JP4968887B2 - Run flat tire - Google Patents

Description

  The present invention relates to a self-support type run flat tire in which a reinforcing rubber layer is disposed on a sidewall portion.

  In such a run-flat tire, flattening is suppressed by supporting the tire in a state where the internal pressure is reduced (run-flat state) due to puncture or the like (run-flat state), so that, for example, it can reach a nearest service facility to some extent. Can travel safely over the distance. However, during running in the run-flat state (run-flat running), the bead portion is easily detached from the rim because the pressure on the rim of the bead portion is weakened and the fitting force of the tire is reduced. there were.

  Further, it is known that noise called road noise is generated in the passenger compartment as a problem different from the above-described bead removal. This road noise is generated when the tires are vibrated by road surface irregularities when traveling on a relatively rough road surface, and the vibration propagates along the route such as the rim, axle, and car body, and finally becomes noise in the passenger compartment. There is a demand for reduction in accordance with the recent upgrade of automobiles.

  Road noise having a frequency range of 200 to 400 Hz is called high-frequency road noise. It is known that the tire vibration that generates this high-frequency road noise creates a standing wave with a pair of bead portions as both ends and forms a vibration mode in the radial direction. In general, it is considered that this vibration mode is related to the secondary cross-section mode in which the maximum width of the tire is a node and the buttress part and the lower part of the side are bellows. It is also known to become a belly.

None of the tires intended to reduce high-frequency road noise is an example of a run-flat tire. However, tires provided with convex portions on both sides of the buttress portion that becomes the antinode of vibration mode (Patent Document 1 below), and conversely concave portions Have been proposed (Patent Document 2 below), and an attenuation layer made of a high attenuation material between a bead filler and a carcass layer (Patent Document 3 below).
JP 2001-130223 A Japanese Patent Laid-Open No. 11-139115 JP 2002-205515 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a run flat tire capable of obtaining a sufficient road noise reduction effect while suppressing bead disengagement during run flat traveling. .

  The inventors of the present invention have intensively studied to achieve the above object, and as a result, it is possible to suppress the amplitude by asymmetrical vibration modes that are generally formed substantially symmetrically on both sides of the tire width direction. It was found to be effective in reducing The present invention has been made paying attention to the asymmetry of the vibration mode, and can achieve the above object with the following configuration.

That is, the run-flat tire according to the present invention includes a pair of bead portions each having an annular bead, a carcass layer disposed between the bead portions and having its end rolled up via the bead, and a tire from each of the bead portions. A sidewall portion extending radially outward, a reinforcing rubber layer arranged in a substantially crescent shape inside the carcass layer of the sidewall portion, and an outer peripheral side end of each of the sidewall portions as shoulder portions A portion of the carcass layer that is wound up, having a higher asymmetric rigidity structure than that of the sidewall portion disposed inside the vehicle. A high turn-up structure that extends to the side wall portion and reaches the end of the belt layer is provided on the side wall portion arranged on the outside of the vehicle. Applied is thereby having the asymmetric rigid structure.

  According to the run flat tire according to the present invention, the rigidity of the sidewall portion arranged on the outer side of the vehicle is higher than that of the sidewall portion arranged on the inner side of the vehicle. The bead detachment can be effectively suppressed against the lateral force that is easily generated on the outside of the vehicle during turning. In addition, since the rigidity of the sidewall portions on both sides is made different from each other, an asymmetric vibration mode can be positively formed with respect to the tire equator, and as a result, road noise can be reduced while suppressing the amplitude. .

The present invention has an asymmetric rigid structure based on a high turn-up structure, but as another example , the asymmetric rigid structure has a rubber hardness or maximum thickness of the reinforcing rubber layer disposed on the outside of the vehicle. It is larger than the reinforcing rubber layer arranged on the inner side, or the central peripheral of the reinforcing rubber layer arranged on the outer side of the vehicle is smaller than the reinforcing rubber layer arranged on the inner side of the vehicle. Based on that. Moreover, the thing of the product of the cross-sectional area of the said reinforcement rubber layer distribute | arranged to the vehicle outer side and rubber hardness is larger than the said reinforcement rubber layer distribute | arranged to the vehicle inner side.

  According to such a configuration, by increasing the rigidity of the reinforcing rubber layer disposed on the outer side of the vehicle, the rigidity of the sidewall portion on the same side is made higher than that on the inner side of the vehicle, and the above-described asymmetric vibration mode is formed. Can do. The central periphery is a length along the radial direction passing through the central portion in the thickness direction of the reinforcing rubber layer having a substantially crescent-shaped cross section, and the maximum thickness, the central periphery, and the cross-sectional area of the reinforcing rubber layer are in the tire meridian cross section. Shall.

