Patent Publication Number: US-2009218865-A1

Title: Rotating vehicle seat

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Japanese Patent Application No. 2008-048988, filed on Feb. 29, 2008. The entire disclosure of Japanese Patent Application No. 2008-048988 is hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a rotating vehicle seat provided in a vehicle. 
     2. Background Information 
     Japanese Laid-Open Patent Application Publication No. 2004-34908 discloses a conventional rotating vehicle seat configured such that a seat main body can be rotated relative to a vehicle. This conventional rotating vehicle seat has a rotating mechanism configured to rotate a seat surface of the vehicle seat between a normal position in which the seat faces toward a front of the vehicle and an embarkation position in which the seat faces toward an embarkation opening. By rotating to the embarkation position, the rotating vehicle seat enables a passenger to embark or disembark more easily through the embarkation opening. 
     In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved rotating vehicle seat. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure. 
     SUMMARY OF THE INVENTION 
     It has been proposed to provide a rotating vehicle seat with a tilt mechanism configured to vary a tilt angle of the seat surface so as to make it easier for a passenger to enter and leave the seat surface. Such a proposed rotating vehicle seat has a simple structure and operates in coordination with a door, thereby enabling the ease of embarkation to be improved without requiring any special manual operation to be performed. However, in such a proposed rotating vehicle seat, separate drive motors are provided for the tilt mechanism serving to vary the tilt angle of the seat surface and the rotating mechanism serving to control the rotation of the seat surface. Consequently, the proposed rotating vehicle seat takes up layout space and the wiring arrangement and control thereof is complex. 
     The present invention was conceived in view of these problems and its object is to provide a rotating vehicle seat that can achieve a greater degree of simplification. 
     In order to achieve the aforementioned object, a rotating vehicle seat according to a first aspect is a rotating seat for a vehicle having a seat surface tilt angle varying mechanism, a seat surface rotating mechanism and a single drive source. The seat surface tilt angle varying mechanism is configured and arranged to vary a tilt angle of a seat surface of a seat body. The seat surface rotating mechanism is configured and arranged to rotate the seat surface. The drive source is configured and arranged to drive the seat surface tilt angle varying mechanism and the seat surface rotating mechanism. 
     With this rotating vehicle seat, since the seat surface tilt angle varying mechanism and the seat surface rotating mechanism are both driven with a single drive source, the tilt angle of the seat surface can be varied and the seat surface can be rotated with one drive source. 
     Consequently, the number of component parts can be reduced and the structure can be simplified in comparison with a case in which a separate drive source is provided for each of the seat surface tilt angle varying mechanism and the seat surface rotating mechanism. 
     Additionally, the layout space can be reduced and the wiring arrangement and control can be simplified. 
     A rotating vehicle seat according to a second aspect, the seat surface tilt angle varying mechanism preferably includes a first link member configured and arranged to raise and lower a first end portion of the seat surface using a drive force from the drive source, and the seat surface rotating mechanism preferably includes a second link member configured and arranged to displace a second end portion of the seat surface in a horizontal direction in response to a displacement of the seat surface by the first link member. 
     More specifically, when the first link member is driven by a drive force from the drive source, the first end portion of the seat surface is raised or lowered and the tilt angle of the seat surface is thereby varied. 
     Meanwhile, the second link member operates in response to the displacement of the seat surface caused by the first link member and causes the second end portion of the seat surface to be displaced in a horizontal direction, thereby rotating the seat surface. 
     In a rotating vehicle seat according to a third aspect, a drive link member is preferably coupled between the first link member of the seat surface tilt angle varying mechanism and the drive source with a retraction position of the drive link member being set such that a force oriented in a return direction is applied to the first link member when the seat body is in a pre-rotation position. 
     More specifically, when the seat surface is in a state of having been returned to a pre-rotation position, a drive link member serving to actuate the first link is moved to a retraction position and a force oriented in a return direction is applied to the first link. 
     Consequently, the backlash that can occur in the mechanisms serving to drive the links is suppressed. 
