JP2012171590A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire for improving wear resistance and developing high-level heating durability on and after a medium-end stage of wear.SOLUTION: The pneumatic tire includes a tread which is provided with a plurality of blocks 3 defined and formed by a plurality of cross grooves 22 and peripheral grooves, and connection portions 4 connecting two peripherally adjacent blocks 3 to each other, and each having a tire-radial height TH from a groove bottom 22a of the cross groove 22 lower than a tire-radial height BH of the block from the groove bottom 22a of the cross groove. The connection portions 4 have recesses 5 in at least one-side faces facing the cross groove 22.

Description

  The present invention relates to a pneumatic tire, specifically, a tread portion, a plurality of blocks defined by a plurality of widthwise grooves and circumferential grooves, and a width connecting two blocks adjacent in the circumferential direction. This relates to a pneumatic tire having a connecting portion in which the height in the tire radial direction from the groove bottom of the directional groove is lower than the height in the tire radial direction from the groove bottom of the width direction groove of the block. The present invention proposes a tire capable of improving the heat resistance and exhibiting high heat durability even after the middle stage of wear.

  Conventionally, improved wear resistance performance of pneumatic tires with treads divided into multiple blocks by main grooves, especially heavy-duty pneumatic radial tires mounted on heavy-duty vehicles such as trucks and buses In order to achieve this, a connecting portion (tie bar) that connects two adjacent blocks is lower in the tire radial direction from the bottom of the main groove than in the tire radial direction from the bottom of the main groove of the block. There is something that provided.

  When two adjacent blocks are connected with a connecting portion, the connected blocks support each other and increase the rigidity of the blocks in the connecting direction. Thereby, the wear resistance of the tire can be improved.

  However, when such a connecting portion is provided between the blocks, the heat radiation area of the block in the tread surface of the pneumatic tire is reduced, so that the rubber forming the block is heated to a high temperature when the tire is rolling. There is a problem that the heat generation durability of the pneumatic tire is impaired.

  On the other hand, for example, in Patent Document 1, “By providing a plurality of longitudinal main grooves extending in the tire circumferential direction in the tread portion, the tread portions are arranged between the longitudinal main grooves and between the longitudinal main grooves and the tread edges. In addition to being divided into rib-shaped land portions in between, at least one rib-shaped land portion is provided with a transverse groove that divides the rib-shaped land portion into a plurality of blocks arranged in the circumferential direction by extending across the rib-shaped land portion Side wall surfaces of both sides of the pneumatic tire, wherein siping is arranged on the outer surface of the block, and the lateral groove rises from the lateral groove bottom surface of the lateral groove and extends in a direction intersecting the lateral groove width center line of the lateral groove And a tie bar that connects between adjacent blocks in the circumferential direction, and the tie bar has a direction in which the side wall surface extends. length By providing one or more concave grooves extending in the direction, at least an upper part of the tie bar is provided with a plurality of rib-shaped convex parts divided by the concave grooves, and the tie bar has a lower end edge of the side wall surface. The tie bar width Lw, which is the distance along the horizontal groove width center line, is 0.5 to 1.5 times the horizontal groove width Wy of the horizontal groove, and along the horizontal groove width center line on the upper surface of the rib-shaped convex portion. Pneumatic tire characterized in that the convex portion width Tw is 0.15 to 0.3 times the tie bar width Lw. According to this, “at least the upper part of the tie bar is A plurality of rib-shaped protrusions are formed which are divided by the groove, and the rib-shaped protrusions extend in the length direction of the tie bar, so that, for example, the length direction of the horizontal groove (the direction of the horizontal groove width center line) Compared to the case of extending in the direction, It is possible to effectively increase the circumferential rigidity and lateral rigidity of the row of racks, and to suppress the decrease in the groove volume of the lateral grooves caused by the tie bars by forming the concave grooves, thereby reducing the performance on snow. It is possible to improve steering stability, wear resistance, and uneven wear resistance on dry road surfaces while minimizing them. "

  In addition, as described above, when a concave groove is provided on the upper surface of the tie bar, an increase in the heat radiation area due to the formation of the concave groove exerts an air cooling effect, thereby improving the heat generation durability of the pneumatic tire in the early wear stage I can say that.

  However, in the above pneumatic tire, the concave groove provided on the upper surface of the tie bar disappears early with the wear of the tire, so that the heat generation durability of the pneumatic tire after the middle stage of wear should be ensured. I can't.

