JP5090644B2 - Pneumatic run flat tire - Google Patents

Description

  The present invention relates to a pneumatic run-flat tire, and more particularly, to a pneumatic run-flat tire provided with a side reinforcing rubber layer having a crescent-shaped cross section in a side portion.

Various pneumatic run-flat tires have been proposed in which a side reinforcing rubber layer having a crescent-shaped cross section is provided on the side portion.
Usually, the side reinforcing rubber portion often breaks due to run-flat running. However, in a pneumatic run flat tire used for an application where the cross-sectional height is relatively high and a heavy load acts, there is a strong tendency to cause a failure near the bead filler.

As failure forms in the bead filler, there are cracks inside the bead filler, separation between the bead filler and the carcass ply adjacent to the bead filler, and the ratio of separation failure is higher.
As a method for suppressing the separation breakdown on the side surface of the bead filler, there is one disclosed in Japanese Patent Application Laid-Open No. 2000-213323.
Japanese Patent Laid-Open No. 2000-213323

As described above, in pneumatic run flat tires used for applications where the cross-sectional height is relatively high and high loads act, failures tend to occur in the vicinity of the bead filler, and the target run flat durability is obtained. Often not.
By using the technology of Japanese Patent Laid-Open No. 2000-213323, a certain degree of destruction suppressing effect can be obtained, but the technology of Japanese Patent Laid-Open No. 2000-213323 aims to suppress the breakage at the side of the bead filler. However, it is not intended to suppress breakage near the end of the bead filler, and a technology that can also suppress breakage at the end of the bead filler is desired in the market.

  An object of the present invention is to provide a pneumatic run flat tire capable of improving the run flat durability as compared with the conventional one by suppressing breakage in the vicinity of the bead filler end in addition to the side surface of the bead filler.

The pneumatic run-flat tire according to claim 1 includes a pair of bead cores,
A carcass composed of at least one carcass ply that straddles the pair of bead cores and whose end portion is wound up from the inner side to the outer side in the tire axial direction;
Of the carcass, a bead filler disposed between a main body part extending from one bead core to the other bead core and a folded part around which the bead core is wound up, and extending from the bead core toward the outer side in the tire radial direction,
A belt disposed on the outer side in the tire radial direction of the carcass;
A tread rubber layer disposed on the outer side in the tire radial direction of the belt;
A side reinforcing rubber layer that is disposed along the inner surface side of the carcass in the tire axial direction and that gradually decreases in thickness toward the tread side and the bead core side;
The bead filler is composed of rubber having a lower hardness than that of the bead filler, and is arranged along the outer surface in the tire width direction of the bead filler. And a shock-absorbing rubber layer located on the side of the.

Next, the operation of the pneumatic run flat tire according to claim 1 will be described.
When a pneumatic run-flat tire rolls under load, there is a problem that stress tends to concentrate in the vicinity of the outer end of the bead filler in the radial direction of the tire, which tends to be a starting point of fracture. In the pneumatic run-flat tire according to claim 1, the buffer rubber layer is disposed along the bead filler, and a part of the buffer rubber layer is positioned on the side of the outer end portion in the tire radial direction of the bead filler. In addition to alleviating the distortion that occurs in the side of the filler, it also reduces the concentration of local strain in the vicinity of the outer end of the bead filler in the radial direction of the tire. The breakdown failure that occurs can be suppressed.

Further, since the buffer rubber layer has a lower hardness than the rubber constituting the bead filler, there is no increase in tire rigidity (longitudinal spring constant), that is, there is no deterioration in riding comfort. Flat durability can be improved.
The side reinforcing rubber layer is disposed along the side surface of the bead filler, but the meaning of “along” here refers to the case where the side reinforcing rubber layer is in close contact with the side surface of the bead filler and the layer such as the carcass ply. This includes the case where they are interposed.

The invention according to claim 2 is the pneumatic run-flat tire according to claim 1 , wherein the buffer rubber layer is disposed between the bead filler and the folded portion of the carcass ply. It is said.

Next, the operation of the pneumatic run-flat tire according to claim 2 will be described .
By disposing the buffer rubber layer between the bead filler and the folded portion of the carcass ply, a separation failure that occurs between the bead filler and the folded portion of the carcass ply can be suppressed.

