JP4398218B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire with improved braking performance.

  In recent years, an increasing number of vehicles are equipped with ABS (anti-lock brake system) in order to prevent tire lock during braking. On the other hand, in a pneumatic tire, in order to improve braking performance, tread rubber is changed, or block rigidity and side rigidity are increased.

  However, changing the tread rubber to improve the braking performance or making the lateral groove shallow to increase the block rigidity often leads to an increase in rolling resistance and deterioration of hydroplaning properties. Yes. Further, it has been found that increasing the side rigidity does not necessarily improve the braking performance under the ABS operation that is currently installed in the vehicle.

  FIG. 9 diagrammatically shows a left-side cross section of the pneumatic tire that has been used in the past with the equator plane E as a boundary. This tire is formed by a pair of bead portions 110, a pair of sidewall portions 120 provided continuously with the bead portions 110, and a tread portion 130 provided with a pair of sidewall portions 120. A single layer of carcass 140 is embedded in the bead portion 110, the sidewall portion 120, and the tread portion 130. Further, a belt 150 composed of two layers is embedded outside the carcass 140 in the tread portion 130. The carcass 140 is folded back to a bead core 160 embedded in the bead part 110, and reinforces the bead part 110, the sidewall part 120, and the tread part 130. The belt 150 reinforces the tread portion 130 outside the carcass 140.

  By the way, when the control torque around the tire rotation axis is applied to the traveling tire, rotational torsion around the tire circumferential direction line occurs in the entire tire. Due to this twist, circumferential deformation occurs in the sidewall portion. Among these deformation amounts, the deformation amount of the side wall portion on the bead side is small because it is pressed by the rim flange, and the deformation amount of the side wall portion on the ground contact surface side is larger than this. The deformation amount of the sidewall portion is mainly inversely proportional to the circumferential rigidity, and the larger the circumferential rigidity, the smaller the circumferential deformation.

  In the tire shown in FIG. 9, the circumferential rigidity of the sidewall portion 120 on the contact surface side is small because the carcass 140 is one layer, and the circumferential deformation is large. For this reason, there is a delay in the transmission of the braking force generated on the tread with respect to the braking torque, making it impossible to increase the braking force at the start of braking. In addition, the delay at the start of braking greatly affects the braking distance.

  On the other hand, in a tire having a reinforcing cord layer, the circumferential rigidity of the ground surface side sidewall portion is increased, and deformation of the side wall portion on the ground surface side having a large circumferential deformation is suppressed. It is possible to suppress power delay and improve braking performance. Conventional tires having such a reinforcing cord layer are disclosed in JP-A-8-310206, JP-A-9-30216, and JP-A-6-320919.

  In the tire disclosed in JP-A-8-310206, the reinforcing cord layer is disposed outside the carcass in the sidewall region, and the positions of the upper end and the lower end of the tire are 55 to 75% and 20 to 30% of the tire cross-sectional height, respectively. The range is set.

  The tire disclosed in Japanese Patent Application Laid-Open No. 9-30216 is provided with a reinforcing cord layer outside the carcass in the side wall portion region, and the total length of the reinforcing cord layer is set to 20 to 70% of the maximum carcass cross-sectional height. The cords of the layers are arranged in the number of shots of 20 to 60 lines / 5 cm, and the number of shots of the latitude lines is set to 5-15 lines / 5 cm.

In the tire disclosed in Japanese Patent Laid-Open No. 6-320919, an annular recess is provided in the sidewall portion on the bead portion side, and a reinforcing cord layer inclined by 40 to 70 degrees with respect to the maximum width position of the sidewall portion is provided. .
JP-A-8-310206 Japanese Patent Laid-Open No. 9-30216 JP-A-6-320919

  However, in any of the conventional tires described above, the rigidity of the tire radial direction increases in addition to the rigidity of the sidewall portion. For this reason, there is a problem that the contact area is reduced and the braking force cannot be increased.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a pneumatic tire with improved braking performance by changing the arrangement of reinforcing cord layers.

