JP3797757B2 - Pneumatic tire - Google Patents

Description

ここで、新品時における従来タイヤ、比較タイヤ、供試タイヤ１、２、３のトレッドパターン形状は同一であるが、75％摩耗時におけるトレッドパターン形状は従来タイヤでは図４に示すような形状、また、比較タイヤでは図５に示すような形状、供試タイヤ３では図３に示すような形状であり、各タイヤにおいて異なっている。また、前述の各タイヤのサイズは11Ｒ22.5であった。次に、これら各タイヤを75％摩耗となるまで走行させ、その後、各タイヤに700kPaの内圧を充填した後、牽引されるトレーラーに装着して30km/hで湿潤路面を走行させながらピークμを測定し、従来タイヤのピークμの平均値を指数 100として各タイヤのウエット性能を求めた。その結果を表１に示すが、比較タイヤ、供試タイヤにおいては従来タイヤよりウエット性能が向上している。次に、前記各タイヤに700kPaの内圧を充填するとともに、10トントラックの前輪に装着（平均荷重 24.5kＮ）した後、約60km/hで一般路（舗装路）を合計２万km走行させた。走行終了後にショルダー領域における平均段差量を測定し、従来タイヤを指数 100として肩落ち摩耗指数を求めた。その結果を表１に示すが、比較タイヤでは90まで肩落ち摩耗指数が悪化したが、各供試タイヤでは肩落ち摩耗指数は従来タイヤと同一で悪化することはなかった。そして、75％摩耗時におけるショルダー領域のネガティブ比を75％摩耗時におけるセンター領域のネガティブ比の0.60倍以下とすれば、肩落ち摩耗の防止およびウエット性能の向上を共に図ることができるのである。
【００１７】
【発明の効果】
以上説明したように、この発明によれば、ショルダー領域における肩落ち摩耗を防止しながらウエット性能を向上させることができる。
【図面の簡単な説明】
【図１】この発明の一実施形態を示す新品時のトレッド部平面図である。
【図２】図１のＩーＩ矢視断面図である。
【図３】 75％摩耗時におけるトレッド部平面図である。
【図４】試験に用いた従来タイヤの75％摩耗時におけるトレッド部平面図である。
【図５】試験に用いた比較タイヤの75％摩耗時におけるトレッド部平面図である。
【符号の説明】
11…空気入りタイヤ 15…トレッド部
24、25…主溝 26、27…トレッド端
31…センター領域 32、33…ショルダー領域
50…広幅溝 Ｓ…タイヤ赤道面
Ｗ… 1/2トレッド幅[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire provided with a wide groove including a pair of main grooves on an outer surface of a tread portion.
[0002]
[Prior art]
As a conventional pneumatic tire, for example, a wide groove including a pair of main grooves provided at a position separated by 0.41 to 0.75 times the 1/2 tread width from the tire equatorial plane toward the tread end is an outer surface of the tread part. A center region in which the outer surface of the tread portion is located between the center in the width direction of the pair of main grooves, and a shoulder region located between the center in the width direction of the pair of main grooves and both tread ends. It is known that it is divided into two areas. Here, since the contact pressure during traveling of such a pneumatic tire is generally lower in the shoulder region than in the center region, drag wear occurs in the shoulder region, resulting in a higher wear rate than in the center region. The shoulder region is worn prior to the center region. For this reason, conventionally, the negative ratio of the shoulder region when new is smaller than the negative ratio of the center region, so that the wear between the center region and the shoulder region proceeds almost evenly. And, in such a pneumatic tire, since the wide groove disappears as wear progresses, the negative ratio decreases in any region, and when it reaches the end of wear, that is, 75% wear, the shoulder, In all the center regions, the negative ratio was almost the same value.
[0003]
Here, as described above, when the negative ratio of both the shoulder and center regions decreased at the end of wear as described above, the wet performance had deteriorated to the extent that there was no practical problem, but in recent years under heavy load and high speed As the number of runs increases, further improvement in tire performance is required, and further improvement in wet performance at the end of wear has been required.
