Seat frame structure

[0001] The disclosure of Japanese Patent Application No. 2012-233930 filed on Oct. 23, 2012 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

[0002] 1. Field of the Invention

[0003] The invention relates to a seat frame structure. More particularly, the invention relates to a seat frame structure in which two mechanism elements are assembled sandwiching a seat frame.

[0004] 2. Description of Related Art

[0005] Japanese Patent Application Publication No. 2012-86609 (JP 2012-86609 A) describes a structure in which various mechanism elements are assembled on both sides of a seat frame so as to sandwich the seat frame therebetween. More specifically, the mechanism elements are assembled one on each side of the seat frame by passing a bolt shaft that is assembled to the mechanism element on one side through both a hole formed in the seat frame and a hole formed in the mechanism element on the other side, and fastening a nut onto the mechanism element on the other side.

[0006] However, with the related art described above, the bolt shaft must be assembled to the mechanism element on one side, and in addition, the bolt shaft must be passed through both the seat frame and the mechanism element on the other side. In order to ensure the assemblability of the bolt shaft to these parts, the hole in each is formed having a wide diameter, so assembly accuracy is poor.

[0007] One aspect of the invention thus relates to a seat frame structure that includes a first mechanism element; a second mechanism element; a bolt shaft; and a seat frame that has a fitting portion that fits together with the first mechanism element, and a hole through which the bolt shaft passes, the seat frame being sandwiched between the first mechanism element and the second mechanism element, and integrated with the first mechanism element and the second mechanism element by fastening of the bolt shaft in the hole in a state extending between the first mechanism element and the second mechanism element. The first mechanism element has a fitting portion that fits together with the seat frame. The second mechanism element is integrally assembled, by the fastening of the bolt shaft, to the first mechanism element in a state positioned on the seat frame by the fitting of the each fitting portion.

[0008] According to this aspect, the first mechanism element and the seat frame are assembled in a state with little assembly error, by the fitting structure between the fitting portion of the first mechanism element and the fitting portion of the seat frame. Therefore, the first mechanism element and the second mechanism element are able to be assembled accurately positioned with respect to the seat frame by assembling, by the fastening of the bolt shaft, the second mechanism element to the first mechanism element that is assembled accurately positioned with respect to the seat frame.

[0009] In the aspect described above, the first mechanism element may be formed as a component of an operating mechanism that releases a slide-locked state of a vehicle seat with respect to a floor, by being pushed around following forward tilting rotation of a seatback. Also, the second mechanism element may be formed as a component of a movable stopper mechanism capable of stopping the forward tilting rotation of the seatback at a position that will be a forward tilting position after the first mechanism element is operated, as well as releasing the stopped state.

[0010] According to the structure described above, the first mechanism element, which picks up the forward tilting (rotation) movement of the seatback and releases the slide-locked state of the vehicle seat and must be accurately positioned with respect to the seat frame, is able to be assembled to the seat frame in a state accurately positioned with respect to the seat frame. Also, the second mechanism element, which stops the forward tilting rotation of the seatback at a position that is to be the forward tilting position after the first mechanism element is operated as described above and must be accurately positioned with respect to the first mechanism element, is able to be assembled to the first mechanism element in a state accurately positioned with respect to the first mechanism element.

[0033] Hereinafter, example embodiments of the invention will be described with reference to the accompanying drawings.

[0034] First, the structure of a vehicle seat 1 according to a first example embodiment to which the seat frame structure of the invention has been applied will be described with reference to FIGS. 1 to 21. As shown in FIG. 1, the vehicle seat 1 in this example embodiment is configured as a seat for sitting, in a second row behind a driver's seat of a vehicle (an automobile) having three rows of seats. A seat main body of the vehicle seat 1 includes a seatback 2 that serves as a backrest for a seated occupant, a seat cushion 3 that serves as a seating portion, and a headrest 4 that serves as a headrest. The seatback 2 is such that lower end portions on both left and right sides are each connected, via a corresponding disc-shaped reclining device 5 that functions as a rotation shaft device that can brake against rotation, to rear end portions on both left and right sides of the seat cushion 3. As a result, the seatback 2 is connected to the seat cushion 3 in such a manner that the backrest angle in a seat front-rear direction is able to be adjusted.

[0035] The reclining devices 5 are constantly kept in a locked state in which the backrest angle of the seatback 2 is fixed. The reclining devices 5 are able to be unlocked at the same time so as to be switched to a state that enables the seatback 2 to be freely rotated in the front-rear direction of the seat as shown in FIG. 2, thus enabling the backrest angle of the seatback 2 to be adjusted, by a user pulling up on a W/I lever 1A provided on a side portion, on a vehicle outside (the side opposite the side shown in the drawing), of the seatback 2. The reclining devices 5 are also able to be unlocked at the same time so as to be switched to a state that enables the seatback 2 to be freely rotated in the front-rear direction of the seat as shown in FIG. 3, thus enabling the backrest angle of the seatback 2 to be adjusted, by a user pulling up on a cushion lever 1B provided on a side portion, on a vehicle outside, of the seat cushion 3.

[0036] Also, after the backrest angle of the seatback 2 has been adjusted to a predetermined angle (i.e., after the seatback 2 has been placed in a predetermined position) by the operation above, the reclining devices 5 are returned to the locked state again, such that the seatback 2 is fixed at the adjusted backrest angle (i.e., in the adjusted position), by stopping the operation of pulling up on the W/I lever 1A or the cushion lever 1B. The basic structure of the reclining devices 5 is the same well-known structure as that described in Japanese Patent Application Publication No. 2011-116303 (JP 2011-116303 A), so a detailed description of this structure will be omitted.

[0037] The seat cushion 3 is in a state connected to the floor of the vehicle via a pair of left and right slide devices 6. As a result, the seat cushion 3 is provided such that a located position thereof is able to be adjusted in the front-rear position of the seat with respect to the floor. The slide devices 6 are constantly kept in a locked state in which the located position of the seat cushion 3 is fixed, by an urging structure of a spring member, not shown, provided inside each of these slide devices 6. The slide devices 6 are unlocked at the same time by the user pulling up on a release lever 6A that is connected to the slide devices 6 and provided extending on a front lower portion of the seat cushion 3. This unlocking operation switches the seat cushion 3 to a state in which it is able to be freely slid in the front-rear direction of the seat, so the located position of the seat cushion 3 is able to be adjusted.

[0038] Also, after the located position of the seat cushion 3 has been adjusted to a predetermined slide position, the slide devices 6 are returned to the slide-locked state again, such that the seat cushion 3 is fixed at the adjusted slide position, by stopping the operation of pulling up on the release lever 6A. The basic structure of the slide devices 6 is the same well-known structure as that described in Japanese Patent Application Publication No. 2010-221935 (JP 2010-221935 A), so a detailed description of this structure will be omitted.

[0039] The headrest 4 is provided attached from above to an upper portion of the seatback 2. More specifically, the headrest 4 is provided fixed (i.e., mounted) to the upper portion of the seatback 2 by two rod-like stays, not shown, that protrude from a lower portion of the headrest 4 being inserted from above into two cylindrical support members that are fixed onto an upper frame 2FA (see FIG. 6) of a seatback frame 2F that forms the frame of the seatback 2. The mounting structure of the headrest 4 is similar to that described in Japanese Patent Application Publication No. 2008-239075 (JP 2008-239075 A), so a detailed description of this structure will be omitted.

