WO1995023299A1

WO1995023299A1 - Device for absorbing energy by plastic deformation for a motor vehicle steering wheel in particular, and steering wheel comprising such a device

Info

Publication number: WO1995023299A1
Application number: PCT/FR1995/000224
Authority: WO
Inventors: Michel Malvy
Original assignee: Michel Malvy
Priority date: 1994-02-25
Filing date: 1995-02-24
Publication date: 1995-08-31
Also published as: FR2716703A1; FR2716703B1

Abstract

Energy absorbing device (100) consisting of two bearing and/or fastening elements (101, 102) arranged at a distance from one another, both elements being joined to one another by a plurality of fingers provided with through recesses (104) arranged in different radial directions, so as to be longitudinally deformable during crushing, resulting from the application of axial compression. Such a device can be advantageously fitted to motor vehicle steering wheels.

Description

Device for absorbing energy by plastic deformation, in particular for a vehicle steering wheel, and steering wheel equipped with such a device.

The invention relates to devices for absorbing energy by plastic deformation, in particular for equipping vehicle steering wheels.

Steering wheels are currently the subject of much research aimed at improving their performance in the event of an accident, and in particular in the event of a frontal impact by the driver on the steering wheel. This area is particularly sensitive for motor vehicles or for nautical vehicles with steering wheel. Research was rather directed towards devices integrated in the steering wheel or in the dashboard and which inflate automatically in the event of an impact from the vehicle, or even devices with telescopic column which retracts automatically in the event of an impact from the vehicle.

The flywheel itself is generally not associated with an energy absorption structure by plastic deformation. However, it has been proposed to practice localized weakening in the branches of a steering wheel (DE-B-1,159,287 and FR-A-2,353,425). We often limit ourselves at best to shock-absorbing padding which softens an abrupt contact, but which absorbs practically no energy in the event of an impact, like an old technique with impact plate mounted on springs in the center of '' a steering wheel (US-A-1, 647, 903).

However, energy absorption hubs have been proposed, such a hub then being mounted between the steering wheel and the steering column. A typical absorber hub is constituted by two flanges against which are welded angular flat branches (the obtuse angle being open on the side of the hub axis), which branches have a hole at mid-height to give a deformation zone. preferential tion at the vertex of the angle. When the hub is crushed by a force whose direction is parallel to the axis of the hub, each of the branches deforms plastic ent by absorbing energy, but this deformation is accompanied by a large radial deformation directed towards the outside, so that this hub requires a bulky environment so as not to interfere with the plastic deformation of its branches in the event of frontal impact.

According to the same approach, reference may be made to FR-Al.586.115 and FR-A-2.463.708, or even to EP-0 369 521 which describes an energy absorption device constituted by plates with ridged faces which are inserted between the steering wheel and the steering column. The parallel ridges create thinning of each pad, which deforms by bending outward. We find the aforementioned drawback of a large radial deformation directed towards the outside, with in addition significant risks of premature rupture.

Many energy absorption structures have also been proposed, produced in the form of a tubular sleeve in the wall of which are provided windows which delimit axial strips capable of being deformed when the sleeve is subjected to compres¬ crushing. axial sion (see for example WO-A-89 09349 and DE-A-2.264.507). As a variant, the tubular sleeve has a wall pierced with circular holes (FR-A-2,352,704 and FR-A-2,284,801).

We have also proposed a biconical structure capable of flattening when it is crushed in axial compression (DE-A-2,025,707).

Finally, it has been proposed to equip rail vehicles with energy absorption structures produced in the form of a stack of Belleville washers, the accordion structure deforming in the event of a frontal impact with great absorption of 'energy. A similar accordion structure is found in FR-Al.541.956. However, this type of structure remains heavy and bulky, and cannot particular not equip a steering wheel.

The invention aims precisely to solve this problem, by designing an energy absorption device which is at the same time efficient, compact and light. The object of the invention is therefore to provide an energy absorption device the structure of which provides high efficiency without inducing a large amount of deformation, while remaining simple to make and assemble, with multiple possibilities. to adapt to a specific location concerned.

The invention also relates to an energy absorption device, the structure of which additionally provides a resistance to torque which is significant, in particular at least greater than 22 m × kg. It is more particularly an energy absorption device by plastic deformation, in particular for a vehicle steering wheel, characterized in that it is constituted by two support and / or fixing parts arranged at a distance one from the other, these two parts being joined together by a plurality of fingers having, on at least part of their length, a succession of through recesses made in the form of bores whose axes are arranged in different radial directions, so as to be able to deform longitudinally when they are subjected to axial forces exceeding a certain threshold.

