CN117917330A - Pneumatic tire - Google Patents

Abstract

The present invention improves noise performance while maintaining rolling resistance performance and high-speed durability. A pneumatic tire (1) is provided with: a tread portion (2); a pair of sidewall portions (3); a pair of bead portions (4); a carcass (6) extending between the pair of bead portions (4); and an inner rubber (10) extending between the pair of bead portions (4) on the inner side of the carcass (6). The inner rubber (10) comprises: a first portion (11) extending at a first thickness (t 1) at the tread portion (2), and a second portion (12) extending at a second thickness (t 2) at the pair of sidewall portions (3). The first thickness (t 1) is greater than the second thickness (t 2). In the radial section of the tire, the cross-sectional area of the inner rubber (10) is 1.5 to 10% of the cross-sectional area of the inner cavity of the pneumatic tire (1).

Description

Pneumatic tire

Technical Field

The present invention relates to a pneumatic tire.

Background

Patent document 1 below describes a pneumatic tire provided with a tread portion, a carcass, a belt layer, and a cushion rubber. In this pneumatic tire, the shape of the belt ply of the above-described belt layer is determined with a view to reducing tire noise.

Patent document 1: japanese patent laid-open publication No. 2005-145429

In recent years, further improvement in noise performance is desired in view of environmental considerations. As a method for improving noise performance, for example, a method of increasing the rubber thickness of the tread portion is known. However, if the rubber thickness of the tread portion is only increased, there is a problem that the rolling resistance performance and the high-speed durability performance are deteriorated due to an increase in the rubber volume.

Disclosure of Invention

The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a pneumatic tire capable of improving noise performance while maintaining rolling resistance performance and high-speed durability performance.

The pneumatic tire of the present invention comprises: a tread portion; a pair of sidewall portions; a pair of bead portions; a carcass extending between the pair of bead portions; and an inner rubber extending between the pair of bead portions inside the carcass, the inner rubber including: the first thickness is greater than the second thickness, and the cross-sectional area of the inner rubber in the tire meridian cross-section is 1.5-10% of the cross-sectional area of the inner cavity of the pneumatic tire.

The pneumatic tire of the present invention can improve noise performance while maintaining rolling resistance performance and high-speed durability performance by adopting the above-described structure.

Drawings

Fig. 1 is a tire radial cross-sectional view showing a pneumatic tire according to an embodiment of the present invention.

Fig. 2A is a view schematically showing the cross-sectional area of the inner cavity of the pneumatic tire, and fig. 2B is a view schematically showing the cross-sectional area of the inner rubber.

Fig. 3 is a side view showing a pneumatic tire in running.

Fig. 4 is an enlarged cross-sectional view of the tread portion of fig. 1.

Fig. 5A is a perspective view of a strapping band, and fig. 5B is a cross-sectional view of a tread portion formed using the strapping band.

Fig. 6 is an expanded view of the ground contact surface of the tread portion of fig. 1.

Fig. 7 is an enlarged cross-sectional view of the tread portion of fig. 1.

Fig. 8 is an enlarged view of the vicinity of the first tread end of fig. 4.

Fig. 9 is a cross-sectional view of the vicinity of the first tread end of another embodiment.

Fig. 10 is a cross-sectional view of the vicinity of the first tread end of another embodiment.

Fig. 11 is an enlarged cross-sectional view of a sidewall portion of another embodiment.

Reference numerals illustrate:

Pneumatic tire; tread portion; sidewall part; bead portion; carcass. Inner rubber; first part; a second part; t1. a first thickness; and t2.

Detailed Description

One embodiment of the present invention will be described below with reference to the drawings. To assist in understanding the invention, the drawings contain exaggerated representations of differing dimensional ratios from the actual construction. In the case where there are a plurality of embodiments, the same or common elements are denoted by the same reference numerals throughout the specification, and overlapping descriptions are omitted.

Fig. 1 is a tire meridian cross-sectional view including a rotation shaft (not shown) of a pneumatic tire 1 (hereinafter, may be simply referred to as "tire 1") according to an embodiment of the present invention. Fig. 1 shows a tire 1 in a normal state. The tire 1 of the present embodiment is suitable for use as a pneumatic tire for a passenger car, for example. However, the present invention is not limited to such a configuration, and may be applied to a pneumatic tire for heavy load, for example.

The "normal state" refers to a state in which the tire is assembled to a normal rim and filled with normal internal pressure and no load is applied when various specifications of pneumatic tires are specified. In the case where tires of various specifications are not specified, the normal state means a standard use state corresponding to the purpose of use of the tire, and a state of no load and not mounted on the vehicle. In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in the above-described normal state. The structure (for example, the internal material of the tire 1) that cannot be measured in the normal state is a value measured in a state where the tire 1 is as close to the normal state as possible.

The "normal Rim" is a Rim in which the specification is defined for each tire in a specification system including the specification according to which the tire is based, and is, for example, "standard Rim" in the case of JATMA, "DESIGN RIM" in the case of TRA, and "Measuring Rim" in the case of ETRTO.

The "normal internal pressure" is the air pressure of each specification defined for each tire in a specification system including the specifications according to which the tire is based, and is "highest air pressure" in the case of JATMA, the maximum value described in table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and "INFLATION PRESSURE" in the case of ETRTO.

The tire 1 includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4. The sidewall portion 3 is connected to the tire axial outer side of the tread portion 2 and extends in the tire radial direction. The bead portion 4 is connected to the tire radial direction inner side of the sidewall portion 3. In addition, the tire 1 includes a carcass 6 and an inner rubber 10. The carcass 6 extends between the pair of bead portions 4. In the present embodiment, the carcass 6 extends from one bead portion 4 to the other bead portion 4 through one sidewall portion 3, the tread portion 2, and the other sidewall portion 3. The inner rubber 10 is disposed inside the carcass 6 and extends between the pair of bead portions 4, 4. The inner rubber 10 of the present embodiment is connected to a chafer rubber composed of a rubber of a different kind from the inner rubber 10 at the bead portion 4. The inner rubber 10 constitutes a tire inner cavity surface 1A surrounding the tire inner cavity 100. In the present embodiment, the inner rubber 10 is composed of vulcanized rubber, and is different from a sealing material for puncture resistance.

The inner rubber 10 comprises a first portion 11 and a second portion 12. The first portion 11 extends at the tread portion 2 by a first thickness t 1. The second portion 12 extends at a second thickness t2 at the pair of sidewall portions 3. The second portions 12 are disposed on both sides of the first portion 11, for example. In the present specification, the first thickness t1 and the second thickness t2 mean lengths from the inner surface 6i of the carcass 6 on the tire inner chamber side to the tire inner chamber surface 1A.

The first thickness t1 is greater than the second thickness t2. Wherein the first thickness t1 is greater than the second thickness t2 means that the average value of the first thickness t1 is greater than the average value of the second thickness t2. The average value of the first thickness t1 corresponds to a value obtained by dividing the cross-sectional area of the first portion 11 in the tire meridian section by the length of the first portion 11 along the tire inner cavity surface 1 i. The same applies to the average value of the second thickness t2. In a preferred embodiment, the above thickness relationship is maintained over the entire circumference of the tire. However, the present invention is not limited to such a configuration.

Fig. 2A is a colored and schematically shows the inner cavity sectional area A1 of the tire 1. The cross-sectional area A2 of the inner rubber 10 is colored and schematically shown in fig. 2B. As shown in fig. 2A and 2B, in the tire meridian section, the cross-sectional area A2 of the inner rubber 10 is preferably 1.5% or more and preferably 10% or less of the inner cavity cross-sectional area A1 of the tire 1. In the present invention, by adopting the above-described structure, it is possible to improve noise performance while maintaining rolling resistance performance and high-speed durability performance. The reason for this is as follows.

