Vehicle seat backrest

Abstract

A vehicle seat back (16) (10) includes a backrest frame (17), at least one headrest mounting rod (38), and a backrest trim (18). The backrest trim (18) includes at least one rear center shell (58), attached to a rear face (17B) of the backrest frame (17). The rear center shell (58) includes at least one hole (60) through which at least one headrest mounting rod (38) passes. (Shortcut figure: Figure 5)

Description

Title of the invention: Vehicle seat backrest technical field

[0001] This description relates to a vehicle seat backrest, particularly for a motor vehicle. A vehicle seat comprising such a backrest, and a method for manufacturing such a vehicle seat backrest, are also described. Previous technique

[0002] In the automotive field, in particular, it is known to produce a vehicle seat back by attaching upholstery to a backrest frame. The backrest frame provides the rigidity of the backrest, while the upholstery provides the comfort and aesthetic appeal of the backrest.

[0003] Typically, the padding includes a quilting covered with one or more covers to protect the quilting and / or to keep it in position on the back of the seat.

[0004] Such a file is, however, difficult to produce using automated systems. In particular, the precise placement of the padding can be challenging.

[0005] It has been proposed to produce the rear part of the upholstery using a shell, without padding. Padding on the rear part of the backrest appears unnecessary since this rear part does not serve to support the seat occupant.

[0006] However, such a shell is also difficult to handle, to position precisely and to fix on the backrest frame, by means of automata. Summary

[0007] This disclosure is intended to improve the situation.

[0008] To this end, a vehicle seat back is described comprising a backrest frame, at least one headrest fixing rod, and a backrest trim, the backrest trim comprising at least one rear center shell, fixed to a rear face of the backrest frame, the rear center shell comprising at least one hole through which at least one headrest fixing rod passes.

[0009] Advantageously, the hole on the rear central shell allows for guiding the positioning of this rear central shell onto the backrest frame. This makes it possible to achieve very precise positioning of the rear central shell, even with the aid of automated systems.

[0010] According to preferred embodiments, the assembly process comprises one or more of the following features, taken alone or in combination: - at least one hole is formed on an upper edge of the rear central hull; - the rear central shell includes one hole, preferably two holes, each hole being traversed by a single respective headrest fixing rod; - the backrest trim includes at least two rear side shells, the rear side shells preferably being fixed to the rear central shell, in particular by elastic interlocking; - the backrest trim also includes a front central trim module, comprising at least one backrest padding, the front central trim module being fixed to a front face of the backrest frame; - the front central trim module includes at least one hole through which at least one headrest fixing rod passes, the front central trim module preferably partially covering the rear central shell in the vicinity of at least one headrest fixing rod; - the backrest frame includes at least one upper crossbar, attached to at least one headrest fixing rod, and a lower crossbar, the front central trim module including means for fixing to the upper crossbar and / or the lower crossbar, in particular means for fixing by elastic interlocking; - the central front trim module includes a support for the padding, the padding being for example overmolded onto the support; - the backrest trim comprises at least two front side trim modules, each of which includes a support fixed to the backrest frame and padding fixed to the respective support, the rear central shell preferably being fixed to the supports of the front side trim modules, in particular by elastic interlocking; and - the rear side panels are also fixed to the supports of the front side trim modules, in particular by elastic interlocking.

[0011] According to another aspect, a vehicle seat back assembly is also described comprising a back as described above, in all its combinations and a headrest, the headrest comprising a headrest frame and a headrest trim, the headrest frame being attached to at least one headrest fixing rod.

[0012] Also described is a motor vehicle seat comprising a seat with a seat frame and a backrest as described above, in all its combinations, in particular in a seat back assembly as described above, in all its combinations, the backrest frame being fixed to the seat frame, preferably in such a way as to be able to pivot about a transverse axis.

[0013] A method for manufacturing a seat back as described above in all its combinations is further described, comprising the steps of: (i) provide a backrest frame to which at least one fixing rod is attached headrest; ii) provide a rear central shell including at least one hole suitable for receiving at least one headrest fixing rod; iii) place the rear central shell on the backrest frame so that at least one headrest fixing rod is received in at least one hole; and iv) fix the rear central shell, in particular by elastic interlocking.

