Abstract:
A safety device for a motor vehicle includes a deformation element which is arranged between a bumper beam and a side rail and moves into the side rail in the event of an impact. The deformation element is configured in the form of an evertable tubular member having a side-rail-proximal rear end provided with an abutment ring. Operatively connected to the deformation element is an actuator which is provided to release a displacement of the deformation element into the side rail in a predefined speed range by liberating the abutment ring in relation to the side rail in a release position, and to block the displacement of the deformation element into the side rail, when the speed range is exceeded or a vehicle speed is below the speed range, by locking the abutment ring in relation to the side rail in an engagement position.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of German Patent Application, Serial No. 10 2007 012 962.0, filed Mar. 14, 2007, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a safety device for a motor vehicle. 
         [0003]    Nothing in the following discussion of the state of the art is to be construed as an admission of prior art. 
         [0004]    Bumper systems, i.e. bumper beams, are generally sized to conform to the standards of the Allianz Zentrum für Technik [Allianz Center for Technique] with respect to high-speed crashes. As a consequence, metal parts are used that are relatively stiff at speeds of above 20 km/h; However, these metal parts pose an increased risk of injury for pedestrians. A shock absorbing action in the event of an impact with a pedestrian is realized only across the outer skin and the subjacent foams which absorb part of the impact energy in the area of the bumper. When newly developed vehicles are involved, the legal load limit values for the various body areas of a pedestrian are tested within the framework of defined Euro-NCAP tests. Therefore, the automobile industry strives to identify and optimize the relevant impact zones. 
         [0005]    To reduce the risk of injury of a pedestrian in the event of a collision with a passenger car in a speed range of 20 km/h to 50 km/h, the supporting vehicle front structure should be constructed as soft as possible. However, a soft design of the vehicle front runs counter to the demands to provide a protection of vehicle occupants in the event of a crash at high speed because such a crash requires a maximum energy absorption in the area of the front structure. The required foam elements in the area of the bumpers have limited energy absorption capability which is exhausted when high speeds are involved. 
         [0006]    Another consideration is the direct effect of the required thickness of the foam material on the design and length of the front structure of the vehicle. Construction-based changes in design are undesired as are vehicles of excess length. 
         [0007]    It has also been proposed to utilize the space inside the side rail by allowing the deformation elements which are arranged between side rail and bumper beam, to move into the side rail. Examples include international publication no. WO 99/15364 or U.S. Pat. No. 3,633,934, which disclose telescoping shock absorbers which move into the side rails in the event of an impact. German Offenlegungsschrift DE 42 38 631 A1 describe a shock absorbing structure having inner and outer tubes which can move within one another, with the outer tube being supported on the side rail by a flange. Even though these types of deformation elements address the shock absorbing behavior, it is still complicated to provide a deformation element which is able to absorb a high-speed crash, e.g. 60 kN to 110 kN, depending on vehicle and manufacturer, and yet has a rigidness of only few newtons for a frontal impact of a pedestrian, i.e. a rigidness that is smaller by several powers to ten. An example for an energy absorbing device which can be blocked in dependence on the impact speed is disclosed in German Offenlegungsschrift DE 10 2004 059 545 A1. 
         [0008]    It would be desirable and advantageous to provide an improved safety device for a motor vehicle to obviate prior art shortcomings. 
       SUMMARY OF THE INVENTION 
       [0009]    According to one aspect of the present invention, a safety device for a motor vehicle includes a deformation element arranged between a bumper beam and a side rail and moving into the side rail in the event of an impact, with the deformation element being configured in the form of an evertable tubular member having a side-rail-proximal rear end provided with an abutment ring, and an actuator operatively connected to the deformation element and constructed to release a displacement of the deformation element into the side rail in a predefined speed range by liberating the abutment ring in relation to the side rail in a release position, and to block the displacement of the deformation element into the side rail, when the speed range is exceeded or a speed is below the speed range, by locking the abutment ring in relation to the side rail in an engagement position. 
