JP2013119307A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire by which high speed durability and steering characteristics can be improved, while maintaining a lane change performance in the pneumatic tire with a plurality of belt layers of different width.SOLUTION: A cushioning rubber layer 10 is disposed between an edge portion and a belt reinforcing layer 8 of the belt layer 7, and tire width direction inner end 10i of the cushioning rubber layer 10 is disposed from a tire width direction outer end 71o of an outer circumference side belt layer 71 in the range of 3 mm to 13 mm toward the tire width direction inside. A tire width direction outer end 10o of the cushion rubber layer 10 is disposed at a tire width direction outside of the tire width direction outer end 8o of the belt reinforcing layer 8, and a thickness G of the cushion rubber layer is 0.5 mm or more at a position corresponding to the tire width direction outer end 71o of the outer circumference side belt layer 71. A hardness of the cushion rubber for constituting the cushion rubber layer 10 is made lower than that of a cap tread rubber.

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that can improve high-speed durability and steering characteristics while maintaining lane change performance.

  Generally, in a pneumatic tire, a belt reinforcing layer is provided on the outer peripheral side of the belt layer so as to cover the edge portion of the belt layer, thereby improving the edge separation resistance of the belt layer and improving the belt durability. Has been.

  By the way, the belt layer has a step at the end of the belt layer due to the difference in width. When the belt reinforcing layer is provided as described above, the belt reinforcing layer is disposed so as to cover the step. Therefore, in a tire having a large step at the belt layer end, there is a risk that air may remain between the belt reinforcing layer and the edge of the belt layer. If air remains in this way, the belt reinforcing layer and the belt layer end And the binding force of the edge portion of the belt layer by the belt reinforcing layer tends to be low. As a result, there is a problem that the edge separation resistance is lowered and the belt durability is deteriorated due to a decrease in tension of the reinforcing cord of the belt layer.

  As a countermeasure against such a problem, there is a proposal to insert a rubber layer containing short fibers between the belt reinforcing layer and the edge portion of the belt layer (see, for example, Patent Document 1). By thus filling the rubber layer in the space where the air between the belt reinforcing layer and the belt layer end portion remains, the occurrence of air accumulation can be suppressed. However, when the rubber layer is interposed in this way, the rubber layer acts as a cushion, and therefore, the tagging effect on the edge portion of the belt layer due to the reinforcing cord of the belt reinforcing layer cannot be sufficiently exerted, and the steering stability There is a problem that (in particular, lane change performance) is lowered. In addition, since short fibers are included to supplement the reinforcing properties, the rigidity of the tread portion corresponding to the edge portion of the belt layer tends to be too high, and the steer characteristic tends to be oversteer, and is understeer. There is a problem that it is not suitable for all-season tires that are required.

Japanese Patent Laid-Open No. 10-044711

  An object of the present invention is to solve the above-described problems, and in a pneumatic tire having a plurality of belt layers having different widths, it is possible to improve high-speed durability and steering characteristics while maintaining lane change performance. Is to provide a pneumatic tire.

  In order to achieve the above object, a pneumatic tire according to the present invention has a carcass layer mounted between a pair of bead portions, and a plurality of belt layers are disposed on the outer peripheral side of the carcass layer in a tread portion. In the pneumatic tire in which at least one belt reinforcing layer covering at least the edge portion of the belt layer is arranged on the outer peripheral side of the rubber layer, a buffer rubber layer is arranged between the edge portion of the belt layer and the belt reinforcing layer, The inner end portion in the tire width direction of the cushioning rubber layer is disposed in the range of 3 mm to 13 mm from the outer end portion in the tire width direction of the outer peripheral belt layer located on the outer side in the tire radial direction of the belt layer toward the inner side in the tire width direction. The outer end of the cushion rubber layer in the tire width direction is disposed on the outer side in the tire width direction of the outer side of the belt reinforcing layer in the tire width direction, and the tire width of the outer peripheral belt layer The buffer rubber layer has a thickness G of 0.5 mm or more at a position corresponding to the outer side end, and the hardness of the buffer rubber constituting the buffer rubber layer is lower than the hardness of the cap tread rubber. And