     In a rotating vehicle seat according to a fourth aspect, an assist spring is preferably provided to apply a biasing force oriented in a raising direction against the first end portion of the seat surface. 
     More specifically, since a sitting passenger causes a downward load to act on the seat surface, a speed at which the first end portion is lowered tends to be faster than a speed at which the same is raised when the tilt angle of the seat surface is varied by raising and lowering the first end portion of the seat surface. 
     By applying a force in the raising direction against the first end portion of the seat surface, the assisting spring can help raise the first end portion of the seat surface. 
     A rotating vehicle seat according to a fifth aspect, a looseness preventing structure is preferably provided to prevent looseness of the seat body with respect to a base frame by fitting a first member coupled to the seat body with a second member provided in the base frame when the seat body is in a pre-rotation position. 
     More specifically, when the seat body is in a state of having been returned to a pre-rotation position, looseness of the seat body is prevented by a looseness preventing structure configured to prevent looseness of the seat body by means of a fitting together of the first and second members. 
     These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the attached drawings which form a part of this original disclosure: 
         FIG. 1  is a disassembled view of a rotating vehicle seat in accordance with an illustrated embodiment of the present invention; 
         FIG. 2  includes top plan views illustrating an operation of the rotating vehicle seat in accordance with the illustrated embodiment; 
         FIG. 3  includes side elevational views illustrating an operation of the rotating vehicle seat in accordance with the illustrated embodiment; 
         FIG. 4  is a rear perspective view of a rotation unit of the rotating vehicle seat in accordance with the illustrated embodiment; 
         FIG. 5  is a frontal perspective view of the rotation unit of the rotating vehicle seat in accordance with the illustrated embodiment; 
         FIG. 6  is a frontal perspective view of the rotation unit of the rotating vehicle seat when the rotation unit is in a post-rotation position in accordance with the illustrated embodiment; 
         FIG. 7  is a rear perspective view of the rotation unit of the rotating vehicle seat showing a retraction limit switch and an extension limit switch provided on the rotation unit in accordance with the illustrated embodiment; 
         FIG. 8  is a side elevational view of the rotation unit showing an operation of the retraction limit switch and the extension limit switch in accordance with the illustrated embodiment; 
         FIG. 9  is a side elevational view of the rotation unit in accordance with the illustrated embodiment; 
         FIG. 10  includes a side elevational view of the rotation unit and an enlarged view perspective view of a looseness preventing mechanism in accordance with the illustrated embodiment; and 
         FIG. 11  includes diagrams illustrating an operation of a link mechanism of the rotating vehicle seat in accordance with the illustrated embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A selected embodiment of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following description of the embodiment of the present invention is provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 
       FIG. 1  is shows a rotating vehicle seat  1  in accordance with the embodiment. 
     As shown in  FIG. 2 , the rotating vehicle seat  1  is installed as a driver&#39;s seat of a vehicle and includes a seat body  11  serving as a seat portion on which a driver sits. The rotating vehicle seat  1  is contrived such that the seat body  11  can be rotated between a pre-rotation position  12  in which the seat body  11  faces toward a front F of the vehicle and a post-rotation position  14  in which the seat body  11  faces toward an embarkation opening  13  provided in a right side portion of the vehicle. Additionally, as shown in  FIG. 3 , the rotating vehicle seat  1  is configured to raise a rearward end portion (first end portion) of a seat surface  16  of a seat cushion  15  of the seat body  11  when the seat body  11  is rotated from the pre-rotation position  12  to the post-rotation position  14 . Since the seat surface  16  is arranged to slant upward toward the front of the vehicle in the pre-rotation position  12 , raising the rearward end portion of the seat surface  16  in the post-rotation position  14  improves the ease with which a passenger can get out of the seat. Thus, the rotating vehicle seat  1  is provided with a seat surface tilt angle varying function whereby it can vary a tilt angle of the seat surface  16  of the seat body  11  and a seat surface rotating function whereby it can rotate the seat surface  16 . 
     As shown in  FIG. 1 , the seat body  11  is supported on the vehicle body through a slide unit  21  that is mounted to a floor of the vehicle body such that it can slide along a longitudinal direction of the vehicle and a rotation unit  22  that is mounted to the slide unit  21 . 
