JPH0463703A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To enhance the lateral rigidity of a tire by making up a carcass layer with polyamide monofilament cords not plied and shaped flat in cross section so that the product of the number of cord ends in the carcass layer at a place where the tire has the maximum width and the number of cord deniers is set in satisfaction with a specified relation. CONSTITUTION:In a carcass layer 2 of a pneumatic radial tire which has both ends wound while being turned inside to outside of the tire around a pair of right and left bead cores 1, polyamide monofilament cords (n) not plied and shaped flat in cross section are used as carcass cords for the carcass layer 2. The cords (n) are arranged in parallel in the carcass layer 2 so that the major dia. (a) may be directed to the periphery of the tire. The product of the number of carcass cord ends (ED) in the carcass layer 2 at a place (t) where the tire has the maximum width and the number of carcass cord deniers (DN) is set in satisfaction with the relation EDXDN>6700.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention improves steering stability by using untwisted polyamide monofilament cords with a flat cross section as reinforcing cords (carcass cords) constituting the carcass layer. Regarding lightweight pneumatic radial tires.

[Conventional technology]

A radial tire has a crown portion reinforced with an extremely rigid belt layer along the tire circumferential direction, and a sidewall portion reinforced with a carcass layer in which cords are arranged in the width direction of the tire. In a radial tire having such a structure, if the rigidity of the sidewall portion decreases, the steering stability of the vehicle will significantly decrease due to an imbalance with the rigidity of the crown portion. Therefore, it is necessary to ensure that the sidewall portion also has a certain degree of rigidity that does not impair the steering stability of the vehicle.

Conventionally, from this point of view, a fiber cord having a relatively large initial modulus, such as a polyester fiber cord, has been used as the carcass cord of the carcass layer of a radial tire. Fiber cords with a small initial modulus, for example polyamide fiber cords such as nylon 6 and nylon 66, have rarely been used. In addition, this conventional carcass cord made of fiber cord is made by bundling multiple thin multifilaments, and this cord is twisted to a certain degree to give it convergence, flexibility, fatigue resistance, etc. .

However, when the carcass layer is made of polyester fiber cord, the ester bonds in the polyester tend to be hydrolyzed by moisture and amine compounds generated from the vulcanization accelerator in the coat rubber, reducing the strength of the cord. It was difficult to ensure sufficient rigidity of the tire, that is, the lateral rigidity of the tire.

Therefore, a pneumatic radial tire that is lightweight by using a polyamide monofilament cord with a flat cross section for the carcass cord has been developed (for example, JP-A-1-148828 and JP-A-2-57405). This polyamide monofilament cord with a flat cross section has a characteristic of having a higher modulus than a conventional twisted cord made of multifilament. moreover,
If the carcass layer is constructed by arranging this monofilament I so that the long axis direction of its flat cross section is along the plane direction of the carcass layer, the thickness of the carcass layer can be reduced,
This has the advantage that the amount of coated rubber used can be reduced. Therefore, if a carcass layer made of such a polyamide monofilament cord with a flat cross section is used in a pneumatic tire, it is possible that the weight of the pneumatic radial tire can be reduced without reducing the rigidity.

However, even when a polyamide monofilament cord with a flat cross section is used in the carcass layer in this way, it is not always possible to sufficiently increase the tire lateral rigidity.

[Problem to be solved by the invention]

The present invention has been made in order to eliminate the above-mentioned drawbacks of pneumatic radial tires whose carcass cords are polyester fiber cords or polyamide monofilament cords with a flat cross section. Its purpose is to provide pneumatic radial tires.

[Means to solve the problem]

The pneumatic radial tire of the present invention has a carcass layer formed by arranging untwisted polyamide monofilament cords with a flat cross section so that the long axis direction of the flat cross section is along the surface direction of the carcass layer. It is characterized in that the product of the cord end number (ED) and the cord denier number (DN) at the tire maximum width position of the carcass layer satisfies the following relationship.

ED x DN > 67,000 Thus, in the present invention, the carcass layer is composed of untwisted polyamide monofilament cords with a flat cross section, and the ED x DN > 67,000, which increases the rigidity of the carcass layer and ensures sufficient lateral rigidity of the tire. can be improved.