         [0010]    The present invention resolves prior art problems by recognizing that the rigidity of the front vehicle structure can be suited to the impact force to be expected and thus to the accident situation at hand. The front structure, comprised of bumper, bumper beam, side rail, and deformation element, is provided with an actuator which is actively controlled, i.e. linked to the vehicle electronics, and provided to release the displacement of the deformation element into the side rail in a predefined speed range, while blocking the displacement, when a speed outside the speed range is involved. In other words, it can be switched between two rigidities in dependence on the vehicle speed. The normal setting is commensurate with the locking position of the deformation element with respect to the side rail. The second setting or second switching mode involves the release of the deformation element. The speed range, within which a displacement of the deformation element is possible, ranges between 20 km/h and 50 km/h. Speeds outside this range result in a blocking of the deformation element. In the event, a pre-crash sensor assembly determines an imminent impact, the switching mode of the actuator can change to suit the situation at hand. The deformation element is released, in particular when the vehicle speed is below 20 km/h, e.g. when a collision with a pedestrian is impending. If no such collision is imminent, the safety and protection of a vehicle&#39;s occupant is the main focus so that the deformation element is blocked. It will be understood by persons skilled in the art that the lower limit can be defined only as approximating  20  km/h so that the lower limit is defined in a range between 16 and 20 km/h. 
         [0011]    In accordance with the invention, there is no need to expand the foam structure disposed anteriorly of the supporting bumper beam. As a consequence, there is also no need for design changes in order to implement the safety device, and the need for an extension of the total vehicle length is also eliminated because the deformation element is able to plunge into the side rail. 
         [0012]    The deformation element, also called energy absorbing structure, is constructed to absorb energy by rolling or inverting. Therefore, the deformation element according to the invention is realized as evertable tubular member having a rear end provided with an abutment ring which is locked or liberated in relation to the side rail by the actuator. 
         [0013]    The deformation elements may be constructed round, oval, or rectangular in cross section. Even shell constructions are conceivable, whereby the tubular member is made from an upper shell and a lower shell. The particular configuration of the deformation element is secondary so long as the entire length of the deformation element can be used, when the deformation element pushes into the side rail. When unlocked, i.e. released, the deformation element is able to plunge into the side rail without almost no force so that the deformation element does not twist and may even be reused when extracted from the side rail. In addition to the foaming of the bumper beam, an added deformation path is created for a soft front vehicle structure which exposes a colliding pedestrian to little resistance. The resistance forces are based essentially on the mass inertia of the bumper beam and the deformation element. 
         [0014]    The safety device according to the invention provides for a securement of the deformation element with the aid of an abutment ring which is connected to the deformation element. Engagement elements may engage the abutment ring so that the abutment ring can be coupled or uncoupled with or from a restraining ring which is secured to the side rail. 
         [0015]    Operatively connected to the restraining ring is an adjustment element which can be moved by the actuator and via which the engagement elements between the abutment ring and the restraining ring can be blocked in the engagement position. Suitably, the engagement elements are constructed in the form of balls arranged in aligned bores of the abutment ring and the restraining ring. As the balls may not fall out from the abutment ring and thus need to be captivated, the bore in the abutment ring are either blind end bores or have one end at a diameter that prevents the balls from slipping through. Suitably, the bores have a tapered configuration. In contrast thereto, the bores in the restraining ring are sized to allow passage of the balls. The bores are suitably disposed evenly spaced about the circumference of the deformation element. 
         [0016]    When the spherical engagement elements are received in part in the abutment ring and in part in the restraining ring, the abutment ring is locked in relation to the restraining ring. Blockage is hereby realized via the adjustment element which prevents escape of the balls from the bores in the restraining ring. The release of the form-fitting connection is realized by providing the adjustment with a pocket in which the engagement elements are able to engage in the release position. Thus, in order to liberate the balls, the pocket is arranged in alignment to the bores. The adjustment element hereby changes its relative position to the restraining ring and may shift in circumferential direction. When several adjustment elements are spaced about the perimeter, each of the adjustment elements may be provided with its own actuator. Currently preferred is however a construction in which the plural adjustment elements are interconnected by coupling elements so as to be movable as a unitary structure by a single actuator. The coupling elements may be a rod linkage or an elastic element via which tension and thrust forces can be transmitted. 
         [0017]    Of course, it is also possible to shift the adjustment element in an axial direction, in particular when the adjustment element is constructed in the form of a ring in radially surrounding relationship to the restraining ring. In this case, the abutment ring is arranged radially inside the restraining ring which, in turn, is surrounded on the outside by the adjustment element designed in the form of a ring. 
