Non-pneumatic tire

Abstract

A non-pneumatic tire (100) having an annular beam (200) and an annular support (103) comprising a plurality of thermoplastic elastic spokes formed by a thermoplastic injection molding process. When manufacturing such a non-pneumatic tire using a mold, a radially extending zone of the mold cavity is defined by an inner radially extending zone of the annular beam (200). The annular beam (200) of the non-pneumatic tire comprises a first elastomer and a circumferential reinforcement extending in a circumferential direction. The annular beam (200) is free of the circumferential reinforcement over a width of at least 8 mm at an axially extending zone comprising the first elastomer. The plurality of thermoplastic elastic spokes are made of a second elastomer and extend radially inwardly from the annular beam (200). The invention also relates to a process for forming a non-pneumatic tire (100).

Description

[0001] This application claims priority to U.S. Patent Application No. 63 / 018,502, filed April 30, 2020. TECHNICAL FIELD

[0002] The present disclosure relates to non-pneumatic tires (NPTs) for vehicles that travel on highways or off-road (e.g., cars, light and heavy trucks, all-terrain vehicles, zero-turn radius mowers, and military vehicles). The present disclosure is particularly directed to off-road vehicles that can have higher requirements for speed, load capacity, and high damage tolerance. BACKGROUND

[0003] Non-pneumatic tires (NPTs) have characteristics that are superior to pneumatic tires. Unlike pneumatic tires, NPTs are not pressure vessels. Such tires do not lose their function due to loss of air pressure.

[0004] The use of a cord-rubber composite construct can enable NPTs to exhibit higher performance. Such a composite construct can provide high stiffness in a preferred direction while being able to bend in the preferred direction. It is apparent that a rubber bearing surface is very effective in the presence of traction while being resistant to wear, enabling a long service life. For these reasons, a reinforced toroidal beam can provide high performance. In addition, a rubber bearing surface disposed in the outer radial extension of the toroidal beam can also be a preferred design.

[0005] Tension-based NPTs can provide an efficient load bearing mechanism. For such NPTs, the radially inner surface of the toroidal beam can be supported by a toroidal support that forms tension. The toroidal support can include a plurality of radially oriented spokes. Because the spokes work under tension, efficient spokes should include a high modulus material. Isotropic rubber is not high modulus. It can be cumbersome or expensive to place cord reinforcement in the spokes. For this reason, other materials, such as thermoplastic elastomers or cast polyurethane elastomers can be a viable option.

[0006] U.S. Patent No. 9,751,270 (owned by the current applicant) discloses a thermoplastic molding process for forming NPT spokes. Thermoplastic injection molding is a mature industry that can enable low cost for NPTs. However, the following disclosure related to processes for NPT formation that include a thermoplastic toroidal support for a toroidal beam that utilizes a cord-rubber composite has not been present in the prior art.

[0007] The present disclosure provides a process for forming a NPT with a cord-rubber annular beam and a thermoplastic annular support. The annular beam is formed in an initial molding operation and then placed in a thermoplastic injection mold. The axially extending region of the annular beam is designed to form a dynamic seal. When placed in the mold, the pressure of the injected elastomer causes a specific deformation within the axially extending region of the beam. In addition, the mold profile that interfaces with the axially extending region of the beam is defined so that the highest contact pressure is generated at the radially inward extending region. This creates a dynamic closure effect allowing for excellent molding control in critical areas. SUMMARY

[0008] Aspects and advantages of the application will be set forth in part in the following description, or can be obvious from the description, or can be learned through practice of the application.

[0009] The present application is generally applicable to vehicles that use tires. In particular, the present application is especially suitable for off-road vehicles that can require high speed, high load and high energy absorption capabilities.

[0010] According to an aspect of the present application, a non-pneumatic tire is provided that includes an annular beam and an annular support extending radially inward from the annular beam, the support including a thermoplastic elastomer. The annular beam has a portion that includes a circumferential reinforcement. The portion extends axially. The annular beam has a portion that does not include a circumferential reinforcement. There is a portion on a laterally extending region of the annular beam and a second portion on a second laterally extending region. The portions each extend at least 8 mm along the axial direction of the annular beam.