[0040] Here, a spiral spring 7 (see FIG. 6) that constantly applies rotational urging force to the seatback 2 in a direction toward the front side of the seat is hooked onto a side portion, on the vehicle outside, between the seatback 2 and the seat cushion 3. As a result, when the fixed state of the backrest angle of the seatback 2 is released, the urging force of the spiral spring 7 raises the seatback 2 to a position where it abuts against the back of the seated occupant, and the backrest angle/position of the seatback 2 is adjusted with the seatback 2 following the forward/rearward tilting movement of the back of the seated occupant. The movable region of the seatback 2 described above is set as a region between positions where a bracket 12 that is joined to a side frame 2FS on the vehicle inside of the seatback frame 2F that forms the frame of the seatback 2 is stopped by abutting against a forward-tilt stopper 3FSd and a rearward-tilt stopper 3FSe that are each formed protruding in a horn-shape in the front and rear directions, respectively, on an upper edge portion on a rear side of a same-side side frame 3FS of a seat cushion frame 3F, as shown in FIGS. 6 and 7.

[0041] As shown in FIG. 2, the fixed state of the backrest angle of the seatback 2 described above is released by a person (the user) seated in a back row seat pulling up on the W/I lever 1A from behind while no one is seated in the vehicle seat 1. Consequently, the seatback 2 tilts forward from the urging force of the spiral spring 7 (see FIG. 6) described above, and stops when it reaches a forward tilting position, not shown. Also, with the tilting rotation of the seatback 2, the slide-lock state of the slide devices 6 is also released, so the seat cushion 3 switches to a state in which it is able to slide in the front-rear direction of the seat.

[0042] Also, as shown in FIG. 3, the fixed state of the backrest angle of the seatback 2 described above is similarly released by the user pulling up on the cushion lever 1B from a position standing outside the vehicle with a passenger door next to the vehicle seat 1 open while no one is seated in the vehicle seat 1. Consequently, the seatback 2 tilts forward from the urging force of the spiral spring 7 (see FIG. 6) described above, and stops when it reaches a forward tilting position, not shown. Also, with the tilting rotation of the seatback 2, the slide-lock state of the slide devices 6 is also released, so the seat cushion 3 switches to a state in which it is able to slide in the front-rear direction of the seat.

[0043] In this way, with the vehicle seat 1 of this example embodiment, a walk-in (W/I) operation in which the entire seat is able to be slid forward and retracted in a compact posture in which the seatback 2 is switched to the forward tilted position, as shown in FIGS. 2 and 3, is able to be performed by the slide devices 6 being released in combination with the seatback 2 being tilted forward. This walk-in operation increases the space for a person that will be seated, or is seated, in a third row seat, which is a seat in a row behind the vehicle seat 1, to get in and out of the vehicle through a passenger door that is next to the vehicle seat 1.

[0044] Also, as shown in FIG. 3, after the seatback 2 has been tilted to the forward tilting position by the user pulling up on the cushion lever 1B from a position standing outside the vehicle with the passenger door of the vehicle open, the seatback 2 is then folded down even farther forward to a folded down position in which the seatback 2 is tilted beyond the forward tilting position and is folded down onto an upper surface portion of the seat cushion 3 (a fold-down (F/D) operation), as shown in FIG. 4, by the user then pulling up on a F/D lever 1C provided on a front side portion, on the vehicle outside (the right side in FIG. 1), of the seat cushion 3. More specifically, the seatback 2 is folded down far forward to a position (i.e., the folded down position) where a bracket 12 that will be described later is stopped by abutting against the forward-tilt stopper 3FSd, as shown in FIG. 11. Also, in combination with this fold-down operation of the seatback 2, the released state of the slide lock of the slide devices 6 described above with reference to FIG. 4 is returned again to the slide-locked state, such that the slide position of the seat cushion 3 is returned to being fixed.

[0045] In this way, in combination with the seatback 2 being folded down by the user pulling up on the F/D lever 1C, the entire vehicle seat 1 is able to be folded down so that is low and compact, and placed in a slide-locked state by the slide devices 6 being returned again to the slide-locked state. As a result, the back surface of the folded down seatback 2 is able to be conveniently used as a table surface to put things on. The fold-down operation of the seatback 2 described above will not be performed even if the F/D lever 1C is operated when the seatback 2 is at an upright angle (in an raised and upright position) at which it is normally used as a backrest.

[0046] Specifically, this is because the fold-down operation of the seatback 2 is performed in stages. That is, first the cushion lever 1B is operated to tilt the seatback 2 to the forward tilting position, and then the F/D lever 1C is operated to release the state in which the seatback 2 is stopped in this forward tilting position so that the seatback 2 folds down to the folded down position. In this way, the fold-down operation is performed by two operations, so the seatback 2 is able to be folded down more safely than it is when the seatback 2 is folded down all at once to the folded down position by a single operation.

[0047] Next, the structure of each portion of the vehicle seat 1 will be described in further detail. In the description below, the operation of tilting the seatback 2 to the forward tilting position by operating the W/I lever 1A or the cushion lever 1B will be referred to as a “walk-in (W/I) operation”, and the operation of further folding down the seatback 2 to the folded down position by operating the F/D lever 1C will be referred to as a “fold-down (F/D) operation”. First, the structure of the seatback 2 will be described. As shown in FIG. 6, the seatback 2 has a seatback frame 2F that forms the internal frame of the seatback 2. This seatback frame 2F is formed by a pair of left and right vertically long plate-shaped side frames 2FS, an upper frame 2FA that is formed by an inverted U-shaped pipe that extends between upper end portions of the side frames 2FS, and reinforcing pipes 2FB formed by two horizontally long pipes lined up in the height direction and extending between the side frames 2FS, that have all been assembled so as to form an integrated frame shape. Hereinafter, whenever possible in this example embodiment, portions provided in plurality will be described in the singular form to facilitate understanding.

[0048] Each of the side frames 2FS is formed by a thin plate part 2FSa made of a thin steel sheet, and a thick plate part 2FSb made of a steel sheet that is thicker than the thin plate part 2FSa, that are integrally connected together one above the other. More specifically, the thin plate part 2FSa is formed by first cutting a single thin steel sheet in a vertically long plate shape, and then bending the edge portions on the front and rear sides into a flange shape toward the seat inside. As a result, the thin plate part 2FSa has increased structural strength with respect to bending and twisting by the press-bent edge portions, and is formed in a shape that has no sharp angles on the outside (the seat front and rear sides and the seat outside).

[0049] The thick plate part 2FSb is formed by a steel sheet that is thicker than the thin plate part 2FSa being cut in a vertically long flat plate shape. The thick plate part 2FSb is placed such that a plate surface of an upper portion overlaps with a surface portion, on the seat inside, of a lower portion of the thin plate part 2FSa, and the two are integrally and strongly fixed together by welding. The thick plate parts 2FSb are joining portions that join together with the reclining devices 5 when the seatback frame 2F is connected to the seat cushion frame 3F, and are portions that receive a high load when in use, so the thickness is made thicker than that of the thin plate parts 2FSa, and as a result, the structural strength is increased. The side frames 2FS that are formed by the thin plate parts 2FSa and the thick plate parts 2FSb form the frame of both the left and right sides of the seatback 2, and are arranged with the plate surfaces facing each other in the seat width direction, on both sides of the seatback 2.

[0050] The upper frame 2FA is formed by first cutting a single circular steel pipe to a predetermined length, and then bending this pipe into a vertically inverted (upside down) U-shape. Both inverted U-shaped leg portions of the upper frame 2FA are integrally and strongly joined to the upper end portions of these thin plate parts 2FSa by being placed against and welded to the upper end portions of the thin plate parts 2FSa of the side frames 2FS. Here, the upper end portions of the thin plate parts 2FSa of the side frames 2FS are formed bent in semicircular cylindrical shapes that match the shapes of the outer peripheral surfaces of the leg portions of the upper frame 2FA. As a result, the leg portions of the upper frame 2FA are placed in a state of wide surface contact with the upper end portions that are bent in the semicircular cylindrical shape of the thin plate parts 2FSa, and then integrally and strongly welded (i.e., joined) over a wide area.

