pneumatic tires

Abstract

We offer pneumatic tires that provide excellent quietness and high-speed durability. [Solution] The pneumatic tire 1 has a tread portion 2 and a sound-dampening body 11 made of a porous material that is fixed to the inner surface 15s of the tire of the tread portion 2. The sound-dampening body 11 extends in the circumferential direction of the tire along the tire equator C. When the pneumatic tire 1 is mounted on a regular rim with regular internal pressure and subjected to a 70% load condition with 70% of the regular load applied and the camber angle set to 0 degrees, the contact surface 14 of the tread portion 2 satisfies the following equation (1) in terms of the ratio L / Lm of the maximum contact length L in the circumferential direction of the tire and the contact length Lm in the circumferential direction of the tire within a range of 70% or less of the maximum contact width W in the axial direction of the tire, centered on the tire equator C. 1.00

Description

Technical Field

[0001] The present invention relates to pneumatic tires.

Background Art

[0002] The following Patent Document 1 describes a pneumatic tire. This tire is provided with a sound-absorbing body made of a sponge material that adheres to the inner cavity surface of the tire and extends in the circumferential direction on the tire equator, and a radiation groove that extends in the circumferential direction on the outer surface of the tread portion and dissipates heat accumulated by the sound-absorbing body.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] With the increase in vehicle output in recent years, it is desired to improve the high-speed durability of pneumatic tires provided with sound-absorbing bodies.

[0005] The present invention has been devised in view of the above actual situation, and the main object is to provide a pneumatic tire that can be expected to have good quietness and high-speed durability.

Means for Solving the Problems

[0006] The present invention relates to a pneumatic tire having a tread portion and a sound-dampening body made of a porous material fixed to the inner surface of the tire of the tread portion, wherein the sound-dampening body extends in the circumferential direction of the tire along the tire equator, and in a 70% load state in which the pneumatic tire is mounted on a regular rim with regular internal pressure and is in contact with a plane with a camber angle of 0 degrees under a 70% load load, the contact surface of the tread portion satisfies the following formula (1) in terms of the ratio L / Lm of the contact length Lm in the circumferential direction of the tire, which is the maximum contact length L in the circumferential direction of the tire and is within a range of 70% or less of the maximum contact width W in the axial direction of the tire, centered on the tire equator. 1.00 <L / Lm<1.10 …(1) [Effects of the Invention]

[0007] By adopting the above configuration, the pneumatic tire of the present invention can be expected to have good quietness and high-speed durability. [Brief explanation of the drawing]

[0008] [Figure 1] This is a meridional cross-sectional view of a tire, showing an example of a pneumatic tire. [Figure 2] This is a magnified section of Figure 1. [Figure 3] This figure shows an example of the footprint of the tread under a 70% load condition. [Figure 4] This is an enlarged perspective view showing an example of a protrusion. [Figure 5] This is an exploded view showing an example of a tire tread. [Figure 6] Figure 5 shows enlarged sections of the central, inner middle, and outer middle land areas. [Figure 7] This figure shows an example of the footprint of the tread under a 70% load condition. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. It should be understood that the drawings contain exaggerations and representations that differ from the actual dimensional ratios of the structures in order to aid in understanding the content of the invention. Furthermore, the same or common elements are denoted by the same reference numerals throughout each embodiment, and redundant explanations are omitted. Moreover, the specific configurations shown in the embodiments and drawings are for the purpose of understanding the content of the present invention, and the present invention is not limited to the specific configurations shown in the drawings.

[0010] [Air-filled tires] Figure 1 is a meridional cross-sectional view of a tire, showing an example of a pneumatic tire 1. Figure 2 is a partially enlarged view of Figure 1. The pneumatic tire (hereinafter sometimes referred to as "tire") 1 of this embodiment is exemplified as a tire for a passenger car. However, the tire 1 is not limited to passenger cars, and may be for heavy loads, for example.

[0011] The tire 1 of this embodiment is composed of a tread portion 2 and a sound dampening body 11.

[0012] [Tread area] In this embodiment, the tread portion 2 has a specified mounting orientation on the vehicle, but it is not limited to this configuration; for example, the mounting orientation may not be specified. The mounting orientation on the vehicle is indicated, for example, by letters or marks (not shown) on the sidewall portion (not shown) of the tire 1. In Figure 1, the right side corresponds to the vehicle's inner side Vi, and the left side corresponds to the vehicle's outer side Vo. The tread portion 2 in this embodiment also includes a pair of tread ends (in this example, the inner tread end 2ti and the outer tread end 2to) and a tread surface 2s between them. The tread surface 2s is the portion intended to contact the ground (road surface) when the tire is running, and is formed of tread rubber 2G.

[0013] A pair of tread ends (inner tread end 2ti and outer tread end 2to) are specified at the ground contact position farthest outward in the tire axial direction under a 70% load condition. Here, the "70% load condition" is a state in which the normal tire 1 is loaded with 70% of the normal load and grounded on a plane with a camber angle of 0 degrees.

[0014] The normal state is a non-loaded state in which the tire 1 is mounted on the normal rim 10 at the normal internal pressure. In this specification, unless otherwise specified, the dimensions of each part of the tire are shown as values measured in the normal state. Note that the dimensions of each part of the tire are allowed to have normal dimensional errors (tolerances) that are inevitable in manufacturing.

[0015] The "normal rim" is the rim defined for each tire in the standard system including the standard on which the tire 1 is based. Therefore, the normal rim is, for example, "Standard Rim" in JATMA, "Design Rim" in TRA, and "Measuring Rim" in ETRTO.

[0016] The "normal internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire 1 is based. Therefore, the normal internal pressure is, for example, "Maximum Air Pressure" in JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, and "INFLATION PRESSURE" in ETRTO.

[0017] The "normal load" is the load defined for each tire in the standard system including the standard on which the tire 1 is based. Therefore, the normal load is, for example, "Maximum Load Capacity" in JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, and "LOAD CAPACITY" in ETRTO.

[0018] The tread portion 2 of this embodiment includes a plurality of circumferential grooves 12 that extend continuously in the circumferential direction of the tire, and a plurality of land portions 13 separated by the plurality of circumferential grooves 12. Furthermore, a belt layer 7 and a band layer 9 are embedded in the tread portion 2 of this embodiment. The belt layer 7 is located on the radially outer side of the carcass 6 and inside the tread portion 2 (in this example, on the radially inner side of the band layer 9).

[0019] [Circumferential groove] Multiple circumferential grooves 12 extend continuously in the circumferential direction of the tire on the tread surface 2s between a pair of tread ends (in this example, the inner tread end 2ti and the outer tread end 2to). These circumferential grooves 12 allow water to be discharged between the tread portion 2 and the road surface (not shown) during wet driving, thereby improving wet performance.

[0020] The multiple circumferential grooves 12 in this embodiment extend linearly along the circumferential direction of the tire, but are not particularly limited. The multiple circumferential grooves 12 may, for example, extend in a wavy or zigzag pattern.

[0021] The groove widths W1a, W1b and groove depths (not shown) of each circumferential groove 12 can be set as appropriate. For example, the groove widths W1a and W1b are set to 2.0% to 8.0% of the maximum contact width W (shown in Figure 2) in the tire axial direction of the contact surface 14 under a 70% load. The groove depth is set to 4.0 to 10.0 mm. As shown in Figure 2, the maximum contact width W is defined as the distance in the tire axial direction between a pair of tread edges (in this example, the inner tread edge 2ti and the outer tread edge 2to) under a 70% load. Also, as shown in Figure 1, the groove widths W1a and W1b are defined as the distance between two adjacent groove edges in a direction perpendicular to the groove centerline (not shown) under normal conditions.

[0022] Each of the multiple circumferential grooves 12 includes at least one center circumferential groove 12A. Furthermore, in this embodiment, the multiple circumferential grooves 12 include a pair of center circumferential grooves 12A, 12A and a pair of shoulder circumferential grooves 12B, 12B. These center circumferential grooves 12A, 12A and shoulder circumferential grooves 12B, 12B allow water to be discharged from the road surface (not shown) over a wide area in the tire axial direction of the tread portion 2, thereby improving wet performance. Note that the multiple circumferential grooves 12 are not limited to an embodiment that includes a pair of center circumferential grooves 12A, 12A and a pair of shoulder circumferential grooves 12B, 12B. For example, depending on the wet performance required for the tire 1, the multiple circumferential grooves 12 may consist of one center circumferential groove 12A and one shoulder circumferential groove 12B. Alternatively, the multiple circumferential grooves 12 may consist of one center circumferential groove 12A and a pair of shoulder circumferential grooves 12B, 12B.

