JP5257412B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire provided with a belt layer in which a plurality of single wire steel wires are aligned and embedded in rubber, and more specifically, the rolling resistance is reduced while maintaining good tire durability performance. It relates to a pneumatic radial tire that has been made possible.

  Conventionally, a steel cord formed by twisting a plurality of filaments is used as a reinforcing cord for a belt layer of a pneumatic radial tire. However, a steel cord formed by twisting a plurality of filaments has a large cord diameter due to an internal gap formed between the filaments, and accordingly, a large amount of coat rubber is required. Therefore, the rolling resistance of a pneumatic radial tire is reduced. Easy to grow.

  Therefore, in order to reduce the rolling resistance of the pneumatic radial tire by reducing the coating rubber of the belt layer, it has been proposed to use a single wire steel wire as a reinforcing cord for the belt layer. Here, in order to sufficiently ensure the tire durability performance based on the belt layer including the single wire steel wire, it is necessary to sufficiently increase the strength of the single wire steel wire by wire drawing. However, in a drawn single-wire steel wire, since the metal structure is excessively oriented toward the wire surface closer to the drawing die, if the single-wire steel wire is used as a reinforcing cord for the belt layer as it is, the single-wire steel There exists a problem that the fatigue resistance of a wire is bad and tire durability performance falls.

  In order to solve such a problem, it has been proposed to braze a three-dimensional shape on a single wire steel wire (see, for example, Patent Documents 1 to 3). However, the use of brazed single wire steel wire increases the belt layer thickness compared to the use of brazed single wire steel wire, and has the effect of reducing the rolling resistance of pneumatic radial tires. It will be damaged.

JP-A-8-300905 JP 2000-343906 A JP 2001-80313 A

  An object of the present invention is to provide a pneumatic radial tire that can reduce rolling resistance while maintaining good tire durability when providing a belt layer in which a plurality of single wire steel wires are arranged and embedded in rubber. Is to provide.

In order to achieve the above object, the pneumatic radial tire of the present invention has a belt layer in which a plurality of single-wire steel wires without brazing are aligned and embedded in rubber on the outer peripheral side of the carcass layer in the tread portion. In the disposed pneumatic radial tire, the cross-sectional shape of the single wire steel wire is a perfect circle , the strand diameter d of the single wire steel wire is 0.25 mm to 0.40 mm, and the tensile strength S of the single wire steel wire is (MPa) is set to a relationship of S ≧ 3870−2000 × d with respect to the wire diameter d, and a twist is applied to each single wire steel wire about its axis, and the wire surface twist angle with respect to the axial direction of the single wire steel wire Is characterized by being 1 ° or more.

  In the present invention, when a single wire steel wire having a large tensile strength S is adopted as a reinforcing cord for the belt layer, the single wire steel wire constituting the belt layer is twisted and the twist angle of the wire surface is defined to thereby determine the single wire steel wire. Since the orientation of the metal structure caused by wire drawing in the wire is relaxed, the fatigue resistance of the single wire steel wire can be improved and the tire durability performance can be improved. Also, when using a twisted single wire steel wire, unlike the case of using a brazed single wire steel wire, the thickness of the belt layer does not increase, so it is based on the use of a single wire steel wire. Thus, the rolling resistance of the pneumatic radial tire can be sufficiently reduced.

  In order to improve the fatigue resistance of the single-wire steel wire, it is desirable to increase the wire surface twist angle. However, if it is excessive, the productivity of the single-wire steel wire is lowered and the manufacture becomes difficult. Therefore, the wire surface twist angle with respect to the axial direction of the single wire steel wire is preferably 1 ° to 15 °.

  Further, in order to sufficiently ensure the tire durability performance, the driving density of the single wire steel wire in the belt layer is preferably 50/50 mm to 90/50 mm.

  Further, it is preferable to wind a belt cover layer around at least the outer peripheral side of the edge portion of the belt layer. Thus, the belt cover layer can compensate for the disadvantages of using a single wire steel wire, that is, the point that separation between the cord and the rubber tends to occur due to the narrow cord interval.

  In the present invention, the wire surface twist angle θ is measured as follows. First, a single wire steel wire is taken out from a pneumatic radial tire, the wire is immersed in an organic solvent to swell the rubber adhering to the surface, and then the rubber is removed. Then, the single wire steel wire is observed with an optical microscope, the strand diameter d (mm) of the single wire steel wire is measured, and the twist pitch P (mm) is ½ of the drawn trace formed on the wire surface. Measure the value and double it to determine the twist pitch P. The twist pitch P is an average value of the measured values at at least 10 locations. Based on the wire diameter d and the twist pitch P, the wire surface twist angle θ is calculated from the following equation (1).

