Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C7/00—Non-inflatable or solid tyres
  • B60C7/10—Non-inflatable or solid tyres characterised by means for increasing resiliency
  • B60C7/14—Non-inflatable or solid tyres characterised by means for increasing resiliency using springs
  • B60C7/146—Non-inflatable or solid tyres characterised by means for increasing resiliency using springs extending substantially radially, e.g. like spokes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C7/00—Non-inflatable or solid tyres
  • B60C7/10—Non-inflatable or solid tyres characterised by means for increasing resiliency
  • B60C7/14—Non-inflatable or solid tyres characterised by means for increasing resiliency using springs
  • B60C7/16—Non-inflatable or solid tyres characterised by means for increasing resiliency using springs of helical or flat coil form
  • B60C7/18—Non-inflatable or solid tyres characterised by means for increasing resiliency using springs of helical or flat coil form disposed radially relative to wheel axis
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C7/00—Non-inflatable or solid tyres
  • B60C2007/005—Non-inflatable or solid tyres made by casting, e.g. of polyurethane

Definitions

• the object of the present invention is an airless tire intended for a vehicle, and relates more particularly to its shear band.
• a conventional tire subjected to the internal pressure of an inflation gas, generally air, has load capacities, transmission of forces between the ground and the vehicle, and shock absorption which make it a preferred choice for use on a vehicle.
• a risk inherent in conventional tires is a more or less rapid loss of pressure, in the event of impact or rolling on a puncturing object, likely to cause the vehicle to be immobilized.
• a solid tire which carries the load by compressing its structure, does not have the performance advantages previously described for a conventional tire.
• a solid bandage is generally heavy and rigid, therefore with less shock absorption capacity.
• it often has a lower load capacity and lower endurance, due to greater heating in use. Consequently, a solid tire has a use limited to specific vehicles, such as, by way of example and not exhaustively, handling equipment.
• An airless tire or more generally a tire without inflation gas, is another known alternative solution, which carries the load thanks to structural components and which has performance comparable to that of a conventional tire.
• An airless tire, mounted on a hub or rim, is sometimes called a "non-pneumatic rubber wheel".
• the circumferential or longitudinal direction denotes the direction of rotation of the tire
• the axial or transverse direction denotes the direction parallel to the axis of rotation of the tire
• the radial direction denotes a direction perpendicular to the axis of rotation of the tire.
• An airless tire generally comprises, radially from the inside to the outside:
• a tread intended to transmit the rolling forces to the shear tread, to be worn and to guarantee the grip of the tire on the ground.
• the load-bearing structure comprises, for example, radially from the inside out, means for connection with a rim or a hub, radial elements or spokes, and means for connection with a shear strip.
• the support structure does not generally delimit a sealed internal cavity intended to contain a pressurized gas, as in a conventional tire. Therefore an airless tire does not need to have a sealed connection to a rim or a hub.
• the shear band comprises, in a known embodiment, radially from the inside outwards:
• -a shear layer consisting of one or more polymeric materials, -a second outer membrane.
• the shear layer is in direct interface with respectively the first and the second membrane.
• the first and the second membrane have a modulus of elasticity in circumferential extension often substantially greater than the shear modulus of elasticity of the shear layer of polymeric material, such that, under the load applied, the membranes stretch little or not at all when the tire is flattened while driving.
• the relative displacement of the Tune membranes with respect to each other occurs by shear in the layer of shear.
• the membranes comprise superposed layers of reinforcements coated in a polymeric material.
• the shear layer of polymeric material consists, by way of example, of a polymeric material, such as natural rubber or synthetic rubber, or of a polyurethane.
• the material of the shear layer has a shear modulus at least equal to 3 MPa and at most equal to 20 MPa, which allows easier flattening of the shear strip under load.
• the Michelin North America company has marketed, for several years, a complete solution of a mounted assembly, consisting of an airless tire, as described above, and a wheel, under the name MICHELIN® TWEEL ®.
• This technical solution mainly consists of a tread, a shear band or "shear-band", a supporting structure, made up of highly resistant spokes or “spokes” in poly-resin and a hub consisting of two reinforced steel pieces.
