JPS63240404A - Pneumatic tire for two-wheeler - Google Patents

Abstract

PURPOSE:To improve the performance of chattering and rolling, by setting a crown radius of a tread shoulder portion, and providing a rubber filler layer having a large loss tangent and a given thickness in the tread shoulder portion. CONSTITUTION:A ratio R1/R2 between a crown radius R1 of a tread center portion 4a and a crown radius R2 of a tread shoulder portion 4b is set to 1.1 or more. A rubber filler layer having a loss tangent of 0.4 or more at 30 deg.C and greater than that of a tread rubber is provided just above a carcass layer 3, for example, in the range such that a distance l from a tread edge 7 toward an axis of rotation of a tire in a meridian plane of the tire is 0.4L or less. A thickness tx of the rubber filler layer 8 in a radial direction of the tire is set to 30-70% of a tread thickness ti from the upper surface of the carcass layer 3 to the upper surface of a tread 4. With this arrangement, the chattering and the rolling in turning are improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a pneumatic tire for two-wheeled vehicles, in particular, a pneumatic tire for two-wheeled vehicles by improving both the chattering and collapse performance of the front tire when turning. This relates to technology for improving machine shaft performance.

(Prior Art) A conventional pneumatic motorcycle tire has a pair of left and right bead portions 1 (only one is shown), as shown in FIG. 4, which is a meridional section of a motorcycle tire with a tire size of 110/90-16. side part 2 from one bead part to the other bead part.
The carcass layer 3 includes two carcass plies 3a and 3b extending through the carcass layer 3, and a tread portion 4 having a thickness ti and a width disposed on the radially outer side of the carcass layer 3. The tread has a loss tangent of 0.3 at 30°C.
The tread center portion 4a and the tread shoulder portion 4b of the tread portion 4 are each formed with crown radii R0 and Rt of 50 mm.

Note that 5 indicates an inner liner, and 6 indicates a single layer of plastic.

Unlike tires for four-wheeled vehicles, such tires for two-wheeled vehicles primarily turn by generating camber thrust, so the portions of the tread surface that contact the road surface are different when driving straight and when driving in a corner. . For this reason, the required performance of the tread portion in the direction of the rotational axis of the tire and the phenomena that occur at that time differ.

Specifically, when traveling straight, the tread center portion 4a is mainly used.
When the fluctuations transmitted from the road surface, that is, the force for absorbing and mitigating disturbances, is small, shimmy (Sh) occurs in the front tires.
Since a phenomenon called "immy" occurs and causes the steering wheel to shake, the disturbance absorption and relaxation power should be appropriate.
It is necessary to improve straight-line running stability.

Conventionally, this problem has been dealt with by optimizing the tread gauge, but this has been insufficient.

Furthermore, during cornering, the shoulder portion 4b is used, and problems such as chattering and collapse occur in this shoulder portion 4b. Chattering is a phenomenon in which self-excited vibration due to tire disturbance and pitching vibration of the vehicle body overlap, resulting in resonance at a frequency of approximately 15 to 16 fiz, causing the vehicle body to bounce.

Conventionally, countermeasures to this problem have been to increase the absorption and relaxation power of the tire by thickening the tread gauge, decreasing the loss tangent of the tread rubber, lowering the side rigidity, and increasing the contact length by decreasing the crown radius. Efforts are being made to suppress resonance.

On the other hand, slumping occurs when turning repeatedly at medium to low speeds.
This is a phenomenon in which the vehicle body falls over from the front wheels on top of the desired camber angle, and requires an operation to generate a force that causes the vehicle to shift. As a countermeasure against this problem, it is effective to increase the ground contact area during cornering, and for this purpose, the crown radius R2 of the tread shoulder portion 4b is changed to the crown radius R2 of the tread center portion 4a as shown in FIG.
, or making the tread gauge thinner to lower the tread bending rigidity of a portion of the shoulder.

