EP3526489A1

EP3526489A1 - Damping bearing with axial preload

Info

Publication number: EP3526489A1
Application number: EP17793707.5A
Authority: EP
Inventors: Philippe Durand
Original assignee: JTEKT Europe SAS
Current assignee: JTEKT Europe SAS
Priority date: 2016-10-11
Filing date: 2017-10-09
Publication date: 2019-08-21
Also published as: US20200018371A1; FR3057310A1; US11209066B2; FR3057310B1; WO2018069617A1; JP6964662B2; JP2019537692A; CN109923328A; BR112019006367A2; CN109923328B

Abstract

The invention relates to a method of manufacturing a damping device (1), notably for a steering tie rod, the said device comprising a rod (20) which extends along a main axis (XX') and which is intended to be connected to a first mechanical component (4), a securing portion (22) which surrounds the said rod (20) and which is intended to be connected to a second mechanical component (2B), and a sleeve (23) made of elastomeric material which is arranged between the rod and the fixing bushing so as, through elastic deformation thereof, to allow at least axial movement of the fixing bushing with respect to the rod, in which method the fixing bushing (22) is offset axially with respect to the rod (20) to force the elastic deformation of the sleeve (23) and the introduction of a corresponding preload, then the sleeve (23) is locked so as to keep it, when the device is at rest, in a state of permanent axial elastic deformation and preload.

Description

Damper bearing with axial preload

The present invention relates to the field of links used to transmit a mechanical movement between a first moving part and a second moving part.

The present invention relates more particularly to the steering rods used in the steering mechanisms of motor vehicles.

It is known to provide, within the steering mechanisms, and more particularly within the steering rods, bearings provided with a damping device formed by an elastomer pad for damping the shocks and vibrations produced by the roughness of the rods. the road.

Moreover, the inventors have discovered that the presence of a suitably sized damping device could advantageously make it possible to create, when the driver maneuvers the steering wheel, a phase shift (a delay) between the steering wheel orientation angle and the angle of the steering wheel, phase shift which has the effect of increasing the turning radius of the vehicle, compared to what would be said turning radius if the wheels followed exactly and instantly the steering wheel angle, and so reduce the yaw rate of the vehicle, so that the vehicle is less likely to survive.

However, the known damping devices exhibit behavior that is sometimes poorly controlled, and in particular asymmetrical behavior depending on whether they are stressed in compression or in traction, so that the damping provided can be imperfect, and disturb the sensations of driving perceived by the driver through the steering wheel, or even affect the dynamic behavior and stability of the vehicle.

The objects assigned to the invention therefore aim at overcoming the aforementioned drawbacks and at proposing a new method of manufacturing a damping device, and more generally of a link equipped with such a damping device, which makes it possible to obtain a damping effect balanced in both traction and compression, and in particular that improves the dynamic behavior of a vehicle, making it safer.

The objects assigned to the invention are achieved by means of a method of manufacturing a damping device comprising a rod, which extends along a main axis (XX ') and which is intended to be connected to a first mechanical part , a fixing sleeve which surrounds said rod and which is intended to be connected to a second mechanical part, and a sleeve of elastomeric material which is arranged between the rod and the fixing sleeve so as to allow, by its deformation elastic, at least one axial displacement of the fixing sleeve relative to the rod, said method being characterized in that it comprises:

a step (a) of preparation, during which the rod is inserted into the fixing sleeve so that the fixing sleeve at least partially surrounds the rod and occupies axially a first position relative to said rod, and provides a filling space radially between the rod and the fixing bush,

a step (b) overmolding, during which at least partially fills the filling space so as to create the elastomeric sleeve which connects the rod to the fixing sleeve,

a step (c) of creating a pre-load, during which the axial displacement of the fixing sleeve with respect to the rod (or vice versa) in a direction referred to as "load direction", so as to axially shifting the securing sleeve from its first position to a second position axially distinct from the first position, against an elastic deformation of the sleeve, to create an axial pre-load of said sleeve, and thus an axial pre-load of the rod relative to the sleeve (that is to say more generally an axial pre-load of the device),

a step (d) of locking, during which the elastomer sleeve is locked against the rod, or against the fixing sleeve, so as to maintain on the one hand a relative mobility of the rod relative to the fixing sleeve , through the sleeve, and secondly at least partly the axial preload of the sleeve, and therefore at least partly the axial pre-load of the rod relative to the fixing sleeve.

The objects assigned to the invention are also achieved by means of a damping device comprising a rod, which extends along a main axis (XX ') and which is intended to be connected to a first mechanical part, a fixing sleeve which surrounds said rod and which is intended to be connected to a second mechanical part, and a sleeve of elastomeric material which is arranged between the rod and the fixing sleeve so as to allow, by its elastic deformation, at least one displacement axial of the fixing sleeve relative to the rod, said device being characterized in that the sleeve is held by the rod, when the device is at rest, in a state of permanent axial elastic deformation which creates and maintains a pre-charge axial of said sleeve, and therefore an axial pre-load of the rod relative to the sleeve (that is to say more generally an axial pre-load device). Advantageously, the introduction of a residual axial pre-load within the elastomer sleeve makes it possible in practice to shift the stiffness curve of said sleeve, and thus to "polarize" the damping device so that it adopts a mechanical behavior. different elastic (stiffer or, on the contrary, more flexible), depending on whether it is stressed in traction or on the contrary in compression along the main axis (XX ').

