JPS63305005A - Tire for motorcycle - Google Patents

Abstract

PURPOSE:To improve durability and rigidity, on a tire for a motor cycle, by using a polyvinylalcohl fibre, specific in strength and a twist coefficient, as a cord for a belt layer, and specifying a count and the twist coefficient in the crown center of the cord. CONSTITUTION:A carcass layer, a cord angle of which is 90-25 deg. against the equatorial face of a tire, is provided in plural number of layers, and a belt layer, a cord angle of which is 0-40 deg., is provided plurally as well. The belt layer is formed by a polyvinylalcohol fibre that satisfies a relational formula I being specific in the strength S and the twist coefficient NT of a cord taken from the belt layer. Additionally, when a count E per 5cm width is 70 or smaller in the crown center portion of the cord in the belt layer, the twist coefficient NT and the count E are set so as to satisfy a specific relational formula II. This constitution can improve the rigidity and the durability of the tire.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a motorcycle tire.

(Prior art) Research into radial tires for motorcycles is still in its infancy among manufacturers, and various tire structures are being adopted.
Conventionally, Kevlar fibers (trade name of aramid fibers manufactured by DuPont) have often been used for members that require increased tire rigidity (belt layers and reinforcing hood layers such as flippers and inserts). This is because radial tires for two-wheeled vehicles are required to have stability during high-speed running, high-speed durability, wear resistance, etc. -In order to satisfy the performance requirements, the belt part has a high elastic modulus that can improve circumferential rigidity. This is because it was desired to use belt material.

(Problems to be Solved by the Invention) However, when Kevlar fibers are used in belt materials, there are the following problems.

■ When running at high speeds, the contact area becomes hot, so Kevlar fibers with low high-temperature adhesion are prone to separation due to interfacial failure. For this reason, it is necessary to maintain durability by, for example, disposing a breaker with good adhesiveness such as nylon fiber as the outermost layer on the belt layer of Kevlar fiber.

■When using a belt material with a high elastic modulus, there is a large concentration of stress at the belt end due to the angle difference with the carcass ply and the difference in elastic modulus, and the ground contact end approaches the belt end especially when running under heavy load and low internal pressure. As the strain increases, cracks occur at the belt ends, which tends to cause belt end separation.

■ Due to the essential characteristic of motorcycles that they turn with a camber, it is necessary to optimize the balance of rigidity between the crown and side parts. There are examples of reinforcing members such as reinforcing rubber or reinforcing cord layers being inserted between the carcass plies, but if the ends of these reinforcing members are placed as part of the buttress or crown shoulder, the adjacent carcass plies Due to the difference in rigidity between the reinforcing member and the belt layer, distortion of the glabella becomes large at the end of the reinforcing member, which is likely to cause failure like the belt end separation.

As a means to avoid the problems described above when using Kevlar fibers, a fiber material with excellent adhesive strength such as nylon fiber is used for the belt layer to ensure the necessary rigidity of the belt layer. Although it was considered to use a plurality of tires, this was not desirable because the total gauge of the tire would become thicker and handling and reliability would deteriorate due to the increased weight of the tire.

In addition, fibers such as polyvinyl alcohol and rayon are sometimes used because they provide a certain degree of rigidity, although they cannot be expected to have the same rigidity as Kevlar fibers. However, conventional polyvinyl alcohol fibers have particularly poor fatigue resistance, and after actual running, a fuzz phenomenon occurs on the cord surface due to filament breakage, which can sometimes lead to cord breakage, which poses a major safety problem. there were. Furthermore, since rayon fibers inherently have low strength, thick cords must be used to increase strength, which leads to an increase in tire total gauge, which is unfavorable in terms of tire performance.

Therefore, an object of the present invention is to provide a two-wheeled vehicle tire that exhibits tire rigidity comparable to when Kevlar fiber is used as a belt material, and has significantly improved durability by providing higher high-temperature adhesive strength than Kevlar fiber. It is about providing.

(Problems to be Solved by the Invention) As a result of intensive studies to solve the above problems, the present inventors have achieved the above object by using polyvinyl alcohol fibers with high strength and high elasticity as a belt material. The present inventors have discovered that the present invention can be obtained, and have completed the present invention.

