pneumatic tires

Abstract

Pneumatic tyre, the mounting direction of which is fixed with respect to a vehicle, comprising: a tread portion (1) extending in a tire circumferential direction and having a ring shape; a pair of sidewall portions (2) arranged on both sides of the tread portion (1); and a pair of bead portions (3) arranged inwardly of the sidewall portions (2) in the tire radial direction; a sound-absorbing member (6) attached via an adhesive layer (5) to an inner surface (4) of the tread portion (1) along the tire circumferential direction, and a center position (P) in a width direction of the sound absorbing member (6) arranged on a vehicle outer side, wherein at least two circumferential grooves (20) are arranged in the tread portion (1) and extend in the tire circumferential direction, and lug grooves (21) are arranged in shoulder regions of the tread portion (1) and extend in a tire width direction; and when a ratio of a distance (D2) from a tire equator (CL) to the center position (P) in the width direction of the sound-absorbing member (6) with respect to a distance (D1) from the tire equator (CL) to a ground contact edge (E) of the tread portion (1) is defined as an offset amount CR, when an average value between a groove depth (d1) from a deepest portion of the lug groove (21) on the vehicle inner side and a groove depth (d2) of the circumferential groove (20) on the vehicle inner side is defined as an average groove depth GDin on the vehicle inner side, and when an average value between a groove depth (d1) from a deepest portion of the lug groove (21) on the vehicle outer side and a groove depth (d2) of the circumferential groove (20) on the vehicle outer side is defined as an average groove depth Gdout on the vehicle outer side,the mean groove depth Gdout on the vehicle outer side is smaller than the mean groove depth Gdin on the vehicle inner side, and the offset size CR, the mean groove depth Gdin on the vehicle inner side and the mean groove depth Gdout on the vehicle outer side correspond to the formula (1): , 0.05 < CR < (Gdout / Gdin) × 0.5

Description

Technical field

[0001] The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire capable of suppressing deterioration of high-speed durability by reducing heat accumulation by applying the sound-absorbing member while maintaining a sound-absorbing effect by the sound-absorbing member. State of the art

[0002] Cavity resonance, caused by air vibration in a tire cavity, is a cause of tire noise. Cavity resonance occurs when a tire tread portion that comes into contact with a road surface when the vehicle is traveling vibrates due to the unevenness of the road surface, and the vibration causes the air in the tire cavity to vibrate. Since sound in a certain frequency band of cavity resonance is perceived as noise, it is important to reduce the sound pressure level (noise level) in that frequency band and reduce cavity resonance.

[0003] A known technique for reducing noise caused by such cavity resonance involves attaching a sound-absorbing member made of a porous material such as sponge to an inner surface of a tread portion on a tire inner surface using an elastic band (see, for example, JP 4281874 B2). However, in a case where the sound-absorbing member is attached with the elastic band, the elastic band may be deformed during high-speed driving.

[0004] Another known method involving the direct adhesion and attachment of a sound-absorbing member to a tire inner surface has been proposed (see, for example, JP 5267288 B2). However, in this case, the sound-absorbing member adheres directly to the tire inner surface, causing heat accumulation in the tread portion, and there is a problem that high-speed durability deteriorates due to heat accumulation. Further related art documents include DE 11 2017 000 668 T5 and WO 2016 / 192 861 A1. Brief description of the invention[Technical problem]

[0005] An object of the present invention is to provide a pneumatic tire capable of suppressing the deterioration of high-speed durability by reducing the accumulation of heat by applying a sound-absorbing member while obtaining a sound-absorbing effect by the sound-absorbing member. [Solution to the problem]