[0051] Each reinforcing pipe 2FB is provided by first cutting a single circular steel pipe to a predetermined length, then inserting it through and extending between the side frames 2FS in the seat width direction, and integrally and strongly joining the inserted end portions by welding to the side frames 2FS. More specifically, the reinforcing pipe 2FB on the upper side is inserted through and extending between the thin plate parts 2FSa of the side frames 2FS in the seat width direction, and the inserted end portions are integrally and strongly joined to the thin plate parts 2FSa by welding. Also, the reinforcing pipe 2FB on the lower side is inserted in the seat width direction through and extending between overlapping portions where the thin plate part 2FSa and the thick plate part 2FSb of each side frame 2FS overlap in the seat width direction, and the inserted end portions are integrally and strongly joined to the overlapping thin plate parts 2FSa and the thick plate parts 2FSb by welding. As a result, the thin plate part 2FSa and the thick plate part 2FSb of each side frame 2FS are integrally and strongly joined together via the reinforcing pipe 2FB on the lower side that is inserted through and extends between the overlapping portions.

[0052] With the seat cushion 3, a seat cushion frame 3F that forms the internal frame of the seat cushion 3 is formed by a pair of left and right plate-shaped side frames 3FS that are long in the front-rear direction, a horizontally long pipe-shaped front frame 3FF that extends between front end portions of the side frames 3FS, and a horizontally long pipe-shaped rear frame 3FR that extends between rear end portions of both side frames 3FS, that have all been assembled so as to form an integrated frame shape.

[0053] Each side frame 3FS is formed by a thin plate part 3FSa made of thin steel plate, and a thick plate part 3FSb made of steel plate that is thicker than the thin plate part 3FSa, that are integrally connected together. More specifically, each thin plate part 3FSa is formed by first cutting a single thick steel sheet in a shape that is long in the front-rear direction, and then bending the edge portions on the front and rear sides into a flange shape toward the seat inside. Further, a reinforcing plate 3FSc that closes the sectional shape that is open in a U-shape to make it a closed box-shape extends between the edge portions on the upper and lower sides of the portions that are bent toward the seat inside, is integrally welded, and thus joined, to the thin plate part 3FSa. As a result, the thin plate part 3FSa has increased structural strength with respect to bending and twisting, and is formed in a shape that has no sharp angles on the outside (the seat upper and lower sides and the seat outside).

[0054] The thick plate part 3FSb is formed by a steel sheet that is thicker than the thin plate part 3FSa being cut in a vertically long plate shape. The thick plate part 3FSb is placed such that a plate surface of a lower portion overlaps with a surface portion, on the seat outside, of an upper portion on a rear end side of the thin plate part 3FSa, and the two are integrally and strongly fixed together by welding. The thick plate parts 3FSb are joining portions that are joined together with the reclining devices 5 when the seat cushion 3 is connected to the seatback frame 2F, and are portions that receive a high load when in use, so the thickness is made thicker than that of the thin plate parts 3FSa, and as a result, the structural strength is increased.

[0055] The side frames 3FS that are formed by the thin plate parts 3FSa and the thick plate parts 3FSb form the frame of both the left and right sides of the seat cushion 3, and are arranged with the plate surfaces facing each other in the seat width direction, on both sides of the seat cushion 3. More specifically, the thin plate parts 3FSa of the side frames 3FS that are long in the seat front-rear direction are fixed arranged on the upper surface portion of the pair of left and right slide devices 6 that are provided on the floor as described above.

[0056] Here, as shown in FIGS. 6 and 7, the forward-tilt stopper 3FSd and the rearward-tilt stopper 3FSe that each protrude in a horn-shape are provided on front and rear portions, respectively, of the upper edge portion of the thick plate part 3FSb of the side frame 3FS, on the vehicle inside, of the seat cushion 3. Also, the bracket 12 that is formed by a thick steel plate that abuts against and engages with the forward-tilt stopper 3FSd and the rearward-tilt stopper 3FSe is provided joined to the outside surface of the thick plate part 2FSb of the same-side side frame 2FS of the seatback 2. In this way, the forward-tilt stopper 3FSd, the rearward-tilt stopper 3FSe, and the bracket 12 that form the stopping structure when the seatback 2 is tilted in the front-rear direction are each provided on the thick plate part 2FSb of the seatback 2 and the thick plate part 3FSb of the seat cushion 3 that have high structural strength, so tilting rotation of a heavy object such as the seatback 2 is able to be stopped with high stopping force.

[0057] Also, as shown in FIG. 6, the spiral spring 7 that applies rotational urging force to the seatback 2 in a direction toward the front side of the seat is hooked between the side frame 2FS on the vehicle outside (the left side when looking at the drawing) of the seatback 2 and the side frame 3FS on the vehicle outside of the seat cushion 3. More specifically, the spiral spring 7 is fixed with an inside end portion thereof hooked onto a catch portion 7A1 that extends toward the seat upper side of a spring catch plate 7A that is joined to an inside surface of the thick plate part 3FSb of the side frame 3FS of the seat cushion 3, and an outside end portion of the spiral spring 7 hooked onto a spring catch recessed portion 7B 1 formed in a recessed shape on a rear edge portion of a spring catch plate 7B that is joined to the inside surface of the thick plate part 2FSb of the side frame 2FS of the seatback 2. The spring catch plate 7B is formed by the structure of the same part as the bracket 12 that will be described later. In this way, the spiral spring 7 is hooked between the thick plate part 2FSb of the seatback 2 and the thick plate part 3FSb of the seat cushion 3 that have high structural strength, so the spiral spring 7 that is set to a strong rotational urging force capable of raising a heavy object such as the seatback 2 is provided firmly hooked between the seatback 2 and the seat cushion 3.

[0058] Also, the thick plate part 3FSb of the side frame 3FS on the vehicle outside of the seat cushion 3 is formed in a stepped shape with a middle portion thereof being an offset portion 3FSf and a lower portion being bent inward in a crank shape toward the seat inside with respect to the upper portion. Forming the thick plate part 3FSb in a stepped shape set in toward the seat inside in this way allows for more legroom when a person that will be seated, or is seated, in a seat in the third row gets in or out through a passenger door, not shown, next to the vehicle seat 1 that is in the second row.

[0059] The front frame 3FF is formed by a single circular steel pipe that has been cut to a predetermined length, placed extending in the seat width direction between upper portions on the front end side of the thin plate parts 3FSa of the side frames 3FS, and then integrally welded and fixed in place. The rear frame 3FR is formed by single circular steel pipe, that has been cut to a predetermined length, being inserted through and extending between the thick plate parts 3FSb of the side frames 3FS in the seat width direction. The inserted end portions are then welded to the side frames 3FS, so as to be integrally and strongly joined to the thick plate parts 3FSb of the side frames 3FS.

[0060] Next, the structure of a detection mechanism 10 that picks up movement when a walk-in operation is performed on the seatback 2, and an operating mechanism 20 for releasing the slide-lock state of the slide devices 6 according to an operation movement amount detected by the detection mechanism 10, will be described. The detection mechanism 10 and the operating mechanism 20 are provided on a side surface portion on the outside of the side frame 3FS on the vehicle inside of the seat cushion 3, as shown in FIGS. 6 and 7. The detection mechanism 10 includes an operating link 11 that is pivotally connected to the side frame 3FS of the seat cushion 3, the bracket 12 that is fixed to the side frame 2FS of the seatback 2, and a tension spring 13 hooked between the bracket 12 and the operating link 11.

[0061] The operating link 11 is assembled in a state pivotally connected to an operating shaft 5A that is inserted through a center portion of the reclining device 5 described above, as shown in FIG. 7. More specifically, the operating link 11 is assembled in a state pivotally connected to the operating shaft 5A, by the operating shaft 5A being inserted through the center portion of the operating link 11, and the inserted tip end portion of the operating shaft 5A then retained so as not to slip out in the axial direction by an E-ring 5D. The operating link 11 is provided so as to be able to rotate smoothly, while positioned in the axial direction with respect to the operating shaft 5A, by being sandwiched from both sides, so as not to be in much planar contact in the axial direction, by the E-ring 5D, and a plate bracket 5C having a shape in which the center portion bulges out in a mountain shape, that is provided integrally joined to the side frame 3FS of the seat cushion 3.

[0062] More specifically, the operating shaft 5A is assembled in a state inserted from the seat inside through the side frame 2FS of the seatback 2, and then inserted through the center portion of the reclining device 5, the side frame 3FS of the seat cushion 3, the plate bracket 5C that is integrally joined to the side frame 3FS, and the operating link 11, in the axial direction in this order. Then the E-ring 5D is attached to the inserted tip end portion to keep the operating shaft 5A from slipping out in the axial direction. The operating shaft 5A is constantly held in a fixed position by the retaining force with which the reclining device 5 is kept in a locked state by the urging force of a spring, not shown.

[0063] The operating shaft 5A rotates against the spring urging force, thereby unlocking the reclining device 5, by an operating arm 5B that is integrally joined to an end portion on the head side (the seat inside) of the operating shaft 5A being rotated via a release cable, not shown, in response to operation of the W/I lever 1A or the cushion lever 1B. As shown in FIG. 16, an operating structure formed by the operating shaft 5A and the operating arm 5B that are rotated in response to operation of the W/I lever 1A or the cushion lever 1B is also arranged on the reclining device 5 on the vehicle outside. A release cable 5E that is pulled in response to operation of the W/I lever 1A or the cushion lever 1B is connected to the operating arm 5B. The operating arm 5B rotates against the spring urging force, and consequently unlocks the reclining device 5, by being rotated via the release cable 5E in response to operation of these levers 1A and 1B. According to this structure, the locked states of the reclining devices 5 on both sides are able to be released at the same time in synchronization on the left and right, by the W/I lever 1A or the cushion lever 1B being operated.

[0064] As shown in FIG. 8, the operating link 11 has a kick portion 11A that extends toward the seat upper side from the center portion that is pivotally connected by the operating shaft 5A. This kick portion 11A passes through the inside the recessed portion 12A of the bracket 12 that will be described later, and is sandwiched from the front and rear by the bracket 12. As a result, when the seatback 2 is tilted forward, the operating link 11 is consequently forcibly rotated counterclockwise in the drawing, with the kick portion 11A that will be described later being pushed and kicked from the rear by a rear portion 12C of the bracket 12, as shown in FIGS. 9 and 10. Also, when the seatback 2 is raised (i.e., pushed back) after being tilted forward, the operating link 11 is consequently forcibly rotated clockwise in the drawing, with the kick portion 11A that will be described later being pushed and kicked from the front by a front portion 12B of the bracket 12, as shown in FIG. 13.

[0065] The bracket 12 is formed bent in an L-shaped plate shape, and a plate portion that is bent such that the surface extends in the height direction is provided integrally fastened and fixed to the outside surface of the thick plate part 2FSb of the side frame 2FS of the seatback 2, as shown in FIG. 7. In this bracket 12, the recessed portion 12A that is cut in a cylindrical shape is formed on a tip edge portion that extends bent toward the seat outside from a joining portion where the bracket 12 joins the side frame 2FS of the seatback 2. The kick portion 11A of the operating link 11 is set inserted from the seat outside into this recessed portion 12A. Thus, the kick portion 11A of the operating link 11 that is set in the recessed portion 12A is sandwiched from the front and rear by the front portion 12B and the rear portion 12C that sandwich the recessed portion 12A of the bracket 12.

[0066] The tension spring 13 is hooked between a push portion 11B that extends out in fan-like shape forward and downward with respect to the seat from the center portion of the operating link 11, and a front portion 12B of the bracket 12. The tension spring 13 is configured to apply rotational urging force to the operating link 11 in a clockwise direction in the drawing. This spring urging force of the tension spring 13 constantly keeps the kick portion 11A of the operating link 11 pushed against a rear portion 12C of the bracket 12, thereby suppressing backlash in the rotational direction between the operating link 11 and the bracket 12.

[0067] Here, the bracket 12 has a spring catch recessed portion 12D that is cut in a cylindrical shape formed on each edge portion on the front and rear sides of a plate portion of the bracket 12 that extends on the seat outside. Further, an extended recessed portion 12E is formed at corner portions on the seat outside of these spring catch recessed portions 12D, in a manner further extending a void shape of these corner portions in a round hole shape. A front-side portion of each extended recessed portion 12E functions as a catch portion for hooking the upper end portion of the tension spring 13 onto the front portion 12B of the bracket 12. A rear-side portion of each extended recessed portion 12E is not used in this example embodiment, but it is formed in advance to enable the versatile use of the same part when the bracket 12 is used facing the opposite direction in the front-rear direction. Also, the spring catch recessed portions 12D are also not used in this example embodiment. The rear-side portion of these spring catch recessed portions 12D, of the spring catch plate 7B formed by the same part as the bracket 12, functions as a portion (i.e., the spring catch recessed portion 7B1) for hooking the outside end portion of the spiral spring 7 onto, as shown in FIG. 6.

[0068] Next, the operating mechanism 20 will be described with reference to FIGS. 7 and 8. The operating mechanism 20 includes an output link 21, an intermediate link 22, a retaining spring 23, a pressing spring 24, a fixing plate 25, and a cable 26. The output link 21 is provided in a state pivotally connected to an outside surface of the thick plate part 3FSb of the side frame 3SF of the seat cushion 3 by a spindle 21A, as shown in FIG. 8. More specifically, the output link 21 is provided in a state pivotally connected by the spindle 21A to the fixing plate 25 that is integrally joined to the thick plate part 3FSb. The fixing plate 25 is provided in a state integrally and strongly joined by a bolt fastening structure, which will be described later, to the outside surface of the thick plate part 3FSb.

[0069] A retaining spring 23 (a torsion spring) is hooked between the output link 21 and a stopping piece 25A that is partially cut out and bent up from a portion of the fixing plate 25, such that the output link 21 is constantly kept rotatably urged in the counterclockwise direction in the drawing, with a stopping arm 21B that extends toward the right in the drawing from the center portion of the output link 21 kept pushed against and engaged with the stopping piece 25A of the fixing plate 25, by the urging force of this retaining spring 23. A wound portion of the center portion of the retaining spring 23 is wound around the spindle 21A. One end on the right side in the drawing is hooked onto the stopping piece 25A, and the other end on the left side is fixed by being hooked onto an operating arm 21C that extends toward the left in the drawing from the center portion of the output link 21.

