tire

Abstract

To provide a tire reduced in pitch noise and improved in cornering power.SOLUTION: In a tire 1, when numbers of respective land parts in land part rows 51, 52, 53 and 54 are defined as numbers of pitches, the numbers of pitches of the inner shoulder land row 51 are same as the numbers of pitches of the first land part row 53, the numbers of pitches of the outer shoulder land row 52 are same as the numbers of pitches of the second land part row 54, and the numbers of pitches of the second land part row 54 are smaller than the numbers of pitches of the first land part row 53.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tire. [Background technology]

[0002] Conventionally, there are known tires that suppress an increase in noise caused by pattern noise generated from the tire while the vehicle is traveling. For example, in Patent Document 1, the pitch numbers of each land row in the tread are set to different prime numbers, thereby eliminating common divisors between the pitch numbers, except for the pitch numbers themselves and 1, and preventing superposition of noise with frequencies caused by common divisors of the pitch numbers. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4266705 Summary of the Invention [Problem to be solved by the invention]

[0004] The tire disclosed in Patent Document 1 prevents pattern noise from being superimposed, but at the same time, the tire is also required to have high cornering power.

[0005] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a tire in which pitch noise is reduced and cornering power is improved. [Means for solving the problem]

[0006] The tire of the present invention is a tire having a tread that constitutes a tread surface that is a contact surface with a road surface, and the tread comprises at least an inner shoulder land row having a plurality of inner shoulder land portions defined by an inner main groove and a ground contact edge that are located on the innermost side in a width direction of a vehicle when the tire is mounted on the vehicle, an outer shoulder land row having a plurality of outer shoulder land portions defined by an outer main groove and a ground contact edge that are located on the outermost side in the width direction, and a center main groove that is located between the inner main groove and the outer main groove in the width direction. and a first land row having a plurality of first land portions defined by the inner main groove, and a second land row having a plurality of second land portions defined by the central main groove and the outer main groove, wherein the number of the land portions in each land row is the pitch number, the number of pitches of the inner shoulder land row is the same as the number of pitches of the first land row, the number of pitches of the outer shoulder land row is the same as the number of pitches of the second land row, and the number of pitches of the second land row is smaller than the number of pitches of the first land row. Effect of the Invention

[0007] According to the present invention, it is possible to provide a tire in which the pitch noise is reduced and the cornering power is improved. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view in the tire width direction of a tire according to a first embodiment. [Diagram 2] FIG. 2 is a view of the tire of FIG. 1 as seen in the direction of arrow II. [Diagram 3] FIG. 2 is a diagram illustrating a ground contact position of the tire of the first embodiment when traveling straight. [Figure 4] FIG. 2 is a diagram illustrating a ground contact position during cornering in the tire of the first embodiment. [Diagram 5] 2 is a view showing the tread of a tire according to a second embodiment, taken in the same direction as the direction of the arrow II in FIG. 1. [Figure 6]FIG. 2 is a view showing a tread of a tire according to a modification of the first embodiment, as viewed in the same direction as the direction of the arrow II in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a first embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a cross-sectional view of a tire 1 in the tire width direction. Fig. 2 is a view of the tire 1 in Fig. 1 as seen in the direction of arrow II. In the drawings, the symbol S1 indicates the tire equatorial plane. The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis (tire meridian) and located at the center in the tire width direction.

[0010] Here, the tire width direction is a direction parallel to the tire rotation axis, and is the left-right direction on the paper in the cross-sectional view of Fig. 1. In Fig. 1, this is illustrated as the tire width direction W. The inner side in the tire width direction is a direction approaching the tire equatorial plane S1. The outer side in the tire width direction is a direction moving away from the tire equatorial plane S1. For ease of explanation, the inner side in the vehicle width direction when the tire is mounted on the vehicle is defined as the left side in Fig. 1, and the outer side in the vehicle width direction when the tire is mounted on the vehicle is defined as the right side in Fig. 1.

