JP2002046418A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire to prevent the occurrence of tear to the bottom of a fine groove when a vehicle rides over a curbstone. SOLUTION: An angle between an axis m of narrow groove 38, hereinafter called groove, in the peripheral direction of the pneumatic tire 10 and the tread normal 1 of a tread is set to a value higher than 20 deg. and lower than 70 deg.. Since a shortmost distance (a) from the earth end of the tread of the tire 10 to the inlet of a groove 38 is set to a value shorter than 30 mm, rigidity of a defense rib 34B can be improved and in turn, the occurrence of tear to a bottom 38A of the groove 38 can be prevented.

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 suitable for heavy-duty vehicles such as trucks and buses.

[0002]

2. Description of the Related Art Various types of pneumatic tires having a plurality of circumferentially extending ribs on a tread have been proposed as pneumatic tires used for heavy-duty vehicles such as trucks and buses.

[0003] Pneumatic tires having ribs extending in the circumferential direction have a problem of uneven wear of the ribs and a problem of rib tearing due to running on rough roads, and various measures have been taken.

[0004] As one of measures against this, for example, a circumferential groove called a defense groove (D / G) is provided on a shoulder-side rib, which is apt to cause uneven wear, called a side edge wear, and a tire of the defense groove is provided. There is a technique for preventing uneven wear of the rib on the inner side in the width direction. In addition, there is a technique for causing uneven wear on the rib by causing a difference in diameter between the ribs on the shoulder side.

In the conventional shape of the narrow groove, the rigidity of the rib (defense rib) outside the narrow groove among the ribs on the shoulder side is low. There is a problem that cracks (tears) occur due to the occurrence of tensile strain in the cross section and circumferential shear strain at the bottom of the groove.

[0006]

SUMMARY OF THE INVENTION In view of the above, the present invention prevents the occurrence of cracks (tear) at the bottom of a narrow groove, for example, even when a vehicle rides on a curb or the like. It is an object to provide a pneumatic tire.

[0007]

The pneumatic tire according to claim 1 is a pneumatic tire in which a narrow groove extending along the circumferential direction of the tire is provided on a rib on the shoulder side of the tread. The tire is characterized by being inclined from the shoulder side in the tire width direction to the center side in the tire width direction from the entrance located on the tread surface to the groove bottom.

Next, the operation and effect of the pneumatic tire according to the first aspect will be described.

[0009] The pneumatic tire is provided with a narrow groove extending along the tire circumferential direction in a rib on the shoulder side of the tread.

Here, since the narrow groove is formed so as to be inclined from the shoulder in the tire width direction to the center in the tire width direction from the entrance located on the tread surface to the groove bottom, the tread is formed from the entrance located on the tread surface to the groove bottom. The rigidity of the ribs (defense ribs) outside the narrow groove among the ribs on the shoulder side of the tread can be increased as compared with the narrow groove formed perpendicular to the surface.

As a result, even when the vehicle rides on a curb or the like, it is possible to prevent the occurrence of circumferential shear strain at the groove bottom of the narrow groove, thereby preventing the occurrence of tare.

In the pneumatic tire according to the second aspect, the angle between the axis of the narrow groove and the normal to the tread of the tread is 2 degrees.
The angle is set to be larger than 0 ° and smaller than 70 °.

Next, the operation and effect of the pneumatic tire according to claim 2 will be described.

Even when the narrow groove is inclined as in the first aspect of the present invention, the angle formed by the axis of the narrow groove and the normal to the tread of the tread is set to be larger than 20 ° and smaller than 70 °. Accordingly, it is possible to minimize the occurrence of circumferential shear strain at the groove bottom of the narrow groove, and to suppress the occurrence of tear.

Conversely, if the angle is not more than 20 °, the rigidity of the defense rib is weakened, and there is a possibility that the shear may be generated due to circumferential shear strain generated at the bottom of the narrow groove. The angle is 70 °
In the above case, the rigidity of the ribs on the shoulder side other than the defense ribs, that is, the rigidity of the ribs inside the narrow groove is reduced,
This is because tearing occurs in the rib inside the narrow groove, which is inappropriate.

