Abstract:
Provided is a vehicle seat device equipped with an anti-submarine vehicle seat device for preventing submarine at the time of an impact without increasing the size and weight of the seat assembly. The casing and/or the restraint member serve the dual purposes as structural members for the seat frame so that the overall amount of the material for the structural members can be reduced.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Copending U.S. patent application Ser. No. 09/334,116 filed Jun. 15, 1999, and three commonly assigned U.S. patent applications of even date are directed to similar subject matters, and the contents of these applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a vehicle seat device, and in particular to a vehicle seat device equipped with an anti-submarine vehicle seat device for preventing a vehicle occupant from slipping forward under the seat belt in case of an impact situation such as a vehicle crash. 
     BACKGROUND OF THE INVENTION 
     It is known that the so-called submarine phenomenon may occur in an impact situation such as a vehicle crash by the vehicle occupant slipping forward under the seat belt and the waist belt failing to restrain the pelvis of the vehicle occupant. This is prone to occur when the vehicle occupant sits in the front end of the seat or when the back rest is tilted rearward, and reduces the effectiveness of the seat belt in restraining the vehicle occupant or prevents the desired parts of the vehicle occupant to be restrained. 
     Therefore, it is conceivable to raise the front end of the seat by providing a projection in a front end of the seat frame, or by installing a panel in a front end of the seat frame. However, a desired effect in preventing submarine may not be achieved if the projection or the panel is too low, and the comfort of the vehicle occupant may be impaired if it is too low. 
     Accordingly, it has been previously proposed to raise the front end of the seat only in case of an impact. Such proposals include those using an air bag (Japanese Patent laid-open (kokai) publications No. 5-229378, No. 7-81466, and No. 3-227745), those which mechanically raise the front end of the seat (Japanese UM laid-open (kokai) publications No. 2-149328, No. 3-121947, and No. 4-93222), and those using a pyrotechnic actuator to mechanically raise the front end of the seat (Japanese UM laid-open (kokai) publication No. 3-61446). 
     However, because such anti-submarine devices involve generation of a large force, the structure of the device is required to have a high mechanical strength, and this prevents a compact and light-weight design of the seat. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of such problems of the prior art, a primary object of the present invention is to provide an anti-submarine device which allows a compact and light-weight design of the seat while ensuring a sufficient mechanical strength to withstand the reaction of the actuator of the anti-submarine seat device at the time of actuation. 
     A second object of the present invention is to provide a low profile anti-submarine seat device which would not impair the sitting comfort and support capability of the seat. 
     A third object of the present invention is to provide an anti-submarine seat device which is economical and easy to manufacture. 
     According to the present invention, such objects can be accomplished by providing a vehicle seat device for raising a front part of a seat member to prevent a vehicle occupant from slipping forward under a seat belt in an impact situation such as a vehicle crash, comprising: a fixed casing; a vehicle occupant restraint member supported by the casing so as to be moveable between a rest position and a deployed position; and a power actuator supported by the casing for selectively driving the restraint member toward the deployed position; the fixed casing and/or the restraint member forming at least a part of a structural member of a seat frame. 
     Thus, the casing and/or the restraint member serve the dual purposes as structural members, and the overall amount of the material for the structural members can be reduced. This results in the reduction in the size and weight of the overall seat arrangement. Typically, the casing forms a side member of the seat frame, and has a front end which pivotally supports the restraint member, the seat frame having a rectangular configuration defined by the side member, a rear cross member, another side member opposing the side member, and the restraint member extending across front ends of the side members. The restraint member preferably consists of a pipe member or any other stamped sheet metal member for a required mechanical strength at a minimum cost. 
     If an additional reinforcement is required, the seat frame may additionally include a front cross member connecting front ends of the side members and extending in parallel with the restraint member. 
     Preferably, the seat member may be provided with a notch to facilitate deformation thereof when the restraint member is actuated. If desired, the seat member may be separated into a plurality of parts, and the device may be adapted to raise only one or two of such parts. Thereby, a favorable deformation of the seat member may be achieved, and the power requirement of the power actuator may be reduced. 