[0004]
[Problems to be solved by the invention]
For this reason, for example, it is also possible to increase the depth of the wide groove that had disappeared by the end of wear out of the wide grooves in both the shoulder and center regions, and to uniformly increase the negative ratio at the end of wear across the entire tread portion. However, when this is done, there is a problem that shoulder wear due to a reduction in rigidity occurs particularly in the shoulder region.
[0005]
An object of the present invention is to provide a pneumatic tire capable of improving wet performance while preventing shoulder fall wear in the shoulder region.
[0006]
[Means for Solving the Problems]
Such a purpose is to have a wide groove on the outer surface of the tread portion including a pair of main grooves provided at a position separated by 0.41 to 0.75 times the 1/2 tread width from the tire equatorial plane toward the tread end, The outer surface of the tread portion is partitioned into a center region located between the center in the width direction of the pair of main grooves and a shoulder region located between the center in the width direction of the pair of main grooves and both tread ends. from a pneumatic tire in which a negative ratio of the center region and the shoulder region is decline while leading at 75% wear, by reducing the rate of decrease in negative ratio of the center region in between, from when new at 75% wear, new Sen negative ratio D of the shoulder region at a value G of the negative ratio B obtained by dividing the negative ratio a of the center region of the shoulder region, 75% wear during It can be achieved by larger than the value H obtained by dividing a negative ratio C of over region.
[0007]
As described above, if the rate of decrease in the negative ratio of the center region during the period from new to 75% wear is reduced, the negative ratio value of the center region at 75% wear will be 75% wear of the conventional tire. It becomes larger than the negative ratio value of the center region at the time. Here, since the contribution ratio of the negative ratio to the wet performance is higher in the center region than in the shoulder region, as described above, when the negative ratio value in the center region is large, the wet performance of the entire tire is greatly improved. On the other hand, since there is no change in the reduction rate of the negative ratio with respect to the shoulder region, the rigidity does not decrease and shoulder wear is prevented. Further, since the value G is set to be larger than the value H as described above, the wet performance can be effectively improved.
[0008]
Et al is, according to the structure as claimed in claim 2, it is possible to greatly improve the wet performance.
Further, if configured as described in claim 3 , a tire excellent in both wet performance and uneven wear resistance can be obtained.
Furthermore, if it comprises as described in Claim 4 , wet performance can be improved significantly.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
1 and 2, reference numeral 11 denotes a pneumatic tire. The tire 11 includes a pair of bead portions in which a bead core (not shown) is embedded, and a pair of sidewalls extending from the bead portions toward the outside in a substantially radial direction. And a tread portion 15 that connects the outer ends of the sidewall portions 14 in the radial direction. The tire 11 extends from one bead core to the other bead core, and includes a toroidal carcass layer 17 that reinforces the sidewall portion 14 and the tread portion 15, and a tread portion 15 that is disposed radially outward of the carcass layer 17. The carcass layer 17 is composed of at least one carcass ply 19 in which a cord extending in the meridian direction (radial direction) is embedded, in this case, one carcass ply 19, while the belt layer Reference numeral 18 denotes a plurality of belt cords 20 in which cords inclined with respect to the tire equatorial plane S are embedded, and three belt plies 20 in this case are overlapped so that the cords cross each other. A tread rubber 21 is disposed on the outer side in the radial direction of the belt layer 18.
[0010]
A pair of main grooves 24, 25 extending linearly continuously in the circumferential direction is formed on the outer surface of the tread portion 15, that is, the tread rubber 21, and the main grooves 24, 25, specifically the center in the width direction are From the tire equatorial plane S toward both tread ends 26 and 27, the tire is provided at a position separated by 0.41 to 0.75 times the 1/2 tread width W, and here at a position separated by 0.52 times. As a result, the outer surface of the tread portion 15 has a center region 31 located between the center in the width direction of both the main grooves 24, 25, and between the center in the width direction of the main groove 24 and one tread end 26 and the main groove. 25 is divided into shoulder regions 32 and 33 located between the center in the width direction and the other tread end 27, respectively.
