JP2003170710A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of delaying occurrence of a crack from a side wall even with low flattening. <P>SOLUTION: On the outer surface of the side wall 12 of the pneumatic tire 10 having low flattening, a peak of distortion by a load is provided near about 60 to 80% of the height of tire cross section. A projecting marked character 14 formed on a surface of the side wall 12 is set so that a curvature radius R1 of a circular arc curved surface 26 of the outside part in the radius direction of the tire near the distortion peak position is larger than a curvature radius R2 of the circular arc curved surface 26 of the inside part in the radius direction of the tire. Therefore, crack occurrence from the outside part in the radius direction of the tire of the marked character 14 can be delayed, and crack occurrence time in the whole tire can be set at a time equivalent to that of a general tire (flattening 70%). <P>COPYRIGHT: (C)2003,JPO

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 capable of suppressing the generation of cracks from tire sidewalls.

[0002]

2. Description of the Related Art In a pneumatic tire, on the surface of a tire sidewall, for example, a trade mark consisting of letters, numbers, symbols or figures, a manufacturer name, a product name,
A display portion for displaying tire size and the like is formed.

In the display portion provided on the surface of such a tire sidewall, the size (curvature radius) of the curved surface of the base portion, the height, the inclination angle of the side wall, the surface roughness near the base portion, etc. are arranged. The setting is the same regardless of the position.

[0004]

By the way, a flat tire (a tire having an oblateness of 55% or less) has a low tire cross-sectional height and a narrow deformation region of the sidewall, so that the tire outer surface can be bent only by a load. Distortion tends to have a peak, and the peak value is 20 to 30% higher than that of a tire having a general flatness (70%).

Therefore, in the flat tire, the strain generated at the end portion of the display portion on the outer surface of the sidewall due to the strain of the outer surface of the tire becomes higher than that of a tire having a general flatness ratio.
There is a problem that cracks easily occur.

For example, compared with a tire having an aspect ratio of 70%,
A tire having an oblateness of 45% starts cracking 20 to 30% earlier in the traveling distance.

Further, in the portion where the display portion is not formed, cracks are likely to occur from a specific portion, that is, a portion where the strain has a peak.

The present invention has been made to solve the above problems, and an object thereof is to provide a pneumatic tire capable of delaying the generation of cracks from sidewalls even if the flatness is small. is there.

[0009]

The invention according to claim 1 is a pneumatic tire in which a convex display portion is formed on the surface of a sidewall toward the outside of the tire and has a tire cross-section height of 30. The display portion is provided in an area of ˜80%, and the base portion of the display portion is formed such that stress is dispersed in the tire radial direction outer side portion than in the tire radial direction inner side portion. Is characterized by.

Next, the operation of the pneumatic tire according to claim 1 will be described.

Pneumatic tires have a tire cross-section height of 3
In the region of 0 to 80%, the outer surface of the sidewall under load has a peak in the vicinity of about 60 to 80% of the tire cross section height when viewed in a cross section along the tire rotation axis.

In the case of having a convex display portion in a region of 30 to 80% of the tire cross-sectional height, first, the base portion of the display portion near the peak of the strain on the outer surface of the sidewall (the display portion and the sidewall are A crack occurs from the boundary part).

That is, since the peak position of the strain is 60 to 80% of the tire cross-section height, the display portion of the tire radial outer side near the strain peak position is closer to the tire radial inner side. Cracks are likely to occur early.

Since the base portion of the display portion of the pneumatic tire according to claim 1 is formed so that the stress is dispersed more in the tire radial outer side portion than in the tire radial inner side portion, It is possible to delay the generation of cracks from the tire radial outside portion.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the base portion of the display portion has an arcuate curved surface having a center of curvature on the outside of the tire and at the outer side portion in the tire radial direction. The radius of curvature of the circular arc curved surface is larger than the radius of curvature of the circular arc curved surface of the inner portion in the tire radial direction,
It is characterized by that.

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

When the shape of the base portion of the display portion is an arcuate curved surface having the center of curvature on the outside of the tire, stress is dispersed, but by increasing the radius of curvature toward the outer side in the tire radial direction, the outside in the tire radial direction is increased. The stress can be more dispersed in the part.

