JP3779427B2 - Pneumatic tire - Google Patents

Description

【０１１０】
【表２】

【０１１１】
なお、上記表１，２中の加硫ゴム組成物の第１独立気泡は前述した実施形態で説明した球状独立気泡を指し、第２独立気泡は同実施形態で説明した長尺状独立気泡を指す。
【０１１２】
シス−１，４−ポリブタジエン：ＪＳＲ製 ＢＲ０１
スチレン−ブタジエン共重合タイヤゴム：旭化成製 タフデン２５３０
カーボンブラック：旭カーボン Ｎ１１０
シリカ：日本シリカ工業（株）製 Ｎｉｐｓｌ ＡＱ
シランカップリング剤：ＤＥＧＵＳＳＡ製 Ｓｉ６９
老化防止剤：Ｎ−（１，３ジメチルブチル）−Ｎ−フェニル−Ｐ−フェニレンジアミン
加硫促進剤：Ｎ−シクロヘキシル−２−ベンゾチアジル−１−スルフェンアミド
発泡剤ＤＰＴ：永和化成工業（株）製 セルラーＤ
発泡助剤（尿素系）：永和化成工業（株） セルペーストＫ５
熱可塑性樹脂：ＰＥ（ポリエチレン）
試験の結果、本発明を適用した実施例１のスタッドレスタイヤは、長尺状独立気泡が全てタイヤ周方向に配向された比較例１のスタッドレスタイヤよりも耐摩耗性が良く、また偏摩耗が少ないことが証明された。
【０１１３】
同様に、本発明を適用した実施例２のサマータイヤは、長尺状独立気泡が全てタイヤ周方向に配向された比較例２のサマータイヤよりも耐摩耗性が良く、また偏摩耗が少ないことが証明された。
【０１１４】
【発明の効果】
以上説明したように、請求項１に記載の空気入りタイヤは上記の構成としたので、氷上性能及びウエット性能の向上を図りつつ、偏摩耗を抑制でき、新品時と走行後での性能変化を抑制することができる、という優れた効果を有する。
【図面の簡単な説明】
【図１】 本発明の適用された第１の実施形態に係る空気入りタイヤの断面図である。
【図２】 第１の実施形態に係る空気入りタイヤのトレッドの平面図である。
【図３】 外側ゴム層の拡大断面図である。
【図４】 タイヤ幅方向内側のトレッドの拡大断面図である。
【図５】 タイヤ幅方向外側のトレッドの拡大断面図である。
【図６】 長尺状の樹脂の斜視図である。
【図７】 長尺状の樹脂の方向を揃える原理を説明する説明図である。
【図８】 （Ａ）〜（Ｄ）は、長尺状独立気泡が形成される順序を説明する説明図である。
【図９】 温度（加硫時間）とゴム及び樹脂の粘度の関係を示したグラフである。
【図１０】 摩耗した外側ゴム層の拡大断面図である。
【図１１】 第２の実施形態に係る空気入りタイヤの断面図である。
【図１２】 第２の実施形態に係る空気入りタイヤのトレッドの平面図である。
【符号の説明】
４ ビードコア
６ カーカス
８ ベルト
１０ 空気入りタイヤ
１２ トレッド
２４ 長尺状独立気泡
２６ 保護層
３２ 樹脂
４０ 空気入りタイヤ [0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire in which a long drainage channel is formed in a tread rubber forming a tread surface portion.
[0002]
[Prior art]
Conventionally, as a studless tire, there is a tire in which a tread is made of foamed rubber having countless closed cells and the friction coefficient (μ) on ice is improved by a water removing effect of closed cells.
[0003]
In addition, there is a tire in which fine grooves are arranged on the tread surface in order to improve the coefficient of friction (μ) on ice when no bubbles appear when new.
[0004]
[Problems to be solved by the invention]
By the way, the lateral force acts on the tire during cornering, and when the tread receives an input in a direction perpendicular to the tire circumferential direction, especially in the shoulder portion (the portions on both sides in the tire width direction of the tread) that is a large input, Wear progresses with respect to the inner part in the tire width direction), and as a result, uneven wear such as reduced wear on both shoulders and tapered wear occurs. For this reason, there is a problem that the performance changes between when it is new and after traveling.
[0005]
Further, in a tire having fine grooves on the tread surface, the fine grooves disappear due to wear, and therefore, the effect of improving the friction coefficient by the fine grooves can be maintained only in the initial stage of use.
[0006]
In consideration of the above-mentioned facts, the present invention provides a pneumatic tire capable of suppressing uneven wear while suppressing improvement in on-ice performance and wet performance, and capable of suppressing performance changes between when new and after running. Is the purpose.
[0007]
[Means for Solving the Problems]
  According to the first aspect of the present invention, the belt layer and the tread rubber are sequentially arranged on the outer periphery of the crown portion of the carcass layer straddling the toroidal shape between the pair of bead cores.Pneumatic tireThe tread rubber has countless long closed cells covered with a protective layer made of resin,The long closed cells have a ratio L / D between the maximum length L and the average hollow diameter D of 3 or more, andThe tread rubber is oriented in the tire circumferential direction on the inner side in the tire width direction and in the tire width direction on the outer side in the tire width direction.
