Abstract:
An energy absorbing device for a collapsible steering column has a plurality of plastically deformable straps each with one end connected to the steering column and an opposite end bent around an anvil connected to stationary vehicle support structure. When the steering column collapses, the straps unwind from the anvils, thereby resisting steering column collapse and absorbing energy. One or more of the straps may be cut in two by a knife at the time of the collision, thereby removing it from the energy absorbing system. In another form of the invention, an energy absorbing strap extends around a piston which has two or more different size anvils. The piston is axially movable in a cylinder to positions surrounding one or another of the anvils. The strap is drawn over the anvil it surrounds when the steering column collapses, thereby resisting collapse of the steering column and absorbing a certain amount of energy depending on the size of the anvil.

Description:
REFERENCE TO RELATED APPLICATION  
         [0001]    This application claims the benefit of U.S. Provisional Application No. 60/342,930, filed Oct. 19, 2001.  
         TECHNICAL FIELD  
         [0002]    This application relates generally to steering columns and more particularly to a responsive energy absorbing device for steering columns.  
         BACKGROUND OF THE INVENTION  
         [0003]    Many steering column assemblies today are equipped with kinetic energy absorption devices to reduce the likelihood of injury in case of an accident. Such devices come in many different forms. One form that is particularly effective in absorbing significant quantities of energy in a relatively small amount of space employs a plastically deformable member such as a metal strap which is bent over an anvil. In the event of a head-on collision, the deformable strap is drawn across the anvil and the deformed shape travels along the length of the strap, causing a reaction force resisting collapse of the steering column and absorbing energy.  
           [0004]    Typically, energy absorbing devices, such as those employing a plastically deformable strap, are designed to protect drivers of average weight in a collision of average severity, without taking into account the fact that all drivers are not of average weight and that collisions vary considerably in severity depending on vehicle speed at the time of the impact.  
         SUMMARY OF THE INVENTION  
         [0005]    In accordance with the present invention, it is possible to vary the reaction force resisting collapse of the steering column. For example, the energy absorbing device of this invention may provide a smaller amount of resistance in the case of a less severe collision or a lower weight driver, or a greater amount of resistance in the case of a more severe collision or a driver of greater weight. Whether the driver is seated close to the steering wheel, or belted, are also factors to be considered in determining the desired amount of reaction force.  
           [0006]    The resistance is preferably provided by a plastically deformable strap having one end portion bent around an anvil. The anvil is connected to the steering column and the other end portion of the strap is connected to stationary vehicle support structure, or vice versa. This arrangement forms a linkage between the steering column and the vehicle support structure so that when the steering column collapses in a collision, the strap will move over the anvil and resist such collapse. Often two or more such straps similarly arranged are provided. By breaking one or more of such linkages, the associated strap will drop out of the system so that the overall resistance to collapse is reduced depending upon conditions detected by a controller either before or at the instant of the collision.  
           [0007]    In one form of the invention, the linkage is broken by a knife operable to bisect the associated strap. Preferably, the knife is actuated by an explosive charge which is ignited by a signal generated by the controller. In another form of the invention, the linkage is broken by an explosive charge which severs one of the connections. The explosive charge in this form of the invention is also ignited by the signal from the controller. One such connection may include a reduced neck portion of the anvil and the explosive charge may be disposed in a hollow interior of the anvil adjacent to the neck portion.  
           [0008]    In yet another form of the invention, an energy absorbing strap extends around a piston which has two or more different size anvils. The piston is axially slidable in a cylinder to positions surrounding one or another of the anvils. The strap is drawn over the anvil it surrounds when the steering column collapses, thereby resisting collapse of the steering column and absorbing a certain amount of energy depending on the size of the anvil.  
           [0009]    One object of this invention is to provide an energy absorbing device having the foregoing features and capabilities.  
