JP5254760B2 - tire - Google Patents

Description

  The present invention relates to a tire in which a center block row is formed in a tread portion, and more particularly to a tire optimal for trucks and buses.

  The lug pattern of TBR tires (truck / bus tires) is generally a pattern assumed mainly for off-road use (assuming 90% to 100% off-road use) Often). For this reason, the pattern shape is set with a focus on driving performance on bad roads, that is, cut resistance, tear resistance, and grip performance on slippery and mud road surfaces (for example, Patent Document 1).

However, in recent years, the road network between major cities has been considerably improved even in developing countries where development is particularly remarkable, and even the off-road tires such as lag patterns are generally formed on asphalt roads. Opportunities to drive on-road such as roads and highways are increasing. When the vehicle travels on a general road or highway in this way, the amount of heat generated due to an increase in travel speed increases, and drainage performance may be insufficient when traveling in rainy weather. For this reason, even with a lug pattern tire, improvement in durability against heat generation (hereinafter referred to as heat generation durability) and improvement in drainage properties have been demanded.
JP 2001-55017 A

  By the way, a belt leave belt (BLB) in which a belt provided on the inner side in the tire radial direction of the tread portion is peeled off due to heat generated by traveling is conventionally known. This phenomenon is likely to occur in a tire having a tread pattern in which a block is formed in the tire center portion and heat is easily generated in the tire center portion due to a change in ground pressure due to traveling. This has been a particular problem when TBR tires are mounted to increase the on-road running speed.

  For this reason, various improvements of the tread pattern have been conventionally performed. For example, Patent Document 1 discloses that the center block is formed with a closed groove, that is, a groove whose both ends are closed in the center block, thereby suppressing heat generation and improving durability (heat generation durability). Yes. However, further improvement in heat generation durability and drainage is desired in the market.

  In view of the above facts, an object of the present invention is to provide a tire having further improved heat generation durability and drainage.

According to the first aspect of the present invention, a center block row is formed in the tread portion by the circumferential groove and the lateral groove, and the block constituting the center block row has a lateral groove adjacent to one side in the tire circumferential direction of the block. A block groove having an opening at one end and an opening at the other end is formed in a lateral groove adjacent to the other side in the tire circumferential direction of the block. The opening position of the other end of the block groove is the other end position in the circumferential direction of the block .

In the first aspect of the present invention, in this way, block grooves that open to the lateral grooves on both sides in the tire circumferential direction are formed in the blocks constituting the center block row. Therefore, the heat radiation area of the block is increased, the fluctuation of the ground pressure distribution of the block is suppressed, and the ground pressure is relieved. Moreover, drainage is improved by opening to the lateral groove.
Furthermore, a block groove can be formed over the entire circumferential width of the block, and the above-described effects can be more remarkably exhibited.

In the invention according to claim 2, the groove depth of the block groove is shallower than the circumferential groove and the lateral groove adjacent to the center block row.
Thereby, even if the block groove is formed, it is easy to suppress a decrease in block rigidity and wear resistance.

According to a third aspect of the present invention, the block has a shape having a step in the tire circumferential direction, and is formed in a crank shape so as to have a step in the tire circumferential direction along the step of the block . .
Thereby, the effect of Claim 1 can be exhibited more remarkably.

In a fourth aspect of the present invention, the tread pattern formed in the tread portion is a lag pattern.
As a result, it is possible to increase the heat radiation area of the block and suppress the fluctuation of the ground pressure distribution of the block to alleviate the ground pressure while maintaining the off-road performance of the lag pattern.

  According to the present invention, it is possible to realize a tire with further improved heat generation durability and drainage performance.

  Hereinafter, a truck / bus tire is taken as an example as an embodiment, and an embodiment of the present invention will be described. In the second and subsequent embodiments, the same components as those already described are denoted by the same reference numerals, and description thereof is omitted.

[First Embodiment]
First, the first embodiment will be described. As shown in FIG. 1, the pneumatic tire 10 according to the present embodiment includes a carcass 12 whose both ends are folded at bead cores 11 </ b> C of bead portions 11.

  A belt layer 14 is embedded outside the crown portion 12C of the carcass 12 in the tire radial direction. In this embodiment, the belt layer 14 is composed of a total of three belts, that is, one belt 14A, two belts 14B, and three belts 14C.

  A tread portion 18 having grooves is formed on the outer side of the belt layer 14 in the tire radial direction. As shown in FIG. 2, the tread portion 18 has a lug pattern formed as a tread pattern, and the circumferential grooves 22L and 22R formed on both sides of the tire equatorial plane CL and the circumferential grooves 22L and 22R Lug grooves 24L and 24R extending outward in the width direction are formed. The lug groove 24 </ b> L and the lug groove 24 </ b> R are connected by a connection groove (lug groove) 26 that is a lateral groove shallower than the circumferential groove 22 and the lug groove 24. With this configuration, a center block row 30 through which the tire equatorial plane CL passes and shoulder block rows 32L and 32R on both sides of the center block row 30 in the tire width direction are formed in the tread portion 18.

