pneumatic tires

Abstract

Pneumatic tires included: a ring-shaped tread section (1) extending in the circumferential direction of the tire; a pair of sidewall sections (2) arranged on both sides of the running surface section (1); a pair of tire bead sections (3) arranged on an inside in the tire radial direction of the sidewall sections (2); a groove pattern formed on the tread section (1); and a strip-shaped, sound-absorbing element (6) which is bonded via an adhesive layer (5) along the circumferential direction of the tire to an area of ​​an inner tire surface (4) corresponding to the tread section (1), wherein, If a first ground contact area (A1) is specified between a ground contact edge (E1) of the tire on one side in the tire width direction and a tire equatorial plane (E0), and a second ground contact area (A2) is defined between a ground contact edge (E2) of the tire on the other side in the tire width direction and the tire equatorial plane (E0), the groove area ratio of the first ground contact area (A1) is greater than the groove area ratio of the second ground contact area (A2), and the sound-absorbing element (6) is arranged in a position that is offset with respect to the tire width direction such that a centroid (G) of a cross-section of the sound-absorbing element (6) in a plane encompassing a tire axis is located within the first ground contact area (A1).where the groove area ratio of the first ground contact area (A1) is the ratio of the total groove area of ​​the first ground contact area (A1) to the total area of ​​the first ground contact area (A1), , the entire groove area of ​​the first ground contact area (A1) is the total sum of the area of ​​all grooves in the first ground contact area (A1), the groove area ratio of the second ground contact area (A2) is the ratio of the total groove area of ​​the second ground contact area (A2) to the total area of ​​the second ground contact area (A2), and the total groove area of ​​the second ground contact area (A2) is the sum of the areas of all grooves in the second ground contact area (A2), wherein the sound-absorbing element (6) is a single sound-absorbing element (6) extending in the circumferential direction of the tire.

Description

Technical field

[0001] The present invention relates to a pneumatic tire with a strip-shaped, sound-absorbing element that is glued to an area of ​​the inner surface of the tire corresponding to the tread section, and more precisely relates to a pneumatic tire that is able to eliminate weight asymmetry between the two sides of the tire's equatorial plane and to reduce peeling of the sound-absorbing element. State of the art

[0002] In pneumatic tires, one cause of noise is cavity resonance, which is caused by the vibration of the air filling the tire. As a tire rolls, uneven road surfaces cause the tread to vibrate. These vibrations of the tread cause the air inside the tire to vibrate, creating cavity resonance.

[0003] It has been proposed that one method for reducing this cavity resonance is to provide a sound-dampening element in the cavity formed between the tire and the wheel rim. More precisely, a strip-shaped sound-dampening element is glued to an area of ​​the inner tire surface corresponding to the tread section. Prior art patents include JP S64 56203 A, US 2005 / 0205183 A1, JP 2005-212524 A, JP 2005-26290 A, and JP 2013-112062 A.

[0004] However, if a strip-shaped, sound-absorbing element is glued to an area of ​​the tire's inner surface corresponding to the tread section, the problem of the sound-absorbing element peeling off can occur when the tire is in use. In particular, with pneumatic tires where the groove area ratio on the tread section differs on the two sides of the tire's equatorial plane, creating a weight imbalance between these two sides, this peeling of the sound-absorbing element tends to be more pronounced when a strip-shaped, sound-absorbing element is glued to the area of ​​the tire's inner surface corresponding to the tread section. Technical problem

[0005] An objective of the present invention is to provide a pneumatic tire with a strip-shaped sound-absorbing element that is glued to an area of ​​the inner surface of the tire, which is able to eliminate weight asymmetry between the two sides of the tire's equatorial plane and to reduce peeling of the sound-absorbing element. Solution to the problem

[0006] The pneumatic tire according to the invention, for achieving the aforementioned objective, comprises: an annular tread section extending in the circumferential direction of the tire, a pair of sidewall sections arranged on both sides of the tread section, and a pair of bead sections arranged on the inner surface of the sidewall sections in the radial direction of the tire. A groove pattern is formed on the tread section, and a strip-shaped, noise-dampening element is bonded via an adhesive layer along the circumferential direction of the tire to an area of ​​the inner surface of the tire corresponding to the tread section. A first ground contact area is defined between the ground contact edge of the tire on one side in the tire width direction and the tire equator plane, and a second ground contact area is defined between the ground contact edge of the tire on the other side in the tire width direction and the tire equator plane.The groove area ratio of the first contact patch is greater than the groove area ratio of the second contact patch, and the sound-dampening element is positioned offset with respect to the tire width direction such that the centroid of a cross-section of the sound-dampening element lies within the first contact patch in a plane encompassing the tire axis. The groove area ratio of the first contact patch is the ratio of the total groove area of ​​the first contact patch to the total area of ​​the first contact patch, and the total groove area of ​​the first contact patch is the sum of the areas of all grooves within the first contact patch.The groove area ratio of the second ground contact area is accordingly the ratio of the total groove area of ​​the second ground contact area to the total area of ​​the second ground contact area, and the total groove area of ​​the second ground contact area is the sum of the areas of all grooves in the second ground contact area. The sound-absorbing element is a single sound-absorbing element that extends in the circumferential direction of the tire. Advantageous effects of the invention

[0007] The inventors conducted thorough research into the behavior of the tread section and the adhesion of the sound-dampening element in pneumatic tires. These tires featured a strip-shaped sound-dampening element bonded across the tread layer along the tire's circumference on the inner surface, corresponding to the tread surface. Due to the groove area ratio of the tread section, there was a weight imbalance between the two sides of the tire's equatorial plane. It was found that in pneumatic tires exhibiting the weight imbalance described above, this imbalance generated stress in the tread section during high-speed driving, and this stress promoted the peeling of the sound-dampening element.