[0023] The pair of center circumferential grooves 12A, 12A are provided adjacent to the tire equator C and extend continuously in the tire circumferential direction. In this embodiment, the pair of center circumferential grooves 12A, 12A are provided on both sides in the tire axial direction relative to the tire equator C. When the orientation of mounting to the vehicle is specified, as in the tread portion 2 of this embodiment, the pair of center circumferential grooves 12A, 12A include an inner center circumferential groove 12Ai located on the inner side Vi of the vehicle and an outer center circumferential groove 12Ao located on the outer side Vo of the vehicle. In this embodiment, the groove widths W1a, W1a of the inner center circumferential groove 12Ai and the outer center circumferential groove 12Ao are the same, but this is not particularly limited, and they may be different from each other.

[0024] The pair of shoulder circumferential grooves 12B, 12B are positioned between the center circumferential grooves 12A, 12A (inner center circumferential groove 12Ai and outer center circumferential groove 12Ao) and the tread ends (inner tread end 2ti and outer tread end 2to). When the orientation of mounting to the vehicle is specified, as in the tread portion 2 of this embodiment, the pair of shoulder circumferential grooves 12B, 12B include an inner shoulder circumferential groove 12Bi positioned on the inner side Vi of the vehicle and an outer shoulder circumferential groove 12Bo positioned on the outer side Vo of the vehicle. In this embodiment, the groove width W1b of the outer shoulder circumferential groove 12Bo is smaller than the W1b of the inner shoulder circumferential groove 12Bi, but they may be the same.

[0025] [Rikube] Multiple land sections 13 are separated by multiple circumferential grooves 12. In this embodiment, the multiple land sections 13 include a center land section 13A, a pair of middle land sections 13B, 13B, and a pair of shoulder land sections 13C, 13C, but the embodiment is not limited to this configuration. The multiple land sections 13 may be composed of, for example, a pair of center land sections 13A, 13A and a pair of shoulder land sections 13C, 13C, depending on the driving performance required for the tire 1.

[0026] The center land portion 13A is divided by a pair of center circumferential grooves 12A, 12A (inner center circumferential groove 12Ai and outer center circumferential groove 12Ao). As a result, the center land portion 13A is positioned on the tire equator C. The pair of middle land portions 13B, 13B are divided between the pair of center circumferential grooves 12A, 12A and the pair of shoulder circumferential grooves 12B, 12B. When the orientation of mounting to the vehicle is specified, as in the tread portion 2 of this embodiment, the pair of middle land portions 13B, 13B include an inner middle land portion 13Bi positioned on the inner side Vi of the vehicle and an outer middle land portion 13Bo positioned on the outer side Vo of the vehicle. The pair of shoulder land portions 13C, 13C are divided outside the pair of shoulder circumferential grooves 12B, 12B in the tire axial direction and include the tread ends (in this example, the inner tread end 2ti and the outer tread end 2to). In the case where the orientation of mounting to the vehicle is specified, as in the tread portion 2 of this embodiment, the pair of shoulder portions 13C, 13C include an inner shoulder portion 13Ci located on the inner side Vi of the vehicle and an outer shoulder portion 13Co located on the outer side Vo of the vehicle.

[0027] [Carcass] The carcass 6 extends between a pair of bead portions 4, 4. The carcass 6 is composed of at least one (one in this example) carcass ply 6A. The carcass ply 6A includes, for example, a main body portion 6a and a pair of folded portions 6b, 6b. The main body portion 6a extends, for example, between the pair of bead portions 4, 4. Each folded portion 6b, 6b is connected to the main body portion 6a and folded back from the inside to the outside in the tire axial direction around the bead core 5, 5.

[0028] The carcass ply 6A is composed of multiple carcass cords (not shown) and a topping rubber (not shown) covering them. For example, organic fiber cords such as aramid or rayon are used for the carcass cords. Preferably, the carcass cords are arranged at an angle of 70 to 90° with respect to the circumferential direction of the tire.

[0029] [Belt layer] In this embodiment, the belt layer 7 is located on the radially outer side of the carcass 6 and inside the tread portion 2. The belt layer 7 in this embodiment is composed of two belt plies 7A and 7B that are stacked in the radial direction of the tire.

[0030] The belt plies 7A and 7B of this embodiment include, for example, belt cords (not shown) arranged at an angle of 10 to 35 degrees with respect to the circumferential direction of the tire. These belt plies 7A and 7B are overlapped in a direction in which the belt cords intersect each other. Suitable materials for the belt cords include, for example, steel, aramid, or rayon.

[0031] [Band layer] The band layer 9 is positioned radially outward of the belt layer 7. This band layer 9 is composed of a band ply 9A in which band cords (not shown) are arranged in the circumferential direction of the tire. Such a band layer 9 (band ply 9A) suppresses the growth of the outer diameter of the tire 1 and improves high-speed durability. From the viewpoint of effectively suppressing such outer diameter growth, it is preferable that the band cords are wound spirally at an angle of 5° or less with respect to the circumferential direction of the tire.

[0032] For example, an organic fiber cord may be used for the band cord (not shown). An example of this organic fiber cord is a nylon fiber cord. In this embodiment, a hybrid cord is used for the band cord, in which an aramid fiber cord (strand of aramid fiber) and a nylon fiber cord (strand of nylon fiber) are twisted together. Such a band cord has a larger modulus than a conventional band cord composed of, for example, a nylon fiber cord, and its high restraining force suppresses the movement of the belt layer 7. As a result, the increase in distortion of the tread portion 2 during high-speed driving can be suppressed, and the heat generation of the tread portion 2 can be suppressed. Therefore, damage such as cord looseness (for example, damage where the carcass cord, belt cord and band cord peel off from the rubber) due to the temperature rise of the tread portion 2 is prevented, and high-speed durability is improved. Furthermore, the cross-sectional secondary resonance peak can be moved away from the vehicle resonance, and road noise can be reduced. The thickness of the band cord and each strand can be appropriately set according to the restraining force required for the band layer 9.

[0033] [Sound control body] The sound dampening element 11 is fixed to the inner surface 15s of the tire tread portion 2. This sound dampening element 11 extends in the circumferential direction of the tire along the tire equator C. In this embodiment, the center position of the sound dampening element 11 in the tire axial direction (not shown) and the tire equator C are approximately coincident. Note that approximately coincidence includes a configuration in which the distance in the tire axial direction between the center position and the tire equator C (not shown) is 5% or less of the maximum contact width W.

[0034] The sound dampening body 11 in this embodiment is formed in the shape of a long strip having a bottom surface fixed to the inner surface 15s of the tire. Furthermore, the sound dampening body 11 may be formed in a substantially annular shape by a pair of outer ends (not shown) on both sides in the circumferential direction of the tire being brought together. However, the sound dampening body 11 is not limited to a configuration in which a pair of outer ends are brought together; for example, they may be spaced apart in the circumferential direction of the tire.

[0035] The sound dampening element 11 may have substantially the same cross-sectional shape at each position in the tire circumferential direction, excluding a pair of outer ends (not shown) in the tire circumferential direction. This may facilitate the manufacture of the sound dampening element 11 and reduce manufacturing costs.

[0036] The sound dampening element 11 is made of a porous material. Such a sound dampening element 11 can mitigate and absorb resonant sound energy generated within the tire cavity 15 during driving through the surface and internal pores (cells) of the porous material. As a result, cavity resonance can be effectively suppressed in the tire 1 of this embodiment. Furthermore, the sound dampening element 11 can reduce road noise by mitigating the impact received from the tread portion 2 during driving. Therefore, the quietness inside the vehicle is improved in the tire 1 of this embodiment.

[0037] In this embodiment, since the center position of the sound damper 11 in the tire axial direction and the tire equator C are substantially coincided, the impact received from the tread portion 2 is relatively greater on the tire equator C side, and this impact can be effectively mitigated by the sound damper 11. Furthermore, since the sound damper 11 in this embodiment is formed in a substantially annular shape, it can effectively mitigate and absorb the resonant sound energy generated in the tire cavity 15 during driving over the entire circumference of the tire.

