JP3568323B2 - Pneumatic radial tire - Google Patents

Description

【００３０】
【表２】

表１から明らかなように、本発明タイヤは、ベルト補強層に故障を招くことなく、タイヤ重量の増加を抑えながら、高周波域におけるロードノイズを効果的に改善することができるのが判る。
【００３１】
【発明の効果】
上述したように本発明は、トレッド部のカーカス層外周側にベルト層を埋設した空気入りラジアルタイヤにおいて、前記ベルト層より外周側でかつ少なくとも該ベルト層両エッジ部を覆うように、熱可塑性樹脂成分とゴムからなるエラストマー成分とをブレンドしたヤング率が５０〜５００ MPa の熱可塑性エラストマー組成物からなるベルト補強層を配置したので、タイヤ重量が増大するのを抑制しながら、高周波域におけるロードノイズの低減を図ることができる。
【図面の簡単な説明】
【図１】本発明の空気入りラジアルタイヤの一例を示すタイヤ子午線半断面図である。
【図２】本発明の空気入りラジアルタイヤの他の例を示すタイヤ子午線半断面図である
。
【図３】図２におけるベルト補強層の他の例を示す要部断面図である。
【符号の説明】
１ トレッド部 ２ ビード部
３ サイドウォール部 ４ カーカス層
７ ベルト層 ７Ａ １番ベルト層
７Ｂ ２番ベルト層 ７ａ，７ｂ エッジ部
８ ベルト補強層 ｘ ベルト層のエッジ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pneumatic radial tire, and more particularly, to a pneumatic radial tire configured to reduce road noise in a high frequency range while suppressing an increase in tire weight.
[0002]
[Prior art]
In recent years, with the improvement in quietness of vehicles, demands for reduction of road noise of tires have become strict in pursuit of passenger comfort. It is known that the transmission rate of vibration in a tire increases when the natural frequency of the vibration transmission system of the vehicle and the natural frequency of the tire match (resonate). Therefore, the tire that controls the natural frequency of the tire is known. If the mechanical factors of the constituent materials are changed, road noise at a specific frequency can be reduced.
[0003]
From such knowledge, it is known that road noise in a high frequency range (around 250 to 315 Hz) can be improved by increasing the rigidity of the belt portion and increasing the secondary natural frequency of the cross section.
Conventionally, as a countermeasure for improving the road noise in the high frequency range, for example, a nylon reinforcing layer is disposed on the outer peripheral side of both edge portions of the belt layer to increase the rigidity of the belt portion and increase the secondary natural frequency of the cross section. There are proposals to avoid resonance and reduce road noise in the high frequency range. However, in order to sufficiently increase the rigidity of the belt portion, it is necessary to adopt a configuration in which reinforcing cords are arranged, so that the thickness is increased to some extent, the tire weight is greatly increased, and this is against the trend of recent tire weight reduction. .
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a pneumatic radial tire capable of improving road noise in a high frequency range while suppressing an increase in tire weight.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a pneumatic radial tire in which a belt layer is embedded on the outer peripheral side of a carcass layer of a tread portion, so that at least the outer peripheral side of the belt layer and at least both edges of the belt layer are covered,Young's modulus of blending a thermoplastic resin component and an elastomer component made of rubber is 50 to 500. MPa ofA belt reinforcing layer made of a thermoplastic elastomer composition is provided.
[0006]
As described above, at least the belt reinforcing layer is provided on the outer peripheral side of the edge portion of the belt layer which greatly affects the increase in the secondary natural frequency of the cross section, and the Young's modulus is set in the above range.Thermoplastic elastomer compositionAnd the rigidity of the belt reinforcing layer is increased, so that the rigidity of the belt portion can be increased as in the case of the conventionally disposed nylon reinforcing layer, thereby increasing the secondary natural frequency of the cross section. Thereby, road noise in a high frequency range around 250 to 315 Hz can be reduced.
In addition, the thickness can be made thinner and lighter than the reinforcing layer having the conventional reinforcing cord, so that a large increase in weight can be suppressed.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows an example of the pneumatic radial 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 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 is provided between the left and right sidewall portions 3.