  In the present invention, as described above, the shock absorbing rubber layer is disposed between the edge portion of the belt layer and the belt reinforcing layer, and the inner end of the shock absorbing rubber layer in the tire width direction is the outer side of the outer peripheral belt layer in the tire width direction. It arrange | positions in the range of 3 mm-13 mm toward the tire width direction inner side from an edge part, and thickness G of the buffer rubber layer in the position corresponding to the tire width direction outer side edge part of an outer peripheral side belt layer shall be 0.5 mm or more By doing so, high-speed durability can be improved while maintaining high steering stability (lane change performance). On the other hand, the outer end portion in the tire width direction of the shock absorbing rubber layer is arranged on the outer side in the tire width direction than the outer end portion in the tire width direction of the belt reinforcing layer, and the hardness of the shock absorbing rubber constituting the shock absorbing rubber layer is set to cap tread rubber. The understeer characteristic can be improved because the hardness is lower than the hardness. In this way, high-speed durability and steering characteristics can be improved while maintaining lane change performance, and these tire performances can be made highly compatible.

  In this invention, it is preferable that the shape in the tire meridian cross section of a buffer rubber layer is a crescent shape or a triangle shape. By setting the cross-sectional shape of the shock absorbing rubber layer in this way, the rigidity of the tread portion decreases toward the outer side in the tire width direction, so that the understeer characteristic can be further improved.

In the present invention, a straight line drawn in the tire radial direction from the ground contact end E _max under the load corresponding to the maximum load capacity defined by the standard and the air pressure corresponding to the maximum load capacity, and the outer side in the tire radial direction of the buffer rubber layer thickness G of the buffer rubber layer at the surface and intersects the point P _max is maximum, it is preferable that the thickness G _max of the buffer rubber layer in this respect P _max is 2.0mm or more. By setting the shape of the buffer rubber layer in this way, the rigidity of the tread portion at the position of the ground contact E _max can be suppressed, and the understeer characteristic can be further improved.

  In the present invention, it is preferable that tan δ at 60 ° C. of the buffer rubber constituting the buffer rubber layer is lower than tan δ at 60 ° C. of the belt coat rubber constituting the belt layer. By defining the properties of the buffer rubber constituting the buffer rubber layer in this manner, heat generation of the buffer rubber layer can be suppressed and high-speed durability can be further improved.

  In addition, the thickness G of the buffer rubber layer in the present invention is a rubber thickness measured in a direction perpendicular to the outer surface of the buffer rubber layer in the tire radial direction. Moreover, the hardness as used in the field of this invention is the durometer hardness prescribed | regulated to JISK6253, Comprising: It is the hardness measured in the temperature of 20 degreeC with the type A durometer. Further, tan δ at 60 ° C. in the present invention is based on JIS K6394, using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho), temperature 60 ° C., frequency 20 Hz, static strain 10%, dynamic strain ± 2 % Is a conditional value.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. It is principal part sectional drawing which expands and shows the belt layer edge part of the pneumatic tire of FIG.

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

  In FIG. 1, 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. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the tire inner side to the outer side around the bead core 5 disposed in each bead portion 3. A bead filler 6 is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body portion and the folded portion of the carcass layer 4.

  On the other hand, a plurality of belt layers 7 having different widths are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. In the illustrated example, two layers of an outer peripheral belt layer 71 and an inner peripheral belt layer 72 are provided as the belt layer 7, and the width of the outer peripheral belt layer 71 is narrower than the width of the inner peripheral belt layer 72. . These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. Further, a belt reinforcing layer 8 is provided on the outer peripheral side of the belt layer 7. The cord angle of the belt reinforcing layer 8 with respect to the tire circumferential direction is 5 ° or less, more preferably 3 ° or less.

