Abstract:
A device for absorbing kinetic energy includes a first stationary component and a second component that can be moved in relation to the first component, wherein at least one of the components converts energy by plastic deformation when a certain force level is exceeded, and comprising a coupling apparatus, which operatively connects the first component and the second component in such a way that the two components can be moved in relation to each other only with low energy conversion when the coupling apparatus is not activated and forces can be transmitted from one component to the other component when the coupling apparatus is activated. The movable component has a deformation element, which initially deforms in the event of a crash, so that a movement of the movable component occurs only thereafter, wherein the coupling apparatus is continuously in engagement with the two components and thus continuously produces a first low coupling force level and, when the coupling apparatus is activated, the coupling forces are increased from the first low coupling force level to a high coupling force level and plastic deformation of at least one component occurs.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of International Application No. PCT/EP2014/000985, filed Apr. 12, 2014, which designated the United States and has been published as International Publication No. WO 2014/177250 and which claims the priority of German Patent Application, Serial No. 10 2013 007 594.7, filed May 2, 2013, pursuant to 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The invention relates to a device for absorbing kinetic energy, in particular for installing in a motor vehicle. 
     In motor vehicle construction, devices for absorbing kinetic energy for protecting persons in the event of a crash are known. These devices include for example a first stationary component and a second component that is movable relative to the first component, and a coupling device operatively connecting the first component and the second component. At least one of the components converts energy by plastic deformation when a certain force level is exceeded. The coupling device connects the two components so that in a non-activated state of the coupling device the two components can be moved in relation to each other with only low energy conversion, and in an activated state of the coupling device forces can be transmitted from one component to the other. 
     From DE 10 2008 048 678 A1 for example, a device for absorbing kinetic energy is known, in particular for installation in a motor vehicle. Depending on the load conditions, a movable component is coupled to a stationary component. In the event of a collision with a pedestrian, the two components are not coupled so that only a minimal amount of energy is absorbed. When no collision with a pedestrian is sensed, the two components are coupled to absorb energy at a high force level without loss of travel. The two components are not coupled continuously and a deformation element with a compressible soft foam is provided which is capable of initially yielding during a collision with a pedestrian. 
     SUMMARY OF THE INVENTION 
     Object of the invention is to provide a device for absorbing kinetic energy, particularly for installation in a motor vehicle, which enables an enhanced protection of pedestrians, wherein good energy absorption is also achieved in higher-intensity crashes. 
     According to the invention, the object is achieved by providing a device for absorbing kinetic energy, particularly for installation in a motor vehicle, including the features of patent claim. Advantageous embodiments and refinements of the invention are disclosed in the dependent claims. 
     Embodiments of the present invention provide a device for absorbing kinetic energy, in particular for installation in a motor vehicle, which includes a first stationary component and a second component that is movable in relation to the first component. At least one of the components converts energy by plastic deformation when a defined force level is exceeded. Furthermore, a coupling device is provided, which operatively connects the first component and the second component so that in a non-activated state of the coupling device the two components are movable in relation to each other with low energy conversion, and in an activated state of the coupling device forces can be transferred from one component to the other. According to the invention, the movable component includes a deformation element which, in the event of a crash, initially deforms, so that the movable component only moves subsequent thereto, wherein the coupling apparatus is continuously in engagement with the two components and thus continuously generates a first low coupling-force level and, upon activation of the coupling apparatus, the coupling forces are increased from the first low coupling-force level to a high coupling-force level and plastic deformation of at least one component occurs. 
     Embodiments of the device according to the invention advantageously enable different levels of pedestrian protection because the movable component includes a deformation element which is advantageously designed as a compressible foam element which, in the event of a crash, initially deforms so that the movable component only moves subsequent thereto. Hereby, the coupling apparatus is continuously in engagement with the two components and thus continuously generates a first low coupling-force level. Due to the low coupling-force level in the deactivated state of the coupling apparatus, the dimensions of the deformation element can be reduced so, an overhang of the vehicle can advantageously be shortened in a range of 30 to 60 mm while providing the same level of pedestrian protection. When, on the other hand, a low-speed or high-speed-crash is sensed, the coupling apparatus is activated and as a result an immediate increase of the coupling forces from the first low coupling-force level to a high coupling-force level so that subsequently a plastic deformation of at least one component occurs. 
