JP2008279900A - Pneumatic studless tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simultaneously enhance braking performance and driving performance on an ice-snow road, and to ensure riding comfortability. <P>SOLUTION: In this pneumatic studless tire with a designated rotation direction R, a plurality of projections 3 are symmetrically arranged on respective side walls 2 regarding a tire equator surface, and inclined in a direction opposite to the rotation direction R as the projections 3 are extended from an inner side in a tire radial direction to an outer side. An inclination angle formed of a projection extending direction and a tire radial direction L is 45-80°. The inner end in the tire radial direction of the projection 3 is positioned at an inner side in the tire radial direction from an outer end in the tire radial direction of a bead filler 4 of a bead 6 by 0-4 mm. The outer end in the tire radial direction of the projection 3 is positioned at an inner side in the tire radial direction from a tread surface at a tire equator surface by 35-45% of the tire cross section height H. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic studless tire intended for use on icy and snowy roads, and more particularly to a pneumatic studless tire with improved braking performance and driving performance on an ice road surface.

  As shown in FIG. 4, during braking, a stress opposite to the traveling direction is generated on the side portion of the tire. Conversely, during driving, the same stress as that in the traveling direction is generated on the side portion of the tire. In a pneumatic tire on a snowy road called a studless tire, the braking performance is improved if the stress generated during braking is large. Conversely, when the stress generated during driving is small, driving performance is improved.

  In general, in a pneumatic tire used for a passenger car, characters, symbols, figures, and the like are only decorated on the surface of the sidewall. Therefore, since the side portion of the tire has no directionality with respect to the rotational direction, stresses having different directions but the same magnitude are generated in the side portion during braking and driving. As a result, braking performance and driving performance could not be improved at the same time.

  Moreover, in the pneumatic tire described in Patent Document 1, the rotation direction of the tire is not specified, and the ribs arranged on the sidewalls are intended to reduce road noise.

JP 2001-39129 A (FIGS. 1 and 2)

  As described above, it is difficult to improve the braking performance and the driving performance at the same time. When ribs are arranged on the sidewall as in the tire of Patent Document 1, there is a concern that the rigidity of the tire becomes too high and the ride comfort is deteriorated. Accordingly, an object of the present invention is to provide a pneumatic studless tire that simultaneously improves braking performance and driving performance on icy and snowy roads and ensures riding comfort.

In order to solve the above-described problems, a pneumatic studless tire according to the present invention includes a pair of bead portions, a carcass wound around the bead portion to form a toroidal shape, a pair of sidewalls covering the side portions of the carcass, and the carcass In a pneumatic studless tire having a rotation direction designated with a tread that covers the crown portion of
A plurality of protrusions are arranged symmetrically with respect to the tire equatorial plane on each sidewall,
As the ridge extends from the inside in the tire radial direction to the outside, the ridge is inclined in a direction opposite to the rotation direction, and an inclination angle formed by the extending direction of the ridge and the tire radial direction is 45 degrees to 80 degrees,
The tire radial inner end of the ridge is on the inner side in the tire radial direction by 0 mm to 4 mm from the tire radial outer end of the bead filler of the bead portion.
The outer end in the tire radial direction of the protrusion is on the inner side in the tire radial direction by 35% to 45% of the tire cross-section height from the tread surface on the tire equatorial plane.
The width of the protrusions is 5 mm to 15 mm, the interval between the protrusions is 5 mm to 20 mm, and the height of the protrusions is 2 mm to 6 mm.

  As the ridge extends from the inner side to the outer side in the tire radial direction, the ridge is inclined in the direction opposite to the rotation direction. The rigidity of the part is increased. Therefore, during braking, a greater stress is generated in the side portion of the tire than in a tire without protrusions. Conversely, during driving, the stress generated at the side portion of the tire is reduced. As a result, braking performance and driving performance on the ice road surface can be improved at the same time.

  The 100% modulus of the ridge is preferably 1.0 to 1.6 times the 100% modulus of the sidewall. By making the 100% modulus of the ridge higher than that of the sidewall, the difference in stress between braking and driving can be increased more effectively. In the present application, 100% modulus means a value at 23 ° C.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a view showing a part of a side surface of a pneumatic studless tire according to the present invention. The tire 1 is a tire in which the rotation direction R at the time of mounting is determined. A plurality of protrusions 3 are arranged on the sidewall 2 of the tire 1. The protrusion 3 is inclined in the direction opposite to the rotational direction R as it extends from the inner side to the outer side in the tire radial direction. The angle formed by the extending direction of the ridge 3 and the tire radial direction L is θ.