One carcass layer 4 is provided inside the tire. Beat cores 5 are respectively arranged on the left and right bead portions 2, and bead fillers 6 are provided on the outer periphery of the beat cores 5. Both ends 4 a of the carcass layer 4 are folded from the inside of the tire to the outside around the beat core 5 so as to surround the bead filler 6.
[0008]
On the outer peripheral side of the carcass layer of the tread portion 1, two belt layers 7 in which reinforcing cords are arranged so as to cross each other in opposite directions are embedded. On the inner first belt layer 7A adjacent to the carcass layer 4, a second belt layer 7B having a width smaller than that of the first belt layer 7A is laminated. CL is the tire equatorial plane.
According to the present invention, in the pneumatic radial tire having the above-described configuration, both edge portions 7a and 7b of the belt layers 7A and 7B which are located on the outer peripheral side of the belt layers 7A and 7B and greatly affect the increase and decrease of the secondary natural frequency of the cross section are used. An annular belt reinforcing layer 8 is provided so as to cover the belt layer 7. The belt reinforcing layer 8 is made of a thermoplastic resin or a thermoplastic elastomer composition obtained by blending a thermoplastic resin component and an elastomer component, and has a Young's modulus of 50 to 500 MPa.
[0009]
As described above, the belt reinforcing layer 8 is disposed on the outer peripheral sides of both the edge portions 7a and 7b of the belt layer 7, which greatly affects the increase in the secondary natural frequency of the cross section, and the thermoplastic resin or the heat Since the rigidity is increased by setting the Young's modulus of the plastic elastomer composition in the above range, the rigidity of the belt portion can be increased similarly to the conventional nylon reinforcing layer. As a result, the secondary natural frequency of the cross section increases, and resonance in a high frequency range around 250 to 315 Hz can be avoided, so that high frequency range road noise can be improved.
[0010]
Moreover, the thickness can be made thinner and lighter than the belt reinforcing layer having the conventional reinforcing cord, so that an increase in weight can be effectively suppressed.
If the Young's modulus is less than 50 MPa, the rigidity of the belt reinforcing layer 8 becomes too low, so that the rigidity of the belt portion cannot be sufficiently increased, and the high frequency band road noise cannot be sufficiently reduced. On the other hand, if it exceeds 500 MPa, the rigidity of the belt reinforcing layer 8 becomes too high, so that the belt reinforcing layer 8 becomes fragile and causes a tire failure.
[0011]
The width FW at which the belt reinforcing layer 8 is disposed is determined from both edges (both edges of the belt layer) x of the first belt layer 7A having the largest belt width to the entire belt width (width of the belt layer having the maximum width, in the figure, respectively). At least 10% of both edges 7a and 7b of the first belt layer 7A (width of the first belt layer 7A adjacent to the carcass layer) can be covered.
The belt reinforcing layer 8 may be provided over the entire outer peripheral side of the belt layer 7 as shown in FIG. 2, and in the present invention, the outer peripheral side of the belt layer 7 which greatly affects the increase and decrease of the secondary natural frequency of the cross section. The belt reinforcing layer 8 may be arranged on at least both edge portions 7a and 7b. The ratio of the total belt reinforcing layer width FW to the total belt width BW can be 20 to 100%.
[0012]
The thickness of the belt reinforcing layer 8 may be partially changed as necessary. As an example, FIG. 3 shows a case where the thickness of both end portions 8a corresponding to the edge portions 7a and 7b is larger than the intermediate portion 8b therebetween.
Further, although the example in which one layer of the belt reinforcing layer 8 is arranged is shown in the drawing, a plurality of layers may be provided, and in the present invention, at least one layer may be arranged. The total thickness can be 0.1 to 1.0 mm. If the thickness is less than 0.1 mm, the rigidity of the belt reinforcing layer 8 becomes too low, and it becomes difficult to sufficiently improve high frequency band road noise. Conversely, if the thickness exceeds 1.0 mm, the weight increases. Become noticeable.
[0013]
The belt reinforcing layer 8 may be formed in an annular configuration in which a sheet-like thin film is seamlessly formed by extrusion molding. Alternatively, a strip material made of a tape-like thin film may be continuously spirally wound without gaps. The film may be formed into an annular shape, and the front and rear ends of the film formed into a wide sheet may be joined.
