JP2010111155A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for reducing rolling resistance while improving a WET braking performance. <P>SOLUTION: The pneumatic tire includes, on a tread surface, a main groove 3 extending in a circumferential direction, a transverse groove 4 extending across the main groove 3, and a block or rib sectioned by the main groove and the transverse groove. Preferably a stepwise reinforcing part 5 is provided around at least one of the corner parts of the block or rib at an intersection of the main groove 3 and the transverse groove 4. The reinforcing part 5 starts from the groove walls of the main groove 3 and the transverse groove 4, and terminates at a groove bottom. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  A pneumatic tire having a tread surface provided with a main groove extending in the circumferential direction, a transverse groove extending across the main groove, and a block or a rib partitioned by them, and improving WET braking performance The present invention relates to a pneumatic tire with reduced rolling resistance.

  Conventionally, in order to reduce rolling resistance of pneumatic tires, loss tangent (loss tangent = loss elastic modulus / storage elastic modulus, hereinafter simply referred to as “tan δ”) is used as a rubber (tread rubber) disposed in the tread portion. ) Is used. However, although the rolling resistance can be reduced by using a rubber having a low tan δ, the tread rubber becomes easy to bend, so the contact area of the tread rubber is reduced, and the wet braking performance of the pneumatic tire (on a wet road surface). There was a tendency for the braking performance) to deteriorate. Therefore, in consideration of the WET braking performance, a technique for reducing the rolling resistance of the pneumatic tire by devising the tread pattern while maintaining tan δ of the tread rubber to some extent is required.

  Here, when the present inventors diligently examined the relationship between the tire running strain and rolling resistance in each part of the tread pattern, at the corner of the block provided in the tread, particularly at the groove bottom portion of the corner. It has been found that the rolling resistance of the pneumatic tire can be reduced by reducing the strain at the corner of the groove bottom at the largest distortion.

  In the following Patent Document 1, in a pneumatic tire in which a large number of polygonal blocks partitioned by a circumferentially extending main groove and a lateral groove are arranged on the tread surface, the groove bottom at the intersection of the main groove and the lateral groove is formed. A pneumatic tire is disclosed in which the rigidity of the corners of each block is improved by raising the bottom. In such a patent document, by improving the rigidity of the corners of each block, the rigidity of the entire block can be averaged, and as a result, uneven wear that occurs when traveling on a dry road surface can be suppressed. Points are listed. However, in such a pneumatic tire, raising the entire groove bottom at the groove intersection portion reduces the groove volume at the portion and lowers the drainage performance, so that the WET braking performance tends to deteriorate particularly.

Moreover, in the following Patent Document 2, in a pneumatic tire having a block defined by a main groove extending in the circumferential direction and a lateral groove on a tread surface, a reinforcing portion is disposed in at least one main groove, thereby A pneumatic tire with improved groove rigidity is described. However, in such a pneumatic tire, although the rigidity of the center portion of the main groove bottom is improved, the rigidity of the corner of the block is not sufficiently improved, and there is room for further improvement regarding the distortion reduction effect of the corner of the block. there were. In addition, by disposing the reinforcing part that terminates at the groove bottom on the block side that faces the main groove beyond the main groove center line, the volume of the main groove tends to decrease and the drainage performance of the main groove tends to decrease. there were. For this reason, the pneumatic tire has room for further improvement in terms of WET braking performance.
Japanese Patent No. 3116243 Japanese Patent No. 3672026

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a pneumatic tire with improved rolling resistance while improving WET braking performance.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention is a pneumatic tire in which a tread surface is provided with a main groove extending in the circumferential direction, a lateral groove extending across the main groove, and a block or a rib partitioned by them. In the tire, a reinforcing part is provided around at least one corner of the block or rib located at the intersection of the main groove and the lateral groove, and the reinforcing part starts from a groove wall between the main groove and the horizontal groove. And terminated at the bottom of the groove.

