Airless tire and manufacturing method thereof

Abstract

To provide an airless tire which can achieve both excellent quality and productivity, and a method for manufacturing the same.SOLUTION: An airless tire 1 includes a tread ring 2, a hub 3, and a spoke 4. The tread ring 2 has a ground plane 2a. The hub 3 is fixed to an axle, and is arranged inside in a tire radial direction of the tread ring 2. The spoke 4 connects the tread ring 2 and the hub 3, and is formed of a resin having a melt index at 230°C of 15-25 g / 10 min.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an airless tire that can support a load by its own structure without using high-pressure air, and a method for manufacturing the same. [Background technology]

[0002] Various airless tires have been known in the past, in which a tread ring and a hub are connected by spokes. For example, Patent Document 1 listed below proposes an airless tire that includes a cylindrical tread ring having a contact surface, a hub fixed to an axle, and spokes made of a polymer material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-130071 Summary of the Invention [Problem to be solved by the invention]

[0004] In airless tires such as those described in Patent Document 1, spokes are typically formed from thermosetting resin. However, because thermosetting resin is poured into a mold without applying pressure, a large amount of burrs are generated due to gaps in the mold, and finishing processing requires a significant amount of time, leaving a need for further improvements in productivity.

[0005] The airless tire of Patent Document 1 also suggests using a thermoplastic resin for the spokes. However, thermoplastic resins have high viscosity, and when injection-molded at high pressure, the tread ring placed in the mold deforms, and when injection-molded at a pressure that does not deform the tread ring, the resin does not fill the mold uniformly, so improvement in terms of quality was desired.

[0006] The present disclosure has been devised in view of the above circumstances, and has as its main object to provide an airless tire that can achieve both excellent quality and productivity, and a method for manufacturing the same. [Means for solving the problem]

[0007] The present disclosure relates to an airless tire comprising: a tread ring having a contact surface; a hub disposed radially inward of the tread ring and fixed to an axle; and spokes for connecting the tread ring and the hub, the spokes being formed from a resin having a melt index at 230°C of 15 to 25 g / 10 min. [Effects of the Invention]

[0008] The airless tire of the present disclosure has the above-described configuration, and thus can achieve both excellent quality and productivity. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view illustrating an embodiment of an airless tire according to the present disclosure. [Figure 2] FIG. 1 is a side view of an airless tire. [Figure 3] FIG. 2 is a partial cross-sectional perspective view of the tread ring and spokes. [Figure 4] 1 is a flowchart illustrating an embodiment of a method for manufacturing an airless tire according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. Fig. 1 is a perspective view showing an airless tire 1 of this embodiment, and Fig. 2 is a side view of the airless tire 1. As shown in Fig. 1 and Fig. 2, the airless tire 1 of this embodiment includes a tread ring 2 having a contact surface 2a, a hub 3 disposed inside the tread ring 2 in the tire radial direction, and spokes 4 for connecting the tread ring 2 and the hub 3. The hub 3 preferably includes a fixing portion 3a that is fixed to an axle (not shown) of a vehicle.

[0011] The spokes 4 include, for example, a plurality of plate-shaped spoke plates 5 whose axial width is greater than the circumferential thickness of the tire. When a load acts on the tread ring 2, such spokes 4 are able to support the load by applying a tensile force to the spoke plates 5 located above the hub 3 and a compressive force to the spoke plates 5 located below the hub 3.

[0012] Such an airless tire 1 can support the load acting on the tread ring 2 by the hub 3 and the spokes 4 without using high-pressure air. Therefore, the airless tire 1 of this embodiment is unlikely to get punctured.

[0013] The spokes 4 of this embodiment are formed from a resin having a melt index of 15 to 25 g / 10 min at 230° C. Here, the melt index in this specification is measured at 230° C. under a load of 2.16 kg in accordance with ASTM D1238.

[0014] In such an airless tire 1, the resin of the spokes 4 has a melt index of 15 g / 10 min or more at 230°C, which allows the resin to be uniformly filled into the mold with an appropriate pressure. Therefore, the airless tire 1 of this embodiment can improve the uniformity of the thickness of the spokes 4 while suppressing deformation of the tread ring 2, thereby improving quality. Here, in this specification, quality is an index evaluated based on the deviation from the design dimensions.

[0015] Furthermore, in this airless tire 1, the resin of the spokes 4 has a melt index of 25 g / 10 min or less at 230°C, which makes it possible to suppress the generation of burrs. Therefore, in the airless tire 1 of this embodiment, the time required for burr removal can be shortened, and productivity can be improved. As a result, the airless tire 1 of this embodiment can achieve both excellent quality and productivity.

