Vehicle seat

[0002] 1. Field of the Invention

[0003] The present invention generally relates to a vehicle seat. More specifically, the present invention relates to a seatback for a vehicle seat, which can mitigate an impact to an occupant at the time of a collision from rear.

[0004] 2. Background Information

[0005] Japanese Laid-Open Patent Application H7-291005 shows a connection member is provided in a connecting portion that connects a seatback frame and a plurality of cushion members. The seatback frame supports a headrest. The cushion members are S springs that are installed in a seatback. The connecting members move in a rearward direction when a load greater than a predetermined amount is applied to the connecting members. When the occupant is pushed against the cushion members as a reaction to the impact of the collision of the vehicle, and accordingly the load applied to the cushion members reaches a predetermined value, the connecting members that are on both sides of the cushion member being pushed extend in the rearward direction. In this manner, the posture of the occupant is maintained, while making the headrest receive the head of the occupant securely.

[0006] However, the shape of seatback and the distribution of the rigidity of seatback generally need to be determined taking into consideration ease of driving operation, comfort to the occupant, and ability to mitigate fatigue. Particularly, in order to allow the occupant to maintain a proper sitting posture effectively, the seatback structure has to support the lumbar vertebrae. Thus, this type of seatback is designed to form a high rigidity part in the lumbar support area.

[0007] At the time of collision of the vehicle, the occupant moves in the rearward direction relative to the vehicle body and the seat due to the inertial force. In the above structure, the connecting portion between the cushion members such as S springs and the seat frame moves in the rearward direction upon receiving a uniform predetermined load. In such structure, when a great load is applied to the lumbar support area, the S spring behind the lumbar support area moves rearward, while other S springs do not move. As a result, the S springs behind the thoracic vertebrae, for instance, do not move rearward until the load in the thoracic support area becomes great enough.

[0008] Furthermore, if the occupant sits on the seat with much speed during a normal operation, a false activation may occur. In order to prevent such false activation, the load at which the connecting portion starts moving rearward has to be set high. Accordingly, it is difficult to configure the structure in a manner that allows activation of the connecting portion easily at the time of a collision of vehicles.

[0009] In view of the above, there exists a need for a seatback for a vehicle which overcomes the above mentioned problems in the prior art. Specifically, there exists a need for a vehicle seatback that can mitigate impact to the occupant at the time of collision without causing an inconvenience during the normal operation. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.

[0010] It is an object of the present invention to provide a seatback for a vehicle that can mitigate impact to the occupant at the time of collision without causing an inconvenience during the normal operation.

[0011] The aforementioned object can be attained by providing a vehicle seat comprising a seat bottom, a seatback, at least two elastic supporting members, a displacement mechanism and a trigger mechanism. The seat bottom supports a buttock of an occupant. The seatback supports an upper body of the occupant. The elastic supporting members is disposed in a transverse direction within the seatback. The elastic supporting members includes a lower support member disposed to support a pelvis of the occupant and an upper support member disposed to support a back of the occupant. The displacement mechanism is disposed within the seatback and is coupled between the seatback and the upper support member to move the upper support member in a rearward direction relative to the seatback. The trigger mechanism is disposed within the seatback and is operatively coupled to the displacement mechanism at the lower support member to activate the displacement mechanism only upon receiving a rearward load greater than a predetermined value.

[0012] 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 preferred embodiments of the present invention.

[0013] Referring now to the attached drawings which form a part of this original disclosure:

[0014] FIG. 1 is a perspective view of an entire structure of a vehicle seat in accordance with a first embodiment of the present invention;

[0015] FIG. 2 is a perspective view of the encircled range A of the seatback in FIG. 1, shown in an assembled state;

[0016] FIG. 3 is a perspective view of the encircled range A of the seatback in FIG. 1, shown in an exploded state;

[0017] FIG. 4 is a partial cross sectional view of the seatback as seen along section line A-A′ of FIG. 2, showing the locked state in accordance with the first embodiment of the present invention;

[0018] FIG. 5 is a partial cross sectional view of the seatback as seen along section line A-A′ of FIG. 2, showing the lock releasing state in accordance with the first embodiment of the present invention;

[0019] FIG. 6 is a partial perspective view of the seatback in accordance with the first embodiment of the present invention, showing the elastic support member in the unstressed state;

[0020] FIG. 7 is a partial perspective view of the seatback in accordance with the first embodiment of the present invention, showing a partial displacement of the elastic support member;

[0021] FIG. 8 is a partial perspective view of the seatback in accordance with the first embodiment of the present invention, showing further displacement of the elastic support member;

[0022] FIG. 9 is a cross sectional view of the seatback in accordance with the first embodiment of the present invention, showing the elastic support member in the unstressed state as partially seen along line A-A′ of FIG. 6 and as partially seen along line B-B′ of FIG. 6;

[0023] FIG. 10 is a cross sectional view of the seatback in accordance with the first embodiment of the present invention, showing a partial displacement of the elastic support member as partially seen along line A-A′ of FIG. 6 and as partially seen along line B-B′ of FIG. 6;

[0024] FIG. 11 is a cross sectional view of the seatback in accordance with the first embodiment of the present invention, showing further displacement of the elastic support member as partially seen along line A-A′ of FIG. 6 and as partially seen along line B-B′ of FIG. 6;

