Abstract:
A seat reclining device has an external gear member and an internal gear member positioned in opposing relation, and a stopper member between the opposing gear members for regulating the reclining movement of the backrest relative to the seat cushion. The stopper member includes a first convex portion on the external gear (or internal gear) member and a stopper provided on the outer peripheral surface of the internal gear (or external gear) member. A second convex portion is also provided on the external gear (or internal gear) member. By engaging the second convex portion with a bore on a ring member that surrounds the periphery of the internal and external gear members, a part of the contact force between the stopper and the first convex portion is transmitted to the ring member.

Description:
[0001]    This application is based on and claims priority under 35 U.S.C. § 119 with respect to Japanese Application No. 2000-313443 filed on Oct. 13, 2000, the entire content of which is incorporated herein by reference.  
         FIELD OF THE INVENTION  
         [0002]    This invention generally relates to a seat reclining device. More particularly, the present invention pertains to a vehicle seat reclining device provided with a stopper member defining the maximum reclining range of the seat.  
         BACKGROUND OF THE INVENTION  
         [0003]    A seat reclining device for adjusting the reclining movement of a backrest relative to a seat cushion of a vehicle seat for positioning the occupant to an optimal or desired seating position is widely known. A known seat reclining device includes an external gear (or internal gear) member secured to a lower arm on the seat cushion side, an internal gear member (the number of gear tooth of the internal gear and the external gear are different) having an internal gear (or external gear) which is secured to an upper arm on the backrest side and is engaged with the external gear, and an actuating member for eccentrically rotating the internal gear member relative to the external gear member.  
           [0004]    In the aforementioned known seat reclining device, the actuating member generally actuated by an electric motor rotates the internal gear (or the external gear) relative to the external gear (or internal gear) for changing the reclining angle of the upper arm relative to the lower arm. In this way, the seatback can be moved relative to the seat cushion to vary the relative degree of recline of the seatback.  
           [0005]    The aforementioned seat reclining device includes stopping mechanism for defining the reclining range between the maximum reclining in the forward direction and the maximum reclining in the backward direction of the backrest. U.S. Pat. No. 4,887,017 discloses a stopper member provided on a seat reclining device. The stopper member includes switches provided on the lower arm and electrical circuitry for controlling the actuator.  
           [0006]    However, this electrical stopper member is not able to achieve accurate stop positions because the actuating mechanism has a relatively significant amount of rotational inertia. As an alternative stopping mechanism, a mechanical stopping mechanism could be provided between the lower arm and the upper arm combined with a protection circuit for excessive electric current. Such a mechanical stopping mechanism may include a stopper pin provided on the lower arm and a pair of receiving members provided on the upper arm for receiving the pin. Even in this case, however, the maximum and/or minimum reclining position is not accurate enough because the stopper member is located away from the reclining device and the stop position is affected by the possible dimensional variation of both the upper arm and the lower arm.  
           [0007]    A need thus exists for a reclining device which is able to more accurately regulate the range of reclining movement of the backrest.  
           [0008]    A need also exists for a stopper mechanism accommodated in the reclining device that is more simple in construction while also possessing a relatively high degree of strength.  
         SUMMARY OF INVENTION  
         [0009]    To achieve the aforementioned objects, the following technical means is provided with a reclining device comprising, a first gear member secured to a lower arm, a second gear member secured to an upper arm, a first gear provided in the first gear member, a second gear provided in the second gear member, wherein numbers of gear teeth between the first gear and the second gear are different and the first gear and the second gear are provided eccentrically, a stopper member provided between the first gear member and the second gear member for restricting relative rotation between the first gear member and the second gear member, and a ring member provided on the outer periphery of the first gear member and the second gear member, wherein at least a part of a contact force on the stopper member is transmitted to the ring member via one of the gear members.  
           [0010]    According to another aspect of the invention, a reclining device for a vehicle seat to change an angle of inclination of a seatback relative to a seat cushion includes a first gear member secured to a first arm that is adapted to be fixed to one of the seatback and the seat cushion, a second gear member secured to a second arm adapted to be fixed to the other of the seatback and the seat cushion, a plurality of first gear teeth provided on the first gear member, and a plurality of second gear teeth provided on the second gear member. The plurality of first gear teeth are different in number than the plurality of second gear teeth, and the first gear teeth and the second gear teeth are positioned eccentrically. A stopper member is provided between the first gear member and the second gear member for restricting relative rotation between the first gear member and the second gear member, and an engaging element is provided on the first gear member. A ring member encircles outer peripheral portions of the first gear member and the second gear member, and the engaging element on the first gear member engages a portion of the ring member so that at least a part of a contact force on the stopper member is transmitted to the ring member via the first gear member and the engaging element.  
