Non-pneumatic tire with balanced spoke stiffness

Abstract

A non-pneumatic tire and method of forming the same. The 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 plurality of spokes extend between and interconnect the lower and upper rings. The plurality of spokes have a tension stiffness of 11 and less than or equal to 150 N / mm° and a compression stiffness of 11 or more and less than or equal to 100 N / mm°.

Description

[Technical Field]

[0001] This disclosure relates to non-pneumatic tires, and more particularly to non-pneumatic tires with balanced tensile and compressive spoke stiffness to distribute loads on the tire. [Background technology]

[0002] Various tire designs have been developed that allow the tire to run in an uninflated or under-inflated 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 the lower ring to the upper ring. Varying the tension and compression stiffness of each spoke, among other design parameters, affects the performance of non-pneumatic tires.

[0003] Tires with spokes that have low tensile stiffness and high compressive stiffness are known as "bottom-loading" tires. These tires carry most of their load in a compressed state. Bottom-loading tires offer good load-bearing characteristics, but can have poor shock absorption performance because the high compressive stiffness of the spokes limits the spokes' ability to "collapse" during an impact event. This can result in a tire with poor ride comfort characteristics.

[0004] Tires with spokes that have high tensile stiffness and low compressive stiffness are known as "top-loading" tires. These tires carry the majority of their load in a tensioned state. While top-loading tires offer improved shock absorption performance over bottom-loading tires, the specific tension and compression values ​​of the spokes in a top-loading tire's overall arrangement can generate undesirably high stresses or strains in tire components. Furthermore, at any given moment of rotation of a top-loading tire, spokes located in the top half of the tire may have a net upward pull, while spokes located in the bottom half of the tire may have a net downward pull. As a result, the tire must not only be designed to carry the rated load, but also to overcome the downward pull of the spokes located in the bottom half of the tire. This exacerbates the design problems of top-loading tires discussed above with regard to the generation of undesirably high stresses or strains in tire components. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, it is desirable to provide a non-pneumatic tire that provides acceptable shock absorption performance while also having acceptable stresses and strains in the tire components.

[0006] In one embodiment, 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 being substantially coaxial with the lower ring. A plurality of spokes extend between and interconnect the lower and upper rings. The plurality of spokes may include 11 or more and

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[0009] In another embodiment, 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 plurality of spokes extend between and interconnect the lower and upper rings. The plurality of spokes have a tension to compression stiffness ratio in the range of 0.3:1 to 8:1.

[0010] In yet another embodiment, a method of manufacturing a non-pneumatic tire includes modeling a model tire having a model width and a model design load capacity, the method including selecting a reference tension stiffness value and a reference compression stiffness value based on the modeling step, the reference tension stiffness value being greater than or equal to 11 and

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[0013] 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 by multiple components, and that elements shown as multiple components may be replaced by 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 front view of one embodiment of a non-pneumatic tire. [Figure 2] FIG. 2 is an enlarged partial front view of the non-pneumatic tire of FIG. [Figure 3] FIG. 3 is a cross-sectional view of the non-pneumatic tire taken along line 3-3 of FIG. [Figure 4] FIG. 4 is a partial front view of an alternative embodiment of a non-pneumatic tire; [Figure 5a] FIG. 5a is a schematic diagram showing a front view of the test setup for determining the tension stiffness of the spokes. [Figure 5b] FIG. 5b is a schematic diagram showing a front view of the test setup for determining the compression stiffness of the spokes. [Figure 5c] FIG. 5c is a graph showing the relationship between spoke deflection and spoke force. DETAILED DESCRIPTION OF THE INVENTION

[0014] The following contains definitions of selected terms employed 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.

[0015] "Axial" and "axially" refer to directions parallel to the axis of rotation of the tire.

[0016] "Circumferential" and "circumferentially" refer to a direction extending along the perimeter of the surface of the tread perpendicular to the axial direction.

[0017] "Radial" and "radially" refer to directions perpendicular to the axis of rotation of the tire.

[0018] 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.