[0038] Since the porous material constituting the sound dampening body 11 is easily deformed, such as by shrinking or bending, the sound dampening body 11 can easily follow the deformation of the inner surface 15s of the tire during driving. This improves the durability of the sound dampening body 11 and helps maintain quietness.

[0039] The porous material can be the same as that used in conventional sound dampening materials. An example of the porous material in this embodiment is a porous sponge material. The sponge material is a sponge-like porous structure. Furthermore, the sponge material may include, for example, a so-called sponge made by foaming rubber or synthetic resin, as well as a material in which animal fibers, plant fibers, or synthetic fibers are intertwined and linked together.

[0040] Examples of sponge materials include synthetic resin sponges such as ether-based polyurethane sponge, ester-based polyurethane sponge, and polyethylene sponge, as well as chloroprene rubber sponge (CR sponge). Other examples of sponge materials include ethylene propylene rubber sponge (EDPM sponge) and nitrile rubber sponge (NBR sponge). In particular, polyurethane-based or polyethylene-based sponges, including ether-based polyurethane sponge, are preferred from the viewpoint of sound dampening (quietness inside the vehicle), lightness, adjustability of foaming, and durability.

[0041] The density of the sound dampening material 11 is 15-35 kg / m³. 3 A density of 15 kg / m³ is preferred. 3 As a result of the above, the resonant sound energy during driving can be effectively mitigated and absorbed by the sound dampening body 11, thereby improving quietness. From the viewpoint of further improving this quietness, the density is preferably 17 kg / m³ 3 The above is preferable to 20 kg / m 3 That's all. On the other hand, the density is 35 kg / m³. 3 By doing so, the heat transferred from the tread section 2, which tends to generate heat during high-speed driving, can be suppressed from being stored in the sound-dampening material 11. This prevents damage such as cord loosening caused by the temperature rise of the tread section 2, and improves high-speed durability. From the viewpoint of further improving such high-speed durability, the density is preferably 33 kg / m³ in any combination of the lower limits mentioned above. 3 The following, and preferably 30 kg / m³ 3 The following applies:

[0042] [Ground surface] Figure 3 shows an example of the footprint 16 of the tread section 2 under a 70% load condition. In Figure 3, the positions of the axial ends 11t, 11t of the sound dampener 11 shown in Figure 2, projected onto the contact surface 14, are indicated by dashed lines.

[0043] In this embodiment, the contact surface 14 of the tread portion 2 satisfies the following equation (1) when under a 70% load condition, the ratio L / Lm of the maximum contact length L in the circumferential direction of the tire to the contact length Lm in the circumferential direction of the tire within a range centered on the tire equator C and within 70% or less of the maximum contact width W in the axial direction of the tire. If circumferential grooves 12 or lateral grooves (not shown) are provided within the range of 70% or less of the maximum contact width W, the contact length Lm can be determined at the virtual contact edge 19, 19 (shown by dashed lines) that smoothly connect the edges of those grooves. 1.00 <L / Lm<1.10 …(1)

[0044] The shape of the contact surface 14 (footprint 16) that satisfies the above equation (1) can be adjusted as appropriate. Examples of adjustments include changing the thickness of the tread rubber 2G shown in Figure 1, or changing the components of the well-known structure (carcass 6, belt layer 7, and band layer 9, etc.) embedded inside the tread portion 2.

[0045] As shown in Figure 2, in region 18 centered on the tire equator C and within a range of 70% or less of the maximum contact width W in the tire axial direction (indicated by the symbol "W70"), the sound dampening body 11 is fixed to the inner tire cavity surface 15s in the radial direction. Furthermore, in region 18, the contact pressure tends to increase during high-speed driving.

[0046] In the tire 1 of this embodiment, as shown in Figure 3, when the load is 70%, the ratio L / Lm satisfies the above equation (1), so that in the above region 18, the contact edges 19, 19 on both sides in the circumferential direction of the tire become flat along the tire axis. As a result, the contact pressure in the region 18 becomes more uniform.

[0047] On the other hand, in conventional tires where the ratio L / Lm does not satisfy the above equation (1) under a 70% load condition (i.e., it is 1.10 or greater), the contact length Lm in the circumferential direction of the tire becomes smaller from the tire equator C toward the tire axial side compared to tire 1 of this embodiment. As a result, the contact edges 19, 19 on both sides of the tire circumferential direction become inclined with respect to the tire axial direction. In such conventional tires, the contact pressure on the tire equator C side becomes relatively larger in the above region 18, resulting in uneven contact pressure. This uneven contact pressure tends to cause large localized strain in the tread portion 2, leading to increased heat generation during high-speed driving.

[0048] Thus, the tire 1 of this embodiment achieves a more uniform contact pressure in the above-mentioned region 18 compared to a conventional tire (not shown). As a result, the tire 1 of this embodiment suppresses localized deformation of the tread portion 2 during high-speed driving, and can suppress heat generation in the tread portion 2, compared to a conventional tire. Furthermore, in the tire 1 of this embodiment, the suppression of heat generation in the tread portion 2 can also suppress heat accumulation in the sound dampening material 11 shown in Figure 2. As a result, in the tire 1 of this embodiment, the synergistic effect of suppressing heat generation in the tread portion 2 and suppressing heat accumulation in the sound dampening material 11 can effectively prevent damage such as cord loosening due to temperature rise in the tread portion 2. Therefore, the tire 1 of this embodiment can be expected to have good quietness and high-speed durability, as it maintains quietness while improving high-speed durability. In order to effectively enhance this effect, the ratio L / Lm shown in Figure 3 is preferably 1.08 or less, and more preferably 1.06 or less.

[0049] As described above, in the tire 1 of this embodiment, the hybrid cord is used in the band cord of the band ply 9A shown in Figure 2, thereby suppressing the movement of the belt layer 7 and reducing road noise. Therefore, the quietness and high-speed durability of the tire 1 of this embodiment can be further improved due to the synergistic effect of the adoption of the hybrid cord and the ratio L / Lm shown in Figure 3 satisfying the above equation (1).

[0050] Furthermore, in the tire 1 of this embodiment, the density of the sound-dampening element 11 shown in Figure 2 is set within the above range, thereby effectively mitigating and absorbing resonant sound energy during driving while suppressing heat accumulation in the sound-dampening element 11. Therefore, the tire 1 of this embodiment can further improve quietness and high-speed durability through the synergistic effect of the above setting of the density of the sound-dampening element 11 and the ratio L / Lm shown in Figure 3 satisfying the above equation (1).

[0051] Furthermore, at the contact surface 14 under a 70% load condition, it is preferable that the ratio L / L2 of the maximum contact length L in the circumferential direction of the tire and the contact length L2 in the circumferential direction of the tire at the position where both ends 11t, 11t of the sound dampener 11 in the tire axial direction are projected onto the contact surface 14 satisfies the following equation (2). If circumferential grooves 12 or lateral grooves (not shown) are provided at the position where both ends 11t, 11t are projected, the contact length L2 can be determined at the virtual contact edge 19, 19 (shown by dashed lines) that smoothly connect the edges of those grooves. 1.00 <L / L2<1.10 …(2)

[0052] When the ratio L / L2 satisfies the above equation (2), the contact edges 19, 19 on both sides in the circumferential direction of the tire become flat along the tire axis in the region T1 where the sound dampening element 11 is projected onto the outer surface (contact surface 14) of the tread portion 2 (hereinafter sometimes referred to as the "projected region"). As a result, the contact pressure becomes more uniform in the projected region T1 where the sound dampening element 11 is located, and heat generation of the tread portion 2 during high-speed driving is suppressed, thereby effectively suppressing heat accumulation in the sound dampening element 11. Therefore, the tire 1 of this embodiment improves high-speed durability while maintaining good quietness. To effectively enhance this effect, the ratio L / L2 is preferably 1.08 or less, more preferably 1.06 or less, and even more preferably 1.03 or less.

