Patent Publication Number: US-11384822-B2

Title: Lifter device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Japanese Patent Applications No. 2019-042310 filed on Mar. 8, 2019, and No. 2019-115233 filed on Jun. 21, 2019 the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a lifter device. Specifically, the present disclosure relates to a lifter device including an output shaft configured to rotate by receiving rotational power transmitted from an operation handle and configured to raise and lower a seat. 
     BACKGROUND 
     There has been a vehicle seat including a lifter device capable of adjusting a seat surface height of a seat cushion as disclosed in JP-A-2016-78850. Specifically, when the operation handle is operated such that the operation handle is raised and lowered, the lifter device transmits a movement amount of the operation as a feeding rotation movement amount of a gear, and raises and lowers the seat surface height by a certain amount. When the operation of the operation handle is released, the lifter device is configured such that the rotation of the gear is locked at that position, and such that the operation handle is returned to the neutral position, at which the operation handle is positioned before the operation, by urging and is returned to an initial state in which the operation can be performed again. 
     The feeding rotation of the gear accompanying the operation of the operation handle is performed by pushing a feed pawl meshed with the gear in an operation direction of the operation handle. Further, the rotation of the gear during the release of the operation of the operation handle is locked as follows. That is, a pair of lock pawls, which is configured by a pair of symmetrical structures meshed with the gear, is a ratchet type meshing structure. The ratchet type meshing structure is that one lock pawl of the pair of lock pawls is disengaged in accordance with the operation of the operation handle, and that the other lock pawl of the pair of lock pawls releases rotation in a feed direction but meshes with the gear in a reverse direction. When the operation of the operation handle is released, the other lock pawl stops the rotation of the gear at that position. 
     The feed pawl, which performs the feeding rotation of the gear, is a pair of symmetrical pawl structures similarly to the lock pawl so as to allow the movement of returning to the neutral position when the operation of the operation handle is released. The pair of feed pawls is the ratchet type meshing structure such that one feed pawl of the pair of feed pawls is disengaged from the gear in accordance with the operation of the operation handle, and such that the other feed pawl of the pair of feed pawls meshes with the gear so as to transmit the power in the feed direction but releases rotation in the reverse direction. A disc spring capable of applying a sliding frictional resistance force is provided between the gear and a support member supporting the gear such that the gear does not slide and rotate due to a load acting in the direction of gravity when the operation handle is pushed down. 
     In the related art disclosed in JP-A-2016-78850, the disc spring is configured to apply the sliding frictional resistance force between the gear and the support member at any time. For this reason, the sliding frictional resistance force is also applied during the pulled-up operation of the operation handle, which does not cause the slip rotation of the gear, and thus, an operation load is increased. The disclosure has been made to solve the above problem, and the problem to be solved by the disclosure is to prevent sliding rotation during the pushed-down operation and to ensure that the rotation can be locked at the neutral position without increasing an operation load during the pulled-up operation of the operation handle. 
     SUMMARY 
     In order to solve the above problems, a lifter device of the present disclosure takes the following solutions. 
     The lifter device of the present disclosure includes: 
     an output shaft configured to rotate by receiving transmission of rotational power from an operation handle and configured to raise and lower a seat; 
     a support member configured to support the output shaft such that the output shaft is rotatable; 
     an input member coupled to the operation handle and configured to be operated to rotate around an axis of the output shaft; 
     a feed portion configured to transmit forward and reverse rotation of the input member to the output shaft; 
     a lock portion configured to lock the rotation of the output shaft with respect to the support member; and 
     a friction generating portion configured to apply a frictional force to the rotation of the output shaft, the friction generating portion including:
         an elastic body provided between the output shaft and the support member;   a rotating cam connected to the input member;   a rotating member configured to rotate integrally with the output shaft; and   a clutch portion configured to be supported by the support member, configured to be pushed in a radial direction by rotation of the rotating cam, and configured to press the elastic body in a thrust direction between the clutch portion and the rotating member to generate friction,       

     wherein the rotating cam is a switching structure of switching to:
         a friction-suppression state, in which generation of friction caused by the elastic body is suppressed, by not pushing the clutch portion in the radial direction when the operation handle is in a neutral position and when the operation handle is turned in a direction of raising the seat from the neutral position; and   a friction-on state, in which friction caused by the elastic body is generated, by pushing the clutch portion in the radial direction when the operation handle is turned in a direction of lowering the seat from the neutral position.       

    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an outer side view showing a schematic configuration of a lifter device according to a first embodiment; 
         FIG. 2  is a side view of an outer side structure as viewed from an inner side of a seat; 
         FIG. 3  is an exploded perspective view showing a state in which an operation handle and a rotation control device are removed from a seat frame; 
         FIG. 4  is a perspective view of the rotation control device as viewed from an outer side of the seat; 
         FIG. 5  is a perspective view of the rotation control device as viewed from the inner side of the seat; 
         FIG. 6  is a front view of the rotation control device as viewed from the outer side of the seat; 
         FIG. 7  is a cross-sectional view taken along a line VII-VII in  FIG. 6 ; 
         FIG. 8  is a cross-sectional view taken along a line VIII-VIII in  FIG. 6 ; 
         FIG. 9  is an exploded perspective view of the rotation control device as viewed from the outer side of the seat; 
         FIG. 10  is an exploded perspective view of the rotation control device as viewed from the outer side of the seat; 
         FIG. 11  is an exploded perspective view showing a state in which some components of the rotation control device shown in  FIG. 9  are assembled; 
         FIG. 12  is an exploded perspective view showing the state in which some components of the rotation control device shown in  FIG. 9  are assembled, as viewed from the inner side of the seat; 
         FIG. 13  is an exploded perspective view showing a state in which some components of the rotation control device shown in  FIG. 11  are assembled; 
         FIG. 14  is an exploded perspective view showing a state in which some components of the rotation control device shown in  FIG. 11  are assembled, as viewed from the inner side of the seat; 
         FIG. 15  is an exploded perspective view showing a state in which some components of the rotation control device shown in  FIG. 13  are assembled; 
         FIG. 16  is a state diagram of a feed portion of the rotation control device at a time when the operation handle is in a neutral position; 
         FIG. 17  is a state diagram of a lock portion at the time when the operation handle is in the neutral position; 
         FIG. 18  is a state diagram of the feed portion at a time when the operation handle is pushed down from the neutral position; 
         FIG. 19  is a state diagram of the lock portion at a time when a clutch portion is meshed with a friction ring by pushing down the operation handle from the neutral position; 
         FIG. 20  is a state diagram of the lock portion at a time when a lock pawl is unlocked by pushing down the operation handle from the neutral position; 
         FIG. 21  is a state diagram of the lock portion at a time when the lock portion is feeding-rotated by the progress of pushing down the operation handle from the neutral position; 
         FIG. 22  is a state diagram of the feed portion at a time when the operation handle is returned from a pushed-down position to the neutral position; 
         FIG. 23  is a state diagram of the lock portion at the time when the operation handle is returned from the pushed-down position to the neutral position; 
         FIG. 24  is a state diagram of the feed portion at a time when the operation handle is pulled up from the neutral position; 
         FIG. 25  is a state diagram of the lock portion at a time when the lock pawl is unlocked by pulling up the operation handle from the neutral position; 
         FIG. 26  is a state diagram of the lock portion at a time when the lock portion is feeding-rotated by the progress of pulling up the operation handle from the neutral position; 
         FIG. 27  is a state diagram of the feed portion at a time when the operation handle is returned from a pulled-up position to the neutral position; 
         FIG. 28  is a state diagram of the lock portion at the time when the operation handle is returned from the pulled-up position to the neutral position; 
         FIG. 29  is a perspective view showing a state of an input member at a time when the operation handle is in the neutral position; 
         FIG. 30  is a perspective view showing a state of the input member at a time when the operation handle is pushed down to a maximum position; 
         FIG. 31  is a perspective view showing a state of the input member at a time when the operation handle is pulled up to a maximum position; 
         FIG. 32  is a diagram showing a state in which rotation of a pinion gear in a downward direction is locked by a stopper; 
         FIG. 33  is a diagram showing a state in which rotation of the pinion gear in an upward direction is locked by the stopper; 
         FIG. 34  is a diagram showing a state in which a temporary holding member is set on a rotating plate; 
         FIG. 35  is a diagram showing a state in which a feed pawl is set between the temporary holding member and the rotating plate; 
         FIG. 36  is a diagram showing a state in which a spring is set between the feed pawl and the pinion gear; 
         FIG. 37  is a diagram showing a state in which an inner lever is set on the feed pawl; 
         FIG. 38  is an enlarged view of a portion XXXVIII in  FIG. 8 ; 
         FIG. 39  is a cross-sectional view showing a state in which a friction generating portion is switched to a friction-on state from  FIG. 38 ; 
         FIG. 40  is a perspective view of a main part of the rotation control device of the lifter device according to a second embodiment as viewed from the outer side of the seat; 
         FIG. 41  is an enlarged perspective view of a clutch portion in a guide member of the rotation control device; 
         FIG. 42  is an explanatory view showing an assembled state of an inner lever and a clutch portion of the rotation control device; 
         FIG. 43  is a sectional enlarged view taken along a line XXXXIII-XXXXIII in  FIG. 42 ; and 
         FIG. 44  is an operational state diagram of the friction generating portion when the operation handle is pushed down from the neutral position. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments for carrying out the present disclosure will be described with reference to drawings. 
