Abstract:
A seat reclining apparatus for a vehicle includes: a first plate adapted to be mounted on one of a seat cushion and a seat back and having inner teeth; a second plate adapted to be mounted on the other one of the seat cushion and the seat back and supporting the first plate to be rotatable; a pole directly and movably supported by the second plate and having outer teeth engageable and disengageable with the inner teeth of the first plate; a pair of guides formed at the second plate and interposing therebetween the pole from both sides, the guide including a pole sliding surface adjusted to slidably come in contact with a side surface of the pole; and a recess formed at the pole sliding surface of the guide.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is based on and claims priority under 35 U.S.C. §119 to Japanese Patent Application 2007-013977, filed on Jan. 24, 2007, the entire content of which is incorporated herein by reference. 
   FIELD OF THE INVENTION 
   The present invention relates to a seat reclining apparatus for a vehicle. 
   BACKGROUND 
   JP2004-105360A discloses therein a conventional seat reclining apparatus for a vehicle, which inclines a seat back relative to a seat cushion. The seat reclining apparatus includes a ratchet having inner teeth, and a base arm attached with multiple poles to be movable in a radial direction. The ratchet is prohibited from rotating relative to the base arm with the inner teeth of the ratchet being engaged with outer teeth of the poles in response to the rotation of a cam provided around a rotational shaft, and the ratchet is allowed to rotate relative to the base arm with the inner teeth of the ratchet being disengaged from the outer teeth of the poles in response to the rotation of a cam provided around a rotational shaft. Accordingly, the pivotal rotation of the seat back relative to the seat cushion is prohibited and allowed, thereby adjusting or maintaining an inclining angle of the seat back at a required inclining angle appropriate to support an occupant seated on the seat cushion. 
   Each pole is guided to move in the radial direction with both side surfaces of the pole being slided on a pair of guides formed at the base arm. In JP2004-105360A, a surface of each guide, which faces the ratchet, is applied with a blanking process in a plate-thickness direction and is formed with multiple pole sliding surfaces in the plate-thickness direction. That is, JP2004-105360A suggests each guide having the multiple pole sliding surfaces formed in a stepped manner. In this case, the blanking or stamping amount of each pole sliding surface is reduced, so that the thickness of the connected portion of each pole sliding surface is increased compared with a conventional structure. Therefore, it is possible to enhance shear strength of each guide (connected portion) against a load applied from the corresponding pole while maintaining a conventional plate-thickness of the base arm. 
   Meanwhile, as described above, because the shear strength of each guide against the load applied from the corresponding pole is increased, the pole is supported by the guide more firmly in response to the increment of the shear strength. Therefore, for example when the seat back is exposed to impact, a sufficient amount of impact energy is not absorbed and an excessive amount of load may be applied to engagement portions of the inner teeth of the ratchet and the outer teeth of the pole. In this case, there is a possibility that the engagement may become unstable and the seat back may not be maintained at the required inclining angle stably. 
   A need thus exists for a seat reclining apparatus for a vehicle, which is not susceptible to the drawback mentioned above. 
   SUMMARY OF THE INVENTION 
   According to an aspect of the present invention, a seat reclining apparatus for a vehicle includes: a first plate adapted to be mounted on one of a seat cushion and a seat back and having inner teeth; a second plate adapted to be mounted on the other one of the seat cushion and the seat back and supporting the first plate to be rotatable; a pole directly and movably supported by the second plate and having outer teeth engageable and disengageable with the inner teeth of the first plate; a pair of guides formed at the second plate and interposing therebetween the pole from both sides, the guide including a pole sliding surface adjusted to slidably come in contact with a side surface of the pole; and a recess formed at the pole sliding surface of the guide. 

   
     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 an exploded perspective view illustrating a seat reclining apparatus according to an embodiment of the present invention; 
       FIG. 2  is a front view illustrating the seat reclining apparatus; 
       FIG. 3  is a sectional view taken along line III-III in  FIG. 2 ; and 
       FIG. 4  is a front view simply illustrating the seat reclining apparatus. 
