Patent Publication Number: US-11376996-B2

Title: Reclining device and seat

Description:
TECHNICAL FIELD 
     The present invention relates to a reclining device attached to a seat of a vehicle or the like to appropriately adjust an angle of inclination of a seat back with respect to a seat cushion, and a seat in which the seat reclining device is assembled. 
     BACKGROUND ART 
     A reclining device is formed so as to fix a guide bracket to one of a seat cushion and a seat back, fix an internal gear to the other, dispose lock plates including external teeth engageable with internal teeth of the internal gear between the guide bracket and the internal gear, keep the seat back at an appropriate angle of inclination by making the internal gear and the lock plates engaged with each other, and allow the seat back to turn forward and backward by releasing their engagement. Further, as indicated in Patent Documents 1 and 2, in a case where a seat back is moved to a forward reclined position by a walk-in operation or the like, there is also known a reclining device including a memory mechanism part which allows a reclining angle of the seat back at a position before the walk-in operation to be memorized, and the seat back to be returned to the memorized inclination position at the time of a return from the walk-in operation. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Patent Application Laid-open No. 2008-119362 
     Patent Document 2: Japanese Patent Application Laid-open No. 2009-226039 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     The reclining devices disclosed in Patent Documents 1 and 2 each include, in addition to a normal lock mechanism part for locking the seat back at a predetermined reclining angle, the above-described memory mechanism part, and an internal gear includes not only locking internal teeth engageable with lock plates at the time of normal locking but also memory internal teeth engageable with a memory gear at the time of a memory operation. The locking internal teeth and the memory internal teeth are continuously provided while having a step in an axial direction. That is, the internal gear is formed in a substantially convex shape including, on an outer end side in the axial direction, a small-diameter portion whose inside diameter and outside diameter are both small and in which the memory internal teeth are formed on an inner peripheral surface, and including, adjacently to the small-diameter portion in the axial direction, a large-diameter portion whose inside diameter and outside diameter are both larger than those of the small-diameter portion and in which the locking internal teeth are formed on an inner peripheral surface. The small-diameter portion and the large-diameter portion, whose inside diameters and outside diameters are both different in this manner, are each normally processed by fine blanking processing so that both the inner peripheral surface and an outer peripheral surface have a stepped shape. The small-diameter portion is a section fixed to a frame of a seat cushion or a seat back, and a load of the frame is directly transmitted thereto, thus bringing about a weak point in terms of strength which makes deformation likely to occur. However, conventionally, although there is a point where the memory internal teeth are formed on the inner peripheral surface of the small-diameter portion having a case where operations of members composing the memory mechanism part are not smoothly performed and a size of the small-diameter portion is restricted when it is fixed by welding, a deformation of the frame also makes the outside diameter of the small-diameter portion small, which easily causes the deformation when a large load is applied to either of the memory internal teeth and the locking internal teeth. Further, the welding compels the small-diameter portion to have a shape in which a convex portion not subjected to heat treatment is formed at its further axial outer end (refer to Patent Document 2), and in that case, a diameter of the convex portion becomes small, and along with this, a coupled range to the frame becomes small, which also affects the strength. Further, both the complicated shapes sometimes make flatness on a stepped surface between the large-diameter portion and the small-diameter portion unlikely to be secured, and sometimes affect smooth operations of the respective members. 
     The present invention was made in consideration of the above, and has an object to provide a reclining device which enhances strength of an internal gear including locking internal teeth and memory internal teeth and is capable of inhibiting deformation when a large load is applied to each of the locking internal teeth and the memory internal teeth, and in which forming the internal gear in a simple shape also makes flatness on a stepped surface between the locking internal teeth and the memory internal teeth likely to be secured to enable further smooth operations of members, and a seat having the reclining device. 
     Means for Solving the Problems 
     In order to solve the above problems, a reclining device of the present invention includes: 
     a lock mechanism part including a guide bracket coupled to one of a seat cushion and a seat back, and including lock plates movable in a radial direction along a plurality of guide wall portions provided on one surface of the guide bracket; 
     an internal gear which is coupled to the other of the seat cushion and the seat back, and rotates relatively to the guide bracket; and 
     a memory mechanism part which includes memory gears provided between the guide bracket and the internal gear, and memorizes a predetermined locked position through the lock mechanism part, 
     wherein, in the internal gear, a thin annular portion and a thick annular portion whose outside diameters are same and whose inside diameters are different are continuously provided integrally in an axial direction, and an axial outer end surface of the thick annular portion is formed to be substantially flat, and 
     wherein, on an inner peripheral surface of the thin annular portion, locking internal teeth with which locking external teeth provided on the lock plate engage are formed, and on an inner peripheral surface of the thick annular portion, memory internal teeth with which memory external teeth provided on the memory gear engage are formed. 