Furthermore, since the long axis direction of the flat cross section of this cord is along the surface direction of the carcass layer, the amount of coat rubber used can be reduced, so that weight reduction can be achieved.

The above means will be explained in detail below.

FIG. 1 is an explanatory half-sectional view in the meridian direction of an example of the pneumatic radial tire of the present invention.

In FIG. 1, the ends of the carcass layer 2 are folded back and rolled up from the inside of the tire to the outside around the pair of left and right bead cores 1, respectively. A heald layer 4 is arranged over one circumference in the tire circumferential direction. As the belt layer 4, steel cords are mainly used, but aromatic polyamide fiber cords may also be used.

Carcass cords constituting the carcass layer 2 are arranged in the tire width direction. This carcass layer 2 may have two or more layers. The cord angle is approximately 70'' to 90'' with respect to the tire circumferential direction.

As the carcass cord of the carcass layer 2, as shown in FIG. 2, a non-twisted polyamide fiber cord consisting of a monofilament with a flat cross-section, ie, a cord n of non-twisted polyamide monofilament with a flat cross-section is used.

The cords n shown in FIG. 2 are arranged in parallel within the carcass layer 2 with the major axis a directed toward the tire circumferential direction. That is, the direction of the major axis a of the flat cross section is the direction of the carcass layer 20.
Arranged along the surface direction. Specifically, as shown in FIG. 3, in the carcass layer 2, the cord n is arranged in the coated rubber 5 so that the direction of the major axis a of the flat cross section is along the direction of the plane m of the carcass layer 2 (that is, the major axis a direction is parallel to the direction of surface m).

By arranging the cord n in this way, the carcass layer 2
Since the thickness of the coat rubber 5 can be reduced, the amount of coat rubber 5 used can be reduced. In addition, since the cord n is flat, the bending rigidity in the direction of the minor axis (direction perpendicular to the major axis a) of the cord n is reduced, so the cord bends in the direction of the minor axis,
Since the tire can be easily bent and deformed in the vertical direction (radial direction), the improvement in handling stability obtained by improving the tire lateral rigidity does not impair ride quality. It is preferable that the ratio α of the major axis a to the minor axis a is 1.5 or more (
α-a/b≧1.5).

The reason why the cord n is made of untwisted monofilament is that the cord rigidity is increased compared to a conventional fiber cord made of twisted multifilaments.

Examples of polyamide fibers constituting cord n include:
Nylon 66 (polyhexamethylene adipamide), nylon 6 (polycaprolactam), which has fiber-forming properties
Examples include nylon 46 (polytetramethylene adipamide).

(1) Furthermore, in the present invention, the product of the end number (ED) of the tire maximum axial position gt of the carcass cord of carcass N2 and the denier number (DN) of the carcass cord satisfies the following relationship.

EDxDN>67000 Here, the end number (ED) of the carcass cord at the tire maximum width position t refers to the number of carcass cords in the carcass layer per 50IllI11 in the carcass cord right angle direction at the tire maximum width position t.

The reason why we focused on the maximum tire axis position is that the lateral rigidity at this position has the greatest effect on steering stability. Note that the distance W between the cords in the carcass layer 2 is set to 0.1 in the green state before molding, because if it is too narrow, the coat rubber is likely to crack or peel between the cords and the coat rubber when the carcass layer is deformed during the manufacturing process. It is preferable that it is more than mm.

The reason for setting it as ED×DN is that the tire lateral rigidity is related to the number of ends (ED) and the number of denier (DN) of the carcass cord. In other words, when the denier number is small (in other words, when the cord is thin), the lateral stiffness cannot be improved unless a large number of cords are placed, whereas when the denier number is large, the lateral stiffness cannot be improved even if a few cords are placed. This is because the rigidity is improved.

In the present invention, ED×DN>67000, preferably E
Let D×DN>90000. This is because if the ED×DN(7) value is 67,000 or less, the tire lateral rigidity will not be sufficiently improved compared to the conventional case where the carcass layer is composed of polyester fiber cords.

