Non-pneumatic tires

Abstract

To provide a non-pneumatic tire that enables a pedestrian or the like to easily sense a very quiet vehicle when the vehicle travels near the pedestrian or the like.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 provided on an outer peripheral surface 32 of the outer annular part 30. An outer reinforcement layer 70 including a carbon fiber-reinforced plastic is embedded over the whole circumference of the outer annular part 30. The outer reinforcement layer 70 has voids 72 serving as sound-generation parts that enable the carbon fiber-reinforced plastic to generate sound when a load is applied to the tire.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 that is provided with noise and vibration prevention spokes made up of a plurality of spoke blades, thereby reducing noise generated during running. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5539479 Summary of the Invention [Problem to be solved by the invention]

[0005] Electric vehicles and hybrid vehicles, which have become increasingly popular in recent years, are quiet, especially when traveling at low speeds. This can make it difficult for pedestrians and others to notice vehicles traveling nearby.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a non-pneumatic tire that allows pedestrians and the like to easily detect a quiet vehicle when the vehicle is traveling near pedestrians and the like. [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 containing carbon fiber reinforced plastic is embedded around the entire circumference of the outer annular portion, and the reinforcing layer has a sound-generating portion that can generate sound from the carbon fiber reinforced plastic when the non-pneumatic tire is loaded. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a non-pneumatic tire that enables pedestrians and the like to easily notice a quiet vehicle traveling near pedestrians and the like. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a side view showing a non-pneumatic tire according to an 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 a material sheet including carbon fiber reinforced plastic that constitutes an outer reinforcing layer of the embodiment. [Figure 5] FIG. 2 is a partial side view schematically illustrating the structure of an outer reinforcing layer of the embodiment. [Figure 6] FIG. 2 is a perspective view showing an outer reinforcing layer of the embodiment. [Figure 7] 5A to 5C are diagrams schematically showing a manufacturing process for the outer reinforcing layer of the embodiment. [Figure 8] FIG. 10 is a side cross-sectional view showing a state in which the outer reinforcing layer of the embodiment is compressed and the voids are collapsed. [Figure 9] 10 is a partially enlarged cross-sectional side view of the outer reinforcing layer showing the process of the voids collapsing. FIG. [Figure 10] 10A and 10B are diagrams showing modified examples of the sound eliciting portion, and are side views showing the configuration of both end portions of the outer reinforcing layer. [Figure 11A] 10 is a photograph of a partial cross section of an outer reinforcing layer of Test Example 2, which was used to examine the relationship between the volume fraction of the voids and the sound emitted from the carbon fiber reinforced plastic in the Examples. [Figure 11B] 10 is a photograph of a partial cross section of an outer reinforcing layer of Test Example 4, which was used to examine the relationship between the volume fraction of the voids and the sound emitted from the carbon fiber reinforced plastic in the Examples. [Figure 11C] 10 is a photograph of a partial cross section of an outer reinforcing layer of Test Example 5, which was used to examine the relationship between the volume fraction of the voids and the sound emitted from the carbon fiber reinforced plastic in the Examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, this embodiment will be described with reference to the drawings. Fig. 1 is a side view of a non-pneumatic tire 1 of this 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, when the portion shown in Fig. 2 is viewed obliquely.

[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 this 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 annular outer reinforcing layer 70 is embedded around the entire periphery inside the outer annular portion 30. The outer reinforcing layer 70 is embedded inside the outer annular portion 30 coaxially with 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] The outer reinforcing layer 70 of this embodiment contains carbon fiber reinforced plastics (CFRP). FIG. 4 shows a material sheet 71 containing carbon fiber reinforced plastics used as the material of the outer reinforcing layer 70. The material sheet 71 is a sheet in which carbon fibers woven into a mesh are embedded in resin. The material sheet 71 is flexible. As shown in FIG. 5, the outer reinforcing layer 70 is formed into a flexible sheet by laminating a plurality of material sheets 71. Note that it is preferable that the resin used to form the outer reinforcing layer 70 is a different type of resin from the resin used to form the spokes 40, which will be described later.

