JP4210101B2 - Pneumatic tire and method for manufacturing pneumatic tire - Google Patents

Description

【００９３】
操縦安定性能の評価ドライバーによれば、実施例の操縦安定性は、概ね従来例１の操縦安定性能と同一であり、超扁平率のタイヤに求められる運動性能を十分に満たすレベルであった。
【００９４】
一方、従来例２では、主にサイド部の剛性の低さに起因して、直進安定性能、操舵時のハンドル応答性能が大幅に劣ってしまっている。
【００９５】
室内ドラム耐久試験では、いずれのタイヤもサイド部の表面に存在する文字端（突起端）を起点としてサイドゴム層に亀裂が発生して故障に至り、それぞれの故障までの走行距離の指数が上表の通りであった。
【００９６】
従来例２のタイヤの耐久性が実施例１ほど向上しなかったのは、サイド部の剛性が低いことにより、同じ条件下でもサイド部の撓み量が大きくなってしまったために、サイド部表面での歪みを増大させることになり、結果として期待したほど効果が得られなかったためと考えられる。
【００９７】
また、実施例２は、サイドゴム層と保護層との間で割れが発生し、結果として実施例１よりは耐久性が劣ってしまったが、従来例に比較しては明らかに耐久性は向上している。
【００９８】
【発明の効果】
以上説明したように本発明の空気入りタイヤは上記の構成としたので、サイド部の表面から亀裂が発生し難くなる、という優れた効果を有する。
【００９９】
また、本発明の空気入りタイヤの製造方法によれば、サイドゴム層と保護層との界面の耐久性を向上することができる、という優れた効果を有する。
【図面の簡単な説明】
【図１】本発明の一実施形態に係る空気入りタイヤの断面図である。
【図２】保護層の拡大断面図である。
【符号の説明】
１０ 空気入りタイヤ
２４ サイドゴム層
２６ 保護層
２８ サイド部
３０ 突起[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire and a method for manufacturing a pneumatic tire, and more particularly to a pneumatic tire that suppresses the occurrence of cracks on the surface of a side portion, and a method for manufacturing the same.
[0002]
[Prior art]
For example, in an ultra flat pneumatic radial tire having a flatness ratio of 55% or less, deformation tends to concentrate on the tire side portion due to the narrow deformation region of the tire side portion due to the load under the use conditions.
[0003]
If there are protrusions representing characters, symbols, etc. on the surface of the tire side portion within this range, distortion concentrates at the base of the protrusions, and the tire side rubber layer is liable to crack.
[0004]
In order to solve this problem, (1) the 50% elastic modulus of the entire side rubber layer is reduced to improve the crack fracture resistance of the side rubber layer, and (2) the finish R of the base of the projection of characters and the like is increased. (3) Measures such as preventing projections such as letters on the side portions are conceivable.
[0005]
In addition, as a prior art, a pneumatic tire (see, for example, Patent Documents 1 to 3) in which a side portion is formed of a plurality of types of rubber has been proposed.
[0006]
[Patent Document 1]
JP 2000-198325 A [Patent Document 2]
JP 2001-199209 A [Patent Document 3]
Japanese Patent Laid-Open No. 5-185810
[Problems to be solved by the invention]
However, when trying to solve the cracking problem of the side part by the measures as described above, there are the following problems respectively.
(1) Generally, the fracture characteristics of rubber are generally related to the 50% elastic modulus (M50) of the rubber, and the softer rubber having a smaller 50% elastic modulus is generally superior in fracture resistance. When attempting to improve the crack resistance of the side rubber layer by reducing the 50% elastic modulus of the entire side rubber layer, the rigidity of the side part becomes too small and the motion performance required for ultra flat tires is achieved. It becomes difficult to achieve.
[0008]
Further, since the rigidity of the side portion is reduced, the amount of bending of the side portion is increased even under the same conditions.
[0009]
Along with this, the distortion on the surface of the side portion increases, and as a result, the effect cannot be obtained as expected.
[0010]
(2) Increasing the finishing radius R of the protrusions of characters, etc. not only increases the number of mold processing steps, but also increases the cost, and evenly finishes the finishing radius R of all protrusions. Is very difficult in terms of accuracy.
[0011]
(3) Changing the arrangement so that no protrusions such as letters are provided on the side portion imposes significant restrictions on the tire appearance design, which is an important component of the tire. Then, the range in the tire cross-section height direction in which characters and the like can be arranged is very narrow, and it is often difficult to implement in practice.
