EP1853456A1

EP1853456A1 - A continuous recliner mechanism for vehicle seats and other applications

Info

Publication number: EP1853456A1
Application number: EP05808437A
Authority: EP
Inventors: Michael Drew
Original assignee: ATL Engineering UK Ltd
Current assignee: ATL Engineering UK Ltd
Priority date: 2005-03-01
Filing date: 2005-11-25
Publication date: 2007-11-14
Also published as: GB0504118D0; JP2008531391A; WO2006092546A1; GB2423701A

Abstract

A seat recliner mechanism for a seat having a seat cushion and a reclinable squab includes a stationary hinge member (108) connectable with the seat cushion, an adjustable hinge member (110) connectable with the squab and an angular position adjuster in the form of a wobble gear mechanism. The wobble gear mechanism includes a primary gear mechanism (114, 116) and a secondary gear mechanism (118, 120), each comprising an inner gear and an outer gear having different numbers of teeth and arranged to provide a point of maximum tooth engagement (Y, X). An eccentric drive element (112) is rotatable to cause eccentric relative rotation of the inner and outer gears and angular adjustment of the hinge members. The points of maximum tooth engagement (Y, X) of the primary and secondary gear mechanisms are diametrically opposed to one another.

Description

A CONTINUOUS RECLINER MECHANISM FOR VEHICLE SEATS AND

OTHER APPLICATIONS

The present invention relates to a continuously variable recliner mechanism for vehicle seats and other applications.

Typically in vehicle seats the two main components are the seat cushion, which is the part one sits on, and the seat squab (or backrest), which is the part one leans against. It is normal for the angle between the cushion and the squab to be adjustable so that the seated occupant can obtain maximum comfort. This is because 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.

To achieve this feature it is normal to provide a recliner mechanism having one part that is attached to the seat cushion and another part that is attached to the seat squab. Sometimes a single recliner mechanism is used on one side of the seat with a simple pivot on the other side for low load/strength applications. Conversely, for high strength seats, recliner mechanisms can be fitted on both sides.

There are a number of recliner mechanisms used throughout the world but in general terms the range of mechanisms used can be divided into two different types, according to whether they provide for discontinuous or continuous adjustment of the squab angle.

The first discontinuous type of recliner mechanism is sometimes called a ratchet type recliner and is operated by the raising and lowering of a lever. The angle of the squab is adjusted by raising the operating lever to release a locking mechanism, resetting the squab angle and then lowering the lever to relock the mechanism. This engages the locking device in a new position on a set of teeth within the mechanism.

Two disadvantages of the ratchet type recliner are: a) The angle of recline has increments of movement normally of about 3 degrees owing to the form of the teeth. This means for example that the seat cannot be set 2 degrees forwards or backwards from a locked position. b) When the lever is raised to unlock the mechanism, the internal teeth are disengaged and the recliner should not therefore be operated while the vehicle is in motion.

The continuous type of recliner mechanism uses a gear mechanism that provides a continuously variable adjustment range. Normally this type of mechanism is operated by a manual hand wheel, although on more expensive seats electric motors are often employed. By turning a hand wheel or operating an electric switch the squab can be adjusted backwards or forwards. When the seat back is moving forwards or backwards the recliner mechanism remains continuously in mesh and can be stopped in any position within a continuously variable range of adjustment.

It can be readily appreciated that the continuous type of mechanism overcomes the disadvantages already outlined for the discontinuous type.

The continuous type of mechanism comes in a range of different designs. These include designs incorporating a worm and wheel system, and others that incorporate a planetary gear system where the planetary gears are meshed with internally stamped gear rings. However, one of the simplest and most successful of the continuously variable types of recliner mechanism is the well tried and tested 'Taumel' system.

The main principle of the 'Taumel' mechanism concerns the use of a wobble gear mechanism comprising a pair of inner/outer tooth rings, which are formed on the squab plate and the cushion plate by fine blanking. These gear rings provide for angular adjustment of the seat squab by rotating eccentrically relative to one another with a wobbling or waltzing movement. Another feature of the Taumel mechanism relates to the use of a wedge device, which is necessary in order to reduce play (chuck) in the seat squab. Brakes may also be added to prevent creep (the slow lowering of the squab under its own weight).

