JP7207166B2 - tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a tire having a tread portion provided with sipes.

Patent Literature 1 listed below proposes a tire in which a sipe extending in the tire axial direction is provided in the tread portion. The tire is expected to have improved on-ice performance due to the sipe.

JP 2018-001803 A

In general, a sipe extending in the axial direction of a tire tends to open wide when coming out from the contact surface of the tread portion as the tire rotates. Such an opening of the sipe tends to increase the amount of slippage between the sipe edge and the road surface, thereby causing uneven wear (for example, heel-and-toe wear) near the edge.

SUMMARY OF THE INVENTION The present invention has been devised in view of the problems described above, and a main object of the present invention is to provide a tire capable of exhibiting excellent performance on ice and resistance to uneven wear.

The present invention is a tire including a tread portion, wherein the tread portion is provided with sipes, the sipes include a portion where a plurality of repeating elements are connected in the longitudinal direction of the sipes, and the repeating elements Each of the four sipe pieces is bent so as to form an acute angle with each other, and the four sipe pieces are a first sipe piece extending in the tire axial direction and a first axial end of the first sipe piece. a second sipe piece extending in the circumferential direction of the first tire; a third sipe piece extending from the second sipe piece in the axial direction of the first tire; and a third sipe piece continuous with the third sipe piece. and a fourth sipe piece extending from the second tire circumferential direction side opposite to the first tire circumferential direction, wherein at least one of the first sipe piece and the third sipe piece is orthogonal to the longitudinal direction The transverse cross section includes an oscillating portion that oscillates in the lateral direction perpendicular to the longitudinal direction and extends in the tire radial direction.

In the tire of the present invention, both the first sipe piece and the third sipe piece preferably include the amplitude portion.

In the tire of the present invention, it is preferable that the amplitude portion of the first sipe piece and the amplitude portion of the third sipe piece oscillate in opposite phases and extend in the tire radial direction.

In the tire of the present invention, it is preferable that each of the first sipe piece and the third sipe piece extends at an angle of 35° or less with respect to the axial direction of the tire.

In the tire of the present invention, it is preferable that the repeating element is bent so that the four sipe pieces form an angle of 30 to 70 degrees with each other.

In the tire of the present invention, it is preferable that a straight bottom portion extending parallel to the tire radial direction continues to the inner side of the amplitude portion in the tire radial direction.

In the tire of the present invention, the radial length of the linear bottom portion is preferably 0.10 to 0.30 times the radial length of the sipe piece to which the linear bottom portion belongs.

In the tire of the present invention, it is desirable that the bending width of the amplitude portion is 0.4 to 1.0 mm.

In the tire of the present invention, it is preferable that the amplitude portion includes two or more first protrusions that protrude on one side in the lateral direction.

In the tire of the present invention, the amplitude portion is composed of two first convex portions and one second convex portion projecting on the other side in the lateral direction between the two first convex portions. preferably

In the tire of the present invention, the center line in the width direction of the amplitude portion includes a first vertex bent at the first convex portion and a second vertex bent at the second convex portion, and connects both ends of the center line. The virtual straight line is parallel to the tire radial direction, and the second vertex is preferably arranged on the virtual straight line.

In the tire of the present invention, the center line of the amplitude portion includes an outer end in the tire radial direction and an inner end in the tire radial direction, and the amplitude portion extends from the outer end to the second vertex. A first bent element and a second bent element extending from the second vertex to the inner end, wherein the length of the first bent element in the tire radial direction is equal to the length of the second bent element in the tire radial direction. preferably the same.

In the sipe repeating element provided in the tread portion of the tire of the present invention, since the first sipe piece and the third sipe piece extend in the axial direction of the tire, a large frictional force is provided in the circumferential direction of the tire when running on ice. , and consequently, traction performance and braking performance on ice can be enhanced. Further, in the repeating element, when a shearing force in the tire circumferential direction acts, the sipe walls facing each other in the second sipe piece and the fourth sipe piece contact each other, and thus the first sipe piece and the third sipe piece can be prevented from opening excessively. Such action reduces the amount of slippage between the edges of the first sipe piece and the third sipe piece and the road surface when the edges of the first sipe piece and the third sipe piece separate from the road surface. Therefore, uneven wear near the edge is suppressed.

