GB2436121A

GB2436121A - Seat reclining means with sliding ratchet lock

Info

Publication number: GB2436121A
Application number: GB0605418A
Authority: GB
Inventors: Michael Drew
Original assignee: ATL Engineering UK Ltd
Current assignee: ATL Engineering UK Ltd
Priority date: 2006-03-16
Filing date: 2006-03-16
Publication date: 2007-09-19
Also published as: GB0605418D0; WO2007104906A1

Abstract

A recliner mechanism for a seat having a seat cushion (2 Fig 1) and an adjustable backrest (4 Fig 1) includes a first hinge member (10) attached to the cushion. A ratchet element (18) is mounted on the first hinge member for linear movement in an adjusting direction and has a curved first tooth segment (62) with a first centre of curvature. A cam (20) is mounted on the first hinge member for rotation about a cam axis to control movement of the ratchet. A second hinge member (12) is connected to the first hinge member (10) by a pivot (24) for angular adjustment about a pivot axis and has a curved second tooth segment (50) with a second centre of curvature that coincides with the pivot axis. The ratchet element (18) is adjustable between a locked configuration in which the tooth segments are engaged and an unlocked configuration in which the tooth segments are disengaged. The recliner mechanism has a principal axis that passes through the pivot axis in a direction that is perpendicular to the pivot axis and parallel to the adjusting direction. The first centre of curvature and the drive axis are offset from the principal axis.

Description

-1-2436121

RECLINER MECHANISM

The present invention relates to a recliner mechanism for vehicle seats and similar applications.

The invention also relates to a vehicle seat including such a mechanism.

Many vehicle seats include a recliner mechanism that allows the angle of the squab (or seat back) to be adjusted relative to the seat cushion (or base), so that the occupant can be seated in maximum comfort. This is important as the body shape and size of occupants can vary greatly. It is also desirable to have a facility for reclining the seat squab, so that the occupant can rest in a more horizontal position. For some vehicles, for example 2-door cars, it may also be necessary to have a facility for folding the seat squab forwards to allow access to the rear seats.

The recliner mechanism has to be able to withstand a number of forces during normal use including in particular the rearwards force caused by a passenger leaning against the squab.

However, for safety and to comply with worldwide legislation, it also has to be able to withstand the much greater forces that might be generated if the vehicle is involved in a collision. In particular, if the squab carries the upper anchoring point for the seat belt, a very large forwards force may be generated in the event of a frontal collision, owing to the inertia of the passenger. Such transient forces may be many times greater than the forces experienced during normal usage and the recliner mechanism must be able to withstand them without collapsing.

A number of other important factors must also be taken into consideration when designing a seat recliner mechanism. The mechanism must be reliable and easy to adjust. There must be no excessive play (chuck) in the mechanism, which would allow the squab to wobble or vibrate when the vehicle is in motion. The mechanism must also be very durable and its performance should be substantially unaffected by wear.

There are two main types of recliner mechanism in common use. The first of these uses a ratchet mechanism to control the position of the squab. The ratchet mechanism can be disengaged using a lever, allowing the angle of the squab to be adjusted. The lever is then released to reengage the ratchet, locking the squab in the chosen position.

The second type of recliner mechanism uses a gear mechanism that has a continual mesh and provides a continuously variable adjustment range. These mechanisms are normally operated by manual hand wheels or electric motors. By turning the hand wheel or operating the electric motor the squab can be adjusted backwards or forwards. During adjustment the gear mechanism remains constantly in mesh. The recliner mechanism can therefore be stopped in any position within a continuously variable range of adjustment.

The present invention relates to the first type of recliner mechanism, which uses a ratchet mechanism for locking the squab at the desired angle.

One such recliner mechanism is described in our earlier patent application EP 1197376 A. That mechanism includes a squab plate and a ratchet plate having complementary tooth segments. The centres of curvature of the tooth segments are offset so that during normal use not all of the teeth are fully engaged. However, in the event of a collision, deformation of the mechanism caused by high transient forces increases the number of teeth in engagement thereby increasing the strength of the mechanism and reducing the risk of failure.

