Patent Application
20210394559
The present invention relates to a non-pneumatic tire.
Priority is claimed on Japanese Patent Application No. 2018-224766, filed on Nov. 30, 2018, the content of which is incorporated herein by reference.
Conventionally, as shown in, for example, Patent Document 1, there is known a non-pneumatic tire including an inner cylinder that is attached to an axle, an outer cylinder that surrounds the inner cylinder from an outside in a tire radial direction and has a tread member mounted on an outer peripheral surface thereof, and a plurality of connecting members that connect an outer peripheral surface of the inner cylinder and an inner peripheral surface of the outer cylinder, in which the outer cylinder and the connecting members are formed to be elastically deformable.
Japanese Unexamined Patent Application, First Publication No. 2016-172522
However, in the conventional non-pneumatic tire, the outer cylinder may be significantly deformed toward the inside in the tire radial direction when riding over a step such as a curb.
The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a non-pneumatic tire capable of suppressing a large deformation of an outer cylinder toward the inside in a tire radial direction, without deteriorating the riding comfort.
A non-pneumatic tire according to an aspect of the present invention includes an inner cylinder that is attached to an axle, an outer cylinder that surrounds the inner cylinder from an outside in a tire radial direction and has a tread member mounted on an outer peripheral surface thereof, and a plurality of connecting members that connect the outer peripheral surface of the inner cylinder and an inner peripheral surface of the outer cylinder, in which the outer cylinder and the connecting members are formed to be elastically deformable, the thickness of a thickest part of the outer cylinder is thicker than the thickness of a thickest part of the connecting member, the connecting member includes a vertical base portion that extends toward the inside in the tire radial direction from the inner peripheral surface of the outer cylinder, a horizontal base portion that extends along a tire circumferential direction from an inner end portion in the tire radial direction of the vertical base portion toward one side in the tire circumferential direction, and an inclined portion that gradually extends toward one side in the tire circumferential direction from an end portion on one side in the tire circumferential direction of the horizontal base portion toward the inside in the tire radial direction and is connected to the outer peripheral surface of the inner cylinder, the thickness of the inclined portion is thinner than the thickness of each of the vertical base portion and the horizontal base portion, and the length of the inclined portion is longer than the length of each of the vertical base portion and the length of the horizontal base portion when viewed from a tire width direction.
According to the present invention, it is possible to suppress a large deformation of an outer cylinder toward the inside in a tire radial direction without deteriorating the riding comfort.
Hereinafter, configurations of the non-pneumatic tire according to the present embodiment will be described with reference to
As shown in
The non-pneumatic tire 1 of the present embodiment is used by being mounted on, for example, a bicycle, a two-wheeled vehicle, an automobile, a handle type electric wheelchair, or the like.
Here, the wheel portion 2 is formed in a disk shape, the tire portion 7 is formed in an annular shape, and each central axis is positioned on a common axis. The common axis is referred to as a central axis O, and a direction along the central axis O is called a tire width direction. In addition, when viewed from the tire width direction, a direction orbiting around the central axis O is referred to as a tire circumferential direction, and a direction intersecting the central axis O is referred to as a tire radial direction.
The center portion of each of the wheel portion 2, the tire portion 7, and the tread member 5 in the tire width direction coincide with each other. In a cross-sectional view along both directions in the tire width direction and the tire radial direction, the wheel portion 2, the tire portion 7, and the tread member 5 exhibit, as a whole, a line symmetrical shape with a straight line passing through the center portion (tire equator part) in the tire width direction as a reference.
The wheel portion 2 includes a cylindrical boss 2d extending in the tire width direction with the central axis O as a center, a mounting cylinder portion 2a fixed to an outer peripheral surface of the boss 2d, an exterior cylinder portion 2c surrounding the mounting cylinder portion 2a from an outside in the tire radial direction, and a plurality of ribs 2b connecting the mounting cylinder portion 2a and the exterior cylinder portion 2c to each other.
Each of the mounting cylinder portion 2a and the exterior cylinder portion 2c are disposed coaxially with the boss 2d. The plurality of ribs 2b are disposed at equal intervals in the tire circumferential direction, for example. Each of the plurality of ribs 2b extends radially with the boss 2d as a center.