[0025] FIG. 12 is a schematic cross sectional view of the seatback in accordance with the first embodiment of the present invention, showing a first occupant protection status or position;

[0026] FIG. 13 is a schematic cross sectional view of the seatback in accordance with the first embodiment of the present invention, showing a second occupant protection status or position;

[0027] FIG. 14 is a partial perspective view of the seatback in accordance with the second embodiment of the present invention, shown in an assembled state;

[0028] FIG. 15 is a partial perspective view of the seatback in accordance with the second embodiment of the present invention, shown in an exploded state;

[0029] FIG. 16 a partial cross sectional view of the seatback as seen along section line A-A′ of FIG. 14, showing the locked state in accordance with the second embodiment of the present invention;

[0030] FIG. 17 is a partial cross sectional view of the seatback as seen along section line A-A′ of FIG. 2, showing the lock releasing state in accordance with the second embodiment of the present invention;

[0031] FIG. 18 is a partial perspective view of the seatback in accordance with the second embodiment, showing the elastic support member in the unstressed state;

[0032] FIG. 19 is a partial perspective view of the seatback in accordance with the second embodiment, showing a partial displacement of the elastic support member;

[0033] FIG. 20 is a partial perspective view of the seatback in accordance with the second embodiment, showing further displacement of the elastic support member;

[0034] FIG. 21 is a cross sectional view of the seatback in accordance with the second embodiment of the present invention, showing the elastic support member in the unstressed state as partially seen along line A-A′ of FIG. 18 and as partially seen along line B-B′ of FIG. 18;

[0035] FIG. 22 a cross sectional view of the seatback in accordance with the second embodiment of the present invention, showing a partial displacement of the elastic support member as partially seen along line A-A′ of FIG. 18 and as partially seen along line B-B′ of FIG. 18;

[0036] FIG. 23 is a cross sectional view of the seatback in accordance with the second embodiment of the present invention, showing further displacement of the elastic support member as partially seen along line A-A′ of FIG. 18 and as partially seen along line B-B′ of FIG. 18;

[0037] FIG. 24 is a partial outside, exploded perspective view of the seatback in accordance with the second embodiment of the present invention;

[0038] FIG. 25 is a partial outside perspective view of the seatback in accordance with the second embodiment of the present invention;

[0039] FIG. 26 is a partial perspective view of a portion of a seatback in accordance with a third embodiment of the present invention, shown in an assembled state;

[0040] FIG. 27 is partial perspective view of a portion of a seatback structure in accordance with the third embodiment of the present invention, shown in an exploded state;

[0041] FIG. 28 is a partial perspective view of the seatback in accordance with the third embodiment of the present invention, showing the elastic support member in the unstressed state;

[0042] FIG. 29 is a partial perspective view of the seatback, showing a partial displacement of the elastic support member in accordance with the third embodiment of the present invention;

[0043] FIG. 30 is a partial perspective view of the seatback, showing further displacement of the elastic support member in accordance with the third embodiment of the present invention;

[0044] FIG. 31 is a partial outside, exploded perspective view of the seatback in accordance with the third embodiment of the present invention;

[0045] FIG. 32 is partial outside perspective view of the seatback in accordance with the third embodiment of the present invention;

[0046] FIG. 33 is a partial perspective view of the seatback in accordance with a fourth embodiment of the present invention, shown in an assembled;

[0047] FIG. 34 is a partial perspective view of the seatback in accordance with the fourth embodiment of the present invention, shown in an assembled;

[0048] FIG. 35 is a partial perspective view of the seatback, showing the elastic support member in the unstressed state in accordance with the fourth embodiment of the present invention;

[0049] FIG. 36 is a partial perspective view of the seatback showing a partial displacement of the elastic support member in accordance with the fourth embodiment of the present invention;

[0050] FIG. 37 is a partial perspective view of the seatback, showing further displacement of the elastic support member in accordance with the fourth embodiment of the present invention;

[0051] FIG. 38 is a partial perspective view of the seatback in accordance with a fifth embodiment of the present invention, shown in an assembled;

[0052] FIG. 39 is a partial perspective view of the seatback in accordance with the fifth embodiment of the present invention, shown in an exploded state;

[0053] FIG. 40 is a partial perspective view of the seatback, showing the elastic support member in the unstressed state in accordance with the fifth embodiment of the present invention;

[0054] FIG. 41 is a partial perspective view of the seatback, showing a partial displacement of the elastic support member in accordance with the fifth embodiment of the present invention;

[0055] FIG. 42 is a partial perspective view of the seatback, showing further displacement of the elastic support member in accordance with the fifth embodiment of the present invention;

[0056] FIG. 43 is a perspective view of a frame structure of a seatback in accordance with a sixth embodiment of the present invention;

[0057] FIG. 44 is a schematic cross sectional view of the seatback in accordance with the sixth embodiment, showing a first operational status or position;

[0058] FIG. 45 is a schematic cross sectional view of the seatback in accordance with the sixth embodiment, showing the second operational status or position; and

[0059] FIG. 46 is a perspective view of a frame structure of a seatback in accordance with a seventh embodiment of the present invention.