[0008]
Next, the operation of the pneumatic tire according to claim 1 will be described.
In the pneumatic tire according to claim 1, when the tread rubber is worn by running, a long concave portion due to long independent bubbles is formed on the ground surface, and the long concave portion serves as a drainage channel. Efficiently removes water in the ground plane.
[0009]
Therefore, when running on ice with the studless tire to which the present invention is applied, the water drawn between the ice surface is removed by the long concave portion, and the friction coefficient on ice can be increased. This provides high on-ice performance. Even on the wet road surface, water in the ground contact surface is eliminated by the long concave portion, so that high wet performance can be obtained.
[0010]
Moreover, since the protective layer made of resin suppresses the crushing of the recesses, water removal is ensured even under high loads.
[0011]
Further, the coefficient of friction with the road surface can be improved by the scratch effect of the resin exposed on the ground contact surface.
[0012]
The present invention can also be applied to tires other than studless tires. For example, even when applied to summer tires or the like, high wet performance can be obtained.
[0013]
By the way, in the case of a conventional general tire, when a lateral force is applied to the tire during cornering or the like, an input is received at a substantially right angle with respect to the tire circumferential direction. Wear progresses toward the inner part (central area) in the direction, resulting in uneven wear.
[0014]
On the other hand, when the wear direction of the tread rubber is compared between the case where the input direction is the longitudinal direction of the elongated recess and the case where the input direction is perpendicular to the longitudinal direction, the long edge of the recess is found when the input is perpendicular to the longitudinal direction. The tread rubber wears quickly because it is caught on the road surface, and when the input is in the longitudinal direction, the tread rubber wear is slow because the edge length to be caught is short.
[0015]
In the pneumatic tire of the present invention, the elongated concave portion appearing on the tread surface is the tire circumferential direction on the inner side in the tire width direction, the tire width direction on the outer side in the tire width direction, and the input direction of the lateral force during cornering is the tire width direction Since it becomes the same as the orientation direction of an outer elongate recessed part, the abrasion of a shoulder part can be suppressed and the abrasion of the whole tread can be made uniform.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
A pneumatic tire according to a first embodiment of the present invention will be described with reference to FIGS.
[0017]
As shown in FIG. 1, a pneumatic tire (size: 185 / 70R13) 10 according to this embodiment includes a case 1 and a tread 12 that covers the outer side in the tire radial direction of the crown portion 2 of the case 1 between the shoulders 3. have.
[0018]
The case 1 includes a pair of bead portions 4, a toroidal carcass 5 formed of a rubberized cord extending from one bead portion 4 to the other bead portion 4, and a tire radially disposed on the crown portion of the carcass 5 in the tire radial direction. The case 1 has a known non-extensible belt 6 extending in the circumferential direction, and a side wall 7 made of ordinary rubber having excellent bending resistance is disposed outside the case 1 in the tire axial direction.
[0019]
The pneumatic tire 10 of the present embodiment is a so-called studless tire. As shown in FIG. 2, the tread 12 has four circumferential grooves 14 arranged at equal intervals in the tire width direction and substantially the tire circumferential direction. A lateral groove 16 extending in the tire width direction is formed at equal intervals, and a plurality of sipes 19 extending in the tire width direction are formed in the block 18 defined by the circumferential groove 14 and the lateral groove 16.
[0020]
As shown in FIG. 1, the tread 12 includes at least two rubber layers, in this embodiment, an outer rubber layer (so-called cap rubber layer) 12A located on the outer side in the tire radial direction and in contact with the road surface, and an inner side in the tire radial direction. A tread tread surface portion composed of two rubber layers with an inner rubber layer (so-called base rubber layer) 12B located on the side, and side rubber portions 12C disposed on both sides of the tread tread surface portion in the tire width direction. .
[0021]
As shown in FIG. 3, the outer rubber layer 12 </ b> A is a foamed rubber that includes an infinite number of spherical closed cells 22 and countless closed cells 24 that are entirely reinforced with a protective layer 26 made of resin. .
[0022]
In the outer rubber layer 12A, the elongated closed cells 24 reinforced by the protective layer 26 are substantially in the tire circumferential direction (in the direction of arrow A) as shown in FIG. 4 on the inner side in the tire width direction (tire equatorial plane CL side). ), The outer side in the tire width direction is substantially oriented in the tire width direction (arrow B direction) as shown in FIG.
[0023]
In addition, the normal rubber | gum which is not foamed is used for the inner side rubber layer 12B, and the rubber whose Shore A hardness is higher than the Shore A hardness of the outer side rubber layer 12A is used.
(Production method)
Next, a method for manufacturing the outer rubber layer 12A of the pneumatic tire 10 of the present embodiment will be described.
