JP6487779B2 - Airless tire - Google Patents

Description

  The present invention relates to an airless tire that ensures excellent steering stability and improves durability while reducing rolling resistance.

  Known as an airless tire is a structure in which a cylindrical tread ring having a ground contact surface and a hub fixed to an axle are connected by a plurality of spoke plate portions arranged radially (for example, a patent) Reference 1).

  In such an airless tire, it is advantageous from the viewpoint of strength, durability, steering stability, grip properties, and the like to use a rubber material of a normal pneumatic tire for a tread rubber layer forming a ground contact surface of the tread ring. It is. However, in an airless tire, a load and an impact are received by the tread ring and the spoke plate portion instead of the filling internal pressure in the pneumatic tire, so that the degree of deformation is larger than that of the pneumatic tire. Therefore, the rigidity and heat generation of the composition constituting the tread ring have a great influence on the rolling resistance and the ride comfort performance.

  From such a point of view, a rubber member other than the tread rubber layer in the tread ring is desired to have higher elasticity and lower heat generation than the rubber member used for the pneumatic tire. However, conventional rubber materials for pneumatic tires tend to have high heat generation if they are made highly elastic, and it has been difficult to make a major improvement.

  Therefore, the present inventor has proposed to use a butadiene-based rubber composition having an α, β-unsaturated carboxylic acid metal salt as a crosslinking agent for at least a part of the rubber member other than the tread rubber layer in the tread ring. did. This rubber composition can achieve high elasticity and low heat generation, which was difficult with sulfur vulcanized rubber. However, since elasticity and elongation are too different between adjacent rubbers, there is a possibility that peeling occurs at the interface and there is a problem in durability.

JP 2008-260514 A

  Therefore, the present invention uses a butadiene-based rubber composition containing α, β-unsaturated carboxylic acid metal salt as a cross-linking agent for the reinforcing rubber layer of the tread ring to ensure excellent steering stability and reduce rolling resistance. In addition, an object is to provide an airless tire in which durability is improved by suppressing separation between adjacent rubbers by providing an interface layer that relieves an elastic difference.

The present invention provides an airless comprising a cylindrical tread ring having a grounding surface, a hub that is arranged radially inside the tread ring and fixed to an axle, and a spoke that connects the tread ring and the hub. Tire,
The tread ring includes a tread rubber layer that constitutes a ground contact surface, and a reinforcing rubber layer that is disposed inside the tire radius of the tread rubber layer,
In addition, the reinforcing rubber layer contains 10 to 80 parts by weight of an α, β-unsaturated carboxylic acid metal salt with respect to 100 parts by weight of the rubber component having a butadiene rubber content of 10 to 100% by weight. Comprising a rubber composition containing an oxide,
At the interface between the reinforcing rubber layer and the adjacent rubber adjacent to the reinforcing rubber layer, the elastic difference gradually decreases from the reinforcing rubber layer toward the adjacent rubber, thereby reducing the elastic difference between the adjacent rubber. It is characterized by having an interface layer.

In the airless tire according to the present invention, the tread ring includes an outer reinforcing cord layer disposed closest to the tread rubber layer, and an inner reinforcing cord layer provided on the inner side in the tire radial direction of the outer reinforcing cord layer. And the reinforcing rubber layer is disposed between the outer reinforcing cord layer and the inner reinforcing cord layer,
It is preferable that a topping rubber of the outer reinforcing cord layer and the inner reinforcing cord layer forms the adjacent rubber.

  In the airless tire according to the present invention, the topping rubber is made of sulfur vulcanized rubber using sulfur as a vulcanizing agent, and at the time of vulcanization, part of the sulfur in the topping rubber moves to the reinforcing rubber layer side. Thus, the interface layer is preferably formed.

  In the airless tire according to the present invention, the content of sulfur in the topping rubber is preferably 0.5 to 10 phr.

