JP5109356B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire suitable as a flat tire with a flatness ratio of 45% or less, and more particularly to a pneumatic tire that can improve durability not only under a low internal pressure but also under a high internal pressure.

  In general, flat tires have a drawback that the ride zone is poor and the durability of the sidewall portion is poor because the flex zone of the sidewall portion is small. In view of such inconveniences, the bead filler disposed on the outer peripheral side of the bead core is made of a relatively soft rubber, and the thickness of the sidewall portion at the tire maximum width position is sufficiently reduced, thereby achieving flatness. It has been proposed to enlarge the flex zone of the sidewall portion of the tire (see, for example, Patent Document 1).

  According to the tire, since the flex zone of the side wall portion is sufficiently secured, the durability of the side wall portion under a low internal pressure is improved, and further, an effect of improving riding comfort is expected. However, when the hardness of the bead filler is lowered, the bead portion is easy to move with the rim flange as a fulcrum, so that there is a problem that durability under high internal pressure is lowered.

  By the way, with the upgrading and quietness of automobiles, reduction of road noise in pneumatic tires is required. On the other hand, a belt reinforcing layer formed by winding a reinforcing cord in the tire circumferential direction is disposed on the outer peripheral side of the belt layer. It has been proposed to use a lightweight and inexpensive aliphatic polyketone fiber cord as a reinforcing cord for such a belt reinforcing layer (see, for example, Patent Documents 2 to 5).

  However, when an aliphatic polyketone fiber cord is used for the belt reinforcing layer, there is a problem that durability and riding comfort of the belt edge portion are deteriorated. Therefore, in putting a belt reinforcing layer made of an aliphatic polyketone fiber cord into practical use, there is a demand for a tire structure that can avoid deterioration of the durability and riding comfort of the belt edge portion.

Japanese Patent Laid-Open No. 2005-1443 JP 2001-334811 A JP 2003-146014 A JP 2003-127612 A JP 2000-142525 A

  An object of the present invention is to provide a pneumatic tire that can improve durability not only under a low internal pressure but also under a high internal pressure.

In order to achieve the above object, the pneumatic tire of the present invention has at least one carcass layer mounted between a pair of left and right bead portions, and a plurality of belt layers are arranged on the outer periphery side of the carcass layer in the tread portion. , At least one belt reinforcing layer is disposed on the outer peripheral side of the belt layer, a cap compound layer is disposed on the outer peripheral side of the belt layer and the belt reinforcing layer, and a bead filler is disposed on the outer peripheral side of the bead core in each bead portion. In the pneumatic tire, the wing tip compound layer is disposed on both shoulder sides of the cap compound layer, the JIS hardness of the wing tip compound layer is set to 60 or less, and the tire radial direction height in the region where the cap compound layer is present. A and the length from the inner peripheral edge of the cap compound layer to the outer peripheral edge of the bead filler. The relationship between the distance F in the radial direction and the tire cross-section height SH is set to A / SH ≦ 0.3, F / SH ≧ 0.45, (A + F) /SH≧0.75, and the bead filler The JIS hardness is 90 or more.

  In the present invention, the height A in the tire radial direction of the region where the cap compound layer exists is set small, and the distance F in the tire radial direction from the inner peripheral end of the cap compound layer to the outer peripheral end of the bead filler is set large. By stiffening the bead filler, not only a sufficient flex zone in the sidewall portion is ensured, but also the rigidity around the bead portion is increased and the rigidity of the buttress portion is lowered. Thereby, since the bending position of the tire moves to the vicinity of the buttress part, the movement of the bead part can be relatively reduced, and the durability under high internal pressure can be improved. Moreover, since the flex zone of the sidewall portion is sufficiently secured as described above, the durability under a low internal pressure is also good.

In the present invention, it is necessary to dispose a wing tip compound layer on both shoulder sides of the cap compound layer, and to set the JIS hardness of the wing tip compound layer to 60 or less. By disposing the soft wing tip compound layer on both shoulder sides of the cap compound layer, the tire is easily bent at the buttress portion. However, JIS hardness means the durometer hardness prescribed | regulated to JISK6253, and is measured according to the said regulation.