As shown in fig. 1, the inner rubber 10 absorbs vibration from the road surface during running, and thus reduces noise in the vehicle and improves noise performance. In particular, since the first portion 11 having a relatively large thickness is disposed in the tread portion 2, the above-described vibration from the tread portion 2 can be effectively absorbed. The inner rubber 10 constituting the tire inner cavity surface 1A can maintain a higher rolling resistance performance than a case of increasing the rubber on the outer side in the tire radial direction than the carcass 6. Further, since the cross-sectional area A2 (shown in fig. 2B) is 1.5% or more of the inner cavity cross-sectional area A1 (shown in fig. 2A), vibrations from the road surface during running can be suppressed from resonating in the tire inner cavity. Further, since the cross-sectional area A2 is 10% or less of the inner cavity cross-sectional area A1, an excessive increase in the tire mass is suppressed. Further, since the second portion 12 having a relatively small thickness is arranged in the sidewall portion 3, the effect of suppressing an excessive increase in the tire mass is improved. As a result, the tire 1 of the present embodiment maintains high rolling resistance performance and high-speed durability. In order to more effectively exert such an effect, the cross-sectional area A2 is more preferably 2.0% or more and still more preferably 5.0% or less of the inner cavity cross-sectional area A1. As shown in fig. 2A, the inner cavity cross-sectional area A1 is the sum of the cross-sectional area A1A surrounded by the bead base line BL and the tire inner cavity surface 1A and the cross-sectional area A1b of the first portion 11 on the inner side in the tire radial direction from the virtual line k1 extending the tire inner cavity surface 12i of the second portion 12 smoothly inward in the tire axial direction. The bead base line BL is a tire axial line passing through a rim diameter position specified by the specification according to which the tire 1 is based. The cross-sectional area A1b is the same as the cross-sectional area of the additional layer 17 described later with reference to fig. 10.

Hereinafter, a more detailed configuration of the present embodiment will be described. Each structure described below represents a specific embodiment of the present embodiment. Therefore, it is needless to say that the present invention can exhibit the above-described effects without having the structure described below. Further, even if any of the structures described below is applied to the tire of the present invention having the above-described features, improvement in performance corresponding to each structure can be expected. Further, when several of the structures described below are applied in combination, improvement of the combination performance corresponding to each structure can be expected.

As shown in fig. 1, the tire 1 preferably has a cross-sectional width W of 205mm or more and 325mm or less, a flatness ratio of 25% or more and 65% or less, and a rim diameter of 16 inches or more and 22 inches or less. The tire 1 of this size is a tire 1 which has a relatively large cross-sectional width W, a low flatness ratio, and a large diameter, is liable to increase in noise and rolling resistance in a vehicle, and is liable to decrease in heat radiation property. By applying the present invention to such a tire 1, the effect of improving noise performance while maintaining rolling resistance performance and high-speed durability performance can be further exerted. In the present specification, the "cross-sectional width W", "flatness ratio" and "rim diameter" are synonymous with "nominal cross-sectional width", "nominal flatness ratio" and "nominal rim diameter" of the tire in JATMA specification. Therefore, the "cross-sectional width W" can be obtained as a width obtained by removing the pattern, the letter, or the like on the side surface of the tire from the tire axial distance (total width of the tire) between the side wall portions 3, 3 including the entire pattern, the letter, or the like on the side surface of the tire.

The cross-sectional width W of the tire 1 shown in fig. 1 in a normal state is preferably 225mm or more. The tire 1 having a large cross-sectional width W has a relatively large tread width TW, and thus the trumpet effect tends to become large. However, in the present embodiment, since the influence of the horn effect on the noise performance is suppressed by the first portion 11, even in the tire 1 having the cross-sectional width W of 225mm or more, deterioration of the noise performance is suppressed.

Fig. 3 shows a case where the tire 1 of the present embodiment having the first portion 11 of the inner rubber 10 generates noise at the time of running.

The tire 1 of the present embodiment has an outer diameter DM of 660mm or more in a normal state. In such a tire 1, the angle α between the ground contact surface 2s of the tread portion 2 and the road surface G is small, and the effect of the horn on the noise performance of the tire becomes remarkable. Therefore, in the tire 1 of the present embodiment, by adopting the above-described configuration, the influence of the horn effect on the noise performance is suppressed.

As shown in fig. 1, the tire 1 of the present embodiment is assigned an orientation for mounting to a vehicle. The direction of mounting to the vehicle is indicated by letters or symbols, for example, at the outer surface of the side wall portion 3 or the like. The tire 1 of the present invention is not limited to such a configuration, and the direction of attachment to the vehicle may not be specified.

The tread portion 2 includes a tire equator C, a first tread end T1 (left side in the drawing), and a second tread end T2 (right side in the drawing). In the present embodiment, the first tread end T1 is located on the vehicle outside when the vehicle is mounted. In the present embodiment, the second tread end T2 is located on the vehicle inner side when the vehicle is mounted. The first tread end T1 and the second tread end T2 correspond to the ground contact positions at the outermost sides in the tire axial direction when the tire 1 in a normal state is loaded with 70% of a normal load, and the tread portion 2 is grounded at an outward inclination angle of 0 °. The distance in the tire axial direction between the first tread end T1 and the second tread end T2 is the tread width TW. The tire equator C is a position separated from the first tread end T1 toward the second tread end T2 by a tire axial distance of 50% of the tread width TW. The outer surface of the tread portion 2 in the tire radial direction between the first tread end T1 and the second tread end T2 is a ground contact surface 2s.

The "normal LOAD" is a LOAD of each specification defined for each tire in a specification system including specifications according to which the tire is based, and is a maximum LOAD CAPACITY in the case of JATMA, a maximum value in table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and a LOAD CAPACITY in the case of ETRTO. In the case where tires of various specifications are not specified, the "normal load" refers to the maximum load that can be applied when the tire is used in accordance with the above specifications.

The carcass 6 is constituted of, for example, 1 carcass ply 6A. The carcass ply 6A includes, for example, a main body portion 6A and a turn-up portion 6b. The main body portion 6a extends between the pair of bead portions 4, for example. The turning-back portion 6b is connected to the main body portion 6a, for example, and turns back from the inner side to the outer side in the axial direction of the tire around the bead core 5.

The carcass ply 6A includes a plurality of carcass cords 6B and a coating (not shown) covering these. The carcass cord 6B is an organic fiber cord such as aramid or rayon. The carcass cords 6B are preferably arranged at an angle of, for example, 70 to 90 ° with respect to the tire circumferential direction.

In the tire 1 of the present embodiment, the twist factor K of the carcass cord 6B is 2000 to 2500. Here, when the number of turns per 100mm is set to T and the total fineness of the carcass cord 6B is set to D (dtex), the coefficient is represented by k=tv D. The twist factor K is a numerical value in the carcass cord 6B after the dipping treatment.

When a cord having a small twist factor K is applied as the carcass cord 6B, the cord fatigue is deteriorated, and the durability of the tire 1 may be affected. In the tire 1 of the present embodiment, since the twist factor of the carcass cord 6B is 2000 or more, the cord fatigue is good, and the durability of the tire 1 is improved.

