JP4502333B2 - 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.

  With respect to this problem of bead dislodgment, in Patent Document 1 below, a pair of bead portions having an annular first bead, and an annular bulge having an annular second bead bulging outward from the bead portion in the tire width direction. A run-flat tire having a so-called double bead structure including a portion has been proposed. According to this structure, when the bead portion is about to come off from the rim during the run-flat running, the annular bulged portion reinforced by the second bead contacts the rim flange, and the bead portion is restricted from being displaced inward. Although it is possible to prevent the detachment, there is a problem that the rim assemblability deteriorates.

  Further, it is known that noise called road noise is generated in the vehicle interior as a problem different from the bead disengagement. 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, this vibration mode is considered to be related to a secondary cross-sectional mode in which the tire maximum width portion is a node and the buttress portion and the side lower portion are belly (see, for example, Patent Documents 2 and 3 below), and in addition, the shoulder portion. It is also known that the center part (crown part) becomes an antinode of vibration with a node as a node.

As countermeasures against this high-frequency road noise, as described in Patent Documents 4 and 5 below, the rubber thickness is increased at a portion that becomes an antinode of tire vibration, or a member having a high density is arranged at that portion to suppress the amplitude. However, there is still a problem that a great increase in tire weight cannot be avoided regardless of which method is employed.
JP 51-116507 A JP 2001-130223 A JP 2002-205515 A JP-A-9-109621 JP-A-9-118111

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a run that can prevent bead disengagement during run-flat travel without deteriorating the rim assembly property and can obtain a sufficient road noise reduction effect. It is to provide a flat tire.

  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 of the present invention includes a pair of bead portions each having an annular first bead, sidewall portions extending outward in the tire radial direction from the bead portions, and a reinforcing rubber layer disposed on the sidewall portions. And in a run flat tire provided with a tread portion that connects each outer peripheral side end of the sidewall portion via a shoulder portion, and bulges outward in the tire width direction from the bead portion arranged outside the vehicle, An annular bulging portion having an annular second bead, the sectional height Hi from the inner periphery of the first bead arranged on the vehicle inner side to the tire maximum diameter point, and the second bead arranged on the vehicle outer side The section height Ho from the inner circumference to the tire maximum diameter point satisfies the relationship of Hi-Ho> 15 mm.

  This tire adopts a double bead structure only on the outside of the vehicle, and effectively removes the bead from the lateral force generated on the outside of the vehicle during cornering, which is the most likely cause of bead disengagement during run-flat running. It can be prevented. Further, by adopting the double bead structure only on the outside of the vehicle, tire vibration is generated with both the first bead arranged on the inside of the vehicle and the second bead arranged on the outside of the vehicle as both ends. Satisfying the above relationship (Hi-Ho> 15 mm), it is possible to achieve both rim assembly and bead detachment resistance, and road noise can be reduced due to asymmetry of the structure.

  Here, the cross-sectional height is the height in the tire radial direction in the tire meridian cross section, and is measured in a no-load state in which the tire is mounted on the specified rim and filled with the specified internal pressure. The specified rim refers to a standard rim determined by JATMA corresponding to the tire size. The specified internal pressure is 180 kPa when the tire is for a passenger car.

  In the above, the belt layer disposed in the tread portion extends on the outer peripheral side in the vicinity of the tire equator at a width of 5 to 15% of the maximum belt width at an angle of substantially 0 ° with respect to the tire circumferential direction. Those provided with a reinforcing material are preferred. According to this configuration, it is possible to reduce the amplitude of the center portion from the shoulder portion that becomes the antinode of tire vibration, and the above-described road noise reduction effect can be suitably enhanced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a tire meridian cross-sectional view showing an example of a run-flat tire of the present invention when a specified rim is mounted. As shown in FIG. 1, the run-flat tire has a pair of bead portions 1, sidewall portions 2 extending outward in the tire radial direction from the bead portions 1, and outer peripheral side ends of the sidewall portions 2. And a tread portion 4 connected through the portion 3.

  The bead portion 1 is provided with a bead 1a (corresponding to the first bead) in which a converging body of bead wires made of, for example, steel wire forms an annular shape in the tire circumferential direction, and a bead filler 15. The end portion of the carcass layer 5 is rewound and locked by the bead 1a, whereby the space between the bead portions 1 is reinforced by the carcass layer 5 and the tire is firmly fitted on the rim 8. During normal internal pressure, the bead portion 1 is disposed on the tire outer peripheral side of the rim base 8b of the rim 8, and is pressed against the rim flange 8a by the internal pressure of the tire.

