Manufacturing method for non-pneumatic tires

Abstract

To provide a method for manufacturing non-pneumatic tires that can reduce vulcanization defects and adhesion failures of the tread rubber. [Solution] A method for manufacturing a non-pneumatic tire 1 is a method for manufacturing a non-pneumatic tire 1 having a support structure 10 having an outer annular portion 30 and a tread 50 fixed to the outer annular portion 30, comprising the steps of: filling a filling member 52 into a void 43 on the inner circumference side of the outer annular portion 30 of the support structure 10 (S2); housing the support structure 10, unvulcanized tread rubber 50a and filling member 52 in a mold 72 (S3); and pressurizing the void 43 of the support structure 10 and the internal space 82 on the inner circumference side of the filling member 52 (S4).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a non-pneumatic tire.

Background Art

[0002] Conventionally, a non-pneumatic tire including a support structure that supports a load from a vehicle, and a tread rubber that is located radially outside the support structure and extends along the tire circumferential direction is known (see, for example, Patent Document 1).

[0003] Generally, as a method for manufacturing a non-pneumatic tire, in the step of providing a tread of the tire, physical properties of the required tread rubber and an adhesive force between the support structure and the tread rubber are expressed by applying an external force to pressurize the adhesive surface of the tread rubber and the support structure.

Prior Art Documents

Patent Documents

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When the tread of a non-pneumatic tire peels off from the support structure, it hinders the running of the vehicle. Therefore, it is important to ensure the adhesive force between the support structure and the tread.

[0006] In the case of vulcanizing and adhering an unvulcanized tread rubber to a support structure in a non-pneumatic tire, a mold that moves from the radially outer side to the radially inner side to pressurize the unvulcanized tread rubber and the adhesive surface can be used. However, for the above pressurization, since a non-pneumatic tire has spokes, unlike a pneumatic tire, it is not possible to pressurize from the radially inner side to the radially outer side using a bladder.

[0007] Therefore, in the manufacturing method of non-pneumatic tires, the support structure deforms from the radially outward to the radially inward due to the pressure from the mold. As a result, the adhesive surface cannot be sufficiently pressurized, which may lead to vulcanization defects or bonding failures.

[0008] The present invention aims to provide a method for manufacturing non-pneumatic tires that can reduce vulcanization defects and bonding defects in the tread rubber. [Means for solving the problem]

[0009] A method for manufacturing a non-pneumatic tire according to one aspect of the present invention, comprising a support structure having an outer annular portion and a tread fixed to the outer annular portion, A step of temporarily bonding the unvulcanized tread rubber to the outer surface of the outer ring portion of the support structure, A step of filling the gap on the inner circumference side of the outer annular portion of the support structure with a filling member, A step of placing the support structure, the unvulcanized tread rubber, and the filling member inside a mold, The process includes a step of pressurizing the gap in the support structure and the inner circumferential space on the inner circumferential side of the filling member. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a method for manufacturing non-pneumatic tires that can reduce vulcanization defects and bonding defects of the tread rubber. [Brief explanation of the drawing]

[0011] [Figure 1] This is a side view showing a non-pneumatic tire according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view of the outer annular portion along line II-II in Figure 1. [Figure 3] This is a cross-sectional view taken along line II-II in Figure 1. [Figure 4] Figure 3 is a perspective view of a portion of a non-pneumatic tire, seen from an oblique angle. [Figure 5]This is a flowchart showing the steps for the vulcanization and bonding method of unvulcanized tread rubber. [Figure 6] This is a cross-sectional view of a non-pneumatic tire filled with a filling material. [Figure 7] This is a schematic diagram of a mold. [Figure 8] This is a magnified view of a portion of Figure 7. [Figure 9] This graph shows the change in tread rubber thickness when filled with a filler material and vulcanized (example). [Figure 10] This graph shows the change in tread rubber thickness when vulcanization is performed without filling with a filler material (comparative example). [Modes for carrying out the invention]

[0012] (Basic structure of non-pneumatic tires) A non-pneumatic tire 1 of one embodiment of the present invention will be described using Figures 1 to 4. Figure 1 is a side view showing a non-pneumatic tire according to one embodiment of the present invention. Figure 2 is a cross-sectional view taken along line II-II of the outer annular portion of Figure 1. Figure 3 is a cross-sectional view taken along line II-II of Figure 1. Figure 4 is a partial perspective view of the non-pneumatic tire, taken from an oblique angle of the portion shown in Figure 3.

