JPH08132830A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE: To enhance driving stability while uncomfortableness to drive caused by vibration is retarded by forming a thin constricted part on the inside in the diameter direction from the tire maximum width position in a rubber stiffener extending along a carcass, and extending with almost the crescent cross section toward the outside in the diameter direction over the tire maximum width. CONSTITUTION: A pair of beat cores 2, and a rubber stiflener 4 having a belt 4 in a crown part of carcass 3 locked to the beat core and toroidally extending, extending along the carcass arranged adjacent to the beat core are used. The rubber stiffener 4 has a thin constricted part 12 on the inside of the tire diameter from the tire maximum width position, has almost the crescent cross section toward the outside direction from the constricted part 12, and extends over a tire maximum width position 5. Since the rubber stiffener extends over the tire maximum width, deformation between the tire maximum width which causes large bending deformation when lateral force is applied to the tire in cornering and the belt edge is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire, particularly a tire for passenger cars and light trucks.

[0002]

2. Description of the Related Art Various proposals have been made as means for improving the steering stability of pneumatic radial tires (hereinafter abbreviated as "tires"), and one of them is a reinforcement for improving the rigidity of the bead portion. There is a suggestion of means. Specifically, the proposal is a bead core as shown in FIG.
Increase the volume of the rubber stiffener 10 that is located adjacent to 2 and extends along the carcass 3,
Use a rubber member with a high Young's modulus. Alternatively, it is a structure in which an organic fiber or steel cord layer is arranged as a reinforcing layer along the rubber stiffener.

[0003]

In the above-mentioned conventional proposal, although the rigidity of the bead portion can be certainly improved, the radial rigidity as well as the lateral rigidity and the circumferential rigidity of the bead rigidity is increased. As a result, the ride comfort of vibration tends to deteriorate. In addition, the cost was often increased due to the increase in the number of members.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to propose a tire having improved steering stability while suppressing deterioration of vibration riding comfort. Then, it is intended to achieve this object while suppressing an increase in members.

[0005]

That is, the inventor changed the cross-sectional shape of the rubber stiffener by changing the cross-sectional shape of the rubber stiffener on the assumption that the cross-sectional area of the rubber stiffener is substantially the same as the cross-sectional area of the conventional rubber stiffener. The present invention has been completed. The present invention provides a pair of bead cores, a carcass that extends in a toroidal shape across the bead cores, a belt at a crown portion of the carcass, and a rubber stiffener that is disposed adjacent to the bead cores and extends along the carcass. In the filled radial tire, the rubber stiffener has a thin constricted portion inside the tire radial direction from the tire maximum width position, and has a substantially crescent-shaped cross-sectional shape toward the tire radial outer side from the constricted portion. The pneumatic radial tire is characterized in that it extends beyond the maximum tire width position.

Here, the "constricted portion" means the "constricted portion".
The thickness of the rubber stiffener is less than half of the maximum thickness of the rubber stiffener. The rubber member used for the rubber stiffener may be a conventionally known one. However, it is preferable that the Young's modulus is larger than that of the rubber member used for the outer surface of the sidewall, which is bent and deformed when the load rolls from the belt end to the bead core.

Further, in the present invention, the rubber stiffener extends to the vicinity of the belt end, the rubber stiffener is composed of at least two kinds of rubber members having different Young's moduli, and the rubber stiffener located at the maximum tire width position has the highest Young's modulus. It is preferable that it is made of a small rubber member and that the constricted portion is made of a rubber member having the largest Young's modulus.

[0008]

In the case of the present invention, since the rubber stiffener extends beyond the maximum tire width position, the circumferential shear deformation of the sidewall is suppressed. That is, since the rigidity of the tire in the circumferential direction can be improved, the transmission of drive braking can be increased during straight traveling and during cornering.

On the other hand, since the rubber stiffener has a constricted portion inside the tire maximum width position in the tire radial direction, bending deformation can be easily performed, and the radial rigidity of the tire can be made equal to or lower than that of the conventional tire. That is, vibrations from unevenness on the road surface can be absorbed here.