  In the airless tire according to the present invention, it is preferable that the thickness of the reinforcing rubber layer is 3 mm or more and 70% or less of the thickness of the tread ring.

  As described above, the airless tire of the present invention uses a rubber composition containing butadiene rubber, an α, β-unsaturated carboxylic acid metal salt and a peroxide in the reinforcing rubber layer in the tread ring. In this rubber composition, a butadiene rubber and an unsaturated carboxylic acid metal salt can be co-crosslinked using a peroxide as an initiator to obtain physical properties excellent in elasticity and fuel efficiency. Thereby, in an airless tire, it is possible to reduce rolling resistance while ensuring excellent steering stability performance.

  Further, an interface layer in which the elasticity gradually decreases from the reinforcing rubber layer toward the adjacent rubber is provided at an interface portion between the reinforcing rubber layer and the adjacent rubber. Therefore, the elastic difference between the reinforcing rubber layer and the adjacent rubber can be relaxed to prevent stress concentration, the occurrence of peeling at the interface portion can be suppressed, and the durability of the tread ring can be improved.

  The rubber composition tends to be inferior to a rubber material of a normal pneumatic tire in terms of stretchability and tensile strength. However, when the reinforcing rubber layer made of this rubber composition has a so-called sandwich structure arranged between the outer reinforcing cord layer and the inner reinforcing cord layer, the problems of stretchability and tensile strength can be solved.

1 is a perspective view showing an embodiment of an airless tire of the present invention. It is a perspective view which shows the tread ring of FIG. It is an expanded sectional view of the tread ring of FIG. It is an expanded sectional view exaggeratingly showing an interface layer. It is a perspective view which shows the other Example of an inner side reinforcement cord layer. It is a perspective view which shows the other Example of an outer side reinforcement cord layer. It is a perspective view which shows the further another Example of an outer side reinforcement cord layer.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, an airless tire 1 according to the present embodiment includes a cylindrical tread ring 2 having a ground contact surface 21, a hub 3 that is arranged radially inside the tread ring 2 and is fixed to an axle, A spoke 4 for connecting the tread ring 2 and the hub 3 is provided. In this example, the case where the airless tire 1 is formed as a tire for a passenger car is shown.

  The hub 3 has a disk part 31 fixed to the axle and a cylindrical part 32 formed on the outer periphery of the disk part 31. The hub 3 can be formed of a metal material such as steel, an aluminum alloy, and a magnesium alloy, for example, similarly to the conventional tire wheel.

  The spoke 4 is formed by a cast molded body made of a polymer material. The spokes 4 have a plate shape and are provided in a plurality in the tire circumferential direction.

  As shown in FIGS. 2 and 3, the tread ring 2 includes a tread rubber layer 22 that constitutes the ground contact surface 21, and a reinforcing rubber layer 7 that is disposed inside the tire radius. In this example, the tread ring 2 further includes an outer reinforcing cord layer 5 provided closest to the tread rubber layer 22 and an inner reinforcing cord layer 6 provided inside the outer reinforcing cord layer 5 in the tire radial direction. In addition, the reinforcing rubber layer 7 is disposed between the outer reinforcing cord layer 5 and the inner reinforcing cord layer 6. That is, a sandwich structure is formed in which both sides of the reinforcing rubber layer 7 are sandwiched between the outer reinforcing cord layer 5 and the inner reinforcing cord layer 6.

  Tread grooves (not shown) are formed in various pattern shapes on the ground contact surface 21 which is the outer peripheral surface of the tread ring 2 in order to provide wet performance. For the tread rubber layer 22, a rubber composition excellent in frictional force against grounding and wear resistance is suitably employed.

  In this example, since the number of outer reinforcing cord layers 5 is greater than the number of inner inner reinforcing cord layers 6, the rigidity of the ground plane 21 can be easily increased. Conversely, the number of layers of the inner reinforcing cord layer 6 is smaller than the number of layers of the outer reinforcing cord layer 5, whereby the weight can be easily reduced.