[0008] In other words, in the present invention, the groove area ratio of the first ground contact area is greater than the groove area ratio of the second ground contact area, and the sound-absorbing element is arranged in a position offset in the tire width direction such that the centroid of the cross-section of the sound-absorbing element is positioned within the first ground contact area in a plane encompassing the tire axis. Therefore, the weight imbalance between the two sides of the tire's equatorial plane, resulting from the difference in the groove area ratio of the first ground contact area and the groove area ratio of the second ground contact area, can be eliminated. Furthermore, the stress occurring in the tread section due to the weight imbalance during high-speed driving can be reduced, and the resulting peeling of the sound-absorbing element can be minimized.As a result, the noise-reducing effect of the sound-absorbing element can be maintained for a long time.

[0009] In the present invention, the tire's ground contact edge is the position of the edge in the tire's axial direction within the ground contact area when the tire is mounted on a standard rim, inflated to the standard internal pressure, placed vertically on a horizontal surface, and subjected to the standard load. The ground contact width is the width in the tire's axial direction within the ground contact area. A "standard rim" is defined by a standard for each tire according to a standards system that includes standards on which tires are based. For example, a "standard rim" is defined by the Japan Automobile Tyre Manufacturers Association (JATMA), a "design rim" is defined by the Tire and Rim Association (TRA), and a "measurement rim" is defined by the European Tyre and Rim Technical Organisation (ETRTO). However, if the tire is to be mounted on a new vehicle, the original wheel on which the tire is mounted must be used."Regular internal pressure" is the air pressure defined by standards for each tire according to a standard system that includes standards on which tires are based. It refers to a "maximum air pressure" in the case of JATMA, the maximum value in the "TIRE ROAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table in the case of TRA, and the "INFLATION PRESSURE" in the case of ETRTO. However, if the tire is to be fitted to a new vehicle, the air pressure must be the one specified on the vehicle."Regular load" is the load defined by standards for each tire according to a standards system that includes the standards on which the tires are based. It refers to a "maximum load capacity" in the case of JATMA, the maximum value in the "TIRE ROAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table in the case of TRA, and "LOAD CAPACITY" in the case of ETRTO. However, the load must be 88% of this load for a tire on a passenger vehicle. In the case of a tire fitted to a new vehicle, the wheel load must be determined by dividing the front and rear axle loads specified in the vehicle type approval certificate by two.

[0010] In the present invention, preferably the entire groove area of ​​the second ground contact area comprises 70 to 92% of the entire groove area of ​​the first ground contact area, and the distance from the centroid of the sound-absorbing element to the tire equator plane is 5 to 30% of the ground contact width of the tread section. In other words, the present invention is particularly effective when the difference between the entire groove area of ​​the first ground contact area and the entire groove area of ​​the second ground contact area lies within the above range, and when the distance from the centroid of the sound-absorbing element to the tire equator plane lies within the above range, excellent performance is demonstrated.

[0011] In the present invention, the pneumatic tire preferably has a predetermined mounting direction with respect to a vehicle, the first contact area being located on the inside of the vehicle and the second contact area being located on the outside of the vehicle. In other words, with the predetermined mounting direction, wet performance is ensured in the pneumatic tire by arranging the first contact area with a comparatively large groove area ratio on the inside of the vehicle. By arranging the second contact area with a comparatively small groove area ratio on the outside of the vehicle, steering stability on dry road surfaces can also be improved. More precisely, in this case, the groove area ratio of the first contact area is preferably between 30 and 43%, and the groove area ratio of the second contact area is between 25 and 35%.

[0012] In the pneumatic tire with the intended mounting direction relative to a vehicle, a belt layer, an inner belt edge cover layer that locally covers the edge of the belt layer on the inside of the vehicle, and an outer belt edge cover layer that locally covers the edge of the belt layer on the outside of the vehicle are preferably embedded in the tread section, and the stiffness of the inner belt edge cover layer is greater than the stiffness of the outer belt edge cover layer. High-performance tires are normally fitted to vehicles with a negative camber angle, and it is necessary that sufficient durability at high speeds be provided under these operating conditions.However, due to the negative camber angle, heat buildup can easily occur in positions on the inner side of the tread section of the vehicle. This heat buildup negatively affects the adhesive layer of the sound-absorbing element, causing it to peel away. In this respect, if the stiffness of the inner belt edge cover layer is greater than that of the outer belt edge cover layer, deformation of the tread section on the inner side of the vehicle is reduced, thus minimizing heat buildup in this area and effectively preventing the peeling of the sound-absorbing element's adhesive.

[0013] Preferably, means include making the stiffness of the inner belt edge cover layer greater than the stiffness of the outer belt edge cover layer, making the width of the inner belt edge cover layer greater than the width of the outer belt edge cover layer, or making the number of layers of the inner belt edge cover layer greater than the number of layers of the outer belt edge cover layer. In this case, an asymmetrical structure of the inner and outer belt edge cover layers can be easily formed, and peeling of the adhesive of the sound-absorbing element can be effectively prevented.

[0014] The sound-absorbing element preferably has a uniform thickness in at least the area corresponding to the contact surface of the sound-absorbing element in a cross-section perpendicular to the longitudinal direction, and its cross-sectional shape is constant in the longitudinal direction. In this way, the capacity of the sound-absorbing element per unit floor contact area is maximized, and excellent sound attenuation can be achieved. The sound-absorbing element can also be easily machined to this shape, thus keeping manufacturing costs low.