  The end portions of the lug grooves 24L, 24R extend beyond the tread end T so as to be drainable outward in the tire width direction. Here, the tread end means that a pneumatic tire is mounted on a standard rim specified in JATMA YEAR BOOK (2008 edition, Japan Automobile Tire Association Standard), and the maximum load in the applicable size and ply rating in JATMA YEAR BOOK. Fills 100% of the air pressure (maximum air pressure) corresponding to the capacity (internal pressure-load capacity correspondence table) as the internal pressure, and indicates the outermost contact portion in the tire width direction when the maximum load capacity is applied. In addition, when TRA standard and ETRTO standard are applied in a use place or a manufacturing place, it follows each standard.

  Each block 34 constituting the center block row 30 is formed with an extending portion 36L that extends outward in the tire circumferential direction, that is, on the lower side in the drawing, at the lower left portion of the drawing in FIG. Each block 34 is formed with an extending portion 36R extending in the tire circumferential direction outer side, that is, on the upper side of the paper, in the upper right portion of the paper in FIG. 2, and the block 34 has a point-symmetric shape.

  Each block 34 is formed with a shallow groove 40 that is shallower than the connecting groove 26. In the present embodiment, the shallow grooves 40 are linear along the tire circumferential direction U and are formed at positions where the tire equatorial plane CL passes. One end 40P of the shallow groove 40 is open to the connecting groove 26R adjacent to one side in the tire circumferential direction of the block 34 (the lower side in the drawing in FIG. 2). The other end 40Q of the shallow groove 40 is open to the connecting groove 26L adjacent to the other side in the tire circumferential direction of the block 34 (the upper side in the drawing in FIG. 2).

  As described above, in this embodiment, each block 34 constituting the center block row 30 is formed with the shallow grooves 40 that are open at both ends in the connecting grooves 26L on both sides in the tire circumferential direction. Therefore, since the surface area of each block 34 increases, the cooling area (heat radiation area) by outside air increases. Then, fluctuations in the ground pressure distribution of each block 34 are suppressed, and the ground pressure is relaxed at the center block row 30 where the ground pressure is highest, so that heat input due to rubber compression is reduced. Therefore, since the tread portion 18 is efficiently cooled and the temperature rise is suppressed, generation of BLB can be suppressed.

  And since the shallow groove | channel 40 opened to the connection groove | channel 26L is formed in this way, the drainage property is improving. Furthermore, since the shallow groove 40 is linear along the tire circumferential direction U, drainage easily passes through the shallow groove 40, and the effect of improving drainage is remarkable.

  The tread pattern formed on the tread portion 18 is a lag pattern. As a result, it is possible to increase the heat radiation area of each block 34 and suppress the fluctuation of the ground pressure distribution of each block 34 to alleviate the ground pressure while maintaining the off-road performance of the lag pattern. .

  The width W (see FIG. 2) of the shallow groove 40 is preferably in the range of 10 to 20 mm. When it is narrower than 10 mm, the effects of increasing the heat radiation area, reducing the ground pressure, and improving drainage as described above are small. On the other hand, if the width is larger than 20 mm, the block rigidity and wear resistance are likely to be lowered.

  And it is preferable that the depth d (refer FIG. 1) of the shallow groove 40 is the range of 5-10 mm. If it is shallower than 5 mm, the effect of increasing the heat radiation area, reducing the ground pressure, and improving drainage is small. On the other hand, if it is larger than 10 mm, the block rigidity and wear resistance are likely to be lowered.

  Note that this preferable range of the width W and the depth d of the shallow groove 40 takes into consideration the performance in the conventional lug pattern (performance such as life and not becoming the core of the tear) and the heat radiation area of the block 34. Range.

[Second Embodiment]
Next, a second embodiment will be described. As shown in FIG. 3, in the pneumatic tire according to this embodiment, the shape of the shallow groove 50 formed in the tread portion is different from that of the first embodiment.

  The shallow groove 50 is linear. The opening position of the one end 50P of the shallow groove 50 is the outermost position on one side in the circumferential direction of the block, that is, the outermost position EL in the tire circumferential direction of the extending portion 36L. Furthermore, the opening position of the other end 50Q of the shallow groove 50 is the outermost position on the other side in the circumferential direction of the block, that is, the outermost position ER in the tire circumferential direction of the extending portion 36R.