     To increase the support surface area of the restraint member, the restraint member may additionally comprise a plate member attached to a rod member at least over a part of length of the rod member, or a wire member attached to the rod member. If desired, the restraint member may be provided with an energy absorbing property through elastic or plastic deformations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Now the present invention is described in the following with reference to the appended drawings, in which: 
     FIG. 1 is an exploded perspective view of an anti-submarine vehicle seat device embodying the present invention; 
     FIG. 2 is a fragmentary side view of the vehicle seat device of FIG. 1; 
     FIG. 3 is a sectional view of the power actuator of the vehicle seat device embodying the present invention; 
     FIG. 4 is a fragmentary perspective view showing a modified embodiment of the vehicle seat device of the present invention; 
     FIG. 5 is a view similar to FIG. 4 showing another modified embodiment of the vehicle seat device of the present invention; and 
     FIG. 6 is a perspective view showing yet another modified embodiment of the vehicle seat device of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a perspective view of a vehicle seat device embodying the present invention, and FIG. 2 is a side view of this device. Seat rails  1  fixed to the vehicle body support a seat frame  2  so as to be slidable in the fore-and-aft direction via holders  23 , and a seat adjustment mechanism not shown in the drawings allows the seat frame  2  to be secured at a desired position. A front part of the seat frame  2  rotatably supports, on either side thereof, a pair of arms  3  via a pivot pin  3   a . These two arms  3  are firmly connected to each other by a pipe  4  extending laterally of the vehicle body, and serving as a restraint member as described hereinafter. The pipe  4  and the arms  3  support a panel member  5 , so that the arms  3  and the panel member  5  may form additional parts of the restraint member. 
     The seat frame  2  includes a pair of tubular casings  2   a  each having a substantially closed, rectangular cross section extending longitudinally on either side, and a power actuator  7  which is described hereinafter is received in each of the casings  2   a . The rear ends of the casings  2   a  are connected by a cross member  18 . Therefore, the seat frame  2  consists of a closed rectangular frame. 
     The free end of a piston rod  9   b  of a piston assembly  9  in the power actuator  7  is connected to a pin  6  which is passed through a horizontally elongated guide slot  2   b  of the casing  2   a  and a vertically elongated slot  3   b  provided in a part of the arm  3  offset from the pivot pin  3   a . The seat member  20  which may consist of hard urethane foam or any other suitable material is provided with a laterally extending notch  20   a  for facilitating deformation thereof. 
     Referring to FIG. 3, the power actuator  7  comprises a cylinder  8  which is received and fixed in the basing  2   a  of the seat frame  2 , a piston main body  9   a  received in an inner bore  8   a  of the cylinder  8 , and a gas generator  10  received in the part of the cylinder  8  more toward the base end thereof than the piston main body  9   a . A compression coil spring  12  is interposed between the piston main body  9   a  and the gas generator  10  via a resilient seal member  11  to normally urge the piston main body  9   a  in the direction of activation (projecting direction). The seal member  11  may consist of any suitable kind such as an O-ring which has a resiliency in the axial direction, and is effective in preventing the leakage of generated gas. 
     The gas generator  10  comprises a large diameter portion  10   a  on the base end thereof, and a small diameter portion  10   b  on the front end thereof, and a shoulder  10   c  defined between these portions engages a corresponding shoulder  8   b  defined in the cylinder  8 . The shoulder  10   c  of the gas generator  10  additionally serves as a seat for the compression coil spring  12  via the seal member  11 . The compression coil spring  12  surrounds the small diameter portion  10   b  on the front end thereof in such a manner that a gap may be defined between the piston main body  9   a  and the front end of the small diameter portion  10   b  even when the compression coil spring  12  is fully compressed. Therefore, even when the piston main body  9   a  is subjected to an external force which would force it toward the gas generator  10 , the piston main body  9   a  would not hit the front end of the small diameter portion  10   b  on the front end of the gas generator  10  so that the gas generator  10  is protected from damages and deformations. 
