JPH06344706A - Combined front and rear tire for passenger car - Google Patents

Abstract

PURPOSE:To enhance the dry as well as wet performance of combined front and rear radial tires by specifying the width of the belt reinforcing layer of each of the front and rear tires relative to that of a belt layer, the front tire being broader than the rear tire. CONSTITUTION:In combined front and rear tires installed in a high-performance passenger car, the front tire being broader than the rear tire, each of which is an oblate pneumatic radial tire having a belt layer 7 both of the shoulder portions of which are covered with right and left independent belt reinforcing layers 9, the width of the belt reinforcing layer 9 of the front tire is set to 20% or more, preferably 22 to 30% of that of the belt layer 7, and the width of the belt reinforcing layer 9 of the rear tire is set to less than 20%, preferably 10 to 18% of that of the belt layer 7. Thereby the shoulder portions of the rear tire have reduced rigidity which enhances the grounding property of the tread during cornering on a wet road surface thus enhancing the wet performance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combination tire in which a rear wheel is provided with a radial tire having a width wider than that of a front wheel, and stability in dry road running (hereinafter, referred to as dry performance) as well as in wet road cornering. The present invention relates to a front / rear wheel combination tire for a passenger vehicle (hereinafter referred to as a combined tire) capable of improving a marginal performance (hereinafter referred to as a wet performance).

[0002]

2. Description of the Related Art Generally, flat radial tires are mounted on high-performance passenger cars, but recent high-performance passenger cars have wider and wider rear tires than front tires in order to improve stability at high speeds. A combination of tires is used. Further, in this way, the pneumatic radial tire used for high-speed traveling is covered with a belt reinforcing layer at least at the shoulder portion of the belt layer in order to prevent lifting of both ends of the belt layer due to centrifugal force during high-speed traveling. The structure is such that the rigidity of the shoulder portion is increased.

[0003] As described above, in a tire having a belt reinforcing layer whose rigidity is increased at the shoulder portion, the wider the tire is, the more improved the stability during running on a dry road surface, but when cornering on a wet road surface, the rigidity of the shoulder portion is improved. Since it is difficult to be deformed to a high degree, there is a problem that the ground contact property is deteriorated and the skid easily occurs, and the maximum speed (limit performance) at which the vehicle can travel is reduced while preventing the skid.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a front / rear wheel combination tire for a passenger vehicle having improved dry performance and wet performance.

[0005]

The tire of the present invention that achieves the above object is a pneumatic radial tire in which the front tire and the rear tire cover both shoulder portions of the belt layer with left and right independent belt reinforcing layers, respectively. In a combined tire for front and rear wheels for a passenger vehicle, in which the rear wheel tire has a tire size wider than the front tire, the width of the belt reinforcing layer of the front tire is 20% or more of the width of the belt layer, and the rear tire is The width of the belt reinforcing layer is less than 20% of the width of the belt layer.

When the front tire is combined with the wide rear tire as described above, the width of the belt reinforcing layer at both end portions of the belt layer of the front tire is 20% or more of the belt layer, whereas the belt of the rear tire is By reducing the width of the reinforcing layer to less than 20% to reduce the rigidity of the shoulder portion, it is possible to improve the ground contact state of the tread during cornering on wet road surfaces and improve the limit performance.

The present invention will be described in detail below with reference to the drawings. FIG. 1 shows a rear tire of a combination tire according to an embodiment of the present invention, and FIG. 2 shows a front tire. All of them are flat tires having an aspect ratio of 55% or less, and the tire cross-section width WTr of the rear wheel tire Tr is W that of the front wheel tire Tf.
The width is wider than Tf (WTr> WTf).

As shown in FIGS. 1 and 2, front tire Tf
The rear tire Tr and the rear tire Tr are both folded from the inside of the tire to the outside so that the carcass layer 3 extends from the tread 1 over the left and right sidewall portions 2 and wraps the bead filler 4 around the bead core 5. There is. Also,
On the tread 1 of the carcass layer 3, two belt layers 7 are annularly arranged so as to intersect each other at a cord angle of 5 to 35 ° with respect to the tire circumferential direction. Belt layer 7
In addition to the two belt reinforcing layers 8 that cover the entire width of the belt, an annular belt reinforcing layer 9 that covers the shoulder portion of the belt layer 7 is further arranged. Each of these belt reinforcing layers 8 and 9 is arranged at a cord angle of substantially 0 ° with respect to the tire circumferential direction.

In the present invention, front and rear tires Tf, Tr
Have the same tire configuration as described above, but are different from each other in the points described below. That is, the front tire Tf
2, the width CWf of the belt reinforcing layer 9 is 20% or more of the width BWf of the belt layer 7, preferably 22 to 30.
%. On the other hand, in the rear wheel tire Tr, the width CWr of the belt reinforcing layer 9 is smaller than 20% of the width BWr of the belt layer 7, preferably 10 to 18%, as shown in FIG. More preferably, the width CWr of the belt reinforcing layer of the rear wheel tire Tr should be smaller than that CWf of the front wheel tire Tf.

In the present invention, in order to improve the limit performance during cornering on wet roads, it is important that the width of the belt reinforcing layer covering the shoulder portion of the belt layer is narrowed as described above to lower the rigidity of the shoulder portion. However, even if the rigidity of the belt layer central region is reduced by reducing the density of the belt reinforcing layer in the belt layer central region, it cannot be achieved.
This is because if the rigidity of the central area of the belt layer is reduced, the high-speed durability will be reduced.