The invention according to claim 3 is the pneumatic tire according to claim 2, characterized in that the radius of curvature of the arcuate curved surface of the outer portion in the tire radial direction is at least 0.35 mm or more. .

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

If the radius of curvature of the arcuate curved surface on the outer side in the radial direction of the tire is less than 0.35 mm, it may not be possible to make the timing of crack generation equal to that of a general tire (oblateness 70%).

The invention according to claim 4 is the pneumatic tire according to any one of claims 1 to 3, wherein:
The display part is characterized in that the height of the tire radial direction outer side portion is lower than that of the tire radial direction inner side portion.

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

The lower the height of the display portion, the easier it is to disperse the stress. Therefore, by lowering the height of the outer portion in the tire radial direction, the stress is more dispersed in the outer portion in the tire radial direction. You can

The invention according to claim 5 is the pneumatic tire according to any one of claims 1 to 4, wherein:
The inclination angle of the side wall of the display portion is smaller in the tire radial direction outer side portion than in the tire radial direction inner side portion.

Next, the operation of the pneumatic tire according to claim 5 will be described.

The smaller the inclination angle of the side wall of the display portion, the easier it is to disperse the stress in the base portion. Therefore, by making the inclination angle of the side wall smaller in the tire radial direction outer side portion, the tire radial direction outer side portion is made smaller. The stress can be more dispersed with.

The invention according to claim 6 is the pneumatic tire according to any one of claims 1 to 5, wherein:
The display portion is characterized in that the surface roughness in the vicinity of the base portion of the tire radial direction outer portion is smaller than that in the vicinity of the base portion of the tire radial direction inner portion.

Next, the operation of the pneumatic tire according to claim 6 will be described.

Since the smaller the surface roughness is, the easier the stress is to be dispersed, the surface roughness near the base of the display portion is made smaller at the tire radial outer side portion to reduce the stress at the tire radial outer side portion. It can be more dispersed.

The pneumatic tire according to claim 7 is 30-80% of the tire cross-sectional height of the outer surface of the sidewall portion.
In this region, a convex portion that smoothly rises to the outside of the tire is provided at the peak position of strain under load.

Next, the operation of the pneumatic tire according to claim 7 will be described.

In the sidewall portion, the thick rubber gauge outside the carcass has higher rigidity than the thin rubber gauge and is less likely to be deformed. As a result, the strain on the outer surface is reduced.

In the pneumatic tire according to the seventh aspect, since the convex portion that smoothly swells to the outside of the tire is provided at the strain peak position under load, the strain peak can be lowered and the generation of cracks can be delayed.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A first embodiment of the pneumatic tire of the present invention will be described with reference to FIG.

As shown in FIG. 1, the surface of the sidewall 12 of the pneumatic tire 10 has a tire cross-section height H of 3
In the region of 0 to 80% (0.3H to 0.8H), the engraved characters 14 that are convex toward the outside of the tire are formed along the tire circumferential direction.

The pneumatic tire 10 of this embodiment is used.
Is a pneumatic tire having an oblateness of 55% or less, and the internal structure is the same as that of a normal pneumatic tire, and therefore the description of the internal structure will be omitted.

In FIG. 1, reference numeral 16 is a bead core, reference numeral 18 is a carcass, reference numeral 20 is a belt, reference numeral 22 is a tread, and reference numeral 24 is a bead portion.

An arcuate curved surface 26 having a center of curvature on the outside of the tire is formed at the base of the engraved character 14.

The stamped character 14 has a radius of curvature R1 of the arcuate curved surface 26 of the tire radial direction outer portion shown in FIG. 1B in order to disperse the stress of the base portion of the tire radial direction outer portion than that of the tire radial direction inner portion. Is larger than the radius of curvature R2 of the arcuate curved surface 26 of the inner portion in the tire radial direction shown in FIG. 1 (C).

The radius of curvature R1 of the arcuate curved surface 26 on the outer side in the radial direction of the tire is preferably 0.35 mm or more and 0.8 mm or less, and more preferably 0.4 mm or more and 0.6 m or less.