  In the present invention, the cross-sectional shape of the tire is not limited to that shown in FIG. 1, and a plurality of belt layers 7 having different widths and a belt reinforcing layer 8 covering at least the edge portion of the belt layer 7 are provided. Any form can be used.

  In the present invention, as shown in FIGS. 1 and 2, the buffer rubber layer 10 is disposed between the outer peripheral side belt layer 71 and the inner periphery between the edge portion of the belt layer 7 and the belt reinforcing layer 8 arranged as described above. It arrange | positions so that the level | step difference produced by the difference in width with the side belt layer 72 may be filled up. A cap tread rubber layer 11 is disposed on the outer peripheral side of the belt reinforcing layer 8 and the buffer rubber layer 10.

  The inner end 10i in the tire width direction of the cushioning rubber layer 10 is 3 mm to 13 mm from the outer end 71o in the tire width direction of the outer peripheral belt layer 71 located on the outer side in the tire radial direction of the belt layer 7 toward the inner side in the tire width direction. It is located in the range. In other words, the distance La from the outer end portion 71o in the tire width direction of the outer peripheral belt layer 71 to the inner end portion 10i in the tire width direction of the shock absorbing rubber layer 10 is set to 3 mm to 13 mm. Further, the thickness G of the buffer rubber layer 10 at a position corresponding to the outer end portion 71o in the tire width direction of the outer peripheral side belt layer 71 is set to 0.5 mm or more.

  Thus, by specifying the shape of the shock absorbing rubber layer 10 on the inner side in the tire width direction, it is possible to improve high-speed durability while maintaining high steering stability (lane change performance). That is, the length at which the belt layer 7 and the cushioning rubber layer 10 overlap (that is, the distance La) is limited to a specific range, and the cushioning is performed at the portion where the belt layer 7 and the cushioning rubber layer 10 overlap. By setting the thickness G of the rubber layer 10, it is possible to prevent a decrease in the tagging effect due to the insertion of the buffer rubber layer 10 between the belt layer 7 and the belt reinforcing layer 8, and to have excellent steering stability ( In particular, while maintaining the lane change performance), it is possible to prevent air accumulation between the belt layer 7 and the belt reinforcing layer 8 to improve the separation resistance and improve the high-speed durability.

  At this time, if the distance La is smaller than 3 mm, the amount of the buffer rubber layer 10 interposed between the belt layer 7 and the belt reinforcing layer 8 is too small, so that the high-speed durability cannot be improved. On the contrary, if the distance La is larger than 13 mm, the steering stability (lane change performance) is affected by the decrease in the tagging effect due to the buffer rubber layer 10 being interposed between the belt layer 7 and the belt reinforcing layer 8. descend. On the other hand, if the thickness G is smaller than 0.5 mm, the buffer rubber layer 10 is too thin, and the effect of improving the high speed durability cannot be obtained. The thickness G is preferably 2.0 mm or less in practice.

  On the other hand, in the present invention, the outer end portion 10o in the tire width direction of the shock absorbing rubber layer 10 is disposed on the outer side in the tire width direction of the outer end portion 8o in the tire width direction of the belt reinforcing layer 8. In other words, the distance Lb from the outer end portion 8o in the tire width direction of the belt reinforcing layer 8 to the outer end portion 10o in the tire width direction of the cushioning rubber layer 10 is set to be greater than 0 mm. Further, the hardness of the buffer rubber constituting the buffer rubber layer 10 is set lower than the hardness of the cap tread rubber constituting the cap tread rubber layer 11.

  Thus, the understeer characteristic can be improved by specifying the shape of the buffer rubber layer 10 on the outer side in the tire width direction and further defining the hardness of the buffer rubber. That is, the cushioning rubber layer 10 is disposed over a wide range of the edge portion beyond the outer end 8o in the tire width direction of the belt reinforcing layer 8, and the edge of the belt layer 10 is formed by making the cushioning rubber relatively low in hardness. The understeer characteristic can be improved by lowering the rigidity of the tread portion 1 in the portion.

