Active control of a vehicle occupant&#39;s body in frontal collision
BACKGROUND OF THE INVENTION 
     Even though efforts have been made to provide greater passive safety for vehicle occupants by the use of seat belts and air bags, accident statistics indicate front end collisions remain as the major accident type, resulting in fatalities and severe injuries. In automatic restraint systems, the air bag prevents the vehicle occupant&#39;s head and upper body from impacting the steering wheel, and the seat belt tightener takes up seat belt slack, applying a distributed load over the occupant&#39;s body contact area, to thereby allow the passenger to decelerate through the course of the collision. At sever impact levels, these contact forces may, however, result in facial bone fractures, and head-neck trauma. 
     After considerable research and experimentation the assembly of the present invention has been devised to provide an active control of a vehicle occupant&#39;s body, without applying direct contact forces to the occupant&#39;s body, and supplementing the passive safety systems provided by seat belts and air bags. 
     SUMMARY OF THE INVENTION 
     The control assembly of the present invention comprises, essentially, a double acting hydraulic cylinder operatively connected between a vehicle seat frame and vehicle frame upon which the seat frame is mounted for slidable movement in a longitudinal direction relative to the vehicle. Hydraulic fluid is supplied to the hydraulic cylinder in a controlled manner, whereby a force is applied to the vehicle seat in a direction opposite to that of the impact force, to thereby control the forward sliding movement of the seat depending upon the severity of the impact level. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic view illustrating the angular position of the upper body portion of a vehicle occupant after a front end collision. 
     FIG. 2 is a diagrammatic view illustrating the active control of the vehicle seat and occupant&#39;s body after impact. 
     FIG. 3 is an enlarged side elevational view partly in section, showing the hydraulic cylinder connected between the vehicle frame and the vehicle seat frame which is slidably mounted on the vehicle frame. 
     FIG. 4 is a view taken along line 4--4 of FIG. 3. 
     FIG. 5 is an enlarged, fragmentary sectional view showing the solenoid actuated pin for releasably locking the seat frame on the vehicle frame. 
     FIG. 6 is a diagrammatic view of the vehicle occupant having a sensor operatively connected thereto for determining the angular position of the occupant. 
     FIG. 7 is a diagrammatic view of the rear of the seat shown in FIG. 6. 
     FIG. 8 is a schematic drawing of the hydraulic control circuit for the double acting hydraulic cylinder; and 
     FIG. 9 is a schematic of the electrical circuit for actuating the directional control valve employed in the hydraulic circuit of FIG. 8. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings and more particularly to FIGS. 1 and 2, the motion of an occupant 1 and vehicle seat 2 are illustrated during a front end collision. In this instance the occupant&#39;s upper body 1a, viz., the head, and upper and center torso, is considered a rigid body hingedly connected as at 3 to the occupant&#39;s lower body 1b, viz., the lower torso and legs, fixed to the seat 2 by a seat belt. 
     To control the motion of the occupant 1 strapped in the seat 2, a double acting hydraulic cylinder 4 is connected between the vehicle seat frame 5 and vehicle frame 6 upon which the seat frame 5 is slidable mounted in a longitudinal direction relative to the vehicle, as shown by the arrow 7 in FIG. 1. The linear position of the occupant 1 before impact is indicated at X 1 , and the subsequent positions of the seat during impact are indicated at X 2  and X 3 . The angular positions of the occupant are indicated at O 1  and O 2  while the corresponding linear position of the occupant is indicated at Z 1  and Z 2 . 
     The details of the connection of the double acting hydraulic cylinder 4 between the vehicle seat frame 5 and vehicle frame 6 are illustrated in FIG. 3 and 4. The seat 2 is a conventional seat having a back rest 2a hingedly connected to the seat as at 8 and having the conventional control handles 9 and 10 for respectively adjusting the angular position of the seat rest 2a and linear position of the seat 2. The hydraulic motor 4 includes a cylinder 4a pivotally connected to the vehicle frame 6 as at 4b, and a piston rod 4c pivotally connected as at 4d to depending bracket 5a integral with seat frame 5. Movement of the seat frame 5 relative to the vehicle frame 6 is prevented by a solenoid actuated detent 11. The seat 2 is provided with a subframe 12 which is mounted on the seat frame 5 and linearly adjustable thereon by the control handle 10. 