Note that if the lateral rigidity is insufficient, for example, it is necessary to increase the volume of the filler in the bead portion or increase the number of carcass layers, which increases the tire weight.

(2) By the way, carcass cords made of monofilament polyamide fiber cords have high rigidity but are inferior in flexibility. Therefore, stress tends to concentrate at the turn-up edge of the carcass layer, and separation tends to occur.

Therefore, before embedding this carcass cord in the coat rubber 5 to form the carcass layer 2, the carcass cord is mixed with a mixed solution (RF L
), and then rubber composition h containing resorcin or a resorcin initial condensate and hexamethoxymethyl melamine (A) Or a rubber containing resorcin or a resorcin initial condensate, hexamethoxymethyl melamine, and organic acid cobalt It is preferable to cover the surface with composition (B). This increases the adhesion between the carcass cord and the coated rubber 5 at the edge of the amplifier, so
It becomes possible to effectively prevent the occurrence of separation.

The proportion of the components in the rubber compositions (A) and (B) is 0.5
~3 parts by weight, 1 to 5 parts by weight of hexamethoxymethylmelamine, and organic acid cobalt containing 0.05 to 0.05 parts by weight of cobalt element.
The amount may be 0.5 part by weight.

Examples are shown below.

Example 1 The tire lateral rigidity of the following pneumatic radial tires (conventional tires r to ■, invention tires 1 to V) was evaluated by calculating the lateral spring constant. To calculate the lateral spring constant, install the tire on a 13 x 4'A-J rim and set the air pressure to 2.
．． 0 kg/Cl11, and with a load of 400 kg applied vertically to this tire, the increment (DF) of lateral force required to change the tire's lateral displacement from a state of 5 Mrrl to 1011IIll was measured, and the lateral spring constant was determined. (K)
= D F / 5 (kg/arm). The results are shown in Table 1 and FIG. 3 using indices.

The larger the number, the higher the tire lateral rigidity.

(1) Conventional tire I0 Tire size 165 SR13° Tire structure shown in Fig. 1. Carcass layer 2 is polyester fiber cord 1500
Consists of d/2.

(2) Conventional tires ■～■.

Tire size 165 SR13° Tire structure shown in Figure 1. The carcass layer 2 is made of untwisted nylon monofilament 4000D with a flat cross-sectional shape. a = 1
．． 2 ++un, b =0.41llI11゜(3)
Tires of the present invention 1 to ■.

Tire size 165 SR13° Tire structure shown in Figure 1. The carcass layer 2 is made of untwisted nylon monofilament 4000D with a flat cross-sectional shape. a = 1
．． 2 mm, b = 0.4 mm.

(4) Tire of the present invention ■.

Tire size 165 SR13° Tire structure shown in Figure 1. The carcass layer 2 is made of untwisted nylon monofilament 6000D with a flat cross-sectional shape. a = 1
．． 4 mm, b = 0.5 mm.

(Margins below the main text) As is clear from Table 1 and Figure 3, EDXD N > 670 tires have higher lateral rigidity than conventional tires.
00 (Examples I to ■) Example 2 ■ A polyester fiber multifilament cord (polyester fiber cord 1500 d/2) was subjected to the treatment of A1 below, and then the surface was coated with the rubber composition of B below. After covering, a carcass layer was constructed as a carcass cord, and the tire shown in FIG. 1 was produced. Tire size is 165
/80) 113.

AI: After surface treatment with epoxy or isocyanate adhesive, the surface was treated with a mixture of resorcinol/formalin initial fasteners and rubber latex (RFL).
conventionally known general surface treatment methods).

BI: Rubber composition (1) in Table 2 was used.

(Left below next summer)! Table ■ Made of untwisted nylon monofilament 3000D with a flat cross-sectional shape, a = 1.0 mm, b
A cord with a diameter of 0.3 mm was subjected to the treatment described in A2 below, and then its surface was covered with the rubber composition described in B above, and a carcass layer was formed as a carcass cord, thereby producing the tire shown in FIG. 1. Tire size is 165/80 R13
And so.

A: The surface was treated with a mixed liquid (RFL) of resorcinol/formalin initial fasteners and rubber latex (a conventionally known general surface treatment method).