Advantageously, the pre-load of the sleeve may in particular be calculated to compensate for the permanent effects of tensile stresses, or compressive stresses, which are induced, in the absence of shocks or vibrations, by the geometric arrangement of the running gear. .

Indeed, the inventors have found that the geometry of the front axle, which carries the steering wheels, generally induces a permanent axial force in the steering rod, due to the adjustment of parallelism. This permanent axial force may be, as the case may be, in tension or in compression, and may disturb the feeling of driving, which differs according to whether the driver maneuvers the steering wheel to the left or to the right.

Advantageously, thanks to the invention, the elastic precharge specific to the sleeve (and more generally the pre-load specific to the damping device) makes it possible to compensate for these permanent axial forces induced by the undercarriage, and thus to recreate in fine behavior symmetrical damping, in order to absorb the forces, shocks and vibrations substantially equally well in traction and in compression.

Therefore, the presence of a damping device which is prestressed so as to compensate for the permanent axial forces makes it possible to restore the symmetry of the behavior of the steering mechanism, and more generally the symmetry of the dynamic behavior of the vehicle.

Indeed, the invention guarantees, on the one hand, a driving feeling that will be symmetrical, since the damping device enables the steering mechanism to provide symmetrical sensations when the steering wheel is turned to the left and when the steering wheel is pointed. the steering wheel on the right, and on the other hand a yaw behavior of the vehicle which will also be symmetrical, since the phase shift between the steering angle and the yaw angle of the steering wheels is generated symmetrically by the damping device, also well in a left turn than a right turn.

Other objects, features and advantages of the invention will appear in more detail on reading the description which follows, and with the aid of the accompanying drawings, provided for purely illustrative and non-limiting purposes, among which: Figure 1 illustrates, in an overall perspective view, a steering mechanism comprising a steering rod whose rod is provided with a damping device according to the invention.

FIG. 2 illustrates, in the form of stiffness curves, the effects of a pre-load in tension, respectively of a pre-load in compression, on the behavior of the sleeve, and more generally on the behavior of the damping device according to FIG. 'invention.

Figure 3 illustrates, in a longitudinal sectional view along the main axis (XX '), a step (a) of setting the fixing sleeve in its first position around the rod.

FIG. 4 illustrates, in a longitudinal sectional view, a step (b) of overmoulding of the sleeve between the rod and the fixing sleeve of FIG. 4.

FIG. 5 illustrates, according to a longitudinal sectional view, a step (c) of creating a pre-load in the sleeve of FIG. 4, according to which the rod is displaced (here in traction upstream) with respect to to the fixing sleeve for placing said sleeve in its second position relative to the rod.

FIG. 6 illustrates, in a view in longitudinal section, a step (d) of locking, during which a portion of the sleeve is tightened in a locking groove of the rod, under the effect of a plastic constriction of the fixing sleeve.

FIG. 7 illustrates, in a longitudinal sectional view, a step (e) of assembly during which the attachment bush is fixed to a housing belonging to the second mechanical part, here a downstream portion of a tie rod rod .

FIG. 8 illustrates, in a longitudinal sectional view, an exemplary tooling for molding the sleeve of the device of FIGS. 3 to 7.

The present invention relates to a method of manufacturing a damping device 1.

Said damping device 1 is more particularly intended to be implanted within a rod 2, which preferably equips a steering system 3.

In a manner known per se, and as shown in FIG. 1, the steering system 3 may comprise a rack 4 which is movable and guided in translation in a steering casing 5, and which is connected to the rod 2 of such that when moving the rack 5, it drives said link 2 which in turn acts on a knuckle 6 to change the yaw orientation (the steering angle) of a steered wheel 7.

The steering system 3 may also include a steering wheel 10 allowing the driver to operate the steering system 3, for example via a steering column 11 carrying a pinion 12 which meshes with the rack 4.

Preferably, the steering system 3 forms a power steering system, equipped with an assistance motor 13, preferably an electric assistance motor, for example brushless type, said assistance motor 13 being intended to produce an assistance effort that assists the driver in maneuvering the steering system 3, according to predetermined assistance laws that are stored in a computer.

According to the invention, the damping device 1 comprises a rod 20, which extends along a main axis (XX ') and which is intended to be connected to a first mechanical part, such as, for example, the above-mentioned rack 4 ( in what follows, for convenience, one can thus assimilate rack 4 and first mechanical part 4).

In a particularly preferred manner, said main axis corresponds to the longitudinal axis of said rod 20.

The rod 20 preferably has a cylindrical shape whose main axis (XX ') forms the central axis, and more preferably a form of revolution about said main axis (XX').

For convenience of description, the term "axial" a direction or dimension considered coaxially or parallel to said main axis (XX '), and "radial" a direction or a dimension considered perpendicular to said main axis (XX').