           [0010]    Other objects, features and advantages of the invention will become more apparent as the following description precedes. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:— 
         [0012]    [0012]FIG. 1A is a fragmentary sectional view of a portion of an energy absorbing device shown in FIG. 1B, constructed in accordance with the invention;  
         [0013]    [0013]FIG. 1B is a fragmentary perspective view, with parts in section, showing the energy absorbing device of which a portion is shown in FIG. 1A;  
         [0014]    [0014]FIG. 1C is a sectional view of the energy absorbing device of FIG. 1B;  
         [0015]    [0015]FIG. 1D is a sectional view of a modification of the energy absorbing device of FIG. 1B;  
         [0016]    [0016]FIG. 1E is a bottom plan view of a portion of the energy absorbing device of FIG. 1B showing three plastically deformable straps;  
         [0017]    [0017]FIG. 2A is a fragmentary sectional view similar to FIGS. 1C and 1D, but showing another embodiment of the energy absorbing device;  
         [0018]    [0018]FIG. 2B is a bottom plan view of a portion of the energy absorbing device of FIG. 2A showing three plastically deformable straps;  
         [0019]    [0019]FIG. 2C is a view similar to FIG. 2A, but showing certain parts in a different position after the steering column has collapsed;  
         [0020]    [0020]FIG. 2D is a bottom plan view of a portion of the energy absorbing device of FIGS. 2A and 2C, showing the plastically deformable straps after the steering column has collapsed;  
         [0021]    [0021]FIG. 3A is a sectional view of a portion of the energy absorbing device in FIG. 3D;  
         [0022]    [0022]FIG. 3B is a fragmentary sectional view of another portion of the energy absorbing device of FIG. 3D;  
         [0023]    [0023]FIG. 3C is a fragmentary sectional view of a portion of FIG. 3A after the ignition of an explosive charge and collapse of the steering column;  
         [0024]    [0024]FIG. 3D is a perspective view of another embodiment of the energy absorbing device;  
         [0025]    [0025]FIG. 4A is a sectional view of a portion of an energy absorbing device similar to the device of FIG. 3A but of modified construction;  
         [0026]    [0026]FIG. 4B is a sectional view of a portion of an energy absorbing device similar to the device of FIG. 4A but actuated by a solenoid-operated actuator rather than an explosive charge;  
         [0027]    [0027]FIG. 4C is a sectional view of an energy absorbing device similar to the device of FIG. 4A but actuated by a spring;  
         [0028]    [0028]FIG. 5A is a sectional view of an energy absorbing device similar to the device of FIG. 4A but operated by an explosive charge at each end;  
         [0029]    [0029]FIG. 5B is a fragmentary sectional view of the device of FIG. 5A from a different angle;  
         [0030]    [0030]FIG. 5C is an enlarged, fragmentary sectional view of a portion of FIG. 5A;  
         [0031]    [0031]FIG. 5D is an enlarged, fragmentary sectional view of a portion of the device of FIG. 5A, but with parts in a different position;  
         [0032]    [0032]FIG. 6 is a perspective view of the piston employed in the construction of FIG. 3A. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]    Referring now more particularly to the drawings and especially to FIGS.  1 A- 1 C and  1 E, an energy absorbing device  10  is shown which includes a plurality of elongated, parallel, spaced apart, plastically deformable metal straps  12 . Each strap  12  has a bent end portion  14  extending through a hole  16  in a jacket portion  18  of a collapsible steering column  20  forming a connection  21  of the strap to the steering column. Each strap has a spiral end portion  22  which is wound around an anvil  24 . The anvils  24  are secured to or integral with stationary vehicle support structure  26  forming a connection  27  of the strap  12  to the vehicle support structure. The connections  21  and  27 , the anvils  24 , and the straps  12  provide a linkage  29  between the steering column  20  and the vehicle support structure  26 , so that when the steering column collapses, the straps will move with the steering column.  
         [0034]    An actuator assembly  30  for each strap is mounted on the vehicle support structure  26 . The actuator assembly  30  has a body  32  formed with a cylinder  34  which has an open inner end. A cap  36  is threaded on the body  32  to close the open end of the cylinder  34 . A mid-portion of each strap extends through the body  32  of the associated actuator assembly  30  and through the cylinder  34 .  
         [0035]    A knife  40  in each cylinder  34  is normally poised over one of the straps  12 . Behind the knife is an actuator  42  comprising an explosive charge  44 . An igniter  46  contained in a cap  48  closes the outer end of the cylinder.  
         [0036]    In the event of a head-on collision, the driver is often thrown forward against the steering column  20 , with a force sufficient to cause the steering column to collapse. The purpose of the straps  12  is to resist the collapse of the steering column and thereby absorb energy and prevent serious injury to the driver. The straps resist collapse of the steering column by unwinding as they are pulled from the anvils. A controller  50  is provided, having sensors for detecting certain conditions existing at the time of impact, such as the severity of the collision, the weight of the driver, the driver&#39;s seat position, and whether or not the driver is belted. If the driver is of less than average weight or the collision is of only moderate severity, less resistance to steering column collapse may be needed and it may therefore be desirable to remove the effect of one or more of the straps  12  of the energy absorbing device  10 . This will be accomplished by a signal from the controller  50  to the igniter  46  for at least one of the actuators  42 , causing the igniter to activate the explosive charge  44  of that actuator to advance the knife  40  and bisect or cut one of the straps in two. The signal may go to the actuator  42  of one strap  12  or more than one strap as determined by the sensors in the controller  50 , or no signal may be sent to the actuators in the case of a very severe collision and a driver of greater than average weight. Under those circumstances it might be desirable to have all of the straps  12  involved in the absorption of energy.  
