JP2008143437A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire allowing the improvement of on-ice performance and uneven wear resistance based on shapes and the arrangement of sipes. <P>SOLUTION: In this pneumatic tire, a tread part has a block 1 having an acute angle 1B tapered toward acute-angled vertex C and a wide width 1A relatively wider than the acute angle part 1B. In the wide width 1A of the block 1, the plurality of sipes A are arranged to be formed into zigzag shapes on a tread surface while being extended in the tire width direction. In the acute angle part 1B of the block 1, at least a sipe B is arranged to be formed into a zigzag shape on the tread surface while being extended in the tire width direction. Each of an amplitude R2 and a period L2 of the sipe B on the tread surface is made smaller than each of an amplitude R1 and a period L1 of the sipe A on the tread surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a plurality of sipes are provided in a block, and more particularly, to a pneumatic tire capable of improving performance on ice and uneven wear resistance based on the shape and arrangement of sipes.

  In pneumatic tires for icy and snowy roads, a plurality of sipe with zigzag shape is provided on the tread surface while extending in the tire width direction on the tread block, and the on-ice performance is demonstrated based on the edge effect of these sipe. (For example, refer to Patent Document 1). Further, as a measure for improving the performance on ice, the tread rubber has been reduced in hardness. However, if a block is provided with a large number of sipes and the tread rubber is reduced in hardness, the rigidity of the block will be insufficient, the block will fall down during braking and cornering, and the ground contact area will be reduced, reducing tire performance in summer and winter. Will do. Therefore, it has been proposed to make the sipe a three-dimensional structure (see, for example, Patent Document 2). When a sipe having a three-dimensional structure is provided in the block as described above, the sipe wall surfaces are engaged with each other, so that the collapse of the block can be suppressed.

However, even when a sipe having a three-dimensional structure is provided in the block, the block tends to fall down at an acute angle portion where the block rigidity is relatively low, and there is a tendency to cause snow clogging at that portion. As a result, there is a problem that the contact area is reduced and the performance on ice and uneven wear resistance are lowered.
JP 2005-297711 A Japanese Patent Laid-Open No. 2005-126055

  An object of the present invention is to provide a pneumatic tire capable of improving performance on ice and uneven wear resistance based on the shape and arrangement of a sipe.

  In order to achieve the above object, the pneumatic tire of the present invention is an air in which a tread portion is provided with a block having an acute angle portion that tapers toward an acute angle apex and a wide width portion that is relatively wider than the acute angle portion. In the tire, a plurality of sipes A having a zigzag shape on the tread surface extending in the tire width direction are arranged in the wide portion of the block, and the tread surface is extended in the tire width direction in the acute angle portion of the block. At least one sipe B having a zigzag shape is arranged, and the amplitude (R2) and period (L2) on the tread surface of the sipe B are respectively set to the amplitude (R1) and period (L1) of the sipe A on the tread surface. ) Smaller than).

  In the present invention, the sipe A is disposed in the wide portion of the block, while the sipe B having a small amplitude and a small period is disposed in the acute angle portion of the block, thereby ensuring a sufficient amount of sipe edge even in the acute angle portion. Can be improved. In addition, the sipe B having a small amplitude and a short period can be disposed at an acute angle portion while ensuring a sufficient distance from the block edge and the distance between the sipe, so that a decrease in block rigidity at the acute angle portion is avoided, and uneven wear resistance is avoided. Can be improved.

  The relationship between the amplitude (R1) and period (L1) of the sipe A on the tread surface and the amplitude (R2) and period (L2) of the sipe B on the tread surface is L2 = L1 × (0.60 to 0.95). ), R2 = R1 × (0.55 to 0.95). Thereby, the improvement effect of on-ice performance and uneven wear resistance can be sufficiently obtained.