     As shown in  FIGS. 4 to 7 , the rotation unit  22  includes a base  31  (base frame) that is fixed to the slide unit  21  and a movable section  32  that is movably supported on the base  31 . A plurality of fastening points  33  are provided on the movable section  32  such that the seat cushion  15  can be fastened thereto. 
     As shown in  FIG. 6 , the base  31  comprises a left side member  41  and a right side member  42  arranged opposite each other and a cross member  43  arranged so as to join the frontward end portions of the two side members  41  and  42 . The base  31  is thus generally C-shaped and the open side thereof faces in a rearward direction. 
     A generally C-shaped front bracket  51  is provided in a middle portion of the cross member  43  and arranged such that the open side thereof faces in a rearward direction. A front link bracket  54  is pivotally supported on side panels  52  and  52  of the front bracket  51  with front shafts  53  and  53 . A front rotary shaft  55  is provided in a rightward position of the front link bracket  54 , and an upper end and a lower end of the front rotary shaft  55  are fixed to the front link bracket  54 . 
     A frontward end portion of a front link  61  serving as a second link member is rotatably supported on the front rotary shaft  55  such that the front link  61  can swing about the front rotary shaft  55  between a state in which a free end thereof is close to the cross member  43  and a state in which the free end extends rearward. 
     A drive section  71  is provided at a middle portion of the left side member  41  of the base  31 . The drive section  71  includes a drive motor  72  that serves as a drive source and is controlled with electric power supplied from a control apparatus not shown in the figures, and a reduction gear unit  73  that has a worm gear actuated by the drive motor  72 . An output shaft  74  extends from the reduction gear unit  73  and passes through an inside surface of the left side member  41 . 
     A pinion gear  81  is fixed to the output shaft  74 , and the pinion gear  81  is configured and arranged to mesh with a rotary gear  83  that is rotatably supported on an inside surface of the left side member  41  with a rotary shaft  82 . The rotary gear  83  is fan-shaped and has a gear portion  84  configured to mesh with the pinion gear  81  formed on an outer circumferential edge thereof. 
     A protruding drive shaft  91  for transmitting a drive force is provided on the circumferential edge of the rotary gear  83 , and a frontward end portion of an elongated plate-like drive link  92  (drive link member) is rotatably supported on the drive shaft  91 . Thus, by rotating the rotary gear  83  with the drive motor  72  such that the drive shaft  91  moves forward or rearward, the drive link  92  supported on the drive shaft  91  can be displaced in a forward or rearward (longitudinal) direction. 
     As shown in  FIGS. 7 and 8 , the rotary gear  83  is configured to be covered with a cover  101  (one side face of the cover  101  is shown in  FIG. 7 ) and a retraction limit switch  102  and an extension limit switch  103  are provided on an inside surface of the cover  101 . 
     The retraction limit switch  102  is arranged rearward of the extension limit switch  103  and configured to turn off when a retraction contact  105  extending from the retraction limit switch  102  touches against the drive shaft  91  of the rotary gear  83 . 
     The extension limit switch  103  is arranged forward of the retraction limit switch  102  and configured to turn off when an extension contact  106  extending from the extension limit switch  103  touches against the drive shaft  91 . 
     As shown in  FIG. 4 , a shaft support bracket  121 ,  121  is provided on a rearward end portion each of the side members  41  and  42  of the base  31 . An end portion of a rear shaft  122  is rotatably supported on each of the shaft support brackets  121  and  121  and the rear shaft  122  is arranged to span between rearward end portions of the two side members  41  and  42  of the base  31 . 
     A left seat surface tilt angle varying link  141  is provided on a left end portion of the rear shaft  122 . The left seat surface tilt angle varying link  141  is an elongated triangular plate-like member that serves as a first link member. A right seat surface tilt angle varying link  142  is provided on a right end portion of the rear shaft  122 . The right seat surface tilt angle varying link  142  is an elongated triangular plate-like member that serves as a first link member. As shown in  FIG. 6 , the right end portion of the rear shaft  122  is fixed in such a state that it passes through a rearward bottom corner portion of the left seat surface tilt angle varying link  141 , and end portion of the rear shaft  122  is fixed in such a state that it passes through a rearward bottom corner portion of the right seat surface tilt angle varying link  142 . 