On the other hand, when a cord having a large twist factor K is applied as the carcass cord 6B, satisfactory attenuation cannot be obtained from the sidewall 3 to the bead 4, and noise performance of the tire 1 may be affected. Further, the deformation of the carcass structure including the carcass 6 from the sidewall portion 3 to the bead portion 4 increases, and the rolling resistance increases. In the tire 1 of the present embodiment, since the twist factor K of the carcass cord 6B is 2500 or less, excellent attenuation is obtained from the sidewall 3 over the bead 4, and the noise performance of the tire 1 is improved and the noise in the vehicle is reduced. In addition, since deformation of the carcass structure is suppressed, rolling resistance can be easily reduced.

In the tire 1 of the present embodiment, the first portion 11 having the first thickness t1 in the inner rubber 10 functions as a mass damper to suppress vibration of the tread portion 2. The vibration energy of the tread portion 2 is attenuated by the viscoelastic properties of the rubber itself disposed in the first portion 11.

Therefore, the tire 1 of the present embodiment allows the use of a cord having a large twist factor K as the carcass cord 6B when compared with a conventional pneumatic tire not provided with the first portion 11. On the other hand, by setting the upper limit of the twist coefficient K to the carcass cord 6B of 2500, an increase in rolling resistance that is feared by providing the first portion 11 is easily suppressed.

That is, in the tire 1 of the present embodiment, by optimizing the carcass cord 6B for the twist coefficient K according to the first thickness t1 of the first portion 11, it is possible to achieve reduction of the noise in the vehicle without causing an increase in rolling resistance.

The tire 1 of the present embodiment is of a so-called high turnup structure in which the end of the turnup portion 6b of the carcass 6 is located further to the outside in the tire radial direction than the maximum width position of the main body portion 6a of the carcass 6. With such a carcass 6, vibration of the side wall portion 3 is less likely to be transmitted to the bead portion 4, and noise in the vehicle can be reduced. In addition, since deformation of the carcass structure at the portion from the sidewall portion 3 to the bead portion 4 is suppressed, rolling resistance can be easily reduced. The tire 1 of the present embodiment may have a so-called ultra-high turnup structure in which the end of the turnup portion 6b of the carcass 6 is located further inward in the tire axial direction than the outer end of the belt layer 7 in the tire axial direction.

Polyethylene terephthalate (PET) is used for the carcass cord 6B of the present embodiment. The relationship between the number of carcass plies 6A and the fineness of the carcass cords 6B and the load index of the tire 1 is preferably as follows.

[ In the case where the carcass ply 6A using PET cords was 1 sheet ]

In the case where the fineness of the carcass cord 6B is 1100dtex/2, the load index is preferably 90 or less.

In the case where the fineness of the carcass cord 6B is 1440dtex/2, the load index is preferably more than 90 and 100 or less.

In the case where the fineness of the carcass cord 6B is 1670dtex/2, the load index is preferably more than 90 and 105 or less.

[ In the case where the carcass ply 6A using PET cords was 2 sheets ]

In the case where the fineness of the carcass cord 6B is 1110dtex/2, the load index is preferably 110 or less.

In the case where the fineness of the carcass cord 6B is 1440dtex/2 or 1670dtex/2, the load index is preferably 115 or less.

Fig. 4 is an enlarged cross-sectional view of the tread portion 2 of fig. 1. As shown in fig. 4, the tread portion 2 of the present embodiment includes, for example, a belt layer 7 and a belt layer 8 disposed on the outer side of the carcass 6 in the tire radial direction. The belt layer 7 includes a first belt ply 7A adjacent to the carcass 6 and a second belt ply 7B disposed on the outer side of the first belt ply 7A in the tire radial direction. The first belt ply 7A and the second belt ply 7B each include a plurality of belt cords aligned at an angle of 15 to 45 ° with respect to the tire circumferential direction and a tape (not shown) covering these. The belt layer 7 is not limited to this configuration.

The length L2 (shown in fig. 1) of the second belt ply 7B in the tire axial direction is preferably smaller than the length L1 (shown in fig. 1) of the first belt ply 7A in the tire axial direction. Both ends (outer ends) 7B, 7B of the second belt ply 7B in the tire axial direction are located further inward in the tire axial direction than both ends 7A, 7A of the first belt ply 7A in the tire axial direction. The length L2 of the second belt ply 7B is preferably 90% to 98% of the length L1 of the first belt ply 7A. The length L2 of the second belt ply 7B is preferably 65 to 80% of the cross-sectional width W of the tire 1 in a normal state. Thereby, the weight increase of the tire 1 is suppressed while suppressing the vibration of the tread portion 2.

The belt layer 8 of the present embodiment is disposed so as to cover the entire belt layer 7. The belt layer 8 is constituted of, for example, 1 belt ply 8A. The belt ply 8A includes, for example, a belt cord Ga (shown in fig. 5A) disposed at an angle of 5 ° or less with respect to the tire circumferential direction, and a tape label Gb covering the belt cord Ga. The belt ply 8A may also be formed by, for example, helically winding a belt strip Gs (shown in fig. 5A) including belt cords Ga. Fig. 5A is a perspective view of the belt strip Gs. Fig. 5B is a partial cross-sectional view of the tread portion 2 using the belt strips Gs. As shown in fig. 5A and 5B, the belt ply 8A may be provided with a slit S, for example, at a portion overlapping the first portion 11 in the tire axial direction, the slit S isolating the belt strips Gs adjacent to each other in the tire axial direction. The width Ws of the slit S in the tire axial direction is preferably 20% or more, more preferably 30% or more, still more preferably 60% or less, and still more preferably 50% or less of the width Wg of the tie strip Gs.

Fig. 6 shows an expanded view of the ground contact surface 2s of the tread portion 2 of fig. 1. As shown in fig. 6, the tread portion 2 is provided with a plurality of circumferential grooves 20, for example. The circumferential groove 20 of the present embodiment is provided between the first tread end T1 and the second tread end T2. The circumferential groove 20 is a groove that extends continuously in the tire circumferential direction. The circumferential grooves 20 of the present embodiment extend in a straight line parallel to the tire circumferential direction, for example. The circumferential grooves 20 may also extend, for example, in a wave shape.

The plurality of circumferential grooves 20 of the present embodiment include a first shoulder circumferential groove 21, a second shoulder circumferential groove 22, a first crown circumferential groove 23, and a second crown circumferential groove 24. The first shoulder circumferential groove 21 is provided between the first tread end T1 and the tire equator C, and is disposed at a position closest to the first tread end T1 among the plurality of circumferential grooves 20 in the present embodiment. The second shoulder circumferential groove 22 is disposed between the second tread end T2 and the tire equator C, and in the present embodiment, is disposed at a position closest to the second tread end T2 among the plurality of circumferential grooves 20. The first crown circumferential groove 23 is provided between the first shoulder circumferential groove 21 and the tire equator C. The second crown circumferential groove 24 is provided between the second shoulder circumferential groove 22 and the tire equator C.

The distance L3 in the tire axial direction from the tire equator C to the groove center line of the first shoulder circumferential groove 21 or the second shoulder circumferential groove 22 is preferably 25% to 35% of the tread width TW, for example. The distance L4 in the tire axial direction from the tire equator C to the groove center line of the first crown circumferential groove 23 or the second crown circumferential groove 24 is preferably 5% to 15% of the tread width TW, for example.

As shown in fig. 4, the groove width Wa of each circumferential groove 20 is preferably at least 3mm or more. The groove width Wa of each circumferential groove 20 is preferably, for example, 4.0% to 8.5% of the tread width TW. The total of the groove widths Wa of the plurality of circumferential grooves 20 is, for example, 20 to 30%, preferably 25 to 30% of the tread width TW. Thus, noise outside the vehicle can be reduced and noise performance can be improved. The groove depth (not shown) of each circumferential groove 20 is preferably 5 to 10mm in the case of a pneumatic tire for a passenger car, for example.

