JP6095292B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  With the recent increase in awareness of global environmental protection, efforts have been made to improve the fuel efficiency of vehicles, and it is necessary to reduce the rolling resistance of tires. In order to reduce the rolling resistance of the tire, it is necessary to reduce the energy at the time of rolling the tire, and in the tire tread portion where the energy contribution is considered to be high, other characteristics such as wear resistance are significantly impaired. The rolling resistance is reduced from the rubbery surface of the tread portion by using a rubber suitable for rolling resistance within a range that is not present, or by embedding the rubber in the base portion of the tread. In addition, studies and proposals have been made on tire structures and shapes that reduce the energy generated at the end of the tread belt.

  Although various methods for reducing tire rolling resistance are improving the tire rolling resistance performance, in recent years, tires that achieve further reduction in rolling resistance are required. Further changes in the rubber physical properties of tires have a considerable impact on the wear resistance and movement performance of tires, which may cause problems with balance with other performances, and can achieve low rolling performance. It is necessary to propose a new tire structure. The main area of energy loss in tires related to rolling resistance is the tread area in contact with the road surface. Displacement due to the local distortion of the grounding edge caused by grounding or wiping deformation generated on the entire grounding surface results in energy loss. The shape having a large curvature is employed to suppress deformation in the tread region.

  Patent Document 1 discloses a pneumatic tire in which a pair of left and right vibration damping rubber layers are arranged inside a tire of an inner liner or between a carcass ply and an inner liner. The pair of left and right vibration damping rubber layers of the tire are provided to reduce noise, and reduction of rolling resistance is not considered.

  Patent Document 2 discloses a pneumatic tire in which a reinforcing layer is disposed in at least one region in the region from the radially inner side of the end portion in the axial direction of the belt layer to the radially outer side of the bead portion. In the tire, although the rolling resistance is considered, the arrangement of the plurality of reinforcing layers is not considered. Therefore, there is room for study on optimization of conditions related to reduction of rolling resistance.

  Patent Document 3 discloses a pneumatic tire provided with a reinforcing rubber layer extending radially outward or inwardly from the tire maximum width region along the inner surface of the carcass of the sidewall portion. In the tire, by specifying the material, thickness, position, etc. of the reinforcing rubber layer, it is possible to minimize the sacrifice to the rolling resistance or achieve a slight reduction in rolling resistance, while maintaining the steering stability and the road. Improve noise performance. Therefore, in this document, the reduction of rolling resistance is not positively improved.

  In Patent Document 4, a first side rubber that is disposed on the outer side in the tire width direction of the carcass layer and forms the outer side in the tire width direction of the bead portion, and joined to the first side rubber to the outer side in the tire radial direction of the first side rubber. A pneumatic tire is disclosed that includes a second side rubber that is disposed and forms the outer side in the tire width direction of the side portion. The tire improves impact stability by improving impact absorption against impacts from road surface unevenness and lateral run-out, but does not consider reduction of rolling resistance.

  In Patent Document 5, in the tire radial direction, three regions are set based on the height from the lower end of the bead core of the bead portion, and the Shore A hardness of a portion that occupies a volume ratio of 90% or more in each region is a predetermined value. A pneumatic tire set to 1 is disclosed. In the tire, road noise is reduced without impairing steering stability and riding comfort, but reduction of rolling resistance is not taken into consideration.

  Patent Document 6 discloses a pneumatic tire having at least one side reinforcing layer along the radial carcass from a tire buttress portion to a region exceeding the tire maximum width point. In the tire, a plurality of reinforcing layers are arranged to suppress transmission of vibration from the tread and reduce side vibration, and reduction of rolling resistance is not taken into consideration.

JP 2000-127709 A JP 2002-59715 A Japanese Patent Laid-Open No. 2002-301912 JP 2006-51872 A JP 2005-53354 A JP 05-58119 A

  An object of the present invention is to reduce an increase in contact pressure locally generated in a tread shoulder portion due to deformation of the tread portion at the time of tire contact or to make a contact pressure distribution uniform and reduce rolling resistance of the tire.