[0011] According to an aspect of the present application, a process for forming a non-pneumatic tire is provided that includes an annular beam and an annular support. The annular beam is formed in a first process. The annular beam is placed in a thermoplastic injection mold. A second forming process includes a thermoplastic injection during which the annular support is formed and attached to the radially inward surface of the annular beam. The annular beam and the mold are configured so that an axially extending region of the annular beam acts as a deformable gasket. During the molding process, a contact pressure is generated between the mold and the radially inward portion of the laterally extending region of the beam. This pressure provides a closure effect and blocks the flow of elastomer between the axially extending region of the beam and the mold. The mold profile of the thermoplastic mold can include a convex section that generates a closure pressure.

[0012] These and other features, aspects, and advantages of the present application will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the application and, together with the description, serve to explain the principles of the application. BRIEF DESCRIPTION OF DRAWINGS

[0013] A detailed description of implementations will be provided below with reference to the attached drawings, only by way of example, in which:

[0014] Figure 1 is a schematic example of an NPT.

[0015] Figure 2 is a schematic example of a toroidal beam comprising a support surface.

[0016] Figure 3 is a R-Y cross-sectional view of a toroidal beam and support surface pattern.

[0017] Figure 4 is a R-Y cross-sectional view of a toroidal beam with a support surface pattern placed in a mold for thermoplastic injection.

[0018] Figure 5 is the undeformed geometry of a toroidal beam and support surface for FEA simulation of the injection process.

[0019] Figure 6 is the deformed geometry of a toroidal beam and support surface for FEA simulation of the thermoplastic molding process after closing the mold. Figure 5 is a close-up of the axial extension zone.

[0020] Figure 7 is the deformed geometry of a toroidal beam and support surface for FEA simulation of the thermoplastic molding process after closing the mold and injecting the thermoplastic material for forming the toroidal support.

[0021] Figure 8 is the deformed geometry of a toroidal beam and support surface for FEA simulation of the thermoplastic molding process after closing the mold and injecting the thermoplastic material for forming the toroidal support. Figure 7 is a close-up of the axial extension zone.

[0022] Figure 9 is the deformed geometry of a toroidal beam and support surface for FEA simulation of the thermoplastic molding process after closing the mold and injecting the thermoplastic material for forming the toroidal support.

[0023] Figure 10 is the deformed geometry of a toroidal beam and support surface for FEA simulation of the thermoplastic molding process after closing the mold and injecting the thermoplastic material for forming the toroidal support. Figure 9 is a close-up of the axial extension zone.

[0024] The use of the same or similar reference signs in different drawings indicates the same or similar features. It is expressly understood that the description and drawings are only for the purpose of illustration of the specific implementations and are to be helped in understanding. The description and drawings are not intended and should not be taken to be limiting.

[0025] Terminology Definitions

[0026] The following terms in the present disclosure are defined as follows, unless otherwise stated, where material properties refer to properties at ambient temperature:

[0027] “Hub” refers to any structure for supporting a tire and capable of being attached to a vehicle axis.

[0028] When referring to thermoplastic elastomers, “modulus” refers to the Young’s tensile modulus of elasticity measured according to ISO 527-1 :2019.

[0029] When referring to reinforcing cords or cables, “modulus” refers to the Young’s tensile modulus of elasticity measured according to ASTM D2969. This tensile modulus can be calculated as the secant modulus at 0.5% stress.

[0030] When referring to rubber, “shear modulus” refers to the dynamic shear modulus measured according to ASTM D5992-96 (2018) at 10 Hz, 23 C and 2% stress. When referring to rubber, “tensile modulus” refers to the Young’s modulus measured according to ASTM D412. DETAILED DESCRIPTION

[0031] The present invention provides a non-pneumatic tire, a mold for manufacturing such non-pneumatic tire and a process for forming such non-pneumatic tire. For purposes of describing the present invention, reference will now be made to embodiments and / or methods of the present invention, one or more examples of which are illustrated in or by the drawings. Each example is provided as illustrative of the present invention and not as a limitation of the present invention. It will be apparent to those of ordinary skill in the art that various modifications and changes can be made without departing from the scope or spirit of the present invention. For example, features or steps illustrated or described as part of one embodiment can be used with another embodiment or step to yield yet another embodiment or method. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents.

