Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. patent application Ser. No. 11/718,309, filed Nov. 21, 2007, which is a PCT national stage entry of international patent application no. PCT/JP2005/19937, filed Oct. 28, 2005, which claims the foreign priority benefit of Japanese patent application no. JP2004-313623, filed Oct. 28, 2004. The contents of these applications are herein incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a vehicle seat, and particularly to a vehicle seat having a cushion plate with a pressure adjusting mechanism. 
     BACKGROUND 
     A conventional seat back cushion for a vehicle seat is resiliently supported by means of a number of seat springs which are located between side frames of a seat back frame. The seat springs generally comprise zigzag springs or formed wire springs. 
     The degree of bending of the seat springs locally vary depending on the magnitude of load imparted. The springs located in the upper and lower portions of the seat back frame are more bent than those located in the central portion of the seat back frame. Even in one spring, the central part of the spring is more bent than the right and left side parts of the spring. Thus, the degree of bending of the springs are locally varied. This brings about deterioration of the stability and comfort of the seat when a person sits on the seat. 
     Japanese Patent Application Laid-Open No. 11-206506 discloses a structural arrangement where an auxiliary plate, which is forwardly and rearwardly movable, is provided in connection with the cushion plate. 
     The auxiliary plate disclosed in Japanese Patent Application Laid-Open No. 11-206506 is integrally formed at the central part of the cushion plate, and the cushion plate is disposed only around the auxiliary plate. Therefore, the cushion plate disposed around the auxiliary plate fails to exhibit its function as the mechanism for resiliently supporting the seat back cushion. This means that a load of the seated person is focused on the auxiliary plate and is not effectively dispersed in the cushion plate. 
     Also in the conventional technique, it is difficult to provide both of a pressure adjusting mechanism of the cushion plate and an active headrest mechanism for moving the headrest to the front when the vehicle rear-end collision occurs in the seat back. In other words, the pressure adjusting mechanism lowers a sensitivity of a collision detector of the active headrest mechanism, and hence, it is difficult to coexistently provide both of the mechanisms. 
     SUMMARY 
     Accordingly, an object of various embodiments of the present invention is to provide a cushion plate with a pressure adjusting mechanism which is able to support the seated person while effectively dispersing the load of the seated person. 
     Another object is to provide a vehicle seat having a cushion plate with a pressure adjusting mechanism and an active headrest mechanism for moving the headrest to the front when the vehicle rear-end collision occurs. 
     In more detail, various embodiments of the invention provide a vehicle seat that comprises a rectangular-shaped seat back frame having right and left side frames; a flexible plate member provided between the right and left side frames; a seat back cushion provided in front of the flexible plate member; a mechanism for pushing the seat back cushion to a front direction by forwardly protruding the flexible plate member that results from the flexible plate member being bent; a headrest for supporting a head of a seat occupant, wherein the headrest is forwardly movably connected to the right and left side frames via right and left link members; and a rear-end collision detecting plate disposed at a portion of the seat back frame behind the seat occupant, wherein the rear-end collision detecting plate detects rearward movement of the seat occupant; wherein: each end portion of the rear-end collision detecting plate extends to a respective outer side of an end of the flexible plate member and is connected to a lower end portion of a respective link member; the flexible plate member is disposed anterior to the rear-end collision detecting plate; an upper end of the flexible plate member is disposed above an upper end of the rear-end collision detecting plate; and all of the rear-end collision detecting plate is positioned within a region between the upper end of the flexible plate member and a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following drawings illustrate an embodiment of the invention that is described in more detail below. 
         FIG. 1  is a perspective view showing a vehicle seat; 
         FIG. 2  is an exploded perspective view showing a seat back frame of the vehicle seat and basic components of an active headrest mechanism; 
         FIG. 3  is a perspective view showing an assembly of the components shown in  FIG. 2 ; 
         FIG. 4  is a perspective view showing a state that a cushion plate and an auxiliary plate are mounted to the assembly of  FIG. 3 ; 
         FIG. 5  is a side view showing a side frame of the seat back frame and the basic components of the active headrest mechanism; 
         FIG. 6  is a perspective view showing the back sides of the cushion plate and the auxiliary plate; 
         FIG. 7  is a side view showing a relationship between a part of skeleton of a seated person and the cushion plate; and 
         FIG. 8  is a longitudinal sectional view showing the cushion plate and the auxiliary plate. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     An embodiment of the present invention will be described with reference to the accompanying drawings. Referring to  FIGS. 1-4 , a vehicle seat  1  of the present invention has a seat back  2 , a seat bottom  3  and a headrest  4  provided at the top of the seat back  2 . Referring to  FIGS. 2 and 3 , a seat back frame  5  of the seat back  2  includes a pair of side frames  6 , an upper frame  7  and a lower frame  8 , and has a substantial rectangular shape. 
