EP2394881B1 - Tilting bed base and secondary suspension comprising same - Google Patents

Description

The subject of the present invention is a rocking bed base and a secondary suspension comprising it, according to the preamble of independent claim 1, which is generally known in the art. Bed springs are already known which are used in secondary suspensions of railway vehicles such as wagons, railcars or locomotives to ensure the suspension of the vehicle body with respect to a chassis on which axle-wheel assemblies are mounted by the vehicle. intermediate of a primary suspension.

For a bogie comprising for example two axles and four wheels (or with three axles for example), it is known to have two or four subsets of secondary suspension, each of which has a single bed base or a pair of bed bases to obtain a horizontal softening, and one or more metal springs arranged (s) in series with the bed frame or between the bed bases and whose function is to obtain the desired vertical flexibility for the secondary suspension.

There are several types of bed bases for such applications, but their performance is limited.

The patent application EP 155 209 A1 relates to an elastic bearing device which consists of a laminated elastomeric ring connected in series with a helical spring to form a secondary suspension of railway bogie. During horizontal stresses, the travel amplitudes of the elastomer ring are limited by a frustoconical central abutment. This device has only poor tilting properties and therefore poor decoupling of the horizontal stiffness as a function of the direction of horizontal stress.

The patent FR 1 540 148 A describes a subassembly comprising two helical springs whose upper end is connected to the body of the vehicle and whose lower end is connected to a support pivoting freely around a hinge (or a knife assembly), lateral buffers being provided to serve as an elastic stop for tilting the pivoting support. In addition to failover, this device has integration and maintenance issues.

The patent BE 700 027 A describes a vehicle body support member associating a spring with a single hemispherical ball. Implementation a ball joint does not differentiate the characteristics along the directions in the horizontal plane.

The patent application FR 2 801 268 A1 combines in series a helical spring and two ball joints laminated elastomer or not, mounted head to tail. Such a device imposes in practice a large footprint in the direction of the height to ensure the required performance. In addition, the use of ball joints does not make it possible to differentiate the characteristics according to the horizontal directions.

The patent application FR 2 354 229 A1 proposes to overcome the metal spring or springs by associating in series a frustoconical spring having a high axial flexibility to ensure vertical deflections of the suspension, and a low horizontal flexibility to provide a vertical guide function, and a cylindrical spring having a high vertical stiffness to support the weight of the body and high horizontal flexibility to accommodate the relative horizontal movements of the body and the bogie. This device also does not differentiate the features in the horizontal directions.

In addition, the laminated frustoconical spring can be problematic to ensure high vertical deflections and to ensure a vertical stiffness independent of the load level (the characteristic axial force / axial displacement tends to be nonlinear for this kind of part), this to what is added the problem of creep and thus of rigging to ensure the height of the floor relative to the platform over time.

The inventors of this patent consider that it would be desirable to make it possible to differentiate the lateral decoupling performance while limiting the vertical space requirement.

To this end, the present invention proposes a tilting bed base that can be integrated with a suspension subassembly, in particular a secondary vehicle suspension, which has a parallel-type architecture in which the functions are distributed between a central pivot and at least a pair of elastic studs mounted on either side of the central pivot.

• un pivot central de guidage vertical comportant un élément élastique cylindrique ou tronconique monté entre une pièce interne et une pièce externe, la pièce interne étant solidaire de l'un desdits premier et deuxième supports et la pièce externe étant solidaire de l'autre desdits premier et deuxième supports, ledit pivot présentant une raideur horizontale supérieure à sa raideur verticale,
• et disposés symétriquement de part et d'autre du pivot central, au moins une paire de plots élastiques dont les centres sont alignés sur un premier axe horizontal et qui sont montés entre le premier et le deuxième support et présentent une raideur verticale ou de compression élevée par rapport à leur raideur horizontale ou de cisaillement.