[0006] To achieve the above-described object, a pneumatic tire whose mounting direction is fixed with respect to a vehicle comprises: a tread portion extending in a tire circumferential direction and having an annular shape; a pair of sidewall portions arranged on both sides of the tread portion; and a pair of bead portions arranged inwardly from the sidewall portions in the tire radial direction; a sound-absorbing member fixed via an adhesive layer on an inner surface of the tread portion along the tire circumferential direction, and a center position in a width direction of the sound-absorbing member is arranged on a vehicle outer side, wherein at least two circumferential grooves are arranged in the tread portion and extend in the tire circumferential direction,and lug grooves are arranged in shoulder regions of the tread portion and extend in a tire width direction; and when a ratio of a distance from a tire equator to the center position in the width direction of the sound-absorbing member with respect to a distance from the tire equator to a ground contact edge of the tread portion is defined as an offset amount CR, when an average value between a groove depth of a deepest portion of the lug groove on the vehicle inner side and a groove depth of the circumferential groove on the vehicle inner side is defined as an average groove depth GDin on the vehicle inner side, and when an average value between a groove depth of a deepest portion of the lug groove on the vehicle outer side and a groove depth of the circumferential groove on the vehicle outer side is defined as an average groove depth Gdout on the vehicle outer side,the mean groove depth Gdout on the vehicle outer side is smaller than the mean groove depth Gdin on the vehicle inner side, and the offset size CR, the mean groove depth Gdin on the vehicle inner side and the mean groove depth Gdout on the vehicle outer side correspond to formula (1):, 0.05 <CR<(Gdout / Gdin)×0,5 [Advantageous effects of the invention]

[0007] In the present invention, a pneumatic tire whose mounting direction is fixed with respect to a vehicle comprises: a tread portion extending in a tire circumferential direction and having an annular shape; a pair of sidewall portions arranged on both sides of the tread portion; and a pair of bead portions arranged inwardly from the sidewall portions in the tire radial direction; a sound-absorbing member fixed via an adhesive layer to an inner surface of the tread portion along the tire circumferential direction, and a center position in a width direction of the sound-absorbing member is arranged on a vehicle outer side, wherein at least two circumferential grooves are arranged in the tread portion and extend in the tire circumferential direction,and lug grooves are arranged in shoulder regions of the tread portion and extend in a tire width direction; and when a ratio of a distance from a tire equator to the center position in the width direction of the sound-absorbing member with respect to a distance from the tire equator to a ground contact edge of the tread portion is defined as an offset amount CR, when an average value between a groove depth of a deepest portion of the lug groove on the vehicle inner side and a groove depth of the circumferential groove on the vehicle inner side is defined as an average groove depth GDin on the vehicle inner side, and when an average value between a groove depth of a deepest portion of the lug groove on the vehicle outer side and a groove depth of the circumferential groove on the vehicle outer side is defined as an average groove depth Gdout on the vehicle outer side,the mean groove depth Gdout on the vehicle outer side is smaller than the mean groove depth Gdin on the vehicle inner side, and the offset size CR, the mean groove depth Gdin on the vehicle inner side and the mean groove depth Gdout on the vehicle outer side correspond to formula (1):, 0.05 <CR<(Gdout / Gdin)×0,5 so that it is possible to suppress the deterioration of the high-speed durability of the pneumatic tire while maintaining the sound-absorbing effect of the sound-absorbing member.

[0008] Generally, since a negative camber angle is set for a vehicle with a high load and high power, the ground contact pressure on the vehicle outer side tends to be lower, so heat accumulation in the tread portion is less likely to occur on the vehicle outer side than on the vehicle inner side. Therefore, disposing the sound-absorbing member toward the vehicle outer side does not promote heat accumulation in the tread portion when the sound-absorbing member is disposed on the tire inner surface. Thus, by offsetting and disposing the sound-absorbing member on the vehicle outer side as described above, the heat accumulation caused by the bonding of the sound-absorbing member can be reduced, and deterioration of high-speed durability can be suppressed.

[0009] In the pneumatic tire described above, at least two circumferential grooves are arranged in the tread portion and extend in the tire circumferential direction, and lug grooves are arranged in shoulder regions of the tread portion and extend in a tire width direction; when a ratio of a distance from a tire equator to the center position in the width direction of the sound absorbing member with respect to a distance from the tire equator to a ground contact edge of the tread portion is defined as an offset amount CR, when an average value between a groove depth of a deepest portion of the lug groove on the vehicle inner side and a groove depth of the circumferential groove on the vehicle inner side is defined as a mean groove depth GDin on the vehicle inner side,and when the average value between a groove depth of a deepest portion of the lug groove on the vehicle outer side and a groove depth of the circumferential groove on the vehicle outer side is defined as a mean groove depth GDout on the vehicle outer side, the mean groove depth GDout on the vehicle outer side is smaller than the mean groove depth GDin on the vehicle inner side, and the offset amount CR, the mean groove depth GDin on the vehicle inner side, and the mean groove depth GDout on the vehicle outer side correspond to the formula (1) shown below. 0.05 <CR<(GDout / GDin)×0,5