Another recliner mechanism described in WO2004/089684 uses a modified wobble gear mechanism in which the inner and outer gear rings have conformal tooth profiles, which are designed such that all but one of the teeth on the inner gear ring engage with teeth on the outer gear ring. Angular adjustment of the seat squab is achieved by rotating an eccentric cam element to cause wobbling or waltzing movement of the gear rings. This mechanism significantly reduces play and does not require a wedge or similar mechanism. However, it does not eliminate play entirely. In particular, we have found that a small but appreciable amount of play at the top of the squab is inevitable, owing to the need for a small clearance gap between the two sets of teeth on the gear rings, and the gap around the cam caused by the force exerted radially through the cam.

WO2004/089684 also discloses a second recliner mechanism in which the squab plate and the cushion plate carry a pair of secondary gear rings in addition to the primary gear rings already mentioned. Most of the teeth on the secondary gear rings are normally disengaged and come into engagement only when the recliner mechanism is deformed, for example in the event of a collision, and then provide additional strength to prevent the recliner mechanism from collapsing. This recliner mechanism suffers a similar degree of play to the first mechanism described above.

A second problem with the recliner mechanism described above is that the eccentric cam element, which causes wobbling or waltzing movement of the gear rings, is subjected in use to a significant torque or turning moment, which acts about an axis that is perpendicular to the rotational axis of the cam element. This causes the cam element to wobble and contributes to both turn and play in the mechanism.

A further problem with the recliner mechanism described above is that it can suffer from creep: i.e. gradual unintended movement of the squab in use. It is an object of the present invention to provide a continuous recliner mechanism that mitigates at least some of the aforesaid disadvantages.

According to the present invention there is provided a seat recliner mechanism for a seat having a seat cushion and a reclinable squab, the mechanism including a stationary hinge member connectable with the seat cushion, an adjustable hinge member connectable with the squab, and an angular position adjuster in the form of a wobble gear mechanism, wherein the wobble gear mechanism includes a primary gear mechanism and a secondary gear mechanism, each comprising an inner gear and an outer gear having different numbers of teeth and arranged to provide a point of maximum tooth engagement, and an eccentric drive element that is rotatable to cause eccentric relative rotation of the inner and outer gears and angular adjustment of the hinge members; characterised in that the points of maximum tooth engagement of the primary and secondary gear mechanisms are diametrically opposed. As the points of maximum tooth engagement of the primary and secondary gear mechanisms are diametrically opposed (i.e. located on opposite sides of the pivot axis), they both contribute to the stability of the mechanism, thereby significantly reducing play. Using this mechanism, we have found that total play at the top of a 500mm squab can be reduced to less than lmm. The mechanism allows for continuous adjustment of the seat squab and does not require a wedge or similar play reduction mechanism. The total number of parts in the mechanism can therefore be significantly reduced.

The secondary gear mechanism also provides additional strength, preventing the recliner mechanism from collapsing when subjected to very large loads, for example in the event of a collision, in particular because a large number of the secondary tooth forms can carry a load.

Advantageously, the primary inner gear and the secondary outer gear are connected to one of the hinge members, and the primary outer gear and the secondary inner gear are connected to the other hinge member. Preferably, the primary inner gear and the secondary outer gear are connected to the stationary hinge member (the cushion plate), and the primary outer gear and the secondary inner gear are connected to the adjustable hinge member (the squab plate).

Advantageously, the gears are formed on the hinge members by semi-shearing (for example by fine blanking) or broaching, eroding or similar techniques.

Advantageously, the primary outer gear has one more tooth than the primary inner gear. The primary inner and outer gears may have conformal tooth profiles, whereby in use not more than one of the teeth on the inner gear is disengaged from the teeth on the outer gear. The inner and outer gears may for example have a tooth form similar to a Wildhaber-Novikov tooth form, although other tooth forms may also be used.