     First Embodiment 
       FIGS. 1 to 3  show a seat  1  for an automobile to which a lifter device  10  according to the first embodiment of the present disclosure is applied. In the drawings, directions of portions in a state in which the seat  1  is mounted on the automobile are indicated by arrows. In the following description, description relating to directions is made based on these directions. 
     &lt;Schematic Configuration of Lifter Device  10 &gt; 
     As shown in  FIG. 1 , the seat  1  includes a seat back  3  serving as a backrest on a rear side of a seat cushion  2  serving as a seating part. The seat back  3  is connected to the seat cushion  2  such that a backrest angle is adjustable in a front-rear direction. The seat cushion  2  includes a lifter device  10  and a seat slide device  8  at a lower part of the seat cushion  2 . The seat cushion  2  is fixed to a floor  4  of a vehicle via a bracket  7 . 
     As shown in  FIG. 2 , the seat slide device  8  is known in the related art. The seat slide device  8  includes a pair of left and right upper rails  6  coupled to a pair of left and right lower rails  5  extending in the front-rear direction so as to be slidable forward and rearward. The left and right lower rails  5  are fixedly supported by a pair of front and rear brackets  7  fixed to the floor  4 , respectively. The lifter device  10  is provided above the left and right upper rails  6 . 
     As shown in  FIGS. 2 and 3 , the lifter device  10  includes support brackets  14  fixed on the upper rails  6  and a plurality of link members  11  rotatably coupled to front and rear end parts of the upper rails  6 . A side frame  13  that is a framework of the seat cushion  2 , the support bracket  14 , and the link members  11  constitute a link mechanism  12  that is a four-bar linkage. Among the plurality of link members  11 , a rear link  11   b  on a right rear side includes a sector gear  16  and is configured to be rotated in the front-rear direction via a pinion gear  18  of a rotation control device  21 . A rotation shaft of the rear link  11   b  on the right rear side with respect to the side frame  13  is configured by a torque rod  17 . A rear link (not illustrated) on a left rear side is also configured to be rotated in synchronization with the rear link  11   b  via the torque rod  17 . 
     A through hole  13   a  for inserting the pinion gear  18  is formed in the side frame  13 . The rotation control device  21  is fixed to a right wall of the side frame  13  such that the pinion gear  18  is inserted into the through hole  13   a . The rotation control device  21  is rotatably operated in forward and reverse directions by an operation handle  20  provided on a right side of the seat cushion  2  and extending in the front-rear direction. When the operation handle  20  is rotated upward from a neutral position, the rotation control device  21  is rotated in a direction in which the rear link  11   b  is raised from the support bracket  14 . When the operation handle  20  is rotated downward from the neutral position, the rotation control device  21  is rotated in a direction in which the rear link  11   b  is laid down on the support bracket  14 . With the configuration of the above four-bar linkage, a front link  11   a  is also rotated in response to the rotation of the rear link  11   b , so that a height position of the seat cushion  2  with respect to the floor  4  is adjusted in response to the operation of the operation handle  20 . 
     &lt;Configuration of Rotation Control Device  21 &gt; 
       FIGS. 4 to 6  show a state in which the rotation control device  21  is detached from the seat cushion  2 . Hereinafter, the configuration of the rotation control device  21  is described with reference to  FIGS. 4 to 15 . For the reference numerals of the constituent members of the rotation control device  21  to be described below, reference will be made to any of  FIGS. 4 to 15  as appropriate. 
     The rotation control device  21  is assembled such that an output shaft  22  penetrates through a center hole  23   c  of a base  23  serving as a support member from a right side, and such that the pinion gear  18  protrudes from a left side surface of the base  23 . The base  23  is fixed to the side frame  13  in a state in which the pinion gear  18  penetrates through the through hole  13   a  of the side frame  13 . 
     A right side surface of the base  23  is formed into a circular container shape as a whole by punching at left side to form a guide recessed portion  23   b  so as to accommodate a disc-shaped rotating plate  31 . Internal teeth  34  are formed on an inner peripheral surface of the guide recessed portion  23   b  to mesh with four pawls  32 ,  33  to-be-described below. A spline hole  31   b  is formed at the center of the rotating plate  31  and fitted to a spline  22   b  formed on the output shaft  22 . Therefore, the rotating plate  31  is rotated in synchronization with the output shaft  22 . Here, the rotating ring  31  corresponds to a “rotating member” of the present disclosure. 
     On an outer peripheral part of a right side surface of the rotating plate  31 , two protrusions  31   d  are formed on an upper side and a lower side, respectively, and each protrusion  31   d  protrudes in a pin shape. Two pairs of upper and lower protrusions  31   e  (i.e. a total of four) are formed on a front side and a rear side, respectively, and each protrusion  31   e  protrudes in a pin shape. The protrusions  31   e  are rotatably fitted into through holes  32   a ,  33   a  of the pawls  32 ,  33 . The pawls  32 ,  33  are swingable about the protrusions  31   e . Winding portions  35   a  of torsion springs  35  are fitted to the protrusions  31   d . Each end portion  35   b  of the torsion springs  35  is engaged with each of the pawls  32 ,  33 , and urges each of the pawls  32 ,  33  toward an outer peripheral side of the rotating plate  31 . For this reason, engaging end portions  32   c ,  33   c  forming external teeth of the pawls  32 ,  33  are always meshed with the internal teeth  34  of the base  23 . 
     A plate-shaped outer lever  41  constitutes an outer side member of an input member N having an inner and outer double-structure. The plate-shaped outer lever  41  is coupled to the operation handle  20  and rotationally operated. The plate-shaped outer lever  41  is provided on a right side surface of a cover  24 . The cover  24  is formed in a container shape that bulges rightward as a whole. A round bar-shaped end portion  22   c  forming a right end portion of the output shaft  22  penetrates through a through hole  24   e  in the center of the cover  24  and is inserted into a center hole  41   b  of the outer lever  41  from the left side. By the insertion, the outer lever  41  is supported so as to be rotatable around the end portion  22   c  of the output shaft  22  with respect to the cover  24 . A plate-shaped inner lever  53  constitutes an inner side member of the input member N. A pair of stopper pins  53   a  protrude in a right direction (thrust direction) from the plate-shaped inner lever  53 . The pair of stopper pins  53   a  are inserted from the left side into a pair of arc-shaped through holes  24   a  formed in the cover  24  and a pair of round-hole-shaped through holes  41   a  formed in the outer lever  41 . 
     Each of the pair of stopper pins  53   a  is inserted into the inner lever  53  from the right direction and is integrally crimped. Each of the pair of stopper pins  53   a  is passed through the corresponding through hole  24   a  of the cover  24  from the left side. Each of the pair of stopper pins  53   a  is inserted into corresponding through hole  41   a  of the outer lever  41  that is set in a superposed manner on the right side surface of the cover  24 , and is integrally coupled to the outer lever  41 . 
     By the above-described coupling, the inner lever  53  and the outer lever  41  are integrally assembled in a state in which the inner lever  53  and the outer lever  41  are rotatable around the output shaft  22  with respect to the cover  24 . At a lower portion of the outer lever  41 , an engaging piece  42  which is bent to the left side is formed. The engaging piece  42  is arranged on an outer peripheral side of an engaging piece  24   b  cut and raised to the right side from the lower part of the cover  24 . 
     Each end portion  43   a  of a ring-shaped torsion spring  43  is hooked between the engaging pieces  42  and  24   b . For this reason, when the outer lever  41  is rotated by the operation handle  20 , the engaging piece  42  moves so as to be separated from the engaging piece  24   b  in a rotational direction. When the rotation operation is released, by an urging force of the torsion spring  43 , the engaging piece  42  and the engaging piece  24   b  return to a state of overlapping each other in the rotational direction, and the outer lever  41  is returned to the neutral position at which the outer lever  41  is positioned before the rotation operation. 
     Further, on the left side of the cover  24 , the inner lever  53  and a temporary holding member  54  are provided so as to be accommodated in the container shape of the cover  24 . The cover  24  sandwiches these components together with the rotating plate  31  and a rotation transmission plate  36 , and is fixed to the base  23 . At this time, leg portions  24   d  of the cover  24  are fixed to through holes  23   a  of the base  23  by rivets (not shown). 
