JPH0958220A - Pneumatic tire with block pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having good wet performance and non- reduced wear resistance by specifying a pattern positive ratio, an effective edge ratio and a pitch. SOLUTION: If a circumferential length of a tire is CL and the maximum touch-down width is TW and the number of pitch is PN and total surface area per one pitch is BA and projection length in the direction of rotation of the tire is EL, a pattern positive ratio PR defined by PN.BA/(TW.CL) is 70 to 76% and an effective edge ratio ER defined by EL/TW is 96 to 104% and a pitch vertical/transverse ratio AR defined by CL/(PN.TW) is 17 to 22%, thereby improving wet performance without impairing wear resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire for trucks / buses having a pattern composed of a large number of blocks arranged at intervals on the circumference of a tread. is there.

[0002]

2. Description of the Related Art Generally, a pneumatic tire having a block pattern has a trade-off relationship between wet performance and wear resistance. If an attempt is made to improve wet performance, for example, a tread made of a rubber compound having excellent grip performance on a wet road surface is used or the number of pitches is increased, the wear resistance performance is deteriorated.

[0003]

SUMMARY OF THE INVENTION The object of the present invention is to solve the problems of the prior art as described above, and to improve the wet performance without lowering the wear resistance performance of a pneumatic tire having a block pattern. Is to provide tires.

[0004]

In order to achieve the above object, a pneumatic tire of the present invention is a pneumatic tire having a pattern composed of a number of blocks arranged at intervals on the circumference of a tread. And the tire circumference is CL,
When the maximum ground contact width is TW, the number of pitches is PN, the total surface area of the block is BA, and the projected edge length in the tire rotation direction is EL, (1) PN ・ BA / (TW ・ CL)
The pattern positive ratio PR defined by is 70 to 7
6%, (2) Effective edge ratio E defined by EL / TW
R is 96 to 104%, (3) CL / (PN ・ TW)
The pneumatic tire is characterized in that the aspect ratio AR of the pitch (the pattern of the minimum unit that constitutes the pattern) defined by is 17.6 to 21.5%.

In order to achieve the above object, the pneumatic tire of the present invention comprises (1) the pattern positive ratio PR.
Is 72 to 74%, and (2) the effective edge ratio ER is 9
7.4 to 102.6%, (3) the aspect ratio AR is 1
It is preferably 8.5 to 20.6%.

In the present specification, "tire circumference CL" means
It refers to the circumference of the tire when it is filled with the regular internal pressure, and the "maximum contact width TW" refers to the maximum width of the contact when the regular internal pressure is filled and the regular load is statically loaded. Indicates the number of pitches (patterns of the smallest unit forming the pattern) on the circumference of the tread, and "block total surface area BA" indicates the total surface area of the block per pitch.
= PR · TW · CL / PN, and the “projected edge length EL in the tire rotation direction” is the tire of a block per pitch in the ground contact state when the regular internal pressure is filled and the regular load is statically applied. Of the sides extending in the width direction, the total length of the sides facing the tire rotation direction D in the circumferential direction is projected, and the “pattern positive ratio PR” is PN · BA / (TW · CL ), The positive ratio of the tread pattern (the ratio of the actual contact area to the apparent contact area), which is defined as "effective edge ratio E".
“R” refers to an effective edge ratio defined by EL / TW, and “aspect ratio AR” is defined by CL / (PN · TW), a pitch (a pattern of a minimum unit forming a pattern).
Refers to the ratio of the vertical length to the horizontal length.

When a groove having a width of 2 mm or more is formed in a certain block when the total surface area BA of the block is calculated, a block having a groove depth of 50% or more of the groove depth between the blocks is the block. When the groove depth is shallower than 50% of the groove depth between the blocks, it is included in the surface area of the block and the total surface area of the block per pitch is calculated as BA. Further, even if a sipe having a width of less than 2 mm is formed in a certain block, the sipe is ignored regardless of the sipe depth and included in the block surface area,
The total surface area of the block per pitch is calculated as BA.

The projected edge length EL in the tire rotation direction will be described with reference to the drawings. FIG. 1 is a block / pattern grounding diagram for one pitch in a grounded state when a normal load is statically applied. There are 3 different shapes
This is a tread pattern in which blocks of different types are symmetrically arranged with the tire equator line in between. In the case of the block pattern as shown in FIG. 1, since the rotation direction D is the illustrated direction, EL = (A + B + C + D + E + F) 2. When a groove with a width of 2 mm or more is formed in a block, the groove depth is 5 times the groove depth between blocks.
Grooves with a groove depth of 0% or more are included in the calculation of the projected edge length in the tire rotation direction, and grooves with a groove depth shallower than 50% of the groove depth between blocks are excluded from the calculation of the projected edge length in the tire rotation direction. Then, the tire rotation direction projected edge length EL is calculated.
Even if a sipe having a width of less than 2 mm is formed in a certain block, it is excluded from the calculation of the tire rotation direction projected edge length.