[0053] It is preferable that the land ratio in the projected region T1 shown in Figure 2 (i.e., the region where the sound dampening body 11 is projected onto the outer surface of the tread portion 2) is smaller than the overall land ratio of the tread portion 2. Here, the "land ratio in the projected region T1" is determined by dividing the area of ​​the actual contact surface 14 in the projected region T1 by the area of ​​a virtual contact surface 14 that fills all the grooves provided in the projected region T1, over the entire circumference in the circumferential direction of the tire. The "overall land ratio of the tread portion 2" is determined by dividing the area of ​​the actual contact surface 14 between a pair of tread ends (inner tread end 2ti and outer tread end 2to) by the area of ​​a virtual contact surface 14 that fills all the grooves provided in the contact surface 14 between a pair of tread ends (inner tread end 2ti and outer tread end 2to), over the entire circumference in the circumferential direction of the tire.

[0054] By making the land ratio in the projected region T1 smaller than the overall land ratio of the tread portion 2, the rubber volume of the tread rubber 2G in the projected region T1 becomes relatively smaller. This can suppress heat generation in the projected region T1 where the sound dampening element 11 is located during high-speed driving. Furthermore, by suppressing heat generation in the projected region T1, heat accumulation in the sound dampening element 11 can also be suppressed. Therefore, the tire 1 of this embodiment improves high-speed durability while maintaining good quietness. In order to effectively exert these effects, the land ratio in the projected region T1 is preferably 90% or less of the overall land ratio of the tread portion 2. On the other hand, if the land ratio in the projected region T1 becomes unnecessarily small, it may become difficult to maintain traction performance and handling stability. From this viewpoint, the land ratio in the projected region T1 is preferably 70% or more of the overall land ratio of the tread portion 2 in any combination of the above upper limits.

[0055] In this embodiment, the pair of center circumferential grooves 12A, 12A (inner center circumferential groove 12Ai and outer center circumferential groove 12Ao) extend continuously in the tire circumferential direction in the projected region T1. On the other hand, the pair of shoulder circumferential grooves 12B, 12B (inner shoulder circumferential groove 12Bi and outer shoulder circumferential groove 12Bo) extend continuously in the tire circumferential direction on both outer sides in the tire axial direction of the projected region T1. As shown in Figure 1, it is preferable that the sum of the groove widths W1a, W1a of the pair of center circumferential grooves 12A, 12A is greater than the sum of the groove widths W1b, W1b of the pair of shoulder circumferential grooves 12B, 12B.

[0056] By making the sum of groove widths W1a and W1a greater than the sum of groove widths W1b and W1b, the rubber volume of the tread rubber 2G in the projected region T1 shown in Figure 2 becomes smaller than the rubber volume of the tread rubber 2G on both outer sides in the tire axial direction of the projected region T1. As a result, heat generation in the projected region T1 can be suppressed during high-speed driving. Furthermore, by suppressing heat generation in the projected region T1, heat accumulation in the sound dampening element 11 can also be suppressed. Therefore, in the tire 1 of this embodiment, high-speed durability is improved while maintaining good quietness. In order to effectively exert this effect, as shown in Figure 1, the sum of groove widths W1a and W1a is preferably 1.1 times or more the sum of groove widths W1b and W1b.

[0057] On the other hand, if the sum of the groove widths W1a, W1a of the pair of center circumferential grooves 12A, 12A (inner center circumferential groove 12Ai and outer center circumferential groove 12Ao) becomes unnecessarily large, it may become difficult to maintain traction performance and handling stability. From this viewpoint, the sum of the groove widths W1a, W1a is preferably 1.5 times or less the sum of the groove widths W1b, W1b in any combination of the lower limits mentioned above.

[0058] As shown in Figure 2, it is preferable that at least one projection 41 protruding in the radial direction of the tire is formed at the groove bottom 40 of the center circumferential groove 12A (in this example, the inner center circumferential groove 12Ai and the outer center circumferential groove 12Ao). Figure 4 is an enlarged perspective view showing an example of a projection 41. In Figure 4, a projection 41 provided in the inner center circumferential groove 12Ai is shown as representative.

[0059] As shown in Figure 4, the projection 41 protrudes radially outward from the groove bottom 40 of the center circumferential groove 12A (in this example, the inner center circumferential groove 12Ai and the outer center circumferential groove 12Ao) in the tire radial direction. Due to the projection 41, the surface area of ​​the groove bottom 40 of the center circumferential groove 12A is increased, so that at high speeds, the heat stored in the sound dampening element 11 shown in Figure 2 can be effectively dissipated (heat dissipated) from the groove bottom 40 (projection 41) of the center circumferential groove 12A. Therefore, the tire 1 of this embodiment has improved high-speed durability. Furthermore, the air passing through the center circumferential groove 12A can be disturbed. Therefore, in the tire 1 of this embodiment, air column resonance noise is reduced and quietness is improved.

[0060] The projection 41 of this embodiment is composed of a first projection 41A and a second projection 41B. The first projection 41A and the second projection 41B are adjacent to each other in the tire axial direction in the center circumferential groove 12A (inner center circumferential groove 12Ai in Figure 4).

[0061] Each of the first projection 41A and the second projection 41B is composed of a first surface 43 and a second surface 44. The first surface 43 extends in the radial direction of the tire. The second surface 44 is positioned on the opposite side of the tire circumferential direction from the first surface 43 and extends at a larger angle than the first surface 43 with respect to the radial direction of the tire.

[0062] The first projection 41A has a first surface 43 facing the other side S2 in the tire circumferential direction, and a second surface 44 facing one side S1 in the tire circumferential direction. On the other hand, the second projection 41B has a first surface 43 facing one side S1 in the tire circumferential direction, and a second surface 44 facing the other side S2 in the tire circumferential direction. In this way, the first projection 41A and the second projection 41B have different orientations in the tire circumferential direction of the first surface 43 and the second surface 44, so that the air in the center circumferential groove 12A (in this example, the inner center circumferential groove 12Ai and the outer center circumferential groove 12Ao) can be effectively disturbed. As a result, heat stored in the sound dampening body 11 can be effectively dissipated (heat dissipation) while reducing air column resonance noise. Such projections 41 can be formed, for example, based on the description in the patent document (Japanese Patent Application Publication No. 2020-196281). Furthermore, the protrusions 41 may be formed not only in the center circumferential groove 12A, but also in the shoulder circumferential grooves 12B (inner shoulder circumferential groove 12Bi and outer shoulder circumferential groove 12Bo) shown in Figure 2. This can effectively reduce air column resonance noise.

[0063] As shown in Figure 1, in the meridional section of the tire in a normal state, the cross-sectional area A1 of the sound dampener 11 is preferably 5% to 15% of the cross-sectional area A2 of the tire cavity 15. Here, the cross-sectional area A1 of the sound dampener 11 is the area determined from the outer shape of the sound dampener 11, including the cells of the cavity, in a normal state. The cross-sectional area A2 of the tire cavity 15 is the area of ​​the space enclosed by the inner surface 15s of the tire cavity 1 and the outer surface 10s of the rim (normal rim) 10 in a normal state. These cross-sectional areas can be easily obtained, for example, from measurement results by CT scanning.

[0064] By setting the cross-sectional area A1 of the sound dampening element 11 to 5% or more of the cross-sectional area A2 of the tire cavity 15, the resonant sound energy generated within the tire cavity 15 can be effectively mitigated and absorbed by the sound dampening element 11. As a result, the quietness inside the vehicle is improved in the tire 1 of this embodiment. From the viewpoint of further improving this quietness, the cross-sectional area A1 of the sound dampening element 11 is preferably 6% or more of the cross-sectional area A2 of the tire cavity 15, and more preferably 7% or more. On the other hand, by setting the cross-sectional area A1 of the sound dampening element 11 to 15% or less of the cross-sectional area A2 of the tire cavity 15, the sound dampening element 11 is prevented from becoming unnecessarily large. As a result, the tire 1 of this embodiment is prevented from accumulating excessive heat in the sound dampening element 11, and its high-speed durability is improved. Furthermore, an increase in the cost and weight of the sound dampening element 11 can be suppressed. From the viewpoint of effectively exerting these effects, the cross-sectional area A1 of the sound dampening body 11 is preferably 12% or less of the cross-sectional area A2 of the tire cavity 15, and more preferably 10% or less, in any combination of the lower limits mentioned above.