[0024]
As the rubber component used in the rubber composition for forming the outer rubber layer 12A, one having a glass transition temperature of −60 ° C. or less is desirable. The glass transition temperature is used because the outer rubber layer 12A of the tread 12 maintains sufficient rubber elasticity in a low temperature region and obtains sufficient performance on ice.
[0025]
The rubber composition for forming the outer rubber layer 12A preferably has at least one rubber selected from the group consisting of natural rubber and diene synthetic rubber.
[0026]
Examples of the diene-based synthetic rubber include styrene-butadiene copolymer, cis-1,4-polyisoprene, cis-1,4-polybutadiene and the like.
[0027]
Of these, cis-1,4-polybutadiene is particularly preferably used because it has a low glass transition temperature and a large effect on ice performance, and polybutadiene having a cis content of 90% or more is particularly preferred.
[0028]
In order to form bubbles in the outer rubber layer 12A, the rubber composition contains a foaming agent and a foaming aid.
[0029]
Examples of blowing agents include dinitrosopentamethylenetetraamine (DPT), azodicarbonamide (ADCA), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivatives, oxybisbenzenesulfonylhydrazide (OBSH), etc. Among them, azodicarbonamide (ADCA) is preferable in consideration of manufacturing processability.
[0030]
As the foaming aid, auxiliary agents usually used for producing foamed products such as urea, zinc stearate, zinc benzenesulfinate and zinc white are preferably applied.
[0031]
In addition, you may use a foaming agent and a foaming auxiliary agent other than the above.
Further, in the rubber composition, carbon black, silica, silane coupling agent, process oil, vulcanizing agent, vulcanization accelerator and the like are used in combination with the above-mentioned components. Besides these, they are usually used in the rubber industry. Additives such as anti-aging agents, zinc oxide, stearic acid and ozone deterioration inhibitors are blended.
[0032]
In the refining process (kneading process) of the rubber composition, a long resin 32 as shown in FIG. 6 is kneaded and the resin 32 is uniformly dispersed.
[0033]
Here, the resin 32 used in the present embodiment is a thermoplastic resin, and a resin having a viscosity lower than that of the rubber matrix in the tire vulcanization process is used.
[0034]
Generally, the pre-melting viscosity of the resin phase is much higher than the crosslinking end viscosity (Max value) of the rubber matrix. However, once the resin phase is melted, its viscosity is greatly reduced. In the tire vulcanization process, the viscosity of the rubber matrix increases due to the crosslinking reaction during the period from the beginning to the end. Among them, the long resin phase is melted, and the vastly high viscosity is lowered by the melting, and is relatively reversed to the rubber matrix viscosity (although being crosslinked).
[0035]
The rubber matrix here refers to a rubber portion excluding the resin 32.
An important condition for obtaining the long closed cells 24 reinforced with the protective layer 26 as a whole is that when the resin 32 blended in the rubber is a crystalline polymer, the melting point of the crystalline polymer is vulcanized to the maximum. It is to be below the temperature.
[0036]
The long closed cells 24 reinforced by the protective layer 26 are melted by the heat of vulcanization during the vulcanization, and the viscosity is lower than that of the rubber matrix. It is formed using the fact that the gas generated and diffused or dissolved in the rubber moves and concentrates in the molten resin 32 having the lowest viscosity in the rubber.
[0037]
Therefore, when the resin 32 is a crystalline polymer, it is important that the melting point is not more than the maximum vulcanization temperature of the tread portion. The maximum vulcanization temperature of the tread here refers to the maximum temperature of the tread until the tire is cooled after entering the mold and exiting the mold.
[0038]
Incidentally, the viscosity of the rubber is in the range of Mooney viscosity of 30 to 100.
What controls the melt viscosity of the resin 32 includes a melting point (in the case of a crystalline polymer) and a molecular weight.
[0039]
The melting point of the resin 32 is preferably lower than the maximum vulcanization temperature of the rubber used. This is because, as the melting point of the resin 32 is lower than the maximum vulcanization temperature of the rubber, it melts earlier during vulcanization, so that the gas generated in the rubber easily enters the resin 32.
[0040]
If the melting point of the resin 32 is too close to the maximum vulcanization temperature of rubber, the resin 32 melts at the end of vulcanization. At this point, since the rubber matrix has taken in the gas and has been cross-linked, it is difficult for the gas to enter the molten resin 32, and it becomes difficult to form the long closed cells 24.
[0041]
On the other hand, if the melting point of the resin 32 is too low, the resin 32 is melted by the heat at the time of rubber kneading, and the viscosity is lowered. Since the dispersibility of resin 32 deteriorates, it is not preferable. If the melting point of the resin 32 is too low, the resin 32 cannot maintain its long shape at the stage of kneading and is divided into a plurality of parts, or in some cases, the resin 32 dissolves in the rubber and is dispersed microscopically. End up.
[0042]
Therefore, the melting point of the resin 32 should be selected within the above concept, and the melting point of the resin 32 is 10 ° C. lower than the maximum vulcanization temperature of the rubber, preferably 20 ° C. lower, Preferably, it should be set lower by 30 ° C or more.
