Backrest and device for detecting size of seat occupant

Abstract

The invention relates to a seat back extending in a longitudinal direction (Z) and a transverse direction (Y), comprising:-at least one first coplanar interdigital electrode capacitive sensor and at least one second coplanar interdigital electrode capacitive sensor arranged on a first area (16) of the back, the first area lying in a horizontal central plane (X, Y); y) and is positioned on one side of the vertical central plane (X, Z); the second capacitive sensor in the first area is located above the first capacitive sensor in the first area; the second capacitive sensor of the first region advances a first distance relative to the first capacitive sensor of the first region in a direction perpendicular to the central plane (X, Z).

Description

Technical Field

[0001] The present invention relates to a backrest, in particular a backrest for a motor vehicle. The present invention also relates to a device for detecting the size of a seat occupant. Background Art

[0002] Deployment of front and side airbags, the front passenger airbag, and seatbelt pretensioners can injure small passengers, such as children. Therefore, there is a need for devices that can detect the size of occupants in motor vehicle seats. SUMMARY OF THE INVENTION

[0004] An object of the present invention is to provide a device for detecting the size of a seat occupant and a backrest comprising the same. Summary of the Invention

[0005] The object of the present invention is to provide a seat backrest, in particular a motor vehicle seat backrest, which extends in a longitudinal direction and in a transverse direction;

[0006] at least one first coplanar interdigitated electrode capacitive sensor and at least one second coplanar interdigitated electrode capacitive sensor, referred to as the first capacitive sensor and the second capacitive sensor of the first region, the capacitive sensors of the first region being arranged on a first region of the backrest, the first region being located above the horizontal center plane and on one side of the vertical center plane;

[0007] The second capacitive sensor of the first region is located above the first capacitive sensor of the first region;

[0008] The second capacitive sensor of the first region is advanced a first distance relative to the first capacitive sensor of the first region in a direction perpendicular to the central plane.

[0009] The features disclosed in the following paragraphs may be implemented selectively. They may be implemented independently of each other or in combination with each other:

[0010] - the first distance measured in the transverse direction is equal to or greater than 5 mm, and preferably equal to or greater than 10 mm.

[0011] - it comprises at least one third coplanar interdigitated electrode capacitive sensor, referred to as the third capacitive sensor of the first area, which is arranged on the first area of ​​the backrest, the third capacitive sensor of the first area being located above the second capacitive sensor of the first area;

[0012] The third capacitive sensor of the first area is advanced relative to the second capacitive sensor of the first area by a second distance in a direction perpendicular to the central plane, the second distance measured in the lateral direction being equal to or greater than 5 mm, and preferably equal to or greater than 10 mm.

[0013] - it comprises at least one fourth coplanar interdigitated electrode capacitive sensor, referred to as the fourth capacitive sensor of the first area, which is arranged on the first area of ​​the backrest, the fourth capacitive sensor of the first area being located above the third capacitive sensor of the first area;

[0014] The fourth capacitive sensor of the first area is advanced relative to the third capacitive sensor of the first area by a third distance in a direction perpendicular to the central plane, the third distance measured in the lateral direction being equal to or greater than 5 mm, preferably equal to or greater than 10 mm.

[0015] The two capacitive sensors in the first area are arranged side by side in the longitudinal direction and are spaced apart from each other by a gap of 5 mm to 20 mm.

[0016] - it further comprises at least one first capacitive sensor and at least one second capacitive sensor of a second area, the first capacitive sensor and the second capacitive sensor of the second area being arranged on a second area of ​​the backrest, the second area being located above the horizontal center plane and on the other side of the vertical center plane;

[0017] The second capacitive sensor of the second region is located above the first capacitive sensor of the second region;

[0018] The second capacitive sensor of the second area is advanced relative to the first capacitive sensor of the second area in a direction perpendicular to the center plane by a fourth distance, the fourth distance measured in the lateral direction being in particular equal to or greater than 5 mm, preferably equal to or greater than 10 mm.

