Vehicle seat tilting backrest locking device

Abstract

The invention relates to a device (1) for locking the backrest of a vehicle seat, comprising a rack (4), a hook (5) comprising at least one tooth (6) adapted to selectively engage or disengage the rack (4), a first surface (7) substantially opposite said at least one tooth (6), and an operating cam (9) comprising a third, substantially circular surface (10), the cam (9) being articulated about a third axis (C) so as to be able to occupy a first default orientation in which the third surface (10) bears against the first surface (7) so as to prevent disengagement, wherein the cam (9) is deformable about a deformation axis (E) substantially perpendicular to the third surface (10) and substantially intersecting the third axis (C). Abstract figure: Figure 1

Description

Title of the invention: Device for locking the tilting backrest of a vehicle seat Technical field

[0001] The invention relates to a device for locking the tilting backrest of a vehicle seat. Prior art

[0002] It is known, mainly for three-door vehicles, that a front seat has a backrest that tilts forward by lying down on the seat, in order to allow access to the rear seat from the single front door. The front seat is equipped with a device for locking the backrest of a vehicle seat, arranged at the articulation between the seat and the backrest. This locking device makes it possible to selectively unlock the articulation to allow rotation of the backrest: tilting forward or raising, and, by default, to lock it, preferably in the raised position.

[0003] For this purpose, the locking device comprises a base secured to the seat base, an upright secured to the seat back and articulated relative to the base along a first axis. The device further comprises a rack, secured to the base and a hook articulated relative to the upright along a second axis, parallel to the first axis. The hook comprises at least one tooth capable of selectively engaging or disengaging the rack when the hook rotates around the second axis. The hook further comprises a first surface, substantially opposite said at least one tooth and substantially circular centered on the first axis and a second surface substantially perpendicular to the first surface. The device further comprises an operating cam comprising a third substantially circular surface centered on a third axis, parallel to the first axis.The cam is articulated relative to the upright along the third axis so as to be able to selectively occupy two orientations. In a first default orientation, the third surface comes to bear on the first surface of the hook, so as to prevent the rack from being released. In a second orientation, the third surface comes to bear on the second surface so as to rotate the hook so as to release the rack.

[0004] In its default orientation the cam prevents disengagement. In the event of a crash, from the rear, the cam is compressed between the hook, which presses on the bearing surface of the cam, and the third axis of rotation, integral with the upright. Under the action of a force, significant in the event of a crash, transmitted from the hook to the cam, provided that this force does not pass exactly through the third axis, the cam risks rotating and, in doing so, to turn the hook and release the clutch. Such a situation is not admissible.

[0005] Also, a means is sought to prevent the cam from rotating, even under significant force. Summary of the invention

[0006] To this end, the invention proposes to replace a rigid cam with a deformable cam. The cam must be sufficiently deformable to dissipate a significant crash-type force, without this force causing the cam to rotate. The deformation must not be too significant so as not to allow disengagement.

[0007] Also, the invention relates to a device for locking the back of a vehicle seat, comprising a base secured to the seat base, an upright secured to the back of the seat and articulated relative to the base along a first axis, a rack secured to the base, a hook articulated relative to the upright along a second axis parallel to the first axis, comprising at least one tooth capable of selectively engaging or disengaging the rack when the hook rotates around the second axis, a first surface substantially opposite said at least one tooth and substantially circular centered on the first axis and a second surface substantially perpendicular to the first surface and an operating cam comprising a third substantially circular surface centered on a third axis parallel to the first axis, the cam being articulated relative to the upright along the third axis,so as to be able to selectively occupy a first default orientation in which the third surface bears on the first surface of the hook so as to prevent disengagement and a second orientation in which the third surface bears on the second surface so as to rotate the hook so as to disengage the rack, where the cam is deformable along a deformation axis substantially perpendicular to the third surface and substantially intersecting the third axis.

