FR2802857A1 - Run flat support for motor vehicle tyre has ring with locating ribs to fit onto rim seating - Google Patents

Abstract

The run-flat tyre support (1) for a motor vehicle is fitted around a rim bearing and has a base with ribs (12) formed on its internal support surface. The ribs form centering guides and can be tapered to allow a friction engagement between the rim and tyre.

Description

The present invention relates to safety supports for vehicle tires which are mounted inside the tires, on their rims, to support the load in case of tire failure. More particularly, it relates to the connection between these safety supports and the rims around which they are mounted.

The main function of the safety supports is to support the load in case of severe loss of tire pressure. When the tires are normally inflated, the safety supports must have the least impact on the dynamic properties of the tires. In particular, they must remain centered around the rim to avoid any unbalance effect, and this regardless of the temperature of the support and the running speed of the vehicle. They must also be able to be mounted around the wheel rims of the vehicles and disassembled easily.

No. 5,690,762 discloses a safety support made of an elastic material intended to be mounted on a rim of a conventional passenger vehicle with a hollow base. This support comprises a body and a base intended to come into contact with the rim. This support further comprises annular reinforcements circumferentially oriented and substantially inextensible whose diameter is slightly greater than the diameter of the hooks of the rims for which the support is provided. The base consists of two annular zones whose inner diameter, in the free state, is less than that of the parts of the rim on which they must rely: compression these annular zones thus ensures a good centering of the support on the rim. The function of the annular reinforcements is in particular to prevent, because of high-speed centrifugation efforts, the annular zones do not extend until losing contact with rim.

When a safety support is intended to equip a rim in two parts or a rim having a bearing for a support whose diameter is greater than that of one of the hooks of the rim as shown in FIG. arrange the ring reinforcements in the base. This is the case of the support disclosed by the application EP 0 796 747 A1. Such a position of the annular reinforcements facilitates the making of the support. For such support, given the manufacturing tolerances of the rim and the support, it is no longer possible to have the radially inner annular zones whose compression ensures a good centering around the rim regardless of the speed while assuring easy assembly disassembly.

Equatorial means a safety support, any plane perpendicular to the axis of rotation of the support and equatorial middle plane, the equatorial plane disposed in the middle of the support.

The invention relates to a safety support intended to be mounted on a rim inside a tire fitted to a vehicle, to support the tread of the tire in the event of loss of inflation pressure, comprising a base substantially cylindrical adapted to fit around the rim, with a zone substantially circumferentially inextensible resistance of low flexural stiffness and whose radially inner diameter is slightly greater than the diameter of the bearing support of the rim, the base also comprising means for centering the support relative to the rim, and a body connected to said base.

This support is characterized in that the centering means are constituted by a plurality of protuberances disposed radially inwardly relative to said resistance zone of said base and whose radially inner walls fit, in the free state, to a diameter less than diameter of the bearing surface of the rim.

The protuberances arranged radially inwardly relative to the zone of resistance generate by their radial compression of the clamping forces during the mounting of the support but also have the advantage of allowing a polygon of the flexible zone of resistance and very little expandable. This polygon setting makes it possible to absorb a certain variation in the diameter of the bearing surface of the rim or the zone of resistance and thus to ensure easy assembly of the support while maintaining excellent resistance to centrifugation. Preferably, the protuberances are arranged symmetrically relative to the axis of rotation of the support.

According to a preferred embodiment, when the bearing axially comprises a first side intended to be mounted first around the rim, the protuberances are arranged axially on the opposite side to this first side relative to the equatorial plane of the middle support.

This facilitates mounting by imposing a polygon setting of the resistance zone of the base at the end of the mounting of the support on the rim.

The protuberances may have at least one lateral face whose average inclination relative to the axis of rotation of the support is between 1 and 55 degrees. The cross section of the protuberances may be trapezoidal.

This facilitates the establishment of the support by avoiding any locking effect protuberances against the rim assembly and / or disassembly.