[0010] In addition, in the pneumatic tire described above, a negative camber angle CA when mounted on a vehicle is assumed to be between 1° and 4°, and the negative camber angle CA, the offset amount CR, the mean groove depth GDin on the vehicle inside and the mean groove depth GDout on the vehicle outside preferably correspond to the formula (2) shown below. 0.2 / CA <CR<(GDout / GDin)×0,5

[0011] Furthermore, in the pneumatic tire described above, when an average value between under-groove thicknesses in the circumferential groove and the lug groove on the vehicle inner side is defined as an average value of the under-groove thickness UGin on the vehicle inner side, and when an average value between under-groove thicknesses in the circumferential groove and in the lug groove on the vehicle outer side is defined as an average value of the under-groove thickness UGout on the vehicle outer side, the average groove depth GDin on the vehicle inner side, the average groove depth GDout on the vehicle outer side, the average under-groove thickness UGin on the vehicle inner side, and the average under-groove thickness UGout on the vehicle outer side preferably correspond to the formula (3) shown below. 1.0<(GDin−GDout) / (UGout−UGin)<1.3

[0012] Generally, in pneumatic tires with asymmetric patterns, improving steering stability on wet road surfaces is achieved by reducing the depth of the grooves arranged on the vehicle outer side and relatively reducing the groove volume on the vehicle outer side. However, when the groove volume is small, the amount of rubber is large, and as a result, heat accumulation is easy to occur. Furthermore, if the sound-absorbing member is excessively arranged with respect to a portion where the groove volume is small, heat accumulation will be promoted, and high-speed durability will be adversely affected. Therefore, to improve high-speed durability, it is effective to appropriately adjust the offset amount of the sound-absorbing member with respect to the camber angle or the groove depth of the tread portion.Therefore, by arranging the sound absorbing member to satisfy the above formulas (1) to (3), it is possible to effectively suppress the deterioration of the durability at high speed.

[0013] In the present invention, a cross-sectional area of the sound-absorbing member is preferably 10% to 30% of a cross-sectional area of a tire cavity. Thus, the sound-absorbing effect of the sound-absorbing member can be sufficiently ensured, resulting in an improvement in quietness. The cross-sectional area of the tire cavity is the cross-sectional area of the tire cavity portion formed between the tire and the rim in a state where the tire is mounted on a regular rim and inflated to the regular internal pressure. However, when the tire is an original equipment tire, the cross-sectional area is calculated using an original wheel on which the tire is mounted.

[0014] In the present invention, an end portion in the width direction of the sound-absorbing member is preferably located on the tire equator side on the ground contact edge of the tread portion. This makes it possible to effectively suppress the peeling of the sound-absorbing member.

[0015] In one embodiment of the present invention, the adhesive layer preferably includes a double-sided adhesive tape, and the adhesive layer has a total thickness of 10 µm to 150 µm. Accordingly, the conformability to deformation during molding can be ensured.

[0016] In one embodiment of the present invention, the sound-absorbing member preferably includes a recessed portion at least at a portion in the tire circumferential direction. Thus, the tire can withstand expansion due to tire inflation or shear stress of an adhesion surface due to tire contact and rolling for a long period of time.

[0017] In the present invention, the ground contact area of the tread portion is determined based on the ground contact width in an axial direction of the tire, measured when a regular load is applied and the tire is placed vertically on a plane, in a state where the tire is inflated to a regular internal pressure and mounted on a regular rim. The ground contact edge is the outermost position in the axial direction of the tire of the ground contact area. "Regular rim" is a rim defined by a standard for each tire according to a system of standards that includes standards on which tires are based, and refers to a "standard rim" in the case of JATMA, a "design rim" in the case of TRA, and a "measuring rim" in the case of ETRTO."Regular inflation pressure" means an air pressure defined by standards for each tire according to a system of standards that includes standards on which tires are based, and refers to a "maximum inflation pressure" in the case of JATMA, to the maximum value in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and to the "INFLATION PRESSURE" in the case of ETRTO; however, if the tire is an original equipment tire, the inflation pressure marked on the vehicle is used, and if the tire is part of a passenger car, the inflation pressure is 180 kPa."Regular load" means a load defined by a standard for each tire according to a system of standards that includes standards on which tires are based, and refers to "maximum load capacity" in the case of JATMA, to the maximum value in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and to "LOAD CAPACITY" in the case of ETRTO; in the case of an original equipment tire, the front and rear axle loads described in the vehicle inspection certificate are each divided by 2 to obtain a wheel load, and if the tire is from a passenger car, the load corresponds to 88% of the load. Brief description of the drawings Fig. 1 is a perspective cross-sectional view of a pneumatic tire according to an embodiment of the present invention. Fig.2 is a cross-sectional view taken along an equator line of a pneumatic tire according to an embodiment of the present invention. Fig. 3 is a meridian cross-sectional view illustrating a pneumatic tire according to an embodiment of the present invention. [Description of embodiments]