     Rising-up portions  24   c  protruding leftward are formed at two front-rear places on an upper portion of the cover  24 . The rising-up portion  24   c  is formed by cutting and raising a partial region of the cover  24  from the inner peripheral side to the left side. The rising-up portions  24   c  are formed in a curved plate shape that is curved in an arc of the same circle drawn around the center of the cover  24 . As to be described below in  FIGS. 18 and 24 , when the inner lever  53  is turned clockwise (see  FIG. 18 ) or counterclockwise (see  FIG. 24 ) by the operation of the operation handle  20 , these rising-up portions  24   c  function such that one of the pair of feed pawls  52  attached to the inner lever  53 , which does not perform the feed function, ride onto the rising-up portion  24   c  and the feed pawl  52  moves out of mesh with internal teeth  51  of the rotation transmission plate  36 . 
     As shown in  FIGS. 34 to 37 , the temporary holding member  54  is set on a right side surface of the rotation transmission plate  36  to-be-described-below. Temporary holding member  54  holds the pair of feed pawls  52  and a torsion spring  55  in a state in which the pair of feed pawls  52  and the torsion spring  55  are positioned with respect to the rotation transmission plate  36 . The torsion spring  55  is urged in the direction of meshing these feed pawls  52  with the internal teeth  51  of the rotation transmission plate  36 . The internal teeth  51  of the rotation transmission plate  36  and the internal teeth  34  of the base  23  have the same number of teeth. 
     As shown in  FIG. 34 , a cylindrical shaft support portion  54   b  formed at a central part of the temporary holding member  54  is passed through the end portion  22   c  on a right side of the output shaft  22  that is passed through a center hole  36   d  of the rotation transmission plate  36  from the left side, and thus the cylindrical shaft support portion  54   b  is set on the right side surface of the rotation transmission plate  36 . With this set, the temporary holding member  54  is supported to be rotatable around the end portion  22   c  of the output shaft  22  with respect to the rotation transmission plate  36 . 
     The temporary holding member  54  further includes a feed pawl holding portion  54   a  protruding radially outward from a partial region in a rotational direction of the shaft support portion  54   b . The temporary holding member  54  holds the pair of feed pawls  52  on respective side surfaces in a rotational direction of the feed pawl holding portion  54   a  protruding radially outward. Specifically, the feed pawl holding portion  54   a  includes a pair of rotation receiving surfaces  54   a   1  recessed in a concave curved shape on side surfaces in the rotational direction of the feed pawl holding portion  54   a.    
     The feed pawl holding portion  54   a  applies the outer peripheral surface on a hinge portion  52   b  side of each feed pawl  52  to each rotation receiving surface  54   a   1  recessed in the concave curved surface shape, and guides each feed pawl  52  to slide and rotate radially inward and outward along a concave curved surface of each rotation receiving surface  54   a   1  (see  FIG. 35 ). Specifically, each feed pawl  52  is set in a state in which an outer peripheral surface of an arc shape curved around the hinge portion  52   b  thereof is applied to each rotation receiving surface  54   a   1 , and is guided so as to be capable of sliding and rotating radially inward and outward around the hinge portion  52   b  which is the rotation center thereof along each rotation receiving surface  54   a   1  (each feed pawl  52 ). 
     Therefore, after setting the pair of feed pawls  52  on the respective rotation receiving surfaces  54   a   1  of the temporary holding member  54 , by sliding and rotating the pair of feed pawls  52  radially outward along respective rotation receiving surfaces  54   a   1 , the pair of feed pawls  52  can be set in a state in which engaging end portions  52   a  forming external teeth thereof are meshed with the internal teeth  51  of the rotation transmission plate  36 . Then, after the setting, as shown in  FIG. 36 , by applying the torsion spring  55  between the end portion  22   c  of the output shaft  22  through which the shaft support portion  54   b  of the temporary holding member  54  is passed and the pair of feed pawls  52 , the pair of feed pawls  52  can be pressed against the internal teeth  51  of the rotation transmission plate  36  by a spring urging force of the torsion spring  55  and can be held in a state of being meshed with the internal teeth  51 . 
     In the torsion spring  55 , a winding portion  55   a  wound in a circular shape at the center thereof is passed through the end portion  22   c  of the output shaft  22 , and end portions  55   b  extending from the winding portion  55   a  are set so as to be pushed against the inner peripheral surfaces of the pair of feed pawls  52  respectively. Accordingly, the torsion spring  55  is set in a state of applying the urging force to mesh the pair of feed pawls  52  with the internal teeth  51  of the rotation transmission plate  36  with the output shaft  22  as a fulcrum. 
     With the above set, as shown in  FIG. 37 , the pair of feed pawls  52  are brought into a state of being fitted to positions where the inner lever  53  can be inserted from the right side thereof. Specifically, the inner lever  53  is assembled to the pair of feed pawls  52  set as described above such that the end portion  22   c  of the output shaft  22  is passed into the center hole  53   d  from a right side of the rotation transmission plate  36 . Accordingly, the hinge portions  52   b  protruding in a pin shape from the right side surface of the feed pawls  52  can be assembled by being inserted into two through holes  53   b  that penetrate the inner lever  53  and that are formed in a round hole shape respectively. The pair of feed pawls  52  are connected to the inner lever  53  in a state in which the pair of feed pawls  52  can rotate around the hinge portions  52   b  by inserting the corresponding through holes  53   b  of the inner lever  53  into the hinge portions  52   b.    
     Therefore, since the temporary holding member  54  sets (temporarily holding) the pair of feed pawls  52  and the torsion spring  55  to the rotation transmission plate  36 , it is possible to simply connect the inner lever  53  to the pair of feed pawls  52  placed on the rotation transmission plate  36  without requiring a holding operation such as pressing the feed pawls  52  urged by the torsion spring  55  by hands. The temporary holding member  54  is made of resin, and the inner lever  53  is connected to the pair of feed pawls  52 , so that the temporary holding member  54  is connected to the inner lever  53  via the pair of feed pawls  52  so as to be integrally rotatable with the inner lever  53 . Incidentally, all of the components of the rotation control device  21  other than the temporary holding member  54  are made of a metal member. 
     As shown in  FIG. 9 , the temporary holding member  54  further includes a spacer portion  54   c  that protrudes in a fan shape outward in the radial direction from a partial region. The partial region faces, in the rotational direction, a region at which the feed pawl holding portion  54   a  of the shaft support portion  54   b  is formed. The spacer portion  54   c  is interposed in the thrust direction between the set rotation transmission plate  36  and a facing portion  53   e  of the inner lever  53 , and ensures a space in the thrust direction therebetween. By interposing the spacer portion  54   c , the inner lever  53  can be smoothly rotated with respect to the rotation transmission plate  36 . 
     As shown in  FIG. 9 , the inner lever  53  has a configuration in which round-pin-shaped stopper pins  53   a  are respectively coupled to two front-rear places on the facing portion  53   e  having a substantially disc shape that faces the thrust direction. Each stopper pin  53   a  protrudes rightward from the facing portion  53   e  of the inner lever  53  and is inserted into corresponding through hole  41   a  of the outer lever  41  by passing through the corresponding through hole  24   a  of the cover  24 , so as to be integrally coupled to the outer lever  41 . 
     Each of the through holes  24   a  of the cover  24  is formed into a hole shape extending in a long shape in the rotational direction. As shown in  FIG. 29 , when the inner lever  53 , which is the input member N, is in the neutral position at which the inner lever  53  is positioned before the operation, the respective through holes  24   a  position the respective stopper pins  53   a  at central positions in the rotational direction of the through holes  24   a . When the inner lever  53  is pushed down from the neutral position as shown in  FIG. 30 , each stopper pin  53   a  abuts on an end surface of each through hole  24   a  corresponding to the rotational direction, and a rotational movement of the inner lever  53  (input member N) in a pushed-down direction is locked. Further, when the inner lever  53  is pulled up from the neutral position as shown in  FIG. 31 , each stopper pin  53   a  abuts on the end surface of each through hole  24   a  corresponding to the rotational direction, and the rotational movement of the inner lever  53  (the input member N) in a pulling direction is locked. 
     The pair of feed pawls  52  are rotatably assembled to a left side surface of the inner lever  53 . The substantially disc-shaped rotation transmission plate  36  is provided on a left side of the inner lever  53 . The rotation transmission plate  36  is disposed between the inner lever  53  and the rotating plate  31 . A substantially disc-shaped control plate  56  is assembled to a left side surface portion of the rotation transmission plate  36  in a shape of being integrated with the rotation transmission plate  36  in the rotational direction. 
