JP2824653B2 - Pneumatic radial tire - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a pneumatic radial tire having improved high-speed durability without deteriorating tire uniformity (RFV, LFV) and free-runout.

[Conventional technology]

Conventionally, as shown in FIGS. 5 and 6, as a radial tire having excellent high-speed performance, a pair of left and right bead portions 1, 1 is used.
In between, the cord angle with respect to the tire circumferential direction EE 'is substantially
While mounting the carcass layer 4 of 90 装, the tread 3
And a plurality of belt layers 5 intersecting each other at a cord angle of 10 ° to 30 ° with respect to the tire circumferential direction EE ′ are arranged on the carcass layer 4, and a cover layer is formed on the outermost layer 5u of the belt layer 5. 6 is arranged. Reference numeral 6a denotes a cord forming the cover layer 6, 5a denotes a cord forming the belt layer 5, and 5d denotes the belt layer 5 located at the innermost layer.

In this conventional tire, the carcass layer 4 and the belt layer 5d are adjacent to each other and are bonded to each other. And the cord with respect to the tire circumferential direction
The carcass layer 4 in the tire after molding and vulcanization causes a pantograph effect (compensating the tire growth with an angle change at the time of tire molding and vulcanization) with the belt layer 5d arranged at 10 ゜ to 30 ゜. Near the section and the tire cross-section direction substantially 2
Molding vulcanization had been shifted by て to 3 ゜. Since the carcass cords are displaced and unevenly arranged in this manner, the tire uniformity, particularly the LFV (Later
al Force Variation) was inevitable.

Further, the cover layer 6 has a function of reinforcing the belt layer 5 to prevent the belt layer 5 from rising during high-speed running, and to improve rigidity in the tire circumferential direction in combination with the belt layer 5. I have. As the cord 6a of the cover layer 6, a textile cord made of a heat-shrinkable material such as a nylon cord is generally used, and the cord 6a is arranged at substantially 0 ° with respect to the tire circumferential direction EE '. .

By the way, in the tire provided with the cover layer 6, after the belt layer 5 is arranged in the manufacturing process, as shown in FIGS. 7A and 7B, a cord is provided on the outermost layer of the belt layer 5. A cover layer 6 having 6a disposed substantially at 0 ° with respect to the tire circumferential direction is arranged, and its terminal portions 62 and 63 are overlapped to form a splice portion 61. In this case the tire circumferential direction length of the splice section 61 of the cover layer 6, l ₁ (see FIG. 7 (A)). Next, after arranging tire constituent members such as the tread portion 3, the unvulcanized tire is vulcanized by heating under pressure in a vulcanization mold (not shown) to obtain a product tire. The condition of the tire after vulcanization is shown in FIG. 7 (B).

Here, the outer circumference of the tire before vulcanization is formed smaller than the inner circumference of the vulcanization mold. The unvulcanized tire is pressed from the inside of the tire in the vulcanization mold to grow the tire, and the outer circumference is vulcanized. It is made to adhere to the inner peripheral surface of the sulfur mold. This is generally referred to as lifting.

When such a lift is applied, the carcass layer 4 and the belt layer 5 can grow in outer peripheral length due to their structures. However, as described above, the cover code It cannot grow due to the arrangement at approximately 0 °.

Therefore, the growth of the cover layer 6 depends on each code constituting the cover layer 6.
This was due to the extension of 6a or the displacement of the terminal portions 62 and 63 in the splice portion 61 thereof.

However, since the adhesion (attachment) force of the splice portion 61 is smaller than the tensile strength of the cord 6a, the growth was almost entirely caused by the displacement of the splice portion 61. Thus, the length l ₂ of the splice portion is shorter than l ₁ before vulcanization. As a result, the growth of the belt layer 5 and the tread portion 3 also
Most of the processing has been performed in the above-described splice portion 61 and a portion adjacent thereto. For this reason, a non-uniform portion is formed on the circumference of the tire, and this non-uniformity has been a cause of vehicle vibration during high-speed running of the vehicle and a factor of deteriorating the high-speed durability of the tire. This is because, when the tire is mounted on the vehicle and the high-speed durability test is performed, the vicinity of the splice portion is abnormally quickly worn, and when the indoor high-speed durability test is performed, a peeling failure occurs almost from the splice portion. Supported.

