JP2006193052A - Radial tire for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent uneven wear in a shoulder part of a pneumatic radial tire for a heavy load. <P>SOLUTION: In the radial tire for a heavy load wherein a tire tread part is provided with a tire peripheral direction main groove, and wherein the ratio (D/W) of the main groove depth (D) to the tire section width (W) is 0.035<D/W<0.06, when the radial tire for the heavy load is under a load, tilting quantity of a buttress portion is set to 5mm or more, and preferably 10mm or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a pneumatic heavy load radial tire, and more particularly to a pneumatic heavy load radial tire capable of preventing shoulder edge uneven wear.

  Conventional heavy-duty radial tires mounted on the steering (steering) shaft of tires tend to concentrate load on the side of the tread compared to the center of the tread. Edge Wear) (hereinafter referred to as “SEW”) is likely to occur.

  As shown in FIG. 9, in the shoulder portion of the heavy duty radial tire, the portion where the load concentrates in the tread lateral region shown by hatching is gradually increased in the width and depth directions due to uneven wear, so that the tire rubber is It is scraped off (wear generated on the shoulder is referred to as SEW).

As a means for preventing this SEW, conventionally, as shown in FIG. 10, for example, a defense groove DG (Defense Groove) in which a circumferential narrow groove is provided in the tread side region along the tire circumference is provided. Is known to be effective.
In order to suppress SEW by this circumferential narrow groove, it is necessary to arrange the circumferential narrow groove as close as possible to the tread end position. However, in this arrangement, a rubber crack, so-called tear, is formed at the bottom of the circumferential bottom groove. It tends to occur. In order to suppress this, conventionally, the position of the circumferential narrow groove, its depth, the positional relationship and distance between the outer inclined belt layer of the reinforcing belt layer and the circumferential narrow groove, etc. are specifically defined ( In addition to being complicated, it is still difficult to completely prevent tears.

In addition, as shown in FIG. 11, a side groove (Side Groove) with a continuous open hole is provided along the outer shoulder portion of the tire to reduce the bending rigidity around the tread shoulder portion. It is also known that the SEW resistance of the shoulder portion is effectively improved by simultaneously suppressing the edge drop that becomes the core of uneven wear by suppressing the contact pressure that is extremely increased at the end of the tread (Patent Literature). 2).
In this case, however, it is difficult to completely prevent cracks from occurring at the bottom of the groove.
Japanese Patent Laid-Open No. 11-78422 Japanese Patent Laid-Open No. 5-139119

  Accordingly, an object of the present invention is to provide a heavy duty radial tire that prevents the occurrence of SEW by the shape of the shoulder portion of the pneumatic heavy duty radial tire without using a groove such as a conventional defense groove DG or side groove SG. There is.

The invention of claim 1 has a tire circumferential main groove in the tire tread portion, and the ratio (D / W) of the depth (D) of the main groove to the tire section width (W) is 0.035 <D / In the heavy-duty radial tire in which W <0.06, the amount of collapse of the buttress portion when the heavy-duty radial tire is loaded is equal to or greater than a predetermined value necessary to suppress SEW.
According to a second aspect of the present invention, in the heavy duty radial tire according to the first aspect, the amount of collapse of the buttress portion when the heavy load radial tire is loaded is 5 mm or more.
The invention of claim 3 has a tire circumferential main groove in the tire tread portion, and the ratio (D / W) of the depth (D) of the main groove to the tire section width (W) is 0.035 <D / In the heavy-duty radial tire with W <0.06, the crown side angle (θ ₂ ) is 110 ° ≦ θ ₂ ≦ 130 °, and the ratio between the intersection perpendicular angle and the intersection angle (θ ₁ / θ ₀ ) Has a shoulder portion shape satisfying θ ₁ / θ ₀ <0.4.
According to a fourth aspect of the present invention, in the heavy duty radial tire according to the third aspect, the ratio (θ ₁ / θ ₀ ) between the intersection perpendicular angle and the intersection angle is 0.35 <θ ₁ / θ ₀ <0. 4 is a feature.