In the present embodiment, the mounting cylinder portion 2a, the plurality of ribs 2b, and the exterior cylinder portion 2c are integrally formed of a thermoplastic resin. As a result, the wheel portion 2 can be formed by insert molding using the boss 2d as an insert product, and is suitable for mass production.
Each of the boss 2d, the mounting cylinder portion 2a, the plurality of ribs 2b, and the exterior cylinder portion 2c may be separately formed. In addition, the mounting cylinder portion 2a, the plurality of ribs 2b, and the exterior cylinder portion 2c may be formed of a material other than the thermoplastic resin.
The tire portion 7 includes an inner cylinder 6 that is externally fitted to the exterior cylinder portion 2c of the wheel portion 2, an outer cylinder 4 that surrounds the inner cylinder 6 from the outside in the tire radial direction and has a tread member 5 mounted on an outer peripheral surface thereof, and a plurality of connecting members 3 that connect the outer peripheral surface of the inner cylinder 6 and the inner peripheral surface of the outer cylinder 4 and are arranged at intervals in the tire circumferential direction. An elastic modulus of a material forming the tire portion 7 is, for example, 300 MPa or more and 1500 MPa or less.
The inner cylinder 6 is attached to the axle via the wheel portion 2. The central axes of the inner cylinder 6 and the outer cylinder 4 are disposed coaxially with the central axis O. The center portion in the tire width direction of each of the inner cylinder 6, the connecting members 3, and the outer cylinder 4 is disposed in coincidence with each other.
In the present embodiment, the inner cylinder 6, the connecting members 3, and the outer cylinder 4 are integrally formed of the thermoplastic resin. As a result, the tire portion 7 can be formed by injection molding and is suitable for mass production. The thermoplastic resin may be, for example, only one kind of resin or a mixture containing two or more kinds of resins, or a mixture containing one or more kinds of resins and one or more kinds of elastomers, and may further include, for example, additives such as anti-aging agents, plasticizers, fillers, or pigments.
The inner cylinder 6, the connecting members 3, and the outer cylinder 4 may be separately formed. The inner cylinder 6, the connecting members 3, and the outer cylinder 4 may be formed of a material other than the thermoplastic resin.
The tire portion 7 and the wheel portion 2 may be integrally formed or may be separately formed. The wheel portion 2 has a function of connecting the axle and the tire portion 7, and the tire portion 7 has a function of absorbing vibration transmitted from the ground to the axle. As described above, since the wheel portion 2 and the tire portion 7 have different functions, they may be formed of different materials. For example, the tire portion 7 is formed of a material having a relatively small elastic modulus to secure vibration absorption performance, and the wheel portion 2 may be formed of a material having a larger elastic modulus than the tire portion 7 to secure robustness. In addition, for example, the wheel portion 2 may be formed of a material having a relatively small specific gravity to reduce the weight of the whole non-pneumatic tire 1.
The tread member 5 is formed in a tubular shape extending in the tire width direction with the central axis O as a center. The tread member 5 is externally fitted to the outer cylinder 4 formed to be elastically deformable. As shown in
The tread member 5 is formed of, for example, natural rubber and/or vulcanized rubber obtained by vulcanizing a rubber composition, a thermoplastic material, or the like. From the viewpoint of wear resistance, it is preferable to form the tread member 5 with the vulcanized rubber. Examples of the thermoplastic material include a thermoplastic elastomer and a thermoplastic resin.
Examples of the thermoplastic elastomer include an amide thermoplastic elastomer (TPA), an ester thermoplastic elastomer (TPC), an olefin thermoplastic elastomer (TPO), a styrene thermoplastic elastomer (TPS), a urethane thermoplastic elastomer (TPU), a thermoplastic rubber cross-linked body (TPV), or other thermoplastic elastomer (TPZ) as defined in JIS K 6418.
Examples of the thermoplastic resin include a urethane resin, an olefin resin, a vinyl chloride resin, a polyamide resin, and the like.
As shown in
The connecting member 3 includes a vertical base portion 11, a horizontal base portion 12, and an inclined portion 13.
The vertical base portion 11 extends toward the inside in the tire radial direction from the inner peripheral surface of the outer cylinder 4. The front and back surfaces of the vertical base portion 11 face the tire circumferential direction. The whole front and back surfaces of the vertical base portion 11 except for the connection part with the outer cylinder 4 extend linearly in the side view from the tire width direction. In the side view, the front and back surfaces of the vertical base portion 11 at the connection part with the outer cylinder 4 gradually extend in a direction apart from each other toward the outside in the tire radial direction, and exhibit a curved shape recessed in the tire circumferential direction.