  Thereby, the shallow groove | channel 50 can be formed over the circumferential direction full width of a block, and the effect by 1st Embodiment can be show | played more notably.

[Third Embodiment]
Next, a third embodiment will be described. As shown in FIG. 4, in the pneumatic tire according to the present embodiment, the shape of the shallow groove 60 formed in the tread portion is different from that in the first embodiment or the second embodiment.

  In the present embodiment, the opening position of one end 60P and the opening position of the other end 60Q of the shallow groove 60 are the same as the shallow groove 50 of the second embodiment, but the shallow groove 60 is a tire along the step shape of the block. It is shaped like a crank so as to have a step in the circumferential direction U.

  The shallow groove 60 includes a first groove portion 60L, a second groove portion 60R, and a central groove portion 60C. The first groove portion 60L extends from the tire circumferential direction outermost position EL to the circumferential center position of the block along the block wall 60L adjacent to the circumferential groove 22L. The second groove portion 60R extends from the tire circumferential direction outermost position ER to the block circumferential center position along the block wall 60R adjacent to the circumferential groove 22R. The central groove 60C extends in the tire width direction so as to connect the end of the first groove 60L and the end of the second groove 60R.

  According to this embodiment, the effect by 1st Embodiment can be show | played more notably than 2nd Embodiment.

  As shown in FIGS. 5 and 6, the belt end of the belt layer 14 is positioned on the inner side in the tire radial direction of the shoulder block row 30, and on the tread side of the shoulder block rows 32 </ b> L and 32 </ b> R, A shallow groove 70 may be further formed at a position facing the outer side in the tire radial direction from the belt disposed on the outermost side in the tire radial direction (that is, the belt end 14T of the three belts 14C). Thereby, the effect which suppresses generation | occurrence | production of BES (belt end separation) can also be show | played together, and the heat_generation | fever durability as the whole tire can further be improved. Further, even if the shallow groove 70 is formed in the first embodiment or the second embodiment, the same effect can be obtained.

<Test example>
In order to confirm the effect of the present invention, the inventor has an example of the pneumatic tire 10 of the first embodiment (hereinafter referred to as a tire of Example 1) and an example of the pneumatic tire of the second embodiment (hereinafter, implementation). Example 2), an example of the pneumatic tire of the third embodiment (hereinafter referred to as the tire of Example 3), and two examples of conventional pneumatic tires (hereinafter referred to as Conventional Example 1 tire, Conventional Example 2). The tire was prepared and a performance test was conducted to evaluate the performance.

Here, as shown in FIG. 7, the tire of Conventional Example 1 is a tire in which shallow grooves are not formed as compared with the tire of Example 1. Further, as shown in FIG. 8, the tire of Conventional Example 2 is a tire in which closed grooves 90 whose both ends are closed in the block are formed instead of the shallow grooves 40 as compared with the tire of Example 1.
Further, in this test example, the tires are all bus / truck tires, and the tire sizes are all “315/80 R225”.

  In this test example, all tires were set to normal internal pressure after being incorporated into normal rims. Here, “regular rim” means, for example, a standard rim in the applicable size specified in the 2008 edition YEAR BOOK issued by JATMA, and “normal load” and “regular internal pressure” are similarly issued by JATMA. This refers to the maximum load in the applicable size and ply rating defined in the 2008 YEAR BOOK and the air pressure for the maximum load. When the TRA standard or ETRTO standard is applied at the place of use or manufacturing, the respective standards are followed.

  For each tire, a drum running test was conducted for heat generation durability, and BLB (belt leave belt) was examined. Regarding drainage, the critical speed of high pressure generation when passing through a wet road surface with a water depth of 5 mm was evaluated by the feeling of the driver.

  The performance index in the tire of Conventional Example 1 was set as the evaluation index 100 for any of the heat generation durability and drainage performance, and the evaluation index for relative evaluation was calculated for the other tires. The evaluation results are shown in Table 1. The evaluation results in Table 1 indicate that the higher the evaluation index, the higher the performance, that is, the better the heat generation durability and drainage.

表１から判るように、発熱耐久性（ＢＬＢ）に関しては、ブロックに溝が形成されていない従来例１のタイヤに比べ、ブロックに閉鎖溝が形成された従来例２のタイヤのほうがＢＬＢが発生し難い（すなわち発熱耐久性が優れている）という結果になった。更に、従来例１、２のタイヤと実施例１のタイヤとで評価指数を比較することにより、センターブロック列３０を構成する各ブロック３４に、タイヤ周方向両側のラグ溝２４Ｌ、２４Ｒに開口する浅溝４０を形成したほうがＢＬＢが発生し難いという結果になった。この理由は、実施例１のタイヤでは、ラグ溝２４Ｌ、２４Ｒに開口する浅溝４０をブロック３４に形成することで、ブロック３４の放熱面積が増大するとともに、ブロック３４の接地圧分布の変動が抑えられて接地圧が緩和されたためと考えられる。