[0014] The method for manufacturing a seat back may further include a step a) of providing two side trim modules and fixing the side trim modules onto the back frame, step a) preferably being before step iii), the rear center shell being, even more preferably, fixed onto the side trim modules.

[0015] Alternatively or additionally, the method of manufacturing a seat back may include a step b) of providing two rear side shells and attaching the rear side shells, step b) preferably being subsequent to step iv) and step a), if applicable, the rear side shells preferably still attached to the side trim modules, if applicable.

[0016] Alternatively or in addition, the method of manufacturing a vehicle seat back may include a step c) of providing a front center trim module and fixing the front center trim module onto the back frame, preferably by elastic interlocking, step c) preferably being further subsequent to steps iv), a) and / or b), as appropriate. Brief description of the drawings

[0017] Other features and advantages will become apparent during the following description of one embodiment thereof, given by way of non-limiting example, with reference to the accompanying drawings. In the drawings:

[0018] [Fig-1] schematically represents in cross-section, an example of a vehicle seat;

[0019] [Fig.2] is a flowchart of an example of a manufacturing process for the file of the vehicle seat of the [Fig.1];

[0020] [Fig.3a] schematically illustrates a first step of the process of [Fig.2];

[0021] [Fig.3b] schematically illustrates a detail of [Fig.3a];

[0022] [Fig.4] schematically represents in perspective a view of the front face of the draft seat file at the end of the [Fig.3a] stage;

[0023] [Fig.5] schematically illustrates a second step of the process of [Fig.2];

[0024] [Fig.6] schematically illustrates a third step of the process of [Fig.2];

[0025] [Fig.7] schematically illustrates a fourth step of the process of [Fig.2];

[0026] [Fig.8] shows in perspective a front view of the seat back obtained at the end of the step illustrated by [Fig. 7]; and

[0027] [Fig.9] represents in perspective a rear view of the seat back obtained at the end of the step illustrated in [Fig.7]. Description of the implementation methods

[0028] In the various figures, the same reference numerals designate identical or similar elements. For the sake of brevity, only the elements that are useful for understanding the described embodiment are shown in the figures and are described in detail below.

[0029] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "rear", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "lower", etc., or to orientation qualifiers, such as "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures or of a vehicle seat in its normal position of use.

[0030] In particular, the longitudinal direction X refers to the longitudinal direction of the seat. The longitudinal direction of the seat is considered to be the same as the longitudinal direction of the motor vehicle in which the seat is mounted. This longitudinal direction X corresponds to the normal direction of travel of the vehicle. The longitudinal direction X is horizontal. The transverse direction Y of the seat thus corresponds to the transverse or lateral direction of the motor vehicle. This transverse direction is perpendicular to the normal direction of travel of the vehicle. The transverse direction Y is horizontal. Finally, the vertical direction Z is a vertical direction of the seat, perpendicular to the longitudinal and transverse directions.

[0031] Fig. 1 schematically represents a motor vehicle seat 10 mounted on a sliding mechanism 12.

[0032] The seat 10 comprises a seat 13, with a seat frame 14 and a seat cushion 15, on which a backrest 16, with a backrest frame 17 and a backrest cushion 18, is mounted. The backrest frame 17 is pivotable about an axis A, relative to the seat frame 14. To achieve this, a hinge mechanism 20 is arranged between the seat frame 14 and the backrest frame 17. The axis A is, for example, substantially parallel to the transverse direction Y.

[0033] The seat 13 is mounted on movable profiles 22, also called slides or male profiles, by means of feet 24, 26. Each movable profile 22 is part of a slide 12 and is associated with a fixed profile 28. The fixed profile 28 is also called a rail or female profile. The fixed profile 28 is fixed to the floor 30 of a motor vehicle.

[0034] In this example, seat 10 includes a manual control element 32, called a rocker arm, for controlling the sliding movement of the slides 12. This manual control element 32 allows, in particular, locking and unlocking the sliding stop systems of the movable profiles 22 relative to the respective fixed profiles 28. Once the stop systems are unlocked, the manual control element 32 can also be used to slide the movable profiles 22 relative to their respective fixed profiles 28 of the slide 12 in the longitudinal direction X of the slides 12. The fixed profiles 28 and movable profiles 22 of the slides 12 can be metallic.

