MXPA01003127A - Deformable non-pneumatic tyre - Google Patents

Abstract

The invention concerns a deformable structure (1) for a vehicle, designed to run about an axis of rotation, comprising an inner ring-shaped element (3) centred on the axis, an outer ring-shaped element (4) forming a flexible and substantially extensible running tread, arranged radially externally relative to said inner element (3), a plurality of spokes (5, 52, 53, 56) arranged substantially radially between the inner element (3) and the outer ring-shaped element (4), each spoke being capable of opposing with a radial compression stress, beyond a specific threshold, a substantially constant force, said outer element (4) having a circumferential lengthuch that said spokes (5, 52, 53, 56) are prestressed with radial compression, and means stabilising (6, 7) relative positions between the inner element (3) and the outer element (4). The invention is characterised in that said spokes (5, 52, 53, 56) are shaped and arranged between the inner (3) and the outer (4) elements such that their flexibility in a meridian plane is much less than their flexibility in a circumferential plane and the stabilising means (6, 7) limit the amplitude of a circumferential relative rotation between the inner element (3) and the outer element (4).

Description

DEFORMABLE NON-PNEUMATIC WHEEL DESCRIPTION OF THE INVENTION The present invention relates to non-pneumatic wheels, especially those susceptible to be used in substitution of tires in vehicles. For a long time it has been tried to conceive such non-pneumatic wheels, that is to say, that they operate without air under pressure, in order to be free of any problem posed by blowouts or decreases in tire inflation pressure. Among many proposals, one can cite the one described in the US patent US 3 234 988. This patent discloses a non-pneumatic deformable wheel comprising a disk, an internal element fixed to the disk, a flexible and substantially inextensible annular outer element intended to enter in contact with the ground, and a plurality of spokes disposed between the interior and exterior elements. The outer element has a length such that it requests said spokes in radial compression.

In other words, they are pre-stressed (that is, preloaded). Beyond a certain threshold of solicitation, since the radii are requested from one end, the radially oriented reaction effort that each of these radii can develop remains constant. The Ref: 128409 wheel also comprises means for stabilizing the relative positions of the outer and inner elements. The spokes flex in a meridian plane and the stabilization means limit the axial relative displacements of the inner and outer elements. This deformable wheel uses as a union between the inner and outer elements prestressed spokes beyond its buckling load. Thus, in the event of an increase in the load borne by the wheel, this increase is compensated only by an increase in the number of spokes that effectively support the load. An increase in the contact length between the wheel and the ground is thus obtained. A behavior of this type is very similar to that of a tire. However, this wheel has a great disadvantage. The different radii flex in their meridian planes, but they do not have, practically, the possibility of circumferential deformation because their section presents a great inertia in the circumferential direction. However, during a taxi, the outer element in contact with the ground undergoes significant longitudinal stresses, especially in the contact area, which causes a rapid destruction of said non-pneumatic wheel. The object of the invention is a deformable structure designed to form, for example with a disc, a non-pneumatic wheel that has the same advantages of comfort and behavior, while solving the preceding problem. The deformable structure for a vehicle, according to the invention, designed to roll around an axis of rotation, comprises an annular inner element centered on the axis, a flexible and substantially inextensible annular outer element forming a tread, arranged in radial direction externally with respect to the inner element, a plurality of spokes disposed between the inner and outer elements, each radius being suitable for opposing a radial compression stress, beyond a given threshold, a substantially constant force, the annular outer element having a length such that the spokes are prestressed in radial compression, as well as means of stabilizing the relative positions of the inner and outer elements. This running structure is characterized in that the spokes are shaped and arranged between the inner element and the outer element in such a way that its flexibility in a meridian plane is much lower than its flexibility in a circumferential plane and because the stabilization means limit the amplitude of a relative circumferential rotation between the inner and outer elements. The wheel obtained from the deformable structure according to the invention, has the following advantage: each radius can deform in a circumferential direction, especially during taxiing, when it is within the contact zone between the outer element and the ground. Preferably, the spokes are prestressed beyond their buckling load. The stabilization means may also comprise elastic connecting elements, such as cables or slender tie rods, which