Patent Publication Number: US-2007108826-A1

Title: Clutch device for a seat lifting apparatus of a vehicle

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application is based on and claims priority under 35 U.S.C §119 with respect to Japanese Patent Application  2005-333257 , filed on Nov. 17, 2005, the entire content of which is incorporated herein by reference.  
     FIELD OF THE INVENTION  
      This invention relates to a seat lifting apparatus for adjusting height of a seat cushion for a vehicle seat.  
     BACKGROUND  
      Conventionally, a vehicle seat is provided with a vehicle seat lifting apparatus for adjusting height of a seat cushion. In the seat lifting apparatus, height of the seat can be adjusted by operation of an operational lever while a passenger is sitting on the seat. An operational force reduction device using a repulsive force of a spring is provided to reduce the operation force.  
      In JP 4 (1992)-116233A, an operational force reduction device using a torsion bar and located in a parallel link type seat lifting apparatus is disclosed. In JP 62 (1987)-77247A, an operational force reduction device, which has a spiral spring coaxially arranged with a friction brake mechanism formed in an operating portion in a parallel link type seat lifting, is disclosed.  
      In the seat lifting apparatus disclosed in JP 4 (1992)-116233A, a deceleration device which increases an operational torque by reducing an operation speed of the operational lever to transmit the operational torque to the lifting mechanism is provided. The torsion bar is arranged to provide the biasing force to the lifting mechanism on the output side of the deceleration device.  
      Accordingly, a large torsion bar having a biasing force which is able to deal with weight of a passenger sitting on the seat is required. Consequently, a space for housing such large torsion bar is increased along with the increase in the cost.  
      In an operational force reduction device disclosed in JP 62 (1987)-77247A, an operational handle is connected to an input shaft and the spiral spring is disposed in the friction brake mechanism wherein a deceleration device is connected to an output shaft. Thus, it is possible to apply a biasing force of the spiral spring to an input side of the deceleration device. Therefore, the sufficient operational force reducing function can be attained even with a spiral spring which has a small biasing force.  
      However, a follower rotationally driven by an operational lever is rotatably supported at only an intermediate portion of the follower by a case and connected to the operational lever at one end. A torsion spring is disposed on the other end of the follower and further connected to the deceleration device at the other end.  
      For the structure, misalignment of a rotational shaft of the follower is likely to occur to deteriorate operational performance of the operational lever or to lower a brake ability. Further, with regard to assembly, the torsion spring and a driving member are needed to be housed in the case with both end portions of the spiral spring engaged with the case and the follower to accumulate the energy of the spring. Therefore, the assembly operation could be complicated.  
      The present invention has been made in view of the above circumstances, and provides a seat lifting apparatus which has an operational force reducing function and a clutch device which stably operates.  
     SUMMARY OF THE INVENTION  
      According to an aspect of the present invention, a clutch device for a seat lifting apparatus of a vehicle includes a friction brake portion for transmitting rotation of an operational lever to an output shaft, an output gear provided at the output shaft, a biasing force receiving portion provided at the output shaft for receiving a biasing force which assists a rotation of the output shaft, a first bearing portion provided at one side of the biasing force receiving portion and the output gear, and a second bearing portion provided at the other side of the biasing force receiving portion and the output gear. The first bearing portion and the second bearing portion support the output shaft at both sides of the biasing force receiving portion and the output shaft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawings, wherein:  
       FIG. 1  is a perspective view of a seat for a vehicle having a seat lifting apparatus of the vehicle;  
       FIG. 2  is a perspective view of a seat lifting apparatus;  
       FIG. 3  is a cross sectional view of a clutch device;  
       FIG. 4  is a front view of a spiral spring; and  
       FIG. 5  is an exploded perspective view of a main portion of the clutch device.  
    
    
     DETAILED DESCRIPTION  
      An embodiment of the present invention will be described below with reference to the attached drawings. A seat  1  illustrated in  FIG. 1  and  FIG. 2  is provided with a seat cushion  1   a  and a seat back  1   b  extending obliquely upward from an upper surface of a rear end portion of the seat cushion  1   a  and movably supported by a lower rail  2   a  and a lower rail  2   b . The lower rail  2   a  and the lower rail  2   b  are fixed on a vehicle floor. A seat lifting apparatus  3  is mounted for adjusting height of a seating surface of the seat cushion l a at the lower end portion of the seat cushion  1   a.    