   

   DETAILED DESCRIPTION 
   Described below is an embodiment of the present invention with reference to the attached drawings.  FIG. 1  is an exploded perspective view illustrating a seat reclining apparatus for a vehicle such as an automobile.  FIG. 2  is a front view illustrating the seat reclining apparatus.  FIG. 3  is a sectional view taken along line III-III in  FIG. 2 . The seat reclining apparatus for the vehicle fundamentally includes a structure illustrated in  FIGS. 1 ,  2  and  3  at the left and right sides in the seat lateral direction respectively. According to the embodiment, the structure arranged at the right side towards the front of the vehicle is illustrated. Therefore, the structure arranged at the right side is described below and the structure at the left side is not described below in order to simplify the description. However, the following description is also applied to the structure at the left side. 
   As illustrated in  FIG. 3 , the seat reclining apparatus includes a seat cushion frame  11  that is made from a metal plate and serves as a framework of a seat cushion. A seat back frame  12 , which is also made from a metal plate and serves as a framework of a seat back, is connected to the seat cushion frame  11  so as to pivotably rotate or incline relative to the seat cushion about a rotational axis O via a lock mechanism  20 . The lock mechanism  20  is adjusted to selectively prohibit and allow a rotation of the seat back frame  12  relative to the seat cushion frame  11 . The lock mechanism  20  is employed fundamentally to maintain the seat back frame  12  in a rotation prohibiting state relative to the seat cushion frame  11 . Therefore, the seat back is maintained at an appropriate inclining angle relative to the seat cushion. 
   Described below is the lock mechanism  20 . As illustrated in  FIG. 3 , a lower plate  21  (serving as a second plate) is firmly welded to an inner side surface of the seat cushion frame  11  and is formed by half-blanking a metal plate. As illustrated in  FIG. 1 , the lower plate  21  is formed into a ring-shaped structure having a through hole  21   a  at a center thereof. The lower plate  21  is formed with an engagement hole  21   b  that is formed continuously with the through hole  21   a  and is recessed radially outwardly. 
   The lower plate  21  is further formed with a recess  22  at an opposite side to the seat cushion frame  11 , a recess  22  exhibiting a round shape recessed towards the seat cushion frame  11 . The recess  22  includes plural protrusions  23  that are arranged in a predetermined angle and protrude from a bottom wall of the recess  22 . According to the embodiment, the recess  22  is formed with the three protrusions  23 . Each protrusion  23  includes two guides  23   a  and  23   b  which are separated from each other in a circumferential direction. Each guide  23   a  and  23   b  of the protrusion  23  is formed with a pole sliding surface  23   c  extending in parallel to the pole sliding surface  23   c  of the adjacent protrusion  23 . The pole sliding surface  23   c  extends radially in a planar manner. The lower plate  21  is still further formed with guiding grooves  24  which are respectively arranged between the pole sliding surfaces  23   c  of the adjacent protrusions  23  and extend in the radial direction. 
   As illustrated in  FIGS. 1 and 3 , an upper plate  26  (serving as a first plate) is firmly welded to an inner side surface of the seat back frame  12 . The upper plate  26  is formed by half-blanking a metal plate and exhibits a ring-shaped structure having an outer diameter substantially identical to an inner diameter of the recess  22  of the lower plate  21  and a shaft insertion hole  26   a  at the center thereof. The upper plate  26  is mounted to the lower plate  21  so that an outer peripheral surface of the upper plate  26  slidably comes in contact with an inner peripheral surface of the recess  22  of the lower plate  21 . In other words, the upper plate  26  is pivotally supported by the lower plate  21  so that the upper plate  26  is rotated relative to the lower plate  21 . Therefore, the seat back frame  12  is linked to the seat cushion frame  11  via the lower plate  21  and the upper plate  26  (the lock mechanism  20 ) so that the seat back frame  12  is rotatable relative to the seat cushion frame  11 . 
