JP7364874B2 - motorcycle tires - Google Patents

Description

The present invention relates to a motorcycle tire, and more particularly, to a motorcycle tire having practically sufficient wet traction, turning performance, and low rolling resistance.

A motorcycle tire is mainly composed of a pair of left and right bead portions and sidewall portions, and a tread portion having a cap tread rubber that is continuous with both sidewall portions and constitutes the tire contact surface. A carcass ply is provided inside the tire, and both ends of the carcass ply are folded back so as to wrap around the bead core from the inside to the outside of the tire. The cap tread rubber constitutes the tire contact surface and extends outward in the tire radial direction in a convex, arcuate manner.

On the other hand, tires for motorcycles are required to have better wet traction (ability to start on wet roads) than four wheels in order to prevent falls in rainy weather. In order to improve wet traction properties, there are methods such as making the cap tread softer and increasing the low-temperature tan δ. However, these methods have problems in that turning performance and rolling resistance deteriorate due to insufficient rigidity.

Note that, for example, Patent Document 1 discloses a technique for improving the wet traction properties of motorcycle tires.

JP2006-321287A

Therefore, an object of the present invention is to provide a motorcycle tire having practically sufficient wet traction properties, turning properties, and low rolling resistance.

As a result of extensive research, the present inventor has determined the composition of the cap tread rubber, the ratio of the 100% modulus of the cap tread rubber (M100 CAP) to the 100% modulus of the carcass coat rubber (M100 carcass), and the 0% modulus of the cap tread rubber. By specifying the ratio of tan δ at 0°C (tan δ 0°C CAP) to tan δ at 60°C (tan δ 60°C carcass) of the rubber for carcass coating, it was discovered that the above problem could be solved, and the present invention was completed.
That is, the present invention is as follows.

1. A motorcycle tire comprising at least one carcass ply, carcass coat rubber that coats the carcass ply, and cap tread rubber disposed on the outside of the carcass ply in the tire radial direction,
The cap tread rubber constitutes a tire contact surface and extends outward in the tire radial direction in a convex and arcuate manner,
The cap tread rubber contains 60 to 120 parts by mass of carbon black with a nitrogen adsorption specific surface area (N ₂ SA) of 70 to 150 m ² /g per 100 parts by mass of rubber,
The 100% modulus of the cap tread rubber (M100 CAP) and the 100% modulus of the carcass coat rubber (M100 carcass) satisfy the following formula,
A motorcycle tire, wherein tan δ (tan δ 0° C. CAP) of the cap tread rubber at 0° C. and tan δ (tan δ 60° C. carcass) of the carcass coat rubber at 60° C. satisfy the following formula.
0.3≦(M100 CAP)/(M100 Carcass)≦1.2
1.0≦(tanδ0℃ CAP)/(tanδ60℃ carcass)≦10.0
2. In the cap tread rubber, the styrene-butadiene copolymer rubber accounts for 60 parts by mass or more in 100 parts by mass of the rubber, and the blending ratio of sulfur is 0.5 to 6 parts by mass with respect to 100 parts by mass of the rubber. The motorcycle tire according to item 1, characterized in that:
3. 3. The motorcycle tire according to item 1 or 2 above, wherein the number of carcass plies is two or less, and the thickness of each carcass ply is 0.7 mm to 1.5 mm.
4. 4. The motorcycle tire according to any one of 1 to 3 above, wherein the cord constituting the carcass ply has a diameter of 0.3 mm to 1.2 mm.

The motorcycle tire of the present invention includes at least one carcass ply, a carcass coat rubber that coats the carcass ply, and a cap tread rubber disposed on the outside of the carcass ply in the tire radial direction, The cap tread rubber constitutes the tire contact surface and extends outward in the radial direction of the tire in a convex arc shape, and the cap tread rubber has a nitrogen adsorption specific surface area (N ₂ SA) of 70 parts by mass per 100 parts by mass of rubber. ~150 m ² /g Contains 60 to 120 parts by mass of carbon black, and the 100% modulus of the cap tread rubber (M100 CAP) and the 100% modulus of the carcass coat rubber (M100 carcass) are 0.3≦(M100 CAP) )/(M100 carcass)≦1.2, and the tan δ of the cap tread rubber at 0°C (tan δ0°C CAP) and the tan δ of the carcass coat rubber at 60°C (tan δ60°C carcass) are 1.0≦( Since it is characterized by satisfying tan δ0°C CAP)/(tan δ60°C carcass)≦10.0, it has practically sufficient wet traction properties, turning properties, and low rolling resistance.

