JP2002362116A - Radial tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress chattering while maintaining high turning performance. SOLUTION: A shock absorbing rubber 10 is arranged on a bead portion 4 outside a turn-around portion 6b of a carcass 6 for absorbing shock of a rim flange Rf. The shock absorbing rubber 10 is formed of a rubber having a rubber hardness of 35-47 deg. and a tangent loss tanδ of 0.3-0.45 and its upper end P2 extends over the upper end of the rim flange Rf.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sports type,
The present invention relates to a radial tire for a motorcycle, which is suitable as an evening ear of a racer and suppresses chatter while maintaining high turning performance.

[0002]

2. Description of the Related Art In motorcycle tires, studies have been made on tire shape, internal structure, rubber, and the like in order to enhance turning performance, which is particularly important among motorcycle motion characteristics. Is being done.

[0003] Normally, motorcycle tires have a sidewall structure with a lower rigidity compared to evening tires for four-wheeled vehicles. For high-speed evening ears such as sports types and racer evening types, the sidewall rigidity is increased by hardening the rubber of the sidewalls and providing a sidewall reinforcement layer to obtain high turning performance. Have been.

[0004] However, when running on a tire having such relatively high sidewall rigidity, during turning, an external force received from unevenness or undulation on the road surface or an external force such as severe braking cannot be completely absorbed, and the tire becomes thin from the road surface. A jumping phenomenon, a so-called chattering phenomenon, may occur. If such a chattering phenomenon occurs, it is impossible to increase the turning speed further,
In addition to being fatal in race competitions,
There is a problem that running stability is lost, such as impairing steering wheel operation.

[0005] Therefore, the present invention is based on the provision of a cushioning rubber made of a soft and excellent energy absorbing rubber at the bead portion in contact with the rim flange. It is an object of the present invention to provide a radial tire for a motorcycle that can reduce transmission and suppress chatter while maintaining high turning performance.

[0006]

In order to achieve the above-mentioned object, the invention according to claim 1 of the present application is directed to a method in which a body portion extending from a tread portion to a bead core of a bead portion through a sidewall portion is folded around the bead core. A motorcycle radial tire having a carcass provided with a folded portion, wherein the bead portion and a tire axially outside the folded portion,
A cushioning rubber for reducing the impact on the rim flange is arranged along the folded portion, and the cushioning rubber has a rubber hardness (durometer A hardness) of 35 to 47 ° and a loss tangent.
It is characterized in that it is made of rubber having a tan δ of 0.3 to 0.45, and the upper end in the tire radial direction extends beyond the upper edge of the rim flange.

[0007] In the invention of claim 2, the cushioning rubber is
The thickness ta is set to 2.0 to 5.0 mm, and the bead core extends from the region between the inner and outer ends in the radial direction as the starting point and the outer surface in the tire axial direction extends along the outer surface of the tire.

[0008] In the invention of claim 3, the cushioning rubber is
Along with disposing in the tire axial direction inward recess formed in the folded portion, a chamfer for preventing rim slippage having a thickness of 1.0 mm or less is disposed outside the cushion rubber in the tire axial direction. I have.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described.
This will be described together with the illustrated example. In FIG. 1, a radial tire 1 for a motorcycle according to the present embodiment (hereinafter referred to as a tire 1).
A carcass 6 extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3;
And a belt layer 7 disposed inside and outside of the carcass 6.

The tread portion 2 has a tread end T
The tire extends from the tire equator C toward the tread end Te in a convex arc shape with a small radius of curvature such that the tread width between e and Te becomes the maximum width of the tire. At this time, the tread end height Hh of the tread end Te from the bead base line BL is 0.4 to 0.6 times the tire cross-section height HT in this example, thereby reducing the camber amount of the tread portion 2. It secures enough to enable turning at a large bank angle.

The carcass 6 is formed of at least one carcass ply 6A in which carcass cords are arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction.

The carcass ply 6A is provided at both ends of a main body 6a straddling the bead cores 5, 5.
Folding part 6 that is turned from inside to outside in the tire axial direction around
The space between the folded portion 6b and the main body 6a is filled with a bead apex rubber 8 having a substantially triangular cross section.

The folded portion 6b is wound radially outward while sequentially contacting the bead apex rubber 8 and the main body 6a. At this time, the folded portion 6b is
At a portion in contact with the bead apex rubber 8, a concave portion 6b1 that is concaved in, for example, an arc shape inward in the tire axial direction is formed. The outer end of the folded portion 6b has the tread end T
e, it extends to the vicinity of the height position, and by adopting such a high turn-up (HTU) structure, the tire lateral rigidity is increased and high turning performance is secured.

Next, the belt layer 7 is exemplified by one or more, in this example, two belt plies 7A, 7B. As the belt plies 7A, 7B, a belt cord is used in the tire circumferential direction. A cut ply arranged at an angle of 10 to 30 degrees is used. The belt code is
The plies are arranged in a direction crossing each other. As the belt layer 7, a jointless parallel cord ply in which a belt cord is spirally wound substantially parallel to the tire circumferential direction can also be used.

In the tire 1 of the present embodiment, the bead portion 4 is provided to reduce the transmission of shock disturbance from the tire to the rim flange and to suppress chattering.
A cushioning rubber 10 is provided to reduce the impact on the rim flange.

As shown in FIG. 2, the cushioning rubber 10
The start point P1 (lower end) of the bead core 5 is located in the height region Y between the inner and outer ends in the radial direction of the bead core 5. And cushioning rubber 1
Numeral 0 extends from the starting point P1 to the upper end P2 which is beyond the upper edge of the rim flange Rf, and its outer surface in the tire axial direction extends along the outer surface S of the tire.

The cushioning rubber 10 has a transition region 10 extending radially outward while gradually increasing in thickness from the starting point P1.
L and a main region 10U which is continuous with the transition region 10L and has a substantially constant or slightly reduced thickness. In this example, the thickness ta of the main region 10U is set to 2.0 to 5.0 m.
m.

Here, in order to provide the buffer rubber 10 with an effect of absorbing and absorbing the disturbance to the rim flange Rf, the rubber rubber (durometer A hardness) is set to 35 to 50.
It is made of a soft rubber having a high energy absorption of 47 ° and a loss tangent tanδ of 0.3 to 0.45.

As described above, the bead portion 4 has the rim flange R
The shock absorbing rubber 10 is formed in the area that comes into contact with the tire f. Therefore, even when a shock is generated in the tire due to unevenness of the road surface or severe braking, the disturbance is transmitted to the rim flange. Can be alleviated,
Chattering can be suppressed without impairing turning performance.

When the thickness ta is less than 2.0 mm, when the rubber hardness exceeds 47 °, or when the loss tangent t
If an δ is less than 0.3, the effect of relaxing and absorbing disturbance is too small, and the suppression of chattering becomes insufficient. Also,
When the thickness ta exceeds 5.0 mm, the rubber hardness is 3
If it is less than 5 °, or if the loss tangent tan δ exceeds 0.45, the handle responsiveness tends to be impaired, and bead durability may be adversely affected.

The rubber hardness is JIS-K6253.
Durometer A hardness at a temperature of 25 ° C. The loss tangent was measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. at a temperature of 70 ° C. and a frequency of 1.
It is a value measured under the conditions of 0 Hz, 10% initial strain, and ± 1% dynamic strain.

In this embodiment, the outer surface of the cushioning rubber 10 in the tire axial direction is covered with a chamfer 11 for preventing rim displacement at least in a range where the cushion rubber 10 is in contact with the rim flange Rf. The chafer 11 is made of a rubber sheet excellent in abrasion resistance or a cloth sheet with a rubber in which organic fiber yarns are woven, and has a thickness of 1.0 mm.
Hereinafter, it is usually formed with a thickness of about 0.5 mm. After covering the cushion rubber 10, the chafer 11 sequentially covers the bead heel surface and the bead bottom surface, and terminates on the bead toe side, as in the related art.

In the tire 1 of this embodiment, since the chattering is suppressed by using the buffer rubber 10, the sidewall rubber 3G is harder than the buffer rubber 10 and has a rubber hardness of 49 to 56 °. Rubber can be used, and excellent turning performance can be ensured. In addition,
The side wall rubber 3G is connected to the upper end P of the cushion rubber 10.
2 is connected to the carcass via a boundary line 12 which is inclined outward in the radial direction from the carcass turn-up portion 6b toward the outside in the tire axial direction.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment, but may be implemented in various forms.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The tire having the structure shown in FIG.
A / 70ZR17 tire was prototyped according to the specifications shown in Table 1, and the turning performance, hand link performance, and chattering performance of each prototype tire were tested. The results are shown in Table 1. In addition, the use other than Table 1 is carcass-Number of plies---1 piece-Cord composition---Nylon (2/1400 dtex)-Cord angle--90 degrees Belt layer-Number of plies---2 pieces (Cross cord・ Ply) ・ Cord composition --- Aromatic polyamide (2 / 1670d)
tex)-Cord angle --- 17 ° is common.

(1) Turning performance, hand link performance, chattering performance: The test tire was mounted on a rim (MT 3.50 × 17), and the internal pressure (22
Under the conditions of 5kPa), it is mounted on the front wheel of a motorcycle (600cc, 4cycles, ports type), runs at high speed on a circuit course (dry pavement road), and turns performance and hand link performance are evaluated by sensory evaluation by the driver. The evaluation was made using an index with the conventional example being 100. The higher the value, the better. At that time, the occurrence of chattering was evaluated on three scales: x (bounce), Δ (slightly bounced), and ○ (not bounced).

The rear wheel has a tire size of 180/55.
R17 commercial tires were used.

[0028]

[Table 1]

As shown in Table 1, it can be confirmed that the tire of the example can suppress chatter while maintaining high turning performance.

[0030]

As described above, according to the present invention, since a cushion rubber having a predetermined physical property which is soft and has excellent energy absorption is arranged in a portion of a bead which comes into contact with a rim flange, an impact disturbance can be prevented. Transmission to the rim flange can be reduced, and chattering can be suppressed while maintaining high turning performance.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view showing a bead portion.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6a Body part 6b Folded part 6b1 Depressed part 10 Buffer rubber 11 Chafer

Claims (3)

[Claims] 1. A motorcycle radial tire comprising a carcass provided on a main body portion extending from a tread portion to a bead core of a bead portion through a sidewall portion to a bead core. At the bead portion and on the outer side in the tire axial direction of the folded portion, a cushioning rubber for relaxing the impact on the rim flange is arranged along the folded portion, and the cushioning rubber has a rubber hardness (durometer A hardness) of 3
5 to 47 ° and a loss tangent tanδ is made of rubber having a tan δ of 0.3 to 0.45, and the upper end in the tire radial direction extends beyond the upper edge of the rim flange. Radial tire. 2. The cushioning rubber has a thickness ta of 2.0 to 2.0.
The radial tire for a motorcycle according to claim 1, wherein the radial length of the bead core is 5.0 mm, and the outer surface in the tire axial direction extends along the outer surface of the tire starting from a region between inner and outer ends in the radial direction of the bead core. . 3. The cushioning rubber is disposed in a recessed portion formed in the folded portion and inward in the tire axial direction, and is provided on the outside of the cushioning rubber in the tire axial direction for preventing a rim from shifting by a thickness of 1.0 mm or less. The radial tire for a motorcycle according to claim 1 or 2, wherein a chafer is arranged.