Tire evaluation method and tire design method

Abstract

To provide a method for evaluating tires based on their noise performance. [Solution] Out of the maximum N intervals Lai (1≦i≦N), let N1 be the number of intervals Lai that satisfy condition C1, N2 be the number of intervals Lai that satisfy condition C2, and N3 be the number of intervals Lai that satisfy condition C3. Then calculate N2 / N1 and N2 / N3.

Description

Technical Field

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[0001] The present invention relates to a method for evaluating a tire for noise performance and a method for designing a tire that preferably exhibits noise performance.

Background Art

[0002] There is known a method for designing a tire that is composed of a plurality of blocks partitioned by circumferential grooves and lateral grooves and includes a block row formed along the tire circumferential direction. In the step of determining the block row phase, the block row phase is determined so as to be shifted by 10% to 30% between one side and the other side of the block row with respect to the tire equator line (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 discloses a method for designing a pneumatic tire that achieves both noise performance and traction performance on a wet road surface. In recent years, however, there has been a demand for the development of a tire that further enhances noise performance among these performances.

[0005] In Patent Document 1, the deviation of the block row phase is 10% to 30% on each side of the tire equator line. However, by more carefully examining this phase deviation or by newly examining a feature that replaces this phase deviation, there is room for improvement to further enhance the noise performance.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for evaluating a tire for noise performance and a method for designing a tire with enhanced noise performance.

Means for Solving the Problem

[0007] The method for evaluating a tire of the present invention is at least two land portions are partitioned by at least one circumferential main groove, a method for evaluating a tire including at least one set of first recesses caused by pass-by noise that partition the same land portion, or at least one set of first recesses caused by pass-by noise that partition two land portions facing each other across one circumferential main groove, the first recess is a groove portion or the entire groove extending in a direction from 0° to 80° with respect to the tire width direction, or a sipe portion or the entire sipe extending in a direction from 0° to 80° with respect to the tire width direction, a step of determining two of the first recesses as a set over the entire circumference of the tire, a step of determining the number of sets N (sets) of the first recesses in the tire circumferential direction, and in order over the entire circumference of the tire, determining the interval Lai (1≦i≦N) between the first recesses within the same set, taking the tire circumference as J (mm), the attention lengths due to sound sources as S1 (mm) and S2 (mm), a step of determining the range of S1 (mm) that satisfies J / (N×1.25×1)≦S1 (mm)≦J / (N×0.75×1) and the range of S2 (mm) that satisfies J / (N×1.25×2)≦S2 (mm)≦J / (N×0.75×2), a step of taking the lower limit value of the S1 (mm) as LFL1 and the upper limit value as HHL1, a step of taking the lower limit value of the S2 (mm) as LFL2 and the upper limit value as HHL2, LFL1×1<Lai (mm)<HFL1×1, or LFL2×1<Lai (mm)<HFL2×1, the condition C1 defined by other than the condition C1, and LFL1×0.5<Lai (mm)<HFL1×0.5, or LFL The steps involve determining a condition C3 that is not condition C1 and is not condition C2, If, among the maximum of N intervals Lai (1≦i≦N), N1 is the number of intervals Lai that satisfy condition C1, N2 is the number of intervals Lai that satisfy condition C2, and N3 is the number of intervals Lai that satisfy condition C3, then The steps include calculating N2 / N1 and N2 / N3, It is characterized by including. [Effects of the Invention]

[0008] In the tire evaluation method according to the present invention, N2 / N1 and N2 / N3 are calculated when N1 is the number of intervals Lai (1≦i≦N) that satisfy condition C1, N2 is the number of intervals Lai that satisfy condition C2, and N3 is the number of intervals Lai that satisfy condition C3, out of a maximum of N intervals Lai (1≦i≦N). This allows evaluation of whether noise performance has improved due to the reduction of pass-by noise, based on the values ​​of N2 / N1 and N2 / N3. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a flowchart showing each step (process) of the tire evaluation method (Type 1) of this embodiment. [Figure 2] Figure 2 is a plan view showing the tread surface for a region that includes two first recesses that demarcate the same land area. [Figure 3] Figure 3 is a plan view showing the tread surface of a region that includes two first recesses, each demarcating two land areas facing each other with a single circumferential main groove in between. [Figure 4] Figure 4 is a flowchart showing each step (process) of the tire evaluation method (Type 2) of this embodiment. [Figure 5] Figure 5 is a plan view showing a portion of the tread surface of a tire manufactured based on the tire design method (Type 2). [Figure 6]FIG. 6 is a plan view of a tire showing an example of determining the interval between two first recesses (second recesses) within the same set when the two first recesses (second recesses) are parallel to each other. [Figure 7] FIG. 7 is a plan view of a tire showing an example of determining the interval between two first recesses (second recesses) within the same set when the two first recesses (second recesses) are not parallel to each other. [Figure 8] FIG. 8 is a plan view showing a part of the tread surface of a tire having four circumferential main grooves 200, 202, 204, 206 and having one or two of the first recesses 208, 210, 212, 214, 216, 218, 220. [Figure 9] FIG. 9 is a plan view showing a part of the tread surface of a tire having four circumferential main grooves 300, 302, 304, 306 and having one or two of the second recesses 208, 310, 312, 314, 316. [Embodiments for Carrying Out the Invention]

[0010] [Embodiments of the Present Invention] The present invention includes the following embodiments. [Embodiment 1] At least two land portions are partitioned and formed by at least one circumferential main groove, An evaluation method of a tire including at least one set of first recesses caused by pass-by noise that partition and form the same land portion, or at least one set of first recesses caused by pass-by noise that partition and form two land portions facing each other across one circumferential main groove, The first recess is a groove portion or the entire groove extending in a direction from 0° to 80° with respect to the tire width direction, or a sipe portion or the entire sipe extending in a direction from 0° to 80° with respect to the tire width direction, A step of determining two of the first recesses as one set over the entire circumference of the tire, A step of determining the number of sets N (sets) of the first recesses in the tire circumferential direction, and in order over the entire circumference of the tire, determining the interval Lai (1≦i≦N) between the first recesses within the same set, Let the tire circumference be J (mm), the attention lengths caused by sound sources be S1 (mm) and S2 (mm), Determining a range of S1 (mm) that satisfies J / (N×1.25×1)≦S1(mm)≦J / (N×0.75×1) and S2 (mm) that satisfies J / (N×1.25×2)≦S2(mm)≦J / (N×0.75×2); Taking the lower limit value of the S1 (mm) as LFL1 and the upper limit value as HHL1; Taking the lower limit value of the S2 (mm) as LFL2 and the upper limit value as HHL2; Condition C1 defined by LFL1×1 < Lai (mm) < HFL1×1, or LFL2×1 < Lai (mm) < HFL2×1; Outside of condition C1 and Condition C2 defined by LFL1×0.5 < Lai (mm) < HFL1×0.5, or LFL2×0.5 < Lai (mm) < HFL2×0.5, and Condition C3 outside of both condition C1 and condition C2 are each determined; When the number of intervals Lai (1≦i≦N) that satisfy condition C1 among a maximum of N intervals is N1, the number of intervals Lai that satisfy condition C2 is N2, and the number of intervals Lai that satisfy condition C3 is N3, Calculating N2 / N1 and N2 / N3; A method for evaluating a tire, characterized by including the above. [Form 2] A method for designing a tire, which determines the interval Lai (1≦i≦N) such that N2 / N1 and N2 / N3 calculated according to the evaluation method described in Form 1 satisfy N2 / N1 > 1 and N2 / N3 > 1. [Form 3] When at least three land portions are partitioned by at least two circumferential main grooves, and on each side in the tire width direction of the tire equatorial plane, with the groove width center line of the outermost circumferential main groove in the tire width direction as a boundary, the inner side in the tire width direction from the groove width center line is a center region, and the outer side in the tire width direction from the groove width center line is a shoulder region, In the center region, an evaluation method of a tire including at least one set of second recesses caused by pass-by noise generation for partitioning the same land portion, or at least one set of second recesses caused by pass-by noise generation for partitioning two land portions facing each other across one of the circumferential main grooves, The second recess is a groove portion or the whole groove extending in a direction from 0° to 80° with respect to the tire width direction, or a sipe portion or the whole sipe extending in a direction from 0° to 80° with respect to the tire width direction, Determining a set of two of the second recesses over the entire circumference of the tire; Determining the number of sets N (sets) of the second recesses in the circumferential direction of the tire, and in order over the entire circumference of the tire, determining the interval Lbi (1≦i≦N) between the second recesses within the same set; Taking the tire circumference as J (mm), the attention lengths due to sound sources as S1 (mm) and S2 (mm), and the attention length due to transmission characteristics as S3 (mm), and determining the ranges of S1 (mm) satisfying J / (N×1.25×1)≦S1 (mm)≦J / (N×J / (N×0.75×1), S2 (mm) satisfying J / (N×1.25×2)≦S2 (mm)≦J / (N×0.75×2), and S3 (mm) satisfying 12.4≦S3 (mm)≦19.5; At the lower limit values and upper limit values of the ranges of S1 (mm) and S3 (mm), taking the larger lower limit value as LFL3 and the smaller upper limit value as HHL3; At the lower limit values and upper limit values of the ranges of S2 (mm) and S3 (mm), taking the larger lower limit value as LFL4 and the smaller upper limit value as HHL4; LFL3×1<Lbi (mm)<HFL3×1, or Condition T1 defined by LFL4×1<Lbi (mm)<HFL4×1, Other than condition T1, and LFL3×0.5<Lbi (mm)<HFL3×0.5, or Condition T2 defined by LFL4×0.5<Lbi (mm)<HFL4×0.5, and The steps involve determining conditions T3 that are not condition T1 and not condition T2, If, out of the maximum N intervals Lbi (1 ≤ i ≤ N), E1 is the number of intervals Lbi that satisfy condition T1, E2 is the number of intervals Lbi that satisfy condition T2, and E3 is the number of intervals Lbi that satisfy condition T3, then The steps include calculating E2 / E1 and E2 / E3, A tire evaluation method described in Form 1, including the method described in Form 1. [Form 4] A tire design method in which the interval Lbi (1≦i≦N) is determined such that E2 / E1 and E2 / E3, calculated according to the evaluation method described in Form 3, satisfy E2 / E1>1 and E2 / E3>1. [Form 5] A tire design method according to Embodiment 4, wherein the interval Lbi (1 ≤ i ≤ N) is determined such that E2 / E1 ≥ 1.2. [Form 6] Within the same set, two of the first recesses or two of the second recesses are parallel, The tire design method according to Embodiment 2 or 4, wherein the interval Lai or Lbi is determined by determining a representative point for each of the two first recesses or each of the two second recesses, which is the midpoint in the direction of extension of each of the five equal parts obtained in the direction of extension and the midpoint in a direction perpendicular to the direction of extension, and the shortest distance between virtual lines obtained by the least squares method using the five representative points. [Form 7] If the two first recesses or the two second recesses within the same set are not parallel, The tire design method according to Embodiment 2 or 4, wherein the interval Lai or Lbi is determined by determining a representative point for each of the two first recesses or each of the two second recesses, which is the midpoint in the extending direction of each portion obtained by dividing the extending direction into five equal parts, and is also the midpoint in a direction perpendicular to the extending direction; the representative point of one of the first recesses or second recesses is combined with the representative point of the other first recess or second recess in order from the vehicle mounting side, the tire circumferential distance between the combined representative points is determined, and the distance is the average of the five tire circumferential distances. [Form 8] In the step of determining a pair of the two first concave portions or the two second concave portions, a pair is determined by selecting any one of the first concave portions or the second concave portions and another one of the first concave portions or the second concave portions that is formed at the closest distance from the selected one, according to the tire evaluation method described in Form 1 or 3. [Form 9] A step of providing a variable pitch tread pattern in which a region including a pair of the first concave portions or a region including a pair of the second concave portions is defined as one pitch, A step of defining a primitive function with one pitch as one period, arranging the primitive functions for one circumference of the tire and performing a Fourier transform, and setting the maximum value of the first-order rotational component with one rotation of the tire as one period as R1 and the maximum value of the second-order rotational component as R2, further including where the interval Lai or the interval LBi satisfies J (mm) / (R1 × 0.9) < Lai (Lbi) (mm) < J (mm) / (R1 × 1.1), or J (mm) / (R2 × 0.9) < Lai (Lbi) (mm) < J (mm) / (R2 × 1.1) and is determined to satisfy the above conditions, according to the tire design method described in Form 2 or 4. [Form 10] In a pair of the second concave portions formed in the center region, according to the tire design method described in Form 4 or 5, the volume of one of the second concave portions is substantially equal to the volume of the other second concave portion. [Form 11] In a pair of the second concave portions formed in the center region, according to the tire design method described in Form 4 or 5, the extension angle of one of the second concave portions with respect to the tire circumferential direction is substantially equal to the extension angle of the other second concave portion with respect to the tire circumferential direction. [Form 12] In a pair of the second concave portions formed in the center region, according to the tire design method described in Form 4 or 5, the tire width direction length of the second concave portion closer to the tire equatorial plane is shorter than the tire width direction length of the second concave portion farther from the tire equatorial plane. [Form 13] A tire design method according to Embodiment 4 or 5, wherein in a pair of second recesses formed in the center region, the groove width of the second recess closer to the tire equator is smaller than the groove width of the second recess further from the tire equator.

