JP3645512B2 - Pneumatic tire - Google Patents

Description

【００３８】
テストの結果、実施例のタイヤは、比較例に比べて短繊維の配向が良好であり、これに基づき氷上性能にも優れていることが確認できた。
【００３９】
【発明の効果】
本発明は叙上の如く構成しているため、加硫中に、トレッドゴムに配合されている短繊維の多くを接地表面とほぼ垂直方向に配向させることができ、生産製を損ねることなく氷上性能を大巾に向上しうる。
【図面の簡単な説明】
【図１】本発明の一実施形態を示す空気入りタイヤの断面図である。
【図２】そのトレッドパターンを示す展開図である。
【図３】ブロックの平面図である。
【図４】ブロックの斜視図である。
【図５】（Ａ）、（Ｂ）はタイヤの製造方法を示す金型の断面略図である。
【図６】ベントホールの拡大断面図である。
【図７】他の形態を示すブロックの平面図である。
【図８】セグメント型の金型による生タイヤの加硫成形を説明する断面図である。
【図９】短繊維入りトレッドゴムを押出し方向に配向する概略図である。
【図１０】従来の技術を説明する斜視図である。
【図１１】従来の技術を説明する断面図である。
【符号の説明】
２ トレッド部
３ サイドウォール部
４ ビード部
５ ビードコア
６ カーカス
７ ベルト層
９ 短繊維入り陸部
１０ ブロック
１１ 凸部
１２ 凸部の切除痕
１４ ベントホール
１５ 短繊維入りゴム
ｆ 短繊維[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire suitable for traveling on an icy road surface.
[0002]
[Prior art and problems to be solved by the invention]
In recent years, so-called studless tires without spikes have become widespread as tires traveling on icy and snowy roads. In this type of tire, the performance on snow is improving to almost the same level as that of the spike tire by improving the rubber material or pattern shape, but the performance on ice is inferior to that of the spike tire. For this reason, for example, in Japanese Patent Application Laid-Open Nos. 2000-168315 and 2001-130220, short fibers are blended into tread rubber, and many of the short fibers are oriented substantially perpendicular to the grounding surface, thereby causing road surface digging friction and adhesive friction. Increase the performance on ice to further improve performance.
[0003]
By the way, when the tread rubber is extruded by a calender roll or an extruder, the short fibers f are oriented along the extrusion direction as shown in FIG. Further, since the extruded short fiber-containing rubber material 15 is usually used so that the extrusion direction is the tire circumferential direction, the short fibers f are parallel to the ground contact surface and are not oriented vertically. Therefore, in Japanese Patent Laid-Open No. 2000-168315, as shown in FIG. 10, the short fibers f are aligned in the thickness direction of the extruded material by continuously folding the extruded material in a small width in the vertical direction. Further, in Japanese Patent Laid-Open No. 2001-130220, as shown in FIG. 11, a large number of knife blades b for forming siping are pushed in during vulcanization molding, and short fibers f are made substantially perpendicular to the ground contact surface d by using the rubber flow c generated at this time. Attempts have been made to orient.
[0004]
However, the former has the problem that the production efficiency of the tread rubber is poor because the folding work is added, and the latter has to be provided with a large number of sipings for orienting the short fibers f, and the design of the block is limited. In addition, there is a problem that the rigidity of the tread surface or the block is easily lowered.
[0005]
The present inventors conducted various experiments in view of the actual situation as described above. As a result, the ground surface contacted with the road surface of the land portion such as a block and a rib mixed with short fibers was substantially removed from the ground surface during vulcanization. As the rubber is sucked up vertically, it has burr-like protrusions protruding outward in the radial direction of the tire and / or their excision marks, and the total area Sa of these protrusions or their excision marks is defined as the area Sb of the ground contact surface. In the present invention, it is found that a rubber flow in a direction substantially perpendicular to the ground surface occurs during vulcanization, and that many short fibers can be oriented substantially perpendicular to the ground surface. It came to complete.
[0006]
As described above, an object of the present invention is to provide a pneumatic tire suitable for running on icy and snowy roads, in which many short fibers can be oriented substantially perpendicularly to the contact surface without impairing productivity.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 of the present invention is a pneumatic tire in which a tread portion is formed with a short fiber-containing land portion made of rubber mixed with short fibers, and is in contact with the road surface of the short fiber-containing land portion. The ground contact surface has burr-like protrusions and / or cut marks that protrude outward in the tire radial direction due to rubber being sucked up substantially perpendicularly from the contact surface during vulcanization, and / or the cut portions thereof. The ratio (Sa / Sb) between the total area Sa of the traces and the area Sb of the ground contact surface is 0.1 to 0.4.