• the shear strips of an airless tire of the state of the art have two main drawbacks, which are a generally high mass and the generation of contact pressures on the ground comprised in a relatively restricted range of values.
• high contact pressures can only be generated by a shear band having a very high mass, which is neither mechanically viable nor economically acceptable.
• the use of such shear strips is limited, in practice, to airless tires operating either at low pressure and at high speed, as on a passenger vehicle, or at high pressure and at low speed, as on a Bobcat® utility vehicle.
• the shear levels of the shear band, necessary to generate low contact pressures are difficult to achieve with a shear layer consisting of the usual polymeric materials.
• the inventors have set themselves the objective of proposing an airless tire comprising a shear band having, for a given load capacity of the tire, and compared to a shear band of the state of the art, a mass reduced and a shear stiffness suitable for obtaining a level of mean contact pressure with the targeted ground.
• an airless tire for a vehicle comprising, radially from the inside outwards, a supporting structure intended to cooperate with a rim or a hub, a shear band and a tread,
• the shear band comprising, radially from the inside out, a radially inner membrane, a shear structure and a radially outer membrane positioned at an average radial distance H from the radially inner membrane,
• the shear structure comprising a plurality of shear elements distributed circumferentially
• any shear element of the plurality of shear elements comprising a running portion having, in any circumferential plane perpendicular to the axis of rotation of the tire, a non-radial generatrix having a radially inner end positioned at a distance dl from the membrane radially inner, and a radially outer end positioned at a distance d2 from the radially outer membrane,
• the shear band of an airless tire essentially comprises a circumferential distribution of a plurality of shear elements distributed according to a pitch that is not necessarily constant.
• a plurality of shearing elements is a set of shearing elements, usually including all of the shearing elements, but possibly possibly including only part of the shearing elements.
• This discrete shear structure makes it possible to have a recessed shear strip, guaranteeing a mass of the crown of the tire without air which can be, for example, quite close to that of the crown of a conventional tire.
• the crown of the tire is the portion of the tire radially external to the load-bearing structure, for a airless tire, or radially external to the carcass reinforcement for a conventional tire.
• the shear strip comprises, radially from the inside out, a radially inner membrane, a shear structure and a radially outer membrane positioned at an average radial distance H from the radially inner membrane.
• the average radial distance H between the two respectively radially inner and radially outer membranes is an average over the circumference of the tire.
• any shear element that is to say any elementary pattern, of the plurality of shear elements, has a circumferential section having an average line , called generator, non-radial and curvilinear in shape. This generatrix extends between a radially inner end, positioned at a distance dl from the radially inner membrane, and a radially outer end, positioned at a distance d2 from the radially outer membrane.
• the respectively radially inner and radially outer ends are not necessarily positioned respectively on the radially inner membrane and on the radially outer membrane, and that there may therefore be a transition zone forming the interface between said common portion of the shear element and the respectively radially inner and radially outer membranes.
• the shape of the generatrix is an open curve and not closed on itself.
• the generator cannot have a closed circular shape.
• the distances d1 and d2 are not necessarily constant according to the axial direction of the tire, i.e. they can vary in the axial width of the shear band.
• this generatrix must have a curvilinear length L, measured along this generatrix between its two respectively radially inner and radially outer ends, at least equal to 1.25 times the shortest distance between its two equal ends to H-(dl+d2)).
• Such a generatrix therefore has a non-zero mean curvature, guaranteeing geometric flexibility of the shearing element.
• this form of generatrix allows either to have a longer effective working length of the shear element, for a given average intermembrane radial distance H, or d having interfaces with the respectively radially inner and radially outer membranes that are sufficiently thick to displace the maximum stresses and deformations at the heart of the shearing element and not at the level of said interfaces.
• the shape of the generatrix in combination with the characteristics of the thickness of the shearing element and of the modulus of elasticity of the material(s) constituting said shearing element, makes it possible to optimize the mechanical characteristics of rigidity of the shear strip, with a view to obtaining the distribution and the value of the contact pressures with the ground, adapted to the use of the vehicle concerned.
• the overall bending stiffness of the shear strip must be high enough to avoid any blistering of the shear strip in contact with the ground. This overall bending rigidity is mainly guaranteed by the radially inner and radially outer membranes respectively.
