JP4290897B2 - Pneumatic radial tire - Google Patents

Description

表１より明らかな様に、実施例に係るタイヤは、比較例１（従来例）のタイヤと比べていずれもアイス性能を維持しながら、ドライ性能と耐偏摩耗性を大幅に改善することができる。これに対して、曲率半径Ｒsoが大きすぎる比較例２では、アイス性能が維持できなかった。またボイド比の倍率が小さすぎる比較例３では、外側ショルダー部の溝面積が小さくなりすぎてアイス性能が低下し、ボイド比の倍率が大き過ぎる（Ｖｏ／Ｖｉ＝１）の比較例４では、ドライ性能、耐偏摩耗性の改善代がほとんどなく，アイス性能も低下気味となった。
【図面の簡単な説明】
【図１】本発明の空気入りタイヤの一例を示す断面の輪郭を示す概略図
【図２】本発明の空気入りタイヤの一例を示す断面の輪郭を示す要部拡大図
【図３】本発明の空気入りタイヤのトレッドパターンの一例を示す展開図
【符号の説明】
１ タイヤトレッド
２ クラウン部
３ ショルダー部
４ バットレス部
５ タイヤ赤道線
７１ 曲率半径Ｒsoの輪郭（外側ショルダー部）
７２ 曲率半径Ｒsiの輪郭（内側ショルダー部）
Ｒso 曲率半径（外側ショルダー部）
Ｒsi 曲率半径（内側ショルダー部）
Ｇｏ 溝の中心線（外側ショルダー部）
Ｇｉ 溝の中心線（内側ショルダー部）
Ｂ１ｏ〜Ｂ４ｉ ブロック[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic radial tire in which a curvature radius of a contour of a shoulder portion and a void ratio in the vicinity of a ground contact end of the shoulder portion are asymmetrical with respect to a tire equator line.
[0002]
[Prior art]
In general, in a pneumatic tire, in order to prevent uneven wear of the shoulder portion due to a difference in contact pressure distribution or the like, the block rigidity of the shoulder portion is set larger than that of the center portion. In addition, high roof vehicles such as minivans and one-boxes often employ asymmetric patterns to increase the shoulder block rigidity on the outside of the vehicle.
[0003]
During cornering when the vehicle travels, load movement due to the roll occurs, and a large load is applied to the outside of the vehicle. For this reason, the outer portion of the tire pattern tends to decrease quickly, and fall-off wear tends to occur. Further, since a large load is applied to the outer side of the tire, if the outer block rigidity is small, sufficient cornering power (CP) cannot be obtained during cornering. In particular, high-roof vehicles such as minivans and one-boxes have a higher center of gravity and larger rolls, so these tendencies tend to appear more remarkably.
[0004]
For this reason, as described above, high roof vehicles often respond by adopting an asymmetric pattern by increasing the pattern rigidity by reducing the void (groove area) on the outer side of the tire or by expanding the block area on the outer side. It was.
[0005]
[Problems to be solved by the invention]
However, in the case of an ice road surface, since the road surface mu (coefficient of friction) is low, load change due to rolls hardly occurs even in a high roof car, and the performance with better block rigidity in the ground contact surface (uniform pattern rigidity) is better. Conversely, when the rigidity of the shoulder portion is increased, the ice performance tends to decrease.
[0006]
In addition, in the case of a studless tire, in order to earn a large ground contact area, the shape of the shoulder portion is often close to a square (a shape where the tread ground end is square), but if the shape is close to a square, the ground contact width when a load is applied The increase is small and sufficient CP cannot be obtained. For this reason, it is difficult to improve cornering performance on a dry road surface.
[0007]
JP-A-11-32214 discloses a left-right asymmetric pneumatic radial tire in which the curvature radius of the shoulder portion located outside the vehicle is smaller than the curvature radius of the shoulder portion located inside. Since the outer radius of curvature is smaller, the effect of increasing the ground contact area cannot be expected when the load is moved by a roll during cornering.
[0008]
Accordingly, an object of the present invention is to provide a pneumatic radial tire capable of improving wear resistance and dry performance while maintaining ice performance.
