JPH05278415A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve off-road running performance and sound performance by arranging U-shaped tire block sets, whose closed sides are connected back to back each other and open sides are faced to the tread end, alternately each other in the tire circumferential direction. CONSTITUTION:Main groove group is formed with zigzag-shaped circumferential- direction main grooves 10 extending on a tread surface along the tire equator face O, main lug grooves 20 extending from each vertex of zigzags to the tread end, and sub lug grooves 21 being unopen to the circumferential-direction main grooves 10 at their tire equator face 0 side. The sub lug grooves 21 and the main lug grooves 20 are connected to the first and second sub grooves 30, 31 and the sub lug grooves 21 and connecting parts 11 of the circumferential-direction main grooves 10 and the main lug grooves 20 are connected to the first and the third sub grooves 30, 32. Formation of these grooves allows to form a block pattern in which U-shaped block sets, whose closed sides are connected back to back each other at the tire equation face O side and open sides are faced to the tread end, are arranged alternately each other in the tire circumferential direction. Thus the pneumatic tire can secure superior performance in start, straight running, traction property and sound property equally during off-road running.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having excellent off-road running performance, especially in muddy ground.

[0002]

2. Description of the Related Art Generally, in tires for off-road running, particularly in muddy ground, when the tire touches the ground, lug grooves efficiently grip dirt and mud, and when the tire kicks out, grip Efficient discharge of accumulated dirt and mud so that it does not become clogged is important to ensure good grip.

In order to secure the above performance,
It is said that it is most effective to arrange the lug grooves continuously in the radial direction from the shoulder part to the center part of the tire.The shape of such lug grooves is the circumferential main groove located in the center area of the tread. A large number of slanted lug grooves are cross-connected to each other and / or the groove width of the lug groove of the tread shoulder portion is increased, and this is arranged parallel to the tire radial direction, and the lug groove is increased in the tread center area. It is known that it is bent and tilted.

That is, FIG. 2 is a tread development view of a conventional off-road running tire.
A circumferential main groove 1 linearly extending in the circumferential direction along the tire equator line, and two circumferential sub-grooves 2a arranged axially on both sides of the circumferential main groove 1 and extending zigzag in the circumferential direction, 2b
With a plurality of lug grooves 3 extending in parallel in the radial direction from the tread end, traversing the circumferential main groove 1 and the circumferential sub groove 2a or 2b, and sloping in the center area of the tread and terminating respectively. , A block 4a having a zigzag-shaped peripheral edge of the center area and a block 4b having a peripheral edge parallel to the radial direction of the shoulder area and bent and inclined toward the center area are formed, and the lug groove 3 is formed. As well as ensuring straightness due to the edge component of, the grip force during off-road driving is secured.

However, although the off-road running property of the pneumatic tire having the above-mentioned conventional block pattern is improved to some extent, the lug groove 3 is divided in the center area of the tread, so that the soil in this portion is soiled. However, it has a problem that the lateral force is weak and the pattern noise becomes large due to the fact that the rug groove 3 in the tire shoulder portion is parallel to the axial direction.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the conventional pneumatic tire for off-road running described above.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a pneumatic tire having improved off-road running property, particularly starting property, straight running property, traction property and noise property during off-road running.

[0008]

In order to achieve the above object, the pneumatic tire of the present invention has a tread tread portion,
A circumferential main groove that extends in a zigzag shape in the circumferential direction along the tire equatorial plane, a main lug groove that extends from each apex of the zigzag of the circumferential main groove toward the tread end direction, and is parallel to these main lug grooves. And a tire equator surface side forms a sub lug groove that does not open to the circumferential main groove, a tire equator surface side of the sub lug groove, and a main lug groove located on both sides of the sub lug groove, The first sub-groove and the second sub-groove are connected to each other, and the sub-lug groove and the connecting portion between the circumferential main groove and the main lug groove are connected to each other by the first sub-groove and the second sub-groove. By connecting with a third sub-groove parallel to the tire, a plurality of U-shaped block aggregates in which the closed side is in contact with the tire equatorial plane side to the back and the open side is open at the tread end are alternately arranged in the tire circumferential direction. It is characterized in that a block pattern arranged in the above is constructed.

