Pneumatic tire

Abstract

To provide a pneumatic tire that is high in cornering power, is low in maximum cornering force and is excellent in ride comfort.SOLUTION: The pneumatic tire comprises: a pair of beads; a pair of side walls respectively extending from the pair of beads to outside in a tire radial direction; a tread arranged between the pair of side walls; and a carcass ply hung across the pair of beads. The bead comprises a bead core 11, a bead filler 12 extending from the bead core 11 to outside in the tire radial direction, and a reinforcement layer 13 reinforcing the outside in a tire width direction of the bead filler 12. The tread includes tread rubber whose hardness is below 60. In the pneumatic tire, a ratio of a length in the tire radial direction of the bead filler to a cross section height is 30% or more and 40% or less, and a ratio of a length in the tire radial direction of the reinforcement layer to the cross section height is 40% or more and 50% or less.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] A pneumatic tire is known that includes a pair of beads, a pair of sidewalls extending radially outward from each of the pair of beads, a tread disposed between the pair of sidewalls, and a carcass ply spanning between the pair of beads. Here, the bead includes a bead core and a bead filler extending radially outward from the bead core.

[0003] Patent Document 1 describes that an inner side reinforcing layer and an outer side reinforcing layer are disposed on the inner side and outer side of the bead filler in the tire width direction, respectively. Here, the inner side reinforcing layer is disposed on the inner side of the tire radial outer end of the bead filler in the tire radial direction. Also, the outer side reinforcing layer has an outer extension portion that extends from the outer end of the bead filler in the tire radial direction to the outer side in the tire radial direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2023-69500 Summary of the Invention [Problem to be solved by the invention]

[0005] It is desirable to increase the cornering power of pneumatic tires. However, increasing the hardness of the tread rubber increases the maximum cornering force of the pneumatic tire and reduces the ride comfort. If the maximum cornering force of the pneumatic tire increases, the pneumatic tire may grip too much when the vehicle is turning with a large steering angle, causing the vehicle to roll.

[0006] An object of the present invention is to provide a pneumatic tire having high cornering power, low maximum cornering force, and a comfortable ride. [Means for solving the problem]

[0007] One aspect of the present invention is a pneumatic tire comprising a pair of beads, a pair of sidewalls extending radially outward from each of the pair of beads, a tread disposed between the pair of sidewalls, and a carcass ply spanning between the pair of beads, wherein the bead comprises a bead core, a bead filler extending radially outward from the bead core, and a reinforcing layer reinforcing the outer side of the bead filler in the tire width direction, the tread including tread rubber having a hardness of 50 or more and 60 or less, a ratio of the radial length of the bead filler to the cross-sectional height being 30% or more and 40% or less, and a ratio of the radial length of the reinforcing layer to the cross-sectional height being 40% or more and 50% or less. Effect of the Invention

[0008] According to the present invention, a pneumatic tire having high cornering power, low maximum cornering force, and a comfortable ride can be provided. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing a half cross section in the tire width direction of a pneumatic tire according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a partially enlarged view of the pneumatic tire of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] 1 and 2 show a pneumatic tire (hereinafter referred to as tire 1) according to one embodiment of the present invention. The tire 1 is a pneumatic tire for passenger cars, but may also be a pneumatic tire for various vehicles such as light trucks, trucks, and buses.

[0012] The basic structure of the tire 1 is symmetrical in a cross section in the tire width direction. Fig. 1 shows a half cross section of the right half of the tire 1, and the left half (not shown) has the same structure. In Fig. 1, the tire equatorial plane S1 is a plane perpendicular to the tire rotation axis (tire meridian) and is located at the center in the tire width direction.

[0013] FIG. 1 shows a tire 1 mounted on a standard rim and inflated to a standard internal pressure under no load. The standard rim refers to a standard rim determined by JATMA for a tire size. The standard internal pressure is also determined by JATMA. For example, the standard internal pressure for pneumatic tires for passenger cars is 180 kPa.

[0014] Here, the tire width direction is a direction parallel to the tire rotation axis, and is the left-right direction on the paper in Fig. 1. In Fig. 1, it is illustrated as the tire width direction X. The inner side in the tire width direction is a direction approaching the tire equatorial plane S1, and is the left side on the paper in Fig. 1. The outer side in the tire width direction is a direction away from the tire equatorial plane S1, and is the right side on the paper in Fig. 1.

[0015] The tire radial direction is a direction perpendicular to the tire rotation axis, and is the up-down direction on the paper in Fig. 1. In Fig. 1, this is illustrated as tire radial direction Y. The outer side in the tire radial direction is a direction away from the tire rotation axis, and is the upper side on the paper in Fig. 1. The inner side in the tire radial direction is a direction approaching the tire rotation axis, and is the lower side on the paper in Fig. 1.

