FR2777224A1 - Anti-percussion suspension arm for vehicle front power train - Google Patents

Abstract

The suspension arm (10) consists of a lower triangle (12), mounted transversely and roughly horizontal and with the primary angle (20) linked to the wheel support and the second (22) and third (24) angles fixed to the primary (14) and secondary (16) elastic supports. An intermediate plate (30) is fixed between the lower triangle and the element (18) of the chassis and is linked to the chassis by a third (32) and fourth (34) elastic supports, which act around roughly vertical pivot axes.

Description

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  The invention relates to a device forming a suspension arm. The invention relates more particularly to a device forming a suspension arm, in particular for a front half-axle of a motor vehicle, of the type comprising a triangle

  lower, transverse orientation and substantially horizontal-

  tale, which comprises a first vertex articulated on an associated wheel support of the vehicle, and second and third io vertices which are integral with first and second elastic supports to filter the transverse movements of the lower triangle by articulating the lower triangle with respect to a structural element of the vehicle body around a substantially longitudinal axis of the vehicle Numerous devices are known forming arm

  suspension and meeting the above definition.

  These devices have lower suspension triangles, one vertex facing the outside of the vehicle carrying a ball joint of a wheel support, and the two other vertices facing inward, being linked to the body of the vehicle by means of two elastic supports forming a joint with a longitudinal axis for each of the two vertices, and therefore for the corresponding side of the triangle. The lower suspension triangles transmit forces exerted in three directions, vertical, transverse and longitudinal, to the vehicle body,

  the latter two being substantially horizontal.

  The vertical forces are generally weak, because the articulation of the lower triangles on the vehicle body around a longitudinal axis does not transmit forces. Most of the vertical forces are transmitted by the wheel support to a damped elastic device, for example a

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  combined shock absorber, linked to the wheel support and substantially vertical orientation. Only a small part of the vertical forces is transmitted to the body via the supports of lower triangles, which are radially elastic. The horizontal transverse forces transmitted by the elastic supports are relatively large. The radial elasticity of the elastic supports makes it possible to filter almost all of the transverse forces applied to the wheel, which appear in particular when the vehicle approaches a turn

  and is subjected to transverse acceleration.

  The horizontal longitudinal forces are generally called "percussion" forces because they are impacts, of longitudinal direction, applied to the vehicle wheel and which occur when, for example, the vehicle approaches a retarder or a sidewalk. The filtration of these so-called "percussion" longitudinal shocks depends on the architecture of the

devices used.

  Among these devices, two architectures are generally used, the "isosceles" type architectures and

  "rectangle" type architectures.

  US-A-4,418,938 describes an example

isosceles architecture.

  In this device, the lower triangle is an isosceles triangle, the first main vertex of which carries a ball joint of a wheel support, and the other two vertices of which are linked to the vehicle body by means of two elastic supports. forming a joint with a longitudinal axis. These elastic supports consist of metal cylinders covered with an annular cylindrical block of elastomeric material which makes it possible to filter the forces.

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  that the lower suspension triangle transmits to

the vehicle body.

  This device allows good filtration of the forces in all horizontal or vertical directions, and also has the advantage of a small footprint,

especially transversely.

  However, a percussion force applied to the main vertex of the lower triangle cannot, for geometric reasons, be absorbed by the elastic supports of the

1o two other summits.

  Indeed, the elastic supports not being arranged in the same vertical transverse plane as the main vertex of the lower triangle, any percussion force applied longitudinally towards the rear of the vehicle at the first vertex is transformed by the lower triangle into a transverse force directed outward at the front elastic support, and in a transverse force directed inward at the rear elastic support. The lower triangle thus behaves as if it pivots around a fictitious vertical axis passing through the midpoint between the

two elastic supports.

  To overcome these drawbacks, it has been imagined to employ rectangle-type architectures, in which the lower suspension triangle has substantially the shape of a right triangle, and is articulated by means of elastic supports arranged at the ends of its base on a structural element of the body

of the vehicle.

  In these widely used devices, the elastic supports provide the same functions for filtering horizontal and vertical forces as in the case of the isosceles type device, but they also provide better filtering of forces.