As mentioned above, there are methods to improve wet traction such as making the cap tread softer and increasing the low-temperature tan δ, but these methods result in lower turning performance and worsening rolling resistance due to insufficient rigidity. There is a problem. In other words, wet traction, turning performance, and low rolling resistance are contradictory performances. In the present invention, the composition of the cap tread rubber, the ratio of the 100% modulus of the cap tread rubber (M100 CAP) to the 100% modulus of the carcass coat rubber (M100 carcass), and the tan δ at 0 °C of the cap tread rubber (tan δ 0 °C CAP) ) and tan δ at 60°C of the rubber for carcass coating (tan δ 60°C carcass). First, by specifying (M100 CAP)/(M100 Carcass) and adjusting the rigidity of the cap tread rubber and carcass coat rubber to an appropriate range, the rigidity of the sidewall section is ensured, resulting in excellent wet traction and turning. Balancing gender. Furthermore, by setting (tan δ0°C CAP)/(tan δ60°C carcass) in an appropriate range, both excellent wet traction properties and low rolling resistance can be achieved. In this way, it has become possible to maintain the contradictory performances of wet traction, turning performance, and low rolling resistance at a practically sufficient level.

The present invention will be explained in more detail below.

The carcass ply used in the motorcycle tire of the present invention is a member that spans between bead cores on both sides in the width direction of the tire to form the frame of the tire. Note that the tire width direction refers to a direction parallel to the tire rotation axis. In the present invention, the thickness of one carcass ply is preferably 0.7 mm to 1.5 mm. The effects of the present invention can be further enhanced when the thickness of one carcass ply is outside this range and/or when the number of carcass plies is two or less.

The type of carcass ply is not particularly limited and can be appropriately selected from known ones, but from the viewpoint of further improving the effects of the present invention, it is preferable that the cords constituting the carcass ply contain organic fibers. Examples of organic fibers include polyester fibers, nylon fibers, aramid fibers, polyimide fibers, polyacrylate fibers, vinylon fibers, acrylic fibers, polyolefin fibers, polyurethane fibers, rayon fibers, and lyocell fibers. Note that the diameter of the cord is preferably 0.3 mm to 1.2 mm.

In the present invention, the composition of the cap tread rubber is specified. That is, the cap tread rubber contains 60 to 120 parts by mass of carbon black with a nitrogen adsorption specific surface area (N ₂ SA) of 70 to 150 m ² /g per 100 parts by mass of rubber.

When the blending ratio of the carbon black is outside the range of 60 to 120 parts by mass, and/or when the nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is outside the range of 70 to 150 m ² /g. , it is impossible to simultaneously obtain practically sufficient wet traction performance, turning performance, and low rolling resistance.

Here, from the viewpoint of improving the effects of the present invention, the following embodiments are preferable.
(1) The blending ratio of the carbon black to 100 parts by mass of the diene rubber is preferably 80 to 110 parts by mass.
(2) The carbon black preferably has a nitrogen adsorption specific surface area (N ₂ SA) of 70 to 120 m ² /g.
The nitrogen adsorption specific surface area (N ₂ SA) is a value measured according to JIS K 6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method".

In the present invention, the rubber component in the cap tread rubber includes, for example, diene rubber, specifically natural rubber (NR), synthetic isoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), Examples include butadiene rubber (BR), acrylonitrile-butadiene copolymer rubber (NBR), and the like. The diene rubber used in the present invention is not particularly limited in its molecular weight or microstructure, and may be terminally modified with amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group, etc., or epoxidized. good.

In addition to the above-mentioned components, the cap tread rubber also contains various fillers, various oils, anti-aging agents, plasticizers, zinc oxide, and other additives that are commonly included in cap tread rubber. can do. Further, during vulcanization, known vulcanization or crosslinking agents and vulcanization or crosslinking accelerators can be used without limitation. The blending amounts of these additives can also be set to conventional and general blending amounts as long as they do not contradict the purpose of the present invention.

In addition, from the viewpoint of further improving wet traction properties, turning properties, and low rolling resistance, the cap tread rubber has a structure in which SBR accounts for 60 parts by mass or more, preferably 80 to 100 parts by mass, in 100 parts by mass of the rubber. , and the blending ratio of sulfur to 100 parts by mass of the rubber is preferably 0.5 to 6 parts by mass, preferably 1.0 to 3.0 parts by mass.

Further, the maximum thickness of the cap tread rubber after vulcanization (maximum length from the contact surface with the carcass to the tire surface in the tire radial direction) is not particularly limited, but is preferably 7.0 mm to 11.0 mm, for example. .

In the present invention, the composition of the carcass coating rubber for coating the carcass ply can satisfy the following relationships of (M100 CAP)/(M100 carcass) and (tan δ0°C CAP)/(tan δ60°C carcass). , can be selected as appropriate without any particular limitation.
For example, various ingredients commonly included in carcass coat rubber such as diene rubber, various fillers such as silica and carbon black, coupling agents, various oils, anti-aging agents, plasticizers, and zinc oxide are mixed. can do. Further, during vulcanization, known vulcanization or crosslinking agents and vulcanization or crosslinking accelerators can be used without limitation. The blending amounts of these additives can also be set to conventional and general blending amounts as long as they do not contradict the purpose of the present invention.