[0011] In the following explanation, the tire radial direction refers to the direction perpendicular to the tire's axis of rotation, the inner side of the tire radial direction refers to the side toward the axis of rotation, and the outer side of the tire radial direction refers to the side away from the axis of rotation. The tire circumferential direction refers to the direction around the aforementioned axis of rotation. Furthermore, the tire width direction refers to the direction parallel to the aforementioned axis of rotation, the inner side of the tire width direction refers to the side toward the tire equatorial plane (tire equator line), and the outer side of the tire width direction refers to the side away from the tire equatorial plane. The tire equatorial plane is a plane perpendicular to the tire's axis of rotation and passing through the center of the tire width.

[0012] Similarly, in the following explanation, "regular rim" refers to the "applicable rim" as defined by JATMA, the "Design Rim" as defined by TRA, or the "Measuring Rim" as defined by ETRTO.

[0013] Similarly, in the following explanation, "normal internal pressure" refers to the "maximum air pressure" specified by JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "INFLATION PRESSURES" specified by ETRTO. Furthermore, "normal load" refers to the "maximum load capacity" specified by JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "LOAD CAPACITY" specified by ETRTO.

[0014] <Tire Evaluation Methods> [Type 1: When there is at least one circumferential main groove] The tire evaluation method (Type 1) of this embodiment is a tire evaluation method comprising a tire having at least two land areas partitioned by at least one circumferential main groove, and at least one pair of first recesses that cause pass-by noise generation formed within the same land area, or at least one pair of first recesses that cause pass-by noise generation formed in two land areas facing each other across one circumferential main groove.

[0015] Figure 1 is a flowchart showing each step (process) of the tire evaluation method (Type 1) of this embodiment. As shown in the figure, the tire evaluation method of this embodiment includes seven steps. Each step is described in detail below.

[0016] (Step 1: Determine pairs of first recesses around the entire circumference of the tire.) In step 1, two first recesses that cause pass-by noise generation are determined to form a single land area around the entire circumference of the tire, or two first recesses that cause pass-by noise generation are determined to form a single land area opposite each other, separated by a single circumferential main groove.

[0017] Figure 2 is a plan view showing the tread surface for a region containing two first recesses that demarcate the same land area. In this figure, the first recesses are grooves, and as will be described later, they may be either a portion of the groove or the entire groove. All plan views of the tread surface described below show the unloaded state (non-contact state) when mounted on a regular rim and subjected to regular internal pressure.

[0018] Figure 2 shows four patterns of pairs of first recesses, each of which consists of a groove portion or the entire groove extending in the direction from 0° to 80° (angle measured on the acute side) with respect to the tire width direction.

[0019] In Figure 2(A), a groove 12 is formed as a groove that demarcates the land area 10. The groove 12 is composed of a groove portion 12a that extends at an angle of approximately 70° to 80° with respect to the tire circumferential direction, a groove portion 12b that extends at an angle of approximately 70° to 80° in the same direction as the groove portion 12a with respect to the tire circumferential direction, interposed by a groove portion 12c that extends at an angle of more than 80° and less than 90° with respect to the tire circumferential direction. In Figure 2(B), a groove 22 is formed as a groove that demarcates the land area 20. The groove 22 is composed of a groove portion 22a that extends at an angle of approximately 70° to 80° with respect to the tire circumferential direction, a groove portion 22b that extends at an angle of approximately 70° to 80° in the opposite direction to the groove portion 22a with respect to the tire circumferential direction, interposed by a groove portion 22c that extends at an angle of more than 80° and less than 90° with respect to the tire circumferential direction. The groove's inclination angle shall be determined by the groove's centerline.

[0020] In contrast, in Figure 2(C), grooves 32 and 34 are formed as grooves that demarcate the land area 30, and grooves 32 and 34 are formed on the same side edge of the land area 30, inclined at approximately 70° with respect to the tire circumferential direction. In Figure 2(D), grooves 42 and 44 are formed as grooves that demarcate the land area 40, and grooves 42 and 44 are formed on the opposite side edge of the land area 40, inclined at approximately 70° with respect to the tire circumferential direction.

[0021] In this embodiment, the first recess refers to a groove portion or the entire groove that extends at an angle of 0° to 80° with respect to the tire circumferential direction, among the recesses (groove portions or the entire groove) shown in Figure 2. That is, among the groove portions or the entire groove shown in Figures 2(A) to 2(D), the first recesses are groove portions 12a, 12b, 22a, 22b, and grooves 32, 34, 42, and 44. In contrast, groove portions 12c and 22c that extend at an angle greater than 80° with respect to the tire circumferential direction do not correspond to the first recesses.

[0022] In this way, it is determined whether a groove portion or the entire groove that demarcates the land area is a first recess or not. In relation to one land area, these two first recesses are determined as a pair, and a set of first recesses is determined. This determination is then performed sequentially around the entire circumference of the tire.

[0023] In the example shown in Figure 2, when determining a pair of first recesses, if the groove portions are in communication with each other, those communicating groove portions are considered a pair. In contrast, if non-communicating groove portions or entire independent grooves are considered a pair, a specific groove portion (or entire groove) and a groove portion (or entire groove) located on either side of that specific groove portion (or entire groove) in the tire circumferential direction can be considered a pair.

[0024] Furthermore, the method for determining a pair of first recesses shown in Figure 2 is exactly the same even when the first recesses are sipes instead of grooves. Even when a pair of first recesses are sipes, the sipe portion or the entire sipe extends at an angle of 0° to 80° with respect to the circumferential direction of the tire. In addition, although the example shown in Figure 2 shows a case where the first recess (e.g., groove 12a) communicates with other grooves that demarcate the land area (e.g., land area 10), this embodiment is not limited to such examples and also includes cases where both ends of the first recesses terminate within the land area.

[0025] In this embodiment, a groove refers to a recess having a width of 1.6 mm or more, and a sipe refers to a recess having a width of less than 1.6 mm.

[0026] Figure 3 is a plan view showing the tread surface of a region that includes two first recesses, each demarcating two land areas facing each other with a single circumferential main groove in between.

[0027] Figure 3 shows two patterns of pairs of first recesses (a set of first recesses), each consisting of a groove portion or the entire groove extending at an angle from 0° to 80° with respect to the circumferential direction of the tire.

[0028] In Figure 3(A), two land areas 60 and 70 are partitioned, facing each other with a single circumferential main groove 50 in between. A groove 62 is formed to partition the land area 60, and the groove 62 consists of a groove portion 62a that extends at an angle of approximately 70° to 80° with respect to the tire circumferential direction and a groove portion 62b that extends at an angle of more than 80° to 90° with respect to the tire circumferential direction. Similarly, a groove 72 is formed to partition the land area 70, and the groove 72 consists of a groove portion 72a that extends at an angle of approximately 70° to 80° with respect to the tire circumferential direction and a groove portion 72b that extends at an angle of more than 80° to 90° with respect to the tire circumferential direction.

