JP6109693B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  The area outside the tread portion of the vehicle when the vehicle is mounted is likely to be subjected to a large load during cornering, so if a main groove extending in the tire circumferential direction is provided in this area, a large load during cornering is received. As a result, the joint between the groove wall on the outside of the vehicle that divides the main groove and the ground contact surface falls to the main groove, and as a result, the steering stability is deteriorated, and the joint is less likely to be worn than other parts. There is a problem that the uneven joint which is said to remain is liable to cause partial wear without being worn.

  Conventionally, in order to improve steering stability during cornering while maintaining performance related to uneven wear and noise, Patent Document 1 discloses a groove wall facing the vehicle outer side in a main groove extending in the circumferential direction arranged on the vehicle outer side. That is, it has been proposed that the groove wall on the vehicle inner side of the main groove is inclined with respect to the normal line of the grounding surface, and a concave portion or a groove portion is provided in the groove wall.

  Further, in Patent Document 2, the groove wall cross-sectional shape of the tire meridian cross section of the circumferential groove in the tread surface of the outer region that is outside the vehicle from the tire equator line when the vehicle is mounted is formed asymmetrically and the groove that is inside the vehicle It has been proposed that the cross-sectional shape of the wall is formed so as to have a curved portion in contact with the tread surface in a tangential direction from the tread surface toward the groove bottom side.

Japanese Patent Laid-Open No. 2003-312212 Japanese Patent Laid-Open No. 10-29409

  The technologies disclosed in Patent Documents 1 and 2 described above are such that the vehicle inner groove wall of the main groove extending in the circumferential direction provided on the vehicle outer side from the tire equator line when the vehicle is mounted is inclined with respect to the normal line of the ground plane. Or, it is a curved part that is tangentially touching the tread surface, and the rigidity of the groove wall outside the vehicle in the main groove is not taken into consideration, and the steering caused by the fall of the groove wall outside the vehicle during cornering as described above It is impossible to suppress the deterioration of stability and the occurrence of uneven wear.

  The present invention has been made in consideration of the above points, and when the vehicle is mounted, the groove wall on the vehicle outer side of the main groove disposed on the vehicle outer side from the tire equator line is prevented from collapsing during cornering traveling, and steering stability is improved. An object of the present invention is to provide a pneumatic tire capable of suppressing uneven wear while improving the above.

The pneumatic tire according to the present invention is a pneumatic tire that is disposed on the vehicle outer side from the tire equator line when mounted on the vehicle and includes a main groove extending along a tire circumferential direction in a tread portion. A plurality of outer joints between the contact surface and the ground contact surface having a curvature radius larger than that of the inner joint portion between the groove wall inside the vehicle and the ground contact surface in the main groove , and extending along the tire circumferential direction only at the outer joint portion. The thin groove is provided .

  In the present invention, when the vehicle is mounted, the outer joint portion of the main groove that is disposed on the outer side of the tire equator line between the groove wall on the outer side of the vehicle and the ground contact surface forms a curved surface, and the outer joint portion is made highly rigid. Therefore, the falling of the outer joint during cornering traveling can be suppressed, and the steering stability can be improved and uneven wear can be suppressed.

It is a development top view of the tread pattern of the pneumatic tire concerning a 1st embodiment of the present invention. It is AA sectional drawing of FIG. FIG. 3 is an enlarged view of a main part of FIG. 2. It is a principal part expanded sectional view of the tread part of the pneumatic tire which concerns on the example of a change of this invention. (A) And (b) is a principal part expanded sectional view of the tread part of the pneumatic tire which concerns on a comparative example.

  The pneumatic tire according to the present embodiment is not shown, but the pair of left and right bead portions and sidewall portions and the radially outer ends of the left and right sidewall portions are connected to each other between the sidewall portions. The tread portion 10 is provided. The pneumatic tire includes a carcass extending across a pair of bead portions.

  The carcass is composed of at least one carcass ply whose both end portions are locked by a bead core embedded in the bead portion from the tread portion 10 through the sidewall portion, and reinforces each portion described above.