[0011]
The center region 31 is formed with a pair of circumferential grooves 35 and 36 extending continuously in the circumferential direction. These circumferential grooves 35 and 36 divide the center region 31 into approximately three equal parts in the width direction and are bent slightly in a zigzag shape. And has substantially the same depth as the main grooves 24 and 25. 37, 38, 39 are a large number of transverse grooves extending in the width direction and equidistant from each other in the circumferential direction.The transverse groove 37 has both ends on the main groove 24 and the circumferential groove 35, and the lateral groove 38 has both circumferential grooves 35, Both ends are connected to 36, and the lateral groove 39 is connected to the circumferential groove 36 and the main groove 25 at both ends. As a result, a large number of blocks 40 are defined by the main grooves 24 and 25, the circumferential grooves 35 and 36, and the lateral grooves 37, 38 and 39 in the center region 31 when new. The lateral grooves 37, 38, 39 have a depth that is 3/4 or more of the depth of the main grooves 24, 25. Here, the deep grooves 41, which are substantially the same as the main grooves 24, 25, and the main grooves 24, As a result, when the tread rubber 21 of the tire 11 is worn down to 75% wear (the end of wear), the lateral grooves 37, 38, and 39 are formed. The shallow groove portion 42 disappears and becomes a land portion. Here, 100% wear means that the tread rubber 21 is worn until the main grooves 24 and 25 are completely disappeared, in other words, the deepest portions of the main grooves 24 and 25 are reached. As the shallow groove portion 42 disappears due to wear in this way, the negative ratio of the center region 31 decreases during 75% wear from the new time. In this embodiment, the deep groove portions 41 and the shallow groove portions 42 of the lateral grooves 37, 38, and 39 are arranged oppositely between the lateral grooves 37, 38, and 39 adjacent to each other in the circumferential direction. Assuming that the portion 41 is disposed on one side of the lateral groove and the shallow groove portion 42 is disposed on the other side of the lateral groove, in the lateral groove adjacent to the lateral groove, the deep groove portion 41 is disposed on the other side and the shallow groove portion 42 is disposed on the one side. Has been.
[0012]
The shoulder regions 32 and 33 are formed with a plurality of lateral grooves 45 and 46 extending substantially in the width direction from the main grooves 24 and 25 to the tread ends 26 and 27, respectively, and these lateral grooves 45 and 46 are spaced apart at equal distances in the circumferential direction. Are arranged. As a result, a large number of blocks 47 are defined by the main grooves 24 and 25 and the lateral grooves 45 and 46 also in the new shoulder regions 32 and 33. And the depth of these transverse grooves 45, 46 is not less than 3/4 of the depth of the main grooves 24, 25. Here, the deep groove portion 48, which is substantially the same as the main grooves 24, 25, and the main grooves 24, 25 As a result, when the tread rubber 21 of the tire 11 is worn down to 75% wear (end of wear), the shallow groove portions 49 of the lateral grooves 45 and 46 are It disappears and becomes a land part. As the shallow groove portion 49 disappears due to wear in this way, the negative ratio of the shoulder regions 32 and 33 also decreases during the period from when new to 75% wear. And the deep groove part 48 and the shallow groove part 49 of the said horizontal groove 45 and 46 are reversely arrange | positioned between the horizontal grooves 45 and 46 adjacent to the circumferential direction similarly to the above. In the lateral grooves 45 and 46 in which the deep groove portion 48 is disposed on the side close to the tread ends 26 and 27, the end portion close to the tread ends 26 and 27 becomes wider as the tread ends 26 and 27 approach. ing. The main grooves 24 and 25, the circumferential grooves 35 and 36, and the lateral grooves 37, 38, 39, 45, and 46 are provided on the outer surface of the tread portion 15 as a whole, and the wide groove 50 having a wide width that does not close even when grounded. Configure. Here, the negative ratio is a numerical value representing the total area of the wide grooves 50 positioned in the unit area in percentage, where the unit area of the outer surface of the tread portion 15 is 100%.