         [0037]    [0037]FIG. 1D shows a slightly modified form of actuator assembly  53 . The actuator assembly  53  is mounted on a vehicle support structure  54 . The end of the cylinder  56  in the body  58  of the actuator assembly  53  is closed by an integral end portion  60  of the body. An actuator  62  includes an explosive charge  64  in the cylinder  56  which is adapted to be actuated by igniters  66  carried by a cap  68  threaded into the body  58 . The knife  69  is advanced by the explosive charge  64  in the same manner as previously described in connection with FIGS.  1 A- 1 C. Otherwise the structure of FIG. 1D is essentially the same as the structure in FIG. 1C and corresponding parts have the same reference numerals.  
         [0038]    In both FIGS. 1C and 1D, the igniters are preferably pyrotechnic devices which are very fast acting, capable of setting off the explosive charge in only milliseconds after the collision and the reception of a signal from the controller.  
         [0039]    Referring now to FIGS.  2 A- 2 D, an energy absorbing device  71  includes a plurality of elongated, parallel, spaced apart, plastically deformable metal straps  72 . Each strap  72  has a bent end portion  74  extending through a hole  76  in a jacket portion  78  of a steering column  80 . Each strap has a U-shaped intermediate portion  82  bent around an anvil  84 . Each anvil  84  is formed as an integral part of a body  86  of an actuator assembly  88 . The bodies  86  are secured in openings of stationary vehicle support structure  90 .  
         [0040]    The body  86  of each actuator assembly  88  is integrally connected to an associated anvil  84  by a reduced neck portion  94  of the anvil. The body  86  of each actuator assembly  88  is hollow to receive an actuator  95  comprising an explosive charge  96 . The charge  96  extends across the neck portion  94  and into a hollow interior of the anvil. Igniters  98  for the explosive charge  96  are carried by a cap  99  threaded into the body  86 .  
         [0041]    In the event of a head-on collision in which the steering column collapses in the direction of the arrows in FIGS. 2C and 2D, a signal to the igniters  98  from a controller  100  sets off the explosive charge  96  causing the neck portion  94  of the anvil to fracture and break away. The strap  72  around the fractured anvil cannot impose any resistance to the collapse of the steering column. FIG. 2D shows only the middle strap  72  unwinding around an anvil which is still intact. The anvils for the two remaining straps have broken away so that those straps have no energy absorbing function.  
         [0042]    Referring next to FIGS.  3 A- 3 D, there is shown an energy absorbing device  101  having a housing  102  secured to stationary vehicle support structure  104  and including a single elongated, plastically deformable metal strap  106  having an end portion secured to a jacket portion  108  of a collapsible steering column  110  as by a rivet  112 . The energy absorbing device  100  includes a cylinder  114  and a piston  116  axially reciprocable within the cylinder. The piston has piston heads  118  and  120  at opposite ends, a large diameter anvil  122  adjacent one head, a small diameter anvil  124  adjacent the other head, and an anvil  126  of intermediate diameter between the anvils  122  and  124 . The strap  106  is perpendicular to the piston  116  and has an intermediate U-shaped portion  128  which extends around the piston.  
         [0043]    Actuator assemblies  130  and  132  have bodies  133  threaded into opposite ends of the cylinder  114 . An actuator  134  comprising an explosive charge  136  fills a cavity in each of the bodies  133 . An igniter  138  is embedded in each explosive charge. A shear pin  140  carried by the cylinder  114  extends into a slot in the piston head  118  to initially hold the piston  116  in the position shown in FIG. 3A in which the U-shaped portion of the strap embraces the anvil  126 .  
