Abstract:
A head-rest of a vehicle seat with a deformable central supporting body which forms an impact zone for the head of a vehicle occupant and into which the kinetic energy of the head in the event of an accident is admitted. On both sides of the impact zone the central supporting bodies are joined by lateral supporting surfaces which are extendable out of the plane of the head-rest in the direction of travel in order to laterally support the head. In order to avoid or at least to reduce the risk of a cervical-spine whiplash injury, it is proposed according to the invention that the head-rest comprises a device for absorbing the energy admitted into the central supporting body and for outputting the absorbed energy in order to activate lateral supporting surfaces.

Description:
This nonprovisional application is a continuation of International Application No. PCT/EP2011/006345, which was filed on Dec. 15, 2011, and which claims priority to German Patent Application No. DE 10 2010 054 651.8, which was filed in Germany on Dec. 15, 2010, and which are both herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a head rest for a vehicle seat. 
     2. Description of the Background Art 
     A frequent type of injury in motor vehicle accidents, in particular in rear-end collisions, is the cervical spine whiplash injury. This is caused by the fact that, during an accident, the abrupt acceleration of the vehicle occupants in the direction of travel results in an extreme extension movement of the head, which is overlaid by a simultaneous rotary and wobbling movement, usually around multiple spatial axes. As a result, the spinal neck musculature is overextended, which ultimately results in the aforementioned cervical spine whiplash injury. 
     To counteract this polyaxial wobbling movement, a headrest is known from DE 195 09 014, in which upper and lateral supporting bodies are extended in the direction of travel to stabilize the head. The supporting bodies are activated by an external drive, which is set in motion by a triggering sensor. The additional structural complexity caused by the external drive, including the associated components, which makes the headrest more expensive, has proven to be disadvantageous. Since the additional components must be accommodated in the headrest or the vehicle seat, the worthwhile implementation of a headrest of a vehicle seat having a compact structure is problematic. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a headrest for a vehicle seat by means of which the risk of injury to the vehicle occupants in the event of a collision between two vehicles is further reduced effectively and at economically justifiable expense. 
     The basic idea of an embodiment of the invention is to absorb the kinetic energy of the head when it is thrust into a head rest, using suitable means, and to convert this energy directly into driving energy for generating lateral supporting surfaces. The invention therefore does not make do with the mere absorption of harmful kinetic energy, as is the case in commonly used headrests, but it uses the kinetic energy for initiating active protective measures for the vehicle occupants, such as generating lateral supporting surfaces. 
     The implementation of this basic idea according to an embodiment of the invention provides for a kinematic coupling of energy-absorbing and therefore deforming function components within a headrest according to the invention, including function components for setting up lateral supporting surfaces. The kinematic coupling may be such that the absorption of the kinetic energy and generation of lateral supporting surfaces take place within the same function component. However, designs in which the described functions are assigned to multiple function components and which are operatively connected to each other, for example via a force-transmitting medium, are also within the scope of the invention. 
     As a first advantage of the invention, this results in a completely energy-autonomous operation of the headrest. Since the energy for setting up the lateral supporting surfaces comes from the kinetic energy of the head when being thrust into the headrest, it is not necessary to supply external energy. 
     Due to the kinematic coupling of the individual function units, it is also possible to dispense with a complex sensor system and a control device. This substantially simplifies the structure of a headrest according to the invention and permits it to be manufactured cost-effectively and compactly. The simplicity of the design also results in a high functional reliability, since the number of possible fault sources is inherently limited, due to the small number of parts. 
     Another advantage of the invention is derived from the direct setup of the lateral supporting surfaces as early as the time at which a head is thrust into the headrest. The completely instantaneous functionality resulting therefrom ensures that the protective action of the lateral supporting areas may take place very early on and therefore extremely effectively. 
     A first part of the embodiments of the invention according to the invention is based on the utilization of the fin ray effect. In this case, due entirely to a special lattice-like design, a supporting structure is created whose free ends move counter to the deformation direction during a deformation of the central area and form lateral supporting surfaces. This way of implementing the invention may consequently be carried out without great complexity and also has the advantage that the lateral supporting surfaces automatically adapt to the contour of the head and thus to its particular position. This results in an equalized and thus reduced pressure distribution on the head of a vehicle occupant. 