[Problems to be solved by the invention]

The present invention eliminates the above-described adjacent bonding relationship (pantograph effect) between the carcass layer and the belt layer, reduces local deformation of a splice portion of the cover layer that occurs when the cover layer is disposed, and improves tire uniformity. Accordingly, it is an object of the present invention to provide a pneumatic radial tire in which steering stability is maintained at a high level and high-speed durability is improved.

[Means for solving the problem]

The present invention provides a pneumatic tire in which a belt layer is disposed on a carcass layer, wherein a carcass auxiliary layer having a cord angle of approximately 0 ° with respect to the tire circumferential direction is provided between the carcass layer and the belt layer located at the innermost layer. The carcass auxiliary layer and the carcass layer are interposed to form an orthogonal structure. Further, the cord of the carcass auxiliary layer is a non-twisted polyamide fiber composed of a single monofilament, and its cross-sectional shape has a major axis a and a minor axis b. The pneumatic radial tire is characterized in that the ratio α is 1.5 or more, and the monofilaments are also arranged in parallel with the major axis direction facing the tire width direction.

Hereinafter, this means will be described in detail with reference to the drawings.
The numbers in FIG. 5 and FIG. 6 are applied mutatis mutandis to the same figures in the following figures.

FIG. 1 is a half-sectional view in the meridian direction showing an example of the pneumatic radial tire of the present invention, and FIG.
FIG. 4 is a developed plan view showing a laminated state of a carcass auxiliary layer and a belt layer.

(1) In the present invention, as shown in FIGS. 1 and 2, between the carcass layer 4 and the belt layer 5d located at the innermost layer, the angle of the cord with respect to the tire circumferential direction EE 'is substantially 0 °. A carcass auxiliary layer 7 composed of a cord is interposed.

As a cord of the carcass layer 4, organic fibers such as nylon and polyester are generally used, and as a cord of the belt layer 5, a steel cord is mainly used. In addition, an aromatic polyamide fiber called an aramid fiber is used. May be used.

When the carcass auxiliary layer 7 is interposed between the carcass layer 4 and the belt layer 5, the cord angle of the carcass auxiliary layer 7 with respect to the tire circumferential direction is substantially 0 °, and the cord angle of the carcass layer 4 with respect to the tire circumferential direction is substantially Since the angle is 90 °, the cord 7a of the carcass auxiliary layer 7 as shown in FIG.
And the carcass cord 4a of the carcass layer 4 are orthogonal to each other,
Thereby, an orthogonal structure is formed by the carcass auxiliary layer 7 and the carcass layer 4.

In the orthogonal structure formed as described above, the directions of the elastic main axes of the carcass layer 4 and the carcass auxiliary layer 7 are perpendicular to each other in the tire cross-sectional direction and the tire circumferential direction. Therefore, at the time of tire molding and vulcanization, the carcass cord does not change in cord angle due to the pantograph effect unlike the conventional tire, so that the carcass cord is substantially arranged in the tire cross-sectional direction, and the tire uniformity, particularly LFV Can be improved.

Further, compared to a conventional radial tire in which the cross-sectional shape of the tire is maintained by the belt layer 5 and the carcass layer 4, the tire of the present invention is formed by interposing a carcass auxiliary layer. The orthogonal structure also has a role of maintaining the cross-sectional shape of the tire. Therefore, the belt layer 5
Will effectively function for improving other characteristics of the tire other than maintaining the cross-sectional shape of the tire, in particular, cornering characteristics during curve running.

Further, when the cover layer 6 is disposed on the belt layer 5 as in the conventional radial tire shown in FIG.
In the tire of the present invention, since the carcass auxiliary layer 7 is inserted between the belt layer 5d and the carcass layer 4, local deformation of the cover layer splice, which is a problem of the conventional radial tire, is less likely to occur. Since the carcass auxiliary layer 7 is sandwiched between the upper and lower cord layers, unlike the cover layer disposed on the conventional belt layer 5u, the deformation of the cover layer at the time of vulcanization molding is performed on the entire circumference of the tire. This is because the local deformation at the splice portion of the carcass auxiliary layer 7 is smaller than that of the conventional tire.

(2) As a code constituting the carcass auxiliary layer,
Untwisted polyamide fibers consisting of a single monofilament are used.

