JP2556915B2 - Pneumatic tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pneumatic tire capable of reducing road noise during traveling.

[Conventional technology]

In recent years, high speed and high performance of vehicles have been required along with quietness during running. Therefore, tires mounted on vehicles are required to have low noise characteristics.

On the other hand, as noise caused by tires, in addition to pattern noise and skill noise, road noise caused by vibrations that are received from the road surface during driving are propagated to the tire rim through the bead portion while being vibrated at the tread portion and sidewall portion. In order to reduce this road noise, for example, soft rubber has been used for the tread portion or the cord angle has been changed to reduce the vibration itself from the road surface.

[Problems to be Solved by the Invention]

However, in such a conventional one, there is a problem that the wear life is shortened and the running performance is impaired.
Moreover, the road noise suppressing effect is not yet sufficiently satisfactory.

Therefore, the present inventors have made various studies on the mucanism of this transmission. As a result, the vibration is mainly transmitted to the rim by using the carcass as a medium. Therefore, by reducing the carcass tension around the bead portion, the vibration transmission coefficient of the carcass can be reduced and the road noise can be suppressed.
As shown in the figure, the carcass line of the carcass body portion B arranged along the inner side surface S1 of the bead portion A is moved to the central region between the inner side surface S1 of the bead portion and the outer side surface S2, whereby the carcass It has been found that the tension acting on the body B can be reduced.

This is because the bead portion A is curved and deformed along the flange R1 of the rim as shown in FIG. 3 when the tire is in contact with the ground, and at the side of the bead portion outer surface S2 which is the inside of the bending, the compression strain is also outside of the bending. Tensile strain acts on the inner surface S1 side of the bead portion.
Therefore, the tension can be reduced by shifting the carcass body portion B to the neutral side where the internal contraction and the tension are neutral, that is, to the central region side between the outer side surface S2 and the inner side surface S1.

That is, the present invention, the bead portion, by providing a rubber reinforcing layer extending radially outward along the inner surface of the carcass body portion, it is possible to shift the carcass line of the carcass body portion to the strain neutral side, An object of the present invention is to provide a pneumatic tire capable of reducing road noise by reducing tension and reducing its vibration transmission coefficient.

[Means for solving the problem]

In order to achieve the above-mentioned object, the pneumatic tire of the present invention has a carcass provided with a folded-back portion that folds back around the bead core at both ends of a main body portion from a tread portion to a sidewall portion through a sidewall portion to a bead core. A belt layer composed of at least two belt plies arranged radially outside of the carcass and inside the tread portion, and a bead apex arranged in a region surrounded by the main body portion and the folded portion of the carcass. Together with the bead portion, while providing a rubber reinforcing layer extending radially outward from the side portion of the bead core along the inner surface of the main body of the carcass facing the tire inner cavity, the rubber reinforcing layer has a JIS A hardness of 80. ≧ 100 ° and ≦ 100 °, the maximum thickness is ≧ 3 mm and ≦ 10 mm, and the height of the reinforcement layer is h1 which is the radial height from the bead bottom of the bead part. 0.4 to 1.00 times the maximum width point height H, which is the radial height from the bead bottom to the tire maximum width point of the sidewall portion, and the radial height of the bead apex from the bead bottom. A tire having a bead apex height h2 that is greater than the above, and in which the radially inner and outer portions of the central portion of the thick wall having the aforementioned maximum thickness are reduced inward and outward in the radial direction, respectively. It has a substantially crescent-shaped cross section that is convex inward in the axial direction.

[Action]

The bead portion of the pneumatic tire thus configured is provided with a rubber reinforcing layer having a predetermined rubber hardness, a maximum thickness and a height extending radially outward from the vicinity of the bead core, inside the carcass body portion. .

Therefore, the carcass has moved its carcass line relative to the thickness of the bead including the rubber reinforcing layer to the central region side, that is, the neutral side where the tensile strain and the compressive strain are neutral, and the bead at the ground contact. During the deformation, the tension acting on the main body of the carcass can be reduced. Further, due to the decrease in the tension, the vibration transmission coefficient of the carcass can be reduced, and the vibration excited by the sidewall portion can be prevented from propagating to the rim to reduce the road noise.

