JP3808778B2 - Heavy duty tire - Google Patents

Description

【００３７】
【発明の効果】
叙上の如く本発明は、角度α、βを規制し接地面形状を特定しているため、肩落ち摩耗、軌道摩耗、センター摩耗等を抑制でき、摩耗の均一化を高レベルで達成しうる。
【図面の簡単な説明】
【図１】本発明の一実施例のタイヤの断面図である。
【図２】そのトレッド部を拡大してを示す断面図である。
【図３】トレッド厚さの分布の一例を示す線図である。
【図４】接地面形状を示す線図である。
【図５】その輪郭線を拡大して示す線図である。
【図６】従来タイヤにおける接地面形状を示す線図である。
【符号の説明】
２ トレッド部
３ サイドウォール部
４ ビード部
５ ビードコア
６ カーカス
７ ベルト層
１０ 接地面形状
Ｆ 接地面形状の輪郭線
Ｇ 縦主溝
Ｇｓ ショルダー溝
Ｎ 溝中心線[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heavy duty tire that suppresses shoulder drop wear at a tread contact end and track wear along a shoulder groove by specifying the shape of the contact surface, thereby achieving uniform wear.
[0002]
[Background Art and Problems to be Solved by the Invention]
For example, in a heavy load evening ear, the tread surface is generally formed by a convex arcuate curve using a single arc or a plurality of arcs. Accordingly, the ground contact surface shape a is also formed in a convex arc shape in which the circumferential contact length b gradually decreases from the tire equator side toward the tread contact end side, as schematically shown in FIG.
[0003]
However, in such a tire, since the contact length b2 on the tread contact end side is significantly reduced with respect to the contact length b1 on the tire equator side, the tread surface on the tread contact end side slips from the road surface. It is likely to cause uneven wear such as so-called shoulder wear.
[0004]
Therefore, the tread curvature radius is increased and the contact length b2 is brought close to the contact length b1 to suppress slipping on the tread contact end side. However, in such a technique, the tread center portion yc on the inner side of the shoulder groove f arranged on the outermost side in the tire axial direction causes so-called center wear that wears compared to the outer tread shoulder portion ys, or A sufficiently satisfactory result has not been obtained with respect to uniform wear, such as so-called orbital wear in which one / other side edge of the shoulder groove f is worn.
[0005]
Accordingly, the inventor of the present invention has a straight tire axial direction line passing through the equator point p1 on the tire equator and the groove side edge point p2 on the tire equator side of the shoulder groove f in the contour line of the ground contact surface shape a. The research was conducted by paying attention to the angle α and the angle β between the groove side edge point p3 on the tread end side of the shoulder groove f and the straight tire axial direction line passing through the ground end point p4 on the tread ground contact end. As a result, it has been found that by controlling the angles α and β within a predetermined range, it is possible to suppress shoulder drop wear, track wear, center wear, and the like, and to achieve uniform wear.
[0006]
In other words, the present invention is based on the fact that the ground surface shape is specified by regulating the angles α and β, and it is possible to suppress shoulder drop wear, track wear, center wear, and the like, and a heavy load that can achieve uniform wear at a high level. The purpose is to provide heavy duty tires.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application includes a carcass extending from a tread portion having two or more longitudinal main grooves extending continuously in a circumferential direction to a bead core of a bead portion through a sidewall portion, A heavy-duty tire comprising a belt layer disposed inside the tread and outside the carcass,
The shoulder groove disposed on the outermost side in the tire axial direction of the longitudinal main groove passes through a region where the groove center line is separated from the tire equator C by a distance 0.4 to 0.7 times the tread ground half width. With
In the contour of the contact surface shape when a normal load is applied to a tire in a normal internal pressure state in which a normal rim is assembled and filled with a normal internal pressure,
An angle α between a tire axial direction line of a straight line J1 passing through the equator point Pa on the tire equator and the groove side edge point Pb on the tire equator side of the shoulder groove is greater than 0 ° and not more than 12 °, and the shoulder groove The angle β between the groove side edge point Pc on the tread ground contact end side and the tire axial direction line of the straight line J2 passing through the ground contact end point Pd on the tread ground contact end is set to be −3 ° or more and the angle α or less,
The ratio La / Ld between the circumferential ground contact length La at the equator point Pa and the circumferential ground contact length Ld at the ground contact point Pd in the ground contact surface shape is greater than 1.0 and not greater than 1.20. It is characterized by being.