Because nearly all of the teeth on the primary gear mechanism are engaged, there is very little play. The mechanism is also very strong, since the forces are carried by many teeth. In certain circumstances, this allows ordinary structural steel to be used without any need for case hardening, which in turn allows the recliner mechanism to be welded direct to the frame of a seat without requiring expensive adaptors. In other situations, case hardening may be desirable. Advantageously, the maximum peak-to-peak gap between the teeth of the primary inner and outer gears is less than 0.15mm, preferably less than 0.1mm. For example, the maximum peak-to-peak gap may be approximately 0.06mm. This provides a total theoretical play at the top of a 500mm squab that is within acceptable limits. Advantageously, one or both of the primary and secondary gear mechanisms may have conical tooth forms.

The rotatable drive element may be mounted in a bearing in one of the hinge members, the rotatable drive element and the bearing having complementary frusto- conical bearing surfaces. Preferably, the frusto-conical bearing surfaces are inclined at an angle of 6-10°, preferably approximately 8°, relative to the rotational axis of the bearing. The provision of a frusto-conical bearing reduces play in the mechanism still further. It also helps to prevent jamming of the mechanism and relieves hard spots (spots where the control knob is difficult to turn, due to tooth engagement tolerances or non-circularity of the gear rings). Advantageously, the primary and secondary gear mechanisms lie in substantially the same plane. Preferably, the primary and secondary gear mechanisms lie in substantially the same plane as the frusto-conical bearing. This prevents twisting of the drive element, so further reducing play.

Advantageously, the seat recliner mechanism includes a latching mechanism for preventing unintended rotation of the eccentric drive element.

Advantageously, the latching mechanism includes a latching element connected to the eccentric drive element for rotation therewith, said latching element being selectively engageable with latching formations associated with one of the hinge members. The latching element is preferably constructed and arranged to disengage the latching formations upon rotation of a drive element for the recliner mechanism.

According to a particularly preferred aspect of the invention there is provided a seat recliner mechanism for a seat having a seat cushion and a reclinable squab, the mechanism including a stationary hinge member connectable with the seat cushion, an adjustable hinge member connectable with the squab, and an angular position adjuster in the form of a wobble gear mechanism that interconnects and controls the relative angular positions of the stationary and adjustable hinge members, wherein the wobble gear mechanism includes a primary gear mechanism comprising an inner gear and an outer gear having different numbers of teeth, the inner and outer gears being arranged in mutual engagement with a point of maximum tooth engagement between the inner and outer gears at one point on the circumference of the inner and outer gears, and a secondary gear mechanism comprising an inner gear and an outer gear having different numbers of teeth, the inner and outer gears being arranged in mutual engagement with a point of maximum tooth engagement between the inner and outer gears at one point on the circumference of the inner and outer gears, and an eccentric drive cam element that is rotatable to cause eccentric relative rotation of the inner and outer gears of each of the primary and secondary gear mechanisms, rotation of the points of maximum tooth engagement of the primary and secondary gear mechanisms, and angular adjustment of the hinge members; characterised in that the points of maximum tooth engagement of the primary and secondary gear mechanisms are diametrically opposed to one another.

An embodiment of the present 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 a schematic sectional side view of a first prior art recliner mechanism; Figure 3 is a schematic sectional side view of a second prior art recliner mechanism;

Figure 4 is a schematic sectional side view of a recliner mechanism according to an embodiment of the present invention;

Figure 5 is an isometric view of the recliner mechanism; Figure 6 is an exploded isometric view of the recliner mechanism; Figure 7 is a side elevation showing a first side of the recliner mechanism; Figure 8 is a front elevation of the recliner mechanism; Figure 9 is a plan view of the recliner mechanism;

Figure 10 is a sectional plan view of the recliner mechanism, on line B-B of figure 7; Figure 11 is a side elevation showing a second side of the recliner mechanism; Figure 12 is a sectional view of the recliner mechanism, on line A-A of figure 7; Figure 13 is an isometric view of a cushion plate; Figure 14 is a side elevation of the cushion plate; Figure 15 is a sectional view of the cushion plate, on line A-A of figure 14; Figure 16 is a detailed view at an enlarged scale of part of the cushion plate, shown as detail X in figure 14;

Figure 17 is an isometric view of a squab plate; Figure 18 is a side elevation of the squab plate; Figure 19 is a sectional view of the squab plate, on line A-A of figure 18; Figure 20 is a detailed view at an enlarged scale of part of the squab plate, shown as detail X in figure 18;

Figure 21 is an isometric view of a cam element; Figure 22 is a front elevation of the cam element; Figure 23 is a first side view of the cam element; Figure 24 is a sectional front view of the cam element; Figure 25 is a second side view of the cam element; Figure 26 is a front view of the cam element;

Figure 27 is a side elevation of the recliner mechanism, with a latching mechanism removed; Figure 28 is an isometric view of the recliner mechanism; Figure 29 is an isometric view of the latching mechanism; Figure 30 is a second isometric view of the latching mechanism; Figure 31 is an isometric view of a latching element; Figure 32 is a sectional view of the latching mechanism in a first configuration; Figure 33 is a sectional view of the latching mechanism in a second configuration; and

Figure 34 is a sectional view of the latching mechanism in a third configuration. The vehicle seat shown schematically in figure 1 includes a seat cushion 2, which is the part one 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 prior art recliner mechanism shown in figure 2 corresponds to that shown in figures 2-8 of WO2004/089684, the content of which is incorporated by reference herein. The recliner mechanism comprises a cushion plate 8, a squab plate 10, and an eccentric cam 12. The squab plate 10 and the cushion plate 8 carry a wobble gear mechanism, comprising an inner gear 14 and an outer gear 16. The cushion plate 8 forms a stationary hinge element and is connectable to the frame of the seat cushion 2. The cushion plate 8 carries the inner gear 14, which comprises an external tooth form semi-sheared out of the base material.

The squab plate 10 forms an adjustable hinge element, which is connectable to the frame of the seat squab 4. The squab plate 10 carries the outer gear 16, which comprises an internal tooth form semi-sheared out of the base material.

The inner gear 14 and the outer gear 16 have a special conformal profile, which may for example be similar to a Wildhaber-Novikov (WN) gear form (although other gear forms may also be used). The outer gear 16 has one more tooth than the inner gear 14, in this example the outer gear 16 having thirty teeth and the inner gear twenty- nine teeth. The diameter of the outer gear 16 is selected such that all except one of the teeth on the outer gear have a touch contact with a corresponding tooth on the inner gear 14.

The profiles of the outer gear 16 and the inner gear 14 are designed so that the teeth of the two gears make contact with one another around almost the entire circumference of the gears. Owing to the fact that the inner gear 14 has one fewer tooth than the outer gear 16, the degree of engagement varies from one tooth to the next, such that the teeth are fully engaged on one side of the mechanism (in this case, at the bottom) and partially engaged around most of the circumference of the gears. Not more than one tooth (at the top) is fully disengaged. This arrangement removes most play (chuck) from the mechanism, within manufacturing tolerances. The position of maximum tooth engagement is determined by the rotational position of the cam 12. Since the outer gear 16 has one more tooth than the inner gear 14, the squab plate 1 advances clockwise by one tooth for each clockwise revolution of the cam 12. The second prior art recliner mechanism shown in figure 3 corresponds to that shown in figures 11 to 14 of WO2004/089684 and is similar in many respects to the first prior art recliner mechanism described above, except that the cushion plate 8 and the squab plate 10 carry a secondary set of gears in addition to the primary gears. The cushion plate 8 thus carries a primary inner gear 14 and a secondary inner gear 18, both with external teeth, and the squab plate 10 carries a primary outer gear 16 and a secondary outer gear 20, both with internal teeth.