B: Rubber composition (2) in Table 2 was used.

■ Made of untwisted nylon monofilament 3000D with a flat cross-sectional shape, a = 1.0 m + n,
A cord with b = 0.3 mm was subjected to the above treatment A2, and then its surface was covered with a rubber composition B2 below, and a carcass layer was formed as a carcass cord to produce the tire shown in FIG. 1. Tire size is 165/80
It was set to R13.

B2: The rubber composition in Table 3 was used.

(Leaving space below next summer) Buds Table 1 Note) Values represent parts by weight. Also, 3C is Tsukurak 3
C(N-phenyl-N'-(1,3-dimethylbutyl)
-p-phenylenediamine), HMM? I is hexamethoxymethylmelamine, and the resorcin condensate is B-18 manufactured by Co-Novers.

■ Made of untwisted nylon monofilament 3000D with a flat cross-sectional shape, a = 1.0 mm, b
A cord having a diameter of 0.3 mm was subjected to the above treatment A2, and then its surface was covered with a rubber composition B3 below, and a carcass layer was formed as a cass cord to produce the tire shown in FIG. 1. Tire size is 165/80 R13
And so.

B3: The rubber composition in Table 4 was used.

(Margins below the main text) Note) Values represent parts by weight. Also, 3C is Tsukurak 3
C(N-phenyl-N“-(1,3-dimethylbutyl)
-p-phenylenediamine), HMMM is hexamethoxymethylmelamine, and the resorcin condensate is B-18 manufactured by Kotzbaz.

■ These tires were evaluated for durability (presence or absence of separation at the turn amplifier edge). In this case, under the following conditions, from step 4 onward, increase the load by 65 kg every 4 hours until the maximum load is 1140 kg.
After that, the vehicle continued to run at 1140 kg until failure occurred, and the distance traveled until failure occurred was defined as durability, and the results are expressed as an index in Table 5. The larger the number, the better the durability.

Speed 80 k+m/h Air pressure 1.9 kgf/ctA Rim 13 Table 5 shows that prior to constructing the carcass layer, the nylon heptanofilaments are treated with A2, and then covered with a B2 or B3 rubber composition (i.e. surface treated with RFL, then resorcin or resorcin initial stage). Rubber composition (A) containing a condensate and hexamethoxymethylmelamine
Alternatively, it is found that covering the surface with a rubber composition (B) containing resorcin or a resorcin initial condensate, hexamethoxymethyl melamine, and organic acid cobalt is preferable in terms of durability.

〔Effect of the invention〕

As explained above, according to the invention, the carcass layer is constructed by arranging untwisted polyamide monofilament cords with a flat cross section so that the long axis direction of the flat cross section is along the surface direction of the carcass layer, The product of the number of cord ends (ED) at the tire maximum width position of the carcass layer and the cord denier number (D N) is ED x DN > 67000
As a result, the tire's lateral rigidity is increased, and steering stability can be sufficiently improved. Further, since the long axis direction of the flat cross section of the carcass cord is aligned with the surface direction of the carcass layer, the amount of coat rubber used can be reduced, so that weight reduction can be achieved.

[Brief explanation of the drawing]

Fig. 1 is an explanatory half-sectional view in the meridian direction of an example of the pneumatic radial tire of the present invention, Fig. 2 is an explanatory view showing an example of the cross-sectional shape of the carcass cord in the invention, and Fig. 3 is the main part of the carcass layer. The cross-sectional explanatory diagram, FIG. 4, is a diagram showing the relationship between ED×DN and the transverse spring constant. DESCRIPTION OF SYMBOLS 1... Bead core, 2... Carcass layer, 3... Trap throat part, 4... Heald layer, 5... Coat rubber,
a: Long axis, b: Short axis. Figure 1

Claims (1)

[Scope of Claims] A carcass layer is constructed by arranging untwisted polyamide monofilament cords with a flat cross section so that the long axis direction of the flat cross section is along the surface direction of the carcass layer. Number of ends of the cord at the tire maximum width position (
A pneumatic radial tire in which the product of the cord denier (DN) and the cord denier (DN) satisfies the following relationship. ED×DN>67000