JP4685918B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having a so-called high turn-up structure in which a folded portion of a carcass ply is terminated at a buttress portion, and more particularly to a pneumatic tire that can improve steering stability, durability, and wear resistance.

  As shown in FIG. 11, a pneumatic tire having a carcass ply a having a so-called high turn-up structure has been proposed in the following Patent Document 1. The pneumatic tire includes a main body a1 straddling a pair of bead cores b in a toroidal shape, and the bead core b connected to the main body a1 is folded from the inner side to the outer side in the tire axial direction and the tire radius of the side wall part c. It has a folded portion a2 that terminates in a buttress portion d that is a region outside in the direction.

  The tread rubber e of the pneumatic tire has a rubber main portion e1 and wing rubber e2 connected to both ends thereof. The wing rubber e2 is made of a soft rubber and extends between the main body portion a1 and the folded portion a2 of the carcass ply.

  In such a pneumatic tire, the rigidity of the sidewall portion c is increased by the folded-back portion a2 extending to the buttress portion, and as a result, excellent steering stability can be exhibited. Further, the distortion of the folded-back portion a2 located in the buttress portion d that is relatively deformed during traveling is effectively relieved and absorbed by the soft wing rubber e2. Therefore, the occurrence of separation damage or the like at the folded portion a2 can be suppressed, and the durability of the tire can be improved.

JP 2002-120514 A

  By the way, in the pneumatic tire of the said patent document 1, wing rubber e2 is exposed to the tire outer surface. In this regard, Patent Document 1 describes that the wing rubber e2 is provided at a position that does not directly contact the road surface during straight traveling. However, if the wing rubber e2 is subjected to severe traveling such as high-speed turning, the wing rubber e2 is disposed on the road surface. There is a possibility of contact. Since the wing rubber is made of a very soft rubber material, uneven wear is likely to occur, in which only the portion of the wing rubber e2 is worn early due to contact with the road surface.

  The present invention has been devised in view of the above problems, and is based on the fact that the wing rubber is covered with a side wall rubber having a hardness higher than that of the wing rubber. The main purpose is to provide a pneumatic tire capable of improving the performance.

  According to the first aspect of the present invention, there is provided a main body portion straddling a pair of bead cores in a toroidal shape from the tread portion through the sidewall portion, and the bead core extending from the inner side in the tire axial direction to the outer side. A carcass including a carcass ply that is folded back and extends outward in the tire radial direction and ends at a buttress portion; a belt layer disposed radially outside the carcass and inside the tread portion; A pneumatic tire having a tread rubber disposed on the outer side in the tire radial direction and a sidewall rubber disposed on the outer side in the tire axial direction of the carcass and in the sidewall region, wherein the tread rubber extends in the tread width direction and contacts the pneumatic tire. A main part forming the ground, and connected to both sides of the main part and the sidewall rubber; A wing rubber made of rubber having a small hardness, and an outer end portion of the wing rubber extends between the main body portion and the turned-up portion of the carcass ply and protrudes outward from the main portion. The outward surface of the wing rubber is covered with a sidewall rubber connected to the main portion without being exposed to the tire outer surface.

Further, in the invention of claim 1 , bead apex rubber that extends in a tapered shape from the bead core to the outer side in the tire radial direction is disposed between the main body portion and the folded portion, and the outer end portion of the bead apex rubber is: it is connected to the wing rubber, connection length along their tire radial direction, characterized in that at 2.0mm or more.

