Seat reclining mechanisms

This application claims priority to Japanese Patent Application Serial Number 2002-358341, the contents of which are incorporated herein by reference.

1. Field of the Invention Deferent

The present invention relates to seat reclining mechanisms for adjusting a tilt angle of a seat back of a seat (e.g., a vehicle seat).

2. Description of the Related Art

Typically, a vehicle seat comprises a seat back and a seat cushion. The seat back and the seat cushion are rotatably interconnected via a seat reclining mechanism for adjusting a tilt angle of the seat back. Such a seat reclining mechanism is taught, for example, by Japanese Laid-Open Patent Publication Number 2002-10851. Such a seat reclining mechanism is known as a “round type” seat reclining mechanism.

As shown in FIG. 11 , the known seat reclining mechanism includes a pair of opposing disk-like housings, i.e., a first or stationary housing 11 and a second or rotational housing 12 . The first housing 11 is affixed to the vehicle seat cushion (not shown). The second housing 12 is affixed to the vehicle seat back (not shown). The first and second housings 11 and 12 are circumferentially connected by an annular fastener or clip ring 2 along peripheral edges 11 a and 12 a thereof, so that the second housing 12 can move or rotate relative to the first housing 11 around a rotational shaft (not shown).

The clip ring 2 comprises an annular guide portion 2 a that slidably support the peripheral edge 12 a of the second housing 12 and an annular fixture portion 2 b that is fixed to the peripheral edge 11 a of the first housing 11 . The guide portion 2 a is circumferentially formed with a plurality of projections or slide portions 2 a - 1 , so that a sliding clearance between the second housing peripheral edge 12 a and the clip ring guide portion 2 a can be easily controlled. As shown in FIG. 10 , the slide portions 2 a - 1 are spaced at equal intervals. The first and second housing 11 and 12 thus assembled are respectively fixed to the seat cushion and the seat back.

The seat reclining mechanism further includes a locking means (not shown) that can prevent the second housing 12 from rotating relative to the first housing 11 , so as to lock the seat reclining mechanism. The locking means essentially consists of a cam member and a pair of pawls (not shown) that are received within the housings 11 and 12 . The cam member is secured to or integrally formed with the rotational shaft, so as to rotate with the rotational shaft. Each of the pawls is provided with a convex toothed portion and is radially movably positioned on the first housing 11 .

When the rotational shaft is rotated to a locking position, the pawls are radially moved outward by the cam member, so that the respective convex toothed portions of the pawls engage a concave toothed portion (not shown) that is circumferentially formed over an inner circular surface of the second housing peripheral edge 12 a . In this state, the second housing 12 is prevented from rotating relative to the first housing 11 , so that the seat reclining mechanism is locked. As a result, the seat back is locked in position relative to the seat cushion.

Often times, a large force can be unexpectedly applied to the seat reclining mechanism in a direction to separate the housings 11 and 12 from each other. Such a large force may concentrate to the slide portions 2 a - 1 of the clip ring guide portion 2 a . As a result, the guide portion 2 a may be deformed outwardly or spread out, as shown by a broken line in FIG. 11 . Such a deformation of the guide portion 2 a may reduce a locking performance of the seat reclining mechanism.

It is, accordingly, one object of the present teachings to provide improved seat reclining mechanisms.

For example, in one aspect of the present teachings, a seat reclining mechanism for a vehicle seat may include a first or stationary housing, a second or rotational housing, a locking means received between the first and second housings, and a fastener for rotatably connecting the second housing to the first housing. The fastener is formed with at least one retainer portion and at least one slide portion that respectively project toward the second housing. Preferably, the at least one slide portion has a height greater than the at least one retainer portion.

Thus, when a large force is applied to the seat reclining mechanism in a direction to separate the first and second housings from each other, the retainer portion may receive and resist such a large force, so that the fastener can be effectively prevented from outwardly deforming. As a result, a desired locking performance of the seat reclining mechanism can be reliably maintained even if the seat reclining mechanism is acted upon by such a large force.

Other objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims.