[0019] - it comprises at least one third coplanar interdigitated electrode capacitive sensor, referred to as the third capacitive sensor of the second area, which is arranged on the second area of ​​the backrest, the third capacitive sensor of the second area being located above the second capacitive sensor of the second area;

[0020] The third capacitive sensor of the second area is advanced relative to the second capacitive sensor of the second area in a direction perpendicular to the center plane by a fifth distance measured in the lateral direction, the fifth distance being in particular equal to or greater than 5 mm, preferably equal to or greater than 10 mm.

[0021] - it comprises at least one fourth coplanar interdigitated electrode capacitive sensor, referred to as the fourth capacitive sensor of the second area, which is arranged on the second area of ​​the backrest, the fourth capacitive sensor of the second area being located above the third capacitive sensor of the second area;

[0022] The fourth capacitive sensor of the second area is advanced relative to the third capacitive sensor by a sixth distance; the sixth distance is measured in the transverse direction and is in particular equal to or greater than 5 mm, preferably equal to or greater than 10 mm.

[0023] The at least two capacitive sensors of the first area and the at least two capacitive sensors of the second area are arranged symmetrically to one another with respect to a vertical center plane.

[0024] - It also includes electrical connection lines, each of which is connected to the capacitive sensor of the first area and / or the capacitive sensor of the second area, and a flexible support carrying the capacitive sensor and the electrical connection lines, a part of which is arranged on the upper edge of the backrest, close to the headrest.

[0025] at least one coplanar interdigitated electrode capacitive sensor comprising a first electrode and a second electrode, each comprising a stem extending along a primary direction and a branch fixed to the stem, the branch extending along a secondary direction, the secondary direction being perpendicular to the primary direction;

[0026] The branches of the first electrode are spaced apart from each other at equal intervals, the branches of the first electrode are interposed between the branches of the second electrode, and the size of the rods and the branches of at least one of the first and second electrodes in the main direction is between 250 microns and 1000 microns.

[0027] The branch of at least one of the first electrode and the second electrode has a dimension in the secondary direction of between 3 mm and 20 mm.

[0028] The branches of the first electrode comprise free ends, wherein the spacing between the free ends of the branches of the first electrode and the facing rod portion of the second electrode is between 250 μm and 1000 μm, preferably between 500 μm and 800 μm.

[0029] The invention also relates to a device for detecting the dimensions of an occupant of a seat, in particular a motor vehicle seat, comprising:

[0030] - at least one flexible support in the form of a strip having two lateral edges, the flexible support extending in the longitudinal direction;

[0031] at least one first coplanar interdigitated electrode capacitive sensor and at least one second coplanar interdigitated electrode capacitive sensor, referred to as a first capacitive sensor and a second capacitive sensor, and

[0032] - an electrical connection line connected to the first capacitive sensor and the second capacitive sensor and extending in the longitudinal direction, the first capacitive sensor and the second capacitive sensor extending perpendicular to the longitudinal direction;

[0033] The second capacitive sensor is advanced from the first capacitive sensor in the direction of the lateral edge by a first distance; the first distance measured in the transverse direction is equal to or greater than 5 mm, and preferably equal to or greater than 10 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] [ Figure 1 ] is a schematic diagram of a seat with a backrest according to the present invention;

[0035] [ Figure 2 ]for Figure 1 a perspective view of a portion of the backrest shown;

[0036] [ Figure 3 ]for Figure 1 A front view of a coplanar interdigitated electrode capacitance sensor shown positioned on a seat. DETAILED DESCRIPTION

[0037] In the following description, for clarity of description, spatial positioning indications such as top, bottom, upper, lower, horizontal, vertical, etc. are given based on the normal use position of the seat, but these indications are not restrictive.

[0038] The seat is relative to Figure 1 The orthogonal reference frame shown is defined. In the longitudinal direction X, the horizontal direction is understood to extend between the front and rear of the vehicle seat. The transverse direction Y is the horizontal direction extending from one side of the vehicle seat to the other side of the seat. The vertical direction Z is the direction perpendicular to the longitudinal direction X and the transverse direction Y.

[0039] Figure 1 An example of a seat 2 is shown, comprising a seat cushion 4 and a backrest 6 connected to the seat cushion, for example via an articulation system. Specifically, the seat 2 is suitable for use in a vehicle, in particular a motor vehicle.

[0040] The backrest comprises a headrest 7 which is attached to an upper edge of the backrest.