  The sipes A and B are bent in the tire circumferential direction at two or more locations in the tire radial direction inside the block to form a bent portion continuous in the tire width direction, and the zigzag shape having an amplitude in the tire radial direction at the bent portion It is preferable to have a three-dimensional structure. Since the sipes A and B have the three-dimensional structure as described above, the collapse of the block can be suppressed and the performance on ice can be further improved. That is, since the sipes A and B are provided with bent portions that are bent in the tire circumferential direction at two or more locations in the tire radial direction and continuous in the tire width direction, the small blocks on both sides of the sipe mesh with each other during braking / driving. Deformation can be suppressed and tire performance during braking / driving can be improved. In addition, since the sipe A and B have a zigzag shape having an amplitude in the tire radial direction at the bent portion, even during cornering, the small blocks on both sides of the sipe mesh with each other to suppress the deformation of the block. The tire performance at the time can be improved. Therefore, even when the hardness of the tread rubber is reduced, it is possible to simultaneously improve the tire performance during braking and driving and the tire performance during cornering.

  The amplitude (b) in the tire radial direction of the bent portion of sipe B is preferably larger than the amplitude (a) in the tire radial direction of the bent portion of sipe A. Thus, by relatively increasing the amplitude in the tire radial direction of the bent portion of the sipe B arranged at the acute angle portion where the block rigidity is low, the turning performance on ice is improved and the uneven wear resistance is improved. be able to. Here, the relationship between the amplitude (a) in the tire radial direction of the bent portion of Sipe A and the amplitude (b) in the tire radial direction of the bent portion of Sipe B is b = a × (1.05 to 1.35). It is preferable that Thereby, the effect of improving the turning performance on ice and the uneven wear resistance can be sufficiently obtained.

  It is preferable that both ends of the sipe B in the tire width direction are stopped inside the block. Thereby, the further rigidity fall of the acute angle part with relatively low block rigidity can be avoided, and the turning performance on ice can be improved.

  It is preferable that the groove depth in the vicinity of the acute vertex of the groove defining the block is shallower than the groove depth in the other part. Thereby, the rigidity of the acute angle part with relatively low block rigidity can be increased, and the turning performance on ice can be improved.

  The sandwiching angle α of the acute angle portion of the block needs to be less than 90 °, and more preferably 20 ° to 60 °. Since the acute angle portion where the included angle α is in the above range has low block rigidity, the above-mentioned sipes A and B are applied to the block having such an acute angle portion, thereby improving the performance on ice and uneven wear resistance. Become prominent.

  The present invention can provide a remarkable effect when applied to a pneumatic tire for icy and snowy roads represented by a studless tire, but can also be applied to a pneumatic tire for all seasons.

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

  FIG. 1 shows an example of a block formed in a tread portion of a pneumatic tire according to an embodiment of the present invention. In FIG. 1, Tc indicates the tire circumferential direction, and Tw indicates the tire width direction. As shown in FIG. 1, the block 1 has a substantially quadrangular shape in plan view, the side 1 a on the tread shoulder side extending in parallel to the tire circumferential direction (Tc), and the tire circumferential direction (Tc). The side 1b on the tread center side extending while being inclined and the sides 1c and 1d connecting both ends of the sides 1a and 1b are provided. The block 1 has an acute angle portion 1B that tapers toward an acute angle vertex C that is an intersection of the sides 1b and 1d, and a wide width portion 1A that is relatively wider than the acute angle portion 1B. Here, a boundary line D (broken line) between the wide portion 1A and the acute angle portion 1B passes through the intersection of the sides 1b and 1c and is parallel to the tire circumferential direction. The position of the boundary line D is wide. It can be arbitrarily set as long as the condition that the portion 1A is wider than the acute angle portion 1B is satisfied.

  In the block 1, a plurality of sipes A having a zigzag shape on the tread surface are disposed in the wide width portion 1A while extending in the tire width direction (Tw), and the acute angle portion 1B extends in the tire width direction (Tw). However, at least one sipe B having a zigzag shape is disposed on the tread surface. Here, sipes A and B have different amplitudes and periods, and the amplitude (R2) and period (L2) on the tread surface of sipe B are respectively the amplitude (R1) and period ( It is smaller than L1).

  In this way, by arranging the sipe A having a desired amplitude and period in the wide portion 1A of the block 1 and by arranging the sipe B having a small amplitude and a small period in the acute angle portion 1B of the block 1, in the acute angle portion 1B In addition, a sufficient amount of sipe edge can be secured and the performance on ice can be improved. In addition, the sipe B having a small amplitude and a short cycle can be disposed in the acute angle portion 1B while sufficiently securing the distance from the block edge and the distance between the sipe, thereby avoiding a decrease in block rigidity in the acute angle portion 1B. Uneven wear can be improved. Although only one sipe B may be arranged in the vicinity of the acute angle vertex C, it is preferable to arrange a plurality of sipes B in the acute angle portion 1B.