     In an advantageous embodiment of the device for absorbing kinetic energy according to the invention, a locking element can be provided for activating the coupling device. This enables a simple and reliable switching of the device according to the invention between the different coupling-force levels. 
     In a further advantageous embodiment of the device for absorbing kinetic energy according to the invention, the coupling device can include at least one bracket, which connects the two components and which is pushed outwardly by the locking element toward the moving component in order to activate the coupling apparatus. The coupling element can be simply designed as movable bolt, which is movable from an unlocked state into a locked state. A good bracing effect of the brackets is achieved when the bolt is designed rotatable and with rounded edges, which act on a surface of the locking element and push the locking element outwardly through corresponding apertures within the movable second component into corresponding receptacles within the stationary component. This enables a simple and reliable implementation of the coupling device for the device for absorbing kinetic energy according to the invention. 
     In a further advantageous embodiment of the device for absorbing kinetic energy according to the invention, the stationary component can be arranged on a baffle plate of a longitudinal member. In the event of a crash, the movable component at least partially moves into the stationary component when the coupling apparatus is deactivated. When the coupling apparatus is activated, the movable component and the stationary component are firmly coupled to each other in the event of a crash and are plastically deformable by folding. Due to the fact that the stationary component rests against the baffle plate and the firm coupling of both components, good energy absorption is advantageously achieved by folding of the two components. 
     Alternatively, the stationary component can be directly connected to the longitudinal member, for example by a connecting flange. Hereby, the movable component at least partially moves into the longitudinal member in the event of a crash when the coupling device is deactivated. In this case the movable component can at least partially move into the longitudinal member in the event of a crash also when the coupling device is activated, wherein the coupling device plastically deforms the movable component during the entering by shearing. This advantageously enables good energy absorption due to shearing of the movable component. Alternatively, the movable component can be blocked in the event of a crash when the coupling apparatus is in the activated state and can be plastically deformed by folding. Due to a firm coupling of both components, good energy absorption is advantageously achieved by folding of the movable component. 
     In a further advantageous embodiment of the device for absorbing kinetic energy according to the invention, the longitudinal member can for example be designed as a single-chamber or two-chamber hollow section. 
     In a further advantageous embodiment of the device for absorbing kinetic energy according to the invention, a pre-crash-sensor present in the vehicle can be used, which activates the coupling apparatus prior to a collision when detecting a crash and which moves the locking element from the unlocked position into the locked position. Additionally or alternatively, the pre-crash-sensor provided in the vehicle can also be used to deactivate the coupling apparatus when detecting an imminent collision with a pedestrian and to move the locking element from the locked position into the unlocked position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Advantageous embodiments of the invention are shown in the drawing and are described below. 
       It is shown in: 
         FIG. 1  a schematic representation of a first embodiment of the device for absorbing kinetic energy according to the invention switched to a soft mode, 
         FIG. 2  a schematic representation of a device to absorb kinetic energy according to the invention switched to a rigid mode. 
