JP2006027516A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To largely improve durability of a bead part in a pneumatic tire. <P>SOLUTION: An internal layer side chafer 20 and an external layer side chafer 22 are disposed along an outside surface (opposite side surface to a bead core 14) of a carcass ply 16. Compression deformation can be suppressed forcibly restraining the flow of rubber 24 toward the outside in the radial direction, and the transmission of the shearing strain to the fold back end 16BE can be reduced by setting the angle relative to the tire circumferential direction of the cord within 70 to 110° for the external layer side chafer 22, and disposing the outer end 22B on the inner side in the tire radial direction than the fold back end 16BE of the carcass ply 16. Large effect is brought to the deformation of the pneumatic tire 10 itself after deterioration with age, and the suppression of the shearing strain of the fold back end 16BE to be able to improve the durability of the bead part 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire with improved bead durability.

  For pneumatic tires applied at high internal pressure, when the internal pressure is filled after assembling the rim, the internal pressure reacts with the rubber on the bead back surface (bead portion outer surface) sandwiched between the carcass folding end and the rim flange by the internal pressure. As a result, compression deformation occurs.

  Since rubber is incompressible, it flows by the amount of compressive deformation toward the radially outer side opened at the rim flange tip.

  Therefore, radial shear strain occurs in the rubber on the axially outer side of the carcass folded end.

  In addition, even when a load is applied, the side part bends greatly, and the bead part also falls outside in the tire width direction, and the tread part with respect to the ground contact surface and the kicking part when the load is applied are separated from the bead part. It has been found that deformation occurs in the substantially circumferential direction at the side portion, and circumferential shear strain also occurs at the carcass end.

  Due to the shear strain, there is a problem in that separation occurs between the carcass folded end and the surrounding rubber, and further progresses from separation to crack growth.

  In other words, the core of the bead failure is the carcass folded end.

In order to solve this, in the prior art, a method of arranging one wire chafer and two nylon chafers on the axially outer side from the carcass, and a method of raising the chafer end to the outer side in the radial direction from the carcass end ( Patent Document 1) and the like have been achieved to reduce shear strain and improve durability.
JP 2003-89305 A

  However, it is difficult to greatly reduce the flow deformation of the rubber on the outer side in the carcass end axial direction by the above method alone, and it has not reached a great leap in durability.

  In particular, the flow of rubber becomes prominent with the passage of time, so that durability performance after deterioration has become a major issue.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a pneumatic tire in which the durability of the bead portion is greatly improved.

  The pneumatic tire according to claim 1 includes a pair of bead cores, a main body portion extending between the bead cores, a carcass ply having a folded portion wound around the bead core from the tire inner side toward the outer side, and a bead portion. At least two chafers including a plurality of cords arranged so as to wrap around the carcass ply and extending in one direction, and on the outer side in the tire axial direction of the folded portion, In the outermost chafer, the angle of the cord with respect to the tire circumferential direction is set within a range of 70 to 110 °, and the end portion thereof is disposed on the inner side in the tire radial direction from the folded end of the folded portion. It is characterized by that.

  Next, the operation of the pneumatic tire according to claim 1 will be described.

  In pneumatic tires for trucks and buses, it is applied at a higher internal pressure than pneumatic tires for passenger cars. When this type of pneumatic tire is applied at a high internal pressure, when the internal pressure is filled after assembling the rim, the internal pressure reacts with the rubber on the back of the bead portion sandwiched between the folded end of the carcass at the bead portion and the rim flange. However, since the rubber is incompressible, it flows by the amount of the compression deformation toward the outside in the radial direction opened at the front end of the rim flange. On the other hand, since the carcass reinforced with the steel cord is difficult to deform, shear strain occurs in the rubber on the axially outer side of the carcass folded end. In addition, when a load is applied, the bead portion bends, and as a result, the reaction force received from the rim flange increases, so that the shear strain is promoted.

  Regarding the shear strain of the carcass folded portion after the change with time, the shear strain of the carcass folded end portion when new is further promoted, and the generation mechanism is the same.