[0008]
In the invention of claim 2, the belt layer includes a first belt ply on the carcass side and a second belt ply on the outside thereof.
When the tread thickness between the contour line of the tread surface and the second belt ply is T, in the region separated from the tire equator C by a distance of 0.60 to 0.7 times the tread ground half width, The tread thickness T has a minimum tread thickness position where the minimum value Tmin is reached, and the tread thickness T increases from the minimum tread thickness position to the position of the outer end of the second belt ply. It is said.
[0009]
In the invention of claim 3, the belt cord of the belt layer and the carcass cord of the carcass are metal cords.
[0010]
In the present specification, the “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, if it is JATMA, the rim width is larger than the standard rim. A size with a narrow rim means “a rim with a rim width that is one rank narrower than a standard rim”, and a size without a rim with a narrower rim width than a standard rim means a “standard rim”.
-For TRA, the size with a rim with a rim width narrower than “Design Rim” is set to “a rim with a rim width one rank lower than“ Design Rim ””, and a rim with a rim width narrower than “Design Rim”. If there is no size, it means “Design Rim”. ・ If it is ETRTO, a rim with a narrower rim width than “Measuring Rim” means a rim with a rim width one rank lower than “Measuring Rim”. , “Measuring Rim” means a size where a rim having a rim width smaller than that of “Measuring Rim” is not set.
[0011]
The “regular internal pressure” is the air pressure specified by the tire for each tire. The maximum air pressure in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, If it is ETRTO, it is “INFLATION PRESSURE”, but if the tire is for a passenger car, it is 180 kPa. The “regular load” is the load specified by the standard for each tire. The maximum load capacity shown in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is the maximum load capacity for JATMA and TRA for TRA. If it is ETRTO, it is "LOAD CAPACITY".
[0012]
Further, in the present specification, the “grounding end” means the outer end in the tire axial direction of the tread grounding surface that is grounded when a normal load is applied to a tire in a normal internal pressure state that is assembled to the normal rim and filled with a normal internal pressure. The distance between the outer end (grounding end) and the tire equator is called a tread grounding half width.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view when the heavy-duty tire of the present invention is for trucks and buses, and FIG. 2 is an enlarged cross-sectional view of the tread portion.
[0014]
In FIG. 1, a heavy load tire 1 includes a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and a belt disposed inside the tread portion 2 and outside the carcass 6. With layer 7.
[0015]
The carcass 6 includes at least one carcass cord in which carcass cords are arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction, in this example, one carcass ply 6A, and a metal cord such as steel is used as the carcass cord. Is done.
[0016]
The carcass ply 6A has folded portions 6b on both sides of the ply main body portion 6a straddling the bead cores 5 and 5 and folded around the bead core 5 from the inside to the outside. A bead apex rubber 8 extending radially outward from the bead core 5 is disposed between the ply main body portion 6a and the folded portion 6b, and is reinforced from the bead portion 4 to the sidewall portion 3.
[0017]
The belt layer 7 is formed of three or more belt plies using metal cords as belt cords. In this example, the steel cord is arranged at an angle of, for example, 60 ± 15 ° with respect to the tire circumferential direction, and is arranged at the innermost radial direction, for example, 10A with respect to the tire circumferential direction. The case of the four-sheet structure of the second to fourth belt plies 7B, 7C, 7D arranged at a small angle of ˜35 ° is illustrated.
[0018]
In this belt layer 7, the ply width in the tire axial direction of the first belt ply 7A is smaller than the ply width of the second belt ply 7B and is substantially the same as the ply width of the third belt ply 7C. By making the ply width WB of the second belt ply 7B, which is the maximum width, 0.80 to 0.95 times the tread grounding width WT, the entire width of the tread portion 2 is reinforced with a tagging effect. And the tread rigidity is increased. The narrowest fourth belt ply 7D functions as a breaker that protects the first to third belt plies 7A to 7D and the carcass 6 from external damage.
[0019]
Next, in the tire 1, a tread pattern having two or more vertical main grooves G extending continuously in the circumferential direction is provided in the tread portion 2. The vertical main groove G is a groove body having a groove width of 3 mm or more, has a linear shape or a zigzag shape, and extends in the circumferential direction.
[0020]
In this example, the case where the vertical main groove G is composed of four vertical main grooves Gi on both sides of the tire equator C and an outer vertical main groove Go on the outer side is illustrated. The outer vertical main groove Go constitutes the outermost shoulder groove Gs in the tire axial direction.