The thickness of the carcass layer after vulcanization (the total thickness of the carcass ply and the carcass coating rubber) is not particularly limited, but is preferably 1.0 mm to 2.5 mm, for example.

In addition, with respect to other members in the motorcycle tire of the present invention, such as members constituting the bead portion, sidewall portion, etc., the blending ratio of each component is not particularly limited and may be appropriately selected.
For example, various commonly used components such as diene rubber, various fillers, various oils, anti-aging agents, plasticizers, zinc oxide, etc. can be blended as rubber compositions for other members. Further, during vulcanization, known vulcanization or crosslinking agents and vulcanization or crosslinking accelerators can be used without limitation. The blending amounts of these additives can also be set to conventional and general blending amounts as long as they do not contradict the purpose of the present invention.

In the motorcycle tire of the present invention, the 100% modulus (M100 CAP) of the cap tread rubber and the 100% modulus (M100 carcass) of the carcass coat rubber must satisfy the following formula.

0.3≦(M100 CAP)/(M100 Carcass)≦1.2

In other words, by having (M100 CAP)/(M100 carcass) in the range of 0.3 to 1.2, as mentioned above, the rigidity of the sidewall portion is ensured and excellent wet traction and turning performance are obtained. It will be done.

Further, in the motorcycle tire of the present invention, tan δ at 0°C (tan δ0°C CAP) of the cap tread rubber and tan δ at 60°C (tan δ60°C carcass) of the carcass coat rubber satisfy the following formula. is necessary.

1.0≦(tanδ0℃ CAP)/(tanδ60℃ carcass)≦10.0

That is, by setting (tan δ0°C CAP)/(tan δ60°C carcass) in the range of 1.0 to 10.0, as described above, both excellent wet traction properties and low rolling resistance can be achieved.

The 100% modulus referred to in the present invention is the value (MPa) obtained by measuring the stress at 100% elongation in a tensile test at 500 mm/min in accordance with JIS K6251.
In addition, tan δ (0°C) and tan δ (60°C) referred to in the present invention are determined using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., with an initial strain of 10%, an amplitude of ±2%, a frequency of 20 Hz, a temperature of 0°C, and Each measurement is performed under the condition of 60°C.

The above (M100 CAP), (M100 carcass), (tan δ 0°C CAP), and (tan δ 60° C. carcass) can be adjusted by, for example, increasing or decreasing the amount of plasticizer, filler, vulcanizing agent, or crosslinking agent, and changing the type.

In addition, from the viewpoint of further improving the effect of the present invention, the above (M100 CAP)/(M100 carcass) is preferably 0.4 to 1.1, and more preferably 0.5 to 0.8. preferable. Further, the above (tan δ0°C CAP)/(tan δ60°C carcass) is preferably from 3.0 to 7.0, more preferably from 3.0 to 5.0.

Further, the motorcycle tire of the present invention can be manufactured according to a conventional motorcycle tire manufacturing method.

EXAMPLES The present invention will be further explained below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Examples 1 to 8 and Comparative Examples 1 to 2
In the formulation (parts by mass) shown in Table 1, the components excluding the vulcanization accelerator and sulfur were kneaded for 5 minutes in a 16 liter closed Banbury mixer, and the rubber was discharged outside the mixer and cooled at room temperature. Next, the rubber was put into the same mixer again, a vulcanization accelerator and sulfur were added, and further kneaded to obtain various cap tread rubber compositions.

On the other hand, by preparing carcass coat rubber according to a conventional method and changing the type and amount of plasticizer or filler, carcass coat rubbers having various types (M100 carcass) and (tan δ 60°C carcass) shown in Table 1 were obtained. Ta.

Next, polyester fibers were used as the cords constituting the carcass ply, and the cords were coated with the carcass coating rubber according to a conventional method. The thickness of the carcass ply and the diameter of the cord were as shown in Table 1, and the thickness of the carcass layer (total thickness of the carcass ply and carcass coat rubber in the tire radial direction) was 2.4 mm.

(M100 CAP), (M100 carcass), (tanδ0°C CAP) and (tanδ60°C carcass) were measured as described above. The results are shown in Table 1.

A carcass ply coated with the carcass coat rubber and the cap tread rubber were incorporated to manufacture test tires for various motorcycles with tire sizes of 100/90-10. Note that the conditions for each member other than the carcass ply, carcass coat rubber, and cap tread rubber were the same among the various motorcycle test tires.

The following evaluations were performed on the various motorcycle test tires obtained. The results are shown in Table 1.

