JP2017226368A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To strike a balance between on-snow performance and wet performance at high level.SOLUTION: A middle lug groove 5 forms an S-shape that is constituted of: an inclined groove part 10 extending while being linearly inclined at an angle θ on a center side of a middle land part 4M; a first circular arc groove part 11 extending along a circular arc of a curvature radius R1 from an inner end of the inclined groove part 10 to a crown main groove 3C; and a second circular arc groove part 11 extending along a circular arc of a curvature radius R2 from an outer end of the inclined groove part 10 to a shoulder main groove 3S.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire that can be suitably used as a winter tire and can achieve both high performance on snow and wet performance.

  In pneumatic tires, especially winter tires with improved snowy road performance, the tread part has a block pattern divided into multiple blocks by circumferential grooves extending in the tire circumferential direction and lug grooves extending in the tire axial direction. Widely used (see, for example, Patent Document 1). In this main pattern, the gripping force in the circumferential direction is obtained by the shearing force of the snow column pressed in the lug groove, and there are cases where it is referred to as “snow traction” (hereinafter referred to as “snow traction”). ) Is demonstrated.

  Therefore, in order to improve snow traction, it is desired to increase the groove volume and the number of grooves of the lug grooves. However, the drainage direction of the lug groove extending in the tire axial direction is inferior in drainage because the drainage direction is orthogonal to the tire rotation direction (circumferential direction). Therefore, in tires having the same land ratio, an increase in the groove volume and the number of grooves of the lug groove increases the snow traction property, but decreases the wet performance, and the snow traction property and the wet performance are in a trade-off relationship. .

  In addition, drainage can be improved by inclining a lug groove at 25-65 degrees, for example with respect to a tire circumferential direction (for example, refer patent document 2). However, even in this case, since the grip force in the circumferential direction is reduced to some extent, further studies are necessary to achieve both high levels of snow traction and wet performance.

JP 2006-298202 A JP 2006-1346 A

  Therefore, the present invention is based on the fact that the middle lug groove is formed in an S shape composed of an inclined groove portion and first and second arc groove portions, and a pneumatic tire capable of achieving both a high level of snow traction and wet performance. The issue is to provide.

The present invention provides the tread portion by providing a shoulder main groove extending in the tire circumferential direction on the tread end side and one or more crown main grooves extending in the tire circumferential direction between the shoulder main grooves. A pneumatic tire divided into four or more land portions including a shoulder land portion outside the shoulder main groove in the tire axial direction, and a middle land portion between the shoulder main groove and the crown main groove,
The middle land portion includes a plurality of middle lag grooves that cross the middle land portion,
The middle lug groove includes an inclined groove portion that linearly inclines the middle side of the middle land portion at an angle θ with respect to the tire circumferential direction, and a radius of curvature from the inner end in the tire axial direction of the inclined groove portion to the crown main groove. The first arc groove portion extending in the arc of R1 and the second arc groove portion extending in the arc of the radius of curvature R2 from the outer end in the tire axial direction of the inclined groove portion to the shoulder main groove are characterized in that the S-shape is formed. .

In the pneumatic tire according to the present invention, the first arc groove portion has an angle α1 of 75 to 90 ° with respect to a tire circumferential direction at a connection portion with the crown main groove,
And it is preferable that angle (beta) 1 with respect to the tire circumferential direction in a connection part with the said shoulder main groove is said 2nd circular arc groove part is 75-90 degrees.

In the pneumatic tire according to the present invention, the middle land portion extends from the crown main groove outward in the tire axial direction and is interrupted in the middle land portion without intersecting the middle lug groove, and the shoulder main portion. A second sipe extending inward in the tire axial direction from the groove and interrupted in the middle land portion without intersecting the middle lug groove;
The first sipe and the second sipe are preferably located on the same straight line.

  In the pneumatic tire according to the present invention, the first arc groove portion has a widened portion that becomes wider toward the crown main groove at the connection portion with the crown main groove, and the second arc groove portion is It is preferable that the connecting portion with the shoulder main groove has a widened portion that becomes wider toward the shoulder main groove.

  In the pneumatic tire according to the present invention, the middle land portion is divided into a plurality of middle blocks by the middle lug groove, and the middle block is bound to the center side by forming the middle lug groove in an S shape. It is preferable that the hook portion has a hook shape and the width Wa of the constricted portion is 30 to 50% of the width Wm of the middle land portion.

In the pneumatic tire according to the present invention, the shoulder land portion includes a plurality of shoulder lug grooves crossing the shoulder land portion,
The connecting portion of the shoulder lug groove with the shoulder main groove and the connecting portion of the middle lug groove with the shoulder main groove are preferably located on the same tire axial direction line.