[0013] The non-pneumatic tire 1 comprises a support structure 10 and a tread 50. Here, the support structure 10 supports the load from the vehicle. The tread 50 is located outside the support structure 10 in the tire radial direction X and extends along the tire circumferential direction C. The support structure 10 comprises an inner annular portion 20, an outer annular portion 30 arranged coaxially with the inner annular portion 20 on the outside of the inner annular portion 20 in the tire radial direction X, and 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.

[0014] As shown in Figure 2, the outer annular portion 30 has a reinforcing layer 32 embedded within the elastic body 31. Here, the reinforcing layer 32 extends along the tire circumferential direction C and is embedded throughout the entire circumference of the outer annular portion 30 and the entire area in the tire width direction Y.

[0015] (Detailed Structure of Non-Pneumatic Tire) FIG. 1 is a side view of the non-pneumatic tire 1 viewed from the side in a direction parallel to the tire rotation axis (tire meridian), that is, in the direction along the front and back sides of the paper in FIG. 1. The non-pneumatic tire 1 shown in FIG. 1 is in an unloaded state.

[0016] In FIGS. 1 and 4, C indicates the tire circumferential direction. In FIGS. 1 to 4, X indicates the tire radial direction. In FIGS. 2 to 4, Y indicates the tire width direction. In FIG. 1, the tire width direction Y is the front and back sides of the paper. In FIG. 3, E indicates the tire equatorial plane. In FIG. 3, the tire circumferential direction C is the front and back sides of the paper.

[0017] The tire circumferential direction C is the direction around the tire rotation axis and is the same direction as the direction in which the non-pneumatic tire 1 rotates. The tire radial direction X is the direction perpendicular to the tire rotation axis. The tire width direction Y is the direction parallel to the tire rotation axis. In FIGS. 2 to 4, one side of the tire width direction Y is shown as Y1, and the other side of the tire width direction Y is shown as Y2. The tire equatorial plane E shown in FIG. 3 is a plane perpendicular to the tire rotation axis and is located at the center of the tire width direction Y.

[0018] The inner annular portion 20 is an annular portion along the tire circumferential direction C that constitutes the inner peripheral portion of the non-pneumatic tire 1. The thickness and width of the inner annular portion 20 are set to be constant in order to improve uniformity. A tire wheel (not shown) is disposed in the space on the inner peripheral side of the inner annular portion 20. The inner peripheral portion of the inner annular portion 20 is fitted and mounted on the outer peripheral portion of the rim of the tire wheel. When the inner annular portion 20 is mounted on the rim, the non-pneumatic tire 1 is mounted on the tire wheel. <e

[0019] <e The inner annular portion 20 transmits the rotation of the tire wheel to the spokes 40 and the outer annular portion 30.

[0020] The outer annular portion 30 is an annular part along the tire circumferential direction C that constitutes the outer circumference of the non-pneumatic tire 1. The outer annular portion 30 is arranged concentrically with the inner annular portion 20 on the outer circumference side of the inner annular portion 20.

[0021] 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.

[0022] Multiple spokes 40 connect the inner annular portion 20 and the outer annular portion 30. The inner annular portion 20 and the outer annular portion 30, connected by the multiple spokes 40, are arranged concentrically with respect to each other. Each of the multiple spokes 40 is arranged independently along the tire circumferential direction C. As shown in Figure 1, when the non-pneumatic tire 1 is unloaded, the multiple spokes 40 extend linearly in the radial direction, approximately parallel to the tire radial direction X, when viewed from the side.

[0023] As shown in Figures 3 and 4, the spokes 40 of this embodiment include a plurality of first spokes 41 and a plurality of second spokes 42. The extending direction of both the first spokes 41 and the second spokes 42 is not parallel to the tire radial direction X when viewed 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 from the first spokes 41. The first spokes 41 and the second spokes 42 are arranged alternately in the tire circumferential direction C.

[0024] More specifically, as shown in Figures 3 and 4, the first spoke 41 extends inclined from the Y1 side, which is one side of the outer annular portion 30 in the tire width direction Y, toward the Y2 side, which is the other side of the inner annular portion 20 in the tire width direction Y. The second spoke 42 extends inclined from the Y2 side, which is the other side of the outer annular portion 30 in the tire width direction Y, toward the Y1 side, which is one side of the inner annular portion 20 in the tire width direction Y.

[0025] The inclination angles of the first spoke 41 and the second spoke 42 are the same. Therefore, when viewed from a direction along the tire circumferential direction C, the first spoke 41 and the second spoke 42 adjacent to each other in the tire circumferential direction C are arranged in a roughly X shape.

[0026] The tread 50 is provided on the outer circumferential surface of the outer annular portion 30 and constitutes the outermost periphery of the non-pneumatic tire 1. The tread 50 has a tread surface 51 on its outer circumferential surface that contacts the road surface. The tread surface 51 of the tread 50 is provided with a tread pattern formed by multiple grooves and flat areas, similar to conventional pneumatic tires.

[0027] (Manufacturing method for non-pneumatic tires) As a method for manufacturing non-pneumatic tires, a vulcanization bonding method for non-pneumatic tires, in which an unvulcanized tread rubber 50a is fixed to a support structure 10, is described.

[0028] The method for manufacturing a non-pneumatic tire 1 involves first preparing a cured support structure 10 and unvulcanized tread rubber 50a.

[0029] The method for manufacturing a non-pneumatic tire further comprises steps S1 to S5, as shown in Figure 5. Figure 5 is a flowchart of the steps for the vulcanization bonding method of unvulcanized tread rubber. Each step can be omitted or replaced as needed. Multiple steps may be performed simultaneously, or some or all of them may be performed in overlapping order.

[0030] (S1) Step of temporarily bonding the unvulcanized tread rubber 50a to the outer peripheral surface 30a of the outer annular portion 30 of the support structure 10. Unvulcanized tread rubber 50a is attached to the outer circumferential surface 30a of the support structure 10. In this case, as shown in Figure 6, a vulcanizing adhesive (not shown) is placed on the outer circumferential surface 30a. Figure 6 is a cross-sectional view of a non-pneumatic tire filled with a filler material.

[0031] The unvulcanized tread rubber 50a is not particularly limited, but may include, for example, natural rubber and carbon black, and may further contain sulfur, silica, etc. Here, the unvulcanized tread rubber 50a may contain synthetic rubber such as polyisoprene rubber or styrene-butadiene rubber together with natural rubber, or in place of natural rubber.

[0032] The vulcanizing adhesive 63 is an adhesive that hardens in a subsequent vulcanization process, and may contain a rubber component blended with a vulcanization accelerator and an acid acceptor. For example, the vulcanizing adhesive 63 may consist of a polymer material, an organic material, and a filler, dispersed in an organic solvent system such as xylene. Halogen-based polymers can be used as the polymer material and organic material. Carbon black, silica, etc. can be used as the filler.

[0033] (S2) A step of filling the gap 43 on the inner circumference side of the outer annular portion 30 of the support structure 10 with a filling member 52. As shown in Figure 6, the gap 43 of the support structure 10 is filled with the filling material 52.

[0034] The gap 43 is the space between multiple spokes 40, as shown in Figures 3 and 4. The filling member 52 is one or more members having the same shape as the gap 43. Filling with the filling member 52 means that the filling member 52 is placed in the gap 43 without any gaps or with small gaps. The filling member 52 may be placed to fill all of the gap 43 or to fill only a part of it. The filling member 52 may have its own void portion, and the void portion may be closed or open. As an example of the filling member 52, a pair of filling members can be inserted into the gap 43 from both sides in the direction of the tire axis.

[0035] The resin material of the filler member 52 is, for example, urethane resin. The elastic modulus of the filler member 52 is 50 MPa or more and 105 MPa or less. In particular, an elastic modulus of 90 MPa or more and 105 MPa or less is preferred. However, the filler member 52 may be made of other materials as long as the resin has a melting point of 160°C (the temperature at which vulcanization occurs) or higher.

[0036] The method for creating the filler member 52 will be explained. First, the first and second components of the material will be described.

[0037] [First agent] Vibracure A250 (manufactured by LANXESS) as 1,4-butanediol and PTMG1000 (manufactured by Mitsubishi Chemical Corporation) as polytetramethylene glycol are mixed in a predetermined mass ratio. Then, the mixture is degassed under vacuum at a predetermined temperature for 2 hours using a vacuum constant-temperature drying oven DP63 (manufactured by Yamato Scientific Co., Ltd.) to obtain the first component.

[0038] [Second drug] Adiprene LFPE560 (manufactured by LANXESS), used as a urethane prepolymer, is degassed under vacuum at a specified temperature for 2 hours using a vacuum constant-temperature drying oven DP63 (manufactured by Yamato Scientific Co., Ltd.) to obtain the second component.