[0060] Selected embodiments 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 embodiments of the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0061] Referring initially to FIGS. 1-13, a vehicle seat is illustrated to explain a first embodiment of the present invention. FIG. 1 shows an entire structure of the seat for a vehicle in accordance with a first embodiment of the present invention. The seat has a seat cushion C that supports a buttock of an occupant and a seatback B that supports an upper body of the occupant.

[0062] In FIG. 1, the seatback B is depicted as a seatback frame from which surface and the urethane cushion material have been removed. The seatback frame has a pair of frames 101aand 101b,and an upper cross 102. The frames 101aand 101bare disposed on the left and right sides, extending in the vertical direction so as to conform to the shape of the spine of the occupant. The upper cross 102 connects upper ends of the frames 101aand 101b.The upper cross 102 also provides the rigidity with which a headrest 116 (shown in FIGS. 19 and 21) is supported. At bottom ends of the frames 101aand 101b,a rotational axis 103 is provided to connect the seat cushion C and a seat pan P via a recliner R.

[0063] In order to secure the rigidity in the bottom end area, a lower cross 104 can be provided so as to connect the frames 101aand 101b,as seen in FIG. 1.

[0064] Since covering the seatback frame with the urethane cushion material and the surface alone will not provide sufficient rigidity to support the upper body of the occupant, a plurality of elastic support members such as S springs is further provided to generate more rigidity. The S springs are disposed in the transverse direction.

[0065] In this embodiment, the S springs 105aand 105bare respectively provided on upper and lower portions. The upper S spring 105aforms an upper support member, which supports the thoracic vertebrae of the occupant. The lower S spring 105bforms a lower support member that supports the lumbar vertebrae of the occupant.

[0066] FIGS. 2 and 3 are assembled and expanded views of a portion of the seat structure encircled by a broken line A in FIG. 1. More specifically, FIGS. 2 and 3 show how the S springs 105aand 105bare attached to the frame 101a.

[0067] As described above, the upper S spring 105ais disposed at a height that substantially corresponds to the thoracic vertebrae of the occupant, while the lower S spring 105bis disposed at a height that substantially corresponds to the lumbar vertebrae of the occupant. The rigidity of the upper S spring 105ais set soft in order to provide comfort to the occupant. On the other hand, the rigidity of the lower S spring 105bis set hard in order to support the lumbar vertebrae.

[0068] An end of the upper S spring 105ais fixed to a rotational plate 106. Preferably, the end of the upper S spring 105ais coupled to a hook 106a,which is formed by rolling a portion of the rotational plate 106.

[0069] The rotational plate 106 is coupled to the frame 101avia a pin 107. The rotational plate 106 can rotate freely about pin 107. The rotational plate 106 has a longitudinally long shape. The hook 106ato which the upper S spring 105ais fixed is positioned above pin 107. An arm 106bextends below pin 107. This freely rotatable mechanism forms a displacement mechanism or displacing means that can move the upper support member in a rearward direction relative to the seatback.

[0070] An end of the lower S spring 105bis fixed to a plate spring 108. The plate spring 108 is fixed to the frame 101avia a pair of rivets 109aand 109b.Alternatively, the plate spring 108 can be fixed by a bolt or welding or other means.

[0071] An attachment point 109 (the rivets 109aand 109b) is positioned on a rear portion (rear side of the vehicle) of the spring plate 108. The lower S spring 105bis fixed to the spring plate 108 at a point that is on a front portion relative to the aforesaid attachment point 109. For instance, the lower S spring 105bis hooked to a hook 108athat is formed by rolling a portion of the plate spring 108.

[0072] A front end of the plate spring 108 is slightly bent toward the frame 101a,thereby forming a lock hook 108b.

[0073] At a portion where the rotational plate 106 and the plate spring 108 are coupled to the frame 101a,the arm 106bof the rotational plate 106 is sandwiched between the frame 101aand the plate spring 108. In this manner, the lock hook 108brestricts the rotation of the rotational plate 106. In this manner, a trigger mechanism or triggering means of the lower support member is formed.

[0074] FIGS. 4 and 5 show a function of the lock hook 108bin accordance with the first embodiment of the present invention. FIGS. 4 and 5 are cross sectional views as viewed from a horizontal cutting line A-A′ of FIG. 2. More specifically, FIG. 4 shows a normal state, whereas FIG. 5 shows a state at the time of a vehicle collision.

[0075] In FIGS. 4 and 5, the letter A indicates the front side of the vehicle, while the letter A′ indicates the rear side of the vehicle.

[0076] Referring to FIG. 4, as described above, the arm 106bof the rotational plate 106 is sandwiched between the frame 101aand the plate spring 108 in the normal state. In this state, the arm 106bof the rotational plate 106 cannot move either frontward or rearward, because the rivets 109aand 109bare attached between the plate spring 108 and the frame 101aon the rear side, and the lock hook 108bis formed on the front end of the plate spring 108 on the front side.

[0077] Referring to FIG. 5, at the time of vehicle collision, when the pelvis of the occupant is pushed against the lower S spring 105b,the portion that forms fixing hook 108adeflects in the rearward direction (right hand side in FIG. 5) inside the frames 101aand 101bdue to the tension of the lower S spring 105b.Accordingly, the lock hook 108bthat is formed on the front end is bent rearward. Thus, the lock of the rotational plate 106 is released.

