JP2010247794A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the transverse rigidity or the like of a bead without spoiling the comfort in riding. <P>SOLUTION: A pneumatic tire includes an inside part in the direction of the radius of a tire of a side wall rubber 12 extending inward along a carcass 6 in the tire radial direction, and a rolling part 12A extending inward in the tire axial direction along the interior region in the tire radial direction of the bead core 8. Inward the tire radial direction of the rolling part 12A, a chafer rubber 13 is disposed which is made of rubber harder than the side wall rubber 12 and which prevents the contact between the rolling part 12A and rim R. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire capable of improving the lateral rigidity of a bead portion without causing an increase in the number of members and a deterioration in riding comfort.

  With the development of the highway network in recent years, further improvements in durability, high-speed stability and riding comfort are desired for passenger car tires. On the other hand, it is important for each tire manufacturer to produce such a high-performance tire at a low cost.

  For example, Patent Document 1 shown below discloses a pneumatic tire having a bead portion in which a chafer rubber c having a substantially U-shaped cross section made of hard rubber is arranged around a bead core b as shown in FIG. Yes. However, such a pneumatic tire tends to cause a decrease in ride comfort.

  Further, in Patent Document 2 below, as shown in FIG. 7, air having a bead portion in which a hard rubber layer g1 is disposed between two carcass plies k and k extending inward in the tire radial direction of the bead core b. An inset tire is disclosed. Further, in Patent Document 3 below, as shown in FIG. 8, a pneumatic layer in which a rubber layer g2 made of a hard rubber material is provided on the inner side in the tire radial direction of the bead core b for the purpose of improving durability and riding comfort. A tire is disclosed.

  However, the pneumatic tires of Patent Document 2 and Patent Document 3 require new rubber layers (rubber members) g1 and g2 for reinforcing the bead portion. For this reason, a number of members increases and a new manufacturing process for attaching them increases. Therefore, it tends to cause a decrease in productivity and an increase in production cost.

Japanese Patent Laid-Open No. 11-320705 JP 2000-177338 A JP 2004-123050 A

  The present invention has been devised in view of the above-described problems, and is provided with an entrainment portion that extends an inner region in the tire radial direction of the bead core by extending the tire radial inner portion of the sidewall rubber. The main purpose is to provide a pneumatic tire capable of improving the bead rigidity and the like without causing deterioration in ride comfort and an increase in the number of members.

  The invention according to claim 1 of the present invention includes a main body portion that extends from the tread portion through the sidewall portion to the bead core of the bead portion, and is connected to the main body portion and folded around the bead core from the inner side to the outer side in the tire axial direction. A pneumatic tire having a carcass including a carcass ply formed of a folded portion and a sidewall rubber disposed on the outer side in the tire axial direction of the carcass and extending inward and outward in the tire radial direction of the carcass. An inner portion of the tire radial direction extends inward in the tire radial direction along the carcass, and has a winding portion extending inward in the tire axial direction on an inner region of the inner surface of the bead core in the tire radial direction. It is made of rubber harder than the sidewall rubber and is wound inwardly in the tire radial direction. Chafer rubber to prevent contact between the saw unit and the rim, characterized in that disposed.

  According to a second aspect of the present invention, the inner side portion of the sidewall rubber extends outward in the radial direction along the inner side surface in the tire axial direction of the main body portion of the carcass ply and the winding portion and the winding portion. The pneumatic tire according to claim 1, comprising a rising portion.

  According to a third aspect of the present invention, the chafer rubber includes a main part extending inward in the tire radial direction of the bead core, a tire axial direction inner side of the main part extending in the tire axial direction, and an inner side in the tire axial direction of the rising part in the tire radial direction. The pneumatic tire according to claim 2, further comprising an inner portion extending outward, wherein an outer end height of the rising portion in a tire radial direction is smaller than an outer end height of an inner portion of the chafer rubber.

  According to a fourth aspect of the present invention, the chafer rubber includes a main portion extending inward in the tire radial direction of the bead core, a tire axial direction inner side of the main portion extending in the tire axial direction, and a tire axial direction inner side of the rising portion in the tire radial direction. 3. The pneumatic tire according to claim 2, further comprising an inner portion extending outward, wherein an outer end height of the rising portion in a tire radial direction is greater than an outer end height of an inner portion of the chafer rubber.

  The invention according to claim 5 is the pneumatic tire according to any one of claims 1 to 4, wherein the entrainment portion has a thickness of 1.3 mm to 2.0 mm.