In the present invention, the thermoplastic resin forming the belt reinforcing layer 8 is not particularly limited as long as it can make the Young's modulus 50 to 500 MPa. For example, a polyamide resin [for example, nylon 6 (N6), nylon 66 (N66), nylon 46 (N46), nylon 11 (N11), nylon 12 (N12), nylon 610 (N610), nylon 612 (N612), nylon 6/66 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 / PPS Copolymers] and their N-alkoxyalkylated products, for example, methoxymethylated product of 6-nylon, Methoxymethylated 10-nylon, methoxymethylated 612-nylon, polyester resin [for example, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), PET / PEI copolymer, poly Arylate (PAR), polybutylene naphthalate (PBN), liquid crystal polyester, aromatic polyester such as polyoxyalkylene diimide diacid / polybutylene terephthalate copolymer), polynitrile resin [eg, polyacrylonitrile (PAN), polymethacrylic Lonitrile, acrylonitrile / styrene copolymer (AS), (meth) acrylonitrile / styrene copolymer, (meth) acrylonitrile / styrene / butadiene copolymer], polymethacrylate-based Resin [eg, polymethyl methacrylate (PMMA), polyethyl methacrylate], polyvinyl resin [eg, vinyl acetate, poevinyl alcohol (PVA), vinyl alcohol / ethylene copolymer (EVOH), polyvinylidene chloride (PDVC) ), Polyvinyl chloride (PVC), a vinyl chloride / vinylidene chloride copolymer, a vinylidene chloride / methyl acrylate copolymer, a vinylidene chloride / acrylonitrile copolymer], a cellulose resin [eg, cellulose acetate, cellulose acetate butyrate], Fluorine-based resin [eg, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer (ETFE)], imide-based resin [eg, aromatic polyimide (PI) It can be preferably used, and the like.
[0014]
Further, the thermoplastic elastomer composition constituting the belt reinforcing layer 8 can be constituted by mixing an elastomer component with the above-mentioned thermoplastic resin component, and this is also blended so that the Young's modulus becomes 50 to 500 MPa. If it is a material, the kind of the material, the mixing ratio, and the like are not particularly limited.
Examples of the elastomer component include diene rubbers and hydrogenated products thereof (for example, NR, IR, epoxidized natural rubber, SBR, BR (high cis BR and low cis BR), NBR, hydrogenated NBR, hydrogenated SBR). Olefin rubber (eg, ethylene propylene rubber (EPDM, EPM), maleic acid-modified ethylene propylene rubber (M-EPM), IIR, isobutylene and aromatic vinyl or diene monomer copolymer, acrylic rubber (ACM), ionomer ], Halogen-containing rubbers (for example, bromide of an isomonoolefin such as Br-IIR, CI-IIR, isobutylene and paramethylstyrene copolymer (Br-IPMS), chloroprene rubber (CR), hydrin rubber (CHR, CHC) , Chlorosulfonated polyethylene rubber (CSM), chlorinated polyether Ren rubber (CM), maleic acid-modified chlorinated polyethylene rubber (M-CM)], silicon rubber [for example, methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber], sulfur-containing rubber [for example, polysulfide rubber], fluorine Rubber (e.g., vinylidene fluoride rubber, fluorine-containing vinyl ether rubber, tetrafluoroethylene-propylene rubber, fluorine-containing silicon rubber, fluorine-containing phosphazene rubber), thermoplastic elastomer (e.g., styrene-based elastomer, olefin-based elastomer) , Ester-based elastomers, urethane-based elastomers, and polyamide-based elastomers) can be preferably used.
[0015]
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 expressed more effectively. 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, capable of reacting 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 types of the thermoplastic resin and the elastomer component to be mixed, and commonly used ones 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).
[0016]
When blending the thermoplastic resin and the elastomer, the composition ratio of the specific thermoplastic resin component (A) and the elastomer component (B) is not particularly limited, and may be appropriately determined according to the Young's modulus and the thickness of the belt reinforcing layer. Although it is good, a preferable range is 90/10 to 15/85 in a weight ratio of (A) / (B).