The radius of curvature R1 of the arcuate curved surface 26 is 0.
When it is larger than 8 mm, the visibility of the engraved character 14 deteriorates.

In order to disperse the stress of the base portion of the tire radial outer side portion from the engraved character 14, the height H1 of the tire radial outer side portion is higher than that of the tire radial inner side portion. Is set lower than H2.

In order to disperse the stress in the base portion of the outer circumferential portion of the marking character 14 in the tire radial direction from that in the inner portion in the tire radial direction, the sidewall 14A of the outer portion of the marking character 14 in the radial direction of the tire.
(Angle of the surface of the sidewall 12 with respect to the tangent line L) θ1 is set smaller than the inclination angle θ2 of the sidewall 14A on the inner side in the tire radial direction.

In order to disperse the stress in the base portion of the tire radial outer side portion than that in the tire radial direction inner portion, the engraved character 14 is closer to the base portion of the tire radial outer portion than to the base portion of the tire radial inner portion. Has a fine surface roughness. (Operation) Next, the operation of the pneumatic tire 10 of the present embodiment will be described.

Pneumatic tire 10 having an oblateness of 55% or less
The outer surface of the side wall 12 has a peak of strain due to load in the vicinity of about 60 to 80% of the tire cross-sectional height.

In addition, the sidewall 12 and the engraved character 14
Stress tends to concentrate at the boundary with the side wall 14A of
In the present embodiment, the engraved character 14 is formed so that the stress is more dispersed in the tire radial outer portion closer to the strain peak position than in the tire radial inner portion as described above. It is possible to delay the generation of cracks from the radially outer portion, and it is possible to make the timing of crack generation in the tire as a whole in a general tire (oblateness 70%).

If the radius of curvature of the arcuate curved surface on the outer side in the radial direction of the tire is less than 0.35 mm, it may not be possible to make the timing of crack generation equal to that of a general tire (oblateness 70%).

In the pneumatic tire 10 having an oblateness of 55% or less, the height H1 of the stamped character 14 on the outer side in the tire radial direction is preferably 1.0 mm or less, and 0.6
mm or less is more preferable.

The inclination angle θ1 of the side wall 14A of the stamped character 14 on the outer side in the tire radial direction is preferably 60 ° or less, and 4
It is more preferably 5 ° or less.

Marking character 14 The surface roughness near the base of the radially outer portion of the tire is 1.6 in terms of arithmetic average roughness (Ra).
a, the maximum height (Ry) is 6.3 s, and the ten-point average roughness (R
z) is preferably smaller than 6.3z. [Second Embodiment] A second embodiment of the pneumatic tire of the present invention will be described with reference to FIG.

The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 2, the surface of the sidewall 12 of the pneumatic tire 10 has a tire cross-section height H of 3
In the region of 0 to 80% (0.3H to 0.8H), the stress-dispersing convex portion 28 is formed along the tire circumferential direction.

The stress-dispersing convex portion 28 is formed at the peak position of strain on the outer surface of the sidewall 12.

The peak position of strain on the outer surface of the sidewall 12 is determined as follows.

A pneumatic tire not provided with the stress-dispersing convex portion 28 is mounted on a standard rim and filled with standard air pressure.

Then, a mesh of 2 mm intervals is drawn on the sidewall of the pneumatic tire mounted on the rim.

Next, a normal load is applied to the pneumatic tire mounted on the rim, and the portion where the mesh interval is most extended is set as the strain peak position.

The standard rim is a rim specified by JATMA (Japan Automobile Tire Manufacturer's Association) Year Book 2001 version, and the standard air pressure corresponds to the maximum load capacity of JATMA (Japan Automobile Tire Manufacturer's Association) Year Book 2001 version. Air pressure, regular load is J
ATMA (Japan Auto Tire Association) Year Boo
k This is the load equivalent to the maximum load capacity when the single wheel of the 2001 version is applied.

At the place of use or the place of manufacture, TRA
When the standards and ETRTO standards are applied, follow each standard.

