Abstract:
A steering column assembly includes a steering column having a selectively collapsible structure that enables said column to collapse in the event of an impact force resulting from a vehicle crash. An adaptive energy absorbing device is associated with said column and operates in a first condition to absorb a first level of energy of the collapsing column and in a second condition to absorb a second level of energy of the collapsing column. The assembly includes a telltale detection device that is associated with the adaptive energy absorbing device and is responsive to a change in condition of the energy absorbing device prior to a collapse event to provide a signal to a user of the condition of the energy absorbing device.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to steering column assemblies for automotive vehicles, and more particularly to such assemblies fitted with energy absorbing devices which are operative to absorb kinetic energy in response to collapse of a steering column in the event of a crash.  
         [0002]     Steering column assemblies for automotive vehicles are known to be equipped with various energy absorbing (“EA”) devices which serve to absorb kinetic energy of a collapsing column in the event of a crash. In a sudden frontal impact situation, there are conditions under which the driver may be thrown forward against the steering column, particularly if the driver is unbelted. Many steering columns are designed to collapse under such conditions. EA devices are designed to cooperate with collapse of the column in order to absorb a certain amount of the kinetic energy of the collapse in an effort to alleviate the full force of impact to the driver.  
         [0003]     Depending upon various factors, the requirements of the EA device may differ. For example, a situation in which a very heavy driver is seated far away from the steering wheel and is unbelted would call for greater energy absorption on the part of the EA device than would that required in a situation involving a very light occupant seated closer to the steering wheel. Various parameters have been taken into account in the design and manufacture of so-called adaptive EA systems, which measure one or more parameters and then make adjustments in the EA system prior to impact to increase, decrease or in some way alter the behavior of the EA system in the event of a crash. For example, in the heavy, unbelted driver situation above, the EA system could react by adjusting the number, position or size of an anvil(s) across which one or more EA straps are drawn in order to increase the amount of energy absorbed in a crash to accommodate the relatively greater forces from such a driver, as compared to a lighter driver where the reverse may be done. This ability to adapt to various parameters can help manage the absorption and dissipation of the energy of the collapsing column when impacted by the driver. Such adaptable EA systems are able to adjust their energy absorption characteristics by altering the position or configuration of the energy absorbing components. For example, an EA device may be fitted with an S-strap routed about two anvils in a pre-set condition to provide a high level of energy absorption, but may be adjusted by sliding one of the anvils out of the way of the path of the S-strap in order to provide a relatively lower energy absorption condition. Other arrangements employ multiple straps, wires, and other arrangements which can be altered in arrangement, quantity, or configuration in order to adjust the energy absorbing characteristics. The known adaptive EA systems are constructed such that the movable anvil or other components which get altered when the device adapts to a changing condition are all contained within a closed housing of the EA system and thus it is not readily apparent upon external inspection of the EA device which of two or more positions of adjustment it may be in. For example, the EA device in which an S-shaped EA strap is initially wrapped about two anvils but adjustable to eliminate one of the anvils and thereby reduce the energy absorbing characteristics of the EA system does not provide a means of telling which position the movable anvil is in at the time the device is installed in the vehicle and during the service life of the vehicle. In the event the device is inadvertently moved to the second position, such as if the vehicle is involved in a collision sufficient to activate the adaptive system, and the operator continues to use the vehicle without repairing or replacing the EA device, the full performance of the device may be diminished.  
         [0004]     It is an object of the present invention to provide a means of telling which position an adaptable EA device is in at any given time during its service life.  
       SUMMARY OF THE INVENTION AND ADVANTAGES  
       [0005]     According to a first aspect of the invention, a telltale system is provided for adaptive EA devices which cooperates with the changeable portion of the EA device and provides a discernable indicator that can be seen or sensed by a mechanic or user to indicate the condition of the EA device.  
         [0006]     According to a further aspect of the invention, the indicating device is in the form of an indicator pin or flag which, upon movement of the EA device from one condition to another, is sprung outwardly of the EA housing to provide a visible indication that the EA device has moved from one condition to another. The flagging feature can take on any of a number of forms, such as a button that pops out, a flag that extends up, a window that changes color, etc. provided it functions indicate a change in condition and which can be seen by a mechanic or user.  