     The piston main body  9   a  engages the wall surface of the inner bore  8   a  via an O-ring  13 . The piston assembly  9  is formed by the piston main body  9   a  and a piston rod  9   b  which abuts the piston mainbody  9   a  from the axial direction and is provided with a free end attached to the arm  3 . The piston main body  9   a  and the piston rod  9   b  engage each other via a contact between a concentrically curved recess, and a corresponding concentrically curved projection having a somewhat smaller curvature so that the two parts are automatically aligned and the piston rod  9   b  would not tilt in the cylinder. Therefore, energy loss and gas leakage can be avoided. In practice, the surfaces are not necessarily required to be curved, but may also consist of tapered surfaces. In that case, the taper of the projection should be steeper than the taper of the recess. 
     As described earlier, the compression coil spring  12  normally urges the piston main body  9   a  in the direction of activation so that the piston rod  9   b  is also urged in the direction of activation, and the plays that may be present in the joint between the piston rod  9   b  and the arm  3  may be absorbed. The compression coil spring  12  may be substituted with a dish spring or a rubber-like elastomer member. 
     The open end  8   c  of the cylinder  8  on the working end is reduced in diameter by swaging so as to slidably engage the outer circumferential surface of the intermediate part of the piston rod  9   b.    
     The front end of the power actuator  7  is provided with a one-way lock mechanism  14 . The one-way lock mechanism  14  comprises a casing  15  surrounding the piston rod  9   b  and fixedly attached to the cylinder  8 , and the casing  15  accommodates therein a plurality of engagement pieces  16 , and a spring  17  urging the engagement pieces  16  toward the base end of the piston rod  9   b  or the cylinder  8 . Each of the engagement pieces  16  is gradually reduced in outer diameter from the free end of the piston rod  9   b  to the base end thereof. The inner bore of the casing  15  includes a large diameter portion  15   a  and a tapered portion  15   b  which is gradually reduced in inner diameter away from the large diameter portion  15   a . Therefore, in the illustrated state, the engagement pieces  16  are pressed onto the tapered portion  15   b  and engage the outer circumferential surface of the piston rod  9   b  under the biasing force of the spring  17 . As the piston rod  9   b  moves in the projecting direction, the engagement pieces  16  are dragged in the projecting direction of the piston rod  9   b  against the spring force of the spring  17 . As they move toward the large diameter portion  15   a , they move away from the piston rod  9   b  so that the piston rod  9   b  is allowed to move freely. When the piston rod  9   b  is pushed back into the cylinder  8 , the engagement pieces  16  move toward the tapered portion  15   b  under the spring force of the spring  17  and engage the outer circumferential surface of the piston rod  9   b  so that the piston assembly  9  is securely fixed relative to the cylinder  8 . The inner circumferential surface of each of the engagement pieces  16  is provided with annular grooves or thread grooves while the outer circumferential surface of the piston rod  9   b  is provided with corresponding annular grooves or thread grooves. Therefore, as the piston rod  9   b  is pushed into the cylinder  8 , the inner circumferential surfaces of the engagement pieces  16  engage the outer circumferential surface of the piston rod  9   b  so that these two parts are firmly retained to each other, and are kept at a fixed position. 
     The cylinder  8  is installed and fixedly secured in the casing  2   a , and the piston rod  9   b  is introduced from the open working end  8   c  of the cylinder  8 . The free end of the piston rod  9   b  is then connected to the arm  3  by the pin  6 . The anti-submarine device is thus formed by the casings  2   a , the power actuator  7 , the restraint member consisting of the arms  3 , the pie  4  and the panel member  5 , the impact sensor consisting of an acceleration sensor or the like not shown in the drawing, and a control unit also not shown in the drawing. 
     When installing the device in a seat during the assembly work, and welding is required to be performed, the power actuator incorporated with a propellant is installed after completing the welding process. The seat frame  2  was supported by the seat rails  1  via the slidable holders in the above described embodiment, but may be attached to mounting brackets in case of a tiltable and/or liftable seat. 
