PNEUMATIC TIRE

Abstract

The present invention provides a pneumatic tire in which a steel cord carcass ply composed of an ultrafine wire having a filament diameter of 0.15 mm or less is used as a reinforcing material, and the carcass ply is positioned between the bead cords without turn-up of the carcass ply for turning up it through an annular bead bundle on an upper side of the carcass ply, such that side rigidity is maintained even when replacing two conventional fiber carcass plies with one steel carcass. Thereby, rather than the conventional turn-up method of turning up the carcass ply on the upper side of the annular bead bundle, the carcass ply passes through the bead bundles as shown in FIG. 3, such that a deformation energy of the bead portion is minimized and a rolling resistance is maximized. The tire of the present invention is characterized by satisfying a correlation equation between a height Bh1 of an inner bead bundle position and a height Ah of the bead portion including an apex of 1.2<Ah/Bh1<4.5.

Claims

1. A pneumatic tire comprising a carcass ply, wherein the carcass ply is formed between an inner liner and a sidewall of the tire in an extended manner while penetrating a bead portion.

2. The pneumatic tire according to claim 1, wherein the bead portion comprises an inner bead bundle which is in contact with the inner liner about the carcass ply, and an outer bead bundle which is formed on a side opposite to the inner bead bundle.

3. The pneumatic tire according to claim 1, wherein Ah/Bh1, which is a ratio of a height Bh1 of the inner bead bundle to a height Ah of an apex, is 1.2 to 4.5.

4. The pneumatic tire according to claim 1, wherein the carcass ply may include a steel cord composed of an ultrafine wire having a filament diameter of 0.15 mm or less, and wherein the steel cord has a breaking strength of 25 kgf or more.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0020] FIG. 1 is a cross-sectional view of a bead portion of a pneumatic tire manufactured by a conventional turn-up method of turning up a carcass ply with two fiber carcass plies through an annular bead bundle on an upper side of the ply;

[0021] FIG. 2 is a cross-sectional view of a bead portion of a pneumatic tire manufactured by a conventional turn-up method of turning up a carcass ply with one steel carcass ply through an annular bead bundle on an upper side of the ply; and

[0022] FIG. 3 is a cross-sectional view of a bead portion prepared according to an embodiment of the present invention without turn-up of the steel carcass ply.

DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, configurations, operations, and effects of a pneumatic tire according to a preferred embodiment will be described with reference to the accompanying drawings. For reference, in the drawings described below, each component is omitted or schematically illustrated for convenience and clarity, and the size of each component does not reflect an actual size. In addition, the same reference numerals are denoted to the same components throughout the specification, and reference numerals for the same components in individual drawings will be omitted.

[0024] A pneumatic tire for an electric vehicle according to the present invention includes a steel carcass ply, and is characterized in that, rather than the conventional turn-up method of turning up the carcass ply through an annular bead bundle on an upper side of the fiber carcass ply or steel carcass ply as shown in FIGS. 1 and 2, the steel carcass ply layer is positioned between one to two layered-flat inner bead bundles which are in contact with an inner portion and one to five layered-stacked outer bead bundles without turn-up of the carcass ply in a bead portion, as shown in FIG. 3.

[0025] In the pneumatic tire according to an embodiment of the present invention, the pneumatic tire including a carcass ply 5 is characterized in that the carcass ply 5 is formed between an inner liner and a sidewall of the tire in an extended manner while penetrating the bead portion.

[0026] In the present invention, the turn-up process itself may be omitted compared to the conventional method in which molding is performed in a turn-up method of turning up fiber carcass plies 1 and 2 or a steel carcass ply 4 through an annular bead bundle 3 as shown in FIG. 1 or 2. More specifically, rather than having a structure in which the carcass is turned up and wrapped about the bead bundle, the carcass ply 5 may be formed between the inner liner and the sidewall in an extended manner while penetrating the bead portion.

[0027] Herein, the bead portion may be formed by dividing it into an inner bead bundle 6 which is in contact with an inner liner layer about the carcass ply 5 and outer bead bundles 7 and 8 positioned on a side opposite to the inner bead bundle 6. In the inner bead bundle 6 and the outer bead bundle 7 and 8, as shown in FIG. 3, the inner bead bundle 6 may be formed in one to two layers, and the outer bead bundles 7 and 8 may be formed in one to five layers. Herein, the bead may be prepared by an annular bead bundle or a steel cord composed of a plurality of layers, or may be an integral type bead formed in a rectangular shape. In addition, the inner bead bundle 6 serves to support an inner surface of the carcass ply 5, and the outer bead bundle 7 serves to support an apex installed above the same.

[0028] According to a preferred characteristic of the present invention, the carcass ply 5 may include a steel cord composed of an ultra-fine wire having a filament diameter of 0.15 mm or less, wherein the steel cord may have a breaking strength of 25 kgf or more.