  According to the first aspect of the present invention, the inner side portion of the sidewall rubber in the tire radial direction extends inward in the tire radial direction along the carcass, and the entangled portion extends inward in the tire radial direction of the bead core in the tire axial direction. Have Since the entraining portion is made of a rubber material that is softer than the chafer rubber, it can absorb the impact in the tire radial direction during traveling. Thereby, riding comfort improves.

  Further, the entangled portion can easily increase the rubber volume between the bead core and the bead bottom surface and between the rim flange and the bead core. Therefore, the compressive force between the bead core and the rim is increased, and the position of the bead core with respect to the rim is stabilized. This is useful for improving the lateral rigidity and the like of the bead portion and exhibiting excellent steering stability and anti-rim displacement performance. Furthermore, since the soft entangled portion is prevented from coming into contact with the rim by the hard chafer rubber, the durability does not deteriorate.

  Moreover, since the entrainment part is formed by extending the sidewall rubber (as a part of the sidewall part), each of the above actions can be exhibited without increasing the number of members. Therefore, productivity is improved and production cost is suppressed.

  In the invention according to claim 2, the inner side portion of the sidewall rubber includes the winding portion and a rising portion that extends to the outer side in the radial direction along the inner side surface in the tire axial direction of the main body portion of the carcass ply. Including. By including such a raised portion, the rubber volume on the toe side of the bead portion can be easily increased, thereby further improving the lateral rigidity of the tire. In particular, the rotation of the bead core at the time of turning of the vehicle is suppressed, and excellent steering stability and anti-rim displacement performance can be exhibited.

  Further, as in the third aspect of the invention, when the outer end height of the rising portion in the tire radial direction is smaller than the outer end height of the inner portion of the chafer rubber, an excessive increase in tire mass is prevented. However, when the height of the outer end of the rising portion in the tire radial direction is larger than the height of the outer end of the inner portion of the chafer rubber, as in the invention described in claim 4, the lateral rigidity is further increased, and thus the steering stability is improved. Improves.

  Further, when the thickness of the sidewall rubber is limited to a predetermined value as in the invention described in claim 5, it is possible to improve the lateral rigidity, riding comfort and tire mass of the bead portion in a well-balanced manner.

It is a right half sectional view of the tire of one embodiment of the present invention. It is a fragmentary sectional view which expands and shows the bead part. It is a fragmentary sectional view of the bead part which shows other embodiments of the present invention. It is a fragmentary sectional view of the bead part which shows other embodiments of the present invention. (A) is a fragmentary sectional view of the bead part which shows the comparative example 1, (b) is a fragmentary sectional view of the bead part which shows the comparative example 2. It is a fragmentary sectional view of the bead part for explaining the conventional technology. It is a fragmentary sectional view of the bead part for explaining the conventional technology. It is a fragmentary sectional view of the bead part for explaining the conventional technology.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a pneumatic tire 1 includes a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both sides thereof, and a bead positioned at an inner end of each sidewall portion 3. In this example, a radial tire for a passenger car is illustrated. FIG. 1 shows an unloaded normal state in which the pneumatic tire 1 of the present embodiment is assembled to the normal rim R and filled with the normal internal pressure.

  The “regular rim” is a rim determined by each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA. For ETRTO, use "Measuring Rim".

  In addition, the “regular internal pressure” is an air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum value described in TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES is "INFLATION PRESSURE" for ETRTO, but 180 kPa for tires for passenger cars.

  Further, the pneumatic tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead portion 4, and a belt layer disposed inside the tread portion 2 and outside the carcass 6 in the tire radial direction. 7, a sidewall rubber 12 disposed outside the carcass 6 in the tire axial direction and extending the sidewall portion 3 inward and outward in the tire radial direction, and disposed inward in the tire radial direction of the bead core 5 and in contact with the regular rim R A chafer rubber 13 forming a bead surface and an inner liner 15 made of a butyl rubber excellent in air impermeability attached to a tire cavity surface are provided.

  In the present embodiment, the carcass 6 includes two carcass plies 6A and 6B. Each of the carcass plies 6A and 6B includes a main body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and connected to the main body portion 6a and around the bead core 5 from the inner side in the tire axial direction to the outer side. And a folded portion 6b folded back.