  In addition, in order to exhibit the heat generation durability of the pneumatic tire even after the middle stage of wear, it is necessary to provide a groove having a depth reaching the lower part of the tie bar. In this case, the rigidity of the tie bar is remarkably lowered, and the tie bar cannot perform its original function, so that the wear resistance of the tire is inevitably lowered.

  Therefore, in order to achieve both high wear resistance and heat generation durability after the middle stage of wear at a high level, the above method is not sufficient, and a more detailed design is required.

JP 2009-227154 A

  Therefore, in view of the above problems, an object of the present invention is to provide a pneumatic tire capable of exhibiting high heat generation durability even in the middle and later stages of wear, in addition to improving wear resistance.

The gist configuration of the present invention for solving the above problems is as follows.
The pneumatic tire according to the present invention includes a plurality of blocks defined by a plurality of widthwise grooves and a circumferential groove in a tread portion, and the widthwise grooves that connect two blocks adjacent to each other in the circumferential direction. A pneumatic tire comprising a connecting portion having a height in the tire radial direction from the groove bottom of the block that is lower than a height in the tire radial direction from the groove bottom of the widthwise groove of the block,
The connecting portion has a recess that can be a shallow groove, for example, on at least one side surface facing the width direction groove.

  Preferably, two or more concave portions are provided on each side of the connecting portion facing the width direction groove.

  Preferably, the depth of the concave portion is in a range of 10 to 30% of the height in the tire radial direction of the connecting portion.

  Here, the “depth of the concave portion” refers to the distance from the opening of the concave portion to the bottom of the concave portion.

  In the place described in any one of Claims 1-3, Preferably, the sum total of the opening area of each recessed part in each side surface which faces the said width direction groove | channel of the said connection part is 50% or less of the area of the said side surface. To do.

  In the place described in any one of Claims 1-4, Preferably, the said recessed part is extended and provided in the connection direction of the said block.

  Here, with respect to the shallow groove, “extending in the connecting direction of the blocks” means that the concave portion extends across both blocks connected by the connecting portion.

In the place described in any one of Claims 1-5, Preferably, the said recessed part is bent and provided.
The “bending” includes a so-called zigzag shape, a wave shape, and the like.

  The pneumatic tire of the present invention is characterized in that a concave portion is provided on at least one side surface facing the groove in the width direction of the connecting portion, and this concave portion reduces the heat radiation area of the tread portion without impairing the rigidity of the connecting portion. Since it can be increased, the wear resistance and heat generation durability of the pneumatic tire can be made sufficiently compatible.

  Moreover, in this pneumatic tire, since the concave portion is provided on the side surface of the connecting portion, the concave portion does not disappear due to wear of the tire unlike the conventional pneumatic tire described in Patent Document 1. Therefore, the heat radiation area of the tread portion can be effectively ensured even after the middle stage of wear, and the heat generation durability of the tire can be exhibited for a long term.

In such a pneumatic tire, the greater the number of concave portions provided on the side surface of the connecting portion, the more the heat dissipation effect by the concave portions is improved.
Therefore, in the pneumatic tire of the present invention, when two or more concave portions are provided on each side face facing the width direction groove of the connecting portion, the heat generation durability of the tire can be improved more effectively.

  Further, in the pneumatic tire of the present invention, when the depth of the recess is in the range of 10 to 30% of the height in the tire radial direction of the connecting portion, the heat dissipation effect by the recess and the rigidity of the connecting portion are As a result, both the heat generation durability and the wear resistance of the tire are better balanced.

  In addition, when the depth of the recess is less than 10% of the height in the radial direction of the connecting portion, there is a small increase in the heat dissipation area due to the recess, and thus there is a possibility that the effect of improving the heat generation durability cannot be obtained sufficiently. On the other hand, if this is deeper than 30% of the height in the radial direction of the connecting portion, the rigidity of the connecting portion may not be sufficiently secured, and the wear resistance performance of the tire may be deteriorated. There is also a risk that the tearing performance and stone biting resistance will be reduced.

  Further, in the tire described above, if the total opening area of each recess in each side surface facing the width direction groove of the connection portion is 50% or less of the area of the side surface, the rigidity of the connection portion is maintained better. Is done.

  In addition, when the opening area of each recessed part is made larger than 50% of the area of the said side surface, there exists a possibility that the abrasion resistance of a tire may fall by impairing the rigidity of a connection part.