[0011] The tire radial direction is a direction perpendicular to the tire rotation axis, and is the up-down direction on the paper in Fig. 1. In Fig. 1, this is illustrated as tire radial direction R. The tire radial outer side is a direction away from the tire rotation axis, and is the upper side on the paper in Fig. 1. The tire radial inner side is a direction approaching the tire rotation axis, and is the lower side on the paper in Fig. 1.

[0012] The cross-sectional view in Fig. 1 is a cross-sectional view in the tire width direction (cross-sectional view including the tire meridian) of the tire 1 mounted on a standard rim and inflated to a standard internal pressure in an unloaded state. The standard rim refers to a standard rim determined by JATMA for the tire size. The standard internal pressure is, for example, 180 kPa when the tire 1 is for a passenger car.

[0013] The tire 1 of this embodiment includes a pair of beads 2 provided on both sides in the tire width direction, sidewalls 3 extending radially outward from each of the beads 2, and an annular tread 4 extending in the circumferential direction of the tire 1, which is connected to the radially outward parts of each of the sidewalls 3 and constitutes a tread surface that is a contact surface with the road surface. A shoulder portion 50 is formed on the outer side of the tread 4 in the tire width direction.

[0014] 1 and 2, the tread 4 includes a plurality of main grooves 41, 42, 43, 44 that extend continuously in the tire circumferential direction and go around the tire 1. The main grooves 41, 42, 43, 44 extend continuously in the tire circumferential direction.

[0015] Of the multiple main grooves 41, 42, 43, 44, the pair of main grooves 41, 42 arranged on the outermost sides in the tire width direction constitute the shoulder main grooves 41, 42. More specifically, the shoulder main groove 41 on the vehicle inner side constitutes the inner shoulder main groove 41 as the inner main groove, and the shoulder main groove 42 on the vehicle outer side constitutes the outer shoulder main groove 42 as the outer main groove. The main grooves 43, 44 arranged between the pair of shoulder main grooves 41, 42 constitute the center main grooves 43, 44 as the center-side main groove.

[0016] The tread 4 includes a plurality of inner shoulder land rows 51 having a plurality of inner shoulder land portions 511, a plurality of outer shoulder land rows 52 having a plurality of outer shoulder land portions 521 which are a plurality of land portions, a mediate land row 53 having an inner intermediate land portion 531 as a first land portion which is a plurality of land portions, an outer intermediate land row 54 having an outer intermediate land portion 541 as a second land portion which is a plurality of land portions, and a center land row 55 having a plurality of center land portions 551 which are a plurality of land portions. The inner intermediate land portion 531 and the outer intermediate land portion 541 will be described later.

[0017] The inner shoulder land portion 511 is composed of multiple land portions defined by the shoulder main groove 41 and the ground contact edge 501. The outer shoulder land portion 521 is composed of multiple land portions defined by the shoulder main groove 42 and the ground contact edge 502. The inner intermediate land portion 531 is composed of land portions defined by adjacent main grooves 41, 43. The outer intermediate land portion 541 is composed of land portions defined by adjacent main grooves 42, 44. The center land portion 551 is composed of multiple land portions defined by adjacent main grooves 43, 44.

[0018] The center land portion 551 constitutes the third land portion. The inner intermediate land portion row 53 constitutes the first land portion row. The outer intermediate land portion row 54 constitutes the second land portion row. The center land portion row 55 constitutes the third land portion row. The center main grooves 43, 44 are arranged to sandwich the tire equatorial plane S1, so that the center land portion 551 is arranged to include the tire equatorial plane S1.

[0019] In the vehicle width direction when tire 1 is mounted on the vehicle, tire 1 comprises, from the inside to the outside, an inner shoulder land portion 511 forming an inner shoulder land row 51, an inner intermediate land portion 531 forming an inner intermediate land row 53, an outer intermediate land portion 541 forming an outer intermediate land row 54, and an outer shoulder land portion 521 forming an outer shoulder land row 52.