[0009]
[Means for Solving the Problems]
The above object can be achieved by the present invention as described below. In other words, the pneumatic radial tire of the present invention has a contour of the radius of curvature that appears on the surface of the crown portion of the tire tread and a surface of both shoulder portions that are inscribed in the contour of the radius of curvature that appears on the surface of the buttress portion. In a pneumatic radial tire in which the contours of the respective curvature radii that appear are asymmetrical with respect to the tire equator line, the curvature radii Rso of the contours that appear on the surface of the shoulder portion located outside the vehicle when the tires are mounted are 10 to 35 mm, the curvature radius Rsi of the contour appearing on the surface of the shoulder portion located inside the vehicle is 0 to 5 mm, Rso> Rsi, and the grounding of the shoulder portion located outside the vehicle When the void ratio in the vicinity of the end is Vo and the void ratio in the vicinity of the ground contact end of the shoulder portion located inside is Vi, 0.65 × Vi ≦ Vo ≦ 0.98 × Vi is satisfied.
[0010]
Here, the ground contact edge of the shoulder portion is defined as a flat road surface when the tire is mounted on the applicable rim, the internal pressure is 180 kPa, and a mass corresponding to 88% of the maximum load capacity of the displayed tire is loaded. Refers to the outermost position on both sides of the ground. In addition, as shown in FIG. 3, the void ratio in the vicinity of the ground end is defined by the center lines Go and Gi of the grooves defining the blocks B3o and B4i where the ground end lines To and Ti intersect, and the ground end lines To and Ti. The percentage (%) of the groove area surrounded by the center lines Go and Gi in the pitch area of one pitch surrounded by. In addition, when the land part where the grounding end lines To and Ti intersect with each other continues without going through the groove, the center line of the circumferential groove adjacent to the grounding end lines To and Ti and the land part in one pitch. The percentage (%) of the groove area in the area between Go and Gi.
[0011]
[Function and effect]
According to the present invention, since the curvature radius Rso and the curvature radius Rsi are in the above relationship, when the void ratio of the shoulder portions on both sides is the same, the ground contact area on the outside of the vehicle during cornering on the ice road surface When the (contact width from the equator line) is reduced, the present invention changes the void ratio on both sides to increase the block area ratio to meet the decrease in the ground contact area. The ice performance can be maintained evenly. On the other hand, when cornering on the dry road surface, the larger radius of curvature Rso increases the ground contact area on the outside of the vehicle, so the block rigidity on the outside of the vehicle increases, preventing wear from falling off, and sufficient cornering power. Obtainable. As a result, wear resistance and dry performance can be improved while maintaining ice performance.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing the outline of a cross section of a pneumatic tire showing an example of the present invention, and FIG. 2 is an enlarged view of the main part.
[0013]
In FIG. 1, 1 is a tire tread, 2 is a crown portion of the tire tread 1, 3 is a shoulder portion, and 4 is a buttress portion. 5 is a tire equator line running in the center of the tire tread 1, and 6 is a virtual line indicating the tire maximum width.
[0014]
The contours 71 and 72 of the radius of curvature Rso and Rsi of the tire outer peripheral surface in the shoulder portion 3 are contours 81 and 82 of the radius of curvature Rt appearing on the surface of the crown portion 2 and the buttress portion 4 as shown in the figure. Inscribed on the contours 91 and 92 of the radius of curvature Rb appearing on the surface, respectively. In FIG. 2, the wavy line 83 is a virtual extension line of the contour 81 having the curvature radius Rt, and the wavy line 93 is a virtual extension line of the contour 91 having the curvature radius Rb.
[0015]
Further, the contours 71 and 72 of the curvature radii Rso and Rsi appearing on the surface of the shoulder portion 3 are asymmetrical with respect to the tire equator 5 as shown in FIG. That is, the contour 71 appearing on the surface of the shoulder portion located on the outer side of the vehicle when the tire is mounted and the contour 72 appearing on the surface of the shoulder portion located on the inner side are configured with an asymmetric radius of curvature.
[0016]
Further, Rso> Rsi, and the curvature radius Rso of the contour 71 of the shoulder portion located outside the vehicle is larger than the curvature radius Rsi of the contour 72 of the shoulder portion located inside the vehicle.
[0017]
As a specific numerical value of the curvature radius Rso of the shoulder portion 3 located outside the vehicle and the curvature radius Rsi of the contour 72 located inside the vehicle, the curvature radius Rso is 5 to 35 mm. The radius of curvature Rsi of the contour appearing on the surface of the shoulder portion positioned is 0 to 10 mm. Preferably, the curvature radius Rso is 15 to 30 mm, and the curvature radius Rsi of the contour appearing on the surface of the shoulder portion located inside the vehicle is 0 to 5 mm. If the radius of curvature Rso of the contour 71 is smaller than 5 mm, the amount of increase in the contact area is small when cornering on the dry road surface, and the dry performance cannot be sufficiently improved. If the radius of curvature Rso of the contour 71 is larger than 35 mm, the shoulder located outside It becomes impossible to ensure a sufficient ground contact area when the part 3 is traveling straight or on an ice road surface. Further, if the curvature radius Rsi of the contour 72 is larger than 10 mm, a sufficient contact area of the shoulder portion 3 located inside cannot be secured.
