Airless tire and method of manufacturing same

Abstract

An airless tire has a cylindrical tread ring 2 having a ground-contacting surface 21, a hub disposed on the radially inside of the tread ring 2 and fixed to an wheel shaft, and spokes connecting between the tread ring 2 and the hub. The tread ring 2 has a side wall 22 continued from the ground-contacting surface 21 and forming a ring side surface. The side wall 22 has a supporting portion 23 which, when the tread ring 2 alone is horizontally laid on a horizontal surface H, contacts with a horizontal surface H and supports the tread ring 2 so that a ring axis A2 is oriented in a direction perpendicular to the horizontal surface H.

Claims

1. An airless tire, comprising: a tread ring having a cylindrical form and a ground contacting surface; a hub positioned on a radially inside of the tread ring and configured to be fixed to a wheel shaft; and a plurality of spokes positioned between the tread ring and the hub such that the plurality of spokes is connecting the tread ring and the hub, wherein the tread ring has a side wall extending from the around contacting surface and forming a ring side surface, the side wall has a supporting portion configured to support the tread ring such that when the tread ring alone is horizontally laid on a horizontal surface, the supporting portion contacts with the horizontal surface and that a ring axis of the tread ring is oriented in a direction perpendicular to the horizontal surface, and the supporting portion is formed in a plurality such that the plurality of supporting portions are intermittently provided in the tire circumferential direction.

2. The airless tire as set forth in claim 1, wherein the tread ring is formed such that the side wall has concave letters or patterns recessed inwardly in a tire axial direction from the supporting portion.

3. The airless tire as set forth in claim 2, wherein the tread ring is formed such that in a front view of the side wall, the plurality of supporting portions has an area which is in a range of 10% to 100% of an area of the side wall.

4. The airless tire as set forth in claim 3, wherein the tread ring comprises a tread rubber portion and a reinforcing cord layer embedded in the tread rubber portion.

5. The airless tire as set forth in claim 4, wherein the plurality of spokes is made of resin material.

6. The airless tire as set forth in claim 2, wherein the tread ring comprises a tread rubber portion and a reinforcing cord layer embedded in the tread rubber portion.

7. The airless tire as set forth in claim 6, wherein the plurality of spokes is made of resin material.

8. The airless tire as set forth in claim 1, wherein the tread ring is formed such that in a front view of the side wall, the plurality of supporting portions has an area which is in a range of 10% to 100% of an area of the side wall.

9. The airless tire as set forth in claim 8, wherein the tread ring comprises a tread rubber portion and a reinforcing cord layer embedded in the tread rubber portion.

10. The airless tire as set forth in claim 9, wherein the plurality of spokes is made of resin material.

11. The airless tire as set forth in claim 1, wherein the tread ring comprises a tread rubber portion and a reinforcing cord layer embedded in the tread rubber portion.

12. The airless tire as set forth in claim 11, wherein the plurality of spokes is made of resin material.

13. The airless tire as set forth in claim 11, wherein the plurality of supporting portions has three supporting portions.

14. The airless tire as set forth in claim 11, wherein the reinforcing cord layer comprises a belt layer.

15. The airless tire as set forth in claim 11, wherein the reinforcing cord layer comprises a first belt layer, a second belt layer and a shear layer interposed between the first belt layer and the second belt layer.

16. The airless tire as set forth in claim 11, wherein the reinforcing cord layer comprises a belt layer comprising at least one belt ply of tire cords.

17. The airless tire as set forth in claim 11, wherein the reinforcing cord layer comprises a first belt layer comprising at least one belt ply of tire cords, a second belt layer comprising at least one belt ply of tire cords, and a shear layer interposed between the first belt layer and the second belt layer.

18. The airless tire as set forth in claim 1, wherein the plurality of spokes is made of resin material.

19. The airless tire as set forth in claim 1, wherein the plurality of supporting portions has three supporting portions.

20. A method of manufacturing an airless tire, comprising: forming, on a side wall of a tread ring, a plurality of supporting portions configured to support the tread ring such that when the tread ring alone is horizontally laid on a horizontal surface, the plurality of supporting portions are intermittently provided in the tire circumferential direction and contact with the horizontal surface and that a ring axis of the tread ring is oriented in a direction perpendicular to the horizontal surface; preparing a mold having a cavity configured to mold a plurality of spokes and a horizontal surface configured to hold the tread ring and a hub; laying the tread ring and the hub on the horizontal surface of the mold; injecting, into the cavity of the mold, a material which forms the plurality of spokes; and curing the material such that an airless tire is formed and has the tread ring having a cylindrical form and a ground contacting surface, the hub positioned on a radially inside of the tread ring and configured to be fixed to an wheel shaft, and the plurality of spokes positioned between the tread ring and the hub and connecting the tread ring and the hub and that the tread ring has the side wall extending from the ground contacting surface and forming a ring side surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 A perspective view showing an embodiment of the airless tire of the present invention.

