FR2787389A1 - WHEEL SUSPENSION ELEMENT, PARTICULARLY FOR A MOTOR VEHICLE, AND SUSPENSION STRUCTURE COMPRISING SUCH AN ELEMENT - Google Patents

Abstract

Wheel suspension element, in particular for a motor vehicle, comprising a flexible arm (11, 12, 13, 14) connected, on the one hand, by an articulation (15, 16, 17, 18) to the wheel support and, d on the other hand, directly or indirectly, to the chassis of the vehicle: in line with its articulation (15, 16, 17, 18) at the wheel support, the flexible arm extends in a transverse extension (11a, 12a, 13a, 14a) whose end (11b, 12b, 13b, 14b) is connected to the vehicle chassis, directly or indirectly, by a flexible connection, each arm and its transverse extension constituting a flexible pseudo-triangle. Suspension structure comprising at at least three such suspension elements, the arms (11, 12, 13, 14) being connected by an inter-arm connection (19) at their end opposite to that which carries the articulation (15, 16, 17, 18).

Description

"Wheel suspension element, in particular for a motor vehicle, and

  suspension structure comprising such an element "The subject of the present invention is a wheel suspension element, in particular for a motor vehicle, more particularly - but not

exclusively - on four wheels.

  Such a suspension element advantageously fits into a suspension structure as described in the French patent application filed on June 1, 1997 under the number 97 07 416 and / or in the application.

  corresponding international PCT / FR 98/01266.

  In terms of suspension, the known technology prior to that illustrated by the documents cited above, as explained therein, uses separate means to provide the guidance and stiffness functions: it employs, on the one hand, parts whose function is to guide each wheel in its relative movement with respect to the suspended part of the vehicle (triangles, pulled arms ...) and, on the other hand, elastic elements constituting the springs (helical springs, torsion bars ...) whose

  function is to store and restore energy.

  This technology has the disadvantage of a large number of

  components, which in particular implies a high mounting cost.

  The body movements generate physiological sensations

  unpleasant for the occupants of the vehicle.

  Obtaining a good level of comfort requires a stiffness seen at the wheel which is higher at the roll movement than at the pumping movement, particularly for unibody vehicles which have a high roll inertia, in order to obtain a minimum roll angle for a given transverse acceleration, while the pumping stiffness is related to

  the natural frequency of walking in humans.

  The traditional solution is to add an anti-roll bar by

axle.

  In addition to the fact that the number of components is increased, it results in additional stiffness to the wheel when it is stressed alone for

cross an isolated obstacle.

  Thus, the forces transmitted to the structure of the vehicle are increased by the same amount and, consequently, the variation in acceleration to which the occupants are subjected is greater, which is detrimental to comfort. In addition, this additional stiffness disappears with the pitching movement for which it would be much appreciated in order to limit the angle corresponding to the

  braking, for a given deceleration.

  This known solution is therefore not satisfactory.

  Obtaining a good level of comfort for the occupants of a vehicle with usual suspension travel requires a variable stiffness: low at the level of the static equilibrium position and high in

  moving away, whether in compression or expansion.

  So a small variation in the position of the wheel around the balance

  static induces a reduced acceleration variation, for the benefit of comfort.

  On the other hand, a significant obstacle requires a high stiffness so that the resulting forces sufficiently modify the trajectory of the vehicle,

  thus creating the conditions for a satisfactory crossing.

  The document Bertin FR-A-2 563 301 proposed a device insensitive to rolling motion, composed of an elastic transverse blade comprised between two rigid end parts. However, such an effect also induces, at the wheel stressed alone, a stiffness twice its stiffness at the pumping movement, which increases the intensity of the "racket stroke" if

unfavorable to comfort.

  One way to limit this perverse effect is to reduce the stiffness of the device when pumping and to compensate for the significant static deflection.

  resulting by a prestressing of the blade.

  In order not to have to install this prestress on the vehicle production line, which increases the assembly time, the document Bertin FR-A-2 600 016 installs the prestressed blade in a support structure then assembled to the vehicle. However, such a solution

  has the disadvantage of a large number of components.

  On the basis of a blade with stiffened ends, the document Bertin FR-

  A-2 624 446 reduces the number of components and erases the aforementioned perverse effect by a law of progressive stiffness. However, this solution requires - in return - a delicate fitting at each end of the blade. Furthermore, beyond these questions, any transverse blade solution has the major drawback of hampering the installation of the engine block between the wheels of the axle it serves. Such an architecture then requires either to position the engine block in cantilever, which in particular has the consequence of increasing the moment of inertia of pitching to the detriment of comfort, or to move the engine block towards the passenger compartment, to the detriment in particular the space allocated to the occupants of the vehicle and the

  quality of treatment of frontal impact.

  The architectures of traditional suspensions, during the relative movements of the wheels relative to the vehicle, produce significant forces at the level of the front block and the rear block which require a high structural rigidity in torsion and in bending. This results in a limitation of the possibilities of reducing the mass of these parts, which penalizes dynamic behavior, safety and energy consumption. The treatment of the shock can be entrusted - at least partially - to light cellular materials by bursting of the constituent micro-structures, a simplification of the front and rear blocks is possible, to the benefit of the mass of the vehicle. Correlatively, the general reduction

  sizing also induces a reduction in mass.

