JP5983038B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire provided with a belt reinforcing layer in a tread portion, and more specifically, the use of a single-strand cord for the belt reinforcing layer reduces weight and maintains tread separation while maintaining high-speed durability. The present invention relates to a pneumatic tire that can be improved.

  In a pneumatic tire in which a belt layer is embedded on the outer peripheral side of the carcass layer in the tread portion, a belt reinforcing layer including a reinforcing cord oriented in the tire circumferential direction on the outer peripheral side of the belt layer is provided for the purpose of improving high-speed durability. Arrangement has been made. Usually, as the reinforcing cord of the belt reinforcing layer, various twisted cords made of organic fibers are used.

  On the other hand, it has been proposed to use a single twisted cord made of an organic fiber as the reinforcing cord of the belt reinforcing layer (for example, see Patent Documents 1 to 4). In addition to the advantage of reducing twisting costs and raw materials used in comparison with various twisted cords, single twisted cords reduce the thickness of the belt reinforcement layer and contribute to weight reduction of pneumatic tires. To do. In addition, when the belt reinforcing layer becomes thin and the rubber volume decreases, an effect of reducing heat generation can be expected.

  However, the single twist cord has a drawback that it has poor adhesion to the coated rubber as compared to the various twist cords. Therefore, when a single-strand cord made of an organic fiber is used as the reinforcing cord of the belt reinforcing layer, peeling between the belt reinforcing layer and the cap tread rubber layer is likely to occur, and the tread separation property is deteriorated. .

JP 2002-154304 A JP 2010-47191 A Japanese Patent Application Laid-Open No. 2011-218882 JP 2011-251583 A

  An object of the present invention is to provide a pneumatic tire that can be reduced in weight by using a single-strand cord for a belt reinforcement layer and that can improve tread separation while maintaining high-speed durability. .

In order to achieve the above object, a pneumatic tire according to the present invention includes at least two layers including a reinforcement cord that embeds a belt layer on the outer peripheral side of the carcass layer in the tread portion and is oriented in the tire circumferential direction on the outer peripheral side of the belt layer. In the pneumatic tire in which the belt reinforcing layer is disposed, a cord of the belt reinforcing layer on the belt layer side is used as a reinforcing cord of the belt reinforcing layer using a single twisted cord in which a multifilament yarn of organic fiber is twisted in one direction. The ratio of the cord driving density (lines / 50 mm) of the belt reinforcing layer on the tread surface side to the driving density (lines / 50 mm) is 0.6 to 0.9, and the cord driving density ( this / 50 mm) and the product of the single twist fineness of cord (dtex) is Ri der 105,000 or less, the piece twisted cord twist number T (times / 0 cm) and the fineness D (dtex) of the single-strand cord, the twist coefficient K defined by K = T√D, the belt reinforcement layer on the tread surface side with respect to the twist coefficient K of the belt reinforcement layer on the belt layer side The ratio of the twist coefficient K is 1.1 to 1.3 .

  As a result of intensive studies on a pneumatic tire using a single-strand cord as a belt reinforcement layer, the present inventors have found that a pneumatic tire having at least two belt reinforcement layers disposed on the outer peripheral side of the belt layer has a tread portion during running. As a result of the present invention, it was found that the belt reinforcement layer on the tread side had a greater strain than the belt reinforcement layer on the belt layer side due to the compressive deformation of the belt layer, and that this induced the peeling of the cap tread rubber layer. is there.

  That is, in the present invention, when using a single twisted cord in which a unidirectional twist is applied to the organic fiber multifilament yarn as the reinforcing cord of the belt reinforcing layer, the cord driving density of the belt reinforcing layer on the belt layer side is relatively high. On the other hand, by relatively lowering the cord driving density of the belt reinforcement layer on the tread side, sufficient adhesion between the cord and the coat rubber in the belt reinforcement layer on the tread side is ensured, and tread separation is improved. be able to. In addition, if the cord driving density of the belt reinforcement layer on the belt layer side is too high, the amount of rubber between the cords may be reduced, and the high-speed durability may be deteriorated due to a decrease in adhesiveness. By defining the product of the cord driving density of the layer (lines / 50 mm) and the fineness (dtex) of the single twisted cord, high-speed durability can be maintained well.

