JPS63134307A - Radial tire - Google Patents

Abstract

PURPOSE:To reduce the rolling resistance and improve the high speed durability by using the cord made of aromatic polyester fiber having a tensile strength over a specific value and tensile modulus over a specific value and applied with twist so that the twist coefficient is set within a specific range, as the reinforcing layer for a tire. CONSTITUTION:The cord made of aromatic polyester fiber having a tensile strength of 15 g/d or more and tensile modulus of 300 g/d or more and applied with twist so that the below-described twist K is set within a range of 800-2800 is used as the reinforcing layer of a radial tire. In this case, K=TD<1/2>. In this case, K is twist coefficient, T is the number of twist (T/10cm), and D is the total denier quantity of the cord. In this tire structure in which a belt layer 5 is arranged in annular form in the direction EE' of the tire periphery on a carcass layer 4 in a tread 1, the above-described cord is used for belt. Therefore, the high speed durability and steering stability, etc., are not deteriorated, and the lightweight tire can be obtained, and the rolling resistance can be reduced.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention reduces tire rolling resistance and improves high-speed performance by effectively utilizing wholly aromatic polyester fibers in the belt and carcass cord of a radial ply tire. The present invention provides a tire with excellent durability and handling stability.

[Prior art]

With the spread of automobiles and the expansion of highways, the use of radial tires has progressed, with the rate of radial tires for passenger cars reaching over 80%, and the rate of radial tires for trucks and buses reaching over 50%.

The reason why radial tires have become so popular is that their unique radial structure provides superior wear resistance, high-speed resistance, and handling stability compared to conventional bias tires.

The structure of the well-known radial ply tire is
A carcass comprising a tread portion, a pair of side portions connected to the tread portion at both shoulders of the tread portion, and a pair of bead portions formed on the inner periphery of the side portions, and cords arranged in the radial direction of the tire; It consists of a belt that surrounds the carcass.

The carcass portion and the belt portion, together with the bead portion, play an important role in maintaining the strength of the tire.

Generally, a belt consists of two or more plies with cords arranged at an angle of 10° to 30° with respect to the circumferential direction of the tire, and a carcass consists of one or two layers with cords arranged at approximately 90° with respect to the circumferential direction. Formed from plies of layers.

Radial tires are characterized by the belt and carcass. The carcass gives flexibility to the tire, and the belt restrains the carcass, acting like a hoop on a bucket.This belt stiffens the tread surface, suppressing the movement of the tread surface. and the above-mentioned good tire characteristics can be obtained.

Since the oil crisis in 1971, energy conservation has been a hot topic, and low fuel consumption has become a major characteristic of automobiles.Radial ply tires, which have better tire characteristics than conventional tires, have been improved from various angles. requested.

Fuel efficiency in automobiles depends on improving the thermal efficiency of the engine and reducing running resistance.

Tires, which are one of the important parts of automobiles, have a large effect on running resistance and play a role in reducing fuel consumption.

The running resistance of a vehicle can generally be divided into: ■ rolling resistance caused by mechanical losses such as bearing friction, ■ air resistance, ■ slope resistance, ■ acceleration resistance, and ■ tire rolling resistance. . Of these, the proportion accounted for by the tire rolling resistance described in (1) above varies depending on the speed of the vehicle, but is said to reach 50% or more in the speed range of 1100 k/h or less where air resistance is low.

The tire rolling resistance is further analyzed from its mechanisms: (a) hysteresis loss, (b) frictional resistance, (C)
The hysteresis loss is said to account for more than 90% of the tire rolling resistance.

It goes without saying that reducing this hysteresis loss is extremely effective in reducing the tire rolling resistance.

It is generally known that the transfer resistance caused by this hysteresis loss is expressed by the following equation.

Transfer resistance = H/2πr Here, H = ΣUi - sin δ · Vir - Tire radius Ui: Strain energy of each part of the tire sin δ: Amount of energy loss in each part of the tire Vi: Volume of each part of the tire From this, factors that reduce hysteresis loss Considering that the tire radius is constant, the hysteresis loss is U
It can be seen that is sin δ is influenced by Vi.

Ui is easily influenced by tire shape and other external factors, and it is difficult to quantitatively understand it. Therefore, as a means to reduce hysteresis loss, sin δ,
A method is being used to reduce Vi.

The methods that have been taken so far to reduce sin δ and Vi include the use of low heat generation treads and compounds, and increasing the rigidity of the tire belt to reduce tread deformation and energy loss. Regarding Vi, the method is to reduce the weight of each member. Making treads and compounds lower in heat generation reduces wet road characteristics and reduces safety on wet roads.
This method cannot be taken lightly. In addition, increasing the rigidity of the tire belt deteriorates ride comfort, so
There are limits.

Furthermore, while reducing the weight of each component is effective, simply reducing the weight of each component not only reduces durability but also reduces the basic performance of the tire. It is a well-known fact that it is difficult to maintain performance and reduce the weight of each member. In order to reduce the weight of tires under these difficult conditions, there was a need for a new material that was lightweight and had properties comparable to conventional materials.