   As illustrated in  FIG. 3 , the upper plate  26  is formed with a first recess  27  at an opposite side to the seat back frame  12  (at the side of the lower plate  21 ), a first recess  27  exhibiting a round shape recessed towards the seat back frame  12 . The first recess  27  is formed with inner teeth  27   a  at its inner peripheral surface. The inner teeth  27   a  face the guiding grooves  24  in the radial direction where the upper plate  26  is mounted to the lower plate  21 . The first recess  27  is further formed with a second recess  28 , which has an inner diameter smaller than the inner diameter of the first recess  27  and exhibits a round shape. The second recess  28  is recessed further towards the seat back frame  12  than the first recess  27  is and is arranged coaxially with the first recess  27 . 
   A ring-shaped holder  29 , which is made from a metal plate, is fitted with an outer circumferential portion of the upper plate  26  and the lower plate  21  integrated where the upper plate  26  is mounted to the lower plate  21 . The holder  29 , which is mounted on the lower plate  21  and the upper plate  26 , prevents the lower plate  21  and the upper plate  26  from dropping in the axial direction while allowing the relative rotation of the lower plate  21  and the upper plate  26 . 
   A cam  31 , which is formed by half-blanking a metal plate, is accommodated in an internal space defined by the recess  22 , the first recess  27  and the second recess  28  where the upper plate  26  is mounted to the lower plate  21 . The cam  31  is accommodated to be rotatable about the rotational axis O. As illustrated in  FIG. 1 , the cam  31  includes multiple cam portions  31   a  extending in the radial direction and arranged in a predetermined angle. According to the embodiment, the cam  31  includes the three cam portions  31   a . Moreover, each cam portion  31   a  is formed with a pin-shaped protrusion  31   b  protruding towards the upper plate  26  in parallel to the axial direction. The cam  31  is formed with a fitting hole  31   c  penetrating its central portion in the axial direction and exhibiting an approximately circular and flattened cross section (like an oval shape). Going back to  FIG. 3 , the cam  31  is further formed with a pin-shaped protrusion  31   d  protruding in parallel to the axial direction and towards the lower plate  21 . 
   As illustrated in  FIG. 1 , the pole  32  is arranged at the corresponding guiding groove  24  of the lower plate  21 , the pole  32  being formed into an approximately rectangular-shaped plate having a circumferential directional length smaller than the one of the guiding groove  24 . Each pole  32  has side surfaces  32   d  (see  FIG. 2 ) that slidably come in contact with the pole sliding surfaces  23   c  of the protrusions  23 , so that the pole  32  is guided to move in the radial direction. That is, each pole  32  is guided to move in the radial direction while being interposed from both sides in the circumferential direction by the guide  23   a  of the corresponding protrusion  23  and the guide  23   b  of the adjacent protrusion  23 . Further, each pole  32  is formed, at its distal end, with outer teeth  32   a  engageable with the inner teeth  27   a  (see  FIG. 3 ) of the upper plate  26  and is formed, at its base end, with a cam hole  32   b  penetrating in a thickness direction. The cam hole  32   b  is arranged in an inclined manner relative to the circumferential direction having the rotational axis O as the center. The pole  32  is engaged with the cam  31  when the protrusion  31   b  of the cam  31  is engaged with the cam hole  32   b.    
   As further illustrated in  FIG. 3 , each pole  32  is provided with an axially-stepped portion between the outer teeth  32   a  and the cam hole  32   b . An end surface of this axially-stepped portion faces in the radial direction and is formed with a pole cam surface  32   c . The pole cam surface  32   c  extends so as to come across the side surfaces  32   d  of the pole  32  and to be inclined relative to a pitch circle of the outer teeth  32   a . The pole  32  is engaged with the cam  31  when the distal surface of the cam portion  31   a  is in contact with the pole cam surface  32   c.    
