JP2018090230A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve vehicle drift at the time of braking and driving and vehicle drift at the time of rotation at high levels.SOLUTION: A pneumatic tire includes a tie bar 10 inclined in the same direction as a lateral groove 5S inside the lateral groove 5S arranged in a shoulder land part 4S. An angle θs of the lateral groove 5S relative to a tire axial direction is 15° or less. The tie bar 10 connects a tire axial outer side part So of one shoulder block 6S1 of adjacent shoulder blocks 6S to a tire axial inner side part Si of the other shoulder block 6S2.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire that can easily suppress a vehicle flow caused by a tread pattern.

  In a pneumatic tire with a so-called block pattern in which a block divided by a circumferential groove and a lateral groove is formed in the tread portion, when the block comes into contact with the ground, the block end on the first landing side hits the road surface, and ride performance and noise performance There is a tendency to lower. Therefore, the block edge in the circumferential direction is inclined with respect to the tire axial direction to reduce the impact with the road surface.

  However, if the block edge in the circumferential direction is inclined, there is a problem in that a directionality (anisotropy) occurs in the block, and a so-called vehicle flow occurs in which the vehicle flows laterally to one side during straight traveling.

  For example, as shown in FIG. 8A, during driving, the block A receives a longitudinal force Ff in the same direction as the traveling direction from the road surface. This front-rear force Ff acts as an applied force point P at the acute-angle end that comes first in contact with the block edge Ae on the first arrival side. Therefore, a clockwise rotational moment Mf acts around the center of gravity of the block A in this example, and as a result, a rightward lateral force Yf is generated in this example.

  Further, as shown in FIG. 8B, at the time of braking, the block A receives a longitudinal force Fr in the direction opposite to the traveling direction from the road surface. This front-rear force Fr acts as an applied force point P at an acute angle side end that comes first in contact with the block edge Ae on the first arrival side. Therefore, a counterclockwise rotational moment Mr in this example acts on the block A around its center of gravity, and as a result, a leftward lateral force Yr is generated in this example.

  Therefore, as shown in FIG. 9A, when the block edge in the circumferential direction in each block A (for example, the crown block A1, the middle block A2, the shoulder block A3) is inclined in the same direction, during driving, The lateral force Yf of each block A increases in the same direction, and a large rightward vehicle flow is generated in this example. During braking, similarly, the lateral force Yr of each block A increases in the same direction, generating a large leftward vehicle flow.

  On the other hand, at the time of rolling, as shown in FIG. 9B, the crown block A1 and the middle block A2 receive the longitudinal force Fr in the direction opposite to the traveling direction from the road surface. A rotational moment Mb acts. In contrast, the shoulder block A3 receives a longitudinal force Ff in the same direction as the traveling direction because the dynamic load radius is small. Therefore, a rotational moment Mf in the same direction as that during driving acts. Therefore, in the case of rolling, the rotational force Mf, Mr in different directions is generated to reduce the lateral force, so the vehicle flow is small.

  Therefore, for example, when the inclination direction of the block edge Ae of the shoulder block A3 is different from the inclination direction of the crown block A1 and the middle block A2, it is possible to reduce the vehicle flow during braking and driving. is there. However, in this case, there is a problem that the vehicle flow at the time of rolling is worsened.

  Thus, the vehicle flow during braking / driving and the vehicle flow during rolling are contradictory, and it has been difficult to improve both at a high level.

  The following Patent Document 1 proposes that in a block pattern having at least six block rows, the inclination directions of the lateral grooves are different between the block rows adjacent in the tire axial direction. However, this has a problem that the pattern design is greatly restricted and the degree of freedom is lost.

JP 2008-201319 A

  Therefore, the present invention is based on the provision of a tie bar inclined in the same direction as the lateral groove in the lateral groove of the shoulder land portion, and improves the vehicle flow during braking / driving and the vehicle flow during rolling at a high level. An object is to provide a pneumatic tire that can be used.