(2) FIG. 2 A perspective view showing a tread ring in FIG. 1.

(3) FIG. 3 A cross-sectional view of the tread ring in FIG. 2 in the state horizontally laid on the horizontal surface.

(4) FIG. 4 A perspective view showing a modification of the tread ring in FIG. 2.

(5) FIG. 5 A flow chart showing an example of the steps of the method of manufacturing the airless tire in FIG. 1.

(6) FIG. 6 A plan view of a casting mold used to mold the spokes of the airless tire in FIG. 1

(7) FIG. 7 A cross sectional view of the casting mold in

(8) FIG. 6 taken along line B-B.

MODE FOR CARRYING OUT THE INVENTION

(9) Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(10) FIG. 1 is a perspective view of an airless tire 1 according to the present embodiment.

(11) As shown in FIG. 1, the airless tire 1 of the present embodiment has a cylindrical tread ring 2 having a ground contacting surface 21, a hub 3 disposed on the radially inside of the tread ring 2 and fixed to a wheel shaft, and spokes 4 connecting between the tread ring 2 and the hub 3.

(12) In the present embodiment, shown is a case in which the airless tire 1 is formed as a passenger car tire.

(13) FIG. 2 shows the tread ring 2. The tread ring 2 has the ground contacting surface 21, and a side wall 22 being continuous from the ground contacting surface 21 and forming a ring side surface. The tread ring 2 has a reinforcing cord layer 6 embedded in a tread rubber portion 20.

(14) For the tread rubber portion 20, a rubber compound which excels in the friction on the ground and the wear resistance is preferably used.

(15) In the ground contacting surface 21 which is an outer circumferential surface of the tread ring 2, tread grooves (not shown) are formed in various configurations in order to provide wet performance.

(16) The reinforcing cord layer 6 of the present embodiment has a first belt layer 61, and a second belt layer 62 laid radially outside the first belt layer.

(17) Between the first belt layer 61 and the second belt layer 62, a shear layer 68 made of a rubber having high hardness is disposed. The reinforcing cord layer 6 may be formed by only the first belt layer 61.

(18) The first belt layer 61 is composed of at least one ply, in this example two belt plies 63 and 64, of tire cords arranged at an angle of for example 10 to 45 degrees with respect to the tire circumferential direction.

(19) Similarly, the second belt layer 62 is composed of at least one ply, in this example two belt plies 65 and 66, of tire cords arranged at an angle of for example 10 to 45 degrees with respect to the tire circumferential direction.

(20) Between the plies, the respective tire cords mutually intersect, and thereby, the rigidity of the tread ring 2 is increased. It is desirable that the thickness of the shear layer 68 is, for example, 2 to 7 mm.

(21) A band ply in which a tire cord is wound helically in the tire circumferential direction may be disposed radially outside the second belt layer 62 where appropriate.

(22) As the tire cords of the first belt layer 61 and the second belt layer 62, steel cords and organic fiber cords can be used as appropriate.

(23) In the case of the organic fiber cords, high modulus fibers such as high strength high modulus aramid, polyethylene naphthalate (PEN), polyethylene terephthalate (PET) can be suitably employed.

(24) Such tread ring 2 is formed by forming a raw tread ring in advance, and then, vulcanization molding the raw tread ring within a vulcanization mold.

(25) The raw tread rings is formed on a cylindrical drum by circumferentially sequentially winding a sheet-like member for forming the first belt layer 61, a sheet-like member for forming the shear layer 68, a sheet-like member for forming the second belt layer 62, and a sheet-like member for forming the tread rubber portion 20.

(26) As shown in FIG. 1, the hub 3 has a disk portion 31 fixed to a wheel shaft, and a cylindrical portion 32 formed at the outer circumference of the disk portion 31.

(27) A side wall 33 is formed at an edge of the cylindrical portion 32. The side wall 33 is made up of a flat surface perpendicular to the hub axis A3.

(28) The hub 3 can be made of a metal material, for example, steel, aluminum alloy, magnesium alloy or the like as in the conventional tire wheels.