[0032] Figure 1 A schematic example of a NPT 100 is shown, which has dimensions of 26 x 10-12. This is a common size for off-road applications. The tire defines a cylindrical coordinate system with radial direction R, circumferential direction Θ and axial direction Y. A convenient Cartesian coordinate system has X as the tire travel direction, Y as the axial direction and Z as the vertical direction.

[0033] The tire comprises an annular beam 200 comprising a support face portion 101. The beam comprises a reinforcement in the circumferential direction. The tire further comprises an annular support portion 103 comprising a thermoplastic elastomer, a rim portion 104 and a hub portion 105. In this embodiment, the annular support portion comprises radially extending spokes to connect the inner surface of the annular beam to the rim without any of the spokes crossing the other spokes.

[0034] In this embodiment, the annular beam is formed in an initial molding operation. Together with the hub portion 105, the annular beam is placed in a mold for a secondary molding operation, in which the spokes are formed by thermoplastic injection molding.

[0035] Constructions in the prior art, such as that described in U.S. Patent No. 9,004,901, use thermoset polyurethane to form spokes. The present disclosure discloses a method of forming spokes by thermoplastic injection molding of a thermoplastic elastomer. The exemplary process provides effective closure at the laterally extending regions of the annular beam, thereby preventing the injected elastomer from flowing between the mold and the beam.

[0036] Figure 2 An exemplary annular beam 200 is shown, including a bearing surface pattern 101. The annular beam has an inner radially extending region 201. The annular beam is formed in a first operation, and then inserted into a thermoplastic injection mold for a second forming operation. In the illustrative example, a hub 105 can also be placed in the mold. The annular support 103 is formed in the injection molding process. In the illustrative example, the rim 104 can also be formed in the same injection molding process. Thus, the injection molding process can form spokes and a rim and further join the beam, spokes, rim, and hub to form an exemplary NPT 100. Figure 1

[0037] Figure 3 An R-Y cross section of the annular beam 200 is shown. The beam includes a reinforced portion 202, which extends axially with a width Wl. The reinforcement provides stiffness primarily in the circumferential direction. At the laterally extending regions of the beam, portion 203 is free of reinforcement. In the exemplary NPT, portion 203 can include isotropic rubber and be free of a bearing surface pattern; that is, it can be a solid of revolution. Portion 203 has a width W2. For effective processes for forming the annular support, the inventors have found that the width W2 should be at least 8 mm; in other cases, at least 12 mm, in other cases, at least 16 mm, and in other cases even wider.

[0038] The annular beam has a profile at the laterally extending regions that can be defined by portions 204 and 205. In the illustrative example, 204 can be generally linear and can be inclined from radial at an angle a. For effective processes for forming the annular support, the inventors have found that a should be at least 15 degrees; in other cases, at least 30 degrees, and in other cases, at least 45 degrees.

[0039] ​Because the annular beam does not include circumferential reinforcement near the laterally extending regions, the beam will have higher compliance at the axially extending regions. The inventors have discovered that this compliance can be controlled by selecting W2 and a. Wider W2 and greater a can form a more compliant portion 203. The inventors have discovered how to coordinate the design of the thermoplastic mold with the use of these design features. Surprisingly, the compliance of the axially extending regions can be used to form a dynamic gasket that deforms under the pressure of the thermoplastic injection and forms the desired contact pressure against the mold. Once deformed, the portion 203 provides a seal to impede the flow of thermoplastic material between the mold and the axially extending regions of the annular beam.