           [0011]    In accordance with another aspect of the invention, a reclining device for a vehicle seat to change an angle of inclination of a seatback relative to a seat cushion includes a first gear member secured to a first arm that is adapted to be fixed to one of the seatback and the seat cushion, a second gear member secured to a second arm adapted to be fixed to the other of the seatback and the seat cushion, a plurality of first gear teeth provided on the first gear member, and a plurality of second gear teeth provided on the second gear member. The number of first gear teeth is different from the number of second gear teeth, and the first gear teeth and the second gear teeth are positioned eccentrically. A plurality of spaced apart stoppers on the outer periphery of the first gear member and a plurality of spaced apart projections on the second gear member are adapted to effect contact with one another to restrict relative rotation between the first gear member and the second gear member. An engaging element is provided on the first gear member. A ring member encircles outer peripheral portions of the first gear member and the second gear member, and is provided with a hole in which is positioned the engaging element on the first gear member so that at least a part of a contact force between the stoppers and the projections is transmitted to the ring member via the first gear member and the engaging element.  
           [0012]    With the reclining device of the present invention, a part of the contact force of the ring member towards the stopper member is dispersed and so smooth gear engagement can be maintained. In addition, the reclining angle can be accurately determined. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0013]    The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawing figures in which like reference numerals designate like elements.  
         [0014]    [0014]FIG. 1 is a side view of a vehicle seat in which is incorporated a seat reclining device according to an embodiment of the present invention.  
         [0015]    [0015]FIG. 2 is an exploded perspective view of the seat reclining device according to an embodiment of the present invention.  
         [0016]    [0016]FIG. 3 is a front view of the seat reclining device shown in FIG. 2.  
         [0017]    [0017]FIG. 4 is a cross-sectional view of the seat reclining device taken along the section line IV-IV in FIG. 3. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    As shown in FIG. 1, a seat  1  for a vehicle includes a seat cushion  2 , a backrest  3 , and a seat reclining device  4  for adjusting the reclining angle of the backrest  3  relative to the seat cushion  2 . The vehicle seat  1  can be moved upwardly and downwardly by a lifter  5  that includes a pair of parallel link mechanisms, one end of which supports the seat cushion  2 . The position of the seat  1  in the forward and reverse directions is adjustable by a seat slide device  8 . The seat slide device  8  includes a lower rail  6  fixed on a vehicle floor and an upper rail  7  slidably positioned relative to the lower rail  6  for supporting the other end of the parallel link mechanism.  
         [0019]    The structure associated with the seat reclining device  4  is illustrated in FIGS.  2 - 4 . An external gear (or an internal gear) member  9  is secured to a lower arm  23  of the seat cushion  2  and is formed as a disc-shaped member. An external gear  10  is formed on the outer periphery of a half-die-cut processed annular portion  11  formed on the external gear member  9 . The half-die-cutting process used to form the annular portion  11  is a kind of press forming process in which a steel plate is pressed and partially sheared in the plate thickness direction to form a concave or recessed portion on the plate while a partially continuous portion on the edge of the concave or recessed portion. A plurality of half-die-cut convex portions or projections  12  are formed on a side surface of the external gear member  9  at positions spaced radially outwardly of the annular portion  11 . Further rectangularly shaped (or cylindrically shaped) convex portions or protuberances  13  are formed on the top surface of the convex portions or projections  12  and extend from the convex portions or projections  12  in the outward direction. Preferably, the convex portions or protuberances  13  are also formed by a half-die-cut process.  
         [0020]    A disc shaped internal gear (or external gear) member  14  is secured to an upper arm  24  of the backrest  3  and is opposed to the external gear (or internal gear) member  9 . The internal gear member  14  includes an annular portion  15  formed by a half-die-cutting process, an internal gear  16  formed on the inner periphery of the annular portion  15 , and a plurality of spaced apart stoppers  17  extending in the radially outward direction from the outer periphery of the annular portion  15 .  