[0016] As shown in FIG. 1, the tire 1 includes a pair of beads 10 provided on both sides in the tire width direction, a pair of sidewalls 20 extending radially outward from each of the pair of beads 10, a tread 30 disposed between the pair of sidewalls 20, a carcass ply 40 spanning between the pair of beads 10, and an inner liner 50 disposed on the tire cavity side of the carcass ply 40.

[0017] The bead 10 includes a bead core 11, a bead filler 12 extending radially outward from the bead core 11, a reinforcing layer 13 that reinforces the outer side of the bead filler 12 in the tire width direction, a chafer 14, and a rim protector 15.

[0018] The bead core 11 is an annular member in which a metal bead wire covered with rubber is wound multiple times in the tire circumferential direction, and is provided to fix the tire 1 to a rim.

[0019] The bead filler 12 is a member made of hard rubber, and since the rigidity of the periphery of the bead filler 12 of the tire 1 is high, the deflection of the tire 1 is small even when a high load is applied to the tire 1. The bead filler 12 has a shape that tapers toward the outside in the tire radial direction.

[0020] The ratio of the length L1 (see FIG. 2) of the bead filler 12 in the tire radial direction to the cross-sectional height L0 (see FIG. 1) of the tire 1 is 30% to 40%, and preferably 35% to 40%. If the ratio of L1 to L0 is less than 30%, the cornering power (hereinafter referred to as CP) of the tire 1 decreases, and if it exceeds 40%, the ride comfort deteriorates.

[0021] In this specification and the claims, the cross-sectional height of a pneumatic tire means the distance between the surface of the tread at the center of the pneumatic tire and the measurement point of the rim diameter when the pneumatic tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.

[0022] The reinforcing layer 13 is a component in which multiple metal cords formed by twisting multiple metal fibers together are covered with topping rubber. Since the rigidity around the reinforcing layer 13 of the tire 1 is increased, the deflection of the tire 1 is reduced even when a high load is applied to the tire 1.

[0023] The multiple metal cords extend at an incline with respect to the radial direction of the tire 1, and are arranged at predetermined intervals in the tire circumferential direction. The intervals between the metal cords arranged in the tire circumferential direction increase toward the outside in the tire radial direction. The inclination angle between the radial direction of the tire 1 and the extending direction of the metal cords of the reinforcing layer 13 is preferably 10° or more and 40° or less.

[0024] The metal cord is not particularly limited, but may be, for example, a steel cord. The steel cord is made by twisting together several to several tens of wires made of high carbon steel with a diameter of about 0.1 mm to 0.5 mm, and may be plated as necessary to improve adhesion to rubber.

[0025] The ratio of the length L2 (see FIG. 2) of the reinforcing layer 13 in the tire radial direction to the cross-sectional height L0 (see FIG. 1) of the tire 1 is 40% or more and 50% or less, and preferably 45% or more and 50% or less. If the ratio of L2 to L0 is less than 40%, the CP of the tire 1 will be low, and if it exceeds 50%, the ride comfort will be poor.

[0026] 2, the carcass ply 40 has a main body portion 40a and a folded-up portion 40b that is connected to the main body portion 40a and folded back along a part of the inner side in the tire radial direction of the bead core 11, while a part of the reinforcing layer 13 is sandwiched between a part of the outer side in the tire radial direction of the bead filler 12 and the folded-up portion 40b. Also, the remaining part of the reinforcing layer 13 is sandwiched between the main body portion 40a and the folded-up portion 40b.

[0027] An inner end 13a in the tire radial direction of the reinforcing layer 13 is located radially outward of an inner end 12a in the tire radial direction of the bead filler 12. An outer end 13b in the tire radial direction of the reinforcing layer 13 is located radially outward of an outer end 12b in the tire radial direction of the bead filler 12.

[0028] The bead 10 does not have a reinforcing layer that reinforces the inner side of the bead filler 12 in the tire width direction.

[0029] The chafer 14 is provided along a part of the carcass ply 40 on the inner side in the radial direction of the tire.

[0030] The rim protector 15 is a member including a rim strip rubber 16, and is arranged on the outer side of the chafer 14 and the folded-back portion 40b in the tire width direction. The rim protector 15 has a peak 15a formed on its outer surface along the tire circumferential direction, and comes into contact with the inside of the rim on which the tire 1 is mounted. The rim protector 15 is continuous in an annular shape in the tire circumferential direction, and is provided to protect the rim.

[0031] The sidewall 20 is a member including a sidewall rubber 21, and is disposed on the outer side in the tire width direction of the carcass ply 40. The sidewall rubber 21 constitutes the outer wall surface of the tire 1, and is the portion that deflects the most when a load is applied to the tire 1.