     The control plate  56  is assembled to the left side surface portion of the rotation transmission plate  36  in the shape of being integrated with the rotation transmission plate  36  in the rotational direction. Specifically, a spline fitting portion  36   a  which is half-cut to protrude in a substantially cylindrical shape to the left side from the central part of the rotation transmission plate  36  is fitted into a spline hole  56   a  formed to penetrate through the central part of the control plate  56 , so that the control plate  56  is assembled to the rotation transmission plate  36  in an integrated state in the rotational direction. 
     On an outer peripheral part of the control plate  56 , each of the pins  32   b ,  33   b  protruding rightward from each of the pawls  32 ,  33  is received from the left side, and control holes  56   b  for controlling the operation of locking and releasing the pawls  32 ,  33  are formed at four places in the rotational direction. Further, engagement long holes  56   c  are formed on a disc surface portion of the control plate  56  at two places facing each other in the rotational direction so as to receive the respective protrusions  31   d  protruding in a pin shape from two corresponding places of the rotating plate  31  to the right side. 
     The engagement long hole  56   c  is formed into a long hole shape extending in the rotational direction. As shown in  FIG. 17 , when a rotation position of the control plate  56  (rotation transmission plate  36 ) with respect to the rotating plate  31  is held at the neutral position by the urging of a torsion spring  37  hooked between the rotation transmission plate  36  and the rotating plate  31 , the protrusions  31   d  of the rotating plate  31  are positioned at substantially central positions of the engagement long holes  56   c  in the long hole shape, respectively. Accordingly, the engagement long holes  56   c  allow the control plate  56  (rotation transmission plate  36 ) to rotate in the forward and reverse directions with respect to the rotating plate  31  from the above state. 
     However, as shown in  FIGS. 21 and 26 , the control plate  56  (rotation transmission plate  36 ) is rotated clockwise (see  FIG. 21 ) or counterclockwise (see  FIG. 26 ) with respect to the rotating plate  31  by the operation of the operation handle  20 , so that each engagement long hole  56   c  makes each protrusion  31   d  abut on an end surface corresponding to a rotational direction thereof. Accordingly, the rotating plate  31  is turned integrally with the control plate  56  (rotation transmission plate  36 ) in the rotational direction. 
     The ring-shaped torsion spring  37  hooked between the rotation transmission plate  36  and the rotating plate  31  is inserted across a long hole  36   c  of the rotation transmission plate  36  and a long hole  31   c  of the rotating plate  31  by bending the end portions  37   a  on both sides of the torsion spring  37  to the left side. Accordingly, the torsion spring  37  is in a state of exerting an urging force in both rotational directions across the long holes  36   c  and  31   c . The torsion spring  37  maintains a rotation angle of the rotation transmission plate  36  at the neutral position with respect to the rotating plate  31  by the urging force of the torsion spring  37 . 
     Here,  FIGS. 9 and 10  show a state in which the components of the rotation control device  21  are disassembled apart. Further,  FIGS. 11 and 12  show a state in which the pawls  32 ,  33  and the torsion springs  35  are assembled to the rotating plate  31 , the feed pawls  52  and the torsion springs  55  are assembled to the inner lever  53 , and the torsion spring  43  is assembled to the cover  24 . Further,  FIGS. 13 and 14  show a state in which the rotating plate  31  is assembled to the base  23  and the control plate  56  is assembled to the rotation transmission plate  36 . 
     Further,  FIG. 15  shows a state in which the rotation transmission plate  36  is assembled to the rotating plate  31  (see  FIG. 13 ) assembled to the base  23 , and the feed pawls  52  and the inner lever  53  are assembled to the rotation transmission plate  36 . Each of the above drawings does not show an assembling procedure of the rotation control device  21 , but shows an assembled state of the respective components. In practice, the rotation control device  21  is configured such that the components shown in  FIG. 9  are set and assembled in the direction of gravity from the left side shown in  FIG. 9 . 
     Here, as shown in  FIG. 9 , a feed portion A, which transmits the rotation of the inner lever  53  (input member N) to the output shaft  22  as feeding rotation, is configured by the pair of feed pawls  52  that are connected to the inner lever  53  (input member N) and transmit the rotationally operated movement to the rotation transmission plate  36  as feeding rotation, the rotation transmission plate  36  that rotates in response to transmission of rotational power from the feed pawls  52 , the control plate  56  that is integrally connected to the rotation transmission plate  36 , and the rotating plate  31  that rotates integrally with the control plate  56  from a half way by engagement with the control plate  56  (rotation transmission plate  36 ). Further, a lock portion B is a lock structure which locks the rotation of the pinion gear  18  feeding-rotated by the feed portion A with respect to the base  23  by the urging of the pawls  32 ,  33 . Further, a support member S is configured by the base  23  and the cover  24  that is integrally assembled to the base  23 . 
     An outer peripheral surface  22   a  that is curved concentrically without a gear shape is formed between the pinion gear  18  and the spline  22   b  of the output shaft  22 . A rotation shaft side protrusion  63  partially protruding outward in the radial direction is formed in a partial region of the outer peripheral surface  22   a  in the rotational direction. The rotation shaft side protrusion  63  is set on a right side surface of the guide recessed portion  23   b  of the base  23  by inserting the pinion gear  18  into the center hole  23   c  of the base  23  from the right side. 
     An arc-shaped support member side protrusion  61  is formed on the right side surface of the guide recessed portion  23   b  of the base  23  by punching. On the other hand, as shown in  FIG. 10 , a sliding surface portion  31   a  that forms a cylindrical inner peripheral surface is formed around the spline hole  31   b  of the rotating plate  31 . The sliding surface portion  31   a  is formed when the central portion of the rotating plate  31  is half-cut into a cylindrical shape to the right side. The sliding surface portion  31   a  is set to be concentric with the spline hole  31   b . When the rotating plate  31  rotates with respect to the base  23 , an outer periphery of the support member side protrusion  61  slides on an inner periphery of the sliding surface portion  31   a . An engaging piece  62  is disposed so as to slide in a gap between the inner periphery of the sliding surface portion  31   a  and the outer peripheral surface  22   a  of the output shaft  22 . 
     Therefore, when the output shaft  22  is rotated in a downward direction by the operation of the rotation control device  21  and reaches a lower limit position as shown in  FIG. 32 , the rotation shaft side protrusion  63  abuts on an end surface of the support member side protrusion  61  with the engaging piece  62  sandwiched therebetween, and further rotation of the output shaft  22  is stopped. Further, when the output shaft  22  is rotated in an upward direction by the operation of the rotation control device  21  and reaches an upper limit position as shown in  FIG. 33 , the rotation shaft side protrusion  63  abuts on an end surface on the opposite side of the support member side protrusion  61  with the engaging piece  62  sandwiched therebetween, and further rotation of the output shaft  22  is stopped. A mechanism for stopping the rotation of the output shaft  22  by making the rotation shaft side protrusion  63  abut on the support member side protrusion  61  in the rotational direction with the engaging piece  62  sandwiched therebetween is configured as a stopper  60 . 
     As shown in  FIG. 9 , a friction generating portion  57  is provided between the base  23  and the cover  24  which form the support member S and the rotating plate  31  to apply a sliding frictional resistance force to the rotational movement of the rotating plate  31  with respect to the support member S. The friction generating portion  57  includes: a ring-shaped guide member  57   c  provided on a left side surface portion of the cover  24 ; three clutch portions  57   a  provided, in a state of being guided, at three places of the guide member  57   c  in the rotational direction; a ring shaped leaf spring  57   b  provided on a left side of the guide member  57   c  and having a ring shape bent into a waveform having substantially the same diameter; and rotating rings  57   d  and fixed rings  57   e  which have substantially the same diameter and which are provided on a left side of the leaf spring  57   b . The leaf spring  57   b  corresponds to an “elastic body” of the present disclosure. 
     The guide member  57   c  is slidably assembled to the left side surface portion of the cover  24  only in the thrust direction. Specifically, round-pin-shaped engaging protrusions  57   c   1  protruding from two left-right places on a right side surface of the guide member  57   c  are inserted into round-hole-shaped engaging holes  24   f  formed at two corresponding places of the cover  24  from the left side. Accordingly, the guide member  57   c  is assembled in a state in which the guide member  57   c  is movable integrally with the cover  24  in the rotational direction and the radial direction, but the guide member  57   c  is assembled in a state in which the guide member  57   c  is slidable in the thrust direction with respect to the cover  24 . 
     The three clutch portions  57   a  are set in corresponding inclined concave surfaces  57   c   2  formed at three places of the right side surface portion of the guide member  57   c  in the rotational direction. As shown in  FIG. 38 , each clutch portion  57   a  is disposed between each inclined concave surface  57   c   2  formed on the right side surface portion of the guide member  57   c  and a left side surface of the cover  24  in the thrust direction. Accordingly, each clutch portion  57   a  is supported by each inclined concave surface  57   c   2  of the guide member  57   c  from both sides in the rotational direction so as to be slidable only in the radial direction oblique to the thrust direction along an inclined direction of each inclined concave surface  57   c   2 . The above-described substantially disc-shaped inner lever  53  is disposed on a radially inner side of each clutch portion  57   a . Here, the inner lever  53  corresponds to a “rotating cam” of the present disclosure. 