As means for solving the above problems, a pneumatic tire according to the present invention includes a tread portion, a pair of side portions continuous with the tread portion, a pair of bead portions continuous with the side portion, the tread portion, In a pneumatic tire comprising a carcass layer provided in an annular shape across the pair of bead portions via the pair of side portions, and a belt provided on the tread portion on the outer side in the tire radial direction of the carcass layer, The region between the end of the belt in the tire rotation axis direction and the upper end of the bead is defined as a flex zone, and the length of the inner surface of the tire in the meridian section parallel to the tire rotation axis is the peripheral length (PERI). In this case, a reinforcing portion is provided in each area of the flex zone that is equally divided in the peripheral length direction outside the carcass layer. The reinforcing portion adjacent to the belt is disposed with a distance from an end of the belt in the tire rotation axis direction, and the reinforcing portions are disposed with a space between each other, and the number of divisions of the flex zone is two The number of the reinforcing portions is 2, and the reinforcing portion adjacent to the upper end of the bead portion is arranged to include a maximum width portion where the tire width is maximum, and the reinforcing portion adjacent to the upper end of the bead portion; The distance from the upper end of the bead part is at least half the thickness of the flex zone located at the upper end of the bead part .

  According to this structure, the flexible zone which consists of a reinforcement part and the part in which the reinforcement part is not provided, ie, the part which has a softness | flexibility, can be provided to a flex zone. And since the reinforcement part close to the belt is arranged at an interval from the end part of the belt in the tire rotation axis direction, the tread part can be connected to the part having rigidity through the part having flexibility. it can. Thereby, it is possible to connect the flex zone and the tread portion via the flexible portion while increasing the rigidity of the flex zone. That is, a certain rigidity and flexibility can be imparted to the tire. As a result, the flex zone can be deformed by moving the tread portion parallel to the road surface, and deformation of only the end portion of the tread portion due to the deformation of the flex zone can be avoided.

The division number of the flex zone is 2, the number of the reinforcing section Ru 2 der. According to this structure, the part which has rigidity can be provided in each of the upper part and lower part of a flex zone. Therefore, rigidity can be ensured in each of the upper part and the lower part of the flex zone.

The interval between the reinforcing portions adjacent to each other disposed in the respective regions on both sides of the equally divided position is longer than the thickness of the flex zone at the equally divided position, and the reinforcing portion adjacent to the belt. the distance between the tire rotational axis direction of the end portion of the belt is preferably the thickness of more than half the length of the flex zone located at the end of the tire rotation axis direction of the belt. According to this configuration, by arranging the reinforcing portions so that the interval between the reinforcing portions becomes a predetermined interval, the flex zone can be deformed by moving the tread portion parallel to the road surface, and the flex zone It is possible to configure the tire that can avoid the deformation only at the end portion of the tread portion due to the deformation.

  The reinforcing part preferably has the reinforcing part made of a material different from that of the one reinforcing part. According to this configuration, the range of adjustment of the rigidity and flexibility of the flex zone can be expanded.

  It is preferable that the modulus of the reinforcing portion adjacent to the bead portion is higher than the modulus of the reinforcing portion adjacent to the belt. According to this structure, when the length of a reinforcement part is the same, the rigidity of the reinforcement part which adjoins a bead part can be improved with respect to the reinforcement part which adjoins a belt. Further, when the rigidity of the reinforcing portion is constant, the length of the reinforcing portion adjacent to the bead portion can be shortened with respect to the reinforcing portion adjacent to the belt.

  The modulus of the reinforcing portion is preferably 4.0 to 10.0 MPa.

  When the length of the reinforcing portion in the peripheral length direction is L, it is preferable that 0.1 × PERI ≦ L ≦ 0.35 × PERI.

  The reinforcing part preferably has a thickness of 0.5 to 1.0 mm.

  According to the present invention, the flex zone is provided with a flexible / flexible structure including a reinforcing portion and a portion where the reinforcing portion is not provided, that is, a portion having flexibility, and the reinforcing portion adjacent to the belt is used as the tire rotation shaft of the belt. Since the tread part is moved in parallel with the road surface, the flex zone can be deformed, and the flex zone can be deformed only at the end of the tread part. It is possible to avoid deformation. As a result, it is possible to reduce the rolling resistance of the tire by reducing the increase in the contact pressure locally generated in the tread shoulder portion due to the deformation of the tread portion at the time of tire contact or making the contact pressure distribution uniform.