FIG. 1 is a vertical, cross-sectional view of a seat reclining mechanism according to a first embodiment of the present teachings; and

FIG. 2 is an exploded perspective view of the seat reclining mechanism; and

FIG. 3 is a cross-sectional view taken along line III—III in FIG. 1 , which illustrates a locking position of a rotational shaft of the seat reclining mechanism; and

FIG. 4 is a plan view of a clip ring, in which first and second housings are omitted; and

FIG. 5 is a cross-sectional view taken along line V—V in FIG. 4 , in which the first and second housings are shown; and

FIG. 6 is a cross-sectional view taken along line VI—VI in FIG. 4 , in which the first and second housings are shown; and

FIG. 7 is a perspective view of a clip ring of a seat reclining mechanism according to a second embodiment of the present teachings; and

FIG. 8 is a plan view of the clip ring, in which first and second housings are omitted; and

FIG. 9 is a cross-sectional view taken along line IX—IX in FIG. 8 , in which first and second housings are shown; and

FIG. 10 is a plan view of a conventional clip ring; and

FIG. 11 is a cross-sectional view taken along line XI—XI in FIG. 10 , in which first and second housings are shown.

Representative examples of the present invention have been described in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Only the claims define the scope of the claimed invention. Therefore, combinations of features and steps disclosed in the foregoing detail description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe detailed representative examples of the invention. Moreover, the various features taught in this specification may be combined in ways that are not specifically enumerated in order to obtain additional useful embodiments of the present teachings.

Detailed representative embodiments of the present teachings are shown in FIG. 1 to FIG. 9 .

A first detailed representative embodiment of the present teachings is shown in FIGS. 1 to 6 .

As shown in FIGS. 1 to 3 , a representative seat reclining mechanism 10 for adjusting a tilt angle of a seat back of a vehicle seat (not shown) is designed to be disposed on one side of the vehicle seat. The seat reclining mechanism 10 includes a pair of opposing dish-like housings, i.e., a first or stationary housing 11 and a second or rotational housing 12 . The first housing 11 is affixed to a vehicle seat cushion (not shown). The second housing 12 is affixed to the vehicle seat back. The first and second housings 11 and 12 are circumferentially connected by an annular fastener or clip ring 22 along oppositely projected peripheral edges 11 a and 12 a thereof, so that the second housing 12 can move or rotate relative to the first housing 11 around a rotational axis L. Further, the rotational axis L corresponds to a common centerline of the first and second housings 11 and 12 .

The seat reclining mechanism 10 also includes a square rotational rod or shaft 13 that extends along the rotational axis L through the seat cushion and the seat back as well as the first and second housings 11 and 12 . The rotational shaft 13 includes an extended portion (manipulating portion) 13 ′, which is typically connected to a seat operation handle or lever 14 .

The seat reclining mechanism 10 further includes a locking means or rotation controlling means that can prevent the second housing 12 from rotating relative to the first housing 11 , so as to lock the seat reclining mechanism 10 . As best shown in FIG. 2 , the locking means preferably consists of four slide pawls (i.e., locking members) 15 , a rotary cam 16 , an operation arm 17 , an active plate 18 , an unlocking plate 19 and a biasing (spiral) spring 21 that are received within the housings 11 and 12 . As shown in FIGS. 1 and 3 , the operation arm 17 is secured to the rotational shaft 13 , so as to rotate with the rotational shaft 13 .

As shown in FIGS. 2 and 3 , the first housing 11 is formed with two pairs of opposite triangular thickened portions lid that are positioned at equal intervals along the peripheral edge 11 a , so that four guide grooves 11 c are defined therebetween. As will be apparent, the guide grooves 11 c may intersect crosswise and radially extend on the first housing 11 . In addition, the first housing 11 is formed with a central circular bore 11 e , which rotatably receives the rotational shaft 13 . Furthermore, the first housing 11 has an inner annular groove 11 f that is formed around the central bore 11 e.

As shown in FIGS. 2 and 3 , the second housing 12 includes a circular concave toothed portions 12 c that is circumferentially formed along an inner surface of the peripheral edge 12 a . In addition, the second housing 12 is formed with a central circular bore 12 d , which is aligned with the central bore lie and rotatably receives the rotational shaft 13 . Moreover, the second housing 12 is formed with four inner engagement projections 12 e , which are appropriately arranged around the central bore 12 d.

As shown in FIGS. 2 and 3 , all of the slide pawls 15 have substantially the same shape and construction. However, one of the slide pawls 15 (which will be referred to as a special slide pawl 15 A) has a special construction different from the other three slide pawls 15 (which will be referred to as normal slide pawls 15 ), so as to have a special function (which will be hereinafter described). The slide pawls 15 (and 15 A) are closely slidably received within the guide grooves 11 c of the first housing 11 , so as to radially move on the first housing 11 . As will be recognized, because the slide pawls 15 (and 15 A) are received in the guide grooves 11 c , the pawls 15 (and 15 A) may preferably be prevented from rotating relative to the first housing 11 .