The primary outer gear 16 again has one more tooth than the primary inner gear, in this case the outer gear having twenty-five teeth and the inner gear twenty-four teeth. The profiles of the primary gears 14,16 are designed so that the teeth of the two gears make contact with one another around substantially the entire circumference of the gears, only one tooth on the outer gear 16 being entirely disengaged. The secondary outer gear 20 also has one more tooth (in this case twenty-five) than the secondary inner gear (twenty-four).

In this prior art arrangement, the primary gears have a full tooth form and are almost entirely responsible for transmitting drive through the mechanism. The profiles of the secondary gears 18,20 are much shallower and are designed so that the teeth of the two gears normally make contact with one another only in one region, which is adjacent to the maximum engagement point of the primary gears. The other teeth of the secondary gears come into engagement only when the recliner mechanism is deformed, for example during an accident. The secondary gears then provide additional strength, to prevent the seat back from collapsing.

An embodiment of a recliner mechanism according to the present invention is shown in figures 4-33. As shown schematically in figure 4, the recliner mechanism is similar in certain respects to the second prior art mechanism shown in figure 3, and includes a cushion plate 108, a squab plate 110 and an eccentric cam element 112. The cushion plate 108 and the squab plate 110 carry primary and secondary gear sets, the primary gear set comprising an outer gear 114 with thirty internal teeth and an inner gear 116 with twenty-nine external teeth, and the secondary gear set comprising an inner gear 118 with thirty external teeth and an outer gear 120 with twenty-nine internal teeth. The primary gears again have full tooth forms and are almost entirely responsible for transmitting drive through the mechanism. The secondary gears have much shallower teeth and merely follow the movement of the primary gears. They do however play an important role in reducing play in the mechanism, as well as increasing its overall strength.

In this embodiment, the secondary gears 118,120 are of larger diameter than the primary gears 114,116. While this arrangement is usually preferred, it is also possible to reverse the arrangement, so that the diameter of the primary gears is larger than that of the secondary gears.

Where the recliner mechanism differs most significantly from the second prior art mechanism is in the arrangement of the primary and secondary gears. In this embodiment, the cushion plate 108 carries the primary inner gear 116 and the secondary outer gear 120, which form the inner and outer circumferential surfaces of a ring-shaped recess 119, formed in the face of the cushion plate 108, for example by fine blanking. The squab plate 110 carries a primary outer gear 114 and a secondary inner gear 118, which form the inner and outer circumferential surfaces of a ring- shaped protrusion 121 that extends from the face of the squab plate 110. Each of the plates therefore carries one outer gear and one inner gear. As a result, the points of maximum engagement of the primary and secondary gears are on opposite sides of the gear sets, rather than being adjacent to one another. For example, in figure 4 the primary gears 114,116 are fully engaged on the left side of the mechanism (at Y), whereas the point of maximum engagement of the secondary gears is on the right side of the mechanism (at Z). This allows the secondary gears to play an active part in defining the relative positions of the squab plate and the cushion plate, and this arrangement virtually eliminates play (chuck) from the mechanism, within manufacturing tolerances.

The profiles of the primary gears 114,116 are again designed so that the teeth of the two gears are fully engaged at one point and make partial contact with one another around almost the entire circumference of the gears. The profiles of the secondary gears 118,120 are complementary to those of the first gears, to allow waltzing rotation of the gear sets. As a result, the secondary gears have an incomplete tooth form which provides only a point contact between the teeth of the inner and outer gears. The degree of engagement varies around the circumference of the secondary gears, the maximum engagement point of the secondary gears being diametrically opposed to the maximum engagement point of the primary gears. Approximately half or more of the secondary gear teeth normally make contact with one another: for example, in the embodiment shown in figure 4 eighteen of the twenty-nine teeth on the secondary outer gear are engaged. However, the other teeth of the secondary gears may come into engagement when the recliner mechanism is deformed, for example during an accident. The secondary gears then provide additional strength, to prevent the seat back from collapsing.