According to a third aspect of the present invention, in the pneumatic run foot tire according to the first or second aspect, the thickness of the cushioning rubber layer is such that the bead filler is in the vicinity of the radially outer end of the bead filler and the bead filler. When compared with a portion away from the outer end portion in the tire radial direction, the vicinity of the outer end portion in the tire radial direction is thicker.

Next, the operation of the pneumatic run flat tire according to claim 3 will be described .
Since the thickness of the buffer rubber layer is increased in the vicinity of the outer end portion in the tire radial direction of the bead filler, the strain concentration in the vicinity of the outer end portion in the tire radial direction of the bead filler can be effectively reduced.

  As described above, according to the pneumatic run flat tire of the present invention, there is an excellent effect that breakage at the end of the bead filler can be suppressed and run flat durability can be improved as compared with the conventional one.

Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the pneumatic run-flat tire 10 of this embodiment is for a passenger car, and includes a pair of bead portions 12 (only one side is shown), a pair of sidewall portions 14 (only one side is shown), The bead core 12 embedded in the pair of bead portions 12, the bead portion 12, the sidewall portion 14, and the tread portion 16 are connected to the carcass 20 and the carcass 20. And a belt 22 that reinforces the tread portion 16 on the outer periphery.

Although the carcass 20 of the present embodiment is composed of a single carcass ply 24 that is rubber-coated with a plurality of radial arrangement codes, the carcass 20 may be composed of two or more carcass plies 24.
The end portion of the carcass ply 24 is folded back around the bead core 18 from the inside to the outside of the tire, the portion straddling the bead cores 18 is a main body portion 24A, and the folded portion is a folded portion 24B.

  The belt 22 of the present embodiment is composed of two belt plies 26 in which a plurality of cords arranged in parallel to each other are covered with rubber. The belt 22 may include one belt ply 26 or three or more belt plies. Furthermore, an organic fiber cord layer or the like may be provided outside the belt 22 in the tire radial direction.

  Between the main body portion 24A and the turn-up portion 24B of the carcass ply 24, a bead filler 28 made of hard rubber extending in a tapered manner from the outer peripheral surface of the bead core 18 toward the outer side in the tire radial direction is provided. Note that the outer end 24Be in the tire radial direction of the folded portion 24B is located on the outer side in the tire radial direction with respect to the outer end 28e in the tire radial direction of the bead filler 28.

  Furthermore, in this pneumatic run-flat tire 10, the cross section is crescent-shaped (inner side in the tire radial direction and in the radial direction of the tire) on the inner surface side of the main body 24 </ b> A of the carcass 20 extending from the position near the bead core 18 of the bead part 12 to the tread part 16. A side reinforcing rubber layer 30 having a shape in which the thickness gradually decreases toward the outside is provided.

  Even if the tire internal pressure becomes zero, the side reinforcing rubber layer 30 stably supports the total weight of the running vehicle, prevents the pneumatic run-flat tire 10 from being detached from the used rim 32, and enters the pneumatic In order to prevent the run-flat tire 10 from being broken, it is made of hard rubber.

  An inner liner 33 having excellent air impermeability is provided on the inner surface of the pneumatic run-flat tire 10.

  Further, a tread rubber layer 34 that forms the tread portion 16 is disposed outside the belt 22 in the tire radial direction, and a side rubber layer 36 that forms the sidewall portion 14 is disposed outside the carcass 20 in the tire axial direction. A rubber chafer 38 extending from the vicinity of the bead core 18 toward the tire maximum width portion is disposed outside the folded portion 24B in the tire axial direction. The vicinity of the outer end in the tire radial direction of the rubber chafer 38 is covered with a side rubber layer 36.

In the pneumatic run-flat tire 10 of the present embodiment, the buffer rubber layer 40 is disposed along the inner surface of the folded portion 24B, and the buffer rubber layer 40 is in the radial direction of the tire radial outer end 28e of the bead filler 28. It extends to both sides.
The rubber constituting the buffer rubber layer 40 has lower hardness than the rubber constituting the rubber chafer 38, the rubber constituting the side rubber layer 36, the rubber constituting the side reinforcing rubber layer 30, and the rubber constituting the bead filler 28. .