In the pneumatic tire according to the third aspect, the shortest distance from the tread contact portion of the tire to the entrance of the narrow groove is:
The length is set shorter than 30 mm.

Next, the operation and effect of the pneumatic tire according to claim 3 will be described.

By setting the shortest distance from the tread portion of the tire tread to the entrance of the narrow groove to be shorter than 30 mm, it is possible to minimize tensile strain in the cross section at the groove bottom of the narrow groove. The occurrence of tare at the bottom can be suppressed.

Conversely, if the shortest distance from the tread contact portion of the tire to the entrance of the narrow groove is 30 mm or more, the uneven wear of the rib inside the narrow groove is deteriorated, which is inappropriate.

The tread contact portion of the tire means "the end portion of the tire with the largest width". "The end of the maximum width of the tire contact area" means the tread of the tread in the axial direction of the tread when the tire is assembled to the "regular rim", filled with the "regular internal pressure", and statically loaded with the "regular load". Refers to the maximum width.

Here, "load" means the maximum load (maximum load capacity) of a single wheel in the applicable size described in the following standard, and "internal pressure" means the applicable size described in the following standard. Means the air pressure corresponding to the maximum load (maximum load capacity) of a single wheel, and the “rim” is a standard rim (or “Approved Rim”, “Recommend”) in an applicable size described in the following standards.
nd Rim ").

The standard is determined by an industrial standard effective in a region where the tire is manufactured or used.
For example, in the United States "The Tire an
dRim Association Inc. YEA
R BOOK ”and“ The Europ ”in Europe.
ean Tire and Rim Technica
l Organizations Standards
Manual ", and in Japan, it is defined by" JATMA Year Book "of the Japan Automobile Tire Association.

In the pneumatic tire according to the fourth aspect, the length of a parallel line drawn parallel to the tread surface from the groove bottom of the narrow groove to the outer surface of the tire is d, and the groove bottom of the narrow groove from the tread is defined as d. D / h> 1.2 (1) where h is the length of a vertical line perpendicular to the tread surface.

Next, the operation and effect of the pneumatic tire according to claim 4 will be described.

The length of a parallel line drawn parallel to the tread surface from the groove bottom of the narrow groove to the outer surface of the tire is d, and the length from the tread to the groove bottom of the narrow groove is drawn perpendicular to the tread surface. When the length of the vertical line is h, d / h> 1.2
Claim 1 by satisfying (1).
Similarly to the above, even when the vehicle rides on a curb or the like, it is possible to prevent circumferential shear strain and in-plane tensile strain from being generated at the groove bottom of the narrow groove, so that it is possible to prevent the occurrence of tear.

On the other hand, when d / h ≦ 1.2, the above effect cannot be obtained, which is inappropriate.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic tire according to one embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a plan view of a tread of a pneumatic tire according to one embodiment of the present invention, and FIG. 2 is a cross-sectional view illustrating an outer contour of the pneumatic tire according to one embodiment of the present invention.

In FIG. 1, the directions of arrows L and R indicate the tire axial direction, and the direction of arrow S indicates the circumferential direction of the tire.

As shown in FIG. 1, the tread 12 (tread width W) of the pneumatic tire 10 of the present embodiment has a zigzag shape along the tire circumferential direction on both sides in the tire axial direction with the tire equatorial plane CL interposed therebetween. An extending circumferential main groove 14 is formed, and a circumferential groove 16 extending linearly along the tire circumferential direction is formed outside the circumferential main groove 14 in the tire axial direction.

As shown in FIGS. 1 and 2, the circumferential main groove 1
A plurality of stone biting prevention projections 18 are formed on the bottom of the base 4 along the longitudinal direction of the groove.

On the other hand, as shown in FIG. 1, the center rib 22 sandwiched between the pair of circumferential main grooves 14 is provided with a plurality of lateral grooves 24 inclined in the tire axial direction in the tire circumferential direction. The lateral groove 24 is formed to have a groove width smaller than the circumferential main groove 14 and a shallower groove depth.

Also, as shown in FIG.
A plurality of short sipes 26 extending in the tire axial direction are formed in the tire circumferential direction at the edge portion on the tread side on the side of the second circumferential main groove 14.