[0032] The tread 30 includes an endless belt 31 , a cap ply 32 , and a tread rubber 33 .

[0033] The belt 31 is provided to reinforce the tread 30, and is disposed on the tire radial outer side of the carcass ply 40. The belt 31 is a laminated structure in which a first belt 311 and a second belt 312 are laminated. Here, the second belt 312 is disposed on the tire radial outer side of the first belt. The first belt 311 and the second belt 312 are members in which a plurality of steel cords are covered with rubber. The tire width direction outer end of the first belt 311 is located on the tire width direction outer side of the tire width direction outer end of the second belt 312. The belt 31 ensures the rigidity of the tire 1, and improves the contact of the tread 30 with the road surface.

[0034] The belt 31 may be a single-layer structure or a laminated structure of three or more layers.

[0035] The cap ply 32 is provided to reinforce the tread 30 together with the belt 31, and is disposed on the outer side of the belt 31 in the tire radial direction. The cap ply 32 is a member in which a plurality of insulating fiber cords (e.g., polyamide cords) are covered with rubber. The outer end of the cap ply 32 in the tire width direction is located on the outer side in the tire width direction than the outer end of the first belt 311 in the tire width direction. Therefore, the belt 31 is covered with the cap ply 32. The cap ply 32 improves the durability of the tire 1 and reduces road noise during running.

[0036] The tread rubber 33 is disposed on the outer side of the cap ply 32 in the tire radial direction. The tread rubber 33 is a member that constitutes the tread surface that comes into contact with the road surface during running. The tread surface of the tread rubber 33 is provided with a tread pattern that is composed of a plurality of grooves, for example.

[0037] The hardness of the tread rubber 33 is 60 or less, and preferably 50 or more and 60 or less. If the hardness of the tread rubber 33 exceeds 60, the maximum cornering force (hereinafter, CF max This can result in higher vehicle height and a less comfortable ride.

[0038] The carcass ply 40 is embedded in the tire 1 in a manner that passes between a pair of beads 10 and on the tire cavity side of a pair of sidewalls 20 and the tread 30 .

[0039] The carcass ply 40 is a member in which a plurality of carcass cords (e.g., polyester cords, polyamide cords) that form the framework of the tire 1 are covered with rubber. The plurality of carcass cords extend along a plane along the tire width direction, and are arranged side by side in the tire circumferential direction. At this time, the carcass cords extend in the radial direction of the tire 1.

[0040] The carcass ply 40 is a laminated structure in which a first carcass ply 401 and a second carcass ply 402 are laminated. Here, the second carcass ply 402 is disposed on the outer side in the tire radial direction or the outer side in the tire width direction of the first carcass ply 401 in the main body portion 40a, and is disposed on the inner side in the tire radial direction or the inner side in the tire width direction of the first carcass ply in the folded-back portion.

[0041] The carcass ply 40 may be a single-layer structure or a laminated structure of three or more layers.

[0042] The inner liner 50 is a member made of air-permeable rubber and is provided to prevent air in the tire cavity from leaking to the outside. The inner liner 50 covers the inner surface of the first carcass ply 401 in the area of ​​the main body 40a that is not covered by the chafer 14. The inner liner 50 also covers the inner surface of the chafer 14 in the area of ​​the main body 40a that is covered by the chafer 14.

[0043] The inner liner 50 is a laminated structure in which a first inner liner 501 and a second inner liner 502 are laminated. Here, the second inner liner 502 is disposed on the outer side of the first inner liner 501 in the tire radial direction or the outer side in the tire width direction.

[0044] The inner liner 50 may be a single-layer structure or a laminated structure of three or more layers.

[0045] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and the above embodiment may be modified as appropriate within the scope of the spirit of the present invention.

[0046] The configuration of the embodiment of the present invention is as follows.

[0047] (1) A pneumatic tire comprising: a pair of beads; a pair of sidewalls extending radially outward from each of the pair of beads; a tread disposed between the pair of sidewalls; and a carcass ply spanning between the pair of beads, wherein the bead comprises a bead core, a bead filler extending radially outward from the bead core, and a reinforcing layer reinforcing an outer side of the bead filler in the tire width direction, the tread comprises tread rubber having a hardness of 60 or less, a ratio of the radial length of the bead filler to a cross-sectional height is 30% or more and 40% or less, and a ratio of the radial length of the reinforcing layer to a cross-sectional height is 40% or more and 50% or less.

[0048] (2) The pneumatic tire described in (1), wherein the carcass ply has a main body portion and a folded-up portion connected to the main body portion and folded back along at least a portion of the bead core, a portion of the reinforcing layer is sandwiched between a portion of the bead filler and the folded-up portion, and the remaining portion of the reinforcing layer is sandwiched between the main body portion and the folded-up portion.

