JPH04159107A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To reduce the weight of tire without sacrificing operational stability by specifying the sum of cross sectional area of a belt cord in a belt ply, and by forming each reinforcing ply out of a specific band ply tilted and wound spirally at a small angle. CONSTITUTION:A pneumatic radial tire 1 is formed as a flat tire, and its tire compression, or the ratio H/WT where H is the cross sectional height in the direction of the tire radius, and WT is a maximum width of the tire, is not more than 55%. For each belt ply 13A, 13B, the sum of cross sectional area of the belt cord in the distance A of 50mm in the cross section where each belt ply crosses with a belt cord 12, is determined as 6.08mm<2>-8.59mm<2>. First and second reinforcing plies 14, 15 of a reinforcing layer 9 are formed by winding a long band ply 20 spirally. The band ply 20 is formed out of a long band- shaped body for which a complex cord 23, for which aromatic polyamide fiber 21 and nylon fiber 22 are twisted together, is coated with a topping rubber 24.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic radial tire that can be made lighter without reducing handling stability.

[Conventional technology]

In recent years, attempts have been made to save fuel even in automobiles in order to prevent deterioration of the global environment such as global warming and an increase in carbon dioxide.

Furthermore, reducing vehicle weight is the most effective way to reduce fuel consumption.
Reducing vehicle weight by 1% has the effect of improving fuel efficiency by 1%, and tires are now required to be even lighter.

Among the members constituting the tire, the belt layer uses steel for its cord in order to increase the rigidity of the tread portion, and therefore the belt layer has a large influence on the tire weight. This tendency is particularly remarkable in, for example, heavy-duty tires with a small aspect ratio.

[Problem to be solved by the invention]

In response to the above request, is there a belt layer in which the Bel I cord of the belt layer is replaced with steel and is made of aramid fibers that have strength such as between steel and track? Although the weight of the tire can be reduced by using organic fibers, there is a problem in that the steering stability is lowered due to insufficient rigidity of the tread compared to tires using steel cords.

As a result of extensive research in an effort to solve both of these two problems of reducing tire weight and maintaining handling stability, the inventor developed a tire by reducing the cross-sectional ratio of the steel cord in the belt layer. In addition to reducing the weight of the steel cord, a reinforcing layer is provided to compensate for the decrease in rigidity of the tread due to a reduction in the cross-sectional ratio of the steel cord.The reinforcing layer is a composite cord made by twisting two organic fiber cords with different performance. The present invention was completed by discovering that forming a belt-like ply in a spiral manner provides efficient reinforcement without significantly increasing the weight of the tire.

An object of the present invention is to provide a pneumatic radial tire that can reduce tire weight without impairing handling stability.

[Means to solve the problem]

The present invention is a pneumatic radial tire having an aspect ratio of 55% or less, which is the ratio of the tire radial cross-sectional height to the maximum width of the tire, wherein A carcass consisting of two or more carcass plies, a belt layer consisting of two or more belt plies disposed inside the tread portion and outside the carcass in the tire radial direction, and having belt cords made of steel arranged in parallel; a reinforcing layer having a first reinforcing ply disposed radially outward and covering the entire surface of the belt layer; and a second reinforcing ply covering at least both ends of the belt layer, the belt ply comprising: 50 in the cross-sectional direction perpendicular to the belt cord
The total cross-sectional area of the belt cord within a distance of mm is 6.08 m.
The belt cords are arranged parallel to each other with a length of at least m2 and less than 8°59 mm2, while the first and second reinforcing plies are topped with a composite cord made by twisting aromatic polyamide fibers and nylon fibers. This is a pneumatic radial tire formed by winding a long belt-shaped ply covered with rubber in a spiral shape at a small angle.

[Effect]

The belt layer is formed by a belt ply using a belt cord made of steel, and the total cross-sectional area occupied by the belt cord of the belt ply is regulated to a smaller and fixed range than conventional belts, which reduces the weight of the belt layer.
Therefore, the total weight of the tire is reduced.

Note that the total cross-sectional area of the cords can be regulated by adjusting the belt cord diameter or by adjusting the number of cords. Furthermore, both may be used together for adjustment.

6.08m when the total cross-sectional area of the belt cord is 50mm
If it is less than 8.59 mm2, the rigidity of the tread portion will be significantly reduced and the steering stability will be significantly inferior, while if it is more than 8.59 mm2, the weight of the tire will not be reduced.