  An inner liner layer 6 for maintaining air pressure is disposed on the inner periphery of the carcass layer 5. In addition, a belt layer 7 is provided on the outer periphery of the carcass layer 5 to reinforce it by the effect, 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.

  On the inner peripheral side of the carcass layer 5 of the sidewall portion 2, reinforcing rubber layers 9 a and 9 b are arranged in which the tire meridian section has a substantially crescent shape. 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. The reinforcing rubber layers 9a and 9b on both sides have different structures, which will be described later.

  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.

  FIG. 1 shows the vehicle outer side on the right side and the vehicle inner side on the left side. In the present invention, the double bead structure is adopted only on the vehicle outer side. That is, an annular bulging portion 10 having an annular bead 1b (corresponding to the second bead) is provided while bulging outward from the bead portion 1 disposed on the vehicle outer side in the tire width direction.

  The annular bulging portion 10 has an inner peripheral side surface 11 that faces the outer peripheral curved surface of the rim flange 8a. The inner peripheral side surface 11 may be gradually separated from the outer peripheral curved surface of the rim flange 8a, but in this embodiment, is in contact with the outer peripheral curved surface. Further, a reduced diameter portion for holding the front end of the rim flange 8a is formed on the front end side, and the bead 1b is disposed on the tire outer peripheral side of the reduced diameter portion. The annular bulging portion 10 is smoothly connected to the sidewall portion 2 with the portion where the bead 1b is disposed as a substantially top portion.

  The shape of the annular bulging portion 10 is not limited to that shown in the present embodiment. For example, the tire meridian cross section may be a semicircular shape or a trapezoidal shape. In addition, the hardness of the rubber mainly constituting the annular bulging portion 10 is determined by taking into consideration that the rubber hardness of the reinforcing rubber layer 9a is reduced as will be described later, and further maintaining the bead detachment drag and the rim displacement performance. In order to improve the comfort, 65 to 78 ° is preferable. In addition, in this specification, rubber hardness refers to the hardness by the durometer hardness test (A type) of JISK6253.

  The bead 1b is arranged so that the center position thereof is located on the tire outer peripheral side and the tire width direction outer side from the outermost point of the rim flange 8a. The bead wire constituting the bead 1b is not limited to the one made of the same steel wire bundling body as the bead 1a, and may be, for example, one made of a bundling body of organic fibers or a rubber bead made of fiber reinforced rubber. .

  In the present embodiment, the rim protector 12 that protects the rim flange 8a is provided on the outer side in the tire width direction of the bead portion 1 disposed on the inner side of the vehicle. However, without such a rim protector 12, the rim flange 12 is provided. It is also possible to form a shape that gently leads to the sidewall portion 2 from a position separated from 8a.

  In the present invention, the cross-sectional height Hi from the inner periphery of the bead 1a disposed on the inner side of the vehicle to the tire maximum diameter point P, and the cross-sectional height from the inner periphery of the bead 1b disposed on the outer side of the vehicle to the tire maximum diameter point P. The height Ho is set so as to satisfy the relationship of Hi-Ho> 15 mm, and this makes it possible to reduce both road noise and improve the anti-bead removal performance.

  That is, by adopting the double bead structure only on the outer side of the vehicle, tire vibration is generated with both ends of the bead 1a disposed on the inner side of the vehicle and the bead 1b disposed on the outer side of the vehicle. Since Ho satisfies Hi-Ho> 15 mm, the cross-sectional heights at both ends of the tire vibration can be appropriately different from each other. As a result, an asymmetric vibration mode can be formed with respect to the tire equator CL, and the road noise can be reduced while suppressing the amplitude. Note that (Hi-Ho) is preferably 20 mm or less in order to appropriately obtain the above-described road noise reduction effect while maintaining the bead detachment drag.

  As described above, since the present invention employs the double bead structure only on the vehicle outer side, the difference in the deflection amount between the side wall portions 2 on both sides in the run-flat state tends to increase. 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. Therefore, in the present embodiment, the deflection of both sides is increased by increasing the rubber hardness of the reinforcing rubber layer 9b inside the vehicle and reducing the thickness of the reinforcing rubber layer 9a with respect to the reinforcing rubber layer 9a outside the vehicle. The amount is balanced.