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 in a range that does not impair the necessary characteristics of the polymer composition for a tire of the present invention. it can. The purpose of mixing other polymers is to improve the compatibility between the thermoplastic resin and the elastomer component, to improve the film forming processability of the material, to improve the heat resistance, to reduce the cost, etc. For example, polyethylene (PE), polypropylene (PP), polystyrene (PS), ABS, SBS, polycarbonate (PC), and the like can be used as the material used for the above. The polymer composition according to the present invention further includes a filler (calcium carbonate, titanium oxide, alumina, etc.), a reinforcing agent such as carbon black and white carbon, a softener, a plasticizer, which are generally added to the polymer compound. Processing aids, pigments, dyes, antioxidants, and the like can be arbitrarily added as long as the requirements for the Young's modulus are not impaired.
[0017]
Further, the elastomer component can be dynamically vulcanized when mixed with a thermoplastic resin. The vulcanizing agent, vulcanization aid, vulcanization conditions (temperature, time) and the like for dynamically vulcanizing 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.
[0018]
Examples of the organic peroxide vulcanizing agent include benzoyl peroxide, t-butyl hydroperoxide, 2,4-bichlorobenzoyl peroxide, and 2,5-dimethyl-2,5-di (t-butyl). Examples thereof include peroxy) hexane and 2,5-dimethylhexane-2,5-di (peroxyl benzoate). For example, about 1 to 20 phr can be used.
[0019]
Further, examples of the phenolic resin-based vulcanizing agent include brominated alkylphenol resins and mixed cross-linking systems containing a halogen donor such as tin chloride or chloroprene and an alkylphenol resin. For example, about 1 to 20 phr may be used. Can be.
In addition, zinc white (about 5 phr), magnesium oxide (about 4 phr), litharge (about 10 to 20 phr), p-quinone dioxime, p-dibenzoylquinone dioxime, tetrachloro-p-benzoquinone, poly-p- Examples thereof include dinitrosobenzene (about 2 to 10 phr) and methylene dianiline (about 0.2 to 10 phr).
[0020]
If necessary, a vulcanization accelerator may be added. Examples of the vulcanization accelerator include aldehyde / ammonia-based, guanidine-based, thiazole-based, sulfenamide-based, thiuram-based, dithioate-based, and thiourea-based general vulcanization accelerators, for example, from 0.5 to 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 guadinine-based vulcanization accelerator, and dibenzothiazyl disulfide (or the like) is used as the thiazole-based vulcanization accelerator. DM), 2-mercaptobenzothiazole and its Zn salt, cyclohexylamine salt, etc., as sulfenamide-based vulcanization accelerators, cyclohexylbenzothiazylsulfenamide (CBS), N-oxydiethylenebenzothiazyl-2- Examples of thiuram-based vulcanization accelerators such as sulfenamide, Nt-butyl-2-benzothiazolesulfenamide, 2- (thymolpolynyldithio) benzothiazole and the like include tetramethylthiuram disulfide (TMTD), tetraethyl Thiuram disulfide, tetrame Examples of dithioate-based vulcanization accelerators such as rutiuram monosulfide (TMTM) and dipentamethylenethiuram tetrasulfide include Zn-dimethyldithiocarbamate, Zn-diethyldithiocarbamate, Zn-di-n-butyldithiocarbamate, Zn -Ethylphenyldithiocarbamate, Te-diethyldithiocarbamate, Cu-dimethyldithiocarbamate, Fe-dimethyldithiocarbamate, pipecoline pipecolyldithiocarbamate, etc., and thiourea-based vulcanization accelerators include ethylenethiourea, diethylthiourea, etc. be able to.
[0021]
As the vulcanization accelerating auxiliary, a general rubber auxiliary may be used in combination, for example, zinc white (about 5 phr), stearic acid, oleic acid and Zn salt thereof (about 2 to 4 phr). Etc. can be used.