[0078] FIGS. 6-8 are step-by-step views of operation of the rotational plate 106 during the release of lock by the lock hook 108b.FIGS. 9-11 show movements of upper and the lower S springs 108aand 105bas seen from the section lines A-A′ and B-B′ of FIG. 6. The left hand sides of FIGS. 6-8 show the cross sectional views of the lower S spring 105bas seen at the height of A-A′ of FIG. 6, while the right hand sides of FIGS. 6-8 show the cross sectional views of the upper S spring 105aas seen at the height of B-B′ of FIG. 6.

[0079] FIGS. 6-8 and 9-11 are respectively perspective views and cross sectional views of the lock hook 108bat corresponding states. FIGS. 6 and 9 show a state during a normal operation. The rotational plate 106 is locked by the lock hook 108bof the plate spring 108. FIGS. 7 and 10 show a state in which the occupant is pushed against the seatback B by the inertia. Since the pelvis pushes the lower S spring 105b,the lower S spring 105bextends rearward. Accordingly, the lock hook 108bof the plate spring 108 releases the lock by the tension of the lower S spring 105b.

[0080] As the occupant approaches the seatback B, the upper S spring 105ais also pushed. However, since the rigidity of the upper S spring 105ais set lower than the rigidity of the lower S spring 105b,the amount of displacement of the upper S spring 105ais smaller than the amount of displacement of the lower S spring 105bas seen in FIG. 10.

[0081] However, in FIGS. 7 and 10, since the lock of the lock hook 108bof the plate spring 108 is released, the rotational plate 106 becomes freely movable. Thus, the rotational plate 106 starts moving even when a small load is applied to the upper S spring 105a.The direction of displacement of the rotational plate 106 is clockwise in FIGS. 6-8, and upward in FIGS. 9-11. FIGS. 8 and 10 show a state in which the rotational plate 106 has been moved.

[0082] Since the rotational plate 106 has a longitudinally long shape, once the rotational plate 106 rotates up to a certain angle, a portion of the rotational plate 106 contacts flanges that are disposed on front and rear sides of the frame 101a.Accordingly, the rotation of the rotational plate 106 stops.

[0083] FIGS. 12 and 13 show how the shape of the spine of the occupant is maintained by the rear displacement of the upper S spring 105adescribed above at the time of vehicle collision. FIG. 12 shows the spine shape before the collision occurs, while FIG. 13 shows the spine shape after the collision. While the occupant is in a normal sitting position, the occupant's spine has an S shape in which the area adjacent the thoracic vertebrae is bulged in the rearward direction.

[0084] At the time of collision, the seat is pushed forward along with the vehicle. On the other hand, the inertia tries to keep the occupant in the initial position. Therefore, when seen with respect to the seat, the occupant moves rearward toward the seatback B. Therefore, with a conventional seatback, the spine of the occupant tends to be straightened at the time of vehicle collision due to the contacting force between the thoracic vertebrae and the seatback.

[0085] According to the present invention, the load in the pelvis area is utilized to quickly activate a trigger mechanism that is provided with the lower S spring 105b.Therefore, while the pelvis of the occupant is stopped from moving further rearward by the lower S spring 105b,the rotational plate 106 moves in the rearward direction even by a slight load generated by the back pushing the upper S spring 105a.

[0086] More specifically, when the occupant moves rearward and the pelvis pushes the lower S spring 105b,the lock of the lock hook 108bis released. Then, the rotational plate 106 is activated to allow the upper S spring 105ato move in the rearward direction. Therefore, the upper body can sink in the seatback B. In this manner, the rearward movement of the upper S spring 105ais enabled via the displacement mechanism. Therefore, even when the chest and pelvis of the occupant move rearward by the same distance at the time of vehicle collision, the trigger mechanism can be activated by the reactionary force at the pelvis portion before the reactionary force at the thoracic vertebrae portion increases. Besides, it is particularly well known that the load in the pelvis portion increases rapidly due to the occupant's pushing the seatback at the time of vehicle collision. Accordingly, the load applied to the thoracic vertebrae of the occupant can be kept small. Also, the occupant can be supported while maintaining the shape of the spine.

[0087] In this manner, the rearwardly bulging shape of the spine can be maintained without being straightened. Furthermore, since the upper body of the occupant sinks in seatback B, the distance between the occipital portion of the occupant's head and the headrest is shortened.

[0088] Furthermore, the length between the sitting surface of the seat and the lumbar vertebrae does not vary person to person as much as the length between the sitting surface and the head does. Therefore, by providing the trigger mechanism in the lower S spring 105bas described above, the aforementioned effect of the present invention can be offered to anybody regardless of the difference in the body sizes.

[0089] Furthermore, the aforementioned series of movements of the present embodiment occurs when the upper S spring 105ais pushed rearward while the lower S spring 105bis pushed rearward with a great force. In other words, the movements occur, or the trigger mechanism and the displacement mechanism are activated, only when the occupant moves toward the seatback B horizontally, such as at the time of collision. More specifically, the rotational plate 106 is not expected to be activated during a normal operation, such as by the occupant's sitting on the pelvis and letting the back lean against the seatback B. Therefore, unwanted rearward displacement is not likely to occur during normal operations. Accordingly, the seat structure of the present invention offers better comfort.

