JPS6067201A - Radial tire - Google Patents

Abstract

PURPOSE:To control uneven expansion and obtain a radial tire with excellent high-speed durability and operational stability by using modified nylon 66, of high modulus and low coefficient of thermal contraction, for a cord of a band covering both end parts of the layer of belts. CONSTITUTION:A radial tire 1 is composed of a bead core 2, a toroidal carcass 3 with its end part extending as far as the central area of a side wall, the layer 4 of belts with cords slanting at a shallow angle and a bead apex rubber 5. A pair of bands 8 is arranged in direct contact with a radially outside ply 4b, which is in the radially outermost position of the layer 4 of the belts, and further circumferentially enclosing both end parts of said ply. The sum of coefficient of dry contraction for 30min at 180 deg.C and medium extension at 2.25g/d is below 12% and above 5% for a modified nylon 66 cord used for a band. Since said cord is used for the modified nylon 66 band, uneven pantagraphing of the cord of the layer of belts is brought under control.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a modified nylon 66 with high modicolus and low heat shrinkage.
This invention relates to a radial tire that has improved high-speed durability and handling stability by using it in the cord of the band that covers both ends of the belt layer.

Generally, radial tires have less rubberized tire cord (
Both have a carcass structure in which one layer of carcass ply is arranged so that the cords thereof are oriented substantially in the tire radial direction. Then, the carcass (In a radial tire consisting of a single layer of carcass ply, the cord angle of the carcass ply is usually arranged at approximately 90 degrees to the ear equatorial plane, while in a radial tire consisting of multiple layers of carcass ply, the cord angle of the carcass ply is 80 for tire equatorial plane
The cords are arranged to intersect between adjacent plies at angles between 90° and 90°. Additionally, radial tires are constructed with a belt layer inserted between the outer crown part of the carcass and the tread part to reinforce the tread part, and the belt layer is usually made of high modulus cord, such as steel or glass fiber. Composed of multiple layers of rubberized plies of cord, such as rayon, high modulus polyester or aromatic polyamide. The cords of the belt layer are arranged at an angle of 10° to 30° with respect to the tire equatorial plane, and intersect with each other in opposite directions between adjacent plies.

This type of radial tire has the disadvantage that when traveling at high speed for a certain distance, the rubber and ply often peel off near both ends of the belt layer. This is because heat accumulates due to repeated deformation when the tire rotates, and the cut ends of the belt layer cords are free ends, which are particularly susceptible to deformation strain when the tire rotates. Rubber peeling is likely to occur.

Furthermore, radial tires meander in a direction perpendicular to the direction of motion of the vehicle on which they are installed, i.e. in the direction of the tire's rotational axis, which impairs steering stability during high-speed driving, as well as premature tire wear and vibration. This causes a decrease in riding comfort. This meandering phenomenon is due to structural non-uniformity of the tire, which is related to the tire manufacturing process. In other words, radial tires are made by combining component parts such as a belt layer, tread rubber, and sidewall rubber with a carcass ply formed in a toroidal shape in advance to form a toroidal raw cover tire, which is then placed in a mold and processed. Sulfurize. When using an undivided mold, that is, a two-piece mold, which has traditionally been widely used as a vulcanization mold, the tire is inflated during the vulcanization process, and at this time, the cords of the belt layer are Transform so that the position is shifted.

In other words, the cords of the belt layer are pantographed so that the angle to the tire equatorial plane is small, but at this time, due to the structural non-uniformity of the tire, the tire expands unevenly, and the cords of the belt layer pantograph. are also pantographed unevenly, which causes the meandering phenomenon mentioned above.

Methods to solve these problems have been proposed in the past, for example, Japanese Patent Publication No. 54-11562,
In this method, a non-metallic cord cap cord having an angle of 0° to the tire equatorial plane is wound circumferentially adjacent to the outside of the belt layer.

Although such a structure significantly solves the problem of ply delamination at both ends of the belt layer, the problem of tire non-uniformity is still insufficient. Therefore, the inventor conducted repeated experiments to determine the cause of uneven expansion during tire vulcanization due to the relationship between the tire vulcanization conditions and the cord physical properties and arrangement of the band, and found that the dry heat shrinkage rate and intermediate elongation of the cord were large. By using modified nylon 66, which has these properties adjusted to specific ranges, for the hand cord, the uneven expansion described above can be suppressed and meandering during running can be prevented. Therefore, an object of the present invention is to provide a radial tire that suppresses uneven expansion by using the modified nylon 66 described above for the band cord, and has excellent performance characteristics such as high-speed durability and handling stability. .