[0019] It should be understood that while 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 one of the following terms to be simply interchangeable with another term used to describe typical tire components.

[0020] 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 "above" or "below" are used in connection with elements, an element that is "above" another element is closer to the tread than the other element.

[0021] The terms "inner" and "inwardly" refer to the general direction toward the tire's equatorial plane, and "outer" and "outwardly" 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.

[0022] 1 and 2 are front views of one embodiment of a non-pneumatic tire 100. The non-pneumatic tire 100 includes a lower ring 110 having a first diameter and an upper ring 120 having a second diameter larger than the first diameter. Each of the lower ring 110 and the upper ring 120 extends axially to define a tire width. The upper ring 120 is substantially coaxial with the lower ring 110. The lower ring 110 is attached to a hub 130. The hub 130 may be used, for example, to mount the non-pneumatic tire 100 to a vehicle. In an alternative embodiment, the hub may be omitted.

[0023] A circumferential tread 140 is disposed about the top ring 120. The tread 140 may include tread elements such as grooves, ribs, blocks, lugs, sipes, studs, and other elements. Shear bands, shear elements, or reinforcing structures (not shown) may be disposed between the top ring 120 and the tread 140. In alternative embodiments, the tread may be omitted and the tread elements may be formed directly on the top ring.

[0024] A plurality of spokes 200 extend between the lower ring 110 and the upper ring 120 to interconnect the rings. In the illustrated embodiment, the design of each one of the plurality of spokes 200 is substantially identical. Accordingly, further description of the plurality of spokes 200 will be made with reference to a single spoke. However, it should be understood that in alternative embodiments, the geometry of different spokes may vary. In other alternative embodiments, webbing may be used to interconnect the lower and upper rings.

[0025] Each one of the spokes 200 extends generally radially of the non-pneumatic tire 100 between a first end 205 and a second end 210. The first end 205 is attached to the lower ring 110. The second end 210 is attached to the upper ring 120. The spokes 200 also extend generally axially of the non-pneumatic tire 100 between a first edge 215 and a second edge 220 to define a spoke width. In the illustrated embodiment, the width of the spoke 200 is slightly narrower than the widths of the lower ring 110 and the upper ring 120. In alternative embodiments, the spokes may have a width equal to the width of the lower or upper ring, or the spokes may have a width wider than the width of the lower or upper ring.

[0026] Each spoke 200 has a stiffness in first tension, k, which may be referred to as the tension stiffness. t Each spoke 200 also has a second compression stiffness k, which may be referred to as the compression stiffness. c The tension stiffness k of each spoke 200 t and compression stiffness k c affects the performance characteristics of the non-pneumatic tire 100.

[0027] Figure 5a shows the tension stiffness of the spoke, k t FIG. 5 is a schematic diagram showing a front view of a test setup for determining tensile strength (S) of spoke sample S. Spoke sample S has a first end 510 that is held stationary and a second end 515 that is free to move relative to first end 510. A load is applied to second end 515 of spoke sample S in a first direction indicated by arrow A1. The load moves second end 515 of spoke S relative to first end 510 by a tension distance d t (not shown in this view). The load is similarly applied when second end 515 is deflected by a tension distance d t When the spoke sample S moves by a distance of t This causes

[0028] Figure 5b shows the compressive stiffness k of spoke sample S. cFIG. 5B is a schematic diagram showing a front view of a test setup for determining the load d of the spoke sample S. In this setup, the load applied to the second end 515 of the spoke sample S is in a second direction indicated by arrow A2, which is opposite to the first direction shown in FIG. 5A. The load compresses the second end 515 of the spoke sample S relative to the first end 510 by a distance d c (not shown in this view). The load also causes second end 515 to compress by a distance d t When the spoke sample S moves by c This causes

[0029] The graph shown in Figure 5c shows the relationship between spoke deflection and spoke force, with deflection plotted along the x-axis and force plotted along the y-axis. The right side of the graph shows the force vs. tension f t and tension distance d t The left side of the graph is a plot of the compressive force f c and compression distance d c The plot of tension stiffness k t The point (0,0) is connected to the point (d t ,f t ) is determined by measuring the slope of the line connecting the c The point (0,0) is connected to the point (d c ,f c ) is determined by measuring the slope of the line connecting

