JP4673496B2 - Pneumatic tire - Google Patents

Description

【００５１】
実施例のタイヤは、低燃費性を維持しながら、操縦安定性及びロードノイズ性能を向上しうるのが確認できる。
【００５２】
【発明の効果】
本発明は叙上の如く構成しているため、転がり抵抗への犠牲を最小限に止める、或いは若干の転がり抵抗の低減を達成しながら、操縦安定性とロードノイズ性能とを向上できる。
【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】外の補強ゴム層を拡大して示す断面図である。
【図３】内の補強ゴム層を拡大して示す断面図である。
【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
９ 外の補強ゴム層
１０ 内の補強ゴム層
１５、１５ａ、１５ｂ 凸部
Ｋ 最大厚さ点
Ｊａ サイドウォール上基準線
Ｊｂ サイドウォール下基準線
Ｐ タイヤ最大巾点
Ｐ１ 離間点
ＴＥ トレッド外縁点
Ｙ タイヤ最大巾領域[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire having improved steering stability and road noise performance while maintaining low fuel consumption.
[0002]
[Background Art and Problems to be Solved by the Invention]
In recent years, as part of improving the global environment, development of fuel-efficient tires with reduced tire rolling resistance has been strongly demanded.
[0003]
This low fuel consumption tire is designed to have a very thin rubber thickness in each part of the tire in order to reduce the tire weight and suppress the heat generation due to the deflection of the tire, and the rubber material used is also from the viewpoint of durability and heat generation A relatively soft rubber compound is used. As a result, there are problems in that the vibration absorption such as road noise is inferior and the steering stability is deteriorated such that the longitudinal rigidity and lateral rigidity of the tire are lowered.
[0004]
The tire has the largest deflection near the tire maximum width point of the low-stiffness sidewall when the load is applied, but the rubber thickness is very thin near the tire maximum width point, so the contribution to rolling resistance is small. On the contrary, it is known that the buttress side portion and the bead side portion have a small rubber thickness but a large rubber thickness, so that the contribution to the rolling resistance is very large.
[0005]
Therefore, the present inventor proposed that the buttress side portion or the bead side portion be reinforced with a rubber layer having a relatively high hardness and a low heat generation property while leaving the vicinity of the tire maximum width point having low rigidity as it is. . Thereby, the bending of the reinforced buttress side portion or the bead side portion is reduced, and the deflection at the center of the sidewall is increased.
[0006]
At this time, by optimally setting the material, thickness, arrangement position, etc. of the rubber layer, the increase in rolling resistance of the entire tire is minimized, or in some cases, a slight reduction in rolling resistance is achieved. However, it has been found that improvement in steering stability can be realized at the same time by increasing rigidity due to the reinforcing effect.
[0007]
Also, by arranging the rubber layer on the inside of the carcass, the internal pressure sharing of the carcass along the rubber layer is reduced, and as a result, the tension of the carcass cord is partially reduced, thereby reducing vibration damping. It was also found that road noise performance was improved.
[0008]
That is, the present invention specifies steering rubber stability while minimizing the sacrifice of rolling resistance or achieving a slight reduction in rolling resistance by specifying the material, thickness, arrangement position, etc. of the rubber layer. The object is to provide a pneumatic tire that can improve road noise performance and is suitable as a fuel-efficient tire.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application is a pneumatic tire having a carcass extending from a tread portion to a bead core of a bead portion through a side wall portion, and the carcass is provided on the side wall portion. together with the along and outside the reinforcing rubber layer which extends radially outward of the tire maximum width region around the maximum width point tire or the inner surface providing the reinforcing rubber layer of which extends radially inwardly The reinforcing rubber layer is made of a rubber having a loss tangent (tan δ) of 0.1 or less and a rubber hardness of 50 degrees or more, and has a crescent cross section having a maximum thickness TM of 1.0 to 5.0 mm. When the layer width W1 along the inner surface of the reinforcing rubber layer is 70 mm or less and the internal pressure state is 5%, the contour shape of the carcass is the maximum thickness that is the apex of the maximum thickness TM of the reinforcing rubber layer. At point K Te is characterized by having a bent portion projecting bent to shape going towards the tire outer side.
[0010]
In the invention of claim 2, the maximum tire width region is a region having a radial length Ly of 10 mm centered on the maximum tire width point.
