JP2008049971A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of simultaneously improving tire performance at braking and tire performance at cornering by enhancing not only block rigidity in the longitudinal direction but also block rigidity in the horizontal direction. <P>SOLUTION: This pneumatic tire is formed by arranging a plurality of vertical grooves 2 extending in the tire peripheral direction, and a plurality of horizontal grooves 3 extending in the tire width direction in a tread 1, and formed by arranging a plurality of sipes 5 extending in the tire width direction in blocks 4 by partitioning a plurality of blocks 4 by these vertical grooves 2 and horizontal grooves 3. The sipe 5s is formed in a zigzag shape in a tread surface S, and forms a bending part 6 continuing in the tire width direction by bending in the tire peripheral direction in two places or more in the tire radius direction on the inside of the blocks 4, and has a three-dimensional structure of forming a zigzag shape having at least two kinds of amplitudes α and β in the tire radius direction in the bending part 6, and a part mutually different in amplitude in the tire radius direction in the bending part 6 of the sipe 5s is arranged in a mutually different position in the width direction of the blocks 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire provided with a plurality of sipes in a block, and more specifically, it is possible to increase not only the block rigidity in the front-rear direction but also the block rigidity in the lateral direction based on the sipe shape. The present invention relates to a pneumatic tire that simultaneously improves tire performance during driving and tire performance during cornering.

  In a pneumatic tire for snowy and snowy roads, as a measure for improving the performance on ice, it is generally performed to increase the edge amount of a sipe provided on a block or to reduce the hardness of a tread rubber. However, when the hardness of the tread rubber is reduced, the block rigidity is lowered, so that the block collapses at the time of braking / driving and cornering, the contact area is reduced, and the tire performance in summer and winter is lowered. Therefore, it has been proposed that the sipe has a three-dimensional structure in order to prevent the block from falling down.

  As a sipe having a three-dimensional structure, a sipe having a zigzag shape on the tread surface and a zigzag amplitude changing inside the block has been proposed (see, for example, Patent Document 1). In this case, although it is possible to increase the block rigidity in the front-rear direction, there is a drawback that the effect of increasing the block rigidity in the horizontal direction is hardly obtained.

  Further, a sipe has been proposed in which a tread surface has a zigzag shape, and a bent portion continuous in the tire radial direction is bent in the tire width direction inside the block (see, for example, Patent Document 2). Also in this case, there is a drawback that the block rigidity in the lateral direction is lower than the block rigidity in the front-rear direction.

On the other hand, the tread surface has a zigzag shape and is 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 in the tire radial direction at the bent portion There has been proposed a sipe in which a zigzag shape having an amplitude is formed in the sipe (for example, see Patent Document 3). In this case, the block rigidity in the front-rear direction and the block rigidity in the lateral direction can be increased at the same time. However, even in a sipe having such a three-dimensional structure, when the amplitude in the tire radial direction at the bent portion of the sipe is increased in order to further increase the lateral block rigidity, the block rigidity in the front-rear direction tends to decrease. Therefore, there is a limit to improving the tire performance during braking and driving and the tire performance during cornering at the same time.
JP 2000-6619 A JP 2002-321509 A Japanese Patent Laid-Open No. 2005-126055

  The object of the present invention is to enable not only the longitudinal block stiffness but also the lateral block stiffness to be increased based on the sipe shape, thereby simultaneously improving the tire performance during braking and cornering. It is to provide a pneumatic tire that enables the above.

In order to achieve the above object, the pneumatic tire of the present invention is provided with a plurality of vertical grooves extending in the tire circumferential direction and a plurality of horizontal grooves extending in the tire width direction in the tread portion. In a pneumatic tire which divides a plurality of blocks and has a plurality of sipes extending in the tire width direction in the blocks,
The sipe has a zigzag shape on the tread surface, and bends 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 in the tire radial direction at the bent portion. A zigzag-shaped three-dimensional structure having at least two kinds of amplitudes, wherein portions having different amplitudes in the tire radial direction in the bent portions of the sipe are arranged at different positions in the width direction of the block. It is what.