When viewed from the tire width direction, the central line CL of the vertical base portion 11 is slightly inclined toward one side in the tire circumferential direction with respect to a straight line L1 passing through the central axis O and an outer end edge P1 in the tire radial direction of a central line CL passing through the center portion in the thickness direction of the vertical base portion 11. An inclination angle θ1 is, for example, 25° or less. The central line CL of the vertical base portion 11 may coincide with the straight line L1.
The thickness of the vertical base portion 11 in the tire circumferential direction is the same over an entire length in the tire radial direction except for the connection part with the outer cylinder 4. The thickness of the vertical base portion 11 is thickest in the connecting member 3.
Here, the thickness of the vertical base portion 11 means the thickness of a part of the vertical base portion 11 which is positioned inside in the tire radial direction from a connection part with the outer cylinder 4 and has the front and back surfaces extending linearly in a side view viewed from the tire width direction, and for example, the thickness means the average value of the thickness when the thickness of the part is different for each position in the tire radial direction.
The horizontal base portion 12 extends from the inner end portion in the tire radial direction of the vertical base portion 11 toward one side in the tire circumferential direction along the tire circumferential direction. The front and back surfaces of the horizontal base portion 12 face in the tire radial direction. The horizontal base portion 12 extends linearly in a side view seen from the tire width direction. In the horizontal base portion 12, when viewed from the tire width direction, at least one of the central line CL passing through the center portion in the thickness direction, a surface facing inside in the tire radial direction, and a surface facing outside in the tire radial direction extend along the tire circumferential direction. In the shown example, in the front and back surfaces of the horizontal base portion 12, the surface facing inside in the tire radial direction extends along the tire circumferential direction, and the surface facing outside in the tire radial direction gradually extends toward the inside in the tire radial direction toward one side in the tire circumferential direction. The thickness of the horizontal base portion 12 in the tire radial direction gradually decreases from the other side in the tire circumferential direction toward one side. The length of the horizontal base portion 12 is the same as the length of the vertical base portion 11.
The connection part (hereinafter, referred to as the first connection part) 14 between the horizontal base portion 12 and the vertical base portion 11 is curved so as to protrude toward the other side in the tire circumferential direction.
The inclined portion 13 gradually extends toward one side in the tire circumferential direction from an end portion on one side in the tire circumferential direction of the horizontal base portion 12 toward the inside in the tire radial direction, and is connected to the outer peripheral surface of the inner cylinder 6.
The connection part (hereinafter, referred to as the second connection part) 15 between the inclined portion 13 and the horizontal base portion 12 is curved so as to protrude toward the one side in the tire circumferential direction. The radius of curvature of the second connection part 15 is larger than the radius of curvature of the first connection part 14 when viewed from the tire width direction.
When viewed from the tire width direction, an inclination angle θ2 toward one side in the tire circumferential direction with respect to the straight line L1 of a straight line L2 connecting an inner end edge P2 in the tire radial direction of the central line CL passing through a center portion in the thickness direction of the inclined portion 13 and the outer end edge P1 in the tire radial direction of the central line CL passing through a center portion in the thickness direction of the vertical base portion 11 is larger than the inclination angle θ1 and is 32° or more and 45° or less.
When viewed from the tire width direction, the whole of the central line CL of the vertical base portion 11 except for the outer end edge P1 in the tire radial direction is positioned on the other side in the tire circumferential direction from the straight line L2, and the whole of the central line CL of the inclined portion 13 except for the inner end edge P2 in the tire radial direction is positioned on one side in the tire circumferential direction from the straight line L2.
When viewed from the tire width direction, the length of the inclined portion 13 is longer than the lengths of the vertical base portion 11 and the horizontal base portion 12. When viewed from the tire width direction, the length of the inclined portion 13 is, for example, about three times the length of each of the vertical base portion 11 and the horizontal base portion 12.
The thickness of the inclined portion 13 is thinner than the thickness of each of the vertical base portion 11 and the horizontal base portion 12. As shown in
In the inclined portion 13, a surface (hereinafter referred to as an abutment surface) 13b facing one side in the tire circumferential direction in the outer part 13c positioned outside the central region in the tire radial direction is gradually extended linearly toward one side in the tire circumferential direction from the outside toward the inside in the tire radial direction when viewed from the tire width direction. At least the outer part 13c in the tire radial direction of the inclined portion 13 is positioned outside in the tire radial direction from the center portion in the tire radial direction between the inner cylinder 6 and the outer cylinder 4.