     A headrest support (lateral member)  10  is arranged near the upper frame  7 . The support  10  horizontally extends and is movable with respect to the seat back frame  5 . Lower parts of pillars  9  of the headrest  4  are inserted into vertical engaging parts  11  which are fixed to the headrest support  10 . The pillars  9  are vertically adjustable with the aid of the vertical engaging parts  11 . 
     Brackets  12  are fixed to the side frames  6 , respectively. The frames comprise a front projecting wall  6   b  and a rear projecting wall  6   c . An upper link (link member) or bell crank  15  is rotatably mounted to each bracket  12  by a shaft  16 . Each upper link  15  includes an upper long arm  22  extending upward and a lower short arm  23  extending downwardly and to the front side. The upper link  15  is urged by resiliency of an upper spring (biasing member)  13  clockwise, as shown in  FIG. 5 . The upper spring  13  includes a first end coupled to the upper link  15  and a second end coupled to the side frame  6 . The right and left ends of the headrest support  10  are coupled to the upper arms  22 , respectively. Each lower arm  23  is axially fixed to the upper part of a longitudinally extending coupling (or load transmission) rod  20  by way of a pin  21 . 
     The upper link  15  is normally held at a position indicated by a solid line in  FIG. 5  by the resiliency of the upper spring  13  or the like, whereby the headrest  4  is also held at a normal position. However, when the upper link  15  is rotated counterclockwise toward a position indicated by a dotted line, the headrest support  10  forwardly moves and the headrest  4  is pushed to the front. 
     A horizontally extending vehicle rear-end collision detector  25  is arranged between the side frames  6 ,  6 . When a rear-end collision occurs and the vehicle seat  1  relatively moves forward against the vehicle seat occupant T ( FIG. 7 ), the collision detector  25  ( FIGS. 3 ,  4 ) moves rearward by being pushed by the seat occupant T. Both ends of the collision detector  25  are coupled to lower links  26 ,  26  by way of pins  27 ,  27  (also “swinging shaft”) which are axially fixed to the side frames  6 ,  6  by support shafts  28 ,  28 , via connecting members  25 ′,  25 ′ respectively. The connecting members  25 ′,  25 ′ comprise a bend portion  25 ′ a  and a strengthening portion  25 ′ b . The collision detector  25  also comprises a contact portion  25   a , and a reinforcing portion (a bead)  25   b . The lower part of the coupling rod  20  is coupled to the lower link (link member)  26  by way of a pin  29 . As shown in  FIG. 5 , one end of a lower spring (biasing member)  14  is coupled to the lower link  26  at a first biasing member engagement portion  26 ′, while the other end thereof is coupled to the side frame  6  at a second biasing member engagement portion  6 ″, whereby the lower links  26  are urged counterclockwise. As a result, the collision detector  25  is held at a normal position, located in the front side. 
     When a rear-end collision occurs, the vehicle rear-end collision detector  25  is pushed by the seat occupant T to move rearward and to turn the lower links  26  counterclockwise in  FIG. 5  and to lower the coupling rod  20 . At this time, a distance between the pin  29  and the shaft  28  is shorter than a distance between the pin  27  and the shaft  28 , so that a backward movement of the collision detector  25  is efficiently transmitted to the coupling rod  20 . A downward movement of the rod  20  rotates the upper link  15  counterclockwise so that the headrest support  10  moves forward. The upper arm  22  of the upper link  15  is longer than the lower arm  23  so that the downward movement of the coupling rod  20  efficiently causes the headrest support  10  to move forward. The forward movement of the headrest support  10  pushes the headrest  4  to the front, thereby protecting a head (neck) of the seat occupant T at the time of the rear-end collision. 
     The side frames  6  are formed with a metal plate having a predetermined width as viewed in the front-and-back direction. A transmission mechanism for transmitting a backward movement of the vehicle rear-end collision detector  25  to the headrest support  10  is located at a position near the side frames  6 . Accordingly, a cushion  17  of the seat back  2  does not interfere with a motion of the transmission mechanism. A mechanism ranging from the collision detector  25  to the headrest support  10  forms an active headrest mechanism. 