As shown in fig. 6, the groove width W3 of the first crown circumferential groove 23 is preferably larger than the groove width W1 of the first shoulder circumferential groove 21, for example. Specifically, the groove width W3 is 150% to 200% of the groove width W1. In addition, the groove width W4 of the second crown circumferential groove 24 is preferably larger than, for example, the groove width W2 of the second shoulder circumferential groove 22. Specifically, the groove width W4 is 140% or less, preferably 105% to 120% of the groove width W2. In addition, in a more preferred form, the first shoulder circumferential groove 21 has a minimum groove width among the plurality of circumferential grooves 20. Thus, the wet performance is ensured, and noise generated in each circumferential groove 20 is less likely to spread to the outside of the vehicle, so that the noise outside the vehicle can be reduced.

The plurality of land portions 25 includes a crown land portion 30, a first intermediate land portion 28, a second intermediate land portion 29, a first shoulder land portion 26, and a second shoulder land portion 27. The crown land portion 30 is divided between the first crown circumferential groove 23 and the second crown circumferential groove 24. The first intermediate land portion 28 is divided between the first shoulder circumferential groove 21 and the first crown circumferential groove 23. Thus, the first intermediate land portion 28 is adjacent to the crown land portion 30 via the first crown circumferential groove 23. The second intermediate land portion 29 is divided between the second shoulder circumferential groove 22 and the second crown circumferential groove 24. Thus, the second intermediate land portion 29 is adjacent to the crown land portion 30 via the second crown circumferential groove 24.

The first shoulder land portion 26 includes a first tread end T1, and is divided on the tire axial outer side of the first shoulder circumferential groove 21. Thus, the first shoulder land portion 26 and the first intermediate land portion 28 are adjacent via the first shoulder circumferential groove 21. The second shoulder land portion 27 includes a second tread end T2, and is divided axially outward of the tire of the second shoulder circumferential groove 22. Thus, the second shoulder land portion 27 and the second intermediate land portion 29 are adjacent via the second shoulder circumferential groove 22.

A plurality of transverse grooves 31 are provided in each of the land portions 25. The arrangement of the lateral grooves 31 shown in fig. 6 is merely an example, and the present invention is not limited to this configuration.

The first intermediate land portion 28 is preferably broken in the tire circumferential direction without being broken by a groove having a groove width of 2mm or more. Similarly, the crown land portion 30 and the second intermediate land portion 29 are also preferably broken in the tire circumferential direction without being broken by a groove having a groove width of 2mm or more. Thus, the pattern noise generated in these land portions is reduced, and the noise outside the vehicle can be reduced.

In general, it is known that if the land ratio of the tread portion becomes smaller, the pattern noise increases, and the noise outside the vehicle increases. On the other hand, it is known that if the land ratio is increased, the pattern noise is reduced, but vibration from the road surface is easily transmitted to the vehicle through the tire, and further, the noise in the vehicle is increased. Therefore, in the conventional tires, the design is often performed with a relatively small land ratio (less than 65%).

In contrast, in the present embodiment, the land ratio of the tread portion 2 is 65% or more. In the present specification, the "land ratio" refers to the ratio Sb/Sa of the actual total ground contact area Sb to the total area Sa of the virtual ground contact area Sa in which all the grooves and sipes of the ground contact surface 2s disposed on the tread portion 2 are buried.

In the present embodiment, by setting the land ratio to 65% or more, the pattern noise and, in turn, the noise outside the vehicle can be reduced. In addition, since the tire 1 of the present embodiment has the first thickness t1 (shown in fig. 1) of the first portion 11 as large as described above, the tread portion 2 can effectively absorb vibrations from the road surface, and in-vehicle noise can be reliably reduced even when the land ratio of the tread portion 2 is large. For this reason, the tire 1 of the present embodiment can reduce both the noise outside the vehicle and the noise inside the vehicle.

The land ratio Lac of the crown land portion 30 is preferably greater than the land ratio Lam1 of the first intermediate land portion 28. Specifically, the land ratio Lac is greater than 105% of the land ratio Lam1, preferably 106% or more and less than 120%. This reduces the pattern noise generated in the crown land portion 30, and improves the steering stability and wear resistance on a dry road surface.

The land ratio Lam1 of the first intermediate land portion 28 is preferably greater than the land ratio Las1 of the first shoulder land portion 26. Specifically, the land ratio Lam1 is greater than 105%, specifically 106% or more and less than 120% of the land ratio Las1. This can further improve the steering stability and wear resistance on a dry road surface.

From the same point of view, the land ratio Lam2 of the second intermediate land portion 29 is preferably larger than the land ratio Las2 of the second shoulder land portion 27. Specifically, the land ratio Lam2 is greater than 105%, specifically 106% or more and less than 120% of the land ratio Las2.

Fig. 7 is a tire meridian sectional view of the tread portion 2. As shown in fig. 7, the groove depth d3 of the first crown circumferential groove 23 is, for example, the same as the groove depth d4 of the second crown circumferential groove 24. In the present embodiment, the groove depth d3 of the first crown circumferential groove 23 is larger than the groove depth d1 of the first shoulder circumferential groove 21 and the groove depth d2 of the second shoulder circumferential groove 22. Thus, the maximum value dx (shown in fig. 1) of the groove depth of the circumferential groove 20 is the groove depth d3 of the first crown circumferential groove 23 and the groove depth d4 of the second crown circumferential groove 24. In this way, the volume of the tread rubber 2G in the vicinity of the tire equator C is reduced by setting the groove depth d3 of the first crown circumferential groove 23 and the groove depth d4 of the second crown circumferential groove 24 adjacent to the tire equator C on which the high ground contact pressure acts during straight running as the maximum value dx of the groove depths. Thereby, the rolling resistance performance is further improved. The groove depth d1 of the first shoulder circumferential groove 21 is preferably, for example, 5 to 10mm in the case of a pneumatic tire for a passenger vehicle, although not particularly limited thereto. The groove depth d1 of the first shoulder circumferential groove 21 and the groove depth d2 of the second shoulder circumferential groove 22 are preferably 75% or more, more preferably 80% or more, still more preferably 95% or less, and still more preferably 90% or less of the groove depth d3 of the first crown circumferential groove 23.

As shown in fig. 1, the maximum value tx of the first thickness t1 of the first portion 11 is set to be 0.25 to 0.60 times the maximum value dx of the groove depth d of the plurality of circumferential grooves 20. In the present embodiment, by adopting the above-described structure, the rolling resistance performance can be improved while maintaining the noise performance and the steering stability performance. The reason for this is as follows.

Since the inner rubber 10 absorbs vibration from the road surface during running, the noise in the vehicle is reduced, the ground contact feeling is improved, and the noise performance and the steering stability performance are maintained high. In addition, since the inner rubber 10 disposed inside the carcass 6 is less likely to undergo compression deformation upon contact with the ground, the rolling resistance performance is improved. Further, since the first portion 11 having a relatively large thickness is disposed in the tread portion 2, the vibration from the tread portion 2 can be effectively absorbed. Further, since the maximum value tx is 0.25 times or more of the maximum value dx, the absorption effect of the first portion 11 on vibration is effectively exhibited. Further, since the maximum value tx is 0.60 times or less of the maximum value dx, an excessive increase in volume of the inner rubber 10 is suppressed, and rolling resistance performance is improved. In addition, since the second portion 12 having a relatively small thickness is arranged in the sidewall portion 3, an increase in the tire mass is suppressed. In order to more effectively exert such an effect, the maximum value tx is more preferably 0.30 times or more, and still more preferably 0.55 times or less of the maximum value dx.