  In the present invention, the belt reinforcement layer on the belt layer side with respect to the twist coefficient K defined by K = T√D from the twist number T (times / 10 cm) of the single twist cord and the fineness D (dtex) of the single twist cord It is preferable that the ratio of the twist coefficient K of the belt reinforcing layer on the tread surface side to the twist coefficient K is 1.1 to 1.3. Thus, the tread coefficient K of the belt reinforcement layer on the belt layer side is relatively reduced while the twist coefficient K of the belt reinforcement layer on the tread surface side is relatively increased, so that the tread is not reduced. Separation improvement effect can be enhanced. In particular, in order to maintain high-speed durability satisfactorily, the twist coefficient K of the belt reinforcing layer on the belt layer side is preferably set to 450 to 900. The organic fiber constituting the single twisted cord is preferably made of nylon 66.

  In the present invention, the “belt reinforcement layer on the belt layer side” means a belt reinforcement layer located closest to the belt layer among at least two laminated belt reinforcement layers, and “the belt reinforcement layer on the tread surface side”. Means a belt reinforcing layer located on the most tread surface side among at least two laminated belt reinforcing layers. Further, the “cord driving density” is the number of cords driven per 50 mm width (so-called number of ends) measured in a direction perpendicular to the reinforcing cords in the belt reinforcing layer.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. It is sectional drawing which expands and shows the principal part of the belt reinforcement layer in the pneumatic tire of FIG. The various forms of the belt reinforcement layer in the pneumatic tire of this invention are shown, (a)-(d) is a schematic diagram which shows each form.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic tire according to an embodiment of the present invention, and FIG. 2 shows a belt reinforcing layer of the pneumatic tire.

  As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, a pair of sidewall portions 2 that are disposed on both sides of the tread portion 1, And a pair of bead portions 3 disposed inside the wall portion 2 in the tire radial direction.

  A carcass layer 4 including a plurality of reinforcing cords extending in the tire radial direction is mounted between the pair of bead portions 3 and 3. As a reinforcing cord for the carcass layer 4, an organic fiber cord is generally used, but a steel cord may be used. An annular bead core 5 is embedded in the bead portion 3, and a bead filler 6 made of a rubber composition having a triangular cross section is disposed on the outer periphery of the bead core 5.

  On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. A steel cord is preferably used as the reinforcing cord of the belt layer 7. On the outer peripheral side of the belt layer 7, at least two belt reinforcing layers 8 formed by arranging reinforcing cords at an angle of 5 ° or less with respect to the tire circumferential direction are arranged for the purpose of improving high-speed durability. . It is desirable that the belt reinforcing layer 8 has a jointless structure in which a strip material formed by aligning at least one reinforcing cord and covering with rubber is continuously wound in the tire circumferential direction. The belt reinforcing layer 8 may be disposed so as to cover the entire width direction of the belt layer 7, or may be disposed so as to cover only the outer edge portion of the belt layer 7 in the width direction.

  In the pneumatic tire, as shown in FIG. 2, a single-twisted cord 9 in which a unidirectional twist is applied to a multifilament yarn of organic fibers is used as a reinforcing cord for the belt reinforcing layer 8. As the single twisted cord 9, one having a fineness D of 900 dtex to 2200 dtex may be used. As the organic fibers constituting the single twisted cord 9, organic fibers such as nylon 66, nylon 46, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), aramid, etc. can be used. preferable.

  The single twisted cord 9 has the advantage that the twisting cost and raw materials used can be reduced compared to the various twisted cords. In addition, since the cord diameter is small, the thickness of the belt reinforcing layer 8 is reduced, and the weight of the pneumatic tire is reduced. Contribute to. Moreover, when the belt reinforcement layer 8 becomes thin and the rubber volume decreases, an effect of reducing heat generation can be expected. On the other hand, the single-stranded cord 9 has a cross-sectional shape close to a perfect circle and has a drawback that the adhesion to the coat rubber is poor because the filaments are not always sufficiently constrained.