The energy absorption obtained with such a device is very important during crushing in axial compression. However, energy absorption is also obtained when the fingers are subjected to high forces in axial traction.

According to a particular embodiment, the fingers extend parallel to a common direction. Alternatively, the fingers are slightly inclined inward or outward at the same angle, or these fingers are arranged in pairs to form deformable V-shaped structures.

It may prove advantageous to provide that at least some of the fingers are of generally cylindrical shape. As a variant, these fingers could be tapered from their ends to a median plane common to all of the fingers, or on the contrary tapered to their ends from a median plane common to all the fingers. According to a particular characteristic, the through holes of the fingers are cylindrical, and the axes of these cylindrical holes are successively orthogonal. In particular, the cylindrical holes of the fingers may or may not be of the same diameter, and their number is the maximum number compatible with the required mechanical strength.

The fingers may moreover be fixed to the support and / or fixing parts in a non-removable manner, for example by welding, or alternatively in a removable manner, for example by screwing.

More preferably, one of the support and / or fixing pieces is a flat flange, and the other is an identical flange or a hub base arranged coaxially with the first flange. According to another conceivable embodiment, the device will consist of a plurality of devices with support and / or fixing parts and with longitudinally deformable fingers, these devices being arranged in the form of coaxial cages, and the fingers of said devices being of decreasing or gradually increasing length from one cage to another.

Advantageously also, the two support and / or fixing parts are joined at the same time by fingers with through holes, and by torque stiffeners arranged to provide resistance to the significant torque. and to deform in the event of crushing in axial compression without affecting the longitudinal deformation of the fingers.

According to a particular embodiment, each torque stiffener is constituted by a folded sheet frame, fixed to the two aforementioned parts being arranged circumferentially, and by a reinforcement insert mounted inside this frame with the possibility of pivoting around an axis essentially perpendicular to the direction of crushing in axial compression, said insert being disposed in said frame in normal operation to provide resistance to high torque, but automatically tilting in the event of crushing in axial compression while allowing the deformation of said frame. Preferably then, the reinforcement insert has a free edge with external chamfer with which cooperates, in the event of crushing in axial compression, an adjacent member carried by a support and / or fixing part, so that the tilting said insert is carried inward. In particular, the adjacent member is the head of a rivet or a fixing screw securing the frame to the bearing and / or fixing part concerned. We can also provide a particular embodiment according to which the frame has a trapezoidal shape, and the insert has two lateral faces inclined in correspondence so as to fit into said frame. Advantageously, finally, the torque stiffeners are arranged alternately with the fingers with through cylindrical bores.

As a variant, each torque stiffener consists of a pair of joined sheets of folded sheet metal fixed to a support and / or fixing piece, said profiles having two divergent branches between which is received a V-shaped corner fixed to the other. support and / or fixing piece. Preferably, the profiles are joined by a member, such as a rivet, forming a fuse mechanical, arranged to break as soon as the force exerted by the V-shaped wedge tending to spread said sections exceeds a certain threshold.

Provision may be made for the V-shaped wedge to be a local deformation of the corresponding support and / or fixing part, or alternatively that the V-shaped wedge is enclosed by two converging branches extending the diverging branches of the profiles, so that the torque stiffener also provides resistance to tearing. The invention also relates to a vehicle steering wheel, in particular of a motor vehicle, having a metal frame with radial branches coated on the one hand with a damping padding enveloping the circular part of the frame and the ends of the branches adjacent to this circular part, and on the other hand a central shock absorbing cushion covering the remaining part of the branches and the central fixing portion of the steering wheel from which these branches depart. According to the invention, the frame has a lowered central portion relative to the branches whose profile is angular, and the central cushion is hollowed out to present an axial inner housing, and moreover, between the top of this housing and said a lowered central portion, an energy absorption device having at least one of the foregoing characteristics is arranged, the fingers of which are essentially parallel to the axis of the steering wheel, said device being completely integrated into the central cushion.

In particular, if it is a steering wheel mounted on an anti-theft mechanism of the steering wheel decoupling type, interposed between said steering wheel and the steering column, it may then be advantageous to have a second device for absorption, of structure similar to the first, directly below the anti-theft mechanism, so that said flywheel is equipped with an energy absorption device intervening both upstream and downstream of the metal frame.