  θ = ATAN (π × d / P) × 180 / π (1)

1 is a meridian half cross-sectional view showing a pneumatic radial tire according to an embodiment of the present invention. It is a side view which shows the single wire steel wire used for a belt layer by this invention. It is a side view which expands and shows a part of FIG.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic radial tire according to an embodiment of the present invention, and FIGS. 2 and 3 show a single wire steel wire used for a belt layer in the present invention.

  In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 is mounted between the pair of left and right bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the tire inner side to the outer side around the bead core 5 disposed in each bead portion 3. As a reinforcing cord for the carcass layer 4, an organic fiber cord is generally used, but a steel cord may be used. A bead filler 6 is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body portion and the folded portion of the carcass layer 4.

  On the other hand, a plurality of belt layers 8 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 8 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 8, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set, for example, in a range of 10 ° to 40 °.

  On the outer peripheral side of the belt layer 8, at least one belt cover layer 9 formed by arranging reinforcing cords at an angle of 5 ° or less with respect to the tire circumferential direction is arranged for the purpose of improving high-speed durability. . The belt cover layer 9 preferably 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. Further, the belt cover layer 9 may be disposed so as to cover the entire width direction of the belt layer 8 as illustrated, or may be disposed so as to cover only the outer edge portion of the belt layer 8 in the width direction. good. As the reinforcing cord of the belt cover layer 9, a cord using organic fibers such as nylon, PET, and aramid alone or in combination may be used.

  In the pneumatic radial tire, a single-wire steel wire 10 (see FIGS. 2 and 3) in which a twist is applied around the shaft is used as a reinforcing cord constituting the belt layer 8. In FIG. 3, a wire trace 11 resulting from the wire drawing is formed on the surface of the single wire steel wire 10, but the wire surface with respect to the axial direction of the single wire steel wire 10 determined based on the wire trace 11. The twist angle θ is in the range of 1 ° or more, more preferably in the range of 1 ° to 15 °.

  In the pneumatic radial tire provided with the belt layer 8 in which a plurality of single wire steel wires 10 are aligned and embedded in rubber as described above, each single wire steel wire 10 is twisted about its axis, and the single wire By defining the wire surface twist angle θ with respect to the axial direction of the steel wire 10, the orientation of the metal structure caused by the wire drawing process in the single wire steel wire 10 is relaxed, so that the fatigue resistance of the single wire steel wire 10 is improved. Thus, the tire durability can be improved. In addition, since the thickness of the belt layer 8 is not increased even if the single wire steel wire 10 is twisted, the rolling resistance of the pneumatic radial tire is reduced by reducing the coating rubber of the belt layer 8 based on the use of the single wire steel wire 10. Can be reduced.

  Here, if the wire surface twist angle θ is less than 1 °, the effect of improving the fatigue resistance of the single-wire steel wire 10 becomes insufficient. Further, if the wire surface twist angle θ exceeds 15 °, the productivity of the single-wire steel wire 10 is lowered, and the manufacture becomes difficult.

  In the pneumatic radial tire, the wire diameter d of the single wire steel wire 10 is set to 0.25 mm to 0.40 mm. If the strand diameter d is less than 0.25 mm, the mutual spacing of the single-wire steel wires 10 becomes narrow in order to secure the total strength of the belt layer 8, and the tire durability performance deteriorates. On the other hand, when the wire diameter d exceeds 0.40 mm, the fatigue resistance of the single wire steel wire 10 is lowered, and the tire durability is deteriorated.

  Further, the tensile strength S (MPa) of the single wire steel wire 10 is in a relationship of S ≧ 3870−2000 × d with respect to the wire diameter d. That is, the single wire steel wire 10 is provided with a high tensile property. Here, if the tensile strength S is too small, the rolling resistance cannot be reduced while maintaining the tire durability performance. The upper limit value of the tensile strength S is not particularly limited, but is set to 4500 MPa, for example.

  Moreover, the driving density of the single wire steel wire 10 in each reinforcement layer is good in it being 50 / 50mm-90 / 50mm. If the driving density is less than 50/50 mm, it is difficult to ensure the total strength of the belt layer 8. Conversely, if it exceeds 90/50 mm, the distance between the single-wire steel wires 10 becomes narrow, and the tire durability performance is improved. Getting worse.

  In pneumatic radial tires with a tire layer of 195 / 65R15 and a belt layer in which a plurality of reinforcement cords are aligned and embedded in rubber, the structure of the reinforcement cord of the belt layer, the wire diameter d, the strength, the tension Tires of Conventional Example 1, Examples 1 to 4, and Comparative Examples 1 to 4 having strength and wire surface twist angle θ set as shown in Table 1 were manufactured.

