JP2006035895A - Run-flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a run-flat tire with a reinforcing rubber layer arranged on a side wall part of it, exhibiting an excellent rim removal resistance. <P>SOLUTION: This run-flat tire is furnished with a pair of bead parts 1 having ring beads 1a, side wall parts 2 respectively extending outside in the tire diametrical direction from the bead parts 1 and the reinforcing rubber layers 9 arranged on the side wall parts 2. It is further furnished with an annular bulged part 10 at least provided on the outside in the tire widthwise direction of the one bead part 1 and having an inner peripheral side surface 11 facing against an outer peripheral side curved surface of a rim flange 8a and a flexible rubber layer 13 arranged on the inner peripheral side surface 11. The flexible rubber layer 13 is arranged in the neighborhood of a contact point P of a tangential line T free to be drawn on the outer peripheral side curved surface of the rim flange 8a from an intersection (c) of a straight line (s) drawn on the inside in the tire diametrical direction from a center of the bead 1a and the outer peripheral side surface of a rim base 8b in installing a specified rim. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  A run-flat tire is a tire that can safely travel a certain distance even when the air pressure inside the tire is reduced due to a failure such as puncture. As one of tire structures for enabling such run flat running, a so-called side reinforcing type run flat tire having a reinforcing rubber layer on a sidewall portion is known. According to such a run-flat tire, in a state where the air pressure inside the tire is lowered, the reinforcing rubber layer supports the tire and prevents it from being completely flattened, and run-flat traveling is possible.

  However, in a state where the air pressure inside the tire is reduced (run-flat state), since the pressure on the rim of the bead portion is weakened, there is a problem that the fitting force with the rim is reduced and the bead portion is easily detached from the rim. there were. When the present inventors diligently researched this problem of rim disengagement, it has been found that the fitting force with the rim is remarkably reduced when grounding in a run-flat state. As shown in FIG. 4, when the sidewall portion 2 is bent and pressed against the rim flange 8 a side during contact, a moment having a fulcrum is generated in a region 14 that contacts the outer peripheral curved surface of the rim flange 8 a. It is considered that the moment causes the bead portion 1 to rise from the rim 8.

Conventionally, as a countermeasure against rim detachment, the volume of the reinforcing rubber layer has been increased or the tread rigidity has been increased. However, these have caused an increase in tire weight and a deterioration in riding comfort. Further, Patent Document 1 below discloses a run flat tire in which a bead reinforcing portion is provided with a rim deviation preventing layer for the purpose of improving running performance in a run flat state. However, in such a run-flat tire, since the rim displacement prevention layer is disposed on the portion facing the rim flange upper portion, the generation of a moment that lifts the bead portion described above has not been suppressed.
Japanese Patent Laid-Open No. 11-157311

  SUMMARY OF THE INVENTION An object of the present invention is to provide a run flat tire that exhibits excellent rim detachment resistance in a run flat tire in which a reinforcing rubber layer is disposed on a sidewall portion.

  The above object can be achieved by the present invention having the following configuration. That is, the run flat tire of the present invention includes a pair of bead portions having an annular bead, sidewall portions extending outward in the tire radial direction from the bead portions, and a reinforcing rubber layer disposed on the sidewall portions. An annular bulging portion that is provided on the outer side in the tire width direction of at least one of the bead portions and has an inner circumferential surface that faces an outer curved surface of the rim flange when the specified rim is mounted, and an annular shape thereof A soft rubber layer disposed on the inner peripheral side surface of the bulging portion, and the soft rubber layer is an intersection of a straight line drawn inward in the tire radial direction from the center of the bead and the outer peripheral side surface of the rim base when the specified rim is mounted To the contact point of the tangent that can be drawn with respect to the outer peripheral curved surface of the rim flange.