Other characteristics and advantages of the invention will appear more clearly in the light of the description which follows and of the appended drawings, concerning a particular embodiment, with reference to the figures where:

- Figures 1 and 2 are side views e from above of an energy absorption device according to the invention, here with three cylindrical fingers; - Figure 4, and Figure 3 which is the blow along III-III illustrate, on a larger scale, a cylindrical finger whose through recesses are formed by three cylindrical holes, and Figure 5 schematically illustrates the same finger after deformation by axial crushing;

- Figures 6 and 7 are top and side views illustrating a steering wheel fitted with an energy absorption device of the aforementioned type, this device and its particular mode of installation can best be seen in Figure 8 which is a selo cup

VIII-VIII of Figure 6;

- Figure 9 illustrates in section an implantation of a steering wheel with two energy absorption devices; - Figure 10 illustrates in section a variant of the previous device, in which the lower flange is replaced by a hub base with peripheral skirt, -

- Figure 11 illustrates, by way of example, five variants showing different deformable finger geometries, noted a) to e);

- Figures 12 and 13 illustrate in section and e top view (Figure 12 being a section along XII-XI of Figure 13, and Figure 13 a section along XIII-XIII of Figure 12), a variant of the device of previous energy absorption, in which stiffeners d frame and tilting insert torque are arranged alternately with the aforementioned cylindrical fingers;

- Figure 14 illustrates in perspective a trapezoidal stiffener frame; - Figures 15 and 16 are two views of a tilting stiffener insert associated with the frame of Figure 14;

- Figures 17 and 18 are partial views illustrating two other variants of torque stiffeners with pairs of contiguous profiles and associated V-shaped corners, arranged alternately with the cylindrical fingers preci¬ ted.

Figures 1 and 2 illustrate an energy absorption device by plastic deformation 100 according to the invention, the general structure of which is here that of an X-axis hub. The device 100 consists of two pieces of support and / or fixing 101, 102, here arranged in the form of flat circular flanges, which are at a distance from each other, these two parts being joined together by a plurality of fingers 103, here three in number .

In accordance with an essential characteristic of the invention, the connecting fingers 103 are solid at the level of their axis (not hollow), and they have, over at least part of their length, a succession of through recesses arranged under form of holes the axes of which are directed in radial directions differen¬ your, so as to be able to deform longitudinally when subjected to axial forces exceeding a certain threshold, especially during crushing in axial compression. In this case, the fingers 103 are of generally cylindrical shape, and the through recesses of these fingers are cylindrical bores 104 whose axes are successively orthogonal. Each of the fingers 103 illustrated in FIG. 1 here presents a set of seven cylindrical bores 104 whose axes are successively orthogonal, but it goes without saying that this number is only an example. The cylindrical holes 104 of the fingers 103 are here of the same diameter, and their number is preferably the maximum number compatible with the required mechanical strength. In this case, the adjacent holes are for each finger very close to each other, and are only separated by a thin fiber on the generatrix of the finger. In addition, the axes of the holes 104 are here all parallel to a plane transverse to the axis X, but it could alternatively provide that some of these axes are inclined relative to the direction of this plane.

In FIG. 2, the upper flange 101 has a circular inner edge 105, allowing a shaft or a central structure to pass through, and a plurality of threads 106 used for fixing the energy absorption device 100. As well as as will be seen later, it is naturally possible to envisage other fixing methods than screwing, for example a clipping of this flange into the bottom of the housing receiving the energy absorption device.

In FIGS. 3 and 4, the structure of an isolated finger 103 can be better distinguished, here with three cylindrical holes 104 whose axes, denoted Dl and D2, are successively orthogonal. Thus, at the axes of the cylindrical bores 104, the material of the finger is reduced to two diametrically opposite lateral fibers, which fibers are capable of being plastically deformed naturally when the finger is subjected to a significant crushing force in axial compression, in the direction of its length. This effect is illustrated in FIG. 5, where the action of the compressive force is shown diagrammatically by the arrows F, and it can be seen that the finger 103 is crushed longitudinally with a significant reduction in its length, while remaining substantially in the same alignment. This has the consequence that, during a crush- ment in axial compression, for example in a frontal impact situation, the two flanges delimiting the energy absorption device 100 approach each other in a movement which remains substantially parallel to the axis X. This is extremely advantageous in practice, not only by the fact that the fingers are deformed by absorbing a large energy, but also insofar as the energy absorption device 100 is not likely to occupy during its deformation a lateral space requirement important, so that this device can be installed in a housing of optimal compactness. Such a device could thus be used in a steering wheel, insofar as the deformation does not interfere with the supports of the steering wheel, or even under the steering wheel, for example between the head of the steering column and the steering wheel, or between the head steering column and an anti-theft mechanism of the steering wheel disconnection type, insofar as this device is not likely to interfere with an armored skirt associated with the anti-theft of the vehicle, which interference could have blocked the radial deformation of the branches of a hub of the traditional type because this deformation occurs with a radially external deformation.