non-radially join the inner and outer elements. These stabilizing means are prestressed in extension in a state of rest to immediately exert a recovery effort during a relative movement of rotation between the inner and outer elements. The ends of the spokes can be fixed, by embedment or by joints, to the inner element and / or the outer element. The stabilization means may also be a thin disc prestressed in radial extension. The deformable structure according to the invention can also constitute a safety insert intended to be mounted in a set consisting of a tire and a rim. Several embodiments of the invention are now described, with the help of the following figures: Figure 1 is an axial view of a wheel constituted by a deformable structure according to the invention fixed to a disc; - figure 2 is a meridian section of the wheel of figure 1; - figure 3 presents a partial axial view of a wheel similar to that of figures 1 and 2, equipped with stabilization means; Figure 4 shows double and articulated spokes, in rest state 4a, and in deformed state 4b; and - Figure 5 shows another embodiment of the radii, double and recessed, in rest state 5a, and in deformed state 5b; Figure 6 shows spokes of the wheel of Figure 1 under load, outside the contact area 6a and inside the contact area 6b; Figure 7 presents means for stabilizing the wheel of Figure 6 under load, outside the contact area 7a and within the contact area 7b: Figures 1 and 2 present, respectively, in axial view and in meridian section, a non-pneumatic wheel constituted by a deformable structure 1 according to the invention affixed to a disk 2. The deformable structure 1 comprises an inner element 3 attached to the disk 2, an outer annular element 4 and spokes 5 joining the inner element 3 and the outer element 4. The spokes 5 are distributed in two sets of 60 elements arranged axially juxtaposed (Figure 2). The spokes 5 have a parallelepiped shape with a small thickness with respect to their length and width. This shape allows them to flex easily in the direction of their thickness. The spokes 5 have their two longitudinal ends fixed, respectively, to the inner element 3 and to the outer element 4 by articulations 51. These spokes are arranged between the inner 3 and outer elements 4 in such a way that their length is in a radial direction, their width in an axial direction and its thickness in a circumferential direction. Consequently, the spokes 5 can flex under a radial compression of their longitudinal ends. This flexion is circumferential. The flexibility of the spokes 5 in a meridian plane is, therefore, much lower than their flexibility in a circumferential plane. In the embodiment of FIGS. 1, 2 and 4, the joints 51 are composed of two parts 511 and 512 (see Fig. 4), fixed together by an axis 513. This fixing mode allows a free rotation between the two parts 511 and 512 of the joints 51. The axes 513 are arranged in the axial direction of the wheel. This connection mode allows a rotation of the spokes 5 with respect to the inner and outer elements in the plane of the wheel. The spokes 5 are made, for example, of a polymer material reinforced with glass fibers. The annular outer element 4 comprises a metal ferrule of small thickness (of the order of 0.1 to 1 mm) covered by an elastomer layer intended to come into contact with the ground (this elastomer layer is not shown in Figure 2) . The outer element thus has little flexural rigidity and is substantially inextensible. The circumferential length of this outer element 4 is such that the spokes 5 are all prestressed in axial compression beyond their buckling load. All these radios 5 are, therefore, in a post-panning state. Consequently, the reaction force that these oppose the inner element 3 and the outer element 4 is substantially constant and independent of the amplitude of its radial compression. The wheel, such as that shown in FIGS. 1 and 2, is in an unstable equilibrium state and the energy stored in the spokes 5 tends to be released by a displacement in rotation of the outer element 4 with respect to the inner element 3. To limit the relative rotation between the inner element 3 and the outer element 4, the deformable structure 1 is provided with stabilization means presented in figure 3. These stabilization means are composed, for example, of cables 6 connecting the inner element 3 and the annular outer element 4. In figure 3, the cable 61 fixed in A to the inner element 3 and fixed in B to the outer element 4 is seen. Being O in the axis of rotation of the wheel, the angle AOB = OI is, in the example represented and at rest, equal to 30 degrees. This angle AOB can vary from 1 to 45 degrees and, preferably, between 25 and 35 degrees. The cables 6 are shaped and arranged to be in tension at rest. These cables 6 thus contain the displacement in rotation of the annular outer element 4 with respect to the inner element 3. However, specific relative displacements in the contact area are still possible. The rigidity, arrangement, pretension in extension and the number of these cables influence the propensity to conserve globally the equilibrium position presented in figure 1. Moreover, these cables allow to regulate the circumferential rigidity of the wheel according to its own rigidity in extension, as well as depending on its inclination with respect to