[0041] The backrest 6 includes a backrest frame, a foam layer covering the backrest frame, and a seat cover covering the foam layer. The backrest 6 extends in a transverse direction Y and a longitudinal direction Z.

[0042] To facilitate understanding of the present invention, a horizontal center plane (X, Y) and a vertical center plane (X, Z) are defined. The horizontal center plane (X, Y) extends horizontally. It passes approximately through the middle of the backrest in the longitudinal direction Z. The middle of the backrest in the longitudinal direction Z is defined by half the backrest length. The backrest length is measured between the upper edge 8 and the lower edge 10 of the backrest.

[0043] The vertical center plane (X, Z) extends vertically. It passes substantially through the middle of the backrest in the transverse direction Y. The middle of the backrest in the transverse direction Y is defined by half the backrest width. The backrest width is measured between a lateral edge 12 and an opposite lateral edge 14 of the backrest.

[0044] See also Figure 1 The seat back includes a first region 16 and a second region 18. The first region 16 is an upper lateral region located on one side of a vertical center plane (X, Z), for example, on the right side. The second region 18 is an upper lateral region located on the other side of the center vertical plane (X, Z), for example, on the left side. The first and second regions are located above the horizontal center plane (X, Y).

[0045] exist Figure 1 and Figure 2 In the example shown, but not limited thereto, the first region 16 of the backrest includes a first flexible support 20 , four capacitive sensors 22 , 24 , 26 , 28 with coplanar interdigitated electrodes (hereinafter referred to as “capacitive sensors of the first region”), and electrical connections 27 , 29 .

[0046] The capacitive sensors 22 , 24 , 26 , 28 and the electrical connection lines 27 , 29 are supported by the first flexible support 20 .

[0047] The electrical connection lines 27 , 29 are connected to an electrical connector not shown.

[0048] The first flexible support 20 is in the form of a strip with two lateral edges 23, 25. The first flexible support 20 rests on the foam layer. It extends vertically and rests on the backrest. A portion of the first flexible support rests on the upper edge 8 of the backrest on the side of the headrest 7.

[0049] Preferably, the four capacitive sensors 22, 24, 26, 28 of the first area are identical. They will be combined below. Figure 3 Details disclosed.

[0050] For example, the first capacitive sensor 22 of the first area is located at a first interval I1 from the intersection of the vertical center plane (X, Z) and the plane formed by the seat surface. For example, the length of the first interval I1 is between 4 and 6 centimeters.

[0051] The first and second capacitive sensors are arranged perpendicular to at least one lateral edge 23, 25. The second capacitive sensor 24 of the first region is positioned above the first capacitive sensor 22 of the first region. The second capacitive sensor 24 of the first region is advanced by a first distance D1 relative to the first capacitive sensor 22 of the first region in a direction perpendicular to the center plane (X, Z). In this specification, the term "advanced" means "displaced," "translated," or "moved" relative to the first capacitive sensor 22 of the first region in the transverse direction Y and the direction perpendicular to the center plane (X, Z). In other words, the second capacitive sensor 24 of the first region is brought closer to the center plane (X, Z) by a distance equal to the first distance D1. The first distance D1 is measured in the transverse direction Y. The first distance D1 is equal to or greater than 5 mm, and preferably equal to or greater than 10 mm.

[0052] The first capacitive sensor 22 of the first region is separated from the second capacitive sensor 24 of the first region by a gap E in the longitudinal direction Z. The gap E is preferably between 5 mm and 20 mm.

[0053] Similarly, third capacitive sensor 26 of the first region is disposed on first region 16 of the backrest. Third capacitive sensor 26 of the first region is positioned above second capacitive sensor 24 of the first region. Third capacitive sensor 26 of the first region is positioned a second distance D2 relative to second capacitive sensor 24 of the first region in a direction perpendicular to the center plane (X, Z). The second distance D2 is measured in the transverse direction Y. Second distance D2 is equal to or greater than 5 mm, and preferably equal to or greater than 10 mm.

[0054] The second capacitive sensor 24 of the first area is separated from the third capacitive sensor 26 of the first area by a gap E in the longitudinal direction Z. In the embodiment shown, the gap E between the second capacitive sensor 24 and the third capacitive sensor 26 is the same as the gap between the first capacitive sensor 22 and the second capacitive sensor 24. According to a variant that is not shown, these gaps have different lengths.