According to the second aspect of the present invention, there is provided a main body part straddling a toroidal shape between a pair of bead cores through a sidewall part from a tread part, and the periphery of the bead core is folded back from the inner side in the tire axial direction to the outer side. A carcass including a carcass ply that extends outward in the tire radial direction and includes a folded portion that terminates at a buttress portion, a belt layer disposed on the outer side in the tire radial direction of the carcass and inside the tread portion, and the radial direction of the tire of the belt layer A pneumatic tire having a tread rubber disposed on the outside and a sidewall rubber disposed on the outer side in the tire axial direction of the carcass and in a sidewall region, wherein the tread rubber extends in the tread width direction to form a ground contact surface A main portion that is connected to both sides of the main portion and is harder than the main portion and the sidewall rubber. A wing rubber made of rubber, and an outer end portion of the wing rubber extends between the main body portion and the folded portion of the carcass ply and terminates, and the wing rubber protrudes outward from the main portion. The outward surface is covered with a sidewall rubber connected to the main portion without being exposed to the outer surface of the tire, and the carcass ply includes a carcass cord and a topping rubber that covers the carcass cord. and said wing rubbers, and said topping rubber and rubber composition and the type of carbon black are substantially identical.

The invention according to claim 3 is a main body part straddling a toroidal shape between a pair of bead cores from the tread part through the sidewall part, and the circumference of the bead core is folded back from the inner side in the tire axial direction to the outer side. A carcass including a carcass ply that extends outward in the tire radial direction and includes a folded portion that terminates at a buttress portion, a belt layer disposed on the outer side in the tire radial direction of the carcass and inside the tread portion, and the radial direction of the tire of the belt layer A pneumatic tire having a tread rubber disposed on the outside and a sidewall rubber disposed on the outer side in the tire axial direction of the carcass and in a sidewall region, wherein the tread rubber extends in the tread width direction to form a ground contact surface A main portion that is connected to both sides of the main portion and is harder than the main portion and the sidewall rubber. A wing rubber made of rubber, and an outer end portion of the wing rubber extends between the main body portion and the folded portion of the carcass ply and terminates, and the wing rubber protrudes outward from the main portion. The outward surface is covered with a sidewall rubber connected to the main portion without being exposed to the tire outer surface, and both end portions of the main portion are gradually reduced in thickness toward the outer side in the tire axial direction. None bifurcated to have a radial outer edge and the inner edge, and an inner portion in the tire axial direction of the wing rubber is sandwiched and axially inward between the outer and inner edges of the main portion It is characterized by extending in a tapered shape.

  In the pneumatic tire of the present invention, the rigidity of the sidewall portion is enhanced by the folded portion extending to the buttress portion, and thus excellent steering stability is exhibited. Further, the distortion of the folded portion located at the buttress portion where the deformation during running is relatively large is effectively relieved and absorbed by the soft wing rubber. Accordingly, the separation damage of the folded portion is suppressed, and the durability of the tire is improved. Furthermore, the outward surface of the wing rubber that protrudes outward from the main part is covered with the sidewall rubber connected to the main part without being exposed to the outer surface of the tire. Therefore, the wing rubber does not come into direct contact with the road surface even in severe turning situations. Accordingly, wear of the wing rubber is prevented, and as a result, wear resistance of the outer surface of the tire is improved.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view of a pneumatic tire according to the present embodiment, and FIG. 2 is a partially enlarged view thereof. The pneumatic tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 disposed on the radially outer side of the carcass 6 and on the inner side of the tread portion 2. With. In this embodiment, an ultra-low flat passenger car radial tire having a flatness ratio of, for example, less than 50% is exemplified.

  FIG. 1 and FIG. 2 show the normal state of a tire in which the tire is assembled on a normal rim (not shown), filled with normal internal pressure, and unloaded. When there is no notice in particular, the dimension of each part of a tire, etc. are values measured in this normal state.

  Here, the “regular rim” is a rim defined for each tire in a standard system including a standard on which a tire is based. For JATA, a standard rim, for TRA, “Design Rim” "ETRTO will be" Measuring Rim ". The “regular internal pressure” is the air pressure defined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE LOAD” is TRA. Maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 180 kPa for tires for passenger cars.