[0018] Configurations of embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Fig. 1 to Fig. 3 show a pneumatic tire according to an embodiment of the present invention. In Fig. 1 and Fig. 3, “INSIDE” refers to an inside of a vehicle when the tire is mounted on a vehicle, and “OUTSIDE” refers to an outside of a vehicle when the tire is mounted on the vehicle.

[0019] In Fig. 1 and Fig.2, the pneumatic tire according to the present embodiment includes 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, and a pair of bead portions 3 arranged inwardly of the sidewall portions 2 in the tire radial direction.

[0020] In the pneumatic tire described above, a sound-absorbing member 6 is fixed through an adhesive layer 5 along the tire circumferential direction in a region of a tire inner surface 4 corresponding to the tread portion 1. The sound-absorbing member 6 is made of a porous material with open cells and has predetermined sound absorption properties based on the porous structure. Preferably, polyurethane foam is used as the porous material of the sound-absorbing member 6. On the other hand, the adhesive layer 5 is not particularly limited, and, for example, an adhesive or a double-sided adhesive tape can be used as the adhesive layer 5.

[0021] As in Fig.As illustrated in Fig. 3, at least one carcass layer 10 is mounted between the pair of bead portions 3, 3. The carcass layer 10 includes carcass cords arranged in the tire radial direction, and organic fiber cords are preferably used as the carcass cords. The carcass layer 10 is turned up from the inside to the outside of the tire around a bead core 11 arranged in each of the bead portions 3. A bead filler 12 having a triangular cross-sectional shape is arranged on the tire outer peripheral side of each of the bead cores 11. Furthermore, an inner liner layer 13 is arranged in a region between the pair of bead portions 3, 3 on a tire inner surface.

[0022] On the other hand, belt layers 14 are embedded on the tire outer peripheral side of the carcass layer 10 in the tread portion 1. The belt layers 14 each include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, with the reinforcing cords of the different layers arranged crosswise. In the belt layers 14, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is in a range of, for example, 10° to 40°. Preferably, steel cords are used as the reinforcing cords of the belt layers 14. In order to improve high-speed durability, at least one belt cover layer 15 formed by arranging reinforcing cords at an angle of 5° or less with respect to the tire circumferential direction is arranged on the tire outer peripheral side of the belt layers 14.The belt cover layer 15 preferably has a seamless structure in which a strip material made of at least a single reinforcing cord laid out and covered with rubber is continuously wound in the tire circumferential direction. Furthermore, the belt cover layer 15 may be arranged to cover the belt layer 14 at all positions in the width direction, or may be arranged to cover only the edge portions of the belt layer 14 in the width direction. Organic fiber cords made of nylon, aramid, or the like are preferably used as the reinforcing cords of the belt cover layer 15.

[0023] It should be noted that the tire internal structure described above is a typical example of a pneumatic tire and the pneumatic tire is not limited to this.

[0024] The tread portion 1 is formed with at least two circumferential grooves 20 extending in the tire circumferential direction on both sides of the tire equator CL, and lug grooves 21 extending in the tire width direction in the shoulder region. The circumferential groove 20 includes a main circumferential groove 22 and a narrow circumferential groove 23. The configuration of the circumferential grooves 20 is not particularly limited; the Fig. However, the configuration shown in Fig. 3 shows an example in which the tire equator CL has an asymmetric pattern on both sides of the tire equator CL in the tread portion 1, two circumferential main grooves 22 are formed on the vehicle inner side, and one circumferential main groove 22 and one circumferential narrow groove 23 are formed on the vehicle outer side.