[0055] Finally, in the same manner, fourth capacitive sensor 28 of the first region is positioned above third capacitive sensor 26 of the first region. Fourth capacitive sensor 28 of the first region is advanced a third distance D3 relative to third capacitive sensor 26 of the first region in a direction perpendicular to the center plane (X, Z). Third distance D3 is measured in the transverse direction Y. Third distance D3 is equal to or greater than 5 mm, and preferably equal to or greater than 10 mm.

[0056] The third capacitive sensor 26 of the first area is separated from the fourth capacitive sensor 28 of the first area by a gap E in the longitudinal direction Z. In the embodiment shown, the gap E between the third capacitive sensor 26 and the fourth capacitive sensor 28 is the same as the gap between the first capacitive sensor 22 and the second capacitive sensor 24. According to a variant not shown, these gaps have different lengths.

[0057] exist Figure 1 and Figure 2 In the example shown, but not limited thereto, the second region 18 of the backrest includes a second flexible support 30 , four capacitive sensors 32 , 34 , 36 , 38 having coplanar interdigitated electrodes (hereinafter referred to as “capacitive sensors of the second region”), and electrical connections 37 , 39 .

[0058] The capacitive sensors 32, 34, 36, 38 and the electrical connections 37, 39 are supported by a second flexible support 30. The second flexible support 30 rests on the foam layer. It is arranged on the upper edge 8 of the backrest, on the side of the headrest 7 opposite to the side supporting the first flexible support 30.

[0059] Similar to the first region 16, the second region 18 includes a first capacitive sensor 32 of the second region, which is located at a second interval I2 from the intersection of the vertical center plane (X, Z) and the plane formed by the seat surface. For example, the length of the second interval I2 is between 4 and 6 centimeters.

[0060] exist Figure 1 and Figure 2 In the example shown, the second interval I2 has the same length as the first interval I1. According to a variant that is not shown, the second interval I2 has a different length than the first interval I1.

[0061] Second capacitive sensor 34 of the second region is positioned above first capacitive sensor 32 of the second region. Second capacitive sensor 34 of the second region is advanced by a first distance relative to first capacitive sensor 32 in a direction perpendicular to the center plane (X, Z). The term "advanced" refers to being "displaced," "translated," or "moved" relative to first capacitive sensor 32 in the transverse direction Y and in a direction perpendicular to the center plane (X, Z). In other words, second capacitive sensor 34 of the second region is closer to the center plane (X, Z) by a spacing length equal to fourth distance D4. Fourth distance D4 is measured in transverse direction Y. Fourth distance D4 is equal to or greater than 5 mm, and preferably equal to or greater than 10 mm.

[0062] The second capacitive sensor 32 of the second region is spaced apart from the second capacitive sensor 34 of the second region by a gap E in the longitudinal direction Z. The gap E is preferably between 5 mm and 20 mm.

[0063] In an exemplary embodiment, the gap between first capacitive sensor 32 of the second region and second capacitive sensor 34 of the second region is the same as the gap between first capacitive sensor 22 of the first region and capacitive sensor 34 of the first region. Alternatively, the gap between first capacitive sensor 32 of the second region and second capacitive sensor 34 of the second region and the gap between first capacitive sensor 22 of the first region and capacitive sensor 34 of the first region have different lengths.

[0064] Second-area third capacitive sensor 36 is disposed on second area 18. Second-area third capacitive sensor 36 is located above second-area second capacitive sensor 24. Second-area third capacitive sensor 36 is advanced a fifth distance D5 relative to second-area second capacitive sensor 34 in a direction perpendicular to the center plane (X, Z). Fifth distance D5 is measured in the transverse direction Y. Fifth distance D5 is equal to or greater than 5 mm, and preferably equal to or greater than 10 mm.

[0065] The second capacitive sensor 34 of the second area is separated from the third capacitive sensor 36 of the second area by a gap E in the longitudinal direction Z. In the embodiment shown, the gap E between the second capacitive sensor 34 and the third capacitive sensor 36 is the same as the gap between the first capacitive sensor 32 and the second capacitive sensor 34. According to a variant that is not shown, these gaps have different lengths.