In addition, such a rubber reinforcing layer is 0.4 times or more of the maximum width point height of the tire from the region where the deformation occurs, that is, the bead portion, and
It is necessary to provide the height of 1.00 times or less in the extreme area.

In the present invention, the carcass line is moved relatively toward the center side relative to the bead thickness even when a rubber reinforcement layer is simply added inside the carcass of the conventional tire to increase the total bead thickness of the bead portion. As a result, the carcass tension can be reduced. It is also possible to reduce the thickness of the outer side of the carcass main body according to the rubber thickness of the rubber reinforcement layer to move the carcass line to the neutral side absolutely.In such a case, the total bead thickness of the bead part and its outer contour can be changed. It can be kept almost the same as a conventional tire.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

In the figure, a pneumatic tire 1 includes a pair of bead portions 3 and 3 through which a bead core 2 passes, sidewall portions 4 and 4 extending outward from each bead portion 3 in a radial direction, and a tread portion 5 connecting both ends thereof. Further, a carcass 6 is bridged between the bead portions 3 and 3, and a bead portion 3 is provided with a rubber reinforcing layer 9 extending radially outward along an inner surface of the carcass 6 facing the tire cavity 8. It is provided.

The carcass 6 has a toroidal main body portion extending from the tread portion 5 through the sidewall portion 4 to the bead portion 3.
6A has fold-back portions 6B that fold back around the bead core 2 from the inside to the outside, and a taper extending radially outward from the bead core 2 between the main body portion 6A and the fold-back portion, for example, JISA hardness. A bead apex 10 made of hard rubber of 60 ° to 90 ° is interposed to improve lateral rigidity of the tire.

The carcass 6 is formed from at least one carcass ply in a radial arrangement or a semi-radial arrangement in which the carcass cords are inclined at an angle of 65 to 90 ° with respect to the tire equator. An organic fiber cord using an aromatic polyamide or the like is preferably adopted.

A belt layer 7 is wound around the carcass 6 in the tire circumferential direction.

The belt layer 7 has at least two high-strength belt cords having a low elongation and a high elastic modulus such as steel fiber cords and aromatic polyamide fiber cords arranged at an angle of, for example, 35 degrees or less with respect to the tire equator. Is formed of two belt plies 7A and 7B. Further, the belt layer 7 has a maximum width of 0.8 times the tread width or more and reinforces the tread portion 5 over substantially the entire width with a hoop effect and enhances tire rigidity and tire running performance and steering stability. It has improved performance.

In the present invention, in order to reduce the tension acting on the body portion 6A of the carcass 6 when the bead is deformed, the bead portion 3
The rubber reinforcing layer 9 is disposed inside the carcass 6 facing the tire inner cavity 8.

The rubber reinforcing layer 9 has an inner portion extending radially inward and outward from the thick central portion 9A as shown in an enlarged view in FIG. 9B and an outer portion 9C are formed to have a substantially crescent-shaped cross section that is convex inward in the tire axial direction, and extends radially outward from the side portion of the bead core 2.

In this example, the bead portion 3 has a rubber thickness of the bead apex 10 in order to prevent the durability of the bead portion 3 from decreasing due to the volume of the bead portion 3 increasing due to the arrangement of the rubber reinforcing layer 9 and resulting increase in heat generation of the bead. By reducing the thickness, the increase in bead thickness is suppressed. Further, as a result, the main body portion 6A passes the bead portion 3 in this example through the central region within 20% of the bead thickness from the center C of the thickness thereof, and therefore absolutely shifts to the neutral side of strain at the time of bead deformation. The tension acting on the carcass 6 is reduced.

In order to prevent the bending rigidity of the bead portion 3 from decreasing due to the transition of the carcass line to the neutral side of strain and the reduction in the thickness of the bead apex 10, the rubber reinforcing layer 9 has a JIS A hardness of 80 ° or more and 100
It is made of hard rubber having a hardness of 3 ° or less, and its maximum thickness t is set to 3 mm or more and 10 mm or less.

If the JISA hardness is less than 80 °, the bending rigidity becomes insufficient, and as a result, the bead deformation amount increases and the tension of the carcass 6 substantially increases, while the tire running performance, steering stability, etc. decrease.

