Patent Publication Number: US-2022219575-A1

Title: Seat state switching mechanism and seat provided with said seat state switching mechanism

Description:
TECHNICAL FIELD 
     The present invention relates to a seat state switching mechanism and a seat including the seat state switching mechanism. 
     BACKGROUND ART 
     Various seat state switching mechanisms have been conventionally proposed for seats for vehicles to be adaptable to each switch a seathack tiltable in a front-rear direction of the seat between a walk-in state of locking the seatback at a walk-in position at a predetermined tilt angle and a reclining state of allowing the seatback to lean to a frontmost position. 
     A seat state switching mechanism described in Patent Literature 1 includes: as shown in  FIGS. 14 to 15 , a cushion frame  51  fixedly attached to a flame of a seat cushion of a seat; a seatback frame  52  fixedly attached to a frame of a seathack so as to be tiltably rotatable about a tilt shaft  52   a;  a lever  53 ; a link  54 ; a stopper  55 ; and a rotational member  61 . The rotational member  61  is fixedly attached to the seatback frame  52 . 
     The lever  53  is swingably supported by a pin  56  fastened to the cushion frame  51 . The lever  53  has a lower end connected to a strap  59 . The strap  59  is pulled in a left direction in  FIGS. 14 to 15  in a reclining operation to thereby allow the lever  53  to swing in a clockwise direction. 
     The stopper  55  is supported on a pin  58  fastened to the cushion frame  51  swingably thereabout in an up-down direction. The stopper  55  is biased upward by an unillustrated spring to fit in a recess  61   a  of the rotational member  61  at an upper position. The stopper  55  is provided with a pin  57  inserted in a slit  51   a  of the cushion frame  51  and guided in the tip-down direction. Besides, the pin  57  is inserted in a slit  53   a  of the lever  53  having a bent shape, and the movement thereof in the up-down direction is restricted depending on a tilt position of the lever  53 . The link  54  is supported on the pin  58  swingably thereabout in the up-down direction, The link  54  has one end (a left end in  FIGS. 14 to 15 ) connected to a slide cable  60  operable to release a slide locking mechanism of the seat. The link  54  has another end (a right end in  FIGS. 14 to 15 ) formed with a protrusion  54   a  protruding to reach and come into contact with a pin  62  provided in the rotational member  61  when the rotational member  61  rotates. 
     The seat ate switching mechanism configured in the above-described manner releases the tilt restriction of the seatback by manipulating a lever for a walk-in operation provided at a shoulder of the seat and operating an unillustrated reclining device in shifting from a normal sittable state to a walk-in state. Then, tilting of the seatback frame  52  as shown in  FIG. 15  makes the stopper  55  fit in the recess  61   a  of the rotational member  61 . Consequently, each of the seathack frame  52  and the seatback are locked at the walk-in position at a predetermined angle. At this time, the protrusion  54   a  of the link  54  is pushed by the pin  62  of the rotational member  61 , and the link  54  rotates in the clockwise direction to thereby pull the slide cable  60 , which results in releasing the slide locking mechanism. 
     in the shifting from the walk-in state to the reclining state, pulling the strap  59  to swing the lever  53  in the clockwise direction disengages the stopper  55  and the rotational member  61  from each other. This achieves the reclining state. In this manner, the seatback frame  52  and the seathack can further tilt from the walk-in position. When the pin  62  of the rotational member  61  having passed through the protrusion  54   a  of the link  54  stops pushing the protrusion  54   a,  the link  54  and the slide cable  60  return to their respective initial positions and the slide locking mechanism is restored to the locking state. 
     However, the seat state switching mechanism disclosed in Patent Literature 1 needs a member (e.g., a manipulation lever, an operation force transmission member, and a mechanism for releasing the tilt restriction of the reclining device) for the shifting to the walk-in state, and another member (e.g., the stopper  55 , the rotational member  61 , and the lever  53 ) for the shifting from the walk-in state to the reclining state. Therefore, the seat state switching mechanism has a problem that it is difficult to reduce the number of components of the seat state switching mechanism, and accordingly the switching mechanism has a complicated structure. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese patent No. 6318611 
     SUMMARY OF INVENTION 
     An object of the present invention is to provide a seat state switching mechanism which is capable of switching between a walk-in state and a reclining state with a smaller number of components, and a seat including the seat state switching mechanism. 
     To achieve the object, a seat state switching mechanism, according to the present invention is a seat state switching mechanism for switching a state of a seatback tiltable in a front-rear direction of a seat between a walk-in state of locking the seatback at a walk-in position at a predetermined tilt angle and a reclining state of releasing the locking and allowing the seatback to lean to a frontmost position. The seat state switching mechanism includes: a movable bracket fixedly attached to the seatback and being tiltable together with the seatback; a locking member for locking the movable bracket at a predetermined walk-in locking position so that the seatback reaches the walk-in position when the movable bracket tilts through a walk-in operation; and a releaser thr releasing the locking of the locking member in receipt of a reclining operation force through a reclining operation and switching the state of the seatback to the reclining state. 