The present invention thus relates to a tilting bed base for a suspension of a vehicle, in particular a rail vehicle such as a wagon, a railcar or a locomotive, to ensure, on the one hand, a recovery of a vertical load generated by the body of the vehicle, and secondly, to accompany with tilting horizontal relative movements, the bed base comprising a first support for mounting on a vehicle element and a second support vertically spaced from the first support, to receive an end of a suspension spring, characterized in that it comprises in parallel:

• a central vertical guide pivot comprising a cylindrical or frustoconical elastic element mounted between an inner part and an outer part, the inner part being integral with one of said first and second supports and the outer part being integral with the other of said first and second second supports, said pivot having a horizontal stiffness greater than its vertical stiffness,
• and arranged symmetrically on either side of the central pivot, at least one pair of elastic studs whose centers are aligned on a first horizontal axis and which are mounted between the first and the second support and have a vertical stiffness or high compression compared to their horizontal stiffness or shear.

The first horizontal axis is a preferred tilting axis of the bed, for which the pivot and the resilient pads are biased mainly angularly.

The presence of one or more pairs of studs disposed on either side of the central pivot makes it possible to increase the tilt stiffness around a second horizontal axis perpendicular to said first axis, because at the previous tilting stiffness s' adds the one induced by the compression of the elastic studs.

This parallel architecture has the significant advantage of limiting the vertical space, and thus avoid a major drawback of known devices which is to limit the performance of the device due to the constraints of vertical space. Indeed, the constraints of vertical space often require undersizing parts that can not therefore fully meet the specifications, which affects among other things the comfort of passengers.

The geometry of the central pivot is preferably frustoconical in order to reduce its conical stiffness, and thus reduce its stiffness in tilting (which is not differentiated by the central pivot.

Said cylindrical or frustoconical elastic element may be at least partly made of elastomer, in particular of laminated elastomer.

Said elastic pads may be metal cushions, or be at least partly elastomeric, especially laminated elastomer.

The ratio between the horizontal stiffnesses of the central pivot and of all the blocks may be greater than or equal to 1 and may be for example between 5 and 50, and preferably at least 10.

The ratio between the vertical stiffness K _PA of all the studs and the central pivot _AP K may be greater than or equal to 1 and may for example be between 5 and 50, and preferably at least equal to 10.

The ratio between the horizontal stiffness and the vertical stiffness of the central pivot may be in particular between 1 and 5 and for example between 2 and 5, and / or the ratio between the vertical stiffness and the horizontal stiffness of a stud may be greater or equal to 10 and can be for example between 50 and 500.

The bed base can be characterized in that the elastic or frustoconical element of the central pivot has at least one pair of cells disposed symmetrically on either side of the central pivot and whose median planes are aligned on a second horizontal axis perpendicular to said first axis.

The bed base can be characterized in that at least one central pivot has an abutment integral with its inner part and in that this abutment has a flange spaced apart by a functional clearance j of the outer part of said central pivot to limit the displacement in tension of the elastic element of said central pivot.

The invention also relates to a suspension subassembly, characterized in that it comprises at least one rocking bed as defined above, the second support receives an end of one or more suspension springs.

The subassembly may be characterized in that it comprises two so-called rocking bases mounted head to tail, or suspension springs being arranged between the second supports of the two bed bases.

The subassembly may be characterized in that the first bed base comprises a first stop and in that the second bed base comprises a stop device comprising a strap secured by strap supports integral with the first stop and passing around a support. semi-cylindrical formed in an abutment support integral with the second frame.

• les figures 1a et 1b sont des schémas représentant une rame respectivement en vue latérale et de dessus,
• la figure 2a illustre en perspective une suspension secondaire intégrant quatre sous-ensembles dont chacun associe au moins un ressort métallique et deux sommiers basculants, qui selon l'invention, sont aptes à procurer un découplage différencié, la figure 2b illustrant en vue de dessus les axes pour définir une orientation des sommiers basculants, les figures 2c et 2d illustrant un sous-ensemble de suspension secondaire (2c) avec intégration de fonctions connexes (2d),

• la figure 3 est un schéma de principe d'un sommier basculant selon l'invention,
• les figures 4a à 4d représentent respectivement en vue de face (4a), en coupe verticale AA (4b), en coupe horizontale BB (4c), et en perspective isométrique (4d), un mode de réalisation d'un sommier basculant selon l'invention,
• les figures 5 et 6 représentent en coupe AA deux modes d'assemblage, respectivement en intégrant l'interface avec le caisson et des supports des ressorts métalliques au niveau du pivot central et en intégrant une butée haute au pivot central (avec en encadré un agrandissement illustrant le jeu fonctionnel j de cette butée).
• et les figures 7a à 7d illustrent des variantes de mise en oeuvre des plots, respectivement avec une paire de plots cylindriques (7b), avec deux (ou plusieurs) paires de plots (7c) et avec une paire de plots en forme de secteurs (7d)