The shape of the stress-dispersing convex portion 28 is preferably a mountain shape that gently rises from the sidewall 12.

The shape of the stress-dispersing convex portion 28 of the present embodiment is an arc shape whose top portion is convex outward, and a skirt is a concave arc shape whose center of curvature is outside the tire. (Operation) Next, the operation of the pneumatic tire 10 of the present embodiment will be described.

In the pneumatic tire 10 of this embodiment, since the stress-dispersing convex portion 28 is provided at the position having the strain peak on the outer surface of the sidewall 12, the rubber gauge outside the carcass becomes thicker at that position. It is possible to disperse the stress and delay the occurrence of cracks.

The height dimension H3 of the stress-dispersing convex portion 28 from the sidewall 12 is preferably 0.8 mm or more, more preferably 1.5 mm or more.

The width W of the stress-dispersing convex portion 28 is 3 mm.
The above is preferable, and 5 mm or more is more preferable. (Test Example 1) In order to confirm the effect of the present invention, a pneumatic tire of a conventional example and a pneumatic tire of an example to which the present invention was applied were prepared and a drum running test was performed.

Drum running test: size 215 / 45R1
The test tire of No. 7 was mounted on the rim (7J) and the internal pressure was 180k
The drum was run at a load of 430 kg and a speed of 50 km / h, and the running distance at the time when a crack was generated in the sidewall was examined.

The test tire has a tire cross-sectional height of 32 to 7
The display portion (company name and brand name) is provided in the area of 8%, and the peak position of the strain on the outer surface of the sidewall at the time of load is 62% of the tire cross-section height.

Table 1 below shows the specifications of each part of the pneumatic tires of the conventional example and the example, and the traveling distance until the occurrence of cracks.
As described in.

The "surface roughness near the base" in the table is
The arithmetic average roughness (Ra) is 0.4a to 1.6a, the maximum height (Ry) is 1.6s to 6.3s, and the ten-point average roughness (R).
z) is within the range of 1.6z to 6.3z,
Ultrafine indicates that it is relatively smoother than normal.

As for the height of the display portion, the distance from the surface of the side portion to the display portion is calculated, and when the side portion virtual contour line (two-dot chain line) can be assumed as shown in FIG. The distance may be calculated.

[0070]

[Table 1] (Test Example 2) In order to confirm the effect of the present invention, size 2
A drum running test was conducted in the same manner as in Test Example 1 on the test tire of 15 / 55R16.

Drum running test: A test tire was mounted on a rim (7
(J), the inner pressure was 180 kPa, the load was 490 kg, the speed was 50 km / h, and the drum was run, and the running distance at the time when a crack was generated in the sidewall was examined.

The test tire had a tire cross-sectional height of 32 to 7
The display portion (company name and brand name) is provided in the 0% area, and the peak position of the strain on the outer surface of the sidewall at the time of load is 64% of the tire cross-section height.

The specifications of each part of the pneumatic tires of Conventional Example 2 and Example 2 and the traveling distance until the occurrence of cracks are as shown in Table 2 below.

[0074]

[Table 2] (Test Example 3) In order to confirm the effect of the present invention, size 2
A drum running test was conducted on the test tire of 15 / 45R17 in the same manner as in Test Example 1.

Drum running test: A test tire was mounted on a rim (7
(J), the inner pressure was 180 kPa, the load was 430 kg, the speed was 50 km / h, and the drum was run, and the running distance at the time when a crack was generated in the sidewall was examined.

The test tire has a tire cross-sectional height of 32 to 7
A display unit (company name and brand name) is provided in 8% of the area.

The specifications of each part of the pneumatic tires of Conventional Example 3 and Example 3 and the traveling distance until the occurrence of cracks are as shown in Table 3 below.

[0078]

[Table 3] (Test Example 4) In order to confirm the effect of the present invention, size 2
A drum running test was conducted in the same manner as in Test Example 1 on the test tire of 15 / 55R16.

Drum running test: A test tire was mounted on a rim (7
(J), the inner pressure was 180 kPa, the load was 490 kg, the speed was 50 km / h, and the drum was run, and the running distance at the time when a crack was generated in the sidewall was examined.

