JP2024059276A - NON-PNEUMATIC TIRE AND ITS MANUFACTURING METHOD - Google Patents

Abstract

[Problem] To provide a non-pneumatic tire capable of improving the durability of a support structure. [Solution] The non-pneumatic tire includes a support structure and a tread located outside the support structure in the tire radial direction X and extending along the tire circumferential direction. The support structure includes an inner annular portion 20, an outer annular portion 30 arranged coaxially with the inner annular portion 20 outside the inner annular portion 20 in the tire radial direction X, and a plurality of spokes connecting the inner annular portion 20 and the outer annular portion 30 and arranged along the tire circumferential direction. The outer annular portion 30 includes a metal plate 32 embedded in an elastic material 31, and a cured epoxy resin 33 is present on the surface of the metal plate 32. [Selected Figure] Figure 2

Description

The present invention relates to a non-pneumatic tire and a method for manufacturing a non-pneumatic tire.

Conventionally, non-pneumatic tires are known that include a support structure that supports the load from a vehicle, and a tread that is located radially outward of the support structure and extends along the tire circumferential direction. Here, the support structure includes an inner annular portion, an outer annular portion that is arranged coaxially with the inner annular portion and radially outward of the inner annular portion, and a plurality of spokes that connect the inner annular portion and the outer annular portion and are arranged along the tire circumferential direction. At this time, it is desirable to improve the creep resistance of non-pneumatic tires in consideration of the durability of the non-pneumatic tires, the ride comfort of the vehicle, low fuel consumption, etc.

In Patent Document 1, the inner and outer annular portions are made of a base material containing an elastic material, in which a fiber-reinforced plastic having a flexural modulus of 1 GPa or more is embedded. The spokes are made of a base material containing an elastic material, in which a fiber-reinforced plastic having a tensile modulus of 50 GPa or more is embedded.

Patent No. 6772055

However, fiber-reinforced plastics are usually made by laminating sheets of fiber with plastic between them, which can lead to the risk of delamination. One option to address this issue is to use a metal plate instead of fiber-reinforced plastic, but this has poor adhesion to elastic materials, which reduces the durability of the support structure.

The present invention aims to provide a non-pneumatic tire that can improve the durability of the support structure.

One aspect of the present invention is a non-pneumatic tire comprising a support structure and a tread located radially outboard of the support structure and extending along the tire circumferential direction, the support structure comprising an inner annular portion, an outer annular portion arranged coaxially with the inner annular portion and radially outboard of the inner annular portion, and a plurality of spokes connecting the inner annular portion and the outer annular portion and arranged along the tire circumferential direction, at least one of the inner annular portion and the outer annular portion has a metal plate embedded in an elastic material, and the metal plate has a cured epoxy resin on its surface.

The present invention provides a non-pneumatic tire that can improve the durability of the support structure.

1 is a side view showing an example of a non-pneumatic tire according to an embodiment of the present invention. 2 is a cross-sectional view showing the structure of the outer annular portion of FIG. 1 along line II-II. This is a cross-sectional view of FIG. FIG. 4 is a partial perspective view of a non-pneumatic tire, as seen obliquely from the portion shown in FIG. 3 .

The following describes an embodiment of the present invention with reference to the drawings.

1 shows an example of a non-pneumatic tire according to the present embodiment. The non-pneumatic tire 1 includes a support structure 10 and a tread 50. The support structure 10 supports a load from a vehicle. The tread 50 is located outside the support structure 10 in the tire radial direction X and extends along the tire circumferential direction C. The support structure 10 includes an inner annular portion 20, an outer annular portion 30 arranged coaxially with the inner annular portion 20 outside the inner annular portion 20 in the tire radial direction X, and a plurality of spokes 40 that connect the inner annular portion 20 and the outer annular portion 30 and are arranged along the tire circumferential direction C. Details of the structure of the non-pneumatic tire 1 will be described later.

Figure 2 shows the structure of the outer annular portion 30. The outer annular portion 30 has a metal plate 32 embedded in an elastic material 31, and the metal plate 32 has a cured epoxy resin 33 present on the entire surface. This increases the adhesion between the elastic material 31 and the metal plate 32, and increases the durability of the support structure 10. This is presumably because hydrogen bonds are formed between the hydroxyl groups present on the surface of the metal plate and the hydroxyl groups of the cured epoxy resin. Here, the adhesion between the elastic material and the cured epoxy resin is high because hydrogen bonds are formed in addition to the entanglement of polymer chains between the elastic material and the cured epoxy resin.