Other features and advantages of the invention will appear better on reading the description below, in conjunction with the drawings in which:

• the Figures 1a and 1b are diagrams representing a train respectively in lateral view and from above,
• the figure 2a illustrates in perspective a secondary suspension incorporating four subassemblies, each of which associates at least one metal spring and two rocking bases, which according to the invention are capable of providing a differentiated decoupling, the figure 2b illustrating in plan view the axes to define a tilting bed bases, the Figures 2c and 2d illustrating a sub-assembly of secondary suspension (2c) with integration of related functions (2d),

• the figure 3 is a block diagram of a rocking bed base according to the invention,
• the Figures 4a to 4d respectively represent in front view (4a), in vertical section AA (4b), in horizontal section BB (4c), and in isometric perspective (4d), an embodiment of a rocking bed base according to the invention,
• the figures 5 and 6 represent in section AA two modes of assembly, respectively by integrating the interface with the box and supports of the metal springs at the central pivot and by integrating an upper stopper with the central pivot (with in box an enlargement illustrating the functional play j of this stop).
• and the Figures 7a to 7d illustrate alternative embodiments of the pads, respectively with a pair of cylindrical studs (7b), with two (or more) pairs of studs (7c) and with a pair of sector-shaped studs (7d)

The Figures 1a and 1b represent a vehicle having a body 1, and two bogies 2 each having two axles 21 and four wheels 22, the axles 21 and the wheels 22 being suspended from the frame 23 of the bogie 2 by a primary suspension 24 comprising four subassemblies 25 .

The secondary suspension 3 of which each bogie 2 is provided comprises four subassemblies 31 distributed in a quadrilateral.

The figure 2a shows four subassemblies 31 each having two rocking bases 32 and 33 disposed between one or more metal springs 4 suspension. The upper rocking bases 32 are secured to an interface piece 11 with the body 1, and the lower rocking bases 33 are integral with an interface piece 26 with the bogie 2, on which part are also mounted the sub-bases. primary suspension assemblies. H _susp designates the height of the secondary suspension incorporating the bulk of the bed frames 32 and 33.

The x direction is the longitudinal direction of the vehicle, which is that of its movement in a straight line.

The direction is the transverse direction of the vehicle, and the direction z, orthogonal to the two previous ones, is the vertical direction.

The direction u (see also figure 2b ) designates the preferred tilting axis of the rocking bases 32 and 33, and the direction v, the horizontal direction perpendicular to the directions u and z. u is the longitudinal direction of the bedsteads, and v is the transverse direction.

According to the invention, the rocking bed bases have the function of providing a differentiated decoupling, with in particular a privileged tilting around the u-axis and a limited tilting around the v-axis of the mattresses, whereas the metal springs typically provide the obtaining the desired vertical stiffness for the secondary suspension. The differentiated decoupling is thus obtained thanks to tilting bed bases that have different stiffness characteristics according to the horizontal directions.

O1 and O2 are the geometric centers of all upper bed bases 32 and 33, each bed frame 32 having a center A1, B1, C1, D1, and each bed base 33, a center A2, B2, C2, D2. O1 is the center of quadrilateral A1, B1, C1, D1 and O2 is the center of quadrilateral A2, B2, C2, D2.

K _x , K _y and K _θz respectively denote the longitudinal stiffness of the suspension (x axis), its transverse stiffness (y axis) and its yaw stiffness (body / bogie rotation around the z axis).

The first horizontal axis u is a preferred tilting axis of the subassembly 31.

The second horizontal axis v is a limited tilt axis (higher rigidity).

L, α are respectively the distance and the angle of implantation of the sub-sets of secondary suspension which are defined by the customer.

β is the orientation angle of the local coordinate system {u, v, z} with respect to the global coordinate system {x, y, z}.

The orientation of the system is chosen based on the preferred softening direction requested by the customer.

When β = 0, we obtain a maximum relaxation of the suspension along the transverse axis (y).

