JP2012006559A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a crack at an inward end of a siping piece and reduction in length of an edge element, and also to prevent opening.SOLUTION: A tire includes a plurality of blocks 5 on a tread 2. The plurality of blocks has a block with a circular sipe. The block includes a sipe-combination body formed of a pair of siping pieces 17i and 17o which extend from both sides of block side edges to a block width direction inward, and having cut-off inward ends P facing each other, and a circular siping 18 which is arranged between the inward ends and on a virtual line X connecting the inward ends.

Description

  The present invention relates to a pneumatic tire suitable for traveling on icy and snowy roads.

  In a pneumatic tire suitable for running on an icy and snowy road, for example, a studless tire, for example, as schematically shown in FIG. 8A, a large number of sipes b are formed in a block a provided in the tread portion, The frictional force is increased by the road surface scratching effect (edge effect) to improve braking performance and traction performance on icy and snowy roads.

  In order to increase the edge component length of the siping b and obtain a higher frictional force, the conventional siping b is a long siping b extending across the block a in the tire axial direction as shown in FIG. Is widely used. However, with such a long siping b, as shown in an exaggerated manner in FIG. 8B, there is a problem that the sipe width t gradually increases on the center side y of the siping b to cause “open mouth”. . When this mouth opening occurs, the rubber parts b1 divided by the siping b are easy to move without being constrained to each other. As a result, the edge effect does not work properly, leading to a decrease in grip performance on icy and snowy roads, and the block rigidity is also reduced, which adversely affects steering stability on good roads.

  Therefore, as shown in FIG. 8C, it is proposed to use a pair of left and right siping pieces c, c whose inner end c1 is interrupted in the block, instead of the long siping b. Although this mouth opening is prevented, since the edge component length is reduced as compared with the long siping b, the grip performance on an icy and snowy road is inferior. Further, when the inner ends c1 and c1 are brought close to each other in order to suppress the decrease in the length of the edge component, there is a problem that the durability of the block is lowered, for example, stress is concentrated on the inner end c1 and cracks are easily generated. Arise.

  In addition, annular siping is known as siping other than linear (for example, refer patent document 1).

JP 2003-127618 A

  The present invention is based on the use of a sipe combination comprising a pair of siping pieces and an annular siping disposed between the inner ends thereof, the occurrence of cracks at the inner ends of the siping pieces, and the edge component length. It is an object of the present invention to provide a pneumatic tire that can prevent the opening of the mouth while suppressing the decrease of the tire, and that can suppress the deterioration of the grip property and the block rigidity of the snowy road over time.

In order to solve the above-described problems, the invention of claim 1 of the present application is directed to a tread portion, a circumferential groove extending in the tire circumferential direction, and a lateral groove extending between the circumferential groove and / or between the circumferential groove and the tread edge. A pneumatic tire formed with a plurality of blocks divided by the circumferential groove and the lateral groove, or the circumferential groove, the tread edge, and the lateral groove,
The plurality of blocks are:
A pair of siping pieces extending inward in the block width direction from the side of the block side edge on both the circumferential groove side or the tread edge side, and inward ends of the inner ends facing each other, and the inward of the pair of siping pieces It is characterized by including at least a block with an annular sipe comprising a sipe combination comprising ends and an annular sipe arranged on a virtual line connecting the inner ends.

  According to a second aspect of the present invention, the annular siping is provided in a block central region at a distance of 40% of the block width on both sides from the center position in the block width direction.

  In the invention of claim 3, the shortest distance W1 between the annular siping and the inner end of the siping piece is in the range of 0.4 to 2.0 mm.

  According to a fourth aspect of the present invention, the annular siping is characterized in that a length W3 in the tire axial direction is smaller than a length W2 in the tire axial direction of the siping piece.

  Further, in the invention of claim 5, the plurality of blocks include shoulder blocks forming a shoulder block row extending in the tire circumferential direction along the tread edge, and the shoulder blocks are the blocks with the annular sipes. It is characterized by.

Further, in the invention of claim 6, the plurality of blocks include an inner block arranged on the inner side in the tire axial direction than the shoulder block, and the inner block includes the block with the annular sipe,
The length W3A in the tire axial direction of the annular sipe arranged in the block with the annular sipe forming the shoulder block is the length W3B in the tire axial direction of the annular sipe arranged in the block with the annular sipe included in the inner block. It is characterized by being larger than.

  According to a seventh aspect of the present invention, the depth of the siping piece forms a maximum depth at the inner end, and the depth of the annular siping is smaller than the maximum depth. .