[0030] Known non-pneumatic tires can generally be categorized as "bottom-loading" or "top-loading." Bottom-loading tires carry load primarily through compression of the tire between the ground on which the tire rests and the point at which the load is applied to the tire, with a small number of spokes positioned near the ground carrying the majority of the load at any given moment during the tire's rotation. Thus, the compression stiffness of the spokes of a bottom-loading tire is a primary design factor, while the tension stiffness of the spokes is less important. Bottom-loading tires can offer good load-carrying characteristics but poor shock absorption performance.

[0031] In comparison, top-loading tires primarily carry loads through the use of a hoop-like structure. Unlike bottom-loading tires, where only a few spokes carry the majority of the load, the hoop-like structure of a top-loading tire distributes the load more evenly to all of the tire's spokes. As such, both the compression stiffness and tension stiffness of the spokes of a top-loading tire are important design factors. In certain top-loading tire configurations, the tension stiffness of the spokes can be orders of magnitude higher than the compression stiffness of the spokes, which can create an imbalance in the tire's forces. Therefore, while top-loading tires can provide good shock absorption performance, they suffer from undesirably high stresses or strains in tire components due to this force imbalance.

[0032] The present disclosure identifies equations and values ​​that can be used to design a non-pneumatic tire that solves the problems discussed above and provides a non-pneumatic tire that has acceptable shock absorption performance while also having acceptable stresses and strains in the tire components. Specifically, the present disclosure provides a formula for determining the ideal tensile stiffness k for a tire of a desired width and a desired load capacity. t,度 and ideal compressive stiffness k c,度 Identify the formula and values ​​that can be used to calculate the ideal tension stiffness k t,度 and ideal compressive stiffness k c,度 are each expressed in spoke stiffness per degree,

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[0034] Since the performance characteristics of the non-pneumatic tire 200 are affected by the total number of spokes 20, the ideal tension stiffness k t,度 and ideal compressive stiffness k c,度 The value of is the spoke stiffness per degree

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[0036] Given the above, the ideal tension stiffness k, expressed in terms of spoke stiffness per degree, can be calculated using the following formula and values: t,度 and ideal compressive stiffness k c,度 The value of can be calculated.

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[0038] Ideal tension stiffness k t,度 and ideal compressive stiffness k c,度 The first step in calculating the value of is to model the model tire and calculate the reference tension stiffness k t,基準 and reference compressive stiffness k c,基準 The aim is to optimise the value of the characteristic model width w 基準 and specific model load capacity f 基準 In one exemplary embodiment, the model tire has a width w of 300 mm. 基準 and a load capacity of 22,200 N 基準 It has.

[0039] When modeling a tire, the designer takes into account the intended use of the non-pneumatic tire. c,基準 Increasing the compression stiffness k provides a tire with a firmer ride and a smaller footprint, while increasing the c,基準 Reducing the reference tensile stiffness k provides a tire with a softer ride and a relatively larger footprint. t,基準 Similar changes can be achieved by increasing and decreasing

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[0048] Also, the reference tension stiffness k t,基準 and reference compressive stiffness k c,基準 Regardless of the eigenvalue of k, the reference tension stiffness k ranges from 0.3:1 to 8:1. t,基準 and reference compressive stiffness k c,基準 It has been found that a ratio of the reference tension stiffness k to the reference tension stiffness k provides desirable non-pneumatic tire performance characteristics. t,基準 and reference compressive stiffness k c,基準 Most preferably, the ratio of the nominal tensile stiffness k to the nominal tensile stiffness k is in the range of 0.5:1 to 8:1. t,基準 and reference compressive stiffness k c,基準 The tire is provided with a ratio of k in the range of 0.5:1 to 1:1. t,基準 If is less than 1, the spokes of the tire may carry most of the load in compression. However, the tire construction may be such that the force is transferred around the circumference of the tire, as in the case of a top-loading tire, whereby all of the spokes play an important role in transferring the load.