In the pneumatic tire according to the present invention, since there are two crown main grooves, a center land portion is formed between the crown main grooves, and the center land portion is located on the inner side in the tire axial direction from the crown main groove. It has a triangular slot that extends,
It is preferable that the connection portion of the slot with the crown main groove and the connection portion of the middle lug groove with the crown main groove are located on the same tire axial line.

  In the pneumatic tire according to the present invention, it is preferable that the inclination direction of the inclined groove portion with respect to the tire circumferential direction is different from the inclination direction of the first and second sipes with respect to the tire circumferential direction.

  In the pneumatic tire according to the present invention, it is preferable that an angle γ of the first and second sipes with respect to the inclined groove portion is 80 to 100 °.

  In the pneumatic tire according to the present invention, the angle θ of the inclined groove portion is preferably 15 to 25 °.

  In the present invention, as described above, the middle lug groove has an S-shape including an inclined groove portion and first and second arc groove portions. When the inclined groove portion of the middle lug groove is linearly inclined with respect to the tire circumferential direction, drainage is improved and wet performance is improved as compared with the lug groove extending in the tire axial direction.

  On the other hand, since the first and second arc groove portions of the middle lug groove have an arc shape, the angle with respect to the tire circumferential direction gradually increases toward the crown main shoulder and the shoulder main groove. Therefore, the circumferential component of the snow column shear force by the first and second arc grooves is larger than when the entire middle lug groove is formed by the inclined groove. In addition, since the snow column in the middle lug groove has an S-shape, the secondary section coefficient of the snow column becomes large, and the snow column is difficult to break even when bent or twisted. Therefore, combined with the increase in the snow column shear force in the circumferential direction described above, the grip force can be improved and the snow traction property can be enhanced.

  Further, the first and second arc groove portions are smoothly connected to the inclined groove portion, and therefore, resistance to drainage is small, and high drainage by the inclined groove portion can be maintained.

It is an expanded view which shows one Example of the tread pattern of the pneumatic tire of this invention. It is an enlarged view of a middle lug groove. (A), (B) is an enlarged view which shows the positional relationship of a 2nd circular arc groove part and a shoulder lug groove, and the positional relationship of a 1st circular arc groove part and a slot.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the pneumatic tire 1 of the present embodiment extends on the tread portion 2 in the tire circumferential direction between the shoulder main groove 3S extending in the tire circumferential direction on the tread end Te side and the shoulder main groove 3S. One or more crown main grooves 3C are provided. As a result, the tread portion 2 includes four or more land including a shoulder land portion 4S outside the shoulder main groove 3S in the tire axial direction and a middle land portion 4M between the shoulder main groove 3S and the crown main groove 3C. Divided into parts 4.

  In this example, there are two crown main grooves 3C. Therefore, the tread portion 2 includes a total of five land portions including a shoulder land portion 4S, a middle land portion 4M, and a center land portion 4C between the crown main grooves 3C. The case where it is divided into land parts 4 is shown.

  In this example, a case is shown in which the shoulder main groove 3S and the crown main groove 3C are formed as linear grooves extending linearly in the tire circumferential direction. Such a straight groove is preferable for suppressing unstable behavior such as wobbling of the vehicle. However, in addition to the linear groove, a zigzag groove (including a wave shape) or the like can also be adopted.

  The middle land portion 4M includes a plurality of middle lug grooves 5 crossing the middle land portion 4M, whereby the middle land portion 4M is divided into a plurality of middle blocks 6.

  As shown in FIG. 2, the middle lug groove 5 has an S shape including an inclined groove portion 10, a first arc groove portion 11, and a second arc groove portion 12.

  The inclined groove portion 10 is disposed on the center side in the width direction of the middle land portion 4M, and is inclined linearly at an angle θ with respect to the tire circumferential direction. The angle θ is preferably in the range of 15 to 25 °.

  The first arc groove portion 11 extends in an arc having a radius of curvature R1 from the inner end in the tire axial direction of the inclined groove portion 10 to the crown main groove 3C. The second arcuate groove 12 extends from the outer end in the tire axial direction of the inclined groove 10 to the shoulder main groove 3S in an arc having a radius of curvature R2. The curvature radius R1 and the curvature radius R2 are preferably in the range of 10 to 15 mm.

  Here, the angle α of the first arc groove portion 11 with respect to the tire circumferential direction gradually increases toward the crown main groove 3C, and becomes the maximum angle α1 at the connection portion E1 of the first arc groove portion 11 with the crown main groove 3C. . Further, the angle β of the second arcuate groove portion 12 with respect to the tire circumferential direction gradually increases toward the shoulder main groove 3S, and becomes the maximum angle β1 at the connection portion E2 of the second arcuate groove portion 12 with the shoulder main groove 3S. The angle α1 and the angle β1 are preferably 75 to 90 °.