Although the recliner mechanism described in our earlier application provides significant advantages over previous known mechanisms, we have found that in certain circumstances the mechanism can become unstable and as a result can suffer from a degree of play/chuck.

It is an object of the present invention to provide a recliner mechanism that mitigates at least some of the disadvantages of known recliner mechanisms.

According to one aspect of the present invention there is provided a recliner mechanism including a first hinge member, a ratchet element mounted on the first hinge member for linear movement in an adjusting direction and having a curved first tooth segment with a first centre of curvature, a drive element mounted on the first hinge member for rotation about a drive axis to control movement of the ratchet element, a second hinge member connected to the first hinge member by a pivot element for angular adjustment about a pivot axis and having a curved second tooth segment with a second centre of curvature, said ratchet element being adjustable between a locked configuration in which the tooth segments are engaged and an unlocked configuration in which the tooth segments are disengaged, wherein the recliner mechanism has a principal axis that passes through the pivot axis in a direction that is perpendicular to the pivot axis and parallel to the adjusting direction, said first centre of curvature and said drive axis being offset from said principal axis, such that the first centre of curvature, the pivot axis and the drive axis do not lie in the same plane.

An effect of this arrangement is to remove any free play of the ratchet element. The mechanism therefore compensates automatically for both tolerance and wear of the components. The mechanism is also able to meet specified load requirements efficiently, including very high transient loads that may be experienced in a collision. The stability of the mechanism is also greatly improved, substantially eliminating chucklplay.

Advantageously, the first centre of curvature and the drive axis are offset on opposite sides of the principal axis.

Advantageously, a drive offset axis that passes through the pivot axis and the drive axis subtends with the principal axis a drive offset angle D in the range 0.50 to 15 . The drive offset angle D is preferably in the range 4 to 100 and is ideally approximately 70* Advantageously, a tooth offset axis that passes through the pivot axis and the first centre of curvature when the tooth segments are engaged subtends with the drive offset axis a tooth offset angle 0 in the range 5 to 30 . The tooth offset angle 0 is preferably in the range 100 to 20 and is typically approximately 15 .

Preferably, the first tooth segment has an effective radius RR and the second tooth segment has an effective radius R, where RR> R. The distance RR -R5 is preferably in the range 1-10mm, more preferably 2-6mm and typically approximately 5mm.

Advantageously, the first tooth segment has an effective radius RR in the range 20-150mm, preferably 30-100mm, typically approximately 45mm.

Advantageously, the drive element comprises a cam. Advantageously, the drive element engages the ratchet element at an engagement point Q that is offset from the principal axis, on the same side as the drive axis.

Conveniently, the first hinge member is constructed and arranged for attachment to a seat cushion and the second hinge member is constructed and arranged for attachment to a seat squab. This ensures that any operating device, for example a lever, remains in the same place, regardless of the position of the squab. However, it is also possible for the recliner mechanism to be inverted, so that the first hinge member is attached to the squab and the second hinge member is attached to the seat cushion.

According to another aspect of the invention there is provided a seat including a seat cushion, an adjustable squab and a recliner mechanism according to any one of the preceding statements of invention.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a vehicle seat having a recliner mechanism; Figure 2 is an exploded isometric view of a recliner mechanism according to the invention; Figure 3 is a sectional side view of the recliner mechanism, and Figure 4 illustrates the geometry of the recliner mechanism.

The vehicle seat shown schematically in Figure 1 includes a seat cushion 2, which is the part the occupant sits on, a seat squab (or backrest) 4, and a recliner mechanism 6 that connects the squab to the cushion and allows the angle of the squab 4 to be adjusted relative to the cushion 2. The recliner mechanism can be released or locked using an operating lever 8. Two recliner mechanisms may be provided, one on either side of the seat. In this case, the mechanism are preferably interconnected for simultaneous operation. Alternatively, the seat may include a recliner mechanism on one side and a plain pivot on the other.