[0021]
The shoulder groove Gs passes through a region where the groove center line N is separated from the tire equator C by a distance 0.4 to 0.7 times the tread ground half width WT / 2. That is, the distance Kn from the tire equator C of the groove center line N is in the range of 0.4 to 0.7 times the tread ground half width WT / 2, whereby the tread portion 2 is located inside the shoulder groove G. Are divided into a tread center portion Yc and an outer tread shoulder portion Ys. When the shoulder groove Gs is a zigzag groove, the center of the zigzag amplitude is defined as a groove center line N.
[0022]
In the present embodiment, in order to achieve uniform wear in the tire 1 as described above, the tire 1 is assembled to a normal rim and connected to the tire in a normal internal pressure state in which the normal internal pressure is filled and a normal load is applied. The ground shape 10 is specified as follows.
[0023]
Specifically, as shown in FIGS.
(1) In the contour line F of the ground contact surface shape 10,
The angle α between the tire equator C on the tire equator C and the tire axial direction line of the straight line J1 passing through the shoulder groove Ps on the tire equator C side of the shoulder groove Gs is greater than 0 ° and not more than 12 °. ,
The angle β between the groove side edge point Pc on the tread ground contact end E side of the shoulder groove Gs and the tire axial direction line of the straight line J2 passing through the ground contact end point Pd on the tread ground contact E is −3 ° or more and Angle α or less,
(2) In the ground contact surface shape 10: The ratio La / Ld between the circumferential ground contact length La at the equator point Pa and the circumferential ground contact length Ld at the ground contact end point Pd is greater than 1.0. 1.20 or less,
Is regulated.
[0024]
Here, the angles α and β are new parameters devised by the present inventor, and it is important for the improvement of uneven wear resistance (uniform wear) to make the angles α and β appropriate. It turned out to be.
[0025]
That is, if the angle α exceeds 12 °, the contact pressure of the tread shoulder portion Ys decreases, and the load load on the tread center portion Yc increases excessively. Therefore, the tread center portion Yc compared to the tread shoulder portion Ys. The center wear progresses, for example, the wear at the time becomes faster, and the uniformity of wear is impaired. Conversely, when the angle α is 0 ° or less, the contact pressure of the tread shoulder portion Ys increases as compared to the tread center portion Yc. As a result, the heat generation of the tread shoulder portion Ys increases, and the temperature rise causes the belt end. It tends to impair durability, such as inducing peeling damage.
[0026]
On the other hand, by restricting the angle β to the range of −3 ° or more and the angle α or less, it is possible to reduce slipping at the tread ground contact E and suppress shoulder wear. When the angle β exceeds the angle α, the contact length Ld at the contact end point Pd becomes too small with respect to the contact lengths Lb and Lc at the groove side edge points Pb and Pc of the shoulder groove Gs. It tends to occur. On the other hand, when the angle β is smaller than −3 °, the contact pressure is lowered at the groove side edge point Pc, and the wear at the groove side edge point Pc is accelerated. The ground pressure of the entire portion Ys becomes extremely small, and center wear occurs.
[0027]
In the present specification, the angles α and β define the direction in which the straight lines J1 and J2 are inclined toward the ground contact length center 10C toward the outer side in the tire axial direction as positive (+).
[0028]
It is also important to limit the ratio La / Ld to a range greater than 1.0 and less than or equal to 1.20 due to shoulder fall wear, and if the ratio La / Ld exceeds 1.20, the ground contact endpoint Since the contact length Ld at Pd is excessively shorter than the contact length La at the equator point Pa, slippage at the tread contact end E is likely to occur regardless of the size of the angle β.
[0029]
From the viewpoint of track wear, the contact length L of the contact surface shape 10 gradually decreases toward the outer side in the tire axial direction, that is, the tangent line at each position of the contour line F is inclined in the positive (+) direction. It is also preferable.
[0030]
Next, in order to obtain such a ground contact surface shape 10, in this example, as shown in FIG. 2, the tread surface contour line S (hereinafter referred to as the tread contour line S) and the second tread surface in the normal internal pressure state. When the thickness of the tread between the belt ply 7B is T, as shown in FIG. 3, the tread is located in a region separated from the tire equator C by a distance of 0.60 to 0.7 times the tread grounding half width WT / 2. The minimum tread thickness position Q where the thickness T is the minimum value Tmin is provided, that is, the distance Kq from the tire equator C at the minimum tread thickness position Q is 0.60 to 0.7 times the tread ground half width WT / 2. At the same time, the tread thickness T is increased from the minimum tread thickness position Q toward the outer side in the tire axial direction to the position of the outer end of the second belt ply 7B.