  Strictly speaking, the radii of curvature R1 and R2 are radii of curvature at the groove center lines of the first and second circular groove portions 11 and 12, respectively. The angles α and β are angles formed by tangents at the groove center lines of the first and second arcuate groove portions 11 and 12 with the tire circumferential direction line. The angle θ is an angle formed by the groove center line of the inclined groove portion 10 and the tire circumferential direction line.

  Such an S-shaped middle lug groove 5 exhibits excellent drainage due to the inclined groove portion 10. Further, the angles α and β of the first and second arc groove portions 11 and 12 gradually increase toward the crown main groove 3C and the shoulder main groove 3S. Therefore, the circumferential direction component of the snow column shear force by the 1st, 2nd circular arc groove parts 11 and 12 becomes large. Moreover, since the snow column in the middle lug groove 5 has an S shape, it is difficult to break even when bent or twisted. Therefore, the snow traction property can be improved in combination with the increase in the snow column shear force in the circumferential direction described above. Further, since the first and second arc groove portions 11 and 12 are smoothly connected to the inclined groove portion 10, resistance to drainage is small, and high drainage by the inclined groove portion 10 can be maintained.

  In this example, the 1st circular arc groove part 11 has the wide part E1a which becomes wide toward 3 C of crown main grooves in the said connection part E1. The second arcuate groove portion 12 has a widened portion E2a that becomes wider toward the shoulder main groove 3S at the connection portion E2. Due to the widened portions E1a and E2a, water and snow can easily flow out from the middle lug groove 5 to the crown main groove 3C and the shoulder main groove 3S, and drainage and snow drainage can be improved. The maximum width WE of the widened portions E1a and E2a is preferably 2.0 times or less of the groove width W10 of the inclined groove portion 10 from the viewpoint of maintaining the ground contact area and block rigidity.

  Here, when the angle θ is less than 15 °, the snow column shearing force in the circumferential direction by the inclined groove portion 10 becomes small, which causes a decrease in snow traction. On the other hand, if it exceeds 25 °, the drainage is reduced and the wet performance tends to be lowered.

  On the other hand, when the angle α1 and the angle β1 are less than 75 °, the snow column shearing force in the circumferential direction becomes small, so that the snow traction tends to be lowered.

  When the radius of curvature R1 and the radius of curvature R2 are less than 10 mm, in the middle block 6, the corner portion 6e sandwiched between the first arc groove portion 11 and the crown main groove 3C, the second arc groove portion 12 and the shoulder main portion. The corner portion 6e sandwiched between the groove 3S has an excessively low rigidity, which leads to a decrease in steering stability. Conversely, if it exceeds 15 mm, the snow traction tends to decrease.

  Further, the middle block 6 has a bowl shape having a constricted portion 15 at the center thereof by forming the middle lug groove 5 in an S shape. Such a middle block 6 is compressed and elastically deformed at the time of ground contact, and is easily restored to its original shape when opened. By repeating this, the effect of discharging the snow in the middle lug groove 5 is enhanced, so that the middle lug groove 5 can be prevented from being clogged, and snow traction can be improved. Therefore, the width Wa of the constricted portion 15 is preferably 30 to 50% of the width Wm of the middle land portion 4M. If it exceeds 50%, the emission effect will decrease. On the other hand, if it is less than 30%, the rigidity of the constricted portion 15 is excessively reduced, leading to a tendency to decrease steering stability and a tendency to cause uneven wear.

  The middle land portion 4 </ b> M of this example includes a plurality of first sipes 16 and a plurality of second sipes 17. The first sipe 16 extends outward from the crown main groove 3C in the tire axial direction. Further, the outer end of the first sipe 16 in the tire axial direction is interrupted in the middle land portion 4 </ b> M without intersecting the middle lug groove 5. On the other hand, the second sipe 17 extends from the shoulder main groove 3S inward in the tire axial direction. Further, the inner end in the tire axial direction of the second sipe 17 is interrupted in the middle land portion 4 </ b> M without intersecting the middle lug groove 5. The first sipe 16 and the second sipe 17 are located on the same straight line.

  Such first and second sipes 16 and 17 alleviate the rigidity of the remaining portion other than the constricted portion 15. Therefore, the rigidity in the middle block 6 can be made uniform, and the deterioration of steering stability and the occurrence of uneven wear can be suppressed. In this example, one each of the first and second sipes 16 and 17 is arranged in each middle block 6.