The figure which shows the meridian cross section parallel to the tire rotating shaft of the pneumatic tire of 1st Embodiment of this invention. The figure which shows the meridian cross section parallel to the tire rotating shaft of the pneumatic tire of 2nd Embodiment of this invention.

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

(First embodiment)
FIG. 1 shows a meridian cross section parallel to a tire rotation axis (not shown) of a pneumatic tire (hereinafter referred to as a tire) 10 according to a first embodiment of the present invention. The tire 10 includes a tread portion 11, a pair of side portions 12 that are continuous with the tread portion 11, a pair of bead portions 13 that are continuous with the side portion 12, and a pair of tread portions 11 and a pair of side portions 12. And a carcass layer 14 provided in an annular shape across the bead portion 13. A plurality of main grooves 24 are formed in the circumferential direction on the outer peripheral surface of the tread portion 11. Of the plurality of main grooves 24 of the tread portion 11, a region of the tread portion 11 outside the main groove 24 located on the outermost side in the tire width direction is a tread shoulder portion 25.

  Two belts 15 having a certain width are provided on the tread portion 11 on the outer side in the tire radial direction of the carcass layer 14 so as to be arranged in the tire circumferential direction. The side portion 12 has a maximum width portion 16 that maximizes the tire width. The bead portion 13 has a ring-shaped bead core 17. The bead core 17 is wound from the inner side to the outer side in the width direction of the tire 10 by the carcass layer 14 so as to be disposed in the bead portion 13 on the inner side in the tire radial direction. A bead filler 18 is disposed in the bead portion 13 on the outer side in the tire radial direction. The bead portion 13 is fixed to a rim (not shown). The carcass layer 14 is folded back so as to wind the bead core 17 and is terminated in the vicinity of the side portion 12.

  A region between the end of the belt 15 in the tire rotation axis direction and the upper end of the bead 13 forms a flex zone. The flex zone is divided into two in the peripheral length direction when the length of the tire inner surface of the flex zone in the meridian cross section parallel to the tire rotation axis (not shown) is defined as the peripheral length (PERI). It has areas A and B. Reinforcing portions (reinforcing rubber) 19 and 20 are provided in the regions A and B of the flex zone outside the carcass layer 14. The reinforcing portion 19 is disposed in the region A with a gap from the end of the belt 15 in the tire rotation axis direction. The reinforcing portion 20 is disposed in the region B with a gap from the upper end of the bead portion 13. Moreover, the reinforcement parts 19 and 20 are arrange | positioned at intervals.

  When the lengths in the peripheral length direction are L1 and L2, the reinforcing portions 19 and 20 are 0.1 × PERI ≦ L1 ≦ 0.4 × PERI, 0.1 × PERI ≦ L2 ≦ 0.4 × PERI It is formed to satisfy. It is desirable that 0.1 × PERI ≦ L1 ≦ 0.35 × PERI and 0.1 × PERI ≦ L2 ≦ 0.35 × PERI. The thicknesses of the reinforcing portions 19 and 20 are T1 and T2, respectively. T1 and T2 are each 0.5 to 1.0 mm.

  The interval between the reinforcing portions 19 and 20 disposed in the respective regions A and B on both sides of the two-divided position is longer than the thickness E of the flex zone at the two-divided position. The distance between the reinforcing portion 19 adjacent to the belt 15 and the end of the belt 15 in the tire rotation axis direction is at least half the thickness D of the flex zone located at the end of the belt 15 in the tire rotation axis direction. It is. The distance between the reinforcing portion 20 adjacent to the upper end of the bead portion 13 and the upper end of the bead portion 13 is at least half the thickness F of the flex zone located at the upper end of the bead portion 13. The reinforcement parts 19 and 20 are arrange | positioned at the time of green tire manufacture.