As shown in fig. 4, the first portion 11 includes: a first end 13 on the first tread end T1 side, a second end 14 on the second tread end T2 side, and a central portion 15 disposed between the first end 13 and the second end 14. The central portion 15 includes a maximum value tx (shown in fig. 1) of the first thickness t 1. In the present embodiment, the thickness tc of the central portion 15 is substantially the same (maximum value tx).

In the first end portion 13, for example, the first thickness T1 continuously decreases toward the outer end 11a of the first portion 11 on the first tread end T1 side. In the second end portion 14, for example, the first thickness T1 continuously decreases toward the outer end 11b of the second tread end T2 side of the first portion 11. In the present embodiment, the position at which the reduction of the first thickness t1 ends corresponds to the outer ends 11a, 11b of the first portion 11 in the tire axial direction.

The outer end 11a of the first portion 11 on the first tread end T1 side of the present embodiment is located closer to the first tread end T1 than the first crown circumferential groove 23, and more preferably is located closer to the first tread end T1 than the first shoulder circumferential groove 21. Thus, the noise in the vehicle can be reliably reduced. The outer end 11a of the first portion 11 on the first tread end T1 side is located, for example, between the first shoulder circumferential groove 21 and the outer end 7a of the belt layer 7, more preferably between the first shoulder circumferential groove 21 and the outer end 7b of the second belt layer. This can improve rolling resistance performance and noise performance in a balanced manner.

Fig. 8 is an enlarged cross-sectional view of the first end 13 side of the first portion 11. As shown in fig. 8, the outer end 11a of the first portion 11 is preferably located at the same position as the outer end 7B of the second belt ply 7B in the tire axial direction or at a position on the inner side in the tire axial direction than the outer end 7B of the second belt ply 7B toward the first tread end T1 side from the tire equator C. In a further preferred form, the distance L5 in the tire axial direction between the outer end 11a of the first portion 11 and the outer end 7B of the second belt ply 7B is within 10 mm. This can sufficiently secure the length of the first portion 11 in the tire axial direction, and can suppress the deformation of the outer end 11a periphery of the first portion 11 at the time of tire running by the belt layer 7, and can further suppress the peeling of the inner rubber 10 around the outer end 11 a. Therefore, the improvement of noise performance can be maintained for a long period of time.

In addition, the first end portion 13 is connected to a portion extending at substantially the same first thickness t1 on the tire equator C side. The length L6 of the first end portion 13 in the tire axial direction is, for example, 2.0% to 4.0% of the tread width TW (shown in fig. 1). This can prevent abrupt thickness changes of the inner rubber 10, and can suppress damage such as peeling of the inner rubber 10.

As shown in fig. 4, the length L7 of the first portion 11 in the tire axial direction is defined by the distance in the tire axial direction from the outer end 11a on the first tread end T1 side to the outer end 11b on the second tread end T2 side of the first portion 11. The length L7 of the first portion 11 in the tire axial direction of the present embodiment is preferably 90% to 110% of the tread width TW. Thus, the in-vehicle noise can be reliably reduced while suppressing an increase in the tire mass. The length L7 of the first portion 11 is, for example, preferably 70% or more, more preferably 80% or more, still more preferably 98% or less, still more preferably 95% or less of the length L2 (shown in fig. 1) of the second belt ply 7B.

The length L7 of the first portion 11 is preferably 65% to 85% of the cross-sectional width W (shown in fig. 1). Since the length L7 of the first portion 11 is 65% or more of the cross-sectional width W, vibration of the tread portion 2 can be suppressed in a wide area. Since the length L7 of the first portion 11 is 85% or less of the cross-sectional width W, an increase in weight of the inner rubber 10 is suppressed.

In the first portion 11 of the present embodiment, the first length L8 from the tire equator C to the outer end 11a on the first tread end T1 side is substantially the same as the second length L9 from the tire equator C to the outer end 11b on the second tread end T2 side. More specifically, the difference between the first length L8 and the second length L9 is 5% or less of the first length L8. In other embodiments, for example, the second length L9 may also be greater than the first length L8. Specifically, the second length L9 is 105% to 110% of the first length L8. Such an embodiment can further reduce noise in the vehicle because the length of the first portion 11 is sufficiently ensured on the second tread end T2 side that becomes the vehicle inner side when the vehicle is mounted.

The first portion 11 extends between the first end 13 and the second end 14 with a constant first thickness t1. The first thickness T1 is substantially the same at the tire equator C and at the first tread end T1 side of the first shoulder circumferential groove 21. In a preferred form, the first thickness t1 is substantially the same from the position of the tire equator C to a position beyond the first shoulder circumferential groove 21. The term "substantially the same" means that an unavoidable error in a rubber product such as a tire can be tolerated, and includes a form in which the difference between the maximum value and the minimum value of the thickness is 5% or less of the maximum value.

In the first portion 11, the outer end 11a thereof is located further inward in the tire axial direction than the first tread end T1 in the present embodiment. Such a tire 1 can maintain high rolling resistance performance and high-speed durability performance due to a decrease in tire quality. The first portion 11 may be configured such that a region extending at a constant first thickness T1 extends to the first tread edge T1 (not shown). In other words, the first thickness T1 may be substantially the same from the position of the tire equator C to the position of the first tread end T1 (an imaginary line passing through the first tread end T1 and extending in parallel with the tire radial direction).

The first portion 11 may have the same structure as the first tread end T1 side on the second tread end T2 side. The outer end 11b of the first portion 11 is located, for example, closer to the second tread end T2 than the second crown circumferential groove 24, more preferably closer to the second tread end T2 than the second shoulder circumferential groove 22. In addition, the outer end 11B of the first portion 11 on the second tread end T2 side is located at the same position as the outer end 7B of the second belt ply 7B in the tire axial direction or at a position on the inner side in the tire axial direction than the outer end 7B of the second belt ply 7B. In addition, for example, the distance L5 in the tire axial direction between the outer end 11B of the first portion 11 and the outer end 7B of the second belt ply 7B is 10mm or less. The second end 14 of the present embodiment has the same structure and shape as the first end 13.

The first thickness T1 is substantially the same at the tire equator C and at the second tread end T2 side of the second shoulder circumferential groove 22, for example. In a preferred form, the first thickness t1 is substantially the same from the position of the tire equator C to a position beyond the second shoulder circumferential groove 22. In addition, the outer end 11b of the first portion 11 is located, for example, at a position axially inward of the tire of the second tread end T2.

The average value of the first thickness t1 is preferably 1.5 to 3.5 times the average value of the second thickness t2 (shown in fig. 1). Specifically, the average value of the first thickness t1 is preferably 1.5 times or more, more preferably 1.75 times or more, further preferably 1.9 times or more, preferably 3.5 times or less, more preferably 2.7 times or less, further preferably 2.2 times or less, the average value of the second thickness t 2. Thus, the in-vehicle noise is reliably reduced while suppressing an increase in the tire mass.

From the same viewpoint, the average value of the first thickness t1 is preferably 2.0mm or more, more preferably 2.5mm or more, preferably 4.5mm or less, more preferably 4.0mm or less, and further preferably 3.5mm or less. On the other hand, the average value of the second thickness t2 is, for example, greater than 0.5mm and less than 2.0mm. In a preferred embodiment, the average value of the second thickness t2 is 1.0 to 1.5mm. The second portion 12 of the present embodiment is connected to the first portion 11 and extends to the bead portion 4 (shown in fig. 1), and the second thickness t2 is constant as a whole. However, the second portion 12 is not limited to this configuration.