  A belt composed of two or more rubber-coated steel coat layers is provided on the outer periphery side of the carcass in the tread portion 10, and the tread portion 10 is reinforced at the outer periphery of the carcass.

  In this embodiment, the right side of FIGS. 1 to 4 is the outer side when the vehicle is mounted, and the left side of FIGS. 1 to 4 is the inner side when the vehicle is mounted.

  As shown in FIG. 1, a plurality of main grooves 12 extending straight along the tire circumferential direction X and a plurality of lateral grooves 14 extending across the main grooves 12 are provided on the surface of the tread portion 10. The groove 12 and the lateral groove 14 define a plurality of land portions 18, 20, 22, and 24 between the ground contact end E1 on the vehicle inner side and the ground contact end E2 on the vehicle outer side.

  Here, the ground contact ends E1 and E2 on the vehicle inner side and the vehicle outer side are the outer ends in the width direction of the tread portion 10 that comes into contact with the road surface when a tire loaded with normal internal pressure is placed vertically on a flat road surface and a normal load is applied. The normal load and the normal internal pressure are the maximum load defined in JIS D4202 (automobile tire specifications) and the air pressure corresponding to the maximum load.

  In the present embodiment, a center main groove 12a and an inner shoulder main groove 12b disposed on the vehicle inner side than the center main groove 12a are provided in a region FI inside the vehicle from the tire equator line C. An outer shoulder main groove 12c is provided in a region FO outside the vehicle.

  As a result, the inner shoulder land groove 18 is defined between the inner shoulder main groove 12b and the ground contact end E1 on the vehicle inner side in the vehicle inner region FI of the tread portion 10, and the inner shoulder main groove 12b and the center main groove 12a. The inner intermediate land portion 20 is partitioned between the two. In the vehicle outer region FO of the tread portion 10, an outer intermediate land portion 22 is defined between the outer shoulder main groove 12c and the center main groove 12a, and between the outer shoulder main groove 12c and the grounding end E2 outside the vehicle. The outer shoulder land portion 24 is partitioned.

  Further, a concave groove 26 extending along the circumferential direction is provided on the vehicle outer side from the outer shoulder main groove 12c, and the outer shoulder land portion 24 is divided by the concave groove 26 in the tire width direction. The groove 26 is narrower than the three main grooves 12a, 12b, and 12c provided in the tread portion 10, and the position 26a that intersects the lateral groove 14 is closer to the ground surface 16 than the other positions 26b. The groove depth differs in the tire circumferential direction X so that the amount of depression is small.

  In the pneumatic tire having such a configuration, the outer shoulder main groove 12c provided in the area FO on the vehicle outer side from the tire equator line C defines the vehicle outer side of the main groove 12c as shown in FIGS. The outer joint portion 30 between the outer groove wall 28 and the ground contact surface 16 constituting the outer side in the tire radial direction of the outer shoulder land portion 24 has an arcuate cross section, and the outer groove wall 28 and the ground contact surface at the outer joint portion 30. 16 are connected by a smooth curved surface.

  In the present embodiment, the inner joint 34 between the inner groove wall 32 that defines the vehicle inner side of the outer shoulder main groove 12c and the ground contact surface 16 that constitutes the outer side in the tire radial direction of the outer intermediate land portion 22 is also an outer joint. Like the portion 30, the cross-section has an arc shape, and the inner groove wall 32 and the ground contact surface 16 are connected by a smooth curved surface at the inner joint portion 34.

  The outer joint portion 30 is a curved surface having a curvature radius RO larger than the curvature radius RI of the inner joint portion 34. In addition, the outer joint portion 30 is provided with a plurality of narrow grooves 36 extending along the tire circumferential direction X. In this example, the plurality of narrow grooves 36 are provided only on the outer joint portion 30, that is, on the curved surface portion having a circular arc cross section, and the pitch P when the bottom of each narrow groove 36 is projected onto the tread surface is constant. It is provided as follows.