The recliner mechanism is shown in more detail in figures 5-24. The mechanism includes the cushion plate 108 to which is attached a cushion clamp plate 122 and optionally a spacer plate 124. A squab clamp plate 126 and optionally a spacer plate 128 are also attached to the squab plate 110. The cam element 112 extends through the squab plate 110 and the cushion plate 108, a first end of the cam being received in a bush 130 that is located within a central hole 132 in the cushion plate 108. The second end of the cam 112 is received within a hole 134 in the centre of the squab plate 110. The first end of the cam 112 is attached to a compression spring 136, by a circlip 137 and a washer 138, which is compressed between the washer 138 and the bush 130.

The cushion clamp plate 122 is attached to the cushion plate 108, for example with rivets, and has an offset arcuate flange 140 that overlaps the edge of the squab plate 110, to clamp it to the cushion plate 108. The cushion clamp plate 122 also includes two retaining brackets 141 that are bent around the edges of the cushion clamp plate 122, to prevent the squab plate 110 and the cushion plate 108 from separating, for example in a collision. The squab clamp plate 126 similarly has an offset arcuate flange 142 that overlaps the edge of the cushion plate 108, and a pair of retaining brackets 143 that are bent around the edges of the squab plate 110 to prevent separation of the cushion plate 108 and the squab plate 110. The optional spacer plates 124,128 act as bearing surfaces between the flanges 140,142 and the edges of the cushion plate 108 and the squab plate 110, allowing the plates to rotate relative to one another about a pivot axis 145.

The recliner mechanism also includes a latching mechanism for preventing creep, comprising a latching element 150, a spring 152, a latching plate 153 and a driver element 154. Some or all of these components may consist of plastics mouldings. The latching mechanism is attached to the second end of the cam element 112. The latching mechanism is described in more detail below.

The primary and secondary gear sets are formed on the cushion plate 108 and the squab plate 110 by semi-shearing, for example using a technique such as a fine blanking. On the cushion plate 108, the primary inner gear 116 and the secondary outer gear 120 are recessed into the surface of the cushion plate 108, whereas on the squab plate 110 the primary outer gear 114 and the secondary inner gear 118 extend outwards from the surface of the squab plate 110. The raised teeth of the squab plate 110 therefore fit within the recessed teeth of the cushion plate 108. In this embodiment, both sets of teeth have a conical tooth form (i.e. the gears are bevelled), typically at a bevel angle of approximately 2°-8°. Alternatively, one or both gear sets may have straight cut teeth.

The gears provided on the cushion plate 108 are shown in more detail in figures 13- 16. The primary inner gear 116 has a profile wherein each tooth has an outer portion with a first radius and an inner portion with a second, smaller radius. The secondary outer gear 120 comprises a set of intersecting curves of a third radius.

The gears provided on the squab plate 110 are shown in more detail in figures 17-20. The primary outer gear 114 has a complex profile, wherein each tooth comprises four sections having different radii of curvature. The secondary inner gear 118 has an outer portion with a first radius and an inner portion with a second radius.

The cam 112 is shown in more detail in figures 21-26. The cam includes a central cylindrical shaft 164 that is received within the bush 130 in the cushion plate 108. Attached to the shaft 164 is an eccentric head 166 having a conical bearing surface 168 that is received within the hole 134 in the squab plate 110, the walls of the hole 134 being tapered to match the conical section of the bearing surface 168. As can be seen in figure 24, the central axis 172 of the eccentric head 166 is offset from the central axis 174 of the cylindrical shaft 164. The first end of the shaft 164 includes a circumferential slot 176, which receives the circlip 137. The circlip 137 is engaged by the spring 136, which urges the conical bearing surface 168 of the cam against the tapered wall of the hole 134 in the squab plate 110. This ensures that the cam element is pressed firmly against the squab plate 110 to minimise play.

As can be seen most clearly in figures 10 and 12, the conical bearing surface 168 of the cam element 112 engages the tapered walls of the hole 134 in the squab plate 110 in the plane of the primary and secondary gear sets 114-120. The cam element 112 is not therefore subjected to any torque or turning moments about an axis perpendicular to the rotational axis of the cam element. This further helps to reduce play in the mechanism.

