat generation and rolling resistance due to its structure. Conversely, a tire T in which the area S of the region Ar surrounded by the locus T0 and the locus T1 is small tends to have a small deformation of the tread portion 2 during rolling, and thus tends to have a small heat generation and rolling resistance due to its structure. Therefore, in the second step S2, it becomes possible to calculate the shear deformation of the tread rubber 21 in the tire axial direction Dr1 based on the comparison between the locus T0 and the locus T1.

[0032] This makes it possible to easily estimate the deformation of the tread portion 2 of the tire T during rolling in a simple step.

[0033] Furthermore, after extensive research, the inventors of the present application have found that the area S of the region Ar enclosed by the locus T0 and the locus T1 can be approximately calculated by introducing a virtual cone shown below, whose axis is the tire axis Ax and whose bottom circumference is the outer circumferential length Lc of the tread rubber 21 passing through point P.

[0034] 7 and 8 show a virtual cone CN for calculating the area S of the region Ar surrounded by the locus T0 and the locus T1 in the tire T. The cone CN has the tire axis Ax as its axis and the outer circumferential length Lc of the tread rubber 21 passing through the point P as its bottom circumference.

[0035] The circumferential length Lc of the tread rubber 21 passing through point P is calculated as 2πr using the distance r from the tire axis Ax of point P, and the cone CN is a cone with the distance r as the radius of the base. From Figures 4 and 5, the distance between points B0 and B1 is the tire axial direction component of the line segment PQ. In addition, since the belt line 8L in the contact area is deformed into a straight line parallel to the road surface G in the meridian section, the belt layer 8 is deformed into a flat plane parallel to the road surface G.

[0036] In this case, the area Ar enclosed by the locus T0 and the locus T1 in the contact patch CP shown in Fig. 8 is congruent with the cross section CS obtained by cutting the cone CN with a plane G' that passes through the point Q and is parallel to the road surface G (i.e., the contact patch CP), and the area S of the area Ar is equal to the area S' of the cross section CS. Therefore, by calculating the area S' of the cross section CS of the cone CN shown in Fig. 8, it becomes possible to approximately and simply calculate the shear deformation of the tread rubber 21 in the tire axial direction Dr1.

[0037] FIG. 9 shows an example of details of the second step S2 of calculating the shear deformation using a cone CN.

[0038] The second step S2 includes a third step S3 of obtaining the outer circumferential length Lc of the tread rubber 21, a fourth step S4 of identifying the belt line 8L, a fifth step S5 of identifying the perpendicular line VL, a sixth step S6 of obtaining the distance Ds2 from the tire axis Ax of the intersection point Q, a seventh step S7 of identifying the locus T0 and the locus T1, and an eighth step S8 of calculating the area S of the region Ar enclosed by the locus T0 and the locus T1.

[0039] In a third step S3, a circumferential length Lc of the tread rubber 21 passing through the point P is obtained. It is preferable that the circumferential length Lc is obtained from a tire T in a normal state.

[0040] "Normal condition" refers to a condition in which the tire is mounted on a normal rim (not shown), inflated to normal internal pressure, and unloaded. Unless otherwise specified, the dimensions of each part of the tire are values ​​measured in this normal condition.

[0041] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "Design Rim," and in the case of ETRTO, it is called a "Measuring Rim."

[0042] "Normal internal pressure" is the air pressure set for each tire by each standard in the standard system including the standard on which the tire is based, such as "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. If the tire is for passenger cars, the normal internal pressure is, for example, 180 kPa.

[0043] When it is desired to calculate the shear deformation of the tread rubber 21 of the tire T mounted on a specific rim other than a regular rim, the tire T mounted on the rim may be actually measured. Also, when it is desired to calculate the shear deformation of the tread rubber 21 of the tire T inflated with a specific internal pressure other than the regular internal pressure, the tire T inflated with that internal pressure may be actually measured.

[0044] The outer circumferential length Lc is obtained by actually measuring the tire T in a normal state, but can also be obtained by a non-rolling simulation using FEM (finite element method) or the like, assuming the tire T in a normal state. In this case, a simulation considering a centrifugal force corresponding to the running speed may be applied.

