JP2749879B2 - Pneumatic tire with asymmetric tread - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to improvement of a pneumatic tire provided with an asymmetric tread, and more particularly, to improve uneven wear in a shoulder portion and improve steering stability. A pneumatic tire with an increased asymmetric tread.

(Prior Art) A pneumatic tire for an automobile is known to form various patterns on a tread, and a block type pattern is one of them.

In response to recent demands for higher performance of tires, for example, tires having a directional pattern and tires having an asymmetric pattern have been proposed as tires particularly suitable for use at high internal pressure and high load.

For example, FIG. 1 shows a development view of a tread of a tire having a block pattern in which the right and left sides are asymmetric with respect to the equatorial plane C and have directionality (a rotation direction is designated). In this example, the tread tread portion T has a linear circumferential main groove 1, a circumferential sub-groove 2, and a zigzag circumferential sub-groove 3, so that the right and left around the equatorial plane C of the tire are asymmetric. 3,3
Are provided, and a large number of laterally inclined grooves 4, 5 extend in a direction of intersection with these circumferential grooves at predetermined intervals in the circumferential direction, so that a large number of land portions (blocks) divided by these groove groups are provided. ) Are arranged asymmetrically.

The left side of the drawing is the outside of the vehicle and the right side is the inside of the vehicle, and the rotation direction of the tire is determined in the direction of the arrow. The groove depth of the laterally inclined groove is the inside and outside with respect to the equatorial plane C. In the example, at the equidistant positions, the distances are set equal to each other.

(Problems to be Solved by the Invention) However, in the conventional pneumatic tire provided with the asymmetric tread described above, although the tread pattern is formed asymmetrically different as described above,
No particular consideration is given to the groove depth, and in particular, the depths of the laterally inclined grooves 4 and 5 are formed equally at positions equidistant to the left and right with respect to the equatorial plane C. As a result,
Uneven wear is likely to occur in the shoulder portion, and the uneven wear may cause vibration, noise, and the like, and steering stability may be impaired.

That is, since the vehicle travels along a curved road, the load on the tires is greater on the outside of the vehicle than on the inside, and therefore, the burden on the outer portions of the vehicle for tire wear is greater. And the first tread or pattern
Since the outer portion shown in the figure does not run on the inner portion of the vehicle, the shoulder portion of the outer portion, particularly the shoulder portion close to the tread end, is liable to wear off the shoulder.

In addition, each block of the shoulder block row of the tread tends to have a higher wear rate on the side that comes in contact with the ground first (the stepping side) than on the side that comes in contact with the ground (the stepping side) during traveling. As a result, vibration and noise are worsened, and steering stability is significantly impaired.

Therefore, an object of the present invention is to solve the problems of the above-described conventional pneumatic tire having an asymmetric tread.

Accordingly, it is an object of the present invention to provide a pneumatic tire provided with an asymmetric tread with improved uneven wear, particularly at a shoulder portion, and improved steering stability.

[Configuration of the Invention] (Means for Solving the Problems) That is, a pneumatic tire provided with an asymmetric tread of the present invention has a plurality of circumferential grooves and a predetermined interval in a circumferential direction in a direction intersecting the circumferential grooves. A number of laterally inclined grooves extending in the shape of arrows and land portions divided by these groove groups are arranged asymmetrically with respect to the equatorial plane of the tire, and the vehicle is mounted on a tire designated for rotation direction and mounting on the vehicle. Sometimes the laterally inclined groove closer to at least the tread edge of the outer vehicle area than the equatorial plane of the tread is 10-50% shallower than the laterally inclined groove closer to the tread edge of the inner vehicle area.

(Operation) The pneumatic tire provided with the asymmetric tread of the present invention includes:
Since the depth of the laterally inclined groove near the tread edge is formed so that the inside area of the vehicle is deep and the outside area of the vehicle is shallow, the block rigidity of the outside area of the vehicle is particularly large, which places a heavy burden on running and is susceptible to wear. And the occurrence of uneven wear and the shoulder drop of the shoulder portion due to the uneven wear can be effectively prevented.

In addition, heel and toe wear in the shoulder portion of the tire is also improved, and vibration and noise problems are eliminated.

Further, by reducing the depth of the laterally inclined groove in the outer region of the tire, the groove volume in this portion is reduced, and the movement (deformation) of the block is also reduced, so that noise during tire driving is further increased. Decrease.