     A flexible plate member  30  comprises a flexible cushion plate  31  and a flexible auxiliary plate  41 . The flexible cushion plate  31  is arranged inside the seat back frame  5 . The cushion plate  31  is preferably made of synthetic resin such as polypropylene, and is substantially a single rectangular plate. The cushion plate  31  is attached to seat springs  32  such as zigzag springs or formed wire springs at mounting portions (wire engagement portions)  31   a ,  31   a ′ that may include a rearward projecting portion  31   b . The seat springs  32  include at least an upper seat spring/wire member  32 A and a lower seat spring  32 B, the lower seat spring  32 B being attached to the cushion plate  31  at a mounting portion  31   a ′ within a protruding portion  31   c , and to the side frame  6  at a wire spring engagement portion  6   a ′. The seat springs  32  horizontally extend and are respectively coupled to the side frames  6  of the seat back frame  5  at wire spring engagement portions  6   a ,  6   a ′. The seat back cushion  17  is provided in front of the cushion plate  31 . The flexible cushion plate  31  has a part  31   d  that extends rearward of the collision detector  25  (see  FIG. 8 ). 
     When the flexible cushion plate  31  receives a load from the seat occupant T, the cushion plate  31  moves rearward against the elasticity of the seat springs  32  and flexibly supports the seat occupant T. The cushion plate  31  supports the seat back cushion  17  in “plane”. Therefore, the cushion plate makes the seat occupant T feel more stable and comfortable than the conventional one in which the seat back cushion  17  is supported by only the seat springs  32 . 
     An upper edge  34  of the flexible cushion plate  31 , as shown in  FIG. 7 , is located somewhat higher than the ninth thoracic vertebra X of the seat occupant T of the average height. The center gravity of the upper body of the seat occupant T is positioned near the ninth thoracic vertebra X. The cushion plate  31  is able to effectively support a part around the center of gravity of the seat occupant T. 
     The upper seat spring  32 A is selected to be at substantially the same height level as the ninth thoracic vertebra X or somewhat lower than it. In  FIG. 7 , the upper seat spring  32 A is located somewhat lower than the ninth thoracic vertebra X. The reason for this is that a load of the upper part of the body to the seat back cushion  17  usually acts on the rearward side. 
     The flexible cushion plate  31  includes a lower part  33  for supporting a portion near the sacrum S of the pelvis. The lower part  33  enhances a holding property at a portion near the hip of the seat occupant T. 
     The vehicle rear-end collision detector  25  is located in the rear of the flexible cushion plate  31  in a state that a predetermined space is present therebetween. Since the cushion plate  31  takes a plate-like shape for broadly covering the back of the seat occupant T, the flexible cushion plate  31  receives a load of the seat occupant T on a wide area when a rear-end collision occurs, and moves rearwardly. The amount of a rearward movement of the flexible cushion plate  31  is the largest between a mid portion as vertically viewed and a portion somewhat lower than the mid position. Therefore, the collision detector  25  is preferably located at a mid position as vertically viewed or a position somewhat lower than the mid position in order to reliably receive the rearward movement of the cushion plate  31 . Since a width of the seat back  2  as viewed in the front-and-back direction becomes narrower upward, it is not preferable that the collision detector  25  is located at an upper position on the rear side of the flexible cushion plate  31 . 
     A flexible auxiliary plate  41  is provided between the flexible cushion plate  31  and the seat back cushion  17 . Collectively, the flexible cushion plate  31  and auxiliary plate  41  may be construed as a load receiving member. The auxiliary plate  41  is preferably made of synthetic resin such as polypropylene, and is substantially a single rectangular plate, which is smaller than the flexible cushion plate  31 . When the auxiliary plate  41  is operated by the seat occupant T, it is bent to the front and pushes the seat back cushion  17  forwardly, thereby adjusting a cushion pressure against the seat occupant T. 
     The auxiliary plate  41 , which has a top portion  41   a , is provided with rearward projecting upper sliders  42  and lower sliders  43 . The upper sliders  42  protrude at a rearward projecting portion  42   a  (a retainer) to the rear side of the flexible cushion plate  31  through vertical upper slits  45  formed in the cushion plate  31 . The lower sliders  43  protrude to the rear side of the cushion plate  31  through vertical lower slits  46  formed in the cushion plate  31 . An upper horizontal mounting shaft (a linear member)  48  is bridged between the upper sliders  42  and  42 , and a lower horizontal mounting shaft  49  is bridged between the lower sliders  43  and  43 . 
     The auxiliary plate  41  is mounted to the cushion plate  31  by using the mounting shafts  48  and  49 . The sliders  42  and  43  are vertically slidable in the slits  45  and  46 , respectively. When the upper sliders  42  are moved downwardly and the lower sliders  43  are moved upwardly, the auxiliary plate  41  is bent to the front. 