At least one of the first sipe piece and the third sipe piece includes an amplitude portion extending in the tire radial direction to oscillate in a lateral direction perpendicular to the longitudinal direction in a cross section perpendicular to the longitudinal direction of the sipe. . When ground pressure is applied to the tread portion, the sipe walls facing each other contact and mesh with each other, so that the tread portion maintains the rigidity of the tread portion in the tire circumferential direction. Therefore, traction performance and braking performance on ice are further improved.

1 is a cross-sectional view of a tread portion of a tire according to one embodiment of the present invention; FIG. FIG. 2 is an enlarged plan view of the land portion of FIG. 1; Figure 3 is an enlarged perspective view of the block of Figure 2; 4 is an enlarged view of a repeating element of the sipe of FIG. 3; FIG. FIG. 10 is an enlarged view of the repeating element when the sipe is open; FIG. 5 is a cross-sectional view taken along line AA of FIG. 4; FIG. 5 is a cross-sectional view taken along line BB of FIG. 4; 7 is a graph showing the stiffness of the block when the amplitude part of the first sipe piece and the amplitude part of the third sipe piece oscillate in opposite phases. 7 is a graph showing the stiffness of the block when the amplitude portion of the first sipe piece and the amplitude portion of the third sipe piece oscillate in the same phase; FIG. 5 is a cross-sectional view taken along line CC of FIG. 4;

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows a cross-sectional view of a tread portion 2 of a tire 1 of this embodiment. Note that FIG. 1 is a meridional sectional view including the tire rotation axis in the normal state of the tire 1 . The tire 1 of the present embodiment is suitably used as, for example, a pneumatic tire for passenger cars. However, it is not limited to such a mode, and the tire 1 of the present invention may be used for heavy loads, for example.

"Normal state" means a no-load state in which the tire is mounted on a normal rim and inflated to a normal internal pressure. Hereinafter, unless otherwise specified, the dimensions of each part of the tire are values measured in this normal state.

A "regular rim" is a rim defined for each tire in a standard system that includes standards on which tires are based. For ETRTO, it is "Measuring Rim".

"Regular internal pressure" is the air pressure specified for each tire by each standard in the standard system including the standards on which tires are based. Maximum value described in VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

As shown in FIG. 1 , the tread portion 2 is provided with, for example, a plurality of main grooves 3 continuously extending in the tire circumferential direction and land portions 4 partitioned by the main grooves 3 .

FIG. 2 shows an enlarged plan view of the land portion 4. As shown in FIG. As shown in FIG. 2, the land portion 4 of the present embodiment is configured, for example, as a row of blocks including a plurality of blocks 6 in the tire circumferential direction. The blocks 6 are partitioned between a plurality of lateral grooves 5 crossing the land portion 4 in the tire axial direction.

An enlarged perspective view of the block 6 is shown in FIG. It should be noted that a part of the block 6 is cut in FIG. 3 for easy understanding of the invention. As shown in FIG. 3 , a plurality of sipes 8 are provided on the contact surface of the tread portion 2 . In this embodiment, one block 6 is provided with a plurality of sipes 8 . However, the present invention is not limited to such blocks, and for example, the sipes 8 may be provided on ribs continuously extending in the tire circumferential direction. As used herein, "sipe" means an incision with a width of 1.5 mm or less. More preferably, the width of the sipe 8 is, for example, 0.2-0.5 mm.

Sipe 8 includes a portion in which a plurality of repeating elements 9 are continuous in the longitudinal direction of sipe 8 . Each repeating element 9 is bent so that four sipe pieces 10 form an acute angle with each other. Also, the four sipe pieces 10 include a first sipe piece 11 , a second sipe piece 12 , a third sipe piece 13 and a fourth sipe piece 14 .