[0016] In a more preferred embodiment, the resin of the spokes 4 is a thermoplastic resin. The thermoplastic resin may be appropriately selected from, for example, a single resin, a composite resin of two or more types, a fiber-reinforced resin, etc. The thermoplastic resin of the spokes 4 in this embodiment is a resin selected from polyester resins.

[0017] Such spokes 4 are made of a thermoplastic resin and can be injection molded under pressure. Therefore, the spokes 4 of this embodiment can remove air from inside the resin, improving the quality of the airless tire 1.

[0018] Furthermore, because the spokes 4 are made of polyester resin, the viscosity of the resin can be reduced, thereby improving the productivity of the airless tire 1. Furthermore, polyester resin has excellent shock absorption properties, which can improve the ride comfort performance of the airless tire 1.

[0019] 3 is a partial cross-sectional perspective view of the tread ring 2 and the spokes 4. As shown in FIGS. 1 to 3, the spokes 4 of this embodiment include a plurality of spoke plates 5, an outer cylindrical portion 6 connected to the tread ring 2, and an inner cylindrical portion 7 connected to the hub 3. As a result, each of the spoke plates 5 is indirectly connected to the tread ring 2 and the hub 3.

[0020] Such spokes 4 can be firmly connected to the hub 3 and the tread ring 2, thereby improving the durability of the airless tire 1. Note that the spokes 4 may be configured such that, for example, the outer cylindrical portion 6 and the inner cylindrical portion 7 are omitted, and each of the spoke plates 5 is directly connected to the tread ring 2 and the hub 3.

[0021] Each of the spoke plates 5 is preferably curved in a substantially S-shape when viewed in the tire axial direction. Such spokes 4 easily deform when a compressive force is applied, and can absorb impact when the tire touches the ground, thereby improving the ride comfort of the airless tire 1.

[0022] The spoke plates 5 include a first spoke plate 5A arranged on one side in the tire axial direction and a second spoke plate 5B arranged on the other side when viewed in the thickness direction of the spoke plate 5. The first spoke plates 5A and the second spoke plates 5B are arranged, for example, alternately in the tire circumferential direction. Such spoke plates 5 can achieve both weight reduction and balance in the tire axial direction, and can achieve both low fuel consumption and durability for the airless tire 1.

[0023] It is desirable that each of the spoke plates 5 extend at an angle with respect to the tire axial direction. Such spokes 4 improve the rigidity in the tire circumferential direction, and can improve the durability of the airless tire 1.

[0024] As shown in Figures 1 and 2, the hub 3 is made of a non-elastic material such as metal. The hub 3 of this embodiment is made of metal. The hub 3 preferably has a disk-shaped fixing portion 3a that is fixed to the axle, and a cylindrical portion 3b that is connected to the spokes 4. The fixing portion 3a of the hub 3 may have, for example, a plurality of fixing holes formed therein. The fixing portion 3a of the hub 3 is not limited to this embodiment, and may, for example, be one that can be attached to a dedicated axle with one touch.

[0025] The airless tire 1 preferably has an inner adhesive layer 8 between the cylindrical portion 3b of the hub 3 and the inner cylindrical portions 7 of the spokes 4. Such an airless tire 1 can improve the adhesive strength between the hub 3 and the spokes 4, and can improve durability.

[0026] 1 and 3, the tread ring 2 has a contact surface 2a that comes into contact with the road surface during running, and a plurality of circumferential grooves 9 (two in this embodiment) extending in the tire circumferential direction are formed in the contact surface 2a. Such a tread ring 2 has good drainage properties and can improve the wet performance of the airless tire 1. The contact surface 2a is not limited to this form, and may be, for example, block-shaped, or may have a plurality of recesses formed therein.

[0027] As shown in Fig. 3, the tread ring 2 of this embodiment is made of rubber. The tread ring 2 includes, for example, an outer rubber layer 10 on which a contact surface 2a is formed, an inner rubber layer 11 on which an inner circumferential surface 2b that contacts the spokes 4 is formed, and an intermediate rubber layer 12 disposed between the outer rubber layer 10 and the inner rubber layer 11. By adjusting the rubber materials of the outer rubber layer 10, the inner rubber layer 11, and the intermediate rubber layer 12, such a tread ring 2 can achieve both excellent quality and productivity for the airless tire 1.

[0028] The tread ring 2 of this embodiment includes a sidewall rubber 13 that connects the outer rubber layer 10 and the inner rubber layer 11 on at least one side of the intermediate rubber layer 12 in the tire axial direction. Such a sidewall rubber 13 can protect the intermediate rubber layer 12 and can improve the durability performance of the airless tire 1.

