WHEEL RIM WITH OPTIMIZED RIM HOLE SHAPE

Description

Field of invention

[0001] The invention relates to a rim and a rolling assembly consisting of a tire, a rigid rim and a connection between the tire and the rim by means of a flexible extender. A tire comprises, as is known, two beads intended to be mounted on seats. The present invention relates to rolling assemblies in which a tire bead is not mounted directly on a rigid rim, but is mounted on a flexible extender, which is mounted on the rim.

[0002] A tire, a rim, and an expander referred to in the present invention are usually described by a representation in a meridian plane, i.e., a plane containing the axis of rotation of the tire. All these products (a tire, a rim, an expander) are objects having a geometry of revolution relative to their axis of rotation. The radial and axial directions respectively designate the directions, the first, perpendicular to the axis of rotation of the tire, and the second, parallel to the axis of rotation of the tire. In the following, the expressions "radially" and "axially" respectively mean "in a radial direction" and "in the axial direction". The expressions "radially inner, respectively radially outer" mean "closer, respectively further, from the axis of rotation of the tire, in a radial direction".A median plane is a plane perpendicular to the tire's axis of rotation, positioned axially so as to intersect the tread surface approximately halfway between the beads of a tire. The expressions "axially inward, respectively axially outward" mean "closer, respectively further, from the tire's median plane, in the axial direction." The expressions "radially inward, respectively radially outward" mean "closer, respectively further, from the axis of rotation, in the radial direction." Finally, let us also recall that "radial cut" or "radial section" means a cut or section along a plane which contains the axis of rotation of the rim (and of the tire with which it is equipped). State of the art

[0003] Document US 4,274,466 presents a tire and wheel assembly comprising a circumferential groove on the rim seat cooperating with a rubber tip on the end of the tire bead to lock the bead in position on the rim.

[0004] In document WO2016 / 046197, it is proposed to insert a flexible extender between a tire bead and a rim. The reader is referred for example to the Figure 5of this document to learn about a rolling assembly belonging to the field of the invention. It shows a rolling assembly comprising a tire, a rim and two identical expanders. Considering the language conventions recalled above, and referring to the way in which such an expander is mounted on a rim, such an expander comprises, axially from the inside to the outside, an axially inner end called an expander bead and intended to ensure the attachment of the expander to the rim. Such an expander also comprises an axially outer end intended to receive and axially immobilize a tire bead. A body connects the two ends, respectively axially inner and axially outer.

[0005] WO 2018 / 007751 discloses a wheel assembly with a rim, a tire, and an extender mounted between the rim flange of the wheel and the tire. The rim flange has an axis of rotation and a radially outer bearing surface for the extender, such that a first portion of the rim flange includes a second portion. The second portion is oriented such that a deformable hubcap can be mounted on the wheel such that the outer periphery of the hubcap has a functional clearance relative to the radial inner face of the extender, while providing radial support for the extender under high radial stress on the wheel.

[0006] The expanders are mounted on a rim, which is most often an aluminum part. The rim has a rim hook on each side, designed to ensure, in particular, the axial immobilization of the expander. Another function of this rim hook is to force the expander to deform so as to form a hump (usually known for rims as a "hump") that the tire crosses when inflated (as for a conventional tire and rim assembly, without expander). This hump helps prevent or delay the tire from coming loose when used at an abnormally low inflation pressure (and we know that, in the event of unblocking, the tire's guiding capacity is greatly reduced and even disappears if the tire leaves the rim, which becomes very likely).

[0007] The radial height of this rim hook, for rolling assemblies with expander, had been chosen during the exploratory work by adopting a type "B" hook as described by ETRTO (height 14.1 mm + or - 0.6), whereas, most frequently, hooks for passenger vehicle wheels are of type "J" (height 17.3 mm + or - 0.6). Such a B hook, which is referred to in this document as a high hook, certainly has the advantage of contributing to good unblocking values ​​for standard tire / rim assemblies (under low pressure), but in the context of an assembly with expanders, it also poses problems.

