JPH02147415A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To obtain both driving stability and the prevention of one-side flow in the captioned tire for a car by quartering a tread on which longitudinal grooves are formed into left/right inside/outside zones in the width direction and forming inner lateral grooves which are inclined at a defined angle in the direction of outer cords on the inside zones while forming outer lateral grooves which are oppositely inclined while opening on tread ends on the outside zones. CONSTITUTION:A tread portion is divided into left/right inside zones CL, CR and left/right outside zones SL, SR while forming longitudinal grooves G1, G2 on each boundary. Inner lateral grooves Gc having an inclination angle of below 40 deg. to a tire axis in the same direction as that of outer belt cords 7a are formed on the inside zones CL, CR while being connected to the longitudinal grooves G1, G2. Outer lateral grooves Gs having an inclination angle of below 40 deg. in the direction opposite to the outer belt cords 7a are formed on the outside zones SL, SR while being opened to the longitudinal grooves G2 and tread end edges (a). By this structure, both driving stability and the prevention of one-side flow can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic radial tire, and particularly to a pneumatic radial tire that can be suitably used for passenger cars while maintaining handling stability.

[Conventional technology]

Radial tires, which can improve handling stability and ride comfort, are increasingly being used, but in order to improve the safety of vehicle driving, there is a need for tires that prevent vehicles from drifting in one direction and are excellent in straight-line driving performance.

Conventionally, the one-sided flow of a vehicle is thought to be caused by so-called conicity, which occurs when the circumferential length of the belt layer differs between the left and right sides of the tire axial direction in the trend section, resulting in a cone shape.
Therefore, various measures have been taken to improve the left and right uniformity of tires in the axial direction.On the other hand, with the progress of tire measurement technology in recent years, as revealed in Fig. 9, the tire traveling direction
When a minute slip angle α is applied to the tire, the cornering force generated in the tire lateral direction Y, that is, the lateral force F, and the self-lining torque SAT that rotates in the direction of the slip angle α around the vertical axis Z passing through the center of the tire. It became possible to measure with high precision.

Measurement results like 2 are, for example, as shown in Figure 10.
The self-lining torque SAT is plotted on the horizontal axis and the lateral force F is plotted on the vertical axis, which is shown using a curve K.

Another song &! In ilK, the slip angle α is 0 degree, +0.
The cases of 1 degree, -0, and 1 degree are indicated by .

Such self-lining torque SAT.

In relation to the lateral force F, there is a lateral force F of 1 at the intersection point where the curve K intersects with the vertical axis, that is, a self-lining torque SAT.
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 exerts 200% on the one-sided drift of the vehicle. If the residual CF of the vehicle is positive, that is, to the right, it means that the vehicle drifts to the right. To prevent this, 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 along with the deformation of the outermost belt bridle, and that the lateral force F is generated by this steer torque.

In this way, it was found that the residual CF is caused by the belt and 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 reducing the amount of belt cord and increasing the angle of inclination with respect to the tire equator direction, the hoop effect is reduced and, in particular, the cornering force exerted when turning is reduced, which impairs 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 one-sided vehicle flow performance.

Means for Solving the Problems] The present invention provides a carcass that passes from a tread portion through a sidewall portion and is folded back at a bead core of a bead portion, and a carcass disposed outside the carcass in the radial direction and inside the tread portion, a belt consisting of two or more belt plies with a steel belt cord tilted with respect to the tire equator, and at least two vertical grooves continuous in the tire equator direction are provided in the tread portion; In the tire axial direction, the left and right outer regions are divided into approximately four equal parts, the left and right inner regions on both sides of the tire equator, and the left and right outer regions reaching the edge of the tread portion on both sides of the left and right inner regions. The belt cord is inclined at an oblique angle of 40 degrees or less with respect to the direction, and is tilted in the opposite direction to the outer belt cord that is the belt cord of the outermost belt blazer, and at least one end thereof is opened at the edge of the tread portion or at the longitudinal groove. While the outer lateral grooves are spaced apart in the tire equator direction, the left and right inner regions are provided with 40 mm grooves in the tire axial direction.
A pneumatic radial tire having inner lateral grooves arranged in parallel in the tire equator direction, the inner lateral grooves having an inclination angle of less than 1.5 degrees and in the same direction as the outer belt cord, and opening at least one end in the longitudinal groove. In the ply, the belt cord driving product Nxs, which is the product of the total cross-sectional area S (IIIm2) of one belt cord and the number N of belt cords driven per 10 belt cords in the direction perpendicular to the belt cord, is 1.
It can be suitably used for pneumatic radial tires in which the angle of inclination of the belt cord with respect to the tire equator is 8.0 or more and 18 degrees or less with respect to the tire equator.