[0008] Particular characteristics or embodiments, usable alone or in combination, are: - the cam also includes a substantially circular notch centered on the third axis, - the notch has an uncut part of width, depending on the force to be dissipated, measured along the arc of the circle of the notch, - the thickness of the notch, at its narrowest point, is much less than the tooth height of said at least one tooth or of the rack, - the cam has a substantially rectangular shape, is pierced with a first hole centered on the third axis and a second hole centered on a fourth axis, sen possibly parallel to the first axis, accommodating a cam operating finger, rotating around the third axis, - the first surface and the third surface are shaped so that a force transmitted from the first surface to the third surface has a slightly open angle relative to the deformation axis, closing, preferably until it is cancelled out, as the cam deforms, - the cam is cut from a sheet of substantially constant thickness, preferably by stamping. Brief description of the drawings

[0009] The invention will be better understood on reading the following description, given solely by way of example, and with reference to the appended figures in which:

[0010] [Fig-1] shows, in perspective view, a locking device according to the invention,

[0011] [Fig.2] in perspective view, a cam according to the prior art, not very likely to deform,

[0012] [Fig.3] shows, as a function of time, graphs of the behavior of the cam of [Fig.2] under stress,

[0013] [Fig.4] shows a cam according to a first embodiment of the invention,

[0014] [Fig.5] shows, as a function of time, graphs of the behavior of the cam of [Fig.4] under stress,

[0015] [Fig.6] shows a cam according to another embodiment of the invention,

[0016] [Fig.7] shows a cam according to another embodiment of the invention,

[0017] [Fig.8] shows a cam according to another embodiment of the invention. Description of the embodiments

[0018] With reference to [Fig.l], the invention relates to a device 1 for locking the backrest of a vehicle seat.

[0019] Such a locking device 1 is intended to equip a front seat of a motor vehicle. The locking device 1 is arranged at the articulation between the seat and the backrest. It makes it possible to selectively unlock the rotation to allow rotation of the backrest: tilting forward or raising, and by default, to lock it, preferably in the raised position.

[0020] For this purpose, the locking device 1 comprises a base 2 secured to the seat base, an upright 3 secured to the seat back and articulated relative to the base along a first axis A. This first axis A coincides with the axis of rotation of the back relative to the seat base, i.e. an axis Y relative to the vehicle. The locking device 1 further comprises a rack 4, secured to the base 2, substantially winding around the first axis A and a hook 5 articulated relative to the upright 3 along a second axis B parallel to the first axis A.

[0021] The hook 5 comprises at least one tooth 6 capable of selectively engaging or disengaging clutch the rack 4 when the hook 5 rotates around the second axis B. Thus, when the hook 5 rotates in a counterclockwise direction, in the plane of [Fig.l], said at least one tooth 6 engages a corresponding tooth of the rack 4 ensuring clutching and locking in rotation of the upright 3 relative to the base 2. On the contrary, when the hook 5 rotates clockwise, in the plane of [Fig.l], said at least one tooth 6 disengages from the rack 4. This releases the rotation of the upright 3 relative to the base 2 around the first axis A.

[0022] The hook 5 further comprises a first surface 7 substantially opposite said at least one tooth 6 and substantially circular centered on the first axis A. Pressing on this first surface 7 presses said at least one tooth 6 against the rack 4 and prevents any disengagement. The hook 5 further comprises a second surface 8 substantially perpendicular to the first surface 7. An action, substantially tangent relative to the first axis A, on said second surface 8, tends to rotate the hook 5 in such a way as to disengage said at least one tooth 6 from the rack 4 and to effect disengagement.

[0023] The device 1 also comprises an operating cam 9. This cam 9 is articulated relative to the upright 3 along a third axis C. The third axis C is substantially parallel to the first axis A and therefore substantially parallel to the second axis B. The cam 9 comprises a third surface 10 substantially circular centered on the third axis C.

[0024] The rotation of the cam 9 around the third axis C allows it to be able to selectively occupy two orientations. In a first default orientation, or locking orientation, the third surface 10 comes to bear on, or at least remains not far from, the first surface 7 of the hook 5, so as to form a stop and to prevent the hook 5 from moving, prevent said at least one tooth 6 from disengaging the rack 4 and prevent a clutch release. In a second orientation, or unlocking orientation, after a rotation of substantially 90°, here in a trigonometric direction, the third surface 10, on the one hand, releases the hold of the first surface 7 and on the other hand, comes to bear on the second surface 8. This pressure on the second surface 8 of the hook 5 causes the hook 5 to rotate. This rotation disengages said at least one tooth 6 from the rack 4 and performs a clutch release.

[0025] In its second orientation, the cam 9 allows the device 1 to be released. In its default orientation, the cam 9, on the contrary, prevents release by maintaining pressure on the first surface 7.

[0026] [Fig.2] illustrates a cam 9 according to the prior art.