  Known anti-roll devices, for example an anti-roll bar, induce stiffness in the warping of the ground support quadrilateral which also penalizes dynamic behavior: braking stability,

  traction on uneven terrain ....

  The document Renault FR-A-2 640 205 proposes an isostatic suspension such that the ground loads are independent of the warping of the support quadrilateral, in order to limit the torsional and bending stresses to which the vehicle structure is subjected. However, in addition to the fact that the transverse leaf springs on the axle axis interfere with the positioning of the engine, this solution requires a number of components and

of links.

  Furthermore, it follows from the very statement of the proposal that the trajectory of the vehicle is not modified by such a relative movement of the wheels with respect to the suspended part of the vehicle. Thus, such a relative displacement can easily reach the maximum value permitted by the geometry of the suspension and, consequently, generate a shock. Such a shock is, on the one hand, detrimental to comfort and, on the other hand, inflicts a

  severe constraint on the structure of the vehicle, contrary to the intended purpose.

  It is necessary that a suspension has a longitudinal flexibility as much to limit the extreme level of the efforts resulting from the crossing of a very severe obstacle, like a pavement, at a speed

  given only to filter the longitudinal component of soil irregularities.

  The pivots and elastic supports traditionally used can only confer - in the context of known architectures - flexibility limited by the need to maintain an acceptable geometry, to the detriment of the

  quality of the longitudinal suspension.

  We know the Popinet suspension structure described in document FR-A-2 552 718, connecting the four wheels of the vehicle by means of a flexible frame composed of two transverse blades and two longitudinal blades, which also incorporates a longitudinal filter. However, such an architecture has the drawback of hampering the positioning of the motor between the wheels of an axle and of presenting a roll stiffness less than the

pumping stiffness.

  To filter the high frequency vibrations resulting from the rolling of tires on the ground, known architectures connect the suspension to the vehicle structure by two flexible connecting stages via an intermediate cradle which, however, does not contribute to the anisotropy of stiffness of the whole thus constituted. In addition, the known material-architecture pairs do not allow

  consider improving iso-cost filtering.

  The transverse arrangement of the engine block on the axis of the front axle imposes a compact suspension, which results in the Mac Pherson type architecture, most commonly used for the front axle, by a lower arm of small dimension which degrades the kinematic qualities of the suspension except to limit the vertical stroke, which

penalizes comfort.

  Only the less restrictive conditions for installing the suspension at the rear allow the use of long linkages, in particular in multi-link Mac Pherson architectures, to the detriment, however, of the bulk. The search for a high level of stability of the vehicle at yaw movement requires a micro-turning induced at the opening in compression

  for the front axle and with the clamp for the rear axle.

  During pumping, any micro-turning is uninteresting, without

  be undesirable because symmetry cancels its effects.

  On the other hand, this is not the case when a single wheel is stressed, a situation where any variation in steering is unfavorable to the stability of the

walking in a straight line.

  On bad roads in particular, the driver perceives untimely course variations that generate unpleasant physiological sensations. The known architectures have a small number of degrees of freedom to influence the movements of the wheel plane and do not allow

  to differentiate the kinematics according to the vertical loading mode.

  This is particularly the case with Mac Pherson type architecture

  yet interesting because of its limited cost and size.

  The object of the invention is to remedy the above drawbacks in a suspension structure which provides an elastic connection between the part of a body to be isolated from vibrations and at least three displacement members by which it rests on a surface. irregular on which it evolves and whose

  the perpendicular direction defines the vertical reference axis.

  More specifically, the present invention has for first object a wheel suspension element, in particular for a motor vehicle, comprising a flexible arm connected, on the one hand, by an articulation to the wheel support and, on the other hand, directly or indirectly , to the chassis of the vehicle, characterized in that, in the region of its articulation with the wheel support, said flexible arm extends in a transverse extension, the end of which is connected to the chassis of the vehicle, directly or indirectly, by a flexible connection, the arm and its transverse extension

  constituting a flexible assembly hereafter designated by pseudo-triangle.

  The end of the arm, other than that placed at the right of the articulation to the wheel support and said retaining end, is retained so that it is subjected to at least one vertical force; this restraint can be complete or partial, that is to say with at least one degree of freedom; she may be

  elastic and obtained for example by an additional stiffness means -

  spring or preferably stopper made of elastomeric material in particular containing a cavity filled with gas under pressure advantageously adjusted to the speed and / or the load of the installed vehicle

  between the vehicle chassis and said end.

  The pseudo-triangle consists of a transverse extension

  substantially rigid in tension-compression and more flexible in bending.

  Each arm of the elastic structure according to the invention is, in general, linked - between its retaining end and its end linked to the

  wheel support - to the vehicle chassis.