[0008]
The “area of the ground contact surface” is the total area of the land portion that contacts the road surface in a state where the tire is assembled on the regular rim and the normal internal pressure and the normal load are applied. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or For ETRTO, use “Measuring Rim”.
[0009]
The “regular internal pressure” is the air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is specified for JATMA, and the table “TIRE LOAD LIMITS” for TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 180 kPa for tires for passenger cars. Further, the “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is set for JATMA, and the table “TIRE LOAD” is set for TRA. The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “LOAD CAPACITY” for ETRTO.
[0010]
According to the first aspect of the present invention, at least the short fiber disposed on the convex portion of the ground surface and / or the cut mark thereof is further separated from the ground surface by a rubber flow accompanying the sucking of the rubber during the vulcanization. The pneumatic tire according to claim 1, wherein the pneumatic tire is oriented substantially vertically.
[0011]
The invention according to claim 2 is characterized in that the convex portion is formed by a cylindrical vent hole provided in a mold and has a diameter of 1.5 to 3.0 mm. Or it is a pneumatic tire of 2.
[0012]
The invention according to claim 3 is characterized in that the convex portion is formed by a minute gap between the mating surfaces of the molds, and the thickness thereof is 0.5 to 2.0 mm. The pneumatic tire according to any one of 1 to 3.
[0013]
The invention according to claim 4 is characterized in that the arrangement density of the convex portions and / or the excision marks thereof is larger in the central portion than in the peripheral portion of the grounding surface. A pneumatic tire according to claim 1.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a right half cross-sectional view of a pneumatic tire 1 as an embodiment of the present invention, and FIG. 2 is a development view in which a tread portion 2 is developed on a plane. In the figure, a pneumatic tire 1 includes a carcass 6 having a radial structure in the present example extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, a radially outer side of the carcass 6 and the tread portion 2. A belt layer 7 disposed inward.
[0015]
The carcass 6 is formed of one or more carcass plies 6A in this example in which carcass cords are arranged at an angle of 75 to 90 ° with respect to the tire equator C. The carcass ply 6 </ b> A is one that is folded around from the inner side in the tire axial direction around the bead core 5. The belt layer 7 includes two or more high-elasticity belt cords, such as steel cords, arranged at an angle of about 10 ° to 30 ° with respect to the tire equator C. Belt plies 7A and 7B, and the cords are overlapped between the plies so as to cross each other.
[0016]
Further, the tread portion 2 is formed with a short fiber-containing land portion 9 made of short fiber-containing rubber 15 blended with short fibers f... In this example, the short fiber-containing land portion 9 is composed of a block 10. ing. The short fiber containing land portion 9 is not limited to the block 10, and for example, a rib (not shown) or the like can be used together with the block 10 or instead of the block 10.
[0017]
In the short fiber-containing rubber 15, for example, about 2 to 30 parts by weight of the short fiber f is blended with 100 parts by weight of the rubber component. If the short fiber f is less than 2 parts by weight, the effect of increasing the coefficient of friction with the road surface tends to be reduced. Conversely, if it exceeds 30 parts by weight, the crack resistance of the rubber tends to be reduced.
[0018]
The rubber component is not particularly limited, but for example, one kind of natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), chloroprene rubber, acrylonitrile butadiene rubber or the like. Two or more kinds can be blended and used. Moreover, as the short fiber f, short fibers, such as glass fiber, an aluminum whisker, polyester, nylon, vinylon, aromatic polyamide, can be used, for example. Particularly preferred are inorganic short fibers having a specific gravity of 2.0 or more, such as glass fibers and aluminum whiskers, which are less scattered during kneading with rubber and softened at the vulcanization temperature during vulcanization molding and have excellent road surface scratching effects. . Moreover, the short fiber f can be used even if it combines 1 type, or 2 or more types of materials.