As can be seen from Table 1, regarding heat generation durability (BLB), BLB occurs more in the tire of Conventional Example 2 in which the block has a closed groove than in the tire of Conventional Example 1 in which the groove is not formed in the block. As a result, it was difficult (that is, the heat generation durability was excellent). Further, by comparing the evaluation indexes of the tires of the conventional examples 1 and 2 and the tire of the example 1, the blocks 34 constituting the center block row 30 are opened to the lug grooves 24L and 24R on both sides in the tire circumferential direction. As a result, the formation of the shallow groove 40 was less likely to generate BLB. The reason for this is that, in the tire of the first embodiment, by forming the shallow groove 40 opened in the lug grooves 24L and 24R in the block 34, the heat radiation area of the block 34 is increased, and the ground pressure distribution of the block 34 is changed. This is thought to be because the ground pressure was relaxed.

In addition, as a shape of the shallow groove, BLB was less likely to occur when the shallow groove 50 of the tire of Example 2 was formed than the shallow groove 40 of the tire of Example 1. The reason for this is considered to be that in the tire of Example 2, the shallow groove 50 was formed over the entire circumferential width of the block.
As a result, the formation of the shallow groove 60 of the tire of Example 3 was less likely to generate BLB than the shallow groove 50 of the tire of Example 2. The reason for this is considered that the shallow groove 60 matched to the step shape in the tire circumferential direction of the block was formed in the tire of Example 3.

Concerning drainage (hydroplaning), by comparing the evaluation index between the tires of the conventional examples 1 and 2 and the tire of the first embodiment, the shallowness opened to the lug grooves 24L and 24R on both sides in the tire circumferential direction of the block 34. The result was that the drainage was better when the groove 40 was formed in the block 34, that is, the running performance on a wet road surface was better. The reason for this is considered that the shallow groove 40 opened to the lug grooves 24L and 24R is formed in the block 34.
Further, as the shape of the shallow groove, the drainage is better when the shallow groove 50 of the tire of Example 2 is formed than the shallow groove 40 of the tire of Example 1, and the shallow groove 60 of the tire of Example 3 is formed. As a result, drainage was better.

  The embodiments of the present invention have been described above with reference to the embodiments. However, these embodiments are merely examples, and various modifications can be made without departing from the scope of the invention. It goes without saying that the scope of rights of the present invention is not limited to these embodiments.

It is tire radial direction sectional drawing of the pneumatic tire which concerns on 1st Embodiment. It is a top view which shows the tread part of the pneumatic tire which concerns on 1st Embodiment. It is a top view which shows the tread part of the pneumatic tire which concerns on 2nd Embodiment. It is a top view which shows the tread part of the pneumatic tire which concerns on 3rd Embodiment. It is a tire radial direction sectional view showing the modification of the pneumatic tire concerning a 3rd embodiment. It is a top view which shows the modification of the tread part of the pneumatic tire which concerns on 3rd Embodiment. It is a top view which shows the tread part of the tire of the prior art example 1 used by the test example. It is a top view which shows the tread part of the tire of the prior art example 2 used by the test example.

Explanation of symbols

10 Pneumatic tire 18 tread portion 22L, R circumferential groove 24L, R lug groove 26 connecting groove (lateral groove)
30 Center block row 34 Block 37P, Q Tire circumferential direction outermost position 40 Shallow groove 40P One end 40Q The other end 50 The shallow groove 50P One end 50Q The other end 60 The shallow groove 60P One end 60Q The other end EL The tire circumferential direction outermost position ( Circumferential one side end position)
ER tire outermost position (circumferential other end position)
U Tire circumferential direction

Claims (4)

A center block row is formed in the tread portion by the circumferential groove and the lateral groove,
The blocks constituting the center block row have one end opened in a lateral groove adjacent to one side in the tire circumferential direction of the block, and the other end opened in a lateral groove adjacent to the other side in the tire circumferential direction of the block. Block grooves are formed ,
The opening position of the one end of the block groove is a circumferential one end side position of the block,
The tire in which the opening position of the other end of the block groove is the other end position on the other side in the circumferential direction of the block .   The tire according to claim 1, wherein a groove depth of the block groove is shallower than a circumferential groove and a lateral groove adjacent to the center block row. The block is shaped to have a step in the tire circumferential direction,
The tire according to claim 1 or 2 , wherein the block groove is formed in a crank shape so as to have a step in the tire circumferential direction along the step of the block . The tire according to any one of claims 1 to 3 , wherein a tread pattern formed in the tread portion is a lag pattern.

Images