  Most generally, it is a flexible connection with anisotropy of stiffness offering mainly a freedom of movement in rotation around an axis close to a horizontal perpendicular to the arm at this place of connection and, secondarily, a certain freedom of movement suitably chosen on each of the other five axes, in particular in translation along its axis of articulation and in rotation about perpendicular axes. This connection can in particular be produced in the form of a flexible pivot, an oblong support, a couple of elastic supports or any

  another elastic device with stiffness anisotropy.

  Most generally, the articulation of the transverse extension to the passenger compartment of the vehicle is a flexible connection with anisotropy of stiffness offering mainly a freedom of movement in rotation around a substantially longitudinal axis but also a certain freedom of movement in translation along the articulation axis, in rotation of small amplitude around a substantially vertical axis and suitably limiting the

  translational movement along the transverse axis.

  This connection can in particular be carried out in the form of a pivot

  flexible or any other elastic device with anisotropy of stiffness.

  Generally, an arm - described according to the theory of beams -

  has an evolving running section along its mean line which is a left curve, said section having at least one restriction of its width intended to soften the suspension structure with longitudinal forces. Advantageously, the width of the current section of the arm - at the level of its connection to the chassis of the vehicle - is restricted on the side of the end of

  retained and is not retained on the side of the link to the wheel support.

  The ratio of the width to the thickness of the current section of the arm advantageously has at least a minimum in the vicinity of the connection of the arm to the chassis and a maximum in the vicinity of the end

of restraint.

  The current section of the arm may in particular be rectangular,

  circular or oval (not necessarily symmetrical) and pinched or not.

  In general, the transverse extension of the arm - described according to the theory of beams - has an evolving section along its mean line which is a left curve. The current section of the transverse extension of the arm can be in particular square, rectangular, circular or oval (not necessarily symmetrical) and pinched or not, full or in thin profile which can be

open or closed.

  The profile of the arm in horizontal projection on a vertical plane can be - under strong vertical load - substantially straight from its connection to the wheel support to its place of connection to the chassis so that these load conditions cancel - in this part of the arm - the torsional stress induced by a horizontal force applied to its articulation at the

wheel support.

  The profile of the transverse extension of the arm, in horizontal projection on a vertical plane, perhaps - under strong vertical load applied to the articulation to the wheel support - substantially straight and slightly

curved in the absence of load.

  Under the constraint of the vertical wheel travel, the deformation

  elastic of the pseudo-triangle influences the movement of the wheel plane.

  The pseudo-triangle, consisting of a substantially rigid transverse extension in tension-compression and more flexible in flexion, has a certain flexibility with a longitudinal force while being rigid with respect to a transverse force both applied to the joint at

wheel support.

  In vertical projection on a horizontal plane, the arm can be curved in particular so that in the region of its articulation to the support

  wheel, it has an angle as small as desired with the transverse axis.

  The transverse extension of the arm may have a slight curvature in this plane such that the vector normal to the curvature directed towards the center of

  curvature is oriented towards the front or rear of the vehicle.

  Under the constraint of the longitudinal wheel travel, the elastic deformation of the pseudo-triangle influences the movement of the wheel plane. In a Mac-Pherson type wheel suspension according to the invention, the pseudo-triangle is articulated to the wheel support by a ball joint and the leg

  telescopic does not require the use of a spring.

  The present invention also relates to a structure for

  suspension comprising at least one such wheel suspension element.

  In particular, the suspension structure according to the invention ensures an elastic connection between the passenger compartment of a motor vehicle and

  at least its three wheels by which it rests on the ground on which it evolves.

  In general, the suspension structure according to the invention consists of at least three flexible arms, linked together at one end where they merge by a so-called inter-arm connection, the other end of

  each of them being linked to a wheel support.

  This inter-arm connection here constitutes the means by which the end of

arm restraint is retained.

  The most advantageous embodiments from a practical point of view are such that the surface projected vertically on a horizontal plane of said inter-arm connection is inside the polygon joining the projections on the same horizontal plane of the ends linked to the contact and displacement members of the adjacent arms, which polygon corresponds

  substantially at the lift polygon.

  In particular, the most advantageous embodiments from a practical point of view for a motor vehicle are such that the surface projected vertically on a horizontal plane of said inter-arm connection is inside the polygon joining the projections on the same horizontal plane of the ends linked to the wheel supports, which polygon is - in practice - little different from the support polygon of said motor vehicle. In order to increase its capacity to store energy, the arm may comprise - in its central part, which is between its end linked to the other arms and its connection to the chassis of the vehicle - one or more ribs

of axis normal to the arm.

  In a variant of the invention, the arm consists of two parts -

  one supporting the connection to the wheel support and the connection to the chassis, the other by which the arms are merged together - connected by a flexible connection which ensures a certain freedom of relative movement of the plane-on-plane type

low amplitude.

  Thus, the two parts of the arm are held in translation along the vertical axis and in rotation about two horizontal axes orthogonal to each other. This improvement limits - beyond the internal filtering due to the material of the suspension structure - the transmission of vibrations from a

  from the wheels to the other wheels of the vehicle and improves longitudinal filtering.

