Vehicle seat

When a tilt-down function is performed, a rotationally-preventing condition of a reclining device connecting a base member and an intermediate member is released, so that a seat back is tiltably rotated forwardly integrally with the intermediate member and a seat cushion is pushed by a boomerang link capable of moving with the intermediate member so as to be sunk downwardly while tiltably rotating a front link. However, when a walk-in function is performed, a rotationally-preventing condition of a memory device connecting the seat back and the intermediate member is released, so that the seat back can be tiltably rotated to a forwardly inclined position independently of the intermediate member that is maintained in a condition in which the intermediate member is integrated with the base member.

TECHNICAL FIELD

The present invention relates to a vehicle seat. More particularly, the present invention relates to a vehicle seat having a tilt-down function to sink down a seat cushion in conjunction with farthest tilting motion in which a seat back is tilted down forwardly and having a walk-in function to make a condition in which a seat body is capable of sliding forwardly relative to a vehicle floor in conjunction with half tilting motion in which the seat back is tilted to a forwardly inclined position.

BACKGROUND ART

Conventionally known is a vehicle seat having a walk-in function that is capable of widening a getting in/out space positioned behind the seat and having a tilt-down function that is capable of compactly folding down the whole seat. Further, U.S. Pat. No. 6,152,533 teaches a vehicle seat having the walk-in function and the tilt-down function described above.

In this disclosure, the vehicle seat is constructed such that when an operation for the walk-in function is performed, a seat back is tilted to a forwardly inclined position, and a slide-lock condition of a seat body relative to a vehicle floor is released, so that a condition in which the whole seat is capable of sliding forwardly can be obtained. Further, the vehicle seat is constructed such that when an operation for the tilt-down function is performed, the seat back is widely tilted forwardly, and a seat cushion is sunk downwardly, so that a tilt-down space of the seat back can be obtained.

In particular, the seat cushion is rotatably connected to the seat back via link members, so as to be sunk forwardly and downwardly due to link motion of the link members that can be operated with the forwardly tiltable rotation of the seat back.

In the conventional art described above, because the seat back and the seat cushion are linked to each other, the seat cushion is moved forwardly even when the walk-in function is performed. Therefore, a retracting space which allows the whole seat to slide forwardly can be narrowed. As a result, a getting in/out space formed behind the seat can be narrowed.

Thus, there is a need in the art to ensure a wide retracting space which allows a seat body of a vehicle seat having a walk-in function and a tilt-down function to move forwardly when the walk-in function is performed.

SUMMARY OF THE INVENTION

A vehicle seat of the present invention has a tilt-down function to sink down a seat cushion in conjunction with farthest tilting motion in which a seat back is tilted down forwardly and has a walk-in function to make a condition in which a seat body is capable of sliding forwardly relative to a vehicle floor in conjunction with half tilting motion in which the seat back is tilted to a forwardly inclined position. The seat back is connected to a base member, that is slidably disposed on a vehicle floor, via first and second rotation preventing devices while an intermediate member is interleaved threrebetween, so as to be capable of rotating relative to both of the intermediate member and the base member about a common axis and to be capable of being prevented from rotating relative thereto. A first link integrally connected to the seat cushion is rotatably connected to the intermediate member via a shaft. A second link is disposed between the seat cushion and the base member in order to rotatably connect the same by link coupling. When the tilt-down function is performed, a rotationally-preventing condition of one rotation preventing device connecting the base member and the intermediate member is released, so that the seat back is rotated and tilted forwardly integrally with the intermediate member and that the seat cushion is pushed by the first link capable of moving with the intermediate member so as to be sunk downwardly while tiltably rotating the second link. However, when the walk-in function is performed, a rotationally-preventing condition of the other rotation preventing device connecting the seat back and the intermediate member is released, so that the seat back can be tiltably rotated to the forwardly inclined position independently of the intermediate member that is maintained in a condition in which the intermediate member is integrated with the base member. The other rotation preventing device, that is capable of being released when the walk-in function is performed, is disposed on an outside position of the intermediate member in a radial direction thereof, so as to prevent the seat back from rotating relative to the intermediate member when an engagement/disengagement member connected to the seat back enters and engage a depressed portion formed in an outer circumferential peripheral portion of the intermediate member from outside in the radial direction.