[0031]
Similarly, the tread thickness T increases from the minimum tread thickness position Q toward the tire equator C toward the inside in the tire axial direction. In this example, the tread thickness Tc at the tire equator C is larger than the thickness Tb at the outer end of the second belt ply 7B, but Tc ≦ Tb can also be set. .
[0032]
In order to obtain such a distribution of the tread thickness T, in this example, the second belt ply 7B is formed by a single arc having a center on the tire equator C as shown in FIG. The tread contour S in the tread center portion Yc is formed by a convex arc-shaped contour S1 using a single arc or a plurality of arcs, and the tread contour S in the tread shoulder Ys is substantially linear. It is formed by the contour line S2.
[0033]
As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.
[0034]
【Example】
A heavy-duty tire having a tire size of 275 / 80R 22.5 having the structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and the wear performance of each sample tire was tested to eliminate shoulder wear, track wear, and uniform wear. The results are shown in Table 1.
[0035]
(1) Wear performance;
A sample tire was mounted on the front wheel of a truck (2-2D type) with a rim (7.50 × 22.5) and internal pressure (875 kPa), and it traveled a distance of 60,000 km. The appearance of wear at the tread contact edge (shoulder fall wear) and the occurrence of wear at the side edge of the shoulder groove (track wear) were visually confirmed.
Further, the wear amounts Zi and Zo at the position of the inner vertical main groove and the position of the outer vertical main groove (shoulder groove) were measured, and the difference Zi-Zo was confirmed. If the difference Zi-Zo is large, center wear has occurred, and conversely, if the difference is small (close to 0), it indicates a uniform wear form and good uneven wear resistance.
[0036]
[Table 1]

[0037]
【The invention's effect】
As described above, the present invention regulates the angles α and β and specifies the contact surface shape, so that it is possible to suppress shoulder drop wear, track wear, center wear, etc., and to achieve uniform wear at a high level. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a tire according to an embodiment of the present invention.
FIG. 2 is an enlarged sectional view showing the tread portion.
FIG. 3 is a diagram showing an example of a distribution of tread thickness.
FIG. 4 is a diagram showing a ground plane shape.
FIG. 5 is an enlarged diagram showing the outline.
FIG. 6 is a diagram showing a contact surface shape in a conventional tire.
[Explanation of symbols]
2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 7 Belt layer 10 Ground surface shape F Ground surface shape contour G Vertical main groove Gs Shoulder groove N Groove center line

Claims (3)

A carcass extending from the tread portion having two or more longitudinal main grooves extending continuously in the circumferential direction to the bead core of the bead portion through the sidewall portion, and a belt layer disposed inside the tread portion and outside the carcass A heavy duty tire with
The shoulder groove disposed on the outermost side in the tire axial direction of the longitudinal main groove passes through a region where the groove center line is separated from the tire equator C by a distance 0.4 to 0.7 times the tread ground half width. With
In the contour of the contact surface shape when a normal load is applied to a tire in a normal internal pressure state in which a normal rim is assembled and filled with a normal internal pressure,
An angle α between a tire axial direction line of a straight line J1 passing through the equator point Pa on the tire equator and the groove side edge point Pb on the tire equator side of the shoulder groove is greater than 0 ° and not more than 12 °, and the shoulder groove The angle β between the groove side edge point Pc on the tread ground contact end side and the tire axial direction line of the straight line J2 passing through the ground contact end point Pd on the tread ground contact end is set to be −3 ° or more and the angle α or less,
The ratio La / Ld between the circumferential ground contact length La at the equator point Pa and the circumferential ground contact length Ld at the ground contact point Pd in the ground contact surface shape is greater than 1.0 and not greater than 1.20. A heavy-duty tire characterized by The belt layer includes a first belt ply on the carcass side and a second belt ply on the outside thereof,
When the tread thickness between the contour line of the tread surface and the second belt ply is T, in the region separated from the tire equator C by a distance of 0.60 to 0.7 times the tread ground half width, The tread thickness T has a minimum tread thickness position where the minimum value Tmin is reached, and the tread thickness T increases from the minimum tread thickness position to the position of the outer end of the second belt ply. The heavy duty tire according to claim 1 . The heavy duty tire according to claim 1 or 2, wherein the belt cord of the belt layer and the carcass cord of the carcass are metal cords.

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