     In an embodiment of the invention, the lattice-like supporting structure comprises a front supporting strap and a rear supporting strap, which are opposite each other and are connected to each other at their facing ends at an acute angle β, while the two remaining ends end at a mutual distance from each other. The two supporting straps are connected to each other by articulated cross-struts. The cross-struts are advantageously positioned at an angle in relation to the front strap, i.e., they are inclined at an angle α in relation to the front supporting strap. 
     The selection of angle β has an influence on the extent of the counter-movement of the supporting surfaces produced by a deformation and the stresses generated in the supporting structure by the deformation. At small angles β, a great counter-movement and high material stresses occur. Conversely, a large angle β generates smaller induced counter-movements and a smaller material load. By suitably selecting angle β, therefore, the movement of the supporting surfaces as well as the material loads produced thereby may be determined. Taking these circumstances into account, angle β in the range of 10° to 25°, preferably from 15° to 20°, has proven to be advantageous. 
     Via angle α, it is possible to influence the deformation behavior of the supporting structure over its longitudinal extension. Small angles α result in larger curvatures of the two supporting straps, large angles α result in smaller curvatures. By suitably varying angle α, the profile of the lateral supporting surfaces may be predetermined. For example, angle α of adjacent cross-struts may decrease, whereby the free ends of the lateral supporting surfaces are additionally curved and the supporting action is thus maintained up to the edge of the supporting surfaces. Angles α in the range of 30° to 75°, preferably from 40° to 65°, have proven to be suitable. 
     In an embodiment of the invention, a supporting structure of this type is designed to be symmetrical in relation to the median plane of a vehicle occupant and is highly preferably equipped with a synchronization mechanism. The synchronization mechanism guarantees a symmetrical deformation of the supporting structure in relation to the symmetry, even if the head of a vehicle occupant does not strike the headrest centrically, i.e., the median plane and the symmetry plane do not coincide. 
     In the embodiment described, all or a portion of the spaces formed between the supporting straps and cross-struts may be filled with an energy-absorbing material for the purpose of controlling the movement sequence over time. 
     Other embodiments of the invention provide for a fluid-based coupling of different function components. The head being thrust into a first function unit causes a fluid flow to be generated, which induces a movement of at least one additional function unit, by means of which the lateral supporting surfaces are set up on the headrest. By using a fluid of a suitable viscosity and by correspondingly selecting the line cross section for the fluid, it is possible to influence the speed of the movement sequences. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein: 
         FIG. 1   a  shows an oblique view of a headrest according to the invention, including a head of a vehicle occupant situated in front thereof, before an accident event occurs; 
         FIG. 1   b  shows the headrest illustrated in  FIG. 1   a , including a vehicle occupant, during the accident event; 
         FIG. 2  shows a horizontal section of a first embodiment of a headrest according to the invention; 
         FIG. 3  shows an oblique view of the headrest illustrated in  FIG. 2 ; 
         FIG. 4  shows an oblique view of a lattice-like supporting structure which is integrated into the headrest according to  FIGS. 2 and 3 ; 
         FIG. 5  shows an oblique view of a second embodiment of a headrest according to the invention in a half exposed representation; 
         FIG. 6  shows an oblique view of a supporting structure which is integrated into the headrest according to  FIG. 5 ; 
         FIG. 7  shows a top view of the supporting structure illustrated in  FIG. 6 ; 
         FIG. 8  shows an oblique view of the supporting structure illustrated in  FIG. 6  to which synchronization components are added; 
         FIG. 9  shows a top view of the supporting structure illustrated in  FIG. 8 ; 
         FIG. 10  shows a top view of the supporting structure illustrated in  FIG. 6 , to which damping components are added; 
         FIG. 11  shows an oblique view of another, fluid-based embodiment of a headrest according to the invention in a half exposed representation, before the accident event occurs; 
         FIG. 12  shows the headrest illustrated in  FIG. 11  during the accident event; 
         FIG. 13  shows a horizontal section of an additional fluid-based embodiment of a headrest according to the invention; and 
         FIG. 14  shows a detail of the area identified by XIV in  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1   a  shows the upper area of a vehicle seat  1  from whose backrest  2  two holding rods  3  project for fastening a headrest  4  according to the invention. Head  5 , including cervical spine  6 , of a vehicle occupant whose torso is indicated by reference numeral  7  is shown in front of headrest  4 . 