Lorsque cette relation est satisfaite, lors de la mise en polygone la base autour de la portée d'appui de la jante, il y a toujours une zone de contact entre la base et la portée d'appui entre les deux protubérances adjacentes. La valeur limite de la hauteur des protubérances correspond à l'efficacité maximale des protubérances. Preferably, where oc is the half-angle at the center separating two adjacent protuberances and R being the radius of the bearing surface 4 of the rim 2, the height h protrusion satisfies the following relationship

When this relationship is satisfied, when placing the base around the bearing surface of the rim in polygon, there is always a contact zone between the base and the bearing surface between the two adjacent protuberances. The limit value of the height of the protuberances corresponds to the maximum efficiency of the protuberances.

The radial height of the protuberances is between 2 and 10 mm and preferably between 3 and 5 mm. The radial height of the protuberances should not be too high not to cause, during a rolling bearing, vibrations that can affect the endurance of the support. These vibrations can also be perceptible by the driver, it may be an advantage to indicate that it is now in rolling conditions that require a reduction in its driving speed. A radial height of the order of 3 to 5 mm appears to be a good compromise. The effectiveness of the backlash in the polygon of the zone of resistance is, for a radial height of protuberances given directly according to their number.For a radial height of 3 to 5, a number of protuberances between 3 and 15 allows to fill all necessary manufacturing games.

When the body of the support has areas adapted to define cavities, each of the protuberances is preferably disposed radially inwardly relative to a body cavity.

 This arrangement has the advantage of limiting the variations in radial stiffness of the support as a function of the azimuth, and consequently, during rolling in support, reducing the variations of force undergone by the support as well as the vibrations produced by the protuberances. This leads to a significant improvement in endurance these supports in operation.

When the base support comprises a plurality of extensions extending axially on the opposite side to the first mounting side, the protuberances can be arranged at the same azimuth extensions.

The radially inner surface of said base may also comprise at least one circumferential zone disposed between two circumferential zones of greater diameter.

This central recess of the base of the support facilitates its assembly by limiting the friction against the bearing surface of the rim. Several embodiments of the invention are now described with the aid of the accompanying drawing in which - Figure 1 shows a partial axial section of a mounted assembly equipped with a safety support; - Figure 2 shows an axial section of a support according to the invention <B>; </ B> - Figure 3 shows a side view of the support of Figure 2; - Figure 4 shows the support of Figure 3 mounted on rim scope; - Figure 5 shows the evolution of the bearing pressure of the protuberances of the support of Figures 2 and 3 against the scope of the rim based centrifugation efforts; - Figure 6 shows an axial section of a second embodiment of a support; and - Figure 7 shows a side view of a support according to the invention; and - Figure 8 shows an axial section of another support according to the invention.

FIG. 1 shows a mounted assembly comprising a tire 1, a wheel rim 2 and a safety support 3 disposed around the bearing surface 4 of the rim 2. The particular geometry of this wheel rim 2 is described in particular in the patent. US 5,634,993. It has two seats of beads, 5 outside and 5 'inside, of different diameters and is particularly suitable for the easy implementation of this safety support 3. This set allows the rolling despite a significant drop in pressure in the tire 1. The safety support 3 comprises two main parts, a base 8 intended to surround the bearing surface 4 of the rim 2 and a body 9 connected to the base 8. The body 9 comprises a top 6 intended to come into contact with the tread 7 of the tire 1 in the event of zero or very low inflation pressure - this is shown in FIG. 1. The body 9 can be of extremely varied shapes.

FIG. 2 shows a schematic view in partial axial section of a support 10 similar to that of FIG. 1, in which a reinforcing reinforcement is shown comprising in this example a ply of reinforcements substantially circumferentially inextensible 11 arranged in the base 8. This reinforcement constitutes a zone of resistance of the base 8, that is to say the zone of the base which is substantially inextensible circumferentially. This frame can be composed of reinforcements such son, cables, assemblies, or any equivalent, for example aramid or nylon. The reinforcing reinforcement may also consist of a circumferential winding of reinforcements in one or more layers, it may also be a crossed binappe whose reinforcements are oriented at angles a; is in the order of 10 to 40 degrees relative to the circumferential direction to ensure good resistance to centrifugation of the support when running at high speed.

