JPH10236115A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure high stability in steering upon running at high speed without increasing the weight of a tire, deteriorating comfortableness to ride in and deteriorating fitness to a rim. SOLUTION: A bead toe part 2a is formed with a bead toe reinforcing part F composed of a thermoplastic resin with Young's modulus of 50 to 500MPa or a thermoplastic elastomer component obtained by blending together thermoplastic resin component and an elastomer component. The axial width L of a tire in the side surface F1 of the inside diameter of the tire which faces the rim R of the reinforcing part F has such a relation as 3Lc<=L<=Lc relative to the axial length Lc of the tire from a bead toe P to the center O of a bead core. The radial height H of the tire of the bead toe reinforcing part F has such a relation as Hc<=H<=2Hc relative to the radial height Hc of the tire from the bead toe P to the center O of the bead core.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that ensures high steering stability during high-speed running.

[0002]

2. Description of the Related Art In recent years, high output power of automobiles, especially passenger cars,
With the advancement of high-tech, improvement of steering stability at high speed driving,
It has become a requirement of the times to simultaneously satisfy the trade-off event that can be handled without deteriorating the living performance (ride comfort). By the way, conventionally, in order to improve the steering stability, for example, there is a proposal to arrange a reinforcing layer in which reinforcing cords are arranged in a sidewall portion. By providing the reinforcing layer in this way, the rigidity of the sidewall portion is increased, and the steering stability during high-speed running is improved. However, on the other hand, there is a problem that the weight of the tire is increased, and the riding comfort is thereby deteriorated due to the increase of the unsprung weight of the vehicle.

[0003] In order to solve the above-mentioned problem, a rubber having a high JIS hardness is arranged at the bead toe to reduce the fall of the bead at the time of turning, thereby suppressing a decrease in a contact area and securing a cornering force. So, there is a proposal to improve the steering stability. As a result, it is only necessary to replace the bead toe portion with rubber having an increased JIS hardness, so that it is possible to avoid an increase in tire weight and an accompanying deterioration in ride comfort due to an increase in unsprung weight of the vehicle. If the rubber is merely replaced with rubber, the bead portion cannot be sufficiently suppressed from falling due to a low modulus, and there is a problem that the effect of improving the steering stability is insufficient.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide high steering stability during high-speed running without increasing the tire weight and accompanying deterioration in ride comfort due to the increase in unsprung weight of the vehicle. It is to provide a pneumatic tire that can be secured. Another object of the present invention is to provide a pneumatic tire that can ensure high steering stability during high-speed running without impairing the fitting property to the rim.

[0005]

SUMMARY OF THE INVENTION The present invention, which achieves the above object, provides a pneumatic tire in which both ends of a carcass layer are turned around a beat core embedded in right and left beads.
The bead toe portion of the bead portion has a Young's modulus of 50 to 50.
A bead toe reinforcing portion made of a thermoplastic resin of 0 MPa or a thermoplastic elastomer composition obtained by blending a thermoplastic resin component and an elastomer component, and a tire axial width L of a tire inner diameter side surface facing a rim of the bead toe reinforcing portion. Is set to 0.3L _C ≦ L ≦ L _{C with} respect to the tire axial length L _C from the beat toe P to the center O of the bead core, and the tire radial height H of the bead toe reinforcement is measured from the beat toe P to the center O of the bead core. characterized in that the H _C ≦ H ≦ 2H _C with respect to the tire radial height H _C.

As described above, the bead toe reinforcement made of a thermoplastic resin or a thermoplastic elastomer composition having a Young's modulus of 50 MPa or more, which is much higher than that of rubber, is used to reduce the width L of the bead toe reinforcement in the tire axial direction to 0 as described above. .3L _C
As described above, by setting the tire radial height H to be equal to or higher than H _C and providing the bead toe portion on the side of the bead toe, even if the bead portion tries to fall into the tire during turning, the bead toe reinforcing portion is disposed, so that This effectively reduces the fall of the tread and minimizes the decrease in the ground contact area of the tread part, thereby ensuring a high cornering force, resulting in high steering stability at high speeds Sex can be obtained.

