Leaf spring support for spoke structure of non-pneumatic tire

Abstract

A non-pneumatic tire includes a lower ring having a first diameter and an upper ring having a second diameter greater than the first diameter. The upper ring is substantially coaxial with the lower ring. A support structure connects the lower ring to the upper ring. The support structure is comprised of a plurality of spokes. The support structure is positioned and configured such that adjacent ones of the plurality of spokes contact one another upon the occurrence of a high impact event.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates to non-pneumatic tires, and more particularly to non-pneumatic tires having a support structure with spokes designed to contact each other during a high impact event. [Background technology]

[0002] Various tire constructions have been developed that allow the tire to run in an uninflated or underinflated state. Non-pneumatic tires do not require inflation, but "run-flat tires" can continue to operate at relatively high speeds for extended periods of time after being partially or completely deflated. Non-pneumatic tires may include support structures such as spokes or webbing that connect a lower ring to an upper ring. In some non-pneumatic tires, a circumferential tread may be attached to the upper ring of the tire.

[0003] The circumferential tread may include a tread band. The tread band may be a single or multi-layer band of material. Such a tread band may also be referred to as a shear band, shear element, or thin annular high strength band element. When used in a non-pneumatic tire or a partially or non-pneumatic pneumatic tire, the shear element acts as a structural compression member. When used in a fully-pneumatic tire, the shear element acts as a tension member.

[0004] Tire design, whether for pneumatic or non-pneumatic tires, involves balancing many factors including, but not limited to, load capacity, handling, and ride comfort. Regardless of the balance selected between these factors, non-pneumatic tires must be durable and able to withstand high impact events such as hitting a curb, pothole, or other obstacle or road defect. Summary of the Invention

[0005] In one embodiment, a non-pneumatic tire includes a lower ring having a first diameter and an upper ring having a second diameter. The upper ring is substantially coaxial with the lower ring. A support structure connects the lower ring to the upper ring. The support structure is comprised of a plurality of spokes. The plurality of spokes are arranged in a first group of spokes and a second group of spokes axially spaced from the first group of spokes. Each of the plurality of spokes includes a first end connected to the lower ring and a second end connected to the upper ring. A transition portion is located between the first end and the second end. A secondary spring is nested with the transition portion of the spoke.

[0006] In another embodiment, a method of manufacturing a non-pneumatic tire includes providing a lower ring having a first diameter and an upper ring having a second diameter greater than the first diameter. A plurality of spokes are formed. Each spoke extends between a first end and a second end. Each spoke has a transition portion between the first end and the second end. Each spoke has a backup spring nested with the transition portion. The plurality of spokes are arranged in a first group of spokes and a second group of spokes axially spaced from the first group of spokes. The lower ring is connected to the upper ring using the first group of spokes and the second group of spokes.

[0007] In yet another embodiment, a non-pneumatic tire includes a lower ring having a first diameter and an upper ring having a second diameter. The upper ring is substantially coaxial with the lower ring. A support structure connects the lower ring to the upper ring. The support structure is comprised of a plurality of spokes. Each of the plurality of spokes is provided with a backup spring that nests with a curved portion of the spoke. The backup springs are arranged and configured to reduce stress in an associated spoke. [Brief description of the drawings]

[0008] The accompanying drawings, together with the detailed description provided below, illustrate structures that describe exemplary embodiments of the claimed invention. Similar elements are identified with the same reference numerals. It should be understood that elements shown as a single component may be replaced with multiple components, and elements shown as multiple components may be replaced with a single component. The drawings are not to scale, and the proportions of certain elements may be exaggerated for illustrative purposes. [Figure 1] FIG. 1 is a side view of one embodiment of a non-pneumatic tire. [Diagram 2] FIG. 2 is another side view of the non-pneumatic tire of FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. [Figure 4] FIG. 4 is a detailed view of area A of FIG. [Diagram 5] FIG. 5 is a detailed view of area A of FIG. 1 with some features removed for clarity. [Figure 6] FIG. 6 is a detailed view of a single spoke used in the non-pneumatic tire of FIG. [Figure 7] FIG. 7 is a side view of a portion of the non-pneumatic tire of FIG. 1 when the tire is on a flat surface and carrying a normal load. [Figure 8] FIG. 8 is a side view of a portion of the non-pneumatic tire of FIG. 1 with some features removed for clarity when the tire is on a flat surface and carrying a normal load. [Figure 9] FIG. 9 is a side view of a portion of the non-pneumatic tire of FIG. 1 when the tire is on an uneven surface. [Figure 10] FIG. 10 is a side view of a portion of the non-pneumatic tire of FIG. 1 when the tire is on an uneven surface, with some features removed for clarity. [Figure 11] FIG. 11 is a flow chart illustrating a method of manufacturing the non-pneumatic tire of FIG. [Figure 12] FIG. 12 is another embodiment of a spoke for a non-pneumatic tire. [Figure 12a] FIG. 12a is an end view of the spoke of FIG. 12 along II. [Figure 13] FIG. 13 is a side view of a portion of an alternative embodiment of a non-pneumatic tire. [Figure 14] FIG. 14 is a detailed view of a single spoke and auxiliary spring used in the non-pneumatic tire of FIG. [Figure 14a] FIG. 14a is a view along line AA in FIG. [Figure 15] FIG. 15 is a detailed view of a portion of FIG. [Figure 16a] FIG. 16a shows a modification of a portion of the auxiliary spring. [Figure 16b] FIG. 16b shows a modification of a portion of the auxiliary spring. [Figure 16c] FIG. 16c shows a modification of a portion of the auxiliary spring. [Figure 17a] FIG. 17a is a graph illustrating performance metrics exhibited by the auxiliary spring variations shown in FIGS. 16a-16c, respectively. [Figure 17b] FIG. 17b is a graph illustrating performance metrics exhibited by the auxiliary spring variations shown in FIGS. 16a-16c, respectively. [Figure 17c] FIG. 17c is a graph illustrating performance metrics exhibited by the auxiliary spring variations shown in FIGS. 16a-16c, respectively. [Figure 18a] FIG. 18a shows a further variation of a portion of the auxiliary spring. [Figure 18b] FIG. 18b shows a further variation of a portion of the auxiliary spring. [Figure 18c] FIG. 18c shows a further variation of a portion of the auxiliary spring. [Figure 18d] FIG. 18d shows a further variation of a portion of the auxiliary spring. [Figure 19] FIG. 19 shows a modified example of the spoke arrangement shown in FIGS. [Figure 20]FIG. 20 shows another modified example of the spoke arrangement shown in FIGS. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The following includes definitions of select terms used herein. The definitions include various examples or forms of components that fall within the scope of the term and that may be used for implementation. The examples are not intended to be limiting. Both the singular and plural forms of a term may fall within the scope of the definition.