According to the structure of the present invention, the seat cushion is connected to the intermediate member via the first link, so as to be sunk downwardly in conjunction with the motion in which the intermediate member rotates with the seat back when the tilt-down function is performed. However, when the walk-in function is performed, the seat back is tiltably rotated forwardly independently of the intermediate member while the intermediate member is maintained in a condition in which it is integrated with the base member. Therefore, in this case, because the seat cushion cannot be moved, a retracting space which allows the seat body to slide forwardly can be maintained without being narrowed. Thus, because the seat cushion cannot be moved when the walk-in function is performed, a wider retracting space which allows the seat body to move forwardly can be obtained in comparison with a structure in which the seat cushion can be moved forwardly as when a tilt-down operation is performed. Further, in the other rotation preventing device that connects the seat back to the intermediate member while the seat back can be maintained in the condition in which it is prevented from rotating relative to the intermediate member, the engagement/disengagement member connected to the seat back is radially aligned with the depressed portion formed in an outer circumferential peripheral portion of the intermediate member, so as to enter the depressed portion from outside in the radial direction or to be disengaged therefrom. Therefore, the other rotation preventing device can be compactly disposed in a direction of a rotational axis thereof

Further, the present invention can be constructed as follows. That is, the engagement/disengagement member constituting the other rotation preventing device is arranged to be capable of moving toward and away from the seat back so as to be capable of being engaged with and disengaged from the depressed portion of the intermediate member. When the engagement/disengagement member is positioned in an engagement condition in which the engagement/disengagement member enters the depressed portion of the inner intermediate member, a pusher member rotatably connected to the seat back is pressed onto a rear surface of the engagement/disengagement member by biasing, so that the engagement/disengagement member can be pressed into the depressed portion of the inner intermediate member and can be prevented from being disengaged therefrom.

According to the structure of the present invention, when the engagement/disengagement member is in the engagement condition in which it enters and engages the depressed portion of the intermediate member, the pusher member that is rotatably attached to the seat back presses the engagement/disengagement member from a rear surface side thereof by rotational biasing. As a result, the engagement/disengagement member is positioned in a condition in which it is pressed into the depressed portion of the intermediate member, so as to be prevented from being disengaged therefrom. Thus, an engagement strength between the engagement/disengagement member and the intermediate member can be increased, so that a rotation preventing strength of the other rotation preventing device can be increased.

Further, the present invention can be constructed as follows. That is, when the walk-in function is performed, the engagement condition of the engagement/disengagement member with the depressed portion of the inner intermediate member can be released, so that the disengaged engagement/disengagement member can slide along a curved outer circumferential surface portion of the intermediate member as the seat back is tiltably rotated. Further, as the seat back is raised from the forwardly inclined position, the engagement/disengagement member can be returned to a position in which the engagement/disengagement member is capable of entering the depressed portion of the inner intermediate member, so as to enter the depressed portion of the intermediate member while being pressed from a rear surface side thereof by the pusher member, thereby being shifted to the engagement condition.

According to the structure of the present invention, the engagement/disengagement member, that is disengaged from the depressed portion of the intermediate member as a result of performance of the walk-in function, can slide along a curved outer circumferential surface portion of the intermediate member as the seat back is tiltably rotated. Therefore, even if the engagement/disengagement member is not maintained in a condition in which it is spaced from the outer circumferential surface portion of the intermediate member, the engagement/disengagement member can smoothly move as the seat back is tiltably rotated.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following, the best mode for carrying out the invention will be described with reference to the drawings.

First, a structure of a vehicle seat of Embodiment 1 will be described with reference toFIGS. 1 to 15.FIG. 1shows a schematic structure of the vehicle seat of the present embodiment. The vehicle seat includes a seat body1as a sitting portion. The seat body1is composed of a seat back2as a backrest and a seat cushion3as a sitting portion. The seat back2and the seat cushion3are respectively connected to and supported on a base member4that is slidably disposed on a vehicle floor F.

In particular, as shown inFIG. 2, the base member4is connected to the floor F via a slider device30, so as to be slidable relative to the floor F in a vehicle longitudinal direction. The slider device30is normally maintained in a condition in which sliding motion thereof is locked, so that a slide position of the base member4(the seat body1) relative to the floor F is can fixed.

Further, the slider device30includes a pair of right and left lower rails31and31that are integrally connected to the floor F, and a pair of right and left upper rails32and32that are respectively longitudinally slidably coupled to the lower rails31and31. The upper rails32and32are respectively integrally affixed to lower surface portions of right and left sides of the base member4, so as to slide the base member4(the seat body1) relative to the floor F due to cooperative sliding motion thereof relative to the lower rails31and31.

The upper rails32and32respectively have slide lock mechanisms37and37that are capable of locking the sliding motion of the upper rails32and32by engaging the lower rails31and31. The slide lock mechanisms37and37are respectively normally biased and maintained in locked conditions in which they engage the lower rails31and31, thereby locking the sliding motion of the upper rails32and32. Further, each of the slide lock mechanisms37and37is connected to an operation lever33that is extended forwardly therefrom, so that the slide lock condition described above can be released when the operation lever33is lifted up.