[0028] The width of the outer reinforcing layer 70, i.e., the dimension in the tire width direction Y, is preferably about 135 mm, for example. 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 outer reinforcing layer 70 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 about 2.0 mm, for example. The outer reinforcing layer 70 is preferably disposed at the center of the outer annular portion 30 in the tire radial direction X and the center in the tire width direction Y.

[0029] The resin outer annular portion 30 is formed using a mold. A sheet-like outer reinforcing layer 70 is wound into a circular shape and set in the mold as shown in FIG. 6, and a resin material is filled into the mold. As a result, the outer reinforcing layer 70 is disposed in a state embedded around the entire circumference inside the outer annular portion 30. Note that FIG. 6 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. The outer reinforcing layer 70 is formed into a circular shape by butting together a first end 70a at one end in the length direction and a second end 70b at the other end.

[0030] Fig. 7 schematically shows the molding process of the outer reinforcement layer 70. As shown in Fig. 7, the outer reinforcement layer 70 of this embodiment is molded by heating and pressurizing a laminate 70F of multiple material sheets 71 at a predetermined temperature and pressure, and then heating and curing it at a predetermined temperature.

[0031] 7, the outer reinforcing layer 70, which is a laminate of carbon fiber reinforced plastic, has therein a plurality of voids 72. The voids 72 are an example of sound-eliciting portions provided in the outer reinforcing layer 70.

[0032] A plurality of voids 72 are likely to be formed between the stacked material sheets 71. Causes of the formation of the voids 72 include, for example, the entrapment of air or gas when the laminate 70F is heated, or the contraction of the carbon fiber reinforced plastic when it is cooled after heating. Therefore, it is possible to adjust the number and size of the voids 72, for example, by adjusting the heating temperature during molding of the outer reinforcing layer 70 or by adjusting the cooling rate. Another method is to adjust the resin filling rate during molding.

[0033] The shape of the voids 72 is often elliptical or a similarly flattened shape in side view, as shown in Fig. 7, for example, but is not limited to this. Because they are formed between stacked material sheets 71, they tend to have a flattened shape in side view. The voids 71 ​​are formed, for example, in rectangular regions defined by the woven carbon fibers, and their shape and size depend on the region.

[0034] The plurality of voids 72 are preferably arranged dispersedly over the entire circumference in the tire circumferential direction C. The volume ratio of the voids 72 to the outer reinforcing layer 70 is preferably 5% or more and 20% or less.

[0035] 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.

[0036] 2 and 3, 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 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.

[0037] 2 and 3, the first spokes 41 generally extend at an incline 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 incline 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.

[0038] 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 39° and equal to or less than 49°.

[0039] 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.

[0040] 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 the spokes 40 are viewed from the direction along the tire circumferential direction C, as also shown in FIG. 2 . In this embodiment, the thickness t of all the spokes 40 is the same. Furthermore, the width w of all the spokes 40 is the same.

[0041] 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.

[0042] 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.

[0043] Although the spokes 40 in this 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] As described above, in this embodiment, all of the spokes 40 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 sufficiently withstand the rotational force from the inner annular portion 20 and the outer annular portion 30 and can be appropriately flexibly deformed when subjected to a load.

[0052] As described above, all spokes 40 in this 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.

[0053] 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.

[0054] 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. In this embodiment, the intervals between the spokes 40 in the tire circumferential direction C are equal, but may be unequal.

[0055] 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.

[0056] 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 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 deterioration in ride comfort.

[0057] The elastic material used as the base material of the spokes 40 may be a thermoplastic elastomer, a crosslinked rubber, or other resin.

[0058] Examples of thermoplastic elastomers include polyester elastomers, polyolefin elastomers, polyamide elastomers, polystyrene elastomers, polyvinyl chloride elastomers, and polyurethane elastomers.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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 the granular fillers that can be added include carbon black, ceramics such as silica and alumina, and other inorganic fillers.

[0064] 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.

[0065] The tread 50 is provided on the outer peripheral surface 32 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.

[0066] 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 32 of the outer annular portion 30 by a vulcanization adhesive layer 52.