[0066] Finally, fourth capacitive sensor 38 of the second zone is positioned above third capacitive sensor 36 of the second zone. Fourth capacitive sensor 38 of the second zone is advanced a sixth distance D6 relative to third capacitive sensor 36 of the second zone in a direction perpendicular to the center plane (X, Z). Sixth distance D6 is measured in the transverse direction Y. Sixth distance D6 is equal to or greater than 5 mm, and preferably equal to or greater than 10 mm.

[0067] exist Figure 1 and Figure 2 In the embodiment shown, the first distance D1 is equal to the second distance and the third distance. Alternatively, the first distance D1 is different from the second distance D2 and the third distance D3.

[0068] Alternatively, the second distance D2 is different from the third distance D3.

[0069] Similarly, in Figure 1 and Figure 2 In the illustrated embodiment, the fourth distance D4 is equal to the fifth distance D5 and the sixth distance D6. Alternatively, the third distance D3 is different from the fifth distance D5 and the sixth distance D6.

[0070] Alternatively, the fifth distance D5 is different from the sixth distance D6.

[0071] According to a first variant, the first area 16 comprises two or three capacitive sensors of the first area, which are offset from one another in the transverse direction Y.

[0072] According to a second variant, the first area 16 and / or the second area 18 comprises five to eight capacitive sensors of the first area, which are all offset relative to one another in the transverse direction Y.

[0073] Alternatively, only one of the first region and the second region includes a capacitive sensor.

[0074] Figure 3 An example of a capacitive sensor 22 according to the present invention, arranged with coplanar interdigitated electrodes on a seat, is shown. This capacitive sensor is not fully disclosed. In particular, not all dimensional characteristics are disclosed. Only those specific features are disclosed here. Other features are disclosed in patent application FR 3126776 in the name of the applicant.

[0075] The coplanar interdigitated electrode capacitive sensor 22 includes a first electrode 40 and a second electrode 42 .

[0076] The first electrode 40 and the second electrode 42 each include a rod 44 and branches 46 attached to the rod. The branches 46 extend perpendicular to the rod 44. The branches 46 of the first electrode are spaced apart from each other by the same interval IN. The branches 46 of the first electrode are interposed between the branches 46 of the second electrode.

[0077] The rods 44 of at least one of the first electrode 40 and the second electrode 42 have a dimension ed in the main direction P1 between 250 and 1000 micrometers, preferably between 500 and 5800 micrometers.

[0078] The branch 46 of at least one of the first and second electrodes has a dimension I in the secondary direction P2 between 3 mm and 20 mm, preferably between 3 and 7 mm. The secondary direction P2 is perpendicular to the main direction P1.

[0079] The branches 46 of the first electrode 40 comprise free ends 48. The spacing S between the free ends 48 of the branches of the first electrode and the portion of the second electrode facing the rod is between 250 and 1000 microns, preferably between 500 and 800 microns.

[0080] The length Ltot of the rod 44 in the main direction P1 is between 3 and 6 centimeters.

[0081] The width Latot of the capacitive sensor 22 in the secondary direction P2 is between 0.5 and 2 cm.

[0082] The present invention relates to a device 50 for detecting the dimensions of an occupant of a seat, in particular a motor vehicle seat; the detection device comprises a first flexible support 20 extending in a longitudinal direction Z;

[0083] at least one first capacitive sensor 22 and a second capacitive sensor 24, and

[0084] - electrical connection lines 27, 29 connected to the first capacitive sensor 22 and the second capacitive sensor 24. The electrical connection lines 27, 29 extend along the longitudinal direction Z. The first capacitive sensor and the second capacitive sensor each extend perpendicularly to the longitudinal direction Z.

[0085] The second capacitive sensor 24 is advanced a first distance D1 from the first capacitive sensor 22 in the direction of the lateral edge; the first distance (D1) measured in the transverse direction (Y) is equal to or greater than 5 mm, and preferably equal to or greater than 10 mm.

[0086] The detection device may also comprise all the above features, in particular a large number of capacitive sensors and a second flexible support.