The present invention provides a carcass in which both ends are folded back around a bead core and the cord angle is arranged at 80° to 90° in the circumferential direction of the tire, and
A belt layer arranged at a cord angle of ~30°, a bead apex arranged in a region sandwiched between a tread part and a carcass and a folded part thereof arranged on the outside of the belt layer and extending in the sidewall direction, and the belt. In direct contact with the radially outermost ply of the layer, at least one ply (circumferentially surrounding both ends of the ply and interposed between the ply and the tread portion) a band of layers, the band having a width sufficient to cover both ends of the widest ply of the belt layer, the cords within the band being substantially parallel to each other and to the equatorial plane of the tire; Moreover, the cord has a dry heat shrinkage rate of 180℃ for 30 minutes and a
．． The sum of the intermediate elongations at 25 g/d is 12% or less and 5% or more, and the strength is 7. 'Modified nylon 66 with Og/d or more
This is a radial tire characterized by the use of

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the right half of a sectional view of the radial tire of the present invention. In the figure, the radial tire (1) of the present invention includes a bead core (2) and a toroidal carcass (3) that is folded around the bead core (2) from the inside to the outside and whose ends extend to the central region of the sidewall. ) and a belt layer (4) provided with a cord arranged in the crown region on the radial outer side of the carcass and inclined at a relatively shallow angle in the circumferential direction of the tire, and the carcass (3) and its folded part (3a). In the enclosed area, a hard bead apex rubber (5) is arranged that extends from the top of the bead core toward the sidewall with a gradually decreasing thickness. Then, a pair of bands (8) are inserted so as to be in direct contact with the radially outer bly (4b) located at the radially outermost side of the belt layer and circumferentially surround both ends of the ply. ing.

First, the modified nylon 66 cord used for the band in the present invention has a dry heat shrinkage rate of 2.25 g/' at 180°C for 30 minutes.
The sum of the intermediate elongations at d is 12% or less and □5% or more.

Here, the dry heat shrinkage rate refers to the sample taken in a skein shape at 20℃, 6
A sample of length lO was measured by applying a load equivalent to 0.1 g/d of a cram school sample that had been left for more than 24 hours in a temperature/humidity secondary chamber at 5% RH.
After being left for a minute, it was taken out of the oven and left for 4 hours in the above-mentioned temperature and humidity cutting chamber, and the value was calculated from the length l by the following formula, which was measured by applying the above-mentioned load again.

That is, the dry heat shrinkage rate △5- ((j2o-1!)/Ro] This is a measure of the dimensional stability of the tire, and the smaller this number, the more uniform the finished tire will be.

On the other hand, the intermediate elongation at 2.25 g/d means 2.25 g/d in the load and elongation curve obtained when measuring tensile strength.
This is the elongation under cl load. This intermediate elongation is a measure of the elastic modulus of the cord, and the smaller this value is, the better the steering stability is.

Therefore, the parameter represented by the sum of dry heat shrinkage and intermediate elongation indicates the characteristics of thermal stability and dimensional stability of the cord, which does not significantly affect the uniformity and handling stability of the tire. The conventional standard nylon 66 cord has a dry heat shrinkage rate and intermediate elongation of approximately 14 as a treated cord.
%, but in the present invention, this is modified to 12% or less and used for the band. If it exceeds 12%, the effect of improving tire uniformity and handling stability will be small.

In addition, the dry heat shrinkage rate of the modified nylon 66 treated cord used in the present invention is in the range of 2.0% to 6.0%, and if it exceeds 6.0%, the uniformity of the tire will not be sufficient, and the The elongation is 5.0% to 8.0%, and if it exceeds 8.0%, handling stability will be impaired.5. If it is less than 0%, thermal shrinkage will be large and the manufacturing process will be difficult.

The modified nylon 66 cord used in the present invention is manufactured by the following method.

(a) Sulfuric acid Nylon 66 having a high degree of polymerization with a relative viscosity of 2.9 or more is melt-spun.

(b) Melt spinning, the yarn is at least 10C[0
The above atmosphere passes through a zone surrounded by a tube heated above the melting point of nylon 66, then is rapidly cooled and taken off, and the birefringence of the yarn passing through the take-up roll is 20
Pick up at a pick up speed of 0 or more.

(c) The yarn passed through the trading roll is heat stretched at a stretching ratio of 3.5 times or less.

(d) When the obtained nylon 66 fibers are first twisted and first twisted, the twist coefficient NT shown by the following formula is 0.34 to 0.64.
, preferably in the range of 0.36 to 0.54° to produce an untreated cord.