Preferably, the rod 20 belongs to a rod 2.

The rod 20 thus forms at least a portion, here for example an upstream portion 2A, of a tie rod pivot rod.

Said upstream portion of connecting rod rod 2A carries at its end a hinge member 21, of the ball-and-socket type, which allows the link 2 to articulate at one end of the rack 4.

The main axis (XX ') preferably coincides substantially with the longitudinal axis of the rod 2.

As illustrated in FIGS. 2 to 8, the damping device 1 also comprises a fixing sleeve 22 which surrounds the rod 20 and which is intended to be connected to a second mechanical part 2B, distinct from the first mechanical part 4, such as for example, as illustrated in FIGS. 1 and 7, a downstream portion 2B of link rod 2, itself connected to the rocket carrier 6.

Preferably, said fixing sleeve 22 is made of a metal material, able to be plastically deformed to effect crimping.

By simple convention, and as shown in particular in FIG. 1, the meaning of the first mechanical part 4 (and more generally of the steering gear 5 and of the rack 4) will be considered as "upstream-downstream". to the second mechanical part 2B (and more generally the knuckle 6 and the wheel 7).

The damping device 1 is advantageously designed to allow a damped relative movement, and in particular at least one damped axial relative movement, in a predetermined limited displacement range, of the rod 20 with respect to the fixing sleeve 22, and therefore more generally of the first mechanical part 4 (upstream) with respect to the second mechanical part 2B (downstream).

In a particularly preferred manner, the damping device 1 is designed to allow at least a relative axial displacement of the rod 20, and therefore of the first mechanical part 4, relative to the fixing sleeve 22 and therefore with respect to the second mechanical part. 2B, in response to axial tensile and compressive force components, which act substantially in the direction of the main axis (XX ') of the rod 20.

Thus, as indicated above, the damping device 1 will damp forces, shocks and / or vibrations at least in the direction of the main axis (XX '), and in the particular case of use within a steering system 3, to create a phase shift (delay) between the maneuvers of the steering wheel 10 made by the driver and the corresponding reactions in the yaw of the steering wheels 7, in order to improve the dynamic behavior of the vehicle by turn.

For this purpose, the damping device 1 further comprises a sleeve 23 of elastomeric material which is arranged between the rod 20 and the fixing sleeve 22 so as to allow, by its elastic deformation, at least one axial displacement of the fixing sleeve. 22 with respect to the rod 20.

The sleeve 23, thanks to its intrinsic elasticity, advantageously acts as a damping pad capable of absorbing, at least axially, the vibratory movements or small amplitude bursts of the attachment sleeve 22 with respect to the rod 20 (and reciprocally), and consequently the vibratory movements or small amplitude bursts of the second mechanical part (downstream part 2B of the link rod connected to the knuckle carrier 6) relative to the first mechanical part (rack 4), and vice versa.

The sleeve 23, and more generally the damping device 1, thus forms a deformable interface which axially separates from each other the first mechanical part 4 and the second mechanical part 2B, 6, which are located respectively upstream of said interface and downstream of said interface, and which are connected to each other via the rod 2, and more particularly via said damping device 1.

It is thus possible to obtain effective damping by means of a device 1 which is particularly compact, reliable and, moreover, easy and inexpensive to manufacture.

According to the invention, the manufacturing method comprises a step (a) of preparation, during which the rod 20 is inserted into the fixing sleeve 22 (or conversely the fixing sleeve 22 is threaded onto the rod 20) so that that the fixing sleeve 22 at least partially surrounds the rod 20 and occupies axially a first position PI with respect to said rod 20, and there is provided radially between the rod 20 and the fixing sleeve 22 a filling space 24, such as that this is illustrated in Figure 3.

The method then comprises a step (b) overmolding, during which is filled at least partially with an elastomeric material or a precursor of elastomeric material, the filling space 24 so as to create the elastomeric sleeve 23 which connects the rod 20 to the fixing sleeve 22, as shown in FIG. 4.

The sleeve 23 thus forms a bridge that extends radially from a portion of the radially outer wall of the rod 20 to a corresponding portion of the radially inner wall of the fixing sleeve 22 (whose diameter is greater than the diameter of the the radially outer wall of the rod 20 at least on the region axially covered by the sleeve 22), and which adheres to said respective walls of the rod 20 and the fixing sleeve 22.

Overmolding advantageously constitutes a quick and inexpensive method of making, and which also makes it possible to manufacture a sleeve which automatically converts, when filling the filling space 24 with the liquid elastomer, into the respective shapes of the rod 20. and the fixing sleeve 22, regardless of the complexity of said shapes. The method then comprises a step (c) of creating a pre-charge, during which the axial displacement of the fixing sleeve 22 with respect to the rod 20 (or vice versa) in a direction referred to as "direction of load "IF, so as to axially shift the attachment sleeve 22 from its first position PI to a second position P2 axially distinct from the first position PI, against an elastic deformation of the sleeve 23, to create a pre-load axial axis of said sleeve 23, and thus an axial pre-load of the rod 20 relative to the fixing sleeve 22, that is to say more generally an axial pre-load of the device 1, as illustrated in FIG. figure 5.

