JP2016078749A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing rolling resistance while securing steering stability and ride comfort.SOLUTION: A bead filler 12 extends from a bead core 11 embedded in a bead part to the outside of a tire radial direction. A carcass ply 7 sandwiches the bead core 11 and the bead filler 12 with a main body part 71 and a wound-up part 72. A rim strip rubber 4 is disposed on the outside of a tire width direction of the wound-up part 72, and forms a tire outside surface of the bead part. An outside end 12a of the bead filler 12 is positioned inside the tire radial direction with respect to an outside end 4a of the rim strip rubber 4 which appears on the tire outside surface. A reinforcement rubber layer 8 is stuck on the outside surface of the main body part 71, an outside end 8a of the reinforcement rubber layer 8 is positioned on the outside of the tire radial direction with respect to the outside end 4a of the rim strip rubber 4, and an inside end 8b of the reinforcement rubber layer 8 is positioned on the inside of the tire radial direction with respect to the outside end 4a of the rim strip rubber 4.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire that can reduce rolling resistance while ensuring steering stability and riding comfort.

  In recent years, there has been an increasing demand for reduction in tire rolling resistance, which is closely related to the reduction in fuel consumption of vehicles. Although weight reduction of tires is effective in reducing rolling resistance, it is difficult to secure tire rigidity simply by reducing the size of the components and other tire performance such as steering stability is deteriorated. There is a risk of causing.

  Patent Document 1 describes a pneumatic radial tire in which the height of a bead filler and the height of a carcass ply winding portion are adjusted in order to reduce rolling resistance. However, in this tire, since the rigidity changes abruptly from the contact area with the rim flange to the non-contact area, the compressive stress at the time of traveling is hardly dispersed, and the rolling resistance improvement effect cannot be sufficiently obtained. Moreover, since the lateral rigidity of the tire is reduced by the low-profile bead filler, there is a concern that the steering stability is deteriorated.

  Patent Documents 2 and 3 describe pneumatic tires in which reinforcing rubber layers for improving steering stability are provided on the sidewall portions. However, in these tires, since a reinforcing rubber layer is provided in addition to a normal bead filler made of hard rubber, it is considered that the longitudinal rigidity of the tire is excessively increased and riding comfort is decreased.

JP 2012-176694 A JP 2000-247115 A JP 2014-54925 A

  This invention is made | formed in view of the said situation, The objective is to provide the pneumatic tire which can reduce rolling resistance, ensuring steering stability and riding comfort.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention includes a bead filler extending from the bead core embedded in the bead portion to the outside in the tire radial direction, a main body portion extending from the tread portion to the bead portion via the sidewall portion, and the main body portion. A carcass ply having a winding portion wound continuously outward in the tire radial direction, sandwiching the bead core and the bead filler between the main body portion and the winding portion, and provided on the outer side in the tire width direction of the winding portion. And a rim strip rubber that forms a tire outer surface of the bead portion, wherein an outer end of the bead filler is located on an inner side in a tire radial direction with respect to an outer end of the rim strip rubber that appears on the tire outer surface. A reinforcing rubber layer is bonded to the outer surface of the main body, and the outer end of the reinforcing rubber layer is Located in the tire radial direction outer side than the outer end of the strip rubber, the inner end of the reinforcing rubber layer is to be located on the inner side in the tire radial direction than the outer end of the rim strip rubber.

  In this tire, since the bead filler has a lower height than usual, an effect of reducing rolling resistance can be obtained by reducing the weight. In addition, since the reinforcing rubber layer as described above is provided, the rigidity gradually changes from the contact area with the rim flange to the non-contact area, and the compressive stress during running is easily dispersed, improving the rolling resistance. The effect is enhanced. Further, by providing the reinforcing rubber layer, a decrease in the lateral rigidity of the tire due to the low profile of the bead filler is suppressed, and steering stability can be ensured. Although the reinforcing rubber layer increases the longitudinal rigidity of the tire, the flex zone is widened by the low profile of the bead filler, so that riding comfort can be ensured.

  It is preferable that the inner end of the reinforcing rubber layer is located on the outer side in the tire radial direction than the outer end of the bead filler. According to such a configuration, since the reinforcing rubber layer is disposed away from the bead filler, the reinforcing rubber layer is easily bent, and an increase in the longitudinal rigidity of the tire can be suppressed to improve riding comfort.

  It is preferable that the outer end of the reinforcing rubber layer is located on the inner side in the tire radial direction from the maximum tire width position. According to such a configuration, it is possible to suppress the increase in the longitudinal rigidity of the tire due to the reinforcing rubber layer, and to ensure better riding comfort.