[0010] "Axial" and "axially" refer to the direction parallel to the axis of rotation of the tire.

[0011] "Circumferential" and "circumferentially" refer to a direction extending along the perimeter of the surface of the tread perpendicular to the axial direction.

[0012] "Radial" and "radially" refer to directions perpendicular to the axis of rotation of the tire.

[0013] As used herein, "tread" refers to that portion of the tire that comes into contact with the road or ground under normal inflation and normal load.

[0014] It should be understood that, although similar terms are used in the following description to describe typical tire components, the terms, of course, have slightly different connotations and one of ordinary skill in the art would not consider any of the following terms to be purely interchangeable with another term used to describe typical tire components.

[0015] As used herein, directions are stated with reference to the tire's axis of rotation. The terms "upward" and "upwardly" refer to the general direction toward the tire's tread, and "downward" and "downwardly" refer to the general direction toward the tire's axis of rotation. Thus, when relative directional terms such as "upper" and "lower" or "top" and "bottom" are used in connection with elements, the "upper" or "top" element is spaced closer to the tread than the "lower" or "bottom" element. Additionally, when relative directional terms such as "on" or "under" are used in connection with elements, an element that is "on" another element is closer to the tread than the other element.

[0016] The terms "inner" and "inwardly" refer to the general direction toward the tire's equatorial plane, and "outer" and "outerly" refer to the general direction away from the tire's equatorial plane, toward the tire's side. Thus, when relative directional terms such as "inner" and "outer" are used in connection with elements, the "inner" elements are spaced closer to the tire's equatorial plane than the "outer" elements.

[0017] 1-5 illustrate one embodiment of a non-pneumatic tire 10. The non-pneumatic tire 10 is merely an exemplary illustration and is not intended to be limiting. In the illustrated embodiment, the non-pneumatic tire 10 includes a generally annular lower ring 20. The lower ring 20 can be engaged with a vehicle hub (not shown) for mounting the tire 10 to a vehicle. The lower ring 20 has an inner surface 23 and an outer surface 24 and can be made from a polymeric material, an elastomeric material, a metal, a composite material composed of a polymer reinforced with fiberglass or carbon fiber, or any other material or combination of materials.

[0018] The non-pneumatic tire 10 further includes a generally annular upper ring 30. The upper ring 30 has a diameter greater than that of the lower ring 20 and is substantially coaxial therewith. The upper ring 30 has an inner surface 33 and an outer surface 34 and may be made from a polymeric material, an elastomeric material, a metal, a glass or carbon fiber reinforced polymer, or any other desired material or combination of materials. A circumferential tread 70 is attached to the outer surface 34 of the upper ring 30. The circumferential tread 70 may be attached to the upper ring 30 with an adhesive, mechanically, or using any other desired configuration.

[0019] As shown in Figure 3, the circumferential tread 70 includes a tread band 72 and a tread layer 74. The tread band 72 and the tread layer 74 may be made of the same material or different materials. The tread layer 74 may be made of rubber and may include tread elements (not shown), such as grooves, ribs, blocks, lugs, sipes, studs, or any other desired elements. The tread band may include a filament assembly.

[0020] In the illustrated embodiment, the tread band 72 is shown as a single layer. In alternative embodiments, the tread band may be a multi-layer band. Such a multi-layer tread band may include one or more layers of substantially inextensible material. The layers may be formed from sheets of material, cords of material, filaments of material, or any other desired configuration. In other alternative embodiments, the multi-layer tread band may include layers of extensible material, such as elastomers. According to one exemplary embodiment, the tread band may include a pair of inextensible layers separated by a layer of extensible material. In yet other alternative embodiments, the tread band may include bands referred to as shear bands, shear elements, or thin annular high strength band elements.

[0021] The support structure 100 connects the lower ring 20 to the upper ring 30. The support structure 100 extends from the exterior surface 24 of the lower ring 20 and the interior surface 33 of the upper ring 30. The support structure 100 is comprised of a plurality of spokes 200. In the illustrated embodiment, the plurality of spokes 200 are arranged in two axially spaced spoke groups, including a first group of spokes 202 and a second group of spokes 204 axially spaced from the first group of spokes 202. In alternative embodiments, the support structure may include three or more axially spaced spoke groups.

[0022] As shown in Figure 3, the first group of spokes 202 and the second group of spokes 204 are axially spaced apart from one another. In alternative embodiments, the spacing between the first group of spokes and the second group of spokes may be greater or less, or the first and second groups of spokes may be arranged with no spacing between them. From the perspective shown in Figure 1, each spoke 200 of the first group of spokes 202 is substantially convex with respect to the clockwise circumferential direction of the non-pneumatic tire 10, and each spoke of the second group of spokes 204 is substantially concave with respect to the clockwise circumferential direction of the non-pneumatic tire 10.