[0008] On the one hand, the hump is large enough to lead to inflation pressure values ​​that are too high for simply fitting the tire mounted on a rim with expanders. On the other hand, this hook imposes a large deformation on the expander at the point where it radially overhangs it. Indeed, the natural shape of the expander when leaving the mold, in the state free of any stress, is substantially cylindrical (in fact very slightly conical), with a diameter much smaller than the diameter measured at the top of the metal hook. Fitting the expander therefore imposes a large local radial deformation on the expander. As at this point the reinforcements within the expander are generally of the "cross carcass" type, the expander opposes a large resistance to this deformation. This results in a large pressure between the expander and the metal hook at the hump location comparable to a conventional rim hump.

[0009] Due to the good adhesion between the rubber and the aluminum, it is understood that a certain part of the axial force generated by the tire under pressure and tending to axially stretch the expander is partly taken up at this interface, whereas it would be preferable, to ensure isostatic mounting of the expander, for all this force to be taken up by the support on the metal hook of the expander bead. As it stands, the fact that the positioning of the expander is not clearly defined since it is not necessarily identically in place throughout its perimeter leads to geometric irregularities, themselves responsible for vibrations when rolling due to non-uniformities.

[0010] The applicant's observations thus led him to deviate from the usual rules of rim construction. Brief description of the invention

[0011] This objective was achieved, surprisingly, by departing from previous teachings regarding the design of the rim, and more particularly its edge.

[0012] The invention therefore relates to a rim for a tire, the rim having an axis of rotation DD', said rim comprising a rim seat extended axially outwardly by a rim flange, said rim flange comprising a radially outer bearing face with a first portion oriented substantially in a perpendicular plane and located radially outwardly relative to said rim seat, a second portion inclined outwardly, located axially outwardly relative to said first portion and located at least partly radially outwardly relative to said rim seat and a connecting portion between said first portion and said second portion. This rim is characterized in that said second portion of said bearing face is substantially frustoconical, the virtual apex determined by extending said substantially frustoconical portion being located axially outwardly relative to said rim seat.

[0013] In fact, the invention proposes a rim whose edge, of significant width, has a shape designed to offer the radially inner face of the expander a bearing face or support of suitable shape so that said expander, in the pneumatic assembly inflated to nominal pressure, deforms and adopts a shape promoting good operation.

[0014] Advantageously, said second substantially frustoconical portion forms with the axis of rotation DD' an angle α of value between 5° and 30°. Preferably, the cumulative axial width of the second portion and the connecting portion is between 15 mm and 21.5 mm.

[0015] According to the state of the art, the expanders mounted on a metal rim actually form the foundation of the tire, in terms of its ability to radially absorb shocks. They provide more radial flexibility to the rolling assembly. While it was thought that it would not be possible to significantly improve this ability to absorb shocks if the tire bead was not axially completely outside the rim, it was found that it is possible to maintain a certain radial flexibility combined with both excellent endurance of the expander and improved road holding performance (which is known to be all the better if the tire is capable of developing significant drift thrusts favorable to the rigorous transverse guidance of the vehicle) by organizing a tilting of the tire bead as well as a radial displacement towards the axis of rotation of the rolling assembly.The extension under the tire bead of the radially outer bearing face of the rim flange effectively allows an improvement in the road holding performance of the rolling assembly relative to rolling assembly geometries presented for example in the cited document WO2016 / 046197.

[0016] The invention provides a new function to the rim, namely, by virtue of the rigid bearing surface present radially under the tip of the bead of the tire, substantially matching the shape of the extender, to offer a rigid support which forces the tire to initiate a tilting movement which does not hinder sufficient radial movement of the bead when considering the axially outermost part of the bead.

[0017] Observations show that the endurance performance against radially oriented impacts is comparable, or even better, than that obtained by applying the lessons of the state of the art. Preferably, the rolling assembly includes two expanders which ensure the junction between the mounting rim and the two beads of the tire.