In practice, one will naturally choose the number and the dimensioning of the cylindrical holes, in relation to the length of the fingers, as well as the diameter of these fingers, and their constituent material, according to the mechanical characteristics and performances required for the problem considered. .

As is better visible in FIGS. 3 to 5, the fingers 103 are here fixed to the support and fixing flanges 101, 102 in a non-removable manner, for example by welding at 107. As will be seen later

(variant a) of FIG. 11), it will naturally be possible to provide a removable fixing method, for example by screwing. The same inventive concept can encompass several modes of execution of the fingers 103 capable of being able to deform longitudinally during a compression in axial compression thanks to the presence of through recesses arranged in different radial directions.

In FIG. 11, five alternative embodiments have been illustrated by way of nonlimiting examples.

In a), there is a geometry similar to that of FIGS. 3 and 4, with however a connection to the lower flange 102 by a screw 110 penetrating into an associated blind hole 111 formed at one end of the finger 103. The axes of the cylindrical holes 104 are successively orthogonal.

In b), there is a finger 103 whose cylindrical holes 104 have successively orthogonal axes, but these fingers 103 are tapered from their ends, towards a median plane common to all of the fingers.

In c), the fingers 103 are instead tapered towards their ends, from a median plane common to all of the fingers.

In d), there is a finger 103 of generally cylindrical shape comprising five cylindrical bore holes 104, the axes of which are successively orthogonal. In e), there is an embodiment identical to that of FIGS. 3 and 4.

In the various embodiments which have just been described, the fingers 103 extend parallel to a common direction, which is the direction of the abovementioned X axis. However, provision may be made for the fingers 103 to be slightly inclined inwards or outwards at the same angle, with a slight taper. The taper angle in this case will remain relatively small, that is to say generally less than 10 °. In accordance with another variant (not illustrated here), we can also provide that the fingers 103 are arranged in pairs to form deformable V-shaped structures. In this case, each pair of fingers will be fixed at its tip on the one hand and at its two ends on the other hand on the associated supporting and / or fixing parts.

The components of the energy absorption device 100 may be made of steel, of composite material, or even of other materials compatible with plastic deformations and the energy absorption required.

The energy absorption device according to the invention is particularly advantageous for equipping a vehicle steering wheel, in particular a motor vehicle. Illustrated in FIGS. 6 to 8 is a flywheel V thus equipped with an energy absorption device 100 of the type previously described.

The flywheel V comprises a rigid metallic frame 10 constituted by a circular part 11, here in a horseshoe section turned towards the axis of the flywheel X (which gives excellent rigidity of the toric part of the flywheel), and of four branches radial 12 connected to a central portion 13 used for fixing the steering wheel, these branches being arranged symmetrically with respect to the median plane of the steering wheel. It is important to note that the fixing part 11 of circular shape is substantially in the lower tangent plane PI of the steering wheel (the upper tangent plane being denoted PS), and that the branches 12 have an angular profile with an obtuse angle turned towards the bottom (with an external section 12.1 and an internal section 12.2).

A damping padding 20 envelops the circular part 11 of the frame, as well as the ends of the sections 12.1 of branches adjacent to this circular part, by portions denoted 20.1. A central energy absorption cushion 30 covers the part remaining radial branches including the section 12.2, by simply being clipped by recesses 34 formed in its radial portions 32 which cover said portions 12.2 of the branches of the frame, going to the padding coating the portion 12.1 of these branches. The radial branches 12 may be formed by a plate (openwork or not) formed or by pairs of formed profiles arranged radially (arrangement in spider legs), the frame 10 forming a one-piece whole which is made of steel or resistant composite material.