(Example) Hereinafter, an example of a pneumatic tire provided with the asymmetric tread of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a development view of a tread showing an example of a pneumatic tire provided with an asymmetric tread according to the present invention, FIG. 2 (a) is a cross-sectional explanatory view taken along the line II in FIG. 1, and FIG. First
FIG. 2 is a sectional view taken along the line II-II in FIG.

That is, in FIG. 1, the left side with respect to the equatorial plane C of the tire is the vehicle outside area, the right side is the vehicle inside area, and the arrow direction indicates the rotation direction of the tire.

In the tread portion T of the tire provided with the asymmetric tread of the present invention, a linear circumferential main groove 1 having the widest groove width is formed in a region outside the axial center of the tire. A linear circumferential sub-groove 2 whose groove width is slightly smaller than the linear circumferential main groove 1 is formed in parallel.
The zigzag circumferential sub-grooves 3, 3 are formed asymmetrically and parallel to the linear circumferential main groove 1 and the linear circumferential sub-groove 2.

In addition, a number of laterally inclined grooves 4 and 5 extend in a circumferential direction at predetermined intervals in a direction intersecting with the circumferential grooves, whereby the groove groups and the land portions ( Blocks 9-1 to 9-6 are formed asymmetrically with respect to the equatorial plane C.

In the drawings, lines A and B indicate tread ends,
The portion close to the tread ends A and B means a shoulder portion.

The circumferential main groove 1 has a circumferential or equatorial plane C as illustrated.
It may be a straight line parallel to the above, but may also be a broken line shape (deformed clamp shape) or a zigzag shape, and the groove width and depth are formed to be the widest and deepest in the groove group.

The circumferential sub-groove 2 may be a linear shape parallel to the circumferential direction as shown in the figure, but may also be a broken line (deformed clang shape) or a zigzag shape. It is formed to be equal to or slightly shallower than the main groove 1.

The laterally inclined grooves 3, 3, 3 may be in a zigzag shape as shown, or may be in a linear shape, and the groove width is formed to be equal to or less than the circumferential main groove 1. Is done.
The groove depth in this embodiment is deep in a portion common to a lateral groove to be described later, and relatively shallow in other tilt components.

In the drawings, zigzag circumferential sub-grooves 3, 3, 3
The rounded chamfer is applied to the acute angle portion of the block 9 at the portion that intersects the laterally inclined groove 5. In the drawings, 6, 7, and 8 are oval notches, which act as a kind of groove. Things.

The laterally inclined grooves 4 and 5 are inclined at an angle of 30 to 70 degrees from the linear circumferential main groove 1 to both sides, and are not limited to the linear shape as shown in the figure.

In the example shown in FIG. 1 for the laterally inclined groove, the groove 5 intersects with the circumferential main groove 1 starts at the same depth as the main groove, and gradually increases in depth while extending to the tread end B. The groove width is relatively narrow at the portion where the main groove 1 intersects, and the tread end B
It is gradually increasing toward. On the other hand, the width of the laterally inclined groove 4 is increased stepwise from the circumferential main groove 1 to the tread end A, and a portion sandwiched between the circumferential main groove 1 and the sub-groove 2 and an intermediate width close to the sub-groove 2 Part is shallower.

In the present invention, at least a portion (vehicle outside area) of the laterally inclined groove 4 close to the tread end A, for example, the groove depth at point D is d ₁ [FIG. 2 (a)]. The groove depth of the portion (vehicle inner area) of the laterally inclined groove 5 close to the tread end B at the point E at the equidistant position is d ₂ [second
(B), the relationship is such that d ₁ <d ₂ and d ₁ = 0.5 to 0.9 × d ₂ .

Here, if d ₁ exceeds 0.9% of d ₂ , there is no effect of suppressing shoulder shoulder drop due to uneven wear and heel and toe wear. On the other hand, if it is less than 0.5, there is no traction and braking effect. The portion of the groove 4 extending between the circumferential sub-groove 2 and the tread end A may be entirely shallow as in the portion adjacent to the sub-groove 2.

In addition to the conditions for the groove depths of the laterally inclined grooves 4 and 5, the inclination angle α of the stepping-side side wall and the inclination angle β of the kick-out side wall according to the tire rotation direction of each of the grooves 4 and 5 are determined. ,
By setting α> β, heel and toe wear can be further improved.

Next, the configuration and effects of the pneumatic tire provided with the asymmetric tread of the present invention will be described in more detail by test examples.

(Test example) Tire size: 31 x 10, 50R15LT6PR, rim used: 15 x 7
-JJ, the asymmetric block pattern shown in FIGS. 1 and 2 (a) and (b) is molded on a tread portion of a mud and snow type tire having an air pressure of 2.0 kg / cm ² , This tire was evaluated.