[0029] The tread ring 2 of this embodiment includes an outer reinforcing layer 14 disposed between the outer rubber layer 10 and the intermediate rubber layer 12, and an inner reinforcing layer 15 disposed between the inner rubber layer 11 and the intermediate rubber layer 12. Such outer reinforcing layer 14 and inner reinforcing layer 15 help to improve the durability performance of the airless tire 1.

[0030] The outer reinforcing layer 14 includes at least one outer ply 14A, 14B in this embodiment, in which outer reinforcing cords are arranged, and the inner reinforcing layer 15 includes at least one inner ply 15A, 15B in this embodiment, in which inner reinforcing cords are arranged.

[0031] The outer plies 14A, 14B include, for example, a first outer ply 14A arranged on the side of the contact surface 2a and a second outer ply 14B arranged adjacent to the first outer ply 14A on the radially inner side of the first outer ply 14A in the tire radial direction.

[0032] In this embodiment, the outer reinforcement cords of the first outer ply 14A and the outer reinforcement cords of the second outer ply 14B are inclined in opposite directions at the same angle relative to the tire circumferential direction. The outer reinforcement cords are preferably inclined at an angle of 15 to 25 degrees relative to the tire circumferential direction. Such an outer reinforcing layer 14 has excellent axial balance and helps maintain the excellent quality of the airless tire 1.

[0033] The outer reinforcing cords are formed of, for example, metal cords, organic fiber cords, etc. The outer reinforcing cords of the first outer ply 14A and the outer reinforcing cords of the second outer ply 14B are preferably formed of the same material. Such an outer reinforcing layer 14 helps to improve the durability of the airless tire 1 while suppressing manufacturing costs.

[0034] The inner plies 15A, 15B include, for example, a first inner ply 15A arranged on the side of the inner circumferential surface 2b that contacts the spokes 4, and a second inner ply 15B arranged adjacent to the first inner ply 15A on the radially outer side of the first inner ply 15A.

[0035] In this embodiment, the inner reinforcing cords of the first inner ply 15A and the inner reinforcing cords of the second inner ply 15B are inclined in opposite directions at the same angle relative to the tire circumferential direction. The inner reinforcing cords are preferably inclined at an angle of 15 to 25 degrees relative to the tire circumferential direction. Such an inner reinforcing layer 15 provides excellent axial balance of the tire, which helps maintain the excellent quality of the airless tire 1.

[0036] The inner reinforcing cords are formed of, for example, metal cords, organic fiber cords, etc. The inner reinforcing cords of the first inner ply 15A and the inner reinforcing cords of the second inner ply 15B are preferably formed of the same material. Such an inner reinforcing layer 15 helps to improve the productivity of the airless tire 1 while suppressing manufacturing costs.

[0037] The airless tire 1 preferably has an outer adhesive layer 16 between the inner circumferential surface 2b of the tread ring 2 and the outer cylindrical portions 6 of the spokes 4. Such an airless tire 1 can improve the adhesive strength between the tread ring 2 and the spokes 4, and can improve durability performance.

[0038] Next, a method for manufacturing the airless tire 1 of this embodiment will be described with reference to FIGS. Fig. 4 is a flowchart showing a method for manufacturing the airless tire 1 of this embodiment. As shown in Fig. 4, in the method for manufacturing the airless tire 1 of this embodiment, first, a first preparation step S1 of preparing a tread ring 2 is performed.

[0039] In the first preparation step S1, for example, rubber is vulcanized to prepare the tread ring 2. Such a first preparation step S1 can improve the precision of the tread ring 2 and is useful for improving the quality of the airless tire 1.

[0040] In the method for manufacturing the airless tire 1 of this embodiment, a second preparation step S2 is then performed to prepare the hub 3. The first preparation step S1 and the second preparation step S2 may be performed simultaneously, or the second preparation step S2 may be performed first.

[0041] In the second preparation step S2, for example, a metal material is cast or forged to prepare the hub 3. Such a second preparation step S2 can improve the strength and processing precision of the hub 3, and is useful for improving the quality of the airless tire 1.

[0042] In the method for manufacturing the airless tire 1 of this embodiment, next, an arrangement step S3 is performed in which the tread ring 2 and the hub 3 are arranged in an integral molding die (not shown). In the arrangement step S3, for example, the tread ring 2 having the contact surface 2a and the hub 3 arranged inside the tread ring 2 in the tire radial direction are arranged in positions of the airless tire 1 after molding.