     A seat according to the present invention having the seat state switching mechanism includes: the seatback; a seat state switching mechanism provided on one side of the seatback in a width direction thereof and serving as the seat state switching mechanism, and an existing scat state switching mechanism provided on the other side of the seatback in the width direction thereof, and having a reclining locking operability for locking the seatback at an initial tilt angle and placing the seatback in a reclining locking state, a reclining, operability for placing the seatback in the reclining state in receipt of the reclining operation force, and a walk-in operability for placing the seatback in the walk-in state in receipt of a walk-in operation force; a reclining operation force transmission part for transmitting the reclining operation force to the seat state switching mechanism and the existing seat state switching mechanism; and a walk-in operation force transmission part for transmitting the walk-in operation force to the existing seat state switching mechanism. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view schematically showing an overall structure of a seat including a seat state switching mechanism according to an embodiment of a seat state switching mechanism of the present invention as provided on one side of a seat, and an existing seat state switching mechanism serving as another seat state switching mechanism as provided on the other side of the seat; 
         FIG. 2  is a front view showing a main configuration of the seat state switching mechanism in  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of the seat state switching mechanism in  FIG. 2 ; 
         FIG. 4  is a perspective view of a movable bracket in  FIG. 3 ; 
         FIG. 5  is a perspective view of a locking member in  FIG. 3 ; 
         FIG. 6  is a perspective view of an input member in  FIG. 3 ; 
         FIG. 7  is a perspective explanatory view showing a first pin and a second pin of the movable bracket, the locking member, the input member, and therearound in the seat state switching mechanism in  FIG. 2 ; 
         FIG. 8  is an explanatory view explaining an operation of the seat state switching mechanism in  FIG. 2  for shifting to a reclining state; 
         FIG. 9  is an explanatory view explaining the operation of the seat state switching mechanism in  FIG. 2  for shifting to the reclining state; 
         FIG. 10  is an explanatory view explaining an operation of the seat state switching mechanism in  FIG. 2  for the shifting to the reclining state; 
         FIG. 11  is an explanatory view explaining an operation of the seat state switching mechanism in  FIG. 2  for shifting to a walk-in state; 
         FIG. 12  is an explanatory view explaining the operation of the seat state switching mechanism in  FIG. 2  for the shifting to the walk-in state; 
         FIG. 13  is an explanatory view explaining the operation of the seat state switching mechanism in  FIG. 2  for the shifting to the walk-in state; 
         FIG. 14  is a front view showing a main configuration of a conventional seat state switching mechanism; and 
         FIG. 15  is a front view showing an operation of the conventional seat state switching mechanism for shifting to a walk-in state. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a preferable embodiment of the present invention will be described with reference to the accompanying drawings. 
     A seat  1  illustrated in  FIG. 1  is a seat which is long in a vehicle width direction and constitutes a rear seat of a vehicle. The seat  1  includes a seat state switching mechanism  5  (a first seat state switching mechanism) and an existing seat state switching mechanism  6  (a second seat state switching mechanism) on the opposite sides of a seatback  3  in a width direction thereof respectively. The seat  1  further includes a reclining manipulation lever  7  and a walk-in manipulation lever  8  on the side (right side in  FIG. 1 ) of the seatback  3  in the width direction thereof where the existing seat state switching mechanism  6  is provided. 
     Specifically, the seat  1  includes: a seat cushion  2 ; the seatback  3  tiltable in a front-rear direction of the seat  1 ; the seat switching mechanism  5  provided on the one side (left side in  FIG. 1 ) of the seat back  3  in the width direction thereof; the existing seat state switching mechanism  6  provided on the other side of the seat back  3  in the width direction thereof; a reclining operation three transmission part; and a walk-in operation force transmission part. 
     Each of the seat state switching mechanism  5  and the existing seat state switching mechanism  6  is operable and configured to switch a state of the seatback between a walk-in state of locking the seatback  3  at a walk-in position at a predetermined tilt angle and a reclining state of releasing the locking and allowing the seatback  3  to lean to a frontmost position. A specific configuration of the seat state switching mechanism  5  will be descried in detail later. 
     The reclining operation force transmission part is configured to transmit a reclining operation force, which is an operation force for shifting to the reclining state, to each of the seat state switching mechanism  5  and the existing seat state switching mechanism  6 . Specifically, the reclining operation force transmission part includes the reclining manipulation lever  7  and a reclining operation force transmission cable  9 . 
     The reclining manipulation lever  7  is provided on the other side of the seatback  3 , i.e., on the side (right side in  FIG. 1 ) where the existing seat state switching mechanism  6  is provided. The reclining manipulation lever  7  serves as a reclining operation force input section for receiving an input of the reclining operation force and adapted to transmit the reclining operation force to the existing seat state switching mechanism  6  via a cable or a link. The reclining operation force transmission cable  9  serves as a transmission member for transmitting the reclining operation force from the reclining manipulation lever  7  to the seat state switching mechanism  5 . 
     The walk-in operation force transmission part is configured to transmit a walk-in operation force for shifting to the walk-in state to the existing seat state switching mechanism  6  or the reclining mechanism. Specifically, the walk-in operation force transmission part includes the walk-in manipulation lever  8  and a walk-in operation force transmission cable  10  for transmitting the operation force input to the walk-in manipulation lever  8  to the existing seat state switching mechanism  6  or the reclining mechanism. 
     Hereinafter, the configuration and the operations of the seat state switching mechanism  5  will he described in more detail. 