[0027] During a crash, from the rear, a cam 9 is compressed between the hook 7, which bears on the bearing surface 10 of the cam 9, and the third axis of rotation C, integral with the upright 3. Under the action of a force, significant in the event of a crash, transmitted from the hook 5 to the cam 9, provided that this force F does not pass exactly through the third axis C, a torque is created and the cam 9 risks rotating and in doing so releasing the hook 5, releasing the anti-clutch support on the first surface 7 and allowing a clutch release by inertia or even causing a rotation of the hook 5 by pressing on the second surface 8 and directly causing a clutch release.

[0028] The cam 9 according to the prior art, as illustrated in [Fig.2] has little compliance. Also, under the effect of a significant shock it behaves as illustrated by the curves in [Fig.3]. Curve C1 shows the torque observed at the articulation between the base 2 and the upright 3. Curve C2 shows the orientation of the cam 9. Curves C3x, C3y and C3z show respectively the force undergone by the cam 9, respectively along each of the axes X, Y and Z. It is visible, at the right of the two vertical lines, that the cam 9 rotates twice.

[0029] The invention proposes to remedy such a drawback.

[0030] Also, to prevent the cam 9 from risking rotating when subjected to a substantially longitudinal force F, applied substantially between the third surface 10 and the third axis C, the cam 9 is made deformable. This deformation is guided to take place substantially along a deformation axis E substantially perpendicular to the third surface 10 and substantially intersecting the third axis C.

[0031] According to another characteristic, in order to allow such deformation, the cam 9 also comprises a substantially circular notch 13 centered on the third axis C.

[0032] According to another characteristic, the notch 13 has an uncut portion 15 of width W, measured along the circular path of the notch 13. This uncut portion 15 will act as the center of deformation, the two lips of the notch 13 approaching substantially according to a rotation centered on the uncut portion 15. Under the effect of a force F substantially along the axis of deformation E, the notch 13 tends to deform by closing. The width W determines the force at which the deformation occurs. The width W of the uncut portion 15 is dimensioned as an increasing function of the desired deformation stiffness. Depending on the material and the thickness of the cam 9, and the force that the deformation is required to absorb, a person skilled in the art knows how to dimension the width W. The width W is more particularly illustrated in [Fig.4].

[0033] It is appropriate to limit the maximum deformation of the cam 9 in such a way that it does not make it possible for the tooth 6 to disengage from the rack 4. Also, another dimension advantageously sizes the notch 13: its thickness G at its narrowest point. Indeed, during the deformation, the two lips will come into contact at least at the right of said narrowest point, preventing any subsequent deformation. Thickness G is the dimension which limits the deformation. It is the thickness of the notch 13 itself or the thickness between a lip of the notch 13 and another part coming into contact, such as the operating finger 14. Thickness G is more particularly illustrated in [Fig.4]. The thickness G must be sufficient so that the deformation can dissipate enough energy without the cam 9 rotating. This thickness G must be limited so that the deformation of the cam 9 is not sufficient to allow the hook 5 to disengage. Also, this thickness G must be much less than the tooth height of said at least one tooth 6 and / or of the rack 4.

[0034] This ability of the cam 9 according to the invention to undergo deformation modifies its behavior under impact.

[0035] [Fig. 5] shows the observable behavior under the effect of a significant impact. Curve C' 1 shows the torque observed at the articulation between the base 2 and the upright 3. Curve C'2 shows the orientation of the cam 9. Curves C'3x, C'3y and C'3z respectively show the force undergone by the cam 9, respectively along each of the axes X, Y and Z. It is visible, on curve C'2 that the cam 9 according to the invention does not turn substantially during the crash.

[0036] According to another characteristic, the cam 9 has a substantially rectangular shape, here rounded, is pierced with a first hole 11 centered on the third axis C and a second hole 12, centered on a fourth axis D, parallel to the third axis C. The first hole 11 accommodates a shaft which allows the rotation of the cam 9 around the third axis C. The second hole 12 accommodates an operating finger 14 of the cam 9. The second hole 12 can be at least partially included in the notch 13. The operating finger 14 allows, via a transmission, typically by cable, from an operating handle, to control the disengagement, by rotating the cam 9 around the third axis C.

[0037] When the handle is released, the cam 9 returns to its locking orientation or rest orientation, under the effect of a return spring 16, acting between the upright 2 and the operating finger 14.

