Non-pneumatic tire

Abstract

This non-pneumatic tire is provided with a tread ring, a wheel which is arranged radially inside of the tread ring, and spokes which are interposed between the tread ring and the wheel. Further, the wheel has a disc part to which the vehicle shaft is linked, and a rim part which is connected on the inner peripheral side to the disc part and is joined on the outer peripheral side to the spokes. In this configuration, the average thickness (T1) of the disc part is set to be less than the average thickness (T2) of the rim part. In other words, the relation T1<T2 holds.

Claims

1. A non-pneumatic tire and wheel assembly comprising a tread part with a cylindrical shape that is in contact with a ground surface, a wheel part disposed inside the tread part in a radial direction, and a spoke part interposed between the tread part and the wheel part, wherein: the wheel part includes a disk part to which an axle is connected, and a rim part whose inner circumferential side is continuously connected to the disk part and outer circumferential side is joined to the spoke part; the thickness of the rim part is substantially constant; an average thickness of the disk part is smaller than an average thickness of the rim part; the thickness of the disk part decreases by tapering radially outwards from a center portion of the disk part; and the disk part is continuously convex from the center portion to the rim part.

2. The non-pneumatic tire and wheel assembly according to claim 1, wherein the spoke part includes an internal ring part to which the rim part is joined, an external ring part for which the tread part is provided, and a plurality of spokes that integrally connect the internal ring part and the external ring part.

3. The non-pneumatic tire and wheel assembly according to claim 1, wherein in the wheel part, the disk part and the rim part are provided as separate members and are joined to each other.

4. The non-pneumatic tire and wheel assembly according to claim 1, wherein the wheel part is formed by a single member that integrally includes the disk part and the rim part.

5. A non-pneumatic tire and wheel assembly comprising a tread part with a cylindrical shape that is in contact with a ground surface, a wheel part disposed inside the tread part in a radial direction, and a spoke part interposed between the tread part and the wheel part, wherein: the wheel part includes a disk part to which an axle is connected, and a rim part whose inner circumferential side is continuously connected to the disk part and outer circumferential side is joined to the spoke part; the thickness of the rim part is substantially constant; an average thickness of the disk part is smaller than an average thickness of the rim part; the disk part comprises a bend in a rotating direction that receives a compressive bending force in a circumferential direction; the thickness of the disk part decreases by tapering radially outwards from a center portion of the disk part; and the disk part is continuously convex from the center portion to the rim part.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is an overall schematic perspective view of a non-pneumatic tire according to one embodiment of the present invention;

(2) FIG. 2 is an exploded perspective view of the non-pneumatic tire in FIG. 1;

(3) FIG. 3 is a side cross-sectional view of the non-pneumatic tire in FIG. 1;

(4) FIGS. 4A, 4B, and 4C are graphs each illustrating a transient characteristic of cornering force of various tires for each vehicle speed;

(5) FIG. 5 is a graph expressing a relation between load and cornering power when a vehicle makes a turn while traveling;

(6) FIG. 6 is a side cross-sectional view of a non-pneumatic tire according to another embodiment; and

(7) FIG. 7 is a side cross-sectional view of a non-pneumatic tire according to still another embodiment.

DESCRIPTION OF EMBODIMENTS

(8) Preferred embodiments of a non-pneumatic tire according to the present invention are hereinafter described in detail with reference to the attached drawings.

(9) FIG. 1 to FIG. 3 are an overall schematic perspective view, an exploded perspective view, and a side cross-sectional view of a non-pneumatic tire 10a according to the present embodiment, respectively. This non-pneumatic tire 10a includes a cylindrical tread ring 12 (tread part), a wheel part 14a disposed inside the tread ring 12 in a radial direction thereof, and a spoke part 16a that connects the tread ring 12 and the wheel part 14a.

(10) The tread ring 12 is formed by an annular body made of rubber with its outer circumferential wall serving as a ground contact surface. Note that the ground contact surface is provided with tread grooves that are not illustrated. By the tread grooves, sufficient grip force is obtained even on a wet road surface.