[0043]
Incidentally, the industrial vulcanization temperature of rubber is about 190 ° C at the maximum, so when the maximum vulcanization temperature is set to 190 ° C, the melting point of the resin 32 is 190 ° C or less, Preferably it should be 180 ° C or lower, more preferably 170 ° C or lower.
[0044]
In consideration of the rubber kneading step, the melting point of the resin 32 should be set to 5 ° C. or higher, preferably 10 ° C. or higher, more preferably 20 ° C. or higher with respect to the maximum temperature during kneading. . Assuming a maximum temperature in the rubber kneading step of approximately 95 ° C., the melting point of the resin 32 is 100 ° C. or higher, preferably 105 ° C. or higher, more preferably 115 ° C. or higher.
[0045]
As is generally known, even if the resin 32 is the same substance, the higher the molecular weight, the higher the melt viscosity at a certain temperature. Therefore, in order to obtain the long closed cells 24, the molecular weight should be selected in such a range that the viscosity of the resin 32 does not become higher than the flow viscosity of the rubber at the maximum vulcanization temperature of the tread rubber.
[0046]
As a result of the test, the weight average molecular weight was 1 to 2 × 10.^FiveIn the rubber composition mixed with the long polyethylene of the order, the long closed cells 24 were formed by vulcanization, but the weight average molecular weight was 7 × 10.^FiveIn the rubber composition mixed with the ultrahigh molecular weight polyethylene described above, the gas produced in the rubber was not concentrated inside the polyethylene, and the long polyethylene was not hollowed out. This is considered to be due to a difference in melt viscosity due to a difference in molecular weight.
[0047]
On the other hand, if the molecular weight is too low, the viscosity of the resin 32 decreases at the stage of rubber kneading, and fusion between the resins 32 occurs, resulting in poor dispersibility in the rubber.
[0048]
The molecular weight of the resin 32 used in the present embodiment is not limited because it is determined by the chemical composition of the material and the state of molecular chain branching, but should be selected within an appropriate range depending on the selected material.
[0049]
In addition, the said melting | fusing point refers to the melting peak temperature measured with the temperature increase rate of 10 degree-C / min and sample weight 5mg by the US DuPont 910 type | mold DSC measuring apparatus.
[0050]
The thermal characteristics of the resin 32 required for the present embodiment have been described above. However, the present embodiment is not limited to the crystalline polymer having a melting point, and the protective layer 26 made of the resin 32 on the outer peripheral portion. The resin 32 may be a non-crystalline polymer as long as the long closed cells 24 formed with can be obtained.
[0051]
Even when the resin 32 is an amorphous polymer, an important condition is that the viscosity of the resin 32 becomes lower than the viscosity of the rubber until the tread rubber reaches the maximum vulcanization temperature in the vulcanization process, and the rubber kneading. This means that the resin 32 has good dispersibility without causing fusion between the resins 32 at a temperature, and the material and molecular weight are selected so as to satisfy these requirements.
[0052]
Specific examples of the crystalline polymer resin 32 include, for example, polyethylene (PE, melting point: 135 ° C), polypropylene (PP, melting point: 167 ° C), polybutylene (melting point: 129 ° C), and polybutylene. Single composition polymers such as succinate (melting point: 115 ° C.), polyethylene succinate (melting point: 105 ° C.), syndiotactic-1,2-polybutadiene (SPB, melting point: 130 ° C.), Those having a melting point adjusted to an appropriate range by polymerization, blending or the like can be used, and an additive may be added to these resins 32.
[0053]
Specific examples of the amorphous polymer resin 32 include polymethyl methacrylate, acrylonitrile butadiene styrene (ABS), polystyrene, and the like.
[0054]
The resin 32 may be a resin 32 other than the specific example as long as the above-described conditions are satisfied. Further, the type of resin 32 to be dispersed is not limited to one type, and may be a plurality of types.
[0055]
For example, when the maximum vulcanization temperature of the pneumatic tire 10 is 175 ° C., polyethylene (melting point: 135 ° C.) can be used as the resin 32. Further, both polyethylene (melting point: 135 ° C.) and polypropylene (melting point: 167 ° C.) may be dispersed.
[0056]
As shown in FIG. 7, when the raw rubber composition 36 kneaded with the long resin 32 is extruded from the die 38 of the extruder whose flow path cross-sectional area decreases toward the outlet, the orientation of the resin 32, That is, the longitudinal direction of the resin 32 is gradually aligned along the extrusion direction (arrow C direction), and when the resin 32 comes out of the base 38, the longitudinal direction of the resin 32 is aligned with the extrusion direction. The composition 36 can be cut to a desired length and used as the rubber of the outer rubber layer 12A.
[0057]
Note that the degree to which the longitudinal direction of the resin 32 is aligned varies depending on the extrusion speed, the viscosity of rubber, and the like while the cross-sectional area of the flow path decreases.
