JP2000025428A - Pneumatic tire for passenger car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire for passenger cars, which has an excellent durability without damaging the normal traveling performance at the time when internal pressure is charged while suppressing the deflection to restrict a tire-temperature rise and to keep the increase in the tire-weight to a minimum during traveling, particularly even during run-flat traveling. SOLUTION: A carcass part 2 is made up of at least one ply of turned-up carcass plies formed of layers in which organic fiber cords having the melting point of 245 deg.C or more is buried in a rubber matrix and at least one ply of down carcass plies which are arranged between the outer surface of the turned-up carcass plies and a side wall part 6 and which are formed of layers in which steel cords are buried in a rubber matrix. In a cord image determined as a plane by X-ray transmission of the down carcass plies, a rate of the area occupied by filaments to the cord-area at a 15 mm long part optionally selected in the axial direction of the cords, is 0.45 or more and 0.95 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for a passenger car, and more particularly, to a pneumatic tire having excellent durability without impairing performance in normal running when the tire internal pressure (hereinafter referred to as internal pressure) is charged. The present invention relates to a pneumatic tire for a passenger car that can safely travel even when the internal pressure decreases.

[0002]

2. Description of the Related Art In a pneumatic tire, a tire capable of running when the tire internal pressure is reduced, that is, a so-called run-flat running (referred to as a pneumatic safety tire), is used as a tire wheel.
A core type in which a metal or synthetic resin annular core is attached to the rim part in the tire air chamber, and a crescent-shaped cross section on the inner surface of the carcass from the bead part of the tire sidewall to the shoulder area. A side reinforcement type in which a hard rubber layer is arranged and reinforced is known. Of these two types, the core type is suitable for cargo transport vehicles and military vehicles that do not have a problem in ride comfort because of its high load-bearing capacity in run-flat driving. It is light and has a good reputation for vehicles that emphasize riding comfort.

A side reinforcing type suitable for application to a pneumatic tire for a passenger car is a crescent-shaped relatively hard reinforcing rubber layer having a crescent-shaped cross section on the inner surface of a carcass portion in a sidewall portion, and one end portion of the carcass portion. A part overlaps with the belt part, and the other end part is arranged so as to overlap with the bead filler and is reinforced. If the tire punctures during running and the air escapes, the load is supported by the inherent rigidity of the sidewall reinforced by the reinforcing rubber layer, and although the speed must be slightly reduced, the run-flat running for a predetermined distance Can do it.

[0004]

However, at present, even the above-mentioned side-reinforced type pneumatic safety tire still cannot be said to have a sufficient run-flat running property. That is, in the case of a general-purpose passenger car tire, the load burden is relatively small, but when the size of the passenger car is increased, the load per tire becomes as large as about 500 kgf. In such a case, the deformation of the sidewall portion in the punctured state becomes large, and the sidewall portion is completely buckled by a several times dynamic load received during traveling, and the vehicle travels while repeating this. As a result, the temperature of the sidewall portion becomes high due to the self-heating caused by the bending, which promotes thermal deterioration of the rubber reinforcing layer. In addition, the bead portion is pushed up by the flange of the rim, and the skin rubber or the carcass folded portion sandwiched between the curved flange and the bead filler is melted or broken by heat, thereby causing a puncture. Even if it is repaired, subsequent use is impossible.

When a safety tire having a general-purpose tire size is run under run-flat conditions, the internal temperature of the tire is 200.
It is said to be excellent in heat resistance due to high temperature of over ℃, for example, polyethylene terephthalate (PE
Even in T), the adhesion to rubber at high temperatures is not sufficient. Specifically, in the case of a tire to which a carcass reinforced with PET is applied, failure during run flat running is caused by separation between PET and a rubber matrix. , PET cord is mainly melted or broken. Therefore, a higher level is desired in terms of run flat durability.

Means for improving the run flat durability in the side reinforcing type include a method of increasing the gauge of a reinforcing rubber layer or a bead filler to suppress bending, reduce the heat generation temperature, and increase the number of carcass. A method of reducing the heat generation temperature by suppressing bending is considered,
When these methods are adopted, the tire generally becomes hard, the weight of the tire increases, and the performance in normal running at the time of filling the internal pressure, such as rolling resistance and vibration riding comfort, tends to deteriorate, which is not preferable. That is, it is naturally required to have not only durability in run-flat running when the internal pressure of the tire is lowered but also performance in normal running when the internal pressure is charged.