         [0018]    As described above, the engagement elements are moved in radial direction. It is, of course, also possible to provide a form-fitting union in which the formfit is realized in axial direction rather than in radial direction. For example, the adjustment element may be configured in the form of an annular disk which is moved in circumferential direction by the actuator and is positioned in axial direction anteriorly of the restraining element in ring shape which in turn is secured to a flange plate of the side rail. The adjustment element, also constructed in the form of an annular disk is arranged on the adjustment-element-distal side of the restraining ring, i.e. inside the side rail. The abutment ring is in engagement with the adjustment element via the engagement elements which point in axial direction. The engagement elements extend hereby through the restraining ring which is supported on the flange plate. Suitably, the engagement elements have hereby a shaft which extends through the restraining ring and the adjustment element and has a wider head to form a bayonet coupling with the adjustment element. The adjustment element may, for example, formed with openings resembling a keyhole, whereby the greater zone of the keyhole-like opening may be brought into coincidence with a respective opening in the restraining ring so that the thickened head of the engagement elements is able to slide through the adjustment element and the restraining ring, causing the deformation element, secured to the restraining ring, to plunge into the side rail. The adjustment element may be guided by suitable pins on the restraining ring. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0019]    Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
           [0020]      FIG. 1  is an isometric illustration of a first embodiment of a safety device according to the present invention; 
           [0021]      FIG. 2  is an exploded view of the safety device of  FIG. 1 ; 
           [0022]      FIG. 3  is a cross sectional view of the safety device of  FIG. 1 ; 
           [0023]      FIG. 4  is an isometric illustration of a second embodiment of a safety device according to the present invention; 
           [0024]      FIG. 5  is an exploded view of the safety device of  FIG. 4 ; 
           [0025]      FIG. 6  is a cross sectional view of the safety device of  FIG. 4 ; 
           [0026]      FIG. 7  is an isometric illustration of a third embodiment of a safety device according to the present invention; 
           [0027]      FIG. 8  is an end view of the safety device of  FIG. 7 ; and 
           [0028]      FIG. 9  is an exploded view of the safety device of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0029]    Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
         [0030]    Turning now to the drawing, and in particular to  FIG. 1 , there is shown an isometric illustration of a first embodiment of a safety device according to the present invention for interaction with a side rail I of a motor vehicle (not shown), with  FIG. 1  showing only an end portion of the side rail  1 . The safety device includes a deformation element  2  which projects into the side rail  1  and has an unillustrated end (on the left hand side of the drawing plane) which is connected to a bumper beam of the motor vehicle. An impact force is transmitted by the bumper beam into the deformation element  2  which plunges hereby into the side rail  1 . 
         [0031]    The deformation element  2  is configured in the form of an evertable tubular member having a rear end  5  which is secured to the side rail  1 . The safety device further includes a housing  3  which is provided with an actuator  4 . The mode of operation of the safety device will now be described with reference to  FIGS. 2 and 3 . 
         [0032]    As shown in  FIG. 2 , which is an exploded view of the safety device, the rear end  5  of the deformation element  2  is folded back outwards to form a collar and is securely fixed, e.g. welded, to an abutment ring  6  in the assembled state. The abutment ring  6  is surrounded in the assembled state radially by a restraining ring  7  which is mounted to a ring-shaped flange plate  8  which is securely fixed to the side rail  1 . 
         [0033]    The abutment ring  6  and the restraining ring  7  are configured in such a manner that they can be brought into a form-fitting engagement or in a position in which they can move relative to one another in a longitudinal direction of the side rail  1 . When the abutment ring  6  should be coupled with the restraining ring  7 , engagement elements  11  engage aligned bores  9 ,  10 , in the abutment ring  6  and restraining ring  7 , respectively. In the shown non-limiting example, the engagement elements  11  have the shape of balls which can be displaced in radial direction. 
         [0034]      FIG. 3 , which is a cross sectional view of the safety device, shows the arrangement of the engagement elements  11  in the locked position inside the bores  9 ,  10 . The bore  10  in the restraining ring  7  is a constructed as a throughbore of cylindrical cross section, whereas the bore  9  in the abutment ring  6  has a tapered configuration so that the spherical engagement elements  11  are captivated and unable to escape the abutment ring  6  radially inwards. 
