Abstract:
The invention provides a steering shaft assembly for a vehicle. The steering shaft assembly includes a first shaft extending along an axis of rotation for connection to one of a steering wheel and a steerable element of a vehicle. The steering shaft assembly also includes a second shaft extending along the axis of rotation for connection to the other of the steering wheel and the steerable element of the vehicle. The first shaft and the second shaft at least partially overlap one another along the axis of rotation for telescoping relative movement. The steering shaft assembly also includes a keyway formed in one of the first shaft and the second shaft and extending along and spaced from the axis of rotation. The steering shaft assembly also includes a key connected to the other of the first shaft and the second shaft and slidably positioned in the keyway. The key and the keyway cooperate to couple the first shaft with the second shaft for concurrent rotation and for telescoping movement along the axis of rotation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part of U.S. patent application Ser. No. 11/116,519 for a TELESCOPING STEERING SHAFT, filed on Apr. 28, 2005, which is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to a telescopically adjustable shaft for a vehicular steering column assembly.  
       BACKGROUND OF THE INVENTION  
       [0003]     Many vehicles, and automobiles in particular, are provided with a steering column assembly in which the upper portion, which carries the steering wheel, is arranged for longitudinal adjustment to enable selective telescopic positioning of the steering wheel through a limited range. This arrangement has been found to be exceptionally advantageous in accommodating vehicle operators of varying stature. Current production designs of telescoping steering shafts employing multi-tooth splines. A tubular female sleeve surrounds the splined shaft with a plastic over-molded feature there between.  
       SUMMARY OF THE INVENTION  
       [0004]     The invention provides a steering shaft assembly for a vehicle. The steering shaft assembly includes a first shaft extending along an axis of rotation for connection to one of a steering wheel and a steerable element of a vehicle. The steering shaft assembly also includes a second shaft extending along the axis of rotation for connection to the other of the steering wheel and the steerable element of the vehicle. The first shaft and the second shaft at least partially overlap one another along the axis of rotation for telescoping relative movement. The steering shaft assembly also includes a keyway formed in one of the first shaft and the second shaft and extending along and spaced from the axis of rotation. The steering shaft assembly also includes a key connected to the other of the first shaft and the second shaft and slidably positioned in the keyway. The key and the keyway cooperate to couple the first shaft with the second shaft for concurrent rotation and for telescoping movement along the axis of rotation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]     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:  
         [0006]      FIG. 1  is a fragmentary side view of a portion of a passenger vehicle with parts broken away to illustrate the general location and range of adjustable movement of a steering column assembly made in accordance with a first exemplary embodiment of the invention;  
         [0007]      FIG. 2  is an exploded view of a limiting device of the first exemplary embodiment of the invention;  
         [0008]      FIG. 3  is a side view, in partial cross-section, of an upper steering shaft of the first exemplary embodiment of the invention;  
         [0009]      FIG. 4  is a side view of the upper steering shaft as in  FIG. 3 , but showing a guide head positioned within a receiving chamber and an end mill simultaneously forming a keyway in a lower tubular section and the guide head;  
         [0010]      FIG. 5  is a view as in  FIG. 4  yet showing an alternative operation to simultaneously form a keyway in the lower tubular section and the guide head;  
         [0011]      FIG. 6  is a fragmentary cross-sectional view of the upper steering shaft assembled to the lower steering shaft;  
         [0012]      FIG. 7  is a cross-sectional view taken along lines  7 - 7  of  FIG. 6 ;  
         [0013]      FIG. 8  is a cross-sectional view taken along lines  8 - 8  of  FIG. 6 ;  
         [0014]      FIG. 9  is a fragmentary perspective view of a second exemplary embodiment of the guide head fitted with a key and a delashing spring;  
         [0015]      FIG. 10  is a fragmentary cross-sectional view of the alternative embodiment according to  FIG. 9  in an assembled condition;  
         [0016]      FIG. 11  is a first side cross-sectional view of a third exemplary embodiment of the invention wherein a key with plastic shear rib is being inserted in an outer steering shaft;  
         [0017]      FIG. 12  is a second side cross-sectional view of the third exemplary embodiment of the invention wherein the key has been inserted in the outer steering shaft and the plastic shear rib has been partially sheared from the key to delash the key with respect to the outer steering shaft; and  
         [0018]      FIG. 13  is front view of the third exemplary embodiment of the invention wherein the outer steering shaft shown in  FIGS. 11 and 12  has been removed for clarity and an inner steering shaft having a keyway is engaging the key to delash the key with respect to the keyway. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]     A plurality of different embodiments of the invention are shown in the Figures of the application. Similar features are shown in the various embodiments of the invention. Similar features have been numbered with a common two-digit reference numeral and have been differentiated by a third digit placed before the two common digits. Also, to enhance consistency, features in any particular drawing share the same third digit designation even if the feature is shown in less than all embodiments. Similar features are structured similarly, operate similarly, and/or have the same function unless otherwise indicated by the drawings or this specification. Furthermore, particular features of one embodiment can replace corresponding features in another embodiment unless otherwise indicated by the drawings or this specification.  