The cured epoxy resin 33 does not have to be present on the entire surface of the metal plate 32, but may be present on only a portion of the surface of the metal plate 32.

The elastic material 31 is not particularly limited, but examples include thermoplastic elastomers, crosslinked rubber, and other resins.

Examples of thermoplastic elastomers include polyester elastomers, polyolefin elastomers, polyamide elastomers, polystyrene elastomers, polyvinyl chloride elastomers, polyurethane elastomers, etc.

As the rubber constituting the crosslinked rubber, either natural rubber or synthetic rubber can be used. Examples of synthetic rubber include styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IIR), nitrile rubber (NBR), hydrogenated nitrile rubber (hydrogenated NBR), chloroprene rubber (CR), ethylene propylene rubber (EPDM), fluororubber, silicone rubber, acrylic rubber, urethane rubber, etc., and two or more types may be used in combination.

As the other resin, either a thermoplastic resin or a thermosetting resin can be used. Examples of the thermoplastic resin include polyethylene resin, polystyrene resin, polyvinyl chloride resin, etc. Examples of the thermosetting resin include epoxy resin, phenol resin, polyurethane resin, silicone resin, polyimide resin, melamine resin, etc.

Among these, polyurethane resin is preferred from the viewpoint of adhesion to the cured product of epoxy resin. Here, since hydrogen bonds are formed between the polyurethane resin and the cured product of epoxy resin, the adhesion between the polyurethane resin and the cured product of epoxy resin is high.

The elastic material 31 may be a foam material.

The metal plate 32 is annular and is embedded around the entire circumference of the outer annular portion 30. The metal constituting the metal plate 32 is not particularly limited, but any carbon steel can be used, with steel having a relatively high carbon content being particularly preferred. Examples of carbon steel include ordinary structural steel, structural alloy steel, high carbon steel, piano wire steel, and the like, which are specified as spring steel by JIS. The Vickers hardness (HV) of the metal plate 32 is not particularly limited, but is, for example, HV400 or more and HV500 or less.

The arithmetic mean roughness Ra of the metal plate 32 is preferably 0.50 μm or more and 5.00 μm or less, and more preferably 1.60 μm or more and 4.00 μm or less. When the arithmetic mean roughness Ra of the metal plate 32 is 0.50 μm or more and 5.00 μm or less, the adhesion between the metal plate 32 and the cured epoxy resin 33 is high.

The thickness of the metal plate 32 is not particularly limited, but is, for example, 1.00 mm or more and 3.00 mm or less. In addition, the ratio of the width of the metal plate 32 to the width of the outer annular portion 30 is not particularly limited, but is, for example, 95% or less.

The outer annular portion 30 is obtained, for example, by forming a coating containing an epoxy resin on the surface of an annular metal plate, and then placing the metal plate with the coating formed on its surface in a precursor of an elastic material, and then curing the epoxy resin and the precursor of the elastic material. At this time, a cylindrical mold is used when curing the epoxy resin and the precursor of the elastic material to form the outer annular portion 30.

The method for forming a coating film containing an epoxy resin on the surface of a metal plate is not particularly limited, but examples include a method in which a coating liquid containing an epoxy resin is applied to the surface of a metal plate and then dried. When applying the coating liquid, for example, a brush, a spray, etc. can be used.

The coating liquid is not particularly limited as long as it contains epoxy resin, but examples thereof include diluted solutions of epoxy resin adhesives. Here, epoxy resin adhesives are adhesives that contain epoxy resin as a main component. Examples of commercially available epoxy resin adhesives include Chemlok (registered trademark) 210 (manufactured by Parker LOAD).

The thickness of the coating is preferably 5.0 μm or more and 20.0 μm or less, and more preferably 6.0 μm or more and 10.0 μm or less.

After roughening the surface of the metal plate, a coating film containing an epoxy resin may be formed on the roughened surface of the metal plate. This increases the adhesion between the metal plate and the cured product of the epoxy resin. There is no particular limitation on the method for roughening the surface of the metal plate, but examples include buffing.