[0029] In contrast, in Figure 3(B), two land areas 90 and 100 are partitioned, facing each other with a single circumferential main groove 80 in between. The groove 92 that partitions the land area 90 extends at an angle of approximately 70° with respect to the tire's circumferential direction, and the groove 102 that partitions the land area 100 also extends at an angle of approximately 70° with respect to the tire's circumferential direction.

[0030] In the example shown in Figure 3, the definition of the first recess is the same as explained in the example shown in Figure 2. Therefore, in Figures 3(A) and 3(B), the first recesses correspond to grooves 62a, 72a, and grooves 92, 102.

[0031] In this way, it is determined whether a recess (groove portion or the entire groove) that demarcates the land area is a first recess or not. In relation to two land areas facing each other across a single circumferential main groove, these two first recesses are determined as a pair, and a set of first recesses is determined. This determination is then performed sequentially around the entire circumference of the tire.

[0032] In the example shown in Figure 3, when determining a pair of first recesses, a specific groove portion (or entire groove) and a groove portion (or entire groove) located on either side of the tire circumferential direction relative to the specific groove portion (or entire groove) can be considered as a pair.

[0033] Furthermore, the method for determining a pair of first recesses shown in Figure 3 is exactly the same even when the first recesses are sipes instead of grooves. Even when a pair of first recesses are sipes, the sipe portion or the entire sipe extends at an angle of 0° to 80° with respect to the circumferential direction of the tire. In addition, although the example shown in Figure 3 shows a case where the first recess (e.g., groove 62a) communicates with other grooves that demarcate the land area (e.g., land area 60), this embodiment is not limited to such examples and also includes cases where both ends of the first recesses terminate within the land area.

[0034] (Step 2: Determine the interval Lai (1 ≤ i ≤ N)) In step 2, the number of sets N (sets) of the first recesses in the tire circumferential direction is determined, and the spacing Lai (1≦i≦N) between the first recesses within the same set is determined sequentially around the entire circumference of the tire.

[0035] In step 1, once pairs of first recesses are determined around the entire circumference of the tire, the number of pairs of first recesses (N) around the entire circumference of the tire is determined.

[0036] The number of sets (N) around the entire circumference of the tire is determined with respect to pairs of first recesses located at approximately the same position in the tire width direction. If, in a plan view of the tire, there are rows of similar first recesses arranged in the tire circumferential direction in different regions in the tire width direction, these rows are recognized as different rows, and the number of sets (N) in each row is determined accordingly.

[0037] The distance between the first recesses within each pair is measured for this number of pairs (N). Here, the distance between the first recesses refers to the shortest distance between a pair of first recesses. In this way, the interval Lai (1 ≤ i ≤ N) is determined.

[0038] (Step 3: Determine the range of attention lengths S1 (mm) and S2 (mm) caused by the sound source.) In Step 3, the tire circumference is defined as J (mm), and the attention lengths due to the sound source are S1 (mm) and S2 (mm). The range of S1 (mm) that satisfies J / (N × 1.25 × 1) ≤ S1 (mm) ≤ J / (N × 0.75 × 1), and the range of S2 (mm) that satisfies J / (N × 1.25 × 2) ≤ S2 (mm) ≤ J / (N × 0.75 × 2) are determined.

[0039] Here, tire circumference J (mm) is the dimension measured as the maximum circumference of the tread surface when the tire is mounted on a standard rim, subjected to standard internal pressure, and under no-load conditions. Furthermore, the range of attention length S1 (mm) due to the sound source means a range of 1st order ± 25% of the pitch order generated when the land area demarcated by the first recess contacts the road surface, and the range of attention length S2 (mm) due to the sound source means a range of 2nd order ± 25% of the pitch order generated when the land area formed by the first recess contacts the road surface.

[0040] Next, the range of attention lengths S1 (mm) and S2 (mm) originating from the sound source, such that the first recess formed at a specific location on the tread surface causes pass-by noise, is as follows: J / (N×1.25×1) <S1(mm)<J / (N×0.75×1) J / (N×1.25×2) <S2(mm)<J / (N×0.75×2)

[0041] (Step 4: Determine the lower limit LFL1 and upper limit HHL1 of the attention length S1 (mm) caused by the sound source.) Next, within the range of S1(mm) that satisfies J / (N×1.25×1)≦S1(mm)≦J / (N×0.75×1), we calculate the lower limit LFL1 of this inequality and the upper limit HFL1 of this inequality.

[0042] (Step 5: Determine the lower limit LFL2 and upper limit HHL2 of the attention length S2 (mm) caused by the sound source.) Similarly, within the range of S2 (mm) that satisfies J / (N×1.25×2) ≤ S2 (mm) ≤ J / (N×0.75×2), the lower limit value LFL2 of this inequality is calculated, and the upper limit value HFL2 of this inequality is calculated.

[0043] (Step 6: Step of determining Conditions C1, C2, and C3) Based on the above calculation results, LFL1×1 < Lai (mm) < HFL1×1, or LFL2×1 < Lai (mm) < HFL2×1, the condition defined by this is set as Condition C1.

[0044] Also, conditions other than Condition C1, and LFL1×0.5 < Lai (mm) < HFL1×0.5, or LFL2×0.5 < Lai (mm) < HFL2×0.5, the condition defined by this is set as Condition C2.

[0045] Furthermore, conditions other than Condition C1 and other than Condition C2 are set as Condition C3.

[0046] Here, the case of satisfying Condition C1 means that when the tire is rolling, the fluctuation timing regarding the opening and closing of the first concave portion (the phenomenon that both edge portions in the width direction of the first concave portion move away from or close to each other) is likely to overlap between the first concave portions adjacent in the tire circumferential direction, so the pass - by noise is large, which is an undesirable case.

[0047] Also, the case of satisfying Condition C2 means that when the tire is rolling, the fluctuation timing regarding the opening and closing of the first concave portion is less likely to overlap between the first concave portions adjacent in the tire circumferential direction, so the pass - by noise is small, which is a desired case.

[0048] Furthermore, the case of satisfying Condition C3 (when neither Condition C1 nor Condition C2 is satisfied) means that when the tire is rolling, the fluctuation timing regarding the opening and closing of the first concave portion is moderately likely to overlap between the first concave portions adjacent in the tire circumferential direction, so the pass - by noise is moderate, which means a case that is neither undesirable nor desired. <00​ The inequalities used to derive any of the conditions C1 to C3 were obtained by the inventors through diligent research and numerous experiments. Although the inventors have not yet found a clear technical basis for these inequalities, they have been supported by a vast amount of experimental data and have concluded that these inequalities are useful for ultimately improving noise performance.

[0050] (Step 7: Calculate N2 / N1 and N2 / N3) Finally, let N1 be the number of intervals Li (1 ≤ i ≤ N) that satisfy condition C1, N2 be the number of intervals Li that satisfy condition C2, and N3 be the number of intervals Li that satisfy condition C3, out of a maximum of N intervals Li (1 ≤ i ≤ N). Then we calculate N2 / N1 and N2 / N3.

[0051] N2 / N1 is the ratio of the number of desired intervals (N2) to the number of undesired intervals (N1), and a larger value is preferable. Similarly, N2 / N3 is the ratio of the number of desired intervals (N2) to the number of intervals that are neither desired nor undesired (N3), and a larger value is also preferable.

[0052] In addition to N2 / N1 and N2 / N3, the ratio of (N2 / N1) to (N2 / N3) can also be used as the basis for evaluation. A larger value for this ratio (N2 / N1) / (N2 / N3) is preferable.

[0053] As described above, by calculating N2 / N1 and N2 / N3, and preferably further calculating (N2 / N1) / (N2 / N3), it is possible to evaluate the extent of noise performance caused by pass-by noise from these values.

[0054] [Type 2: When there are at least two circumferential main grooves] The tire evaluation method (Type 2) of this embodiment is a tire evaluation method that, as a prerequisite, comprises a tire in which at least three land areas are partitioned by at least two circumferential main grooves, and on each side of the tire width direction of the tire equatorial plane, with the groove width centerline of the outermost circumferential main groove in the tire width direction as the boundary, the area from the groove width centerline in the tire width direction is defined as the center region and partitions the same land area, or at least one pair of second recesses that cause pass-by noise generation to partition two land areas opposite each other, separated by one circumferential main groove.

[0055] Furthermore, Type 1 (an evaluation method for tires with at least one circumferential main groove) and Type 2 (an evaluation method for tires with at least two circumferential main grooves) described above can sometimes be applied in conjunction with each other. For example, in the case of a tire with two or more circumferential main grooves (two, three, four, ...), either type of evaluation method can be applied (individually or simultaneously). On the other hand, in the case of a tire with only one circumferential main groove, only the Type 1 evaluation method can be applied, and the Type 2 evaluation method cannot be applied.

[0056] Figure 4 is a flowchart showing each step (process) of the tire evaluation method (Type 2) of this embodiment. The Type 2 tire evaluation method can also be carried out using the same seven steps shown in Figure 4 as the Type 1 tire evaluation method. In the following, only the evaluation methods of the Type 2 tire evaluation method that differ from the Type 1 tire evaluation method will be described in detail, and the evaluation methods that are the same will be omitted.

[0057] First, as a premise, the evaluation method for Type 2 evaluates the second recess formed within the center region, as described above. That is, in this embodiment, the second recess refers to a recess (groove portion or entire groove, or sipe portion or entire sipe) formed within the center region, where the widthwise centerline (along the extension direction of the recess) extends at an angle of 0° to 80° with respect to the tire circumferential direction (groove portion or entire groove, or sipe portion or entire sipe). Therefore, in the case of a tire with two or more circumferential main grooves, if a recess (at least a part of the groove or at least a part of the sipe) formed in a region other than the center region is to be evaluated, the evaluation method for Type 1 will be used.