Claims

1. A backrest (6) of a seat (2), in particular a motor vehicle seat backrest, the backrest extending in a longitudinal direction (Z) and a transverse direction (Y); - at least one first coplanar interdigitated electrode capacitive sensor (22) and at least one second coplanar interdigitated electrode capacitive sensor (24), referred to as first and second capacitive sensors of a first area, the capacitive sensors of the first area being arranged in a first area (16) of the backrest, the first area being located above the horizontal center plane (X, Y) and on one side of the vertical center plane (X, Z); The second capacitive sensor (24) of the first region is located above the first capacitive sensor (22) of the first region; The second capacitive sensor (24) of the first region is advanced a first distance (D1) relative to the first capacitive sensor (22) of the first region in a direction perpendicular to the center plane (X, Z).

2. The backrest (6) according to claim 1, characterized in that The first distance (D1) measured in said transverse direction (Y) is equal to or greater than 5 mm.

3. The backrest (6) according to claim 2, comprising at least one third coplanar interdigitated electrode capacitive sensor (26), referred to as the third capacitive sensor of the first area, which is arranged on the first area (16) of the backrest, the third capacitive sensor of the first area (26) being located above the second capacitive sensor (24) of the first area; The third capacitive sensor (26) of the first area is advanced a second distance (D2) relative to the second capacitive sensor (24) of the first area in a direction perpendicular to the center plane (X, Z), and the second distance (D2) measured in the transverse direction (Y) is equal to or greater than 5 mm.

4. The backrest (6) according to claim 3, comprising at least one fourth coplanar interdigitated electrode capacitive sensor (28), referred to as the fourth capacitive sensor of the first area, which is arranged on the first area (16) of the backrest, the fourth capacitive sensor of the first area being located above the third capacitive sensor (26) of the first area; The fourth capacitive sensor (28) of the first area is advanced a third distance (D3) relative to the third capacitive sensor (26) of the first area in a direction perpendicular to the central plane (X, Z), and the third distance (D3) measured in the transverse direction (Y) is equal to or greater than 5 mm, preferably equal to or greater than 10 mm.

5. The backrest (6) according to claim 1, characterized in that The two capacitive sensors (22, 24, 26, 28) of the first area are arranged side by side in the longitudinal direction (Y) and are spaced apart from each other by a gap (E) between 5 mm and 20 mm.

6. The backrest (6) according to claim 1, further comprising at least one first capacitive sensor (32) and at least one second capacitive sensor (34) of a second area (18), the first capacitive sensor (32) and the second capacitive sensor (34) of the second area being arranged on a second area (18) of the backrest, the second area being located above the horizontal center plane (X, Y) and on the other side of the vertical center plane (X, Z); The second capacitive sensor (34) of the second region is located above the first capacitive sensor (32) of the second region; The second capacitive sensor (34) of the second area is advanced by a fourth distance (D4) relative to the first capacitive sensor (32) of the second area in a direction perpendicular to the center plane (X, Z), and the fourth distance (D4) measured in the transverse direction (Y) is particularly equal to or greater than 5 mm.

7. The backrest (6) according to claim 6, comprising at least one third coplanar interdigitated electrode capacitive sensor (36), referred to as the third capacitive sensor of the second area, the third capacitive sensor of the second area (36) being arranged on the second area (18) of the backrest, the third capacitive sensor of the second area (36) being located above the second capacitive sensor (34) of the second area; The third capacitive sensor (36) of the second area is advanced a fifth distance (D5) relative to the second capacitive sensor (34) of the second area in a direction perpendicular to the center plane (X, Z), the fifth distance (D5) being measured in the transverse direction (Y), and the fifth distance (D5) being in particular equal to or greater than 5 mm.

8. The backrest (6) according to claim 7, comprising at least one fourth coplanar interdigitated electrode capacitive sensor (38), referred to as the fourth capacitive sensor of the second area, which is arranged on the second area (18) of the backrest, the fourth capacitive sensor of the second area (38) being located above the third capacitive sensor (36) of the second area; The fourth capacitive sensor (38) of the second region is advanced a sixth distance (D6) relative to the third capacitive sensor (36), the sixth distance (D6) being measured in the transverse direction (Y), and the sixth distance (D6) being equal to or greater than 5 mm.