  The outer joint portion 30 is preferably formed in the outer groove wall 28 in a region of 50% or more of the depth H of the shoulder main groove 12c from the ground contact surface 16, and when it is smaller than 50%, the outer joint portion 30 is formed during cornering traveling. Tends to fall to the shoulder main groove 12c side (that is, the inside of the vehicle), the steering stability is deteriorated, and the outer shoulder land portion 24 and the vicinity of the outer joint portion 30 are less likely to be worn compared to the ground contact E2 side. Uneven wear that remains without the portion 30 being worn is likely to occur.

  The inner joint 34 is not particularly limited as long as it has a radius of curvature RI smaller than the radius of curvature RO of the outer joint 30 as described above. For example, as shown in FIG. Although it may have an angular shape that abuts the ground contact surface 16 of the outer intermediate land portion 22, it is preferably a curved surface that smoothly connects the inner groove wall 32 and the ground contact surface 16 of the outer intermediate land portion 22. Thereby, the partial wear which the inner side groove wall 32 remains without wearing at the time of normal driving | running | working can be suppressed.

  Moreover, when providing the inner side junction part 34 in a curved surface shape, it is preferable to form in the 20%-50% area | region of the depth H of the shoulder main groove 12c from the ground surface 16 in the inner side groove wall 32. FIG. If it is smaller than 20% of the depth H of the shoulder main groove 12c, the uneven wear remaining on the inner groove wall 32 during normal running without being worn cannot be sufficiently suppressed. The rigidity in the vicinity becomes too high, and the vicinity of the inner joint portion 34 is more easily worn than the other portions of the outer intermediate land portion 22 during cornering traveling, and uneven wear tends to occur.

  Here, an example of each dimension will be described with reference to FIG. 3. When the outer shoulder main groove 12 has a groove depth of 8 mm, the radius of curvature RO of the outer joint portion 30 is 4 to 5 mm and the curvature of the inner joint portion 34. The radius RI is 3 mm, the groove width W of the narrow groove 36 is 0.4 to 1.0 mm, the depth h of the narrow groove 36 is 0.2 to 1.0 mm, and the bottom of each narrow groove 36 is projected onto the tread surface. The hour pitch P can be set to 0.6 to 2.0 mm.

  In the pneumatic tire of the present embodiment described above, the outer joint portion between the outer groove wall 28 of the outer shoulder main groove 12c and the ground contact surface 16 of the outer shoulder land portion 24 provided in the region FO outside the vehicle from the tire equator line C. 30 has a curved surface with a larger radius of curvature than the inner joint portion 34, so that the outer joint portion 30 is prevented from falling to the shoulder main groove 12c side during cornering traveling and the steering stability is improved. It is possible to suppress uneven wear that remains without being worn.

  In addition, in the present embodiment, the inner joint portion 34 has a curved surface having a smaller radius of curvature than the outer joint portion 30, so that it is possible to suppress uneven wear that the inner groove wall 32 remains without being worn during normal travel. In addition, it is possible to suppress uneven wear in which the vicinity of the inner joint portion 34 is worn compared to other portions of the outer intermediate land portion 22 during cornering traveling.

  In the present embodiment, the outer joint 30 has a curved surface shape, so that the rigidity in the vicinity of the outer joint 30 is increased, and the rigidity balance of the outer shoulder land portion 24 may be uneven. 30 is provided with a plurality of narrow grooves 36 extending along the tire circumferential direction X, the rigidity of the outer joint portion 30 can be reduced and the rigidity of the outer shoulder land portion 24 can be made uniform. Therefore, it is possible to suppress uneven wear in which the vicinity of the outer joint portion 30 is worn compared to other portions of the outer shoulder land portion 24 during normal traveling.

  Moreover, since the plurality of narrow grooves 36 provided in the outer joint portion 30 face the outer shoulder main groove 12c, the frictional resistance between the air in the outer shoulder main groove 12c and the outer groove wall 28 is increased. Thus, air columnar resonance noise caused by the air trapped between the road surface and the shoulder main groove 12c during traveling can be suppressed.

  Further, if the narrow groove 36 is provided on the ground contact surface 16 of the outer shoulder land portion 24, the ground contact surface 16 near the narrow groove 36 is likely to be worn. However, in the present embodiment, the narrow groove 36 includes only the outer joint portion 30. Since it is not provided on the ground contact surface 16 of the outer shoulder land portion 24, uneven wear of the ground contact surface 16 due to the narrow groove 36 can be suppressed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to these Examples.