[0039] After mixing the first and second agents, the mixture is stirred using a Mazelstar KK-5000W (manufactured by Kurabo Industries Ltd.) as a rotational and revolving mixer to obtain a thermosetting resin composition. Finally, the thermosetting resin composition is injected into a mold and then heat-cured at 130°C for 16 hours or more. As a result, a filler member 52 is obtained.

[0040] (S3) A step of placing the support structure 10, unvulcanized tread rubber 50a, and filling member 52 into the mold 72. Step S3 will be explained using Figures 7 and 8. Figure 7 is a schematic diagram of the mold. Figure 8 is a magnified view of a portion of Figure 7. The support structure 10, the unvulcanized tread rubber 50a, and the filling member 52 are sandwiched between the disc members 75 and 76, and the multiple sectors 77 and 78, which are divided in the circumferential direction of the tire, are clamped together.

[0041] The mold 72 has a pair of disc members 75 and 76. The disc members 75 and 76 are disc-shaped members. The disc members 75 and 76 are spaced apart in the direction of the tire rotation axis.

[0042] The mold 72 has a plurality of sectors 77 and 78 divided in the circumferential direction of the tire. The sectors 77 and 78 are arranged on the outer circumference side of the disc members 75 and 76. The sectors 77 and 78 each have recesses 77a and 78a extending in the circumferential direction on their inner circumferential surfaces. The recesses 77a and 78a are the parts in which the unvulcanized tread rubber 50a is stored during mold clamping. The sectors 77 and 78 are movable in the radial direction, and in the clamped state, the sectors 77 and 78 move towards the center and merge into an annular shape. After vulcanization molding is completed, the sectors 77 and 78 move radially outward to open the mold.

[0043] The temperature of the multiple sectors 77 and 78, which are divided in the circumferential direction of the tire, is preferably between 150°C and 165°C.

[0044] The mold 72 is supported by a support plate 79 and a number of legs 80.

[0045] As shown in Figures 7 and 8, the non-pneumatic tire 1 is set to be sandwiched between the outer ends of the disc members 75 and 76. In this state, a sealing member 88 is positioned between the pair of axial annular planes 30b of the outer annular member of the non-pneumatic tire 1 and the disc members 75 and 76, as shown in Figure 8. The sealing member 88 is, for example, a silicone packing. The thickness of the sealing member 88 is, for example, 7 mm or more and 9 mm or less.

[0046] The disc members 75 and 76 are tightened together by a tightening mechanism 86 consisting of nuts and bolts, bringing them closer to each other. As a result, the sealing member 88 is compressed, and the inner and outer circumferences of the outer annular portion 30 of the support structure 10 are sealed, creating a tightly sealed internal space 82.

[0047] (S4) A step of pressurizing the void 43 of the support structure 10 and the internal space 82 on the inner circumference side of the filling member 52. The gap 43 in the support structure 10 and the internal space 82 on the inner circumference side of the filling member 52 are pressurized. Specifically, the internal space 82 inside the mold 72 is pressurized.

[0048] As a pressurizing device, for example, an air compressor (not shown) is used. Gas from the air compressor is supplied into the mold 72 via port 73.

[0049] The pressure in the internal space 82 is preferably between 0.9 MPa and 1.0 MPa. The timing for initiating pressurization is either simultaneously with the start of vulcanization (mold clamping) or, for example, within 5 minutes after the start of vulcanization.

[0050] The pressurization time is controlled by opening and closing a valve. The temperature is controlled by PID control, and the pressure is controlled by an air booster.

[0051] The air temperature should be set between 20°C and 25°C (compressed air from an air compressor). However, an air temperature of 130°C or lower is acceptable.

[0052] The temperature of the filling member 52 is preferably, for example, above room temperature, 90°C or higher, and between 150°C and 165°C. If the filling member 52 is at a high temperature, it functions as a heat transfer medium, thus shortening the vulcanization time.

[0053] As explained above, in the method for manufacturing a non-pneumatic tire, during the vulcanization process of the non-pneumatic tire 1, a filler member 52 having a predetermined elasticity is placed in the gap 43 between the spokes 40, and the internal space 82 on the inner circumference side of the outer annular portion 30 is pressurized with air. As a result, the following effects are obtained.

[0054] In other words, the deformation of the support structure 10 due to the pressure exerted by sectors 77 and 78 moving from the outer circumference to the inner circumference is suppressed, and the unvulcanized tread rubber 50a is pressed firmly against the outer surface 30a. As a result, vulcanization defects and bonding defects of the unvulcanized tread rubber 50a can be reduced.