[0012]
The invention described in Japanese Patent Application Laid-Open No. 2000-198325 is intended to prevent damage caused by cracking or peeling between tire rubbers, and is not intended to prevent cracks occurring on the surface of the side portion.
[0013]
In the invention described in Japanese Patent Laid-Open No. 2001-199209, since a reinforcing rubber layer harder than the side rubber layer is provided on the side portion, it is impossible to prevent cracks generated on the surface of the side portion.
[0014]
In addition, the invention described in Japanese Patent Laid-Open No. 5-199209 is intended to provide a protective rubber layer containing a fiber reinforcing material on the side part to prevent the side part from being cut by curbstones and the like. It does not prevent the occurrence of.
[0015]
In view of the above facts, an object of the present invention is to provide a pneumatic tire that hardly generates cracks from the surface of the side portion, and a method for manufacturing the same.
[0016]
[Means for Solving the Problems]
In order to solve such a problem, the inventor has conducted various experimental studies, and as a result, the side rubber layer that constitutes most of the other part of the other part of the other part of the present invention, which performs an accurate response only to the region where the strain that causes cracking occurs. By placing rubber that meets the required performance other than crack resistance, it is possible to improve the crack resistance of ultra flat tires without sacrificing the performance required for side parts other than crack resistance. I found that I can plan.
[0017]
In addition, as a result of the three-dimensional strain distribution analysis of the side portion, the strain that causes crack fracture starting from the root of the protrusion of the side portion is mainly due to the tensile strain along the tire surface in the tire deformation direction. It turned out to be.
[0018]
The invention according to claim 1 has been made in view of the above-described facts, and includes a pair of bead portions, a toroidal carcass extending from one bead portion to the other bead portion, and a tire diameter of the carcass. A reinforcing layer positioned on the outer side in the direction, a tread rubber layer positioned on the outer side in the tire radial direction of the reinforcing layer and constituting a tread portion, and a side rubber layer positioned on the outer side in the tire axial direction of the carcass and forming a side portion , Wherein a protective layer made of rubber having a modulus of elasticity 50% lower than that of the side rubber layer is provided on the tire outer surface of the side portion, and the protective layer has a height of 0. 0. When a protrusion of 5 mm or more is provided, and the thickness of the protective layer measured along the normal line standing on the outer surface of the tire is t, and the thickness of the side part measured along the normal line is T And 0.1 ≦ t Satisfy T ≦ 0.3, wherein the projection is provided at a position apart more than 5mm from the end in the range of 68% 58% or more of the tire section height, and the protective layer, that It is a feature.
[0019]
Next, the operation of the pneumatic tire according to claim 1 will be described.
[0020]
A tensile strain is generated along the tire radial direction on the surface of the side portion of the pneumatic tire by running, but a protective layer made of rubber having a modulus of elasticity 50% lower than that of the side rubber layer is provided on the surface of the side portion. For this reason, the crack fracture resistance of the side surface is improved.
[0021]
Therefore, even if a projection such as a character is formed on the surface of the side portion, it is possible to suppress the generation and growth of a crack from the base of the projection.
In addition, since the protrusion with a height of 0.5 mm or more tends to concentrate strain near the base and easily crack, the base of this protrusion has excellent crack fracture resistance in order to achieve improved durability. It is necessary to cover effectively with a protective layer. Accordingly, the protrusion having a height of 0.5 mm or more is provided in a range of 58% or more and 68% or less of the tire cross-sectional height of the tire outer surface of the side portion, and at a position 5 mm or more away from the end of the protective layer.
[0022]
If the ratio t / T between the thickness t of the protective layer and the thickness T of the side portion is less than 0.1, the effect of suppressing cracks generated from the surface of the side portion is insufficient.
[0023]
On the other hand, when the ratio t / T exceeds 0.3, the rigidity of the side portion is lowered and the original performance of the tire is lowered.
[0024]
Therefore, the ratio t / T between the thickness t of the protective layer and the thickness T of the side portion needs to satisfy 0.1 ≦ t / T ≦ 0.3.
[0025]
In addition, 50% elasticity modulus (M50) here is the tensile stress (unit: Pa. According to JIS K 6251) at the time of 50% elongation.
[0026]
According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the protective layer is provided in a range of 55 to 70% of a tire cross-sectional height.
[0027]
Next, the operation of the pneumatic tire according to claim 2 will be described.
[0028]
Among the side portions, the range of 55 to 70% of the tire cross-sectional height is a portion having a particularly large tensile strain. Therefore, the range is made of rubber having a low 50% elastic modulus and excellent crack fracture resistance. It is preferable to arrange a protective layer.