In order to achieve the above object, a pneumatic tire according to a first aspect of the present invention includes a pair of bead portions, a pair of sidewall portions, a tread portion connecting a pair of sidewall portions, and a bead core at the end of the bead portion. And a carcass disposed over the bead portion, sidewall portion, and tread portion in a folded state, and a reinforcing cord layer provided outside the carcass on the left and right sidewall portions of the tire equatorial plane a is the upper end of the reinforcing cord layer is located on the ground end, the lower end portion of the reinforcing cord layer is located above the folded end of the carcass, until the ground terminal from said folded end to the length L along the carcass of the length Lt along the carcass of the reinforcing cord layer is set so that Lt <0.5 L, before Reinforcing cord layer, when the expansion of the tire, characterized in that it is arranged such that the shape of the wafer.

In the invention of claim 1, the reinforcing cord layer disposed outside the carcass in the service id wall portion, situated upper end thereof to the ground terminal, a lower end positioned higher than the folded end of the carcass, and folded end The length Lt along the carcass of the reinforcing cord layer is set such that Lt <0.5L, preferably 0.2L ≦ Lt <0.5L, with respect to the length L along the carcass from the ground to the ground end. By setting, the rigidity in the tire circumferential direction can be improved, and a decrease in the contact area can be suppressed. Thereby, braking performance can be improved.

  A second aspect of the present invention is the pneumatic tire according to the first aspect, wherein the reinforcing cord layer has an inclination angle of 40 to 50 degrees with respect to a tire radial direction on both left and right sides of the tire, and precedes in the tire rotation direction. The cord ends are arranged at the upper end side in the tire radial direction.

The deformation of the side wall portion on the ground contact surface with respect to the braking torque is shear deformation. In the invention of claim 2, the inclination angle of the reinforcing cord layer with respect to the tire radial direction is 40 to 50 degrees,
In addition, since the leading cord ends in the tire rotation direction are arranged at the upper end side in the tire radial direction, the shear deformation can be reduced, thereby improving the braking performance.
The invention according to claim 3 is characterized in that the reinforcing cord layer has substantially the same inclination angle on both the left and right sides of the tire.

  According to the invention of claim 1, since the length of the reinforcing cord layer provided outside the carcass in the side wall portion is less than ½ of the length along the ground contact end from the folded end of the carcass, The rigidity can be improved and the reduction of the ground contact area can be suppressed, and thus the braking performance can be improved.

  In the invention of claim 2, in addition to the effect of the invention of claim 1, shear deformation acting on the sidewall portion can be reduced, and the braking performance can be further improved.

  1 and 2 show a pneumatic tire 1 (hereinafter referred to as a tire 1) according to a first embodiment of the present invention, and FIG. 1 schematically shows a left cross section of the tire 1 with an equatorial plane E as a boundary. FIG. 2 shows a side view of the running state of the tire 1.

  The tire 1 includes a pair of bead portions 2, a pair of sidewall portions 3 provided continuously with the bead portion 2, and a tread portion 4 provided continuously so as to span the pair of sidewall portions 3. A carcass 5 is embedded over the bead part 2, the sidewall part 3, and the tread part 4.

  The carcass 5 is a single layer, and is turned up by rolling up around the bead core 6 embedded in the bead portion 2 from the inside of the tire to the outside. The folded portion 5a folded toward the outer side of the tire extends from the bead portion 2 to the sidewall portion 3. Reference numeral 5 b denotes a folded end of the carcass 5. By arranging in this way, the carcass 5 reinforces the bead part 2, the sidewall part 3, and the tread part 4. The carcass 5 is formed of a rubber-coated array cord, and as the cord, an organic fiber cord such as a nylon cord, a polyester cord, a rayon cord, a Kevlar (aramid fiber) cord, or a steel cord is used.

  The tire 1 includes a belt 7. The belt 7 has two layers embedded in the tread portion 4 region of the carcass 5. As the cord of the belt 7, an organic fiber cord such as a nylon cord, a polyester cord, a Kevlar cord, or a steel cord is used.

In addition to the above, a reinforcing cord layer 10 is embedded in the tire 1. The reinforcing cord layer 10 is provided so as to be buried outside the carcass 5 in the side wall 3 regions on the left and right sides of the tire equatorial plane E. As the cord of the reinforcing cord layer 10, a nylon cord, a polyester cord are used. Organic fiber cords such as Kevlar cords or steel cords can be used.

The reinforcing cord layer 10 is arranged so as to have a “C” shape when the tire is developed so that the side wall portions are on both sides , so that the reinforcing cord layer 10 becomes a rotation-oriented type. Placed in. Accordingly, the reinforcing cord layer 10 is disposed on both the left and right sides of the tire 1, but has substantially the same inclination angle on both the left and right sides. This inclination angle will be described later.