This support 10 comprises a set of protuberances 12 arranged radially inwardly relative to the base 8. As shown in Figure 3, protuberances are evenly distributed around the inner circumference of the base 8. Their number is here 6. The protuberances have a thickness of 3 to 5 mm and a circumferential length of the order of 3 to 5 cm. The protuberances are arranged here on one side of the support, on the side II of the equatorial plane middle P. The side I is the one that will be threaded first around the bearing surface 4 of the rim 2 (see figure 1). The protuberances arranged on the side II will therefore be in contact with the bearing surface 4 only at the end of the mounting operation. This reduces the mounting effort required. The cross section of these protuberances is substantially trapezoidal. They comprise a first bias 14, disposed towards the side I. This first bias 14 makes with the direction of the axis of rotation of the support a low angle of the order of 15 to 20 degrees. This bias 14 facilitates the progressive implementation of the support around the rim. A second bias 13 is arranged on the outer side II, to facilitate disassembly of the support. This bias has an average inclination of about 45 degrees. In the example shown in FIG. 2, the base 8 also has a set of circumferentially discontinuous extensions 15 intended to bear against the outer bead of the tire 1 and thus axially block the support 10. These extensions 15 are discontinuous circumferentially allow easy disassembly of the tire 1 of its rim 2. The extensions and the protuberances are arranged at the same azimuths and bear against each other as shown in the section of Figure 2.

It is also possible to arrange these protuberances on both sides of the support.

The role of the protuberances 12 is twofold. Their first function is to generate radial clamping and centering forces during the mounting of the support 10 on the bearing surface 4 of the rim 2. For a radius RA of the reinforcement reinforcement 11 given, the support 10 can be mounted on any support bearing 4 whose radius R is substantially (the radius RA may be substantially coincident with the inner radius of the base 8) between RA and RA - h where h is the height of the protuberances. For R> _ RA, the support can not be mounted, for R <RA - h, the unrecoverable game. When mounting the support 10 around the bearing surface 4 of the rim 2 and due to the great stiffness in extension of the reinforcing armature 11 and its low stiffness in bending, the armature 11 will start polygon around the staff 4 (see Figure 4). The base 8 of the support is thus in indirect contact with the bearing surface 4 of the rim 2 via the 6 protuberances 12 and in direct contact with circumferentially disposed zones between two protuberances 12. The effective inner diameter of the base 8 (Almost equal to 2RA) therefore varies substantially between the diameter of the range 4 and this diameter increased by twice the radial height of the protuberances 12 compressed. The mounting of the support 11 around the scope 4 is thus possible with very limited efforts, only due to the friction of the protuberances on the bearing surface, the compression of the protuberances 12 and the flexion of the base 8 of the support for to put oneself in polygon. This mounting takes place virtually without the need to circumferentially extend the frame 11. Such an extension would require much too great efforts for it to be possible.

The second role of the protuberances is illustrated by a numerical simulation performed for a rubber support 117 mm wide, 50 mm high and 220 mm inside radius. The base of this support comprises protuberances of 3 mm in height arranged over the entire width of the support and 20 mm in circumferential length. The curves of FIG. 5 show the evolution of the bearing pressure (P in bars) of the protuberances 12 against the bearing surface 4 of the rim 2 as a function of the centrifugal forces (F in daN) for a width support slice axial 10 mm. The total weight of the support is 4 kg.

The simulation considers for a given armature radius 11 RA, several spokes R of the bearing surface of the rim 2 - R = RA - 1.35 mm - curve 1 - in this case the development of the armature 11 corresponds exactly the development of the polygon shown in Figure 4; - R = RA - 1 mm - curve 2; - R = RA - 0.5 mm - curve 3; - R = RA - 1, 5 mm - curve 4; and -R = -2 mm-curve 5.