     (Configuration of Seat State Switching Mechanism  5 ) 
     The seat state switching mechanism  5  is configured to switch the state of the seatback  3  between a walk-in state of locking the seatback at a walk-in position at a predetermined tilt angle (such an angle at which the seatback  3  leans forward for allowing a person to easily get into and out of a space in the rear of the seatback  3 ) and a reclining state of releasing the locking and allowing the seatback  3  to lean to a frontmost position (such a position substantially parallel to the seat cushion  2 ). 
     Specifically, as shown in  FIGS. 2 to 3 , the seat state switching mechanism  5  includes: a base member  11  fixedly attached to the seat cushion  2  (see  FIG. 1 , specifically attached to a frame supporting the seat cushion  2 ); a locking member  12 , an input member  13 , and a movable bracket  14  each serving as a movable member rotatably attached to the base member  11 ; a tension coil spring  17  (a second biasing member) for biasing the input member  13  in a clockwise direction when viewed in  FIG. 2 ; and a torsion coil spring  18  (a first biasing member) for biasing the locking member  12  in a counter-clockwise direction when viewed in  FIG. 2 . 
     The movable bracket  14  is fixedly attached to a side surface of the seatback  3  and configured to be tiltable together with the seatback  3 . Specifically, the movable bracket  14  has a main body  14   a  formed with a through hole  14   c  and an arm  14   b  as shown in  FIG. 4 . The arm  14   b  has a lower end connected to the main body  14   a.  The main body  14   a  and the arm  14   b  are integrated. The arm  14   b  is fastened to the side surface of the seatback  3  with, for example, a screw. A first pin  20  and a second pin  2  are fastened to the main body  14   a  around the through hole  14   c.  The first pin  20  and the second pin  21  extend in parallel to a shaft member  16  horizontally extending through the through hole  14   c,  which will be described later. 
     As shown in  FIGS. 2 to 3 , the movable bracket  14  is rotatably supported on the shaft member  16  fixedly attached to an upper part of the base member  11  so as to horizontally extend and inserted in the through hole  14   c.  Further, the shaft member  16  receives a swirl spring  19  wound thereon. The swirl spring  19  has an outer end engaging with the pin  23  provided to the movable bracket  14 . Therefore, the movable, bracket  14  is biased with a rotational biasing force of the swirl spring  19  in a direction (the counter-clockwise direction in  FIG. 2 ) corresponding to the forward direction of the seat  1  in which the movable bracket leans together with the seatback  3  to the front of the seat  1 . 
     The first pin  20  and the second pin  21  of the movable bracket  14  are arranged so that the first pin  20  reaches the locking member  12  earlier than the second pin  21  when the movable bracket  14  leans forward (rotates in the counter-clockwise direction in  FIG. 2 ). The first pin  20  in the embodiment serves as an abutment part which abuts the locking member  12  when the movable bracket  14  tilts. 
     The locking member  12  is configured to lock the movable bracket  14  at a predetermined walk-in locking position so that the seatback  3  reaches a walk-in position when the movable bracket  14  tilts. Specifically, the locking member  12  includes a main body  12   a  having a through hole  12   d,  and an arm  12   b  and a hook  12   c  extending different directions from the main body  12   a  as shown in  FIG. 5 . 
     The main body  12   a  is provided with a pin  12   e  penetrating the main body  12   a.  The pin  12   e  has one end (an end located in the depth of the sheet in  FIG. 5 ) inserted in a slit  11   b  of the base member  11  having a curving shape (see  FIG. 3 ) for regulating a rotatable range of the locking member  12 . The pin  12   e  has the other end (an end at the front of the sheet in  FIG. 5 ) engaged with one end of the opposite ends of the torsion coil spring  18  (see  FIG. 3 ) from below. 
     The hook  12   c  has a bent shape, specifically, has a recess  12   g  (engagement part) and an outer peripheral surface  12   h.  In the walk-in state of the seat state switching mechanism  5  (see  FIGS. 11 to 13 ), the recess  12   g  is engageable with the first pin  20  of the movable bracket  14 . Conversely, in the reclining state (see  FIGS. 8 to 10 ), the outer peripheral surface  12   h  comes into contact with the first pin  20  and the locking member  12  is pushed downward, and hence the first pin  20  does not engage with the recess  12   g.    
     The arm  12   b  of the locking member  12  has an end provided with a pin  12   f.  The pin  12   f  is inserted in a slit  11   c  of the base member  11  having a curving shape (see  FIG. 3 ). The pin.  12   f  is coupled to a certain portion, via a cable or the like, for releasing locking of the slide mechanism (not shown) for sliding the seat  1  in the front-rear direction. The pin  12   f  rises as the locking member  12  rotates in the clockwise direction in the shifting to the walk-in state where the locking member  12  engages with the first pin  20 , thereby releasing the locking of the slide mechanism. 
     The seat state switching mechanism  5  according to the embodiment has a releaser for releasing a biasing state of the locking member  12  (i.e., locking of the locking member  12 ) and switching to the reclining state in receipt of a reclining operation force via the reclining manipulation lever  7  and the reclining operation force transmission cable  9 . The releaser is composed of the input member  13 , the torsion coil spring  18  (first biasing member), and the tension coil spring  17  (second biasing member). 
     The input member  13  receives an input of the reclining operation force by the manipulation lever  7  via the reclining operation force transmission cable  9 . The input member  13  holds the locking member  12  at the locking position (c.f., the walk-in state in  FIGS. 11 to 13 ) for locking the movable bracket  14  at the walk-in locking position in no receipt of the reclining operation, and releases the holding of the locking member  12  (c.f., the reclining state in  FIGS. 8 to 10 ) in receipt of the reclining operation force. 
