JP2006056502A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire in which wet performance degradation associated with wear progress can be reduced while favorable mold release characteristics are ensured and wet performance in a brand-new condition is maintained. <P>SOLUTION: A sipe 5 is formed in a corrugation to gradually increase a variable range e as a sipe depth D is increased from an opening 6 to 80% of the wear position P of a block 4. Straight lines SL1, SL2 orthogonal to each other are drawn from one end a and the other end b of the sipe 5, respectively, with respect to a center line O passing through the center of the variable range e of the corrugation at the same depth position of the sipe 5, and the sipe length L to be defined by a center line length between intersections I1, I2 of the center line O with the straight lines SL1, SL2 is gradually reduced as the sipe depth D is increased. The ratio L<SB>80</SB>/M<SB>0</SB>of the sipe length L80 to the opening length M0 at the 80% wear position P is 0.8-0.95, and the ratio M<SB>80</SB>/M<SB>0</SB>of the actual length M<SB>80</SB>to the opening length M<SB>0</SB>at the 80% wear position P is 1.0-1.15, respectively. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that suppresses a decrease in wet performance as wear progresses.

  Conventionally, in a pneumatic tire in which a block is defined by a groove on a tread surface, a sipe is provided on the block in order to improve drainage. The grip effect is enhanced by cutting the water film on the wet road surface by the edge effect by sipe, and grounding the block to the road surface from which the water film has been cut. However, as the wear of the block progresses, the groove volume decreases, so a reduction in wet performance is inevitable.

  Accordingly, a pneumatic tire is known in which the length of the sipe is gradually increased toward the sipe bottom in order to suppress a decrease in wet performance during wear (see, for example, Patent Documents 1 and 2). Since the length of the sipe exposed to the block becomes longer as the wear progresses, the edge effect of the sipe is increased during the wear, thereby suppressing a decrease in wet performance.

However, when the sipe length on the sipe bottom side is made longer than the block surface side, at least one end is located in the block without communicating with the groove, and in the pneumatic tire having a sipe that increases the block rigidity, The releasability of the blade that molds the sipe of the mold is poor, and cracks are likely to occur on the sipe wall at the end of the sipe. Moreover, since the block rigidity at the time of a new article before wear is lower than that at which the sipe length is made constant to the sipe bottom, the wet performance at the time of a new article is lowered.
JP-A-2-246810 Japanese Patent Laid-Open No. 9-183303

  An object of the present invention is to provide a pneumatic tire capable of ensuring good mold releasability and suppressing a decrease in wet performance with progress of wear while maintaining wet performance when new. It is in.

The present invention that achieves the above object is a pneumatic tire in which a block is defined by a groove on a tread surface, and a sipe having at least one end located in the block is extended on the tread surface of the block. The sipe has an opening on the surface of the tread and has a waveform that repeatedly curves or bends from one end to the other while gradually increasing the swing width as the sipe depth increases from the opening to at least 80% wear position of the block. At the same depth position, draw a straight line from one end and the other end of the sipe with respect to the center line passing through the center of the wobble width of the waveform, and the center line length between the intersections of the straight line and the center line The defined sipe length L is gradually decreased as the sipe depth increases, the sipe opening length is set to M ₀ (mm), and the sipe length L at the 80% wear position. Is L ₈₀ (mm), and the actual length of the sipe at the 80% wear position is M ₈₀ (mm), the ratio L ₈₀ / M ₀ and the ratio M ₈₀ / M ₀ satisfy the following relationship: It is characterized by.
0.8 ≦ L ₈₀ / M ₀ ≦ 0.95
1.0 ≦ M ₈₀ / M ₀ ≦ 1.15

  According to the present invention described above, by gradually decreasing the sipe length L as the sipe depth becomes deeper, the mold releasability of the mold blade for molding the sipe can be improved, while the sipe is swung out. Even if it is formed into a gradually increasing waveform, the block rigidity at the time of a new article can be made to be the same level as that of the same sipe length to the bottom, so that it is possible to avoid a decrease in wet performance at the time of a new article.

Further, by specifying the sipe lengths L ₈₀ and M ₈₀ of the corrugated shape at the 80% wear position as described above in relation to the opening length M ₀ , the edge effect of the sipe and the good grounding property at the time of wear progress Since the block rigidity which exhibits can be ensured, the fall of the wet performance accompanying wear progress can be suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of a pneumatic tire of the present invention, and 1 is a tread surface. The tread surface 1 is provided with a plurality of circumferential grooves 2 extending along the tire circumferential direction T and a plurality of lateral grooves 3 extending in the tire width direction. The lateral grooves 3 are arranged at predetermined intervals in the tire circumferential direction T, and a plurality of blocks 4 are partitioned and formed on the tread surface 1 by the circumferential grooves 2 and the lateral grooves 3.

  A plurality of sipes 5 extending in the tire width direction are provided on the tread surface 4 a of each block 4. Each sipe 5 does not communicate with the circumferential groove 2, and both ends a and b thereof are located in the block 4. The sipe 5 may have a configuration in which one end a is located in the block 4 without communicating with the circumferential groove 2, and the other end b is communicated with the circumferential groove 2, and at least one end is located in the block 4. If it is sipe.