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  longitudinal "percussion". Indeed, a first elastic front support is located in the same transverse vertical plane as the main vertex of the lower triangle, which main vertex is turned towards the outside of the vehicle and carries the articulation ball joint on the wheel support. A second rear elastic support is arranged at the other

  end of the base of the lower right triangle considered.

  The first front elastic support transforms any percussion force into a torque which is applied to the center of the first elastic support, this torque being a consequence of the lever arm which constitutes the height of the right triangle and of the percussion force which is applied to the main vertex. No effort other than a couple can be transmitted

by this elastic support.

  Furthermore, the forces transmitted by the second elastic support are very low, because it has a stiffness

  lower than that of the first elastic support.

  However, such a device is bulky, both transversely and longitudinally, the lengths of the base and of the height of the lower right triangle being essential for reducing the forces transmitted by the

second elastic support.

  To remedy these drawbacks, the invention proposes to reconcile the advantages of an isosceles-type device architecture and the advantages of an architecture

rectangle type.

  To this end, the invention proposes a device of the type described above, characterized in that it comprises an intermediate plate, interposed between the lower triangle and the body structure element, which is linked to the structure element of body by a third elastic support filtering the horizontal movements of the intermediate plate in

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  articulating said intermediate plate relative to the body structure element around a substantially vertical axis of the vehicle, and which is linked to the body structure element by a fourth elastic support filtering movements

  s horizontal of the intermediate plate.

  According to other characteristics of the invention - the lower triangle is an isosceles triangle whose main vertex is said first vertex; the intermediate plate is substantially longitudinal 0o and has a shape matching on the outside that of a spar constituting said body structure element to be linked to it in a central part by the third elastic support which extends vertically in the spar and, in a rear part, by the fourth elastic support which extends vertically in the beam; - The intermediate plate has a horizontal transverse tab which extends over its length and which includes fasteners of the first and second elastic supports linked to the second and third vertices of the triangle, these fasteners being arranged on either side of a plane vertical passing through the first vertex of the triangle and the third elastic support of the intermediate plate; each elastic support comprises a cylindrical frame crossed by a screw for fixing to the intermediate plate, and which is covered with an annular cylindrical block of elastomeric material, of determined stiffness,

  intended to be received in a complementary cylindrical seat

  associated with a vertex of the triangle or the side member; - The stiffness of the elastomeric material of the third elastic support is greater than the stiffness of the elastomeric material of the fourth elastic support;

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  - The intermediate plate has two upper and lower parts which have vertical holes for the passage of the fixing screws for the third and fourth elastic supports, and four parallel transverse ears which form the attachments of the lower triangle in pairs and which have longitudinal passage holes fixing screws of the first and second elastic supports; - The second and third vertices of the triangle have bores of longitudinal orientation which define the cylindrical bearing surfaces which receive the blocks of the first and second elastic supports; - The spar has bores of vertical orientation which define the cylindrical bearing surfaces which receive the blocks of the third and fourth elastic supports; - the intermediate plate, and the spar are made of

stamped, folded and welded sheet metal.

  Other characteristics and advantages of the invention

  will appear on reading the detailed description which will

  follow for the understanding of which reference will be made to the appended drawings in which: - FIG. 1 is a diagram in top view of an architecture of the "rectangle" type previously mentioned, - FIG. 2 is a diagram of the type of that of Figure 1 of an architecture of the "isosceles" type previously mentioned, - Figure 3 is a diagram of the type of that of Figure 1 of an architecture according to the invention for a suspension arm of a half-train front of a motor vehicle, - Figure 4 is an exploded perspective view of an embodiment according to the invention, and - Figure 5 is a view according to Figure 4 of the device

shown assembled.

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  In the following description, the figures will be

  described in a nonlimiting manner with reference to a

  front axle architecture of a motor vehicle.

  In FIGS. 1 to 3, identical reference numerals designate identical or similar subsets. FIGS. 1 and 2 show a schematic illustration of the devices forming the suspension arms

  known from the prior art.

  In a known manner, a device 10 of “rectangle” type architecture comprises a lower suspension triangle 12 articulated by means of a first front elastic support 14 and a second rear elastic support 16 on a

  body structure element 18 of the vehicle.