  Specifically, the rubber hardness of the reinforcing rubber layer 9a is set to 60 to 82 °, the rubber hardness of the reinforcing rubber layer 9b is set to 65 to 90 °, and the rubber hardness of the reinforcing rubber layer 9b is equal to or higher than that of the reinforcing rubber layer 9a. In addition, the maximum thickness is increased by 0.5 mm or more. By adjusting the relationship between the rubber hardness and the maximum thickness of the reinforcing rubber layers 9a and 9b in this way, the amount of deflection on both sides can be properly balanced. The above-described vibration mode having asymmetry is formed without any problem even if such balance adjustment is performed.

  The rubber hardness of the reinforcing rubber layer 9a disposed on the vehicle outer side is 60 to 82 ° as described above, and preferably 65 to 78 °. If this is less than 60 °, durability during run flat running will be insufficient, and if it exceeds 82 °, it will be difficult to balance the amount of deflection inside the vehicle, causing uneven wear on the tread surface. There is a tendency for the ride comfort to deteriorate.

  On the other hand, the rubber hardness of the reinforcing rubber layer 9b disposed on the inner side of the vehicle is 65 to 90 ° as described above, and preferably 70 to 85 °. If this is less than 65 °, it is difficult to balance the amount of deflection on the outside of the vehicle, and uneven wear tends to occur on the tread surface. If it exceeds 90 °, the ride comfort tends to deteriorate. The reinforcing rubber layer 9b has a rubber hardness equal to or higher than that of the reinforcing rubber layer 9a within a range of 65 to 90 °, and preferably 5 ° or more higher than that of the reinforcing rubber layer 9a.

  The maximum thickness of the reinforcing rubber layer 9b disposed on the inside of the vehicle is preferably 4% or more, and preferably 5-13% larger than that of the reinforcing rubber layer 9a disposed on the outside of the vehicle. That is, when the maximum thickness of the reinforcing rubber layer 9a is 100, the maximum thickness of the reinforcing rubber layer 9b is preferably 104 or more, and more preferably 105 to 113.

  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. In this case, for example, when the reinforcing rubber layer 9a is composed of two rubber layers, it is calculated from the formula {(ha ′ × ta ′) + (ha ″ × ta ″)} / (ta ′ + ta ″). It is sufficient that the value is within the range of the rubber hardness of the reinforcing rubber layer 9a, where ta ′ and ha ′ are the maximum thickness and rubber hardness of one of the rubber layers constituting the reinforcing rubber layer 9a. In the figure, the reinforcing rubber layer 9a is formed of a single rubber layer, and the reinforcing rubber layer 9b interposes one layer of the carcass layer 5. In this embodiment, the carcass layer 5 is composed of two layers, and a reinforcing rubber layer 9b is arranged on the inner peripheral side of each carcass layer 5 located in the sidewall portion 2. Has been.

  In the present embodiment, the reinforcing layer 16 is disposed substantially along the inner peripheral side surface 11 of the annular bulging portion 10, thereby suppressing wear due to contact with the rim flange 8 a. Examples of the reinforcing layer 16 include a chafer composed of steel cords and organic fibers such as rayon, nylon, polyester, and aramid.

[Other Embodiments]
(1) In the present invention, on the outer peripheral side of the belt layer 7 in the vicinity of the tire equator CL, the belt has a width of 5 to 15%, preferably 10 to 15% of the maximum belt width W, and is substantially 0 with respect to the tire circumferential direction. It is preferable to arrange a reinforcing material (not shown) extending at an angle of °. 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 road noise reduction effect according to the present invention is mainly due to the vibration mode having the asymmetry described above, and the tire weight is not excessively increased by the provision of the reinforcing material.

  (2) 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. Therefore, for example, the reinforcing rubber layer disposed on the inside of the vehicle may be formed with a single rubber layer, or the carcass layer may be configured with one layer.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. As evaluation items of Examples and the like, bead detachment resistance and road noise level 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 with Comparative Example 1 being 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 A test tire is mounted on a real vehicle (domestic 2000cc class FF vehicle), the front and rear have an air pressure of 200 kPa, a microphone is attached to the ear of the driver's seat, and at a constant speed of 60 km / h, 200 to 400 Hz. The road noise level was measured. The measured value is indexed with Comparative Example 1 as 100, and the smaller the value, the lower the road noise level.

(3) Rim assembly property Hump pressure was evaluated as an index of rim assembly property. Index evaluation is performed with Comparative Example 1 being 100, and the larger the value, the worse the rim assembly property.