  As described above, in the present invention, instead of the long siping extending across the block, a pair of siping pieces extending from the side edge of the block and having their inner ends facing each other and interrupted are arranged between the inner ends. A sipe combination comprising an annular sipe is used.

  The pair of siping pieces have a structure in which the central ends of the long sipings are closed because the inner ends of the pair of siping pieces face each other and are interrupted. Therefore, it is possible to reliably prevent the opening of the mouth, and it is possible to suppress the deterioration of the grip performance on the icy and snowy road and the reduction of the block rigidity due to the opening of the mouth.

  Further, the decrease in the length of the edge component due to the break between the inner ends is compensated for or further increased by the annular siping formed between the inner ends. Therefore, the grip performance on an icy and snowy road when it is new can be maintained at the same level as before or improved to a higher level than before. Also, the annular siping can relieve stress concentration even when the inner ends of the siping pieces are close to each other, for example, as compared with the case where the inner ends are close to each other. Therefore, the generation of cracks from the inner end can be suppressed, and the durability of the block can be improved.

It is an expanded view which expands and shows the tread pattern of one example of the pneumatic tire of the present invention on a plane. It is a top view which expands and shows the block with an annular sipe as a shoulder block. It is a top view which illustrates annular siping. It is sectional drawing which shows the relationship of the depth of a siping piece and cyclic | annular siping. It is a top view which shows the other example of a block with a ring sipe. It is a top view which expands and shows the block with an annular sipe as an inner block. FIG. 3 is a development view of a pattern showing siping of a conventional tire in Table 1. (A)-(C) are the top views which show the conventional siping explaining a background art, and the problem by it.

Hereinafter, embodiments of the present invention will be described in detail.
In FIG. 1, the pneumatic tire 1 of the present embodiment includes a tread portion 2, a circumferential groove 3 extending in the tire circumferential direction, and between the circumferential grooves 3 and 3 and / or the circumferential groove 3 and a tread edge Te. And a plurality of blocks 5 defined by the circumferential groove 3 and the lateral groove 4 or the circumferential groove 3 and the tread edge Te and the lateral groove 4 are formed in the tread portion 2. Yes.

  The plurality of blocks 5 are arranged on a shoulder block 5A forming a shoulder block row R5A extending in the tire circumferential direction along the tread edge Te, and on the inner side in the tire axial direction (tire equatorial plane side) than the shoulder block 5A. Block 5B.

  Specifically, the pneumatic tire 1 of the present example includes first circumferential grooves 3i and 3i disposed on both sides of the tire equatorial plane C, and second circumferential grooves 3m and 3m disposed on the outer sides thereof. And a total of six circumferential grooves 3 including third circumferential grooves 3o and 3o arranged on the outer side thereof.

  A first block row Ra including a first block 5a is formed between the first circumferential grooves 3i and 3i. Between the first and second circumferential grooves 3i and 3m, a second block row Rb composed of a second block 5b divided by a transverse groove 4 crossing the gap is formed. A third block row Rc is formed between the second and third two circumferential grooves 3m and 3o. The third block row Rc is formed by a third block 5c divided by a transverse groove 4 crossing the groove. In addition, a fourth block row Rd is formed between the third circumferential groove 3o and the tread end edge Te. The fourth block row Rd is composed of fourth blocks 5d separated by a transverse groove 4 crossing the third circumferential groove 3o.

  That is, the tread pattern of this example is formed as a block pattern composed of a total of seven block rows Ra to Rd, the fourth block 5d constitutes the shoulder block 5A, and the first to third The blocks 5a to 5c constitute the block 5B. As the tread pattern, various patterns such as a block pattern of 6 rows, 5 rows, and 4 rows can be applied.

  The circumferential groove 3 is preferably a straight groove extending linearly in the tire circumferential direction as in this example in order to improve snow drainage and improve performance on snow, but a zigzag groove may be adopted as required. You can also. Further, the groove width and groove depth of the circumferential groove 3 and the groove width and groove depth of the lateral groove 4 are not particularly limited, and the groove width and groove depth of the circumferential groove in a conventional studless tire are not restricted. Further, those having the same range as the groove width and groove depth of the lateral grooves can be suitably applied.

  And in the pneumatic tire 1 of this embodiment, the said several block 5 is comprised including the block 6 with an annular sipe.

  Preferably, the shoulder block 5A is formed by the block 6 with the annular sipe as in this example, and the block 6 with the annular sipe is included in the inner block 5B. In particular, it is preferable that both the shoulder block 5A and the inner block 5B are respectively formed by the blocks 6 with annular sipes.

