JP4363902B2 - Heavy duty tire - Google Patents

Description

【００４０】
表の如く、実施例のタイヤは、偏摩耗を招くことなく、領域Ｒ１ｃ、領域Ｒ２ｃの双方における温度上昇を抑制しうることが確認できる。
【００４１】
【発明の効果】
叙上の如く本発明は、正規内圧のタイヤに正規荷重を負荷した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、タイヤ赤道近傍、及びベルト層外端近傍の双方における温度上昇を両立して抑えることができ、ベルト層のトッピングゴムにおける熱老化、及びコードルースを抑制し、タイヤ寿命や高速耐久性の向上を達成することができる。
【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】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
Ｃ タイヤ赤道上
Ｇ１ 中央の縦主溝
Ｇ２ 外の縦主溝
Ｒ１ 内のリブ状陸部
Ｒ１ｃ 内のリブ状陸部のタイヤ赤道側半分領域
Ｒ１ｅ 内のリブ状陸部の接地端側半分領域
Ｒ２ 外のリブ状陸部
Ｒ２ｃ 外のリブ状陸部のタイヤ赤道側半分領域
Ｒ２ｅ 外のリブ状陸部の接地端側半分領域[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heavy load tire that can improve the tread durability by suppressing the temperature rise in the vicinity of the tire equator and the belt end in the tread portion by specifying the distribution of the contact load.
[0002]
[Background Art and Problems to be Solved by the Invention]
For example, in the case of 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 such a tire, in a normal internal pressure state in which a rim is assembled on a normal rim and a normal internal pressure is filled, in a region Y separated from the tire equator C 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. In particular, in a tire in which a tread portion is divided into inner and outer rib-like land portions R1 and R2 by three vertical main grooves G, the tendency is strong because the outer vertical main grooves Gs usually pass through the region Y. Therefore, the ground contact pressure in the tire equator-side half region R1c of the inner rib-shaped land portion R1 and the tire equator-side half region R2c of the outer rib-shaped land portion R2 are increased, and this region R1c during traveling is increased. , The temperature rises at R2c.
[0004]
Here, the temperature increase in the region R1c causes a shortening of the tire life such as promoting the heat aging of the topping rubber in the belt layer b, and the temperature increase in the region R2c is outside the belt layer b in the initial running. It leads to the result of impairing high-speed durability, such as inducing cord looseness at the end.
[0005]
For example, Patent Documents 1 and 2 disclose that a tread rubber is formed of a cap rubber layer on the tread surface side and a base rubber layer on the inner side in the radial direction, and a low heat-generating rubber is used for the base rubber layer. Has been proposed. However, since low heat-generating rubber is generally inferior in wear performance, when a part of the base rubber layer is exposed from the middle to the late stage of the tire wear life, the wear progresses remarkably in this exposed portion and impairs running performance. There is a problem.
[0006]
[Patent Document 1]
JP-A-49-80703 [Patent Document 2]
Japanese Patent No. 2634704 [0007]
Therefore, the present invention is based on specifying the distribution of the contact load in the normal contact state when the normal load is applied to the tire in the normal internal pressure state in which the rim is assembled to the normal rim and the normal internal pressure is filled, and the region R1c, An object of the present invention is to provide a heavy-duty tire that can suppress both R2c temperature rises at the same time and can improve tire life and high-speed durability.