Now, with reference toFIG. 1again, the vehicle seat of the present embodiment has a tilt-down function that is capable of compactly folding down the seat body1onto the floor F, and a walk-in function that is capable of making the seat body1to a posture in which the seat back2is inclined forwardly and is capable of sliding the seat body1forwardly so as to widen a getting in/out space formed therebehind. As shown inFIG. 6, the former tilt-down function can be performed by lifting up a tilt-down operation lever9that is disposed on a side of a shoulder portion of the seat back2. Upon lifting up of the tilt-down operation lever9, the seat cushion3is sunk downwardly in conjunction with farthest tilting motion in which the seat back2is tilted down forwardly, so that the seat body1can be compactly folded down onto the floor F.

Conversely, as shown inFIG. 9, the latter walk-in function can be performed by forwardly rotating a walk-in operation lever8that is disposed on a top of the shoulder portion of the seat back2. Upon rotation of the walk-in operation lever8, the slide lock condition of the slider device30described above can be released in conjunction with half tilting motion in which the seat back2is tilted to a forwardly inclined position, so that the seat body1can be slid and retracted forwardly while the seat body1is made to the posture in which the seat back2is inclined forwardly.

Operative mechanisms of the tilt-down function and the walk-in function described above will be hereinafter described in detail. First, a basic structure of the seat body1is described. As shown inFIG. 2, the seat back2constituting the backrest of the seat body1includes an inner framework that is constructed of plate-shaped side frames2A and2A extending along right and left side peripheries thereof, and an inverted U-shaped tubular curved upper frame2B that connects upper end portions of the side frames2A and2A. Further, in the seat back2, lower portions of the right and left side frames2A and2A are respectively rotatably hinge-connected to upper portions of right and left sides of the base member4via reclining devices20and20and are supported thereon.

Each of the reclining devices20and20corresponds to one rotation preventing device of the present invention. Further, in the vehicle seat of the present embodiment, a right half of the seat body1has the substantially same frame shapes and various additional structures as the left half thereof unless otherwise described. Therefore, in the following description, the structure of either one of the right and left halves of the seat body1may be representatively described with identified by reference numerals.

FIG. 3shows an exploded perspective view, which illustrates a connecting structure of one side frame2A (one positioned at the right side inFIG. 2) of the seat back2and the base member4. As shown in the drawing, the side frame2A of the seat back2has a double layer structure in which a plate-shaped inner side frame2Aa and a plate-shaped outer side frame2Ab are integrally coupled to each other in a thickness direction. The side frame2A is rotatably connected to the base member4via the reclining device20while an intermediate member6(an outer intermediate member6Q) is interleaved therebetween.

The intermediate member6is constructed of a ring-shaped inner intermediate member6P and an elongated plate-shaped outer intermediate member6Q that are coupled to each other in a thickness direction and are connected to each other by welding. In particular, the inner intermediate member6P is formed by die-cutting a steel sheet into a ring shape. Further, a cylindrically projected cylindrical portion Pa is formed between an outer circumferential peripheral portion and a central portion of the inner intermediate member6P by half die-cutting the outer circumferential peripheral portion in a thickness direction relative to the central portion.

As shown inFIG. 10, the inner intermediate member6P is disposed between the inner side frame2Aa and the outer side frame2Ab and is coupled thereto while the projected cylindrical portion Pa is fitted into a through hole bh formed in the outer side frame2Ab. Thus, the cylindrical portion Pa is held against an inner circumferential surface of the through hole bh, so that the side frame2A can be rotatably supported by the inner intermediate member6P.

Now, with reference toFIG. 3again, the inner intermediate member6P has a substantially precise circular large through hole Pb that is formed in a central portion thereof so as to penetrate the same in a thickness direction. The through hole Pb has diametrically enlarged portions that are partially formed in circumferentially four portions thereon. Therefore, when a guide22of the reclining device20, which will be hereinafter described, is welded to the outer side frame2Ab, the through hole Pb can be avoided from interfering with dowels22aof the guide22that are projected beyond the through hole bh of the outer side frame2Ab.

Formed in an outer circumferential portion of the inner intermediate member6P are depressed portions Pc that are partially depressed radially inwardly, and a slide ledge Pd that has a circular arc shaped curved outer circumferential surface. The slide ledge Pd defines an outer circumferential surface that gently extends circumferentially from a circumferential end surface of one of the depressed portions Pc. Further, formed in the outer circumferential portion of the inner intermediate member6P is a stopper Pe that is partially projected radially outwardly. The stopper Pe is formed in a position that is circumferentially spaced from the depressed portions Pc and the slide ledge Pd.

Further, the depressed portions Pc of the inner intermediate member6P are respectively shaped to be engageable with an engagement/disengagement member11of a memory device10that is disposed on an outside position in a radial direction thereof and is connected to the side frame2A. Conversely, as shown inFIG. 10, the outer intermediate member6Q is held against the cylindrical portion Pa of the inner intermediate member6P fitted into the through hole bh of the outer side frame2Ab and is welded thereto. Thus, the outer intermediate member6Q is integrally connected to the inner intermediate member6P.