The recliner mechanism 6 is shown in detail in Figures 2 and 3. The mechanism comprises a first hinge member 10 for connection to the frame of the seat cushion 2 and a second hinge member 12 (or "squab plate") for connection to the squab 4.

The first hinge member 10 includes a box-shaped housing 14 comprising an outer housing element 1 6a and an inner housing element 1 6b. The housing 14 accommodates the lower part of the squab plate 12 as well as a ratchet plate 18, a cam 20, a cam drive element 22, a pivot bearing 24 and a slide bearing 26. The recliner mechanism also includes a spring 28 and an E-clip 30, which are located externally of the housing 14. Optionally, the recliner mechanism may also include a clock spring or similar device (not shown) to bias the squab towards an upright position, so that it returns automatically to that position from a reclined position when the recliner mechanism is released.

Each housing element 16a,16b is formed of pressed steel and includes a flat face plate 32 with a raised peripheral ridge 34 that increases the strength and rigidity of the housing element.

Each housing element 1 6a, I 6b also includes a pair of parallel flanges 36a,36b that overlap when the recliner mechanism is assembled to form the side walls of the housing 14, the flanges 36a of the first housing element 16a fonning the inner walls and the flanges 36b of the first housing element 16b forming the outer walls. The parallel inner flanges 36a serve as guide elements for the ratchet plate 18. The upper part of the housing 14 is open, providing a slot 38 through which the squab plate 12 extends.

In the upper part of each housing element 1 6a, 1 6b there is a circular hole 40, which acts as a support for the pivot bearing 24. A second circular hole 42 is provided in the lower part of each housing element I 6a, 1 6b and serves as a support for the slide bearing 26. A third circular hole 44 is provided in the middle part of each housing element I 6a, 1 6b and acts as a pivot bearing for the cam drive element 22. The first housing element I 6a includes a press-formed hook element 46 that supports one end of the spring 28.

The squab plate 12 is a fine blanked component having a convex arcuate lower edge 48 that carries a set of gear teeth 50. The gear teeth 50 are separated into two gear segments 50a,50b by a protruding toothless segment 52. The arcuate lower edge 48 also includes a toothless recessed segment 54 and a stop member 55 at the rear end of that segment. In the centre of the squab plate 12 is a circular hole 56 that provides a second bearing surface for the pivot bearing 24. Two holes 58 are provided at the top of the squab plate 12 for receiving tubular fixing rivets (not shown), for attaching the squab plate to the frame of the squab 4.

The ratchet plate 18 is also a fine blanked component, having a concave arcuate upper edge 60 that carries a set of gear teeth 62. These teeth are engageable with the gear teeth 50 on the squab plate 12. The two gear segments have different curvatures, as described in more detail below. As a result, the two sets of gear teeth 5 0,62 are fully engaged only at an engagement point P and are less fully engaged forwards and rearwards of that point.

The sides of the ratchet plate 18 include two parallel guide surfaces 64 that engage the inner side walls 36a of the housing 14. The ratchet plate 18 also includes a parallel-sided slot 66 at its lower end, which has a sliding fit with the slide bearing 26. In use, the guide surfaces 64 and the slot 66 guide the ratchet plate 18 for linear sliding movement in an adjusting direction A between a locked position in which the two sets of gear teeth 50,62 are engaged and adjustment of the recliner mechanism is prevented, and an unlocked position in which the gear teeth are disengaged and adjustment is allowed. The upper end of the rear guide surface 64 provides a stop member 67.

Sliding movement of the ratchet plate 18 is controlled by the cam 20, which is located within an irregular aperture 68 in the centre of the ratchet plate 18. The cam 20 engages the ratchet plate 18 at a cam engagement point Q when urging the ratchet plate into engagement with the gear teeth 50 on the squab plate 12.