[0065] As shown in Figure 2, the cross-sectional shape of the sound damper 11 in the tire meridian cross-section is preferably a flattened, elongated shape (in this embodiment, an elongated rectangle) in which the maximum thickness D3 in the tire radial direction is smaller than the maximum width W3 in the tire axial direction. The maximum width W3 and maximum thickness D3 are assumed to be determined in the normal state.

[0066] The sound-dampening body 11, which is formed in a flat, elongated shape, can effectively prevent tilting and deformation during tire operation. As a result, the tire 1 of this embodiment can maintain quietness during operation and high-speed durability. Furthermore, the manufacturing of the sound-dampening body 11 can be simplified, and manufacturing costs can be reduced. In order to effectively exert these effects, the maximum thickness D3 is preferably 15% to 45% of the maximum width W3, and more preferably 20% to 40% of the maximum width W3.

[0067] The maximum width W3 of the sound dampening body 11 in the tire axial direction is preferably set to 25% to 55% of the maximum contact width W. By setting the maximum width W3 to 25% or more of the maximum contact width W, the sound dampening body 11 is positioned over a wide area in the tire axial direction of the inner surface 15s of the tire, thereby mitigating cavity resonance and impact from the tread portion 2, and improving quietness inside the vehicle. From the viewpoint of improving quietness, the maximum width W3 is preferably 26% or more of the maximum contact width W. On the other hand, by setting the maximum width W3 to 55% or less of the maximum contact width W, it is possible to suppress the positioning of the sound dampening body 11 over an unnecessarily wide area in the tire axial direction. This prevents excessive heat accumulation in the sound dampening body 11 and improves high-speed durability. From this viewpoint, the maximum width W3 is preferably 48% or less of the maximum contact width W, and more preferably 40% or less, in any combination of the lower limits mentioned above.

[0068] [Tread pattern] Figure 5 is an exploded view showing an example of the tread portion 2 of the tire 1 shown in Figure 1. In Figure 5, the aforementioned protrusion 41 (shown in Figure 4) is omitted.

[0069] The tread portion 2 of this embodiment has a tread pattern 2P in which 1-pitch regions P constituting pattern constituent units are arranged in the circumferential direction of the tire. The 1-pitch regions P may have a common pattern, for example, multiple regions with the same circumferential length may be arranged, or multiple types with different circumferential lengths may be arranged randomly. The circumferential length L1 of the 1-pitch region P is set to, for example, 19 to 36 mm.

[0070] The tread pattern 2P preferably has multiple types of 1-pitch regions P with different lengths L1 in the tire circumferential direction arranged in the tire circumferential direction. This changes the natural frequencies between the 1-pitch regions P, improving noise performance (quietness). To effectively enhance this effect, it is preferable to have 2 to 10 types of 1-pitch regions P.

[0071] [Multiple groove-like sections] Each of the multiple land sections 13 in this embodiment has multiple groove-like sections 20 that are inclined with respect to the tire axis. These multiple groove-like sections 20 improve wet performance. Figure 6 is a partially enlarged view of the center land section 13A, the inner middle land section 13Bi, and the outer middle land section 13Bo of Figure 5.

[0072] As shown in Figure 6, each of the multiple groove-shaped portions 20 has a first end 20a on one side S1 in the tire circumferential direction and a second end 20b on the other side S2 in the tire circumferential direction. In this embodiment, the first end 20a and the second end 20b are identified by the ends of the groove centerline 20c along the longitudinal direction of the groove-shaped portion 20. Note that if a chamfered portion 29 is provided, as in the groove-shaped portion 20 of this embodiment, the first end 20a and the second end 20b are identified excluding the chamfered portion 29 (in this example, based only on the sipe body portion 28).

[0073] The multiple groove-shaped portions 20 of this embodiment (in this example, groove-shaped portions provided in the center land portion 13A, the inner middle land portion 13Bi, and the outer middle land portion 13Bo) include a sipe body portion 28 with a width (i.e., a width perpendicular to its longitudinal direction) of 2 mm or less. The sipe body portion 28 of this embodiment is formed in a slit shape. These multiple groove-shaped portions 20 (sipe body portion 28) make it possible to form an edge component in the tread portion 2 while suppressing the reduction in rigidity of the land portion 13 when it comes into contact with the road surface, thereby improving steering stability.

[0074] The groove-shaped portion 20 is not limited to an embodiment that includes the sipe body portion 28, and may, for example, include a groove body portion (not shown) with a width (i.e., a width perpendicular to its longitudinal direction) greater than 2 mm. Such a groove body portion improves wet performance. The depth of the groove-shaped portion 20 (not shown) is set to, for example, 2 to 8 mm.

[0075] As shown in Figure 5, the plurality of groove-shaped portions 20 in this embodiment include a plurality of first groove-shaped portions 21, a plurality of second groove-shaped portions 22, a plurality of third groove-shaped portions 23, a plurality of fourth groove-shaped portions 24, a plurality of fifth groove-shaped portions 25, a plurality of sixth groove-shaped portions 26, and a plurality of seventh groove-shaped portions 27. However, the plurality of groove-shaped portions 20 is not limited to an embodiment that includes all of these first groove-shaped portions 21 to seventh groove-shaped portions 27. For example, depending on the performance required of the tire 1, some of these may be omitted, or other groove-shaped portions (not shown) may be included.

[0076] Multiple first groove-shaped portions 21 and multiple second groove-shaped portions 22 are provided on the center land portion 13A. In this embodiment, the multiple first groove-shaped portions 21 are arranged on the vehicle-side Vi of the center land portion 13A. On the other hand, the multiple second groove-shaped portions 22 are arranged on the vehicle-side Vo of the center land portion 13A. Note that the center land portion 13A is not limited to the configuration in which these first groove-shaped portions 21 and second groove-shaped portions 22 are provided; for example, some of them may be omitted, or other groove-shaped portions (not shown) may be included.

[0077] Multiple third groove-like portions 23 are provided in the inner middle land portion 13Bi. However, the inner middle land portion 13Bi is not limited to being provided only with the third groove-like portions 23; for example, it may also include other groove-like portions (not shown).

[0078] Multiple fourth groove-shaped portions 24 and multiple fifth groove-shaped portions 25 are provided on the outer middle land portion 13Bo. In this embodiment, the multiple fourth groove-shaped portions 24 are located on the vehicle-inside Vi of the outer middle land portion 13Bo. On the other hand, the multiple fifth groove-shaped portions 25 are located on the vehicle-outside Vo of the outer middle land portion 13Bo. Note that the outer middle land portion 13Bo is not limited to the configuration in which these fourth groove-shaped portions 24 and fifth groove-shaped portions 25 are provided; for example, some of them may be omitted, or other groove-shaped portions (not shown) may be included.

[0079] Multiple sixth groove-like portions 26 are formed in the inner shoulder land portion 13Ci. However, the inner shoulder land portion 13Ci is not limited to being provided only with the sixth groove-like portions 26; for example, it may also include other groove-like portions (not shown).

[0080] Multiple seventh groove-like portions 27 are formed in the outer shoulder land portion 13Co. However, the outer shoulder land portion 13Co is not limited to being provided only with the seventh groove-like portions 27; for example, it may also include other groove-like portions (not shown).

[0081] [Arrangement rules] As shown in Figure 6, the multiple groove-shaped portions 20 of this embodiment are arranged around the entire circumference of the tire in the circumferential direction, based on a predetermined arrangement rule 30. The arrangement rule 30 of this embodiment applies to the multiple groove-shaped portions 20 arranged on the center land portion 13A and the pair of middle land portions 13B (inner middle land portion 13Bi and outer middle land portion 13Bo), but is not limited to this configuration. For example, only some of these land portions 13 may be subject to the arrangement rule 30, or other land portions 13 (the pair of shoulder land portions 13C shown in Figure 1) may be subject to the arrangement rule 30.

[0082] In arrangement rule 30, for each pair 31 of adjacent groove-shaped portions 20 in the tire circumferential direction, the first end 20a of one groove-shaped portion 20 in the pair 31 and the second end 20b of the other groove-shaped portion 20 in the pair 31 are formed at the same position in the tire circumferential direction. Furthermore, the groove-shaped portions 20 constituting a pair 31 are formed on the same land area 13, or on different land areas 13.