That is, the present invention includes a pair of bead portions, at least one carcass layer including the bead portions, at least one carcass layer having a cord that is folded back and intersecting at an angle of 90° to 25° with respect to the tire equatorial plane, and O.

In a motorcycle tire comprising at least one belt layer having cords that intersect at an angle of ~40°, the cord taken out from the belt layer is determined by the following formula: % formula % (S in the formula is the strength of the cord ( g/d), Nt is N.

-Nx5] and the twist coefficient expressed as D/pX10-3,
N is the twist coefficient per 10cm cord length (T/10cm)
, D is the cord torque denier of 172 and ρ is the specific gravity of the cord), and the number of implants per 5C11 width in the crown center part of the belt layer cord is E ( book/5 cm),
The invention also relates to a two-wheeled vehicle tire, characterized in that the relationship between the twist coefficient N and the number of strokes E satisfies the following: E<70 E >36.3NY''+24.7.

The high tenacity polyvinyl alcohol fiber used in the present invention is disclosed in Japanese Patent Application Laid-open No. 60-126311 and Japanese Patent Application Laid-open No. 60-126311.
As disclosed in Japanese Patent No. 0-126312, it can be obtained by significantly increasing the draw ratio after dry-wet spinning. In addition, methods to increase the draw ratio during spinning by using polymers with significantly increased molecular weights compared to those used in the production of conventional polyvinyl alcohol fibers, or ultra-high molecular weight polymers such as gel spinning, It can also be produced by a method such as spinning a polymer from a dilute solution.

The high-strength polyvinyl alcohol fiber produced in this way is made by first twisting and final twisting the yarn to increase its cohesiveness as a cord, and at the same time improve its fatigue resistance8.
Next, the obtained twisted cord is woven into a blind weave using weft yarns in some cases, and in some cases, the twisted cord is immersed in a typical tire cord dip solution such as resorcinol/formaldehyde/latex. ,
Used as tire cord for heat treatment.

The above-mentioned high-strength polyvinyl alcohol fibers have the advantage of not only high strength due to the densification of the amorphous portion of the fibers, but also the advantage of having a high modulus of elasticity. Furthermore, surprisingly, due to the densification of the amorphous portion, the fatigue resistance of the cord is significantly improved compared to conventional polyvinyl alcohol fibers, and at the same time, the moisture and heat resistance, which was a drawback of conventional polyvinyl alcohol fibers, is also significantly improved. It turns out that there are other benefits as well.

(Function) Table 1 shows the measurement results of the physical properties of the high-strength polyvinyl alcohol fiber used in the present invention in comparison with known fibers. Further, FIG. 1 shows the relationship between the cord strength (g/d) taken out from the tire and the twist coefficient N.

In addition, in measuring the physical properties of the cord, the denier of the raw yarn before twisting was used as the denier number. This is to avoid trouble associated with changes in denier due to changes in cord length due to twisting, dipping treatment, shrinkage during tire vulcanization, and the like.

As is clear from Table 1, the high-strength polyvinyl alcohol fibers used in the present invention have significantly improved fatigue resistance compared to conventional fibers, and have strength values close to those of aramid fibers.

In the present invention, it is necessary to use such high-strength polyvinyl alcohol fibers and satisfy the following relationship with the twist coefficient N7: This is because it is necessary to maintain a certain level of strength without causing any damage. In other words, if the twist coefficient Nr is small, the strength and elastic modulus of the cord will improve, but the adhesion and fatigue resistance will decrease, and no matter how much the fatigue resistance of the raw filament is improved, it will no longer be usable as a tire cord. be.

As is clear from FIG. 1, it has been impossible to satisfy the above relationship with conventional polyvinylalcono fibers.

In fact, it is essential that the twist coefficient NT is larger than 0.33 from the viewpoint of tire safety, but if it is larger than 0.6, the strength and elastic modulus of the cord will be significantly reduced, and the twist coefficient NT according to the present invention will be This is not preferable because the benefits of using strong polyvinyl alcohol fibers are reduced. Therefore, in the present invention, the twist coefficient N is required to satisfy the following relationship: o, 3j<Na<0.6.

