Abstract:
An apparatus for releasably locking the tilt steering column assembly. The apparatus includes a housing, a lock member, a pawl, a rack and a rack trunnion. The rack and the rack trunnion, which are slidable relative to one another, form a link that determines the angle to which the tilt steering column is adjusted. The pawl is pivotably coupled to the rack trunnion and pivotable between a first position, wherein teeth formed on the pawl meshingly engage teeth formed on the rack to fix the position of the rack trunnion relative to the rack, and a second position, wherein the teeth of the pawl are rotated out of engagement with the teeth of the rack to permit the rack trunnion and the rack to be moved relative to one another. The lock member is disposed between a wall of the housing and the pawl such that relative movement of the housing toward the rack trunnion engages the lock member to the pawl and rotates the pawl into the first

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to tilt steering columns for automotive vehicles and more particularly to an apparatus for releasably locking a tilt steering column in adjusted opposition. 
     BACKGROUND OF THE INVENTION 
     Many automobiles have steering columns which can be tilted to an adjusted position selected by the vehicle operator. A locking mechanism is typically provided to maintain the steering column in its selected position. The known locking mechanisms include pawl-and-rack and rotary actuated designs. The known pawl-and-rack designs tend to be relatively complex and have difficulty in maintaining the steering column in its selected position when considerable force is applied to the steering column in a direction that is highly skewed to the axis of the steering column. 
     The rotary actuated designs appear to be relatively less complex, but in practice must address issues relating to vibration of the steering column as a result of the lash within these mechanisms. Attempts to minimize lash to thereby attenuate the vibration of the steering wheel typically utilize highly toleranced components and the matching of components to minimize lash and as such, these mechanisms tend to be relatively expensive to manufacture and service. 
     SUMMARY OF THE INVENTION 
     In one preferred form, the present invention provides an apparatus for releasably locking a tilt steering column of an automotive vehicle. The apparatus includes a housing, a rack, a first coupling member, a rack trunnion, a pawl member, a second coupling member, a pawl spring and a locking member. The housing has a central cavity and a slotted aperture that is formed through the housing and intersects the central cavity. The rack has a first trunnion mount and a rack body. The rack body includes a plurality of rack teeth and a first coupling aperture into which the first coupling member is disposed. The rack trunnion has a wall member and a first pivot trunnion. The wall member has a second coupling aperture formed therethrough, the first coupling member extending into the second coupling aperture and coupling the rack to the rack trunnion such that the rack and the rack trunnion are movable relative to one another along an axis that is generally perpendicular to an axis of the first coupling member, the first pivot trunnion being disposed in the housing and defining a first pivot aperture, the first pivot aperture being aligned to the slotted aperture. The pawl member has a second trunnion mount, which defines a second pivot aperture, a plurality of pawl teeth, which are configured to meshingly engage the rack teeth, and a locking cam. The second coupling member is disposed through the slotted aperture, the first pivot aperture and the second pivot aperture to pivotably couple the pawl member and the rack trunnion and slidably couple the housing to the pawl member and the rack trunnion. The spring is coupled to the pawl member and biases the pawl teeth out of engagement with the rack teeth. The locking member is coupled to the housing and extends into the central cavity. The apparatus is operable in an engaged condition, wherein engagement between the locking member and the locking cam of the pawl member overcomes the spring and rotates the pawl member toward the rack to cause meshing engagement of the pawl teeth and the rack teeth and thereby inhibit relative movement between the rack and the rack trunnion. The apparatus is further operable in a disengaged condition, wherein the spring rotates the pawl member away from the rack such that the pawl teeth are not meshingly engaged to the rack teeth to thereby permit relative movement between the rack and the rack trunnion. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a side view of a steering column having a tilt lock apparatus constructed in accordance with the teachings of the present invention; 
     FIG. 2 is a top view of the steering column of FIG. 1; 
     FIG. 3 is a perspective view of a portion of the steering column of FIG. 1 illustrating the lock mechanism in greater detail; 
     FIG. 4 is an exploded view of the lock mechanism; 
     FIG. 5 is a sectional view of the lock mechanism illustrating the pawl teeth in meshing engagement with the rack teeth; and 
     FIG. 6 is a sectional view similar to that of FIG. 5 but illustrating the housing slid rearwardly relative to the pawl member and the pawl member rotated away from the rack to disengage the pawl teeth from the rack teeth. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIGS. 1 and 2 of the drawings, a tilt lock apparatus constructed in accordance with the teachings of the present invention is generally indicated by reference numeral  8 . The tilt lock apparatus  8  is illustrated in operative association with a steering column assembly  10  having a steering column  12  mounted in a housing  14 , with a steering wheel  16  on the upper end of the steering column  12 . The steering column housing  14  extends between a pair of trunnions  18  that are formed on a support structure  20  and is pivoted to the trunnions  18  by horizontal pivots  22  for vertical adjustment about an axis perpendicular to the longitudinal center line of the vehicle and of the steering column  12 . The pivotal support for the housing  14  permits the steering column  12  to be adjusted vertically, as shown in FIG. 1 to a positioned desired by the vehicle operator, but within a range in which the steering column extends at an angle generally upwardly and rearwardly of the motor vehicle. A coil spring  24  is secured at its ends to the support structure  20  and to the housing  14  and urges the housing  14  to swing upwardly to a limiting position making ingress to and egress from the vehicle easier for the vehicle operator. 