  The folded portion 6b of the present embodiment extends outward in the tire radial direction to reach the tread portion 2 and terminates between the belt layer 7 and the main body portion 6a of the carcass ply. Such a folded portion 6b is useful for effectively increasing the bending rigidity of the sidewall portion 3 with a small number of carcass plies. However, it goes without saying that the pneumatic tire of the present invention is not limited to such a structure of the folded portion 6b.

  Each of the carcass plies 6A and 6B has a carcass cord arranged at an angle of 75 ° to 90 ° with respect to the tire equator C. For the carcass cord, for example, an organic fiber cord such as nylon, polyester, rayon, or aromatic polyamide is suitably employed. A bead apex made of hard rubber with a JISA hardness of about 75 to 95 ° extends from the bead core 5 outwardly in the tire radial direction between the main body portion 6a and the folded portion 6b of the carcass ply. Rubber 8 is arranged. Thereby, the bending rigidity of the bead part 4 is reinforced.

  The belt layer 7 is formed of two belt plies 7A and 7B in which the belt cord is overlapped with the tire equator C at an angle of, for example, 10 ° to 35 ° and intersecting each other. As the belt cord, a steel cord is suitable, but a highly elastic organic fiber cord such as an aromatic polyamide fiber can also be used.

  The chafer rubber 13 is formed of a hard rubber and has a substantially U-shaped cross section. The chafer rubber 13 extends to the inner side in the tire radial direction of the bead core 5 and to the inner side in the tire axial direction of the main portion 13A. An inner portion 13B extending outward in the tire radial direction and an outer portion 13C extending outward in the tire radial direction in a tire axial direction outside of the main portion 13A are included. The main portion 13A and the outer portion 13B of the chafer rubber 13 form a bead outer surface that contacts the rim R. Such a chafer rubber 13 effectively prevents wear or chipping due to friction with the rim, and helps to prevent defects such as rim displacement by suppressing deformation of the bead portion. As shown in FIG. 2, in order to further reinforce the outer surface of the chafer rubber 13, a rubber-coated canvas material 17 or the like may be added.

  The sidewall rubber 12 is made of rubber having excellent adhesiveness mainly composed of natural rubber, for example, and is made of softer rubber than the chafer rubber 13. Further, the outer side portion 12o of the sidewall rubber 12 in the tire radial direction extends, for example, into a gap between the outer end portion of the belt layer 7 and the carcass 6 and terminates in a tapered shape. On the other hand, as shown in FIG. 2 in which the bead portion of FIG. 1 is enlarged, an inner portion 12i in the tire radial direction of the sidewall rubber 12 extends along the carcass 6 in the tire radial direction, and the bead core 5 A winding portion 12A is formed that extends inwardly in the tire axial direction in the inner region P2 on the inner side surface in the tire radial direction. The inward region P2 is a region in which the inner surface 5i in the tire radial direction of the bead core 5 is projected inward in the tire radial direction.

  The entrainment portion 12A of the present embodiment terminates at the inward region P2. That is, the inner end S of the inner part 12i of the sidewall rubber 12 is located in the inner region P2.

  Since the entraining portion 12A is made of a rubber material that is softer than the chafer rubber 13, the vibration input from the tread portion 2 during traveling can be effectively absorbed before being transmitted to the rim R. Thereby, riding comfort improves. Further, the entrainment portion 12A can easily increase the rubber volume between the bead core 5 and the bead bottom surface 14 and between the rim flange and the bead core. Therefore, the compressive force between the bead core 5 and the rim R is increased, and the position of the bead core 5 with respect to the rim R is stabilized. This is useful for improving the lateral rigidity and the like of the bead portion 4 and exhibiting excellent steering stability. Note that the inner end portion 15i of the tapered inner liner 15 is terminated between the inner portion 13B of the chafer rubber 13 and the carcass 6 so as to be terminated.

  Further, the entrainment portion 12A is formed as a part of the sidewall rubber 12 (the same composition as the sidewall rubber) by extending the sidewall rubber 12, so that the lateral rigidity of the bead portion 4 can be increased without increasing the number of members. Improve. Therefore, productivity can be improved and an increase in production cost can be suppressed.

  Further, since the chafer rubber 13 made of rubber harder than the sidewall rubber 12 is disposed inward of the winding portion 12A in the tire radial direction, the winding portion 12A does not come into contact with the rim R. It is also possible to prevent deterioration of durability, for example, by suppressing damage at the surface.