[0040] Figure 4 An R-Y cross section of an annular beam placed in a mold for thermoplastic injection is shown. A mold profile 301 contacts the outer laterally extending regions of the annular beam. A profile 302 contacts the outer laterally extending regions of the axially extending regions of the annular beam. A profile 303 contacts the inner laterally extending regions of the axially extending regions of the annular beam.

[0041] The mold can be configured in any suitable manner. An exemplary mold configuration has a radially actuated mold part A that includes the profile 301 and the profile 302. Part A can include a segment portion. Those skilled in the art of tire design will be familiar with mold designs for segment portions. Mold part B can include the profile 303. An exemplary mold configuration has an axially actuated mold part B.

[0042] An exemplary thermoplastic molding process for forming the annular support can include the following process steps:

[0043] - radially retracting the mold profiles 301 and 302 of mold part A.

[0044] - axially retracting the mold profile 303 of mold part B.

[0045] - placing the annular beam in the mold.

[0046] - radially extending mold part A to contact the outer laterally extending regions of the beam.

[0047] - axially extending mold part B to contact the axially extending regions of the beam.

[0048] - closing the mold to form a mold cavity into which a thermoplastic elastomer can be injected to form the annular support.

[0049] - the outer laterally extending regions of the mold cavity include the inner laterally extending regions 201 of the annular beam. Thus, the annular beam defines the surface of the mold cavity.

[0050] - injecting a thermoplastic elastomer into the mold cavity.

[0051] - The molding pressure deforms the annular beam portion 203.

[0052] - This deformation creates a contact pressure on the mold profile 303.

[0053] - This contact pressure creates a closure that hinders the flow of elastomer between the annular beam and the mold.

[0054] - The annular support 103 is formed.

[0055] - The mold is opened, which includes the axial retraction of the profile 303 and the radial retraction of the profile

[0056] - The exemplary NPT is removed from the mold.

[0057] The inventors put this process into practice by applying an exemplary annular beam. Further, two different versions of the mold profile 303 were designed and put into practice. Figures 5 to 10 Several of the steps described above were shown by 2D axisymmetric finite element modeling (FEA). The two different profiles were analyzed and compared to empirical observations.

[0058] Figure 5 An FEA model of the exemplary annular beam R-Y cross section placed in the mold is shown. Design A is a first design of the mold profile 303a. Design B is a second design of the mold profile 303b. Design B is an exemplary design, which will be explained below.

[0059] For both Design A and Design B, the figure shows the mold profile 301 and the profile 302 radially extended and in contact with the annular beam. The mold profile 303 is adjacent to the annular beam but not in contact with the annular beam. The annular beam has the reinforcement 202, the support face pattern portion 101, and the portion 203 at the axial extension zone (i.e., isotropic rubber).

[0060] Figure 6 Close-up of the annular beam and the axial extension zone of the profile 303a and the profile 303b. The profile 303a has a section 401. This pointed section is designed to create a high pressure on the lateral extension zone of the annular beam when the mold is closed. The profile 303b has a section 501. This rounded section is designed to create a high pressure on the inner radial extension zone of the lateral extension zone of the annular beam. Furthermore, as shown below, the profile 303b enables the deformation of the portion 203 and effectively creates a closure of most of the profile 303b.

[0061] Figure 7 Design A and Design B after the closure of the profile 303a and the profile 303b, respectively, are shown. No thermoplastic injection is performed at this step. The mold is simply closed and in contact with the outer radial extension zone and the axial extension zone of the annular beam.

[0062] Figure 8 For Figure 7 Close-up of the axially extending region. Due to section 401, profile 303a creates a higher local pressure. 303b creates a lower but larger surface area pressure. Region 210 in design B is a critical region because it is located in the area requiring the most to create a closing action that inhibits the injected elastomer from flowing between the mold and the annular beam.

[0063] In at least one embodiment, the closing pressure comes from a set of deformations caused by interference with the radially inward convex feature, while also caused by the pressure generated by the injected material during the molding process. Due to this pressure increase, the un-reinforced rubber is forced to adapt to the convexity between the inner and outer radial convex features, creating a stronger closing that can prevent blow-by during the resin molding process.