     With additional reference to FIGS. 3 and 4, the tilt lock apparatus  8  is shown to include a lock mechanism  30 , a housing spring  32 , a stationary plunger  34  and a tilt lock lever  36 . The lock mechanism  30  includes a housing  40 , a rack  42 , a first coupling member  44 , a rack trunnion  46 , a pawl member  48 , a second coupling member  50 , a pawl spring  52  and a locking member  54 . In the example illustrated, the housing  40  is shown to have a wall member  60  that is formed to provide the housing  40  with a generally rectangular tubular configuration. The wall member  60  thus defines a central cavity  62  that is formed along the longitudinal axis  64  of the housing  40 . A slotted aperture  66  is formed through the housing  40 . 
     The rack  42  has a first trunnion mount  70  and a rack body  72 . The first trunnion mount  70  includes a yoke pivot aperture  74  that is configured to receive a first pivot pin  76  (FIG. 2) that pivotably couples the rack  42  to the housing  14 . The rack body  72  includes a plurality of rack teeth  78  that are spaced axially apart from the first trunnion mount  70  and which are defined by a pitch line  80  (FIG.  6 ). The rack body  72  also includes a first coupling aperture  82 , which in the particular embodiment illustrated, is a cylindrical hole that is offset from the rack teeth  78 . 
     The first coupling member  44  is illustrated to be a cylindrical pin that is disposed through the first coupling aperture  82  such that its axis is generally perpendicular to the pitch line  80  of the rack teeth  78 . The first coupling member  44  is preferably sized in a slip-fit or running-fit manner relative to the first coupling aperture  82 , but could also be sized relatively larger than the first coupling aperture  82  to thereby create an interference fit between the first coupling member  44  and the rack  42 . Alternatively, the rack  42  and the first coupling member  44  may be integrally formed. 
     The rack trunnion  46  is illustrated to include a C-shaped body  90  and a pair of first pivot trunnions  92  that are fixed to the opposite sides  94  of the body  90 . The sides  94  of the body  90  are spaced apart to receive the rack  42 . A second coupling aperture  96 , which is sized to receive the first coupling member  44 , is formed through the sides of the body  90 . In the example provided, the second coupling aperture  96  includes a first slotted portion  98  and a second slotted portion  100 . The first slotted portion  98  is offset from and generally parallel to the upper edge  102  of the sides  94  of the body  90 . The second slotted portion  100  intersects the first slotted portion  98  and tapers upwaredly toward the upper edge  102  and rearwardly away from the first pivot trunnions  92 . The first pivot trunnions  92  each define a first pivot aperture  104  having an axis that is generally perpendicular to the first slotted portion  98 . 
     With the first coupling member  44  coupled to the rack  42  and disposed within the first slotted portion  98  of the second coupling aperture  96 , the rack  42  and the rack trunnion  46  are movable relative to one another along an axis that is generally perpendicular to an axis of the first coupling member  44 . The rack trunnion  46  is positioned relative to the housing  40  such that the first pivot trunnions  92  are disposed in the housing  40  and are aligned to the slotted aperture  66 . 
     The pawl member  48  includes a second trunnion mount  110 , a plurality of pawl teeth  112  and a locking cam  114 . The second trunnion mount  110 , which is disposed between the first pivot trunnions  92 , defines a second pivot aperture  118 . In the particular example provided, the pawl member  48  has a goose-neck configuration, wherein the pawl teeth  112  are spaced axially apart from the second trunnion mount  110  and formed along a pitch line  122  (FIG. 6) that intersects the centerpoint of the second pivot aperture  118 . The locking cam  114  is defined by a portion of the upper surface  124  of the pawl member  48 . The locking cam  114  tapers upwardly toward the end of the pawl member  48  opposite the second trunnion mount  110 . A slight recess  126  is formed in the locking cam  114  just prior to the point at which the locking cam  114 intersects the end of the pawl member  48 . 
     The pawl member  48  is positioned relative to the rack trunnion  46  such that the second trunnion mount  110  is disposed between the first pivot trunnions  92  and the second pivot aperture  118  is aligned to both the first pivot apertures  104  and the slotted aperture  66 . The second coupling member  50 , which is illustrated to be a cylindrically shaped pin, is disposed through the slotted aperture  66 , the first pivot apertures  104 , the second pivot aperture  118  and a third pivot aperture  130  (FIG. 2) formed in a pair of spaced apart trunnions  132  that are formed onto the support structure  20 . The second coupling member  50  thereby pivotably couples the pawl member  48  to the rack trunnion  46 , slidingly couples the housing  40  to the rack trunnion  46 , and anchors the rack trunnion  46  relative to the spaced apart trunnions  132  that are formed onto the support structure  20 . The pawl member  48  is thus rotatable between a first position, wherein the pawl teeth  112  are meshingly engaged to the rack teeth  78 , and a second position, wherein the pawl teeth  112  are not meshingly engaged to the rack teeth  78 . Accordingly, placement of the pawl member  48  in the first position operatively fixes the rack  42  relative to the rack trunnion  46 , while placement of the pawl member  48  in the second position permits relative sliding movement between the rack  42  and the rack trunnion  46 . 