According to this configuration, by arranging the reinforcing portions 19 and 20 in the flex zone, it is possible to have a change in rigidity and flexibility with respect to bending deformation of the flex zone, and the region where the reinforcing rubber is not disposed when the tire is grounded is deformed. As a result, the tread portion 11 is easily deformed in parallel to the road surface. It is also possible to disperse the ground contact pressure locally increased in the tire width direction in a region adjacent to the main groove 24 of the tread shoulder portion 25 generated when the shape of the tread portion 11 is flattened. And the effect which equalizes the contact pressure distribution of the tread part 11 with large contribution to rolling resistance is high.
That is, according to the present invention, it is possible to give the flex zone a flexible structure consisting of the reinforcing portions 19 and 20 and a portion where the reinforcing portion is not provided, that is, a portion having flexibility. And since the reinforcement part 19 close | similar to the belt 15 is arrange | positioned at intervals with the edge part of the tire rotating shaft direction of the belt 15, the part which has the said rigidity through the part which has the tread part 11 a softness | flexibility, Can be linked. Thereby, it is possible to connect the flex zone and the tread portion 11 via the portion having flexibility while increasing the rigidity of the flex zone. In other words, the tire 10 can be given a certain rigidity and flexibility. As a result, when the tire 10 rolls and a force is applied to the tread portion 11 that is in contact with the ground contact surface, the flex zone can be deformed while the tread portion 11 is moved parallel to the road surface, and the flex zone is deformed. In this case, the deformation is transmitted to and absorbed by the flexible portion continuous with the tread portion 11, so that it is possible to avoid the deformation only at the end portion of the tread portion 11. As a result, the increase in contact pressure locally generated in the tread shoulder portion 25 due to deformation of the tread portion at the time of tire contact can be reduced, or the contact pressure distribution can be made uniform to reduce the rolling resistance of the tire.

(Second Embodiment)
FIG. 2 shows a meridian cross section parallel to the tire rotation axis (not shown) of the pneumatic tire 10 of the second embodiment of the present invention. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  The flex zone has areas A, B, and C divided into three in the peripheral length direction. Reinforcing portions 21, 22, and 23 are provided in the regions A, B, and C of the flex zone outside the carcass layer 14. The reinforcing portion 21 is disposed in the region A with a distance from the end of the belt 15 in the tire rotation axis direction. The reinforcing portion 23 is arranged in the region C with a gap from the upper end of the bead portion 13. Further, in the flex zone B between the reinforcing portions 21 and 23, the reinforcing portion 22 is disposed with a space from each of the reinforcing portions 21 and 23.

  The distance between the reinforcing portions 21 and 22 is equal to or longer than the thickness E of the flex zone at the division position of the region A and the region B. The interval between the reinforcing portions 22 and 23 is a length equal to or greater than the thickness F of the flex zone at the division position of the region B and the region C. The distance between the reinforcing portion 21 in the vicinity of the belt 15 and the end of the belt 15 in the tire rotation axis direction is more than half the thickness D of the flex zone located at the end of the belt 15 in the tire rotation axis direction. It is. The distance between the reinforcing portion 23 adjacent to the upper end of the bead portion 13 and the upper end of the bead portion 13 is at least half the thickness G of the flex zone located at the upper end of the bead portion 13. The reinforcing portions 21, 22, and 23 are disposed when the green tire is manufactured.

  Also in the second embodiment, the same effect as in the first embodiment can be obtained.

(Example)
A pneumatic radial tire (195 / 65R15 91S, rim size: 15 × 6J, PERI = 80 mm) was used as a tire as a base for evaluation. Under the conditions shown below, for Comparative Examples 1-2 and Examples 1-16, the strain of the tread shoulder, the strain dispersion of the tread shoulder, and the rolling resistance were evaluated. The distortion of the tread shoulder and the strain dispersion of the tread shoulder were indexed with Comparative Example 1 set to 100 based on the contact pressure distribution calculated using the contact pressure image analyzer. The rolling resistance was measured by a drum running test conducted in accordance with ISO 28580 (JIS D4243), and indexed with Comparative Example 1 as 100. They are shown in Tables 1 and 2. A value obtained by indexing the distortion of the tread shoulder portion indicates that the smaller the maximum contact pressure is, the smaller the value is. The smaller the value obtained by indexing the strain dispersion of the tread shoulder portion, the more uniform the tread shoulder portion is. A value obtained by indexing the rolling resistance indicates that the smaller the rolling resistance is, the smaller the rolling resistance is. The conditions by the ground pressure image analysis apparatus are air pressure = 230 kPa and load = 4.5 kPa. The conditions of the drum running test are: drum diameter = 1.7 m, camber angle = 0 °, air pressure = 230 kPa, speed = 80 km / h, load = 4.5 kN.