[0007] Therefore, an object of the present invention is to reduce the tire temperature during running, particularly during run-flat running, to suppress the rise in tire temperature, and to minimize the weight increase of the tire while maintaining the normal pressure during internal pressure filling. An object of the present invention is to provide a pneumatic tire for a passenger car having excellent durability without impairing the performance in running.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the structure of the carcass is at least one of the folded carcass ply reinforced with an organic fiber cord having a melting point of 245 ° C. or more. And a carcass ply reinforced with a steel cord having a specific structure, thereby improving the durability performance of run-flat running, The present inventors have found that the normal running performance at the time of filling the internal pressure can be maintained at a high level as compared with a safety tire having a rubber reinforcing layer of the present invention, and have completed the present invention.

(1) That is, a pneumatic tire for a passenger car according to the present invention comprises a carcass comprising at least two of a pair of left and right bead cores and a carcass ply composed of a layer in which a plurality of parallel cords are embedded in a rubber matrix. Part, a belt portion composed of a plurality of layers disposed on the tire radial direction outside of the carcass portion, a tread portion disposed on the tire radial direction outside of the belt portion, and a pair of left and right disposed on the tread portion. In a pneumatic tire for a passenger car comprising a sidewall portion, the carcass portion has at least one folded carcass ply having a layer in which an organic fiber cord having a melting point of 245 ° C. or higher is embedded in a rubber matrix, The steel cord is disposed between an outer surface of the folded carcass ply and the sidewall portion, and a steel matrix is provided. Consisting of at least one down carcass ply comprising a buried layer, in the code image obtained as a plane by X-ray transmission of the down carcass ply, the selected code axial length 15mm optionally
The ratio of the filament area to the cord area of the portion is 0.45 or more and 0.95 or less.

(2) In the pneumatic tire for a passenger car, the steel cord is a pneumatic tire for a passenger car in which each filament is substantially independently present in a rubber matrix.

(3) In the pneumatic tire for a passenger car, the twisted structure of the steel cord is 1 × n or 1+.
This is a pneumatic tire for a passenger car having a structure of n (2 ≦ n ≦ 7).

(4) In the pneumatic tire for a passenger car, a filament diameter of the steel cord is:
This is a pneumatic tire for a passenger car having a range of 0.125 to 0.275 mm.

(5) The pneumatic tire for a passenger car, wherein the sidewall portion is reinforced by a rubber reinforcing layer.

In the present invention, a carcass ply reinforced by a steel cord (hereinafter sometimes referred to as a steel ply) and a carcass ply reinforced by an organic fiber cord inside thereof (hereinafter sometimes referred to as an organic fiber ply)
Works in the following manner. That is, in the characteristic of suppressing the bending of the tire, the steel ply having excellent tensile rigidity is responsible for the outer layer, and the organic fiber plays a role in bending the inner layer of the tire due to the bending of the tire. Also, by disposing the steel ply in the outer layer, the effect of improving the cut resistance from the outside can be obtained. Further, from the viewpoint of the weight of the tire, the combination of one steel ply and one organic fiber ply further reduces the weight.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have made intensive studies on the structure of a rubber-steel cord composite as a down carcass ply, and as a result, determined the occupancy of filaments of a steel cord embedded in a rubber matrix by a specific method. In the code image obtained as a plane by X-ray transmission of the down carcass ply, the ratio of the filament area to the code area of the arbitrarily selected portion having a length of 15 mm in the code axis direction is set to 0 in the specific range based on .
45 or more and 0.95 or less, preferably 0.50 or more and 0.9
By setting it to 0 or less, more preferably 0.55 or more and 0.75 or less, it becomes easy for the rubber to enter the inside of the cord, and as a result, it is excellent in durability and corrosion resistance by compression, and even at high temperatures. It has been found that the adhesion between the steel cord and the steel cord is not impaired. Specifically, the contact area between each filament of the steel cord and the rubber can be specified, and the entry of moisture between the steel cords can be suppressed by increasing the contact area. If the ratio of the contact area between each filament and rubber is increased, friction between filaments, so-called fretting, can be suppressed. Further, as a result of the above, corrosion propagation due to moisture, which is a main cause of deterioration in durability of the steel cord, can be suppressed, and furthermore, corrosion from fretting can be significantly improved.