NT=NX V [1T block XD10 Xl0-' (N in the formula
(T is the twist coefficient, N is the number of twists per 10 cm, D is 1/2 of the total fineness of the cord; ρ is the fiber density) The untreated cord is made of resorcinol formaldehyde latex (RFL) as the main component. After applying the adhesive and drying, a tension heat treatment is performed at an ambient temperature of 180 to 235°C, preferably 210 to 230°C, for 30 to 300 seconds to produce a treated cord.

Table 1 shows the basic characteristics of the modified nylon 66 yarn and treated cord used in the present invention.

Table 1 To form a ply using the above-mentioned treated cord, the cord filling rate per ply expressed by the following formula is 30 to 30.
The cords are arranged in a range of 60% and buried in rubber.

Code filling rate (%) = number of finished ends (number of embedded 15c
m) x raw cord gauge (mm) x 1/50 x0
0 Here, the raw cord gauge is a cord gauge (wholesale) of the same tenier cord according to JISL-1017. If the cord filling rate (%) is less than 30%, the durability and handling stability will be insufficient, while if it exceeds 60%, the riding comfort will be reduced.

The cords of the band are arranged parallel to each other at substantially Oo with respect to the tire equatorial plane. Also, the width of the band (WC)
It is preferable that both of them be in the range of 5 to 30% of the width (WB) of the belt layer. Preferably, the band is placed so as to completely cover the ends of the belt layer, that is, the ends of the band extend beyond the ends of the belt layer. By arranging the bands at both ends of the belt layer in this way, it is possible to suppress uneven pantographs of the cords of the belt layer during vulcanization, but in the present invention, as shown in Fig. It is even more effective to add a full pant (9) on the side or top side with a width substantially equal to or exceeding the width of the belt layer.

Next, in FIG. 3 showing a schematic side view of the band (8) shown in FIG. arranged to form a This is because in order to suppress tire expansion during the vulcanization process, it is necessary to minimize slippage at both ends (8a) and (8b), and from this point of view, the band should be It can be said that it is more preferable to adopt a winding structure.

When a tire equipped with a band is cured in a mold by a conventional method, the cords of the band are subjected to expansion stress and are elongated in the longitudinal direction. will be elongated by 1 to 4% from the state before vulcanization. Therefore, the band cord applies compressive stress to and restrains the belt layer placed inside the cord, further increasing the tire hoop effect, making the tire characteristics more uniform during transfers, and plying at both ends of the belt layer. It also has the effect of suppressing peeling.

The carcass cord used in the tire of the present invention can be made of nylon, polyester, rayon, aromatic polyamide, high modulus polyester, steel, etc., and the type can be selected as appropriate depending on the tire size. The carcass cords are arranged in an angle range of 80'' to 90'' with respect to the tire equatorial plane.

The belt layer used in the present invention usually has a plurality of plies, and the cords are arranged so as to cross each other at the ply plane at an angle of 5 to 30 degrees to the tire equatorial plane. For the cord, steel cord, glass fiber, or organic fiber cord with relatively high elastic modulus such as aromatic polyamide fiber cord, high elastic modulus polyester fiber cord, or rayon fiber cord is used, but steel cord is particularly preferred. It is.

The bead apex has a modulus at 20% elongation of at least 20 kg/βd1, preferably 55 to 70 k.
g/cn! It is within the range of .

In this invention, the vertical distance from the base of the bead portion to the tip of the bead apex is 1/3 or more of the vertical distance H from the base to the tread apex, and in order to further improve the high-speed performance of the tire, h/H is about 1/2 or 1
It is more preferable that the flex zone F is extended in the direction of the tread by 1/2 or more, and that the flex zone F is limited to a small area between the breaker and the breaker.

In the embodiment shown in Figure 11, a reinforcing layer (6) is provided between the bead apex (5) and the carcass (3) at the bead portion.
One piece is sandwiched so that it is long on the carcass side and shorter on the side where the carcass is folded (3a). This reinforcing layer (6
) is a cord with a higher modulus than the carcass cord, such as a fiber cord made of Kevlar (manufactured by DuPont, trade name), which is tilted at a maximum angle of 45° to 75° with respect to the radial plane of the tire, and is not necessarily used. Although it is not necessary to do so, it is preferable to use it for reinforcement (G).

Next, in the tire of the present invention, the folded part (3a) of the carcass extends beyond the upper end of the rim flange to the center region of the sidewall, and the upper end thereof is connected to the peed knee peck (5).
It ends beyond the top of the . By adopting such a structure, the rigidity of the bead portion is increased by integrating with the bead apex having a high elastic modulus, and the steering stability is improved.

Note that the carcass folded portion (3a) may be disposed below with a step from the upper end of the bead apex.