The direction of charge SI will be chosen according to the nature of the pre-charge desired, according to whether it will be desired to pre-load in compression or a preload in tension of the damping device 1.

By convention, it will be considered that a "pre-load in tension" means that axial traction is exerted on the rod 20 upstream, while retaining the bushing 22 in traction downstream, c that is to say that a traction is exerted on the upstream portion of the device 1 against the downstream portion of the device 1 (and vice versa), thus pulling the device 1 on either side of the deformable interface that forms the sleeve 23, in a direction away from the sleeve 22 the upstream portion 2A of said rod 20, that is to say in a direction that is equivalent to axially moving the first mechanical part 4 upstream of the second mechanical part 2B downstream, as illustrated by the "SI load direction" in FIG.

By convention, it will therefore be considered that such a tensile pre-load, which tends to increase the overall axial length of the device 1, corresponds to a "stretched" configuration of the device 1.

In fact, taking into account the particular arrangement illustrated in FIGS. 3 to 7, this pre-load in tension of the device 1 has the effect of locally compressing (and in axial shearing) the sleeve 23 which is located at the interface between the rod 20 and the downstream part 2B, and whose elastic deformation accommodates the displacement (here at a distance) of the upstream portion of the device 1, situated upstream of the interface, with respect to the downstream portion of this same device 1, located downstream of the interface.

Conversely, performing a pre-load in compression is to force the axial approach of the upstream of the rod 20 to the attachment sleeve 22 (that is to say downstream), which is equivalent to bring the upstream mechanical part 4 of the downstream mechanical part 2B, opposite the elastic deformation of the sleeve 23, in a direction opposite to the load direction S1 illustrated in FIG. 5. By convention, it will be considered that such a pre-load in compression, which tends to reduce the axial length overall of the device 1, corresponds to a "compressed" configuration of the device 1.

In any case, whatever the direction (traction or compression) chosen to pre-load the device 1, the elastic sleeve 23, under the effect of the pre-load, naturally tends to recall (elastically) the fixing sleeve 22 to its first position Pl.

As an indication, the axial offset d1, that is to say the axial distance between the first position PI of the second position P2, may be between 0.2 mm and 5 mm.

The method finally comprises a step (d) of locking, during which the elastomer sleeve 23 is locked against the rod 20, or, if appropriate, against the fixing sleeve 22, so as to keep at least partly the axial load of said sleeve 23, and more generally so as to keep at least partly the axial pre-load of the device 1, as shown in Figure 6.

In other words, the method therefore comprises a step (d) of locking, in which the elastomer sleeve 23 is locked against the rod 20, or, alternatively, against the fixing sleeve 22, so as to preserve on the one hand a relative mobility of the rod 20 relative to the fixing sleeve 22, through the sleeve 23, and secondly at least partly the axial pre-load of the sleeve (23) and therefore to the less in part the axial pre-load of the rod 20 relative to the fixing sleeve 22.

The lock is used to lock the sleeve 23 in the deformed configuration (stretched, or otherwise compressed) which corresponds to the pre-charge (residual) desired.

This locking also has the effect of preventing the sleeve 23 from spontaneously returning the fixing sleeve 22 in its first position PI, said fixing sleeve 22 being thus kept in its second position P2, after locking, and at rest, c that is to say when the damping device 1 is not biased in tension or in axial compression by the first and second mechanical parts 4, 2B.

On the other hand, the locking does not have the effect of blocking the fixing sleeve 22 with respect to the rod 20, since said sleeve 22 remains, and must remain, elastically mobile with respect to the rod 20, and can in particular move by axial sliding, through the sleeve 23 which is elastically deformed to accompany said sliding.

Thus, finally, after locking, and at rest, the fixing sleeve 22 is in its second position P2, and can be moved elastically relative to the rod 20 (or conversely, the rod 20 can be moved elastically relative to the sleeve 22), in particular in axial translation, on either side of said second position P2, in the vicinity of said second position P2, against the elastic return exerted by the pre-loaded sleeve 23 which can be deformed to accommodate such displacements.

Note that the rod 20 advantageously serves as a rigid support capable of axially holding the sleeve 23 in said deformed configuration and therefore pre-loaded.

Alternatively, it could however be envisaged that it is the fixing sleeve 22, and not the rod 20, which acts as a rigid support against the sleeve 23, so that said sleeve 23, once deformed by the step (c) pre-charge creation, would be maintained in pre-charge, in the deformed configuration, exclusively by the fixing sleeve 22, rather than by the rod 20 exclusively.

Of course, as can be seen in FIG. 2, the preload will have the effect of shifting the stiffness curve of the damping device 1 with respect to its unloaded stiffness curve L0.

Thus, when the device 1 is pre-loaded in tension (stiffness curve with pre-load in traction), said device 1 will oppose more tensile strength, that is to say, allow, for the same given tensile force axial displacement of the sleeve 22 is lower than in the absence of pre-charge (curve L0).