         [0021]    The outer peripheral portions of the external gear member  9  and the internal gear member  14  are covered with a ring member  18 . The ring member  18  is appropriately configured to be engaged by or to receive the convex portions or protuberances  13 . In the illustrated embodiment, the ring member  18  includes several holes or bores  19  into which the convex portions or protuberances  13  are inserted and positioned. The protuberances or convex portions  13  thus form engaging elements that engage a portion of the ring member  18 , and the ring member  18  is appropriately configured to receive or be engaged by the engaging elements  13 .  
         [0022]    In this embodiment, each of the bores  19  in the ring member  18  is located at the central portion of respective concave or recessed portions  20  which are formed on the side surface of the ring member  18 . The bores  19  are engaged with the foot portion of the convex portions or protuberances  13 .  
         [0023]    Referring to FIGS.  2 - 4 , the external (or internal) member  9  is supported via a pair of wedge shaped members  22  and a spring  25  on a boss portion of an actuating member  21  which receives the input from the operation member. The internal gear (or external gear) member  14  is geared with the external gear (or internal gear) member  9  having one or two less gear teeth in number. The actuating member  21  and the external gear (or the internal gear) member  9  eccentrically rotate with respect to each other. As a result, the meshing condition between the external gear  10  and the internal gear  16  will be as shown in FIG. 3. In this case, the stoppers  17  are positioned between the convex portions or projections  12  of the external gear (or internal gear) member  9 .  
         [0024]    The ring member  18  for maintaining the relative positional relationship between the external gear member  9  and the internal gear member  14  is provided on the outer periphery of the external gear member  9  and the internal gear member  14 . The convex portions or protuberances  13  are fixedly inserted into the bores  19  in the ring member  18 .  
         [0025]    When rotational torque is inputted to the actuating member  21  via a shaft  30  from an electrical motor (not shown), the internal gear (or external gear) member  14  which is co-centered or co-axial with the axis of the actuating member  21  rotates around the axis of the external gear (or internal gear) member  9 . The internal gear member  14  is moved by the wedge shaped members in the radially outward direction. Then the internal gear member  14  is rotated relative to the external gear (or internal gear) member  9  with decreased rotational speed from that of the shaft  30  in accordance with the difference in the number of gear teeth between the external gear  10  and the internal gear  16 . The upper arm  24  reclines relative to the lower arm  23  and the reclining angle of the backrest  3  is thus adjusted.  
         [0026]    As a result, in accordance with the direction of input of the rotational torque, the backrest  3  reclines in the forward or backward direction relative to the seat cushion  2 .  
         [0027]    The range of the reclining movement is restricted by the contact of the stoppers  17  with the convex portions or projections  12 . The contact force (i.e., the stopper force) of the stopper  17  to the convex portion  12  is transmitted from the convex portions or projections  12  to the external (or internal) gear member  9  and to the lower arm  23 . Simultaneously, at least a part of the contact force is transmitted to the ring member  18  via the convex portions or protuberances  13 . Accordingly, the strength of the convex portions or projections  12  increases and the force applied on the external gear (or internal gear) member  9  is reduced.  
         [0028]    It is apparent from the foregoing that although the stopper member including the stopper(s)  17  and the convex portion(s) or projection(s)  12  is provided between the external gear member  9  and the internal gear member  14 , because at least a part of the stopper force is transmitted to the ring member  18  via the convex portion(s) or protuberance(s)  13 , excessive load is not input on the external gear member  9  and the internal gear member  14 , and thus the relative rotation between the external gear member  9  and the internal gear member  14  is ensured.  
         [0029]    This configuration is especially effective when the backrest  3  is reclined rearwardly to the maximum angle and is used, for example, as a flat bed. In this case, an excessive force may sometimes be applied on the reclining device, such as when children jump on the backrest  3 . The relatively simple but strengthened stopper configuration of the present invention inhibits or substantially prevents the external and internal gear member  9 ,  14  from being deformed, and helps ensure that a smooth meshing engagement between the external gear  10  and the internal gear  16  is maintained.  
         [0030]    Also, the stoppers  17  are fully accommodated in the reclining mechanism and so the reclining range is affected from dimensional variations in the backrest  3  or the seat cushion  2 . An accurate reclining range is thus obtained.  
         [0031]    The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiment disclosed. Further, the embodiment described herein is to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the apart and scope of the present invention as defined in the claims, be embraced thereby.