[0070] The intermediate link 22 is formed curved in a C-shape. A lower end portion of the intermediate link 22 in the drawing is provided pivotally connected to the output link 21 by a connecting shaft 22A. More specifically, the connecting shaft 22A is integrally joined to the intermediate link 22, and is pivotally connected to the stopping arm 21B of the output link 21. The pressing spring 24 (a torsion spring) is hooked between the intermediate link 22 and the output link 21, such that the intermediate link 22 is constantly kept in a state rotatably urged in the clockwise direction in the drawing, with an atm shape of the intermediate link 22 that is curved in a C-shape kept in a rotated position in which it is pushed against and engaged with the spindle 21A of the output link 21, by the urging force of this pressing spring 24. The inside end portion of the pressing spring 24 is fixed by being hooked onto a head portion of the connecting shaft 22A that is integrated with the intermediate link 22. The outside end portion of the pressing spring 24 is fixed by being hooked onto a bent stopping piece 21B1 at a tip end portion of the stopping arm 21B of the output link 21.

[0071] When the seatback 2 is at an angle/position in which it is used as a backrest, as shown in FIG. 8, a kick pin 22B that is joined to an upper end portion of the intermediate link 22 is kept in an initial position in which it is separated to the rear from the push portion 11B of the operating link 11. However, as shown in FIG. 9, when a walk-in operation starts to be performed on the seatback 2 and the kick portion 11A of the operating link 11 is pushed around to the front side by the rear portion 12C of the bracket 12, the push portion 11B of the operating link 11 abuts against the kick pin 22B of the intermediate link 22. As a result, as shown in FIG. 10, the intermediate link 22 is pushed around in the direction in which it is pushed against the spindle 21A, and rotates, together with the output link 21 that is connected via the connecting shaft 22A, in the clockwise direction in the drawing around the spindle 21A. When the output link 21 rotates in this way, the cable 26 that is connected to the tip of the operating arm 21C of the output link 21 is consequently pulled, thereby releasing the slide-lock state of the slide device 6.

[0072] The cable 26 has a double layered cable structure in which a linear wire member is inserted through the inside of a flexible tubular member. The upper end portion of the tubular member of the cable 26 that is shown is fixed by being hooked onto a cable catch piece 25B that is partially cut out and bent up from the fixing plate 25. The upper end portion of the wire member that runs out from the upper end portion of this tubular member is fixed by being hooked onto a tip end portion of the operating arm 21C of the output link 21, which extends to the left in the drawing. Also, the other end portion of the cable 26, not shown, is connected to the release lever 6A that releases the slide-lock state of the slide device 6 in the FIG. 6. Therefore, as shown in FIG. 10, when the intermediate link 22 and the output link 21 rotate together in the clockwise direction in the drawing in response to a walk-in operation of the seatback 2, the cable 26 is pulled upward in the drawing by the output link 21, thereby operating the release lever 6A that is connected to the other end portion of the cable 26 (see FIG. 6) and releasing the slide-lock state of the slide device 6.

[0073] As shown in FIG. 10, when the seatback 2 is tilted to the forward tilting position and stopped there, the cable 26 is kept in a pulled state by the kick pin 22B of the intermediate link 22 being kept in a state in which it is riding up on the outer peripheral surface 11B1 of the push portion 11B of the operating link 11. As a result, the slide device 6 (see FIG. 6) is kept in a state in which the slide lock is released.

[0074] When the seatback 2 is tilted to the forward tilting position and stopped there, pressing force radially inward toward the center portion of the operating link 11 is applied toward the outer peripheral surface 11B1 of the push portion 11B of the operating link 11 from the kick pin 22B of the intermediate link 22 by the spring force action of the retaining spring 23 and the pressing spring 24, as well as the spring force action of a spring member that is not shown that is provided inside the slide device 6 (FIG. 6) and urges it in the slide-lock direction. Therefore, when a walk-in operation of the seatback 2 is performed, the operating link 11 is forcibly pushed around toward the front side by the rear portion 12C of the bracket 12 that is integrally joined to the side frame 2FS of the seatback 2, so the operating link 11 is able to smoothly push the kick pin 22B around, which is good. However, when an attempt is made to return the tilted seatback 2 from the state in which the kick pin 22B is riding on the outer peripheral surface 11B1 of the push portion 11B of the operating link 11, the operating link 11 may not easily return to its original position due to resistance from the pressing force in the radially inward direction from the kick pin 22B.

[0075] However, as shown in FIG. 13, when the seatback 2 is raised toward the rear from the forward tilting position as well, the operating link 11 is forcibly pushed back by the front portion 12B of the bracket 12 from the raising of the seatback 2. Therefore, the operating link 11 is able to be smoothly returned to its original rotational position together with the seatback 2, even when it receives resistance from the pressing force of the kick pin 22B.

[0076] When the seatback 2 is tilted farther forward (i.e., folded down) from the forward-tilting position (the position shown in FIG. 10) of the walk-in operation by a fold-down operation, the kick pin 22B of the intermediate link 22 rides forward off of (i.e., past) the outer peripheral surface 11B1 of the push portion 11B of the operating link 11 following this movement, and separates from the push portion 11B (i.e., disengages from the push portion 11B), as shown in FIG. 11. Accordingly, the intermediate link 22 and the output link 21 that had been pushed around together with the intermediate link 22 return to their initial positions before being rotated, such that the cable 26 is no longer being pulled on. As a result, the slide device 6 (see FIG. 6) again returns to the slide-locked state.

[0077] If the kick pin 22B of the intermediate link 22 ends up riding forward off of (i.e., past) the push portion 11B of the operating link 11 in this way, the front-rear positional relationship of the two ends up reversing, and when the seatback 2 is raised, the push portion 11B of the operating link 11 will end up pushing the kick pin 22B of the intermediate link 22 from the direction opposite that described above (i.e., from the rear). However, in this case, as shown in FIG. 12, the intermediate link 22 is pushed around in the counterclockwise direction in the drawing independently with respect to the output link 21, with the connecting shaft 22A as the fulcrum, against the urging force of the pressing spring 24, so the movement described above is relieved by the intermediate link 22 rotating idly. This relieving operation ensures that the operation of raising the seatback 2 to the rear from the folded down position will not be impeded. When the seatback 2 is raised from the folded down position, the kick pin 22B of the intermediate link 22 rides rearward off of (i.e., past) the outer peripheral surface 11B1 of the push portion 11B of the operating link 11, and separates from the push portion 11B (i.e., disengages from the push portion 11B). As a result, the intermediate link 22 returns to its original position before rotating idly, as shown in FIG. 8.

[0078] As described above, when the seatback 2 is returned to the raised angle/position from the folded down position as well, the operating link 11 is forcibly pushed around by the front portion 12B of the bracket 12 from the raising of the seatback 2. Therefore, the operating link 11 is able to be smoothly pushed back to a predetermined raised rotational position by rotating together with the seatback 2, even when it receives resistance when pushing the kick pin 22B of the intermediate link 22 from the rear.

[0079] Continuing on, the structure of a stopper mechanism 30 that stops forward-tilting rotation of the seatback 2 at the forward tilting position when the walk-in operation is performed on the seatback 2, illustrated in FIG. 10, will be described. The stopper mechanism 30 is provided on a side surface portion on the inside of the side frame 3FS on the vehicle inside of the seat cushion 3, as shown in FIG. 6. The stopper mechanism 30 is a structure that stops the tilting rotation of the seatback 2 at the forward tilting position by abutting a stopping portion 2FSc formed protruding in a horn-shape on a front lower edge portion of the thick plate part 2FSb of the side frame 2FS of the seatback 2 against a receiving pin 32A that will be described later, when the seatback 2 is tilted (rotated) forward by an operation of the W/I lever 1A or the cushion lever 1B, as shown in FIG. 10. Also, when the user operates the F/D lever 1C, the stopper mechanism 30 consequently retracts the receiving pin 32A downward, which releases the stopped state of the seatback 2 from the forward tilting position, thus enabling the seatback 2 to be folded down far forward to the folded down position, as shown in FIG. 11.

[0080] Hereinafter, the specific structure of the stopper mechanism 30 will be described in detail. As shown in FIG. 14, the stopper mechanism 30 includes a base plate 31, a receiving link 32, an operating link 33, a stopper link 34, a retainer plate 35, a first rotating shaft 36A, a second rotating shaft 37A, a first urging spring 36B, a second urging spring 37B, and a release cable 38. The base plate 31 is provided fixed by being integrally fastened to a side surface portion on the inside of the side frame 3FS on the vehicle inside of the seat cushion 3 by two fastening pins 31A that will be described later. The structure by which this base plate 31 is fixed to the side frame 3FS will be described in detail later. A spring catch portion 31B, a stopping piece 31D, and a cable catch portion 31E, that are formed bent in the plate thickness direction, are formed on upper and lower edge portions, respectively, of the base plate 31 in the drawing.

[0081] The spring catch portion 31B is a portion formed to be hooked onto by one end of the second urging spring 37B (a torsion spring). Also, the cable catch portion 31E is a portion formed to be hooked onto by an end portion of an outer tubular member of the release cable 38 that has a double layered cable structure and that is connected to the F/D lever 1C. The stopping piece 31D is formed having a stopping surface 31D1 that stops rotation of the stopper link 34 by abutting against a leg portion 34B of the stopper link 34 that will be described later in the direction of rotation, a deformation inhibiting surface 31D2 that is placed against the leg portion 34B of the stopper link 34 in the axial direction (i.e., the seat width direction) and inhibits deforming movement in the axial direction of the stopper link 34 when the leg portion 34B abuts against the stopping surface 31D1, and a groove 31 D3 that is formed recessed at a corner portion of the stopping surface 31D1 and the deformation inhibiting surface 31D2. The groove 31 D3 is formed recessed from the corner portion at the boundary between the stopping surface 31D1 and the deformation inhibiting surface 31D2, such that the leg portion 34B of the stopper link 34 that will be described later is able to surface-abut with both the stopping surface 31D1 and the deformation inhibiting surface 31D2 at the same time.

[0082] Also, a guide surface 31D2a having an inclined surface shape that serves to relieve interference with the leg portion 34B of the stopper link 34 in the axial direction so that the leg portion 34B of the stopper link 34 will not bump into anywhere other than the stopping surface 31D1 in the rotational direction when the leg portion 34B of the stopper link 34 rotates to the position where it abuts against the stopping surface 31D1, is formed on the stopping piece 31D. This guide surface 31D2a is formed so as to chamfer, at an angle, an edge portion (a corner portion) of a tip end side (seat front side) of the stopping piece 31D that the leg portion 34B of the stopper link 34 first passes by when the leg portion 34B of the stopper link 34 rotates toward the stopping surface 31D1, and is formed as an inclined surface that connects the edge portion surface on the tip end side of the stopping piece 31D with the deformation inhibiting surface 31D2 at an angle, as shown in FIGS. 14 and 15.

[0083] By setting the guide surface 31D2a, when the leg portion 34B of the stopper link 34 rotates in the direction in which it abuts against the stopping surface 31D1, even if the position where the leg portion 34B of the stopper link 34 bumps into the edge portion on the tip end side of the stopping piece 31D in the rotational direction changes due to variation in the assembly position in the axial direction (the seat width direction) between the stopper link 34 and the stopping piece 31D, the leg portion 34B of the stopper link 34 will abut against the guide surface 31D2a, and be guided to move in the axial direction toward the side where the deformation inhibiting surface 31D2 is formed, so as to ride along the deformation inhibiting surface 31D2 and bump into the stopping surface 31D1 in the rotational direction. Therefore, because of the guide surface 31D2a, even if the stopper link 34 and the stopping piece 31D are provided close together in the axial direction, the deformation inhibiting surface 31D2 is able to be placed next to the leg portion 34B of the stopper link 34, while the leg portion 34B of the stopper link 34 appropriately abuts against the stopping surface 31D1.

[0084] As shown in FIG. 14, the receiving link 32 is formed by a pair of link members that are lined up in the axial direction. A round bar-shaped receiving pin 32A extends between the tip end portions of the link members and is integrally joined thereto. An end portion on the base side of each link member is provided rotatably shaft-connected to the base plate 31 by a first rotating shaft 36A. As a result, the receiving link 32 is provided so as to be able to move the receiving pin 32A that is attached to the tip end portion thereof upward, as well as retract the receiving pin 32A downward, by rotating with respect to the base plate 31. A recessed spring catch groove 32B onto which one end of a first urging spring 36B (a torsion spring) that will be described later is hooked is formed on a side portion of a link member on one side of the receiving link 32.

[0085] The operating link 33 is formed by a flat plate-shaped member. A horizontally long recessed portion 33A and a vertically long long hole 33B are formed in a plate portion of this operating link 33. In addition, a spring catch portion 33C that is bent in the direction of plate thickness is formed on an edge portion, on the right side in the drawing, of the operating link 33. This operating link 33 is shaft-connected in a state able to rotate, together with the receiving link 32, coaxially around the base plate 31. By this connection, the operating link 33 and the receiving link 32 are provided so as to both be able to relatively rotate individually with respect to the base plate 31. The spring catch portion 33C is a portion formed to hook the other end of the first urging spring 36B (a tension spring) onto.

[0086] The stopper link 34 is formed by a steel plate member that is thicker than the link members of the receiving link 32. This stopper link 34 is formed in an L-shaped link shape having a receiving surface 34A that receives the rotation of the receiving link 32 by abutting against the receiving pin 32A, and a leg portion 34B that is restricted from rotatably moving in the retracting direction (i.e., downward) by abutting against the stopping surface 31D1 formed on the base plate 31. The stopper link 34 is provided with a middle portion of the L-shape thereof rotatably shaft-connected to the base plate 31 by the second rotating shaft 37A. As a result, the stopper link 34 is provided such that the leg portion 34B abuts against the stopping surface 31D1 of the base plate 31, thus placing the receiving surface 34A in a state facing upward abutting against the receiving pin 32A of the receiving link 32, or placing the receiving surface 34A in a state retracted downward not abutting against the receiving pin 32A, depending on the rotational movement of the stopper link 34 with respect to the base plate 31.

[0087] A recessed spring catch groove 34C that one end of the second urging spring 37B (a torsion spring) that will be described later hooks onto is provided on a side portion of the leg portion 34B of the stopper link 34. Also, a protruding portion 34D that protrudes in a round pin shape that is assembled in the horizontally long recessed portion 33A formed in the operating link 33, is formed pushed out in the direction of plate thickness by half blanking on the plate portion of the stopper link 34. The stopper link 34 is assembled in a state engaged in the horizontally long recessed portion 33A formed in the operating link 33. As a result, the operating link 33 rotatably operates the receiving surface 34A in a direction in which the receiving surface 34A retracts downward, in conjunction with movement in which the operating link 33 is rotatably operated by being pulled by the release cable 38, as will be described later with reference to FIG. 19.

[0088] The retainer plate 35 is provided extending between the first rotating shaft 36A and the second rotating shaft 37A, and integrally joined to these. This retainer plate 35 suppresses strong inter-shaft repulsion force from being applied between the first rotating shaft 36A and the second rotating shaft 37A when the load of the seatback 2 is applied to the stopper mechanism 30. The retainer plate 35 also prevents the parts assembled between it and the base plate 31 from slipping off in the axial direction.