[0058] Under these premises, the evaluation method for Type 2 tires involves, in Step 1, determining pairs of second recesses formed within the center region around the entire circumference of the tire, and in Step 2, determining the interval Lbi (1 ≤ i ≤ N). Steps 1 and 2 are the same as those described in the evaluation method for Type 1 tires.

[0059] However, in step 3 of the evaluation method for type 2 tires, unlike step 3 described above in the section on the evaluation method for type 1 tires, in addition to determining the ranges of attention lengths S1 (mm) and S2 (mm) caused by the sound source, a new range of attention length S3 (mm) caused by the transmission characteristics is also determined.

[0060] Here, the attention length S3 (mm) due to transmission characteristics refers to the range between the lower and upper limits calculated by dividing the representative speed of pass-by noise (for example, 50 km / h when the tire is mounted on the vehicle body and rolled) by the upper and lower limits of the frequency range that is emphasized in the center region due to the horn effect when measuring the acoustic characteristics of the space around the tire. Thus, the attention length S3 (mm) due to transmission characteristics takes into account the frequency range that is emphasized in the center region. For this reason, in the evaluation method for Type 2 tires, the recess (second recess) that is the source of the pass-by noise to be targeted is defined as the recess formed in the center region (groove portion or the entire groove, or sipe portion or the entire sipe).

[0061] Based on the above, in the evaluation method of the type 2 tire, in step 3, when the tire circumference is J (mm), the attention lengths due to the sound source are S1 (mm) and S2 (mm), and the attention length due to the transmission characteristics is S3 (mm), the range of S1 (mm) that satisfies J / (N×1.25×1)≦S1(mm)≦J / (N×0.75×1), the range of S2 (mm) that satisfies J / (N×1.25×2)≦S2(mm)≦J / (N×0.75×2), and the range of S3 (mm) that satisfies 12.4≦S3(mm)≦19.5 are determined.

[0062] Next, the ranges of the attention lengths S1 (mm) and S2 (mm) due to the sound source, and the range of the attention length S3 (mm) due to the transmission characteristics, such that the second recess formed in the center region causes the sound of the pass-by noise, shall be as follows, respectively. J / (N×1.25×1)<S1(mm)<J / (N×0.75×1) J / (N×1.25×2)<S2(mm)<J / (N×0.75×2) 12.4<S3(mm)<19.5

[0063] Furthermore, in the evaluation method of the type 2 tire, in step 4, at each lower limit value and each upper limit value of the range of the attention length S1 (mm) due to the sound source and the attention length S3 (mm) due to the transmission characteristics, the larger lower limit value is taken as LFL3, and the smaller upper limit value is taken as HHL3.

[0064] Similarly, in the evaluation method of the type 2 tire, in step 5, at each lower limit value and each upper limit value of the range of the attention length S2 (mm) due to the sound source and the attention length S3 (mm) due to the transmission characteristics, the larger lower limit value is taken as LFL4, and the smaller upper limit value is taken as HHL4.

[0065] Subsequently, in the evaluation method of the type 2 tire, in step 6, LFL3×1<Lbi(mm)<HFL3×1, or LFL4×1<Lbi(mm)<HFL4×1, the condition defined by this is taken as condition T1, Conditions other than condition T1, and LFL3×0.5 < Lbi (mm) < HFL3×0.5, or LFL4×0.5 < Lbi (mm) < HFL4×0.5, the conditions defined thereby are taken as condition T2, and Conditions other than condition T1 and other than condition T2 are taken as the above T3.

[0066] Here, the case of satisfying condition T1 means an undesired case where the pass-by noise is large because, when the tire is rolling, the timing of variation regarding the opening and closing of the second recess is likely to overlap between the second recesses adjacent in the tire circumferential direction.

[0067] Also, the case of satisfying condition T2 means a desired case where the pass-by noise is small because, when the tire is rolling, the timing of variation regarding the opening and closing of the second recess is unlikely to overlap between the second recesses adjacent in the tire circumferential direction.

[0068] Furthermore, the case of satisfying condition T3 (the case where neither condition T1 nor condition T2 is satisfied) means a case where the pass-by noise is moderate because, when the tire is rolling, the timing of variation regarding the opening and closing of the second recess is moderately likely to overlap between the second recesses adjacent in the tire circumferential direction, and it is neither an undesired nor a desired case.

[0069] Regarding each of the above inequalities used to derive any one of conditions T1 to T3, similar to conditions C1 to C3 described in type 1, they are the result of extensive studies and numerous experiments conducted by the inventors. Although the inventors have not clearly found a technical basis for these inequalities, they are supported by a large amount of experimental data, and finally, they have obtained the knowledge that these inequalities are useful for improving the noise performance.

[0070] Finally, in the evaluation method for Type 2 tires, in step 7, if E1 is the number of intervals Lbi that satisfy condition T1 out of a maximum of N intervals Lbi (1 ≤ i ≤ N), E2 is the number of intervals Lbi that satisfy condition T2, and E3 is the number of intervals Lbi that satisfy condition T3, then E2 / E1 and E2 / E3 are calculated.

[0071] E2 / E1 is the ratio of the number of desired intervals (E2) to the number of undesired intervals (E1), and a larger value is preferable. Similarly, E2 / E3 is the ratio of the number of desired intervals (E2) to the number of intervals that are neither desired nor undesired (E3), and a larger value is also preferable.

[0072] In addition to E2 / E1 and E2 / E3, the ratio of (E2 / E1) to (E2 / E3) can also be used as the basis for evaluation. A larger value for this ratio (E2 / E1) / (E2 / E3) is preferable.

[0073] As described above, by calculating E2 / E1 and E2 / E3, and preferably further calculating (E2 / E1) / (E2 / E3), it is possible to evaluate the extent of the noise performance caused by pass-by noise from these values.

[0074] [A suitable configuration for evaluating Type 1 and Type 2 tires in common] The above describes tire evaluation methods (Type 1) and tire evaluation methods (Type 2). Below, we will detail the preferred configuration common to both evaluation methods.

[0075] In other words, in the evaluation method for Type 1 (Type 2) tires, in the step of determining two first recesses (two second recesses) as a pair, it is preferable to determine an arbitrary first recess (arbitrary second recess) and another first recess (other second recess) formed at the closest distance from the arbitrary first recess (or arbitrary second recess) as a pair.

[0076] Here, the case where the first recesses (or second recesses) are formed at the closest possible distance is when, in a plan view of the two first recesses (or two second recesses), 1) When the distance between the centroids of the two first recesses (two second recesses) (the centroids obtained by image processing of the tire surface image or tire contact image, and obtained using the general image processing formula for calculating the centroid [(sum of brightness value × position)] / [sum of brightness value]) is shortest, or, 2) When the shortest distance between the two first recesses (the two second recesses) is the shortest, This refers to any of the following cases.

[0077] When measuring the distance between two first recesses (or two second recesses), if multiple pairs of recesses are to be measured on a single tire, the distance between all pairs of recesses shall be measured using either method 1) or 2) above.

[0078] In this way, by treating the closest first recesses (or second recesses) as a pair and calculating N2 / N1 and N2 / N3 (E2 / E1 and E2 / E3), it is possible to efficiently evaluate whether or not noise performance has improved due to the reduction of pass-by noise.

[0079] <Tire Design Methods> Next, we will detail the tire design method based on the tire evaluation method described above.

[0080] [Type 1: When there is at least one circumferential main groove] In the tire design method (Type 1) based on the tire evaluation method (Type 1) described above, the spacing between the first recesses is determined such that N2 / N1 and N2 / N3 satisfy N2 / N1>1 and N2 / N3>1, and more preferably (N2 / N1) / (N2 / N3)>1.

[0081] As described above, N2 / N1 is the ratio of the number of desired intervals (N2) to the number of undesired intervals (N1), and a larger value is more preferable. In the present embodiment, by setting N2 / N1 to be greater than 1 and substantially N2 > N1, the tire is designed such that the number of desired intervals (N2) is greater than the number of undesired intervals (N1).

[0082] Similarly, N2 / N3 is the ratio of the number of desired intervals (N2) to the number of intervals that are neither desired nor undesired (N3), and a larger value is also more preferable. In the present embodiment, by setting N2 / N3 to be greater than 1 and substantially N2 > N3, the tire is designed such that the number of desired intervals (N2) is greater than the number of intervals that are neither desired nor undesired (N3).

[0083] The tire design method (Type 1) of the present embodiment focuses only on the intervals between the first recesses, and is not a method of improving the noise performance by reducing the so-called negative ratio (the ratio of recesses (grooves and sipes) on the tread surface) with respect to conventional tires. Therefore, according to the tire design method (Type 1) of the present embodiment, the noise performance can be improved without deteriorating the wet performance.

[0084] Furthermore, in the tire design method (Type 1) of the present embodiment, it is preferable to also consider the magnitude relationship between (N2 / N1) and (N2 / N3). Specifically, it is preferable to design the tire such that (N2 / N1) > (N2 / N3). This condition substantially means N1 < N3, and means designing the tire such that the number of undesired intervals (N1) is less than the number of intervals that are neither desired nor undesired (N3).

[0085] In the tire design method (Type 1) of this embodiment, as described above and also in the tire evaluation method (Type 1), the tire circumference is defined as J (mm), and the attention lengths due to the sound source are defined as S1 (mm) and S2 (mm). The ranges of S1 (mm) that satisfy J / (N×1.25×1)≦S1 (mm)≦J / (N×0.75×1) and S2 (mm) that satisfy J / (N×1.25×2)≦S2 (mm)≦J / (N×0.75×2) are determined. This is because if the attention lengths due to the sound source S1 (mm) and S2 (mm) are within the above range, there is a high possibility that sound source components will be generated from the first recess, while if they are outside the above range, there is a low possibility that sound source components will be generated from the first recess.

[0086] [Type 2: When there are at least two circumferential main grooves] In the tire design method (Type 2) based on the tire evaluation method (Type 2) described above, the spacing of the second recess is determined such that E2 / E1 and E2 / E3 satisfy E2 / E1>1 and E2 / E3>1, and more preferably (E2 / E1) / (E2 / E3)>1.