         [0020]     Referring to  FIGS. 1-8 , a portion of a conventional passenger automobile is generally shown at  12 . Although the preferred application of the invention is within the field of automobiles and other road vehicles, the invention can be practiced with equal affect in other vehicular fields, including marine and aeronautic applications, as well as non-vehicular fields. The automobile  12  is shown including a conventional steering wheel  14  supported at the end of a steering shaft assembly  16 . A column assembly, such as steering column jackets and/or a tilt housing can enclose the steering shaft assembly  16  from the interior of the vehicle  12 . In order to accommodate personal preferences in the positioning of the steering wheel  14 , the steering shaft assembly  16  is telescopically adjustable so that the steering wheel  14  can be moved to various axially adjusted positions. Although not a subject of this invention, the steering shaft assembly  16  can be further modified to provide angular adjustment of the steering wheel  14  through any of the know tilt adjust or rake adjust mechanisms.  
         [0021]     The steering shaft assembly  16  functions to transmit rotary motion from the steering wheel  14  to the steered element which, in the case of an automobile  12 , usually comprises the two front wheels. However, in marine applications, the steered element may include a rudder or articulated propulsion unit; in the case of aeronautical applications, the steered element may comprise a rudder or other features. Thus, the novel steering shaft assembly  16  can be deployed in any application in which a steering wheel  14  or other steering grip device is telescopically adjustable.  
         [0022]     The steering shaft assembly  16  is comprised of an upper steering shaft, generally indicated at  18 . The upper steering shaft  18  can also be referred to as a first shaft  18 . The steering shaft assembly  16  also includes a lower steering shaft, generally indicated at  20 . The lower steering shaft  20  can also be referred to as a second shaft  20 . In the first exemplary embodiment of the invention, the first shaft  18  is operatively connected to the steering wheel  14  while the second shaft  20  is operatively connected (typically through additional controls or linkages) to the steered element. In alternative embodiments of the invention, the first shaft  18  can be operatively connected to the steered element while the second shaft  20  can be operatively connected (typically through additional controls or linkages) to the steering wheel  14 .  
         [0023]     The first and second shafts  18 ,  20  at least partially overlap and extend along a longitudinal axis A which is coincident with the turning axis of the steering wheel  14 . The first and second shafts  18 ,  20  are engaged for telescopic movement relative to one another. The first shaft  18  includes an upper tubular section  22  and a lower tubular section  24 . A traditional coupling feature  26  is carried on the end of the upper tubular section  22  for attaching the steering wheel  14 . The coupling feature may include splines and/or tapers, together with threaded fastening elements, to securely attach the steering wheel  14 . The lower tubular section  24  presents, at its open end, an axially extending receiving chamber  28 . The receiving chamber  28  is preferably formed in a precision machining operation which includes drilling, reaming, and honing to very precise tolerances for proper mating engagement with the second shaft  20 . The interface between the upper  22  and lower  24  tubular sections results in a narrowing of the interior region of the first shaft  18  and forms an internal step  30  whose purpose is described below.  
         [0024]     The first exemplary embodiment of the invention also includes a limiting device  56 . The limiting device  56  is operably disposed to limit relative telescoping movement between the first shaft  18  and the second shaft  20 . The second shaft  20  receives includes a guide head  32  of the limiting device. The guide head  32  is disposed radially between the first shaft  18  and the second shaft  20  with respect to the axis (A) of rotation in the receiving chamber  28 . The guide head  32  is releasibly connected to the second shaft  20 . As best shown in  FIG. 2 , the guide head  32  is a generally tubular member which slips over the end of the second shaft  20  and is secured with a plastic sheer material  54  introduced through side injection ports  34 . The exemplary second shaft  20  is formed with a double truncated circular cross-section, such that a pair of opposing flats  38  interrupt an otherwise cylindrical exterior configuration. The guide head  32  is shaped to mate over the second shaft  20  so that rotary motion can be transmitted directly between the two components. During the assembly process, when the guide head  32  is in position over the end of the second shaft  20 , the injection ports  34  align with injection grooves  36  machined into the second shaft  20 . Once the fluidic plastic material  54  has solidified and become a locking member  54 , the guide head  32  is securely affixed in an operative position to the second shaft  20 . The annular groove  36  includes first and second arcuate portions  70 ,  72  and at least one straight portion  74  disposed between the first and second arcuate portions  70 ,  72  to reduce the likelihood of relative rotation between the second shaft  20  and the guide head  32 . Like the receiving chamber  28 , the guide head  32  is also precision machined to a surface finish and dimensional tolerance that allows a smooth axially slideable engagement into the receiving chamber  28 .  