Conversely, when the device 1 is pre-loaded in compression (stiffness curve with pre-load in compression Le), said device 1 will oppose more compressive strength, that is to say, allow, for the same given compression force, an axial displacement of the bushing 22 lower than in the absence of pre-load (curve L0).

Preferably, the sleeve 23 has, along the main axis (XX ') on the one hand a downstream portion 23B, which stops axially, in the load direction SI, against a stop shoulder 25, 26 arranged on the rod 20, and further by an upstream portion 23A, which is displaced by force relative to the downstream portion 23B, and preferably here which is forcefully brought closer to the downstream portion (by compression), in the load direction SI, when shifting the fixing sleeve 22 from its first position PI to its second position P2 during the step (c) of creating the preload, and which is placed, when the step (d) of locking, against a locking flange 30 provided on the rod 20, as shown in Figure 6, so that said upstream portion 23A can not move (by springback) in one direction opposite to the load direction SI, and more particularly here so that said upstream portion 23A can not redeploy upstream.

In other words, sleeve 23 is thus found, after locking, hooked to rod 20 on the one hand by its downstream portion 23, which clings to, and more particularly which axially bears on (when moving). the bushing 22 with respect to the rod 20 in the selected direction of load SI), the radial asperities formed by the stop shoulders 25, 26 of said rod 20, and secondly by its upstream portion 23A, which clings to, and more particularly which axially bears against, the radial asperity that forms, at axial distance from the stop shoulders 25, 26, the locking flange 30 of the same rod 20.

The sleeve 23, and more particularly the intermediate portion of said sleeve which is axially between the upstream portion 23A and the downstream portion 23B is thus maintained (e) in forced axial deformation (here forced compression in Figures 5 and 6).

Advantageously, the ratio between the distance separating the locking flange 30 from the stop shoulders 25, 26 and the distance separating at rest (before deformation) the corresponding portions 23A, 23B of the sleeve 23 thus defines the degree of deformation of the sleeve 23 and therefore the intensity of the pre-charge.

Preferably, the rod 20 has a plurality of stop grooves 31, 32 (here two stop grooves 31, 32 in FIGS. 3 to 8) which are staggered axially in order to provide a plurality of stop shoulders 25, 26 annular, which follow one another axially, and which cooperate with the downstream portion 23B of the sleeve 23.

The multiplication, in this case the doubling, of the stop shoulders 25, 26 offers a better grip of the sleeve 23, and more particularly of the downstream portion 23B of said sleeve 23, on the rod 20, which makes it possible to stop and even to immobilize axially the downstream portion 23B of the sleeve on the rod 20 while shifting the sleeve 22, and the upstream portion 23A of the sleeve, to create the preload.

The annular geometry of the stop grooves 31, 32 makes it possible to reinforce this grip and to distribute all around the main axis (XX ') the retaining stresses of the sleeve 23.

The assembly is therefore particularly robust. Preferably, the stop grooves 31, 32 of the rod have (in longitudinal section) rounded shapes so as to define axially, on the surface of the rod, a corrugated hanging profile, as shown in FIGS. 3 to 8.

Advantageously, such a profile hooked to the rounded shapes limits the stress concentrations, in particular in the sleeve 23, during the preload.

Moreover, in a similar way, the fixing sleeve 22 will preferably have radial asperities, and in particular a hook profile comprising at least one male alternating 40, 42 convex forming a radial projection (boss type) towards the main axis (XX ') and a concave female alternation 41 forming radial centrifugal (well-type) shrinkage with respect to the male hook profile and the main axis (XX').

Advantageously, the hooked profile of the fixing sleeve 22 may be substantially conjugated to the hooked profile of the rod 20, so that the sleeve 23 has a substantially constant radial thickness, at least in the zone between the hooked profile 31, 32 of the rod 20 and the hook profile 40, 41, 42 of the fixing sleeve 22 (here at least in the downstream portion 23B of the sleeve 23).

Thus, the fixing sleeve 22 preferably has an internal wall which has, at a radial distance from the rod 20, a hooked profile 40, 41, 42 of a sinuous bushing which is substantially exactly identical to the hooked rod profile. 31, 32 formed by the stop grooves which serve to retain (at least axially) the downstream portion 23B of the sleeve 23.

Such an arrangement limits the shear stresses and improves the longevity of the sleeve and therefore of the damping device 1.

It will be noted that, preferably, during step (a) of preparation (FIG. 3) and, especially, during step (b) of overmolding (FIG. 4), the male alternation (s) 40, 42 of the profile hooked from the fixing sleeve 22 will be offset axially relative to the female alternation (s) (the bottoms of stop grooves) 31, 32 corresponding to the hanging profile of the rod 20 of a value substantially equal to the value of the offset dl which is moved the fixing sleeve 22 relative to the rod 20 (or vice versa) during step (c) of creating the preload.

In this way, when the fixing bush 22 is brought into its second position P2, and the sleeve 23 (and more generally the device 1) is therefore preloaded to the desired value, the male alternation (s) 40, 42 of the hooked profile of the fixing sleeve 22 are found axially vis-à-vis the alternations or alternations females (the bottoms of stop grooves) 31, 32 corresponding to the hooked profile of the rod 20, substantially in the same plane normal to the main axis (XX '), so that the respective hanging profiles the bushing 22 and the rod 20 are (perfectly) superimposed, as shown in particular in FIG. 5.