  FIG. 2 shows an example of a block 6A with an annular sipe used for the shoulder block 5A. The shoulder block 5A includes one block side edge AEi on the circumferential groove 3 side and a tread edge Te. The other block side edge AEo which becomes the side is provided.

  The block 6A with an annular sipe according to the present example has a pair of siping pieces 7i extending inward in the block width direction from the one and other block side edges AEi and AEo, respectively, and the inner ends P facing each other. , 7o, and a sipe combination 9 comprising the pair of siping pieces 7i, 7o and an annular siping 8 disposed in a non-contact manner with the inner end P between the inner ends P, P.

  In this example, the one siping piece 7i is formed as a closed sipe with one end closed extending in a zigzag shape along the length direction from the outer end Q opened at the block side edge AEi to the inner end P. The In the present example, the other siping piece 7o is a closed closed end extending in a zigzag shape along the length direction from the outer end Q separated from the block side edge AEo by a small distance D to the inner end P. Formed as a sipe. The small distance D is 35% or less of the block width WB in the tire axial direction of the block 6A with an annular sipe, and in this example, the outer end is between the block side edge AEo and the outer end Q. For example, a zigzag vertical siping 10 extending in the tire circumferential direction without contact with Q is arranged.

  The siping pieces 7i and 7o are sipes having the same shape as each other. When the siping pieces 7i and 7o have a zigzag shape (including a wave shape and a sine curve) as in this example, the amplitude and pitch length of the zigzag are substantially equal to each other. Set equal. The length direction lines (zigzag center line in the case of zigzag) J and J of the pair of siping pieces 7i and 7o constitute one straight line or a part of a smooth curve.

  Next, the annular siping 8 is a continuous body without a continuous cutout extending continuously in an annular shape. For example, as shown in FIG. 3, a circular shape K1, an elliptical shape K2 (including an oval shape), and a polygonal shape K3. Can be mentioned. Among these, in the case of the polygonal shape K3, in order to prevent stress from concentrating on the corners and generating cracks, the polygonal shape is preferably a quadrilateral or more, further a pentagon or more, and further a hexagon or more. .

  The annular siping 8 is disposed on an imaginary line X connecting the inner ends P, P of the pair of siping pieces 7i, 7o. That is, at least a part of the annular siping 8 is arranged so as to pass on the virtual line X, and it is particularly preferable that the center of the annular siping 8 passes on the virtual line X as in this example.

  In the sipe combination body 9 configured in this way, the inner ends P, P of the pair of siping pieces 7i, 7o are interrupted to face each other, and the center portion of the long sipe is closed. Opening can be reliably prevented.

  Further, the decrease in the length of the edge component due to the interruption at each inner end P is compensated for or further increased by the annular siping 8. Therefore, the grip performance on an icy and snowy road when it is new can be maintained at the same level as before or improved to a higher level than before.

  Further, since the annular siping 8 is continuous without interruption, stress concentration is increased even when the inner ends P of the siping pieces 7i and 7o are close to each other, for example, compared with the case where the inner ends P and P are close to each other. Can be relaxed. Therefore, the occurrence of cracks from the inner end P can be suppressed, and the durability of the block can be improved.

The shortest distance W1 between the annular siping 8 and the inner end P is preferably in the range of 0.4 to 2.0 mm. Cannot be sufficiently relaxed, and cracks tend to occur. On the other hand, when the shortest distance W1 exceeds 2.0 mm, it becomes difficult to cover the decrease in the edge component length with the annular siping 8 and the grip performance on icy and snowy roads is reduced. From this perspective,
The minimum value of the shortest distance W1 is more preferably 0.5 mm or more, and the upper limit value is more preferably 1.5 mm or less. It is also preferable that the shortest distance W1 is not more than 1/4 times the length W2 of the siping pieces 7i, 7o in the tire axial direction.

  The annular siping 8 exhibits an edge effect to increase the frictional force on the icy and snowy road, but is inferior to the edge effect of the linear siping pieces 7i, 7o. Therefore, in order to sufficiently secure the grip performance on an icy and snowy road, the length W3 of the annular siping 8 in the tire axial direction is made smaller than the length W2 of the siping pieces 7i, 7o in the tire axial direction. preferable. When the lengths W2 of the siping pieces 7i and 7o are different from each other, the length W3 of the annular siping 8 is smaller than the length W2 of the smaller siping piece 7i. On the other hand, if the length W3 of the annular siping 8 is too small, the strength of the columnar body 12 (shown in FIGS. 3 and 4) surrounded by the annular siping 8 is reduced, which may cause chipping. Therefore, the lower limit of the length W3 is preferably 1.0 mm or more, and more preferably 1.6 mm or more. In order to prevent the columnar body 12 from being chipped, the annular siping 8 is preferably formed on the block center side with little block deformation. Therefore, as in the present example, it is preferable that the annular siping 8 is provided in the block central region Y at a distance of 40% of the block width WB on both sides from the center position in the block width direction. The provision in the block central region Y means that the entire annular siping 8 is accommodated in the block central region Y.