[0067] The non-pneumatic tire 1 of this embodiment having the above configuration has an outer reinforcing layer 70 containing carbon fiber reinforced plastic embedded inside the outer annular portion 30. This outer reinforcing layer 70 suppresses the occurrence of buckling, in which the outer annular portion 30 bends in the tire radial direction X at the center in the tire width direction Y. In addition, the outer reinforcing layer 70 ensures the rigidity of the non-pneumatic tire 1 and improves the contact of the tread 50 with the road surface.

[0068] The outer reinforcing layer 70 has a plurality of voids 72 therein. When a vehicle equipped with the non-pneumatic tire 1 travels on a road surface, the tread 50 strikes the road surface and then kicks off. During this driving operation of the tire, the outer annular portion 30 and the outer reinforcing layer 70 in the lower portion corresponding to the portion of the tread 50 that contacts the road surface receive a load and are subjected to stress that compresses them in the thickness direction. As the outer reinforcing layer 70 compresses in the thickness direction, the plurality of voids 72 are instantaneously crushed as shown in FIG. 8 , and then the outer reinforcing layer 70 elastically recovers, causing the voids 72 to return to their original holes.

[0069] FIG. 9 shows transitional states in which the outer reinforcing layer 70 is compressed and the voids 72 are crushed. When the voids 72 are crushed, the carbon fiber reinforced plastic 71a on the inner circumferential side of the tire and the carbon fiber reinforced plastic 71b on the outer circumferential side of the tire, which sandwich the voids 72, come into contact. At the time of contact, impact sounds and friction sounds of the carbon fiber reinforced plastic are generated. In addition, when the voids 72 are crushed, a contraction sound may be generated as the carbon fiber reinforced plastic contracts. In this specification, the sound generated from the carbon fiber reinforced plastic due to the compression of the outer reinforcing layer 70 is referred to as compression sound. Because multiple voids 72 are dispersed and arranged all around the tire circumferential direction C, the compression sound is continuously dispersed to the surroundings. In this embodiment, the voids 72 function as sound generating portions that can generate sound from the carbon fiber reinforced plastic of the outer reinforcing layer 70 when a load is applied to the non-pneumatic tire 1.

[0070] When the non-pneumatic tire 1 is mounted on a vehicle that is quiet when traveling at low speeds, such as an electric vehicle or a hybrid vehicle, the compression noise generated by the collapse of the voids 72 can be detected by nearby pedestrians and the like as the sound of the vehicle traveling. The compression noise is preferably audible to nearby pedestrians and the like when the vehicle is traveling at a speed of, for example, 10 km / h or less. By detecting the compression noise, pedestrians and the like can avoid the vehicle and walk safely. If the volume ratio of the voids 72 to the outer reinforcing layer 70 is 5% or more and 20% or less as described above, the compression noise is reliably generated, which is preferable.

[0071] The non-pneumatic tire 1 according to this embodiment has the following advantages.

[0072] (1) The non-pneumatic tire 1 according to this embodiment comprises an inner annular portion 20, an outer annular portion 30 arranged coaxially on the outer circumferential 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 32 of the outer annular portion 30, in which an outer reinforcing layer 70 containing carbon fiber reinforced plastic is embedded around the entire circumference of the outer annular portion 30, and the outer reinforcing layer 70 has voids 72 as sound-generating portions that can generate sound from the carbon fiber reinforced plastic when the tire is loaded.

[0073] As a result, the voids 72 collapse during driving, causing continuous compression noise from the carbon fiber reinforced plastic. For example, if the non-pneumatic tire 1 of this embodiment is mounted on a vehicle that is quiet when driving at low speeds, such as an electric vehicle or a hybrid vehicle, the compression noise emitted from the carbon fiber reinforced plastic will be perceived as a driving noise by pedestrians and others near the vehicle. As a result, pedestrians and others can avoid the vehicle and pass safely.

[0074] Furthermore, the outer reinforcing layer 70 containing carbon fiber reinforced plastic effectively reinforces the outer annular portion 30, ensuring the rigidity of the non-pneumatic tire 1 and improving the contact of the tread 50 with the road surface.