[0018] Each expander is flexible; this means that it is elastically deformable, allowing, seen in meridian section, bending and radial displacement without leaving the elastic domain, under service stresses, when using the tire inflated to nominal pressure; Note that axial deformation of the expander is not desirable during normal operation of the tire inflated to nominal pressure.

[0019] The rim is preferably made of a material chosen from steel or aluminum and / or magnesium alloys, composite materials based on carbon fibers, glass fibers, aramid fibers, plant fibers, said fibers being included in a matrix based on thermosetting compounds or thermoplastic compounds, or from a complex compound comprising an elastomer and a complex based on resin and fibers chosen from carbon fibers, glass fibers, aramid fibers, plant fibers or from any combination of materials.

[0020] With regard to other aspects of the rim itself or the extender itself, the reader is referred to the aforementioned documents WO2015 / 086662 and WO2016 / 046197. Description of Figures

[0021] The invention is described below with the aid of figures 1 to 7 , given for illustration purposes only: there Figure 1is a meridian section of a rolling assembly with a rim according to the invention, the Figure 2 is an enlargement of the left part of the whole, the Figure 3 is a partial meridian section of a rim according to the invention, the Figures 4 and 5 present a test of resistance to a curb impact, respectively in side view and in top view, the Figure 6 presents performance results of rolling assemblies according to the invention in the curb impact test, and the Figure 7 is a partial meridian section of another embodiment of a rim according to the invention. Detailed description of the invention

[0022] There Figure 1 shows a rolling assembly with a rim according to the invention. This assembly comprises two identical extenders 1, a tire 2 and a rim 3. The tire 2 has two beads 21. Generally speaking, let us point out that the choice of rim width is such that, taking into account the width L of the extenders (see Figure 2), the tire is in a configuration as similar as possible to the configuration it would have if it were mounted directly, without extenders, on a suitable rim.

[0023] By consulting more particularly the Figure 3, it can be seen that the rim 3 has two rim seats 31, each extended by a rim flange 32. The rim flange 32 has a radially outer bearing face 33 intended to serve as a support for the body of the expander. The bearing face 33 of the rim flange 32 is in contact with the expander 1 when the tire is mounted on the expanders and the latter are mounted on the rim, the tire being inflated to the nominal pressure. This bearing face 33 has a first portion 321 oriented substantially in a plane perpendicular to the axis of rotation DD' of the rolling assembly, and located radially to the outside relative to said rim seat 31.The bearing face 33 of the rim flange 32 comprises a second, substantially frustoconical portion 322, located axially to the outside relative to said first portion 321 and located at least partly radially to the outside relative to said rim seat 31, said second portion 322 is substantially frustoconical, with an angle α of 15°. The bearing face 33 also comprises a connecting portion 320 between said first portion 321 and said second portion 322. In the example shown, the axial width WR of the rim flange 32 is 18.3 mm.

[0024] The E and I markers at the Figure 3indicate the axially outer side of the rim, respectively the axially inner side. The second portion 322 is inclined axially outwards: thus, by extending it axially outwards, we join the axis DD' (position not to scale with respect to the rim 3) at a virtual vertex S axially rejected very far outwards, which is symbolized by an arrow under S at the Figure 3 .

[0025] The invention can be used with numerous variants of internal construction of the tire 2, which are therefore not shown, as well as with numerous variants of internal construction of the extender 1, which are therefore not shown.

[0026] Coming back to the Figure 2, it can be seen that each extender 1 has an axially inner end 10 intended to be mounted on one of said rim seats 31. It has an axially outer end 11 as well as a body 12 oriented substantially axially and arranged between said axially outer end 11 and said axially inner end 10. The body 12 has a radially inner face 122. The axially inner end 10 of the extender has an axial positioning face 101 substantially perpendicular to the axis of rotation DD', and is immobilized by being pressed axially against the rim flange 32, under the effect of the inflation pressure of the rolling assembly. The axially outer end 11 has a shoulder 111 forming in part a face substantially perpendicular to the axis of rotation DD'. Said expander 1 comprises an expander seat 13. The bead 21 has an axial width WB at the interface of the bead 21 with the expander seat 13.The bead 21 is immobilized by being pressed axially against said axially outer end 11 of the extender, under the effect of the inflation pressure of the rolling assembly.