When β = α, we obtain a maximum relaxation in yaw (θz) of the suspension.

When β = 90 °, we obtain a maximum relaxation of the suspension along the longitudinal axis (x).

The Figures 2c and 2d show a secondary suspension subassembly which comprises a pair of upper and lower tilting basins 33 and one or more suspension metal springs 4 mounted between the bedsteads 32 and 33, with an upper surface 42 and lower 43 assembly of the springs 4. A system of high and low stops (46, 47, 48) may be located in the center of the spring or springs 4.

• en partie centrale, un système déformable 50 à raideur prédominante dans le sens horizontal dénommé pivot qui permet :
  • de transmettre des sollicitations longitudinales et transversales (guidage),
  • d'assurer un guidage satisfaisant suivant l'axe vertical,
  • le pivot pouvant être de différentes technologies : type élastomérique (lamifié parallèlement aux armatures ou non lamifié), alvéolé ou non, ou de type à coussins métalliques.
• en partie périphérique, un ensemble de supports 60 (dénommés plots) à raideur prédominante dans le sens vertical qui permet :
  • de reprendre la charge verticale de la caisse du train,
  • de favoriser le basculement dans une direction u grâce à la disposition particulière retenue à savoir par exemple, une paire de plots 60 alignés suivant l'axe u,
  • à l'inverse, d'accroître la raideur en basculement suivant la direction perpendiculaire à la précédente,
  • et limiter l'encombrement vertical du système, tout en libérant de l'espace entre les sommiers,

To meet the primary function of the subassembly (differentiated lateral decoupling) the rocking bed base architecture is based on the separation of the product into different functions ( figure 3 ):

• in the central part, a deformable system 50 with stiffness predominant in the horizontal direction called pivot which allows:
  • to transmit longitudinal and transverse stresses (guiding),
  • to ensure satisfactory guidance along the vertical axis,
  • the pivot can be of different technologies: elastomeric type (laminated parallel to the reinforcements or not laminated), honeycombed or not, or type of metal cushions.
• in the peripheral part, a set of supports 60 (called studs) with stiffness predominant in the vertical direction which allows:
  • to take up the vertical load of the body of the train,
  • to favor the tilting in a direction u thanks to the particular arrangement chosen namely, for example, a pair of studs 60 aligned along the axis u,
  • conversely, to increase the tilt stiffness in the direction perpendicular to the previous one,
  • and limit the vertical congestion of the system, while freeing space between the bedsteads,

The pads 60 may be of different technologies: laminated elastomeric type (parallel to the reinforcements) or non-laminated, or metal cushion type to choose.

The pivot 50 and the pads 60 are arranged in parallel, and they act in parallel both in the vertical direction and in the horizontal directions.

In a horizontal direction, the stiffnesses are added and is therefore the sum of the radial stiffness K _RP of the pivot 50 and the shear stiffness K _CP of all the pads 60. As the radial stiffness K _RP of the pivot 50 is much greater than the K _CP shear stiffness of the set of pads 60, it is the pivot 50 which takes up most of the horizontal force.

In the vertical direction, the stiffnesses are also added, and the stiffness in this direction is the sum of the axial stiffness K _AP of the pivot 50 and the axial stiffness K ' _AP of the pads 60 taken as a whole (namely the sum stiffness of the pads), and as the axial stiffness K _AP of the pivot 50 is very lower than the Axial stiffness K ' _AP of the pads 60, it is the pads 60 which take up most of the vertical force.

This parallel architecture makes it possible to significantly reduce vertical congestion, and consequently to meet the requirements of a specification in a space of reduced height.

The use of pairs of pads 60 in parallel with the central pivot 50 makes it possible to take up the vertical force (according to z) and to control the conical tilting θv about the axis v (limited tilting axis) while keeping a constant tilting flexibility in the other directions, including tilting about the u-axis, for which the flexibility tilt is defined primarily by the cylindrical or conical layer of laminated elastomer or not the central pivot.

To the figure 3 , the pads 60 are represented as being cylindrical of revolution, but other shapes (polygon, etc ...) can be implemented.