  Therefore, the ridge 3 increases the rigidity of the side portion so that the side portion of the tire 1 is not deformed in the direction R ′ opposite to the rotation direction R. As a result, during braking, a greater stress is generated in the side portion of the tire 1 than in a tire without the protrusions 3. Conversely, during driving, the stress generated at the side portion of the tire 1 is reduced. As a result, braking performance and driving performance on the ice road surface can be improved at the same time.

  The inclination angle θ of the protrusion 3 is preferably 45 to 80 degrees. When the angle θ is less than 45 degrees, the longitudinal rigidity of the tire becomes too large, and the ride comfort is deteriorated or the steering stability is lowered. Conversely, when the angle θ exceeds 80 degrees, many protrusions 3 cannot be arranged, and the effect of increasing the rigidity of the side portion is low.

  FIG. 2 is a cross-sectional view taken along the line AA in FIG. The carcass 7 winds up a bead portion 6 including a bead filler 4 and a bead wire 5 to form a toroidal shape. A pair of sidewalls 2 covering the side portion of the carcass 7 and a tread 8 covering the crown portion of the carcass 7 are provided. These are well-known pneumatic tire structures, and grooves and sipes cut into the tread, a belt reinforcing layer inserted between the carcass 7 and the tread, and the like are omitted.

  The radially inner end 3 a of the protrusion 3 is radially inward from the radially outer end 4 a of the bead filler 4 by 0 mm to 4 mm. If the end portion 3a exceeds 4 mm and is radially inward, the longitudinal rigidity of the tire becomes too large, and the ride comfort is deteriorated or the steering stability is lowered. On the other hand, if the end 3a is less than 0 mm and the outer end 4a in the radial direction of the bead filler 4 is on the outer side in the radial direction, the effect of increasing the rigidity of the side portion is reduced.

  As the tire cross-section height H at the equator plane C, the distance H1 from the tread surface at the tire equator plane to the radially outer end 3b of the ridge 3 is 35% to 45% of the tire cross-section height H. It is preferable. That is, it is preferable that the end portion 3b on the radially outer side of the protrusion 3 is 35% to 45% of the tire cross-section height H from the tread surface on the tire equatorial plane to the inner side in the tire radial direction. If H1 is less than 35% of H, the concave portion of the mold for molding the protrusion 3 will straddle the joint surface between the mold for molding the tread and the mold for molding the sidewall, which is difficult to manufacture. Become. Conversely, if H1 exceeds 45% of H, the ridge 3 may not be provided to such an extent that the rigidity of the side portion can be increased in a tire having a low flatness ratio.

  The ridge 3 on the right half cross section and the ridge 3 (not shown) on the left half cross section are arranged so as to be symmetric with respect to the tire equatorial plane C. In both braking and driving, the stress is generated at a symmetric position with respect to the tire equatorial plane C of the side portion, so that the rigidity of the side portion can be effectively increased.

  FIG. 3 is a view showing a cross section in the tire circumferential direction of the ridge 3 in the cross section taken along line BB in FIGS. The width α of the protrusion 3 is preferably 5 mm to 15 mm, the interval β is preferably 5 mm to 20 mm, and the height γ is preferably 2 mm to 6 mm. Outside these ranges, if the width α is narrow, the interval β is wide, or the height γ is low, the difference in stress between braking and driving is small and the effect is low. On the other hand, if the width α is wide, the interval β is narrow, or the height γ is high, the tire's longitudinal rigidity becomes too large and the ride comfort deteriorates or the steering stability is exceeded. Or drop. In addition, when the interval β is narrow, it is difficult to manufacture a mold for molding a tire.

  The protrusion 3 may be a rubber having the same composition as that of the sidewall 2, but the protrusion 3 has a 100% modulus that is 1.0 to 1.6 times the 100% modulus of the sidewall 2. The rubber composition of Article 3 may be changed. The difference in stress between braking and driving can be increased more effectively. By making the 100% modulus of the ridge higher than that of the sidewall, the difference in stress between braking and driving can be increased more effectively. In addition, when it exceeds 1.6 times, the longitudinal rigidity of the tire becomes too large, and the riding comfort is deteriorated or the steering stability is lowered.

  In this case, as shown in FIG. 5, a side wall rubber 10 composed of a rubber 13 constituting the ridge 3 and a rubber 12 constituting the side wall 2 is integrally extruded and attached to a carcass to attach a green tire. The green tire can be molded and vulcanized to increase only the 100% modulus of the ridge 3.