[0064] The lateral outside deformation of the axially outer portion of the annular beam causes the radially inner surface to deform radially outward in the un-reinforced region near the axially extending region. After the injection molding process, when the thermoplastic is cooling and shrinking, the deformation caused by the sealing process is released since the NPT has been demolded, thus the radially inner surface moves radially inward in the same direction as the thermoplastic is being pulled back by the adhesive thermoplastic. Therefore, those components do not create tension to each other along the edge of the annular beam between the thermoplastic and the rubber, but instead, the components create a compression force, which helps to reduce the tension at the bond between the thermoplastic and the rubber, resulting in an improved bond.

[0065] Figure 9 The deformed geometry is shown after the thermoplastic injection molding process has created pressure on the inner radial surface of the annular beam. 201u is the "undeformed" profile, while 201d is the "deformed" profile at a pressure of 3.5 MPa (500 psi). For both designs, the deformed profile 201d is close to and parallel with 201u in the region radially inward from the reinforcement 202. Then, radially inward from region 203, the deformation is greater. This is because of the lack of reinforcement in region 203. Surprisingly, the inventors have found that this behavior can create a dynamic seal or gasket effect.

[0066] Related to this is the deformation of design B. The isotropic rubber of portion 203 deforms and rotates into profile 303b, creating a larger contact area and contact pressure.

[0067] Figure 10 The deformed geometry is shown after the thermoplastic injection molding process has created pressure on the inner radial surface of the annular beam. 201u is the "undeformed" profile, while 201d is the "deformed" profile at a pressure of 3.5 MPa (500 psi). For both designs, the deformed profile 201d is close to and parallel with 201u in the region radially inward from the reinforcement 202. Then, radially inward from region 203, the deformation is greater. This is because of the lack of reinforcement in region 203. Surprisingly, the inventors have found that this behavior can create a dynamic seal or gasket effect. Figure 9Close-up of the medially extending region. Due to the profile 401, design A does create higher contact pressure locally. This is beneficial for creating a closing action. Design B, however, allows for a large area of contact between the tire and the mold, and does not risk damaging the rubber due to the local high pressure. Due to the lack of reinforcement, the entire region 203 deflects radially outward under the injection pressure. Then, due to the profile 303b, and especially due to the convex profile portion 501, a relatively large area 210 of rubber is pressed tightly against the mold profile. This creates an effective closing, while there is no risk of damaging the annular beam.

[0068] As previously described, designs A and B were implemented and tires were manufactured using the mold profiles 303a and 303b. While both designs provided closing, profile 303b was more successful. The mold profile 303b and the design of the annular beam in the region near the axially extending region combined, and thus, the tires manufactured using 303b had very clean molding characteristics and high quality. The design of the mold acted in conjunction with the design of the annular beam to create the exemplary molding process.

[0069] Certain additional elements, which are assumed to be within the ability of one of ordinary skill in the art, are not described or shown, some embodiments can not, can lack, and / or can function without any elements not specifically disclosed herein.

[0070] In some examples of embodiments, any feature of any embodiment discussed herein can be combined with any feature of any other embodiment discussed herein.

[0071] While various embodiments and examples have been presented, this is for the purpose of description only, and should not be taken as limiting. Various modifications and enhancements will become apparent to one of ordinary skill in the art.

[0072] As used herein, the terms "method" or "process" refer to one or more steps that can be performed in a different order than shown without departing from the scope of the invention.

[0073] The terms "a," "an," and the singular forms of words are to be construed to cover both singular and plural forms of the identical word, such that the terms include one or more of the items. The terms "at least one" and "one or more" are used interchangeably. A range described as "between a and b" includes the values "a" and "b."

