JPS62113606A - Pneumatic radial tire for motorcycle - Google Patents

Abstract

PURPOSE:To enhance the handling ability of a pneumatic tire having a casing reinforcing layer, by specifying the stored elastic modulus, the ratio between the elastic modulus and a loss-tangent and the ratio between the thickness of the tread rubber and the thickness of the casing reinforcing layer. CONSTITUTION:In a tire in which the tread section 1 is reinforced by a casing reinforcing layer including a carcass layer 4 having therein organic fiber cords laid at an angle of 70-90 deg. and a belt layer 5, the stored elastic modulus E' of the tread rubber layer 8 is set to be 70-170kg/cm<2>, and the ratio between the loss-tangent and the stored elastic modulus, tandelta/E', is set to be from 2.2X10<-3>-6X10<-3>cm<2>/kg. Further, the thickness of the tread rubber layer 8 excepting the casing reinforcing layer is set to a value which is 0.65-1.20 times as large as that of the casing reinforcing layer. With this arrangement it is possible to enhance the handling ability of the tire.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pneumatic radial tire for two-wheeled vehicles, and in particular to a tread structure for improving the Hanl-IJ song.

(Prior Art) Conventionally, pneumatic radial tires for motorcycles generally have a carcass layer made of organic fiber cords arranged at a cord angle of 70 to 90 degrees with respect to the circumferential direction of the tire. One or two layers of fiber cords or metal cords are arranged at a cord angle of 0 to 25 degrees with respect to the tire circumferential direction, and various reinforcing materials are arranged in the sidewall area, especially from the lower sidewall area to the bead area. It is being strengthened.

The thickness of the case reinforcement material in the tread area, that is, the tread rubber layer excluding the carcass layer and the belt layer, is substantially the same thickness as that of a bias tire.For example, in the case of a bias tire, the thickness of the case reinforcement material in the center area of the tire is ,
1.50 to 3.00 times, 1.3 for radial tires
0 to 2.50 times, and the tread width direction thickness is substantially the same from the tire center area to both tire side areas, or
On the contrary, both sides are slightly thicker, and the tread width has a shape and structure that is substantially wider than the maximum width of the tire. or,
Unlike four-wheel vehicle tires, the tread rubber layer uses a material with relatively large hysteresis loss. This is because the wetness and grip characteristics are directly affected.

Furthermore, the thickness of the tread rubber layer on the front wheels is considered to be slightly smaller than the thickness of the tread rubber layer on the rear wheels for both bias tires and radial tires.

(Problem to be solved by the invention) The conventional radial tire described above is mounted on a motorcycle,
When running slalom (zigzag), there are problems with handling performance, and under certain conditions, handling performance may deteriorate significantly. In particular, there is a problem in that the generation of camber thrust necessary for cornering is insufficient. Such problems do not occur with general bias tires.

(Means for solving the problem) As a result of various investigations into the causes of this problem, the inventor of the present invention found that, unlike bias tires, radial tires have a small ground contact area, especially when turning, and as a result, camber thrust is less likely to occur. It was found that the handling performance deteriorated. As a result of further investigation into the cause of this problem, we found that the case rigidity on the road surface is higher than that of bias tires, which means that it is less flexible, resulting in less ground contact area during load transfer, especially when applying a camber angle, and that the tread rubber It was found that since the thickness of the layer was as thick as that of the bias, the ground contact area became smaller and smaller, and as a result, the occurrence of camber thrust was small and the handling performance was degraded. In particular, it was found that there was a problem with the tires mounted on the front wheels, but the tires mounted on the rear wheels were not so much of a problem.

Therefore, the inventor of the present invention has investigated ways to increase the ground contact area, especially the ground contact area when the camber angle is applied, while providing the functions of a radial tire. found that the thickness distribution is important.

Therefore, the pneumatic radial tire for two-wheeled vehicles according to the present invention has a tread portion 1, a pair of sidewall portions 2, and a bead portion 3 as shown in the drawings, and the organic fiber cords are arranged in the tire circumferential direction. Said parts 1, 2 and 3 are reinforced in their entirety by at least one carcass layer 4 arranged at a cord angle of 70° to 90°, the carcass layer 4 and at least one carcass layer 4 arranged radially outwardly of said carcass layer 4. The tread portion 1 is reinforced by a case reinforcing layer including one belt layer 5, and the sidewall portion 2 and bead portion 3 are reinforced.
is reinforced with a reinforcing material such as a rubber filler 6 or an organic fiber cord layer 7 □ In a radial tire, a tread rubber layer 8 constituting the tread portion
When the storage modulus E' is 70 to 170 kg/cm2, the ratio of the storage modulus to the loss tangent is tan δ/E'
is 2.2xlO-' to 6xlO-3cm2/kg, and the thickness Sl of the tread rubber layer at the tire center is equal to the thickness S of the case reinforcing layer (mainly carcass layer 4 and belt layer 5) at the tire center. 0.65~
It is characterized by being 1.20 times larger.