  As an example, a tire according to the present invention and a tire according to a comparative example were prototyped and mounted on all wheels of a front-wheel drive passenger car having a displacement of 2000 cc for evaluation. Each tire size was 195 / 65R15, the rim size was 15 × 6-JJ, and the internal pressure was 200 kPa.

  Ice braking indicates the ABS braking distance from 40 km / h on the ice road surface, and the larger the number, the shorter the braking distance and the better the braking performance of the tire. Ice acceleration indicates the time required to travel 30 m from a state where the vehicle is stopped on the ice road surface. The larger the number, the shorter the traveling time and the better the driving performance of the tire. All are expressed as indexes with Comparative Example 1 as 100. The riding comfort is a score obtained by 10-level sensory evaluation by one person on the evaluation course, and the larger the number, the better the riding comfort.

  Table 1 shows the results of evaluation by changing the inclination angle of the ridges. Comparative Example 3 is a tire that is inclined in the rotational direction as the protrusions extend from the inner side in the tire radial direction to the outer side, and the inclination angle θ is expressed as a negative value. Comparative Example 4 is a tire in which the left and right sidewall ridges are not arranged symmetrically with respect to the equator plane, and the other ridge is arranged at a position corresponding to the circumferential middle position of one of the ridges.

  According to Table 1, the braking performance and the driving performance are not improved so much in Comparative Example 2 where the inclination angle θ is small, and the braking performance and the driving performance are lowered in Comparative Example 3 inclined in the opposite direction, and the riding comfort is also deteriorated. Yes. In Comparative Example 4, since the protrusions on the left and right sidewalls are not symmetrically arranged with respect to the equator plane, the braking performance and driving performance are not improved, and the riding comfort is also deteriorated. On the other hand, in Examples 1 to 5, by setting the inclination angle θ to 45 degrees to 80 degrees, braking performance and driving performance on the ice road surface can be improved at the same time, and riding comfort can be ensured.

  Tables 2 and 3 show the results of evaluation by changing the dimensions of the ridges. In Table 3, the distance from the radially outer end of the bead filler to the radially inner end of the ridge is a negative value because the radially inner end of the ridge is the radially outer end of the bead filler. Indicates that it is radially outward from the end. According to Tables 2 and 3, in Comparative Examples 5 to 12, since the dimensions and positions of the protrusions are not appropriate, it is impossible to simultaneously improve the braking performance and driving performance and ensure the riding comfort. On the other hand, in the embodiment, by appropriately setting the dimensions of the protrusions, the braking performance and driving performance on the ice road surface can be improved at the same time, and the riding comfort can be secured.

  Table 4 shows the results of evaluation by changing the 100% modulus of the ridge as compared with the sidewall. By properly setting the 100% modulus of the ridge, braking performance and driving performance on the ice road surface could be improved at the same time, but in Comparative Example 13, the 100% modulus of the ridge was larger than the sidewall, so the ride comfort Worsened.

It is a figure which shows a part of side surface of the pneumatic studless tire which concerns on this invention. It is a figure which shows the right half cross section of the pneumatic studless tire which concerns on this invention. It is the BB sectional view taken on the line of FIG. It is a figure which shows the stress which generate | occur | produces at the time of braking and a drive. It is a figure which shows an example of the sidewall rubber used for manufacture of the pneumatic studless tire which concerns on this invention.

Explanation of symbols

1 tire 2 side wall 3 ridge 4 bead filler 5 bead core 6 bead part 7 carcass 8 tread

Claims (2)

A rotation direction is specified, which includes a pair of bead portions, a carcass wound around the bead portion to form a toroidal shape, a pair of sidewalls covering the side portions of the carcass, and a tread covering the crown portion of the carcass. In a pneumatic studless tire,
A plurality of protrusions are arranged symmetrically with respect to the tire equatorial plane on each sidewall,
As the ridge extends from the inside in the tire radial direction to the outside, the ridge is inclined in a direction opposite to the rotation direction, and an inclination angle formed by the extending direction of the ridge and the tire radial direction is 45 degrees to 80 degrees,
The tire radial inner end of the ridge is on the inner side in the tire radial direction by 0 mm to 4 mm from the tire radial outer end of the bead filler of the bead portion.
The outer end in the tire radial direction of the protrusion is on the inner side in the tire radial direction by 35% to 45% of the tire cross-section height from the tread surface on the tire equatorial plane.
The pneumatic studless tire characterized in that the width of the protrusions is 5 mm to 15 mm, the interval between the protrusions is 5 mm to 20 mm, and the height of the protrusions is 2 mm to 6 mm.   The pneumatic studless tire according to claim 1, wherein a 100% modulus of the ridge is 1.0 to 1.6 times a 100% modulus of the sidewall.

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