[0090] Referring now to FIGS. 14-25, an alternate seatback is illustrated in accordance with the second embodiment of the present invention. In view of the similarity between the first and second embodiments, the parts of second embodiment that are identical to the parts of the first embodiment will be given the same reference numerals as the parts of the first embodiment. Moreover, the descriptions of the parts of the second embodiment that are identical to the parts of the first embodiment may be omitted for the sake of brevity. The parts of the second embodiment that significantly differ from the parts of the first embodiment will be indicated with new reference numbers.

[0091] In the second embodiment, two S springs 105aand 105bare utilized as the elastic support members. The upper S spring 105ais supported by a plate 126 that is slidable in a front-rear direction (hereinafter referred to as slidable plate). The lower S spring 105bis fixed to a slide frame 128. The upper S spring 105ais fixed by hooking an end portion of the upper S spring 105ato a hook 126a,which is formed by rolling up a portion of the slidable plate 126.

[0092] The slidable plate 126 has a longitudinally long shape that extends between the S springs 105aand 105b.At the height of the lower S spring 105b,a small protrusion that protrudes in a frontward direction is formed. A bore 126cis formed in the protrusion. In bore 126c,a lock hook 128b,which will be described later, engages to fix slidable plate 126.

[0093] The slidable plate 126 is stored within slidable frame 128. At a position at which the upper S spring 105aand hook 126aengage each other, a window 128cis formed in the slide frame 128. The slide frame 128 is fixed to the frame 101aby welding. The slide frame 128 is oriented so as to move in a substantially front-rear direction. In a bottom portion of the slide frame 128, a plate spring portion that is protruding by a short distance is formed. A hook 128ais formed in the protruding plate spring portion to which the lower S spring 105bis fixed.

[0094] Furthermore, a front end of the slide frame 128 is slightly bent toward the frame 101ato form a lock hook 128b.During normal operations, the lock hook 128bengages a bore 126cformed in the slidable plate 126. In other words, in this state, the lock hook 128brestricts a rear displacement of the slidable plate 126.

[0095] FIGS. 16 and 17 show operations of slidable plate 126 during release of the lock by the lock hook 128b.FIG. 16 shows a cross sectional view during the normal operation. The lock hook 128bthat is disposed at the plate spring position of the slide frame 128 engages the bore 126cof the slidable plate 126. Therefore, the movement of the slidable plate 126 is restricted. FIG. 17 shows a cross sectional view after a vehicle collision. As the pelvis of the occupant pushes against the lower S spring 105b,the lower S spring 105bextends in a diagonally rearward direction, which is the upward right direction in FIG. 17. The lock hook 128cthat is at the front of the plate spring portion is released from the bore 126cof the slidable plate 126 by the tension of the lower S spring 105b.Accordingly, the lock is released. After the lock is released, slidable plate 126 moves in a rearward direction or the upward direction in FIG. 17 by the tension of the upper S spring 105a.

[0096] FIGS. 18-20 shows step-by-step views of movements of the slidable plate 126 during the release of the lock by lock hook 128b.FIGS. 21-23 show cross sectional views as seen from the horizontal section lines A-A′ and B-B′ of FIG. 18, showing movements of upper and the lower S springs 105aand 105bat corresponding positions. More specifically, the left hand sides of FIGS. 21-23 show cross sectional views at the height of the line A-A′, at which there is the lower S spring 105b.The right hand sides of FIGS. 21-23 show the cross sectional views at the height of the line B-B′, at which there is the upper S spring 105a.FIGS. 18-20 and FIG. 21-23 are views of corresponding states.

[0097] FIGS. 18 and 21 show a normal state, in which slidable plate 126 is locked by lock hook 128b.FIGS. 19 and 22 show a state where the occupant is pushed against the seatback B by the inertia at the time of vehicle collision. Since the pelvis pushes against the lower S spring 105b,the lower S spring 105bextends in the rearward direction. The lock hook 128bthat is at the plate spring portion releases the lock due to the tension of the lower S spring 105b.At this point, the slidable plate 126 becomes available for activation. Thereafter, the slidable plate 126 moves rearward even with a slight load applied to the upper S spring 105a.The sliding of the slidable plate 126 stops when the slidable plate 126 contacts the flange of the frame 101a.However, it is also possible to provide a separate stopper.

[0098] In the second embodiment, since the displacement mechanism includes the slidable plate 126, the upper S spring 105amoves in the same rearward direction as the direction of the load input. The effect of maintaining the spinal shape of the occupant at the time of vehicle collision in the second embodiment is the same as the aforementioned first embodiment.

[0099] In the second embodiment, as seen in FIG. 11, a lever 110 is provided on an opposite side of the slidable plate 126. The lever 110 passes through a bore in the frame 101ato the side surface of the seat, such that lever 110 is exposed. Therefore, after the slidable plate 126 moves rearward at the time of collision, if the occupant moves lever 110 and returns the slidable plate 126 to its original position, the occupant can resume normal operation without having to disassemble the seatback B. In other words, this forms a return mechanism, which allows the seatback B to return to its original position after activation of the displacement mechanism. Therefore, when the vehicle collision is a minor one, the return mechanism returns the displacement mechanism to its initial position. Thereafter, the occupant can continue to use the seatback. Furthermore, by adjusting the bending angle of the lock hook 128, the amount of resistance generated while the slidable plate 126 is returned to initial position to reengage the bore 126ccan be adjusted.