Further, since the bead toe side is merely replaced with a thermoplastic resin or a thermoplastic elastomer composition having substantially the same density as rubber, the weight does not increase, thereby reducing the unsprung weight of the vehicle. Since it does not increase, the ride comfort does not deteriorate. Also, by setting the Young's modulus to 500 MPa or less, the tire axial width L of the bead toe reinforcement to L _C or less, and the tire radial height H to 2H _C or less, a bead toe reinforcement significantly harder than rubber is provided. It does not affect the rim assembly.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows an example of the pneumatic tire of the present invention, wherein 1 is a tread portion, 2 is a bead portion, and 3 is a sidewall portion. Left and right sidewall portions 3 are extended outwardly (outer diameter side) in the tire radial direction in connection with the left and right bead portions 2, and a tread portion 1 extending in the tire circumferential direction between the left and right sidewall portions 3. Is provided.

A single carcass layer 4 is provided inside the tire, and an inner liner layer 5 for maintaining the tire internal pressure is provided inside the carcass layer 4. Beat cores 6 each having a square tire meridian section are arranged in the left and right bead portions 2, and a bead filler 7 is continuously provided on the outer periphery of the beat core 6. Both ends 4 a of the carcass layer 4 are folded from the inside of the tire to the outside around the beat core 6 so as to surround the bead filler 7. A plurality of belt layers 8 are embedded on the outer side of the carcass layer of the tread portion 1. CL is a tire center line passing through the tire equator line.

In the present invention, in the pneumatic tire having the above-described structure, as shown in FIG.
The bead toe portion 2a is composed of a bead toe reinforcing portion F having a Young's modulus of 50 to 500 MPa and made of a thermoplastic resin or a thermoplastic elastomer composition obtained by blending a thermoplastic resin component and an elastomer component. Both end portions 5 a of the inner liner layer 5 are arranged so as to be located outside the tire of the bead toe reinforcing portion F, and are embedded in the bead portion 2.

The bead toe reinforcing portion F is formed in a substantially triangular cross section along the meridian of the tire, and has a width L in the tire axial direction of the tire inner diameter side surface F1 facing the mounted rim R (located at the bead toe P on the tire inner diameter side surface F1). (Length in the tire width direction between the inner end to be formed and the outer end in contact with the inner liner layer 5) is 0.3L _C ≦ 0.3 with respect to the length L _C in the tire axial direction from the beat toe P to the center O of the bead core 6. L ≦ L _C
Is in a relationship. Further, the tire radial height H from the bead toe P of the bead toe reinforcing portion F to the outer peripheral end F2 is:
The relationship H _C ≦ H ≦ 2H _C is established with respect to the tire radial height H _C from the beet toe P to the center O of the bead core.

As described above, the bead toe reinforcing portion F constituted by using a hard thermoplastic resin or a thermoplastic elastomer composition having a Young's modulus significantly higher than that of rubber and having a pressure of 50 MPa or more can be replaced with the bead toe reinforcing portion F as described above. By providing the tire axial width L of 0.3 L _C or more and the tire radial height H of H _C or more and providing them on the bead toe side, even if the bead part 2 tries to fall inward during turning, the bead toe reinforcement is provided. By the bead portion 2 in which the portion F is arranged, it is possible to sufficiently suppress the inward fall. Therefore, it is possible to suppress the decrease in the contact area of the tread portion 1 as much as possible,
As a result, a high cornering force can be secured, so that the steering stability during high-speed running can be effectively improved.