Now, with reference toFIG. 3again, the outer intermediate member6Q has a cam hole-shaped large through hole Qa that is formed in a lower portion thereof so as to penetrate the same in a thickness direction. Further, the outer intermediate member6Q has four precise circular small dowel insertion holes Qb that are positioned around the through hole Qa. Further, formed in an outer circumferential portion of the outer intermediate member6Q is a stopper Qc that is partially projected radially outwardly and is bent in the thickness direction. Further, the disk-shaped guide22, a construction element of the reclining device20, which will be hereinafter described, is integrally fixedly connected to the outer intermediate member6Q.

In particular, the guide22has the four dowels22athat cylindrically projected from an outer disk surface thereof. The dowels22aare positioned so as to be fitted into the four dowel insertion holes Qb that are formed in the outer intermediate member6Q and penetrating therethrough. The dowels22aare respectively fitted into the dowel insertion holes Qb and fitted portions thereof are bonded by welding. Thus, the guide22is securely integrally connected to the outer intermediate member6Q while it is closely faced thereto (FIG. 10).

In the reclining device20, a disk-shaped ratchet21is positioned opposite to the guide22and is relatively rotatably connected thereto. The ratchet21is integrally secured to the base member4. In particular, the ratchet21has five dowels21athat substantially cylindrically projected from an outer disk surface thereof. The dowels21aare positioned so as to be fitted into five dowel insertion holes4B that are formed in the base member4and penetrating therethrough in a thickness direction. The dowels21aare respectively fitted into the dowel insertion holes4B and fitted portions thereof are bonded by welding. Thus, the ratchet21is securely integrally connected to the base member4while it is closely faced thereto (FIG. 10).

Thus, the reclining device20is integrally connected to the outer intermediate member6Q and the base member4. As a result, the seat back2is connected to the base member4via a locking/unlocking operation mechanism of the reclining device20, so as to be capable of rotating relative thereto and to be capable of being prevented from rotating relative thereto. Further, in the reclining device20, the ratchet21is coupled to the guide22while a projected cylindrical portion formed in an outer circumferentially peripheral portion of the ratchet21is fitted into a projected cylindrical portion formed in an outer circumferentially peripheral portion of the guide22. Thus, the ratchet21and the guide22are connected to each other while they are mutually supported, so as to be relatively rotatable about a center of these cylindrical portions.

The ratchet21and the guide22are secured to each other by an outer circumferential ring23that is attached to outer circumferential portions thereof while straddling the same, so as to be prevented from being axially separated from each other. Further, disposed between the ratchet21and the guide22is locking components24that are capable of locking relative rotation of thereof by meshing therewith. The locking components24are normally guided by a guide22so as to be capable of moving radially outwardly and inwardly.

Further, the locking components24are normally pushed out radially outwardly by a biasing force of a spring member26that is disposed between the locking components24and the guide22, thereby meshing outwardly-faced teeth formed in an outer circumferential surface thereof with inwardly-faced teeth formed in an inner circumferential surface of the cylindrical portion of the ratchet21. As a result, the relative rotation of the ratchet21and the guide22is locked. Further, upon rotation of an operation shaft25that is passed through the ratchet21and the guide22, the locking components24are drawn back radially inwardly against the biasing force of the spring member26, so as to be released from a locked condition in which the locking components24engage the inwardly-faced teeth formed of the ratchet21.

Further, as shown inFIG. 10, the operation shaft25that is capable of performing an unlocking operation of the locking components24are integrally connected to an operation arm27that is connected to the tilt-down operation lever9described above via an operation cable9A. As shown inFIG. 4, the operation cable9A has a double layer structure in which a line-shaped inner cable is inserted into a tubular outer cable. A lower end portion of the outer cable is engaged with and secured to an engagement portion ac that is formed in the inner side frame2Aa, and a lower end portion of the inner cable is engaged with and secured to the operation arm27.

Upon operation of the tilt-down operation lever9that is linked to an upper end side of the operation cable9A, the inner cable of the operation cable9A is pulled and drawn into the outer cable upwardly, so that the operation arm27can be rotated by the inner cable. As a result, the operation shaft25is rotated in such a direction in which the engaged and locked condition of the locking components24(FIG. 10) can be released. Thus, upon operation of the tilt-down operation lever9, a locked condition of the reclining device20in which it is prevented from rotating can be released.

Therefore, when the reclining device20is in the rotationally-locked condition, each of the outer intermediate member6Q and the inner intermediate member6P that are previously described with reference toFIG. 3can be maintained in a condition in which it is prevented from rotating relative to the base member4. Further, the side frame2A of the seat back2that is rotatably coupled to the inner intermediate member6P is normally maintained in a condition in which it is prevented from rotating relative to the inner intermediate member6P because the engagement/disengagement member11of the memory device10that is connected to the side frame2A is maintained in a condition in which it enters and engages the depressed portions Pc of the inner intermediate member6P.