[0027] By extending the trace of the shoulder 111 of the axially outer end 11 radially inwards and by extending the trace of the seat on the extender 13, a point is obtained which is the trace of a circle of diameter D 1 , a diameter which itself corresponds to the standardized diameter of the tire of the rolling assembly using the extender 1 according to the invention. By extending the trace of the axial positioning face 101 radially inwards and by extending the trace of the seat on the rim 31, a point is obtained which is the trace of a circle of diameter D 0 which is the standardized diameter of the seat on the rim 31. For information on the standards referred to, the reader should consult the documentation of the ETRTO (European Tire and Rim Technical Organization).The height h of the rim flange measured between the point of intersection between the trace of the rim seat 310 and the trace of the radial portion 321 of the flange 32 and the radially outermost point F of the flange 32 is 8.5 mm (see . Figure 7 ). This allows for an expander boss suitable for holding the tire bead on the expander seat without causing excessive stresses in the expander structure.

[0028] Once the assembly is carried out, the bead of the tire imposes a circumferential contraction of the expander 1. The rim flange 32 extends axially under the bead 21 over a distance S such that the ratio S / WB is equal to 0.3. Thus, it can be seen that the radially inner face 122 bears on the radially outer bearing face 33 of the rim flange 32 over its entire axial width WR, which is 18.3 mm and is much greater than in known embodiments, which forces the bead 21 of the tire to tilt in a rotational movement (in the trigonometric direction for the side of the tire 2 shown in FIG. Figure 2 ) when it experiences a significant increase in radial load.

[0029] There Figure 7 shows in partial meridian section an alternative embodiment of a rim according to one of the objects of the invention. Identical references correspond to identical or similar parts.

[0030] This rim 3 differs from the one illustrated in the Figure 3 by a substantially cylindrical rim seat 310 between two transition zones 311 and 312 and a greatly reduced axial width P, of the order of 15.3 mm. These two modifications make it possible to lock the expander bead of the expander 1 in the service position as soon as it is mounted on the rim without having to rely on the inflation pressure of the rolling assembly at the time of mounting the tire on the rim and expander assembly.

[0031] The curb impact resistance was quantified by passing the rolling assemblies over a 90 mm high curb 50 with an angle β of 60° relative to the direction of travel of the tire (an angle of 90° corresponding to a direction perpendicular to the direction of travel of the tire, see Figures 4 and 5); the edge of the pavement has a radius of curvature of 10 mm; successive passes are made at different speeds until the tire loses its inflation pressure or until the tire or the extender or the wheel becomes permanently deformed and the forces transmitted to the pavement and / or to the hub on the vehicle are acquired for each pass. A reference assembly is compared to an assembly according to the invention. The reference assembly T1 is a conventional assembly without extender comprising a 245 / 35 R 20 tire of the MICHELIN ®< PS4S type, and a rim with a width of 8 inches, the edge being that of the J hook. As shown in Figure 4 , the 4 wheels of the tested rolling assemblies are 42 spoke wheels.

[0032] Four rolling assemblies with expanders were tested with varying S / WB ratio values: The first E1, with a rim as presented at the Figure 3has an S / WB ratio equal to 0.27; The second E2 with a rim as shown in the Figure 7 has an S / WB ratio equal to 0.27; The third E3 with a rim as shown in the Figure 7 has an S / WB ratio equal to 0.49; and The fourth E4 with a rim as shown in the Figure 7 has an S / WB ratio of 0.70.

[0033] The results of the curb impact tests are presented in Figure 6 .

[0034] The graph of the Figure 6 shows on the abscissa the forward speed of the tire in km / h and on the ordinate the maximum value of the radial force measured on the ground during the impact expressed in daN.