[Purpose of the invention]

An object of the present invention is to provide a radial tire that has reduced rolling resistance and improved high speed, durability, and handling stability.

[Structure of the invention]

The present invention is a radial tire, and the reinforcing layer of the tire has a tensile strength of 15 g/d or more and a tensile modulus of 300 g/d.
The following twist coefficient K is 8 for the above fully aromatic polyester fibers.
The gist of this invention is a radial tire using cords twisted in a range of 00 to 2800.

K=TJ■− ：Twist coefficient T: Number of twists (T/10cm) D: Total denier of cord Hereinafter, the configuration of the present invention will be explained in detail.

Among the radial tires commonly used at present, radial ply tires for passenger cars have a carcass ply structure in which the cords are arranged at approximately 90 degrees to the tire circumferential direction, and a carcass ply in which the cords are arranged at approximately 90 degrees to the tire circumferential direction. It consists of belts arranged in degrees.

Organic fibers such as nylon and polyester are used as the carcass member.

Steel is mainly used for belts.

Steel has a larger initial modulus than the organic fiber,
Therefore, the rigidity of the belt portion is increased, and it is an important material for maintaining the excellent characteristics of the radial ply tire for passenger cars.

However, on the other hand, steel has extremely low tensile strength per unit of weight, so the weight of the tire, especially the weight of the belt, is large, so the weight of the steel belt accounts for 15 to 17% of the total weight of the tire. .

That is, how to reduce the weight of the belt portion is important in reducing tire rolling resistance.

In terms of weight reduction, the above-mentioned organic fibers are used as belt materials, but since these have a lower initial modulus than steel, the rigidity of the belt part is insufficient, and the steering stability and abrasion resistance are reduced. Due to the decrease in modulus at high temperatures, durability at high speeds deteriorates, and it cannot be used as a substitute for steel. Therefore, it has been desired to develop a lightweight, high-strength, and highly elastic fiber material that can replace steel.

As a result of various studies, the present inventors have found that by effectively using fully aromatic polyester fibers consisting of aromatic rings and ester bonds, the weight can be significantly reduced compared to steel belt tires, and various performances can be satisfied. I found out that it can be done.

Generally, radial ply tires for passenger cars use different materials for the carcass and belt depending on their respective functions, but the code of the present invention allows the use of the same material for the belt and carcass, improving productivity. It is also advantageous in terms of

The wholly aromatic polyester fiber used in the pneumatic tire of the present invention is the following material.

That is, it is a wholly aromatic polyester fiber obtained by copolymerizing two or more compounds selected from aromatic dicarboxylic acids, aromatic diols, and aromatic hydroxycarboxylic acids as shown below.

H Since these fibers generally have rigid molecules, they have poor bending fatigue resistance, and when used for reinforcing tires, they must be twisted appropriately.

That is, the twist coefficient K expressed by the following formula is 800 to 280.
It is necessary to give a twist in the range of 0.

In particular, when this fiber is used for the belt layer,
200, 1300-280 when used for carcass layer
0 is more preferred.

When used in belts, if the twist coefficient is too high, the strength and modulus (tensile modulus) will be greatly reduced. In particular, a decrease in modulus will reduce belt rigidity and worsen steering stability.

On the other hand, if it is too low, the convergence of the cord will decrease and the adhesiveness will decrease, resulting in a decrease in the durability of the tire.

On the other hand, if the number of twists in the carcass is too low, the fatigue resistance will decrease, resulting in a decrease in the durability of the tire, and if the number of twists is too high, the strength and modulus will decrease, resulting in poor handling performance and high speed performance. This results in a problem of decreased performance.

K=TJ1-: Twist coefficient T: Number of twists (twists/10cm) D: Total denier of the cord Also, the tensile strength of the fully aromatic polyester fiber before being twisted is 15 g/d or more, preferably 20 g /d or more, and the tensile modulus is 300 g/d or more, preferably 4
00g/d or more is required.

This is because when twisting is applied to improve fatigue resistance and adhesion, strength and modulus are significantly reduced. Therefore,
In order to create a cord with appropriate strength and modulus as a substitute for steel cord, it is necessary to use fibers with the above-mentioned strength and modulus.

The cord thus obtained is coated with adhesive and heat treated, then embedded in rubber and used.

From the viewpoint of adhesion, it is more preferable for this fiber cord to be pretreated with an epoxy resin or an isocyanate compound, and then treated with a mixture of resorcinol, formalin, and latex (RFL).

Examples are shown below.

<Example> As a wholly aromatic polyester fiber used in the pneumatic tire of the present invention, a fiber represented by the following formula (I) obtained by copolymerization of oxybenzoic acid (I) and 2oxy6-naphthoic acid (II) was used. The OOH polymer was produced by hot melt spinning and heat treatment. This fiber consists of 1500 filaments of 5d.
d fiber, tensile strength is 23g/d, tensile modulus is 5
It has a characteristic of 60 g/d.

A first twist is added to this yarn, and a second cord is made by adding a second twist.
A 1500d/2 cord was created by putting the final twist together.