(Function) According to the present invention, the storage elastic modulus E' of the tread rubber layer constituting the tread portion is set to 70 to 170 kg/cm2, and the storage elastic modulus to loss tangent ratio tan δ/B'
By setting 2.2
It is possible to prevent deterioration in grip performance, etc., which directly leads to fall accidents, and improve safety.

Ru.

In addition, the thickness of the tread rubber layer in the center area of the tire attached to the front wheel is the case reinforcement layer (
Mainly carcass layer and belt layer) thickness of 0.65
~1.20 times, and by making the thickness of the tread rubber layer of the tire attached to the front wheel smaller than that of the tire attached to the rear wheel, the handling performance can be improved. The reason for this is that the thickness of the tread of the rear tire does not significantly affect handling performance, and on the contrary, wear resistance and wear life are also important, so the thickness of the tread rubber layer of the rear tire is While 1.50 to 3.00 times the thickness of the case reinforcement layer is required, if the thickness of the tread rubber layer of the front wheel tire is 1.20 times or more, the rigidity of the entire tread increases as in the past, resulting in better ground contact. This is because there is no effect of increasing the area, the bundling performance is poor, and if it is 0.65 times or less, it is preferable in terms of the ground contact area, but there are undesirable problems such as wear resistance life and shimmy.

As described above, the tire according to the present invention is effective when installed on the front wheel of a two-wheeled vehicle, and even if a conventional radial tire is used on the rear wheel, there will be no problem in handling performance.

(Example) The tire size of the radial tire is 100790 for the front wheel.
R16 and 110/90R18 for the rear wheels will be described in detail with reference to the drawings.

The two carcass 9 are arranged so that their 1260d/2 nylon cords cross each other at an angle of 75° to the tire circumferential direction, and are folded back around the bead core 10 from the inside to the outside, and this folded end 9a is used as a sidewall. Finish at the bottom 2a of 2. In the illustrated example, two carcass 9 are provided, and a rubber filler 6 with a Shore A hardness of 70° is arranged between the carcass 9 folded around the bead core 10, and the organic fiber cord layer 7 is 6 and bead core 10, Kevlar (araamide>m fibers of 1500 d/2 are arranged at an angle of 45° in the circumferential direction of the tire, and the inner end 7a of the organic fiber cord layer 7 ends in the upper area of the sidewall part 2. Furthermore, the outer end 7b ends by partially overlapping the belt layer 5.The belt layer 5 is made of 1500 d/2 Kevlar cords arranged to intersect with each other at a cord angle of 20 degrees with respect to the tire circumferential direction. Thickness Sl of the tread rubber layer 8 in the tire center area
Similarly, the thickness Sn of the case reinforcing material (carcass layer 4 and belt layer 5) in the tire center area is 4.2 mm.
．． 4+nm, and therefore the thickness of the tread rubber layer in the center area of the tire was 0.95 times the thickness of the case reinforcing layer. This tread thickness Sl gradually decreases toward both side areas. The rear tire is essentially different from the front tire in that the thickness Sl of the tread rubber layer 8 at the tire center area is 81IlflI, and both side areas have substantially the same thickness. Therefore, the thickness S of the case reinforcing layer. is 5.2
mm, and the ratio (S+/Sn) is 154%, which is the same thickness as a normal radial tire.

(Effects of the Invention) In order to confirm the effects of the present invention, a comparative test was conducted between the tire of the present invention described in the above-mentioned Examples and a conventional tire (same as the tire mounted on the rear wheel). The results are shown in the table below.

Table 1

[Brief explanation of drawings]

FIG. 1 is a partial longitudinal sectional view of a tire according to an embodiment of the present invention.

Claims (1)

[Claims] 1. It has a tread portion, a pair of sidewall portions, and a bead portion, and the organic fiber cord has a width of 70° in the tire circumferential direction.
Said sections are generally reinforced by at least one carcass layer arranged at a cord angle of between 90° and 90°, said carcass layer and at least one belt layer arranged radially outwardly of said carcass layer. In the pneumatic radial tire for two-wheeled vehicles in which the tread portion is reinforced by a case reinforcing layer containing a reinforcing material, and the sidewall portion and bead portion are reinforced by a reinforcing material, the storage elastic modulus E′ of the tread rubber layer constituting the tread portion is is 70~170kg/
In cm^2, the ratio of loss tangent to storage modulus ta
nδ/E' is 2.2 x 10^-^3 ~ 6 x 10^-^3
cm^2/kg, and the thickness of the tread rubber layer excluding the case reinforcing layer at the center of the tire is 0.65 to 1.20 times the thickness of the case reinforcing layer. radial tire. 2. Claim 1, characterized in that the ratio of the thickness of the tread rubber layer excluding the case reinforcing layer of the front tire to the thickness of the case reinforcing layer is smaller than that of the rear tire. tires. 3. The tire according to claim 1 or 2, wherein the reinforcing material includes a rubber filler layer or an organic fiber cord layer. 4. The tire according to claim 1 or 2, wherein the thickness of the tread rubber layer gradually decreases from the center area to both side areas.