  Here, the rubber hardness Hsw of the sidewall rubber 12 is not particularly limited, but if it is too large, the vibration absorbability tends to be lowered, and there is a tendency that sufficient improvement in riding comfort cannot be expected, and conversely it is too small. In addition, the lateral rigidity of the bead portion and the resistance to rim displacement tend to decrease. From such a viewpoint, the rubber hardness Hsw of the sidewall rubber 12 is preferably 45 ° or more, more preferably 55 ° or more, and preferably 70 ° or less, more preferably 60 ° or less. In addition, in this specification, rubber hardness shall be the hardness by durometer type A based on JIS-K6253.

  Further, if the length Ws in the tire axial direction of the entraining portion 12A extending over the inward region P2 is too small, the above-described actions tend not to be sufficiently exhibited. From such a viewpoint, the length Ws in the tire axial direction extending over the inner region P2 of the entraining portion 12A is preferably 30% or more, more preferably 50%, of the tire axial direction length W1 of the inner region P2. More preferably, 80% or more is desirable. The inner end S of the entraining portion 12A (sidewall rubber 12) is preferably formed in a tapered shape as in the present embodiment.

  Further, if the thickness t1 of the entraining portion 12A is too large, the tire mass may be excessively increased. Conversely, if the thickness t1 is too small, the above-described action may not be sufficiently exhibited. From such a viewpoint, the thickness t is preferably 0.8 mm or more, more preferably 1.3 mm or more, and preferably 2.5 mm or less, more preferably 2.0 mm or less. In the present embodiment, in the region E that is ½ or less of the tire cross-section height H, it is formed with the thickness t1.

  Note that the rubber hardness Hch of the chafer rubber 13 is not particularly limited, but if it is too large, a significant difference in rigidity occurs between the side wall rubber 12 and concentration of strain is likely to occur, and rim assembly is difficult. Conversely, if it is too small, there is a tendency that sufficient rim displacement resistance performance cannot be exhibited. From such a viewpoint, the rubber hardness Hch of the chafer rubber 13 is preferably 70 ° or more, more preferably 80 ° or more, and preferably 95 ° or less, more preferably 85 ° or less.

  FIG. 3 shows another embodiment of the present invention. In this embodiment, the inner side portion 12i of the sidewall rubber 12 extends to the outer side in the radial direction along the inner side surface 6ai in the tire axial direction of the main body portion 6a of the carcass ply and connected to the winding portion 12A and the winding portion 12A. It is comprised from the starting part 12B. Such a rising portion 12B can further improve the lateral rigidity of the tire, and can effectively suppress the fall of the bead portion 4 during turning by increasing the rubber volume on the bead toe side.

  In this embodiment, the shear strain at the interface between the inner portion 13B of the chafer rubber 13 and the carcass 6 can be relaxed and absorbed by the rising portion 12B made of a flexible rubber. Therefore, it is useful for suppressing damage such as ply loose at this portion and improving the durability of the bead portion 4. Further, in the present embodiment, the outer end of the rising portion 12B is interposed between the inner liner 15 made of butyl rubber and the main body portion 6a of the carcass ply and terminates. Thereby, the adhesion area between the inner liner 15 and the carcass ply 6A, which is likely to be a starting point of damage, is reduced, which is useful for improving durability.

  In the present embodiment, the outer end height Hs in the tire radial direction of the raised portion 12B with respect to the bead base line BL is larger than the outer end height H1 in the tire radial direction of the inner portion 13B of the chafer rubber. Is set to In such an embodiment, the lateral rigidity of the bead portion 4 can be sufficiently increased, and the rim displacement resistance can be improved. However, if the outer end height Hs of the rising portion 12B becomes excessively large, the effect of improving the lateral rigidity of the bead portion is peaked, but the tire mass is unnecessarily increased. From such a viewpoint, the ratio (Hs / H1) is preferably 150% or less, more preferably 130% or more, and still more preferably 110% or less.

  Further, as shown in FIG. 4, the outer end height Hs of the rising portion 12B in the tire radial direction can be set smaller than the outer end height H1 of the inner portion 13B of the chafer rubber in the tire radial direction. However, in such an embodiment, the outer end height Hs of the rising portion 12B of the sidewall rubber 12 is larger than the height of the outer surface 5o of the bead core 5 and is larger than the outer end height H1 of the inner portion 13B of the chafer rubber. It is desirable to make it small. Accordingly, it is possible to sufficiently increase the lateral rigidity of the bead portion 4 while minimizing an increase in tire mass and to improve the resistance to rim displacement.