  The reinforcing rubber layer preferably has a 100% tensile modulus lower than the 100% tensile modulus of the bead filler, and the difference is 20% or more of the 100% tensile modulus of the bead filler. By making the reinforcing rubber layer have a low modulus in this way, it is possible to better ensure riding comfort.

  A rubber hardness of the reinforcing rubber layer is preferably higher than that of the rim strip rubber and lower than that of the bead filler. By making the reinforcing rubber layer harder than the rim strip rubber, it is possible to secure better steering stability.

The tire meridian half section view showing the pneumatic tire concerning one embodiment of the present invention

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  A pneumatic tire according to an embodiment of the present invention is shown in FIG. The dimensions and positional relationship of each part of the pneumatic tire T are measured in a no-load state in which the tire is mounted on a regular rim and filled with a regular internal pressure. The rubber interface as shown in the figure can be specified in the tire cross section after the vulcanization treatment. For example, by cutting the tire with a sharp blade, the rubber interface can be discriminated by the property of the rubber interface that is thinly observed in the cross section.

  In the above, the regular rim is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, a design rim for TRA, or a design rim for ETRTO. Become Measuring Rim. In addition, the normal internal pressure is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum value described in PRESSURES, INFLATION PRESSURE for ETRTO, but 180 kPa for passenger car tires.

  The pneumatic tire T includes a pair of bead portions 1, a sidewall portion 2 extending outward in the tire radial direction from each of the bead portions 1, and a tread portion 3 connected to each tire radial direction outer end of the sidewall portion 2. With. An annular bead core 11 formed by covering a converging body such as a steel wire with rubber is embedded in the bead portion 1. The tire T further includes a bead filler 12 extending from the bead core 11 to the outer side in the tire radial direction, a carcass ply 7 having a main body portion 71 and a winding portion 72, and a rim provided at a portion in contact with a rim flange (not shown). A strip rubber 4 is provided.

  The bead filler 12 is formed of a hard rubber having a triangular cross section, and is set to be lower than usual as will be described later. The carcass ply 7 is formed by covering a cord arranged in a direction substantially orthogonal to the tire circumferential direction with rubber. The main body portion 71 extends from the tread portion 3 through the sidewall portion 2 to the bead portion 1, and the winding portion 72 is continuously wound on the tire radial direction outside the main body portion 71. The carcass ply 7 sandwiches the bead core 11 and the bead filler 12 between the main body portion 71 and the winding portion 72, and is formed in a toroid shape as a whole. An inner liner rubber 5 for holding air pressure is provided on the inner peripheral side of the main body 71.

  The rim strip rubber 4 is provided on the outer side in the tire width direction of the rolled-up portion 72 to form the tire outer surface of the bead portion 1. In order to suppress wear due to contact with the rim flange, the rim strip rubber 4 is formed of a hard rubber having excellent wear resistance. The sidewall rubber 9 forms the outer surface of the tire of the sidewall portion 2, and the rim strip rubber 4 is connected to the inside of the sidewall rubber 9 in the tire radial direction. In the present embodiment, a rim line is provided at the interface between the rim strip rubber 4 and the sidewall rubber 9. The rim line helps to confirm that the tire T is properly assembled to the rim.

  The outer end 4a is an end on the outer side in the tire radial direction of the rim strip rubber 4 appearing on the outer surface of the tire. The inner side in the tire radial direction from the outer end 4a is a contact area with the rim flange, and the outer side in the tire radial direction from the outer end 4a is a non-contact area with the rim flange. The rim line is set at the same height as the outer end 12a. In this pneumatic tire T, the outer end 12a of the bead filler 12 is located on the inner side in the tire radial direction than the outer end 4a of the rim strip rubber 4 appearing on the outer surface of the tire. The bead filler 12 has a structure that is lower than a general bead filler.

  A reinforcing rubber layer 8 is bonded to the outer surface of the main body 71. The reinforcing rubber layer 8 of the present embodiment is formed of a single rubber without including fibers. The reinforcing rubber layer 8 extends with a constant thickness along the main body 71, and the thickness is set to 0.4 to 1.0 mm, for example. When the thickness is less than 0.4 mm, the reinforcing effect by the reinforcing rubber layer 8 tends to be small, and when the thickness exceeds 1.0 mm, the effect of improving rolling resistance tends to be small due to an increase in mass. The reinforcing rubber layer 8 extends in an annular shape along the tire circumferential direction, and is also provided on a bead portion on the opposite side (not shown).