  In the shear strain accompanying the compression deformation of the rubber, it has been found that the radial rigidity at the compression deformation position greatly contributes, and the cord extending in the radial direction to the same position, that is, the angle with respect to the tire circumferential direction is 70. A chafer including a cord set in a range of ˜110 ° (in other words, a cord extending substantially in the tire radial direction) is disposed at the outermost position in the tire axial direction, and an end of the chafer is disposed on the carcass ply. By disposing the inner side in the tire radial direction from the folded end of the folded portion, the flow of rubber (adjacent to the chafer) toward the outer side in the tire radial direction is forcibly restrained to suppress the compression deformation. It is possible to reduce shear strain transmission to the carcass folded end.

  In particular, it has a great effect on the deformation of the pneumatic tire itself after the change with time and the suppression of the shear strain at the end of the folded carcass, and the durability of the bead portion can be improved.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein all the filaments constituting the cord have an elastic modulus of 3.0 GPa or more in an untwisted state before vulcanization. It is characterized by that.

  Next, the operation of the pneumatic tire according to claim 2 will be described.

  By setting the elastic modulus in an untwisted state before vulcanization of all the filaments constituting the cord to 3.0 GPa or more, the chafer has a high ability to restrain the flow of rubber toward the radially outer side. .

  According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the end portion of the chafer disposed on the inner side in the tire axial direction on the outer side in the tire axial direction of the folded portion is: It is characterized in that it is located on the outer side in the tire radial direction from the folded end of the carcass.

  Next, the operation of the pneumatic tire according to claim 3 will be described.

  By positioning the chafer end located on the inner side in the tire axial direction on the outer side in the tire axial direction of the turned-up portion, the chafer is positioned from the turned-up end of the carcass to the chafer. Can move to the edge. As a result, the durability is improved due to the structure contrast that the chafer end is lower than the folded end of the carcass.

  According to a fourth aspect of the present invention, in the pneumatic tire according to the first or second aspect, the end portion of the chafer disposed on the inner side in the tire axial direction on the outer side in the tire axial direction of the folded-back portion includes: It is characterized in that it is located on the inner side in the tire radial direction from the folded end of the carcass.

  Next, the operation of the pneumatic tire according to claim 4 will be described.

  When the chafer end is located on the inner side in the tire radial direction from the folded end of the carcass ply on the outer side in the tire axial direction of the bead core, a chafer including a cord extending in the radial direction for suppressing compression deformation of rubber is added. Therefore, further performance improvement can be aimed at, and especially the durability improvement after deterioration becomes remarkable.

  According to a fifth aspect of the present invention, in the pneumatic tire according to the third aspect, the chafer disposed on the inner side in the tire axial direction on the outer side in the tire axial direction of the turned-up portion is on the outer side in the tire axial direction of the bead core. It is characterized by being continuous from the inside to the inside.

  Next, the operation of the pneumatic tire according to claim 5 will be described.

  Since the chafer disposed on the inner side in the tire axial direction is continuous from the outer side in the tire axial direction of the bead core to the inner side, efficiency and cost reduction can be achieved on the work surface during tire manufacture. Further, the rigidity of the chafer can be increased as much as there is no divided end as compared with the case where it is divided, and an effect of suppressing the falling deformation of the bead portion and reducing the shear strain at the folded end of the carcass ply can be obtained.

  According to a sixth aspect of the present invention, in the pneumatic tire according to the third aspect, the chafer disposed on the inner side in the tire axial direction on the outer side in the tire axial direction of the turned-up portion is more in the tire axial direction than the bead core. It is characterized by being separated in the radial width direction on the outside.

  Next, the operation of the pneumatic tire according to claim 6 will be described.

  When the chafer disposed on the inner side in the tire axial direction is separated in the radial width direction on the outer side in the tire axial direction from the bead core, the chafer is separated from the carcass ply along the folded portion (hereinafter referred to as the chafer of the chafer as appropriate). And a cut-off portion extending to the main body side of the carcass ply (hereinafter referred to as the chafer winding side as appropriate).

  When the chafer is divided into two in this way, the action of the chafer folding side being restrained by the winding side is reduced, and the shear strain at the chafer end of the chafer folding side, which is a new failure nucleus, can be alleviated. And failure from the chafer end can be suppressed.

  According to a seventh aspect of the present invention, in the pneumatic tire according to the sixth aspect of the present invention, one of the separated portions of the chafer and the other separated portion are attached to each other at the ends. It is characterized by that.

  Next, the operation of the pneumatic tire according to claim 7 will be described.

  By connecting the end of one of the separated portions of the chafer and the end of the other separated portion of the chafer together, the folded back side of the chafer can reduce the effect of restraining by the winding side as much as possible. it can.