(Comparative Example 1)
As shown in Table 1, in Comparative Example 1, a tire (reinforcing layer ((reinforcing portion) number 0)) in which nothing is arranged outside the carcass layer 14 in the flex zone was used. The strain of the tread shoulder, the strain dispersion of the tread shoulder portion, and the rolling resistance were set to 100, respectively, and used as reference values.

(Comparative Example 2)
In Comparative Example 2, a tire in which one reinforcing layer was disposed outside the carcass layer 14 in the flex zone was used. The thickness D of the side rubber is 6 mm, and the length L1 is 25 mm. The modulus MD1 of the reinforcing layer is 5 (MPa). The thickness T of the reinforcing layer is 0.5 (mm). In this tire, the distortion in the tread shoulder portion was 95, the strain dispersion in the tread shoulder portion was 105, and the rolling resistance was 100.

  In Examples 1 to 7, tires in which the reinforcing layers 19 and 20 were arranged at two locations of the divided areas A (40 mm) and B (40 mm) outside the carcass layer 14 in the flex zone were used. The thicknesses of the side rubbers at positions D, E, and F are 6, 4, and 5 (mm), respectively.

  In Examples 1 to 7, the values of the reinforcing layer widths L1 and L2, the reinforcing layer moduli MD1 and MD2, and the reinforcing layer thicknesses T1 and T2 are as follows.

Example 1
L1 = 25 (mm)
L2 = 25 (mm)
MD1 = 5 (MPa)
MD2 = 5 (MPa)
T1 = 0.5 (mm)
T2 = 0.5 (mm)
The tire had a tread shoulder strain of 96, a tread shoulder strain distribution of 95, and a rolling resistance of 95.

(Example 2)
L1 = 25 (mm)
L2 = 15 (mm)
MD1 = 10 (MPa)
MD2 = 5 (MPa)
T1 = 1.0 (mm)
T2 = 0.5 (mm)
In this tire, the distortion of the tread shoulder portion was 98, the strain dispersion of the tread shoulder portion was 99, and the rolling resistance was 98.

(Example 3)
L1 = 15 (mm)
L2 = 25 (mm)
MD1 = 5 (MPa)
MD2 = 10 (MPa)
T1 = 0.5 (mm)
T2 = 1.0 (mm)
The tire had a tread shoulder strain of 97, a tread shoulder strain distribution of 96, and a rolling resistance of 96.

Example 4
L1 = 25 (mm)
L2 = 15 (mm)
MD1 = 5 (MPa)
MD2 = 10 (MPa)
T1 = 0.5 (mm)
T2 = 1.0 (mm)
The tire had a tread shoulder strain of 97, a tread shoulder strain strain of 97, and a rolling resistance of 96.

(Example 5)
L1 = 25 (mm)
L2 = 15 (mm)
MD1 = 10 (MPa)
MD2 = 5 (MPa)
T1 = 0.5 (mm)
T2 = 1.0 (mm)
The distortion of the tread shoulder portion in this tire was 98, the strain dispersion of the tread shoulder portion was 98, and the rolling resistance was 98.

(Example 6)
L1 = 15 (mm)
L2 = 25 (mm)
MD1 = 5 (MPa)
MD2 = 10 (MPa)
T1 = 1.0 (mm)
T2 = 0.5 (mm)
The tire had a tread shoulder strain of 97, a tread shoulder strain strain of 97, and a rolling resistance of 96.

(Example 7)
L1 = 15 (mm)
L2 = 25 (mm)
MD1 = 10 (MPa)
MD2 = 5 (MPa)
T1 = 1.0 (mm)
T2 = 0.5 (mm)
In this tire, the distortion of the tread shoulder portion was 98, the strain dispersion of the tread shoulder portion was 97, and the rolling resistance was 97.

  As shown in Table 2, in Examples 8 to 16, reinforcement was made at three locations of divided areas A (26.7 mm), B (26.7 mm), and C (26.7 mm) outside the carcass layer 14 in the flex zone. Tires with layers were used. The thicknesses of the side rubbers at the positions D, E, F, and G are 6, 4, 4, 5 (mm), respectively.

  In each Example 8-16, each value of reinforcement layer width L1, L2, L3, reinforcement layer modulus MD1, MD2, MD3, and reinforcement layer thickness T1, T2, T3 is as follows.