Therefore, when both of the reclining device20and the memory device10are in the rotationally-locked conditions, the side frame2A (the seat back2) is maintained in a condition in which it is prevented from rotating relative to the base member4via the intermediate member6. Further, as shown inFIG. 4, the engagement/disengagement member11of the memory device10is constructed to be operated by a pusher member12that is rotatably connected to the side frame2A via a shaft, so as to be pushed into and engage the depressed portions Pc of the inner intermediate member6P or disengaged therefrom.

The pusher member12is connected to the walk-in operation lever8described above via an operation cable8A. In a normal condition before the walk-in operation lever8is operated, the pusher member12is maintained in a condition in which it presses the engagement/disengagement member11into the depressed portions Pc of the inner intermediate member6P by biasing and engages the same therewith. Further, as shown inFIG. 7, when the walk-in operation lever8is operated such that the operation cable8A is pulled, the pusher member12is rotated so as to disengage the engagement/disengagement member11from the depressed portions Pc of the inner intermediate member6P.

When the engagement/disengagement member11is disengaged from the depressed portions Pc of the inner intermediate member6P, the rotationally-prevented condition of the side frame2A relative to the inner intermediate member6P can be released. As a result, the side frame2A is changed to a condition in which it is capable of rotating relative to the intermediate member6that is integrated with the base member4via the locked reclining device20. Further, a center axis line on which the side frame2A rotates relative to the inner intermediate member6P is set to be aligned with a rotation center axis line on which the ratchet21and the guide22of the reclining device20rotate relative to each other.

Thus, a rotation center about which the side frame2A rotates relative to the inner intermediate member6P corresponds to a rotation center about which the side frame2A rotates relative to the base member4while it is integrated with the intermediate member6. Further, because a basic structure of the reclining device20is known as described in, for example, JP 2002-360368A and JP 2005-312891A, detailed description with regard to the reclining device20will be omitted.

With reference toFIG. 3again, the inner side frame2Aa has a precise circular large through hole ah that is formed in a central portion thereof so as to penetrate the same. Further, formed in an outer circumferential peripheral portion of the inner side frame2Aa is a stopper as that is partially bent in a thickness direction. As shown inFIG. 8, when the walk-in operation lever8is operated such that the side frame2A (the seat back2) is tiltably rotated forwardly relative to the intermediate member6, the stopper as interferes with the stopper Pe that is formed in the inner intermediate member6P, thereby stopping forwardly tiltable rotation of the side frame2A at a forwardly inclined position shown in the drawing.

Further, conditions of the components shown inFIG. 8are shown inFIG. 13in detail. Further,FIG. 13is shown as a sectional view taken along line XIII-XIII ofFIG. 8. Further, inFIG. 14, some of the components shown inFIG. 13are highlighted by cross-hatching. The highlighted components correspond to the components that are capable of moving integrally with the seat back2when the seat back2is tiltably rotated forwardly to the forwardly inclined position by operation of the walk-in operation lever8.

Conversely, as shown inFIG. 5, when the tilt-down operation lever9is operated, the stopper Qc that is formed in and projected from the outer circumferential portion of the outer intermediate member6Q interferes with a stopper4A that is fixedly attached to the base member4, thereby stopping the forwardly tiltable rotation of the side frame2A at a farthest tilted position shown in the drawing. Further, conditions of the components shown inFIG. 5are shown inFIG. 11in detail. Further,FIG. 11is shown as a sectional view taken along line XI-XI ofFIG. 5. Further, inFIG. 12, some of the components shown inFIG. 11are highlighted by cross-hatching. The highlighted components correspond to the components that are capable of moving integrally with the seat back2when the seat back2is tiltably rotated forwardly to the farthest tilted position by operation of the tilt-down operation lever9.

Now, with reference toFIG. 2again, rear upper end portions of L-shaped boomerang links5and5are rotatably connected to upper end portions of the outer intermediate members6Q and6Q via connector pins5A and5A. Further, each of the boomerang links5and5corresponds to a first link. The boomerang links5and5include forwardly extended arms. End portions of the arms are respectively applied to and integrally rigidly connected to side portions of a frame3F that constitutes a framework of the seat cushion3. Thus, the seat cushion3is supported on the outer intermediate members6Q and6Q from a rear side thereof via the boomerang links5and5.

Further, front side portions of the frame3F of the seat cushion3are respectively rotatably connected to front end portions of the base member4via front links7and7by link coupling. Each of the front links7and7corresponds to a second link. Upper end portions of the front links7and7are respectively rotatably connected to the side portions of the frame3F via shafts. Conversely, lower end portions of the front links7and7are respectively rotatably connected to side portions of the base member4via shafts. Thus, front end portions of the seat cushion3are supported on the base member4from lower side thereof via the front links7and7.