[0011]
In the invention of claim 3, in the tire meridional section, the outer surface of the sidewall portion is
Provided in the vicinity of the maximum thickness point of the outer reinforcing rubber layer is a protrusion protruding outward from the tire from a reference line on the sidewall formed by an arc passing through the tire maximum width point and the tread outer edge point, or the inner In the vicinity of the maximum thickness point of the reinforcing rubber layer, a convex portion that protrudes outwardly from the sidewall lower reference line formed by an arc passing through a separation point where the outer surface of the bead portion is separated from the rim flange and the tire maximum width point It is characterized by comprising. According to a fourth aspect of the present invention, the radius of curvature RA of the bent portion is not more than 0.1 times the radius of curvature RB of the portion adjacent to the bent portion. In the invention of claim 4, the tire lumen surface of the sidewall portion approximates an arcuate curve having a center on a tire axial line passing through the tire maximum width point P in the 5% internal pressure state. It is characterized by a smooth curve.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a meridional sectional view showing a state (5% internal pressure state) in which a tire according to the present invention is a fuel-efficient tire and a rim is assembled to a normal rim and an internal pressure of 5% of the normal internal pressure is applied.
[0013]
The “regular rim” is a rim determined for each tire size in a standard system including a standard on which a tire is based. For example, a standard rim for JATMA and a “Design Rim” for TRA. Or ETRTO means "Measuring Rim". The “regular internal pressure” is the air pressure defined by the above standard. If it is JATMA, it is the maximum air pressure. "INFLATION PRESSURE" means 200 kPa in the case of passenger car tires.
[0014]
In the figure, a pneumatic tire 1 includes a carcass 6 that extends from a tread portion 2 to a sidewall portion 3 to a bead core 5 of a bead portion 4, and a belt layer 7 that is disposed inside the tread portion 2 and outside the carcass 6. With.
[0015]
Further, the sidewall portion 3 includes an outer reinforcing rubber layer 9 extending radially outward from the tire maximum width region Y along the inner surface of the carcass 6, or an inner portion extending radially inward. A reinforcing rubber layer 10 is provided. The “tire maximum width region Y” is a region having a radial length Ly of 10 mm centered on the tire maximum width point P, and is a portion having the greatest deflection when a load is applied.
[0016]
The belt layer 7 is formed of two or more belt plies 7A and 7B in this example, in which highly elastic belt cords such as steel cords are arranged at an angle of, for example, 10 to 35 degrees with respect to the tire equator C. The The belt plies 7A and 7B are placed in different directions so that the belt cords cross each other between the plies, thereby increasing the belt rigidity and reinforcing the substantially full width of the tread portion 2 with a tagging effect. .
[0017]
The carcass 6 is formed of one or more carcass plies 6A in which the carcass cords are arranged at an angle of, for example, 75 to 90 degrees with respect to the tire circumferential direction, and in this example, one carcass ply 6A. Organic fiber cords such as rayon and aromatic polyamide are preferably used. In addition, the carcass ply 6A includes a folded portion that is folded around the bead core 5 at both ends of the body portion that spans between the bead cores 5 and 5, and the bead reinforcement is provided between the body portion and the folded portion. The bead apex rubber 8 is arranged.
[0018]
The bead apex rubber 8 has a triangular cross section extending radially outward from the bead core 5 and is formed of a hard rubber having a rubber hardness of 80 to 98 degrees, thereby imparting necessary bead rigidity. The radial height H1 from the bead base line BL of the bead apex rubber 8 is preferably in the range of 25 to 45 mm from the viewpoint of bead durability and low fuel consumption.
[0019]
Further, in this example, a so-called inner linerless tire in which the conventional inner liner rubber is eliminated by using a low air-permeable rubber composition for the topping rubber of the carcass ply 6A and giving the carcass ply 6A a pneumatic holding force. The case where it forms as is illustrated. As a result, the tire can be further reduced in weight, which is more preferable as a fuel-efficient tire.
[0020]
Here, as the low air permeability rubber composition, butyl rubber, halogenated butyl rubber, and low air permeability rubber such as isobutylene / paramethylstyrene copolymer halide are contained in a rubber base material in an amount of 25% by weight or more. Can be preferably used. Examples of the commercially available halide of isobutylene / paramethylstyrene copolymer include EXXPRO90-10, EXXPRO89-4 and EXXPRO93-5 manufactured by Exxon Chemical. Further, as the balance of the rubber base material, diene rubbers such as natural rubber, butadiene rubber, styrene / butadiene rubber, isoprene rubber, chloroprene rubber, acrylonitrile butadiene rubber can be used alone or in combination.
[0021]
The topping rubber may have a so-called two-layer structure in which only the tire lumen side is formed of a low air permeability rubber composition and the outside is formed of, for example, a diene rubber.