  The outer end 8a is an end on the outer side in the tire radial direction of the reinforcing rubber layer 8, and the inner end 8b is also an end on the inner side in the tire radial direction. The outer end 8 a of the reinforcing rubber layer 8 is positioned on the outer side in the tire radial direction from the outer end 4 a of the rim strip rubber 4, and the inner end 8 b of the reinforcing rubber layer 8 is a tire diameter from the outer end 4 a of the rim strip rubber 4. Located inside the direction. Therefore, the outer end 4a of the rim strip rubber 4 is located between the outer end 8a and the inner end 8b, and the reinforcing rubber layer 8 is disposed from the contact area to the non-contact area with the rim flange.

  In the tire T, since the bead filler 12 has a lower height than usual, an effect of reducing rolling resistance can be obtained by reducing the weight. In addition, by providing the reinforcing rubber layer 8, the rigidity gradually changes from the contact area with the rim flange to the non-contact area, and the compressive stress during traveling is easily dispersed, thereby improving the rolling resistance. Is increased. Further, by providing the reinforcing rubber layer 8, a decrease in the lateral rigidity of the tire T due to the low profile of the bead filler 12 is suppressed, and steering stability can be ensured. The reinforcing rubber layer 8 increases the longitudinal rigidity of the tire T. However, since the flex zone is widened by the low profile of the bead filler 12, riding comfort can be ensured.

  The heights H4a and H12a are heights in the tire radial direction from the base line BL serving as a reference for the tire cross-section height TH to the outer ends 4a and 12a, respectively. The height H4a is larger than the height H12a, and is set to 15 to 25% of the tire cross-section height TH, for example. In reducing the rolling resistance, the height H12a is preferably 28% or less, more preferably 23% or less, and still more preferably 18% or less of the tire cross-section height TH. Further, from the viewpoint of not excessively reducing the rigidity of the bead portion 1, the height H12a is preferably 10% or more, more preferably 15% or more of the tire cross-section height TH.

  The reinforcing rubber layer 8 may come into contact with the bead filler 12, but in that case, the riding comfort is lowered due to the increase in the longitudinal rigidity of the tire, and the improvement effect due to the low profile of the bead filler 12 is not sufficiently obtained. . On the other hand, in this embodiment, the inner end 8b of the reinforcing rubber layer 8 is positioned on the outer side in the tire radial direction with respect to the outer end 12a of the bead filler 12, and the reinforcing rubber layer 8 is disposed away from the bead filler 12. Therefore, the reinforcing rubber layer 8 is easily bent, and the ride comfort can be improved by suppressing an increase in the longitudinal rigidity of the tire. In order to enhance this improvement effect, the distance G between the reinforcing rubber layer 8 and the bead filler 12 is preferably 3 mm or more.

  The height H8b is a height in the tire radial direction from the base line BL to the inner end 8b. The distance G is calculated as a difference (H8b−H12a) between the height H8b and the height H12a. As described above, the inner end 8b of the reinforcing rubber layer 8 is located on the inner side in the tire radial direction with respect to the outer end 4a of the rim strip rubber 4, and therefore the height H8b is smaller than the height H4a. According to such a configuration, since the inner end 8b is disposed on the inner side in the tire width direction of the rim flange, the movement of the inner end 8b during traveling can be suppressed, and the occurrence of a failure such as separation starting from the inner end 8b can be suppressed. .

  The inner end 8 b of the reinforcing rubber layer 8 is sandwiched between the main body portion 71 and the winding portion 72. In the present embodiment, the outer end of the winding part 72 does not reach the outer end 8a while being positioned on the outer side in the tire radial direction with respect to the outer end 4a, but is not limited thereto. The outer end 8a of the reinforcing rubber layer is preferably located on the inner side in the tire radial direction from the tire maximum width position 20 in order to ensure better riding comfort. In the present embodiment, the interface between the rim strip rubber 4 and the sidewall rubber 9 is inclined outward in the tire radial direction toward the inner side in the tire width direction, but is not limited thereto.

  The reinforcing rubber layer 8 has a 100% tensile modulus (hereinafter sometimes referred to as “M100”) lower than the M100 of the bead filler 12, and the difference is preferably 20% or more of the M100 of the bead filler 12. Thus, by making the reinforced rubber layer 8 have a low modulus, it is possible to better ensure riding comfort. For example, M100 of the bead filler 12 is 10 to 13 MPa, M100 of the reinforcing rubber layer 8 is 4 to 7 MPa, M100 of the rim strip rubber 4 is 3.5 to 6.5 MPa, and M100 of the side wall rubber 9 is 1 to 4 MPa. . The 100% tensile modulus is a tensile stress at 100% elongation when a tensile test is performed at 25 ° C. in accordance with JISK6251.