The pneumatic tire of the present invention, as described above, is a pneumatic tire having a pattern of a large number of blocks arranged at intervals on the circumference of the tread,
(1) The pattern positive ratio PR defined by PN · BA / (TW · CL) is 70 to 76%, preferably 72 to 74%, and (2) the effective edge ratio ER defined by EL / TW. Is 96 to 104%, preferably 97 to 103%, and (3) the aspect ratio AR of the pitch defined by CL / (PN · TW) (the pattern of the smallest unit constituting the pattern) is 17 to 22%. , Preferably 18 to 21%
Therefore, a tire having excellent wet performance can be obtained without lowering the wear resistance performance.

As described above, the pneumatic tire of the present invention has a pattern positive ratio PR defined by PN.BA/(TW.CL) of 70 to 76%, preferably 7
Although it is 2 to 74%, when the pattern positive ratio PR exceeds this range and becomes a large value, the wet performance deteriorates, and conversely, when it becomes a small value outside this range, the wear resistance performance deteriorates.

As described above, the pneumatic tire of the present invention has an effective edge ratio ER defined by EL / TW of 96 to 104%, more preferably 97 to 103%. When the value exceeds the above range and becomes large, the block rigidity is lowered and the wear resistance performance is remarkably deteriorated. On the contrary, when the value is smaller than this range, the wet performance is deteriorated.

In the pneumatic tire of the present invention, as described above, the aspect ratio AR of the pitch (the smallest unit pattern constituting the pattern) defined by CL / (PN · TW) is 17 to 22%, which is preferable. Is 18. However, if the pattern positive ratio PR becomes a large value exceeding this range, the wet performance deteriorates, and conversely, if it becomes a small value exceeding this range, the wear resistance performance deteriorates.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment according to the present invention will be described with reference to the drawings. FIG. 2 is a perspective view of a pneumatic radial tire for trucks and buses according to the embodiment of the present invention.
FIG. 3 is a partially enlarged view of the tread pattern,
The tire size is 315 / 80R225. As shown in the figure, the tread of the pneumatic radial tire for trucks and buses has a circumferential groove 1 provided at the center of the tread, two circumferential grooves 2 provided on the left and right sides thereof, and a circumferential groove. Two circumferential grooves 3 provided outside the directional groove 2 and a number of lateral grooves 4 circumferentially spaced apart;
5, 6 and these three kinds of circumferential grooves 1, 2,
A large number of blocks 7, 8, 9 are formed by three and three lateral grooves 4, 5, 6 on the circumference of the tread. The tire circumferential length CL when filled with the regular internal pressure of 8.4 kg / cm ² was 3443 mm, and the regular internal pressure of 8.4
The maximum ground contact width TW is 270 mm when the regular load of 3250 kg is statically loaded with kg / cm ^2, and the number P of pitches P, which is the smallest unit pattern constituting the tread pattern, is 67. Block total surface area B
A is 10130 mm ² , and the tire rotation direction projected edge length EL is 268.1 mm. When calculated from the above numerical values, the pattern positive ratio PR defined by PN · BA / (TW · CL) is 73.0%, and EL /
The effective edge ratio ER defined by TW is 99.3%, and C
The aspect ratio AR of the pitch defined by L / (PN · TW) (the pattern of the minimum unit that constitutes the pattern) is 19.0%.

Explaining the conventional example, the conventional tire is a pneumatic radial tire for trucks and buses having a block pattern as in the example, and the tire size is 315 / 80R225 as in the example. is there.
The conventional tire is a tire circumferential length CL when filled with the normal inner pressure 8.4 kg / cm ² is 3443Mm, ground when the static load pressure 8.4 kg / cm ² was filled with normal load 3250kg The maximum width TW is 248 mm, the number of pitches P, which is the smallest unit pattern forming the tread pattern, is 45, the total block surface area BA per pitch is 13570 mm ² , and the regular internal pressure is filled to maintain the regular load. Tire projection direction edge length E of a block per pitch in the ground contact state under static load
L is 257.4 mm. When calculated from the above numerical values, the pattern positive ratio PR defined by PN · BA / (TW · CL) is 71.5%, and the effective edge ratio ER defined by EL / TW is 103.8%, CL /
The aspect ratio AR of the pitch defined by (PN · TW) (the pattern of the smallest unit that constitutes the pattern) is 30.9%.