[0020] Here, the number of lands in each land row is referred to as the pitch number. More specifically, the pitch number means the number of times that the pattern of each land defined by the lateral grooves 45, 46, 47, 48, and 49 extending in a direction intersecting with the main grooves 41 to 44 is repeated in each land row.

[0021] In this embodiment, the number of pitches in the inner shoulder land row 51 is the same as the number of pitches in the inner intermediate land row 53. The number of pitches in the outer shoulder land row 52 is the same as the number of pitches in the outer intermediate land row 54. The number of pitches in the outer intermediate land row 54 is smaller than the number of pitches in the inner intermediate land row 53. In this embodiment, the number of pitches in the center land row is the same as the number of pitches in the inner shoulder land row 51 and the number of pitches in the inner intermediate land row 53.

[0022] The number of pitches of the outer shoulder land row 52 and the number of pitches of the outer intermediate land row 54 are preferably 54 or more and 70 or less, and more preferably 58 or more and 66 or less. In this embodiment, the number of pitches of the outer shoulder land row 52 is 62.

[0023] Fig. 3 is a diagram illustrating the ground contact position of the tire 1 when traveling straight. Fig. 4 is a diagram illustrating the ground contact position of the tire 1 when cornering. If the number of pitches is less than 54, the rigidity of each land portion (so-called pattern rigidity) becomes too large, making it difficult to extend the contact length, that is, the length in the circumferential direction (the vertical direction in Figs. 3 and 4) of the contact portion of the tire 1 surrounded by the dashed line in Figs. 3 and 4. Also, as shown in Fig. 3, the contact length of the elliptical contact portion when the vehicle is traveling straight in the direction of the arrow becomes extremely short only on the outside of the vehicle, and there is a risk that the contact portion will become asymmetrical on the left and right.

[0024] Also, if the number of pitches exceeds 70, the pattern rigidity of each land portion becomes smaller and each land portion becomes softer. In particular, since the contact length when cornering in the direction of the arrow shown in Fig. 4 is long in the outer intermediate land row 54 as shown in Fig. 4, if the number of pitches in the outer intermediate land row 54 is large, the pattern rigidity becomes too small and sufficient cornering power cannot be obtained. By setting the number of pitches to 58 or more and 66 or less, it is possible to increase the pattern rigidity and increase the contact length.

[0025] The number of pitches of the inner shoulder land row 51 and the number of pitches of the inner intermediate land row 53 are preferably 66 to 82, and more preferably 70 to 78. In this embodiment, the number of pitches of the inner shoulder land row 51 is 74.

[0026] As with the number of pitches of the outer intermediate land row 54, if the number of pitches is less than 66, the rigidity of each land portion (so-called pattern rigidity) becomes too large, making it difficult to extend the contact length, i.e., the length in the circumferential direction (vertical direction in Figs. 3 and 4) of the contact portion of the tire 1 surrounded by the dashed line in Figs. 3 and 4. If the number of pitches exceeds 82, the pattern rigidity of each land portion becomes small, each land portion becomes soft, and the vehicle drift occurs. By setting the number of pitches to 70 or more and 78 or less, it is possible to increase the pattern rigidity and increase the contact length.

[0027] The difference between the number of pitches of the inner mediate land row 53 and the number of pitches of the outer mediate land row 54 is preferably 8 or more, and in this embodiment, the difference between the number of pitches is 12.

[0028] Next, a second embodiment of the present disclosure will be described with reference to the drawings. FIG. 5 is a view showing the tread 4A of the tire 1A as seen in the same direction as the direction of the arrow II in FIG. 1. In the second embodiment, the configuration of the center land portion 551A is different from that of the first embodiment. Since the other configurations are the same as those of the first embodiment, the same reference numerals are used and the description is omitted. Specifically, as shown in FIG. 5, the number of pitches of the center land portion row 55A is the same as the number of pitches of the outer shoulder land portion row 52 and the number of pitches of the outer mediate land portion row 54. In the center land portion row 55A, the adjacent center land portions 551A are partitioned by the lateral grooves 47A in the circumferential direction of the tire.

