JPH01278802A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To make it possible to shift the cornering power to a low load side area of a pneumatic tire for a front-engine/front drive vehicle by providing a belt cover member in the crown center section of the tire so as to reinforce the latter section in order to make the strength thereof greater than that of the shoulder section. CONSTITUTION:A cover member 2 is superposed on a belt layer 1 in the center section of a tire to reinforce the center section so as make the strength of the center section greater than that of the shoulder section. The cover member 2 may covers the crown alone or including the shoulder section as shown in the drawings. Further, the ground contact area of the tire is formed in a rectangular shape. With this arrangement, the load dependency of the C. P. (cornering power) is made to be flat, thereby it is possible to shift the C. P. toward a low load side area.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a pneumatic tire with improved handling stability, particularly to a pneumatic tire for front-wheel drive vehicles.

[Conventional technology]

In recent years, demand for front-wheel drive vehicles has been increasing due to their light weight and large living space.

The tire characteristics of the above-mentioned front-wheel drive vehicle tires from the perspective of handling stability are that the load dependence (CP-load curve) of cornering power (hereinafter abbreviated as CP) is flatter, and that the level of CP is High stability and self-aligning torque stability (S
AT-3) is desired to be large.

However, in order to flatten the load dependence of CP in the above tire, that is, to shift CP to a low load range, it is possible to reduce the belt bending rigidity of the tire or reduce the side part rigidity. On the other hand, the CP level decreases. On the other hand, if the rigidity of the tread section is increased, for example by increasing the hardness of the tread rubber or the rigidity of the blocks, the CP level will increase and it will be possible to shift to a lower load range, but the comfort performance such as noise and vibration will deteriorate. There was a problem.

The above CP can generally be expressed as a function of the belt section rigidity (El), side section rigidity (k), and ground contact length (J), that is, the following equation.

CPoc+f (El・k, 6) Conventional tires usually have a ground contact length β at the center of the tire crown, as shown in FIG. It has an elliptical ground contact pattern in which the ground contact length 1fik on the shoulder side is the longest and the ground contact length 1fik on the shoulder side is the shortest, and β in the above equation is often represented by the ground contact length lc at the center of the crown. However, the ground contact patterns of such tires are not necessarily the same, so depending on the ground contact pattern, the ground contact length at the center of the tire crown!
! . In many cases, the relationship represented by the above equation was no longer recognized as having any particular technical significance.

The present inventor has determined that not only the ground contact length lc of a part of the tire center but also the ground contact length 1 of the shoulder part. We have focused on the desirability of considering the total ground contact length including the ground contact length, and have conducted extensive studies to discover the present invention.

[Purpose of the invention]

An object of the present invention is to provide a pneumatic tire, particularly for front-wheel drive vehicles, which can flatten the load dependence of CP and shift CP to a low load range without lowering the CP level or deteriorating occupant comfort. To provide a pneumatic tire for use.

[Structure of the invention]

In the tire of the present invention, a cover material made of an organic fiber cord is provided at the crown center of the tire, and the tire has a ground contact length 1c at the crown center and a ground contact length l at the shoulder side. It has a substantially rectangular ground contact pattern (hereinafter simply referred to as a rectangle) whose long sides are parallel to the tire width direction.

A feature of the present invention is that a cover material made of organic fiber cord is provided at the crown center portion of the tire so that the ground contact pattern of the tire approaches a rectangular shape as shown in FIG. If the ground contact pattern of this tire is made closer to a rectangular shape, for example, within a range where the load applied to the tire is small, the trend (radius) will be made flatter, thereby reducing the contact length of the shoulder part relative to the center part. Can be made smaller. As a result, the total ground contact length increases and the rigidity of the trend section increases, making it possible to increase the CP.

In other words, in the case of a tire with a rectangular ground contact pattern according to the present invention, the ground contact length lc of a part of the center thereof is 1! of a tire with a conventional oval ground contact pattern. , even if it is shorter than
The "fib" in the shoulder portion of the tire is long and the total ground contact length is large, resulting in a thicker tire tread rigidity and CP level.

The tire of the present invention having such a rectangular (rectangular) ground contact pattern can be obtained by reinforcing the center part of the tire more strongly than the shoulder part. Add more than the shoulder area.

■ Increase the number of ends of the belt cover material at the center of the tire than at the tire shoulder.

■ One possibility is to make the intermediate elongation of the belt cover material in the center of the tire smaller than that of each tire shoulder.

Among these, method (1) is industrially the simplest and easy to implement.

FIGS. 3a to 3d are schematic cross-sectional views of a tread portion showing a specific example of such a tire in which the center portion of the tire is reinforced and strengthened more than the shoulder portion thereof.

Among these figures, FIG. 3a shows a belt cover material 2 provided only on the crown center portion of the belt layer 1, and FIG. A cover material 3 is sequentially laminated to cover both the center part and the shoulder part at the same time,
In the same figure C, one covering material of 2.2° each covers only the shoulder area and two covering materials of 3.3° that cover only the crown center area are laminated and arranged, and in the same figure d shows a belt. One cover material 4 on the top of layer 1 that covers both the crown center part and shoulder part at the same time.
, and on top of that, 1 each covering only both shoulders.
This is a tire in which two pieces of cover material 2.2' and two pieces of cover material 3.3' that cover only the crown center portion are laminated.

However, the cover material is not particularly limited.
A screen-like fabric made of various organic fiber cords can be used, but preferably a fabric made of polyamide fibers, especially nylon cords.

〔Example〕

Hereinafter, the effects of the tire of the present invention will be explained in more detail with reference to Examples.

Examples and Comparative Examples The tire of the present invention shown in FIG. The following cornering test was conducted on a comparative tire having a belt portion on which the cover material 2 was not laminated, and the results shown in FIG. 4 were obtained.

CP is the average value of the lateral force generated on the test tire when a slip angle of ±1" is applied to the test tire loaded on a steel drum with a diameter of 2.5 m.

Speed: 10m/hour, tire pressure: 1.9 Kgf/
cm! After starting the test with an initial load of 100Kgf, the load was increased in 6 steps by 100Kgf, and then 700Kgf was applied.
The load was measured up to Kgf, and the CP for each load was plotted to create the load-CP curve diagram in Figure 4.

In FIG. 4, the solid line indicates the tire of the present invention, and the dotted line indicates the comparative tire. From the figure, the tire of the present invention has a larger CP in the low load region than the comparative tire, and the entire curve is flat.

〔Effect of the invention〕

The pneumatic tire of the present invention is a tire that can shift CP to a low load range without reducing the CP level, and can improve the steering stability of FF vehicles under low load conditions, especially under low load conditions. can.

Selfa Lining Torque Stiffness (SAT-3
), the steering performance is excellent, and the increase in protrusion impact force is small, resulting in good riding comfort.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the ground contact shape of the pneumatic tire of the present invention, FIG. 2 is a plan view showing the ground contact shape of a conventional tire,
FIG. 3 is a schematic cross-sectional view showing the laminated structure of the belt portion provided with the belt cover material of the tire of the present invention, and FIG. 4 is a curve diagram showing the load-cp amount relationship of the tire of the present invention and the comparative tire. 1... Belt layer, 2.3.4... Cover material, 2c.
...Center part ground contact length, 1. ...shoulder ground contact length. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Scope of Claims] 1) A pneumatic tire having a belt cover material provided at the crown center portion of the tire, the crown center portion having stronger reinforcement than the shoulder portion of the tire. 2) The pneumatic tire according to claim 1, wherein the tire has a substantially rectangular ground contact pattern.