[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 is formed of three or more belt plies using a metal cord as a belt cord,
The belt ply includes a first belt ply on the innermost side in the tire radial direction and a second belt ply arranged on the outer side and having a maximum width, and the ply width of the second belt ply is tread grounding. 0.80 to 0.95 times the width WT,
The tread portion is provided with a central longitudinal main groove extending on the tire equator and outer longitudinal main grooves extending in the circumferential direction on both outer sides thereof, so that the tread surface has a rib-like land portion on the tire equator side. And divide it into a rib-like land outside the ground end , and
The groove center line of the outer vertical main groove passes through a region Y separated from the tire equator C by a distance 0.5 to 0.7 times the tread grounding half width WT / 2 , and
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,
When the tread thickness between the contour line of the tread surface and the second belt ply is T, the tread thickness Ty at each position in the region Y is the tread thickness Tc at the tire equator C position. In the range of 0.94 to 0.99 times,
The tread thickness Tb at the outer end position of the second belt ply is 0.98 to 1.03 times the tread thickness Tc, and the tread thickness T extends from the region Y to the tire equator. C and gradually increase toward the outer end of the second belt ply 7B,
The ratio P1e / P1c of the total contact load P1c applied to the tire equator-side half region and the total contact load P1e applied to the contact end-side half region in the rib-shaped land portion is 0.8-1. A range of 0,
The ratio P2c / P1e between the total ground load P1e and the total ground load P2c applied to the tire equator-side half region in the outer rib-shaped land portion is in the range of 0.5 to 0.8.
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 region in the outer rib-shaped land portion is in the range of 0.9 to 1.1.
Moreover, the ratio P2e / P1c between the total sum P1c of the ground loads and the total sum P2e of the ground loads is in the range of 0.5 to 0.8.
[0009]
In the invention of claim 2, the carcass cord of the carcass is a metal cord.
[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”. For sizes that are not, it means “Design Rim”
・ In ETRTO, rims with a rim width narrower than “Measuring Rim” are set as “rims with a rim width one rank lower than“ Measuring Rim ”, and rims with a rim width narrower than“ Measuring Rim ”. For sizes that do not, it means “Measuring Rim”.
[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, the tire 1 includes, in the tread portion 2, a central vertical main groove G1 extending on the tire equator C, and an outer vertical main groove G2 extending in the circumferential direction on both outer sides thereof. , It is divided into a rib-like land portion R1 on the tire equator C side and a rib-like land portion R2 outside on the ground contact end side. The rib-like land portions R1 and R2 may be block rows or ribs.
[0020]
Each of the vertical main grooves G1 and G2 is a groove body having a groove width of 3 mm or more, and has a linear shape or a zigzag shape (including a wave shape) and extends in the circumferential direction. The longitudinal main grooves G1 and G2 have a groove width of 5 mm or more, more preferably 7 to 10 mm, and a groove depth of 9 mm or more, more preferably 14.5 to 17.5 mm. In addition to the three vertical main grooves G, the tread portion 2 is appropriately provided with a horizontal main groove in a direction intersecting with the vertical main groove G and a vertical narrow groove Gh having a groove width of less than 3 mm extending in the tire circumferential direction. Can be provided.
[0021]
Further, in the present example, the outer vertical main groove G2, that is, the shoulder groove Gs, which is the outermost side in the tire axial direction, has a groove centerline N of 0.5 to 0. 0 of the tread ground half width WT / 2 from the tire equator C. It passes through the region Y separated by 7 times. Thus, the tread portion 2 is divided into a tread center portion Yc on the inner side than the shoulder groove Gs and an outer tread shoulder portion Ye. That is, the inner rib-shaped land portion R1 is disposed on the tread center portion Yc, and the outer rib-shaped land portion R2 is disposed on the tread shoulder portion Ye. 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 invention, in such a tire 1, 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 order to suppress a decrease in tire life and high-speed durability due to temperature rise. In the normal grounding state when a normal load is applied to, the grounding load at that time is specified as follows.
[0023]
Specifically, as shown in FIG. 2, the inner rib-like land portion R1 is further virtually divided into a tire equator-side half region R1c and a ground contact end-side half region R1e, and the outer rib-like land portion R2 is divided. Furthermore, when virtually dividing into the tire equator half region R2c and the ground contact end half region R2e,
(1) The ratio P1e / P1c between the sum P1c of ground loads loaded on the tire equator half region R1c and the sum P1e of ground loads loaded on the ground end side half region R1e in the rib-like land portion R1 in Set it in the range of 0.8-1.0,
(2) A ratio P2c / P1e between the total P1e of the ground load and the total P2c of the ground load applied to the tire equator-side half region R2c in the outer rib-shaped land R2 is 0.5 to 0.8. To the range of
(3) A 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 region R2e in the outer rib-shaped land R2 is 0.9 to 1.1. To the range of
(4) The ratio P2e / P1c between the total ground load P1c and the total ground load P2e is set in the range of 0.5 to 0.8.