The arrangement of the steering wheel V precisely allows the integration of an energy absorption device 100 of the type previously described. Indeed, the frame 10 has a central portion 13 lowered relative to the branches 12 whose profile is angular, and the central cushion 30 is hollowed out to present an axial internal housing 33. Then, between the top of this housing 33, at level of the central cap 31 of the cushion 30, and the lowered central portion 13, is arranged an energy absorption device 100 which is ready to fulfill its function in the event of a frontal impact on a part of the body of the driver on the central portion of the steering wheel. The energy absorption device 100 is held, at its upper flange 101 against the top of the interior housing of the central cushion, preferably by clipping into a circular groove formed for this purpose in said cushion, and, by its lower flange 102, which bears directly against the central fixing portion 13 of the frame. The energy absorption devices which are used here have three fingers 103 with cylindrical bores whose axes are successively orthogonal.

FIG. 9 illustrates a complementary mode of integration of the energy absorption device according to the invention. The actual steering wheel V is of a design similar to that which has just been illustrated, receiving here an energy absorption device 100 comprising four fingers 103 liable to deform longitudinally ^¬ during a crushing in axial compression. The actual steering wheel V is mounted on an anti-theft mechanism 50 of the steering wheel decoupling type, interposed between the steering wheel and the steering column. This anti-theft mechanism 50 comprises a body 51, a lever 52 for uncoupling the steering wheel, and a lower extension 53 carrying an armored cylindrical skirt 54 fixed by a rod 55. It is then possible to accommodate a second absorption absorption device. energy 100, similar to the previous one, inside the armored skirt 54. In the lower part of the anti-theft mechanism housing, a disc-shaped projection 56 is provided here which is received in a homologous recess of the flange upper 101 of the energy absorption device 100, which makes it possible to have a perfect setting of said device on the axis X of the steering wheel. In this way, the steering wheel is equipped with an energy absorption device intervening both upstream and downstream of the metal frame 10. Thus, in the event of a violent frontal impact, a double deformation action is obtained. axial with a maximum of absorbed energy. It is interesting to note that the mode of deformation of the fingers 103 of the device according to the invention is perfectly compatible with its integration inside the cylindrical armored skirt 54, because the deformation of these fingers is perfectly controlled, and does not not risk presenting an undesirable radial expansion which would induce a jamming with the armored skirt.

As a variant, it is possible to provide several energy absorption devices arranged coaxially one inside the other.

FIG. 10 illustrates another variant in which the lower flange of the energy absorption device 100 is no longer a flat circular flange as previously, but is produced in the form of a base of hub 102 'arranged coaxially with the first flange 101. The hub base 102' has a fluted central passage 60 used for coupling with the fluted end of the section of the steering column, and a widening 61 associated with the housing of the 'fixing nut. The hub base 102 'is further surmounted by an armored skirt 62, inside which is disposed an energy absorption device 100. The fingers 103 of the energy absorption device are fixed to the hub base 102 'by screwing, said fingers then having threaded coaxial extensions 108 coming to be screwed into blind tapped holes associated with the hub base. These same fingers 103 are fixed to the upper flange 101 by means of pins 113 secured by welding or gluing to this upper flange 101. It should be noted the presence of the circular recess 112 of the upper flange 101, making it possible to receive the projection centering disc-shaped 56 of the above-mentioned anti-theft mechanism 50.

In certain situations, the absorption device is integrated into a structure which is subjected to torques.

In particular, in the case of integration into the environment of a vehicle steering wheel, it is desirable to have a mechanical resistance to the torque at least equal to 22 m × kg.

It is then advisable to design means improving the torque resistance of the device described above, these means however having to be designed in such a way that they do not interfere with the essentially axial deformation of the fingers during a crushing in axial compression.

Such an arrangement of the energy absorption device will be described below with reference to FIGS. 12 to 18. Basically, it is intended that the two Supporting and / or fixing parts are also joined together by torque stiffeners arranged to provide high torque resistance and to deform in the event of crushing in axial compression without affecting the longitudinal deformation of the fingers. Two embodiments of such torque stiffeners are illustrated here by way of example, respectively in FIGS. 12 to 16, and in FIGS. 17 and 18.