Each of the slide pawls 15 (and 15 A) has an outwardly curved outer surface and a specially shaped inner surface. The curved outer surface of each pawl 15 (and 15 A) is provided with a corresponding convex toothed portion 15 b for releasably engaging the concave toothed portion 12 c of the second housing 12 . Also, the inner surface of each slide pawl 15 (and 15 A) is provided with a pair of leg portions or cam contacts (first and second) 15 c and 15 d that extend in parallel along each of the guide grooves 11 c . In addition, the inner surface of each pawl 15 (and 15 A) is provided with an additional or central cam contact (third) 15 f.

Each of the normal slide pawls 15 has a substantially square cam projection 15 e that projects toward the second housing 12 . The cam projection 15 e is disposed along the inner surface of the slide pawl 15 . The special slide pawl 15 A also has a substantially square cam projection 15 e ′ similar to the cam projection 15 e of the slide pawl 15 . However, the cam projection 15 e ′ is different from the cam projection 15 e in that the cam projection 15 e ′ is longer than the cam projection 15 e . The special slide pawl 15 A also has an additional cam projection 15 g that projects in parallel with the cam projection 15 e ′. The additional cam projection 15 g also is disposed along the inner surface of the slide pawl 15 A and has substantially the same length as the longer cam projection 15 e ′. The cam projection 15 e ′ of the special slide pawl 15 A may perform the same function as the cam projection 15 e as well as an additional function (which will be hereinafter described).

As shown in FIGS. 2 and 3 , the rotary cam 16 is a specially contoured plate-like member. The rotary cam 16 is received in a space defined by the inner surfaces of the slide pawls 15 (and 15 A), so as to be rotatable around the rotational axis L over a desired angle. The rotary cam 16 has four sets of three cam portions (first to third), 16 c , 16 b , and 16 d , that are formed in a circumferential end surface thereof. The first cam portions 16 c of the respective sets are positioned at equal intervals along the circumferential end surface. Similarly, the second and third cam portions 16 b and 16 d of the respective sets also are positioned at equal intervals along the circumferential end surface, respectively. As best shown in FIG. 3 , the first to third cam portions 16 c , 16 b , and 16 d , of each set are respectively arranged and constructed to contact the first to third cam contacts 15 c , 15 d , and 15 f , of each pawl 15 (and 15 A), so that the slide pawls 15 (and 15 A) can be moved outwardly along the guide grooves 11 c when the rotary cam 16 is rotated to a locking position ( FIG.3 ). That is, the rotary cam 16 may function as a cam mechanism for outwardly moving the slide pawls 15 (and 15 A) when it is rotated to the locking position.

In addition, the rotary cam 16 is formed with a noncircular central bore 16 e . Further, the rotary cam 16 has three engagement projections 16 f that are positioned around the central bore 16 e at desired intervals and project toward the second housing 12 .

The operation arm 17 comprises a square tubular connecting portion 17 a and a noncircular arm portion 17 b . The arm portion 17 b is integrally formed with the connecting portion 17 a and has an outer profile that substantially corresponds to an inner profile of the rotary cam central bore 16 e . As shown in FIG. 3 , the connecting portion 17 a has a rectangular through bore that corresponds to an outer profile of the rotational shaft 13 . The connecting portion 17 a is journaled on the rotational shaft 13 , so that the operation arm 17 (the arm portion 17 b ) can rotate with the rotational shaft 13 . As will be appreciated, the operation arm 17 is appropriately positioned on the shaft 13 , so that the arm portion 17 b unrotatably engages the rotary cam central bore 16 e.

As shown in FIG. 2 , the active plate 18 is a substantially circular plate-like member and is positioned adjacent to the slide pawls 15 (and 15 A). The active plate 18 is formed with a circular central bore 18 b , which is aligned with the central bores 11 e and 12 d , of the housings 11 and 12 , and rotatably receives the rotational shaft 13 . Also, the active plate 18 has three small engagement apertures 18 c , which are positioned around the central bore 18 b at desired intervals. As will be appreciated, the engagement apertures 18 c respectively receive the engagement projections 16 f of the rotary cam 16 , so that the active plate 18 can be rotated with the rotary cam 16 as a unit. In addition, the active plate 18 further includes three window-like normal cam slots 18 d and a window-like special cam slot 18 d - a that are formed along a periphery thereof at equal intervals. Each of the normal cam slots 18 d has an arcuate normal cam contact surface 18 d 1 . Similarly, the special cam slot 18 d - a has an arcuate special cam contact surface 18 d - a 1 , which is partially identical with the normal cam surface 18 d 1 . As will be recognized, the normal cam grooves 18 d respectively receives the cam projections 15 e of the slide pawl 15 . Also, the special cam groove 18 d - a receives both of the cam projections 15 e ′ and 15 g of the special slide pawl 15 A. As a result, the active plate 18 may function as a cam mechanism for inwardly moving the slide pawls 15 (and 15 A) when the rotary cam 16 is rotated clockwise in FIG. 3 .

