JP6136712B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which an annular bead core is embedded in each of a pair of bead parts, and more particularly to a pneumatic tire that can be reduced in weight while maintaining tire performance.

  In the pneumatic tire, an annular bead core is embedded in each of the pair of bead portions. As such a bead core, it is composed of at least one bead wire wound in the tire circumferential direction, and a plurality of layers in which a plurality of circumferential portions of the bead wire are arranged in the tire axial direction overlap with the tire radial direction. There is something to do. In general, a single bead wire that is continuously wound is called a single-winding bead, and a plurality of bead wires that are continuously wound together are called a layer-winding bead. The bead core having such a structure is widely used in, for example, pneumatic tires for passenger cars.

  The bead core having the above-described structure increases the number of bead wires and increases the cross-sectional area of the bead wire, thereby increasing its rigidity and contributing to improvements in tire performance such as steering stability. On the other hand, in recent years, from the viewpoint of resource saving and energy saving, it is required to reduce the weight of pneumatic tires, thereby reducing the rolling resistance of the tires, and as part of this, weight reduction of bead cores is required. .

  However, in the bead core of a pneumatic tire, if the number of bead wires is reduced or the bead wire cross-sectional area is reduced, the rigidity of the bead core is lowered, and the tire performance such as steering stability is lowered. . In addition, attempts have been made to replace a part of the bead wire with an organic fiber cord (see, for example, Patent Documents 1 and 2). However, in such a case, the tire performance is also deteriorated.

JP 2009-280119 A JP 2013-56566 A

  An object of the present invention is to provide a pneumatic tire that can be reduced in weight while maintaining tire performance.

In order to achieve the above object, a pneumatic tire according to the present invention comprises at least one bead wire in which an annular bead core is embedded in each of a pair of bead portions, and each bead core is wound in the tire circumferential direction. In a pneumatic tire in which a plurality of circumferential portions of the plurality of rows are arranged in the tire axial direction and a plurality of layers overlapping in the tire radial direction are formed .
The bead core includes a titanium wire containing steel wire and titanium as the bead wire, and all the innermost layers of the bead core are made of the steel wire, and all the layers positioned radially outside the innermost layer are all made of the titanium. Composed of wires,
Alternatively, the bead core includes a titanium wire containing steel wire and titanium as the bead wire, and the diameter of the titanium wire is smaller than the diameter of the steel wire .

  In the present invention, in a pneumatic tire having a bead core in which a plurality of circumferential portions of the bead wire are arranged in a plurality of rows and a plurality of layers, a lightweight and highly rigid titanium wire is used as the bead wire of the bead core, which is represented by steering stability. The pneumatic tire can be reduced in weight while maintaining good tire performance. Such weight reduction makes it possible to reduce the rolling resistance of pneumatic tires, and as a result, improves the fuel efficiency of the vehicle and can greatly contribute to resource and energy savings.

In the present invention, the bead core preferably includes a steel wire and a titanium wire containing titanium as a bead wire. In particular, it is preferable that the innermost layer of the bead core is made of a steel wire, while the composition ratio of the titanium wire is made higher than that of the innermost layer in each layer positioned radially outward from the innermost layer. More specifically, all the layers positioned radially outward from the innermost layer are all made of titanium wire, or in each layer positioned radially outer than the innermost layer, the composition ratio of the titanium wire is set radially outward. It is preferable to increase gradually. Here, the composition ratio of the titanium wire in each layer is the ratio of the total cross-sectional area of the titanium wire to the total cross-sectional area of the bead wire included in each layer.

  That is, according to the knowledge of the present inventor, the titanium wire has the advantage of being lightweight and highly rigid, but because the toughness is not high, the titanium wire is disposed in the innermost layer of the bead core having the above structure. In this case, the durability of the bead portion is impaired. On the other hand, even if a titanium wire is disposed in each layer located radially outside the innermost layer, the durability of the bead portion is hardly lowered. Therefore, by configuring all the innermost layers of the bead core with steel wires, the durability of the bead portion is sufficiently ensured, and in each layer located radially outside the innermost layer, the composition ratio of the titanium wire is higher than that of the innermost layer. By making it high, weight reduction can be achieved more effectively.