The embedding position of the reinforcing cord layer 10 is set so that the upper end portion 10a of the reinforcing cord layer 10 is positioned at the ground end 9 and the lower end portion 10b of the reinforcing cord layer 10 is positioned above the folded end 5b of the carcass 5. ing. The ground contact end 9 indicates a line along the direction (thickness direction) from the end of the contact area toward the inside of the tire (the inside of the tire) so as to be substantially orthogonal to the carcass 5.

  Further, the length Lt along the carcass 5 of the reinforcing cord layer 10 is less than 0.5L, that is, Lt <0.5L with respect to the length L along the carcass 5 from the folded end 5b to the ground contact end 9. Is set to By setting the length Lt of the reinforcing cord layer 10 in this way, the rigidity in the tire circumferential direction can be improved without increasing the rigidity in the tire radial direction more than necessary, and the reduction of the contact area is suppressed. can do. As a result, the braking performance can be improved. When the length Lt of the reinforcing cord layer 10 is 0.5 L or more, the rigidity in the tire deformation direction becomes unnecessarily large and the contact area decreases, which is not preferable.

  FIG. 2 shows the inclination angle K of the reinforcing cord layer 10 disposed on both the left and right sides of the tire. The inclination angle K is substantially the same on both the left and right sides of the tire and is 40 to 50 with respect to the tire radial direction. Set to a range of degrees. When deviating from this range, the circumferential rigidity of the tire cannot be increased.

  In this embodiment, the leading cord end 11 of the reinforcing cord layer 10 with respect to the tire rotation direction is arranged at the upper end side in the tire radial direction. With such an arrangement, when a braking torque in the direction of the arrow is applied to the rotating tire 1, tension in the direction opposite to the tire traveling direction is brought from the tread surface to the reinforcing cord layer 10. And since the tension | tensile_strength acts, the rigidity of the reinforcement cord layer 10 increases and it becomes possible to improve the shear rigidity of the side wall part 3. FIG.

3 and 4 show a second embodiment of the present invention, and the same members as those in the first embodiment described above are assigned the same reference numerals and correspond to each other. Also in this embodiment, the reinforcing cord layer 10 is disposed outside the carcass 5 in the side wall portion 3 region so as to be a rotation-oriented type. Further, the upper end portion 10 a of the reinforcing cord layer 10 is located at the ground contact end 9, and the lower end portion 10 b is located above the folded end 5 b of the carcass 5. Further, the length Lt of the reinforcing cord layer 10 is less than 0.5L.

  In the second embodiment, as shown in FIG. 4, the leading cord end 11 of the reinforcing cord layer 10 in the tire rotation direction is arranged at the lower end side in the tire radial direction. Even with such an arrangement, when a braking torque in the direction of the arrow is applied to the rotating tire 1, tension in the direction opposite to the traveling direction acts on the reinforcing cord layer 10. Can be improved.

  In the following examples and comparative examples, tires having a size of 195 / 65R15 were used, and the equatorial line E was sandwiched between the tread portions 4 to form a total of four circumferential grooves of 8 mm each.

  In Example 1, the tire shown in FIGS. 1 and 2 was used. That is, the inclination angle K of the reinforcing cord layer 10 is 45 degrees with respect to the tire radial direction, and substantially the same inclination angle on both the left and right sides of the tire, and the leading cord end 11 of the tire rotation is the upper end in the tire radial direction. It is arranged as follows. The length Lt of the reinforcing cord layer 10 is Lt = 0.4L, and the end portion 10b on the bead portion 2 side of the reinforcing cord layer 10 is located closer to the ground plane than the folded end 5b of the carcass 5. .

  In Example 2, the tire shown in FIGS. 3 and 4 was used. In this tire, the inclination angle K of the reinforcing cord layer 10 is 45 degrees with respect to the tire radial direction, and substantially the same inclination angle on the left and right sides of the tire, and the leading cord end 11 of the tire rotation is the lower end in the tire radial direction. It is arranged so that The length Lt of the reinforcing cord layer 10 is Lt = 0.4L as in the first embodiment, and the end portion 10b on the bead portion 2 side of the reinforcing cord layer 10 is more than the ground contact surface than the folded end 5b of the carcass 5. Located on the side.