[0029] Next, tire 1 according to the first embodiment was evaluated as Example 1, and tire 1 according to the second embodiment was evaluated as Example 2. In addition, as Comparative Example 1, a tire having one main groove and an inner shoulder land row and an outer shoulder land row, each having 68 pitches, was prepared and evaluated. In addition, as Comparative Example 2, a tire having two main grooves and an inner shoulder land row, a center land row, and an outer shoulder land row was prepared and evaluated. The number of pitches of the inner shoulder land row was 74, the number of pitches of the center land row was 68, and the number of pitches of the outer shoulder land row was 62.

[0030] <Cornering power evaluation> Using a drum testing machine with a diameter of 2500 mm, the cornering force generated in tire 1 of 195 / 65R15 at an internal pressure of 200 kPa and a load of 4.2 kN was measured, and the cornering power at a slip angle of 1 degree was calculated. The result of Comparative Example 1 was set at 100 and the result was evaluated using an index. The larger the value, the greater the cornering power and the more excellent the steering stability performance on dry road surfaces.

[0031] <Noise performance evaluation> Tire 1 was mounted on a test vehicle, and a microphone was placed at the driver's ear inside the vehicle to measure the sound pressure when the vehicle was driven at 80km / h on a flat, dry asphalt road surface. The evaluation results were expressed as an index using the reciprocal of the measured value, with the value of Comparative Example 1 being set at 100. The higher the index, the greater the pitch noise reduction effect, and the better the result.

[0032] [Table 1]

[0033] As shown in Table 1, in Comparative Example 2, which is a configuration of the prior art, the performance is improved with respect to pitch noise compared to Comparative Example 1, but the cornering power is not sufficiently improved. In contrast, in Examples 1 and 2, the pitch noise is slightly inferior to Comparative Example 2, but is sufficiently improved, and the cornering power is dramatically improved.

[0034] The tire 1 of the present embodiment provides the following advantages. In the tire 1 of this embodiment, the number of pitches in the inner shoulder land row 51 is the same as the number of pitches in the inner central land row, the number of pitches in the outer shoulder land row 52 is the same as the number of pitches in the outer central land row, and the number of pitches in the outer intermediate land row 54 is smaller than the number of pitches in the inner intermediate land row 53.

[0035] This makes it possible to disperse the pitch noise frequency, lower the noise peak, and ensure a sufficient contact length, improving cornering power. As a result, it is possible to provide a tire 1 with reduced pitch noise and improved cornering power.

[0036] Furthermore, in the tire 1 according to this embodiment, a plurality of center main grooves 43, 44 are formed. The tire 1 also includes a center land row 55 having a plurality of center land portions 551 located between the plurality of center main grooves 43, 44 adjacent to each other in the width direction and partitioned by the plurality of center main grooves 43, 44. This allows the tire 1 to be configured with four or more main grooves extending in the circumferential direction.

[0037] In the tire 1 according to the first embodiment, the number of pitches in the center land row 55 as the third land row is the same as the number of pitches in the inner intermediate land row 53 as the first land row. Thus, even if the number of pitches is the same, in the center land portion 551, the inner intermediate land portion 531, and the outer intermediate land portion 541, the shapes of the portions where the tire 1 comes into contact with the ground are shown by the dashed lines in Figures 3 and 4. Therefore, when the vehicle is traveling, the tread surfaces, which are the contact surfaces with the road surface in each land portion, come into contact with the road surface at different times, which makes it possible to reduce pitch noise.

[0038] In addition, in the circumferential direction of the tire 1, the lateral grooves extending in the width direction of the tire 1, which separate the center land portions 551 from each other, the inner intermediate land portions 531 from each other, and the outer intermediate land portions 541 from each other, can be positioned so as to coincide in the width direction of the tire 1. This allows water to be easily drained and snow to be removed from the lateral groove 47 in the center land row 55 through the lateral grooves 46, 45 in the inner intermediate land row 53 and the inner shoulder land row 51.