(29) The spokes 4 are formed by cast molding of a polymer material.

(30) The spoke 4 has a plate-like shape, and a plurality of the spokes are disposed in the tire circumferential direction.

(31) FIG. 3 shows a state of the tread ring 2 horizontally laid on a horizontal surface H.

(32) The expression horizontally laid refers to a state being put on a horizontal surface H in a lay down posture so that the side wall 22 of the tread ring 2 becomes opposite to the horizontal surface H.

(33) The side wall 22 of the tread ring 2 is provided with a supporting portion 23 contacting with the horizontal surface H when the tread ring 2 alone is horizontally laid on the horizontal surface H to support the tread ring 2.

(34) The support portion 23 projects outward most in the axial direction of the tread ring 2 so as to contact with the horizontal surface H when the tread ring 2 is horizontally laid. The supporting portion 23 supports the tread ring 2 such that the ring axis A2 is oriented in a direction perpendicular to the horizontal surface H when the tread ring 2 is horizontally laid. On the other hand, when the hub 3 is horizontally laid on the horizontal surface H, the side wall 33 supports the hub 3 so that the hub axis A3 is oriented in a direction perpendicular to the horizontal surface H.

(35) Thereby, the ring axis A2 of the tread ring 2 coincides with the hub axis A3 of the hub 3 shown in FIG. 1, that is, the tire axis A1 of the airless tire 1 with a high degree of accuracy, and the uniformity of the airless tire 1 is improved.

(36) In this embodiment, as shown in FIG. 2, the supporting portion 23 is a flat surface 24 which is continuous in the tire circumferential direction.

(37) The flat surface 24 constituting the supporting portion 23 is the side surface of the main body of the tread ring 2, which is parallel with the tire equatorial plane, namely, perpendicular to the ring axis A2.

(38) As the supporting portion 23 is continuous in the tire circumferential direction, the lay down posture of the tread ring 2 becomes more stable, and it becomes possible to coincide the ring axis A2 of the tread ring 2 with the hub axis A3 of the hub 3 with a high degree of accuracy.

(39) The side wall 22 of the tread ring 2 is provided with characters 25 denoting the brand name, size and the like of the airless tire 1.

(40) Likewise, the side wall 22 of the tread ring 2 may be patterned (not shown) in order to improve the ornamental design of the airless tire 1.

(41) As already mentioned, since the supporting portion 23 is formed by the flat surface 24 at the axially outermost position of the tread ring 2, the characters 25 and the like of the present embodiment are concaves which are recessed axially inwardly from the supporting portion 23.

(42) Such characters 25 and the like do not adversely effect on the contact between the supporting portion 23 and the horizontal surface H, therefore, the orientation of the ring axis A2 with respect to the horizontal surface H can be maintained vertically.

(43) It is desirable that the supporting portion 23 has no sprues sucked into air channels of a mold used to vulcanization molding the tread ring 2.

(44) Similarly, it is desirable that the supporting portion 23 has no sprues overflowed from mold parting surfaces of the mold used to vulcanization molding the tread ring 2. In the case where overflow sprues are formed in the supporting portion 23, it is desirable that the overflow sprues are formed uniformly in the tire circumferential direction.

(45) As a result of the overflow sprues formed uniformly in the tire circumferential direction, the orientation of the ring axis A2 with respect to the horizontal surface H can be maintained vertically.

(46) It is preferable that, in a front view of the side wall 22, the area of the supporting portion 23 is at least 10% of the area of the side wall 22.

(47) If the area of the supporting portion 23 is less than 10% of the area of the side wall 22, there is a possibility that the supporting portion 23 is deformed when the tread ring 2 is laid on the horizontal surface H, and the direction of the ring axis A2 with respect to the horizontal surface H is varied.

(48) Most preferably, the area of the supporting portion 23 is 100% of the area of the side wall 22, namely, the entire side wall 22 is constituted by the supporting portion 23.

(49) In this case, the deformation of the supporting portion 23 can be minimized, therefore, it becomes possible to maintain the orientation of the ring axis A2 with respect to the horizontal surface H with high accuracy.

(50) FIG. 4 shows a tread ring 2A which is a modification of the tread ring 2. In this tread ring 2A, a plurality of supporting portions 23A are provided intermittently in the tire circumferential direction.

(51) The supporting portions 23A protrude outwardly in the axial direction of the tread ring 2A from the side surface of the main body of the tread ring 2A.