[0035] Alternatively, the movement of the movable profiles 22 relative to the fixed profiles 28 is controlled by means of an actuator. One or more control buttons for the actuator may then be provided on the seat 10, in particular on the seat 13.

[0036] The seat 10 further includes a headrest 34. The headrest 34 comprises a headrest frame 35 and a headrest cover 36. The headrest frame 35 is connected to the backrest frame 17 by means of at least one headrest fixing rod 38, preferably two headrest fixing rods 38. The headrest fixing rod(s) 38 may be of variable length to allow height adjustment of the headrest position 34. Alternatively or additionally, the headrest frame 35 is movable relative to the headrest fixing rod(s) 35 to allow this height adjustment of the headrest position 34. The headrest cover 36 and / or the backrest cover 18 may cover all or part of the headrest fixing rods 38, for example to improve the aesthetics of the vehicle seat 10.

[0037] In the following, the file 16 of the vehicle seat 10 and its manufacturing process 100 illustrated in [Fig.2] are described in more detail.

[0038] As illustrated in [Fig. 2], the method 100 comprises a first step 102 of providing a backrest frame 17. As illustrated in [Fig. 3a], the backrest frame 17 essentially comprises a first upright 171, a second upright 172, a first crossbar 173, hereinafter referred to as the "lower crossbar 173," and a second crossbar 174, hereinafter referred to as the "upper crossbar 174." The uprights 171, 172 and the crossbars 173, 174 form a frame-shaped backrest frame 17. To achieve this, the uprights 171, 172, and the crossbars 173, 174 can be fastened together, in particular by welding them together. Alternatively, the backrest frame 17 is a single piece, for example, by being molded.

[0039] Here, the headrest fixing rods 38 are already fixed to the upper cross member 174 of the backrest frame 17 at this first step 102. Alternatively, however, these headrest fixing rods 38 can be fixed to the upper cross member 174 of the backrest frame 17 at a later step.

[0040] In a second step 104 of the manufacturing process 100, a first side trim module 40 and a second side trim module 42 are fixed to the front face 17A of the backrest frame 17, visible in [Fig. 3a], respectively, on an upright 171, 172 of the backrest frame 17. Thus, a side trim module 40, 42 is arranged on each side of the backrest frame 17. The front face 17A of the backrest frame 17 is the face of the backrest frame 17 intended to be oriented towards an occupant of the vehicle seat 10. The rear face 17B of the backrest frame 17 is the face opposite the front face 17A.

[0041] Each side padding module 40, 42 here comprises a secure mattress in the form of a foam block 44, 46, each foam block 44, 46 being fixed to a respective support 48, 50. For example, each foam block 44, 46 is overmolded onto the respective support 48, 50. Each support 48, 50 can be fixed to the respective upright 17i, 172 of the backrest frame 17, by elastic interlocking and / or welding and / or screwing and / or riveting and / or press-fitting of a relief into a complementary relief, in particular. Here, each support 48, 50 comprises a respective upright 51, 53 with elastic interlocking ridges 52 allowing an airbag support 54 to be attached, by elastic interlocking, to the upright 51, 53. An airbag is then attached to this support. Each airbag is connected to a pump for inflation. The airbags thus improve the lateral support of the occupant of the vehicle seat 10.In the illustrated example, each elastic interlocking relief 52 takes the form of a "U" shaped hook, into which a rod formed by the inflatable cushion support 54 is elastically inserted. Other forms of the elastic interlocking reliefs 52 are accessible to those skilled in the art.

[0042] The first side trim module 40, intended to be positioned as centrally as possible in the motor vehicle equipped with the seat 10, further includes a side airbag 56. Such an airbag 56 is designed to prevent direct head-to-head collisions between the occupants of two seats arranged transversely, one next to the other. The airbag 56 is at least partially covered by the foam block 44 of the first side trim module 40.

[0043] The manufacturing process 100 then continues with a step 106 of attaching a rear central shell 58 to the backrest frame 17. The rear central shell 58 provides a very aesthetically pleasing seat back 10. The rear central shell may be without foam, since it is not intended to provide support for an occupant of the vehicle seat 10.