[0009]

The pneumatic tire of the present invention has the zigzag circumferential main groove, the main lug groove, the sub lug groove, the first sub groove, the second sub groove and the third sub groove as described above. A plurality of U-shaped block aggregates in which the closed side is in contact with the tire equatorial side back to back and the open side is open at the tread end constitute a block pattern in which they are alternately arranged in the tire circumferential direction. The soil and mud can be continuously gripped from the shoulder part to the center part of the, and the gripping power and the soil and mud discharge performance are extremely excellent.

Further, the inclination angles of the main lug groove and the sub lug groove measured from the acute angle side with respect to the tire equatorial plane are made larger on the tread end side and smaller on the tire equatorial plane side, respectively, so that soil and mud dischargeability is improved. Can be made even smoother, and pattern noise can be suppressed.

Therefore, according to the pneumatic tire of the present invention, excellent off-road running property, especially excellent starting property, straight running property, traction property and noise property during off-road running can be secured in a balanced manner. For example, good performance as a four-wheel drive tire for passenger cars, light trucks, agricultural work vehicles, etc. can be expected.

[0012]

Embodiments of the pneumatic tire of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a development view of a tread showing an example of the pneumatic tire of the present invention.

In FIG. 1, a tire center line (equatorial plane) O is formed on the tread surface T of the pneumatic tire of the present invention.
Circumferential main groove 10, which extends in a zigzag shape in the circumferential direction along
The main lug grooves 20 extending from the respective apex 11 of the zigzag of the circumferential main groove 10 inclining toward the tread end, and the main lug grooves 20 are arranged in parallel with each other, and the tire equatorial plane O side is the circumferential main groove 10 described above. A main groove group is formed which includes a sub-lug groove 21 that does not open at the bottom.

The tire equatorial plane O side of the sub lug groove 21 and the main lug grooves 20 located on both sides of the sub lug groove 21 are connected by a first sub groove 30 and a second sub groove 31. In addition, the auxiliary lug groove 21 and the circumferential main groove 10
And the connection portion (11) between the main lug groove 20 and the third sub groove 32 which is parallel to the first sub groove 30 and the second sub groove 31.
Are connected by.

Here, the main lug groove 20 and the sub lug groove 21.
The inclination angle measured from the acute angle side with respect to the tire equatorial plane O is formed such that the inclination angle α on the tread end side and the inclination angle β on the tire equatorial plane O side have a relation of α> β. The first sub-groove 30, the second sub-groove 31, and the third sub-groove 32 are inclined so as to intersect with the main lug groove 20 and the sub-lug groove 21, respectively, and are substantially parallel to each other. Has become.

Therefore, by forming the main groove group and the sub groove group as described above, the tire equatorial plane O on the closed side is formed.
Side-to-side contact with each other, open side open to the tread end multiple U-shaped block aggregates (indicated by alternate long and short dash line 40)
However, a block pattern is formed in which the block patterns are alternately arranged opposite to each other in the tire circumferential direction.

That is, the U-shaped block aggregate 40 is
Each of the blocks is composed of an assembly of four blocks 41, 42, 43 and 44, the blocks 41 and 44 are open to the tread end side, and the block 43 is back-to-back with another U-shaped block assembly 40 'on the tire equatorial plane O side. Is adjacent to.

In each U-shaped block aggregate 40, the number of blocks on both sides of the sub-lug groove 21 is different, and the combination of the different numbers of blocks is alternately located on the tire circumference. Thus, each U-shaped block aggregate 40 is arranged in the tire circumferential direction.

Further, in the pneumatic tire of the present invention, the groove area ratio showing the ratio of the groove ground contact surface to the total ground contact area (ground contact width × perimeter) of the tread surface is 40 to 60%,
Particularly, it is desirable that it is in the range of 50 to 60%.

In the pneumatic tire of the present invention formed with the block pattern having the above-mentioned structure, when running on off-road, dirt or mud is continuously applied from the shoulder portion of the tread to the center portion. It has a very good gripping power and discharges dirt and mud.

The inclination angles of the main lug groove 20 and the sub lug groove 21 measured from the acute angle side with respect to the tire equatorial plane O are large on the tread end side and small on the tire equatorial plane O side, so that soil and dirt The mud discharging property can be further smoothed, and the pattern noise can be suppressed.

Next, the construction and effects of the pneumatic tire of the present invention will be described in more detail with reference to test examples.

[Test Example] Tire size: 30 × 9.50
R15, rim used: 15 × 7JJ, air pressure used: 2.0
The block pattern shown in FIG. 1 was formed on the tread surface of a tire of kg / cm ^{2, and} the tire was evaluated.