      An upper rail  4   a  is slidably attached on the lower rail  2   a  and an upper rail  4   b  is silidably attached on the lower rail  2   b . A base frame  5   a  of the seat cushion  1   a  is supported by the upper rail  4   a  and a base frame  5   b  of the seat cushion  1   a  is supported by the upper rail  5   b  so that the base frame  5   a  and the base frame  5   b  are able to move upward or downward.  
      In other words, a lower end portion of a lifer link  6   a  is rotatably supported by a front end portion of the upper rail  4   a  and a lower end portion of a lifter link  7   a  is supported by a rear end portion of the upper rail  4   a . An upper end portion of the lifter link  6   a  is rotatably connected to a front end portion of the base frame  5   a  and an upper end portion  7   a  is rotatably connected to a rear end portion of the base frame  5   a.    
      Similarly, a lower end portion of a lifter link  6   b  is rotatably supported by a front end portion of the upper rail  4   b  and a lower end portion of lifter link  7   b  is rotatably supported by a rear end portion of the upper rail  4   b . An upper end portion of the lifter link  6   b  is rotatably connected by a front end portion of the base frame  5   b  and an upper end portion of the lifter link  7   b  is rotatably connected by a rear end portion of the base frame  5   b.    
      A connecting portion between  7   a  and  5   a  is connected to a connecting portion between  7   b  and  5   b  by a cylindrical torque rod  9 . Therefore, the base frame  5   a  and the base frame  5   b  can move upward and downward relative to each other.  
      A clutch device  11  is mounted on the base frame  5   b  and the operational lever  12  is mounted on the clutch device  11 . An output shaft is formed with a pinion gear  13  and the pinion gear  13  rotates by the operation of the operational lever  12 .  
      A proximal lower potion of a sector gear  14  is rotatably supported on a rear side of the clutch device  11  and teeth  14   a  is formed in a tip portion of the sector gear  14 . The teeth  14   a  meshes the pinion gear  13  and the sector gear  14  rotates in response to rotation of the pinion  13 .  
      A proximal upper portion of the sector gear  14  is connected to the upper end portion of the lifter link  7   b  by a driving link  15 . The driving link  15  is rotatably connected to the sector gearl 4  and the lifter link  7   b.    
      Therefore, when the sector gear  14  rotates, the lifter link  7   b  rotates via the driving link  15  and the lifer link  7   a  rotates via the torque rod  9 . Consequently, the base frame  5   a  and the base frame  5   b  move upward and downward relative to each other.  
      Next, the specific structure of clutch device  11  will be described. As illustrated in  FIG.3 , an auxiliary flame  16  is attached to the base frame  5   b  in the position where the clutch device  11  is supported. The auxiliary frame  16  is fixed to the base frame  5   b  at an proximal end portion, for example by bolts or other tools, and a tip portion of the auxiliary frame  16  extends in a way that the auxiliary frame  16  is positioned in parallel to the base frame  5   b  at a predetermined distance.  
      A through hole is formed in the tip portion of the auxiliary frame  16  to form a first bearing portion  17 . A through hole is formed in the base frame  5   b  so that a central line of the through hole is aligned to a central line of the first bearing portion  17 . The bearing member  18  is fitted into the through hole to form the second bearing portion  19 . The diameter of the second bearing portion  19  is larger than the diameter of the first bearing portion  17 .  
      As illustrated in  FIG. 5 , the pinion gear  13  (the output gear) is provided at an intermediate portion of the output shaft  20  and the first bush  21  is unrotatably fitted into part of the pinion gear  13  relative to each other in the clutch device  11 . Further, a tip portion of the output shaft  20  is formed with a diameter which allows the tip portion of the output shaft  20  to be inserted into the first bearing portion  17 .  
      The intermediate portion of the output shaft  20  is rotatably supported by the second bearing portion  19  via the bush  21  and the tip portion of the output shaft  20  is rotatably supported by the first bearing portion  17 . The teeth  14   a  of the sector gear  14  is meshed with a pinion gear  13  between the auxiliary frame  16  and the base frame  5   b.    
      A spline  22  is formed by cutting the mark in the tip portion of the output shaft  20  on the side where the pinion gear  13  is positioned and a second bush  23  is unrotatably fitted into the spline  22  relative to each other. Therefore, the second bush  23  is fitted into the output shaft  20  so as to prevent a relative rotation between the output shaft  20  and the bush  23 . An engaging groove  24  (biasing force receiving portion) is formed on an outer circumference surface of the second bush  23 . That is to say, a biasing force receiving portion provided at the output shaft  20 .  