The dynamic elastic modulus of the rubber constituting the buffer rubber layer 40 is preferably 30 to 55% of the dynamic elastic modulus of the rubber constituting the bead filler 28.
The dynamic elastic modulus of the rubber constituting the buffer rubber layer 40 is preferably 3.5 to 5.0 MPa.

The hysteresis loss tan δ of the rubber constituting the buffer rubber layer 40 is preferably 0.18 or less. The value of tan δ is determined in accordance with JIS K6394 “Testing method for dynamic properties of vulcanized rubber” (1) Among the non-resonant methods, “In the case of load waveform and deflection waveform”, the type of deformation is pulled. Is the value obtained as The value of tan δ is determined under the test conditions of an initial tensile load of 160 gf, a dynamic strain of 1.0%, and a frequency of 52 Hz in an actual test.
The thickness of the buffer rubber layer 40 is preferably 0.5 to 1.5 mm.

  The buffer rubber layer 40 may have a constant thickness. However, when the vicinity of the tire radial direction outer end portion 28e of the bead filler 28 is compared with the portion away from the tire radial direction outer end portion of the bead filler 28, the tire It is preferable to increase the thickness in the vicinity of the radially outer end 28e. In addition, the buffer rubber layer 40 of this embodiment is the latter structure, and thickness is reducing gradually toward inner side from the tire radial direction outer side.

  The tire radial direction outer end portion 40 oe of the cushioning rubber layer 40 is preferably disposed at a position of 15 mm or more outward in the tire radial direction from the tire radial direction outer end portion 28 e of the bead filler 28.

  When the length measured along the tire radial direction of the bead filler 28 with respect to the inner peripheral portion of the bead core 18 is H, the tire radial inner end 40ie of the buffer rubber layer 40 is the tire of the bead filler 28. It is preferable to be at a position spaced 0.8H or more from the radially outer end 28e toward the inside in the tire radial direction. Note that the end portion 40ie in the tire radial direction of the shock absorbing rubber layer 40 extends to a position where it does not enter the inner side in the radial direction of the bead core 18.

(Function)
FIG. 2 is a schematic view of the pneumatic run flat tire 10 during run flat running. As shown in FIG. 2, in the pneumatic run flat tire 10 during run flat running, a shear strain εa in the direction of the arrow A shown in the figure is present on the joint surface between the main body portion 24 </ b> A of the carcass ply 24 and the bead filler 28. In addition, a shear strain εb in the direction of the arrow B shown in the figure is present at the joint surface between the folded portion 24B of the carcass ply 24 and the bead filler 28, and a joint surface between the main body portion 24A of the carcass ply 24 and the side reinforcing rubber layer 30 is A shear strain εc in the direction of arrow C, opposite to the direction of action of the shear strains εa and εb, respectively occurs, and stress tends to concentrate near the tire radial direction outer end 28e of the bead filler 28. Yes.

  In the pneumatic run-flat tire 10 of the present embodiment, the buffer rubber layer 40 is disposed along the inner surface of the folded portion 24B so as to be along the bead filler 28 and adjacent to the tire radial direction outer end portion 28e of the bead filler 28. Therefore, the strain generated on the side portion of the bead filler 28 facing the shock-absorbing rubber layer 40 is relieved, and the shock-absorbing rubber layer 40 is locally present in the vicinity of the tire radial direction outer end portion 28e of the bead filler 28. The concentration of strain is alleviated, and separation failure occurs between the cord of the folded portion 24B and the side surface of the bead filler 28 and between the cord of the folded portion 24B and the bead filler 28 that occurs from the vicinity of the tire radial direction outer end portion 28e. Can be suppressed.

  Moreover, since the buffer rubber layer 40 has a lower hardness than the rubber constituting the bead filler 28 and is thinner than the bead filler 28, the rigidity of the pneumatic run-flat tire 10 (longitudinal spring constant) is increased. There is virtually no increase. Therefore, the pneumatic run-flat tire 10 of the present embodiment can improve the run-flat durability without deteriorating riding comfort.