In the first embodiment, these are torque stiffeners with tilting insert, each stiffener essentially being constituted by a folded sheet frame fixed to the two aforementioned parts being arranged circumferentially, and by a reinforcement insert of the aforementioned frame which is mounted inside thereof, to pivot about an axis essentially orthogonal to the direction of crushing in axial compression. The basic principle of such a stiffener is that it makes it possible, during normal operation, to provide resistance to the significant torque by virtue of the insert which laterally holds the connection frame, this insert then remaining essentially immobile. On the other hand, in the event of crushing in axial compression, a pivoting of the insert around its axis is triggered, which causes its tilting, while allowing the deformation of the sheet metal frame. In FIGS. 12 and 13, a device 200 for absorbing energy by plastic deformation is thus distinguished, consisting of two support and / or fixing pieces 201, 202, here arranged in the form of flat circular flanges, which are at a distance from each other, these two parts being joined together by a plurality of axially deformable fingers 203 which conform to at least one of the examples previously described. In the event of an impact, the upper structure E secured to the flywheel, which is fixed by bolts 206 to the upper flange 201, crushes the fingers 203 which under axial compression, over at least part of their length, a succession of through recesses in the form of cylindrical holes, the axes of which are arranged in different radial directions. The device is now completed by torque stiffeners with tilting insert, here three in number, which are advantageously arranged alternately with the energy absorbing fingers 203. Each torque stiffener with tilting insert is denoted 220. It is essentially constituted by a tilting reinforcement insert 221, constituting the "rocker" of the stiffener, and by a support frame 222 arranged circumferentially, which ensures the connection between the flanges 201 and 202. The frame 222, preferably made of sheet metal folded, is fixed by its base by means of a bolt 223 to the hub flange 202, and, at its upper part, for example by means of a blind rivet 226, to the upper flange 201. The insert forming a rocker 221 is mounted to pivot about an axis 224, which may consist of a pin or any other equivalent member forming a pivot axis (for example a localized deformation of the frame defining a sai internal link forming axis point).

In normal operation, the insert 221 forming a rocker is disposed parallel to the central axis X, and it is in direct contact by its two lateral facets with the frame 222, so as to thus constitute a substantially rigid element which is capable of transmit high torques. In this position, the insert 221 laterally holds the frame 222, being integral with it.

Each rocker 221 has, on the outside, a free chamfered edge 225 against which a protuberance 227 comes to bear which can be, as is the case here, the head of a blind fixing rivet 226 fastening the frame 222 to the upper flange 201, or alternatively one screw end. In normal operation, the rocker ^¬ their 221 remains in its vertical position which is illustrated in FIGS. 12 and 13, whereas, in the case of an axial compression crushing the aforementioned fingers 203, the movement for bringing the two flanges closer together has effect of causing the rivet head 227 to cooperate with the chamfer 225, and to cause the rocker 221 associated with the rocker 221 to tilt on the internal side, that is to say towards the X axis. After pivoting of the rocker 221, the sheet metal frame can be crushed normally, and neither the rocker during its pivoting nor the frame during its crushing deformation interfere with the axial deformation of the aforementioned fingers.

The fact that the inserts 221 all tilt inwards in the event of impact makes it possible to preserve the minimum space requirement outwards during the plastic deformation of the device, and to use a housing of optimal compactness.

Because the tilting of the inserts 221 only occurs in the event of an impact inducing axial compression of the device, it is possible to provide a temporary connection such as bonding between each rocker and the frame which surrounds it, in order to avoid any risk of inadvertent tipping.

As can be seen in Figures 12 and 14, there is provided in this case a frame 222 having a trapezoidal shape. The lower base 228, which is the large base of the trapezoid, is fixed against the base area of the hub 202 by a bolt 223 passing through an associated opening 231. In the upper part, there is a covering of the two ends 230, with a hole common 232 corresponding for example to the passage of a blind rivet for fixing to the upper flange 201. The two wings 229 of the trapezoidal frame 222 finally have a bore 233 corresponding to the passage of a pin forming a pivot axis for the corresponding rocker . In FIGS. 15 and 16, a more detailed distinction is made between the structure of an insert forming a rocker 221. This insert has a flat internal face 236, and an external chamfer 225 inclined at an angle a which is for example close to 25 °. The insert 221 has two lateral faces 235 which are inclined, with an inclination forming an angle β and which corresponds to that of the lateral branches 229 of the trapezoidal frame 222. As an indication, an angle β close to 20 ° may be chosen. The insert 221 also has here a horizontal recess 234 associated with the passage of the axis allowing pivoting relative to the trapezoidal frame 222 in the event of impact. Each insert 221 forming the rocker can for example be made of synthetic material such as Delrin ^®. As a variant of the torque stiffeners previously described, it is possible to provide stiffeners each consisting of a pair of joined sheets of folded sheet metal fixed to one of the flanges and by a V-shaped corner penetrating between these two sections. FIGS. 17 and 18 illustrate such stiffeners, inserted between fingers 203 with cylindrical holes 204 of the type previously described (the representation given in these figures is essentially schematic according to a "flat" view which does not highlight the circumferential arrangement of the stiffeners, the median planes of which may or may not be radial).