  As described above, a moment having a fulcrum is generated in the region in contact with the outer peripheral curved surface of the rim flange as the tire is deformed, but this moment is inward of the tire radial direction from the center of the bead. When the contact point of the tangent that can be drawn with respect to the outer peripheral side curved surface of the rim flange is used as a fulcrum from the intersection of the extending straight line and the outer peripheral side surface of the rim base, the effect of floating the bead portion becomes remarkable. Therefore, according to the configuration of the present invention, since the soft rubber layer is disposed in the vicinity of the contact on the inner peripheral side surface of the annular bulge portion, the moment with the contact as a fulcrum can be dispersed. As a result, lifting of the bead portion can be effectively suppressed, a fitting force with the rim can be secured, and excellent rim removal resistance can be exhibited. Here, the specified rim refers to a standard rim determined by JATMA corresponding to the tire size, and when the specified rim is mounted refers to a state where the specified rim is mounted at an air pressure of 180 kPa. The soft rubber layer refers to a rubber layer that is softer than the other rubber layers disposed on the inner peripheral side surface of the annular bulging portion.

  In the above, it is preferable that the soft rubber layer has a hardness of 50 to 65 ° according to a JISK6253 durometer hardness test (A type).

  By setting the hardness of the soft rubber layer within the above range, the durability of the bead portion can be secured, and the moment for lifting the bead portion as described above can be dispersed to improve the rim detachment resistance.

  In the above description, a point facing the contact point on the inner peripheral side surface of the annular bulging portion is used as a reference point, the distance in the tire width direction from the reference point to the center of the bead is L, the tire inner peripheral side of the soft rubber layer When the distance in the tangential direction from the end to the reference point is a and the distance in the tangential direction from the tire outer peripheral end of the soft rubber layer to the reference point is b, 0.2 L ≦ a ≦ 0.5 L And those satisfying 0.3L ≦ b ≦ 0.5L are preferable.

  By setting the region where the soft rubber layer is disposed in the above range, the durability of the bead portion can be ensured, and the moment to lift the bead portion as described above can be dispersed to improve the rim detachment resistance. . Here, the point facing the contact point refers to the intersection of the normal drawn from the contact point and the inner peripheral side surface of the annular bulging portion.

  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 mounted on a specified rim. FIG. 2 is a cross-sectional view of a main part of a bead portion of the run flat tire shown in FIG.

  The run-flat tire shown in FIG. 1 includes 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 via a shoulder portion 3. And a tread portion 4 connected to each other.

  The bead portion 1 is provided with a bead 1a in which a converging body of a bead wire such as a steel wire forms an annular shape in the tire circumferential direction, and a bead filler 1b. The bead 1a winds the end portion of the carcass layer 5 around. By stopping, the tire is firmly fitted onto the rim 8 in a state where the space between the bead portions 1 is reinforced by the carcass layer 5. During normal internal pressure, the bead portion 1 is arranged 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 air pressure inside the tire.

  An inner liner layer 6 for maintaining air pressure is disposed on the inner peripheral side of the carcass layer 5. In addition, a belt layer 7 is provided on the outer peripheral side of the carcass layer 5 to reinforce it with the effect of warping, and a tread pattern is formed on the outer peripheral surface of the belt layer 7 by tread rubber. As a constituent material of the carcass layer 5 and the belt layer 7, steel, organic fibers such as polyester, rayon, nylon, and aramid are used. These materials are usually subjected to surface treatment, adhesion treatment or the like in order to improve adhesion to rubber.

  On the inner side of the carcass layer 5 of the sidewall portion 2, a reinforcing rubber layer 9 having a substantially crescent-shaped tire meridian cross section is disposed. As a result, when the air pressure inside the tire decreases, the deformation of the tire is suppressed, and run-flat traveling is possible. The reinforcing rubber layer 9 is made of, for example, rubber having a hardness of 65 to 90 ° according to a JISK6253 durometer hardness test (A type). The reinforcing rubber layer 9 included in the run-flat tire of the present invention can be applied to any reinforcing rubber layer used in a conventional side-reinforcing type run-flat tire without being particularly limited in terms of hardness and thickness. Can do. The reinforcing rubber layer 9 is not limited to a single rubber layer, and may be composed of a plurality of rubber layers having different physical properties such as hardness.