Further, since the rubber stiffener has a substantially crescent-shaped cross section and extends beyond the maximum width of the tire toward the outer side in the tire radial direction from the constricted portion, conventionally, the lateral force at the time of cornering is the tire. It becomes difficult to deform between the maximum width of the tire and the belt end, which are greatly bent and deformed when the tire is loaded on the tire, and the lateral rigidity of the tire can be made equal to or higher than the conventional value. Therefore, the transmission of drive braking during cornering can be further increased in addition to the effect of improving the circumferential rigidity described above.

Further, from the viewpoint of improving the circumferential rigidity and lateral rigidity of the tire, it is preferable that the rubber stiffener extends to the vicinity of the belt end.

However, the rolling resistance of the tire having the rubber stiffener of the present invention may be deteriorated. This is because the deformation at the time of load rolling is the largest near the tire maximum width position, and if a rubber member with a large Young's modulus such as that used in a rubber stiffener is placed here, the energy required for this deformation becomes large. is there. Further, a rubber member having a large Young's modulus also generally has a large tan δ, which may also contribute to an increase in rolling resistance. Therefore, it is preferable that the rubber stiffener is made of at least two kinds of rubber members having different Young's moduli, and the rubber stiffener located at the tire maximum width position is made of a rubber member having the smallest Young's modulus.

Similarly, from the viewpoint of suppressing rolling resistance, the rubber stiffener is made of at least two kinds of rubber members having different Young's moduli, and the constricted portion located inside the tire maximum width position in the tire radial direction has the largest Young's modulus. It is preferable that the rubber member is made of a rubber member, and the rubber member having a small Young's modulus is formed on the outer side in the tire radial direction of the rubber member. The constricted portion is made of a rubber member having the largest Young's modulus in order to sufficiently improve the circumferential rigidity of the tire as described above.

[0014]

EXAMPLE A further explanation will be given based on the example of the present invention shown in FIG. This pneumatic radial tire 1 is size 1
95 / 65R16, a pair of bead cores 2 and a belt 4 at the crown portion of a carcass 3 that is anchored to and extends in a toroidal shape. A belt stiffener 10 is disposed adjacent to the bead cores and extends along the carcass. Have. The above-mentioned points will not be described in detail because they are conventionally known structures.

The present invention is characterized by the sectional shape of the rubber stiffener 10, and the rubber stiffener 10 has a narrowed portion 12 which is thinner in the tire radial direction inner side than the tire maximum width position 5. The maximum width position of the tire has a crescent-shaped cross section toward the tire radial direction outer side from the constricted portion 12.
It extends beyond 5. In the actually manufactured tire (Example 1), the rubber stiffener 10 was extended up to the vicinity of the belt end, more specifically, between the belt end and the carcass 3. Further, the thickness of the rubber stiffener 10 is maximized with the portion adjacent to the bead core 2 being 8 mm (Ta), the constricted portion 12 is 1 mm (T ₁₂ ), and the thickness is gradually increased from the constricted portion 12 toward the tire radial outside. After reaching 2 mm (T _b ) at the thickest portion, the thickness was gradually reduced again.
The position of the constricted portion 12 was located slightly outside the tire radial direction from the portion where the bending deformation of the tire was restrained by the rim flange when the tire was mounted on the rim. This point is
It can be inferred from the fact that the constricted portion 12 is involved in the reduction of the radial rigidity of the tire. In the first embodiment, the rubber stiffener 10 is made of the same rubber member. As this rubber member, one conventionally known as a rubber stiffener may be used, and a rubber member having a Young's modulus of 2.8 MPa is used here.

For comparison, the conventional example shown in FIG. 1 was also prototyped. The rubber stiffener 10 has a substantially triangular cross-sectional shape, and the tire radial outer end is located near the tire maximum width position 5. The same rubber member as in Example 1 is used,
The cross-sectional areas were also the same.

Regarding radial rigidity, lateral rigidity, and circumferential rigidity, the displacement amount and its displacement when radial, lateral, and rotational displacements are applied to the rim with the specified internal pressure filled after mounting on the specified rim. The force per unit displacement required to give Regarding this measurement result, the conventional example 10
When the result of Example 1 when 0 is shown as an index, the radial rigidity is 97, the lateral rigidity is 102, and the circumferential rigidity is 160.
Met. That is, while the radial rigidity is equal to or less than the conventional value, the lateral rigidity is equal to or more than the conventional value, and the circumferential rigidity can be improved. In particular, the circumferential rigidity was remarkably improved.