[0089] As shown in FIGS. 14 and 15, the first rotating shaft 36A is formed in a stepped shape, with one end on the left side in FIG. 14 integrally joined to the base plate 31, and the other end on the right side in FIG. 14 integrally joined to the retainer plate 35. As a result, the first rotating shaft 36A is assembled in a state in which the operating link 33, the ring member on one side of the receiving link 32, and the link member on the other side of the receiving link 32 are positioned in the axial direction, with the operating link 33 and the ring member on one side of the receiving link 32 being sandwiched in a rotatable state between the bulge-shaped portion in the center in the axial direction of the first rotating shaft 36A and the base plate 31, and with the link member on the other side of the receiving link 32 being sandwiched in a rotatable state between the portion of the first rotating shaft 36A bulge-shaped center and the retainer plate 35.

[0090] The second rotating shaft 37A is also formed in a stepped shape, with one end on the left side in the drawing integrally joined to the base plate 31, and the other end on the right side in the drawing integrally joined to the retainer plate 35. As a result, the second rotating shaft 37A is assembled in a state in which the stopper link 34 is positioned in the axial direction, with the stopper link 34 being sandwiched in a rotatable state between the bulge-shaped portion in the center in the axial direction of the second rotating shaft 37A and the retainer plate 35.

[0091] As shown in FIG. 14, the first urging spring 36B (a torsion spring) is arranged with the wound portion in the center thereof being wound around the first rotating shaft 36A, one end being hooked onto the spring catch groove 32B formed in the receiving link 32, and the other end being hooked onto the spring catch portion 33C formed in the operating link 33. As a result, the first urging spring 36B is provided so as to constantly rotatably urge the receiving link 32 in the counterclockwise direction in the drawing, i.e., in a direction that retractably moves the receiving pin 32A downward (in a direction that pushes the receiving pin 32A against the receiving surface 34A of the stopper link 34), with respect to the operating link 33, as shown in FIG. 16.

[0092] The second urging spring 37B (a torsion spring) is arranged with the wound portion in the center thereof being wound around the second rotating shaft 37A, one end being hooked onto the spring catch portion 31B formed on the base plate 31, and the other end being hooked onto the spring catch groove 34C formed in the stopper link 34, as shown in FIG. 14. As a result, as shown in FIG. 16, the second urging spring 37B is provided constantly rotatably urging the stopper link 34 in the counterclockwise direction in the drawing with respect to the base plate 31, and pushes the leg portion 34B of the stopper link 34 against the stopping surface 31D1 formed on the base plate 31, thus engaging the leg portion 34B of the stopper link 34 with the stopping surface 31D1 formed on the base plate 31. The second urging spring 37B is formed in a thicker, larger line shape than the first urging spring 36B, and is able to display stronger spring force.

[0093] Therefore, the stopper link 34 is constantly maintained in a state receiving the receiving pin 32A of the receiving link 32 by the receiving surface 34A that faces upward angled toward the front, with the leg portion 34B of the stopper link 34 being pushed against the stopping surface 31D1 of the base plate 31 by the urging force of the second urging spring 37B. Also, when the release cable 38 that will be described later is operated, the stopper link 34 is rotatably operated in a direction that pushes the receiving surface 34A downward against the urging force of the second urging spring 37B, as shown in FIG. 19, so even after the receiving pin 32A of the receiving link 32 that receives the urging force of the first urging spring 36B is pushed against the upper surface of the stopper link 34, the urging force of the second urging spring 37B that displays a stronger urging force than the first urging spring 36B causes the stopper link 34 to rotate in a manner that pushes the receiving pin 32A back upward. As a result, the stopper link 34 returns to its initial position (i.e., the position in which the leg portion 34B abuts against the stopping surface 31D1 of the base plate 31) in which the receiving surface 34A faces upward angled toward the front, as shown in FIG. 16.

[0094] Also, while the stopper link 34 is held in the initial position by the urging force of the second urging spring 37B, the receiving pin 32A of the receiving link 32 that receives the urging force of the first urging spring 36B is pushed against the receiving surface 34A of the stopper link 34. At this time, the receiving surface 34A is formed in a shape curved in an arc centered around the second rotating shaft 37A that is the rotational center of the stopper link 34. While the stopper link 34 is held in the initial position described above, pressing force received from the receiving pin 32A of the receiving link 32 is transmitted directly toward the second rotating shaft 37A, such that the receiving surface 34A firmly receives the load received from the receiving pin 32A at a fixed position, without receiving a load that would move it in the rotational direction.

[0095] As shown in FIG. 14, the release cable 38 is a double layered cable structure in which a linear wire member is inserted through the inside of a flexible tubular member. With the release cable 38, an upper end portion of the tubular member in the drawing is fixed by being hooked onto the cable catch portion 31E formed on the base plate 31. The upper end portion of the wire member that runs out from the upper end portion of this tubular member is hooked in a slidable state inside the long hole 33B of the operating link 33. Also, the other end portion of the release cable 38 on the side not shown in the drawing is connected to the F/D lever 1C illustrated in FIG. 1. Therefore, as shown in FIG. 19, when the F/D lever 1C is operated, the release cable 38 is consequently pulled on in a manner in which the upper end portion of the wire member that is shown is drawn into the tubular member. As a result, the operating link 33, rotates counterclockwise in the drawing around the first rotating shaft 36A. This rotation of the operating link 33 causes the stopper link 34, in which the protruding portion 34D is engaged in the recessed portion 33A of the operating link 33 to then rotate in the clockwise direction in the drawing around the second rotating shaft 37A, and thus retract.

[0096] As shown in FIG. 16, when the seatback 2 is at an upright angle/position in which it is normally used as a backrest, the stopper mechanism 30 having this structure is maintained in a state in which the leg portion 34B of the stopper link 34 is pushed against and stopped by the stopping surface 31D1 of the base plate 31 by the urging force of the second urging spring 37B, and the receiving pin 32A of the receiving link 32 is pushed against and stopped by the receiving surface 34A of the stopper link 34 by the urging force of the first urging spring 36B.

[0097] Also, as shown in FIG. 17, when the W/I lever 1A or the cushion lever 1B is operated from the state described above and the seatback 2 is tilted to the forward tilting position, a stopping portion 2FSc formed on the side frame 2FS of the seatback 2 consequently abuts against the receiving pin 32A, and is received by the stopper link 34 that supports the receiving pin 32A. As a result, the forward tilting rotation of the seatback 2 is received and stopped at the forward tilting position. At this time, as shown in FIG. 18, a large load is applied to the stopper link 34 that receives the receiving pin 32A, as a result of receiving a heavy object such as the seatback 2. Specifically, a high load that attempts to push and bend the stopper link 34 in the axial direction (i.e., the seat width direction) with the second rotating shaft 37A, which is supports the stopper link 34 in a cantilevered manner with respect to the base plate 31, as the fulcrum is applied to the stopper link 34. More specifically, the stopper link 34 receives a load in which a section of the stopper link 34 where the receiving surface 34A above the second rotating shaft 37A is formed is pushed and bent so as to be inclined toward the inside of the seat (i.e., the right side in the drawing), with the second rotating shaft 37A as the fulcrum, and a section of the stopper link 34 where the leg portion 34B below the second rotating shaft 37A is formed is pushed and bent so as to be inclined toward the outside of the seat (i.e., the left side in the drawing) closer to the base plate 31, also with the second rotating shaft 37A as the fulcrum.

[0098] However, as shown in FIG. 15, the stopper link 34 is in a state in which the leg portion 34B thereof is placed against, and supported from the seat outside by, the deformation inhibiting surface 31D2 of the stopping piece 31D formed on the base plate 31, so the stopper link 34 will not deform in the seat width direction even if it receives the load described above. Therefore, the forward tilting rotation of the seatback 2 is firmly received at a fixed position by the stopper link 34 that is inhibited from deforming.