     The pawl spring  52 , which is illustrated to be a conventional coil spring, is disposed between the body  90  of the rack trunnion  46  and the pawl member  48  and is operable for urging the pawl member  48  toward the second position. 
     The locking member  54  is coupled to the housing  40  and is operable for contacting the locking cam  114  to position the pawl member  48  into the first position. In the particular example provided, the locking member  54  is a cylindrically shaped pin that is disposed in a second slotted aperture  140  formed through the housing  40  in a direction that is transverse to the longitudinal axis  64  of the housing  40 . The locking member  54  includes a body portion  142  and a pair of heads  144  that are fixedly coupled to the opposite ends of the body portion  142 . Each of the heads  144  has a diameter that is relatively larger than a diameter of the body portion  142 . A first end  146  of the second slotted aperture  140  is formed to receive therethrough at least one of the heads  144 , while the second end  148  of the second slotted aperture  140  is formed to receive therethrough only the body portion  142  of the locking member  54 . Configuration in this manner ensures that the body portion  142  will not dislodge from the housing  40  during the operation of the tilt lock apparatus  8 , but will permit the body portion  142  of the locking member  54  to rotate as it contacts the locking cam  114  to thereby reduce friction and enhance the performance of the tilt lock apparatus  8 . 
     The housing spring  32 , is illustrated to be a conventional compression spring and is disposed between the housing  40  and the stationary plunger  34  so as to exert a force on the housing  40  that biases the housing  40  away from the spaced apart trunnions  132  that are formed on the support structure  20 . In the particular embodiment illustrated, the stationary plunger  34  is unitarily formed with the support structure  20 , although those skilled in the art will understand that the stationary plunger  34  may also be separately formed. The stationary plunger  34  serves as a locating tab for maintaining a first end of the housing spring  32  in a predetermined position relative to the support structure  20 . A pair of spring tabs  170  are formed onto the housing  40  and extend rearwardly into the interior of the housing spring  32  to thereby position the opposite end of the housing spring  32  relative to the housing  40 . An optional protective sleeve (not shown) may be employed to cover a portion of the housing spring  32  to prevent other components in the vicinity of the steering column  12 , such as wire harnesses (not shown), from being pinched between the coils of the housing spring  32  during the operation of the tilt lock apparatus  8 . 
     The tilt lock lever  36  includes a handle  200 , for receiving a rotary input from a vehicle operator, and a contact arm  202 . The tilt lock lever  36  is mounted to the support structure  20  so as to pivot between a first rotational position and a second rotational position. Positioning of the tilt lock lever  36  into the first rotational position causes the contact arm  202  to push the end  210  of the housing  40  toward the spaced apart trunnions  132  that are formed on the support structure  20 . As the locking member  54  is carried by the housing  40 , the locking member  54  is moved toward the second trunnion mount  110  and away from the locking cam  114 , thereby permitting the pawl spring  52  to rotate the pawl member  48  into the second position (as shown in FIG. 6) wherein the pawl teeth  112  are not meshingly engaged to the rack teeth  78 . As mentioned above, this condition permits the link that is formed by the rack  42  and the rack trunnion  46  to be lengthened or shortened to thereby adjust the angle to which the tilt steering column  12  is adjusted. 
     With the tilt steering column  12  adjusted to a desired angle, the handle  200  of the tilt lock lever  36  is released and the housing  40  is urged in an opposite direction toward the housing  14  by the housing spring  32 . The locking member  54 , which is carried by the housing  40 , traverses along the upper surface  124  of the pawl member  48 . Contact between the locking member  54  and the locking cam  114  operably rotates the pawl member  48  into the first position wherein the pawl teeth  112  are meshingly engaged to the rack teeth  78 . As mentioned above, this condition fixes the link that is formed by the rack  42  and the rack trunnion  46  and thereby maintains the angle of the tilt steering column  12  at the angle to which it has been adjusted. 
     While the tilt lock apparatus  8  has been described thus far in the context of the illustrated embodiment, those skilled in the art will appreciate that the invention, in its broader aspects, may be constructed somewhat differently. For example, the locking member  54  may be integrally formed with the housing  40 . In this regard, the locking member  54  may be a tab that is bent over or into or the central cavity  62 . As another example, the locking cam  114  may be formed into or coupled to the housing  40  and the locking member  54  may be formed onto or coupled to the pawl member  48 . 
     While the invention has been described in the specification and illustrated in the drawings with reference to a preferred 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 as defined in the claims. 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 illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this invention, but that the invention will include any embodiments falling within the foregoing description and the appended claims.