[0087] As described above, E2 / E1 is the ratio of the number of desired intervals (E2) to the number of undesired intervals (E1), and a larger value is preferable. In this embodiment, by setting E2 / E1 to greater than 1, and effectively making E2 > E1, the tire is designed so that the number of desired intervals (E2) is greater than the number of undesired intervals (E1).

[0088] Similarly, E2 / E3 is the ratio of the number of desired intervals (E2) to the number of undesired or non-desired intervals (E3), and a larger value is preferable. In this embodiment, by setting E2 / E3 to greater than 1, and effectively making E2 > E3, the tire is designed so that the number of desired intervals (E2) is greater than the number of undesired or non-desired intervals (E3).

[0089] Further, the tire design method (Type 2) of the present embodiment does not focus only on the interval between the second recesses, and is not a method of improving the noise performance by reducing the so-called negative ratio (the ratio of recesses (grooves and sipes) on the tread surface) with respect to a conventional tire. Therefore, even with the tire design method (Type 2) of the present embodiment, the noise performance can be improved without deteriorating the wet performance.

[0090] Furthermore, it is more preferable to also consider the magnitude relationship between (E2 / E1) and (E2 / E3). Specifically, it is preferable to design the tire such that (E2 / E1) > (E2 / E3). This condition substantially means E1 < E3, and means designing the tire so that the number of occurrences (E1) of an undesired interval is less than the number of occurrences (E3) of an interval that is neither desired nor undesired.

[0091] In the tire design method (Type 2) of the present embodiment, as described above and also described in the tire evaluation method (Type 2), after setting the attention lengths S1 (mm) and S2 (mm) caused by the sound source for the same reasons as in the case of Type 1, furthermore, regarding the attention length S3 (mm) caused by the transmission characteristics, a range of S3 (mm) satisfying 12.4 ≦ S3 (mm) ≦ 19.5 is determined. This is because when the attention length S3 (mm) caused by the transmission characteristics is within the above range, the sound generated in the second recess formed in the center region is likely to be emphasized by the horn effect, while when it is outside the above range, the sound generated in the second recess is less likely to be emphasized by the horn effect.

[0092] In the tire design method (Type 2) of the present embodiment, it is more preferable to determine the interval between the second recesses so as to satisfy E2 / E1 ≧ 1.2. By designing the tire so as to satisfy E2 / E1 ≧ 1.2, the number of occurrences (E2) of a desired interval can be made even more than the number of occurrences (E1) of an undesired interval, and thereby, due to the reduction of the pass-by noise, the noise performance of the tire can be further improved.

[0093] In the tire design method of this embodiment (Type 2), it is even more preferable to design the tire so that E2 / E1≧1.2 is satisfied, as well as E3 / E1>1, that is, to add a relationship between the number of gaps that are neither desired nor undesirable (E3) and the number of gaps that are undesirable (E1).

[0094] The relationship between E1, E2, and E3 shown above is very preferably such that E2 / E1 ≥ 2 and E3 / E1 > 1.

[0095] Next, in the tire design method of this embodiment (Type 2), it is preferable that in a pair of second recesses formed in the center region, the volume of one second recess is approximately equal to the volume of the other second recess.

[0096] Here, "approximately equal in volume" means that the volume ratio (volume of the larger second recess / volume of the smaller second recess) does not exceed 1.1.

[0097] Factors that can change the volume include the tire width dimension of the second recess, the groove width, and the depth. However, by changing at least one of these factors, the volume ratio should be kept below 1.1.

[0098] Here, the tire width dimension of the second recess is measured in plan view, by measuring the tire width dimension between the outer end and inner end of the second recess in the tire width direction. The groove width of the second recess is measured in plan view, by dividing the second recess into five equal parts in the extending direction (along the widthwise centerline), measuring the width at the center of the extending direction in each of the five parts (the dimension perpendicular to the extending direction), and then taking the average of the five measured widths. The depth of the second recess is measured in plan view, by dividing the second recess into five equal parts in the extending direction (along the widthwise centerline), measuring the depth at the center of the extending direction in each of the five parts (the minimum radial dimension of the tire from the tire profile line (the outermost position in the tire radial direction) to the groove bottom (the innermost position in the tire radial direction) as if there were no groove), and then taking the average of the five measured depths.

[0099] By adopting this configuration (in terms of volume), each of the paired second recesses can be formed with a shape as uniform as possible, thereby efficiently demonstrating wet performance while reducing pass-by noise.

[0100] Furthermore, in the tire design method of this embodiment (Type 2), it is preferable that in a pair of second recesses formed in the center region, the extension angle of one second recess with respect to the tire circumferential direction is approximately equal to the extension angle of the other second recess with respect to the tire circumferential direction.

[0101] Here, the statement that the extension angles with respect to the tire circumferential direction are approximately equal means that the angle ratio (extension angle of the second recess with a larger angle with respect to the tire circumferential direction / extension angle of the second recess with a smaller angle with respect to the tire circumferential direction) does not exceed 1.1.

[0102] Here, the extension angle of the second recess with respect to the tire circumferential direction is calculated as follows. First, the second recess is divided into five equal parts in the extension direction (along the center line in the width direction), and the midpoint in the direction perpendicular to the extension direction is determined for each of the five parts. Next, a virtual line is found using the least squares method based on these five midpoints. Finally, the angle that this virtual line makes with the tire circumferential direction (the angle on the acute side) is measured and taken as the extension angle with respect to the tire circumferential direction.

[0103] By adopting this configuration (regarding the extension angle), each of the paired second recesses can be formed with an extension angle as uniform as possible, thereby efficiently achieving wet performance while reducing pass-by noise.

[0104] Furthermore, in the tire design method of this embodiment (Type 2), it is preferable that in a pair of second recesses formed in the center region, the length in the tire width direction of the second recess closer to the tire equator is shorter than the length in the tire width direction of the second recess further away from the tire equator.

[0105] Figure 5 is a plan view showing a part of a tire manufactured based on the tire design method (Type 2) of this embodiment. In the tire shown in the figure, four circumferential main grooves 110, 112, 114, and 116 divide five land areas 118, 120, 122, 124, and 126. In the region between two adjacent circumferential main grooves 110, 112, 114, and 116, two of the second recesses 128, 130, 132, 134, 136, and 138 are formed, respectively. In Figure 5, CP represents the tire equatorial plane, CR represents the center region, and SR1 and SR2 represent the shoulder regions. Here, the center region CR refers to the region inward in the tire width direction from the groove width centerlines of the outermost circumferential main grooves 110 and 116 in the tire width direction, on each side of the tire equatorial plane CP in the tire width direction. Furthermore, shoulder areas SR1 and SR2 refer to the outer areas of the center area CR in the tire width direction.

[0106] As shown in Figure 5, in a pair of second recesses 128 and 130 formed in the region between the circumferential main grooves 110 and 112, the length in the tire width direction of the second recess 130 closer to the tire equatorial plane CP is shorter than the length in the tire width direction of the second recess further from the tire equatorial plane CP.

[0107] Sound transmission characteristics are maximized at the center of the tire width (tire equatorial plane CP). Therefore, assuming that the total length (tire width dimension) of the second recesses 128 and 130 that partition the land portion 120 is kept constant, shortening the tire width dimension of the second recesses as it approaches the center of the tire width reduces pass-by noise without degrading wet performance, and consequently further improves noise performance.

[0108] Furthermore, by making the ratio (<1) of the tire widthwise lengths of the second recess 130 on the side closer to the tire equatorial plane CP and the second recess 128 on the side further from the tire equatorial plane CP less than or equal to the reciprocal of the ratio (>1) of the sound transmission characteristics at the tire widthwise center position of each second recess 130, 128, pass-by noise can be efficiently reduced.

[0109] In contrast, the pair of second recesses 132 and 134 formed in the region between the circumferential main grooves 112 and 114 (where the centerline in the tire width direction coincides with the tire equatorial plane CP) are both at the same distance from the tire equatorial plane CP. For this reason, the lengths of the second recesses 132 and 134 in the tire width direction are equal. This is because the region between the circumferential main grooves 112 and 114 is symmetrical with respect to the tire equatorial plane CP, and therefore the sound transmission characteristics are the same on each side in the tire width direction in this region.

[0110] Furthermore, in a pair of second recesses 136 and 138 formed in the region between the circumferential main grooves 114 and 116, the length in the tire width direction of the second recess 136 on the side closer to the tire equatorial plane CP is shorter than the length in the tire width direction of the second recess 138 on the side further from the tire equatorial plane CP.

[0111] The relationship between these second recesses 136 and 138 with respect to the tire width direction length is the same as the relationship between the second recesses 130 and 128 described above. In the region sandwiched between the circumferential main grooves 114 and 116, by making the tire width direction length of the second recess 136 closer to the tire equatorial plane CP shorter than the tire width direction length of the second recess 138 further from the tire equatorial plane CP, pass-by noise can be reduced without degrading wet performance, and consequently, noise performance can be further improved.

[0112] In addition, in the tire design method of this embodiment (Type 2), it is preferable that in a pair of second recesses formed in the center region, the groove width of the second recess closer to the tire equator is smaller than the groove width of the second recess further from the tire equator.

[0113] As shown in Figure 5, in a pair of second recesses 128 and 130 formed in the region between the circumferential main grooves 110 and 112, the groove width (maximum dimension in the direction perpendicular to the extending direction) of the second recess 130 on the side closer to the tire equatorial plane CP is shorter than the groove width (maximum dimension in the direction perpendicular to the extending direction) of the second recess 128 on the side further from the tire equatorial plane CP.

[0114] As described above, the sound transmission characteristics are greatest at the center of the tire width (tire equatorial plane CP). Therefore, assuming that the average groove width of the second recesses 128 and 130 formed in the region between the circumferential main grooves 110 and 112 is kept constant (the average value of the groove widths of the second recesses 128 and 130), by shortening the groove width of the second recesses as one approaches the center of the tire width, pass-by noise can be reduced without degrading wet performance, and consequently, noise performance can be further improved.