(Problems to be solved by the invention) However, in the past, there have been many contradictory phenomena regarding tire performance.
This is an example of that. As mentioned above, as a result of thinning the tread gauge in order to improve slumping performance, the disturbance absorption and relaxation ability and vehicle body vibration absorption properties are reduced.In addition, in order to suppress slumping, the ground contact area during cornering is increased. As a result of increasing the crown radius R2 of the tread shoulder portion 4b compared to the tread center portion 4a, the ground contact pressure decreases, making it more susceptible to lateral input.
Since the restraining force of the tread surface within the contact surface is reduced, a problem arises in that chattering is more likely to occur. Thus, there is a problem in that it is difficult to improve to a level that satisfies both simultaneously.

The present invention simultaneously improves the two-dimensional performance of two-wheeled vehicle tires, namely chattering and falling down, and
Moreover, it is intended to satisfy the straight running performance level.

(Means for solving the problems) As shown in FIG. 1, the motorcycle tire according to the present invention has the following features:
A pair of left and right bead portions 1 and at least two or more carcass plies 3 extending from one bead portion to the other bead portion
A carcass layer 3 consisting of a and 3b, and this carcass layer 3
and a tread portion 4 having a width disposed radially outwardly, the ratio Rz of the crown radius R1 of the tread center portion 4a to the crown radius R2 of the tread shoulder portion 4b.
/R+ is 1.1 or more, and the distance 1z from the tread end 7 to the tire rotation axis direction in the tire meridian section is 0.4.
In the range below L, the loss tangent at 30℃ is 0.
．． A rubber filler layer 8 that is larger than 4 and has a higher value than the tread rubber is placed in the tread 4 directly above the carcass N3 or, if there is a breaker layer 6, and the rubber filler layer 8 is larger than the tread rubber measured in the tire radial direction. The thickness tx of the filler layer 8 is 30% of the tread thickness ti from directly above the carcass layer 3 or directly above the breaker layer 6 to the surface of the tread 4.
It is characterized by being in the range of 70% from .

In carrying out the present invention, it is preferable that an extension rubber M9 of the same quality as the rubber filler layer 8 is connected to the rubber filler N8 at the tread end 7, and the extension rubber layer 9 is extended to the bead portion 1.

Here, the loss tangent of the rubber is a value measured at a temperature of 30° C. and a vibration frequency of 5082 using a normal viscoelastic property testing machine (manufactured by Iwamoto Seisakusho).

(Function) In the pneumatic tire for a two-wheeled vehicle according to the present invention having the above-described structure, as a countermeasure against collapse, the crown radius Rt of the tread shoulder portion 4b is increased to increase the ground contact area during cornering as described above. There is. However, at the same time, this causes chattering, so the crown radius R2 of the tread shoulder portion 4b, which is effective for improving the collapse, is increased, that is, Rz /
Even if Rt is 1.1 or more, by arranging a rubber filler layer 8 with a larger loss tangent than the tread rubber in the tread of the cylinder portion 4b, this rubber filler layer 8 attenuates the input from the ground plane, In other words, it dampens chattering vibrations and makes it difficult to transmit them to the car body. At this time, in order to effectively damp vibration, the loss tangent of the rubber filler layer 8 must be 0.4 at 30°C.
The above will be necessary. Moreover, when the thickness tx of the rubber filler M8 is 30% or less of the thickness ti of the tread layer 4,
The damping effect is small in terms of volume fraction, and when it exceeds 70%, the rubber filler layer 8 tends to appear on the tread surface after wear, and in that case, the grip property increases, so chattering tends to occur. In this sense, the thickness tx of the rubber filler N8 is set to 3 of the thickness ti'' of the tread 4.
A range of 0% to 70% is a necessary and sufficient condition.

Furthermore, if the width of the rubber filler layer 8 extends beyond 0.4L from the tread end 7, heat generation in the tread center portion 4a increases during straight running, which adversely affects high-speed performance, so the width is set to 0.4L or less. It is necessary.