     A rearward end portion of the drive link  92  is rotatably supported on a frontward bottom corner portion of the left seat surface tilt angle varying link  141  through with a shaft part  150 . Thus a longitudinal (forward or rearward) displacement of the drive shaft  91  accompanying a rotation of the rotary gear  83  can be transmitted to the left seat surface tilt angle varying link  141  through the drive link  92 . 
     The apex portions of the two seat surface tilt angle varying links  141  are connected with a connecting pipe  151 , and a frontward end portion of a rear link bracket  152  is rotatably fitted on the outside of the connecting pipe  151 . The rear link bracket  152  is configured to extend rearward from the connecting pipe  151 , and an upwardly extending rear rotary shaft  153  is provided on the rear link bracket  152 . An upper end portion of the rear rotary shaft  153  is rotatably supported in a roof panel  155  of a hat-shaped part  154  provided in the rear link bracket  152 . 
     As shown in  FIGS. 4 and 6 , spiral-type assist springs  161  and  161  are provided at both end portions of the rear shaft  122 . The end portion of each of the assist springs  161  that is at the center of the spiral is fixed to the rear shaft  122  and the other end, i.e., the outer end, is securely engaged with the corresponding shaft support bracket  121 . Thus, the assist springs  161  and  161  apply spring forces against the rear shaft  122  in directions acting to stand the seat surface tilt angle varying links  141  and  142  upright. 
     As shown in  FIG. 6 , the movable section  32  has the form of a rectangular frame comprising a left side plate  201  and a right side plate  202  arranged opposite each other, a front connecting plate  203  connecting frontward end portions of the side plates  201  and  202 , and a rear connecting plate  204  connecting rearward end portions of the side plates  201  and  202 . 
     A clamping plate  212  is provided on a middle portion of the front connecting plate  203  with column-like support parts (spacers)  211  arranged in-between, and a coupling shaft  213  is provided between the clamping plate  212  and the front connecting plate  203  in a leftward position. The front link  61  extends from the base  31  and a rearward end portion thereof is rotatably supported on the coupling shaft  213 . Thus, when the front link  61  rotates about the front rotary shaft  55 , the frontward end portion of the movable section  32  is displaced in a horizontal direction. 
     As a result, a frontward end portion (second end portion) of the seat body  11  supported on the movable section  32  can be moved in a horizontal direction, and a seat surface rotating mechanism  221  that can rotate the seat surface  16  is achieved. 
     The rear connecting plate  204  of the movable section  32  is generally V-shaped and arranged such that a middle portion thereof protrudes rearward. A boss  231  having a vertically oriented through-hole formed therein is integrally formed at the middle portion of the rear connecting plate  204 . The rear rotary shaft  153  provided on the rear link bracket  152  passes through the boss  231  such that it can rotate freely therein. 
     The rear connecting plate  204  of the movable section  32  is supported on the base  31  through the rear link bracket  152  and the seat surface tilt angle varying links  141  and  142  on which the rear link bracket  152  is supported, and rotation of the seat surface tilt angle varying links  141  and  142  causes the rear connecting plate  204  to move up and down. The seat cushion  15  is supported on the movable section  32  through the seat surface tilt angle varying links  141  and  142 . As a result, a seat surface tilt angle varying mechanism  255  is achieved which can vary a tilt angle of the seat surface  16  of the seat cushion  15 . 
     Since the seat surface tilt angle varying links  141  and  142  are supported on the rear shaft  122  and the assist springs  161  and  161  apply spring forces against the rear shaft  122  in directions acting to stand the seat surface tilt angle varying links  141  and  142  upright, a force oriented in a raising direction can be applied against the rearward end portion of the seat surface  16  of the seat cushion  15  supported on the movable section  32 . 
     Thus, the spring forces from the assist springs  161  and  161  can serve to counteract the weight load of a seated passenger. 