  According to an eighth aspect of the present invention, in the pneumatic tire according to the sixth aspect, one part of the separated chafer and the other part of the separated chafer overlap each other. It is characterized by that.

  Next, the operation of the pneumatic tire according to claim 8 will be described.

  By connecting the end of one part of the separated chafer and the end of the other part so that they overlap each other, the folded side of the chafer is restrained by the winding side. The distortion of the chafer end can be controlled by adjusting the overlap amount while giving the effect to some extent.

  The invention according to claim 9 is the pneumatic tire according to any one of claims 6 to 8, wherein the cord of the one separating portion and the cord of the other separating portion are: The inclination direction is the same as the tire radial direction.

  Next, the operation of the pneumatic tire according to claim 9 will be described.

  If the cord of one part of the chafer and the cord of the other part of the chafer are inclined in the same direction with respect to the tire radial direction, interference with the tensile deformation of the carcass ply due to internal pressure filling causes the chafer Although cracks propagate in the ends in the cord direction, shear strains that are difficult to connect to the cracks act in the circumferential direction, which is advantageous in terms of durability.

  The invention according to claim 10 is the pneumatic tire according to any one of claims 6 to 8, wherein the cord of the one separating portion and the cord of the other separating portion are: The inclination direction is opposite to the tire radial direction.

  Next, the operation of the pneumatic tire according to claim 10 will be described.

  If the cord of one part of the chafer and the cord of the other part are inclined in opposite directions with respect to the tire radial direction, cracks tend to be easily connected in the circumferential direction. Since the shear strain acts on the chafer edge so as to slow down the rate at which cracks propagate in the cord direction, there is no disadvantage in terms of durability.

  The invention according to claim 11 is the pneumatic tire according to claim 5, wherein the folded tire is arranged on the inner side in the tire axial direction and continuously from the inner side to the outer side in the tire axial direction on the outer side in the tire axial direction. The cord of the chafer is characterized in that an angle with respect to the tire circumferential direction is set within a range of 30 to 150 °.

  Next, the operation of the pneumatic tire according to claim 11 will be described.

  When the end portion of the chafer disposed on the inner side in the tire axial direction on the outer side in the tire axial direction of the turned-up portion is located on the inner side in the tire radial direction with respect to the turned-up end of the carcass, it is arranged on the inner side in the tire axial direction. By setting the angle of the chafer cord to the tire circumferential direction within the range of 30 to 150 °, it has the effect of suppressing the falling deformation of the bead part, reducing the flow caused by the compression deformation of the rubber and reducing the shear strain at the folded end Can be reduced.

  If the angle is less than 30 ° or more than 150 °, the chafer cord is too oriented in the circumferential direction, and the bead portion cannot be prevented from falling down.

  The invention according to claim 12 is the pneumatic tire according to any one of claims 6 to 10, wherein both the cord of one of the chafers and the cord of the other detaching portion of the chafer are both. The angle with respect to the tire circumferential direction is set within a range of 30 to 150 °.

  Next, the operation of the pneumatic tire according to claim 12 will be described.

  When the end portion of the chafer disposed on the inner side in the tire axial direction on the outer side in the tire axial direction of the turned-up portion is positioned on the outer side in the tire radial direction with respect to the turned-up end of the carcass, By setting the angle with respect to the tire circumferential direction within the range of 30 to 150 ° for both the cord and the cord of the other cut-off portion, it has the effect of suppressing the falling deformation of the bead portion and reduces the flow due to the compression deformation of the rubber Thus, the shear strain at the folded end can be reduced.

  If the angle is less than 30 ° or more than 150 °, the chafer cord is too oriented in the circumferential direction, and the bead portion cannot be prevented from falling down.

  According to a thirteenth aspect of the present invention, in the pneumatic tire according to the fourth aspect of the present invention, the end portion of the pneumatic tire is disposed on the inner side in the tire axial direction on the outer side in the tire axial direction of the folded portion, and the end portion thereof is more than the folded end of the carcass. The cord of the chafer located on the inner side in the tire radial direction is characterized in that an angle with respect to the tire circumferential direction is set within a range of 30 to 150 °.

  Next, the operation of the pneumatic tire according to claim 13 will be described.