      The spiral spring  25  is arranged around the second bush  23  and, as illustrated in  FIG.4 , an inner circumferential side end portion  26   a  of the spiral spring  25  is supported by an engaging groove  24 . An outer circumferential side end portion  26   b  is supported by a supporting shaft  27  supported between the auxiliary frame  16  and the base frame  5   b . Therefore, a biasing force of the spiral spring  25  provides a needed rotational torque to the output shaft  20  using a base frame  5   b  as a supporting point and the torque acts in a direction to move the base frame  5   a  and the base frame  5   b  upward. An engaging groove  24  receives the biasing force which assists a rotation of the output shaft  20 .  
      One side of the output shaft  20  is projected to a side of the base frame  5   b , and a friction brake portion  28  which is fixed to the base frame  5   b  is arranged therearound. The operational lever  12  engages a plate  29  which is rotatably supported by the proximal portion of the output shaft  20 . The friction brake portion  28  transmits the rotation force of the plate  29  caused by the operation of the operational lever  12  to the output shaft  20 . Hence, the friction brake portion  28  performs a known effect which blocks the rotation of the output shaft  20  by a rotation torque acting on the output shaft  20  from the sector gear  14  and the spiral spring  25 .  
      In order to assemble the clutch device  11  described above, the friction brake portion  28  into which the output shaft  20  is fitted is fixed to the base frame  5   b  and the output shaft  20  is supported by the second bearing portion  19 .  
      Subsequently, the second bush  23  and the spiral spring  25  are attached to the tip portion of the output shaft  20 . Additionally, a proximal end portion of the auxiliary frame  16  is fixed to the base frame  5   b  with the tip portion of the output shaft fitted into the first bearing portion  17  of the auxiliary frame  16 . The outer circumferential side end portion  26   b  of the spiral spring  25  is hung on the supporting shaft  27  and the plate  29  is rotated to adjust an initial torque of the spiral spring.  
      Next, operation of the seat lifting apparatus having the clutch device  11  described above will be described. When rotating the operational lever  12  in a direction which the seat is moved upwardly, the output shaft  20  is rotated via the friction brake portion  28  to rotate the sector gear  14 .  
      In response to the rotation of the sector gear  14 , the lifter link  7   a  and the lifter link  7   b  are rotated via the driving link  15 . Consequently, the base frame  5   a  and the base frame  5   b  are moved upwardly. Thus, the seat cushion  1   a  is moved upward.  
      At this time, the biasing force of the spiral spring  25  acts in a direction which the biasing force assists the rotation of the output shaft  20 . Therefore, the operational force of the operational lever  12  is reduced. On the other hand, when the operational lever  12  is rotated in a direction which the seat is moved downward, and the output shaft  20  is rotated via the friction brake portion  28  to rotate the sector gear  14 .  
      In response to the rotation of the sector gear  14 , the lifter link  7   a  and lifter link  7   b  are rotated via the driving link  15 . Consequently, the base frame  5   a  and the base frame  5   b  are moved downward. Thus, the seat cushion  1   a  is moved downward.  
      At this time, the energy of the spiral spring  25  is accumulated in response to the rotation of the output shaft  20 . Therefore, the seat cushion  1   a  is not quickly moved downward.  
      The clutch device  11  formed as described above can attain the following effects. (1) The output shaft  20  is supported by two portions which are the first bearing portion  17  and the second bearing portion  19 . The pinion gear  13  of the output shaft  20  is meshed with the sector gear  14  between both bearing portions and the biasing force of the spiral spring  25  acts on the output shaft  20 . Furthermore, the first bearing portion  17  and the second bearing portion  19  are positioned on both sides of the output shaft  20  in the axial direction relative to a meshing portion between the pinion gear  13  and the sector gear  14  and the biasing force receiving portion from the spiral spring  25 . Thus, the occurrence of the shaft misalignment of the output shaft  20  caused by acting forces from the sector gear  14  and the spiral spring  25  can be prevented.  
      (2) The misalignment of the output  20  is restricted and this enables the friction brake  28  to operate stably.  
      (3) After fixing the friction brake portion  28  to the base frame  5   b , the spiral spring  25  is attached to the output shaft  20 . Subsequently, the auxiliary shaft  16  can be attached to the base frame  5   b . Thus, the spiral spring  25  can be readily attached.  
      The embodiment described above may be changed as follows. The inner circumferential side end portion of the spiral spring  25  may be directly engaged with the output shaft  20 .  
      Further, according to the invention, the seat lifting apparatus which has an operational force reducing function and a clutch device which stably operates can be provided.  
      The principles, of the preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention, which is intended to be protected, is not to be construed as limited to the particular embodiment disclosed. Further, the embodiment described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents that fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.