         FIG. 3  a schematic representation of a second and third embodiment of a device to absorb kinetic energy according to the invention switched to a soft mode, 
         FIG. 4  a schematic representation of a second embodiment of the device according to the invention to absorb kinetic energy according to  FIG. 3  switched to a rigid mode, and 
         FIG. 5  a schematic representation of a third embodiment of a device according to the invention for absorbing kinetic energy according to  FIG. 3  switched to a rigid mode. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIGS. 1 to 5  show embodiments of the device  1   a ,  1   b ,  1   c  according to the invention for absorbing kinetic energy for installation particularly in the front section of a motor vehicle.  FIGS. 1 and 2  show a first embodiment of the device  1   a  according to the invention, which is designed as so-called folding box, in which a movable first component  3   a  with a smaller diameter moves into a stationary second component  4   a  with a greater diameter, until a deformation of at least one of the components  3   a ,  4   a  results. The second stationary component  4   a  is mounted to a longitudinal member  5   a  of the vehicle and has a terminal baffle plate  6 . The movable first component  3   a  is for example designed as a tubular component and toward an exterior  10  of the vehicle is mounted to a bumper cross member  12 , which may be designed as a hollow section. Further toward the vehicle exterior  10  a deformation element  15 , configured as a foam element having a length of approximately 15 to 35 mm, is installed between the bumper cross member  12  and a bumper cover  14 . The device  1   a  according to the invention is part of a bumper system for the motor vehicle front, which is essentially formed by the bumper cover  14 , the foam element  15 , the bumper cross member  12 , the first movable component  3   a  and the second stationary component  4   a  and the baffle plate  6  on the longitudinal member  5   a . Both components  3   a ,  4   a  are configured deformable. The first component  3   a  and the second component  4   a  form a so-called low-speed crash element. According to the invention, both components  3   a ,  4   a  are permanently connected to each other by a coupling device  20 . The coupling device  20  is formed by at least one bracket  21  and a locking element  22 . The second component  4   a  is supported on the baffle plate  6 , which is arranged toward the vehicle interior  11  on the longitudinal member  5  of the vehicle. Hereby, the longitudinal member  5  is configured as a two-chamber section  5   a.    
     The coupling device  20  is configured so that the movable component  3   a  and the stationary component  4   b  are constantly coupling. For this purpose, at least one bracket  21  is provided, wherein multiple brackets  21  can be provided on the circumference. 
     As further shown in  FIGS. 1 and 2 , the brackets  21  are advantageously arranged on the circumferences as pairs so as to oppose each other. The brackets  21  are inserted into receiving apertures  25  of the stationary component  4   a  and lead through apertures  26  of the movable component  3   a  into the interior of the movable components  3   a . In the shown embodiment, the brackets  21  are overall configured in the form of a convergent nozzle, which tapers in longitudinal direction x of the vehicle, as viewed from left to right. In the shown embodiment, a locking element  22  is provided centrally in the movable component  3   a  between the brackets  21 , and in the shown exemplary embodiment is configured as pivotable elongated bolt. Of course, other suitable embodiments of the coupling device are possible that ensure a rigid or loose coupling of the two components  3   a ,  4   a  in the event of a crash, to provide different force levels for absorbing crash energy. 
       FIG. 1  shows the device  1   a  in a normal state, i.e., prior to a collision, in which the bumper cover  14 , shown in dashed lines, represents the position of the bumper cover  14  with a conventional deformation element having a length of 60 to 70 mm in a conventional motor vehicle. Due to the device  1   a  according to the invention for absorbing kinetic energy, a shortening a of the vehicle overhang in a range from 35 to 55 mm is possible, because compared to the conventional deformation element, the deformation element  15  of the device  1   a  according to the invention is configured significantly shorter while providing the same protection for persons. 
     In  FIG. 1  the locking element  22  is in an unlocked position so that the locking element  22 , configured as pivotable elongated bolt, is oriented in longitudinal direction x of the vehicle. Upon activation, the locking element  22  pivots into a locked position, in which it extends perpendicular relative to the longitudinal direction x of the vehicle, and in this case is oriented in vertical direction z of the vehicle. In the locked position, the locking element  22  pushes both brackets  21  outwardly in the direction of the stationary component  4   a , so that the ends of the brackets  21  are held in corresponding receiving apertures  25  of the stationary component  4   a . This results in a rigid coupling of both components  3   a ,  4   a  and prevents that the two brackets  21  move towards each other and that the rigid coupling between both components  3   a ,  4   a  is lost. The locked state of the coupling apparatus  20  is shown in  FIG. 2 . 