In FIG. 17, a raidis¬ 220 is thus distinguished, consisting of two contiguous profiles 250 made of folded sheet metal secured to the flange 202, and by a V-shaped corner 254 secured to the flange 201. In this case, the two profiles 250 are welded at their base, but it is naturally possible to provide bolting on two folded lower edges, and the V-shaped corner 254 is a local deformation of the flange 201. The two sections 250 end in two divergent branches 251 between which is received the corner in V 254. Torque transmission is therefore ensured by the coopera ^¬ V between the corner 254 and one or the other (depending on the direction) of the legs 251. In the case of crushing in the axial compression, the wedge 254 penetrates V further between the two sections 250, without affecting the axial deformation of the fingers 203. It may also be advantageous to provide a rivet 253 which joins the two sections 250 together: this rivet (which may be replaced by a screw or the like ) constitutes a mechanical fuse which breaks as soon as the force exerted by the V-shaped wedge 254 tending to separate these sections exceeds a certain threshold.

In FIG. 18, the stiffener 220 "differs from the previous one by the fact that the divergent branches 251 of the profiles 250 are extended by two convergent branches 252, and by the fact that the V-shaped corner 255 has a profile in ace of counterpart of the shape of the passage defined between the ends of the profiles 250. The cooperation of the V-shaped corner with the divergent branches 251 is similar to that encountered for the preceding variant, but in addition, thanks to the labeling produced between the convergent branches 252 , a resistance to tearing off. In these types of torque stiffeners with folded sheet profi¬ les, the thickness of the sheet will be chosen as a function of the value of the torque to be transmitted. has just been described can be used individually, as illustrated in the figures, or in duplication. It is indeed possible to provide a plurality of devices to supporting and / or fixing parts and with longitudinally deformable fingers, which are arranged in the form of coaxial cages, with fingers which are of length progressively decreasing or increasing from one cage to another. With such a variant, which has not been shown here, it is possible to obtain a successive energy absorption effect which can prove to be particularly beneficial during very violent frontal impacts.

The invention is not limited to the modes of ENFORCE ^¬ which have just been described, but the contrary covers any variant using equivalent means, the essential characteristics specified above.

In particular, the energy absorption device can be used in very diverse fields, such as the longitudinal members of the structure of motor or rail vehicles, the deformable frames for seat frames, or the rail buffers, or even the caissons of transport of dangerous goods.

Claims

1. Device for absorbing energy by plastic deformation, in particular for a vehicle steering wheel, characterized in that it consists of two support and / or fixing parts (101, 201; 102, 102 ';

202) arranged at a distance from each other, these two parts being joined together by a plurality of fingers (103,

203) having, over at least part of their length, a succession of through recesses (104) produced in the form of holes, the axes of which are arranged in different radial directions, so as to be able to deform longitudinally when they are subjected to axial forces exceeding a certain threshold.

2. Device according to claim 1, characterized in that the fingers (103) extend parallel to a common direction.

3. Device according to claim 1, caracté¬ ized in that the fingers (103) are slightly inclined inwardly or inwardly at the same angle.

4. Device according to claim 1, caracté¬ ized in that the fingers (103) are arranged in pairs to form deformable structures in V.

5. Device according to one of claims 1 to 4, characterized in that at least some of the fingers (103) are of generally cylindrical shape.

6. Device according to one of claims 1 to 4, characterized in that at least some of the fingers (103) are tapered from their ends, towards a median plane common to all of the fingers.

7. Device according to one of claims 1 to

4, characterized in that at least some of the fingers (103) are tapered towards their ends, from a median plane common to all of the fingers.

8. Device according to one of claims 1 to 7, characterized in that the through holes (104) of fingers (103, 203) are cylindrical, and the axes (Dl, D2) of the cylindrical bores are successively orthogo ^¬ nal.

9. Device according to claim 8, characterized in that the cylindrical holes (104) of the fingers

(103) are of the same diameter, and their number is the maximum number compatible with the required mechanical strength.

10. Device according to one of claims 1 to 9, characterized in that the fingers (103, 203) are fixed to the support and / or fixing parts (101, 201; 102, 102 ', 202) so not removable, for example by welding.

11. Device according to one of claims 1 to 9, characterized in that the fingers (103, 203) are fixed to the support and / or fixing pieces (101, 201; 102, 102 ', 202) so removable, for example by screwing.

