Abstract:
A vehicle steering column has a rake adjustment mechanism which includes a rake bracket having a rake slot provided with rake slot teeth. A tooth lock is supported in the rake slot with teeth opposing the rake slot teeth. A rake bolt is rotatable to a first rotative position to move the tooth lock to a retracted position with the teeth of the tooth lock out of engagement with the rake slot teeth. The bolt is axially rotatable to a second rotative position permitting the tooth lock to be moved to a locking position by a spring in which the teeth of the tooth lock engage the rake slot teeth. The bolt, when in the second rotative position, is movable, in response to an application of an impact force on the steering column to collapse the steering column, into bearing engagement with the tooth lock to positively retain the tooth lock in the locking position. The steering column is also provided with a release mechanism having shear pins and an energy absorption mechanism.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. provisional application Serial No. 60/292,214 filed May 18, 2001, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to steering columns and more particularly to a steering column having improved locking, release and energy absorption mechanisms. 
     BACKGROUND OF THE INVENTION 
     Various locking mechanisms are known for use with steering columns capable of rake adjustment, such as that disclosed in co-pending U.S. patent application Ser. No. 09/664,032 dated Sep. 18, 2000, which is incorporated herein by reference. The locking mechanism in that co-pending application includes a rake bolt and associated tooth locks on both sides of the steering column. It would be desirable from the standpoint of both simplicity and cost, for the locking mechanism to have a single tooth lock on only one side of the steering column. 
     It is also known to provide a release mechanism to allow the steering column to collapse following a frontal impact event of great magnitude, such as a head-on collision. However, such release mechanisms typically are not aligned with the rake bolt and thus lead to undesirable moments being applied to the release mechanism upon impact. 
     Energy absorption mechanisms that allow the steering column to collapse at a controlled rate for the protection of the driver are also known. Such mechanisms, however, typically are not well integrated with the rake adjustment and release mechanisms. 
     SUMMARY OF THE INVENTION 
     The locking system of the present invention includes a tooth lock movable selectively into engagement with a toothed slot of a fixed bracket. The tooth lock is normally supported in meshing engagement with the toothed slot to lock the steering column in adjusted position, but is movable out of engagement with the toothed slot to enable the steering column to be adjusted. A rake bolt moves into positive engagement with the tooth lock to hold the tooth lock in meshing engagement with the toothed slot in response to an applied impact force on the steering column to prevent the steering column from accidentally moving away from adjusted position during controlled collapse of the steering column. 
     Further in accordance with the invention, the steering column has telescoping upper and lower jackets. The rake bolt extends through a tubular capsule. The capsule is connected to a compression bracket secured to the upper jacket by one or more shear pins. The shear pin or pins are adapted to shear to enable the steering column to collapse when the driver&#39;s chest hits the steering wheel in response to a frontal vehicle impact of great magnitude. A deformable energy absorbing strap extends over the capsule which serves as an anvil to bend and then restraighten the strap to absorb energy as the steering column collapses. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing as well as other features, objects and advantages of this invention will become more apparent as the following description proceeds, especially when considered with the accompanying drawings, wherein: 
     FIG. 1 is perspective view of a steering column and associated structure constructed in accordance with the invention; 
     FIG. 2 is an exploded perspective view of the structure shown in FIG. 1; 
     FIG. 3 is a side elevational view of the steering column and attached compression bracket, showing an operating handle in broken lines; 
     FIG. 4 is an exploded view in perspective showing certain parts associated with the rake adjustment mechanism; 
     FIG. 5 is a sectional view taken on the line  5 — 5  in FIG. 3; 
     FIG. 5A is an exploded perspective view of a tubular capsule, a portion of the compression bracket and bushings also shown in FIG. 5; 
     FIG. 6 is an enlargement of a portion of FIG. 5 shown within the circle  6  in FIG. 5; 
     FIGS. 7A,  7 B and  7 C show the pre-crash adjustment position of the rake adjustment mechanism shown in FIGS. 2 and 4; 
     FIGS. 8A,  8 B and  8 C show the same mechanism in a pre-crash locked position; 
     FIGS. 9A,  9 B and  9 C show the same mechanism in a post-crash condition; 
     FIG. 10 is a side elevational view of the jacket of the steering column with attached compression bracket; 
     FIG. 11 is a view similar to FIG. 10 but is in section to better illustrate are energy absorption mechanism; 
     FIG. 12 is a view similar to FIG. 11 but shows the parts in a different position; 
     FIG. 13 is a side elevational view of a steering column and associated mechanism of a modified construction, also in accordance with the invention; 
     FIG. 14 is an exploded view in perspective of the structure shown in FIG. 13; 
     FIG. 15 is an enlarged view with parts in section of portions of FIG. 13; and 
     FIG. 16 is essentially the same as FIG. 15, but with different directional arrows. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now more particularly to the drawings, and especially FIGS. 1-3, a steering column  20  for an automotive vehicle has a jacket assembly  22  including a lower tubular jacket  24  telescoped in an upper tubular jacket  26 . A steering shaft  28  is journaled for rotation in the jacket assembly  22 . A steering wheel (not shown) has splines which engage splines  30  on the rear end of the steering shaft  28 . The forward end of the lower jacket  24  receives a horizontal pivot pin  32  which attaches the steering column  20  to a vehicle frame for pivotal movement about a horizontal transverse rake axis of the pivot pin. 
     The upper jacket  26  extends lengthwise within an elongated, channel-shaped compression bracket  34  and is welded or otherwise rigidly secured parallel to opposite side walls  36  and  38  of the compression bracket. 
     Straddling the steering column  20  and the compression bracket  34  are a left side rake bracket  40  and a right side rake bracket  42 . The rake brackets  40  and  42  are parts of a rake adjustment mechanism  43  for adjusting the vertical tilt, or rake, of the steering column  20  and are rigidly secured to a vehicle frame. 
     The left side rake bracket  40  has a vertical wall  44  formed with a generally vertically extending opening  46 . An elongated rake plate  48  is secured to the outer side of the vertical wall  44  over the opening  46 , and has a vertically elongated rake slot  50  generally in register with the opening  46 . The rake slot  50  has a series of rake teeth  52  on its front edge. A pilot projection  54  on the inner side of the plate  48  is closely received and fits snugly in the opening  46  in the wall  44  of the left side rake bracket  40  to locate the plate  48 . 
     The right side rake bracket  42  has a vertical wall  54  formed with a generally vertically elongated rake slot  56  in a portion  57  of the wall  54 . The rake slot  56  in the wall  54  of the right side rake bracket  42  is in substantial transverse alignment with the rake slot  50  in the plate  48  on the wall  44  of the left side rake bracket  40 . An elongated, generally vertical, narrow slit  58  in the wall  54  of the right side rake bracket  42  is generally parallel to, and closely spaced forwardly from the rake slot  56 , providing a narrow, flexible, deformable strip  60  of the material of the wall  54  between the front wall  61  of the slot  56  and the slit  58 . 
     A transverse, horizontal rake bolt  62  has ends  63  and  65  disposed in the respective rake slots  50  and  56  of the left and right side rake brackets  40  and  42 . See FIGS. 2,  4  and  5 . The rake bolt  62  also passes through the elongated, transversely aligned slots  64  and  66  which are formed in and extend lengthwise of the side walls  36  and  38  of the compression bracket  34  parallel to the steering column. A nut  68  is threaded on the threaded right end portion  70  of the bolt  62 , clamping a thrust bearing  72  between the nut  68  and the wall  54  of the right side rake bracket  42 . The rake bolt  62  is D-shaped in cross-section from a cylindrical portion  74  adjacent the polygonal head  76  of the bolt to the threaded end portion  70 . The D-shaped cross section of the rake bolt  62  includes a flat surface  75 . 