[0015] Preferably, the volume of the sound-absorbing element, as a percentage of the volume of the cavity formed within the tire when the tire is mounted on the rim, is greater than 20%. Increasing the volume of the sound-absorbing element in this way achieves excellent noise reduction and, furthermore, ensures good adhesion over a long period, even with a large sound-absorbing element. The cavity volume is the volume of the cavity formed between the tire and the rim when the tire is mounted on the standard rim and inflated to its standard internal pressure.

[0016] The hardness of the sound-absorbing element is preferably between 60 and 170 N / mm², and the tensile strength of the sound-absorbing element is between 60 and 180 kPa. A sound-absorbing element with these physical properties exhibits excellent resistance to shear stress. The hardness of the sound-absorbing element is measured using Method D (method for calculating the thickness after constant 25% compression for 20 seconds) according to JIS-K6400-2 "Flexible cellular polymeric materials - Physical properties - Part 2: Determination of hardness and stress-strain characteristics in compression".Furthermore, the tensile strength of the sound-absorbing element is measured according to JIS-K6400-5 “Flexible cellular polymeric materials - Physical properties - Part 5: Determination Of Tensile Strength, Elongation At Break and Tear Strength”.

[0017] Preferably, the adhesive layer is formed from double-sided adhesive tape, and its peel strength is in the range of 8 to 40 N / 20 mm. This allows for easy application of the sound-dampening element and disassembly when the tire is disposed of, while maintaining good adhesion of the sound-dampening element. The peel strength of the double-sided adhesive tape is measured according to JIS Z0237. In other words, the double-sided adhesive tape is coated by applying a 25 µm thick PET film. Test specimens are produced by cutting the coated adhesive sheet into rectangles measuring 20 mm × 200 mm. The peel layer is removed from the test specimen, and the exposed adhesive surface is placed on a stainless steel plate (SUS304, surface finish BA) as the bonding surface. A 2 kg roller is then rolled back and forth over this surface.After storing the test specimen in an environment of 23°C and RH 50% for 30 minutes, the test specimen must be peeled off the SUS board at 180° in an environment of 23°C, RH 50% at a peeling speed of 300 mm / minute using a tensile testing machine to measure peel adhesion strength in accordance with JIS Z0237. Brief description of the drawings Fig. Figure 1 is a perspective cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. Fig. Figure 2 is a cross-sectional view at the equator line, representing an air tire according to an embodiment of the present invention. Fig. Figure 3 is a meridian cross-sectional view showing an air tire according to an embodiment of the present invention. Fig.Figure 4 is a flattened view showing a tread pattern of a pneumatic tire according to an embodiment of the present invention. Fig. Figure 5 is a meridian cross-sectional view showing an air tire according to another embodiment of the present invention. Fig. Figure 6 is a meridian cross-sectional view showing a pneumatic tire according to another embodiment of the present invention. Fig. Figure 7 is a meridian cross-sectional view showing a pneumatic tire according to another embodiment of the present invention. Fig. Figure 8 is a meridian cross-sectional view showing a pneumatic tire according to another embodiment of the present invention. Description of embodiments

[0018] A detailed description of the configuration of the present invention is given below with reference to the accompanying drawings. Fig. Figures 1 to 4 illustrate a pneumatic tire according to an embodiment of the present invention. The pneumatic tire is a tire with a specified mounting direction (inside / outside) when mounted on a vehicle. Fig. 1 to 4 corresponds to INSIDE the inside of a vehicle when the tire is mounted on a vehicle, and OUTSIDE the outside of a vehicle when the tire is mounted on a vehicle. This mounting direction in relation to the vehicle is indicated on the tire's outer surface.

[0019] In Fig.1 to 3 the pneumatic tire according to the present embodiment is equipped with an annular tread section 1 extending in the circumferential direction of the tire, a pair of sidewall sections 2 arranged on both sides of the tread section 1, and a pair of bead sections 3 arranged on the inner sides of the sidewall sections 2 in the radial direction of the tire.

[0020] In the pneumatic tire, as described above, a strip-shaped, sound-absorbing element 6 is bonded to an area of ​​the inner tire surface 4 corresponding to the tread section 1 via an adhesive layer 5 along the tire's circumference. The sound-absorbing element 6 is configured from a porous, open-cell material and exhibits predetermined sound-absorbing properties based on its porous structure. Urethane foam can be used as the porous material of the sound-absorbing element 6. A paste-like adhesive or double-sided adhesive tape can be used as the adhesive layer 5.

[0021] As in Fig.As shown in Figure 4, the required groove pattern is formed in tread section 1. In other words, the four longitudinal grooves 21 (21a, 21b, 21c, 21d), which extend in the circumferential direction of the tire, are formed in tread section 1. These longitudinal grooves 21 divide and form five rows of rib sections 22. The longitudinal groove 21d, which is located on the outer side of the vehicle, has a narrower groove width than the other longitudinal grooves 21a to 21c. Additionally, lug grooves 23, inclined grooves 24, or kerf grooves 25, which run in the tire width direction, are formed in the rib sections 22.

[0022] If a first ground contact area A1 is specified between the ground contact edge E1 of the tire on one side in the tire width direction (the inside of the vehicle) and the tire equator plane E0, and a second ground contact area A2 is specified between the ground contact edge E2 of the tire on the other side in the tire width direction (the outside of the vehicle) and the tire equator plane E0, the groove area ratio R1 of the first ground contact area A1 is set larger than the groove area ratio R2 of the second ground contact area A2.