[0025] In the pneumatic tire as described above, the sound-absorbing member 6 is arranged offset from the vehicle outer side. That is, the center position P in the width direction of the sound-absorbing member 6 is located on the vehicle outer side of the tire equator CL. Furthermore, an end portion in the width direction of the sound-absorbing member 6 is preferably arranged on the tire equator CL side of a ground contact edge E of the tread portion 1 to suppress the peeling of the sound-absorbing member 6. In other words, the both ends of the sound-absorbing member 6 can be located within the ground contact width.

[0026] The pneumatic tire described above includes 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, and a pair of bead portions 3 arranged inwardly in the tire radial direction from the sidewall portions 2. In the pneumatic tire for which the mounting direction is set to the vehicle, the sound-absorbing member 6 is fixed to the inner surface of the tread portion 1 along the tire circumferential direction via the adhesive layer 5, and the center position P of the sound-absorbing member 6 in the width direction is arranged on the vehicle outer side, so that it is possible to suppress the deterioration of the high-speed durability of the pneumatic tire while maintaining the sound-absorbing effect by the sound-absorbing member 6.

[0027] In the pneumatic tire described above, as shown in the Fig.3, the distance from the tire equator CL to the ground contact edge E of the tread portion 1 is defined as a distance D1, a distance from the tire equator CL to the center position P of the sound absorbing member 6 in the width direction is defined as a distance D2, and a ratio of the distance D2 with respect to the distance D1 is defined as an offset amount CR. Further, an average value between a groove depth d1 of the deepest portion of the lug groove 21 on the vehicle inner side and a groove depth d2 of the circumferential groove 20 on the vehicle inner side is defined as an average groove depth GDin on the vehicle inner side, and the average value between a groove depth d1 of the deepest portion of the lug groove 21 on the vehicle outer side and a groove depth d2 of the circumferential groove 20 on the vehicle outer side is defined as an average groove depth GDout on the vehicle outer side.It should be noted that the groove depth d1 of the lug groove 21 and the groove depth d2 of the circumferential groove 20 are groove depths measured in the normal direction of the tread surface.

[0028] At this time, the mean groove depth GDout on the vehicle outer side is configured to be smaller than the mean groove depth GDin on the vehicle inner side, and the offset amount CR, the mean groove depth GDin on the vehicle inner side, and the mean groove depth GDout on the vehicle outer side are according to the formula (1) shown below. 0.05 <CR<(GDout / GDin)×0,5

[0029] Specifically, it is assumed that the pneumatic tire, when mounted on a vehicle, has a negative camber angle CA of 1° to 4°, where the negative camber angle CA, the offset amount CR, the average groove depth GDin on the vehicle inner side, and the average groove depth GDout on the vehicle outer side preferably conform to formula (2) below. In other words, when the negative camber angle CA is set small, the offset amount CR is increased, and when the negative camber angle CA is set large, the offset amount CR is reduced. 0.2 / CA <CR<(GDout / GDin)×0,5

[0030] Furthermore, the average value between the under-groove thicknesses in the circumferential groove 20 and the lug groove 21 on the vehicle inner side is referred to as an average under-groove thickness UGin on the vehicle inner side, and the average value between the under-groove thicknesses in the circumferential groove 20 and the lug groove 21 on the vehicle outer side is an average under-groove thickness UGout on the vehicle outer side. At this time, the average groove depth GDin on the vehicle inner side, the average groove depth GDout on the vehicle outer side, the average under-groove thickness UGin on the vehicle inner side, and the average under-groove thickness UGout on the vehicle outer side preferably correspond to the formula (3) shown below.In other words, the mean groove depth GDout on the vehicle outer side is relatively small, and the difference between the mean under-groove thickness UGin on the vehicle inner side and the mean under-groove thickness UGout on the vehicle outer side is not excessively large. If (GDin-GDout) / (UGout-UGin) is made greater than 1.0, it is possible to displace the sound-absorbing member 6 offset from the vehicle outer side while avoiding excessive preload in the ground contact pressure between the vehicle inner side and the vehicle outer side. However, if (GDin-GDout) / (UGout-UGin) is 1.3 or greater, a substantially uneven contact shape will occur, and steering stability and quietness will be adversely affected, which is not preferable. Note that the under-groove thickness is the thickness of the tread rubber on the inner side in the tire radial direction of the groove bottom of the groove in the meridian cross section of the tire. 1.0<(Gdin−Gdout) / (UGout−UGin)<1.3