As shown in FIG. 2 , the unlocking plate 19 is a substantially circular plate-like member and is positioned adjacent to the active plate 18 . The unlocking plate 19 is formed with a circular central bore 19 b , which is aligned with the active plate central bore 18 b and rotatably receives the rotational shaft 13 . Also, the unlocking plate 19 has two small engagement apertures 19 d , which are positioned around the central bore 19 b . In addition, the unlocking plate 19 further includes a substantially annular or horseshoe-shaped cam slot 19 c extending along a periphery thereof. The cam slot 19 c includes a pair of (first and second) symmetrical wide sections 19 c - 1 and 19 c - 3 , and a narrow mid section 19 c - 2 . Each of the first and second wide sections 19 c - 1 and 19 c - 3 is formed with an end engagement portion 19 c - 4 . As will be recognized, the engagement apertures 19 d and the end engagement portions 19 c - 4 respectively engage the inner engagement projections 12 e of the second housing 12 , so that the unlocking plate 19 can be rotated with the second housing 12 as a unit.

The first wide section 19 c - 1 has substantially the same shape and size as the second wide section 19 c - 3 . That is, the first wide section 19 c - 1 includes a cam surface that has the same radius of curvature as that of the third wide section 19 c - 3 . However, the mid section 19 c - 2 includes a cam surface that has a smaller radius of curvature than that of the wide section 19 c - 1 or 19 c - 3 . The cam slot 19 c thus shaped receives the cam projections 15 e ′ and 15 g of the special slide pawl 15 A. As will be recognized, the cam slot 19 c does not receives the cam projections 15 e of the normal slide pawl 15 , because the cam projections 15 e terminate in the active plate cam slots 18 d and do not extend to the unlocking plate 19 . As a result, the unlocking plate 19 may function as a cam mechanism for inwardly moving only the special slide pawl 15 A.

It should be noted that the unlocking plate 19 is preferably positioned such that the cam projections 15 e ′ and 15 g of the slide pawl 15 A are received in the first wide section 19 c - 1 of the cam slot 19 c , so as to contact the cam surface of the first wide section 19 c -l when the rotary cam 16 is in the locking position ( FIG. 3 ). In addition, the unlocking plate 19 also is preferably positioned such that the cam projection 15 g of the slide pawl 15 A is disposed adjacent to the beginning of the mid section 19 c - 2 of the cam slot 19 c.

The biasing (spiral) spring 21 is disposed within the annular groove 11 f of the first housing 11 . The spiral spring 21 includes an inner end portion 21 a that is coiled in rectangles and an outer end portion 21 b that is simply outwardly folded. The inner end portion 21 a unrotatably receives the square connecting portion 17 a of the operation arm 17 . The outer end portion 21 b is appropriately secured in the first housing annular groove 1 If, so that the biasing spring 21 is not rotated therein. As will be recognized, the spiral spring 21 thus arranged and constructed may preferably urge (bias) the operation arm 17 (and the rotational shaft 13 ) to a desired rotational direction (i.e., counterclockwise in FIG. 3 ), so that the rotational shaft 13 can be normally retained in a locking position ( FIG. 3 ).