[0083] Here, whether the first end 20a of one grooved portion 20 of pair 31 and the second end 20b of the other grooved portion 20 of pair 31 are in the same position in the tire circumferential direction is determined using their groove centerlines 20c. That is, the first end 20a of one grooved portion 20 of pair 31 and the second end 20b of the other grooved portion 20 of pair 31 are identified by the ends of the groove centerlines 20c. However, in consideration of the characteristics of the vulcanized rubber product, tire 1, and from the viewpoint of allowing manufacturing tolerances, the "same position" includes a configuration in which the first end 20a and the second end 20b are offset by a small distance in the tire circumferential direction. In this case, the distance between the first end 20a and the second end 20b in the tire circumferential direction is 5% or less, preferably 3% or less, and more preferably 1% or less, of the sum of the lengths of the two grooved portions 20 constituting pair 31 in the tire circumferential direction. Furthermore, it is most preferable that the first end 20a and the second end 20b are not misaligned in the circumferential direction of the tire (for example, less than 0.1%).

[0084] The pair 31 of this embodiment includes a first pair 31a, a second pair 31b, a third pair 31c, a fourth pair 31d, and a fifth pair 31e. Note that some of these pairs may be omitted, or other pairs may be included. The groove-shaped portions 20 constituting the pair 31 of this embodiment are formed on different land portions 13.

[0085] The first pair 31a consists of a fourth groove-shaped portion 24 and a second groove-shaped portion 22 adjacent to the fourth groove-shaped portion 24 on the other side S2 in the tire circumferential direction. In this embodiment, the fourth groove-shaped portion 24 is formed on the outer middle land portion 13Bo, and the second groove-shaped portion 22 is formed on the center land portion 13A. Therefore, the groove-shaped portions 20 constituting the first pair 31a are formed on different land portions 13. In addition, in the first pair 31a, the first end 20a of the second groove-shaped portion 22 and the second end 20b of the fourth groove-shaped portion 24 are formed at the same position in the tire circumferential direction.

[0086] The second pair 31b consists of a second groove-shaped portion 22 and a third groove-shaped portion 23 adjacent to the second groove-shaped portion 22 on the other side S2 in the tire circumferential direction. In this embodiment, the second groove-shaped portion 22 is formed in the center land portion 13A, and the third groove-shaped portion 23 is formed in the inner middle land portion 13Bi. Therefore, the groove-shaped portions 20 constituting the second pair 31b are formed in different land portions 13, similar to the first pair 31a. In addition, in the second pair 31b, the first end 20a of the third groove-shaped portion 23 and the second end 20b of the second groove-shaped portion 22 are formed at the same position in the tire circumferential direction.

[0087] The third pair 31c consists of a third groove-shaped portion 23 and a fifth groove-shaped portion 25 adjacent to the third groove-shaped portion 23 on the other side S2 in the tire circumferential direction. In this embodiment, the third groove-shaped portion 23 is formed in the inner middle land portion 13Bi, and the fifth groove-shaped portion 25 is formed in the outer middle land portion 13Bo. Therefore, the groove-shaped portions 20 constituting the third pair 31c are formed in different land portions 13, similar to the first pair 31a and the second pair 31b. In addition, in the third pair 31c, the first end 20a of the fifth groove-shaped portion 25 and the second end 20b of the third groove-shaped portion 23 are formed at the same position in the tire circumferential direction.

[0088] The fourth pair 31d consists of a fifth groove-shaped portion 25 and a first groove-shaped portion 21 adjacent to the fifth groove-shaped portion 25 on the other side S2 in the tire circumferential direction. In this embodiment, the fifth groove-shaped portion 25 is formed on the outer middle land portion 13Bo, and the first groove-shaped portion 21 is formed on the center land portion 13A. Therefore, the groove-shaped portions 20 constituting the fourth pair 31d are formed on different land portions 13, similar to the first pair 31a to the third pair 31c. In addition, in the fourth pair 31d, the first end 20a of the first groove-shaped portion 21 and the second end 20b of the fifth groove-shaped portion 25 are formed at the same position in the tire circumferential direction.

[0089] The fifth pair 31e consists of a first groove-shaped portion 21 and a fourth groove-shaped portion 24 adjacent to the first groove-shaped portion 21 on the other side S2 in the tire circumferential direction. In this embodiment, the first groove-shaped portion 21 is formed in the center land portion 13A, and the fourth groove-shaped portion 24 is formed in the outer middle land portion 13Bo. Therefore, the groove-shaped portions 20 constituting the fifth pair 31e are formed in different land portions 13, similar to the first pair 31a to the fourth pair 31d. In addition, in the fifth pair 31e, the first end 20a of the fourth groove-shaped portion 24 and the second end 20b of the first groove-shaped portion 21 are formed at the same position in the tire circumferential direction.

[0090] In this embodiment, the first pair 31a to the fifth pair 31e constitute a 1-pitch region P shown in Figure 5, and these first pair 31a to the fifth pair 31e are repeated in order. As a result, the arrangement rule 30 of this embodiment ensures that the groove-shaped portions 20 constituting each pair 31 (first pair 31a to fifth pair 31e) are formed on different land areas 13.

[0091] Generally, pitch noise is known as a type of noise produced when tires are in motion. For example, an impact force is generated each time the region 32 (tread surface 2s) divided by the first groove section 21 to the fifth groove section 25 makes contact with the road surface. This impact force tends to cause the tread section 2 and sidewall section 3 shown in Figure 1 to vibrate periodically, thereby generating pitch noise (pitch sound).

[0092] In this embodiment, according to the arrangement rule 30 described above, when the tire is running, the first groove portion 21 to the fifth groove portion 25 alternately and continuously make contact with the ground from one side S1 to the other side S2 (or from the other side S2 to the one side S1) in the circumferential direction of the tire. As a result, the fluctuation of the impact force is reduced. Therefore, the tire 1 of this embodiment can reduce pitch noise (pitch sound) generated from the ground portion 13 (region 32) and improve noise performance. The synergistic effect of this improvement in noise performance and the mitigation of resonant sound energy by the sound dampening body 11 described above can improve overall noise performance and enable high quietness.

[0093] In this embodiment, the arrangement rule 30 is such that the groove-shaped portions 20 constituting each pair 31 are formed on different land portions 13. As a result, in this embodiment, the groove-shaped portions 20 constituting each pair 31 are not formed continuously on each land portion 13. Therefore, in order to form the first end 20a and the second end 20b at the same position, it is not necessary to increase the angle θb of the groove-shaped portion 20 with respect to the tire axis direction, or to increase the number of groove-shaped portions 20 formed on each land portion 13. Consequently, the rigidity of each land portion 13 in the tire axis direction is prevented from decreasing more than necessary, making it possible to achieve both handling stability and noise performance (quietness).

[0094] In this embodiment, the arrangement rule 30 is such that the groove-shaped portions 20 constituting each pair 31 are formed in the center land portion 13A and a pair of middle land portions 13B (inner middle land portion 13Bi and outer middle land portion 13Bo). Since the ground pressure of these center land portion 13A and pair of middle land portions 13B tends to be relatively high during straight-line driving, pitch noise (pitch sound) can be effectively reduced. Furthermore, since the groove-shaped portions 20 constituting each pair 31 are formed in three or more different land portions 13, a decrease in the rigidity of the land portion 13 in the tire axial direction is prevented, and steering stability is further improved.

[0095] In this embodiment, the arrangement rule 30 is such that the groove-shaped portions 20 constituting each pair 31 are formed on different land areas 13, but the embodiment is not limited to this configuration. For example, the groove-shaped portions 20 constituting each pair 31 may be formed on the same land area 13. In this case, since the groove-shaped portions 20 constituting each pair 31 make contact with the land area 13 alternately and continuously, the fluctuation in the impact force is further reduced. Also, if the number of groove-shaped portions 20 is increased in order to form the first end 20a and the second end 20b at the same position, for example, the edge component increases, which improves wet performance and the like.

[0096] Figure 7 is a diagram illustrating the tread pattern 2P at the footprint 16 of the tread section 2 under a 70% load condition. The footprint 16 in Figure 7 shows a tread pattern in which one side S1 and the other side S2 in the tire circumferential direction, as shown in Figures 5 and 6, are reversed.