     When the seat surface tilt angle varying links  141  and  142  are rotated by the drive section  71 , the longitudinal (rearward or forward) displacements of the free ends of the seat surface tilt angle varying links  141  and  142  cause the rear link bracket  152  supported on the seat surface tilt angle varying links  141  and  142  and the movable section  32  supported on the rear link bracket  152  to move in a longitudinal direction (rearward or forward). The longitudinal movement of the movable section  32  causes the front link  61  supported on the front rotary shaft  55  of the base  31  to swing such that the frontward end portion of the movable section  32  (which is supported on the free end portion of the front link  61 ) is displaced in a leftward or rightward direction. 
     Since the seat cushion  15  is supported on the movable section  32  by the seat surface tilt angle varying links  141  and  142 , the displacement of the movable section  32  causes the seat surface  16  of the seat cushion  15  to be displaced such that a frontward end portion of the seat surface  16  is displaced in a horizontal direction. 
     In this way, the seat surface tilt angle varying mechanism  225  (including the seat surface tilt angle varying links  141  and  142 , which serve to vary a tilt angle of the seat surface  16 ) and the seat surface rotating mechanism  221  (including the front link  61 , which serves to rotate the seat surface  16 ) can be driven with a single drive motor  72  because when the drive motor  72  rotates the seat surface tilt angle varying links  141  and  142 , the front link  61  rotates in coordination with the movement of the seat surface tilt angle varying links  141  and  142 . 
     As shown in  FIGS. 7 and 8 , the retraction limit switch  102  and the extension limit switch  103  are provided on the cover  101  that covers the rotary gear  83  and are configured to turn off when contacted by the drive shaft  91  of the rotary gear  83 . The extension limit switch  103  is provided in such a position that the drive shaft  91  touches against the extension contact  106  of the extension limit switch  103  when the drive motor  72  rotates the rotary gear  83  such that the seat body  11  reaches the post-rotation position  14 . 
     The extension limit switch  103  is connected to the aforementioned control apparatus and the control apparatus is configured to cut off electric power to the drive motor  72  and stop driving the drive link  92  in a feed direction when it receives a signal indicating that the extension limit switch  103  has turned off. As a result, the rotation and tilting of the seat body  1 I can be stopped when the seat body  11  reaches the post-rotation position  14 . 
     The retraction limit switch  102  is provided in such a position that the drive shaft  91  touches against the retraction contact  105  of the retraction limit switch  102  when the drive motor  72  rotates the rotary gear  83  such that the seat body  11  reaches the pre-rotation position  12 . 
     The retraction limit switch  102 , too, is connected to the control apparatus and the control apparatus is configured to cut off electric power to the drive motor  72  and stop driving the drive link  92  in a return direction when it receives a signal indicating that the retraction limit switch  102  has turned off. As a result, the rotation and tilting of the seat body  11  can be stopped when the seat body  11  reaches the pre-rotation position  12 . 
     The retraction limit switch  102  is fixed in a slightly forward position such that a force is applied in a return direction against the left seat surface varying link  141  when the set surface  16  has been returned to the pre-rotation position  12 . The retraction position  241  of the drive link  92  (which drives the seat surface tilt angle varying links  141  and  142 ) is determined by the position in which the retraction limit switch  102  is fixed. 
     Electric power continues to be supplied to the drive motor  72  when the seat body  11  reaches the per-rotation position  12  and the electric power is cut off when the rotary gear  83  has been rotated further. The seat surface tilt angle varying links  141  and  142  are stopped at a tension application position  252  reached when the seat surface tilt angle varying links  141  and  142  have rotated slightly beyond a return complete position  251  in the return direction. The return complete position  251  is a position the seat surface tilt angle varying links  141  and  142  reach when the seat body  11  is returned to the pre-rotation position  12 . The seat body  11  is held in the pre-rotation position  12  by being mechanically locked. 
     The rotary gear  83  is connected to a reduction gear unit  73  that includes a worm gear having a reverse rotation preventing function. Consequently, while the drive motor is stopped, a tension can be applied continuously in a return direction against the seat surface tilt angle varying links  141  and  142 . 