An enlarged view of the repeating element 9 is shown in FIG. As shown in FIG. 4, the first sipe piece 11 extends in the tire axial direction. The second sipe piece 12 extends from the end of the first sipe piece 11 in the first tire axial direction (right direction in FIG. 4) toward the first tire circumferential direction a (upward direction in FIG. 4). ing. The third sipe piece 13 extends from the second sipe piece 12 in the axial direction of the first tire. The fourth sipe piece 14 continues to the third sipe piece 13 and extends from the third sipe piece 13 toward the second tire circumferential direction b (downward in FIG. 4) opposite to the first tire circumferential direction. ing.

In the repeating element 9 of the sipe 8 of the present invention, since the first sipe piece 11 and the third sipe piece 13 extend in the axial direction of the tire, it provides a large frictional force in the circumferential direction of the tire when running on ice. traction performance and braking performance can be enhanced.

FIG. 5 shows an enlarged view of repeating element 9 when sipe 8 is open. For easy understanding of the invention, in FIG. 5, the opening portions of the repeating elements 9 are colored. As shown in FIG. 5 , in the repeating element 9, when a shear force in the tire circumferential direction acts, the sipe walls facing each other in the second sipe piece 12 and the fourth sipe piece 14 come into contact with each other, and thus the first sipe Excessive opening of the piece 11 and the third sipe piece 13 can be suppressed. Such action reduces the amount of slippage between the edges of the first sipe piece 11 and the third sipe piece 13 and the road surface when the edges are separated from the road surface. Therefore, uneven wear near the edge is suppressed.

6 shows a cross-sectional view of the first sipe piece 11 of FIG. 4 along the line AA, and FIG. 7 shows a cross-sectional view of the third sipe piece 13 of FIG. 4 along the line BB. As shown in FIGS. 6 and 7, at least one of the first sipe piece 11 and the third sipe piece 13 oscillates in the lateral direction perpendicular to the longitudinal direction in a cross section perpendicular to the longitudinal direction, and the tire is It includes a radially extending amplitude portion 15 . As a desirable aspect, both the 1st sipe piece 11 and the 3rd sipe piece 13 contain the amplitude part 15 in this embodiment. When ground pressure is applied to the tread portion 2 , the sipe walls facing each other contact and mesh with each other in the amplitude portion 15 , so that the rigidity of the tread portion 2 in the tire circumferential direction is maintained. Therefore, traction performance and braking performance on ice are further improved. Moreover, such an amplitude portion 15 also improves steering stability on a dry road surface.

As shown in FIG. 4 , the first sipe piece 11 and the third sipe piece 13 extend at an angle of 35° or less with respect to the tire axial direction, for example. The angle of the first sipe piece 11 and the third sipe piece 13 with respect to the tire axial direction is preferably 15° or less, more preferably 5° or less. As a more desirable aspect, the first sipe piece 11 and the third sipe piece 13 of this embodiment extend parallel to the tire axial direction.

The length of the first sipe piece 11 is desirably the same as the length of the third sipe piece 13 . Moreover, the length of the second sipe piece 12 and the length of the fourth sipe piece 14 are preferably smaller than the length of the first sipe piece 11 or the length of the third sipe piece 13, for example. In this embodiment, the length of the second sipe piece 12 is the same as the length of the fourth sipe piece 14 .

In the repeating element 9 of this embodiment, four sipe pieces 10 are bent so as to form an angle θ1 of 30 to 70° with each other. More preferably, the angle θ1 is 30-40°. If the angle of the corner portion 10a formed by each sipe piece 10 is less than 30°, the rigidity of the corner portion 10a may decrease and the effect of suppressing the opening and displacement of the sipe 8 may decrease. There is a risk that the axial frictional force provided by the element 9 will be reduced. Further, when the angle is larger than 70°, the effect of suppressing the opening of the sipe 8 tends to be small in the second sipe piece 12 and the fourth sipe piece 14 . In this embodiment, the angles of the corner portions 10a formed by the sipe pieces 10 are all the same. However, the present invention is not limited to such an aspect.

As shown in FIGS. 6 and 7, each amplitude portion 15 preferably extends in a zigzag shape from the outer surface of the tread portion 2 in the tire radial direction. However, the present invention is not limited to such an aspect, and each amplitude portion 15 may extend, for example, in a sinusoidal shape in the radial direction of the tire.