(Example 8)
L1 = 15 (mm)
L2 = 15 (mm)
L3 = 15 (mm)
MD1 = 5 (MPa)
MD2 = 5 (MPa)
MD3 = 5 (MPa)
T1 = 0.8 (mm)
T2 = 0.8 (mm)
T3 = 0.8 (mm)
The tire had a tread shoulder strain of 97, a tread shoulder strain distribution of 96, and a rolling resistance of 96.

Example 9
L1 = 20 (mm)
L2 = 15 (mm)
L3 = 10 (mm)
MD1 = 10 (MPa)
MD2 = 7 (MPa)
MD3 = 5 (MPa)
T1 = 1.0 (mm)
T2 = 0.8 (mm)
T3 = 0.5 (mm)
In this tire, the distortion of the tread shoulder portion was 99, the strain dispersion of the tread shoulder portion was 99, and the rolling resistance was 99.

(Example 10)
L1 = 20 (mm)
L2 = 10 (mm)
L3 = 20 (mm)
MD1 = 10 (MPa)
MD2 = 5 (MPa)
MD3 = 10 (MPa)
T1 = 1.0 (mm)
T2 = 0.5 (mm)
T3 = 1.0 (mm)
In this tire, the distortion of the tread shoulder portion was 99, the strain dispersion of the tread shoulder portion was 100, and the rolling resistance was 99.

(Example 11)
L1 = 10 (mm)
L2 = 15 (mm)
L3 = 20 (mm)
MD1 = 5 (MPa)
MD2 = 7 (MPa)
MD3 = 10 (MPa)
T1 = 0.5 (mm)
T2 = 0.8 (mm)
T3 = 1.0 (mm)
In this tire, the distortion of the tread shoulder portion was 98, the strain dispersion of the tread shoulder portion was 97, and the rolling resistance was 97.

(Example 12)
L1 = 10 (mm)
L2 = 20 (mm)
L3 = 10 (mm)
MD1 = 5 (MPa)
MD2 = 10 (MPa)
MD3 = 5 (MPa)
T1 = 0.5 (mm)
T2 = 1.0 (mm)
T3 = 0.5 (mm)
In this tire, the distortion of the tread shoulder portion was 99, the strain dispersion of the tread shoulder portion was 100, and the rolling resistance was 99.

(Example 13)
L1 = 20 (mm)
L2 = 15 (mm)
L3 = 10 (mm)
MD1 = 5 (MPa)
MD2 = 7 (MPa)
MD3 = 10 (MPa)
T1 = 0.5 (mm)
T2 = 0.8 (mm)
T3 = 1.0 (mm)
The distortion of the tread shoulder portion in this tire was 98, the strain dispersion of the tread shoulder portion was 98, and the rolling resistance was 98.

(Example 14)
L1 = 20 (mm)
L2 = 15 (mm)
L3 = 10 (mm)
MD1 = 10 (MPa)
MD2 = 7 (MPa)
MD3 = 5 (MPa)
T1 = 0.5 (mm)
T2 = 0.8 (mm)
T3 = 1.0 (mm)
In this tire, the distortion of the tread shoulder portion was 99, the strain dispersion of the tread shoulder portion was 99, and the rolling resistance was 99.

(Example 15)
L1 = 10 (mm)
L2 = 15 (mm)
L3 = 20 (mm)
MD1 = 5 (MPa)
MD2 = 7 (MPa)
MD3 = 10 (MPa)
T1 = 1.0 (mm)
T2 = 0.8 (mm)
T3 = 0.5 (mm)
The distortion of the tread shoulder portion in this tire was 98, the strain dispersion of the tread shoulder portion was 98, and the rolling resistance was 98.

(Example 16)
L1 = 10 (mm)
L2 = 15 (mm)
L3 = 20 (mm)
MD1 = 10 (MPa)
MD2 = 7 (MPa)
MD3 = 5 (MPa)
T1 = 1.0 (mm)
T2 = 0.8 (mm)
T3 = 0.5 (mm)
In this tire, the distortion of the tread shoulder portion was 99, the strain dispersion of the tread shoulder portion was 98, and the rolling resistance was 98.