  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.

  On the outer side in the tire width direction of the bead portion 1, an annular bulging portion 10 having an inner peripheral side surface 11 facing the outer peripheral side curved surface of the rim flange 8 a is formed. In the present embodiment, the inner peripheral side surface 11 of the annular bulging portion 10 is gradually separated from the outer peripheral curved surface of the rim flange 8a, and is continuously connected to the sidewall portion 2 from the outer peripheral end. The annular bulging portion 10 is preferably formed on each of the bead portions 1 on both sides. However, the annular bulging portion 10 only needs to be formed on at least one of the bead portions 1, and is formed only on the side that is on the vehicle outer side when mounted, for example. It doesn't matter. The annular bulging portion 10 is not limited to the shape shown in the present embodiment. For example, the annular meridian section has a semicircular or trapezoidal cross section, or the rim flange 8a is greatly bulged outward in the tire width direction. It may be configured such that it can be held.

  In the present invention, as shown in FIG. 2, a soft rubber layer 13 that is softer than the other rubber layers 12 disposed on the inner peripheral side surface 11 is disposed on the inner peripheral side surface 11 of the annular bulging portion 10. . The soft rubber layer 13 preferably has a hardness by 5 ° or more lower than that of the other rubber layer 12 according to the JISK6253 durometer hardness test (A type). Moreover, the hardness by the said test of the soft rubber layer 13 becomes like this. Preferably it is 50-65 degrees, More preferably, it is 55-60 degrees. If the hardness of the soft rubber layer 13 is less than 50 °, the problem of abrasion due to contact with the rim flange 8a tends to occur. On the other hand, if it exceeds 65 °, the effect of dispersing the moment having a fulcrum in the soft rubber layer 13 is poor, and the effect of improving the rim detachment resistance tends to be small.

  The soft rubber layer 13 is a contact point of a tangent line T that can be drawn from the intersection c between a straight line s extending inward in the tire radial direction from the center of the bead 1a and the outer peripheral side surface of the rim base 8b with respect to the outer peripheral curved surface of the rim flange 8a. Arranged in the area near P. The moment generated by the deformation of the tire has a remarkable effect of lifting the bead portion 1 when the contact point P is a fulcrum, but with this configuration, the fulcrum of the moment can be effectively dispersed.

  Here, a point facing the contact P on the inner peripheral side surface 11 of the annular bulging portion 10 is defined as a reference point P ′. In this embodiment, since the soft rubber layer 13 is in contact with the outer peripheral curved surface of the rim flange 8a at the contact P, the contact P is at the same position as the reference point P ′. In the present invention, as shown in FIG. 2, it is preferable that the soft rubber layer 13 is disposed in a region having the reference point P ′ as a substantially center.

  Further, the distance in the tire width direction from the center of the bead 1a to the reference point P ′ is L, the distance in the tangential T direction from the tire inner peripheral end 13a of the soft rubber layer 13 to the reference point P ′ is a, and the soft rubber layer 13 When the distance in the tangential T direction from the tire outer peripheral side end 13b to the reference point P ′ is b, it is preferable that 0.2L ≦ a ≦ 0.5L and 0.3L ≦ b ≦ 0.5L are satisfied. Those satisfying 3L ≦ a ≦ 0.4L and 0.3L ≦ b ≦ 0.4L are more preferable. If a <0.2L or b <0.3L, the region where the soft rubber layer 13 is disposed is too small, and the effect of dispersing the moment fulcrum tends to be small. On the other hand, if a> 0.5L or b> 0.5L, the region where the soft rubber layer 13 is disposed is too large, and the durability of the bead portion 1 tends to decrease.

