JP3411058B2 - Front and rear wheel combination tire - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention makes it possible to improve stability when driving on a dry road surface (hereinafter referred to as "dry performance") in a combination in which a rear tire is provided with a radial tire having a width wider than that of the front wheels, and a wet tire The present invention relates to a front / rear wheel combination tire (hereinafter referred to as a combination tire) capable of improving a limit characteristic (hereinafter referred to as wet performance) during cornering on a road surface.

[0002]

2. Description of the Related Art Generally, flat radial tires are mounted on high-performance passenger cars, but recent high-performance passenger cars use rear tires rather than front tires to improve steering stability at high speeds. There are some which use wide tires in combination. However, this combination tire improves dry performance by using wide tires for the rear wheels, but when cornering on wet road surface, the rigidity of the shoulder part is not easily deformed, so the tread's ground contact state is There was a problem in that the skid condition deteriorates and the skid easily occurs, and the maximum speed limit (critical characteristic) at which the skid does not occur decreases.

[0003]

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

[0004]

According to the present invention to achieve the above object, the front tire and the rear tire are pneumatic radial tires, respectively, and the rear tire has a tire size wider than that of the front tire. In the combined tire, the width of the cap tread of the front tire is configured to be 1.1 times or more and 1.2 times or less the width of the belt layer, while
The width of the cap tread of the rear wheel tire is substantially the same as the width of the belt layer, and the hardness of the rubber layers adjacent to both sides of the cap tread is smaller than that of the cap tread. It is a thing.

When a tire having a wider width than that of the front tire is combined as the rear tire, the width of the cap tread of the rear tire is made substantially the same as the width of the belt layer, and the cap tread is provided on both sides of the cap tread. Since the rubber layers having a hardness lower than that of the cap tread are adjacent to each other, the rigidity of the shoulder portion can be reduced, the ground contact state of the tread during cornering on wet road surfaces can be improved, and the limit characteristics can be improved.

The present invention will be described in detail below with reference to the drawings. FIG. 1 shows a rear tire of a combined 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-sectional width TWr of the rear wheel tire Tr is equal to that of the front wheel tire Tf.
The width is wider than Wf (TWr> TWf).

As shown in FIGS. 1 and 2, front tire Tf
In each of the rear wheel tire Tr and the rear tire Tr, two inner and outer carcass layers 3 and 4 from a tread (cap tread) 1 are mounted on a bead core 5 across the left and right sidewall portions 2. The inner carcass layer 3 is folded around the bead core 5 from the tire inner side to the outer side and wound up, and the outer carcass layer 4 is unwound so as to cover the folded end of the inner carcass layer 3. Further, in the portion of the cap tread 1, two belt layers 7 are annularly arranged on the outer periphery of the outer carcass layer 4 so as to intersect each other at a cord angle of 5 to 30 ° with respect to the tire circumferential direction. Further, on the belt layer 7, two belt cover layers 8 that cover the entire width of the belt layer 7 are annularly arranged at a cord angle of 0 ° with respect to the tire circumferential direction.

The front and rear wheel tires Tf and Tr have the same structure as described above, but the relative relationship between the cap tread 1 and the belt layer 7 is different as follows. First, as shown in FIG. 2, the front tire Tf has a width C of the cap tread 1.
Wf is 1.1 to 1.2 times the width Lf of the belt layer 7. This structure has the same structure as a conventional front tire.

On the other hand, in the rear tire Tr, as shown in FIG. 1, the width CWr of the cap tread 1 is the belt layer 7
Is substantially the same as the width Lr of (CWr≈Lr),
This is a configuration unique to the present invention. When the width CWr of the cap tread becomes larger than the width Lr of the belt layer, the structure becomes the same as that of the conventional structure, so that the rigidity of the shoulder portion increases together with the flat structure, and the ground contact state of the tread during cornering on wet road surface deteriorates. As a result, the marginal characteristics deteriorate.

In the present invention, as described above, the belt layer 7
Wing chips 6 are provided on both sides of the cap tread 1 of the rear tire Tr having substantially the same width.
The wing tip 6 is made of rubber having a hardness lower than that of the cap tolled 1. Desirably, the hardness of the cap Torredo 1 is 62 or more, preferably 66 to 7 as the JIS-A hardness defined in JIS K-6301.
3 and the wing tip 6 has a JIS-A hardness of 50 to 60. By using such a combination of hardnesses, it becomes possible to appropriately reduce the rigidity of the shoulder portion and enhance the grounding property when cornering on the wet road surface. However, if the hardness of the wing tip 6 is too low, the rigidity of the shoulder portion is excessively decreased, which deteriorates the dry performance.
It is preferable that the A hardness is 50 as the lower limit.