The precursor of the elastic material is not particularly limited, but examples thereof include thermosetting polyurethane resin, epoxy resin, thermoplastic polyurethane resin, etc. Among these, thermosetting polyurethane resin is preferred because it has high adhesion to the cured product of epoxy resin. Examples of thermosetting polyurethane resin include polyurethane having an isocyanate group at the end. Polyurethane having an isocyanate group at the end can be obtained by reacting p-phenylene diisocyanate and polytetramethylene glycol. Examples of commercially available polyurethane having an isocyanate group at the end include Adiprene LFP-E560 (manufactured by LANXESS). Note that the thermosetting polyurethane resin may be mixed with a curing agent for use. Examples of the curing agent include diols such as 1,4-butanediol. Examples of commercially available curing agents include Vibracure A250 (manufactured by LANXESS).

The inner annular portion 20 has glass fibers embedded in an elastic material. There is no particular limitation on the glass fibers, but any known glass fibers can be used.

In addition, instead of glass fiber, the inner annular portion 20 may be a metal plate with a hardened epoxy resin present on the entire surface, embedded in an elastic material. In this case, the elastic materials constituting the inner annular portion 20 and the outer annular portion 30 may be the same or different. Also, the metals constituting the metal plates embedded in the inner annular portion 20 and the outer annular portion 30 may be the same or different.

On the other hand, the configurations of the inner annular portion 20 and the outer annular portion 30 may be reversed. That is, the inner annular portion 20 may be configured with a metal plate with a hardened epoxy resin present on the entire surface embedded in an elastic material, and the outer annular portion 30 may be configured with glass fiber embedded in an elastic material.

The non-pneumatic tire 1 is obtained by vulcanizing and bonding the support structure 10 and the tread rubber composition, for example, using a vulcanizing adhesive.

For example, first, the outer peripheral surface of the outer annular portion 30 of the support structure 10 is roughened. This increases the adhesion between the support structure 10 and the tread 50. The method for roughening the outer peripheral surface of the outer annular portion 30 is not particularly limited, but examples thereof include buffing. In this case, the arithmetic mean roughness Ra of the outer peripheral surface of the outer annular portion 30 is not particularly limited, but is, for example, 2 μm or more and 18 μm or less.

Next, a vulcanizing adhesive is applied to the outer peripheral surface of the roughened outer annular portion 30 and dried. At this time, the dry thickness of the vulcanizing adhesive is not particularly limited, but is, for example, 1 μm or more and 23 μm or less.

Next, a rubber composition for a tread is wrapped around the outer peripheral surface of the outer annular portion 30 to which the vulcanization adhesive has been applied, and then vulcanization adhesion is performed. The rubber composition for a tread contains, for example, natural rubber and carbon black, and may further contain sulfur, silica, etc. Here, the rubber composition for a tread may contain synthetic rubber such as polyisoprene rubber, styrene butadiene rubber, etc. together with the natural rubber, or instead of the natural rubber.

The structure of the non-pneumatic tire 1 will be described in detail below. Fig. 1 is a side view of the non-pneumatic tire 1 as viewed from the side in a direction parallel to the tire rotation axis (tire meridian), i.e., along the front-to-back direction of the paper in Fig. 1. The non-pneumatic tire 1 shown in Fig. 1 is in an unloaded state. Fig. 3 is a cross-sectional view taken along line II-II in Fig. 1. Fig. 4 is a partial perspective view of the non-pneumatic tire 1 as viewed obliquely from the portion shown in Fig. 3.

In Figures 1 and 4, C indicates the tire circumferential direction. In Figures 1 to 4, X indicates the tire radial direction. In Figures 2 to 4, Y indicates the tire width direction. In Figure 1, the tire width direction Y is the front-to-back direction on the page. In Figure 3, E indicates the tire equatorial plane. In Figure 3, the tire circumferential direction C is the front-to-back direction on the page.

The tire circumferential direction C is a direction around the tire rotation axis, and is the same direction as the direction in which the non-pneumatic tire 1 rotates. The tire radial direction X is a direction perpendicular to the tire rotation axis. The tire width direction Y is a direction parallel to the tire rotation axis. In Figures 3 and 4, one side of the tire width direction Y is indicated as Y1, and the other side of the tire width direction Y is indicated as Y2. The tire equatorial plane E shown in Figure 3 is a plane perpendicular to the tire rotation axis and located at the center of the tire width direction Y.

The thickness of the inner annular portion 20 and the outer annular portion 30 is the dimension in the tire radial direction X. The width of the inner annular portion 20 and the outer annular portion 30 is the dimension in the tire width direction Y shown in FIG. 3.