[0023] All of the spokes 200 in the first group of spokes 202 and the second group of spokes 204 have the same configuration. Accordingly, the description of the spokes 200 will be made with reference to a single spoke 200 shown in Figure 6. The spokes 200 may be manufactured from a metal, such as steel or aluminum, a polymer, such as polyester or nylon, a composite material, such as fiberglass or carbon fiber reinforced polymer, or any other desired material or combination of materials. The spokes 200 may include reinforcements (not shown).

[0024] The spokes 200 extend between a first end 206 and a second end 208 and have a substantially rectangular cross-section including a first surface 210 and a second surface 212 opposite the first surface 210. The spoke thickness t refers to the distance between the first surface 210 and the second surface 212. In the illustrated embodiment, the spokes 200 have a constant thickness between the first end 206 and the second end 208. In alternative embodiments, the thickness of the spokes may vary between the first end and the second end. For example, the spokes may have relatively thick portions at the first end and the second end and relatively thin portions between the ends. In other alternative embodiments, the spokes may have any desired cross-sectional shape (e.g., circular, diamond, hexagonal, etc.) or a combination of different cross-sectional shapes.

[0025] Towards the first end 206 of the spoke 200, there is an integral foot portion 214. The first surface 210 of the spoke 200 at the foot portion 214 is attached to the outer surface 24 of the lower ring 20 to connect the first end 206 of the spoke 200 to the lower ring 20. The foot portion 214 may be attached to the outer surface 24 of the lower ring 20 using welding, brazing, soldering, adhesives, mechanical fasteners (e.g., bolts, rivets), keys / keyways, or any other desired configuration. In the illustrated embodiment, the foot portion 214 is substantially straight and has an overall length (the dimension of the foot portion extending along the circumferential direction of the tire) and an overall width (the dimension of the foot portion extending along the axial direction of the tire) fixed to the outer surface 24 of the lower ring 20. In alternative embodiments, the foot portion may be a separate component attached to the spoke. In other alternative embodiments, the foot portion may be curved to match the radius of curvature of the outer surface of the lower ring, or may have any other desired curvature. In yet other alternative embodiments, only a portion of the foot portion, or multiple separate portions, may be attached to the exterior surface of the lower ring. In yet other alternative embodiments, the foot portion may be attached below the exterior surface of the lower ring, or the spokes may extend through the lower ring such that the foot portion may be attached to the interior surface of the lower ring.

[0026] The second ends 208 of the spokes 200 are provided with flexures 216. The flexures 216 have a width that extends along the axial direction of the tire. The flexures 216 may be fabricated from a polymer (e.g., urethane or rubber), a thin curved piece of metal, or any other desired material or combination of materials. In the illustrated embodiment, the flexures 216 are provided as rectangular parallelepipeds and are arranged such that the ends of the flexures 216 are aligned with the second ends 208 of the spokes 200. In other alternative embodiments, the flexures may be arranged such that the ends of the flexures are set back from the second ends of the spokes or such that the ends of the flexures extend beyond the second ends of the spokes. In yet other alternative embodiments, the flexures may be replaced with mechanical pin joints (i.e., hinges).

[0027] The flexible member 216 includes a spoke-facing surface 218 and a ring-facing surface 220. The spoke-facing surface 218 of the flexible member 216 is attached to the second surface 212 of the spokes 200, and the ring-facing surface 220 is attached to the inner surface 33 of the top ring 30 to connect the second ends 208 of the spokes 200 to the top ring 30. The attachment between the flexible member 216 and the spokes 200 or between the flexible member 216 and the top ring 30 may be accomplished using welding, brazing, soldering, adhesives, mechanical fasteners (e.g., bolts, rivets), key / keyway, or any other desired configuration. For example, the attachment may be made by casting urethane directly onto the spokes, with or without the spokes first being coated with a primer.

[0028] The flexible members 216 provide flexibility to the connection between the second ends 208 of the spokes 200 and the top ring 30. This flexibility reduces the likelihood of high stresses developing in the spokes 200, thereby improving the robustness of the non-pneumatic tire 10. In comparison to the flexible connection provided by the flexible members 216, the connection provided by the foot portions 214 at the first ends 206 of the spokes 200 is more rigid.

[0029] In alternative embodiments, the flexible members may have different shapes or configurations than those specifically shown and described. In other alternative embodiments, additional structures or mechanisms may supplement the flexible members to attach the second ends of the spokes to the top ring. In still other alternative embodiments, the flexible members may be omitted and the second ends of the spokes may be attached directly to the top ring. In these alternative embodiments, the second ends of the spokes may be attached directly to the top ring on the inner surface of the top ring, or the spokes may extend through the top ring such that the second ends may be attached to the outer surface of the top ring.

[0030] The spoke 200 includes a knee portion 222 between the first end 206 and the second end 208. The knee portion 222 has a first radius of curvature r 1 According to an exemplary embodiment, the first radius of curvature r 1 When attached to the upper and lower rings 20, 30, the knee portion 222 is concavely curved relative to the lower ring 20.

[0031] A transition portion 224 is provided between the knee portion 222 and the first end 206. The transition portion 224 has a second radius of curvature r 2 According to an exemplary embodiment, the second radius of curvature r 2 is 0-2 inches (0-5 cm). When attached to the upper and lower rings 20, 30, the transition section 224 is convexly curved relative to the lower ring 20. Thus, relative to a single spoke 200, the knee section 222 and transition section 224 are concavely curved in opposite directions. In an alternative embodiment, the knee section and transition section are concavely (or convexly) curved in the same direction.

[0032] The foot portion 214 extends from the transition portion 224 to the first end 206 of the spoke 200. A first connecting portion 226 connects the transition portion 224 to the knee portion 222, and a second connecting portion 228 connects the knee portion 222 to the second end 208 of the spoke 200. In the illustrated embodiment, the first connecting portion 226 and the second connecting portion 228 are both straight. In alternative embodiments, the first connecting portion or the second connecting portion may be curved or have any other desired configuration. In other alternative embodiments, the transition portion and the foot portion may be omitted. In such alternative embodiments, the first end of the spoke is disposed at the end of the first connecting portion.