  The angle with respect to the tire circumferential direction of the cord of the chafer that is disposed on the inner side in the tire axial direction on the outer side in the tire axial direction of the turned-up portion and whose end is located on the inner side in the tire radial direction with respect to the turned-up end of the carcass. By setting it within the range of 150 °, it has the effect of suppressing the falling deformation of the bead portion, and the flow due to the compression deformation of the rubber can be reduced to reduce the shear strain at the folded end.

  If the angle is less than 30 ° or more than 150 °, the chafer cord is too oriented in the circumferential direction, and the bead portion cannot be prevented from falling down.

  According to a fourteenth aspect of the present invention, in the pneumatic tire according to any one of the first to thirteenth aspects, an end of the chafer on the outermost side in the tire axial direction on the outer side in the tire axial direction of the folded portion. The portion is arranged within a range of 15 mm from the folded end of the folded portion to the inside in the tire radial direction.

  Next, the operation of the pneumatic tire according to claim 14 will be described.

  On the outer side in the tire axial direction of the folded portion, the end portion of the outermost chafer in the tire axial direction is disposed within 15 mm from the folded end of the folded portion to the inner side in the tire radial direction, thereby returning to the folded end due to rubber flow. Distortion transmission can be effectively suppressed.

  When the end portion of the outermost chafer on the tire axial direction outer side of the turned-up portion is more than 15 mm away from the turned-up end inward in the tire radial direction, the strain transmission can be effectively suppressed. Disappear.

  On the other hand, on the outer side in the tire axial direction of the folded portion, when the end of the outermost chafer in the tire axial direction moves away from the folded end to the outer side in the tire radial direction, the same mechanism as the shear strain that affects the folded end failure is used. This results in failure at the chafer end.

  A fifteenth aspect of the present invention is the pneumatic tire according to any one of the first to fourteenth aspects, wherein the chafer cord on the outermost side in the tire axial direction of the folded portion is on the outermost side in the tire axial direction. The elastic modulus in the direction is set in the range of 0.7 to 70 GPa.

  Next, the operation of the pneumatic tire according to claim 15 will be described.

  When the elastic modulus in the cord direction of the chafer becomes less than 0.7 GPa, it is impossible to forcibly restrain the rubber flow toward the outer side in the radial direction to suppress the compressive deformation, and to transmit the shear strain to the carcass folded end. Can not be reduced.

  On the other hand, when the elastic modulus in the cord direction of the chafer exceeds 70 GPa, the difference in rigidity between the cord and rubber becomes too large, and separation from the end portion of the chafer tends to occur, resulting in a decrease in durability of the bead portion. Leads to

  As described above, according to the pneumatic tire of the present invention, there is an excellent effect that the durability of the bead portion can be significantly improved.

[First Embodiment]
Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view of a bead portion 12 of a pneumatic tire 10 according to the present embodiment.

  The pneumatic tire 10 of the present embodiment has a pair of bead cores 14 and at least one (one in the present embodiment) radial cord in which both side portions in the tire width direction are folded back from the tire inner side to the outer side. The carcass ply 16 is included.

  Hereinafter, in the carcass ply 16, a portion straddling between one bead core 14 and the other bead core 14 is referred to as a main body portion 16A, and a portion outside the bead core 14 in the tire axial direction is referred to as a folded portion 16B.

  A stiffener (not shown) is disposed outside the bead core 14 in the tire radial direction and between the main body portion 16A and the folded portion 16B.

  The bead portion 12 includes at least two chafers along the outer surface of the carcass ply 16 (the surface opposite to the bead core 14). In the present embodiment, the inner layer chafer 20 and the outer layer chafer 22 are provided. Is arranged.

  In other words, in the present embodiment, the inner layer chafer 20 is disposed along the outer surface of the carcass ply 16 (the surface opposite to the bead core 14), and the outer surface of the inner layer chafer 20 (what is the bead core 14)? An outer layer chafer 22 is disposed along the opposite surface.

  The outermost chafer on the outer side in the tire axial direction of the bead core 14, that is, in the present embodiment, the outer layer side chafer 22 has an inner end 22 </ b> A on the inner side in the tire axial direction located on the inner side in the tire radial direction of the bead core 14. The outer end 22B on the outer side in the tire axial direction is located on the inner side in the tire radial direction with respect to the folded end 16BE of the carcass ply 16.