     Preferably, a coupling cover member coupled to the seat cushion or the seat back is fixed so as to project to an outside of the axial outer end surface of the thick annular portion of the internal gear. 
     Preferably, a projecting pin projecting in the memory gear direction is provided on the lock plate, the projecting pin is inserted through a pin insertion hole with a predetermined length which is provided along a circumferential direction in the memory gear, and the projecting pin moves relatively in the pin insertion hole at a time of a rotation of the memory gear, whereby the lock plate is held in a memory position. 
     Preferably, the projecting pin is provided with a flange portion at one end of a shaft portion, the guide bracket has a pin restricting hole which is formed long in a radial direction so as to allow the projecting pin to move in the radial direction together with the lock plate, and whose width along a direction orthogonal to the radial direction is formed to be almost same as a diameter of the shaft portion of the projecting pin, the projecting pin is inserted in the pin restricting hole of the guide bracket from an axial outer end side of the guide bracket, a tip of the shaft portion penetrates the lock plate to project, and the flange portion is located on the axial outer end side of the guide bracket, and the shaft portion of the projecting pin is restricted by the pin restricting hole, and can move in the radial direction with wobbling in the direction orthogonal to the radial direction of the lock plate reduced. 
     Preferably, the shaft portion of the projecting pin is integrated with the lock plate. 
     Further, the present invention provides a seat which includes a seat cushion and a seat back, the seat including the reclining device. 
     Effect of the Invention 
     According to the present invention, in the internal gear, the thin annular portion and the thick annular portion whose outside diameters are the same and whose inside diameters are different are continuously provided integrally in the axial direction, and the outer peripheral surface of the thin annular portion and the thick annular portion is formed in a substantially L shape in a flush cross section. Therefore, a conventionally substantially convex section formed with the memory internal teeth does not become the weak point in terms of strength. Further, in the present invention, since the axial outer end surface of the thick annular portion of the internal gear is formed to be substantially flat, the coupling cover member is fixed to this thick annular portion to be coupled to the frame of the seat cushion or the seat back. Since the coupling can be performed with the thick annular portion interposed, high coupling strength can be obtained. Further, since the internal gear is in the substantially L shape in the cross section as described above, the shape is simple, which also makes the stepped surface between the thick annular portion and the thin annular portion likely to secure high smoothness. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  each illustrate an external appearance of a reclining device according to one embodiment of the present invention, and  FIG. 1( a )  is a perspective view from a coupling cover member side, and  FIG. 1( b )  is a perspective view from a mounting ring side. 
         FIG. 2( a )  is a plane view of the reclining device of the above-described embodiment,  FIG. 2( b )  is a sectional view taken along the A-A line in  FIG. 2( a ) ,  FIG. 2( c )  is a sectional view taken along the B-B line in  FIG. 2( a ) , and  FIG. 2( d )  is a sectional view taken along the C-C line in  FIG. 2( a ) . 
         FIG. 3  is an exploded perspective view illustrated by dividing the reclining device of the above-described embodiment into a mounting ring, a lock mechanism part, a memory mechanism part, an internal gear, and a coupling cover member. 
         FIG. 4  is an exploded perspective view illustrated by further dividing the lock mechanism part and the memory mechanism part in  FIG. 3  for each part. 
         FIG. 5( a )  is a plane view illustrating a memory gear, and  FIG. 5( b )  is a sectional view illustrating the internal gear. 
         FIG. 6( a )  is an explanatory view of the action of the lock mechanism part at the time of locking,  FIG. 6( b )  is an explanatory view of the action of the lock mechanism part at the time of unlocking,  FIG. 6( c )  is a view illustrating a state of the memory mechanism part at the time of locking the lock mechanism part, and  FIG. 6( d )  is a view illustrating a state of the memory mechanism part at the time of unlocking the lock mechanism part. 
         FIGS. 7( a ) to ( f )  are explanatory views of the action of the memory mechanism part. 
         FIG. 8( a )  is an explanatory view of a walk-in mechanism provided for a back frame and a cushion frame,  FIG. 8( b )  is a view illustrated by enlarging an area to which the reclining device in  FIG. 8( a )  is attached, and  FIG. 8( c )  is a view illustrating a movement when the back frame is reclined forward. 