On the other hand, if the ratio of the filament area to the cord area is less than 0.45, the contact area between each filament and the rubber is increased, and the corrosion propagation due to moisture can be further suppressed. As a result, the tensile modulus of the carcass decreases, and the rigidity requirement of the carcass cannot be satisfied. On the other hand, if it exceeds 0.95, the deformation of the steel filament itself becomes small,
The effect of improving the compression fatigue resistance is reduced.

In the code image obtained as a plane by the X-ray transmission of the down carcass ply, the arbitrarily selected portion having a length in the axial direction of the code of 15 mm means that the actual length of the code is 15 mm. The ratio of the filament area to the code area is the area of the entire cord indicated by the hatched area in FIG. 1 in the code image obtained as a plane shown in FIGS. 1 and 2, and the black area in FIG. When the area of all the filaments indicated by is represented by F, the ratio (R) of the filaments is represented by R = F / A. The X-ray transmission of the down carcass ply can be measured in or out of the tire.

In the present invention, the steel cord used for the down carcass ply has a low tensile stress and a high elongation at the time of cutting by increasing a molding amount with respect to a filament pitch length of the cord. It is a code that can be used. Preferably, each filament is substantially independently present in the rubber matrix.

Such a steel cord is preferably 1 ×
It has an n or 1 + n structure (2 ≦ n ≦ 7), and n is a natural number of 7 or less, more preferably 6 or less and 3 or more. When n exceeds 7, the filaments are likely to come into contact with each other, which may cause fretting, which is not preferable in terms of adhesion between steel cord and rubber, durability and corrosion resistance. The filament diameter of the filament of the steel cord is preferably 0.125 to 0.275 mm, and more preferably 0.125 to 0.230 mm. When the diameter is less than 0.125 mm, the cord is hardly drawn during production and the tensile strength is hardly produced, so that the tensile strength of the cord is reduced, and as a result, the strength of the case member of the tire is reduced. on the other hand,
If it exceeds 0.275 mm, fatigue resistance deteriorates,
Not preferred.

On the other hand, the reinforcing cord of the folded carcass ply has a tire temperature of 200 during run flat running.
Since the temperature is higher than 0 ° C., it is necessary to use an organic fiber having a melting point of 245 ° C. or higher and having heat stability. Specifically, 66-nylon (66Ny), 46-nylon (46Ny), polyethylene terephthalate (PE
T), polyethylene-2,6-naphthalate (PE
N), aramid, polybenzoxazole (PBO),
And polyolefin ketone (POK).

The rubber component used in the down carcass ply, the folded carcass ply, and the rubber reinforcing layer in the present invention is not particularly limited, but is preferably a diene rubber, for example, natural rubber (NR), butadiene rubber (B
R), styrene-butadiene rubber (SBR), and isoprene rubber (IR). In addition, compounding agents usually used in the rubber industry, for example, a reinforcing agent such as carbon black, a vulcanizing agent, a vulcanizing aid, a vulcanization accelerator, an antioxidant, a softening agent, and the like can be appropriately provided. Of course it is.

Regarding the physical properties of the rubber composition used for the carcass ply reinforced with a steel cord, the tensile stress (M ₅₀ ) at 50% elongation is 1.2 to 6.0 MPa,
At 100% elongation of tensile stress _{(M 100)} is 3.0 to 1
It is preferably 0.0 MPa. With respect to the carcass ply reinforced with organic _{fibers, M 50} 0.9
In _～3.0MPa, it is preferred _{M 100} is 1.5～5.0MPa. Furthermore, regarding the rubber reinforcing layer,
M ₅₀ is in _{2.0~9.0MPa, M 100} is 4.0 to
Preferably, it is 15.0 MPa.

The number of carcass plies used in the present invention is preferably 35 for organic fiber cords.
~ 70 lines / 5cm, more preferably 40-60 lines / 5
cm, preferably 2 for steel ply cords
5 to 50 pieces / 5 cm, more preferably 30 to 45 pieces /
5 cm. A green tire is formed by applying this carcass ply, and the green tire is subjected to vulcanization molding.