[Effect]

It is necessary to achieve both steering stability and one-sided vehicle flow performance (
As a result of various studies, the inventors of the present invention have found that the tread pattern of a tire causes a unidirectional flow of the vehicle.

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

The direction and inclination angle of this lateral groove are larger than the residual CF (
However, it has been found that the lateral grooves have a small contribution to the cornering performance of the tire, and therefore do not significantly affect the steering stability performance.

Moreover, the tread part is located in the left inner area C across the tire equator.
L, in the case where the right inner region CR, the left outer region SL outside of it, and the right outer region SR are divided into four equal parts, the left and right outer regions S (left outer region SL, right outer region SR (collectively referred to as the outer region S), the outer lateral grooves are arranged in the opposite direction to the outer belt cord, which is the belt cord of the outermost belt bridle, and at an inclination angle of 0 to 40 degrees with respect to the tire axial direction. Through tests, it was found that the residual CF was reduced.

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. In the figure, the outermost outer belt cord 7a is shown by a chain line. In FIG. 11(a), the outer lateral groove Gs is inclined in the same direction as the outer belt cord 7a. Further, in FIG. 11(b), the tire is provided in the axial direction of the tire, and in FIG. 11(C), it is provided in the opposite direction. Such a pattern SA, 5BSSC
As shown in FIG. 13, the residual CF in patterns SA, SB, and SC is -14.4 kg, -7.8 kg, and -3.6 kg, respectively, and the outer belt cord It can be seen that the residual CF of the pattern SC in which the outer lateral groove Gs having a different direction from 7a is provided is reduced. Therefore, in the present invention, the outer lateral groove G provided in the outer region S
s is different from the direction of the outer belt cord 7a, and is tilted within a range of 0 to 40 degrees with respect to the tire axial direction.

Further, in the inner region C (the left inner region CL and the right inner region CR are collectively referred to as the inner region C), the belt cord 7a is oriented in the same direction as the outer belt cord 7a and at an inclination angle of 40 degrees or less with respect to the tire axis direction. This is shown in Figure 12 (a).
~(C) shows the pattern CA in which the inner lateral groove Gc is inclined in the same direction as the outer belt cord 7a, the pattern CB in which it is inclined in the tire axial direction, and the residual CF in the case of a pattern ratio in which it is inclined in the opposite direction.
As shown in Figure 13, -5,9kg, -8,1k, respectively.
This is because the absolute value of the residual CF can be reduced by tilting it in the same direction as the outer belt cord 7a.

In this way, by tilting the outer belt cord 7a in the opposite direction in the outer region S and in the same direction as the outer belt cord 7a in the inner region C, the remaining C
F can be reduced and the one-sided flow performance of the vehicle can be improved.

Furthermore, such arrangement of the lateral grooves Gs and Gc results in a belt cord driving product NXS of 18. .

In addition, the oblique angle of the belt cord with respect to the tire equator is 18 degrees or less, and the belt can exhibit a strong hoop effect and can be suitably employed in a tire having a belt that can improve steering stability.

〔Example〕

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

In Figure 1.2, pneumatic radial tire l:yo,
From the tread part 2 to the sidewall part 3 and the door part 4
A carcass 6 folded back at a bead core 5, and a belt 7 disposed radially outside the carcass 6 and inside the tread portion 2.

The belt 7 is a belt braai 7A with two layers: inner and outer layers.

The outer belt cords 7a, which are the belt cords of the outermost, in this example, outer belt blazer 7B, are tilted oppositely to each other at an inclination angle β of 18 degrees or less with respect to the tire equator CO. In this example, in FIG. 2, the belt cord is tilted in the upper right direction with respect to the tire equator CO, and the belt cord is made of steel wires 7b twisted together, for example, 2+7X0.22, as illustrated in FIG. , lX5
X 0.23, I By setting the belt cord driving product N x S, which is the product of the number N of cords, to 18.0 or more, the hoop effect of the belt 7 is enhanced and the steering stability is improved.

The tread portion 2 virtually includes, in the tire axial direction, a left inner region CL, a right inner region CR, and a left outer region S on both sides in the tire equator direction 00, which reaches the end Iia of the tread portion outside of the left inner region CL.
L and right outer region SR, and the left and right outer regions S have an outer lateral groove Gs having an inclination angle θS of 40 degrees or less with respect to the tire axial direction and inclining in the opposite direction to the outer belt cord 7a. . Established. In addition, if the inclination angle θS of the outer lateral groove Gs is increased and the inclination angle θC is greater than 40 degrees, pattern noise is likely to occur. Therefore, the range is set as above.In this example, the left and right inner areas C1 and the left and right outer areas S
Vertical grooves G1 and G2 that are continuous in the tire equator direction are provided at intermediate positions between the tire axial direction CO that divides the tire axial direction CO and the tire equator CO and the edge a of the tread portion 2. Note that even if the iα groove G (generally referred to as longitudinal groove G) is a straight groove,
Alternatively, it may be a zigzag groove.