  In the present invention, since the sipe is bent in the tire circumferential direction at two or more locations in the tire radial direction and is provided with a bent portion continuous in the tire width direction, the small blocks on both sides of the sipe mesh with each other during braking / driving and the block deformation Can be suppressed, and the tire performance during braking / driving can be improved. In addition, since the sipe has a zigzag shape having an amplitude in the tire radial direction at the bent portion, the small blocks on both sides of the sipe mesh with each other even during cornering to suppress block deformation, and the tire during cornering The performance can be improved. In addition, the sipe has a zigzag shape having at least two types of amplitude in the tire radial direction at the bent portion, and the portions having different amplitudes in the tire radial direction in the bent portion are arranged at different positions in the width direction of the block. Therefore, a portion with a relatively large amplitude in the tire radial direction mainly contributes to an increase in the block rigidity in the lateral direction, and a portion with a relatively small amplitude in the tire radial direction mainly contributes to an increase in the block stiffness in the front-rear direction. Both characteristics can be effectively 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.

  In the present invention, it is preferable that the portion having the maximum amplitude in the tire radial direction at the sipe bend is disposed at a position outside the width direction of the block. As a result, the block rigidity in the lateral direction at the outer position in the width direction of the block is increased, so that the tire performance during cornering can be more effectively improved while maintaining the tire performance during braking / driving.

  Moreover, it is preferable to arrange | position the part where the amplitude of the tire radial direction in the bending part of a sipe becomes the maximum in the position on the tread shoulder side of a block. In this case, the block rigidity in the lateral direction at the tread shoulder side position of the block is increased, so that the tire performance during cornering is more effectively improved while maintaining the tire performance during braking / driving, and the mold release property is further improved. Can be improved.

  In other words, since the tread part has a curvature, when a tire is vulcanized using a sectional type mold, the angle between the normal direction of the tread surface and the mold release direction is closer to the position on the tread shoulder side of the block. Due to the increase, the releasability deteriorates. On the other hand, since the part where the amplitude in the tire radial direction at the sipe bend is maximum is relatively easy to remove the mold, the part is placed at the position on the tread shoulder side of the block, so that the releasability is improved. It is possible to improve and prevent the chipping of the block and the deformation of the sipe forming blade.

  It is preferable that the maximum value α of the amplitude in the tire radial direction at the bent portion of the sipe is 1.2 times to 3.0 times the minimum value β. As a result, the block rigidity in the front-rear direction and the block rigidity in the lateral direction can be increased in a balanced manner.

  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 a tread pattern of a pneumatic tire for icy and snowy roads according to an embodiment of the present invention, and FIG. 2 shows a basic structure of the block. FIG. 3 shows a sipe inner wall surface in the block.

  As shown in FIG. 1, the tread portion 1 is formed with a plurality of vertical grooves 2 extending in the tire circumferential direction and a plurality of horizontal grooves 3 extending in the tire width direction. Block 4 is partitioned. Each block 4 is formed with a plurality of sipes 5 extending in the tire width direction. The shape of the block 4 and the number of sipes 5 are not particularly limited.

  As shown in FIG. 2, the sipe 5 has a zigzag shape on the tread surface S, and is bent in the tire circumferential direction (Tc) at two or more locations in the tire radial direction (Tr) inside the block to be tire width direction (Tw). A plurality of bent portions 6 are formed. These bent portions 6 have convex bent portions 6a and concave bent portions 6b. On one wall surface of the sipe 5, convex bent portions 6a and concave bent portions 6b are alternately arranged. On the other wall surface (not shown) facing each other, the positional relationship between the convex bent portion 6a and the concave bent portion 6b is reversed. When the sipe 5 is provided with the bent portion 6 that bends in the tire circumferential direction, the small blocks on both sides of the sipe 5 mesh with each other during braking / driving to suppress the deformation of the block 4 and to prevent the block 4 from falling in the tire circumferential direction. can do. In addition, by providing two or more bent portions 6 in each sipe 5, it is possible to avoid a difference in block rigidity due to normal rotation and reverse rotation of the tire.