  For example, an extrusion-molded product extruded in advance with a predetermined cross section may be used as the sidewall rubber 12 described above, and a ribbon-shaped rubber strip having a small width and a small thickness is spirally formed in the tire circumferential direction. Any of the strip laminated bodies formed by winding the films may be used. In particular, when forming the sidewall rubber 12 with a small thickness, the latter manufacturing method is preferably employed.

  As mentioned above, although the especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect. For example, the present invention can be applied to various categories of tires such as heavy duty tires and motorcycle tires in addition to passenger car tires.

  A radial tire having a tire size of 215 / 45R17 was prototyped based on the specifications shown in FIGS. 2 to 5 and Table 1, and the performance of each sample tire was tested. Each test method is as follows.

<Tire mass>
The mass per tire was measured. The result is displayed as an index with the mass of Comparative Example 1 as 100. The smaller the value, the lighter the weight.

<Productivity>
The production time required to produce one tire was measured. The results are displayed as an index with the manufacturing time of Comparative Example 1 as 100. The larger the value, the better the manufacturing time.

<Ride comfort and lateral rigidity>
The following vehicles with test tires mounted on four wheels drive on dry asphalt road steps, Belgian roads (cobblestone roads), Bitzmann roads (roads covered with pebbles), and drivers for ruggedness, thrust and damping The sensory evaluation was performed. The sense of lateral stiffness during turning on dry asphalt roads was evaluated by the driver's sensuality. All results are displayed as an index with Comparative Example 1 as 100. Larger numbers are better.
Vehicle: displacement 3500cm ³ domestic FF car Rim: 6JJ × 17
Internal pressure: 180 kPa
Crew: Only one driver

<Rim slip resistance>
One cycle of accelerating the dry asphalt road surface to a speed of 100 km / H with the above vehicle, braking with a sudden brake and stopping was repeated 10 times. Thereafter, the amount of relative deviation between the tire and the rim in the tire circumferential direction was measured. The result was expressed as an index where the average value of the shift amount of the four wheels was calculated and the reciprocal of the value of Comparative Example 1 was taken as 100. The larger the value, the better.
Table 1 shows the test results.

  As a result of the test, it is possible to confirm that the ride comfort and the lateral rigidity of all the examples are improved without excessively increasing the mass. It can also be confirmed that the amount of rim displacement is small.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 5b The inner surface 6 of a tire radial direction of a bead core 6 Carcass 6a Main part 6b Turn-up part 6A Carcass ply 6B Carcass ply 12 Side wall rubber 12A Roll-in part 13 Chafer rubber P2 Inner region R rim on the inner surface in the tire radial direction

Claims (5)

A carcass including a carcass ply including a main body part extending from the tread part through the sidewall part to the bead core of the bead part, and a folded part connected to the main body part and folded around the bead core from the inner side in the tire axial direction; And a pneumatic tire having a sidewall rubber disposed on the outer side in the tire axial direction of the carcass and extending a sidewall portion inward and outward in the tire radial direction,
The inner side portion of the sidewall rubber in the tire radial direction has a winding portion extending inward in the tire radial direction along the carcass and extending inward in the tire axial direction on an inner region of the inner side surface in the tire radial direction of the bead core. A pneumatic tire comprising a chafer rubber made of rubber harder than sidewall rubber and preventing contact between the entangled portion and the rim is disposed inward of the entrained portion in the tire radial direction.   The inner side portion of the sidewall rubber includes the entrainment portion and a rising portion that is continuous with the entrainment portion and extends radially outward along the inner surface in the tire axial direction of the main body portion of the carcass ply. The described pneumatic tire. The chafer rubber includes a main part extending inward in the tire radial direction of the bead core, and an inner part extending inward in the tire axial direction of the main part and extending inward in the tire axial direction of the rising part.
The pneumatic tire according to claim 2, wherein an outer end height of the rising portion in a tire radial direction is smaller than an outer end height of an inner portion of the chafer rubber. The chafer rubber includes a main part extending inward in the tire radial direction of the bead core, and an inner part extending inward in the tire axial direction of the main part and extending inward in the tire axial direction of the rising part.
The pneumatic tire according to claim 2, wherein an outer end height of the rising portion in a tire radial direction is larger than an outer end height of an inner portion of the chafer rubber.   The pneumatic tire according to any one of claims 1 to 4, wherein a thickness of the entrainment portion is 1.3 mm to 2.0 mm.

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