     An upper U-shaped bracket  51  is rotatably mounted on the upper horizontal mounting shaft  48 . The bracket  51  includes a pair of arms  52  mounted to the mounting shaft  48  and a coupling part  53  provided between the arms  52 . A cable head  56 A of an inner cable  56  of a wire cable  55  is placed on and secured to the coupling part  53 . A lower bracket  66  is rotatably mounted to the lower horizontal mounting shaft  49 . The lower bracket  66  includes a pair of arms  67  mounted to the mounting shaft  49  and a coupling part  68  provided between the arms  67 . A tube head  57 A of an outer tube  57  of the wire cable  55  is placed on and secured to the lower bracket  66 . The other end of the wire cable  55  is coupled to an operation member  58  provided on the vehicle seat  1 . 
     When the operation member  58  is operated, a distance between the cable head  56 A and the tube head  57 A, i.e., a distance between the upper sliders  42  and the lower sliders  43  is adjusted. When the distance becomes long, the auxiliary plate  41  is parallel to the flexible cushion plate  31 , and when it becomes short, the auxiliary plate  41  bends to project to the front. Thus, by operating the operation member  58 , a degree of bending (forward projecting quantity) of the auxiliary plate  41  can be adjusted. 
     The auxiliary plate  41  includes a thin part  60  for defining a curved shape of the auxiliary plate  41 . When the distance between the upper sliders  42  and the lower sliders  43  becomes short, the auxiliary plate  41  is curved with respect to the thin part  60 . Accordingly, the curved shape of the auxiliary plate  41  is kept in a predetermined shape, and the cushion pressure adjustment by the auxiliary plate  41  is made effective by setting the thin part  60  at the lumber part of the seat occupant T. 
     A spring  61 , having an upper end attaching portion  61   a  for urging the upper horizontal mounting shaft  48  upwardly is provided between the upper horizontal mounting shaft  48  and the flexible cushion plate  31  (or the upper seat spring  32 A). 
     The flexible cushion plate  31  bends under a load from the seat occupant T and moves rearward against the elasticity of the seat springs  32 , and flexibly supports the seat occupant T. The flexible cushion plate  31  supports the seat back cushion  17  in “plane”. Therefore, the cushion plate makes the seat occupant T feel more stable and comfortable than the conventional one in which the seat back cushion  17  is supported by only the seat springs  32 . 
     When a physique of the seat occupant T presents an insufficient pressure from the seat back cushion  17 , the seated person pulls the inner cable  56  by operating the operation member  58  to reduce the distance between the upper sliders  42  and the lower sliders  43 . Then, the auxiliary plate  41  protrudes forward with respect to the thin part  60 , pushes the seat back cushion  17  forward to increase the cushion pressure, whereby the cushion pressure is adjusted as the seat occupant T desires. 
     When the auxiliary plate  41  is curved by the operation member  58 , the cushion pressure is changed. Since the auxiliary plate  41  and the flexible cushion plate  31  are in overlapping relation, the load by the seat occupant T that the auxiliary plate  41  receives is directly dispersed into the flexible cushion plate  31  as a single large plate. Accordingly, the good stability and comfort of the seat back cushion  17  are not lost. 
     When a rear-end collision occurs, the flexible cushion plate  31  greatly moves rearward by the load from the seat occupant T to come into contact with the vehicle rear-end collision detector  25  and to move it backward. In turn, the lower links  26 , in  FIG. 5 , rotate counterclockwise to lower the coupling rod  20 . The downward movement of the coupling rod  20  turns the upper links  15  counterclockwise to move the headrest support  10  to the front. As a result, the headrest  4  pushed to the front to protect the head (neck) of the seat occupant T against the impact by the rear-end collision. 
     In this case, the distance between the pin  29  and the shafts  28  is shorter than that between the pins  27  and the shafts  28 . Accordingly, the lower links  26  efficiently transmits the rearward movement of the collision detector  25  to the coupling rod  20 . Since the upper arms  22  of the upper links  15  are longer than the lower arms  23 , the downward movement of the coupling rod  20  is efficiently transmitted to the headrest support  10 . Therefore, the forward movement of the headrest  4  is satisfactorily secured. 
     Since the cushion plate  31  is shaped like a plate broadly covering the back of the seat occupant T, it reliably receives the rearward movement of the seat occupant T at the time of the rear-end collision in a broad area to reliably transmit the rearward movement of the seat occupant T to the collision detector  25 . 
     When the auxiliary plate  41  is bent by the operation member  58 , the cushion pressure is changed. Since the flexible cushion plate  31  is shaped like a plate broadly covering the back of the seat occupant T, and receives the load from the seat occupant T in a dispersing manner, the change of the cushion pressure by the auxiliary plate  41  does not substantially move the positions of the flexible cushion plate  31  and the collision detector  25 . Accordingly, the relative position of the cushion plate  31  to the collision detector  25  is retained and the change of the cushion pressure by the auxiliary plate  41  does not substantially interfere with the function of the active headrest mechanism.

Technology Category: 7