[0039] In the tire 1A according to the second embodiment, the number of pitches in the central land row 55A is the same as the number of pitches in the outer intermediate land row 54. As a result, even though the number of pitches is the same, the timing at which the tread surfaces, which are the contact surfaces with the road surface, come into contact with the road surface differs in the central land portion 551A, the inner intermediate land portion 531, and the outer intermediate land portion 541 during vehicle travel, thereby making it possible to reduce pitch noise.

[0040] In addition, in the circumferential direction of the tire 1A, the lateral grooves extending in the width direction of the tire 1, which separate the center land portions 551A from each other, the inner intermediate land portions 531 from each other, and the outer intermediate land portions 541 from each other, can be positioned to coincide in the width direction of the tire 1. This allows water to be easily drained and snow to be removed from the lateral groove 47A in the center land portion row 55A through the lateral grooves 48, 49 in the outer intermediate land portion row 54 and the outer shoulder land portion row 52.

[0041] In the tire 1 according to the present embodiment, the number of pitches in the outer shoulder land row 52 and the number of pitches in the outer intermediate land row 54 are equal to or greater than 54 and equal to or less than 70. This makes it possible to increase the rigidity (pattern rigidity) of the outer intermediate land row 54.

[0042] In the tire 1 according to the present embodiment, the number of pitches in the outer shoulder land row 52 and the number of pitches in the outer intermediate land row 54 are equal to or greater than 58 and equal to or less than 66. This makes it possible to reliably increase the rigidity (pattern rigidity) in the outer intermediate land row 54.

[0043] In the tire 1 according to this embodiment, the number of pitches of the inner shoulder land row 51 and the number of pitches of the inner intermediate land row 53 are equal to or greater than 66 and equal to or less than 82. This makes it possible to suppress vehicle drift.

[0044] In the tire 1 according to the present embodiment, the number of pitches of the inner shoulder land row 51 and the number of pitches of the inner intermediate land row 53 are equal to or greater than 70 and equal to or less than 78. This makes it possible to reliably suppress vehicle drift.

[0045] In the tire 1 according to the present embodiment, the difference between the number of pitches of the inner shoulder land row 51 and the number of pitches of the inner intermediate land row 53 and the number of pitches of the outer shoulder land row 52 and the number of pitches of the outer intermediate land row 54 is 8 or more. This makes it possible to reliably disperse the frequency of the pitch noise.

[0046] The present invention is not limited to the above-described embodiment, and even if modifications and improvements are made within the scope of the present invention, they will still be included in the scope of the present invention. For example, in the present embodiment, the inner intermediate land portions 531, the outer intermediate land portions 541, the center land portions 551, and the center land portions 551A adjacent to each other in the circumferential direction of the tire 1 are each divided by the wide lateral grooves 46, 48, 47, and 47A extending in a direction intersecting the main grooves 41 to 44, but the present invention is not limited to this configuration. For example, instead of the wide lateral grooves, the center land portions, the inner intermediate land portions, and the outer intermediate land portions may be divided by sipes, which are narrow grooves, in the circumferential direction of the tire. Specifically, the sipes have a groove width of about 0.6 mm to 1.2 mm. This can increase the pattern rigidity of the center land portion, the outer intermediate land portion, and the inner intermediate land portion, and can further improve the cornering power.

[0047] Also, for example, the inner shoulder land portions 511 and the outer shoulder land portions 521 adjacent to each other in the circumferential direction of the tire 1 are divided by the lateral grooves 45, 49 extending in a direction intersecting the main grooves 41-44, but the present invention is not limited to this configuration. For example, the outer shoulder land portions and the inner shoulder land portions may be divided by narrow slits instead of the lateral grooves. Specifically, the slits are wider than the sipes and have a groove width of 3.5 mm or less. In this case, in each land row, the patterns of the individual land portions divided by the slits or sipes extending in a direction intersecting the slits or sipes are provided repeatedly, and the number of pitches means the number of times the pattern is repeated in each land row.