After mounting, at zero speed, the bearing pressure of the protuberances 12 on the bearing surface 4 is directly related to the radius of the span 4. It can be considered that for the curves 1, 4 and 5, this initial pressure is the result of the forces compression of the protuberances which balance the forces related to the flexion of the base 8 when it is placed in a polygon. For the curves 2 and 3, the forces increase substantially because of the necessity of a much stronger compression of the protuberances 12.

When the centrifugation efforts increase, it is found on the curves 1, 4 and 5, that the bearing pressure of the protuberances 12 on the scope 4 increases very substantially up to a maximum. The pressing pressure then decreases to a zero value. This evolution is related to the increase in forces applied to the armature 11 due to the centrifugation of the support which will cause an elongation of the armature and a change in the geometry of the latter which tends to become circular again. Increasing the forces the polygon-shaped armature involves an increase in the compression forces of the protuberances and the progressive lengthening of the armature causes a decrease in this compression. The presence of the maximum must be related to the combination of these two phenomena. When the armature 11 has become circular and a development substantially equal to R + h, the compressive forces of the protuberances have become null. It should be noted that the rotational speed corresponding to this state is, in all cases considered, the support comprising a reinforcement 11 consisting of three windings of a sheet of aramid circumferential reinforcements, greater than 400 The centrifugal force value equal to 230 daN corresponds to a speed of about 170 In case of curves 2 and 3, there is an initial decrease in the pressure of the protuberances followed by the previously described evolution.

The preceding curves illustrate that the protuberances, thanks to the polygon setting of the armature that they induce during assembly, make it possible to obtain sufficient centering forces over a very wide range of speeds in order to maintain a good centering of the support. , unbalanced, while having a mounting of easy support.

The use of such protuberances is possible as the bending stiffness of the base 8 of the supports is much less than its extension rigidity. This is quite the case for supports made elastomeric materials with substantially inextensible reinforcements disposed in their bases. This support 10 is preferably made of an elastomeric material having a modulus of elasticity of between 1 and 50 MPa. This material may be a diene elastomer, such as natural or synthetic rubber, a polyurethane elastomer.

Figure 4 allows to clarify the relationship that must meet the height of the protuberances to achieve maximum efficiency. When placing in base polygon around the bearing surface of a rim, between two adjacent protuberances, the base must maintain a zone of direct contact with the bearing surface.

Lorsque les protubérances sont régulièrement réparties sur la circonférence de la base 8, (i étant l'angle au centre correspondant à une protubérance et N le nombre de protubérances, on a:

Les deux relations précédentes montrent que, pour rattraper un jeu donné, on peut faire varier à la fois le nombre et la hauteur des protubérances. La figure 6 présente un autre mode de réalisation d'un appui 20 selon l'invention. La coupe présentée se situe à un azimut différent de ceux des protubérances. Cet appui comprend comme précédemment un corps 9 avec un sommet 6 et une base 21. La base 21 comprend un évidement circonférentiel 22 dont le diamètre (D2 est supérieur à celui (DI des zones 23 et 24 qui lui sont adjacentes. This state corresponds to the following relation: a being the half-angle at the center separating two adjacent protuberances, R being the radius of the bearing surface 4 of the rim 2, the height h of a protrusion satisfies

When the protuberances are evenly distributed on the circumference of the base 8, (i being the center angle corresponding to a protuberance and N the number of protuberances, we have:

The two previous relationships show that, to catch a given game, one can vary both the number and the height of the protuberances. Figure 6 shows another embodiment of a support 20 according to the invention. The section presented is at an azimuth different from that of the protuberances. This support comprises as before a body 9 with a vertex 6 and a base 21. The base 21 comprises a circumferential recess 22 whose diameter (D2 is greater than that (DI zones 23 and 24 adjacent thereto.

