JP3798697B2 - Heavy duty tire - Google Patents

Description

【００３４】
【発明の効果】
叙上の如く本発明は、正規内圧状態のタイヤに正規荷重を負荷した時の正規接地状態における接地荷重の分布を特定しているため、ゴムゲージ厚さの過度の上昇を招くことなく肩落ち摩耗を含む偏摩耗を抑制でき、摩耗の均一化を図りうる。
【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】表１のタイヤにおける、各半分領域に負荷される接地荷重の総和の分布を示す線図である。
【図４】従来タイヤにおけるトレッド輪郭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
７Ａ 第１のベルトプライ
７Ｂ 第２のベルトプライ
Ｃ タイヤ赤道
Ｅ 接地端
Ｇ１ 内の縦主溝
Ｇ２ 外の縦主溝
Ｒ１ 内のリブ状陸部
Ｒ２ 中のリブ状陸部
Ｒ３ 外のリブ状陸部
Ｒ１ａ 半分領域
Ｒ２ｃ、Ｒ３ｃ タイヤ赤道側半分領域
Ｒ２ｅ、Ｒ３ｅ 接地端側半分領域[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heavy duty tire that suppresses uneven wear and makes wear uniform by specifying the distribution of contact load.
[0002]
[Background Art and Problems to be Solved by the Invention]
For example, in a heavy load evening ear, the tread outline a is generally formed in a single arc shape in the vulcanization mold as schematically shown in FIG.
[0003]
However, in a normal internal pressure state in which such a tire is assembled with a normal rim and filled with a normal internal pressure, in a region Y separated from the tire equator by a distance 0.5 to 0.7 times the tread ground half width, The tread surface tends to bulge outward in the radial direction. For this reason, the circumferential length difference between the bulging portion b and the tread ground contact end e becomes large, and the tread surface on the tread ground contact end side slips with the road surface, so that uneven wear such as so-called shoulder drop wear is likely to occur. Become.
[0004]
Therefore, in order to suppress this shoulder wear, for example, as disclosed in Japanese Patent Application Laid-Open No. 7-164823, etc., in the tread contour shape, the tread grounding end side portion (so-called tread shoulder portion) is replaced with the tire equator side portion (so-called tread center). It has been proposed to form a flat arc having a larger radius of curvature than the part) and to increase the contact length in the contact surface shape of the tread shoulder part.
[0005]
However, such a technique involves an increase in the thickness of the rubber gauge at the tread shoulder portion. Therefore, an excessive increase in the radius of curvature is disadvantageous in terms of durability, such as causing belt end peeling due to a temperature increase due to heat storage. From this point of view, there is a limit to the increase in the radius of curvature, and therefore, it has not been possible to sufficiently exhibit the effect of suppressing shoulder wear and the like.
[0006]
Therefore, the present inventor studied by paying attention to the relationship between the contact load and the uneven wear. As a result, there is a strong correlation between contact load and wear energy, and by specifying the load distribution of this contact load, uneven wear including shoulder drop wear can be suppressed without causing excessive increase in rubber gauge thickness. It was found that it was possible to achieve uniformization.
[0007]
That is, the present invention is based on identifying the distribution of contact load in a normal contact state when a normal load is applied to a tire in a normal internal pressure state that is assembled with a normal rim and filled with a normal internal pressure. An object of the present invention is to provide a heavy-duty tire that can suppress uneven wear including shoulder drop wear without causing excessive rise and can achieve uniform wear.