  In Comparative Example 1, the tire shown in FIGS. 5 and 6 was used. In this tire, the inclination angle K of the reinforcing cord layer 10 is 45 degrees with respect to the tire radial direction, and substantially the same inclination angle on the left and right sides of the tire, and the leading cord end 11 of the tire rotation is the upper end in the tire radial direction. It is arranged so that In Comparative Example 1, the length Lt of the reinforcing cord layer 10 is Lt = 0.4L, but the entire reinforcing cord layer 10 is located closer to the bead core 6 than the folded end 5b.

  In Comparative Example 2, the tire shown in FIGS. 7 and 8 was used. In this tire, the inclination angle K of the reinforcing cord layer 10 is 45 degrees with respect to the tire radial direction, and substantially the same inclination angle on the left and right sides of the tire, and the leading cord end 11 of the tire rotation is the upper end in the tire radial direction. It is arranged so that In Comparative Example 2, the length Lt of the reinforcing cord layer 10 is set to Lt = 0.9L, while the end portion 10b on the bead portion 2 side of the reinforcing cord layer 10 is more grounded than the folded end 5b of the carcass 5 It is located on the side.

  In Comparative Example 3, a tire without the reinforcing cord layer 10 was used as shown in FIG.

  The tires of the above examples and comparative examples were assembled to a rim of 6.0 J at an internal pressure of Front220 / Rear200 KPa, mounted on a real image, and subjected to a braking test under the following conditions.

(Brake test conditions)
・ Vehicle: FF passenger car ・ Installation position: 4 wheels ・ Front wheel load: 4.5KN
・ Rear wheel load: 3.4KN
・ Equivalent to two passengers
・ Initial speed: 100km / h
-Road surface: DRY asphalt / ABS operation Table 1 shows a comparative evaluation by the above braking test. The comparative evaluation in Table 1 was performed by displaying the braking distance (distance traveled from the start to the stop of braking) performed under the above conditions as an index with the tire of Comparative Example 3 as 100. That is, the smaller the value, the shorter the braking distance and the better.

FIG. 2 is a cross-sectional view schematically showing the left half of the tire of the first embodiment with the equator plane E as a boundary. It is a side view showing the running state of the tire of a 1st embodiment. It is sectional drawing which shows diagrammatically the left half with the equator plane E as a boundary in the tire of the second embodiment. It is a side view which shows the running state of the tire of 2nd Embodiment. FIG. 4 is a cross-sectional view schematically showing the left half of the tire of Comparative Example 1 with the equator plane E as a boundary. It is a side view which shows the running state of the tire of the comparative example 1. FIG. 6 is a cross-sectional view schematically showing the left half of the tire of Comparative Example 2 with the equator plane E as a boundary. It is a side view which shows the running state of the tire of the comparative example 2. It is sectional drawing which shows diagrammatically the left half with the equator plane E as a boundary in the tire used from before.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Bead part 3 Side wall part 4 Tread part 5 Carcass 5b Carcass folding end 6 Bead core 9 Grounding end 10 Reinforcement cord layer 10a Reinforcement cord layer upper end portion 10b Reinforcement cord layer lower end portion 11 Reinforcement cord layer preceding cord end

Claims (3)

A pair of bead portions, a pair of sidewall portions, a tread portion connecting the pair of sidewall portions, and a bead core at the end of the bead portion are disposed over the bead portion, the sidewall portions, and the tread portion. that together and a carcass, a pneumatic tire reinforcement cord layer on the outer side of the carcass is provided in Sa id wall portions of the left and right sides of the tire equatorial plane,
The upper end of the reinforcing cord layer is located on the ground terminal,
The lower end of the reinforcing cord layer is located above the folded end of the carcass,
The relative length L along the carcass from the folded end to said ground terminal, the length Lt along the carcass of the reinforcing cord layer is set so that Lt <0.5 L,
The pneumatic tire is characterized in that the reinforcing cord layer is disposed so as to have a square shape when the tire is developed . The pneumatic tire according to claim 1,
The reinforcing cord layer has an inclination angle with respect to the tire radial direction on both the left and right sides of the tire of 40 to 50 degrees, and the leading cord end in the tire rotating direction is arranged in the tire radial direction upper end side. And pneumatic tires. The pneumatic tire according to claim 2,
  The pneumatic tire is characterized in that the reinforcing cord layer has substantially the same inclination angle on both the left and right sides of the tire.

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