[0023] The groove area ratio R1 of the first ground contact area A1 and the groove area ratio R2 of the second ground contact area A2 are specified based on the groove pattern, including the circumferential grooves 21, the lug grooves 23, the inclined grooves 24, and the kerf grooves 25 formed in the tread section 1. More precisely, as in Fig.As shown in Figure 4, if the width of the first ground contact area A1 is W1, the width of the second ground contact area A2 is W2, and the tire circumference length is L, the total area S1 of the first ground contact area A1 and the total area S2 of the second ground contact area A2 are calculated as S1 = W1 × L and S2 = W2 × L, respectively. The total groove area G1 of the first ground contact area A1 is the portion (hatched section) of the tread surface in the first ground contact area A1 that does not touch the ground over its entire circumference. Similarly, the total groove area G2 of the second ground contact area A2 is the portion (hatched section) of the tread surface in the second ground contact area A2 that does not touch the ground over its entire circumference. Then the groove area ratio R1 of the first ground contact area A1 and the groove area ratio R2 of the second ground contact area A2 are calculated from R1 = G1 / S1 × 100 % respectively.R2 = G2 / S2 × 100 % calculated.

[0024] On the other hand, the sound-absorbing element 6 is arranged in a position that is offset in the direction of tire width, as in Fig. Figure 3 shows that the centroid G of the cross-section of the sound-absorbing element 6 is positioned within the first ground contact area A1 in a plane encompassing the tire axis (meridian cross-section). It should be noted that a single sound-absorbing element 6 is arranged on the tread section 1 in the tire meridian cross-section and that no multiple sound-absorbing elements 6 are arranged in the tire width direction.

[0025] In the pneumatic tire configured in this way, the strip-shaped, sound-dampening element 6 is bonded via the adhesive layer 5 along the tire's circumferential direction to an area of ​​the inner tire surface 4 corresponding to the tread section 1. The groove area ratio R1 of the first ground contact area A1 is greater than the groove area ratio R2 of the second ground contact area A2, and the sound-dampening element 6 is positioned offset in the tire's width direction such that the centroid G of the cross-section of the sound-dampening element 6 is located within the first ground contact area A1 in a plane encompassing the tire axis. Therefore, the weight asymmetry between the two sides of the tire's equatorial plane E0, resulting from the difference in the groove area ratio R1 of the first ground contact area A1 and the groove area ratio R2 of the second ground contact area A2, can be corrected.If there is a large weight imbalance in tread section 1, the relatively heavy section expands significantly due to centrifugal force at high speeds, resulting in stress in tread section 1. However, by correcting the weight imbalance, the stress in tread section 1 during high speeds is reduced, thus minimizing the peeling of the sound-absorbing element 6 caused by this stress. As a result, the noise-reducing effect of the sound-absorbing element 6 can be maintained for a long time.

[0026] Furthermore, by correcting the weight imbalance in tread section 1, improved steering stability at high speeds can be achieved. In other words, if a weight imbalance exists in tread section 1, at high speeds of, for example, 270 km / h or more, the road contact pattern on both sides of the tire's equator plane E0 becomes asymmetrical due to centrifugal force on tread section 1, and steering stability is reduced. However, by correcting the weight imbalance, excellent steering stability at high speeds can be demonstrated.

[0027] Fig. Figures 5 and 6 each illustrate pneumatic tires according to other embodiments of the present invention. In the embodiments of Fig. 5 and Fig. 6 The width of the sound-absorbing element 6 is smaller compared to the embodiment of Fig. 3 and the offset in its arrangement is larger. In Fig.3 the sound-absorbing element 6 is arranged such that it extends over the tire equator plane E0 on both sides, but in Fig. The sound-absorbing element 6 is located only on one side of the tire equator plane E0. In other words, the sound-absorbing element is contained within the first ground contact area A1.

[0028] In the pneumatic tire described above, the total groove area G2 of the second ground contact area A2 can be 70 to 92% of the total groove area G1 of the first ground contact area A1, and the distance D from the centroid G of the sound-absorbing element 6 to the tire equator plane E0 can be 5 to 30% of the ground contact width TCW of the tread section 1. In this case, a significant effect can be expected.

[0029] If the total groove area G2 of the second ground contact area A2 is less than 70% of the total groove area G1 of the first ground contact area A1, the wear characteristics deteriorate. Conversely, if it is greater than 92%, the difference between the two becomes small, so that the need to correct the weight imbalance is essentially eliminated. In particular, the total groove area G2 of the second ground contact area A2 is preferably 72% to 90% of the total groove area G1 of the first ground contact area A1, and more preferably it can be 75% to 90% of the total groove area G1 of the first ground contact area A1.

[0030] If the distance D from the centroid G of the sound-absorbing element 6 to the tire equator plane E0 is less than 5% of the ground contact width TCW of the tread section 1, the effect of correcting the weight imbalance is insufficient. Conversely, if it is greater than 30%, it is necessary to position the sound-absorbing element 6 on the curved section at the shoulder, thus reducing the adhesion of the sound-absorbing element 6. In particular, the distance D from the centroid G of the sound-absorbing element 6 to the tire equator plane E0 can be from 7% to 25% of the ground contact width TCW of the tread section 1, and more preferably from 10% to 20% of the ground contact width TCW of the tread section 1.