The cam 20 includes a hexagonal drive aperture 70 that is drivingly engaged with a hexagonal drive part 72 of the cam drive element 22. On either side of the hexagonal drive part 72, the cam drive element 22 has a cylindrical trunnion bearing 74 that is received in one of the corresponding holes 44 in the housing elements 16a,16b. The cam drive element 22 has a square-sided bore 76 that receives a square drive shaft (not shown), which may be connected to the operating lever 8. The shaft is retained in position within the bore by the E-clip 30, which engages a slot in the shaft. The E-clip 30 includes a tab 78 that is engaged by one end of the spring 28, the other end being attached to the hook 46. The spring 28 acts in tension to bias the cam 20 and the ratchet plate 18 to the locked position.

The geometry of the recliner mechanism is illustrated in figure 4. The squab plate 12 is arranged for rotation about the pivot bearing 24, which has a pivot axis 80. The pivot axis 80 is also the centre of curvature of the convex squab plate tooth segment 82, which has an effective radius R. The effective radius is equal to the mean of the inner and outer tooth radii, measured from the centre of curvature to the roots and the tips of the teeth: i.e. R = (R' + R")/2 where R' is the radius to the tooth roots and R" is the radius to the tooth tips.

The recliner mechanism has a principal axis 84 that extends through the pivot axis 80. The principal axis 84 is perpendicular to the pivot axis 80 and parallel to the direction of movement A of the ratchet plate 18.

The cam 20 is rotatable about a drive axis 86, which coincides with the axis of the cam drive element 22. The drive axis 86 is offset from the principal axis 84 by an offset distance DD The line that passes through the pivot axis 80 and the drive axis 86 is referred to as the drive offset axis 88. This drive offset axis 88 subtends with the principal axis 84 a drive offset angle D* The cam engagement point Q is also offset to the same side of the principal axis 84.

The concave ratchet plate tooth segment 90 has an effective radius RR that is greater than the effective radius R of the squab plate tooth segment 82. The centre of curvature 92 of the ratchet plate tooth segment 90 is offset from the principal axis 84 by an offset distance DR, and is located above the centre of curvature 80 of the convex squab plate tooth segment 82. The cam drive axis 86 and the centre of curvature 92 of the ratchet plate tooth segment 90 are offset on opposite sides of the principal axis 84.

is The geometry of the mechanism is such that when the ratchet plate 18 is in a locked position, the two sets of gear teeth 50,62 are fully engaged at an engagement point P that is displaced from the principal axis 84. The line that passes through the pivot axis 80, the centre of curvature 92 of the ratchet plate tooth segment 90 and the engagement point P when the gear teeth 50,62 are fully engaged is referred to as the tooth offset axis 94. This tooth offset axis 94 subtends with the drive offset axis 88 a tooth offset angle T* It should be noted that the drive offset axis 88 and the tooth offset axis 94 are both displaced to the same side of the principal axis 84, the tooth offset axis 94 being displaced further than the drive offset axis 88 from the principal axis 84.

In an illustrative example of the recliner mechanism, the ratchet plate tooth segment 90 has a radius RR of approximately 40mm and the squab plate tooth segment 82 has a radius R of approximately 37mm. The difference in tooth radii RR-Rs is therefore approximately 3mm.

The drive offset angle O) is approximately 7 and the tooth offset angle 0 is approximately 15.5 . The engagement point P is therefore displaced from the principal axis 84 by an angle of approximately 22.5 .

Preferred ranges and values for the various dimensions and angles of the recliner mechanism geometry are indicated below.

Preferred range More preferred Typical value ________________________________ ______________ range Drive offset angle O) 0.5 -J50 4 -10 approx. 70 Tooth offset angle 0 50 30 10 -20 approx. 15 Ratchet tooth radius RR 20 -150mm 30 -100mm approx. 45mm Difference in tooth radii RR-Rs 1 -10mm 2 -6mm 5mm In order to adjust the recliner mechanism, the cam 20 is rotated (by means of the operating lever 8) from the position shown in the drawings through an angle of approximately 30 . The cam 20 drives the ratchet plate 18 downwards from the locked position shown in Figs. 2 & 3 to an unlocked position. This unlocks the ratchet mechanism and allows the position of the squab 4 to be adjusted. The squab is moved to the desired angle and the recliner mechanism is then locked in the selected position by reversing the rotation of the operating lever 8 and the cam 20, thereby driving the ratchet plate 18 back to the locked position. If the operating lever 8 is simply released, the spring 28 acts on the cam 20 to return the ratchet plate 18 to the locked position. Rearwards adjustment of the recliner mechanism is limited by engagement of the squab plate stop member 55 with the ratchet plate stop member 67.