In the present invention, the side wall portion is preferably reinforced with a rubber reinforcing layer. Specifically, a rubber reinforcing layer having a crescent cross section is provided on the inner surface and / or outer surface of the carcass layer. In particular, by arranging it on the inner surface, the run flat durability is further improved.

[0025]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it should not be construed that the invention is limited thereto without departing from the gist of the present invention. The schematic cross-sectional view of the tire in FIG. 3 shows a structural example (structure I) of a test passenger car tire 1 having a tire size of 225/60 R16. Under the conditions shown in Tables 4 and 5 below, the carcass portion 2 has a first ply 2 in which cords are arranged in a direction substantially perpendicular to the equatorial plane.
a and the second ply 2b, both ends of the first ply 2a are wound around the bead core 4 to form a winding end, and between the first ply 2a on the bead core 4 and the ply winding end. Has a hard rubber bead filler 5 embedded in a tapered shape. On the other hand, the second ply 2
b is a down carcass ply, both ends of which are disposed between the sidewall portion 6 and the outer surface of the first ply 2a. The number of cords to be driven is 50 / for the first ply 2a.
5 cm, and the second ply 2b is 36 pieces / 5 cm.

On the inner peripheral surface of the side wall portion 6 of the first ply 2a, a rubber reinforcing layer 7 having a crescent cross section (JIS A hardness 80 °, maximum thickness 13 mm, M ₅₀ : 4.5 MPa, M
₁₀₀ : 10.5 MPa) from the position overlapping with the bead filler 5 via the first ply 2a to below the belt so that the sidewall portions 6 have substantially the same thickness throughout. The belt 3 is formed by superposing two steel cords having a twist structure of 1 × 5 arranged at an angle of 26 ° with respect to the equatorial plane so that the cords cross each other. Reference numeral 8 denotes a tread portion.

The structure II of FIG. 4 is the same as the structure I except that the second ply 2b is disposed between the bead filler 5 and the folded inner surface of the first ply 2a.

The above-mentioned rubber reinforcing layer having a crescent cross section,
The contents of the rubber composition of the first ply coating rubber and the second ply coating rubber are as shown in Tables 1 to 3 below.

[0029]

[Table 1] 1) BR01 (trademark, manufactured by JSR Corporation) 2) FEF 3) spindle oil 4) Noxeller NS (trademark, Ouchi Shinko Chemical Industry Co., Ltd.)
5) Nocrack 6C (trademark, Ouchi Shinko Chemical Industry Co., Ltd.)
_{Ltd.) M 50 = 4.5MPa M 100 =} 10.5MPa

[0030]

[Table 2] 1) HAF 2) Spindle oil 3) Nocrack 6C (trademark, Ouchi Shinko Chemical Industry Co., Ltd.)
4) Noxeller NZ (trademark, Ouchi Shinko Chemical Industry Co., Ltd.)
_{Ltd.) M 50 = 1.6MPa M 100 =} 2.6MPa

[0031]

[Table 3] 1) HAF 2) Spindle oil 3) Noxeller CZ (trademark, Ouchi Shinko Chemical Industry Co., Ltd.)
4) Nocrack 6C (trademark, Ouchi Shinko Chemical Industry Co., Ltd.)
5) The active ingredient contains 10% as a cobalt metal. M ₅₀ = 2.4 MPa M ₁₀₀ = 4 MPa

Various evaluation methods used for the tires of the examples and comparative examples are as follows. The tensile stress and hardness of the rubber composition were measured according to JIS K6301-1995.

The cutting load of the reinforcing steel cord of the carcass ply and the total elongation at the time of cutting were determined according to JIS G3510-1.
It was measured in accordance with 992.

The area occupancy of the filaments of the carcass ply steel cord was determined by using K-2 type manufactured by Softex Co., Ltd. from the normal direction of the surface of the rubber-steel cord composite taken out from the vicinity of the tire maximum width on the tire sidewall. From an image obtained by irradiating X-rays, 10 points were measured and the average value was obtained.