Therefore, in a normal condition or a condition in which the reclining device20and20are locked so that the seat back2is fixed to a normal angular position for sitting purposes, the seat cushion3thus constructed can be maintained in a condition in which each of the front links7and7is raised, because the outer intermediate members6Q and6Q are positionally fixed to the base member4. Further, as previously described with reference toFIGS. 8 and 9, when the seat back2is tilted to the forwardly inclined position by the operation of the walk-in operation lever8, the seat cushion3can be maintained in an initial condition without being substantially moved, because a condition in which the outer intermediate members6Q and6Q are positionally fixed to the base member4can be maintained.

However, as previously described with reference to FIGS.5and6,when the seat back2is tilted forwardly to the farthest tilted position by the operation of the tilt-down operation lever9, the outer intermediate members6Q and6Q are rotated relative to the base member4, so that the connector pins5A and5A supporting the rear upper end portions of the boomerang links5and5are transferred in the same rotational direction. As a result, the seat cushion3can be transferred forwardly and downwardly. Thus, as shown inFIG. 6, the seat cushion3can be sunk forwardly and downwardly toward the floor F while rotating the front links7and7forwardly.

Further, disposed on connecting portions of the front links7and7and the base member4are spring members (not shown) that are capable of biasing the front links7and7in a rotational direction in which they are raised. Therefore, when the seat cushion3is sunk down onto the floor F, downward motion thereof can be dampened by biasing forces of the spring members. Conversely, when the seat cushion3is raised up from the floor F, upward motion thereof can be assisted by the biasing forces of the spring members.

Now, with reference toFIG. 2again, the memory devices10and10that are capable of preventing the side frames2A and2A of the seat back2from rotating relative to the inner intermediate members6P and6P are respectively disposed on positions between the inner side frames2Aa and2Aa and the outer side frames2Ab and2Ab. Further, each of the memory devices10and10corresponds to the other rotation preventing device of the present invention. Further,FIG. 3shows a structure of the engagement/disengagement member11of the memory device10positioned at the right side inFIG. 2as an exploded perspective view. Also,FIG. 4shows a structure of the pusher member12of the memory device10, which member functions to engage the engagement/disengagement member11with the inner intermediate member6P or disengage the same therefrom.

As shown in these drawings, the engagement/disengagement member11is formed to have a link-arm shape and is rotatably connected to the side frame2A via connector shafts11A. The engagement/disengagement member11has projected portions11B that are formed in a side surface of a rotational distal end thereof. The projected portions11B are capable of being fitted into the depressed portions Pc that are formed in the outer circumferential portion of the inner intermediate member6P. As shown inFIG. 7, when the engagement/disengagement member11is rotated about the connector shafts11A, the projected portions11B are introduced into and engaged with the depressed portions Pc or disengaged therefrom.

As shown inFIG. 3, the engagement/disengagement member11has an engagement pin11C that is projected in a thickness direction thereof to have a pin shape. The engagement pin11C is fitted into an elongated through hole ab that is formed in the inner side frame2Aa to penetrate therethrough. Thus, the engagement/disengagement member11is capable of rotating about the connector shafts11A within a range that the engagement pin11C is capable of moving in the elongated through hole ab. Further, as shown inFIG. 4, the link-arm shaped pusher member12is disposed between the engagement/disengagement member11and the inner side frame2Aa.

The pusher member12is rotatably connected to the side frame2A via a connector shaft12A. Further, a pressure cam12B is integrally connected to the pusher member12. The pressure cam12B is capable pushing an upper surface portion (a head surface portion11D) of the engagement/disengagement member11downwardly when the pusher member12is rotated counterclockwise. Also, disposed between the pusher member12and the outer side frame2Ab is a tension spring12S that rotationally biases the pusher member12counterclockwise relative to the outer side frame2Ab.

Therefore, in a normal condition, the pusher member12is applied with a rotational force due to a biasing force of the tension spring12S, so as to push the engagement/disengagement member11downwardly via the pressure cam12B, thereby pressing the engagement/disengagement member11onto an outer circumferential surface of the inner intermediate member6P. Thus, the engagement/disengagement member11can be positioned in a condition in which the projected portions11B formed therein can enter the depressed portions Pc of the inner intermediate member6P. Consequently, the engagement/disengagement member11is positioned in a condition in which it is pressed into the depressed portions Pc due to the pushing force described above while a rear surface portion (the head surface portion11D) thereof is pushed by the pressure cam12B, so as to be prevented from being disengaged therefrom.

Thus, the side frame2A of the seat back2can be maintained in a condition in which it is prevented from rotating relative to the intermediate member6. Further, as shown inFIG. 7, an engagement condition of the engagement/disengagement member11with the inner intermediate member6P can be released when the pusher member12is rotated clockwise via the operation cable8A by the operation of the walk-in operation lever8.