  In the above pneumatic tire, at least one corner of the block or rib located at the intersection of the main groove and the lateral groove is provided with a reinforcing portion that starts from the groove wall of the main groove and the lateral groove and ends at the groove bottom. Therefore, the rigidity of the corners of the block or rib is increased. Thereby, since distortion can be reduced at the groove bottom portion of the corner portion of the block or rib where the distortion is most likely to occur during tire travel, the rolling resistance of the pneumatic tire can be reduced. In addition, the corners of the blocks or ribs that are easy to move are reinforced by the reinforcements, and the ground contact area at the corners of the blocks or ribs is ensured and the proportion of the reinforcements occupied by the main grooves and lateral grooves during tire running Since it is small, these groove volumes can be sufficiently secured. As a result, the wet braking performance of the pneumatic tire can be improved.

  In the pneumatic tire, it is preferable that the reinforcing portion is provided in a step shape. Since such a pneumatic tire is provided with a reinforcing portion provided in a step shape, the rigidity of the corner portion of the block or rib can be further increased. Thereby, since distortion can be further reduced at the groove bottom portion of the corner of the block or rib, the rolling resistance of the pneumatic tire can be particularly reduced. Furthermore, the corner portions of the blocks or ribs that are easy to move are reinforced by the reinforcing portions provided in a step shape, and a sufficient contact area is secured at the corner portions of the blocks or ribs when the tire is running. Thereby, the WET braking performance of the pneumatic tire can be particularly improved.

In the pneumatic tire, in a center region located inside a main groove located on the outermost side in the width direction of the tread surface, a circumferential length of a portion of the reinforcing portion adjacent to the groove wall of the main groove is set. L ₁ , where L ₂ is the length in the width direction of the portion adjacent to the groove wall of the lateral groove, it is preferable that 1.3L ₁ ≦ L ₂ ≦ 3L ₁ .

In general, during tire running, due to the influence of in-plane contraction force (force that acts toward the center within the contact surface when the tire is grounded), there is a block or rib in the circumferential direction in the center region of the tread surface. easy to move. However, by setting L ₁ and L ₂ as described above, the rigidity of the corners of the blocks or ribs is particularly enhanced in the center region of the tread surface while sufficiently securing the groove volumes of the main groove and the lateral groove. be able to. As a result, the rolling resistance of the pneumatic tire can be further reduced, and in addition, the wet braking performance can be further improved.

In the pneumatic tire, in a shoulder region located outside a main groove located on the outermost side in the width direction of the tread surface, a circumferential length of a portion of the reinforcing portion adjacent to the groove wall of the main groove is set. When L ₁ is L ₂ , the length in the width direction of the portion adjacent to the groove wall of the lateral groove is preferably 1.3L ₂ ≦ L ₁ ≦ 3L ₂ .

When the tire is running, the blocks or ribs easily move in the width direction in the shoulder region of the tread surface due to the influence of the in-plane contraction force. However, by setting L ₁ and L ₂ as described above, the rigidity of the corners of the block or rib is particularly enhanced in the shoulder region of the tread surface while sufficiently securing the groove volumes of the main groove and the lateral groove. be able to. As a result, the rolling resistance of the pneumatic tire can be further reduced, and in addition, the wet braking performance can be further improved.

  FIG. 1 is a schematic development view of a tread pattern showing an embodiment of a pneumatic tire according to the present invention. FIG. 2 is an enlarged schematic plan view of FIG. 3A and 3B are cross-sectional views taken along arrows II in FIG.

  In the figure, 1 is a tread surface, and 2 is a block provided on the tread surface 1. The block 2 is divided and arranged by a main groove 3 extending in the circumferential direction and a lateral groove 4 extending so as to intersect the main groove 3. 1 and 2, S indicates the tire circumferential direction, and TC indicates the center line of the tire tread surface. In the present embodiment, the main groove 3 is linear, but may be zigzag or wavy. Further, the lateral groove 4 extends in the width direction (extends perpendicularly to the center line TC), but may extend in an inclined manner in the width direction. In the present embodiment, an example is shown in which the block 2 partitioned into a rectangular shape is provided by the main groove 3 and the lateral groove 4, but the shape of the block is not particularly limited. Note that sipes may be formed in the block 2 as necessary.