     As shown in  FIG. 9 , the inner lever  53  has relief surfaces  53   f  partially recessed radially inward and rising-up surfaces  53   g  bulge radially outward at three places of an outer peripheral surface of the inner lever  53  in the circumferential direction. The relief surfaces  53   f  and rising-up surfaces  53   g  are arranged in the rotational direction. The relief surfaces  53   f  and the rising-up surface  53   g  are formed into arc shapes concentric with each other and drawn around the center of the inner lever  53 . A step surface between the relief surface  53   f  and the rising-up surfaces  53   g  is an inclined surface  53   h  that connects the two surfaces in an inclined manner instead of a right angle. 
     As shown in  FIGS. 16 and 38 , when the inner lever  53  is in the neutral position at which the inner lever  53  is positioned before the operation, each of the clutch portions  57   a  is located at a boundary with the inclined surface  53   h  on the corresponding relief surface  53   f  on the outer peripheral surface of the inner lever  53 . As shown in  FIG. 24 , even if the inner lever  53  is turned from the neutral position in the direction of rotating the output shaft  22  upward, each of the clutch portions  57   a  slides on the corresponding relief surface  53   f  of the inner lever  53  and is not changed to a position in the corresponding inclined concave surface  57   c   2  of the guide member  57   c  (friction-suppression state P 1 : see  FIG. 38 ). 
     However, as shown in  FIG. 18 , when the inner lever  53  is turned from the neutral position in the direction of rotating the output shaft  22  downward, each of the clutch portions  57   a  slides from the corresponding inclined surface  53   h  of the inner lever  53  onto the rising-up surface  53   g  and is pushed radially outward along the corresponding inclined concave surface  57   c   2  of the guide member  57   c  simultaneously (friction-on state P 2 : see  FIG. 39 ). 
     Accordingly, each clutch portion  57   a  presses the guide member  57   c  to the left side (thrust direction) and presses the guide member  57   c  against the leaf spring  57   b  with a contact point pressed against the left side surface of the inner lever  53  as a fulcrum. The leaf spring  57   b  pressed to the left side is pressed against the rotating ring  57   d  provided on the left side of the leaf spring  57   b . Further, the pressed rotating ring  57   d  is pressed against the fixed ring  57   e  provided on the left side of the rotating ring  57   d . The rotating ring  57   d  is integrally connected to the rotating plate  31  in the rotational direction, and the fixed ring  57   e  is integrally connected to the base  23  (support member S) in the rotational direction. Therefore, by the above-described pressing, the sliding frictional resistance force is applied to the rotational movement of the rotating plate  31  with respect to the base  23 . 
     As shown in  FIG. 9 , the three rotating rings  57   d  are arranged in the thrust direction, and the two fixed rings  57   e  are arranged in the thrust direction so as to be sandwiched between the rotating rings  57   d  one by one. The rotating ring  57   d  is assembled to a right side surface portion of the rotating plate  31  so as to be slidable only in the thrust direction. Specifically, each of the left two rotating rings  57   d  has round-hole-shaped first engaging holes  57   d   1  formed in pieces which protrude radially inward from the inner peripheral edge portion at two upper-lower places. The respective first engaging holes  57   d   1  are inserted from the right side into respective round-pin-shaped first engagement pins  31   f  protruding to the right side from the two corresponding places of the rotating plate  31 . Accordingly, the left two rotating rings  57   d  are assembled in a state in which the left two rotating rings  57   d  are movable integrally with the rotating plate  31  in the rotational direction and the radial direction, but the left two rotating rings  57   d  are assembled in a state in which the left two rotating rings  57   d  are slidable in the thrust direction with respect to the rotating plate  31 . 
     Further, the remaining right rotating ring  57   d  has round-hole-shaped second engaging holes  57   d   2  formed in pieces which protrude radially inward from the inner peripheral edge portion at two upper-lower places of the remaining right rotating ring  57   d . The second engaging holes  57   d   2  are inserted from the right side into respective round-pin-shaped second engagement pins  31   g  protruding to the right side from the two corresponding places of the rotating plate  31 . Accordingly, the right rotating ring  57   d  is also assembled in a state in which the right rotating ring  57   d  is movable integrally with the rotating plate  31  in the rotational direction and the radial direction, but the right rotating ring  57   d  is assembled in a state in which the right rotating ring  57   d  is slidable in the thrust direction with respect to the rotating plate  31 . 
     The first engagement pin  31   f  and the second engagement pin  31   g , which are formed on the rotating plate  31 , are formed at positions shifted from each other in the rotational direction. Each second engaging hole  57   d   2 , which is formed in the right rotating ring  57   d  and is inserted into each second engagement pin  31   g , is formed in each crank-shaped piece bent leftward and protruding radially inward from the inner peripheral edge portion of the same rotation ring  57   d . With such a configuration, the protruding lengths of the first engaging pin  31   f  and the second engaging pins  31   g  protruding rightward from the rotating plate  31  are differentiated and shortened. 
     On the other hand, the two fixed rings  57   e  are assembled to an outer peripheral edge portion of the base  23  in a state in which each fixed rings  57   e  is slidable only in the thrust direction with respect to an outer peripheral edge portion of the base  23 . Specifically, an engaging pawl  57   e   1  protruding from the outer peripheral edge portion at each of four places in the rotational direction of the fixed ring  57   e  to the left side in a curved shape is inserted from the right side into each engaging groove  23   d  formed on the outer peripheral edge portion of the base  23  at each of the four corresponding places. Accordingly, the fixed ring  57   e  is assembled in a state in which the fixed ring  57   e  is movable integrally with the base  23  in the rotational direction and the radial direction, but the fixed ring  57   e  is assembled in a state in which the fixed ring  57   e  is slidable with respect to the base  23  in the thrust direction. 
     When the rotating ring  57   d  and the fixed ring  57   e  are subjected to a pressing force from the right side by the leaf spring  57   b , the rotating ring  57   d  slides leftward with respect to the rotating plate  31  and the fixed ring  57   e  slides leftward with respect to the base  23 . Accordingly, the rotating ring  57   d  and the fixed ring  57   e  are pressed against each other in the thrust direction so as to be overlapped. Then, the leftmost rotating ring  57   d  is pressed against the right side surface on an outer peripheral side of the internal teeth  34  of the base  23 . Therefore, when the rotating plate  31  is turned from the above state in the direction of rotating the output shaft  22  downward, the sliding frictional resistance force is applied to the rotational movement of the rotating plate  31  with respect to the base  23  by: a force with which the leaf spring  57   b  is pressed against the right rotating ring  57   d ; a force with which each rotating ring  57   d  and each fixed ring  57   e  are pressed against each other in the thrust direction; and a force with which the left rotation ring  57   d  is pressed onto the right side surface of the base  23 . 
     The sliding frictional resistance force can be obtained as a force for rubbing the plurality of rotating rings  57   d  and fixed rings  57   e  in a stacked manner by an elastic force exerted by one leaf spring  57   b . Therefore, a large sliding frictional resistance force corresponding to the set number of the rotating rings  57   d  can be obtained by setting one leaf spring  57   b . As shown in  FIG. 16 , when the inner lever  53  is in the neutral position at which the inner lever  53  is positioned before the operation, each clutch portion  57   a  is set to the friction-suppression state P 1  in which the clutch portion  57   a  is not pressed radially outward by the inner lever  53 . In this state, as shown in  FIG. 38 , although the guide member  57   c  guiding each clutch portion  57   a  is not pushed in the thrust direction by each clutch portion  57   a , there is a gap T (see  FIG. 7 ) in the thrust direction between the guide member  57   c  and the left side surface of the cover  24  via each clutch portion  57   a.    
     That is, the guide member  57   c  is set to have the gap T in the thrust direction between the guide member  57   c  and the left side surface of the cover  24  even in the friction-suppression state P 1 , that is, even in the state in which the elastic force in the thrust direction caused by the leaf spring  57   b  is not affected. Accordingly, in the friction-suppression state P 1 , the guide member  57   c  is less likely to generate abnormal noise due to rubbing or hitting against the left side surface of the cover  24 . Further, as shown in  FIG. 39 , even when each clutch portion  57   a  is pushed outward in the radial direction and switched to the friction-on state P 2 , each clutch portion  57   a  is pushed in the thrust direction between the guide member  57   c  and the left side surface of the cover  24 , so that there is the gap T in the thrust direction between the guide member  57   c  and the left side surface of the cover  24 . Accordingly, even in the friction-on state P 2 , the guide member  57   c  is less likely to generate abnormal noise due to rubbing or hitting against the left side surface of the cover  24 . 