[0031] In a pneumatic tire with the intended mounting direction relative to the vehicle, as described above, wet performance is ensured by providing the first contact patch A1 with a comparatively large groove area ratio R1 on the inside of the tire, while steering stability on dry road surfaces can be improved by providing the second contact patch A2 with a comparatively small groove area ratio R2 on the outside of the tire. In this case, however, the groove area ratio R1 of the first contact patch A1 is preferably between 30 and 43%, and the groove area ratio R2 of the second contact patch A2 is between 25 and 35%. In particular, the groove area ratio R1 of the first contact patch A1 can be between 33 and 49%, and the groove area ratio of the second contact patch can be between 28 and 33%.Furthermore, the difference between the groove area ratio R1 of the first ground contact area A1 and the groove area ratio R2 of the second ground contact area A2 is preferably 4.0 percentage points or more, and more preferably 5.5 percentage points or more. By adjusting the groove area ratio R1 of the first ground contact area A1 and the groove area ratio R2 of the second ground contact area A2 to the above values, wet performance and steering stability on dry road surfaces can be balanced.

[0032] Fig. 7 and Fig. Figure 8 illustrates a pneumatic tire according to another embodiment of the present invention. Fig. 7 and Fig. 8 are components that make up the in Fig. The components shown in points 1 to 6 correspond to those marked with the same reference numbers. A detailed description of these components is omitted. As in Fig. 7 and Fig. As shown in Figure 8, the pneumatic tire of this embodiment is provided with a tread section 1 which extends in the circumferential direction of the tire to form a ring shape, a pair of sidewall sections 2 which are arranged on both sides of the tread section 1, and a pair of tire bead sections 3 which are arranged on the inside in the radial direction of the sidewall sections 2.

[0033] A strip-shaped, sound-absorbing element 6 is bonded via the adhesive layer 5 along the tire's circumferential direction to an area of ​​the inner tire surface 4 corresponding to the tread section 1. The groove area ratio R1 of the first ground contact area A1 is also set higher than the groove area ratio R2 of the second ground contact area A2, as described in each of the embodiments above. Furthermore, the sound-absorbing element 6 is positioned offset in the tire's width direction such that the centroid G of the cross-section of the sound-absorbing element 6 is located within the first ground contact area A1 in a plane encompassing the tire axis.

[0034] A carcass layer 11 is arranged between the pair of tire bead sections 3, 3. The carcass layer 11 has a plurality of reinforcing cord threads extending in the tire radial direction and is folded from the inside to the outside of the tire around a tire bead core 12, which is arranged in each of the tire bead sections 3. A bead filler 13 made of a rubber compound with a triangular cross-sectional shape is arranged on one circumference of the bead core 12. An inner liner layer 14 is applied to the inside of the carcass layer 11 along an inner surface 4 of the tire.

[0035] On the other hand, a plurality of belt layers 15 are embedded on the outer circumferential side of the carcass layer 11 in the tread section 1. These belt layers 15 comprise a plurality of reinforcing cord threads inclined with respect to the tire's circumferential direction, and the reinforcing cord threads are arranged such that the reinforcing cord threads of the different layers overlap. In the belt layers 15, the angle of inclination of the reinforcing cord threads with respect to the tire's circumferential direction is specified in a range of, for example, 10° to 40°. Steel cords are preferably used as the reinforcing cord threads of the belt layers 15.

[0036] For the purpose of improving durability at high speeds, at least one layer of a belt cover layer 16 (16a, 16b, 16c), formed by arranging reinforcing cord threads at an angle of, for example, no more than 5° with respect to the tire's circumferential direction, is embedded on the outer circumferential side of the belt layers 15. Aramid or similar organic fiber cords are used as the reinforcing cord threads of the belt cover layer 16. The belt cover layer 16 comprises a full belt cover layer 16a, which covers the belt layers 15 across their entire width, an inner belt edge cover layer 16b, which covers the edge of the belt layers 15 locally on the inside of the vehicle, and an outer belt edge cover layer 16c, which covers the edge of the belt layers 15 on the outside of the vehicle.

[0037] In Fig.7. The width of the inner belt edge cover layer 16b is greater than the width of the outer belt edge cover layer 16c, and consequently, the stiffness of the inner belt edge cover layer 16b is greater than the stiffness of the outer belt edge cover layer 16c. In Fig. 8. The number of layers (two layers) of the inner belt edge cover layer 16b is also greater than the number of layers (one layer) of the outer belt edge cover layer 16c, and as a result, the stiffness of the inner belt edge cover layer 16b is greater than the stiffness of the outer belt edge cover layer 16c.

[0038] Among pneumatic tires where the mounting direction is indicated relative to the vehicle, high-performance tires are typically fitted to vehicles with negative camber, and sufficient durability at high speeds is required under these operating conditions. However, heat buildup can easily occur in areas on the inner side of the tread section 1, and this heat buildup negatively affects the adhesive layer 5 of the sound-dampening element 6, causing peeling of the adhesive layer from the sound-dampening element 6.In this respect, if the stiffness of the inner belt edge cover layer 16b is greater than the stiffness of the outer belt edge cover layer 16c, deformation of the tread section 1 on the inside of the vehicle is reduced, so that heat build-up at this position is reduced, and peeling of the adhesive of the sound-absorbing element 6 can be effectively prevented.

[0039] In the embodiment described above, increasing the width of the inner belt edge cover layer 16b compared to the width of the outer belt edge cover layer 16c and increasing the number of layers of the inner belt edge cover layer 16b compared to the number of layers of the outer belt edge cover layer 16c were described as means of making the stiffness of the inner belt edge cover layer 16b greater than the stiffness of the outer belt edge cover layer 16c. However, increasing the number of cord threads of the inner belt edge cover layer 16b compared to the number of cord threads of the outer belt edge cover layer 16c or increasing the elastic modulus of the reinforcing cords of the inner belt edge cover layer 16b compared to the elastic modulus of the reinforcing cords of the outer belt edge cover layer 16c can also be used.