• the overall shear stiffness of the shear band must also be adapted to guarantee, in particular, the desired level of average pressure in the contact area.
• This overall shear stiffness is mainly imparted by the shear structure interposed between the radially inner and radially outer membranes respectively. The overall shearing of such a shear band, under the action of the rolling forces, generates, in each shear element, a local bending resulting in a deformation of this shear element.
• the invention makes it possible to design shear strips generating high contact pressures on the ground with a tire crown mass of the same order of magnitude as that of the crown of a conventional tire.
• Optimization of the shear strip is achieved by adapting the modulus of the material(s) constituting the shear element and the curvilinear length of the generator, such that the latter is large enough for the stresses and deformations induced in the material(s) constituting the shearing element to be compatible with the breaking strength and/or fatigue limit properties of said material.
• a circumferential distribution of a plurality of shear elements according to the invention makes it possible to obtain a volume of material comprised between the respectively radially inner and outer membranes, making it possible to achieve high pressures on the ground at high rolling speeds. . This makes it possible to extend the scope of use of current airless tires.
• the invention makes it possible to design very flexible shear bands, compatible with severe environmental constraints, such as extremely low temperatures encountered, for example, in extraterrestrial environments. This is possible by adapting the length of the generatrix of the shear elements, so that it is large enough for the stresses and deformations induced in the constituent material(s) to be compatible with the properties of resistance to rupture and /or fatigue limit of said material.
• the distance dl from the radially inner end of the generatrix to the radially inner membrane is at most equal to 0.5 times the average radial distance H between the radially inner membrane and the radially outer membrane.
• the distance dl from the radially inner end of the generatrix to the radially inner membrane is equal to 0. This implies that there is no transition zone forming the interface between said current portion of the shear element and the radially inner membrane.
• the distance d2 from the radially outer end of the generatrix to the radially outer membrane is at most equal to 0.5 times the mean radial distance H between the radially inner membrane and the radially outer membrane.
• the distance d2 from the radially outer end of the generatrix to the radially outer membrane is equal to 0. This implies that there is no there is no transition zone making the interface between said common portion of the shearing element and the radially outer membrane.
• the tangent to the generatrix at its radially inner end forms, with a radial direction of the airless tire, an angle A1 at least equal to 45°.
• the tangent to the generatrix at its radially outer end forms, with a radial direction of the airless tire, an angle A2 at least equal to 45°.
• the generatrix of the current portion of any shearing element has a shape having a single inversion of its direction of curvature, such as an S-shape.
• the current portion of any shear element has a non-constant thickness E0.
• This thickness variation makes it possible to optimize the distribution of stresses and deformations in this shear element.
• the thickness E0 measured in a given circumferential plane, can also vary between two distinct circumferential planes, i.e. according to the axial direction of the tire.
• the shearing elements are distributed circumferentially at a constant pitch.
• any shear element consists of a material having a modulus of elasticity in extension at 4% elongation at least equal to 20 MPa, preferably at least equal to 30 MPa. This modulus of elasticity in extension is measured statically.
• the shape of the generators of the shear elements induces that the stresses generated by the shearing of the shear band, resulting from the rolling forces, are low enough to allow the use of materials having higher moduli of elasticity than those of the elastomeric materials commonly used in the field of conventional tires.
• FIG. 1 is an overview of an airless tire 1 according to the invention.
• the airless tire 1 comprises, radially from the inside outwards, a supporting structure 2, intended to cooperate with a rim or a hub 3, a shear band 4 and a tread 6.
• the shear band 4 comprises, radially from the inside out, a radially inner membrane 41, a shear structure 40 and a radially outer membrane 42.
• the shear structure 40 is constituted by a plurality of shear elements 5 distributed circumferentially. Each shear element 5 of the plurality of shear elements has a non-radial generatrix having a radially inner end II and a radially outer end 12.
• FIG. 2 is a circumferential sectional view of a shearing element 5 according to a first embodiment (with d1 and d2 not miles).
• the shear element 5 comprises a running portion 50 having, in any circumferential plane XZ perpendicular to the axis of rotation of the tire, a non-radial generatrix G having a radially inner end II positioned at a distance d1 from the radially inner membrane 41 , and a radially outer end 12 positioned at a distance d2 from the radially outer membrane 42, and the generatrix G of the running portion 50 of the shear element 5 has a curvilinear length L at least equal to 1.25*(H-(dl+d2)), H being the average radial distance between the radially inner membrane 41 and the radially outer membrane 4.