  The outer reinforcing cord layer 5 includes a first cord ply 51 and a second cord ply 52 provided outside the first cord ply 51 in the tire radial direction.

  In this example, the width of the first cord ply 51 and the width of the second cord ply 52 are set to be approximately equal in the tire axial direction. The term “substantially equal” includes the case where the width of the first cord ply 51 and the width of the second cord ply 52 match, and the case where each width is different within a range of 10 mm or less.

  The first cord ply 51 includes a first reinforcing cord 56 that is inclined with respect to the tire circumferential direction at an angle θ1. The first reinforcing cord 56 is covered with a topping rubber G (shown in FIG. 4).

  The second cord ply 52 has a second reinforcement cord 57 that is inclined with respect to the tire circumferential direction at the same angle θ2 as the first reinforcement cord 56 and in the opposite direction. The second reinforcing cord 57 is covered with a topping rubber.

  As the 1st reinforcement cord 56 and the 2nd reinforcement cord 57, the material equivalent to the belt cord of a pneumatic tire, for example, a steel cord, can be adopted suitably. However, for example, high modulus organic fiber cords such as aramid, polyethylene naphthalate (PEN), and polyethylene terephthalate (PET) having high strength and elastic modulus can be used as required.

  The first reinforcing cord 56 and the second reinforcing cord 57 are inclined and arranged in directions opposite to each other with respect to the tire circumferential direction, whereby the rigidity of the outer reinforcing cord layer 5 is increased and the tread ring 2 can be effectively used. Reinforce to. Further, the outer reinforcing cord layer 5 exhibits high resistance to in-plane torsion and generates cornering power, like the belt cord reinforcing layer of a pneumatic tire, when a slip angle is imparted to the airless tire 1. Provides a good turning performance.

  The inner reinforcement cord layer 6 includes a third cord ply 61 having a third reinforcement cord 66. The third reinforcing cord 66 is covered with a topping rubber G (shown in FIG. 4).

  The third reinforcing cords 66 in this example are arranged in parallel to the tire circumferential direction. Here, “parallel to the tire circumferential direction” means that the arrangement of the third reinforcing cords 66 is substantially parallel to the tire circumferential direction. In consideration of manufacturing tolerances, the tires of the third reinforcing cords 66 are arranged. An angle θ3 (not shown) with respect to the circumferential direction is, for example, about 0 ° ± 5 °. In this example, the third reinforcing cord 66 is wound spirally. As the third reinforcing cord 66, for example, a steel cord can be suitably used, but a high modulus organic fiber cord such as aramid, polyethylene naphthalate (PEN), polyethylene terephthalate (PET) can also be used as required.

  The rigidity of the tread ring 2 in the tire circumferential direction is enhanced by the third reinforcing cord 66 arranged in the inner reinforcing cord layer 6. Thereby, the shape of the contact surface 21 at the time of deceleration and acceleration is stabilized, and the braking performance and the traction performance are improved. Further, the third cord ply 61 having the third reinforcing cords 66 arranged in parallel to the tire circumferential direction can ensure symmetry with respect to the tire circumferential direction line while reducing the weight by a single layer.

  Next, in the tread ring 2, as shown in an enlarged view in FIG. 3, the outer reinforcing cord layer 5, the inner reinforcing cord layer 6, and the reinforcing rubber layer 7 disposed therebetween form a sandwich structure. . As a result, the tension and compression forces acting when the tread ring 2 receives a load can be supported on the outer reinforcing cord layer 5 and the inner reinforcing cord layer 6 on both sides of the reinforcing rubber layer 7. Can be suppressed.

  Then, the following rubber composition (A) is used for the reinforcing rubber layer 7 in order to sufficiently enhance the above-described functions to ensure better driving stability and reduce rolling resistance.