The test tire has a tire cross-sectional height of 32 to 7
A display unit (company name and brand name) is provided in the 0% area.

The specifications of each part of the pneumatic tires of Conventional Example 4 and Example 4 and the traveling distance until the occurrence of cracks are as shown in Table 4 below.

[0082]

[Table 4] (Test Example 5) In order to confirm the effect of the present invention, size 2
A drum running test was conducted on the test tire of 15 / 45R17 in the same manner as in Test Example 1.

Drum running test: A test tire was mounted on a rim (7
(J), the inner pressure was 180 kPa, the load was 430 kg, the speed was 50 km / h, and the drum was run, and the running distance at the time when a crack was generated in the sidewall was examined.

The specifications of the respective parts of the pneumatic tires of Conventional Example 5 and Example 5 and the traveling distance until the occurrence of cracks are as shown in Table 5 below.

The peak position of the strain is 1 at the sectional height.
This is the position when set to 00%.

The peak value of the strain is the ratio of the increased mesh spacing.

[0087]

[Table 5] (Test Example 6) In order to confirm the effect of the present invention, size 2
A drum running test was conducted in the same manner as in Test Example 1 on the test tire of 15 / 55R16.

Drum running test: A test tire was mounted on a rim (7
(J), the inner pressure was 180 kPa, the load was 490 kg, the speed was 50 km / h, and the drum was run, and the running distance at the time when a crack was generated in the sidewall was examined.

The specifications of each part of the pneumatic tires of Conventional Example 6 and Example 6 and the traveling distance until the occurrence of cracks are as shown in Table 6 below.

[0090]

[Table 6]

[0091]

As described above, the pneumatic tire according to the present invention has an excellent effect that the generation of cracks from the sidewall can be delayed even if the flatness is small.

[Brief description of drawings]

FIG. 1A is a cross-sectional view taken along a rotation axis of a pneumatic tire according to a first embodiment of the present invention, and FIG. 1B is a tire radial direction outer side of an engraved character of FIG. 1A. FIG. 1C is an enlarged cross section near the portion, and FIG. 1C is an enlarged cross section near the inner portion in the tire radial direction of the engraved character in FIG.

FIG. 2 is a cross-sectional view taken along a rotation axis of a pneumatic tire according to a second embodiment of the present invention.

[Explanation of symbols]

10 pneumatic tire tire 12 Sidewall 14 Engraved characters (display) 28 Convex portion for stress dispersion

Claims (7)

[Claims] 1. A pneumatic tire in which a convex display portion is formed on the surface of a sidewall toward the outside of the tire, and the display portion is provided in an area of 30 to 80% of the tire cross-sectional height. The pneumatic tire, wherein the base portion of the display portion is formed so that the stress is dispersed in the tire radial direction outer side portion than in the tire radial direction inner side portion. 2. The base portion of the display portion has an arcuate curved surface having a center of curvature on the outside of the tire, and the radius of curvature of the arcuate curved surface of the tire radial outer side is the arcuate curved surface of the tire radial inner side. The pneumatic tire according to claim 1, wherein the pneumatic tire has a larger radius of curvature. 3. The pneumatic tire according to claim 2, wherein the radius of curvature of the arcuate curved surface of the tire radial outside portion is at least 0.35 mm or more. 4. The display unit according to claim 1, wherein a height of an outer portion in the tire radial direction is lower than a height of an inner portion in the tire radial direction of the display portion. Pneumatic tires. 5. The inclination angle of the side wall of the display portion is smaller in a tire radial direction outer side portion than in a tire radial direction inner side portion.
The pneumatic tire according to item. 6. The surface roughness of the display portion near the base portion of the tire radial outer side portion is smaller than that near the base portion of the tire radial inner side portion. The pneumatic tire according to any one of items. 7. A convex portion that smoothly rises to the outside of the tire is provided at a peak strain position under load within a region of 30 to 80% of the tire cross-sectional height of the outer surface of the sidewall portion. Pneumatic tires.