[0045] In addition, when a design drawing of a vulcanization mold for the tire T can be obtained, the outer circumferential length Lc may be obtained based on the design drawing. In this case, it is possible to easily obtain the outer circumferential length Lc.

[0046] By obtaining the peripheral length Lc in the third step S3, the radius r of the base of the cone CN can be calculated (see FIG. 8).

[0047] In a fourth step S4, a belt line 8L along which the belt layer 8 extends in the tire axial direction Dr1 is identified on an arbitrary meridian section of the tire T. The belt line 8L is identified, for example, based on an X-ray image of the tire T in a normal state.

[0048] When the design drawings of the tire T can be obtained, the beltline 8L may be obtained based on the design drawings of the tire T. In this case, it is possible to easily obtain the beltline 8L.

[0049] In a fifth step S5, a perpendicular line VL to the belt line 8L that passes through the point P on the meridian section is specified by geometric calculation.

[0050] In a sixth step S6, first, an intersection Q between the belt line 8L and the perpendicular line VL is identified by geometric calculation, and a distance Ds2 of the intersection Q from the tire axis Ax is obtained.

[0051] In a seventh step S7, the locus T0 and the locus T1 are identified based on the outer perimeter Lc acquired in the third step S3 and the distance Ds2 acquired in the sixth step S6.

[0052] In an eighth step S8, the area S of the region Ar enclosed by the locus T0 and the locus T1 is calculated.

[0053] FIG. 10 shows an example of details of the eighth step S8 of calculating the area S of the region Ar surrounded by the locus T0 and the locus T1.

[0054] The eighth step S8 includes a ninth step S9 of obtaining the contact length Lg at the point P.

[0055] In the ninth step S9, the contact length Lg is obtained, for example, by actually measuring the tire T in a normal state when a normal load is applied, but it can also be obtained by a non-rolling simulation assuming the tire T in a normal state using FEM (finite element method) or the like.

[0056] "Normal load" refers to the load that each standard specifies for each tire in the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is "maximum load capacity." For the TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For the ETRTO, it is "LOAD CAPACITY." If the tire is for passenger cars, the normal load is, for example, a load equivalent to 88% of the load.

[0057] When it is desired to calculate the shear deformation of the tread rubber 21 under a specific load other than the normal load, the contact length Lg is obtained by, for example, actually measuring the tire T to which that load is applied.

[0058] In addition, when it is desired to calculate the shear deformation of the tread rubber 21 of a tire T to which a specific slip angle and camber angle are applied, the contact length Lg is obtained by, for example, actually measuring the tire T to which the slip angle and camber angle are applied.

[0059] In FIG. 8, if the difference r-Ds2 between the radius r of the base of the cone CN and the distance Ds2 is a, and the central angle of a sector of radius r with the ground contact length Lg as a chord is θ, then: cos(θ / 2)=Ds2 / r=1-a / r (1) and sin(θ / 2)=Lg / 2r (2) It is.

[0060] According to formula (1), the central angle θ is determined from the radius r calculated from the outer circumferential length Lc in the third step S3 and the distance Ds2 obtained in the sixth step S6. Furthermore, according to formula (2), the contact length Lg is determined from the central angle θ and the radius r. Therefore, the contact length Lg can also be obtained by calculation based on the outer circumferential length Lc obtained in the first step S1 and the distance Ds2 obtained in the sixth step S6.

[0061] That is, the ninth step S9 may include a tenth step S10 of calculating the contact length Lg at the point P based on the outer circumferential length Lc obtained in the first step and the distance Ds2 obtained in the sixth step.

[0062] The eighth step S8 includes an eleventh step S11 of calculating a distance Ds3 from the tire equator to an intersection point R between the perpendicular line VL and the tire axis Ax. The intersection point R constitutes the apex of the cone CN. Since the base of the cone CN is separated from the tire equator CL by a distance Ds1 in the tire axial direction Dr1, the difference Ds1-Ds3 between the distance Ds1 and the distance Ds3 is the height h of the cone CN.

[0063] The eighth step S8 includes a twelfth step S12 for identifying a cone CN. The circumference of the cone CN identified in the twelfth step S12 is the peripheral length Lc obtained in the first step S1, and the height h of the cone CN is calculated from an arbitrary distance Ds1 in the first step S1 and the distance Ds3 calculated in the eleventh step S11.