According to the present invention, the tire tread portion has the tire circumferential main groove, and the ratio (D / W) of the depth (D) of the main groove to the tire section width (W) is 0.035 <D / W. In a heavy-duty radial tire of <0.06, the collapse of the shoulder portion of the load radial tire can be reduced more than a predetermined value, and the collapse of the shoulder portion can be alleviated, and SEW can be suppressed or completely prevented. it can.
Further, by setting the ratio (θ ₁ / θ ₀ ) between the intersection perpendicular angle and the intersection angle in the range of 0.35 <θ ₁ / θ ₀ <0.4, not only the SEW is suppressed, but also the braking performance and the driving performance. And cornering performance can be maintained.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a representative half-section in the width direction of a heavy load radial tire according to the present invention. In the figure, 1 is a heavy load radial tire, 2 is a bead core, 3 is a carcass, 4 is a reinforcing belt, 5 And 6 is a circumferential main groove of depth (D), 7 is a tread portion, 8 is a section width (W) (here, the maximum width of the maximum position of the ply width, that is, ETRTO (The European Tire and Rim Technical Organization) 10 is the center point (A) of the tire tread, 11 is the intersection (C) of the side surface and the section width (W), 12 is the tangent of the tire tread center (A), This is the point (B) that intersects by extending the line that touches the left end of the tire hump from the intersection (C). When the circumferential main groove is installed on the equator, the center connecting the groove ends with a straight line is defined as the center point (A).

The angle between the line AB between the center point (A) and the intersection (B) and the line BC between the intersection (C) and the intersection (B) is defined as θ ₀ (here, defined as “intersection angle”), section Obtained by drawing a perpendicular from the intersection (B) to the circumference of the circumference of the radius OC drawn with the point O intersecting the width (W) line and the perpendicular of the center point (A) as the center point The angle formed by the line and the line BC is defined as θ ₁ (here, defined as “intersection perpendicular angle”).

FIG. 2 is a diagram illustrating the crown side angle. In the figure, 13 is a crown surface, 14 is a side surface, and when the shoulder portion has a round shape as shown in FIGS. 1 and 2, the angle obtained by the intersection of the extension line of the crown region and the extension line of the side region ( Here, defined as “crown side angle” is θ ₂ .

  By the way, if it is a heavy duty radial tire having a shape in which the ratio (D / W) of the main groove depth (D) to the section width (W) satisfies the relationship of 0.035 <D / W <0.06, the shoulder It has been found by the inventors' research and research that the occurrence of SEW can be prevented by increasing the collapse of the buttress portion.

As a condition for increasing the collapse of the buttress portion of the shoulder portion, the ratio (θ ₁ / θ ₀ ) between the intersection perpendicular angle θ ₁ and the point angle θ ₀ is in the range of 0.35 <θ ₁ / θ ₀ <0.4. In particular, it was also found that if the shoulder side shape is such that the crown side angle θ ₂ is in the range of 110 ° ≦ θ ₂ ≦ 130 °, the buttress portion can be greatly collapsed.

FIG. 3 (1) to FIG. 3 (3) are diagrams for explaining the SEW progress of the heavy duty radial tire.
SEW is known to be self-excited wear caused by scratches due to tire diameter differences, but as shown in FIG. 3 (1), an initial nucleus of uneven wear is formed in the shoulder portion. As shown in FIG. 3 (2), in the next stage, the initial nucleus shifts to SEW, and further, SEW expands as shown in FIG. 3 (3).

  FIG. 4 is a diagram schematically showing the mechanism of SEW initial nucleation. The initial nuclear mechanism of SEW was found to be explained below by the inventors' research and research.

  The initial nucleus is generated when the tire hump portion under load is crushed and moves in the width direction, for example, by forced wear with a feeling that the corner of the eraser is scraped. That is, since the movement of the tire hump portion is generated by the collapse of the tire rubber, the generation of the initial nucleus can be suppressed by suppressing the collapse of the tire rubber. Further, the conventional side groove is also a means for suppressing the collapse of the tire rubber, which is consistent with this finding.

  FIG. 5 is a diagram schematically showing a mechanism for suppressing the initial nucleation of SEW. In order to suppress the collapse of the tire rubber without using the side groove means, as shown in FIG. 5, it is possible to offset the collapse force of the tire rubber by applying a pushing force from the tire side. It was found that the movement in the width direction can be suppressed.

  FIG. 6 is a diagram illustrating the content (mechanism of initial nucleus generation) described in the schematic diagram of FIG. 4 in more detail. In the figure, “A” indicates the magnitude of the buttress part collapse, “A” indicates the magnitude of the pushing force (wiping), “U” indicates the magnitude of the pressure, and “D” indicates the magnitude of the crushing (crushing). .

  In the state shown in FIG. 6, since the pressure (c) of the hump rectangle is large, the ground pressure increases, the crushing (d) increases, and the frictional energy in the width direction increases. However, since the collapse of the buttress part (a) is small, the pushing force (b) is small, and therefore the size of the crushing (d) cannot be reduced and SEW cannot be suppressed, and an initial SEW nucleus is generated. To do.