[0040] It should be noted that a description of the reinforcement structure is not included in the following. Fig.The embodiments described in points 1 to 6 above have been omitted, but it is understood that the same reinforcement structure as for Fig. 7 and Fig. 8 or another reinforcement structure can be applied.

[0041] In the pneumatic tire described above, a single sound-absorbing element 6 extends in the circumferential direction of the tire. In a cross-section perpendicular to the longitudinal direction, the sound-absorbing element 6 has a constant thickness at least in the area corresponding to the contact patch, and its cross-sectional shape is constant along the longitudinal direction. In particular, the cross-sectional shape in a cross-section perpendicular to the longitudinal direction of the sound-absorbing element 6 is preferably rectangular (including a square shape), but depending on the circumstances, it may be an inverted trapezoid, narrowing towards the side of the ground contact surface. In this way, the capacity of the sound-absorbing element 6 per unit ground contact area is increased as much as possible, and excellent sound attenuation can be achieved.The sound-absorbing element 6 can also be easily processed to have this shape, so that the manufacturing costs are low.

[0042] When the pneumatic tire described above is mounted on a rim, a cavity 7 is formed between the inner surface 4 of the tire and the rim. Preferably, the volume of the sound-absorbing element 6 is greater than 20% of the volume of the cavity 7. By increasing the volume of the sound-absorbing element 6 in this way, excellent noise reduction can be achieved, and, moreover, good adhesion can be maintained over a long period, even with a large sound-absorbing element 6. It should be noted that the width of the sound-absorbing element 6 is preferably in the range of 30 to 90% of the ground contact width. Furthermore, the sound-absorbing element 6 is preferably not annular.

[0043] The hardness of the sound-absorbing element 6 (JIS-K6400-2) is preferably from 60 to 170 N / mm², and the tensile strength of the sound-absorbing element 6 (JIS-K6400-5) is from 60 to 180 kPa. A sound-absorbing element 6 with these physical properties exhibits excellent resistance to shear stress. If the hardness or the tensile strength of the sound-absorbing element 6 is too low, its resistance is reduced. In particular, the hardness of the sound-absorbing element 6 is preferably from 70 to 160 N / mm², and more preferably from 80 to 140 N / mm². The tensile strength of the sound-absorbing element 6 is also preferably from 75 to 165 kPa, and more preferably from 90 to 150 kPa.

[0044] The peel strength (JIS-Z0327: 2009) of the adhesive layer 5 is preferably in the range of 8 to 40 N / 20 mm. This ensures that the application of the sound-dampening element 6 and its subsequent disassembly when the tire is disposed of can be carried out smoothly, while maintaining good adhesion of the sound-dampening element 6. In other words, the adhesion of the sound-dampening element 6 becomes unstable if the peel strength of the adhesive layer 5 is too low, and conversely, if the peel strength of the adhesive layer 5 is too high, it becomes difficult to change the attachment position during the process of bonding the sound-dampening element 6 and to remove the sound-dampening element 6 when the tire is disposed of. More precisely, the peel strength of the adhesive layer 5 is preferably from 9 to 30 N / 20 mm and more preferably from 10 to 25 N / 20 mm.

[0045] In each of the embodiments described above, it was explained that a significant effect can be achieved if the groove area ratio and the position of the sound-absorbing element are both appropriately adapted for pneumatic tires where the mounting direction is intended to be relative to the vehicle. However, the present invention can also be applied to pneumatic tires where the mounting direction is not intended to be relative to the vehicle. Examples of implementation

[0046] Pneumatic tires are manufactured with a tire size of 275 / 35R20 100Y, an annular tread section extending in the circumferential direction of the tire, a pair of sidewall sections arranged on both sides of the tread section, and a pair of bead sections arranged on the inner surface of the sidewall sections in the radial direction of the tire. A groove pattern was formed on the tread section, and a strip-shaped, noise-dampening element was bonded along the circumferential direction of the tire to an area of ​​the inner surface of the tire corresponding to the tread section. The position of the noise-dampening element was varied to produce Comparative Example 1 and Exemplary Embodiments 1 to 5.

[0047] The pneumatic tires described above were designed for directional mounting on the vehicle. The groove area ratio of the first contact patch, located on the inside of the vehicle, was 35%, and the groove area ratio of the second contact patch, located on the outside of the vehicle, was 30%. The total groove area of ​​the second contact patch was 85% smaller than the total groove area of ​​the first contact patch. In the pneumatic tires described above, the belt plies, the inner belt edge cover ply (locally covering the edge of the belt plies on the inside of the vehicle), and the outer belt edge cover ply (locally covering the edge of the belt plies on the outside of the vehicle) were embedded in the tread section.

[0048] In comparative example 1, the centroid of the cross-section of the sound-absorbing element was located in a plane encompassing the tire axis, on the tire equator plane. Furthermore, the inner belt edge cover layer and the outer belt edge cover layer had the same structure.

[0049] In embodiments 1 to 3, the position of the sound-absorbing element was offset in the tire width direction such that the centroid of the cross-section of the sound-absorbing element is located in the first ground contact area in a plane encompassing the tire axis, as shown in Fig. Figure 3 shows the distance D from the centroid of the sound-absorbing element to the tire equator plane as a percentage of the ground contact width TCW of tread section 1. Furthermore, the inner belt edge cover layer and the outer belt edge cover layer had the same structure.

[0050] In embodiment 4, the sound-absorbing element was arranged in a position offset in the tire width direction, as shown in Fig. Figure 7 shows that the centroid of the cross-section of the sound-absorbing element was positioned within the first ground contact area in a plane encompassing the tire axle. Furthermore, the width of the inner belt edge cover layer was greater than the width of the outer belt edge cover layer.