  As shown in FIG. 3, the sipe 5 forms a zigzag shape having an amplitude in the tire radial direction (Tr) at the bent portion 6. When the sipe 5 has a zigzag shape with an amplitude in the tire radial direction (Tr) at the bent portion 6, the small blocks on both sides of the sipe 5 mesh with each other during cornering to suppress deformation of the block 4, and the tire width of the block 4 Falling in the direction can be suppressed.

  The rubber composition constituting the tread portion 1 has a JIS-A hardness (0 ° C.) of 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.

  According to the pneumatic tire for snowy and snowy roads, the sipe 5 includes the bent portions 6 that are bent in the tire circumferential direction (Tc) at two or more locations in the tire radial direction (Tr) and continuous in the tire width direction (Tw). Therefore, the small blocks on both sides of the sipe 5 are engaged with each other during braking / driving to suppress the deformation of the blocks, and the tire performance during braking / driving can be improved. Further, since the sipe 5 has a zigzag shape having an amplitude in the tire radial direction (Tr) at the bent portion 6, the small blocks on both sides of the sipe 5 are engaged with each other even during cornering to suppress deformation of the block. The tire performance during cornering can be improved.

  However, when the amplitude in the tire radial direction at the bent portion 6 of the sipe 5 is uniformly increased in order to further increase the block rigidity in the lateral direction, the block rigidity in the front-rear direction tends to decrease. Therefore, in order to further improve the tire performance during braking and driving and the tire performance during cornering, the following structure is adopted for at least a part of the sipe 5 formed in the tread portion 1.

  4 (a) to 4 (d) show the inner wall surface of the sipe located on the most tread shoulder side formed in the block on the most tread shoulder side, (a) is a side view, and (b) is an XX arrow view. Sectional drawing, (c) is a YY arrow sectional view, (d) is a ZZ arrow sectional view. In FIG. 4A, the tread shoulder side is indicated by Sh and the tread center side is indicated by Ce.

  4A to 4D, the sipe 5s located closest to the tread shoulder in the sipe 5 has two kinds of amplitudes α and β in the tire radial direction (Tr) at the bent portion 6. A zigzag shape is formed. Here, the amplitude α is set larger than the amplitude β. The portions having different amplitudes in the tire radial direction in the bent portion 6 of the sipe 5 s are arranged at different positions in the width direction of the block 4. More specifically, the portion where the bent portion 6 of the sipe 5s has the maximum amplitude α is disposed at the tread shoulder side (Sh) position of the block 4, and the portion where the bent portion 6 of the sipe 5s has the minimum amplitude β is a block. 4 at the tread center side (Ce) position.

  In the development view of FIG. 1, the grounding region of the tread portion 1 is a portion defined by the grounding width TCW, and the tread surface S is curved from the grounding region to the non-grounding region to form the side wall of the block 4. . Therefore, it can be considered that the part where the bent portion 6 of the sipe 5 s has the maximum amplitude α is disposed outside the block 4 in the width direction.

  When the above configuration is adopted for the sipe 5s located closest to the tread shoulder, the lateral block rigidity is increased at the position of the tread shoulder side of the block 4 having the sipe 5s, so that the tire performance during braking / driving is maintained. The tire performance during cornering can be effectively improved. Moreover, disposing the portion of the sipe 5s where the bent portion 6 has the maximum amplitude α at the position on the tread shoulder side of the block 4 also contributes to the improvement of mold release.

  The maximum value α of the amplitude in the tire radial direction at the bent portion 6 of the sipe 5s is 1.2 times to 3.0 times the minimum value β, and more preferably 1.5 times to 2.5 times. If the maximum value α is less than 1.2 times the minimum value β, the lateral block rigidity will be insufficient. Conversely, if the maximum value α exceeds 3.0 times the minimum value β, the block rigidity in the front-rear direction will be insufficient. . Further, the amplitudes α and β in the tire radial direction of the bent portion 6 are preferably set within a range of 0.5 to 5.0 mm. If the amplitudes α and β are less than 0.5 mm, the block rigidity in the lateral direction becomes insufficient, and conversely if it exceeds 5.0 mm, the block rigidity in the front-rear direction decreases.