Further, since it is only necessary to replace the bead toe side with a thermoplastic resin or a thermoplastic elastomer composition having substantially the same density as rubber, ride comfort due to an increase in tire weight and an accompanying increase in unsprung weight of the vehicle. It does not cause deterioration of sex. Also, in order to make the Young's modulus 500 MPa or less, the tire axial width L of the bead toe reinforcement F to L _C or less, and the tire radial height H to 2H _C or less, a bead toe reinforcement which is significantly harder than rubber is provided. Even when the rim is assembled, the fit is not hindered.

Further, the bead toe reinforcing portion F having the above-mentioned structure is provided.
Rim can be improved by disposing the chafer (bead reinforcing layer) so as to cover the beat portion 2 from the bead toe to the bead heel. Can be removed. When the Young's modulus of the thermoplastic resin or the thermoplastic elastomer composition constituting the bead toe reinforcing portion F is less than 50 MPa, the bead portion 2 cannot be sufficiently suppressed from falling down, and furthermore, the rim may be detached.
On the other hand, if it exceeds 500 MPa, poor fitting to the rim occurs, which is not practical.

If the width L of the bead toe reinforcing portion F in the tire axial direction is less than 0.3 L _C or the height H in the tire radial direction is lower than H _C , the bead portion 2 can be effectively prevented from falling down. Conversely, if the width L in the tire axial direction exceeds L _C or the height H in the tire radial direction is higher than 2H _C , poor fitting to the rim tends to occur.

In the present invention, in the above embodiment, the inner liner layer 5 is made of a conventionally known rubber capable of preventing air permeation, for example, butyl rubber or the like, but instead has an air permeability coefficient of 25 × 10 ^{−. 12} cc · cm / cm ²
An air permeation prevention layer made of a thermoplastic resin having a Young's modulus of 1 to 500 MPa or less and a thermoplastic elastomer composition obtained by blending a thermoplastic resin component and an elastomer component at a temperature of not more than sec and cmHg may be used. By using the air permeation preventing layer made of such a thermoplastic resin or a thermoplastic elastomer composition for the inner liner layer 5, the thickness can be made smaller than that of the inner liner layer in which rubber is arranged. Therefore, the weight can be reduced, and the unsprung weight of the vehicle is also reduced, so that the riding comfort can be improved. Another advantage is that the rolling resistance of the tire can be reduced by reducing the weight.

The thickness of the air permeation preventing layer comprising the thermoplastic resin or the thermoplastic elastomer composition is as follows:
It is preferable to set it in the range of 0.02 to 0.2 mm. When the wall thickness is less than 0.02 mm, it is difficult to sufficiently block air permeation. On the contrary, when the wall thickness is more than 0.2 mm, the effect of weight reduction is poor. As a method of arranging the bead toe reinforcing portion F in the bead toe portion 2a, a rubber capable of preventing air permeation is extruded into a sheet shape (an inner liner layer after vulcanization) at the same time as a thermoplastic resin or a thermosetting resin. The thermoplastic elastomer composition may be extruded and pressed, or the thermoplastic resin or the thermoplastic elastomer composition constituting the bead toe reinforcing portion F which has been extruded in advance may be thermally fused to the inside of a rubber sheet capable of preventing air permeation. May be good.

When the inner liner layer 5 is also composed of the above-mentioned thermoplastic resin or thermoplastic elastomer composition, the thermoplastic resin or thermoplastic elastomer composition constituting the bead toe reinforcing portion F and the inner liner layer 5 It is preferable from the viewpoint of productivity that the thermoplastic resin or the thermoplastic elastomer composition constituting the above is integrally extruded and molded.