In the present invention, the tread portion is divided into a plurality of land portions including a shoulder land portion on the tread end side by a plurality of circumferential main grooves, and at least the shoulder land portion is 15 with respect to a tire axial line. A pneumatic tire divided into a plurality of shoulder blocks by lateral grooves inclined at an angle of less than or equal to °,
By providing the horizontal groove with a tie bar inclined in the same direction as the horizontal groove, the horizontal groove has an outer region outside the tire axial direction than the tie bar, a tie bar region where the tie bar is disposed, and a tire axial direction from the tie bar. It is divided into the inner area inside,
The tie bar connects a tire shoulder direction outer side portion of the first shoulder block on one side and a tire shoulder direction inner side portion of the second shoulder block on the other side among the shoulder blocks adjacent to each other. It is a feature.

  In the pneumatic tire according to the present invention, the plurality of land portions further include a crown land portion on the tire equator side, and a middle land portion between the crown land portion and the shoulder land portion, and the crown land portion. It is preferable that the portion and the middle land portion are each divided into a plurality of crown blocks and middle blocks by lateral grooves that are inclined in the same direction at an angle of 5 to 30 ° with respect to the tire axial direction line.

In the pneumatic tire according to the present invention, when the depth of the outer region is ha, the depth of the tie bar region is hb, and the depth of the inner region is hc, it is preferable that the following expression is satisfied.
hb / ha ≦ 0.8 --- (1)
0.2 ≦ hc / ha ≦ 1.0 --- (2)

In the pneumatic tire according to the present invention, a distance from the tread end to the center of gravity of the first shoulder block is Lg1,
The distance from the tread edge to the center of gravity of the second shoulder block is Lg2,
The distance from the tread end to the tire axial direction inner end point of the first intersection where the tie bar intersects the first shoulder block is L1,
When the distance from the tread end to the outer end point in the tire axial direction of the second intersection where the tie bar intersects the second shoulder block is L2,
The distances Lg1, Lg2, L1, and L2 preferably satisfy the following formula.
L1 ≦ Lg1 --- (3)
L2 ≧ Lg2 --- (4)

In the pneumatic tire according to the present invention, it is more preferable that the distances Lg1, Lg2, L1, and L2 satisfy the following expression.
0.4 ≦ L1 / Lg1 ≦ 1.0 (5)
1.0 ≦ L2 / Lg2 ≦ 1.6 (6)

  In the present invention, as described above, a tie bar that is inclined in the same direction as the lateral groove is provided in the lateral groove of the shoulder land portion. This tie bar connects a tire axial direction outer side portion of one shoulder block of shoulder blocks adjacent to each other and a tire axial direction inner side portion of the other shoulder block.

  Therefore, for example, when a longitudinal force is applied to an applied force point on the outer side in the tire axial direction of the shoulder block on one side, the longitudinal force can be transmitted to the inner side in the tire axial direction of the other shoulder block via the tie bar. .

  Therefore, in the shoulder block on the other side, the rotational moment generated by the longitudinal force acting on the applied force point on the outer side in the tire axial direction is opposite to the rotational moment generated by the longitudinal force transmitted from the shoulder block on the one side via the tie bar. It acts in a direction that counteracts each other. That is, the lateral force itself generated in the shoulder block can be reduced both during braking / driving and during rolling.

  For this reason, there is no contradiction, and the vehicle flow during braking / driving and the vehicle flow during rolling can be improved at a high level.

It is an expanded view which shows an example of the tread pattern in the pneumatic tire of this invention. (A), (B) is the elements on larger scale which show the shoulder area | region of FIG. (A), (B) is a conceptual diagram which shows the other example of a horizontal groove. (A), (B) is a conceptual diagram explaining the function of a tie bar at the time of a drive and a braking. It is sectional drawing along the length direction of a horizontal groove. (A), (B) is a conceptual diagram explaining the function of a tie bar in case the inclination direction of a horizontal groove differs. It is an expanded view which shows the other tread pattern of this invention. (A), (B) is a conceptual diagram explaining the generation | occurrence | production mechanism of the transverse groove force which arises in an anisotropic block at the time of a drive and a braking. (A), (B) is a conceptual diagram explaining the contradiction between the vehicle flow during braking / driving and the vehicle flow during rolling.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the pneumatic tire 1 of the present embodiment includes a plurality of circumferential main grooves 3 extending in the tire circumferential direction in the tread portion 2. Thereby, the tread portion 2 is divided into a plurality of land portions 4 including a shoulder land portion 4S on the tread end Te side.