[0044] Here, remarkably, an upper rim 58i of the rear center shell 58 has two holes 60 adapted to receive one of the respective headrest fixing rods 38. Thus, it is possible to install the center shell The rear center shell 58 is positioned on the backrest frame 17, guided by the reception of the headrest fixing rods 38 in the openings 60. This greatly facilitates the installation of the rear center shell 58. Such installation can thus be carried out efficiently by an automated system. In the illustrated example, the rear center shell 58 is then secured by the elastic interlocking of second elastic interlocking ridges 62 of the supports 48, 50 of the side trim modules 40, 42, with complementary ridges 64 of the rear center shell 58. Here, the second elastic interlocking ridges 62 take the form of deformable studs with an extremal bead, each received in a respective opening 64 in the rear center shell 58, with a diameter smaller than the diameter of the extremal bead of the studs.Here again, this fixing, achieved by moving the rear central shell 58 relative to the backrest frame 17, can be carried out using one or more automated systems.

[0045] The rear central shell 58 can, however, be attached in an alternative or complementary manner, using any fastening method accessible to those skilled in the art, in particular by screwing, welding, riveting, or force-fitting a fastening element into a complementary element. Such fastening methods can also be implemented using one or more automated systems.

[0046] Also, in the example described, the rear central shell 58 is fixed on the side trim modules 40, 42. Alternatively or in addition, the rear central shell 58 is fixed directly on the backrest frame 17, in particular on the uprights 17i, 172 and / or on the lower cross member 173.

[0047] It may be noted here that the rear central shell 58 has openings 66, distinct from the holes 60, allowing free access to third elastic interlocking reliefs 68 of the side trim modules 40, 42, in particular of the supports 48, 50 of the side trim modules 40, 42.

[0048] The manufacturing process 100 then continues with a step 108 of attaching rear side shells 70, 72, here so as to cover at least part of the lateral ends of the rear central shell 58. To do this, each rear side shell 70, 72 includes attachment means 74, here in the form of elastic interlocking reliefs complementary to the third elastic interlocking reliefs 68 of the supports 48, 50 of the side trim modules 40, 42. In addition, each rear side shell 70, 74 may include a relief 76 intended to be received in an additional housing 78 of the corresponding side trim module 40, 42, to facilitate the positioning and attachment of the rear side shells 70, 72.

[0049] Here again, the rear side panels 70, 72 essentially serve an aesthetic function, particularly in that they conceal the means for attaching the rear central panel 58. As these rear side panels 70, 72 are not intended to to serve as support for a vehicle seat occupant, they may also be without padding, particularly foam.

[0050] The manufacturing process 100 then continues with a final step 110 of fixing a central front trim module 80.

[0051] As illustrated in [Fig.7], the central front trim module 80 essentially comprises a support 82 and padding, here in the form of a foam block 84, fixed to the support 82. The foam block 84 can in particular be overmolded onto the support 82.

[0052] The support 82 of the front central trim module 80 may comprise at least three parts assembled together forming an upper part 82x, a middle part 822 and a lower part 823 of the support 82.

[0053] The upper part 82x can be shaped to facilitate the placement of the central trim module 80 on the backrest frame 17. To this end, the upper part 82x and the foam block 84 can have openings (not visible in the figures) adapted to receive the headrest fixing rod(s) 38. Thus, this upper part 82i is positioned above the rear central shell 58, in the vicinity of the headrest fixing rods 38. The central trim module 80 thus covers at least partially, preferably completely, the edge 58i of the rear central shell 58. To achieve this, the upper end of the front central trim module 80 can be curved.

[0054] The central portion 822 essentially serves to support the foam block 84, where the occupant of the vehicle seat 10 primarily rests against the seat back 16. The central portion 822 thus advantageously provides sufficient mechanical resistance to prevent the foam block 84 from sinking completely when an occupant of the vehicle seat 10 leans against the seat back 16. However, the central portion 822 is advantageously still relatively flexible to ensure the comfort of the occupant of the vehicle seat 10.

[0055] In addition, the middle part 822 can support one or more components enabling the fulfillment of one or more comfort and / or safety functions for the occupant of the seat 10. For example, a fan can be fixed to this middle part, adapted to blow air towards the occupant of the seat, through openings 86 in the central trim module 80.

[0056] The middle portion 822 can take different forms. Here, the middle portion 822 is made in the form of a flexible plate, notably more flexible than the upper portion 82i and / or the lower portion 823. Alternatively, the middle portion 822 consists of spring wires extending between the upper portion 82i and the lower portion 823, to ensure that the foam block 84 is held in position, with elastic support for this foam block 84.