[0051] In embodiment 5, the sound-absorbing element was arranged in a position offset in the tire width direction, as shown in Fig. Figure 8 shows that the centroid of the cross-section of the sound-absorbing element was positioned within the first ground contact area in a plane encompassing the tire axle. Furthermore, the number of layers of the inner belt edge cover layer was greater than the number of layers of the outer belt edge cover layer.

[0052] The following points were common to Comparative Example 1 and Exemplary Designs 1 to 5. The cross-sectional shape of the sound-absorbing element, in a cross-section perpendicular to the longitudinal direction, was rectangular, and this cross-sectional shape was constant along the tire's circumference. The volume of the sound-absorbing element, as a percentage of the volume of the cavity formed within the tire when the tire is mounted on the rim, was 30%. The hardness of the sound-absorbing element was 91 N, and its tensile strength was 132 kPa. The peel strength of the adhesive layer was 16 N / 20 mm.

[0053] The pneumatic tires of Comparative Example 1 and Exemplary Embodiments 1 to 5 were mounted on a wheel with a rim size of 20 × 9.5J. After a 40-hour running test on a roller test rig under the conditions of an air pressure of 200 kPa, a load of 6.9 kN, and a speed of 300 km / h, they were visually inspected for peeling of the adhesive on the sound-dampening element. The results are recorded in Table 1. [Table 1-I] Comparative example 1 Example 1 Example 2 Position of the center of gravity of the sound-absorbing element On the equatorial plane of the tire In the first ground contact area ( Fig. 3) In the first ground contact area ( Fig. 3) D / TCW × 100% - 20 10 Structure of the belt edge cover layer Inside and outside are the same Inside and outside are the same Inside and outside are the same Presence / absence of peeling of the adhesive on the sound-absorbing element Available Unavailable Unavailable Performance in preventing adhesive peeling (index) - 100 88 [Table 1-II] Example 3 Example 4 Example 5 Position of the center of gravity of the sound-absorbing element In the first ground contact area ( Fig. 3) In the first ground contact area ( Fig. 7) In the first ground contact area ( Fig. 8) D / TCW × 100% 30 20 20 Structure of the belt edge cover layer Inside and outside are the same wider inside ( Fig. 7) More layers inside ( Fig. 8) Presence / absence of peeling of the adhesive on the sound-absorbing element Unavailable Unavailable Unavailable Performance in preventing adhesive peeling (index) 88 113 113

[0054] As shown in Table 1, there was a considerable occurrence of peeling of the adhesive of the sound-absorbing element in the tire of comparison example 1, but in the case of the tires of embodiments 1 to 5, no peeling of the adhesive of the sound-absorbing element was observed.

[0055] For the pneumatic tires of embodiments 1 to 5, the same running test as described above was also carried out in 10-hour increments, and the distance traveled before peeling of the adhesive on the sound-dampening element was observed was determined. The results were expressed as an index of resistance to peeling of the adhesive, with the measured value for embodiment 1 being assumed to be 100. The higher the index value, the more difficult it is for the adhesive on the sound-dampening element to peel.

[0056] Next, tires were prepared according to embodiments 6 to 12 with the same structure as embodiment 1, except that the hardness of the sound-absorbing element, the tensile strength of the sound-absorbing element, the peel strength of the adhesive layer, the groove area ratio of the first ground contact area and the groove area ratio of the second ground contact area were changed.

[0057] The presence or absence of peeling of the adhesive on the sound-dampening element and the performance in preventing peeling of the adhesive after 40 hours of running testing were evaluated for the tires according to embodiments 6 to 12 using the same methods as described above. The results are recorded in Table 2. [Table 2-I] Example 6 Example 7 Example 8 Example 9 Position of the center of gravity of the sound-absorbing element In the first ground contact area ( Fig. 3) In the first ground contact area ( Fig. 3) In the first ground contact area ( Fig. 3) In the first ground contact area ( Fig. 3) D / TCW × 100% 20 20 20 20 Structure of the belt edge cover layer Inside and outside are the same Inside and outside are the same Inside and outside are the same Inside and outside are the same Hardness of the sound-absorbing element (N) 60 170 91 91 Tensile strength of the sound-absorbing element (kPa) 60 180 132 132 Peel adhesion strength of the adhesive (N / 20 mm) 16 16 8 40 Groove area ratio of the first ground contact area (%) 35 35 35 35 Groove area ratio of the second ground contact area (%) 30 30 30 30 Presence / absence of peeling of the adhesive on the sound-absorbing element Unavailable Unavailable Unavailable Unavailable Performance in preventing adhesive peeling (index) 100 100 95 105 [Table 2-II] Example 10 Example 11 Example 12 Position of the center of gravity of the sound-absorbing element In the first ground contact area ( Fig. 3) In the first ground contact area ( Fig. 3) In the first ground contact area ( Fig. 3) D / TCW × 100% 20 20 20 Structure of the belt edge cover layer Inside and outside are the same Inside and outside are the same Inside and outside are the same Hardness of the sound-absorbing element (N) 91 91 91 Tensile strength of the sound-absorbing element (kPa) 132 132 132 Peel adhesion strength of the adhesive (N / 20 mm) 16 16 16 Groove area ratio of the first ground contact area (%) 30 43 39 Groove area ratio of the second ground contact area (%) 25 30 35 Presence / absence of peeling of the adhesive on the sound-absorbing element Unavailable Unavailable Unavailable Performance in preventing adhesive peeling (index) 100 90 95