Examples 1 and 2
A test tire having the tire structure shown in FIG. 1 and having a size of 245 / 40R18 with Hi-Ho as shown in Table 1 was produced. In order to balance the deflection amount of the sidewall portions on both sides, the rubber hardness of the reinforcing rubber layer on the vehicle outer side was 76 °, and the rubber hardness of the reinforcing rubber layer on the vehicle inner side was 78 °. Further, the maximum thickness of the reinforcing rubber layer disposed on the vehicle outer side is made smaller than that on the vehicle inner side, and the difference between them is 10% of the maximum thickness of the reinforcing rubber layer disposed on the vehicle outer side.

Comparative example 1 (conventional product)
A test tire having a size of 245 / 40R18 having no double bead structure in the tire structure shown in FIG. 1 was produced. The reinforcing rubber layers on both sides were each composed of a single rubber layer having a rubber hardness of 77 °. Further, the reinforcing rubber layers on both sides were set to the same maximum thickness, and both were set to thicknesses that were intermediate between the maximum thicknesses of the reinforcing rubber layers on both sides in the examples.

Comparative Examples 2 and 3
Except for the point that Hi-Ho is a value as shown in Table 1, test tires that were the same as those in Example 1 were produced, and Comparative Examples 2 and 3 were obtained, respectively. The evaluation results of each example are shown in Table 1.

  As shown in Table 1, in Examples 1 and 2, road noise can be reduced while exhibiting excellent bead resistance, and the hump pressure is equivalent to that of the conventional product, preventing deterioration of rim assembly. Yes. On the other hand, Comparative Example 1 having no double bead structure has low resistance to bead detachment and a road noise reduction effect is not obtained. Further, in Comparative Examples 2 and 3 in which the double bead structure is simply employed only on the outside of the vehicle, a sufficient road noise reduction effect is obtained, but the hump pressure is greatly disadvantageous with respect to rim assembly.

  FIG. 2 is a vibration mode diagram of the test tire according to (a) Example 1 and (b) Comparative Example 1. The initial shape before the tire vibrates is indicated by a broken line BL, and the tire vibration mode is indicated by a solid line SL. Show. Such a vibration mode diagram can be created from the amplitude and phase of the transfer function obtained experimentally. As disclosed in detail in Japanese Patent Application Laid-Open No. 2004-82858, the transfer function includes a plurality of measurement points (circular marks in the figure) when vibration is input to the tread portion of the tire within a frequency range of 200 to 400 Hz. Equivalent)).

  First, in (b) Comparative Example 1, it can be seen that a vibration mode substantially symmetrical with respect to the tire equator is formed with the first beads arranged in the pair of bead portions as both ends. This vibration mode is a secondary cross-sectional mode in which the tire maximum width portion is a node and the buttress portion and the side lower portion are antinodes, and the vibration nodes and antinodes are substantially at the same positions on the vehicle outer side and the vehicle inner side.

  In contrast, (a) in the first embodiment, the first bead arranged in the bead portion inside the vehicle and the second bead arranged in the annular bulge portion outside the vehicle are both ends, and asymmetric with respect to the tire equator. It can be seen that a simple vibration mode is formed. This is because the double bead structure is adopted only on the vehicle outer side, and the amplitude can be suppressed by providing asymmetry to the vibration mode.

Tire meridian cross-sectional view showing an example of a run-flat tire of the present invention (A) Vibration mode diagram of test tire according to Example 1 and (b) Comparative Example 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 1a 1st bead 1b 2nd bead 2 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)
10 Annular bulging portion CL Tire equator P Tire maximum diameter point W Belt maximum width

Claims (2)

A pair of bead portions each having an annular first bead, a sidewall portion extending outward in the tire radial direction from the bead portion, a reinforcing rubber layer disposed on the sidewall portion, and an outer periphery of each of the sidewall portions In a run flat tire provided with a tread portion connecting side ends via a shoulder portion,
An annular bulging portion having an annular second bead and bulging outward from the bead portion arranged on the vehicle outer side in the tire width direction;
The cross-sectional height Hi from the inner periphery of the first bead arranged on the vehicle inner side to the tire maximum diameter point, and the cross-sectional height Ho from the inner periphery of the second bead arranged on the vehicle outer side to the tire maximum diameter point Satisfies the relationship of Hi-Ho> 15 mm.   On the outer peripheral side of the belt layer disposed in the tread portion in the vicinity of the tire equator, there is a reinforcing material that is 5 to 15% of the maximum belt width and extends at an angle of substantially 0 ° with respect to the tire circumferential direction. The run-flat tire according to claim 1, which is arranged.

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