In the present invention, the thermoplastic resin includes:
When configuring the bead toe reinforcing portion F, the Young's modulus is set to 5
When forming the inner liner layer 5 from 0 to 500 MPa, the material is not particularly limited as long as the inner liner layer 5 can be made from 1 to 500 MPa. For example, polyamide-based resins [for example, nylon 6 (N6), nylon 66 (N6
6), nylon 46 (N46), nylon 11 (N1
1), nylon 12 (N12), nylon 610 (N6
10), nylon 612 (N612), nylon 6/6
6 copolymer (N6 / 66), nylon 6/66/610
Copolymer (N6 / 66/610), nylon MXD6
(MXD6), nylon 6T, nylon 6 / 6T copolymer, nylon 66 / PP copolymer, nylon 66 / PP
S copolymer] and N-alkoxyalkylated products thereof, for example, methoxymethylated product of 6-nylon,
Methoxymethylated product of 610-nylon, methoxymethylated product of 612-nylon, polyester resin [for example, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), PET / PEI copolymer, poly Arylate (PAR), polybutylene naphthalate (PB)
N), liquid crystal polyesters, aromatic polyesters such as polyoxyalkylenediimidic acid / polybutylene terephthalate copolymers), polynitrile resins [eg, polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile / styrene copolymers (AS) ),
(Meth) acrylonitrile / styrene copolymer, (meth) acrylonitrile / styrene / butadiene copolymer], polymethacrylate resin [for example, polymethyl methacrylate (PMMA), polyethyl methacrylate], polyvinyl resin [for example, Vinyl acetate, poevinyl alcohol (PVA), vinyl alcohol / ethylene copolymer (EVOH), polyvinylidene chloride (PDV)
C), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymer, vinylidene chloride / methyl acrylate copolymer, vinylidene chloride / acrylonitrile copolymer], cellulose resin [eg, cellulose acetate, cellulose acetate butyrate] , Fluororesin [for example, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PV
F), polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer (ETF
E)], imide-based resin [for example, aromatic polyimide (P
I)] and the like can be preferably used.

The above-mentioned thermoplastic elastomer composition can be constituted by mixing an elastomer component with the above-mentioned thermoplastic resin component. When the bead toe reinforcing portion F is also constituted, the Young's modulus is 50 to 500 MPa. In the case where the inner liner layer 5 is formed, as long as it is blended so as to have a pressure of 1 to 500 MPa, the kind of the material and the mixing ratio are not particularly limited.

Examples of the elastomer include diene rubbers and hydrogenated products thereof (for example, NR, IR, epoxidized natural rubber, SBR, BR (high cis BR and low cis B).
R), NBR, hydrogenated NBR, hydrogenated SBR], olefin-based rubber [for example, ethylene propylene rubber (EPD)
M, EPM), maleic acid-modified ethylene propylene rubber (M-EPM), IIR, copolymer of isobutylene and aromatic vinyl or diene monomer, acrylic rubber (AC
M), ionomers], halogen-containing rubbers [for example, Br
-IIR, CI-IIR, bromide of isobutylene paramethylstyrene copolymer (Br-IPMS), chloroprene rubber (CR), hydrin rubber (CHR), chlorosulfonated polyethylene rubber (CSM), chlorinated polyethylene rubber (CM) , Maleic acid-modified chlorinated polyethylene rubber (M-CM)], silicone rubber [for example, methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber], sulfur-containing rubber [for example, polysulfide rubber], fluorine rubber [for example, Vinylidene fluoride rubber, fluorine-containing vinyl ether rubber,
Tetrafluoroethylene-propylene-based rubber, fluorine-containing silicon-based rubber, fluorine-containing phosphazene-based rubber], thermoplastic elastomer [for example, styrene-based elastomer,
Olefin elastomer, ester elastomer,
Urethane-based elastomer, polyamide-based elastomer)
Etc. can be preferably used.

