Seat reclining device

1. A seat reclining device comprising:

a cover adapted to be fixedly connected to one of a seat-cushion side arm attached to a seat cushion and a seat-back side arm attached to a seat back, and having internal teeth;

a base member adapted to be fixedly connected to the other of the seat-cushion side arm and the seat-back side arm, and configured to be rotatable relatively to the cover;

an external gear configured to have fewer external teeth than a number of the internal teeth of the cover, one axial part of the external gear being press-fitted to an inner periphery of a recessed structure of the base member, and another axial part of the external gear partly meshing with the internal teeth;

a joining ring configured to join the base member and the cover together by retaining outer peripheries of the base member and the cover, while permitting relative rotation between the base member and the cover but restricting axial movement of both of the base member and the cover;

a pair of wedge-shaped members located in an annular eccentric space defined between an outer peripheral surface of a cylindrical portion of the cover and an inner peripheral surface of the external gear with the external teeth of the external gear brought into meshed-engagement with the internal teeth, wider basal ends of the pair of wedge-shaped members being arranged to be circumferentially opposed to each other;

a guide plate located in the eccentric space, and axially juxtaposed to the pair of wedge-shaped members, and kept in sliding contact with both the outer peripheral surface of the cylindrical portion of the cover and the inner peripheral surface of the external gear;

a ring-shaped spring configured to circumferentially bias the wider basal ends of the pair of wedge-shaped members apart from each other; and

a driving member configured to have a cylindrical-hollow portion rotatably fitted into the cylindrical portion of the cover, a flanged portion formed integral with the cylindrical-hollow portion, and a pushing lug formed integral with the flanged portion so as to axially protrude toward the eccentric space and configured to circumferentially push either one of narrower ends of the pair of wedged-shaped members,

wherein an inside-perimeter portion of the external gear is formed as a cylindrical protrusion configured to axially protrude toward the base member,

wherein the base member has a first annular axially-recessed portion whose inner periphery is configured as an internal-toothed portion so as to press-fit the one axial part of the external gear to the base member, a second annular axially-recessed portion formed on an inside perimeter of the first annular axially-recessed portion and configured to accommodate therein the cylindrical protrusion of the external gear, and a third annular axially-recessed portion formed on an inside perimeter of the second annular axially-recessed portion and configured to accommodate therein the spring,

wherein the base member has an annular outer peripheral portion formed on a backface of the second annular axially-recessed portion and an annular outer peripheral portion formed on a backface of the third annular axially-recessed portion, and the other of the seat-cushion side arm and the seat-back side arm has at least one fitting recessed portion, and either one of the annular outer peripheral portion of the backface of the second annular axially-recessed portion and the annular outer peripheral portion of the backface of the third annular axially-recessed portion is fitted to the at least one fitting recessed portion so as to be integrally connected thereto,

wherein the pair of wedge-shaped members, axially juxtaposed to the guide plate, are located in the eccentric space so as to face the cover, whereas the guide plate, axially juxtaposed to the pair of wedge-shaped members, is located in the eccentric space so as to face the base member; and

wherein the guide plate has an outer peripheral protrusion integrally formed with a circumference of the guide plate and configured to axially protrude toward the base member so as to accommodate the flanged portion of the driving member in a recessed internal space defined on an inside perimeter of the guide plate as a result of the outer peripheral protrusion being integrally formed with the circumference of the guide plate.

2. The seat reclining device as claimed in claim 1 , wherein:

the annular outer peripheral portion of the backface of the second annular axially-recessed portion of the base member is formed with a plurality of fitting protrusions configured to protrude radially outward from a circumference of the annular outer peripheral portion of the backface of the second annular axially-recessed portion;

the other of the seat-cushion side arm and the seat-back side arm has a plurality of fitting recessed portions; and

the plurality of fitting protrusions of the annular outer peripheral portion of the backface of the second annular axially-recessed portion are fitted to the respective fitting recessed portions and then welded together so as to integrally connect the base member and the other of the seat-cushion side arm and the seat-back side arm.