Other structures and manufacturing conditions such as the tire radial carcass and the belt layer are the same as those of the conventional tire, and therefore the details thereof will be omitted.

That is, in FIG. 1, the ground contact width of the tread: 210 mm, the groove width of the circumferential main groove 10: 16.5 mm, the groove depth: 14.6 mm, and the groove width of the main lug groove 20: 13 to 23 m.
m, groove depth: 14.6 mm, groove width of the sub-lug groove 21: 13 ~
23 mm, groove depth: 14.6 mm, first auxiliary groove 30, second auxiliary groove 31, third auxiliary groove 32 groove width: 12 mm, groove depth: 1
4.6 mm, inclination angle α at the tread ends of the main lug groove 20 and the sub lug groove 21: 66 °, the tire equatorial plane O
The tire of the present invention was obtained with an inclination angle β on the side of 26 ° and a groove area ratio of 53%.

On the other hand, for comparison, a conventional tire having the block pattern shown in FIG. 2 was obtained. In this conventional tire, the groove width of the circumferential main groove 1 is 8 mm, the groove depth is 14.6 mm, the groove width of the circumferential auxiliary grooves 2a and 2b is 8 mm,
Groove depth: 14.6 mm, groove width at tire shoulder portion of lug groove 3: 28.5 mm, groove depth: 14.6 mm, groove width at tire center portion: 9 mm, groove depth: 14.
6 mm, groove area ratio: 53%.

These two types of tires were subjected to an actual vehicle filling test under the conditions of JIS regular internal pressure and two occupants, and the starting performance, straightness and traction performance on a muddy road surface, running performance on a dirt road surface, and snow test. Table 1 shows the results of evaluation of running performance on the course and noise performance on the pattern noise test course.

In Table 1, all the conventional tires are 100
The results are shown by the index evaluation when the value is "1" and the larger the index, the better the result.

[Table 1] Tires of the present invention Conventional tires Mud-starting property 110 100 〃 Straight running property 105 100 〃 Traction property 110 100 Dirt running property 110 100 Snow running property 110 100 Noise performance 105 100 As is apparent from the results in Table 1. In the tire of the present invention, as compared with the conventional tire, the starting property during off-road running, straightness,
Excellent in traction and noise.

[0031]

As described above in detail, according to the pneumatic tire of the present invention, excellent off-road running performance,
In particular, it is possible to balance excellent starting properties, straightness properties, traction properties, and noise properties when traveling off-road. Good performance as a four-wheel drive tire for passenger cars, light trucks, agricultural work vehicles, etc. Can be expected.

[Brief description of drawings]

FIG. 1 is a development view of a tread showing an example of a pneumatic tire of the present invention.

FIG. 2 is a development view of a tread showing an example of a conventional pneumatic tire.

[Explanation of symbols]

 T Tread surface O Tire equatorial plane 10 Circumferential main groove 11 Zigzag apex 20 Main lug groove 21 Sub lug groove 30 First sub groove 31 Second sub groove 32 Third sub groove 40 U-shaped block assembly 41 , 42, 43, 44 blocks

Claims (3)

[Claims] 1. A circumferential main groove that extends in a zigzag shape in the circumferential direction along a tire equatorial plane on a tread surface, and a main lug that extends from each apex of the zigzag of the circumferential main groove to incline toward a tread end. A groove and a sub lug groove which is arranged in parallel between these main lug grooves and whose tire equatorial plane side does not open to the circumferential main groove is formed, and the tire equatorial plane side of the sub lug groove and this sub lug groove The main lug grooves located on both sides are connected to each other by the first sub groove and the second sub groove, and the sub lug groove and
The circumferential main groove and the connecting portion of the main lug groove are connected to the first
By connecting with the third sub-groove parallel to the second sub-groove and the second sub-groove, a plurality of U-shaped block aggregates in which the closed side is in back-to-back contact with the tire equatorial plane side and the open side is open at the tread end are formed. , A pneumatic tire having a block pattern in which the blocks are arranged alternately in the tire circumferential direction. 2. The inclination angle of the main lug groove and the auxiliary lug groove measured from the acute angle side with respect to the tire equatorial plane is large on the tread end side and small on the tire equatorial plane side, respectively. Pneumatic tires. 3. The pneumatic tire according to claim 1, wherein the groove area ratio of the tire is in the range of 40 to 60%.