(11) The wheel part 14a includes a disk part 20a with a disk shape, and a rim part 22a with a cylindrical shape that is continuously connected to the outside of the disk part 20a in a radial direction thereof. In this structure, a hub hole 24 is formed at a center of the disk part 20a. Through the hub hole 24, a front end part 28 of an axle 26 indicated by a virtual line in FIG. 3 is inserted. Around the hub hole 24, a plurality of bolt insertion holes 30 are formed. To each bolt insertion hole 30, a bolt part 34 provided on the axle 26 side is inserted, and the bolt part 34 is fixed by a nut that is not illustrated.

(12) The disk part 20a is manufactured by, for example, press-forming a metal plate material similar to that of a conventional tire wheel, such as a steel material, aluminum alloy, or magnesium alloy.

(13) On the other hand, the rim part 22a is formed by a cylindrical body, and in this case, the rim part 22a is a member manufactured separately from the disk part 20a. The rim part 22a is obtained by, for example, cutting the aforementioned metal plate member as a belt-shape body, thereafter bending the belt-shape body to bring end surfaces thereof into contact with each other, and joining the end surfaces in contact by a suitable method such as friction stir joining or welding. After the entire disk part 20a is housed inside the rim part 22a, an outer edge part of the disk part 20a and an inner circumferential wall of the rim part 22a are joined to each other by welding or the like, for example.

(14) Here, when the average thickness of the disk part 20a is T1 and the average thickness of the rim part 22a is T2 (see FIG. 3), the relation of T1<T2 is satisfied. That is to say, the average thickness T1 of the disk part 20a is smaller than the average thickness T2 of the rim part 22a.

(15) In this case, each of the disk part 20a and the rim part 22a is manufactured by a metal plate material with substantially the same thickness. Therefore, the thickness of each of the disk part 20a and the rim part 22a is substantially constant over the entire part. Thus, the relation of T1<T2 is satisfied entirely over the disk part 20a and the rim part 22a.

(16) The spoke part 16a includes an external ring part 40a with an annular shape to which the tread ring 12 is fitted, an internal ring part 42a with an annular shape that is joined to the rim part 22a, and a plurality of spokes 44 that extend radially along the diameter of the non-pneumatic tire 10a. An inner circumferential side of each spoke 44 is integrally connected to the internal ring part 42a, and an outer circumferential side thereof is integrally connected to the external ring part 40a. The spoke part 16a as described above is formed of, for example, a polymer material such as thermoplastic resin or thermosetting resin. Preferred examples of the thermosetting resin include epoxy-based resin, phenol-based resin, urethane-based resin, silicone-based resin, polyimide-based resin, and melamine-based resin.

(17) The non-pneumatic tire 10a according to the present embodiment is basically configured as described above, and next, the operation effect thereof is described.

(18) As described above, the disk part 20a and the rim part 22a in the wheel part 14a of the non-pneumatic tire 10a are the separate members that are manufactured individually. Therefore, the shape of the disk part 20a can be changed variously and the thickness and the height of the rim part 22a can be changed variously. Thus, the collapse (or tilting) rigidity of the disk part 20a and/or the flexural rigidity of the rim part 22a in the radial direction thereof can be set particularly easily.

(19) The non-pneumatic tire 10a with the above structure contributes to travelling when, for example, the non-pneumatic tire 10a is attached to the axle 26 of an MEV and rotated through the axle 26 by an action of a motor. In this case, the tread ring 12 is in contact with a ground surface (road surface). In addition, the spokes 44 of the spoke part 16a and the disk part 20a of the wheel part 14a receive the compressive bending force that acts in a circumferential direction of the non-pneumatic tire 10a so as to be bent in a rotating direction. That is to say, the spokes 44 and the disk part 20a function as an elastic body.

(20) When the MEV or the like travels, the vehicle is turned at a curve or the like. In other words, cornering is performed. Here, a lateral force along a longitudinal direction of the axle 26 acts on the tread ring 12.

(21) In a case where the slip angle of the tire has suddenly changed because of a sudden steering operation, a cornering force occurs with a time delay. This phenomenon is known as a transient characteristic of cornering, and occurs because of an influence from a change speed of the slip angle, a lateral rigidity of the tire, and a travel speed.