  The carcass layer wraps around the bead core so as to wrap the bead filler from the inside to the outside of the tire, and the folded portion of the carcass layer extends from the outer peripheral edge of the bead filler to the outside in the tire radial direction. It is preferable to laminate the portions. Such a folded structure of the carcass layer is advantageous in enhancing the durability of the bead portion while expanding the flex zone.

  The belt reinforcing layer preferably has a winding structure in which a strip including one or a plurality of fiber cords is spirally wound so that the fiber cords are substantially parallel to the tire circumferential direction. . The belt reinforcing layer is composed of a high elastic fiber cord having an elongation rate of 1.8% to 3.5%, more preferably 2.0% to 3.0% when loaded with 2.0 cN / dtex. Is preferred. By using such a highly elastic fiber cord for the belt reinforcing layer, the effect of reducing road noise can be sufficiently exhibited. However, the elongation ratio in the present invention is measured according to JIS L1017. For the same reason, the dry heat shrinkage stress at 150 ° C. of the highly elastic fiber cord is preferably 0.3 cN / dtex or more. However, the dry heat shrinkage stress is measured according to JIS L1017.

The high elastic fiber cord is preferably an aliphatic polyketone fiber cord. The high elastic fiber cord has a structure represented by the following formula (1) and includes an aliphatic polyketone fiber satisfying a relationship of 1.05 ≧ (n + m) /n≧1.00. Is preferred.
_{- (CH 2 -CH 2 -CO)} n- (R-CO) m- ··· (1)
Here, R is an alkylene group having 3 or more carbon atoms.

  According to the present invention, A / SH ≦ 0.3, F / SH ≧ 0.45, (A + F) / SH ≧ 0 even when the above-described highly elastic fiber cord is used for the belt reinforcing layer. Since the flex zone of the side wall portion is enlarged based on the relationship of .75, the road noise reduction effect by the belt reinforcing layer made of high elastic fiber cord is obtained while improving the durability and riding comfort of the belt edge portion. It becomes possible.

  The present invention can be applied to various types of pneumatic tires. In particular, the present invention has a remarkable effect when applied to a flat tire having a flatness ratio of 45% or less in which the flex zone of the sidewall portion tends to be small. Obtainable.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a pneumatic tire according to an embodiment of the present invention, wherein 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. Two carcass layers 4 are mounted between the pair of left and right bead portions 3, 3, and these carcass layers 4 surround a bead core 5 so as to enclose a bead filler 6 disposed on the outer peripheral side of the bead core 5. It is folded from the inside to the outside. Each carcass layer 4 has a main body portion 4 a passing through the inside of the bead filler 6 in the tire width direction and a folded portion 4 b passing through the outside of the bead filler 6 in the tire width direction. The folded portion 4b of the carcass layer 4 located on the inner side of the tire extends to the outer side in the tire radial direction from the outer peripheral end of the bead filler 6, and is laminated on the main body portion 4a of the carcass layer 4 located on the outer side of the tire.

  On the other hand, two belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 are arranged such that the reinforcing cords are inclined with respect to the tire circumferential direction and the reinforcing cords cross each other between the layers. Further, on the outer peripheral side of the belt layer 7, a three-layer belt reinforcing layer 8 in which the reinforcing cord is oriented in the tire circumferential direction is disposed. More specifically, the belt reinforcing layer 8 has a laminated structure of a two-layer full cover that covers the entire width direction of the belt layer 7 and a one-layer edge cover that locally covers both ends of the belt layer 7 in the width direction. ing. The belt reinforcing layer 8 has a winding structure in which a strip including one or a plurality of fiber cords is spirally wound so that the fiber cords are substantially parallel to the tire circumferential direction.

  A cap compound layer 11 is disposed on the outer peripheral side of the belt layer 7 and the belt reinforcing layer 8. In order to ensure the necessary tire running performance, the cap compound layer 11 has a JIS hardness of 55 or more, preferably 60 to 75. On the other hand, wing tip compound layers 12 are disposed on both shoulder sides of the cap compound layer 11. The JIS hardness of the wing chip compound layer 12 is lower than the JIS hardness of the cap compound layer 11 and is set to 60 or less, preferably in the range of 54 to 58. By disposing the soft wingtip compound layer 12 on both shoulder sides of the cap compound layer 11, the tire is easily bent at the buttress portion.