the circumferential direction. The cables can also be of several different rigidities on either side of their anchor point on the inner element and the outer element, which causes a variation of the response of the wheel to a circumferentially applied torque. In order to obtain such mechanical response asymmetry, the inclination angles on both sides of their anchoring points can also be modified. It is also possible to replace the cables with more monolithic elements or by any equivalent stabilization means. Figures 4 and 5 present other modes of arrangement and connection of the spokes to the interior 3 and exterior 4 elements. In figure 4, two radii 52 and 53, with their articulations 51 are seen. As previously, the articulations 51 comprise two parts, the first 511, wherein one longitudinal end of the radius 52, 53 is recessed, and the second 512, rigidly fixed to the internal element or the outer element. These two parts are joined by a shaft 513 arranged on the wheel mounted in the axial direction of the deformable structure 1. In the embodiment of Figure 4, the spokes are arranged circumferentially two to two between the interior and exterior elements , as above, with its plane of circumferentially oriented flexion. The longitudinal ends of the spokes 52 and 53 are embedded in the supports 511 in such a way that the distance D separating the two spokes is greater than the distance d separating the two axes 513. Consequently, during an axial compression, it is applied a pair to the spokes that imposes a circumferential flexion of the two spokes in two opposite directions such that their central parts separate (Figure 4b). This assembly has the advantage of facilitating the buckling of the spokes always in the same direction. Figure 5 shows a double radius 56 embedded in a support 57. Contrary to the previous embodiments, this support 57 comprises a single part rigidly connected to the interior or exterior elements. The radius 56 is constituted by two parallelepiped semi-radii 561 and 562 arranged circumferentially juxtaposed and embedded in the supports 57. The supports 57 are fixed to the inner and outer elements. These two half radii are circumferentially separated by a plate 563. This plate orientates, as before, the circumferential bending of the two half radii in two opposite directions such that their central parts separate (FIG. 5b). Figures 6 and 7 illustrate, schematically, the behavior of a wheel comprising a deformable structure 1 during a flattening on a flat floor. This wheel comprises two sets of spokes 5 similar to those of FIGS. 1, 2 and 3 and stabilization means 7 constituted by two sets of tiers of square section of polyurethane material. The two sets of struts 7 have a non-radial inclination and are arranged symmetrically on either side of the radial direction, as illustrated in Figure 3. The extension module of these struts is of the order of 20 MPa. The orientation of the straps 7 is similar to that of the cables 6 presented in Figure 3. In Figures 6b and 7b only, the outer element 4 is represented with a layer of elastomeric material which ensures contact with the ground 8. This layer has a thickness of the order of 10 mm. For reasons of clarity of presentation, the evolution of the behavior of only one of the two sets of radii 5 outside the contact area (6a) and within the contact area (6b), and in FIG. 7a and 7b, the evolution of only one of the two sets of braces inside (7b) and outside the contact area (7a). During a crushing of the wheel 1 on a floor 8, it is noted that the spokes 5 are all maintained in a post-tapping condition, but with large radial compression variations. Three cases are presented: outside the contact area (6a) - radii Rl - the spokes have a slight radial compression; within the contact area, between the points E and F, the radii R2 have a radial compression more important; in the vicinity of the entrance and exit of the contact area, the radii R3 have intermediate radial compression. The radial compression of the spokes 5 is directly a function of the radial distance between the inner element and the outer element, therefore, of the arrow adopted by the wheel during its crushing on the ground. Since each radius is in the postpanning state, it exerts a substantially constant reaction force on the outer element 4. In the area of contact between the ground and the wheel, the contact area, the outer element or tread band therefore exerts a substantially constant average pressure on the ground. As this force is practically not modified by the amplitude of the radial compression supported by the radius 5, the pressure exerted by the annular outer element in the corresponding area is thus substantially independent of the amplitude of the arrow adopted by the crushed wheel. This behavior is, thus, very similar to that of a tire. This makes it possible to absorb soil irregularities without provoking violent reactions transmitted to the wheel disc, nor to generate significant variations in the contact surface between the wheel and the ground. This is a behavior very similar to that of a tire. Figure 7 illustrates the evolution of only one of the two sets of struts within the contact area (7b) and outside it (7a). Three cases are presented: the braces whose anchoring points to the inner and outer elements are outside the contact