     In addition,  FIG. 1   a  shows three orthogonally disposed spatial axes, of which the horizontal spatial axis pointing in the direction of travel is identified by X, the vertical spatial axis is identified by Z, and the spatial axis pointed transversely to the direction of travel is identified by Y. Axes X and Z span the median plane in relation to the vehicle passengers. 
       FIG. 1   a  shows the situation before an accident event occurs, in which head  5  is held at a distance from headrest  4 . The area of headrest  4  which is located behind head  5  in the direction of travel has a central impact zone  8 ; the adjacent area on both sides in the Y direction is formed by lateral supporting surfaces  8 , which are essentially still located on the plane of impact zone  8  at a point in time before the accident event. 
     Conversely,  FIG. 1   b  shows a snapshot during an accident event. Head  5  is thrust into headrest  4  in the area of impact zone  8 , means being activated after the thrusting action which absorb the kinetic energy of head  5  and convert it into a driving force for setting up lateral supporting surfaces  9  in the X direction. 
       FIGS. 2 through 14  show different embodiments of the aforementioned means, all embodiments having in common the fact that the kinetic energy of head  5  is converted directly into driving energy for lateral supporting surfaces  9 , i.e., without any additional sensors and controllers and without supplying external energy. This permits an instantaneous stabilization reaction of the headrest, so that a possible wobbling movement of the head is absorbed as early as possible at a point in time at which no or only a minimal overextension of the neck musculature has taken place. The danger of a cervical spine whiplash trauma can thus be effectively ruled out, or at least greatly reduced. 
       FIGS. 2 through 10  relate to embodiments which are based on the implementation of the fin ray effect in connection with the activation of lateral supporting surfaces  9 .  FIGS. 2 through 4  show a first embodiment, in which headrest  4  is illustrated transparently to make it easier to see the means according to the invention. In this embodiment, multiple lattice-like supporting structures  10 , as described in greater detail in  FIG. 4 , are disposed on a common baseplate  11  supported by holding elements  3 . The baseplate has an approximately concentric position in relation to centric impact zone  8 , individual lattice-like supporting structures  10  being oriented in a ray-shaped manner around the center, so that a head  5  being thrust into headrest  4  during an accident event applies compressive force oriented in the direction of the X axis to supporting structures  10 . 
       FIG. 4  shows an oblique view of an isolated supporting structure  10  in its initial position, i.e., before an accident event. Supporting structure  10  has a front supporting strap  12  and a rear supporting strap  13 , which converge at an acute angle β ( FIG. 7 ) in the direction of their first ends  13 ,  14 , illustrated on the left on the plane of projection, where they are rigidly connected to each other. 
     The linear course of front supporting strap  12  and rear supporting strap  13  in connection with acute angle β results in the fact that front supporting strap  12  and rear supporting strap  13  are disposed at a distance from each other at their diametrically opposed second ends  16 ,  17 . Deviating herefrom, the course of front supporting strap  12  and/or rear supporting strap  13  may have a slight pre-curvature, provided that second ends  16  and  17  end at a mutual distance from each other in this case as well. 
     Pairs of diametrically opposed pivot bearings  18 , on each of which cross-struts  19  are hinged, are disposed on diametrically opposed inner sides of front supporting strap  12  and rear supporting strap  13 . The two supporting straps  12  and  13  are not interrupted by pivot bearings  18  but instead run past it, so that the action of a continuous support sets in with regard to the load transfer system. Pivot bearings  18 , each of which forms a pair, have a slight offset in the longitudinal extension direction of supporting structure  10 , resulting in a slight angled position of cross-struts  19  at an angle α in relation to front supporting strap  12 . The angled position is such that cross-struts  19  are inclined toward the outside, starting from front supporting strap  12  to free first ends  14 ,  15 . In the present exemplary embodiment, the angle of adjacent cross-struts  19  increases in the direction of first ends  14 ,  15  and is 60°, for example, for cross-strut  19  forming second end  16 ,  17  and 45° for cross-strut  19  closest to first end  14 ,  15 . The inclined position of cross-struts located therebetween may be determined by interpolation. Instead of pivot bearings  18 , cross-struts  19  may also be joined to front supporting strap  12  and rear supporting strap  13  via live hinges. 