The inner annular portion 20 is an annular portion along the tire circumferential direction C that constitutes the inner periphery of the non-pneumatic tire 1. The thickness and width of the inner annular portion 20 are set to be constant to improve uniformity. A tire wheel (not shown) is placed in the space on the inner periphery side of the inner annular portion 20. The inner periphery of the inner annular portion 20 is fitted and attached to the outer periphery of the rim of the tire wheel. With the inner annular portion 20 attached to the rim, the non-pneumatic tire 1 is attached to the tire wheel. The inner periphery of the inner annular portion 20 may be provided with a fitting portion consisting of a protrusion, groove, etc. for fitting with the rim.

The inner annular portion 20 transmits the rotation of the tire wheel to the spokes 40 and the outer annular portion 30. The thickness of the inner annular portion 20 is determined from the viewpoint of achieving light weight and durability while fully transmitting the rotational force to the spokes 40. The thickness of the inner annular portion 20 is not particularly limited, but is preferably 2% to 7% of the tire cross-sectional height H shown in FIG. 3, and more preferably 3% to 6%.

The inner diameter of the inner annular portion 20 is determined according to the dimensions of the rim of the tire wheel on which the non-pneumatic tire 1 is mounted, the use of the vehicle, etc. For example, when assuming a replacement for a general pneumatic tire, the inner diameter of the inner annular portion 20 may be, for example, 250 mm or more and 500 mm or less, but is not limited to this.

The width of the inner annular portion 20 is determined appropriately depending on the purpose of the vehicle on which the non-pneumatic tire 1 is mounted, the length of the axle, etc. For example, when assuming a replacement for a general pneumatic tire, the width of the inner annular portion 20 may be, but is not limited to, a dimension of 100 mm or more and 300 mm or less.

The outer annular portion 30 is an annular portion along the tire circumferential direction C that constitutes the outer periphery of the non-pneumatic tire 1. The outer annular portion 30 is disposed concentrically with the inner annular portion 20 on the outer periphery side of the inner annular portion 20. The thickness and width of the outer annular portion 30 are set constant to improve uniformity.

The outer annular portion 30 transmits the rotation of the inner annular portion 20 and the spokes 40 to the road surface via the tread 50. The thickness of the outer annular portion 30 is determined from the viewpoint of achieving light weight and durability while fulfilling the function of sufficiently transmitting rotational force from the spokes 40 to the road surface. The thickness of the outer annular portion 30 is not particularly limited, but is preferably 2% to 7% of the tire cross-sectional height H shown in FIG. 3, and more preferably 2% to 5%.

The inner diameter of the outer annular portion 30 is determined appropriately depending on the dimensions of the rim of the tire wheel on which the non-pneumatic tire 1 is mounted, the use of the vehicle, etc. For example, when assuming a replacement for a general pneumatic tire, the inner diameter of the outer annular portion 30 may be, but is not limited to, a dimension of 420 mm or more and 750 mm or less.

The width of the outer annular portion 30 is determined appropriately depending on the use of the vehicle on which the non-pneumatic tire 1 is mounted. For example, when assuming a replacement for a general pneumatic tire, the width of the outer annular portion 30 may be, but is not limited to, a dimension of 100 mm or more and 300 mm or less.

The multiple spokes 40 connect the inner annular portion 20 and the outer annular portion 30. The inner annular portion 20 and the outer annular portion 30 connected by the multiple spokes 40 are arranged concentrically with each other. Each of the multiple spokes 40 is arranged independently along the tire circumferential direction C. As shown in FIG. 1, when the non-pneumatic tire 1 is in an unloaded state, the multiple spokes 40 extend linearly in the radial direction approximately parallel to the tire radial direction X when viewed from the side.

3 and 4, the multiple spokes 40 of this embodiment include multiple first spokes 41 and multiple second spokes 42. The extension direction of both the first spokes 41 and the second spokes 42 is not parallel to the tire radial direction X when viewed in a direction along the tire circumferential direction C. The first spokes 41 are inclined toward one side of the tire axial direction, i.e., the tire width direction Y. The second spokes 42 are inclined toward the opposite side to the first spokes 41. The first spokes 41 and the second spokes 42 are arranged alternately in the tire circumferential direction C.

More specifically, as shown in Figures 3 and 4, the first spoke 41 extends at an angle from the Y1 side, which is one side of the outer annular portion 30 in the tire width direction Y, toward the Y2 side, which is the other side of the inner annular portion 20 in the tire width direction Y. The second spoke 42 extends at an angle from the Y2 side, which is the other side of the outer annular portion 30 in the tire width direction Y, toward the Y1 side, which is one side of the inner annular portion 20 in the tire width direction Y.