  In the pneumatic tire, as shown in FIG. 1, the height A in the tire radial direction of the region where the cap compound layer 11 exists, and the tire diameter from the inner peripheral end of the cap compound layer 11 to the outer peripheral end of the bead filler 6. The relationship between the direction distance F and the tire cross-section height SH is set to A / SH ≦ 0.3, F / SH ≧ 0.45, and (A + F) /SH≧0.75. Moreover, the JIS hardness of the bead filler 6 is set to 90 or more.

  Thus, the height A in the tire radial direction of the region where the cap compound layer 11 exists is set small, and the distance F in the tire radial direction from the inner peripheral end of the cap compound layer 11 to the outer peripheral end of the bead filler 6 is set large. In addition, by hardening the bead filler 6, not only a sufficient flex zone of the sidewall portion 2 is ensured, but also the rigidity around the bead portion 3 is increased, so that the buttress portion (the tread portion 1 and the sidewall portion) is increased. 2 can be reduced in rigidity. Thereby, since the bending position of the tire moves to the vicinity of the buttress portion, the movement of the bead portion 3 can be relatively reduced, and the durability under high internal pressure can be improved. In addition, since the pneumatic tire sufficiently secures the flex zone of the sidewall portion 2, the durability under a low internal pressure is also good.

  Here, if A / SH> 0.3, the flex zone is insufficient and the durability under low internal pressure is lowered. A practical lower limit of A / SH is 0.05. Therefore, it is desirable that 0.05 ≦ A / SH ≦ 0.3.

  Further, if F / SH <0.45, the flex zone is insufficient, and the durability under low internal pressure is lowered. In order to sufficiently ensure the effect of increasing the rigidity by the bead filler 6, the upper limit value of F / SH is preferably set to 0.65. Therefore, it is desirable that 0.45 ≦ F / SH ≦ 0.65.

  Furthermore, if (A + F) / SH <0.75, the flex zone is insufficient and the durability under low internal pressure is reduced. In order to sufficiently secure the effect of increasing the rigidity by the bead filler 6, the upper limit value of (A + F) / SH is preferably set to 0.95. Therefore, it is desirable that 0.75 ≦ (A + F) /SH≦0.95.

  If the JIS hardness of the bead filler 6 is less than 90, the rigidity of the bead portion 3 is insufficient and the durability under high internal pressure is lowered. The practical upper limit of the JIS hardness of the bead filler 6 is 100. Therefore, it is desirable that the bead filler 6 has a JIS hardness of 90 or more and 100 or less.

  As the reinforcing cord of the belt reinforcing layer 7, it is preferable to use a high elastic fiber cord having an elongation rate of 1.8% to 3.5% at a load of 2.0 cN / dtex. When the stretch rate of the highly elastic fiber cord exceeds 3.5%, the effect of reducing road noise becomes insufficient, and conversely, when it is less than 1.8%, vulcanization failure tends to occur. Further, the dry heat shrinkage stress at 150 ° C. of the highly elastic fiber cord is 0.3 cN / dtex or more, more preferably 0.3 cN / dtex or more and 0.45 cN / dtex or less. If the dry heat shrinkage stress at 150 ° C. of the highly elastic fiber cord is less than 0.3 cN / dtex, the effect of reducing road noise becomes insufficient.

  Examples of the highly elastic fiber cord include an aliphatic polyketone fiber cord (POK), a polyester fiber cord, a lyocell fiber cord, and a composite fiber cord obtained by twisting an aromatic polyamide fiber and an aliphatic polyamide fiber. Aliphatic polyketone fiber cords are preferred.

The highly elastic fiber cord may be a cord including an aliphatic polyketone fiber having a structure represented by the following formula (1) and satisfying a relationship of 1.05 ≧ (n + m) /n≧1.00. . The high elastic fiber cord may be a hybrid cord of the aliphatic polyketone fiber and other fibers.
_{- (CH 2 -CH 2 -CO)} n- (R-CO) m- ··· (1)
Here, R is an alkylene group having 3 or more carbon atoms.