     As shown in  FIG. 10 , the guide member  57   c  has a flange portion  57   c   3  protruding from the ring-shaped inner peripheral edge of the guide member  57   c  to the left side in a substantial cylindrical shape. The flange portion  57   c   3  is set inside the ring of the leaf spring  57   b . The flange portion  57   c   3  supports the leaf spring  57   b  from the inner peripheral side, and holds the leaf spring  57   b  in a position concentric with the guide member  57   c . The leaf spring  57   b  is connected to the guide member  57   c  in a state in which the leaf spring  57   b  is movable in the rotational direction integrally with the guide member  57   c . Specifically, a locking pawl  57   b   1  protruding radially inward from an inner peripheral edge portion of the plate spring  57   b  is fitted into a locking hole  57   c   4  formed at a corresponding place of the flange portion  57   c   3  of the guide member  57   c , so that the leaf spring  57   b  is connected to the guide member  57   c  in a state in which the leaf spring  57   b  is movable in the rotational direction integrally with the guide member  57   c . Accordingly, since the leaf spring  57   b  does not rotate and the frictional resistance force exerted by the leaf spring  57   b  hardly changes, the operation feeling of the operation handle  20  can be kept constant. 
     &lt;Operation of Rotation Control Device  21  (Operation Handle  20  is not Operated)&gt; 
     Hereinafter, a height adjustment operation of the seat cushion  2  performed by the rotation control device  21  is described with reference to  FIGS. 16 to 28 . 
       FIGS. 16 and 17  show a state of the neutral position in which the operation handle  20  is not operated, and in which the outer lever  41  and the inner lever  53 , which constitute the input member N, are not rotated. At this time, as shown in  FIG. 16 , the engaging end portion  52   a  forming the external teeth of the feed pawl  52  is meshed with the internal teeth  51  of the rotation transmission plate  36  by the urging of the torsion spring  55 . Further, as shown in  FIG. 17 , the engaging end portions  32   c ,  33   c  respectively forming the external teeth of the pawls  32 ,  33  are engaged with the internal teeth  34  of the base  23  by the urging of the torsion springs  35 . Therefore, the rotation of the rotating plate  31  is locked via the engagement of the pawls  32 ,  33 , and the height of the seat  1  is not changed on a raised side and a lowered side. Further, each clutch portion  57   a  is located on the corresponding relief surface  53   f  of the inner lever  53 , so that the friction-suppression state P 1  that suppresses the occurrence of friction is set. 
     &lt;Operation of Rotation Control Device  21  (Operation Handle  20  is Pushed Down)&gt; 
       FIGS. 18 and 21  show a state in which the operation handle  20  is pushed down from the neutral position. At this time, as shown in  FIG. 18 , the inner lever  53  is rotated in an arrow direction by the rotation of the outer lever  41 . As a result, each feed pawl  52  is moved in the same direction. Therefore, the engaging end portion  52   a  forming the external teeth of the front feed pawl  52  transmits a force to the internal teeth  51  of the rotation transmission plate  36  to push and turn the rotation transmission plate  36  in the arrow direction. At this time, the engaging end portion  52   a  forming the external teeth of the rear feed pawl  52  is not meshed with the internal teeth  51  of the rotation transmission plate  36 . That is, with the rotation of the rotation transmission plate  36 , the rear feed pawl  52  rides on the rising-up portion  24   c  on the rear side, and the engaging end portion  52   a  is moved out of mesh with the internal teeth  51 . 
     When the inner lever  53  is turned as described above, each clutch portion  57   a  rides on the corresponding rising-up surface  53   g  of the inner lever  53  and is switched to the friction-on state P 2 . At this time, as shown in  FIG. 19 , the pawls  32 ,  33  are still held in a state of being meshed with the internal teeth  34  of the base  23 . Then, when the rotation transmission plate  36  is further turned by the inner lever  53  from the above state, as shown in  FIG. 20 , the control hole  56   b  of the control plate  56  integrated with the rotation transmission plate  36  is engaged with the pin  33   b  of the two pawls  33  at a diagonal position to push and turn the engaging end portion  33   c  of each pawl  33  inward in the radial direction such that the engaging end portion  33  is moved out of mesh with the internal teeth  34  of the base  23 . 
     Specifically, when the rotation transmission plate  36  is in the neutral position by the urging of the torsion spring  37  with respect to the rotation plate  31  as shown in  FIG. 17 , the four control holes  56   b  formed in the control plate  56  are positioned as follows with respect to the pins  32   b ,  33   b  of the pawls  32 ,  33 . That is, the two corresponding control holes  56   b , into which the pins  32   b  of the two pawls  32  in the diagonal positions are inserted, are positioned at positions deviated in the rotational direction with inclined side surfaces facing the rotational direction of the pins  32   b  approaching an illustrated counterclockwise direction. Further, the two corresponding control holes  56   b , into which the pins  33   b  of the two pawls  33  in the diagonal positions different from the above are inserted, are positioned at positions deviated in the rotational direction with inclined side surfaces facing the rotational direction of the pins  33   b  approaching an illustrated clockwise direction. 
     With such a configuration, by turning the rotation transmission plate  36  from the neutral position described above in the clockwise direction as shown in  FIG. 20 , the inclined side surfaces of the two control holes  56   b , into which the pins  33   b  of the two pawls  33  in the diagonal positions are inserted, are made to abut on the two pins  33   b , and are made to slide the pins  33   b  inward in the radial direction along the inclined side surfaces of the control holes  56   b  with progress of the rotation. Then, the engaging end portion  33   c  of each pawl  33  is moved out of mesh with the internal teeth  34  of the base  23  while keeping the engaging end portions  32   c  of the other two pawls  32  in a state of being meshed with the internal teeth  34  of the base  23 . 
     Accordingly, the lock state of the rotating plate  31  in the downward rotational direction is released. Thereafter, when the protrusion  31   d  of the rotating plate  31  abuts on the end portion of the engagement long hole  56   c  of the control plate  56 , the rotation of the rotation transmission plate  36  is in a state of being transmitted to the rotating plate  31 . Therefore, as shown in  FIG. 21 , the rotating plate  31  is feeding-rotated with respect to the base  23  in the illustrated clockwise direction in which the rotation transmission plate  36  is feeding-rotated, so that the output shaft  22  integrated with the rotating plate  31  can be integrally fed and rotated in the same direction. At this time, the engaging end portions  32   c  of the two pawls  33  at the other diagonal positions are not meshed with the internal teeth  34  of the base  23 . That is, in this state, the teeth of the engaging end portion  32   c  receive a load in a normal direction of the teeth of the internal teeth  34  and are moved in a direction to release meshing. Therefore, when the rotating plate  31  rotates, the engaging end portions  32   c  of the two pawls  32  are slid so as to slide on the internal teeth  34  of the base  23 . 
     When the feeding-rotation of the rotation plate  31  by the rotation transmission plate  36  is stopped and the operation handle  20  is returned to the neutral position as shown in  FIG. 22 , for the two pawls  33  which are released at the diagonal positions, as shown in  FIG. 23 , a release holding state of each pawl  33  is released by each control hole  56   b  of the control plate  56 , the control plate  56  (rotation transmission plate  36 ) is returned to the neutral position by the urging action of the torsion spring  37  with respect to the rotating plate  31 , and the engaging end portions  33   c  are meshed with the internal teeth  34  of the base  23 . Accordingly, the output shaft  22 , which rotates integrally with the rotating plate  31 , is returned to the state in which the rotation of the output shaft  22  with respect to the base  23  is stopped. When the operation handle  20  is returned to the neutral position, as shown in FIG.  16 , each clutch portion  57   a  is returned from the rising-up surface  53   g  of the inner lever  53  onto the relief surface  53   f , and becomes the friction-suppression state P 1 . 
     &lt;Operation of Rotation Control Device  21  (Operation Handle  20  is Pulled Up)&gt; 
       FIGS. 24 and 26  show a state in which the operation handle  20  is pulled up from the neutral position. At this time, as shown in  FIG. 24 , the inner lever  53  is rotated in the arrow direction by the rotation of the outer lever  41 . As a result, each feed pawl  52  is moved in the same direction. Therefore, the engaging end portion  52   a  forming the external teeth of the rear feed pawl  52  transmits a force to the internal teeth  51  of the rotation transmission plate  36  to push and turn the rotation transmission plate  36  in the arrow direction. At this time, the engaging end portion  52   a  forming the external teeth of the front feed pawl  52  is not meshed with the internal teeth  51  of the rotation transmission plate  36 . That is, with the rotation of the rotation transmission plate  36 , the front feed pawl  52  rides on the rising-up portion  24   c  at the front side, and the engaging end portion  52   a  is moved out of mesh with the internal teeth  51 . 