[0074] Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any application disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such application. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

Claims

1. A process for forming a non-pneumatic tire, the process comprising - forming a toroidal beam comprising a first elastomer, the toroidal beam further comprising a circumferential reinforcement extending in a circumferential direction; the toroidal beam being free of the circumferential reinforcement over a width of at least 8 mm at an axially extending region, the axially extending region comprising the elastomer; - molding a toroidal support attached to an innermost radially extending region of the toroidal beam by a thermoplastic injection molding process using a mold, the mold contacting and sealing against an outermost radially extending region of the toroidal beam; and - removing the non-pneumatic tire from the mold, wherein the thermoplastic injection molding process further comprises: - placing the toroidal beam in the mold, the mold comprising a first portion A contacting the outermost radially extending region of the toroidal beam and a second portion B contacting the axially extending region of the toroidal beam, the second portion B being axially extendable, - axially extending the second portion B to contact the axially extending region of the toroidal beam, forming a mold cavity for which the outermost radially extending region is defined by the innermost radially extending region of the toroidal beam; - injecting a second elastomer, a thermoplastic elastomer, into the mold cavity, forming the toroidal support; - deforming the axially extending region of the toroidal beam by the molding pressure, the deformation creating a contact pressure between the toroidal beam and the mold portion B, the contact pressure being sufficient to inhibit flow of the thermoplastic elastomer between the toroidal beam and the mold, and thereby forming the toroidal support and attaching it to the innermost radially extending region of the toroidal beam; - opening the mold, the opening comprising axially retracting the mold portion B.

2. A process for forming a non-pneumatic tire, the process comprising - forming a toroidal beam comprising a first elastomer, the toroidal beam further comprising a circumferential reinforcement extending in a circumferential direction; the toroidal beam being free of the circumferential reinforcement over a width of at least 8 mm at an axially extending region, the axially extending region comprising the elastomer; - molding a toroidal support attached to an innermost radially extending region of the toroidal beam by a thermoplastic injection molding process using a mold, the thermoplastic injection molding process comprising: - placing the toroidal beam in the mold, the mold comprising a first portion A contacting the outermost radially extending region of the toroidal beam and a second portion B contacting the axially extending region of the toroidal beam, the second portion B being axially extendable, - axially extending the second portion B to contact the axially extending region of the toroidal beam, forming a mold cavity for which the outermost radially extending region is defined by the innermost radially extending region of the toroidal beam; - injecting a second elastomer, a thermoplastic elastomer, into the mold cavity, forming the toroidal support; - deforming the axially extending zone of the annular beam by the molding pressure, the deformation creating a contact pressure between the annular beam and the mold portion B, the contact pressure being sufficient to inhibit the flow of the thermoplastic elastomer between the annular beam and the mold, and thereby forming the annular support and attaching it to the innermost radially extending zone of the annular beam; - opening the mold, the opening comprising axially retracting the mold portion B; - removing the non-pneumatic tire from the mold.

3. A non-pneumatic tire formed by the process of claim 1 or 2, the non-pneumatic tire comprising: - an annular beam comprising a first elastomer and a circumferential reinforcement extending in a circumferential direction, the annular beam being free of the circumferential reinforcement at an axially extending zone over a width of at least 8 mm, the axially extending zone comprising the first elastomer, a radially tilted portion of the annular beam at a laterally extending zone having a profile with an angle a of at least 15 degrees; - an annular support extending radially inwardly from the annular beam, the support comprising a second elastomer; the support being formed by a thermoplastic injection molding process, wherein an outermost radially extending zone of a mold cavity is defined by an innermost radially extending zone of the annular beam.

4. The non-pneumatic tire of claim 3, wherein, the annular beam being free of the circumferential reinforcement at an axially extending zone over a width of at least 12 mm.

5. The non-pneumatic tire of claim 4, wherein, the annular beam being free of the circumferential reinforcement at an axially extending zone over a width of at least 16 mm.

6. The non-pneumatic tire of claim 3, 4, or 5, wherein, the first elastomer comprises rubber.

7. The non-pneumatic tire of claims 3, 4, or 5, wherein, the second elastomer is a thermoplastic.

8. The non-pneumatic tire of claims 3, 4, or 5, wherein, the first elastomer comprises rubber, the second elastomer being a thermoplastic.

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