[0100] Referring now to FIGS. 26-32, an alternate seatback B is illustrated in accordance with a third embodiment of the present invention. In view of the similarity between this embodiment and the prior embodiments, the parts of third embodiment that are identical to the parts of the prior embodiments will be given the same reference numerals as the parts of the prior embodiments. Moreover, the descriptions of the parts of the third embodiment that are identical to the parts of the prior embodiments may be omitted for the sake of brevity. The parts of the third embodiment that significantly differ from the parts of the prior embodiments will be indicated with new reference numbers.

[0101] In this embodiment, three S springs 105a,105band 105care utilized as the elastic support members. The upper S spring 105ais disposed at a height that substantially corresponds to the thoracic vertebrae of the occupant. The intermediate S spring 105cand the lower S spring 105bare disposed at heights that substantially correspond to the lumbar vertebrae of the occupant. Therefore, the feel of support for the lumbar vertebrae during normal operations is improved in the third embodiment. Alternatively, three S springs can be utilized to broadly and uniformly support the lumbar vertebrae of the occupant.

[0102] The upper S spring 105aand intermediate S spring 105care fixed to the rotational plate 106. The rotational plate 106 is rotatably coupled to the frame 101aby a pin 107. The rotational plate 106 has a longitudinally long shape. Upper and intermediate S springs 105aand 105care disposed at fixing positions 106athat are above the position of pin 107. An arm 106bextends below pin 107. The arm 106bis shaped to have a broad width.

[0103] An end of the lower S spring 105bis fixed to a plate spring 108. The plate spring 108 is coupled to the frame 101avia a pair of rivets 109aand 109b.

[0104] Attachment point 109 formed by rivets 109aand 109bis positioned on a rear portion of the plate spring 108. A fixing point 108aof the lower S spring 105bis positioned on a front portion of the plate spring 108 relative to attachment points 109. A front end of the plate spring 108 is slightly bent toward the frame 101a,so as to form a lock hook 108b.Where the rotational plate 106 and the plate spring 108 are coupled to the frame 101a,the arm 106bof the rotational plate 106 is sandwiched between the frame 101aand the plate spring 108. In this manner, the rotation of the rotational plate 106 is restricted by the lock hook 108b.

[0105] FIGS. 28-30 show step-by-step views of the movements of the rotational plate 106 during the release of lock by the lock hook 108b.Since the trigger mechanism of the present embodiment is activated by the elastic displacement of the lower S spring 105b,the upper S spring 105acan be moved rearward securely by synchronizing the elastic displacement of the lower S spring 105band the activation of the trigger mechanism.

[0106] FIG. 28 shows a normal state, in which rotation of the rotational plate 106 is locked by the lock hook 108b.

[0107] FIG. 29 shows a state where the occupant is pushed against the seatback B by the inertia at the time of vehicle collision. Since the pelvis pushes the lower S spring 105b,the lower S spring 105bextends in the rearward direction. Then, the lock hook 108bof the plate spring 108 releases the lock due to the tension of the lower S spring 105b.Accordingly, the slidable plate 106 becomes available for activation. Thus, the slidable plate 106 starts moving with even a slight load applied to the upper S spring 105aand the intermediate S spring 105c.

[0108] As seen in FIG. 30, the rotational plate 106 moves in a clockwise direction. The amount of rearward movement of the upper S spring 105a,which is farther from pin 107 than intermediate S spring 105c,is greater than the amount of movement of the intermediate S spring 105c.

[0109] Therefore, while maintaining continuous inclination at the upper, intermediate, and lower levels, the seatback B of the third embodiment can maintain the spinal shape of the occupant. Furthermore, in this embodiment, the pin 107 of the rotational plate 106 passes through the frame 101aand is exposed to the seat surface. A lever 110 is fixedly coupled to the protruding end of the pin 107 to form a return mechanism, as seen in FIGS. 31 and 32.

[0110] Therefore, after the rotational plate 106 moves rotationally due to vehicle collision, the rotational plate 106 can be returned to its original position by moving the lever 110. In this manner, the occupant can resume the normal operation without having to disassemble the seatback B.

[0111] Furthermore, in this embodiment, the arm 106bof the rotational plate 106 has a broad width. Therefore, even after the rotational plate 106 is activated due to the collision, the lock hook 108bmaintains the state shown in FIG. 30, in which the lock hook 108bis off and above the arm 106b.In this manner, the resistance while the rotational plate 106 is returned to the initial position can be reduced.

[0112] Furthermore, even for an occupant whose seated height is so short that a portion of his thoracic vertebrae is supported by the intermediate S spring 105c,the intermediate S spring 105cmoves rearward at the time of vehicle collision. Therefore, the seatback B of the third embodiment prevents the spine from being straightened.

[0113] Referring now to FIGS. 33-37, an alternate seatback B is illustrated in accordance with a fourth embodiment of the present invention. In view of the similarity between this embodiment and the prior embodiments, the parts of fourth embodiment that are identical to the parts of the prior embodiments will be given the same reference numerals as the parts of the prior embodiments. Moreover, the descriptions of the parts of the fourth embodiment that are identical to the parts of the prior embodiments may be omitted for the sake of brevity. The parts of the fourth embodiment that significantly differ from the parts of the prior embodiments will be indicated with new reference numbers.