  The rubber hardness of the reinforcing rubber layer 8 is preferably higher than that of the rim strip rubber 4 and lower than that of the bead filler 12. By making the reinforcing rubber layer 8 harder than the rim strip rubber 4 in this way, it is possible to secure better steering stability. For example, the rubber hardness of the bead filler 12 is 85 to 100, the rubber hardness of the reinforcing rubber layer 8 is 75 to 85, the rubber hardness of the rim strip rubber 4 is 60 to 75, and the rubber hardness of the sidewall rubber 9 is 45 to 60. . The rubber hardness is a hardness measured at 25 ° C. according to JIS K6253 durometer hardness test (type A).

  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.

  Examples that specifically illustrate the structure and effects of the present invention will be described. The performance evaluation of the tire was performed as follows.

[Rolling resistance]
The rolling resistance was measured according to the international standard ISO28580 (JIS D4234) by assembling to a rim of 14 × 4.5 J and adjusting the air pressure to 210 kPa. The result of Comparative Example 1 is evaluated as an index with the value of 100, and the smaller the index, the better the rolling resistance.

[Steering stability]
It was assembled on a 14x4.5J rim and the air pressure was set to 240 kPa, and it was mounted on an actual vehicle (domestic light vehicle) and subjected to sensory evaluation by an evaluation panel (driver). The result of Comparative Example 1 was evaluated as an index with the value of 100, and the larger the index, the better the steering stability.

[Ride comfort]
It was assembled on a 14x4.5J rim and the air pressure was set to 240 kPa, and it was mounted on an actual vehicle (domestic light vehicle) and subjected to sensory evaluation by an evaluation panel (driver). The result of Comparative Example 1 is evaluated as an index with the value 100, and the larger the index, the better the ride comfort.

  The size of the tire used for the evaluation was 155 / 65R14 75S. Except for the items shown in Table 1, the tire structure and the rubber composition in each example are common. None of Comparative Examples 1 and 2 has a reinforcing rubber layer, and the bead filler of Comparative Example 1 has a general size. In Example 1, the inner end of the reinforcing rubber layer is in contact with the bead filler, but in Example 2, the inner end of the reinforcing rubber layer is separated from the bead filler by a distance of 3 mm outward in the tire radial direction. The evaluation results are shown in Table 1.

  As shown in Table 1, in Comparative Example 2, riding comfort is improved as compared to Comparative Example 1, but steering stability is deteriorated and the effect of improving rolling resistance is not sufficient. On the other hand, in Examples 1 and 2, rolling resistance can be reduced more than Comparative Examples 1 and 2 while ensuring steering stability and riding comfort. In particular, in Example 2, the riding comfort is improved by disposing the reinforcing rubber layer away from the bead filler.

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4 Rim strip rubber 4a Outer end 7 of rim strip rubber 7 Carcass ply 8 Reinforcement rubber layer 8a Outer end 8b of reinforcement rubber layer Inner end 9 of reinforcement rubber layer Filler 12a Outside end 20 of bead filler 20 Maximum tire width position 71 Body 72 Winding part

Claims (5)

A bead filler extending outward in the tire radial direction from a bead core embedded in the bead part;
A main body part extending from the tread part through the sidewall part to the bead part; and a winding part wound up continuously in the tire radial direction continuously to the main body part, and the bead core is formed by the main body part and the winding part. And a carcass ply sandwiching the bead filler,
In a pneumatic tire comprising: a rim strip rubber that is provided on the outer side in the tire width direction of the winding part and forms a tire outer surface of the bead part,
The outer end of the bead filler is located on the inner side in the tire radial direction than the outer end of the rim strip rubber appearing on the outer surface of the tire,
A reinforcing rubber layer is bonded to the outer surface of the main body, the outer end of the reinforcing rubber layer is positioned on the outer side in the tire radial direction than the outer end of the rim strip rubber, and the inner end of the reinforcing rubber layer is the rim. A pneumatic tire characterized by being positioned on the inner side in the tire radial direction from the outer end of the strip rubber.   The pneumatic tire according to claim 1, wherein an inner end of the reinforcing rubber layer is located on an outer side in a tire radial direction with respect to an outer end of the bead filler.   The pneumatic tire according to claim 1 or 2, wherein an outer end of the reinforcing rubber layer is located on an inner side in a tire radial direction from a tire maximum width position.   The 100% tensile modulus of the reinforcing rubber layer is lower than the 100% tensile modulus of the bead filler, and the difference is 20% or more of the 100% tensile modulus of the bead filler. The described pneumatic tire.   The pneumatic tire according to any one of claims 1 to 4, wherein a rubber hardness of the reinforcing rubber layer is higher than a rubber hardness of the rim strip rubber and lower than a rubber hardness of the bead filler.

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