When the compatibility between the specific thermoplastic resin component and the elastomer component is different, the two components can be compatibilized by using an appropriate compatibilizer as the third component. By mixing the compatibilizer with the blend system, the interfacial tension between the thermoplastic resin and the elastomer component decreases, and as a result, the rubber particle diameter forming the dispersion layer becomes fine, so that the properties of both components are reduced. It will be more effectively expressed. As such a compatibilizer, generally, a copolymer having a structure of both or one of a thermoplastic resin and an elastomer component, or an epoxy group, a carbonyl group, a halogen group, which can react with the thermoplastic resin or the elastomer component, The copolymer may have a structure having an amino group, an oxazoline group, a hydroxyl group, or the like. These may be selected according to the type of the thermoplastic resin and the elastomer component to be mixed, and those usually used include styrene / ethylene / butylene block copolymer (SEBS) and its maleic acid-modified product, EPDM, EPM And EPDM / styrene or EPDM / acrylonitrile graft copolymers and their maleic acid-modified products, styrene / maleic acid copolymers, and reactive phenoxines.
The amount of the compatibilizer is not particularly limited, but is preferably 0.5 to 10 parts by weight based on 100 parts by weight of the polymer component (the total of the thermoplastic resin and the elastomer component).

When the thermoplastic resin and the elastomer are blended, the composition ratio between the specific thermoplastic resin component (A) and the elastomer component (B) is not particularly limited, and includes a Young's modulus, a bead toe reinforcing portion and an inner liner. The thickness may be appropriately determined depending on the thickness, but a preferable range is 90/10 by weight.
３０30/70. In the polymer composition according to the present invention, in addition to the essential polymer component, other polymers such as the above-described compatibilizer polymer may be mixed as long as the necessary properties of the polymer composition for a tire of the present invention are not impaired. it can. The purpose of mixing other polymers is to improve the compatibility between the thermoplastic resin and the elastomer component, to improve the moldability of the material, to improve the heat resistance, to reduce the cost, etc. As a material to be used, for example, polyethylene (PE) polypropylene (P
P), polystyrene (PS), ABS, SBS, polycarbonate (PC) and the like. The polymer composition according to the present invention further comprises a filler (calcium carbonate, titanium oxide,
A reinforcing agent such as alumina, carbon black and white carbon, a softening agent, a plasticizer, a processing aid, a pigment, a dye, an antioxidant, and the like can be arbitrarily added as long as the requirements for the Young's modulus are not impaired.

The elastomer component can be dynamically vulcanized when mixed with a thermoplastic resin. Vulcanizing agent, vulcanization aid, when dynamically vulcanizing the elastomer component,
Vulcanization conditions (temperature, time) and the like may be appropriately determined according to the composition of the elastomer component to be added, and are not particularly limited.

As the vulcanizing agent, a general rubber vulcanizing agent (crosslinking agent) can be used. Specifically, examples of the ionic vulcanizing agent include powdered sulfur, precipitated sulfur, highly dispersible sulfur, surface-treated sulfur, insoluble sulfur, dimorpholine disulfide, and alkylphenol disulfide. About 4 phr [parts by weight per 100 parts by weight of the rubber component (polymer)] can be used.

As the organic peroxide vulcanizing agent,
Benzoyl peroxide, t-butyl hydroperoxide, 2,4-bichlorobenzoyl peroxide,
Examples thereof include 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and 2,5-dimethylhexane-2,5-di (peroxylbenzoate).
About 1 to 20 phr can be used.

Further, as a phenol resin-based vulcanizing agent, bromide of alkylphenol resin, tin chloride,
A mixed crosslinking system containing a halogen donor such as chloroprene and an alkylphenol resin can be exemplified.
About 20 phr can be used.

Others include zinc white (about 5 phr), magnesium oxide (about 4 phr), litharge (10 to 20 phr).
phr), p-quinone dioxime, p-dibenzoylquinone dioxime, tetrachloro-p-benzoquinone,
Poly-p-dinitrosobenzene (about 2 to 10 phr),
Methylene dianiline (about 0.2 to 10 phr) can be exemplified.

[0029] If necessary, a vulcanization accelerator may be added. Examples of the vulcanization accelerator include general vulcanization accelerators such as aldehyde / ammonia, guanidine, thiazole, sulfenamide, thiuram, dithioate, and thiourea, for example, About 2 phr can be used.