If the JISA hardness exceeds 100 °, it will be difficult to manufacture a tire, and the rigidity difference between the rubber reinforcing layer 9 and the surrounding rubber will be excessive, and rubber peeling will easily occur.

If the maximum thickness t is less than 3 mm, the amount of transition to the neutral side becomes small, the tension of the carcass 6 cannot be sufficiently reduced, and if it exceeds 10 mm, tire production becomes difficult.

It is necessary to form such a rubber reinforcing layer 9 in almost the entire area Q where bead deformation occurs. Therefore, the rubber reinforcing layer 9 has a reinforcing layer height h1 which is the radial height from the bead bottom. The maximum width point height H of the tire is 0.4 times or more and 1.0 times or less. The tire maximum width point height H is the height in the radial direction from the bead bottom of the tire maximum width point at which the tire extends most outward in the tire axial direction. If the tire maximum width point height H is less than 0.4 times, the effect of reducing the vibration transmission coefficient of the carcass 6 is inferior, and if it exceeds 1.0 times, on the contrary, vibration is easily transmitted through the rubber reinforcing layer 9 as a medium to reduce road noise. Along with the deterioration, the tire rigidity is excessively increased and the riding comfort is deteriorated.

Also, the bead apex height h2, which is the height in the radial direction of the bead apex 10, is preferably smaller than the reinforcing layer height h1, whereby the transition of the main body portion 6A to the neutral side over the region Q. Further, since the rubber reinforcing layer 9 has a substantially crescent-shaped cross section as described above, the concentration of strain and stress at the time of bead deformation can be relaxed and its durability can be improved.

In the present invention, the rubber reinforcing layer 9 may be formed without reducing the thickness of the bead apex 10. In such a case, the carcass line is relatively located on the strain neutral side with respect to the increasing bead thickness. Can move. It should be noted that the rubber reinforcing layer 9 may be provided with a reinforcing ply having a reinforcing cord on its inner surface. The applied tension can be further reduced.

〔Concrete example〕

A tire having a tire structure shown in FIG. 1 and having a tire size of 185 / 70R14 was prototyped based on the specifications in Table 1, and the road noise of the tire during actual running was compared with that of a conventional tire. The conventional tire has the bead structure shown in FIG. 4 and the contour shape thereof is substantially the same as that of the example product. The road noise is indicated by an index value with the conventional product as 100 when the road noise is evaluated at 50 km / h, and the higher the value, the better.

〔The invention's effect〕

As described above, since the pneumatic tire of the present invention is provided with the rubber reinforcing layer extending along the inner surface of the carcass in the bead portion, the carcass line can be shifted to the neutral side of strain, and the carcass tension is reduced to transmit its vibration. Road noise can be reduced by lowering the coefficient.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is an enlarged sectional view showing a bead portion, FIG. 3 is a diagram explaining bead deformation, and FIG. 4 is a sectional view showing a conventional technique. It is a figure. 2 ... bead core, 3 ... bead part, 4 ... sidewall part, 5 ... tread part, 6 ... carcass, 6A ... main body part, 6B ... folded part, 7 ... belt layer, 7A, 7B ...... Belt ply, 8 …… Tire lumen, 9 …… Rubber reinforcement layer.

Claims (1)

(57) [Claims] 1. A carcass having folding-back portions for folding back around the bead core at both ends of a main body from a tread portion to a bead core of a bead portion, and a carcass radially outside and inside the tread portion. A belt layer including at least two belt plies arranged, and a bead apex arranged in a region surrounded by the main body portion and the folded portion of the carcass, and the bead portion and the tire inner cavity. While providing a reinforcing layer extending radially outward from the side portion of the bead core along the inner surface of the body portion of the carcass facing, the rubber reinforcing layer has a JIS A hardness of 80 ° or more and 100 ° or less,
Moreover, the maximum thickness is 3 mm or more and 10 mm or less, and the reinforcing layer height h1 which is the radial height from the bead bottom of the bead portion is from the bead bottom to the tire maximum width point of the sidewall portion. It is 0.4 to 1.00 times the maximum width point height H which is the radial height, and is larger than the bead apex height h2 which is the radial height from the bead bottom of the bead apex, and the maximum thickness is The inner part and outer part of the center of the thick wall have a reduced thickness toward the inner side and the outer side in the radial direction, respectively. tire.