[0013]
Here, the negative ratio B of the shoulder regions 32 and 33 when new is smaller than the negative ratio A of the center region 31 so that the wear in the center region 31 and the shoulder regions 32 and 33 is almost equal as described above. In general, the value of the negative ratio A is 25 to 33% (27% in this embodiment), and the value of the negative ratio B is 18 to 27% (20% in this embodiment). And when such a tire 11 is run until 75% wear as shown in FIG. 3, the shallow groove portions 42, 49 of the lateral grooves 37, 38, 39, 45, 46 described above disappear and become land portions, As described above, the negative ratios C and D of the center region 31 and the shoulder regions 32 and 33 are almost the same value (a value between 5 and 15%, for example, 8%) as described above.
[0014]
On the other hand, in this embodiment, the negative ratio reduction rate of the shoulder regions 32 and 33 during the period from 75% wear to 75% wear is not changed, and only the negative ratio reduction rate of the center region 31 is reduced. Thus, the negative ratio C of the center region 31 at 75% wear is larger than the value of the negative ratio C of the center region 31 at 75% wear of the conventional tire (8% as described above), here 12%. It is. Here, since the contribution ratio of the negative ratio to the wet performance is higher in the center region 31 than in the shoulder region 32, as described above, if the value of the negative ratio C in the center region 31 at 75% wear increases, 11 The overall wet performance is greatly improved. On the other hand, since the reduction ratio of the negative ratio does not change with respect to the shoulder regions 32 and 33, the rigidity of the block 47 is not lowered and the shoulder drop wear is prevented. As described above, in order to make the negative ratio C of the center region 31 at the time of 75% wear larger than that of the conventional tire, in this embodiment, the ratio of the shallow groove portion 42 to the lateral grooves 37, 38, 39 is small ( However, the groove wall angle with respect to the outer surface of the tread portion 15 of the main grooves 24 and 25, the circumferential grooves 35 and 36, and the lateral grooves 37, 38, and 39 is close to 90 degrees. When the groove width of the deep groove portion 41 of the circumferential grooves 35, 36 and the lateral grooves 37, 38, 39 becomes narrow at 75% wear, the circumferential grooves 35, 36 and the lateral grooves 37, 38 The groove width may be increased by further deepening the deep groove portion 41 of 39.
[0015]
Here, the value of the negative ratio C of the center region 31 at the time of 75% wear is preferably in the range of 10 to 25%. The reason is that if the negative ratio C is less than 10%, the wet performance is not sufficiently improved. On the other hand, if it exceeds 25%, the rigidity of the block 40 in the center region 31 decreases. This is because uneven wear may occur. Further, as described above, by reducing the negative ratio reduction rate in the center region 31, the value G obtained by dividing the negative ratio B of the shoulder regions 32 and 33 at the time of the new product by the negative ratio A of the center region 31 at the time of the new product is obtained. If the negative ratio D of the shoulder regions 32, 33 at 75% wear is divided by the negative ratio C of the center region 31 at 75% wear, it will be understood from the test examples described later. Thus, the wet performance of the tire 11 can be effectively improved while preventing the shoulder wear in the shoulder regions 32 and 33. When the value obtained by subtracting the value H from the above-mentioned value G is 10% or more, the wet performance can be greatly improved as will be understood from the test examples described later. The value obtained by dividing the negative ratio B of the shoulder regions 32 and 33 when new is divided by the negative ratio D of the shoulder regions 32 and 33 when 75% worn is the negative ratio A of the center region 31 when 75% worn. By making the value larger than the value divided by the negative ratio C of the center region 31 in the tire, the wet performance of the tire 11 is effectively prevented while preventing the shoulder fall wear in the shoulder regions 32 and 33, as will be understood from the following test example. Can be improved.