  The relationship between the amplitude (R1) and period (L1) of the sipe A on the tread surface and the amplitude (R2) and period (L2) of the sipe B on the tread surface is L2 = L1 × (0.60 to 0.95). ), R2 = R1 × (0.55-0.95). Thereby, the improvement effect of on-ice performance and uneven wear resistance can be sufficiently obtained. When R2 <R1 × 0.55, the performance on ice decreases, and when R2> R1 × 0.95, uneven wear resistance decreases. Further, when L2 <L1 × 0.60, the releasability is lowered, and when L2> L1 × 0.95), the performance on ice is lowered.

  The sipes A and B may maintain the shape on the tread surface as they are inside the tread, but preferably have the following three-dimensional structure to ensure block rigidity.

  FIG. 2 is a partially cutaway view of a block (sipe A and B shown in common) having a three-dimensional sipe. 3A and 3B show a part of the inner wall surface of the sipe A in the block, where FIG. 3A is a plan view and FIG. 3B is a side view. 4A and 4B show a part of the inner wall surface of the sipe B in the block, where FIG. 4A is a plan view and FIG. 4B is a side view.

  As shown in FIG. 2, the sipe A (or B) forms a zigzag shape having an amplitude in the tire circumferential direction (Tc) on the tread surface S, and at two or more locations in the tire radial direction (Tr) inside the block. A plurality of bent portions W bent in the tire circumferential direction (Tc) and continuous in the tire width direction (Tw) are formed. These bent portions W have a convex bent portion W1 and a concave bent portion W2. On one wall surface of the sipe A, the convex bent portions W1 and the concave bent portions W2 are alternately arranged. On the other wall surface (not shown) facing each other, the positional relationship between the convex bent portion W1 and the concave bent portion W2 is reversed. When the sipe A, B is provided with a bent portion W that bends in the tire circumferential direction, the small blocks on both sides of the sipe A, B mesh with each other at the time of braking / driving to suppress the deformation of the block 1 and the block 1 in the tire circumferential direction. Can be suppressed. In addition, by providing two or more bent portions W in each sipe A and B, it is possible to avoid a difference in block rigidity due to normal rotation and reverse rotation of the tire.

  As shown in FIGS. 3A to 3B, the sipe A disposed in the wide portion 1A forms a zigzag shape having an amplitude (a) in the tire radial direction (Tr) at the bent portion W. When the sipe A has a zigzag shape with an amplitude in the tire radial direction (Tr) at the bent portion W, the small blocks on both sides of the sipe A mesh with each other during cornering to suppress the deformation of the block 1 and the tire width of the block 1 Falling in the direction can be suppressed.

  On the other hand, as shown in FIGS. 4A to 4B, the sipe B disposed in the acute angle portion 1B has a zigzag shape having an amplitude (b) in the tire radial direction (Tr) at the bent portion W. Yes. When the sipe B has a zigzag shape having an amplitude in the tire radial direction (Tr) at the bent portion W, the small blocks on both sides of the sipe B mesh with each other during cornering to suppress the deformation of the block 1 and the tire width of the block 1 Falling in the direction can be suppressed.

  The amplitude (a, b) of the bent portion W in the tire radial direction is preferably set to 0.5 to 5.0 mm. If the amplitude is less than 0.5 mm, the effect of supporting the collapse of the block 1 during cornering becomes insufficient. Conversely, if the amplitude exceeds 5.0 mm, the removal from the mold becomes worse.

  In particular, the amplitude (b) of the bent portion of sipe B in the tire radial direction is preferably larger than the amplitude (a) of the bent portion of sipe A in the tire radial direction. Thus, by relatively increasing the amplitude (b) in the tire radial direction of the bent portion of the sipe B disposed in the acute angle portion 1B having a low block rigidity, the turning performance on ice is improved and the uneven wear resistance is also improved. Can be improved. Here, the relationship between the amplitude (a) in the tire radial direction of the bent portion of Sipe A and the amplitude (b) in the tire radial direction of the bent portion of Sipe B is b = a × (1.05 to 1.35). It is preferable that Thereby, the effect of improving the turning performance on ice and the uneven wear resistance can be sufficiently obtained. When b <a × 1.05, the effect of improving the turning performance on ice and uneven wear resistance is insufficient, and when b> a × 1.35, the releasability is lowered.