     When the inner lever  53  is turned as described above, each clutch portion  57   a  slides on the relief surface  53   f  of the inner lever  53  and is held in the friction-suppression state P 1 . Then, by the rotation of the rotation transmission plate  36 , as shown in  FIG. 25 , the control holes  56   b  of the control plate  56  integrated with the rotation transmission plate  36  are engaged with the pins  32   b  of the two pawls  32  at the diagonal positions while leaving the engaging end portions  33   c  of the two pawls  33  at other diagonal positions engaged with the internal teeth  34  of the base  23 , and the engaging end portions  32   c  of the two pawls  32  are pushed and turned inward in the radial direction so as to be moved out of mesh with the internal teeth  34  of the base  23 . 
     Accordingly, the locked state of the rotating plate  31  in the ascending rotational direction is released. Thereafter, when the protrusion  31   d  of the rotating plate  31  abuts on the end portion of the engagement long hole  56   c  of the control plate  56 , the rotation of the rotation transmission plate  36  is in the state of being transmitted to the rotating plate  31 . Therefore, as shown in  FIG. 26 , the rotating plate  31  is feeding-rotated with respect to the base  23  in the illustrated counterclockwise direction in which the rotation transmission plate  36  is feeding-rotated, so that the output shaft  22  integrated with the rotating plate  31  can be integrally fed and rotated in the same direction. At this time, the engaging end portions  33   c  of the two pawls  33  at the other diagonal positions are not meshed with the internal teeth  34  of the base  23 . That is, in this state, the teeth of the engaging end portion  33   c  receive a load in the normal direction of the internal teeth  34  and are moved in the direction to release meshing. Therefore, when the rotating plate  31  rotates, the engaging end portions  33   c  of the two pawls  33  are slid so as to slide on the internal teeth  34  of the base  23 . 
     When the feeding-rotation of the rotation plate  31  by the rotation transmission plate  36  is stopped and the operation handle  20  is returned to the neutral position as shown in  FIG. 27 , for the two pawls  32  which are released at the diagonal positions, as shown in  FIG. 28 , the release holding state of each pawl  32  is released by each control hole  56   b  of the control plate  56 , the control plate  56  (rotation transmission plate  36 ) is returned to the neutral position by the urging of the torsion spring  37  with respect to the rotating plate  31 , and the engaging end portions  32   c  are meshed with the internal teeth  34  of the base  23 . Accordingly, the output shaft  22  integrated with the rotating plate  31  is returned to the state in which the rotation of the output shaft  22  with respect to the base  23  is stopped. 
     When the engaging end portions  32   c ,  33   c  of the pawls  32 ,  33  are engaged with the internal teeth  34  of the base  23  as shown in  FIG. 17 , each of the pins  32   b ,  33   b  is positioned at an intermediate part in the radial direction between the protrusion  31   e , which is the rotation center of each of the pawls  32 ,  33  with respect to the rotating plate  31 , and a tooth tip of the internal teeth  34 . Accordingly, the pawls  32 ,  33  can be efficiently rotated inward in the radial direction with respect to the rotational movement amount of the rotation transmission plate  36 , and can be moved out of mesh with the internal teeth  34  of the base  23  (see  FIGS. 20 and 25 ). Therefore, it is possible to shorten a stroke required for the unlocking operation of each of the pawls  32 ,  33  accompanying the operation of the operation handle  20 . 
     &lt;Operation of Rotation Control Device  21 &gt; 
     As described above, when the operation handle  20  is pushed down, the seat  1  is lowered by the movement amount corresponding to the operation. By repeating the pushed-down operation, the seat  1  can be adjusted to a desired height. Conversely, when the operation handle  20  is pulled up, the seat  1  is similarly raised by the movement amount corresponding to the operation. By repeating the pulled-up operation, the seat  1  can be adjusted to a desired height. When the seat  1  reaches the lower limit position or the upper limit position by the above operation, the further rotation of the output shaft  22  is stopped as shown in  FIG. 32 or 33 . 
     Second Embodiment 
       FIGS. 40 to 43  illustrate a second embodiment of the present disclosure. A characteristic point of the second embodiment as compared to the first embodiment is that the configuration of the friction generating portion  57  of the rotation control device  21 , in particular, the configuration of the clutch portion  57   a  ( 157   a ) is changed. Other configurations are the same, and descriptions of the same parts are not repeated.  FIG. 40  shows only components that are changed in the second embodiment as compared to the first embodiment. Further, in  FIGS. 42 and 44 , regarding the inner lever  153 , only the outer shape that is changed in the second embodiment as compared to the first embodiment is shown, and the description of other shapes is omitted. 
     As shown in  FIGS. 40 to 43 , a guide member  157   c  has a circular ring shape, and engaging protrusions  157   c   1  are formed at three places on a right circumferential surface thereof at equal intervals. The engaging protrusion  157   c   1  is fitted into a through hole  124   f  of a cover  124  to fix a guide member  157   c  such that the guide member  157   c  does not move in a direction other than the thrust direction. Pressing surfaces  157   c   2  for pressing the leaf spring  57   b  are formed at three places on a left side surface of the guide member  157   c  opposite to the surface on which the engaging protrusions  157   c   1  are formed. The pressing surface  157   c   2  is formed to protrude leftward from a general surface of the guide member  157   c.    
     Clutch portions  157   a  are provided adjacent to the three engaging protrusions  157   c   1  respectively on the right side surface of the guide member  157   c . As shown in an enlarged view in  FIG. 41 , the clutch portion  157   a  is a member, which is rotatable around one end of the clutch portion  157   a , placed on the right side surface of the guide member  157   c  along a ring shape of the guide member  157   c . A protrusion  157   a   1  is formed on the clutch portion  157   a  to protrude rightward from the one end of the clutch portion  157   a  serving as a rotation center. As shown in a solid line in  FIG. 41  (a state in which the clutch portion  157   a  is separated from the guide member  157   c ), an abutting surface  157   a   3  is formed toward the right side surface of the guide member  157   c  at the other end (rotating end portion) of the clutch portion  157   a . Similarly to the engaging protrusion  157   c   1 , the protrusion  157   a   1  is fitted into the through hole  124   f  of the cover  124 , and the clutch portion  157   a  is rotatably supported around the protrusion  157   a   1 . A spiral surface  157   c   3  is formed on a portion of the right side surface of the guide member  157   c  on which the abutting surface  157   a   3  of the clutch portion  157   a  abuts. The spiral surface  157   c   3  is centered on the axis of the rotation shaft (protrusion  157   a   1 ) of the clutch portion  157   a . The spiral surface  157   c   3  is continuously bulged rightward from an inner peripheral side to an outer peripheral side of the guide member  157   c . A protruding portion  157   a   2  is formed on an inner peripheral side of the abutting surface  157   a   3  of the clutch portion  157   a , and the protruding portion  157   a   2  protrudes toward the inner peripheral side of the ring shape of the guide member  157   c  when the clutch portion  157   a  is placed along the ring shape of the guide member  157   c.    
     As shown in  FIGS. 42 and 43 , an inner lever  153  is provided on the inner peripheral side of the guide member  157   c , and rising-up surfaces  153   g  that protrude radially outward at three places in a peripheral direction are formed on an outer periphery of the inner lever  153 . The rising-up surface  153   g  of the inner lever  153  is disposed adjacent to the clutch portion  157   a  of the guide member  157   c  in the peripheral direction of the guide member  157   c . Therefore, as shown in  FIG. 44 , when the inner lever  153  is rotated in the direction of lowering the seat  1  (arrow direction), the protruding portion  157   a   2  of the clutch portion  157   a  is pressed outward in the radial direction of the guide member  157   c  by an outer circumferential surface of the rising-up surface  153   g  as shown by an arrow. Therefore, the guide member  157   c  is moved in the thrust direction of the output shaft  22  by the relative movement of the abutting surface  157   a   3  with respect to the spiral surface  157   c   3 , and functions to be pressed against the leaf spring  57   b . As a result, the friction generating portion  57  becomes the friction-on state P 2 . 
     According to the friction generating portion  57  of the second embodiment, since the movement locus of the clutch portion  157   a  is determined to be a rotational movement around the axis of the protrusion  157   a   1 , the clutch portion  157   a  does not move excessively during movement, and frictional resistance during movement is reduced. Therefore, an operation force for rotating the inner lever  153  is reduced. 
     &lt;Summary&gt; 
     In summary, the lifter device  10  according to the first embodiment has the following configuration. That is, a lifter device ( 10 ) includes: an output shaft ( 22 ) configured to rotate by receiving transmission of rotational power from an operation handle ( 20 ) and configured to raise and lower a seat ( 1 ); a support member (S) configured to support the output shaft ( 22 ) such that the output shaft ( 22 ) is rotatable; an input member (N) coupled to the operation handle ( 20 ) and configured to be operated to rotate around an axis of the output shaft ( 22 ); a feed portion (A) configured to transmit forward and reverse rotation of the input member (N) to the output shaft ( 22 ); a lock portion (B) configured to lock the rotation of the output shaft ( 22 ) with respect to the support member (S); and a friction generating portion ( 57 ) configured to apply a frictional force to the rotation of the output shaft ( 22 ). 