In the present invention , the high turn-up structure in which the rolled-up portion of the carcass layer extends to the sidewall portion and reaches the end portion of the belt layer is applied only to the sidewall portion disposed on the outside of the vehicle. Yes. In addition, as another example, there may be mentioned one in which a side reinforcing member is disposed on the outer side of the carcass layer only on the sidewall portion disposed on the outer side of the vehicle.

  According to such a configuration, the rigidity of the side wall portion arranged on the outer side of the vehicle is increased by the rolled-up portion of the carcass layer and the side reinforcing member, so that it is higher than the reinforcing rubber layer arranged on the inner side of the vehicle. Asymmetric vibration modes can be formed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is provided with a high turn-up structure as shown in FIG. 2, but the structure of this run-flat tire will be described in advance in the case where the high turn-up structure is not provided in FIG. FIG. 1 is a tire meridian cross-sectional view showing an example of a run flat tire of the present invention. The run-flat tire includes a pair of bead portions 1, a carcass layer 5 disposed between the bead portions 1, sidewall portions 2a and 2b extending from the bead portion 1 outward in the tire radial direction, sidewall portions 2a, The tread part 4 which connects each outer peripheral side edge of 2b via the shoulder part 3 is provided.

  In the bead portion 1, a bead 1 a in which a bead wire concentrator made of, for example, a steel wire forms an annular shape in the tire circumferential direction, and a bead filler 15 are disposed. The end portion of the carcass layer 5 is locked in a state of being wound outward through the bead 1 a, and the space between the bead portions 1 is reinforced by the carcass layer 5. Each bead portion 1 is disposed on the outer periphery of the rim base 8b and pressed against the rim flange 8a during normal internal pressure, and the tire is firmly fitted onto the rim 8.

  An inner liner layer 6 for maintaining air pressure is disposed on the inner periphery of the carcass layer 5. Further, a belt layer 7 is provided on the outer periphery of the carcass layer 5 to reinforce it with the effect of warping, and a tread rubber 13 is disposed on the outer periphery thereof. The carcass layer 5 and the belt layer 7 are each composed of a cord material arranged at a predetermined angle, and as the cord material, organic fibers such as polyester, rayon, nylon, and aramid, steel, and the like are preferably used.

  Reinforcing rubber layers 9a and 9b each having a substantially crescent-shaped cross section are disposed inside the carcass layer 5 of the sidewall portions 2a and 2b. As a result, even if puncture or the like occurs, the tire in the run-flat state can be supported and flattening can be suppressed, and run-flat running is possible.

  A rim protector 12 that protects the rim flange 8a is provided outside the bead portion 1 in the tire width direction. In addition, without providing such a rim protector 12, it is also possible to form a shape that is smoothly connected to the sidewall portions 2a and 2b from a position away from the rim flange 8a.

  Examples of the raw rubber such as the rubber layer described above include natural rubber, styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR), and the like. Used in combination with more than one species. These rubbers are reinforced with fillers such as carbon black and silica, and a vulcanizing agent, a vulcanization accelerator, a plasticizer, an anti-aging agent and the like are appropriately blended.

In FIG. 1, the outer side of the vehicle is shown on the right side and the inner side of the vehicle is shown on the left side. In this run-flat tire, the side wall 2b arranged on the inner side of the vehicle has the rigidity of the side wall 2a arranged on the outer side of the vehicle. Higher asymmetrical rigid structure. The present invention has an asymmetric rigid structure based on a high turn-up structure, which will be described later. However, in the example shown in FIG. 1, a reinforcing rubber layer 9a disposed outside the vehicle and a reinforcing rubber layer 9b disposed inside the vehicle. The rubber hardness of the reinforcing rubber layer 9a is larger than that of the reinforcing rubber layer 9b, and thereby the rigidity of the sidewall portion 2a is higher than that of the sidewall portion 2b.

  In run-flat running, bead detachment tends to occur on the outside of the vehicle due to lateral force generated during turning, but by having such an asymmetrical rigid structure, it can effectively resist the lateral force and suppress bead detachment. can do. In addition, since the rigidity of the sidewall portions 2a and 2b on both sides is made different from each other, an asymmetric vibration mode can be formed with respect to the tire equator CL, and the road noise can be reduced by suppressing the amplitude. it can.