  FIG. 7 is a diagram for explaining the details (mechanism for suppressing initial nucleation) described in the schematic diagram of FIG. 5 in more detail. The symbols in the figure are the same as the symbols in FIG.

  In the state shown in FIG. 7, since the pressure (c) of the hump rectangle is small, the ground pressure is also small, the crushing (d) is small, and the frictional energy in the width direction is also small. And since the fall (a) of a buttress part is large, pushing force (a) is large, Therefore, the collapse (d) of a shoulder part is eased. SEW can be suppressed because the shape of the shoulder portion of the tire increases the collapse of the buttress portion.

  Based on the knowledge of the inventor described above, the pushing force is a force caused by the side collapse, so the ratio (D / W) of the main groove depth (D) to the section width (W) is 0.035 to 0.06. In the case of radial tires for heavy loads that fall within the numerical range, it is possible to prevent the occurrence of SEW, for example, if the shoulder part has a large buttressed part and the amount of movement is, for example, 5 mm or more. It became clear from the result of the experiment.

  It was also found that the occurrence of SEW can be prevented by using the shoulder shape defined by the ratio of the crown side angle and the intersection perpendicular angle to the intersection angle in order to increase the collapse of the buttress portion of the shoulder portion.

Specifically, the ratio (θ ₁ / θ ₀ ) to the intersection perpendicular angle θ ₁ and / or the point angle θ ₀ is 0.35θ ₁ / θ ₀ <0.4, and the crown side angle (θ ₂ ) Is 110 ° ≦ θ ₂ ≦ 130 °, the SEW can be prevented from occurring.

That is, in the heavy duty radial tire in which the ratio of the main groove depth (D) to the section width (W) (<D / W) is in the range of 0.035 <D / W <0.06, the shoulder portion shape is by the shape collapse of the buttress portion is larger at the time of loading, it can prevent the occurrence of SEW, and a shoulder portion shaped to increase the tilting of the buttress portion, and the intersection perpendicular angle θ1 and the point angle theta ₀ It is that it is the said shoulder part shape prescribed | regulated by ratio ((theta) ₁ / (theta) ₀ ) and said crown side angle ((theta) ₂ ).

  Next, the meaning of the above numerical limitation in the present invention will be described. The ratio of the main groove depth (D) to the section width (W) (<D / W) is limited to 0.035 <D / W <0.06, especially for heavy-duty radial tires with deep grooves It means that. Usually, the section width is about 300 mm, and the depth of the groove is about 13 mm (D / W is 0.053) to 15 mm (D / W is 0.050). Therefore, when the section width is 300 mm, heavy duty radial tires having a groove depth of 18 mm (D / W is 0.060) or more are excluded.

The ratio (θ ₁ / θ ₀ ) between the intersection perpendicular angle θ ₁ and the intersection angle θ ₀ is limited to the range of 0.35 <θ ₁ / θ ₀ <0.4 when 0.35 or less. SEW occurs because the tread width becomes too narrow and the braking performance, driving performance and cornering performance deteriorate, and the wear resistance is adversely affected. It is to do. Therefore, as a condition for preventing the occurrence of SEW, the ratio (θ ₁ / θ ₀ ) between the intersection perpendicular angle θ ₁ and the intersection angle θ ₀ is 0.35 <θ ₁ / θ ₀ <0.4. It is necessary to be.

In addition, the crown side angle (θ ₂ ) is limited to 110 ° ≦ θ ₂ ≦ 130 °. When the angle is 110 ° or less, side tilting is small and SEW occurs, and when it exceeds 130 °, the tread width is narrow. This is because the same problem as described above occurs.

  In order to confirm the effect of the heavy-duty radial tire according to the present invention, tests were performed using Examples 1 and 2 of the present invention and conventional heavy-duty radial tires that do not have the defending groove DG or the side groove SG.

The tire dimensions are all 315 / 80R225, and the angles are the dimensions measured at the ETRTO normal internal pressure and the rim width. Table 1 shows the actual measured dimensions.
Since the ratio of the intersection perpendicular angle θ ₁ and the crown side angle θ _{0 in} Examples 1 and 2 is 0.39 and 0.36, it is in the range of 0.35 to 0.4, and 0 in the comparative example. .418, out of range. The crown side angle θ ₂ of Examples 1 and ₂ is in the range of 110 ° to 130 °, and is 105 ° in the comparative example, so it is out of the range. Further, the ratio (D / W) between the main groove depth (D) and the section width (W) in Examples 1 and 2 is 0.0442 and 0.0438, and in the comparative example is 0.0457. , Both are in the range of numerical values of 0.035 to 0.06.