  The carcass 6 has at least one carcass cord arranged at an angle of 75 ° to 90 ° with respect to the tire equator C. In the present embodiment, the carcass 6 overlaps the inside and outside of the tire in the tread portion 2. A ply 6A and an outer carcass ply 6B are shown. For each of the carcass plies 6A and 6B, a sheet-like one made of the carcass cord and a topping rubber covering the carcass cord is used.

  The inner carcass ply 6A includes a main body portion 6a1 straddling a pair of bead cores 5 and 5 through a sidewall portion 3 from the tread portion 2 and a toroidal shape, and is connected to the main body portion 6a1 around the bead core 5 in the tire axial direction. And a folded portion 6b1 which is folded outward from the tire and extends outward in the tire radial direction. Further, the outer carcass ply 6B also includes a main body portion 6a2 and a folded portion 6b2 (note that the main body portion and the folded portion of the carcass ply are collectively referred to as "main body portion 6a" and "folded portion 6b"). Sometimes.).

  The carcass cord is preferably an organic fiber cord such as polyester, nylon, or rayon, but a steel cord may be used if necessary.

  Further, a bead apex rubber 8 made of, for example, hard rubber is disposed between the carcass ply main body portion 6a and the turn-up portion 6b and extends outward from the bead core 5 in the tire radial direction. In order to improve the handling stability, it is desirable that the bead apex rubber 8 has a hardness of 65 to 95 degrees. The height Ha in the tire radial direction from the bead base line BL to the outer end 8t in the tire radial direction of the bead apex rubber 8 is preferably about 20 to 40% of the tire cross-sectional height H.

  In addition, the hardness of rubber | gum is defined as the hardness by the durometer type A based on JIS-K6253.

  In the vicinity of the outer end 8t of the bead apex rubber 8, as shown in an enlarged view in FIG. 2, a rim protector 4a is formed which projects outward in the tire axial direction and continuously extends in the circumferential direction. The rim protector 4a protects a flange of a rim (not shown) and increases the bending rigidity of the bead portion 4, thereby improving the steering stability.

  As shown in FIG. 2, the outer end 6t2 of the folded portion 6b2 of the outer carcass ply 6B of the present embodiment is a region where the distortion during running is small, specifically, the outer end 8t of the bead apex rubber 8 is a tire. Terminated radially inward. On the other hand, the outer end 6 t 1 of the folded portion 6 b 1 of the inner carcass ply 6 A extends outward in the tire radial direction from the outer end of the bead apex rubber 8, and terminates in the buttress portion B without reaching the belt layer 7. As an example, the height H1 of the outer end 6t1 of the folded portion 6b1 from the bead base line BL is preferably 50% or more of the tire cross-section height H. The folded portion 6b1 having such a high turn-up structure extending to the buttress portion B effectively increases the bending rigidity of the sidewall portion 3 or the bead portion 4 by the main body portion 6a and the folded portion 6b of the carcass ply, thereby improving steering stability. Help to improve.

  The carcass 6 may be composed of a single carcass ply. However, when the carcass ply is composed of a plurality of carcass plies, it is sufficient if the folded portion 6b includes one carcass ply extending on the buttress portion B. Therefore, the remaining ply can be a ply consisting only of the main body portion 6a.

  In this example, the belt layer 7 is formed by inclining a belt cord at a small angle of 10 to 40 ° with respect to the tire equator, and the two outer belt plies 7A and 7B are arranged so that the belt cords intersect each other. Constructed by overlapping. The belt cord is preferably a steel cord, for example. Although not shown, a band layer or the like may be appropriately disposed outside the belt layer 7.

  Further, a sidewall rubber Sg is disposed on the outer side in the tire axial direction of the carcass 6 and in the sidewall region, and a bead rubber Bg is disposed in the bead region. These are connected to each other in the vicinity of the rim protector 4a. Since the sidewall rubber Sg and the bead rubber Bg are respectively exposed on the outer surface of the tire, a rubber material excellent in cut resistance and weather resistance is used. In particular, the bead rubber Bg is desirably formed of a rubber material having a hardness higher than that of the side wall rubber Sg in order to improve steering stability.