Specifically, hexamethylenetetramine or the like is used as the aldehyde / ammonia-based vulcanization accelerator, diphenylguanidine is used as the guanidine-based vulcanization accelerator, and dibenzothiazyl is used as the thiazole-based vulcanization accelerator. Examples of sulfenamide-based vulcanization accelerators such as disulfide (DM), 2-mercaptobenzothiazole and its Zn salt and cyclohexylamine salt include cyclohexylbenzothiazylsulfenamide (CBS) and N-oxydiethylenebenzothiazyl. Examples of thiuram-based vulcanization accelerators such as -2-sulfenamide, Nt-butyl-2-benzothiazolesulfenamide, and 2- (thymolpolynyldithio) benzothiazole include tetramethylthiuram disulfide (TMTD). ), Tetraethylthiuram disulfi , Tetramethylthiuram monosulfide (TMTM), dipentamethylenethiuram tetrasulfide and the like, as the dithio acid salt-based vulcanization accelerator,
Zn-dimethyldithiocarbamate, Zn-diethyldithiocarbamate, Zn-di-n-butyldithiocarbamate, Zn-ethylphenyldithiocarbamate, T
e-diethyldithiocarbamate, Cu-dimethyldithiocarbamate, Fe-dimethyldithiocarbamate,
Examples of thiourea-based vulcanization accelerators such as pipecoline pipecolyl dithiocarbamate include ethylene thiourea and diethyl thiourea.

As a vulcanization accelerating auxiliary, a general rubber auxiliary can be used in combination. For example, zinc white (about 5 phr), stearic acid, oleic acid and their Zn salts (2 to 2 phr) can be used. About 4 phr) can be used.

The method for producing the thermoplastic elastomer composition is as follows. A thermoplastic resin component and an elastomer component (unvulcanized product in the case of rubber) are melt-kneaded in advance by a twin-screw kneading extruder or the like.
By dispersing an elastomer component as a dispersed phase (domain) in a thermoplastic resin forming a continuous phase (matrix phase). When vulcanizing the elastomer component,
A vulcanizing agent may be added under kneading to dynamically vulcanize the elastomer component. The various additives (excluding the vulcanizing agent) to the thermoplastic resin or the elastomer component may be added during the kneading, but it is preferable to mix them before kneading. The kneader used for kneading the thermoplastic resin and the elastomer component is not particularly limited, and a screw extruder, a kneader, a Banbury mixer, a twin-screw kneader or the like can be used. Above all, it is preferable to use a twin-screw kneading extruder for kneading the thermoplastic resin and the elastomer component and for dynamic vulcanization of the elastomer component. Further, two or more kinds of kneaders may be used and the kneading may be performed sequentially. As the conditions for the melt-kneading, the temperature may be at least the temperature at which the thermoplastic resin melts. The shear rate during kneading is 1000 to 7500 Se.
Preferably it is c ^-1 . The total kneading time is preferably 30 seconds to 10 minutes, and when a vulcanizing agent is added, the vulcanization time after the addition is preferably 15 seconds to 5 minutes. The polymer composition prepared by the above method is then used in the bead toe reinforcing portion F
When forming the inner liner layer 5, it is formed into a sheet-like film by extrusion or calendering when forming the inner liner layer 5. The method of forming a film may be a method of forming a normal thermoplastic resin or thermoplastic elastomer into a film.

The strip or film thus obtained (hereinafter, the strip and the film are referred to as a molded article) is obtained by dispersing an elastomer component (B) in a continuous phase (matrix) of a thermoplastic resin (A). (Domain) has a distributed structure. By taking such a dispersed structure, thermoplastic processing becomes possible, and by taking such a structure,
Along with providing the molded article with sufficient flexibility and sufficient rigidity due to the effect of the resin layer as a continuous phase, regardless of the amount of the elastomer component, moldability for a resin equivalent to that of a thermoplastic resin, that is, Workability such as injection molding and extrusion molding can be obtained, and in the case of forming a normal resin molding machine, that is, the bead toe reinforcing portion F, the inner liner is formed by extrusion molding into a strip having a cross-sectional shape thereof. When the layer 5 is formed, it can be formed into a film by extrusion molding or calendar molding.