The squab 4 can also be adjusted forwards from its normal design position, for example to allow access to the rear seats of a vehicle. When the squab is folded fully forward it may be locked in position by engaging the second squab plate tooth segment SOb with the ratchet plate tooth segment 62. The squab cannot be locked in an intermediate position between the upright position and the fully folded position, owing to provision on the squab plate 12 of the protruding toothless segment 52, which prevents engagement between the squab plate tooth segments 50a,b with the ratchet plate tooth segment 62.

Movement of the ratchet plate 18 is guided by the slide bearing 26 and the parallel inner side walls 36a of the housing 14. This ensures that the recliner mechanism has very little chucklplay. Chuck/play is further reduced by the geometrical arrangement of the mechanism.

When the cam 20 is in the "locked" position shown in Fig. 3, it exerts an upwards force on the ratchet plate 18, which is transmitted through the squab plate 12 to the pivot bearing 24. That / force is transmitted through the engagement point P. However, the engagement point P does not lie on the drive offset axis 88 that intersects the axes of the pivot pin 16 and the cam element 46, but is instead located to the rear of that axis. Therefore, in addition to the radial force that acts along the tooth offset axis 94, the compressive force also generates a resultant tangential force that presses the ratchet plate 18 hard against the rear side wall 36a.

The effect of this resultant force is to remove any free play between the ratchet plate 18 and the housing 14. The mechanism therefore compensates automatically for both tolerance and wear of the components.

During normal use, the two tooth segments 50,62 mesh fully only at the engagement point P. The teeth are not fully engaged forward and rearwards of that point, the gap between the tooth segments being larger at the front edge than the rear edge of the ratchet plate 18. The engagement between the two tooth segments is however sufficiently strong to withstand the forces and wear encountered during normal usage.

Should the vehicle be involved in a frontal collision, there may be some plastic deformation of the pivot mechanism. Generally, this will cause the pivot bearing 24 to be displaced forwards from its usual position and, as a result, the teeth towards the front edge of the squab plate 12 will be brought into full engagement with the corresponding teeth of the ratchet plate 18, thereby increasing the number of teeth in full contact. The force is thus shared between an increased number of teeth, so reducing the likelihood of failure. There may also be some deformation of the teeth around the original engagement point P, but this is not usually sufficiently serious to cause those teeth to fail. This arrangement is described in more detail in EP 1197376 A, the content of which is incorporated by reference herein.

The locking mechanism is therefore able to meet the specified load requirements more efficiently, and its strength increases with the severity of the crash. Testing has shown that this arrangement significantly increases the strength of the mechanism.

Finally, in the present invention, both the ratchet plate centre of curvature 92 and the cam drive axis 86 are offset from the principal axis 84, such that the ratchet plate centre of curvature 92, the pivot axis 80 and the cam drive axis 86 do not lie in the same plane. The direction of the force exerted by the cam 20 on the ratchet element 18 through the cam engagement point Q is thus offset by the drive offset angle D from the adjusting direction A of the ratchet plate (which is along the principal axis 84). 11 is also offset by the tooth offset angle T from the tooth offset axis 94 (which passes through the engagement point P). We have found that by offsetting both the ratchet plate centre of curvature and the cam drive axis from the principal axis, such that the centre of curvature, the pivot axis and the cam drive axis do not lie in the same plane, the stability of the mechanism can be greatly improved, substantially eliminating chucklplay.