     Lattice-like supporting structures  10  designed in this manner are each connected to baseplate  11  by their rear supporting straps  13  in the area of second ends  16 ,  17  and cushioned in the direction of the front side of headrest  4 . 
     If a head  5 , as illustrated by the dashed line in  FIG. 2 , is thrust into impact zone  8  of a headrest  4 , the compressive force acting upon front support strap  12  induces a deformation of supporting structures  10 , whose first ends  14 ,  15  are each moved counter to the direction of force, i.e., in the direction of travel, and in this manner form lateral and upper supporting surfaces  9  around all spatial axes X, Y and Z to stabilize head  5 . 
     An embodiment of the invention which builds thereupon is illustrated in  FIGS. 5 ,  6  and  7 .  FIG. 5  shows a corresponding headrest  4  which is exposed on the symmetry plane in order to clearly illustrate the invention. The embodiment according to  FIGS. 5 through 7  has three lattice-like supporting structures  20  which are located on vertically staggered horizontal planes and which are described in greater detail under  FIGS. 6 and 7 . Instead of three supporting structures  20 , fewer or more supporting structures  20  may also be provided. Supporting structures  20  may also be inclined around the Y axis toward the center of gravity of head  5  in order to counteract a movement of head  5  around the Y axis. 
     Lattice-like supporting structures  20  may be foam-injected into, for example, headrest  4 , whereby they are possibly disposed directly in front of the holding structure epitomized by holding rods  3 . A headrest  4  of this type brings about a stabilization of a head  5  during movements around the X and Z axes. 
     As is apparent, in particular, from  FIGS. 6 and 7 , lattice-like supporting structure  20  is formed by two supporting structures  10 ′,  10 ″ according to  FIGS. 2 through 4  in a mirror-image configuration, whose two front supporting straps  12 ′ and  12 ″ continuously merge with each other monolithically on the symmetry plane, which normally coincides with the median plane, thus forming a common front supporting strap  12 ′  12 ″ in this manner. Conversely, rear supporting straps  13 ′,  13 ″ are not connected to each other. 
     Due to the other correspondences with lattice-like supporting structures  10  according to  FIGS. 2 through 4 , reference is hereby made to the discussion of these figures, in particular with regard to their geometry. 
     The deformation of lattice-like supporting structure  20  during an accident event is shown in the dashed representation in  FIG. 7 . The pressure applied by head  5  is symbolized by arrow  21 . This force  21  induces a concave deformation of front supporting strap  20 ′,  20 ″, which, due to the lattice effect, causes first ends  14 ′,  15 ′ and  14 ″,  15 ″ to move counter to force  21  symmetrically to the symmetry plane and to set up lateral supporting surfaces  9  in headrest  4  over the course of this movement. 
     The embodiment of the invention illustrated in  FIGS. 8 and 9  relates to a refinement of the lattice-like supporting structure  20  described in  FIGS. 5 through 7 , so that reference is hereby made to the discussions thereof to avoid repetition. 
     To supporting structure  20  according to  FIGS. 8 and 9  is added a holding and synchronization mechanism  22 , by means of which lattice-like supporting structure  20  is fastened to vertical axes, preferable to holding rods  3  of headrest  4 . 
     Holding and synchronization mechanism  22  comprises two articulated levers  23 , each of which is rotatably positioned on holding rod  3  by one end and connected to rear supporting strap  13 ′,  13 ″ of supporting structure  20  by its other end via a pivot joint  24 . In the area of pivot joint  24 , each articulated lever  23  has a foot  24  which is spread to the outside in the direction of first ends  14 ′,  15 ′ and  14 ″,  15 ″, which acts as a stop for the swiveling movement. In the initial position of headrest  4 , foot  25  joins each of rear supporting straps  13 ′,  13 ″. 
     To synchronize the deformation movement of the two mirror-image parts  10 ′ and  10 ″ of supporting structure  20  during the course of the impact of head  5 , a toothed wheel  26  is pushed onto each holding rod  3 , which is rigidly connected to articulated levers  23 , for example by forming a single piece therewith or by gluing, but which otherwise may rotate with articulated level  23 . Finally, the synchronization activates a cam belt  27 , which is guided around both toothed wheels  26  and is wound 180°. 
