JPH10329511A - Pneumatic radial tyre - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the anti-noise performance in a car without increasing a tyre weight by arranging a strength distribution for the bending of a tread part most suitably, in a pneumatic radial tyre. SOLUTION: The cord angle of a belt layer 6 is made to 28 deg.-35 deg. for a tyre periphery direction. In rubber thickness L, M, N from treat surfaces at a point P1, point P2 and point P3 which are the position divided the distance from the center C of the tread 5 surface to a grounding end E into quarters up to the belt layer 6 or the reinforcement layer 7 on this belt layer, the rubber thickness M of the point P2 is made as a standard and the rubber thickness L of the point P1 is made to 0.7 M-0.8 M and the rubber thickness N of the point P3 is made to 1.2 M-1.3 M. Further, when the tread outer periphery at an air pressure 390 KPa is divided into four areas A1-A4 after dividing the read surface into quaters alike above, at least one of the first-third areas A1-A3 from the center C side is made to a shape having a reverse R part Ra whose carature center stays the outside of the tyre.

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 for a passenger car.

[0002]

2. Description of the Related Art As shown in FIG. 3, a pneumatic radial tire has a bead portion (53) having bead cores (52) on both sides and a radially outward portion from the bead portion (53). A carcass (51) having a sidewall portion (54) extending in the direction and a tread portion (55) connecting the upper end thereof, both ends of which are folded back by a bead core (52) along the inner periphery thereof, and a tread portion; (55) and carcass (5
1) and a belt layer (56) disposed therebetween, and a reinforcing layer (57) made of a fiber cord called an edge ply is disposed outside the belt layer if necessary.

In recent years, in such radial tires, weight reduction of tires has been promoted due to various factors such as demand for low cost and low fuel consumption.

[0004] On the other hand, the reduction in weight of the tire has a problem that the driving performance of the vehicle is reduced, the noise in the vehicle, and the abrasion of the tire is deteriorated. Among the in-vehicle noises, road noise when traveling on a rough road surface is particularly problematic. In addition, road noise has a problem in a vehicle in a frequency range of 200 Hz or more, which is generally called high frequency road noise. Therefore, it is required to solve these problems as well.

Conventionally, as a method for solving the above problems, vibration input is absorbed by softening the tread rubber and increasing the rubber thickness, and vibration transmission characteristics are improved by softening the rigidity of the tire case, or a cord is provided. It has been considered to increase the number of drivings to increase the out-of-plane bending rigidity.

In particular, it has been found that the most effective way to reduce the road noise is to increase the tread bending stiffness near both ends of the tire contact width as compared with the middle portion. A method of adding a reinforcing layer and the like have been proposed.

However, the method according to the above-mentioned conventional method leads to an increase in cost and weight, which is contrary to a reduction in tire weight. At the same time, the relationship between the tire characteristics and the in-vehicle noise performance (suppression performance) is unclear, so that much labor and man-hours were required to actually find an improvement effect.

The present invention has been made in view of the above, and relates to the relationship with tire characteristics by an FEM analysis method (finite analysis method).
As a result of repeated examinations, it was found that if the tire has a concave tread outer periphery (center is concave), the growth of the tread center part due to internal pressure filling is large, and the belt tension of the tread shoulder part becomes high. Focusing on this, the present invention provides a radial tire capable of improving the in-vehicle noise performance without increasing the tire weight by optimizing the distribution of the strength distribution with respect to bending of the tire tread portion.

[0009]

A pneumatic radial tire according to the present invention for solving the above-mentioned problems has a carcass whose both ends are folded back at a bead portion and which is supported between the tread portion and the carcass. A radial tire having a belt layer, wherein a cord angle of the belt layer is in a range of 28 ° to 35 ° with respect to a tire circumferential direction, and a width direction center (C) on a tread surface from a ground contact end (E). Are divided into four equal parts in order from the center (C) side
1/4 point (P1), 2/4 point (P2) and 3/4 point (P3)
When the rubber thickness from the tread surface to the belt layer or the reinforcing layer on the belt layer at each of the points (P1), (P2) and (P3) is (L), (M) and (N), respectively, The rubber thickness (L) at the quarter point (P1) and the rubber thickness (L) at the quarter point (P1) are referred to based on the rubber thickness (M) at the quarter point (P2).
The rubber thickness (N) at the point (P3) is L = 0.7M-0.8M N = 1.2M-1.3M, respectively, and the outer peripheral shape of the tread at an air pressure of 30 KPa is the same as described above. When the area is divided into four and divided into four areas (A1) to (A4), at least one of the first to third areas (A1) to (A3) is arranged from the center (C) side to the outside of the tire. It has an inverted radius portion having a center of curvature.