  The opening 6 of the sipe 5 exposed on the tread surface 4a of the block 4 extends linearly in the tire width direction from one end a to the other end b. The shape of the opening 6 is not limited to the illustrated linear shape, and may be a curved shape or a bent shape in which a straight line and a straight line are combined. FIG. 2 shows an example of the sipe 5 in which the opening 6 extends in a curved shape with a predetermined radius of curvature. When the opening 6 of the sipe 5 is formed in a curved shape having a radius of curvature, the radius of curvature is preferably 5 mm or more.

  As shown in FIG. 3, the sipe 5 has a depth D from the tread surface 4a to the 100% wear position Q where the tire (block 4) is 100% worn. The 100% wear position Q mentioned here is a position where a slip sign as a guide for tire replacement appears and the remaining groove depth D0 of the circumferential groove 2 is 1.6 mm.

  The sipe 5 has a swing width e (see FIG. 5) as the sipe depth D increases from the opening 6 to the 80% wear position P of the block 4, preferably to the sipe bottom c as shown in FIGS. It is formed into a waveform that repeats bending from one end a to the other end b while gradually increasing.

  This waveform is formed so as to have a deflection width e that swings to the left and right with respect to a virtual surface 7 that passes through the opening 6 and extends along the tire radial direction. Preferably, it is formed so that a waveform center line O described later is positioned on the virtual plane 7. This waveform may be a waveform in which a bent portion is formed in a curved shape and the curve is repeated. An example is shown in FIG.

  As shown in FIG. 5, at the same depth position of the sipe 5, straight lines SL1 and SL2 orthogonal to the center line O passing through the center of the waveform fluctuation width e from the one end a and the other end b of the sipe 5 are respectively shown. The sipe length L defined by the center line length between the intersections I1 and I2 of the straight lines SL1 and SL2 and the center line O gradually decreases as the sipe depth D increases from the opening 6 to the sipe bottom c. . When the center line O is a curve, the straight lines SL1 and SL2 are normal to the center line O.

As shown in FIGS. 1 and 4, the opening length (actual length of the opening) of the sipe 5 is M ₀ (mm), and the sipe length L at the 80% wear position P is L ₈₀ as shown in FIG. When the actual length of the sipe 5 at the 80% wear position P is M ₈₀ (mm), the ratio L ₈₀ / M ₀ and the ratio M ₈₀ / M ₀ satisfy the following relationship. Yes. The actual length M ₈₀ of the sipe 5 is a length measured along the sipe 5 from one end a to the other end b at the 80% wear position P as shown in FIG.
0.8 ≦ L ₈₀ / M ₀ ≦ 0.95
1.0 ≦ M ₈₀ / M ₀ ≦ 1.15

  Thus, by gradually decreasing the sipe length L as the sipe depth D becomes deeper, it is possible to improve the mold releasability of the mold blade for molding the sipe, while the swing width e of the sipe 5 gradually increases. Even if it is formed into a corrugated shape, the block rigidity in a new article before wear can be made the same level as that in which the sipe length is constant up to the sipe bottom, so that the wet performance in the new article does not deteriorate.

Further, by defining the lengths L ₈₀ and M ₈₀ of the sipe 5 at the 80% wear position P as described above in relation to the opening length M ₀ , the edge effect of the sipe 5 and the good grounding at the time of wear progress. Therefore, it is possible to secure the block rigidity that exhibits the properties, so that it is possible to suppress a decrease in wet performance as the wear progresses.

When the ratio L ₈₀ / M ₀ is smaller than 0.8, it becomes difficult to effectively suppress the decrease in wet performance due to a decrease in edge effect during wear. If the ratio L ₈₀ / M ₀ is larger than 0.95, the block 4 is likely to fall down due to a decrease in block rigidity at the time of wear, and it becomes difficult to effectively suppress a decrease in wet performance.

When the ratio M ₈₀ / M ₀ is smaller than 1.0, it becomes difficult to effectively suppress the decrease in wet performance due to a decrease in edge effect during wear. When the ratio M ₈₀ / M ₀ is larger than 1.15, the heel and toe wear of the block portion divided by the sipe 5 at the time of wear deteriorates.

Preferably, the ratio L ₈₀ / M ₀ is in the range of _0.8 to 0.9, and the ratio M ₈₀ / M ₀ is in the range of 1.0 to 1.1. It is good in improving heel and toe wear.

  In the said embodiment, although the pneumatic tire which provided only the block 4 in the tread surface 1 was illustrated, this invention may be a pneumatic tire which has a pattern with which a block and a rib are mixed, and a groove | channel is provided in a tread surface. Any pneumatic tire can be used as long as it has a sipe having at least one end located in the block on the tread surface of the block formed with the partition.