[0019]
The shape of the short fiber f is not particularly limited, but it is preferable that the average fiber diameter is 30 μm or less and the average length is about 0.3 to 20 mm. When the average fiber diameter of the short fibers f exceeds 30 μm, the short fibers f become thick, so that the rubber 15 containing the short fibers is hardened and the adhesion friction is likely to be lowered. When the average fiber diameter of the short fibers f is less than 5 μm, the bending strength is not sufficient and the road surface scratching effect cannot be expected so much. Therefore, the average fiber diameter is preferably 5 μm or more, more preferably 10 μm or more. Further, if the length of the short fiber f is less than 0.3 mm, the effect of scraping the road surface is reduced. Conversely, if the length exceeds 20 mm, the viscosity of unvulcanized rubber becomes high and the workability is impaired, and at the time of vulcanization molding. The rubber flow becomes worse. From such a viewpoint, the average length of the short fibers f is preferably about 5 to 10 mm.
[0020]
Such a short fiber-containing rubber material 15 is first kneaded in accordance with a conventional method using a Banbury mixer, a kneading machine such as a roll in a rubber kneading step, and, as shown in FIG. By forming into a predetermined cross-sectional shape by rolling with R or extrusion with an extruder (not shown), a short fiber-containing rubber material 15 for a tread with the short fibers f oriented in the extrusion direction is prepared. The
[0021]
FIG. 3 is a plan view showing an example of the block 10 as the short fiber containing land portion 9, and FIG. 4 is a perspective view thereof. The block 10 is partitioned and formed in the tread portion 2 by arranging a plurality of vertical grooves G1 extending in the tire circumferential direction and horizontal grooves G2 extending in a direction intersecting with the vertical grooves G1. The siping S indicates that only one is formed in each block 10.
[0022]
Further, the block 10 has a burr-like convex portion 11 (see FIG. 4) that protrudes outward in the tire radial direction due to rubber being sucked up substantially perpendicularly from the ground contact surface 10a during vulcanization to the ground contact surface 10a that contacts the road surface. And / or an excision mark 12 obtained by excising the convex portion 11. In this example, all the convex portions 11 are cut off, and only the cut marks 12 are formed on the ground contact surface 10a. The cut mark 12 is slightly raised from the ground contact surface 10a, for example, or the surface is slightly uneven due to rubber breakage at the time of cut, and has a difference in appearance from the other parts, so that it can be specified by visual observation or the like. Is possible.
[0023]
FIG. 5A illustrates a partial cross-sectional view of a mold M for molding such a block 10. In the mold M, a large number of cylindrical vent holes 14 are formed on the main molding surface Ma for molding the ground contact surface 10a of the block 10 and one end communicates with the main molding surface Ma and rises substantially perpendicularly from the main molding surface Ma. Has been. The other end side of the vent hole 14 communicates with a negative pressure generator such as a vacuum pump.
[0024]
The shape of the vent hole 14 is not particularly limited. For example, it is desirable that the vent hole 14 has a cylindrical shape having a diameter of 1.5 to 3.0 mm, more preferably about 1.8 to 2.5 mm. When the diameter is less than 1.5 mm, it is difficult to suck up rubber even if air can be discharged, and it becomes difficult to create a rubber flow for orienting short fibers f as described later in the tread rubber. If it exceeds 3.0 mm, the amount of rubber flowing to the vent hole 14 is greatly increased, and the material is likely to be wasted.
[0025]
Such a mold M is used to contact the unvulcanized short fiber-containing rubber 15 at high pressure and high temperature as shown in FIG. 5 (B) at the time of vulcanization molding of the tire, and to prevent the occurrence of molding defects. The air between the mold M and the rubber 15 is evacuated from the vent hole 14. As a result, the air in the mold M can be discharged and the rubber 15 can be brought into close contact with the main molding surface Ma to reduce molding defects and the like. Further, after the air is discharged from the vent hole 14, a part of the rubber 15 containing short fibers heated and having fluidity can be sucked up and enter the vent hole 14. Thus, by the rubber flow E accompanying the suction from the vent hole 14, the fine short fibers f are oriented so that the flow resistance is minimized, that is, the longitudinal direction thereof is along the rubber flow direction. Accordingly, the rubber flow E as described above serves to orient the many short fibers f, f in the rubber in a direction substantially perpendicular to the ground surface 10a. Further, by releasing the tire from the mold M, the ground contact surface 10a of the block 10 is formed with a lot of rubber scraps that are originally unnecessary for the tire, that is, burr-like projections 11. Excised.