     The rake bolt  62  extends lengthwise within a transverse tubular capsule  80 . See FIGS. 5 and 5A. The ends  81  and  83  of the capsule  80  extend through the slots  64  and  66  in the side walls  36  and  38  of the compression bracket  34 . Bushings  82  and  84  in the ends of the capsule have heads  86  and  88  which extend across the ends  81  and  83  of the capsule in confronting relation to the vertical walls  44  and  54  of the side rake brackets  40  and  42 . An annular cam  90  rotatable on the cylindrical portion  74  of the rake bolt  62  has a flange  92  engaged over an edge of the rake plate  48  to keep the cam from rotating. A cam follower  94  secured on the end of a tilt adjustment control handle  96  has a polygonal socket  98  fitted over the polygonal head  76  of the bolt  62  so that the bolt  62  is rotated when the handle  96  is turned. The cam  90  has a cam track  99  bearing against the cam follower  94 . 
     A left annular tooth lock  100  on the rake bolt  62  has a D-shaped hole  101  with a flat surface  103  and is generally similar to but slightly larger than the D-shaped rake bolt so that the rake bolt  62  may rotate relative to the tooth lock  100 . The tooth lock  100  cannot rotate because it is generally rectangular and is confined between the walls of the rake slot  50 . The tooth lock  100  is disposed in the rake slot  50  between the bushing head  86  and the cam  90  and has teeth  102  facing the rake teeth  52  in the rake slot. 
     The D-shaped rake bolt  62  extends through and is rotatable in the rake slot  56  in the vertical wall  44  of the right side rake bracket  40 , but there is no associated tooth lock for the right side of the rake adjustment mechanism  43 . 
     The left and right rake brackets  40  and  42  have transversely aligned, vertically elongated slots  104  and  106  in the vertical walls  44  and  54  thereof. The slots  104  and  106  are spaced forwardly from the rake slots  50  and  56 . A bolt  108  extends through the slots  104  and  106  and also through the elongated, transversely aligned slots  110  and  112  which are formed in and extend lengthwise of the side walls  36  and  38  of the compression bracket  34  parallel to the steering column. A nut  114  is threaded on an end of the bolt  108 , with a washer  116  between the nut and the side wall  38  of the compression bracket. The bolt  108  assists in stabilizing the steering column  20  but does not interfere with the vertical adjustment or collapse of the steering column. 
     To adjust the vertical tilt of the steering column  20 , the adjustment control handle  96  is raised from the position shown in FIGS. 1 and 3 so that the rake bolt  62  is rotated to the position shown in FIGS. 7A-7C. In this position of the rake bolt, the tooth lock  100  is withdrawn to the position of FIG. 7B to disengage its rake teeth  102  from the rake teeth  52  in the rake slot  50 , freeing the steering column  20  for vertical adjustment. After the tilt of the steering column  20  is adjusted as desired, the rake bolt  62  is reverse rotated to the position of FIGS. 8A-8C, such that the flat surface  75  of the rake bolt is opposed to the flat surface  103  of the hole  101  in the tooth lock  100 , enabling the tooth lock to be pressed forwardly by an actuator comprising a spring  118 , causing the teeth  102  of the tooth lock to engage the teeth  52  in the rake slot  50 . This engagement of the teeth  52  and  102  locks the steering column  20  in vertically adjusted position. The spring  118  is secured in the rake slot  50  opposite to rake teeth  52 . With the rake bolt  62  reverse rotated to the position of FIGS. 8A-8C, the cam track  99  on the cam  90 , in cooperation with the cam follower  94 , causes the bushing heads  86  and  88  to be compressed against the walls  44  and  54  of the rake brackets  40  and  42  to frictionally resist movement of the steering column  20  away from the adjusted position. 