In addition, since other structures and manufacturing conditions such as a radial carcass and a belt layer of the tire were the same as those of a conventional tire,
Details are omitted.

That is, in FIG. 1, the width of the tread is 206 mm, the groove width of the linear circumferential main groove 1 is 14 mm, the depth is 12.7 mm, the groove width of the linear circumferential sub groove 2 is 10 mm, the depth is 12.7 mm, zigzag. The groove width of the circumferential auxiliary groove 3 is 8-9 mm, the depth is 10.8 mm, the groove width of the laterally inclined groove 4 is 10 mm, the depth is 10.8 mm, and the groove width of the laterally inclined groove 5 is 11-1.
The tire of the present invention was obtained with a depth of 2 mm and a depth of 12.7 mm.

On the other hand, for comparison, a conventional tire was obtained in the same manner as described above, except that the groove depths of the laterally inclined grooves 4 and 5 were each 12.7 mm.

The following table shows the results of evaluating the performance of these two types of tires under the following conditions.

(Evaluation method) 1. Shoulder part uneven wear Load: 650 kg / piece Internal pressure: 2.0 kg / cm ² Forbidden Shoulder part uneven wear occurring after traveling 20,000 km on a real road is compared with the conventional tire to 100. The index evaluation at the time of the evaluation (the larger the index, the smaller the uneven wear) The roadway ratio and the speed of the actual road are as follows.

General road 55% 30-50 kg / h Expressway 35% 50-100 〃 Unpaved road 5% 20-60 〃 Yamasaka road 5% 20-50 〃 2. Heel and toe wear After traveling 10,000 km, the wear level difference between the stepping side and the protruding side of each block was compared, and the index was evaluated when the conventional tire was set to 100 (the larger the index, the better).

3. Wetability Brake deceleration index on wet roads (Brake initial speed; average of 40, 60, 80 km / h).

4. Steering stability Evaluation of general feeling including vibration and noise (the index is better with the conventional tire set as 100).

From the above results, it is clear that the pneumatic tire provided with the asymmetric tread of the present invention has significantly improved uneven wear and handling stability.

[Effects of the Invention] As described above in detail, the pneumatic tire provided with the asymmetric tread of the present invention has a structure in which the depth of the laterally inclined groove close to the tread end is increased by increasing the depth of the inner area of the vehicle and the outer area of the vehicle. Since the section is formed to be shallow, the burden on running is particularly large, and the rigidity of the block outside the vehicle, which is susceptible to wear, is increased, so that uneven wear and the shoulder drop of the shoulder due to uneven wear can be effectively prevented. Can be.

In addition, heel and toe wear in the shoulder portion of the tire is also improved, and vibration and noise problems are eliminated.

Further, by reducing the depth of the laterally inclined groove in the outer region of the tire, the groove volume in this portion is reduced, and the movement (deformation) of the block is also reduced, so that noise during tire driving is further increased. Decrease.

Therefore, the pneumatic tire provided with the asymmetric tread of the present invention has improved uneven wear, particularly at the shoulder portion, and has excellent steering stability due to reduced vibration and noise, especially for high internal pressure and high load. It has suitable performance as a tire.

[Brief description of the drawings]

FIG. 1 is a tread developed view showing an example of a pneumatic tire provided with an asymmetric tread of the present invention, FIG. 2 (a) is a cross-sectional explanatory view taken along the line II in FIG. 1, and FIG. FIG. 2 is an explanatory sectional view taken along line II-II in FIG. 1. T: Tread portion A: Tread end B: Tread end C: Equatorial plane 1 ... Linear circumferential main groove 2 ... Linear circumferential sub groove 3 ... Zigzag circumferential sub groove 4 ... Horizontal inclined groove 5 Horizontal inclined groove 6 Notch 7 Notch 8 Notch d Groove depth

Claims (1)

(57) [Claims] A plurality of circumferential grooves, a large number of laterally inclined grooves extending in a direction of intersection with the circumferential grooves at predetermined intervals in a circumferential direction at an angle, and a land portion divided by these groove groups,
In a tire which is arranged asymmetrically with respect to the equatorial plane of the tire and whose rotation direction and mounting on the vehicle are specified, a laterally inclined groove closer to at least the tread edge of the outer area of the vehicle than the equatorial plane of the tread when the vehicle is mounted is formed on the inner side of the vehicle. A pneumatic tire with an asymmetric tread, characterized in that it is 10-50% shallower than a laterally inclined groove adjacent the tread edge of the area.