[0033] Base plane p 1 The base plane p intersects the transition portion 224 and the second end 208 of the spoke 200 and serves as a reference for various dimensional aspects of the spoke 200. 1 and a second plane p that extends tangentially to the outer surface 24 of the lower ring 20 at the transition portion 224. 2 The angle between the base plane p is α. According to an exemplary embodiment, the angle α is +0 to +20 degrees. 1 The distance between the transition portion 224 and the second end 208 of the spoke 200 along a direction parallel to is is d 1 According to an exemplary embodiment, the distance d 1 is 10 to 25 inches (25 to 63.5 cm). 1 The first curvature r of the transition portion 224 and the knee portion 222 along a direction parallel to 1 The distance between the centers of 2 According to an exemplary embodiment, the distance d 2 The value of is the distance d 1 20 to 70 percent of the base plane p 1 The knee portion 222 and the base plane p 1 The maximum distance between 3 According to an exemplary embodiment, the distance d 3 is 2 to 4 inches (5 to 10 cm).

[0034] Referring to FIG. 10, the transition portion 224 of one spoke 200 is spaced a first spacing distance s from the first end 206 of the adjacent spoke 200. 1 The second ends 208 of adjacent spokes 200 are separated by a second spacing distance s 2 (See also Figure 5).

[0035] A non-pneumatic tire constructed according to the above design parameters can provide a more robust assembly, particularly with respect to impact performance. Figures 7 and 8 show the tire in an exemplary first state. As shown in Figures 7 and 8, by way of non-limiting example, in the first state, when the tire 10 rolls on a flat surface while carrying a load (i.e., normal operation), the non-pneumatic tire 10 deforms but adjacent spokes 200 do not contact each other. The lack of contact between adjacent spokes 200 during normal operation is desirable to avoid the creation of unnecessary stresses in the structure of the non-pneumatic tire 10.

[0036] During its life, the non-pneumatic tire 10 is expected to be subjected to high impact events, such as hitting a curb, a pothole, or other obstacle or road defect. During a high impact event, the non-pneumatic tire 10 may deform to a level significantly higher than that which occurs during normal operation. One example of a high impact event is the non-pneumatic tire 10 hitting a curb at a low speed (e.g., a 6 inch (15 centimeter) curb at 5 miles per hour (8 kilometers per hour)). Another example of a high impact event is the non-pneumatic tire 10 hitting a step road defect at a high speed (e.g., a 1 inch (2.5 centimeter) at 70 miles per hour (113 kilometers per hour)). These are merely examples and are not intended to limit the definition of "high impact event."

[0037] 9 and 10 show the tire in an exemplary second state, which is different from the first state. As shown in FIGS. 9 and 10, according to a non-limiting example, in the second state, the non-pneumatic tire 10 experiences a high impact event in which the tire rolls on an uneven surface. According to one non-limiting example, the uneven surface is a road defect that protrudes above or sinks into the ground over a distance of 3 inches (8 cm). According to another non-limiting example, the uneven surface is a road defect that protrudes above or sinks into the ground over a distance of 4.5 inches (11 cm). According to yet another non-limiting example, the uneven surface is a road defect that protrudes above or sinks into the ground over a distance of 6 inches (15 cm).

[0038] The non-pneumatic tire 10 responds to a high impact event by deforming adjacent spokes 200 such that adjacent spokes 200 contact one another. Surprisingly, it has been found that contact between adjacent spokes 200 during a high impact event significantly reduces the stress experienced by an individual spoke 200 compared to a non-pneumatic tire in which the spokes do not contact one another during a high impact event. The reduction in stress in an individual spoke 200 is a result of the contact between adjacent spokes 200 because the contact distributes the load among multiple spokes 200. In other words, rather than a single spoke 200 absorbing the load resulting from a high impact event, multiple spokes 200 share the same load, thus reducing the peak load of any one single spoke 200.

[0039] In the illustrated embodiment, the non-pneumatic tire 10 is positioned and configured such that at least three adjacent spokes 200 contact each other simultaneously during a high impact event, and the contacting spokes 200 are located adjacent to the obstacle or road defect causing the high impact event. In alternative embodiments, the non-pneumatic tire may be positioned and configured to have fewer or more adjacent spokes that contact each other simultaneously during a high impact event. In other alternative embodiments, the adjacent spokes that contact each other simultaneously may be located anywhere along the circumference of the tire (i.e., may be located away from the obstacle or road defect causing the high impact event).

[0040] The design parameters of the spokes 200 and other components of the non-pneumatic tire 10 may be varied to provide desired performance characteristics for the non-pneumatic tire 10. Preferably, these design parameters are selected so that contact between adjacent spokes 200 occurs before the spokes 200 begin to yield or suffer any other form of damage.

[0041] Base plane p 1 The knee portion 222 and the base plane p 1 The maximum distance d between 3 affects the stiffness of the spokes and when contact occurs between adjacent spokes 200. 3 Increasing the distance d will physically move each spoke 200 closer to its neighbors, thus causing contact between adjacent spokes 200 to occur more quickly. 3 Increasing the distance d reduces the stiffness of the spokes 200 and therefore increases the amount of deflection for a given load, thereby increasing the likelihood of contact between adjacent spokes 200. 3 Reducing the distance d has the opposite effect, causing each spoke 200 to physically move farther away from adjacent spokes 200, and therefore causing contact between adjacent spokes 200 to occur relatively slower. 3Reducing φ increases the stiffness of the spokes 200 and therefore reduces the amount of deflection for a given load, thereby reducing the likelihood of contact between adjacent spokes 200.