     During a head on collision the detent 11 is retracted and hydraulic fluid is supplied to the hydraulic cylinder 4a in a controlled manner depending upon the angular motion, O, of the occupant and the seat position, X, to thereby extend the fluid motor 4, whereby a force is applied to the vehicle seat 2 in a direction opposite to the impact force., i.e., in the direction of arrow 7, FIG. 1. 
     FIGS. 6 and 7 illustrate the assembly for measuring the angular motion O of the occupant 1 during impact. A rigid strip 13 is connected at its upper end to the occupant&#39;s upper torso 1a by a clip 14. The lower end of the strip 13 is pivotally connected to the seat frame at 15; the pivotal connection also includes a rotary variable differential transformer (RVDT) 16. 
     The seat position, X, is measured by a linear variable differential transformer (LVDT) 17, FIG. 4, mounted between the seat frame 5 and vehicle frame 6. 
     FIG. 8 illustrates the hydraulic circuit for the supply and exhaust of hydraulic circuit for the supply and exhaust of hydraulic fluid to the fluid motor 4. Hydraulic fluid is supplied to an accumulator 18 from a motor driven pump 19. The hydraulic fluid is fed from the accumulator 18 to a conventional directional control valve 20 of of the type disclosed in Automotive Handbook, 2nd Edition, published by Robert Bosch GmbH, 1986. From the control valve 20 the hydraulic fluid is directed to either port P 1  or P 2  of the fluid motor 4 to retract or extend the fluid motor 4, to thereby slide the seat 2 in a longitudinal direction. 
     The position of the spool within the control valve 20 is determined by a control signal fed to the control valve 20 from the electrical circuit shown in FIG. 9. Measurements of the occupant&#39;s angular position O are read by the RVDT 16, and the linear position, X, of the seat by LVDT 17. These measurements are fed to a microprocessor 21 which in turn sends a control signal to the directional control valve 20. As in automatic restraint systems, such as air bags and seat belt tightening systems, a triggering circuit is provided to ensure that the active control is not energized at low impact speeds. To this end, an accelerometer 22 is mounted on the vehicle and an integrator 23 and mercury switch 24 are included in the triggering circuit, whereby if an output signal from the integrator 23 exceeds a preset value, a signal is sent to the microprocessor 21 and transmitted there from to the solenoid 11 for the actuation thereof. 
     In the operation of the active control assembly of the present invention, under normal driving conditions the seat 2 is locked to the vehicle frame 6, and the directional control valve 20 is in the neutral position so that the fluid motor 4 is in the neutral or balanced position. In the event of a frontal collision the solenoid detent 11 is retracted to release the seat 2 from the vehicle frame 6. A signal from the microprocessor 21 in response to the signals from the RVDT 16 and LVDT 17 is transmitted to the directional control valve 20, whereby pressurized hydraulic fluid is fed through port P 2  into the fluid motor cylinder 4a to apply a force against the fluid motor piston in a direction opposite to the impact force, thereby arresting the extension of the piston rod 4c and resultant forward movement of the seat 2. 
     If the impact force from the frontal collision is greater than a further threshold limit, the vehicle&#39;s seat belt and/or air bag are actuated to dampen the remaining kinetic energy of the occupant. 
     After the force of the impact has dissipated, the selector valve 20 is actuated to supply hydraulic fluid to the fluid motor 4 to return the seat to the original position, whereby the solenoid detent 11 is actuated to once again lock the seat frame 5 to the vehicle frame 6. 
     From the above description, it will readily be apparent to those skilled in the art that the assembly of the present invention provides an active control for resisting the forward inertial movement of the vehicle occupant to protect the occupant&#39;s head and upper body from impacting the steering wheel or dashboard, and also preventing facial bone fractures and head-neck trauma experienced when only air bags and seat belts are employed. 
     It is to be understood that the form of the invention herewith shown and described is to be taken as a preferred example of the same, and that various changes in the shape, size and arrangement of parts may be resorted to, without departing from the spirit of the invention or scope of the subjoined claims.