     Now the mode of operation of this embodiment is described in the following. First of all, when a vehicle crash is detected by a deceleration sensor not shown in the drawing, gas is generated from the gas generator  10 , and the resulting rapid increase in the inner pressure of the cylinder  8  instantaneously pushes out the free end of the piston assembly  9  from the cylinder  8 . As a result, the arm  5  attached to the free end of the piston rod  9   b  turns in clockwise direction as indicated by the imaginary lines in FIG. 2, and the restraint member consisting of the pipe  4  and the panel member  5  is raised along with the corresponding part of the seat so that the submarining of the vehicle occupant can be prevented. Because an intermediate part of the seat cushion  20  has a relative small thickness or is provided with the notch  20   a , the seat cushion  20  would not excessively resist the lifting of the seat by the restraint member. In practice, it is also possible to form the part of the seat that can be raised by the restraint member from a separate member. Further, by using an elastic or otherwise readily deformable material in a selected part of the surface skin member of the seat, the resistance to the raising motion of the seat can be even further reduced. 
     Even after the generation of gas from the gas generator  10  has ceased, and the drive force of the power actuator  7  has been lost, the raised slip preventing member would not come down, and maintains the action to prevent submarining of the seat&#39;s occupant. 
     The one-way lock mechanism may be provided only on one side of the seat, but a higher mechanical strength can be achieved if two of them are arranged on either side of the seat to support the load of the vehicle occupant from both sides. In this case, two one-way lock mechanisms having different constructions may be arranged on either side. For instance, the above described one-way lock mechanism may be provided on one side while a ball-type one-way lock mechanism capable of locking at any desire position is provided on the other side. When two power actuators are used on either side of the seat, each of the power actuators may consist of a relatively small device so that any localized increase in the size of the device can be avoided by proper distribution of compact devices. 
     FIG. 4 is a perspective view of a modified embodiment of the vehicle seat device according to the present invention, showing only the restraint member. In this embodiment, to raise the leg of the vehicle occupant near the door, the panel member  21  is provided only over one half the length of the pipe  4 . This is based on the recognition that the leg which is relatively stretched for stepping on the pedal is desired to be particularly protected in the case of an offset crash which causes a relatively large deformation on the associated side part of the vehicle body. Furthermore, when the panel member is provided only over one half the length of the pipe, because the lifting area is smaller than having the panel member extend over the entire length of the pipe, the force required to raise the panel member is substantially reduced so that the required size of the power actuator can be reduced, and the component parts may have smaller thicknesses and masses. If the panel member is provided only over one half the length of the pipe, and inclined upward from inside to outside, it is possible to raise the outer leg of the vehicle occupant both upward and inward. 
     The submarine preventing device of the present invention can be adapted for different kinds and sizes of the vehicles, and the positions of the seats. For instance, when the panel member is provided substantially over the entire length of the pipe  4 , and the central part of the panel member projects higher than the remaining part of the panel member, the legs of the vehicle occupant can be raised while keeping them wide apart in case of a vehicle crash so that the interference with the steering handle can be avoided. A similar result can be achieved if the panel member is inclined downward from inside to outside. 
     FIG. 5 is a perspective view of another modified embodiment of the vehicle seat device according to the present invention, showing only the restraint member. In this embodiment, a wire frame  22  made of a wire member is provided substantially over the entire length of the pipe  4 , instead of the panel member, and the weight of the restraint member is thereby reduced. This embodiment is otherwise similar to the previous embodiments. 
     FIG. 6 is a perspective view of yet another modified embodiment of the vehicle seat device according to the present invention, showing only the restraint member. In this embodiment, not only the rear parts of the casings  2   a  or the longitudinal members are joined together by the cross member  18 , but also the front parts of the casings  2   a  are joined together by another cross member  19 . Thereby, the seat frame  2  is further reinforce. This embodiment is otherwise similar to the previous embodiments. 
     As can be appreciated from the foregoing description, according to a certain aspect of the present invention, the anti-submarine vehicle seat device for raising a seat cushion to prevent a vehicle occupant from slipping forward under a seat belt in an impact situation such as a vehicle crash comprises a restraint member moveably supported by a casing which is in turn integrally attached to a seat frame, and the casing and/or the restraint member form a part of the seat frame. By using the structural member of the anti-submarine device as a part of the seat frame, the number of component parts of the seat device, as well as the size and weight of the device, can be reduced. 
     Although the present invention has been described in terms of preferred embodiments thereof, it is obvious to a person skilled in the art that various alterations and modifications are possible without departing from the scope of the present invention which is set forth in the appended claims.