The amplitude portion 15 of the first sipe piece 11 and the amplitude portion 15 of the third sipe piece 13 are configured to have the same amplitude wavelength and amplitude width. In a desirable aspect, the amplitude portion 15 of the first sipe piece 11 and the amplitude portion 15 of the third sipe piece 13 oscillate in opposite phases and extend in the tire radial direction.

FIG. 8 shows the stiffness of the block 6 (shown in FIG. 2) when the amplitude portion 15 of the first sipe piece 11 and the amplitude portion 15 of the third sipe piece 13 oscillate in opposite phases as described above. A representative graph is shown. FIG. 9 shows a graph showing the stiffness of the block 6 when the amplitude portion 15 of the first sipe piece 11 and the amplitude portion 15 of the third sipe piece 13 oscillate in the same phase. 8 and 9, the horizontal axis represents the load acting on the block 6 in the tire circumferential direction, and the vertical axis represents the rigidity of the block 6 in the tire circumferential direction. Graph a in FIG. 8 and graph c in FIG. 9 indicated by solid lines show the stiffness of the block 6 during traction, and graphs b in FIG. 8 and graph d in FIG. shows the stiffness of the block 6 of .

As shown in FIG. 8, in this embodiment, it can be understood that the rigidity of the block 6 is similar even during traction and braking. Thus, in the present embodiment, the amplitude portion 15 of the first sipe piece 11 and the amplitude portion 15 of the third sipe piece 13 oscillate in opposite phases and extend in the tire radial direction. Regarding the rigidity of the tire, the anisotropy in the tire circumferential direction is unlikely to occur, and the traction performance and the braking performance can be equally improved, so the tread pattern can be made non-directional.

On the other hand, as shown in FIG. 9, when the first sipe piece 11 and the third sipe piece 13 oscillate in the same phase, the maximum values of the graph c and the graph d differ by about 15%. It can be seen that the rigidity of the blocks differs during braking. That is, in this embodiment, since both the first sipe piece 11 and the third sipe piece 13 increase the rigidity of one side of the block 6 in the tire circumferential direction, the rigidity of the other side in the tire circumferential direction is relatively low. As a result, the rigidity of the block 6 tends to be anisotropic in the tire circumferential direction.

As shown in FIG. 4, in the present embodiment in which the third sipe piece 13 is arranged closer to the first tire circumferential direction a than the first sipe piece 11, the amplitude of the first sipe piece 11 closest to the tread surface The starting portion 11a (shown in FIG. 6) is desirably inclined inward in the tire radial direction toward the second tire circumferential direction b. Similarly, the amplitude starting portion 13a (shown in FIG. 7) of the third sipe piece 13 closest to the tread surface is desirably inclined inward in the tire radial direction toward the first tire circumferential direction a. In other words, the amplitude start portion 11a of the first sipe piece 11 and the amplitude start portion 13a of the third sipe piece 13 are inclined inward in the tire radial direction so as to separate from each other. As a result, a large rubber volume is ensured for the rubber pieces surrounded by the sipe pieces, so that chipping of the rubber during demolding in the manufacturing process can be suppressed.

As shown in FIG. 6, preferably, the amplitude portion 15 includes two or more first protrusions 16 protruding on one side in the horizontal direction. The amplitude section 15 of the present embodiment is composed of two first protrusions 16 and one second protrusion 17 that protrudes toward the other side in the horizontal direction between the two first protrusions 16. . Such an amplitude portion 15 effectively suppresses shear deformation of the block 6 when the sipe walls come into contact with each other.

A widthwise center line 15 c of the amplitude portion 15 includes a first vertex 16 a bent at the first convex portion 16 and a second vertex 17 a bent at the second convex portion 17 . A virtual straight line (not shown) connecting both ends of the center line 15c of the amplitude portion 15 is preferably parallel to the tire radial direction. Moreover, it is desirable that the second vertex 17a be arranged on the virtual straight line. As a result, the anisotropy of the rigidity of the blocks 6 in the tire circumferential direction is suppressed. Further, the knife blade of the vulcanization mold that forms the amplitude portion 15 is not easily deformed when it comes into contact with raw rubber of the tire during vulcanization molding, and excellent moldability can be obtained.