  At least one additional stiffness means - spring or preferably stopper made of elastomeric material in particular containing a cavity filled with pressurized gas advantageously adjusted to the speed and / or the load of the vehicle - can be installed between the chassis of the vehicle and the material central of the suspension structure, which is

  limited by its connections to the vehicle chassis.

  Particularly for four-wheeled vehicles usually having a vertical plane of symmetry containing the longitudinal axis, the suspension structure can be linked to the vehicle chassis by means of a rigid cradle in its plane, symmetrical with respect to the vertical plane containing the longitudinal axis of the vehicle, flexible to warping and more rigid with respect to stresses other than warping, hollowed out in particular in the manner of a substantially rectangular frame whose sides can however be curved and whose current section is advantageously decreasing towards the junction points which support the connections to the suspension structure between which the cradle is linked to the vehicle by four connections, two connections called "longitudinal" because located in the longitudinal plane of symmetry of the cradle and two connections called "transverse "because located on a transverse axis which intersects said plane d symmetry at a point located at

  suitable distance from the longitudinal links.

  In general, these are flexible connections with anisotropy of stiffness, each conferring mainly a freedom of rotation around respectively longitudinal and transverse axes and also offering a certain freedom of movement suitably chosen on each of the other five axes, in particular in translation along the articulation axis and in

  rotation around perpendicular axes.

  Each of these connections can in particular be produced in the form of a flexible pivot, an oblong support, a pair of elastic supports

  or any other elastic device with stiffness anisotropy.

  The flexibility thus obtained reduces the stiffness of the suspension to the warping movement thus favored, which in particular makes it possible to optimize comfort by reducing the stiffness seen at the wheel requested

alone.

  For a given vertical clearance, the arms of the suspension structure are subjected to a stress field depending on the vertical stressing mode (pumping, rolling, warping, etc.), which induces a

  differentiation of the corresponding vertical stiffnesses.

  For a given vertical movement, the pseudo-triangle belonging to the suspension structure is subjected to a stress field depending on the vertical stressing mode (pumping, rolling ...), which induces a differentiated deformation field; we thus have access to a differentiated adjustment of the

  kinematics of the vertical travel of the wheel plane.

  All or part of the suspension structure according to the invention can be made of any material, the ratio of the resistance to fatigue to

  high modulus of elasticity, preferably made of composite material -

  especially glass-epoxy - consisting of fibers embedded in a synthetic resin. The characteristics of the invention are described in

claims.

  To better understand the object of the invention, we will now describe, by way of example, purely illustrative and not limiting, modes

  of production shown in the accompanying drawings.

  In these drawings: - Figure 1 is a longitudinal sectional view, along B2-B2 'of Figure 2, of a suspension structure according to the invention shown in the silhouette of a vehicle; - Figure 2 is a top view in section along AI-AI 'of Figure 1; - Figure 3 is a view similar to Figure 1, a wheel crossing an obstacle; Figure 4 is a perspective view of a flexible pseudo-triangle according to the invention under high vertical load applied to the articulation to the wheel support; - Figure 5 is a schematic view, in three positions, of the transverse extension of an arm, in horizontal projection on a vertical plane orthogonal to the axis of the articulation of said extension; - Figures 6A and 6B are partial schematic views in vertical projection on a horizontal plane illustrating the elastic deformation of a half axle before suspension under the constraint of a longitudinal wheel travel here strongly amplified; Figure 7 is a view similar to Figure 1 and corresponds to a variant in which the suspension structure is linked to the vehicle chassis via a cradle; - Figure 8 is a top view of the cradle of Figure 7 - Figure 9 is an enlarged view in partial section along A8-A8 'of Figure 8 of the mounting of a connection of the suspension structure to cradle; - Figure 10 is a view similar to Figure 2 and shows an alternative embodiment of the suspension structure; - Figure 11 is a sectional view of an arm of the structure of

  suspension according to A10-A10O 'in Figure 10.

  Referring to Figures 1 and 2, we see an elastic suspension structure 1, according to the invention, which provides an elastic connection between the chassis 3 of a motor vehicle and its four wheels, front 2 and rear 2 ',

  by which it rests on the ground on which it is brought to evolve.

  The suspension structure 1 here consists of four flexible arms 11, 1 2, 1 3, 1 4, each associated with a wheel and linked together at one end 19, called inter-arm connection, where they merge, I ' other end of each of the arms being articulated on a front wheel support 2

or rear 2 '.

  Each arm 11, 12, 13, 14 is linked by a link 6 to the chassis 3 of the vehicle; this connection 6 is a connection with anisotropy of stiffness offering to each arm a freedom of movement in rotation around an axis 7 close to a horizontal perpendicular, in this place of connection, to the direction in

  which extends the arm; each link 6 is arranged between the inter- link

  arm 19 and its articulation 15, 16, 17, 18 to the wheel support; here, it is provided by a simple elastomer support, which can be simply glued. Each arm 11, 12, 13, 14 is left: in horizontal projection on a vertical plane, FIG. 1, it has at least one curvature such that the vector normal to the arm directed towards the center of curvature is oriented towards the ground and in the horizontal plane of Figure 2; this curvature is such that, in the region of its articulation 15, 16, 17, 18 to the wheel support, it forms an angle of the order of 30 with the transverse axis connecting the articulations 15,

17 front or 16, 18 rear.