In the sipe combination 9, as shown in FIG. 4, in this example, the depth H7 of the siping pieces 7i, 7o gradually increases from the outer end Q toward the inner end P. The maximum depth H7max is formed at the end P. As a result, the occurrence of cracks from the outer end Q is suppressed.
It is allowed to provide an arc-shaped chamfered portion having a curvature radius within 1.0 mm at the bottom of the inner end P. In the annular siping 8, the depth H8 is smaller than the maximum depth H7max, thereby preventing the columnar body 12 from being chipped. The difference between the depth H8 and the depth H7 at the outer end Q (that is, the minimum value H7min) is preferably within 1.0 mm, and more preferably the same depth.

  Moreover, in the said block 6A with an annular sipe, according to the block length BL of the tire circumferential direction, the said sipe combination body 9 is formed 1 or more, and also two or more. In addition, in the block 6A with an annular sipe, another linear siping 11 can be additionally formed on the outer side in the tire circumferential direction of the sipe combination 9 as in this example. The siping 11 is preferably a sipe having the same shape as the siping pieces 7i and 7o.

  Further, in the block 6A with an annular sipe, as described above, the case where the vertical siping 10 extending in the tire circumferential direction is formed between the block side edge AEo and the outer end Q is illustrated. This vertical siping 10 is a closed sipe that is closed at both ends in the tire circumferential direction, and has an effect of preventing side skidding and improving grip performance. In this example, the case where the vertical siping 10 is not in contact with the outer end Q is exemplified, but it may be formed so as to intersect with the outer end Q as shown in FIG. The siping 10 may be a straight sipe extending linearly as shown in FIG. The annular siping 8, the siping pieces 7i and 7o, and the sipings 10 and 11 are formed in a cut line shape having a groove width of 0.8 or less, for example, as in the conventional siping. A narrow groove having a groove width of about 0.8 to 2.0 mm can be formed between the end Q and the vertical siping 10.

  Next, FIG. 6 shows an example of a block 6B with an annular sipe used for the block 5B. Among these, the block 5B has the other block side edge BEi, BEo on the circumferential groove 3 side. Further, the block 6B with the annular sipe extends inward in the block width direction from the side of the one and other block side edges BEi and BEo, and the inner ends P face each other, like the block 6A with the annular sipe. A sipe combination 19 comprising a pair of siping pieces 17i, 17o that are interrupted, and an annular siping 18 that is disposed between the inner ends P, P of the pair of siping pieces 17i, 17o in a non-contact manner with the inner end P. With

The sipe combination 19 provided in the inner block 5B and the sipe combination 9 provided in the shoulder block 5A have substantially the same configuration. In this example,
(1) The siping pieces 17i and 17o in the sipe combination body 19 are closed sipe with one end closed with the respective outer ends Q opened at the block side edges BEi and BEo, and (2) the sipe combination body 19 The length W3B of the annular siping 18 in the tire axial direction is smaller than the length W3A of the annular siping 8 of the sipe combination 9 in the tire axial direction,
And the sipe combination 9 in FIG.

  The reason for the difference (1) is that the inner block 5B has no fear of shoulder fall wear unlike the shoulder block 5A, and therefore, in order to maximize the edge effect, The siping pieces 17i, 17o are closed sipes with one end closed. The reason for the difference (2) is that the shoulder block 5A has a larger external force than that of the inner block 5B, and the columnar body 12 in the annular siping 18 is chipped. It tends to be easy. Therefore, the length W3A is set to be larger than the length W3B, preferably about 1.25 to 1.5 times the length W3B, and the strength of the columnar body 12 is increased so that the columnar body 12 is not chipped. We are trying to prevent the occurrence.

  Further, as described above, in the shoulder block 5A, the external force acting as compared with the inner block 5B is large, so that the mouth opening deformation in siping occurs more significantly. Therefore, as in this example, among the plurality of blocks 5, the shoulder block 5A is preferably a block 6A with an annular sipe, and in addition to the shoulder block 5A, an inner block 5B is a block with an annular sipe. 6B is preferable.

  In the above, the especially preferable embodiment of this invention was explained in full detail. However, in the block 6A with an annular sipe, the vertical siping 10 is deleted, and the outer end Q of the siping piece 7o is a closed sipe with one end closed at the block side edge AEo, and the block with the annular sipe The present invention is not limited to the illustrated embodiment, and can be implemented by being modified in various ways.