[0055] Figure 9 illustrates the thickness of the tire tread rubber obtained by the manufacturing method of the embodiment. In the example in Figure 9, unvulcanized tread rubber with a uniform thickness across the tire width direction is used. Figure 9 is a graph showing the change in tread rubber thickness when filled with a filler material and vulcanized (example). As is clear from Figure 9, the central part of the tread rubber is slightly thicker than the ends across the entire width. The maximum thickness difference between the central part and the ends is 0.32 mm, indicating that the thickness is nearly uniform. This means that the support structure did not deform, and therefore sufficient pressure was applied to both ends and the adhesive surface of the tread rubber.

[0056] Figure 10 illustrates the thickness of the tire tread rubber obtained by the manufacturing method of the comparative example. In the example in Figure 10, unvulcanized tread rubber with a uniform thickness across the tire width direction is used. Figure 10 is a graph showing the change in tread rubber thickness when vulcanized without filling with a filler (comparative example). As is clear from Figure 10, the ends of the tread rubber are thicker than the center across the entire width. The thickness difference between the center and the ends is 0.5 mm. This means that the support structure deformed, and therefore sufficient pressure was not applied to the ends and adhesive surfaces of the tread rubber.

[0057] (Description of the embodiment) <1> A method for manufacturing a non-pneumatic tire 1 is a method for manufacturing a non-pneumatic tire 1 having a support structure 10 having an outer annular portion 30 and a tread 50 fixed to the outer annular portion 30, Step (S1) involves temporarily bonding the unvulcanized tread rubber 50a to the outer peripheral surface 30a of the outer annular portion 30 of the support structure 10, Step (S2) involves filling the gap 43 on the inner circumference side of the outer annular portion 30 of the support structure 10 with the filling member 52, Step (S3) involves placing the support structure 10, the unvulcanized tread rubber 50a, and the filling member 52 into the mold 72. The process includes a step (S4) of pressurizing the void 43 in the support structure 10 and the internal space 82 on the inner circumference side of the filling member 52. Steps S3 and S4 may be performed partially or entirely simultaneously.

[0058] <2> <1> In the method for manufacturing a non-pneumatic tire 1 described above, the support structure 10 has an inner annular portion 20 and a plurality of spokes 40 that connect the outer annular portion 30 and the inner annular portion 20. The gap 43 is the space between multiple spokes 40.

[0059] <3> <1> <2> In the method for manufacturing a non-pneumatic tire 1 as described in any of the above, the filling member 52 has an elastic modulus of 50 MPa or more and 105 MPa or less.

[0060] <4> <1> ~ <3> In the method for manufacturing a non-pneumatic tire as described in any of the above, the step of pressurizing the internal space 82 includes the step of pressurizing the internal space 82 of the support structure 10 so that the pressure is 0.9 MPa or more and 1.0 MPa or less.

[0061] (Other embodiments) Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. In particular, the multiple embodiments and modifications described herein can be arbitrarily combined as needed. [Explanation of Symbols]

[0062] 1: Non-pneumatic tires 10:Support structure 40: Spokes 43 :Void 50: Tread 50a: Unvulcanized tread rubber 52: Filling material 82: Internal space (inner space) 86: Tightening mechanism

Claims

1. A method for manufacturing a non-pneumatic tire having a support structure having an outer annular portion and a tread fixed to the outer annular portion, A step of temporarily bonding the unvulcanized tread rubber to the outer surface of the outer ring portion of the support structure, A step of filling the gap on the inner circumference side of the outer annular portion of the support structure with a filling member, A step of pressurizing the gap in the support structure and the inner circumferential space on the inner circumferential side of the filling member, A method for manufacturing a non-pneumatic tire, comprising the following features.

2. The support structure has an inner annular portion and a plurality of spokes connecting the outer annular portion and the inner annular portion. The method for manufacturing a non-pneumatic tire according to claim 1, wherein the gap is the space between the plurality of spokes.

3. The method for manufacturing a non-pneumatic tire according to claim 1 or 2, wherein the filling member has an elastic modulus of 50 MPa or more and 105 MPa or less.

4. The method for manufacturing a non-pneumatic tire according to claim 2, wherein the step of pressurizing the inner circumferential space includes a step of pressurizing the inner circumferential space of the support structure so that the pressure is 0.9 MPa or more and 1.0 MPa or less.

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