The center line 15c of the amplitude portion 15 includes a tire radially outer outer end 15o and a tire radially inner inner end 15i. The amplitude portion 15 includes a first bent element 18 from the outer end 15o to the second vertex 17a and a second bent element 19 from the second vertex 17a to the inner end 15i. The length L1 of the first bent element 18 in the tire radial direction is preferably 0.8 to 1.2 times the length L2 of the second bent element 19 in the tire radial direction. The length L2 is the same. Such an amplitude portion 15 can uniformly improve traction performance and braking performance on ice.

If the bending width A of the amplitude portion 15 is small, the rigidity of the block 6 may not be sufficiently improved. On the other hand, if the bending width A of the amplitude portion 15 is large, the block 6 will flex more when a load perpendicular to the tread surface of the block 6 is applied, which may lead to a decrease in steering stability on dry road surfaces. Further, when the bending width A is large, the vulcanizing die forming the vulcanizing knife blade tends to be difficult to remove from the vulcanizing mold. From this point of view, the bending width A of the amplitude portion 15 is, for example, 0.4 to 1.0 mm. The bending width A is the horizontal distance from the first vertex 16a to the second vertex 17a.

It is preferable that a linear bottom portion 22 extending parallel to the tire radial direction continues to the inner side of the amplitude portion 15 in the tire radial direction. As a result, during vulcanization molding, the knife blade of the vulcanization mold that forms the amplitude portion 15 can easily pierce the raw rubber of the tire, thereby suppressing deformation and breakage of the knife blade.

From the viewpoint of achieving both on-ice performance of the tire and moldability during vulcanization molding of the tire, the length L4 of the linear bottom portion 22 in the tire radial direction is the length of the sipe piece 10 to which the linear bottom portion 22 belongs in the tire radial direction. It is desirable that the height is 0.10 to 0.30 times L3.

FIG. 10 shows a CC line cross-sectional view of the second sipe piece 12 of FIG. As shown in FIG. 10, the second sipe piece 12 preferably extends linearly in the tire radial direction. The 4th sipe piece 14 is also the same. As a result, when the first sipe piece 11 and the third sipe piece 13 are opened, the sipe walls of the second sipe piece 12 and the fourth sipe piece 14 are easily brought into close contact with each other over a large surface, and the block 6 is thus positioned in the circumferential direction of the tire. rigidity is improved. If the second sipe piece 12 and the fourth sipe piece 14 extend in a zigzag pattern in the radial direction of the tire, the gap between the sipe walls facing each other becomes large, which may reduce the rigidity of the block 6 in the tire circumferential direction. .

The sipe 8 of this embodiment can be vulcanized by a well-known method using a knife blade including a portion extending in a zigzag shape.

Although the tire of one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be implemented in various ways.

A pneumatic tire of size 195/65R15 having the above-described sipe was produced as a trial based on the specifications in Table 1. As a comparative example, a prototype tire was produced in which the sipe did not have an oscillating portion and the entire sipe extended linearly in the tire radial direction. Each test tire had substantially the same construction, except for the shape of the sipes. Each test tire was tested for traction performance on ice, braking performance on ice, turning performance on ice, steering stability on dry roads, and resistance to uneven wear. Common specifications and test methods for each test tire are as follows.
Mounting rim: 15×6.0JJ
Tire internal pressure: front wheel 230kPa, rear wheel 230kPa
Test vehicle: 1500cc displacement, front-wheel drive Tire mounting position: All wheels

<Traction performance on ice>
The traction performance of the test vehicle equipped with each test tire was evaluated by the driver's sensory perception when the test vehicle was driven on an icy road. The results are scored with the traction performance of the comparative example being 100, and the larger the value, the better the traction performance on ice.