[0058]
In order to arrange the long resin 32 along the desired direction, that is, along the extrusion direction, it is important to control the fluidity of the rubber within a limited temperature range. That is, by appropriately adding a processability improver such as oil or liquid polymer to the rubber composition, the viscosity of the rubber matrix is lowered, and the fluidity is increased, so that the extrusion temperature such as the melting point of the long resin 32 or less is reduced. Even under the constraint conditions, it is possible to extrude very well and ideally align the long resin 32 in the direction along the extrusion direction.
[0059]
The strip-shaped raw outer rubber layer 12A made of the rubber composition thus made is pasted on the raw inner rubber layer 12B previously pasted on the crown portion of the raw tire case, and predetermined with a predetermined mold. The pneumatic tire 10 of the present embodiment can be molded by vulcanization molding under temperature and predetermined pressure.
[0060]
In order to orient the direction of the long closed cells 24 in the tire circumferential direction on the inner side in the tire width direction and in the tire width direction on the outer side in the tire width direction, the long resin 32 is oriented in the tire circumferential direction on the inner side in the tire width direction. The raw rubber composition may be attached so as to face the tire, and the raw rubber composition may be attached so that the long resin 32 faces the tire width direction on the outer side in the tire width direction.
[0061]
When the raw outer rubber layer 12A is heated in the mold, gas 34 starts to be generated by the foaming agent as shown in FIG.
[0062]
When the raw outer rubber layer 12A is heated and the resin 32 is melted (or softened) and its viscosity is lower than the viscosity of the rubber matrix (see FIG. 9), as shown in FIG. The gas 34 generated in the step moves into the molten resin 32. Eventually, the bubbles of the gas 34 that have moved in the molten resin 32 are connected to each other to form a long space, and the gas generated at a site away from the resin 32 stops at that position.
[0063]
As shown in FIGS. 8C and 8D, the outer rubber layer 12A after cooling is a long closed cell reinforced with a spherical closed cell 22 and a protective layer 26 of a resin 32 whose outer peripheral portion is solidified. 24 is formed foamed rubber.
(Function)
Next, the operation of this embodiment will be described.
[0064]
When the pneumatic tire 10 of the present embodiment is run, as shown in FIG. 10, the recesses 22 </ b> A formed by the substantially spherical spherical closed cells 22 and the groove-shaped recesses 24 </ b> A formed by the long closed cells 24 are extremely early in wear. Appears on the tread 12 contact surface in stages.
[0065]
When the pneumatic tire 10 is run on ice, a water film is generated between the tire and the ice surface due to the contact pressure and frictional heat, but the infinite number of recesses 22A and 24A formed on the contact surface of the tread 12 causes The water (water film) is quickly removed and removed.
[0066]
In the outer rubber layer 12A of the present embodiment, the long closed cells 24 covered with the protective layer 26 are oriented in the tire circumferential direction on the inner side in the tire width direction and in the tire width direction on both sides in the tire width direction. The groove-like recesses 24A appearing in FIG. 5 are directed in the tire circumferential direction on the inner side in the tire width direction and in the tire width direction on the outer side in the tire width direction, and the input direction of the lateral force during cornering is a groove-like shape on the outer side in the tire width direction. Since it becomes the same as the orientation direction of the recessed portion 24A, it is possible to suppress the wear of the shoulder portion and uniform the wear of the entire tread. For this reason, the performance change at the time of a new article and after a run can be controlled.
[0067]
Further, the groove-like recess 24A is reinforced by a protective layer 26 whose outer peripheral portion is harder than the rubber matrix, so that it is difficult to be crushed even under a high load and always maintains a high drainage water without being affected by a change in load. Can do.
[0068]
Furthermore, in the pneumatic tire 10 of the present embodiment, the protective layer 26 exposed on the ground contact surface can further improve the frictional force with the road surface based on the action of scratching the road surface.
[0069]
According to the method for manufacturing the pneumatic tire 10 of the present embodiment, the long resin 32 can be hollowed out even under high temperature and high pressure during vulcanization molding, and sufficient drain water performance is achieved. The long closed cells 24 reinforced with the protective layer 26 that can be obtained can be reliably formed.
[0070]
Here, in the foamed rubber portion constituting the outer rubber layer 12A, if the total foaming ratio of the foaming ratio Vs1 of the spherical closed cells 22 and the foaming ratio Vs2 of the long closed cells 24 is Vs, all foamed The rate Vs is desirably in the range of 3 to 40%, and preferably 5 to 35%. The total foaming rate Vs of the foamed rubber is Vs = (ρ₀ / Ρ₁ −1) × 100 (%), ρ₁ Is the density of foam rubber (g / cm^Three ), Ρ₀ Is the density of the solid phase part of the foam rubber (g / cm^Three ).
[0071]
If the total foaming rate Vs is less than 3%, sufficient drained water is not performed due to an absolute lack of the concave volume with respect to the generated water film, and an improvement in performance on ice cannot be expected.
[0072]
If the total foaming rate Vs exceeds 40%, the performance improvement effect on ice is sufficient, but since there are too many voids in the rubber, the fracture limit of the compound is greatly reduced, which is not preferable in terms of durability.