  In the present invention, the reinforcing portion 5 is provided around at least one of the corner portions of the block 2 located at the intersection of the main groove 3 and the lateral groove 4. By providing the reinforcing part 5 around, the block rigidity of the corner part of the block 2 is increased. Thereby, since distortion can be reduced in the groove bottom part of the corner | angular part of the block 2 where distortion becomes the largest at the time of tire driving | running | working, rolling resistance of a pneumatic tire can be reduced. Furthermore, the corners of the block 2 that are easy to move are reinforced by the reinforcements 5, and the ground contact area at the corners of the blocks 2 is ensured when the tire is running, and the reinforcements 5 occupy the main grooves 3 and the lateral grooves 4. Since the ratio is small, these groove volumes can be sufficiently secured. As a result, the wet braking performance of the pneumatic tire can be improved.

  As shown in FIG. 2, in the present embodiment, the reinforcing portions 5 provided in a tapered shape are provided around all corner portions of the block 2 located at the intersections of the main grooves 3 and the lateral grooves 4. In this case, the block rigidity can be increased in all corners of the block 2, and the effect of reducing the rolling resistance of the pneumatic tire and the effect of improving the WET braking performance can be further increased. The reinforcing portion 5 starts from the groove wall between the main groove 3 and the lateral groove 4 and ends at the groove bottom. In order to secure the groove volume of the main groove 3 and the lateral groove 4 and improve the wet braking performance of the pneumatic tire, the reinforcing portion 5 does not exceed the groove center 3C of the main groove 3 and the groove center 4C of the lateral groove 4. It is preferable to terminate at a position.

Here, as shown in FIG. 3 (a), if D a groove depth of the main groove 3, the reinforcing portion 5, a height from the groove bottom of the main groove 3 was set to d _1, 0.1D ≦ d ₁ It is preferable that ≦ 0.4D. If d ₁ is less than 0.1D, the reinforcing effect of the reinforcing part 5 may be insufficient. If d ₁ exceeds 0.4D, the reinforcing effect of the reinforcing part 5 is improved, but the main groove 3 When the groove volume of the tire is reduced and the drainage performance is lowered, the wet braking performance of the pneumatic tire may be deteriorated. Although not shown in the drawings, when the groove depth of the lateral groove 4 is D ′ and the height of the reinforcing portion 5 from the groove bottom of the lateral groove 4 is d ₁ ′, 0.1D ′ for the same reason as described above. It is preferable that ≦ d ₁ ′ ≦ 0.4D ′. The groove depth of the main groove 3 is specifically exemplified as 7.5 mm to 8.5 mm, and the groove depth of the lateral groove 4 is specifically exemplified as 6.5 mm to 7.5 mm. The 3A, the boundary between the reinforcing portion 5 and the groove wall of the main groove 3 (and the lateral groove 4), and the boundary between the reinforcing portion 5 and the groove bottom of the main groove 3 (and the lateral groove 4). In order to prevent the occurrence of cracks at the portions, it is preferable to form these boundary portions in an arc shape having a concave surface.

When the width of the main groove 3 is W and the length of the reinforcing portion 5 in the width direction from the groove wall of the main groove 3 is W ₁ , the reinforcing portion 5 is 0.1W ≦ W ₁ ≦ 0.3W. This is preferable because the groove volume of the main groove 3 is secured and the wet braking performance of the pneumatic tire is improved. Although not shown, when the groove width of the lateral groove 4 is W ′ and the circumferential length of the reinforcing part 5 from the groove wall of the lateral groove 4 is W ₁ ′ for the same reason as described above, 0. It is preferable that 1W ≦ W ₁ ′ ≦ 0.3W.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that it includes the tread surface as described above, and any conventionally known material, shape, structure, manufacturing method, etc. can be employed in the present invention.

[Other Embodiments]
Hereinafter, other embodiments of the present invention will be described.