  In the pneumatic tire, as shown in FIG. 5, both ends of the sipe B in the tire width direction may be stopped inside the block 1. In other words, both ends of the sipe B in the tire width direction may not communicate with the grooves that define the block 1. In this case, further reduction in rigidity of the acute angle portion 1B having relatively low block rigidity can be avoided, and the turning performance on ice can be improved.

  Further, as shown in FIG. 6, the groove depth in the vicinity 2a (shaded portion in the figure) of the acute angle apex portion of the groove 2 such as the lug groove and the main groove that divides the block 1 is determined from the groove depth in the other part. Also shallower. That is, the groove 2 is preferably raised at the acute angle apex vicinity portion 2a of the block 1. Thereby, the rigidity of the acute angle part 1B with relatively low block rigidity can be increased, and the turning performance on ice can be improved. The degree of raising the bottom of the groove 2 is not particularly limited, but the groove depth at the bottom raised portion may be 50% to 80% of the groove depth at the other portion.

  Further, as shown in FIG. 1, the sandwiching angle α of the acute angle portion 1B of the block 1 is preferably 20 ° to 60 °. The acute angle portion 1B having the included angle α in the above range has low block rigidity. Therefore, by applying the above-described sipes A and B to the block 1 having such an acute angle portion 1B, performance on ice and uneven wear resistance are improved. Improvement effect becomes remarkable. The sandwiching angle α of the acute angle portion 1B is an angle formed by the acute angle vertex C between the sides 1b and 1d of the block 1 extending along the acute angle portion 1B. If the acute angle portion 1B is chamfered and there is no clear acute angle vertex C on the block edge, the sides 1b and 1d of the block 1 sandwiching the acute angle portion 1B are extended, and the intersection of the virtual extension lines is determined. It may be regarded as an acute angle vertex C.

  In the pneumatic tire, the JIS-A hardness (0 ° C.) of the rubber composition constituting the tread portion is 40 to 60, preferably 45 to 55. If the JIS-A hardness of the tread rubber is less than 40, the block 4 is liable to fall, and conversely if it exceeds 60, the frictional force on ice decreases.

  In a pneumatic tire for icy and snowy roads having a block pattern including a block having a tire size of 195 / 65R15 and a tread portion having an acute angle portion tapered toward an acute vertex and a wide portion relatively wider than the acute angle portion. Conventional tires and tires of Examples 1 to 3 in which only the shapes of sipes provided on the blocks were varied were manufactured.

  In the conventional example, a plurality of sipes A having a zigzag shape on the tread surface are arranged in the wide portion of the block while extending in the tire width direction, and the zigzag is formed on the tread surface while extending in the tire width direction in the acute angle portion of the block. A plurality of sipes B having a shape are arranged, and the amplitude (R2) and period (L2) of the sipe B on the tread surface are the same as the amplitude (R1) and period (L1) of the sipe A on the tread surface, respectively. It is a thing. On the other hand, in Examples 1 to 3, a plurality of sipe A having a zigzag shape on the tread surface is arranged in the wide portion of the block while extending in the tire width direction, and the block is extended in the tire width direction at an acute angle portion of the block. A plurality of sipe B having a zigzag shape is arranged on the tread surface, and the amplitude (R2) and period (L2) on the tread surface of the sipe B are respectively set to the amplitude (R1) and period ( It is smaller than L1). In Examples 2 to 3, a sipe having a three-dimensional structure shown in FIG. 2 is adopted. In particular, in Example 3, the amplitude (b) of the bent portion of sipe B in the tire radial direction is set to the tire radial direction of the bent portion of sipe A. It was made larger than the amplitude (a). In all the test tires, the sipe depth was 7.0 mm, the sipe thickness was 0.4 mm, and the sipe arrangement interval was 4.0 mm.