[0075] (2) In the non-pneumatic tire 1 of the present embodiment, the sound generating portion is preferably a void 72 formed in the outer annular portion 30 .

[0076] The voids 72 can be easily formed inside the outer reinforcing layer 70 during the manufacturing process of the outer reinforcing layer 70. Furthermore, the number and size of the voids 72 can be adjusted by changing the molding conditions of the outer reinforcing layer 70, which makes it possible to adjust the compression sound, frequency, etc. emitted from the carbon fiber reinforced plastic.

[0077] (3) In the non-pneumatic tire 1 of the present embodiment, the volume ratio of the voids 72 to the outer reinforcing layer 70 is preferably 5% or more and 20% or less.

[0078] This ensures that compression noise emanating from the carbon fiber reinforcement is generated.

[0079] (4) In the non-pneumatic tire 1 of this embodiment, the spokes 40 include first spokes 41 inclined to one side in the tire axial direction and second spokes 42 inclined to the opposite side from the first spokes 41, and it is preferable that the first spokes 41 and the second spokes 42 are arranged alternately in the tire circumferential direction C.

[0080] 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.

[0081] Next, with reference to FIG. 10 , a modified example in which the sound elicitation portion of the above embodiment is modified will be described. In the above embodiment, as shown in FIG. 6 , the outer reinforcing layer 70 is formed in an annular shape, and the first end 70a and the second end 70b at both ends are butt-joined. In contrast, in the outer reinforcing layer 70 of the modified example, when no load is applied, as shown in the left diagram in FIG. 10 , the first end 70a is bent toward the inner periphery (downward in FIG. 10 ) and separated from the second end 70b. When a load is applied to the non-pneumatic tire 1 and the outer reinforcing layer 70 is compressed, as shown in the right diagram in FIG. 10 , the bent first end 70a deforms toward the second end 70b and comes into contact with the second end 70b. When the first end 70a comes into contact with the second end 70b, the carbon fiber reinforced plastics come into contact with each other, generating compression noise. The first end 70a and the second end 70b are another example of a sound elicitation portion provided in the outer reinforcing layer 70.

[0082] (5) In the modified example, the sound generating portion is a pair of ends, namely, a first end 70a and a second end 70b, of the outer reinforcing layer 70, and the first end 70a and the second end 70b come into contact when the tire is loaded.

[0083] As a result, the first end 70a and the second end 70b come into contact with each other during driving, causing continuous compression noise of the carbon fiber reinforced plastic. Therefore, similar to the above embodiment, when the non-pneumatic tire 1 is mounted on a vehicle that is quiet when driving at low speeds, the compression noise emitted from the carbon fiber reinforced plastic will be detected as driving noise by pedestrians and the like near the vehicle, allowing pedestrians and the like to pass safely. [Example]

[0084] Next, an example will be described in which the relationship between the volume fraction of voids in the outer reinforcing layer, the generation of compression noise due to carbon fiber reinforced plastic, and the state of tire failure in a non-pneumatic tire having a configuration similar to that of the above embodiment was investigated. Table 1 shows test examples 1 to 5 of non-pneumatic tires with different void volume fractions relative to the outer reinforcing layer. Test example 1 had no voids, and test examples 2 to 5 had void volume fractions of 4%, 6%, 20%, and 25%, respectively. The "void fraction" shown in Table 1 is a numerical value obtained by regarding the area fraction of voids relative to the outer reinforcing layer in a cross section of the outer reinforcing layer taken along the tire circumferential direction as the void volume fraction. The basic molding conditions for the outer reinforcing layer in test examples 1 to 5 were generally the same. For example, the temperature was 90°C when heating and pressurizing the carbon fiber reinforced plastic laminate to mold it into the outer reinforcing layer, and the curing temperature after molding was 130°C.