[0073]
It is important that the long closed cells 24 occupy 10% or more of the total foaming rate Vs in the setting range of the total foaming rate Vs 3 to 40%. This is because if it is less than 10%, there are few appropriate long water channels, and the effect on the case of only spherical closed cells is reduced.
[0074]
The average diameter of the long resin 32 is practically 2.3 to 400 μm. The reason for this is that, in the general production conditions for tire vulcanization, in order for the desired hollow diameter of the long closed cells 24 to be 20 to 500 μm, the average diameter of the resin 32 is in the stage before hollowing. This is because the thickness is about 2.3 to 400 μm.
[0075]
On the other hand, the average hollow diameter D of the long closed cells 24 (= the inner diameter of the protective layer 26; see FIG. 3) is preferably in the range of 20 to 500 μm.
[0076]
When the average hollow diameter D of the long closed cells 24 is less than 20 μm, the water rejection is not preferable. On the other hand, when the average hollow diameter D of the long closed cells 24 is larger than 500 μm, the cut resistance and the block chipping are deteriorated, and the wear resistance on the dry road surface is deteriorated.
[0077]
Further, the ratio L / D between the maximum length L of each of the long closed cells 24 and the average hollow diameter D is preferably 3 or more.
[0078]
By setting the ratio L / D to 3 or more, the groove-like recess 24A appearing on the worn rubber surface becomes longer, and the volume can be increased while keeping the average hollow diameter D within the above optimum range. Water can be eliminated. In particular, the groove-shaped recess 24 </ b> A whose ends are connected to the circumferential groove 14, the lateral groove 16, the sipe 19, and the like is effective because the absorbed water can be discharged to the circumferential groove 14, the lateral groove 16, and the sipe 19.
[0079]
In the pneumatic tire 10, the longitudinal direction of the long closed cells 24 is oriented in the tire circumferential direction on the inner side in the tire width direction and in the tire width direction on the outer side in the tire width direction. A part of the long closed cells 24 may be oriented in a direction other than the above.
[Second Embodiment]
A second embodiment of the pneumatic tire of the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the same structure as 1st Embodiment, and the description is abbreviate | omitted.
[0080]
The pneumatic tire 40 (size: 185 / 70R13) of the present embodiment shown in FIGS. 11 and 12 is a so-called summer tire, and three circumferential grooves arranged at equal intervals in the tire width direction on the tread 12. 14 and a block 18 defined by a lateral groove 16 extending slightly inclined with respect to the tire width direction at substantially equal intervals in the tire circumferential direction.
[0081]
As shown in FIG. 11, the tread 12 includes a tread tread surface portion constituted by a single rubber layer 42 and side rubber portions 12 </ b> C disposed on both sides of the tread tread surface portion in the tire width direction.
[0082]
Although not shown in the drawing, the rubber layer 42 of the pneumatic tire 40 of the second embodiment also has a substantially spherical spherical closed cell 22 and the entire outer rubber layer 12A of the pneumatic tire 10 of the first embodiment. Is a foamed rubber containing countless closed cells 24 reinforced with a protective layer 26 of resin, and the closed cells 24 covered with the protective layer 26 are arranged on the inner side of the tire in the tire width direction. In the tire width direction on both sides in the tire width direction.
[0083]
Similarly to the first pneumatic tire 10, the pneumatic tire 40 of the present embodiment also has a recess 22 </ b> A formed by a substantially spherical closed cell 22 and a groove-shaped recess 24 </ b> A formed by a long closed cell 24 at an extremely early stage of wear. It appears on the ground contact surface of the tread 12 at a stage, and water rejection by the recess 22A and the groove-like recess 24A is obtained.
[0084]
Similarly to the pneumatic tire 10 of the first embodiment, the pneumatic tire 40 of the present embodiment has a groove-like recess 24A that appears on the ground contact surface in the tire circumferential direction on the inner side in the tire width direction and on the outer side in the tire width direction. Since the direction of the lateral force during cornering is the same as the orientation direction of the groove-shaped recess 24A on the outer side in the tire width direction, the wear of the shoulder portion can be suppressed and the wear of the entire tread can be made uniform. Can be.
[0085]
The pneumatic tires 10 and 40 described above are for so-called passenger cars, but the present invention is naturally applicable to tires for trucks and buses, for example, other than tires for passenger cars.
[0086]
In the above embodiment, the vulcanization temperature is 175 ° C., but the vulcanization temperature is appropriately changed depending on the material of the rubber, the type of the tire, and the like.
[0087]
In the present invention, combinations with tire shapes such as sipes and block shapes are free.
[0088]
The pneumatic tire may be a so-called retreaded tire. In this case, a belt-like rubber composition containing a long resin 32 is vulcanized with a predetermined mold to form a tread for replacement. And this can be applied to the base tire.