  These test tires were evaluated for ice braking performance, ice turning performance, and uneven wear resistance by the following test methods, and the results are shown in Table 1.

Ice braking performance:
The test tire was mounted on an FR vehicle with a displacement of 2000 cc under the conditions of a rim size of 15 × 6.5 JJ and an air pressure of 200 kPa, and braking was performed on a frozen road surface from a traveling state at a speed of 40 km / h, and the braking distance was measured. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. The larger the index value, the better the braking performance on ice.

Ice turning performance:
The test tire was mounted on a FR vehicle with a displacement of 2000 cc under the conditions of a rim size of 15 × 6.5 JJ and an air pressure of 200 kPa, and the vehicle was turned on a frozen road surface with a radius of 30 m, and the average speed was obtained. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the turning performance on ice.

Uneven wear resistance:
Heal and toe wear on a block with sharp and wide parts after a test tire is mounted on an FR vehicle with a displacement of 2000cc under the conditions of a rim size of 15 x 6.5 JJ and an air pressure of 200 kPa. Was measured. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. The larger the index value, the better the uneven wear resistance.

  As can be seen from Table 1, the tires of Examples 1 to 3 were superior in performance on ice and uneven wear resistance compared to the conventional examples.

It is a top view which shows an example of the block formed in the tread part of the pneumatic tire which consists of embodiment of this invention. It is a perspective view which cuts out and partially shows the block (Sipe A and B are shown in common) provided with the three-dimensional structure sipe. A part of inner wall surface of the sipe A in a block is shown, (a) is a top view, (b) is a side view. A part of inner wall surface of the sipe B in a block is shown, (a) is a top view, (b) is a side view. It is a top view which shows the modification of the block in this invention. It is a top view which shows the bottom raising structure in the acute angle vertex vicinity of the groove | channel which divides the block in this invention.

Explanation of symbols

1 block 1A wide portion 1B acute angle portion 2 groove A, B sipe C acute angle vertex D boundary line L1, L2 sipe tread surface period R1, R2 sipe tread surface amplitude W, W1, W2 bent portions a, b The amplitude of the sipe bend in the tire radial direction

Claims (8)

  In a pneumatic tire having a tread portion provided with a block having an acute angle portion tapering toward an acute angle apex and a wide width portion relatively wider than the acute angle portion, the pneumatic tire extends in the tire width direction to the wide width portion of the block. While arranging a plurality of sipe A having a zigzag shape on the tread surface, disposing at least one sipe B having a zigzag shape on the tread surface while extending in the tire width direction at the acute angle portion of the block, A pneumatic tire characterized in that the amplitude (R2) and period (L2) of the sipe B on the tread surface are smaller than the amplitude (R1) and period (L1) of the sipe A on the tread surface, respectively.   The relationship between the amplitude (R1) and period (L1) of the sipe A on the tread surface and the amplitude (R2) and period (L2) of the sipe B on the tread surface is expressed as L2 = L1 × (0.60-0 .95), R2 = R1 × (0.55 to 0.95). The pneumatic tire according to claim 1, wherein:   The sipes A and B are bent in the tire circumferential direction at two or more locations in the tire radial direction inside the block to form a bent portion continuous in the tire width direction, and the zigzag having an amplitude in the tire radial direction at the bent portion The pneumatic tire according to claim 1, wherein the pneumatic tire has a three-dimensional structure having a shape.   4. The pneumatic tire according to claim 3, wherein an amplitude (b) of the bent portion of the sipe B in a tire radial direction is larger than an amplitude (a) of the bent portion of the sipe A in the tire radial direction.   The relation between the amplitude (a) in the tire radial direction of the bent portion of the sipe A and the amplitude (b) in the tire radial direction of the bent portion of the sipe B is b = a × (1.05 to 1.35). The pneumatic tire according to claim 4, wherein   The pneumatic tire according to any one of claims 1 to 5, wherein both ends of the sipe B in the tire width direction are stopped inside the block.   The pneumatic tire according to any one of claims 1 to 6, wherein a groove depth in the vicinity of an acute vertex of the groove defining the block is made shallower than a groove depth in another portion.   The pneumatic tire according to any one of claims 1 to 7, wherein a sandwich angle α of an acute angle portion of the block is 20 ° to 60 °.

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