     As shown in  FIG. 10 , a wedge  261  (first member) is provided on a lower portion of the front connecting plate  203  of the movable section  32 . The wedge  261  comprises a neck portion  262  and a tapered insertion portion  263  provided on the neck portion  262  such that the wedge  261  has a mushroom-like shape. 
     An elliptical positioning plate  270  (second member) is provided on the cross member  43  of the base  31  in a position corresponding to the wedge  261 . A circular insertion hole  264  configured for the insertion portion  263  of the wedge  261  to fit into is provided in the positioning plate  270 . 
     The positioning plate  270  is fixed in such a position that the insertion portion  263  of the wedge  261  fits into the insertion hole  264  when the seat body  11  is in the pre-rotation position  12  and the seat surface  16  is facing toward the front of the vehicle. The fitting together of the wedge  261  and the insertion hole  264  constitutes a looseness preventing structure  271  that serves to prevent looseness of the seat surface  16 . 
     Since a rotating vehicle seat  1  according to this embodiment is contrived such that the seat surface tilt angle varying mechanism  255  and the seat surface rotating mechanism  221  can be driven with a single drive motor  72 , both variation of the tilt angle and rotation of the seat surface  16  of the seat cushion  15  can be accomplished with one drive motor  72 . 
     Consequently, the number of component parts can be reduced and the structure can be simplified in comparison with a case in which the seat surface tilt angle varying mechanism  255  and the seat surface rotating mechanism  221  are driven by separate drive motors. Additionally, the wiring arrangement and control can be simplified. As a result, the cost can be reduced. 
     Also, since the layout space can be reduced, the degree of layout freedom can be increased. 
     Driving the seat surface tilt angle varying mechanism  255  and the seat surface rotating mechanism  221  with a single drive motor  72 , i.e., a dual action with one motor, can feasibly be accomplished using a wire configuration or a link configuration. This embodiment uses a link configuration. Thus, the tilt angle of the seat surface  16  can be varied by using a drive force from the drive motor  72  to drive the seat surface tilt angle links  141  and  142  so as to raise and lower the rearward end portion of the seat surface  16 . 
     In response to the displacement of the seat surface  16  caused by the seat surface tilt angle varying links  141  and  142 , the front link  61  operates and displaces the frontward end portion of the seat surface  16  in a horizontal direction, thereby rotating the seat surface  16 . As a result, both tilting and rotation of the seat surface  16  can be accomplished with a single drive motor  72 . 
       FIG. 11  is a schematic view of a link mechanism in which parts corresponding to the preceding drawings are indicated with corresponding reference numerals. 
     This figure, too, illustrates that the rotary operation of the rotary gear  83  rotated by the drive motor  72  serves to raise/lower and rotate a rearward end portion of the movable section  32  in a coordinated manner such that the seat surface  16  of the seat body  11  supported on the movable section  32  can be tilted and rotated. 
     When a passenger sits on the seat surface  16  of the seat body  11 , the weight of the passenger generates a downward load and the rearward end portion of the seat surface  16  tends to move downward faster than it moves upward when it is raised and lowered to vary the tilt angle. 
     In this embodiment, the assist springs  161  and  161  provided on the rear shaft  122  apply a spring force against the seat surface tilt angle varying links  141  and  142  in a direction of raising the rearward end portion of the seat surface  16  of the seat body  11 , thereby providing assistance when the rearward end portion of the seat surface  16  is raised. 
     As a result, an increase in the lowering speed of the rearward end portion of the seat surface  16  caused by the weight of a passenger can be suppressed and the difference between the raising speed and lowering speed can be decreased. 
     Additionally, since the drive force required in order to raise the rearward end portion can be reduced, a motor having a smaller output can be used, i.e., the drive motor  72  can be made more compact. 
     The retraction position  241  of the drive link  92  that drives the seat surface tilt angle varying links  141  and  142  is set according to the position in which the retraction limit switch  102  is fixed such that when the seat surface has been returned to the pre-rotation position  12 , a force acting in the return direction is applied against each of the seat surface tilt angle varying links  141  and  142 . 