Further, since a reinforcing layer is provided on the outside of the belt layer, and the reinforcing layer is formed by a first reinforcing ply that covers the entire width of the belt layer and a second reinforcing ply that covers at least both ends of the belt layer, The entire region of the belt layer is reinforced by the first reinforcing ply to maintain the rigidity of the tread portion, while the second reinforcing ply can further reinforce the end portions of the belt layer where peeling tends to occur during running.

Moreover, since the first and second reinforcing plies are formed by spirally winding long belt-shaped plies, they can be formed thinner and lighter than the sheet body, thereby reducing the thickness of the tread portion. It is possible to reduce the number of worn tires.

In addition, since the belt-shaped ply forming the reinforcing layer uses a composite cord made by twisting aromatic polyamide fibers and nylon fibers, the composite cord uses nylon fibers in the low elasticity region and aromatic polyamide fibers in the high elasticity region. Each fiber does its part.

Therefore, the elongation of the reinforcing cord during the tire vulcanization process (approximately 3%) is in the low elasticity range, and compared to a cord formed only of high elasticity cords such as aromatic polyamide fibers, the elongation of the reinforcing cord during the tire vulcanization process is in the low elasticity range. During vulcanization on the inner surface of the mold, the inner pressure inside the raw tire can press the outer peripheral surface of the tire against the inner surface of the vulcanized mold along with the elongation of the composite cord, making it easy to vulcanize and mold the tire while using aromatic polyamide fibers. This improves the finishing accuracy and improves steering stability.

On the other hand, when running with high deformation, the composite cord of the reinforcing layer exhibits high elasticity and exhibits a hoop effect together with the belt cord of the belt layer, suppressing the generation of standing waves and reducing vibration. Improves handling stability.

In this way, the pneumatic radial tire of the present invention has the above-mentioned configurations organically combined and integrated, so that
The reinforcing layer compensates for the decrease in rigidity of the belt layer, making it possible to reduce the weight of the tire without reducing steering stability.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

In the figure, a pneumatic radial tire 1 has a tread portion 2
It has a sidewall part 3 extending radially inward from both sides of the tire, and a bead part 4 located at the radially inner end of the sidewall part 3, and further extending substantially parallel to the radial direction of the tire. A toroid-shaped carcass 6 made of a cord extending from the center and having both ends folded around the bead core 5, and a belt layer 7 located inside the tread portion 2 and outside the carcass 60 in the radial direction are arranged. Further, a reinforcing layer 9 is disposed on the outer side of the belt layer 7 in the radial direction.

The pneumatic radial tire 1 is formed as a flat tire having a tire flattening ratio, which is the ratio H/WT of the cross-sectional height H in the tire radial direction to the tire maximum width WT, of 55% or less.

Carcass 6 has a carcass code of 6 with respect to the tire equator.
It consists of one or more, in this embodiment two, radial or semi-radial carcass plies 11 arranged in parallel at an angle of 0 to 90°.

The belt layer 7 consists of two or more belt cords 12 made of steel arranged at an angle with respect to the tire equator C, in this embodiment two belt plies A and B, and the belt cords of each belt ply cross each other. placed in the direction of

Each of the belt plies 13A and 13B has a belt cord 1.
2, the total cross-sectional area of the belt cord within distance A of 50 m is 6.08 mm" above and 8.59 m.
m”.This value is smaller than belt code 12
This means that one or both of the cross-sectional area of the single body, that is, the belt cord diameter d and the number of strokes per 50 mm (ends) n, is restricted.

The reinforcing layer 9 includes a first reinforcing ply 14 that covers the entire surface of the belt layer 7, and at least both end portions FXF of the belt layer 7.
and a second reinforcing ply 15 that covers. In this embodiment, the second reinforcing ply 15 is formed in a small hole that covers only the end F of the belt layer 7, and at the end F, the second reinforcing ply 15 is formed between the belt layer 7 and the first reinforcing ply 14. It is interposed in between.

Both the first and second reinforcing plies 14,15 are formed by spirally winding a long strip-shaped ply 20.

As shown in FIGS. 4 and 5(a), the belt-shaped ply 20 is made of a long belt-shaped body in which a composite cord 23 made of twisted aromatic polyamide fibers 21 and nylon fibers 22 is covered with a topping rubber 24.

The aromatic polyamide fiber 21 has an elastic modulus of 1000 kg/m
Fibers with a high modulus of elasticity of more than 1500 kg/mm" are used. Also, its thickness is
800-3000 denier preferably 1000 d/1
are used.