  The lower triangle 12 is of the "rectangle" type, that is to say that it has substantially, in top view, the shape of a right triangle of which an external main vertex 20, or first vertex, carries an articulation (not shown) of a wheel pivot of the vehicle (not shown), for example a ball joint, and including a second apex 22 and a third apex 24, situated at the ends of a base 26 of the right triangle, of longitudinal orientation L, are connected to the elastic supports 14 and 16 of articulation on the element of

  body structure 18 of the vehicle.

  In this configuration, a height 28 of the triangle

  rectangle connects the first vertex 20 to the second vertex 22.

  The height 28, of transverse orientation, of the lower right triangle 12 is arranged towards the front of the vehicle, and consequently the first elastic support 14, connecting the second apex 22 to the element 18 of the body structure of the vehicle, is him too

arranged towards the front of the vehicle.

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  The elastic supports 14 and 16 play a double role of articulation and spring. They allow in fact an articulation in rotation around the longitudinal direction of axis L and, as they are elastic radially, they also play the role of deformable springs in transverse vertical planes T1 and T2 of which we see the trace in the plane

horizontal of figure 1.

  In this way, the elastic supports 14 and 16 are capable of filtering any shock of transverse direction

  o0 included in the T1 and T2 transverse plans.

  Thus, when the vehicle is in motion and encounters, for example, an obstacle such as a retarder or a sidewalk, the first peak 20 is subjected to a percussion shock or to a substantially longitudinal directional force Cp, directed towards the rear of the vehicle. The height 28 of the triangle 12 plays the role of a lever arm which exerts on the second front apex 22, and consequently on the elastic support 14, a couple Mp of vertical axis tending to make the triangle pivot

  lower 12 around the second vertex 22 in an anti-direction

timetable viewed from above.

  In the majority of devices forming suspension arms of the rectangle type, the stiffness of the elastic support which is arranged towards the front of the vehicle, in this case the first elastic support 14, is greater than the stiffness of the elastic support arranged towards the rear of the vehicle,

  namely the second elastic support 16.

  In the suspension arm architecture described with reference to FIG. 1, the longitudinal impact shock Cp is reflected, at the level of the first elastic support 14, by the couple of vertical axis transmitted Mp and, at the level of the elastic support 16 , by a horizontal transverse force Rp turned towards the interior of the vehicle. The transverse force Rp is transmitted

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  to the elastic support 16 via the base 26 of the

  lower triangle rectangle 12 which also forms a lever arm.

  The stiffness of the first elastic support 14 being greater than that of the second elastic support 16, the second elastic support 16 is practically the only one to be compressed during the application of the percussion shock Cp, the lower triangle 12 pivoting substantially around the center Ip of the connection produced by the first elastic support 14 between the second apex 22 and the body structure element 18

io of the vehicle.

  This device is advantageous, since most of the deformations of the device are controlled and located around a single area, corresponding to the second support.

elastic 16.

  t5 The maximum permissible opening angle of the wheels of the vehicle, corresponding to a closed angle towards the rear between two planes parallel to the edges of the wheels of the vehicle, is known and it makes it possible to optimize the values of the toe-in of the wheels, corresponding at an angle closed forwards between two planes parallel to the edges of the vehicle wheels, so that the opening angle of the wheels remains in all circumstances within admissible values for optimizing the guidance of the

train before.

  On the other hand, the transformation of the longitudinal percussion shock Cp, respectively into a torque Mp applied to the first elastic support 14 and into a transverse force Rp applied to the second elastic support 16, requires a height 28 and a base 26 of the lower right triangle 12 of important dimensions. The device 10 is therefore strongly

  bulky longitudinally and transversely.

  In the schematic view of FIG. 2, the device 10 has an architecture of the isosceles type in which the

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  lower triangle 12 is now an isosceles triangle with a main apex, or first apex 20, and a second and third apex 22 and 24 articulated longitudinally by means of elastic supports 14 and 16 on the body structure element 18 of the vehicle . In this configuration, the two branches or sides of the same length 40 of the lower triangle 12 connect the first vertex 20, which carries the articulation of the vehicle wheel support (not shown), to the second and third vertices io 22 and 24. The elastic supports 14, 16 provide the same

  longitudinal articulation and transverse filtration functions

  dirty than those previously described with reference to Figure 1, but they both have a transverse stiffness in

  plans T1 and T2 substantially equal.