[0024]
The total sum P1c, P1e, P2c, and P2e of the ground loads can be obtained as follows. For example, the tire 1 is grounded in a state where a normal load is applied on a sheet-like body on which a large number of sensors are spread, and the load applied to each sensor is measured. For each half area, the sum of the ground loads applied to the half areas R1c to R2e can be obtained by summing up the outputs of the sensors grounded in the half area.
[0025]
Here, the inventor of the present invention has a strong correlation between the sum of the ground loads and the heat generation energy. In particular, the sums P1c to P2e of the ground loads applied to the half regions R1c to R2e are the above-described (1) to (4). In the half region R1c, R2c, it is possible to suppress both temperature rises at the same time, heat aging of the topping rubber in the belt layer 7, and cord looseness at the outer end of the belt layer 7. It has been clarified that the generation of tires can be suppressed and the tire life and high-speed durability can be improved.
[0026]
If the values of the ratio P1e / P1c, the ratio P2c / P1e, the ratio P2e / P2c, and the ratio P2e / P1c are out of the range, the balance of the ground load is lost, so that the temperature rise in the half regions R1c and R2c is suppressed. Cannot be achieved, and uneven wear such as orbital wear and shoulder wear is generated.
[0027]
That is, when the ratio P1e / P1c is less than 0.8, the contact pressure of the half region R1c is excessively increased, so that the temperature rises in the half region R1c and the topping rubber of the belt layer is thermally aged. On the other hand, if the ratio P1e / P1c exceeds 1.0, the contact pressure in the half region R1c is excessively reduced, so that track wear along the central vertical main groove G1 tends to occur.
[0028]
If the ratio P2c / P1e exceeds 0.8, the temperature rises in the half region R2c, leading to cord looseness at the outer edge of the belt layer. Conversely, if the ratio P2c / P1e is less than 0.5, the half region R2c Since the contact pressure decreases excessively, track wear along the shoulder groove Gs tends to occur.
[0029]
Similarly, when the ratio P2e / P2c is less than 0.9, the temperature rises in the half region R2c, leading to cord looseness at the outer end of the belt layer. Since the pressure decreases, track wear along the shoulder groove Gs tends to occur.
[0030]
On the other hand, when the ratio P2e / P1c is less than 0.5, the temperature rises in the half region R1c, leading to heat aging of the topping rubber, and shoulder wear is likely to occur at the tread end. On the other hand, if the ratio P2e / P1c exceeds 0.8, the heat generation in the half region R2e is increased, which adversely affects the cord looseness at the outer end of the belt layer.
[0031]
From such a viewpoint, the ratio is more preferably set to the following range.
P1e / P1c = 0.85-0.95
P2c / P1e = 0.55-0.75
P2e / P2c = 0.95 to 1.05
P2e / P1c = 0.55-0.75
[0032]
Next, in order to obtain such a distribution of contact load, in the present invention , 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 T is T, the tread thickness Ty at each position in the region Y is 0.94 to 0.99 times the tread thickness Tc at the tire equator C position. The tread thickness Tb at the outer end position of the second belt ply is set to 0.98 to 1.03 times the tread thickness Tc. In particular, the ratio Ty / Tc of the tread thickness is set smaller than the ratio Tb / Tc. In other words, the tread thickness T, from the region Y, toward the outer end of the tire equator C and the second belt ply 7B, and is respectively gradually increased.
[0033]
By adopting such a distribution of the tread thickness T, it is possible to obtain a distribution of the total sum of the ground loads.
[0034]
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 a tread contour line at the tread center portion Yc. S is formed by a convex arcuate contour S1 using a single arc or a plurality of arcs, and the tread contour S in the tread shoulder portion Ye is formed by a substantially linear contour S2.
[0035]
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.