The adhesion between the molded article and the rubber layer opposite to the molded article is performed by applying an adhesive obtained by dissolving a general rubber-based, phenolic resin-based, acrylic copolymer-based, or isocyanate-based polymer and a crosslinking agent to a solvent. And bonding by heat and pressure at the time of vulcanization molding, or bonding resin such as styrene butadiene styrene copolymer (SBS), ethylene ethyl acrylate (EEA), and styrene ethylene butylene block copolymer (SEBS). A co-extrusion with the molded body or laminating to produce a laminate,
There is a method of bonding to a rubber layer during vulcanization. As the solvent-based adhesive, for example, a phenol resin-based (Chemrock 22)
0 Road Co., Ltd.), chlorinated rubber (Chemrock 205, Chemlock 234B), isocyanate system (Chemrock 40)
2) and the like.

Although the present invention can be suitably used for any pneumatic tires, high steering stability and good ride comfort during high-speed running are particularly high with high output and high technology. It can be suitably used for pneumatic tires for passenger cars that are required at the same time.

[0036]

【Example】

 Example 1 Preparation of Bead Toe Reinforcement Material Table 1 shows the material of the bead toe reinforcement used in the present invention.

[0037]

[Table 1]

The bead toe reinforcement was produced by a method of extruding the above material. With the above material width, Young's modulus 40,5
For those with 0 MPa, the composition in Table 1 shows zinc flower, zinc stearate, and stearic acid as elastomers, and 0.4 phr, 2 phr, and 1 phr as dynamic vulcanizing systems, respectively. After the rubber component was dispersed, it was continuously added and kneaded to prepare a dynamically vulcanized thermoplastic elastomer, which was subjected to extrusion molding.

As an adhesive between the bead toe reinforcing portion and the rubber portion material, Chemlock 2 is used beforehand.
34B (Road for East Co.) was applied. Production of Tires Using the bead toe reinforcements produced as described above, each test tire was molded and vulcanized according to a conventional method.

As a comparative example, a conventional tire 1 having no bead toe reinforcing portion was compared with a conventional tire 1 having no bead toe portion.
A conventional tire 2 in which rubber having an IS hardness of 75 and high rubber was arranged was also manufactured. The size of the manufactured tire is 205 /
65R15.

The test tires were evaluated for steering stability and rim fitting property under the following measurement conditions, and the results shown in Tables 2 to 4 were obtained. Table 2 shows test tires in which the Young's modulus was changed, Table 3 shows test tires in which the tire axial width L of the bead toe reinforcement was changed, and Table 4 shows test tires in which the tire radial height H of the bead toe reinforcement was changed. Driving stability

Each test tire was subjected to a 15 × 6-JJM JATM.
A standard rim was mounted, the air pressure was set to 200 kPa, the vehicle was mounted on a 3000 cc passenger car, a feeling test was conducted by a panelist on a test course, and the result was evaluated by an index value with the conventional tire 2 being 100.
The larger the value, the better the steering stability. Rim fitting

Each test tire (excluding conventional tires) was used for 15
The easiness of fitting when the rim was assembled to the JATMA standard rim of × 6-JJ was examined, and the result was indicated by ××. ○ indicates that there is no problem in fitting property, and X indicates that there is a problem in fitting property.

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

[Table 4]

As can be seen from Tables 2 to 4, the conventional tire 2 is somewhat improved compared to the conventional tire 1, but is still insufficient, and the thermoplastic resin or thermoplastic elastomer having a Young's modulus of 50 to 500 MPa. The bead toe reinforcing portion made of the composition has a width L in the tire axial direction of 0.3 L _C ≦
It is understood that the tire of the present invention in which L ≦ L _C and the height H in the tire radial direction is H _C ≦ H ≦ 2H _C can improve steering stability effectively without occurrence of a fitting failure.