         FIG. 9  is an exploded perspective view illustrating another embodiment of the present invention. 
         FIG. 10  is a sectional view of the embodiment in  FIG. 9 . 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
     The present invention will be hereinafter described in more detail based on embodiments illustrated in the drawings.  FIG. 1  to  FIG. 5  illustrate a reclining device  10  according to one embodiment of the present invention. The reclining device  10  is attached between a cushion frame  1  of a seat cushion and a back frame  2  of a seat back, and reclines the seat back with respect to the seat cushion (refer to  FIG. 8 ). As illustrated in  FIG. 1  to  FIG. 5 , the reclining device  10  includes a lock mechanism part  20 , a memory mechanism part  30 , and an internal gear  40 . 
     The lock mechanism part  20  has a guide bracket  21  and lock plates  22 . For the guide bracket  21 , on its inner surface (a surface opposing the internal gear  40 ), four guide wall portions  21   a ,  21   a  are projectingly provided at equal intervals in a circumferential direction, and the lock plates  22 ,  22  are each disposed between the adjacent guide wall portions  21   a ,  21   a . The lock plates  22 ,  22  are each disposed between the guide wall portions  21   a ,  21   a  located at 180-degree symmetrical positions in this embodiment. The lock plates  22 ,  22  are formed with locking external teeth  22   a ,  22   a  on outer peripheral surfaces, and are each movable in a radial direction between the guide wall portions  21   a ,  21   a , and the locking external teeth  22   a ,  22   a  move outward and engage with locking internal teeth  411  formed on the later-described internal gear  40  to thereby perform locking. 
     An unlocking cam  23  is disposed between the two lock plates  22 ,  22 , and spiral springs  24 ,  24  are disposed at two portions each between the guide wall portions  21   a ,  21   a  where the lock plates  22 ,  22  are not disposed. The spiral springs  24 ,  24 , in each of which one end is engaged with the unlocking cam  23 , bias the unlocking cam  23  in a direction in which it is rotated in one direction. That causes the lock plates  22 ,  22  with which the unlocking cam  23  is engaged to be biased radially outward, namely, in a direction of engaging with the locking internal teeth  411  of the internal gear  40 . Through a center hole  23   a  of the unlocking cam  23 , a lever shaft  25  connected to a reclining operating lever (not illustrated) is inserted, and by rotating the lever shaft  25  in a predetermined direction, the unlocking cam  23  is rotated in the reverse direction to the biased direction, which pulls the lock plates  22 ,  22  radially inward to separate the locking external teeth  22   a ,  22   a  and the locking internal teeth  411 , resulting in unlocking. 
     The memory mechanism part  30  is provided between the lock mechanism part  20  and the internal gear  40 . The memory mechanism part  30  has a memory cam  31 , memory gears  32 ,  32 , a memory guide plate  33 , and a cylindrical shaft portion  34 . The memory cam  31 , whose outer periphery has a disc shape in this embodiment, is also responsible for a function of a partition wall portion between the lock mechanism part  20  and the memory gears  32 ,  32 . Around a through hole  31   b  at the center, cam portions  31   a ,  31   a  projecting to the internal gear  40  side are formed in plurality. Note that, coaxially with the through hole  31   b , a cylindrical shaft portion  34  is integrated so as to project to the internal gear  40  side. As illustrated in  FIG. 8 , the cylindrical shaft portion  34  is provided so as to project to the inside of the back frame  2 , and a coupling plate  34   a  is coupled to a section where the cylindrical shaft portion  34  projects inward. The coupling plate  34   a  is engaged with the other end of a coil spring  34   b  whose one end is engaged with the seat frame  1 , to be biased in a direction of the seat frame  1 . This causes the cylindrical shaft portion  34  to be biased constantly in one direction, and this direction becomes a biased direction of the memory cam  31 , namely, a direction in which memory external teeth  32   b ,  32   b  of the memory gears  32 ,  32  separate from memory internal teeth  421  of the internal gear  40 . The coupling plate  34   a  is coupled to a walk-in lever  3   a  composing a walk-in mechanism  3  with a cable  3   b  interposed therebetween, and is rotated in the reverse direction to the above-described biased direction by operating the walk-in lever  3   a.    