  A studless tire with a tire size of 195 / 65R15 based on the tread pattern shown in FIG. 1 was prototyped according to the specifications in Table 1 and tested on ice performance, crack resistance performance, and opening resistance performance of each sample tire. Compared. Each tire has substantially the same specifications except for siping. FIG. 7 shows a conventional tread pattern.

(1) Performance on ice:
After mounting tires on all wheels of a vehicle (2000cc, 4WD vehicle) under conditions of rim (15x6JJ) and internal pressure (200 kPa), running on a dry pavement for about 100 km (speed 80 km / h) A braking test on an icy road was conducted. The braking test is performed by running on the test road surface at a speed of 30 km / h, locking the four wheels, applying a sudden brake, measuring the braking distance until the car stops twice, and calculating the average value. It was broken. The evaluation is indicated by an index with the average value of the braking distance of the conventional tire as 100. The larger the value, the shorter the braking distance and the better the performance.

(2) Opening resistance:
Using the above vehicle, the dry pavement was run for 5000 km, and after running, the state of mouth opening in siping was visually observed and comprehensively evaluated. Evaluation is performed in three stages, and the higher the value, the better.

(3) Crack resistance performance:
Using a drum testing machine, traveling 30,000 km at a speed of 60 km / h under conditions of a rim (15x6JJ), internal pressure (200 kPa), and load (4.24 kN), and the distance traveled when cracks occur in siping ( The generated distance) is displayed as an index with the conventional example being 100. The larger the value, the better the performance.

    As shown in the table, it can be confirmed that the tires of the examples can improve both the grip performance on the snowy and snowy road and the opening resistance. In Example 3, since the axial length W3 of the annular siping is as small as 1.0 mm, the strength of the columnar body surrounded by the annular siping is reduced, resulting in rubber chipping, and the crack resistance performance is lowered. In addition, as compared with Example 2 and Comparative Example 2, since Example 2 has an annular siping close to the inner end of the linear siping, the inner ends of the linear siping are close to each other. In comparison, it can be confirmed that the stress concentration is small and the crack resistance is improved.

2 Tread portion 3 Circumferential groove 4 Horizontal groove 5 Block 5A Block 6A in shoulder block 5B Blocks 6i and 6B with annular sipe 7i, 7o Siping piece 8 Annular siping 9 Sipe combination 17i, 17o Siping piece 18 Annular siping 19 , AEo block side edge BEi, BEo block side edge P inner end R5A shoulder block row Te tread edge X imaginary line Y block central area

Claims (7)

By providing a circumferential groove extending in the tire circumferential direction and / or a lateral groove extending between the circumferential grooves and / or between the circumferential groove and the tread edge in the tread portion, the circumferential groove and the lateral groove or the circumferential groove are provided. A pneumatic tire formed with a plurality of blocks divided by a tread edge and a lateral groove,
The plurality of blocks are:
A pair of siping pieces extending inward in the block width direction from the side of the block side edge on both the circumferential groove side or the tread edge side, and inward ends of the inner ends facing each other, and the inward of the pair of siping pieces A pneumatic tire characterized by including at least a block with an annular sipe comprising a sipe combination composed of an annular sipe arranged between imaginary lines connecting the ends and between the inner ends.   2. The pneumatic tire according to claim 1, wherein the annular siping is provided in a block central region at a distance of 40% of the block width on both sides from the center position in the block width direction.   The pneumatic tire according to claim 1 or 2, wherein a shortest distance W1 between the annular siping and an inner end of the siping piece is in a range of 0.4 to 2.0 mm.   The pneumatic tire according to any one of claims 1 to 3, wherein the annular siping has a length W3 in the tire axial direction smaller than a length W2 in the tire axial direction of the siping piece.   The plurality of blocks include a shoulder block forming a shoulder block row extending in a tire circumferential direction along the edge of the tread, and the shoulder block is the block with an annular sipe. 4. The pneumatic tire according to any one of 4 above. The plurality of blocks include an inner block arranged on the inner side in the tire axial direction than the shoulder block, and the inner block includes the annular siped block,
The length W3A in the tire axial direction of the annular sipe arranged in the block with the annular sipe forming the shoulder block is the length W3B in the tire axial direction of the annular sipe arranged in the block with the annular sipe included in the inner block. The pneumatic tire according to claim 5, wherein the pneumatic tire is larger.   7. The depth of the siping piece makes a maximum depth at the inner end, and the depth of the annular siping is smaller than the maximum depth. Pneumatic tire described in 2.

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