Wet traction performance: The test tires were installed on a test vehicle (scooter) with a displacement of 100cc, the air pressure was adjusted to 175kPa at the front and 225kPa at the rear, and the tires were run on a paved road surface with a water depth of 1mm, accelerating from 6 to 21km/h. The slip rate of the rear wheels at the same time was measured. The results were expressed as an index with the value of Example 1 as 100. The larger the index, the better the wet traction properties.

Turning performance: Measured by a sensory test using the test vehicle (scooter) with a displacement of 100 cc, performed by a test driver while actually driving the vehicle. The evaluation was performed on a five-level scale, with a score of "3" as the standard, and a relative evaluation was made.
5: Significant improvement in turning performance compared to point "3".
4: Compared to point "3", there is an improvement in turning performance.
3: Criterion 2: Compared to score "3", turning performance was poor.
1: The turning performance was significantly inferior to the score "3".

Rolling resistance: A test tire filled with a specified air pressure of 200 kPa was pressed vertically against the drum surface, and the energy loss (force in the opposite direction of travel) per unit travel distance during rolling was measured. The results were expressed as an index with the value of Example 1 as 100. The larger the index, the lower the rolling resistance.

*1:NR (TSR20)
*2: SBR (NIPOL 1502 manufactured by Zeon Corporation)
*3: Carbon black (trade name: Showblack N330, manufactured by Cabot Japan, N ₂ SA = 80 m ² /g)
*4: Stearic acid (Stearic acid YR manufactured by NOF Corporation)
*5: Zinc oxide (3 types of zinc oxide manufactured by Seido Kagaku Kogyo Co., Ltd.)
*6: Anti-aging agent (SANTOFLEX 6PPD manufactured by FLEXSYS)
*7: Aroma oil (Diana Process NH-60 manufactured by Idemitsu Kosan Co., Ltd.)
*8: Sulfur (Mukron OT-20 manufactured by Shikoku Kasei Kogyo Co., Ltd.)
*9: Vulcanization accelerator (Noxeler NS-P manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)

As is clear from Table 1 above, the motorcycle tires prepared in each example differed in the composition of the cap tread rubber, the 100% modulus of the cap tread rubber (M100 CAP), and the 100% modulus of the carcass coat rubber (M100 CAP). We specified the ratio of tan δ (tan δ 0°C CAP) of the cap tread rubber at 0°C (tan δ 0°C CAP) to the tan δ (tan δ 60°C carcass) of the carcass coat rubber at 60°C, so compared to the comparative example, wet traction was It maintains performance, turning performance, and low rolling resistance at a practically sufficient level.
On the other hand, in Comparative Example 1, the blending amount of carbon black exceeds the upper limit specified by the present invention, and (M100 CAP)/(M100 carcass) is less than the lower limit specified by the present invention, so wet traction properties deteriorate. did.
In Comparative Example 2, the blending amount of carbon black is less than the lower limit specified by the present invention, (M100 CAP) / (M100 carcass) is less than the lower limit specified by the present invention, and (tan δ 0 ° C CAP) / (tan δ 60 ° C Since the carcass) exceeded the upper limit specified in the present invention, turning performance and rolling resistance deteriorated.

Claims (4)

A motorcycle tire comprising at least one carcass ply, carcass coat rubber that coats the carcass ply, and cap tread rubber disposed on the outside of the carcass ply in the tire radial direction,
The cap tread rubber constitutes a tire contact surface and extends outward in the tire radial direction in a convex and arcuate manner,
The cap tread rubber contains 60 to 120 parts by mass of carbon black with a nitrogen adsorption specific surface area (N ₂ SA) of 70 to 150 m ² /g per 100 parts by mass of rubber,
100% modulus of the cap tread rubber (M100 CAP) and 100% modulus of the carcass coat rubber (M100 carcass) satisfy the following formula,
The tan δ (tan δ 0° C. CAP) of the cap tread rubber at 0° C. and the tan δ (tan δ 60° C. carcass) of the carcass coat rubber at 60° C. satisfy the following formula,
The above (M100 CAP) is 1.8 to 2.5 MPa, and the above (tan δ 60 ° C carcass) is 0.07 to 0.2,
A motorcycle tire characterized by:
0.3≦(M100 CAP)/(M100 Carcass)≦1.2
1.0≦(tanδ0℃ CAP)/(tanδ60℃ carcass)≦10.0 In the cap tread rubber, the styrene-butadiene copolymer rubber accounts for 60 parts by mass or more in 100 parts by mass of the rubber, and the blending ratio of sulfur is 0.5 to 6 parts by mass with respect to 100 parts by mass of the rubber. The motorcycle tire according to claim 1, characterized in that: The motorcycle tire according to claim 1 or 2, wherein the number of carcass plies is two or less, and the thickness of each carcass ply is 0.7 mm to 1.5 mm. The motorcycle tire according to any one of claims 1 to 3, wherein the diameter of the cord constituting the carcass ply is 0.3 mm to 1.2 mm.