[0031] Generally, in pneumatic tires with asymmetric patterns, improving steering stability on wet road surfaces is achieved by reducing the depth of the grooves arranged on the vehicle outer side and relatively reducing the groove volume on the vehicle outer side. However, when the groove volume is small, the amount of rubber is large, and as a result, heat accumulation is easy to occur. Furthermore, if the sound-absorbing member is excessively arranged with respect to a portion where the groove volume is small, heat accumulation will be promoted, and high-speed durability will be adversely affected. Therefore, to improve high-speed durability, it is effective to appropriately adjust the offset amount of the sound-absorbing member with respect to the camber angle or the groove depth of the tread portion.Therefore, by appropriately setting the offset amount CR or (GDin-GDout) / (UGout-UGin) to satisfy the above formulas (1) to (3), it is possible to effectively suppress the deterioration of high-speed durability.

[0032] The pneumatic tire described above preferably has a configuration in which the adhesive layer 5 is made of double-sided adhesive and the total thickness of the adhesive layer 5 is from 10 μm to 150 μm. By configuring the adhesive layer 5 as described above, the followability with respect to deformation during molding can be ensured. If the total thickness of the adhesive layer 5 is less than 10 μm, the strength of the double-sided adhesive tape is insufficient, and the adhesion to the sound-absorbing member 6 cannot be sufficiently ensured. If the total thickness of the adhesive layer 5 is more than 150 μm, heat dissipation during high-speed running is inhibited. Thus, the high-speed durability is liable to deteriorate.

[0033] In a pneumatic tire, the cross-sectional area of the sound-absorbing member 6 is preferably 10% to 30% of the cross-sectional area of the tire cavity. Furthermore, the width of the sound-absorbing member 6 is preferably in the range of 30% to 90% of the ground contact width of the tire. In this way, the sound-absorbing effect of the sound-absorbing member 6 can be sufficiently ensured, resulting in an improvement in quietness. If the cross-sectional area of the sound-absorbing member 6 is less than 10% of the cross-sectional area of the tire cavity, the sound-absorbing effect cannot be properly achieved. Furthermore, if the cross-sectional area of the sound-absorbing member 6 is larger than 30% of the cross-sectional area of the tire cavity, the noise reduction effect due to cavity resonance becomes weak, and thus a further noise reduction effect cannot be obtained.

[0034] As in Fig.As illustrated in Fig. 2, the sound-absorbing member 6 preferably includes a recessed portion 8 at least at a portion in the tire circumferential direction. The recessed portion 8 is a portion where the sound-absorbing member 6 is not present along the tire circumference. The recessed portion 8 is provided in the sound-absorbing member 6. This allows expansion due to inflation of the tire or shear stress of an adhesion surface due to contact and rolling to be endured for a long period of time, and shear stress on the adhesion surface of the sound-absorbing member 6 to be effectively reduced. One recessed portion 8 or three to five recessed portions 8 may be provided along the tire circumference.In other words, when two recessed portions 8 are provided along the tire circumference, the tire uniformity deteriorates significantly due to mass imbalance, and when six or more recessed portions 8 are provided along the tire circumference, the production cost increases significantly.

[0035] Note that in a case where two or more recessed portions 8 are provided along the tire circumference, the sound-absorbing member 6 is divided into portions in the tire circumferential direction. However, even in such a case, the divided portions of the sound-absorbing member 6 are bonded together with another layer member such as the adhesive layer 5 made of double-sided tape, for example. Thus, the sound-absorbing member 6 can be treated as an integral member and easily attached to the tire inner surface 4. [Example]

[0036] The tires of Examples 1 to 5 were manufactured with: a tire size of 275 / 35ZR20, a tread portion in the tire circumferential direction having a ring shape, a pair of sidewalls arranged on both sides of the tread portion, and a pair of bead portions arranged on the inner sides of the sidewall portions in the tire radial direction; in the pneumatic tire for which the mounting direction is set toward the vehicle, a sound-absorbing member was attached via an adhesive layer to the inner surface of the tread portion along the tire circumferential direction, and the sound-absorbing member was staggered on the vehicle outer side.