  (1) In the above-described embodiment, an example in which the reinforcing portion 5 provided in a tapered shape is provided around at least one corner of the block 2 located at the intersection of the main groove 3 and the lateral groove 4 is shown. However, as shown in FIG.3 (b), the reinforcement part 5 may be provided in the step shape. In the present embodiment, the reinforcing portion 5 is provided in a columnar shape particularly in a longitudinal sectional view. Thus, it is preferable that the reinforcing portion 5 is provided in a stepped shape because the block rigidity of the corner portion of the block 2 can be further increased. Thereby, since the distortion can be further reduced at the groove bottom portion of the corner portion of the block 2, the rolling resistance of the pneumatic tire can be particularly reduced. Further, the corner portions of the block 2 that are easy to move are reinforced by the reinforcing portions 5 provided in a step shape, and a sufficient contact area is secured at the corner portions of the block 2 when the tire is running. Thereby, the WET braking performance of the pneumatic tire can be particularly improved. In addition, as shown in FIG.3 (b), the boundary part of the step-shaped reinforcement part 5 and the groove wall of the main groove 3 (and horizontal groove 4), and the groove bottom of the reinforcement part 5 and the main groove 3 (and horizontal groove 4) In order to prevent the occurrence of cracks at the boundary portion, the boundary portion is preferably formed in an arc shape having a concave surface.

Here, as shown in FIG. 3 (b), D a groove depth of the main groove 3, if the stepped reinforcing portion 5, a height from the groove bottom of the main groove 3 was set to d _2, 0.2D ≦ It is preferable that d ₂ ≦ 0.8D. If d ₂ is less than 0.2D, the reinforcing effect of the reinforcing part 5 may be insufficient. If d ₂ exceeds 0.8D, the reinforcing effect of the reinforcing part 5 is improved, but the main groove 3 When the groove volume of the tire is reduced and the drainage performance is lowered, the wet braking performance of the pneumatic tire may be deteriorated. Although not shown, when the groove depth of the lateral groove 4 is D ′ and the height of the reinforcing portion 5 from the bottom of the lateral groove groove is d ₂ ′, 0.2D ′ ≦ d for the same reason as described above. ₂ ′ ≦ 0.8D ′ is preferable.

When the groove width of the main groove 3 is W and the length of the reinforcing portion 5 in the width direction from the groove wall of the main groove 3 is W ₂ , the main groove 3 is 0.1W ≦ W ₂ ≦ 0.3W. This is preferable because the groove volume is ensured and the wet braking performance of the pneumatic tire is improved. Further, when the not shown, for the same reason as described above, lateral grooves 4 of the groove width W ', the reinforcing portion 5, a circumferential length from the lateral grooves 4 of the groove wall W _2' was set to 0. It is preferable that 1W ≦ W ₂ ′ ≦ 0.3W.

(2) In the above-described embodiment, the circumferential length of the portion of the reinforcing portion 5 adjacent to the groove wall of the main groove 3 and the widthwise length of the portion adjacent to the groove wall of the lateral groove 4 are set to be approximately equal. In the center region located inside the main groove 3 located on the outermost side in the width direction of the tread surface 1 shown in FIG. 1 and as shown in FIG. When the circumferential direction length of the portion adjacent to the groove wall of the groove 3 is L ₁ and the width direction length of the portion adjacent to the groove wall of the lateral groove 4 is L ₂ , 1.3L ₁ ≦ L ₂ ≦ 3L ₁ Preferably there is. In this case, the rigidity of the corner portion 2 of the block can be particularly increased in the center region of the tread surface 1 while sufficiently securing the groove volumes of the main groove 3 and the lateral groove 4. As a result, the rolling resistance of the pneumatic tire can be further reduced, and in addition, the wet braking performance can be further improved.

(3) Further, in the shoulder region located outside the main groove 3 located on the outermost side in the width direction of the tread surface 1 shown in FIG. 1, as shown in FIG. 4B, the main groove 3 of the reinforcing portion 5. If L ₁ the circumferential length of the portion adjacent to the groove _wall, the widthwise length of the portion adjacent to the lateral groove 4 of the groove wall was L ₂ of, it is 1.3L ₂ ≦ L ₁ ≦ 3L ₂ Is preferred. In this case, it is possible to particularly increase the block rigidity of the corners of the block in the shoulder region of the tread surface 1 while sufficiently securing the groove volumes of the main groove 3 and the lateral groove 4. As a result, the rolling resistance of the pneumatic tire can be further reduced, and in addition, the wet braking performance can be further improved.