The pivot 50 is shown as having a frustoconical elastic element 53, with a half opening angle δ. It could also be cylindrical of revolution. The value of the opening angle δ can also be between 0 ° and 60 ° and more particularly between 8 ° and 30 °. The pivot comprises an internal frame 51 cylindrical or frustoconical, an outer frame 52 cylindrical or frustoconical and an elastic member 53, for example laminated elastomer or not.

The ratio between the horizontal stiffness of the central pivot 50 (radial stiffness K _RP ) and the pads (stiffness in shear K _CP ) can be between 5 and 50, and preferably at least equal to 10. A typical value of the order of 20 can be advocated.

The value of this ratio is defined essentially by the geometry (cylindrical shape of the studs, with opposite reinforcement, cylindrical or frustoconical shape of the pivot with an internal reinforcement and an external reinforcement).

The ratio between the axial (vertical) stiffnesses of all the pads 60 (K ' _AP ) and the central pivot 50 (K _AP ) can be between 5 and 50. This ratio is preferably at least equal to 10. typical value of the order of 20 may be recommended.

The vertical stiffness of the pads 60 is chosen by acting on their geometry, their characteristics (materials) as well as on the manufacturing process (elastomer laminate or not, metal cushions).

• Le rapport entre la raideur horizontale K_RP et la raideur verticale (K_Z pivot) du pivot central est supérieur à 1 et peut être par exemple, compris entre 2 et 5 ; la valeur de ce rapport s'explique par le fait que la fonction principale du pivot est de limiter les déplacements horizontaux.
• et/ou le rapport entre la raideur verticale (K_Z plots) et la raideur horizontale K_CP des plots est au moins égal à 10 et peut être par exemple compris entre 50 et 500 ; la valeur élevée de ce dernier rapport s'explique par le fait que la raideur horizontale K_CP est une raideur en cisaillement et que la fonction principale des plots est de reprendre la charge verticale. En particulier, l'utilisation de coussins métalliques ou de plots élastomériques lamifiés permet de répondre à ce besoin.

In practice :

• The ratio between the horizontal stiffness K _RP and the vertical stiffness (K _Z pivot) of the central pivot is greater than 1 and can be for example between 2 and 5; the value of this ratio is explained by the fact that the main function of the pivot is to limit the horizontal displacements.
• and / or the ratio between the vertical stiffness (K _Z pads) and the horizontal stiffness K _CP of the pads is at least 10 and may be for example between 50 and 500; the high value of this latter ratio is explained by the fact that the horizontal stiffness K _CP is a stiffness in shear and that the main function of the pads is to resume the vertical load. In particular, the use of metal cushions or laminated elastomeric pads makes it possible to meet this need.

The value of the two aforementioned reports, intrinsic to each component taken independently, is not critical for the decoupling performance of the product.

The Figures 4a to 4d represent a preferred embodiment of a suspension subassembly comprising two rocking bed bases according to the invention, which are mounted head to tail.

An upper rocking bed 32 includes a central pivot 50 whose inner armature 51 is integral with a plate 71 which constitutes the interface piece 11 with the body 1 and whose outer armature 52 is integral with a plate 70 of which the lower face is the bearing face 42 of the springs 4 (here two in number). The opening of the cone of the elastic element 53 is directed upwards, which favors the proximity or the coincidence of the natural centers of tilting of the pivot and the studs. Disregarding the tilt stiffness induced by the compression component of the pads 60, that is to say in practice by considering the u axis, this particular arrangement of these natural centers makes it possible to obtain a lower resistance to tilting. along the axis u.

The cylindrical pads 60 each comprise two plates 62 and 63, and a cushion 61 preferably a metal cushion, the whole being arranged between the plates 70 and 71. The centering of the cushions 61 is provided by pins 56. They are mounted to be diametrically opposed, with respect to the axis ZZ, and aligned in the direction u. On the inner frame 51 is also mounted the low elastic stop 46 and its support 46b through the stud 57 by sandwiching the assembly (50, 60, 61, 62, 63, 70, 71). The plates 62 and 63 are chosen from a material of sufficient hardness to withstand the contact pressure of the cushions 61.

The lower bed base 33, which is mounted head to tail with respect to the frame 32, has a central block 50 whose inner frame 51 is integral with a plate 71, but which constitutes the interface piece 26 with the bogie 2, and whose outer armature 52 is integral with a plate 70 whose upper face is the bearing surface 43 of the springs 4. The described architecture for the upper bed base 32 is similar for the lower bed base 33, except that on the inner frame 51 is mounted the lower abutment support 47 via the fixing screw 58 and the opening of the cone is oriented downwards.