[0035] The T1 control rolling assembly without extenders had a sidewall blowout from the test at 18 km / h and a puncture from 20 km / h.

[0036] For the four rolling assemblies with extenders, over the entire speed range tested, no tire showed any damage although the maximum values ​​of radial forces increased very significantly with speed.

[0037] It should be noted that the maximum values ​​of radial forces are significantly different depending on the location of the impact on the wheel. Fz is higher if the impact is on one spoke of the wheel compared to an impact between two spokes.

[0038] Consequently, it is not possible to differentiate the results for these four sets; however, it is noted that the increase in the S / WB ratio does not reduce the resistance of the rolling assembly to sidewalk impacts even if an increase in radial forces seems to emerge with the increase in the value of the S / WB ratio.

[0039] For the E1 rolling assembly, permanent deformation of the wheel at the location of the impact was noted from 42 km / h. The better resistance of the other three rolling assemblies according to the invention can be linked to the modification of the geometry of the rim flange as well as to the outward extension of the rim flange.

[0040] On the other hand, during handling tests, a significant improvement in driving precision was noted with the increase in the S / WB ratio.

Claims

1. Rim (3) for a tire mounted on the rim by means of a flexible expander, the rim (3) having an axis of rotation (DD'), said rim comprising a rim seat (31) axially extended outwardly by a rim flange (32), said rim flange (32) comprising a radially outer supporting face (33) with a first portion (321) oriented substantially in a perpendicular plane and located radially on the outside with respect to said seat on rim (31), in which a second outwardly inclined portion (322) is located axially on the outside with respect to said first portion (321) and located at least partially radially on the outside relative to said rim seat (31) and a connecting portion (320) between said first portion (321) and said second portion (322), characterized in that said second portion (322) is substantially frustoconical and forms with the axis of rotation (DD') an angle (α) of value, the virtual apex determined by extending the said substantially frustoconical portion meets the axis of rotation (DD') which is situated axially towards the outside in relation to the said rim seat (31) in order to provide a bearing surface or support for a radially inner surface of the expander over the entire axial width (WR) of the said flange (32).

2. Rim according to claim 1, characterized in that the angle (α) has a value of between 5° and 30°.

3. Rim according to one of claims 1 or 2, in which said second portion (322) and said connecting portion (320) have a combined axial width (WR) of between 15 mm and 21.5 mm.

4. A wheeled assembly consisting of a tire, a rigid rim (3) for the tire and a flexible expander mounted on the rim (3) between the tire and the rim, characterized in that the rim (3) is made according to one of claims 1 to 3.

5. An assembly according to claim 4, characterized in that this assembly comprises two expanders (1), each expander (1) having an axially inner end (10) intended to be mounted on one of the said rim seats (31), and an axially outer end (11) as well as a substantially axially oriented body (12) disposed between said axially outer end (11) and said axially inner end (10), the body (12) having a radially inner face (122), the axially inner end (10) of the expander has an axial positioning face (101) substantially perpendicular to the axis of rotation (DD'), and is immobilized by being axially pressed against the rim flange (32) under the effect of the inflation pressure of the rolling assembly, and the axially outer end (11) has a shoulder (111) forming in part a face substantially perpendicular to the axis of rotation (DD'), and said expander (1) includes an expander seat (13), and the bead (21) has an axial width (WB) at the interface of the bead (21) with the seat on the expander (13), and the bead (21) is immobilized by being axially pressed against said axially outer end (11) of the expander, under the effect of the inflation pressure of the rolling assembly.

6. Assembly according to claim 5, characterized in that the rim flange (32) has an axial width (WR), in which the axial width (WB) of the bead (21) and the axial width of the rim flange (32) overlap each other, the axial width of the bead and the axial width of the rim flange overlap, and each of the flexible expanders defines a width and the axial width of the rim flange and the axial width of the bead are within the width of each of the flexible expanders.