[0016]
【Example】
Next, test examples will be described. In this test, the negative ratios A and B of the center and shoulder regions at the time of a new article, these ratios G = B / A, the negative ratios C and D of the center and shoulder regions at 75% wear, and these ratios H = D Conventional tires, comparative tires, and test tires 1, 2, and 3 in which each value of / C and the ratio difference GH are values as shown in Table 1 below were prepared.
[Table 1]

Here, the tread pattern shape of the conventional tire, the comparative tire, and the test tires 1, 2, and 3 when they are new is the same, but the tread pattern shape when 75% worn is the shape shown in FIG. Further, the comparative tire has a shape as shown in FIG. 5, and the test tire 3 has a shape as shown in FIG. The size of each tire described above was 11R22.5. Next, run each of these tires until they are 75% worn, then fill each tire with an internal pressure of 700 kPa, then attach it to the trailer to be pulled and peak μ while running on a wet road surface at 30 km / h. The wet performance of each tire was determined with an average value of the peak μ of the conventional tire as an index of 100. The results are shown in Table 1. In the comparative tire and the test tire, the wet performance is improved as compared with the conventional tire. Next, each tire was filled with an internal pressure of 700 kPa, mounted on the front wheels of a 10-ton truck (average load 24.5 kN), and then traveled on a general road (paved road) at a total speed of about 20,000 km at about 60 km / h. After running, the average level difference in the shoulder area was measured, and the conventional tire index 100 was used to determine the shoulder drop wear index. The results are shown in Table 1. Although the shoulder drop wear index deteriorated to 90 for the comparative tires, the shoulder drop wear index for each test tire was the same as that of the conventional tire and did not deteriorate. If the negative ratio of the shoulder region at 75% wear is 0.60 times or less than the negative ratio of the center region at 75% wear, it is possible to both prevent shoulder fall wear and improve wet performance.
[0017]
【The invention's effect】
As described above, according to the present invention, it is possible to improve wet performance while preventing shoulder drop wear in the shoulder region.
[Brief description of the drawings]
FIG. 1 is a plan view of a tread portion in a new article showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line II of FIG.
FIG. 3 is a plan view of a tread portion when 75% worn.
FIG. 4 is a plan view of a tread portion at 75% wear of a conventional tire used in a test.
FIG. 5 is a plan view of a tread portion when 75% of a comparative tire used in the test is worn.
[Explanation of symbols]
11 ... Pneumatic tire 15 ... Tread part
24, 25 ... main groove 26, 27 ... tread edge
31… Center area 32, 33… Shoulder area
50 ... Wide groove S ... Tire equatorial plane W ... 1/2 tread width

Claims (4)

The tread portion outer surface has a wide groove including a pair of main grooves provided at a position separated by 0.41 to 0.75 times the 1/2 tread width W from the tire equatorial plane toward the tread end. Is divided into a center region located between the center in the width direction of the pair of main grooves and a shoulder region located between the center in the width direction of the pair of main grooves and both tread ends. a pneumatic tire which negative ratio of the center region and the shoulder region are decline between leading, by Rukoto reduce the reduction rate of negative ratio of the center region in between, from when new at 75% wear, shoulder at new region Negate value G obtained by dividing the negative ratio a of the negative ratio B center region, the negative ratio D of the shoulder region of the center region at 75% wear A pneumatic tire, characterized in that set to be larger than the value H obtained by dividing the blanking ratio C. The pneumatic tire of claim 1, wherein a value obtained by subtracting the value H from the value G is 10% or more.     The pneumatic tire according to claim 1, wherein a negative ratio value of the shoulder region at 75% wear is 5 to 15%, and a negative ratio value of the center region at 75% wear is 10 to 25%.     The pneumatic tire according to claim 1, wherein a negative ratio of the shoulder region at 75% wear is 0.60 times or less of a negative ratio of the center region at 75% wear.

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