Furthermore, the nylon fiber 22 is 6.6 nylon with 840
The elastic modulus is 1000 kg/
It is preferably less than mm 2 , preferably less than 700 kg/mm''.

One or more aromatic polyamide fibers 21 such as No. 2 are first twisted at the same time, and one or more nylon fibers that have been first twisted in the same direction are twisted together in the opposite direction to form the composite cord. 23 is formed. Note that a plurality of aromatic polyamide fibers 21 and nylon fibers 2
2, each strand may be pre-twisted, or a plurality of strands may be pre-twisted together.

Further, the composite cord 23 may be made by twisting one each of the aromatic polyamide fiber 21 and the nylon fiber 22, as shown in FIG. Alternatively, the composite cord 23 can be formed by twisting a plurality of cords together.

When a tensile force is applied to such a composite cord 23, as shown in FIG. 5(b), the composite cord 23 is untwisted and elongated.

Also, due to the elongation, the initial twist pitch P of the composite cord 23
1 increases to pitch P2 due to elongation. This elongation is shown in FIGS. 6(a) and (b) for the aromatic polyamide fiber 21.
As schematically shown in , the aromatic polyamide fiber 21A, which had a coiled shape in the initial state, becomes a straight filament 21B by a predetermined elongation. Therefore, from this state, the aromatic polyamide exhibits its originally high elastic modulus.

By winding the aromatic polyamide fiber 21 in a spiral shape in advance, the relative elongation between the helical state shown in FIG. 6(a) and the straight state shown in FIG. 6(b) is achieved. It is clear that it can have a large low elasticity region and a high elasticity region with small elongation when a load is further applied from the state shown in Fig. 6(b). This state forms the inflection point of the elongation-stress curve.

In the composite cord 12, the inflection point V is thus set to be located within the range of 2 to 7% of the elongation. The composite cord 12 is a twisted body of aromatic polyamide fibers 21 and nylon fibers 22. Therefore, as shown in FIG. 5(b), the aromatic polyamide fibers 21 and nylon fibers 2
2 has a twist even when a load is applied, so the inflection point V is not as pronounced as in the schematic cases shown in FIGS. 6(a) and 6(b). The stress elongation curve of the composite cord 23 is illustrated in FIG. In the same figure, curve a
6.6 is nylon fiber 22, 840d, and curved line is 1
2 shows an elongation curve of aromatic polyamide fiber 21 of 000d. In addition, two of these aromatic polyamide fibers 21,
Composite cord 23 made by twisting one nylon fiber 22
The case is shown by curve C. It can be seen that the curve C is located between the curve a and the curve A, and the inflection point V is in the elongation range of 2 to 7%. In addition, in the composite code 23, the inflection point V is the intersection point of the vertical line passing through the intersection X of the tangent S1 that is in contact with the curve in the state of 0 elongation and the tangent S2 drawn to the curve C at the breaking point. Defined.

Further, the composite cord 23 has a high elasticity region from the inflection point V to the breaking point, a low elasticity region from the origin where elongation is 0 to the inflection point V, and has an elastic modulus EH in the high elasticity region. The ratio EH/EL of the elastic modulus EL in the low elasticity range is in the range of 2 to 10. Such a composite cord 23 is produced by appropriately selecting the thickness, number, elastic modulus, etc. of the aromatic polyamide fiber 21, and the thickness, number elastic modulus, etc. of the nylon fiber 22, and by adjusting the twisting conditions such as the twisting angle of both fibers. By adjustment, a composite cord 23 that can satisfy the above range can be formed. The composite cord 23 can also be adjusted by selecting the stretching treatment applied to the aromatic polyamide.

In addition, since the inflection point V exists in the range of 2 to 7% elongation, when the green tire is mounted in a vulcanization mold and the green tire is filled with internal pressure during tire production, the internal pressure causes The reinforcing layer 9 swells as the composite cord 23 expands, and by pressing the outer circumferential surface of the tread portion 2 against the inner surface of the mold, a groove shape having a metal diameter can be carved in the tread portion 2. Note that the expansion caused by filling the green tire with internal pressure is performed by elongating the composite cord 12 in a low elasticity region. For this reason, the inflection point V is set in the range of elongation of 2 to 7%. In addition, the necessary composite code 1 inside the mold due to internal pressure filling
2 is preferably located near the inflection point V.