The performance of the tire was measured by the following method. (1) Run flat durability After assembling the rim with an internal pressure of 3.0 kg / cm ² and leaving it at room temperature of 38 ° C. for 24 hours, the core of the valve was removed, the internal pressure was set to atmospheric pressure, a load of 570 kg, a speed of 89 km / hrs, Room temperature 3
A drum running test was performed at 8 ° C. The run distance until the occurrence of the failure at this time was defined as run flat durability, and the control (structure I: comparative example 1, structure II: comparative example 3) was 10
It was represented by an index as 0. The larger the index, the better the run flat durability.

(2) Normal internal pressure running durability Using a drum tester having a smooth drum surface and a diameter of 1.707 m, the ambient temperature is controlled to 30 ± 3 ° C., and a standard rim size specified by JATMA. Using the rim of
At a maximum internal pressure of the JATMA standard, a load of twice the maximum load capacity of the JATMA standard was applied, and a durability drum running test was performed to measure the distance until the tire was broken. The evaluation of the practical application of the tire was evaluated as 20,000 km or less.
Those exceeding 10,000 km were rated as ○.

(3) Durability of Water Drum In addition to the same conditions as the normal internal pressure running durability described above, before the test was started, 300 cc of water was injected into the tire to perform a durability drum running test. The distance was measured.
The evaluation of the practical use of the tire was evaluated as x when it was 15,000 km or less and as ○ when it exceeded 15,000 km. The obtained results are shown in Tables 4 and 5 below.

[0038]

[Table 4]

[0039]

[Table 5]

From Tables 4 and 5, it can be seen that, regardless of the structure of the carcass portion, the tires of any of the examples have improved internal pressure durability and run flat durability.

[0041]

The present invention has good adhesive durability even during running, especially during run-flat running, and has a reduced durability due to compression due to concerns about steel cords and a reduction in durability due to corrosion due to moisture. Thus, it is possible to provide a pneumatic tire for a passenger car which is excellent in durability.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a code area of a code image obtained as a plane by X-ray transmission.

FIG. 2 is an explanatory diagram showing a filament area of a code image obtained as a plane by X-ray transmission.

FIG. 3 is a schematic sectional view of a pneumatic tire (FIG. I) used in an example.

FIG. 4 is a schematic sectional view of a pneumatic tire (FIG. II) used in an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Carcass part 2a 1st ply 2b 2nd ply 3 Belt part 4 Bead core 5 Bead filler 6 Side wall part 7 Rubber reinforcement layer 8 Tread part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B60C 9/00 B60C 9/00 BC D 9/08 9/08 C 13/00 13/00 G 17 / 00 17/00 B D07B 1/06 D07B 1/06 A

Claims (5)

[Claims] 1. A carcass part comprising at least two carcass plies each comprising a pair of left and right bead cores, a plurality of parallel cords embedded in a rubber matrix, and a carcass part disposed outside the carcass part in the tire radial direction. Pneumatic passenger car, comprising: a belt portion having a plurality of layers, a tread portion disposed radially outward of the belt portion, and a pair of sidewall portions disposed on the left and right sides of the tread portion. In the tire, the carcass portion has at least one folded carcass ply having a layer in which an organic fiber cord having a melting point of 245 ° C. or more is embedded in a rubber matrix, and an outer surface of the folded carcass ply and the sidewall portion. The lower carcass ply consists of a layer in which a steel cord is embedded in a rubber matrix. In the code image obtained as a plane by X-ray transmission of the down carcass ply, the ratio of the filament area to the code area of the arbitrarily selected 15 mm length in the code axis direction is 0.45. A pneumatic tire for a passenger car, which is not less than 0.95. 2. The pneumatic tire for a passenger car according to claim 1, wherein the steel cord has each filament substantially independently present in a rubber matrix. 3. The twist structure of the steel cord is 1 × n
3. The pneumatic tire for a passenger car according to claim 1, wherein the pneumatic tire has a structure of 1 + n (2 ≦ n ≦ 7). 4. The pneumatic tire for a passenger car according to claim 1, wherein a filament diameter of the filament of the steel cord is in a range of 0.125 to 0.275 mm. 5. The pneumatic tire for a passenger car according to claim 1, wherein said sidewall portion is reinforced by a rubber reinforcing layer.