  In the present invention, it is preferable to make the diameter of the titanium wire smaller than the diameter of the steel wire. Since the titanium wire has higher rigidity than the steel wire, it can be made thinner than the steel wire while maintaining the required rigidity, and as a result, further weight reduction is possible.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. It is sectional drawing which shows an example of the bead core in the pneumatic tire of this invention. It is sectional drawing which shows the modification of the bead core in the pneumatic tire of this invention. It is sectional drawing which shows the modification of the bead core in the pneumatic tire of this invention. (A)-(c) is sectional drawing which shows the modification of the bead core in the pneumatic tire of this invention, respectively. (A)-(c) is sectional drawing which shows the modification of the bead core in the pneumatic tire of this invention, respectively.

  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. 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 carcass cords extending in the tire radial direction is mounted between the pair of bead portions 3 and 3. As the carcass cord constituting the carcass layer 4, an organic fiber cord such as nylon or polyester is preferably used. An annular bead core 5 is embedded in each bead portion 3, and a bead filler 6 made of a rubber composition 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 one belt cover layer 8 in which reinforcing cords are arranged at an angle of 5 ° or less with respect to the tire circumferential direction is disposed for the purpose of improving high-speed durability. . It is desirable that the belt cover 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. Further, the belt cover 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. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

  FIG. 2 shows an example of a bead core in the pneumatic tire of the present invention. As shown in FIG. 2, in the pneumatic tire, each bead core 5 is composed of a bead wire 50 wound in the tire circumferential direction, and a plurality of rows 50A of the bead wires 50 are arranged in the tire axial direction Tw. And a plurality of layers overlapping the tire radial direction Tr. It is preferable that the number of rows of the bead wires 50 in the bead core 5 is in the range of 3 to 6, and the number of layers is in the range of 3 to 6. Insulation rubber is disposed around the bead wire 50, but the illustration of the insulation rubber is omitted here.

The bead core 5 includes a steel wire 51 and a titanium wire 52 containing titanium as a bead wire 50. More specifically, all the circumferential portions 50A included in the innermost layer (the lowermost layer in the figure) of the bead core 5 are configured by the steel wires 51, and are all included in each layer located radially outside the innermost layer. The surrounding portion 50 </ b> A is composed of a titanium wire 52.

  Thus, in the pneumatic tire having the bead core 5 in which the plurality of circumferential portions 50A of the bead wire 50 are arranged in a plurality of rows and in a plurality of layers, a lightweight and high-rigidity titanium wire 52 is used as the bead wire 50 of the bead core 5. While maintaining good tire performance represented by stability, the weight of the pneumatic tire can be reduced. In particular, by configuring all the surrounding portions 50A included in the innermost layer of the bead core 5 with the steel wires 51, the durability of the bead portion 3 can be sufficiently ensured, and the outermost layer is positioned radially outside the innermost layer. By configuring all the surrounding portions 50A included in each layer with the titanium wire 52, the effect of weight reduction can be enjoyed to the maximum.

  FIG. 3 shows a modification of the bead core in the pneumatic tire of the present invention. In FIG. 3, the arrangement of the steel wire 51 and the titanium wire 52 is the same as that in FIG. 2, but the diameter of the titanium wire 52 is smaller than the diameter of the steel wire 51. Since the titanium wire 52 is higher in rigidity than the steel wire 51, it can be made thinner than the steel wire 51 while maintaining the required rigidity, and as a result, further weight reduction is possible. For example, the diameter of the steel wire 51 may be set in a range of 0.8 mm to 2.0 mm, and the diameter of the titanium wire 52 may be set in a range of 70% to 90% of the diameter of the steel wire 51.