  In view of such inconveniences, in the pneumatic tire, the belt reinforcing layer on the tread surface side with respect to the cord driving density E1 (line / 50 mm) of the belt reinforcing layer 81 on the belt layer side of at least two belt reinforcing layers 8. The ratio (E2 / E1) of the cord driving density E2 (lines / 50 mm) of 82 is set in the range of 0.6 to 0.9. During running, the belt reinforcement layer 82 on the tread surface side is more distorted than the belt reinforcement layer 81 on the belt layer side due to the compression deformation of the tread part 1, which peels off the cap tread rubber layer disposed on the tread part 1. As described above, the cord driving density E1 of the belt reinforcing layer 81 on the belt layer side is relatively increased while the cord driving density E2 of the belt reinforcing layer 82 on the tread surface side is relatively decreased as described above. In addition, the adhesiveness between the cord and the coat rubber in the belt reinforcing layer 82 on the tread surface side can be sufficiently secured, and the tread separation property can be improved.

  Here, if the ratio (E2 / E1) is less than 0.6, the product of the cord driving density E1 (50/50 mm) of the belt reinforcing layer 81 on the belt layer side and the fineness D (dtex) of the single twisted cord is Since it becomes excessively large, the amount of rubber between the cords of the belt reinforcing layer 81 on the belt layer side is reduced, and there is a risk that high-speed durability is deteriorated due to a decrease in adhesiveness. Conversely, if the ratio (E2 / E1) is greater than 0.9, the effect of improving the tread separation becomes insufficient. The range of the cord driving density E1, E2 is not particularly limited, but in order to sufficiently ensure high-speed durability, for example, the cord driving density E1 is set to 50/50 mm to 70/50 mm, and the code driving is performed. The density E2 may be 40/50 mm to 50/50 mm.

  In the pneumatic tire, the product of the cord driving density E1 (line / 50 mm) of the belt reinforcing layer 81 on the belt layer side and the fineness D (dtex) of the single twisted cord 9 is 105000 or less, preferably 85000 to 105000. Is set in the range. By increasing the above-mentioned product, the strength of the belt reinforcing layer 81 can be increased and the improvement effect of high-speed durability can be ensured, but if the value is too large, the rubber between the cords of the belt reinforcing layer 81 on the belt layer side The amount decreases, and high-speed durability may be deteriorated due to a decrease in adhesiveness. For the same reason, the product of the cord driving density E2 (line / 50 mm) of the belt reinforcing layer 82 on the tread surface side and the fineness D (dtex) of the single twisted cord 9 is preferably set in the range of 60000-70000.

  In the above pneumatic tire, the belt layer side of the twist coefficient K defined by K = T√D from the number T of twisted cords 9 (times / 10 cm) and the fineness D (dtex) of the twisted cords 9 The ratio (K2 / K1) of the twist coefficient K (K2) of the belt reinforcing layer 82 on the tread surface side to the twist coefficient K (K1) of the belt reinforcing layer 81 is preferably set in the range of 1.1 to 1.3. Thus, the high-speed durability is lowered by relatively reducing the twist coefficient K1 of the belt reinforcing layer 81 on the belt layer side and relatively increasing the twist coefficient K2 of the belt reinforcing layer 82 on the tread surface side. Therefore, the effect of improving the tread separation can be enhanced.

  Here, when the ratio (K2 / K1) is less than 1.1, the twisting coefficient K2 of the belt reinforcing layer 82 on the tread surface side is small, so that the adhesive force is insufficient and the effect of improving the tread separation property is lowered. On the contrary, if the ratio (K2 / K1) is larger than 1.3, the cord modulus of the belt reinforcing layer 82 on the tread surface side is lowered, so that the high-speed durability is lowered.

  The twist coefficient K1 of the belt reinforcing layer 81 on the belt layer side is preferably set in the range of 450 to 900. If the twist coefficient K1 is less than 450, the high-speed durability is reduced due to a combination of fatigue and adhesion deterioration of the single twisted cord 9 included in the belt reinforcing layer 81 on the belt layer side. Since the cord modulus of the belt reinforcing layer 81 is lowered, the high-speed durability is lowered. For the same reason, the twist coefficient K2 of the belt reinforcing layer 82 on the tread surface side is preferably set in the range of 350 to 800.