[0018]
In the present invention, the radius of curvature Rt of the arcs 81 and 82 appearing on the surface of the crown portion and the radius of curvature Rb of the arcs 91 and 92 appearing on the surface of the buttress portion 4 are not particularly limited. Note that the tire shape of the present invention is all specified based on the standard internal pressure.
[0019]
In the present invention, when the void ratio in the vicinity of the ground contact end of the shoulder portion located outside the vehicle is Vo and the void ratio in the vicinity of the ground contact end of the shoulder portion located inside is Vi, 0.65 × Vi ≦ Vo. ≦ 0.98 × Vi, preferably 0.75 × Vi ≦ Vo ≦ 0.9 × Vi. If the void ratio Vo is smaller than 0.65 × Vi, the void ratio Vo becomes too small, and it becomes difficult to maintain the ice performance by bringing the block rigidity of the outer shoulder portion 3 and the inner shoulder portion 3 close to each other. Further, if the void ratio Vo is larger than 0.98 × Vi, the void ratio Vo becomes too large, and similarly it is difficult to maintain the ice performance by bringing the block rigidity of the outer shoulder portion 3 and the inner shoulder portion 3 close to each other. become.
[0020]
In the present invention, the shape of the tread pattern is not particularly limited, and examples thereof include a tread pattern having asymmetry with respect to the equator line 5 of the tire as shown in FIG. In this example, the ground contact end lines To and Ti intersect with the blocks B3o and B4i. Inside the blocks B3o and B4i, the blocks B1o and B1i disposed near the tire equator line 5 are disposed on both sides thereof. Blocks B2o, B2i, and B3i.
[0021]
Each of the blocks B1o to B4i is divided by a circumferential groove 11, a zigzag oblique groove 12, and a lateral groove 13. Each block B1o to B4i includes a plurality of wave sipes.
[0022]
In the present invention, any block may have a rib shape, and the rib may be provided with a lug (lateral groove).
[0023]
In the present embodiment, the groove area surrounded by the center line Go in the pitch area of one pitch surrounded by the center line Go of the groove defining the block B3o intersected by the ground end line To and the ground end line To. The void ratio Vo, which is a percentage of the above, is smaller than the void ratio Vi defined similarly. In other words, when the block area ratio of the block B3o inside the ground contact end lines To and Ti is larger than the block area ratio of the block B4i, and thus the void ratio of the shoulder portions on both sides is the same, during cornering on the ice road surface Where the ground contact area on the outside of the vehicle (the ground contact width from the equator line) is reduced, the present invention increases the block area ratio and equalizes the block rigidity on both sides of the ice road surface in proportion to the decrease in the ground contact area. Ice performance can be maintained.
[0024]
In the present invention, when the rubber composition in the tread pattern or the rigidity of the rubber itself is the same, while maintaining the ice performance, the effect of improving the wear resistance and the dry performance can be exhibited in a balanced manner. The rubber composition and the like in the inside may be different. However, the rigidity of the rubber itself in the tread pattern is preferably approximated.
[0025]
Since the tire of the present invention has an asymmetric tread pattern, the mounting direction or the rotation direction is designated. The present invention is a pneumatic radial tire having an asymmetric tread pattern, and can be suitably used particularly for pneumatic radial tires for high roof vehicles such as minivans and one-box vehicles. This is a pneumatic radial tire having the above-mentioned asymmetric tread pattern, but when applied to a high roof vehicle such as a minivan or a one-box vehicle, the center of gravity of the vehicle is higher than that of a normal passenger car tire. This is because a large force acts on the shoulder portion located outside the vehicle during traveling, especially during turning, and the problems of uneven wear and cornering performance on dry roads as described above are large. Moreover, since ice performance can be maintained, it is also useful as a studless tire.
[0026]
However, the tire of this invention is not limited to these, It can use for the tire for passenger cars which satisfy | fills the nominal of cross-sectional width: 135-325 (mm), and flatness ratio: 30-80 (%). In addition, the tire of the present invention can be easily manufactured by vulcanization molding using a mold or the like in which the curvature radius of the shoulder portion is asymmetric.
[0027]
【Example】
Examples and the like specifically showing the configuration and effects of the present invention will be described below.