     In order to provide different levels of pedestrian protection, the locking element  22  can, as shown in  FIG. 1 , remain in its unlocked position during a collision with a pedestrian. This only marginally impedes the movement of the first component  3   a , so that it can pass through a travel switched to soft configuration, designated b in  FIG. 1 , and can at least partially move into the stationary component  4   a  until a front side  8   a  of the first component  3   a  impacts an inside of the baffle plate  6 . Thereby, the travel b is traversed with more or less low resistance due to the counteracting rigidity of the brackets  21 . This allows providing an energy absorption with a lower force level adapted to a collision with a pedestrian so as to ensure higher protection for pedestrians. 
     The decision whether a collision with a pedestrian or a stronger low-speed or high-speed crash occurs, is detected, as is known, with a pre-crash-sensor which then activates the coupling device  20  during the low-speed or high-speed-crash and moves the locking element  22  from the unlocked position into the locked position. Additionally or alternatively, when an imminent collision with a pedestrian is detected, the coupling device can be deactivated and the locking element can be moved from the locked position into the unlocked position. Activation of the coupling device  20  leads to pivoting of the locking element  22 , which is configured as a bolt, which pivoting pushes the brackets  21  apart, thus resulting in a high-force coupling of the two components  3   a ,  4   a . As a consequence, directly after the deformation of the foam element  15 , the movable component  3   a  and also the stationary component  4   a  are significantly deformed, which leads to a folding of both components  3   a ,  4   a  so that a higher collision- or crash energy can be absorbed. By appropriately selecting the stability or rigidity of the brackets  21  and their longitudinal extent in longitudinal direction x of the vehicle, a good control of the desired energy absorption can be achieved. 
       FIGS. 3 to 5  show two further exemplary embodiments of the device  1   b ,  1   c  according to the invention for absorbing kinetic energy, in which all components that are the same or have the same effect are provided with the same reference signs as the first exemplary embodiment according to  FIGS. 1 and 2 . 
     Analogous to the first embodiment, the locking element  22  in  FIG. 3  is in the unlocked position so that the locking element  22 , which is configured as a bolt, is oriented in longitudinal direction x of the vehicle. Analogous to  FIG. 1 ,  FIG. 3  shows the device  1   b ,  1   c  in the normal state i.e., prior to a collision with a pedestrian. Also in this case the bumper cover  14 , shown in dashed lines, represents the position of the bumper cover  14  in a conventional deformation element with a length of 60 to 70 mm in a conventional motor vehicle. Also in the second and third exemplary embodiment of the device  1   b ,  1   c  according to the invention for absorbing kinetic energy, the vehicle overhang can be shortened in the range of 35 to 55 mm compared to conventional deformation elements, because the deformation element  15  of the device  1   b ,  1   c  according to the invention is configured significantly shorter compared to the conventional deformation element, while providing the same pedestrian protection. 
     In modification to the first embodiment, the second embodiment of the device  1   b  is configured as a so-called shear-box. No baffle plate is provided and the stationary component  4   b  is arranged on the longitudinal member  5  so that the movable component  3   b  can move into the longitudinal member  5  further to the right in longitudinal direction x of the vehicle. For this the longitudinal member  5  is constructed as single-chamber hollow section  5   b . In  FIG. 3 , a soft mode for enhanced pedestrian protection is shown, in which the coupling device  20  is in the non-activated state. Analogous to the first exemplary embodiment according to  FIG. 1 , a travel b is provided, wherein the brackets  21  only pose a low resistance. The movable component  3   b  can be moved backward quasi unimpeded, wherein only the friction and the holding force or the restoring force of the brackets  21  counteract the movement. This only insignificantly impedes the movement of the first component  3   b , so that it can move along the travel b which is switched to a soft mode. The maximum travel b is reached when the front face  8  of the bumper cross member  12 , which is moved with the first component  3   b , impacts the front face  7  of the stationary component  4   b . Of course shorter travels can also be provided by appropriate measures. As described for  FIG. 1 , also in  FIG. 3  the first component  3   b  moves only after deformation of the foam element  15 , so that different levels of pedestrian protection are achieved. 