[0029]
The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein the 50% elastic modulus of the side rubber layer is M50a, and the 50% elastic modulus of the rubber of the protective layer is M50b. Further, 0.3 ≦ M50b / M50a ≦ 0.8 is satisfied.
[0030]
Next, the operation of the pneumatic tire according to claim 3 will be described.
[0031]
The ratio M50b / M50a between the 50% elastic modulus M50a of the side rubber layer and the 50% elastic modulus M50b of the protective layer rubber is set to 0.3 ≦ M50b / M50a ≦ 0.8. This is to clarify and properly use the characteristics required for each.
[0032]
Here, when the ratio M50b / M50a is less than 0.3, the protective layer is too soft and the durability against cuts due to external factors such as curbstones and pebbles is greatly inferior.
[0033]
On the other hand, when the ratio M50b / M50a exceeds 0.8, the 50% elastic modulus M50b of the rubber of the protective layer becomes too close to the elastic modulus M50a of the side rubber layer, that is, the effect of providing the protective layer, that is, crack resistance from conventional tires. Almost no effect of improving destructibility can be expected.
[0034]
Therefore, the ratio M50b / M50a between the 50% elastic modulus M50a of the side rubber layer and the 50% elastic modulus M50b of the rubber of the protective layer preferably satisfies 0.3 ≦ M50b / M50a ≦ 0.8.
[0035]
The invention according to claim 4 is the pneumatic tire according to any one of claims 1 to 3, wherein the 50% elastic modulus of the side rubber layer is 1.1 MPa or more and 2.0 MPa or less, and the protective layer. The 50% elastic modulus of the rubber constituting is set to 0.7 MPa or more and 0.9 MPa or less.
[0036]
Next, the operation of the pneumatic tire according to claim 4 will be described.
[0037]
When the 50% elastic modulus of the side rubber layer is set to 1.1 MPa to 2.0 MPa and the 50% elastic modulus of the rubber constituting the protective layer is set to 0.7 MPa to 0.9 MPa, for example, the flatness is 55% or less. It is possible to achieve the best balance between the durability and the performance required for the ultra-flat tire.
[0038]
Here, if the 50% elastic modulus of the side rubber layer is less than 1.1 MPa, the deterioration of the steering stability as represented by the lane change is conspicuous, and it becomes difficult to satisfy the required performance as an ultra flat tire.
[0039]
On the other hand, if the 50% elastic modulus of the side rubber layer exceeds 2.0 MPa, the rigidity of the side rubber layer becomes too high, resulting in a significant deterioration in riding comfort typified by overcoming the protrusion.
[0040]
Further, if the 50% elastic modulus of the rubber constituting the protective layer is less than 0.7 MPa, the difference in rigidity between the side rubber layer and the side rubber layer becomes too large, and the strain distribution in the boundary region between the side rubber layer and the protective layer is distorted. On the contrary, there is a concern that the deterioration of the fracture resistance is caused.
[0041]
On the other hand, if the 50% elastic modulus of the rubber constituting the protective layer exceeds 0.9 MPa, the physical properties are very close to the 50% elastic modulus of the side rubber layer, and the effect of suppressing cracking cannot be expected.
[0042]
Therefore, it is preferable to set the 50% elastic modulus of the side rubber layer to 1.1 MPa to 2.0 MPa and the 50% elastic modulus of the rubber constituting the protective layer to 0.7 MPa to 0.9 MPa.
[0047]
According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects, the protrusion is formed when the side portion is viewed in a cross section perpendicular to the tire outer surface. The base portion of is formed in an arc shape having a center of curvature on the outer side of the tire, and satisfies 0.2 mm ≦ R ≦ 1.0 mm, where R is the radius of curvature of the arc shape.
[0048]
Next, the operation of the pneumatic tire according to claim 5 will be described.
[0049]
If the radius of curvature R of the arc shape is less than 0.2 mm, distortion tends to concentrate at the base of the protrusion, which is not preferable.
[0050]
On the other hand, if the radius of curvature R of the arc shape exceeds 1.0 mm, the number of steps for processing a mold for vulcanizing a pneumatic tire increases, which causes an increase in cost.
[0051]
In addition, it is very difficult in terms of work accuracy to finish the finish R of all the bases of the protrusions uniformly.
[0052]
The method for manufacturing a pneumatic tire according to claim 6 is characterized in that the side rubber layer and the protective layer are formed by integral extrusion.