  In this example, the four circumferential main grooves 3 cause the tread portion 2 to become the shoulder land portion 4S, the crown land portion 4C on the tire equator Co side, and the middle between the shoulder land portion 4S and the crown land portion 4C. The case where it is divided into five land portions 4 including land portions 4M is shown.

  The shoulder land portion 4S is divided into a plurality of shoulder blocks 6S by lateral grooves 5S. In this example, the crown land portion 4C is divided into a plurality of crown blocks 6C by horizontal grooves 5C, and the middle land portion 4M is divided into a plurality of middle blocks 6M by horizontal grooves 5M.

  In the present example, the lateral grooves 5C and 5M are inclined in the same direction (for example, to the right). The angles θc and θm of the lateral grooves 5C and 5M with respect to the tire axial direction line are preferably in the range of 5 to 30 °. The lateral grooves 5S are inclined in the same direction as the lateral grooves 5C and 5M or in a different direction. In this example, a case where the vehicle is inclined in the same direction (for example, upward to the right) is shown. An angle θs of the lateral groove 5S with respect to the tire axial direction line is 15 ° or less.

  In addition to the straight groove, the lateral groove 5S may be an arc-shaped or broken line-shaped bent groove as shown in FIGS. 3 (A) and 3 (B). In this case, the angle θs is an angle of a straight line X connecting the midpoint Qo of the groove width at the outer end in the tire axial direction of the lateral groove 5S and the midpoint Qi of the groove width at the inner end in the tire axial direction with respect to the tire axial direction line. Is defined as The lateral grooves 5C and 5M can also be similar bent grooves, and in this case, the angles θc and θm are defined similarly.

  As shown in FIG. 2A, a tie bar 10 that is inclined in the same direction as the lateral groove 5S is provided in the lateral groove 5S of the shoulder land portion 4S. This tie bar 10 includes tire shoulder direction outside portions So of the first shoulder block 6S1 on one side of the shoulder blocks 6S adjacent to each other, and tire shaft direction inside portions Si of the second shoulder block 6S2 on the other side. And The outer portion So means a region outside the center of gravity G of the shoulder block 6S in the tire axial direction, and the inner portion Si means a region inside the center of gravity G of the shoulder block 6S in the tire axial direction.

  “Connecting the outer portion So of the first shoulder block 6S1 and the inner portion Si of the second shoulder block 6S2” means that at least a part of the tie bar 10 is the outer portion So of the first shoulder block 6S1. And at least a part of the tie bar 10 is connected to the inner portion Si of the second shoulder block 6S2.

Preferably, as shown in FIG.
(A) The distance from the tread end Te to the center of gravity G1 of the first shoulder block 6S1 is Lg1,
(A) The distance from the tread end Te to the center of gravity G2 of the second shoulder block 6S2 is Lg2,
(C) The distance from the tread end Te to the tire axial direction inner end point J1i of the first intersecting portion J1 where the tie bar 10 intersects the first shoulder block 6S1 is L1,
(D) When the distance from the tread end Te to the tire axial direction outer end point J2o of the second intersection J2 where the tie bar 10 intersects the second shoulder block 6S2 is L2, it is preferable to satisfy the following equation.
L1 ≦ Lg1 --- (3)
L2 ≧ Lg2 --- (4)

  Next, the function of the tie bar 10 will be described. As shown in FIG. 4A, during driving, a longitudinal force Ff in the same direction as the advancing direction acts on the shoulder block 6S at the applied force point P, and the moment around the center of gravity G, in this example, is clockwise. M is generated. When the tie bar 10 is provided, a part Ffa of the front / rear force Ff acting on the adjacent shoulder block 6S on the first arrival side (the lower side in FIG. 4A) is connected to the inner portion Si of the shoulder block 6S via the tie bar 10. In this example, a counterclockwise moment Ma is generated around the center of gravity G. In other words, the moment M and the moment Ma act in directions that cancel each other, and the lateral force itself generated in the shoulder block 6S can be reduced. When rolling, it functions in the same way as during driving, and the lateral force itself can be reduced.