[0058] As shown in Table 2, in the tires of embodiments 6 to 9, where the hardness of the sound-absorbing element, the tensile strength of the sound-absorbing element, and the peel strength of the adhesive layer were modified, as in Example 1, no detachment of the adhesive of the sound-absorbing element was observed after the 40-hour running test. The same results were also obtained in the tires according to embodiments 10 to 12, where the groove area ratio of the first and second ground contact areas was modified. List of reference symbols 1 tread section 2 Side wall section 3 tire bead section 4 inner tire surface 5 Adhesive layer 6 Sound-absorbing element 7 Cavity E0 Tire equator plane E1 Ground contact edge of the tire on one side E2 Ground contact edge of the tire on the other side A1 First ground contact area A2 Second ground contact area G Center of gravity

Claims

[1] Pneumatic tires comprising: an annular tread portion (1) extending in the tire circumferential direction; a pair of sidewall portions (2) arranged on both sides of the tread portion (1); a pair of tire bead portions (3) arranged on an inner side in the tire radial direction of the sidewall portions (2); a groove pattern formed on the tread portion (1); and a strip-shaped sound-damping element (6) which is bonded via an adhesive layer (5) along the tire circumferential direction to a region of a tire inner surface (4) corresponding to the tread portion (1), wherein, when a first ground contact area (A1) is specified between a ground contact edge (E1) of the tire on one side in the tire width direction and a tire equator plane (E0) and a second ground contact area (A2) is defined between a ground contact edge (E2) of the tire on the other side in the tire width direction and the tire equator plane (E0), a groove area ratio of the first ground contact area (A1) is greater than a groove area ratio of the second ground contact area (A2), and the sound-absorbing element (6) is arranged in a position offset with respect to the tire width direction such that a center of gravity (G) of a cross section of the sound-absorbing element (6) in a plane including a tire axis is located within the first ground contact area (A1),wherein the groove area ratio of the first ground contact area (A1) is the ratio of the total groove area of the first ground contact area (A1) to the total area of the first ground contact area (A1), the total groove area of the first ground contact area (A1) is the total area of all grooves in the first ground contact area (A1), the groove area ratio of the second ground contact area (A2) is the ratio of the total groove area of the second ground contact area (A2) to the total area of the second ground contact area (A2), and the total groove area of the second ground contact area (A2) is the total sum of the area of all grooves in the second ground contact area (A2), wherein the sound-absorbing element (6) is a single sound-absorbing element (6) extending in the tire circumferential direction. [2] A pneumatic tire according to claim 1, wherein a total groove area of the second ground contact area (A2) is from 70 to 90% of a total groove area of the first ground contact area (A1), and a distance (D) from the centroid (G) of the sound absorbing member (6) to the tire equatorial plane (E0) is from 5 to 30% of a ground contact width (TCW) of the tread portion (1). [3] A pneumatic tire according to claim 1 or 2, wherein the pneumatic tire has an intended mounting direction with respect to a vehicle, the first ground contact area (A1) is arranged on a vehicle inner side, and the second ground contact area (A2) is arranged on a vehicle outer side. [4] A pneumatic tire according to claim 3, wherein the groove area ratio of the first ground contact area (A1) is from 30 to 43% and the groove area ratio of the second ground contact area (A2) is from 25 to 35%. [5] A pneumatic tire according to claim 3 or 4, wherein a belt layer (15), an inner belt edge cover layer (16b) locally covering an edge of the belt layer (15) on the vehicle inner side, and an outer belt edge cover layer (16c) locally covering an edge of the belt layer (15) on the vehicle outer side are embedded in the tread portion (1), and a rigidity of the inner belt edge cover layer (16b) is greater than a rigidity of the outer belt edge cover layer (16c). [6] A pneumatic tire according to any one of claims 3 to 5, wherein a belt layer (15), an inner belt edge cover layer (16b) locally covering an edge of the belt layer (15) on the vehicle inner side, and an outer belt edge cover layer (16c) locally covering an edge of the belt layer (15) on the vehicle outer side are embedded in the tread portion (1), and a width of the inner belt edge cover layer (16b) is larger than a width of the outer belt edge cover layer (16c). [7] A pneumatic tire according to any one of claims 3 to 5, wherein a belt layer (15), an inner belt edge cover layer (16b) locally covering an edge of the belt layer (15) on the vehicle inner side, and an outer belt edge cover layer (16c) locally covering an edge of the belt layer (15) on the vehicle outer side are embedded in the tread portion (1), and the number of layers of the inner belt edge cover layer (16b) is greater than the number of layers of the outer belt edge cover layer (16c). [8] A pneumatic tire according to any one of claims 1 to 7, wherein the sound-absorbing member (6) has a constant thickness in at least a region corresponding to an adhesion surface in a cross section perpendicular to the longitudinal direction of the sound-absorbing member (6), and a cross-sectional shape thereof is constant in the longitudinal direction. [9] A pneumatic tire according to any one of claims 1 to 8, wherein a volume of the sound-absorbing member (6) as a percentage of a volume of a cavity (7) formed inside the tire when the tire is mounted on a rim is more than 20%. [10] A pneumatic tire according to any one of claims 1 to 9, wherein a hardness of the sound-absorbing member (6) is from 60 to 170 N and a tensile strength of the sound-absorbing member (6) is from 60 to 180 kPa. [11] A pneumatic tire according to any one of claims 1 to 10, wherein the adhesive layer (5) is formed of double-sided adhesive tape having a peel adhesion strength in the range of 8 to 40 N / 20 mm. [12] A pneumatic tire according to any one of claims 1 to 11, wherein the sound-damping member (6) is configured from a porous, open-cell material. [13] A pneumatic tire according to claim 12, wherein the sound-damping member (6) is polyurethane foam.

Images