     In this manner, an absolutely symmetrical deformation of supporting structure  20 , and thus a symmetrical setup of lateral supporting surfaces  9 , is ensured even if head  5  is thrust eccentrically into headrest  4 . 
       FIG. 10  finally shows a modification of lattice-like supporting structure  20  described in  FIGS. 5 through 9 , in which the cells formed by front supporting straps  12 ′,  12 ″, rear supporting straps  13 ′,  13 ″ and cross-struts  19 ′,  19 ″ are filled with an elastic or plastically deformable and energy-absorbing material  28 , for example with a foam, gel or the like. Filling material  28  induces a damping of the deformation movement, it being possible to influence the speed curve of the deformation movement by selecting a suitable filling material  28 . In  FIG. 10 , all cells are filled with a material  28 , which, however, does not rule out the possibility of filling only individual cells with a material  28 , while other cells remain empty, in order to achieve a special deformation characteristic. It is furthermore possible to also dampen supporting structures  20  described in  FIGS. 2 through 4  in a similar manner. 
     The other embodiments of the invention according to  FIGS. 11 through 14  provide for activation of lateral supporting surfaces  9  of a headrest  4  on the basis of multiple communicating, fluid-filled volumes, the volume reduction of one volume causing the growth of other volumes to form supporting surfaces  9 . 
     To implement this idea, in a headrest  4  according to  FIGS. 11 and 12 , a plurality of cylinder piston units  29  are disposed in a matrix-like manner on a supporting plate  30  in the direction of travel. Supporting plate  30 , in turn, is fastened to holding rods  3 . Individual cylinder piston units  29  are connected to each other via lines  31  and in this manner form a closed communication system filled with a fluid such as oil or gas, which may be foam-injected, for example, into a headrest  4 . It is apparent from  FIG. 11  that moving pistons  32  of cylinder piston units  29  are inserted or extended approximately halfway in the initial state of headrest  4 . 
       FIG. 14  represents the state of headrest  4  after a head  5  has been thrust into it during an accident event. It is apparent that cylinder piston units  29  disposed in the area of impact zone  8  have inserted pistons  32  due to the force applied thereto. During the course of the inwardly directed piston movement, the volume in cylinder piston units  29  is reduced, and the fluid located therein is displaced via lines  32  into less loaded or unloaded cylinder piston units  29 . At this location, moving pistons  32  are extended linearly in the direction of travel by the pressure of the fluid and, due to their anisotropic deformation behavior, form lateral supporting surfaces  9  which counteract a movement of head  5  around the X and/or Z axes. 
     Finally,  FIGS. 13 and 14  show an embodiment of the invention, in which a compressible impact cushion  33 , which is filled with fluid such as oil or gas, is integrated in the area of central impact area  8 . An expansion cushion  34  disposed on each side of impact cushion  33  is connected to the volume of impact cushion  33  via lines  35 . Each expansion cushion  34  has an approximately triangular contour, viewed from the top, having a first side facing impact cushion  33 , a second side  36  facing the front of headrest  4  and a rear side  37  facing the back of headrest  4 . Rear side  37  of expansion cushion  34  has a wavy or pleated design to permit widening of expansion cushion  34  along this side  37 . 
     If head  5  of a vehicle occupant is thrust into impact cushion  33  during an accident, fluid is pumped into expansion cushions  34  via lines  35  during the course of the volume decrease of impact cushion  33  associated therewith, the expansion cushions  34  subsequently increasing in volume. Since each expansion cushion  34  is made of a non-expandable or only slightly expandable material, the volume increase of expansion cushion  34  takes place primarily by an elongation of rear side  37 , which permits an unhindered increase in length, due to its wavy or pleated design. Since front side  36  does not have this ability to increase in length, a swiveling movement of expansion cushion  34  toward the front in the direction of travel sets in, which is identified by arrow  38 , front side  36  of expansion cushion  34  forming lateral supporting surfaces  9  for stabilizing a head  5 . This state is illustrated by the dashed lines in  FIGS. 13 and 14 . The course of movement may be controlled by selecting the viscosity of the fluid and/or by providing a throttle in line  35 . 
     It is understood that the invention is not limited to the combination of features of the embodiments described above. Instead, a combination of features of different embodiments is within the scope of the invention, provided that they are readily apparent to the average person skilled in the art. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.