In the pneumatic tire of the present invention, when the concave portion is provided along the connecting direction of the blocks, that is, along the extending direction of the connecting portion extending in the circumferential direction, each land portion partitioned on the side surface of the connecting portion by the concave portion is provided. Because the land portion is continuous between both adjacent blocks, the land portion supports both blocks evenly in the connecting direction. As a result, uneven wear due to local distortion of the block surface is prevented. And the rigidity fall of the block connection direction by the recessed part of the said connection part is suppressed.
Thereby, the heat dissipation effect can be obtained more effectively while maintaining the wear resistance of the pneumatic tire.

  In the pneumatic tire of the present invention, when the concave portion is bent, the amount of expansion of the heat radiation area due to the provision of the shallow groove is further increased, so that the heat generation durability of the pneumatic tire is more effectively achieved. Can be improved.

(A) is an expansion | deployment top view which shows one Embodiment of the pneumatic tire of this invention about a tread pattern about the half part, (b) is sectional drawing which follows the AA line of (a). It is a partial expanded sectional view of the connection part of FIG.1 (b). (A) is a BB arrow line view which shows the block and connection part of the tread part of the pneumatic tire of FIG. 1 (a), (b) is a figure which shows the other example of a connection part. (C) is a figure which shows the further another example of a connection part. (A) is an expansion | deployment top view which shows the tread pattern of the conventional pneumatic tire about the half part, (b) is sectional drawing which follows the CC line of (a).

Hereinafter, the present invention will be described in detail with reference to the drawings.
In the place shown in FIG. 1A, the pneumatic tire of the present invention has, in the tread portion 1, five circumferential grooves 21 extending along the tire circumferential direction, and a width extending in a direction crossing the equator plane of the tire. A plurality of blocks 3 are provided by a main groove 2 including a lateral groove 22 as a directional groove, and the plurality of blocks 3 that are partitioned on the outermost side in the tire width direction and are adjacent to each other in the tread circumferential direction are the main grooves 2. The tire radial height from the groove bottom (in the illustrated example, the groove bottom 22a of the lateral groove 22) (hereinafter sometimes simply referred to as "tire radial height") is greater than the height of the block 3 in the tire radial direction. Also, the adjacent portions in the circumferential direction are connected by the lower connecting portion 4.

  In the illustrated example, each block 3 of the tread portion 1 has a narrow groove 6 extending in a direction crossing the block 3 in the tire width direction and having a smaller width and depth than the main groove 2. Here, the narrow groove 6 is provided, for example, to improve the drainage performance of the tire.

  Here, in the pneumatic tire of the present invention, as shown in FIG. 1B, the connecting portion 4 has a recess, for example, a shallow groove, on at least one side surface facing the main groove 2 (in the illustrated example, the lateral groove 22). It is important to have 5.

  According to this, as in the conventional pneumatic tire shown in FIGS. 4A and 4B, the shallow groove 305 provided on the upper surface of the connecting portion 304 does not disappear early due to wear. A good heat dissipation effect can be obtained even after the middle stage of wear.

The tread pattern of the conventional pneumatic tire shown in FIGS. 4A and 4B is the same as that of the pneumatic tire of the present invention shown in FIGS. Same as tread pattern.
In the example shown in FIGS. 1A and 1B, three shallow grooves are provided on both side surfaces facing the lateral groove 22 of the connecting portion 4, but in the present invention, either one of the two side surfaces is provided. You may provide only in either.

Further, as shown in FIG. 2 in which the connecting portion 4 is partially enlarged, the depths d ₁ to d ₃ of the respective shallow grooves 5 are in the range of 10 to 30% of the height TH in the tire radial direction of the connecting portion 4. The specific numerical value is preferably, for example, about 2 to 3 mm.

  Each shallow groove 5 shown in FIG. 2 extends linearly in a direction along the connecting direction of the blocks 3, that is, the circumferential direction of the tire, as shown in FIG. A land portion 7 that is continuous in the three connecting directions is formed. Since this land part 7 supports both the blocks 3 in a connection direction, the fall of the tire circumferential direction rigidity of the connection part 4 is suppressed.

Further, in the above case, the widths w _{1 to} w ₃ of the respective shallow grooves 5 are set such that the total opening area of the respective shallow grooves 5 in the side surface of the connecting portion 4 is 50% or less of the area of the side surface. It is preferable to adjust appropriately. For example, when three shallow grooves 5 as shown in the drawing are provided on the side surface of the connecting portion having a height TH of 15.5 mm, the widths w _{1 to} w ₃ of each shallow groove 5 are about 2 to 3 mm. It is preferably set.