  As described above, when both the strain of the tread shoulder portion and the strain distribution of the tread shoulder portion of the tire of Comparative Example 1 are set to 100, in the tire of Comparative Example 2 in which the number of reinforcing layers is 1, the strain of the tread shoulder portion is reduced. Although the value is 95, indicating a good value of less than 100, the strain dispersion value of the tread shoulder is 105, which is lower than that of the tire of Comparative Example 1. The rolling resistance value of the tire of Comparative Example 2 is 100, and the performance of the tire of Comparative Example 2 is equivalent to the performance of the tire of Comparative Example 1 and is not improved.

  On the other hand, in the tires of Examples 1 to 7 in which the number of reinforcing layers is two at a predetermined interval and Examples 8 to 16 in which the number of reinforcing layers is three at a predetermined interval, the distortion of the tread shoulder portion and the tread shoulder portion In each of the values of the strain dispersion, at least one is less than 100 and the other is 100 or less, and the performance is improved as compared with those of the tire of Comparative Example 1. Moreover, the value of the rolling resistance of the tires of Examples 1 to 16 is also less than 100, and the performance of the tires of Examples 1 to 16 is improved with respect to the performance of the tire of Comparative Example 1. Therefore, in the tires of Examples 1 to 16, by providing at least two reinforcing portions 19 to 23 at predetermined intervals on the outer side of the carcass layer 14 in the flex zone, the tread shoulder portion 25 due to deformation of the tread portion 11 at the time of tire contact is provided. It is possible to reduce the rolling resistance of the tire 10 by reducing the increase in the contact pressure that occurs locally or making the contact pressure distribution uniform.

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 11 Tread part 12 Side part 13 Bead part 14 Carcass layer 15 Belt 16 Maximum width part 17 Bead core 18 Bead filler 19, 20, 21, 22, 23 Reinforcement part 24 Main groove 25 Tread shoulder part

Claims (7)

A tread portion, a pair of side portions continuous with the tread portion, a pair of bead portions continuous with the side portion, and an annular shape across the pair of bead portions via the tread portion and the pair of side portions In a pneumatic tire comprising a carcass layer provided and a belt provided on the tread portion on the outer side in the tire radial direction of the carcass layer,
The region between the end of the belt in the tire rotation axis direction and the upper end of the bead is defined as a flex zone, and the length of the inner surface of the tire in the meridian section parallel to the tire rotation axis is the peripheral length (PERI). If
In each region of the flex zone that is equally divided in the peripheral length direction outside the carcass layer, a reinforcing portion is provided,
The reinforcing portion adjacent to the belt is disposed with a distance from an end of the belt in the tire rotation axis direction, and the reinforcing portions are disposed with a space between each other,
The number of divisions of the flex zone is 2, and the number of reinforcing parts is 2.
The reinforcing portion adjacent to the upper end of the bead portion is disposed so as to include a maximum width portion where the tire width is maximum,
The pneumatic tire according to claim 1, wherein an interval between the reinforcing portion adjacent to the upper end of the bead portion and the upper end of the bead portion is at least half the thickness of the flex zone located at the upper end of the bead portion . The interval between the reinforcing portions adjacent to each other arranged in each region on both sides of the equally divided position is a length that is equal to or greater than the thickness of the flex zone at the equally divided position,
The distance between the reinforcing portion adjacent to the belt and the end of the belt in the tire rotation axis direction is at least half the thickness of the flex zone located at the end of the belt in the tire rotation axis direction. the pneumatic tire according to claim 1, characterized in that.   The pneumatic tire according to claim 1, wherein the reinforcing portion includes the reinforcing portion made of a material different from that of the one reinforcing portion.   The pneumatic tire according to any one of claims 1 to 3, wherein a modulus of the reinforcing portion adjacent to the bead portion is higher than a modulus of the reinforcing portion adjacent to the belt.   The pneumatic tire according to any one of claims 1 to 4, wherein a modulus of the reinforcing portion is 4.0 to 10.0 MPa.   The length of the reinforcement part in the peripheral length direction is 0.1 × PERI ≦ L ≦ 0.35 × PERI, where L is a length. Pneumatic tires.   The pneumatic tire according to any one of claims 1 to 6, wherein a thickness of the reinforcing portion is 0.5 to 1.0 mm.

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