This makes it possible to very substantially limit the friction forces between the base of the support and bearing surface 4 during assembly and disassembly.

FIG. 7 shows a side view of the support 10 of FIG. 2. The body 9 of this support comprises connecting zones 16 which connect the base 8 and the crown 6. These connection zones define cavities 17 between them. FIG. 7 illustrates a preferred arrangement of the protuberances 12 at the right of the cavities 17 of the body 9.

 This arrangement makes it possible not to increase the right of the protuberances the radial stiffness of the support, which limits the variations of force sustained by the support in rolling support and thus improves its endurance. It has indeed been found that, if the protuberances are arranged in line with a connecting zone 16, it is here that the damage in operation of this support is preferably developed.

Figure 8 shows in axial section a support 30 according to the invention, the body 31 is constituted by a closed-cell foam rubber bead. This support comprises the body 31, a base 32 comprising a first reinforcement of annular reinforcements and a second reinforcing armature 34 oriented perpendicularly to the circumferential direction. The base 32 is extended axially on both sides by wings. These wings have an inclination y relative to the axial direction of between 30 and degrees.

 These wings 36 may comprise only reinforcement reinforcement 34. These wings 36 are glued to the body 31 and promote its lateral retention during rolling inflated at high speed. The base 32 and the body 31 are glued by conventional adhesives. The base 32 comprises a set of protuberances 35 arranged radially inwardly on the surface of the base 32. The operation of these protuberances is identical to that previously described.

Claims (14)

 1. Safety support, intended to be mounted on a rim inside a tire fitted to a vehicle, to support the tread of the tire in case of loss of inflation pressure, comprising a substantially cylindrical base for to fit around the rim, with a zone of substantially circumferentially inextensible resistance of low flexural rigidity and whose radially inner diameter is slightly greater than the diameter of the bearing surface of the rim, said base also comprising means for centering the support relative to the rim, and a body connected to said base, characterized in that the centering means are constituted by a plurality of protuberances arranged radially inwardly relative to said resistance zone said base and whose radially inner walls s enter, in the free state, a diameter smaller than the diameter of the port support of the rim. 2. Support according to claim 1, wherein said protuberances are arranged symmetrically relative to the axis of rotation of the support. 3. Support according to one of claims 1 or 2, wherein, said support having axially first side intended to be mounted first around said rim, said protuberances are arranged axially on the opposite side to said first side relatively equatorial plane middle of the 'support. 4. Support according to one of claims 1 to 3, wherein said protuberances have at least one side face whose average inclination relative to the rotation axis support is between 15 and 55 degrees. 5. Support according to one of claims 1 to 4, wherein the cross section of said protuberances is trapezoidal shape. 6. Support according to one of claims 1 to 5, wherein, oc being the central half-angle separating two adjacent protuberances, R being the radius of the bearing surface of the rim, height of a protrusion satisfies the next relationship

    7. Support according to one of claims 1 to 6, wherein the radial height of said protuberances is between 2 and 10 8. Support according to one of claims 6, wherein the radial height of said protuberances is between 3 and 5 9. Support according to one of claims 1 to 8, wherein the number of protuberances is between 3 and 15. 10. Support according to one of claims 1 to 9, wherein said body having areas adapted to define cavities each of said protuberances is disposed radially inwardly relative to a cavity of said body. 11. Support according to one of claims 1 to 10, wherein, said base comprising a plurality of extensions extending axially on the opposite side to the first side, said protuberances are arranged at the same azimuth as these extensions. 12. Support according to one of claims 1 to 11, wherein the radially inner surface of said base comprises at least one circumferential zone disposed between two circumferential zones of greater diameter. 13. Support according to one of claims 1 to 12, wherein the body is constituted by a substantially toroidal form of bead made of cellular rubber closed cell. The support according to claim 13, wherein the base extends axially on both sides by a flange extending radially outwardly at an angle θ of between 30 and 50 degrees relative to the axial direction.