The average value of the first thickness t1 is preferably 0.45% or more of the outer diameter DM (shown in fig. 3). This further suppresses the influence of the horn effect on the noise performance, and thus can be expected to improve the noise performance of the tire 1.

The average value of the first thickness t1 is preferably 30% to 60% of the maximum depth of the plurality of circumferential grooves 20. The maximum depth is the maximum depth among the depth of the first shoulder circumferential groove 21, the depth of the second shoulder circumferential groove 22, the depth of the first crown circumferential groove 23, and the depth of the second crown circumferential groove 24.

The average value of the first thickness t1 is 30% or more of the maximum depth, thereby further suppressing the influence of the horn effect on the noise performance. The average value of the first thickness t1 is 60% or less of the maximum depth, thereby suppressing an increase in weight of the inner rubber 10.

By setting the twist factor K of the carcass cord 6B to 2000 to 2500 and setting the average value of the first thickness t1 of the first portion 11 to 2.0mm to 4.5mm, the present inventors confirmed that the noise in the vehicle is reduced in the low frequency band of 160Hz or less, the intermediate frequency band of 160Hz to 350Hz, and the high frequency band of 350Hz or more.

In addition, the inventors confirmed that the rolling resistance was not deteriorated by setting the twist factor K of the carcass cord 6B to 2000 to 2500 and the average value of the first thickness t1 of the first portion 11 to 2.0mm to 3.5 mm.

In the present embodiment, the first portion 11 and the second portion 12 of the inner rubber 10 are formed of a rubber material having air impermeability. As the rubber material, for example, butyl-based or halogenated butyl-based rubber materials can be used. In the present embodiment, the first portion 11 and the second portion 12 are formed of the same rubber material.

The tread portion 2 includes tread rubber 2G constituting the ground contact surface 2 s. The tread portion 2 includes, for example, a top rubber 2A constituting the ground contact surface 2s and a base rubber 2B disposed on the inner side of the top rubber 2A in the tire radial direction. The tread portion 2 is not limited to such a configuration, and may be made of, for example, 1 layer of rubber material or 3 or more layers of rubber material.

The volume V2 of the inner rubber 10 is preferably 0.30 times or more, more preferably 0.35 times or more, still more preferably 0.50 times or less, still more preferably 0.45 times or less the volume V1 of the tread rubber 2G. Since the volume V2 of the inner rubber 10 is 0.30 times or more the volume V1 of the tread rubber 2G, the noise performance and the steering stability performance can be maintained high. Since the volume V2 of the inner rubber 10 is 0.50 times or less the volume V1 of the tread rubber 2G, an increase in the tire mass is suppressed, and therefore the rolling resistance performance can be improved. The volume V1 of the tread rubber 2G is a total volume of abradable material disposed between a tire radial line n1 (shown in fig. 7) passing through the first tread end T1 and a tire radial line n2 passing through the second tread end T2 in this specification. The abradable material is a rubber material sandwiched between the outermost surface of the reinforcing layer disposed on the outer side in the tire radial direction of the carcass 6 and the ground contact surface 2 s. The above-mentioned reinforcing layer means a ply material composed of cords and a topping. In the present embodiment, the outermost surface is an outer surface 8a of the band layer 8 on the ground plane 2s side. The volume V1 of the tread rubber 2G includes a cavity volume of a recess formed in the ground contact surface 2 s. The concave portion includes grooves and sipes other than a circumferential groove extending continuously in the tire circumferential direction. In the present embodiment, the volume V1 of the tread rubber 2G is constituted by the top rubber 2A and the base rubber 2B.

As shown in fig. 4, the loss tangent tan δ1 at 70 ℃ of the first part 11 of the present embodiment is preferably equal to or greater than the loss tangent tan δ2 at 70 ℃ of the second part 12. Such first portion 11 contributes to suppressing vibration of tread portion 2, and can improve noise performance of pneumatic tire 1.

The loss tangent tan δ1 at 70 ℃ of the first portion 11 is preferably not more than tan δa at 30 ℃ of the tread rubber 2G. Among them, since the tread rubber 2G constituting the ground contact surface 2s is cooled by contact with the outside air, the measurement temperature is set to 30 ℃. Such a first portion 11 can further reduce the influence on the rolling resistance of the tread portion 2, contributing to an improvement in the rolling resistance performance of the pneumatic tire 1. Therefore, the pneumatic tire 1 of the present embodiment can achieve both rolling resistance performance and noise performance.

In this specification, the loss tangent tan δ is a value measured by using an dynamic viscoelasticity measuring device under the following conditions in accordance with the specification of JIS-K6394. The rubber sample at the time of measuring the loss tangent tan δ is collected from the vulcanized pneumatic tire 1, for example, and is collected such that the longitudinal direction of the sample coincides with the circumferential direction of the pneumatic tire 1.

Initial strain: 5% (at a measurement temperature of 30 ℃) or 10% (at a measurement temperature of 70 ℃)

Amplitude of dynamic strain: 1%

Frequency: 10Hz

Deformation mode: stretching

Measuring temperature: 30 ℃ or 70 DEG C

The loss tangent tan δ can be appropriately adjusted according to the glass transition point Tg of the rubber composition, the types of the various compounding agents, and the compounding amount. Specifically, the loss tangent tan δ can be increased by increasing the glass transition point Tg of the rubber composition, decreasing the average particle diameter of a reinforcing agent such as carbon or silica, increasing the amount of the reinforcing agent, decreasing sulfur, a vulcanizing agent such as a promoter, or the like.

Here, the loss tangent tan δ1 of the first portion 11 is the loss tangent tan δ1 of a single rubber material in the case where the first portion 11 is composed of the rubber material. When the first portion 11 is made of a plurality of rubber materials, the loss tangent tan δ1 of the first portion 11 is an average value obtained by averaging the weights obtained by weighting the loss tangtan δ1 of the rubber materials with the cross-sectional areas of the rubber materials. The same applies to other loss tangent tan delta.

In a more preferred embodiment, the loss tangent tan δ1 at 70 ℃ of the first portion 11 is 1.0 to 2.0 times the loss tangent tan δ2 at 70 ℃ of the second portion 12. By making the loss tangent tan δ1 at 70 ℃ of the first portion 11 1.0 times or more the loss tangent tan δ2 at 70 ℃ of the second portion 12, the vibration suppressing effect of the tread portion 2 can be reliably exhibited. From such a viewpoint, the loss tangent tan δ1 at 70 ℃ of the first portion 11 is more preferably 1.1 times or more the loss tangent tan δ2 at 70 ℃ of the second portion 12.

By setting the loss tangent tan δ1 at 70 ℃ of the first portion 11 to 2.0 times or less the loss tangent tan δ2 at 70 ℃ of the second portion 12, breakage such as peeling due to excessive differences in physical properties can be suppressed, and the durability of the pneumatic tire 1 can be improved. From such a viewpoint, the loss tangent tan δ1 at 70 ℃ of the first portion 11 is more preferably 1.5 times or less the loss tangent tan δ2 at 70 ℃ of the second portion 12.