  At this time, if the distance Lb is 0 mm or less, the region where the hardness becomes relatively low decreases, so that the rigidity of the edge portion of the belt layer 10 cannot be sufficiently reduced, and the steering characteristic tends to be oversteered. . The distance Lb is preferably 3 mm or more. The distance Lb is preferably as large as possible, and the buffer rubber layer 10 may be exposed from the sidewall portion 2 to the tire surface.

  If the hardness of the buffer rubber constituting the buffer rubber layer 10 is larger than that of the cap tread rubber, the rigidity of the tread portion 1 at the edge portion of the belt layer 10 becomes too high, and the steering characteristic tends to be oversteer. The hardness of the buffer rubber constituting the buffer rubber layer 10 is preferably 40-60.

  In the present invention, the shape of the shock absorbing rubber layer 10 in the tire meridian cross section is not particularly limited, but the shape in the tire meridian cross section is preferably a crescent or triangular shape. As shown in FIGS. 1 and 2, the cross-sectional shape is a crescent shape, and the thickness G of the cushioning rubber layer 10 is maximized near the center of the tire meridian section in the tire meridian cross section toward both ends in the tire width direction. Thus, the thickness G of the buffer rubber layer 10 is gradually reduced. Further, the triangular shape has, in the tire meridian cross section, the tire radial direction outer end portion 10o of the shock absorbing rubber layer 10, the tire radial direction inner end portion 10i of the shock absorbing rubber layer 10 and the point where the thickness G is maximized. The shape to be formed.

  By setting the cross-sectional shape of the shock absorbing rubber layer 10 in this way, the thickness of the shock absorbing rubber layer 10 in the tire meridian cross section in the tire radial direction becomes larger on the outer side in the tire width direction than on the inner side in the tire width direction. As a result, the cushion by the cushioning rubber layer 10 increases toward the outer side in the tire width direction, the rigidity of the tread portion 1 can be lowered toward the outer side in the tire width direction, and the understeer characteristic can be further improved. .

  At this time, if the thickness G of the cushioning rubber layer 10 is constant or the thickness G of the cushioning rubber layer 10 is thicker toward both ends of the cushioning rubber layer 10 in the tire width direction, the cushioning rubber layer The cushion according to No. 10 cannot be effectively increased toward the outer side in the tire width direction, and the effect of improving the steering characteristics cannot be sufficiently obtained.

In the present invention, a straight line drawn in the tire radial direction from the ground contact E _max under a load corresponding to the maximum load capacity defined by JATMA and a pneumatic pressure corresponding to the maximum load capacity, and the outer side in the tire radial direction of the buffer rubber layer 10. thickness G of the buffer rubber layer 10 in the P _max point where the surface intersects is maximum, it is preferred maximum thickness G _max of the buffer rubber layer 10 in this respect P _max is 2.0mm or more. In addition, it is preferable that the maximum thickness G _max is practically 10.0 mm or less. By setting the shape of the buffer rubber layer 10 in this way, the rigidity of the tread portion 1 at the position of the ground contact E _max can be suppressed, and the understeer characteristic can be further improved.

At this time, a 2.0mm smaller maximum thickness G _max is the maximum thickness G _max is improved understeer characteristics too small the effect of the buffer rubber layer 10 can not be obtained sufficiently.

As described above, the buffer rubber layer 10 may be exposed from the sidewall portion 2 to the tire surface. However, in practice, the outer end portion 10o in the tire width direction of the buffer rubber layer 10 is defined by JATMA. it is preferably disposed on the inner side than the position of 5.0mm in the tire width direction outside from the ground contact edge E _max under conditions of air pressure corresponding to the load and said maximum load capacity corresponding to the maximum load capacity. In other words, the distance Lc from the ground contact end E _max to the outer end 10o in the tire width direction of the shock absorbing rubber layer 10 under the condition of the load corresponding to the maximum load capacity defined by JATMA and the air pressure corresponding to the maximum load capacity is It is preferably within 5.0 mm.