  The thickness t of the soft rubber layer 13 based on the inner peripheral side surface 11 is preferably 1.5 mm or more, and more preferably 1.8 to 2.5 mm. If the thickness t is less than 1.5 mm, the soft rubber layer 13 is too thin and the effect of dispersing the moment tends to be small. Further, in the present embodiment, an example in which the soft rubber layer 13 has a substantially crescent shape in the tire meridian section has been shown, but the present invention is not limited thereto, and may be, for example, a sheet shape, a semicircular shape, a trapezoidal shape, or the like. Good.

  When the air pressure inside the tire decreases from the state shown in FIG. 2, the inner peripheral side surface 11 of the annular bulging portion 10 comes into contact with the outer peripheral side curved surface of the rim flange 8 a as the tire deforms. At that time, a moment having a fulcrum is generated in a region in contact with the outer peripheral curved surface of the rim flange 8a. In the present invention, the soft rubber layer 13 is disposed in the vicinity of the contact P as described above. It is possible to disperse moments that have a remarkable effect of raising the portion 1 and to effectively prevent the bead portion 1 from rising from the rim 8.

[Another embodiment]
In the above-described embodiment, an example in which the soft rubber layer 13 contacts the outer peripheral curved surface of the rim flange 8a at the contact point P when the specified rim is mounted has been described, but the present invention is not limited to this. For example, as shown in FIG. 3, the inner peripheral side surface 11 of the annular bulging portion 10 may be separated from the outer peripheral side curved surface of the rim flange 8a when the specified rim is mounted. Even with such a configuration, an effect of suppressing the above-described lifting of the bead portion 1 is exhibited. Further, as long as the soft rubber layer 13 is disposed in the vicinity of the contact point P, the soft rubber layer 13 does not have to be in close contact with the outer peripheral curved surface of the rim flange 8a during run-flat travel.

  Examples that specifically illustrate the structure and effects of the present invention will be described below.

(1) Rim 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 on a circular course with a radius of 20 m from straight ahead. Each test tire was in a run flat state with an internal pressure of 0 kPa, and the rim detachment resistance was evaluated based on the running speed (proportional to the lateral G) when rim detachment occurred. The running speed was started from 25 km / h, and the vehicle was run until the rim came off by a method of incrementing 5 km / h. The index is evaluated with Comparative Example 1 as 100, and the larger the value, the higher the running speed when rim detachment occurs, that is, the better rim detachment resistance.

(2) Bead durability Based on a method conforming to ISO draft, run on a drum with a diameter of 1700 mm at a pneumatic pressure of 0 kPa and a speed of 80 km / h with a load of JATMA 65%, cracking, separation, and abrasion in the bead part. Test time until failure such as failure due to was confirmed was measured. The index is evaluated with Comparative Example 1 as 100, and the higher the value, the longer the test time, that is, the better the bead durability.

Conventional Example and Example A test tire having the structure shown in FIGS. 1 and 2 and having a tire size of 225 / 45ZR17 was produced. However, in the conventional example, the soft rubber layer 13 is not provided, and only the rubber layer 12 is disposed on the inner peripheral side surface 11 of the annular bulging portion 10. In the examples, the dimensions (L, a, b, and t) of the soft rubber layer 13 and the hardnesses of the rubber layer 12 and the soft rubber layer 13 were values shown in Table 1, respectively. When evaluating the above items, each test tire was mounted on a rim having a wheel size of 17 × 7.5-JJ and tested. The results are shown in Table 1.