  (4) In the above-described embodiment, the tread surface 1 is provided with the block 2 partitioned by the main groove 3 extending in the circumferential direction and the lateral groove 4 extending intersecting the main groove 3. As shown in FIG. 5, ribs 6 defined by two main grooves 3 may be provided on the tread surface 1. In this case, the reinforcing portion 5 is formed in at least one of the corners of the rib located at the intersection of the main groove 3 and the lateral groove 4 that is open to one main groove 3 and closed to the other main groove 3. It is installed around.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, each performance evaluation of the tire was performed as follows.

(1) Rolling resistance Using a test tire (tire size: 195 / 65R15), the rolling resistance measured in the drum running test was evaluated as an index. The rolling resistance of Comparative Example 1 is indexed as 100, and the smaller the index is, the lower the rolling resistance is. The running conditions were as follows: drum diameter = 1.7 m, camber angle = 0 °, air pressure = 210 kPa, speed = 80 km / h, load = 4300 N.

(2) WET braking performance After assembling the test tire (tire size: 195 / 65R15) to the rim (15 * 6-JJ), it is filled with internal pressure of 210 kPa and mounted on an actual vehicle (domestic 4-door sedan). The vehicle traveled on a wet road surface (WET road surface) under the load condition of the ride, traveled at a speed of 100 km / h, and then applied a brake to measure the braking distance. The braking performance is indexed with the reciprocal of the braking distance of Comparative Example 1 being 100, and the larger the index, the better the WET braking performance.

Comparative Example 1
In the pneumatic tire provided with the tread surface 1 shown in FIG. 1, the groove width of the main groove 3 is 8 mm, the groove depth is 8 mm, the groove width of the lateral groove 4 is 5 mm, and the groove depth is 7 mm. A pneumatic tire was manufactured in which no reinforcing portion was provided at the corner of the block 2 located at the intersection of the horizontal groove 4 and the horizontal groove 4. Table 1 shows the results of the above performance evaluations using such tires.

Comparative Example 2
The pneumatic tire having the tread surface 1 shown in FIG. 1 has the same configuration as that of Comparative Example 1 except that a bottom raised portion having a groove depth of 4 mm is provided at the entire intersection portion of the main groove 3 and the lateral groove 4. A pneumatic tire was manufactured. Table 1 shows the results of the above performance evaluations using such tires.

Comparative Example 3
In the pneumatic tire provided with the tread surface 1 shown in FIG. 1, the main groove starts from only the groove wall of the main groove 3 at all corners of the block 2 located at the intersections of the main groove 3 and the lateral grooves 4. A pneumatic tire having the same configuration as that of Comparative Example 1 was manufactured, except that a reinforcing portion terminating at the groove bottom on the block side facing the three center lines was provided. Table 1 shows the results of the above performance evaluations using such tires.

Example 1
In the pneumatic tire provided with the tread surface 1 shown in FIG. 1, the taper-shaped reinforcing part 5 shown in FIG. 3A is provided at all corners of the block 2 located at the intersections of the main groove 3 and the lateral groove 4. The circumferential length of the reinforcing portion 5 is 1.5 mm from the groove wall of the main groove 3, the height from the groove bottom of the main groove 3 is 3 mm, and the circumferential length from the groove wall of the lateral groove 4. Was set to 1.5 mm, and the height of the horizontal groove 4 from the groove bottom was set to 3 mm. A pneumatic tire having the same configuration as Comparative Example 1 was manufactured. Table 1 shows the results of the above performance evaluations using such tires.

Example 2
In the pneumatic tire provided with the tread surface 1 shown in FIG. 1, the step-shaped reinforcing portions 5 shown in FIG. 3B are provided at all corners of the block 2 located at the intersections of the main grooves 3 and the lateral grooves 4. The circumferential length of the reinforcing portion 5 from the groove wall of the main groove 3 is 1 mm, the height from the groove bottom of the main groove 3 is 5 mm, and the circumferential length from the groove wall of the lateral groove 4 is 1 mm. A pneumatic tire having the same configuration as Comparative Example 1 was manufactured except that the height of the lateral groove 4 from the groove bottom was set to 5 mm. Table 1 shows the results of the above performance evaluations using such tires.