  The outer end 22B of the outer layer side chafer 22 is preferably disposed within a range of 15 mm from the folded end 16BE of the carcass ply 16 inward in the tire radial direction.

  The inner layer side chafer 20 has an inner end 20A on the inner side in the tire axial direction positioned on the outer side in the tire radial direction with respect to the turning end 16BE of the carcass ply 16, and an outer end 20B on the outer side in the tire axial direction has a tire with respect to the turning end 16BE. It is located radially outside.

  Both the inner layer chafer 20 and the outer layer chafer 22 have a structure in which a plurality of cords are arranged in parallel to each other and rubber-coated.

  Here, the cord has a structure in which a plurality of filaments are twisted together, and all the filaments constituting the cord have an elastic modulus of 3.0 GPa or more when not twisted before tire vulcanization. The cord is preferably steel (for example, 150 to 200 GPa) or high-strength organic fiber such as aramid, but other materials may be used as long as the above physical properties can be secured.

  In addition, it is preferable that the outer-layer chafer 22 has an elastic modulus in the cord direction within a range of 0.7 to 70 GPa.

  Further, the cord of the outer layer chafer 22 and the cord of the inner layer chafer 20 cross each other.

  The cord of the outer layer side chafer 22 is set within a range of 70 to 110 ° with respect to the tire circumferential direction.

The cord of the inner layer chafer 20 is preferably set within an angle of 30 to 150 ° with respect to the tire circumferential direction.
(Function)
In pneumatic tires used at high internal pressures for trucks, buses, etc., as described in the prior art, due to internal pressure filling, shear strain is generated in the axially outer rubber of the folded end of the carcass, and a load is applied. Thus, the shear strain is promoted. The same applies to the shear strain of the folded portion of the carcass after the change with time.

  In the pneumatic tire 10 of the present embodiment, the outer end 20B of the inner layer side chafer 20 is disposed on the outer side in the tire radial direction with respect to the folded end 16BE of the carcass ply 16, and therefore the failure nucleus is turned from the folded end 16BE to the inner layer side chafer 20. Can be shifted to the outer end 20B.

  Furthermore, the outer layer side chafer 22 including a cord set with an angle with respect to the tire circumferential direction in a range of 70 to 110 ° is disposed in the tire axial direction outermost region in the tire axial direction outer region of the bead core 14, and Since the outer end 22B of the outer layer side chafer 22 is disposed on the inner side in the tire radial direction than the turned-back end 16BE of the carcass ply 16, the rubber 24 on the outer side in the axial direction of the turned-up end 16BE is forced to flow (going radially outward). Therefore, compressive deformation can be restrained and shear strain transmission to the folded end 16BE can be reduced.

By these actions, particularly the deformation of the pneumatic tire 10 itself with the lapse of time and the suppression of shear distortion at the end of the folded carcass are brought about, and the occurrence of separation with the folded end 16BE as the core can be suppressed. The durability of the portion 12 can be greatly improved.
[Second Embodiment]
Next, a pneumatic tire 10 according to a second embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same structure as 1st Embodiment mentioned above, and the description is abbreviate | omitted.

  Unlike the first embodiment described above, the pneumatic tire 10 of the present embodiment has an outer end 20B on the outer side in the tire axial direction of the inner layer side chafer 20 positioned on the inner side in the tire radial direction with respect to the folded end 16B of the carcass 16. ing.

  When the outer end 20B of the inner layer chafer 20 is positioned on the inner side in the tire radial direction from the folded end 16B, the angle of the cord of the inner layer chafer 20 with respect to the tire circumferential direction is set within a range of 30 to 150 °. It is preferable.

Other configurations are the same as those of the first embodiment.
(Function)
The outer end 20B of the inner layer chafer 20 is positioned on the inner side in the tire radial direction from the folded end 16BE of the carcass 16, and the angle of the cord of the inner layer chafer 20 with respect to the tire circumferential direction is set within a range of 30 to 150 °. Thus, on the outer side in the tire axial direction of the folded portion, the cord of the inner-layer chafer 20 that is disposed on the inner side in the tire axial direction and whose end is located on the inner side in the tire radial direction from the folded end 16B of the carcass 16 By setting the angle with respect to the tire circumferential direction within a range of 30 to 150 °, it has an effect of suppressing the falling deformation of the bead portion 12 and reduces the flow caused by the compression deformation of the rubber to reduce the shear strain of the folded end 16BE. I can do it. In addition, when the said angle is less than 30 degrees and exceeds 150 degrees, the code | cord | chord of the inner layer side chafer 20 will face too much in the circumferential direction, and it will become impossible to suppress the fall deformation of the bead part 12.
[Third Embodiment]
Next, a pneumatic tire 10 according to a third embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same structure as embodiment mentioned above, and the description is abbreviate | omitted.