  The difference in rubber hardness between the reinforcing rubber layer 9a and the reinforcing rubber layer 9b is preferably in the range of 5 to 30 °, and more preferably in the range of 5 to 15 °. If this is less than 5 °, the difference in stiffness between the sidewall portions 2a, 2b on both sides is small, and the amplitude suppression effect due to the asymmetric vibration mode tends to be reduced. In addition, if the angle exceeds 30 °, the difference in deflection between the side wall portions 2a and 2b on both sides increases, the asymmetry of the contact pressure distribution on the tread surface increases, and uneven wear occurs and steering stability decreases. May cause problems.

  The rubber hardness of the reinforced rubber layers 9a and 9b is preferably in the range of 60 to 90 °, taking into consideration the durability and run comfort during run-flat travel. In addition, rubber hardness shall be the hardness by the durometer hardness test (A type) of JISK6253.

  The reinforcing rubber layers 9a and 9b are not limited to those made of a single rubber layer, and may be made up of a plurality of rubber layers having different physical properties such as rubber hardness. For example, when the reinforcing rubber layer 9a is composed of two rubber layers, a value calculated from the formula {(ha ′ × ta ′) + (ha ″ × ta ″)} / (ta ′ + ta ″). Is within the range of the rubber hardness of the reinforcing rubber layer 9a, and the same applies to the reinforcing rubber layer 9b, where ta ′ and ha ′ are one of the rubber layers constituting the reinforcing rubber layer 9a. The maximum thickness and rubber hardness of ta, and ta ″ and ha ″ are the maximum thickness and rubber hardness of the other.

Reinforcing rubber layer 9a on both sides, without rubber hardness of 9b is limited to different, even they equal the maximum thickness of the reinforcing rubber layer 9a is larger than the reinforcing rubber layer 9b, or the reinforcing rubber layer 9a The central peripheral may be smaller than the reinforcing rubber layer 9b, thereby having an asymmetric rigid structure. In other words, the reinforcing rubber layer 9a disposed on the outside of the vehicle is based on the fact that the rubber hardness or maximum thickness of the reinforcing rubber layer 9a is greater than that of the reinforcing rubber layer 9b disposed on the inside of the vehicle, or the reinforcing rubber layer disposed on the outside of the vehicle. Based on the fact that the central periphery of 9a is smaller than the reinforcing rubber layer 9b disposed on the inner side of the vehicle, the necessary asymmetric rigidity structure can be provided.

  In the above, when the rubber hardness and the central peripheral of the reinforcing rubber layers 9a and 9b on both sides are the same, the difference in the maximum thickness is within the range of 5 to 30% with respect to the maximum thickness of the reinforcing rubber layer 9a. It is preferable that it is in the range of 5 to 20%. When the rubber hardness and the maximum thickness are the same, the difference between the central peripherals is preferably in the range of 3 to 15% with respect to the central peripheral of the reinforcing rubber layer 9a. It is more preferable to be within the range.

  In this case, if the difference in the maximum thickness is less than 5% of the reinforcing rubber layer 9a or the difference in the central peripheral is less than 3% of the reinforcing rubber layer 9a, the difference in rigidity between the side wall portions 2a and 2b on both sides is small, and the vibration mode Tends to be less effective in suppressing amplitude. Further, if the difference in maximum thickness exceeds 30% of the reinforcing rubber layer 9a or the difference in central periphery exceeds 20% of the reinforcing rubber layer 9a, the difference in the deflection amount between the side wall portions 2a and 2b on both sides becomes too large. As a result, the asymmetry of the contact pressure distribution on the tread surface increases, which may cause problems such as the occurrence of uneven wear and a decrease in steering stability.

  Further, in the case where a plurality of the rubber hardness, the maximum thickness, and the central peripheral of the reinforcing rubber layers 9a and 9b are different, the product of the cross-sectional area and the rubber hardness of the reinforcing rubber layer 9a is larger than that of the reinforcing rubber layer 9b. It is preferable that the asymmetric rigid structure can be reliably formed, and the above-described asymmetric vibration mode can be appropriately formed.

In the present invention, the high turn-up structure in which the rolled-up portion of the carcass layer extends to the side wall portion and reaches the end portion of the belt layer is applied only to the side wall portion arranged outside the vehicle, thereby asymmetric Has a rigid structure .

  As shown in FIG. 2, such a structure has a winding end portion of the carcass layer 5 disposed on the vehicle outer side that is positioned on the outer side in the tire radial direction from the vehicle inner side, and only on the sidewall portion 2 a disposed on the vehicle outer side. By arranging the rolled-up portion of the carcass layer 5, the rigidity of the sidewall portion 2a is higher than that of the sidewall portion 2b. In this example, the wound-up end portion of the carcass layer 5 disposed on the vehicle outer side reaches the end portion of the belt layer 7.