In addition, in the present invention, in order to further ensure the rigidity of the tire within the range of the twist coefficient N, and to satisfy the steering stability performance, the number of cords inserted in the belt layer per 5 cm width of the crown center part (E) / 5 cm)
It is essential that the relationship between the twist coefficient NA and the twist coefficient NA satisfies the following formula: % formula %. This is because, as mentioned above, when the twist coefficient N of the cord is increased, the elastic modulus of the cord decreases, so in order to ensure tire rigidity, it is necessary to increase the number of strokes E, but when the twist coefficient N is small, This is an experimental formula obtained as a result of intensive study by the present inventors from the viewpoint that the number of implantations E can be reduced. As can be seen from FIG. 2, the steering stability performance can be satisfied only within the range that satisfies the relationship of this experimental formula.

As mentioned above, it is preferable to increase the number of strokes E from the viewpoint of ensuring tire rigidity, but if E is too large, the rubber will not be able to enter between the cords, resulting in decreased adhesion and separation between the belt layers. Not only does this occur more easily, which poses a safety problem, but it is also undesirable in terms of tire manufacturing, as it causes problems such as cords overlapping. Therefore, the present invention is also required to satisfy the relationship E x 70.

(Example) Next, the present invention will be explained with reference to Examples and Comparative Examples.

First, codes used in the following examples and comparative examples will be explained.

As shown in Table 1 above, 1500 is a high-strength, high-modulus polyvinyl alcohol fiber that has significantly higher strength, higher modulus of elasticity, and higher fatigue resistance than conventional polyvinyl alcohol fibers.
Denier (single yarn denier approx. 2g/d) with various twist numbers
After twisting the two gold threads in the S direction, twist the threads in the S direction so that the number of twists is the same as that of the first twist.
After applying a system adhesive or dipping the cord in this adhesive, 130°C x 40 seconds, 200°C x 40 seconds, 2
2g/d, Ig/d, at each exposure time of 40 seconds at 00°C
The cord was subjected to tension heat treatment and adhesive curing treatment under each tension of 1 g/d.

In addition, as controls for such cords, aramid fibers, 6.6-nylon fibers, and conventional polyvinyl alcohol fibers were used and subjected to conventional RF/L adhesive and tension heat treatment. However, only the aramid fibers were pretreated with epoxy before applying the RF/L adhesive. At this time, the twist coefficient for conventional polyvinyl alcohol fibers and 6,6-nylon fibers was set to 0.486, but in the case of aramid fibers, the same twist coefficient poses a safety problem, so the twist coefficient was increased by approximately 8%. Ta. In the case of aramid fibers, there are some safety concerns even with this twist coefficient, but since it has been commercially available in some markets, we decided to use it as a control, although it may not be sufficient in terms of tire durability.

The more specific code structure of each code is shown in Tables 2 and 3 below.

1-7 91-12 The various cords described above were used as belt materials for radial structure tires for medium-sized 400 cc class sports motorcycles. Tires with a size of 110/70R17 for the front wheel and a size of 140/60R1B for the rear wheel were prototyped and various tests shown below were conducted.

The basic structure of each tire is as shown in FIG. 3, and the belt structure is as shown in Table 2.

A real vehicle feeling test was carried out at speeds of 160 to 200 km/h to determine (i) straight-line stability, (ii) turning stability,
The four items of (it) rigidity and (iv) handling were given a score of 1 to 10, and each item was averaged to determine the actual vehicle handling stability rating. A race driver was used as the driver, and the average of the scores of the two drivers was calculated. The following is a guideline for scoring.

0 to 2 points: unusable, 2 to 4 points: poor, 4 to 6 points: fair, 6 to 8 points: good, 8 to 10 points: very good.

High-speed durability test: JATMA at 210 km/hour
The vehicle is run with 100% load, then the load is reduced by 5%, the speed is increased by 10 km/hour, and the vehicle is run for 20 minutes. Thereafter, the steps of increasing the speed by 10 km/hour, reducing the load by 5%, and driving for 20 minutes are repeated until the tire fails. Tires that do not break down are 27
0km/hour x 20 minutes running was discontinued.