   That is, when the cam  31  rotates to one side (clockwise in  FIG. 1 ) in a situation where the cam  31  and the poles  32  are accommodated between the lower plate  21  and the upper plate  26  (inner space), the poles  32  are moved so as retract in the radial direction along the guiding grooves  24  as a result of that the cam holes  32   b  of the poles  32  are pushed by the protrusions  31   b  of the cam  31 . In this case, the upper plate  26  is allowed to rotate relative to the lower plate  21  when the outer teeth  32   a  of the poles  32  are disengaged from the inner teeth  27   a  of the upper plate  26 . As a result, a rotation allowing state is established, in which the upper plate  26  is allowed to rotate relative to the lower plate  21 . 
   On the other hand, when the cam  31  rotates to the other side (counterclockwise in  FIG. 1 ), the poles  32  are moved so as to move radially outwardly along the guiding grooves  24  as a result of that the cam holes  32   b  of the poles  32  are pushed by the protrusions  31   b  of the cam  31  and that the pole cam surfaces  32   c  are pushed by a distal surface of the cam portions  31   a . In this case, the outer teeth  32   a  of the poles  32  are engaged with the inner teeth  27   a  of the upper plate  26 , so that the upper plate  26  is prohibited from rotating relative to the lower plate  21 . As a result, a rotation prohibiting state is established, in which the upper plate  26  is prohibited from rotating relative to the lower plate  21 . 
   The seat reclining apparatus according to the embodiment of the present invention further includes a spring  33  formed by spirally winding a wire. The spring  33  is accommodated at the central portion of the lower plate  21 , i.e., at an inner side of the through hole  21   a . One end  33   a  of the spring  33  is engaged at the engagement hole  21   b  of the lower plate  21  and the other end  33   b  thereof is engaged with the protrusion  31   d  (see  FIG. 3 ) of the cam  31 . This spring  33  biases the cam  31  to the other side (counterclockwise in  FIG. 1 ) so that the cam  31  rotates relative to the lower plate  21 , i.e., so that the rotation prohibiting state is established, in which the upper plate  26  is prohibited from rotating relative to the lower plate  21 . 
   Therefore, by use of the biasing force of the spring  33 , the cam  31  basically maintains the rotation prohibiting state in which the upper plate  26  is prohibited from rotating relative to the lower plate  21  and maintains the rotation prohibiting state in which the seat back frame  12  is prohibited from rotating relative to the seat cushion frame  11 . Further, when the cam  31  rotates clockwise in  FIG. 1  against the biasing force of the spring  33 , the rotation prohibiting state is shifted to the rotation allowing state in which the upper plate  26  is allowed to rotate relative to the lower plate  21 . 
   A connecting shaft  34 , which is made from a metal bar, is inserted sequentially into the through hole  21   a  of the lower plate  21  housing the spring  33 , the fitting hole  31   c  of the cam  31  and the shaft insertion hole  26   a  of the upper plate  26 . The connecting shaft  34  includes integrally a flange  34   a  extending outwardly, an approximately circular and flattened cross section (like an oval shape) fitting portion  34   b , which protrudes to one axial side (towards the lower plate  21 ) at the flange  34   a  and is fitted into the fitting hole  31   c , and a connecting portion  34   c , which is continuous with the fitting portion  34   b  and protrudes to the further axial side (towards the lower plate  21 ). The connecting shaft  34  is fittedly mounted with an annular-shaped bush nut  35  at an end portion of the connecting shaft  34 , an end portion protruding out of the shaft insertion hole  26   a . Therefore, the connecting shaft  34  is positioned in the axial direction between the bush nut  35  and the flange  34   a  adjacent to the spring  33 . Here, the fitting portion  34   b  is positioned in the axial direction so as to fit into the fitting hole  31   c  (see  FIG. 3 ) and is connected to the cam  31  so as to rotate integrally therewith. 