     Specifically, as shown in  FIG. 6 , the input member  13  includes: a main body  13   a  having a through hole  13   e;  a cable linkage  13   b  linked to the reclining operation force transmission cable  9 ; a bulging part  13   c  bulging in a mountain shape; and a spring engagement part  13   d  having a hook shape or hole shape for receiving the tension coil spring  17  to be engaged therewith. The bulging part  13   c  has an outer peripheral surface composed of a straight section  13   f  and a bulging section  13   g  for respectively receiving the first pin  20  and the second pin  21  of the movable bracket  14  which abut the sections. The cable linkage  13   b  and the spring engagement part  13   d  are located on both side of the through hole  13   e.    
     As shown  FIG. 3  and  FIG. 7 , the input member  13  is rotatably supported about a support shaft in common with the locking member  12 , i.e., about a shaft member  15  fixedly attached to the base member  11  so as to horizontally extend. The input member  13  and the locking member  12  are supported about the shaft member  15  to be rotatable independently of each other even in a mutually overlapped state. 
     The tension coil spring  17  has the opposite ends to be engaged with the spring engagement part  13   d  of the input member  13  and with a spring engagement part  11   a  of the base member  11  respectively (see  FIG. 3 ). The engagement makes the tension coil spring  17  bias the input member  13  in the clockwise direction rotatably about the shaft member  15  (see  FIG. 7 ). Specifically, the input member  13  is biased by the tension coil spring  17  (second biasing member) from the releasing position for releasing the locking of the locking member  12  by the input member  13  to the holding position for holding the locking member  12 . 
     Moreover, due to the engagement of the opposite ends of the torsion coil spring  18  with the cable linkage  13   b  of the input member  13  and the pin  12   e  of the locking member  12  respectively, the locking member  12  is biased by the torsion coil spring  18  in the counter-clockwise direction rotatably about the shaft member  15 . Specifically, the locking member  12  is biased by the torsion coil spring  18  (first biasing member) from the locking position (walk-in locking position) of the locking member  12  to the lock releasing position (reclining position). In this state, the pin  12   e  of the locking member  12  is pinched between the end of the torsion coil spring  18  and the lower surface of the input member  13 , and hence the locking member  12  is rotatable by following the rotation of the input member  13 . 
     Accordingly, the locking member  12  is arranged at such a position as to lock the movable bracket  14  at the walk-in locking position in no receipt of the reclining operation force by the input member  13  in the releaser. 
     (Operations of Seat State Switching Mechanism  5 ) 
     &lt;Operation of Shifting to Reclining State&gt; 
     The input member  13  in the scat state switching mechanism  5  having the above-described configuration receives an input of a reclining operation force by the manipulation lever  7  via the reclining operation force transmission cable  9 , as shown in  FIGS. 8 to 10 , in shifting from an initial state where the seat I shown in  FIG. 1  is sittable to a reclining state (i.e., a state where the seatback  3  can lean to a frontmost position near the seat cushion  2 ) At this time, the seat  1  is released from the reclining locking, and the seatback  3  is tiltable. 
     As shown in  FIGS. 8 to 10 , the input member  13  is pulled downward by the reclining operation force transmission cable  9 . The pulled input member  13  rotates about the shaft member  15  in the counter-clockwise direction. Specifically, the input member  13  moves from the holding position for holding the locking member  12  to the releasing position against the biasing force from the tension coil spring  17  (second biasing member) in receipt of the reclining operation force. 
     The locking member  12  is released from the holding by the input member  13 , and rotates about the shaft member  15  in the counter-clockwise direction with the biasing force from the torsion cod spring  18 . At this time, the locking member  12  rotates in the counter-clockwise direction at mostly the same time as the rotation of the input member  13  by following the rotation of the input member  13 . 
     The movable bracket  14  can lean to the frontmost position in the state where the locking member  12  rotates in the counter-clockwise direction. In other words, the movable bracket  14  tilts in the counter-clockwise direction with the biasing force from the swirl spring  19  (see  FIGS. 2 to 3 ), and moves in the counter-clockwise direction from the initial position where the first pin  20  abuts the straight section  13   f  of the input member  13  shown in  FIGS. 8 to 19 . At this time, the first pin  20  pushes the input member  13  and the locking member  12  downward while abutting the bulging section  13   g  of the input member  13  and the outer peripheral surface  12   h  of the hook  12   c  of the locking member  12 . Therefore, the first pin  20  does not engage with the recess  12   g  of the locking member  12 . As shown in  FIG. 10 , when the movable bracket  14  further tilts, the first pin  20  passes through the input member  13  and the locking member  12 , and instead, the subsequent second pin  21  pushes the input member  13  and the locking member  12  downward. As a result, the movable bracket  14  and the seatback  3  are smoothly shiftable to the reclining state of allowing each of the bracket and the seatback to lean to the frontmost position. 
     Meanwhile, when a user manually returns the seatback  3  from the reclining state to the initial state again, the movable bracket  14  shown in  FIGS. 8 to 10  rotates in the clockwise direction. Simultaneously, the first pin  20  can smoothly return to the initial position shown in  FIG. 8  while abutting the bulging section  13   g  of the input member  13  and the outer peripheral surface  12   h  of the hook  12   c  of the locking member  12 . That is to say, a returning operation of to the initial position can be easily and reliably performed as well. 