<Brake performance on ice>
The braking performance of the test vehicle on which each test tire was mounted was evaluated by the driver's senses when the test vehicle was driven on an icy road. The results are scores with the braking performance of the comparative example being 100, and the larger the number, the better the braking performance on ice.

<Swing performance on ice>
The turning performance of the test vehicle on which each test tire was mounted was evaluated by the driver's sensory perception when the test vehicle was driven on an icy road. The results are scored with the turning performance of the comparative example being 100, and the larger the number, the better the turning performance on ice.

<Driving stability on dry road surface>
The steering stability of the test vehicle on which each test tire was mounted was evaluated by the driver's senses when the test vehicle was driven on a dry road surface. The results are scored with the steering stability of the comparative example being 100, and the larger the number, the better the steering stability on dry road surfaces.

<Uneven wear resistance performance>
A wear energy measuring device was used to measure the wear energy of the sipe edge of each test tire. The results are indexed with the reciprocal of the wear energy of Comparative Example 1 being 100, and the larger the figure, the smaller the wear energy and the better the uneven wear resistance.
The results of the tests are shown in Table 1.

As a result of the test, it was confirmed that the tires of Examples exhibited excellent performance on ice and resistance to uneven wear. In addition, it was confirmed that the tires of the examples had improved steering stability on dry road surfaces.

2 tread portion 8 sipe 9 repeating element 10 sipe piece 11 first sipe piece 12 second sipe piece 13 third sipe piece 14 fourth sipe piece 15 amplitude portion

Claims (10)

A tire including a tread portion,
The tread portion is provided with a sipe,
The sipe includes a portion in which a plurality of repeating elements are continuous in the longitudinal direction of the sipe,
each of the repeating elements has four sipe pieces that are bent to form an acute angle with each other;
The four sipe pieces are
a first sipe piece extending in the axial direction of the tire;
a second sipe piece extending from the first tire axial end of the first sipe piece to the first tire circumferential direction side;
a third sipe piece extending in the axial direction of the first tire from the second sipe piece;
a fourth sipe piece continuous with the third sipe piece and extending from the third sipe piece to a second tire circumferential direction side opposite to the first tire circumferential direction,
Both the first sipe piece and the third sipe piece include an amplitude portion that oscillates in a lateral direction orthogonal to the longitudinal direction and extends in the tire radial direction in a cross section orthogonal to the longitudinal direction,
The amplitude portion of the first sipe piece and the amplitude portion of the third sipe piece extend in the tire radial direction while oscillating in phases opposite to each other.
tire. The tire according to claim 1, wherein each of said first sipe piece and said third sipe piece extends at an angle of 35° or less with respect to the tire axial direction. The tire according to claim 1 or 2, wherein the repeating element is bent such that the four sipe pieces form an angle of 30 to 70 degrees with each other. The tire according to any one of claims 1 to 3, wherein a linear bottom portion extending parallel to the tire radial direction continues to the inner side of the amplitude portion in the tire radial direction. The tire according to claim 4, wherein the radial length of the linear bottom portion is 0.10 to 0.30 times the radial length of the sipe piece to which the linear bottom portion belongs. The tire according to any one of claims 1 to 5, wherein the bending width of said amplitude portion is 0.4 to 1.0 mm. The tire according to any one of claims 1 to 6, wherein the amplitude portion includes two or more first protrusions that protrude on one side in the lateral direction. 8. The amplitude portion is composed of two of the first convex portions and one second convex portion projecting to the other side in the horizontal direction between the two first convex portions. Tires as stated. A center line in the width direction of the amplitude portion includes a first vertex that is bent at the first convex portion and a second vertex that is bent at the second convex portion,
A virtual straight line connecting both ends of the center line is parallel to the tire radial direction,
The tire according to claim 8, wherein said second vertex is arranged on said imaginary straight line. the center line of the amplitude portion includes an outer end on the radially outer side of the tire and an inner end on the inner side in the tire radial direction;
The amplitude portion includes a first bent element from the outer end to the second vertex and a second bent element from the second vertex to the inner end,
10. Tire according to claim 9, wherein the tire radial length of the first bent element is the same as the tire radial length of the second bent element.

Images