  When a longitudinal percussion shock Cp, directed towards the rear of the vehicle, is applied to the first vertex 20 of the lower triangle 12, a torque is exerted Mp at the point Ip of intersection of the theoretical height 28 of the lower triangle 12 and base 26 which constitutes an instant center

  of rotation of the lower triangle 12 about a vertical axis.

  As the lower triangle 12 is not articulated at point lp, the transmitted torque Mp is transformed into two efforts

  opposite transverse Rp1 and Rp2 which apply respectively

  vement to the first elastic support 14, towards the outside of the vehicle, and to the second elastic support 16 towards the interior of the vehicle. On either side of the instantaneous center of rotation lp, the half-lengths of the base 26 act as a lever arm for the transformation of the torque Mp applied at the point Ip into transverse forces Rp1 and Rp2. Also, in this suspension arm architecture, the lower suspension triangle 12 pivots substantially.

  around a vertical axis passing through point Ip.

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  This construction is advantageous insofar as it allows the use of a lower triangle of suspension of reduced dimensions, but it does not allow a guidance of the wheel linked to the first vertex 20 as precise as in the previous configuration, the rotation of the lower triangle 12 being defined around the instantaneous center of rotation Ip whose

position may vary.

  The schematic top view of Figure 3 illustrates the operation of a suspension arm produced in accordance

to the invention.

  In a manner analogous to that described with reference to FIG. 2, a preferred embodiment of the invention comprises an isosceles lower triangle 12 articulated on the element

  18 of the vehicle body structure.

  A rigid intermediate plate 30, of substantially longitudinal direction, is interposed between the base 26 of the

  lower triangle 12 and the body structure element 18.

  In a similar manner to the embodiment in FIG. 2, the lower triangle 12 is linked, no longer directly to the body structure element of the vehicle but to the intermediate plate, by the first elastic front support 14 and by the second rear elastic support 16, which both allow articulation around the longitudinal axis L and filtration of the transverse forces in the vertical planes

transverse T1 and T2.

  The intermediate plate 30 is linked to the body structure element 18 of the vehicle via a third front elastic support 32 and a fourth rear elastic support 34 allowing rotations of vertical axes V2 and V3 respectively. that strainings of efforts

  transverse in transverse vertical planes T3 and T4.

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  In a manner analogous to that described with reference to FIG. 2, a percussion shock Cp is transformed by the isosceles triangle 12 into a vertical couple Mp1 applied to the point Ip1 of intersection between the height 28 of the isosceles triangle and its base 26 The torque Mp, is transformed at the second and third vertices 22 and 24 respectively into transverse forces Rpl, directed towards the outside of the vehicle, and Rp2, directed towards the inside of the vehicle, these transverse forces Rp1

  and Rp2 being transmitted to the intermediate plate 30.

  io In a preferred embodiment of the invention, the first vertex 20, the point of application Ip1 of the transmitted torque Mp1 and the center of the third elastic support 32, of vertical axis of articulation V2 are aligned in the plane

vertical transverse T3.

  s5 The transverse forces Rp1 and Rp2 applying to the first and second elastic supports 14 and 16 are transmitted to the third elastic support 32 in the form of a

couple Mp2 of vertical axis V2.

  The device 10 of FIG. 3 behaves in a similar manner to the device described with reference to FIG. 1, the fourth elastic support 34 transmitting to the body structure element 18 of the vehicle a transverse force Rp3

  directed towards the interior of the vehicle.

  In fact, the third elastic support 32 is, in a manner analogous to that described with reference to FIG. 1, of a transverse stiffness greater than that of the fourth elastic support 34, the third elastic support 32 thus being able to behave as a pivot link with axis V2, while the fourth elastic support 34 behaves like a spring capable of filtering out any effort included

  in the transverse vertical plane T4.

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  In the exploded perspective view of Figure 4, there is shown an embodiment of the invention. We recognize in Figure 4 the elements described above forming arms

suspension.

  The device 10 includes the lower suspension triangle 12 intended to be fixed at its top 20 to a support (not shown) of the vehicle wheel by means of a vertical bore 21, and to be connected by its tops 22 and 24 to the intermediate plate 30, itself intended to be connected to a beam 36 forming part of

  the body structure element 18 of the vehicle.