[0029] First of all, FIGS. 1 and 2 are cross-sectional views illustrating the bead portion of a pneumatic tire prepared by the conventional turn-up method of turning up the carcass ply with two fiber carcass plies or one steel carcass ply through an annular bead bundle on an upper side of the ply, which are the prior art and comparative examples for the present invention.

[0030] Hereinafter, physical properties of the pneumatic tires according to the present invention and the comparative examples will be compared.

[0031] First, weights and rolling resistances of the pneumatic tire prepared by turning up two fiber carcass plies or one steel carcass ply as Comparative Examples 1 and 2, and the pneumatic tire including the steel carcass ply prepared without turn-up according to an embodiment of the present invention as Example 1 were measured, and results thereof are shown in Table 1 below.

TABLE-US-00001 TABLE I Comparative Comparative Item Example 1 Example 2 Example 1 Carcass ply 1300D/2P 2 + 7 * 0.095 2 + 7 * 0.095 breaking strength (kgf) 20.2 28.4 26.5 Number of plies Two plies One ply One ply Bead portion With turn-up With turn-up No turn-up Tire weight (Index) 100 94 92 Rolling resistance 100 103 110 (Index)

[0032] From Table 1 above, it can be confirmed that the weight and the rolling resistance of the pneumatic tire to which the steel carcass ply is applied without turn-up of the carcass ply in the bead portion are significantly improved.

[0033] Next, the weights and the rolling resistance values, a force & moment value, which is one of the alternative characteristics of the tire driving performance, and driving performance sensitivity of the pneumatic tire prepared by turning up two fiber carcass plies or one fiber carcass ply as Comparative Examples 3 and 4, and the pneumatic tire including the steel carcass ply prepared without turn-up according to an embodiment of the present invention as Example 1 were measured and evaluated, and results thereof are shown in Table 2 below.

TABLE-US-00002 TABLE 2 Comparative Comparative Item Example 1 Example 2 Example 1 Carcass ply 1300D/2P 1300D/2P 2 + 7 * 0.095 Number of plies Two plies One ply One ply Bead portion With turn-up With turn-up No turn-up Tire weight (Index) 100 87 92 Rolling resistance (Index) 100 109 110 Force & Moment CC (1°) 100 89 103 (Index) ATC (1°) 100 90 102 Results of driving Ride 100 95 101 performance Handling 100 92 105 sensitivity Noise 100 97 102 evaluation (Index)

[0034] As shown in Table 2 above, it can be confirmed that when reducing two fiber carcass plies to one, the weight and the rolling resistance are improved, but the force & moment value is significantly reduced due to a decrease in the stiffness of the side portion. However, from the tire of Example 1, to which one steel carcass ply is applied without turn-up, it can be seen that the driving performance was significantly improved through an enhancement of the rolling resistance together with an improvement of the side rigidity.

[0035] Further, the following Table 3 shows evaluation results of fraction defective in air intake of apex generated when the tire having the above-described structure of Comparative Examples 3 and 4 and the tire having the structure of Example 1 were molded and vulcanized.

TABLE-US-00003 TABLE 3 Comparative Comparative Item Example 3 Example 4 Example 1 Carcass ply 1300D/2P 2 + 7 * 0.095 2 + 7 * 0.095 Number of plies Two plies One ply One ply Bead portion With turn-up With turn-up No turn-up Number of evaluation samples 90 samples 90 samples 90 samples Fraction defective Left for one day 0%  6.6%(2) 0% in air intake for each (30 samples) leaving time of Left for three days 0% 16.6%(5) 0% green case (30 samples) Left for five days 0% 23.3%(7) 0% (30 samples)

[0036] Commonly, a fraction defective in manufacture of the tire is maintained at a level of 0.5% or less. When a tire is manufactured in a form having a bead turn-up with the steel carcass ply, the tire exhibits a fraction defective of 130 times or more than the fraction defective of the normal tire, and it can be confirmed that the fraction defective is more rapidly increased as the leaving time of the green case is increased. Therefore, in comparison with the effect of reducing the rolling resistance while improving the durability and driving performance of the tire compared to the fiber cord, which is the advantage of the tire to which the steel carcass ply is applied, it should take a decrease in the manufacturing yield in an aspect of mass production while the fraction defective in manufacture is significantly increased. However, it can be confirmed that the pneumatic tire to which the steel carcass ply is applied without turn-up of the carcass ply as disclosed in the present invention exhibits the same manufacturing yield as that of the conventional pneumatic tire prepared by turning up the fiber carcass ply.

[0037] Further, according to a preferred characteristic of the present invention, Ab/Bh1, which is a ratio of a height Bh1 of the inner bead bundle 6 to a height Ah of the apex, may be 1.2 to 4.5.

[0038] Referring to FIG. 3, the carcass ply 5 is formed between the inner bead bundle 6 and the outer bead bundles 7 and 8 in an extended manner so as to penetrate therebetween. When the height of the inner bead bundle 6 is defined as Bh1 and the height of the apex is defined as Ah, the ratio of Ah to Bh1 is preferably 1.2 to 4.5.