In the shown example, the whole of the outer part 13c of the connecting member 3 is positioned outside in the tire radial direction from the center portion in the tire radial direction between the inner cylinder 6 and the outer cylinder 4.
In the outer part 13c of the connecting member 3, for example, only the outer end portion in the tire radial direction may be positioned outside in the tire radial direction from the center portion in the tire radial direction between the inner cylinder 6 and the outer cylinder 4, or the whole of outer part 13c of the connecting member 3 may be positioned inside in the tire radial direction from the center portion in the tire radial direction between the inner cylinder 6 and the outer cylinder 4.
When viewed from the tire width direction, a center portion of the abutment surface 13b of the inclined portion 13 in the other connecting member 3 positioned on the other side in the tire circumferential direction of the connecting members 3 adjacent in the tire circumferential direction, and a top portion of the first connection part 14 in the one connecting member 3 positioned on one side in the tire circumferential direction face each other in a direction orthogonal to the abutment surface 13b. A gap between the connecting members 3 adjacent in the tire circumferential direction is minimized between the center portion of the abutment surface 13b of the inclined portion 13 of the other connecting member 3 and the top portion of the first connection part 14 of the one connecting member 3.
When viewed from the tire width direction, the gap between the vertical base portions 11 adjacent in the tire circumferential direction is wider than the gap between the inclined portions 13 adjacent in the tire circumferential direction.
As shown in
The thickness of the center portion 4a of the outer cylinder 4 in the tire width direction is thicker than the thickness of the vertical base portion 11 which has the thickest thickness in the connecting member 3. The thickness of the center portion 4a of the outer cylinder 4 in the tire width direction is 1.1 to 3.0 times the thickness of the vertical base portion 11.
As described above, with the non-pneumatic tire 1 according to the present embodiment, since the thickness of the center portion 4a in the tire width direction, which has the thickest thickness in the outer cylinder 4, is larger than the thickness of the vertical base portion 11, which has the thickest thickness in the connecting member 3, the rigidity of the outer cylinder 4 can be secured, and when the non-pneumatic tire 1 rides over a step such as a curb, the large deformation of the outer cylinder 4 toward the inside in the tire radial direction can be suppressed.
The thickness of the inclined portion 13 is thinner than the thicknesses of each of the vertical base portion 11 and the horizontal base portion 12, and the length of the inclined portion 13 is longer than the length of each of the vertical base portion 11 and the horizontal base portion 12 when viewed from the tire width direction. That is, since the length of the inclined portion 13, which has the thinnest thickness in the connecting member 3, is the longest, the bending rigidity of the inclined portion 13 is reliably reduced, and the connecting member 3 can be easily elastically deformed when the non-pneumatic tire 1 is grounded, and the riding comfort can be secured.
Moreover, since the inclined portion 13 is arranged at a position where the outer end portion in the tire radial direction where the stress is most concentrated when the non-pneumatic tire 1 is grounded is avoided in the connecting member 3, the deterioration of durability can be prevented.
Since the horizontal base portion 12 extends along the tire circumferential direction, for example, the length of the inclined portion 13 viewed from the tire width direction can be easily secured as compared with the configuration in which the horizontal base portion 12 extends from the vertical base portion 11 toward the inside in the tire radial direction, and the outer part 13c in the tire radial direction of the inclined portion 13 can be easily deflected and deformed toward one side in the tire circumferential direction when the non-pneumatic tire 1 is grounded, and thus the riding comfort can be reliably secured.
As shown in
Since the thickness of the center portion 4a in the tire width direction, which has the thickest thickness of the outer cylinder 4, is 1.1 to 3.0 times the thickness of the vertical base portion 11, the rigidity of the outer cylinder 4 can be reliably secured while suppressing an increase in weight.
Since the inclination angle θ2 is 32° or more and 45° or less, it is possible to reliably suppress the deterioration of riding comfort while suppressing the increase in weight.
When the inclination angle θ2 is less than 32°, the connecting member 3 cannot be easily elastically deformed when the non-pneumatic tire 1 is grounded, and when the inclination angle θ2 is more than 45°, the connecting member 3 becomes too long to be excessively elastically deformed and the weight thereof also increases.