  The rubber composition (A) contains 10 to 80 parts by weight of an α, β-unsaturated carboxylic acid metal salt with respect to 100 parts by weight of a rubber component having a butadiene rubber (BR) content of 10 to 100% by weight. Containing and containing peroxide. In this rubber composition (A), butadiene rubber (BR) and an α, β-unsaturated carboxylic acid metal salt are co-crosslinked using a peroxide as an initiator. This achieves high elasticity and low heat buildup, which was difficult with sulfur vulcanized rubber. In particular, by using the rubber composition (A) for the tread ring 2 of the airless tire 1, it is possible to provide a great effect on steering stability performance and rolling resistance.

  The rubber component contains 10 to 100% by mass of butadiene rubber (BR) in 100 parts by mass. When butadiene rubber (BR) is used by blending with other rubber, natural rubber (NR), styrene butadiene rubber (SBR), isoprene rubber (IR), chloroprene rubber (CR), styrene isoprene butadiene rubber are used as the rubber for blending. (SIBR), styrene isoprene rubber (SIR), epoxidized natural rubber (ENR) and the like can be mentioned, and these can be used alone or in combination of two or more. Among these, NR is preferable because it is excellent in low heat generation.

  The content of butadiene rubber (BR) is 10% by weight or more, preferably 20% by weight or more. If it is less than 10% by weight, the effect of reducing heat generation tends to decrease. Further, when the content of butadiene rubber (BR) is 100% by weight, the strength tends to decrease. Therefore, the upper limit of the content of butadiene rubber (BR) is preferably 90% by weight or less, more preferably 80% by weight or less. .

  As the co-crosslinking agent, α, β-unsaturated carboxylic acid metal salt which is a metal salt of α, β-unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid and the like is employed. In particular, since it is excellent in durability, a metal salt of acrylic acid and / or a metal salt of methacrylic acid is preferable, and a metal salt of methacrylic acid is more preferable. Examples of the metal in the α, β-unsaturated carboxylic acid metal salt include zinc, sodium, magnesium, calcium, and aluminum, and zinc is preferable because sufficient hardness can be obtained.

  The content of the co-crosslinking agent (α, β-unsaturated carboxylic acid metal salt) is 10 to 80 parts by weight with respect to 100 parts by weight of the rubber component. If it is less than 10 parts by weight, a sufficient crosslinking density cannot be obtained. On the other hand, when the content of the α, β-unsaturated carboxylic acid metal salt exceeds 80 parts by weight, it becomes too hard and the strength is lowered. From such a viewpoint, the lower limit of the content of the α, β-unsaturated carboxylic acid metal salt is preferably 12 parts by weight or more, and the upper limit is preferably 50 parts by weight or less, and more preferably 35 parts by weight or less.

  Examples of the peroxide include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2, 5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxybenzene, 2,4-dichlorobenzoyl peroxide, 1,1- Examples include di-t-butylperoxy-3,3,5-trimethylcyclohexane, n-butyl-4,4-di-t-butylperoxyvalerate, and these may be used alone. You may use combining more than a seed. Of these, dicumyl peroxide is preferable.

  The content of the peroxide is preferably 0.1 to 6.0 parts by weight with respect to 100 parts by weight of the rubber component. When the amount is less than 0.1 part by weight, sufficient hardness tends not to be obtained. On the other hand, if the peroxide content exceeds 6 parts by weight, the crosslinking density becomes excessive and the strength tends to decrease. From such a viewpoint, the lower limit of the peroxide is more preferably 0.2 parts by weight or more, and the upper limit is more preferably 2 parts by weight or less.

  The rubber composition (A) may contain a reinforcing filler. Examples of the reinforcing filler include carbon black, silica, calcium carbonate, clay, talc, alumina, and aluminum hydroxide, and carbon black is particularly preferable. When the reinforcing filler is contained, the content of the reinforcing filler is 90 parts by weight or less, more preferably 50 parts by weight or less with respect to 100 parts by weight of the rubber component. If the content of the reinforcing filler exceeds 90 parts by weight, there is a possibility that excellent low heat buildup property cannot be obtained.