  FIG. 4 shows a further modification of the bead core in the pneumatic tire of the present invention. In FIG. 4, all the circumferential portions 50 </ b> A of the bead wires 50 that constitute the bead core 5 are composed of titanium wires 52. In this case, although the effect of reducing the weight can be obtained to the maximum, since the titanium wire 52 having low toughness is disposed in the innermost layer of the bead core 5, there is a drawback that the durability of the bead portion 3 is slightly lowered.

  5 (a) to 5 (c) each show a further modification of the bead core in the pneumatic tire of the present invention. 5A to 5C, all the circumferential portions 50A included in the innermost layer (the lowermost layer in the drawing) of the bead core 5 are configured by the steel wires 51 and are located on the outer side in the radial direction than the innermost layer. In each layer, the composition ratio of the titanium wire 52 is higher than that of the innermost layer. That is, the steel wire 51 and the titanium wire 52 are mixed in each layer located radially outside the innermost layer of the bead core 5. In this case, it is possible to reduce the weight of the bead core 5 while maintaining the durability of the bead portion 3 well.

  6 (a) to 6 (c) each show a further modification of the bead core in the pneumatic tire of the present invention. 6A to 6C, all the circumferential portions 50A included in the innermost layer (the lowermost layer in the drawing) of the bead core 5 are configured by the steel wires 51, and are located on the outer side in the radial direction than the innermost layer. In each layer, the constituent ratio of the titanium wire 52 is higher than that of the innermost layer, and the constituent ratio of the titanium wire 52 gradually increases toward the outer side in the radial direction. That is, the steel wire 51 and the titanium wire 52 are mixed in each layer located radially outside the innermost layer of the bead core 5, but the constituent ratio of the steel wire 51 gradually decreases toward the radially outer side. Yes. Also in this case, the weight of the bead core 5 can be reduced while maintaining the durability of the bead portion 3 well.

  In the present invention, the titanium wire containing titanium can be composed of not only a titanium metal alone but also a titanium alloy obtained by adding a small amount of other metals such as aluminum, vanadium, molybdenum, and tin to titanium. For titanium metal alone or titanium alloy, α type with α phase (dense hexagonal lattice) metal structure, β type with β phase (body centered cubic lattice) metal structure, α + β with α phase and β phase mixed There is a type. The titanium wire is preferably composed of an α-type, β-type, or α + β-type titanium alloy from the viewpoint of stabilizing various mechanical and chemical properties. In particular, from the viewpoints of strength and workability, among titanium alloys, β-type titanium alloys or α + β-type titanium alloys are more preferable.

  As the β-type titanium alloy, a titanium alloy obtained by adding a small amount of an alloy element such as vanadium, molybdenum, aluminum, or chromium to titanium, for example, vanadium 15.0 wt%, chromium 3.0 wt%, tin 3.0 wt%, Examples thereof include a titanium alloy containing 3.0% by weight of aluminum, a titanium alloy containing 15.0% by weight of molybdenum, 5.0% by weight of zirconium, and 3.0% by weight of aluminum.

  As the α + β type titanium alloy, a titanium alloy obtained by adding a small amount of an alloy element such as aluminum, vanadium, molybdenum, and tin to titanium, for example, a titanium alloy containing 6.0 wt% aluminum and 4.0 wt% vanadium, or aluminum 6 A titanium alloy containing 0.0 wt%, vanadium 6.0 wt%, and tin 2.0 wt% can be used.

  Furthermore, in order to improve the adhesion between the titanium wire and the rubber, it is preferable that the surface of the titanium wire is plated with copper, zinc, brass, bronze or the like.

In tire size 215 / 45R17, an annular bead core is embedded in each of a pair of bead portions, and each bead core is constituted by at least one bead wire wound in the tire circumferential direction, and a plurality of circumferential portions of the bead wire are tire shafts Conventional tires and test examples 1 to 5 were manufactured in which the bead wires constituting the bead core were varied in the pneumatic tire in which a plurality of rows arranged in the direction and a plurality of layers overlapping in the tire radial direction were formed.