  As shown in FIG. 3, in the pneumatic tire 10 of the present embodiment, the outer end 20 </ b> B of the inner layer chafer 20 is located on the outer side in the tire radial direction than the folded end 16 </ b> BE of the carcass ply 16.

  Furthermore, the inner-layer chafer 20 of the present embodiment is configured such that the tire shaft direction outer side portion of the bead core 14, more specifically, the vicinity of the line L connecting the center of the bead core 14 and the rim flange base, is the boundary. It is divided into a first inner layer side chafer 20-1 on the outer side in the direction and a second inner layer side chafer 20-2 on the inner side in the tire axial direction.

  In the present embodiment, the end portion of the first inner layer side chafer 20-1 and the end portion of the second inner layer side chafer 20-2 are abutted (in FIG. Although it is illustrated that there is a gap between the end portion of the inner layer side chafer 20-1 and the end portion of the second inner layer side chafer 20-2, it is actually abutted so that there is no gap. Yes.)

  Here, the cord of the first inner layer side chafer 20-1 and the cord of the second inner layer side chafer 20-2 have the same inclination direction with respect to the tire radial direction, and the tire diameter. In some cases, the direction of inclination is opposite to the direction.

In addition, the cord of the first inner layer chafer 20-1 and the cord of the second inner layer chafer 20-2 are each set within an angle range of 30 to 150 ° with respect to the tire circumferential direction. Is preferred.
(Function)
As in the present embodiment, the inner-layer chafer 20 is divided into a first inner-layer chafer 20-1 and a second inner-layer chafer 20-2, and the respective end portions are attached to each other. Then, the first inner layer chafer 20-1 disposed on the outer side in the tire axial direction reduces the action restrained by the second inner layer chafer 20-2 disposed on the inner side in the tire axial direction as much as possible. Can do.

Furthermore, by setting the angle of the cord of the first inner layer side chafer 20-1 and the cord of the second inner layer side chafer 20-2 to the tire circumferential direction within a range of 30 to 150 °, the bead portion 12 has the effect of suppressing the falling deformation of the rubber 12 and can reduce the flow caused by the compression deformation of the rubber to reduce the shear strain of the folded end 16BE. If the angle is less than 30 ° and exceeds 150 °, the cord of the first inner layer chafer 20-1 and the cord of the second inner layer chafer 20-2 are too oriented in the circumferential direction, and the bead The collapse deformation of the part 12 cannot be suppressed.
[Fourth Embodiment]
Next, a pneumatic tire 10 according to a fourth embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same structure as embodiment mentioned above, and the description is abbreviate | omitted.

As shown in FIG. 4, in the pneumatic tire 10 of the present embodiment, as in the second embodiment, the inner layer side chafer 20 includes the first inner layer side chafer 20-1 and the second inner layer side chafer. However, the second embodiment differs from the second embodiment in the vicinity of the end portion of the first inner layer side chafer 20-1 and the end portion of the second inner layer side chafer 20-2. This is the point where the neighborhood is superimposed on each other. Other configurations are the same as those of the second embodiment.
(Function)
As in the present embodiment, the vicinity of the end portion of the first inner layer side chafer 20-1 and the vicinity of the end portion of the second inner layer side chafer 20-2 are overlapped and joined to each other. While the inner layer side chafer 20-1 has an effect of being restrained by the second inner layer side chafer 20-2 to some extent, the distortion of the outer end of the inner layer side chafer 20-1 is adjusted by adjusting the overlap amount. Can be controlled.
(Test Example 1)
In order to confirm the effect of the present invention, a drum test was performed on three types of pneumatic tires according to comparative examples and five types of pneumatic tires of examples to which the present invention was applied. A comparison was made.

  Example 1: A pneumatic tire having the structure described in the first embodiment.

  Example 2: A pneumatic tire having the structure described in the second embodiment.

  Example 3: A pneumatic tire having the structure described in the third embodiment.