(52) The support portions 23A support the tread ring 2A so that the ring axis A2 is oriented in a direction perpendicular to the horizontal surface H when the tread ring 2A is horizontally laid. Thereby, the ring axis A2 of the tread ring 2A coincides with the hub axis A3 of the hub 3 or the tire axis A1 of the airless tire 1 with high accuracy, and the uniformity of the airless tire 1 is improved.

(53) In the tread ring 2A, since the supporting portions 23A protrude from the main body of the side wall 22 of the tread ring 2A, characters 25A denoting the brand name, size and the like of the airless tire 1 can be formed so as to protrude from the main body of the side wall 22 of the tread ring 2A. In this case, the protruding height of the characters 25A is less the protruding height of the supporting portions 23A. If the protruding height of the characters 25A is equal to the protruding height of the supporting portions 23A, the character 25A or the like constitute part of the supporting portions 23A in substance.

(54) It is desirable that, in a front view of the side wall 22, the area S3 of the supporting portions 23A is more than 10% of the area S2 of the side wall 22.

(55) If the area S3 of the supporting portions 23A is less than 10% of the area S2 of the side wall 22, there is a possibility that the supporting portions 23A are deformed when the tread ring 2A is horizontally laid on the horizontal surface H, and the direction of the ring axis A2 with respect to the horizontal surface H is varied.

(56) FIG. 5 is a flowchart exemplifying the steps of a method of manufacturing the airless tire 1. As shown in FIG. 5, the method of manufacturing the airless tire 1 comprises a step (#1) of forming the supporting portion 23 in the side wall 22 of the tread ring 2, a step (#2) of preparing a casting mold defining the cavity for molding the spokes 4, a step (#3) of horizontally laying the tread ring 2 and the hub 3 on the horizontal surface of the casting mold, a step (#4) of closing the casting mold, a step (#5) of injecting the material forming the spokes 4 into the cavity of the casting mold, and curing it, a step (#6) of opening the casting mold, and a step (#7) of demolding the airless tire 1 from the casting mold.

(57) In the step (#1), there is formed the supporting portion 23 which contacts with the horizontal surface H when the tread ring 2 alone is horizontally laid on the horizontal surface H. The supporting portion 23 supports the tread ring 2 in the horizontally laid state of the tread ring 2 so that the ring axis A2 is oriented in a direction perpendicular to the horizontal surface H.

(58) In this embodiment, by the use of a vulcanization mold for vulcanization molding the tread ring 2, the supporting portion 23 is molded together with the ground contacting surface 21 and the main body of the side wall 22.

(59) FIGS. 6 and 7 show the casting mold 100 for molding the spokes 4 of the airless tire 1 prepared in the step (#2). The casting mold 100 has a first side part 101, an outer circumferential part 102, an inner circumferential part 103, and a second side part 104.

(60) The first side part 101 comes into contact with the side walls 22 and 33 on one side, of the tread ring 2 and the hub 3 which are laid horizontally.

(61) The outer circumferential part 102 positions and holds the ground contacting surface 21 of the tread ring 2.

(62) The inner circumferential part 103 positions and holds the inner circumferential surface of the hub 3.

(63) The second side part 104 contacts with the side walls 22 and 33 on the other side, of the tread ring 2 and the hub 3.

(64) The first side part 101 and second side part 104 are provided with first spoke forming portions 105 and second spoke forming portions 106 which are comb-shaped and for forming the spokes 4.

(65) The first spoke forming portions 105 and the second spoke forming portions 106 are arranged alternately in the tire circumferential direction, and protrude into a space between the inner circumferential surface of the tread ring 2 and the outer circumferential surface of the hub 3.

(66) A cavity 107 for molding the spokes 4 is partitioned by the inner circumferential surface of the tread ring 2, the outer circumferential surface of the hub 3, the first side part 101, the first spoke forming portions 105, the second side part 104, and the second spoke forming portions 106.

(67) As shown in FIG. 7, the first side part 101 has a horizontal surface 108 for holding the tread ring 2 and the hub 3. Similarly, the second side part 104 has a horizontal surface 109 for holding the tread ring 2 and the hub 3.

(68) In the step (#3), the tread ring 2 and the hub 3 are horizontally laid on the horizontal surface 108 of the casting mold 100.

(69) At this time, the tread ring 2 is positioned and held by the horizontal surface 108 of the first side part 101, the outer circumferential part 102, and the horizontal surface 109 of the second side part 104.

(70) The supporting portion 23 is in contact with the horizontal surface 108, and supports the tread ring 2 so that the ring axis A2 is oriented in a direction perpendicular to the horizontal surface 108.