  The lower triangle 12 comprises a substantially horizontal lower plate 38 which has the shape of an isosceles triangle whose first vertex 20, or main vertex, is Is transversely turned outwards. The lower triangle 12 also comprises two transverse vertical wings 40 intended on the one hand to stiffen the lower triangle 12 and on the other hand to provide surfaces receiving bores 42 of longitudinal orientation intended to receive the first and second elastic supports 14 and 16. Sectional views in a longitudinal vertical plane, the wings 40 have a U-shaped profile turned substantially downwards intended for

  stiffen the lower triangle 12.

  Advantageously, the lower triangle 12 is made of stamped and welded sheet metal, which reduces costs

  mass production and the weight of the triangle.

  The first and second elastic supports 14 and 16, commonly called "silentblocs" comprise a cylindrical frame 44, produced for example in the form of a cylinder of metallic material, which is covered with a cylindrical block 46 of elastomeric material, this cylindrical block

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  being received in the cylindrical bores 42 of the wings 40 of the

lower triangle 12.

  The first and second elastic supports 14 and 16 are force-fitted into the bores 42, the elastomeric material of the cylindrical body 42 being compressed radially when the first and second elastic supports 14 and 16 are introduced into the cylindrical bores 42. The cylindrical armatures 44 of the elastic supports 14 and 16 are intended to be fixed by io fasteners 48 to the intermediate plate 30, by means of fixing screws 50, washers 52 and nuts 54. For this purpose, the fasteners 48 have two pairs of parallel transverse legs 56 each pierced with a longitudinal hole 58 allowing the passage of a screw 50. The clips 48 are fixed to the intermediate plate 30 according to a method of

  realization described later.

  The intermediate plate 30 is composed of an upper part 30A and a lower part 30B which are joined by welding during assembly. When combined, the parts 30A and 30B have a shape of a coated U whose concavity is turned transversely inward so as to cooperate with the outer surface of the beam 36 and to provide satisfactory support. To this end, the upper part A has an L-shaped section, the largest branch of which is turned transversely inwards, while the lower part 30B is a substantially horizontal plate. The upper part 30A comprises, in an intermediate part, a recess 60 forming a clearance for the passage of a transmission shaft (not shown) of the vehicle. The upper part 30A comprises, in an upper part 62 and towards the interior of the vehicle, holes 64 for attachment to the beam 36. In a similar manner, the

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  lower part 30B comprises, in a part 66 facing the interior of the vehicle, fixing holes 68 aligned axially vertically with the holes 64 of the part

  upper 30A of the intermediate plate 30.

  The upper part 30A has over its entire length a lower transverse horizontal tab facing outwards 70, intended to bear on the lower part 30B to allow assembly of the parts 30A

and 30B, for example by welding.

  io The transverse tab 70 has two recesses 72 in the shape of a U, of concavity turned towards the outside, arranged vertically in line with two similar recesses 74 of the lower plate 30B so as to allow the passage of the wings 40 of the lower triangle 12 for large deflections

suspension.

  The beam 36 is complementary to the U-shaped internal shape defined by the assembly of the upper parts 30A and 30B of the intermediate plate 30, and its cross section is substantially rectangular. It has in a central part 37 a bore 76 of vertical orientation with a previously defined axis V2 which is aligned in the transverse vertical plane T3 with the main vertex 20 of the lower isosceles triangle 12. The vertical bore 76 is intended to receive the third elastic support 32 for fixing the intermediate plate 30 to the spar 36. In a rear portion 39, the spar 36 has a bore 78 of vertical orientation with axis V3 intended similarly to receive the fourth elastic support 34 of attachment to

intermediate plate 30.

  The third and fourth elastic supports 32 and 34 comprise, in a manner analogous to the elastic supports 14 and 16, cylindrical reinforcements 80 covered with blocks

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  cylindrical rings of elastomeric material 84 which are intended to be mounted by radial compression in the vertical bores 76 and 78 during the assembly of the device 10. The assembly of the elastic supports 32 and 34 is ensured by screws 88, washers 90 and nuts 92, of axis V2 and V3. The assembly of the different elements is shown in FIG. 5. The assembly of the fasteners 48 allowing the fixing in clevis of the lower triangle 12 on the intermediate plate 30 is particularly noticeable, these fasteners 48 being fixed directly on the intermediate plate 30 by of

weld beads 86.