Further, the circumferential pitches Ps and Pc of the outer and inner lateral grooves Gs and Gc in the tire equator direction are both 40 mm or less,
Preferably, it is set to 20 mm or less.

The scales are tilted in the opposite direction to the outer belt cord 7a in the left and right outer regions S (by providing outer lateral grooves Gs and providing inner lateral grooves Gc in the same direction in the left and right inner regions C, the remaining CF is changed). is as described above.

It has been confirmed that the residual CF is further reduced by preferably setting the circumference and sauté Pc, Ps to 20 holes or less.

FIG. 3 shows an example of a pond in which the outer lateral groove Gs has an oblique angle θS of O.

Fig. 2.3 shows the case where vertical grooves G1 and G2 are provided in the portion that divides the inner region C5 and the outer region S, but as shown in Fig. 4, two ri! When using groove 02, G2,
Also, as shown in Fig. 5, one vertical groove G2A at equal intervals,
02B, and five garden grooves C1 and G2 as shown in Figure 6.
A, 2B>, the inner region C1 and the outer region S are divided by an imaginary line F on the rib apart from the a groove G, and at least one end of the inner lateral groove Gc is a joint groove. At least one end of the Manjushri lateral groove Os is opened at the edge a of the tread portion or at the joint groove G.

〔Concrete example〕

Tire size i75/70R13, 2.3
A prototype was manufactured according to the specifications shown in Figure 1 and Table 1, and the steering stability performance and residual CF were measured. As a comparative example, a sample having the pattern shown in FIG. 14 was similarly produced and compared. The results are also shown in Table 1.

The test was carried out with the rim 5JX13 installed and with an internal pressure of 2.0.
The residual CF was determined to be 111 using a flat trunk machine manufactured by MTS, USA, with kg/c4 and a load of 3'00 kg. Note that the residual CF is expressed by a residual CF index, with Comparative Example 1 being 100. The smaller the index, the residual C
This shows that F is small and preferable.

In addition, the handling stability performance is improved by installing it in a 2000 cc passenger car.
We conducted a feeling test using driving sounds and compared IX.
The higher the score is, the higher the score is, the better the score.

In both cases, the height measurements performed were superior to those of the comparative products, and in terms of steering stability performance, the tendency for one-sided drift was reduced, which seems to have improved the driver's feeling.

〔Effect of the invention〕

In this way, the present invention can be achieved without impairing steering stability.
The vehicle's one-sided flow performance can be improved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, FIG. 2 is a plan view showing other patterns in 2, FIG. 3 is a plan view illustrating a pond pattern, and FIGS. 4 to 6 are respectively showing other patterns. 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 residual CF, FIG. 10 is a line diagram thereof, and FIG. 11 (a)～(
C), Figures 12 (a) to (C) are plan views showing the patterns used in the experiments, Figure 13 is a diagram showing the experimental results,
FIG. 14 is a plan view showing a pattern of a comparative product. 2--Trend part, 3--Side wall part, 4
...Bead part, 5...Bead core, 6...-
Carcass, 7...-belt, 7A, 7B...-belt ply, 7a...-outer belt cord, C...-inner area, C
L...Left inner area, CR...Right inner area, G-
... Lateral groove, Gc--Inner lateral groove, Gs--Outer lateral groove, S...Outer area, SL...Left outer area, SR-
-Right outer area. Figure 1 Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Tadashi Naemura Figure 3 Figure ', 4j1 Otsu Figure Figure 10; 9 Zuho sAT Hiderei CF Figure 13 rA

Claims (1)

[Scope of Claims] 1. A carcass that passes from the tread portion through the sidewall portion and is folded back at the bead core of the bead portion, and a steel belt cord disposed on the outside of the carcass in the radial direction and inside of the tread portion. a belt consisting of two or more layers of belt plies tilted with respect to the tire equator, and at least two vertical grooves continuous in the tire equator direction are provided in the tread portion, and the tread portion is arranged in the tire axial direction. In the left and right outer regions, which are divided approximately into four, into left and right inner regions on both sides of the equator, and left and right outer regions reaching the edges of the tread portion on both sides of the left and right inner regions,
An outer lateral groove that is inclined in the opposite direction to the outer belt cord that is the belt cord of the outermost belt ply and has at least one end opening at the edge of the tread portion or the longitudinal groove in the tire equator direction. While the
Inner lateral grooves are provided in the left and right inner regions in parallel in the tire equator direction at an inclination angle of 40 degrees or less with respect to the tire axial direction, inclined in the same direction as the outer belt cord, and having at least one end opened with the longitudinal groove. A pneumatic radial tire. 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.