[0026]
As shown in an enlarged view in FIG. 6, when chamfering the intersection between the molding surface Ma and the vent hole 14, if the chamfering angle α formed by the vertical surface V and the chamfered portion 14 a of the vent hole 14 is too large. The rubber flow tends to move away from the vertical direction with respect to the ground contact surface 10a. From this point of view, the chamfer angle α is not particularly limited, but is preferably about 10 to 30 °, for example.
[0027]
Further, such an orientation effect of the short fibers f becomes more prominent as the number of the vent holes 14 increases. In order to improve the performance on ice, the cutting marks 12 formed per block 10 are improved. It is important to set the total area Sa and the area Sb and ratio (Sa / Sb) of the ground contact surface 10a to 0.1 to 0.4. 3 and 4 illustrate the case where the ratio (Sa / Sb) is 0.1, and FIG. 7 illustrates the case where the ratio (Sa / Sb) is 0.3.
[0028]
As a result of various experiments by the inventors, it has been found that if the ratio (Sa / Sb) is less than 0.1, the effect of orienting the short fibers f perpendicular to the ground surface 10a cannot be obtained sufficiently. On the other hand, if it exceeds 0.4, the appearance of the block 10 is likely to be damaged, and the time required for the excision work is likely to deteriorate the productivity of the tire. From such a viewpoint, it is particularly preferable that the ratio (Sa / Sb) is about 0.2 to 0.4, and more preferably about 0.3 to 0.4. It should be noted that conventional pneumatic tires also have burr-shaped protrusions called “Supee” or those having this excision mark, but these are generally in the ratio (Sa / Sb). Is only about 0.01 to 0.02, and at this level, it is impossible to create a rubber flow for orienting the short fibers f substantially perpendicular to the ground contact surface 10a of the block. .
[0029]
In this example, the excision mark 12 is described as an example, but the embodiment may be implemented in a manner in which the convex portion 11 remains in place of the excision mark 12 or together with the excision mark 12. At this time, the area of the convex portion 11 is specified by the intersection of the front convex portion 11 and the ground contact surface 10a.
[0030]
The mold M is formed with a knife blade b (shown in FIG. 11) for forming siping, a sub-molding surface Mb (shown in FIG. 5) for forming block side surfaces, and the like. Since these also incline substantially perpendicularly to the ground contact surface 10a, a rubber flow along the knife blade b or the sub-molded portion Mb can be created in the rubber material 15 with short fibers when pushed, so that the short fibers can be vertically aligned. Useful for orienting. Therefore, it is effective to provide more protrusions 11 and / or excision marks 12 at positions away from the siping S or the side surface of the block. Therefore, it is desirable that the arrangement density of the convex portions 11 and / or the excision marks 12 thereof is provided so as to be larger in the central portion P1 than in the peripheral portion P2 of the ground contact surface 10a as shown in FIG. The peripheral portion P2 of the ground surface 10a is a region having a width of 5 mm in a direction perpendicular to the block side surface 10b or the siping surface S as shown in FIG. The central portion P1 of the ground contact surface 10a is a region inside the peripheral portion P2. In FIG. 3, the boundary between the central portion P1 and the peripheral portion P2 is indicated by a chain line.
[0031]
Moreover, in the said embodiment, although what formed the convex part 11 using the cylindrical vent hole 14 was illustrated, for example, while comprising the metal mold | die M with several segments M1, M2, ... as shown in FIG. It can also be formed by slit-like minute gaps 17 provided between the mating surfaces of the segments M1, M2,. At this time, the thickness of the convex portion formed by the minute gap 17 and / or the excision mark thereof is preferably about 0.5 to 2.0 mm, and the length thereof is, for example, the same as the width dimension of the block 10. Is desirable.
[0032]
As described above, in the pneumatic tire according to the present embodiment, even when the tread rubber material in which the short fibers f are oriented along the tire circumferential direction is used, the short fibers f are caused to stand by the above-described effects. Can do. Therefore, unlike JP 2000-168315, it is not necessary to stand the short fiber f in the vertical direction with respect to the ground surface before vulcanization, and the productivity can be greatly improved as compared with the conventional method. In addition, providing siping is not an essential requirement for raising the short fiber f, so that problems such as a significant decrease in the rigidity of land portions such as blocks can be prevented.