  Example 4: A pneumatic tire having the structure described in the fourth embodiment.

  Example 5: A pneumatic tire having the structure described in the fourth embodiment.

  Comparative Example 1: A pneumatic tire having the structure shown in FIG. 5 (the same reference numerals are given to the same components as those in the embodiment).

  Comparative Example 2: Pneumatic tire having the structure shown in FIG. 6 (the same reference numerals are assigned to the same components as those in the embodiment).

  Comparative Example 3: Pneumatic tire having the structure shown in FIG. 7 (the same components as those in the embodiment are given the same reference numerals. Reference numerals 30 and 32 are nylon chafers made of nylon cords).

  Life index after degradation: A new heavy-duty radial tire with a tire size of 11 / 70R22.5 (275 / 70R22.5) is assembled into a rim, filled with oxygen, left for 30 days, and the tire after degradation Obtained. Then, the durability test was done using the tire which extracted oxygen and was filled with air.

  In the test, the bead part is broken at a speed of 60 km / h by a drum tester having a radius of 1.7 m with a maximum air pressure of 900 kPa, an applied rim of 7.50 × 22.5 and a load 1.8 times the maximum load capacity of 3150 kg. This was done by rolling the tire until the load. In the evaluation, the reciprocal of the travel distance from the start of the test to the bead portion destruction was obtained, and the reciprocal of the travel distance of Comparative Example 1 was taken as 100 and displayed as an index. The larger the index, the better the durability after deterioration.

  The test results were as described in the table below.

  Life index when new: A test similar to the above test for obtaining the life index after deterioration was performed on a new tire (without oxygen filling). In the evaluation, the reciprocal of the travel distance from the start of the test to the bead portion destruction was obtained, and the reciprocal of the travel distance of Comparative Example 1 was taken as 100 and displayed as an index. The larger the index, the better the durability when new.

  The test results were as described in the table below.

-Explanation of description in table Elastic modulus: Elastic modulus of filament constituting cord (unit: Pa)
Flexural rigidity: Flexural rigidity per twisted cord (unit: Pa)
Number of shots: book / 50mm
Angle: The angle of the cord with respect to the circumferential direction (unit: degree). Note that the letter R indicates that the code is inclined upward and L indicates that the code is inclined upward.
(Test Example 2)
A drum test was conducted to confirm the relationship between the position of the outer edge of the outer chafer and the tire life. The test method is the same as in Test Example 1.

  The test results were as shown in FIG. In addition, the vertical axis | shaft of the graph of FIG. 8 shows the life index | exponent, and the horizontal axis | shaft has shown the distance H (refer FIG. 1) from the carcass folding | turning end measured to the tire radial direction to the outer end of an outer layer side chafer. Note that the minus of the distance indicates that the outer end of the outer layer side chafer is located on the inner side in the tire radial direction from the carcass folded end.

From the test results, it is understood that the position of the outer end of the outer layer side chafer is preferably within a range of 15 mm from the carcass folding end to the inside in the tire radial direction.
(Test Example 3)
A drum test was conducted to confirm the relationship between the angle of the outer chafer cord and the tire life. The test method is the same as in Test Example 1.

  The test results were as shown in FIG. The vertical axis of the graph in FIG. 9 indicates the life index, and the horizontal axis indicates the angle of the cord with respect to the tire circumferential direction.

From the test results, it can be seen that the cord angle of the outer layer chafer is preferably in the range of 30 to 150 °.
(Test Example 4)
A drum test was conducted to confirm the relationship between the elastic modulus in the cord direction of the outer layer chafer and the tire life. The test method is the same as in Test Example 1.

  The test results were as shown in FIG. In addition, the vertical axis | shaft of the graph of FIG. 10 represents the life index | exponent and the horizontal axis | shaft represents the elasticity modulus of the cord direction of the outer layer side chafer.

  From the test results, it is understood that the elastic modulus in the cord direction of the outer layer side chafer is preferably in the range of 0.7 to 70 GPa.