  The rubber composition (A) includes the rubber component, the co-crosslinking agent (α, β-unsaturated carboxylic acid metal salt), the peroxide, and the reinforcing filler, as long as the effects of the present invention are not impaired. Thus, it may contain a compounding agent usually used in the tire industry, for example, zinc oxide, wax, stearic acid, oil, anti-aging agent, vulcanization accelerator and the like. The rubber composition (A) contains a co-crosslinking agent (α, β-unsaturated carboxylic acid metal salt) and therefore does not contain a vulcanizing agent such as sulfur or a sulfur compound.

  Further, when the rubber composition (A) is used for the reinforcing rubber layer 7, the elasticity and elongation are too different between the reinforcing rubber layer 7 and the adjacent rubber 10 adjacent to the reinforcing rubber layer 7. May occur. Therefore, as exaggeratedly shown in FIG. 4, an interface layer 11 whose elasticity gradually decreases from the reinforcing rubber layer 7 toward the adjacent rubber 10 is provided at the interface portion between the reinforcing rubber layer 7 and the adjacent rubber 10. It is formed. Thereby, the elastic difference between adjacent rubber | gum 10 can be relieve | moderated.

  In the case of this example, the reinforcing rubber layer 7 is adjacent to the topping rubbers G of the outer reinforcing cord layer 5 and the inner reinforcing cord layer 6. That is, the topping rubber G constitutes the adjacent rubber 10. The topping rubber G is formed of sulfur vulcanized rubber using sulfur as a vulcanizing agent, as in the case of a normal pneumatic tire. At the time of vulcanization, a part of the sulfur in the topping rubber G moves to the reinforcing rubber layer 7 side, so that the interface layer 11 in which the sulfur transferred in the rubber composition (A) is dispersed at the interface part. Is formed.

  Specifically, when the tread ring 2 is manufactured, the unvulcanized inner reinforcing cord layer 6, the unvulcanized reinforcing rubber layer 7, the unvulcanized outer reinforcing cord layer 5, and the unvulcanized tread rubber layer 22. Etc. are stacked to form a raw tread ring, and then the raw tread ring is vulcanized in a mold to form the tread ring 2. And at the time of this vulcanization molding, a part of the sulfur contained in the unvulcanized topping rubber G (adjacent rubber 10) penetrates into the adjacent unvulcanized rubber composition (A) at the interface portion, A composite interface layer 11 composed of sulfur blending and peroxide crosslinking is formed.

  In terms of composition, the interface layer 11 is obtained by adding sulfur to the composition of the rubber composition (A), and the permeation amount of sulfur gradually increases toward the topping rubber G side. In addition, as for the physical properties of the interface layer 11, the elastic modulus decreases according to the amount of sulfur permeated with respect to the high elastic modulus of the rubber composition (A). That is, the elasticity gradually decreases toward the topping rubber G, and stress concentration occurring at the interface portion can be suppressed to suppress peeling damage.

  Further, the rubber composition (A) tends to be inferior to the sulfur vulcanized rubber in stretchability and tensile strength. However, in this example, the reinforcing rubber layer 7 made of the rubber composition (A) has a sandwich structure arranged between the outer reinforcing cord layer 5 and the inner reinforcing cord layer 6. Therefore, the reinforcing rubber layer 7 becomes a neutral portion where neither the tension nor the compression works, and the problems of stretchability and tensile strength are solved. That is, with the sandwich structure, the advantages of the rubber composition (A) can be effectively exhibited while overcoming the drawbacks of the rubber composition (A).

  The thickness T (shown in FIG. 3) of the reinforcing rubber layer 7 is preferably 3 mm or more and 70% or less of the thickness T0 of the tread ring 2. When the thickness T is less than 3 mm, the rigidity of the tread ring 2 is insufficient and the steering stability is lowered. On the other hand, if the thickness exceeds 70% or less of the thickness T0, the rigidity of the tread ring 2 becomes excessive, and the running performance becomes inappropriate such as the vibration characteristics and the turning characteristics are deteriorated.