[0008]
[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 the tread portion through the sidewall portion to the bead core of the bead portion, and a belt layer disposed inside the tread portion and outside the carcass. A heavy duty tire with
The belt layer includes a first belt ply on the carcass side and a second belt ply on the outside thereof,
When the thickness of the tread between the contour line of the tread surface and the second belt ply is T, in a region Y separated from the tire equator C by a distance of 0.5 to 0.7 times the tread ground half width, The tread thickness T has a minimum tread thickness position Qt at which the tread thickness T is a minimum value T min, and
The minimum value T min is 0.89 to 0.97 times the tread thickness Tc at the position of the tire equator C, and the tread thickness Tb at the outer end position of the second belt ply is the tread thickness. 0.95 to 1.10 times the thickness Tc, and the tread portion is provided with an inner longitudinal main groove extending on both sides of the tire equator and an outer longitudinal main groove extending in the circumferential direction on the outer side thereof. The tread surface is divided into an inner rib-like land on the tire equator, an outer rib-like land on the ground contact end side, and an inner rib-like land between them,
In a normal ground contact state when a normal load is applied to a tire in a normal internal pressure state that is assembled with a normal rim and filled with a normal internal pressure,
A sum P1a of the ground load applied to the half region obtained by dividing the rib-like land portion of the inner portion by the tire equator, and a sum P2c of the ground load applied to the tire equator-side half region of the inner rib-like land portion. The ratio P2c / P1a is in the range of 0.9 to 1.05,
The ratio P2e / P2c between the total sum P2c of the ground loads and the total sum P2e of the ground loads loaded on the ground end side half area in the rib-shaped land portion in the range of 0.75 to 1.0,
The ratio P3c / P2e between the total P2e of the ground load and the total P3c of the ground load loaded on the tire equator half region in the outer rib-shaped land portion is in the range of 0.9 to 1.2.
The ratio P3e / P3c of the total sum P3c of the ground loads and the total sum P3e of the ground loads loaded on the ground end side half region in the outer rib-shaped land portion is in a range of 0.8 to 1.1.
Moreover, the ratio P3e / P1a between the total sum P3e of the ground contact load and the sum P1a of the ground load is characterized in that in the range of 0.75 to 1.0.
[0009]
In the invention of claim 2, the tread thickness T increases from the tread thickness minimum position Qt to the tread thickness Tc toward the inner side in the tire axial direction, and from the tread thickness minimum position Qt, The tread thickness Tb increases outward in the tire axial direction .
[0010]
In the invention of claim 3, the belt cord of the belt layer and the carcass cord of the carcass are metal cords.
[0011]
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.
[0012]
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".
[0013]
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.
[0014]
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.
[0015]
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.
[0016]
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.
[0017]
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.
[0018]
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.
[0019]
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.
[0020]
Next, the tire 1 includes, in the tread portion 2, an inner vertical main groove G1 extending on both sides of the tire equator C, and an outer vertical main groove G2 extending in the circumferential direction on the outer side thereof. Thus, the tread surface is divided into an inner rib-like land portion R1 on the tire equator C, an outer rib-like land portion R3 on the ground contact end E side, and an inner rib-like land portion R2 therebetween. ing. The rib-like land portions R1 and R2 may be block rows or ribs.
[0021]
Each vertical main groove G1, G2 is a groove body having a groove width of 3 mm or more, and has a linear shape or a zigzag shape and extends in the circumferential direction. Of these, the outer longitudinal main groove G2 that is the outermost side in the tire axial direction, that is, the shoulder groove Gs, in this example, the groove center line N is 0.5 to 0 of the tread ground half width WT / 2 from the tire equator C. Through the region Y separated by a distance of 7 times, the tread portion 2 is divided into a tread center portion Jc inside the shoulder groove Gs and an outer tread shoulder portion Js. That is, the inner and inner rib-shaped land portions R1 and R2 are disposed in the tread center portion Jc, and the outer rib-shaped land portion R3 is disposed in the tread shoulder portion Js. 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 suppress uneven wear in the tire 1 and make the wear uniform, a normal load is applied to a tire in a normal internal pressure state in which the tire 1 is assembled on a normal rim and filled with a normal internal pressure. In the normal grounding state when loaded, the grounding load at that time is specified as follows.