[0039] In the case of the pneumatic tire for an electric vehicle having the steel carcass ply 5 disclosed in the present invention, as the turn-up process of the carcass ply in the bead portion is omitted, in order to prevent the carcass ply from separating when the casing is expanded during the molding process, the carcass ply layer is positioned between the inner bead bundle 6 and the outer bead bundles 7 and 8. In this case, the main purpose of the outer bead bundles 7 and 8 is to allow them to be seated on the rim, which plays a role of the conventional bead. Further, in the case of the inner bead bundle 6, it is possible to improve the balance of driving performance by holding the carcass ply layer and complementing to increase the rigidity of the bead portion as a steel insert through adjustment of the height. In addition, referring to FIG. 3, the carcass ply 5 is formed between the inner bead bundle 6 and the outer bead bundles 7 and 8 in an extended manner so as to penetrate therebetween. When the height of the inner bead bundle 6 is defined as Bh1 and the height of the apex is defined as Ah, in order to resolve the concentration of deformation energy, if satisfying a correlation equation between Ah and Bh1 of 1.2<Ah/Bh1<4.5, stress concentration is minimized, such that it may have an excellent value of deformation energy of the bead portion and an optimal value of rolling resistance.

[0040] Next, in a product of 225/45 R17 tire, the rolling resistance and deformation energy value of the tires having Ah/Bh1 values of 0.2 and 5.5 as Comparative Examples 5 and 6 and the tires having Ah/Bh1 values of 1.2 to 4.5 as Examples 2 to 4 were measured and evaluated, and results thereof are shown in Table 4 below.

TABLE-US-00004 TABLE 4 Comparative Comparative Item Example 5 Example 2 Example 3 Example 4 Example 6 Carcass 2 + 7 * 0.095 2 + 7 * 0.095 2 + 7 * 0.095 2 + 7 * 0.095 2 + 7 * 0.095 Bead portion No turn-up No turn-up No turn-up No turn-up No turn-up Ah/Bh1 0.2 1.2 2.5 4.5 5.5 Deformation energy 87 97 100 94 83 Rolling 96 99 100 98 95 resistance

[0041] It can be seen that the tire of Example 3 having an Ah/Bh1 value of 2.5 exhibits a rolling resistance values of 100 which is an optimal value, and the tires of Example 2 or 6 having an Ah/Bh1 value of 0.2 and 5.5 shows a tendency of decreasing the rolling resistance to 4% or more. In addition, it can also be confirmed that the deformation energy of the bead portion also exhibits a dominant result value in a range of 1.2<Ah/Bh1<4.5.

[0042] In a product of 225/60 R18 tire, the rolling resistance and deformation energy values of tires having Ah/Bh1 values of 0.2 and 5.5 as Comparative Examples 7 and 8 and tires having Ah/Bh1 values of 1.2 to 4.5 as Examples 5 to 7 were measured and evaluated, and results thereof are shown in Table 5 below.

TABLE-US-00005 TABLE 5 Comparative Comparative Item Example 7 Example 5 Example 6 Example 7 Example 8 Carcass 2 + 7 * 0.095 2 + 7 * 0.095 2 + 7 * 0.095 2 + 7 * 0.095 2 + 7 * 0.095 Bead portion No turn-up No tum-up No tum-up No tum-up No tum-up Ah/Bh1 0.2 1.2 2.5 4.5 5.5 deformation energy 84 96 100 97 86 Rolling 94 98 100 98 96 resistance

[0043] As shown in Table 5 above, it can be confirmed that the tire having an Ah/Bh1 value of 2.5 exhibits the optimum rolling resistance value, and the tires having Ah/Bh1 values of 0.2 and 5.5 show a tendency of decreasing the rolling resistance to 4% or more. In addition, it can also be confirmed that the deformation energy of the bead portion also exhibits a dominant result value in a range of 1.2<Ah/Bh1<4.5.

[0044] Although preferred embodiments of the present invention have been described with reference to the accompanying drawings, the embodiments and drawings described and illustrated in the present disclosure are simply the most preferred embodiment and do not represent all the technical sprites of the present invention, and it will be understood that various modifications and equivalents may be made to take the place of the embodiments at the time of filling the present application. Thus, it is clear that the above-described embodiments are illustrative in all aspects and do not limit the present disclosure. The scope of the present disclosure is defined by the following claims rather than by the detailed description of the embodiment. It shall be understood that all modifications and embodiments conceived from the meaning and scope of the claims and their equivalents are included in the scope of the present disclosure.

DESCRIPTION OF REFERENCE NUMERALS

[0045] 1, 2: Fiber carcass ply [0046] 3: Bead bundle [0047] 4: Steel carcass ply [0048] 5: Carcass ply [0049] 6: Inner bead bundle [0050] 7: First layer of outer bead bundle [0051] 8: Second layer of outer bead bundle