(71) similarly, the hub 3 is positioned and held by the horizontal surface 108 of the first side part 101, the inner circumferential part 103, and the horizontal surface 109 of the second side part 104.

(72) The side wall 33 of the hub 3 supports the hub 3 so that the hub axis A3 is oriented in a direction perpendicular to the horizontal surface 108.

(73) Thus, the hub axis A3 of the hub 3 and the ring axis A2 of the tread ring 2 are arranged parallel with each other. Further, the ground contacting surface 21 of the tread ring 2 is positioned in the radial direction by the outer circumferential part 102, and

(74) the inner circumferential surface of the hub 3 is positioned in the radial direction by the inner circumferential part 103, therefore, the tread ring 2 and the hub 3 are accurate centered, and the ring axis A2 coincides with the hub axis A3 with a high degree of accuracy. Thus, the uniformity of the airless tire 1 is improved.

(75) In the subsequent step (#4), the second side part 104 is moved, and the casting mold 100 is closed.

(76) Thus, the cavity 107 for molding the spokes 4 is made out within the casting mold 100.

(77) In the step (#5), the resin material for forming the spokes 4 is injected into the cavity 107 and cured.

(78) Thereby, the tread ring 2 is united with the hub 3 through the spokes 4, and the airless tire 1 is formed.

(79) As to the injected resin material, a thermoplastic resin or a thermosetting resin can be used.

(80) From the viewpoint of safety, the thermosetting resins, for example, epoxy resins, phenolic resins, urethane resins, silicone resins, polyimide resins, melamine resins and the like are preferred.

(81) Particularly, urethane-based resins can be used more preferably because of the excellent elastic properties.

(82) In the subsequent step (#6), the second side part 104 is moved upward in FIG. 7 to open the casting mold 100.

(83) In the step (#7), the airless tire 1 is demolded from the casting mold 100.

(84) While detailed description has been made of the airless tire and the method of manufacturing the same according to the present invention, the present invention can be embodied in various forms without being limited to the illustrated embodiments.

WORKING EXAMPLES

(85) Airless tires having the basic structure in FIG. 1 were experimentally manufactured based on the specifications listed in Table 1. And the stability of the tread ring itself in the lay down posture, the RRO, and the vibration of a vehicle were evaluated.

(86) <Stability in Lay Down Posture>

(87) The tread ring alone was horizontally laid on a horizontal surface, and the stability of the posture was sensorily evaluated by a tester.

(88) <RRO>

(89) The airless tire was measured for the RRO at a tire equator portion and both shoulder portions, and their average value was calculated. In the results, a smaller value is better.

(90) <Vehicle Vibration Test>

(91) Small electrical vehicles fitted with the respective airless tires were brought into a test course, and vibrations during running were sensorily evaluated by a tester.

(92) In the results, A denotes a level where no vibrations were felt, B denotes a level where vibrations being acceptable in the market were felt, and C denotes a level where large vibrations being not acceptable in the market were felt.

(93) TABLE-US-00001 TABLE 1 comparative working working working working working working working working example example 1 example 2 example 3 example 4 example5 example 6 example 7 example 8 supporting portion(s) absent present present present present present present present present form of continuous continuous continuous continuous intermittent intermittent intermittent intermittent supporting portion(s) number of 0 1 1 1 1 3 3 3 3 supporting portion(s) form of characters convex none concave concave concave concave convex concave concave or the like spews present absent absent present absent absent absent absent absent overflow spews present absent absent absent present absent absent absent absent (uniform) S3/S2 (%) 0 100 95 95 95 50 50 10 5 stability in lay down unstable stable stable stable stable stable stable stable stable posture (grade) average RRO (mm) 2.5 0.5 0.6 0.7 0.7 0.8 0.8 0.9 1.0 vehicle vibration C A A A A A A A B test (grade)

(94) As shown in Table 1, it was confirmed that the airless tires as Working Examples were improved in the uniformity as compared to comparative examples.

DESCRIPTION OF THE SIGNS

(95) 1 airless tire

(96) 2 tread ring

(97) 2A tread ring

(98) 3 hub

(99) 4 spoke

(100) 21 ground contacting surface

(101) 22 side wall

(102) 23 supporting portion

(103) 23A supporting portion

(104) 25 character

(105) 25A character

(106) 100 casting mold

(107) 108 horizontal surface

(108) A2 ring axis

(109) H horizontal surface