     An energy absorption mechanism  120  is best shown in FIGS. 10-12. The capsule  80  is part of this mechanism. One end  81  of the capsule  80  has dual spaced apart flanges  122  and  124  and the opposite end  83  has dual spaced apart flanges  126  and  128  (FIGS. 5,  5 A and  6 ). The flanges  122  and  124  embrace the side wall  36  of the compression bracket  34  at one end  130  of the slot  64  therein. The flange  122  has a hole  132  registering with a hole  134  in the wall  36 . The flanges  126  and  128  embrace the side wall  38  of the compression bracket  34  at one end  136  of the slot  66  therein. The flange  126  has a hole  138  registering with a hole  140  in the wall  38 . The registering holes  132  and  134  are injected with a flowable material such as a suitable plastic, for example Acetel, to produce a shear pin  142 . The registering holes  138  and  140  are also injected with the same or similar material to produce a shear pin  144 . The shear pins  142  and  144  retain the capsule  80  at the ends  130  and  136  of the slots  64  and  66  where such slots preferably have bottom wall portions  146  tapered about 15° to their lengthwise dimension. The ends  81  and  83  of the capsule  80  run on the bottoms of slots  64  and  66  and have similarly tapered bottoms  148 . 
     A generally U-shaped energy absorption strap  150  of metal, for example, has a curved mid portion  152  extending around the capsule  80  and has one end  151  secured to a bottom wall  154  of the compression bracket  34  by a fastener  155 . There is a space or gap  156  of about 5 millimeters, more or less, between the curved mid portion  152  of the strip  150  and the capsule  80 . 
     In the event of a high impact load, such as a head-on collision, of sufficient magnitude to shear the pins  142  and  144  and to overcome the friction hold of the capsule heads  86  and  88  on the compression bracket  34 , the steering column  20  will collapse causing the upper jacket  26  to telescope relative to the lower jacket  24 . The energy absorption strap  150  will travel a few millimeters to take up the gap  156  before contacting the capsule  80 . The gap  156  serves to eliminate the inertial effects associated with high initiation loads. It essentially separates the release loads so that they are not superimposed on one another. It also reduces the tendency of the capsule  80  to bind during the initial portion of the impact. This also prevents high initiation spike loads on impact. 
     During continuing collapse of the steering column  20  the strap  150  will be bent in an arc around the capsule  80  and then restraightened to absorb energy. The 15° taper of the bottom wall portions  146  at the forward ends of the slots  64  and  66  together with the similar taper of the bottoms  148  of the ends of the capsule  80  eliminate any lash between the slots and the capsule and also eliminate sticking of the capsule upon initial engagement of the curved portion  152  of the strap  150  with the capsule. 
     Also during collapse of the steering column  20  in response to a high impact load, the rake bolt  62  moves forwardly relative to the rake slot  50  (see FIGS. 9A-9C) so that that left end  63  of the rake bolt  62  positively engages and holds the tooth lock  100  in the position in which its teeth  102  engage the rake teeth  52  in the rake slot  50 , thus preventing the steering column  20  from accidentally tilting upwardly. The bolt  62  moves forward during collapse of the steering column because the bolt is inside the capsule  80  which is being pushed forward by the strap  150 . The right end  65  of the rake bolt  62  is normally prevented from moving forwardly by the front wall  61  of the rake slot  56  but on collapse of the steering column is permitted to move forwardly with the left end portion due to the deformation of the flexible strip  60  of the wall  54  between the slot  56  and the slit  58  (see FIG.  9 C), thus preventing binding of the rake bolt. 
     Referring now to FIGS. 13-16, there is shown a modification of the invention which includes a steering column  180  having a jacket assembly  182  including a lower tubular jacket  184  telescoped within an upper tubular jacket  186 . A steering shaft  188  extends lengthwise within the jacket  182  and has a splined rear end  190  to receive the splined opening in a steering wheel (not shown). A housing  192  supports the rear end of the upper jacket  186 . A horizontal transverse pivot pin  194  pivots the front end of the steering shaft to enable up and down rake adjustment. Normally the steering column is supported at an angle A to the horizontal. 