         [0007]     The invention has the advantage of providing a means of enabling a mechanical user to determine which condition an adaptable EA device is in without having to disassemble the device. This is particularly advantageous in the event, for example, that the EA device is dropped or somehow tampered with prior to installation or during the service life or involved in an accident which may cause the EA device to shift from one condition to another. For example, if the EA system were preset to handle heavy loads and the device was inadvertently adjusted to the low load condition, the EA device may be less able to accommodate the heavy load condition in the event of a crash. Similarly, if the vehicle were involved in a frontal crash situation and the vehicle were to be repaired, a mechanic could look to the visible indicator device to determine whether the EA system changed its condition as indicated by the projecting button or upstanding flag, or whether the EA system remains in its original pre-set condition and can continue in service.  
         [0008]     According to another aspect of the invention, a sensor is provided on an adaptive EA system which senses a change in condition and then sends an alarm signal to alert the driver and/or mechanic that the condition of the EA device is changed. For example, the sensor can be wired to light up the air bag warning light, check engine light, or its own EA warning light on the instrument panel, or could further operate to disable operation of the vehicle until the problem is corrected. The electronic signaling device can work in conjunction with or separate from the mechanical telltale system above. Such an electronic system has the additional advantage of providing the indicator feature in clear view of the driver and which can be associated with other common warning signals which would encourage drivers to have their vehicles serviced so that the problem can be corrected. 
     
    
     THE DRAWINGS  
       [0009]     Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:  
         [0010]      FIG. 1  is a dramatic elevation view of the vehicle, shown partially broken away, equipped with a steering column having an adaptive EA system and telltale device according to the invention;  
         [0011]      FIG. 2  is a diagrammatic view of an adaptive EA system and mechanical telltale device according to a first embodiment of the invention;  
         [0012]      FIG. 3  is an exploded perspective view of the adaptive EA system and telltale device constructed according to a presently preferred embodiment of the invention;  
         [0013]      FIG. 4  is an enlarged perspective view of a pin retainer of the telltale device;  
         [0014]      FIG. 5  is an enlarged elevation view of a closeout member of the telltale device;  
         [0015]      FIG. 6  is a perspective view of the anvil pin having an alternative threaded hole end;  
         [0016]      FIG. 7  is a cross-sectional view through the adaptive EA system and telltale device with the pin shown in the installed first conditional;  
         [0017]      FIG. 8  is a view like  FIG. 7 , but showing the EA pin and telltale device to a second position in response to the EA pin;  
         [0018]      FIG. 9  is a diagrammatic view of an adaptive EA system and electronic telltale device constructed according to a second embodiment of the invention;  
         [0019]      FIG. 10  is a plan view of an adaptive EA system and telltale device according to the second embodiment with the EA pin shown in the installed first position; and  
         [0020]      FIG. 11  is a view like  FIG. 10  but with the EA pin and telltale device shown moved to the second position. 
     
    
     DETAILED DESCRIPTION  
       [0021]     The present invention is directed to collapsible steering columns outfitted with adaptive energy absorption (EA) systems which are movable in a manner to adjust the energy absorption characteristics of the EA system in response to the collapse of the column. One type of adaptive EA system is shown as being exemplary of any of a number of adaptive EA devices which are adjustable or moveable from one position to another in order to adjust the energy absorption characteristics of the EA system. A telltale device is shown associated with the adaptive EA system and is operative in response to movement of the adaptive EA system from one position to another to provide external indication of the repositioning of the EA device that is visible by a mechanic and/or the driver of the vehicle to indicate a need to service the vehicle, and particularly the adaptive EA system. It is contemplated that those skilled in the art will appreciate that the telltale device can be readily adapted to work with any of the various adaptive EA systems presently available or to be developed which are capable of moving from one position to another, and which movement can trigger activation of a telltale device to indicate a change of position to a mechanic or user. Accordingly, the embodiments disclosed below are merely exemplarily of the invention.  