In use, rotation of the eccentric cam element 112 causes waltzing movement of the squab plate 110 relative to the cushion plate 108. This causes rotation of the squab plate relative to the cushion plate, the squab plate rotating by an angle equivalent to the separation of two teeth for each complete rotation of the cam element 112. At all times, the primary and secondary gear sets are fully engaged on opposite sides of the gear rings, thereby minimising play in the mechanism.

The cam element 112 also includes a support structure for the latching mechanism, including two support brackets 180 that extend outwards from the rear surface of the head 166, each of which has a through hole 182 towards its end. The support structure also includes a subshaft 184 that also extends outwards from the rear surface of the head 166, and which includes a circumferential groove 186 towards its free end.

The latching element 150, which is shown in detail in figure 31, is generally wishbone-shaped, having two arcuate arms 190 that extend away from a central locking element 192. At the free end of each arm a pivot pin 194 is provided, which is received within one of the holes 182 of the cam element 112. A drive member 196 having a line of three inwards-facing drive pins 198a, 198b, 198c is provided on the inner surface of each arcuate arm 190. The cylindrical surface of middle pin 198b is knurled. The central locking element 192 includes two inclined locking faces 200 and a tapered slot 202. The driver element 154 comprises a cap that fits over the subshaft 184 of the cam element 112. The driver element includes a cylindrical sleeve 210 and an end plate 212 having a D-shaped hole 214, which in use receives a drive shaft connected to a control knob (not shown). The driver element 154 is attached to the subshaft 184 by a pair of detents 216 that engage the groove 186, thus allowing rotational movement but preventing axial movement of the driver element relative to the cam element 112.

A pair of slots 220 are provided on opposite sides of the sleeve 210, which accommodate the drive pins 198a, 198b, 198c of the latching element 150. Each slot 220 includes an outer portion 220a having opposed walls that extend perpendicular to the end face of the sleeve 210, a central portion 220b having inclined walls, and an inner portion 220c having walls that are perpendicular to the end face of the sleeve. The walls of the middle portion 220b are knurled to match the knurled middle pins 198b of the latching element 150.

The spring 152 is attached to the driver element 154 and engages the latching element 150 so that, in use, it urges the locking member 192 downwards, towards the latching plate 153.

The latching plate 153 is attached to the squab plate 110, for example with screws or rivets (not shown). Alternatively, the squab plate and the latching plate may be formed as a single component. The latching plate 153 is provided on its outward face with a ring of radially-extending teeth 224. The size and spacing of these teeth are matched to the width of the locking member 200 and the tapered slot 202, allowing the latching element 150 to engage the latching plate 153 with either the locking member between two adjacent teeth 224 or with the slot 202 located over one of the teeth 224. The latching element 150 is urged towards this latched position by the spring 152, and when latched this prevents relative rotation between the cam element 112 and the squab plate 110, thus preventing creep. The latching element may however be disengaged as described below to allow the recliner mechanism to be adjusted.

When the recliner mechanism is adjusted by rotating a control knob, a rotary drive is applied via a shaft engaged in the D-shaped hole 214 to the driver element 154. As the driver element 154 rotates forwards, as shown in figure 33, the vertical wall forming the outer portion 220a of the slot engages the lower drive pin 198a, causing the latching element 150 to pivot about the pins 194. This lifts the locking member 192 out of engagement with the teeth on the latching plate 153, thereby releasing the latching mechanism. Rotation of the driver element 154 relative to the cam element 112 continues until the knurled middle pin 198b engages the knurled drive surface of the wall forming the middle part 220b of the slot. Upon contacting that surface, continued rotation of the driver element is transmitted through the middle pins 198b and the pivot pins 194 to the cam element, thereby causing rotation of the adjustment mechanism. The knurlings on the middle pins 198b and the middle portions 220b of the slots prevent the latching element from dropping back into engagement with the teeth on the latching plate 153 until rotation of the driver element ceases.