The inclination angle of the first spoke 41 and the second spoke 42 is the same. Therefore, the first spoke 41 and the second spoke 42 adjacent to each other in the tire circumferential direction C are arranged in a substantially X-shape when viewed from a direction along the tire circumferential direction C. As shown in FIG. 3, the first spoke 41 and the second spoke 42 are inclined at an angle θ with respect to the tire width direction Y, and the angle θ is preferably, for example, 30° or more and 60° or less.

As shown in FIG. 3, the first spoke 41 and the second spoke 42 have the same shape as each other when viewed in the direction along the tire circumferential direction C, and are symmetrical with respect to the tire equatorial plane E. Therefore, in the following description, when there is no need to distinguish between the first spoke 41 and the second spoke 42 and they can be described together, the first spoke 41 and the second spoke 42 will be collectively referred to as spoke 40.

The spokes 40 are plate-shaped and extend obliquely from the inner annular portion 20 to the outer annular portion 30 at an angle θ as described above. As shown in FIG. 4, the spokes 40 have a thickness t along the tire circumferential direction that is smaller than the width w, and the direction of the thickness t is along the tire circumferential direction C. That is, the spokes 40 are formed in a plate shape extending along the plane of the tire radial direction X and the tire width direction Y. Note that the width w here is the dimension in the direction perpendicular to the inclination direction in which the spokes 40 extend when the spokes 40 are viewed from the direction along the tire circumferential direction C, as shown in FIG. 3. In this embodiment, the thickness t of all the spokes 40 is the same. In addition, the width w of all the spokes 40 is the same.

Since the spokes 40 are long and plate-shaped, even if the plate thickness t is thin, the durability of the spokes 40 can be improved by setting the plate width w wide. Furthermore, by reducing the plate thickness t and increasing the number of spokes 40, the spacing between adjacent spokes 40 in the tire circumferential direction C can be reduced while maintaining the rigidity of the entire non-pneumatic tire 1. This distributes the ground contact pressure caused by the spokes 40 when the tire rolls, making it possible to reduce the ground contact pressure.

Although the spokes 40 are parallel to the tire radial direction X in side view, the spokes 40 may be arranged at an angle to the tire radial direction X so as to intersect with the tire radial direction X in side view.

3 and 4, the first spoke 41 has a first inner connection portion 411 that connects to the tire width direction Y2 side of the inner annular portion 20, and a first outer connection portion 412 that connects to the tire width direction Y1 side of the outer annular portion 30. The second spoke 42 has a second inner connection portion 421 that connects to the tire width direction Y1 side of the inner annular portion 20, and a second outer connection portion 422 that connects to the tire width direction Y2 side of the outer annular portion 30. Each of the first outer connection portion 412 and the second outer connection portion 422 is an example of a connection portion of the spoke 40 that is connected to the outer annular portion 30 in this embodiment.

As shown in FIG. 3, the first inner connection portion 411 of the first spoke 41 has a shape that widens in the tire width direction Y as it approaches the inner annular portion 20. The side surface 411a on the tire width direction Y2 side of the first inner connection portion 411 extends with a gentle curve to the end portion 20b on the tire width direction Y2 side of the inner annular portion 20. The side surface 411b on the tire width direction Y1 side of the first inner connection portion 411 extends with a curve toward the tire width direction Y1 side to the position of the tire equatorial plane E of the inner annular portion 20.

The first outer connection portion 412 of the first spoke 41 has a shape similar to that of the first inner connection portion 411, and has a shape that widens along the tire width direction as it approaches the outer annular portion 30. The side surface 412a on the tire width direction Y1 side of the first outer connection portion 412 extends in a gently curved manner to the end portion 30a on the tire width direction Y1 side of the outer annular portion 30. The side surface 412b on the tire width direction Y2 side of the first outer connection portion 412 extends in a curved manner toward the tire width direction Y2 side to the position of the tire equatorial plane E of the outer annular portion 30.

The first inner connection portion 411 is provided in half of the area of the inner annular portion 20 on the tire width direction Y2 side. The first outer connection portion 412 is provided in half of the area of the outer annular portion 30 on the tire width direction Y1 side.

As shown in FIG. 3, the second inner connection portion 421 of the second spoke 42 has a shape that widens in the tire width direction Y as it approaches the inner annular portion 20. The side surface 421a on the tire width direction Y1 side of the second inner connection portion 421 extends in a gently curved manner to the end portion 20a on the tire width direction Y1 side of the inner annular portion 20. The side surface 421b on the tire width direction Y2 side of the second inner connection portion 421 extends in a curved manner toward the tire width direction Y2 side to the position of the tire equatorial plane E of the inner annular portion 20.

The second outer connection portion 422 of the second spoke 42 has a shape similar to that of the second inner connection portion 421, and has a shape that widens along the tire width direction as it approaches the outer annular portion 30. The side surface 422a on the tire width direction Y2 side of the second outer connection portion 422 extends in a gently curved manner to the end portion 30b on the tire width direction Y2 side of the outer annular portion 30. The side surface 422b on the tire width direction Y1 side of the second outer connection portion 422 extends in a curved manner toward the tire width direction Y1 side to the position of the tire equatorial plane E of the outer annular portion 30.

The second inner connection portion 421 is provided in half of the area of the inner annular portion 20 on the tire width direction Y1 side. The second outer connection portion 422 is provided in half of the area of the outer annular portion 30 on the tire width direction Y2 side.

As described above, in this embodiment, all spokes 40 have the same thickness t. The dimension of thickness t is not particularly limited, but in order for the spokes 40 to be able to fully receive rotational forces from the inner annular portion 20 and the outer annular portion 30 while being able to bend and deform appropriately when subjected to a load, it is preferable that the thickness t be 1 mm or more and 30 mm or less, and more preferably 5 mm or more and 25 mm or less.

As described above, in this embodiment, the width w of all spokes 40 is the same. The width w of the spokes 40 is not particularly limited, but is preferably 5 mm or more and 25 mm or less, and more preferably 10 mm or more and 20 mm or less, so as to be able to adequately receive rotational forces from the inner annular portion 20 and the outer annular portion 30 while being able to bend and deform appropriately when a load is applied. In addition, the width w is preferably 110% or more of the thickness t, and more preferably 115% or more, from the viewpoint of being able to disperse ground pressure while improving durability.

The number of spokes 40 is preferably between 80 and 300, and more preferably between 100 and 200, from the viewpoint of being able to adequately support the load from the vehicle while being lightweight and improving both power transmission and durability.

The spokes 40 can be made of the elastic materials listed below. First, in terms of the characteristics of the elastic material, from the viewpoint of providing adequate rigidity while ensuring sufficient durability, it is preferable that the tensile modulus calculated from the tensile stress at 10% elongation in a tensile test conducted in accordance with JIS K7312:1996 is 3 MPa or more and 12 MPa or less.

If the tensile modulus of a spoke 40 calculated from the tensile stress at 10% elongation falls below 3 MPa, sufficient rigidity cannot be obtained, and there is a possibility that adjacent spokes 40 in the tire circumferential direction C may come into contact with each other. On the other hand, if the tensile modulus calculated from the tensile stress at 10% elongation exceeds 12 MPa, the rigidity becomes excessively high, resulting in a poor ride.

Elastic materials that can be used as the base material for the spokes 40 include thermoplastic elastomers, crosslinked rubber, and other resins.

Examples of thermoplastic elastomers include polyester elastomers, polyolefin elastomers, polyamide elastomers, polystyrene elastomers, polyvinyl chloride elastomers, polyurethane elastomers, etc.

Either natural rubber or synthetic rubber can be used as the rubber material constituting the crosslinked rubber. Examples of synthetic rubber include styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IIR), nitrile rubber (NBR), hydrogenated nitrile rubber (hydrogenated NBR), chloroprene rubber (CR), ethylene propylene rubber (EPDM), fluororubber, silicone rubber, acrylic rubber, urethane rubber, etc. Two or more types of rubber materials may be used in combination as necessary.

Other resins include thermoplastic resins and thermosetting resins. Thermoplastic resins include polyethylene resin, polystyrene resin, polyvinyl chloride resin, etc. Thermosetting resins include epoxy resin, phenolic resin, polyurethane resin, silicone resin, polyimide resin, melamine resin, etc.

Of the above elastic materials, polyurethane resin is preferably used for the spokes 40 from the viewpoints of moldability, processability, and cost. Note that foamed materials can also be used as the elastic material. In other words, foamed materials made from the above thermoplastic elastomers, crosslinked rubber, and other resins can be used.

The elastic material used as the base material of the spokes 40 may be reinforced with reinforcing fibers. Examples of reinforcing fibers include long fibers, short fibers, woven fabrics, and nonwoven fabrics. Types of reinforcing fibers include rayon cords, polyamide cords such as nylon-6,6, polyester cords such as polyethylene terephthalate, aramid cords, glass fiber cords, carbon fibers, and steel cords.

The reinforcement of the elastic material is not limited to reinforcement with reinforcing fibers. For example, reinforcement may be performed by adding granular fillers. Examples of granular fillers that can be added include ceramics such as carbon black, silica, and alumina, and other inorganic fillers.

Incidentally, the inner annular portion 20 and the outer annular portion 30 are preferably formed from the same resin material as the spokes 40. In that case, the inner annular portion 20, the outer annular portion 30 and the spokes 40 can be integrally molded, for example, by a cast molding method.

The tread 50 is provided on the outer peripheral surface of the outer annular portion 30 and constitutes the outermost peripheral portion of the non-pneumatic tire 1. The tread 50 has a tread surface 51 on its outer peripheral surface that comes into contact with the road surface. The tread surface 51 of the tread 50 has a tread pattern formed of multiple grooves and land portions, similar to that of a conventional pneumatic tire.

The tread 50 may also be constructed by laminating multiple vulcanized rubber layers with different compositions and characteristics (e.g., two or three layers).

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and the above embodiments may be modified as appropriate within the scope of the spirit of the present invention.

The configuration of the embodiment of the present invention is as follows:

(1) A non-pneumatic tire comprising a support structure and a tread located radially outboard of the support structure and extending along the tire circumferential direction, the support structure comprising an inner annular portion, an outer annular portion arranged coaxially with the inner annular portion and radially outboard of the inner annular portion, and a plurality of spokes connecting the inner annular portion and the outer annular portion and arranged along the tire circumferential direction, at least one of the inner annular portion and the outer annular portion having a metal plate embedded in an elastic material, and the metal plate having a cured epoxy resin present on the surface.

(2) The non-pneumatic tire described in (1), in which the metal plate has an arithmetic mean roughness Ra of 0.50 μm or more and 5.00 μm or less.

(3) A non-pneumatic tire according to (1) or (2), in which the elastic material is a polyurethane resin.

(4) A method for manufacturing a non-pneumatic tire according to any one of (1) to (3), comprising the steps of forming a coating film containing an epoxy resin on the surface of the metal plate, and placing the metal plate on which the coating film is formed in the precursor of the elastic material, and curing the epoxy resin and the precursor of the elastic material to obtain the inner annular portion and the outer annular portion, respectively.

(5) The method for manufacturing a non-pneumatic tire described in (4), wherein the coating has a thickness of 5.0 μm or more and 20.0 μm or less.

(6) The method for manufacturing a non-pneumatic tire according to (4) or (5) further includes a step of roughening the surface of the metal plate, and forming the coating film on the roughened surface of the metal plate.

(7) The method for manufacturing a non-pneumatic tire according to any one of (4) to (6), wherein the precursor of the elastic material is a thermosetting polyurethane resin.

Below, examples of the present invention are described, but the present invention is not limited to these examples. Since it is difficult to directly measure the adhesive strength between the elastic material and the metal plate using the inner and outer rings, the adhesive strength between the elastic material and the metal plate was measured using test pieces that mimic the inner and outer rings.

[Example 1]
A 10 mm long adhesive region from one end of a carbon tool steel (SK85) plate having a width of 8-10 mm, a length of 120 mm, a thickness of 0.9 mm, and a Vickers hardness (HV) of 470 was buffed using a sanding belt and a belt sander with a grain size of #80 so that the arithmetic mean roughness Ra was 3.95 μm. Next, the adhesive region was air-blowed and then degreased and washed with ethanol. Next, epoxy resin adhesive Chemlok (registered trademark) 210 (manufactured by Parker LOAD) was diluted 1.5 times with methyl ethyl ketone, and then applied to the adhesive region of the SK85 plate with a brush and dried at room temperature for 10 minutes to form a coating film with a thickness of 8.8 μm. Next, a mixture of thermosetting polyurethane resin and curing agent was poured into a mold having a width of 8 to 10 mm, a length of 120 mm, and a thickness of 5 mm, and the SK85 plate was placed so that the adhesive area of the plate was in contact with the mixture of thermosetting polyurethane resin and curing agent, and then the epoxy resin adhesive and thermosetting polyurethane resin were thermally cured for 16 hours in an oven at 130°C to obtain a test piece. At this time, Adiprene LFP-E560 (manufactured by Lanxess) was used as the thermosetting polyurethane resin, and Vibracure A250 (manufactured by Lanxess) was used as the curing agent.

[Examples 2 to 5]
Test pieces were obtained in the same manner as in Example 1, except that the arithmetic mean roughness Ra of the bonding area of the SK85 plate was changed to 3.29 μm, 2.65 μm, 2.40 μm, and 1.60 μm, respectively.

[Example 6]
A test piece was obtained in the same manner as in Example 1, except that the bonding area of the SK85 plate was not buffed.

[Comparative Example 1]
A test piece was obtained in the same manner as in Example 3, except that no epoxy resin adhesive (diluted solution) was applied to the bonding area of the SK85 plate.

[Comparative Example 2]
A test piece was obtained in the same manner as in Example 6, except that no epoxy resin adhesive (diluted solution) was applied to the bonding area of the SK85 plate.

[Arithmetic mean roughness Ra of adhesive area]
The arithmetic mean roughness Ra of the bonded area was measured using a contact type surface roughness meter.

[Coating film thickness]
The dry weight of the applied epoxy resin adhesive was divided by the dry specific gravity and the applied area to calculate the coating thickness.

[Tensile shear adhesive strength test]
The adhesive strength [N/100 mm ² ] between the SK85 plate and the cured product of the thermosetting polyurethane resin was measured by the tensile shear adhesive strength test method (based on JIS 6180).

Table 1 shows the preparation conditions of the test pieces and the measurement results of the adhesive strength.

From Table 1, it can be seen that the test pieces of Examples 1 to 6 have high adhesive strength. In contrast, the test piece of Comparative Example 1, in which no epoxy resin adhesive (diluted solution) was applied to the bonding area of the SK85 plate, has low adhesive strength compared to Examples 1 to 5, in which the bonding area of the SK85 plate was buffed. Also, the test piece of Comparative Example 2, in which no epoxy resin adhesive (diluted solution) was applied to the bonding area of the SK85 plate, has low adhesive strength compared to Example 6, in which the bonding area of the SK85 plate was not buffed.

REFERENCE SIGNS LIST 1 Non-pneumatic tire 10 Support structure 20 Inner annular portion 20a, 20b End portion 30 Outer annular portion 30a, 30b End portion 31 Elastic material 32 Metal plate 33 Cured epoxy resin 40 Spoke 41 First spoke 42 Second spoke 411 First inner connection portion 411a, 411b Side surface 412 First outer connection portion 412a, 412b Side surface 421 Second inner connection portion 421a, 421b Side surface 422 Second outer connection portion 422a, 422b Side surface 50 Tread 51 Tread surface C Tire circumferential direction E Tire equatorial plane O Axial center X Tire radial direction Y Tire width direction

Claims (7)

A tire tread is provided on an outer side of the support structure in a tire radial direction and extends in a tire circumferential direction.
the support structure includes an inner annular portion, an outer annular portion disposed coaxially with the inner annular portion and radially outward of the inner annular portion, and a plurality of spokes connecting the inner annular portion and the outer annular portion and arranged along a tire circumferential direction,
At least one of the inner annular portion and the outer annular portion has a metal plate embedded in an elastic material,
The metal plate has a cured epoxy resin present on a surface thereof. The non-pneumatic tire according to claim 1, wherein the metal plate has an arithmetic mean roughness Ra of 0.50 μm or more and 5.00 μm or less. The non-pneumatic tire according to claim 1 or 2, wherein the elastic material is a polyurethane resin. 10. A method for manufacturing a non-pneumatic tire according to claim 1, comprising the steps of:
forming a coating film containing an epoxy resin on a surface of the metal plate;
and curing the epoxy resin and the precursor of the elastic material in a state in which the metal plate having the coating film formed on its surface is placed in the precursor of the elastic material, thereby obtaining the inner annular portion and the outer annular portion, respectively. The method for manufacturing a non-pneumatic tire according to claim 4, wherein the coating has a thickness of 5.0 μm or more and 20.0 μm or less. The method further comprises a step of roughening the surface of the metal plate;
The method for producing a non-pneumatic tire according to claim 4 or 5, wherein the coating film is formed on a surface of the roughened metal plate. The method for manufacturing a non-pneumatic tire according to claim 4 or 5, wherein the precursor of the elastic material is a thermosetting polyurethane resin.

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