  According to the pneumatic tire for snowy and snowy roads, even when the tread rubber has a low hardness, it is possible to simultaneously improve the tire performance during braking and the tire performance during cornering. In particular, it is possible to increase the number of sipes per block and to use a low-hardness rubber for the tread rubber, so that the tire performance in summer can be maintained while improving the performance on ice.

  In the above-described embodiment, a case has been described in which two types of amplitudes are set in the sipe bent portion positioned on the most tread shoulder side formed in the block on the tread shoulder side. It is possible to set more than one type, for example, two to four types of amplitudes. Further, it is possible to set at least two kinds of amplitudes in the bent portion of the sipe formed in the block on the tread center side or all the sipe formed in the tread portion. Furthermore, a portion where the amplitude in the tire radial direction in the bent portion of the sipe is maximum may be disposed at a position on the outer side in the width direction of the block and on the tread center side.

  In the pneumatic tires for ice and snowy roads having a tire size of 195 / 65R15 and having a block pattern, tires of conventional examples and examples 1 to 3 in which only the shapes of sipes provided on the blocks were varied were manufactured. In the conventional example and Examples 1 to 3, the sipe has a zigzag shape on the tread surface, and bends 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. The bent portion has a three-dimensional structure having a zigzag shape with amplitude in the tire radial direction. Further, in Examples 1 to 3, two types of amplitudes α and β are set in the sipe bend, and the portion having the maximum amplitude in the tire radial direction in the sipe bend is disposed at the position on the tread shoulder side of the block. did.

  These test tires were evaluated for braking performance on ice, wet turning performance and vulcanization failure occurrence rate 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.

Wet 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. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the wet turning performance.

Vulcanization failure rate:
For the test tire after vulcanization, the presence or absence of vulcanization failure such as chipping of blocks or cut scratches was investigated, and the ratio (%) of the number of tires with vulcanization failure to the total number of test tires was determined. Was the vulcanization failure rate.

  As can be seen from Table 1, the tires of Examples 1 to 3 can improve the wet turning performance while maintaining the braking performance on ice as compared with the conventional example, and the vulcanization failure occurrence rate is extremely low. It was.

It is a top view which shows the tread pattern of the pneumatic tire for snowy and icy roads which consists of embodiment of this invention. FIG. 2 is a partially cutaway perspective view showing a basic structure of a block in the pneumatic tire for an icy and snowy road of FIG. 1. It is a side view which shows the sipe inner wall surface in the block of FIG. The inner wall surface of the sipe located in the most tread shoulder side block formed in the block on the most tread shoulder side in the pneumatic tire for snowy and snowy roads of FIG. 1 is shown, (a) is a side view, (b) is an XX arrow view. Sectional drawing, (c) is a YY arrow sectional view, (d) is a ZZ arrow sectional view.

Explanation of symbols

1 Tread part 2 Vertical groove 3 Horizontal groove 4 Block 5, 5s Sipe 6 Bent part S Tread surface α, β Amplitude

Claims (4)

A plurality of longitudinal grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire width direction are provided in the tread portion, and a plurality of blocks are defined by the longitudinal grooves and the lateral grooves, and the blocks extend in the tire width direction. In pneumatic tires with multiple sipes,
The sipe has a zigzag shape on the tread surface, and bends 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 in the tire radial direction at the bent portion. A zigzag-shaped three-dimensional structure having at least two kinds of amplitudes, wherein portions having different amplitudes in the tire radial direction in the bent portions of the sipe are arranged at different positions in the width direction of the block. And pneumatic tires.   2. The pneumatic tire according to claim 1, wherein a portion having a maximum amplitude in a tire radial direction at a bent portion of the sipe is disposed at a position on the outer side in the width direction of the block.   The pneumatic tire according to claim 1 or 2, wherein a portion having a maximum amplitude in a tire radial direction in a bent portion of the sipe is disposed at a position on a tread shoulder side of the block. The pneumatic tire according to any one of claims 1 to 3, wherein the maximum value α of the amplitude in the tire radial direction at the bent portion of the sipe is 1.2 times or more and 3.0 times or less than the minimum value β.

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