  Each arm has a current section, not shown, which evolves from a non-symmetrical oval at the level of the articulation 15, 16, 17, 18 at the wheel support to a wide and thin rectangle at the level of the

inter-arm connection 19.

  In the horizontal plane of Figure 2, the suspension structure 1 has two semi-elliptical recesses 101 and 102 symmetrical with respect to the longitudinal axis, a recess 101 open towards the front and a recess 102 open towards the rear; these recesses 101 and 102 form a restriction on the width of the current section of each arm between the

  link 6 and the inter-arm link 19.

  The ratio of the width to the thickness of the current section of each arm has a minimum in the vicinity of its connection 6 to the chassis and

  a maximum in the vicinity of the inter-arm connection 19.

  In this embodiment of the invention, each wheel suspension is of the "Mac Pherson" type in which the telescopic leg 31 does not include a spring; each arm 11, 12, 13, 14 of the suspension structure 1 has, in the region of the articulation 15, 16, 17, 18 to the wheel support, a generally transverse extension 11 a, 12a, 13a, 14 substantially rigid in traction-compression and more flexible in flexion; The free end 11b, 12b, 13b, 14b of each transverse extension 1a, 1 2a, 13a, 14a, respectively, is mounted articulated to the chassis 3 of the vehicle by a connection

  flexible axis 27 generally parallel to the longitudinal axis of the vehicle.

  Each pseudo-triangle thus formed 1-1 1a, 12-12a, 13-13a, 14-14a is articulated to the wheel support by the articulation 15, 16, 17, 18 already mentioned

  here, this articulation 1 5, 1 6, 1 7, 1 8 is a ball joint.

  The flexible link of axis 27 is a flexible link with stiffness anisotropy mainly offering freedom of rotation, extensions 11a, 12a, 13a, 14a relative to the frame 3, around the axis 27 generally longitudinal but also a certain relative freedom of movement both in translation along the articulation axis 27 and in rotation, of small amplitude, around a substantially vertical axis, while suitably limiting the

  relative movement in translation along the transverse axis.

  In this embodiment, it is a flexible pivot.

  FIG. 3 shows the crossing of an obstacle by the right front wheel 2 of the vehicle; this crossing results in the vertical displacement Dz of the stressed wheel 2, linked to the arm 11, the telescopic leg 31 of the "Mac Pherson" type but without compressing spring; the suspension structure 1 is subjected at its articulation 15, not visible in the figure, to a vertical force fz, in the ratio of the vertical flexibility Dz / fz desired by

construction.

  Figure 4 shows in perspective the arm 11 of the suspension structure 1; in this figure, the pseudo-triangle 11-1 la is subjected to a strong vertical load Fz applied to the joint 15, here a ball joint; in this loading condition, the profile of the arm 11, in horizontal projection on a vertical plane, is substantially rectilinear from its articulation 15 to the wheel support to its axis connection 7 to the chassis 3 of the

  vehicle, here an elastic pivot 26.

  Similarly, the profile of the transverse extension 1 1a of the arm 11, in horizontal projection on a vertical plane, is substantially rectilinear from the articulation 15 to its end 11b by which it is connected to the

vehicle chassis.

  In this form of the invention, the arm 11 is connected to the chassis 3 of the vehicle by an elastic pivot 26 whose axis 7 is substantially horizontal in

  being orthogonal to the arm 1 1 in this articulation zone.

  The arm 11 has a substantially rectangular running section with increasing dimensions from the connection to the wheel support 1 5 to the

  connection 26 to the vehicle chassis.

  Here, the ratio of the width to the thickness of the current section of the arm 11 has a minimum at the elastic pivot 26 and, simultaneously, as already said above, a restriction of the width of said current section in the vicinity of the elastic pivot 26 but on the side of the

inter-arm connection 19.

  The transverse extension 1 1 a of the arm 1 1 has an evolving running section, substantially square, the dimensions of which are slightly narrowed towards its end 1 1 b. The end 1 1 b of the transverse extension 1 1 a is connected to the chassis 3 of the vehicle by a flexible connection with anisotropy of stiffness offering mainly a freedom of movement in rotation around the axis 27 substantially longitudinal but also a certain freedom of movement in translation along the axis 27 of articulation, in rotation of small amplitude about a substantially vertical axis and suitably limiting the

  translational movement along the transverse axis.

  This flexible connection is here a flexible pivot, but could be made at

  using any other elastic device with stiffness anisotropy.

  The pseudo-triangle 11-11 thus constituted presents a certain flexibility to a longitudinal force, while being rigid with respect to a transverse force, less than a critical load, these two forces being applied to

Articulation 1 5.

  In vertical projection on a horizontal plane, the arm 11 of the suspension structure is curved in such a way that in the region of its articulation 15 to the wheel support, it has an angle of the order of 30

with the transverse axis.