[0038] According to another characteristic, the first surface 7 and the third surface 10, which are opposite each other in the device 1 when the cam 9 is in the locking orientation, are shaped so that a force F transmitted from the first surface 7 to the third surface 10 has, relative to the deformation axis E, an angle a which is slightly open initially, before the impact, and which closes, preferably until it is cancelled out, as the cam 9 deforms. With such a configuration, the angle a performs two functions. Firstly, the initial orientation of the angle a is such that the lever arm which it creates and which could potentially transform a force applied along the axis F into a torque tending to rotate the cam 9, is oriented so as to rotate the cam 9 in the direction opposite to the unlocking orientation. Secondly, this angle a constitutes a reserve. Indeed, during the deformation, the notch 13 closes, the angle a decreases. Also, the angle a is dimensioned so that at the end of the deformation, the angle a is at most zero, without being able to change sign.

[0039] It follows from the above that the angle α is preferentially open on the side of the opening of the notch 13. Similarly, it can be deduced that the notch 13 advantageously opens on the side opposite the second surface 8 and the unlocking orientation.

[0040] According to another characteristic, in order to facilitate its manufacture, the cam 9 is advantageously cut from a sheet of substantially constant thickness. It is preferably produced by stamping.

[0041] Figures 6-8 show three other embodiments of the cam 9 and particularly different shapes of the notch 13. The notch 13 is functionally described entirely by the two dimensions width W and minimum thickness G. Provided that these dimensions W, G are respected, the shape of the notch 13 can be almost any. Some of the shapes of notches 13 presented in Figures 4, 6-8 result from feasibility constraints, in particular linked to the possible passage of a stamping punch.

[0042] The invention has been illustrated and described in detail in the drawings and the preceding description. This should be considered as illustrative and given by way of example and not as limiting the invention to this description alone. Numerous alternative embodiments are possible. List of reference signs

[0043] 1: device, 2: base, 3: upright, 4: rack, 5: hook, 6: tooth, 7: first surface, 8: second surface, 9: cam, 10: third surface, 11: first hole, 12: second hole, 13: notch, 14: operating finger, 15: uncut part, 16: means of recall, A: first axis, B: second axis, C: third axis, D: fourth axis, E: deformation axis, F: axis of application of the effort, G: thickness of the notch, W: width of the uncut part.

Claims

Claims

1. Device (1) for locking the back of a vehicle seat, comprising a base (2) secured to the seat base, an upright (3) secured to the back of the seat and articulated relative to the base (2) along a first axis (A), a rack (4) secured to the base (2), a hook (5) articulated relative to the upright (3) along a second axis (B) parallel to the first axis (A), comprising at least one tooth (6) capable of selectively engaging or disengaging the rack (4) when the hook (5) rotates around the second axis (B), a first surface (7) substantially opposite said at least one tooth (6) and substantially circular centered on the first axis (A) and a second surface (8) substantially perpendicular to the first surface (7) and an operating cam (9) comprising a third surface (10) substantially circular centered on a third axis (C) parallel to the first axis (A),the cam (9) being articulated relative to the upright (3) along the third axis (C), so as to be able to selectively occupy a first default orientation in which the third surface (10) comes to bear on the first surface (7) of the hook (5) so as to prevent disengagement and a second orientation in which the third surface (10) comes to bear on the second surface (8) so as to rotate the hook (5) so as to disengage the rack (4), characterized in that the cam (9) is deformable along a deformation axis (E) substantially perpendicular to the third surface (10) and substantially intersecting the third axis (C).,

2. Device (1) according to claim 1, wherein the cam (9) further comprises a substantially circular notch (13) centered on the third axis (C).

3. Device (1) according to claim 2, where the notch (13) has an uncut portion (15) of width (W), depending on the force to be dissipated, measured along the arc of the circle of the notch (13).

4. Device (1) according to any one of claims 2 or 3, where the thickness (G) of the notch (13), at its narrowest point, is much less than the tooth height of said at least one tooth (6) or of the rack (4).

5. Device (1) according to any one of claims 1 to 4, wherein the cam (9) has a substantially rectangular shape, is pierced with a first hole (11) centered on the third axis (C) and a second hole (12) centered on a fourth axis (D) parallel to the third axis (C), accommodating an operating finger (14) of the cam (9) rotating around the third axis (C).

6. Device (1) according to any one of claims 1 to 5, wherein the first surface (7) and the third surface (10) are shaped so that a force (F) transmitted from the first surface (7) to the third surface (10) has, relative to the deformation axis (E), a slightly open angle (a), closing, preferably until it is cancelled, as the cam (9) deforms.

7. Device (1) according to any one of claims 1 to 6, wherein the cam (9) is cut from a sheet of substantially constant thickness, preferably by stamping.

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