  In the present invention, it is preferable that tan δ at 60 ° C. of the buffer rubber constituting the buffer rubber layer 10 is lower than tan δ at 60 ° C. of the belt coat rubber constituting the belt layer 7. The belt coat rubber is a rubber that covers a reinforcing cord embedded in the belt layer 7.

  By defining the properties of the buffer rubber constituting the buffer rubber layer 10 in this manner, heat generation of the buffer rubber layer 10 can be suppressed and high-speed durability can be further improved. At this time, if tan δ at 60 ° C. of the buffer rubber constituting the buffer rubber layer 10 is higher than tan δ at 60 ° C. of the belt coat rubber constituting the belt layer 7, heat generation of the buffer rubber layer 10 cannot be suppressed. The effect of improving the high-speed durability cannot be sufficiently obtained.

  At this time, the tan δ at 60 ° C. of the buffer rubber constituting the buffer rubber layer 10 is preferably 0.15 or less, more preferably 0.05 to 0.15.

In a pneumatic tire having a tire size of 245 / 40R18 97Y, a distance La from the outer end in the tire width direction of the outer peripheral side belt layer to an inner end in the tire width direction of the shock absorbing rubber layer, from the outer end in the tire width direction of the belt reinforcing layer The distance Lb to the outer end of the cushioning rubber layer in the tire width direction, the hardness of the cushioning rubber constituting the cushioning rubber layer, the thickness G of the cushioning rubber layer at the position corresponding to the outer end of the outer side belt layer in the tire width direction In the conventional example 1 and the comparative examples 1 to 3, the shape of the buffer rubber layer, the maximum thickness G _{max of} the buffer rubber layer, and the tan δ at 60 ° C. of the buffer rubber constituting the buffer rubber layer were changed as shown in Tables 1 and 2, respectively. 4. Thirteen types of test tires of Examples 1 to 8 were manufactured.

  The distance Lb is positive when the outer end portion in the tire width direction of the cushioning rubber layer is located on the outer side in the tire width direction with respect to the outer end portion in the tire width direction of the belt reinforcing layer. The case where the end portion is located on the inner side in the tire width direction than the outer end portion in the tire width direction of the belt reinforcing layer is indicated by a negative value. As for the shape of the buffer rubber layer, “crescent shape” means the shape shown in FIGS. 1 and 2, and “sheet shape” means a form in which the thickness of the buffer rubber layer is constant.

  These 13 types of test tires were evaluated for high-speed durability, steering characteristics, and lane change performance by the following evaluation methods, and the results are also shown in Tables 1 and 2.

High-speed durability Each test tire is mounted on an aluminum wheel with a rim size of 18 x 8.5 J, filled with air pressure of 230 kPa, and mounted on an indoor drum testing machine (drum diameter 1707 mm) in accordance with JIS D4230, at a speed of 81 km / h. Then, 88% of the load corresponding to the pneumatic conditions specified by JATMA was applied, and the vehicle was run for 120 minutes. Next, after cooling for more than 3 hours, readjust the air pressure to 210 kPa, start the test from a speed of 121 km / h, and gradually increase the speed by 8 km / h every 30 minutes until the failure occurs The mileage until a tire failure occurred was measured. The evaluation results are shown as an index with Conventional Example 1 as 100. It means that high speed durability is excellent, so that this index value is large.

Steer characteristics Each test tire is mounted on an aluminum wheel with a rim size of 18 x 8.5 J, filled with air pressure of 230 kPa, mounted on a 3.5 L class domestic FR car, speed 80 km / h, turning radius on the test course The accelerator was turned off during cornering at 100 m, and the behavior of the vehicle was sensory evaluated. The evaluation results are shown as sensory evaluation points when Conventional Example 1 is set to 0. 0 means neutral, the negative value is oversteer, and the positive value is understeer. An evaluation score of 0 or more means that the steer characteristic is excellent.