  The transverse extension 11 a of the arm 11 has a slight curvature in its plane such that the vector normal to the curvature directed towards the center of curvature is oriented towards the front of the vehicle for example,

  as is the case with this realization of the front half-axle.

  FIG. 5 shows in gray at the end the profile of the transverse extension 1a of the arm 11 under strong vertical load Fz applied to the joint 15: as can be seen in the figure, this profile is rectilinear; in the absence of vertical load (Fz = O), this profile, shown in gray shaded in the figure, is slightly curved so that the vector normal to the curvature, directed towards the center of curvature, is oriented towards the ground ; the profile shown

  in strong lines corresponds to the normal load of the vehicle.

  This representation highlights the variation in curvature of said profile by elastic deformation during the vertical movement, which influences the trajectory of the joint 15, with this in particular that the instantaneous center of rotation or C.l.R. does not exactly coincide with the articulation point of the end 1 1 b, which offers additional adjustment possibilities compared to known wheel suspensions, by playing on the linear flexibility and the initial curvature of the extension 1 la and arm

11.

  FIGS. 6-A and 6-B show - schematically - seen in plan an arm 1 1 of the suspension structure and its transverse extension 1 1 a,

  especially for a "Mac Pherson" type wheel suspension.

  The arm 11 is curved in the horizontal plane so that, in the region of its articulation 1 5 to the wheel support, it has an angle of the order of 15 with the transverse axis. On figure 6-A, transverse extension 1 1a of arm 1 1 is slightly curved in this plane, so that the normal vector with the curvature directed towards the center of curvature is directed towards the front for this half train before; on the figure 6-B, such

  vector is oriented backwards.

  Under the constraint of a longitudinal movement Dl, here strongly amplified, the arm 11 and its transverse extension 1 flex it, in a horizontal plane, towards the rear and their curvature in this plane changes, as shown in gray shaded on these figures; the trajectory of the articulation 15 at the wheel support has the particularity that the instantaneous center of rotation (ClR) does not exactly coincide with the physical articulation of the end 11b of the transverse extension 11a, which offers additional adjustment possibilities compared to known wheel suspensions, by varying the linear flexibility and the initial curvature of the extension 1a and of the arm

1 1.

  In particular, under the constraint of a longitudinal movement, the elastic deformation of the pseudo-triangle 11-11 influences the movement of the

wheel plane.

  Figures 7 and 8 show an embodiment in which the suspension structure 1 is linked to the chassis 3 of the vehicle by means of a

cradle 5 flexible.

  Each arm 11, 12, 13, 14 of the suspension structure 1 is linked to the

  cradle 5 by a pivot link of axis 7.

  The flexible cradle 5, symmetrical with respect to the vertical plane containing the longitudinal axis of the vehicle, constructed hollowed out in the manner of a substantially rectangular frame, here trapezoidal, the width of the current section of which is greater than the thickness, is rigid in its plan, flexible to warping and more rigid with respect to stresses other than the

  warping, for example when rolling or pumping.

  The sides of the cradle 5 are shown here rectilinear but they can

to be curved.

  The cradle 5 has a lower warpage stiffness than that of the structure 1 and a roll stiffness of the order of 10 to 20 times its

stiffness in warping.

  The cradle 5 is linked to the chassis 3 of the vehicle by four pivot links

  elastic, two so-called longitudinal 41 and two others said to be transverse 42.

  Advantageously, the current section of the sides of the cradle decreases towards the junction points which support the connections to the suspension structure and between which the connections are located.

  longitudinal 41 and transverse 42.

  The longitudinal links 41 are located on the longitudinal axis of the vehicle and the transverse links 42 are on a transverse axis, which intersects the vertical plane containing the longitudinal axis at a suitable distance, by

  substantially equal example, longitudinal connections 41.

  The connections 41 and 42 each confer mainly a freedom of rotation around their axis and also offer a certain freedom of movement on each of the other five axes, two of rotation and three of translation, in particular in translation along the axis of articulation and in

  rotation around perpendicular axes.

  The flexibility of the cradle 5 suitably high at warping, having regard to that of the suspension structure 1, induces a low rigidity of the assembly constituted by the suspension structure 1 and the cradle 5, owing to the fact that the constituent elements of this assembly are installed in series between the

chassis 3 and wheels.

  The resulting suspension advantageously has a low stiffness seen in the solicited wheel alone, close to the stiffness seen in the pumping movement. FIG. 9 shows an exemplary embodiment of the mounting of the flexible pivot of axis 7 of the arm 13 of the suspension structure 1 mounted on an axis

  37 carried by two legs 51 of the cradle 5.

  The other arms 11, 12 and 14 of the suspension structure 1 are

mounted identically.

  The elastic connections 41 and 42 are similarly mounted

  each on two legs 35 of the chassis 3 of the vehicle.