     Moreover, the movable bracket  14  rotates in the clockwise direction when the seatback  3  leans backward. Simultaneously, the first pin  20  can smoothly and reliably move by abutting the straight section  13   f  of the input member  13 . 
     &lt;Operation of Shifting to Walk-In State&gt; 
     In the seat state switching mechanism  5 , only an operation of tilting the seatback  3  and the movable bracket  14  as shown in  FIGS. 11 to 13  is sufficient for shifting the state of the seatback  3  from the initial state where the seat  1  shown in  FIG. 1  is sittable to the walk-in state, i.e., to the state where the seatback tilts to the walk-in position at the predetermined angle. 
     Specifically, in the operation of shifting to the walk-in state in the seat state switching mechanism  5 , the tilting of the movable bracket  14  in the counter-clockwise direction in accordance with the tilting of the seatback  3  makes the first pin  20  of the movable bracket  14  rotate in the counter-clockwise direction while pushing the input member  13  downward by abutting the bulging section  13   g  of the input member  13 , as shown in  FIGS. 11 to 13 . However, the amount of pushing the input member  13  downward only by the first pin  20  is small. Hence, the locking member  12  is kept in the range of the walk-in locking position. This allows the first pin  20  to get under the hook  12   c  of the locking member  12  and engage with the recess  12   g.  At this time, the locking member  12  is pushed by the first pin  20  and rotates in the clockwise direction. However, the rotation of the locking member  12  is regulated when the second pin  21  attached to the movable bracket  14  abuts a contact surface  12   j  of the locking member  12 . The movable bracket  14  and the seatback  3  can shift to the walk-in state at the predetermined tilt angle owing to the regulation. 
     Moreover, as shown in  FIG. 13 , the pin  12   f  fixedly attached to the locking member  12  rises at a predetermined distance S when the locking member  12  rotates in the clockwise direction. Such rise enables the operation of releasing the slide locking mechanism of the seat  1  via an unillustrated cable connected to the pin  12   f.    
     (Characteristics of Embodiment) 
     (1) The seat state switching mechanism  5  according to the embodiment includes: the movable bracket  14  fixedly attached to the seatback  3  and being tiltable together with the seatback  3 ; the locking member  12  for locking the movable bracket  14  at the walk-in locking position when the movable bracket  14  tilts; and the releaser (specifically, the releaser composed of the input member  13 , the torsion coil spring  18 , i.e., the first biasing member, and the tension coil spring  17 , i.e., the second biasing member) for releasing the locking of the locking member  12  in receipt of a reclining operation force, and switching the state to the reclining state. 
     In this configuration, only the operation of tilting the seatback  3  permits the locking member  12  to lock the movable bracket  14  fixedly attached to the seatback  3  at the predetermined walk-in locking position (that is to say, the tilting is restricted) so that the seatback  3  reaches the walk-in position at the predetermined tilt angle. In this manner, the seatback  3  is shiftable to the walk-in state of locking the seatback at the walk-in position. This configuration thus eliminates the necessity of providing a member for operating the locking member  12  by receiving a walk-in operation force in the shifting to the walk-in state. As a result, the number of components of the seat state switching mechanism  5  is reduceable. Accordingly, the number of components constituting the structure of the mechanism is reduceable. 
     Incidentally, when the input member  13  composing the releaser receives the reclining operation force, the received force releases the locking of the locking member  12  to thereby enable the switching to the reclining state. In this manner, the seatback  3  is shiftable to the reclining state where the seatback can lean to the frontmost position. Consequently, the seat state switching mechanism  5  having the above-described configuration can achieve the switching between the walk-in state and the reclining state with the smaller number of components. 
     (2) The movable bracket  14  in the seat state switching mechanism  5  according to the embodiment has the first pin  20  serving as the abutment part which abuts the locking member  12  when the movable bracket  14  tilts. The locking member  12  has the recess  12   g  serving as the engagement part which engages with the abutment part for locking the movable bracket  14  at the walk-in locking position in no receipt of the reclining operation force by the input member  13  composing the releaser, and the outer peripheral surface  12   b  which comes into contact with the first pin  20  (abutment part) in receipt of the reclining operation force by the input member  13  (releaser). The outer peripheral surface  12   h  is configured to, when coming into contact with the first pin  20 , be pushed by the first pin  20  in a direction in which the locking member  12  moves to the locking releasing position. 
     in this configuration, the recess  12   g  (engagement part) of the locking member  12  engages with the first pin  20  (abutment part) of the movable bracket  14  in no receipt of the reclining operation force by the input member  13 , and thus the movable bracket  14  can be reliably locked at the walk-in locking position. In contrast, the outer peripheral surface  12   h  of the locking member  12  comes into contact with the first pin  20  in receipt of the reclining operation force by the input member  13  (releaser), so that the locking member  12  is pushed by the first pin  20  (abutment part) in a direction in which the locking member moves to the locking releasing position. The pushing can ensure the movement of the locking member  12  to the locking releasing position. As a result, the locking member  12  can reliably perform both the operation of locking the movable bracket  14  at the walk-in locking position and the operation of releasing the locking even with the smaller number of components. 