The loss tangent tan δ1 at 70℃of the first portion 11 is preferably 0.4 to 0.7 times the loss tangent tan δA at 30℃of the tread rubber 2G. By making the loss tangent tan δ1 at 70 ℃ of the first portion 11 0.4 times or more the loss tangent tan δa at 30 ℃ of the tread rubber 2G, vibration of the tread portion 2 can be reduced while maintaining the rolling resistance performance of the pneumatic tire 1.

By making the loss tangent tan δ1 at 70 ℃ of the first portion 11 0.7 times or less the loss tangent tan δa at 30 ℃ of the tread rubber 2G, vibration of the tread portion 2 can be reduced while suppressing high-speed durability performance of the pneumatic tire 1.

The loss tangent tan δ1 at 70 ℃ of the first portion 11 is preferably 0.14 or more. By setting the loss tangent tan δ1 at 70 ℃ of the first portion 11 to 0.14 or more, vibration of the tread portion 2 can be reliably suppressed, and generation of noise can be reduced. From such a viewpoint, the loss tangent tan δ1 at 70 ℃ of the first portion 11 is more preferably 0.15 or more, and still more preferably 0.20 or more.

The loss tangent tan delta at 30 ℃ of the first part 11 is preferably 0.4 to 0.7 times the loss tangent tan delta at 30 ℃ of the tread rubber 2G. By setting the loss tangent tan δ of the first portion 11 to 0.4 times or more the loss tangent tan δ of the tread rubber 2G, vibration of the tread portion 2 can be reduced. By setting the loss tangent tan δ of the first portion 11 to 0.7 times or less the loss tangent tan δ of the tread rubber 2G, the rolling resistance of the tire 1 can be reduced.

In the tire 1 of the present embodiment, the effect of the superposition of the carcass cord 6B having the twist factor K of 2000 to 2500 and the rubber of the first portion 11 having the loss tangent tan δ can easily reduce the noise in the vehicle without causing an increase in rolling resistance.

The loss tangent tan delta at 30 ℃ of the first part 11 is preferably 0.4 to 0.7 times the loss tangent tan delta at 30 ℃ of the base rubber.

By making the loss tangent tan δ of the first portion 11 0.4 times or more the loss tangent tan δ of the base rubber, the vibration of the tread portion 2 can be reduced. By making the loss tangent tan δ of the first portion 11 0.7 times or less the loss tangent tan δ of the base rubber, the rolling resistance of the tire 1 can be reduced.

The loss tangent tan delta 2 at 70 deg.c of the second part 12 is preferably equal to the loss tangent tan delta 1 at 70 deg.c of the first part 11. Such an inner rubber 10 can integrally form the first portion 11 and the second portion 12, contributing to a reduction in manufacturing cost of the pneumatic tire 1.

The loss tangent tan δa of the tread rubber 2G at 30 ℃ is preferably 0.30 or less. By setting the loss tangent tan δa of the tread rubber 2G at 30 ℃ to 0.30 or less, the rolling resistance can be reduced, and the burnup performance of the pneumatic tire 1 can be improved. From such a viewpoint, the loss tangent tan δa of the tread rubber 2G at 30 ℃ is more preferably 0.25 or less, and still more preferably 0.20 or less.

In the case where the tread portion 2 is composed of a plurality of rubber materials, the loss tangent tan δa of the tread rubber 2G means the loss tangent of the rubber material (for example, the top rubber 2A) constituting the ground contact surface 2 s. In addition, the base rubber 2B preferably has a loss tangent tan δb at 70 ℃ that is smaller than that tan δa of the top rubber 2A at 30 ℃. Such tread portion 2 contributes to improvement in rolling resistance performance while maintaining good high-speed durability performance of the pneumatic tire 1.

The loss tangent tan δb of the base rubber 2B at 70 ℃ is preferably 0.21 or less. By setting the loss tangent tan δb of the base rubber 2B at 70 ℃ to 0.21 or less, it is possible to contribute to suppressing heat generation at the tread portion 2 during running and to maintain good rolling resistance performance of the pneumatic tire 1. From such a viewpoint, the loss tangent tan δb of the base rubber 2B at 70 ℃ is more preferably 0.20 or less.

Fig. 9 is a cross-sectional view of the tread portion 2 of the other embodiment in the vicinity of the first tread end T1. As shown in fig. 9, the first portion 11 of the inner rubber 10 of this embodiment includes: an inner liner 16 made of a rubber material having air impermeability (hereinafter referred to as a first rubber material), and an additional layer 17 disposed between the inner liner 16 and the carcass 6. The additional layer 17 is made of a second rubber material different from the first rubber material. As the second rubber material, for example, a rubber material having air permeability is used. That is, the first portion 11 of this embodiment is formed by compounding a rubber material having air impermeability and a rubber material having air permeability.

In this embodiment, the first portion 11 includes the additional layer 17, whereby various performances can be improved. For example, as the second rubber material constituting the additional layer 17, a rubber material having a larger loss tangent tan δ than the first rubber material constituting the inner liner 16 may be used. The maximum value of the loss tangent tan δ1 of the first portion 11 in this case is the loss tangent tan δ of the additional layer 17. The maximum value of the loss tangent tan δ2 of the second portion 12 corresponds to the loss tangent tan δ of the inner liner 16. This can further absorb vibrations of the tread portion 2 during running on the road surface, and can further reduce in-vehicle noise.

The rubber material having air impermeability preferably has a loss tangent tan delta at 70 ℃ of 0.14 or more. Thereby, the vibration of the tread portion 2 is further suppressed.

The arrangement position of the additional layer 17 is not limited to the configuration shown in fig. 9. Fig. 10 is a cross-sectional view of the tread portion 2 of another embodiment in the vicinity of the first tread end T1. As shown in fig. 10, the additional layer 17 may be disposed inside the inner liner 16 in the tire radial direction. The additional layer 17 constitutes, for example, a part of the tire inner cavity surface 1A.

As shown in fig. 9 and 10, even in the case where the first portion 11 of the inner rubber 10 includes the additional layer 17, the first thickness t1 corresponds to the thickness from the inner surface 6i of the carcass 6 to the tire inner cavity surface 1A in the tread portion 2.

Fig. 11 shows an enlarged cross-sectional view of a sidewall portion 3 according to another embodiment of the present invention. As shown in fig. 11, the second portion 12 of this embodiment includes: an inner liner 16 made of a first rubber material having air impermeability, and an intermediate layer 18 disposed between the inner liner 16 and the carcass 6. In fig. 11, dots are applied to this intermediate layer 18. The intermediate layer 18 is composed of a rubber material different from the first rubber material. The intermediate layer 18 may be made of, for example, the same second rubber material as the additional layer 17 of the first portion 11 described with reference to fig. 9 and 10. By including such an intermediate layer 18 in the second portion 12, the above-described vibration generated in the tread portion 2 can be further suppressed from being transmitted to the vehicle side. The intermediate layer 18 may be made of a rubber material different from the first rubber material and the second rubber material.

The intermediate layer 18 overlaps with the belt layer 8 in the tire axial direction, for example. In a preferred form, the intermediate layer 18 overlaps the belt layer 7 in the tire axial direction. The intermediate layer 18 may also be connected to the first portion 11 of the inner rubber 10. The intermediate layer 18 extends, for example, to a position on the inner side in the tire radial direction than the outer end of the turn-up portion 6b of the carcass 6 in the tire radial direction. In other words, in this embodiment, the intermediate layer 18 overlaps the folded portion 6b in the tire radial direction. Such an intermediate layer 18 helps to further reduce in-vehicle noise.

Although some embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described specific embodiments, and may be implemented in various forms.

[ Additionally remembered ]

The present invention includes the following aspects.