[0037] In Examples 1 to 5, the offset amount CR, GDout / GDin, (GDin-GDout) / (UGout-UGin), and the cross-sectional area ratios of the sound-absorbing member were set as shown in Table 1. Note that the cross-sectional area ratio of the sound-absorbing member is the ratio of the cross-sectional area of the sound-absorbing member to the cross-sectional area of the tire cavity.

[0038] For comparison, a tire according to Comparative Example 1 was manufactured in which a sound-absorbing member was not bonded to a tire inner surface. The tire of Comparative Example 2 was manufactured with the same structure as that of Example 1 except that the sound-absorbing member was arranged without offset, and the tire of Comparative Example 3 was manufactured with the same structure as that of Example 1 except that the direction in which the sound-absorbing member was offset was different. In addition, the tire of Comparative Example 4 was manufactured with the same structure as Example 1 except that the offset amount CR was different, and the tire of Comparative Example 5 was manufactured with the same structure as Example 1 except that the offset amount CR and (GDin-GDout) / (UGout-UGin) were different.

[0039] For these test tires, the high-speed durability with camber angle and resonance strength was evaluated by the following test methods, and the results are shown in Table 1. High speed stability with camber angle:

[0040] Each test tire was mounted on a 20 × 9 1 / 2 J wheel, and a running test was conducted using a drum tester under conditions of air pressure of 340 kPa, a load of 5 kN, and a negative camber angle of 3°. Specifically, an initial speed of 250 km / h was used, the speed was increased by 10 km / h every 20 minutes, and the tires were driven until failure, after which the arrival step (speed) was measured. The larger the arrival step (speed), the higher the high-speed durability with camber angle. Resonance strength:

[0041] Each test tire was mounted on a 20 × 9 1 / 2 J wheel and mounted on a test vehicle with an air pressure of 250 kPa. Afterward, the tire was driven on a smooth road surface at a speed of 100 km / h, and a sensory evaluation was conducted by a test driver. The evaluation results are expressed as index values, with Comparative Example 2 assigned an index value of 100. Larger index values indicate lower cavity resonance noise levels perceived by the test driver and a greater noise reduction effect. [Table 1-I] Comparison example 1 Comparison example 2 Comparison example 3 Example 1 Example 2 Presence of the sound-absorbing member No Yes Yes Yes Yes Offset direction - - Vehicle interior Vehicle exterior Vehicle exterior Offset size CR - 0 0,1 0,1 0,2 GDout / GDin 0,7 0,7 0,7 0,7 0,7 (GDin-GDout) / (UGout-UGin) 0,75 0,75 0,75 0,75 0,75 Cross-sectional area ratio of the sound-absorbing member (%) - 20 20 20 20 High speed stability with camber angle [km / h] 350 310 300 320 330 Resonance strength 95 100 100 100 100 [Table 1-II] Example 3 Comparison example 4 Example 4 Example 5 Comparison example 5 Presence of the sound-absorbing member Yes Yes Yes Yes Yes Offset direction Vehicle exterior Vehicle exterior Vehicle exterior Vehicle exterior Vehicle exterior Offset size CR 0,3 0,4 0,2 0,3 0,4 GDout / GDin 0,7 0,7 0,7 0,7 0,7 (GDin-GDout) / (UGout-UGin) 0,75 0,75 1,0 1,2 1,4 Cross-sectional area ratio of the sound-absorbing member (%) 20 20 20 20 20 High speed stability with camber angle [km / h] 320 310 340 350 350 Resonance strength 100 100 100 100 96

[0042] As can be seen from Table 1, the pneumatic tires of Examples 2 to 1 had improved high-speed durability with camber angle while maintaining the resonance strength compared with Comparative Example 5.