  Similarly, as shown in FIG. 4B, during braking, a longitudinal force Fr in the direction opposite to the advancing direction acts on the shoulder block 6S at the applied force point P, and around the center of gravity G, in this example, left A rotating moment M is generated. When the tie bar 10 is provided, a part Fra of the longitudinal force Fr acting on the adjacent shoulder block 6S on the first arrival side (the lower side in FIG. 4B) is connected to the inner portion Si of the shoulder block 6S via the tie bar 10. In this example, a clockwise moment Ma is generated around the center of gravity G. In other words, the moment M and the moment Ma act in directions that cancel each other, and the lateral force itself generated in the shoulder block 6S can be reduced.

  FIG. 5 conceptually shows a cross-sectional view along the length direction of the lateral groove 5S. As shown in the figure, the lateral groove 5S is divided into an outer region 5Sa on the outer side in the tire axial direction from the tie bar 10, a tie bar region Sob on which the tie bar 10 is disposed, and an inner region 5Sc on the inner side in the tire axial direction from the tie bar 10. When sectioned, the depth hb of the tie bar region 5Sb is smaller than the depth ha of the outer region 5Sa and the depth hc of the inner region 5Sc.

In particular, in order to reduce the lateral force generated from the shoulder block 6S, the groove depths ha to hc preferably satisfy the following expression.
hb / ha ≦ 0.8 --- (1)
0.2 ≦ hc / ha ≦ 1.0 --- (2)
When hb / ha exceeds 0.8, the raised height of the tie bar 10 becomes too low, and the effect of transmitting the longitudinal force by the tie bar 10 is not sufficiently achieved. Therefore, hb / ha is preferably 0.6 or less, more preferably 0.4 or less, and even more preferably 0.2 or less.

  On the other hand, when hc / ha is less than 0.2, the inner region 5Sc becomes shallow, the rigidity of the inner portion Si increases, and the moment Ma in the direction to cancel out becomes too small. On the other hand, when hc / ha exceeds 1.0, the inner region 5Sc becomes deep and the rigidity of the inner portion Si becomes small, and the moment Ma in the direction to cancel out becomes excessive. In either case, the lateral force reducing effect tends to be reduced. Therefore, the lower limit of hc / ha is preferably 0.4 or more, and the upper limit is preferably 0.5 or less.

In order to reduce the lateral force generated from the shoulder block 6S, it is preferable that the distances Lg1, Lg2, L1, and L2 satisfy the following expression.
0.4 ≦ L1 / Lg1 ≦ 1.0 (5)
1.0 ≦ L2 / Lg2 ≦ 1.6 (6)

  When L2 / Lg2 is out of the above range, the effect of converting the force transmitted from the tie bar 10 into a moment Ma in a direction to cancel each other is reduced. Further, if L1 / Lg1 is out of the above range, the tie bar 10 cannot effectively transmit the force for generating the moment Ma in the direction to cancel each other.

  FIG. 6A shows a case where the lateral groove 5S is inclined in a direction different from the lateral grooves 5C and 5M (in this example, left upward). Also in this example, a tie bar 10 that is inclined in the same direction as the horizontal groove 5S is disposed in the horizontal groove 5S. The tie bar 10 has a tire axial direction outer portion So of the first shoulder block 6S1 on one side (upper side in FIG. 6) and a tire axial direction of the second shoulder block 6S2 on the other side (lower side in FIG. 6). The inner part Si is connected.

  As shown in FIG. 6 (B), during driving, a longitudinal force Ff in the same direction as the traveling direction acts on the applied point P of the shoulder block 6S, and a counterclockwise moment M is generated around the center of gravity G in this example. Let When the tie bar 10 is provided, a part Ffa of the longitudinal force Ff acting on the adjacent shoulder block 6S on the first arrival side (lower side in FIG. 6) is transmitted to the outer portion So of the shoulder block 6S via the tie bar 10. In this example, a clockwise moment Ma is generated around the center of gravity G.

  In FIG. 7, the circumferential main groove 3 can extend in a zigzag shape in the tire circumferential direction as shown in another embodiment of the present invention. Further, the crown block 6C, the middle block 6M, and the shoulder block 6S can be appropriately provided with siping K. Further, the groove depth and groove width of the circumferential main groove 3 and the lateral grooves 5C, 5M, and 5S are not particularly limited, and a conventional size can be adopted.

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

  A pneumatic tire (LT265 / 70R17) having the tread pattern of FIG. 1 as a basic pattern was prototyped based on the specifications in Table 1. Then, the vehicle flowability during rolling of each sample tire and the vehicle flowability during braking / driving were tested.