         [0025]     Referring to  FIG. 4 , a step in the assembly operation of the first exemplary embodiment of the invention is illustrated by the simultaneous forming of an axially extending keyway  40  through the guide head  32  (which is fixed to the second shaft  20 ) and a slot  58  through the lower tubular section  24 . With the guide head  32  in a generally central position along the length of the receiving chamber  28 , a common tool, such as an end mill  42 , is used to machine the keyway  40  and slot  58 . The keyway  40  has a length that fully traverses fully the length of the guide head  32  to increase the likelihood of a full running length of keyway  40  through the guide head  32 . Once the keyway  40  has been thus formed, the end mill  42  is retracted and the components disassembled and deburred.  
         [0026]     Those skilled in the art will appreciate that other machining techniques can be used to form the keyway  40 . As one example of many possible alternatives,  FIG. 5  illustrates a cutting wheel  42 ′ which can be used to form the keyway  40  and the slot  58 . The particular type of machining operation is not critical. By simultaneously forming the keyway  40  through the guide head  32  and the slot  58  through the lower tubular section  24  using the same cutting tool  42 , the keyway  40  achieves exactly the same width in both parts.  
         [0027]     After the deburring operation, the guide head  32  is reinserted into the receiving chamber  28  and a key  44  positioned within the keyway  40  and the slot  58 . By welding or other fixation technique, the key  44  is securely joined to the lower tubular section  24 . Once the welding (or other fastening) operation is completed, the lower tubular section  24  is staked or otherwise modified on its distal, open end to create a lower stop  46  at the end of the keyway  40  to prevent disassembly. The internal step  30  forms an upper stop  30  and one limit of travel for the guide head  32  within the receiving chamber  28 . Thus, during telescoping adjustment of the steering wheel  14 , the first shaft  18  moves over the second shaft  20  within a first range of telescoping movement defined by the guide head  32  abutting either the upper stop  30  or the lower stop  46 . All the while, the key  44  remains in registry with the keyway  40  in the guide head  32  which enables rotary motion to be transmitted between the first shaft  18  and the second shaft  20 . A suitable clamping mechanism, not shown but of any conventional design, secures the first shaft  18  in an adjusted position. Release of the clamping mechanism allows readjustment of the axial position of the steering wheel  14 .  
         [0028]     In the event of an overwhelming compressive force applied against the steering wheel  14 , such as might occur in a collision, the steering shaft assembly  16  is designed to collapse in a controlled manner. In such an emergency, the first shaft  18  will be pressed against the second shaft  20  in a direction  60 . Assuming that the telescoping clamp mechanism has been overcome or released, the first shaft  18  will continue sliding over the second shaft  20  until the guide head  32  reaches the upper stop  30 . At this point, an overwhelming force will cause the plastic locking member  54  interconnecting the guide head  32  to the second shaft  20  through the injection grooves  36  to shear. At this catastrophic failure point, the second shaft  20  may continue traveling into the hollow regions of the upper tubular section  22 , i.e., past the upper stop  30 , while the guide head  32  remains in the receiving chamber  28 . During the series of events, external energy absorbing devices or other collision and safety mechanisms can be deployed. Movement of the second shaft without the guide head  32  defines a second range of telescoping movement in the form of collapsing telescoping movement.  
         [0029]      FIGS. 9 and 10  show a second embodiment of the invention. This alternative design is characterized by the key  144  being fixed relative to the guide head  132  and slideable in a keyway  140  formed internally in the receiving chamber  128 . Here, the guide head  132  includes a key slot  148  into which the key  144  is seated. A delashing spring  150  may be positioned between the key slot  148  and the key  144  to minimize torsional lash. Although the delashing spring  150  is shown for illustrative purposes as a compression spring seated in a pocket  152  in the side of the key  144 , the delashing spring  150  may take alternative forms, including a formed leaf spring, a torsion spring, or any other type of biasing element.  
         [0030]     The keyway  140  is finely machined into the receiving chamber  128  to provide appropriate sliding tolerances with the key  144 . To facilitate formation of the keyway  140 , the upper tubular section  122  can be formed separately from the lower tubular section  124 , and the two components later joined in a subsequent operation to form the complete upper steering shaft  118 . For example, the separately formed upper  122  and lower  124  tubular sections can be friction welded, traditionally welded, induction welded, threaded and pinned, or any other type of joining operation which does not interfere with the movement of the guide head  132  within the receiving chamber  128  to the full limits of the upper stop  130  nor of the necessary continued travel of the lower steering shaft  120  into the upper tubular section  122  in the event of a catastrophic event.  