  Next, Table 2 shows the test results of the uneven wear performance of the shoulder-shaped heavy duty radial tire. As shown in FIG. 9, the values of a, b, and Vol in Table 2 were calculated by calculating width a, depth b, width a × depth b = Vol on the tire surface as SEW evaluation. In addition, the ETRTO normal internal pressure, the rim width, and the normal load (single wheel) were run on a drum for 100,000 km, and the occurrence of SEW was compared. When the width a and the depth b of Example 2 are 0, it means that SEW is not generated, and means that the most excellent effect is achieved. Vol means an index with the comparative example as 100.

  V in Table 2 indicates ETRTO normal internal pressure, rim width, and amount of movement of point Z at normal load (V: line drawn parallel to the tread at 30 mm perpendicular to the tread as shown in FIG. 8 and tire buttress The amount of movement of the position of the intersection with the part, defined here as the amount of collapse of the buttress part), is a result of measurement with a three-dimensional shape assumption device.

  As is apparent from the test results of uneven wear performance in Table 2, from the results of Example 1, excellent prevention against SEW is achieved if the buttress part's collapse amount (moving amount) defined above is 5 mm or more. It turns out that there is an effect.

  That is, the amount of collapse of the buttress portion is 0 mm in the conventional example, 5.3 mm in the first example, and 10.2 mm in the second example, and the SEW in each case is 100 when the conventional example is set to Vol (index). In Example 1, it is 13, and in Example 2, it is 0 (no occurrence). From this result, it was found that SEW was significantly reduced when the amount of collapse was 5 mm or more, and SEW could be completely prevented when the amount was 10 mm or more.

It is the figure which showed the body surface width direction judgment surface of the radial tire for heavy loads according to this invention. It is a figure explaining crown side angle (theta) ₂ . It is a figure explaining the development form of SEW of the radial tire for heavy loads. It is the figure typically shown in order to demonstrate the mechanism of the initial nucleus generation of SEW. It is the figure which showed typically the mechanism which suppresses the initial nucleus generation of SEW. It is the figure which demonstrated the content demonstrated by the schematic diagram of FIG. 4 in detail. It is the figure which demonstrated the content demonstrated with the schematic diagram of FIG. 5 in detail. It is a figure for demonstrating the fall of a buttress part. It is a figure which shows the shoulder edge wear (Shoulder Edge Wear) of the shoulder part of a tire. It is a figure which shows the defense groove | channel (Defense Groove) which consists of the conventional circumferential narrow groove. It is a figure which shows the side groove | channel (Side Groove) which consists of the drill opened toward the side of the conventional tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Heavy load radial tire, 2 ... Bead core, 3 ... Carcass, 4 ... Reinforcement belt, 5, 6 ... Circumferential main groove, 7 ... Tread part, 8 ... Section width, 9 ... Depth of circumferential main groove, 13 ... Crown surface, 14 ... Side surface

Claims (4)

The tire tread portion has a tire circumferential main groove, and the ratio (D / W) of the depth (D) of the main groove to the tire section width (W) is 0.035 <D / W <0.06. In heavy duty radial tires,
A heavy-duty radial tire, wherein the amount of collapse of the buttress portion when the heavy-duty radial tire is loaded is equal to or greater than a predetermined value required to suppress SEW. In the heavy duty radial tire according to claim 1,
A heavy-duty radial tire, wherein the buttress portion collapses at a load of 5 mm or more when the heavy-duty radial tire is loaded. The tire tread portion has a tire circumferential main groove, and the ratio (D / W) of the depth (D) of the main groove to the tire section width (W) is 0.035 <D / W <0.06. In heavy duty radial tires,
A shoulder where the crown side angle (θ ₂ ) is 110 ° ≦ θ ₂ ≦ 130 °, and the ratio of the perpendicular angle to the intersection angle (θ ₁ / θ ₀ ) is θ ₁ / θ ₀ <0.4. Heavy duty radial tire characterized by having a part shape. In the heavy duty radial tire according to claim 3,
A heavy duty radial tire characterized in that a ratio (θ ₁ / θ ₀ ) between the intersection perpendicular angle and the intersection angle is 0.35 <θ ₁ / θ ₀ <0.4.

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