ノ\11N After the drum durability test described above and the drum durability test described below, the cord was taken out from the tire, and the fuzziness of the cord surface was evaluated according to the following rating scale.

O: No fluff Δ: Some fluff is seen. ×: Frequent fluffing The results of each of the above tests are also listed in Table 2 below.

From the test results shown in Table 2 above, the following was confirmed.

Comparative Example 1 is a control using aramid fiber, which is also available on the market, as the belt material.

Although the driving stability of this actual vehicle is satisfactory, the drum durability is TLB (tread-
Separation between players occurred. This is thought to be due to a decrease in adhesive strength at high temperatures, and further improvement is required. Comparative Example 2 uses 6.6-nylon fiber instead of the aramid fiber.

When using nylon fibers, the tire rigidity decreases significantly, so we tried to increase this as much as possible by using a thicker cord, but the steering stability of the actual vehicle was still significantly inferior to Comparative Example 1, so we were not satisfied. It wasn't at the level I could do it.

Comparative Example 3 used conventional polyvinyl alcohol fibers (PVA) instead of the aramid fibers, but the steering stability was still slightly lower than in Comparative Example 1. Although the drum high-speed durability level was improved over Comparative Example 1, a lot of fuzz was observed on the surface of the cord taken out from the destroyed tire, and there was a problem in the fatigue resistance of the cord.

Comparative Examples 4 to 7 use the high strength and high elasticity polyvinyl alcohol fibers according to the present invention, but the twist coefficient was set to 0.
．． 253 (number of twists: 20x20T/10cm), which is lower than the range of the present invention, although the steering stability is improved, TLB occurs due to insufficient adhesive strength, and the level is also equal to or lower than Comparative Example 1. Ta. Furthermore, the fuzz on the surface of the cord after running on the drum was quite noticeable, and it was determined that there was a problem with the fatigue resistance of the cord.

In Comparative Example 8.9 and Examples 1 to 3, the twist coefficient was changed to Comparative Example 4.
7, the above-mentioned separation, which is thought to be due to insufficient adhesion, did not occur, and the drum high-speed durability level was 270 km/hour or higher, except for Comparative Example 9. Drum running stopped at one point at the rear of the 270 km/hour x 20 minute drive, and the cord was then taken out from the tire and observed for fuzz on the cord, but no fuzz was observed and the fatigue resistance of the cord was at a level with no problem. Ta. However, in Comparative Example 9, the number of cords to be driven was too large and deviated from the scope of the present invention, so that some cords overlapped and chunks of the tread rubber occurred due to abnormal heat generation. On the other hand, in Comparative Example 8, because the number of strokes was too small in relation to the twist coefficient, a decrease in steering stability was observed, which is thought to be due to insufficient tire rigidity, and the steering stability was inferior to that of the control tire of Comparative Example 1. Ta.

Comparative Example 10.11 and Examples 4 to 6 have high strength and high elasticity polyvinyl alcohol fibers with a twist coefficient of 0.53.
7 (Number of twists: 42.4 x 42.4 T/1
0 cm ), which is approximately the same twist coefficient as Comparative Example 1. In this case, compared to Comparative Example 1, the drum high-speed durability level was significantly improved, which is thought to be due to improved adhesion, and there was no fuzzing of the cord after running on the drum, and the fatigue resistance of the cord was also a problem. There wasn't.

However, in Comparative Examples 10 and 11, the number of strokes was small in relation to the twist coefficient, so steering stability could not be ensured due to insufficient tire rigidity.

In Comparative Example 12 and Example 7, the twist coefficient was 0.590 (number of twists:
46.6X46.6T/10cm). In this case, although there is no problem with the tire durability or the fatigue resistance of the cord, the cord rigidity tends to be insufficient due to the increase in the twist coefficient, and the number of driving strokes is reduced as in Example 7 (40 cords 1
I found out that I needed to make it more than 5 bites.

8 and 13-15 The various cords described above were used as belt materials for large 1200cc class touring back tires, and the same material was used as reinforcement N (flipper).