[0033]
【Example】
A tire having the tire structure shown in FIGS. 1 and 2 and a tire size of 225 / 80R17.5 having a tread pattern is made on the basis of the specifications shown in Table 1, and on-ice performance, uneven wear resistance, and short fiber orientation of each sample tire. Sex was compared. In addition, about the Example, the diameter of the vent hole was unified into 1.8 mm. Moreover, the brand name "micro glass" (average diameter of 9 micrometers, average length of 13 mm) by Nippon Sheet Glass Co., Ltd. was used for the short fiber.
[0034]
<Performance on ice (braking performance on ice)>
Carried out by an indoor drum test, friction was caused by running a test tire T on an ice path (-1 ° C) at a speed of 30 km / h under the conditions of a rim (17.5 × 6.00), tire internal pressure 700 kPa, and load 8.0 kN. The coefficient-slip characteristic was determined, and the determination was made based on the friction coefficient (lock μ) with a slip rate of 100%, which is a state where the rotation of the tire stopped and 100% slip. The evaluation was expressed as an index with Comparative Example 1 as 100. The larger the value, the better.
[0035]
<Uneven wear resistance>
It is mounted on the front wheel (idling wheel) of a fully loaded truck (gross weight of 8.5 kg) under the condition of an internal pressure of 700 kPa, and decelerated every 1500 m during the test course from a speed of 90 km / H to 50 km / H (0 The amount of heel & toe wear of the block after running for 500 km was measured, and the index of Comparative Example 1 was set to 100. The larger the value, the better.
[0036]
<Orientation of short fibers>
The surface of the surface of the block of the prototype tire was sliced thinly along the surface, and the cut surface was observed with a microscope to examine the degree of orientation of the short fibers. Table 1 shows the test results.
[0037]
[Table 1]

[0038]
As a result of the test, it was confirmed that the tires of the examples had better orientation of the short fibers than the comparative examples, and based on this, the performance on ice was also excellent.
[0039]
【The invention's effect】
Since the present invention is configured as described above, during the vulcanization, many of the short fibers blended in the tread rubber can be oriented in a direction substantially perpendicular to the ground surface, and on the ice without impairing production. The performance can be greatly improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a pneumatic tire showing an embodiment of the present invention.
FIG. 2 is a development view showing the tread pattern.
FIG. 3 is a plan view of a block.
FIG. 4 is a perspective view of a block.
FIGS. 5A and 5B are schematic sectional views of a mold showing a method for manufacturing a tire. FIGS.
FIG. 6 is an enlarged sectional view of a vent hole.
FIG. 7 is a plan view of a block showing another embodiment.
FIG. 8 is a cross-sectional view illustrating vulcanization molding of a green tire using a segment mold.
FIG. 9 is a schematic view of orienting tread rubber containing short fibers in the extrusion direction.
FIG. 10 is a perspective view for explaining a conventional technique.
FIG. 11 is a cross-sectional view illustrating a conventional technique.
[Explanation of symbols]
2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 9 Land part 10 with short fiber Block 11 Protrusion part 12 Cut mark 14 Convex part 15 Vent hole 15 Short fiber containing rubber f Short fiber

Claims (4)

A pneumatic tire in which a tread portion is formed with a land portion containing short fibers made of rubber mixed with short fibers,
When the rubber is sucked up substantially perpendicularly from the grounding surface during vulcanization to the grounding surface that contacts the road surface of the land portion containing the short fiber, the short fiber is caused by the rubber flow accompanying the rubber sucking up during the vulcanization. Has a burr-like convex portion and / or a cut mark thereof protruding outward in the tire radial direction and oriented substantially perpendicular to the ground contact surface ;
A pneumatic tire characterized in that a ratio (Sa / Sb) of the total area Sa of the convex portions or the cut marks and the area Sb of the ground contact surface is 0.1 to 0.4. 2. The pneumatic tire according to claim 1 , wherein the convex portion is formed by a cylindrical vent hole provided in a mold and has a diameter of 1.5 to 3.0 mm. The pneumatic tire according to claim 1 or 2 , wherein the convex portion is formed by a minute gap between the mating surfaces of the mold and has a thickness of 0.5 to 2.0 mm. The pneumatic tire according to any one of claims 1 to 3 , wherein an arrangement density of the convex portions and / or excision marks thereof is larger at a central portion than at a peripheral portion of the ground contact surface.

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