When these test examples were mounted on an actual vehicle and a sensory evaluation by a test driver when driving on a test course was conducted for steering stability, a conventional example of 100 was obtained.
In Example 1, the index was improved to 115. Similarly, a sensory evaluation was performed by a test driver when driving on a rough road surface where vibration is likely to occur, in terms of vibration riding comfort. In the index display with the conventional example being 100, Example 1 is 101. The effect of the present invention was confirmed.

As described above, in the case of the first embodiment, there is a fear that the rolling resistance may deteriorate. Therefore, it is preferable that the rubber stiffener 10 is composed of at least two types of rubber members having different Young's moduli. FIG. 3 shows an example thereof (Example 2). Example 2 is a rubber stiffener
10 is composed of three types of rubber members having different Young's moduli. In the trial production, the lower part of the rubber stiffener 14 has Young's modulus of 2.8 M
A rubber member of Pa, a rubber member having a Young's modulus of 1.4 MPa was used for the central portion 16 of the rubber stiffener, and a rubber member of 2.1 MPa was used for the upper portion 18 of the rubber stiffener. The rubber member having the smallest Young's modulus has a larger Young's modulus than the rubber member used for the outer surface of the sidewall 6. The constricted portion 12 is made of a rubber member having the largest Young's modulus, and the rubber stiffener located at the maximum tire width position is made of a rubber member having the smallest Young's modulus. Except for the points described above, the second embodiment is the same as the first embodiment, so the description thereof will be omitted.

For Examples 1 and 2 as described above, the tires were run at 150 km / h on a drum with the tires being mounted on a prescribed rim, filled with a prescribed internal pressure, and loaded with a load of 425 kgf. In this state, the drum was inertially rotated, the deceleration degree during the inertial rotation was measured, and the rolling resistance of each tire at 50 km / h was obtained. The result is that the index of Example 2 is 100 with that of Example 1 being 90 (the smaller the index, the better).
It is clear that Example 2 is superior to Example 1 in rolling resistance. The radial rigidity, the lateral rigidity, and the circumferential rigidity of Example 2 were measured by the same tests as above, and the results were 90, 100, and 130 in comparison with the conventional example, and the effect of the present invention is also in Example 2. Can be considered to play.

[0021]

As described above, according to the present invention, the steering stability can be improved while suppressing the deterioration of vibration riding comfort. Moreover, it can be achieved while suppressing an increase in the number of members.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a conventional tire. Since it is symmetrical, the right side is omitted.

FIG. 2 is a cross-sectional view of a tire according to the present invention. The right side is omitted as in FIG.

FIG. 3 is a cross-sectional view of another tire according to the present invention. FIG.
The right side is omitted as well.

[Explanation of symbols]

1 Pneumatic radial tire 2 Bead core 3 Carcass 4 Belt 5 Tire maximum width position 6 Sidewall 10 Rubber stiffener 12 Constriction part 14 Lower part of rubber stiffener 16 Upper part of rubber stiffener 18 Upper part of rubber stiffener T _a , T ₁₂ , T _b Rubber stiffener Thickness of

Claims (4)

[Claims] 1. A pair of bead cores, a carcass extending in a toroidal shape across the bead cores, a belt at a crown portion of the carcass, and a rubber stiffener disposed adjacent to the bead cores and extending along the carcass. In a pneumatic radial tire, the rubber stiffener has a thin constricted portion on the tire radial inner side than the tire maximum width portion, and a substantially crescent-shaped cross-sectional shape from the constricted portion toward the tire radial outer side. A pneumatic radial tire having and extending beyond the maximum tire width position. 2. The tire according to claim 1, wherein the rubber stiffener extends to the vicinity of the belt end. 3. The tire according to claim 1, wherein the rubber stiffener is made of at least two kinds of rubber members having different Young's moduli, and the rubber stiffener located at the maximum tire width position is made of a rubber member having the smallest Young's modulus. 4. The tire according to claim 1, wherein the rubber stiffener is made of at least two kinds of rubber members having different Young's moduli, and the constricted portion is made of a rubber member having the largest Young's modulus.