This is because such large tires may lack durability if a reinforcing layer (flipper) is not provided.
This is because there are problems such as poor motion characteristics due to insufficient rigidity, and it is necessary to compensate for this problem. Incidentally, tires of 130/90 R16 size for the front wheels and 150/90R15 tires for the rear wheels were prototyped. The basic structure of these tires is shown in FIG. 4, and their belt and flipper structures are shown in Table 3.

The prototype tires were subjected to the actual vehicle handling stability test and fluffing test as well as the drum durability test described below.

Heavy load durability test: JATMA A condition, 81
110% after running for 4 hours with 100% load at a speed of h/h
The steps were increased to load x 6 hours, 117% load x 6 hours, and thereafter the steps were increased to +15% load x 4 hours, and this was repeated until tire failure.

(ii) Low internal pressure durability drum test: Internal pressure 1.2 kg/
The vehicle was continuously driven under the conditions of cia, JATMA MAX load, and speed of 80 km/hour, and the travel distance until tire failure was determined.

The results of each of the above tests are also listed in Table 3 below.

From the test results shown in Table 3 above, the following was confirmed.

Comparative Example 13 uses aramid fiber as a control. In this case, the drum durability level was relatively low and was significantly inferior to Comparative Example 14 using 6.6-nylon. This is due to insufficient adhesive strength and fatigue resistance of the cord, and can be said to be at a level that requires further improvement.

Comparative Example 14 uses a cord made of <6.6-nylon fiber as described above. In this case, although the durability of the tire was at a satisfactory level, the lack of tire rigidity resulted in a significant decrease in steering stability.

Comparative Example 15 uses conventional polyvinyl alcohol fibers. In this case, although the durability level of the tire is improved compared to Comparative Example 13, there is a lot of fuzz on the cord after running on the drum, and there are concerns about the fatigue resistance of the cord in terms of whether it can withstand long-term use. was there. Further, the level of steering stability was also slightly inferior to Comparative Example 13.

Example 8 uses the high strength and high elasticity polyvinyl alcohol fiber according to the present invention. In this case, the drum durability was significantly improved compared to Comparison 13, and there was no damage to the cord after running on the drum, indicating a significant improvement in the fatigue resistance of the cord. Furthermore, the steering stability of the tire was almost the same as that of Comparative Example 13, which was at a somewhat satisfactory level for a large size tire.

In Comparative Examples 13 to 15 and Example 8, no failure was observed due to the reinforcing layer (flipper) itself.

(Effects of the Invention) As explained above, the motorcycle tire of the present invention exhibits tire rigidity comparable to that when aramid fiber is used as the belt material, and has superior high-temperature adhesion than aramid fiber. This has the effect of significantly improving tire durability.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the twist coefficient N7 of the cord taken out from the tire and the strength S, and Figure 2 is a diagram showing the relationship between the cord twist coefficient NT and the number of cords inserted in the crown center part E of the actual vehicle. Figure 3, a diagram showing the influence on handling stability, is for the medium-sized 400
110/70R for CC class sports motorcycles
Cross section of 17 size and 140/60R1B size tires, Figure 4 shows 150/90R15 size and 130/90 size tires for large 1200cc class touring bikes.
It is a sectional view of an R16 size tire.

Claims (1)

[Scope of Claims] 1. At least one carcass layer having a pair of bead portions, a cord folded back including the bead portions, and intersecting at an angle of 90° to 25° with respect to the tire equatorial plane; A two-wheeled vehicle tire comprising at least one belt layer having a cord that intersects at an angle of 0° to 40° with respect to a plane, wherein the cord taken out from the belt layer has the following formula: S>15.
5-12N_r 0.33<N_r<0.6 (S in the formula is the strength of the cord (g/d), N_r is N_r
= N×√(0.139×D/ρ)×10^-^3 where N is the twisting coefficient per 10cm cord length (
T/10cm), D is 1 of the total denier of the cord
/2 and ρ indicate the specific gravity of the cord.
), and a relationship between the twist coefficient N_r and the number of strokes E satisfies the following formula: E<70 E>36.3N_r^2+24.7.