[0022]
In the present embodiment, at least one of the outer reinforcing rubber layer 9 or the inner reinforcing rubber layer 10 is formed on the sidewall portion 3, and the steering stability and road noise performance are maintained while maintaining low rolling resistance. And have improved. In addition, in this example, the case where both the outer reinforcement rubber layer 9 and the inner reinforcement rubber layer 10 are formed is illustrated.
[0023]
The outer reinforcing rubber layer 9 reinforces the buttress side portion of the sidewall portion 3 by extending along the inner surface of the carcass 6 and radially outward from the tire maximum width region Y.
[0024]
As shown in an enlarged view in FIG. 2, the outer reinforcing rubber layer 9 has a crescent-shaped cross section in which the thickness is gradually reduced from the central portion having the maximum thickness TMa toward both sides, and extends along the inner surface 9S. The layer width W1a is regulated to 70 mm or less, and the maximum thickness TMa is regulated to a range of 1.0 to 5.0 mm.
[0025]
In the outer reinforcing rubber layer 9, the radially outer end 9 </ b> U is terminated at the inner side in the tire axial direction of the outer end of the belt layer 7, and the tire axial width between 0 and 30 mm between the belt layer 7 and the outer reinforcing rubber layer 9. It is preferable to form the overlapping portion 11 of W2 in order to enhance the reinforcing effect. At this time, the vertex K (maximum thickness point K) that forms the maximum thickness TM by being farthest from the inner surface 9S is set at a distance L1a of 20 mm or more in the radial direction from the tire maximum width point P. It is desirable. The radial distance L2a from the tire maximum width point P of the radially inward end 9L of the outer reinforcing rubber layer 9 is naturally larger than 5 mm and preferably 8 mm or more.
[0026]
The outer reinforcing rubber layer 9 is formed of a relatively hard and low heat-generating rubber having a loss tangent (tan δ) of 0.1 or less and a rubber hardness of 50 degrees or more. This loss tangent (tan δ) is a value measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of ± 1%. Means durometer A hardness measured based on JIS-K6253.
[0027]
Next, the inner reinforcing rubber layer 10 reinforces the bead side portion of the sidewall portion 3 by extending radially inward from the tire maximum width region Y along the inner surface of the carcass 6. .
[0028]
As shown in the enlarged view of FIG. 3, the reinforcing rubber layer 10 in this is a crescent cross section in which the thickness is gradually decreased from the central portion having the maximum thickness TMb toward both sides, similarly to the outer reinforcing rubber layer 9. The layer width W1b along the inner surface 10S is regulated to 70 mm or less, and the maximum thickness TMb is regulated to a range of 1.0 to 5.0 mm.
[0029]
In this example, the case where the radially inner end 10L of the inner reinforcing rubber layer 10 terminates in the vicinity of the outer end of the bead apex rubber 8 is illustrated, and the maximum thickness that is farthest from the inner surface 10S. A radial distance L1b from the tire maximum width point P of the saddle point K is set to 20 mm or more. It should be noted that the radial distance L2b of the radially outer end 10U from the tire maximum width point P is naturally greater than 5 mm, and preferably 8 mm or more.
[0030]
Similarly, the reinforcing rubber layer 10 is formed of a relatively hard and low heat-generating rubber having a loss tangent (tan δ) of 0.1 or less and a rubber hardness of 50 degrees or more. If the loss tangent (tan δ) and the rubber hardness are within the above ranges, the outer and inner reinforcing rubber layers 9 and 10 may have different rubber compositions.
[0031]
In the present embodiment, the tire lumen surface TS of the sidewall portion 3 including the inner surfaces 9S and 10S passes through the tire maximum width point P in the 5% internal pressure state as in the conventional tire. It curves smoothly by approximating an arcuate curve centered on the tire axial line. Therefore, the contour shape of the carcass 6 is different from the conventional one, and at the maximum thickness point K of the reinforcing rubber layers 9 and 10, a bent portion 12 is formed that is bent in a square shape and protrudes outward from the tire. . Note that the radius of curvature RA of the bent portion 12 is sufficiently smaller than the radius of curvature RB of the portion adjacent to the bent portion 12, and in this example, a preferable case of 0.1 or less times the radius of curvature RB is illustrated.
[0032]
In such a tire 1, when the internal pressure is filled, the reinforcing rubber layers 9 and 10 support a part of the pressure, and the internal pressure sharing of the carcass 6 is partially reduced. That is, the tension of the carcass cord is partially reduced and the vibration damping performance is improved, so that the road noise performance is improved. In particular, since the vibration transmission characteristics greatly change due to the formation of the bent portion 12, the effect of improving road noise performance is further enhanced.