     The friction generating portion ( 57 ) includes: an elastic body ( 57   b ) provided between the output shaft ( 22 ) and the support member (S); a rotating cam ( 53 ) connected to the input member (N); a rotating member ( 31 ) configured to rotate integrally with the output shaft ( 22 ); and a clutch portion ( 57   a ) configured to be supported by the support member (S), configured to be pushed in a radial direction by rotation of the rotating cam ( 53 ), and configured to press the elastic body ( 57   b ) in a thrust direction between the clutch portion ( 57   a ) and the rotating member ( 31 ) to generate friction. The rotating cam ( 53 ) is configured by a switching structure of switching to: a friction-suppression state (P 1 ), in which generation of friction caused by the elastic body ( 57   b ) is suppressed, by not pushing the clutch portion ( 57   a ) in the radial direction when the operation handle ( 20 ) is in the neutral position and when the operation handle ( 20 ) is turned in a direction of raising the seat ( 1 ) from the neutral position; and a friction-on state (P 2 ), in which friction caused by the elastic body ( 57   b ) is generated, by pushing the clutch portion ( 57   a ) in the radial direction when the operation handle ( 20 ) is turned in a direction of lowering the seat ( 1 ) from the neutral position. 
     According to the above configuration, when the operation handle ( 20 ) is not operated and when the operation handle ( 20 ) is operated in a direction of raising the seat ( 1 ), the friction generating portion ( 57 ) is brought into the friction-suppression state (P 1 ). Therefore, an operation load is not increased when the seat ( 1 ) is raised by the operation handle ( 20 ). Further, when the operation handle ( 20 ) is returned to the neutral position, the lock portion (B) can be smoothly locked without being affected by the friction. 
     On the other hand, when the operation handle ( 20 ) is operated in a direction of lowering the seat ( 1 ), the friction generating portion ( 57 ) is brought into the friction-on state (P 2 ). Therefore, it is possible to appropriately prevent the output shaft ( 22 ) from sliding and rotating due to self-weight applied to the seat (I). Further, since the clutch portion ( 57   a ) presses the elastic body ( 57   b ) between the clutch portion ( 57   a ) and the rotating member ( 31 ) in the thrust direction, the turning of the operation handle ( 20 ) is hardly hindered when the operation handle ( 20 ) is returned to the neutral position. 
     The “friction-suppression state” is a state including a state in which no friction is generated and a state in which friction smaller than that in the friction on state is generated. If no friction is generated in the friction-suppression state, the operation load is not increased when the seat is raised by the operation handle. Further, when the operation handle is returned to the neutral position, the lock portion can be smoothly locked without being affected by the friction. On the other hand, if friction smaller than that in the friction-on state is generated in the friction-suppression state, the friction change from the friction-on state can be reduced, and an operation feeling of the operation handle can be easily kept constant. 
     Further, the lock portion (B) is a release structure that the lock portion (B) is unlocked from the support member (S) when the operation handle ( 20 ) is turned by a predetermined amount in each of forward and reverse directions from the neutral position. The rotating cam ( 53 ) is configured to push the clutch portion ( 57   a ) in the radial direction and switch to the friction-on state while the operation handle ( 20 ) is turned by the predetermined amount. 
     According to the configuration, when the operation handle ( 20 ) is operated in a direction of lowering the seat ( 1 ) and the lock of the lock portion (B) is released, the friction generating portion ( 57 ) is always in the friction-on state (P 2 ). Therefore, it is possible to appropriately prevent the output shaft ( 22 ) from sliding and rotating due to self-weight applied to the seat ( 1 ). 
     Further, a surface configured to support the clutch portion ( 57   a ) to the support member (S) is configured by an inclined surface ( 57   c   2 ) such that the inclined surface is configured to guide the clutch portion ( 57   a ) to move obliquely in the thrust direction with respect to the support member (S) in accordance with a radial movement of the clutch portion ( 57   a ) by the rotating cam ( 53 ). 
     According to the above configuration, it is possible to smoothly switch the clutch portion ( 57   a ) between the friction-on state (P 2 ) and the friction-suppression state (P 1 ) in response to the operation of turning the operation handle ( 20 ) in forward and reverse directions or returning the operation handle ( 20 ) to the neutral position. 
     Further, a member configured to support a clutch portion ( 157   a ) to the support member (S) is configured by a guide member ( 157   c ) such that the guide member ( 157   c ) is configured to be supported to the support member (S) so as to be movable only in the thrust direction. The clutch portion ( 157   a ) is supported on the guide member ( 157   c ) so as to be rotatable in the radial direction. One of a rotating end portion of the clutch portion ( 157   a ) and a support surface, which is configured to support the rotating end portion, on the guide member ( 157   c ) is a spiral surface ( 157   c   3 ) whose center is a rotation center of the clutch portion ( 157   a ), and the other is an abutting surface ( 157   a   3 ) configured to abut on and slide on the spiral surface ( 157   c   3 ) in accordance with the rotation of the clutch portion ( 157   a ). When the rotating end portion of the clutch portion ( 157   a ) is pushed in the radial direction by the rotating cam ( 153 ), the clutch portion ( 157   a ) is rotates and presses the elastic body ( 57   b ) in the thrust direction via the guide member ( 157   c ). 
     According to the above configuration, since the movement locus of the clutch portion ( 157   a ) is a rotational movement with the center of rotation determined, the clutch portion ( 157   a ) does not move excessively during movement, and frictional resistance during the movement is reduced. Therefore, the operation force for rotating the rotating cam ( 153 ) is reduced. 
     Further, a member configured to support the clutch portion ( 57   a ) to the support member (S) is configured by a guide member ( 57   c ) such that the guide member ( 57   c ) is configured to be supported to the support member (S) so as to be movable only in the thrust direction. When the clutch portion ( 57   a ) is pushed in the radial direction by the rotating cam ( 53 ), the clutch portion ( 57   a ) is pushed in the thrust direction between the support member (S) and the guide member ( 57   c ), and presses the elastic body ( 57   b ) in the thrust direction via the guide member ( 57   c ). 
     In the friction-suppression state (P 1 ), a gap (T) is provided in the thrust direction between the guide member ( 57   c ) and the support member (S) via the clutch portion ( 57   a ) therebetween. 
     According to the above configuration, since the support member (S) and the guide member ( 57   c ) are hardly in direct contact with each other, it is possible to suppress the generation of abnormal noise due to the contact therebetween. 
     Further, the elastic body ( 57   b ) is coupled to the guide member ( 57   c ) in a state in which the elastic body ( 57   b ) is movable in the rotational direction integrally with the guide member. 
     According to the above configuration, since the frictional resistance force exerted by the elastic body ( 57   b ) hardly changes, the operation feeling of the operation handle ( 20 ) can be kept constant. 
     OTHER EMBODIMENTS 
     Although the embodiment of the present disclosure has been described above using one embodiment, the present disclosure can be implemented in various forms described below in addition to the above embodiment. 
     1. The lifter device of the present disclosure can be widely applied to a seat provided in a vehicle other than an automobile, such as a railway, and other types of conveyance such as an aircraft and a marine vessel. Further, the lifter device of the present disclosure can be widely applied to non-vehicle seats installed in facilities such as movie theaters. 
     2. The elastic body configuring the friction generating portion does not necessarily need to be formed of an annular member, but may be formed of pieces (small pieces) dispersedly provided at one or more places in the rotational direction. Further, the elastic body may be made of a material other than metal, such as rubber or resin. Further, the elastic body may be configured to be attached to the guide member when there is a guide member configured to support the clutch portion, but may be configured to be attached to a support member or a rotating member configured to rotate integrally with the output shaft. 
     3. The clutch portion may be indirectly supported by the support member through the guide member supported to be movable only in the thrust direction with respect to the support member, but may be configured to be directly supported by the support member. The clutch portion may be provided at one, two, or four or more places in the rotational direction. 
     In the second embodiment, although the spiral surface is provided on the guide member and the abutting surface is provided on the rotating end portion of the clutch portion, the abutting surface may be provided on the guide member, and the spiral surface may be provided on the rotating end portion of the clutch portion. In this case, the spiral surface at the rotating end portion of the clutch portion is continuously formed from the outer peripheral side to the inner peripheral side of the guide member and bulges toward the abutting surface of the guide member. 
     4. A friction-suppression state of the friction generating portion may be a state in which friction is not generated, in addition to a state in which friction smaller than the friction-on state is generated.