[0043] In the disposing step S3, it is desirable to apply an adhesive in advance to the inner circumferential surface 2b of the tread ring 2 and the cylindrical portion 3b of the hub 3. As the adhesive, for example, an adhesive for elastomers is preferably used. Such a disposing step S3 can form the inner adhesive layer 8 and the outer adhesive layer 16, which is useful for improving the durability performance of the airless tire 1.

[0044] In the method for manufacturing the airless tire 1 of this embodiment, next, a molding step S4 is performed in which a resin is injected between the tread ring 2 and the hub 3 of the integral molding die. In the molding step S4 of this embodiment, the spokes 4 that connect the tread ring 2 and the hub 3 are molded, thereby integrally molding the airless tire 1.

[0045] The resin injected in the molding step S4 of this embodiment has a melt index at 230°C of 15 to 25 g / 10 min. In such molding step S4, since the resin of the spokes 4 has a melt index at 230°C of 15 g / 10 min or more, the resin can be uniformly filled into the mold with an appropriate pressure. Therefore, the manufacturing method of the airless tire 1 of this embodiment can improve the uniformity of the thickness of the spokes 4 while suppressing deformation of the tread ring 2, thereby improving quality.

[0046] Furthermore, in this molding step S4, the melt index at 230°C of the resin of the spokes 4 is 25 g / 10 min or less, which makes it possible to suppress the generation of burrs. Therefore, the method for manufacturing the airless tire 1 of this embodiment can shorten the time required for burr removal and improve productivity. As a result, the method for manufacturing the airless tire 1 of this embodiment can achieve both excellent quality and productivity.

[0047] The method for manufacturing the airless tire 1 of this embodiment then carries out a demolding step S5 in which the airless tire 1, in which the tread ring 2, hub 3, and spokes 4 are integrally molded, is removed from the integral molding mold. The demolding step S5 may be carried out automatically or manually, for example. This method for manufacturing the airless tire 1 allows the airless tire 1 to be smoothly removed from the mold, which helps to achieve both excellent quality and productivity for the airless tire 1.

[0048] Although particularly preferred embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above-described embodiments and can be modified and implemented in various forms. [Example]

[0049] The airless tires shown in Figures 1 to 3 were prototyped using the manufacturing method shown in Figure 4 and based on the specifications in Table 1. The prototype airless tires were tested for productivity and quality. The main common specifications and test methods are as follows:

[0050] <Common specifications> Spokes: Thermoplastic polyester resin Hub: Aluminum Tread ring width: 145mm Tread ring outer diameter: 507mm Tread ring vulcanization temperature: 170℃ Tread ring curing time: 15 minutes Outer reinforcement layer: 2 outer plies Outer reinforcement cord: Steel cord Outer reinforcement cord angle: +21° / -21° Inner reinforcement layer: 2 inner plies Inner reinforcing cord: Steel cord Inner reinforcing cord angle: +21° / -21° Injection molding temperature: 230℃

[0051] <Productivity> The appearance of the spokes of the airless tires removed from the mold was evaluated. The results were evaluated based on the presence or absence of burrs, with the absence of burrs indicating excellent productivity.

[0052] <Quality> The variation in spoke thickness of airless tires removed from the mold was evaluated. The results were evaluated as the difference between the maximum and minimum spoke thickness, with a smaller difference indicating better quality.

[0053] The test results are shown in Table 1. [Table 1]

[0054] As a result of the test, it was confirmed that the airless tire of the example had both superior quality and productivity compared to the comparative example.

[0055] [Note] The present disclosure is as follows.

[0056] [Disclosure 1] An airless tire comprising: a tread ring having a contact surface; a hub disposed radially inward of the tread ring and fixed to an axle; and spokes for connecting the tread ring and the hub, the spokes being formed from a resin having a melt index at 230°C of 15 to 25 g / 10 min.

[0057] [Disclosure 2] The airless tire according to Disclosure 1, wherein the resin is a thermoplastic resin.

[0058] [Disclosure 3] 3. The airless tire according to Disclosure 1 or 2, wherein the resin is a polyester resin.

[0059] [Disclosure 4] The airless tire according to any one of Disclosures 1 to 3, wherein the tread ring is formed from rubber and the hub is formed from metal.

[0060] [Disclosure 5] A method for manufacturing an airless tire, the method including: a first preparation step of preparing a tread ring having a contact surface; a second preparation step of preparing a hub to be disposed radially inward of the tread ring; an arrangement step of arranging the tread ring and the hub in a one-piece mold; a molding step of molding spokes that connect the tread ring and the hub by injecting a resin between the tread ring and the hub in the one-piece mold; and a demolding step of removing from the one-piece mold the airless tire in which the tread ring, the hub, and the spokes are integrally molded, wherein the resin has a melt index at 230°C of 15 to 25 g / 10 min.