     The memory gears  32 ,  32  are formed from two sheets of plate material formed in a substantially arc shape, and are provided at 180-degree symmetrical positions sandwiching the cylindrical shaft portion  34  adjacently to the internal gear  40  side of the memory cam  31 . Further, the two cam portions  31   a ,  31   a  of the memory cam  31  are disposed with a space accessible to inner peripheral edges  32   a ,  32   a  of the respective memory gears  32 ,  32 . The memory external teeth  32   b ,  32   b  are formed on outer peripheral surfaces of the memory gears  32 ,  32 , and the inner peripheral edges  32   a ,  32   a  are pressed outward by the cam portions  31   a ,  31   a , whereby the memory external teeth  32   b ,  32   b  engage with the memory internal teeth  421  of the internal gear  40 . 
     The memory guide plate  33  has a through hole  33   a  through which the cylindrical shaft portion  34  is inserted at the center, and is formed with hole portions  33   b ,  33   b  each having a small diameter at 180-degree symmetrical positions close to an outer peripheral edge. In the hole portions  33   b ,  33   b  each having a small diameter, projecting portions  32   c ,  32   c  formed on the memory gears  32 ,  32  respectively so as to project to the internal gear  40  side are fitted to be assembled. This allows the memory gears  32 ,  32  to rotationally move with the projecting portions  32   c ,  32   c  centered as illustrated in  FIG. 4  and  FIG. 5( a ) . One-end-side end wall portions  32   d ,  32   d  extending inward are provided at circumferential one ends of the memory gears  32 ,  32 , and the projecting portions  32   c ,  32   c  are provided slightly closer to circumferential other ends than the one-end-side end wall portions  32   d ,  32   d . The memory cam  31  is biased in one direction so that the cam portions  31   a ,  31   a  abut on the one-end-side end wall portions  32   d ,  32   d . The memory cam  31  is integrated with the cylindrical shaft portion  34 , and is biased constantly in one direction by the above-described coil spring  34   b  via the cylindrical shaft portion  34 . This causes the memory gears  32 ,  32  to have other ends  32   e ,  32   e  of the memory gears  32 ,  32  biased inward with the projecting portions  32   c ,  32   c  centered, and causes the memory external teeth  32   b ,  32   b  to separate from the memory internal teeth  421  of the internal gear  40 . When the seat back (back frame  2 ) is reclined forward by operating the walk-in lever  3   a  of the walk-in mechanism  3 , the memory cam  31  rotates in the reverse direction, and the cam portion  31   a ,  31   a  press the inner peripheral edges  32   a ,  32   a  of the memory gears  32 ,  32  outward, whereby the memory external teeth  32   b ,  32   b  engage with the memory internal teeth  421  of the internal gear  40  (refer to  FIG. 7 ). 
     Further closer to the internal gear  40  side of the memory guide plate  33 , a nut member  35  is mounted around the cylindrical shaft portion  34  projecting from the through hole  33   a . This causes the memory mechanism part  30  including the memory cam  31 , the memory gears  32 ,  32 , the memory guide plate  33 , the cylindrical shaft portion  34 , and the nut member  35  to be integrated to form a unit. 
     Here, in any of the memory cam  31 , the memory gears  32 ,  32 , and the memory guide plate  33 , substantially arc-shaped pin insertion holes  311 ,  321 ,  331  are formed respectively at 180-degree symmetrical positions sandwiching the cylindrical shaft portion  34 . 
     Among them, the pin insertion holes  321 ,  321  formed in the memory gears  32 ,  32  are formed with long groove portions  321   a ,  321   a  extending in outer peripheral edge directions of the memory gears  32 ,  32  respectively on circumferential one end sides as illustrated in  FIG. 5( a ) . In the pin insertion holes  321 ,  321  of the memory gears  32 ,  32 , projecting pins  221 ,  221  made to project to the internal gear  40  side on the lock plates  22 ,  22  are inserted, and the projecting pins  221 ,  221  are provided in a positional relationship in which at a locked position of the lock plates  22 ,  22 , the projecting pins  221 ,  221  are inserted in the long groove portions  321   a ,  321   a , and at the time of a walk-in operation, after releasing the engagement of the locking external teeth  22   a ,  22   a  of the lock plates  22 ,  22  with the locking internal teeth  411  of the internal gear  40 , when the memory gears  32 ,  32  rotate together with the internal gear  40 , the projecting pins  221 ,  221  relatively move from the long groove portions  321   a ,  321   a  toward circumferential other end sides in the pin insertion holes  321 ,  321 . 