The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.
In the above embodiment, a configuration in which the non-pneumatic tire 1 includes the wheel portion 2 and the tread member 5 is shown, but a configuration in which the non-pneumatic tire 1 may be configured to include only the tire portion 7 without the wheel portion 2 and the tread member 5 may be employed.
In the embodiment described above, a configuration in which the thickness of the minimum stress part 13a of the inclined portion 13 is thinner than the thickness of the other parts is shown, but the present invention is not limited to this, and the thickness of the whole inclined portion 13 including the minimum stress part 13a may be suitably changed to be equal, for example.
In the above embodiment, the minimum stress part 13a is curved so as to protrude toward the other side in the tire circumferential direction, but the present invention is not limited to this, and it may be curved so as to protrude toward one side in the tire circumferential direction, or it may be appropriately changed such that the minimum stress part 13a is not curved but is simply recessed in the tire circumferential direction.
In the above embodiment, a configuration in which the thickest part of the outer cylinder 4 is the center portion 4a in the tire width direction is shown, but the present invention is not limited to this, and may be suitably changed, for example, to the end portion 4b in the tire width direction.
In the above embodiment, the thickness of the vertical base portion 11 is made to be thickest in the connecting member 3, but instead, for example, the thickness of the horizontal base portion 12, the first connection part 14, or the second connection part 15 may be made to be thickest in the connecting member 3.
In addition, it is possible to replace the components in the above-described embodiment with known components without departing from the scope of the present invention, and the above-described modification examples may be combined appropriately.
According to the present invention, since the thickness of the thickest part of the outer cylinder is thicker than the thickness of the thickest part of the connecting member, the rigidity of the outer cylinder can be secured, and when the non-pneumatic tire rides over a step such as a curb, the large deformation of the outer cylinder toward the inside in the tire radial direction can be suppressed.
The thickness of the inclined portion is thinner than the thicknesses of each of the vertical base portion and the horizontal base portion, and the length of the inclined portion is longer than the length of each of the vertical base portion and the horizontal base portion when viewed from the tire width direction. That is, in the connecting member, since the length of the thinnest inclined portion is the longest, the bending rigidity of the inclined portion is reliably reduced, and the connecting member can be easily elastically deformed when the non-pneumatic tire is grounded, and the riding comfort can be secured.
Moreover, since the inclined portion is arranged at a position where the outer end portion in the tire radial direction where the stress is most concentrated when the non-pneumatic tire is grounded is avoided in the connecting member, the deterioration of durability can be prevented.
Since the horizontal base portion extends along the tire circumferential direction, for example, the length of the inclined portion viewed from the tire width direction can be easily secured as compared with the configuration in which the horizontal base portion extends from the vertical base portion toward the inside in the tire radial direction, and the outer part in the tire radial direction of the inclined portion can be easily deflected and deformed toward one side in the tire circumferential direction when the non-pneumatic tire is grounded, and thus the riding comfort can be reliably secured.
Here, when the non-pneumatic tire is grounded to the ground plane, in the inclined portion of the connecting member where the vertical base portion is positioned between the ground plane and the inner cylinder, the thickness of a part, in which the minimum stress is generated, may be thinner than the thickness of the other parts.
In this case, when the non-pneumatic tire is grounded to the ground plane, in the inclined portion of the connecting member where the vertical base portion is positioned between the ground plane and the inner cylinder, since the thickness of the part, in which the minimum stress is generated, is thinner than the thickness of the other parts, the bending rigidity of the inclined portion can be more reliably reduced while suppressing the deterioration of durability.
In addition, the thickness of the vertical base portion may be the thickest in the connecting member, and the thickness of the thickest part in the outer cylinder may be 1.1 to 3.0 times the thickness of the vertical base portion.
In this case, since the thickness of the part, which has the thickest thickness in the outer cylinder, is 1.1 to 3.0 times the thickness of the vertical base portion, the rigidity of the outer cylinder can be reliably secured while suppressing an increase in weight.
By applying the non-pneumatic tire of the present invention to the field, it is possible to suppress a large deformation of an outer cylinder toward the inside in a tire radial direction without deteriorating the riding comfort.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-224766 | Nov 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/044500 | 11/13/2019 | WO | 00 |