  Figure 10 shows an alternative embodiment of the invention: each arm of the suspension structure 10 consists of two parts 1 1 x and 1 1y, 12x and 12y, 13x and 13y and 14x and 14y, one said upstream 11x, 12x, 13x, 14x carrying the articulation 15, 16, 17, 18 to the wheel support and the other called downstream 11y, 12y, 13y, 14y carrying the inter-arm connection; the upstream part and the downstream part of each arm are connected by a flexible link which gives them a certain freedom of relative movement of the plane type on a plane of small amplitude, in rotation about a vertical axis and in translation along

  two horizontal axes orthogonal to each other.

  The downstream parts 1 1 y, 1 2y, 1 3y, 1 4y are linked together and are made up, in Figure 1 1, of two half-shells 1 99a and 1 99b made of high-grade steel.

  elastic limit, stamped and welded together by point.

  The two welded half-shells 199a and 199b enclose the upstream parts 11x, 12x, 13x, 14x of the arms; each upstream portion 11, 1x, 12x, 13x, 14, of the arms is kept at a distance from the lower half-shell 1 99a and from the upper half-shell 1 99b, respectively, by a lower elastomer block 201 and an upper elastomer block 202 installed in housings provided for this purpose forming a slight boss on the half-shell

  lower 1 99a and on the upper half-shell 1 99b.

  By stressing the elastomeric blocks 201 and 202 in shear and due to the arm-shell lateral spacing, a certain freedom of relative movement of the two parts of each arm is obtained:

  translation in the horizontal plane and in rotation around a vertical axis.

  For the sake of simplicity, the two half-shells 199a, 199b

  can be perforated as much as possible.

  The suspension structure 1 or 10 according to the invention is preferably made of a material whose ratio of the modulus of elasticity to the resistance to fatigue is low, preferably made of composite material - in particular glass-epoxy - consisting of embedded fibers

in synthetic resin.

Claims (32)