Further, as shown in FIGS. 1 , 2 , and 4 – 6 , the annular clip ring 22 comprises an annular guide portion 22 a that slidably rotatably supports the peripheral edge 12 a of the second housing 12 , an annular fixture portion 22 b that is fixed to the peripheral edge 11 a of the first housing 11 by crimping, and an annular connecting portion or transient portion 22 c that interconnects the guide portion 22 a and the fixture portion 22 b . The guide portion 22 a is circumferentially formed with a plurality of (six in this embodiment) elongated proximal projected portions or retainer portions 22 a - 1 that are projected inwardly (i.e., toward the second housing peripheral edge 12 a ), so that a sliding clearance between the second housing peripheral edge 12 a and the clip ring guide portion 22 a can normally be easily controlled. As best shown in FIG. 4 , the proximal projected portions 22 a - 1 are spaced at equal intervals. Also, the guide portion 22 a is circumferentially formed with a plurality (six in this embodiment) of circular distal projected portions or slide portions 22 a - 2 that are projected inwardly (i.e., toward the second housing peripheral edge 12 a ). As best shown in FIG. 4 , the distal projected portions 22 a - 2 are positioned between the proximal projected portions 22 a - 1 and are spaced at equal intervals. Typically, the proximal and distal projected portions 22 a - 1 and 22 a - 2 are simultaneously formed by depressing the guide portion 22 a during press forming of the clip ring 22 . Preferably, the proximal and distal projected portions 22 a - 1 and 22 a - 2 are alternately positioned at equal intervals. Also, the distal projected portions 22 a - 2 are preferably constructed to be higher than the proximal projected portions 22 a - 1 .

A representative process for manufacturing the seat reclining mechanism 10 will now be simply described. First, the slide pawls 15 and 15 A, the biasing spring 21 , the operation arm 17 connected to the rotational rod 13 , the rotary cam 16 , and the active plate 18 , are assembled into the first housing 11 . On the other hand, the unlocking plate is assembled into the second housing 12 . The first and second housings 11 and 12 thus assembled are preferably coupled such that the peripheral edges 11 a and 12 a telescopically engage each other. Thereafter, the clip ring 22 is disposed on the engaged peripheral edges 11 a and 12 a of the housings 11 and 12 . Finally, the fixture portion 22 b of the clip ring 22 is fixed to the peripheral edge 11 a of the first housing 11 by crimping such that desired clearances are produced between the second housing peripheral edge 12 a and the proximal and distal projected portions 22 a - 1 and 22 a - 2 of the clip ring guide portion 22 a . It should be noted that the clip ring 22 may preferably be attached to the first and second housings 11 and 12 such that the proximal projected portions 22 a - 1 are at least partly opposed to the slide pawls 15 and 15 A. However, the proximal projected portions 22 a - 1 can be automatically opposed to the slide pawls 15 and 15 A even if the clip ring 22 is randomly attached to the housings 11 and 12 due to the number of the proximal projected portions 22 a - 1 .

According to the seat reclining mechanism 10 thus constructed, the rotational shaft 13 is normally retained in the locking position by means of the biasing force of the biasing spring 21 . When the shaft 13 is retained in the locking position, the rotary cam 16 is urged counterclockwise ( FIG. 3 ), so that the cam mechanism of the rotary cam 16 is actuated. That is, the first to third cam surfaces 16 c , 16 b , and 16 d , thereof cooperate with the corresponding cam contacts 15 c , 15 d and 15 f of the slide pawls 15 (and 15 A), so as to outwardly push the respective slide pawls 15 (and 15 A). As a result, the slide pawls 15 (and 15 A) are moved to the outermost position ( FIG. 3 ). When the slide pawls 15 is retained in the outermost position, the convex toothed portions 15 b of the pawls 15 (and 15 A) engage the concave toothed portions 12 c of the second housing 12 . That is, when the rotary cam 16 is urged counterclockwise, the pawls 15 (and 15 A) are positioned in engaging positions ( FIG. 3 ). In this state, the second housing 12 is prevented from rotating relative to the first housing 11 , thereby locking the seat reclining mechanism 10 . As a result, the seat back is locked in position relative to the seat cushion.

The rotational shaft 13 can be rotated clockwise against the urging force of the biasing spring 21 by operating the lever 14 . When the rotational shaft 13 is rotated to an unlocking position (not shown), the rotary cam 16 also is rotated clockwise to an unlocking position (not shown), so that the first to third cam surfaces 16 c , 16 b , and 16 d , thereof are disengaged from the cam contacts 15 c , 15 d , and 15 f , of the slide pawls 15 (and 15 A). Simultaneously, the active plate 18 also is rotated in the same direction as the rotary cam 16 , so that the cam mechanism of the active plate 18 is actuated. As a result, the slide pawls 15 (and 15 A) are inwardly moved, so that the convex toothed portions 15 b of the pawls 15 (and 15 A) are disengaged from the concave toothed portions 12 c of the second housing 12 . Consequently, the pawls 15 (and 15 A) are positioned in non-engaging positions (not shown). In this state, the second housing 12 can freely rotate relative to the first housing 11 , thereby unlocking the seat reclining mechanism 10 . As a result, the seat back can freely rotate relative to the seat cushion, such that the seat back can be tilted forwardly and rearwardly relative to the seat cushion.