In the pneumatic radial tire according to the present invention, the profile of the outer periphery of the tread at an air pressure of 30 KPa has a concave shape at the air pressure of 30 KPa, and the rubber thickness of the tread shoulder portion is larger than that of the tread center portion. The cord angle of the layer is larger than before.

When the radial tire is mounted on a prescribed rim and filled with a prescribed internal pressure, the growth of the tread center portion becomes considerably larger than that of the tread shoulder portion, and therefore the belt tension of the tread shoulder portion increases. .

Therefore, the synergistic effect of the increase in the rubber thickness of the tread shoulder portion and the increase in the bending rigidity due to the increase in the belt tension at the time of filling the internal pressure significantly improves the noise performance in the vehicle. In addition, the out-of-plane bending stiffness of the tread shoulder portion is increased as compared with the tread center portion, the deformation of the tire shoulder portion where vibration is easily transmitted to the tire center axis (axle) is suppressed, and the vibration input to the tire due to unevenness of the road surface is reduced. .

In the present invention, the quarter points (P1), 2/4 points (P2) and 3/4 which divide the tread surface from the center (C) to the grounding end (E) into four equal parts. Point (P
3) When the difference between the rubber thicknesses (L), (M), and (N) is small, the weight increases, and when the difference between the rubber thicknesses (L), (M), and (N) is too large, the effect of suppressing noise in the vehicle is reduced. Will be unsatisfactory.

The cord angle (α) of the belt layer is 28
Angle smaller than °, for example, 20 ° to 25 ° as before
When the cord angle is in the range, the growth of the tread center portion is suppressed, and it is not possible to expect an increase in rigidity due to an increase in belt tension.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a half sectional view of a pneumatic radial tire according to the present invention.

The radial tire shown in FIG. 1 has a bead portion (3) having bead cores (2) on both sides, a sidewall portion (4) extending radially outward from the bead portion (3), and a tread portion connecting the upper end thereof. (5), and a carcass (1) supported along the inner periphery thereof with both ends folded by a bead core (2), and a belt layer (5) between the tread portion (5) and the carcass (1). The carcass (1), which has a reinforcing layer (7) made of a fiber cord called an edge ply on the outside thereof as necessary, is provided with a line at the center (C) of the tire in the width direction. And a cord arrangement layer arranged at an angle of 80 ° to 90 ° with respect to the tire circumferential direction along the line, and a fiber cord such as rayon, aramid, polyester, or a steel cord is used as the cord. The belt layer (6) is made of a cord arrangement layer in which steel cords and fiber cords having high tension are arranged in a predetermined angle direction. The reinforcing layer (7) has a cord arrangement at an angle of 0 to 10 ° with respect to the tire circumferential direction.

In such a radial tire, the cord angle of the belt layer (6), that is, the cord angle (α) with respect to the tire circumferential direction along the line of the center (C) in the width direction of the tire is defined as the cord angle of a conventional tire (normally). 20 ~
25 °) and slightly larger than 28 ° to 35 °.
Further, the number of cords (number of cords / 25 mm) is slightly reduced (usually 70 to 90% less) than the conventional tire. Thereby, the growth of the tread center portion is made larger than that of the tread shoulder portion.
From the viewpoint of such an effect, the cord angle (α) is 30
More preferably, the angle is in the range of ° to 35 °.

In the cross-sectional shape of the tire, the position on the surface of the tread portion (5) that divides the distance from the center (C) in the width direction to the grounding end (E) into four equal parts is set in order from the center (C) side. / 4 points (P1), 2/4 points (P2) and 3/4 points (P3), and the belt layer or reinforcement on the belt layer from the tread surface at these points (P1), (P2) and (P3). When the rubber thicknesses up to the layers are (L), (M) and (N), the rubber at the 1/4 point (P1) is based on the rubber thickness (M) at the 2/4 point (P2). The thickness (L) and the rubber thickness (N) at the 3/4 point (P3) are
L = 0.7M-0.8M N = 1.2M-1.3M, respectively.

Further, as a profile of the outer periphery of the tread at an air pressure of 30 KPa, when the tread surface is divided into four equal parts as described above and divided into four regions (A1) to (A4), the first to the first (from the center (C) side) At least one of the three regions (A1) to (A3) has a shape having an inverted radius portion (Ra) having a center of curvature outside the tire. As a result, the profile of the outer periphery of the tread at an air pressure of 30 KPa has a concave shape.

The inflection points from the inverted radius portion (Ra) to the normal radius portion are defined by the four regions (A1) to (A1).
4), so that the connection of the outer surface shape is made smooth.

The inverted round portion (Ra) includes first to third
Any of one or more of the regions (A1) to (A3) may be used. However, in practice, as shown in FIG. 1, the first region (A1) near the center (C) or the region An inverted radius portion (R) is formed continuously with the second region (A2).
It is particularly preferable to provide a) in order to form the concave shape.