[0064] The eighth step S8 includes a thirteenth step S13 of specifying a cutting plane CS. The cutting plane CS specified in the thirteenth step S13 is a plane cut by a plane G' that passes through the intersection point Q and is parallel to the road surface G. The cutting plane CS has an arch shape as shown in FIG.

[0065] The eighth step S8 includes a fourteenth step S14 of calculating the area S of the cut surface CS. The area S of the cut surface CS calculated in the fourteenth step S14 is expressed by the following formula (3).

number

[0066] As already described, the area S of the cross section CS represents the shear deformation in the tire axial direction of the tread rubber 21. Therefore, the lateral force generated at a point P on the outer circumferential surface separated by a distance Ds1 from the tire equator CL can be calculated by multiplying the area S by the spring constant in the tire axial direction of the tread rubber 21.

[0067] When a normal tire T designed symmetrically with respect to the tire equator CL is loaded with a slip angle of 0 and a camber angle of 0, the lateral force generated at point P on the outer circumferential surface at a distance Ds1 from the tire equator CL within the contact patch CP and the lateral force generated at a point on the outer circumferential surface at a distance -Ds1 from the tire equator CL cancel each other out. Therefore, if plysteer caused by the rolling of the belt layer 8 is ignored, the lateral force generated on one side of the tire equator CL and the lateral force generated on the other side of the tire equator CL are balanced, and the lateral force generated by the tire T as a whole is not detected.

[0068] In this embodiment, the lateral force generated at a point P on the outer circumferential surface at an arbitrary distance Ds1 from the tire equator CL can be calculated, which can be useful in reducing heat generation and rolling resistance in the tread portion 2.

[0069] FIG. 11 shows a concept for more simply calculating the shear deformation of the tread rubber 21 in the tire axial direction.

[0070] The area S of the cross section CS in Fig. 8 is approximated by the area S' of a triangle CS' whose base is the contact length Lg in Fig. 11 and whose height is the axial component of the line segment PQ. Therefore, the area S of the region Ar enclosed by the locus T0 and the locus T1 can be roughly calculated by calculating the area S' of the triangle CS'.

[0071] That is, instead of the above-mentioned 14th step S14 of calculating the area S of the cross section CS, the 8th step S8 may include a 15th step S15 of calculating the area S' of a triangle CS' whose base is the contact length Lg and whose height is the axial component of the line segment PQ.

[0072] In the tread portion 2 of the tire T, a circumferential groove is usually formed extending continuously in the tire circumferential direction, and the tread rubber 21 is divided into a plurality of land portions by the circumferential groove. Accordingly, the shear deformation of the tread rubber 21 is divided by the circumferential groove, and significantly differs for each land portion.

[0073] 4, it can be seen that when the friction between the tread rubber 21 and the road surface G is zero, the amount of movement of the point P in the tire axial direction before and after contact with the ground depends on the amount of deformation of the belt line 8L. The amount of deformation of the belt line 8L increases toward the outside in the tire axial direction.

[0074] As a result, the amount of axial movement of point P before and after contact with the ground increases toward the outer side in the tire axial direction. That is, as the distance Ds1 from the tire equator CL increases, the area S of region Ar (i.e., the shear deformation of the tread rubber 21) increases, and the effect on heat generation and rolling resistance of the tread portion 2 increases.

[0075] From this viewpoint, it is desirable that point P be positioned on the outermost land portion of the tread portion 2 in the axial direction.

[0076] For example, the inventors have confirmed that the lateral force based on shear deformation calculated by applying the deformation estimation method 100 of the present invention shows a tendency similar to that of the lateral force calculated by a rolling simulation using FEM in the profile of a plurality of tread rubbers 21 and a belt line 8L. In this comparison, the shear deformation was calculated at a point P that is a distance Ds1 that is 80% of the half tread contact width from the tire equator CL.

[0077] The shear deformation of the tread rubber 21 in the tire axial direction may be calculated at a plurality of points P. That is, in the first step S1, a plurality of circumferential lengths Lc may be obtained by the plurality of points P. In this case, in the second step S2, the shear deformation of the tread rubber 21 in the tire axial direction at the plurality of points P is calculated.