[0053]
In the method for manufacturing a pneumatic tire according to claim 6 , since the side rubber layer and the protective layer are integrally formed using, for example, a rubber two-layer extruder, the side rubber layer and the protective layer are firmly formed. It is possible to improve the durability of the interface by pressure bonding.
[0054]
Further, compared with the case where the side rubber layer and the protective layer are bonded on the tire molding drum, the pressure bonding is sufficient, and since cement or the like is not used, there is an advantage that an extra interface is not increased.
[0055]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.
[0056]
As shown in FIG. 1, the pneumatic tire 10 of the present embodiment includes a carcass 14 including a plurality of carcass 14 plies straddling a pair of bead portions 12 (one side omitted in FIG. 1) in a toroidal shape.
[0057]
The carcass 14 is wound up with a bead core 16 embedded in the bead portion 12 from the tire inner side toward the outer side.
[0058]
A belt 18 composed of a plurality of belt plies is provided outside the carcass 14 in the tire radial direction, and a belt reinforcing layer 20 and a tread rubber layer 22 are provided outside the belt 18 in the tire radial direction.
[0059]
A side rubber layer 24 is provided on the outer side of the carcass 14 in the tire axial direction.
[0060]
A protective layer 26 made of rubber different from the side rubber layer 24 is provided on a part of the surface of the side rubber layer 24 within a range of 55 to 70% of the tire cross-section height SH.
[0061]
When the thickness of the protective layer 26 measured along the normal line standing on the outer surface of the tire is t and the thickness of the side portion 28 measured along the normal line is T, 0.1 ≦ t / It is preferable to satisfy T ≦ 0.3.
[0062]
When the 50% elastic modulus of the side rubber layer 24 is M50a and the 50% elastic modulus of the rubber of the protective layer 26 is M50b, it is preferable that 0.3 ≦ M50b / M50a ≦ 0.8 is satisfied.
[0063]
The 50% elastic modulus M50a of the side rubber layer 24 is preferably 1.1 MPa to 2.0 MPa, and the 50% elastic modulus M50b of the rubber constituting the protective layer 26 is preferably 0.7 MPa to 0.9 MPa.
[0064]
As shown in FIG. 2, a protrusion 30 having a height of 0.5 mm or more forming characters, numerical values, and the like is formed on the outer surface of the tire of the protective layer 26.
[0065]
As shown in FIG. 1, the protrusions 30 are preferably provided in a range of 58% or more and 68% or less of the tire cross-section height SH and at a position 5 mm or more away from the end of the protective layer 26.
[0066]
As shown in FIG. 2, when the side portion 28 is viewed in a cross section perpendicular to the outer surface of the tire, the root of the protrusion 30 (the connection portion between the side surface of the protrusion 30 and the outer surface of the side portion) is on the outer side of the tire. It is formed in an arc shape having a center of curvature.
[0067]
When the radius of curvature of the connecting portion is R, it is preferable that 0.2 mm ≦ R ≦ 1.0 mm is satisfied.
(Function)
Next, the effect | action of the pneumatic tire 10 of this embodiment is demonstrated.
[0068]
When the pneumatic tire 10 rolls under load, a tensile strain along the tire radial direction is generated on the surface of the side portion 28, and the strain tends to concentrate on the base of the projection 30. Since the protective layer 26 made of rubber having a low% elastic modulus is formed on the outer surface of the tire, cracks hardly occur.
[0069]
Among the side portions 28, the range of 55 to 70% of the tire cross-section height SH is a portion having a particularly large tensile strain. Therefore, from this range, a rubber having a low 50% elasticity and excellent crack fracture resistance is included. This embodiment in which a protective layer 26 to be formed and a protrusion 30 is formed on this protective layer 26 is a preferred embodiment.
[0070]
Since the 50% elastic modulus of the side rubber layer 24 is set to 1.1 MPa to 2.0 MPa, and the 50% elastic modulus of the rubber constituting the protective layer 26 is set to 0.7 MPa to 0.9 MPa, as in the present embodiment. The exercise performance, riding comfort characteristics, etc. required in the pneumatic tire 10 with a flatness ratio of 55% or less can be best balanced with durability.
[0071]
Here, when the ratio t / T between the thickness t of the protective layer 26 and the thickness T of the side portion 28 is less than 0.1, the effect of suppressing the occurrence of cracks is insufficient.
[0072]
On the other hand, if the ratio t / T exceeds 0.3, the rigidity of the side portion 28 is lowered and the original performance of the tire is lowered.