  Further, the inclination direction of the first and second sipes 16 and 17 with respect to the tire circumferential direction (upward to the right in FIG. 2) is preferably different from the inclination direction of the inclined groove portion 10 with respect to the tire circumferential direction (upward to the left in FIG. 2). . In particular, the angle γ of the first and second sipes 16 and 17 with respect to the inclined groove portion 10 is preferably 80 to 100 °. Thereby, in the middle block 6 that is long in the tire axial direction, the balance between the tire circumferential rigidity and the tire axial rigidity can be optimized, which helps to ensure steering stability.

  As shown in FIG. 1, in this example, a plurality of shoulder lug grooves 18 are arranged across the shoulder land portion 4S. As a result, the shoulder land portion 4 </ b> S is divided into a plurality of shoulder blocks 19. A slot 20 is disposed in the center land portion 4C.

  The shoulder lug groove 18 extends from the outer side of the tread end Te to the inner side in the tire axial direction, and is connected to the shoulder main groove 3S. In this example, the inclination direction of the shoulder lug groove 18 with respect to the tire circumferential direction is different from the inclination direction of the middle lug groove 5 with respect to the tire circumferential direction. For example, two auxiliary lug grooves 21 are arranged between the shoulder lug grooves 18 and 18. The auxiliary lug groove 21 extends substantially parallel to the shoulder lug groove 18, and at least one end, in this example, the outer end in the tire axial direction is interrupted in the shoulder land portion 4S.

  The slot 20 has a triangular shape extending inward in the tire axial direction from the crown main groove 3C, and its inner end is interrupted in the center land portion 4C. Accordingly, the center land portion 4C is formed as a circumferential rib extending continuously in the tire circumferential direction. In this example, the inclination direction of the slot 20 with respect to the tire circumferential direction is different from the inclination direction of the middle lug groove 5 with respect to the tire circumferential direction.

  In this example, the pitch numbers of the shoulder lug grooves 18 and the slots 20 are each set to be twice the pitch number of the middle lug grooves 5. In this case, the shoulder block 19 having a large circumferential rigidity and the middle block 6 having a small circumferential rigidity are combined to balance wet performance, snow traction, and driving stability on a dry road surface. It can be made.

  In this example, the connection portion E3 of the shoulder lug groove 18 with the shoulder main groove 3S is located on the same tire axial direction line as the connection portion E2 of the middle lug groove 5 with the shoulder main groove 3S. Further, the connection portion E4 of the slot 20 with the crown main groove 3C is located on the same tire axial direction line as the connection portion E1 of the middle lug groove 5 with the crown main groove 3C.

  Thereby, the water from the shoulder lug groove | channel 18 and the water from the middle lug groove | channel 5 can be effectively poured in into the shoulder main groove | channel 3S, and it is preferable for hydro performance. Similarly, water from the middle lug groove 5 and water from the slot 20 can be effectively flowed into the crown main groove 3C, which is preferable for hydro performance.

  In addition, as shown to FIG. 3 (A), when the connection part E3 is located on the same tire axial direction line j as the connection part E2, it is a part of opening of the connection part E3 on the same tire axial direction line j. And a part of the opening of the connection portion E2 may be located together. However, it is preferable that the opening width center of the connection portion E3 and the opening width center of the connection portion E2 coincide. Also, as shown in FIG. 3B, when the connecting portion E4 is located on the same tire axial direction line j as the connecting portion E1, a part of the opening of the connecting portion E4 on the tire axial direction line j, and A part of the opening of the connection part E1 should just be located together. However, it is preferable that the opening width center of the connection portion E4 and the opening width center of the connection portion E1 coincide.

  In this example, the connection part E1 of the middle lug groove 5 arranged in one middle land part 4M and the connection part E1 of the middle lug groove 5 arranged in the other middle land part 4M are on the same tire axial line. positioned.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to illustrated embodiment, It can deform | transform and implement in a various aspect.

  A pneumatic tire of size 215 / 60R16 having the basic pattern of FIG. The test stability, snow traction, on-ice performance, and wet performance of each prototype tire were tested by the following methods, and the results are shown in Table 1. Each tire has substantially the same specifications except those listed in Table 1.

(1) Steering stability:
The prototype tires were mounted on all the wheels of the vehicle (2500cc, FF vehicle) under the conditions of rim (16 x 6.5J) and internal pressure (230kPa), and sports running on dry asphalt road test courses in various driving modes. . The evaluation was made with an index with Comparative Example 1 as 100 by sensory evaluation of the driver. The larger the value, the better the steering stability.