The tires of Comparative Examples 1 and 2 are pneumatic radial tires for trucks and buses having a block pattern as in the examples, and the tire size is 315 / 80R225 as in the examples. . The tire of Comparative Example 1 had a tire circumference CL of 3416 mm when filled with a regular internal pressure of 8.4 kg / cm ^2, and an internal pressure of 8.4 kg / cm ^2.
The maximum ground contact width TW is 259 mm when cm ² is filled and a regular load of 3250 kg is statically loaded. The number P of pitches P is the smallest unit pattern constituting the tread pattern.
Is 96, and the total block surface area BA per pitch is 6
A tire rotation direction projected edge length EL of the block per pitch in the ground contact state when the regular internal pressure is 180 mm ² and the regular load is statically applied is 241.2.
mm. Calculated from the above values, PN / BA /
Pattern positive ratio P defined by (TW / CL)
R is 67.1%, the effective edge ratio ER defined by EL / TW is 93.1%, and the pitch defined by CL / (PN · TW) (pattern of the smallest unit that constitutes the pattern)
Has an aspect ratio AR of 13.7%. The tire of Comparative Example 2 had a tire peripheral length CL of 3442 mm when filled with a regular internal pressure of 8.4 kg / cm ² , and an internal pressure of 8.4 kg / cm ^2.
The maximum contact width TW is 259 mm when statically loaded with a normal load of 3250 kg and the number P of pitches P, which is the smallest unit pattern constituting the tread pattern, is 60.
The total block surface area BA per pitch is 1088
When the regular inner pressure is 0 mm ² and the regular load is statically applied, the block per pitch in the ground contact state has a projected edge length EL of 270.2 m in the tire rotation direction.
m. Calculated from the above values, PN / BA /
Pattern positive ratio P defined by (TW / CL)
R becomes 73.3%, the effective edge ratio ER defined by EL / TW is 104.3%, and the pitch (horizontal and vertical) of the pitch defined by CL / (PN · TW) The ratio AR is 22. %.

With respect to the pneumatic tires of the examples according to the present invention, the pneumatic tires of the conventional example, and the tires 1 and 2 of the comparative example, wear resistance and wet
An evaluation test of traction performance was carried out. The results of the evaluation test are shown in Table 1 in index notation with the evaluation result of the pneumatic tire of the conventional example as 100.

[0017]

[Table 1]

[0018]

From the evaluation results shown in Table 1, the pneumatic tires of the examples according to the present invention have an extremely high wet traction performance as compared with the pneumatic tires of the prior art without sacrificing wear resistance. You can see that it has been improved. Further, the pneumatic tires 1 and 2 of the comparative example are
It can be seen that the wet traction performance is slightly improved as compared with the pneumatic tire of the conventional example, but at the same time, the wear resistance performance is sacrificed.

[Brief description of drawings]

FIG. 1 is a grounding drawing just below a load of a block pattern.

FIG. 2 is a perspective view of a pneumatic tire according to the present invention.

FIG. 3 is a tread pattern diagram of a pneumatic tire according to the present invention.

[Explanation of symbols]

 1, 2, 3 Circumferential groove 4, 5, 6 Lateral groove 7, 8, 9 Block

Claims (2)

[Claims] 1. A pneumatic tire having a pattern composed of a number of blocks arranged at intervals on the tread circumference, wherein the tire circumference when the normal internal pressure is filled is C
Let L be TW, the maximum contact width when the regular internal pressure is filled and the regular load is statically applied, and TW is the pitch of the tread circumference (the smallest unit pattern that constitutes the pattern), and PN is 1
Let BA be the total surface area of the block per pitch, and of the sides extending in the tire width direction of the block per pitch in the ground contact state when the internal pressure is filled and the regular load is statically applied, the surface in the tire rotation direction D direction When the sum of the lengths of the sides to be projected in the circumferential direction is EL, (1)
The pattern positive ratio PR defined by PN / BA / (TW / CL) is 70 to 76%, and (2) EL / TW.
The effective edge ratio ER defined by
(3) A pneumatic tire characterized by having an aspect ratio AR of 17 to 22% of a pitch (a pattern of a minimum unit constituting a pattern) defined by CL / (PN · TW). 2. The pattern positive ratio PR is 72 to 74%, and the effective edge ratio ER is 97 to 103%.
2. The pneumatic tire according to claim 1, wherein the aspect ratio AR is 18 to 21%.