Also, as shown in FIG.
A plurality of lateral grooves 30 with sipe inclined with respect to the tire axial direction are formed in the second rib 28 sandwiched by the circumferential groove 16 and the circumferential groove 16.

Also, as shown in FIG.
A plurality of short sipes 32 extending in the tire axial direction are respectively formed in the tire circumferential direction at the tread side edge portion of the circumferential main groove 14 and the tread side edge portion of the circumferential groove 16.

In the shoulder rib 34, a plurality of short sipes 36 extending in the tire axial direction are formed at the edge portion on the tread side on the circumferential groove 16 side in the tire circumferential direction.

The shoulder ribs 34 extend linearly in the circumferential direction toward the shoulder and extend in the circumferential groove 1.
A circumferential narrow groove 38 that is narrower than 6 is formed.

Here, the circumferential width narrow groove 38 will be described in detail.

As shown in FIG. 3, the circumferential narrow groove 38 is
The shortest distance a from the tread surface contact end of the tire 10 to the entrance of the circumferential narrow groove 38 on the tread surface is formed to be shorter than 30 mm.

The circumferential narrow groove 38 is formed in a range where the angle α between the axis m of the circumferential narrow groove 38 and the tread normal l of the tread 12 is larger than 20 ° and smaller than 70 °. ing.

As described above, the circumferential narrow groove 38 is formed so as to be inclined from the shoulder in the tire width direction toward the center in the tire width direction from the inlet to the groove bottom 38A.

The length of a parallel line k drawn from the groove bottom 38A of the circumferential narrow groove 38 to the outer surface of the tire in parallel to the tread surface is d, and the length of the circumferential narrow groove 38 from the tread 12 is d. When the length of a vertical line 1 drawn perpendicular to the tread surface up to the groove bottom 38A is defined as h, d / h> 1.2 (1) is satisfied.

Next, the operation and effect of the pneumatic tire of the present embodiment will be described.

When the circumferential narrow groove 38 is formed as described above, the following operations and effects are obtained.

First, by setting the angle α between the axis m of the circumferential narrow groove 38 and the tread normal l of the tread 12 to be larger than 20 ° and smaller than 70 °, the circumferential narrow groove 38 is formed. The generation of circumferential shear strain on the groove bottom 38A can be prevented as much as possible, and the occurrence of tear can be suppressed.

On the other hand, if the angle is not more than 20 °, the rigidity of the defense rib 34B is weakened, and a tear may occur due to a circumferential shear strain generated at the groove bottom 38A of the circumferential narrow groove 38. If the angle is 70 ° or more, the rigidity of the shoulder ribs 34 other than the defense ribs 34B, that is, the ribs 34A inside the narrow groove 38 in the circumferential direction decreases, and the ribs 34A This is because it is inappropriate due to the occurrence of tare.

Further, by setting the shortest distance a from the tread contact portion of the tire 10 to the entrance of the circumferential narrow groove 38 to be shorter than 30 mm, the groove bottom 38A of the circumferential narrow groove 38 is set.
As a result, it is possible to minimize the occurrence of tear on the groove bottom 38A of the circumferentially narrow groove 38.

Conversely, when the shortest distance a from the tread contact portion of the tire 10 to the entrance of the circumferential narrow groove 38 is 30 mm or more, the uneven wear of the rib 34A inside the circumferential narrow groove 38 deteriorates. This is because it is inappropriate.

Further, the length of a parallel line k drawn from the groove bottom 38A of the circumferential narrow groove 38 to the outer surface of the tire in parallel to the tread surface is d, and the length of the circumferential narrow groove 38 from the tread 12 is d. When the length of a vertical line n drawn perpendicular to the tread surface up to the groove bottom 38A is h, d / h> 1.2
By satisfying (1), it is possible to prevent circumferential shear strain and in-section tensile strain from occurring at the groove bottom 38A of the circumferential narrow groove 38 even when the vehicle rides on a curb or the like. Therefore, occurrence of tare can be prevented.

On the other hand, when d / h ≦ 1.2, the above effect cannot be obtained and the result becomes inappropriate. (Test Example) Next, a test example of the pneumatic tire of the present invention will be described.