[0073]
If the ratio M50b / M50a is less than 0.3, the protective layer 26 is too soft and the durability against cuts due to external factors such as curbstones and pebbles is greatly inferior.
[0074]
On the other hand, if the ratio M50b / M50a exceeds 0.8, the 50% elastic modulus M50b of the rubber of the protective layer 26 becomes too close to the elastic modulus M50a of the side rubber layer 24, and the effect of improving crack fracture resistance is hardly expected.
[0075]
When the 50% elastic modulus of the side rubber layer 24 is less than 1.1 MPa, the deterioration of steering stability as typified by lane change is conspicuous, and it becomes difficult to satisfy the required performance as an ultra flat tire.
[0076]
On the other hand, if the 50% elastic modulus of the side rubber layer 24 exceeds 2.0 MPa, the rigidity of the side rubber layer 24 becomes too high, resulting in a significant deterioration in riding comfort represented by overcoming the protrusion.
[0077]
If the 50% elastic modulus of the rubber constituting the protective layer 26 is less than 0.7 MPa, the difference in rigidity with the side rubber layer 24 becomes too large, and the strain distribution in the boundary region between the side rubber layer 24 and the protective layer 26 is increased. There is a concern that the distortion may occur and the deterioration of the fracture resistance may be caused.
[0078]
On the other hand, if the 50% elastic modulus of the rubber constituting the protective layer 26 exceeds 0.9 MPa, the properties are very close to the 50% elastic modulus of the side rubber layer 24, and the effect of suppressing cracking cannot be expected.
[0079]
If the radius of curvature R of the base of the protrusion 30 is less than 0.2 mm, it is not preferable because distortion tends to concentrate on the base of the protrusion 30.
[0080]
On the other hand, if the curvature radius R of the base of the protrusion 30 exceeds 1.0 mm, the number of steps for processing the mold increases, which causes an increase in cost. In addition, it is very difficult in terms of work accuracy to finish the finish R of all the bases of the protrusions 30 uniformly.
[0081]
When the side portion 28 is composed of two layers having different elastic moduli of the side rubber layer 24 and the protective layer 26 and is prepared as separate members and then bonded together to form a raw tire before vulcanization. If there is insufficient pressure bonding or the like, there is a concern that peeling occurs at the interface between the side rubber layer 24 and the protective layer 26.
[0082]
Therefore, it is better to extrude the side rubber layer 24 and the protective layer 26 integrally with an extruder.
(Test example)
In order to confirm the effect of the present invention, the tire of the example to which the present invention was applied, the tire of the conventional example, and the tire of the comparative example were prepared, and an actual vehicle handling stability test and an indoor drum durability test were performed.
(1) Actual vehicle handling stability test tire size: 225 / 45R17
Rim: 7.5JJ
Air pressure: Front 220kPa, Rear 270kPa
Test vehicle: 3000cc engine with front engine / rear drive Sport type Vehicle loading conditions: Only driver Evaluation item: Steering stability on dry road Steering stability is controlled by high speed circuit including long straight part, course regulation Trained in a wide range of speeds from low speeds to high speeds of around 200 km / h on a test course consisting of handling evaluation roads with many curves, etc., and was trained in straight-line stability performance, steering wheel response performance, and road surface grip performance. Two evaluation drivers performed a feeling evaluation, and this average score was used as an evaluation result.
[0083]
The results are shown as an index when the result of Conventional Example 1 is set to 100, and the larger the value, the better.
(2) Indoor drum durable tire size: 225 / 45R17
Rim: 7.5JJ
Air pressure: 130kPa
Test load: 5kN
Drum diameter 1.7m
Speed: 60km / h
This test was set up to reproduce the most severe conditions in consideration of various usage conditions (load, tire pressure, vehicle alignment, road surface conditions), etc. in the actual market. Therefore, the mileage until failure in this test does not directly represent the mileage until failure in the market, but is sufficient to compare a tire with excellent durability with a tire that does not.
[0084]
The result is shown by an index when the result of Conventional Example 1 is set to 100 with respect to the travel distance until the failure occurs, and indicates that the larger the numerical value, the better.
[0085]
Next, the tire used for the test will be described.
[0086]
Conventional Example 1 uses a rubber having a relatively large elastic modulus for the side rubber layer, while Conventional Example 2 uses a rubber having a relatively small elastic modulus. These are all tires having a conventional structure in which the side rubber layer is composed of only one layer.