[0089]
It should be noted that the adhesion between the protective layer 26 and the surrounding matrix rubber is important for suppressing the collapse of the long closed cells 24. The polyethylene or the like used in the embodiment of the present invention is bonded to the rubber to some extent so as to melt once. As a method for further improving the adhesion between the matrix rubber and the protective layer 26, for example, the surface of the resin 32 is applied to the resin 32. There are a method of performing the treatment, a method of adding a component for improving the adhesion to rubber to the resin 32, and the like.
[0090]
In the above-described embodiment, the long resin 32 is kneaded with a rubber raw material or the like so as not to melt, and the longitudinal direction is aligned along the extrusion direction by extruding this from the die of the extruder where the cross-sectional area is gradually reduced. Although the rubber composition containing the long resin 32 was obtained, a similar rubber composition can be obtained by other methods.
[0091]
For example, if a granular resin is kneaded with a rubber raw material or the like, the temperature at the time of extrusion is set so that the resin melts or softens, and the resin is melted or softened in the direction of extrusion gradually. When the rubber composition is extruded while being stretched and extruded from the die, the resin has a long shape whose longitudinal direction is the extrusion direction.
(Test example)
In order to confirm the effect of the present invention, the studless tire of Comparative Example 1 and the studless tire of Example 1 to which the present invention was applied were prototyped, and the brake performance on ice, the traction performance on ice, the feeling on ice, the wear resistance, and the uneven wear were observed. Each vehicle is tested for comparison and compared, and the summer tire of Comparative Example 2 and the summer tire of Example 2 to which the present invention is applied are prototyped to produce dry feeling, wet brake performance, wear resistance and uneven wear. A real car test was conducted for each of these and compared.
[0092]
The tires of Comparative Examples 1 and 2 and Examples 1 and 2 will be described below.
The tire size of each example tire is 185 / 70R13. The studless tire of Example 1 is the tire having the structure described in the first embodiment (see FIGS. 1 to 5), and the studless tire of Comparative Example 1 has the same pattern as the studless tire of Example 1 and has a long shape. In the tire, all the closed cells 24 are oriented in the tire circumferential direction.
[0093]
On the other hand, the summer tire of Example 2 is the tire having the structure described in the second embodiment (see FIGS. 11 and 12), and the summer tire of Comparative Example 2 has the same pattern as the summer tire of Example 2. In the tire, all the long closed cells 24 are oriented in the tire circumferential direction.
[0094]
Next, other specifications and test methods for the tires of each example will be described below.
Volume ratio of spherical closed cells to long closed cells: A block piece is cut out from a tire tread, and an observation surface is cut out with a sharp razor perpendicular to the tire circumferential direction and perpendicular to the tread surface. The cut sample is photographed with a scanning electron microscope at a magnification of 100 times. In addition, the photo shooting location is extracted at random. Next, the spherical closed cell part and the long closed cell part provided with the resin protective layer in this photograph are separated, the respective areas are measured, and the area of the spherical closed cell and the long closed cell within a certain area is measured. Calculate the ratio. The above measurement was performed 10 times, the average of the area ratio was calculated | required, and this was made into the volume ratio of a spherical closed cell and an elongate closed cell.
[0095]
Hardness: A vulcanized rubber composition was measured at room temperature (24 ° C.) according to JIS K6301.
[0096]
Average inner diameter of long closed cells: For the average inner diameter of the long closed cells, the total area of the long closed cells in the above measurement is divided by the number of observed long closed cells, and the average per closed cell The cross-sectional area was obtained, and the diameter when the cross-section was assumed to be a complete circle was calculated by the following formula.
[0097]
Elongated closed cell inner diameter = (cross-sectional area per closed cell ÷ π)^0.5× 2
The above measurement was performed 10 times, and the average value was defined as the long closed cell inner diameter.
[0098]
  The length of the long closed cells is assumed to be measured by cutting a sample along the closed cells.
[0099]
The thickness of the long closed cell resin layer: For the thickness of the long closed cell resin layer, the cut sample used for the above measurement is used, and the scanning electron microscope is set to a high magnification enough to measure the resin thickness. Take a picture and measure the thickness at four locations for each long closed cell. This measurement was performed on 40 long closed cells, and the average value was defined as the thickness of the protective layer of the long closed cells.
[0100]
The actual vehicle test was performed by mounting a test tire filled with an internal pressure of 200 kPa on a Japanese 1600CC class passenger car (two passengers). The method of each test is as described below.
[0101]
Brake performance on ice: The braking distance was measured when full braking was performed from 20km / h on an icy road. As a result, the reciprocal of the braking distance is indicated as an index with the comparative tire 1 being 100. The larger the value, the better the braking performance on ice.
[0102]
On-ice traction performance: Accelerated transit time from starting at a distance of 20 m on an ice board road was measured. As a result, the reciprocal of the acceleration transit time is shown as an index with the comparative tire 1 as 100. In addition, it shows that traction performance on ice is so good that a numerical value is large.
[0103]
Feeling on ice: Total feeling of braking, startability, straightness and cornering on a test course on an ice surface (feeling evaluation by a test driver). The results are shown as an index with the comparative tire 1 as 100. In addition, it shows that the feeling on ice is so good that a numerical value is large.