  In the pneumatic tire of the present invention, the form of the arrangement of the shallow grooves 5 provided on the side surface of the connecting portion 4 is not limited to the form shown in FIG. As shown in FIG. 3, the shallow groove 105 can be provided in the radial direction of the tire, or as shown in FIG. 3C, the shallow groove 105 can be provided by being bent in a wavy shape in the direction along the circumferential direction of the tire. In any form, it is possible to obtain the effect of improving the heat generation durability expected by the present invention.

  In particular, as shown in FIG. 3C, when the shallow groove 205 is bent, the amount of expansion of the heat radiation area due to the provision of the shallow groove 205 is further increased. Can be improved.

According to the configuration of the tread pattern shown in FIG. 1 (a), the tire size 315 / of three patterns in which the configuration of shallow grooves provided in the connecting portion is different as shown in FIGS. 3 (a) to 3 (c). Pneumatic radial tires for 80R22.5 trucks and buses were manufactured, and these were designated as inventive tires 1 to 3, respectively.
Here, three shallow grooves are provided on the side surfaces of each connecting portion on both sides in the tire width direction.

Details of these tires are as follows.
Number of circumferential grooves: 5, tire outer diameter: 1092 mm, main groove depth (block height BH): 21.1 mm, connecting portion width: 20.0 mm, connecting portion height TH: 15. 5 mm, shallow groove depth d ₁ to d ₃ : 2.0 to 3.0 mm, shallow groove width w _{1 to} w ₃ : 2.0 to 3.0 mm.

  Next, according to the structure of the tread pattern shown in FIG. 4A, a pneumatic radial tire for trucks and buses having the same size as the tires 1 to 3 of the invention is formed without providing the shallow groove 305 in the connecting portion 304. This was manufactured as a conventional tire 1.

The details of the conventional tire 1 are as follows.
Number of circumferential grooves: 5, tire outer diameter: 1092 mm, main groove depth (block height BH): 21.1 mm, connecting part width: 15.0 mm, connecting part height TH: 15. 5 mm.

Each of the inventive tires 1 to 3 and the conventional tire 1 thus obtained was mounted on a rim having a rim size of 8.50 22.5, and the internal pressure was set to 825 kPa. Each was evaluated. Table 1 shows the evaluation results.
The heat generation durability and the circumferential rigidity of the block are shown in Table 1 as index values with the conventional tire 1 being 100, and the larger the value, the better the performance.

  Here, the heat generation durability was measured by performing a heat generation endurance drum test on the tire of the size described above.

  Further, the circumferential rigidity of the block was measured by simulation by creating a pattern shape with FEM and inputting a shearing force acting on the block.

  From the results shown in Table 1, the inventive tires 1 to 3 satisfying the configuration of the present invention have improved heat generation durability with almost no decrease in circumferential rigidity compared to the conventional tire 1. Recognize.

  In particular, the inventive tires 1 and 3 in which the narrow grooves are provided along the circumferential direction are less deteriorated in the circumferential rigidity than the inventive tire 2, and in particular, the inventive tire 3 in which the narrow grooves are wavy. Excellent results were obtained for both heat generation durability and circumferential rigidity.

C Tire Equatorial Surface 1 Tread Part 2 Main Groove 21 Circumferential Groove 22 Lateral Groove 22a Lateral Groove Bottom 3 Block 4 Connecting Part 5 Shallow Groove 6 Narrow Groove 7 Land Part TH Connecting Part Height BH Block Height d ₁ to d ₃ shallow groove depth w ₁ to w ₃ shallow groove width

Claims (6)

The tire radial direction from the groove bottom of the width direction groove that connects the plurality of blocks defined by the width direction groove and the circumferential direction groove to the tread portion and the two blocks adjacent to each other in the circumferential direction. A pneumatic tire comprising a connecting portion whose height is lower than the height in the tire radial direction from the groove bottom of the width direction groove of the block,
The pneumatic tire according to claim 1, wherein the connecting portion has a recess on at least one side surface facing the widthwise groove.   The pneumatic tire according to claim 1, wherein the connecting portion has two or more concave portions on each side faced to the width direction groove.   The pneumatic tire according to claim 1 or 2, wherein a depth of the concave portion is in a range of 10 to 30% of a height in a tire radial direction from a groove bottom of the width direction groove of the connecting portion.   The pneumatic tire according to any one of claims 1 to 3, wherein the total opening area of the recesses in each side surface facing the width direction groove of the connecting portion is 50% or less of the area of the side surface.   The pneumatic tire according to claim 1, wherein the recess extends in a connecting direction of the blocks. The pneumatic tire according to claim 1, wherein the recess has a bent shape.

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