[0115] Furthermore, by setting the ratio (<1) of the groove width of the second recess 130 on the side closer to the tire equatorial plane CP to the groove width of the second recess 128 on the side further from the tire equatorial plane CP to be less than or equal to the reciprocal of the ratio (>1) of the sound transmission characteristics at the center position in the tire width direction of each second recess 130, 128, pass-by noise can be efficiently reduced.

[0116] In contrast, the pair of second recesses 132 and 134 formed in the region between the circumferential main grooves 112 and 114 (whose centerline in the tire width direction coincides with the tire equatorial plane CP) are both at the same distance from the tire equatorial plane CP. Therefore, the groove widths of the second recesses 132 and 134 are equal. This is because the region between the circumferential main grooves 112 and 114 is symmetrical with respect to the tire equatorial plane CP, and therefore the sound transmission characteristics are the same on each side in the tire width direction in this region.

[0117] Furthermore, in a pair of second recesses 136 and 138 formed in the region between the circumferential main grooves 114 and 116, the groove width of the second recess 136 closer to the tire equatorial plane CP is shorter than the groove width of the second recess 138 further from the tire equatorial plane CP.

[0118] The relationship between these second recesses 136 and 138 with respect to groove width is the same as the relationship between the second recesses 130 and 128 described above. In the region between the circumferential main grooves 114 and 116, by making the groove width of the second recess 136 on the side closer to the tire equatorial plane CP shorter than the groove width of the second recess 138, pass-by noise can be reduced without degrading wet performance, and consequently, noise performance can be further improved.

[0119] [A suitable configuration for both Type 1 and Type 2 tire design methods] The following describes in detail preferred embodiments common to the tire design method (Type 1) and tire design method (Type 2) described above. Note that the following examples show embodiments for the first recess, but similar embodiments apply to the second recess as well.

[0120] In the tire design method (Type 1), when two first recesses within the same set are parallel, it is preferable that the distance between the first recesses be determined by dividing each first recess into five equal parts in the extending direction (along the widthwise centerline), determining a representative point for each part that is both the midpoint in the extending direction and the midpoint in a direction perpendicular to the extending direction, and then determining the shortest distance between the imaginary lines obtained by the least squares method using the five representative points. Here, two first recesses within the same set are considered parallel if the difference in angle with respect to the circumferential main groove is within 5°.

[0121] Figure 6 is a tire plan view showing an example of determining the spacing between two first recesses (second recesses) when they are parallel to each other within the same set. As shown in the figure, two first recesses 142 and 144 are formed as part of the recesses that demarcate the land portion 140. In this case, the spacing between the first recesses 142 and 144 is preferably determined as follows. Note that in Figure 6, the first recesses 142 and 144 are straight grooves, but this embodiment is not limited to this configuration and also includes cases where the grooves are curved or zigzag.

[0122] Specifically, the first recess 142 is divided into five equal parts in its extending direction (along the center line in the width direction), and representative points 142a, 142b, 142c, 142d, and 142e of each part are determined, which are the midpoints of each part in the extending direction and the midpoints in the direction perpendicular to the extending direction. Then, a virtual line 142L is obtained using the least squares method with the five representative points 142a, 142b, 142c, 142d, and 142e.

[0123] Similarly, the first recess 144 is divided into five equal parts along its extension direction (along the center line in the width direction), and representative points 144a, 144b, 144c, 144d, and 144e of each part are determined, which are the midpoints of each part in the extension direction and the midpoints in the direction perpendicular to the extension direction. Then, a virtual line 144L is obtained using the least large squares method with the five representative points 144a, 144b, 144c, 144d, and 144e.

[0124] Finally, the shortest distance L1 between the two virtual lines 142L and 144L is obtained (however, this is limited to the distance that can be measured within the land portion 140 where the two first recesses 142 and 144 are formed), and this shortest distance L1 is taken as the distance between the two first recesses 142 and 144.

[0125] In this way, by determining the distance between the two first recesses 142 and 144 within the same set, it is possible to suppress the radiated sound generated when the recess comes into contact with the road surface.

[0126] In contrast, in the tire design method (Types 1 and 2), when two first recesses within the same set are not parallel, it is preferable to determine the distance between the first recesses by dividing the first recess into five equal parts in the extending direction (along the widthwise centerline), determining a representative point for each part which is the midpoint in the extending direction and also the midpoint in a direction perpendicular to the extending direction, combining the representative point of one first recess with the representative point of the other first recess in order from one side of the vehicle mounting, determining the tire circumferential distance between the combined representative points, and averaging the five tire circumferential distances.

[0127] Figure 7 is a tire plan view showing an example of determining the spacing between two first recesses (second recesses) when they are not parallel to each other within the same set. As shown in the figure, two non-parallel first recesses 152 and 154 are formed as part of the recesses that demarcate the land portion 150. In this case, it is preferable to determine the spacing between the first recesses 152 and 154 as follows. Note that in Figure 7, the first recesses 152 and 154 are straight grooves, but this embodiment is not limited to this configuration and also includes cases where the grooves are curved or zigzag.

[0128] Specifically, the first recess 152 is divided into five equal parts along its extending direction (along the center line in the width direction), and representative points 152a, 1552b, 152c, 152d, and 152e of each part are determined, which are the midpoints of each part in the extending direction and the midpoints in the direction perpendicular to the extending direction.

[0129] Similarly, the first recess 154 is divided into five equal parts along its extending direction (along the center line in the width direction), and representative points 154a, 154b, 154c, 154d, and 154e of each part are determined, which are the midpoints of each part in the extending direction and the midpoints in the direction perpendicular to the extending direction.

[0130] Furthermore, representative points 152a to 152e of one first recess 152 and representative points 154a to 154e of the other first recess 154 are combined sequentially from one side of the vehicle mounting (for example, the upper side in Figure 7) to determine the tire circumferential distance (for example, distance sa) between the combined representative points (for example, representative point 152a and representative point 154a). The same procedure is followed for distances sb, sc, sd, and se.

[0131] Finally, the average value of the circumferential distances of the five tires from sa to se is taken as the distance L2 between the two first recesses 152 and 154.

[0132] In this way, by determining the distance between the two first recesses 152 and 154 within the same set, it is possible to suppress the radiated sound generated when the recess comes into contact with the road surface.

[0133] In addition, the tire design method (Type 1) includes the step of creating a variable-pitch tread pattern in which a region containing a set of first recesses is defined as one pitch, The process further includes the step of defining an original function with one pitch as one period, arranging the original functions for one full rotation of the tire and performing a Fourier transform, and setting the maximum value of the first-order rotation component with one tire rotation as one period to R1, and the maximum value of the second-order rotation component to R2, Of the variable pitch, the spacing Lai of at least one pair of first recesses is J(mm) / (R1×0.9)<Lai(mm)<J(mm) / (R1×1.1), or J(mm) / (R2×0.9)<Lai(mm)<J(mm) / (R2×1.1), It is preferably determined to satisfy the above conditions.

[0134] In the region sandwiched between the circumferential main grooves 110 and 112 in FIG. 5, a plurality of sets of first recesses (128a, 130a), (128b, 130b), (128c, 130c), etc. are sequentially formed in the tire circumferential direction. Here, focus on a set of first recesses (128b, 130b).

[0135] Determine the circumferential intermediate line L3 of the first recess 130b and the first recess 128a adjacent to one side in the tire circumferential direction of the first recess 130b (the side opposite to the first recess 128b) (a tire width direction line that is equidistant from a tire width direction line passing through the end point on one side in the tire circumferential direction (upper side of the paper surface) of the first recess 130b and a tire width direction line passing through the end point on the other side in the tire circumferential direction (lower side of the paper surface) of the first recess 128a).

[0136] On the other hand, determine the circumferential intermediate line L4 of the first recess 128b and the first recess 130c adjacent to the other side in the tire circumferential direction of the first recess 128b (the side opposite to the first recess 130b) (a tire width direction line that is equidistant from a tire width direction line passing through the end point on the other side in the tire circumferential direction (lower side of the paper surface) of the first recess 128b and a tire width direction line passing through the end point on one side in the tire circumferential direction (upper side of the paper surface) of the first recess 130c).

[0137] Then, the region surrounded by the circumferential intermediate lines L3 and L4 determined in this way, and the circumferential main grooves 110 and 112 (the region having the tire circumferential dimension R in FIG. 5) is defined as the region including a set of first recesses (128b, 130b).

[0138] In addition, in the present embodiment, the variable pitch refers to a pitch arrangement in which the regions including the above-described set of first recesses are arranged unevenly in the tire circumferential direction (that is, the tire circumferential dimensions of a plurality of the above regions continuous in the tire circumferential direction are different in at least one of the above regions).

[0139] Next, a primitive function with one pitch (a region including a set of first recesses) as one cycle is defined, and this primitive function is arranged for one tire circumference and subjected to Fourier transform. Let the maximum value of the rotational primary component with one tire rotation as one cycle be R1, and the maximum value of the rotational secondary component be R2.

[0140] Here, the rotational primary component is the number of tire rotations × the number of pitches, and the rotational secondary component is the number of tire rotations × the number of pitches × 2.

[0141] Furthermore, among the variable pitches, the interval Lai between at least a set of first recesses is J(mm) / (R1×0.9) < Lai(mm) < J(mm) / (R1×1.1), or J(mm) / (R2×0.9) < Lai(mm) < J(mm) / (R2×1.1), and is determined to satisfy the above conditions.

[0142] Here, J(mm) is the tire circumference, and Lai(mm) is the interval between the first recesses sequentially measured over the entire tire circumference as described above. The primitive function can be appropriately selected from a pulse wave, a rectangular wave, a triangular wave, a cosine wave, a sine wave, etc.

[0143] In this way, regarding the rotational primary component R1 and the rotational secondary component R2, the maximum value in the squared amplitude value in the result of the analysis by Fourier transform is selected, and the interval Lai(mm) is determined from the order in which the rotational order component increases and the tire circumference. Thus, each of the rotational primary component and the rotational secondary component with a relatively large input component in the variable pitch can be canceled out, and the pass-by noise can be more efficiently reduced, and thus the noise performance can be further enhanced.