Example 2 The tire size was the same as above, and the bead toe reinforcement and
The Young's modulus of both the inner liner layer is 250 (see Table 1).
The present invention tire 10 was produced. Inner rye
The air permeability coefficient of the toner layer is 1.0 × 10^-12cccm / cm^Two・
sec · cmHg, the width L of the bead toe reinforcement in the tire axial direction is
0.7L_C, The height H in the tire radial direction is 1.3H _CIt is.
The air permeability coefficient is 25 × 10^-12cccm / cm^Two・ Sec
・ If the pressure exceeds cmHg, sufficient air pressure cannot be maintained.

The test tire and the conventional tire 1 were mounted on a 3000 cc passenger car in the same manner as above.
On a test course, a rider's feeling test was conducted by panelists, and the results
The evaluation was made with an index value of 0, and the results are shown in Table 5. The larger the value, the better the ride comfort.

[0050]

[Table 5] By using the above-described thermoplastic resin or thermoplastic elastomer composition for the inner liner layer from Table 5,
It can be seen that the riding comfort can be improved.

[0051]

As described above, the present invention has a Young's modulus of 5
A bead toe reinforcing portion made of a thermoplastic resin of 0 to 500 MPa or a thermoplastic elastomer composition obtained by blending a thermoplastic resin component and an elastomer component is provided in the bead toe portion, and the width L in the tire axial direction and the height H in the tire radial direction are set as described above. By setting as described above, it is possible to prevent the increase in tire weight and the accompanying increase in unsprung weight of the vehicle, thereby deteriorating ride comfort, and without impairing the fitting property to the rim, and at the time of high-speed running. High steering stability can be secured.

[Brief description of the drawings]

FIG. 1 is a half sectional view of a tire meridian showing an example of a pneumatic tire of the present invention.

FIG. 2 is an enlarged sectional explanatory view showing a main part of FIG. 1 excluding a carcass layer and a bead filler.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Tread part 2 Bead part 2a Bead toe part 4 Carcass layer 4a End part 5 Inner liner layer 6 Bead core F Bead toe reinforcement part F1 Inner side surface R rim

Claims (4)

[Claims] 1. A pneumatic tire in which both ends of a carcass layer are folded around beat cores embedded in left and right bead portions, a bead toe portion of the bead portion has a Young's modulus of 5
A bead toe reinforcing portion made of a thermoplastic resin of 0 to 500 MPa or a thermoplastic elastomer composition obtained by blending a thermoplastic resin component and an elastomer component, and a tire axial direction on a tire inner diameter side surface facing a rim of the bead toe reinforcing portion. Width L from beat toe P to bead core center O
0.3 L _C ≦ L ≦ respect to the tire axial direction length L _C of up to
L _C , a pneumatic tire in which the tire radial height H of the bead toe reinforcing portion is set to H _C ≦ H ≦ 2H _C with respect to the tire radial height H _C from the beet toe P to the center O of the bead core. 2. The method according to claim 1, wherein the inner liner layer provided inside the carcass layer has an air permeability coefficient of 25 × 10 ⁻¹² cc · cm / c.
^{2. The} air permeation preventing layer according to claim 1, wherein the air permeation preventing layer comprises a thermoplastic resin having a m ² · sec · cmHg or less and a Young's modulus of 1 to 500 MPa or a thermoplastic elastomer composition obtained by blending a thermoplastic resin component and an elastomer component. Pneumatic tire. 3. The thickness of the air permeation preventing layer is 0.02 to 0.02.
The pneumatic tire according to claim 2, which is 0.2 mm. 4. The pneumatic tire according to claim 1, wherein the bead toe reinforcing portion has a substantially triangular cross-sectional shape in a tire meridian.