It should be understood that the recliner mechanism described above and shown in the drawings represents only one exemplary embodiment of the invention as defined by the claims.

Various modifications of the invention are of course possible, as will be apparent to a person skilled in the art. For example, the mechanism may be inverted, so that the first hinge member is attached to the squab 4 and the second hinge member 12 is attached to the frame of the seat cushion 2. The number and form of the teeth on the ratchet plate and the squab plate may also be varied. If only a few positions of adjustment are required (for example, upright and reclined), very few teeth may be required. Alternatively, if a wider range of movement is required, a full set of teeth may be provided on the squab plate, the toothless segment 52 being omitted. The drive mechanism for the ratchet plate (the cam 20) may also be replaced by an alternative drive mechanism.

Claims

CLAIMS

I. A recliner mechanism including a first hinge member, a ratchet element mounted on the first hinge member for linear movement in an adjusting direction and having a curved first tooth segment with a first centre of curvature, a drive element mounted on the first hinge member for rotation about a drive axis to control movement of the ratchet element, a second hinge member connected to the first hinge member by a pivot element for angular adjustment about a pivot axis and having a curved second tooth segment with a second centre of curvature, said ratchet element being adjustable between a locked configuration in which the tooth segments are engaged and an unlocked configuration in which the tooth segments are disengaged, wherein the recliner mechanism has a principal axis that passes through the pivot axis in a direction that is perpendicular to the pivot axis and parallel to the adjusting direction, said first centre of curvature and said drive axis being offset from said principal axis, such that the first centre of curvature, the pivot axis and the drive axis do not lie in the same plane.
2. A recliner mechanism according to claim 1, in which the first centre of curvature and the drive axis are offset on opposite sides of the principal axis.
3. A recliner mechanism according to claim I or claim 2, in which a drive offset axis that passes through the pivot axis and the drive axis subtends with the principal axis a drive offset angle O) in the range 0.5 to 15 .
4. A recliner mechanism according to claim 3, in which the drive offset angle O) is in the range 4 to 100.
5. A recliner mechanism according to claim 3, in which the drive offset angle D is approximately 7 .
6. A recliner mechanism according to any one of the preceding claims, in which a tooth offset axis that passes through the pivot axis and the first centre of curvature when the tooth segments are engaged subtends with the drive offset axis a tooth offset angle T in the range 5 to3O .
7. A recliner mechanism according to claim 6, in which the tooth offset angle T is in the range 100 to 20 .
8. A recliner mechanism according to claim 6, in which the tooth offset angle T is approximately 150.
9. A recliner mechanism according to any one of the preceding claims, in which the first tooth segment has an effective radius RR and the second tooth segment has an effective radius R5, where RR > R.
10. A recliner mechanism according to claim 9, in which the distance RR -R is in the range 1-10mm.

11. A recliner mechanism according to claim 9, in which the distance RR -R is in the range 2-6mm.

12. A rec liner mechanism according to claim 9, in which the distance RR -R is approximately 5mm.

13. A recliner mechanism according to any one claims 9 to 12, in which the first tooth segment has an effective radius RR in the range 20-150mm.

14. A recliner mechanism according to any one claims 9 to 12, in which the first tooth segment has an effective radius RR in the range 30-100mm.

15. A recliner mechanism according to any one claims 9 to 12, in which the first tooth segment has an effective radius RR of approximately 45mm.

16. A recliner mechanism according to any one of the preceding claims, in which the drive element comprises a cam.

17. A recliner mechanism according to any one of the preceding claims, in which the drive element engages the ratchet element at an engagement point Q that is offset from the principal axis.

18. A recliner mechanism according to any one of the preceding claims, in which the first hinge member is constructed and arranged for attachment to a seat cushion and the second hinge member is constructed and arranged for attachment to a seat squab.

19. A recliner mechanism substantially as described herein, with reference to and as illustrated by the accompanying drawings.

20. A seat including a seat cushion, an adjustable squab and a recliner mechanism according to any one of the preceding claims.