[0049] With the above guidelines established, the reference tension stiffness k t,基準 and reference compressive stiffness k c,基準 The exact value of is selected based on the modeling of the model tire and the desired performance characteristics. t,基準 and reference compressive stiffness k c,基準into the equation to determine the ideal tensile stiffness k for a desired tire design having a first design width and a first design load capacity. t,度 and ideal compressive stiffness k c,度 The value of can be calculated. The width of the tire to be designed (i.e., the first design width) is represented by w and is measured in millimeters, assuming the spokes, bottom ring, and top ring are all the same width. The design load capacity of the tire to be designed (i.e., the first design load capacity) is represented by f and is measured in Newtons.

[0050] In one non-limiting example, the tire being modeled has an ideal tensile stiffness k of the tire being designed. t,度 and ideal compressive stiffness k c,度 To arrive at the value of the reference tension stiffness k t,基準 and reference compressive stiffness k c,基準 When adjusting the value of , the model width w of 300 mm 基準 and a model load capacity f of 22,200 N 基準 is used again, so that the formula becomes:

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[0052] In this example, the model width w is 300 mm. 基準 and a model load capacity f of 22,200 N 基準 When the first modeling was performed using a tire with ideal tension stiffness k t,度 and ideal compressive stiffness k c,度 The value of the ideal tensile stiffness k for a tire having a first design width and a first design load capacity can be quickly adjusted for different tire widths and different tire design load capacities. t,度 and ideal compressive stiffness k c,度 Once the value of has been calculated, the equation can be used again to calculate the ideal tensile stiffness k for a tire having a second design width and a second design load capacity. t,度 and ideal compressive stiffness k c,度can be calculated, which allows for the rapid design of first, second and subsequent tire designs.

[0053] Ideal tension stiffness k t,度 and ideal compressive stiffness k c,度 After calculating the specific tension stiffness k of each spoke, use the following formula: t,固有 and specific compressive stiffness k c,固有 can be determined.

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[0055] According to these equations, the specific tension stiffness of each spoke, k t,固有 and specific compressive stiffness k c,固有 is the ideal tension stiffness k t,度 and ideal compressive stiffness k c,度 can be determined by multiplying each of the spokes by (360° / n), where n is the total number of spokes in the tire being designed. By performing this operation, the specific tension stiffness k of each spoke, expressed in N / mm, can be determined. t,固有 and specific compressive stiffness k c,固有 This provides the value of the specific tension stiffness k t,固有 and specific compressive stiffness k c,固有 can be quickly adjusted for tires with different numbers of spokes.

[0056] Various spoke designs are designed to achieve the desired specific tension stiffness k, calculated according to the formula above. t,固有 and specific and specific compressive stiffness k c,固有 , and can be achieved, for example, through a combination of geometry, material selection, and reinforcement. t,固有 and specific compressive stiffness k c,固有4 illustrates a portion of a non-pneumatic tire 400 having an exemplary spoke design that can provide a tire with a tread pattern that is substantially similar to the non-pneumatic tire 100 of FIGS. 1-3. Accordingly, a description of the tire of FIG. 4 is omitted, and similar features are identified by numerals increased by "300."

[0057] The non-pneumatic tire 400 includes a lower ring 410 having a first diameter and an upper ring 420 having a second diameter larger than the first diameter. The distance between the lower ring 410 and the upper ring 420 is represented by R. The upper ring 420 is substantially coaxial with the lower ring 410. A plurality of spokes 500 extend between the lower ring 410 and the upper ring 420 to interconnect the rings. The design of each one of the plurality of spokes 500 is substantially identical. As such, further description of the plurality of spokes 500 will be made with reference to a single spoke.

[0058] Each one of the spokes 500 is substantially C-shaped and extends generally radially around the non-pneumatic tire 400 between a first end 505 and a second end 510. The first end 505 is attached to the lower ring 410. The second end 510 is attached to the upper ring 420. A line drawn between the attachment points of the first end 505 and the lower ring 410 may be referred to as the base, designated B. The apex A of the C-shaped spoke is offset from the base B by a distance r along the circumferential direction of the tire.