[0061] [Disclosure 6] The method for manufacturing an airless tire according to Disclosure 5, wherein the first preparation step prepares the tread ring by vulcanizing and molding rubber. [Explanation of symbols]

[0062] 1. Airless tires 2 tread rings 2a Ground plane 3. Hub 4 spokes

Claims

1. An airless tire, a tread ring having a contact surface; a hub disposed radially inward of the tread ring and fixed to an axle; and spokes for connecting the tread ring and the hub, the spokes are formed from a resin having a melt index at 230°C of 15 to 25 g / 10 min; The tread ring includes an outer reinforcing layer disposed on the contact surface side, and an inner reinforcing layer disposed radially inward of the outer reinforcing layer, the inner reinforcing layer includes at least one inner ply having inner reinforcing cords arranged therein; the inner ply includes a first inner ply arranged on a side of an inner circumferential surface that contacts the spokes, and a second inner ply arranged adjacent to the first inner ply on the outer side of the first inner ply in the tire radial direction, the inner reinforcing cords of the first inner ply and the inner reinforcing cords of the second inner ply are inclined in opposite directions to each other at the same angle with respect to the tire circumferential direction, the spokes include a plurality of spoke plates; Each of the spoke plates is indirectly connected to the tread ring and the hub, and extends obliquely with respect to the tire axial direction, The spoke plates include a first spoke plate disposed on one side in the tire axial direction and a second spoke plate disposed on the other side when viewed from a thickness direction of the spoke plates, The first spoke plates and the second spoke plates are arranged alternately in the tire circumferential direction. Airless tires.

2. the outer reinforcing layer includes at least one outer ply having outer reinforcing cords arranged therein; The outer plies include a first outer ply disposed on the side of the contact surface, and a second outer ply disposed adjacent to the first outer ply on the inner side of the first outer ply in the tire radial direction. The airless tire according to claim 1.

3. 3. The airless tire of claim 2, wherein the outer reinforcing cords of the first outer ply and the outer reinforcing cords of the second outer ply are formed from the same material.

4. The airless tire according to claim 1 , wherein the resin is a thermoplastic resin.

5. The airless tire according to claim 1 , wherein the resin is a polyester resin.

6. The tread ring is formed from rubber, The airless tire according to claim 1 , wherein the hub is made of metal.

7. The hub has a cylindrical portion connected to the spokes, the spokes include inner cylindrical portions connected to the hub; The airless tire according to claim 6, further comprising an inner adhesive layer between the cylindrical portion and the inner cylindrical portion.

8. A method for manufacturing an airless tire, comprising: a first preparation step of preparing a tread ring having a contact surface; a second preparation step of preparing a hub disposed radially inward of the tread ring; a placement step of placing the tread ring and the hub in an integral molding die; a molding step of molding spokes that connect the tread ring and the hub by injecting resin between the tread ring and the hub in the integral molding die; a demolding step of removing the airless tire, in which the tread ring, the hub, and the spokes are integrally molded, from the integral molding die, The resin has a melt index of 15 to 25 g / 10 min at 230°C, The tread ring includes an outer reinforcing layer disposed on the contact surface side, and an inner reinforcing layer disposed radially inward of the outer reinforcing layer, the inner reinforcing layer includes at least one inner ply having inner reinforcing cords arranged therein; the inner ply includes a first inner ply arranged on a side of an inner circumferential surface that contacts the spokes, and a second inner ply arranged adjacent to the first inner ply on the outer side of the first inner ply in the tire radial direction, the inner reinforcing cords of the first inner ply and the inner reinforcing cords of the second inner ply are inclined in opposite directions to each other at the same angle with respect to the tire circumferential direction, the spokes include a plurality of spoke plates; Each of the spoke plates is indirectly connected to the tread ring and the hub, and extends obliquely with respect to the tire axial direction, The spoke plates include a first spoke plate disposed on one side in the tire axial direction and a second spoke plate disposed on the other side when viewed from a thickness direction of the spoke plates, The first spoke plates and the second spoke plates are arranged alternately in the tire circumferential direction. A method for manufacturing airless tires.

9. A method for manufacturing an airless tire as described in Claim 8, wherein the first preparation step prepares the tread ring by vulcanizing and molding rubber.

10. The second preparation step includes preparing the hub by casting or forging a metal material; The method for manufacturing an airless tire according to claim 9 , wherein in the positioning step, an adhesive is applied to the cylindrical portion of the hub in advance.

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