[0097] In this embodiment, under a 70% load condition, the contact edges 19 on both sides in the tire circumferential direction of at least one of the multiple land portions 13 have an angle θa with respect to the tire axis. In this embodiment, the absolute value of the difference between angle θa and angle θb of the groove-shaped portion 20 formed on at least one land portion 13 with respect to the tire axis is set to 5 degrees or more. The angle θb used in calculating the absolute value is determined under a 70% load condition, similar to angle θa. Furthermore, angles θa and θb may be obtained from a footprint 16 acquired by a known procedure, or from the calculation results of a contact simulation using a computer.

[0098] The angle θa is defined at the contact edge 19 of each land portion 13 by a straight line 36 passing through both ends 35, 35 in the width direction of the land portion 13. Furthermore, the angle θa in this embodiment is defined at the land portions 13 (in this example, the center land portion 13A, the inner middle land portion 13Bi, and the outer middle land portion 13Bo) where the groove-shaped portion 20 subject to the arrangement rule 30 shown in Figure 6 is formed. Therefore, the angle θa includes the angle θa1 of the contact edge 19 on one side S1 in the tire circumferential direction of the center land portion 13A, and the angle θa2 of the contact edge 19 on the other side S2 in the tire circumferential direction of the center land portion 13A. In addition, the angle θa includes the angle θa3 of the contact edge 19 on one side S1 in the tire circumferential direction of the inner middle land portion 13Bi, and the angle θa4 of the contact edge 19 on the other side S2 in the tire circumferential direction of the inner middle land portion 13Bi. Furthermore, the angle θa includes the angle θa5 of the contact edge 19 on one side S1 in the tire circumferential direction of the outer middle land portion 13Bo, and the angle θa6 of the contact edge 19 on the other side S2 in the tire circumferential direction of the outer middle land portion 13Bo.

[0099] The angles θa1 to θa6 of the contact edge 19 of each land portion 13 are defined as follows: the angle of inclination from one side S1 to the other side S2 in the tire circumferential direction is positive, and the angle of inclination from the other side S2 to the one side S1 in the tire circumferential direction is negative, when moving from the inside Vi of the vehicle to the outside Vo of the vehicle. In this case, in the inner middle land portion 13Bi, the angle θa3 of the contact edge 19 on one side S1 is negative, and the angle θa4 of the contact edge 19 on the other side S2 is positive. Also, in the outer middle land portion 13Bo, the angle θa5 of the contact edge 19 on one side S1 is positive, and the angle θa6 of the contact edge 19 on the other side S2 is negative.

[0100] The angle θa of the contact edge 19 and the shape of the contact surface 14 (footprint 16) can be adjusted as appropriate, as described above, by changing the thickness of the tread rubber 2G shown in Figure 1, or by changing the components of the well-known structure (carcass 6, belt layer 7, and band layer 9, etc.) embedded inside the tread portion 2.

[0101] The angle θb is determined by the position 39 (first end 20a or second end 20b) where, under a 70% load condition, the groove centerline 20c along the longitudinal direction of the groove-shaped portion 20 (sipe body portion 28 described later) shown in Figure 5 intersects with the edges 38 extending in the circumferential direction of the tire on both sides of the tire axis direction of each land portion 13. Furthermore, the angle θb in this embodiment is determined by the groove-shaped portion 20 subject to the arrangement rule 30 shown in Figure 5. Therefore, the angle θb includes the angle θb1 of the first groove-shaped portion 21, the angle θb2 of the second groove-shaped portion 22, the angle θb3 of the third groove-shaped portion 23, the angle θb4 of the fourth groove-shaped portion 24, and the angle θb5 of the fifth groove-shaped portion 25.

[0102] The angles θb1 to θb5 of each groove-shaped portion 20 are defined as positive when they inclinate from one side S1 to the other side S2 in the tire circumferential direction, from the inside Vi of the vehicle to the outside Vo of the vehicle, similar to the angle θa of the contact edge 19 of each land portion 13. Also, the angles θb1 to θb5 of each groove-shaped portion 20 are defined as negative when they inclinate from the other side S2 to the one side S1 in the tire circumferential direction. For this reason, the angles θb1 of the first groove-shaped portion 21, θb2 of the second groove-shaped portion 22, and θb4 of the fourth groove-shaped portion 24 are negative. On the other hand, the angles θb3 of the third groove-shaped portion 23 and θb5 of the fifth groove-shaped portion 25 are positive.

[0103] In this embodiment, the absolute value of the difference (θa1-θb1) between the angle θa1 of the ground-contacting edge 19 on one side S1 of the center land portion 13A and the angle θb1 of the first groove-shaped portion 21 formed in the center land portion 13A is set to 5 degrees or more. Furthermore, the absolute value of the difference (θa2-θb1) between the angle θa2 of the ground-contacting edge 19 on the other side S2 of the center land portion 13A and the angle θb1 of the first groove-shaped portion 21 is set to 5 degrees or more.

[0104] In this embodiment, the absolute value of the difference (θa1-θb2) between the angle θa1 of the ground-contacting edge 19 on one side S1 of the center land portion 13A and the angle θb2 of the second groove-shaped portion 22 formed in the center land portion 13A is set to 5 degrees or more. Furthermore, the absolute value of the difference (θa2-θb2) between the angle θa2 of the ground-contacting edge 19 on the other side S2 of the center land portion 13A and the angle θb2 of the second groove-shaped portion 22 is set to 5 degrees or more.

[0105] In this embodiment, the absolute value of the difference (θa3-θb3) between the angle θa3 of the grounding edge 19 on one side S1 of the inner middle land portion 13Bi and the angle θb3 of the third groove-shaped portion 23 formed in the inner middle land portion 13Bi is set to 5 degrees or more. Furthermore, the absolute value of the difference (θa4-θb3) between the angle θa4 of the grounding edge 19 on the other side S2 of the inner middle land portion 13Bi and the angle θb3 of the third groove-shaped portion 23 is set to 5 degrees or more.

[0106] In this embodiment, the absolute value of the difference (θa5-θb4) between the angle θa5 of the ground-contacting edge 19 on one side S1 of the outer middle land portion 13Bo and the angle θb4 of the fourth groove-shaped portion 24 formed in the outer middle land portion 13Bo is set to 5 degrees or more. Furthermore, the absolute value of the difference (θa6-θb4) between the angle θa6 of the ground-contacting edge 19 on the other side S2 of the outer middle land portion 13Bo and the angle θb4 of the fourth groove-shaped portion 24 is set to 5 degrees or more.

[0107] In this embodiment, the absolute value of the difference (θa5-θb5) between the angle θa5 of the ground-contacting edge 19 on one side S1 of the outer middle land portion 13Bo and the angle θb5 of the fifth groove-shaped portion 25 formed in the outer middle land portion 13Bo is set to 5 degrees or more. Furthermore, the absolute value of the difference (θa6-θb5) between the angle θa6 of the ground-contacting edge 19 on the other side S2 of the outer middle land portion 13Bo and the angle θb5 of the fifth groove-shaped portion 25 is set to 5 degrees or more.

[0108] Thus, in this embodiment, by setting the absolute value of the difference between angles θa and θb to 5 degrees or more, the direction of inclination between the contact edge 19 and the groove-shaped portion 20 is suppressed from coinciding. As a result, during tire travel, the groove-shaped portion 20 can be gradually brought into or out of contact with the contact edge 19. Therefore, since the air inside the groove-shaped portion 20 is not suddenly compressed or released when the contact edge 19 is brought into or out of contact, the amplification of pitch noise can be suppressed. This improves quietness.

[0109] In the tire 1 of this embodiment, as shown in Figure 6, pitch noise can be reduced by forming the first end 20a of one groove-shaped portion 20 of the pair 31 and the second end 20b of the other groove-shaped portion 20 of the pair 31 at the same position in the circumferential direction of the tire. Furthermore, in the tire 1 of this embodiment, as shown in Figure 7, the absolute value of the difference (θa-θb) between the angle θa of the contact edge 19 and the angle θb of the groove-shaped portion 20 at each ground portion 13 is set to 5 degrees or more, thereby suppressing the amplification of the pitch noise volume. Therefore, the tire 1 of this embodiment can reduce pitch noise, and consequently, improve noise performance (quietness). Thus, high quietness can be achieved.