  A tread rubber Tg is disposed outside the belt layer 7. The tread rubber Tg includes a main portion 10 that extends in the tread width direction to form the ground contact surface 2A, and a wing made of a rubber material that is connected to both sides of the main portion 10 and has a smaller hardness than the main portion 10 and the sidewall rubber Sg. It consists of rubber 11 and has a width wider than the belt layer 7.

  The main portion 10 has a thickness T substantially from the outside of the belt layer 7 to the ground contact surface 2A, for example. The main portion 10 is preferably arranged at least between the tread grounding ends E and E. Here, the tread ground contact end E is the ground contact position on the outermost side in the tire axial direction when a normal load is applied to the tire in the normal state and pressed against a flat surface with a camber angle of 0 degrees. In addition, “regular load” is the load that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is specified for JATMA, and the table “TIRE LOAD LIMITS” for TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” in the case of ETRTO.

  The main portion 10 is preferably made of a rubber material having a good balance between grip performance on the road surface and wear resistance. Although not particularly limited, the hardness of the main portion 10 is preferably 55 degrees or more, more preferably 60 degrees or more, and preferably 70 degrees or less, more preferably 67 degrees or less. Although not shown, the main portion 10 is formed by laminating a plurality of types of rubber layers having different hardness such as cap rubber, base rubber, and under rubber, for example, from the outer side to the inner side in the tire radial direction. It may be formed. In this case, the average value weighted by the volume of each rubber layer is adopted as the hardness of the main portion 10.

  FIG. 3 shows a cross-sectional view of the tread rubber Tg before vulcanization. The main portion 10 of the tread rubber Tg has an intermediate portion 10a extending in the width direction with a substantially constant thickness, and bifurcated portions 10b formed at both ends thereof. In the cross section, the bifurcated portion 10b has a thickness that gradually decreases toward the outer side in the tire axial direction and an outer edge portion 14 that is positioned on the outer side in the tire radial direction, and a thickness that gradually decreases toward the outer side in the tire axial direction. And an inner edge 15 located radially inward. A recess having a substantially triangular cross section that is recessed toward the tire equator C side and continuous in the circumferential direction is formed between the outer edge portion 14 and the inner edge portion 15.

  2 and 3, the wing rubber 11 of this embodiment is sandwiched between the outer edge portion 14 and the inner edge portion 15 of the bifurcated portion 10b of the main portion 10, and the recess The inner portion 11a is tapered to the inner side in the tire axial direction so as to satisfy the condition, and the outer portion 11b protrudes outward from the main portion 10 in the tire axial direction and gradually decreases in thickness toward the outer side in the tire axial direction. . Therefore, the wing rubber 11 of this embodiment is formed in a substantially diamond shape in cross section before vulcanization.

  The outer end 11t of the wing rubber 11 extends between the carcass ply main body portion 6a and the folded portion 6b, and is disposed so as to come into contact with the topping rubbers of the main body portion 6a and the folded portion 6b. Since the wing rubber 11 is made of a rubber material that is softer than the main portion 10, the wing rubber 11 can effectively relieve and absorb the distortion during traveling of the folded portion 6b1 located in the buttress portion B. Therefore, separation damage of the folded portion 6b1 is suppressed, and the durability of the tire is enhanced.

  In order to exhibit such an effect more reliably, the hardness of the wing rubber 11 is preferably 55 degrees or less, more preferably less than 55 degrees, and further preferably 50 degrees or less. On the other hand, when the hardness of the wing rubber 11 is extremely small, it is preferable for the strain absorption effect, but a rigidity step with the main portion 10 and the side wall rubber Sg is likely to occur, and as a result, each rubber portion is caused by the difference in deformation amount. There is a possibility that peeling or the like is likely to occur on the connection surface. From such a viewpoint, the hardness of the wing rubber 11 is preferably 40 degrees or more, more preferably 45 degrees or more. In order to further enhance the above effect, the difference in hardness between the wing rubber 11 and the main portion 10 is preferably 10 degrees or more, more preferably 12 degrees or more, and preferably 20 degrees or less, more preferably 18 degrees or less is desirable.