[0087]
The tires of Examples 1 and 2 have two side rubber layers within the range specified in the present invention, the side rubber layer is made of rubber having a relatively large elastic modulus as in Conventional Example 1, and the side rubber layer of Conventional Example 2 is formed on the surface thereof. And a protective layer made of rubber having the same elastic modulus.
[0088]
The 50% elastic modulus of the side rubber layer and the protective layer is as shown in the table.
[0089]
In Example 1, a side rubber layer and a protective layer were co-extruded, and in Example 2, a protective layer was attached on the side rubber layer on a tire molding drum.
[0090]
About the distribution (cross-sectional shape) of the protective layer in the depth direction, the central portion is the thickest, and the shape becomes thinner as it approaches the end portion.
[0091]
In addition, although the Example shown in the table | surface is an example for verifying the effect of this invention, in selecting the elastic modulus of a side rubber layer, if it is in the range shown in the claim, it is substantially the same. The effect can be obtained.
[0092]
[Table 1]

[0093]
According to the evaluation driver of steering stability performance, the steering stability of the example was almost the same as the steering stability performance of the conventional example 1, and it was a level that sufficiently satisfied the motion performance required for the tire having a super flat rate.
[0094]
On the other hand, in the conventional example 2, the straight running stability performance and the steering wheel response performance during steering are greatly deteriorated mainly due to the low rigidity of the side portion.
[0095]
In the indoor drum endurance test, all tires start from the character end (projection end) on the surface of the side part and cause cracks in the side rubber layer, leading to failures. It was as follows.
[0096]
The durability of the tire of Conventional Example 2 did not improve as much as in Example 1, because the side part surface had a large amount of deflection under the same conditions due to the low rigidity of the side part. This is thought to be due to the fact that the effect was not obtained as much as expected.
[0097]
Further, in Example 2, cracking occurred between the side rubber layer and the protective layer, and as a result, the durability was inferior to that of Example 1, but the durability was clearly improved as compared with the conventional example. is doing.
[0098]
【The invention's effect】
As described above, since the pneumatic tire of the present invention has the above-described configuration, it has an excellent effect that cracks are hardly generated from the surface of the side portion.
[0099]
Moreover, according to the manufacturing method of the pneumatic tire of this invention, it has the outstanding effect that durability of the interface of a side rubber layer and a protective layer can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a pneumatic tire according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of a protective layer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Pneumatic tire 24 Side rubber layer 26 Protective layer 28 Side part 30 Protrusion

Claims (6)

A pair of beads,
A toroidal carcass extending from one bead portion to the other bead portion;
A reinforcing layer located on the outer side in the tire radial direction of the carcass;
A tread rubber layer that is located on the outer side in the tire radial direction of the reinforcing layer and that constitutes a tread portion;
A pneumatic tire comprising a side rubber layer that is located on the outer side in the tire axial direction of the carcass and constitutes a side part,
The tire outer surface of the side portion is provided with a protective layer made of rubber having a modulus of elasticity 50% lower than that of the side rubber layer, and the protective layer is provided with a projection having a height of 0.5 mm or more.
When the thickness of the protective layer measured along the normal line standing on the outer surface of the tire is t, and the thickness of the side portion measured along the normal line is T, 0.1 ≦ t / T ≦ 0.3 is satisfied,
The pneumatic tire according to claim 1, wherein the protrusion is provided within a range of 58% or more and 68% or less of a tire cross-sectional height and at a position 5 mm or more away from an end of the protective layer .   The pneumatic tire according to claim 1, wherein the protective layer is provided at least in a range of 55 to 70% of a tire cross-sectional height. When the 50% elastic modulus of the side rubber layer is M50a and the 50% elastic modulus of the rubber of the protective layer is M50b,
The pneumatic tire according to claim 1, wherein 0.3 ≦ M50b / M50a ≦ 0.8 is satisfied.   The 50% elastic modulus of the side rubber layer is set to 1.1 MPa to 2.0 MPa, and the 50% elastic modulus of the rubber constituting the protective layer is set to 0.7 MPa to 0.9 MPa. The pneumatic tire according to any one of claims 1 to 3. When the side portion is viewed in a cross section perpendicular to the tire outer surface, the base portion of the protrusion is formed in an arc shape having a center of curvature on the outer side of the tire, and the radius of curvature of the arc shape is R. The pneumatic tire according to claim 1 , wherein 0.2 mm ≦ R ≦ 1.0 mm is satisfied. The method for manufacturing a pneumatic tire according to any one of claims 1 to 5, wherein the side rubber layer and the protective layer are formed by integral extrusion.

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