Under extreme conditions, the abutment 46 may come into contact with the support 47 to limit the compression amplitude of the springs 4.

Since the space between the bedsteads is available, the lower abutment support 47 can be arranged to integrate the passage 47 ₁ with a strap (not shown) making it possible to perform the function of a lift limit limiting the amplitude. extension of the secondary suspension subassembly 31 during the lifting of the vehicle and ensuring possible preload of the spring or springs 4.

Preferably, the assembly 47 is located below the abutment 46 because, under the effect of gravity, the strap suspended after its two attachments 46c integrated with the abutment 46 is suitably in place vis-à-vis the semi contour -cylindrical 47 ₂ of passage 47 ₁ . Provided that the strap behaves satisfactorily having its fixings 46c down, the stop 46 could be permuted with the abutment support 47 and the passage 47 ₁ .

• en atelier de montage, l'ensemble de suspension secondaire 31 n'est pas placé sous le train et n'est donc pas assujetti à la charge de la caisse 1. La plage de débattement vertical entre butée haute et butée basse tendant à être optimisé avec les conditions rencontrées lors de l'exploitation du matériel, l'absence de précharge du ou des ressorts 4 conduirait à un fort débattement vertical ou à une rigidification de la raideur verticale au détriment du confort des passagers. En effet, la raideur verticale du ou des ressorts 4 est relativement faible au regard de la forte charge verticale appliquée par la caisse 1 considérée vide de ses passagers. Cette précharge du ou des ressorts 4 se traduit donc par une tension dans la sangle une fois le montage finalisé.
• en conséquence, avant serrage, le ou les ressorts 4 englobe(nt) les composants 46, 46b, 46c, 47, ainsi que la sangle.
• les fixations 46c de la sangle de relevage doivent donc être montées avant de disposer le ou les ressorts 4 sur les plateaux 70.
• le support de butée 46b n'étant non plus pas accessible de l'extérieur, les goupilles 55 assurent la localisation angulaire dans cette zone inaccessible et permettent de finaliser le montage du sous-ensemble 31.
• en revanche, le montage de l'appui de butée 47 peut être préparé à l'avance.

In addition to the function of angular alignment of the plate 71 and its pins 56 with the assembly (50, 70, 56), the pins 55 ensure the transfer of the tightening torque of the screw 58 or the nut 59 on the plates 71. These have another function when mounting the subassembly 31 because:

• in the assembly workshop, the secondary suspension assembly 31 is not placed under the train and is therefore not subject to the load of the body 1. The range of vertical movement between the upper stop and the lower stop tending to be optimized with the conditions encountered during the operation of the equipment, the absence of preload of or springs 4 would lead to a high vertical deflection or a stiffening of the vertical stiffness at the expense of passenger comfort. Indeed, the vertical stiffness of the spring or springs 4 is relatively low in view of the high vertical load applied by the body 1 considered empty of its passengers. This preload of the spring or springs 4 therefore results in a tension in the strap once the final assembly.
• therefore, before tightening, the spring or springs 4 include (s) the components 46, 46b, 46c, 47, and the strap.
• the bindings 46c of the lifting strap must therefore be mounted before arranging the spring or springs 4 on the trays 70.
• the abutment support 46b is also not accessible from the outside, the pins 55 provide the angular location in this inaccessible area and allow to finalize the assembly of the subassembly 31.
• on the other hand, the mounting of the abutment support 47 can be prepared in advance.

The number of steps of assembly of a rocking bed base can be optimized during its industrialization by grouping in one piece of the components 51 and 71, as illustrated by the variant of the figure 5 . In this, the part 51 'has a flange 51 "which serves as a plate 71. In both cases, it is also possible to dispense plates 62 and 63 if the matting pressure exerted by the blocks is acceptable for the material of the plate 71 (or the flange 51 "), that is to say if the material has sufficient hardness.

The axial flexibility of the pivot 50 can be used to help the mounting of the pads 60. The pins 56 of centering pads 60 can be reported from the outside.