     In the memory cam  31  provided between the lock plates  22 ,  22  and the memory gears  32 ,  32 , when the memory cam  31  is rotated in one direction together with the cylindrical shaft portion  34 , and, when the memory gears  32 ,  32  rotate in the other direction together with the internal gear  40  after unlocking, the projecting pins  221 ,  221  are provided in a relatively movable range in the pin insertion holes  311 ,  311  of the memory cam  31 . Further, at least when the projecting pins  221 ,  221  are located in the long groove portions  321   a ,  321   a , the pin insertion holes  311 ,  311  are each provided in a shape having a section with a groove width allowing movement in the radial direction. 
     The memory guide plate  33  rotates together with the memory gears  32 ,  32  since the hole portions  33   b ,  33   b  are fitted to the projecting portions  32   c ,  32   c  of the memory gears  32 ,  32 . Accordingly, its pin insertion holes  331 ,  331  are formed at least at positions corresponding to the pin insertion holes  321 ,  321  of the memory gears  32 ,  32 , and formed with a width allowing the movement of the projecting pins  221 ,  221  in the radial direction of the long groove portions  321   a ,  321   a . Note that memory operation of the memory mechanism part  30  is described later. 
     In the internal gear  40 , as illustrated in  FIG. 3 ,  FIG. 4 , and  FIG. 5( b ) , a thin annular portion  41  and a thick annular portion  42  whose outside diameters are the same and whose inside diameters are different are continuously provided integrally in the axial direction. The thin annular portion  41  is on an end side opposed to the guide bracket  21  along the axial direction, and the thick annular portion  42  is on an end edge side opposite to the thin annular portion  41 . The same outside diameters cause an outer peripheral surface of the thin annular portion  41  and an outer peripheral surface of the thick annular portion  42  to be a flush outer peripheral surface  40   a , whose cross-sectional shape is in a substantially L shape. Further, an axial outer end surface  42   a  of the thick annular portion  42  is formed to be substantially flat. 
     Then, on an inner peripheral surface of the thin annular portion  41 , the locking internal teeth  411  with which the locking external teeth  22   a ,  22   a  of the lock plates  22 ,  22  are engageable are formed, and on an inner peripheral surface of the thick annular portion  42 , the memory internal teeth  421  with which the memory external teeth  32   b ,  32   b  of the memory gears  32 ,  32  are engageable are formed. 
     In this embodiment, since the internal gear  40  only needs to be processed to have the substantially L-shaped cross-sectional shape, the flatness of a stepped surface  43  between the locking internal teeth  411  being the inner peripheral surface of the thin annular portion  41  and the memory internal teeth  421  being the inner peripheral surface of the thick annular portion  42  is easy to highly process, differently from the case where an internal gear is formed to be in a conventional convex shape. This enables a smooth rotational operation of the lock mechanism part  20  or the memory mechanism part  30 . 
     A coupling cover member  50  is provided so as to project outward from the axial outer end surface  42   a  of the thick annular portion  42  of the internal gear  40 . The coupling cover member  50  is in a substantially convex shape in a cross section having a large-diameter portion  51  and a small-diameter portion  52 , and the large-diameter portion  51  is welded on the outer peripheral surface close to the thick annular portion  42  of the outer peripheral surface  40   a  of the internal gear  40 . A section formed with the memory internal teeth  421  with which the memory gears  32 ,  32  engage is the thick annular portion  42  provided with a predetermined thickness. In a conventional internal gear, an axial outer end side of a small-diameter portion is set as a range where memory internal teeth are not formed, or a coupling plate portion having a smaller diameter is formed on the axial outer end side (refer to Patent Document 2), to be coupled to a back frame or a cushion frame, but in this embodiment, the section formed with the memory internal teeth  421  has the predetermined thickness, and the section itself formed with the memory internal teeth  421  is higher in strength as compared with the conventional one. Therefore, in the internal gear  40  of this embodiment, deformation strength against external force is naturally high, and when the memory internal teeth  421  are subjected to heat treatment to have high surface hardness, the vicinity of the outer peripheral surface of the thick annular portion  42  is unlikely to be affected by the heat treatment, which allows the coupling cover member  50  to be easily welded. Further, since the thick annular portion  42  has sufficient strength, the coupling cover member  50  having a conversely small plate thickness is enough for the one integrated with the thick annular portion  42 , also thereby improving processability at the time of welding. 