[0078] This allows for more detailed calculation of the shear deformation in the tire axial direction of the tread rubber 21. Even in the calculation of the shear deformation at a plurality of points P, the tread deformation estimation method 100 of the present invention can perform the calculation in an extremely short time, compared with a rolling simulation using FEM or the like.

[0079] In particular, it is desirable to calculate the shear deformation of the tread rubber 21 in the tire axial direction at a plurality of points P in the outermost land portion of the tread portion 2 in the axial direction.

[0080] Moreover, the shear deformation of the tread rubber 21 in the tire axial direction can be calculated only from the profiles of the tread rubber 21 and the belt line 8L, regardless of the structures of the sidewall portion 3 and the bead portion 4. Therefore, in the tread deformation estimation method 100 of the present invention, preparation for calculation is also simplified.

[0081] Furthermore, the tread deformation estimation method 100 of the present invention can easily calculate the shear deformation of the tread rubber 21 in the tire axial direction, so it can also be incorporated into a part of an automatic design method for the tire T.

[0082] The automated design method for tire T includes, for example, a step of setting various design parameters for tire T, a step of calculating various performances of tire T by successively changing design variables included in the set design parameters, a step of evaluating the calculated performances of tire T, and a step of determining optimal design parameters based on the performance evaluation. The profiles of the tread rubber 21 and the belt line 8L are included in the design parameters of tire T.

[0083] Although the method 100 for estimating deformation of a tread portion of a tire T according to the present invention has been described in detail above, the present invention is not limited to the above specific embodiment and may be modified and carried out in various aspects.

[0084] [Note] The present invention includes the following aspects.

[0085] [Invention 1] A method for estimating axial deformation of a tread portion of a tire during rolling, comprising: The tread portion includes a tread rubber and a belt layer, A first step of identifying a point P on an outer peripheral surface of the tread rubber that is an arbitrary distance Ds1 that is equal to or less than half the width of the belt layer from the tire equator in the tire axial direction; A second step of calculating a shear deformation of the tread rubber in the tire axial direction based on a comparison between a locus T0 of the point P in the contact patch when a friction coefficient between the tread rubber and the road surface is assumed to be zero and a locus T1 of the point P in the contact patch when it is assumed that no slip occurs between the tread rubber and the road surface. A method for estimating deformation of the tread. [Invention 2] The second step is A third step of acquiring a circumferential length Lc of the tread rubber passing through the point P; A fourth step of identifying a belt line along which the belt layer extends along the tire axial direction on an arbitrary meridian section of the tire; A fifth step of identifying a perpendicular line VL to the belt line that passes through the point P on the meridian section; A sixth step of acquiring a distance Ds2 from a tire axis Ax to an intersection Q between the belt line and the perpendicular line VL; a seventh step of calculating the trajectory T0 and the trajectory T1 based on the outer circumferential length Lc acquired in the third step and the distance Ds2 acquired in the sixth step; and an eighth step of calculating an area of ​​a region surrounded by the locus T0 and the locus T1. [Invention 3] The method for estimating deformation of a tread portion according to the second aspect of the present invention, wherein the eighth step includes a ninth step of acquiring a contact length Lg at the point P. [Invention 4] The deformation estimating method of a tread portion described in present invention 3, wherein the ninth step includes a tenth step of calculating a contact length Lg at the point P based on the outer circumferential length Lc obtained in the first step and the distance Ds2 obtained in the sixth step. [Invention 5] The method for estimating deformation of a tread portion according to the third aspect of the present invention, wherein the eighth step includes an eleventh step of calculating a distance Ds3 from the tire equator to an intersection R between the perpendicular line VL and the tire axis Ax. [Invention 6] The method for estimating deformation of a tread portion described in the present invention 5, wherein the eighth step includes a twelfth step of identifying a virtual cone whose bottom circumference is the outer circumferential length Lc obtained in the first step and whose height is the difference D1-D3 between the distance Ds1 and the distance Ds3. [Invention 7] The method for estimating deformation of a tread portion described in invention 6, wherein the eighth step includes a thirteenth step of identifying a cut surface of the cone cut by a plane G' that passes through the intersection point Q and is parallel to the road surface. [Invention 8] The method for estimating deformation of a tread portion according to the seventh aspect of the present invention, wherein the eighth step includes a fourteenth step of calculating an area S of the cut surface. [The present invention 9] The deformation estimating method of a tread portion according to the eighth aspect of the present invention, wherein in the fourteenth step, the area S of the cut surface is calculated by the following formula (3).