[0042] Base plane p 1 A first curvature r of the transition portion 224 and the knee portion 222 along a direction parallel to 1 Distance d between the centers of 2 affects when contact with adjacent spokes 200 occurs. 2 d 1 , this results in contact between adjacent spokes 200 occurring relatively quickly. 2 d 1 , this will result in contact between adjacent spokes 200 occurring relatively late.

[0043] Radius of curvature r of knee portion 222 1 influences when contact with adjacent spokes 200 occurs. 1 By decreasing the radius of curvature r, contact between adjacent spokes 200 occurs relatively late. 1 Increasing spoke thickness t will result in contact between adjacent spokes 200 occurring relatively sooner. The spoke thickness t affects the stiffness of the spokes 200. Increasing the spoke thickness t will increase the stiffness of the spokes 200 and decreasing the spoke thickness will decrease the stiffness of the spokes 200.

[0044] In addition, the vertical stiffness of the tire is a function of the spoke thickness t and the distance d 3 It is known that the distance d is affected by the combination of 3 Increasing the distance d 3 Decreasing t increases tire stiffness. As a result, spokes with a larger thickness t must be spaced apart for a larger distance d to meet tire stiffness targets. 3 and the spokes with smaller thickness t should be combined with the spokes with smaller distance d. 3It was found that it should be combined with

[0045] FIG. 11 is a flow chart illustrating an exemplary method of manufacturing a non-pneumatic tire. At 1010, a lower ring and an upper ring are provided. The lower ring and the upper ring have a first diameter and a second diameter that is greater than the first diameter. At 1020, a plurality of spokes are formed. The spokes may be formed using hot stamping, cold forming, extrusion, rolling, bending, or any other desired method. In addition, the spokes may be formed using a plurality of composite fabrication techniques (e.g., resin transfer molding and high pressure resin transfer molding). Further examples of methods of forming the spokes include wet layup, prepreg lamination. Each spoke extends between a first end and a second end. A knee portion is located between the first end and the second end, and a transition portion is located between the first end and the knee portion. The knee portion and the transition portion are concavely curved in opposite directions. A foot portion extends from the transition portion.

[0046] At 1030, a flexible member is attached to the spokes. At 1040, the spokes are arranged into a first group of spokes and a second group of spokes axially spaced from the first group of spokes. Further, a plurality of spokes in the first group of spokes are arranged to be concavely curved relative to a first circumferential direction of the tire, and a plurality of spokes in the second group of spokes are arranged to be convexly curved relative to the first circumferential direction of the tire.

[0047] At 1050, the lower ring is connected to the upper ring using first and second groups of spokes. A foot portion of each of the spokes is attached to the lower ring to connect a first end of each spoke to the lower ring. A flexible member is attached to the upper ring to connect a second end of each spoke to the upper ring.

[0048] In alternative embodiments, the steps described above may be performed in an order other than that specifically described. In other alternative embodiments, the method may include more or fewer steps.

[0049] Figures 12 and 12a show another embodiment of a spoke 1200. The spoke 1200 of Figures 12 and 12a is substantially similar to the spoke 200 of Figures 1-10, except for the differences described herein. Accordingly, like features will be identified by like numerals increased by a factor of "1000". In the spoke 200 shown in Figures 1-10, the second connecting portion 228 is straight. In comparison, the spoke 1200 of Figures 12 and 12a has a radius of curvature r 3 In comparison to a straight second connecting portion, the curved second connecting portion 1228 in the spoke 1200 of Figures 12 and 12a significantly improves the self-supporting behavior. According to one exemplary embodiment, the curved second connecting portion 1228 has a radius of curvature r 3 The range is 10 to 50 inches (25 to 127 cm).

[0050] In addition to the variations in design parameters and resulting performance characteristics discussed above with respect to the spoke 200 shown in FIGS. 1-10, the radius of curvature r of the curved second connecting portion 1228 in the spoke 1200 of FIGS. 12 and 12a may also be varied. 3 can be varied to affect performance. The radius of curvature r of the curved second connecting portion 1228 3 and the length l of the flexible member 1216 flexure The smaller radius of curvature r of the curved second connecting portion 1228 interacts with each other to affect the self-supporting performance. 3 The larger radius of curvature r of the curved second connecting portion 1228 reduces the self-support and therefore increases the stress during high impact events. 3 increases self-support and therefore reduces stress during high impact events. However, this reduction in stress only occurs up to a point. 3 As increases (the limit is the radius of curvature r equal to infinity) 3, resulting in a linear second connection), the effectiveness of the self-support begins to decrease again.

[0051] The length l of the flexible member 1216 flexure affects its ability to exert a torque on the end of the spoke 1200. This torque acts to straighten the curved second connecting portion 1228 when the tire rolls under normal load or undergoes a high impact event. As a result, the smaller radius of curvature r 3 The curved second connecting portion 1228 has a longer length l flexure 1216 having a larger radius of curvature r 3 The curved second connecting portion 1228 has a shorter length l flexure It has been found that the ability of the flexure 1216 to exert a torque on the spokes 1200 is a function of the length l of the flexure 1216. flexure In addition to the length, the length is also affected by the stiffness of the material used to manufacture the flexible member 1216. As a result, if a softer material is used, a longer length l flexure and if a stiffer material is used, a shorter length l flexure It may be desirable to provide a flexible member 1216 having a

[0052] The non-pneumatic tires described herein improve the robustness of non-pneumatic tires by providing an arrangement in which adjacent spokes contact each other during high impact events. Contact between adjacent spokes results in multiple spokes sharing the load, thus significantly reducing the stress experienced by any single spoke within the non-pneumatic tire. This improves the durability of the non-pneumatic tire.