[0033]
On the other hand, since the reinforcing rubber layers 9 and 10 are disposed inside the carcass 6, it is possible to carry the deflection of the tire when a load is applied by the compression rigidity of the reinforcing rubber layers 9 and 10. . Therefore, with a smaller rubber volume, the deflection of the tire can be efficiently reduced, the tire rigidity can be increased and the steering stability can be improved while suppressing an increase in weight. In particular, since the reinforcing rubber layers 9 and 10 are formed of the above-mentioned relatively hard and low heat-generating rubber, the sacrifice to the rolling resistance is minimized, or in some cases, the rolling resistance is slightly reduced. However, improvement in steering stability can be achieved at the same time by increasing the rigidity due to the reinforcing effect.
[0034]
Here, if a reinforcing rubber layer is provided in the tire maximum width region Y, stress concentrates at the tire maximum width point, so it is difficult to suppress bending, but rather heat generation becomes excessive due to an increase in rubber thickness, This will cause a significant increase in rolling resistance.
[0035]
If the loss tangent (tan δ) of the reinforcing rubber layers 9 and 10 exceeds 0.1, the rolling resistance is excessively increased, which is not suitable as a fuel-efficient tire. On the other hand, if the rubber hardness is less than 50 degrees, the reinforcing effect is insufficient, and the improvement in steering stability cannot be sufficiently achieved. If the loss tangent (tan δ) is less than 0.03, it is difficult to obtain a rubber hardness of 50 degrees or more while securing the necessary elastic force. Conversely, if the rubber hardness exceeds 90 degrees, the necessary elastic force is reduced. It is difficult to obtain a loss tangent (tan δ) of 0.1 or less while ensuring. Therefore, the loss tangent (tan δ) is preferably in the range of 0.03 to 0.1, and the rubber hardness is preferably in the range of 50 to 90 degrees.
[0036]
If the maximum thickness TM of the reinforcing rubber layers 9 and 10 is less than 1.0 mm, the reinforcing effect is insufficient. On the other hand, when the maximum thickness TM is greater than 5.0 mm and the layer width W1 is greater than 70 mm, the weight and heat generation increase, and the rolling resistance is unnecessarily increased. Further, in order to obtain a good balance of the reinforcing effect, the layer width W1 is preferably set in a range of 5 to 20 times the maximum thickness TM.
[0037]
Next, the sidewall rubber 13 forming the sidewall portion 3 extends radially outward from the bead portion 4 along the outer surface of the carcass 6, and the outer end portion 13 </ b> E of the carcass 6 and the belt layer in this example. 7 and is terminated between the outer end portions.
[0038]
At this time, the sidewall rubber 13 extends between the bent portions 12 and 12 of the carcass 6 with a substantially constant thickness T. At the positions facing the bent portions 12, 12, convex portions 15, 15 projecting outward of the tire are formed.
[0039]
In other words, in the vicinity of the maximum thickness point K of the outer reinforcing rubber layer 9, a convex portion 15a that protrudes outward from the tire reference line Ja is provided. Further, in the vicinity of the maximum thickness point K of the inner reinforcing rubber layer 10, there is provided a convex portion 15b protruding outward from the tire from the sidewall lower reference line Jb.
[0040]
Here, “the reference line Ja on the sidewall” is an arc passing through the tire maximum width point P and the tread outer edge point TE, and has its center on the tire axial line passing through the tire maximum width point P. ing. The "side wall lower reference line Jb" is an arc passing through the separation point P1 where the outer surface of the bead portion 4 is separated from the rim flange and the tire maximum width point P, and the tire passes through the tire maximum width point P. It has its center on an axial line.
[0041]
In addition, in this example, the top portion of each convex portion 15 has a distance L3 from the maximum thickness line X passing through the maximum thickness point K and orthogonal to the inner surfaces 9S, 10S of the reinforcing rubber layers 9, 10 to 10 mm or less.
[0042]
In addition, the said convex part 15 is formed by providing the recessed part which fits this convex part 15 in the said part of the metal mold | die of a tire. At the time of vulcanization, the tire inner surface TS is pressed by a bladder or the like that expands in a balloon shape. Therefore, if the mold has the recess, the carcass 6 is easily pushed out by the reinforcing rubber layers 9 and 10. The bent portion 12 can be easily formed. At this time, the thickness T of the sidewall rubber 13 can be kept uniform, and the distortion of the tire surface is also dispersed, which is advantageous from the viewpoint of rolling resistance and durability.
[0043]
The sidewall rubber 13 has a thickness T in the range of 0.5 to 3.0 mm, preferably in the range of 1.0 to 2.0 mm, in order to ensure low fuel consumption. The tangent (tan δ) is 0.15 or less, preferably 0.06 to 0.12.
