JP5404012B2 - 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 mainly considering that the running performance on a bad road, that is, the cut resistance, the tear resistance, and the grip performance on a slippery road surface and a mud road surface are enhanced.

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 a highway in this way, the amount of heat generated by an increase in travel speed increases. For this reason, even with a lug pattern tire, improvement in durability against heat generation (hereinafter referred to as heat generation durability) has been required (see, for example, Patent Document 1).
JP 2007-191087 A

  By the way, BES (belt edge separation) is known in the art that causes peeling by using the end of the belt of the belt layer as a core due to heat generated by running. 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 a structure in which the end portion of the outermost belt in the tire radial direction of the crossing belt layer serving as the core of the BES is wrapped with a cord layer. However, further improvement is required in that the productivity decreases as the number of members increases.

  In view of the above facts, an object of the present invention is to provide a tire with improved heat durability without increasing the number of members.

According to the first aspect of the present invention, a center block row through which the tire equatorial plane passes is formed by a circumferential groove and a lateral groove in a tread portion on the outer side in the tire radial direction of the belt layer, and adjacent to both sides in the tire width direction of the center block row A shoulder block row is formed, a block groove is formed in a tread surface portion of the block constituting the shoulder block row, and one end of the block groove opens into a lateral groove adjacent to one side in the tire circumferential direction of the block. The other end of the block groove opens into a lateral groove adjacent to the other side in the tire circumferential direction of the block, and forms a belt layer, and the belt end is located on the inner side in the tire radial direction of the shoulder block row. At least a part of the block groove is located outwardly in the tire radial direction at the belt end of the radially outermost belt.

In the invention according to claim 1, a center block row through which the tire equatorial plane passes and a shoulder block row adjacent to both sides in the tire width direction of the center block row are formed in the tread portion, and the inner side in the tire radial direction of the shoulder block row In the belt where the belt end is located at the outermost tread portion of the outermost belt in the tire radial direction, the contact pressure is reduced by the formation of the block groove, so that the contact pressure is reduced and the rubber is reduced. The amount of heat generated by compression is reduced. Moreover, since the heat radiation area of a block increases with a block groove | channel, the cooling effect of the block by external air improves. Furthermore, since the amount of rubber corresponding to the volume of the block groove is reduced, the amount of heat generated by running can be reduced. And these things have an effect which controls generating of BES.

Further, the one end of the block groove, open to the lateral grooves adjacent in the tire circumferential direction on one side of the block, the other end of the block groove is open to the lateral grooves adjacent in the tire circumferential direction the other side of the block Therefore, the above effect can be more remarkably exhibited. Moreover, the drainage of the tire is improved.

Furthermore, Bed groove depth of the locking groove is so shallower than the circumferential groove and the lateral groove adjacent to tio Ruda block row, easily suppress drops in the block rigidity and wear resistance by forming block groove.

According to a second aspect of the present invention, the block groove has a width of 10 to 20 mm.
When it is narrower than 10 mm, the effect of forming the block groove is small. On the other hand, if the width is larger than 20 mm, the block rigidity and wear resistance are likely to be lowered.

According to a third aspect of the present invention, the depth of the block groove is in the range of 5 to 10 mm.
If it is shallower than 5 mm, the effect of forming the block groove is small. On the other hand, if it is deeper than 10 mm, the block rigidity and wear resistance tend to be lowered.

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 improved heat durability without increasing the number of members.

  Hereinafter, a truck / bus tire is taken as an example as an embodiment, and an embodiment of the present invention will be described. As shown in FIG. 1, a pneumatic tire 10 according to an embodiment of the present invention 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. In this embodiment, the belt ends of the three belts are all located on the inner side in the tire radial direction of a shoulder block row 30 described later.

  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 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.

  A shallow groove 40 is formed on the tread surface side of each block 38 constituting the shoulder block rows 32L and 32R. In the present embodiment, the shallow groove 40 is linear along the tire circumferential direction U. The shallow groove 40 is located on the outer side in the tire radial direction of the belt end 14T (hereinafter referred to as the 3 belt end 14T) of the 3 belt 14C which is the outermost belt in the tire radial direction.

  Further, one end 40P of the shallow groove 40 opens to the lug groove 24L or the lug groove 24R adjacent to one side in the tire circumferential direction of the block 38 (the lower side in the drawing in FIG. 2). The other end 40Q of the shallow groove 40 is open to the lug groove 24L or the lug groove 24R adjacent to the other side in the tire circumferential direction of the block 38 (the upper side in FIG. 2).

  As described above, in the present embodiment, the shallow grooves 40 that are open at both ends of the lug grooves 24 on both sides in the tire circumferential direction are formed in each block 38 constituting the shoulder block row 32. Therefore, since the surface area of each block 38 increases, the cooling area (heat radiation area) by outside air increases. The ground pressure is reduced by forming the shallow groove 40 at the tread portion where the shallow groove 40 is formed, that is, at the tread portion on the outer side in the tire radial direction of the 3 belt end 14T. Therefore, the contact pressure is relaxed, and the amount of heat generated by rubber compression is reduced in the vicinity of the three belt ends 14T that are the core of BES generation. Furthermore, since the amount of rubber corresponding to the volume of the shallow groove 40 is reduced, the amount of heat generated by running is reduced. And these things have a big effect in suppressing generation | occurrence | production of BES.

  Moreover, since the both ends of the shallow groove 40 are each opened to the lug groove 24 of the tire circumferential direction both sides of the block 38, 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 38 and suppress the fluctuation of the ground pressure distribution of each block 38 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 of the conventional lug pattern (performance such as life and not becoming the core of the tear) and the heat radiation area of the block 38. Range.