[0110] In this embodiment, it is preferable that the absolute value of the difference (θa-θb) between the angle θa of the grounding edge 19 and the angle θb of the groove-shaped portion 20 is 5 degrees or more for all of the center ground portion 13A and the pair of middle ground portions (inner middle ground portion 13Bi and outer middle ground portion 13Bo). Since these ground portions 13 mainly make contact with the ground during both straight-line and turning travel, setting the absolute value to 5 degrees or more effectively suppresses the amplification of pitch noise volume, enabling further improvement in noise performance (quietness).

[0111] On the other hand, if the absolute value of the difference (θa-θb) between the angle θa of the contact edge 19 and the angle θb of the groove-shaped portion 20 becomes excessively large, the angle θb of the groove-shaped portion 20 will increase, reducing the tread rigidity, which may lead to a decrease in handling stability. For this reason, the absolute value of the difference (θa-θb) is preferably 50 degrees or less.

[0112] The absolute values ​​of the angle θb1 of the first groove 21 with respect to the tire axis, the absolute values ​​of the angle θb2 of the second groove 22 with respect to the tire axis, and the absolute values ​​of the angle θb4 of the fourth groove 24 with respect to the tire axis can be set to, for example, 10 to 30°. On the other hand, the absolute value of the angle θb3 of the third groove 23 with respect to the tire axis can be set to, for example, 20 to 40°. Also, the absolute value of the angle θb5 of the fifth groove 25 can be set to, for example, 5 to 25°. The absolute values ​​of the angle θb6 of the sixth groove 26 with respect to the tire axis and the absolute values ​​of the angle θb7 of the seventh groove 27 with respect to the tire axis can be set to, for example, 0 to 15°. Note that the absolute values ​​of these angles θb1 to θb7 are not limited to the above ranges.

[0113] Although particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments and can be implemented in various modified forms.

[0114] [Note] The present invention includes the following embodiments.

[0115] [Invention 1] A pneumatic tire having a tread portion and a sound-dampening body made of a porous material fixed to the inner surface of the tire cavity of the tread portion, The sound dampening body extends along the tire equator in the circumferential direction of the tire, When the aforementioned pneumatic tire is mounted on a regular rim with regular internal pressure and subjected to a 70% load condition with a camber angle of 0 degrees and in contact with a flat surface, the contact surface of the tread portion satisfies the following equation (1): the ratio L / Lm of the maximum contact length L in the circumferential direction of the tire to the contact length Lm in the circumferential direction of the tire within a range of 70% or less of the maximum contact width W in the axial direction of the tire, centered on the tire equator, satisfies equation (1). Pneumatic tires. 1.00 <L / Lm<1.10 …(1) [Invention 2] The pneumatic tire according to Invention 1, wherein the maximum width of the sound dampening body in the tire axial direction is 25% to 55% of the maximum contact width W. [Invention 3] The pneumatic tire according to invention 1 or 2, wherein the pneumatic tire is mounted on the regular rim at the regular internal pressure, and in the tire meridional cross-section under normal conditions (no load), the cross-sectional area of ​​the sound dampening element is 5% to 15% of the cross-sectional area of ​​the tire cavity. [4th Invention] The density of the sound-dampening material is 15-35 kg / m³. 3 A pneumatic tire according to any one of inventions 1 to 3. [5th ​​Invention] The ratio L / L2 of the maximum contact length L to the circumferential contact length L2 at the position where both ends of the sound damper in the tire axial direction are projected onto the contact surface satisfies the following formula (2), wherein the pneumatic tire according to any one of inventions 1 to 4. 1.00 <L / L2<1.10 …(2) [Invention 6] A pneumatic tire according to any one of invention 1 to 5, wherein the land ratio in the region where the sound dampening material is projected onto the outer surface of the tread portion is smaller than the land ratio of the entire tread portion. [7th Invention] The aforementioned tread portion is In the region where the sound-dampening material is projected onto the outer surface of the tread portion, a pair of center circumferential grooves extending continuously in the circumferential direction of the tire are provided, The region includes a pair of shoulder circumferential grooves that extend continuously in the tire circumferential direction on both outer sides in the tire axial direction, A pneumatic tire according to any one of invention 1 to 6, wherein the sum of the groove widths of the pair of center circumferential grooves is greater than the sum of the groove widths of the pair of shoulder circumferential grooves. [8th Invention] The tread portion includes at least one center circumferential groove provided adjacent to the tire equator and extending continuously in the tire circumferential direction, A pneumatic tire according to any one of inventions 1 to 7, wherein at least one projection protruding in the radial direction of the tire is formed at the bottom of the center circumferential groove. [Invention 9] The tread portion has a belt layer and a band layer arranged radially outward of the belt layer embedded within it. The band layer includes a band ply in which band cords are arranged in the circumferential direction of the tire. The aforementioned band cord is a hybrid cord in which an aramid fiber cord and a nylon fiber cord are twisted together, as described in any one of invention 1 to 8, for a pneumatic tire. [Invention 10] The sound dampening element is a flattened, elongated shape in which the maximum thickness in the radial direction of the tire is smaller than the maximum width in the axial direction of the tire, as described in any one of inventions 1 to 9. [Explanation of Symbols]

[0116] 1. Pneumatic tire 2 Tread section 11 Sound damping body 14 Ground plane 15s tire inner surface

Claims

1. A pneumatic tire having a tread portion and a sound-dampening body made of a porous material fixed to the inner surface of the tire cavity of the tread portion, The sound dampening body extends along the tire equator in the circumferential direction of the tire, When the aforementioned pneumatic tire is mounted on a regular rim with regular internal pressure and subjected to a 70% load condition with a camber angle of 0 degrees and in contact with a flat surface, the contact surface of the tread portion satisfies the following equation (1): the ratio L / Lm of the maximum contact length L in the circumferential direction of the tire and the contact length Lm in the circumferential direction of the tire within a range of 70% or less of the maximum contact width W in the axial direction of the tire, centered on the tire equator, satisfies the following equation (1): Pneumatic tires. 1.00<L / Lm<1.10...(1)

2. The pneumatic tire according to claim 1, wherein the maximum width of the sound dampening body in the tire axial direction is 25% to 55% of the maximum contact width W.

3. The pneumatic tire according to claim 1, wherein the pneumatic tire is mounted on the regular rim at the regular internal pressure, and in the tire meridional cross-section under normal conditions with no load, the cross-sectional area of ​​the sound dampening body is 5% to 15% of the cross-sectional area of ​​the tire cavity.

4. The density of the sound-dampening material is 15 to 35 kg / m³. 3 The pneumatic tire according to claim 1.

5. The pneumatic tire according to claim 1, wherein the ratio L / L2 of the maximum contact length L to the circumferential contact length L2 at the position where both ends of the sound damper in the tire axial direction are projected onto the contact surface satisfies the following formula (2). 1.00<L / L2<1.10...(2)

6. The pneumatic tire according to claim 1, wherein the land ratio in the region where the sound dampening material is projected onto the outer surface of the tread portion is smaller than the land ratio of the entire tread portion.

7. The aforementioned tread portion is In the region where the sound-dampening material is projected onto the outer surface of the tread portion, a pair of center circumferential grooves extending continuously in the circumferential direction of the tire are provided, The region includes a pair of shoulder circumferential grooves that extend continuously in the tire circumferential direction on both outer sides in the tire axial direction, The pneumatic tire according to claim 1, wherein the sum of the groove widths of the pair of center circumferential grooves is greater than the sum of the groove widths of the pair of shoulder circumferential grooves.

8. The tread portion includes at least one center circumferential groove provided adjacent to the tire equator and extending continuously in the tire circumferential direction, The pneumatic tire according to claim 1, wherein at least one projection protruding in the radial direction of the tire is formed at the bottom of the center circumferential groove.

9. The tread portion has a belt layer and a band layer arranged radially outward of the belt layer embedded within it. The band layer includes a band ply in which band cords are arranged in the circumferential direction of the tire. The pneumatic tire according to claim 1, wherein the band cord is a hybrid cord in which an aramid fiber cord and a nylon fiber cord are twisted together.

10. The pneumatic tire according to claim 1, wherein the sound dampening element is flat and elongated in shape, with a maximum thickness in the radial direction of the tire being smaller than the maximum width in the axial direction of the tire.

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