JPH02151506A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To reduce residual CF and make maneuverability consist with the performance of preventing a vehicle from swerving to one side by dividing a tread portion into three portions of a center portion and outer portions, and defining blocks having a specific maximum length with lateral grooves. CONSTITUTION:A tire 1 is provided with a carcass 6 extending from a tread section 2 via a side wall section 3 to a bead section 4 where the carcass is turned back at a bead core 5 and with a belt 7 disposed radially outside the carcass 6 and inside the tread section 2. In the tread section 2 are formed a center portion M including the tire equatorial direction CO and an outer portion N extending to the tread edges (a). Diamond-shaped blocks B are formed with skew lateral grooves Gc in the center portion M. The maximum length L in the direction normal to the lateral groove Gc of the block B is set to be 10mm or less. At the positions where the center portion M and the outer portions N are equally divided to form three portions, a longitudinal continuous groove G is formed in the equatorial direction of the tire.

Description

[Detailed Description of the Invention] This Industrial Field of Application] The present invention provides a pneumatic radial tire, particularly for use in passenger cars, by improving straight running performance while maintaining steering stability and suppressing noise generation. The present invention relates to a pneumatic radial tire that can be suitably used.

[Conventional technology]

Radial tires, which can improve handling stability and ride comfort, are increasingly being used, while tires that prevent vehicles from drifting in one direction and are excellent in straight-line running performance are required to improve vehicle running safety.

Conventionally, the one-sided flow of a vehicle is thought to be caused by so-called conicity, in which the belt layer becomes cone-shaped due to differences in circumferential length of the belt layer on the left and right sides of the tread in the axial direction of the tire.
Therefore, various measures have been taken to improve the left and right uniformity of the tire in the axial direction.

On the other hand, with recent advances in tire measurement technology, as shown schematically in Figure 9, the cornering force generated in the tire lateral direction Y when a small slip angle α is applied to the tire traveling direction X, It has become possible to measure with high precision the force F and the self-lining torque SAT that rotates in the direction of the slip angle α around the vertical axis 2 passing through the center of the tire.

Such measurement results are, for example, as shown in Fig. 10.
It is shown using a curve K with the self-lining torque SAT on the horizontal axis and the lateral force F on the vertical axis. Further, in the curve K, the cases where the slip angle α is 0 degrees, +0, 1 degree, -0, and 1 degree are indicated by .

Such self-lining torque SAT.

In relation to the lateral force F, a lateral force F1 of 1, that is, a self-lining torque SAT, is generated at the intersection point where the curve K intersects with the vertical axis.
The lateral force F when no lateral force F is generated is called the residual CF, and it has been found that this residual CF is a tire characteristic that affects the one-sided flow of the vehicle. In other words, when this residual CF is in a positive direction, that is, to the right, it means that the vehicle drifts to the right.The direction and size of the residual CF are used to evaluate the vehicle's unilateral drift, and to prevent the vehicle from drifting in one direction. In order to do so, it is necessary to reduce this residual CF.

This residual CF is caused by the expansion and contraction of the belt within the ground contact area, and the belt to the radial tire arranged in the cross ply undergoes in-plane shear deformation such that the cord moves in parallel due to expansion and contraction. It is thought that the tread rubber generates steer torque due to in-plane shearing deformation that occurs with the deformation of the outermost belt ply, and that the lateral force F is generated by this steer torque.

In this way, it has been found that the residual CF is caused by the belt and also depends on the amount of steel cord in the belt and the angle of the belt cord.

Therefore, it can be assumed that the residual CF can be suppressed by reducing the amount of cord and increasing the angle of inclination of the belt cord with respect to the tire equator direction to reduce the hoop effect.

[Problem to be solved by the invention]

However, when the belt cord amount is reduced and the inclination angle with respect to the tire equator direction is increased in this way, the hoop effect is reduced, and especially the cornering force during turning is reduced, thereby impairing steering stability.

An object of the present invention is to provide a pneumatic radial tire that can reduce residual CF without impairing handling stability and can achieve both handling stability performance and unidirectional vehicle drift prevention performance.

[Means to solve the problem]

The present invention provides a carcass that passes from a tread part through a sidewall part and is folded back at a bead core in a bead part, and a steel belt cord that is disposed radially outside the carcass and inside the tread part and directed toward the tire equator. a belt consisting of two or more layers of belt plies tilted at a tilt angle, and the tread portion is provided with longitudinal grooves connecting at least two tires in the equator direction, and the tread portion is arranged in a central region including the tire equator in the axial direction of the tire. and an outer region extending to the edge of the tread portion on both sides of the central region, and the central region is divided into approximately three equal parts, and the blocks are spaced apart in the tire equator direction and separated by lateral grooves extending in a direction crossing the tire equator. are arranged in parallel, and ``the block has a maximum length of 10 mm or less in the direction perpendicular to the lateral groove, and in particular, the belt ply is
Belt cord driving product N× which is the product of the total cross-sectional area 5 (an”) of one belt cord and the number S of driving belt cords per 10 cm in the direction perpendicular to the belt cord
It can be suitably used for pneumatic radial tires in which S is 18.0 or more and the angle of inclination of the belt cord with respect to the tire equator is 18 degrees or less.