[0057] Finally, the lower portion 823 is shaped here to secure the front central upholstery module 80, in this case to the backrest frame 17. Here, this lower portion 823 is curved at its lower end and has elastic interlocking ridges (not shown in the figures) adapted to cooperate with complementary ridges on the lower crossbar 173 of the backrest frame 17. As can be seen in particular in [Fig. 9], once the front central upholstery module 80 is secured to the backrest frame 17, the foam block 84 extends locally under the rear central shell 58. In other words, part of the foam block 84 of the central upholstery module 80 extends between the backrest frame 17, in particular the lower crossbar 173, and the rear central shell 58. This results in a very aesthetically pleasing finish for the backrest upholstery 18. In particular, the means for securing the assembly elements forming the backrest trim 18 are concealed..

[0058] However, other means of attaching the central trim module 80 to the backrest frame 17 can be considered, such as screwing, welding, riveting, or press-fitting a mounting relief into a complementary relief. Alternatively or in addition, the central trim module 80 can be attached to the rear center shell 58 and / or the side trim modules 40, 42, or even to the rear side shells 70, 72.

[0059] It should be noted that the elements forming the backrest trim 18 can be attached successively, particularly by means of automated systems. In this respect, manufacturing the trim using only trim and shell modules allows for easy handling, especially by automated systems.

[0060] A headrest 34 can finally be fixed onto the headrest fixing rods 38. Advantageously, the headrest trim 36 covers the headrest fixing rod(s) 38, so that the whole of the backrest 18 and the headrest 34 thus obtained is particularly aesthetic.

[0061] The present invention is not limited to the examples described above. On the contrary, the invention is susceptible to numerous variations accessible to those skilled in the art.

[0062] Thus, in the illustrated example, the front part of the backrest trim 18 is made using modules 40, 42, 80. As previously stated, such a construction using modules 40, 42, 80 makes it easy to automate the manufacture of the backrest 16 while obtaining a very aesthetic appearance of the backrest 16. Alternatively, however, the backrest trim 18, in particular its front part intended to be in contact with an occupant of the vehicle seat 10, can be made in another form, in particular in a unitary form, without separate modules.

[0063] Also, each trim module 40, 42, 80 may include a cover covering all or part of the respective foam block 44, 46, 84. The cover may Specifically, the cover can be placed in the mold used for overmolding the foam block 44, 46, 84 onto the respective support 48, 50, 82. The cover then adheres to the foam block 44, 46, 84. Alternatively, the cover can be attached to the foam block 44, 46, 84 and / or to the support 48, 50, 82 after the foam block 44, 46, 84 has been formed. In other words, the cover can be attached to the foam block 44, 46, 84 and / or to the support 48, 50, 82. The cover is then attached by any means accessible to those skilled in the art.

[0064] According to yet another variant, a single cover is used to cover the three foam blocks 44, 46, 84 of the upholstery modules 40, 42, 80. Here again, in this case, the cover is advantageously attached to the foam blocks 44, 46, 84 and / or to the respective supports 48, 50, 82 of the upholstery modules 40, 42, 80, or even to the backrest frame 17 and / or the rear central shell 58. Here again, the cover is attached by any means accessible to those skilled in the art.

[0065] Advantageously, each packing module 40, 42, 80 is packed independently of the other two, as described above. Alternatively, however, it is conceivable that a foam block, for example, could be common to several packing modules, in particular to all packing modules 40, 42, 80.

[0066] It can be noted that here the side upholstery modules 40, 42 pre-exist before being attached to the backrest frame 17. Thus, these side upholstery modules 40, 42 are not formed by overmolding the backrest frame 17 and / or structural elements already attached to the backrest frame 17. This does not preclude the foam blocks 44, 46, 84 of the various upholstery modules 40, 42, 80 from being formed by overmolding a possible support for the respective upholstery module 48, 50, 82. However, this overmolding is carried out prior to attaching the support in question to the backrest frame 17.

Claims

Demands

1. Vehicle seat back (16) (10) comprising a backrest frame (17), at least one headrest fixing rod (38), and a backrest trim (18), the backrest trim (18) comprising at least one rear center shell (58), fixed to a rear face (17B) of the backrest frame (17), the rear center shell (58) comprising at least one hole (60) through which at least one headrest fixing rod (38) passes, backrest wherein the backrest trim (18) comprises at least two rear side shells (70, 72), the rear side shells (70, 72) being fixed to the rear center shell (58).