[0144] Note that the interval Lai is J (mm) / (R1 × 0.95) < Lai (mm) < J (mm) / (R1 × 1.05), or J (mm) / (R2 × 0.95) < Lai (mm) < J (mm) / (R2 × 1.05) By being determined to satisfy the above, it is possible to further reduce the pass-by noise more efficiently, and thereby further improve the noise performance.

Example

[0145] Hereinafter, regarding the tire design method, three types of Examples 1 to 3 are shown. That is, in Example 1, the effect according to the above Form 2 (regarding the tire design method (Type 1)) is shown, in Example 2, the effects according to the above Forms 4 and 5 (regarding the tire design method (Type 2)) are shown, and in Example 3, the effects according to the above Forms 10 to 13 (regarding the tire design methods Types 1 and 2) are shown.

[0146] Also, in Examples 1 to 3 shown below, the tire size is 245 / 70R18 110H (specified by JATMA), having four circumferential main grooves, having any one of the seven tread patterns shown in FIGS. 8 and 9, and satisfying the specifications shown in any one of Tables 1 to 3. Using the design methods of each test tire (the design methods of the conventional example, Invention Examples 1 to 8, and Comparative Examples 1 to 4), each tire (the tire corresponding to each design method) was manufactured. In addition, each term in Table 1 conforms to the terms described in this embodiment.

[0147] Next, each test tire was mounted on a rim of size 18x71 / 2J, and the air pressure was set to 230 kPa, and these were mounted on a 4WD vehicle with a displacement of 3500 cc. For all these test tires, an evaluation of the noise performance (regarding the pass-by noise) was conducted according to the following procedure.

[0148] (Evaluation method of noise performance) Then, on the test course, the noise level (dB) of each test tire was measured when the vehicle was driven at a speed of 50 km / h, the transmission was put in neutral, and the engine was stopped. The difference in noise level between each invention's tire and a conventional tire (reference) was calculated, and this difference itself was used as a score. A lower score indicates better noise performance. The results are shown in Tables 1 to 3.

[0149] In Examples 1 to 3 described below, the first or second recess is a sipe rather than a groove, and the noise performance was evaluated by varying the various conditions shown in Tables 1 to 3.

[0150] <Example 1: Proof of the effect of the above form 2> Figure 8 is a plan view showing a portion of the tread surface of a tire having four circumferential main grooves 200, 202, 204, and 206, and one or two of the first recesses 208, 210, 212, 214, 216, 218, and 220. In Figure 8, the horizontal direction of the paper is the tire circumferential direction, and the vertical direction of the paper is the tire width direction. Note that Example 1 is an example relating to the first recesses (entire sipes) 208-220 that are formed not limited to the center region CR.

[0151] Note that, in Figure 8, the circumferential main grooves 200-206 are labeled with reference numerals only in Figure 8(A), but the same applies to Figures 8(B) to 8(D). Also, the center region CR and shoulder regions SR1 and SR2 are labeled with reference numerals only in Figure 8(D), but the same applies to Figures 8(A) to 8(C).

[0152] In Figure 8(A), the first recess 208 is formed around the entire circumference of the tire so as to communicate with both circumferential main grooves 202 and 204 (conventional example). In Figure 8(B), the first recesses 210 and 212 are alternately formed around the entire circumference of the tire so as to communicate with only one of the circumferential main grooves 202 and 204 (Inventive Example 1). In Figure 8(C), the first recesses 214 and 216 are alternately formed around the entire circumference of the tire so as to communicate with only one of the circumferential main grooves 204 and 206 (Comparative Example 1). In Figure 8(D), the first recesses 218 and 220 are alternately formed around the entire circumference of the tire so as to communicate with the circumferential main groove 206 from one side or the other side in the tire width direction (Comparative Example 2). In all of Inventive Example 1 and Comparative Examples 1 and 2, the two first recesses enclosed by dotted lines (for example, sipes 210 and 212) represent a pair of first recesses in the present invention.

[0153] Furthermore, in all of the conventional example, inventive example 1, and comparative examples 1 and 2 shown in Figures 8(A) to 8(D), the total volume of the first recess in the region sandwiched between the two circumferential main grooves is the same, although its formation position in the tire width direction differs. As a result, there is no significant difference in wet performance among the four examples.

[0154] In the case of the conventional example, all first recesses 208 were assumed to meet condition C3, and none met conditions C1 or C2, and N2 / N1 and N2 / N3 were calculated accordingly.

[0155] Furthermore, in Invention Example 1 and Comparative Examples 1 and 2, the attention length S1 (mm) caused by the sound source was 24 mm or more and 40 mm or less, and the attention length S2 (mm) caused by the sound source was 12 mm or more and 20 mm or less. Therefore, the lower limit LFL1 of S1 (mm) was 24, the upper limit HFL1 of S1 (mm) was 40, the lower limit LFL2 of S2 (mm) was 12, and the upper limit HFL2 of S2 (mm) was 20.

[0156] From these results, condition C1 is defined as 24 < Li (mm) < 40 or 12 < Li (mm) < 20, condition C2 is defined as 12 < Li (mm) < 20 or 6 < Li (mm) < 20, and condition C3 is defined as a condition other than condition C1 and other than condition C2. Table 1 shows other specifications and also shows the results of the noise performance together.

[0157]

Table 1

[0158] According to Table 第1, it can be seen that Invention Example 1 belonging to the technical scope of the present invention (that is, N2 / N1 and N2 / N3 satisfy N2 / N1 > 1 and N2 / N3 > 1) has improved noise performance while maintaining wet performance compared to the tires of Conventional Example and Comparative Examples 1 and 2 that do not belong to the technical scope of the present invention.

[0159] <Example 2: Proof of the effects according to the above Forms 4 and 5> FIG. 9 is a plan view showing a part of the tread surface of a tire having four circumferential main grooves 300, 302, 304, 306 and having one or two of the second recesses 208, 310, 312, 314, 316. In FIG. 9, the horizontal direction of the paper surface is the tire circumferential direction, and the vertical direction of the paper surface is the tire width direction. Example 2 is an example regarding the second recesses (the entire sipe) 308 to 316 formed only in the center region CR.

[0160] In FIG. 9, for the circumferential main grooves 300 to 306, reference numerals are attached only in FIG. 9(A), but the same applies to FIGS. 9(B) and 9(C). Also, for the center region CR, shoulder regions SR1, SR2, reference numerals are attached only in FIG. 9(C), but the same applies to FIGS. 9(A) and 9(B).

[0161] In Fig. 9(A), the second recesses 308 are formed over the entire circumference of the tire so as to communicate with both of the circumferential main grooves 302 and 304 (conventional example). In Fig. 9(B), the second recesses 310 and 312 are alternately formed over the entire circumference of the tire so as to communicate with only one of the circumferential main grooves 302 and 304 (Inventive Example 2 and Comparative Examples 3 and 4). In Fig. 9(C), the second recesses 314 and 316 are alternately formed over the entire circumference of the tire so as to communicate with one side or the other side in the tire width direction with respect to the circumferential main groove 304 (Inventive Example 3). For any of Inventive Examples 2 and 3 and Comparative Examples 3 and 4, the two second recesses (for example, the sipe 310 and the sipe 312) surrounded by the dotted line are a set of second recesses in the present invention.

[0162] Further, for any of the conventional example, Inventive Examples 2 and 3, and Comparative Examples 3 and 4 shown in Figs. 9(A) to 9(C), with respect to the second recesses in the region sandwiched by the two circumferential main grooves, although the formation positions in the tire width direction are different, their total volumes are equal. As a result, there is no significant difference in wet performance among the three examples.

[0163] Regarding the conventional example, all of the second recesses 308 are assumed to correspond to condition T3, and those corresponding to conditions T1 and T2 are assumed not to exist, and E2 / E1 and E2 / E3 are calculated.

[0164] Also, in Inventive Examples 2 and 3 and Comparative Examples 3 and 4, the attention length S1 (mm) due to the sound source is 24 mm or more and 40 mm or less, the attention length S2 (mm) due to the sound source is 12 mm or more and 20 mm or less, and the attention length S3 (mm) due to the transmission characteristics is 12.4 or more and 19.5 or less. Therefore, there is no predetermined lower limit value LFL3, there is no predetermined upper limit value HFL3, the predetermined lower limit value LFL4 is 12.4, and the predetermined upper limit value HFL4 is 19.5.

[0165] From these results, condition T1 is defined as 12.4 < Li (mm) < 19.5, condition T2 is defined as 6.2 < Li (mm) < 9.75, and condition T3 is defined as a condition other than condition T1 and other than condition T2. Table 2 shows other specifications and also lists the results of the noise performance.

[0166] [Table 2]

[0167] According to Table 2, Invention Examples 2 and 3, which fall within the technical scope of the present invention (i.e., satisfying E2 / E1 > 1 and E2 / E3 > 1), show improved noise performance while maintaining wet performance compared to the conventional example and comparative examples 3 and 4, which do not fall within the technical scope of the present invention. Furthermore, Invention Example 3, which satisfies E2 / E1 ≥ 1.2, shows even greater noise performance than Invention Example 2, where E2 / E1 = 1.1.

[0168] <Example 3: Proof of the effects of the above forms 10-13> Inventive Examples 5 to 8 were manufactured, having the tread pattern shown in Figure 8(D), and further improving upon the tire of Comparative Example 2 shown in Example 1. The manufacturing conditions for Inventive Examples 5 to 8 are as shown in Table 3, and all other matters are the same as those for Comparative Example 2.

[0169] Specifically, in Invention Example 5, the depth of the first recess 218 was reduced compared to Comparative Example 2, and the volumes of the first recesses 218 and 220 were made the same. In Invention Example 6, the angle of the first recess 220 with respect to the tire circumferential direction was set to 90°, making the angles of the first recesses 218 and 220 the same. In Invention Example 7, the length of the first recess 218 in the tire width direction was made shorter than the length of the first recess 220 in the tire width direction. In Invention Example 8, the groove width of the first recess 218 was made smaller than the groove width of the first recess 220.