It is sectional drawing of the bead part of the pneumatic tire which concerns on 1st Embodiment. It is sectional drawing of the bead part of the pneumatic tire which concerns on 2nd Embodiment. It is sectional drawing of the bead part of the pneumatic tire which concerns on 3rd Embodiment. It is sectional drawing of the bead part of the pneumatic tire which concerns on 4th Embodiment. 3 is a cross-sectional view of a bead portion of a pneumatic tire according to Comparative Example 1. FIG. 6 is a cross-sectional view of a bead portion of a pneumatic tire according to Comparative Example 2. FIG. 6 is a cross-sectional view of a bead portion of a pneumatic tire according to Comparative Example 3. FIG. It is the graph which showed the relationship from the distance from a carcass folding | turning end to the outer end of an outer layer side chafer, and a life index. It is the graph which showed the angle of the cord with respect to the tire peripheral direction, and the relationship with a life index. It is the graph which showed the rigidity of the cord direction of an outer layer side chafer, and the relationship with a life index.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Bead part 14 Bead core 16 Carcass ply 20 Inner layer side chafer 22 Outer layer side chafer

Claims (15)

A pair of bead cores;
A carcass ply having a main body portion extending between the bead cores and a turn-up portion wound around the bead cores from the inside to the outside of the tire;
And at least two chafers that are arranged so as to wrap around the carcass ply in the bead portion and include a plurality of cords extending in one direction,
On the outer side in the tire axial direction of the folded portion, the chafer on the outermost side in the tire axial direction is set such that the angle of the cord with respect to the tire circumferential direction is within a range of 70 to 110 °, and the end portion is the folded portion It is arranged on the inner side in the tire radial direction than the folded end of
A pneumatic tire characterized by that.   2. The pneumatic tire according to claim 1, wherein all the filaments constituting the cord have an elastic modulus of 3.0 GPa or more in an untwisted state before vulcanization.   The end portion of the chafer disposed on the inner side in the tire axial direction on the outer side in the tire axial direction of the folded portion is located on the outer side in the tire radial direction with respect to the folded end of the carcass. The pneumatic tire according to claim 1 or 2.   The end portion of the chafer disposed on the inner side in the tire axial direction on the outer side in the tire axial direction of the turned-up portion is located on the inner side in the tire radial direction with respect to the turned-up end of the carcass. The pneumatic tire according to claim 1 or 2.   The air according to claim 3, wherein the chafer disposed on the inner side in the tire axial direction on the outer side in the tire axial direction of the folded portion is continuous from the outer side in the tire axial direction of the bead core to the inner side. Enter tire.   4. The chafer disposed on the inner side in the tire axial direction on the outer side in the tire axial direction of the folded portion is separated in the radial width direction on the outer side in the tire axial direction with respect to the bead core. The described pneumatic tire.   The pneumatic tire according to claim 6, wherein one end portion of the chafer and the other end portion of the chafer are separated from each other.   The pneumatic tire according to claim 6, wherein one part of the separated chafer and the other part of the chafer overlap each other.   9. The cord according to any one of claims 6 to 8, wherein the cord of the one cut-off portion and the cord of the other cut-off portion are inclined in the same direction with respect to the tire radial direction. The pneumatic tire according to item 1.   9. The cord according to any one of claims 6 to 8, wherein the cord of the one cut-off portion and the cord of the other cut-off portion are inclined in directions opposite to the tire radial direction. The pneumatic tire according to item 1.   The cord of the chafer disposed on the inner side in the tire axial direction on the outer side in the tire axial direction of the folded portion and continuing from the inner side to the outer side in the tire axial direction has an angle with respect to the tire circumferential direction within a range of 30 to 150 °. The pneumatic tire according to claim 5, wherein the pneumatic tire is set to   An angle with respect to a tire circumferential direction is set within a range of 30 to 150 ° in both the cord of one cut-off portion of the chafer and the cord of the other cut-off portion. The pneumatic tire according to claim 10.   The cord of the chafer, which is disposed on the inner side in the tire axial direction on the outer side in the tire axial direction of the folded portion and whose end is located on the inner side in the tire radial direction with respect to the folded end of the carcass, is in the tire circumferential direction. The pneumatic tire according to claim 4, wherein an angle with respect to is set within a range of 30 to 150 °.   The outer end in the tire axial direction of the folded portion, the end of the chafer on the outermost side in the tire axial direction is disposed within a range of 15 mm from the folded end of the folded portion inward in the tire radial direction. The pneumatic tire according to any one of claims 1 to 13.   The elastic modulus in the cord direction of the chafer on the outermost side in the tire axial direction is set in a range of 0.7 to 70 GPa on the outer side in the tire axial direction of the folded portion. The pneumatic tire according to claim 14.

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