number

[0086] 100: Method for estimating deformation of tread 2: Tread area 8: Belt layer 8L: Belt line 21: Tread rubber 22: Outer surface Ar: area Ax: Tire axle CL: Tire equator CN: Cone CP: Ground plane CS: Cut surface CS' :Triangle Dr1: Tire axial direction Ds1 :Distance Ds2 :Distance Ds3 :Distance G: Road surface G': Plane Lc: Outer circumference length P: Plane PQ: Line segment Q: Intersection R: Intersection S :Area S' :Area T: Tire T0 :Trajectory T1 :Trajectory VL: Perpendicular h : Height r: radius

Claims

1. A method for estimating axial deformation of a tread portion of a tire during rolling, comprising: The tread portion includes a tread rubber and a belt layer, A first step of identifying a point P on an outer peripheral surface of the tread rubber, the point P being an arbitrary distance Ds1 that is equal to or less than half the width of the belt layer from the tire equator in the tire axial direction; a second step of calculating a shear deformation of the tread rubber in the tire axial direction based on a comparison between a locus T0 of the point P in the contact patch when a friction coefficient between the tread rubber and the road surface is assumed to be zero and a locus T1 of the point P in the contact patch when it is assumed that no slip occurs between the tread rubber and the road surface; A method for estimating deformation of the tread.

2. The second step comprises: A third step of acquiring a circumferential length Lc of the tread rubber passing through the point P; A fourth step of identifying a belt line along which the belt layer extends in an axial direction of the tire on an arbitrary meridian section of the tire; A fifth step of identifying a perpendicular line VL of the belt line that passes through the point P on the meridian section; A sixth step of acquiring a distance Ds2 from a tire axis to an intersection Q between the belt line and the perpendicular line VL; a seventh step of calculating the locus T0 and the locus T1 based on the outer circumferential length Lc acquired in the third step and the distance Ds2 acquired in the sixth step; The method for estimating deformation of a tread portion according to claim 1 , further comprising: an eighth step of calculating an area of ​​a region surrounded by the locus T0 and the locus T1.

3. The method for estimating deformation of a tread portion according to claim 2 , wherein the eighth step includes a ninth step of acquiring a contact length Lg at the point P.

4. 4. The method for estimating deformation of a tread portion according to claim 3, wherein the ninth step includes a tenth step of calculating a contact length Lg at the point P based on the outer circumferential length Lc acquired in the first step and the distance Ds2 acquired in the sixth step.

5. 4. The method for estimating deformation of a tread portion according to claim 3, wherein the eighth step includes an eleventh step of calculating a distance Ds3 from a tire equator to an intersection R between the perpendicular line VL and the tire axis Ax.

6. 6. The method for estimating deformation of a tread portion according to claim 5, wherein the eighth step includes a twelfth step of specifying a virtual cone having a circumference of a bottom surface that is the outer circumferential length Lc acquired in the first step and a height that is a difference D1-D3 between the distance Ds1 and the distance Ds3.

7. 7. The method for estimating deformation of a tread portion according to claim 6, wherein the eighth step includes a thirteenth step of identifying a cut surface of the cone cut by a plane G' that passes through the intersection Q and is parallel to the road surface.

8. 8. The method for estimating deformation of a tread portion according to claim 7, wherein the eighth step includes a fourteenth step of calculating an area S of the cut surface.

9. 9. The method for estimating deformation of a tread portion according to claim 8, wherein in the fourteenth step, the area S of the cut surface is calculated by the following formula (3): [0010]

10. 4. The method for estimating deformation of a tread portion according to claim 3, wherein said eighth step includes a fifteenth step of calculating an area of ​​a triangle having a base equal to said contact length Lg and a height equal to a component of a line segment PQ in the tire axial direction.

11. The method for estimating deformation of a tread portion according to claim 1 , wherein the point P is positioned on an axially outermost land portion of the tread portion.

12. The method for estimating deformation of a tread portion according to claim 1 , wherein in the first step, a plurality of the outer circumferential lengths Lc are obtained by a plurality of the points P.

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