     (3) In the seat state switching mechanism  5  according to the embodiment, the releaser includes: the torsion coil spring  18  serving as the first biasing member for biasing the locking member  12  in the direction from the locking position to the lock releasing position; and the input member  13  for receiving the reclining operation force, the input member holding the locking member  12  at the locking position in no receipt of the reclining operation, and releasing the holding of the locking member  12  in receipt of the reclining operation three. 
     In this configuration, the input member  13  holds the locking member  12  at the locking position in no receipt of the reclining operation force, and releasing the holding of the locking member  12  in receipt of the reclining operation force. The locking member  12  can move from the locking position to the lock releasing position with the biasing three from the torsion coil spring  18  serving as the first biasing member when the holding of the locking member  12  by the input member  13  is released. Accordingly, the locking member  12  is reliably shiftable from the locking position to the lock releasing position. 
     (4) In the seat state switching mechanism  5  according to the embodiment, the releaser further includes the tension coil spring  17  serving as the second biasing member for biasing the input member  13  from the releasing position for releasing the holding of the locking member  12  to the holding position for holding the locking member  12 . The input member  13  is configured to move from the holding position to the releasing position against the biasing force from the tension coil spring  17  in receipt of the reclining operation force. 
     This configuration allows the input member  13  to reliably hold the locking member  12  at the locking position with the biasing force from the tension coil spring  17  (second biasing member) in no receipt of the reclining operation force. Conversely, the input member  13  moves from the holding position to the releasing position against the biasing force from the tension coil spring  17  in receipt of the reclining operation force. Therefore, the holding of the locking member  12  by the input member  13  is reliably releasable. 
     (5) In the seat state switching mechanism  5  according to the embodiment, the locking member  12  is at such a position as to lock the movable bracket  14  at the walk-in locking position in no receipt of the reclining operation force by the releaser (specifically, the input member  13 ). 
     This configuration including the locking member  12  which can lock the movable bracket  14  at the walk-in locking position in an initial state where the releaser (specifically, the input member  13 ) does not receive the reclining operation force can avoid a risk that the seatback  3  leans to the frontmost position in the reclining state in no receipt of the reclining operation force. 
     In other words, in the seat state switching mechanism  5  according to the embodiment, each of the locking member  12  and the input member  13  is always at the walk-in locking position in the initial state without any input of the reclining operation force, as shown in  FIG. 2  and  FIG. 7 . Therefore, as shown in  FIGS. 11 to 13 , when the seatback  3  leans forward (rotates in the counter-clockwise direction) in no receipt of the reclining operation force, the first pin  20  attached to the movable bracket  14  always engages with the recess (engagement part)  12   g  of the locking member  12  and allows the locking member  12  to rotate in the clockwise direction. Simultaneously, the first pin  20  can push the input member  13  downward. As a result, the seatback  3  can avoid the risk of leaning to the frontmost position in the reclining state without an input of the reclining operation force. 
     (6) In the seat state switching mechanism  5  according to the embodiment, the locking member  12  is configured to release the slide locking state of the slide locking mechanism for locking the slide movement of the seat in the front-rear direction thereof when locking the movable bracket  14  at the walk-in locking position (specifically, configured to release the locking of the slide locking device via the cable in accordance with a rise of the pin  12   f  of the locking member  12 ). 
     In this configuration, the locking member  12  can release the slide locking state of the slide locking mechanism when locking the movable bracket  14  at the walk-in locking position, resulting in contribution to a reduction in the number of components for operating the slide locking mechanism. 
     (7) In the seat state switching mechanism  5  according to the embodiment, when the seatback  3  leans backward, the movable bracket  14  rotates in the clockwise direction. Simultaneously, the first pin  20  can smoothly and reliably move by abutting the straight section  13   f  of the input member  13 . 
     (8) The seat state switching mechanism  5  according to the embodiment is adoptable as a module to be easily assembled in an existing seat structure. 
     (9) The seat  1  according to the embodiment includes: the seatback  3 ; the seat at-switching mechanism  5  provided on one side of the seatback  3  in the width direction thereof and serving as the seat state switching mechanism according to claim  1 ; the existing seat state switching mechanism  6  or the reclining mechanism  6  provided on the other side of the seatback  3  in the width direction thereof, and having the reclining locking operability for locking the seatback  3  at the initial tilt angle and placing the seatback in the reclining locking state, the reclining operability for placing the seatback in the reclining state in receipt of the reclining operation force, and the walk-in operability for placing the seatback  3  in the walk-in state in receipt of the walk-in operation force; the reclining operation force transmission part for transmitting the reclining operation force to the seat state switching mechanism  5  and the existing seat state switching mechanism  6 ; and the walk-in operation force transmission part for transmitting the walk-in operation force to the existing seat state switching mechanism  6 . 
     In this configuration, the seat state switching mechanism  5  and the existing seat state switching mechanism  6  are provided on the opposite sides of the seatback  3  in the width direction thereof respectively, and therefore the seatback  3  is maintainable in a stably tilted manner in the walk-in state even in the seat  1  having a large width. 