     Here, as the heat treatment for hardening surfaces of the locking internal teeth  411  and the memory internal teeth  421  of the internal gear  40 , induction heating is preferably used. The induction heating allows only the vicinities of the locking internal teeth  411  and the memory internal teeth  421  to be partially heated. When the induction heating is performed, a heating unit may be confronted with the locking internal teeth  411  and the memory internal teeth  421 , but the heating may be performed from surfaces being different from those of the locking internal teeth  411  and the memory internal teeth  421  and excluding the outer peripheral surface  40   a  on which the coupling cover member  50  and a later-described mounting ring  60  are welded. For example, it is possible to heat a section close to the inside diameter of an axial inner end surface  41   a  of the thin annular portion  41  and to adjust a frequency to have an influence of heat on a section up to the locking internal teeth  411 . Similarly, it is possible to heat a section close to the inside diameter of the axial outer end surface  42   a  of the thick annular portion  42  to have an influence of heat on the memory internal teeth  421 . Using such a heating method makes it possible to inhibit the surfaces of the locking internal teeth  411  and the memory internal teeth  421  from becoming rough, resulting in allowing the surfaces of the teeth to have high surface accuracy. 
     The memory mechanism part  30  is disposed adjacently to the internal gear  40  side of the above-described lock mechanism part  20 , and the lever shaft  25  of the lock mechanism part  20  is assembled so as to be inserted through into the cylindrical shaft portion  34  of the memory mechanism part  30 , and the memory mechanism part  30  and the lock mechanism part  20  are inserted into the internal gear  40  in that order to confront the memory external teeth  32   b ,  32   b  of the memory gears  32 ,  32  with the memory internal teeth  421  formed on the thick annular portion  42  and to confront the locking external teeth  22   a ,  22   a  of the lock plates  22 ,  22  with the locking internal teeth  411  formed on the thin annular portion  41 . 
     Next, through a center through hole  52   a  formed in the small-diameter portion  52  of the coupling cover member  50 , the cylindrical shaft portion  34  through which the lever shaft  25  is inserted is inserted. Meanwhile, from the axial outer end surface side in the guide bracket  21  of the lock mechanism part  20 , the mounting ring  60  for holding the lock mechanism part  20  and the memory mechanism part  30  in an assembled state is mounted with balls  62  interposed therebetween. Thereafter, the large-diameter portion  51  of the coupling cover member  50  is welded on the outer peripheral surface close to the thick annular portion  42  of the outer peripheral surface  40   a  of the internal gear  40 , and a peripheral wall portion  61  of the mounting ring  60  is welded and fixed on the outer peripheral surface close to the thin annular portion  41  of the outer peripheral surface of the internal gear  40 . 
     Next, a movement of the reclining device  10  of this embodiment is described. Before a normal reclining operation, in the lock mechanism part  20 , as illustrated in  FIG. 6( a ) , the lock plates  22 ,  22  are biased outward by the spiral springs  24 ,  24 , and the locking external teeth  22   a ,  22   a  engage with the locking internal teeth  411  of the internal gear  40 . This causes the seat back to have a predetermined reclining angle maintained. When the reclining operation is performed, the lever shaft  25  is rotated by operating the reclining operating lever. As illustrated in  FIG. 6( b ) , this causes the unlocking cam  23  to move the lock plates  22 ,  22  inward to release the engagement of the locking external teeth  22   a ,  22   a  and the locking internal teeth  411 , which enables reclining of the seat back. When the operation of the reclining operating lever is stopped at a predetermined angle, the lock plates  22 ,  22  are moved outward by the spiral springs  24 ,  24 , and the locking external teeth  22   a ,  22   a  and the locking internal teeth  411  engage with each other, resulting in fixing the reclining angle, as illustrated in  FIG. 6( a )  again. Note that since the lever shaft  25  rotates in the cylindrical shaft portion  34  of the memory mechanism part  30 , the memory mechanism part  30  does not operate at the time of this normal reclining operation (refer to FIGS.  6 ( a ), ( b )). 
     Meanwhile, when the seat back is reclined forward at the time of the walk-in operation, the walk-in lever  3   a  illustrated in  FIG. 8( a )  is operated. Operating the walk-in lever  3   a  makes the coupling plate  34   a  rotate in the reverse direction to a biasing direction of the coil spring  34   b  via the cable  3   b , which rotates the cylindrical shaft portion  34 . When the cylindrical shaft portion  34  rotates, a state in  FIG. 7( a )  becomes a state in  FIG. 7( b ) , and the memory cam  31  integrated with the cylindrical shaft portion  34  rotates in a direction of the other ends  32   e ,  32   e  of the memory gears  32 ,  32 . This rotation causes the cam portions  31   a ,  31   a  to push the inner peripheral edges  32   a ,  32   a  of the memory gears  32 ,  32  outward and causes the memory external teeth  32   b ,  32   b  of the memory gears  32 ,  32  to engage with the memory internal teeth  421  of the internal gear  40 . 