2. Vehicle seat back according to claim 1, wherein at least one hole (60) is formed on an upper rim (58i) of the rear center shell (58).

3. Vehicle seat back according to claim 1 or 2, wherein the rear central shell (58) includes a hole (60), preferably two holes (60), each hole (60) being traversed by a single respective headrest fixing rod (38).

4. Vehicle seat back according to any one of claims 1 to 3, wherein the rear side shells (70, 72) are fixed to the rear central shell (58) by elastic interlocking.

5. Vehicle seat back according to any one of claims 1 to 4, wherein the backrest trim (18) also includes a front center trim module (80), comprising at least one backrest padding (84), the front center trim module (80) being fixed to a front face (17A) of the backrest frame (17).

6. Vehicle seat back according to claim 5, wherein the front center trim module (80) includes at least one hole through which at least one headrest fixing rod (38) passes, the front center trim module (80) preferably partially covering the rear center shell (58) in the vicinity of at least one headrest fixing rod (80).

7. A vehicle seat back according to claim 5 or 6, wherein the backrest frame (17) comprises at least one upper cross member (174), integral with at least one headrest fixing rod (38), and a lower cross member (173), the front central trim module (80) comprising means for fixing to the upper cross member (174) and / or the lower cross member (173), in particular means for fixing by interlocking elastic.

8. Vehicle seat back according to any one of claims 5 to 7, wherein the front central trim module (80) includes a support (82) for the padding (84), the padding (84) being, for example, overmolded onto the support (82).

9. Vehicle seat back according to any one of the preceding claims, wherein the backrest trim (18) comprises at least two front side trim modules (40, 42), the at least two front side trim modules (40, 42) each comprising a support (48, 50) fixed to the backrest frame (17) and a padding (44, 46) fixed to the respective support (48, 50), the rear central shell (58) preferably being fixed to the supports (48, 50) of the front side trim modules (40, 42), in particular by elastic interlocking.

10. Vehicle seat back according to claim 9, wherein the rear side shells (70, 72) are further fixed to the supports (48, 50) of the front side trim modules (40, 42), in particular by elastic interlocking.

11. Vehicle seat back assembly, comprising a backrest (16) according to any one of the preceding claims and a headrest (34), the headrest (34) comprising a headrest frame (35) and a headrest trim (36), the headrest frame (35) being attached to at least one headrest fixing rod (38).

12. Motor vehicle seat comprising a seat (13) with a seat frame (14) and a backrest (16) according to any one of claims 1 to 10, in particular in a seat back assembly according to claim 11, the backrest frame (17) being fixed to the seat frame (14), preferably so as to be able to pivot about a transverse axis (A).

13. A method for manufacturing a seat back (16) according to any one of claims 1 to 10, comprising the steps of: i) providing a backrest frame (17) to which at least one headrest fixing rod (38) is fixed; ii) providing a rear center shell (58) comprising at least one hole (60) adapted to receive at least one headrest fixing rod (38); iii) mounting the rear center shell (58) on the backrest frame (17) such that at least one headrest fixing rod (38) is received in at least one hole (60); and (iv) fix the rear central shell (58), in particular by elastic interlocking, process comprising a step (b) consisting of providing two rear side shells (70, 72) and fixing the rear side shells (70, 72).

14. Method of manufacturing a seat back (16) according to claim 13, further comprising a step a) of providing two side trim modules (40, 42) and of fixing the side trim modules on the back frame (17), step a) preferably being prior to step iii), the rear central shell (58) preferably being fixed on the side trim modules (40, 42).

15. Method of manufacturing a seat back (16) according to claim 13 or 14, wherein step b) is subsequent to step iv) and step a), if applicable, the rear side shells (70, 72) preferably still attached to the side trim modules (40, 42), if applicable.

16. Method of manufacturing a vehicle seat back (16) according to any one of claims 13 to 15, comprising a step c) of providing a front center trim module (80) and of fixing the front center trim module (80) onto the backrest frame (17), preferably by elastic snap-fit, step c) preferably being further subsequent to steps iv), a) and / or b), as appropriate.