     (10) In the seat  1  according to the embodiment, the reclining, operation force transmission part includes: the reclining manipulation lever  7  serving as the reclining operation force input section provided on the other side of the seatback  3  in the width direction thereof for receiving an input of the reclining operation force and adapted to transmit the reclining operation force to the existing seat state switching mechanism  6 ; and the reclining operation force transmission cable  9  serving as the transmission member for transmitting the reclining operation force from the reclining manipulation lever  7  to the seat state switching mechanism  5 . 
     in this configuration provided with the reclining manipulation lever  7  (reclining operation force input section) only on the other side of the seatback  3  in the width direction thereof, the reclining operation force transmission cable  9  (transmission member) can transmit the reclining operation force from the reclining manipulation lever  7  to the seat state switching mechanism  5  located opposite the reclining manipulation lever across the seatback  3 . This simplifies the structure by eliminating the necessity of providing the reclining manipulation lever  7  on each of the opposite sides of the seatback  3  in the width direction thereof. Additionally, the seat state switching mechanism  5  and the existing seat state switching mechanism  6  provided on the opposite sides of the seathack  3  in the width direction thereof respectively are simultaneously shiftable to the reclining state, and accordingly the two switching mechanisms can exert high synchronization. 
     (11) In the seat  1  according to the embodiment, each of the locking member  12  and the input member  13  is always at the initial position in the walk-in in the seat state switching mechanism  5  when no reclining operation is performed. A route for transmitting the operation force from the walk-in manipulation lever  8  to the seat state switching mechanism  5  includes the seathack  3 . Therefore, the member for transmitting the operation force to the seat state switching mechanism  5  is only the wire cable (i.e., the reclining operation force transmission cable  9 ) for transmitting the reclining operation force. In this configuration of the seat  1 , only the releasing of the locking of the reclining mechanism is sufficient in the walk-in operation without the necessity of transmitting the operation force to the seat state switching mechanism  5  via the wire cable. This configuration thus can exclude a cable and a link required for the walk-in operation in a structure of a conventional seat state switching mechanism, and considerably reduce the number of components. 
     (12) A seat, such as a conventional rear seat, having a large width is highly likely to include a reclining mechanism and a switching mechanism collectively arranged on one side of the seat, and have only a hinge structure freely rotatable on the other side thereof. The seat configured in this manner has a possibility that the seatback  3  is twisted and deforms when a load is applied on the other side where no mechanism, such as the reclining mechanism, is provided in a state where the seatback  3  leans forward through the walk-in operation. In contrast, in the seat  1  according to the embodiment, the seat state switching mechanism  5  and the existing seat state switching mechanism  6  are provided on the opposite sides of the seatback  3  in the width direction thereof respectively as shown in  FIG. 1 , and these switching mechanisms exert the operability of restricting the seatback  3  at the walk-in position at the predetermined tilt angle on the opposite sides of the seatback  3  respectively. Accordingly, the seatback  3  is maintainable in a stably tilted manner in the walk-in operation. 
     (13) The seat  1  according to the embodiment configured in the above-described manner additionally includes the seat state switching mechanism  5  composed of the smaller number of components while adopting the structure of the existing seat state switching mechanism on a side of the seat where the reclining locking mechanism is absent (i.e., on the side opposite to the side where the existing seat state switching mechanism  6  has the reclining locking operability or the walk-in position switching operability, or both). This configuration is adaptable to the seat  1  having the large width and can maintain the stable tilting in the walk-in operation. 
     &lt;Summary of Embodiment&gt; 
     The embodiment is summarized in the following manner. 
     A seat state switching mechanism according to the embodiment is a seat state switching mechanism for switching a state of a seat seatback liftable in a front-rear direction of a seat between a walk-in state of locking the seatback at a walk-in position at a predetermined tilt angle and a reclining state of releasing the locking and allowing the seatback to lean to a frontmost position. The seat state switching mechanism includes: a movable bracket fixedly attached to the seatback and being tiltable together with the seatback; a locking member for locking the movable bracket at a predetermined walk-in locking position so that the seatback reaches the walk-in position when the movable bracket tilts through a walk-in operation; and a releaser (specifically, a releaser composed of the input member, the torsion coil spring, i.e., the first biasing member, and the tension coil spring, i.e., the second biasing member) for releasing the locking of the locking member in receipt of the reclining operation force through an reclining operation and switching the state of the seatback, to the reclining state. 
     In this configuration, for example, only the operation of tilting the seatback after releasing the reclining through the operation of the walk-in lever permits the locking member to lock the movable bracket (specifically, the first pin attached to the movable bracket) of the seatback at the predetermined walk-in locking position (specifically, by the engagement of the locking member with the first pin) so that the seatback reaches the walk-in position at the predetermined tilt angle (that is to say, the tilting is restricted). Accordingly, the seatback is shiftable to the walk-in state of locking the seatback at the walk-in position. This configuration thus eliminates the necessity of providing a member for operating the locking member by receiving a walk-in operation force in the shifting to the walk-in state. As a result, the number of components of the seat state switching mechanism is reduceable, and further the structure of the mechanism is simplified. 
     On the other hand, for instance, when the reclining is released through an operation of the reclining lever, the relevant operation force is transmitted to the releaser. The transmitted operation force releases the locking of the locking member to thereby enable the switching to the reclining state for reaching the frontmost position. In this manner, the seatback is shiftable to the reclining state where the seatback can lean to the frontmost position. Consequently, the seat state switching mechanism having the above-described configuration can achieve the switching between the walk-in state and the reclining state with the smaller number of components. 