[0059] The desired specific tension stiffness k calculated using the formula above t,固有 and compression stiffness k c,固有 It has been found that spokes 500 having a .gtoreq..times ... r=(0.5)R This equation allows the distance R between the lower ring 410 and the upper ring 420 to be calculated for a non-pneumatic tire 400 having known inner and outer diameters. According to one exemplary embodiment, multiplying the distance R by 0.5 to calculate the offset distance r has been found to provide desirable non-pneumatic tire performance characteristics. In other exemplary embodiments, multiplying the distance R by a value in the range of 0.5 to 2 has been found to provide acceptable non-pneumatic tire characteristics. Desired inherent tension stiffness k t,固有 and specific compressive stiffness k c,固有 In addition to providing a spoke with a tensile strength of 0.1 MPa, it has been found that the above formula also provides a spoke with approximately linear tension and compression behavior.

[0060] According to one exemplary embodiment, the C-shaped spokes 500 are fabricated from steel with an elastic modulus of approximately 200 gigapascals, a circumferential thickness of 1.575 mm, and an axial width of 305 mm. These parameters define the intrinsic tensile stiffness k t,固有 and compression stiffness k c,固有 The design parameters may vary without departing from the design objectives discussed above. For example, the spokes may be made from carbon fiber reinforced polymer, glass reinforced polymer, plastic (thermoplastic or thermoset), and other metals such as stainless steel. As another example, the spokes may have a thickness of 1 to 25 mm, more preferably 1 to 10 mm. As yet another example, the spokes may have a width of 200 to 305 mm, more preferably 260 to 305 mm. To vary one design parameter, the specific tension stiffness k t,固有 and compression stiffness k c,固有 It is understood that other design parameters may need to be modified to maintain the desired design objectives. For example, if the spokes are made of a polymer rather than steel, it may be necessary to increase the thickness of the spokes to 23 mm, assuming the spoke width remains 305 mm. As another example, if the spoke width is reduced, it may be necessary to increase the thickness of the spokes.

[0061] The aforementioned spoke designs have the inherent tensile stiffness k t,固有 and compression stiffness k c,固有 is just one design possibility to provide the inherent tension stiffness k t,固有 and compression stiffness k c,固有 Other spoke designs are possible that meet the design objectives.

[0062] To the extent that it is used in this specification or in the claims, the terms "includes" or "including" are intended to be inclusive, similar to the interpretation of the term "comprising" when used as a transitional phrase in a patent claim. Furthermore, to the extent that the term "or" is used (e.g., A or B), it is intended to mean "A or B, or both." Where 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, not exclusive. See Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995). Also, to the extent that the terms "in" or "into" are used in this specification or in the claims, they 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 connecting via another component.

[0063] 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 way limit the scope of the appended claims to such details. Additional advantages and improvements will be readily apparent to those skilled in the art. Therefore, the present application in its broader aspects is not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept.

Claims

1. A non-pneumatic tire, a lower ring having a first diameter; an upper ring having a second diameter greater than the first diameter and substantially coaxial with the lower ring; a plurality of spokes extending between and interconnecting the lower and upper rings; Width: 300 mm, load capacity: 22,200 N, the plurality of spokes is 11 or more; and [Equation 1] Tension stiffness of 11 or more and [Equation 2] Non-pneumatic tires having the following compression stiffness:

2. The non-pneumatic tire of claim 1 , wherein each one of said plurality of spokes is substantially C-shaped.

3. 3. The non-pneumatic tire of claim 2, wherein for each one of the plurality of spokes, the apex of the spoke is offset circumferentially from the base of the spoke by a distance in a range of 0.5 to 2 times the difference between the second diameter and the first diameter.

4. 10. The non-pneumatic tire of claim 1, wherein the plurality of spokes have a tension to compression stiffness ratio in the range of 0.3:1 to 8:1.

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