In the conventional tire, the bead core is composed only of a steel wire. As shown in FIG. 4, the tire of Test Example 1 (Reference Example) has a bead core made of only titanium wire. In the tire of Test Example 2 , as shown in FIG. 2, all the innermost layers of the bead core are made of steel wires, and all the layers positioned radially outside the innermost layers are made of titanium wires. As shown in FIG. 3, the tire of Test Example 3 has the same structure as that of Example 2 except that the diameter of the titanium wire is smaller than the diameter of the steel wire. In the tire of Test Example 4 (Reference Example) , as shown in FIG. 5A, the innermost layer of the bead core is made of steel wire, and the titanium wire is made of each layer located radially outside the innermost layer. The ratio is higher than the innermost layer. In the tire of Test Example 5 (reference example) , as shown in FIG. 6 (a), the innermost layer of the bead core is composed of steel wire, and the titanium wire is composed of each layer positioned radially outside the innermost layer. The ratio is made higher than that of the innermost layer, and the constituent ratio of the titanium wire is gradually increased outward in the radial direction.

 These test tires were evaluated for tire weight, steering stability, and bead strength by the following evaluation methods, and the results are also shown in Table 1.

Tire weight:
The weight of each test tire was measured. The evaluation results are shown as an index with the conventional example being 100. A smaller index value means a lighter weight.

Steering stability:
Each test tire was assembled on a wheel having a rim size of 17 × 7 J and mounted on a test vehicle, and sensory evaluation was performed on a test course by a test driver under the condition of an air pressure of 210 kPa. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the steering stability.

Bead strength:
Each test tire was assembled on a wheel having a rim size of 17 × 7 J and mounted on a drum durability tester. After a predetermined load durability test, a bead wire was taken out from the bead core of the test tire and its strength was measured. The evaluation results are indicated by an index with the strength of the bead wire as new as 100. A larger index value means less decrease in bead strength and better bead durability. In the evaluation of the bead strength, the strength was measured for all the round portions of the bead core, and the index value was the average value of all the round portions.

As can be seen from Table 1, the tires of Test Examples 1 to 5 were able to achieve weight reduction while maintaining good steering stability in comparison with the conventional examples. In Test Example 1, the bead strength slightly decreased, but in Test Examples 2 to 5, no decrease in bead strength was observed.

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 Belt cover layer 50 Bead wire 50A Circulation part 51 Steel wire 52 Titanium wire

Claims (5)

An annular bead core is embedded in each of the pair of bead portions, each bead core is composed of at least one bead wire wound in the tire circumferential direction, and a plurality of rows in which a plurality of circumferential portions of the bead wire are arranged in the tire axial direction; In a pneumatic tire configured to form a plurality of layers overlapping in a tire radial direction, the bead core includes a steel wire and a titanium wire containing titanium as the bead wire, and the innermost layer of the bead core is configured by the steel wire. On the other hand, a pneumatic tire characterized in that each layer located radially outside of the innermost layer is composed of the titanium wire . An annular bead core is embedded in each of the pair of bead portions, each bead core is composed of at least one bead wire wound in the tire circumferential direction, and a plurality of rows in which a plurality of circumferential portions of the bead wire are arranged in the tire axial direction; In a pneumatic tire configured to form a plurality of layers overlapping in a tire radial direction, the bead core includes a titanium wire containing steel wire and titanium as the bead wire, and the diameter of the titanium wire is larger than the diameter of the steel wire. A pneumatic tire characterized by being made smaller .   The innermost layer of the bead core is composed of the steel wire, while the composition ratio of the titanium wire is set higher than that of the innermost layer in each layer positioned radially outward from the innermost layer. 2. The pneumatic tire according to 2.   4. The pneumatic tire according to claim 3, wherein each of the layers positioned radially outward from the innermost layer is composed of the titanium wire.   4. The pneumatic tire according to claim 3, wherein in each layer positioned radially outward from the innermost layer, the composition ratio of the titanium wire is gradually increased toward the radially outer side.

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