In this test example, the size 315 / 80R2
After running a vehicle to which a pneumatic tire of 2.5 is applied for 10,000 km, the tire repeatedly goes on and off the curb five times, and cracks are formed at the bottom of the circumferential narrow groove of the tire. The (tea) depth was measured. Also, size 31
After the vehicle using the 5 / 80R22.5 pneumatic tire was driven for 100,000 km, the wear amount of the rib located inside the circumferentially narrow groove was measured.

The test results are shown in Table 1 below.

[0052]

[Table 1]

Here, "a" in the above Table 1 means the shortest distance from the tread end of the tire to the entrance of the narrow groove in the circumferential direction.

"D" means the length of a parallel line drawn parallel to the tread surface from the groove bottom of the circumferential narrow groove to the tire outer surface.

"Α" means the angle α between the axis of the circumferentially narrow groove and the tread normal to the tread.

"H" means the length of a vertical line perpendicular to the tread surface from the tread to the groove bottom of the circumferentially narrow groove.

"Tear property" means that the tire travels 10,000 km in the market, and goes up and down the curb five times.
The index indicates the depth of a crack (tea) generated. This numerical value is a ratio to the conventional tire when the conventional tire is set to 100, and the smaller the numerical value, the shallower the depth of the tear, which means that the tearability is improved.

The term “uneven wear” is an index indicating the amount of wear of a rib located inside a circumferentially narrow groove of a tire that has traveled 100,000 km in the market. This numerical value is a ratio of the conventional tire to 100 when the conventional tire is set, and the smaller the numerical value, the more the uneven wear property is improved.

The above-mentioned "conventional tire" means a tire having a circumferentially narrow groove formed perpendicular to the tread surface.

As shown in Table 1 above, it was found that the tires of Examples, Examples, Comparative Examples, and Comparative Examples to which the present invention was applied had improved tearing properties as compared with conventional tires. did.

In particular, it was found that not only the tear property but also the uneven wear property of the tires of Examples and Examples were improved.

In the tire of the comparative example, the value of α is out of the applicable range of the present invention, and the value of a and the value of d / h are in the applicable range of the present invention. As a result, uneven abrasion was improved.

In the tire of the comparative example, the value of α and d /
The value of h is out of the applicable range of the present invention, and the value of a is in the applicable range of the present invention, but the tear property and uneven wear property are improved as compared with the conventional tire.

In the tire of the comparative example, the value of a is out of the applicable range of the present invention, and the value of α and the value of d / h are in the applicable range of the present invention. The tearing property was improved.

[0065]

According to the pneumatic tire of the present invention, it is possible to prevent a crack (tear) from being generated at the bottom of the narrow groove even when the vehicle rides on a curb or the like.

[Brief description of the drawings]

FIG. 1 is a plan view of a tread of a pneumatic tire according to one embodiment of the present invention.

FIG. 2 is a sectional view showing an outer contour of the pneumatic tire according to one embodiment of the present invention.

FIG. 3 is an enlarged view showing a narrow groove cross section of the pneumatic tire according to one embodiment of the present invention.

[Explanation of symbols]

 10 Pneumatic tire 12 Tread 38 Circumferentially narrow groove (narrow groove)

Claims (4)

[Claims] 1. A pneumatic tire in which a narrow groove extending along the circumferential direction of a tire is provided in a rib on a shoulder side of a tread, wherein the narrow groove extends from an entrance located on a tread surface to a groove bottom in a tire width direction. A pneumatic tire characterized by being inclined from the side toward the center in the tire width direction. 2. The pneumatic tire according to claim 1, wherein an angle between an axis of the narrow groove and a normal to a tread of the tread is set to be larger than 20 ° and smaller than 70 °. . 3. The pneumatic tire according to claim 2, wherein the shortest distance from the tread portion of the tire to the ground contact end to the entrance of the narrow groove is set shorter than 30 mm. 4. The length of a parallel line drawn parallel to the tread surface from the groove bottom of the narrow groove to the tire outer surface is d, and the distance from the tread to the groove bottom of the narrow groove is relative to the tread surface. 4. The device according to claim 1, wherein d / h> 1.2 (1) is satisfied, where h is the length of a vertical line drawn vertically.
The pneumatic tire according to the paragraph.