     In the state where the memory mechanism part  30  does not operate, as illustrated in  FIG. 7( a ) , the projecting pins  221 ,  221  of the lock plates  22 ,  22  are located in the long groove portions  321   a ,  321   a  of the pin insertion holes  321 ,  321  in the memory gears  32 ,  32 . When the other ends  32   e ,  32   e  of the memory gears  32 ,  32  are pushed outward by the rotation of the memory cam  31 , first, the projecting pins  221 ,  221  move relatively inward in the long groove portions  321   a ,  321   a  in just the state where the lock plates  22 ,  22  engage with the locking internal teeth  411  of the internal gear  40 , namely, with a locked state maintained, as illustrated in  FIG. 7( b ) . 
     Thereafter, when the memory cam  31  is further rotated, the projecting pins  221 ,  221  move further inward in the long groove portions  321   a ,  321   a , and the locking external teeth  22   a ,  22   a  of the lock plates  22 ,  22  separate from the locking internal teeth  411  of the internal gear  40 , resulting in unlocking, as illustrated in  FIG. 7( c ) . Then, the seat back is reclined forward by the spiral spring which biases the back frame  2  with respect to the cushion frame  1  constantly in a forward reclining direction (refer to  FIG. 8( c ) ). At this time, a state in  FIG. 7( c )  becomes a state in  FIG. 7( d ) , and the internal gear  40  fixed to the back frame  2  with the coupling cover member  50  interposed therebetween rotates forward. Since the memory gears  32  engage with the memory internal teeth  421  of the internal gear  40 , the memory mechanism part  30  also rotates forward together with the internal gear  40 . A rotation angle is the angle at which the projecting pins  221 ,  221  rotate relatively up to the circumferential other end sides in the pin insertion holes  321 ,  321 . During the rotation, since the lock plates  22 ,  22  and the projecting pins  221 ,  221  are in an unlocked state, they hold the positions before the walk-in operation without rotating together with the internal gear  40 . 
     At the forward reclined position, the position is held by a forward-reclining locking portion  70  having a spring  71 , a fixing plate  72 , a shaft  73 , a rivet  74 , and so on illustrated in  FIG. 4 . At the time of a return after the walk-in operation, the forward-reclining locking portion  70  is unlocked by operating the walk-in lever  3   a . When the seat back is returned backward, the internal gear  40  rotates backward. As illustrated in  FIG. 7( e ) , since the memory external teeth  32   b ,  32   b  of the memory gears  32 ,  32  engage with the memory internal teeth  421  of the internal gear  40 , the memory gears  32 ,  32  rotate backward together with the internal gear  40 . Thereafter, the projecting pins  221 ,  221  of the lock plates  22 ,  22  holding the position before the walk-in operation (memory position) are moved relatively to the one end sides in the pin insertion holes  321 ,  321  by the backward rotation of the memory gears  32 ,  32 , and reach positions corresponding to the long groove portions  321   a ,  321   a  as illustrated in  FIG. 7( f ) . When the projecting pins  221 ,  221  correspond to the long groove portions  321   a ,  321   a , the projecting pins  211 ,  211  can move radially outward in the long groove portions  321   a ,  321   a . That causes, the lock plates  22 ,  22  biased constantly outward by the spiral springs  24 ,  24  to move radially outward and return to the state in  FIG. 7( a ) , the locking external teeth  22   a ,  22   a  to engage with the locking internal teeth  411  of the internal gear  40  at the memory position, and the seat back to return to the predetermined reclining angle at the memory position before the walk-in operation. Note that when the locking external teeth  22   a ,  22   a  engage with the locking internal teeth  411  of the internal gear  40 , the memory cam  31  of the memory mechanism part  30  is returned to an original position by biasing force of the coil spring  34   b  to separate the memory external teeth  32   b ,  32   b  of the memory gears  32 ,  32  from the memory internal teeth  421  of the internal gear  40 . 
     Incidentally, in the above-described embodiment, in the memory mechanism part  30 , the memory gears  32 ,  32  are sandwiched and held by the disk-shaped memory cam  31  integrated with the cylindrical shaft portion  34  and the memory guide plate  33 , and they are formed as a unit by the nut member  35 . Accordingly, using the one having such a structure as to be formed as a unit as the memory mechanism part  30  enables easy replacement with one having a different internal structure and makes it easy to variously adjust the function of the reclining device  10 . 