Lane change performance Each test tire is mounted on an aluminum wheel with a rim size of 18 x 8.5 J, filled with air pressure of 230 kPa, mounted on a 3.5 L class domestic FR vehicle, and at a speed of 120 km / h on the test course. Lane change performance was evaluated by sensual evaluation of responsiveness and gripping power, with lane changes assuming passing cars. The evaluation results are shown as sensory evaluation points when Conventional Example 1 is set to ± 0. Zero means equal, negative value decreases, positive value increases, and an evaluation score of 0 or higher means that the lane change performance is excellent.

As can be seen from Tables 1 and 2, each of Examples 1 to 8 has excellent high-speed durability, steer characteristics, as compared to Conventional Example 1 that does not have a buffer rubber layer between the belt layer and the belt reinforcing layer. And lane change performance. In particular, Examples 1 to 4 and 6 to 7 in which the maximum thickness G _max of the buffer rubber layer is included in a preferable range, and belt coat rubber in which tan δ at 60 ° C. of the buffer rubber constituting the buffer rubber layer constitutes the belt layer. Example 8, which is lower than tan δ at 60 ° C., achieved a high degree of compatibility between these performances.

  On the other hand, Comparative Example 1 in which both the distance La and the distance Lb are too small cannot obtain the effect of improving the tire performance as compared with the conventional example. In Comparative Example 2 in which the distance La is too large and the distance Lb is too small, the high-speed durability is improved, but the lane change performance is deteriorated. In Comparative Example 3 in which the hardness of the buffer rubber constituting the buffer rubber layer is higher than the hardness of the cap tread rubber, although the high-speed durability is improved, the steering characteristic is deteriorated. In Comparative Example 4 in which the thickness G of the buffer rubber layer is small, the effect of improving the tire performance as compared with the conventional example was not obtained.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 71 Outer peripheral side belt layer 71o Tire width direction outer end portion 72 Inner circumferential side belt layer 72 _o Tire width direction outer end portion 8 Belt reinforcing layer 8o Tire width direction outer end 10 Buffer rubber layer 10i Tire width direction inner edge 10o Tire width direction outer end 11 Cap tread rubber layer

Claims (4)

A carcass layer is mounted between a pair of bead portions, a plurality of belt layers are disposed on the outer peripheral side of the carcass layer in the tread portion, and at least one edge portion of the belt layer is covered on the outer peripheral side of the belt layer. In the pneumatic tire in which the belt reinforcement layer of the layer is arranged,
A shock absorbing rubber layer is disposed between the edge portion of the belt layer and the belt reinforcing layer, and an outer peripheral belt layer in which an inner end portion in the tire width direction of the shock absorbing rubber layer is located on the outer side in the tire radial direction of the belt layer. Is disposed in a range of 3 mm to 13 mm from the outer end in the tire width direction toward the inner side in the tire width direction, and the outer end in the tire width direction of the cushion rubber layer is more tire than the outer end in the tire width direction of the belt reinforcing layer. A buffer that is arranged on the outer side in the width direction and has a thickness G of 0.5 mm or more at the position corresponding to the outer end in the tire width direction of the outer peripheral side belt layer and that constitutes the buffer rubber layer A pneumatic tire characterized in that the hardness of rubber is lower than that of cap tread rubber.   2. The pneumatic tire according to claim 1, wherein a shape of the cushion rubber layer in a tire meridian cross section is a crescent shape or a triangular shape. A tire radial direction outer surface of the straight line and the buffer rubber layer obtained by subtracting from the ground contact edge E _max in the tire radial direction under conditions of air pressure corresponding to the load and said maximum load capacity corresponding to the maximum load capability defined by the standard the thickness G of the buffer rubber layer is maximum, to claim 1 or 2, wherein the thickness G _max of the cushion rubber layer in this respect P _max is 2.0mm or more at P _max that intersects The described pneumatic tire.   4. The pneumatic tire according to claim 1, wherein tan δ at 60 ° C. of the buffer rubber constituting the cushion rubber layer is lower than tan δ at 60 ° C. of the belt coat rubber constituting the belt layer. .

Images