In general, a conventional tire cord is formed by bundling a plurality of thin multifilaments, and a predetermined twist is applied to the cord to provide convergence and fatigue resistance. On the other hand, in the present invention, a non-twisted polyamide fiber composed of a single monofilament is used. This is because the cord is made of a single monofilament having a relatively high denier and is not twisted in order to obtain a high modulus. As the polyamide fiber, for example, nylon 66 having a fiber forming property
(Polyhexamethylene adipamide), nylon 6 (polycaprolactam), nylon 46 (polytetramethylene adipamide) and the like.

(3) The cross-sectional shape of the non-twisted monofilament is flattened, and the ratio α between the major axis a and the minor axis b is 1.5 or more (α = a / b ≧ 1.5).

The flattening is intended to improve the durability (fatigue resistance) as described below. That is, FIG. 3 (A),
As shown in (B), for a circular cross section cord m and a flat cross section cord n having the same cross-sectional area and different cross-sectional shapes, the bending strain generated in the cords when the same bending deformation force is applied is given by the following equation. Is represented.

ε = ε ₀ + ZK, where ε ₀ : strain at the neutral axis t of bending Z: distance from the neutral axis t of the bending K: curvature change Accordingly, as Z increases, the bending strain generated increases. Larger than the maximum value Z _max of the maximum value Z _max is a flat code n Z of Z circular code m, consists of a single filament in the cord untwisted, twisted fatigue resistance of not over Reduce the cross-sectional shape with code n
By flattening as described above, the bending strain generated in the cord can be reduced and prevented.

In the case of such flattening, in FIG. 4 in which the cord n is enlarged, if the ratio α of the major axis a to the minor axis b is less than 1.5, it is not possible to sufficiently prevent the deterioration of the fatigue resistance. Therefore, in the present invention, α = a / b ≧ 1.5.

Further, when arranging the cords n, it is necessary to arrange the cords in parallel with the longer diameter side facing the tire width direction. This is because the thickness of the carcass auxiliary layer becomes smaller as compared with the case where the cord m is arranged, so that the bending strain can be reduced.

(4) In the present invention, in addition to the above, the physical properties of the cord after the heat treatment for bonding, that is, the elongation under a load of 2.25 g / d is 6.5% or less and the heat shrinkage at 150 ° C. is 4.5% The following is preferred.

Here, the term “adhesive heat treatment” refers to heat treatment after RFL treatment of a cord by a conventional method in order to enhance adhesion to rubber. The heat shrinkage is the shrinkage after treatment at 150 ° C. for 30 minutes.

If the elongation of the cord under a load of 2.25 g / d exceeds 6.5%, the initial modulus will be low, and when the cord is used as a carcass auxiliary layer cord, improvement in high-speed performance cannot be obtained. Also, 150
If the heat shrinkage at 4.5 ° C. is more than 4.5%, the cord shrinks significantly during vulcanization of the tire, the unevenness on the tire circumference becomes remarkable, and the uniformity deteriorates. Less than,
The effects of the present invention will be specifically described with reference to examples.

〔Example〕

1 and 2, a tire (the present invention tire) to which a monofilament cord is applied as a carcass auxiliary layer 7 interposed between a carcass layer 4 and an innermost belt layer 5d, and the following nylon fiber A prototype tire (conventional tire) to which the code was applied was manufactured.

Monofilament cord: A 3,000 denier nylon 66 monofilament, a non-twisted cord having an aspect ratio α = 3 is produced, and this cord is treated with a resorcinol-formalin rubber latex (RFL) adhesive and subjected to 2.0 / 220 ° C. Heat treatment under tension of 1.0 g / d to produce an adhesive treatment cord with an elongation under load of 2.25 g / d of 6.0% and a dry heat shrinkage at 150 ° C of 3.5%. (The cords are arranged in parallel with the major axis direction facing the tire width direction).

Nylon 66 fiber cord: Two 840D nylon 66 fiber cords are aligned and twisted,
The number of twists is 46 times / 10cm, the number of twists is 46 times / 10cm, the twist coefficient K is 18.
55 twisted cords made D indicates the total denier number of the code).

This cord was treated with the RFL adhesive and 2.0 / 2 at 220 ° C.
Heat treatment under 0g / d tension, elongation under 2.25g / d load
An adhesive cord having 7.0% and a dry heat shrinkage at 150 ° C. of 5.0% was prepared and used as a cord for the carcass auxiliary layer.