  The topping rubber G preferably has a sulfur content of 0.5 to 10 phr. When the content is less than 0.5 phr, the migration of sulfur is reduced and the interface layer 11 is hardly formed, and it is easy to peel off, resulting in a decrease in durability. On the other hand, if it exceeds 10 phr, problems occur in terms of rubber processability and rubber properties.

  Next, another embodiment of the airless tire 1 is shown. FIG. 5 shows another embodiment of the inner reinforcing cord layer 6. In this example, in the third cord ply 61 constituting the inner reinforcing cord layer 6, the third reinforcing cord 66 is arranged in parallel to the tire axial direction. Here, “parallel to the tire axial direction” means that the arrangement of the third reinforcing cords 66 is substantially parallel to the tire axial direction, and considering the manufacturing tolerance, the tire of the third reinforcing cord 66 An angle θ3 (not shown) with respect to the circumferential direction is, for example, about 90 ° ± 5 °.

  When the third reinforcing cords 66 are arranged in parallel to the tire axial direction, the rigidity of the tread ring 2 in the tire axial direction is increased. In this case, when the large slip angle is given to the airless tire 1, the shape of the ground contact surface 21 is stabilized. Further, the third cord ply 61 having the third reinforcing cords 66 arranged in parallel to the tire axial direction can ensure symmetry with respect to the tire circumferential direction line while reducing the weight by a single layer.

  Here, in the outer reinforcement cord layer 5 and the inner reinforcement cord layer 6, symmetry with respect to the tire circumferential direction line is important. If there is no symmetry, the tread ring 2 is deformed into a strain due to torsion by the outer reinforcing cord layer 5 and the inner reinforcing cord layer 6 at the time of loading, resulting in a difficulty in smooth rolling.

  In a pneumatic tire, in order to suppress expansion of a tread portion accompanying internal pressure filling, generally, an angle of a belt cord with respect to a tire circumferential direction is limited to a required range. On the other hand, in the airless tire 1 of the present embodiment, since it is not necessary to consider the internal pressure filling, the angles θ1 and θ2 of the first and second reinforcing cords 56 and 57 are determined in a wide range. Specifically, the angles θ1 and θ2 are preferably 5 ° to 85 °. When the angles θ1 and θ2 are less than 5 °, the rigidity of the tread ring 2 in the tire axial direction is insufficient, which may adversely affect the turning performance. On the other hand, when the angles θ1 and θ2 exceed 85 °, the rigidity of the tread ring 2 in the tire circumferential direction is insufficient, which may adversely affect the straightness and turning performance at a minute slip angle.

  In this example, the case where the 1st cord ply 51 is formed in the tire radial direction innermost side among the outer side reinforcement cord layers 5 is shown. However, at least one other cord ply can be provided further inside the tire radial direction than the first cord ply 51. In this example, the case where the second cord ply 52 is formed on the outermost side in the tire radial direction of the outer reinforcing cord layer 5 is shown. However, the outer side in the tire radial direction further than the second cord ply 52 is shown. It is also possible to provide at least one other cord ply. Since such a cord ply reinforces the tread ring 2 and improves the load carrying capacity of the airless tire 1, for example, it is suitably used for a tire having a large load such as a commercial vehicle tire.

  Specifically, in the embodiment of FIG. 6, the outer reinforcing cord layer 5 further includes a fourth cord ply 53 in which a fourth reinforcing cord 58 is arranged on the outer side in the tire radial direction of the second cord ply 52. Composed. In addition, the other structure which is not demonstrated in FIG. 6 is the same as that of previous embodiment.