  1. Wheel suspension element, in particular for vehicle   automobile, with a flexible arm (11,12,13,14,11 x-1 y, 12x-   12y, 13x-13y, 14x-14y) connected, on the one hand, by an articulation (15,16,17, 18) to the wheel support and, on the other hand, directly or indirectly, to the chassis (3) of the vehicle, characterized in that, in the region of its articulation (15,16,17,18) to the wheel support, said flexible arm extends according to a transverse extension (11a, 12a, 13a, 14a) whose l end (11b, 12b, 13b, 14b) is connected to the chassis (3) of the vehicle, directly or indirectly, by a flexible connection, each arm and its transverse extension constituting   a flexible set called pseudo-triangle.   2. Suspension element according to claim 1, characterized by the   causes the end of the arm (11,12,13,14,11x-11y, 12x-12y, 13x-13y, 14x-   14y), other than that placed at the right of the articulation (15,16,17,18) at the wheel support and said retaining end, is retained so that it is   subjected to at least one vertical force.   3. Suspension element according to claim 2, characterized in that the arm (11,12,13,14,11x-11y, 12x-12y, 13x-13y, 14x-14y) is linked between its retaining end and its end linked to the wheel support, vehicle chassis.   4. Suspension element according to claim 3, characterized in that this connection of the arm to the chassis is a flexible connection with anisotropy of stiffness offering mainly freedom of movement in rotation about an axis close to a horizontal perpendicular to the arm at this connection point and, secondarily, a certain freedom of movement suitably chosen on each of the other five axes, in particular in translation along its axis of articulation and in rotation about perpendicular axes.   5. Suspension element according to one of claims 1 to 4,   characterized in that the flexible connection by which the end (11b, 1 2b, 1 3b, 1 4b) of the transverse extension (11a, 1 2a, 1 3a, 1 4a) is connected to the chassis (3 ) is a flexible connection with anisotropy of stiffness offering mainly a freedom of movement in rotation around a substantially longitudinal axis (27) but also a certain freedom of movement in translation along said axis (27), in rotation of small amplitude around d '' a substantially vertical axis and limiting the following translational movement the transverse axis.   6. Suspension element according to claim 5, characterized by the   that said flexible connection is a flexible pivot.   7. Suspension element according to one of claims 1 to 6,   characterized by the fact that the mean line of the transverse extension   (11a, 12a, 13a, 14a) and / or the arm (11,12,13,14,11x-lly, 12x-12y, 13x-   13y, 1 4x- 14y) is a left curve.   8. Suspension element according to one of claims 1 to 7,   characterized by the fact that the cross section of the extension   (11a, 12a, 13a, 14a) and / or the arm (11,12,13,14,11x-11y, 12x-12y, 13x-   13y, 14x-14y) is evolutionary along its midline.   9. Suspension element according to one of claims 1 to 8,   characterized by the fact that the current section of the transverse extension   (11a, 12a, 13a, 14a) and / or the arm (11,12,13,14,11x-11y, 12x-12y, 13x-   13y, 14x-14y) is generally square, rectangular, circular or oval, symmetrical or not, pinched or not, solid or in thin profile which can be open or closed.   10. Suspension element according to one of claims 2 to 9,   characterized by the fact that the arm (1 1.1 2.1 3.1 4.11 x, 1 2x, 1 3x, 1 4x) has a running section which evolves from an asymmetrical oval in line with the joint ( 15,16,17,18) to the wheel support up to a wide rectangle and   thin to the right of the retaining end.   11. Suspension element according to one of claims 2 to 10,   characterized in that the width of the current section of the arm (11,12,13,14,11x-11y, 12x-12y) is restricted between its connection (26) to the   chassis (3) and its retaining end.   12. Suspension element according to one of claims 2 to 11,   characterized in that the arm (11,12,13,14,11 x, 1 2x, 1 3x, 1 4x) has a substantially rectangular running section with increasing dimensions from the joint (15,16,17,18) to the wheel support to the retaining end.   13. Suspension element according to one of claims 1 to 12,   characterized by the fact that the profile of the transverse extension (1 1a, 12a, 13a, 14a), in horizontal projection on a vertical plane, is substantially rectilinear under high vertical load (Fz) applied to the joint (15,16 , 17,18) to the wheel support, and slightly curved in the absence of charge.   14. Suspension element according to one of claims 1 to 13,   characterized in that, in horizontal projection on a vertical plane, the arm (11, 1 2.1 3.14.1 1 x, 1 2x, 1 3x, 1 4x) has at least one curvature such as the normal vector with the arm directed towards the center of curvature is oriented to the ground.   15. Suspension element according to one of claims 1 to 14,   characterized by the fact that the flexible pseudo-triangle has a certain flexibility with a longitudinal force while being rigid with respect to a transverse force, when said forces are applied to the joint (15,16,17,18) to the wheel support.   16. Suspension element according to one of claims 1 to 15,   characterized in that, in vertical projection on a horizontal plane, the arm (11,12,13,14,11 x, 12x, 13x, 14x) is curved and in the region of the joint (15,16,17 , 18) at the wheel support it makes a slight angle with the transverse axis.   17. Suspension element according to one of claims 1 to 16,   characterized by the fact that the transverse extension (11a, 12a, 13a, 14a) has, in vertical projection on a horizontal plane, a slight curvature such that the vector normal to the curvature directed towards the center of curvature is   oriented towards the front or rear of the vehicle.   18. Suspension element according to one of claims 1 to 17,   characterized in that it is associated with a telescopic leg (31) of the type Mac Pherson without a spring.   19. Suspension element according to one of claims 1 to 18,   characterized in that the articulation (15,16,17,18) to the wheel support is a ball joint.   20. Suspension element according to one of claims 1 to 19,   characterized in that the arm (11,12,13,14) is in one piece.   21. Suspension element according to one of claims 1 to 19,   characterized by the fact that the arm (11 x-11 y, 12x-12y, 13x-13y, 14x14y) is   in two parts called upstream (11 x, 12x, 13x, 14x) and downstream (11 y, 12y, 13y, 14y).   22. Suspension element according to claim 21, characterized in that the upstream and downstream parts of the arm are connected by a flexible connection   which gives them a certain freedom of movement of the plan-on-plan type.   23. Suspension structure, in particular for a motor vehicle, comprising at least one wheel suspension element, characterized in that said wheel suspension element has the characteristics of   the wheel suspension element according to at least one of claims 1 to   22. 24. Suspension structure according to claim 23, characterized by   the fact that it has at least three arms (11,12,13,14,11x-11y, 12x-   12y, 13x-13y, 14x-14y) linked together at their end, other than that at the right of the joint, where they merge by an inter-arm connection (1 9,199a-199b).   25. Suspension structure according to claim 24 taken   together with one of claims 21 or 22, characterized by   fact that the downstream parts (11y, 12y, 13y, 14y) are linked together and consist of two half-shells (199a, 199b) enclosing the upstream parts   (11x, 12x, 13x, 14x) with interposition of elastomer blocks (201,202).   26. Suspension structure according to one of claims 23 to 25,   characterized in that the arms are connected to the chassis (3) directly by a flexible link (26).   27. Suspension structure according to one of claims 23 to 25,   characterized in that the arms are connected to the chassis (3) by   via a flexible cradle (5) linked to the chassis (3).   28. Suspension structure according to one of claims 23 to 27,   in which the vehicle is four-wheeled, characterized in that it has four arms.   29. Suspension structure according to claims 27 and 28 taken   jointly, characterized in that the connection of the cradle (5) to the chassis (3) is made by four elastic pivot connections, two longitudinal (41) and two transverse (42).   30. Suspension structure according to one of claims 27 to 29,   characterized in that the cradle (5) is rigid in its plane, flexible to warping and more rigid with respect to stresses other than the   warping, such as rolling or pumping.   31. Suspension structure according to one of claims 27 to 30,   characterized in that the cradle (5) has a stiffness at   lower warpage than that of the structure (1, 10).   32. Suspension structure according to one of claims 23 to 31,   characterized by the fact that all or part of the structure is made of a material of which the ratio of the resistance to fatigue to the modulus of elasticity is high, preferably made of composite material, in particular glass-epoxy, consisting   glass fibers embedded in a synthetic resin.