Two Effects] In order to achieve both AM stability performance and unidirectional vehicle flow performance, the present inventors have conducted various studies and found that the tire tread pattern affects the unidirectional vehicle flow performance.

In pneumatic radial tires for passenger cars, a so-called rib pattern is used, which has a plurality of straight or zigzag longitudinal grooves extending in the circumferential direction, and the ribs are provided with lateral grooves that intersect with the tire equator direction. ,
They form a row of blocks.

It was found that the direction and inclination angle of this lateral groove greatly influenced the residual CF.

For example, as shown in FIG. 11(a), the tread portion is
The left inner region CL, the right inner region CR across the tire equator,
In the case where the outer left outer area SL and the right outer area SR are divided into approximately four equal parts, the left and right outer area S (the left inner area CL
, the right inner region CR and the right inner region CR are collectively referred to as the outer region S). It was found through tests that the residual CF was reduced by arranging it at an inclination angle of .

For this test, tires with different directions of the outer lateral grooves Gs in the outer region S shown in FIGS. 11(a) to 11(C) were manufactured as prototypes. As shown in FIG. 11(a), the outermost outer belt cord 7a is indicated by a dashed line.
is inclined in the same direction as the outer belt cord 7a. In addition, Fig. 11(b) is provided in the tire axial direction, and Fig. 11(C)
is set in the opposite direction. Such patterns SA, SB
As shown in FIG. 12, the results of measuring the residual CF applied to the patterns SA, SB, and SC are as follows.
F is -14.4kg, -7.8kg, -3.6k respectively
g, it can be seen that the residual CF of the pattern SC in which the outer lateral groove Os is provided in a direction different from that of the outer belt cord 7a is reduced.

As described above, by providing the lateral groove Gs in the outer region S in a direction different from that of the outer belt cord 7a, the residual CF can be reduced, and as the inclination angle Cs is increased, the residual CF
can be reduced.

However, it has been found that when the inclination angle θ3 is increased around 1, on the other hand, the noise generated from the tread pattern increases. Therefore, when emphasis is placed on noise characteristics, the inclination angle θS of the other lateral grooves Gs is limited.

Therefore, as a result of further research on suppressing this residual CF, we found that the central region M
of the block B formed by the horizontal groove Gc provided in the
As shown in FIG. 4, the results of measuring the residual CF by changing the maximum length in the direction perpendicular to the lateral groove Gc, the residual CF can be reduced by sequentially decreasing the maximum length. found. Furthermore, by setting the maximum length to 10 mm or less, the residual CF can be kept to 5 kg or less in absolute value, and therefore, the maximum length of block B in the central area M is set to 10 plates or less. .

This makes it possible to improve straight running stability without impairing steering stability or noise characteristics.

Furthermore, the belt cord is the product of the total cross-sectional area 5 (ru+") of the belt cord and the number of wires driven per 10 cm in the direction perpendicular to the belt cord. It can be suitably adopted for tires having a driving volume N×S of 18.0 or more and an inclination angle of the belt cord with respect to the tire equator of 18 degrees or less, which can exhibit a strong hoop effect and improve steering stability. .

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

In FIG. 1.2, the pneumatic radial tire 1 includes a carcass 6 which passes from the trend part 2 through the sidewall part 3 and is folded back at the bead core 5 of the bead part 4, and a carcass 6 which is located on the outside in the radial direction of the carcass 60 and on the tread part 2. It has a belt placed on the inside.

The belt 7 is made up of two layers of belt plies 7A and 7B, an inner and outer layer, and the belt cords are arranged oppositely to each other at an inclination angle β of 18 degrees or less with respect to the tire equator CO. In this example, the outer belt cord 7a, which is the belt cord of the outer belt ply 7B, is shown in FIG.
Move the tire 1 circle in the upper right direction relative to the equator CO. In addition, the belt cord is made of steel wire 7 as shown in FIG.
Twist b together, for example 2〒7x0.22, lX, 5
If wires such as Belt cord driving product N
By setting S to 18.0 or more, the hoop effect of the belt 7 is enhanced and the steering stability is improved.

The tread portion 2 is virtually divided in the tire axial direction into a central region M including the tire equator direction CO, and an outer region N extending outside of the center region to the edge a of the tread portion. In the region N, an outer lateral groove Cs-. extending in the tire axial direction, that is, with an oblique angle θn around 1 O, is provided in the tire equator direction, and in the central region M, an outer lateral groove Cs-. An inner lateral groove Gc is provided which is inclined at an angle θm of 45 degrees or less. In this example, the inner lateral groove Gc has a width of 0.5 to 3 m.
The lateral grooves GC, which are small grooves of about m in diameter and within the core, intersect in opposite directions at about 40 degrees with respect to the tire axis direction to form a groove, so that a diagonal lattice-like groove is formed in the central region M. A large number of diamond-shaped blocks B-- are formed.