  Particularly preferably, the wing rubber 11 has substantially the same rubber composition and type of carbon black as the topping rubber of the carcass plies 6A and 6B with which the wing rubber 11 is in contact. Such a wing rubber 11 further improves the adhesion strength of the carcass plies 6A and 6B with the topping rubber, and further reliably prevents separation at the rubber interface.

Here, in two rubber materials, that the rubber composition is substantially the same means that the types of rubber polymers constituting each rubber material are completely the same. This is because high adhesiveness can be exhibited. However, it goes without saying that their blending ratio (mass% ratio) may be different. Accordingly, in the present specification, for example, the following rubber materials A and B are treated as having substantially the same rubber composition.
Rubber material A NR: BR = 60: 40 (mass%)
Rubber material B NR: BR = 30: 70 (mass%)

  In addition, in the two rubber materials, the types of the carbon blacks are substantially the same. When the average particle sizes of the carbon blacks blended in the two rubber materials are r1 and r2, respectively, It is defined as the case where they are the same or the ratio (r1 / r2) (where r1> r2) of the average particle diameter is 2.0 or less.

  Further, if the thickness of the wing rubber 11 is too small between the main body portion 6a and the folded portion 6b1, the above-described strain relaxation and absorption effects tend not to be obtained. From such a viewpoint, the thickness t1 of the wing rubber 11 on the tire axial direction line passing through the outer end 6t1 of the folded portion 6b1 is preferably 0.3 mm or more, more preferably 1.0 mm or more. On the other hand, if the thickness t1 of the wing rubber 11 is too large, for example, the outer end 6t1 of the folded portion 6b1 may excessively approach the outer surface of the tire, and a new strain concentration portion may be generated. From such a viewpoint, the thickness t1 is preferably 5 mm or less, more preferably 3 mm or less.

  Further, in the pneumatic tire 1 of the present invention, the outward facing surface 12 which is the surface on the tire outer surface side of the outer portion 11b of the wing rubber 11 protruding outward from the main portion 10 is a sidewall rubber connected to the main portion 10. It is covered with Sg without being exposed to the outer surface of the tire. The sidewall rubber Sg extends along the outer side of the folded portion 6b1 of the carcass ply in the tire radial direction, extends outside the outer end 6t1 of the folded portion 6b1, and covers the outward surface 12. It is tapered and connected to the outer side in the tire radial direction of the main part 10 of the tread rubber Tg (so-called SOT structure).

  For example, in the case of severe traveling such as high-speed turning, the tire outer surface on the outer side in the tire axial direction from the tread ground contact E may contact the road surface. At this time, if the flexible wing rubber 11 is brought into contact with the road surface, the wing rubber is quickly worn and the appearance of the tire is remarkably impaired. On the other hand, in the pneumatic tire 1 of the present invention, since the outward surface 12 of the outer portion 11b of the wing rubber 11 is covered with the sidewall rubber Sg, the wing rubber 11 does not directly contact the road surface.

  In addition, since the side wall rubber Sg is made of a rubber material harder than the wing rubber 11, the wear resistance can be improved. However, when a rubber material that is softer than the main portion 10 is used for the sidewall rubber Sg, it is desirable that the outer end Sgt of the sidewall rubber Sg in the tire radial direction is positioned on the outer side in the tire axial direction from the tread ground contact end E. . This reduces the opportunity for the sidewall rubber Sg to directly contact the road surface and suppresses its wear. From such a viewpoint, the shortest distance t2 between the outward surface 12 and the tire outer surface is preferably 2 mm or more, more preferably 3 mm or more.