[0053] As discussed above, the foot portions 214 connect the first ends 206 of the spokes 200 to the lower ring 20, and the flexible members 216 connect the second ends 208 of the spokes 200 to the upper ring 30. The flexible members 216 provide a relatively flexible connection between the second ends 208 of the spokes 200 and the upper ring 30, while the foot portions 214 provide a relatively stiff connection between the first ends 206 of the spokes 200 and the lower ring 20.

[0054] According to this embodiment, the spoke 200 behaves like a cantilever beam, whereby the second end 208 flexes (i.e., moves) relative to the first end 206 as the tire 10 rolls and deforms. While this behavior is not inherently undesirable, it can cause the spoke 200 to compress, stretch, or shear, thereby creating stresses in the spoke 200. It has been found that the greatest stresses occur toward the spoke's first end 206, particularly near where the attachment between the foot portion 214 and the lower ring 20 ends, propagating through the transition portion 224 and halfway to the first connection portion 226.

[0055] Figures 13-15 show an alternative non-pneumatic tire with spokes 2200 having features designed to dampen the above stresses. The embodiment shown in Figures 13-15 is substantially the same as the embodiment shown in Figures 1-6, except for any differences described herein. Thus, like features will be identified by like numerals increased by the value of "2000".

[0056] Each spoke 2200 has first and second surfaces 2210, 2212 each extending between a first end 2206 and a second end 2208. A foot portion 2214 is provided toward the first end 2206 of the spoke 2200. A flexible member 2216 is provided at the second end 2208 of the spoke 2200. The foot portion 2214 is attached to the lower ring 2020 to connect the first end 2206 of the spoke 2200 to the lower ring 2020, and the flexible member 2216 is attached to the upper ring 2030 to connect the second end 2208 of the spoke 2200 to the upper ring 2030.

[0057] A knee portion 2222 is provided between the first end 2206 and the second end 2208. The knee portion 2222 has a first radius of curvature r 1 The transition portion 2224 is disposed between the knee portion 2222 and the first end 2206, and the foot portion 2214 extends from the transition portion 2224 toward the first end 2206. The transition portion 2224 has a second radius of curvature r 2 A first connecting portion 2226 connects the transition portion 2224 to the knee portion 2222. A second connecting portion 2228 connects the knee portion 2222 to the second end 2208 of the spoke 1200.

[0058] In this embodiment, the spokes 2200 are provided with secondary springs 2500. The secondary springs 2500 may be made of metal (e.g., steel, stainless steel, titanium), composite materials (e.g., carbon fiber reinforced polymer, glass reinforced polymer), or any other desired material or combination of materials. The secondary springs 2500 may include reinforcements (not shown) or other features that affect the stiffness of the secondary springs. In the illustrated embodiment, the secondary springs 2500 are separate and independent components from the spokes 2200. In alternative embodiments, the secondary springs may be formed integrally with the spokes, for example, by folding the ends of the spokes back over themselves.

[0059] The auxiliary spring 2500 extends between a first end 2502 and a second end 2504 and has a substantially rectangular cross-section including opposing first and second surfaces 2506, 2508. The auxiliary spring length l hs refers to the total distance between the first end 2502 and the second end 2504, measured along the longitudinal axis of the secondary spring 2500. hs is its length l hs The thickness of the secondary spring t refers to the distance between the first edge 2507 and the second edge 2509 of the secondary spring 2500 along a direction extending across the hs refers to the distance between the first surface 2506 and the second surface 2508. In the illustrated embodiment, the auxiliary spring thickness t hs is constant between the first end 2502 and the second end 2504, and the thickness t l In addition, the auxiliary spring width w hs is constant between the first end 2502 and the second end 2504 and is equal to the width of the spoke 2000. In alternative embodiments, the thickness or width of the secondary spring may vary between the first end 2502 and the second end, or the secondary spring and spokes may have different thicknesses or widths. In other alternative embodiments, the secondary spring may have any desired cross-sectional shape or combination of different cross-sectional shapes.

[0060] The secondary spring 2500 has a curved portion 2510 between the first end 2502 and the second end 2504. In the illustrated embodiment, the curved portion 2510 has a radius of curvature r 2 A radius of curvature r substantially equal to 3 In alternative embodiments, the curved portion may have a different radius of curvature than the radius of curvature of the transition portion.

[0061] A first arm portion 2512 connects the first end 2502 to the curved portion 2510. A second arm portion 2514 connects the second end 2504 to the curved portion. In the illustrated embodiment, the first and second arm portions 2512, 2514 are both straight. In alternative embodiments, the first arm portion or the second arm portion may be curved or have any other desired configuration.

[0062] 15, a first surface 2506 of the secondary spring 2500 is attached to a second surface 2212 of the spoke 2200 along a bond area 2516. The secondary spring 2500 may be attached to the spoke 2200 using welding, brazing, soldering, adhesives, mechanical fasteners, or any other desired attachment method. According to this embodiment, the secondary spring 2500 is located radially above the spoke 2200 (i.e., the radial distance between the secondary spring and the lower ring is greater than the radial distance between the spoke and the lower ring).

[0063] In the illustrated embodiment, the bond area 2516 begins at the first end 2502 of the secondary spring 2500 and extends along the length l of the secondary spring 2500. hs 33% of the total width of the auxiliary spring w hs The joint length l that extends continuously along b The portion of the auxiliary spring 2500 that is not attached to the spokes 2200 is called the free portion 2571 and has a free length l f In alternative embodiments, the bonded region may extend along 20-100% of the length of the auxiliary spring or 20-100% of the width of the auxiliary spring. In other alternative embodiments, the bonded region may not begin at the first end of the auxiliary spring, but instead there may be a non-bonded region of any desired length prior to the start of the bonded region. In yet other alternative embodiments, the bonded region may be provided intermittently along the length of the auxiliary spring.