       FIG. 9  and  FIG. 10  each illustrate the reclining device  10  according to another embodiment of the present invention. The structures of the memory mechanism part  30 , the internal gear  40 , the coupling cover member  50 , and the mounting ring  60  composing the reclining device  10  are exactly the same as those of the above-described embodiment, and the characteristic of having the thin annular portion and the thick annular portion of the internal gear  40  is also the same. Further, the action of the memory mechanism part  30  at the time of the memory operation is also the same. However, structures of a projecting pin  2110 , the guide bracket  21 , and the lock plate  22  composing the lock mechanism part  20  are different. 
     That is, in this embodiment, as the projecting pins  2210 ,  2210 , flange portions  2212 ,  2212  are integrally provided at one ends of shaft portions  2211 ,  2211 . The shaft portions  2211 ,  2211  include wide-diameter portions  2211   a ,  2211   a  each having a wide diameter on sides of the flange portions  2212 ,  2212  and narrow-diameter portions  2211   b ,  2211   b  each having a narrow diameter from the wide-diameter portions  2211   a ,  2211   a  to tips. 
     Pin restricting holes  2110 ,  2110  penetrating in a thickness direction are opened on a surface of the guide bracket  21  on which the lock plates  22 ,  22  are disposed. The pin restricting holes  2110 ,  2110  are formed long in the radial direction, and a width in the circumferential direction orthogonal to the radial direction (width direction) is formed to be almost the same as that of each of the wide-diameter portions  2211   a ,  2211   a  of the shaft portions  2211 ,  2211  of the projecting pins  2210 ,  2210 . 
     Also in the lock plates  22 ,  22 , through holes  22   b ,  22   b  through which the shaft portions  2211 ,  2211  of the projecting pins  2210 ,  2210  are inserted are formed. 
     The projecting pins  2210 ,  2210  are inserted from an axial outer end surface  21   b  side of the guide bracket  21  with the shaft portions  2211 ,  2211  on sides of the lock plates  22 ,  22 . That causes the flange portions  2212 ,  2212  to come into contact with and stay on the axial outer end surface  21   b  of the guide bracket  21 . Note that the projecting pins  2210 ,  2210  are preferably integrated with the lock plates  22 ,  22  by welding or the like. The projecting pins  2210 ,  2210  are inserted in the pin insertion holes  321 ,  321  of the memory gears  32 ,  32 , or the like formed in the memory mechanism part  30  after the narrow-diameter portions  2211   b  of the shaft portions  2211  penetrate the through holes  22   b ,  22   b  of the lock plates  22 ,  22 . 
     The function of the projecting pins  2210 ,  2210  is similar to that of the above-described embodiment, and makes the lock plates  22 ,  22  stay at the memory position before the walk-in operation regardless of the rotation of the memory mechanism part  30  at the time of the walk-in operation. 
     On the other hand, in this embodiment, the wide-diameter portions  2211   a ,  2211   a  of the projecting pins  2210 ,  2210  are inserted in the pin restricting holes  2110 ,  2110  of the guide bracket  21  as described above. The width of the pin restricting holes  2110 ,  2110  is almost the same as that of the wide-diameter portions  2211   a ,  2211   a , and there is only a slight clearance for operation. Accordingly, when the lock plates  22 ,  22  operate in the radial direction at the time of normal locking, it is possible to reduce the wobbling caused by the movement of the lock plates  22 ,  22  in the circumferential direction (width direction). Further, similarly to the above-described embodiment, since the lock plates  22 ,  22  are disposed between the memory cam  31  of the memory mechanism part  30  and the guide bracket  21 , the wobbling in the axial direction is also reduced by them, and according to this embodiment, it is possible to make the movement of the lock plates  22 ,  22  smoother and to also inhibit strange noise resulting from the wobbling from occurring or the like. Further, fixing the projecting pins  2210 ,  2210  to the lock plates  22 ,  22  by welding leads to an improvement in strength of the reclining device  10 . 
     EXPLANATION OF REFERENCE SIGNS 
     
         
         
           
               10  reclining device 
               20  lock mechanism part 
               21  guide bracket 
               22  lock plate 
               22   a  locking external teeth 
               221  projecting pin 
               23  unlocking cam 
               24  spiral spring 
               30  memory mechanism part 
               31  memory cam 
               32  memory gear 
               32   b  memory external teeth 
               33  memory guide plate 
               40  internal gear 
               40   a  outer peripheral surface 
               41  thin annular portion 
               411  locking internal teeth 
               42  thick annular portion 
               421  memory internal teeth 
               50  coupling cover member 
               51  large-diameter portion 
               52  small-diameter portion