When the recliner mechanism is to be adjusted backwards, the control knob is rotated in the opposite direction. Thus, as shown in figure 34, the upper drive pin 198c is engaged by the wall at the inner part 220c of the slot, again lifting the latching element 150 away from the latching plate 153. Rotary drive is transmitted to the cam element 112 when the middle pin 198b engages the middle portion 220b of the slot. Again, the knurlings retain the latching elements in an unlocked condition until rotation of the driver element 154 ceases.

Various modifications of the mechanism described above are of course possible. For example, the arrangement of the gear rings may be reversed, so that the cushion plate carries the primary outer gear and the secondary inner gear, and the squab plate carries the primary inner gear and the secondary outer gear. The relative diameters and the number of teeth carried by the primary and secondary gear rings may also be altered: for example, the primary gears may be of larger diameter than the secondary gears. However, packaging requirements and reduced play generally make it more convenient for the diameter of the secondary gears to be larger than that of the primary gears.

The gear rings and other components of the mechanism may be made using alternative manufacturing methods, such as blanking, broaching, eroding and so on. Various of the components, for example the cam or the gear teeth, may also have alternative forms or shapes, according to their specific requirements.

Claims

1. A seat recliner mechanism for a seat having a seat cushion and a reclinable squab, the mechanism including a stationary hinge member connectable with the seat cushion, an adjustable hinge member connectable with the squab, and an angular position adjuster in the form of a wobble gear mechanism, wherein the wobble gear mechanism includes a primary gear mechanism and a secondary gear mechanism, each comprising an inner gear and an outer gear having different numbers of teeth and arranged to provide a point of maximum tooth engagement, and an eccentric drive element that is rotatable to cause eccentric relative rotation of the inner and outer gears and angular adjustment of the hinge members; characterised in that the points of maximum tooth engagement of the primary and secondary gear mechanisms are diametrically opposed.

2. A seat recliner mechanism according to claim 1, in which the primary inner gear and the secondary outer gear are connected to one of the hinge members, and the primary outer gear and the secondary inner gear are connected to the other hinge member.

3. A seat recliner mechanism according to claim 2, in which the primary inner gear and the secondary outer gear are connected to the stationary hinge member, and the primary outer gear and the secondary inner gear are connected to the adjustable hinge member.

4. A seat recliner mechanism according to any one of the preceding claims, in which the gears are formed on the hinge members by semi-shearing.

5. A seat recliner mechanism according to any one of the preceding claims, in which the primary outer gear has one more tooth than the primary inner gear.

6. A seat recliner mechanism according to claim 5, in which the primary inner and outer gears have conformal tooth profiles, whereby in use not more than one of the teeth on the inner gear is disengaged from the teeth on the outer gear.

7. A seat recliner mechanism according to claim 6, in which the maximum peak-to-peak gap between the teeth of the primary inner and outer gears is less than 0.15mm, preferably less than 0.1mm.

8. A seat recliner mechanism according to any one of the preceding claims, in which one or both of the primary and secondary gear mechanisms have conical tooth forms.

9. A seat recliner mechanism according to any one of the preceding claims, in which the primary and secondary gear mechanisms lie in substantially the same plane.

10. A seat recliner mechanism according to any one of the preceding claims, in which the rotatable drive element is mounted in a bearing in one of the hinge members, the rotatable drive element and the bearing having complementary frusto-conical bearing surfaces.

11. A seat recliner mechanism according to claim 10, in which the primary and secondary gear mechanisms lie in substantially the same plane as the bearing.

12. A seat recliner mechanism according to claim 10 or claim 11, including a resilient element that is constructed and arranged to urge the drive element axially against the bearing.

13. A seat recliner mechanism according to any one of the preceding claims, including a latching mechanism for preventing unintended rotation of the eccentric drive element.

14. A seat recliner mechanism according to claim 13, in which the latching mechanism includes a latching element connected to the eccentric drive element for rotation therewith, said latching element being selectively engageable with latching formations associated with one of the hinge members.

15. A seat recliner mechanism according to claim 14, in which the latching element is constructed and arranged to disengage the latching formations upon rotation of a drive element for the recliner mechanism.