   Further, the connecting portion  34   c  of the connecting shaft  34  illustrated in  FIG. 1  is connected to a corresponding connecting portion  34   c  (not illustrated) of the other connecting shaft  34  (not illustrated) forming a pair with the connecting shaft  34  in  FIG. 1 . The connecting shaft  34  in  FIG. 1  is hence rotatable integrally with the other connecting shaft  34  (not illustrated. Therefore, because the connecting shafts  34  at both sides are operatively associated with each other and rotate, the cams  31  at both sides are rotated integrally via the fitting portions  34   b  of the connecting shafts  34  fitted into the fitting bores  31   c.    
   The connecting shaft  34  further includes an attachment portion  34   d  protruding at the flange  34   a  in the other axial side (to the opposite side to the lower plate  21 ). The connecting shaft  34  illustrated in  FIG. 1  is attached with an operation lever  36  that is inserted with the attachment portion  34   d  and is operatively associated with the connecting shaft  34 . Therefore, the operation lever  36  is rotatable integrally with the connecting shaft  34  illustrated in  FIG. 1 . The operation lever  36  is employed to input an operation force to the cams  31  via the connecting shaft  34 . The operation force serves to rotate the cams  31  clockwise in  FIG. 1  relative to the lower plate  21  against the spring  33 , i.e., to switch the state of the upper plate  26  relative to the lower plate  21  to the rotation allowing state. 
   Described below are the guides  23   a ,  23   b  and the poles  32  according to the embodiment. As being simply illustrated in  FIG. 4 , each side surface  32   d  of each pole  32  is formed to be flat (planar) along the moving direction of the pole  32 . The pole sliding surface  23   c  of each guide  23   a  ( 23   b ) is formed with a recess  41  so that a part of the pole sliding surface  23   c  is separated away in the circumferential direction from the corresponding side surface  32   d  of the pole  32 . The recess  41  defines a space  41   a  relative to the corresponding circumferential side surface  32   d  of the pole  32 . For example when an excessive amount of load is applied from the pole  32 , deformation (plastic deformation) of the guide  23   a  ( 23   b ) starts at the recess  41 . 
   As described above, the following effects are obtained according to the embodiment. 
   The pole sliding surface  23   c  includes the recess  41 . Therefore, for example when an excessive amount of load is transmitted through the pole  32 , the deformation (plastic deformation) of the guide  23   a  ( 23   b ) is encouraged by the recess  41  formed at the guide  23   a  ( 23   b ). Therefore, even when an impact is applied to the seat back, compression of the pole sliding surface  23   c  of the protrusion  23  is started at the recess  41  and the compressed pole sliding surface  23   c  absorbs energy of the impact. It is hence possible to reduce a load (peak load) to be applied to an engagement portion between the inner teeth  27   a  of the upper plate  26  and the outer teeth  32   a  of the pole  32 . As a result, it is possible to maintain the engagement, i.e., to maintain the inclining angle of the seat back in a more stable manner. Further, it is possible to appropriately adjust characteristics of energy absorbing in response to a condition of input load by modifying the shape, the quantity, or the like of the recess  41  formed at the pole sliding surface  23   c.    
   The embodiment of the present invention can be modified as follows. 
   The shape of the recess  41  can be formed into any shape, such as an arc shape, a triangular shape, and a rectangular shape, as far as impact energy is absorbed appropriately. Further, each pole sliding surface  23   c  may be provided with plural recesses  41 . 
   According to the embodiment, the poles  32  are moved in the radial direction, so that the inclining angle of the seat back relative to the seat cushion is maintained or adjusted. However, the movement direction of the poles  32  is not limited to the radial direction. 
   The quantity of the poles  32  engageable with the cam  31  may be two or less than that or may be four or more than that. 
   According to the embodiment, the seat cushion frame  11  and the lower plate  21  are separate mechanical components. However, the scope of the present invention can be retained even when the seat cushion frame  11  and the lower plate  21  are formed integrally. 
   According to the embodiment, the lower plate  21  is supported by the seat cushion and the upper plate  26  is supported by the seat back. However, the upper plate  26  may be supported by the seat cushion and the lower plate  21  may be supported by the seat back. 
   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.