[0023]
Specifically, as shown in FIG. 2, the inner rib-shaped land portion R1 is located on the outer half of the tire equator C, R1a and R1a, and the inner and outer rib-shaped land portions R2 and R3 are disposed on the tire equator side. When virtually divided into half regions R2c, R3c and grounded end side half regions R2e, R3e,
{Circle around (1)} The total contact load P1a applied to the half region R1a of the rib-like land portion R1 in the inner portion and the total contact load P2c applied to the tire equator-side half region R2c of the inner rib-like land portion R2 And the ratio P2c / P1a is set in the range of 0.9 to 1.05,
(2) A ratio P2e / P2c between the total P2c of the ground load and the total P2e of the ground load applied to the ground end side half region R2e in the rib-like land portion R2 is 0.75 to 1.0. To the range of
(3) A ratio P3c / P2e between the total ground load P2e and the total ground load P3c applied to the tire equator half region R3c in the outer rib-shaped land R3 is 0.9 to 1.2. To the range of
(4) A ratio P3e / P3c between the total sum P3c of the ground loads and the total sum P3e of the ground loads loaded on the ground end side half region R3e in the outer rib-shaped land R3 is 0.8 to 1.1. To the range of
(5) The ratio P3e / P1a between the total sum P1a of the ground loads and the total sum P3e of the ground loads is set in the range of 0.75 to 1.0.
[0024]
Note that the total sum P1a, P2c, P2e, P3c, and P3e of the ground load is measured by, for example, grounding the tire 1 with a normal load on the sheet-like body on which the sensor is placed, and measuring the load applied to each sensor. Thus, the total sum of the ground loads applied to the respective half regions R1a to R3e is calculated.
[0025]
Here, the present inventor has found that the grounding load has a strong correlation with the wear energy, and in particular, the sums P1a to P3e of the grounding loads applied to the respective half regions R1a to R3e are the above-mentioned (1) to (5). When the set range of ▼ is reached, it was found that uneven wear including shoulder drop wear can be suppressed and wear can be made uniform.
[0026]
In particular, in (1) to (3), when the ratios are outside the set range, the balance of wear energy in the half regions R1a to R3e is lost, and therefore, track wear and punching wear tend to occur. In addition, in (4), when the ratio P3e / P3c is out of the range of 0.8 to 1.1, shoulder drop wear tends to occur. In addition, in (5), by setting the ratio P3e / P1a in the range of 0.75 to 1.0, wear of the entire tread portion can be suppressed.
[0027]
Next, in order to obtain such a distribution of contact load, 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 are used. When the tread thickness between the belt ply 7B and the belt ply 7B is T, a tread thickness minimum position Qt at which the tread thickness T becomes the minimum value Tmin is provided in the region Y, and the minimum value Tmin is set as the tire equator. The tread thickness Tb at the position C is 0.89 to 0.97 times the tread thickness Tc and the outer belt end position of the second belt ply 7B is 0.95 to the tread thickness Tc. 1.10 times. At this time, the tread thickness T increases from the minimum tread thickness position Qt to the tread thickness Tc toward the inner side in the tire axial direction and to the tread thickness Tb toward the outer side in the tire axial direction. It is preferable to do so.
[0028]
By adopting such a distribution of the tread thickness T, it is possible to obtain the distribution of the contact load. This also means that the tread thickness Tb is 1.10 × Tc or less, and the increase in the rubber gauge thickness at the tread shoulder portion Js can be suppressed. It is also possible to do.
[0029]
In this example, in order to obtain the distribution of the tread thickness T, the second belt ply 7B is formed by a single arc having a center on the tire equator C, and the rib-like land portion in the inside is formed. The tread contour S in R1 and R2 is a convex arc-shaped contour S1 using a single arc or a plurality of arcs, and the tread contour S in the outer rib-shaped land R3 is substantially straight contour S2. Is formed by.
[0030]
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.
[0031]
【Example】
A tire for a heavy load having a tire size of 295 / 80R22.5 having the structure shown in FIG. 1 was made on the basis of the specifications shown in Table 1, and the wear performance of each sample tire was tested. The results are shown in Table 1. FIG. 3 is a diagram showing the distribution of the sum total of ground loads applied to each half region in the examples and comparative examples.