  The tire of Conventional Example 1 uses a steel cord having a 1 × 3 structure in which three filaments having a strand diameter d of 0.28 mm are twisted as a reinforcing cord for the belt layer. On the other hand, the tires of Examples 1 to 4 and Comparative Examples 1 to 4 use a single wire steel wire having a strand diameter d of 0.23 mm to 0.42 mm as a reinforcing cord for the belt layer. In Conventional Example 1, Examples 1 to 4 and Comparative Examples 1 to 4, the product of the strength (N) of the belt layer reinforcing cord and the driving density (lines / 50 mm) is made constant.

  With respect to these test tires, the tire durability performance and rolling resistance were evaluated by the following evaluation methods, and the results are also shown in Table 1.

Tire durability:
Each test tire was assembled into a rim, and the tire was filled with oxygen, and subjected to dry heat deterioration for 5 days under the conditions of an oxygen internal pressure of 350 kPa and a temperature of 80 ° C. After dry heat deterioration, the oxygen filled in the tire was replaced with air and the air pressure was set to 200 kPa. Then, a running test of the test tire was started under conditions of a speed of 120 km / h and a load load of 5 kN, the speed was increased by 10 km / h every 24 hours, and the running distance until the test tire failed was measured. The evaluation results are shown as an index with Conventional Example 1 as 100. It means that tire durability performance is excellent, so that this index value is large.

Rolling resistance:
Each test tire was assembled with a rim, set to an air pressure of 230 kPa, and the rolling resistance of the test tire was measured under the conditions of a speed of 80 km / h and a load of 6.15 kN. The evaluation results are shown as an index with Conventional Example 1 as 100. It means that rolling resistance is so small that this index value is small.

  As can be seen from Table 1, the tires of Examples 1 to 4 were able to reduce rolling resistance while maintaining good tire durability in comparison with Conventional Example 1. In contrast, in the tires of Comparative Examples 1 to 4, although the rolling resistance reduction effect was recognized, the tire durability performance was lowered. In particular, in Comparative Examples 1 and 3, separation occurred between the single wire steel wire of the belt layer and the coated rubber, and in Comparative Examples 2 and 4, the single wire steel wire of the belt layer was broken.

  Next, a tire of Conventional Example 2 having the same structure as Conventional Example 1 except that a belt cover layer is added to the outer peripheral side of the belt layer, a belt cover layer is added to the outer peripheral side of the belt layer, and a single wire steel wire Tires of Examples 5 to 8 having the same structures as those of Examples 1 to 4, respectively, except that the wire diameter d was varied were manufactured. In Conventional Example 2 and Examples 5 to 8, the product of the strength (N) of the reinforcing cord of the belt layer and the driving density (lines / 50 mm) is made constant.

  About these test tires, the tire durability performance and rolling resistance were evaluated by the above-described evaluation method, and the results are shown in Table 2. The evaluation criteria for tire durability performance and rolling resistance were Conventional Example 2.

  As can be seen from Table 2, the tires of Examples 5 to 8 were able to reduce rolling resistance while maintaining good tire durability in comparison with Conventional Example 2. Particularly, in Examples 5 to 8, the rolling resistance is further reduced by making the wire diameter d of the single wire steel wire thinner than in the case of Examples 1 to 4, but the belt cover layer is a belt layer. Since the single wire steel wire was pressed in, the tire durability performance could be maintained well.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 8 Belt layer 9 Belt cover layer 10 Single wire steel wire 11 Wire trace

Claims (4)

In a pneumatic radial tire in which a belt layer is formed by arranging a plurality of single-wire steel wires without brazing on the outer peripheral side of the carcass layer in the tread portion and embedded in rubber, the cross-sectional shape of the single-wire steel wire Is a round shape , the wire diameter d of the single wire steel wire is 0.25 mm to 0.40 mm, and the tensile strength S (MPa) of the single wire steel wire is S ≧ 3870− with respect to the wire diameter d. A pneumatic radial tire characterized by having a relationship of 2000 × d and twisting each single wire steel wire around its axis so that the wire surface twist angle with respect to the axial direction of the single wire steel wire is 1 ° or more.   The pneumatic radial tire according to claim 1, wherein a wire surface twist angle with respect to an axial direction of the single wire steel wire is set to 1 ° to 15 °.   3. The pneumatic radial tire according to claim 1, wherein a driving density of the single wire steel wire in the belt layer is 50/50 mm to 90/50 mm. 4.   The pneumatic radial tire according to any one of claims 1 to 3, wherein a belt cover layer is wound around at least an outer peripheral side of the edge portion of the belt layer.

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