Here again, this will make it possible to obtain a better distribution of the stresses in the sleeve 23, both when the fastening sleeve 22 is at rest in its second position P2 and when said sleeve 22 is requested later, within the steering system. 3, in axial displacement on one side or the other of said second position P2.

According to a preferred feature which can constitute an entirely separate invention, during the locking step (d), an upstream portion 23A of the elastomeric sleeve 23 is pushed radially by centripetal plastic deformation of the fixing sleeve 22, so as to radially penetrate, as shown in Figure 6, said upstream portion of the sleeve 23A, but not the fixing sleeve 22 itself, against the locking flange 30.

More particularly, an upstream portion 23A of the elastomer sleeve 23 is pushed radially by centripetal plastic deformation of the fastening sleeve 22, so as to penetrate radially said upstream portion of the sleeve 23A, but not the fastening sleeve 22 itself, in a locking groove 33 which is hollowed in the rod 20 and which has a wall, here in particular an upstream wall, forming a locking flange 30 for preventing said upstream portion 23A of the sleeve from making a return movement opposed to the movement which corresponds to the SI load direction.

Here, insofar as the device 1 is pre-loaded in tension, which causes a compression of the sleeve 23, so that the upstream portion 23A is axially close to the downstream portion 23B during movement in the load direction SI , then said locking groove 33 is thus more preferably intended to prevent the upstream portion 23A of the sleeve from redeploying axially and elastically upstream, with respect to the rod 20, and thus for the purpose of thus axially locking the portion upstream 23A of the sleeve relative to said rod 20.

Advantageously, the locking is thus operated by a plastic constriction of the sleeve 22, which drives towards and in the locking groove 33 an annular bead 23A-1 of the sleeve 23, so as to create a radial interference between the upstream portion 23A of the sleeve 23 and the rod 20.

Fixing the upstream portion 23A of the sleeve 23 on the rod 20 is thus provided in a stable and solid manner. Here again, the locking groove 33, which cooperates with the bead 23A-1 of the sleeve 23, will preferably have a rounded profile, in order to avoid stress concentrations.

However, the locking does not have the effect of creating interference between the fixing sleeve 22 and the rod 20, and in particular does not clamp the sleeve 22 on the rod 20, so that the device 1 retains after the locking, the relative axial mobility of said rod 20 relative to said sleeve 22.

Furthermore, the method preferably comprises, and preferably after the sleeve has been pre-loaded and locked, a step (e) assembly, during which is fixed, preferably by crimping, the fixing sleeve 22 in a housing 50 belonging to the second mechanical part 2B.

The housing 50 may advantageously form a terminal bulge on the upstream end of the downstream portion 2B of the link rod, in which is bored a receiving housing 51 which receives the subassembly formed by the downstream end of the rod 20 , the sleeve 22 and the sleeve 23 which cap said downstream end of the rod 20, as shown in Figure 7.

Before crimping, the bushing 22 can be nested in the housing 50 in an adjusted manner (for example according to an H7h6 type adjustment), or in force according to a tight fit (of the H7k6 type, for example), which will allow positioning said bushing 22 with respect to said housing 50, and an alignment of these elements along the main axis (XX ').

Fixing by crimping of the fixing sleeve 22 in the housing 50 can advantageously be carried out by plastically folding a flange 52 (preferably annular) of the housing 50 on a flange 53 of the fixing sleeve 22, preferably located at the end upstream of said bushing 22.

Such an assembly will indeed be particularly reproducible, simple and fast to achieve.

Figure 8 schematically illustrates a tool 60 suitable for performing the steps (b) overmoulding and (c) creation of pre-load.

For convenience, only half of the tooling 60 has been represented with respect to the main axis (XX '), the other half being able to be deduced by symmetry.

Said tool 60 comprises a base 61, a sheath 62, and two shells 63 (with radial opening movement).

The base 61 is provided on the one hand with a bore 64 arranged to receive the rod 20, and on the other hand with a bearing surface 65, here preferably flat, and preferably normal to the main axis (XX '), and which blocks axially, here on the upstream side, the fixing sleeve 22 (by the flange 53)

It will be noted that, advantageously, the bearing surface 65 forms an axial abutment which, after overmoulding, blocks the upstream portion 23A of the sleeve against the shifting movement of the rod 20 in the load direction SI, and, more particularly, which simultaneously locks the bushing 22 and said upstream portion 23A of the sleeve, thus temporarily securing said bushing 22 and said upstream portion of the sleeve, while the rod 20 is shifted to create the pre-load.

The sheath 62 is arranged to center the fixing sleeve 22 with respect to the rod 20, on the main axis (XX '), and thus reproducibly define the filling space 24 which radially separates the bushing 22 from the rod 20.

The shells 63 complete the tooling to define the casting path of the elastomer, located around the downstream end of the rod 20, and intended to form the sleeve (as shown schematically by a tapping 23 referenced in Figure 8 ).