  In the formula (1), when the fraction of m (an alkylene unit other than ethylene) increases, the tire traveling growth increases and the durability decreases. This is presumably because the crystal structure of the spun fiber changes with an increase in m units, and the secondary binding force between the molecular chains decreases. In addition, when the strength of the fiber is lowered, the strength is further reduced when a twisted cord is used. Therefore, it is necessary to increase the amount of cord used to secure the breaking strength of the tire, and the provision of a lightweight and highly economical tire is provided. It becomes difficult. More preferably, an alternating copolymer consisting essentially of ethylene and carbon monoxide with m = 0 is preferably used. It is preferable to use wet spinning to produce such fibers.

  In the pneumatic tire, even when a high elastic fiber cord is used for the belt reinforcing layer 7, A / SH ≦ 0.3, F / SH ≧ 0.45, (A + F) /SH≧0.75. Since the flex zone of the sidewall portion 2 is enlarged based on the relationship, the road noise reduction effect by the belt reinforcing layer 7 made of a high elastic fiber cord is obtained while improving the durability and riding comfort of the belt edge portion. Can do.

  With tire size 225 / 35R19 84W, two carcass layers are mounted between a pair of left and right bead portions, two belt layers are arranged on the outer periphery side of the carcass layer in the tread portion, and the outer periphery side of the belt layer is arranged Three belt reinforcing layers (laminated structure of two full covers and one edge cover) are arranged, and a cap compound layer is arranged on the outer peripheral side of these belt layers and belt reinforcing layers, and a bead core in each bead portion. In the pneumatic tire in which the bead filler is disposed on the outer peripheral side of the tire, the height A in the tire radial direction of the region where the cap compound layer exists and the tire radial direction from the inner peripheral end of the cap compound layer to the outer peripheral end of the bead filler Conventional Example 1, Example 1 in which the relationship between the distance F and the tire cross-section height SH and the JIS hardness of the bead filler are varied as shown in Table 1. It was produced a pneumatic tire of Comparative Examples 1 to 6.

  For these test tires, the durability under low internal pressure and the durability under high internal pressure were evaluated by the following methods, and the results are also shown in Table 1.

Durability under low internal pressure:
The test tire was assembled on a wheel having a rim size of 19 × 9 J, a drum durability test was performed under the conditions of an internal pressure of 130 kPa, a load of 4.9 kN, and a speed of 81 km / h, and the travel distance until failure occurred was measured. The evaluation results are shown as an index with Conventional Example 1 as 100. The larger the index value, the better the durability under low internal pressure.

Durability under high internal pressure:
The test tire was assembled on a wheel having a rim size of 19 × 9 J, a drum durability test was performed under the conditions of an internal pressure of 330 kPa, a load of 7.4 kN, and a speed of 81 km / h, and the travel distance until failure occurred was measured. The evaluation results are shown as an index with Conventional Example 1 as 100. The larger the index value, the better the durability under high internal pressure.

  As is clear from Table 1, the tire of Example 1 was superior in both durability under low internal pressure and durability under high internal pressure as compared with Conventional Example 1. Although the tires of Comparative Examples 1 to 6 had good durability under low internal pressure, the durability under high internal pressure was insufficient.

  Next, with a tire size of 225 / 35R19 84W, two carcass layers are mounted between a pair of left and right bead portions, and two belt layers are disposed on the outer peripheral side of the carcass layer in the tread portion. Three belt reinforcement layers (laminated structure of two full covers and one edge cover) are arranged on the outer circumference side, and a cap compound layer is arranged on the outer circumference side of these belt layers and belt reinforcement layers. In a pneumatic tire in which a bead filler is disposed on the outer peripheral side of the bead core in the portion, the material of the reinforcing cord of the belt reinforcing layer, the height A in the tire radial direction of the region where the cap compound layer exists, and the inner peripheral end of the cap compound layer Table 2 shows the relationship between the distance F in the tire radial direction from the outer peripheral edge of the bead filler to the tire cross-section height SH, and the JIS hardness of the bead filler. Various different conventional example 11 was, were fabricated pneumatic tires of Examples 11 and Comparative Examples 11 to 25 in. As the reinforcing cord of the belt reinforcing layer, 66 nylon fiber cord (66N) or aliphatic polyketone fiber cord (POK) was used.