To the figure 5 , the interface between the body 1 or the bogie 2 and the supports 70 of the metal springs is integrated at the central pivot.

On the figure 6 , the focus is on an embodiment of a high stop (or lifting) without the use of an internal strap. The mattresses each have their own high abutment 46b '/ 46 "/ 47", while an external lifting system (cables or straps for example) can be integrated between the two plates 70 in order to limit the extension of the springs 4.

The abutment abutment 46b '/ 47' forms a collar 46 "/ 47" which has at its periphery a vertical clearance j with the outer armature 52. The functional clearance j is kept under normal operating conditions, in order not to clamp the tilting of the bed base. The flange 46 "/ 47" limits to the value of the functional clearance j the displacement in traction of the elastic element 53 of the pivot, which limits the stress in traction of the pivot during the lifting of the body and thus ensures the stop function high intrinsic to the rocking bases 32 and 33.

The Figures 7a to 7d show three embodiments of the pairs of pads. In each of them, the pads are diametrically opposed with respect to the center A2 located on the axis ZZ '. The figure 7a (vertical section) is common to Figures 7b to 7d .

To the figure 7b there is only one pair of cylindrical studs 60 each of which extends on either side of the axis u over an angle γ1, possibly with minus one pair of diametrically opposed through-cells 65 extending on either side of the axis v on an angular sector γ2.

To the Figure 7c there are two pairs of pins 60 ₁ , 60 ₂ , and 60 ₃ , 60 _{4 respectively} , extending on either side of the axis u over an angular sector γ1. Their centers P ₁ , P ₂ , P ₃ , P ₄ are situated on a straight line respectively A2P ₁ , A2P ₂ , A2P ₃ , A2P ₄ forming with the axis u an angle respectively γP ₁ , γP ₂ , γP ₃ , γP ₄ . An even number of pads greater than 4 could also be used. Preferably, the value of the angles γP ₁ , γP ₂ , γP ₃ , γP ₄ is chosen to be identical in order to balance the system.

The stiffness in compression K ' _AP of the pads is greater than or equal to the axial stiffness K _AP of the pivot, ie K' _AP ≥ K _AP with a ratio advantageously at least equal to 5 and preferably at least equal to 10, and which can for example between 5 and 50.

Similarly, K _RP ≥ K _CP with a ratio of at least 5 and preferably 10, and which may be for example between 5 and 50.

• γ1 est choisi le plus faible possible (à l'extrême, plots matérialisant des appuis ponctuels) afin de réduire la raideur conique Kθu des plots (rotation autour de l'axe u).
• γ2 peut être choisi différent de 0° (création d'alvéoles 65) pour réduire la raideur conique Kθu du pivot. Néanmoins, la valeur de l'angle γ2 est limitée par le fait que la présence d'alvéoles 65 ne doit pas affecter la reprise des efforts horizontaux suivant l'axe v.
• le diamètre d'implantation D des plots (distance entre les centres C des plots d'une même paire) est de préférence aussi grand que le permet l'espace alloué au produit. En effet, puisque la raideur en basculement des paires de plots autour de l'axe v (Kθ_VP) est fonction du carré du diamètre D, lorsque D double, Kθ_VP est multiplié par 4 pour la même caractéristique K'_AP des plots. On notera que la raideur en basculement intrinsèque des plots est un terme du second ordre qui ne dépend pas de D, mais qui peut être négligé.

To optimize the performance, that is to say to maximize the Kθv / Kθu ratio, Kθv designating the stiffness in tilting of the bed base around the axis v and Kθu denoting the stiffness in tilting of the bed base around the u axis:

• γ1 is chosen as low as possible (at the extreme, studs materializing punctual supports) in order to reduce the conical stiffness Kθu of the studs (rotation about the axis u).
• γ2 can be chosen different from 0 ° (creation of cells 65) to reduce the conical stiffness Kθu of the pivot. However, the value of the angle γ2 is limited by the fact that the presence of cavities 65 must not affect the recovery of horizontal forces along the axis v.
• the implantation diameter D of the pads (distance between the centers C of the pads of the same pair) is preferably as large as the space allocated to the product allows. Indeed, since the stiffness in tilting pairs of pads around the axis v (Kθ _VP ) is a function of the square of the diameter D, when D double, Kθ _VP is multiplied by 4 for the same characteristic K ' _AP pads. It should be noted that the stiffness in intrinsic tilting of the pads is a second order term which does not depend on D, but which can be neglected.