To vulcanize the radial tire of the present invention, a toroidal green tire is placed in the lower mold. The inside diameter of the mold is adjusted to be slightly larger than the outside diameter of the tire. After the upper and lower molds of the mold are closed, they are heated with high-pressure heating fluid such as steam, and the carcass is expanded so that the outer surface of the tire comes into contact with the inner surface of the mold, and the tire is formed on the inner surface of the mold. The tread shape is imprinted on the tire surface. The final expansion rate of the carcass after vulcanization is 1 to 1 from the state before vulcanization.
It is 4%. Here, during expansion in the vulcanization process, the cords at the ends of the belt layer are similarly stretched and pantographed, but in the present invention, as described above, the cords are made of modified nylon 66 bands having specific thermal properties. Since the cord force of the belt layer is used for this purpose, it is possible to suppress uneven pantographing of the belt layer.

EXAMPLE A tire having the cross-sectional structure shown in FIG. 1 was experimentally manufactured by using a polyester fiber cord as the carcass of the tire and using cords made of different materials as shown in Table 2 for the band. The tire size was 165SR13, and the composition shown in Table 3 was used as the coating rubber for the band. Ride comfort, rolling resistance, ply end crack resistance, etc. were evaluated. The evaluation direction was as follows, and the results are shown in Table 4.

(a) Ride comfort A protrusion 5 cm wide and 1 cm high was attached to a steel drum with a diameter of 3 m. After the tire was brought into contact with the drum, the drum was rotated. The vertical vibration when the tire runs over a protrusion is measured as the force of the tire mounting shaft using an accelerometer, and from the waveform recorded at this time, the amplitude of the first period is used as the hit index, and the relative reciprocal number for Comparative Example 1 is calculated. , and vibration damping is determined by the damping coefficient from the recorded waveform and expressed as an index in comparison with the comparative example. The smaller the value, the better.

(b) Transfer resistance A tire is brought into contact with an iron drum with a diameter of 2 m, the drum is rotated, and after reaching a constant speed, the drum drive switch is turned off, the drum is allowed to rotate freely, and the transfer resistance is determined based on the degree of deceleration, and the tires are compared. The example was set as 100 and expressed as an index. The smaller the index, the better the transfer resistance.

(c) Resistance to cracking at ply end After driving 60,000 km on general roads, cut out the ply end of the tire with a knife, measure the size of the crack at the ply end, and take the reciprocal. Comparative Example 1 was set as 100 and expressed as an index. The higher the index, the better the ply end crack resistance.

(d) Tire uniformity Rim assembly and internal pressure 2. A tire filled with 0 kg/cnf was pressed against a drum with a load of 357 kg, and the tire and drum were rotated, and the changes in stress in the horizontal and vertical directions with respect to the axle were measured and expressed as an index. The smaller the value, the better.

(e) Driving stability Comparison test of driver's senses based on actual vehicle driving test was expressed as an index. The larger the index, the better the steering stability.

From Table 4, it can be seen that the examples of the present invention have excellent overall properties.

[Brief explanation of drawings]

1 and 4 are the right half of a sectional view of the radial tire of the present invention, FIG. 2 is a schematic plan view showing the arrangement of bands, and FIG. 3 is a schematic side view of the same. 1. Kuiya 4. Belt layer 2, bead core 5. bead knee pec 3, carcass 6. Reinforcement layer 8, band patent applicant Sumitomo Rubber Industries Co., Ltd. agent Patent attorney Yoshinori Nakamura Figure 1

Claims (1)

[Scope of Claims] (1) A carcass whose both ends are folded back around a bead core and whose cord angle is arranged at an angle of 80° to 90° in the tire circumferential direction, and a carcass having cord angles of 5° to 90° in the tire circumferential direction on the outside of the carcass. 3
A belt layer arranged at a cord angle of 0°, a tread part and a carcass arranged on the outside of the belt layer, and a bead apex arranged in a region sandwiched by the folded part thereof and extending in the sidewall direction, and the bell) At least one layer of band is in direct contact with the radially outermost ply of No. 11, surrounds at least both ends of the ply in the circumferential direction, and is inserted between the ply and the tread portion. the band has a width sufficient to cover both ends of the widest braai of the belt layer, the cords within the band are substantially parallel to each other and to the equatorial plane of the tire; 180℃, 30 minutes dry heat shrinkage rate and 2.25g
The sum of the intermediate elongations at /d is 12% or less and 5% or more, and the strength is 7. A radial tire characterized by using modified nylon 66 having a resistance of Og/d or more. 2) The radial tire according to claim 1, wherein the band is wound twice in the tire circumferential direction. (3) The radial tire according to claim 1, wherein the band has a width in the range of 5 to 30% of the width of the belt layer.