For reference, a tire (comparative tire) in which the cover layer 6 made of the above-mentioned nylon 66 fiber cord was disposed on the belt layer 5 as shown in FIGS. 5 and 6 was produced.

 The dimensions of these three types of tires are as follows.

 Tire size: 185 / 70R13 85H.

Belt layer: (1) Steel cord configuration: (same for 3 persons), 1 × 5
(Element diameter 0.25), 40 ends (number of cords per 50mm width).

(2) Cord angle: 20 ° to the tire circumferential direction.

(3) Number of plies: 2 (the cord crosses the upper and lower layers)
(Same for all three).

Carcass layer: One ply of polyester cord of 1500d / 2, cord angle is 90 ° with respect to the tire circumferential direction (the same for all three).

The following tests were performed on these tires. Table 1 shows the results.

Tire uniformity test: (1) RFV (Radial Force Variation), LFV (Latera)
l Force Variation).

The test was performed in accordance with JASO C607 "Method for testing uniformity of automobile tires".

(2) Free run out.

The free run-out indicates a dimensional change in the tire radial direction over one circumference of the tire. The peak to peak of this change is defined as a free-runout pp value.

This is a measure of the circumferential dimensional non-uniformity of the tire.

 The internal pressure during the measurement was measured according to JASO C607.

High-speed endurance test: The test conditions for the indoor high-speed endurance test are: internal pressure P = 3.0 kg / cm ² load W = JATMA design normal load 450 kg speed V = 10 km / hr every 10 minutes from 170 km / hr Drum diameter = 1707 mm Drive until the tires break.

Table 1 shows that the tire of the present invention has a smaller LFV than the conventional tire and the comparative tire. Also, RF
V and free run-out (pp value) are also smaller in the tire of the present invention than in the conventional tire and the comparative tire.
Further, regarding the high-speed durability, it can be seen that the tire of the present invention is improved as compared with the conventional tire and the comparative tire.

〔The invention's effect〕

As described above, according to the present invention, a carcass auxiliary layer is interposed between a carcass layer and a belt layer, an orthogonal structure is formed between the carcass auxiliary layer and the carcass layer, and the cord of the carcass auxiliary layer is simply formed. Because it is a non-twisted polyamide fiber consisting of one monofilament, its cross-sectional shape is flat where the ratio α of the major axis a to the minor axis b is 1.5 or more, and the monofilaments are arranged in parallel with the major axis direction oriented in the tire width direction. Thus, the tire uniformity can be improved and the high-speed durability can be improved.

[Brief description of the drawings]

FIG. 1 is a half sectional view in the meridian direction showing an example of the pneumatic radial tire of the present invention, FIG. 2 is a developed plan view thereof, and FIGS. 3 (A) and 3 (B) are explanatory diagrams each showing a code arrangement. FIG. 4 is an enlarged explanatory view of the code in FIG.
The figure is a half-sectional view in the meridian direction of an example of a conventional pneumatic radial tire, FIG. 6 is a developed plan view, FIG.
(B) is an explanatory view showing a state of occurrence of displacement of a splice portion of a cover layer in a tire manufacturing process. DESCRIPTION OF SYMBOLS 1 ... Bead part, 3 ... Tread part, 4 ... Carcass layer, 5 ... Belt layer, 5u ... Belt outermost layer, 5d ... Belt innermost layer, 6 ... Cover layer, 7 ... Carcass auxiliary layer .

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-2-57405 (JP, A) JP-A-62-170543 (JP, A) JP-A-2-185805 (JP, A) JP-A-2- 179504 (JP, A) JP-A-60-5003 (JP, A) JP-A-63-61604 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60C 9 / 00-9 / 22 D02G 3/48 D01F 6/60

Claims (1)

(57) [Claims] 1. A pneumatic tire having a belt layer disposed on a carcass layer, wherein a carcass auxiliary layer having a cord angle of about 0 ° with respect to the tire circumferential direction between the carcass layer and an innermost belt layer. To form an orthogonal structure between the carcass auxiliary layer and the carcass layer. Further, the cord of the carcass auxiliary layer is a non-twisted polyamide fiber composed of a single monofilament, and its cross-sectional shape has a major axis a and a minor axis. b. The pneumatic radial tire is a flat tire having a ratio α of 1.5 or more and the monofilaments are arranged in parallel with the major axis direction oriented in the tire width direction.