[0028]
In accordance with the above-described embodiment shown in FIGS. 1 to 3, the tires of Example 215 / 60R16 with tire radius 215 / 60R16 at the curvature radius Rso, the curvature radius Rsi, and the void ratio magnification Vo / Vi shown in Table 1 and A comparative tire was prototyped. About these, ice performance, dry performance, and abrasion resistance were evaluated by the following evaluation methods, respectively. The results are also shown in Table 1.
[0029]
Each tire had the same configuration except for “curvature radius of shoulder” and “magnification of void ratio”, and the void ratio of the entire pattern was constant. Further, the curvature radius of the shoulder portion of 0 mm means that the shoulder portion has a square shape.
[0030]
(Ice performance test)
The ice road surface was actually run on a domestic minivan (3000 cc) equipped with each prototype tire of the example and comparative example, and evaluated by a feeling test with two drivers. The evaluation was performed by index evaluation in which each driver was given the type of prototype tire and the vehicle was run, and was assigned a score of 10 points, and the average value was set to 100 for the tire of Comparative Example 1. The results are shown in Table 1. Each numerical value in the table indicates that the ride comfort is better as the value is larger.
[0031]
(Dry performance test)
The dry road surface was actually driven by a domestic minivan (3000 cc) equipped with the prototype tires of Examples and Comparative Examples, and evaluated by a feeling test with two drivers. The evaluation was performed by index evaluation in which each driver was given the type of prototype tire and the vehicle was run, and was assigned a score of 10 points, and the average value was set to 100 for the tire of Comparative Example 1. The results are shown in Table 1. Each numerical value in the table indicates that the ride comfort is better as the value is larger.
[0032]
(Uneven wear resistance test)
After running a domestic minivan (3000 cc) fitted with each prototype tire of the example and comparative example for 6000 km on our test course, the shoulder portion and the tire center portion located outside the vehicle for each of the four tires. The difference in the amount of wear was measured, and the reciprocal of the measured value was indexed with the tire of Comparative Example 1 as 100. In each of the examples and comparative examples, the driving conditions were for five passengers, and the tires were not rotated until completion. The results of this uneven wear resistance test are shown in Table 1. In addition, it shows that uneven wear resistance is so favorable that each numerical value is large.
[0033]
[Table 1]

As is clear from Table 1, the tires according to the examples can significantly improve dry performance and uneven wear resistance while maintaining ice performance as compared with the tires of Comparative Example 1 (conventional example). it can. On the other hand, in Comparative Example 2 in which the curvature radius Rso is too large, the ice performance could not be maintained. Further, in Comparative Example 3 in which the magnification of the void ratio is too small, the groove area of the outer shoulder portion becomes too small and the ice performance is lowered, and in Comparative Example 4 in which the magnification of the void ratio is too large (Vo / Vi = 1), There was almost no cost for improvement in dry performance and uneven wear resistance, and ice performance seemed to decline.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an outline of a cross section showing an example of a pneumatic tire of the present invention. FIG. 2 is an enlarged view of a main part showing an outline of a cross section showing an example of the pneumatic tire of the present invention. Development view of an example of a tread pattern of a pneumatic tire
DESCRIPTION OF SYMBOLS 1 Tire tread 2 Crown part 3 Shoulder part 4 Buttress part 5 Tire equator line 71 Contour of radius of curvature Rso (outer shoulder part)
72 Contour of radius of curvature Rsi (inner shoulder)
Rso radius of curvature (outer shoulder)
Rsi radius of curvature (inner shoulder)
Go Groove center line (outer shoulder)
Gi Groove center line (inner shoulder)
B1o-B4i block

Claims (1)

The contour of the radius of curvature that appears on the surface of the crown portion of the tire tread, and the contour of the radius of curvature that appears on the surfaces of the shoulder portions on both sides that are inscribed in the contour of the radius of curvature that appears on the surface of the buttress portion, respectively. In a pneumatic radial tire that is asymmetrical with respect to the equator line, the curvature radius Rso of the contour that appears on the surface of the shoulder portion located outside the vehicle when the tire is mounted is 10 to 35 mm, and is located inside the vehicle. The radius of curvature Rsi of the contour appearing on the surface of the shoulder portion is 0 to 5 mm, Rso> Rsi, and the void ratio in the vicinity of the ground contact edge of the shoulder portion located outside the vehicle is Vo, located inside. When the void ratio in the vicinity of the ground contact edge of the shoulder portion is Vi, 0.65 × Vi ≦ Vo ≦ 0.98 × Vi is satisfied. Pneumatic radial tire.

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