Further, the operation cable8A has a double layer structure in which a line-shaped inner cable is inserted into a tubular outer cable. A lower end portion of the outer cable is engaged with and secured to an engagement portion be that is formed in the outer side frame2Ab, and a lower end portion of the inner cable is engaged with and secured to the pusher member12. Upon operation of the walk-in operation lever8that is linked to an upper end portion of the operation cable8A, the inner cable is pulled upwardly relative to the outer cable, so as to rotate the pusher member12clockwise against the biasing force of the tension spring12S.

Upon operation thereof, the engagement/disengagement member11is rotated counterclockwise about the connector shafts11A while it is pulled upwardly by the pusher member12, so that the engagement condition of the engagement/disengagement member11with the depressed portions Pc of the inner intermediate member6P can be released. Further, the pusher member12has a curved elongated through hole12H that1212Hthat is formed therein so as to penetrate the same in a thickness direction. The engagement pin11C projected from the engagement/disengagement member11in the thickness direction thereof is inserted into the elongated through hole1211while penetrating therethrough.

Thus, the pusher member12, when rotated clockwise by the motion of the operation cable8A, acts on the engagement pin11C so as to pull the same upwardly along the curved shape of the elongated through hole12H. As a result, the engagement condition of the engagement/disengagement member11with the inner intermediate member6P can be released, so that the rotationally-prevented condition of the seat back2relative to the intermediate member6can be released.

Therefore, when the seat back2is tiltably rotated forwardly relative to the intermediate member6from this condition, the seat back2is shifted to a condition in which it is tilted to the forwardly inclined position shown inFIG. 8, and is maintained in the condition. At this time, when the operation of the walk-in operation lever8is discontinued during the forwardly tiltable rotation of the seat back2, due to the biasing force of the tension spring12S applied to the pusher member12, the engagement/disengagement member11can be shifted to a condition in which the projected portions11B thereof is pressed onto the slide ledge Pd that is formed in the outer circumferential portion of the inner intermediate member6P.

The outer circumferential surface of the slide ledge Pd has a curved circular arc shape that is centered on a tiltable rotation center of the seat back2. Therefore, even when the engagement/disengagement member11is shifted to a condition in which it is pressed onto the outer circumferential surface of the slide ledge Pd, the engagement/disengagement member11can smoothly slide along the curved outer circumferential shape of the slide ledge Pd with the tiltable rotation of the seat back2. Thus, once the seat back2is tilted forwardly even a little by the operation of the walk-in operation lever8until the projected portions11B is positionally displaced relative to the depressed portions Pc, even if the operation of the walk-in operation lever8is discontinued in the middle thereof, the seat back2can be smoothly tiltably rotated forwardly to the forwardly inclined position shown inFIG. 8.

Further, the engagement/disengagement member11described above can be maintained in a condition in which it is disposed on the slide ledge Pd even when the seat back2is shifted to the condition in which it is tilted to the forwardly inclined position. Therefore, the seat back2can be returned to the normal angular position before it is tilted forwardly by simply raising the seat back2to a position in which the projected portions11B can fit into the depressed portions Pc without operating the walk-in operation lever8again.

That is, the memory device10is constructed to function as a normal angle memory device that is capable of memorizing a normal angle before the seat back2is tilted forwardly by the operation of the walk-in operation lever8, and returning the seat back2to the normal angular position before the seat back2is tilted forwardly by simply raising the seat back2toward the normal angular position after a walk-in operation is performed.

Further, with reference toFIG. 2, the operation cable9A connected to the tilt-down operation lever9has a cable structure that is intermediately-branched to two portions. The branched portions are respectively connected to the operation arms27and27that are connected to the reclining devices20and20. Conversely, the operation cable8A connected to the walk-in operation lever8has a cable structure that is intermediately-branched to two portions. Each of the branched portions is connected to the pusher member12of each of the memory devices10and10that are respectively disposed in the side frames2A.

Further, with reference toFIG. 2, projecting surfaces aa and projecting surfaces ba are respectively formed in the inner side frame2Aa and the outer side frame2Ab, so as to project from plate surfaces thereof in a line shape. The projecting surfaces aa and the projecting surfaces ba are respectively formed in portions that face the inner intermediate member6P and the engagement/disengagement member11in a thickness direction thereof. Thus, the inner intermediate member6P and the engagement/disengagement member11can contact the inner side frame2Aa and the outer side frame2Ab with reduced areas, so that frictional resistance produced therebetween caused by sliding motion thereof can be reduced. As a result, the inner intermediate member6P and the engagement/disengagement member11can rotate smoothly.

Now, as shown inFIG. 15, when the seat back2is tilted forwardly by the operation of the walk-in operation lever8, the locking condition of the slide lock mechanism37that locks the seat body1so as to not slide relative to the floor F can be released. In particular, connected to the slide lock mechanism37is an operation cable36that is capable of performing an unlocking operation of the slide lock mechanism37.