  In addition, since the thickness of the buffer rubber layer 40 is increased in the vicinity of the outer end portion 28e in the tire radial direction of the bead filler 28, the strain concentration in the vicinity of the outer end portion 28e in the tire radial direction of the bead filler 28 is effectively reduced. I am relaxed.

  Further, when the dynamic elastic modulus of the rubber constituting the buffer rubber layer 40 exceeds 55% of the dynamic elastic modulus of the rubber constituting the bead filler 28, the buffer rubber layer 40 is too hard and local strain is concentrated. The effect of relaxing is insufficient. On the other hand, if the dynamic elastic modulus of the rubber composing the buffer rubber layer 40 is less than 30% of the dynamic elastic modulus of the rubber composing the bead filler, the buffer rubber layer 40 is too soft and the deformation becomes large. The buffer rubber layer itself may cause early destruction.

  Moreover, when the dynamic elastic modulus of the rubber constituting the buffer rubber layer 40 exceeds 5.0 MPa, the buffer rubber layer 40 is too hard and the effect of relaxing local strain concentration is insufficient. On the other hand, if the dynamic elastic modulus of the rubber constituting the shock absorbing rubber layer 40 is less than 3.5 MPa, the shock absorbing rubber layer 40 is too soft and the deformation becomes large. is there.

  Further, when the outer end portion 40oe in the tire radial direction of the buffer rubber layer 40 is located at a position less than 15 mm from the outer end portion 28e in the tire radial direction to the outer side in the tire radial direction of the bead filler 28, the outer end in the tire radial direction of the bead filler 28 There is a possibility that the effect of relaxing the local strain concentration in the vicinity of the portion 28e is insufficient, and the breakdown failure cannot be suppressed.

  On the other hand, if the position of the outer end portion 40oe in the tire radial direction of the cushioning rubber layer 40 is too far from the outer end portion 28e in the tire radial direction of the bead filler 28, the effect becomes a peak and the material is wasted. . Therefore, the position of the tire radial direction outer end portion 40 oe of the buffer rubber layer 40 is preferably stopped from the tire radial direction outer end portion 28 e of the bead filler 28 to 20 mm or less outward in the tire radial direction.

  Further, when the tire radial direction inner end portion 40ie of the buffer rubber layer 40 is located at a position less than 0.8H from the tire radial direction outer end portion 28e of the bead filler 28 to the tire radial direction inner side, the tire diameter of the buffer rubber layer 40 is increased. The inner end portion in the direction is not positioned in the vicinity of the bead core, and a separation failure occurring on the side surface of the bead filler cannot be suppressed.

  On the other hand, when the thickness of the buffer rubber layer 40 is less than 0.5 mm, the buffer rubber layer 40 is too thin and the effect of relaxing local strain concentration is insufficient. On the other hand, when the thickness of the buffer rubber layer 40 exceeds 1.5 mm, the buffer rubber layer 40 is too thick and the heat generation amount becomes excessive, the heat resistance is lowered, and the run-flat durability cannot be improved.

[Other Embodiments]
In the said embodiment, although the buffer rubber layer 40 was arrange | positioned along the inner surface of the folding | turning part 24B, the arrangement | positioning location can be changed suitably according to the location where a failure | problem easily occurs.

As shown in FIG. 3, the buffer rubber layer 40 may be disposed along the outer surface of the folded portion 24B, between the rubber chafer 38 and the folded portion 24B, and between the side rubber layer 36 and the folded portion 24B. . In this case, a separation failure between the cord of the folded portion 24B and the rubber chafer 38 in the vicinity of the tire radial direction outer end portion 28e of the bead filler 28 can be suppressed.

  Further, as shown in FIG. 5, the buffer rubber layer 40 may be disposed along the inner surface (surface on the side reinforcing rubber layer 30 side) of the main body portion 24 </ b> A of the carcass ply 24. In this case, a separation failure between the side reinforcing rubber layer 30 and the cord of the main body portion 24A in the vicinity of the tire radial direction outer end portion 28e of the bead filler 28 can be suppressed.