         [0035]      FIG. 3  shows the safety device in a locked position which is realized by adjustment elements  12  that can move in circumferential direction in the shown non-limiting example. Each of the adjustment elements  12  has a pocket  13  in which the spherical engagement elements  11  are able to enter in the release position, in which case the pocket  13  is in alignment with the bores  9 ,  10 . The pocket  13  includes an inclined surface  14 , serving as a ramp, on which the engagement elements  11  can slide when being pushed into the bore  9 ,  10  during displacement of the adjustment element  12 . 
         [0036]    As shown in  FIG. 3  by way of example, four engagement elements  11  and thus also four adjustment elements  12  are provided. The adjustment elements  12  are evenly spaced about the circumference and interconnected by strip-shaped coupling elements  15  so as to establish overall a ring-shaped configuration. The coupling elements  15  enable a transmission of a movement of the adjustment element  12  shown on top of  FIG. 3  to all the other adjustment elements  12  so that the single actuator  4  can be used to switch the safety device between the locked position and the release position. The coupling elements  15  are hereby supported on guide blocks  16  which are securely fixed to the flange plate  8  of the side rail  1 . 
         [0037]      FIGS. 4-6  show a second embodiment of a safety device according to the present invention. In the following description, parts corresponding with those in  FIGS. 1-3  will be identified, where appropriate for the understanding of the invention, by corresponding reference numerals followed by an “a”. The description below will center on the differences between the embodiments. In this embodiment, provision is made for an adjustment element  12   a  which is configured in the form of an annular structure which surrounds the restraining ring  7  radially on the outside and is movable in an axial direction. The adjustment element  12   a  has a pocket  13   a  which is formed with an inclined surface  14   a . The pocket  13   a  is configured in the form of a radially inwardly provided circumferential annular groove. The spherical engagement elements  11  may engage this pocket  13   a  in unison and can be fixed in place through linear axial shift by means of the actuator  4   a  into the bores  9 ,  10  of the abutment ring  6  and the restraining ring  7 , respectively. Otherwise, the basic configuration of this safety device corresponds to the safety device shown in  FIGS. 1-3  so that a further description is omitted for the sake of simplicity. The deformation element  2  is again configured as an evertable tube with its inner end  5  being folded back to form a collar. 
         [0038]      FIGS. 7-9  show a third embodiment of a safety device according to the present invention. In the following description, parts corresponding with those in  FIGS. 1-3  will be identified, where appropriate for the understanding of the invention, by corresponding reference numerals followed by an “b”. The description below will center on the differences between the embodiments. In this embodiment, provision is made for axial offset disposition between the restraining ring  7   b  and the abutment ring  6   b .  FIG. 9  shows the side rail  1  with an end flange plate  8   b . The flange plate  8   b  is sized to allow the abutment ring  6   b  to be pushed through the flange plate  8   a  into the side rail  1 . The abutment ring  6   b  has a disk-shaped configuration and has openings  17  in the corner areas for anchoring engagement elements  11   b  in the form of bolts which project out in axial direction. The openings  17  are aligned with bores  17   b  of the restraining ring  7   b  which is also configured in the form of a plate. The restraining ring  7   b  is placed in surrounding relationship to the deformation element  2  and is securely bolted together with the flange plate  8   b . Following the restraining ring  7   b  is an adjustment element  18  in the form of an annular disk which is guided on the restraining ring  7   b  by pins  19 . The pins  19  extend out in axial direction and permit a limiting pivoting in circumferential direction. 
         [0039]    The bolt-like engagement elements  11   b  which extend out from the abutment ring  6   b  in axial direction extend through openings  21  in the adjustment element  18 . The openings  21  are configured in the shape of a keyhole, with the region of the openings  21  that is smaller in diameter matching a diameter of a shank of the bolt-like engagement elements  11   b . The engagement elements  11   b  have each a head  20  which is sized to fit through the region of the openings  21  that is greater in diameter. Depending on its position, the adjustment element  18  is able to block or release the heads  20  of the engagement elements  11   b . This is possible by a slight pivoting in circumferential direction, triggered by the actuator  4   b . When the heads  20  of the engagement elements  11   b  are released, the heads  20  slip out of the adjustment element  18  and the restraining ring  7   b  and plunge jointly with the deformation element  2  into the side rail  1 . On the other hand, when the heads  20  are blocked by the adjustment element  18 , a traction force is applied upon the engagement elements  11   b  and introduced via the heads  20  into the engagement elements  11   b  and via the abutment ring  6   b  into the flange plate  8   b  of the side rail  1 . 
         [0040]    While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. 
         [0041]    What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: