Non-pneumatic tires

Abstract

To provide a non-pneumatic tire that can be effectively improved in durability.SOLUTION: A non-pneumatic tire 1 comprises: an inner annular part 20; an outer annular part 30 arranged on an outer periphery side of the inner annular part 20, concentrically therewith; a plurality of spokes 40 arranged along a tire circumferential direction C to connect the inner annular part 20 to the outer annular part 30; and a tread 50 provided on an outer peripheral surface of the outer annular part 30. A reinforcement layer 70 including a reinforcement member 71 made of spring steel materials is embedded over the whole circumference of the outer annular part 30.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a non-pneumatic tire. [Background technology]

[0002] In recent years, non-pneumatic tires have been developed that are free from problems such as punctures and do not require air pressure adjustment. Non-pneumatic tires generally have a structure in which an inner annular portion and an outer annular portion are coaxially arranged and connected by a plurality of spokes. The spokes are arranged radially at intervals around the tire circumference. A tread that comes into contact with the road surface is provided on the outer peripheral surface of the outer annular portion.

[0003] For example, Patent Document 1 discloses a non-pneumatic tire in which a widthwise reinforcing layer is disposed between the radially outer ends of the spokes and the tread to suppress buckling at the tire widthwise center of the outer annular portion, thereby improving the durability of the spokes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-43505 A Summary of the Invention [Problem to be solved by the invention]

[0005] In this type of non-pneumatic tire, the outer annular portion is repeatedly deformed as the vehicle travels, and therefore it is required to increase the fatigue strength of the outer annular portion to improve durability.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a non-pneumatic tire in which the outer annular portion is effectively reinforced to improve durability. [Means for solving the problem]

[0007] The non-pneumatic tire of the present invention is a non-pneumatic tire comprising an inner annular portion, an outer annular portion arranged coaxially on the outer peripheral side of the inner annular portion, a plurality of spokes connecting the inner annular portion and the outer annular portion and arranged along the tire circumferential direction, and a tread provided on the outer peripheral surface of the outer annular portion, wherein a reinforcing layer including a reinforcing member made of spring steel is embedded around the entire circumference of the outer annular portion. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a non-pneumatic tire in which the outer annular portion is effectively reinforced and durability is improved. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a side view showing a non-pneumatic tire of a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Figure 3] FIG. 3 is a partial perspective view of a non-pneumatic tire, as seen obliquely from the portion shown in FIG. 2. [Figure 4] FIG. 2 is a perspective view of an outer reinforcing layer of the first embodiment. [Figure 5] FIG. 10 is a perspective view of a reinforcing member that constitutes an outer reinforcing layer of a second embodiment. [Figure 6] FIG. 10 is a perspective view showing an outer reinforcing layer of a third embodiment. [Figure 7] FIG. 11 is a partial perspective view of a belt-shaped member constituting an outer reinforcing layer of a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (First embodiment) A first embodiment will be described below with reference to the drawings. Fig. 1 is a side view of a non-pneumatic tire 1 of the first embodiment, viewed from the side in a direction parallel to the tire rotation axis (tire meridian), i.e., in a direction 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. 2 is a cross-sectional view taken along II-II in Fig. 1. Fig. 3 is a partial perspective view of the non-pneumatic tire 1, as viewed obliquely from the portion shown in Fig. 2.

[0011] In Fig. 1 and Fig. 3, arrow C indicates the tire circumferential direction. In Fig. 1 to Fig. 3, arrow X indicates the tire radial direction. In Fig. 2 and Fig. 3, arrow Y indicates the tire width direction. In Fig. 1, the tire width direction Y is the front-to-back direction of the paper. In Fig. 2, symbol E is the tire equatorial plane. In Fig. 2, the tire circumferential direction C is the front-to-back direction of the paper.

[0012] The tire circumferential direction C is a direction around the tire rotational axis and is the same direction as the rotational direction of the non-pneumatic tire 1. The tire radial direction X is a direction perpendicular to the tire rotational axis. The tire width direction Y is a direction parallel to the tire rotational axis. In FIGS. 2 and 3, 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 FIG. 2 is a plane perpendicular to the tire rotational axis and located at the center of the tire width direction Y.

[0013] The non-pneumatic tire 1 of the first embodiment includes an inner annular portion 20, an outer annular portion 30, a plurality of spokes 40, and a tread 50.

[0014] In the following description, the thicknesses of the inner annular portion 20 and the outer annular portion 30 refer to the dimensions in the tire radial direction X. The widths of the inner annular portion 20 and the outer annular portion 30 refer to the dimensions in the tire width direction Y shown in FIG.

[0015] The inner annular portion 20 is an annular portion along the tire circumferential direction C that constitutes the inner circumferential portion 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 circumferential side of the inner annular portion 20. The inner circumferential portion of the inner annular portion 20 is fitted onto the outer circumferential portion of the rim of the tire wheel. The inner annular portion 20 is fitted onto the rim, and the non-pneumatic tire 1 is then fitted onto the tire wheel. The inner circumferential surface of the inner annular portion 20 may be provided with a fitting portion consisting of a protrusion, a groove, etc. for fitting with the rim.

[0016] The inner annular portion 20 can be made of, for example, a resin material having elasticity, but the material is not limited to resin.

[0017] 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 fulfilling the function of sufficiently transmitting 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. 2, and more preferably 3% to 6%.

[0018] The inner diameter of the inner annular portion 20 is determined 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 inner annular portion 20 may be, for example, a dimension of 250 mm or more and 500 mm or less, but is not limited to this.

[0019] The width of the inner annular portion 20 is determined appropriately depending on the application of the vehicle on which the non-pneumatic tire 1 is mounted, 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.

[0020] An inner reinforcing layer 60 is embedded inside the inner annular portion 20. The inner reinforcing layer 60 functions to enable the inner annular portion 20 to fit onto the rim of the tire wheel with high elasticity and strength. The inner reinforcing layer 60 may be, for example, a mesh-like arrangement of cords made of fiber-reinforced plastic such as GFRP, but is not limited to this. The inner reinforcing layer 60 can be embedded in the inner annular portion 20 by, for example, placing it in a mold during molding of the inner annular portion 20 and filling it with the resin material of the inner annular portion 20 and molding it.

[0021] 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 coaxially with the inner annular portion 20 on the outer circumferential side of the inner annular portion 20. The thickness and width of the outer annular portion 30 are set to be constant to improve uniformity.

[0022] The outer annular portion 30 can be made of, for example, an elastic resin material, but the material is not limited to resin.

[0023] 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 also 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, for example, 2% to 7% of the tire cross-sectional height H shown in FIG. 2, and more preferably 2% to 5%.

[0024] 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.

[0025] The width of the outer annular portion 30 is determined appropriately depending on the application of the vehicle on which the non-pneumatic tire 1 is mounted, etc. 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.

[0026] An outer reinforcing layer 70 is embedded inside the outer annular portion 30. The outer reinforcing layer 70 is an example of a reinforcing layer embedded in the outer annular portion 30.

[0027] FIG. 4 is a perspective view showing an outer reinforcing layer 70 of the first embodiment. As shown in FIG. 4, the outer reinforcing layer 70 includes a reinforcing member 71 having an annular plate shape. The reinforcing member 71 of the first embodiment is made of metal, and is a steel plate made of heat-treated spring steel. The reinforcing member 71 is embedded inside the outer annular portion 30 coaxially with the outer annular portion 30. FIG. 4 shows the tire circumferential direction C, tire radial direction X, and tire width direction Y in a state in which the outer reinforcing layer 70 is embedded inside the outer annular portion 30 of the tire 1. Note that the indications of these directions are the same as in FIGS. 5 and 6, which will be described later.

[0028] The spring steel of the first embodiment can include all carbon steels used for springs, and is preferably steel with a relatively high carbon content. Examples include structural ordinary steel, structural alloy steel, high-carbon steel, and steel for piano wire, all of which are specified as spring steels by JIS. The reinforcing member 71 of the first embodiment is preferably made of spring steel that contains a relatively high proportion of carbon and has properties such as a high elastic limit as a spring and resistance to creep deformation under repeated loads.

[0029] Specific examples of the spring steel material that constitutes the reinforcing member 71 include the following carbon steels. These spring steel materials exhibit the required spring properties by undergoing specific heat treatments such as quenching or quenching and tempering on the raw steel.

[0030] This is a carbon tool steel material called SK material specified in JIS G 4401:2009, and among them, SK85 (carbon content: 0.80 to 0.90%) is preferable. Ribbon steel, which is obtained by further quenching the SK material, is considered to be even more preferable.

[0031] This is a carbon steel material for machine structures called SC material, specified in JIS G 4051:2016, and among these, SC materials such as S60C (carbon content: 0.55-0.65%), S65C (carbon content: 0.60-0.70%), and S70C (carbon content: 0.65-0.75%) are preferred. Bainite steel, which is SC material that has been further quenched, is considered even more preferred.

[0032] This is a spring steel material called SUP material specified in JIS G 4801:2021, and among them, SUP9 (manganese chromium steel material, carbon content: 0.52 to 0.60%), SUP10 (chromium vanadium steel material, carbon content: 0.47 to 0.55%), etc. are suitable.

[0033] It is a carbon steel material for machine structures specified by SAE, and among them, SAE1060 (carbon content: 0.55 to 0.65%), SAE1065 (carbon content: 0.60 to 0.70%), SAE1070 (carbon content: 0.65 to 0.75%), etc. are suitable.

[0034] The reinforcing member 71 of the first embodiment is formed into an annular shape by winding a plate-shaped material having a width slightly smaller than the outer annular portion 30 in the tire width direction Y and a length corresponding to the circumferential length of the outer annular portion 30 into an annular shape and welding the butted ends together. Alternatively, the reinforcing member 71 can be obtained by cutting a tubular material having a diameter corresponding to the outer annular portion 30 and an axial length longer than the axial length of the tire 1 so as to divide it in the axial direction. For example, when the outer annular portion 30 is resin-molded in a mold, the reinforcing member 71 formed into an annular shape in this manner is set in the mold, and resin material is filled in and molded. This allows the reinforcing member 71 to be disposed in a state where it is embedded in the outer annular portion 30 over the entire circumference.

[0035] The width of the reinforcing member 71, i.e., the dimension in the tire width direction Y, is preferably, for example, 95% or less of the tire width direction Y of the outer annular portion 30. The tire width direction Y of the outer annular portion 30 is substantially equal to the tire width direction Y of a tread 50, which will be described later. The thickness of the reinforcing member 71 embedded inside the outer annular portion 30, i.e., the dimension in the tire radial direction X, is naturally smaller than the thickness of the outer annular portion 30, and this thickness is preferably 1.00 mm or more and 3.00 mm or less. The reinforcing member 71 is preferably disposed at the center of the outer annular portion 30 in the tire radial direction X and in the tire width direction Y.

[0036] The hardness of the spring steel material constituting the reinforcing member 71 is preferably HV400 or more and HV500 or less. If the hardness is less than HV400, the tensile strength, creep resistance, and fatigue resistance may be insufficient. On the other hand, if the hardness is more than HV500, the spring properties may be insufficient because the material is too hard and loses toughness and becomes brittle.

[0037] The plurality of 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 plurality of spokes 40 are arranged coaxially with each other. The plurality of spokes 40 are 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 plurality of spokes 40 extend linearly in the radial direction substantially parallel to the tire radial direction X in a side view.

[0038] 2 and 3, the multiple spokes 40 of the first 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 in 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.

[0039] 2 and 3, the first spokes 41 extend at an angle from the Y1 side, which is one side in the tire width direction Y of the outer annular portion 30, toward the Y2 side, which is the other side in the tire width direction Y of the inner annular portion 20. The second spokes 42 generally extend at an angle from the Y2 side, which is the other side in the tire width direction Y of the outer annular portion 30, toward the Y1 side, which is one side in the tire width direction Y of the inner annular portion 20.

[0040] The inclination angles of the first spokes 41 and the second spokes 42 are the same. Therefore, the first spokes 41 and the second spokes 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. 2 , the first spokes 41 and the second spokes 42 are inclined at an angle θ with respect to the tire width direction Y, and the angle θ is preferably, for example, equal to or greater than 30° and equal to or less than 60°.

[0041] 2, when viewed in a direction along the tire circumferential direction C, the first spokes 41 and the second spokes 42 each have the same shape and are symmetrical with respect to the tire equatorial plane E. Therefore, hereinafter, when there is no need to distinguish between the first spokes 41 and the second spokes 42 and they can be described together, the first spokes 41 and the second spokes 42 will be collectively referred to as spokes 40.

[0042] The spokes 40 are plate-shaped and extend obliquely at the angle θ from the inner annular portion 20 toward the outer annular portion 30 as described above. As shown in FIG. 3 , the thickness t of the spokes 40 along the tire circumferential direction 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 in the plane of the tire radial direction X and the tire width direction Y. Note that the width w here refers to the dimension in the direction perpendicular to the oblique direction in which the spokes 40 extend when viewed from the direction along the tire circumferential direction D, as also shown in FIG. 2 . In the first embodiment, all of the spokes 40 have the same thickness t. All of the spokes 40 also have the same width w.

[0043] The spokes 40 are arranged at equal intervals in the tire circumferential direction C. That is, among the spokes 40, the interval between the centers of the thickness t of a pair of spokes 40 adjacent in the tire circumferential direction C is equal.

[0044] Because the spokes 40 are long and plate-shaped, the durability of the spokes 40 can be improved by widening the plate width w even if the plate thickness t is thin. Furthermore, by thinning the plate thickness t and increasing the number of spokes 40, the distance 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 of the spokes 40 when the tire rolls, thereby reducing the ground contact pressure.

[0045] Although the spokes 40 in the first embodiment are parallel to the tire radial direction X in a side view, the spokes 40 may be disposed obliquely with respect to the tire radial direction X so as to intersect with the tire radial direction X in a side view.

[0046] 2 and 3, the first spoke 41 has a first inner connection portion 411 connected to the tire width direction Y2 side of the inner annular portion 20, and a first outer connection portion 412 connected to the tire width direction Y1 side of the outer annular portion 30. The second spoke 42 has a second inner connection portion 421 connected to the tire width direction Y1 side of the inner annular portion 20, and a second outer connection portion 422 connected to the tire width direction Y2 side of the outer annular portion 30.

[0047] 2, 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. A side surface 411a on the tire width direction Y2 side of the first inner connection portion 411 extends while gently curving to an end portion 20b of the inner annular portion 20 on the tire width direction Y2 side. A side surface 411b on the tire width direction Y1 side of the first inner connection portion 411 extends while curving toward the tire width direction Y1 side to the position of the tire equatorial plane E of the inner annular portion 20.

[0048] 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 in the tire width direction as it approaches the outer annular portion 30. A side surface 412a on the tire width direction Y1 side of the first outer connection portion 412 extends while gently curving to an end portion 30a of the outer annular portion 30 on the tire width direction Y1 side. A side surface 412b on the tire width direction Y2 side of the first outer connection portion 412 extends while curving toward the tire width direction Y2 to the position of the tire equatorial plane E of the outer annular portion 30.

[0049] The first inner connecting portion 411 is provided in a half region on the tire width direction Y2 side of the inner annular portion 20. The first outer connecting portion 412 is provided in a half region on the tire width direction Y1 side of the outer annular portion 30.

[0050] 2, 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. A side surface 421a on the tire width direction Y1 side of the second inner connection portion 421 extends while gently curving to an end portion 20a of the inner annular portion 20 on the tire width direction Y1 side. A side surface 421b on the tire width direction Y2 side of the second inner connection portion 421 extends while curving toward the tire width direction Y2 to the position of the tire equatorial plane E of the inner annular portion 20.

[0051] 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 in the tire width direction as it approaches the outer annular portion 30. A side surface 422a on the tire width direction Y2 side of the second outer connection portion 422 extends while gently curving to an end portion 30b on the tire width direction Y2 side of the outer annular portion 30. A side surface 422b on the tire width direction Y1 side of the second outer connection portion 422 extends while curving toward the tire width direction Y1 side to the position of the tire equatorial plane E of the outer annular portion 30.

[0052] The second inner connecting portion 421 is provided in a half region on the tire width direction Y1 side of the inner annular portion 20. The second outer connecting portion 422 is provided in a half region on the tire width direction Y2 side of the outer annular portion 30.

[0053] As described above, all of the spokes 40 in the first embodiment have the same thickness t. The dimension of the thickness t is not particularly limited, but is preferably 1 mm or more and 30 mm or less, and more preferably 5 mm or more and 25 mm or less, so that the spokes 40 can adequately receive rotational forces from the inner annular portion 20 and the outer annular portion 30 and can be appropriately flexibly deformed when subjected to a load.

[0054] As described above, all spokes 40 in the first embodiment have the same width w. 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 withstand rotational forces from the inner annular portion 20 and the outer annular portion 30 while being able to flex and deform appropriately when subjected to a load. Furthermore, 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 distribute ground pressure while improving durability.

[0055] The number of spokes 40 is preferably 80 to 300, and more preferably 100 to 200, from the viewpoint of being able to adequately support the load from the vehicle while being lightweight and achieving both improved power transmission and durability.

[0056] The intervals between the spokes 40 in the tire circumferential direction C are preferably set to, for example, 1.0 mm or more and 4.1 mm or less. Note that, although the intervals between the spokes 40 in the tire circumferential direction C are equal in the first embodiment, they may be unequal.

[0057] The spokes 40 can be made of any of the following elastic materials. First, in terms of the properties of the elastic material, from the viewpoint of imparting appropriate 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 be 3 MPa or more and 12 MPa or less.

[0058] If the tensile modulus of the spokes 40 calculated from the tensile stress at 10% elongation is less than 3 MPa, sufficient rigidity cannot be obtained, and there is a possibility that adjacent spokes 40 in the tire circumferential direction D 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 deterioration in ride comfort.

[0059] The elastic material used as the base material of the spokes 40 may be a thermoplastic elastomer, a crosslinked rubber, or other resin.

[0060] Examples of thermoplastic elastomers include polyester elastomers, polyolefin elastomers, polyamide elastomers, polystyrene elastomers, polyvinyl chloride elastomers, and polyurethane elastomers.

[0061] The rubber material constituting the crosslinked rubber can be either natural rubber or synthetic 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, and urethane rubber. Two or more of these rubber materials may be used in combination as needed.

[0062] Other resins include thermoplastic resins and thermosetting resins. Thermoplastic resins include polyethylene resins, polystyrene resins, polyvinyl chloride resins, etc. Thermosetting resins include epoxy resins, phenolic resins, polyurethane resins, silicone resins, polyimide resins, melamine resins, etc.

[0063] Of the above elastic materials, polyurethane resin is preferably used for the spokes 40 from the viewpoints of moldability, processability, and cost. However, foamed materials can also be used as the elastic material. That is, foamed materials made from the above thermoplastic elastomers, crosslinked rubbers, and other resins can be used.

[0064] 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. Examples 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.

[0065] The reinforcement of the elastic material is not limited to reinforcement with reinforcing fibers. For example, reinforcement may be performed by adding a granular filler. Examples of the granular filler to be added include carbon black, ceramics such as silica and alumina, and other inorganic fillers.

[0066] Incidentally, it is preferable that the inner annular portion 20 and the outer annular portion 30 are formed from the same resin material as the spokes 40. In this case, the inner annular portion 20, the outer annular portion 30 and the spokes 40 can be integrally molded, for example, by a casting molding method.

[0067] The tread 50 is provided on the outer peripheral surface of the outer annular portion 30. The tread 50 constitutes the outermost peripheral portion of the non-pneumatic tire 1. As shown in FIGS. 2 and 3, the tread 50 includes tread rubber 51. The tread rubber 51 has a tread surface 51a on its outer peripheral surface that comes into contact with the road surface. There are no particular restrictions on the type of rubber material for the tread rubber 51, and general vulcanized rubber, etc., used for constituting the tread of a vehicle tire, can be used. The tread surface 51a of the tread rubber 51 is provided with a tread pattern formed of a plurality of grooves and land portions, similar to that of a conventional pneumatic tire.

[0068] The tread rubber 51 may be configured by laminating multiple rubber layers (for example, two or three layers) with different components and properties. The tread 50 may also be formed from resin. The tread rubber 51 is adhered to the outer peripheral surface of the outer annular portion 30 by a vulcanization adhesive layer 52.

[0069] The tire 1 according to the first embodiment described above has an outer reinforcing layer 70 formed of a reinforcing member 71 made of spring steel embedded in the outer annular portion 30. In the tire 1 according to the embodiment, which is a non-pneumatic tire, stress is applied to the outer annular portion 30 as the vehicle travels, causing repeated deformation in which the outer annular portion 30 bends and buckles in the tire radial direction X. However, in the tire 1 according to the present embodiment, the outer annular portion 30 is reinforced by the outer reinforcing layer 70, and therefore repeated deformation is less likely to occur in the outer annular portion 30. As a result, the fatigue strength and rigidity of the outer annular portion 30 are increased, and durability can be improved.

[0070] In this embodiment, the reinforcing members 71 constituting the outer reinforcing layer 70 are made of spring steel, and therefore are less likely to creep under repeated loads. As a result, the outer annular portion 30 is also less likely to deform following the reinforcing members 71. Therefore, when the vehicle is stopped, flat spots are less likely to occur, where the tread surface 51a of the tread rubber 51 becomes flat due to friction with the road surface.

[0071] The reinforcing member 71 made of spring steel exhibits sufficient reinforcing strength while being low cost compared to reinforcing materials made of fiber-reinforced plastics such as CFRP and GFRP. Furthermore, spring steel is easier to recycle than CFRP and GFRP, which are difficult to dispose of, and is therefore advantageous in terms of environmental protection. Furthermore, while CFRP and GFRP contain fibers and therefore may exhibit strength in a biased direction, the reinforcing member 71 of this embodiment is a solid plate material, and therefore does not exhibit a bias in the reinforcing direction.

[0072] Furthermore, spring steel has a high affinity with resins such as urethane resin, and therefore has a high adhesive strength to the outer annular portion 30. Therefore, the presence of the reinforcing member 71 reduces the occurrence of damage that would cause the outer annular portion 30 to split in the thickness direction. To increase the adhesive strength to the resin that constitutes the outer annular portion 30, it is more preferable to perform a surface roughening treatment such as sandblasting on the surface of the reinforcing member 71.

[0073] The non-pneumatic tire 1 according to the first embodiment described above provides the following effects.

[0074] (1) The non-pneumatic tire 1 according to the first embodiment comprises an inner annular portion 20, an outer annular portion 30 arranged coaxially on the outer peripheral side of the inner annular portion 20, a plurality of spokes 40 connecting the inner annular portion 20 and the outer annular portion 30 and arranged along the tire circumferential direction C, and a tread 50 provided on the outer peripheral surface of the outer annular portion 30, and an outer reinforcing layer 70 including reinforcing members 71 made of spring steel is embedded around the entire circumference of the outer annular portion 30.

[0075] This effectively reinforces the outer annular portion 30, improving the durability of the tire 1. Furthermore, compared to reinforcing materials made of fiber-reinforced plastics such as CFRP and GFRP, the reinforcing member 71 is made of spring steel, which provides sufficient reinforcing strength at low cost and is easy to recycle, making it advantageous in terms of environmental protection. Furthermore, the reinforcing member 71 made of spring steel has high adhesive strength to the outer annular portion 30, which prevents damage to the outer annular portion 30, such as breakage.

[0076] (2) In the non-pneumatic tire 1 according to the first embodiment, the spring steel constituting the reinforcing member 71 is preferably any one of SK85, S60C, S65C, S70C, SAE1060, SAE1065, SAE1070, SUP9, SUP10, bainite steel, and ribbon steel.

[0077] This allows the reinforcing member 71 to have high spring properties, further enhancing the reinforcing effect of the outer annular portion 30.

[0078] (3) In the non-pneumatic tire 1 according to the first embodiment, the hardness of the spring steel material constituting the reinforcing member 71 is preferably HV400 or more and HV500 or less.

[0079] This allows the reinforcing member 71 to have high rigidity, and the reinforcing effect of the outer annular portion 30 is further enhanced.

[0080] (4) In the non-pneumatic tire 1 according to the first embodiment, the reinforcing member 71 is preferably in the shape of an annular plate extending along the circumferential direction C of the tire.

[0081] This prevents bias in the reinforcing direction of the reinforcing member 71, and allows the reinforcing member 71 to exert high reinforcing strength in a variety of directions.

[0082] In the non-pneumatic tire 1 of the first embodiment, the spokes 40 include a first spoke 41 inclined to one side in the tire axial direction and a second spoke 42 inclined to the opposite side of the first spoke 41, and it is preferable that the first spokes 41 and the second spokes 42 are arranged alternately in the tire circumferential direction D.

[0083] As a result, the first spokes 41 and the second spokes 42 are arranged in a substantially X-shape when viewed from a direction along the tire circumferential direction D. Because the first spokes 41 and the second spokes 42 are each inclined toward the tire axial direction, excessive rigidity is prevented, thereby improving ride comfort.

[0084] Hereinafter, a second embodiment and a third embodiment will be described, which are examples in which the outer reinforcing layer 70 of the first embodiment described above is modified.

[0085] (Second embodiment) 5 is a perspective view of a reinforcing member 72 constituting an outer reinforcing layer 70 according to the second embodiment. This reinforcing member 72 has a plurality of circular holes 71a formed by punching that penetrate the reinforcing member 71 of the first embodiment in the plate thickness direction. The plurality of holes 71a are evenly arranged in a staggered pattern over the entire area of ​​the reinforcing member 71. The number and size of the holes 71a are set so as not to impair the strength of the reinforcing member 71. The shape of the holes 71a is not limited to a circular shape, but a circular shape including an ellipse is preferable from the viewpoint that the holes are less likely to become starting points for cracks due to stress concentration.

[0086] (5) A reinforcing member 72 according to the second embodiment is the reinforcing member 71 of the first embodiment, with a plurality of holes 71a formed therethrough in the plate thickness direction.

[0087] This makes it possible to suppress an increase in the weight of the tire 1 while maintaining the strength to reinforce the outer annular portion 30. The reinforcing member 72 embedded inside the outer annular portion 30 made of resin is integrated with the outer annular portion 30 because resin is filled into each of the multiple holes 71a. Therefore, even if the holes 71a are formed, sufficient reinforcing strength is ensured.

[0088] (Third embodiment) Fig. 6 is a perspective view of an outer reinforcing layer 70 according to the third embodiment. Fig. 7 is a perspective view showing a belt-shaped member 76 that will become the outer reinforcing layer 70.

[0089] The outer reinforcing layer 70 is an annular member including wires 74 as reinforcing members and a covering layer 75 that covers the plurality of wires 74. The outer reinforcing layer 70 is formed by winding a belt-shaped member 76 shown in FIG. 7 into an annular shape. The belt-shaped member 76 is formed in a belt shape by covering a plurality of wires 74 arranged in parallel at equal intervals with a covering layer 75. The plurality of wires 74 extend in the length direction of the belt-shaped member 76.

[0090] The wire material 74 is formed into a linear shape using the above-mentioned spring steel material. For example, a hard steel wire material such as SWRH72B (carbon content: 0.69 to 0.76%) can be used as the wire material 74. The covering layer 75 is formed of, for example, resin or rubber. When the covering layer 75 is made of resin, it is preferably formed of the same resin as the resin constituting the outer annular portion 30 described above. The width of the belt-shaped member 76 is set to a dimension slightly smaller than the dimension of the outer annular portion 30 in the tire width direction Y.

[0091] The outer reinforcing layer 70 is formed into an annular shape by cutting a belt-shaped member 76 to a length corresponding to the circumferential length of the outer annular portion 30, winding the cut belt-shaped member 76 into an annular shape, and joining the butted ends. The ends are joined by welding the ends of the wires 74 to each other and adhering the ends of the covering layer 75 to each other. For example, when the outer annular portion 30 is resin-molded in a mold, the outer reinforcing layer 70 is set in the mold and filled with resin material, thereby being arranged in a state where it is embedded in the outer annular portion 30 over its entire circumference. In this state, the multiple wires 74 extend over the entire circumference in the tire circumferential direction C and are aligned in parallel in the tire width direction Y. In this embodiment, the multiple wires 74 are arranged in a single row in the width direction of the belt-shaped member 76, but may be arranged in two or more rows.

[0092] (6) In the third embodiment, the reinforcing member is a plurality of wires 74 extending around the entire circumference of the tire in the circumferential direction C and arranged in parallel in the tire width direction Y. The plurality of wires 74 are covered with a covering layer 75 to form the outer reinforcing layer 70.

[0093] As a result, the outer annular portion 30 is effectively reinforced by the outer reinforcing layer 70, improving the durability of the tire 1. Furthermore, the wire rods 74 serving as reinforcing members are made of spring steel, similar to the reinforcing member 71 of the first embodiment, and therefore exhibit sufficient reinforcing strength while being low in cost, and are easy to recycle, which is advantageous in terms of environmental protection. Furthermore, the wire rods 74 made of spring steel have high adhesive strength to the outer annular portion 30, and therefore damage to the outer annular portion 30, such as breakage, is suppressed.

[0094] (7) In the third embodiment, the covering layer 75 that covers the wires 74 is preferably made of the same material as the outer annular portion 30 .

[0095] This allows the coating layer 75 to be easily and firmly bonded to the outer annular portion 30, and the plurality of wires 74 are also integrally bonded to the outer annular portion 30. This improves the reinforcing effect of the outer annular portion 30.

[0096] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and any modifications and improvements made within the scope of the present invention are included within the scope of the present invention.

[0097] For example, the reinforcing member may be made of spring steel and may be in any form as long as it can be embedded in the outer annular portion 30. For example, it may be in a mesh form in which a plurality of wire rods are incorporated in a lattice pattern, or in a form in which a plurality of wire rods extending in the tire width direction Y are evenly arranged in the tire circumferential direction C.

[0098] In the second embodiment, a plurality of holes 71a penetrating in the plate thickness direction are provided, but the holes 71a may be replaced with recesses that do not penetrate through, grooves that extend in the tire circumferential direction C, or the like.

[0099] In the third embodiment, the outer reinforcing layer 70 is formed by covering a plurality of wires 74 with a covering layer 75, but the covering layer 75 may be omitted and the plurality of wires 74 may be directly embedded in the outer annular portion 30, so that the outer reinforcing layer 70 is formed only by the plurality of wires 74. Conversely, the reinforcing member 71 of the first embodiment or the reinforcing member 72 of the second embodiment may be covered with a covering layer of resin or the like to form a reinforcing layer. [Explanation of symbols]

[0100] 1 Non-pneumatic tires 20 Inner annular portion 30 Outer annular part 40 spokes 41 First Spoke 42 Second Spoke 50 tread 70 Outer reinforcement layer (reinforcement layer) 71 Reinforcement member 71a hole 74 Wire rod 75 Covering layer C Circumferential direction of tire Y Tire width direction

Claims

1. an inner annular portion; an outer annular portion disposed coaxially on the outer circumferential side of the inner annular portion; a plurality of spokes that connect the inner annular portion and the outer annular portion and are arranged along the tire circumferential direction; a tread provided on an outer peripheral surface of the outer annular portion, a reinforcing layer including a reinforcing member made of spring steel is embedded around the entire periphery of the outer annular portion; the reinforcing member has an annular plate shape extending along the tire circumferential direction, The reinforcing member has a plurality of holes formed therein that penetrate the reinforcing member in the thickness direction.

2. 2. The non-pneumatic tire according to claim 1, wherein the spring steel is any one of SK85, S60C, S65C, S70C, SAE1060, SAE1065, SAE1070, SUP9, SUP10, bainite steel, and ribbon steel.

3. 3. The non-pneumatic tire according to claim 1, wherein the spring steel has a hardness of HV400 or more and HV500 or less.

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