[0032]
(1) Wear performance;
A sample tire was mounted on the front wheel of a truck (2-2 D type) with a rim (22.5 × 9.00) and internal pressure (850 kPa), and traveled a distance of 100,000 km. The edge position j1 of the grounded end side of the rib-like land portion R1 in the tire inside;
The tire equator side edge position j2 of the inner rib-like land R2;
A grounding edge side edge position j3 of the rib-like land portion R2 in the middle,
-Tire equator side edge position j4 of the outer rib-shaped land R3,
-Grounding edge side edge position j5 of outer rib-shaped land R3 (corresponding to grounding edge E)
The amount of wear was measured and indicated as an index with Comparative Example 1 taken as 100. The smaller the value, the less wear.
[0033]
[Table 1]

[0034]
【The invention's effect】
As described above, the present invention specifies the distribution of the contact load in the normal contact state when a normal load is applied to the tire in the normal internal pressure state, so that the shoulder fall wear without causing an excessive increase in the rubber gauge thickness. It is possible to suppress uneven wear including, and to achieve uniform wear.
[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 the distribution of the sum total of ground loads applied to each half region in the tire of Table 1.
FIG. 4 is a diagram showing a tread contour 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 7A First belt ply 7B Second belt ply C Tire equator E Longitudinal main groove G2 in the ground contact end G1 In the longitudinal main groove R1 outside Rib-like land portion R3 in rib-like land portion R2 Outside rib-like land portion R1a Half region R2c, R3c Tire equator-side half region R2e, R3e Grounding end-side half region

Claims (3)

A heavy duty tire comprising a carcass extending from a tread portion through a sidewall portion to a bead core of the bead portion, and a belt layer disposed inside the tread portion and outside the carcass,
The belt layer includes a first belt ply on the carcass side and a second belt ply on the outside thereof,
When the thickness of the tread between the contour line of the tread surface and the second belt ply is T, in a region Y separated from the tire equator C by a distance of 0.5 to 0.7 times the tread ground half width, The tread thickness T has a minimum tread thickness position Qt at which the tread thickness T is a minimum value T min, and
The minimum value T min is 0.89 to 0.97 times the tread thickness Tc at the position of the tire equator C, and the tread thickness Tb at the outer end position of the second belt ply is the tread thickness. 0.95 to 1.10 times the thickness Tc, and the tread portion is provided with an inner longitudinal main groove extending on both sides of the tire equator and an outer longitudinal main groove extending in the circumferential direction on the outer side thereof. The tread surface is divided into an inner rib-like land on the tire equator, an outer rib-like land on the ground contact end side, and an inner rib-like land between them,
In a normal ground contact state when a normal load is applied to a tire in a normal internal pressure state that is assembled with a normal rim and filled with a normal internal pressure,
A sum P1a of the ground load applied to the half region obtained by dividing the rib-like land portion of the inner portion by the tire equator, and a sum P2c of the ground load applied to the tire equator-side half region of the inner rib-like land portion. The ratio P2c / P1a is in the range of 0.9 to 1.05,
The ratio P2e / P2c between the total sum P2c of the ground loads and the total sum P2e of the ground loads loaded on the ground end side half area in the rib-shaped land portion in the range of 0.75 to 1.0,
The ratio P3c / P2e between the total P2e of the ground load and the total P3c of the ground load loaded on the tire equator half region in the outer rib-shaped land portion is in the range of 0.9 to 1.2.
The ratio P3e / P3c of the total sum P3c of the ground loads and the total sum P3e of the ground loads loaded on the ground end side half region in the outer rib-shaped land portion is in a range of 0.8 to 1.1.
Moreover, the heavy load tire is characterized in that a ratio P3e / P1a between the total P1a of the ground loads and the total P3e of the ground loads is in a range of 0.75 to 1.0. The tread thickness T increases from the tread thickness minimum position Qt to the tread thickness Tc inward in the tire axial direction.
2. The heavy duty tire according to claim 1, wherein the tire increases from the minimum tread thickness position Qt to the tread thickness Tb toward the outer side in the tire axial direction . 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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