In the present invention, a structure in which a side reinforcing member (not shown) is disposed on the outside of the carcass layer 5 only on the sidewall portion disposed on the outside of the vehicle may be employed. Examples of such side reinforcing members include chafers made of organic fibers such as steel, rayon, nylon, polyester, and aramid.

In the present invention, on the outer peripheral side of the belt layer 7 near the tire equator CL, the belt has a width of 5 to 20%, preferably 10 to 15% of the maximum belt width W, and an angle of substantially 0 ° with respect to the tire circumferential direction. It is preferable to dispose a reinforcing material (not shown) extending in the area. According to this configuration, the amplitude of the center portion that becomes the antinode of tire vibration can be reduced, and the road noise reduction effect can be suitably enhanced. As the constituent material of the reinforcing material, the constituent materials of the carcass layer 5 and the belt layer 7 described above can be preferably used.

The present invention is not limited to the embodiment described above, and various improvements and modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, an example in which the carcass layer is configured by two layers has been described, but this may be configured by one layer.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. As evaluation items of the examples and the like, bead detachment resistance, road noise level and steering stability were adopted, and evaluation was performed as follows.

(1) Bead detachment resistance A so-called J-turn running was performed in which a test tire was mounted on the left front side of an actual vehicle (domestic 3000cc class FR vehicle) and turned clockwise from a straight course on a circular course with a radius of 20 m. At this time, the internal pressure of the test tire was set to 0 kPa, and the bead detachment resistance was evaluated based on the running speed when the bead detachment occurred. The running speed was started from 25 km / h, and the vehicle was run until bead detachment occurred by incrementing 5 km / h. The index is evaluated as Comparative Example 100, and the larger the value, the higher the traveling speed when bead detachment occurs, that is, the better the bead detachment resistance.

(2) Road noise level 200 to 400 Hz at a constant speed of 60 km / h with a test tire mounted on a real vehicle (domestic 2000cc class FF vehicle) with a front and rear air pressure of 200 kPa and a microphone attached to the ear of the driver's seat The road noise level was measured. The comparative example is 100, and the measured values are indexed. The smaller the numerical value, the lower the road noise level.

(3) Steering stability The test tires were mounted on all the wheels of the above-described actual vehicle, traveled on a predetermined course, and sensory evaluation was performed on the steering stability with a maximum score of 10 points. It shows that it is excellent in steering stability, so that a score (pt) is high.

  A pneumatic tire (tire size: 245 / 40ZR18) having the structure shown in FIG. 1 was produced, and the rubber hardness and the like of the reinforcing rubber layer were variously changed to be Comparative Examples (conventional products) and Examples 1 to 10. In Table 1, the maximum thickness and the central peripheral of the reinforcing rubber layer are represented by an index with the comparative example being 100. The evaluation results are shown in Table 1.

  From Table 1, in Examples 1-10, while having the asymmetric rigidity structure where the rigidity of the side wall part arranged on the vehicle outer side is higher than the vehicle inner side, It can be seen that road noise can be reduced. These asymmetric rigid structures are reinforced with the rubber hardness of the reinforced rubber layer in Examples 1, 4, and 5, the maximum thickness of the reinforced rubber layer in Examples 2, 6, 7, and 10, and reinforced in Examples 3, 8, and 9. It is based on the central periphery of the rubber layer, and it is understood that it is preferable to be within the above-mentioned range in consideration of the size of the effect improvement allowance and the handling stability.

Tire meridian cross-sectional view showing an example of a run-flat tire not included in the present invention Cross sectional view showing an example of a run-flat tire of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 1a Bead 2a, 2b Side wall part 3 Shoulder part 4 Tread part 8 Rim 8a Rim flange 9a Reinforcement rubber layer (vehicle outer side)
9b Reinforced rubber layer (vehicle inside)
CL tire equator W belt maximum width

Claims (1)

A pair of bead portions having an annular bead; a carcass layer disposed between the bead portions; and an end portion of the bead portion being wound up via the bead; and a sidewall portion extending outward in the tire radial direction from the bead portion; A reinforcing rubber layer disposed in a substantially crescent-shaped cross section inside the carcass layer of the sidewall portion, and a tread portion connecting the outer peripheral side ends of the sidewall portions via a shoulder portion,
The sidewall portion disposed on the vehicle outer side has an asymmetric rigidity structure higher than the sidewall portion disposed on the vehicle inner side,
A high turn-up structure that extends the rolled-up portion of the carcass layer to the sidewall portion and reaches the end portion of the belt layer is applied only to the sidewall portion disposed on the outside of the vehicle , thereby the asymmetric A run-flat tire with a rigid structure .

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