[0104]
Dry feeling: Comprehensive feeling of straightness, lane changeability and cornering on a dry pavement test course (feeling evaluation by a test driver). The results are shown as an index with the comparative tire 2 as 100. In addition, it shows that dry feeling is so good that a numerical value is large.
[0105]
Wet braking performance: The braking distance when a full braking was performed at a speed of 80, 60 and 40 km / h on a paved road having a water depth of 2 mm was measured to obtain an average braking distance. As a result, the reciprocal of the average braking distance is shown as an index with the new comparison tire 2 as 100. In addition, it shows that wet brake performance is so good that a numerical value is large.
[0106]
Abrasion resistance: The amount of wear per km when traveling on a general road from 10,000 to 20,000 km was measured, and the reciprocal of the amount of wear was indicated as an index with a new comparison tire as 100. In addition, it shows that abrasion resistance is so good that a numerical value is large.
[0107]
Uneven wear: The degree of uneven wear when traveling on a general road from 10,000 to 20,000 km was shown as an index with the comparative tire as 100. In addition, it shows that there is little uneven wear, so that a numerical value is large.
[0108]
The specifications and test results of the studless tire are shown in Table 1 below, and the specifications and test results of the summer tire are shown in Table 2 below.
[0109]
[Table 1]

[0110]
[Table 2]

[0111]
In addition, the 1st closed cell of the vulcanized rubber composition of the said Table 1, 2 points out the spherical closed cell demonstrated in embodiment mentioned above, and a 2nd closed cell is the elongate closed cell demonstrated in the same embodiment. Point to.
[0112]
Cis-1,4-polybutadiene: BR01 manufactured by JSR
Styrene-butadiene copolymer tire rubber: Toughden 2530 manufactured by Asahi Kasei
Carbon black: Asahi Carbon N110
Silica: Nippl AQ manufactured by Nippon Silica Industry Co., Ltd.
Silane coupling agent: SiUS manufactured by DEGUSSA
Anti-aging agent: N- (1,3 dimethylbutyl) -N-phenyl-P-phenylenediamine
Vulcanization accelerator: N-cyclohexyl-2-benzothiazyl-1-sulfenamide
Foaming agent DPT: Eiwa Kasei Kogyo Co., Ltd. Cellular D
Foaming aid (urea): Eiwa Chemical Industry Co., Ltd. Cell paste K5
Thermoplastic resin: PE (polyethylene)
As a result of the test, the studless tire of Example 1 to which the present invention is applied has better wear resistance and less uneven wear than the studless tire of Comparative Example 1 in which all the long closed cells are oriented in the tire circumferential direction. It was proved.
[0113]
Similarly, the summer tire of Example 2 to which the present invention is applied has better wear resistance and less uneven wear than the summer tire of Comparative Example 2 in which all the long closed cells are oriented in the tire circumferential direction. Proved.
[0114]
【The invention's effect】
As described above, since the pneumatic tire according to claim 1 has the above-described configuration, it is possible to suppress uneven wear while improving on-ice performance and wet performance, and to prevent a change in performance between when new and after running. It has an excellent effect that it can be suppressed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a pneumatic tire according to a first embodiment to which the present invention is applied.
FIG. 2 is a plan view of a tread of the pneumatic tire according to the first embodiment.
FIG. 3 is an enlarged cross-sectional view of an outer rubber layer.
FIG. 4 is an enlarged cross-sectional view of a tread on the inner side in the tire width direction.
FIG. 5 is an enlarged cross-sectional view of the tread on the outer side in the tire width direction.
FIG. 6 is a perspective view of a long resin.
FIG. 7 is an explanatory diagram illustrating the principle of aligning the direction of a long resin.
FIGS. 8A to 8D are explanatory views illustrating the order in which long closed cells are formed.
FIG. 9 is a graph showing the relationship between temperature (vulcanization time) and the viscosity of rubber and resin.
FIG. 10 is an enlarged sectional view of a worn outer rubber layer.
FIG. 11 is a cross-sectional view of a pneumatic tire according to a second embodiment.
FIG. 12 is a plan view of a tread of a pneumatic tire according to a second embodiment.
[Explanation of symbols]
          4 Bead core
          6 Carcass
          8 belt
          10Pneumatic tire
          12 tread
          24 long closed cells
          26 Protective layer
          32 resin
          40Pneumatic tire

Claims (1)

A pneumatic tire in which a belt layer and a tread rubber are sequentially arranged on the outer periphery of a crown portion of a carcass layer straddling a toroidal shape between a pair of bead cores,
The tread rubber has innumerable elongated closed cells covered with a protective layer made of resin,
In the long closed cells, the ratio L / D between the maximum length L and the average hollow diameter D is set to 3 or more, and the tread rubber has a tire circumferential direction on the inner side in the tire width direction and an outer side in the tire width direction. Then, a pneumatic tire characterized by being oriented in the tire width direction.

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