(2) Snow traction:
Using the vehicle, the braking distance was measured when full braking was performed on the snow from a speed of 50 km / h. The evaluation was performed using an index with the reciprocal of the braking distance of Comparative Example 1 as 100. The larger the value, the better the snow traction.

(3) Performance on ice:
Using the vehicle, the vehicle traveled on an icy road at a temperature of −2 ° C., and the characteristics relating to steering response, stability during turning, grip feeling, and the like were evaluated by an index with Comparative Example 1 set to 100 by sensory evaluation of the driver. The larger the value, the better the performance on ice.

(4) Wet performance:
Using the above vehicle, a circular turn was performed on a course provided with a puddle having a depth of 5 mm and a length of 20 m, and the maximum lateral G was measured. The larger the value, the better the wet performance.

  As shown in the table, it can be confirmed that the tires of the examples can achieve both high levels of snow traction and wet performance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3C Crown main groove 3S Shoulder main groove 4 Land part 4C Center land part 4M Middle land part 4S Shoulder land part 5 Middle lug groove 6 Middle block 10 Inclined groove part 11 First circular groove part 12 Second circular groove part 15 Narrow part 16 1st sipe 17 2nd sipe 18 Shoulder lug groove 20 Slot E1a, E2a Widened part E1-E4 Connection part Te Tread end

Claims (10)

The tread portion is provided with a shoulder main groove extending in the tire circumferential direction on the tread end side and one or more crown main grooves extending in the tire circumferential direction between the shoulder main grooves, so that the tread portion becomes the shoulder main groove. A pneumatic tire partitioned into four or more land portions including a shoulder land portion outside the tire axial direction, and a middle land portion between the shoulder main groove and the crown main groove,
The middle land portion includes a plurality of middle lag grooves that cross the middle land portion,
The middle lug groove includes an inclined groove portion that linearly inclines the middle side of the middle land portion at an angle θ with respect to the tire circumferential direction, and a radius of curvature from the inner end in the tire axial direction of the inclined groove portion to the crown main groove. The first arc groove portion extending in the arc of R1 and the second arc groove portion extending in the arc of the radius of curvature R2 from the outer end in the tire axial direction of the inclined groove portion to the shoulder main groove are characterized in that the S-shape is formed. Pneumatic tire. The first arc groove portion has an angle α1 of 75 to 90 ° with respect to a tire circumferential direction at a connection portion with the crown main groove,
2. The pneumatic tire according to claim 1, wherein the second arcuate groove portion has an angle β <b> 1 with respect to a tire circumferential direction at a connection portion with the shoulder main groove of 75 to 90 °. The middle land portion includes a plurality of first sipes extending outward in the tire axial direction from the crown main groove and interrupted in the middle land portion without intersecting the middle lug groove, and extending inward in the tire axial direction from the shoulder main groove. Including a second sipe that breaks in the middle land without intersecting the middle lag groove,
The pneumatic tire according to claim 1 or 2, wherein the first sipe and the second sipe are located on the same straight line.   The first arcuate groove portion has a widened portion that is wider toward the crown main groove at the connection portion with the crown main groove, and the second arcuate groove portion is at the connection portion with the shoulder main groove. The pneumatic tire according to claim 1, further comprising a widened portion that becomes wider toward a shoulder main groove.   The middle land portion is divided into a plurality of middle blocks by the middle lug groove, and the middle block has a saddle shape having a constricted portion at the center side by forming the middle lug groove into an S shape, and The pneumatic tire according to any one of claims 1 to 4, wherein a width Wa of the constricted portion is 30 to 50% of a width Wm of the middle land portion. The shoulder land portion includes a plurality of shoulder lug grooves that cross the shoulder land portion,
The connection part with the shoulder main groove of the said shoulder lug groove and the connection part with the shoulder main groove of the said middle lug groove are located on the same tire axial direction line, The said any one of Claims 1-5 characterized by the above-mentioned. The described pneumatic tire. By having two crown main grooves, a center land portion is formed between the crown main grooves, and the center land portion has a triangular slot extending inward in the tire axial direction from the crown main groove. ,
The connection part with the crown main groove of the said slot and the connection part with the crown main groove of the said middle lug groove are located on the same tire axial direction line | wire. Pneumatic tires.   The pneumatic tire according to claim 3, wherein an inclination direction of the inclined groove portion with respect to the tire circumferential direction is different from an inclination direction of the first and second sipes with respect to the tire circumferential direction.   The pneumatic tire according to claim 8, wherein an angle γ of the first and second sipes with respect to the inclined groove portion is 80 to 100 °.   The pneumatic tire according to claim 1, wherein the angle θ of the inclined groove portion is 15 to 25 °.

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