  This device is particularly advantageous because, the stiffness of the elastic support 32 being greater than the stiffness of the elastic support 34, the intermediate plate 30 is capable of pivoting around the axis V2 when a longitudinal shock is applied to the end 20 of the lower triangle 12, thus ensuring good filtration of vibrations

  caused by unevenness in the road.

  Indeed, the evolution of tire mounting on current vehicles, which confirms a trend towards a reduction in the height of tire belts, and thereby a decrease in the capacity of tires to filter longitudinal shocks, finds a consideration in the use of such a device, which also has the advantage of being little more bulky than an "isosceles" device, while retaining the performance of a device of the conventional "rectangle" type.

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Claims (10)

  1. Device (10) forming a suspension arm, in particular for a front half-axle of a motor vehicle, of the type comprising a lower triangle (12), of transverse and substantially horizontal orientation, which comprises a first vertex (20) articulated on a wheel support associated with the vehicle, and second (22) and third (24) vertices which are integral with first (14) and second (16) elastic supports to filter the transverse movements of the lower triangle (12) by articulating the lower triangle (12) relative to an element (18) of the vehicle body structure around a substantially longitudinal axis (L) of the vehicle, characterized in that it comprises an intermediate plate (30) i5, interposed between the lower triangle (12) and the body structure element (18), which is linked to the body structure element (18) by a third elastic support (32) filtering the horizontal movements of the intermediate plate (30 ) by articulating said intermediate plate (30) relative to the body structure element (18) about a substantially vertical axis (V1) of the vehicle, and which is linked to the structure structure element (18) body by a fourth elastic support (34) filtering the horizontal movements of the intermediate plate (30).   2. Device according to claim 1, characterized in that the lower triangle (12) is an isosceles triangle, the   main vertex is said first vertex (20).   3. Device according to any one of the claims   previous, characterized in that the intermediate plate (30) is substantially longitudinal and has a shape matching externally that of a spar (36) constituting said body structure element (18) to be linked to it, in B332.DOC   a central part (37) by the third elastic support (32) which extends vertically in the beam (36) and, in a rear part (39), by the fourth elastic support (34) which   extends vertically in the beam (36).   4. Device according to claim 3, characterized in that the intermediate plate (30) comprises a horizontal transverse lug (70) which extends over its length and which comprises attachments (48) of the first (14) and second (16) ) elastic supports linked to the second (22) and third (24) io vertices of the triangle (12), these fasteners (48) being arranged on either side of a vertical plane (T3) passing through the first vertex (20 ) of the triangle (12) and the third elastic support   (32) of the intermediate plate (30).   5. Device according to any one of the claims   3 or 4, characterized in that each elastic support (14, 16, 32, 34) comprises a cylindrical frame (44, 80), crossed by a fixing screw (50, 88) to the intermediate plate (30), and which is covered with an annular cylindrical block (46, 84) of elastomeric material, of determined stiffness, intended to be received in a complementary cylindrical bearing associated with a vertex of the triangle (12) or of the side member (36).   6. Device according to claim 5, characterized in that the stiffness of the elastomeric material of the third elastic support (32) is greater than the stiffness of the material   elastomer of the fourth elastic support (34).   7. Device according to one of claims 5 or 6,   characterized in that the intermediate plate (30) has two upper (30A) and lower (30B) parts which have vertical holes (64, 68) for the passage of the screws (88) for fixing the third (32) and fourth (34) ) elastic supports, and four parallel transverse ears (56) which B332.DOC,   form in pairs the attachments (48) of the lower triangle (12) and which comprise longitudinal holes (58) for the passage of the screws (50) for fixing the first (14) and second (16) elastic supports.   8. Device according to any one of claims   to 7, characterized in that the second (22) and third (24) vertices of the triangle (12) have bores (42) of longitudinal orientation which define the cylindrical bearings which receive the blocks (46) of the first (14) and   to second (16) elastic supports.   9. Device according to any one of claims   àa8, characterized in that the spar (36) has bores (76, 78) of vertical orientation which define the cylindrical bearing surfaces which receive the blocks (84) of the third (32) and fourth (34) elastic supports.   10. Device according to any one of the claims   previous, characterized in that the intermediate plate (30), and the side member (36) are made of pressed sheet metal, folded and welded.