Under an unlocking condition of the seat reclining mechanism 10 , when the seat back is tilted forwardly or folded relative to the seat cushion, the second housing 12 and the unlocking plate 19 are rotated counterclockwise in FIG. 3 , so that the cam surface of the mid section 19 c - 2 of the unlocking plate 19 sequentially engages the cam projections 15 e ′ and 15 g of the slide pawl 15 A. As will be recognized, when the cam surface of the mid section 19 c - 2 is engaged with either one of the cam projections 15 e ′ and 15 g, the slide pawl 15 A can be effectively retained in the non-engaging position even if the lever 14 is released. Therefore, the seat back can be tilted forwardly, with the lever 14 released. When the seat back is further tilted over a desired angle (e.g., when the seat back is folded on the seat cushion), the cam surface of the mid section 19 c - 2 of the plate 19 is disengaged from both of the cam projections 15 e ′ and 15 g of the slide pawl 15 A, so that the cam projections 15 e ′ and 15 g fall within the second wide section 19 c - 3 of the cam slot 19 c . As a result, the rotary cam 16 is immediately rotated counterclockwise to the locking position, so that the slide pawls 15 ( 15 A) are outwardly moved toward the engaging positions. Consequently, the convex toothed portions 15 b of the pawls 15 (and 15 A) are engaged with the concave toothed portions 12 c of the second housing 12 , so that the seat reclining mechanism 10 is preferably locked.

Next, the function of the clip ring 22 of the seat reclining mechanism 10 will now be described in detail.

A large force can be unexpectedly applied to the seat reclining mechanism 10 , possibly resulting in an outward component force. Such an outward component force may act on the first and second housings 11 and 12 via the slide pawls 15 and 15 A. The component force may act on the proximal and distal projected portions 22 a - 1 and 22 a - 2 of the guide portion 22 a of the clip ring 22 and may work to deform outwardly or spread out the clip ring guide portion 22 a . However, the clip ring guide portion 22 a can be effectively inhibited from outwardly deforming, because the proximal projected portions 22 a - 1 preferably increase geometrical moment of inertia or flexural rigidity of the clip ring 22 against the outward component force that acts on the clip ring 22 , thereby providing the proximal projected portions 22 a -l with excellent rigidity or deformation resistance. As a result, a desired locking performance of the seat reclining mechanism 10 can be reliably maintained even if the seat reclining mechanism 10 experiences a large force.

The second detailed representative embodiment will now be described with reference to FIGS. 7–9 . Because the second embodiment relates to the first embodiment, only constructions and elements that are different from the first embodiment will be explained in detail. Elements that are the same in the first and second embodiments will be identified by the same reference numerals and detailed descriptions of such elements will be omitted.

In this embodiment, the clip ring 22 is circumferentially formed with a plurality (six in this embodiment) of elongated outwardly deformed portions or beads 22 a - 3 , which are formed in the transient portion 22 c interconnecting the guide portion 22 a and the fixture portion 22 b . As will be apparent, the beads 22 a - 3 are respectively radially aligned with the proximal projected portions 22 a - 1 . The beads 22 a - 3 thus constructed may effectively contribute to increase the rigidity or deformation resistance of the proximal projected portions 22 a - 1 , because the beads 22 a - 3 cooperate with the proximal projected portions 22 a - 1 to further increase the geometrical moment of inertia or the flexural rigidity of the clip ring 22 against the outward component force that acts on the clip ring 22 . Therefore, the clip ring guide portion 22 a can be further effectively inhibited from outwardly deforming. As a result, a desired locking performance of the seat reclining mechanism 10 can be more reliably maintained even if the seat reclining mechanism 10 suffers from a large force.

Although the six elongated proximal projected portions 22 a - 1 are exemplified in these representative embodiments, the number, shape, and arrangement, of the proximal projected portions 22 a - 1 can be changed provided that the proximal projected portions 22 a - 1 can be at least partly opposed to the slide pawls 15 and 15 A, if necessary.

Moreover, the construction of the clip ring 22 also can be applied to other similar seat reclining mechanisms, for example, a continuously variable seat reclining mechanism having a locking means that is different from the locking means used in these embodiments.