For the rubber layers on both sides of the cap tread of the rear tire, it is possible to substitute the same rubber as the sidewall for the wing tips. However, in order to facilitate the production of the tire and firmly bond the cap tread, it is desirable to interpose a wing tip made of a rubber compound having the same composition as the sidewall rubber.

In the present invention, as the rubber composition used for the rubber layers of the cap tread, the wing chips, the sidewall portion, etc. of the front and rear tires, known rubber compositions for tires can be used, and particularly limited. It is not something that will be done. For example, rubber components such as natural rubber and styrene
Butadiene copolymer rubber (SBR), polybutadiene rubber (BR), etc. are used, and the types and blending amounts of carbon black, process oil, stearic acid, vulcanization accelerator, antioxidant, sulfur, etc. to be blended therein What is appropriately selected and adjusted may be used.

In the present invention, as the front and rear tires, particularly when tires having an aspect ratio of 50% 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 more effectively exhibited.

[0014]

Examples As shown below, the tire structure, the tire size, the rim size, and the air pressure are made common, and the ratio W / L of the width of the cap tread to the width of the belt layer is different as shown in Table 1. Common road tire structure, tire size, rim size, air pressure,
Ratio of width of cap tread to width of belt layer W /
The combination tires of the present invention and the combination tires of Comparative Examples 1 and 2 in which the rear wheel tires in which the hardnesses of L and the wing tips are different as shown in Table 1 are respectively combined are prepared.

Front wheel tire : Tire structure: Fig. 2 Tire size: 225 / 45ZR17 Rim size: 17x8J Air pressure: 260kPa Rear wheel tire : Tire structure: Fig. 1 Tire size: 255 / 40ZR17 Rim size: 17x9J Air pressure: 260kPa Above 3 With respect to the combined tires of the set (the present invention, Comparative Examples 1 and 2), dry performance and wet performance were evaluated by the following methods, and the evaluation results are shown in Table 1.

Dry performance : engine displacement 3000 cc
A rear-wheel drive vehicle is used, and a test driver drives the circuit, and the steering performance, straightness and limit characteristics of the steering wheel at that time are evaluated for feeling, and the value of Comparative Example 1 is used as an index (100). displayed. The larger this index value, the better the dry performance.

Wet performance : Using the same vehicle used for the dry performance test, running was started at a speed of 40 km / h on a circular road surface with a water film of 3 mm and a diameter of 60 m, and the speed was increased. At this time, the steering performance of the steering wheel by the test driver was evaluated and the maximum lateral acceleration of the vehicle was measured. It is indicated by an index with the measured value of Comparative Example 1 as a reference (100). The larger this index value, the better the wet performance.

[0018]

[Table 1] From Table 1, it can be seen that the present invention has the same steering performance and straightness of the steering wheel among the dry performances as compared with the comparative example 1, but the limit characteristics of the dry performance and the wet performance are remarkably improved. On the other hand, in Comparative Example 2, although the limit performance of the wet performance is improved, the steering performance of the steering wheel and the dry performance are deteriorated.

[0019]

According to the present invention, in the combination in which the rear tire is wider than the front tire,
For front tires, change the width of the cap tread to the width of the belt layer.
In contrast to 1.1 to 1.2 times , in the rear tire, the width of the cap tread is substantially the same as the width of the belt layer, and low hardness rubber layers are adjacent to both sides of the cap tread. Since the structure is adopted, the rigidity of the shoulder portion is lowered, the ground contact state of the tread is improved during cornering on wet road surfaces, and 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 an embodiment of a rear tire for a front and rear tire combined tire according to the present invention.

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

[Explanation of symbols]

1 Cap tread 2 Side wall part 6 Wing tip 7 Belt layer CWf, CWr Cap tread width Lf, Lr
Belt layer width Tf Front wheel tire Tr Rear wheel tire

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60C 1/00-19/12

Claims (2)

(57) [Claims] 1. A front and rear wheel combination tire in which the front tire and the rear tire are pneumatic radial tires respectively, and the rear tire has a tire size wider than that of the front tire, and a width of a cap tread of the front tire is The width of the belt layer is 1.1 times or more and 1.2 times or less , while the width of the cap tread of the rear tire is substantially the same as the width of the belt layer, and both sides of the cap tread are provided. A front and rear wheel combination tire in which the hardness of adjacent rubber layers is smaller than that of the cap tread. 2. The cap tread is JIS-A hardness
62 to 73 rubber, while the rubber layer is made of JI
The rubber composition according to claim 1, wherein the rubber has an S-A hardness of 50 to 60.
Front and rear wheel combination tires.