[0049] (3) The pneumatic tire according to (1) or (2), wherein an inner end in the tire radial direction of the reinforcing layer is located radially outward of an inner end in the tire radial direction of the bead filler.

[0050] (4) The pneumatic tire according to any one of (1) to (3), wherein a radially outer end of the reinforcing layer is radially outward of a radially outer end of the bead filler. EXAMPLES

[0051] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0052] (Reference Example 1, Examples 1 to 3, Comparative Examples 1 to 4) The raw tire was vulcanized and molded using a vulcanization mold to obtain a vulcanized tire. Next, the vulcanized tire was cooled while being inflated using a post-cure inflation device to obtain a pneumatic tire for passenger cars (see Figures 1 and 2). At this time, the hardness of the tread rubber, the cross-sectional height L0, the length L1 of the bead filler in the tire radial direction, and the length L2 of the reinforcing layer in the tire radial direction were adjusted to predetermined values ​​(see Table 1).

[0053] (Tread rubber hardness) The hardness of the tread rubber was measured in an atmosphere of 23° C. using a type A durometer in accordance with JIS K6253.

[0054] (CP) After mounting the pneumatic tire on a specified rim, a drum-type testing machine was used to measure the CF by setting the air pressure to 230 kPa and applying a load that was 70% of the maximum load of the load index. At this time, the CP was calculated from the CF at a slip angle of 1°, and an index evaluation was performed based on the CP of the pneumatic tire of Reference Example 1. Here, the target value of CP is 102 or more.

[0055] (CF max ) After mounting the pneumatic tire on the specified rim, a flat belt type tire testing machine is used, the air pressure is set to 230kPa, and the running speed is 80km / h. A load of 70% of the maximum load of the load index is applied, and the steering angle is gradually increased. The CF max The CF of the pneumatic tire of Reference Example 1 was measured. maxThe index was evaluated based on the following: CF max The target value is 99 or less.

[0056] (Ride comfort) After mounting the pneumatic tire on a specified rim, the tire was mounted on a passenger car and the vehicle's designated air pressure was set. Next, a professional driver drove the tire on a dry, uneven road surface and evaluated the ride comfort from the viewpoint of shock and vibration using a scoring method out of 100 points. The evaluation criteria for ride comfort are as follows: A: 97 points or more B: 95 points or more but less than 97 points C: Less than 95 points

[0057] Table 1 shows the evaluation results of the pneumatic tires.

[0058] [Table 1]

[0059] From Table 1, the pneumatic tires of Examples 1 to 3 have high CP and CF max On the other hand, the pneumatic tires of Comparative Examples 1 and 2 have a tread rubber hardness of 62, so the CF max The pneumatic tires of Comparative Examples 3 and 4 have an L1 / L0 ratio of 45 to 50% and an L2 / L0 ratio of 55 to 60%, resulting in poor ride comfort. [Explanation of symbols]

[0060] 1 Tire 10 Beads 11 Bead core 12 Bead filler 13 Reinforcement layer 20 Sidewall 30 Tread 33 Tread rubber 40 Carcass ply 40a Main body 40b Folded part L0 Section height L1: The radial length of the bead filler L2: Length of the reinforcing layer in the radial direction of the tire

Claims

1. A pair of beads; a pair of sidewalls extending radially outward from each of the pair of beads; a tread disposed between the pair of sidewalls; A carcass ply is provided between the pair of beads, The bead includes a bead core, a bead filler extending from the bead core toward an outer side in a tire radial direction, and a reinforcing layer that reinforces an outer side of the bead filler in a tire width direction, The tread includes a tread rubber having a hardness of 60 or less, A ratio of the length of the bead filler in the tire radial direction to the cross-sectional height is 30% or more and 40% or less, A pneumatic tire, wherein a ratio of a length of the reinforcing layer in a radial direction of the tire to a cross-sectional height is 40% or more and 50% or less.

2. The carcass ply has a main body portion and a turn-up portion connected to the main body portion and turned up along at least a portion of the bead core, A portion of the reinforcing layer is sandwiched between a portion of the bead filler and the folded-back portion, The pneumatic tire according to claim 1 , wherein the remaining portion of the reinforcing layer is sandwiched between the main body portion and the folded-back portion.

3. The pneumatic tire according to claim 1 , wherein an inner end in the tire radial direction of the reinforcing layer is located radially outward of an inner end in the tire radial direction of the bead filler.

4. The pneumatic tire according to claim 1 or 2, wherein an outer end in the tire radial direction of the reinforcing layer is located outer in the tire radial direction than an outer end in the tire radial direction of the bead filler.

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