     As further shown in  FIG. 4 , upon activation, the locking element  22 , analogous to the first exemplary embodiment, pivots into a locked position, which extends perpendicular relative to the longitudinal direction x of the vehicle, and which in the present case is oriented in a vertical direction z of the vehicle. In the locked position, the locking element  22  pushes the two brackets  21  outwardly towards the stationary component  4   b , so that the ends of the brackets  21  are held in corresponding receiving apertures  25  of the stationary component  4   b . This results in a rigid coupling between the two components  3   b ,  4   b  and prevents that the two brackets  21  move towards each other and that the rigid coupling between both components  3   b ,  4   b  is lost. 
     When a low-speed or high-speed crash is sensed, the coupling device  20  is activated thereby resulting in a strong coupling of the components  3   b ,  4   b  at the beginning of the crash. In the locked state of the coupling device  20  the brackets  21  engaging into the apertures  26  of the movable component  3   b  then lead to a shear-effect of the bracket  21  in the aperture  26 , which is then increased in correspondence to the traveled deformation path so that collision- or crash energy is absorbed. The rigid component  4   b  also absorbs forces and transmits them into the longitudinal member  5  without being significantly deformed. The longitudinal member itself, however, can change its structure due to the entering component  3   b.    
     In modification to the second exemplary embodiment, the third exemplary embodiment of the device  1   c  is, analogous to the first embodiment, constructed as so-called folding box. However, no baffle plate is provided and the stationary component  4   c  is arranged on the longitudinal member  5 , so that the movable component  3   c  can move into the longitudinal member  4  further to the right in longitudinal direction x of the vehicle. Analogous to the second exemplary embodiment, the longitudinal member  5  is hereby configured as a single-chamber hollow section  5   c .  FIG. 3  shows the soft mode for enhanced pedestrian protection, with the coupling device  20  in the non-activated state. Analogous to the second embodiment, a travel b is provided, wherein the brackets  21  only pose a low resistance. The movable component  3   c  is displaceable substantially freely backwards, wherein only the friction and the holding force or restoring force of the brackets  21  counteract the displacement. Thereby, the movement of the first component  3   c  is only inconsiderably impeded so that it can move along the travel b which is switched to a soft mode. The maximum travel b is reached when the front surface  8  of the bumper cross member  12 , which is moved with the first component  3   c , impacts the front surface  7  of the stationary component  4   c . Shorter travels can of course also be provided by appropriate measures. As described for the first and second embodiment, also in the third embodiment, the first component  3   c  only moves subsequent to deformation of the foam element  15 , so that different levels of pedestrian protection are achieved. 
     As further shown in  FIG. 5 , analogous to the first and second exemplary embodiments, upon activation the locking element pivots into a locked position, which extends perpendicular relative to the longitudinal direction x of the vehicle, and which in the present case is oriented in vertical direction z of the vehicle. In the locked position, the locking element  22  pushes the two brackets  21  outwardly towards the stationary component  4   c , so that the ends of the brackets  21  are held in corresponding receiving apertures  25  of the stationary component  4   b . This results in the rigid coupling between the two components  3   b ,  4   b  and prevents that both brackets  21  move towards each other and that the rigid coupling between the two components  3   c ,  4   c  is lost. 
     When a low-speed or high-speed crash is sensed, the coupling device  20  is activated thereby resulting in a strong coupling of both components  3   c ,  4   c  at the beginning of the crash. The brackets  21 , which are engaging in the apertures  26  of the movable component  3   b  then, in the locked state of the coupling device  20 , lead to a blocking of the movable component  3   c  so that collision- or crash energy is absorbed by folding of the movable component  3   c . The rigid component  4   c  also absorbs forces and transmits them into the longitudinal member  5  without being significantly deformed.