Example 3
In the center region located inside the main groove 3 located on the outermost side in the width direction of the tread surface 1 shown in FIG. 1, all the corners of the block 2 located at the intersection of the main groove 3 and the lateral groove 4 are 3 (b) is provided around the step-shaped reinforcing portion 5, and as shown in FIG. 4 (a), the circumferential length of the portion of the reinforcing portion 5 adjacent to the groove wall of the main groove 3 is L ₁ , If the widthwise length of the portion adjacent to the lateral groove 4 of the groove walls and _{L 2, L 1} = _1mm, except for setting the _{L 2 = 2mm (L 2 =} 2L 1), the same configuration as Comparative example 1 A pneumatic tire was manufactured. Table 1 shows the results of the above performance evaluations using such tires.

Example 4
In the shoulder region located outside the main groove 3 located on the outermost side in the width direction of the tread surface 1 shown in FIG. 1, all the corners of the block 2 located at the intersection of the main groove 3 and the lateral groove 4 are 3 (b) is provided around the step-shaped reinforcing portion 5 and, as shown in FIG. 4 (b), the circumferential length of the portion of the reinforcing portion 5 adjacent to the groove wall of the main groove 3 is L ₁ , If the widthwise length of the portion adjacent to the lateral groove 4 of the groove walls and _{L 2, L 1} = _2mm, except for setting the _{L 2 = 1mm (L 1 =} 2L 2), the same configuration as Comparative example 1 A pneumatic tire was manufactured. Table 1 shows the results of the above performance evaluations using such tires.

  From the results in Table 1, it can be seen that in the pneumatic tires of Examples 1 to 4, the rolling resistance is reduced while maintaining the WET braking performance better than the pneumatic tire of Comparative Example 1. On the other hand, in the pneumatic tire of Comparative Example 2, since the entire intersection part of the main groove 3 and the lateral groove 4 is raised, the groove volume at the intersection part is reduced, and compared with the pneumatic tires of Examples 1 to 4. It can be seen that the WET braking performance deteriorates. Moreover, in the pneumatic tire of Comparative Example 3, the rolling resistance increases and the WET braking performance tends to be inferior as compared with the pneumatic tires of Examples 1 to 4.

Schematic development view of a tread pattern showing one embodiment of a pneumatic tire according to the present invention Enlarged schematic plan view of FIG. (A) And (b) is II sectional view taken on the line in FIG. The enlarged schematic plan view of the tread pattern which shows another embodiment of the pneumatic tire which concerns on this invention. The enlarged schematic plan view of the tread pattern which shows another embodiment of the pneumatic tire which concerns on this invention.

Explanation of symbols

1: Tread surface 2: Block 3: Main groove 4: Horizontal groove 5: Reinforcement portion 6: Rib

Claims (4)

In the pneumatic tire provided with a main groove extending in the circumferential direction on the tread surface, a lateral groove extending across the main groove, and a block or a rib partitioned by them,
At least one corner of the block or rib positioned at the intersection of the main groove and the lateral groove is provided with a reinforcing portion, and the reinforcing portion starts from a groove wall between the main groove and the horizontal groove and is grooved. A pneumatic tire characterized by terminating at the bottom.   The pneumatic tire according to claim 1, wherein the reinforcing portion is provided in a step shape. In the center region located on the inner side of the main groove located on the outermost side in the width direction of the tread surface, the circumferential length of a portion of the reinforcing portion adjacent to the groove wall of the main groove is L ₁ , 3. The pneumatic tire according to claim ₁ , wherein 1.3 L ₁ ≦ L ₂ ≦ 3L ₁ when a width direction length of a portion adjacent to the groove wall is L ₂ . In the shoulder region located outside the main groove located on the outermost side in the width direction of the tread surface, the circumferential length of a portion of the reinforcing portion adjacent to the groove wall of the main groove is L ₁ , If the widthwise length of the portion adjacent to the groove walls was _{L 2,} pneumatic tire according to claim 1 is _{1.3L 2 ≦ L 1 ≦ 3L 2} .

Images