  As shown in FIGS. 3 and 4, shallow grooves 60 that open at both ends of the connecting grooves 26 on both sides in the tire circumferential direction may be further formed on the tread surface side of each block 34 constituting the center block row 30. . As a result, the effect of increasing the heat radiation area, reducing the contact pressure, and improving drainage can be further obtained, and the effect of suppressing the occurrence of BLB (belt leave belt) can also be achieved. It is possible to improve the performance. In this case, as shown in FIG. 3 and FIG. 4, the shallow groove 60 is shaped like a crank so as to have a step in the tire circumferential direction U along the step shape of the block 34. This effect can be achieved more remarkably.

<Test example>
In order to confirm the effect of the present invention, the inventor made six examples of the pneumatic tire 10 of the above embodiment (hereinafter referred to as tires of Examples 1 to 6) and two examples of pneumatic tires for comparison (hereinafter referred to as tires). A tire of Comparative Example 1 and a tire of Comparative Example 2) and an example of a conventional pneumatic tire (hereinafter referred to as a tire of a conventional example) were prepared, and a performance test was performed to evaluate the performance. In this test example, all tires were bus / truck tires, and the tire sizes were all “315/80 R225”.

  Here, as shown in FIG. 5, the conventional tire is a tire in which a shallow groove is not formed as compared with the pneumatic tire 10 of the above embodiment.

  The tires of Examples 1 to 6 are tires in which the width W, the depth d, and the tire width direction position of the shallow groove 40 are changed as parameters. The tires of Comparative Examples 1 and 2 are tires in which the position of the shallow groove is largely moved in the tire width direction as compared with the pneumatic tire 10 of the above-described embodiment. The tire has no shallow groove. Table 1 shows the tire conditions for each tire.

ここで、表１の距離ａは、３ベルト端１４Ｔ（タイヤ径方向最外側のベルト端）からタイヤ半径方向外方に延びる平面とタイヤ踏面との交線と、浅溝４０の幅方向中央線との距離のことである。符号の正負は、浅溝４０の幅方向中央線の移動方向がタイヤ赤道面側かトレッド端側かの違いを示す。

Here, the distance a in Table 1 is the intersection of the plane extending from the 3 belt end 14T (the outermost belt end in the tire radial direction) and the tire tread surface in the tire radial direction, and the center line in the width direction of the shallow groove 40. It is the distance. Whether the sign is positive or negative indicates a difference in whether the movement direction of the center line in the width direction of the shallow groove 40 is the tire equator side or the tread end side.

  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.

  And about each tire, regarding heat_generation | fever durability, the load was changed for every step in the drum running test, and BES (belt end separation) was investigated.

  And the performance in the tire of Conventional Example 1 was set as the evaluation index 100, 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 less likely BES is generated, that is, the better the heat generation durability.

  As can be seen from Table 1, regarding heat generation durability (BES), the tires of Examples 1 to 6 were less likely to generate BES than the conventional tires in which no grooves were formed in the block. . In addition, compared with the tires of Comparative Examples 1 and 2 in which the shallow groove formation position is not the outer position in the tire radial direction of the 3 belt end 14T, the tires of Examples 1 to 6 are less likely to generate BES. .

  Further, by comparing the evaluation indexes of the tires of Examples 1 to 6, BES is less likely to occur when the width W of the shallow groove 40 is 15 mm than that of 5 mm, and the depth d of the shallow groove 40 is less than 2.0 mm. As a result, BES was less likely to occur at 5.0 mm. With regard to the position of the shallow groove 40 in the tire width direction, the result is that the center line in the width direction of the shallow groove 40 is most preferably located at the outer position in the tire radial direction of the 3 belt 14C.

  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.

1 is a tire radial direction cross-sectional view of a pneumatic tire according to an embodiment of the present invention. It is a top view which shows the tread part of the pneumatic tire which concerns on one Embodiment of this invention. It is tire radial direction sectional drawing which shows the modification of the pneumatic tire which concerns on one Embodiment of this invention. It is a top view which shows the modification of the tread part of the pneumatic tire which concerns on one Embodiment of this invention. It is a top view which shows the tread part of the tire of the prior art example 1 used by the test example.

Explanation of symbols

10 Pneumatic tire 14 Belt layer 14C 3 belt (outermost belt in the tire radial direction)
14T 3 belt end (belt end)
18 tread portion 22L, R circumferential groove 24L, R lug groove (lateral groove)
30 Center block row 32L, R Shoulder block row 38 Block 40 Shallow groove (block groove)
40P One end 40Q The other end d Depth U Tire circumferential direction W Width

Claims (4)

A center block row through which the tire equator plane passes, and a shoulder block row adjacent to both sides in the tire width direction of the center block row are formed by a circumferential groove and a lateral groove in the tread portion on the outer side in the tire radial direction of the belt layer,
A block groove is formed in the tread portion of the blocks constituting the shoulder block row,
One end of the block groove opens to a lateral groove adjacent to one side in the tire circumferential direction of the block,
The other end of the block groove opens to a lateral groove adjacent to the other side in the tire circumferential direction of the block,
The groove depth of the block groove is shallower than the circumferential groove and the lateral groove adjacent to the shoulder block row,
At least a part of the block groove is formed on the outer side in the tire radial direction of the belt end of the outermost belt in the tire radial direction among the belts constituting the belt layer and having a belt end positioned on the inner side in the tire radial direction of the shoulder block row. Located on the tire.   The tire according to claim 1, wherein a width of the block groove is in a range of 10 to 20 mm.   The tire according to claim 1 or 2, wherein the block groove has a depth of 5 to 10 mm.   The tire according to any one of claims 1 to 3, wherein a tread pattern formed on the tread portion is a lug pattern.

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