In addition, a rubber layer 9 of the same quality as the rubber filler layer 8 is added to the bead portion 1.
The vibration damping effect can be further improved by extending the length up to . On the other hand, if the entire tread shoulder portion 4b is made of rubber with a high loss tangent, the damping will be good, but the grip will be increased and chattering will be more likely to occur, which will have the opposite effect. Therefore, the surface of the tread shoulder portion 4b needs to be made of the same rubber as the tread center portion 4a.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

In the embodiment shown in FIG. 1, the ratio Rt/RI of the crown radius R1 of the tread center portion 4a of the tread 4 to the crown radius Rt of the tread shoulder portion 4b is 1.
3, the loss tangent of the tread rubber at 30°C is 0.319, and 30
Rubber filler N with loss tangent at °C of 0.492
8, the distance l in the tire rotation axis direction measured from the tread end 7 is within the range of 0.08L to 0.35L, and the thickness tx
is 0-. of the thickness ti of the tread 4. It is buried five times as thick.

The carcass layer 3 is made of organic fiber cord, has an angle of 30 degrees with respect to the tire circumferential direction, and consists of two layers that intersect with each other. Moreover, the breaker layer 6 is also made of organic fiber cord, has an angle of 30 degrees with respect to the tire outer circumferential direction, and is made of one layer that intersects with the carcass layer immediately below.

FIG. 2 is a modification of the embodiment shown in FIG. 1, in which the two types of rubber layers constituting the tread 4 have the same rubber quality, and the thickness Lx of the rubber filler layer 8 approaches the tire equatorial plane. (As the camber angle gradually increases, it becomes tapered.) By creating this shape, when the camber angle is gradually increased from 0@, the characteristics of the tread rubber gradually change, resulting in smooth axle handling. There is an advantage that it becomes

In FIG. 3, a rubber layer 9 of the same quality as the rubber filler layer 8 is connected to the rubber filler layer 8 at the tread end 7, and the rubber F
An example is shown in which i9 is extended to bead portion 1 and used instead of side rubber.

(Effects of the Invention) In order to confirm the effects of the present invention, the tires shown in FIGS. 1 to 3 according to the present invention, the conventional tire shown in FIG. 4, and the improved tilting tire shown in FIG. 5 were used as front tires. Test riders conducted an actual vehicle feeling test on a 4.5km circuit course, and the following results were obtained.

The feeling rating is based on a 10-point system, and the higher the value, the better.
Ru.

Trial 1 E-sho Tire size: Front 110/9O-16 (test tire of the present invention) Rear 130/80-18 (Conventional tire shown in the fourth diagram) Tire structure type: A...Conventional tire shown in the fourth diagram B.・・Conventional tire C with improved collapse shown in the 5th drawing ・・Invention tire D shown in the 1st drawing ・・Invention tire E shown in the 2nd drawing ・・Invention tire shown in the 3rd drawing Internal pressure: Front 2.25 kg /cm” rear 2.
25 kg/c is the load: 1 person riding condition test vehicle: From the test results of a two-wheeled vehicle with a displacement of 750 cc or more, it is clear that by using the tire according to the present invention, chattering when turning is reduced without changing straight-line performance. , collapse can be improved at the same time.

[Brief explanation of drawings]

Figures 1 to 3 are meridional cross-sectional views showing embodiments of a motorcycle tire according to the present invention. Figure 4 is a meridional cross-sectional view of a conventional motorcycle tire. Figure 5 is a conventional motorcycle tire with improved collapse. FIG. 1...Bead part 2...Side part 3...
Carcass 4...Tread part 4a...Tread center part 4b...Tread center part 5...Inner liner layer

Claims (1)

[Claims] 1. A pair of left and right bead portions, a carcass layer consisting of at least two or more carcass plies extending from one bead portion to the other bead portion, and a tread portion having a width L arranged on the outside in the radial direction of this carcass layer. In a pneumatic tire for two-wheeled vehicles, the crown radius R_1 of the tread center portion and the crown radius R of the tread shoulder portion
The ratio R_2/R_1 of _2 is 1.1 or more, the loss tangent at 30°C is 0.4 or more in the range of 0.4 L or less from the tread end in the tire rotational axis direction of the tire meridian section, and the tread rubber The higher value rubber filler layer
It is placed in the tread directly above the carcass or directly above the breaker if there is a breaker, and the thickness t_x of the rubber filler layer measured in the tire radial direction is the tread thickness t_ from directly above the carcass or breaker to the tread surface.
A pneumatic tire for a two-wheeled vehicle, characterized in that the i is in the range of 30% to 70%.