[0064] The secondary spring 2500 is aligned with the spoke 2200 such that the curved portion 2510 of the secondary spring 2500 nests adjacent to the transition portion 2224 of the spoke 2200. In the illustrated embodiment, the first arm portion 2512 of the secondary spring 2500 is sized and configured such that the first end 2502 of the secondary spring 2500 is aligned with the first end 2206 of the spoke 2200, and the second arm portion 2514 is sized and configured such that the second end 2504 of the secondary spring 2500 is located slightly below midway between the transition portion 2224 and the knee portion 2222 of the spoke 2200. In alternative embodiments, the first or second arm portions may be sized and configured to place the first or second end of the secondary spring in any desired location relative to the spoke.

[0065] It has been found that the provision of the auxiliary spring 2500 significantly reduces the maximum stress experienced during compression of the spoke 2200. The design parameters of the auxiliary spring 2500, the spoke 2200, and other components of the non-pneumatic tire may be altered to provide the non-pneumatic tire with desired performance characteristics. For example, increasing the length of the second arm portion 2514 of the auxiliary spring 2500 may reduce the maximum stress experienced in the spoke 2200, but may create a greater contact pressure between the auxiliary spring 2500 and the spoke 2200. As another example, increasing the thickness of the auxiliary spring 2500 may reduce the maximum stress experienced in the spoke 2200, but may increase the contact pressure between the auxiliary spring 2500 and the spoke 2200. Additionally, increasing the thickness of the auxiliary spring 2500 may increase the stress in the bond region 2516.

[0066] In the illustrated embodiment, the spoke arrangement includes only a single auxiliary spring 2500. In alternative embodiments, the spoke arrangement may include multiple auxiliary springs. In one exemplary embodiment, each of the multiple auxiliary springs are identical to one another. In other exemplary embodiments, each of the multiple auxiliary springs may have different lengths, thicknesses, widths, or may be made from different materials, or may have different reinforcements, or may have other design variables selected to provide desired performance characteristics for the non-pneumatic tire.

[0067] In addition to the design variables discussed above, the second end 2504 of the auxiliary spring 2500 may be provided as various planar shapes or with specific edge configurations to further tune the spoke 2200 and provide performance characteristics for the desired non-pneumatic tire. Figures 16a-16c show three variations in planar shape of the second end 2502 of the auxiliary spring 2500, and Figures 17a-17c are graphs showing performance metrics associated with each design variation. In Figure 16a, the second end 2502 of the auxiliary spring 2500 is square in plan view. This square shape has been found to allow the entire auxiliary spring 2500 to uniformly support the spoke 2200, resulting in the performance metrics shown and described in Figure 17a. Additionally, the square shape has been found to provide the greatest stress reduction in the spoke 2200. In Figure 16b, the second end 2502 of the auxiliary spring 2500 has chamfered corners in plan view. It has been found that using beveled corners instead of right angle corners reduces the contact pressure between the secondary spring 2500 and the spoke 2200 and results in the performance metrics shown and described in FIG. 17b. Additionally, it has been found that the beveled shape can improve the fatigue performance of the spoke 2200. In FIG. 16c, the second end 2502 of the secondary spring 2500 is elliptical in plan view. It has been found that this elliptical shape provides reduced stress reduction similar to a square shaped end, while also reducing contact pressure similar to a chamfered corner design, resulting in the performance metrics shown and described in FIG. 17c.

[0068] 18a-d show four variations of edge shapes of the second end 2502 of the auxiliary spring 2500. Here, "edge" refers to the surface of the auxiliary spring 2500 at the second end 2502 that connects the first surface 2506 to the second surface 2508. In FIG. 18a, the second end 2502 of the auxiliary spring 2500 has a chamfered upper portion and a chamfered lower portion with a straight portion extending therebetween. When attached to the spoke 2200, the lower portion abuts the second surface 2212 of the spoke 2200. This configuration can reduce local contact stresses or, by reducing local contact stresses, can reduce the tendency for fretting damage to occur. In FIG. 18b, the second end 2502 of the auxiliary spring 2500 has a rounded upper portion and a rounded lower portion with a straight portion extending therebetween. This configuration may further reduce the tendency for fretting damage to occur than the chamfered design described above. In FIG. 18c, the upper and lower portions are chamfered such that the entire second end 2502 is angled. In other words, there is no straight section between the chamfered upper and lower portions. This configuration may provide similar reduction in localized stresses and fretting damage as the configuration shown in FIG. 18a. In FIG. 18d, the upper and lower portions are rounded such that the entire second end 2502 is curved. In other words, there is no straight section between the rounded upper and lower edges. This configuration may further reduce stresses than the configuration shown in FIG. 18b.

[0069] Figure 19 shows a variation of the spoke arrangement of Figures 12-14. The spoke arrangement of Figure 18 is substantially the same as the spoke arrangement of Figures 12-14, except for the differences described herein. Thus, like features will be identified by like numerals increased by the value of "1000."

[0070] According to a variant shown in FIG. 19, the second surface 3508 of the auxiliary spring 3500 is attached to the first surface 3210 of the spoke 3200, and the second end 3208 of the spoke 3200 is attached to the lower ring 3020 by attaching the first surface 3506 of the auxiliary spring 3500 to the lower ring 3020. According to this embodiment, the auxiliary spring 3500 is located radially below the spoke 3200 (i.e. the radial distance between the auxiliary spring and the lower ring is smaller than the radial distance between the spoke and the lower ring). By placing the auxiliary spring 3500 radially below the spoke 3200, the load support efficiency due to tension or shear forces can be improved. In another variant (not shown), two auxiliary springs may be attached to the spoke (i.e. one auxiliary spring may be located above the spoke and one auxiliary spring may be located below the spoke), with a first auxiliary spring attached to the second surface of the spoke and a second auxiliary spring attached to the first surface of the spoke.