In a method for producing a thermoplastic elastomer composition, 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 to form a continuous phase (matrix phase). By dispersing an elastomer component in a thermoplastic resin as a dispersed phase (domain). When vulcanizing the elastomer component, a vulcanizing agent may be added under kneading to dynamically vulcanize the elastomer component. Further, various compounding agents (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 kneading machine 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 kneading extruder or the like can be used. Among them, for kneading the thermoplastic resin and the elastomer component and for dynamic vulcanization of the elastomer component, it is preferable to use a twin-screw kneading extruder. Further, two or more kinds of kneaders may be used to knead 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 sec.^-1It is preferred that The total kneading time is preferably from 30 seconds to 10 minutes, and when a vulcanizing agent is added, the vulcanizing time after the addition is preferably from 15 seconds to 5 minutes. The polymer composition produced by the above method is then formed into a sheet-like film by extrusion or calendering. The method of forming a film may be a method of forming a normal thermoplastic resin or thermoplastic elastomer into a film.
[0022]
The film thus obtained has a structure in which the elastomer component (B) is dispersed as a dispersed phase (domain) in a matrix of the thermoplastic resin (A). By taking such a dispersed structure, thermoplastic processing becomes possible, and sufficient rigidity can be imparted to the film as the belt reinforcing layer by the effect of the sufficient flexibility and the resin layer as the continuous phase. At the same time, regardless of the amount of the elastomer component, at the time of molding, it is possible to obtain molding processability equivalent to that of a thermoplastic resin, so that it can be formed into a film by a usual resin molding machine, that is, extrusion molding, or calender molding. It becomes possible.
[0023]
Adhesion between these films and the rubber layer opposite to each other is performed by applying an adhesive obtained by dissolving a polymer such as a normal rubber-based, phenolic resin-based, acrylic copolymer-based, or isocyanate-based polymer and a crosslinking agent to a solvent, and vulcanizing and molding. Bonding by heat and pressure at the time, or by bonding an adhesive resin such as styrene butadiene styrene copolymer (SBS), ethylene ethyl acrylate (EEA), and styrene ethylene butylene block copolymer (SEBS) together with a thermoplastic film. There is a method in which a multilayer film is prepared by extrusion or lamination and then adhered to a rubber layer during vulcanization. Examples of the solvent-based adhesive include a phenol resin-based resin (Chemrock 220, Road Co., Ltd.), a chlorinated rubber-based resin (Chemrock 205, Chemlock 234B), and an isocyanate-based resin (Chemrock 402).
[0024]
In the present invention, an example in which the two belt layers 7 are arranged in the above embodiment has been described. However, the present invention is not limited to this, and the present invention embeds the belt layer on the outer side of the carcass layer of the tread portion. Any of the pneumatic radial tires described above can be suitably used, and can be particularly preferably applied to a pneumatic radial tire for a passenger car.
[0025]
【Example】
In the pneumatic radial tire having the structure shown in FIG. 1, the tire sizes of the tires 165SR13 and 165SR13 were changed, and the Young's modulus of the belt reinforcing layer was changed as shown in Table 1. In the pneumatic radial tire having the configuration shown in FIG. 1, a conventional tire 1 without a belt reinforcing layer and a conventional tire 2 in which a nylon reinforcing layer reinforced with a nylon fiber cord was disposed on the belt reinforcing layer were manufactured.
[0026]
The composition materials shown in Table 2 were used for the belt reinforcing layers of the tire of the present invention and the comparative tire. The elastomer components shown in Table 2 were mixed with a rubber Banbury mixer, the sheet was rolled out to a thickness of about 3 mm with a rubber roll, and the sheet was pelletized with a rubber beretizer, and kneaded with a biaxial kneading extruder described later. Was served. To knead the thermoplastic elastomer composition, nylon 11 pellets are charged from a first input port of a twin-screw kneading extruder and melted and kneaded. Then, the above-mentioned elastomer component is charged from a second input port, and nylon 11 is added. After the elastomer component is finely dispersed in the thermoplastic resin of the above, a predetermined amount of the dynamic vulcanization system component shown in Table 2 with respect to 100 parts by weight of the polymer component of the elastomer component from the third inlet. Was continuously charged, the elastomer component was cross-linked during kneading, and the dispersion of the elastomer component was fixed (compositions (I) and (II)). Composition (III) is not subjected to dynamic crosslinking.