         [0031]     After installing the key  144  into the guide head  132  and inserting this subassembly into the lower tubular section  124 , the receiving chamber  128  is staked at the end of the keyway  140  to prevent disassembly of the two components. Thus, like in the preceding embodiment, the alternative embodiment of  FIGS. 9 and 10  functions to allow free telescoping movement of the upper steering shaft  118  relative to the lower steering shaft  120  while transmitting rotary motion therebetween.  
         [0032]     A column assembly manufactured according to these designs and techniques is low in cost relative to existing designs, and at the same time is strong and exhibits good telescoping loads. The individual components are relatively easy to manufacture with relatively few surfaces requiring precision machining. The design also accommodates catastrophic impact scenarios in that once the guide head  32 ,  132  reaches the upper stop  30 ,  130 , the injected plastic  54  sheers so that the second shaft  20 ,  120  translates into the non-machine area of upper tubular section  22 ,  122 .  
         [0033]     Lashing occurs between two components that are intended to concurrently rotate when one of the components rotates slightly relative to the other component. The first shaft  18 , the second shaft  20 , the keyway  40 , and the key  44  are intended to concurrently rotate in the exemplary embodiments of the invention. In the first exemplary embodiment of the invention, the key  44  is delashed with respect to the first shaft  18  by welding the key  44  to the slot  58 . The key  44  is delashed with respect to the keyway  40  (as well as the second shaft  20  since the keyway  40  is formed in the guide head  32  and the guide head  32  is fixed to the second shaft  20  during normal vehicle handling) by sizing the key  44  to fit the keyway  40  after the keyway  40  has been formed.  
         [0034]     The second and third embodiments of the invention include delashing devices  162 ,  262 ,  264  to delash the respective keys  144 ,  244  with respect to one of the keyways  140 ,  240 , the first shafts  118 ,  218 , and the second shaft  120 ,  220  to limit relative movement about the axis A of rotation. In the second embodiment of the invention shown in  FIGS. 9 and 10 , the delashing device  162  limits relative movement between the key  144  and the second shaft  120  about the axis A of rotation. The delashing device is a spring  150  directly disposed between the key  144  and the second shaft  120 . The spring  150  urges a portion of the key  144  (the bottom of the pocket  152 ) and a portion of the second shaft  120  (the interior of the slot  148 ) apart.  
         [0035]     In the third embodiment of the invention shown in  FIGS. 11-13 , the delashing device  262  is operably disposed to limit relative movement between the key  244  and the first shaft  218  about the axis A of rotation. The delashing device  262  is a plastic shear rib  266  at least partially sheared from the key  244  by the first shaft  218 . The key  244  is formed with plastic material and with the plastic shear rib  266 . The key  244  is inserted in a slot  276  formed by the first shaft  218 . During insertion of the key  244  in the slot  276 , at least part of the plastic shear rib  266  is sheared from the key  244  by the first shaft  218 . The portion of the plastic shear rib  266  that is not sheared off is disposed between the key  244  and the first shaft  218  and takes up any slack between the key  244  and the first shaft  218  that could allow lash.  
         [0036]     Any embodiment of the invention could include more than one delashing device. The third embodiment of the invention includes delashing devices  262 ,  264 . The delashing device  262 ,  264  are integrally formed with the key  244 . The delashing device  264  limits relative movement between the key  244  and the keyway  240  about the axis A of rotation. The delashing device is a plastic shear rib  268  at least partially sheared from the key  244  by the keyway  240 . The key  244  is formed with plastic material and with the plastic shear rib  268  having a ramp  278 . The ramp  278  is angled at five (5) degrees in the third exemplary embodiment of the invention. The base or bottom of the ramp  278  is disposed at the right-hand of the key  244  with respect to  FIG. 13 . The ramp  278  extends and increases in height to the left end of the key  244 . The keyway  240  is formed with an opening  280  having first and second sides  282 ,  284 . A cutting edge  286  is defined at the first side  282 . The cutting edge  286  is positioned on the ramp  278  adjacent the base to insert the key  244  in the keyway  240 . At least one of the first shaft  218  and the second shaft  220  is moved relative to the other along the axis A of rotation. For example, the second shaft  220  can be moved to the left with respect to  FIG. 13  as the key  244  remains stationary. During this movement, the cutting edge  286  moves up the ramp  278  some distance. The cooperation between the cutting edge  286  and the ramp  278  is cam—cam-follower like. For example, during the moving step the cutting edge  286  urges the ramp  278  and the key  244  against the second side  284  of the keyway  240  to substantially eliminate any slack or gaps that could lead to lash. During this cooperative action, the first and second shafts  218 ,  220  can rotate relative to one another. At some point during movement up the ramp  278 , the key  244  is urged against the second side  284  to the furthest extent and the cutting edge  286  will then bite into the ramp  278 . The cutting edge  286  then shears at least part of the second plastic shear rib  268  from the key  244 . The delashing device  264  allows for a custom fit of the key  244  in the keyway  240 .  
         [0037]     While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.