  Here, the hardness of the side wall rubber Sg is not particularly limited, but is preferably made of a rubber material of 45 degrees or more, more preferably 50 degrees or more so that premature wear does not occur even in contact with the road surface. It is desirable to be done. On the other hand, if the hardness of the sidewall rubber Sg is excessively large, the flexibility of the sidewall portion 3 is lowered and the ride comfort may be impaired. Therefore, it is preferably 60 degrees or less, more preferably 55 degrees or less, and still more preferably Is preferably less than 55 degrees.

  Moreover, since the wing rubber 11 is not exposed to the outer surface of the tire, the wing rubber 11 is not easily affected by ultraviolet rays or oxygen. Therefore, the anti-aging agent is not blended in the wing rubber 11 of the present embodiment. This helps to increase the non-oil resource ratio of the tire.

  Moreover, the shape of the wing rubber 11 is not limited to the said embodiment. For example, the wing rubber 11 may be formed with a substantially triangular cross section as shown in FIGS. 4 and 5. FIG. 4 shows a cross-sectional view of the tread rubber Tg before vulcanization. The main portion 10 of the tread rubber Tg includes an intermediate portion 10a extending in the width direction with a substantially constant thickness T, and a gradually decreasing portion 10c formed at both ends of the tread rubber Tg and gradually decreasing toward the outer side in the tire axial direction. Consists of.

  Further, the wing rubber 11 of this embodiment is disposed on the inner side in the tire radial direction of the gradually decreasing portion 10c and extends in a tapered shape toward the inner side in the tire axial direction, and protrudes outward from the main portion 10 in the tire axial direction. The outer portion 11b has a thickness that gradually decreases toward the outer side in the tire axial direction. Therefore, the wing rubber 11 of this embodiment is formed in a substantially triangular cross section before vulcanization.

  Each of the tread rubbers Tg in FIGS. 3 to 4 may be an extrudate that is simultaneously and integrally formed by an extruder having a plurality of heads or the like. Preferably, as shown in FIG. It may be formed of a strip laminate formed by winding the rubber strips P1 to P3 spirally. In this embodiment, the radially inner portion ST1 of the main portion 10 is first formed by the first rubber strip P1, and then the wing rubber 11 is formed by using the second rubber strip P2 on both sides thereof. Further, a third rubber strip P3 having the same composition as that of the first rubber strip P1 is spirally wound around the radially inner portion ST1 of the main portion 10. As a result, a tread rubber Tg having substantially the same cross-sectional shape as FIG. 3 is formed.

  By the way, the pneumatic tire 1 of this embodiment is manufactured through a stitching process in the green tire molding stage. As shown in FIG. 7, the stitching step is an unvulcanized carcass 6 inflated in a toroid shape, an unvulcanized belt layer 7 disposed on the outside thereof, and further disposed on the outside thereof. A raw tire base RT including an unvulcanized ring-shaped tread rubber Tg is rotated around its central axis, and a stitching roller j pressed against the tread rubber Tg and rotated in the circumferential direction by the frictional force is provided. This is performed by slowly moving from the vicinity of the tire equator C toward the tread end side and along the contour of the carcass 6. This is performed for the purpose of pressing the tread rubber Tg against the belt layer 7 and the carcass 6 to bring them into close contact with each other and discharging the air between them to the outside in the tire axial direction. In addition, after this stitching process, the side wall rubber Sg is wound up with the folding | turning part 6b of a carcass ply.

  3 and 4 are both covered with the outer edge portion 14 of the main portion 10 or the gradually decreasing portion 10c, the stitching roller j moves from the main portion 10 to the wing rubber 11. When this occurs, the wing rubber 11 is difficult to peel off from the main portion 10.

  On the other hand, for example, in the wing rubber 11 shown in FIG. 8 shown in FIG. 8, when the stitching roller j contacts the wing rubber 11 as shown in FIG. In some cases, the wing rubber 11 may be peeled off from the portion 10 or the wing rubber 11 may be provided at the boundary between them. Such a defective product is particularly likely to occur when the tread rubber Tg is made of the above-described strip laminate. These damages may deteriorate the appearance and uniformity of the tire. In the wing rubber 11 of this embodiment, such a malfunction can be prevented more reliably.