  Test tires of Examples 1 and 2 and Comparative Examples 1 and 2 (size: 215 / 55R17) were prototyped.

  As Example 1, a pneumatic tire in which the outer joint portion 30 and the inner joint portion 34 having a cross-sectional shape as shown in FIG. As Example 2, a pneumatic tire in which an outer joint portion 30 and an inner joint portion 34 having a cross-sectional shape as shown in FIG. In addition, as Comparative Examples 1 and 2, pneumatic tires in which the outer joint portion 30 and the inner joint portion 34 having cross-sectional shapes as illustrated in FIGS. 5A and 5B were formed were manufactured. The tires of Examples 1 and 2 and Comparative Examples 1 and 2 all have a common configuration except for the shapes of the outer joint portion 30 and the inner joint portion 34 of the outer shoulder main groove 12a. 5A and 5B, as in FIGS. 1 to 4, the right side in the drawing is the outside when the vehicle is mounted, and the left side is the inside when the vehicle is mounted.

  Each prototype tire manufactured was mounted on a real vehicle (domestic 2500cc class sedan) as a use rim 17 × 7.5J, and the performance evaluation was performed. The evaluation method is as follows.

(1) Steering stability during cornering (high load) Comparison of sensory evaluation of each driver when two drivers drive a vehicle equipped with the target tire on a slalom dry road and a wet road Example 1 was evaluated with an index of 100. The higher the value, the higher the rating.

(2) Uneven wear during cornering running (during high load running) After running on a slalom dry road, the difference in the amount of wear between the outer groove wall of the outer shoulder main groove and the inner groove wall is shown as 100 in Comparative Example 1. The index was evaluated. The larger this value, the smaller the degree of uneven wear.

(3) Uneven wear during normal running After running on a general road of 20,000 km, the difference in the amount of wear near the outer groove wall of the outer shoulder main groove and the inner groove wall was evaluated by an index with Comparative Example 1 as 100. The larger this value, the smaller the degree of uneven wear.

  As shown in Table 1, with the pneumatic tires of Examples 1 and 2, compared to Comparative Examples 1 and 2, it was possible to improve steering stability during cornering traveling and to suppress uneven wear. Moreover, in Example 1, the uneven wear at the time of normal driving | running | working was able to be improved by providing the inner side junction part 34 in a curved surface shape.

DESCRIPTION OF SYMBOLS 10 ... Tread part, 12 ... Main groove, 12a ... Center main groove, 12b ... Inner shoulder main groove, 12c ... Outer shoulder main groove, 14 ... Lateral groove, 16 ... Ground surface, 18 ... Inner shoulder land part, 20 ... Inner middle Land part, 22 ... Outer intermediate land part, 24 ... Outer shoulder land part, 26 ... Concave groove, 28 ... Outer groove wall, 30 ... Outer joint part, 32 ... Inner groove wall, 34 ... Inner joint part, 36 ... Narrow groove , C ... tire equator line, E1 ... ground contact edge inside vehicle, E2 ... ground contact edge outside vehicle, FI ... vehicle inside region, FO ... vehicle outside region

Claims (3)

In the pneumatic tire which is arranged on the vehicle outer side from the tire equator line when the vehicle is mounted and has a main groove extending along the tire circumferential direction in the tread portion,
The outer joint portion between the vehicle outer groove wall and the ground contact surface in the main groove has a curved surface with a larger radius of curvature than the inner joint portion between the vehicle inner groove wall and the ground contact surface in the main groove ,
A pneumatic tire characterized in that a plurality of fine grooves extending along the tire circumferential direction are provided only in the outer joint portion . The pneumatic tire according to claim 1 , wherein the main groove is a shoulder main groove that defines a shoulder land portion between the main groove and the ground contact end. The pneumatic according to claim 2 , further comprising a concave groove extending along a tire circumferential direction on the vehicle outer side from the shoulder main groove, wherein the shoulder land portion is divided in the tire width direction by the concave groove. tire.

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