     As a result, when the seat surface  16  of the seat body  11  is returned to the pre-rotation position  12 , the drive link  92  that drives seat surface tilt angle varying links  141  and  142  is moved to the retraction position  241  and the force acting in the return direction can be applied against the seat surface tilt angle varying links  141  and  142  in a continuous fashion. 
     As a result, the backlash that can occur in the links  92 ,  141 , and  142 , the rotary gear  83 , the pinion gear  81 , and other mechanisms can be suppressed and undesired looseness of the seat surface  16  of the seat body  11  driven by the seat surface tilt angle varying links  141  and  142  can be prevented. 
     When the seat body  11  is in the pre-rotation position  12 , the insertion portion  263  of the wedge  261  provided on the movable section  32  fits into the insertion hole  264  of the positioning plate  270  provided on the base  31 , thus constituting a looseness preventing structure  271  that can prevent undesired looseness of the seat surface  16  of the seat body  11  from occurring. 
     Although in this embodiment the looseness preventing structure  271  is accomplished using the wedge  261 , the invention is not limited to such a structure. For example, a dovetail could be used. 
     With a rotating vehicle seat according to the illustrated embodiment, since the seat surface tilt angle varying mechanism and the seat surface rotating mechanism can be driven with a single drive source, both variation of the tilt angle of the seat surface and rotation of the seat surface can accomplished with one drive source. 
     Consequently, the number of component parts can be reduced in comparison with a case in which a separate drive source is provided for each of the seat surface tilt angle varying mechanism and the seat surface rotating mechanism and the structure can be simplified. Furthermore, the wiring arrangement and the control can be simplified. As a result, the cost of the rotating vehicle seat can be reduced. 
     Also, since the amount of layout space required can be reduced, a higher degree of freedom can be obtained with respect to the layout of the rotating vehicle seat. 
     With a rotating vehicle seat according to the illustrated embodiment, the tilt angle of the seat surface can be varied by driving the first link member with a drive force from the drive source so as to raise and lower the first end portion of the seat surface. 
     When this is done, the second link member displaces the second end portion of the seat surface in a horizontal direction in response to a displacement of the seat surface by the first link member, thereby enabling the seat surface to be rotated. 
     As a result, both tilting and rotation of the seat surface can be accomplished with a single drive source. 
     With a rotating vehicle seat according to the illustrated embodiment, when the seat surface returns to a pre-rotation position, a drive link member serving to actuate the first link member moves to a retraction position and thereby applies a force oriented in a return direction against the first link member. 
     As a result, the backlash that can occur in the mechanisms serving to drive the links can be suppressed and undesired looseness of the seat surface driven by the links can be prevented. 
     With a rotating vehicle seat according to the illustrated embodiment, assistance can be accomplished with respect to raising the first end portion of the seat surface by means of the assisting spring applying a force oriented in a raising direction against the first end portion of the seat surface. 
     As a result, when the first end portion of the seat surface is lowered while bearing a load from a seated passenger, an increase in the lowering speed can be suppressed. Thus, the difference between the raising speed and the lowering speed of the first end portion can be reduced. 
     A rotating vehicle seat according to the illustrated embodiment is provided with a looseness preventing structure configured to prevent looseness of the seat surface by means of a fitting together of members when the seat surface has been returned to a pre-rotation position. As a result, undesired looseness of the seat surface can be prevented. 
     General Interpretation of Terms 
     In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. Also as used herein to describe the above embodiment, the following directional terms “forward”, “rearward”, “above”, “downward”, “vertical”, “horizontal”, “below” and “transverse” as well as any other similar directional terms refer to those directions of a vehicle equipped with the present invention. Accordingly, these terms, as utilized to describe the present invention should be interpreted relative to a vehicle equipped with the present invention. The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. 
     While only selected embodiment has been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired. Components that are shown directly connected or contacting each other can have intermediate structures disposed between them. The functions of one element can be performed by two, and vice versa. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing description of the embodiment according to the present invention is provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.