Initially, the shells 63 being open, the fixing sleeve 22 is placed in the sleeve 62 (by engaging the sleeve 22 in said sheath 62 from the upstream) and then the plate 61 is pressed axially (from upstream). the sleeve 62 to lock the sleeve 22, by pressing the bearing surface 65 of the base 61 against the flange 53 of said sleeve 22.

The rod 20 (from downstream) is then engaged through the bushing 22 and into the bore 64 of the base until it reaches the first position P1.

The shells 23 are then closed and the elastomer material which constitutes the sleeve 23 is injected.

Note that the tool 60, and more preferably the base 61, advantageously has a baffle 66, here preferably in the form of a tubular extension 66 of the base 61 which extends the bore 64, deflector 66 which temporarily masks the locking groove 33 (and therefore more generally the locking flange 30) of the rod 20 during the overmolding step (b), in order to prevent the elastomeric material (constituting the sleeve 23) from filling said locking groove 33 (And thus come into contact with the locking record 30), and thus to provide an empty radial space, between the upstream portion 23A of the sleeve 23 and the locking groove 33 (respectively the locking flange 30), which will allow the rod 20, and more particularly to the locking groove 33 (and thus to the locking flange 30), to be displaced with respect to said upstream portion 23A of the sleeve (or vice versa) during the step (c) of creation pre-charge, before step (d) locking. Once the sleeve 23 has solidified, the shells 63 are opened and the rod 20 is pulled from the upstream (FIG. 5), or, in an equivalent manner, said stem 20 is pushed downstream, so that forcing the displacement of the rod 20 upstream, in the load direction SI, and by a value equal to the desired offset d1, so as to bring the rod 20 into the second position P2 with respect to the bushing 22, and in doing so, so as to create a pre-load of the sleeve 23 by elastic deformation; in FIG. 5, a pre-load in tension of the device 1 is carried out here, which results in a compression of said sleeve 23.

A radial crimping tool, which replaces the sheath 62, or which is optionally guided by said sheath 62, is then used to lock the sleeve 23 in its pre-loaded configuration by centripetal radial plastic deformation of the sleeve 22 and resulting formation 23A-1 bead in the locking groove 33 of the rod 20.

It will be noted that the offset d1 is preferably chosen such that, during the creation of the pre-load, and as illustrated in FIG. 5, the rod 20 does not bring the axial abutment against the bushing. fastening 22 in the load direction SI, that is to say that the offset d1 is chosen so as to preserve an axial clearance JA which allows the rod to be still axially movable relative to the sleeve 22 in the SI load direction, from the second position P2, against an elastic deformation (additional) of the sleeve 23.

Here, in the case of FIG. 5, a traction displacement reserve (of the rod 20) will then be maintained after having pre-loaded the device 1 by a first traction which has made the rod 20 from the first position PI to the second position P2.

Note that, as shown in Figure 7, the total axial stroke of the rod 20 relative to the fixing sleeve 22, and more generally with respect to the second mechanical part 2B, may be delimited by an upstream stop formed by the downstream edge 22L of the sleeve 22, and by a downstream stop formed by the bottom 54 of the receiving housing 51, with which alternately cooperates a collar 55 of the rod 20 (said collar 55 bearing against the downstream stop 54 at the maximum compression of the device 1, and in abutment against the upstream stop 22L at the maximum extension of the device 1).

Of course, the invention also relates as such to a damping device 1 obtained according to one or other of the characteristics of the method described in the foregoing. In particular, the invention relates to a damping device 1 comprising a rod 20 which extends along a main axis (XX ') and which is intended to be connected to a first mechanical part 4, a fixing sleeve 22 which surrounds said rod 20 and which is intended to be connected to a second mechanical part 2B, 50, and a sleeve 23 of elastomeric material which is arranged between the rod 20 and the fixing sleeve 22 so as to allow, by its elastic deformation, to less an axial displacement of the fixing sleeve relative to the rod, device 1 in which the sleeve 23 is held (by the rod 20 alone, or by the sleeve 22 alone), when the device is at rest, in a state of permanent axial elastic deformation which creates and maintains an axial pre-load of said sleeve 23, and more generally an axial pre-load of the rod 20 relative to the sleeve 22, and therefore an axial pre-load of the device 1.

The invention also relates to a steering rod 2 whose rod 2A, 2B, 20 is equipped with a damping device 1 according to the invention, and a steering system 3, preferably a power steering system, which includes such a steering rod 2.

The invention finally relates to a vehicle, and more particularly to a motor vehicle with wheels, provided with such a steering system 3.

Of course, the invention is in no way limited to the variants of embodiment described in the foregoing, the person skilled in the art being able in particular to isolate or combine freely between them one or the other of the aforementioned characteristics, or substitute equivalents for them.

In particular, it could be envisaged that the sleeve 23 is maintained in pre-load by the fixing sleeve 22 (exclusively), rather than by the rod 20 (exclusively), in which case it would be the sleeve 22 which would on the one hand carry a or stop shoulders designed to axially block the downstream portion 23B of the sleeve and secondly one or more locking flanges for axially locking the upstream portion 23A of the sleeve, after elastic axial deformation and pre-loading of the sleeve 23.