[0044]
In the present invention, only one of the inner and outer reinforcing rubber layers 9 and 10 may be formed. In particular, the outer reinforcing rubber layer 9 is more stable in handling than the inner and outer reinforcing rubber layers 10. The improvement effect of is high and preferable. In addition, an inner liner rubber may be provided inside the carcass 6. In such a case, the reinforcing rubber layers 9 and 10 may be arranged inside the inner liner rubber or between the inner liner rubber and the carcass 6. It can also be placed in between.
[0045]
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.
[0046]
【Example】
A fuel-efficient tire with a tire size of 195 / 65R15 and the configuration shown in FIG. 1 is prototyped based on the specifications in Table 1, and the rolling resistance, steering stability, riding comfort, and road noise performance of each sample tire are measured. The results are shown in Table 1. The test conditions are as follows.
[0047]
(1) Rolling resistance Using a rolling resistance tester, rolling resistance was measured under the conditions of a rim (15 × 6JJ), internal pressure (200 kPA), and load (4 kN). The smaller the value, the less rolling resistance and the better.
[0048]
(2) Steering stability and riding comfort test tires are mounted on all wheels of a passenger vehicle (2000cc) under the conditions of rim (15 × 6JJ) and internal pressure (200kPA), and on the dry asphalt road surface of the test course. The vehicle was allowed to run, and the handling stability and ride comfort were evaluated by a 10-point method with the conventional example 6 based on the sensory evaluation of the driver. The larger the value, the better.
[0049]
(3) Road noise performance Using the passenger vehicle, a smooth road surface was run at a speed of 50 km / h, and the overall noise level dB (A) was measured at the left seat of the driver's seat.
[0050]
[Table 1]

[0051]
It can be confirmed that the tires of the examples can improve steering stability and road noise performance while maintaining low fuel consumption.
[0052]
【The invention's effect】
Since the present invention is configured as described above, it is possible to improve steering stability and road noise performance while minimizing the sacrifice of rolling resistance or achieving a slight reduction in rolling resistance.
[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 cross-sectional view showing an outer reinforcing rubber layer.
FIG. 3 is an enlarged sectional view showing an inner reinforcing rubber layer.
[Explanation of symbols]
2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 9 Reinforcing rubber layer 15, 15a, 15b in outer reinforcing rubber layer 10 Convex part K Maximum thickness point Ja Side wall upper reference line Jb Side wall lower reference line P tire maximum width point P1 separation point TE tread outer edge point Y tire maximum width region

Claims (5)

A pneumatic tire having a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion,
An inner side extending along the inner side of the carcass and extending outward in the radial direction from the tire maximum width region centered on the tire maximum width point or extending radially inward along the inner surface of the carcass. While providing a reinforcing rubber layer,
The reinforcing rubber layer is made of a rubber having a loss tangent (tan δ) of 0.1 or less and a rubber hardness of 50 degrees or more, and has a crescent cross section with a maximum thickness TM of 1.0 to 5.0 mm. The layer width W1 along the inner surface of this reinforced rubber layer is 70 mm or less ,
In addition, in the 5% internal pressure state, the contour shape of the carcass is a bent portion that is bent into a square shape and protrudes outward from the tire at the maximum thickness point K that is the apex forming the maximum thickness TM of the reinforcing rubber layer. a pneumatic tire characterized by having a.   2. The pneumatic tire according to claim 1, wherein the tire maximum width region is a region having a radial length Ly of 10 mm centered on the tire maximum width point. In the tire meridian cross section, the outer surface of the sidewall portion is
In the vicinity of the maximum thickness point of the outer reinforcing rubber layer, a convex portion protruding outward from the tire from the reference line on the sidewall formed by an arc passing through the tire maximum width point and the tread outer edge point is provided.
Alternatively, in the vicinity of the maximum thickness point of the inner reinforcing rubber layer, the outer surface of the bead portion protrudes outward from the sidewall lower reference line formed by an arc passing through a separation point where the bead portion is separated from the rim flange and the tire maximum width point. The pneumatic tire according to claim 1, further comprising a convex portion that performs the above operation. The pneumatic tire according to any one of claims 1 to 3, wherein a radius of curvature RA of the bent portion is not more than 0.1 times a radius of curvature RB of a portion adjacent to the bent portion. The tire lumen surface of the sidewall portion is smoothly curved to approximate an arcuate curve having a center on a tire axial line passing through the tire maximum width point P in the 5% internal pressure state. 4. The pneumatic tire according to any one of 4 above.

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