  These test tires were evaluated for road noise, durability, and riding comfort by the following methods, and the results are also shown in Table 2.

Road noise:
The test tire was assembled on a wheel having a rim size of 19 × 9 J and mounted on a vehicle having a displacement of 2000 cc under the condition of an air pressure of 230 kPa. The evaluation results are shown by a five-point method with the conventional example 11 as three points. A larger score means less road noise and better noise performance.

durability:
The test tire was assembled on a wheel having a rim size of 19 × 9 J, a drum durability test was performed under the conditions of an internal pressure of 330 kPa, a load of 7.4 kN, and a speed of 81 km / h, and the travel distance until failure occurred was measured. The evaluation results are shown as an index with the conventional example 11 as 100. The larger the index value, the better the durability.

Ride comfort:
The test tire was assembled on a wheel with a rim size of 19 × 9 J and mounted on a vehicle with a displacement of 2000 cc under the condition of an air pressure of 230 kPa. The evaluation results are shown by a five-point method with the conventional example 11 as three points. A larger score means better ride comfort.

  As is clear from Table 2, the tire of Example 11 had less road noise and superior durability and riding comfort compared to Conventional Example 11. On the other hand, the tires of Comparative Examples 11 to 25 could not obtain the improvement effect for all the evaluation items.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 4a Main body part 4b Folding part 5 Bead core 6 Bead filler 7 Belt layer 8 Belt reinforcement layer 11 Cap compound layer 12 Wing chip compound layer

Claims (8)

At least one carcass layer is mounted between the pair of left and right bead portions, a plurality of belt layers are disposed on the outer circumferential side of the carcass layer in the tread portion, and at least one belt reinforcing layer is disposed on the outer circumferential side of the belt layer. In a pneumatic tire in which a cap compound layer is disposed on the outer peripheral side of the belt layer and the belt reinforcing layer, and a bead filler is disposed on the outer peripheral side of the bead core in each bead portion , on both shoulder sides of the cap compound layer. A wing tip compound layer is disposed, a JIS hardness of the wing tip compound layer is set to 60 or less, a height A in a tire radial direction of an area where the cap compound layer exists, and the bead from an inner peripheral end of the cap compound layer The relationship between the distance F in the tire radial direction to the outer peripheral edge of the filler and the tire cross-section height SH A / SH ≦ 0.3, F / SH ≧ 0.45, (A + F) while the /SH≧0.75, a pneumatic tire in which the JIS hardness of the bead filler 90 or more. The pneumatic tire according to claim 1, wherein the JIS hardness of the wing tip compound layer is lower than the JIS hardness of the cap compound layer .   The carcass layer is wrapped around the bead core from the tire inner side to the outer side so as to wrap the bead filler, and the folded portion of the carcass layer extends from the outer peripheral end of the bead filler to the tire radial outer side. The pneumatic tire according to claim 1, wherein the pneumatic tire is laminated on a main body portion of the layer.   The pneumatic tire according to any one of claims 1 to 3, wherein the belt reinforcing layer is composed of a high elastic fiber cord having an elongation rate of 1.8% to 3.5% at a load of 2.0 cN / dtex.   The pneumatic tire according to claim 4, wherein the high elastic fiber cord has a dry heat shrinkage stress at 150 ° C. of 0.3 cN / dtex or more.   The pneumatic tire according to claim 4, wherein the highly elastic fiber cord is an aliphatic polyketone fiber cord. The high elastic fiber cord is a cord including an aliphatic polyketone fiber having a structure represented by the following formula (1) and satisfying a relationship of 1.05 ≧ (n + m) /n≧1.00. 4. The pneumatic tire according to 4.
_{- (CH 2 -CH 2 -CO)} n- (R-CO) m- ··· (1)
Here, R is an alkylene group having 3 or more carbon atoms.   The belt reinforcing layer has a winding structure in which a strip including one or more fiber cords is spirally wound so that the fiber cords are substantially parallel to the tire circumferential direction. The pneumatic tire according to any one of the above.

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