  The fourth reinforcing cord 58 is parallel to the tire circumferential direction, that is, the angle θ4 (not shown) with respect to the tire circumferential direction is arranged at 0 ° ± 5 °, similarly to the third reinforcing cord 66. Such a fourth reinforcing cord 58 increases the rigidity of the tread ring 2 in the tire circumferential direction. Thereby, the shape of the contact surface 21 at the time of deceleration and acceleration is stabilized, and the braking performance and the traction performance are improved.

  The elastic modulus E4 of the fourth reinforcing cord 58 is preferably equal to or lower than the elastic modulus E0 of the first and second reinforcing cords 56 and 57. When the elastic modulus E4 of the fourth reinforcing cord 58 exceeds the elastic modulus E0, the fourth cord ply 53 becomes a working ply, and when the slip angle is given to the airless tire 1, the cornering power can be sufficiently generated. Without adversely affecting the turning performance. For the fourth reinforcing cord 58, for example, an organic fiber such as nylon is suitably employed.

  FIG. 7 shows still another embodiment of the outer reinforcing cord layer 5. Other configurations not described here are the same as those in the previous embodiment. In the embodiment of FIG. 6, the outer reinforcing cord layer 5 further includes a fifth cord ply 54 in which a fifth reinforcing cord 59 is arranged on the inner side in the tire radial direction of the first cord ply 51.

  The fifth reinforcement cord 59 is parallel to the tire circumferential direction, that is, the angle θ5 (not shown) with respect to the tire circumferential direction is arranged at 0 ° ± 5 ° in the same manner as the third reinforcement cord 66. Such a fifth reinforcing cord 59 increases the rigidity of the tread ring 2 in the tire circumferential direction. Thereby, the shape of the contact surface 21 at the time of deceleration and acceleration is stabilized, and the braking performance and the traction performance are improved.

  The structure of the embodiment of FIG. 6 and the embodiment of FIG. 7, that is, in the outer reinforcing cord layer 5, the fourth cord ply 53 is provided outside the second cord ply 52 in the tire radial direction, and the first cord ply The fifth cord ply 54 can also be arranged on the inner side in the tire radial direction of 51.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  An airless tire (a tire corresponding to a tire size 145 / 70R12) having the basic structure shown in FIGS. 1 and 2 was prototyped and tested for steering stability, rolling resistance, and durability. In Example 5, the outer reinforcing cord layer and the inner reinforcing cord layer are adjacent to each other, and the reinforcing rubber layer is disposed on the radially inner side of the inner reinforcing cord layer. Other than that, a reinforcing rubber layer is disposed between the outer reinforcing cord layer and the inner reinforcing cord layer.

Each tire had substantially the same specifications except for the tread ring, and the spoke was integrally formed with the tread ring and the hub by a casting method using urethane resin (thermosetting resin). The outer reinforcing cord layer and the inner reinforcing cord layer are as follows, and each tire has the same specifications.
<Outer reinforcement cord layer>
・ Ply number: 2 ・ Reinforcement cord: Steel cord ・ Cord angle: +21 degrees / -21 degrees <Inner reinforcement cord layer>
-Number of plies: 1-Reinforcement cord: Steel cord-Cord angle: 0 degree (spiral winding)
<Tread ring>
・ Total thickness T0: 25mm

  In Table 1, the rubber composition of adjacent rubber (topping rubber) is the same, and rubber blend B shown in Table 3 is used. In Table 2, the rubber composition of the reinforcing cord layer is the same, and rubber blend A shown in Table 3 is used.

  In Comparative Example 4, when forming the raw tread ring, the outer reinforcing cord layer 5 and the inner reinforcing cord layer 6 are pre-vulcanized first, so that there is no migration of sulfur from the topping rubber, and the interface layer 11 Is not formed.

  In Comparative Example 5, the rubber was too hard because the content of the α, β-unsaturated carboxylic acid metal salt (zinc methacrylate) was too high, and the tread ring could not be vulcanized. In Example 13, the tread ring became too hard, and the steering stability, rolling resistance, and durability could not be measured.