Further, as shown in FIG. 4, the buffer rubber layer 40 is folded along the outer surface of the body portion 24 </ b> A of the carcass ply 24 and the inner surface of the folded portion 24 </ b> B so as to be folded at the tire radial direction outer end portion 28 e of the bead filler 28. It may be arranged. In this case, a separation failure between the cord of the partial carcass ply 24 where the buffer rubber layer 40 is provided and the bead filler 28 from the tire radial direction outer end 28e of the bead filler 28 can be suppressed.

The arrangement position of the buffer rubber layer 40 is not limited to one place with respect to one bead filler 28 , and the examples shown in FIGS. 3 and 4 may be appropriately combined.

(Test example)
In order to confirm the effect of the present invention, one kind of pneumatic run-flat tire of a conventional example and four kinds of pneumatic run-flat tires of an example to which the present invention was applied were prepared, and a run-flat drum test was performed.
Example 1: A tire having the structure shown in FIG.
Example 2: A tire having the structure shown in FIG.
Conventional example: a tire having the structure shown in FIG .
The tire size is 225 / 60R17.
In the test, a tire was mounted on a rim of 6.5J-17, and running was performed under the conditions of an internal pressure of 0 kPa, a load of 650 kPa, and an ambient temperature of 38 ± 3 ° C. using a drum testing machine. Here, the run-flat durability was evaluated by the running time from the time when the drum was accelerated and reached 80 km / h to the time when a failure occurred inside the tire and the vibration level increased at a stroke.

  In the run-flat durability evaluation method, an index with the running time of the conventional tire as 100 was defined as run-flat durability. In addition, it represents that run flat durability is excellent, so that the numerical value of an index | exponent is large.

試験の結果から、本発明の適用された実施例の空気入りランフラットタイヤは、従来例の空気入りランフラットタイヤに比較して、ランフラット耐久性に優れていることが分かる。

From the test results, it can be seen that the pneumatic run-flat tire of the example to which the present invention is applied is superior in run-flat durability compared to the pneumatic run-flat tire of the conventional example.

1 is a cross-sectional view of a pneumatic run flat tire according to an embodiment of the present invention. It is sectional drawing which shows the tire at the time of run flat driving | running | working. It is sectional drawing of the pneumatic run flat tire which concerns on other embodiment. It is sectional drawing of the pneumatic run flat tire which concerns on other embodiment. It is sectional drawing of the pneumatic run flat tire which concerns on a prior art example .

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic run-flat tire 12 Bead part 14 Side wall part 16 Tread part 18 Bead core 20 Carcass 22 Belt 24 Carcass ply 24A Main part 24B Turn-up part 26 Belt ply 28 Bead filler 30 Side reinforcement rubber layer 32 Use rim 33 Inner liner 34 Tread Rubber layer 36 Side rubber layer 38 Rubber chafer 40 Buffer rubber layer 40 oe Tire radial direction outer end 40ie Tire radial direction inner end

Claims (3)

A pair of bead cores;
A carcass composed of at least one carcass ply that straddles the pair of bead cores and whose end portion is wound up from the inner side to the outer side in the tire axial direction;
Of the carcass, a bead filler disposed between a main body part extending from one bead core to the other bead core and a folded part around which the bead core is wound up, and extending from the bead core toward the outer side in the tire radial direction,
A belt disposed on the outer side in the tire radial direction of the carcass;
A tread rubber layer disposed on the outer side in the tire radial direction of the belt;
A side reinforcing rubber layer that is disposed along the inner surface side of the carcass in the tire axial direction and that gradually decreases in thickness toward the tread side and the bead core side;
The bead filler is composed of rubber having a lower hardness than that of the bead filler, and is arranged along the outer surface in the tire width direction of the bead filler. A cushioning rubber layer located on the side of
A pneumatic run-flat tire comprising:   2. The pneumatic run-flat tire according to claim 1, wherein the buffer rubber layer is disposed between the bead filler and a folded portion of the carcass ply.   The thickness of the buffer rubber layer is determined by comparing the vicinity of the outer end portion in the tire radial direction of the bead filler and the portion near the outer end portion in the tire radial direction of the bead filler. The pneumatic run-flat tire according to claim 1, wherein the tire is thick.

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