If the width CWf of the belt reinforcement layer 9 of the rear tire Tr having a large tire width is made larger than 20% of the width BWr of the belt layer 7, the reduction of the rigidity of the shoulder portion of the rear tire Tr is insufficient. Therefore, it becomes impossible to improve the limit performance during cornering on wet road surfaces. Further, if the width CWf of the belt reinforcing layer 9 of the front wheel tire Tf is made smaller than 20% of the width BWf of the belt layer 7, the steerability of the steering wheel during high speed running on a dry road surface deteriorates.

As the cord of the belt reinforcing layer, a known organic fiber cord may be used and is not particularly limited. For example, nylon, polyester, aramid, etc., but nylon cord is most suitable. The belt reinforcing layer is formed by endlessly spirally winding one or several cords, or by preliminarily aligning a plurality of cords into a sheet and splicing both ends in the tire circumferential direction. You can

In the present invention, as the front and rear tires, especially when tires having an aspect ratio of 55% or less are used, the above-mentioned effects become remarkable. The vehicle on which the combination tire of the present invention is mounted is not particularly limited, but it is preferably mounted on a rear-wheel drive type vehicle or a four-wheel drive type vehicle. When mounted on these vehicles, the excellent effect can be further exerted.

[0014]

Example As follows, the tire structure, the tire size, the rim size, and the air pressure were made common, and the ratio of the width CW of the belt reinforcing layer wound around the shoulder portion to the width BW of the belt layer (CW / BW) × 100% As shown in Table 1, 11 different tire combinations (Examples 1 to 4 and Comparative Examples 1 to 7) were prepared by combining different front tires and rear tires as shown in Table 1.

Front wheel tire: Tire size: 205 / 55ZR16 Rim size: 16 × 6J Air pressure: 250 kPa Rear wheel tire: Tire size: 245 / 45ZR16 Rim size: 16 × 8J Air pressure: 300 kPa These ten sets of combined tires (Examples 1 to 4) And Comparative Examples 1 to 6), dry performance and wet performance were evaluated by the following methods, and the results are shown in Table 1.

Dry performance : engine displacement 3000 cc
Using a rear-wheel drive type vehicle, a driving test was conducted by a test driver, and the steering characteristics and limit characteristics of the steering wheel at that time were evaluated by a 10-point evaluation method.
The average value was displayed as an index with the value of Comparative Example 1 as the reference (100). The larger the index value, the better the above performance.

Wet performance : Using the same vehicle used for the dry performance test, the vehicle was started at a speed of 50 km / h on a circular road surface having a water film of 3 mm and a diameter of 60 m, and then the speed was increased. The steerability of the steering wheel by the test driver at that time was evaluated by the 10-point evaluation method, and the maximum acceleration (critical performance) of the vehicle was measured. The measured value was expressed as an index with the measured value of Comparative Example 1 as the reference (100).
The larger this index value, the better the wet performance.

[0018] From Table 1, the combined tires of Examples 1 to 4 of the present invention have a width of the belt reinforcing layer which is the same (20%) with respect to the width of the belt layers for both the front and rear tires. Both dry performance and wet performance are improved. On the other hand, in Comparative Examples 2 and 5 (the width of the belt reinforcing layer is less than 20% in both the front and rear wheels), not only the dry performance is deteriorated as compared with Comparative Example 1, but also the steering performance of the steering wheel on the wet road surface is deteriorated. is doing.

In the combined tires of Comparative Examples 3 and 6 (where the width of the belt reinforcing layer is less than 20% for the front wheels and 20% or more for the rear wheels), the dry performance is deteriorated and the limit performance on the wet road surface is reduced. Not only the steering performance but also the steering performance is degraded.

[0020]

According to the present invention, in the combination tire in which the rear tire is a tire wider than the front tire, the width of the belt reinforcing layer of the front tire is 20% or more of the width of the belt layer. On the other hand, since the width of the belt reinforcement layer of the rear wheel tire is smaller than 20% of the width of the belt layer, the rigidity of the shoulder portion of the rear wheel tire is reduced, and the ground contact of the tread at the time of cornering on wet road surface is improved. Wet performance (marginal performance) can be improved. Moreover, it is possible to maintain the original effect of improving the dry performance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a rear tire for a front and rear wheel combination tire for passenger cars of the present invention.

FIG. 2 is a cross-sectional view showing one embodiment of a front tire of a front / rear tire combination tire for passenger cars of the present invention.

[Explanation of symbols]

 1 tread 7 belt layer 8 and 9 belt reinforcing layer Tf front wheel tire Tr rear wheel tire BWf, BWr belt layer width CWf, CWr belt reinforcing layer width covering the shoulder portion

Claims (1)

[Claims] 1. A front tire and a rear tire are pneumatic radial tires in which both shoulder portions of a belt layer are covered with left and right independent belt reinforcing layers, respectively, and the rear tire is wider than the front tire. In the combined front and rear wheel tire for a passenger car, the width of the belt reinforcement layer of the front wheel tire is equal to the width of the belt layer.
A combined tire for front and rear wheels for passenger cars, in which the width of the belt reinforcing layer of the rear tire is smaller than 20% of the width of the belt layer, while being 0% or more.