[0085] [Table 1]

[0086] The presence or absence of "compression noise" in Table 1 is indicated by a mark of "O" if the observer judged that the compression noise emanating from the carbon fiber reinforced plastic was audible when a vehicle fitted with a tire from each test example was traveling in an open space at a speed of 5 to 20 km / h and the observer passed within 1 m of the traveling vehicle in a straight line, and an X if the observer judged that the compression noise was audible. Furthermore, the occurrence of separation in the outer reinforcing layer with the void as the boundary was deemed to be a "failure," and in Table 1, cases where no separation occurred were marked with an O, indicating no failure, and cases where separation occurred were marked with an X, indicating a failure.

[0087] Fig. 11A is a partial cross-sectional photograph of the outer reinforcing layer of Test Example 2, in which the void volume fraction was 4%. Fig. 11B is a partial cross-sectional photograph of the outer reinforcing layer of Test Example 4, in which the void volume fraction was 20%. Fig. 11C is a partial cross-sectional photograph of the outer reinforcing layer of Test Example 5, in which the void volume fraction was 25%. All cross-sectional photographs were taken of part of a cross section of the outer reinforcing layer along the tire circumferential direction.

[0088] As shown in Table 1, Test Example 1, which had no voids in the carbon fiber reinforced plastic of the outer reinforcing layer, and Test Example 2, which had a void volume fraction of 4%, did not experience any breakdowns but did not generate compression noise. Therefore, the running noise could not be detected by those around. As shown in the cross-sectional photograph of Figure 11A, Test Example 2 had a small number of voids, and it was found that compression noise did not occur when the void volume fraction was around 4%.

[0089] As shown in Table 1, Test Example 3 and Test Example 4 generated compression noise but were free of failure. As shown in the cross-sectional photograph of Figure 11B, Test Example 4 had multiple voids dispersed in the circumferential direction within the outer reinforcing layer 70, and it was confirmed that compression noise was effectively generated when the void volume ratio was 20%. On the other hand, Test Example 5 generated compression noise, but as shown in Figure 11C, long voids in the tire circumferential direction existed as cracks, causing separation in the outer reinforcing layer.

[0090] From the above results, it was found that in order to ensure that compression noise is generated by the carbon fiber reinforced plastic and to prevent separation from occurring in the outer reinforcement layer, it is preferable that the volume ratio of voids in the outer reinforcement layer be between 5% and 20%.

[0091] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and modifications and improvements made within the scope of the present invention are also included within the scope of the present invention.

[0092] For example, the sound generating portion that causes the carbon fiber reinforced plastic of the outer reinforcing layer 70 to emit sound during running is not limited to the above embodiment, and may be in any form as long as the sound is generated by the behavior of the carbon fiber reinforced plastic, such as deformation, contraction, contact, friction, etc. Furthermore, the behavior is not limited.

[0093] The spokes 40 in the embodiment include a first spoke 41 and a second spoke 42 that intersect in an approximately X-shape when viewed from a direction along the tire circumferential direction C, but the spokes 40 are not limited to this and may be composed of a plate-shaped portion that extends straight in the tire radial direction X. [Explanation of symbols]

[0094] 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) 70a First end (sound-inducing part) 70b Second end (pronunciation part) 72 Void (pronunciation part) C Circumferential direction of tire

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 carbon fiber reinforced plastic is embedded in the outer annular portion over the entire circumference; the reinforcing layer has a sound generating portion that can generate sound from the carbon fiber reinforced plastic when a tire load is applied, The sound generating portion is a void formed in the reinforcing layer.

2. The non-pneumatic tire according to claim 1 , wherein a volume ratio of the voids to the reinforcing layer is 5% or more and 20% or less.

3. 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 carbon fiber reinforced plastic is embedded in the outer annular portion over the entire circumference; the reinforcing layer has a sound generating portion that can generate sound from the carbon fiber reinforced plastic when a tire load is applied, The sound generating portion is a pair of end portions of the reinforcing layer, and the pair of end portions come into contact when the tire is loaded.

4. The spokes are a first spoke inclined toward one side in the tire axial direction; a second spoke inclined opposite to the first spoke; The non-pneumatic tire according to any one of claims 1 to 3, wherein the first spokes and the second spokes are arranged alternately in the tire circumferential direction.

Images