[0071] Figure 20 illustrates another variation of the spoke arrangement of Figures 12-14. The configuration of Figure 20 is substantially the same as the configuration of Figures 12-14, except for the differences described herein. Accordingly, like features will be identified by like numerals increased by the value of "4000."

[0072] According to the variation shown in FIG. 20, a bumper 4519 is provided between the secondary spring 4500 and the spoke 4200, specifically between the free portion 4517 of the spoke 4200 adjacent the joint area 4516. The bumper 4519 is positioned and configured to minimize the occurrence of stress-induced damage as a result of any contact between the secondary spring 4500 and the spoke 4200. In the illustrated embodiment, the bumper 4500 is a separate component from both the secondary spring 4500 and the spoke 4200 and may be manufactured from plastic, metal, carbon fiber reinforced polymer, glass reinforced polymer, ceramic, or any other desired material or combination of materials. The bumper 4519 may be attached to the secondary spring 4500 or the spoke 4200 using adhesives, mechanical fasteners, brazing, soldering, welding, or any other desired configuration. In alternative embodiments, the bumper may be integrated directly into the secondary spring or spoke. In other alternative embodiments, the bumper may be a coating applied to the spoke or secondary spring. In yet other embodiments, the buffer may be a thin air gap. According to one example, the air gap is 0.0020 inches (0.05 mm) thick.

[0073] Although different embodiments and variants have been shown and described in various figures, the features disclosed are not exclusive to each described embodiment. Instead, various features from the different embodiments or variants can be combined as desired.

[0074] The terms "includes" or "including", to the extent used in this specification or the claims, are intended to be inclusive, similar to the term "comprising", as interpreted when used as a transitional word in the claims. Furthermore, to the extent the term "or" is used (e.g., A or B), it is intended to mean "A or B, or both". When applicants intend to indicate "only A or B but not both", the term "only A or B but not both" is used. Thus, the use of the term "or" herein is inclusive and not exclusive. See Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d.Ed.1995). Also, the terms "in" or "into", to the extent used in this specification or the claims, are intended to additionally mean "on" or "onto". Furthermore, to the extent the term "connect" is used in this specification or the claims, it is intended to mean not only "directly connected to," but also "indirectly connected to," such as connected via one or more other components.

[0075] While the present application has been illustrated by the description of its embodiments, and those embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any manner limit the scope of the appended claims to such details. Additional advantages and modifications will be readily apparent to those skilled in the art. Thus, the present application in its broader aspects is not limited to the specific details, representative apparatus and methods, and examples shown and described. Thus, departures may be made from such details without departing from the spirit or scope of the applicants' general inventive concept.

Claims

1. A non-pneumatic tire, a lower ring having a first diameter; an upper ring having a second diameter and substantially coaxial with the lower ring; a support structure connecting the lower ring to the upper ring, the support structure being comprised of a plurality of spokes arranged in a first group of spokes and a second group of spokes axially spaced from the first group of spokes, each of the plurality of spokes comprising: a first end connected to the lower ring; a second end connected to the upper ring; and a transition portion located between the first end and the second end; and an auxiliary spring nested with the transition portion of the spoke.

2. The non-pneumatic tire of claim 1 , wherein the auxiliary springs are disposed radially above the spokes.

3. The non-pneumatic tire of claim 1 , wherein the auxiliary springs are disposed radially below the spokes.

4. 2. The non-pneumatic tire of claim 1, wherein the auxiliary spring includes a curved portion between a first end and a second end, the radius of curvature of the curved portion being substantially equal to the radius of curvature of the transition portions of the spokes.

5. 2. The non-pneumatic tire of claim 1, wherein the auxiliary spring is attached to the spoke along a bond area, the bond area extending along between 20% and 100% of the length of the auxiliary spring.

6. 2. The non-pneumatic tire of claim 1, wherein the spoke further includes a knee portion located between the transition portion and the second end, and the auxiliary spring includes a first end and a second end, the first end of the auxiliary spring aligned with the first end of the spoke and the second end of the auxiliary spring located below the midpoint between the transition portion and the knee portion of the spoke.

7. 2. The non-pneumatic tire of claim 1, wherein the auxiliary spring includes a curved portion between a first end and a second end, the curved portion adjacent the transition portion of the spoke, and the second end is one of a square, a chamfer, and an elliptical shape in a plan view.

8. 2. The non-pneumatic tire of claim 1, wherein the auxiliary spring includes a curved portion between a first end and a second end, and an edge of the second end is one of square, chamfered, and rounded.

9. The non-pneumatic tire of claim 1 , wherein at least one spoke includes a buffer between said auxiliary spring and said spoke.

10. 10. The non-pneumatic tire of claim 9, wherein the dampening portion is constructed from at least one of plastic, metal, carbon fiber reinforced polymer, glass reinforced polymer, and ceramic.

11. 1. A method for manufacturing a non-pneumatic tire, comprising: providing a lower ring having a first diameter and an upper ring having a second diameter greater than the first diameter; forming a plurality of spokes, each spoke extending between a first end and a second end, each spoke having a transition portion between said first end and said second end, each spoke having a back-up spring nested with said transition portion; arranging the plurality of spokes into a first group of spokes and a second group of spokes axially spaced from the first group of spokes; and connecting the lower ring to the upper ring with the first set of spokes and the second set of spokes.

12. 12. The method of manufacturing a non-pneumatic tire of claim 11, wherein forming the plurality of spokes includes at least one of hot stamping, cold forming, extrusion, and composite lay-up.

13. 12. The method of claim 11 further comprising forming the ends of the auxiliary springs into one of a square, a chamfer, and an ellipse in plan view.

14. 12. The method of manufacturing a non-pneumatic tire of claim 11, further comprising forming an end of the assist spring with one of a squared end, a chamfered end, and a rounded end.

15. 12. The method of manufacturing a non-pneumatic tire according to claim 11, further comprising the step of providing a buffer between said spokes and said auxiliary spring.

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