At this time, four types of cords with different twist coefficients were created. Attach 1% water-soluble epoxy resin to these cords,
After heat treatment, 8% RFL was further attached and heat treated,
Obtained adhesive processing code. Obtained adhesive processed cord a
-d characteristics are shown in Table 1.

a b b c d note) The measurement method is based on JIS J 1017.

Tires were prototyped using the codes a to d and evaluated.

The prototype tire is 205/60R15.

The evaluation items were high-speed durability performance, durability performance, rolling resistance, handling stability, and tire weight.

High-speed durability performance and durability performance were tested in accordance with JIS D 4230. In addition, the rolling resistance is determined by rotating the tire on a drum at a circumferential speed of 150 km/hr, then letting the drum follow along, and calculating the rolling resistance of the tire and drum from the relationship between the damping speed of the drum and time. The rotational resistance of the drum was subtracted to obtain the tire rolling resistance.

Driving stability was determined by a feeling test conducted by a test driver.

Belt test Tire specifications.

Tires were produced using each of the codes a, b, and d for belts. The cords were placed on the belt layer on the carcass layer side at a number of 55 cords per 5 cm and the cord angle was 24° with respect to the tire circumferential direction, and both left and right ends were bent toward the trend part side. A so-called folded belt structure was obtained in which both left and right ends of the tread side belt layer (crossing the carcass side belt layer and having a cord angle of 24° with respect to the tire circumferential direction) were covered by the bent portions.

As a comparison, we also created a tire using a steel cord belt. The steel coat I used was I x 5.
(0,25).

The belt structure of this tire has the following specifications.

The carcass of the tire in the above belt test was made of polyethylene terephthalate fiber 1500 d/2 with a number of twists of 40, which had a two-layer belt structure that crossed each other, with a cord angle of 21° in the tire circumferential direction with 40 cords per 5ω. X 4
Using 0 times/10 cm, the cords were arranged in one layer so that the cord angle was 90° with respect to the tire circumferential direction, and the number of cords was 40 per 5 cm in the tire equatorial plane.

Figures 1 and 2 show a tire structure using the cords a, b, and d for the belt, and Figure 2 shows a tire structure using the steel cord for the belt.

In these figures, a carcass layer 4 is installed between a pair of left and right bead wires 3.3, and in the tread 1, a belt layer 5 is placed on the carcass layer 4 in the tire circumferential direction EE'.
are arranged in a ring. In Figure 1■, the first
As shown in Figure 3, both ends of the lower belt layer 5d are bent upward and folded back to cover both ends of the upper belt layer 5u. 2 is a side wall.

<Carcass test> Using cords a, c, and d, make sure that the cord angle is 90° with respect to the tire circumferential direction, and
A tire was created in which the layers were arranged so that the number of strokes per cm was 40.

The belt structure of this tire has the same specifications as the one using steel cord in the belt test described above.

The tire evaluation results are shown in Table 2.

(Margins below this page) As shown in Table 2, when the cord of the present invention is used in a tire belt, the weight of the tire is reduced and the rolling resistance is clearly improved compared to conventional tires. In addition, the same level of steering stability as conventional tires can be obtained. Moreover, when the twist coefficient is less than 800, high-speed durability and durability performance are reduced. All of these tires suffered from belt edge separation caused by poor adhesion of the belt cord.

On the other hand, when the twist coefficient exceeds 2800, the modulus of the cord decreases, resulting in a decrease in the rigidity of the belt portion, a decrease in steering stability, and no improvement in high-speed durability.

On the other hand, when used as a tire carcass material, the tire weight is not reduced, but high-speed durability is improved due to the high modulus of the carcass material, and rolling resistance is also improved. This is considered to be a result of the carcass cord having a high modulus, which suppresses the phenomenon of the belt section rising during tire rotation.

When used as a carcass cord, it can be seen that if the twist coefficient is low, the durability performance is extremely deteriorated.

Furthermore, if the twist coefficient is too high, the characteristics will be no different from those of conventional tires.

〔Effect of the invention〕

As explained above, by using the cord of the present invention in a tire belt, the weight of the tire can be reduced without impairing high-speed durability, durability, and handling stability, and the rolling resistance can be reduced. Also, it can be used for carcass for high speed durability,
Rolling resistance is improved over conventional tires. It goes without saying that the cord of the present invention can also be used for tires for trucks, buses, etc.

[Brief explanation of the drawing]

Figure 1) is a partially cutaway half-section perspective explanatory diagram of a tire, Figure 1■ is a cross-sectional explanatory diagram showing the structure of the belt layer in Figure 1), and Figure 2 is a partially cutaway explanatory diagram of another tire. FIG. 2 is a perspective explanatory diagram showing a cutaway half section. 1...Tread, 2...Sidewall, 3...
Bead wire, 4... carcass layer, 5... belt layer.

Claims (1)

[Scope of Claims] A radial tire, in which the reinforcing layer of the tire is made of wholly aromatic polyester fibers having a tensile strength of 15 g/d or more and a tensile modulus of 300 g/d or more, and a twist coefficient K of 800 to 28 as shown below.
A radial tire made of cord twisted to a range of 0.00. K=T√D K: Twist coefficient T: Number of twists (T/10cm) D: Total denier of cord