  FIG. 3 shows various forms of the belt reinforcing layer in the pneumatic tire of the present invention. In FIG. 3A, on the outer peripheral side of the belt layer 7, a belt reinforcing layer 81 on the belt layer side that covers the entire width direction of the belt layer 7, and a tread that covers only the edge portion on the outer side in the width direction of the belt layer 7. A belt reinforcement layer 82 on the side is disposed. 3B, on the outer peripheral side of the belt layer 7, a belt reinforcing layer 81 on the belt layer side that covers only the edge portion on the outer side in the width direction of the belt layer 7, and a tread that covers the entire width direction of the belt layer 7 A belt reinforcement layer 82 on the side is disposed. In FIG. 3C, a belt reinforcement layer 81 on the belt layer side and a belt reinforcement layer 82 on the tread surface side that cover only the edge portion on the outer side in the width direction of the belt layer 7 are arranged on the outer peripheral side of the belt layer 7. . In FIG. 3D, a belt reinforcing layer 81 on the belt layer side and a belt reinforcing layer 82 on the tread surface side that cover the entire width direction of the belt layer 7 are disposed on the outer peripheral side of the belt layer 7. In each figure, the end positions of the belt reinforcing layers 81 and 82 are depicted so as to coincide with the end positions of the belt layer 7, but when covering the entire area of the belt layer 7 in the width direction and outside of the belt layer 7 in the width direction. In any case where only the edge portion is covered, the belt reinforcing layers 81 and 82 may be disposed so as to protrude outward in the tire width direction from the end position of the belt layer 7.

  Although the pneumatic tire provided with the laminated | stacked two-layer belt reinforcement layer was demonstrated in embodiment mentioned above, in this invention, it is also possible to provide three or more belt reinforcement layers. In this case, with respect to the other belt reinforcement layers positioned between the belt reinforcement layer on the belt layer side and the belt reinforcement layer on the tread surface side, the structure thereof is either the belt reinforcement layer on the belt layer side or the belt reinforcement layer on the tread surface side. It is preferable to set the same value as one of them, or to adopt an intermediate set value of the belt reinforcing layer on the belt layer side and the belt reinforcing layer on the tread surface side. In the latter case, the characteristics of the belt reinforcing layer can be gradually changed from the belt layer side toward the tread surface side.

Pneumatic with tire size 205 / 55R16, a belt layer embedded in the outer periphery of the carcass layer in the tread portion, and two belt reinforcing layers including reinforcing cords oriented in the tire circumferential direction on the outer periphery of the belt layer In the tire, the cord structure of the belt reinforcing layer, the ratio of the cord driving density (lines / 50 mm) of the belt reinforcing layer on the tread side to the cord driving density (lines / 50 mm) of the belt reinforcing layer on the belt layer side (in the table, “cord ) And the product of the cord driving density (lines / 50 mm) and the fineness (dtex) of the single twisted cord in the belt layer side and the tread side belt reinforcing layer (in the table, “cord driving density and fineness”). Product) and the ratio of the twist coefficient of the belt reinforcing layer on the tread surface side to the twist coefficient of the belt reinforcing layer on the belt layer side (in the table, "twist coefficient ratio" Shown), and, the set conventional example 1-2 as shown in Table 1 the twist coefficient of the belt layer side and the tread side of the belt reinforcing layer, was fabricated tire of Reference Examples 1 to 3 and Comparative Example 1.

The tire of Conventional Example 1 uses a twisted cord (940 dtex / 2) made of nylon 66 as a reinforcing cord for the belt reinforcing layer. The tires of Conventional Example 2, Reference Examples 1 to 3 and Comparative Example 1 use a single twisted cord (1400 dtex / 1) made of nylon 66 as the reinforcing cord of the belt reinforcing layer.

  These test tires were evaluated for lightness, high-speed durability and tread separation by the following evaluation methods, and the results are also shown in Table 1.

Lightweight:
The weight of the belt reinforcing layer used for each test tire was measured. The evaluation results are shown as an index with Conventional Example 1 as 100. A smaller index value means a lighter weight.

High speed durability:
Each test tire is assembled to a wheel with a rim size of 16 × 6 1/2 JJ, the air pressure is set to 230 kPa, and after running a high-speed durability performance test with an indoor drum type tire testing machine in accordance with JIS-D4230, the running test is continued. The distance traveled until the tire was damaged was measured. The evaluation results are shown as an index with Conventional Example 1 as 100. It means that high speed durability is excellent, so that this index value is large.