         [0022]      FIG. 1  is a schematic representation of an automotive vehicle  10  equipped with a collapsible steering column assembly  12  of the type which is normally rigidly mounted to the vehicle structure and held against forward movement in the vehicle (apart from normal telescopic movement of the hand wheel if the column is so equipped) but which, when subjected to impact from a frontal collision, separates from the vehicle structure enabling the column to move forward in the vehicle to minimize injury to the driver in the event the driver strikes the steering wheel. The steering column assembly  12  is equipped with an adaptive EA device, schematically illustrated at  14 , which operates to absorb at least some of the kinetic energy of the collapse of the column to minimize the impact force to the driver.  
         [0023]     The steering column  12  is equipped with a conventional steering wheel  16  or other hand operated steering controller to enable the driver to steer the vehicle  10  with the column  12 . The EA device  14  is operatively coupled to a telltale device schematically shown at  18  in  FIG. 1  which is operative to react in response to a change in condition of the adaptive EA device  14  and provide a means of indicating the condition to the driver or a mechanic.  
         [0024]     Referring additionally to  FIG. 2 , according to the first embodiment of the invention, the telltale device  18  is a mechanical device, the details of the preferred embodiment of which are further illustrated in  FIGS. 3-8 . Effectively, the mechanical telltale device  18  provides some physical indicator that a change in the position of the EA sensor has occurred from an initial preset position. Those skilled in the art will appreciate that such a telltale device may take on any of a number of forms once the concept is appreciated. For example, the disclosed embodiment shows a telltale device in which a button protrudes from the adaptive EA device  14  when the EA device  14  moves from its initial pre-set position to a second position, which button can be visibly detected and/or felt by the operator or mechanic upon an external examination of the adaptive EA device  14 .  
         [0025]      FIG. 3  illustrates an exploded perspective view of the EA device  14  and telltale device  18 . The EA device includes an EA housing  20  having cylindrical bore or chamber  22  in which an adaptive EA anvil or pin  24  is accommodated. The housing  20  is mountable on the column  12  and may be either stationary or moveable with respect to the collapse movement of the column.  FIGS. 7 and 8  show further features of the EA device  14  and telltale device  18  when in the assembled condition, and further illustrate the adaptive pin  24  being moveable between a first pre-set position shown in  FIG. 7 , and a second position illustrated in  FIG. 8  in which the pin has been moved to a second position.  
         [0026]     The pin  24  is slidable in the cylinder bore  22  between the first set position shown in  FIG. 7  and the second position shown in  FIG. 8 . The movement is preferably driven by an explosive charge (not shown) which explodes in the cylinder bore  22  behind a head  26  of the pin, driving it toward the end  28  of the chamber where it strikes and is captured by a retaining ring  30  such that the pin  24  does not bounce back toward the first position once fired. The principle of explosive moveable pin devices are well know to those of ordinary skill in the art and thus will not be expounded upon here.  
         [0027]     When the first position of  FIG. 7 , and anvil portion  32  of the pin projects though a strap passage  34  which is an extension of the cylinder bore  22  adjacent a second fixed anvil or pin  36 . An S-strap  38  is routed through the passage  34  and around the fixed pin  36  in position to engage both the fixed pin  36  and the adaptive pin  24  to provide a first level of energy absorption. When the pin  24  is fired to the second position of  FIG. 8 , the anvil portion  32  moves out of the path of the S-strap  38 , such that only the fixed pin  36  is engaged by the strap  38  during collapse of the column, representing a lessor energy absorption condition than that of the initial condition of  FIG. 7 . During collapse, the strap  38  is drawn across one or both anvils and is cause to bend and unbend along the S-shaped path to absorb kinetic energy. By eliminating the adaptive pin  24  as in  FIG. 8 , one of the anvils is eliminated and thus the S-strap absorbs less energy than in the first condition of  FIG. 7 .  