The operation cable36has a double layer structure in which a line-shaped inner cable is inserted into a tubular outer cable. An upper end portion of the outer cable shown in the drawing is engaged with and secured to an engagement portion Qd that is formed in the outer intermediate member6Q, and an upper end portion of the inner cable is engaged with and secured to the outer side frame2Ab. Further, when the seat back2is tiltably rotated forwardly relative to the intermediate member6by the operation of the walk-in operation lever8, the inner cable of the operation cable36is pulled upwardly relative to the outer cable, so that the slide-locking condition of the slide lock mechanism37can be released.

As shown inFIGS. 1 to 2, disposed between one lower rail31of the slider device30and the base member4is a tension spring34that biases the base member4to move the same forwardly in the vehicle longitudinal direction. Front end portion of the tension spring34is connected to a spring engagement portion35that is fixed to a front portion of the lower rail31. Conversely, rear end portion of the tension spring34is connected to a spring engagement portion4S that is formed in both side portions of the base member4. Therefore, the seat body1can be moved forwardly in the vehicle longitudinal direction by a biasing force of the tension spring34in conjunction with the motion in which the seat back2is tilted to the forwardly inclined position by the operation of the walk-in operation lever8.

Thus, according to the vehicle seat of the present embodiment, the seat cushion3is connected to the intermediate member6via the boomerang link5, so as to be sunk downwardly in conjunction with the motion in which the intermediate member6rotates with the seat back2when the tilt-down function is performed. However, when the walk-in function is performed, the seat back2is tiltably rotated forwardly independently of the intermediate member6while the intermediate member6is maintained in a condition in which it is integrated with the base member4.

Therefore, in this case, because the seat cushion3cannot be moved, a retracting space which allows the seat body1to slide forwardly can be maintained without being narrowed. Thus, because the seat cushion3cannot be moved when the walk-in function is performed, a wider retracting space which allows the seat body1to move forwardly can be obtained in comparison with a structure in which the seat cushion3can be moved forwardly as when a tilt-down operation is performed.

Further, in the memory device10that connects the seat back2to the intermediate member6while the seat back2can be maintained in the condition in which it is prevented from rotating relative to the intermediate member6, the engagement/disengagement member11connected to the seat back2is radially aligned with the depressed portions Pc formed in an outer circumferential peripheral portion of the intermediate member6, so as to enter the depressed portions Pc from outside in the radial direction or to be disengaged therefrom. Therefore, the memory device10can be compactly disposed in a direction of a rotational axis thereof.

When the engagement/disengagement member11is in the engagement condition in which it enters the depressed portions Pc of the intermediate member6, the pusher member12of the memory device10that is rotatably attached to the seat back2pushes the engagement/disengagement member11from a rear surface side thereof by rotational biasing. As a result, the engagement/disengagement member11is positioned in a condition in which it is pressed into the depressed portions Pc of the intermediate member6, so as to be prevented from being disengaged therefrom. Thus, an engagement strength between the engagement/disengagement member11and the intermediate member6can be increased, so that a rotation preventing strength of the memory device10can be increased.

The engagement/disengagement member11, that is disengaged from the depressed portions Pc of the intermediate member6as a result of performance of the walk-in function, can slide along a curved outer circumferential surface portion (the slide ledge Pd) of the intermediate member6as the seat back2is tiltably rotated. Therefore, even if the engagement/disengagement member11is not maintained in a condition in which it is spaced from the outer circumferential surface portion of the intermediate member6, i.e., even if the operation of the walk-in operation lever8is discontinued in the middle thereof, the engagement/disengagement member11can smoothly move as the seat back2is tiltably rotated.

The present invention has been described using one embodiment. However, various changes and modifications may be made to the present invention. For example, in the embodiment, the engagement/disengagement member11of the memory device10constituting the other rotation preventing device is capable of being engaged with or disengaged from the depressed portions Pc of the intermediate member6by rotational motion. However, the engagement/disengagement member11can be modified so as to be capable of being engaged with or disengaged from the depressed portions Pc by linear motion or other such motion. Further, the engagement structure between the engagement/disengagement member11and the intermediate member6can be formed by a tooth-meshing engagement or a frictional engagement.

Further, in the embodiment, when the seat back2is tiltably rotated forwardly by the operation of the walk-in operation lever8, the slide locking condition of the slider device30can be released, so that the seat body1can be automatically moved forwardly in the vehicle longitudinal direction by the biasing force of the tension spring34. However, the walk-in function of the present invention may include a type in which the slide locking condition can be released by manual operation after the seat back2is tilted to the forwardly inclined position and a type in which the seat body1can be manually moved forwardly after the seat back2is tilted to the forwardly inclined position.