  Except as described in Table 1, the tires have the same specifications. In Comparative Example 1, the inclination direction of the shoulder lateral groove is different from the inclination direction of the crown lateral groove and the middle lateral groove. In Comparative Example 2, no tie bar is formed, and in Comparative Example 3, the shoulder lateral groove is divided into an outer region and a tie bar region, and no inner region is formed.

(1) Vehicle flowability during rolling:
Using a flat belt tester, slip angle 0 °, camber angle 0 ° on the belt under conditions of internal pressure (340 kPa), rim (17 x 7.5 JJ), longitudinal load (8.34 kN) (front wheel conditions) The vehicle was run at a speed of 10 km / h, and the lateral flow force (PRCF) generated at that time was measured. A smaller numerical value (absolute value) is preferable.

(2) Vehicle flowability during braking and driving:
Using a flat belt tester, the slip angle on the belt was 0 ° and the camber angle was 0 on the conditions of the internal pressure (550 kPa), rim (17 x 7.5 JJ), and longitudinal load (5.69 kN) (rear wheel conditions). ° Drive at a speed of 10 km / h. Then, when a driving force (braking force) was applied during traveling, evaluation was performed based on a rising gradient of a lateral force generated with respect to the driving force (braking force). A smaller numerical value (absolute value) is preferable.

  As shown in the table, it can be confirmed that the tires of the examples can improve the vehicle flowability during braking / driving while ensuring low vehicle flowability during rolling.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Circumferential main groove 4 Land part 4C Crown land part 4M Middle land part 4S Shoulder land part 5C, 5M, 5S Lateral groove 5Sa Outer area 5Sb Tie bar area 5Sc Inner area 6C Crown block 6M Middle block 6S Shoulder Block 6S1 First shoulder block 6S2 Second shoulder block 10 Tie bar Si Tire axially inner portion So Tire axially outer portion

Claims (5)

The tread portion is divided into a plurality of land portions including a shoulder land portion on the tread end side by a plurality of circumferential main grooves, and at least the shoulder land portion has an angle of 15 ° or less with respect to the tire axial line. A pneumatic tire divided into a plurality of shoulder blocks by lateral grooves inclined at
By providing the horizontal groove with a tie bar inclined in the same direction as the horizontal groove, the horizontal groove has an outer region outside the tire axial direction than the tie bar, a tie bar region where the tie bar is disposed, and a tire axial direction from the tie bar. It is divided into the inner area inside,
The tie bar connects a tire shoulder direction outer side portion of the first shoulder block on one side and a tire shoulder direction inner side portion of the second shoulder block on the other side among the shoulder blocks adjacent to each other. A featured pneumatic tire.   The plurality of land portions further include a crown land portion on the tire equator side, and a middle land portion between the crown land portion and the shoulder land portion, and the crown land portion and the middle land portion each have a tire shaft. 2. The pneumatic tire according to claim 1, wherein the pneumatic tire is divided into a plurality of crown blocks and middle blocks by lateral grooves inclined in the same direction at an angle of 5 to 30 ° with respect to the direction line. The pneumatic tire according to claim 1 or 2, wherein when the depth of the outer region is ha, the depth of the tie bar region is hb, and the depth of the inner region is hc, the following expression is satisfied. .
hb / ha ≦ 0.8 --- (1)
0.2 ≦ hc / ha ≦ 1.0 --- (2) The distance from the tread edge to the center of gravity of the first shoulder block is Lg1,
The distance from the tread edge to the center of gravity of the second shoulder block is Lg2,
The distance from the tread end to the tire axial direction inner end point of the first intersection where the tie bar intersects the first shoulder block is L1,
When the distance from the tread end to the outer end point in the tire axial direction of the second intersection where the tie bar intersects the second shoulder block is L2,
The pneumatic tire according to claim 1, wherein the distances Lg1, Lg2, L1, and L2 satisfy the following expression.
L1 ≦ Lg1 --- (3)
L2 ≧ Lg2 --- (4) The pneumatic tire according to claim 4, wherein the distances Lg1, Lg2, L1, and L2 satisfy the following expression.
0.4 ≦ L1 / Lg1 ≦ 1.0 (5)
1.0 ≦ L2 / Lg2 ≦ 1.6 (6)