[0036]
【Example】
A heavy-duty tire having a tire size of 11R22.5 having the structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and the heat generation and wear performance of the tread portion of each sample tire were tested. The results are shown in Table 1. Show.
[0037]
(1) Heat generation:
The sample tire was run on the drum at a speed of 80 km / h for 2 hours under the conditions of a rim (22.5 × 7.50), internal pressure (700 kPa), load (26.52 kN), and room temperature (35 ° C.) The internal temperature in region R1c and region R2c was measured. In addition, the internal temperature of area | region R1c measured the temperature in the position of the tire axial direction inner edge of this area | region R1c in a belt layer outer surface. The internal temperature of the region R2c was measured at the third belt ply outer end position on the outer surface of the belt layer.
[0038]
(2) Wear performance:
A sample tire was mounted on the front wheel of a truck (2-2, D type) with a rim (7.50 × 22.5) and internal pressure (700 kPa) and traveled a distance of 100,000 km. The appearance of the track wear along the longitudinal main grooves G1 and G2 and the occurrence of shoulder drop wear along the tread edge was visually confirmed.
[0039]
[Table 1]

[0040]
As shown in the table, it can be confirmed that the tires of the examples can suppress the temperature rise in both the region R1c and the region R2c without causing uneven wear.
[0041]
【The invention's effect】
As described above, the present invention specifies the distribution of contact load in a normal contact state in which a normal load is applied to a tire having a normal internal pressure, so both temperature increases near the tire equator and near the outer edge of the belt layer are compatible. Thus, it is possible to suppress thermal aging and cord looseness in the topping rubber of the belt layer, thereby achieving improvement in tire life and high-speed durability.
[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 a tread contour shape in a conventional tire.
[Explanation of symbols]
2 tread portion 3 sidewall portion 4 bead portion 5 bead core 6 carcass 7 belt layer C tire equator G1 center longitudinal main groove G2 outer longitudinal main groove R1 inside rib-like land portion R1c tire-like tire equator Grounded end side half region R2e outside the rib-like land portion R2c Outside the rib-like land portion R2c Outside the tire-equal-side half region R2e Outside the rib-like land portion R2e

Claims (2)

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 is formed of three or more belt plies using metal cords as belt cords,
The belt ply includes a first belt ply on the innermost side in the tire radial direction and a second belt ply arranged on the outer side and having a maximum width, and the ply width of the second belt ply is tread grounding. 0.80 to 0.95 times the width WT,
The tread portion is provided with a central longitudinal main groove extending on the tire equator and outer longitudinal main grooves extending in the circumferential direction on both outer sides thereof, so that the tread surface has a rib-like land portion on the tire equator side. Divide it into a rib-like land outside the grounded end , and
The groove center line of the outer vertical main groove passes through a region Y separated from the tire equator C by a distance 0.5 to 0.7 times the tread grounding half width WT / 2 , and
In a normal grounding 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,
When the tread thickness between the contour line of the tread surface and the second belt ply is T, the tread thickness Ty at each position in the region Y is the tread thickness Tc at the tire equator C position. In the range of 0.94 to 0.99 times,
The tread thickness Tb at the outer end position of the second belt ply is 0.98 to 1.03 times the tread thickness Tc, and the tread thickness T extends from the region Y to the tire equator. C and gradually increase toward the outer end of the second belt ply 7B,
The ratio P1e / P1c of the total contact load P1c applied to the tire equator-side half region and the total contact load P1e applied to the contact end-side half region in the rib-shaped land portion is 0.8-1. A range of 0,
The ratio P2c / P1e between the total ground load P1e and the total ground load P2c applied to the tire equator-side half region in the outer rib-shaped land portion is in the range of 0.5 to 0.8.
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 region in the outer rib-shaped land portion is in the range of 0.9 to 1.1.
Moreover, the heavy load tire is characterized in that the ratio P2e / P1c between the total P1c of the ground loads and the total P2e of the ground loads is in a range of 0.5 to 0.8. The heavy duty tire according to claim 1, wherein the carcass cord of the carcass is a metal cord.

Images