Tread separation:
Each test tire is assembled on a wheel with a rim size of 16 × 6 1/2 JJ, the air pressure is 350 kPa, and three cleats (projections) with a radius of 9.5 mm are placed on the outer periphery of the drum of the indoor drum type tire testing machine. Installed at equal intervals, a running test of 8000 km was performed using the tire testing machine. After running, the peeling force between the tire tread rubber layer and the belt reinforcing layer was measured. The evaluation results are shown as an index with Conventional Example 1 as 100. A larger index value means that the cap tread rubber layer is more difficult to peel off and the tread separation property is better.

As can be seen from Table 1, the tire of Conventional Example 2 was inferior in tread separation, although the effect of weight reduction was recognized in comparison with Conventional Example 1. In contrast, the tires of Reference Examples 1 to 3 were able to maintain good high-speed durability and tread separation properties while enjoying the effect of weight reduction in comparison with Conventional Example 1. On the other hand, in the tire of Comparative Example 1, the ratio of the cord driving density of the belt reinforcing layer on the tread surface side to the cord driving density of the belt reinforcing layer on the belt side is too low, and the cord driving density and fineness in the belt reinforcing layer on the belt layer side Since the product of is too large, high-speed durability could not be secured sufficiently.

Next, tires of Example 1 and Reference Examples 4 and 5 having the same structure as Reference Example 2 were manufactured except that the twist coefficient ratio of the belt reinforcing layer was changed as shown in Table 2. These test tires were evaluated for lightness, high-speed durability and tread separation by the above-described evaluation methods, and the results are also shown in Table 2. The standard for the index value is Conventional Example 1.

As shown in Table 2, in Example 1 and Reference Examples 4 and 5 , by changing the ratio of the twist coefficient of the belt reinforcing layer on the tread surface side to the twist coefficient of the belt reinforcing layer on the belt layer side, high speed durability and The tread separation property was changed, and the most excellent result was obtained particularly in Example 1 in which the twist coefficient ratio was included in the range of 1.1 to 1.3.

Next, tires of Examples 2 to 4 having the same structure as Example 1 were manufactured except that the twist coefficient of the belt reinforcing layer was changed as shown in Table 3. These test tires were evaluated for lightness, high-speed durability and tread separation by the above-described evaluation methods, and the results are also shown in Table 3. The standard for the index value is Conventional Example 1.

As shown in Table 3, in Examples 2 to 4 , by changing the twist coefficient of the belt reinforcement layer on the belt layer side, the high-speed durability and the tread separation properties are changed. In particular, the belt reinforcement layer on the belt layer side The most excellent result was obtained in Example 2 in which the twist coefficient was in the range of 450 to 900.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8, 81, 82 Belt cover layer 9 Single twist cord

Claims (3)

In the pneumatic tire in which a belt layer is embedded on the outer peripheral side of the carcass layer in the tread portion, and at least two belt reinforcing layers including reinforcing cords oriented in the tire circumferential direction are arranged on the outer peripheral side of the belt layer, the belt reinforcement A single-strand cord in which a unidirectional twist is applied to an organic fiber multifilament yarn is used as a reinforcing cord for the layer, and the belt-reinforcing layer on the tread surface side with respect to the cord driving density (main / 50 mm) of the belt-reinforcing layer on the belt layer side. The ratio of cord driving density (lines / 50 mm) is 0.6 to 0.9, and the cord driving density (lines / 50 mm) of the belt reinforcing layer on the belt layer side and the fineness (dtex) of the single twisted cord product is Ri der 105,000 or less, the piece twist twist code T and (times / 10 cm) and the piece twist fineness of cord D (dtex) For the twist coefficient K defined by K = T√D, the ratio of the twist coefficient K of the belt reinforcing layer on the tread surface side to the twist coefficient K of the belt reinforcing layer on the belt layer side is 1.1 to 1.3. a pneumatic tire characterized by that. For the twist coefficient K defined by K = T√D from the number of twists T (times / 10 cm) of the single twisted cord and the fineness D (dtex) of the single twisted cord, the belt reinforcing layer on the belt layer side The pneumatic tire according to claim 1 , wherein the twist coefficient K is 450 to 900. The pneumatic tire according to claim 1 or 2 , wherein the organic fiber constituting the single twisted cord is made of nylon 66.

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