  2 and 5, the outer end 11t of the wing rubber 11 is illustrated as being separated from the bead apex rubber 8. This is because when the outer end 11t approaches the outer end 8t of the bead apex rubber, distortion tends to concentrate on that portion, which is not preferable in terms of durability. From this point of view, when the wing rubber 11 and the bead apex rubber 8 are separated from each other, the outer end 11t of the wing rubber 11 and the outer end 8t of the bead apex rubber have a distance R of 5.0 mm or more in the tire radial direction. It is desirable to separate.

  In contrast to these embodiments, for example, as shown in FIG. 10, the bead apex rubber 8 and the wing rubber 11 may be directly connected. In this case, the connection length D along the tire radial direction between the bead apex rubber 8 and the wing rubber 11 is preferably 2.0 mm or more, more preferably 3.0 mm or more. Accordingly, the outer end 11t of the wing rubber 11 can be separated from the outer end 8t of the bead apex rubber 8 as described above. Moreover, according to this embodiment, the distortion of the outer end 8 t of the bead apex rubber 8 is absorbed by the wing rubber 11. Further, since the soft wing rubber 11 is disposed in the entire region between the carcass ply main body portion 6a and the folded portion 6b outside the outer end 8t in the tire radial direction, the main body portion 6a and the folded portion 6b Since the interlayer distortion is effectively absorbed by the wing rubber 11, the durability of the carcass ply is further improved.

  Although the embodiment of the present invention has been described in detail above, it is needless to say that the present invention is not limited to the above-described specific embodiment but can be variously modified.

Pneumatic radial tires for passenger cars (size: 215 / 40R18) were prototyped based on the specifications in Table 1 and tested for durability, handling stability and wear resistance. Each carcass of each tire was composed of one carcass ply. In addition, since each tire was manufactured through a stitching process, tests were also performed on the defective product occurrence rate and uniformity.
The test method is as follows.

<Durability>
The test tire is assembled on a rim (8 x 18) and filled with an internal pressure of 220 kPa, and running on a drum tester with a radius of 0.85 m until the tire breaks at a speed of 80 km / H and a longitudinal load of 5.5 kN. I checked the distance. The result is displayed as an index with the traveling distance of Comparative Example 2 as 100. The larger the value, the better.

<Steering stability>
A Japanese passenger car with a displacement of 2500 cc is fitted with four test tires (rim: 8 × 18, internal pressure 220 kPa) and travels on a dry asphalt road with one driver on board, as well as steering response, rigidity, grip, etc. The characteristic regarding is shown by an index with a comparative example of 100 by sensory evaluation of the driver. A larger value is better.

<Abrasion resistance>
Under the above vehicle conditions, one driver rides on a dry asphalt road surface for 3000 km, and the wear condition of the tire outer surface including the tread portion was observed with the naked eye.

<Defect product incidence>
When 100 tires were prototyped, the number of defective products in which wing rubber was peeled off or rolled during the stitching process in the green tire molding stage was examined.
Table 1 shows the test results and Table 2 shows the wing rubber composition.

It is sectional drawing of the pneumatic tire which shows one Embodiment of this invention. FIG. It is a fragmentary sectional view of tread rubber. It is a fragmentary sectional view of tread rubber of other embodiments. It is a fragmentary sectional view of the pneumatic tire which shows other embodiment of this invention. It is a fragmentary sectional view of tread rubber of other embodiments. It is a fragmentary sectional view of the tire explaining a stitching process. It is a fragmentary sectional view of tread rubber of other embodiments. It is a fragmentary sectional view of the tire explaining a stitching process. It is a fragmentary sectional view of the pneumatic tire which shows other embodiment of this invention. It is a fragmentary sectional view of the conventional pneumatic tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A, 6B Carcass ply 6a1, 6a2 Main part 6b1, 6b2 Folding part 7 Belt layer 10 Main part 11 Wing rubber 12 Outward surface Sg Side wall rubber Tg tread rubber