Inventive tires 1-7 and comparative tires 1-3 in which the tire size is 205 / 65R15, the tread pattern is the same in FIG. 1, and the ratio L ₈₀ / M ₀ and the ratio M ₈₀ / M ₀ are as shown in Table 1, and Conventional tires each having a sipe length constant to the sipe bottom were prepared.

  Each of these test tires was evaluated for wet performance when new and 80% worn by the evaluation method shown below, and evaluation tests for heel and toe wear resistance of the block portion divided by sipe were as shown in Table 1. The result was obtained.

Each test tire wet performance unused when new mounted on a rim having a rim size of 15 × 6J, and then the air pressure in 210KP a mounted on a test vehicle exhaust quantity 2.4 l. In the wet road test course, braking was applied to the test vehicle running at a speed of 100 km / h, and the distance to stop was measured. The measurement results are shown as index values with the conventional tire as 100. The larger this value, the shorter the braking distance and the better the wet performance when new.

Wet Performance at 80% Wear Each test tire worn to approximately 80% wear position of the block was evaluated in the same manner as the wet performance at the time of new article. The results are shown as index values with the conventional tire as new being 100. The larger this value, the shorter the braking distance and the better the wet performance at 80% wear.

Heel and toe wear resistance of the block part In the same manner as above, each unused test tire is mounted on a test vehicle with a displacement of 2.4 liters, runs on a dry road test course, and the block is worn to a wear position of about 40%. The amount of uneven wear at the block portion when measured was measured. The measurement results are shown as index values with the conventional tire as 100. The smaller this value, the smaller the amount of uneven wear and the better the heel and toe wear resistance of the block portion.

  From Table 1, it can be seen that the tire of the present invention can suppress a decrease in wet performance as the wear progresses while maintaining wet performance when new.

It can also be seen that the heel and toe wear resistance of the block portion can be improved by setting the ratio L ₈₀ / M ₀ to 0.8 to 0.9 and the ratio M ₈₀ / M ₀ to 1.0 to 1.10. .

1 is a partial development view of a tread surface showing an embodiment of a pneumatic tire of the present invention. It is an enlarged plan view showing another example of a sipe having a curved opening. It is a partial expansion perspective view of the block of FIG. It is explanatory drawing which expands and shows only a sipe with a continuous line. It is the elements on larger scale of a block when a block is cut | disconnected in the same depth position of a sipe. It is an enlarged view which shows the other example of the waveform of Sipe. It is the elements on larger scale of a block when a block is cut | disconnected in the 80% abrasion position of a sipe.

Explanation of symbols

1 Tread surface 2 Circumferential groove 3 Horizontal groove 4 Block 4a Tread surface 5 Sipe 6 Opening 7 Virtual surface D Sipe depth I1, I2 Intersection O Center line P 80% Wear position Q 100% Wear position SL1, SL2 Straight line T Tire circumferential direction a one end b other end c sipe bottom e runout

Claims (10)

In a pneumatic tire in which a block is defined by a groove on a tread surface, and a sipe in which at least one end is located in the block is extended on the tread surface of the block,
The sipe has an opening on the tread surface and has a waveform that repeatedly curves or bends from one end to the other while gradually increasing the swing width as the sipe depth increases from the opening to at least 80% wear position of the block. Formed,
At the same depth position of the sipe, with respect to a center line passing through the center of the wobbling width of the waveform, a straight line perpendicular to one end and the other end of the sipe is drawn, and the center line length between the intersections of the straight line and the center line The sipe length L defined by is gradually decreased as the sipe depth becomes deeper,
The opening length of the sipe is M ₀ (mm), the sipe length L at the 80% wear position is L ₈₀ (mm), and the actual length of the sipe at the 80% wear position is M ₈₀ (mm). Then, a pneumatic tire in which the ratio L ₈₀ / M ₀ and the ratio M ₈₀ / M ₀ satisfy the following relationship.
0.8 ≦ L ₈₀ / M ₀ ≦ 0.95
1.0 ≦ M ₈₀ / M ₀ ≦ 1.15 The pneumatic tire according to claim 1, wherein the ratio L ₈₀ / M ₀ is set to 0.8 to 0.9, and the ratio M ₈₀ / M _{0 is set} to 1.0 to 1.1.   The pneumatic tire according to claim 1 or 2, wherein the corrugated wave has a runout width that swings from side to side with respect to a virtual plane that passes through the opening and extends along the tire radial direction.   The pneumatic tire according to claim 3, wherein the center line is located on the virtual plane.   The pneumatic tire according to any one of claims 1 to 4, wherein the sipe has a depth reaching a 100% wear position of the block.   The pneumatic tire according to claim 5, wherein the sipe gradually increases the runout width to the sipe bottom.   The pneumatic tire according to any one of claims 1 to 6, wherein an opening of the sipe extends linearly.   The pneumatic tire according to any one of claims 1 to 6, wherein an opening of the sipe extends in a curved shape.   The pneumatic tire according to claim 1, wherein both ends of the sipe are located in the block.   The pneumatic tire according to any one of claims 1 to 9, wherein an opening of the sipe extends in a tire width direction.

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