         [0044]    When the steering column  110  collapses, the strap  106  is pulled over the anvil which it surrounds. The anvil which the strap surrounds is determined by a signal from a controller  142  to the igniter of one of the actuator assemblies  130 ,  132 . A signal to the igniter of the actuator assembly  130  will explode the explosive charge in that actuator assembly (see FIG. 3C), breaking the shear pin  140  and moving the piston to the right so that the anvil  122  is surrounded by the strap. A signal to the igniter of the actuator assembly  132  will explode the charge in that actuator assembly, breaking the shear pin and moving the piston to the left so that the anvil  124  is surrounded by the strap. If no signal is received by either igniter, the piston  116  will remain in the position of FIG. 3A with the strap embracing the center anvil  126 . The amount of resistance to steering column collapse depends on the position of the piston  116 , which determines which anvil the strap bends around when it is pulled by the collapsing column.  
         [0045]    [0045]FIG. 4A shows a piston and cylinder assembly which may be used in the energy absorbing device  100  of FIG. 3D in place of the piston and cylinder assembly shown in FIG. 3A. The assembly in FIG. 4A includes a cylinder  150  and a piston  152  axially reciprocable within the cylinder. The piston has piston heads  154  and  156  at opposite ends, a large diameter anvil  158  adjacent one head, and a small diameter anvil  160  adjacent the other head. The same strap  106  seen in FIG. 3D is employed in FIG. 4A and extends around the piston and embraces the large diameter anvil  158  in the position shown, established by a shear pin  164  which is carried by the cylinder and extends into a slot in the piston head  154 . An actuator assembly  132 , which is identical to the similarly numbered actuator assembly in FIG. 3A closes one end of the cylinder. The opposite end of the cylinder is closed by a cap  166  which has an air vent  168 .  
         [0046]    When the steering column collapses, the strap  106  may be pulled over the anvil  158  to absorb energy, or, in the event a signal is received from the controller  170  to the igniter in the actuator assembly  132  moving the piston to the left in FIG. 4A, the strap will be pulled around the smaller anvil  160 . In the FIG. 4A embodiment, only a single actuator assembly  132  is needed to shift the piston.  
         [0047]    Referring to FIG. 4B, the same piston  152  and cylinder  150  as shown in FIG. 4A are here illustrated, but instead of an actuator assembly of the form in FIG. 4A, a solenoid actuated mechanical power unit  172  is provided. The power unit, which may be a piston and cylinder assembly, has a rod  174  connected to one end of the piston  152 . The power unit is operable by an extremely fast-acting solenoid  176  when the solenoid receives a signal generated by the controller  170  in response to a collision. When operated, the power unit  172  extends the rod  174 , moving the piston  152  to the left to a position in which the strap  106  surrounds the smaller diameter anvil  160 .  
         [0048]    Referring to FIG. 4C, the same piston  152  and cylinder  150  as shown in FIGS. 4A and 4B are illustrated, but instead of an actuator assembly of the form in FIG. 4A or  4 B, the piston  152  is adapted to be moved leftward from the FIG. 4C position by a compression spring  180 . The spring  180  is normally held under compression by a spring retainer  182  which has a stem projecting through one end of the cylinder  150  and is held by a releasable gripper  184 . The gripper  184  releases under the impact of a collision, causing the pressure of the spring  180  to be applied to the piston  152  and move the piston to the left in FIG. 4C to a position in which the smaller diameter anvil  160  is surrounded by the strap  106 .  
         [0049]    Referring next to FIGS.  5 A- 5 D, the cylinder  190  and the actuator assemblies  192  and  194  are similar to the cylinder  114  and actuator assemblies  130  and  132  shown in FIG. 3A, but the piston  198  is of a somewhat different construction. The piston  198  has a large diameter anvil  200  which is actually part of the piston head  202 . The diameter of the anvil  200  approximates the inside diameter of the cylinder  190 . The strap  106  occupies a recess  204  in the inner wall  205  of the cylinder  190  such that the inner surface of the strap is substantially flush with the inner wall of the cylinder and therefore does not interfere with the movement of the large diameter anvil when the piston moves upward in FIG. 5B.  
         [0050]    [0050]FIG. 5A also shows a stop pin  210  under pressure of a spring  211  which normally bears against the piston head  202 . When the piston  198  moves to the FIG. 5D position, the pin  210  snaps out and positively prevents reverse movement of the piston.  
         [0051]    [0051]FIG. 6B illustrates a piston  212  similar to the piston shown in FIG. 3A but in which only the large diameter anvil  214  is on the longitudinal centerline of the piston, the other two anvils  216  and  218  being laterally offset as shown. Operation of the piston  212  would be similar to the operation of the piston in FIG. 3A.