area (7a) - braces Hl - are in a state of slight tension; the suspenders - suspenders H2 - whose anchor points to the outer element are within the contact area, between the points E and F, are in the buckling state; the straps arranged at the entrance and exit of the contact area - tie rods H3 - are in an intermediate state. It is thus verified that the straps whose anchoring point is inside the contact area are relieved of their tension by the radial compression of the outer element, which approximates the anchoring points of the braces between the inner element and the outer element. Accordingly, these struts, whose section is small, buckle and only weakly oppose this radial compression of the outer element within the contact area or during a taxiing over an obstacle. The shown wheel also has the advantage of having an excellent homogeneity of the contact pressures between the annular outer element and a flat floor in the axial direction due to the symmetry of construction of the spokes shown in figure 2. easily realize an outer element 4 vulcanizing a thickness of rubber on a ring. This ring can be a flat steel plate of width L and of thickness 0.1 mm. The deformable structure according to the invention can also be provided with means, such as stops, for limiting the radial compression of the spokes. By way of example, between the two sets of spokes of figures 1 to 3 axially juxtaposed, an annular stop fixed to the inner element of outer diameter can be provided such that it limits up to approximately 50% the maximum axial compression of these spokes. In the examples presented in FIGS. 1 to 3, two sets of axially juxtaposed spokes are arranged, it is perfectly possible to substantially increase this number of axially juxtaposed assemblies to improve the behavior on an uneven floor of the wheel or insert formed. Also, the outer element can be formed by one or more axially juxtaposed elements.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (6)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. Deformable structure for a vehicle, designed to roll around an axis of rotation, characterized in that it comprises an annular interior element centered on the axis, an element annular exterior forming a flexible and substantially inextensible tread, arranged in radial direction externally with respect to the inner element, a plurality of spokes disposed substantially radially between the inner element and the outer annular element, each radius being suitable for opposing at a radial compression stress, beyond a given threshold, a substantially constant stress, said outer element having a circumferential length such that said spokes are preloaded in radial compression, as well as means of stabilizing the relative positions of the inner element and the elemen outer, characterized in that said spokes are shaped and arranged between the inner and outer elements in such a way that their flexibility in a meridian plane is much lower than their flexibility in a circumferential plane and because said stabilization means limit the amplitude of a Circumferential relative rotation between the inner element and the outer element.
2. 2. Deformable structure according to claim 1, characterized in that the spokes are pre-loaded beyond their buckling load.
3. 3. Deformable structure according to one of claims 1 or 2, characterized in that the stabilization means comprise elastic connecting elements that non-radially join the outer element and the inner element.
4. 4. Deformable structure according to claim 3, characterized in that the elastic connecting elements are in tension when said structure is at rest.
5. 5. Deformable structure according to one of claims 3 and 4, characterized in that the elastic connecting elements join points of the outer annular element and the inner element angularly separated, at rest, at an angle OI comprised between 1 and 45 degrees.
6. 6. Deformable structure according to claim 5, characterized in that the elastic connecting elements join points of the outer annular element and the inner element angularly separated, at rest, at an angle a comprised between 25 and 35 degrees. . A deformable structure according to one of claims 3 to 6, characterized in that the elastic connecting elements are prestressed cables in extension. Deformable structure according to one of claims 1 to 7, characterized in that the stabilization means comprise a thin disc prestressed in radial extension arranged between the inner and outer elements. 9. A deformable structure according to one of claims 1 to 8, characterized in that the ends of the spokes are fixed by embedding the inner element and / or the outer element. 10. Deformable structure according to one of claims 1 to 9, characterized in that the ends of the spokes are fixed by joints to the inner element and / or to the outer element. Deformable structure (1) according to one of claims 1 to 10, characterized in that it comprises means for limiting the amplitude of the radial compression of the spokes. 12. Non-pneumatic vehicle wheel characterized in that it comprises a disc and a deformable structure according to one of claims 1 to 11. 13. Vehicle safety insert, intended to be assembled in a set consisting of a tire and a rim, characterized in that it is constituted by a deformable structure according to one of claims 1 to 11.