[0114] In this embodiment, two S springs 105aand 105bare utilized as the elastic support members. The upper S spring 105ais fixedly coupled to the rotational plate 106. The rotational plate 106 has a longitudinally long shape. A pin 107ais provided at an upper end of the rotational plate 106, such that the rotational plate 106 rotates about pin 107a.

[0115] A fixing position 106aof the upper S spring 105ais disposed at a height that corresponds to a center area of the rotational plate 106. An arm 106bextends in a downward direction below fixing position 106a.An end of the lower S spring 105bis directly attached to the frame 101a.

[0116] A bar 111 is provided behind the lower S spring 105b.The bar 111 has a length that fits between the left and right frames. The bar 111 is fixedly coupled to an arm 112aof a rotatable link 112. The link 112 is coupled to the frame 101avia a pin 107b.A stopper hook 112bextends toward the arm 106bof the rotational plate 106.

[0117] A stopper that is not shown in the Figures restricts the forward displacement of the arm 112aof the link 112. Where the rotational plate 106 and the link 112 are attached to the frame 101a,the arm 106bof the rotational plate 106 contacts the stopper hook 112bof the link 112. Accordingly, rotation of the rotational plate 106 is restricted (locked) by the stopper hook 112b.

[0118] FIGS. 35-37 show step-by-step views of the movements of the rotational plate 106 during the release of lock by the stopper hook 112b.FIG. 35 shows a normal state, in which the rotational plate 106 is locked by the stopper hook 112b.FIG. 36 shows a state where the occupant is pushed against the seatback B by the inertia at the time of vehicle collision. Since the pelvis pushes the lower S spring 105b,the lower S spring 105bextends in the rearward direction. Once the lower S spring 105bmoves rearward by a certain distance, a lever 111 is pushed. Accordingly, the link 112 starts rotating in a counter clockwise direction as seen in FIG. 36. In this manner, the stopper hook 112bis disengaged from the arm 106bof the rotational plate 106, and lock is released.

[0119] In this manner, the rotational plate 106 becomes available for activation. Once a load is applied to the upper S spring 105a,the rotational plate 106 starts rotating in the counter clockwise direction as seen in FIG. 37.

[0120] Therefore, the fourth embodiment can achieve the same effects as those of the first embodiment. Furthermore, a trigger mechanism or triggering means in this embodiment includes the link 112 that is rotated by the bar 111, instead of by the lower S spring 105b,in response to a rearward load. Therefore, conditions for activating the rotational plate 106 can be freely set based on the amount of displacement of the link 112. Particularly, conditions for activating the rotational plate 106 can be set without affecting the rotational plate's function of supporting the lumbar vertebrae of the occupant, which is what the rotational plate 106 is originally designed for.

[0121] Referring now to FIGS. 38-42, an alternate seatback B is illustrated in accordance with a fifth embodiment of the present invention. In view of the similarity between this embodiment and the prior embodiments, the parts of fifth embodiment that are identical to the parts of the prior embodiments will be given the same reference numerals as the parts of the prior embodiments. Moreover, the descriptions of the parts of the fifth embodiment that are identical to the parts of the prior embodiments may be omitted for the sake of brevity. The parts of the fifth embodiment that significantly differ from the parts of the prior embodiments will be indicated with new reference numbers.

[0122] In this embodiment, two S springs 105aand 105bare utilized as the elastic support members. The upper S spring 105ais fixedly coupled to a slidable plate 126. The slidable plate 126 is coupled to the slide frame 128 so as to be slidable in a front-rear direction. The slide frame 128 is fixed within the frame 101a.The lower S spring 105bis directly fixed to the frame 101a.Adjacent the lower S spring 105b,a wire 113 is attached so as to fit between the left and right frames. The wire 113 passes through a through ring 114, which is formed on an inner surface of the frame 101a.The wire 113 then extends in an upward direction of the frame 101a,and is connected to a lock pin 115.

[0123] The lock pin 115 is inserted into and supported by a bore formed on a bottom surface of the slide frame 128. The lock pin 115 restricts (locks) rearward displacement of the slidable plate 126.

[0124] FIGS. 40-42 show step-by-step views of the movements at the time of vehicle collision in accordance with the present embodiment. FIG. 40 shows a normal state, in which the slidable plate 126 is locked by the lock pin 115. FIG. 41 shows a state where the occupant is pushed against the seatback B by the inertia at the time of vehicle collision. Since the pelvis pushes the lower S spring 105b,the lower S spring 105bextends in the rearward direction. As the lower S spring 105bmoves rearward by a certain distance, the wire 113 is pushed and extended in the rearward direction. Accordingly, the lock pin 115 is pulled out in the downward direction and disengages from the slidable plate 126. In this manner, lock is released.

[0125] Thus, the slidable plate 126 becomes available for activation. Thereafter, once a load is applied to the upper S spring 105a,the slidable plate 126 moves rearward as seen in FIG. 42. Accordingly, the upper S spring 105amoves in a rearward direction.

[0126] Therefore, the fifth embodiment can achieve the same effects as those of the second embodiment. Furthermore, trigger mechanism or triggering means of the fifth embodiment includes the lock pin 115, instead of the lower S spring 105b.The lock pin 115 releases the lock based on the wire 113 that moves rearward in response to a rearward load. Therefore, conditions for activating the trigger mechanism can be set freely based on stretch characteristic of the wire 113, regardless of the elasticity of the lower S spring 105b.Particularly, the conditions for activating the trigger mechanism can be set without affecting the lower S spring's function of supporting the lumbar vertebrae of the occupant, which is what the lower S spring 105bis originally designed for.