9. The backrest (6) according to any one of claims 6 to 8, characterized in that At least two capacitive sensors (22, 24, 26, 28) of the first region and at least two capacitive sensors (32, 34, 36, 38) of the second region are arranged symmetrically to each other with respect to a vertical center plane (X, Z).

10. The backrest (6) according to claim 1 further comprises electrical connection lines (27, 29, 37, 39), each of which is connected to a capacitive sensor (22, 24, 26, 28) of the first area and / or a capacitive sensor (32, 34, 36, 38) of the second area, and a flexible support (20, 30) carrying the capacitive sensor and the electrical connection lines, a portion of the flexible support (20, 30) being arranged on the upper edge of the backrest, close to the headrest (7).

11. The backrest (6) according to claim 1, characterized in that At least one coplanar interdigitated electrode capacitive sensor (22, 24, 26, 28, 32, 34, 36, 38) comprises a first electrode (40) and a second electrode (42), each of the first electrode (40) and the second electrode (42) comprising a rod (44) extending along a main direction (P1), and a branch (46) fixed to the rod, the branch (46) extending along a secondary direction (P2), the secondary direction (P2) being perpendicular to the main direction (P1); The branches (46) of the first electrode are spaced apart from each other at the same interval (IN), the branches (46) of the first electrode (40) are located between the branches (46) of the second electrode (42), and the dimensions (ed) of the rod (44) and the branches (46) of at least one of the first electrode and the second electrode in the main direction (P1) are between 250 micrometers and 1000 micrometers.

12. The backrest (6) according to claim 9, characterized in that The dimension (I) of the branch (46) of at least one of the first electrode and the second electrode in the secondary direction (P2) is between 3 mm and 20 mm.

13. The backrest (6) according to claim 9, the branch (46) of the first electrode (40) comprising a free end (48), wherein: The spacing (S) between the free ends (48) of the branches (46) of the first electrode and the facing rod portions of the second electrode is 250 micrometers to 1000 micrometers.

14. The backrest (6) according to claim 2, characterized in that The first distance (D1) is equal to or greater than 10 mm.

15. The backrest (6) according to claim 3, characterized in that The second distance (D2) is equal to or greater than 10 mm.

16. The backrest (6) according to claim 4, characterized in that The third distance (D3) is equal to or greater than 10 mm.

17. The backrest (6) according to claim 6, characterized in that The fourth distance (D4) is equal to or greater than 10 mm.

18. The backrest (6) according to claim 7, characterized in that The fifth distance (D5) is equal to or greater than 10 mm.

19. The backrest (6) according to claim 8, characterized in that The sixth distance (D6) is equal to or greater than 10 mm.

20. The backrest (6) according to claim 11, characterized in that The dimension (ed) in the main direction (P1) is between 500 μm and 800 μm.

21. The backrest (6) according to claim 12, characterized in that The dimension (I) in the secondary direction (P2) is between 3 mm and 7 mm.

22. The backrest (6) according to claim 13, characterized in that The spacing (S) is between 500 microns and 800 microns.

23. A device (50) for detecting the size of an occupant of a motor vehicle seat, the detection device (50) comprising: - at least one flexible support (20, 30) in the form of a strip having two lateral edges (23), said flexible support (20, 30) extending in the longitudinal direction (Z); - at least one first coplanar interdigitated electrode capacitive sensor (22, 32) and at least one second coplanar interdigitated electrode capacitive sensor (24, 34), referred to as a first capacitive sensor and a second capacitive sensor, and - electrical connection lines (27, 29, 37, 39) connected to the first capacitive sensor (22, 32) and the second capacitive sensor (24, 34) and extending along a longitudinal direction (Z), the first capacitive sensor and the second capacitive sensor extending perpendicularly to the longitudinal direction (Z); The second capacitive sensor (24) is advanced a first distance (D1) from the first capacitive sensor (22) in the direction of the lateral edge (23); the first distance (D1) measured in the transverse direction (Y) is equal to or greater than 5 mm, and preferably equal to or greater than 10 mm.

24. The device (50) according to claim 23, characterized in that The first distance (D1) is equal to or greater than 10 mm.

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