         [0028]     The telltale device  18  comprises a pin or plug  40  which extends through an opening  42  into the end chamber  28  and fits into an opening or bore  44  and in the end of the adaptive pin  24  when the pin  24  is first condition of  FIG. 7 . The plug  40  is inserted with a friction fit into the bore  44  by means of a flexible end  46  comprising a series of axial spaced flexible annular flanges  47  which engage and are radially compressed by the walls of the bore (i.e., sometimes referred to as a “Christmas tree”-type fitting) and is made of a plastics material, such as nylon or the like. The opposite end of the plug  40  is formed with an enlarged head  48  which is received in the opening  42  of the housing  20  when in the fully installed condition, as in  FIG. 7 , against the compression force of the spring  50  acting to constantly urge the head  48  axially outwardly of the opening against the frictional retaining force of the flexible end  46  within the bore  44 . The plug  40  is formed with an axial slot  52  that extends axially along the flexible end portion  46  for a distance and then continues along a shank  54  of the plug  40  between the head  48  and flexible end  46  and an angularly offset (preferably 90° offset) orientation to that of the slot along the flexible end portion  46 .  
         [0029]     The opening  42  of the EA device  14  is fitted with a closeout device or member  56  shown best in  FIG. 5  which fits into the housing  20  and is provided with diametrically opposed projections  58 . The plug  40  is inserted into the closeout device  56  with the projections  58  received in the slots  52  and guided along the flexible end portion  46 , and then turned 90° and further guided along the slot  52  extending along the shank  54  as the flexible end  46  is forcibly guided into the bore  44  of the adaptive pin  24  where it is retained in the position shown in  FIG. 7  against the outward spring force of spring  50 . When in the fully recessed position, the plug  40  serves as a telltale device to indicate that the adaptive pin  24  is in the first position shown in  FIG. 7 .  
         [0030]     In the event that the pin  24  moves to the second position either under the explosive force or inadvertently as a result of being dropped or improperly assembled, or the like, the pin  24  is then spaced from the flexible end  46  of the plug  40  such that there is no longer any frictional force holding back the outward biasing force exerted by the spring  50 . Consequently, the spring  50  forces the head  48  of the plug  40  outwardly of the opening  42 , thereby giving a telltale signal that the pin  24  is in the second position of  FIG. 8 . With the offset slot arrangement, the plug  40  is prevented from being completely ejected under the action of the spring  50 . As the projections  58  travel along the slot  52  of the shank  54 , they eventually confront the flexible end portion  46  of the plug at the point where the slot  52  transitions to the 90° offset and is no longer in line with the projections.  FIG. 4  shows details of the construction of the telltale plug  40 , and  FIG. 6  shows an alternative threaded end bore  44  design of the adaptive pin  24 , which can be used in lieu of the straight bore to enhance gripping of the plug  40 .  
         [0031]     Preferably, at least the head  48  of the telltale plug  40  is brightly colored (e.g., red) such that it is readily visible when extending from the opening  42  when in the second condition corresponding with  FIG. 8 . When a mechanic or user sees the head  48  projecting from the opening  42 , it is an indication that the adaptive pin  24  is moved from its initial first position of  FIG. 7  to the second position of  FIG. 8  and that the vehicle may need servicing.  
         [0032]      FIGS. 10 and 11  illustrate a further embodiment in the invention, in which the telltale device is at least, in part, an electronic device which sends a signal to the user or mechanic that the adaptive pin  24  has moved from a first condition to a second condition. According to the preferred embodiment, the telltale device of the second embodiment is identical in all respects to the first embodiment, except that a sensor  60  is positioned adjacent the opening  42  of the housing  20  and is engaged by or at least senses the movement of the head  48  of the plug  40  as it advances out of the opening  42  in response to movement of the adaptive pin  24  from the first position to the second position. As shown in  FIG. 11 , the head  48  preferably extends from the opening  42  and contacts the sensor  60 , which in turn processes the information and activate a display/alarm  62 , which can take on the form of a warning light on the instrument panel, such as “check engine”, “air bag”, “EA system”, etc., which would alert the driver to the fact that the adaptive EA pin has moved from the first position to the second position and to take the vehicle in for service.  
         [0033]     In addition to or as alternative, the sensor  60  could cooperate with the ignition system or other vehicle control system to disable operation of the vehicle if the vehicle manufacturer deems it significant enough to warrant disablement of the vehicle until the condition is corrected. Of course, those skilled in the art will appreciate that the electronic telltale device may not necessarily need the mechanical component of the first embodiment, but could simply have a sensor that senses the movement of the adaptive pin  24  from the first position to the second then activates a signal.  
         [0034]     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practice otherwise than as specifically described.