[0127] Furthermore, when the wire 113 is utilized, there is more flexibility as to where to position the wire 113. Therefore, it is easy to prevent conflict between the wire 113 and other members that are to be stored within the seatback B.

[0128] Referring now to FIGS. 43-45, a seatback B is illustrated in accordance with a sixth embodiment of the present invention. In view of the similarity between this embodiment and the prior embodiments, the parts of sixth embodiment that are identical to the parts of the prior embodiments will be given the same reference numerals as the parts of the prior embodiments. Moreover, the descriptions of the parts of the sixth embodiment that are identical to the parts of the prior embodiments may be omitted for the sake of brevity. The parts of the sixth embodiment that significantly differ from the parts of the prior embodiments will be indicated with new reference numbers.

[0129] In this embodiment, two S springs 105aand 105bare utilized as the elastic support members. Also, the seatback B of the sixth embodiment basically has the structure of the fourth embodiment, in that the displacement mechanism or displacing means is formed by the rotational plate 106 and that the trigger mechanism or triggering means is formed by the link 112.

[0130] In this embodiment, the rod members 117aand 117bare coupled to the rotational plate 106. The rod members 117aand 117bsupport a headrest 116.

[0131] Instead of the upper cross 102 as in the fourth embodiment, a rotational axis 118 is fixedly coupled to the frames 101aand 101bso as to connect the left and right frames 101aand 101b.The rotational plate 106 is coupled to the rotational axis 118 so as to be rotatable about this rotational axis 118. Therefore, since the rotational plate 106 rotates about the rotational axis 118, which has small friction force, the upper S spring 105 can move rearward smoothly.

[0132] A reinforcing member 119 is fixedly coupled below the rotational axis 118 so as to connect the rotational plates 106 on both left and right sides. The headrest support members 117aand 117bare fixed to the rotational axis 118 and the reinforcing member 119.

[0133] FIGS. 44 and 45 show the movements of the seatback B in accordance with the sixth embodiment at the time of vehicle collision. In the sixth embodiment, the upper S spring 105amoves rearward due to rotation of the rotational plates 106. Also, the bottom portions of the headrest support members 117aand 117bmove rearward due to the rotation of the rotational plate 106. Accordingly, the portion of the headrest 116 that is above the rotational axis 118 moves forward. Therefore, the distance between the occupant's head and the headrest can be shortened.

[0134] FIG. 44 shows a normal state, in which rotation of the rotational plate 106 is locked by the link 112. FIG. 45 shows a state where the occupant is pushed against the seatback B by the inertia at the time of vehicle collision. Since the pelvis of the occupant pushes the lower S spring 105b,the lower S spring 105bmoves in the rearward direction. Accordingly, a bar 111 is also pushed.

[0135] As the bar 111 moves rearward, the link 112 releases the lock. Accordingly, the rotational plate 106 becomes available for activation.

[0136] Thereafter, as the back of the occupant pushes the upper S spring 105a,the rotational plate 106 rotates in a counter clockwise direction about rotational axis 118 as seen in FIG. 45. Accordingly, headrest 116 moves forward to protrude in the forward direction, as indicated by the circular arrows in FIG. 45. In this manner, the distance between the occipital portion of the occupant's head and headrest 116 can be shortened. Therefore, protection of the head can be ensured.

[0137] Referring now to FIG. 46, a seatback B is illustrated in accordance with a seventh embodiment of the present invention. The basic structure of the seatback of the seventh embodiment is the same as that of the sixth embodiment. In view of the similarity between this embodiment and the prior embodiments, the parts of seventh embodiment that are identical to the parts of the prior embodiments will be given the same reference numerals as the parts of the prior embodiments. Moreover, the descriptions of the parts of the seventh embodiment that are identical to the parts of the prior embodiments may be omitted for the sake of brevity. The parts of the seventh embodiment that significantly differ from the parts of the prior embodiments will be indicated with new reference numbers.

[0138] The difference between the seventh embodiment and the sixth embodiment is that vertical positions of the rotational axis 118 and the reinforcing member 119 are switched in the seventh embodiment. As a result, the distance between the rotational axis 118 and the upper S spring 105ais shorter, whereas the distance between the rotational axis 118 and the headrest 116 is longer. Therefore, even when the amount of rearward displacement of the upper S spring 105ais small, a large forward displacement of the headrest 116 can be obtained.

[0139] Furthermore, in the seventh embodiment, since the rotational axis 118 which connects the left and right frames 101aand 101bis positioned low, a separate upper cross 102 is provided. In the upper cross 102, oval bores are formed in order to allow forward displacement of the headrest support members 117.

[0140] 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. These terms should be construed as including a deviation of ±5% of the modified term if this would not negate the meaning of the word it modifies.

[0141] This application claims priority to Japanese Patent Application No. 2000-186897. The entire disclosure of Japanese Patent Application No. 2000-186897 is hereby incorporated herein by reference.

[0142] While only selected embodiments have 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. Furthermore, the foregoing description of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.