Claims (3)

A body part straddling between the pair of bead cores from the tread part through the sidewall part, and a buttress part extending from the inner side to the outer side in the tire axial direction and extending outward from the inner side in the tire axial direction. A carcass including a carcass ply comprising a folded portion terminating in
A belt layer disposed radially outside the carcass and inside the tread,
A pneumatic tire having a tread rubber disposed on the outer side in the tire radial direction of the belt layer and a sidewall rubber disposed on the outer side in the tire axial direction of the carcass and in a sidewall region,
The tread rubber has a main part that extends in the tread width direction to form a ground contact surface, and a wing rubber that is connected to both sides and is made of rubber having a smaller hardness than the main part and the sidewall rubber,
The outer end portion of the wing rubber extends between the main body portion and the folded portion of the carcass ply and terminates,
The outward surface of the wing rubber that protrudes outward from the main part is covered with the sidewall rubber connected to the main part without being exposed to the tire outer surface ,
In addition, a bead apex rubber extending in a tapered shape from the bead core to the outside in the tire radial direction is disposed between the main body portion and the folded portion, and
A pneumatic tire characterized in that an outer end portion of the bead apex rubber is connected to the wing rubber and has a connection length of 2.0 mm or more along the tire radial direction . A body part straddling between the pair of bead cores from the tread part through the sidewall part, and a buttress part extending from the inner side to the outer side in the tire axial direction and extending outward from the inner side in the tire axial direction. A carcass including a carcass ply comprising a folded portion terminating in
A belt layer disposed radially outside the carcass and inside the tread,
A tread rubber disposed on the outer side in the tire radial direction of the belt layer; and
A pneumatic tire having sidewall rubber disposed on the outer side in the tire axial direction of the carcass and in a sidewall region,
The tread rubber has a main part that extends in the tread width direction to form a ground contact surface, and a wing rubber that is connected to both sides and is made of rubber having a smaller hardness than the main part and the sidewall rubber,
The outer end portion of the wing rubber extends between the main body portion and the folded portion of the carcass ply and terminates,
The outward surface of the wing rubber that protrudes outward from the main part is covered with the sidewall rubber connected to the main part without being exposed to the tire outer surface,
Moreover, the carcass ply has a carcass cord and a topping rubber that covers the carcass cord, and
The pneumatic tire according to claim 1, wherein the wing rubber has substantially the same rubber composition and carbon black as the topping rubber . A body part straddling between the pair of bead cores from the tread part through the sidewall part, and a buttress part extending from the inner side to the outer side in the tire axial direction and extending outward from the inner side in the tire axial direction. A carcass including a carcass ply comprising a folded portion terminating in
A belt layer disposed radially outside the carcass and inside the tread,
A tread rubber disposed on the outer side in the tire radial direction of the belt layer; and
A pneumatic tire having sidewall rubber disposed on the outer side in the tire axial direction of the carcass and in a sidewall region,
The tread rubber has a main part that extends in the tread width direction to form a ground contact surface, and a wing rubber that is connected to both sides and is made of rubber having a smaller hardness than the main part and the sidewall rubber,
The outer end portion of the wing rubber extends between the main body portion and the folded portion of the carcass ply and terminates,
The outward surface of the wing rubber that protrudes outward from the main part is covered with the sidewall rubber connected to the main part without being exposed to the tire outer surface,
Moreover, both end portions of the main portion have a bifurcated shape having an outer edge portion and an inner edge portion in the tire radial direction in which the thickness gradually decreases toward the outer side in the tire axial direction, and
The pneumatic tire is characterized in that an inner portion in the tire axial direction of the wing rubber is sandwiched between an outer edge portion and an inner edge portion of the main portion and extends in a tapered shape toward the inner side in the tire axial direction .

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