(22) Each of FIG. 4A to FIG. 4C illustrates the transient characteristics of the cornering forces when the vehicle (MEV) including various tires travels at 20 km/h, 40 km/h, and 80 km/h, respectively. In the drawings, a solid line expresses a slip angle input and a dashed line expresses the transient characteristic obtained by the non-pneumatic tire 10a. In addition, a one-dot chain line and a two-dot chain line respectively express the transient characteristic of the pneumatic tire, and the transient characteristic of the non-pneumatic tire in which the average thickness T1 of the disk part 20a is larger than the average thickness T2 of the rim part 22a. FIG. 4A to FIG. 4C indicate that the non-pneumatic tire 10a can obtain the transient characteristic similar to that of the pneumatic tire.

(23) Here, the average thickness T1 of the disk part 20a is smaller than the average thickness T2 of the rim part 22a. Therefore, the disk part 20a is easily bent. Thus, a linear relation as illustrated in FIG. 5 is obtained between the load at the turning and the cornering power corresponding to the increase rate of the cornering force. As the load is smaller, the speed is lower, and as the load is larger, the speed is higher.

(24) In FIG. 5, a curved line C corresponds to the result obtained from the pneumatic tire, and a straight line M drawn with a thick solid line corresponds to the result obtained from the non-pneumatic tire satisfying T1>T2. Straight lines L1, L2, L3, and L4 drawn with a thin solid line, a dashed line, a one-dot chain line, and a two-dot chain line respectively are obtained from the non-pneumatic tire 10a and a non-pneumatic tire 10b according to the present embodiment satisfying T1<T2 (see FIG. 6). More specifically, the straight line L1 corresponds to a result obtained from the non-pneumatic tire 10b including a wheel part 14b formed by a single member that integrally includes a disk part 20b and a rim part 22b obtained from an aluminum alloy expanded material, and T1 is 4 mm and T2 is 7 mm. The straight lines L2 to L4 correspond to results obtained from the non-pneumatic tire 10a including the wheel part 14a in which the disk part 20a and the rim part 22a are manufactured individually as separate parts, having T1 of 2 mm, 2 mm, and 2 mm, respectively, and T2 of 2.3 mm, 2.5 mm, and 2.8 mm, respectively.

(25) In FIG. 5, it can be realized that by setting T1<T2, the change of the responsiveness by the speed increase can be reduced although the responsiveness is low in the low-speed range, and in the high-speed range, the transient characteristic similar to that of the pneumatic tire can be obtained. Therefore, it is possible to dispel concerns that the user feels a sense of discomfort. That is to say, according to the present embodiment, the user feels as comfortable as he feels in the vehicle having pneumatic tires.

(26) The present invention is not limited particularly to the aforementioned embodiment and various changes can be made within the range not departing from the gist of the present invention.

(27) For example, as is understood from the above description, the wheel part may be formed by a single member that integrally includes the disk part and the rim part. The non-pneumatic tire 10b with such a structure is illustrated in FIG. 6. Note that the same components as those in FIG. 1 to FIG. 3 are denoted with the same reference signs. In addition, the reference signs 14b, 20b, and 22b respectively denote the wheel part, the disk part, and the rim part.

(28) In addition, as illustrated in FIG. 6, the thickness of the disk part 20b may be changed. In this case, the average thickness T1 may be calculated from the thicknesses of the respective portions of the disk part 20b (for example, T1′, T1″, and the like) and this calculated value may be made smaller than the average thickness T2 of the rim part 22b.

(29) In addition, a non-pneumatic tire 10c illustrated in FIG. 7 may be provided. In this case, a wheel part 14c includes a disk part 20c that is flat, and a spoke part 16c includes an internal ring part 42c provided with a thick part 50. Corresponding to the thick part 50, a rim part 22c includes an annular concave part 52.

REFERENCE SIGNS LIST

(30) 10a to 10c: non-pneumatic tire 12: tread ring 14a to 14c: wheel part 16a, 16c: spoke part 20a to 20c: disk part 22a to 22c: rim part 26: axle 30: bolt insertion hole 40a: external ring part 42a, 42c: internal ring part 44: spoke 50: thick part