     A mounting bracket  198  is provided for the steering column  180 . The mounting bracket  198  is rigidly secured to the upper jacket  186 . The mounting bracket is generally channel-shaped having a bottom wall  200  beneath the upper jacket  186  of the steering column and laterally spaced upwardly extending vertical side walls or plates  202  and  204  on opposite sides of the upper jacket. The side walls each having a notch  206  in the rear edge. The notches of the two plates are transversely aligned. Each notch has a straight top edge  208  and a straight bottom edge  210  which diverge away from one another in a rearward direction at a predetermined angle and open through the rear edge of the notch. The top edge  208  is parallel to the longitudinal axis or center line  212  of the steering column and the bottom edge  210  diverges in a rearward direction away from the top edge at an arcuate angle B to the longitudinal center line. 
     Shear capsules  214  and  216  are provided. The shear capsules  214  and  216  are identical and are rigidly supported and anchored in fixed positions on opposite sides of the steering column by a transverse bolt or bar  218  which extends horizontally across the top of the upper jacket  186  and is secured in holes  220  in the capsules. The bar  218  is secured to rigid frame structure of the vehicle. 
     Each shear capsule has a configuration similar to the configuration of the notches  206 . Each shear capsule is in the form of a flat plate which is wider or thicker than the side walls  202  and  204  of the mounting bracket  198 . The top and bottom edges  224  and  226  of each capsule diverge at the same angle as the top and bottom edges  208  and  210  of the notches  206 . Each capsule is provided with straight open-ended grooves  228  and  230  along the top and bottom edges  224  and  226  thereof which also diverge at the same angle as the top and bottom edges  208  and  210  of the notches. The grooves  228  and  230  slideably receive the top and bottom edges  208  and  210  of the notches. 
     Shear pins  232  and  234  are provided to hold the capsules  214  and  216  in the notches  206  of the respective side walls  202  and  204 . The shear pins  232  and  234  are preferably made of the same material as the shear pins  142  and  144  described in connection with the first embodiment. The shear pin  232  has its ends received in holes  236  and  238  in the capsule  214  and the side wall  202  of the mounting bracket, and the shear pin  234  has its ends received in holes  240  and  242  in the capsule  216  and the side wall  204 . 
     In the normal operation of the vehicle, the capsules  214  and  216  are held in the notches  206  of the side walls  202  and  204  by the shear pins  232  and  234 , preventing collapse of the steering column  180 . However, in a frontal vehicle impact of great magnitude, when the driver is thrown forward and his chest strikes the steering wheel, the pins  232  and  234  shear and the upper jacket  186  collapses and telescopes relative to the lower jacket  184 . 
     When entering or leaving a vehicle, the driver will often grasp the steering wheel and apply a downward force. This force is represented by the vector F 1  in FIG.  15  and is perpendicular to the central axis of the steering column. It is resisted by the capsules  214  and  216 . The force is applied by contact of the top edges  208  of the notches  206  of the side walls  202  and  204  of the mounting bracket  198  against the bottoms of the grooves  228  along the top edges  224  of the capsules. This force is perpendicular to such contact surfaces and hence does not place any stress on the shear pins  232  and  234  and thus will not accidentally shear the pins and allow the steering column to collapse. 
     However in a sudden and violent frontal impact event, when the driver is thrown forward against the steering wheel, the force against the steering column may be great enough to shear the pins  232  and  234  and allow the steering column to collapse. During such an event, the force of the driver against the steering wheel typically applies an upward force on the steering column represented by the vector F 2  in FIG.  16  and is applied by contact of the bottom edges  210  of the notches against the bottoms of the grooves  230  along the bottom edges  226  of the capsules. This force is perpendicular to the central axis of the steering column but is not perpendicular to such contact surfaces and in fact has a component F 3  in a direction which increases the stress on the shear pins and thus assists in causing the shear pins to shear, promoting collapse of the steering column. 
     The disclosed embodiments are representative of presently preferred forms of the invention, but are intended to be illustrative rather than definitive thereof. The invention is defined in the claims.