12. Device according to one of claims 1 to 11, characterized in that one (101, 201) of the support and / or fixing parts is a flat flange, and the other is an identical flange (102 , 202) or a hub base (102 ') arranged coaxially with the first flange (101, 201).

13. Device according to one of claims 1 to 12, characterized in that it is constituted by a plurality of devices (100, 200) with supporting and / or fixing parts and with deformable fingers (103, 203) longitudinally, these devices being arranged in the form of coaxial cages, and the fingers (103, 203) of said devices being of length decreasing or progressively increasing from one cage to another.

14. Device according to one of claims 1 to 13, characterized in that the two support and / or fixing parts (201, 202) are joined both by fingers (203) with through holes and by torque stiffeners (220; 220 '; 220 ") arranged to provide high torque resistance and to deform in the event of crushing in axial compression without affecting the longitudinal deformation of the fingers (203).

15. Device according to claim 14, charac¬ terized in that each torque stiffener (220) is constituted by a folded sheet frame (222), fixed to the two aforementioned parts (201, 202) being arranged circumferentially, and by a reinforcement insert (221) mounted inside this frame with the possibility of pivoting about an axis (224) essentially perpendicular to the direction of crushing in axial compression, said insert being disposed in said frame in operation normal to provide a high torque resistance, but automatically tilting in the event of crushing in axial compression while allowing the deformation of said frame.

16. Device according to claim 15, characterized in that the reinforcement insert (221) has a free edge with external chamfer (225) with which cooperates, in the event of crushing in axial compression, an adjacent member (227 ) carried by a support and / or fixing part (201), so that the tilting of said insert takes place inwards.

17. Device according to claim 16, charac¬ terized in that the adjacent member (227) is the head of a rivet or a fixing screw (226) securing the frame (222) to the support piece and / or fixing concerned (201).

18. Device according to one of claims 15 to 17, characterized in that the frame (222) has a trapezoidal shape, and the insert (221) has two side faces (235) inclined in correspondence so as to register in said frame.

19. Device according to claim 14, charac¬ terized in that each torque stiffener (220 '; 220 ") is constituted by a pair of contiguous sections of folded sheet metal (250) fixed to a piece of support and / or fixing (202), said sections having two divergent branches (251) between which is received a V-shaped corner (254; 255) fixed to the other support and / or fixing part (201).

20. Device according to claim 19, charac ^¬ terized in that the profiles (250) are joined by a member (253), such as a rivet, forming a mechanical fuse, arranged to break as soon as the force exerted by the wedge in V (254; 255) tending to separate said sections exceeds a certain threshold.

21. Device according to claim 19 or claim 20, characterized in that the V-shaped corner (254) is a local deformation of the corresponding support and / or fixing piece (201).

22. Device according to claim 19 or claim 20, characterized in that the V-shaped corner (255) is enclosed by two converging branches (252) extending the diverging branches (251) of the profiles (250), so that the torque stiffener (220 ") also provides pullout resistance.

23. Device according to one of claims 15 to 22, characterized in that the torque stiffeners (220; 220 '; 220 ") are arranged alternately with the fingers (203) with through cylindrical holes.

24. Steering wheel for a vehicle, in particular a motor vehicle, having a metal frame (10) with radial branches (12) coated on the one hand with a shock-absorbing padding (20) enveloping the circular part of the frame and the ends branches adjacent to this circular part, and on the other hand a central cushion (30) shock absorber covering the remaining part of the branches and the central portion (13) for fixing the steering wheel from which these branches start, characterized in that the 'frame (10) has a central portion (13) surbais¬ sée relative to the branches (12) whose profile is angular, and the central cushion (30) is hollowed out to present an axial internal housing (33), and in this that between the top of this housing (33) and the portion a lowered central unit (13) is arranged a device for absorbing energy (100, 200) according to any one of the preceding claims, the fingers (103, 203) of which are essentially parallel to the axis of the flywheel (V ), said device being completely integrated into the central cushion (30).

25. Steering wheel according to claim 24, mounted on an anti-theft mechanism (50) of the disengaging type of the steering wheel, interposed between the steering wheel and the steering column, characterized in that a second absorption device for energy (100, 200), similar in structure to the first, is arranged directly below the anti-theft mechanism (50), so that said flywheel is equipped with an energy absorption device (100, 200) intervening both upstream and downstream of the metal frame (10).