As a result, inflation of the molded tire and expansion of the tire due to centrifugal force acting during high-speed rotation can be suppressed by the high elasticity region. For this reason, the ratio EH/EL of the elastic modulus EH in the high elasticity region and the elastic modulus EL in the low elasticity region is set to 2 to 2.
It is preferable to set it to 10. When it is less than 2, the above-mentioned suppressing effect is poor, and when it exceeds 10, it is unnecessary from the viewpoint of tire balance.

The band ply 7A is formed by spirally winding the band layer 7 from one end edge E1, across the tire equator C, toward the other end edge E2, and approximately parallel to the tire equator C. Ru. In this embodiment, when winding the belt-shaped ply 20, as shown in FIG. 6, the opposite side edges 20a, 20a of the belt-shaped ply 20 are wrapped so as to be wrapped.

Since the band-shaped ply 20 is spirally wound in the tire circumferential direction, there is no seam in the direction crossing the tire circumferential direction, so it is possible to further improve running stability and ride comfort during running, and to reduce noise. .

Note that, like the first reinforcing ply 14, the second reinforcing ply 15 may be formed as a full pant covering the entire belt layer 7.

〔Concrete example〕

A tire with a tire size of 225150R16 and a configuration shown in FIG. 1 was prototyped according to the specifications shown in Table 1, and a tire with conventional specifications (Comparative Example 1) and a tire other than the structure of the present application (Comparative Example 2.3) were manufactured. ) were also manufactured and their performance was compared.

In the indoor test, each sample tire was mounted on a regular rim, and the maximum internal pressure and load specified by the JATMA standards were applied.

In the actual vehicle test, each sample tire was mounted on a four-wheeled vehicle with a non-volatile air capacity of 3000 cc, and the tires were run on a test course by a dedicated driver, and judgments were made based on the driver's feeling.

Test results confirmed that the weight of the tires could be reduced without compromising handling stability.

〔Effect of the invention〕

As described above, the pneumatic radial tire of the present invention, having the above-mentioned configuration, can reduce the tire weight without impairing the steering stability when driving straight or turning, and can reduce the fuel consumption of the vehicle.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing one embodiment of the present invention, Fig. 2 is a plan view showing a part of the belt ply, and Fig. 3 is a sectional view showing an embodiment of the present invention.
A line sectional view, FIG. 4 is a perspective view showing a band-shaped ply, and FIG.
a) is a front view illustrating a composite cord; FIG. 6(a), (
b) is a diagram schematically showing the initial and stretched state of the aromatic polyamide fiber, Figure 7 is a diagram showing an example of the elongation curve of the cord, and Figure 8 is a cross-sectional view showing the winding of the belt-shaped ply. be. 2-tread part, 3-sidewall part, 4-bead part, 5-bead core, 6-carcass, 7-belt layer, 9-reinforcement layer, 11-
Carcass ply, 12-belt cord, 13A, 13
B-belt ply, 14-first reinforcing ply, 15-second reinforcing ply, A-1 distance, H-section height, W T , - maximum tire width. Fig. 2 Fig. 3 Fig. 4 Fig. 8 Fig. 0a Fig. 5 (a) Fig. 6 (a) 7] Address: 1-1 Tsutsui-cho, Chuo-ku, Kobe @ 1-4 Address: 4-2-26 Nishinakajima, Yodoyou-ku, Osaka I Supplementary B Kami B
Date of February 12, 1991 1)-12 Subject of amendment (1) Summary 7 of "Brief description of drawings" in the description, contents of amendment

Claims (1)

[Claims] 1 A pneumatic radial tire with an aspect ratio of 55% or less, which is the ratio of the tire radial cross-sectional height to the tire maximum width, with one or more tires that pass through the tread and sidewall parts and are folded around the bead core of the bead part. A carcass consisting of carcass plies, a belt layer consisting of two or more belt plies disposed inside the tread portion and outside the carcass in the radial direction of the tire, and having belt cords made of steel arranged in parallel, and an outside in the radial direction of the belt layer. a reinforcing layer having a first reinforcing ply disposed on the belt layer and covering the entire surface of the belt layer, and a second reinforcing ply covering at least both ends of the belt layer, the belt ply having a first reinforcing ply that covers the entire surface of the belt layer; The total cross-sectional area of the belt cord within a distance of 50 mm in the cross-sectional direction perpendicular to is 6.08 mm^2
The belt cords are arranged parallel to each other with a length of 8.59 mm^2 or more and less than 8.59 mm^2, while the first and second reinforcing plies are made of composite cords made by twisting aromatic polyamide fibers and nylon fibers. A pneumatic radial tire formed by spirally winding a long belt-shaped ply covered with topping rubber at a small angle.