Preferably, the system is symmetrical center A2 to balance the recovery efforts.

The section of the studs can be of any shape: they are schematized in the examples in the form of cylinders or sectors for simplify the representation. Their section can be optimized taking into account the parameters listed above (γ1, D).

In practice, γ1 is chosen less than 45 ° and preferably between 0 ° and 25 ° and / or γ2 can be chosen up to 60 ° and preferably between 5 ° and 25 °.

Claims (15)

1. Tilting bed base for suspension of a vehicle in order to ensure, on the one hand, recovery of a vertical load generated by the vehicle body, and on the other hand in order to accompany, with tilting, the relative horizontal movements, wherein the bed base comprises a first support for its assembly on a vehicle element, and a second support spaced apart vertically from the first support, in order to receive an extremity of a suspension spring, characterised in that it comprises, in parallel:

   - a central pivot (50) for vertical guiding, comprising a cylindrical or frusto-conical elastic element (53) assembled between an internal piece (51) and an external piece (52), wherein the internal piece (51) is interdependent with one of said first (70) and second (71) supports and the external piece is interdependent with the other of said first and second supports, said pivot (50) having a greater horizontal rigidity than vertical rigidity,

   - and, arranged symmetrically on both sides of the central pivot, at least one pair of elastic cones (60) whose centres are aligned on a first horizontal axis and which are assembled between the first (70) and the second (71) support and have greater vertical rigidity than horizontal rigidity.
2. Bed base according to claim 1, characterised in that said cylindrical or frusto-conical elastic element (53) is at least partly elastomeric.
3. Bed base according to claim 2, characterised in that said cylindrical or frusto-conical elastic element (53) is laminated.
4. Bed base according to one of claims 1 to 3, characterised in that the elastic cones (60) are metal cushions.
5. Bed base according to one of claims 1 to 3, characterised in that the elastic cones (60) are at least partly elastomeric.
6. Bed base according to claim 5, characterised in that the elastic cones (60) are laminated.
7. Bed base according to one of the preceding claims, characterised in that the relationship between the vertical rigidity of all the cones (60) and of the central pivot (50) is greater than or equal to 1 and is in particular between 5 and 50.
8. Bed base according to one of the preceding claims, characterised in that the relationship between the horizontal rigidity of the central pivot (50) and of all the cones (60) is greater than or equal to 1 and is in particular between 5 and 50.
9. Bed base according to one of the preceding claims, characterised in that the relationship between the horizontal rigidity and the vertical rigidity of the central pivot (50) is between 2 and 5.
10. Bed base according to one of the preceding claims, characterised in that the relationship between the vertical rigidity and the horizontal rigidity of a cone (60) is between 50 and 500.
11. Bed base according to one of the preceding claims, characterised in that the cylindrical or frusto-conical elastic element (53) of the central pivot (50) has at least one pair of alveoli (65) arranged symmetrically on both sides of the central pivot (50) and its median planes are aligned on a second horizontal axis perpendicular to the first axis.
12. Bed base according to one of the preceding claims, characterised in that at least one central pivot (50) has an abutment (46, 46b', 47') that is interdependent with its internal piece (51) and this abutment (46, 46b', 47') has a collar (46", 47") that is spaced apart from the external piece (52) of said central pivot (50) by a running clearance j in order to limit the tractive displacement of the elastic element (53) of said central pivot (50).
13. Suspension sub-assembly of a vehicle, characterised in that it comprises at least one tilting bed base according to one of the preceding claims, the second support of which receives an extremity of at least one suspension spring.
14. Suspension sub-assembly according to claim 13, characterised in that it comprises a first and a second of said tilting bed bases, assembled head-to-tail, wherein at least one of said suspension springs (4) is arranged between the second supports of the two bed bases.
15. Sub-assembly according to claim 14, characterised in that the first bed base comprises a first abutment (46) and the second bed base comprises an abutment device (47) comprising a belt that is fixed by belt supports (46c) that are interdependent with the first abutment (46) and passing around a semi-cylindrical sill (47₂) formed in an abutment sill (47) that is interdependent with the second bed base.

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