Further, the maximum length of the block B in the direction perpendicular to the lateral groove Gc is approximately 10 mm or less.

Furthermore, in this example, vertical grooves G, G that are continuous in the tire equator direction are provided at approximately three equal positions dividing the central region M and the outer region N. Note that the vertical groove G may be a straight groove or a zigzag groove.

Further, the circumferential pitch Ps, which is the interval between the outer lateral grooves Crs in the tire equator direction, is set to 40 mm or less, preferably 20 Wn or less.

By making the length of the block B in the central region M in the perpendicular direction of the inner lateral groove Gc to 10 mm or less, pattern noise is suppressed by providing an outer lateral groove Gs extending in the tire axial direction in the outer region N. As mentioned above, the residual CF can sometimes be lowered.

However, the outer lateral groove Gs is not limited to this, and as shown in FIG. It can also be tilted in the tire axial direction at an angle θn of preferably 5 degrees or less.

In addition, although Fig. 2.3 shows the case where vertical grooves G are provided in the portions that divide the central region M and the outer region N, as shown in Fig. 5, three vertical grooves G1, G2, and G2 are provided. In addition, as shown in FIG.
It will be divided by an imaginary line F on the rib that is far away from . The inner horizontal groove Gc is also not lattice-like (Fig. 5.6-
As shown in FIG. 2, the grooves can be formed parallel to the tire axial direction or grooves that do not intersect with each other.

〔Concrete example〕

Tires of tire size 175/70 R13 with different block lengths were manufactured according to the specifications shown in FIG. 2 and Table 1, and the steering stability, residual CF, and noise characteristics were measured. The results are also shown in Table 1. In addition, the test was installed on the rim 5JX13 and the internal pressure was 2-0 kg/
cffl and a load of 300 kg, the residual CF was measured using a flat track machine manufactured by MTS, USA. In addition, in the table, the residual CF is indicated by the residual CF index expressed as an index with Comparative Example 1 as 100, and the smaller the value, the more
This means that the residual CF is small, which is preferable. In addition, the steering stability performance and noise characteristics were evaluated by installing the product in a 2000 cc passenger car and conducting a feeling test with the driver, with the comparative example being rated 100. The higher the score, the better. Furthermore, the noise characteristics are similarly displayed using a feeling test to determine the degree of harshness felt by the driver.

Note that the larger the value, the worse the noise characteristics.

In all cases, the actual product was superior to the comparative product, and in terms of steering stability performance, it is thought that the driver's feeling was improved because the number of one-way and one-way drifts was reduced.

C. Effects of the Invention] As described above, the present invention provides the following advantages without impairing steering stability performance:
The vehicle's one-sided flow performance can be improved.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an embodiment of the present invention, Fig. 2 is a plan view showing an external pattern, Fig. 3 is a plan view illustrating a pond pattern, and Fig. 4 is a line showing an example of a test. Figure 5.
6 is a plan view showing other patterns, FIG. 7 is a sectional view of the belt ply, FIG. 8 is a sectional view illustrating the belt cord, FIG. 9 is a perspective view illustrating the remaining CF, and FIG.
The figure shows the line section, FIGS. 11(a) to 11(c) are plan views showing the patterns used in the experiment, and FIG. 12 is a line diagram illustrating the test results. 2- Tread portion, 3- Sidewall portion, 4
-・Bead part, 5-bead core, 6-carcass,
7-・Belt, 7A, 7B・・・Belt ply, 7a・・Outer belt cord, Gc・・Inner horizontal groove, M・・Central area, G・・・・Horizontal groove, Gs‐・・・Outer transverse groove, N.--Outer area. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Tadashi Naemura 1 Figure 30-

Claims (1)

[Scope of Claims] 1. A carcass that passes from the tread portion to the sidewall portion and is folded back at the bead core of the bead portion, and a steel belt cord that is disposed on the outside of the carcass in the radial direction and inside the tread portion of the tire. a belt consisting of two or more belt plies inclined with respect to the equator, and at least two vertical grooves continuous in the tire equator direction are provided in the tread portion, and the tread portion is provided with the tire equator in the tire axial direction. The central region is divided into approximately three equal parts, a central region including the central region, and an outer region extending to the edge of the tread portion on both sides of the central region, and separated by lateral grooves spaced apart in the direction of the tire equator and extending in a direction intersecting the tire equator. In addition to placing the blocks in parallel,
The block has a maximum length of 10 in the direction perpendicular to the horizontal groove.
A pneumatic radial tire with a diameter of less than mm. 2 The belt ply has a total cross-sectional area S (mm^2) of one belt cord and 10 mm in the direction perpendicular to the belt cord.
Claim 1 characterized in that the belt cord driving product N×S, which is the product of the belt cord driving number N per cm, is 18.0 or more, and the inclination angle of the belt cord with respect to the tire equator is 18 degrees or less. Pneumatic radial tires listed.