[0027]
Thereafter, the thermoplastic elastomer composition obtained from the tip of the twin-screw kneading extruder was extruded into strands, cooled with water, and then pelletized with a resin pelletizer. Then, using a 40 mm uniaxial resin extruder equipped with a T-shaped die at the tip, the pellets obtained in this manner and the thermoplastic resin pellets used for the compositions (IV) to (VI) as they are Then, the mixture was put into an extruder and melted, and a sheet having a width of 400 mm and a thickness of 0.3 mm was formed from a T-shaped die at the tip to obtain a test film.
[0028]
In each of the test tires (except for the conventional tire 1), the belt reinforcing layer was arranged so as to cover 22% of the entire belt width BW from both edges of the belt layer.
The test tires were evaluated for road noise, tire belt weight, and durability under the following measurement conditions, and the results shown in Table 1 were obtained.
High frequency road noise (R / N)
Each test tire was mounted on a rim with a rim size of 13 x 5 J, mounted on a 1500 cc vehicle with an air pressure of 210 kPa, running on a pavement at a speed of 50 km / h, and a sound pressure level in a high frequency range was mounted by a microphone mounted at a central position in the vehicle. Were measured, and the tire 1 was evaluated with ± [dB (A)] using the conventional tire 1 as a reference (0). The higher the sign is +, the higher the numerical value is, the higher the high-frequency road noise is compared to the conventional tire, and the larger the sign is, the higher the numerical value is, the lower the high-frequency road noise is than the conventional tire.
Tire belt weight
The total weight of the belt layer and the belt reinforcing layer of each test tire was measured, and the result was evaluated as an index value with the conventional tire 1 being 100. The greater the value, the greater the weight of the tire belt.
durability
Each test tire (excluding conventional tires) was mounted on a rim having a rim size of 13 × 4.50B, the air pressure was set at 210 kPa, and the speed was increased by 10 km / h every 30 minutes (test conditions based on JISD-4230). A drum test was performed to check the state of the belt reinforcing layer after running at a speed of 180 km / h for 30 minutes. ○ indicates no abnormality, and × indicates that the belt reinforcing layer was broken.
[0029]
[Table 1]

[0030]
[Table 2]

As is clear from Table 1, it can be seen that the tire of the present invention can effectively improve road noise in a high-frequency range while suppressing an increase in tire weight without causing a failure in the belt reinforcing layer.
[0031]
【The invention's effect】
As described above, the present invention relates to a pneumatic radial tire in which a belt layer is embedded on the outer peripheral side of a carcass layer of a tread portion, so that at least the outer peripheral side of the belt layer and at least both edge portions of the belt layer are covered.Young's modulus of blending a thermoplastic resin component and an elastomer component made of rubber is 50 to 500. MPa ofSince the belt reinforcing layer made of the thermoplastic elastomer composition is disposed, road noise in a high frequency range can be reduced while suppressing an increase in tire weight.
[Brief description of the drawings]
FIG. 1 is a tire meridian half sectional view showing an example of a pneumatic radial tire of the present invention.
FIG. 2 is a tire meridian half sectional view showing another example of the pneumatic radial tire of the present invention.
.
FIG. 3 is a sectional view of a main part showing another example of the belt reinforcing layer in FIG.
[Explanation of symbols]
1 Tread section 2 Bead section
3 Side wall part 4 Carcass layer
7 belt layer 7A 1st belt layer
7B 2nd belt layer 7a, 7b Edge
8 Belt reinforcement layer x Edge of belt layer

Claims (3)

In a pneumatic radial tire in which a belt layer is embedded on a carcass layer outer peripheral side of a tread portion,
A belt made of a thermoplastic elastomer composition having a Young's modulus of 50 to 500 MPa , in which a thermoplastic resin component and an elastomer component made of rubber are blended so as to cover at least the outer edge of the belt layer and both edges of the belt layer. A pneumatic radial tire with a reinforcing layer. The pneumatic radial tire according to claim 1, wherein the belt reinforcing layer is disposed so as to cover at least 10% of a total belt width BW from both edges of the belt layer. 3. The pneumatic radial tire according to claim 1, wherein the thickness of the belt reinforcing layer is 0.1 to 1.0 mm.

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