[0043] In Comparative Example 1, the sound-absorbing member was not bonded, resulting in a deterioration in resonance strength. In Comparative Example 3, the sound-absorbing member was offset and bonded to the vehicle interior, adversely affecting high-speed durability with camber angle. In Comparative Example 4, since the offset amount CR of the sound-absorbing member was set to a large value, the high-speed durability with camber angle was adversely affected. In Comparative Example 5, the offset amount CR and (GDin-GDout) / (UGout-UGin) of the sound-absorbing member were set too large, resulting in a deterioration in resonance strength. List of reference symbols 1 tread section 2 side wall section 3 bead section 4 Tire inner surface 5 Adhesive layer 6 Sound-absorbing element 7 Cavity section 8 Recessed section 20 circumferential groove 21 Main circumferential groove 23 Narrow circumferential groove CL Tire Equator E Ground contact edge P Center position in the width direction of the sound-absorbing member

Claims

[1] Pneumatic tyre, the mounting direction of which is fixed with respect to a vehicle, comprising: a tread portion (1) extending in a tire circumferential direction and having a ring shape; a pair of sidewall portions (2) arranged on both sides of the tread portion (1); and a pair of bead portions (3) arranged inwardly of the sidewall portions (2) in the tire radial direction; a sound-absorbing member (6) attached via an adhesive layer (5) to an inner surface (4) of the tread portion (1) along the tire circumferential direction, and a center position (P) in a width direction of the sound absorbing member (6) arranged on a vehicle outer side, wherein at least two circumferential grooves (20) are arranged in the tread portion (1) and extend in the tire circumferential direction, and lug grooves (21) are arranged in shoulder regions of the tread portion (1) and extend in a tire width direction; and when a ratio of a distance (D2) from a tire equator (CL) to the center position (P) in the width direction of the sound-absorbing member (6) with respect to a distance (D1) from the tire equator (CL) to a ground contact edge (E) of the tread portion (1) is defined as an offset amount CR, when an average value between a groove depth (d1) from a deepest portion of the lug groove (21) on the vehicle inner side and a groove depth (d2) of the circumferential groove (20) on the vehicle inner side is defined as an average groove depth GDin on the vehicle inner side, and when an average value between a groove depth (d1) from a deepest portion of the lug groove (21) on the vehicle outer side and a groove depth (d2) of the circumferential groove (20) on the vehicle outer side is defined as an average groove depth Gdout on the vehicle outer side,the mean groove depth Gdout on the vehicle outer side is smaller than the mean groove depth Gdin on the vehicle inner side, and the offset size CR, the mean groove depth Gdin on the vehicle inner side and the mean groove depth Gdout on the vehicle outer side correspond to formula (1):, 0.05 <CR<(Gdout / Gdin)×0,5 [2] A pneumatic tire according to claim 1, wherein when mounted on a vehicle, the negative camber angle CA is assumed to be from 1° to 4°, and the negative camber angle CA, the offset size CR, the mean groove depth Gdin on the inside of the vehicle, and the mean groove depth Gdout on the outside of the vehicle correspond to formula (2): 0.2 / CA <CR<(Gdout / Gdin)×0,5 [3] The pneumatic tire according to claim 1 or 2, wherein, when an average value between the under-groove thicknesses in the circumferential groove (20) and in the lug groove (21) on the vehicle inner side is defined as an average value of the under-groove thickness Ugin on the vehicle inner side, and when an average value between under-groove thicknesses in the circumferential groove (20) and in the lug groove (21) on the vehicle outer side is defined as an average value of the under-groove thickness Ugout on the vehicle outer side, the average groove depth Gdin on the vehicle inner side, the average groove depth Gdout on the vehicle outer side, the average under-groove thickness Ugin on the vehicle inner side, and the average under-groove thickness Ugout on the vehicle outer side correspond to formula (3): 1.0<(Gdin−Gdout) / (Ugout−Ugin)<1.3 [4] A pneumatic tire according to any one of claims 1 to 3, wherein a cross-sectional area of the sound absorbing member (6) is 10% to 30% of a cross-sectional area of a tire cavity (7). [5] A pneumatic tire according to any one of claims 1 to 4, wherein an end portion in the width direction of the sound absorbing member (6) is located on a tire equator side of the ground contact edge (E) of the tread portion (1). [6] A pneumatic tire according to any one of claims 1 to 5, wherein the adhesive layer (5) comprises a double-sided adhesive tape and the adhesive layer (5) has a total thickness of 10 µm to 150 µm. [7] A pneumatic tire according to any one of claims 1 to 6, wherein the sound absorbing member (6) comprises a recessed portion (8) at least at a portion in the tire circumferential direction.

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