     In the seat state switching mechanism, the movable bracket preferably has an abutment part (specifically, the first pin attached to the movable bracket) which abuts the locking member when the movable bracket tilts. The locking member preferably has an engagement part which engages with the abutment part for locking the movable bracket at the walk-in locking position in no receipt of the reclining operation force by the releaser, and an outer peripheral surface which comes into contact with the abutment part in receipt of the reclining operation force by the releaser. The outer peripheral surface is preferably configured to, when coming into contact with the abutment part, be pushed by the abutment part in a direction in which the locking member moves to a lock releasing position. 
     In this configuration, the engagement part of the locking member engages with the abutment part of the movable bracket (specifically, the first pin attached to the movable bracket) in no receipt of the reclining operation force by the releaser, and thus the movable bracket can be reliably locked at the walk-in locking position. In contrast, the outer peripheral surface of the locking member comes into contact with the abutment part in receipt of the reclining operation force by the releaser, so that the locking member is pushed by the abutment part in the direction in which the locking member moves to the lock releasing position. The pushing can ensure the movement of the locking member  12  to the locking releasing position. As a result, the locking member can reliably perform both the operation of locking the movable bracket at the walk-in locking position and the operation of releasing the locking even with the smaller number of components. 
     In the seat state switching mechanism, the releaser preferably includes: a first biasing member for biasing the locking member in a direction from a locking position to the lock releasing position; and an input member for receiving the reclining operation force, the input member holding the locking member at the locking position in no receipt of the reclining operation, and releasing the holding of the locking member in receipt of the reclining operation force. 
     In this configuration, the input member holds the locking member at the locking position in no receipt of the reclining operation force, and releases the holding of the locking member in receipt of the reclining operation force. The locking member can move from the locking position to the lock releasing position with the biasing force from the first biasing member when the holding of the locking member by the input member is released. Accordingly, the locking member is reliably shiftable from the locking position to the lock releasing position. 
     In the seat state switching mechanism, the releaser preferably further includes a second biasing member for biasing the input member from a releasing position for releasing the holding of the locking member to a holding position for holding the locking member, and the input member is preferably configured to move from the holding position to the releasing position against a biasing force from the second biasing member in receipt of the reclining operation force. 
     This configuration allows the input member to reliably hold the locking member at the locking position with the biasing force from the second biasing member in no receipt of the reclining operation three. Conversely, the input member moves from the holding position to the releasing position against the biasing force from the second biasing member in receipt of the reclining operation force. Therefore, the holding of the locking member by the input member is reliably releasable. 
     In the seat state switching mechanism, the locking member is preferably at such a position as to lock the movable bracket at the walk-in locking position in no receipt of the reclining operation three by the releaser. 
     This configuration including the locking member which can lock the movable bracket at the walk-in locking position in the initial state where the releaser does not receive the reclining operation three can avoid the risk that the seatback leans to the frontmost position in the reclining state in no receipt of the reclining operation force. 
     In the seat state switching mechanism, the locking member is preferably configured to release a slide locking state of a slide locking mechanism for locking a slide movement of the seat in the front-rear direction thereof when locking the movable bracket at the walk-in locking position. 
     In this configuration, the locking member can release the slide locking state of the slide locking mechanism when locking the movable bracket at the walk-in locking position, resulting in contribution to a reduction in the number of components for operating the slide locking mechanism. 
     The seat according to the embodiment is a seat including the seat state switching mechanism. The seat includes: the seatback; a seat state switching mechanism provided on one side of the seatback in a width direction thereof and serving as the seat state switching mechanism; an existing seat state switching mechanism provided on the other side of the seatback in the width direction thereof, and having a reclining locking operability for locking the seatback at an initial tilt angle and placing the seatback in a reclining locking state, a reclining operability for placing the seathack in the reclining state in receipt of the reclining operation three, and a walk-in operability for placing the seat back in the walk-in state in receipt of a walk-in operation force; a reclining operation three transmission part for transmitting the reclining operation force to the seat state switching mechanism and the existing seat state switching mechanism; and a walk-in operation force transmission part for transmitting the walk-in operation force to the existing seat state switching mechanism. 
     In this configuration, the seat state switching mechanism and the existing seat state switching mechanism are provided on the opposite sides of the seatback in the width direction thereof respectively, and therefore the seatback is maintainable in a stably tilted manner in the walk-in state even in the seat having a large width. 
     In the seat, the reclining operation force transmission part preferably includes: a reclining operation force input section provided on the other side of the seatback in the width direction thereof for receiving an input of the reclining operation force and adapted to transmit the reclining operation force to the existing seat state switching mechanism; and a transmission member for transmitting the reclining operation force from the reclining operation force input section to the seat state switching mechanism. 
     In this configuration provided with the reclining operation force input section only on the other side of the seatback in the width direction thereof, the transmission member can transmit the reclining operation force from the reclining operation force input section to the seat state switching mechanism located opposite the reclining operation force input section across the seatback. This eliminates the necessity of providing the reclining operation force input section on each of the opposite sides of the seatback in the width direction thereof, and thus simplifies the structure. Additionally, the seat state switching mechanisms provided on the opposite sides of the seatback in the width direction thereof respectively are simultaneously shiftable to the reclining state, and accordingly the two switching mechanisms can exert high synchronization. 
     The seat state switching mechanism and the seat including the seat state switching mechanism according to the embodiment can achieve the switching between the walk-in state and the reclining state with the smaller number of components.