(1) Steering stability:
A sample tire is mounted on four wheels of a vehicle (compact EV: trade name COMS), and a one-seater ride runs on a tire test course on a dry asphalt road surface. evaluated. A larger value is better.

(2) Rolling resistance:
Using a rolling resistance tester, the rolling resistance count (rolling resistance / load × 10 ⁴ ) measured under the conditions of a speed of 40 km / h and a load of 1 kN was evaluated by an index with Conventional Example 1 being 100. Smaller numbers are better.

(3) Durability:
The tire was run using a drum durability tester under conditions of a speed of 60 km / hr and a load of 1 kN. And based on the travel distance until damage occurs in a tread ring, it evaluated by the index which sets the prior art example 1 to 100. A larger value is better.

The rubber composition materials in Table 3 are as follows.
・ Natural rubber (NR): RSS # 3
-Butadiene rubber (BR): BR150B manufactured by Ube Industries, Ltd.
Carbon black: Diamond Black E (FEF) manufactured by Mitsubishi Chemical Corporation
Zinc methacrylate (α, β-unsaturated carboxylic acid metal salt): Sunester SK-30 manufactured by Sanshin Chemical Industry Co., Ltd.
・ Peroxide: Park Mill D (dicumyl peroxide) manufactured by Nippon Oil & Fats Co., Ltd.
・ Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd.
・ Sulfur: Powder sulfur manufactured by Karuizawa Sulfur Co., Ltd. ・ Vulcanization accelerator: Noxeller NS (N-tert-butyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

  As shown in the table, it can be confirmed that the tires of the examples can improve durability while ensuring excellent steering stability performance and reducing rolling resistance.

DESCRIPTION OF SYMBOLS 1 Airless tire 2 Tread ring 3 Hub 4 Spoke 5 Outer reinforcement cord layer 6 Inner reinforcement cord layer 7 Reinforcement rubber layer 10 Adjacent rubber 11 Interface layer 21 Grounding surface 22 Tread rubber layer G Topping rubber

Claims (5)

An airless tire comprising a cylindrical tread ring having a ground contact surface, a hub that is arranged radially inside the tread ring and fixed to an axle, and a spoke that connects the tread ring and the hub. ,
The tread ring includes a tread rubber layer that constitutes a ground contact surface, and a reinforcing rubber layer that is disposed inside the tire radius of the tread rubber layer,
In addition, the reinforcing rubber layer contains 10 to 80 parts by weight of an α, β-unsaturated carboxylic acid metal salt with respect to 100 parts by weight of the rubber component having a butadiene rubber content of 10 to 100% by weight. Comprising a rubber composition containing an oxide,
Elasticity gradually decreases from the reinforcing rubber layer toward the adjacent rubber at an interface portion between the reinforcing rubber layer and an adjacent rubber made of sulfur vulcanized rubber adjacent to the reinforcing rubber layer and containing at least butadiene rubber. An airless tire comprising an interface layer that relieves an elastic difference between adjacent rubbers. The tread ring includes an outer reinforcing cord layer disposed closest to the tread rubber layer, and an inner reinforcing cord layer provided on the inner side in the tire radial direction of the outer reinforcing cord layer, and the outer reinforcing cord. The reinforcing rubber layer is disposed between the layer and the inner reinforcing cord layer,
The airless tire according to claim 1, wherein a topping rubber of the outer reinforcing cord layer and the inner reinforcing cord layer forms the adjacent rubber. The adjacent rubber is made of sulfur vulcanized rubber using sulfur as a vulcanizing agent, and at the time of vulcanization, a part of sulfur in the adjacent rubber moves to the reinforcing rubber layer side to form the interface layer. The airless tire according to claim 1, wherein the tire is an airless tire.
The airless tire according to claim 3, wherein the content of sulfur in the adjacent rubber is 0.5 to 10 phr. The airless tire according to any one of claims 1 to 4, wherein the thickness of the reinforcing rubber layer is 3 mm or more and 70% or less of the thickness of the tread ring.

Images