表１の結果に示すように、各実施例は、環状膨出部の内周側面に軟質ゴム層を備えることによって、ビード部を浮き上がらせるモーメントを分散することができ、従来例に比べて耐リム外れ性に優れていることがわかる。ここで、実施例３では軟質ゴム層が軟らかすぎるために、また、実施例６では軟質ゴム層の寸法が大きすぎるために、環状膨出部の内周側面とリムフランジとの接触による摩滅の問題が生じやすく、ビード耐久性が比較的低くなる傾向にあった。そして、実施例４では軟質ゴム層が硬すぎるために、また、実施例５および７では、軟質ゴム層の寸法が小さすぎるために、モーメントの分散効果が小さく、耐リム外れ性の向上効果が小さくなる傾向にあった。これに対して、実施例１および実施例２では、ビード耐久性を確保しながら耐リム外れ性を大きく改善できており、軟質ゴム層の各寸法（Ｌ、ａ、ｂおよびｔ）および硬さを、上述した範囲内とすることが好ましいことがわかる。

As shown in the results of Table 1, each example has a soft rubber layer on the inner peripheral side surface of the annular bulging portion, so that the moment to lift the bead portion can be dispersed, which is more resistant than the conventional example. It can be seen that it has excellent rim detachability. Here, since the soft rubber layer is too soft in Example 3 and the size of the soft rubber layer is too large in Example 6, wear due to contact between the inner peripheral side surface of the annular bulging portion and the rim flange is prevented. Problems were likely to occur and the bead durability tended to be relatively low. In Example 4, the soft rubber layer is too hard, and in Examples 5 and 7, since the size of the soft rubber layer is too small, the moment dispersion effect is small, and the rim detachment resistance is improved. There was a tendency to become smaller. On the other hand, in Example 1 and Example 2, the rim detachment resistance can be greatly improved while ensuring the bead durability. Each dimension (L, a, b and t) and hardness of the soft rubber layer It is understood that it is preferable to set the value within the above-described range.

Tire meridian cross-sectional view showing an example of a run-flat tire according to the present invention mounted on a specified rim Fig. 1 is a cross-sectional view of a main part showing a bead portion of the run flat tire shown in Fig. 1. Sectional drawing which shows the principal part which shows the bead part of the run flat tire which concerns on another form of this invention. Cross-sectional view of the main part showing the bead portion of a conventional run-flat tire

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 1a Bead 1b Bead filler 2 Side wall part 5 Carcass layer 8 Rim 8a Rim flange 8b Rim base 9 Reinforcement rubber layer 10 Annular bulging part 11 Inner peripheral side surface 12 Rubber layer 13 Soft rubber layer a Tire inner circumference of soft rubber layer Distance b from the side edge to the reference point Distance c from the tire outer peripheral side edge of the soft rubber layer to the reference point c Intersection s Straight line t Thickness L of the soft rubber layer P Distance in the tire width direction from the reference point to the intersection P Contact point P ′ Reference point T Tangent

Claims (3)

In a run flat tire comprising a pair of bead portions having an annular bead, sidewall portions extending outward in the tire radial direction from the bead portions, and a reinforcing rubber layer disposed on the sidewall portions,
An annular bulging portion provided on the outer side in the tire width direction of at least one of the bead portions and having an inner circumferential side surface facing the outer circumferential side curved surface of the rim flange when the specified rim is mounted, and an inner circumferential side surface of the annular bulging portion With a soft rubber layer arranged,
The soft rubber layer has a tangent that can be drawn to the outer peripheral curved surface of the rim flange from the intersection of a straight line drawn inward in the tire radial direction from the center of the bead and the outer peripheral side surface of the rim base when the specified rim is mounted. A run-flat tire that is placed near the contact point.   The run-flat tire according to claim 1, wherein the soft rubber layer has a hardness of 50 to 65 degrees according to a durometer hardness test (A type) of JIS K6253. The point facing the contact point on the inner peripheral side surface of the annular bulging portion is a reference point, the distance in the tire width direction from the reference point to the center of the bead is L, the tire inner peripheral side end of the soft rubber layer When the distance in the tangential direction to the reference point is a and the distance in the tangential direction from the tire outer peripheral end of the soft rubber layer to the reference point is b, 0.2 L ≦ a ≦ 0.5 L and 0. The run flat tire according to claim 1 or 2, satisfying 3L ≦ b ≦ 0.5L.

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