Claims

1. A method of manufacturing a damping device (1) comprising a rod (20), which extends along a main axis (XX ') and which is intended to be connected to a first mechanical part (4), a socket fastener (22) which surrounds said rod (20) and which is intended to be connected to a second mechanical part (2B), and a sleeve (23) of elastomeric material which is arranged between the rod (20) and the fixing sleeve (22) so as to allow, by its elastic deformation, at least an axial displacement of the fixing sleeve (22) with respect to the rod (20), said method being characterized in that it comprises:

a step (a) of preparation, during which the rod (20) is inserted into the fixing sleeve (22) so that the fixing sleeve (22) at least partially surrounds the rod (20) and occupies axially a first position (PI) with respect to said rod (20), and there is provided radially between the rod (20) and the fixing sleeve (22) a filling space (24),

an overmolding step (b), during which the filling space (24) is filled at least partially so as to create the elastomer sleeve (23) which connects the rod to the fixing sleeve,

a step (c) of creating a pre-load, during which the axial displacement of the fixing sleeve (22) with respect to the rod (20) in a direction referred to as "load direction" (SI ), so as to axially shift the attachment sleeve (22) from its first position (PI) to a second position (P2) axially distinct from the first position, against an elastic deformation of the sleeve (23), in order to creating an axial pre-load of said sleeve (23), and thus an axial pre-load of the rod (20) with respect to the fixing sleeve (22),

a step (d) of locking, during which the elastomer sleeve (23) is locked against the rod (20) or against the fixing sleeve (22), so as to maintain on the one hand a relative mobility of the rod (20) relative to the fixing sleeve (22), via the sleeve (23), and secondly at least partly the axial pre-load of the sleeve (23) and therefore at least partly the axial pre-load of the rod (20) relative to the fixing sleeve (22).

2. Method according to claim 1 characterized in that the sleeve (23) has, along the main axis (XX ') on the one hand a downstream portion (23B), which abuts axially, in the direction of charge ( SI), against a stop shoulder (25, 26) arranged on the rod (20), and further by an upstream portion (23A), which is displaced by force relative to the downstream portion (23B), and preferably which is forcefully brought closer to the downstream portion (23B), in the direction of load (SI), when the fixing sleeve (22) is shifted from its first position (PI) to its second position (P2) during the step (c) of creating the pre-charge, and which is placed, during the step (d) of locking, against a locking flange (30) provided on the rod (20), so that it can not move in a direction opposite to the load direction (SI).

3. Method according to claim 2 characterized in that the rod (20) has a plurality of stop grooves (31, 32) axially staggered to provide a plurality of annular stop shoulders (25, 26) which cooperate with the downstream portion of the sleeve.

4. Method according to claim 3 characterized in that the stop grooves (31, 32) of the rod (20) have rounded shapes so as to define axially, on the surface of the rod, a hooked profile of corrugated stem.

5. Method according to claim 3 or 4 characterized in that the fixing sleeve (22) has an inner wall which has, at radial distance from the rod (20), a serpentine profile (40, 41, 42) sinuous which is substantially even exactly conjugated to the hooked profile of the rod formed by the stop grooves (31, 32) which serve to retain the downstream portion of the sleeve (23B).

6. Method according to one of the preceding claims characterized in that, in the step (d) of locking, radially pushes an upstream portion (23A) of the sleeve (23) of elastomer by centripetal plastic deformation of the sleeve of fastener (22), so as to radially penetrate said upstream portion of the sleeve (23A) into a locking groove (33) which is hollowed in the rod (20) and which has a wall forming a locking flange (30) for to prevent said upstream portion (23A) of the sleeve from making a return movement opposite to the movement corresponding to the load direction (SI), and more preferably to prevent said upstream portion (23A) of the sleeve from redeploying upstream .

7. Method according to one of the preceding claims characterized in that it comprises a step (e) assembly, during which is fixed, preferably by crimping, the fixing sleeve (22) in a housing (50). ) belonging to the second mechanical part (2B).

8. Method according to one of the preceding claims characterized in that the rod (20) belongs to a rod (2).

9. damping device (1) comprising a rod (20) which extends along a main axis (XX ') and which is intended to be connected to a first mechanical part (4), a fixing sleeve (22) which surrounds said rod (20) and which is intended to be connected to a second mechanical part (2B), as well as a sleeve (23) made of elastomeric material which is arranged between the rod and the fixing sleeve so as to allow, by its elastic deformation, at least one axial displacement of the fixing sleeve relative to the rod, said device being characterized in that the sleeve (23) is maintained, when the device is at rest, in a state of permanent axial elastic deformation which creates and maintains an axial pre-load of said sleeve (23) and thus an axial pre-load of the rod (20) relative to the attachment sleeve (22).

10. Power steering system (3) comprising a steering rod (2) whose rod (20, 2A, 2B) is equipped with a damping device (1) according to claim 9.