In the radial tire having the above structure, the profile of the outer periphery of the tread at an air pressure of 30 KPa has a concave shape, the rubber thickness of the tread shoulder portion is larger than that of the tread center portion, and the belt layer (6) has a cord. The angle (α) is larger than before.

Therefore, in a state where this is mounted on the specified rim and the specified internal pressure is filled, the growth of the tread center portion is considerably larger than that of the tread shoulder.
The tension in the tread shoulder will increase.

Therefore, the synergistic effect of the increase in the rubber thickness of the tread shoulder portion and the increase in the flexural rigidity due to the increase in the belt tension at the time of filling the internal pressure increases the out-of-plane flexural rigidity of the tread shoulder portion, and the vibration is reduced by the tire center axis ( axle)
The deformation of the tire shoulder portion, which is easily transmitted to the vehicle, is suppressed, and the vibration input to the tire due to the unevenness of the road surface is reduced. Further, it is possible to improve the in-vehicle noise performance in a frequency range of 200 Hz or more while maintaining the tire weight after the weight reduction.

In order to confirm the above-mentioned effects, a tire having a cord angle of a belt layer and a rubber thickness of a tread portion within the range of the present invention and having an inverted radius portion (Example 1) was used.
Conventional general tire having no inverted radius portion (Comparative Example 1)
And tires (Comparative Examples 2 to 5) having an inverted radius portion but having at least one of the cord angle of the belt layer and the rubber thickness of the tread portion deviating from the scope of the present invention, the tire weight and the in-car sound were examined and compared.

However, the tires used in the tests were all one ply made of a polyester fiber cord with a carcass (1) of 1500 denier / 2 wires and the belt layer (6) was made of “2+
2 × 0.25 ”steel cord with two layers of belt, reinforcement layer (7) with one layer of edge ply (drive: 20/25 mm) with nylon cord, tire size 195 / 65R16 Was used.

With respect to the in-vehicle sound, a test tire was mounted on the vehicle, a real vehicle running test was performed at a speed of 60 km / h, and road noise around the front seat headrest portion in the vehicle was measured. The value is shown as an increase or decrease as a reference. The tire weight is indicated by an index with Comparative Example 1 being 100.

[0029]

[Table 1] As is clear from Table 1 above, in each of Comparative Examples 2 to 5, either one of the tire weight or the vehicle interior sound was deteriorated as compared with Comparative Example 1 of the conventional tire. In the case of the example tire, the in-vehicle sound could be reduced without increasing the tire weight.

[0030]

As described above, according to the pneumatic radial tire of the present invention, the tread shoulder has a synergistic effect of an increase in the rubber thickness of the tread shoulder portion and an increase in the flexural rigidity due to an increase in the belt tension at the time of filling the internal pressure. It increases the out-of-plane bending stiffness of the part, suppresses deformation of the tire shoulder part where vibration is easily transmitted to the tire center axis (axle), and reduces vibration input to the tire due to unevenness of the road surface. Further, it is possible to improve the in-vehicle noise performance in a frequency range of 200 Hz or more without increasing the tire weight.

[Brief description of the drawings]

FIG. 1 is a half sectional view of a tire showing one embodiment of the present invention.

FIG. 2 is a schematic development view showing a part of a structure of a carcass and a belt layer.

FIG. 3 is a half sectional view of a conventional tire.

[Explanation of symbols]

(1) Carcass (2) Bead core (3) Bead part (4) Sidewall part (5) Tread part (6) Belt layer (7) Reinforcement layer (C) Center in width direction (E) Grounding end (P1) (P2 ) (P3) The position from the center to the grounding end which is divided into four equal parts. (A1) (A2) (A3) (A4) The area divided into four parts

Claims (1)

[Claims] 1. A radial tire having a carcass whose both ends are folded back at a bead portion and supported, and a belt layer disposed between the tread portion and the carcass, wherein the cord angle of the belt layer is in the tire circumferential direction. 28 ° ~
Positions that divide the distance from the center (C) in the width direction to the grounding end (E) on the tread surface into four equal parts are 1/4 points (P1) and 2 (P1) in order from the center (C) side. / 4 point (P2) and 3/4 point (P3), and the rubber thickness from the tread surface to the belt layer or the reinforcing layer on the belt layer at each of these points (P1), (P2) and (P3) is ( L)
When (M) and (N) are used, the rubber thickness (L) at the 1/4 point (P1) and the 3/4 point (P) are based on the rubber thickness (M) at the 2/4 point (P2). P3) has a rubber thickness (N) of L = 0.7M to 0.8M and N = 1.2M to 1.3M, respectively. Dividing into four areas (A1)
When divided into (A4), the first (1) from the center (C) side
A pneumatic radial tire characterized in that at least one of the third regions (A1) to (A3) has an inverted radius portion having a center of curvature outside the tire.