[0048] In the present embodiment, the tire 1 has four main grooves, including an inner shoulder land row 51, an inner intermediate land row 531, a center land portion 551, an outer intermediate land portion 541, and an outer shoulder land portion 521, but is not limited to this configuration. For example, as shown in Fig. 6, the tire 1 may have three or more main grooves 41, 42, 43, and may have an inner shoulder land row 51, an inner center land row 53 as a first land row, an outer center land row 54 as a second land row, and an outer shoulder land row 52. Fig. 6 shows a tread 4B of a tire 1B according to a modified example of the first embodiment, viewed in the same direction as the direction of the arrow II in Fig. 1. [Explanation of symbols]

[0049] 1 1A 1B Tire 4 4A 4B Tread 41 Inner shoulder main groove (inner main groove) 42 Outer shoulder main groove (outer main groove) 43 44 Center main groove (center main groove) 51 Inner shoulder land row 52 Outer shoulder land row 53 Inner Mediate Land Row (First Land Row) 54 Inner Mediate Land Row (Second Land Row) 55 Center Land Row (3rd Land Row) 501 502 Ground end 511 Inner shoulder land area 521 Outer shoulder land area 531 Inner Mediate Land Section (First Land Section) 541 Inner Mediate Land (Second Land) 551 Center Land Section (Third Land Section)

Claims

1. A tire having a tread that constitutes a tread surface that contacts the road surface, The tread comprises at least an inner shoulder land portion row including a plurality of inner shoulder land portions defined by an inner main groove disposed on the innermost side in a width direction of a vehicle when the tire is mounted on the vehicle and a ground contact edge; an outer shoulder land portion row including a plurality of outer shoulder land portions defined by an outer main groove disposed outermost in the width direction and a ground contact edge; a first land portion row including a plurality of first land portions defined by the inner main groove and a center main groove disposed between the inner main groove and the outer main groove in the width direction; a second land portion row having a plurality of second land portions defined by the center main groove and the outer main groove; a lateral groove extending in a width direction of the tire, which divides the inner shoulder land portions, the outer shoulder land portions, the first land portions, and the second land portions in a circumferential direction of the tire; Equipped with the number of the land portions in each of the land rows is defined as a pitch number, the number of pitches of the inner shoulder land row is equal to the number of pitches of the first land row, the number of pitches of the outer shoulder land row is equal to the number of pitches of the second land row, and the number of pitches of the second land row is smaller than the number of pitches of the first land row, a lateral groove that separates the inner shoulder land portions from each other and a lateral groove that separates the first land portions from each other are positioned to coincide with each other in the tire width direction, A tire in which a lateral groove separating the outer shoulder land portions and a lateral groove separating the second land portions are aligned in a same positional relationship in the tire width direction.

2. 2. The tire according to claim 1, wherein a plurality of the center side main grooves are formed, and the tire has a third land row having a plurality of third land rows located between a plurality of the center side main grooves adjacent to each other in the width direction and partitioned by the plurality of center side main grooves.

3. The tire according to claim 2 , wherein the number of pitches in the third land row is the same as the number of pitches in the first land row.

4. The tire according to claim 2 , wherein the number of pitches in the third land row is equal to the number of pitches in the second land row.

5. The tire according to any one of claims 1 to 4, wherein the number of pitches of the second land portion row is 54 or greater and 70 or less.

6. The tire according to claim 5 , wherein the number of pitches of the second land portion row is 58 or greater and 66 or less.

7. The tire according to any one of claims 1 to 6, wherein the number of pitches of the first land row is 66 or greater and 82 or less.

8. The tire according to claim 7 , wherein the number of pitches in the first land row is equal to or greater than 70 and is equal to or less than 78.

9. The tire according to any one of claims 5 to 8, wherein a difference between the number of pitches of the first land row and the number of pitches of the second land row is 8 or more.

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