[ Invention 1]

A pneumatic tire, wherein,

The pneumatic tire includes:

a tread portion;

A pair of sidewall portions;

a pair of bead portions;

A carcass extending between the pair of bead portions; and

An inner rubber extending between the pair of bead portions on an inner side of the carcass;

The inner rubber includes: a first portion extending at a first thickness in the tread portion and a second portion extending at a second thickness in the pair of sidewall portions,

The first thickness is greater than the second thickness,

In the radial cross section of the tire, the cross section of the inner rubber is 1.5 to 10% of the cross section of the cavity of the pneumatic tire.

[ Invention 2]

The pneumatic tire according to the invention 1, wherein,

The average value of the first thickness is 1.5 to 3.5 times the average value of the second thickness.

[ Invention 3]

The pneumatic tire according to the invention 1 or 2, wherein,

The average value of the first thickness is 2.0-4.5 mm.

[ Invention 4]

The pneumatic tire according to any one of the present invention 1 to 3, wherein,

In the pneumatic tire, the cross-sectional width is 205-325 mm, the flatness is 25-65%, and the rim diameter is 16-22 inches.

[ Invention 5]

The pneumatic tire according to any one of the present invention 1 to 4, wherein,

The tread portion includes: a first tread end, a tire equator, and a first shoulder circumferential groove disposed between the tire equator and the first tread end,

The first portion of the inner rubber has an outer end in the tire axial direction at a position closer to the first tread end than the tire equator,

The outer end is located axially outward of the first shoulder circumferential groove.

[ Invention 6]

The pneumatic tire according to any one of the present invention 1 to 5, wherein,

The tread portion includes tread rubber constituting a ground contact surface,

The loss tangent tan delta 1 at 70 ℃ of the first part is greater than or equal to the loss tangent tan delta 2 at 70 ℃ of the second part and less than or equal to the loss tangent tan delta A at 30 ℃ of the tread rubber.

[ Invention 7]

The pneumatic tire according to any one of the present invention 1 to 6, wherein,

The above tread portion includes a plurality of circumferential grooves extending continuously in the tire circumferential direction,

The maximum value of the first thickness of the first portion is 0.25 to 0.60 times the maximum value of the groove depths of the plurality of circumferential grooves.

[ Invention 8]

The pneumatic tire according to claim 7, wherein,

The tread portion includes tread rubber constituting a ground contact surface,

The volume of the inner rubber is 0.30 to 0.50 times the volume of the tread rubber.

[ Invention 9]

The pneumatic tire according to the invention 7 or 8, wherein,

The first portion is formed by compounding a rubber material having air impermeability and a rubber material having air permeability.

[ Invention 10]

The pneumatic tire according to any one of the present invention 1 to 9, wherein,

The pneumatic tire has an outer diameter of 660mm or more in a normal state in which the pneumatic tire is assembled on a normal rim and is filled with a normal internal pressure and is not loaded,

The tread portion has a plurality of circumferential grooves extending continuously in the tire circumferential direction,

The total of the widths of the plurality of circumferential grooves in the tire axial direction is 25 to 30% of the tread contact width.

[ Invention 11]

The pneumatic tire according to the present invention 10, wherein,

The cross-sectional width in the normal state is 225mm or more.

[ Invention 12]

The pneumatic tire according to the invention 11, wherein,

The length of the first portion in the tire axial direction is 65% to 85% of the cross-sectional width.

[ Invention 13]

The pneumatic tire according to any one of the present invention 10 to 12, wherein,

The first thickness is 0.45% or more of the outer diameter.

[ Invention 14]

The pneumatic tire according to any one of the present invention 1 to 13, wherein,

The above-mentioned carcass comprises carcass cords,

The carcass cord has a twist multiplier of 2000 to 2500.

[ Invention 15]

The pneumatic tire of claim 14, wherein,

The tread portion includes tread rubber constituting a ground contact surface,

The loss tangent tan delta at 70 ℃ of the first part is less than or equal to the loss tangent tan delta at 30 ℃ of the tread rubber.

Claims (15)

1.A pneumatic tire, wherein,

The pneumatic tire includes:

a tread portion;

A pair of sidewall portions;

a pair of bead portions;

A carcass extending between the pair of bead portions; and

An inner rubber extending between the pair of bead portions inside the carcass;

The inner rubber includes: a first portion extending at a first thickness at the tread portion and a second portion extending at a second thickness at the pair of sidewall portions,

The first thickness is greater than the second thickness,

In the radial section of the tire, the sectional area of the inner rubber is 1.5 to 10% of the sectional area of the inner cavity of the pneumatic tire.

2. The pneumatic tire of claim 1, wherein,

The average value of the first thickness is 1.5-3.5 times of the average value of the second thickness.

3. The pneumatic tire of claim 1 or 2, wherein,

The average value of the first thickness is 2.0-4.5 mm.

4. A pneumatic tire as in any one of claims 1 to 3, wherein,

In the pneumatic tire, the cross-sectional width is 205-325 mm, the flatness ratio is 25-65%, and the rim diameter is 16-22 inches.

5. The pneumatic tire of any one of claims 1-4, wherein,

The tread portion includes: a first tread end, a tire equator, and a first shoulder circumferential groove disposed between the tire equator and the first tread end,

The first portion of the inner rubber has an outer end in the tire axial direction at the first tread end side from the tire equator,

The outer end is located axially outward of the tire than the first shoulder circumferential groove.

6. The pneumatic tire of any one of claims 1-5, wherein,

The tread portion includes tread rubber constituting a ground contact surface,

The loss tangent tan delta 1 at 70 ℃ of the first portion is greater than or equal to the loss tangent tan delta 2 at 70 ℃ of the second portion and less than or equal to the loss tangent tan delta a at 30 ℃ of the tread rubber.

7. The pneumatic tire of any one of claims 1-6, wherein,

The tread portion includes a plurality of circumferential grooves extending continuously in the tire circumferential direction,

The maximum value of the first thickness of the first portion is 0.25 to 0.60 times the maximum value of the groove depths of the plurality of circumferential grooves.

8. The pneumatic tire of claim 7, wherein,

The tread portion includes tread rubber constituting a ground contact surface,

The volume of the inner rubber is 0.30-0.50 times of the volume of the tread rubber.

9. The pneumatic tire of claim 7 or 8, wherein,

The first portion is formed by compounding a rubber material having air impermeability and a rubber material having air permeability.

10. The pneumatic tire of any one of claims 1 to 9, wherein,

The pneumatic tire has an outer diameter of 660mm or more in a normal state in which the pneumatic tire is assembled on a normal rim and is filled with a normal internal pressure and is not loaded,

The tread portion has a plurality of circumferential grooves extending continuously in the tire circumferential direction,

The total of the widths of the plurality of circumferential grooves in the tire axial direction is 25 to 30% of the tread ground contact width.

11. The pneumatic tire of claim 10, wherein,

The cross-sectional width in the normal state is 225mm or more.

12. The pneumatic tire of claim 11, wherein,

The length of the first portion in the tire axial direction is 65% -85% of the cross-sectional width.

13. The pneumatic tire of any one of claims 10-12, wherein,

The first thickness is 0.45% or more of the outer diameter.

14. The pneumatic tire of any one of claims 1-13, wherein,

The carcass includes carcass cords that,

The twist factor of the carcass cord is 2000-2500.

15. The pneumatic tire of claim 14, wherein,

The tread portion includes tread rubber constituting a ground contact surface,

The first portion has a loss tangent tan delta at 70 ℃ of 30 ℃ or less of the tread rubber.