[0170] Table 3 lists other specifications and noise performance results.

[0171] [Table 3]

[0172] Table 3 shows that Invention Examples 5 to 8, which have been improved with respect to specific matters (depth of the first recess, extension angle of the first recess with respect to the tire circumferential direction, length of the first recess in the tire width direction, and groove width of the first recess) compared to Comparative Example 2, have further improved noise performance compared to Comparative Example 2. [Explanation of symbols]

[0173] 10, 20, 30, 40, 60, 70, 90, 100, 118, 120, 122, 124, 126, 140, 150 Land 50, 80, 110, 112, 114, 116, 200, 202, 204, 206,300, 302, 304, 306 Circumferential main groove 12, 22, 62, 72, 92, 102 groove 12a, 12b, 22a, 22b, 32, 34, 42, 44, 62a, 72a, 92, 102, 208, 210, 212, 214, 216, 218, 220 First recess 128, 128a, 128b, 128c, 130, 130a, 130b, 130c, 132, 134, 136, 138, 308, 310, 312, 314, 316 Second recess 142, 142a, 142b, 142c, 142d, 142e, 144, 144a, 144b, 144c, 144d, 144e, 152, 152a, 152b, 152c, 152d, 152e, 154, 154a, 154b, 154c, 154d, 154e First recess or second recess 142L, 144L virtual lines CP Tire Equatorial Plane CR Center Area Shortest distance between virtual lines 142L and 144L of L1 L3, L4 Tire Circumferential Center Line R Tire Circumferential Dimensions SR1, SR2 shoulder region

Claims

1. At least two land areas are demarcated by at least one circumferential main groove, A method for evaluating a tire comprising at least one pair of first recesses that cause pass-by noise generation and form a partition of the same land area, or at least one pair of first recesses that cause pass-by noise generation and form partitions of two land areas facing each other with a single circumferential main groove in between, The first recess is a groove portion or the entire groove extending in a direction from 0° to 80° with respect to the tire width direction, or a sipe portion or the entire sipe extending in a direction from 0° to 80° with respect to the tire width direction. The steps include determining that two of the first recesses form a set around the entire circumference of the tire, The steps include determining the number of sets N (sets) of the first recesses in the tire circumferential direction, and sequentially determining the spacing Lai (1 ≤ i ≤ N) between the first recesses within the same set around the entire circumference of the tire, Let J (mm) be the tire circumference, and S1 (mm) and S2 (mm) be the attention lengths originating from the sound source. The steps include determining the range of S1 (mm) that satisfies J / (N × 1.25 × 1) ≤ S1 (mm) ≤ J / (N × 0.75 × 1), and the range of S2 (mm) that satisfies J / (N × 1.25 × 2) ≤ S2 (mm) ≤ J / (N × 0.75 × 2), The steps include setting the lower limit of S1 (mm) to LFL1 and the upper limit to HHL1, The steps include setting the lower limit of S2 (mm) to LFL2 and the upper limit to HHL2, LFL1×1 < Lai (mm) < HFL1×1, or, Condition C1 is defined as LFL2×1 < Lai(mm) < HFL2×1. Other than condition C1, and LFL1 × 0.5 < Lai (mm) < HFL1 × 0.5, or Condition C2 defined by LFL2 × 0.5 < Lai (mm) < HFL2 × 0.5, and The steps involve determining a condition C3 that is other than condition C1 and other than condition C2, If, out of a maximum of N intervals Lai (1 ≤ i ≤ N), the number of intervals Lai satisfying condition C1 is N1, the number of intervals Lai satisfying condition C2 is N2, and the number of intervals Lai satisfying condition C3 is N3, The steps include calculating N2 / N1 and N2 / N3, A method for evaluating tires, characterized by including the following:

2. A tire design method, comprising determining the interval Lai (1 ≤ i ≤ N) such that N2 / N1 and N2 / N3 calculated according to the evaluation method described in claim 1 satisfy N2 / N1 > 1 and N2 / N3 > 1.

3. At least three land areas are demarcated by at least two circumferential main grooves, and on each side of the tire's equatorial plane in the tire width direction, with the groove width centerline of the outermost circumferential main groove in the tire width direction as the boundary, the area inward from the groove width centerline in the tire width direction is defined as the center region, and the area outward from the groove width centerline in the tire width direction is defined as the shoulder region, A method for evaluating a tire comprising, within the center region, at least one pair of second recesses that cause pass-by noise generation and form a partition of the same land area, or at least one pair of second recesses that cause pass-by noise generation and form partitions of two land areas facing each other across one of the circumferential main grooves, The second recess is a groove portion or the entire groove extending in a direction from 0° to 80° with respect to the tire width direction, or a sipe portion or the entire sipe extending in a direction from 0° to 80° with respect to the tire width direction. The steps include determining that two of the aforementioned second recesses form a set around the entire circumference of the tire, The steps include determining the number of sets N (sets) of the second recesses in the tire circumferential direction, and sequentially determining the spacing Lbi (1 ≤ i ≤ N) between the second recesses within the same set around the entire circumference of the tire, The tire circumference is defined as J (mm), the attention lengths due to the sound source are S1 (mm) and S2 (mm), and the attention length due to the transmission characteristics is defined as S3 (mm). The steps involve determining the range of S1 (mm) that satisfies J / (N × 1.25 × 1) ≤ S1 (mm) ≤ J / (N × 0.75 × 1), S2 (mm) that satisfies J / (N × 1.25 × 2) ≤ S2 (mm) ≤ J / (N × 0.75 × 2), and S3 (mm) that satisfies 12.4 ≤ S3 (mm) ≤ 19.

5. The steps include setting the lower limit and upper limit of each of the ranges S1 (mm) and S3 (mm) to be LFL3 and the lower limit to be HHL3, The steps include setting the lower limit and upper limit of each of the ranges S2 (mm) and S3 (mm) to be LFL4 and the lower limit to be HHL4, respectively. LFL3×1 < Lbi (mm) < HFL3×1, or Condition T1 is defined as LFL4×1 < Lbi(mm) < HFL4×1. Other than condition T1, and LFL3×0.5 < Lbi(mm) < HFL3×0.5, or Condition T2 defined by LFL4×0.5 < Lbi(mm) < HFL4×0.5, and The steps involve determining a condition T3 that is other than condition T1 and other than condition T2, If, among the maximum of N intervals Lbi (1 ≤ i ≤ N), the number of intervals Lbi satisfying condition T1 is E1, the number of intervals Lbi satisfying condition T2 is E2, and the number of intervals Lbi satisfying condition T3 is E3, The steps include calculating E2 / E1 and E2 / E3, A tire evaluation method according to claim 1, including the method described in claim 1.

4. A tire design method, comprising determining the interval Lbi (1 ≤ i ≤ N) such that E2 / E1 and E2 / E3 calculated according to the evaluation method described in claim 3 satisfy E2 / E1 > 1 and E2 / E3 > 1.

5. A tire design method according to claim 4, wherein the interval Lbi (1 ≤ i ≤ N) is determined such that E2 / E1 ≥ 1.

2.

6. Within the same set, two of the first recesses or two of the second recesses are parallel, The tire design method according to claim 2 or 4, wherein the interval Lai or Lbi is determined by determining a representative point for each of the two first recesses or each of the two second recesses, which is divided into five equal parts in the extending direction, and which is the midpoint in the extending direction and the midpoint in a direction perpendicular to the extending direction, and the shortest distance between virtual lines obtained by the least squares method using the five representative points.

7. If the two first recesses or the two second recesses within the same set are not parallel, The tire design method according to claim 2 or 4, wherein the interval Lai or Lbi is determined by determining a representative point for each of the two first recesses or each of the two second recesses, which is the midpoint in the extending direction of each portion obtained by dividing the extending direction into five equal parts, and is also the midpoint in a direction perpendicular to the extending direction; the representative point of one of the first recesses or second recesses and the representative point of the other first recesses or second recesses are combined sequentially from one side of the vehicle mounting to determine the tire circumferential distance between the combined representative points, and the distance is the average of the five tire circumferential distances.

8. The tire evaluation method according to claim 1 or 3, wherein in the step of determining two of the first recesses or two of the second recesses as a pair, the set is determined to consist of any first recess or any second recess and another first recess or other second recess formed at the closest distance from the arbitrary first recess or any second recess.

9. The steps include: creating a variable-pitch tread pattern in which a region containing a pair of first recesses or a region containing a pair of second recesses is defined as one pitch; The method further includes the step of defining an original function with one pitch as one period, arranging the original function for one full rotation of the tire and performing a Fourier transform, and setting R1 as the maximum value of the first-order rotational component with one tire rotation as one period, and R2 as the maximum value of the second-order rotational component, The interval Lai or the interval LBi is J (mm) / (R1 × 0.9) < Lai (Lbi) (mm) < J (mm) / (R1 × 1.1), or J (mm) / (R2×0.9)<Lai(Lbi)(mm)<J(mm) / (R2×1.1) Determined to satisfy, A tire design method according to claim 2 or 4.

10. The tire design method according to claim 4 or 5, wherein in a pair of second recesses formed in the center region, the volume of one of the second recesses is approximately equal to the volume of the other second recess.

11. The tire design method according to claim 4 or 5, wherein in a pair of second recesses formed in the center region, the extension angle of one of the second recesses with respect to the tire circumferential direction is approximately equal to the extension angle of the other second recess with respect to the tire circumferential direction.

12. The tire design method according to claim 4 or 5, wherein in a pair of second recesses formed in the center region, the length in the tire width direction of the second recess closer to the tire equator is shorter than the length in the tire width direction of the second recess further away from the tire equator.

13. A tire design method according to claim 4 or 5, wherein in a pair of second recesses formed in the center region, the groove width of the second recess on the side closer to the tire equator is smaller than the groove width of the second recess on the side further from the tire equator.

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