[0099] Also, after the forward tilting rotation of the seatback 2 is stopped in the forward tilting position shown in FIG. 18, the release cable 38 is pulled, such that the operating link 33 is drawn in downward, as shown in FIG. 19, by the user then operating the F/D lever 1C (see FIG. 1). As a result, the stopper link 34 rotates together with the operating link 33 in a manner led by the operating link 33, so the receiving surface 34A is released from having to support the receiving pin 32A. As a result, the receiving link 32 is no longer prevented from rotating by the stopper link 34, so the receiving link 32 is also rotated so as to retract the receiving pin 32A downward by the urging force of the first urging spring 36B. Thus, the seatback 2 is no longer stopped in the forward tilting position, and thus is able to be folded down to the folded down position.

[0100] Continuing on, the assembly structure for assembling the operating mechanism 20 and the stopper mechanism 30 described above onto each side surface on the inside and outside of the side frame 3FS (the thick plate part 3FSb) of the seat cushion 3 will be described with reference to FIGS. 20 and 21. The operating mechanism 20 and the stopper mechanism 30 described above are assembled integrated together with the side frame 3FS of the seat cushion 3, so as to sandwich the side frame 3FS from both sides. More specifically, as shown in FIG. 20, the operating mechanism 20 and the stopper mechanism 30 are such that a bolt shaft 31A1 provided in a state integrally joined beforehand to the base plate 31 of the stopper mechanism 30 extends through a through-hole 3FSg2 open in the side frame 3FS of the seat cushion 3 and a through-hole 25F open in the fixing plate 25 of the operating mechanism 20, and the tip of this bolt shaft 31A1 is fastened with a nut 31C1. As a result, the operating mechanism 20 and the stopper mechanism 30 are integrally assembled to the side frame 3FS of the seat cushion 3 in such a way as to sandwich the side frame 3FS from both sides. Here, the thick plate part 3FSb that forms the side frame 3FS of the seat cushion 3 described above is one example of the “seat frame” of the invention, the fixing plate 25 is one example of the “first mechanism element” of the invention, and the base plate 31 is one example of the “second mechanism element” of the invention.

[0101] Also, with the operating mechanism 20, a bolt shaft 25C provided in a state integrally joined beforehand to the fixing plate 25 of the operating mechanism 20 passes through another through-hole 3FSg1 open in the side frame 3FS of the seat cushion 3, and the tip of this bolt shaft 25C is then fastened with a nut 25D. As a result, this portion is also integrally joined to the side frame 3FS of the seat cushion 3. Also, with the stopper mechanism 30 as well, another bolt shaft 31A2 provided in a state integrally joined beforehand to the base plate 31 of the stopper mechanism 30 passes through another through-hole 3FSg3 open in the side frame 3FS of the seat cushion 3, and the tip of this bolt shaft 31A2 is fastened with a nut 31C2. As a result, this portion is also integrally joined to the side frame 3FS of the seat cushion 3.

[0102] More specifically, the operating mechanism 20 and the stopper mechanism 30 are integrally fitted together by first pushing two dowel holes 25E formed through the fixing plate 25 of the operating mechanism 20 over two dowels 3FSg5 formed pushed out on the side frame 3FS of the seat cushion 3. Then the operating mechanism 20 and the stopper mechanism 30 are finally integrally fitted both together and to the side frame 3FS of the seat cushion 3, by fastening the nuts 31C1, 25D, and the 31C2 onto the bolt shafts 31A1, 25C, and 31A2. With this kind of assembly structure, the fixing plate 25 of the operating mechanism 20 is first assembled, in a state accurately positioned by the fitting structure of the dowel holes 25E and the dowels 3FSg5, to the side frame 3FS of the seat cushion 3, and then the base plate 31 of the stopper mechanism 30 is assembled to this positioned fixing plate 25 of the operating mechanism 20. Here, the fitting structure of the dowel holes 25E and the dowels 3FSg5 are examples of the “fitting portions”.

[0103] Therefore, the fixing plate 25 of the operating mechanism 20, which picks up the forward tilting (rotating) movement of the seatback 2 and releases the slide-locked state of the vehicle seat 1 and must be accurately positioned with respect to the side frame 3FS of the seat cushion 3, is able to be assembled in a state accurately positioned with respect to the side frame 3FS of the seat cushion 3. Also, the base plate 31 of the stopper mechanism 30, which stops the forward tilting rotation of the seatback 2 at a position that is to be the forward tilting position after the operating mechanism 20 is operated as described above and must be accurately positioned with respect to the operating mechanism 20, is able to be assembled in a state accurately positioned with respect to the fixing plate 25 of the operating mechanism 20.

[0104] Also, as described above, the fixing plate 25 of the operating mechanism 20 is assembled in a state accurately positioned with respect to the side frame 3FS of the seat cushion 3, by the fitting structure of the dowel holes 25E and the dowels 3FSg5. Therefore, the through-hole 3FSg1 open in the side frame 3FS for passing the bolt shaft 25C that is joined to the fixing plate 25 through is able to be formed in a shape with a narrowed tolerance range that takes variation into account, so the fixing plate 25 is able to be more strongly joined to the side frame 3FS. Also, the through-hole 25F open in the fixing plate 25 of the operating mechanism 20 and the through-hole 3FSg2 open in the side frame 3FS for passing the bolt shaft 31A1 that is joined to the base plate 31 of the stopper mechanism 30 through are also able to be formed in a shape with a narrowed tolerance range that takes variation into account, so the fixing plate 25 is able to be more strongly joined to the side frame 3FS and the base plate 31 of the stopper mechanism 30.

[0105] Also, in the fitting structure of the dowel holes 25E and the dowels 3FSg5, the dowels 3FSg5 formed pushed out in the direction of plate thickness are formed on the thick plate part 3FSb of the side frame 3FS that is thick. As a result, the dowels 3FSg5 are able to be formed in an appropriately protruding shape, so a good fit with the dowel holes 25E is able to be obtained. As shown in FIG. 20, a clearance hole 3FSg4 for avoiding interference with the head portion of the second rotating shaft 37A when the base plate 31 of the stopper mechanism 30 is assembled to the side frame 3FS of the seat cushion 3 described above is formed through the side frame 3FS.

[0106] Above, one example embodiment of the invention has been described, but the invention may also be carried out in a variety of modes other than this example embodiment. For example, the two mechanism elements assembled to a seat frame of the invention in a manner sandwiching the seat frame from both sides may be component parts of the operating mechanism 20 or the stopper mechanism 30 assembled to the side frame 3FS of the seat cushion 3 described in the foregoing example embodiment, or any of various mechanism elements assembled to the seat frame. Aside from being a structural frame of a seat cushion, the seat frame of the invention may also be a structural frame of a seatback, or a structural frame of a base that supports a seatback or a seat cushion with respect to a floor.

[0107] Also, in the example embodiment described above, a fitting structure of a protruding portion (i.e., the two dowels 3FSg5) formed on the seat frame (i.e., the side frame 3FS) and a recessed portion (i.e., the two dowel holes 25E) formed on one mechanism element (i.e., the fixing plate 25 of the operating mechanism 20) are given as examples of the fitting portions of the invention, but the structure may also be one in which a recessed portion is formed on the seat frame and a protruding portion is formed on one mechanism element. Also, the fitting portions may be a structure provided in only one location between the seat frame and one mechanism element. In this case, making the shape of the fitting portion a shape other than a circle also enables positioning in the rotational direction to be performed even if fitting is only performed in one location. Further, the bolt shaft (i.e., the bolt shaft 31A1) of the invention may be provided either integrally joined beforehand to one (i.e., the base plate 31) of the two mechanism elements, or assembled inserted through the two mechanism elements.