• the distance dl from the radially inner end II of the generator G to the radially inner membrane 41 and the distance d2 from the radially outer end 12 of the generator G to the radially outer membrane 42 are less than 0.5 times the average radial distance H and not miles.
• the tangent T1 to the generatrix G at its radially inner end II forms, with a radial direction ZZ' of the airless tire 1, an angle Al at least equal to 45° and even close to 90°.
• the tangent T2 to the generatrix G at its radially outer end 12 forms, with a radial direction ZZ' of the airless tire 1, an angle A2 at least equal to 45° and even close to 90°.
• generatrix G of running portion 50 of shearing element 5 has an S-shape and running portion 50 of shearing element 5 has a constant thickness E0.
• Figure 3 is a circumferential sectional view of a portion of shear strip 4 according to a first embodiment (with d1 and d2 not miles).
• the shear strip 4 comprises, radially from the inside outwards, a radially inner membrane 41, a shear structure 40 and a radially outer membrane 42.
• the shear elements 5 are of the type described in FIG. .
• Figure 4 is a circumferential sectional view of a shearing element 5 according to a second embodiment (with d1 and d2 miles).
• This shearing element 5 differs from that of FIG. 2 by a generatrix shape G with more marked curvatures, a longer generatrix length G and a lower current portion thickness.
• the distance dl from the radially inner end II of the generatrix G to the radially inner membrane 41 and the distance d2 from the radially outer end 12 of the generatrix G to the radially outer membrane 42 are miles.
• the common portion 50 is in direct interface with the respectively radially inner 41 and radially outer 42 membranes.
• Figure 5 is a circumferential sectional view of a portion of shear strip 4 according to a second embodiment (with d1 and d2 miles).
• the shear strip 4 comprises, radially from the inside outwards, a radially inner membrane 41, a shear structure 40 and a radially outer membrane 42.
• the shearing elements 5 are of the type described in FIG. 4.
• the inventors have more particularly studied this invention according to two different embodiments R1 and R2.
• a first embodiment RI relates to an airless tire intended to replace a reference tire of size 235/65 R16 LI/SI 121R, within the meaning of the European standard of the “European Tire and Rim Technical Organization” (Organization European tire and wheel technology) or "E.T.R.T.O” in its “Standards Manual 2020", intended to equip vehicles of the van type.
• the modulus of elasticity in extension at 4% elongation of the constituent material of a shear element is equal to 150 MPa, corresponding, for example, to a thermoplastic elastomer (TPE).
• a second embodiment R2 relates to an airless tire having an outer diameter equal to 800 mm and an overall width equal to 300 mm, intended to equip a vehicle able to run in an extreme environment at very low temperatures.
• the modulus of elasticity in extension at 4% elongation and at -200°C of the material constituting a shear element is equal to 5800 MPa, corresponding, for example, to a thermoplastic of the polyetheretherketone type (PEEK ) or a polyimide.
• the average ground contact pressure generated by the shear strip of the tire according to the first embodiment R1 is equal to 5 bars for a mass of shear strip equal to 8.7 kg, according to the numerical simulations carried out by the inventors, using finite element calculation software.
• the average ground contact pressure generated by the shear strip of the tire according to the second embodiment R2 is equal to 0.075 bars, according to the numerical simulations carried out by the inventors, using finite element calculation software

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Tires In General (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (6)

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Family Cites Families (8)

• 2021
  • 2021-12-14 FR FR2113425A patent/FR3130201B1/fr active Active
• 2022
  • 2022-12-09 CN CN202280080936.2A patent/CN118369219A/zh active Pending
  • 2022-12-09 WO PCT/EP2022/085108 patent/WO2023110657A1/fr not_active Ceased
  • 2022-12-09 EP EP22835605.1A patent/EP4448302A1/fr active Pending
  • 2022-12-09 JP JP2024535793A patent/JP2024544288A/ja active Pending
  • 2022-12-09 US US18/719,816 patent/US20250144961A1/en active Pending

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